JP3944209B2 - Image forming apparatus and process cartridge - Google Patents

Description

  The present invention relates to a process cartridge and an electrophotographic image forming apparatus to which the process cartridge can be attached and detached.

  Here, examples of the electrophotographic image forming apparatus include an electrophotographic copying machine, an electrophotographic printer (for example, an LED printer, a laser beam printer, etc.), an electrophotographic facsimile apparatus, and an electrophotographic apparatus that form an image by an electrophotographic image forming system. A word processor etc. are included.

  The process cartridge is a cartridge in which at least the developing roller, the cleaning member, and the electrophotographic photosensitive drum are integrally formed into a cartridge that can be easily attached to and detached from the image forming apparatus main body.

  2. Description of the Related Art In recent years, image forming apparatuses such as printers, copiers, and facsimiles using electrophotographic technology are increasingly used not only in large-scale offices but also in small offices such as Small offices and Home offices. There is an increasing demand from the market for the small size, low cost, and reliability of image forming apparatuses.

  A process cartridge for forming an image has various process elements such as a charging roller and a developing roller, and it is required to maintain functions required for each element for a long period of time at a small size and at a low cost.

  There is a cleaning blade as a process means included in the process cartridge.

  The cleaning blade removes the developer remaining on the photosensitive drum. In many cases, an elastic cleaning blade is brought into contact with the photosensitive drum to scrape the residual toner. The contact direction of the cleaning blade is a counter direction with respect to the rotation direction of the photosensitive drum during image formation. Therefore, when used for a long time, the cleaning blade may be deformed, and the function of removing the developer remaining on the photosensitive drum may be impaired.

  Conventionally, the shape, material, and arrangement of the cleaning blade have been optimized to increase reliability. However, as the speed and image quality of image forming apparatuses are further increased, it has become difficult to realize further low cost and downsizing with high reliability.

  Further, there is a charging roller as a process means included in the process cartridge. This applies a uniform potential to the photosensitive drum. In this configuration, an elastic body having a rotating shaft is brought into contact with the photosensitive drum, and a bias is applied while rotating by being driven by the photosensitive drum.

  However, this charging roller is always in contact with the photosensitive drum. Therefore, the developer that could not be sufficiently cleaned by the cleaning blade may stay between the photosensitive drum. Conventionally, the reliability of the charging roller has been improved by optimizing the material of the charging roller. However, as the speed and image quality of image forming apparatuses are further increased, it has become very difficult to achieve further reduction in cost and size while maintaining high reliability.

To solve these problems, there is a countermeasure that the photosensitive drum or the like is rotated by a predetermined amount in the opposite direction to the rotation direction at the time of image formation. As a reverse rotation method, a method using a drive motor in which the rotation speed, rotation amount, etc. are guaranteed in both forward and reverse directions is described in Patent Document 1 below. In addition, when the accuracy of reverse rotation is not so required, Patent Document 2 discloses a method of using a reverse bias applied to a motor that is guaranteed to have a rotation speed, rotation amount, etc. only in forward rotation. .
JP-A-7-84498 JP 2002-304103 A

  Compared with a drive motor that is guaranteed only for forward rotation, the drive motor that is guaranteed for both forward and reverse rotations is expensive.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a process cartridge and an image forming apparatus that realizes prevention of deformation of a craning member by using a mechanism for contacting or separating an electrophotographic photosensitive drum and a developing roller. There is to do.

  Another object of the present invention is to provide a process cartridge and an image forming apparatus in which the electrophotographic photosensitive drum is reversed with a simple structure to prevent deformation of the craning member.

