JP2013130662A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tandem full-color image forming device that solves the following problem: in switching from contact mono mode to full-color mode, all the primary transfer means are ATVC-controlled, resulting in reduction in productivity.SOLUTION: The tandem full-color image forming device has a contact mono mode and a separation mono mode for mono-mode printing, and includes control means that selects the contact mono mode or the separation mono mode on the basis of printing information input from an external device, to control image forming operation. The control means determines whether to cause current detection means to detect an output current for a plurality of transfer means, in the contact mono mode, on the basis of the printing information when the mode is changed from the contact mono mode to the separation mono mode, and reduces downtime in switching from the contact mono mode to the color mode, to prevent reduction in productivity.

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine or a printer, and in particular, has a plurality of image forming units including an image carrier, a charging unit, a developing unit, and the like, The present invention relates to an image forming apparatus to be formed.

  In recent years, as an electrophotographic multi-color or full-color image forming apparatus, a plurality of photosensitive drums are arranged in a line according to each color, and toner images of each color formed on each photosensitive drum are transferred to an intermediate transfer body (intermediate transfer body). A so-called tandem type image forming apparatus has been proposed that forms a color image on a belt or a transfer material in sequence. FIG. 1 is a schematic diagram showing an example of a conventional electrophotographic tandem full-color image forming apparatus. The image forming apparatus includes an image forming unit 1Y that forms a yellow image, an image forming unit 1M that forms a magenta image, an image forming unit 1C that forms a cyan image, and a black image. The image forming unit 1K to be formed includes four image forming units (image forming units).

  In this image forming apparatus, first, the photosensitive drums 2a, 2b, 2c, and 2d are uniformly charged by the primary charging unit, and then the exposure unit performs exposure according to the image signal, whereby the photosensitive drums 2a, 2b, Electrostatic latent images are formed on 2b, 2c and 2d. Thereafter, the electrostatic latent image is developed as a toner image by the developing unit, and the toner image is sequentially primary transferred onto the intermediate transfer belt 8 by the primary transfer unit. At this time, transfer residual toner (primary transfer residual toner) remaining on the photosensitive drums 2a, 2b, 2c, and 2d is collected by the photosensitive drum cleaners 6a, 6b, 6c, and 6d.

  The four color toner images sequentially transferred and superimposed on the intermediate transfer belt 8 are secondarily transferred collectively onto the recording material P by the secondary transfer means. At this time, the transfer residual toner (secondary transfer residual toner) remaining on the intermediate transfer belt 8 is collected by the intermediate transfer belt cleaner 15. The four color toner images transferred onto the recording material P are fixed by a fixing unit. Thereby, a full-color image of four colors is obtained.

  The transfer roller used as the above-mentioned transfer means is usually one in which conductive particles are dispersed in rubber, sponge, etc., and this resistance value is appropriately adjusted. It is known that the resistance value greatly changes due to the influence of the above. In order to always obtain a good transferability, it is ideal to control the amount of electric charge applied to the transfer site, and an ATVC control method (Active Transfer Voltage Control) has already been used so that an appropriate bias can be applied. Proposed. The ATVC control is a basic bias sequence shown in FIG. 2, but the primary transfer rollers 5 a, 5 b, A predetermined bias is applied to 5c and 5d by a constant voltage applying means. At this time, the photosensitive drums 2a, 2b, 2c, and 2d, the intermediate transfer belt 8, and primary transfer rollers 5a, 5b, 5c, and 5d are configured. On the basis of the detected current flowing in the primary transfer portion, the resistance fluctuation of the primary transfer portion is detected (hereinafter referred to as “ATVC control 1”), and a current corresponding to the environment and mode flows during image formation. As a result of the calculation, constant voltage control (hereinafter referred to as “ATVC control 2”) is performed. By doing so, an overcurrent flowing from the primary transfer portion is prevented, the memory of the photosensitive drum is eliminated, and an appropriate bias can be applied at the time of image formation, enabling stable and good transfer image output. Yes.

  For example, Patent Document 1 discloses an image forming apparatus that performs ATVC control in order to solve problems related to environmental fluctuations and resistance unevenness of an intermediate transfer belt.

