JP2011075910A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus having a developing device for preventing deterioration of a developer and suppressing deterioration of the image quality. <P>SOLUTION: This image forming apparatus includes the developing device 71 for developing an electrostatic latent image formed in a photoreceptor drum 37 using toner, a developer consumption calculation section 111 for calculating the consumption of the toner per unit time, and a controller 100 for switching the operation in normal mode to the operation in low output amount mode of making the deterioration of the developer smaller than that in the normal mode when the consumption M of the developer per unit time calculated by the developer consumption calculation section 111 is a threshold or less. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multifunction machine including the developing device.

  In general, an image forming apparatus such as a copying machine or a printer is provided with a saving mode for reducing power consumption of an apparatus when the apparatus has not been used for a long time in addition to a normal operation mode. In recent years, with increasing interest in energy saving and environmental problems, the time during which the image forming apparatus is used in the saving mode has become longer, and the frequency of switching to the saving mode has increased.

  In this case, since the normal mode can be switched to the saving mode in a relatively short time, power consumption can be suppressed. However, when returning from the saving mode to the normal mode, the fixing unit is heated to a predetermined preheat temperature, and the returning operation of stirring the developer to charge the toner contained in the developer is frequently performed. It becomes. As described above, when the return operation from the saving mode is frequently performed, the developer is deteriorated every time the developer is stirred, and the charged state of the developer becomes unstable. There has been a problem that the image quality deteriorates due to a decrease or image fogging. In particular, when the printing rate on the image (the ratio of the printed area to the area where the image can be formed (paper area); the same applies hereinafter) is low, the electrostatic latent image is carried from the developer carrying member (developing roller). Since the amount of toner that is used for development by flying to the body (photosensitive drum) is small, the toner particles in the developing device are hardly replaced, and the developer is likely to deteriorate. In a high-speed machine, since the developer is frequently stirred at a high speed, the above problem becomes more remarkable. Also, in order to reduce paper consumption, there is a tendency to capture as image data without printing out on paper. In this case, although the number of sheets that are actually output is reduced, the above-described return operation is frequently performed. Therefore, a countermeasure against a decrease in image quality due to the deterioration of the developer is strongly demanded. Yes.

  With respect to the above problem, Patent Document 1 proposes a configuration in which the deterioration state of the developer is monitored and the deteriorated developer is forcibly discharged to the image carrier.

JP 2008-139400 A

  In the method of Patent Document 1 described above, the deteriorated developer is forcibly discharged, so that it is possible to prevent the image quality from being deteriorated due to the deterioration of the developer. However, the above-described conventional method discards the deteriorated developer on the assumption that the developer is deteriorated, and does not prevent the deterioration of the developer itself. Further, since the developer is consumed and collected unnecessarily, it is not an effective measure for energy saving and environmental problems.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus including a developing device that can prevent deterioration of a developer and suppress deterioration in image quality. It is said.

  An image display device according to one aspect of the present invention includes a developing device that develops an electrostatic latent image formed on an image carrier using a developer, and the consumption amount of the developer per unit time in the developing device. When the developer consumption per unit time calculated by the developer consumption calculation means and the developer consumption calculation means is less than or equal to a threshold value, the operation in the normal mode is more effective than the normal mode. Control means for switching to the operation in the low output amount mode for reducing the deterioration of the developer.

  According to the above configuration, when the developer consumption per unit time is equal to or less than the threshold value, it can be determined that the user has a relatively small number of printed output sheets. Control is performed so as to switch to the operation in the low output amount mode that reduces the deterioration of the developer. For this reason, when the amount of developer consumption per unit time is small and the developer is likely to deteriorate, it is possible to operate in the low output amount mode in which the deterioration of the developer is reduced as compared with the normal mode. As a result, it is possible to realize an image forming apparatus including a developing device that can prevent deterioration of the developer and suppress deterioration of image quality.

  In the above-described image forming apparatus, the developer consumption calculating unit calculates a cumulative consumption calculating unit that calculates the cumulative consumption of the developer for a predetermined time, and calculates a cumulative development driving time of the developing device for the predetermined time. A cumulative driving time calculating unit that calculates the cumulative consumption of the developer at the predetermined time calculated by the cumulative consumption calculating unit, and the cumulative development at the predetermined time calculated by the cumulative driving time calculating unit. It is preferable to calculate the consumption amount of the developer per unit time from the driving time.

  According to the above configuration, the cumulative consumption of the developer at the predetermined time calculated by the cumulative consumption calculation means and the cumulative development driving time at the predetermined time calculated by the cumulative driving time calculation means. The consumption amount of the developer per unit time is calculated. For this reason, the developer consumption per unit time can be accurately detected as the developer consumption per unit time. Accordingly, it is possible to accurately detect the case where the developer consumption amount per unit time is small and the developer is in a state of being easily deteriorated.

  Further, a developer replenishing motor for replenishing the developer to the developing device is further included, and the cumulative consumption calculating means is configured to rotate the developer replenishing motor or the rotation speed and rotation time of the developer replenishing motor. Based on the above, it is preferable to calculate the cumulative consumption of the developer.

  According to the above configuration, the cumulative consumption calculation means calculates the cumulative consumption of the developer based on the number of rotations of the developer supply motor or the rotation speed and rotation time of the developer supply motor. ing. For this reason, the developer consumption per unit time can be accurately detected as the developer consumption per unit time. Accordingly, it is possible to accurately detect the case where the developer consumption amount per unit time is small and the developer is in a state of being easily deteriorated.

