JP2016090793A - Image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation apparatus capable of relaxing an impact applied to an image carrier and a transfer member when the image carrier and transfer member are released from being held apart from each other with simple constitution.SOLUTION: An image formation apparatus has a first gear 16 rotating together with an image carrier 6, and a second gear 17 provided movably together with the transfer member 7 and engaging the first gear 16 to rotate. The second gear 17 has a first gear part 17a engaging the first gear 16 with the transfer member 7 at a separate position, a release part 17b allowing disengagement from the first gear 16 with the transfer member 7 at an abutting position, and a second gear part located between the first gear part 17a and release part 17b. Then the second gear part is smaller in pitch circle radius at a part adjoining the release part 17b than the first gear part 17a, and has a part which gradually decreases in pitch circle radius from the side of the first gear part 17a toward the part adjoining the release part 17b.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile. More specifically, the present invention relates to an image forming apparatus having a separation release mechanism for switching from a state in which an image carrier and a transfer member are separated to a state in which the separation is released.

  Conventionally, for example, in an image forming apparatus such as a copying machine, a printer, and a facsimile using an electrophotographic image forming process, generally, a photosensitive drum as an image carrier, a transfer roller as a transfer member in contact with the photosensitive drum, Thus, a transfer portion is formed. Then, an image is formed by transferring the toner image on the photosensitive drum onto a recording material that is nipped and conveyed between the photosensitive drum and the transfer member in the transfer portion. At this time, the transfer roller is always in pressure contact with the photosensitive drum.

  Further, in such an image forming apparatus, there are many cartridge systems in which the photosensitive drum and the process means acting on the photosensitive drum are integrally formed into a cartridge, and this cartridge can be attached to and detached from the apparatus main body of the image forming apparatus. It has been adopted. In such a cartridge system, when an image forming apparatus is shipped from a factory, a form in which the cartridge is shipped in a state where the cartridge is mounted in the apparatus main body is increasing in order to improve packing efficiency by reducing the size of the packing box. .

  In such a packing form, the state in which the transfer roller is in pressure contact with the photosensitive drum as described above continues for a long time. For this reason, for example, due to environmental changes such as vibration, impact, and temperature / humidity changes during product transportation, there is a risk of permanent deformation of the transfer roller and image defects due to rubbing between the transfer roller and the photosensitive drum.

  In order to avoid the above problems, a separation member is mounted between the transfer roller and the photosensitive drum at the time of shipment to separate the transfer roller from the photosensitive drum. However, the spacing member needs to be removed when the image forming apparatus is used. For this reason, it is necessary for the user to pull out the cartridge once before using the image forming apparatus, remove the separation member, attach the cartridge again, and dispose of the separation member.

  Therefore, in order to eliminate the need for such user work, a configuration has been proposed in which the separated state between the photosensitive drum and the transfer member is released using the driving force when the image forming apparatus is powered on (patent). Reference 1).

JP 2010-262215 A

  In the image forming apparatus described in Patent Document 1, at the time of shipment, a drum helical gear provided on the rotating shaft of the photosensitive drum and a transfer helical gear provided on the rotating shaft of the transfer roller are separated. By contact, the transfer roller is retracted, and the photosensitive drum and the transfer roller are separated. The transfer helical gear is moved in the axial direction by the thrust force of the helical gear generated by the driving of the photosensitive drum, and the meshing with the helical gear of the drum is disengaged. The separated state from the roller is released.

  As a result, the photosensitive drum and the transfer roller are separated from each other even in a packing form in which the cartridge is mounted in the apparatus main body. Further, since the separated state is released by the driving force when the power of the image forming apparatus is turned on, a special operation for the user to remove the separating member is unnecessary, and usability can be improved.

