JP4935657B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly, to a technique for determining an execution timing of image stabilization processing such as color misregistration correction in a color image forming apparatus.

In a color image forming apparatus, for example, a tandem type color image forming apparatus, color image quality deterioration is prevented in advance by executing image stabilization processing such as color misregistration periodically or according to a change in environmental temperature. I am doing so.
The color image stabilization process is performed by forming a toner pattern of each color on a transfer belt or a photosensitive drum and detecting the pattern, but even when monochrome print jobs are overwhelmingly executed, Performing the color image stabilization process mechanically consumes a relatively expensive color toner, which is not desirable from the viewpoint of maintenance cost.

  Therefore, for example, in Patent Document 1, a color user mode that executes color image stabilization processing when a predetermined condition is satisfied, and until a color print job is actually accepted even if the predetermined condition is satisfied. In addition, there is described an image forming apparatus configured to prepare two modes of a monochrome user mode in which image stabilization processing is not performed, and an image forming apparatus administrator or the like can select one of the modes in advance.

In this case, for example, in an environment where monochrome print jobs are overwhelmingly executed, if the monochrome user mode is set, the color print job will not be executed even if other predetermined conditions are satisfied. Since the image stabilization process is not executed, the color toner is not wasted.
On the other hand, if the color user mode is set in a usage environment where a color print job is executed relatively frequently, the image stabilization process is automatically executed when a predetermined condition is satisfied. It is possible to obtain a high-quality color image smoothly without waiting for the image stabilization process to be executed immediately before the execution.

Therefore, an image forming apparatus administrator or the like sets the monochrome user mode or the color user mode in consideration of the actual use environment at the time of delivery of the apparatus, so that an image corresponding to the needs of the use environment can be obtained. The stabilization process can be expected to be executed.
JP-A-2005-244829

However, according to the technique of Patent Document 1, for example, when the image forming apparatus is moved to another department and the usage environment changes, it is necessary to review the mode setting each time, which is very troublesome. Moreover, it is impossible to determine which user mode should be set unless the execution status of the print job is known.
Also, the user mode was set after receiving the explanation when the first image forming apparatus was delivered, but after that, it may be used by a user who does not even have such a mode switching function. The image stabilization process cannot be executed.

  The present invention has been made in view of the above problems, and an image forming apparatus with improved convenience is obtained by automatically determining the execution time of image stabilization processing reflecting the use environment of the apparatus. The purpose is to provide.

  An image forming apparatus according to the present invention includes a first mode for executing image stabilization processing when a predetermined condition is satisfied, and an image when a color image forming job that satisfies the predetermined condition is received. An image forming apparatus having a second mode for executing a stabilization process, wherein a history storage unit that stores a history relating to image formation, and at a predetermined timing, refers to the latest predetermined section of the history. A selection unit that selects one of the first mode and the second mode, and an image stabilization unit that executes an image stabilization process according to the selected mode are provided.

In the above configuration, at a predetermined timing, one of the first mode and the second mode is selected based on the latest predetermined section of the history relating to image formation.
As a result, it is possible to automatically determine the execution time of the image stabilization process reflecting the most recent use environment where the image forming apparatus has been placed. It is not necessary to review the selection of the mode and the second mode, and it is not necessary to grasp and analyze the usage environment of the image forming apparatus.

That is, maintenance cost and convenience can be improved, and user friendliness can be improved.
The history includes information on the number of image formations performed and information on the number of color image formations, and the selection unit obtains a ratio of the number of color image formations to the total number of image formations executed in the predetermined section. It is desirable to select the first mode when this ratio is equal to or greater than a predetermined value, and to select the second mode otherwise.

As a result, when the color image forming job is executed at a low frequency, the second mode is selected, and if the predetermined condition is satisfied and the instruction for executing the color image forming job is not accepted, the image is stabilized. Since the image stabilization process is not executed, it is possible to minimize the execution of the image stabilization process and save the consumption of toner of each color.
On the other hand, when the first mode is selected, the image stabilization process is executed only by satisfying a predetermined condition. Therefore, when an instruction to execute a color image forming job is received, color printing is promptly performed. Can be executed without causing discomfort to the user.

As described above, since the execution time of the image stabilization process is determined in accordance with the use environment of the image forming apparatus, it is possible to improve both convenience and economy.
The history includes information on the number of executed image forming jobs and information on the number of color image forming jobs, and the selection unit sets the number of color image forming jobs with respect to the total number of image forming jobs executed in the predetermined section. A ratio is obtained, and when the ratio is equal to or greater than a predetermined value, the first mode can be selected, and otherwise, the second mode can be selected.

Here, the color image forming job includes a case where execution of color image formation is included in one page among image formation of a plurality of pages.
Thus, since the ratio of the number of color image forming jobs is calculated in a large unit called the number of image forming jobs, the amount of data to be calculated can be reduced, and the calculation time can be shortened.

