JP2013041162A - Image forming apparatus, control device, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To approximate an image density or a toner concentration of a specific position to a vale when the sensitivity of a plurality of detecting means that are provided at mutually different positions is normal, even if any sensitivity of the plurality of detecting means is lower than the normal sensitivity, in a case where the image density or the toner concentration of the specific position is obtained by using the plurality of detecting means.SOLUTION: An image forming apparatus 100 includes a plurality of sensors 24 for optically detecting an image on any surface of a photoreceptor 11, an intermediate transfer body 20, and a recording medium P at mutually different positions in the direction crossing with a moving direction. A control section 4 forms an adjustment image on a forming surface by an image forming section 7, calculates the density of the adjustment image on the basis of output signals of the sensors 24 and calculates a weighted average value of the density by using weights determined to the mutually different positions so as to, when a difference of outputs of the plurality of sensors 24 exceeds a threshold, compensate low sensitivity of a sensor the sensitivity of which is relatively low among the plurality of sensors 24.

Description

  The present invention relates to an image forming apparatus, a control apparatus, and a program.

The density of the image formed by the image forming apparatus may deviate from the density corresponding to the image data. Therefore, a technique has been proposed in which the density of the formed image is measured and the image forming apparatus is adjusted so that the difference between the density and the density corresponding to the image data is small.
For example, in Patent Document 1, two sensors that measure the amount of reflected light are provided near the surface of an intermediate transfer member, and the output values of the two sensors are compared in the absence of a toner image on the intermediate transfer member. It has been proposed to measure the density of an image using the larger sensor.
In Patent Document 2, two sensors for measuring the amount of reflected light are provided near the surface of the intermediate transfer member at positions corresponding to the upstream side and the downstream side in the toner supply direction with respect to the developing roller, and the developing device is set for a predetermined time. After the toner is replenished, the output values of the two sensors are compared, the presence or absence of dirt on the intermediate transfer member is determined based on the difference between the two output values, and the toner density or the like is changed according to the presence or absence of dirt. Has been proposed.

JP-A-2005-17542 Japanese Patent No. 4051533

  In the present invention, when the image density or the toner density at a specific position is obtained using a plurality of detection means provided at different positions, even if the sensitivity of any of the plurality of detection means is lower than the normal sensitivity. An object of the present invention is to bring the image density or toner density at a specific position close to the value when the sensitivity of a plurality of detection means is normal.

  The image forming apparatus according to claim 1 is a photosensitive member that is a roller whose surface potential changes when irradiated with light, a charging device that charges the surface, and a latent image formed on the charged surface by exposure based on image data. An exposure device for writing an image, a developing device for developing a latent image written on the surface, and an image formed on the surface by development to an image carrier whose surface is moved as the photoconductor rotates. A plurality of image forming means having a transfer device for transferring, and a plurality of optically detecting images provided at different positions in a direction intersecting a moving direction of the surface of one of the photosensitive member and the image carrier. When an event defined as an opportunity to adjust the density of the image is detected, an image for adjustment is formed on the surface of either the photoconductor or the image carrier by the image forming unit, Density calculating means for calculating the density of the image for adjustment based on the output signals of the plurality of detecting means; and the density of the image at a specific position on the surface of either the photoconductor or the image carrier. Weighted average value calculating means for calculating a weighted average value of the density calculated by the density calculating means using weights determined for the different positions as determined by a weighted average of the densities of images at different positions. And when the difference between the output values of the plurality of detection means exceeds a threshold value, the weight is determined to compensate for the low sensitivity of the detection means having a relatively low sensitivity among the plurality of detection means. Changing means for changing to the weight, and adjusting means for adjusting the image forming means to make the weighted average value calculated by the weighted average value calculating means close to the target value corresponding to the adjustment image. The features.

The image forming apparatus according to claim 2 is the image forming apparatus according to claim 1, wherein the changing unit detects each of the detection values based on a ratio of output values of the detection units to a sum of output values of the plurality of detection units. A weight for the means is calculated.
An image forming apparatus according to a third aspect is the image forming apparatus according to the first or second aspect, wherein the adjustment image has the same area ratio determined at the different positions.
The image forming apparatus according to claim 4 is the image forming apparatus according to claim 1 or 2, wherein the adjustment images have different area ratios at the different positions, and each of the positions has a step. A plurality of different area ratios are defined.

  The image forming apparatus according to claim 5 is a photosensitive member which is a roller whose surface potential changes when irradiated with light, a charging device which charges the surface, and a latent image formed by exposure based on image data on the charged surface. An exposure device for writing an image, a developing device for developing the latent image with toner conveyed in one direction on a conveying path along an axial direction of a developing roller provided with an outer peripheral surface facing the surface, and the developing device Image forming means having a transfer device for transferring an image formed on the surface to an image holding body whose surface is moved in accordance with rotation of the photoconductor, and provided at different positions on the conveyance path; When a plurality of measuring means for measuring the toner density and an event defined as an opportunity to adjust the density of the image are detected, the toner density at a specific position on the conveyance path is A weighted average value for calculating a weighted average value of the densities measured by the plurality of measuring means using a weight determined for the plurality of positions as determined by a weighted average of the density of toner at a plurality of positions. When the difference between the output values of the calculating means and the plurality of measuring means exceeds a threshold value, the weight is compensated for the low sensitivity of the measuring means having relatively low sensitivity among the plurality of measuring means. The image forming apparatus includes: a changing unit that changes the weight to a predetermined weight; and an adjusting unit that adjusts the developing device to bring the weighted average value calculated by the weighted average value calculating unit closer to a target value.

According to a sixth aspect of the present invention, there is provided a control device comprising: a photosensitive member that is a roller whose surface potential changes when irradiated with light; a charging device that charges the surface; and a latent image formed by exposing the charged surface based on image data. An exposure device for writing the image, a developing device for developing the latent image written on the surface, and an image formed on the surface by development is transferred to an image carrier whose surface is moved in accordance with the rotation of the photoconductor And a plurality of optically detecting images provided at different positions in a direction crossing a moving direction of the surface of either the photoconductor or the image carrier. A communication unit that communicates with an image forming apparatus having a detection unit; and an event defined as an opportunity to adjust the density of the image, and the photosensitive member and the image are detected by the image forming unit. A density calculation unit that forms an adjustment image on any surface of the holder and calculates a density of the adjustment image based on output signals of the plurality of detection units; and one of the photoconductor and the image carrier Calculated by the density calculation means using weights determined for the different positions so that the density of the image at a specific position on the surface is obtained by a weighted average of the densities of the images at different positions. A weighted average value calculating means for calculating a weighted average value of the density and a difference between output values of the plurality of detecting means exceeds a threshold value, the weight is relatively sensitive among the plurality of detecting means. A changing means for changing to a weight determined so as to compensate for the low sensitivity of the low detection means, and the weighted average value calculated by the weighted average value calculating means to be close to the target value corresponding to the adjustment image Adjustment of And having an adjusting means for performing said image forming means.
According to a seventh aspect of the present invention, there is provided a control device comprising: a photosensitive member that is a roller whose surface potential changes when irradiated with light; a charging device that charges the surface; and a latent image formed by exposing the charged surface based on image data. An exposure device for writing the latent image, a developing device for developing the latent image with toner conveyed in one direction on a conveying path along an axial direction of a developing roller provided with an outer peripheral surface facing the surface, and the surface by developing. Image forming means having a transfer device for transferring the image formed on the image holding member whose surface is moved in accordance with the rotation of the photosensitive member; and the toner provided at different positions on the conveyance path A communication unit that communicates with an image forming apparatus having a plurality of measurement units that measure the density of the image, and an event defined as an opportunity to adjust the density of the image. The toner density at a specific position on the road was measured by the plurality of measuring means using the weights determined for the plurality of positions so that the weighted average of the toner densities at the plurality of positions was obtained. When the difference between the weighted average value calculating means for calculating the weighted average value of the concentration and the output values of the plurality of measuring means exceeds a threshold, the weight is relatively low in sensitivity among the plurality of measuring means. An adjustment unit for changing the weight to a predetermined weight so as to compensate for the low sensitivity of the measurement unit, and an adjustment for adjusting the developing device to make the weighted average value calculated by the weighted average value calculating unit close to the target value Means.