In order to achieve the above object, a representative invention according to the present application is a process cartridge that is attachable to and detachable from an electrophotographic image forming apparatus main body, an electrophotographic photosensitive drum, and an electrostatic formed on the electrophotographic photosensitive drum. A developing roller that develops the latent image using a developer, a cleaning member that contacts the electrophotographic photosensitive drum to remove the developer from the electrophotographic photosensitive drum, and supports the electrophotographic photosensitive drum. A first frame and a second frame that is movably provided with the first frame and supports the developing roller when the process cartridge is mounted on the apparatus main body; A contact position where the electrophotographic photosensitive drum and the developing roller are in contact with each other by a movable contact member provided in the apparatus main body, the electrophotographic photosensitive drum and the developing roller A second frame that can be separated from each other, and a second frame that is provided on the first frame for transmitting driving in a direction opposite to that at the time of image formation to the electrophotographic photosensitive drum. One drive transmission means and a second drive transmission means provided on the second frame, wherein the first drive transmission when the second frame is located at the contact position And when the second frame is located at the separated position , the driving force is transmitted to the first drive transmission means by engaging with the first drive transmission means . And second drive transmission means.

  As described above, according to the present invention, the electrophotographic photosensitive drum is reversely rotated with a simple configuration by using a mechanism for contacting or separating the electrophotographic photosensitive drum and the developing roller, and the deformation of the crane member is performed. Can be prevented.

Example 1
The image forming apparatus according to the present embodiment is a laser beam printer that receives image information from a host computer, a network, and the like, and outputs the image information on a recording sheet. The process cartridge can be detached from the main body and replaced.

  The configuration of this embodiment will be described with reference to FIG. 1 and FIGS.

[Entire configuration of image forming apparatus]
FIG. 7 shows a four-color color electrophotographic image forming apparatus A (referred to as image forming apparatus A) which is an embodiment of the electrophotographic image forming apparatus according to the first embodiment of the present invention.

  An image forming apparatus A shown in FIG. 7 is an inline type color printer, and has photosensitive drums 1 (1a, 1b, 1c, 1d) which are four electrophotographic photosensitive members arranged in parallel in the vertical direction. ing. Around each photosensitive drum 1 (1a, 1b, 1c, 1d), charging rollers 7 (7a, 7b, 7c, 7d) for charging the surface of the photosensitive drum to a predetermined potential in order along the rotation direction. A scanner unit 11 (11a, 11b, 11c, 11d) that irradiates a laser beam based on image information and forms an electrostatic latent image on the photosensitive drum, and attaches toner to the electrostatic latent image to form a toner image. Developing unit 2 (2a, 2b, 2c, 2d) for developing, transfer device 12 for transferring the toner image on the photosensitive drum 1 to the recording medium P, residual toner remaining on the surface of the photosensitive drum 1 after transfer A cleaning blade 8 (8a, 8b, 8c, 8d) or the like for removing the water is disposed.

  In this embodiment, a process cartridge C (Ca, Cb, Cc, Cd) (hereinafter referred to as a cartridge) includes a photosensitive drum 1, a charging roller 7 as a process unit that acts on the photosensitive drum 1, and a developing unit. 4. Integrated with cleaning means (8, 9). The process cartridge C is detachable from the apparatus main body A.

  In this embodiment, the cartridges C (Ca, Cb, Cc, Cd) all have the same shape and have yellow, cyan, magenta, and black toners, respectively.

  The conveying belt 12 that conveys the recording medium is disposed so as to face all the photosensitive drums 1 of the cartridge C. Transfer rollers 121 (121a, 121b, 121c, 121d) as transfer members are in contact with the inside of the conveyor belt 12 and are provided side by side.

  In this embodiment, the conveyor belt 12 is stretched around three rollers, that is, a driving roller 122, a driven roller 123, and a tension roller 124. Then, as the drive roller 122 is rotated by a drive motor (not shown), the conveyor belt 12 rotates in the arrow direction V2 as shown in FIG. The toner image is transferred to the recording medium P while the conveying belt 12 circulates and the recording medium P is conveyed from the tension roller 123 side to the driving roller 122 side.

  The feeding unit 43 feeds the recording medium P to the image forming unit, and a plurality of recording media P are stored in the cassette 44. At the time of image formation, the feeding roller 42 rotates according to the image forming operation to separate and feed the recording media 5 in the cassette 44 one by one. Then, it is conveyed to the conveyor belt 12.

  The fixing device 13 fixes the toner image transferred to the recording medium P. When the recording medium P to which the toner image on the photosensitive drum 1 is transferred passes through the fixing device 13, heat and pressure are applied to the recording medium P so that the toner image transferred to the recording medium P is permanently applied to the surface of the recording medium P. It is fixed. Then, it is discharged outside the main body.

