JP2006079002A - Image forming apparatus and transfer conveyance belt position control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve productivity by making shorter the time to be required for completing all-image formation of a job with mixed monochromatic image formation and color image formation. <P>SOLUTION: A CPU 210 calculates the ratio of the frequency of multi-color image formation and the frequency of monochromatic image formation and decides, when monochromatic image formation is requested, either the transfer conveyance belt is at a 1st position, where the transfer conveyance belt is made to abut against all of a plurality of image carriers or at a 2nd position where only an image carrier, corresponding to black is made to abut against the transfer conveyance belt and other image carriers, except the image carrier corresponding to black are all set apart from the transfer conveyance belt. When it is decided that the transfer conveyance belt is at the 1st position, the calculated ratio is compared with a predetermined ratio; and when the calculated ratio is smaller than the predetermined ratio, a transfer conveyance belt position control part 201 moves the transfer conveyance belt to the 2nd position. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus in which a plurality of image carriers are arranged in tandem, and to a transfer conveyance belt position control method for controlling the position of a transfer conveyance belt for conveying a transfer material.

  In recent years, with the spread of color image forming apparatuses using an electrophotographic system, there has been an increasing demand for speeding up color output in addition to the demand for recording quality of color images. A tandem type color image forming apparatus described in Patent Document 1 is known as a device that meets this requirement.

  This tandem type color image forming apparatus performs full color image formation. In this tandem type color image forming apparatus, as shown in FIG. 2, a transfer material is stored in a transfer material cassette 150. The transfer material is taken out from the transfer material cassette 150 one by one by the paper feed roller 151 and fed to the image forming unit by the roll pair 140.

  In this image forming unit, a transfer conveyance belt 11a that conveys a transfer material is stretched flat in a transfer material conveyance direction (from the bottom to the top in the figure) by a plurality of rotating rollers. The transfer material is electrostatically attracted to the transfer conveyance belt 11a by the suction roller 153 to which a bias is applied. Four drum-shaped image carriers (hereinafter referred to as “photosensitive drums”) 101C, 101Y, 101M, and 101Bk are arranged in a straight line so as to face the conveyance surface of the transfer conveyance belt 11a, and an image forming unit. Is configured. Each of the photosensitive drums 101C, 101Y, 101M, and 101Bk sequentially surrounds the vicinity of the peripheral surface thereof, and a charging device and a developing device are arranged, and a transfer member is arranged with the conveyance surface of the transfer conveyance belt 11a interposed therebetween.

  Then, the toner of each color of C (cyan), Y (yellow), M (magenta), and Bk (black) is accommodated in the housing of each developing device from the upstream side in the conveyance direction of the transfer material (downward in FIG. 2). The latent images on the photosensitive drums 101C, 101Y, 101M, and 101Bk are visualized as toner images by the toners of the respective colors, and the toner images are transferred by the transfer and transport belt 11a. The material is sequentially transferred at each transfer position. The toner image on the transfer material is conveyed and fixed to fixing means 152 located on the upper side of the apparatus, and then the fixed transfer material is discharged out of the apparatus.

  Also known is a tandem type color image forming apparatus capable of performing not only full color image formation but also monochrome image formation. In this tandem type color image forming apparatus, switching between full color image formation and monochrome image formation is photosensitive. This is performed by controlling the contact and separation between the body drum and the transfer conveyance belt which is a transfer material conveyance means.

  An example of forming a monochrome image in the tandem color image forming apparatus will be described. FIG. 10A shows a state in which the photosensitive drum 101 in the developing device is in contact with the transfer conveyance belt 11a. In this example, since the photosensitive drums 101Bk, 101M, 101Y, and 101C for all colors are in contact with the transfer conveyance belt 11a, full-color image formation is possible. A latent image is formed on the photosensitive drum 101 by the image writing laser beam, and the latent image is developed with toner of a developing device to be visualized as a toner image. The toner image is conveyed by a transfer conveyance belt. It is transferred to the transfer material.

  FIG. 10B shows a state in which the developing device and the transfer conveyance belt are separated from each other. In order to separate the photosensitive drums 101M, 101Y, 101C in the developing device other than Bk from the transfer conveyance belt 11a, the positions of the transfer rollers 102C, 102Y, 102M and the driven roller 11e of the transfer conveyance belt 11a are moved. . In this state, the toner image on the photosensitive drum in the developing device other than black is not transferred to the transfer material conveyed by the transfer conveyance belt.

The contact / separation operation of the transfer / conveying belt is performed by swinging the transfer / conveying belt driven roller 11e and the transfer rollers 102C, 102Y, and 102M. When color image formation is performed, the driven roller 11e and the transfer rollers 102C, 102Y, and 102M are driven in a direction in contact with the photosensitive drum, and when monochrome image formation is performed, the driven roller 11e and the transfer roller 102C, After driving 102Y and 102M in a direction away from the photosensitive drum, an image forming operation is started.
FIG. 2 is a schematic diagram of a tandem color image forming apparatus having a transfer conveyance belt separation mechanism, and includes photosensitive drums 101C, 101Y, 101M, and 101Bk, and developing rollers 103C, 103Y that convey toner from the image writing apparatus. 103M and 103Bk and the transfer conveyance belt 11a are shown.

  First, as shown in FIG. 10A, when forming a color image, the photosensitive drums 101C, 101Y, 101M, and 101Bk for four colors are brought into contact with the transfer conveyance belt 11a. On the other hand, as shown in FIG. 10B, when a monochrome image is formed, the photosensitive drums 101C, 101Y, and 101M are separated from the transfer conveyance belt 11a in order to reduce the performance deterioration of the image writing apparatus. Only the body drum 101Bk is brought into contact with the transfer conveyance belt 11a.

JP 09-288396 A

  However, for jobs in which monochrome image formation and full-color image formation are mixed, before the completion of all image formation, it is switched from monochrome image formation to full-color image formation, and conversely, from full-color image formation to monochrome image formation. Each time the transfer / conveying belt and the image writing device are brought into contact with or separated from each other, the image forming operation is stopped while switching from contact to separation, and conversely from separation to contact. It has been difficult to improve the productivity by further reducing the time required to complete the image formation of a job in which image formation and full-color image formation are mixed.

  In addition, it is difficult to further reduce the consumption of the transfer conveyance belt and the image writing apparatus due to the contact and separation between the transfer conveyance belt and the image writing apparatus.

  Therefore, the present invention solves such a problem, further shortens the time taken to complete all image formation of a job in which single color image formation and multicolor image formation are mixed, and improves productivity, and An object of the present invention is to provide an image forming apparatus and a transfer / conveying belt position control method capable of further reducing the consumption of the transfer / conveying belt and the image carrier.

  According to the first aspect of the present invention, visible images on a plurality of image carriers arranged in tandem corresponding to a plurality of colors including black used for image formation are transferred onto a transfer material conveyed by an endless transfer conveyance belt. An image forming apparatus that sequentially transfers images at a transfer position, wherein only the image carrier corresponding to the black color is transferred to or from the first position where the transfer and conveyance belt contacts all of the plurality of image carriers. And a movement control means for moving the transfer conveyance belt to any one of the second positions where all the image carriers excluding the image carrier corresponding to the black color are separated from the transfer conveyance belt. In the image forming apparatus, a multi-color image formation counting unit that counts the number of times of multi-color image formation, a single-color image formation count unit that counts the number of times of single-color image formation, and the multi-color image formation count Calculating means for calculating a ratio between the count value of the means and the count value of the monochromatic image formation counting means, and whether the transfer conveying belt is in the first position or the second position at the time of the monochromatic image formation request. Determining means for determining, and comparing means for comparing the ratio calculated by the calculating means with a predetermined ratio when the determining means determines that the transfer conveyance belt is in the first position; The movement control unit moves the transfer conveyance belt to the second position when the calculated ratio is less than the predetermined ratio as a result of comparison by the comparison unit. .

