JP2010145676A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus stably outputting a high quality image over a long period of time by always maintaining the amount (density) of developer recovered by both cleaning means of an image carrier and an intermediate transfer body at a predetermined value or below in operation for forcible developer consumption, thereby preventing the occurrence of problems such as cleaning failures. <P>SOLUTION: The image forming apparatus includes: a first detection means which is disposed downstream from a primary transfer means in the moving direction of the intermediate transfer body and detects the density of a patch image for forcible developer consumption; and a control part which changes the transfer conditions of the patch image, based on the detection result of the first detection means and the image forming apparatus can always maintain the amount (density) of the developer recovered by both cleaning means at a predetermined value or below. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  In the present invention, when image formation with a low image density (printing rate) is continuously performed, the image forming apparatus prevents the phenomenon that the developer in the developing device stagnates and the adsorptivity to the image is deteriorated to cause image deterioration. About.

  An image forming apparatus using an electrophotographic method has a process of developing an electrostatic latent image and transferring it onto a transfer material as an image forming material. If this developability and transferability are reduced, an image defect occurs. Stability of image quality is hindered. One of the causes is that there is a continuous image output request that consumes a small amount of toner per page in an image to be formed. In this case, the toner stays in the developing device for a long time and is stirred. The toner that stays and is agitated changes its electrostatic attraction force, making it impossible to obtain proper adsorption with the image carrier. In particular, in a developing system having a two-component developer composed of toner and a magnetic carrier, the amount of toner consumed is reduced with respect to the rate at which the developing device is operating, resulting in more than necessary toner staying for a long time. The material is agitated with the magnetic carrier, and the material added to the surface in advance is changed. As a result, image quality defects such as transfer defects and fogging occur. As countermeasures against such a deterioration in image quality, various techniques for forcibly discharging toner that forcibly discharge toner staying in the developing means and replace with new toner have been proposed.

As materials showing these techniques, there are, for example, Patent Documents 1 and 2 shown below.
JP 2006-171788 A. JP-A-6-138760.

  The technique described in Patent Document 1 forms a solid image in an area other than the normal output image area, forcibly consumes the developer from the developing device, and outputs the output of the primary transfer unit in response to the developing operation. The point that the output is reduced to 1/2 or less of the output during image formation is described. As a result, it is possible to prevent the occurrence of problems such as poor cleaning due to forced consumption developer by distributing and reducing the burden of collecting forced consumption developer to both the intermediate transfer member cleaning means and the photoreceptor cleaning means. ing.

  However, according to the technique described in Patent Document 1, the amount of forced consumption developer is recovered by both cleaning means in a balanced manner over a long period against environmental conditions (particularly humidity) or fluctuations in developer characteristics. It is difficult. As a result, the balance is lost, and there remains a problem that the above problem occurs in the cleaning means in which the collective consumption developer is excessively recovered. In other words, the technique described in Patent Document 1 cannot sufficiently solve problems such as cleaning defects associated with forced consumption developer.

  In the technique described in Patent Document 2, in order to perform load distribution between the cleaning device (51) for cleaning the photosensitive member and the belt cleaning device (64) for cleaning the belt, the current of the transfer charger is usually set in the toner consumption mode. Is changed to a value smaller than the current at the time of image formation (see paragraphs 0076 to 0078). In addition, a density sensor that detects the density of the image formed on the photoconductor is provided on the upstream side of the transfer, and is changed to a value smaller than the transfer current during normal image formation according to the detection value of the density sensor. It is described that it may be. That is, based on the detection result of the density sensor, control is performed so that the current value during normal image formation is switched to a current value smaller than the current during normal image formation.

  However, the technique described in Patent Document 2 does not prevent the loss of the forced consumption developer recovery balance of each cleaning means caused by environmental conditions (particularly humidity) or fluctuations in developer characteristics, and the above-described cleaning problem is not solved. It cannot be solved sufficiently.

  An object of the present invention is to make it possible to always maintain the amount (concentration) of developer collected by both the image carrier and intermediate transfer member cleaning means in a forced developer consuming operation, and to prevent problems such as poor cleaning. It is an object of the present invention to provide an image forming apparatus that prevents the occurrence of the above and stably outputs a high-quality image over a long period of time.

  The object of the present invention is achieved by the following configuration.

1. An image forming unit that forms an image on an image region in the rotation direction of the image carrier using the developer of the developing device;
Primary transfer means for transferring the image formed in the image area on the image carrier to an intermediate transfer body under primary transfer conditions;
First cleaning means for recovering the developer remaining on the image carrier;
A second cleaning means for recovering the developer remaining on the intermediate transfer member;
A patch image for forcibly consuming the developer of the developing device is formed in a non-image area outside the image area on the image carrier, and the first non-image condition different from the primary transfer condition is used. A control unit that controls at least the image forming unit and the primary transfer unit so that the patch image is transferred to the intermediate transfer member, and the patch image is distributed and collected by the first cleaning unit and the second cleaning unit. ,
The first transfer unit is disposed on the downstream side in the moving direction of the image carrier or the intermediate transfer member with respect to the primary transfer unit, and detects the density of the patch image on the image carrier or the intermediate transfer member. Detecting means,
The image forming apparatus, wherein the control unit changes the first non-image condition based on a detection result of the first detection unit.

