JP4042791B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a color copying machine or a color printer, and more particularly to an image forming apparatus capable of switching between color image formation and single color image formation.

Conventionally, as a full-color image forming apparatus having a high processing speed, there is a four-tandem tandem type in which four photosensitive drums are arranged along a transfer belt. In this method, cyan (C), magenta (M), yellow (Y), and black (K) toner images are formed on each photosensitive drum, and the toner images are sequentially transferred to one transfer material. In this method, a color image is obtained by transfer.
In the quadruple tandem system, even if it is a full-color image, it can be obtained by a single paper feed as in the case of a monochrome image, so high-speed color printing is possible. On the other hand, in forming a monochrome image, a photosensitive drum for black is used. In addition, cyan, magenta, and yellow photosensitive drums that are not required for image forming operations must be rotated because the transfer material is passed through while being in contact with the photosensitive drums. A member such as a cleaning blade provided by being pressed is consumed, and toner is also consumed although it is minute. Such unnecessary consumption and consumption increase the frequency of maintenance work such as replacement of members and toner supply, which is not preferable.

  Therefore, as a conventional technique, for the purpose of extending the product life by avoiding wasteful consumption of members, the cyan, magenta, and yellow photosensitive drums that are not used and the transfer material conveying unit are separated from each other during monochrome image formation. There are methods (Japanese Patent Laid-Open Nos. 3-288173, 6-258914, and 6-102769). Here, the mode in which the transfer process is performed in a state in which the unused photosensitive drum and the transfer material transporting unit are separated from each other is referred to as a “single color print mode”. A mode in which processing is performed is referred to as a “color print mode”.

In addition, regarding the degree of consumption of the member such as the photosensitive drum and the toner consumption, there are aspects as a guide for setting the service life of the member (replacement time) and setting the device usage fee (lease fee, copy unit price). There has been a technique for monitoring this conventionally. In general, the number of copies is used as a guide for monitoring. Japanese Laid-Open Patent Application No. 8-63048 is a technique related to consumption level monitoring in an image forming apparatus that performs tandem transfer processing. As described above, the number of copies in the color print mode and the number of copies in the single color print mode are different from the color print mode and the single color print mode. Are separately counted, thereby trying to accurately grasp the degree of consumption and the toner consumption status.
JP-A-3-288173 JP-A-6-258914 JP-A-6-102767

  However, when the mode is switched, it is necessary to separate some of the photosensitive drums from the transfer material transport unit that has been in contact, or conversely, to contact the transfer material transport unit that has been separated. During the separation / contact process, if there is a transfer material being transferred on the transfer material transfer means, the transfer material moves on the transfer means, and this causes the transfer material to be transferred to the transfer material. Transfer or misalignment occurs in the image.

  In view of the above problems, the present invention is a tandem-type image forming apparatus that employs a method for switching between a color print mode and a single color print mode, and an image transferred to a transfer material has a transfer shift or a position shift due to mode switching. An object of the present invention is to provide an image forming apparatus that does not occur.

  In order to achieve the above object, an image forming apparatus according to the present invention writes images of different colors on a plurality of image carriers arranged along a transfer belt, and transfers images on the image carriers to a transfer material. An image forming apparatus for forming an image by superimposing and transferring the image on the image forming apparatus, wherein a first mode for forming an image in a state where all of the image carrier is in contact with the transfer belt and one necessary for image formation. Switching means for switching two types of modes, ie, a second mode in which image formation is performed by bringing a part of the image carrier into contact with the transfer belt by relatively separating some of the image carriers and the transfer belt; A control unit for controlling the transfer timing of the transfer material so that image transfer to the transfer material is not performed during the switching process when the mode is switched by the switching unit during continuous image formation; Having And butterflies.

  With this configuration, in the image forming apparatus of the present invention, the transfer process to the transfer material is not executed until the mode switching is completed, so that no transfer shift or position shift occurs in the transferred image.

Hereinafter, an embodiment of an image forming apparatus according to the present invention will be described by taking a tandem type digital color copying machine (hereinafter simply referred to as “copying machine”) as an example.
(1) Overall Configuration of Copying Machine FIG. 1 is a cross-sectional view showing the overall configuration of a copying machine 1 according to the present embodiment. As shown in FIG. 1, the copying machine 1 is roughly divided into an automatic document feeder 10 for conveying a document, an image reader unit 20 for reading an image of a document, processing of data of a read image, and processing of each component. A control unit 30 that performs control and a printer unit 40 that reproduces an image of a document on recording paper in accordance with image data. In addition to these, an operation panel 90 (shown in FIG. 9) not shown in FIG. 1 is provided on the upper surface of the main body of the copying machine 1. The operation panel 90 is for accepting setting of the number of copies, processing method, and the like from the operator, and will be described later in connection with the control contents of the control unit 30.

