JP7658216B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming device such as a printer.

Image forming devices that perform gamma correction processing to correct gamma data that indicates the correspondence between the gradation value of input image data and the exposure area ratio of output exposure data are known as prior art. In the technology disclosed in Patent Document 1, the correspondence is corrected so as to gradually correct the difference between the density detection result and image data.

JP 2010-102182 A

In the technology disclosed in Patent Document 1, a process for correcting the development bias and a gamma correction process are performed, and the development bias after the density correction process is used to print the exposure data that has been binarized by applying the gamma data after the gamma correction process.

However, if there is a certain amount of time between when the image forming device generates the exposure data and when it starts printing, and if a density correction process or toner cartridge replacement is performed during that time, there is a risk that the printed matter that is output when the exposure data is printed will differ significantly from the appropriate gradation.

The present disclosure aims to prevent the printed matter from deviating from the appropriate gradation when there is a time lag between generating exposure data and starting printing in an image forming device.

In order to solve the above-mentioned problem, an image forming apparatus according to one aspect of the present invention is an image forming apparatus including a photoconductor, a developing roller that supplies developer to the photoconductor, a communication interface, a user interface, a memory, and a controller, and the controller executes a developing bias correction process that sets a first developing bias and stores the set first developing bias in the memory, a RIP process that analyzes print job data input to the communication interface to generate exposure data and stores the generated exposure data in the memory, and a print process, and executes the developing bias correction process when a predetermined condition is satisfied, and updates the first developing bias stored in the memory each time the developing bias correction process is executed, and updates the first developing bias stored in the memory each time the developing bias correction process is executed, and executes a print process when a predetermined condition is satisfied. In the case where the print job data is data for accumulation printing, accumulation specification information indicating that the data is for accumulation printing is stored in the memory in association with the generated exposure data, and the printing process of the exposure data associated with the accumulation specification information is started in response to a print instruction being input via the user interface, and in the printing process, the photoconductor is exposed using the exposure data generated in the RIP process, and if the accumulation specification information is not associated with the exposure data to be printed, a first developing bias stored in the memory is applied to the developing roller, and if the accumulation specification information is associated with the exposure data to be printed, a second developing bias different from the first developing bias is applied to the developing roller.

According to the above configuration, when accumulation printing is performed, a second development bias different from the first development bias stored in the memory in the development bias correction process is used for the printing process. This makes it possible to prevent the printed matter from deviating from the appropriate gradation when accumulation printing is performed.

In order to solve the above problem, an image forming apparatus according to one aspect of the present invention is an image forming apparatus including a photoconductor, a developing roller that supplies a developer to the photoconductor, a communication interface, a memory, and a controller, and the controller executes a developing bias correction process that sets a first developing bias and stores the set first developing bias in the memory, a gamma correction process that sets gamma data corresponding to the first developing bias each time the first developing bias is updated and stores the set gamma data in the memory, a RIP process that analyzes print job data input to the communication interface, generates exposure data using the gamma data stored in the memory, and stores the generated exposure data in the memory, and a print process, and exposes the photoconductor using the exposure data generated in the RIP process to print. and a printing process for printing the image, and when a predetermined condition is satisfied, the developing bias correction process is executed, and the first developing bias stored in the memory is updated each time the developing bias correction process is executed, and the gamma data stored in the memory is updated each time the gamma correction process is executed. In the RIP process, the date and time when the exposure data was generated is stored in the memory in association with the generated exposure data. In the printing process, the photoconductor is exposed using the exposure data generated in the RIP process, and if the exposure data to be printed has not been generated for a predetermined time or more, the first developing bias stored in the memory is applied to the developing roller, and if the exposure data to be printed has been generated for a predetermined time or more, a second developing bias different from the first developing bias is applied to the developing roller.

According to the above configuration, when printing exposure data that has been generated for a predetermined time or more before printing, a second development bias different from the first development bias stored in memory in the development bias correction process is used for the printing process. This makes it possible to prevent the printed matter from deviating from the appropriate gradation when printing is performed with a time lag between the generation of the exposure data and the start of printing.

In order to solve the above problem, an image forming apparatus according to one aspect of the present invention includes a photoconductor, a developing roller that supplies developer to the photoconductor, a communication interface, a memory, and a controller, and the controller executes a developing bias correction process that sets a first developing bias and stores the set first developing bias in the memory, a gamma correction process that sets gamma data corresponding to the first developing bias each time the first developing bias is updated and stores the set gamma data in the memory, a RIP process that analyzes print job data input to the communication interface, generates exposure data using the gamma data stored in the memory, and stores the generated exposure data in the memory, and a printing process that exposes the photoconductor using the exposure data generated in the RIP process to print. and execute the developing bias correction process when a predetermined condition is satisfied, and update the first developing bias stored in the memory each time the developing bias correction process is executed, and update the gamma data stored in the memory each time the gamma correction process is executed, and in the printing process, expose the photoconductor using the exposure data generated in the RIP process, and apply the first developing bias stored in the memory to the developing roller if the container that contains the developer has not been replaced between the generation of the exposure data to be printed and the start of printing of the exposure data, and apply a second developing bias different from the first developing bias to the developing roller if the container that contains the developer has been replaced between the generation of the exposure data to be printed and the start of printing of the exposure data.

According to the above configuration, if the container is replaced between the generation of exposure data and the start of printing, a second developing bias different from the first developing bias stored in the memory in the developing bias correction process is used in the printing process. This makes it possible to prevent the printed matter from deviating from the appropriate gradation when the container is replaced in the image forming device.

According to one aspect of the present invention, in an image forming device, when there is a time lag between generating exposure data and starting printing, it is possible to prevent the printed matter from deviating from the appropriate gradation.

FIG. 1 is a diagram illustrating a schematic configuration of a color printer. FIG. 2 is a block diagram showing the functional configuration of a color printer. 13 is a flowchart of a correction parameter update process. 4 is a flowchart of a RIP process according to the first embodiment. 13 is a flowchart of a printing process. 10 is a flowchart of a correction parameter determination process according to the first embodiment. FIG. 4 is a sequence diagram including a RIP process according to the first embodiment. FIG. 4 is a sequence diagram of a printing process according to the first embodiment. 10 is a flowchart of a RIP process according to a second embodiment. 10 is a flowchart of a correction parameter determination process according to a second embodiment.

[Embodiment 1]
Hereinafter, an embodiment of the present invention will be described in detail. For the sake of convenience, the same components are denoted by the same reference numerals, and their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

(Configuration of Color Printer 1)
Fig. 1 is a diagram showing a schematic configuration of a color printer 1. As shown in Fig. 1, color printer 1, which is an example of an image forming apparatus, includes a housing 10, a sheet supply unit 20, and an image forming unit 30. In Fig. 1, the left side of color printer 1 is referred to as the "front", the right side as the "rear", the upper side as the "top", and the lower side as the "bottom".

The housing 10 has an opening 10A and a cover 11 that can open and close the opening 10A. The cover 11 is arranged on the opposite side of the housing 10 from the side on which the photoconductor 51 of the exposure head 40 is arranged in the vertical direction, specifically, on the upper side of the housing 10. The cover 11 is supported so as to be rotatable about a rotation shaft 11A provided at the rear of the housing 10, and opens and closes the opening 10A formed in the housing 10. The cover 11 is rotatable between a closed position where the opening 10A is closed and an open position where the opening 10A is opened. The cover sensor 12 is a sensor that detects when the cover 11 is opened and closed. When the cover 11 is opened, the cover sensor 12 outputs an ON signal until the cover 11 is closed.