  In the tandem type full-color image forming apparatus as shown in FIG. 1, when performing monochrome printing, printing is performed in either the separation mode or the contact mode. In the separation mode, if only the black image forming unit 1K is operating, the printing operation can be performed. Therefore, the other three color forming units 1Y, 1M, and 1C of yellow, magenta, and cyan are stopped, The three image forming units are separated from the intermediate transfer belt 8 to perform monochrome printing (hereinafter referred to as “separated mono mode”). In the contact mode, all four colors including the three-color image forming units that are not used for actual image formation are kept in operation, and are in contact with the intermediate transfer belt 8 to perform monochrome printing (hereinafter referred to as “contact mono”). Called "mode"). Accordingly, the yellow, magenta, and cyan image forming units perform operations such as rotation without performing actual printing. In color printing, all four color image forming units are operated, and color printing is performed by bringing all four colors into contact with the intermediate transfer belt in a manner similar to the above contact mode (hereinafter referred to as “full color mode”). ).

JP 2001-125338 A

However, the above-described conventional image forming apparatus has the following problems.
When the contact mono mode is switched to the full color mode, black ATVC control is performed in the contact mono mode, and all color ATVC control is performed again in the subsequent full color mode. For this reason, when switching from the contact mono mode to the full color mode, downtime due to the ATVC control operation for all colors occurs, resulting in a reduction in productivity.

  Therefore, in the present invention, the ATVC control of yellow, magenta, cyan, and black is performed in advance in the contact mono mode based on the print information, thereby reducing the downtime during the subsequent switching operation to the full color mode. It becomes possible to suppress a decrease in productivity.

  The present invention has been made for the purpose of solving the above-described problems, and includes the following configuration as one means for achieving such an object.

  1st invention transfers the said image to the said intermediate transfer body from the several image carrier to which the image carrier which carries an image, the intermediate transfer body to which the said image of the said image carrier is transcribe | transferred A plurality of transfer means for controlling a constant voltage of the plurality of transfer means and detecting an output current value at the time of the constant voltage control, and all of the plurality of transfer means and the intermediate transfer body are in contact with each other In this state, the first mode in which an image is formed using one of the plurality of image carriers, and all of the plurality of transfer units and the intermediate transfer member are in contact with each other. In a color image forming apparatus having a second mode for forming an image using all of them, the image forming operation is performed by selecting the first mode or the second mode based on print information input from an external apparatus. Control means for controlling, said control means Whether to perform the output current detection operation by the current detection unit for all of the plurality of transfer units in the first mode based on the print information when the first mode is switched to the second mode. It is characterized by judging.

  According to a second aspect of the present invention, in the first aspect of the present invention, when switching from the first mode to the second mode, the printing information that the printing speeds at the time of image formation in the first mode and the second mode are equal is the same. In the first mode, it is determined whether or not to perform the output current detection operation by the current detection unit for all of the plurality of transfer units.

  According to a third aspect of the invention, a plurality of image carriers that carry an image, an intermediate transfer member to which the image of the image carrier is transferred, and the image are transferred from the plurality of image carriers to the intermediate transfer member. A plurality of transfer means for controlling a constant voltage of the plurality of transfer means and detecting an output current value at the time of the constant voltage control, and all of the plurality of transfer means and the intermediate transfer body are in contact with each other In this state, the first mode in which an image is formed using one of the plurality of image carriers, and all of the plurality of transfer units and the intermediate transfer member are in contact with each other. In a second mode in which an image is formed using all of them, in a state where one of the plurality of image bearing members is in contact with the intermediate transfer member and the other transfer unit and the intermediate transfer member are separated from each other. The transfer means and the intermediate transfer member are in contact with each other. In a color image forming apparatus having a third mode for forming an image using a carrier, the first mode, the second mode, or the third mode is selected based on print information input from an external device Control means for controlling the image forming operation, and the control means includes a plurality of control means in the first mode based on the print information when switching from the third mode to the first mode and the second mode. It is determined whether or not to perform an output current detection operation by the current detection unit for the transfer unit.

  In a fourth aspect based on the third aspect, when the mode is switched from the third mode to the first mode and the second mode, the printing speed during image formation in the first mode, the second mode and the third mode is Based on the print information that is equal, it is determined whether or not to perform an output current detection operation by the current detection unit for the plurality of transfer units in the first mode.

  As described above, according to the present invention, in the contact mono mode printing, the ATVC control of the image forming unit necessary for the generation of the full color mode image is performed based on the print information. It is possible to reduce the downtime at the time of switching to the full color mode, and to suppress the decrease in productivity.

