JP2013202835A - Image forming device and method of correcting light quantity of light exposure member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for restraining image quality from deteriorating due to light exposure onto a photoreceptor.SOLUTION: An image forming device has a photoreceptor, a light exposure member to expose the photoreceptor to light, a distance regulating member regulating the separation distance between the photoreceptor and the light exposure member to a prescribed distance, and a control section. The control section carries out a decision step (Step S30) to estimate the separation distance varied by wear of the distance regulating member (Step S20) and deciding on the amount of correction to correct the light quantity of the light exposure member on the basis of the estimated separation distance and a correction step (Step S40) to correct the light quantity by the amount of correction decided by the decision process.

Description

  The present invention relates to an image forming apparatus and a light amount correction method for an exposure member, and more particularly to a technique for accurately performing exposure on a photoreceptor in an image forming apparatus.

  Conventionally, for example, a technique described in Patent Document 1 is known as a technique for accurately performing exposure on a photosensitive member in an image forming apparatus. In the prior art document, by providing spacers for regulating the distance between the optical head (exposure member) and the photosensitive drum (photosensitive member) at both ends in the longitudinal direction of the photosensitive member, the optical type is accurately provided on the photosensitive member. A technique for imaging light from a head is disclosed.

JP 2002-361931 A

  However, in the technique of the above-mentioned prior art document, although the image can be accurately formed on the photosensitive member at first, the positioning accuracy of the optical head is lowered due to the wear of the spacer that is in sliding contact with the photosensitive member, and the image quality is lowered. There was a risk of inviting.

  The present invention provides a technique for suppressing deterioration in image quality caused by exposure on a photoreceptor.

An image forming apparatus disclosed in this specification includes a photoconductor, an exposure member that exposes the photoconductor, a distance regulating member that regulates a separation distance between the photoconductor and the exposure member to a predetermined distance, A control unit, wherein the control unit estimates the separation distance that changes due to wear of the distance regulating member, and determines a correction amount for correcting the light amount of the exposure member based on the estimated separation distance. A determination process and a correction process for correcting the light amount by the correction amount determined in the determination process are executed.
According to this configuration, the amount of light is corrected in consideration of the separation distance between the photoconductor and the exposure member, which changes due to wear of the distance regulating member, so that it is possible to suppress deterioration in image quality associated with exposure on the photoconductor.

In the image forming apparatus, the photoconductor has a rotation axis, the distance regulating member contacts the photoconductor, and the control unit counts a parameter whose value changes with the rotation of the photoconductor. A count process may be further executed, and in the determination process, the separation distance may be estimated from the count value counted in the count process.
Since the distance regulating member is in contact with the photosensitive member, it is considered that the distance regulating member is worn with the rotation of the photosensitive member, and the separation distance is changed accordingly. Therefore, according to this configuration, the change in the separation distance when the distance regulating member wears due to contact with the photosensitive member is preferably estimated by counting the parameter whose value changes with the rotation of the photosensitive member. be able to. Then, by reflecting the estimated change in the separation distance in the correction amount, it is possible to suppress a decrease in image quality related to exposure on the photoreceptor.

The image forming apparatus includes an image forming unit that forms an image on a recording medium, the image forming unit includes the photosensitive member, and the parameter is the recording target on which an image is formed by the image forming unit. It may be the number of media.
The degree of wear of the distance regulating member increases in accordance with the number of recording media on which images are formed, that is, the number of printed sheets. Therefore, according to this configuration, by counting the number of printed sheets, the count value can be reflected in the correction amount.

The image forming apparatus may further include a main body frame, and the distance regulating member may include a roller that contacts the photoconductor, and a fixing member that supports the roller and is fixed to the main body frame. Good.
According to this configuration, the distance regulating member has a longer life than the case where the spacer contacts and slides on the photosensitive member, and it is not necessary to replace the spacer. Therefore, the distance regulating member can be fixed to the apparatus main body frame. Therefore, the cartridge can be reduced in size as compared with the case where a short-life spacer is provided in the cartridge for replacement.

In the image forming apparatus, the control unit may increase the rate of change of the estimated amount as the count value increases when estimating the separation distance in the determination process.
Since the roller diameter of the distance regulating member decreases with wear, the degree of wear (thickness reduction in the roller diameter direction) accelerates. According to this configuration, the separation distance is increased corresponding to the acceleration. Since the light quantity can be corrected according to the estimation, it is possible to favorably suppress the deterioration of the image quality.