In addition, the housing 10 is provided with a temperature sensor 92 near the inside of the air intake port (not shown) that acquires the ambient temperature of the color printer 1.

The sheet supply unit 20 is provided at the bottom inside the housing 10. The sheet supply unit 20 includes a sheet tray 21 and a pickup roller 22. The sheet tray 21 stores sheets P. The pickup roller 22 supplies the sheets P from the sheet tray 21 to the image forming unit 30. The sheets P in the sheet tray 21 are separated one by one by the pickup roller 22 and supplied to the image forming unit 30.

The image forming unit 30 is disposed above the sheet tray 21 within the housing 10. The image forming unit 30 includes a plurality of exposure heads 40, a plurality of process cartridges PC as an example of a plurality of photosensitive cartridges, a transfer unit 70, and a fixing unit 80. In FIG. 1, the number of exposure heads 40 and process cartridges PC is four each.

The exposure head 40 is an exposure device that exposes the photoconductor 51, and is supported by the cover 11 so as to be suspended from the cover 11. When the cover 11 is closed, the exposure head 40 is disposed above and facing the photoconductor 51. In detail, the exposure head 40 can be moved between an exposure position where the photoconductor 51 is exposed and a retracted position that is farther away from the photoconductor 51 than the exposure position by opening and closing the cover 11.

The multiple process cartridges PC are arranged in parallel in the front-rear direction between the cover 11 and the sheet tray 21. When the cover 11 is open, the multiple process cartridges PC are detachable from the housing 10 through the opening 10A. The process cartridge PC includes a drum unit 50 and a developing cartridge 60 as an example of a storage section.

The drum unit 50 includes a photoconductor 51, a charger 52, a pressure spring 53, a cleaning roller 54, a drum frame 55, a memory 56, and a cartridge side terminal 57. The photoconductor 51 is a cylindrical drum that carries toner, which is an example of a developer. The charger 52 charges the photoconductor 51. The pressure spring 53 biases the developing cartridge 60 toward the photoconductor 51 in the process cartridge PC. The cleaning roller 54 removes foreign matter such as toner remaining on the photoconductor 51. The cleaning roller 54 is rotatable in contact with the photoconductor 51. The drum frame 55 supports the photoconductor 51 and the like in the process cartridge PC.

The memory 56 stores information about the process cartridge PC. The cartridge side terminal 57 is electrically connected to the memory 56. Each of the multiple housing side terminals 13 is provided in the housing 10 for each process cartridge PC. When the corresponding process cartridge PC is provided in the housing 10, the cartridge side terminal 57 is connected to the cartridge side terminal 57 corresponding to that process cartridge PC.

The developing cartridge 60 is a cartridge that can be attached to and detached from the drum unit 50. The developing cartridge 60 includes a toner storage section 61 and a developing roller 62. The toner storage section 61 stores therein toner of a specific color, which is an example of a developer. In detail, each toner storage section 61 stores toner of one of the following colors: cyan, magenta, yellow, and black. The developing roller 62 supplies the toner in the corresponding toner storage section 61 to the corresponding photoconductor 51. The toner is a non-magnetic, single-component, positively charged toner.

The process cartridge PC is attached to and detached from the housing 10 with the removable developing cartridge 60 attached to the process cartridge PC. The memory 56 may be provided in the developing cartridge 60 and connected to the housing side terminal 13 via the cartridge side terminal 57 of the process cartridge PC. Not limited to this, the developing cartridge 60 may be removable from the housing 10 separately from the process cartridge PC. Alternatively, the process cartridge PC may include a toner storage section 61 and a developing roller 62 as an example of a storage section that is integrated with the process cartridge PC. In this example, the toner storage section 61 and the developing roller 62 are not removable from the process cartridge PC.

The transfer unit 70 is provided between the sheet tray 21 and the process cartridge PC. The transfer unit 70 includes a drive roller 71, a driven roller 72, a belt 73, a plurality of transfer rollers 74, and a sensor 75. The belt 73 is an endless belt stretched between the drive roller 71 and the driven roller 72. The outer surface of the belt 73 is in contact with each photoconductor 51. A toner image made of toner is transferred from each photoconductor 51 to the outer surface of the belt 73. Here, the toner image is an example of a developer image in this disclosure. Each transfer roller 74 is disposed inside the belt 73 so as to sandwich the belt 73 between each photoconductor 51. The sensor 75 is disposed outside the belt 73 and near the drive roller 71. The sensor 75 is an optical sensor that irradiates the belt 73 with light and receives reflected light from the belt 73 to read the density of the toner image formed on the belt 73.

The fixing unit 80 is provided behind the process cartridge PC and the transfer unit 70. The fixing unit 80 includes a heating roller 81 and a pressure roller 82. The pressure roller 82 is disposed opposite the heating roller 81 and presses against the heating roller 81.

The color printer 1 forms an image on the sheet P according to the following procedure. The image forming unit 30 first uniformly charges the surface of each photoconductor 51 with the charger 52. Next, the photoconductor 51 is exposed to light by the exposure head 40 to form an electrostatic latent image on the photoconductor 51 based on the image data. Then, a developing bias is applied to the developing roller 62, which supplies toner to the photoconductor 51 and makes the electrostatic latent image visible. The developing bias has the same polarity as the toner and is the bias amount of the voltage applied to the developing roller 62. A toner image is formed on the photoconductor 51 by applying the developing bias. The image forming unit 30 transfers the toner images formed on each photoconductor 51 in sequence, superimposed on the sheet P transported on the belt 73 by the driving roller 71 and the driven roller 72. The transfer unit 70 transports the sheet P to which the toner image has been transferred between the heating roller 81 and the pressure roller 82. The fixing unit 80 heats the sheet P with a heating roller 81, thereby thermally fixing the toner image to the sheet P. The color printer 1 then ejects the sheet P from inside the housing 10 to the outside with a transport roller 91, and places the sheet P on a discharge sheet tray 11B provided on the top surface of the cover 11.

The image forming unit 30 may also form an image on the sheet P by an intermediate transfer method. According to the intermediate transfer method, the image forming unit 30 first forms a toner image on the outer surface of the belt 73, and then transfers the toner image on the belt 73 to the sheet P.

(Functional Configuration of Color Printer 1)
FIG. 2 is a block diagram showing the functional configuration of the color printer 1. However, in FIG. 2, some of the components included in the color printer 1 shown in FIG. 1 are omitted. As shown in this figure, the color printer 1 includes a control unit 100, an image forming unit 30 having a sensor 75 and the like, a display unit 110, an operation unit 120, a communication unit 130, and a temperature sensor 92. Here, the operation unit 120 is an example of a user interface in the present disclosure, and the communication unit 130 is an example of a communication interface in the present disclosure. The control unit 100 is electrically connected to the image forming unit 30, the display unit 110, the operation unit 120, and the communication unit 130. The control unit 100 includes a CPU 101, a ROM 102, a RAM 103, and a NVM (abbreviation of Non-Volatile Memory) 104. Here, the control unit 100 is an example of a controller in the present disclosure, and the RAM 103 and the NVM 104 are examples of memories in the present disclosure.

The CPU 101 performs processing according to the programs read from the ROM 102, and controls each part of the color printer 1 while storing the results of that processing in the RAM 103 or the NVM 104. The ROM 102 stores various programs, including, for example, programs for controlling each part of the color printer 1. The RAM 103 is used as a working area when the CPU 101 executes the various programs, and as a temporary storage area for data. The NVM 104 is a rewritable non-volatile memory.