According to an eighth aspect of the present invention, there is provided a program for executing a computer on a photoconductor that is a roller whose surface potential changes when irradiated with light, a charging device that charges the surface, and exposure based on image data on the charged surface. An exposure device that writes a latent image, a developing device that develops the latent image written on the surface, and an image carrier that moves the surface of the image formed on the surface by development as the photoconductor rotates. An image forming means having a transfer device for transferring the image to the surface, and optically detecting the image provided at different positions in a direction intersecting a moving direction of the surface of one of the photosensitive member and the image holding member. A communication unit that communicates with an image forming apparatus having a plurality of detection units; and an event that is defined as an opportunity to adjust the density of the image. A density calculating unit that forms an adjustment image on the surface of either the recording member or the image holding member, and calculates the density of the adjustment image based on output signals of the plurality of detection units; Using weights defined for the different positions so that the density of the image at a particular position on any surface of the image carrier is determined by a weighted average of the densities of the images of the different positions; The weighted average value calculating means for calculating the weighted average value of the density calculated by the density calculating means, and the difference between the output values of the plurality of detecting means exceeds a threshold value, the weight is determined as the plurality of detecting means. The weighting average value calculated by the weighted average value calculating means corresponds to the adjustment image, the changing means for changing to a weight determined so as to compensate for the low sensitivity of the detection means of relatively low sensitivity To the target value The adjustment for characterizing to function as an adjustment means for performing said image forming means.
According to a ninth aspect of the present invention, there is provided a computer program comprising: a photosensitive member that is a roller whose surface potential changes when irradiated with light; a charging device that charges the surface; and an exposure based on image data on the charged surface. An exposure device for writing a latent image, a developing device for developing the latent image with toner conveyed in one direction on a conveying path along an axial direction of a developing roller provided with an outer peripheral surface facing the surface, and development An image forming unit having a transfer device for transferring the image formed on the surface to an image holding member whose surface is moved in accordance with the rotation of the photoconductor, and provided at different positions on the conveyance path; Communication means for communicating with an image forming apparatus having a plurality of measurement means for measuring the toner density, and an event defined as an opportunity for adjusting the image density The weights determined for the plurality of positions using the weighted average of the toner concentrations at the plurality of positions so that the toner density at the specific position on the conveyance path is obtained by a weighted average of the toner densities at the plurality of positions. The weighted average value calculating means for calculating the weighted average value of the concentration measured by the measuring means, and when the difference between the output values of the plurality of measuring means exceeds a threshold value, the weight is selected from the plurality of measuring means. Changing means for changing to a weight determined so as to compensate for the low sensitivity of the measuring means having relatively low sensitivity, and adjustment for bringing the weighted average value calculated by the weighted average value calculating means closer to the target value It functions as an adjusting means applied to the developing device.

According to the first, sixth, and eighth aspects of the invention, when the image density at a specific position is obtained using a plurality of detection units provided at different positions, the sensitivity of any of the plurality of detection units is high. Even if the sensitivity is lower than the normal sensitivity, the image density at a specific position can be brought close to the value when the sensitivity of the plurality of detection means is normal.
According to the invention which concerns on Claim 2, a weight can be defined reflecting the difference in the sensitivity of a some detection means.
According to the invention of claim 3, the amount of calculation can be reduced as compared with the case where different area ratios are determined.
According to the fourth aspect of the invention, the number of adjustment images can be reduced as compared with the case where the same area ratio is determined.
According to the fifth, seventh, and ninth aspects of the invention, when the toner density at a specific position is obtained using a plurality of detection units provided at different positions, the sensitivity of any of the plurality of detection units is Even if the sensitivity is lower than the normal sensitivity, the toner density at a specific position can be brought close to the value when the sensitivity of the plurality of detection means is normal.

2 is a diagram illustrating a hardware configuration of the image forming apparatus 100. FIG. 1 is a diagram illustrating a configuration of an image forming engine 10 from the front side of an image forming apparatus 100. FIG. FIG. 2 is a diagram showing the internal structure of the developing device 14 from the front side of the image forming apparatus 100. FIG. 2 is a diagram showing the internal structure of the developing device 14 from the upper side of the image forming apparatus 100. 3 is a diagram illustrating a configuration of a toner density sensor 17. FIG. It is a figure which shows the position in which the 1st sensor 24A and the 2nd sensor 24B were provided. 2 is a diagram illustrating a configuration of a sensor 24. FIG. It is a figure which shows the image 25 for adjustment. It is a figure which shows distribution of the image density formed with the image forming apparatus. FIG. 6 is a diagram illustrating an example of sensitivity abnormality caused by components constituting the sensor 24. It is a figure which shows the example of the sensitivity abnormality resulting from the white spot of the image for adjustment 25. It is a figure which shows the density | concentration when the sensitivity of 1st sensor 24A is normal, and when it is low. It is a figure which shows the procedure of the process which the control part 4 performs. 2 is a block diagram illustrating a functional configuration of the image forming apparatus 100. FIG. It is a figure which shows the example which set the weight according to the area ratio. 2 is a block diagram illustrating functional configurations of a control device 200 and an image forming apparatus 300. FIG.

(1) Basic Configuration of Embodiment FIG. 1 is a diagram illustrating a hardware configuration of the image forming apparatus 100.
The storage unit 5 is, for example, a hard disk storage device, and stores an OS (Operating System), application programs, and the like. The control unit 4 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory) (all not shown). The ROM stores firmware that describes hardware and OS startup procedures. The RAM is used for storing data when the CPU executes a program.
The instruction receiving unit 1 includes various operators for a user to input instructions to the image forming apparatus 100. The instruction received by the instruction receiving unit 1 is sent to the control unit 4, and the control unit 4 controls the operation of the image forming apparatus 100 according to this instruction.
A communication I / F (Interface) 6 is connected to communication means (not shown) such as a LAN (Local Area Network) and mediates communication between the image forming apparatus 100 and other apparatuses.

The image reading unit 2 optically reads a document and generates an image signal. Specifically, the image reading unit 2 includes a platen glass, a light source, an optical system, and an imaging device (all of which are not shown), and the light source irradiates light onto the document placed on the platen glass. The reflected light that has been reflected is separated into R (Red), G (Green), and B (Blue) colors via the optical system and enters the image sensor. The imaging element converts incident light into an image signal and supplies the image signal to the image processing unit 3.
The image processing unit 3 performs A / D conversion on the image signal supplied from the image reading unit 2, and performs noise removal, gamma correction, R color, G color, B color to Y (Yellow) color, M (Magenta) color, Conversion to C (Cyan) color, K (Black) color, screen processing, and the like are performed. Thus, image data representing the gradation for each color and each pixel is generated.

The main components of the image forming unit 7 are the image forming engines 10Y, 10M, 10C, and 10K, the intermediate transfer member 20, the medium transport unit 30, and the fixing device 50.
The image forming engines 10Y, 10M, 10C, and 10K transfer toner images of Y color, M color, C color, and K color to the intermediate transfer body by electrophotography based on the image data supplied from the image processing unit 3, respectively. Overlaid on the surface of 20. Since the image forming engines have the same configuration, the image forming engines are collectively referred to as the image forming engines when it is not necessary to distinguish the image forming engines. In that case, Y, M, C, and K are also omitted for the components of the image forming engine 10.

FIG. 2 is a diagram showing the configuration of the image forming engine 10 from the front side of the image forming apparatus 100. The image forming engine 10 includes a charging device 12, an exposure device 13, a developing device 14, a primary transfer device 15, and the like around a photoconductor 11.
The photoconductor 11 is a roller that is rotationally driven in the direction of arrow A, and a photosensitive layer made of a semiconductor whose potential changes when irradiated with light is provided on the surface thereof.
The charging device 12 is, for example, a corotron charging device, a roller charging device, or the like, and charges the surface of the photoconductor 11 to a predetermined potential.
The exposure device 13 writes a latent image on the surface of the photoconductor 11. Specifically, a laser beam LB corresponding to the gradation of each pixel represented by the image data supplied from the image processing unit 3 is generated, and the main scanning in which the surface of the photoconductor 11 is defined by the laser beam LB. Scan in the direction (for example, the axial direction of the photoconductor 11). Then, a latent image is formed on the surface of the photoconductor 11 by lowering the potential of the portion irradiated with the laser beam LB. When the photosensitive member 11 is driven to rotate, writing of latent images in units of scanning lines in the main scanning direction is repeated in the circumferential direction (sub-scanning direction).