In the image forming apparatus, at least two ranges corresponding to the count value may be set, and the correction amount corresponding to each range may be set.
According to this configuration, the correction amount according to the degree of wear of the distance regulating member can be set, and the correction amount is accurately achieved.

In the image forming apparatus, the exposure member exposes the photosensitive member by line scanning, and the correction amount corresponding to each range is further set according to the scanning line in the line scanning. You may do it.
According to this configuration, the correction amount is set in accordance with the scan line, for example, 4 lines or 2 lines within the range set according to the count value, for example, the predetermined range of the number of printed sheets. The amount is refined. Therefore, it is possible to reduce inconveniences in which the correction amount is stepwise depending on the count value range unit, for example, the print number range unit.

In the image forming apparatus, the distance between the exposure member and the focal point of the exposure member may be DI, which is the separation distance before wear of the distance regulating member and is an initial value of the separation distance. If the working distance is Dw, the initial separation distance may be set so as to satisfy the relationship Dw <DI.
According to this configuration, since the exposure starts from a position far from the focal position when viewed from the exposure member and ends at a position shorter than the focal position, the depth-of-focus range of the exposure member can be used effectively. Can extend the service life.

In the image forming apparatus, if the final separation distance that is the final value of the separation distance, which is the separation distance after wear of the distance regulating member, is DE, the relationship of Dw−DE <DI−Dw is satisfied. As described above, the initial separation distance and the final separation distance may be set.
When the distance between the exposure member and the photosensitive member (separation distance) deviates from the working distance, which is the distance between the exposure member and the focus of the exposure member, image quality degradation is usually caused by the optical characteristics of the exposure member used. The case where the same interval becomes smaller than the case where it becomes larger than the same working distance is larger. Therefore, by setting the separation distance larger than the working distance, it is possible to lengthen the time until the image quality reaches its limit due to wear of the distance regulating member. That is, the service life of the distance regulating member can be extended.

Further, in the image forming apparatus, in the determination process, the correction unit reduces the light amount as the count value increases until the separation distance becomes equal to the working distance due to wear of the distance regulating member. The amount may be determined, and then the correction amount for increasing the light amount as the count value increases may be determined.
According to this configuration, since the correction amount is determined in consideration of the difference so as to compensate for the deterioration in image quality related to the difference between the working distance and the separation distance, the deterioration in image quality can be suitably suppressed.

Further, in the image forming apparatus, two distance regulating members are provided corresponding to both ends in the longitudinal direction of the photoconductor, and when the wear speeds of the respective distance regulating members are different, the control unit includes: In the determination process, the separation distance between the both end portions may be estimated based on each estimated wear amount, and the correction amount may be determined accordingly.
According to this configuration, even if the amount of wear of each distance regulating member is different due to a difference in applied mechanical pressure, it is possible to estimate each separation distance at an arbitrary position between both ends by Correct correction amount can be determined.

  Further, the exposure member light amount correction method disclosed in this specification regulates a photosensitive member, an exposure member that exposes the photosensitive member, and a separation distance between the photosensitive member and the exposure member to a predetermined distance. In the image forming apparatus comprising a distance regulating member, a method for correcting the amount of light from the exposure member, the estimating step estimating the separation distance that changes due to wear of the distance regulating member, and the estimating step A determination step of determining a correction amount for correcting the light amount of the exposure member based on the estimated separation distance; and a correction step of correcting the light amount by the correction amount determined in the determination step.

  In the above method, in the light amount correction method, the photosensitive member has a rotation axis, and the distance regulating member is in contact with the photosensitive member, and the value of the method changes as the photosensitive member rotates. A counting step for counting parameters may be further included, and in the determination step, the separation distance may be estimated from the count value counted in the counting step.

  According to the present invention, the separation distance that changes due to wear of the distance regulating member is estimated, and the correction amount for correcting the light amount of the exposure member is determined based on the estimated separation distance. For this reason, even when the separation distance changes due to wear of the distance regulating member, it is possible to suppress deterioration in image quality due to exposure on the photoreceptor.