The control unit 100 also functions as an RIP and engine by using the CPU 101, etc. The control unit 100 functioning as an RIP executes RIP processing and the like to generate exposure data based on print job data input to the color printer 1. Here, print job data is data that indicates the object to be printed, written in a page description language.

The control unit 100, which functions as an engine, also executes the development bias correction process, gamma correction process, correction parameter update process, printing process, and temporary bias setting process, which will be described later.

For convenience, in the following explanation, the control unit 100 that functions as an RIP according to the RIP program is also referred to as the RIP unit 100A. In contrast, the control unit 100 that operates as an engine according to the correction parameter update processing program is also referred to as the correction parameter update unit 100B, and the control unit 100 that operates as an engine according to the print control program is also referred to as the print control unit 100C.

The RIP unit 100A, the correction parameter update unit 100B, and the print control unit 100C operate independently, regardless of the operating status of the other components. In other words, the RIP process, the correction parameter update process, and the print process are each performed separately with asynchronous operation timing.

The display unit 110 has an LCD display and displays various setting screens and the operating status of the color printer 1. The operation unit 120 has multiple buttons and accepts various input instructions from the user. The multiple buttons on the operation unit 120 may be buttons displayed on a touch panel that constitutes the operation unit 120, or may be physical buttons provided on the operation unit 120. The communication unit 130 communicates with an external device 200 such as a PC by a wireless communication method or a wired communication method, and receives data. The communication unit 130 is a LAN interface or the like. The communication unit 130 may communicate with multiple external devices 200.

The print job data input from the external device 200 to the communication unit 130 may contain information that specifies that accumulation printing is to be performed on the print job data. Accumulation printing here refers to printing in which the printing process of the exposure data generated based on the print job data is started in response to a print instruction being separately input to the color printer 1 after the exposure data is generated. In the color printer 1, the print instruction is input via the operation unit 120.

The correction parameter update process, RIP process, and print process in the color printer 1 according to this embodiment will be described with reference to Figs. 3 to 8. Fig. 3 is a flowchart of the correction parameter update process. Fig. 4 is a flowchart of the RIP process. Fig. 7 is a sequence chart of a series of processes including the correction parameter update process and the RIP process. Fig. 5 is a flowchart of the print process. Fig. 6 is a flowchart of the correction parameter determination process. Fig. 6 corresponds to the process of S301 in Fig. 5. Fig. 8 is a sequence chart of the print process.

(Correction parameter update process flow)
The correction parameter update process will be described with reference to Fig. 3. The development bias correction process and gamma correction process in Fig. 3 are examples of the correction parameter update process in the present disclosure, and the development bias and gamma data are examples of the correction parameters in the present disclosure. The process shown in the flowchart in Fig. 3 can be executed at regular intervals, for example, after the color printer 1 is started up, or after the cover sensor 12 detects that the cover 11 is closed.

In S101, the correction parameter update unit 100B determines whether or not the conditions for starting the development bias correction process are satisfied. Here, the cases where the conditions are satisfied include, for example, the following cases. As exemplified below, the development bias correction process can be said to be a process for performing development suitable for the current toner state, atmospheric temperature, etc.
When a predetermined number of prints have been printed after the previous development bias correction process has been performed When the ambient temperature acquired by the temperature sensor 92 has changed by a predetermined temperature or more after the previous development bias correction process has been performed When the development cartridge 60 that contains the toner has been replaced When the operation unit 120 or the communication unit 130 receives a command to perform development bias correction Although not particularly limited, the predetermined number may be, for example, 1000 sheets, and the predetermined temperature may be, for example, 6 degrees Celsius. In addition, the condition for starting the development bias correction process may be satisfied between the generation of the exposure data for accumulation printing and the start of printing. In other words, the correction parameter update unit 100B may perform the development bias correction process and the gamma correction process between the generation of the exposure data for accumulation printing and the start of printing.

In S101, if the correction parameter update unit 100B determines that the above condition is satisfied (YES in S101), in S102, it executes a development bias correction process to set a development bias for printing to be applied to the development roller 62. For example, the correction parameter update unit 100B applies a test development bias to the development roller 62 to form a toner image corresponding to the first exposure area ratio on the belt 73. The toner image can be realized, for example, as a toner patch printed in a rectangle for each toner color. In addition, the correction parameter update unit 100B sets the development bias for printing according to the density of the toner image on the belt 73 read by the sensor 75.

The exposure area ratio means the ratio of the area of the photoconductor 51 to which light is exposed within the range in which an electrostatic latent image corresponding to a binarized image is formed on the photoconductor 51. The first exposure area ratio and the second exposure area ratio described below are not limited to specific values, and may be values specified for each color. In other words, the first exposure area ratio corresponding to the toner image of the first color and the first exposure area ratio corresponding to the toner image of the second color do not necessarily have to be the same. Normally, the development bias correction process and the gamma correction process described below are performed on toners of all colors when it is determined in S101 that the above conditions are met.

In addition, in S102, the correction parameter update unit 100B executes the above-mentioned development bias correction process, and when the development bias is set, it associates an ID for identifying the development bias that has already been set with the development bias. Then, the correction parameter update unit 100B stores the development bias and the ID associated with the development bias in the NVM 104. Here, the ID that identifies the development bias is an example of development bias identification information in this disclosure. Hereinafter, the ID that identifies the development bias will also be simply referred to as "ID". The ID may be, for example, a number specific to each development bias that is generated in sequence each time the correction parameter update unit 100B executes the development bias correction process.

The development bias for printing that the correction parameter update unit 100B sets in the development bias correction process and stores in the NVM 104 is an example of the first development bias in this disclosure. A second development bias that is different from the first development bias will be described later.

The developing bias and ID stored in NVM 104 are not erased from NVM 104, but are accumulated in NVM 104 as history. The developing bias for the latest print set most recently on NVM 104 is also simply referred to as the "latest developing bias." The ID associated with the "latest developing bias" is also referred to as the "latest ID." In other words, the correction parameter update unit 100B generates the "latest developing bias" and associates it with the "latest ID" each time the process of S102 is performed.

Also, in S101, if the correction parameter update unit 100B determines that the above condition is not satisfied (NO in S101), the processing in FIG. 3 ends.

In S103, the correction parameter update unit 100B executes a gamma correction process to set gamma data that corresponds the input gradation value in the input image data to the exposure area ratio of the exposure data for exposing the photoconductor 51, according to the result of a predetermined process using the latest development bias in the development bias correction process in S102.

For example, the correction parameter update unit 100B uses the latest development bias to form toner images corresponding to a plurality of exposure area ratios on the belt 73. The correction parameter update unit 100B then sets gamma data according to the density of the toner image on the belt 73 read by the sensor 75. In the above example, the density of the toner image corresponds to the result of a predetermined process. That is, in one embodiment, the correction parameter update unit 100B sets gamma data according to the shading of the toner image. The exposure data is raster image data in which multi-tone image data is binarized by applying gamma data. The gamma data may also be stored in the NVM 104 in the form of a lookup table, for example.

In addition, in S103, the correction parameter update unit 100B executes the above-mentioned gamma correction process, and when the gamma data is set, the correction parameter update unit 100B associates the set gamma data with the latest ID stored in the NVM 104. Then, the correction parameter update unit 100B stores the gamma data in the NVM 104. In other words, the ID is associated with the development bias and the gamma data. In other words, the gamma data is associated with the development bias via the ID.