1 is a schematic configuration diagram illustrating an image forming apparatus according to a first embodiment of the present invention. It is a basic bias sequence of ATVC control concerning a 1st embodiment of the present invention. 1 is a circuit diagram schematically showing a high-voltage power supply in a first embodiment of the present invention. FIG. 3 is a schematic configuration diagram for explaining the operation of the image forming apparatus in a separated mono mode, a contact mono mode, and a full color mode according to the first embodiment of the present invention. 1 is a block diagram illustrating a system configuration of an image forming apparatus according to a first embodiment of the present invention. It is a figure which shows the interface signal of the engine control part and controller part which concern on 1st Embodiment of this invention. 3 is a timing chart showing a time difference between a reference vertical synchronizing signal and an image data signal of each color in the image forming apparatus according to the first embodiment of the present invention. 3 is a control timing chart of primary transfer bias application according to the first embodiment of the present invention. It is a control flowchart for demonstrating the ATVC control 1 execution judgment processing at the time of the contact | abutting mono mode which concerns on 1st Embodiment of this invention. 6 is a control timing chart of primary transfer bias application according to a second embodiment of the present invention. It is a control flow chart for explaining ATVC control 1 execution judgment processing at the time of contact mono mode concerning a 2nd embodiment of the present invention.

[Example 1]
The present embodiment relates to a method for suppressing a decrease in productivity by performing ATVC control of all colors based on print information in contact mono mode printing when switching from contact mono mode to full color mode. belongs to.

  FIG. 1 shows an electrophotographic multicolor image forming apparatus of this embodiment. Details thereof will be described in order according to the process of image formation. First, as shown in FIG. 1, each image forming unit for toner of, for example, yellow, magenta, cyan, and black, which is disposed along a plane portion of an intermediate transfer belt 8 as an intermediate transfer member that is an image receiving member. Since the basic configurations of 1Y, 1M, 1C, and 1K are all the same, the following description of the image forming unit will be made only for the yellow image forming unit 1Y.

  In the yellow image forming section 1Y in FIG. 1, the image carrier 2a is a cylindrical photosensitive drum, and is driven to rotate in the direction of arrow a at a peripheral speed of 100 mm / sec. A charger 3a as a charging unit is pressed against the surface of the photosensitive drum 2a, and AC and DC biases are applied from a charging bias power source (not shown) while being driven to rotate along with the rotation of the photosensitive drum 2a. The surface is charged to a desired potential.

  Next, the photosensitive drum 2a is exposed in accordance with recorded image information by an image exposure unit 7a which is a latent image forming unit. The exposure is performed by a laser beam scanner / LED or the like. The developing device 4a, which is a developing unit, conveys developer (toner) from the developing roller 4a1 to the surface of the photosensitive drum 2a, and applies a predetermined DC voltage from a power source (not shown), thereby generating a latent image on the photosensitive drum 2a. It is visualized as a toner image. The toner image on the photosensitive drum 2a visualized by the developing device 4a is conveyed to a primary transfer portion formed between the intermediate transfer belt 8 and the photosensitive drum 2a according to the rotation of the photosensitive drum 2a. The intermediate transfer belt 8 contacts the photosensitive drum 2a and is driven in the direction of arrow c. The toner image that has reached the primary transfer portion is applied with a bias controlled by the CPU 17 from a high-voltage power supply 9a to a primary transfer roller 5a, which is a primary transfer means that is pressed against the intermediate transfer belt 8, and the toner is transferred to the toner. The image is transferred to the surface of the intermediate transfer belt 8. The intermediate transfer belt 8 is stretched and driven by a drive roller 11, a secondary transfer counter roller 12, and a support roller 13, and is formed by other image forming units 1M, 1C, and 1K in the same manner as the image forming unit 1Y. The toner images are sequentially superimposed on the intermediate transfer belt 8 to form a full color toner image.

  During mono printing, the toner image formed by the image forming unit 1K is transferred onto the intermediate transfer belt 8 to form a mono toner image. When the toner image on the intermediate transfer belt 8 reaches the secondary transfer portion formed by the secondary transfer roller 14 as the secondary transfer means and the intermediate transfer belt 8, the transfer material P is fed in time with this. At the same time, a predetermined bias is applied to the secondary transfer roller 14 to transfer the toner image to the transfer material P. The transfer material P onto which the toner image has been transferred is separated from the intermediate transfer belt 8 by the curvature of the secondary transfer counter roller 12, and is transferred to the fixing device 16 while the toner image is placed on the transfer material P. As a result, the toner image is fixed on the transfer paper P and discharged outside the apparatus. On the other hand, the transfer residual toner after the completion of the primary transfer is cleaned by the photosensitive drum cleaner 6a, and the residual toner on the intermediate transfer member after the secondary transfer is removed by the intermediate transfer member cleaner 15.