2. The first detection means is disposed to face the intermediate transfer member;
The control unit changes the first non-image condition so as to reduce a transfer rate by the primary transfer unit when a detection result of the first detection unit is a predetermined value or more. The image forming apparatus described in 1.

3. The first detection means is disposed to face the intermediate transfer member;
The control unit may change the first non-image condition so as to increase a transfer rate of the primary transfer unit when a detection result of the first detection unit is a predetermined value or less. The image forming apparatus described.

4). The first detection means is disposed to face the image carrier;
The control unit may change the first non-image condition so as to increase a transfer rate by the primary transfer unit when a detection result of the first detection unit is a predetermined value or more. The image forming apparatus described.

5). The first detection means is disposed to face the image carrier;
The control unit changes the first non-image condition so as to reduce a transfer rate by the primary transfer unit when a detection result of the first detection unit is a predetermined value or less. The image forming apparatus described in 1.

6). An image forming unit that forms an image on an image region in the rotation direction of the image carrier using the developer of the developing device;
Primary transfer means for transferring the image formed in the image area on the image carrier to an intermediate transfer member;
Secondary transfer means for transferring the image transferred onto the intermediate transfer member to a transfer material under secondary transfer conditions;
A second cleaning means for recovering the developer remaining on the intermediate transfer member;
Third cleaning means for recovering the developer remaining in the secondary transfer means;
A patch image for forcibly consuming the developer of the developing device is formed in a non-image area outside the image area on the intermediate transfer member, and further, under a second non-image condition different from the secondary transfer condition. At least the image forming unit, the primary transfer unit, and the secondary transfer unit are configured to transfer the patch image to the transfer material and distribute the patch image to the second cleaning unit and the third cleaning unit for collection. A second control unit that detects a density of the patch image on the intermediate transfer member on the downstream side in the moving direction of the intermediate transfer member with respect to the secondary transfer unit;
The image forming apparatus, wherein the controller changes the second non-image condition based on a detection result of the second detection unit.

  7). The control unit changes the second non-image condition so as to increase a transfer rate by the secondary transfer unit when a detection result of the second detection unit is a predetermined value or more. The image forming apparatus described in 1.

  8). The control unit calculates a difference between a detection result of the first detection unit and a detection result of the second detection unit, and changes the second non-image condition based on the difference. The image forming apparatus described in 1.

  9. 7. The image forming apparatus according to any one of 1 to 6, wherein the patch image formed on the image carrier is a solid image.

  10. 10. The image forming apparatus according to any one of 1 to 9, wherein the secondary transfer unit has a roller shape.

  11. The image forming apparatus according to any one of 1 to 9, wherein the secondary transfer unit has a belt shape.

  According to the present invention, it is possible to always maintain the amount of the developer collected by the cleaning means for the photosensitive member and the cleaning means for the intermediate transfer member at a predetermined value or less in the operation of forced developer consumption, resulting in poor cleaning over a long period of time. It is possible to provide an image forming apparatus that can output a high-quality image without any problem.

  Embodiments of the present invention will be described below.

  FIG. 1 is a schematic configuration diagram showing a color image forming apparatus as an embodiment of the present invention.

  This color image forming apparatus is called a tandem type color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, an intermediate transfer body unit 7, a sheet feeding and conveying means 21, and a fixing means. The fixing device 24. On the upper part of the main body of the image forming apparatus A, a document image reading apparatus SC is arranged.

  The image forming unit 10Y that forms a yellow image includes a drum-shaped photosensitive member 1Y as an image carrier, a charging unit 2Y, an exposing unit 3Y, a developing unit 4Y, and a primary transfer unit arranged around the photosensitive unit 1Y. Primary transfer roller 5Y and first and first cleaning means 6Y. An image forming unit 10M that forms a magenta image includes a drum-shaped photoconductor 1M as an image carrier, a charging unit 2M disposed around the photoconductor 1M, an exposure unit 3M, a developing unit 4M, and a primary transfer unit. Primary transfer roller 5M and first cleaning means 6M. The image forming unit 10C for forming a cyan image includes a drum-shaped photoconductor 1C as an image carrier, a charging unit 2C arranged around the photoconductor 1C, an exposure unit 3C, a developing unit 4C, and a primary transfer unit. Primary transfer roller 5C and first cleaning means 6C. The image forming unit 10K that forms a black image includes a drum-shaped photoconductor 1K as an image carrier, a charging unit 2K arranged around the photoconductor 1K, an exposure unit 3K, a developing unit 4K, and a primary transfer unit. A primary transfer roller 5K and first cleaning means 6K are provided.

  The intermediate transfer body unit 7 includes an intermediate transfer body 70 that is a semiconductive endless belt wound around a plurality of rollers and rotatably supported.

  The images of the respective colors formed by the image forming units 10Y, 10M, 10C, and 10K are sequentially transferred onto the rotating intermediate transfer body 70 by the primary transfer rollers 5Y, 5M, 5C, and 5K as primary transfer units. A synthesized color image is formed. A transfer material P such as a sheet as a recording medium accommodated in the sheet feeding cassette 20 is fed by a sheet feeding / conveying means 21, passes through a plurality of intermediate rollers 22 A, 22 B, 22 C, 22 D, and a registration roller 23, and then is secondary. It is conveyed to a secondary transfer roller 5A as a transfer means, and color images are collectively transferred onto the transfer material P by the secondary transfer roller 5A. The transfer material P on which the color image is formed is fixed by the fixing device 24. Then, the paper is discharged out of the apparatus by the paper discharge roller 25 and placed on the paper discharge tray 26.