The automatic document feeder 10 is known as an automatic document feeder (ADF), and after a set document is conveyed to a document reading position on the platen glass 170, the reading process by the image reader unit 20 is awaited. Then, it is discharged to the document discharge tray 180.
The image reader unit 20 includes a scanner 210 having an exposure lamp 211 and a mirror 212, a reflection mirror pair 220, a condenser lens 230, and a linear full color sensor 240 (hereinafter referred to as a CCD sensor 240). When a document is transported onto the platen glass 170 by the automatic document transport device 10, the scanner 210 is driven by the scanner motor M1 to scan the document while moving in the arrow Y1 direction. The document image irradiated by the scanner 210 is reflected by the reflecting mirror pair 220, then condensed by the condenser lens 230, and enters the CCD sensor 240. The CCD sensor 240 photoelectrically converts the information of the incident image and outputs it to the control unit 30 as a three-component electric signal of red (R), green (G), and blue (B).

  The control unit 30 performs correction processing on the electrical signals (image data) of the respective color components of red (R), green (G), and blue (B), so that cyan (C), magenta (M), yellow (Y), and After converting into gradation data of each reproduction color of black (K) and temporarily storing it in the memory, the image data of each reproduction color is sequentially read from the memory, converted into a laser diode drive signal, and output to the printer unit 40. . The control unit 30 controls the transfer processing pattern by the printing unit 40 in accordance with the color (color / monochrome) of the image data and the setting by the operator. The control unit 30 will be described in detail later.

The printer unit 40 forms an image on recording paper using a known electrophotographic technique, and includes an optical system 50, an image forming process system 60, and a paper supply / discharge system 70.
The optical system 50 includes a laser diode (not shown), a polygon mirror 510, f-θ lenses 520C, 520M, 520Y, and 520K provided for each color. The laser diode is modulated and driven according to a laser diode drive signal (image data) output from the control unit 30 and emits laser light. The emitted laser light is reflected by a polygon mirror 510 that is rotationally driven by a motor (not shown), and then is divided for each color and reflected by a folding mirror through f-θ lenses 520C, 520M, 520Y, and 520K. The surface of the photosensitive drums 611C, 611M, 611Y, and 611K (hereinafter referred to as photosensitive drums 611C to 611K) of the image forming process system 60 is exposed and scanned in the main scanning direction to form an electrostatic latent image.

The image forming process system 60 develops the electrostatic latent images for each color generated on the photosensitive drums 611C to 611K with the toner by the optical system 50, and then sequentially transfers and overlays them on the recording paper to reproduce the image. The image forming process system 60 will be described in more detail later.
The feed / discharge system 70 includes a paper feed cassette 710, a pickup roller 720, a timing roller 730, a transport belt 740, and the like. During the copying process, the recording paper of the selected size is fed from the paper feed cassette 710 by the pickup roller 720 and is conveyed through the conveying belt 740 to the transfer position of the photosensitive drums 611C-K. Here, the recording paper to which the toner image has been transferred is further conveyed on a conveying belt 740 and discharged to a discharge tray 760 through a fixing device 750. In transferring the toner image onto the recording paper, the timing roller 730 performs adjustment for matching the transfer positions of the respective color images.

(2) Configuration of Imaging Process System FIG. 2 is a cross-sectional view showing the configuration of the imaging process system 60 of the copying machine 1. The image forming process system 60 includes image forming units 610C, 610M, 610Y, and 610K (hereinafter, collectively referred to as 610C to K) for each reproduction color and a transfer unit 620.
First, the configuration of the image forming units 610C to 610K will be described. Since all the four image forming units have the same structure, the image forming unit 610K will be described as an example. The image forming unit 610K has a structure in which a charging unit 612K, a developing unit 613K, a transfer blade 614K, and a cleaner 615K are arranged around a photosensitive drum 611K. The surface of the photosensitive drum 611K is uniformly charged by the charger 612K, and the laser light emitted from the optical system 50 forms an electrostatic latent image on the surface of the photosensitive drum 611K. This electrostatic latent image is developed by the developing device 613K to become a toner image. This toner image is transferred to the transfer material by the transfer blade 614K of the transfer unit 620. The cleaner 615K removes toner remaining on the surface of the photosensitive drum 611K even after the transfer process.