The most recently set gamma data on the NVM 104 is also referred to simply as the "latest gamma data." In other words, the correction parameter update unit 100B updates the "latest gamma data" each time the process of S103 is performed.

The gamma data that the correction parameter update unit 100B sets in the gamma correction process and stores in the NVM 104 is an example of the first gamma data in this disclosure. Each time the correction parameter update unit 100B updates the latest development bias in S102, it updates the latest gamma data corresponding to the latest development bias in S103. The second gamma data, which is different from the first gamma data, will be described later.

The set gamma data is not erased from NVM 104, but is stored in NVM 104 as history. As described above, the control unit 100 can grasp the gamma data used to generate the exposure data when the development bias indicated by the ID was used for printing by reading a certain ID and the gamma data associated with the ID from NVM 104. In FIG. 7 and FIG. 8, the area in which the correction parameters are stored is shown as NVM 104A. "ID: A" is the latest ID. "Development bias A" is the latest development bias. "Gamma data A" is the latest gamma data. In FIG. 7, the rectangle P10A corresponds to one correction parameter update process. Step (1A) in FIG. 7 corresponds to the correction parameter update process in FIG. 3. The vertical length of the rectangle P10A indicates the time required for the process. Rectangles such as the rectangle P11A described later also indicate the time required for the corresponding process.

As described above, the control unit 100 updates the ID for identifying the latest development bias each time the development bias correction process is performed, so that the latest development bias and gamma data can be distinguished from the development bias and gamma data that were set before the update.

Normally, gamma correction processing is performed following development bias correction processing, because gamma correction processing is performed to obtain print results with the same color tone even if the development bias is updated. From another perspective, normally, when performing printing processing of exposure data using the latest development bias, it is not possible to print a printed product with the appropriate color tone unless the exposure data is generated using the latest gamma data corresponding to the latest development bias.

Note that it is not essential that the steps in the correction parameter update process are performed in the order described above. For example, the correction parameter update unit 100B may perform a process in which, after setting the gamma data, the ID is associated with the development bias and stored in the NVM 104. The configuration exemplified in the above embodiment is also included in the scope of the present application.

Before the correction parameter update process is executed, NVM 104 stores a predetermined developing bias that is not updated by executing the developing bias correction process. The predetermined developing bias is an example of a second developing bias in this disclosure. Hereinafter, the predetermined developing bias is also referred to as the "default developing bias."

In addition, NVM 104 stores an ID for identifying the default development bias. Hereinafter, the predetermined ID is also referred to as the "default ID." The ID generated by correction parameter update unit 100B in S102 will not overlap with the default ID.

In addition, before the correction parameter update process is executed, NVM 104 stores predetermined gamma data that is not updated by the execution of the gamma correction process. The predetermined gamma data is an example of second gamma data in this disclosure. The second gamma data is data corresponding to the second development bias. Hereinafter, the predetermined gamma data is also referred to as "default gamma data." The default ID is associated with the default development bias and the default gamma data. In other words, the default development bias and the default gamma data are associated with each other via the default ID.

In Figures 7 and 8, "ID:X" means the default ID, and "Development bias X" means the default development bias. Also, "Gamma data X" means the default gamma data.

In addition, although there are no particular limitations on the values of the default development bias and the default gamma data, it is desirable that they are intermediate values within the range that can be set in the color printer 1, rather than values near the upper or lower limits of the range that can be set.

The default development bias and default gamma data may be configured to be stored in NVM 104, for example, when color printer 1 is manufactured, or may be configured to be updated when the firmware of color printer 1 is updated.

(RIP processing flow)
Next, the RIP process for analyzing print job data input to the color printer 1 and generating exposure data will be described.

The RIP process shown in the flowchart of FIG. 4 is initiated when the communications unit 130 acquires print job data input from the external device 200 and supplies it to the RIP unit 100A. Below, an example is described in which the color printer 1 prints multiple pages based on the print job data, but the print job data may also be data for printing a single page. Note that the configuration in which the color printer 1 accepts input of print job data may be a configuration in which a communications interface realized as, for example, a USB interface reads print job data stored in a USB memory.

In S201, the RIP unit 100A determines whether the print job data input to the color printer 1 is data for accumulation printing. In other words, the RIP unit 100A determines whether the print job data includes information specifying that accumulation printing is to be performed.

If the RIP unit 100A determines that the print job data is data for accumulated printing (YES in S201), in S202 it obtains the default gamma data and default ID stored in the NVM 104.

On the other hand, if the RIP unit 100A determines that the print job data is not data for accumulated printing (NO in S201), in S203, it acquires the latest gamma data and the latest ID associated with the gamma data that the correction parameter update unit 100B generated and stored in the NVM 104. Also, step (2A) in FIG. 7 corresponds to the processing of S202 and S203. In step (2A), the RIP unit 100A acquires either ID:X and gamma data X, or ID:A and gamma data A.

In S204, the RIP unit 100A performs rasterization based on one page of the page data for multiple pages included in the print job data, to generate a bitmap image.

In S205, the control unit 100, such as the RIP unit 100A, performs color conversion on the bitmap image, for example by referring to a color conversion lookup table stored in the NVM 104.

In S206, the RIP unit 100A applies gamma correction to the bitmap image using the default gamma data obtained in S202 or the latest gamma data obtained in S203.

In S207, the RIP unit 100A performs halftone processing using a dithering method or the like on the bitmap image, and binarizes the bitmap image. Hereinafter, the binarized bitmap image is referred to as exposure data.

In S208, the RIP unit 100A determines whether the acquired ID is the default ID. In other words, the RIP unit 100A determines whether gamma correction was performed using default gamma data in S206. Note that the RIP unit 100A may be configured to determine whether gamma correction was performed using default gamma data in S206 by performing processing similar to that of S201, for example.

If the RIP unit 100A determines that the acquired ID is the default ID (YES in S208), in S209, it associates the default ID with the exposure data and stores the exposure data together with the default ID in RAM 103.

On the other hand, if the RIP unit 100A determines that the acquired ID is not the default ID (NO in S208), in S210, it associates the latest ID with the exposure data and stores the exposure data together with the latest ID in RAM 103.

In Figures 7 and 8, the area in which the exposure data is stored is shown as RAM 103A. Also, step (3A) in Figure 7 corresponds to the processing of S209 and S210. In step (3A), the RIP unit 100A stores either ID:X and the exposure data, or ID:A and the exposure data, in RAM 103A.

The RAM 103 also has a first area that stores exposure data for which printing processing is to begin, and a second area that stores exposure data that has not yet been printed in accumulated printing. In S209, the RIP unit 100A stores the exposure data and ID in the second area, and in S210 stores the exposure data and ID in the first area.

The second area may be a component of the NVM 104, or may be a component of a storage device such as a USB memory connected to the color printer 1. The second area may also be a component of an external device such as a server connected to the color printer 1 via the communication unit 130.

In S211, the RIP unit 100A determines whether or not there is any page data for which exposure data has not yet been generated among the multiple pages of page data included in the print job data. If the RIP unit 100A determines that there is page data for which exposure data has not yet been generated (YES in S211), it executes the process from S201 for that page data. From another perspective, the RIP unit 100A executes the processes from S201 to S210 for the exposure data for all page data included in the print job data. In FIG. 7, the rectangle P11A corresponds to the generation of exposure data for all page data included in one print job data. If the RIP unit 100A determines that there is no page data for which exposure data has not yet been generated and exposure data based on all page data has been generated (NO in S211), the process in FIG. 4 ends.