  On the other hand, the residual toner on the intermediate transfer body 70 on which the color image is transferred to the transfer material P is removed and collected by the second second cleaning means 6A.

  During the image forming process, the primary transfer roller 5K is always in pressure contact with the photoreceptor 1K. The other primary transfer rollers 5Y, 5M, and 5C are in pressure contact with the corresponding photoreceptors 1Y, 1M, and 1C, respectively, only during color image formation.

  The secondary transfer roller 5A is always in pressure contact with the intermediate transfer member 70 during the image forming process. The residual toner on the secondary transfer roller 5A is removed by the third and third cleaning means 6B.

  FIG. 2 is a side cross-sectional view showing the configuration of the secondary transfer roller 5A and the third third cleaning means 6B. The third, third and third cleaning means 6B will be described with reference to FIG.

  In the present invention, a brush roller can be used as the third cleaning means 6B, but here the cleaning blade 6B1 is used. The cleaning blade 6B1 is held by the cleaning holding member 6B2, and the tip thereof is in contact with the surface of the secondary transfer roller 5A by the urging force of the spring 6B3. The cleaning holding member 6B2 is fixed to the casing 6B5 so as to be rotatable about the rotation shaft 6B4C.

  As described above, the cleaning blade 6B1 is always in contact with the secondary transfer roller 5A that is rotatably fixed to the casing 6B5.

  Further, the housing 8 can be pulled out from the image forming apparatus A through the support rails 82L and 82R.

  The housing 8 includes image forming units 10Y, 10M, 10C, and 10K, and an intermediate transfer body unit 7.

  The image forming units 10Y, 10M, 10C, and 10K are arranged in tandem in the vertical direction. An intermediate transfer body unit 7 is arranged on the left side of the photoreceptors 1Y, 1M, 1C, and 1K in the figure. The intermediate transfer body unit 7 includes an intermediate transfer body 70 that can be rotated by winding rollers 71, 72, 73, 74, and 76, primary transfer rollers 5Y, 5M, 5C, and 5K, and second cleaning means 6A.

  The image forming units 10Y, 10M, 10C, and 10K and the intermediate transfer body unit 7 are integrally pulled out from the main body of the image forming apparatus A by the drawer operation of the housing 8.

  In this way, a toner image is formed on the photoreceptors 1Y, 1M, 1C, and 1K by charging, exposure, and development, and the toner images of each color are primarily transferred and superimposed on the intermediate transfer body 70, and then transferred together. The material is secondarily transferred to the material P, and fixed and fixed by the fixing device 24 by pressure and heating. The photoreceptors 1Y, 1M, 1C, and 1K after transferring the toner image to the intermediate transfer body 70 clean the residual toner remaining on the photoreceptors at the time of transfer by the first cleaning means 6Y, 6M, 6C, and 6K. Then, the charging, exposure and development cycle described above is entered, and the next image formation is performed.

This process speed is 300 mm / s, and this is a tandem full-color copying machine employing the intermediate transfer member 70 as an intermediate transfer member. The primary transfer roller is a sponge roller having a diameter of 20 mm, and its resistance value is 1 × 10 ⁷ Ω. The secondary transfer roller is an elastic roller having a diameter of 30 mm, and its resistance value is 1 × 10 ⁷ Ω.

  A bias is applied to the primary transfer roller from a constant current control type primary transfer power supply. Similarly, a bias is applied to the secondary transfer roller from a constant current control type secondary transfer power supply.

[First detection means and second detection means]
The first detection unit 91 and the second detection unit 92 are disposed to face the surface of the intermediate transfer body 70 that circulates.

  The first detection means 91 is disposed downstream of the primary transfer rollers 5Y, 5M, 5C, and 5K in the moving direction of the intermediate transfer body 70 with respect to the primary transfer rollers 5Y, 5M, 5C, and 5K. The density of each color patch image sequentially transferred onto the transfer body 70 is detected.

  The second detection unit 92 is disposed downstream of the secondary transfer roller 5 </ b> A in the moving direction of the intermediate transfer body 70 and detects the density of each color patch image remaining on the intermediate transfer body 70.

  FIG. 3 is a schematic diagram of the first detection unit 91 and the second detection unit 92, and shows the positional relationship with the patch image on the intermediate transfer body 70.

  As shown in the figure, the detection units 91 and 92 are configured by light emitting units 911 and 921 that emit infrared light, and light receiving units 912 and 922 that receive secondary light diffused by the intermediate transfer body 70. Light rays from the light emitting units 911 and 921 enter the incident point on the surface of the intermediate transfer body 70 with a 45 ° inclination. The light receiving units 912 and 922 are positioned on a vertical line with respect to the intermediate transfer body 70 passing through the incident point, and detect the surface of the intermediate transfer body 70 and the reflected light of the vertical component scattered by the toner on the surface.