Further, since the capacity of the history information stored in the storage means is reduced, the memory consumption of the storage means can be saved.
Further, it is desirable that the predetermined section is a period from a point in time before a predetermined number of days to the present.
Thereby, the selection of the 1st or 2nd mode which reflected the last use condition can be performed.

  Also, according to the received print job, a color print mode in which a color image is formed using a plurality of color toners and a monochrome print mode in which a monochrome image is formed using a single color toner are switched. A printing mode switching means and a counting means for counting the number of times the color printing mode and the monochrome printing mode are switched to each other, and the predetermined section extends from a predetermined number of times of mode switching to the present from the past. It is desirable to be a section.

  As a result, the number of color image formations can be determined based on the total number of image formations and the number of color image formations performed during the period from when the print mode was switched a predetermined number of times back to the past. Since the ratio is calculated, the calculated ratio of the number of color image formations is a value that reflects the actual switching of the print mode, and is in accordance with the actual environment of the image forming apparatus. The first mode and the second mode can be selected.

  The predetermined timing preferably includes at least one of a timing when the apparatus is turned on, when an image forming job is received, and when a predetermined time has elapsed since the previous image stabilization processing.

Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.
<First Embodiment>
(Configuration of image forming apparatus)
First, the configuration of the image forming apparatus according to the present embodiment will be described.

FIG. 1 is a diagram showing a schematic configuration of a tandem type full-color printer according to the present embodiment.
As shown in the figure, a color printer (hereinafter referred to as “printer”) 1 as an image forming apparatus according to the first embodiment has image forming corresponding to each of Y, M, C, and K colors. Units 10Y, 10M, 10C, and 10K, an image forming unit 20 including an intermediate transfer belt 25, a paper feeding unit 30, a fixing unit 40, and a control unit 60 are provided.

When the printer 1 is connected to a network such as a LAN and receives an instruction to execute a print job from an external terminal device (not shown), the printer 1 executes image formation based on the instruction.
As shown in FIG. 1, the image forming unit 20 includes a primary transfer roller 24 that faces the photosensitive drum 11, an intermediate transfer belt 25 that is stretched between the rollers 21, 22, and 23, an optical sensor 26, A cleaning blade 51 and the like are provided.

The optical sensor 26 is a reflection type photosensor, which irradiates light onto the intermediate transfer belt 25 and outputs a voltage value corresponding to the intensity of the reflected light to the control unit 60.
The paper feeding unit 30 includes a paper feeding cassette 31 that stores recording sheets, a feeding roller 32 that feeds the recording sheets in the paper feeding cassette 31 one by one, a pair of conveying rollers 33 that convey the fed recording sheets, A pair of timing rollers 34 for taking the timing of sending the recording sheet to the secondary transfer position, a secondary transfer roller 35 and the like are provided.

As shown in FIG. 1, the image forming units 10Y, 10M, 10C, and 10K are arranged in a predetermined order in the order of 10Y, 10M, 10C, and 10K along the intermediate transfer belt 25 while facing the intermediate transfer belt 25. They are arranged in series at intervals.
The image forming unit 10K includes a photosensitive drum 11, and a charger 12, an exposure unit 13, a developing device 14, a cleaner 15, and a temperature sensor 9K disposed around the photosensitive drum 11.

Since the image forming units 10Y, 10M, and 10C have the same configuration as the image forming unit 10K, the description thereof is omitted here.
The exposure unit 13 includes a light emitting element such as a laser diode, a lens, and the like, receives a drive signal from the control unit 60, emits a laser beam for exposing the photoconductive drum 31, and performs a main operation on the photoconductive drum 11. Exposure scanning is performed in the scanning direction.

The photosensitive drum 11 is uniformly charged by the charger 12 after the toner remaining on the surface is removed by each cleaner 15 before being subjected to the exposure, and after being discharged by irradiating an unillustrated eraser lamp. When exposed to the laser beam in such a uniformly charged state, an electrostatic latent image is formed on the surface of the photosensitive drum 11.
Each electrostatic latent image is developed by the developing device 14 of each color, whereby a toner image as a developer image of Y, M, C, and K is formed on the surface of the photosensitive drum 11.

The image forming operation for each color is executed at different timings so that the toner image is superimposed and transferred at the same position on the intermediate transfer belt 25, and receives the electrostatic force from the primary transfer roller 24 to receive the toner image on the intermediate transfer belt 25. And a full color toner image is formed.
The superimposed color toner images on the intermediate transfer belt 25 are moved to the secondary transfer position by the rotation of the intermediate transfer belt 25.

On the other hand, in accordance with the movement timing of the intermediate transfer belt 25, the recording sheet is fed from the paper feeding unit 30 via the timing roller 34, and is applied to the secondary transfer roller 35 at the secondary transfer position. The toner image on the intermediate transfer belt 25 is secondarily transferred onto the recording sheet by the electrostatic force generated by the applied voltage.
The recording sheet that has passed the secondary transfer position is conveyed to the fixing unit 40, where the toner image is heated and pressed to be fixed on the recording sheet, and is then placed on the discharge tray 42 via a pair of discharge rollers 41. Discharged.

