JP4695387B2 - Image forming apparatus - Google Patents

Description

The present invention includes an image bearing member on which an image information is written, an image forming apparatus provided with a process cartridge which is detachably attached to the image forming apparatus.

  Image forming apparatuses that use a light beam to write image information in the form of a latent image on a photoconductor, which is an image carrier, are visualized by a developing device, and are transferred to a recording medium such as transfer paper. Widely used in In response to demands from the market, color image forming apparatuses that perform color processing on images are also widely used. As a color image forming apparatus, a plurality of photoconductors are juxtaposed, each photoconductor is provided with a developing device, a single color toner image is formed on each photoconductor, and the single color toner images are sequentially transferred to transfer paper. A so-called tandem type that forms a composite color image has become widespread due to the advantage of speeding up image formation.

  FIG. 11 is a schematic configuration diagram showing an example of this tandem type image forming apparatus. In the tandem type image forming apparatus, an endless belt-like intermediate transfer member 10 is wound around three support rollers 11, 12, and 13 and can rotate clockwise in FIG. In this conventional example, an intermediate transfer member cleaning device 14 for removing residual toner remaining on the intermediate transfer member 10 after image transfer is provided on the left of the support roller 11.

  Further, on the intermediate transfer member 10 that is stretched between the support rollers 11 and 12, monochrome images of yellow (Y), cyan (C), magenta (M), and black (K) are formed along the conveyance direction. Four image forming units 15Y, 15C, 15M, and 15K for forming are arranged side by side to constitute a tandem image forming unit. An exposure device 16 is provided on the tandem image forming unit. The alphabet after the reference number represents the color, Y for yellow, C for cyan, M for magenta, K for black, and redundant description is omitted.

  The image forming unit 15Y includes a photosensitive drum 17Y on which a latent image is formed by the light beam from the exposure device 16, a developing device 18Y, a photosensitive cleaner 19Y, and a charger (illustrated) disposed around the photosensitive drum 17Y. Not). The surface of the photoconductor drum 17Y is uniformly charged by a charger, and then exposed by a laser beam corresponding to a yellow image by the exposure device 16 to form an electrostatic latent image. The formed electrostatic latent image is developed by the developing device 18Y, and a toner image is formed on the photosensitive drum 6Y. The toner image is transferred onto the intermediate transfer member 10 by the transfer device 20Y at a position (transfer position) where the photosensitive drum 17Y and the intermediate transfer member 10 are in contact with each other, and a yellow single color image is formed on the intermediate transfer member 10. After the transfer, the photoreceptor drum 17Y is cleaned with unnecessary toner remaining on the drum surface by the photoreceptor cleaner 19Y to prepare for the next image formation.

  In this way, the intermediate transfer body 10 having the single color (yellow) transferred by the first image forming unit 15Y is conveyed to the second image forming unit 15M, and magenta image formation is performed. Similarly to the first image forming unit 15Y, the second image forming unit 15M also includes a photoconductive drum 17M, a developing device 18M disposed around the photoconductive drum 6M, a photoconductive cleaner 19M, and a charger (not shown). It is composed of In this case, similarly to the yellow image formation, the magenta toner image formed on the photosensitive drum 17M is transferred onto the intermediate transfer member 10 in an overlapping manner.

  Thereafter, the toner image is conveyed to the third image forming unit (cyan) and the fourth image forming unit (black) on the intermediate transfer body 10, and similarly formed toner images are copied to form a color image. . The third and fourth image forming units have the same configuration as that of the first and second image forming units. After the reference numbers indicating the respective constituent members, C in the case of cyan and black In this case, K is attached and detailed description is omitted.

  On the other hand, a secondary transfer device 22 is provided on the opposite side of the intermediate transfer body 10 from the image forming unit. In the illustrated example, the secondary transfer device 22 is configured by spanning a secondary transfer belt 24, which is an endless belt, between two rollers 23, and presses against the support roller 13 via the intermediate transfer body 10. The image on the intermediate transfer body 10 is transferred to the transfer paper 1 on the secondary transfer device 22.

  A fixing device 25 for fixing the transferred image on the transfer paper is provided downstream of the secondary transfer device 22 in the transfer paper transport direction. The fixing device 25 includes a fixing roller and a pressure roller disposed so as to be pressed against the fixing roller. The secondary transfer device 22 also has a transfer paper transport function for transporting the transfer paper 1 after image transfer to the fixing device 25. Reference numeral 26 denotes a registration roller for starting the rotation at the timing of the composite color image of the intermediate transfer body 10 and feeding the transfer paper 1 between the intermediate transfer body 10 and the secondary transfer device 22. A color image is recorded on the transfer paper 1 by being transferred by the secondary transfer device 22. Reference numeral 14 denotes a cleaning device for the intermediate transfer member 10.