  The developer consumption calculating means includes a paper counter that counts the total number of sheets output during the predetermined time, a dot number counter that counts the total number of dots printed during the predetermined time, and the paper counter. A printing rate calculating unit that calculates an average printing rate from the counted total number of sheets and the total number of dots counted by the dot number counter, and is based on the average printing rate calculated by the printing rate calculating unit Thus, it is preferable to calculate the consumption amount of the developer per unit time.

  According to the above configuration, the printing rate calculation means for calculating the average printing rate from the total number of output paper sheets and the total number of printing dots in a predetermined time, respectively counted by the paper counter and the dot number counter, Based on the average printing rate calculated by the printing rate calculation means, the consumption amount of the developer per unit time is calculated. Thereby, the consumption amount of the developer per unit time can be accurately detected. For this reason, it is possible to accurately detect the case where the developer consumption amount per unit time is small and the developer is easily deteriorated.

  In the above image forming apparatus, when the control unit switches from the normal mode to the low output amount mode, the development aging time after the power is turned on or after returning from the saving mode is determined as the development in the normal mode. It is preferable to control so as to be shorter than the aging time.

  According to the above configuration, when the developer consumption amount per unit time is small and the state in which the developer is likely to deteriorate is detected and switched to the low output amount mode, after the power is turned on or in the saving mode Control is performed such that the development aging time after returning from (such as a sleep state) is shorter than that in the normal mode. Thus, by shortening the development aging time in a state where the developer is likely to deteriorate, deterioration due to stirring of the developer can be suppressed.

  In the above configuration, the control unit sets at least one of a charging condition of the image carrier, a developing bias condition applied to the developing device, and an exposure condition of the image carrier to a condition different from the normal mode. Thus, it is preferable to compensate for a decrease in the charge amount of the developer due to the development aging time in the low output amount mode being shorter than in the normal mode.

  According to the above configuration, when the developer is switched to the low output amount mode in which the developer consumption per unit time is small and the developer is likely to deteriorate, the developer due to the development aging time being shorter than that in the normal mode. At least one of the charging condition of the image carrier, the developing bias condition applied to the developing device, and the exposure condition of the image carrier is changed so as to compensate for the decrease in the charging amount. Accordingly, it is possible to form a high-quality image while compensating for the decrease in the charge amount of the developer while preventing the developer from deteriorating.

  In the image forming apparatus, a heating unit for maintaining the surface temperature of the image carrier at a predetermined temperature, a sensor for detecting the temperature in the apparatus, and a humidity sensor for detecting the humidity in the apparatus are further provided. The control means includes a condition that the temperature detected by the temperature sensor is lower than the normal mode or the humidity detected by the humidity sensor when the normal mode is switched to the low output amount mode. It is preferable to operate the heating means under high conditions.

  According to the above configuration, when the consumption of the developer per unit time is small and the state where the developer is likely to deteriorate is detected and the mode is switched to the low output amount mode, the temperature sensor is more than the normal mode. The heating means is controlled to operate under a condition where the temperature detected by the sensor is low or a condition where the humidity detected by the humidity sensor is high. Thereby, in the low output amount mode, the opportunity for the heating means to operate can be reduced as compared with the normal mode. The heating means has a function of stabilizing the surface potential of the image carrier. However, when the number of print outputs is small, the surface potential fluctuation of the image carrier is small, so that the heating means operates in the low output amount mode. Can be reduced as compared with the normal mode. Therefore, the deterioration of the developer due to the influence of the heat of the heating unit can be suppressed.

  In the above image forming apparatus, the image forming apparatus further includes a heating unit for maintaining the surface temperature of the image carrier at a predetermined temperature, and a temperature sensor for detecting a temperature in the apparatus, and the control unit includes the normal mode. The heating device is operated at a lower speed than during the printing operation while the heating unit is in operation and the printing operation is not performed, while in the low output amount mode, the heating unit is operated. It is preferable that the developing device is operated at a lower speed than during the printing operation only when the printer is in operation and the printing operation is not performed and the temperature detected by the temperature sensor is equal to or lower than a predetermined temperature. .

  According to the above configuration, in the normal mode, the developing device is operated at a lower speed than during the printing operation in conjunction with the operation of the heating unit during the standby time when the printing operation is not performed. This is to prevent the image carrier side of the developing device from being heated intensively and expanding and deforming due to the image carrier being heated by the heating means. Depending on the operation, the developer is deteriorated by stirring. Therefore, when the mode is switched to the low output amount mode, the temperature condition that the temperature detected by the temperature sensor is equal to or lower than the predetermined temperature is satisfied even when the heating unit is operating during standby in which the printing operation is not performed. Unless otherwise, the developing device is controlled not to operate at a low speed. Here, the problem that the image carrier side of the developing device is heated and deformed is a problem that occurs when the temperature difference between the image carrier side portion of the developing device and other portions is large. Even if the necessity of the operation of the developing device at a low speed is controlled based on the above, the problem does not occur. In this way, by introducing the above temperature condition in the low output amount mode, the opportunity for operation of the developing device at a lower speed than in the normal mode is reduced, and deterioration due to stirring of the developer can be suppressed.