In the present embodiment, in the system configuration of the four drums as described above, the environmental fluctuation and resistance unevenness of the intermediate transfer belt 8 and the primary transfer rollers 5a, 5b, 5c, and 5d are corrected for the primary transfer bias control, The ATVC control method (Active Transfer Voltage Control) shown in FIG. 2 was adopted so that an optimum bias could be stably applied. This method aims at optimizing the transfer bias value applied to the transfer roller at the time of transfer, and a desired constant current (referred to as I ₀ ) flows from the transfer roller to the photosensitive drum during the pre-rotation immediately before image formation (ATVC). Control 1) A transfer bias value (referred to as Vt) determined from a bias value (referred to as V ₀ ) required to flow the current value is applied at the time of image transfer (ATVC control 2). Regardless of the conditions that affect the transfer, the transfer charge flowing from the transfer roller to the photosensitive member via the recording material P is always applied as an optimum value for transfer.

For example, considering the case where the resistance value of the transfer roller changes to a high level due to variations in the resistance value within the allowable range in manufacturing or changes in the resistance value due to the environment where the transfer roller is placed, the resistance value has increased. Thus, by setting a large Vt required for flowing the desired I ₀ , a desired constant transfer current value can always flow as I ₀ . Actually, in consideration of the presence of the recording material P when the recording material P passes through the transfer nip, the constant voltage value Vt as an actual transfer bias value is expressed by the following equation (ATVC equation). expressed.

Vt = A · V ₀ + B (A and B are constants)
Thus, in the contact transfer method, the optimum transfer bias value to be applied to the recording material P varies depending on the resistance value of the transfer roller. Further, since the transfer roller is made of semiconductive rubber, the individual resistance values vary greatly, and the resistance value also varies depending on the environment in which the transfer roller is placed. Similarly, the characteristic represented by the resistance value of the recording material P also changes drastically. Taking advantage of these characteristics, it is possible to distinguish between high temperature and high humidity environment (H / H) and low temperature and low humidity environment (L / L) from the resistance value of the transfer roller. It is possible to prevent the transferability from being changed by the resistance value fluctuation accompanying the above. Further, Vt is calculated from V ₀ obtained by the pre-rotation in order to prevent a phenomenon due to transfer current failure such as transfer explosion at the front end of the recording material P.

  Next, the high voltage power supplies 9a, 9b, 9c and 9d for bias applied to the primary transfer rollers 5a, 5b, 5c and 5d will be described with reference to FIG. A voltage setting circuit unit 42 changes the high voltage output voltage in accordance with the PWM signal output from the CPU 17. 43 is a transformer drive circuit unit, and 44 is a high voltage transformer. When the CPU 17 outputs the clock signal CLOCK, the transformer 44 is driven and a rectified DC high voltage is output to the secondary side of the transformer 44. A feedback circuit unit 46 monitors the output voltage via R71 and is a circuit provided so as to obtain an output voltage value corresponding to the setting of the PWM signal. Reference numeral 45 denotes a current detection circuit unit. A current value I73 obtained by adding the current value I72 flowing through the transfer member and the current value I71 flowing from the feedback circuit is detected by R73 and transmitted as an analog value to the control unit. The transfer roller is formed of a resistance component. Therefore, with respect to the applied output voltage, currents flowing through the detection resistor R73 are I71 and I72 flowing from the feedback circuit unit. I71 is determined by Vpwm and Vref, R74, R75 set by the PWM signal.

I71 = (Vref−Vpwm) / R74−Vpwm / R75
Further, the output voltage is set by the current value I71 flowing through the feedback resistor R71. That is, the voltage applied to the transfer roller is set.

Vout = I71 × R71 + Vpwm≈I71 × R71
Since this Vout is always stabilized by the negative feedback circuit, even if the load fluctuates, it can be a voltage faithfully corresponding to Vpwm.

  The current flowing through the transfer roller is a value I72 obtained by subtracting the current I71 flowing through the feedback circuit from the detected current I73. The resistance value of the transfer roller can be calculated based on the output voltage when this value I72 becomes a desired current value.

  Next, the operation of the image forming apparatus when performing monochrome printing and full color printing will be described with reference to FIG. When performing monochrome printing, printing is performed in either the separated mono mode or the contact mono mode.

  In the separated mono mode, if only the black image forming unit is operating, the printing operation can be performed. Therefore, the other three color image forming units of yellow, magenta, and cyan are stopped. At this time, the developing rollers 4a1, 4b1, and 4c1 of the three color developing devices 4a, 4b, and 4c are separated from the photosensitive drums 2a, 2b, and 2c, and the photosensitive drums 2a, 2b, and 2c are separated from the intermediate transfer belt 8. To print in black and white.