  FIG. 11 shows the detection characteristics of the first detection means 91 and the second detection means 92. FIG. 11A shows the relationship between the density (toner mass per unit area) of the patch image formed on the intermediate transfer body 70 and the detection output D (j = y, m, c). FIG. 11B shows the same relationship between the K color patch images. Here, the unit of the detection output D is a volt, and the detection sensitivity when detecting a K-color patch image is more amplified than when detecting a Y-color, M-color, and C-color patch image.

[Control Block Diagram of Image Forming Apparatus]
FIG. 4 is a control block diagram of the image forming apparatus A, and a control unit according to the embodiment of the present invention will be described based on FIG.

  The image forming apparatus A includes a print engine unit 101, a control unit 102, an image processing unit 103, an operation display unit 105, a storage unit 104, a transmission / reception unit 106, a print controller unit 107, and the like. Each unit is connected by a bus 110. Further, it communicates with a document image reading device SC installed on the upper part of the image forming apparatus A via the bus 110.

  The control unit 102 includes a CPU, ROM, RAM, and the like. The CPU of the control unit 102 reads the system program and various processing programs stored in the ROM by operating the operation display unit 105 and develops them in the RAM, and performs centralized control of the operations of each unit of the image forming apparatus A according to the developed programs. To do.

  The operation display unit 105 is configured by an LCD (Liquid Crystal Display), and displays various operation buttons, device status display, operation status of each function, etc. on the display screen in accordance with an instruction of a display signal input from the control unit 102. Do.

  The LCD display screen is covered with a pressure-sensitive (resistive film pressure) touch panel configured by arranging transparent electrodes in a grid pattern, and the XY coordinates of the force point pressed by a finger or a touch pen are expressed as voltage values. The detected position signal is output to the control unit 102 as an operation signal.

  The operation display unit 105 includes various operation buttons such as a numeric button and a start button, and outputs an operation signal generated by the button operation to the control unit 102.

  The document image reading device SC reads a document as R, G, and B analog signals, converts the analog signals into digital signals by an A / D converter, and generates R, G, and B image data. Thereafter, the image data is output to the image processing unit 103 of the image forming apparatus A via the bus.

  The image processing unit 103 converts the R, G, and B image data input from the document image reading device SC into Y, M, C, and K color image data that can be processed by the print engine unit 101. Further, γ correction processing is performed in accordance with the output characteristics of the print engine unit 101, or binarization processing such as a misdiffusion method is performed to generate print data of Y, M, C, and K colors. The print data is output to the print engine unit 101.

  When the transmission / reception unit 106 receives a print job from a personal computer on the network, the transmission / reception unit 106 transfers the received print job to the print controller unit 107. The print job is composed of processing information related to print processing and print data (file).

  The print controller unit 107 generates print data that is image data of Y, M, C, and K colors based on the contents of the print job, and outputs the print data to the print engine unit 101 corresponding to the processing information.

  The print engine unit 101 develops the image data input from the image processing unit 103 and the print controller unit 107 on the image memory 108. Next, the image data developed on the image memory 108 is sequentially scanned to form each color toner image by the image forming units 10Y, 10M, 10C, and 10K. Further, the color toner images of the image forming units 10Y, 10M, 10C, and 10K are transferred onto the intermediate transfer body 70 by the primary transfer units 5Y, 5M, 5C, and 5K, and the color composed of the color toner images is formed on the intermediate transfer body 70. Form an image. Further, the color image on the intermediate transfer member is transferred onto the sheet by the secondary transfer roller 5A. Then, the sheet is fixed by the fixing unit 30 and then output from the image forming apparatus A.

  A portion indicated by a thick line in the broken line is a control block according to “execution of forced toner consumption operation” of the present invention, which will be described below.

[Control of patch image creation]
A patch image creation unit 109 develops and creates a patch image of each color for forcibly consuming toner from each developing device 4Y, 4M, 4C, 4K in the image memory 108 based on information input from the control unit 102. Is. The print engine unit 101 sequentially scans the patch image data created by the patch image creation unit 109 and the image data developed in the image memory 108, and the photoreceptors 1Y, 1M, 1C, 1K of each image forming unit. An image is formed in the image area Ap, and a patch image is formed in the non-image area An.

  FIG. 5 shows the positional relationship between the image area Ap on the intermediate transfer body 70 that circulates in the direction of the arrow during the image forming process and the non-image area An between the image areas Ap. Here, A4 size images from page 1 to page 3 are formed in the image area Ap. In addition, Y, M, C, and K color patch images PGy, PGm, PGc, and PGk are formed in the non-image area An.

  The size of the patch image of each color is 300 mm in the width direction orthogonal to the rotation direction and 15 mm in the rotation direction. The length in the width direction corresponds to the length in the width direction of the developing device, and the length in the circumferential direction is less than a length that divides the non-image area An in the circumferential direction into approximately four equal parts.

  Each color patch image is created in the following procedure.

  First: Based on the image data, the control unit 102 accumulates the total number of prints of all the images processed by the image forming units 10K, 10M, 10C, and 10K in a predetermined period, and each color in the period The total travel distance Lj in which the developing device is operated is acquired in cooperation with the storage unit 104.

  2; The control unit 102 calculates the average print density Dj by dividing the cumulative print number Nj by the total travel distance Lj. Dj = Nj / Lj.

  3: The control unit 102 calculates the difference Rj of the average print density Dj with respect to the reference value Dr. Rj = Dr-Dj. Then, Rj is transferred to the patch image creation unit 109 via the bus 110.