  The image forming apparatus of the present invention is operated in the low output amount mode that reduces the deterioration of the developer as compared with the normal mode when the developer consumption per unit time is small and the developer is likely to deteriorate. be able to. Accordingly, it is possible to realize an image forming apparatus including a developing device that can prevent deterioration of the developer and suppress deterioration in image quality.

1 is a schematic cross-sectional view illustrating an overall configuration of a multifunction machine including a developing device according to an embodiment of the present invention. 1 is a cross-sectional view illustrating a schematic configuration of a developing device according to an embodiment of the present invention. It is explanatory drawing explaining the image development low speed drive which concerns on embodiment of this invention. It is a functional block diagram of a controller concerning one embodiment of the present invention. It is a flowchart which shows the control process which concerns on one embodiment of this invention. It is a time chart which shows development aging in each power saving mode concerning one embodiment of the present invention. It is explanatory drawing which shows the effect which concerns on one embodiment of this invention.

  Hereinafter, an image forming apparatus including a developing device according to an embodiment of the present invention will be described in detail with reference to the drawings.

  First, a multifunction peripheral that is an example of an image forming apparatus according to an embodiment of the present invention will be described. FIG. 1 is a schematic cross-sectional view illustrating the overall configuration of the multifunction machine 1 including the developing device 71.

  The multi-function device 1 has a box-shaped device main body 1a. In the apparatus main body 1a, an image forming unit that feeds a sheet P, and an image formation that transfers a toner image based on image data or the like to the sheet P while conveying the sheet P fed from the sheet feeding unit 2. The fixing unit 4 that performs a fixing process for fixing the unfixed toner image transferred onto the sheet P by the unit 3 and the image forming unit 3 to the sheet P is provided. Further, on the upper surface of the apparatus main body 1a, a paper discharge unit 5 for discharging the paper P subjected to the fixing process by the fixing unit 4 is provided.

  The paper feed unit 2 includes a paper feed cassette 21, a pickup roller 22, paper feed rollers 23, 24, 25, and a registration roller 26. The paper feed cassette 21 is provided so as to be detachable from the apparatus main body 1a, and stores the paper P of each size. The pickup roller 22 is provided at the upper left position of the paper feed cassette 21 shown in FIG. 1 and takes out the paper P stored in the paper feed cassette 21 one by one. The paper feed rollers 23, 24 and 25 send out the paper P taken out by the pickup roller 22 to the paper transport path. The registration roller 26 temporarily waits for the paper P sent to the paper transport path by the paper feed rollers 23, 24, 25, and then supplies it to the image forming unit 3 at a predetermined timing.

  The paper feeding unit 2 further includes a manual feed tray (not shown) and a pickup roller 27 that are attached to the left side surface of the device main body 1a shown in FIG. The pickup roller 27 takes out the paper P placed on the manual feed tray. The paper P taken out by the pickup roller 27 is sent out to the paper conveyance path by the paper feed rollers 23 and 25 and is supplied to the image forming unit 3 by the registration roller 26 at a predetermined timing.

  The image forming unit 3 includes an image forming unit 7, an intermediate transfer belt 31 on which a toner image based on image data transmitted from a computer or the like to the surface (contact surface) of the image forming unit 7 is primarily transferred, A secondary transfer roller 32 is provided for secondary transfer of the toner image on the intermediate transfer belt 31 onto the paper P fed from the paper feed cassette 21.

  The image forming unit 7 includes a black unit 7K, a yellow unit 7Y, a cyan unit 7C, and a magenta unit 7M, which are sequentially arranged from the upstream side (right side in FIG. 1) to the downstream side. I have. Each of the units 7K, 7Y, 7C, and 7M includes a photosensitive drum 37 (image carrier) at each central position. The photosensitive drum 37 is arranged so that the direction indicated by the arrow in FIG. 1 can rotate in the direction of an arrow (clockwise). Around each photosensitive drum 37, a charger 39, an exposure device 38, a developing device 71, a cleaning device (not shown), a static eliminator, and the like are sequentially arranged from the upstream side in the rotation direction.

  The photosensitive drum 37 is formed by laminating photosensitive layers made of, for example, amorphous silicon (a-Si), and the surface is charged by a charger 39. Examples of the charger 39 include a non-contact discharge type corotron type and scorotron type charger, a contact type charging roller, a charging brush, and the like. The exposure device 38 is a so-called laser scanning unit, which irradiates the peripheral surface of the photosensitive drum 37 uniformly charged by the charger 39 with laser light based on the image data input from the image reading device or the like, and thereby the photosensitive member. An electrostatic latent image based on the image data is formed on the drum 37. The developing device 71 supplies toner to the peripheral surface of the photosensitive drum 37 on which the electrostatic latent image is formed, thereby forming a toner image based on the image data. The toner image is primarily transferred to the intermediate transfer belt 31. The cleaning device cleans the toner remaining on the peripheral surface of the photosensitive drum 37 after the primary transfer of the toner image to the intermediate transfer belt 31 is completed. The static eliminator neutralizes the peripheral surface of the photosensitive drum 37 after the primary transfer is completed. The peripheral surface of the photosensitive drum 37 cleaned by the cleaning device and the charge eliminator goes to the charger for a new charging process, and a new primary transfer is performed.