  The developing device 14 develops the latent image formed on the surface of the photoconductor 11. FIG. 3 is a view showing the internal structure of the developing device 14 from the front side of the image forming apparatus 100. FIG. 4 is a view showing the internal structure of the developing device 14 from the upper side of the image forming apparatus 100. Inside the housing 141, a developing roller 142, a first conveying member 143, and a second conveying member 144 are provided in this order from the photosensitive member 11 side. The developing roller 142 is a roller that attracts a magnetic material by magnetic force. The 1st conveyance member 143 and the 2nd conveyance member 144 are the screws which provided the helical blade | wing around the axis | shaft. An opening 141A is provided at a portion of the housing 141 facing the photoconductor 11 so as to expose the outer peripheral surface of the developing roller 142, whereby the outer peripheral surfaces of the developing roller 142 and the photoconductor 11 are opposed to each other. It has been made. A partition 145 extending in the axial direction of both members is provided between the first transport member 143 and the second transport member 144, and a gap 145 </ b> A is provided between both ends in the longitudinal direction of the partition 145 and the side wall of the housing 141. 145B is provided. The space on the first transport member 143 side with the partition wall 145 as a boundary is referred to as a first transport path 143A, and the space on the second transport member 144 side is referred to as a second transport path 144A.

Inside the housing 141, a two-component developer composed of toner and carrier is accommodated. The toner is obtained by coloring resin powder with a color material of Y color, M color, C color, or K color. The carrier is a powder made of a magnetic material. When the first conveying member 143 and the second conveying member 144 are driven to rotate, the two-component developer is frictionally charged by stirring, and in the first conveying path 143A, in the direction of the arrow J, and in the second conveying path 144A, the arrow. Although transported in directions opposite to each other in the K direction, the first transport path 143A and the second transport path 144A are connected to each other by gaps 145A and 145B to form a peripheral circuit. Is circulated along this circuit.
When the two-component developer is transported along the first transport path 143A, it adheres to the outer peripheral surface of the developing roller 142 that is rotationally driven by a magnetic force. A developing bias voltage is applied to the developing roller 142, whereby the toner is charged with a polarity opposite to that of the latent image. As a result, the toner is transferred onto the photoconductor 11 and the latent image is developed to form a toner image. The carrier deprived of toner is continuously conveyed along the first conveyance path 143A.

  A toner replenishing port 141B is provided at a position corresponding to the second transport path 144A on the top plate of the housing 141, and a toner replenishing device 146 containing toner is connected to the toner replenishing port 141B by a pipe 146A. A first toner concentration sensor 17 </ b> A and a second toner concentration sensor 17 </ b> B are provided on the surface of the top plate of the housing 141 that faces the developing roller 142. The first toner density sensor 17A and the second toner density sensor 17B are provided to face two different points on the outer peripheral surface of the developing roller 142. The two different points are, for example, two points in the axial direction of the developing roller 142, and the first toner density sensor 17 </ b> A is located on the back side of the image forming apparatus 100 across the middle point of the shaft of the developing roller 142. The second toner density sensor 17B is located on the front side.

  Since the first toner density sensor 17A and the second toner density sensor 17B have the same configuration, they are collectively referred to as the toner density sensor 17 when it is not necessary to distinguish between them. FIG. 5 is a diagram showing the configuration of the toner density sensor 17. An opening 172 is provided on the side of the housing 171 facing the developing roller 142, and when the light generated by the light source 173 passes through the opening 172 and is irradiated onto the developing roller 142, the surface of the developing roller 142 is provided. Or the toner reflects light. The light receiving element 174 receives the diffuse reflected light and outputs a signal indicating the intensity of the diffuse reflected light to the control unit 4. The light receiving element 175 receives the specular reflection light and outputs a signal indicating the intensity of the specular reflection light to the control unit 4. The light receiving element 174 is used to measure the C, M, and Y toner densities, and the light receiving element 175 is used to measure the K toner density.

The control unit 4 calculates the reflectance from the output signal of the toner density sensor 17, and converts this reflectance into the toner density. The control unit 4 issues a toner supply instruction to the toner supply device 146 when the toner density falls below the target value. Upon receiving this instruction, the toner replenishing device 146 discharges toner into the housing 141 through the pipe 146A.
The control unit 4 adjusts the amount of toner replenishment per time by adjusting the length of time spent for one toner replenishment (hereinafter referred to as “toner replenishment time”). The control unit 4 determines the toner replenishment time according to the speed of toner consumption. For example, the toner replenishment time is increased as the average value per page of the image count value within a predetermined period is higher. The image count value is a cumulative value of the number of pixels developed with toner.

The intermediate transfer member 20 is an endless belt wound around the driving roller 21 and the roller 22, and the intermediate transfer member 20 circulates in the direction of arrow B as the driving roller 21 is driven to rotate. A primary transfer device 15 is provided at a position facing the photoconductor 11 with the intermediate transfer body 20 interposed therebetween. The primary transfer device 15 is, for example, a corotron charging device, and applies a transfer bias voltage having a polarity opposite to that of the toner image to the intermediate transfer member 20. The intermediate transfer member 20 is charged with a reverse polarity to the toner image by the transfer bias voltage, and the toner image is transferred to the intermediate transfer member 20. This transfer operation is called primary transfer.
The above is the configuration of the image forming engine 10. The toner images formed by the image forming engines 10Y, 10M, 10C, and 10K are transferred onto the intermediate transfer member 20 in an overlapping manner.

The medium transport unit 30 transports the recording medium P. Specifically, recording media P such as paper are stacked and stored in the medium storage unit 31, and the feed roller 32 is rotationally driven in synchronization with the movement of the toner image on the intermediate transfer body 20. Thus, the recording medium P is sent out one by one to the transport path 34. The recording medium P is transported along the transport path 34 by rotating the transport roller 33 provided on the transport path 34.
The secondary transfer device 23 is a roller that applies a transfer bias voltage having a polarity opposite to that of the intermediate transfer member 20 to the recording medium P. The outer peripheral surface of the secondary transfer device 23 is the outer periphery of the roller 22 with the intermediate transfer member 20 interposed therebetween. It is abutted against the surface. When the recording medium P enters a position where the secondary transfer device 23 and the intermediate transfer body 20 are in contact with each other, the recording medium P is charged with a polarity opposite to that of the intermediate transfer body 20 by the transfer bias voltage. Transferred to the surface. This transfer operation is called secondary transfer.
The recording medium P on which the toner image is transferred is conveyed to the fixing device 50. The fixing device 50 fixes the toner image on the surface of the recording medium P by heating and pressing the toner image. The recording medium P on which the toner image is fixed is discharged to the discharge unit 37.

  In short, the image forming unit 7 according to the present embodiment has an image formed on the photosensitive member which is a roller whose potential on the outer peripheral surface changes when irradiated with light, a charging device which charges the photosensitive member, and the charged photosensitive member. An exposure device for writing a latent image by exposure based on data, a developing device for developing the latent image written on the photoconductor, and an image formed on the photoconductor by development on the surface as the photoconductor rotates. 2 is an example of an image forming unit having a transfer device that transfers to an image holding member to which the image is moved. The transfer device is a concept including the primary transfer device 15 and the secondary transfer device 23 of the present embodiment. The image carrier is a concept including the intermediate transfer member 20 and the recording medium P of the present embodiment. The intermediate transfer member 20 is not limited to a belt, and may be a roller, for example. In short, the image carrier is a concept including all objects to which an image formed on the photosensitive member is transferred.

  A first sensor 24A and a second sensor 24B are provided downstream of the image forming engine 10K in the driving direction of the intermediate transfer member 20. FIG. 6 is a diagram illustrating positions where the first sensor 24A and the second sensor 24B are provided. The first sensor 24 </ b> A and the second sensor 24 </ b> B are provided to face two different points on the surface of the intermediate transfer body 20. The two points that are different from each other are two points in a direction intersecting the driving direction of the intermediate transfer member 20, and the first sensor 24 </ b> A is located on the back side of the image forming apparatus 100 across the center line of the intermediate transfer member 20. The second sensor 24B is located on the front side.