  In the contact mono mode, all four colors including the three colors not used for actual image formation are kept in operation. At this time, although the developing rollers 4a1, 4b1, and 4c1 of the three-color developing devices 4a, 4b, and 4c that are not used for image formation are separated from the photosensitive drums 2a, 2b, and 2c, the photosensitive drums 2a, 2b, and 2c for all four colors are separated. 2d performs monochrome printing in contact with the intermediate transfer belt 8.

  During full-color printing, the image forming units for all colors of yellow, magenta, cyan, and black are operated. At this time, the developing rollers 4a1, 4b1, 4c1, 4d1 of the developing devices 4a, 4b, 4c, 4d and the photosensitive drums 2a, 2b, 2c, 2d, the photosensitive drums 2a, 2b, 2c, 2d and the intermediate transfer belt 8 are brought into contact with each other. To perform full-color printing.

  Next, the system configuration and interface of the printer will be described.

  FIG. 5 is a block diagram showing a system configuration around the printer shown in FIG. 1, in which 200 is a host computer, 201 is a controller unit, and 203 is an engine control unit. The engine control unit 203 includes a video interface unit 204, a CPU (central processing unit) 17, an image processing GA 206, an image control unit 207, a fixing control unit 208, a transfer material transport unit 209 and a drive control unit 210, a high pressure control unit 211, A paper feed retry execution determination unit 212 is provided.

  The controller unit 201 can communicate with the host computer 200 and the engine control unit 203.

  FIG. 6 is a diagram showing interface signals between the engine control unit 203 and the controller unit 201.

  In FIG. 6, reference numeral 103 denotes a serial command transmission signal line, which transmits a command from the controller unit 201 to the engine control unit 203. A serial status transmission signal line 104 transmits status data from the engine control unit 203 to the controller unit 201 by serial communication in response to a command.

  Reference numeral 105 denotes a reference vertical synchronization signal line which transmits a reference vertical synchronization signal from the engine control unit 203 to the controller unit 201. Reference numeral 106 denotes a Y horizontal synchronizing signal line, and a yellow horizontal synchronizing signal is transmitted from the engine control unit 203 to the controller unit 201. Similarly, 107, 108, and 109 are M, C, and K horizontal synchronizing signal lines, respectively. 203 transmits a horizontal synchronizing signal of magenta, cyan and black from the controller unit 201.

  A Y image data signal line 110 transmits a yellow image data signal from the controller unit 201 to the engine control unit 203. Similarly, reference numerals 111, 112, and 113 denote M, C, and K image data signal lines, respectively. The engine control unit 203 transmits magenta, cyan, and black image data signals.

  The controller unit 201 receives image information and a print command from the host computer 200, analyzes the received image information, converts it into bit data, and prints a print reservation command and a print start command for each transfer material via the video interface unit 210. The video signal is sent to the engine control unit 203.

  The controller unit 201 transmits a print reservation command to the engine control unit 203 in accordance with a print command from the host computer 200, and transmits a print start command to the engine control unit 203 at a timing when printing is possible.

  The engine control unit 203 prepares for execution of printing in the order of print reservation commands from the controller unit 201 and waits for a print start command from the controller unit 201. When the engine control unit 203 receives the print instruction signal, the engine control unit 203 outputs a / TOP signal serving as a reference timing for outputting the video signal to the controller unit 201, and starts a printing operation in accordance with a print reservation command.

  The transmission timing of each color image data transmitted from the controller unit 201 to the engine control unit 203 when the image forming process is executed in the image forming apparatus showing the embodiment of the present invention will be described below with reference to FIG.

  FIG. 7 is a timing chart showing the time difference between the reference vertical synchronizing signal 105 and the image data signal of each color during the printing operation of the image forming apparatus showing the first embodiment of the present invention.

  In FIG. 7, T <b> 1 is a time difference between the reference vertical synchronization signal and the yellow image data, from when the controller unit 201 receives the reference vertical synchronization signal 105 from the engine control unit 203 to when the yellow image data is transmitted to the engine control unit 203. Corresponds to the time difference.

  Similarly, T2, T3, and T4 are the time differences between the reference vertical synchronization signal 105 and the magenta, cyan, and black image data, respectively. The controller unit 201 receives the reference vertical synchronization signal 105 from the engine control unit 203, and then outputs each color image data. This corresponds to the time difference until transmission to the engine control unit 203.

  When the controller unit 201 receives a print start command from the host computer 200 shown in FIG. 5, the controller unit 201 selects an image print mode and prints to the engine control unit 203 via the serial command transmission signal line 103. Issue an operation start command.

  When the engine control unit 203 receives the print operation start command, the engine control unit 203 starts the print operation and notifies the controller unit 201 that the print operation is started via the serial status transmission signal line 104.