Upon receiving a print instruction from an external terminal device, the control unit 60 receives the transmitted image signal, converts it into a digital image signal for Y, M, C, K reproduction colors, and exposes the exposure unit. A drive signal for driving 13 is generated.
Here, the configuration of the control unit 60 of the printer 1 will be described with reference to the block diagram of FIG.

As shown in the figure, the control unit 60 includes a CPU 61, an interface (I / F) unit 62, a RAM 63, a ROM 64, an EEPROM 65, and a real-time clock 66 as main components.
Unlike the other functional units, the real-time clock 66 is always operated by a battery even when the power of the printer 1 is OFF, and information indicating the current date and time (hereinafter referred to as “date and time”). Information ") is output to the CPU 61 every second.

A CPU (Central Processing Unit) 61 reads a necessary program from the ROM 64 and controls various operations in a unified manner while measuring the timing, for example, smooth execution of operations such as execution of a print job and color misregistration correction processing described later. Let it run.
More specifically, the CPU 61 executes the following contents.
That is, each time printing is completed, as shown in Table 1 below, an initial value is set to 1, and a print number 601 obtained by adding 1 to the initial value and a print type indicating the monochrome / color type of the print A set of information 602 and date / time information 603 indicating the date and time of printing and the hour / minute / second is stored in the EEPROM 65 as history information 600.

When the printer 1 is turned off, date / time information is acquired from the real-time clock 66 in advance and stored in a dedicated storage area reserved in advance in the EEPROM 65. Further, when the printer is turned off for the second time and thereafter. Overwrite the date / time information data already stored in the storage area.
Hereinafter, information stored in the dedicated storage area when the printer 1 is turned off is defined as “power-off date / time information”.

Further, signals output from the temperature sensors 9Y to 9K are periodically acquired, for example, every minute, and a value obtained by converting the signal into a temperature (hereinafter referred to as “temperature information”) is stored in the EEPROM 65.
When color misregistration correction described later is executed, the temperature information data stored in the EEPROM 65 is cleared.

Further, the number of sheets printed by the image forming unit 20 is counted, and the value is stored in the EEPROM 65.
The interface unit 62 is a LAN card, a LAN board, or the like for connecting the CPU 61 to a network such as a LAN. The interface unit 62 receives a print job transmitted from a client terminal via the LAN and sends it to the CPU 61.

A RAM (Random Access Memory) 62 is a volatile memory and serves as a work area when the CPU 61 executes a program.
A ROM (Read Only Memory) 63 stores various programs such as a program related to print processing in the image forming unit 20 and a program related to image stabilization processing.

An EEPROM (Electronically Erasable and Programmable Read Only Memory) 65 is a nonvolatile memory and serves as a data storage area when the CPU 61 executes a program.
The operation unit 73 includes a numeric keypad, a start key, a liquid crystal display panel, and the like, and receives an instruction input from a user. When each key is pressed by the user, the information is transmitted to the CPU 61.

(Color shift correction processing)
Next, the color misregistration correction process will be described.
A color image is formed by superimposing toner images of four colors Y, M, C, and K. At this time, if a phenomenon in which the toner images of the respective colors shift, that is, color misregistration occurs, the image quality deteriorates.
The color misregistration correction processing is processing for detecting and correcting the color misregistration amount between the toner colors in order to prevent such deterioration of the image quality. "Registry pattern") is formed on the intermediate transfer belt 25, and an optical sensor 26 is used to detect a shift in the resist pattern of each color.

A method for obtaining the color misregistration amount by the optical sensor 26 is known, but an example thereof will be briefly described.
The optical sensor 26 can calculate the toner adhesion amount from the output voltage.
Since the output voltage is a waveform voltage having a certain width and height, the barycentric position of the waveform is a value representative of the position of the detected resist pattern of each color. Therefore, by calculating the barycentric position of the output voltage waveform and taking the difference between the barycentric position interval of each color and the normal value, the color misregistration amount between the respective colors can be obtained.

By correcting the image writing position in the main scanning direction and the sub-scanning direction based on the detected color misregistration amount, color misregistration can be prevented and a high-quality image can be formed. It becomes possible.
When the execution of the color misregistration correction is completed, the current date and time information is acquired from the real-time clock 66, and this information is stored in a dedicated storage area in the EEPROM 65 where only the date and time of color misregistration correction is stored.

Next, the operation of color misregistration correction processing in the CPU will be described.
FIG. 3 is a flowchart showing a subroutine of color misregistration correction processing of the printer 1 according to the present embodiment. The CPU 61 executes the following contents.
First, when color misregistration correction has not been performed once after the most recent power-on (step S100: NO), it is determined whether the most recent power-off time has continued for 12 hours or more (step S101).