  In the transfer unit 620, a transfer material conveyance belt 621 is stretched around a driving roller 622, a driven roller 624, and a tension roller 625, and transfer blades 614 </ b> C to 614 </ b> K are disposed inside the transfer material conveyance belt 621. The transfer material conveyance belt 621 rotates in the direction of the arrow by the rotation of the driving roller 622, and conveys the recording paper toward the image forming units 610C to 610K. The tension roller 625 is urged outward by a spring 627 and applies a certain tension to the transfer material conveyance belt 621.

  The swing unit 630 is configured by attaching transfer blades 614C to 614 to a frame 631 that is held so as to be swingable up and down with the rotation shaft of the driven roller 624 as a fulcrum. The frame 631 is biased upward by a spring 627, and the peripheral surface of the cam 640 is in contact with the upper surface of the swing frame 631. The cam 640 is rotated by a driving device (not shown), whereby the swing unit 630 is driven to swing up and down. As a result, the transfer material conveyance belt 621 and the three image forming units 610C to 610 except for the image forming unit 610K come into contact with or are separated from each other. The driving of the plate cam 640 is controlled by the control unit 30.

  FIG. 3 shows a state of the transfer material transport belt 621 in the color print mode. All of the four image forming units 610 </ b> C to 610 </ b> K are in contact with the transfer material conveyance belt 621. FIG. 4 shows a state of the transfer material transport belt 621 in the single color print mode. The cam 640 is rotated 180 degrees from the state shown in FIG. As a result, the swing unit 630 is pushed down, and only the image forming unit 610K of the image forming units 610C to 610 is in contact with the transfer material transport belt 621, and the other image forming units 610C, 610M, and 610Y and the transfer material transport belt. It is separated from 621.

  The effect of providing the single color print mode as shown in FIG. 4 is exhibited when a monochrome image is formed. When a monochrome image is generated in the color print mode (see FIG. 3), the actual transfer process is performed only in the black (K) image forming unit 610K, but in all the image forming units 610C to K, the photoconductors. The rotation of the drums 611C to K and accompanying rotation contact between the photosensitive drums 611C to K and the cleaners 615C to K are performed, and the surface of the photosensitive drum is worn. On the other hand, when a monochrome image is generated in the single color print mode, the photosensitive drum and the cleaner member are not consumed in the image forming units 610C, 610M, and 610Y other than the image forming unit 610K.

  However, switching between the color print mode and the single color print mode according to the type of document (color document / monochrome document) during continuous copying of the document may adversely affect the image quality of the copy result. Each time the two modes are switched, the swing unit 630 is moved up and down, so that the image transfer position on the recording paper becomes unstable, and transfer and color shifts occur. In order to prevent such a situation, it is necessary to control the waiting time by the timing roller 730 so that the image transfer onto the recording paper is not executed while the swinging unit 630 is moved up and down.

  The timing roller 730 feeds recording paper continuously conveyed from the paper feed trays 711 to 714 to the transfer unit at regular intervals. This paper feed interval is obtained by waiting the recording paper at the timing roller 730 for a predetermined time. The time for waiting the recording paper is called a paper feed waiting time, and the interval between the recording papers can be adjusted by changing the paper feed waiting time. Therefore, in order to prevent the copy result image from being adversely affected by the vertical movement of the swing unit 630 (switching of the transfer mode), the transfer unit 620 is next only the time required until the vertical movement of the swing unit 630 is completed. What is necessary is just to lengthen the paper supply waiting time of the recording paper supplied to the printer.

  The procedure for adjusting the paper feed waiting time will be described below with reference to the drawings. FIG. 5 is a diagram illustrating information related to paper feed waiting time adjustment. The transfer position 501K is a contact position between the photosensitive drum 611K and the recording paper. The transfer position 501C is a contact position between the photosensitive drum 611C and the recording paper. The interval between the transfer position 501K and the transfer position 501C is L2. The exposure position 502K is an exposure position on the photosensitive drum 611K, and the distance along the circumferential surface of the photosensitive drum 611K from the exposure position 502K to the transfer position 501K is L1. The meaning of these pieces of information and the purpose of reference will be described later with reference to FIGS.