  Part 4: The patch image creation unit 109 creates patch image data PDj of each color based on Rj transferred from the control unit 102. That is, the patch image data PDj for each color is developed in a predetermined area of the image memory 108. Note that. The developed patch image data PDj is binary data subjected to pseudo gradation processing.

  No. 5: The print engine unit sequentially scans the image data and patch image data PDj developed on the image memory 108, and uses the image forming units 10Y, 10M, 10C, and 10K to apply patch images PGj of the respective colors to the image areas. Then, each color patch image in the non-image area is formed.

  The above j is a number corresponding to each color, and is representative of y, m, c, and k.

  Further, the density of the patch image PGj can be made constant and maximum, and the size thereof can be determined corresponding to the difference Rj. It is also possible to define the patch image PGj by both the density and the size thereof and determine the patch image corresponding to the difference Rj.

  In any case, when a print job including an image having an average print density Dj lower than the reference value Dr is processed in a predetermined period, the above difference is applied to the non-image area of each photoconductor corresponding to the above difference Rj. A patch image having a density (or size) to be formed is formed.

  For example, in the case of a print job including a document composed only of black characters and red characters, the average print density Dc is zero in the C color image forming unit, and the solid density data in which the C color patch image data PDc is the highest density. become. As a result, the C color patch image PGc is formed in a solid density state in which all the patch images have the highest density.

  Each color patch image PGj between the first page and the second page shown in FIG. 5 has a constant size and a different density. Each color patch image PGj between the second page and the third page has a maximum density and has a different size in the circulation direction. Here, the forced toner consumption is gradually increased in the order of the Y color patch image PGy, the M color patch image, the C color patch image PGm, and the K color patch image PGk. The K-color patch image PGk corresponds to the maximum forced toner consumption.

  As described above, full-color printing is performed immediately after a print job that outputs a large amount of documents consisting only of black characters and red characters, for example, by a forced toner consumption operation that forms a patch image of an appropriate amount of toner in non-image area processing. Even when a document is printed, it is possible to prevent the occurrence of an image problem of “decrease in C color density” in which the density of the C color image is insufficient.

[Adjustment control of patch image transfer]
Next, the inside of the broken line (thick line part) of FIG. 4 which concerns on embodiment of this invention is described.

  The primary transfer power supplies 51Y, 51M, 51C, and 51K output bias voltages to be applied to the primary transfer rollers 5Y, 5M, 5C, and 5K based on the primary transfer conditions instructed by the control unit 102. The secondary transfer power source 51A also outputs a bias voltage to be applied to the secondary transfer roller 5A based on the secondary transfer condition instructed from the control unit 102. The primary transfer power supplies 51Y, 51M, 51C, 51K and the secondary transfer power supply 51A are current-type high-voltage power supplies with a constant output current. Therefore, the primary and secondary transfer conditions instructed from the control unit 102 are instruction values corresponding to the output current values.

  Each transfer condition includes image conditions Ta1 and Ta2 output when the image area on the intermediate transfer body passes through each transfer position, and non-image condition Tn1 output when the non-image area passes through each transfer position. , Tn2. The patch image PGj for forced toner consumption formed in the non-image area is transferred under the non-image conditions Tn1 and Tn2, and the normal image formed in the image area is transferred under the image conditions Ta1 and Ta2. Is done.

  The first detection means 91 is provided on the intermediate transfer body 70 after the primary transfer in order to monitor the recovery loads of the first cleaning means 6Y, 6M, 6C, 6K and the intermediate transfer body 70A of the respective color photoconductors. The density of the residual patch image PGj for forced toner consumption is detected. The detection result is D1j.

  The second detection unit 92 remains on the intermediate transfer member 70 after the secondary transfer in order to monitor the recovery load of the second cleaning unit 6A of the intermediate transfer member 70 and the third cleaning unit 6B of the secondary transfer roller 5A. The density of the patch image PGj for forced toner consumption is detected. The detection result is D2j.

  Based on the detection results D1j and D2j of the first detection unit 91 and the second detection unit 92, the control unit 102 sets the transfer condition for the patch image PGj so that the forced consumption developer is collected within an appropriate range by each cleaning unit. Control to optimize is executed. Specifically, it is determined whether or not it is necessary to change the non-image condition Tn1j for primary transfer and the non-image condition Tn2 for secondary transfer based on the detection results D1j and D2j.

[Overall flow of image formation processing control]
FIG. 6 is a flowchart of the image forming process executed by the control unit 102 shown in FIG. The “patch image creation process” and “patch image transfer optimization control” executed during the “normal image forming process” will be described below with reference to FIG.

  In step S103, "patch image creation control" is performed to create each color patch image data PDj based on the cumulative number of prints Nj described above.

  Step S105 is a step of performing “normal image forming processing”. Images and patch images are transferred under primary transfer conditions (Ta1j, Tn1j) and secondary transfer conditions (Ta2, Tn2).

  In step S105, the number of prints nj of each color image data constituting the processed image is calculated. Step S106 is a step of updating the cumulative number of prints, and is equivalent to the “normal image forming process” of step S105. A process of calculating Nj = Nj + nj and storing a new cumulative print number Nj is also included.

  Step S108 is the above-described “patch image transfer optimization control” step.

