JP2006030625A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform developing operation at an always accurate position at the time of printing operation in an image forming apparatus having a rotary developing device holder for holding a plurality of developing devices. <P>SOLUTION: In the image forming apparatus having the rotary developing device holder for holding a plurality of developing devices and capable of judging the position of the developing device holder from an output of a sensor for detecting the rotation quantity of a motor for driving the developing device holder through a gear and an output of a sensor for detecting a reference position of the developing device holder, the reference position of the developing device holder is detected again after setting all the developing devices. When developing device detection is performed without opening a developing device replacing door after setting the reference position and the existence of all the developing devices is determined, second origin detection is omitted. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrophotographic multicolor image forming apparatus that forms a color image by a multiple transfer method using one image carrier, a plurality of developing cartridges, and an intermediate transfer member.

  A color image forming method in the image forming apparatus as shown in FIG. 2 will be described. First, a latent image formed by image information sent for each color by the optical unit 101 on the photosensitive drum 100 is a color developing device 151a, which is held by a rotary developing device holder 150 (hereinafter referred to as a rotary). A developing device of a color corresponding to the image information from 151b, 151c, 151d is brought into contact with the photosensitive drum 100, and developed and visualized by a developer included in the developing device. The visualized image is transferred to an endless image carrier 108 (hereinafter referred to as an intermediate transfer body). By repeating this four times, a multicolor image is formed on the intermediate transfer member 108. Thereafter, the transfer material P fed from the transfer material holder (hereinafter referred to as a paper feed tray) 200 is transported between the endless image carrier and the transfer and transport belt, and the transfer material P is transferred to the intermediate transfer body 108. Transfer the multicolor image above. The multicolor image transferred onto the transfer material P is thermally fixed to the transfer material P by the fixing unit 126. Thereafter, the transfer material P is conveyed and discharged to the upper discharge tray portion 128 or the lower discharge tray portion 125. When forming a monocolor image, the multiple image is a single color image developer.

  Next, the operation of the developing device selection mechanism will be described in detail.

  The rotary 150 rotates in the direction of the arrow in FIG. 2, that is, in the counterclockwise direction. By controlling the amount of rotation, the developing device 151 of any color can be moved to the position of the photosensitive drum 100. FIG. 3 is a diagram showing a portion related to driving of the rotary 150. A developing device holder 150 holds the developing devices 151a to 151d. Reference numerals 152a to 152d denote developing sleeves attached to the developing devices 151a to 151d, which are in contact with the photosensitive drum 100 and develop latent images. Here, 151c and 151d are not shown in FIG. Reference numeral 161 denotes a motor for rotating the rotary 150. Reference numeral 170 denotes a reflector having a large number of slit patterns attached on the shaft of the motor 161, and reference numeral 171 denotes an encoder for detecting the amount of rotation of the motor 161 by detecting reflected light from the reflector 170. Since the rotation amount of the motor 161 and the rotation amount of the rotary 150 are in a proportional relationship, the rotation amount of the rotary 150 can be detected by the encoder 171. Reference numeral 131 denotes a rotary developer reference position detection sensor (hereinafter referred to as a home position sensor) for detecting the reference position of the rotary 150, and reference numeral 132 is attached to the reference position of the rotary 150, and a reference for shielding the home position sensor 131 from light. It is a position indicating member.

FIG. 4 is a control block diagram of the developing device selection mechanism. Outputs from the home position sensor 131 and the encoder 171 are input to the CPU 201. The CPU 201 can confirm the origin position of the rotary 150 based on the input signal from the home position sensor 131. Further, the amount of rotation of the rotary 150 can be detected from the input signal of the encoder 171. That is, by checking the inputs of the home position sensor 131 and the encoder 171, the rotation amount from the reference position, that is, the current position of the rotary 150 can be recognized. By adjusting the gain of the variable gain amplifier 202 based on these pieces of information, the rotary 150 can be controlled to an arbitrary position. Finally, a specific operation for detecting the reference position of the rotary 150 will be described. When the power of the laser beam printer is turned on, the CPU (not shown) controls the variable gain amplifier 202 to rotate the rotary 150 at a constant speed. The position at which it is detected that the rotary 150 has rotated and the reference position indicating member 132 has reached the home position sensor 131 is defined as a reference position. Thereafter, the amount of rotation from the origin is detected by the encoder 171, and the current position of the rotary 150 is determined to perform control. At this time, if the rotary 150 is rotated once or more, the reference position indicating member 132 passes the home position sensor 131 again, but the detection result is not used again as the reference position. In other than the reference position detection operation, the rotational speed of the rotary developing device holder 150 is higher and the rotational speed is not constant. Therefore, the output signal of the home position sensor 131, the sampling delay of the CPU 201, etc. This is to prevent a reference position detection error due to the influence of.
JP 09-006076 A