  The above-described tandem type image forming apparatus temporarily transfers the images formed in the respective image forming portions to the intermediate transfer body 10 and then transfers the images on the intermediate transfer body 10 to the transfer paper by the secondary transfer apparatus 22. However, a direct transfer system that sequentially transfers images onto a transfer sheet transported by a transport belt in each image forming unit is also provided.

  FIG. 12 is a diagram schematically showing a drive mechanism for each of the photosensitive drums 17Y, 17C, 17M, and 17K. Each of the photosensitive drums 17Y, 17C, 17M, and 17K is rotationally driven by motors 31Y, 31C, 31M, and 31K, respectively, as illustrated. Looking at the drive transmission mechanism in the case of the photosensitive drum 17Y, a gear 33Y is attached to the motor shaft 32Y of the motor 31Y, and this gear 33Y is engaged with a driving gear 35Y attached to the shaft 34Y of the photosensitive drum 17Y. I am letting. Hereinafter, the photosensitive drums 17C, 17M, and 17K have the same configuration.

  In addition, a developing device that develops, cleans, and charges the photosensitive drum, a photosensitive cleaner, and a processing device such as a charging device are integrated into a cartridge for each color, and the cartridge can be attached to and detached from the image forming apparatus main body. A process cartridge system is also proposed. In this case, the shaft 36K of the drum drive gear 35K and the shaft 34K of the photosensitive drum 17K are separated by a joint 37K, as shown in FIG. 13 schematically showing the drive transmission mechanism in the case of the process cartridge, as an example. The process cartridge 41 is configured to be freely configured so that the process cartridge 41 can be easily removed.

  In the drive transmission mechanism as described above, the rotational speed of the photosensitive drum may be uneven due to the influence of the eccentricity of the drive gear. Such rotation unevenness may cause color misregistration in the case of a tandem type color printer. In addition to the eccentricity of the driving gear, the influence of the uneven rotation of the photosensitive member includes the influence of the joint that connects the driving gear and the photosensitive drum, and the influence of variations when the process cartridge is fixed to the main body from the front. However, when an encoder is attached to the drive gear, these effects are mixed.

Therefore, for example, Patent Document 1 proposes that an encoder is provided on the motor shaft and the photosensitive drum shaft to detect the rotational speed, and the rotational speed of the photosensitive drum is controlled to be constant based on the detection result. Yes. That is, as shown in FIGS. 12 and 13, motor shaft encoders 42Y, 42C, 42M, and 42K are provided on the motor shafts 32Y, 32C, 32M, and 32K, and the shafts of the photosensitive drums 17Y, 17C, 17M, and 17K are provided. Photosensitive shaft encoders 43Y, 43C, 43M, and 43K are also provided in 34Y, 34C, 34M, and 34K, and the rotational speeds of the motor shaft and the photosensitive drum shaft are detected, and the rotational speed of the rotating drum is based on the result. Is controlled to be constant.
JP 2002-278366 A

  However, when the encoder is attached to the motor shaft or the photosensitive drum shaft, there is a problem that it cannot be easily attached or detached. Furthermore, when performing rotational speed correction control, an encoder must be attached to all the photosensitive drums. In the conventional method, when a process cartridge is formed, the attachment becomes difficult.

  The present invention has been made in view of such a state of the prior art, and an object thereof is to make it possible to easily and accurately detect the rotational speed of an image carrier in a process cartridge.

To achieve the above object, the first means includes an image bearing member on which image information is written as a latent image, a plurality of process cartridges having at least one means and respectively for developing the latent image, said plurality of A plurality of fixing face plates to which shafts of the image carriers extending from the process cartridge are respectively attached, a main body frame to which the plurality of fixing face plates are attached, and the image carrier of one of the plurality of fixing face plates An encoder that is attached to the body and detects the rotational speed of the image carrier; and a calculation unit that calculates a speed control correction value detected by the encoder based on the rotational speed detected by the encoder; A storage unit that stores the speed control correction value calculated by the calculation unit, wherein the storage unit is the fixing unit. Storing said speed control correcting value of the plurality of image bearing members at the time of sequentially replacing the plate, characterized by.
The second means is the first means, respectively, provided at the position where the plurality of fixing face plates are attached to the main body frame, and the main body side terminals to be electrically connected by contacting with other terminals, Of the plurality of fixing face plates, the fixing face plate is provided only on a fixing face plate to which an encoder is attached, and the fixing face plate side terminal is provided at a position corresponding to the main body side terminal.

