JP2006030707A - Process cartridge and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of realizing the simplification of the rotational speed control mechanism of an image carrier and the improvement in the accuracy of the rotational speed control of the image carrier by a rotary encoder. <P>SOLUTION: In the image forming apparatus having a code wheel 70 for controlling rotation in the image carrier 7, a sensor 71 for detecting the pattern of the code wheel is installed in the process cartridges BY, BM, BC and BK having the image carrier 7 and an electrophotographic processing means for performing an image forming process to the image carrier 7. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine and a printer facsimile apparatus, and a process cartridge.

2. Description of the Related Art Conventionally, in an image forming apparatus using an electrophotographic image forming process, an electrophotographic photosensitive member as an image bearing member and process means acting on the electrophotographic photosensitive member are integrally formed into a cartridge, and this cartridge is formed into an image. A process cartridge system that is detachable from the apparatus main body is employed.
According to this process cartridge system, the apparatus can be maintained by the user himself / herself without depending on the service person, so that the operability can be remarkably improved. Therefore, this process cartridge system is widely used in image forming apparatuses.
In such a process cartridge type image forming apparatus, the rotation speed of the photosensitive drum as an image carrier is controlled by a rotary encoder attached to a drive shaft that transmits a driving force to the photosensitive drum. This is performed by detecting a speed fluctuation and performing feedback control or feedforward control on the rotation speed of the photosensitive drum based on the detection signal (see, for example, Patent Document 1).
JP 2003-122189 A

The drive shaft of the image carrier is likely to generate one rotation of the gears constituting the drive system and one-cycle rotation fluctuation. In order to suppress these rotational fluctuations, a code wheel, a sensor, and a control circuit for rotational control have been conventionally prepared to suppress rotational speed fluctuations. By the way, the relative position between the code wheel for rotation control and the sensor greatly affects the reading accuracy, and greatly affects the performance of the rotation control using the reading result. Even if the center of the code wheel pattern and the center of rotation are slightly deviated, the pattern detection result, that is, the target signal of the rotation control is displaced, and the rotation performance is deteriorated.
In particular, when a code wheel is installed on the image carrier, in order not to deteriorate the detachability of the image carrier, for example, a fitting hole with a drive shaft provided on the image carrier, a drive shaft that is a drive transmission member, There is a case where a minute gap is provided between the two, and in this case, a deviation occurs between the center of the code wheel pattern and the center of rotation. Further, in the tandem type image forming apparatus, the rotational fluctuation of each image carrier causes a positional deviation on the transfer material, and the positional deviation between the image carriers becomes an overlay deviation.
An object of the present invention is to provide an image forming apparatus capable of simplifying the rotational speed control mechanism of an image carrier and improving the accuracy of rotational speed control of the image carrier by a rotary encoder.

In order to achieve the above object, the invention according to claim 1 is characterized in that, in addition to an image carrier having a code wheel for rotation control, and at least one set of sensors for detecting a code wheel pattern, charging means, developing At least one of the means and the cleaning means is integrally formed into a cartridge.
According to a second aspect of the present invention, in the image forming apparatus having the code wheel for rotation control on the image carrier, the sensor for detecting the pattern of the code wheel performs an image forming process on the image carrier and the image carrier. An image forming apparatus installed in a process cartridge having the electrophotographic process means is the main feature.
The invention according to claim 3 is characterized in that the process cartridge is detachably attached to the apparatus main body and the image forming apparatus according to claim 2 takes in the signal detected by the sensor into the apparatus main body.
According to a fourth aspect of the present invention, an image forming apparatus having a code wheel for rotation control on an image carrier, the image forming apparatus having two or more sets of sensors for detecting the pattern of the code wheel is the main feature. .
According to a fifth aspect of the present invention, in the image forming apparatus having a code wheel for rotation control on the image carrier, the number of patterns of the code wheel is equal to the number of teeth of at least one gear provided on the drive shaft of the image carrier. An image forming apparatus that is an integral multiple is the main feature.
According to the sixth aspect of the present invention, in an image forming apparatus in which a plurality of image carriers are arranged and each image carrier has a code wheel for rotation control, the rotational speed fluctuations of the plurality of image carriers detected by a sensor. An image forming apparatus in which the rotation and activation timing of the image carrier are controlled so that the phases of the image recording medium substantially coincide on the recording medium is the main feature.