  FIG. 6 is a diagram showing adjustment of the paper feed waiting time of the timing roller when switching from the color print mode to the single color print mode. FIG. 6A shows a transfer unit 620 that generates a color image in the color print mode, and the interval between the recording sheets P1, P2, and P3 conveyed on the transfer material conveying belt 621 is X3. It has become. The shorter the interval between recording sheets, the higher the productivity (number of processed sheets per unit time), and the interval X3 is a value set so that the productivity is maximized. This X3 is realized by setting the paper feed waiting time of the timing roller 730 to t3.

Here, in FIG. 5B, it is assumed that a monochrome image is formed on the recording paper P5 in the single color print mode. In this case, for stable image formation, the end of the recording paper P5 must reach the transfer position 501K of the photosensitive drum 611K after the switching to the single color print mode is completed. For this purpose, the interval between the recording papers P4 and P5 required is X1, the distance from the exposure position 502K to the transfer position 501K on the surface of the photosensitive drum 611K is L1 (see FIG. 5), the time required for separation is t, and the system speed is Assuming V, the interval X1 is required to satisfy the following (Formula 1).
X1> = L1 + V · t (Formula 1)
Let t1 be a paper feed waiting time that satisfies this equation and minimizes X1. After that, as shown in FIG. 5C, when the monochrome image is continuously formed on the recording papers P6 and P7 in the single color printing mode, the recording paper interval is again returned to X3 (the paper feed waiting time is t3). It is.

  Next, FIG. 7 shows how the paper feed waiting time by the timing roller 730 is adjusted when switching from the single color print mode to the color print mode. FIG. 6A shows a transfer unit 620 that generates a monochrome image in the single-color print mode, and the interval between recording sheets is X3 as in FIG. This is realized by setting the paper feed waiting time to t3.

Here, in FIG. 7B, it is assumed that a color image is formed in the color print mode on the recording paper P4. In this case, for stable image formation, the end of the recording paper P4 must reach the transfer position 501C of the photosensitive drum 611C after the switching to the color print mode is completed. For this purpose, the interval between the recording papers P3 and P4 required is X2, the distance from the exposure position 502K to the transfer position 501K on the surface of the photosensitive drum 611K is L1 (see FIG. 5), and the interval between the transfer position 501K and the transfer position 501C is set. When L2 is t and the time required for mode switching is t and the system speed is V, the interval X2 is required to satisfy the following (Equation 2).
X2> = L1 + L2 + V · t (Expression 2)
Let t2 be a paper feed waiting time that satisfies this equation and minimizes X2. Thereafter, as shown in FIG. 5C, when the color image is continuously formed in the color print mode, the recording paper interval is returned to X3 (the paper feed waiting time is t3) again. All of the three types of paper feed waiting times t1, t2, and t3 are calculated in advance and held in the control unit 30, and are switched by the control unit 30.

  Here, consider the relationship between transfer mode switching and productivity. When image transfer is continuously performed on recording paper, productivity is maximized when the recording paper feed waiting time is t3. However, when color and black and white images are mixed and the transfer mode is switched, adjustment (extension) of the paper feed waiting time by the timing roller 730 occurs, and the paper feed waiting time temporarily reaches t1 or t2. become longer. Therefore, in the copy of an original (for example, an original in which color and black and white are mixed alternately) in which the transfer mode is frequently switched, the average of the paper feed waiting time becomes longer than t3, and the productivity is lowered. However, this is not a general problem because the image quality is guaranteed instead of a decrease in productivity, and unnecessary consumption of the image forming unit and developer can be avoided. However, this is an operation that emphasizes productivity over avoiding consumption. The person may feel dissatisfied. Thus, in the copying machine 1, the operator can specify whether to place importance on productivity or to place importance on extending the product life by avoiding wear. The designation from the operator is accepted by the operation panel, and the control unit 30 performs control according to the designation. The processing of the control unit 30 will be described next.

  (3) Configuration of Control Unit 30 FIG. 8 is a block diagram showing the configuration of the control unit 30. The control unit 30 includes an image signal processing unit 310, a document recognition unit 320, an image memory 330, a laser diode driving unit 340, a transfer control unit 350, a ROM 360, a RAM 370, and the like with the main control unit 300 as a center. Each component other than the ROM 360 and the RAM 370 is configured around a CPU.