Note that if the RIP unit 100A judges "YES" in S211, the process may transition to S204. In this configuration, the gamma data and ID acquired in the most recent process of S202 or S203 are used in the subsequent process.

(Printing process flow)
The printing process shown in the flowchart of Fig. 5 and the sequence diagram of Fig. 8 described later is executed when the exposure data to be printed is stored in the first area of RAM 103. The exposure data stored in the second area of RAM 103 is data for accumulated printing, and the printing process for the exposure data is performed in response to a print instruction input via operation unit 120. In other words, when the print job data input to color printer 1 is data for accumulated printing, even if exposure data is generated based on the print job data, the printing process for the exposure data will not start unless a print instruction is input via operation unit 120.

Specifically, when a print instruction is input via the operation unit 120, the print control unit 100C moves the exposure data stored in the second area of the RAM 103 to the first area and starts the printing process of the exposure data. Note that the process of moving the exposure data for accumulated printing from the second area to the first area may be defined in a program that accepts print instructions and may be performed by the control unit 100 in accordance with the program.

The color printer 1 may also be configured to require the selection of a user name or the input of a password, etc., in addition to the selection of exposure data to be used for the print process, when inputting a print command.

The user interface is not limited to a configuration that accepts input of print instructions by operating a button, such as the operation unit 120. The user interface may be configured to accept input of print instructions by, for example, having a user bring an ID card that can identify each user close to a contactless IC card reader.

The above-mentioned accumulated printing is generally also called "secure printing." This name comes from the fact that the purpose of this printing is to prevent a user who has not performed the operation to output print job data to color printer 1 from obtaining a printed copy when multiple users use color printer 1.

On the other hand, if the exposure data is not data for accumulated printing, a printing process is subsequently started for the exposure data stored in the first area of RAM 103. However, regardless of whether it is accumulated printing or not, if exposure data based on certain print job data is already being printed, the exposure data based on the next print job data is printed after the printing is completed. Also, the printing process can be performed in parallel with the RIP process even if the generation of exposure data for all page data included in the print job data has not been completed.

In S301, the print control unit 100C performs a process to determine the correction parameters when printing the exposure data stored in the RAM 103. In this embodiment, the process of S301 corresponds to the flowchart in FIG. 6. The correction parameter determination process shown in the flowchart in FIG. 6 will be described below. In the correction parameter determination process, the print control unit 100C sets the development bias to be applied to the development roller 62.

In S401, the print control unit 100C reads and acquires from the RAM 103 the exposure data of the page to be printed and the ID associated with the exposure data. The print control unit 100C also reads and acquires from the NVM 104 the default ID.

Step (4A) in FIG. 8 and the process of acquiring ID:X in step (5A) correspond to the process of S401. In step (4A), the print control unit 100C acquires either ID:X and exposure data, or ID:A and exposure data.

In S402, the print control unit 100C determines whether the ID associated with the exposure data of the page to be printed matches the default ID obtained from NVM 104.

If the print control unit 100C determines that the ID associated with the exposure data of the page matches the default ID (YES in S402), in S403, it reads and acquires the default development bias from the NVM 104. The process of acquiring the development bias X in step (5A) of FIG. 8 corresponds to the process of S403. In S209, the default ID is associated with the exposure data generated from the print job data for accumulated printing.

The processes from S404 to S407 correspond to the temporary bias setting process in this disclosure. The temporary bias setting process described below uses the test development bias described in the development bias correction process of S102 in FIG. 3, and the toner image density described in the gamma correction process exemplified in S103. The temporary development bias is a development bias that is set to print exposure data associated with a default ID.

In S404, the print control unit 100C calculates the rate of change Y, which indicates the amount of change ΔD in the developing bias applied to the developing roller 62 relative to the amount of change ΔR in the density of the toner image for the target color.

In the following, the development biases X1, X2, and X3 are the test development biases used in the previous development bias correction process, and correspond to the densities dens1, dens2, and dens3 of the toner images formed using each development bias, respectively.

The test developing biases X1', X2', and X3' used in the most recent, i.e., current, developing bias correction process correspond to the densities dens1', dens2', and dens3' of the toner images formed using each developing bias, respectively. In the previous and current developing bias correction processes, the first exposure area ratio may be set to, for example, 60%.

In the following explanation, the printing development bias set in the previous development bias correction process may be referred to as the "development bias before correction." Also, the printing development bias set in the current or most recent development bias correction process may be referred to as the "development bias after correction."

As an example, the exposure area ratios applied in the previous gamma correction process of 16%, 30%, 43%, and 64% correspond to the densities of the toner images formed by applying each exposure area ratio: dens4, densOld, dens5, and dens6, respectively. In addition, the exposure area ratio values of 16%, 30%, 43%, and 64% roughly correspond to halftone print densities of 20%, 40%, 60%, and 80%, respectively.

The exposure area ratios of 16%, 30%, 43%, and 64% applied in the current gamma correction process correspond to the densities of the toner images formed by applying each exposure area ratio: dens4', densNew, dens5', and dens6', respectively. In the previous and current gamma correction processes, for example, 30% may be set as the second exposure area ratio.

The print control unit 100C may set the second exposure area ratio so that the density of the toner image to which the second exposure area ratio is applied is closer to the density corresponding to 50% of the maximum input gradation value than the density of the toner image to which the first exposure area ratio is applied. The print control unit 100C may also set the second exposure area ratio to a value smaller than the first exposure area ratio, for example, by setting the first exposure area ratio to 75% or 60% and the second exposure area ratio to 30%. Furthermore, densOld is an example of the first density in this disclosure, and densNew is an example of the second density in this disclosure.

In the following explanation, the gamma data set in the previous gamma correction process may be referred to as "gamma data before correction." Also, the gamma data set in the current or most recent gamma correction process may be referred to as "gamma data after correction."

In S404, the print control unit 100C may calculate the rate of change Y based on multiple test developing biases and the densities of the toner images corresponding to each of the multiple test developing biases. The multiple test developing biases are the developing biases used when the toner image corresponding to the first exposure area ratio was formed on the belt 73 in the developing bias correction process.

Furthermore, X2' and X3' are values in the vicinity of the developing bias for printing that are set in the developing bias correction process. The rate of change Y in the vicinity of the developing bias for printing is approximated by the following formula.
Y=ΔD/ΔR=(X3'-X2')/(dens3'-dens2')
In S405, the print control unit 100C executes a process of converting the value of the change rate Y for the target color into a change rate Y' corresponding to the second exposure area ratio. For example, the print control unit 100C may refer to the ambient temperature of the color printer 1 acquired from the temperature sensor 92 and convert the value of the change rate Y according to environmental parameters including the ambient temperature. The conversion is based on the fact that the lower the ambient temperature, the higher the charge amount of the toner becomes, and the smaller the change in density of the toner image becomes with respect to the change in the development bias. Examples of environmental parameters other than the ambient temperature include humidity and air pressure.

Furthermore, the rate of change Y may be converted to a rate of change Y', for example, by the following formula, using predetermined coefficients a and b for converting the value of the rate of change Y according to the ambient temperature. For example, the higher the ambient temperature, the smaller the values of a and b may be.
Y'=a*Y+b
In S406, the print control unit 100C acquires the value of densOld, which is the density of the toner image corresponding to the second exposure area ratio when the uncorrected gamma data is applied to the target color, and the value of densNew, which is the density of the toner image corresponding to the second exposure area ratio when the corrected gamma data is applied.