  The intermediate transfer belt 31 is an endless belt-like rotating body, and includes a driving roller 33, a driven roller 34, a backup roller 35, and a surface (contact surface) side so as to abut on the circumferential surface of each photosensitive drum 37. It is spanned across a plurality of rollers such as the primary transfer roller 36. The intermediate transfer belt 31 is configured to rotate endlessly by the plurality of rollers in a state in which the intermediate transfer belt 31 is pressed against the photosensitive drum 37 by a primary transfer roller 36 disposed to face each photosensitive drum 37. The driving roller 33 is rotationally driven by a driving source such as a stepping motor, and gives a driving force for rotating the intermediate transfer belt 31 endlessly. The driven roller 34, the backup roller 35, and the primary transfer roller 36 are rotatably provided, and are driven to rotate with the endless rotation of the intermediate transfer belt 31 by the driving roller 33. These rollers 34, 35, 36 are driven to rotate via the intermediate transfer belt 31 in accordance with the main rotation of the drive roller 33 and support the intermediate transfer belt 31.

  The primary transfer roller 36 applies a primary transfer bias (a polarity opposite to the toner charging polarity) to the intermediate transfer belt 31. As a result, the toner image formed on each photosensitive drum 37 circulates in the direction of the arrow (counterclockwise) by driving the driving roller 33 between each photosensitive drum 37 and the primary transfer roller 36. The images are sequentially transferred (primary transfer) to the intermediate transfer belt 31 in an overcoated state.

  The secondary transfer roller 32 applies a secondary transfer bias having a polarity opposite to that of the toner image to the paper P. As a result, the toner image primarily transferred onto the intermediate transfer belt 31 is transferred to the paper P between the secondary transfer roller 32 and the backup roller 35, and a color transfer image (unfixed toner image) is transferred to the paper P. Is transcribed.

  The fixing unit 4 performs a fixing process on the transfer image transferred to the paper P by the image forming unit 3. The fixing unit 4 is disposed opposite to the heating roller 41 heated by the energized heating element and the heating roller 41. And a pressure roller 42 whose surface is pressed against the peripheral surface of the heating roller 41.

  Then, the transfer image transferred to the paper P by the secondary transfer roller 32 in the image forming unit 3 is subjected to a fixing process by heating when the paper P passes between the heating roller 41 and the pressure roller 42. Fixed to P. The paper P subjected to the fixing process is discharged to the paper discharge unit 5. Further, in the multifunction machine 1 according to the present embodiment, a transport roller 6 is disposed between the fixing unit 4 and the paper discharge unit 5 at an appropriate position.

  The paper discharge unit 5 is formed by recessing the top of the device main body 1a of the multifunction machine 1, and a paper discharge tray 51 for receiving the discharged paper P is formed at the bottom of the recessed portion. .

  Next, the configuration of the developing device 71 according to the present embodiment will be described. FIG. 2 is a schematic cross-sectional view showing the configuration of the developing device 71 according to the embodiment of the present invention, and shows an enlarged peripheral portion of the developing device 71 provided in the multifunction machine 1 shown in FIG. It is.

  The developing device 71 includes a developing roller 72, a magnetic roller 73, a paddle mixer 74, a stirring mixer 75, a spike cutting blade 76, a partition plate 77, and a developing bias voltage applying unit 90. The photosensitive drum 37 and the developing roller 72 are configured to be independently driven by a drum motor M1 and a developing motor M2, respectively.

  The developing roller 72 carries (conveys) toner on the surface thereof, and visualizes (develops) an electrostatic latent image formed in advance on the surface of the photosensitive drum 37 as a toner image. The developing roller 72 has a built-in magnet so that a magnetic pole is formed at a position facing the magnetic roller 73. The magnetic roller 73 attracts the two-component developer by a magnet disposed therein to generate a magnetic brush, and supplies toner to the developing roller 72. The developing roller 72 has a built-in magnet. For this reason, the magnetic brush formed of the two-component developer formed between the developing roller 72 and the magnetic roller 73 can be formed more securely. Further, since the toner that has not been used for development on the developing roller 72 can be peeled off, hysteresis and fogging can be suppressed, and high development performance can be exhibited.

  The paddle mixer 74 and the agitation mixer 75 have spiral blades and agitate the two-component developer in opposite directions to charge the toner. Further, the paddle mixer 74 supplies a two-component developer containing charged toner and a carrier to the magnetic roller 73. The ear cutting blade 76 regulates the thickness of the magnetic brush formed on the magnetic roller 73. The partition plate 77 is provided between the paddle mixer 74 and the stirring mixer 75 so that the two-component developer can freely pass outside the both end sides of the partition plate 77.

  The two-component developer containing the toner and the carrier charged by the paddle mixer 74 and the stirring mixer 75 is supplied to the magnetic roller 73. The two-component developer supplied to the magnetic roller 73 is conveyed as a magnetic brush by a magnet inside the magnetic roller 73. Thereafter, the magnetic brush is moved by the rotation of the sleeve on the surface of the magnetic roller 73, and the thickness thereof is regulated when passing between the ear cutting blade 76 and the magnetic roller 73.

  The developing bias voltage applying unit 90 includes an AC power source 91 that applies an AC voltage to the developing roller 72 and a DC power source 92 that applies a DC voltage. A potential difference is generated between the photosensitive drum 37 and the developing roller 72 by applying a voltage from the developing bias voltage applying unit 90. The electrostatic latent image formed on the photosensitive drum 37 is developed by this potential difference.