Since the first sensor 24 </ b> A and the second sensor 24 </ b> B have the same configuration, they are collectively referred to as the sensor 24 when it is not necessary to distinguish between them. FIG. 7 is a diagram illustrating the configuration of the sensor 24. An opening 242 is provided on the side of the housing 241 facing the recording medium P, and when the light generated by the light source 243 passes through the opening 242 and is irradiated onto the intermediate transfer body 20, the intermediate transfer body 20. The surface or toner reflects the light. The light receiving element 244 receives the diffuse reflected light and outputs a signal indicating the intensity of the diffuse reflected light to the control unit 4. The light receiving element 245 receives the specular reflection light and outputs a signal indicating the intensity of the specular reflection light to the control unit 4. The light receiving element 244 is used for detecting an image formed in C, M, and Y colors, and the light receiving element 245 is used for detecting an image formed in K color.
In short, the sensor 24 is an example of a plurality of detection means that optically detect the image provided at different positions in the direction intersecting the moving direction of the surface of either the photoconductor or the image carrier. is there.
The control unit 4 uses the output signal of the sensor 24 for two purposes of image density adjustment and image formation position adjustment. Specifically, it is as follows.

(1.1) Image Density Adjustment Image density adjustment is a process for adjusting the image forming apparatus 100 so that the density of an image formed by the image forming apparatus 100 approaches a target value. The control unit 4 performs the image density adjustment when detecting an event defined as a trigger for executing the image density adjustment. The predetermined events include, for example, turning on the power to the image forming apparatus 100, receiving an instruction for image formation by the instruction receiving unit 1, completion of image formation corresponding to the instruction, and image count value after the previous image density adjustment. Reaching the threshold value, reaching the threshold value of the amount of change in the temperature or humidity inside the image forming apparatus 100 after the previous image forming position adjustment, filling the toner supply device 146 with toner, and a recording medium jammed in the conveyance path 34 P removal, reception of an image density adjustment instruction by the instruction receiving unit 1, and the like. The image count value is a cumulative value of the number of pixels developed with toner. The control unit 4 executes image density adjustment according to the procedure described by the program stored in the storage unit 5.

  The storage unit 5 stores adjustment image data. FIG. 8A is a diagram illustrating an adjustment image 25 formed on the intermediate transfer body 20 based on the adjustment image data. The adjustment image 25 includes adjustment images 25Y, 25M, 25C, and 25K, and is formed with toners of Y color, M color, C color, and K color, respectively. The same adjustment image 25 is formed on the intermediate transfer body 20 at positions corresponding to the first sensor 24A and the second sensor 24B. FIG. 8B shows the adjustment image 25Y. The adjustment image 25Y is obtained by arranging a plurality of rectangular images along the driving direction of the intermediate transfer body 20. Each of the rectangular images has steps such as 100%, 80%, 60%, 40%, and 20%. Different area ratios are specified. The adjustment images 25M, 25C, and 25K are the same as the adjustment image 25Y except that the toner colors are different.

  When any of the above-mentioned events set as the trigger for executing the image density adjustment is detected, the control unit 4 reads out the adjustment image data from the storage unit 5 and supplies it to the exposure device 13. The adjustment image 25 is formed, and the reflected light reflected by the adjustment image 25 is read by the first sensor 24A and the second sensor 24B. The control unit 4 calculates each reflectance from the signals output from the first sensor 24A and the second sensor 24B, converts the reflectance into an image density (optical density), and a weighted average of the two image densities. The image density at the comparison position 24C is obtained by calculating the value. On the other hand, the image density corresponding to the area ratio specified by the adjustment image data is called a target value. The comparison position 24C is a specific position predetermined as a position for comparing the weighted average value with the target value. A method for calculating the weighted average value will be described later. Then, the control unit 4 performs adjustment for bringing the weighted average value closer to the target value based on the difference between the weighted average value and the target value. The contents of the adjustment include, for example, adjustment of the toner supply amount from the toner supply device 146, adjustment of the charging potential of the charging device 12, adjustment of the exposure amount of the exposure device 13, adjustment of the developing bias potential of the developing device 14, and image data. Any one or two or more combinations of rewriting of the lookup table to be corrected or the like is used, but since a well-known technique is applied to this adjustment, a description of a specific procedure is omitted.

(1.2) Image Forming Position Adjustment In the image forming position adjustment, the image forming apparatus 100 is adjusted so that the position of the image formed by the image forming apparatus 100 on the recording medium P approaches the position specified by the image data. It is processing. The control unit 4 performs the image formation position adjustment when detecting an event defined as an opportunity to execute the image formation position adjustment. The predetermined events include, for example, power-on to the image forming apparatus 100, reception of an image formation instruction by the instruction receiving unit 1, completion of image formation corresponding to the instruction, and image count after the previous image formation position adjustment. Reaching the threshold value, reaching the threshold value of the amount of change in the temperature or humidity inside the image forming apparatus 100 after the previous image forming position adjustment, removing the recording medium P jammed in the transport path 34, and the instruction receiving unit 1 For example, accepting an image forming position adjustment instruction. The control unit 4 performs image forming position adjustment according to the procedure described by the program stored in the storage unit 5.

The image forming position adjustment includes adjustment of the image forming position in the driving direction of the intermediate transfer body 20, adjustment of the image forming position in the direction intersecting with the driving direction of the intermediate transfer body 20, and adjustment of the inclination of the image. For example, in the case of adjustment in the driving direction of the intermediate transfer member 20, the control unit 4 forms the adjustment image 25 on the intermediate transfer member 20, the timing when the front end of the adjustment image 25 is detected, and the adjustment image 25. Based on the difference from the target time when the front end reaches the measurement position of the sensor 24, the amount of deviation of the formation position in the driving direction of the intermediate transfer member 20 is obtained. And the control part 4 performs the adjustment for reducing this deviation | shift amount. The content of the adjustment is, for example, adjustment of the start time of writing of the latent image by the exposure device 13, but since a known technique is applied for this adjustment, a description of a specific procedure is omitted.
The basic configuration of the image forming apparatus 100 has been described above.

(2) Calculation of Weighted Average Value Next, calculation of the weighted average value at the comparison position 24C will be described.
First, the reason for obtaining the weighted average value of image density will be described.
FIG. 9 is a diagram showing a distribution of image density formed by the image forming apparatus. Specifically, image data designating a uniform area ratio in the main scanning direction is input to the image forming unit 7 and the optical density of the image formed on the recording medium P is measured with a densitometer. The vertical axis represents the image density, and the horizontal axis represents the position in the main scanning direction. Reference numerals 100A and 100B denote measurement results of the image forming apparatuses 100A and 100B, respectively. The image forming apparatuses 100A and 100B are apparatuses having the same configuration as the image forming apparatus 100 described above.

As shown in the figure, the density of the images formed by the image forming apparatuses 100A and 100B is different from the target value except for a part thereof. Further, although the image forming apparatuses 100 </ b> A and 100 </ b> B have the same configuration, the image density distributions formed by the two are different. There are various causes for the image density to deviate from the target value. For example, the following can be cited as causes derived from the components of the image forming unit 7.
Unevenness in the main scanning direction of the thickness of the photosensitive layer of the photoreceptor 11.
Unevenness of the charging voltage of the charging device 12 in the main scanning direction.
Unevenness in the main scanning direction of the light amount of the exposure device 13
Unevenness in the main scanning direction of the toner density of the developing device 14
Unevenness in the main scanning direction of the developing bias voltage of the developing device 14
Unevenness in the main scanning direction of the transfer bias voltage of the primary transfer device 15 and the secondary transfer device 23.
Unevenness in the main scanning direction of heat and pressure of the fixing device 50.
Deformation of the photosensitive member 11, the developing roller 142, the intermediate transfer member 20, the secondary transfer device 23, and the like.
Since the size of the unevenness and deformation differs for each individual image forming apparatus 100, the image density distribution and the degree of deviation from the target image density value also differ for each individual image forming apparatus 100. .

Now, sensors for the purpose of adjusting the image forming position are usually provided at two points sandwiching the center line of the intermediate transfer member 20 as shown in FIGS. On the other hand, the image density adjustment is normally performed based on the image density in the vicinity of the center line of the intermediate transfer member 20, but if the sensor for adjusting the image forming position is also used for image density adjustment. This is advantageous in terms of cost. For this reason, in the present embodiment, the image density at the comparison position 24C is calculated based on the image density at the measurement position of the first sensor 24A and the second sensor 24B. The weighted average value of the image density at the position is obtained. The reason is as follows.
In the example of the image forming apparatus 100A shown in FIG. 9, the image densities at the measurement positions of the first sensor 24A and the second sensor 24B are 0.8 and 1.0, respectively. If the first sensor 24A and the second sensor 24B are provided at a position equidistant from the comparison position 24C, the change in image density is linear in this example, and therefore the density at the comparison position 24C is the first sensor. It is equal to the arithmetic average value 0.9 of the image density at the measurement positions of 24A and the second sensor 24B. Therefore, for example, when the target value is 0.95, the control unit 4 performs image density adjustment so as to increase the density of the formed image by 0.05.