[Outline of process cartridge]
As shown in FIG. 6, the process cartridge C (hereinafter referred to as cartridge C) includes an electrophotographic photosensitive drum (hereinafter referred to as photosensitive drum 1) and a charging roller 7 for uniformly charging the photosensitive drum 1. A developing roller 2 as a developing means disposed in contact with and in contact with the photosensitive drum 1, and a developer supplying roller having a function of peeling off the toner on the developing roller 2 and a function of supplying the toner to the developing roller 2. 15, a developing frame 4 that is a storage portion of the toner T connected to the toner regulating member 5, a cleaning blade 8, and a waste toner container 9 that stores waste toner removed from the photosensitive drum 1 by the cleaning blade 8. Are integrally configured. The toner is an insulating nonmagnetic one-component toner.

  The cartridge C includes a cleaning unit 101 (101a, 101b, 101c, 101d) having a photosensitive drum 1, a charging roller 7, a cleaning blade 8, and a waste toner container 9, a developing roller 2, a developing blade 5, and an elastic roller 15. Development unit 102 (102a, 102b, 102c, 102d). The cleaning unit 101 and the developing unit 102 are coupled to each other at the support portion 103 so as to be rotatable about the coupling pin A. The cleaning unit 101 and the developing unit 102 are configured to abut the photosensitive drum 1 and the developing roller 2 by being biased by a spring (not shown).

[Separation]
As in this embodiment, in an image forming apparatus that outputs a full color image using process cartridges of four colors of yellow, cyan, magenta, and black, for example, when printing a monochrome image, yellow, cyan The magenta process cartridge need not operate.

  When the driving force is transmitted to the process cartridge, the developing roller 2, the toner, and the like rub against each other, so that the process cartridge deteriorates to some extent regardless of the presence or absence of printing, which may affect the life of the process cartridge.

  Therefore, in this embodiment, when printing a monochrome image, in the process cartridges of three colors not related to printing, (1) contact between the developing roller 2 and the photosensitive drum 1, and (2) photosensitive drum 1 and the transfer member. The separation operation for releasing the contact with 12 is performed.

  The specific configuration will be described with reference to FIG.

(1) Configuration for Releasing Contact between Developing Roller 2 and Photosensitive Drum 1 In FIG. 8A, the developing separation cam 22 is always in contact with the toner container 4.

  When the contact between the developing roller 2 and the photosensitive drum 1 is released (separated), the developing separation cam 22 is rotated to apply an upward force to the toner container 4. In the toner container 4, since the coupling pin A is at the center of rotation, when the upward force is received at the position of the developing separation cam 22, the developing unit 102 rotates with respect to the cleaning unit 101. Then, as shown in FIG. 8B, the contact between the developing roller 2 and the photosensitive drum 1 is released. (Second posture). Then, the developing separation cam 22 is further rotated to return to the original position, thereby returning to the contact state as shown in FIG. 8A (first posture).

  In other words, the separation and contact between the developing roller 2 and the photosensitive drum 1 is controlled by rotating the developing separation cam 22. The developing separation cam 22 (22a, 22b, 22c, 22d) is provided so as to act on each cartridge C (Ca, Cb, Cc, Cd) as shown in FIG.

(2) Configuration for Releasing Contact between the Photosensitive Drum 1 and the Transfer Member 12 In FIG. 9, when the photosensitive drum 1 and the transfer member 12 are in contact with each other in FIG. 9A, FIG. And when the transfer member 12 is separated. In this figure, a rotatable transfer separation member 23 is provided, and the transfer member 12 is separated by rotating the transfer separation member. That is, the separation and contact between the photosensitive drum 1 and the transfer member 12 are controlled by rotating the transfer separation member 23.

[Separation timing]
Next, specific timing of the separation operation will be described with reference to the sequence diagram of FIG.