  When the printing operation is started, the photosensitive drum driving motor for rotating the photosensitive drums 2a, 2b, 2c and 2d, the intermediate transfer belt driving motor for rotating the intermediate transfer body 8, and the exposure devices 7a, 7b and 7c for the respective colors. , 7d driving is started, and heating of the fixing unit 16 is also started.

  Next, when preparation for image formation for each color is completed, the engine control unit 203 outputs a reference vertical synchronization signal (hereinafter referred to as / TOP signal) to the controller unit 201 via the reference vertical synchronization signal line 105. Hereinafter, the operation from the start of driving of each actuator and the start of fixing heating to the completion of preparation for image formation will be referred to as a pre-rotation operation.

  The controller unit 201 inputs a reference vertical synchronization signal (/ TOP signal) output from the engine control unit 203 to a time difference from the input of the reference vertical synchronization signal stored in the memory to the output of yellow image data (FIG. 7). And output yellow print image data information (specifically, an ON / OFF signal of the laser beam) via the Y image data signal line 110 in synchronization with the horizontal synchronization signal. The laser beam scanning system in the yellow exposure device 7a emits a laser beam based on the image information input from the controller unit 201 to form an electrostatic latent image on the photosensitive drum 2a.

  Then, the yellow developing device 4a visualizes the electrostatic latent image formed on the photosensitive drum 2a with toner, and the visible image on the photosensitive drum 2a is arranged on the intermediate transfer member 8 at the lowest point of the photosensitive drum 2a. The primary transfer is performed by the primary transfer roller 5a.

  Then, the visible image of magenta toner is transferred to the lowest point of the magenta photosensitive drum 2b at the timing when the visible image of yellow toner transferred to the intermediate transfer body 8 passes the lowest point of the magenta photosensitive drum 2b. The image data information is output via the M image data signal line 111 after a time (T2 shown in FIG. 7) from the predetermined reference synchronization signal to the magenta image data output timing.

  The laser beam scanning system in the magenta exposure device 7b emits a laser beam based on the image information input from the controller unit 201 to form an electrostatic latent image on the photosensitive drum 2b, and the developing device 4b is on the photosensitive drum 2b. The electrostatic latent image formed on the photosensitive drum 2b is visualized with toner, and the visible image on the photosensitive drum 2b is visualized as a yellow visible image on the intermediate transfer member 8 by the primary transfer roller 5b disposed at the lowest point of the photosensitive drum 2b. The first transfer is performed with the position just aligned.

  Similarly to magenta, visible images of cyan and black are spaced by a time (T3 and T4 shown in FIG. 7) from a predetermined reference synchronization signal to the image data output timing so that the four color images just overlap. An image is formed, and an image is formed on the intermediate transfer member 8.

  As described above, the printing toner image formed by the image data of the four colors is formed on the intermediate transfer member 8 and conveyed to the secondary transfer position.

  A control timing chart of primary transfer bias application of this embodiment shown in FIG. 8 will be described. FIG. 8 is a control timing chart of the primary transfer bias when switching from contact mono-mode printing to full-color mode printing.

  Conventionally, at the time of contact monomode printing, the black transfer bias value Vt used for image transfer is obtained in the state of the contact monomode shown in FIG. 4 (ATVC control 1), and the constant voltage value Vt is used at the time of image transfer. Application (ATVC control 2) to form a mono image. Thereafter, in order to obtain the constant voltage Vt of each color applied during full color image transfer, ATVC control 1 for yellow, magenta, cyan, and black is performed in the state of the full color mode shown in FIG. At this time, the reason why the ATVC control 1 is sequentially performed for each color is that the ATVC control 1 is performed in accordance with the timing before image data transmission as shown in FIG.

In this embodiment, when the full color mode print is switched from the contact mono mode, the transfer bias values Vt for all colors are obtained in the state of the contact mono mode shown in FIG. 4 (ATVC control 1), and only black is a constant voltage value. Vt is applied during image transfer (ATVC control 2) to form a mono image. Since the transfer bias value Vt for all colors has already been determined before the full color image transfer, the ATVC control 1 can be skipped, and the time for the switching operation can be reduced. In this embodiment, as compared with the conventional, ATVC control 1 embodiment when the yellow, magenta, since the contact-separation state of the developing roller of the cyan are different, the bias value V ₀ taken to flow the target current value I ₀ Although it is conceivable, the transfer bias value Vt can be made as constant as possible by a method of setting a different target current value I ₀ between the contact state and the separation state of the developing roller.