  On the other hand, in the example of the image forming apparatus 100B shown in FIG. 9, the image densities at the measurement positions of the first sensor 24A and the second sensor 24B are 0.8 and 1.0, respectively, which is the same as the example of the image forming apparatus 100A. However, since the change in the image density is curvilinear, the image density at the comparison position 24C is different from the arithmetic average value 0.9 of the image density at the measurement position of the first sensor 24A and the second sensor 24B. Become. In this example, it is 0.86. If the image density adjustment is executed based on the arithmetic average value 0.9, the density increases only by 0.05, so that the image density at the adjusted comparison position 24C is 0.86 + 0.05 = 0.91. The target value of 0.95 is not reached.

In order to eliminate such inconvenience, in the present embodiment, the image density at the comparison position 24C is calculated by the following method.
If the image densities obtained from the output signals of the first sensor 24A and the second sensor 24B are V1 and V2, respectively, the weighted average value Vw at the comparison position 24C is obtained by the following equation.
[Equation 1]
Vw = (W1 · V1 + W2 · V2) / (W1 + W2) Formula (1)
However, W1 and W2 are weights for V1 and V2, respectively.

The weights W1 and W2 may be determined by any method, but an example is as follows. When W1 + W2 = 1 and formula (1) is transformed,
[Equation 2]
W1 = (Vw−V2) / (V1−V2) Formula (2)
It becomes. Image data designating a uniform area ratio in the main scanning direction is input to the image forming unit 7 of the image forming apparatus 100, and the density of the image formed on the intermediate transfer member 20 is measured with the measurement position of the first sensor 24A and the first position. Measurement is performed at the measurement position of the two sensors 24B and the comparison position 24C, and is substituted into the equation (2). For example, in the case of the image forming apparatus 100B shown in FIG. 9, the weights W1 = 0.7 and W2 = 0.3 are obtained by substituting the image densities V1 = 0.8, V2 = 1.0, and Vw = 0.86. Is obtained. The weighted average value calculated by Equation (1) using the weight determined in this manner is a value that approximates the actual image density at the comparison position 24C.

Note that any method may be used as the method of determining the weight. As described above, there are several possible causes of the image density deviating from the target value, such as unevenness of the thickness of the photosensitive layer of the photoconductor 11, and the like. 11 is known, the image density distribution is predicted based on the measured value of the photosensitive layer thickness, and the image densities V1, V2, Vw in the predicted image density distribution are predicted. May be substituted into equation (2) to determine the weight.
Further, the image density distribution may vary during the operation of the image forming apparatus 100. For example, the two-component developer passes through the gap 145B from the second conveyance path 144A and enters the first conveyance path 143A, but the conveyance direction of the two-component developer changes before and after passing through the gap 145B. In the vicinity, the two-component developer repeats stay and flow alternately. Therefore, in the first conveyance path 143A, the image density is more likely to fluctuate toward the upstream side, so that the weighted average value is also affected by this fluctuation. In order to suppress the influence of this variation on the weighted average value, the upstream weight W2 may be set to a value smaller than the downstream weight W1.

(3) Change of weight Next, the change of the weight according to the sensitivity of the sensor 24 will be described.
FIG. 10 is a diagram illustrating an example of an abnormality in sensitivity caused by the components constituting the sensor 24. In FIG. This figure shows the result of measuring the density of the adjustment image 25 formed on the intermediate transfer member 20. The horizontal axis is the area ratio of the adjustment image, and the vertical axis is the output value of the sensor 24. In this example, the density is obtained based on the output value of the diffuse reflected light. In this case, the higher the area ratio, the greater the amount of diffusely reflected light, so the output value of the sensor 24 increases.
In this example, the same adjustment image 25 is measured by the first sensor 24A and the second sensor 24B. Therefore, the difference between the output values of the first sensor 24A and the second sensor 24B is solely due to the sensitivity of the first sensor 24A being lower than that of the second sensor 24B. The cause of the low sensitivity of the sensor 24 is that the minus side offset voltage of an amplifier (not shown) that amplifies the output signal of the light receiving element 244 and the light amount of the light source 243 are lower than the designed values. In the case of such a sensitivity abnormality due to the components of the sensor 24, the difference between the output value of the sensor 24 and the normal value tends to increase as the area ratio decreases.

FIG. 11 is a diagram illustrating an example of sensitivity abnormality due to white spots in the adjustment image 25. When the toner aggregates in the developing device 14 due to abnormal charging or insufficient stirring, the aggregated toner is difficult to be transferred from the developing roller 142 to the photoconductor 11, so that a portion corresponding to the aggregated toner may not be developed. When white spots occur, the amount of diffusely reflected light decreases, so even if the sensitivity of the sensor 24 is normal, the output value of the sensor 24 is lower than the normal value. That is, the apparent sensitivity of the sensor 24 is low. In this example, since the whiteout has occurred in the adjustment image 25 on the first sensor 24A side, the output value of the first sensor 24A is lower than the output value of the second sensor 24B. In the case of such an abnormality in sensitivity due to white spots, the difference between the output value of the sensor 24 and the normal value increases as the area ratio increases.
The sensitivity abnormality as in the above two examples may progress with time and reach a magnitude that cannot be ignored, or may be a magnitude that cannot be ignored from the beginning of installation of the image forming apparatus 100. Here, an example is shown in which the sensitivity of the first sensor 24A is lower than the sensitivity of the second sensor 24B, but the reverse is also possible.

  FIG. 12 is a diagram showing the density when the sensitivity of the first sensor 24A is normal and when the sensitivity is low. When the sensitivity of the first sensor 24A is low, the weighted average value obtained by the expression (1) using the measured value is lower than the actual image density at the comparison position 24C. When the image density adjustment is performed using this weighted average value, the difference between the weighted average value and the target value becomes larger than the actual value, so that the adjusted image density becomes higher than necessary. Therefore, it is necessary to change the weight so as to compensate for the low sensitivity of the first sensor 24A having a relatively low sensitivity. Therefore, in the present embodiment, when the sensitivity difference between the first sensor 24A and the second sensor 24B reaches a threshold value, the control unit 4 is based on the output value of the first sensor 24A and the output value of the second sensor 24B. Change the weight of the weighted average.

FIG. 13 is a diagram illustrating a procedure of processing executed by the control unit 4. The control unit 4 executes this process according to the procedure described by the program stored in the storage unit 5. The control unit 4 starts this process when detecting an event defined as an opportunity to execute image density adjustment. The storage unit 5 stores the weights W1 and W2 determined by the above-described method as initial values Wini1 and Wini2, respectively.
In step S <b> 11, the control unit 4 reads out the adjustment image data from the storage unit 5 and supplies the adjustment image data to the exposure device 13 to form the adjustment image 25 on the intermediate transfer member 20, and the reflection reflected by the adjustment image 25. The first sensor 24A and the second sensor 24B are caused to read the light.
In step S12, the control unit 4 obtains a difference between the output value of the first sensor 24A and the output value of the second sensor 24B, and compares this difference with a threshold value. Here, of the two output values, the higher one is UH, the lower one is UL, and if the difference between UH and UL is larger than the threshold T (step S12: YES), the process proceeds to step S13, where UH and UL When the difference between is smaller than the threshold T (step S12: NO), the process proceeds to step S14.

In step S13, the control unit 4 calculates weights as follows. The weight for the sensor 24 with the higher output value is WH, and the weight for the sensor 24 with the lower output value is WL.
[Equation 3]
WH = UH / (UH + UL)
WL = 1−WH Formula (3)
For example, when UH = 500 and UL = 400 are obtained, WH = 0.56 and WL = 0.44 (rounded to the second decimal place).
On the other hand, in step S14, the control unit 4 reads the initial values Wini1 and Wini2 from the storage unit 5, and sets Wini1 and Wini2 as the weights W1 and W2, respectively.