  In the first aspect of the invention, the comparison means can compare with a ratio designated from the outside instead of the predetermined ratio.

  According to the invention of claim 3, visible images on a plurality of image carriers arranged in tandem corresponding to a plurality of colors including black used for image formation are each transferred onto a transfer material conveyed by an endless transfer conveyance belt. An image forming apparatus that sequentially transfers images at a transfer position, wherein only the image carrier corresponding to the black color is transferred to or from the first position where the transfer and conveyance belt contacts all of the plurality of image carriers. And a movement control means for moving the transfer conveyance belt to any one of the second positions where all the image carriers excluding the image carrier corresponding to the black color are separated from the transfer conveyance belt. In the image forming apparatus, the movement control unit moves the transfer conveyance belt according to the position of the transfer conveyance belt designated from the outside of the first position or the second position during monochromatic image formation. And characterized in that.

  According to the invention of claim 4, visible images on a plurality of image carriers arranged in tandem corresponding to a plurality of colors including black used for image formation are each transferred onto a transfer material conveyed by an endless transfer conveyance belt. An image forming apparatus that sequentially transfers images at a transfer position, wherein only the image carrier corresponding to the black color is transferred to or from the first position where the transfer and conveyance belt contacts all of the plurality of image carriers. And a movement control means for moving the transfer conveyance belt to any one of the second positions where all the image carriers excluding the image carrier corresponding to the black color are separated from the transfer conveyance belt. In the image forming apparatus, a multi-color image formation counting unit that counts the number of times of multi-color image formation, a single-color image formation count unit that counts the number of times of single-color image formation, and the multi-color image formation count Calculating means for calculating the ratio between the count value of the means and the count value of the monochromatic image formation counting means, the ratio calculated by the calculating means at the normal end of monochromatic and multicolor image formation, and a predetermined ratio Comparing means for comparing, and determining means for determining whether the transfer / conveying belt is in the first position or the second position at the normal end of monochromatic and multi-color image formation, the movement control When the comparison unit determines that the calculated ratio is equal to or greater than the predetermined ratio and the determination unit determines that the transfer conveyance belt is in the second position, the transfer unit On the other hand, as a result of moving the conveyor belt to the first position and comparing by the comparing means, the calculated ratio is less than the predetermined ratio, and the determining means When the copy transport belt is determined to be in the first position, and wherein the moving the transfer conveyor belt in the second position.

  In the invention of claim 4, the comparison means can compare with a ratio designated from the outside, instead of a predetermined ratio.

  In the invention of claim 6, visible images on a plurality of image carriers arranged in tandem corresponding to a plurality of colors including black used for image formation are each transferred onto a transfer material conveyed by an endless transfer conveyance belt. An image forming apparatus that sequentially transfers images at a transfer position, wherein only the image carrier corresponding to the black color is transferred to or from the first position where the transfer and conveyance belt contacts all of the plurality of image carriers. And a movement control means for moving the transfer conveyance belt to any one of the second positions where all the image carriers excluding the image carrier corresponding to the black color are separated from the transfer conveyance belt. In the image forming apparatus, the transfer control unit is configured to transfer the transfer conveyance belt according to a position of the transfer conveyance belt designated from the outside of the first position or the second position when the monochrome image formation is normally completed. Wherein the moving the door.

  According to the seventh aspect of the present invention, visible images on a plurality of image carriers arranged in tandem corresponding to a plurality of colors including black for image formation are each transferred onto a transfer material conveyed by an endless transfer conveyance belt. An image forming apparatus that sequentially transfers images at a transfer position, wherein only the image carrier corresponding to the black color is transferred to or from the first position where the transfer and conveyance belt contacts all of the plurality of image carriers. And a movement control means for moving the transfer conveyance belt to any one of the second positions where all the image carriers excluding the image carrier corresponding to the black color are separated from the transfer conveyance belt. In a transfer conveyance belt position control method of an image forming apparatus, a multi-color image formation count step for counting the number of times of multi-color image formation, and a single-color image formation count for counting the number of times of single-color image formation A calculation step for calculating a ratio between the count value obtained by the step and the count value obtained by the multi-color image formation count step and the count value obtained by the single-color image formation count step; A determination step for determining which of the positions, and a ratio calculated by the calculation step when the determination step determines that the transfer conveyance belt is at the first position; A comparison step for comparing the ratio, and when the calculated ratio is less than the predetermined ratio as a result of the comparison in the comparison step, the transfer control belt moves the transfer conveyance belt to the second position. And a step of causing the step to occur.

  In the invention of claim 7, the comparison step can compare with a ratio designated from the outside instead of a predetermined ratio.

  According to the ninth aspect of the present invention, visible images on a plurality of image carriers arranged in tandem corresponding to a plurality of colors including black used for image formation are respectively transferred onto a transfer material conveyed by an endless transfer conveyance belt. A transfer conveyance belt position control method for sequentially transferring at a transfer position, wherein only the image carrier corresponding to the black color is in a first position where the transfer conveyance belt is brought into contact with all of the plurality of image carriers. Movement control for moving the transfer conveyance belt to any one of the second positions where all the image carriers except the image carrier corresponding to the black color are brought into contact with the transfer conveyance belt and separated from the transfer conveyance belt In the transfer conveyance belt position control method, the movement control means according to the position of the transfer conveyance belt designated from the outside of the first position or the second position when forming a monochrome image. Characterized by comprising the step of further moving the transfer conveyor belt.

  According to the invention of claim 10, visible images on a plurality of image carriers arranged in tandem corresponding to a plurality of colors including black used for image formation are each transferred onto a transfer material conveyed by an endless transfer conveyance belt. A transfer conveyance belt position control method for sequentially transferring at a transfer position, wherein only the image carrier corresponding to the black color is in a first position where the transfer conveyance belt is brought into contact with all of the plurality of image carriers. Movement control for moving the transfer conveyance belt to any one of the second positions where all the image carriers except the image carrier corresponding to the black color are brought into contact with the transfer conveyance belt and separated from the transfer conveyance belt And a multi-color image formation counting step for counting the number of times of multi-color image formation, and a single-color image formation count for counting the number of times of single-color image formation. And a calculation step for calculating a ratio between the count value by the multi-color image formation count step and the count value by the single-color image formation count step, and at the normal end of single-color and multi-color image formation, A comparison step comparing the ratio with a predetermined ratio, and determining whether the transfer / conveying belt is in the first position or the second position at the normal end of monochromatic and multi-color image formation As a result of comparison between the determination step and the comparison step, when the calculated ratio is equal to or greater than the predetermined ratio, and the determination step determines that the transfer conveyance belt is in the second position, The transfer control belt is moved to the first position by the movement control means, and on the other hand, the result of the comparison in the comparison step is compared. When the calculated ratio is less than the predetermined ratio and the determination step determines that the transfer conveyance belt is in the first position, the movement control means moves the transfer conveyance belt to the first position. And a step of moving to two positions.

  In the invention of claim 10, the comparing step can compare with a ratio designated from the outside, instead of a predetermined ratio.