For example, when the printer 1 is turned on, the power-off date / time information stored in the EEPROM 65 is acquired and output from the real-time clock 66. The difference with the current date and time information to be taken is taken, and it can be judged by whether or not this is 12 hours or more.
If the most recent power-off time has not continued for 12 hours or more, at the end of the print job, there is at least one exposure unit where the temperature change from the previous execution of color misregistration correction is 7 ° C. or more. Whether or not (step S102).

Specifically, for example, for temperature information corresponding to each color of Y, M, C, K stored in the EEPROM 65, the maximum temperature and the minimum temperature are extracted, and the difference is 7 ° C. or more. Determine whether or not.
If there is no such exposure unit (step S102: NO), this subroutine is terminated and the process returns to a main routine (not shown) that controls the entire image forming process.

In addition, when the color misregistration correction is performed one or more times after the most recent power ON (step S100: YES), the temperature change from the time when the previous color misregistration correction is performed becomes 7 ° C. or more at the end of the print job. It is determined whether or not there is only one exposure unit (step S102), and the subsequent processing is performed.
If the most recent power-off time continues for 12 hours or longer (step S101: YES), or when the print job ends, the temperature change from the previous color misregistration correction is 7 ° C. or higher. If there is even one exposed portion (step S102: YES), it is determined that there is a high necessity for color misregistration correction, and the user mode is determined (step S103).

The user mode includes a color user mode as a first mode assuming a usage environment with a high frequency of color printing, and a monochrome user mode as a second mode assuming a usage environment with a high frequency of monochrome printing. Yes, the color user mode is set in the default state.
Here, the reason why it is determined in step S102 whether or not there is at least one exposure unit whose temperature change from the previous execution point of color misregistration correction is 7 ° C. or more will be described.

In the exposed portion where the temperature change from the previous execution of color misregistration correction to the present is 7 ° C. or more, the optical axis is likely to be misaligned due to thermal distortion, and color misregistration is likely to occur.
It is considered that the optical axis shift in this optical system cannot be resolved no matter what the temperature is, after that, once a change of 7 ° C. or more occurs in the exposed portion.
Under such circumstances, an exposed portion having a temperature change of 7 ° C. or more is detected even once.

In addition, when the latest power-off time continues for 12 hours or more, temperature sampling in the exposure unit is stopped, and therefore, determination based on the temperature change in the exposure unit as described above cannot be performed. It is judged that there is a high possibility of color misregistration.
When the user mode is the monochrome user mode (step S103: YES) and a color print request is received (step S104: YES), color misregistration correction is performed (step S105), and this subroutine is terminated. Return to the main routine.

If a color print request has not been received (step S104: NO), this subroutine is terminated and the process returns to the main routine.
If the user mode is the color user mode (step S103: color user mode), color misregistration correction is performed (step S105), this subroutine is terminated, and the process returns to the main routine.

In this way, in the monochrome user mode where the frequency of color printing is low, the color misregistration correction is not performed until just before color printing, and the toner consumption is suppressed as much as possible, so the maintenance cost can be reduced, Also, in the color user mode where color printing is frequently performed, color misregistration correction is performed when various conditions that are likely to cause color misregistration are satisfied. Can be increased. In other words, it is possible to improve both convenience and economy.
(User mode selection process)
The printer 1 according to the present embodiment automatically selects the user mode instead of manually selecting the user mode as in the conventional machine.

Next, the user mode selection process A for automatically selecting the user mode will be described.
FIG. 4 is a flowchart showing a subroutine of user mode selection processing A of the printer 1 according to the present embodiment.
Here, the CPU 61 refers to the data in the EEPROM 65 and executes the following contents.

In FIG. 4, first, when not immediately after the power is turned on and when 24 hours have not elapsed since the previous execution of the determination of the color print ratio described later (step S100: NO), this subroutine is ended and the entire image forming process is completed. Return to the main routine (not shown) for controlling the control.
Also, immediately after the power is turned on, or when 24 hours have passed since the previous execution of the determination of the color print ratio described later (step S200: YES), history information regarding pages printed in the past week from the history information 600 is displayed. If the total number of prints has not been obtained in the past week (step S202: NO), the current user mode is continued (step S203), this subroutine is terminated, and the process returns to the main routine. .

If there is even one print in the past week (step S202: YES), the power error print ratio calculation (I) is executed (step S204).
The calculation formula of this force llprint ratio calculation (I) is shown below.
Color print ratio (%) = A / (A + B) x 100 (Formula 1)
A: Number of pages printed in color
B: Number of pages printed in monochrome When the color print ratio is 10% or more (step S205: YES), the user mode is set to the color user mode (step S206), and this subroutine is terminated and the main routine is entered. Return.