  In step S15, the control unit 4 obtains a weighted average value of the image density using the weight determined in this way, and executes image density adjustment using the weighted average value. Specifically, the control unit 4 calculates the respective reflectances from the signals output from the first sensor 24A and the second sensor 24B, and converts this reflectance into an image density. The control unit 4 substitutes the weighted average value at the comparison position 24C by substituting the image densities V1 and V2 thus obtained and the weights W1 and W2 determined in step S13 or S14 into the equation (1). calculate. The weighted average value thus calculated is a value that approximates the actual image density at the comparison position 24C. Then, the control unit 4 adjusts the image forming unit 7 so that the weighted average value approaches the target value. For example, the control unit 4 adjusts the toner supply amount from the toner supply device 146, adjusts the charging potential of the charging device 12, adjusts the exposure amount of the exposure device 13, adjusts the development bias potential of the developing device 14, and stores the image data. An adjustment instruction such as rewriting of the lookup table to be corrected is given to the image forming unit 7.

FIG. 14 is a block diagram illustrating a functional configuration of the image forming apparatus 100.
The image forming apparatus 100 includes an image forming unit 101, a detecting unit 102, a density calculating unit 103, a weighted average value calculating unit 104, an adjusting unit 105, and a changing unit 106.
The image forming unit 101 is a photosensitive member that is a roller whose surface potential changes when irradiated with light, a charging device that charges the surface, and exposure that writes a latent image on the charged surface based on image data. And a developing device for developing a latent image written on the surface, and a transfer device for transferring an image formed on the surface by development to an image holding member whose surface is moved as the photosensitive member rotates. And an image forming unit.
The detection means 102 is a plurality of detection means for optically detecting the image, which are provided at different positions in the direction intersecting the moving direction of the surface of either the photoconductor or the image carrier.
The density calculation unit 103 forms an adjustment image on the surface of either the photoconductor or the image carrier by the image forming unit when detecting an event defined as an opportunity to adjust the density of the image, A density calculating unit that calculates a density of the image for adjustment based on output signals of the plurality of detecting units;
The weighted average value calculation means 104 is different from each other so that the density of the image at a specific position on the surface of either the photoconductor or the image carrier can be obtained by the weighted average of the densities of the images at different positions. The weighted average value calculating means calculates a weighted average value of the density calculated by the density calculating means using a weight determined for the position.
The changing unit 106 compensates for the low sensitivity of the detection unit having a relatively low sensitivity among the plurality of detection units when the difference between the output values of the plurality of detection units exceeds a threshold value. It is a change means to change to the weight defined in (1).
The adjusting unit 105 is an adjusting unit that performs adjustment on the image forming unit so that the weighted average value calculated by the weighted average value calculating unit approaches a target value corresponding to the adjustment image.

(4) Modified Example The above embodiment may be modified as in the following modified example. Moreover, you may combine each modification.
(4.1) Modification 1
In the embodiment, the example in which the control unit 4 calculates the weight based on the output value of the sensor 24 when the difference between the output values of the two sensors 24 exceeds the threshold value is shown. A fixed value may be used as a weight when the difference exceeds the threshold. In this case, an appropriate weight may be obtained by experiment and stored in the storage unit 5.
(4.2) Modification 2
The weight may be varied according to the area ratio. Specifically, it is as follows.
As shown in FIGS. 10 and 11, the sensitivity difference of the sensor 24 may differ depending on the area ratio. Here, as an example, the case of FIG. 10 will be described. FIG. 15 is a diagram illustrating an example in which weights are set according to the area ratio. Cin1 to Cin4 are the four area ratios shown in FIG. UH is the higher output value of the sensor 24 at each area ratio, and UL is the lower output value. The weights calculated by Equation (3) based on this output value are WH and WL. In the image density adjustment, as shown in FIG. 8, the adjustment images 25 having different area ratios are used step by step. Therefore, if the image density adjustment is executed using a weight corresponding to the area ratio of the adjustment image 25. Good.

(4.3) Modification 3
In the embodiment, as shown in FIG. 8, an example in which adjustment images having the same area ratio are formed at positions corresponding to the first sensor 24A and the second sensor 24B has been described. However, the first sensor 24A and the second sensor 24B are illustrated. The adjustment images having different area ratios may be formed at the positions corresponding to. For example, an adjustment image with an area ratio of 100%, 70%, and 40% is formed on the first sensor 24A side, and an adjustment image with an area ratio of 85%, 55%, and 25% is formed on the second sensor 24B side, An approximate curve representing the relationship between the area ratio and the output value is drawn separately on the first sensor 24A side and the second sensor 24B side, and output values corresponding to the area ratio other than the area ratio of the adjustment image 25 are drawn from the approximate curve. Ask.
Further, such an approximate curve representing the relationship between the area ratio and the output value is approximated by a function in advance, and the coefficient is stored in the storage unit 5 or the like, and the coefficient other than the area ratio of the adjustment image 25 is used. An output value corresponding to the area ratio may be obtained.
In short, in the adjustment image, the same area ratio may be determined at the plurality of positions, or different area ratios may be determined at the plurality of positions. The area ratio may be determined.

(4.4) Modification 4
When the density is obtained based on the output value of the specular reflection light, the light amount of the specular reflection light increases as the area ratio decreases, so that the output value of the sensor 24 increases. However, if the sensitivity of the sensor 24 is low, the output value decreases. Since it is lower than the normal value, an image density higher than the original value is calculated. That is, the relationship between when the sensitivity is normal and when the sensitivity is low is opposite to that in FIG. Therefore, in the case of a specular reflection type sensor, the weight is calculated by the following equation.
[Equation 4]
WH = UL / (UH + UL)
WL = 1−WH Formula (4)

(4.5) Modification 5
In the embodiment, the example in which the sensor 24 is provided to face the intermediate transfer member 20 is shown, but the sensor 24 may be provided to face the formation surface on the photoreceptor 11 where the toner image is formed. In this case, for example, the sensors 24 are provided on the back side and the front side of the image forming apparatus 100 with the midpoint of the axis of the photoconductor 11 interposed therebetween.
Alternatively, the sensor 24 may be provided to face the recording medium P on the conveyance path 34. In this case, on the downstream side of the secondary transfer position on the conveyance path 34, it is opposed to the formation surface on which the toner image is formed on the recording medium P, and the back surface of the image forming apparatus 100 across the center line of the conveyance path. Sensors 24 are provided on the side and the front side.
In the embodiment, the example in which the two sensors 24 are provided at two different points on the surface to which the toner image of the intermediate transfer body 20 is transferred has been described. However, three or more sensors are provided for adjusting the image forming position. In this case, an adjustment image is formed at a position corresponding to three or more sensors, and a weighted average value of image densities obtained by measuring the adjustment image is obtained. May be. In this case, the weight is increased toward the upstream side of the first transport path 143A in the transport direction.
In short, the sensor 24 according to the embodiment and the present modification is provided at a plurality of positions in a direction intersecting the moving direction of the formation surface on which the image is formed on either the photoconductor or the transfer body. It is an example of the several detection means which detects an image optically.

(4.6) Modification 6
You may make it correct | amend the output signal of the sensor 24 with a reference value. The reference value may be, for example, a measured value when there is no toner image on the surface of the intermediate transfer member 20, a measured value of a reference plate provided in the sensor 24, or a dark current when there is no reflected light. The component which originates may be sufficient.
(4.7) Modification 7
You may make it determine a weight unconditionally based on the output value of the sensor 24. FIG. Specifically, steps S12 and S14 in FIG. 13 may be omitted, and the process may proceed to step S13 unconditionally following step S11. In this case, the weight is determined based only on the output value of the sensor 24. For example, when the measurement error due to the density distribution shown in the example of the image forming apparatus 100B in FIG. 9 is negligibly small as compared with the measurement error due to the low sensitivity of the sensor 24, the application target of this modification example is Become.
In short, the image forming apparatus according to the present modification includes a photoconductor that is a roller whose electric potential on the outer peripheral surface changes when light is irradiated, a charging device that charges the photoconductor, and image data on the charged photoconductor. An exposure device for writing a latent image by exposure based on the above, a developing device for developing the latent image written on the photoconductor, and an image formed on the photoconductor by development is moved as the photoconductor rotates. An image forming unit having a transfer device for transferring to a transfer member to be transferred, and provided at different positions in a direction intersecting a moving direction of a forming surface on which the image is formed on either the photosensitive member or the transfer member. A plurality of detection means for optically detecting the image and an adjustment image on the forming surface by the image forming means when an event defined as an opportunity to adjust the density of the image is detected. Configured to compensate for the low sensitivity of the density calculation means for calculating the density of the adjustment image based on the output signals of the plurality of detection means and the detection means having a relatively low sensitivity among the plurality of detection means. As described above, the weighted average value calculating means for calculating the weighted average value of the density calculated by the density calculating means using the weights determined for the different positions, and the weighted average value calculating means The image forming apparatus includes an adjusting unit that adjusts the image forming unit to make a weighted average value close to a target value corresponding to the adjustment image.