In S407, the print control unit 100C sets a temporary development bias for printing the exposure data to which the pre-correction gamma data has been applied for the target color, according to the above-mentioned change rate Y' and the difference between the first density densOld and the second density densNew. Note that the process of S405 is not essential, and a configuration may be adopted in which the change rate Y before conversion is used to calculate the temporary development bias instead of the change rate Y'. Also, the temporary development bias set in this step S407 is an example of the second development bias in this disclosure.

If the rate of change is Y and the reference developing bias is Vb, the temporary developing bias Vbx may be calculated based on the developing bias Vb, for example, by the following formula. In the flowchart of Fig. 6, the reference developing bias Vb is the default developing bias acquired by the print control unit 100C in S403. In Fig. 8, the temporary developing bias Xx indicates the temporary developing bias calculated based on the developing bias X. By using the temporary developing bias calculated based on the default developing bias in the printing process, it is possible to maintain print quality at a certain level or higher.
Vbx=(dens_Old-dens_New)*Y+Vb
In S408, the print control unit 100C determines whether the temporary bias setting process has been completed for all colors to be processed. If the print control unit 100C determines that the process has been completed for each color (YES in S408), the process of Fig. 6 ends. If the print control unit 100C determines that the process has not been completed for a certain color (NO in S408), the process from S403 onwards is executed for that color.

On the other hand, if in S402 the print control unit 100C determines that the ID associated with the exposure data of the page to be printed does not match the default ID (NO in S402), it executes the process of S409. The process of acquiring the development bias A in step (5A) of FIG. 8 corresponds to the process of S409.

In S409, the print control unit 100C reads and acquires from the NVM 104 the latest development bias associated with the latest ID associated with the exposure data of the page, and sets it as the development bias for printing the exposure data of the page. The development bias set in step S409 is an example of the first development bias in this disclosure.

The correction parameter determination process in FIG. 6 has been described above. In another embodiment, the print control unit 100C may be configured to set the default development bias acquired in S403 as the temporary development bias in S407.

In addition, in S407, the print control unit 100C may be configured to calculate a temporary development bias based on the most recently acquired development bias and set the calculated temporary development bias. In addition, the above-mentioned default development bias and the temporary development bias calculated based on the most recently acquired development bias are examples of the second development bias in this disclosure.

In S302 of FIG. 5, the print control unit 100C performs a process of printing one page of exposure data using the determined correction parameters. That is, the print control unit 100C applies the development bias set in S301 to the development roller 62, and performs a process of printing the exposure data.

In S303, the print control unit 100C determines whether all the exposure data stored in the RAM 103 has been printed out. If the print control unit 100C determines that the printing out of all the exposure data has been completed (YES in S303), the process in FIG. 5 ends. If the print control unit 100C determines that the printing out has not been completed (NO in S303), the process from S301 is performed for the next page of exposure data. From another perspective, the print control unit 100C performs the processes of S301 and S302 for the exposure data for all the page data included in one print job data. In FIG. 8, the rectangle P12A corresponds to the print process for the exposure data for all the page data. Note that the print process usually requires a much longer time than the RIP process because it includes not only the process of the print control unit 100C itself, but also processes such as paper transport, exposure in the image forming unit, and toner transfer. However, in FIG. 8, the time required for the print process is shown to be somewhat shorter for the purpose of explanation.

In addition, since the correction parameter update process and the printing process are executed asynchronously, in S409, it may happen that the ID associated with the exposure data of the page to be printed is not the latest. If the ID is not the latest, the print control unit 100C may calculate a temporary development bias based on the development bias associated with the ID, and set the calculated temporary development bias as the development bias for printing the exposure data of the page. In addition, if some condition for setting a temporary development bias is met, in S409, the calculated temporary development bias may be set as the development bias for printing the exposure data of the page.

As described above, in the RIP process of the color printer 1 according to this embodiment, if the print job data is data for accumulated printing, the RIP unit 100A generates exposure data using default gamma data, i.e., appropriate gamma data corresponding to the development bias used in the print process. The RIP unit 100A also associates the generated exposure data with a default ID and stores it in the RAM 103. On the other hand, if the print job data is not data for accumulated printing, the RIP unit 100A generates exposure data using the latest gamma data and associates the generated exposure data with the latest ID and stores it in the RAM 103.

The control unit 100 can also identify whether the exposure data is data for accumulated printing by referring to the ID associated with the exposure data. From another perspective, the default ID is an example of accumulation designation information that specifies that the exposure data associated with the default ID is data for accumulated printing.

In addition, in the printing process, if the latest ID is associated with the exposure data to be printed, the print control unit 100C applies the latest development bias to the development roller 62. On the other hand, if the default ID is associated with the exposure data to be printed, the print control unit 100C applies a temporary development bias or a default development bias to the development roller 62. In addition, the temporary development bias may be a temporary development bias calculated based on the default development bias, or may be a temporary development bias calculated based on the latest development bias.

According to the configuration of this embodiment, when performing accumulation printing where there is a time lag between generating exposure data and starting printing, a temporary development bias or a default development bias is used for the print process, rather than the latest development bias, which may be significantly different from the value suitable for printing. This makes it possible to prevent the printed matter from deviating from the appropriate gradation when performing accumulation printing.

[Embodiment 2]
A second embodiment of the present invention will be described below. For ease of explanation, the same reference numerals are used for components having the same functions as those described in the above embodiment, and redundant explanations will not be repeated. In this embodiment, as in the first embodiment, the configuration of the color printer 1 shown in Figs. 1 and 2 is used. However, as described below, each unit of the color printer 1 may perform an operation different from that in the first embodiment. Fig. 9 is a flowchart of the RIP process according to this embodiment. Fig. 10 is a flowchart of the correction parameter determination process according to this embodiment.

(Correction parameter update process flow)
In the correction parameter update process according to this embodiment, the same process as that shown in the flowchart of Fig. 3 in embodiment 1 is performed. However, in the correction parameter update process according to this embodiment, the correction parameter update unit 100B does not need to generate an ID for identifying the development bias, that is, ID: A in step (1A) in Fig. 7.

In other words, the correction parameter update unit 100B performs the same process as S102 in FIG. 3, but does not need to perform the process of associating the development bias with the ID. Also, the correction parameter update unit 100B performs the same process as S103 in FIG. 3, but does not need to perform the process of associating the gamma data with the ID.

(RIP processing flow)
Next, the RIP process according to this embodiment will be described. The start timing of the process shown in the flowchart of FIG.

In S501, the RIP unit 100A acquires the latest developing bias and the latest gamma data that the correction parameter update unit 100B has generated and stored in the NVM 104. That is, the RIP unit 100A acquires the developing bias A and the gamma data A in FIG. 7 from the NVM 104. The RIP unit 100A may also acquire the latest ID, i.e., ID:A, from the NVM 104. The processing of this step S501 differs from process (2A) in FIG. 7 in that the RIP unit 100A acquires the developing bias A and in that the gamma data X is not acquired or used.

In steps S204 to S207, the RIP unit 100A performs the same processes as steps S204 to S207 in FIG. 4. In step S206, the latest gamma data acquired in step S501 is used for gamma correction.