  Step S102 is a step of determining whether or not the image forming process has reached a predetermined time for executing “patch image creation control”. C2 is a count, and is reset when the “patch image creation process” is performed, and is controlled so that 1 count is added when the image forming process for one page is completed (described in S104 and S107).

  Next, an embodiment of “patch image transfer optimization control” according to the invention will be described below.

[First Embodiment]
FIG. 7 is a control flowchart executed by the control unit 102, and a first embodiment of “patch image transfer optimization control” according to the present invention will be described with reference to FIG.

  The processes from S201 to S206 are processes in which the secondary transfer non-image condition Tn1j is sequentially changed based on the detection result D1j of the first detection unit 91 for each color.

  As shown in steps S201 and S206, steps S201 to S106 are repeated in the order of j = y, j = m, j = c, and j = k.

  Step S202 is a step of acquiring the detection result D1j from the first detection unit 91 for each color.

  In step S203, it is determined whether or not the detection result D1j is equal to or greater than a predetermined value Raj. When it is determined that the density of the patch image PGj is equal to or higher than the predetermined value Raj (in the case of Yes), the process proceeds to S204.

  In step S204, a calculation process for subtracting the predetermined value α from the current primary transfer non-image condition is performed to obtain a new non-image condition Tn1j (Tn1j-α).

  Next, the process proceeds to step S205. In S205, the new non-image condition Tn1j is changed as the primary transfer condition in the subsequent processing. Specifically, the primary transfer non-image condition stored in the storage unit 104 is rewritten from the current value to the new non-image condition Tn1j.

  If it is detected in step S203 that the value is less than the predetermined value Ra (in the case of No), the process proceeds to step S206. If it is determined in step S106 that j = k is not satisfied, the process returns to step S201, and the next color patch. The process from S202 to S206 is repeated for the image.

  When j = k, the process proceeds to S207.

  The processes from S207 to S212 are processes in which the secondary transfer non-image condition Tn2 is changed based on the detection result D2j of the second detection unit 92.

  Step S207 is the same process as step S202, and a description thereof is omitted here.

  Step S208 is a step of obtaining the detection result D2j from the second detection unit 92 for each color.

  In step S209, it is determined whether or not the detection result D2j is equal to or greater than a predetermined value Rbj. If it is detected that the density of the patch image PGj is equal to or higher than the predetermined value Rbj (Yes), the process proceeds to step S210.

  In step S210, a calculation process for adding a predetermined value β from the current condition is performed for the non-image condition of the secondary transfer, and a new condition Tn2 is acquired.

  Next, the process proceeds to step S211. In S211, the new condition Tn2 (= Tn2 + β) is changed as a condition in the subsequent processing. That is, the secondary transfer non-image condition stored in the storage unit 104 is rewritten from the current value to the new condition Tn2.

  Here, unlike the case of the primary transfer, when the detection result in a patch image of a certain color becomes “Yes”, the non-image condition of the secondary transfer is changed and a series of “patch image transfer optimization control” is finished. .

  If it is determined “No” in step S209, the process proceeds to S212. As long as it is determined “No” in the step S209, the steps from S207 to S209 are repeated until j = k.

  As described above, in the first embodiment, when the detection result D1j of the first detection unit is equal to or greater than the predetermined value Raj, non-primary transfer in the next image forming process is performed so as to reduce the transfer rate by primary transfer. The image condition Tn1j is changed. Further, when the detection result D2j of the second detection means is equal to or greater than the predetermined value Rbj, the secondary transfer non-image condition Tn2 in the next image forming process is changed so as to increase the transfer rate by the secondary transfer. As a result, it is possible to prevent the occurrence of a cleaning problem associated with the processing of both forced developer consumptions.

[Second Embodiment]
FIG. 8 is a control flowchart of the second embodiment, and “patch image transfer optimization control” according to the present invention will be described with reference to FIG.

  Here, the non-image condition Tn2 for secondary transfer is controlled based on the detection results D1j and D2j of the first detection unit 91 and the second detection unit 92, respectively, so that the third cleaning unit 6B of the secondary transfer roller 5A On the other hand, the recovery load of the forced consumption developer can be suppressed below a predetermined level.

  Step S302 is a step of acquiring the detection result D1j and the detection result D2j from the first detection unit 91 and the second detection unit.

  Step S303 is a step of subtracting the detection result D2j from the detection result D1j for each color to obtain the difference DDj.

  Step S304 is a step of determining whether or not the difference DDj acquired in step S303 is equal to or greater than a predetermined value DDr. If it is equal to or greater than the predetermined value DDr, the process proceeds to S305.

  In the above-described step S304, the forced consumption developer distributed in the secondary transfer and remaining on the secondary transfer roller 5A has a concentration within a limit (less than a predetermined value) at which the third cleaning unit 6B does not cause a problem for a long time. Judging whether there is. If the limit is exceeded, the process moves to step S305.

  In step S305, a calculation process for subtracting the predetermined value β from the current condition Tn2 for the non-image condition for secondary transfer is performed to obtain a new condition Tn2 (= Tn2−β).

  In the next step S306, the non-image condition for secondary transfer in the subsequent image forming process is changed to the new condition Tn2 acquired in step S305, and the current condition stored in the control unit 102 is written in the new condition Tn2. It has changed.