  However, since the rotation amount of the developing device holder is determined based on the rotation amount of the motor shaft, there is a possibility that an error may occur in the reference position detection due to the margin of engagement of the drive gear during that time. Normally, if the developing device holder is driven by a motor, the gear always comes into contact with the edge determined by the rotational direction as shown in FIG. 6, so the motor drive shaft and the developing device regardless of the gear engagement margin. The amount of rotation of the holder is completely the same and no detection error occurs. However, the developing device holder can hold four developing devices, but since the developing devices can be detached, not all the developing devices are necessarily provided. For this reason, there is a possibility that a significant imbalance of the weight balance may occur, for example, only one developing device is attached when the reference position is detected. In this case, when the mounted developing device moves from the upper part to the lower part, the developing device holder may rotate at a higher speed than the driving speed by the motor due to the weight of the developing device. At this time, as shown in FIG. 7, the drive gear contacts the edge opposite to the normal side. In this case, there is a problem that an error may occur in the reference position detection in FIGS. 6 and 7 because the positions of the developing device holders are different on the motor shaft even if they are at the same position. This error has a level that does not affect the attachment / detachment of the developing device and the detection of the presence / absence of the developing device, but affects the image formation such as a change in contact pressure with the photosensitive drum during development. In addition, this detection error can be reduced by reducing the drive gear meshing margin. However, reducing the meshing margin has the negative effects of increasing the motor drive torque and requiring high precision in the gear parts. Will occur.

  According to the present invention, in order to accurately detect the origin regardless of the gear engagement between the rotary developer holder and the motor that drives the rotary developer holder, the presence or absence of the developer attached to the developer holder is determined. In the image forming apparatus having the detecting means, after all the developing devices are mounted, the origin confirmation of the developing device holder is performed again.

  According to the present invention, by detecting the origin position of the rotary developing device holder after all the developing devices are mounted, the gear meshing between the rotary developing device holder and the motor that drives the rotating developer holder is performed. Regardless of accuracy, accurate origin detection can be performed.

  The best mode for carrying out the present invention will be described below based on examples.

  First, FIG. 2 shows an example of an image forming apparatus used in the present invention.

  The image forming apparatus of the present embodiment is a reversal development system that visualizes by attaching a developer to an exposed portion of an image carrier, and a developer carrier carrying a negatively charged developer is brought into contact with the image carrier. A one-component image forming apparatus that performs development. First, the image forming apparatus used in the present invention will be described with reference to FIG. The main functions are a photosensitive drum 100, an optical unit 101, a charging roller 102, a primary transfer roller 103, an intermediate transfer member tension roller 104, an intermediate transfer member driving roller 105, an intermediate transfer member cleaning roller 107, and a rotary developing device holder 150. (Hereinafter, referred to as a rotary), a rotary developer holder driving unit 161, four developing units 151a to 151d, a rotary developer reference position detection sensor 131 (hereinafter referred to as a home position sensor), a conveyance belt 121, a fixing unit 126, A sheet feeding tray 200, a manual sheet feeding tray 124, a density and timing sensor 130, a secondary transfer roller 120, a sheet discharge roller 162, a sheet discharge tray 125, an upper sheet discharge tray 128, and the like are included.