  The image signal control unit 310 performs shading correction on the image data output from the CCD sensor 240 of the image reader unit 20, and then outputs the image data to the document recognition unit 320 for each document, and four reproduction colors (C, C, M, Y, K) image data and stored in the image memory 330. However, if there is a specific instruction from the operator (details of “mono copy setting” will be described in the description of the processing of the main control unit 310), the image signal control unit 310 converts the image data of the color original into a black (K) monochrome image. Convert to data.

  The document recognition unit 320 determines conditions regarding the document based on the image data. The main processes are determination of the orientation of the document and determination of whether the document is color or monochrome. The color / monochrome determination method uses a known technique called automatic color selection (ACS). This is because the image signal control unit 310 extracts the components of the color difference signals from the image data of the three primary colors (R, G, B) for which the shading correction has been completed, forms a histogram, and obtains the ratio of chromatic color dots in the image data from the histogram. If the ratio exceeds a certain value, it is determined as a color image. The document recognition unit 320 outputs the determination result to the main control unit 300.

In response to an instruction from the main controller 300, the image memory 330 outputs image data to be processed to the laser diode driver 340. The laser diode driving unit 340 converts each reproduction color data into a laser diode driving signal for monitoring, and modulates and drives the laser diode corresponding to each color.
The main control unit 300 receives an operator's designation from the operation panel 90 (FIG. 9), and controls the operation of each component of the control unit 30 based on this to realize a smooth copying process. The following describes the contents that can be set for the operation panel 90 that accepts the contents specified by the operator and the processing of the main control unit 310 for the setting contents.

  FIG. 9 shows the operation panel 90. In the copy type setting area 91, a color copy key 911 and a mono copy key 912 are provided. The color copy key 911 is a key for setting a color copy for reproducing the original color as it is, and the mono copy key 912 is for setting a mono copy to output a monochrome copy while ignoring the original color. It is a key to do. The main control unit 300 stores the designation by these keys in the RAM 370 as copy type information (color copy: “1”, mono copy “0”). The default value of the copy type information is color copy (“1”). When monocopy is designated, the main control unit 300 instructs the image signal processing unit 310 to generate a copy of a color original as a mono image.

  Further, the transfer mode of the transfer unit 620 is initialized by setting from the copy type setting area 91. If the setting content is color copy, the main control unit 300 controls the transfer control unit 350 to set the transfer unit 620 in the color print mode, and if it is mono copy, the main control unit 300 sets the single color print mode. Then, transfer mode information (color print mode: “1”, single color print mode: “0”) is stored in the RAM 370.

  In the operation policy setting area 92, a productivity priority key 921 and a product life priority key 922 are provided. The productivity priority key 921 is a key for instructing to operate the copying machine 1 in a system in which productivity is given priority over extending the product life. The product life priority key 922 is the product life even if the productivity is lowered. This is a key for instructing to adopt a method in which priority is given to extending the length.

To give priority to productivity is to perform transfer processing in the color print mode even when copying a monochrome document, and the paper feed waiting time is constant at t3, and the productivity is high. Prioritizing the product life is to switch the transfer mode between the color print mode and the single color print mode as described above according to the type of document (color / monochrome).
The main control unit 300 stores operation information (productivity priority: “1”, product life priority: “0”) according to the contents set by these keys in the RAM 370. Note that the default value of the operation information is the product life priority (“0”). The operation information is referred to in the transfer mode switching process during the copying process. The transfer mode switching will be described in detail in the description of the transfer control unit 350. The numeric input unit 93 accepts input of numerical values such as the number of copies, and the main control unit 300 stores the value of the number of copies accepted by the numeric input unit 93 in the RAM 370. The display unit 94 is a display that displays a message indicating the value of a numerical value or an illegal designation or out of paper. Information on messages and numerical images is stored in the ROM 360, and the main control unit 300 reads out the information and outputs it to the display unit 94 as necessary.

  The start key 95 is a key for designating the start of the copying process, and the stop key 96 is a key for designating a halfway stop of the copying process. The main control unit 300 receives the designation of these keys and issues a start / stop instruction to each component of the control unit 30. The display lamps 97a, 97b, 97c, and 97d indicate the setting contents in the copy type setting area 91 and the operation policy setting area 92, and the ones beside the keys that are set valid are displayed in red.