  However, in the conventional image forming apparatus, when the transfer roller is separated from the photosensitive drum, the pressure by the transfer spring is applied to the transfer roller. When the transfer roller is released from the state of being separated from the photosensitive drum, that is, when the transfer helical gear moves in the axial direction and disengages from the drum helical gear, the pressure of the transfer spring is rapidly increased. Will be released. For this reason, when the photosensitive drum and the transfer roller are brought into contact with each other, an impact may be applied to the photosensitive drum and the transfer roller.

  Further, in order to ensure that the photosensitive drum and the transfer roller are separated from each other and do not come into contact with each other even when an impact on a product due to physical distribution or deformation of a part due to creep occurs, it is preferable that the separation amount is large. However, in the above-described conventional configuration, the greater the separation amount, that is, the greater the retraction amount of the transfer roller, the greater the pressure of the transfer spring during separation. As a result, the impact that can be generated on the photosensitive drum and the transfer roller at the time of releasing the separated state is also increased. In addition, using a damper member to reduce such an impact leads to an increase in product cost.

  In the above, the conventional problem has been described by taking as an example a configuration in which the photosensitive drum and the transfer roller are separated when the cartridge is mounted on the apparatus main body and shipped in the cartridge type image forming apparatus. However, even in an image forming apparatus that does not employ a cartridge system, it is desirable that the photosensitive drum and the transfer roller be separated from each other at the time of shipment in order to avoid the same problem as described above during product transportation. is there. Therefore, even in such an image forming apparatus, a problem similar to that of the above-described cartridge type image forming apparatus may occur.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus capable of reducing the impact applied to the image carrier and the transfer member when the separated state between the image carrier and the transfer member is released with a simple configuration. It is to be.

  The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention relates to an image carrier that is rotatable and carries a toner image, a first gear that rotates together with the image carrier, a contact position that contacts the image carrier, and the image carrier. It is provided so that it can move between the separated positions, and the image bearing member is moved from the image bearing member to the transfer member sandwiched between the image bearing member and the transfer member in the state of being disposed at the contact position. A transfer member for transferring a toner image; an urging means for urging the transfer member in a direction from the separation position toward the contact position; and movement of the transfer member between the separation position and the contact position. A second gear which is provided so as to be movable along with the transfer member along the direction, and which can rotate by meshing with the first gear. The second gear has the transfer member at the separated position. In the state where the image carrier is arranged and stopped, the first gear A first gear portion that meshes with the first gear portion, a release portion that is disengaged from the first gear in a state where the transfer member is disposed at the contact position, and the first gear in the rotational direction during image formation. When the rotation direction of the second gear when the second gear rotates along with the rotation of the second gear is defined as a predetermined direction, the first gear portion extends along a direction opposite to the predetermined direction. A second gear portion located between the release portion, and the second gear portion has a pitch circle radius of a portion adjacent to the release portion, the pitch circle radius of the first gear portion. And a portion having a pitch circle radius that gradually decreases from the first gear portion side to a portion side adjacent to the release portion along a direction opposite to the predetermined direction. Forming device.

  According to the present invention, the impact applied to the image carrier and the transfer member when the separated state between the image carrier and the transfer member is released can be reduced with a simple configuration.

1 is a cross-sectional configuration diagram of an image forming apparatus. It is a perspective view of a transfer part. It is a perspective view which shows the separation state and separation release state of a transfer part. It is a side view of a separation gear. It is a side view of the separation release mechanism showing the separation release operation of the transfer unit. It is a figure which shows the time displacement of the transfer roller in a space | interval release operation | movement. It is a side view of the other example of a separation gear. It is a side view of the other example of the separation release mechanism which shows the separation release operation of a transfer part. FIG. 12 is a perspective view of still another example of a transfer unit separation release mechanism. It is a side view which shows the separation state in the further another example of the separation release mechanism of a transfer part.

  The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

[Example 1]
1. FIG. 1 is a cross-sectional configuration diagram of an image forming apparatus 100 according to an embodiment of the present invention. The image forming apparatus 100 of the present embodiment is a laser beam printer that employs a cartridge system that forms an image using an electrophotographic image forming process.