  A configuration of the photosensitive drum 37 according to the embodiment of the present invention will be described. As the photoreceptor drum 37, for example, an amorphous silicon (a-Si) photoreceptor is used. Amorphous silicon photoconductors are more expensive than organic photoconductors, but are preferable from the viewpoints of environmental measures and total cost because they are harmless and easy to handle and have a long life. Furthermore, by using an amorphous silicon (a-Si) photoconductor, the charge density on the surface of the photoconductor drum 37 at the time of electrostatic latent image formation can be improved, so that the development performance can be improved.

  However, when an a-Si photosensitive member is used, particularly in a high-humidity environment, a phenomenon in which the image becomes blurred or the periphery of the image becomes blurred (so-called image flow) is likely to occur. The cause of this image flow is that moisture in the air is adsorbed on the circumferential surface of the photosensitive drum 37 due to dew condensation or the like and the surface resistance is lowered, and the electrostatic latent image formed on the photosensitive drum 37 is charged in the circumferential direction. This is thought to be because the electric potential decreases and the boundary becomes unclear.

  Therefore, on the inner surface of the photosensitive drum 37, as shown in FIG. 3, a drum heater 37a (heating means) for maintaining the surface temperature of the drum 37 at a preset target temperature (for example, 42 ° C.). ) Is provided. The drum heater 37a is configured, for example, by arranging heating coils (not shown) at appropriate intervals on a heat-resistant insulating sheet having elasticity. A drum temperature sensor (not shown) including a thermistor for detecting the surface temperature of the photosensitive drum 37 is disposed inside the photosensitive drum 37 and at a position adjacent to the heating coil. The drum heater 37a is inserted inside the cylindrical base material of the photosensitive drum 37 while being rolled up, is spread by the elasticity of the insulating sheet, is in close contact with the inner surface thereof, and is fixed by a frictional force. Further, a temperature control circuit (not shown) is provided inside the photosensitive drum 37 so as to be surrounded by an appropriate insulating heat insulating mechanism (not shown). This temperature control circuit has a function of executing temperature control of the drum heater 37a based on the detection result of the drum temperature sensor and the like.

  When the surface of the photosensitive drum 37 is warmed by the drum heater 37a, the moisture attached to the photosensitive drum 37 starts to evaporate. As a result, moisture on the surface of the photosensitive drum 37 is removed, and image flow can be prevented.

As shown in FIG. 1, a controller 100 (control means) composed of a microcomputer is provided on the upper part of the apparatus main body 1a. FIG. 4 is a functional block diagram of the controller 100. As shown in FIG. 4, the controller 100 includes a CPU (Central Processing Unit) 110, a ROM (Read Only Memory) 101 for storing programs, a RAM (Random Access Memory) 102 for storing programs and data when various processes are executed, An input / output interface 103 and a bus 104 connecting them can be configured.
The CPU 110 includes a developer consumption amount calculation unit 120 that calculates toner (developer) consumption amount per unit time, and includes a paper counter 121, a dot number counter 122, a print rate calculation unit 123, via the input / output interface 103. A development drive time counter 124, a temperature sensor S1, and a humidity sensor S2 are connected.

  As will be described in detail later, the temperature sensor S1 and the humidity sensor S2 are provided at appropriate positions in the developing device 71, and detect the temperature and humidity in the developing device 71, respectively. The sheet counter 121 counts the total number of sheets output during the predetermined time T (for example, 24 hours). The development drive time measuring unit 124 calculates the cumulative development drive time in the predetermined time T based on the drive time of the development motor M2 that drives the development roller 72. The dot number counter 122 counts the total number of dots printed during the predetermined time T. The printing rate calculation unit 123 calculates an average printing rate from the total number of sheets counted by the sheet counter 121 and the total number of dots counted by the dot number counter 122. Then, the developer consumption amount calculation unit 120 calculates a toner consumption amount M (M = toner consumption amount / cumulative development drive time) with respect to the cumulative development drive time at a predetermined time T as the developer consumption amount per unit time. . Here, the development driving time is the driving time of the developing motor M2 that drives the developing roller 72.

  As shown in FIGS. 3 to 6, the multifunction device 1 as the image display device according to the present embodiment has a function of automatically adjusting the setting so as to prevent the deterioration of the toner by determining the use state of the user. I have. That is, the multifunction device 1 operates in the low output amount mode when it is determined that the user has a small number of output sheets from the toner consumption amount and the driving time of the developing motor M2 (FIG. 2) that drives the developing roller 72. It is controlled to let you. Specifically, the toner consumption amount M per unit time is calculated, and when the toner consumption amount M per unit time is equal to or less than a predetermined value, the toner consumption is small with respect to the development driving time. It can be said that it is in an easy state. Therefore, in this case, control is performed so as to suppress the toner deterioration by switching to the low output amount mode.