In S506, the RIP unit 100A associates the latest developing bias acquired in S501 and the date and time when the exposure data was generated with the generated exposure data, and stores the exposure data, the latest developing bias, and the date and time when the exposure data was generated in RAM 103. Here, the data format of the date and time when the exposure data was generated is not limited to a specific format. The RIP unit 100A may also associate the latest ID with the exposure data and store it in RAM 103. If accumulation printing is specified, each data is stored in the second area of RAM 103, and if accumulation printing is not specified, each data is stored in the first area of RAM 103. The processing of this step S506 differs from process (3A) in that the developing bias A and the date and time when the exposure data was generated in FIG. 7 are stored in RAM 103.

In S211, the RIP unit 100A performs a determination similar to S211 in FIG. 4. If the RIP unit 100A determines "YES" in S211, the process transitions to S501, and if the RIP unit 100A determines "NO" in S211, the process in FIG. 9 ends.

(Flow of correction parameter determination process)
Next, the correction parameter determination process according to this embodiment will be described. In this embodiment, the flowchart of the print process in Fig. 5 itself is the same as in the first embodiment, but in this embodiment, the process of S301 corresponds to the flowchart in Fig. 10. In other words, the first embodiment and this embodiment differ from each other in the manner of the correction parameter determination process, etc.

In S601, the print control unit 100C reads and acquires from the RAM 103 the exposure data of the page to be printed, the development bias associated with the exposure data, and the creation date and time of the exposure data. The print control unit 100C may also acquire from the RAM 103 an ID associated with the exposure data. The process of this step S601 differs from step (4A) in that the print control unit 100C acquires the development bias A in FIG. 7 and the creation date and time of the exposure data.

In S602, the print control unit 100C determines whether the developing cartridge 60 has been replaced after the exposure data to be printed was generated. If the print control unit 100C determines that the developing cartridge 60 has not been replaced after the exposure data to be printed was generated (NO in S602), it executes the process of S603. On the other hand, if the print control unit 100C determines that the developing cartridge 60 has been replaced after the exposure data to be printed was generated (YES in S602), it executes the process of S403.

In S603, the print control unit 100C determines whether or not a predetermined time has passed since the exposure data to be printed was generated. Specifically, the print control unit 100C compares the generation date and time associated with the exposure data with the current date and time, and determines whether or not the difference between the dates and times is a predetermined time or more. Furthermore, the predetermined time is not limited to a specific time, and may be, for example, 10 minutes or 1 hour. If the print control unit 100C determines that a predetermined time or more has passed since the exposure data to be printed was generated (YES in S603), it executes the process of S403.

Furthermore, a situation in which a predetermined time or more has passed since the exposure data to be printed was generated, or a situation in which enough time has passed to replace the developing cartridge 60, can occur due to, for example, the following factors.
- When accumulation printing is specified and color printer 1 waits for input of a print command - When sheet P is not stored in sheet tray 21 - When cover 11 is open In S403 to S408, print control unit 100C performs the same process as S403 to S408 in Fig. 6. S403 differs from step (5A) in that print control unit 100C acquires only developing bias X in Fig. 8.

In addition, in S407, the print control unit 100C may be configured to calculate a temporary development bias based on the development bias associated with the exposure data of the page to be printed, obtained in S601, and set the calculated temporary development bias as the development bias to be applied to the development roller 62.

The temporary development bias set in step S407 described above and the temporary development bias calculated based on the development bias associated with the exposure data are examples of the second development bias in this disclosure.

If the print control unit 100C determines in S603 that a predetermined time has not elapsed since the exposure data to be printed was generated (NO in S603), it executes the process of S604.

In S604, the print control unit 100C sets the development bias associated with the exposure data of the page to be printed, acquired in S601, as the development bias for printing the exposure data of that page. The development bias set in this step S604 is an example of the first development bias in this disclosure. Note that the print control unit 100C may be configured to acquire the development bias associated with the exposure data in this step S604 instead of S601.

Note that one of the processes S602 and S603 may be omitted. In a configuration in which the process S602 is omitted, the process S603 is executed following S601. Also, in a configuration in which the process S603 is omitted, if the determination in S602 is "NO", the process S604 is executed.

The print control unit 100C may also be configured to set the default development bias obtained in S403 as the development bias to be applied to the development roller 62 in S407.

In addition, in the processing of S604, the print control unit 100C may be configured to calculate a temporary development bias based on the development bias associated with the exposure data of the page to be printed, for example, if the acquired ID is not the latest one, and set the calculated temporary development bias as the development bias to be applied to the development roller 62.

In the above-described first embodiment, the exposure data may be associated with the development bias in the RIP process and stored in the RAM 103. For example, in a print process corresponding to this configuration, when the accumulation specification information exemplified as the default ID is associated with the exposure data of the page to be printed, the print control unit 100C may set the temporary development bias calculated based on the development bias associated with the exposure data as the development bias for printing the exposure data of the page. According to this configuration, the temporary development bias calculated based on the development bias corresponding to the gamma data used to generate the exposure data is used in the print process. This makes it possible to prevent the printed matter from deviating from the appropriate gradation even if the latest development bias is significantly changed by the development bias correction process after the exposure data is generated.

As described above, in this embodiment, the RIP unit 100A generates exposure data using the latest gamma data, and stores the generated exposure data in RAM 103 in association with the latest development bias and the generation date and time. This allows the control unit 100 to derive the timing at which the exposure data was generated by referring to the generation date and time associated with the exposure data.

In addition, in the printing process according to this embodiment, if the developing cartridge 60 has not been replaced and a predetermined time has not elapsed between the generation of the exposure data to be printed and the start of printing, the print control unit 100C applies the latest developing bias to the developing roller 62. On the other hand, if the developing cartridge 60 has been replaced or a predetermined time has elapsed between the generation of the exposure data to be printed and the start of printing, the print control unit 100C applies a temporary developing bias or a default developing bias to the developing roller 62. In this way, when setting the developing bias to be applied to the developing roller 62, the print control unit 100C according to this embodiment does not make a judgment based on the ID as in S402 in FIG. 6.

The temporary development bias may be a temporary development bias calculated based on a default development bias, or may be a temporary development bias calculated based on a development bias associated with the exposure data.

According to the configuration of this embodiment, if the developer cartridge 60 is replaced or a predetermined time has passed between the generation of the exposure data and the start of printing, a temporary developer bias or a default developer bias is used in the printing process. This makes it possible to prevent the printed matter from deviating from the appropriate gradation.

[Software implementation example]
The control unit 100 may be realized by a logic circuit (hardware) formed in an integrated circuit (IC chip) or the like, or may be realized by software.

In the latter case, the control unit 100 includes a computer that executes the instructions of a program, which is software that realizes each function. This computer includes, for example, one or more processors, and a computer-readable recording medium that stores the program. The object of the present invention is achieved by the processor reading the program from the recording medium and executing it in the computer. The processor can be, for example, a CPU. The recording medium can be a "non-transient tangible medium," such as a ROM, tape, disk, card, semiconductor memory, programmable logic circuit, etc. The computer may also include a RAM for expanding the program. The program may be supplied to the computer via any transmission medium (such as a communication network or broadcast waves) that can transmit the program. One aspect of the present invention can also be realized in the form of a data signal embedded in a carrier wave, in which the program is embodied by electronic transmission.

The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. The technical scope of the present invention also includes embodiments obtained by appropriately combining the technical means disclosed in different embodiments.

In the above embodiment, the color printer 1 is configured to include an exposure head 40 as an exposure device that exposes the photoconductor 51, but is not limited to this and may be configured to include a laser scanner as an exposure device.