  In the invention of claim 12, visible images on a plurality of image carriers arranged in tandem corresponding to a plurality of colors including black used for image formation are each transferred onto a transfer material conveyed by an endless transfer conveyance belt. A transfer conveyance belt position control method for sequentially transferring at a transfer position, wherein only the image carrier corresponding to the black color is in a first position where the transfer conveyance belt is brought into contact with all of the plurality of image carriers. Movement control for moving the transfer conveyance belt to any one of the second positions where all the image carriers except the image carrier corresponding to the black color are brought into contact with the transfer conveyance belt and separated from the transfer conveyance belt In the transfer conveyance belt position control method of the image forming apparatus having the means, the position of the transfer conveyance belt designated from the outside of the first position or the second position at the normal end of monochromatic image formation Accordingly, it characterized by comprising the step of moving the transfer conveyor belt by the movement control means.

  According to a thirteenth aspect of the present invention, there is provided an image forming apparatus that forms an image using a plurality of image carriers, and a transfer unit that transfers images on the plurality of image carriers to a transfer material; Mode control means for switching between a first mode in which image formation is performed using all of the image carriers and a second mode in which image formation is performed using a predetermined image carrier among the plurality of image carriers; and the transfer A first position where the means abuts all of the plurality of image carriers, and a predetermined image carrier of the plurality of image carriers, and all image carriers other than the predetermined image carrier Movement control means for moving the transfer means at a second position separated from the body, the movement control means when the mode control means is switched to the second mode, the transfer means Executes image formation while moving to the first position Number of times and based on the number of times of executing the image formation while moving the to the transfer means and the second position, and performs image formation while moving the transfer means to the first position.

  According to a fourteenth aspect of the present invention, there is provided an image forming apparatus that forms an image using a plurality of image carriers, and a transfer unit that transfers images on the plurality of image carriers to a transfer material; Mode control means for switching between a first mode in which image formation is performed using all of the image carriers and a second mode in which image formation is performed using a predetermined image carrier among the plurality of image carriers; and the transfer A first position where the means abuts all of the plurality of image carriers, and a predetermined image carrier of the plurality of image carriers, and all image carriers other than the predetermined image carrier A movement control means for moving the transfer means at a second position to be separated from the body, and the movement control means is configured to receive an external signal when switched to the second mode by the mode control means. Based on the designation, the transfer means is moved to the first position. And determining whether to move to the second position or.

  According to the present invention, since it is configured as described above, it is possible to further reduce the time taken until the completion of all image formation of a job in which single-color image formation and multi-color image formation are mixed, and to improve productivity, and The consumption of the transfer conveyance belt and the image writing apparatus can be further reduced.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<First Embodiment>
FIG. 1 shows a first embodiment of the present invention. This is an example of a tandem type color image forming apparatus, and this structure is shown in FIG.

  A color image forming apparatus 2 in FIG. 1 is connected to an external device 1, and in the color image forming apparatus 2, a transfer conveyance belt control unit 201, a fixing control unit 202, a sheet conveyance control unit 203, a memory 211, The CPU 210 and the input / output unit 212 are connected to each other via a system bus.

The transfer / conveying belt position control unit 201 controls the position of the transfer / conveying belt 11a to either the position shown in FIG. 2 or the position shown in FIG. The transfer conveyance belt 11a is in a position where it abuts with the image writing devices 106C, 106Y, 106M and 106Bk in FIG. 2, and is in a position where it abuts only with the image writing device 106Bk in FIG.
The fixing control unit 202 controls driving of the fixing unit 152. The paper conveyance control unit 203 controls conveyance of the transfer material. The memory 211 stores a control program and is used as a work area for the CPU 210. The CPU 210 controls each unit according to the control program in the memory 211. The input / output unit 212 functions as an interface with the external device 1.

  Further, the color image forming apparatus shown in the present embodiment has a color image forming counter for counting the number of times of color image formation and a monochrome image forming counter for counting the number of times of monochrome image formation in the CPU 210. These counter values are counted up by the CPU 210 and stored in the memory 211. These counter values are initialized when the power of the image forming apparatus is turned on, and count values obtained by performing each image formation at a timing described later are counted and held.

(overall structure)
FIG. 2 will be described. The tandem type color image forming apparatus 2 includes four photosensitive drums 101 (101C, 101Y, 101M, and 101Bk), and two inner photosensitive drums with respect to the upper and lower photosensitive drums 101C and 101Bk. 101Y and 101M are arranged so as to protrude about 1 mm toward the transfer conveyance belt. The four photosensitive drums 101 are driven to rotate counterclockwise in FIG. 2 by driving means (not shown).

  A charging unit 104 (104C, 104Y, 104M, 104Bk) for uniformly charging the surface of the photosensitive drum 1 in order according to the rotation direction, and a laser beam are irradiated on the periphery of each photosensitive drum based on image information. Exposure means 108 (108C, 108Y, 108M, 108Bk) for forming an electrostatic latent image on the photosensitive drum 101, and developing means 103 (visualizing the toner image by attaching toner to the electrostatic latent image) 103C, 103Y, 103M, 103Bk) and transfer means (transfer blade) 102 (102C, 102Y, 102M, 102Bk) for transferring the toner image on the photosensitive drum 101 to a transfer material are provided to form an image. Means are configured.

  Here, the photosensitive drum 101, the charging unit 104, and the developing unit 103 are integrated into a cartridge to form a process cartridge 106 (106C, 106Y, 106M, 106Bk).

  Further, the transfer material fed from the feeding unit 150 is transported by the transport means 11 constituted by the transfer transport belt 11a, and the toner image on each photosensitive drum is sequentially transferred to the transfer material at each transfer position. The toner image on the transfer material is fixed by the fixing unit 152, and the transferred transfer material is discharged out of the apparatus by the discharge roller pair.

(Image formation)
Each photoconductive drum 101 as an image carrier is configured by applying an organic photoconductive layer (OPC) to the outer peripheral surface of an aluminum cylinder having a diameter of 30 mm. The photosensitive drum 101 is rotatably supported at both ends by flanges, and is driven to rotate counterclockwise in FIG. 2 by transmitting a driving force from a driving motor (not shown) to one end. .

  Each charging means 104 is a conductive roller formed in the shape of a roller. The roller is brought into contact with the surface of the photosensitive drum 101, and a charging bias voltage is applied by a power source (not shown), whereby the photosensitive drum. The surface of 101 is charged uniformly.

  The exposure unit 108 forms an electrostatic latent image on the photosensitive drum 101 by irradiating a laser beam based on image information by a drive circuit (not shown).

  The developing unit 103 (103C, 103Y, 103M, 103Bk) has a toner storage unit that stores toner of each color of black, cyan, magenta, and yellow, and is adjacent to the surface of the photosensitive drum 101, and a driving unit (not shown). , And the development is performed by applying a development bias voltage from a development bias power source (not shown). The toner storage portion stores toners of cyan, yellow, magenta, and black in order from the upstream side in the transfer material conveyance direction.

  Inside the transfer conveyance belt 11a, transfer rollers 102C, 102Y, 102M, and 102Bk that are in contact with the transfer conveyance belt 11a are arranged in parallel, corresponding to the four photosensitive drums 101C, 101Y, 101M, and 101Bk. These transfer rollers 102 are connected to a transfer bias power source (not shown), and a positive electric field is applied from the transfer roller 102 to the transfer material via the transfer conveyance belt 11a. The negative toner images on the photosensitive drum 101 are sequentially transferred to the transfer material in contact with the photosensitive drum 101.