  In the present embodiment, when the multifunction device 1 is turned on, time measurement by a timer (not shown) starts (S1), and it is determined whether a predetermined time T (for example, 24 hours) has elapsed (S2). ). When the predetermined time T has elapsed (YES in S2), the toner consumption amount detection unit 111 (developer consumption amount detection unit) calculates the cumulative development drive time at the predetermined time T by the development drive time measuring unit 124 (S3). . Next, the total toner consumption amount within a predetermined time T is calculated from the total number of output sheets counted by the sheet counter 121 and the accumulated dot number count value counted by the dot number counter 122 (S4). The toner consumption amount detection unit 111 performs processing for converting the cumulative dot number count value into the toner consumption amount by referring to a table in which the dot number count value is associated with the toner consumption amount. Then, a toner consumption amount M (M = toner consumption amount / cumulative development drive time) with respect to the cumulative development drive time at the predetermined time T is calculated (S5).

  The developer consumption amount calculation unit 120 is counted by a paper counter that counts the total number of sheets output at a predetermined time T, a dot number counter 122 that counts the total number of dots printed at the predetermined time T, and a paper counter. The average printing rate is calculated from the total number of sheets and the total number of dots counted by the dot number counter 122, and the toner consumption amount M per unit time is calculated based on the calculated average printing rate. You can also

  Next, it is determined whether the toner consumption amount M per unit time is 1 (g / min) or less (S6). If the toner consumption amount M per unit time is 1 (g / min) or less (YES in S6), the mode is switched to the low output amount mode (S7). On the other hand, if the toner consumption M is greater than 1 (g / min) (NO in S6), the normal mode is maintained (S8). Thereafter, the process proceeds to S2, and the routine of S2 to S7 is repeated.

  In the present embodiment, the total toner consumption amount is calculated from the cumulative dot number count value counted by the dot number counter 122. However, the method for calculating the total toner consumption during the predetermined time T is not limited to the above calculation method. For example, the amount of developer consumption based on the cumulative number of rotations of the developer supply motor M3 (FIG. 2) that drives the paddle mixer 74 that supplies the developer to the developing roller 72 or the rotation speed and rotation time of the developer supply motor M3. It is good also as a structure which calculates.

  Next, setting in the low output amount mode of the present embodiment will be described with reference to FIG. 6 and Tables 1 to 3.

  In the low output amount mode, the toner is prevented from being deteriorated and the deterioration in image quality can be suppressed.

  Generally, the toner charge amount decreases as the driving suspension time of the developing motor M2 becomes longer after the previous printing operation is completed. For this reason, in the multi-function device 1, the development aging time (drive time of the development motor M2) is set to be longer according to the drive suspension time of the development motor M2. Specifically, after the previous printing operation is completed, if the next printing operation is not performed and a predetermined time or more elapses, the saving mode is set. The saving mode is a sleep state in which the power is turned off or a low power state in which the power supply amount is reduced. As an example of the low power state, the temperature of the heating roller 41 of the fixing unit 4 is decreased and the motors of the respective units are stopped. Here, the sleep state is applied as the saving mode. In the present embodiment, when returning from the sleep state after entering the sleep state, the longer the standing time T1 from the end of the previous print operation to the release of sleep, the longer the development aging time (drive time of the development motor M2). To do.

  In this embodiment, as shown in Table 1 below, the development aging time in the low output amount mode is set shorter than the development aging time in the normal mode.

  Here, the operation of the multifunction machine 1 will be described with reference to FIG. After completion of the printing operation of FIG. 6 (b), timing by a timer (not shown) is started. After that, if there is no instruction for the next printing operation within a predetermined time (for example, within 15 minutes), the multifunction device 1 enters the sleep state (saving mode) and the power is temporarily turned off (see FIG. 6A). Then, when the next printing operation is instructed or the like, for example, if the leaving time T1 is not less than 4 hours and less than 7 hours, and if it is the normal mode, FIG. 6C and FIG. As shown in (d), development aging for 30 seconds is performed with warm-up (see Table 1). On the other hand, in the low output amount mode, as shown in FIGS. 6C and 6E, only warm-up is performed without performing development aging (see Table 1). Further, for example, when the standing time T1 is 7 hours or longer, and in the normal mode, as shown in FIGS. 6C and 6D, development aging is performed for 60 seconds as shown in FIGS. 6C and 6D (see Table 1). . On the other hand, in the low output amount mode, as shown in FIGS. 6C and 6E, development aging for 20 seconds is performed together with warm-up.

  In other words, in the present embodiment, when the toner consumption amount per unit time is small and the state where the toner is likely to deteriorate is detected and switched to the low output amount mode, after the power is turned on or in the sleep state (saving) The development aging time after returning from (mode) is controlled to be shorter than that in the normal mode. Thus, by shortening the development aging time in a state where the toner is likely to deteriorate, deterioration due to stirring of the toner can be effectively prevented.

However, when the driving time of the developing motor M2 is shortened and the developing driving time is shortened, the charge amount of the toner is lowered. Therefore, in this embodiment, in order to compensate for a decrease in the charge amount of the toner, at least one condition of the charging condition of the photosensitive drum 37, the developing bias condition applied to the developing roller 72, and the exposing condition of the photosensitive drum 37 is set. Be changed. Specifically, as shown in Table 2 below, the DC component (Vdc) of the developing bias applied from the DC power supply 93 to the developing roller 72 is 200 V in the normal mode, but is normal in the low output amount mode. It is set to 220V, which is 20V higher than the mode. As a result, the toner easily adheres to the electrostatic latent image on the photosensitive drum 37, and it is possible to avoid the toner image from becoming thin even if the toner has a reduced charge amount. However, when the DC component (Vdc) of the developing bias is increased, the toner with the reverse polarity adheres to the surface of the photosensitive drum 37 and fogging is likely to occur. Therefore, the surface potential (Vo) of the photosensitive drum 37 is similarly set to 320 V, which is 20 V higher than that in the normal mode, while it is 300 V in the normal mode, while in the normal mode. Further, in this case, since the laser power of the laser light applied to the surface of the photosensitive drum 37 is insufficient by the increase in the surface potential of the photosensitive drum 37, the laser power is 0.35 mW in the normal mode. On the other hand, in the low output amount mode, it is set to 0.4 mW which is 0.05 mW higher than the normal mode.