1 is a side sectional view of a main part of a color printer according to an embodiment. Enlarged view of LED unit and process cartridge Side view showing positional relationship between LED unit and photosensitive drum Illustration of LED exposure head Block diagram of light emission control unit and control device Explanatory diagram showing the relationship between working distance and imaging state Plan view schematically showing each imaging state of beam spot A flowchart schematically showing processing related to light amount correction Table showing the relationship between the light intensity correction value table and the number of printed sheets (estimated friction) Graph showing the relationship between the number of printed sheets and the estimated friction amount of the guide roller

<Embodiment>
An embodiment will be described with reference to FIGS. 1 to 10.
1. FIG. 1 is a side sectional view schematically showing a main part of an electrophotographic color printer 1 according to an embodiment. The color printer 1 is an example of an image forming apparatus. As shown in FIG. 1, the color printer 1 includes a main body housing 10 in which a paper feeding unit 20 that supplies paper S, an image forming unit 30 that forms an image on the fed paper S, and an image are formed. A paper discharge unit 90 that discharges the printed paper S, and a control device 100 that controls the operation of each unit.

  In the following description, the direction will be described with reference to the user when using the color printer. That is, in FIG. 1, the left side toward the paper surface is “front side”, the right side toward the paper surface is “rear side”, the rear side toward the paper surface is “left side”, and the front side toward the paper surface is “right side”. To do. In addition, the vertical direction toward the page is defined as the “vertical direction”. Further, the image forming apparatus is not limited to the color printer 1 and may be, for example, a monochrome printer, a multifunction machine having a copy function and a FAX function.

  An openable and closable upper cover 12 is provided on the upper portion of the main body casing 10. The upper surface of the upper cover 12 is a paper discharge tray 13 for accumulating paper (an example of a recording medium) S discharged from the main body housing 10, and an LED unit 40 that is an example of an exposure member is provided below the upper cover 12. It has been. Light emission of the LED print head 41 as a print head included in the LED unit 40 is controlled by the control device 100 and the light emission control unit 110 (see FIG. 5).

  The paper feeding unit 20 is provided in the lower part of the main body housing 10, and is a paper feeding tray 21 that is detachably attached to the main body housing 10, and a paper that conveys the paper S from the paper feeding tray 21 to the image forming unit 30. A supply mechanism 22 is mainly provided. The paper supply mechanism 22 is provided on the front side of the paper feed tray 21 and mainly includes a paper feed roller 23 and a separation roller 24.

  In the sheet feeding unit 20 configured as described above, the sheets S in the sheet feeding tray 21 are separated one by one and sent upward, and are turned backward through the conveyance path 28, and the image forming unit 30. To be supplied.

  The image forming unit 30 includes four LED units 40K to 40C, four process cartridges 50K to 50C, a transfer unit 70, and a fixing unit 80. The four LED units 40K, 40Y, 40M, and 40C and the four process cartridges 50K, 50Y, 50M, and 50C correspond to four colors of black K, yellow Y, magenta M, and cyan C.

  The process cartridges 50K to 50C are arranged side by side in the front-rear direction between the upper cover 12 and the paper feeding unit 20, and are detachably attached to the drum unit 51 as shown in FIG. Development unit 61. The process cartridges 50K to 50C have the same configuration except that the color of the toner stored in the toner storage chamber 66 of the developing unit 61 is different.

  The drum unit 51 includes a photosensitive drum 53 as an example of a photosensitive member and a scorotron charger 54. The photosensitive drum 53 has a rotation shaft 53B and rotates as the rotation shaft 53B rotates.

  The developing unit 61 includes a developing roller 63, a supply roller 64, and a toner storage chamber 66 that stores toner. The developing unit 61 is mounted on the drum unit 51, thereby forming an exposure hole 55 that faces the photosensitive drum 53 from above, as shown in FIG. The LED unit 40 holding the LED print head 41 is inserted into the lower end of the exposure hole 55. Details of the LED unit 40 will be described later.

  Further, a cartridge drawer 15 that detachably accommodates each process cartridge 50 is provided in the main body housing 10.

  As shown in FIG. 1, the transfer unit 70 is provided between the sheet feeding unit 20 and each process cartridge 50, and includes a drive roller 71, a driven roller 72, a conveyance belt 73, and a transfer roller 74.

  A conveying belt 73 is stretched between the driving roller 71 and the driven roller 72. The outer surface of the conveyance belt 73 is in contact with each photosensitive drum 53. In addition, four transfer rollers 74 that sandwich the conveyor belt 73 between the photosensitive drums 53 are arranged inside the conveyor belt 73 so as to face the photosensitive drums 53. A transfer bias is applied to the transfer roller 74 during transfer.