  The apparatus main body 110 of the image forming apparatus 100 is provided with a feeding device 19. The feeding device 19 includes a feeding cassette 1 for stacking recording materials (recording sheets) P such as recording paper, a feeding roller 2 for feeding the recording materials P stacked on the feeding cassette 1, and the like. The recording material P loaded on the feeding cassette 1 is sent out by the rotation of the feeding roller 2 in pressure contact with the recording material P. Further, the recording material P sent out in this way is separated one by one by a separating means (not shown) included in the feeding device 19. The separated and fed recording material P is conveyed to a pair of intermediate conveyance rollers 3 and 4 including an intermediate conveyance roller 3 included in the feeding device 19 and a conveyance roller 4 opposed to the intermediate conveyance roller 3, and a cartridge 5 as an image forming unit. It is conveyed in the direction of.

  The cartridge (process cartridge) 5 is configured by integrally forming a photosensitive drum 6 and charging means, developing means, and cleaning means as process means acting on the photosensitive drum 6. The cartridge 5 is detachable from the apparatus main body 110. The process cartridge generally includes a photosensitive member and at least one of a charging unit, a developing unit, and a cleaning unit as a processing unit that acts on the photosensitive unit, and is integrally formed into a cartridge so that the main body of the image forming apparatus. It can be attached to and detached from. In this embodiment, at least the photosensitive member may be included in a cartridge that can be attached to and detached from the apparatus main body.

  In a state where the cartridge 5 is mounted inside the apparatus main body 110, the photosensitive drum 6 which is a rotatable drum-shaped electrophotographic photosensitive member (photosensitive member) as an image carrier rotates in the direction of arrow A in the figure. Driven. The surface of the rotating photosensitive drum 6 is uniformly charged by a charging roller 21 which is a roller-shaped charging member as a charging unit. The surface of the photosensitive drum 6 that has been charged is subjected to scanning exposure by a laser beam 9 that is irradiated in accordance with image information by a laser scanner 8 as an exposure unit provided in the apparatus main body 110. As a result, an electrostatic latent image (electrostatic image) is formed on the photosensitive drum 6. The electrostatic latent image formed on the photosensitive drum 6 is developed (visualized) as a toner image using toner as a developer by a developing device 22 as developing means. The developing device 22 includes a toner container that accommodates toner, a developing roller as a developer carrying member disposed facing the photosensitive drum 6 in the opening of the toner container, and the like.

  The toner image formed on the photosensitive drum 6 is transferred to the photosensitive drum at a transfer portion (transfer nip) N where the photosensitive drum 6 and a transfer roller 7 which is a roller-shaped transfer member as a transfer unit abut. 6 and the transfer roller 7 and transferred onto the recording material P conveyed. At this time, a transfer voltage (transfer bias) having a polarity opposite to the charge polarity (normal charge polarity) of the toner at the time of development is applied to the transfer roller 7 from a transfer power source (not shown) as a voltage application unit. The recording material P is conveyed to the transfer unit N by the above-described feeding device 19 in synchronization with the toner image on the photosensitive drum 6.

  The recording material P to which the toner image has been transferred is conveyed to a fixing device 24 as a fixing unit. The fixing device 24 includes a fixing roller 10 and a pressure roller 11. The fixing roller 10 has a heat source therein, and the pressure roller 11 presses against the fixing roller 10 to form a fixing portion (fixing nip). In the fixing unit, the recording material P is heated and pressed between the fixing roller 10 and the pressure roller 11 and conveyed, whereby the toner image is fixed on the recording material P. . The recording material P on which the toner image is fixed is discharged to the outside (outside of the apparatus) of the apparatus main body 110 by the discharge roller pairs 12 and 13 and stacked on the tray 25.