  A control flowchart of this embodiment shown in FIG. 9 will be described. Based on the print information from the controller unit 201, the engine control unit 203 determines which image forming unit ATVC control 1 is to be performed in the contact mono-mode printing in the control flowchart of FIG. First, the engine control unit 203 determines whether the print is a color mode print (S11).

  In the case of color mode printing, it is determined whether or not the transfer bias values Vt for all colors have been determined (S12). At this time, if the printing has been once completed or the printing speed has been changed, the resistance value of the transfer roller is expected to change, and therefore the transfer bias value Vt is determined to be undetermined. If the transfer bias value Vt for all colors has not been determined, the ATVC control 1 for all colors is performed before image transfer (S13). If the transfer bias value Vt for all colors has been determined, the ATVC control 1 is performed. Not implemented (S14).

  If it is not the contact mono mode, that is, the separated mono mode (S15), it is determined whether or not the black transfer bias value Vt has been determined (S16), and the black ATVC control 1 is performed (S17). Alternatively, it is determined that the ATVC control 1 is not performed (S14).

  When the contact mono mode is selected (S15), it is determined whether there is color mode print information after the contact mono mode (S18), and whether the printing speed is switched after the contact mono mode (S19). Judging. When there is print information in the color mode after the contact mono mode and it is found that the printing speed is not switched after the contact mono mode, the ATVC control 1 for all colors is executed in advance during the contact mono mode print (S13). ). In other cases, the ATVC control 1 for yellow, magenta, and cyan is not performed during contact mono-mode printing.

  The control flowchart of the first embodiment shown in FIG. 8 can realize the control timing chart of the first embodiment shown in FIG.

  As described above, according to the present embodiment, when switching from the contact mono mode to the full color mode, by performing ATVC control for all colors based on print information in the contact mono mode print, In addition, the downtime at the time of switching to the color mode is reduced, and it becomes possible to suppress a decrease in productivity.

[Example 2]
Next, a second embodiment of the present invention will be described. In addition, about the structure similar to 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted. In this embodiment, color ATVC control is performed in the contact mono mode based on the print information when the separated mono mode is changed to the contact mono mode and the contact mono mode is changed to the full color mode. The downtime at the time of switching to the mode is reduced, and it becomes possible to suppress a decrease in productivity.

  A control timing chart of primary transfer bias application of this embodiment shown in FIG. 10 will be described. FIG. 10 shows a control timing chart of the primary transfer bias when continuously switching from the separated mono mode print to the contact mono mode print and from the contact mono mode print to the full color mode print.

  Conventionally, a black transfer bias value Vt is obtained (ATVC control 1) at the time of separated mono mode printing, and a constant voltage value Vt is applied at the time of image transfer (ATVC control 2) to form a mono image. At the time of the next contact mono-mode printing, the already obtained black constant voltage value Vt is applied during image transfer to form a mono image. Thereafter, when the full color mode printing is switched from the contact mono mode, the ATVC control of yellow, magenta, cyan, and black is performed in the state of the full color mode shown in FIG. 1 is carried out.

  In this embodiment, a black transfer bias value Vt is obtained (ATVC control 1) at the time of separated mono mode printing, and a constant voltage value Vt is applied at the time of image transfer (ATVC control 2) to form a mono image. At the time of the next contact mono-mode printing, in the state of the contact mono-mode shown in FIG. 4, black applies a constant voltage value Vt that has already been obtained at the time of image transfer (ATVC control 2), and yellow, magenta, and For cyan, the transfer bias value Vt of each color is obtained (ATVC control 1). Since the transfer bias value Vt for all colors has already been determined before the full color image transfer, the ATVC control 1 can be skipped, and the time for the switching operation can be reduced.

  A control flowchart of this embodiment shown in FIG. 11 will be described. Based on the printing information from the controller unit 201, the engine control unit 203 determines which image forming unit ATVC control 1 is to be performed in the contact mono mode printing in the control flowchart of FIG. First, the engine control unit 203 determines whether the print is a color mode print (S21).

  In the case of color mode printing, it is determined whether or not the transfer bias values Vt for all colors have been determined (S22). At this time, if the printing has been once completed or the printing speed has been changed, the resistance value of the transfer roller is expected to change, and therefore the transfer bias value Vt is determined to be undetermined. If the transfer bias value Vt for all colors has not been determined, the ATVC control 1 for all colors is performed before image transfer (S23). If the transfer bias value Vt for all colors has been determined, the ATVC control 1 is performed. Not implemented (S24).

  If it is not the contact mono mode, that is, the separated mono mode (S25), it is determined whether or not the black transfer bias value Vt has been determined (S26), and the black ATVC control 1 is performed (S27). Alternatively, it is determined that the ATVC control 1 is not performed (S24).