  The fixing unit 80 is disposed on the back side of each process cartridge 50 and the transfer unit 70, and includes a heating roller 81 and a pressure roller 82 that presses the heating roller 81. A paper discharge sensor 26 that detects the discharge of the paper S is provided on the downstream side of the fixing unit 80 in the paper conveyance direction.

  In the image forming unit 30 configured as described above, first, the surface (photosensitive surface) 53A of each photosensitive drum 53 is uniformly charged by the scorotron charger 54 and then irradiated from each LED print head 41. It is exposed by LED light. As a result, the potential of the exposed portion is lowered, and an electrostatic latent image based on the image data is formed on each photosensitive drum 53.

  Further, the toner in the toner storage chamber 66 is supplied and carried on the developing roller 63 by the rotation of the supply roller 64. The toner carried on the developing roller 63 is supplied to the electrostatic latent image formed on the photosensitive drum 53 when the developing roller 63 comes into contact with the photosensitive drum 53. As a result, the toner is selectively carried on the photosensitive drum 53 to visualize the electrostatic latent image, and a toner image is formed by reversal development.

  Next, the sheet S supplied on the conveyance belt 73 passes between each photosensitive drum 53 and each transfer roller 74, whereby the toner image formed on each photosensitive drum 53 is transferred onto the sheet S. The Then, as the sheet S passes between the heating roller 81 and the pressure roller 82, the toner image transferred onto the sheet S is thermally fixed. The heat-fixed paper S is discharged to the outside of the main body housing 10 via the paper discharge unit 90 and accumulated in the paper discharge tray 13.

2. Configuration of LED Unit The LED unit 40 is an example of an exposure member. As shown in FIGS. 2 and 3, the LED print head 41, the frame portion 42, the roller support member 43, the guide roller 44, and the coupling portion 45 are included. Including. The LED unit 40 exposes the photosensitive drum 53 by line scanning in the longitudinal direction (axial direction) of the photosensitive drum 53.

  As shown in FIG. 3, the LED print head 41 is attached and fixed at the lower end of the frame portion 42 by, for example, two clips 41 </ b> A.

  The roller support member 43 is, for example, screwed to both ends of the frame portion 42 made of an insulating resin member. The roller support member 43 is provided with a roller shaft 43A that extends toward the inner side in the left-right direction at the lower end. The roller shaft 43A is a shaft that rotatably supports the guide roller 44.

  The guide roller 44 is an example of a distance regulating member and a roller, and is a substantially cylindrical roller. The guide roller 44 regulates the separation distance D between the photosensitive drum 53 and the LED print head 41 to a predetermined distance. As shown in FIG. 3, the guide roller 44 abuts on the surface 53A of the photosensitive drum 53 and rolls to define the positional relationship between the LED unit 40 and the photosensitive drum 53, specifically, the LED print head 41 and the surface 53A. Is defined. The material constituting the guide roller 44 is not particularly limited, but it is preferable to use a material having an appropriate coefficient of friction with the surface 53A of the photosensitive drum 53 and having excellent wear resistance. For example, a polyamide-based resin can be used.

  The coupling portion 45 is provided at both ends of the frame portion 42 and has a protrusion 45A. When the upper cover 12 is closed, the protrusion 45 </ b> A engages with the engaging portion 10 </ b> A formed on the main body frame 10 to fix the LED unit 40 to the main body frame 10. The frame part 42 and the coupling part 45 constitute a fixing member.

  The frame part 42 and the LED print head 41 are always urged downward by a compression spring (not shown), for example.

  As shown in FIG. 2, the LED unit 40 is attached to the upper cover 12 via the connection link 14 </ b> A and the LED attachment member 14.

  Each LED unit 40 extends downward from the upper cover 12 when attached to the upper cover 12. In the LED unit 40, the guide roller 44 provided at the lower end is in contact with the vicinity of the upper end of the surface 53A of the photosensitive drum 53 at the exposure position, and thereby the distance D between the surface 53A and the LED head 41 is kept constant. Be drunk.

  The LED print head 41 has a plurality of light emitting elements (LEDs) P arranged in the main scanning direction (left-right direction) orthogonal to the transport direction (front-rear direction) of the paper S. The main scanning direction is equal to the axial direction of the photosensitive drum 53. As shown in FIG. 4, the LED print head 41 includes a circuit board 41a, an LED array chip 41b, and a gradient index rod lens array 41c. Specifically, for example, 20 LED array chips 41b are staggered in the main scanning direction on the circuit board 41a. Each LED array chip 41b is obtained by forming a plurality of LEDs (light emitting diodes) as an example of the light emitting element P on a semiconductor substrate by a semiconductor process. A single-row gradient index rod lens array 41c is provided on the light output side of the LED array chip 41b.