When the color print ratio is less than 10% (step S205: NO), the user mode is set to the monochrome user mode (step S207), and this subroutine is terminated and the process returns to the main routine.
As described above, according to the first embodiment, when the power is turned on or every 24 hours, the color information is stored based on the history information about pages printed in the past week of the stored history information 600. By calculating the print ratio and automatically selecting the user mode, the user mode corresponding to the situation is periodically reviewed even if the user's usage environment changes.

In addition, since the type of color / monochrome print is determined for each page, which is the minimum unit of printing, the calculation accuracy of the color print ratio can be improved, so that it is possible to make a determination in accordance with the actual situation of the user's usage environment. .
(Other matters)
In the present embodiment, the history information 600 associates the print number 601, the print type information 602, and the date / time information 603. However, in the present embodiment, the present invention is not limited to this. Since the color print ratio can be calculated if there is only the date of printing in the information 602 and the date / time information 603, the history information 600 may be composed of only these two pieces of information.

In the case of duplex copying, it goes without saying that the pages described in this embodiment count each front and back print as one page.
<Second Embodiment>
(Configuration of image forming apparatus)
The second embodiment is different from the first embodiment in that the history information used to select the user mode and the processing contents of the control unit are the same, and the others are the same. The description of the part other than is omitted.

The CPU in the second embodiment executes the following contents.
That is, when the print job is completed, instead of the history information 600, as shown in Table 2 below, each time the print job is executed, the job is obtained by adding 1 to the initial value every time the print job is executed. A set of a number 611, print job type information 612 indicating a monochrome / color job type, and a print job completion date / time 613 indicating the date and time of completion of the print job is stored in the EEPROM 65 as history information 610. .

Here, the monochrome / color job type determination method is as shown in FIG. 5 in the case where even one color print is included in one print job (see jobs 1, 3, and 4 in FIG. 5). If the type is a color job and all the print jobs are monochrome prints (see job 2 in FIG. 5), the type is a monochrome job.
Furthermore, the printer according to the second embodiment executes a user mode selection process B instead of the user mode selection process A.
(User mode selection processing B)
FIG. 6 is a flowchart illustrating a subroutine of user mode selection processing B of the printer according to the second embodiment.

Here, the CPU of the second embodiment executes the following contents.
In FIG. 5, first, not immediately after the power is turned on, and when 24 hours have not elapsed since the previous execution of the determination of the color print ratio described later (step S300: NO), this subroutine is terminated and the entire image forming process is completed. Return to the main routine (not shown) for controlling the control.
Also, immediately after the power is turned on, or when 24 hours have passed since the previous execution of the determination of the color print ratio described later (step S300: YES), the print job executed in the past one week from the history information 610 is displayed. History information is acquired (step S301), and if no print job has been executed within the past week (step S302: NO), the current user mode is continued (step S303), and this subroutine is terminated and the main Return to the routine.

If a print job has been executed within the past week (step S302: YES), a power error job ratio calculation (II) is executed (step S304).
The formula for calculating the power error job ratio (II) is shown below.
Color job ratio (%) = C / (C + D) × 100 (Formula 2)
C: Total number of color jobs
D: Total number of monochrome jobs When the power error job ratio is 30% or more (step S305: YES), the user mode is set to the color user mode (step S306), this subroutine is terminated, and the process returns to the main routine.

When the color job ratio is less than 30% (step S305: NO), the user mode is set to the monochrome user mode (step S307), and this subroutine is terminated and the process returns to the main routine.
As described above, in the second embodiment, when the power is turned on or every 24 hours, the color job is based on the history information relating to the print job executed in the past week in the stored history information 610. By calculating the ratio and automatically selecting the user mode, the user mode corresponding to the situation is periodically reviewed even if the user's usage environment changes.

In the second embodiment, the history information 610 used as the basis for selecting the user mode has a smaller data amount than the history information 600 used in the first embodiment. Further, the calculation time can be shortened because the processing amount at the time of calculation can be reduced.
(Other matters)
The history information 610 of the present embodiment associates the job number 611, the print job type information 612, and the print job completion date and time 613. However, in the present embodiment, the present invention is not limited to this. Since at least the print job type information 612 and the information indicating only the date of completion of the print job in the print job completion date and time 613 are associated with each other, the color print ratio can be calculated. The information 610 may be composed of only these two pieces of information.

<Third Embodiment>
(Configuration of image forming apparatus)
The third embodiment is different from the first embodiment in the processing contents of the control unit and the others are the same, and therefore, the description of the parts other than the above differences is omitted.
The CPU in the third embodiment executes a printer user mode selection process C instead of the printer user mode selection process A.
(User mode selection process C)
FIG. 7 is a flowchart showing a subroutine of user mode selection processing C of the printer according to the third embodiment.