  In the embodiment described above, it is determined whether or not the forced consumption developer distributed on the secondary transfer roller 5A has a density equal to or higher than a predetermined value based on the detection results of the first detection unit and the second detection unit. When the density is determined to be equal to or higher than the predetermined value, the amount of forced consumption developer transferred to the secondary transfer roller 5A side is reduced by reducing the secondary transfer non-image condition Tn2 in the next image forming process. Control is performed so that the transfer rate by the secondary transfer roller is reduced. As a result, it is possible to prevent the occurrence of a cleaning problem associated with forced developer consumption processing.

[Third Embodiment]
FIG. 9 is a control flowchart of the third embodiment, and “patch image transfer optimization control” according to the present invention will be described with reference to FIG.

  Here, the embodiment according to the present invention is most suitable when the form of the patch image formed in the non-image area An of each color photoconductor is a solid density.

  Based on the detection result of the solid density patch image PG by the first detection means, the density of the patch image PG transferred to the intermediate transfer body 70 can be directly acquired, and the remaining patch image without being transferred to each photoconductor. The concentration of PG can also be obtained indirectly. When the detection result D1j of the first detection unit for the patch image PGj is low, it means that the density of the patch image remaining on the photoconductor corresponding to j is high. Using this relationship, when the detection result D1j for the patch image PGj is equal to or smaller than the predetermined value Rcj, the non-image condition Tn1j for primary transfer is decreased by the predetermined value α.

  Step S406 is a step of determining whether or not the detection result D1j for the patch image PGj is equal to or less than a predetermined value Rcj. In the case of “Yes”, the process proceeds to S407.

  In step S407, a calculation process of adding a predetermined value α to the current condition for the non-image condition for primary transfer is performed to obtain a new condition Tn1j (= Tn1 + α).

  In the next step S405, the non-image condition of the secondary transfer in the subsequent image forming process is changed to the new condition Tn1j acquired in step S407, and the current condition stored in the control unit 102 is written in the new condition Tn1j. It has changed.

  The process from S401 to S405 is the same as the process from S201 to S205 in the first embodiment. In the process during this period, it is determined whether or not the detection result D1j is equal to or greater than the predetermined value Raj. Processing is performed to acquire a new condition Tn1j (= Tnj1-α). Then, the process proceeds to step S407.

  As described above, in the third embodiment, when the detection result D1j of the first detection unit deviates from between the predetermined value Raj and the predetermined value Rcj, the primary transfer non-image condition Tn1j in the next image forming process. To change. As a result, it is possible to prevent the occurrence of a cleaning problem associated with forced developer consumption processing.

[Fourth Embodiment]
FIG. 10 is a control flowchart of the fourth embodiment, and “patch image transfer optimization control” according to the present invention will be described with reference to FIG.

  In the image forming apparatus of this embodiment, a first detection unit 91 that detects a patch image PGj that is not transferred by the primary transfer and remains on the photosensitive member is disposed to face the photosensitive members 1Y, 1M, 1C, and 1K. Has been. The patch image PGj has a solid density.

  The control unit according to the fourth embodiment directly acquires the density of the patch image PGj remaining on each photoconductor based on the detection result of the first detection unit 91, and does not transfer the image to the intermediate transfer body 70, thereby remaining. The density of the patch image PGj to be obtained is also acquired indirectly.

  The primary transfer non-image condition Tn1j is increased by a predetermined value α when the detection result D1j of the first detection means is greater than or equal to the predetermined value Rdj, and the primary transfer non-image condition when the detection result D1j is less than or equal to the predetermined value Rej. Tn1j is decreased by a predetermined value α.

  The process from S502 to S505 is to change the non-image condition Tn1j for primary transfer to a new condition obtained by adding α from the current condition when the detection result D1j of the first detection unit 91 is equal to or greater than Rdj.

  The process from S502 through S503, S506, and S507 to S505 is such that when the detection result D1j of the first detection unit 91 is less than Rdj and greater than or equal to Rej, the non-image condition Tn1j for primary transfer is determined from the current condition. The new condition is changed by subtracting α.

  As described above, in the fourth embodiment, when the detection result D1j of the first detection unit deviates from between the predetermined value Rdj and the predetermined value Rej, the primary transfer non-image condition Tn1j in the next image forming process. To change. As a result, it is possible to prevent the occurrence of a cleaning problem associated with forced developer consumption processing.

  The typical values of the primary and secondary transfer conditions are as follows. The primary transfer image condition is 30 μA, and the non-image condition can be changed within a predetermined range with 10 μA as a reference. The image condition of the secondary transfer is 60 μA, and the non-image condition can be changed within a predetermined range with reference to 15 μA.

  In the above-described embodiment, the predetermined value Raj can be set as appropriate according to the difference in the ability of the first cleaning means of each color photoconductor in the collection of the forced consumption developer. However, the predetermined value Raj is set for all colors. Both may be the same.

  The predetermined values Raj, Rbj, Rcj, Rdj or the predetermined value DDr are determined by various specifications including the type of the associated cleaning means, and are limit values for preventing problems such as defective cleaning. The image forming apparatus can be set as appropriate depending on the situation in which the image forming apparatus is operating in the market.

  Further, in the above embodiment, the patch image PGj for forced developer consumption is formed in the non-image area in the normal image forming process. However, the present invention interrupts the normal image forming process, This is also effective and applicable when the forced developer consumption mode formed in the non-image area on the image carrier is executed.