The ROM 360 stores information with fixed contents referred to by each component of the control unit 30. The RAM 370 stores information specified by the operator (copy type information, operation information, number of copies) received from the operation panel 90 by the main control unit 300, and document type information, transfer mode information, and paper feed waiting time information as a result of ACS. Store information that needs to be temporarily saved.
(4) Configuration of Transfer Control Unit 350 FIG. 10 shows the configuration of the transfer control unit 350. The transfer control unit 350 includes a CPU 351, a count unit 354, a cam drive circuit 352 that outputs a rotation drive signal to the cam 640 according to an instruction from the CPU 351, and a drive / stop signal for the timing roller 730 according to an instruction from the CPU 351. For example, a timing roller driving circuit 353 that outputs a transfer mode, and performs a transfer mode switching process and a transfer process sheet count process for determining the degree of member consumption and toner consumption.

  The transfer control unit 350 controls the sheet feeding waiting time of the timing roller 730, switches the transfer mode (color print mode and single color print mode), the degree of consumption of the transfer member (photosensitive drum and cleaner), and the amount of toner consumption. The number of processed sheets is counted to measure The transfer mode is switched based on the designation of the operator from the operation panel 90 and the ACS result by the image recognition unit 320 described above.

  The control of the paper feed waiting time of the timing roller 730 by the transfer control unit 350 is as follows. First, when the end of the recording paper being conveyed on the transfer material conveying belt 621 passes a predetermined position, a signal is sent from the sensor (not shown) to the CPU 351. Upon receiving this signal, the CPU 351 instructs the timing roller drive circuit 353 to stop the timing roller 730, and selects a paper feed waiting time according to the setting by the operator and the document type from t1, t2, and t3. The timing roller 730 is restarted after the elapse of the paper feed waiting time, and the recording paper is provided to the transfer unit 620. The procedure for selecting the paper feed waiting time will be described together with the description of the transfer mode switching process.

  Next, transfer mode switching processing by the transfer control unit 350 will be described. First, the CPU 351 refers to the copy type information in the RAM 370 at the timing when the timing roller 730 is stopped. If the content of the copy type information is mono-copy (“0”), a monochrome copy is generated regardless of whether the document is color or monochrome. Therefore, the transfer process is performed only in the monochrome print mode. It is unnecessary. The CPU 351 sets the paper feed waiting time to t3.

  If the content of the copy type information is color copy (“1”), the transfer mode needs to be switched according to the document type (color / monochrome) and the operation information. Therefore, the CPU 351 further stores the operation information in the RAM 370. refer. When the content of the operation information is “productivity priority (“ 1 ”)”, the transfer process is always performed in the color print mode regardless of the document type (color / monochrome), so the transfer mode switching is unnecessary. is there. The CPU 351 sets the paper feed waiting time to t3. If the content of the operation information is “life priority (“ 0 ”)”, it is necessary to switch the transfer mode according to the document type, so the CPU 351 further refers to the document type (color / monochrome) information in the RAM 370. .

  If the document type information is color (“1”), the CPU 351 further refers to the transfer mode information in the RAM 370 and confirms the current transfer mode. If it is in the color print mode (“1”), it is not necessary to switch the transfer mode, so the CPU 351 continues the processing with the paper feed waiting time t3. If the transfer mode information is the single color print mode (“0”), it is necessary to switch the transfer mode (monochrome-> color), so the CPU 351 instructs the cam drive circuit 352 to place the cam 640 in the state shown in FIG. And the content of the transfer mode information in the RAM 370 is switched to a value (“1”) indicating the color print mode. At the same time, the CPU 351 sets the paper feed waiting time to t2.

  Even when the document type is monochrome (“0”), the CPU 351 refers to the transfer mode information in the RAM 370 and confirms the current transfer mode. If the single color print mode (“0”) is set, it is not necessary to switch the transfer mode, so the CPU 351 continues the processing with the paper feed waiting time t3. Since it is necessary to switch the transfer mode (color-> single color) in the color print mode, the CPU 351 instructs the cam drive circuit 352 to rotate the cam 640 to the state shown in FIG. The content of the transfer mode information in the RAM 370 is switched to a value (“0”) indicating the single color print mode. At the same time, the CPU 351 sets the paper feed waiting time to t1.

Further, the transfer control unit 350 counts the number of processed sheets for calculating the degree of consumption. At this time, the transfer control unit 350 obtains information that accurately represents the degree of consumption by using a processed number counter for each transfer pattern. In the transfer process, there are three patterns with different degrees of wear depending on the transfer mode and the document type.
Full color transfer: Transfers a color image in the color print mode.
Bk transfer 1: Transfers a monochrome image in a single color print mode.
Bk transfer 2: Transfers a monochrome image in the color print mode.
Table 1 shows whether or not the transfer member is consumed and the toner is consumed in each of the transfer patterns.