3. Description of Control Device 100 and Light Emission Control Unit 110 The control device 100 controls the entire color printer 1, and includes an arithmetic control unit 100A, an EEPROM 100B, and a counter 100C that are composed of a CPU and the like. The control device 100 is an example of a control unit, and is configured by, for example, an ASIC (specific application IC).

  The light emission control unit 110 controls the light emission of each light emitting element P of the LED print head 41 in cooperation with the control device 100. In the present embodiment, the light emission control unit 110 receives corrected light emission data (light amount data) from the control device 100, and controls the light emission of each light emitting element P based on the corrected light emission data. The light emission control unit 110 includes a RAM 120, an ASIC (Application Specific IC) 130, and an oscillation circuit 140 as shown in FIG. Four LED print heads 41K, 41Y, 41M, and 41C are commonly connected to the light emission control unit 110, and the light emission control unit 110 controls the light emission of the four LED print heads 41 at once.

  Each LED print head 41 is provided with an EEPROM 43, for example. In the EEPROM 43, light emission data necessary for the light emission control unit 110 to perform light emission control of each light emitting element P is written. Specifically, drive signal data corresponding to each light emitting element P is stored in the EEPROM 43. The drive signal data is read in a light amount correction process described below during image formation of the color printer 1 and is corrected according to a parameter whose value changes with the rotation of the photosensitive member, for example, the number of printed sheets. Here, the drive signal data includes, for example, information on drive time. Then, a drive signal for adjusting the amount of light according to the drive time is generated, and each light emitting element P emits light by the drive signal during the corresponding drive time. The parameter whose value changes with the rotation of the photosensitive member is not limited to the number of printed sheets, and may be the cumulative rotational number of the photosensitive member. The drive signal data is not limited to the drive time, and may be the drive current value of each light emitting element P, for example.

3. Next, the light amount correction processing of the LED unit 40 will be described with reference to FIGS. The light amount correction process is executed by the control device 100 according to a predetermined program, for example, when a printing instruction is given to the color printer 1. Note that the present invention is not limited to this, and the light amount correction process may be executed by the light emission control unit 110, for example. In this case, the light emission control unit 110 is an example of a control unit.

As shown in FIG. 6, normally, the image formed from the light emitting element P and formed via the rod lens array 41c is a composite image formed by overlapping a plurality of images by a plurality of rod lenses. The imaging state CS varies depending on the distance from the rod lens array 41c, and the exposure amount varies depending on the imaging state CS. Therefore, the distance D between the rod lens array 41c and the surface 53A of the photosensitive drum 53 is the working distance Dw of the LED unit 40, specifically, the working distance that is the distance from the end surface of the rod lens array 41c to the focal point of the rod lens array 41c. When it deviates from Dw, it is necessary to correct the light emission amount from the light emitting element P in order to obtain a desired exposure amount. Here, the working distance Dw corresponds to the distance between the exposure member and the focal point of the exposure member.
At that time, generally, the imaging state CS differs between the case where the separation distance D is shorter than the working distance Dw and the case where the separation distance D is longer than the working distance Dw (see FIG. 7). It is necessary to correct the amount of emitted light.

  In the present embodiment, as shown in FIG. 6, an imaging state CS1 with a working distance Dw + 200 μm (defocus value), an imaging state CS2 with a working distance Dw + 100 μm, according to the deviation amount of the separation distance D from the working distance Dw, The light quantity correction will be described by taking as an example five imaging states CS1 to CS5 of an imaging state CS3 with a working distance Dw, an imaging state CS4 with a working distance Dw-100 μm, and an imaging state CS5 with a working distance Dw-200 μm.

  As shown in FIG. 7 (simulation diagram), the dispersion of the beam spot is usually less when the separation distance D is longer than the working distance Dw than when the separation distance D is shorter than the working distance Dw. Specifically, even if the difference (deferred value) between the separation distance D and the working distance Dw is the same, the case where the separation distance D is longer than the working distance Dw is compared to the case where the separation distance D is shorter than the working distance Dw. Less beam spot dispersion. That is, the LED unit 40 can be used more effectively when the separation distance D is longer than the working distance Dw.