  Further, the toner (transfer residual toner) remaining on the surface of the photosensitive drum 6 after the transfer process is removed from the surface of the photosensitive drum 6 and collected by a cleaning device 23 as a cleaning unit. The cleaning device 23 includes a cleaning blade as a cleaning member disposed in contact with the photosensitive drum 6, a collected toner container for storing transfer residual toner scraped off from the surface of the photosensitive member rotated by the cleaning blade, and the like.

  Further, inside the apparatus main body 110, a control unit (not shown) having a power source and electric parts for driving and controlling each part is provided.

  The image forming apparatus 100 according to the present exemplary embodiment is packaged and shipped with the cartridge 5 mounted on the apparatus main body 110. At this time, the photosensitive drum 6 and the transfer roller 7 are separated from each other. When the use of the image forming apparatus 100 is started by the user, the apparatus main body 110 is turned on and the photosensitive drum 6 is started to rotate, so that details will be automatically described later. The separated state between the photosensitive drum 6 and the transfer roller 7 is released.

2. Next, the transfer portion N will be further described with reference to FIG. FIG. 2 is a perspective view showing the transfer portion N in a state where the transfer roller 7 is in contact with the photosensitive drum 6 (separation release state). FIG. 2 shows only one end side of the photosensitive drum 6 in the rotational axis direction. However, in relation to this embodiment, the other end portion of the photosensitive drum 6 in the rotational axis direction is shown. The side is also substantially the same structure. The same applies to FIGS. 3, 5, and 8 to 10.

  A photosensitive drum 6 is rotatably held on the cartridge 5. By the drive transmission from the apparatus main body 110, the photosensitive drum 6 rotates in the direction of arrow A in the figure. A transfer roller 7 that is in contact with the photosensitive drum 6 is disposed along the rotational axis direction of the photosensitive drum 6 so as to face the photosensitive drum 6. The transfer roller 7 is rotatably held by transfer roller bearings 14 serving as bearing members (support members) at both ends in the rotation axis direction substantially parallel to the rotation axis direction of the photosensitive drum 6. The transfer roller bearing 14 is attached to the frame 18 of the apparatus main body 110 so as to be movable (translatable) in a direction approaching the photoreceptor drum 6 and a direction away from the photoreceptor drum 6. Further, the transfer roller bearing 14 is urged in a direction approaching the photosensitive drum 6 indicated by an arrow B direction in the drawing by a transfer spring 15 as an urging means. With such a configuration, the transfer roller 7 is in contact with the photosensitive drum 6 (contact position) in a direction approaching the photosensitive drum 6 and in a direction away from the photosensitive drum 6, and a position separated from the photosensitive drum 6. It can be moved between (separated position). Further, with such a configuration, the transfer roller 7 is urged toward the photosensitive drum 6 by the urging force of the transfer spring 15, and contacts the photosensitive drum 6 to form a transfer portion N.

3. Next, with reference to FIGS. 3 and 4, the separated state and the separated release state of the photosensitive drum 6 and the transfer roller 7 in the transfer unit N will be described. 3A shows a state in which the transfer roller 7 is separated from the photosensitive drum 6 (separated state), and FIG. 3B shows that the state in which the transfer roller 7 is separated from the photosensitive drum 6 is released, and the transfer roller 7 is released. A state of being in contact with the photosensitive drum 6 (a separation release state) is shown. FIG. 4 is a side view of the separation gear 17 described later. A one-dot chain line in FIG. 4 indicates a pitch circle of the gear.

  The photosensitive drum 6 has drum gears (first gears) 16 at both ends in the rotation axis direction. The drum gear 16 is used to transmit driving to the charging roller 21 inside the cartridge 5. In this embodiment, the drum gear 16 is also used for a separation release mechanism that switches between a separation state and a separation release state between the photosensitive drum 6 and the transfer roller 7. The drum gear 16 is fixed on the rotation shaft of the photosensitive drum 6 and rotates integrally with the photosensitive drum 6.