  The toner image transferred to the transfer material is fixed by being heated and pressurized when passing through a fixing means 152 comprising a heating roller that is driven to rotate and a pressure roller that is driven to rotate.

(Transfer material transfer)
The transfer material is fed from the feeding unit and conveyed to the image forming area by the transfer conveyance belt 11a.

  In this paper feed unit, a plurality of transfer materials are stored in a paper feed cassette 150, and a semi-moon pickup roller 151 for picking up the transfer materials one by one is rotatable in the vicinity of the paper feed cassette 150. Is provided. The transfer material picked up by the intermittent rotation of the pickup 151 is fed to the transfer conveyance belt 11 a by the feed roller pair 140.

The transfer conveyance belt 11a as a transfer material carrier constituting the conveyance means is stretched and supported by four rollers of a driving roller 11b and driven rollers 11c, 11d, and 11e, and all the photosensitive drums 101C, 101Y, 101M, and 101Bk. It is arrange | positioned facing. This transfer / conveying belt 11a is generally composed of an endless film-like member having a thickness of 100 to 150 μm and having a volume resistivity of 10 ¹⁰ to 10 ¹⁴ Ω · cm. The transfer conveyance belt 11 a is circulated and moved by a driving roller 11 b so as to electrostatically attract a transfer material to the outer peripheral surface facing the photoconductor drum 101 and bring the transfer material into contact with the photoconductor drum 101. The toner image on the photosensitive drum 101 is transferred to the transfer material conveyed by the transfer conveyance belt 11a at the transfer position.

  An adsorption roller 153 is disposed at the most upstream position of the transfer conveyance belt 11a, the transfer material is sandwiched between the adsorption roller 153 and the transfer conveyance belt 11a, and the transfer material is adsorbed to the transfer conveyance belt 11a by the adsorption roller 153. Is done. When the transfer material is conveyed, a bias voltage is applied to the attracting roller 153, whereby an electric field is formed between the opposed grounded transfer conveyance belt 11a, and a dielectric is formed between the transfer conveyance belt 11a and the transfer material. Polarization occurs, and electrostatic attracting force is generated on both.

(Switching between color image formation and monochrome image formation)
The operation when color image formation and monochrome image formation are performed will be described.

  First, color image formation will be described with reference to FIG. In color image formation, first, the development roller 103C, 103Y, 103M, and 103Bk is moved to a position where the development roller 103C, 103Y, 103M, and 103Bk comes into contact with the photosensitive drums 101C, 101Y, 101M, and 101Bk for four colors. The latent images on the photosensitive drums 101C, 101Y, 101M, and 101Bk are developed by the developing rollers 103C, 103Y, 103M, and 103Bk using the toner conveyed from the image writing devices 106C, 106Y, 106M, and 106Bk, and the toner images As a visible image. Thereafter, the toner image on the photosensitive drum 101 is sequentially transferred onto the transfer material by the transfer devices 102C, 102Y, 102M, and 102Bk, and the toner image (color image) transferred onto the transfer material is fixed to the fixing unit 152. It is fixed by.

  Next, monochrome image formation will be described with reference to FIG. In monochrome image formation, image formation is performed using only the image writing device 106Bk in order to reduce performance degradation of the image writing devices 106C, 106Y, and 106M that are not related to image formation. Therefore, at the time of monochrome image formation, as shown in FIG. 10, the developing roller 103Bk is moved to a position where only the Bk photosensitive drum 101Bk is brought into contact with the developing separation plate 16, and then, on the photosensitive drum 101Bk. A latent image is formed, and this latent image is developed using the toner conveyed from the image writing device 106Bk by the developing roller 103Bk to be visualized as a toner image. Thereafter, the toner image on the photosensitive drum 101Bk is transferred onto the transfer material by the transfer device 102Bk, and the toner image (Bk monochrome image) transferred onto the transfer material is fixed by the fixing unit 152.

  In monochrome image formation, the transfer conveyance belt position control unit 201 moves the pair of the driven roller 11e and the suction roller 153 of the transfer conveyance belt 11a away from the image writing devices 106C, 106Y, and 106M. Since the images 106C, 106Y, and 106M are separated from the transfer conveyance belt 11a, the image writing devices 106C, 106Y, and 106M that are not related to image formation are not driven at all, and therefore are not consumed in the monochrome image formation.

  Depending on the size of the transfer material or the type of transfer material, the transfer material may be transported without being properly attracted to the transfer transport belt 11a. In this case, since the transfer conveyance belt 11a is separated from the image writing devices 106C, 106Y, and 106M, the transfer material is not properly attracted to the transfer conveyance belt 11a and an image is formed. Therefore, even when the transfer material is conveyed without being properly attracted to the transfer conveyance belt 11a in the monochrome image formation, the transfer conveyance belt 11a is transferred to the image writing devices 106C, 106Y, and 106M in the same manner as in the color image formation. Further, it is necessary to transport the transfer material in a state where the contact is also made.

(Image forming operation)
When the image forming request is made, the external device 1 notifies the color image forming device 2 of an image forming mode for designating whether an image to be formed from now on is a monochrome image or a color image. To do.

  The operation of the color image forming apparatus 2 when a color image formation request is generated from the external apparatus 1 will be described with reference to the timing chart of FIG.

  When a color image formation request from the external device 1 is generated, first, a pre-rotation operation for image formation is started. In this pre-rotation operation, when the transfer conveyance belt 11a and the image writing devices 106C, 106Y, and 106M are separated from each other at the start of the image forming operation, the transfer conveyance belt 11a and the image writing devices 106C, 106Y, and 106M are moved. The operation of bringing into contact is also performed.

  Furthermore, when a time T11 has elapsed since the start of the pre-rotation operation, the transfer unit starts feeding the transfer material. The first color image can be formed after a lapse of T12 hours from the start of the pre-rotation operation, and this T11 time is a time after a predetermined time has elapsed since the T12 time.

  The transfer material reaches the registration sensor 141 after a lapse of T13 time from the start of paper feeding. A TOP signal as an image formation synchronization signal is output when T14 time determined in advance by the mechanical arrangement has elapsed from the time when the transfer material reaches the registration sensor 141. When the TOP signal is output, 1 is added to the value of the color image formation counter. In the example of FIG. 4, the color image formation counter value N is set to N + 1.

  Then, toner images of respective colors are formed on the four photosensitive drums 101 based on the TOP signal. Thereafter, the toner image on the photosensitive drum 101 is acted on by the transfer rollers 102C, 102Y, 102M, and 102Bk arranged in correspondence with the four photosensitive drums 101C, 101Y, 101M, and 101Bk on the inner side of the transfer conveyance belt 11a. Thus, the image is sequentially transferred onto the transfer material in contact with the photosensitive drum 101. The toner image on the transfer material is fixed by being heated and pressurized when the transfer material passes through a fixing unit 152 including a heating roller that is driven and rotated and a pressure roller that is driven and rotated. Is discharged out of the device.

  Thereafter, the color image forming apparatus 2 performs a post-rotation operation for shifting to the stop state, and stops the operation after a predetermined post-rotation operation is completed.

  Thereafter, when the rotation operation is completed, the transfer conveyance belt 11a and the image writing devices 106C, 106Y, and 106M stop the operation in contact with each other.

  Next, the operation of the color image forming apparatus 2 when a monochrome image formation request is generated from the external apparatus 1 will be described with reference to the timing chart of FIG.