(4.8) Modification 8
In the embodiment, the example in which the image density is adjusted based on the weighted average value of the image density has been described. However, the toner density may be adjusted based on the weighted average value of the toner density in the developing device 14. Specifically, it is as follows.
When any of the events defined as the trigger for executing the image density adjustment is detected, the control unit 4 calculates the toner density based on the output signals from the first toner density sensor 17A and the second toner density sensor 17B. The weighted average toner density at the comparison position is obtained by calculating the weighted average value of the two toner densities. The comparison position is a position determined in advance as a position for comparing the weighted average value of the toner density and the target value. For example, one point on a straight line passing through the first toner density sensor 17A and the second toner density sensor 17B. It is. The weight for obtaining the weighted average value is calculated, for example, by measuring the toner density distribution on the developing roller 142 by experiment and using the same method as the above-described equation (2) based on this distribution. Then, the control unit 4 adjusts the toner supply amount from the toner supply device 146 based on the difference between the weighted average toner density and the target toner density.
In the embodiment, an example in which a sensor that outputs a signal indicating the intensity of reflected light is used as the toner concentration sensor 17 is provided. However, a sensor that measures magnetic permeability is provided, and the toner concentration is calculated from the measured magnetic permeability. You may make it calculate.

  In short, the image forming apparatus 100 according to the present modification example is based on a photoconductor that is a roller whose surface potential changes when irradiated with light, a charging device that charges the surface, and image data on the charged surface. An exposure device that writes a latent image by exposure, a developing device that develops the latent image with toner conveyed in one direction on a conveyance path along an axial direction of a developing roller provided with an outer peripheral surface facing the surface, and Image forming means having a transfer device for transferring an image formed on the surface by development to an image carrier whose surface is moved in accordance with the rotation of the photoconductor, and provided at different positions on the conveyance path. In addition, when a plurality of measuring means for measuring the toner density and an event defined as an opportunity to adjust the density of the image are detected, toner at a specific position on the conveyance path is detected. The weighted average value of the density measured by the plurality of measuring means is obtained using a weight determined for the plurality of positions so that the density of the toner is obtained by a weighted average of the toner density at the plurality of positions. When the difference between the weighted average value calculating means to be calculated and the output values of the plurality of measuring means exceeds a threshold value, the weight of the measuring means having a relatively low sensitivity among the plurality of measuring means is reduced. Changing means for changing the weight to a weight determined so as to compensate, and adjusting means for adjusting the developing device to make the weighted average value calculated by the weighted average value calculating means close to the target value. 1 is an example of a featured image forming apparatus.

(4.9) Modification 9
The instruction receiving unit 1, the image processing unit 3, the control unit 4, and the storage unit 5 are separated from the image forming unit 7 and configured as a separate control device from the image forming device, and the control device and the image forming device are connected by communication means. It is also possible to connect and control the image forming apparatus via the communication means. That is, this control device is configured as a computer.
FIG. 16 is a block diagram illustrating functional configurations of the control device 200 and the image forming apparatus 300. The control device 200 includes, among the functions of the image forming apparatus 100 according to the embodiment, a density calculating unit 103, a weighted average value calculating unit 104, an adjusting unit 105, and a changing unit 106. Communication means 201 for performing communication. Among the functions of the image forming apparatus 100 according to the embodiment, the image forming apparatus 300 includes an image forming unit 101 and a detecting unit 102, and further includes a communication unit 301 that performs communication with the control device 200. The communication units 201 and 301 are specifically the communication I / F 6. The control device 200 detects an event defined as an opportunity to adjust the image density in the image forming apparatus 300 via the communication unit 201, instructs the image forming apparatus 300 to form the adjustment image 25, and detects the sensor 24. The information indicating the content of adjustment of the image forming apparatus 300 is transmitted to the image forming apparatus 300.

  In short, the control device 200 according to the present modification includes a photoconductor that is a roller whose surface potential changes when light is irradiated, a charging device that charges the surface, and exposure based on image data on the charged surface. An exposure device for writing a latent image by means of a developing device, a developing device for developing the latent image written on the surface, and an image holding on which the image formed on the surface by development is moved as the photoconductor rotates. An image forming unit having a transfer device for transferring to the body, and optically detecting the image provided at different positions in a direction intersecting a moving direction of the surface of one of the photoconductor and the image carrier. A communication unit that communicates with an image forming apparatus having a plurality of detection units and an event defined as an opportunity to adjust the density of the image. A density calculating unit that forms an adjustment image on a surface of one of the photoconductor and the image carrier, and calculates a density of the adjustment image based on output signals of the plurality of detection units; the photoconductor; Using weights defined for the different positions so that the density of the image at a particular position on any surface of the image carrier is determined by a weighted average of the densities of the images at the different positions; The weighted average value calculating means for calculating the weighted average value of the density calculated by the density calculating means, and the difference between the output values of the plurality of detecting means exceeds a threshold value, the weight is set to the weight of the plurality of detecting means. The changing means for changing to a weight determined so as to compensate for the low sensitivity of the detection means having relatively low sensitivity, and the weighted average value calculated by the weighted average value calculating means correspond to the adjustment image. Close to target value Is an example of a control device, characterized in that it comprises an adjusting means for applying kick adjustment for the image forming means.

  When the modification similar to the present modification is applied to the modification 8, the image forming apparatus 100 includes a photoconductor that is a roller whose surface potential changes when light is irradiated, and a charging device that charges the surface. And an exposure apparatus for writing a latent image on the charged surface by exposure based on image data, and a conveyance path along an axial direction of a developing roller provided with an outer peripheral surface facing the surface, and is conveyed in one direction. Image forming means comprising: a developing device that develops the latent image with toner; and a transfer device that transfers an image formed on the surface by the development to an image holding member whose surface is moved as the photoconductor rotates. A communication unit that communicates with the image forming apparatus provided at different positions on the conveyance path and that measures the toner density, and adjusts the image density When the event defined as an opportunity is detected, the toner density at a specific position on the transport path is determined for the plurality of positions so as to be obtained by a weighted average of the toner density at the plurality of positions. When the difference between the weighted average value calculating means for calculating the weighted average value of the concentrations measured by the plurality of measuring means using the weight and the output value of the plurality of measuring means exceeds a threshold value, the weight is calculated. A weighting average value calculated by the weighted average value calculating means, a changing means for changing to a weight determined so as to compensate for the low sensitivity of the measuring means having a relatively low sensitivity among the plurality of measuring means, And an adjusting means for adjusting the developing device so as to approach the target value.

(4.10) Modification 10
In the embodiment, an example using a two-component developer has been described, but a one-component developer not including a carrier may be used.
In the embodiment, an example in which the image forming apparatus 100 is a copying machine has been described. However, an apparatus that receives bitmap format or vector format data from the outside via the communication I / F 6 and forms an image based on the data. But you can.
A plurality of embodiments may be combined. Moreover, you may combine embodiment and a modification.
In the embodiment, the example in which the control unit 4 executes the process by executing the program has been described. However, a similar function may be implemented by hardware. The program is provided by being recorded on a computer-readable recording medium such as an optical recording medium or a semiconductor memory, and the program is read from the recording medium and stored in the storage unit 5 of the image forming apparatus 100. Also good. Further, this program may be provided via a telecommunication line.