  Therefore, in this embodiment, the defercus value is set to +200 μm, and the initial separation distance before wear of the guide roller 44 is set to “Dw + 200 μm”. That is, assuming that the initial separation distance, which is the initial value of the separation distance D, is DI, the initial separation distance DI is set so as to satisfy the relationship of Dw <DI. With this configuration, the depth of focus can be used effectively by starting the exposure from a place farther than the working distance Dw and ending at a place shorter than the working distance Dw, so that the service life of the guide roller 44 can be extended.

  Here, the initial separation distance DI is set by a distance regulating member that regulates the separation distance D between the photosensitive drum 53 and each LED print head 41 to a predetermined distance, specifically, the diameter of the guide roller 44 to be used. Is done. Here, the initial separation distance DI (Dw + 200 μm) corresponds to the predetermined distance.

  In the light amount correction process, as shown in FIG. 8, the control device 100 first calculates the count value of the number of printed sheets counted by the counter 100C based on the paper detection signal from the paper discharge sensor 26. Obtained from 100C (step S10). Here, the number of printed sheets is the number of sheets S on which an image is formed by the image forming unit 30, and corresponds to a parameter whose value changes with the rotation of the photosensitive member.

  Next, the control device 100 estimates the wear amount of the guide roller 44 from the count value of the counter 100C, and estimates the separation distance D that changes due to the wear of the guide roller 44 based on the estimated wear amount (step S20). ). The degree of wear of the guide roller 44 increases according to the number of sheets S on which an image is formed, that is, the number of printed sheets. Therefore, by counting the number of printed sheets, the count value can be reflected in the correction amount.

  For example, as shown in FIG. 9, when the number of printed sheets is between 0 and 25000 sheets (corresponding to the range corresponding to the count value), the estimated wear amount is 0 μm, and when the number of printed sheets is between 25000 and 35000 sheets, it is estimated. The wear amount is set to 50 μm, and the estimated wear amount is set to 100 μm when the number of printed sheets is 35,000 to 50,000. When the estimated wear amount is 0 μm, the separation distance D is estimated as “Dw + 200 μm”, when the estimated wear amount is 100 μm, the separation distance D is estimated as “Dw + 100 μm”, and when the estimated wear amount is 200 μm The separation distance D is estimated as “Dw”. Further, when the estimated wear amount is 300 μm, the separation distance D is estimated as “Dw−100 μm”, and when the estimated wear amount is 400 μm, the separation distance D is estimated as “Dw−200 μm”.

  Next, the control device 100 determines a correction amount for correcting the light amount of the LED print head 41 based on the estimated separation distance D (step S30). When determining the correction amount, the control device 100 refers to, for example, a light amount correction table as shown in FIG. The light amount correction table is a table showing the correspondence between each estimated wear amount of the guide roller 44, that is, the estimated separation distance D and the light amount correction amount (correction data) of each light emitting element P. For example, the light amount correction table is stored in the EEPROM 100B. ing. At that time, the relationship between the number of printed sheets and the amount of wear of the guide roller 44 is acquired in advance through experiments and evaluations, for example, and the estimated amount of wear corresponding to each range of the number of printed sheets is set from the acquired relationship. The light amount correction table may be stored in the EEPROM 43 provided in each LED print head 41.

  Thus, in the present embodiment, six (corresponding to at least two) ranges corresponding to the count value of the number of printed sheets are set, and correction amounts corresponding to the respective ranges are set. Therefore, a correction amount corresponding to the degree of wear of the guide roller 44 can be set, and the correction amount can be accurately determined.

  As shown in FIG. 9, the control device 100 reduces the light amount of the correction amount of each light emitting element P as the count value increases until the separation distance D becomes equal to the working distance Dw from “Dw + 200 μm”. Decide on a value. In addition, after the separation distance D becomes equal to the working distance Dw, the control device 100 determines the correction amount of each light emitting element P to a value that increases the light amount as the count value increases.

  That is, normally, as the difference between the separation distance D and the working distance Dw increases, the deterioration in image quality increases. Therefore, the correction amount is determined in consideration of the working distance Dw so as to compensate for the deterioration in image quality related to the working distance Dw. Is done. For this reason, it is possible to suitably suppress the deterioration of the image quality.