  When a monochrome image formation request is generated from the external device 1, first, a pre-rotation operation for image formation is started. In this pre-rotation operation, it is determined whether to perform image formation in a state where the transfer conveyance belt 11a and the image writing devices 106C, 106Y, and 106M are in contact with each other, or to perform image formation in a state of being separated from each other. Take control. This determination means will be described later.

  Next, when T21 time has elapsed since the start of the pre-rotation, the transfer material is started to be fed from the paper feed unit. The fourth color image can be formed after a lapse of T12 hours from the start of the pre-rotation operation, and this T21 time is a time after a predetermined time has elapsed from the T12 time.

  In monochrome image formation, since image formation is performed from the fourth color, it is not necessary to consider the timing at which image formation of the first color necessary for color image formation is possible. Therefore, the time T21 from the start of the pre-rotation operation to the start of the transfer material feeding operation can be set shorter by T15 hours than the T11 time (FIG. 5) necessary for color image formation.

  The transfer material fed from the paper feed cassette 150 reaches the registration sensor 141 after T13 time has elapsed since the start of paper feed. A TOP signal is output as an image formation synchronization signal when a time T13 determined in advance by mechanical arrangement has elapsed from the time when the transfer material reaches the registration sensor 141. When the TOP signal is output, 1 is added to the value of the monochrome image formation counter. In the example of FIG. 5, the monochrome image formation counter value M is M + 1.

  Using this TOP signal as a reference, image formation is not performed on the three photosensitive drums 101C, 101Y, and 101M not related to monochrome image formation, and a toner image is formed only on the photosensitive drum 101Bk related to monochrome image formation. To do.

  Thereafter, the toner image formed on the photosensitive drum 101Bk is transferred to the transfer material by the action of the transfer roller 102Bk, and the toner image on the transfer material is added to the transfer material that is driven and rotated by the heating roller that is driven to rotate. When passing through the fixing means 152 comprising a pressure roller, it is fixed by heat and pressure, and the transfer material after fixing is discharged to a paper discharge tray.

  Thereafter, a post-rotation operation for shifting to the stop state is performed. After the post-rotation operation is finished, the operation is stopped in a state where the transfer conveyance belt 11a and the image writing devices 106C, 106Y, and 106M are separated from each other.

(Contact / separation operation of the transfer / conveying belt 11a)
FIG. 6 is a program stored in the RAM of FIG. 1, and when an image forming request is made from the external device 1, the image is transferred with the transfer conveyance belt 11 a and the image writing devices 106 </ b> C, 106 </ b> Y, 106 </ b> M in contact with each other. 6 is a flowchart illustrating an example of a program for determining whether to perform image formation or to perform image formation in a separated state.

  It is determined whether the image formation mode notified from the external device 1 is color image formation or monochrome image formation (S1000).

  If it is determined in step S1000 that the image formation mode is color image formation, either the transfer conveyance belt 11a is in contact with or separated from the image writing devices 106C, 106Y, and 106M. Is determined (S1005).

  If it is determined in step S1005 that the transfer conveyance belt 11a is in contact with the image writing devices 106C, 106Y, and 106M, the image forming operation is started according to the control described above.

  On the other hand, if it is determined in step S1005 that the transfer conveyance belt 11a is separated from the image writing devices 106C, 106Y, 106M, first, the transfer conveyance belt 11a is moved to the image writing devices 106C, 106Y, It is moved to a position where it abuts against 106M (S1006). Thereafter, after the transfer / conveying belt 11a is brought into contact with the image writing devices 106C, 106Y, and 106M, the image forming operation is started in accordance with the control described above.

  On the other hand, if it is determined in step S1000 that the image formation mode is monochrome image formation, the transfer conveyance belt 11a is in contact with or separated from the image writing devices 106C, 106Y, 106M. Is determined (S1001).

  If it is determined in step S1001 that the transfer / conveying belt 11a is separated from the image writing devices 106C, 106Y, and 106M, the image forming operation is started according to the control described above.

  On the other hand, if it is determined in step S1001 that the transfer conveyance belt 11a is in contact with the image writing devices 106C, 106Y, 106M, the color image formation counter value and the monochrome image formation counter value are used to calculate The ratio of the frequency of color image formation / monochrome image formation in which the image is formed in the color image forming apparatus 2 is calculated. Here, this ratio is a value obtained by dividing the color image formation counter value N by the monochrome image formation counter value M (S1002).

  The value obtained in step S1002 is compared with a reference value held in advance in the memory 211 (S1003).

  If the obtained value is greater than or equal to the reference value, image formation is performed according to the control described above in a state where the transfer conveyance belt 11a is in contact with the image writing devices 106C, 106Y, and 106M. Start operation.

  On the other hand, when the obtained value is smaller than the reference value, the transfer / conveying belt 11a is separated from the image writing devices 106C, 106Y, and 106M (S1004), and then an image forming operation is started in accordance with the control described above. .

  As a means for detecting whether the transfer conveyance belt 11a is in a contact state or a separation state, a method of detecting by a sensor or a method of detecting by monitoring a transfer current is applicable. When detecting by a sensor, the sensor may be arranged at a position where the logic is inverted between the contact position and the separation position when the driven roller 11e is operated. When detecting by monitoring the transfer current, the first station is mainly used for image formation. In this embodiment, the current flowing when the transfer current is applied to 102C at Cyan position 106C is monitored. Thus, the contact / separation may be detected.

  In the present embodiment, at the time of image formation, the contact or separation position of the transfer material transport belt 11a at the time of monochrome image formation is determined according to the frequency of color / monochrome image formation by the user. The time required for contact or separation of the transfer material conveyance belt 11a performed based on the change of the formation mode is minimized, and the degree of wear of the image writing device and the transfer conveyance belt 11a necessary for the image forming operation can be controlled. .

<Second Embodiment>
In the present embodiment, when an image formation request is generated from the external apparatus 1, image formation is performed with the transfer conveyance belt 11a and the image writing apparatuses 106C, 106Y, and 106M in contact with each other, or the image is formed in a separated state. It was decided to make the formation. FIG. 7 is a flowchart illustrating an example of a program stored in the memory 211 of FIG. 1 in the present embodiment.

  When a monochrome image is formed from the external device 1 in advance, the transfer conveyance belt 11a and the image writing device are brought into contact with each other to perform an image forming operation, or the transfer conveyance belt 11a and the image writing device are separated from each other to form an image. The transfer conveyance belt position designation that can be designated is received.

  First, it is determined whether the image forming mode notified from the external device 1 is a color image or a monochrome image (S1100).

  If it is determined in step S1100 that the image formation mode is color image formation, the transfer conveyance belt 11a is in contact with or separated from the image writing devices 106C, 106Y, and 106M. Is determined (S1104).

  If it is determined in step S1104 that the transfer conveyance belt 11a is in contact with the image writing devices 106C, 106Y, and 106M, the image forming operation is started according to the control described above.

  On the other hand, if it is determined in step S1104 that the transfer conveyance belt 11a is separated from the image writing devices 106C, 106Y, 106M, first, the transfer conveyance belt 11a is moved to the image writing devices 106C, 106Y, It is moved to a position where it abuts against 106M (S1105). After that, after the transfer / conveying belt 11a shifts to a state where it abuts on the image writing devices 106C, 106Y, and 106M, the image forming operation is started in accordance with the control described above.