  Next, an outline of the process up to printing will be described. First, the surface of the photosensitive drum 100 is uniformly charged to a desired polarity (for example, −600 V) by the charging roller 102 disposed on the photosensitive drum 100. Next, an electrostatic latent image is formed on the photosensitive drum 100 by exposing the photosensitive drum 100 with the laser L using the optical unit 101 based on the image data sent from the controller based on the image synchronization signal. As an example of a process for visualizing the electrostatic latent image, for example, an electrostatic latent image formed on the photosensitive drum 100 by the image forming unit (developing unit) 151a for Y (yellow) is applied to the developing sleeve 152 with a predetermined value. A voltage is applied (for example, −300 V), and the electrostatic latent image on the photosensitive drum 100 is developed with a developer such as a developer to form a visualized developer image on the photosensitive drum 100.

  Thereafter, the developer image on the photosensitive drum 100 is transferred to the intermediate transfer member by the primary transfer roller 103 to hold the image for the time being.

  Similarly, for M (magenta), C (cyan), and Bk (black), a latent image corresponding to each image data is sequentially formed on the photosensitive drum 100 by each color developing device 151b to 151d and a sleeve of each developing unit. A developer image is formed by developing with a developer. The above operation is performed to hold the formed image on the intermediate transfer member sequentially for each color.

  The retained developer images of the respective colors on the intermediate transfer body are transferred at a predetermined timing, so that multiple developer images are formed on the intermediate transfer body. On the other hand, after the development for the last image forming color is completed, the secondary transfer roller 120 and the intermediate transfer member cleaning roller 107 are brought into contact with the intermediate transfer member driving roller 105 via the intermediate transfer member at a predetermined timing. After contacting the intermediate transfer member, a high voltage (for example, +1000 V) having a polarity (for example, plus polarity) opposite to the developer image is applied to each roller at a predetermined timing to the secondary transfer roller 120. Similarly, a positive polarity voltage (for example, +1000 V and a rectangular wave voltage (for example, 1 KHZ, 2 KVpp)) is applied to the cleaning roller 107, and the intermediate transfer body driving roller 105 has, for example, the same polarity and the same potential as the primary transfer roller 103. Apply voltage and wait for transfer material transfer.

  Further, the transfer material is extracted from the paper feed tray 200 by the paper feed roller 125 or from the manual paper feed tray 124 by the paper feed roller 123 at a predetermined timing required for transferring the developer image. The extracted transfer material is temporarily stopped by the registration roller 122 and waits for completion of the final color image formation on the intermediate transfer member.

  The registration roller 122 starts re-transfer of the transfer material at a desired timing after the image formation of the final color is completed. The conveyed transfer material is conveyed between the abutting secondary transfer roller and the intermediate transfer member driven by the intermediate transfer member driving roller 105, and the multicolor multiple developer image on the intermediate transfer member is driven by the intermediate transfer member. Transfer is performed on the transfer material based on the potential difference between the bias applied to the roller 105 and the secondary transfer roller 120. Thereafter, the developer remaining on the intermediate transfer member after the transfer is removed or recharged by the cleaning roller 107, and the residual developer on the intermediate transfer member returns to the photosensitive drum 100 by recharging and contacts the photosensitive drum 100. It is collected by the blade. The residual developer collected by the blade is accumulated in the lung developer area 108 by driving (not shown). Further, the residual developer adhering to the cleaning roller 107 is collected on the photosensitive drum 100 later by a predetermined process.

  After the transfer to the transfer material is completed, the cleaning roller 107 and the secondary transfer roller 120 are separated from the intermediate transfer member driving roller 105 to prepare for the next image formation.

  The cleaned photosensitive drum 100 is charged uniformly to the desired polarity on the surface of the sightseeing drum 100 again by the charging roller 102 to prepare for the next latent image forming and developing process. The same applies to the intermediate transfer member from which the residual developer has been cleaned.

  On the other hand, the transfer material onto which the developer image has been transferred fixes the developer image onto the transfer material from the conveyance belt 121 by the fixing roller 126. The transfer material on which the developer image is fixed is discharged to the upper discharge tray 128 or the lower discharge tray 125.