According to the present invention, when the fixing face plate is replaced, electrical connection can be easily performed, and speed measurement for four colors can be performed only by preparing one encoder .

  Hereinafter, the best mode for carrying out the present invention will be described. In addition, the same reference number is attached | subjected to the structure substantially the same as the structure of the prior art example mentioned above, and those detailed description is abbreviate | omitted.

  FIG. 1 is a diagram schematically illustrating a configuration of a process cartridge according to the present embodiment, and FIG. 2 is a diagram schematically illustrating a state in which the process cartridge is attached to a main body frame. The process cartridge device 41 includes four independent four-color process cartridges 41Y, 41C, 41M, and 41K. Each of the process cartridges 41Y, 41C, 41M, and 41K has one photosensitive drum 17Y, 17C, and 17M, respectively. , 17K and developing devices acting on these photosensitive drums, photosensitive cleaners 19Y, 19C, 19M, 19K, and a charging device (not shown). As shown in FIG. 2, the process cartridge device 41 is disposed in the mounting opening 52 of the process cartridge device 41 of the main body frame 51 of the image forming apparatus.

  3 to 4 show a first embodiment of the present invention, FIG. 3 is a view showing a state in which a fixing face plate is attached to a main body frame, and FIG. 4 is a view for explaining the attachment state. a) shows the encoder attached to the fixing face plate, and (b) shows the positional relationship between the fixing face plate and the photosensitive drum. In the first embodiment, as shown in FIG. 3, a single fixing face plate 53 is provided so as to close the opening 52 from the front surface of the main body frame 51. The fixing face plate 53 includes a process cartridge device 41 including four color process cartridges 41Y, 41C, 41M, and 41K and photosensitive drums 17Y, 17C, and 17M extending from the process cartridges 41Y, 41C, 41M, and 41K. , 17K shafts 34Y, 34C, 34M, 34K are fixed and positioned. An encoder for detecting the rotational speed of each of the photosensitive drums 17Y, 17C, 17M, and 17K is integrally attached to the fixing face plate 53. That is, the case of the cartridge 41K shown in FIG. 4 will be described as an example. As shown in FIG. 4A, an encoder 54K is attached to a position of the fixing face plate 53 facing the photosensitive drum 17K of the cartridge 41K. It has been. Therefore, as shown in FIG. 4B, the fixing face plate 53 is mounted by being attached to the main body frame 51 so that the center position of the encoder 54 is located at the same position as the shaft 34K of the photosensitive drum 17K. be able to. Similarly, encoders (not shown) are provided at positions of the fixing face plate 53 facing the remaining three photosensitive drums 17Y, 17C, and 17M. As a result, the rotational speed of each of the photoconductive drums 17Y, 17C, 17M, and 17K can be detected directly by simply attaching the fixing face plate 53 to the main body frame 51, and is accurately not affected by other disturbances. Measurement can be performed. It can also be attached and detached very easily.

  5 and 6 are diagrams for explaining the second embodiment, and FIG. 5 shows a state in which four fixing face plates are attached to the main body frame. FIG. 6 is a view for explaining each fixing face plate. FIG. 6A shows the fixing face plate. FIG. 6B shows a state in which the shaft of the photosensitive drum is inserted. In the second embodiment, the fixing face plate is divided into four colors. That is, as shown in FIG. 5, three fixing face plates 61 and one fixing face plate 62 are provided so as to close the opening 52 from the front surface of the main body frame 51. These four fixing face plates 61, 62 fix and position the shafts 34Y, 34C, 34M, 34K of the photosensitive drums 17Y, 17C, 17M, 17K extending from the cartridges 41Y, 41C, 41M, 41K. Is for. An encoder 63 for detecting the rotational speed of the photosensitive drum 17M is integrally attached to one fixing face plate 62. As shown in FIG. 6A, the fixing face plate 62 has an encoder 63 attached at a position facing the photosensitive drum 17M. Screw holes 65 for fixing to the main body frame are formed at the four corners of the fixing face plates 61 and 62. A shaft hole 64 into which the shaft of the photosensitive drum is inserted is provided at the center of the encoder 63. Accordingly, as shown in FIG. 6B, accurate measurement is possible by inserting the shaft 34M of the photosensitive drum 17M into the shaft hole 64 of the encoder 63 (or positioning by abutting against the encoder 63). Become. As a result, the rotational unevenness of the magenta photosensitive drum 17M is measured, the corresponding speed control correction value is calculated, and stored in the memory (not shown) of the control unit. Thereafter, the fixing face plates 61 and 62 are sequentially replaced, and the speed unevenness of the photosensitive drums 17Y, 17C, and 17K of other colors is measured. As described above, it is possible to measure four colors only by preparing one encoder 63.