  On the other hand, if it is determined in step S1100 that the image forming mode is monochrome image formation, the transfer conveyance belt position designation designated by the external device 1 causes the transfer conveyance belt 11a and the image writing device to contact each other to make an image. It is determined whether or not it is designated to form the image, or whether or not it is designated to form an image by separating the transfer conveyance belt 11a from the image writing device (S1101).

  If it is determined in step S1101 that the transfer conveyance belt position designation designated by the external device 1 designates that the transfer conveyance belt 11a and the image writing device are in contact with each other to form an image, the transfer conveyance belt. It is determined whether 11a is in contact with or separated from the image writing devices 106C, 106Y, and 106M (S1104).

  If it is determined in step S1104 that the transfer conveyance belt 11a is in contact with the image writing devices 106C, 106Y, and 106M, the image forming operation is started according to the control described above.

  On the other hand, if it is determined in step S1104 that the transfer conveyance belt 11a is separated from the image writing devices 106C, 106Y, 106M, first, the transfer conveyance belt 11a is moved to the image writing devices 106C, 106Y, It is moved to a position where it abuts against 106M (S1105). After that, after the transfer / conveying belt 11a shifts to a state where it abuts on the image writing devices 106C, 106Y, and 106M, the image forming operation is started in accordance with the control described above.

  On the other hand, if it is determined in step S1101 that the transfer conveyance belt position designation designated by the external device 1 designates that the transfer conveyance belt 11a and the image writing device are separated from each other to form an image, It is determined whether the conveyor belt 11a is in contact with or separated from the image writing devices 106C, 106Y, and 106M (S1102).

  If it is determined in step S1102 that the transfer / conveyance belt 11a is separated from the image writing devices 106C, 106Y, and 106M, the image forming operation is started according to the control described above.

  On the other hand, if it is determined in step S1102 that the transfer conveyance belt 11a is in contact with the image writing devices 106C, 106Y, 106M, first, the transfer conveyance belt 11a is moved to the image writing devices 106C, 106Y, Move to a position away from 106M (S1103). After that, after the transfer / conveying belt 11a shifts to a state where it abuts on the image writing devices 106C, 106Y, and 106M, the image forming operation is started in accordance with the control described above.

  In the present embodiment, when an external device 1 that allows the user's use frequency of color / monochrome image formation or some other user setting at the time of image formation is provided, the monochrome device is specified according to the designation from the external device 1. Since the contact or separation of the transfer material conveyance belt 11a at the time of image formation is determined, the time required for the contact or separation of the transfer material conveyance belt 11a caused by the change of the image formation mode is minimized, and further, the image It is possible to further reduce the consumption of the image writing device and the transfer material transport belt 11a necessary for the forming operation.

<Third Embodiment>
In the first embodiment, at the end of the post-rotation operation when color image formation is performed, the operation is stopped while the transfer conveyance belt 11a and the image writing devices 106C, 106Y, and 106M are in contact with each other. At the end of the post-rotation operation when image formation was performed, the operation was stopped in a state where the transfer conveyance belt 11a and the image writing devices 106C, 106Y, and 106M were separated.

  On the other hand, in the present embodiment, at the end of a predetermined post-rotation operation during the image forming operation, the operation is stopped while the transfer conveyance belt 11a is in contact with the image writing devices 106C, 106Y, and 106M. Whether to stop the operation in a separated state is determined.

  FIG. 8 is a flowchart showing an example of a control program stored in the RAM of FIG. 1 in the present embodiment. When the post-rotation is started after the image forming operation is completed, the color image forming frequency and the monochrome image forming frequency are determined from the color image forming counter value and the monochrome image forming counter value, as in the first embodiment. Calculate the ratio. Here, this ratio is a division value obtained by dividing the color image formation counter value N by the monochrome image formation counter value M (S1200).

  The division value obtained in step S1200 is compared with a reference value stored in advance in the memory 211 (S1201).

  If it is determined in step S1201 that the value obtained in step S1200 is greater than or equal to the reference value stored in advance in the memory 211, the transfer conveyance belt 11a and the image writing devices 106C, 106Y, It is determined whether 106M is in contact or separated (S1204).

  If it is determined in step S1204 that the transfer conveyance belt 11a is in a state of being separated from the image writing devices 106C, 106Y, 106M, first, the transfer conveyance belt 11a is moved to the image writing devices 106C, 106Y, 106M. It moves to the contact position (S1205). Thereafter, after the transfer / conveying belt 11a is brought into contact with the image writing devices 106C, 106Y, and 106M, the post-rotation operation described above is performed.

  If it is determined in step S1204 that the transfer conveyance belt 11a is in contact with the image writing devices 106C, 106Y, and 106M, the post-rotation operation described above is performed.

  With this control, when the usage state of the user is in a state where the ratio of color images is large, the transfer conveyance belt 11a is moved to the image writing devices 106C, 106Y, and 106M at the end of the subsequent rotation of the color image forming apparatus 2. The color image forming apparatus 2 stops in a state where the state is shifted to the contact state.

  Therefore, when the next image formation is color image formation, it is possible to reduce the time required for the transfer conveyance belt 11a to contact the image writing devices 106C, 106Y, and 106M.

  If it is determined in step S1201 that the calculation result in S1200 is smaller than the reference value held in advance in the memory 211, the transfer conveyance belt 11a and the image writing devices 106C, 106Y, and 106M come into contact with each other. It is determined whether it is in a separated state or in a separated state (S1202).

  If it is determined in step S1202 that the transfer conveyance belt 11a is in contact with the image writing devices 106C, 106Y, 106M, first, the transfer conveyance belt 11a is moved from the image writing devices 106C, 106Y, 106M. It moves to the position which leaves | separates (S1203). After that, after the transfer / conveying belt 11a is moved away from the image writing devices 106C, 106Y, and 106M, the post-rotation operation described above is performed.

  On the other hand, if it is determined in step S1204 that the transfer / conveying belt 11a is separated from the image writing devices 106C, 106Y, and 106M, the post-rotation operation described above is performed.

  By controlling as described above, at the end of the post-rotation of the color image forming apparatus 2, the color image forming apparatus 2 is moved in a state in which the transfer conveyance belt 11a is moved away from the image writing apparatuses 106C, 106Y, and 106M. Stops.

  Therefore, when the next image formation is monochrome image formation, it is possible to reduce the time for separating the transfer conveyance belt 11a from the image writing devices 106C, 106Y, and 106M.

  In the present embodiment, at the end of the image forming operation, the position of contact or separation between the transfer conveyance belt 11a and the image writing device after the end of image formation is determined according to the use frequency of color / monochrome image formation by the user. As a result, the time required for contact or separation of the transfer / conveying belt 11a generated by changing the image forming mode during the next image forming operation is minimized, and the image writing device and the transfer / conveying belt necessary for the image forming operation are further reduced. The consumption degree of 11a can be controlled.

<Fourth embodiment>
In the present embodiment, at the end of a predetermined post-rotation operation during the image forming operation, the operation is stopped while the transfer conveyance belt 11a and the image writing devices 106C, 106Y, and 106M are in contact with each other, or the operation is performed in a separated state. Judged whether to stop.

  FIG. 9 is a flowchart illustrating an example of a program stored in the memory 211 of FIG. 1 in the fourth embodiment.

  At the start of post-rotation after the end of the image forming operation from the external device 1, the image forming operation is stopped by contacting the transfer conveying belt 11a and the image writing device, or the transfer conveying belt 11a and the image writing device are stopped. A transfer conveyance belt stop position designation that can designate whether to stop image formation after being separated is received.