In FIG. 7, first, when not immediately after turning on the power and when there is no print request (step S400: NO), this subroutine is terminated and the process returns to the main routine.
Also, immediately after the power is turned on or when there is a print request (step S400: YES), the history information 610 is referred to and it is determined whether or not there have been 100 or more printed results in the past (step S401). ).

This determination can be quickly made, for example, based on whether the print number 601 of the last printed page is 100 or more.
If the cumulative print record is less than 100 sheets, the user mode is set to the color user mode (step S402), the subroutine is terminated, and the process returns to the main routine. This is because if the cumulative print record is less than 100, it is considered that the printer has been delivered, and the color user mode, which is the default setting, is to be maintained.

If there are 100 or more print results, history information for the last 100 pages printed most recently is acquired.
The history information for 100 pages is obtained by, for example, obtaining a value obtained by subtracting 99 from the value of the print number 601 of the last printed page, and extracting all history information having a print number 601 equal to or greater than this value. Thus, the acquisition target can be quickly identified.

Then, the power error print ratio calculation (I) described in the first embodiment is executed (step S404), and when the color print ratio is 10% or more (step S405: YES), the user mode is set to the color user mode. (Step S402), this subroutine is terminated and the process returns to the main routine.
If the color print ratio is less than 10% (step S405: NO), the user mode is set to the monochrome user mode (step S406), the subroutine is terminated, and the process returns to the main routine.

As described above, in the third embodiment, when the power is turned on or when there is a print request, the color print ratio is calculated based on the history information for the last 100 pages printed most recently, By automatically selecting the user mode, the user mode corresponding to the situation is appropriately selected even if the user's usage environment changes.
In addition, since the user mode is reviewed each time a print request is made, it is possible to respond quickly even when the user's usage environment varies greatly.
(Other matters)
The history information 600 according to the present embodiment associates the print number 601, the print type information 602, and the date / time information 603, but the present embodiment is not limited to this.

  For example, even if a dedicated storage area for storing only the history information 600 is provided in the EEPROM 65 and the print type information 602 is sequentially stored from the area having the smallest address value in this storage area, the type is set using this address value as a key. By extracting the information 602, it is possible to grasp the print type information 602 for 100 sheets printed in the past, so the history information 600 may be only the print type information 602.

In this embodiment, the user mode is selected based on the history information of the last 100 pages printed most recently, but the value of 100 pages is merely an example, and the user's usage environment It can be changed as appropriate.
<Fourth embodiment>
(Configuration of image forming apparatus)
The fourth embodiment is different from the first embodiment in the processing contents of the control unit 60, and the others are the same, and thus the description of the parts other than the above differences is omitted.

The CPU in the fourth embodiment executes the following contents.
That is, as shown in FIG. 8, when a monochrome print job is requested after execution of a color print job, or when a color print job is requested after execution of a monochrome print job, date / time information is acquired from the real-time clock 66. Then, it is stored in a dedicated storage area secured in advance in the EEPROM 65.

At this time, for example, when the storage area is set such that exactly four pieces of date / time information are entered, and the fifth date / time information is stored, the date / time information indicating the oldest date / time information already stored. By overwriting, it is possible to save memory consumption.
Hereinafter, the information stored in the dedicated storage area when the print mode is switched is defined as “print mode switching time information”.

Further, the CPU according to the fourth embodiment executes a user mode selection process D instead of the user mode selection process A.
(User mode selection processing D)
FIG. 9 is a flowchart illustrating a subroutine of user mode selection processing D of the printer according to the fourth embodiment.

First, when not immediately after turning on the power and when there is no print request (step S500: NO), this subroutine is terminated and the process returns to the main routine.
Also, immediately after the power is turned on or when there is a print request (step S500: YES), it is determined whether or not there is a record of printing even one sheet with reference to the history information 600 (step S501).

If there is no cumulative print record, the user mode is set to the color user mode (step S502), the subroutine is terminated, and the process returns to the main routine. This is because if there is no cumulative print record, it is considered that the printer has been delivered, and the color user mode which is the default setting is maintained.
If there is even one print record (step S501: YES), it is determined whether the print mode has been switched four times or more in the past (step S503).

This determination is made, for example, based on whether or not four pieces of print mode switching time information are stored in the dedicated storage area in the EEPROM 65.
If the print mode has been switched four times or more in the past, the history information 600 of pages printed in the period from the time when the fourth print mode is switched back to the present to the present. (Hereinafter referred to as “history information A”) is acquired (step S504), and the power error print ratio calculation (I) described in the first embodiment is executed (step S505), and the color print ratio is 10%. At the above time (step S506: YES), the user mode is changed to the color user mode (step S502), this subroutine is terminated, and the process returns to the main routine.

  Here, as a specific acquisition method of the history information A, for example, among the four print mode switching time information stored in the dedicated storage area in the EEPROM 65, the oldest date / time information (hereinafter referred to as “oldest date / time information”). And the history information 600 is referred to, and all the print type information 602 associated with the date and time information 603 after the date and time indicated by the oldest date and time information is acquired.