  In the case of the contact mono mode (S25), whether there is print information in the color mode after the contact mono mode (S28) and whether the printing speed is switched after the contact mono mode (S29). Judging. If there is no color mode print information after the contact mono mode, or if printing speed switching occurs after the contact mono mode, it is determined whether the black transfer bias value Vt has been determined (S26). It is determined whether the ATVC control 1 is executed (S27) or the ATVC control 1 is not executed (S24). In other cases, it is determined whether or not the printing speed has been switched before the contact mono mode (S30), and if it is determined that the printing speed has not been switched before the contact mono mode, At the time of close mono mode printing, yellow, magenta, and cyan ATVC control 1 is performed (S31). If the printing speed has been switched before the contact mono mode, ATVC control 1 for all colors is performed (S23).

  The control flowchart of the second embodiment shown in FIG. 10 can be realized by the control flowchart of the present embodiment shown in FIG.

  As described above, according to the present embodiment, the color ATVC control 1 is performed in the contact mono mode based on the print information in the contact mono mode from the separation mono mode and from the contact mono mode to the full color mode. By doing so, the downtime at the time of switching to the color mode is reduced, and it becomes possible to suppress the decrease in productivity.

1Y, 1M, 1C, 1K Image forming units 2a, 2b, 2c, 2d Photosensitive drum (image carrier)
3a, 3b, 3c, 3d Charging rollers 4a, 4b, 4c, 4d Developing devices 5a, 5b, 5c, 5d Primary transfer rollers 6a, 6b, 6c, 6d Photosensitive drum cleaners 7a, 7b, 7c, 7d Exposure device 8 Intermediate Transfer belts 9a, 9b, 9c, 9d High-voltage power supplies 10a, 10b, 10c, 10d Reflection mirror 11 Drive roller 12 Secondary transfer counter roller 13 Support roller 14 Secondary transfer roller (transfer means)
15 Intermediate transfer member cleaner 16 Fixing device 17 CPU

Claims (4)

A plurality of image carriers that carry an image, an intermediate transfer member to which the image of the image carrier is transferred, and a plurality of transfer means for transferring the image from the plurality of image carriers to the intermediate transfer member A plurality of the transfer means with constant voltage control, a current detection means for detecting an output current value at the time of the constant voltage control, a plurality of the transfer means and a plurality of the intermediate transfer members in contact with each other, A first mode in which an image is formed using one of the image carriers, and an image is formed using all of the plurality of image carriers in a state where all of the plurality of transfer units are in contact with the intermediate transfer member. A color image forming apparatus having a second mode to form, and control means for controlling the image forming operation by selecting the first mode or the second mode based on print information input from an external device. , The control means includes the first module. When the mode is switched to the second mode, it is determined, based on the print information, whether or not to perform the output current detection operation by the current detection unit for all of the plurality of transfer units in the first mode. An image forming apparatus. When switching from the first mode to the second mode, based on print information that the print speeds at the time of image formation in the first mode and the second mode are the same, in the first mode, the plurality of transfer means The image forming apparatus according to claim 1, wherein it is determined whether or not to execute an output current detection operation by the current detection unit for all. A plurality of image carriers that carry an image, an intermediate transfer member to which the image of the image carrier is transferred, and a plurality of transfer means for transferring the image from the plurality of image carriers to the intermediate transfer member A plurality of the transfer means with constant voltage control, a current detection means for detecting an output current value at the time of the constant voltage control, a plurality of the transfer means and a plurality of the intermediate transfer members in contact with each other, A first mode in which an image is formed using one of the image carriers, and an image is formed using all of the plurality of image carriers in a state where all of the plurality of transfer units are in contact with the intermediate transfer member. In the second mode to be formed, one of the plurality of image bearing members is in contact with the intermediate transfer member, and the other transfer unit and the intermediate transfer member are separated from each other. Using the one image carrier in contact with the intermediate transfer member In a color image forming apparatus having a third mode for forming an image, an image forming operation by selecting the first mode, the second mode, or the third mode based on print information input from an external device Control means for controlling the plurality of transfer means in the first mode based on the print information when switching from the third mode to the first mode or the second mode. An image forming apparatus that determines whether or not to perform an output current detection operation by the current detection unit. When switching from the third mode to the first mode and the second mode, the first mode, the second mode, and the third mode are based on print information that the print speeds at the time of image formation are the same. The image forming apparatus according to claim 3, wherein it is determined whether or not to perform an output current detection operation by the current detection unit for the plurality of transfer units in one mode.