1 is a schematic configuration diagram of an image forming apparatus as an embodiment according to the present invention. It is a sectional side view showing the configuration of the secondary transfer roller 5A and the third cleaning means 6B. 3 is a schematic diagram of first detection means 91 and second detection means 92. FIG. 3 is a block diagram illustrating a configuration of a control unit of the image forming apparatus A. FIG. FIG. 4 is a schematic diagram showing a positional relationship between an image area Ap on the intermediate transfer body 70 and a non-image area An located between the image areas Ap. It is a flowchart which shows the image formation process performed with the control part 102 which concerns on this invention. FIG. 6 is a flowchart showing “patch image transfer optimization control” according to the first embodiment. It is a flowchart which shows "optimization control of patch image transfer" concerning a 2nd embodiment. It is a flowchart which shows "optimization control of patch image transfer" concerning a 3rd embodiment. It is a flowchart which shows "optimization control of patch image transfer" concerning a 4th embodiment. 6 is a characteristic diagram showing detection characteristics of first detection means 91 and second detection means 92. FIG.

Explanation of symbols

1Y, 1M, 1C, 1K Photoconductor 4Y, 4M, 4C, 4K Developer 5Y, 5C, 5M, 5K Primary transfer roller 5A Secondary transfer roller 6Y, 6M, 6C, 6K First cleaning means 6A Second cleaning means 6B Third cleaning unit 10Y, 10M, 10C, 10K Image forming unit 70 Intermediate transfer member 91 First detection unit 92 Second detection unit 102 Control unit

Claims (11)

An image forming unit that forms an image on an image region in the rotation direction of the image carrier using the developer of the developing device;
Primary transfer means for transferring the image formed in the image area on the image carrier to an intermediate transfer body under primary transfer conditions;
First cleaning means for recovering the developer remaining on the image carrier;
A second cleaning means for recovering the developer remaining on the intermediate transfer member;
A patch image for forcibly consuming the developer of the developing device is formed in a non-image area outside the image area on the image carrier, and the first non-image condition different from the primary transfer condition is used. A control unit that controls at least the image forming unit and the primary transfer unit so that the patch image is transferred to the intermediate transfer member, and the patch image is distributed and collected by the first cleaning unit and the second cleaning unit. ,
The first transfer unit is disposed on the downstream side in the moving direction of the image carrier or the intermediate transfer member with respect to the primary transfer unit, and detects the density of the patch image on the image carrier or the intermediate transfer member. Detecting means,
The image forming apparatus, wherein the control unit changes the first non-image condition based on a detection result of the first detection unit. The first detection means is disposed to face the intermediate transfer member;
The control unit changes the first non-image condition so as to reduce a transfer rate by the primary transfer unit when a detection result of the first detection unit is a predetermined value or more. The image forming apparatus according to 1. The first detection means is disposed to face the intermediate transfer member;
2. The control unit according to claim 1, wherein the first non-image condition is changed so as to increase a transfer rate by the primary transfer unit when a detection result of the first detection unit is a predetermined value or less. The image forming apparatus described in 1. The first detection means is disposed to face the image carrier;
2. The control unit according to claim 1, wherein the first non-image condition is changed so as to increase a transfer rate by the primary transfer unit when a detection result of the first detection unit is a predetermined value or more. The image forming apparatus described in 1. The first detection means is disposed to face the image carrier;
The control unit changes the first non-image condition so as to reduce a transfer rate by the primary transfer unit when a detection result of the first detection unit is a predetermined value or less. The image forming apparatus according to 1. An image forming unit that forms an image on an image region in the rotation direction of the image carrier using the developer of the developing device;
Primary transfer means for transferring the image formed in the image area on the image carrier to an intermediate transfer member;
Secondary transfer means for transferring the image transferred onto the intermediate transfer member to a transfer material under secondary transfer conditions;
A second cleaning means for recovering the developer remaining on the intermediate transfer member;
Third cleaning means for recovering the developer remaining in the secondary transfer means;
A patch image for forcibly consuming the developer of the developing device is formed in a non-image area outside the image area on the intermediate transfer member, and further, under a second non-image condition different from the secondary transfer condition. At least the image forming unit, the primary transfer unit, and the secondary transfer unit are configured to transfer the patch image to the transfer material and distribute the patch image to the second cleaning unit and the third cleaning unit for collection. A second control unit that detects a density of the patch image on the intermediate transfer member on the downstream side in the moving direction of the intermediate transfer member with respect to the secondary transfer unit;
The image forming apparatus, wherein the controller changes the second non-image condition based on a detection result of the second detection unit. The control unit may change the second non-image condition so as to increase a transfer rate by the secondary transfer unit when a detection result of the second detection unit is a predetermined value or more. 6. The image forming apparatus according to 6. The control unit calculates a difference between a detection result of the first detection unit and a detection result of the second detection unit, and changes the second non-image condition based on the difference. 6. The image forming apparatus according to 6. The image forming apparatus according to claim 1, wherein the patch image formed on the image carrier is a solid image. The image forming apparatus according to claim 1, wherein the secondary transfer unit has a roller shape. The image forming apparatus according to claim 1, wherein the secondary transfer unit has a belt shape.

Images