When the color print ratio is less than 10% (step S506: NO), the user mode is set to the monochrome user mode (step S507), this subroutine is terminated, and the process returns to the main routine.
If the print mode has not been switched four times or more in the past (step S503: NO), all the history information in the history information 600 is acquired (step S508), and the power error print ratio calculation (I). Is executed (step S505), and the subsequent processing is executed.

  As described above, in the fourth embodiment, the color print ratio is based on the history information of pages printed in the period from the time when the print mode is switched for the fourth time in the past to the present. Since it is calculated, the calculated color print ratio reflects the actual switching of the print mode, and the user mode can be selected in accordance with the actual situation of the user's usage environment. Become.

In the present embodiment, the history information of pages printed in the period from the time when the print mode is switched for the fourth time back to the present to the present is used for selecting the user mode. However, the number of times of the fourth time is merely an example, and can be appropriately changed based on the use environment of the user.
<Modification>
As described above, the present invention has been described based on the embodiments. However, the content of the present invention is not limited to the specific examples shown in the above-described embodiments. For example, the following modifications are possible. Can think.

That is, in the above-described embodiment, the execution time of color misregistration correction is determined based on the user mode selected based on the past history information, but the color misregistration correction is originally performed to improve the image quality. It is one of the image stabilization processes, and the execution time of another image stabilization process, for example, density correction, may be determined based on the user mode.
For example, the density correction is performed by forming a patch with a predetermined gradation on the intermediate transfer belt 25, detecting the toner density of the patch with the optical sensor 26, and adjusting the sensor output value and the predetermined gradation stored in the ROM 64. This is a process of comparing the corresponding data value, adjusting the transfer voltage or the like according to the difference, and setting the target toner density.

Normally, in this density correction, a full color density correction is performed in which the color density and the monochrome density are corrected simultaneously. I have to say that I'm wasting it.
Therefore, in the density correction, the density correction is performed by performing only the black density correction or the full color density correction according to the user mode selected in the user mode selection process in the above-described embodiment. The time spent can be shortened and the consumption of color toner can be reduced.

Specific examples thereof will be described below.
FIG. 10 and FIG. 11 are flowcharts showing a subroutine of printer density correction processing in the present modification.
The CPU of this modification executes the following contents.
First, when the full color density correction has not been performed once after the most recent power ON (step S600: NO) and the flag F is “0” (step S601: NO), the most recent power OFF It is determined whether or not the time has continued for 12 hours or more (step S602).

The flag F is stored in the EEPROM 65, for example, and is reset to “0” when the power is turned off.
If the latest power-off time continues for 12 hours or longer (step S602: YES), the flag F is set to “1” (step S603), and the process proceeds to (A) of FIG. Is in the color user mode (step S604: color user mode), full color density correction is performed (step S605), the full color density correction flag is set to 0 (step S606), and this subroutine is terminated. Then, the process returns to a main routine (not shown) for controlling the entire image forming process.

If the user mode is the monochrome user mode (step S604: monochrome user mode), the density correction is performed using only black (step S607), and the full color density correction flag is set to 1 (step S608). This subroutine is terminated and the process returns to the main routine.
Returning to step S600 in FIG. 10, the full color density correction is performed at least once after the most recent power-on (step S600: YES), and the previous density correction (only black is performed) at the end of the print job. In addition, there is no exposure part having a temperature change of 12 ° C. or more from the time of execution (step S609: NO), and at the end of the print job, the previous density correction (including only black) is performed. The number of prints from the time of execution is not 1000 or more (step S610: NO), and the process proceeds to FIG. 11B, where the full color density correction flag is 1 and a color print request is received. If this condition is not met (step S611: NO), this subroutine is terminated and the process returns to the main routine.

If the full color density correction flag is 1 and a color print request has been received (step S611: YES), full color density correction is performed (step S605), and the subsequent processing is executed.
Returning to FIG. 10, 1) At the end of the print job, if there is also one exposed portion where the temperature change from the time of the previous density correction (including black only) is 12 ° C. or more (step S609: YES) 2) When the print job ends, if the number of prints from the previous execution of density correction (including black only) is 1000 or more (step S610: YES) If it is determined that the necessity of density correction is high, the process proceeds to (A) of FIG. 11 to determine the user mode (step S604), and the subsequent processing is executed.

  Returning to FIG. 10, when the flag F is 1 (step S601: YES), or when the latest power-off time has not continued for 12 hours or more (step S602: NO), at the end of the print job, Judgment is made as to whether or not there is even one exposed portion whose temperature change from the time of the previous density correction (including black only) is 12 ° C. or more (step S609), and the subsequent processing is executed. To do.