In addition, in this embodiment, the color printer 1 is configured to use positively charged toner and apply a positive developing bias, but this is not limited to this, and it may be configured to use negatively charged toner and apply a negative developing bias. In this configuration, a small developing bias means that the absolute value of the developing bias is small, that is, the amount of deviation from the reference potential is small.

REFERENCE SIGNS LIST 1 Color printer 51 Photoconductor 52 Charger 60 Development cartridge 62 Development roller 73 Belt 75 Sensor 92 Temperature sensor 100 Control unit 100A RIP unit 100B Correction parameter update unit 100C Print control unit 101 CPU
102 ROM
103, 103A RAM
104, 104A NVM
120 Operation unit 130 Communication unit

Claims (10)

A photoconductor;
a developing roller for supplying a developer to the photoconductor;
A communication interface;
A user interface;
Memory,
A controller and an image forming apparatus comprising:
The controller:
a developing bias correction process for setting a first developing bias and storing the set first developing bias in the memory;
a RIP process for analyzing print job data input to the communication interface to generate exposure data and storing the generated exposure data in the memory;
Execute the printing process;
executing the developing bias correction process when a predetermined condition is satisfied, and updating the first developing bias stored in the memory every time the developing bias correction process is executed;
In the RIP process, when the print job data is data for accumulation printing, accumulation designation information indicating that the data is for accumulation printing is stored in the memory in association with the generated exposure data;
a printing process of the exposure data associated with the storage designation information is started in response to a print instruction being input via the user interface;
In the printing process,
exposing the photoconductor using exposure data generated in the RIP process;
When the storage designation information is not associated with the exposure data to be printed, a first developing bias stored in the memory is applied to the developing roller;
When the storage specification information is associated with exposure data to be printed, a second developing bias different from the first developing bias is applied to the developing roller. The controller:
executing a gamma correction process for setting first gamma data corresponding to the first developing bias and storing the set first gamma data in the memory every time the first developing bias is updated;
updating the first gamma data stored in the memory every time the gamma correction process is executed;
In the RIP process,
If the print job data is not data for storage printing, generating the exposure data using first gamma data stored in the memory;
When the print job data is data for accumulation printing, generating the exposure data using second gamma data that is different from the first gamma data and corresponds to the second developing bias;
the second gamma data is predetermined gamma data stored in the memory before the gamma correction process is executed, and is not updated by the execution of the gamma correction process;
In the printing process,
2. The image forming apparatus of claim 1, wherein when the accumulation specification information is associated with the exposure data to be printed, a predetermined developing bias stored in the memory before the developing bias correction process is executed and which is not updated by execution of the developing bias correction process is applied to the developing roller as the second developing bias. The controller:
executing a gamma correction process for setting first gamma data corresponding to the first developing bias and storing the set first gamma data in the memory every time the first developing bias is updated;
updating the first gamma data stored in the memory every time the gamma correction process is executed;
In the RIP process,
If the print job data is not data for storage printing, generating the exposure data using first gamma data stored in the memory;
If the print job data is data for storage printing, generating the exposure data using second gamma data different from the first gamma data;
the second gamma data is predetermined gamma data stored in the memory before the gamma correction process is executed, and is not updated by the execution of the gamma correction process;
In the printing process,
2. An image forming apparatus as described in claim 1, wherein when the accumulation specification information is associated with the exposure data to be printed, a temporary developing bias, which is a developing bias set in the printing process, is set as the second developing bias, and the set temporary developing bias is applied to the developing roller. The controller:
In the printing process,
4. The image forming apparatus according to claim 3, wherein when the accumulation specification information is associated with the exposure data to be printed, a temporary developing bias calculated based on a predetermined developing bias stored in the memory before the developing bias correction process is executed and which is not updated by execution of the developing bias correction process is set as the second developing bias, and the set temporary developing bias is applied to the developing roller. The controller:
In the RIP process,
storing the first developing bias stored in the memory when the exposure data was generated in association with the generated exposure data in the memory;
In the printing process,
4. An image forming apparatus as described in claim 3, wherein when the accumulation specification information is associated with the exposure data to be printed, a temporary developing bias calculated based on the first developing bias associated with the exposure data to be printed is set as the second developing bias, and the set temporary developing bias is applied to the developing roller. A photoconductor;
a developing roller for supplying a developer to the photoconductor;
A communication interface;
Memory,
A controller and an image forming apparatus comprising:
The controller:
a developing bias correction process for setting a first developing bias and storing the set first developing bias in the memory;
a gamma correction process for setting gamma data corresponding to the first developing bias and storing the set gamma data in the memory every time the first developing bias is updated;
a RIP process for analyzing print job data input to the communication interface, generating exposure data using gamma data stored in the memory, and storing the generated exposure data in the memory;
Execute the printing process;
executing the developing bias correction process when a predetermined condition is satisfied, and updating the first developing bias stored in the memory every time the developing bias correction process is executed;
updating the gamma data stored in the memory each time the gamma correction process is performed;
In the RIP process, the date and time when the exposure data was generated is stored in the memory in association with the generated exposure data;
In the printing process,
exposing the photoconductor using exposure data generated in the RIP process;
If a predetermined time has not elapsed since the exposure data to be printed was generated, a first developing bias stored in the memory is applied to the developing roller;
When a predetermined time has elapsed since the exposure data to be printed was generated, a second developing bias different from the first developing bias is applied to the developing roller. A photoconductor;
a developing roller for supplying a developer to the photoconductor;
A communication interface;
Memory,
A controller,
The controller:
a developing bias correction process for setting a first developing bias and storing the set first developing bias in the memory;
a gamma correction process for setting gamma data corresponding to the first developing bias and storing the set gamma data in the memory every time the first developing bias is updated;
a RIP process for analyzing print job data input to the communication interface, generating exposure data using gamma data stored in the memory, and storing the generated exposure data in the memory;
Execute the printing process;
executing the developing bias correction process when a predetermined condition is satisfied, and updating the first developing bias stored in the memory every time the developing bias correction process is executed;
updating the gamma data stored in the memory each time the gamma correction process is performed;
In the printing process,
exposing the photoconductor using exposure data generated in the RIP process;
applying a first developing bias stored in the memory to the developing roller when a container that contains the developer has not been replaced during the period from when the exposure data to be printed is generated until when printing of the exposure data is started;
An image forming apparatus that applies a second developing bias, which is different from the first developing bias, to the developing roller when a container that contains the developer is replaced between the time when the exposure data to be printed is generated and the time when printing of the exposure data is started. The controller:
In the printing process,
8. An image forming apparatus as described in claim 6 or 7, wherein a predetermined developing bias stored in the memory before the developing bias correction process is executed and which is not updated by execution of the developing bias correction process is applied to the developing roller as the second developing bias. The controller:
In the printing process,
8. An image forming apparatus as described in claim 6 or 7, wherein a temporary developing bias calculated based on a predetermined developing bias stored in the memory before the developing bias correction process is executed and which is not updated by execution of the developing bias correction process is set as the second developing bias, and the set temporary developing bias is applied to the developing roller. The controller:
In the RIP process,
storing the first developing bias stored in the memory when the exposure data was generated in association with the generated exposure data in the memory;
In the printing process,
8. An image forming apparatus as described in claim 6 or 7, wherein a temporary developing bias calculated based on the first developing bias associated with the exposure data to be printed is set as the second developing bias, and the set temporary developing bias is applied to the developing roller.

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