  When a job signal is input while waiting for a job signal (S101), it is determined whether the job is a monochrome print job (S102). If the job is not monochrome printing, color printing is performed (S103), and it is confirmed whether there is a next continuous job (S104). If there is no next job, the next job signal standby mode is entered (S101).

  If there is a continuous job, it is checked again whether it is a monochrome printing job (S102). In the case of a monochrome printing job, the separation operation of the developing roller 2 and the transfer member 12 is performed (S105), and monochrome printing is performed (S106).

  Thereafter, it is confirmed whether there is a continuous job (S107). If there is no continuous job, the next job signal standby mode (S109) is entered. Then, it is checked again whether there is a monochrome printing job (S108). If the job is monochrome printing, monochrome printing is performed again (S106). If the job is a color job, color printing is performed after the development / transfer contact operation (S110) (S103).

  The above sequence is summarized as follows.

  When the separating operation of the developing roller 2 and the transfer member 12 is performed, the developing roller 2 and the transfer member 12 operate in a separated state until a color printing job comes. Further, when the abutting operation of the developing roller 2 and the transfer member 12 is performed, the developing roller 2 and the transfer member 12 operate in a contact state until a monochrome printing job comes.

[Configuration of reverse rotation]
Next, the feature of the present embodiment, which is the feature of the portion where the drive transmission portion of the toner container and the drive transmission portion of the toner container are connected when the development separation state is reached, will be described with reference to FIG. .

  FIG. 11A shows a state in which the developing roller 2 and the photosensitive drum 1 are in contact with each other and the electrostatic latent image formed on the photosensitive drum 1 can be developed. In this embodiment, as shown in FIG. 11, drive motors 24 and 25 are connected to the photosensitive drum 1 and the developing roller 2, respectively, and can be driven separately. The cleaning unit 101 is provided with drive transmission members 26 (a) to (d). Here, the drive transmission members 26 (a) to (d) are gears. The developing unit 102 is provided with drive transmission members 27 (a) to (d). Similarly, the drive transmission members 27 (a) to (d) are gears.

  FIG. 11B shows a state when the developing separation cam 22 that contacts the developing frame 4 rotates and the developing roller 2 and the photosensitive drum 1 are separated from each other. At this time, the drive transmission member 27 (d) of the developing unit 102 and the drive transmission member 26 (d) of the cleaning unit 101 are connected to each other so that a driving force can be transmitted. In the present embodiment, the drive transmission member has been described using a gear, but a friction wheel made of a material such as rubber may be used.

  The position of the coupling pin A is set at the center of the gear 27 (a). Therefore, since the gear 25a of the drive motor 25 on the main body side is connected to the gear 27 (a), even if the posture of the developing device frame 4 is changed by the developing separation cam 22, the gear 25a is connected to the gear 27 (a). Little effect on meshing. Therefore, it is possible to stably transmit the driving force from the driving motor 25 regardless of the state where the developing roller 2 and the photosensitive drum 1 are in contact with each other or the state where they are separated from each other.

  At this time, when the drive motor 25 starts driving, the driving force is transmitted to the drive transmission units 27 (a) to (d) on the developing unit 102 side. Since the drive transmission member 27 (d) and the drive transmission member 26 (d) are in a state where the drive transmission is possible, the drive transmission members 26 (a) to (d) on the cleaning unit 101 side also have a drive force. Is transmitted. Then, rotation in the direction opposite to normal (during image formation) is transmitted to the photosensitive drum 1.

  At this time, since the drive motor 24 and the photosensitive drum 1 are connected by a triangular coupling described later, even if the photosensitive drum rotates in the reverse direction, the drive motor 24 does not reverse.

  Moreover, you may use the one-way clutch which transmits only rotation of one direction to the connection part with the drive motor 24 even if it is not a triangular coupling.

  That is, the photosensitive drum 1 can be rotated with high accuracy by using the above-described configuration even if the drive motor 24 is guaranteed for the rotational speed or rotational amount in the normal rotational direction (one direction). Is possible.