The reason why the density correction is performed on the exposure unit according to the temperature change as in step S609 is that the charge amount of the toner in the exposure unit changes depending on the temperature and the density change may occur.
Further, as in step S610, at the end of the print job, the reason for determining whether or not the number of prints from the point of execution of the previous density correction (including black only) is 1000 or more is the long time photoconductor. This is because if the drum 11 continues to rotate, the protective film formed on the surface of the photosensitive drum 11 is worn, and the amount of toner attached changes, which may cause a density change.

In step S609 described above, the temperature of all the exposure units is detected and the temperature detection accuracy is increased. However, in order to reduce the cost, it is not necessary to provide a temperature sensor for each exposure unit in this way. For example, one temperature sensor for measuring the temperature inside the printer may be provided in the printer, and the determination may be made based on the value of this temperature sensor.
In this modification, density correction may be performed by density correction using only black. This is because a monochrome print is normally printed in black. In some cases, other colors such as cyan may be used. Since monochrome printing is also conceivable, in this case, it goes without saying that density correction may be performed only with cyan instead of black only in this modification.

  Furthermore, the tone correction performed for the purpose of correcting the gamma curve also consumes toner by forming a plurality of patches with different tone values for each color toner as in the density correction. The execution time may be determined based on the user mode.

  The present invention can be widely applied to color image forming apparatuses. In addition, the present invention can provide an image forming apparatus that can suppress a decrease in image stability and can reduce a waiting time of a user until the completion of printing. Therefore, its industrial utility value is extremely high.

1 is a diagram illustrating a schematic configuration of a tandem type color printer according to an embodiment. FIG. 2 is a block diagram illustrating a configuration of a printer. 3 is a flowchart illustrating an operation of a printer. 4 is a flowchart illustrating an operation of the printer 1 according to the first embodiment. It is a figure explaining the judgment method of the job type of the monochrome / color job which concerns on a 2nd form. It is a flowchart which shows operation | movement of the printer 1 which concerns on a 2nd form. 10 is a flowchart illustrating an operation of a printer according to a third embodiment. It is a figure for demonstrating the switching of the print mode which concerns on 4th Embodiment. 14 is a flowchart illustrating an operation of a printer according to a fourth embodiment. It is a flowchart which shows operation | movement of the printer in a modification. It is a flowchart which shows operation | movement of the printer in a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printer 9 Temperature sensor 10 Image forming unit 11 Photoconductor drum 11 The photoconductor drum 12 Charger 13 Exposure part 14 Developer 15 Cleaner 20 Image formation part 21, 22, 23, 32 Roller 24 Primary transfer roller 25 Intermediate transfer belt 25 Intermediate transfer belt 26 Optical sensor 30 Paper feed unit 31 Photosensitive drum 31 Paper feed cassette 33 Conveying roller 34 Timing roller 35 Secondary transfer roller 40 Fixing unit 41 Ejection roller 42 Ejection tray 51 Cleaning blade 60 Control unit 61 CPU
62 Interface unit 63 RAM
64 ROM
65 EEPROM
66 Real time clock 73 Operation section

Claims (7)

A first mode in which image stabilization processing is executed when a predetermined condition is satisfied; and a second mode in which image stabilization processing is executed when a color image forming job is received that satisfies the predetermined condition. An image forming apparatus having a mode,
History storage means for storing a history relating to image formation;
Selecting means for selecting one of the first and second modes at a predetermined timing with reference to the latest predetermined section of the history;
An image forming apparatus comprising: an image stabilization unit that executes an image stabilization process according to the selected mode. The history includes information on the number of executed image formations and the number of color image formations,
The selection unit obtains a ratio of the number of color image formations to the total number of image formations executed in the predetermined section, selects the first mode when the ratio is equal to or greater than a predetermined value, and otherwise The image forming apparatus according to claim 1, wherein the second mode is selected. The history includes information on the number of executed image forming jobs and the number of color image forming jobs,
The selection unit obtains a ratio of the number of color image forming jobs to the total number of image forming jobs executed in the predetermined section, selects the first mode when the ratio is equal to or greater than a predetermined value, and otherwise The image forming apparatus according to claim 1, wherein the second mode is selected. The image forming apparatus according to any one of claims 1 to 3, wherein the predetermined section is a period from a point in time before a predetermined number of days to the present. A print mode that switches between a color print mode that forms a color image using a plurality of color toners and a monochrome print mode that forms a monochrome image using a single color toner according to the received print job Switching means;
A counting means for counting the number of times the color print mode and the monochrome print mode are switched to each other;
The image forming apparatus according to any one of claims 1 to 3, wherein the predetermined section is a section from the time of mode switching a predetermined number of times retroactively to the present.   The predetermined section is a section from a predetermined number of times of image formation to the present, counting from the most recent image formation among predetermined image formation executed in the past. The image forming apparatus according to 2.   7. The predetermined timing includes at least one of timing when the apparatus is turned on, when an image forming job is received, and when a predetermined time has elapsed since the previous image stabilization processing. The image forming apparatus according to any one of the above.

Images