  The manual paper feed tray 124 can be opened and closed as required by the user, and the tray itself can be expanded and contracted according to the size of the transfer material. Similarly, for the lower discharge tray 125, the sub-stay of the discharge tray can be expanded and contracted. Further, the upper paper discharge tray 128 can also extend and contract a stopper guide (not shown) according to the size of the transfer material. The density / timing sensor 130 is for controlling the density of each color developer image at the time of warm-up when the color image forming apparatus is turned on or at a predetermined timing. As for timing, a reference position on an intermediate transfer member (not shown) is read by reflection or transmission optical means, and used as a means for detecting a reference at the time of image formation. In the present invention, the density and timing sensor 130 is described as one unit, but it may be a separate unit.

  The above is the outline of the printing process in the color image forming apparatus used in the present invention.

  Next, FIG. 1 shows a flowchart of the embodiment of the present invention.

  In order to perform the printing process described above, it is necessary to accurately move the rotary 150 to the developing position. Therefore, it is necessary to accurately detect the origin position of the rotary 150 before the printing process. FIG. 1 is a flowchart of the origin position detection operation of the rotary 150. When the color image forming apparatus is turned on, the engine checks the opening and closing of the TOP cover 110, and if it is closed, it enters a print preparation operation (S1). In the printing preparation operation, the origin position of the rotary 150 is confirmed (S2). Note that the driving configuration and control details of the rotary 150 are the same as those of the prior art, and thus description thereof is omitted. Thereafter, the rotary 150 is controlled to sequentially move the developing devices of the respective colors to the nonvolatile memory access position to perform nonvolatile memory access. At this time, if the nonvolatile memory can be accessed, it is determined that the developing device is present, and if it is not accessible, it is determined that there is no developing device (S3). The presence / absence of all developing units in YMCK is checked, and if it is confirmed that all the developing units are mounted (S4), the origin of the rotary 150 is detected again (S5). Thereafter, an initialization operation of the electrophotographic process is performed (S6), and preparation for printing is completed (S7). Note that the initialization operation of the electrophotographic process is mainly a cleaning operation of the intermediate transfer member, but the description thereof is omitted because it is not directly related to the present invention. If there is even one developing unit that is not installed after the presence / absence detection of the developing unit (S4), if all the developing units are not installed, the reference position is detected due to the imbalance in the weight balance of the rotary 150. May not be performed correctly, so first wait for the upper cover 110 to be opened (S8). This is because it is necessary to open the upper cover 110 in order to mount the developing device, and therefore it is possible to determine the possibility that the developing device has been replaced by monitoring the state of the upper cover 110. When the opening of the upper cover 110 is detected, it is determined that there is a possibility that the developing device may be replaced, and it waits for the upper cover 110 to be closed again (S1), and the same processing as when the power is turned on is repeated. By doing so, the reference position of the rotary 150 is detected with all the developing devices mounted without fail before image formation.

  Next, a second embodiment according to the present embodiment will be described with reference to FIG. Note that the schematic configuration of the image forming apparatus according to the present embodiment is the same as the schematic configuration of the image forming apparatus described in the first embodiment, and a description thereof will be omitted instead of FIG. Further, since the driving configuration and control details of the rotary 150 are the same as those of the prior art, description thereof will be omitted.