[Coupling configuration]
In this embodiment, the driving force is transmitted to the photosensitive drum 1 with the configuration as shown in FIG. The gear 20 is a large-diameter gear that is connected to the drive motor 24 to transmit a driving force. At the rotation center of the gear 20, a protrusion 20b having a twisted hole 20a having a regular triangle cross section is provided. On one end side in the longitudinal direction of the photosensitive drum 21, a twisted protrusion 21 a having a regular triangle cross section that fits into the twisted hole 20 a is provided. The twist direction of the twisted hole 20a and the twisted protrusion 21a is the same. Accordingly, as shown in FIG. 12A, when an image is formed, the twisted hole 20a and the twisted protrusion 21a are fitted to each other, and a driving force (rotated in the direction of arrow a) is transmitted to the gear 20. The photosensitive drum 1 is drawn in the direction of the gear 20, that is, in the c direction (FIG. 12C). Conversely, as described above, when the driving force is transmitted in the state of FIG. 11B, the photosensitive drum 1 rotates in the direction of the arrow b. That is, the photosensitive drum 21 receives a force that moves in the direction away from the gear 20, that is, the d direction (FIG. 12C). At this time, the twisted hole 20a and the twisted protrusion 21a are not fitted. Therefore, even if the photosensitive drum 1 rotates in the direction of the arrow b, the drive motor 24 does not rotate in the reverse direction.

  In this embodiment, the connecting portion between the photosensitive drum 1 and the gear 20 has been described using a twisted hole having a regular triangle cross section and a protrusion having a regular triangle twisted cross section. A twisted projection having a polygonal cross section that can be coupled to the hole may be used.

[Reverse rotation of photoconductor drum when separated]
In this embodiment, using this configuration, every time the image formation is completed, a sequence of rotating the photosensitive drum 1 in the opposite direction to that during the image formation is performed. Specifically, each time a continuous job ends, the stress (8a) applied to the cleaning blade 8 due to the forward rotation of the photosensitive drum can be temporarily released by rotating in the reverse direction in FIG. . Further, if it is a charging means, the clogged toner can be dispersed by returning the developer staying in the portion B in FIG. 3 in the reverse direction and removed again by the cleaning blade 8.

  In this case, the rotation to the edge of the toner container, which is greater than α degrees shown in FIG. 4 in contact with the cleaning blade 8, that is, the reverse angle of β degrees or less, and forward rotation again from that position. Perform a sequence.

  By performing this sequence, as shown in FIG. 2, the stress (8a) to the cleaning blade 8 due to the positive rotation of the photosensitive drum can be temporarily released. In addition, as shown in FIG. 3, the toner staying in the portion B of the charging roller 7 is returned in the reverse direction (arrow f direction) so that the clogged toner can be dispersed and removed again by the cleaning blade 8. It becomes.

  A process cartridge in which toner was retained in the portion B in FIG. 3 was prepared, and 1000 sheets were printed in a state where the reverse rotation sequence was entered and a state where the reverse rotation sequence was not entered. As a result, the process cartridge printed in the state where the reverse rotation sequence is included has run out of toner to the extent that the staying toner cannot be visually confirmed. However, the amount of staying toner did not change in the process cartridge printed without the reverse rotation sequence.

It is sectional drawing which shows the development separation state of the process cartridge which concerns on this invention. It is sectional drawing of the process cartridge which concerns on this invention. FIG. 3 is an enlarged cross-sectional view of a charging roller portion of a process cartridge according to the present invention. FIG. 3 is an enlarged cross-sectional view of the vicinity of a charging roller and a cleaning blade of a process cartridge according to the present invention. It is a figure which shows the drive connection part between the main body of the process cartridge which concerns on this invention, and a process cartridge. It is sectional drawing of the process cartridge of 1st Example which concerns on this invention. 1 is a cross-sectional view of a lower image forming apparatus according to a first embodiment of the present invention. It is sectional drawing which shows the development separation and contact | abutting of 1st Example which concerns on this invention. FIG. 4 is a cross-sectional view illustrating transfer member separation and contact according to the first embodiment of the present invention. It is a flowchart for demonstrating separation | spacing and contact | abutting of 1st Example which concerns on this invention. It is sectional drawing which shows the development separation and contact | abutting of 1st Example which concerns on this invention. It is a figure which shows the drive connection part between the main body and process cartridge of 1st Example which concerns on this invention. It is sectional drawing which shows the other Example which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Developing roller 22 Developing separation cam 26 Drive transmission means on toner container side 27 Drive transmission means on development frame 4 side C Process cartridge