  Next, the control device 100 corrects the light amount of each light emitting element P based on the determined correction amount, generates corrected light amount data, and supplies the corrected light amount data to the light emission control unit 110. The light emission control unit 110 controls the light emission of each light emitting element P based on the corrected light amount data.

4). Method for Interpolating Light Correction Data Next, a method for interpolating light correction data will be described with reference to FIG.

4-1.
When interpolating the light amount correction data, first, the number of printed sheets for a deferred value (position) to be interpolated is calculated using the graph of number of printed sheets-estimated wear amount shown in FIG. Note that the graph of FIG. 10 is created based on experiments on the number of printed sheets and the amount of wear.

4-2.
Next, when the calculated number of prints is printed, the data corresponding to the single imaging state CS in the correction value table is used until the data corresponding to the imaging state CS different for each scanning line is used. Use it to print.

  More specifically, for example, as shown in FIG. 9, when the defercus value = 150 μm, the defercus value is intermediate between 200 μm and 100 μm, so when the number of printed sheets is 25,000, every scanning line Then, printing is performed while switching data corresponding to the imaging state CS1 and data corresponding to the imaging state CS2. Further, for example, when it is desired to correct at a defocus value = 175 μm, for example, one of four scans is scanned with data corresponding to the imaging state CS2, and the remaining three scans are data corresponding to the imaging state CS1. To scan.

  By such interpolation, a correction amount corresponding to each print sheet number range may be further set according to the scanning line in the line scanning. In this case, within a range set according to the count value, for example, within a predetermined range of the number of printed sheets, a correction amount is set according to the scanning line, for example, 4 lines or 2 lines. Densified. Therefore, it is possible to reduce inconveniences in which the correction amount is stepwise depending on the count value range unit, for example, the print number range unit.

4). Effects of the Embodiment According to the present embodiment, the separation distance D between the photosensitive drum 53 and the LED print head 41 that changes due to wear of the guide roller 44 is estimated, and LED printing is performed based on the estimated separation distance D. A correction amount for correcting the light amount of the head 41 is determined. Based on the correction amount, the light amount of the light emitting element P is corrected. Therefore, even when the guide roller 44 is worn and the separation distance D changes, it is possible to suppress the deterioration of the image quality related to the exposure on the photosensitive drum 53.

  At this time, the number of printed sheets S is used as a parameter for estimating the wear amount of the guide roller 44, and the wear amount of the guide roller 44, that is, the separation distance D is estimated from the count value of the number of printed sheets. Normally, the degree of wear of the guide roller 44 increases in accordance with the number of sheets S on which an image is formed, that is, the number of printed sheets. Therefore, by counting the number of printed sheets, the count value is reflected in the light amount correction amount. be able to.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.

  (1) When estimating the separation distance D in the determination process, the control device 100 (control unit) may increase the rate of change of the estimated amount as the count value increases. For example, as shown in FIG. 10, the amount of friction, that is, the separation distance D, follows an estimated curve in which the estimated rate of change ΔW2 for 40000 printed sheets is greater than the estimated rate of change ΔW1 for 30000 printed sheets. May be estimated. In this case, since the roller diameter of the distance regulating member becomes smaller in accordance with wear, the degree of wear (the degree of reduction in thickness in the roller diameter direction) is accelerated, but the separation distance is estimated in accordance with the acceleration, Since the amount of light can be corrected accordingly, deterioration in image quality can be suitably suppressed.

  (2) The initial separation distance so as to satisfy the relationship Dw−DE <DI−Dw, where DE is the separation distance D after the guide roller 44 is worn and the final separation distance D is the final value of the separation distance D. DI and final separation distance DE may be set.

  Usually, when the separation distance D deviates from the working distance Dw of the LED print head 41, the deterioration in image quality is usually caused by the optical characteristics of the exposure member used, compared to the case where the separation distance D is usually larger than the working distance Dw. Is smaller (see FIG. 7). Therefore, by setting the separation distance D to be larger than the working distance Dw, it is possible to lengthen the time until the image quality reaches its limit due to wear of the guide roller 44. That is, the service life of the guide roller 44 can be extended.