  In the present invention, in an image forming apparatus having a code wheel for rotation control on an image carrier, a sensor for detecting the pattern of the code wheel is used to perform an image forming process on the image carrier and the image carrier. By being installed in a process cartridge having a flow means, and in an image forming apparatus having a code wheel for rotation control in an image carrier, two or more sets of sensors for detecting the code wheel pattern are installed, Further, in the image forming apparatus having the code wheel for rotation control on the image carrier, the number of code wheel patterns is an integral multiple of the number of teeth of at least one gear provided on the drive shaft of the image carrier. In addition, in the image forming apparatus in which a plurality of image carriers are arranged and each image carrier has a code wheel for rotation control, a sensor More it is detected, so that the phase of the rotation velocity fluctuation of the plurality of image bearing members are generally coincident with the recording medium, by rotation and timing of starting the image bearing member is controlled, the intended purpose can be achieved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is described to the member common to each figure. In the following description, the longitudinal direction refers to a direction parallel to the recording medium that intersects the recording medium conveyance direction. The left and right are left and right as viewed in the conveyance direction of the recording medium.
FIG. 1 is an overall configuration diagram of an image forming apparatus according to the present embodiment. In FIG. 1, the image forming apparatus includes photosensitive drums 7Y, 7M, 7C, and 7K as image carriers provided for the respective colors of yellow, magenta, cyan, and black, and for each color on each photosensitive drum. The image forming units 31Y, 31M, 31C, and 31K that form toner images, the intermediate transfer belt 4a that temporarily transfers the toner images formed on the respective photosensitive drums, and the toner image on the intermediate transfer belt 4a are recorded. A secondary transfer roller 40 which is a transfer means for transferring to the medium 2, a paper feed means for feeding the recording medium 2 from the paper feed cassette 3 a, and the recording medium 2 are conveyed between the intermediate transfer belt 4 a and the secondary transfer roller 40. A feeding unit, a fixing unit 5 that fixes a toner image on the recording medium 2, and a paper discharge unit that discharges the recording medium 2 to a paper discharge tray 6 are provided.

Hereinafter, the image forming operation will be described. In FIG. 1, a paper feed cassette 3a for stacking and storing a plurality of recording media (for example, recording paper, OHP sheet, cloth, etc.) 2 is detachably attached to the image forming apparatus. The recording medium 2 fed from the paper feed cassette 3a by the pickup roller 3b is separated one by one by the retard roller pair 3c and conveyed to the registration roller pair 3f by the conveyance roller 3d. When the recording medium 2 is transported, the registration roller pair 3f stops rotating, and the recording medium 2 is corrected in skew by being abutted against the nip thereof.
On the other hand, the image forming units 31Y, 31M, 31C, and 31K are configured integrally as process cartridges BY, BM, BC, and BK, except for the optical scanning systems 1Y, 1M, 1C, and 1K. In the case of the 4-drum tandem type full color system, the process cartridges BY, BM, BC, and BK provided for each color of yellow, magenta, cyan, and black are arranged in parallel.
Optical scanning systems 1Y, 1M, 1C, and 1K are provided for the process cartridges BY, BM, BC, and BK, respectively, and toner images are formed on the photosensitive drums 7Y, 7M, 7C, and 7K by image signals. Thereafter, the respective color toners are transferred onto the intermediate transfer belt 4a running in the clockwise direction in the drawing by the transfer rollers 4Y, 4M, 4C, and 4K. The recording medium 2 is sent to the secondary transfer roller 40 at a predetermined timing, and the toner image on the intermediate transfer belt 4a is transferred and fixed by the fixing device 5, and then discharged by the discharge roller pairs 3h and 3i. The paper is loaded on the paper discharge tray 6 on the apparatus main body 14.