Claims (10)

In a process cartridge that can be attached to and detached from the electrophotographic image forming apparatus main body,
An electrophotographic photosensitive drum;
A developing roller for developing the electrostatic latent image formed on the electrophotographic photosensitive drum using a developer;
A cleaning member in contact with the electrophotographic photosensitive drum to remove the developer from the electrophotographic photosensitive drum;
A first frame for supporting the electrophotographic photosensitive drum;
A second frame that is movably provided with the first frame and supports the developing roller, and is provided on the apparatus main body when the process cartridge is mounted on the apparatus main body. A movable contact member can take a contact position where the electrophotographic photosensitive drum and the developing roller are in contact with each other, and a separation position where the electrophotographic photosensitive drum and the developing roller are separated from each other. A frame,
A first drive transmission means provided on the first frame for transmitting a drive in a direction opposite to that at the time of image formation to the electrophotographic photosensitive drum;
Second drive transmission means provided on the second frame, wherein the second drive body is separated from the first drive transmission means when the second frame is located at the contact position; and the time of the second frame is positioned at the separated position, the first engaged with drive transmission means, the second drive transmission means you transmit a driving force to said first drive transmission means When,
A process cartridge comprising:   2. The process according to claim 1, wherein, during the image formation, the electrophotographic photosensitive drum is engaged with a first main body driving unit provided in the main body of the apparatus to transmit a driving force. cartridge. The process cartridge according to claim 1, wherein a driving force is transmitted to the developing roller from a second main body driving unit provided in the apparatus main body.   The process cartridge according to claim 3, wherein the driving force is transmitted to the developing roller via the second drive transmission unit. The first body driving means provided in the apparatus body is a twisted hole having a polygonal cross section,
The process cartridge according to claim 2, wherein the electrophotographic photosensitive drum has a twisted polygonal column that engages with the twisted hole. An image forming apparatus for forming an image on a record medium,
(I) a movable contact member;
(Ii) an electrophotographic photosensitive drum, a developing roller for developing an electrostatic latent image formed on the electrophotographic photosensitive drum using a developer, and the electrophotographic photosensitive drum in contact with the electrophotographic photosensitive drum A cleaning member that removes the developer from the photosensitive drum, a first frame that supports the electrophotographic photosensitive drum, and a first frame that is movably provided with the first frame and that supports the developing roller. A contact position where the electrophotographic photosensitive drum and the developing roller are contacted by the contact member when the process cartridge is mounted on the apparatus main body of the image forming apparatus; A second frame that can take a separation position where the electrophotographic photosensitive drum and the developing roller are separated from each other; and when the image is formed on the electrophotographic photosensitive drum provided in the first frame. Is the reverse drive A first drive transmission means for transmitting the second drive transmission means provided in the second frame, wherein the second frame is located at the contact position, When separated from the first drive transmission means, and when the second frame is located at the separation position, the first drive transmission means is engaged with the first drive transmission means. a process cartridge; and a second drive transmission means you transmitting a driving force to,
(Iii) a mounting member for detachably mounting the process cartridge ;
(Iv) conveying means for conveying the recording medium;
An image forming apparatus comprising: Furthermore, the image forming apparatus includes:
7. The image forming apparatus according to claim 6, further comprising a first main body driving unit that engages with the electrophotographic photosensitive drum and transmits a driving force during the image formation. Furthermore, the image forming apparatus includes:
The image forming apparatus according to claim 6, further comprising a second main body driving unit that transmits a driving force to the developing roller. Said second main assembly driving means, the image forming apparatus according to claim 8, characterized in that for transmitting the driving force in engagement with said second drive transmission means. Said first body drive means, according to claim 7, wherein for polygonal engagement with twisted provided an electrophotographic photosensitive drum, characterized in that it has a twisted hole having a cross-section of the polygonal column Image forming apparatus.

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