  As means for accurately grasping the difference between the consumption level and the toner consumption amount, the transfer control unit 350 includes a counting unit 354 having three types of counters, a first counter 355a, a second counter 355b, and a third counter 355c. Information on the number of processed sheets for each transfer pattern is stored. The first counter 355a stores the number of copies in the full color transfer pattern. The second counter 355b stores the number of copies in one Bk transfer pattern. The third counter 355c stores the number of copies in the Bk transfer 2 pattern.

  After the transfer mode switching determination process is completed, the transfer control unit 350 determines a transfer pattern with reference to the transfer mode information and the document type information, and increments a counter corresponding to the determined transfer pattern by one. Table 2 below shows the relationship between the transfer mode information, the document type information, and the counter to be counted up.

  Since these counters 355a, 355b, and 355c are referred to during maintenance work, the counters 355a, 355b, and 355c are configured by a nonvolatile memory so that the contents are saved even when the power of the copying machine 1 is turned off. These contents can be referred to on the display unit 94 by, for example, inputting a password from the operation panel 90 by a service person. Further, when the member is replaced, it is necessary to initialize (return to 0) the value of the counter, but this can also be executed by inputting the personal identification number from the operation panel.

(Operation of transfer controller 350)
FIG. 11 is a flowchart showing a process flow of the transfer control unit 350 in the transfer process for one recording sheet. Hereinafter, the operation of the transfer control unit 350 will be described with reference to the flowchart with the CPU 351 as the center.
The CPU 351 is activated by an instruction from the main control unit 310 (S1101: Yes). First, copy type information is referred to. If the copy type is mono copy (S1102), the CPU 351 sets the paper feed waiting time to t3 (S1114) and counts up the second counter 355b (S1121).

  If the copy type is color copy (S1102), the CPU 351 further refers to the operation information. If the content of the operation information is productivity priority (S1103), the CPU 351 sets the paper feed waiting time to t3 regardless of the document type (S1112, S1113). If the document type is color (S1105), the first counter 355a is incremented (S1120). If the document type is monochrome (S1105), the third counter 355c is incremented (S1119).

  If the content of the operation information has a product life priority (S1103), the CPU 351 further refers to the document type information and the transfer mode information. If the document is in color (S1104) and the transfer mode is the color print mode (S1107: Yes), only the process of setting the paper feed waiting time to t3 is performed (S1110). If the transfer mode is the monochrome print mode, the CPU 351 sets the paper feed waiting time to t2 (S1111). Further, the cam 640 is rotated to the state shown in FIG. 3 to set the color print mode, and the content of the transfer mode information in the RAM 370 is changed to a value (“1”) indicating the color print mode (S1116). When the above processing (steps S1107 to S1116) is completed, the first counter 355a is counted up (S1118).

  On the other hand, if the document type is monochrome (S1104), the CPU 351 refers to the transfer mode information, and if it is the monochrome print mode (S1106: Yes), sets the paper feed waiting time to t3 (S1108). If the transfer mode information is the color transfer mode (S1106: No), the paper feed waiting time is set to t1 (S1109). Further, the cam 640 is rotated to the position shown in FIG. 4 to set the single color transfer mode, and the transfer mode information in the RAM 370 is changed to a value (“0”) indicating the single color transfer mode (S1115). When the above processing (steps S1106 to S1115) is completed, the third counter 355c is incremented (S1117). Then, after the paper feed waiting time has elapsed (S1122: Yes), the timing roller 730 is driven to feed the recording paper to the transfer unit 620 (S1123). The CPU 351 repeats the above processing as many times as the number of copies stored in the RAM 370, and ends the processing (S1124).

  As described above, according to the present embodiment, the transfer patterns are divided into three types based on the operator designation and the document type, and the number of transfer processes for each pattern is counted separately. Accurately understand consumption status. Thereby, it is possible to collect a usage fee according to the degree of consumption and the toner consumption. An example of such a charge setting is shown in Table 3 below.