  When the post-rotation is started after the image forming operation is finished, the transfer conveyance belt stop position designation designated by the external device 1 designates that the image forming operation is stopped by contacting the transfer conveyance belt 11a and the image writing device. Or whether it is specified to stop the image formation by separating the transfer conveyance belt 11a from the image writing device (S1300).

  As a result of the determination in step S1300, when the transfer conveyance belt stop position designation designated from the external device 1 designates that the transfer conveyance belt 11a and the image writing device are brought into contact with each other to stop the image forming operation. Determines whether the transfer conveyance belt 11a is in contact with or separated from the image writing devices 106C, 106Y, 106M (S1303).

  If it is determined in step S1303 that the transfer conveyance belt 11a is in a state of being separated from the image writing devices 106C, 106Y, 106M, first, the transfer conveyance belt 11a is moved to the image writing devices 106C, 106Y, 106M. It moves to the contact position (S1304). Thereafter, after the transfer / conveying belt 11a is brought into contact with the image writing devices 106C, 106Y, and 106M, the post-rotation operation described above is performed.

  If it is determined in step S1303 that the transfer conveyance belt 11a is in contact with the image writing devices 106C, 106Y, and 106M, the post-rotation operation described above is performed.

  As a result of the determination in step S1300, when the transfer conveyance belt stop position designation designated from the external device 1 designates that the transfer conveyance belt 11a and the image writing device are separated from each other to stop the image forming operation. Determines whether the transfer conveyance belt 11a is in contact with or separated from the image writing devices 106C, 106Y, 106M (S1301).

  If it is determined in step S1301 that the transfer conveyance belt 11a is in contact with the image writing devices 106C, 106Y, 106M, first, the transfer conveyance belt 11a is moved from the image writing devices 106C, 106Y, 106M. It moves to the position which leaves | separates (S1302). Thereafter, after the transfer / conveying belt 11a is brought into contact with the image writing devices 106C, 106Y, and 106M, the post-rotation operation described above is performed.

  If it is determined in step S1301 that the transfer conveyance belt 11a is separated from the image writing devices 106C, 106Y, and 106M, the post-rotation operation described above is executed.

  In the present embodiment, when there is an external device 1 capable of user color / monochrome image formation use frequency or some other user setting, this external image 1 to this color image forming device 2 On the other hand, by designating the contact or separation position between the transfer material conveying belt 11a and the image writing device at the end of the image forming operation, the image forming mode is changed at the next image forming operation. The time required for the contact or separation of the transfer material conveyance belt 11a is minimized, and the consumption of the image writing device and the transfer conveyance belt 11a necessary for the image forming operation can be further reduced.

It is a block diagram which shows the 1st Embodiment of this invention. FIG. 2 is a cross-sectional view showing the structure of the color image forming apparatus of FIG. FIG. 2 is a cross-sectional view illustrating a structure of the color image forming apparatus in FIG. 1 in a state where a photosensitive drum and a conveyance belt are separated from each other. 6 is a timing chart illustrating an example of timing when forming a color image. It is a timing chart which shows an example of the timing at the time of monochrome image formation. 2 is a flowchart illustrating an example of a program stored in a memory 211 of FIG. 1 in the first embodiment. It is a flowchart which shows an example of the program stored in the memory 211 of FIG. 1 in 2nd Embodiment. It is a flowchart which shows an example of the program stored in the memory 211 of FIG. 1 in 3rd Embodiment. It is a flowchart which shows an example of the program stored in the memory 211 of FIG. 1 in 4th Embodiment. FIG. 4 is an explanatory diagram for explaining a contact / separation relationship between a photosensitive drum and a transfer conveyance belt in color image formation and monochrome image formation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 External apparatus 2 Color image forming apparatus 11a Transfer conveyance belt 11b Transfer conveyance belt drive roller 11c, 11d, 11e Transfer conveyance belt driven roller 16 Development separation plate 101 Photosensitive drum 102 Transfer means 106 Image writing device 150 Paper feed part 152 Fixing means 201 Transfer conveyance belt position control unit 202 Fixing control unit 203 Paper conveyance control unit 210 CPU
211 Memory 212 Input / output unit

Claims (14)