  FIG. 2 is a flowchart of the origin position detection operation of the rotary 150. When the power of the color image forming apparatus is turned on, the engine checks whether the TOP cover 110 is opened or closed, and if it is closed, it enters a print preparation operation (S20). In the printing preparation operation, the origin position of the rotary 150 is confirmed (S21). Since it is unclear at this point that all the developing devices are present, the detected origin may have a detection error due to the effect of imbalance in the weight balance due to the presence or absence of the developing devices. For this reason, the temporary origin position is set and the temporary origin setting flag is set (S22). Thereafter, detection of the presence or absence of the developing device is started (S23). The presence / absence detection of the developing device is performed as follows. First, the rotary 150 is controlled to sequentially move the developing devices of the respective colors to the nonvolatile memory access position to perform nonvolatile memory access. At this time, if the nonvolatile memory can be accessed, it is determined that the developing device is present, and if it is not accessible, it is determined that there is no developing device. The presence / absence of all developing units in YMCK is checked (S25), and if all the developing units are installed (S26), the origin position detected in S21 is an imbalance in weight balance depending on the presence / absence of developing units. Therefore, it is determined that the origin position is accurate (S28). Thereafter, an initialization operation of the electrophotographic process is performed (S29), and preparation for printing is completed (S30). If it is detected in S26 that no developing device is mounted, the process waits for the opening of the upper door in order to wait for the mounting of a new developing device as in the first embodiment (S31). When it is detected that the upper door is opened, the temporary origin setting flag of the rotary 150 is cleared. This is because if the upper door is opened, the position of the rotary 150 may slightly move by the user's hand. If the rotary 150 does not move at all with the upper door opened or the amount of movement can be detected accurately, S32 need not be performed. Thereafter, it waits for the upper cover 110 to be closed (S33), and the same processing is repeated from the detection of the developing device. By doing so, the reference position of the rotary 150 is detected with all the developing devices mounted without fail before image formation.

It is a flowchart figure which concerns on the 1st Embodiment of this invention. 1 is a schematic fragmentary diagram illustrating a schematic configuration of a conventional image forming apparatus according to an embodiment of the present invention. FIG. 3 is a block diagram illustrating a schematic configuration of a rotary developing device holder. FIG. 6 is a block diagram illustrating a control configuration of a rotary developing device holder. It is a flowchart figure which concerns on the 2nd Embodiment of this invention. FIG. 7 is a first diagram showing a positional relationship of gears when a rotary developing device holder according to the related art is driven. FIG. 10 is a second diagram showing a positional relationship of gears when driving a rotary developing device holder according to the related art.

Explanation of symbols

100 Photosensitive drum 101 Optical unit 102 Charging roller 103 Primary transfer roller 104 Intermediate transfer member tension roller 105 Intermediate transfer member driving roller 107 Intermediate transfer member cleaning roller 108 Intermediate transfer member 120 Secondary transfer roller 121 Conveying belt 124 Manual feed tray 125 Paper tray 126 Fixing unit 128 Upper discharge tray 130 Density and timing sensor 131 Rotating developer reference position detection sensor (home position sensor)
150 Rotary developer holder (rotary)
151a to 151d Developing means (developing device)
152 Developing sleeve 154 Developing blade 161 Rotating developer holder driving means (motor)
162 Paper discharge roller 200 Paper feed tray 201 CPU

Claims (2)

  A latent image is formed on the photosensitive member by laser beam scanning or LED light emission corresponding to image information, and the latent image on the photosensitive member is selected from a plurality of developing devices held on a rotary developing device holder. The developer is developed using the developer, and the image on the photoconductor is transferred to the transfer material to form an image with the developer on the transfer material, and the developer is formed on the transfer material. In an image forming apparatus having means for fixing an image on a transfer material by a fixing means, a driving means for driving the rotary developing device holder via a gear, and detecting a rotation amount of the driving means First detecting means for detecting, a second detecting means for detecting a reference position of the rotary developing device holder, and the result of the first detecting means and the second detecting means for holding the rotary developing device. Calculate body position and drive Control means for rotating the rotary developing device holder to an arbitrary position by controlling the stage, and third detecting means for detecting the presence or absence of the developing device, and the third detecting means After detecting that all of the developing devices are mounted on the developing device holder, the second detection means detects the reference position of the rotary developing device holder again. apparatus.   The image forming apparatus according to claim 1, further comprising: an exterior opening / closing unit that needs to be opened to attach or detach the developing device; and a fourth detection unit that detects an open / closed state of the exterior opening / closing unit. After detecting the reference position of the rotary developing device holder by the second detecting means in a state where it is not detected that all of the developing devices are mounted on the developing device holder by the detecting means, The fourth detection means does not detect that the exterior opening / closing means has been opened, but the third detection means detects that all of the developing devices are mounted on the developing device holder. In this case, the image forming apparatus is characterized in that the result of the second detection means is validated, and image formation can be performed without detecting the reference position of the rotary developing device holder again.