Hereinafter, the configuration of the process cartridges BY, BM, BC, and BK will be described. Since the process cartridges BY, BM, BC, and BK have the same configuration, the process cartridge BY will be described in the following description.
FIG. 2 shows a configuration diagram of the process cartridge BY. In the following description, the subscript (Y) is omitted. In FIG. 2, a process cartridge B has a magnetic brush charger 8 as a charging unit, an exposure unit, a developing unit 10 and a transfer opening 13n around a photosensitive drum 7 that rotates counterclockwise in the drawing. Is provided. The photosensitive drum 7 is driven to rotate by a driving member (not shown) installed at the rear side end portion in the longitudinal direction of the drawing, and is rotated at a predetermined speed by a rotary encoder installed on the rear side of the drawing in the longitudinal direction. It is controlled by control means (not shown).
In the present embodiment, a two-component developer having magnetic carrier powder is used as the toner. Therefore, as the photosensitive drum 7 used in the present embodiment, a commonly used organic photosensitive member or the like can be used. Preferably, the resistance is 10 ² to 10 ¹⁴ Ω · on the organic photosensitive member. If a material having a surface layer having a material of cm or an amorphous silicon photoconductor is used, charge injection charging can be realized, which is effective in preventing ozone generation and reducing power consumption. In addition, the chargeability can be improved. Therefore, in the present embodiment, a photosensitive drum 7 in which a negatively charged organic photosensitive member is provided on an aluminum drum base is used.

FIG. 3 shows a rear view of the process cartridge B, that is, an end surface on the back side (hereinafter abbreviated as the back side) when viewed from the mounting direction of the process cartridge B. In FIG. 3, on the back end surface of the process cartridge B, the back end portions in the longitudinal direction of the photosensitive drum 7, the magnetic brush charger 8 and the developing sleeve 10d are centered on the respective longitudinal axes. Three driving force receiving portions 37d, 38, and 39 serving as rotating shaft couplings are provided.
When the process cartridge B is mounted on the apparatus main body 14, the three driving force receiving portions 37 d, 38, and 39 are respectively connected to driving members (not shown) provided on the apparatus main body 14. The driving force receiving portions 37d, 38, and 39 are a drum coupling 37d, a charging portion coupling 38, and a developing portion coupling 39, respectively, and are provided facing the outside at positions retreated from the end surface on the back side of the process cartridge B. It is.
An encoder signal transmission device 72a is provided on the inner side of the process cartridge B, and an encoder signal is transmitted to and from the transmission device 72b provided in the apparatus main body. As a signal transmission method of the transmission devices 72a and 72b, a contact method using a metal terminal, a non-contact method using electromagnetic induction, or the like is used.
A drive-side drum flange 37 as a flange member that is disposed on the back side of the process cartridge B, that is, on the end surface on the drive side including the drive mechanism, and supports the longitudinal end of the drum shaft 42 that is the rotation shaft of the photosensitive drum 7. A code wheel 70 which is a plastic molded product and is a part of a rotary encoder is integrated.
FIG. 4 is a cross-sectional view showing the configuration of the photosensitive drum 7 and its surroundings. In FIG. 4, the support portion of the non-driving side end portion on the left side in the longitudinal direction of the drum shaft 42 is configured such that the drum shaft 42 does not move to the non-driving portion side. A shaft retaining ring 53 is fitted into a non-driving side end portion of the drum shaft 42 in the longitudinal direction. A bearing 55 housed in a bearing case 54 fixed to the cover 16 fixed to the end plate portion 12i of the developing frame 12 is fitted into the drum shaft 42, and the shaft retaining ring 53 and the bearing case 54 are connected in the axial direction. By contacting the inner and outer ring end faces on the opposite side, the movement of the drum shaft 42 to the non-driving side is stopped. On the other hand, the photosensitive drum 7 is restricted from moving to the drive side through a collar in which the drum flange 37 is fitted into the journal portion.

As shown in FIG. 5, the code wheel 70 and the drive-side drum flange 37, which are a part of the rotary encoder, are integrated by molding integrally or by connecting different members, and the code wheel 70 is a photosensitive drum. 7 is configured to rotate in synchronism with 7. In the present embodiment, the code wheel 70 is provided on the drive side drum flange 37, but the code wheel 70 is provided on a non-drive side drum flange (not shown) installed on the non-drive side of the photosensitive drum 7. Also good.
The material of the code wheel 70 is preferably a transparent resin material such as polyacetal, polystyrene, polyethylene, polycarbonate, or nylon (trademark), and in this embodiment, polycarbonate is used. The code wheel 70 is of a reflective type having a large number of V-grooves 70a, and a reflective portion and a non-reflective portion are formed at predetermined intervals in the circumferential direction.
In FIG. 6, a reading member 71 as a sensor which is a part of the rotary encoder is attached to the process cartridge B. The reading member 71 has a light emitting unit (not shown) and a light receiving unit (not shown), and each is integrated or separated. The fluctuation of the rotational speed of the photosensitive drum 7 generates light from the light emitting portion of the reading member 71, and detects the pulse wave of the light totally reflected through the code wheel 70 by the light receiving portion.
Data detected by the light receiving portion of the reading member 71 is sent to the arithmetic processing / output means 100 provided in the apparatus main body 14 via the transmission device 72. The rotation speed fluctuation detection signal output by the arithmetic processing / output means 100 is sent to a drive control means (control means) 101 for controlling the photosensitive drum drive motor 45. A signal for canceling the detection signal of the rotational speed fluctuation is fed forward or fed back to the photosensitive drum drive motor 45 to correct and suppress the rotational speed fluctuation of the drum drive shaft 46 that rotates synchronously with the photosensitive drum 7. Yes.