DESCRIPTION OF SYMBOLS 100 ... Image forming apparatus, 1 ... Instruction reception part, 2 ... Image reading part, 3 ... Image processing part, 4 ... Control part, 5 ... Memory | storage part, 6 ... Communication I / F, 7 ... Image formation part, 10Y, 10M DESCRIPTION OF SYMBOLS 10C, 10K ... Image formation engine, 11 ... Photoconductor, 12 ... Charging device, 13 ... Exposure device, 14 ... Developing device, 141 ... Housing, 142 ... Developing roller, 143 ... First conveying member, 144 ... Second Conveying member, 145 ... partition, 146 ... toner replenishing device, 141A ... opening, 141B ... toner replenishing port, 143A ... first conveying path, 144A ... second conveying path, 145A, 145B ... gap, 15 ... transfer device, 17A ... 1st toner density sensor, 17B ... 2nd toner density sensor, 20 ... intermediate transfer body, 24A ... 1st sensor, 24B ... 2nd sensor, 30 ... medium conveyance part, 101 ... image forming means, 102 ... detection means, 103 ... Degree calculating means, 104 ... weighted mean value calculating means, 105 ... adjustment means, 106 ... changing means, 200 ... controller, 300 ... image forming apparatus, 201, 301 ... communication unit

Claims (9)

A photoreceptor that is a roller whose surface potential changes when irradiated with light, a charging device that charges the surface, an exposure device that writes a latent image on the charged surface by exposure based on image data, and Image forming means comprising: a developing device that develops the written latent image; and a transfer device that transfers the image formed on the surface by the development to an image carrier whose surface is moved as the photosensitive member rotates. When,
A plurality of detection means for optically detecting the image, provided at different positions in a direction intersecting with the moving direction of the surface of either the photoreceptor or the image carrier;
When an event defined as an opportunity to adjust the density of the image is detected, an image for adjustment is formed on the surface of either the photoconductor or the image carrier by the image forming unit, and the plurality of detection units Density calculating means for calculating the density of the image for adjustment based on an output signal;
Weights determined for the different positions so that the density of the image at a specific position on the surface of either the photoreceptor or the image carrier is determined by a weighted average of the densities of the images at the different positions. A weighted average value calculating means for calculating a weighted average value of the concentration calculated by the concentration calculating means,
The weight determined so as to compensate for the low sensitivity of the detection means having a relatively low sensitivity among the plurality of detection means when a difference between output values of the plurality of detection means exceeds a threshold value. Change means to change to,
An image forming apparatus comprising: an adjusting unit that adjusts the image forming unit to adjust the weighted average value calculated by the weighted average value calculating unit to a target value corresponding to the adjustment image.   The image forming apparatus according to claim 1, wherein the changing unit calculates a weight for each detection unit based on a ratio of an output value of each detection unit to a sum of output values of the plurality of detection units.   The image forming apparatus according to claim 1, wherein the adjustment image has the same area ratio determined at the different positions.   3. The adjustment image has different area ratios determined at different positions, and a plurality of different area ratios are determined stepwise at each of the positions. The image forming apparatus described. A photosensitive member that is a roller whose surface potential changes when irradiated with light, a charging device that charges the surface, an exposure device that writes a latent image on the charged surface based on image data, and an outer peripheral surface. A developing device that develops the latent image with toner that is conveyed in one direction on a conveying path along an axial direction of a developing roller that is provided to face the surface, and an image formed on the surface by the development. An image forming means having a transfer device for transferring to an image carrier whose surface is moved with the rotation of the body;
A plurality of measuring means for measuring the density of the toner provided at different positions on the transport path;
The plurality of positions such that when an event defined as an opportunity to adjust the image density is detected, the toner density at a specific position on the conveyance path is obtained by a weighted average of the toner density at the plurality of positions. A weighted average value calculating means for calculating a weighted average value of the concentrations measured by the plurality of measuring means using the weights determined for
When the difference between the output values of the plurality of measurement means exceeds a threshold value, the weight is determined to compensate for the low sensitivity of the measurement means having relatively low sensitivity among the plurality of measurement means. Change means to change to,
An image forming apparatus comprising: an adjusting unit that adjusts the developing device so that the weighted average value calculated by the weighted average value calculating unit approaches a target value. A photoreceptor that is a roller whose surface potential changes when irradiated with light, a charging device that charges the surface, an exposure device that writes a latent image on the charged surface by exposure based on image data, and Image forming means comprising: a developing device that develops the written latent image; and a transfer device that transfers the image formed on the surface by the development to an image carrier whose surface is moved as the photosensitive member rotates. And an image forming apparatus having a plurality of detection means for optically detecting the image, which are provided at different positions in a direction crossing the moving direction of the surface of either the photoconductor or the image carrier. Communication means for performing communication between,
When an event defined as an opportunity to adjust the density of the image is detected, an image for adjustment is formed on the surface of either the photoconductor or the image carrier by the image forming unit, and the plurality of detection units Density calculating means for calculating the density of the image for adjustment based on an output signal;
Weights determined for the different positions so that the density of the image at a specific position on the surface of either the photoreceptor or the image carrier is determined by a weighted average of the densities of the images at the different positions. A weighted average value calculating means for calculating a weighted average value of the concentration calculated by the concentration calculating means,
The weight determined so as to compensate for the low sensitivity of the detection means having a relatively low sensitivity among the plurality of detection means when a difference between output values of the plurality of detection means exceeds a threshold value. Change means to change to,
And a controller for adjusting the image forming unit to adjust the weighted average value calculated by the weighted average value calculating unit to a target value corresponding to the adjustment image. A photosensitive member that is a roller whose surface potential changes when irradiated with light, a charging device that charges the surface, an exposure device that writes a latent image on the charged surface based on image data, and an outer peripheral surface. A developing device that develops the latent image with toner that is conveyed in one direction on a conveying path along an axial direction of a developing roller that is provided to face the surface, and an image formed on the surface by the development. An image forming unit having a transfer device for transferring the image to an image carrier whose surface is moved in accordance with the rotation of the body, and a plurality of measuring units for measuring the density of the toner provided at different positions on the conveyance path Communication means for communicating with an image forming apparatus having
The plurality of positions such that when an event defined as an opportunity to adjust the image density is detected, the toner density at a specific position on the conveyance path is obtained by a weighted average of the toner density at the plurality of positions. A weighted average value calculating means for calculating a weighted average value of the concentrations measured by the plurality of measuring means using the weights determined for
When the difference between the output values of the plurality of measurement means exceeds a threshold value, the weight is determined to compensate for the low sensitivity of the measurement means having relatively low sensitivity among the plurality of measurement means. Change means to change to,
And a controller for adjusting the developing device to adjust the weighted average value calculated by the weighted average value calculator to a target value. Computer
A photoreceptor that is a roller whose surface potential changes when irradiated with light, a charging device that charges the surface, an exposure device that writes a latent image on the charged surface by exposure based on image data, and Image forming means comprising: a developing device that develops the written latent image; and a transfer device that transfers the image formed on the surface by the development to an image carrier whose surface is moved as the photosensitive member rotates. And an image forming apparatus having a plurality of detection means for optically detecting the image, which are provided at different positions in a direction crossing the moving direction of the surface of either the photoconductor or the image carrier. Communication means for performing communication between,
When an event defined as an opportunity to adjust the density of the image is detected, an image for adjustment is formed on the surface of either the photoconductor or the image carrier by the image forming unit, and the plurality of detection units Density calculating means for calculating the density of the image for adjustment based on an output signal;
Weights determined for the different positions so that the density of the image at a specific position on the surface of either the photoreceptor or the image carrier is determined by a weighted average of the densities of the images at the different positions. A weighted average value calculating means for calculating a weighted average value of the concentration calculated by the concentration calculating means,
The weight determined so as to compensate for the low sensitivity of the detection means having a relatively low sensitivity among the plurality of detection means when a difference between output values of the plurality of detection means exceeds a threshold value. Change means to change to,
A program for causing the image forming unit to function as an adjustment unit that adjusts the weighted average value calculated by the weighted average value calculation unit to approach a target value corresponding to the adjustment image. Computer
A photosensitive member that is a roller whose surface potential changes when irradiated with light, a charging device that charges the surface, an exposure device that writes a latent image on the charged surface based on image data, and an outer peripheral surface. A developing device that develops the latent image with toner that is conveyed in one direction on a conveying path along an axial direction of a developing roller that is provided to face the surface, and an image formed on the surface by the development. An image forming unit having a transfer device for transferring the image to an image carrier whose surface is moved in accordance with the rotation of the body, and a plurality of measuring units for measuring the density of the toner provided at different positions on the conveyance path Communication means for communicating with an image forming apparatus having
The plurality of positions such that when an event defined as an opportunity to adjust the image density is detected, the toner density at a specific position on the conveyance path is obtained by a weighted average of the toner density at the plurality of positions. A weighted average value calculating means for calculating a weighted average value of the concentrations measured by the plurality of measuring means using the weights determined for
When the difference between the output values of the plurality of measurement means exceeds a threshold value, the weight is determined to compensate for the low sensitivity of the measurement means having relatively low sensitivity among the plurality of measurement means. Change means to change to,
A program for causing the developing device to function as an adjustment unit for adjusting the weighted average value calculated by the weighted average value calculation unit to a target value.

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