(3) When the wear speed of each guide roller 44 is different, the control device 100 (control unit) estimates each separation distance D between both ends based on each wear estimation amount, and accordingly, that is, The light amount correction amount may be determined according to each estimated separation distance D. In this case, even if the wear amount of each guide roller 44 is different due to the difference in applied mechanical pressure, it is appropriate for each light emitting element P by estimating the separation distance D between both ends. Correct correction amount can be determined.
In this case, the wear rate (amount of wear) is obtained in advance through experiments and evaluations. Then, from the result of the experiment / evaluation, the wear amount when the parameter (number of printed sheets) is changed is estimated. The estimated wear amount is interpolated between the two distance regulating members.

  DESCRIPTION OF SYMBOLS 1 ... Color printer, 40 ... LED unit, 41 ... LED print head, 44 ... Guide roller, 53 ... Photosensitive drum, 100 ... Control apparatus, 110 ... Light emission control part, P ... Light emitting element

Claims (13)

A photoreceptor,
An exposure member for exposing the photoreceptor;
A distance regulating member for regulating a separation distance between the photosensitive member and the exposure member to a predetermined distance;
A control unit,
The controller is
A determination process for estimating the separation distance that changes due to wear of the distance regulating member, and determining a correction amount for correcting the light amount of the exposure member based on the estimated separation distance;
An image forming apparatus that executes correction processing for correcting the light amount by the correction amount determined in the determination processing. The image forming apparatus according to claim 1.
The photoreceptor has a rotation axis;
The distance regulating member abuts on the photoconductor,
The controller is
Further executing a counting process for counting parameters whose values change with the rotation of the photoconductor,
In the determination process, the separation distance is estimated from the count value counted in the count process. The image forming apparatus according to claim 2.
An image forming unit for forming an image on a recording medium;
The image forming unit includes the photoconductor,
The image forming apparatus, wherein the parameter is the number of recording media on which an image is formed by the image forming unit. The image forming apparatus according to claim 2 or 3,
It has a body frame,
The distance regulating member includes a roller that contacts the photosensitive member, and a fixing member that supports the roller and is fixed to the main body frame. The image forming apparatus according to claim 4.
The control unit, when estimating the separation distance in the determination process, increases the rate of change of the estimated amount as the count value increases. The image forming apparatus according to any one of claims 2 to 5,
An image forming apparatus, wherein at least two ranges corresponding to the count value are set, and the correction amount corresponding to each range is set. The image forming apparatus according to claim 6.
The exposure member exposes the photoreceptor by line scanning,
The image forming apparatus, wherein the correction amount corresponding to each range is further set according to a scanning line in the line scanning. The image forming apparatus according to any one of claims 2 to 7,
The separation distance before wear of the distance regulating member, where the initial separation distance that is the initial value of the separation distance is DI, and the working distance that is the distance between the exposure member and the focal point of the exposure member is Dw. ,
Dw <DI
The image forming apparatus in which the initial separation distance is set so as to satisfy the above relationship. The image forming apparatus according to claim 8.
DE is a final separation distance that is the final separation distance after the wear of the distance regulating member and is the final value of the separation distance.
Dw-DE <DI-Dw
The image forming apparatus in which the initial separation distance and the final separation distance are set so as to satisfy the relationship. The image forming apparatus according to claim 8 or 9, wherein
The controller is
In the determination process, the correction amount for decreasing the light amount is determined as the count value increases until the separation distance becomes equal to the working distance due to wear of the distance regulating member, and then the count value increases. An image forming apparatus that determines the correction amount to increase the amount of light. The image forming apparatus according to any one of claims 1 to 10,
The distance regulating member is provided in two corresponding to both ends in the longitudinal direction of the photoconductor,
When the wear speeds of the respective distance regulating members are different, the control unit estimates the separation distance between the both ends based on each wear estimation amount in the determination process, and sets the correction amount accordingly. An image forming apparatus to be determined. An image forming apparatus comprising: a photoconductor; an exposure member that exposes the photoconductor; and a distance regulating member that regulates a separation distance between the photoconductor and the exposure member to a predetermined distance. A method for correcting the amount of light,
An estimation step of estimating the separation distance that changes due to wear of the distance regulating member;
A determination step of determining a correction amount for correcting the light amount of the exposure member based on the separation distance estimated in the estimation step;
A correction step of correcting the light amount by the correction amount determined in the determination step. The light amount correction method for an exposure member according to claim 12,
The photoconductor has a rotation shaft, and the distance regulating member is configured to contact the photoconductor, and the method includes:
A counting step of counting a parameter whose value changes with the rotation of the photosensitive member;
The exposure member light amount correction method in which, in the determination step, the separation distance is estimated from the count value counted in the counting step.

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