Visible images on a plurality of image carriers arranged in tandem corresponding to a plurality of colors including black used for image formation are sequentially transferred at each transfer position onto a transfer material conveyed by an endless transfer conveyance belt. An image forming apparatus, wherein the transfer conveying belt is brought into contact with all of the plurality of image carriers, or only the image carrier corresponding to the black color is brought into contact with the transfer conveying belt, and In the image forming apparatus having movement control means for moving the transfer conveyance belt to any one of the second positions where all the image carriers excluding the image carrier corresponding to black are separated from the transfer conveyance belt,
Multi-color image formation counting means for counting the number of times of multi-color image formation;
Monochrome image formation counting means for counting the number of times of monochrome image formation;
Calculating means for calculating a ratio between the count value of the multi-color image formation counting means and the count value of the single-color image formation counting means;
Determination means for determining whether the transfer conveyance belt is in the first position or the second position when a monochrome image formation request is made;
A comparison unit that compares the ratio calculated by the calculation unit with a predetermined ratio when the determination unit determines that the transfer conveyance belt is in the first position;
The movement control unit moves the transfer conveyance belt to the second position when the calculated ratio is less than the predetermined ratio as a result of comparison by the comparison unit. apparatus.   2. An image forming apparatus according to claim 1, wherein said comparing means compares with a ratio designated from outside instead of said predetermined ratio. Visible images on a plurality of image carriers arranged in tandem corresponding to a plurality of colors including black used for image formation are sequentially transferred at each transfer position onto a transfer material conveyed by an endless transfer conveyance belt. An image forming apparatus, wherein the transfer conveying belt is brought into contact with all of the plurality of image carriers, or only the image carrier corresponding to the black color is brought into contact with the transfer conveying belt, and In the image forming apparatus having movement control means for moving the transfer conveyance belt to any one of the second positions where all the image carriers excluding the image carrier corresponding to black are separated from the transfer conveyance belt,
The movement control means moves the transfer conveyance belt in accordance with the position of the transfer conveyance belt designated from the outside of the first position or the second position at the time of monochromatic image formation. apparatus. Visible images on a plurality of image carriers arranged in tandem corresponding to a plurality of colors including black used for image formation are sequentially transferred at each transfer position onto a transfer material conveyed by an endless transfer conveyance belt. An image forming apparatus, wherein the transfer conveying belt is brought into contact with all of the plurality of image carriers, or only the image carrier corresponding to the black color is brought into contact with the transfer conveying belt, and In the image forming apparatus having movement control means for moving the transfer conveyance belt to any one of the second positions where all the image carriers excluding the image carrier corresponding to black are separated from the transfer conveyance belt,
Multi-color image formation counting means for counting the number of times of multi-color image formation;
Monochrome image formation counting means for counting the number of times of monochrome image formation;
Calculating means for calculating a ratio between the count value of the multi-color image formation counting means and the count value of the single-color image formation counting means;
Comparison means for comparing the ratio calculated by the calculation means with a predetermined ratio at the normal end of monochromatic and multicolor image formation;
Determination means for determining whether the transfer / conveying belt is in the first position or the second position at the normal end of monochromatic and multicolor image formation;
The movement control unit, when the comparison unit determines that the calculated ratio is greater than or equal to the predetermined ratio and the determination unit determines that the transfer conveyance belt is in the second position. The transfer conveyance belt is moved to the first position, and, on the other hand, as a result of comparison by the comparison means, the calculated ratio is less than the predetermined ratio, and the transfer conveyance belt is moved to the first position by the determination means. An image forming apparatus that moves the transfer conveyance belt to the second position when it is determined that the transfer conveyance belt is at the first position.   5. The image forming apparatus according to claim 4, wherein the comparison unit compares with a ratio designated from the outside instead of the predetermined ratio. Visible images on a plurality of image carriers arranged in tandem corresponding to a plurality of colors including black used for image formation are sequentially transferred at each transfer position onto a transfer material conveyed by an endless transfer conveyance belt. An image forming apparatus, wherein the transfer conveying belt is brought into contact with all of the plurality of image carriers, or only the image carrier corresponding to the black color is brought into contact with the transfer conveying belt, and In the image forming apparatus having movement control means for moving the transfer conveyance belt to any one of the second positions where all the image carriers excluding the image carrier corresponding to black are separated from the transfer conveyance belt,
The movement control means moves the transfer / conveyance belt according to the position of the transfer / conveyance belt designated from the outside of the first position or the second position at the normal end of monochromatic image formation. Image forming apparatus. Visible images on a plurality of image carriers arranged in tandem corresponding to a plurality of colors including black used for image formation are sequentially transferred at each transfer position onto a transfer material conveyed by an endless transfer conveyance belt. An image forming apparatus, wherein the transfer conveying belt is brought into contact with all of the plurality of image carriers, or only the image carrier corresponding to the black color is brought into contact with the transfer conveying belt, and The transfer / conveying belt of the image forming apparatus having movement control means for moving the transfer / conveying belt to any one of the second positions in which all the image-bearing members except for the black image-bearing member are separated from the transfer / conveying belt. In the position control method,
A multi-color image formation counting step for counting the number of times of multi-color image formation;
A monochrome image formation counting step for counting the number of times of monochrome image formation;
A calculation step of calculating a ratio between a count value by the multi-color image formation count step and a count value by the single-color image formation count step;
A determination step of determining whether the transfer / conveying belt is in the first position or the second position when a monochrome image formation request is made;
A comparison step of comparing the ratio calculated by the calculation step with a predetermined ratio when the determination step determines that the transfer conveyance belt is in the first position;
And a step of moving the transfer conveyance belt to the second position by the movement control means when the calculated ratio is less than the predetermined ratio as a result of the comparison in the comparison step. Transfer transfer belt position control method.   8. The transfer conveyance belt position control method according to claim 7, wherein the comparison step compares with a ratio designated from the outside instead of the predetermined ratio. Visible images on a plurality of image carriers arranged in tandem corresponding to a plurality of colors including black used for image formation are sequentially transferred at each transfer position onto a transfer material conveyed by an endless transfer conveyance belt. A transfer conveyance belt position control method, wherein the transfer conveyance belt is in contact with the transfer conveyance belt at a first position where the transfer conveyance belt is in contact with all of the plurality of image carriers, or only the image carrier corresponding to the black color And a transfer conveyance belt position having movement control means for moving the transfer conveyance belt to any one of the second positions where all the image carriers except the image carrier corresponding to the black color are separated from the transfer conveyance belt. In the control method,
And a step of moving the transfer conveyance belt by the movement control unit according to a position of the transfer conveyance belt designated from the outside of the first position or the second position at the time of monochromatic image formation. A transfer conveyance belt position control method. Visible images on a plurality of image carriers arranged in tandem corresponding to a plurality of colors including black used for image formation are sequentially transferred at each transfer position onto a transfer material conveyed by an endless transfer conveyance belt. A transfer conveyance belt position control method, wherein the transfer conveyance belt is in contact with the transfer conveyance belt at a first position where the transfer conveyance belt is in contact with all of the plurality of image carriers, or only the image carrier corresponding to the black color And a transfer conveyance belt position having movement control means for moving the transfer conveyance belt to any one of the second positions where all the image carriers except the image carrier corresponding to the black color are separated from the transfer conveyance belt. In the control method,
A multi-color image formation counting step for counting the number of times of multi-color image formation;
A monochrome image formation counting step for counting the number of times of monochrome image formation;
A calculation step of calculating a ratio between a count value by the multi-color image formation count step and a count value by the single-color image formation count step;
A comparison step for comparing the ratio calculated by the calculation step with a predetermined ratio at the normal end of monochromatic and multicolor image formation;
A determination step of determining whether the transfer / conveying belt is in the first position or the second position at the normal end of monochromatic and multicolor image formation;
As a result of the comparison in the comparison step, when the calculated ratio is greater than or equal to the predetermined ratio and the determination step determines that the transfer conveyance belt is in the second position, the movement control means On the other hand, as a result of moving the transfer / conveying belt to the first position and comparing in the comparing step, the calculated ratio is less than the predetermined ratio and the determining / conveying belt is moved to the first position. And a step of moving the transfer / conveyance belt to the second position by the movement control means when it is determined that the transfer / conveyance belt is in the position.   11. The transfer conveyance belt position control method according to claim 10, wherein the comparison step compares with a ratio specified from the outside instead of the predetermined ratio. Visible images on a plurality of image carriers arranged in tandem corresponding to a plurality of colors including black used for image formation are sequentially transferred at each transfer position onto a transfer material conveyed by an endless transfer conveyance belt. A transfer conveyance belt position control method, wherein the transfer conveyance belt is in contact with the transfer conveyance belt at a first position where the transfer conveyance belt is in contact with all of the plurality of image carriers, or only the image carrier corresponding to the black color And an image forming apparatus having movement control means for moving the transfer conveyance belt to any one of the second positions where all the image carriers except the image carrier corresponding to the black color are separated from the transfer conveyance belt. In the transfer conveyance belt position control method,
A step of moving the transfer / conveyance belt by the movement control means according to the position of the transfer / conveyance belt designated from the outside of the first position or the second position at the normal end of monochromatic image formation; And a transfer conveying belt position control method. An image forming apparatus that forms an image using a plurality of image carriers,
Transfer means for transferring images on the plurality of image carriers to a transfer material;
Mode control means for switching between a first mode in which image formation is performed using all of the plurality of image carriers and a second mode in which image formation is performed using a predetermined image carrier among the plurality of image carriers; ,
A first position at which the transfer means is brought into contact with all of the plurality of image carriers, and a predetermined image carrier of the plurality of image carriers, and all the members other than the predetermined image carrier. A movement control means for moving the transfer means at a second position to be separated from the image carrier,
When the mode control unit is switched to the second mode by the mode control unit, the movement control unit performs the number of times image formation is performed in a state where the transfer unit has moved to the first position and the transfer unit performs the second position. An image forming apparatus that performs image formation in a state in which the transfer unit is moved to the first position based on the number of times image formation has been performed in the state of being moved to the first position. An image forming apparatus that forms an image using a plurality of image carriers,
Transfer means for transferring images on the plurality of image carriers to a transfer material;
Mode control means for switching between a first mode in which image formation is performed using all of the plurality of image carriers and a second mode in which image formation is performed using a predetermined image carrier among the plurality of image carriers; ,
A first position at which the transfer means is brought into contact with all of the plurality of image carriers, and a predetermined image carrier of the plurality of image carriers, and all the members other than the predetermined image carrier. A movement control means for moving the transfer means at a second position to be separated from the image carrier,
Whether the movement control unit moves the transfer unit to the first position or the second position based on an external designation when the mode control unit switches to the second mode. Determining an image forming apparatus.

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