  In the present embodiment, the controller 100 controls the drum heater 37a to light up under high humidity conditions. As a result, the moisture on the surface of the photosensitive drum 37 is removed to prevent the occurrence of image flow. On the other hand, since the photosensitive drum 37 is difficult to be charged under a low temperature condition, the controller 100 controls to turn on the drum heater 37a even under a low temperature condition. Thereby, the photosensitive drum 37 is controlled so as to obtain a desired charge amount stably.

  The drum heater 37a has a function of stabilizing the surface potential of the photosensitive drum 37. However, when the number of output sheets is small, the surface potential fluctuation is small. On the other hand, when the drum heater 37a is turned on, although the fluctuation of the surface potential can be suppressed, the heat of the heater raises the temperature of the toner and promotes the deterioration. Therefore, in this embodiment, as shown in the drum heater lighting conditions in Table 3, when the mode is shifted to the low output amount mode, the temperature / humidity range in which the drum heater 37a is controlled to be OFF is widened.

That is, as shown in Table 3, in the normal mode, the drum heater 37a is lit in a low temperature and high humidity environment of 15 ° C. or lower and an absolute humidity of 100 g / m ³ or higher, whereas in the low output amount mode, The drum heater 37a is lit only in a low temperature environment of not higher than ° C. or absolute humidity of 200 g / m ³ or higher. In order to determine the temperature condition and the humidity condition described above, the multi function device 1 of the present embodiment has a temperature sensor S1 for detecting the temperature in the apparatus and a humidity sensor S2 for detecting the humidity in the developing roller 72. is doing.

  As described above, the multi function device 1 according to the present embodiment detects the drum heater 37a for maintaining the surface temperature of the photosensitive drum 37 at a predetermined temperature (for example, 42 ° C.) and the temperature in the apparatus. The controller 100 includes a temperature sensor S1 and a humidity sensor S2 that detects humidity in the apparatus. When the controller 100 switches from the normal mode to the low output amount mode, the temperature detected by the temperature sensor S1 is lower than that in the normal mode. It is preferable to operate the drum heater 37a under conditions or high humidity detected by the humidity sensor S2.

  According to the above configuration, when the toner consumption amount per unit time is small and the toner is easily deteriorated and is switched to the low output amount mode, it is detected by the temperature sensor S1 rather than the normal mode. The drum heater 37a is controlled to operate under conditions where the temperature is low or the humidity detected by the humidity sensor S2 is high. Thereby, in the low output amount mode, the opportunity for the drum heater 37a to operate can be reduced as compared with the normal mode. The drum heater 37a has a function of stabilizing the surface potential of the photosensitive drum 37. However, since the surface potential fluctuation of the photosensitive drum 37 is small when the number of print outputs is small, the drum heater 37a is in the low output amount mode. It is possible to reduce the opportunity to operate than in the normal mode. Therefore, it is possible to suppress toner deterioration due to the heat of the drum heater 37a.

  Further, when the developing roller 72 is stopped while the drum heater 37a is lit, the photosensitive drum 37 side of the developing roller 72 is heated intensively and expands to increase the deflection of the developing roller 72 so that the pitch is increased. Unevenness occurs. For this reason, when the printing operation in the normal mode is not performed, the developing roller 72 is driven at a low speed (for example, 1/100 of the rotational speed of the photosensitive drum 37) in conjunction with the lighting of the drum heater 37a. Yes. However, even when the developing roller 72 is driven at a low speed, the toner is deteriorated due to stirring.

  Here, the problem that the photosensitive drum 37 side of the developing roller 72 is heated and deformed is a problem that occurs when the temperature difference between the photosensitive drum 37 side portion of the developing device 71 and other portions is large. Therefore, in the present embodiment, even when the drum heater 37a is operating during the standby time when the printing operation is not performed, the temperature near the surface of the photosensitive drum 37 (for example, about 42 ° C.) and the developing roller 72 The developing motor M2 is driven to rotate the developing roller 72 at a low speed only when the difference between the temperature near the surface on the magnetic roller 73 side is larger than a predetermined value (for example, 32 ° C. or more). Therefore, in the low output amount mode of the present embodiment, as shown in Table 3, for example, the developing roller 72 is controlled to be driven at a low speed only in a low temperature environment of 10 ° C. or less.

  As described above, in the normal mode, the controller 100 of the MFP 1 according to the present embodiment causes the developing device 71 to perform the printing operation while the drum heater 37a is operating and the printing operation is not performed. On the other hand, in the low output amount mode, the drum heater 37a is operating and the printing operation is not performed, and the temperature detected by the temperature sensor S1 is equal to or lower than the predetermined temperature. Only in this case, the developing device 71 is controlled to operate at a lower speed than during the printing operation. In this way, by introducing the above temperature condition in the low output amount mode, the opportunity for the developing device 71 to operate at a lower speed than in the normal mode is reduced, and deterioration due to toner agitation can be suppressed.