The present embodiment is an example in which the arithmetic processing / output means 100 is installed in the apparatus main body 14. However, the detection signal output by providing the arithmetic processing / output means 100 in the process cartridge B is output via the transmission device 72 to drive control means. A configuration for sending to 101 is also conceivable.
FIG. 7 shows an installation example of the code wheel 70 and the reading member 71. The two reading members 71 are disposed at positions that are generally 180 degrees opposite to the rotation center 42c. If the center 70c of the code wheel pattern and the rotation center 42c are deviated, for example, even if there is no rotation speed fluctuation, the detection signal detects a fluctuation of one rotation cycle as shown in FIG. 8a. At this time, the detection signal by the second reading member 71 provided at the opposite position is in the opposite phase of the detection signal a as shown in b in FIG. 8, and the above-described axis deviation is detected using the detection signals a and b. It can correct | amend so that the misdetection by may be canceled.
FIG. 9 shows an example of a graph representing the rotational speed fluctuation and its detection signal. In FIG. 9, “a” represents the rotational speed fluctuation of one gear period provided on the drive shaft. The code wheel pattern reading cycle slightly deviates from the rotation fluctuation cycle, resulting in a detection signal having low-frequency undulations as shown in FIG. In this image forming apparatus, the erroneous detection is prevented by setting the number of code wheel patterns to an integral multiple of the number of teeth of the gear 46G provided on the drive shaft.

FIG. 10 is a graph showing the positional deviation on the transfer material due to the rotational speed fluctuation of the image carrier. In the example of FIG. 10, the two misregistration graphs are substantially opposite in phase. At this time, the relative misregistration (color misregistration) is the sum of the misregistrations.
FIG. 11 is a graph showing the positional deviation on the transfer material due to fluctuations in the rotation speed of the image carrier in the image forming apparatus. The two misregistration graphs are substantially aligned in phase, and the relative misregistration (color misregistration) is the difference between the misregistrations, and can be suppressed to a smaller value than the example of FIG.
In this embodiment, the process cartridge in which the developing unit, the charging unit, and the photosensitive drum are integrally formed is described. However, the support structure for the cartridge frame of the photosensitive drum and the driving force receiving force of the photosensitive drum are described. The engagement / disengagement structure between the image forming apparatus and the driving member of the image forming apparatus main body is applicable to a process cartridge in general.
The process cartridge is a cartridge in which at least one of a charging unit, a developing unit, and a cleaning unit and an electrophotographic photosensitive drum are integrally formed, and the cartridge can be attached to and detached from the image forming apparatus main body. . Alternatively, at least one of the charging unit, the developing unit, and the cleaning unit and the electrophotographic photosensitive drum are integrally formed into a cartridge that can be attached to and detached from the main body of the image forming apparatus. Further, it means that at least the developing means and the electrophotographic photosensitive drum are integrated into a cartridge so that it can be attached to and detached from the image forming apparatus main body.

In the present embodiment, by installing the sensor together with the image carrier in the process cartridge, the code wheel pattern can be read with higher accuracy, and the rotation can be stably controlled with higher accuracy. Further, since the sensor can be taken out of the apparatus together with the process cartridge, the sensor can be easily cleaned and replaced, and the reading performance of the code wheel can be maintained for a long time.
Further, two or more sets of sensors for reading the code wheel are provided at a predetermined angle, and the rotation of the code signal can be controlled with higher accuracy by eliminating the error of the read signal caused by the above-described center shift. In particular, in order to cancel a reading error in one rotation cycle, it is effective to provide two sets of sensors at positions approximately opposite to the rotation center by 180 degrees.
In addition, by making the number of code wheel patterns used for rotation control an integer multiple of the number of gear teeth on the drive shaft, it avoids interference between the rotation fluctuation of one tooth cycle and the detection signal for control, resulting in false detection. Can be prevented.
By matching the phase of the rotational fluctuation of each image carrier on the recording medium, even if a positional deviation due to the rotational fluctuation occurs, the overlay deviation is suppressed by the amplitude difference of the positional deviation caused by the rotational fluctuation of each image carrier, Deviation can be reduced.