  On the other hand, separation gears (second gears) 17 that can be brought into contact with and meshed with the drum gear 16 are provided at both ends of the transfer roller 7 in the rotational axis direction. The separation gear 17 is held on the transfer roller bearing 14 so as to be rotatable coaxially with the transfer roller 7. Accordingly, the separation gear 17 moves in a direction approaching the photosensitive drum 6 and a direction away from the photosensitive drum 6 as the transfer roller 7 moves in a direction approaching the photosensitive drum 6 and in a direction away from the photosensitive drum 6. . In this embodiment, the separation gear 17 is configured to be rotatably held by the transfer roller bearing 14, but is configured to hold the separation gear 17 on the transfer roller 7 (for example, on the rotation shaft) so as to be directly rotatable. It is good.

The separation gear 17 has a separation gear portion 17 a that meshes with the drum gear 16 in a state where the transfer roller 7 is separated from the photosensitive drum 6 and the photosensitive drum 6 is stopped. In this embodiment, the separation gear portion 17 a meshes with the drum gear 16 to bring the photosensitive drum 6 and the transfer roller 7 into a separation state. In the separated state as shown in FIG. 3 (a), the length La is obtained by adding the pitch circle radius _{R dr} of the pitch circle radius _{R a} and drum gear 16 of spaced gear portions 17a, the radius _{r tr} of the transfer roller 7 And the radius r _dr of the photosensitive drum 6 is larger than the length l. As a result, when the cartridge 5 is mounted on the apparatus main body 110, the transfer roller 7 can be in a separated state in which it does not press against the photosensitive drum 6.

  Further, the separation gear 17 has a chipped portion 17 b as a release portion that does not mesh with the drum gear 16. When the power of the apparatus main body 110 is turned on while the separation gear 17 is engaged with the drum gear 16, the photosensitive drum 6 starts to rotate, and the drum gear 16 rotates in the direction of arrow A in the drawing together with the photosensitive drum 6. . As a result, the drive is transmitted to the separation gear 17 via the drum gear 16, the separation gear 17 rotates in the direction of arrow C in the figure, and the meshing with the drum gear 16 is released at the missing tooth portion 17b. As a result, as shown in FIG. 3B, the transfer roller 7 and the photosensitive drum 6 are shifted to the separated release state where they are in pressure contact with each other.

  In this embodiment, the center of gravity of the separation gear 17 comes to the opposite side of the drum gear 16 with respect to the center of the rotation axis of the transfer roller 7 when the engagement of the separation gear 17 is released. As a result, when the separation gear 17 is released from meshing with the drum gear 16, the separation gear 17 rotates to the side that does not mesh with the drum gear 16 by its own weight, and the separation release state can be maintained. Further, in order to maintain the separation release state with certainty, a biasing means such as a spring for biasing the separation gear 17 in the direction away from the drum gear 16 may be provided.

  When the cartridge 5 is mounted on the apparatus main body 110, the separation gear 17 is manually placed at a predetermined phase position so that the separation gear portion 17a meshes with the drum gear 16, so that the separation gear 17 can be Can be set in position.

4). Next, the shape of the teeth of the separation gear 17 will be described with reference to FIGS. 4 and 5. 5A to 5E show how the transfer roller 7 and the photosensitive drum 6 move from the separated state to the separated release state as the drum gear 16 and the separated gear 17 rotate. 5A is a separated state of the photosensitive drum 6 and the transfer roller 7, FIG. 5E is a released state of separation of the photosensitive drum 6 and the transfer roller 7, and FIGS. 5B, 5C, and 5D. Indicates the state on the way.