  FIG. 7 is a view for explaining the third embodiment, and shows attachment of the fixing face plate to the main body frame and electrical connection to the encoder. Positioning holes 72 are formed at the four corners of the fixing face plate 71. A contact terminal 73 such as a power supply terminal or a detection output terminal of the encoder 63 is provided on the back side of the fixing face plate 71, that is, the surface to which the encoder 63 is attached. On the other hand, positioning holes 74 are formed in the body frame 74 at positions corresponding to the positioning holes 72 at the four corners of the four fixing face plates 71. Among the positioning holes 74 for fixing each fixing face plate 71, between the positioning holes 74 positioned below, contact terminals 76 that are in contact with and electrically connected to the contact terminals 73 formed on the fixing face plate 71. Is provided. Signals from the four contact terminals 76 are taken out from the main body frame 75 by the connector 77. As a result, the fixing face plate 71 is aligned with the positioning holes 72 and 74 at predetermined positions of the main body frame 75 and fixed with screws or the like, so that the two contact terminals 73 and 76 are pressed against each other to ensure contact. Thus, transmission and reception of electrical signals are performed with the main body side. Therefore, a connection harness is not necessary, and electrical connection is automatically performed while the fixing face plate 71 is being replaced. Note that the encoder 63 may be provided on only one of the four fixing face plates 71 as in the second embodiment.

  FIG. 8 is a diagram showing a basic configuration of a control circuit for controlling the speed of the photosensitive drum. Simple encoders 81Y, 81C, 81M, and 81K are attached to the four photosensitive drums 17Y, 17C, 17M, and 17K, respectively, and two simple encoders 81Y, 81C, 81M, and 81K are provided for each photosensitive drum. Two sensors 82 are provided. The signals of these eight sensors 82 are output to the control board 83. The control board 83 includes a sensor input timing detector 84, a motor drive timer 85 for the motors 31Y, 31C, 31M, and 31K that rotationally drive the photosensitive drums 17Y, 17C, 17M, and 17K, and a CPU 86 that calculates a speed correction value. And a speed correction unit 87 that updates the speed correction value from the CPU 86. The clock output from the control board 83 is output to the motors 31Y, 31C, 31M, 31K via the motor drivers 88Y, 88C, 88M, 88K, respectively.

  Therefore, the information of the simple encoders 81Y, 81C, 81M, 81K is input to the controller board 83 by the eight sensors 82. The CPU 86 in the controller board 83 calculates the speed correction value and stores it in a memory (not shown) inside the controller. When the motors 31Y, 31C, 31M, and 31K are driven, the correction value is periodically updated and set in the motor drive timer 85, thereby adjusting the four clock cycles and adjusting the four photosensitive drums 17Y, Control is performed so that the rotational speeds of 17C, 17M, and 17K are constant. The four motor drivers 88Y, 88C, 88M, 88K operate according to the cycle of the input clock. As a result, it is possible to correct the rotational speed unevenness of the photosensitive drums 17Y, 17C, 17M, and 17K due to the eccentricity of the drum drive gears 35Y, 35C, 35M, and 35K.

  FIG. 9 is a flowchart showing a processing procedure from taking in a sensor signal to detecting rotation unevenness and calculating a correction value. First, the photosensitive drums 17Y, 17C, 17M, and 17K are rotated (step S101), and it is checked whether or not these photosensitive drums 17Y, 17C, 17M, and 17K are at the home position (step S102). When not at the home position, the photosensitive drums 17Y, 17C, 17M, and 17K are further rotated and checked again. When k at the home position is confirmed, the signal of the sensor 82 is captured (step S103). When measurement is performed, in order to eliminate the influence of variation due to noise or the like when the sensor signal is captured, a plurality of times (normally Is approximately 10 times) and sampling is repeated to perform the averaging process (step S104). It is checked whether or not the specified number of samples have been acquired. If the specified number of samples has not been acquired, the process returns to step S102. If the specified number of times is taken in, the CPU 86 calculates a speed correction value (step S105).