  Table 4 below shows the output model of the machine segment according to the TEC (Typical Electricity Consumption) test method. FIG. 7 shows the result of a simulation performed on an 82 sheet machine having a print processing capacity of 82 sheets continuously printed per minute.

  If the configuration of the present embodiment is not adopted, the toner per unit time as shown in the left graph in FIG. It becomes consumption. Further, from the actual market results, there has been a problem of concentration reduction when the consumption per unit time is 1 mg / min or less.

  On the other hand, by adopting the configuration of the present embodiment, the result shown in the right graph in FIG. 7 is obtained, and it can be seen that the toner stress is reduced.

  In the above embodiment, a tandem type image forming apparatus has been described as an example of the image forming apparatus of the present invention. However, any image forming apparatus using an electrophotographic system may be used, and the tandem type image forming apparatus may be used. It is not limited. Note that the developing device of the present invention can suppress the occurrence of image unevenness due to a change in the developing gap. Therefore, it is preferable to apply the developing device of the present invention to a small tandem type image forming apparatus in that the small tandem type image forming apparatus can easily solve the defect that the image unevenness due to the fluctuation of the developing gap easily occurs. In addition, as an example of the image forming apparatus, a multifunction peripheral has been described as an example. Further, the image bearing member has been described by taking a photosensitive drum as a drum-shaped photosensitive member as an example. However, the image bearing member is not limited to this, and is not limited to this. Even applicable.

1 ... Machine (image forming device)
37 …… Photoreceptor drum (image carrier)
37a: Drum heater (heating means)
71... Developing device 72... Developing roller 100... Controller (control means)
111... Toner consumption detector (developer consumption calculation means)
121... Paper counter (developer consumption calculation means)
122... Dot number counter (developer consumption calculation means)
123... Printing rate calculation unit (developer consumption calculation means)
124... Development drive time counter (cumulative drive time calculation means)
S1... Temperature sensor S2... Humidity sensor M1... Drum motor M2... Development motor M3.

Claims (8)

A developing device for developing the electrostatic latent image formed on the image carrier using a developer;
A developer consumption calculating means for calculating consumption of the developer per unit time in the developing device;
When the developer consumption per unit time calculated by the developer consumption calculation means is less than or equal to a threshold value, the low output amount mode that reduces the deterioration of the developer more than the normal mode from the operation in the normal mode And an image forming apparatus characterized by comprising: The developer consumption calculating means is:
An accumulated consumption calculating means for calculating an accumulated consumption of the developer in a predetermined time;
An accumulated driving time calculating means for calculating an accumulated developing driving time of the developing device at the predetermined time,
Development per unit time from the cumulative consumption of the developer for the predetermined time calculated by the cumulative consumption calculation means and the cumulative development drive time for the predetermined time calculated by the cumulative drive time calculation means The image forming apparatus according to claim 1, wherein a consumption amount of the agent is calculated. A developer replenishing motor for replenishing the developer to the developing device;
The cumulative consumption calculation means calculates the cumulative consumption of the developer based on the number of rotations of the developer supply motor or the rotation speed and rotation time of the developer supply motor. The image forming apparatus according to 2. The developer consumption calculating means is:
A paper counter for counting the total number of paper sheets output during the predetermined time;
A dot number counter that counts the total number of dots printed during the predetermined time;
Printing rate calculation means for calculating an average printing rate from the total number of sheets counted by the sheet counter and the total number of dots counted by the dot number counter;
The image forming apparatus according to claim 1, wherein the consumption amount of the developer per unit time is calculated based on the average printing rate calculated by the printing rate calculation unit.   When the control unit switches from the normal mode to the low output amount mode, the development aging time after starting the power supply or returning from the saving mode is shorter than the development aging time in the normal mode. The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled as follows.   The control means sets at least one of a charging condition of the image carrier, a developing bias condition applied to the developing device, and an exposure condition of the image carrier as a condition different from the normal mode, and reduces the low output. 6. The image forming apparatus according to claim 5, wherein a decrease in the charge amount of the developer due to the development aging time in the force mode being made shorter than in the normal mode is compensated. Heating means for maintaining the surface temperature of the image carrier at a predetermined temperature; and
A temperature sensor for detecting the temperature in the device;
A humidity sensor for detecting humidity in the apparatus,
When the control unit switches from the normal mode to the low output amount mode, the temperature detected by the temperature sensor is lower than the normal mode or the humidity detected by the humidity sensor is higher. The image forming apparatus according to claim 1, wherein the heating unit is operated. Heating means for maintaining the surface temperature of the image carrier at a predetermined temperature; and
A temperature sensor for detecting the temperature in the apparatus,
The control means includes
In the normal mode, while the heating means is in operation and the printing operation is not performed, the developing device is operated at a lower speed than during the printing operation,
In the low output amount mode, the developing device is operated only when the heating unit is operating and the printing operation is not performed and the temperature detected by the temperature sensor is equal to or lower than a predetermined temperature. The image forming apparatus according to claim 1, wherein the image forming apparatus is operated at a lower speed than during a printing operation.

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