As shown in FIG. 4, the separation gear 17 has a variable pitch gear portion 17c as a second gear portion between the separation gear portion 17a and the missing tooth portion 17b. A pitch circle radius R _b of a portion (hereinafter also referred to as “immediately before release”) 17c1 of the variable pitch gear portion 17c adjacent to the chipped portion 17b is smaller than _a pitch circle radius Ra of the separation gear portion 17a. Then, the variable Pitchigia unit 17c, the pitch circle radius R _c is formed so as to gradually become smaller from the pitch circle radius R _a of spaced gear portions 17a to the pitch circle radius R _b of the release part immediately before 17c1.

  As shown in FIG. 5A, when the drum gear 16 is stopped while the photosensitive drum 6 and the transfer roller 7 are separated from each other, the separation gear portion 17a of the separation gear 17 and the drum gear 16 are brought into contact with each other. I'm engaged.

As shown in FIG. 5B, when the drum gear 16 is driven in the direction of arrow A in the figure, the separation gear 17 rotates in the direction of arrow C in the figure, and the pitch circle radius of the meshing portion of the separation gear 17 from a certain phase. R _c starts to become smaller than the pitch circle radius _{R a} of spaced gear portion 17a. At this time, the state where the separation gear 17 and the drum gear 16 are engaged with each other is maintained, and the urging force of the transfer spring 15 in the direction of the drum gear 16 is received by the tooth surface of the drum gear 16. Since the drum gear 16 has a sufficient static torque, it does not rotate due to the biasing force of the transfer spring 15, and as a result, the separation gear 17 rotates following the rotational speed of the drum gear 16.

Then, as shown in FIG. 5 (b) ~ (c) , with the rotation of the separation gear 17, by the pitch circle radius R _c of the engagement portion between the drum gear 16 becomes smaller, the transfer roller 7 photoreceptor It moves in the direction of arrow B in the figure toward the drum 6 side. Further, as shown in FIG. 5D, when the meshing portion of the separation gear 17 with the drum gear 16 becomes a portion 17c1 (pitch circle radius R _b ) immediately before the disengagement portion 17b, the transfer roller 7 And the photosensitive drum 6 come into contact with each other.

  Thereafter, as described above, after the meshing of the separation gear 17 with the drum gear 16 is released, the separation gear 17 rotates due to its own weight, and is separated to the portion facing the drum gear 16 as shown in FIG. The missing tooth portion 17b of the gear 17 is arranged. Thereby, the separation release state between the photosensitive drum 6 and the transfer roller 7 is maintained.

  FIG. 6 is a graph showing the time displacement of the transfer roller 7 when the separated state between the photosensitive drum 6 and the transfer roller 7 is released. FIG. 6A shows a configuration using the separation gear 17 of the present embodiment, and FIG. 6B shows a configuration using a simple chip gear (chip gear without a variable pitch gear portion) as the separation gear. It is a graph in the case of. The horizontal axis indicates time, and the vertical axis indicates the displacement of the transfer roller 7.

  As shown in FIG. 6 (b), when the separation gear is a simple chipped gear, the displacement of the transfer roller 7 suddenly rises when the disengagement occurs at the chipped portion and instantaneously moves as indicated by an arrow E '. I understand that On the other hand, as can be seen from FIG. 6A, in this embodiment, as indicated by the arrow E, the transfer roller 7 gradually moves from the separated position to the contact position. As described above, in this embodiment, the transfer roller 7 and the photosensitive drum 6 are gradually brought closer to each other while the separation state is maintained at the meshing portion between the separation gear 17 and the drum gear 16. it can. Thereby, it is possible to mitigate the impact when the separated state between the photosensitive drum 6 and the transfer roller 7 is released.

Here, as shown in FIG. 5 (d), a length obtained by adding the pitch circle radius _{R dr} of the pitch circle radius _{R b} and the drum gear 16 of the release part immediately before 17c1 and Lb. A length obtained by adding the radius r _tr of the transfer roller 7 and the radius r _dr of the photosensitive drum 6 is assumed to be l. At this time, the length Lb and the length l are preferably configured to be substantially equal. Thereby, after the transfer roller 7 and the photosensitive drum 6 are reliably in contact with each other, the meshing can be released by rotating the separation gear 17 to the missing tooth portion 17b. Therefore, it is possible to more reliably alleviate the impact when releasing the separated state between the photosensitive drum 6 and the transfer roller 7.