1 is an overall configuration diagram of an image forming apparatus according to an embodiment of the present invention. The block diagram of the process cartridge which concerns on embodiment of this invention. The rear view of the process cartridge which concerns on embodiment of this invention. 1 is a configuration diagram around a photosensitive drum according to an embodiment of the present invention. FIG. 1 is a perspective view of a photosensitive drum according to an embodiment of the present invention. The figure which shows the general structure of the drive system which concerns on embodiment of this invention, a detection system, and a control system. The figure which shows the example of installation of the code wheel pattern and reading member which concern on embodiment of this invention. The graph figure which shows an example of the rotation fluctuation detection signal which concerns on embodiment of this invention. The graph figure of the example of incorrect detection of the rotational speed fluctuation | variation which this invention prevents. The graph showing the position shift and color shift which this invention prevents. The graph showing the position shift and color shift which concern on embodiment of this invention.

Explanation of symbols

B (BY, BM, BC, BK) Process cartridge, C charging unit, D development unit, 1 (1Y, 1M, 1C, 1K) optical scanning system, 2 recording medium, 3a paper feed cassette, 3b pickup roller, 3c retard Roller pair, 3d conveying roller, 3f registration roller pair, 3h, 3i discharge roller, 4 intermediate transfer device, 4a intermediate transfer belt, 4b drive roller, 4c driven roller, 4d secondary transfer counter roller, 4 (4Y, 4M, 4C) 4K) transfer roller, 5 fixing device, 6 paper discharge tray, 7 (7Y, 7M, 7C, 7K) photosensitive drum, 8 magnetic brush charger, 8a charging roller, 8b magnet, 8c regulating blade, 10 developing means, 10c magnet, 10d developing sleeve, 10e regulating blade, 10f partition, 10g, 10h Screw, 11 Conductive brush, 12 Developing frame, 12a Guide part, 12e Seat part, 12f Lower part, 12g Side part, 12h, 12i End plate part, 13 Charging frame, 13a Lower edge, 13c Corner part, 13d Top plate part, 13n transfer opening, 14 apparatus main body, 16 front cover, 17 rear cover, 24 gear train, 31 (31Y, 31M, 31C, 31K) image forming unit, 37 drum flange, 37d drum coupling, 38 charging unit coupling, 39 Developing unit coupling, 40 Secondary transfer roller, 42 Drum shaft, 42c Drum shaft rotation center, 45 Photosensitive drum drive motor, 46 Drum drive shaft, 46G Drum drive gear, 53 Shaft retaining ring, 54 Bearing case, 55 Bearing, 56 collar, 70 code wheel, 70c code wheel pad Over down the center, 71 reading member (sensor), 72 (a, b) transmitting apparatus, 100 arithmetic processing and output means 101 drive control means

Claims (6)

  In addition to the image carrier having a code wheel for rotation control and at least one set of sensors for detecting the code wheel pattern, at least one of charging means, developing means, and cleaning means is integrally formed into a cartridge. A process cartridge characterized by that.   In an image forming apparatus having a code wheel for rotation control on an image carrier, a sensor for detecting the pattern of the code wheel has an electrophotographic process means for performing an image forming process on the image carrier and the image carrier. An image forming apparatus installed in a process cartridge.   3. The image forming apparatus according to claim 2, wherein the process cartridge is detachably attached to the apparatus main body, and a signal detected by the sensor is taken into a control device of the apparatus main body.   An image forming apparatus having a code wheel for rotation control on an image carrier, wherein two or more sets of sensors for detecting the pattern of the code wheel are installed.   In an image forming apparatus having a code wheel for rotation control on an image carrier, the number of code wheel patterns is an integral multiple of the number of teeth of at least one gear provided on a drive shaft of the image carrier. Image forming apparatus. In an image forming apparatus in which a plurality of image carriers are arranged and each image carrier has a code wheel for rotation control, the phase of the rotational speed fluctuation of the plurality of image carriers is detected on the recording medium. An image forming apparatus comprising control means for controlling rotation and activation timing of an image carrier so as to match.

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