In the conventional method, since there was only a distinction between color image formation in the color print mode and monochrome image formation in the single color print mode, a charge specific to the BK2 mode for forming a monochrome image in the color print mode must be set. I couldn't. Charge setting in the BK2 mode is possible by providing three types of counters.
In this embodiment, the separation between the image forming units 610C to 610K and the transfer unit 620 is realized by moving the transfer unit 620 downward. Conversely, the image forming units 610C to K are moved upward. They may be moved away from each other.

  In addition, when each of the image forming units 610C to 610K forms an image on a recording sheet (when an image is formed with a full-color transfer pattern, Bk transfer pattern 1, and Bk transfer pattern 2), it contacts the recording sheet. The image was not formed (the image was not formed with the Bk transfer pattern 2), and the image was not rotated away from the recording paper (the image was not formed with the Bk transfer pattern 1). If a counter for counting the number of times is provided and the number of processed sheets is counted, the degree of wear for each image forming unit can be grasped more accurately.

In this embodiment, a method is described in which an image is superimposed and transferred onto the recording paper conveyed by the transfer material conveying belt 621. However, after the image is superimposed and transferred onto the intermediate transfer belt, the image is reproduced on the recording paper. An intermediate transfer method of transferring may be used.
The present embodiment relates to a digital color copying machine, but an image forming apparatus such as a color printer may be used in addition to the copying machine.

1 is a diagram showing an overall configuration of a digital color copying machine according to the present invention. FIG. 2 is an enlarged view showing a configuration of a transfer unit in the copying machine. It is a figure which shows the state in the color print mode of the said transfer unit. It is a figure which shows the state in the monochrome printing mode of the said transfer unit. FIG. 6 is a diagram illustrating information related to a paper feed waiting time adjustment process in a transfer unit. FIG. 7 is a diagram illustrating a state of a transfer unit and a change in recording sheet interval in accordance with transfer mode switching (from a color print mode to a single color print mode). FIG. 6 is a diagram illustrating a state of a transfer unit and a change in a recording sheet interval according to transfer mode switching (from a single color print mode to a color print mode). FIG. 2 is a block diagram illustrating a configuration of a control unit in the copying machine. It is a figure which shows an operation panel. It is a block diagram which shows the structure of the transfer control part among the said control parts. It is a flowchart figure which shows the flow of a process of the said transfer control part.

Explanation of symbols

1 Copier 30 Control Unit 310 Main Control Unit 350 Transfer Control Unit 351 CPU
352 Cam drive circuit 353 Timing roller drive circuit 354 Counter unit 370 RAM
60 Image forming process system 610C, 610M, 610Y, 610K Image forming unit 611C, 611M, 611Y, 611K Photosensitive drum 620 Transfer unit 630 Swing unit 640 Cam

Claims (4)

An image forming apparatus for writing images of different colors on a plurality of image carriers arranged along a transfer belt, and superimposing and transferring the images on the image carriers on a transfer material to form images. ,
A first mode in which image formation is performed with all of the image carriers in contact with the transfer belt; and a second mode in which image formation is performed with one image carrier necessary for image formation in contact with the transfer belt; Switching means for switching the two types of modes by relatively separating the image carrier excluding the image carrier located on the most downstream side in the moving direction of the transfer belt and the transfer belt;
A timing roller that is provided in the transfer path of the transfer material and feeds the transfer material to the transfer belt while timing;
When the mode is switched by the switching unit during the continuous image formation, the transfer material is conveyed via the control to the timing roller so that the image transfer to the transfer material is not performed during the switching process. Control means for controlling the timing to be delayed,
In the mode switching by the switching means, the first mode corresponds to the case where the type of the formed image is color, and the second mode corresponds to the case where the type of the formed image is monochrome,
An instruction receiving unit for receiving an instruction to form an image in the first mode even if the formed image is monochrome;
The switching means determines whether or not to switch the mode according to whether or not the instruction accepting means accepts the instruction in addition to the type of formed image;
An image forming apparatus. The control means determines the width of the transfer material conveyance timing delay depending on whether the mode switching performed by the switching means is from the first mode to the second mode or from the second mode to the first mode. Changing the
The image forming apparatus according to claim 1. The control unit delays the transfer material conveyance timing when the mode switching performed by the switching unit is switching from the second mode to the first mode, compared to when switching from the first mode to the second mode. To be controlled,
The image forming apparatus according to claim 2. The control unit controls the conveyance timing in such a manner that when the mode is switched by the switching unit during continuous image formation, the conveyance timing of the transfer material is delayed as compared with the case where the switching is not performed. To do,
The image forming apparatus according to claim 1.

Images