  FIG. 10 is a flowchart showing a processing procedure for keeping the motor rotational speed constant by periodically changing the cycle of the clock signal output from the timer based on the calculated correction value. The correction of the motor speed is performed starting from the home position of the drum. That is, the drive initial values of the photosensitive drums 17Y, 17C, 17M, and 17K are set (step S201), and it is checked whether the photosensitive drums 17Y, 17C, 17M, and 17K are positioned at the home position (step S202). If it is at the home position, it is replaced with the drive values of the photosensitive drums 17Y, 17C, 17M, and 17K (correction values calculated in step S105 in FIG. 9) at a predetermined correction interval (step S203) (step S204). ) It is checked again whether each of the photosensitive drums 17Y, 17C, 17M, and 17K is located at the home position (step S205). This is repeated until the photosensitive drums 17Y, 17C, 17M, and 17K are positioned at the home position, and the photosensitive drums 17Y, 17C, 17M, and 17K are positioned at the home position, and the photosensitive drums 17Y, 17C, 17M, and 17K are moved. When stopping (step S206), driving of the motors 31Y, 31C, 31M, and 31K is stopped (step S207). When not stopping, the initial driving value of the photosensitive drum is set again (step S208), and step S203. The subsequent processing is repeated. In this manner, the rotational speed unevenness of the four photosensitive drums 17Y, 17C, 17M, and 17K can be corrected by changing the correction value at regular intervals starting from the home position.

It is a figure which shows schematic structure of a process cartridge. FIG. 2 is a diagram schematically showing a state in which the process cartridge of FIG. 1 is attached to a main body frame. It is a figure which shows the 1st Embodiment of this invention which attached the faceplate for fixing to the main body frame. It is a figure for demonstrating the attachment state of the faceplate for fixation. It is a figure which shows the 2nd Embodiment of this invention which attached four face plates for fixing to the main body frame. It is a figure for demonstrating each fixing faceplate. It is a figure which shows the 3rd Embodiment of this invention regarding the attachment of the fixing faceplate to a main body frame, and the electrical connection structure with respect to an encoder. FIG. 2 is a basic configuration diagram for performing speed control of a photosensitive drum. It is a flowchart which shows the process sequence after taking in a sensor signal, detecting a rotation nonuniformity, and calculating a correction value. It is a flowchart which shows the process sequence for changing the period of the clock signal output from a timer based on the calculated correction value, and keeping a motor rotational speed constant. It is a schematic block diagram which shows an example of the tandem type image forming apparatus currently implemented. It is a figure which shows schematically the drive mechanism of each photoconductor drum. It is a figure which shows roughly an example of the drive transmission mechanism in the case of a process cartridge.

Explanation of symbols

10 Intermediate transfer member 15Y, 15C, 15M, 15K Image forming unit 16 Exposure device 17Y, 17C, 17M, 17K Photosensitive drum 18Y, 18C, 18M, 18K Developing device 19Y, 19C, 19M, 19K Photoconductor cleaner 22 Secondary transfer Device 31Y, 31C, 31M, 31K Motor 34Y, 34C, 34M, 34K Photosensitive drum shaft 35Y, 35C, 35M, 35K Drum drive gear 41 Process cartridge device 41Y, 41C, 41M, 41K Process cartridge 51, 74 Main body frame 52 , 61, 62 Mounting opening 53, 71 Fixing face plate 54, 63 Encoder 64 Shaft hole 72, 74 Positioning hole 73, 76 Contact terminal 81Y, 81C, 81M, 81K Simple encoder 82 Sensor 83 Control board 84 Sensor Power timing Kenchi portion 85 motor drive timer 86 CPU
87 Speed corrector 88Y, 88C, 88M, 88K Motor driver

Claims (2)

An image bearing member on which an image information is written as a latent image, a plurality of process cartridges each comprise at least one means for developing the latent image,
A plurality of fixing face plates to which shafts of the image carriers extending from the plurality of process cartridges are respectively attached;
A body frame to which the plurality of fixing face plates are attached;
Attached to one of said image bearing member of the plurality of fixing faceplate, an encoder for detecting the rotational speed of the image bearing member,
Calculation means for calculating a speed control correction value of the image carrier detected by the encoder based on the rotation speed detected by the encoder;
Storage means for storing a speed control correction value calculated by the calculation means;
An image forming apparatus comprising:
The storage means stores speed control correction values for the plurality of image carriers when the fixing face plate is sequentially replaced;
An image forming apparatus . A main body side terminal that is provided at a position where the plurality of fixing face plates are attached to the main body frame, and is electrically connected by contact with another terminal;
Of the plurality of fixing face plates, provided only on the fixing face plate to which the encoder is attached, and the fixing face plate side terminal provided at a position corresponding to the main body side terminal;
The image forming apparatus according to claim 1, characterized in that it comprises a.

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