  Note that the length Lb and the length l being substantially equal include not only the case where they are completely the same, but also the case where they are different within an allowable error range. For example, an error within ± 30% may be allowed. For example, even when the transfer roller 7 comes into contact with the photosensitive drum 6 after the engagement of the separation gear 17 with the drum gear 16 is released, the transfer roller 7 gradually reaches a position sufficiently close to the photosensitive drum 6 until then. It is displaced. Therefore, even in this case, the same effect as that in the case where the engagement of the separation gear 17 with the drum gear 16 is released after the transfer roller 7 abuts on the photosensitive drum 6 can be expected.

  As described above, the image forming apparatus 100 according to the present exemplary embodiment includes the photosensitive drum 6 that can rotate and carries the toner image, and the drum gear (first gear) 16 that rotates together with the photosensitive drum 6. In addition, the image forming apparatus 100 includes a transfer roller 7 provided so as to be movable between a contact position where the image forming apparatus 100 is in contact with the photosensitive drum 6 and a separated position where the image forming apparatus 100 is separated from the photosensitive drum 6. The transfer roller 7 is configured to transfer a toner image from the photosensitive drum 6 to a recording material P as a transfer target sandwiched between the photosensitive drum 6 and the transfer roller 7 in a state where the transfer roller 7 is disposed at the contact position. It is. Further, the image forming apparatus 100 includes a transfer spring 15 that urges the transfer roller 7 in a direction from the separated position toward the contact position. In addition, the image forming apparatus 100 is provided so as to be movable together with the transfer roller 7 along the moving direction between the separation position and the contact position of the transfer roller 7, and is a separation gear that meshes with the drum gear 16 and can rotate. (Second gear) 17 is provided. The separation gear 17 has a first gear portion (separation gear portion) 17a that meshes with the drum gear 16 in a state where the transfer roller 7 is disposed at the separation position and the photosensitive drum 6 is stopped. Further, the separation gear 17 has a release portion (missing tooth portion) 17b that is released from meshing with the drum gear 16 in a state where the transfer roller 7 is disposed at the contact position. Here, the rotation direction of the separation gear 17 when the separation gear 16 rotates in accordance with the rotation of the drum gear 16 in the rotation direction during image formation is defined as a predetermined direction. At this time, the separation gear 17 further includes a second gear portion (variable pitch gear portion) 17c positioned between the first gear portion 17a and the release portion 17b along the direction opposite to the predetermined direction. In the second gear portion 17c, the pitch circle radius of the portion adjacent to the release portion 17b is smaller than the pitch circle radius of the first gear portion 17a. Further, the second gear portion 17c has a portion where the pitch circle radius gradually decreases from the first gear portion side to the portion side adjacent to the release portion along the direction opposite to the predetermined direction.

  In particular, in this embodiment, after the separation gear 17 rotates in the predetermined direction and the transfer roller 7 comes into contact with the photosensitive drum 6, the second gear portion 17 c of the separation gear 17 is in contact with the drum gear 16. The meshing is released. More specifically, the sum of the pitch circle radius of the portion adjacent to the release portion 17 b of the second gear portion 17 c and the pitch circle radius of the drum gear 16 is the sum of the radius of the transfer roller 7 and the radius of the photosensitive drum 6. Is almost equal. In this embodiment, the drum gear 16 receives the urging force of the transfer spring 15 via the separation gear 17 in a state where the photosensitive drum 6 and the transfer roller 7 are separated from each other.

  As described above, according to this embodiment, the pitch circle radius of the portion 17c1 immediately before the release of the variable pitch gear portion 17c of the separation gear 17 is made smaller than the pitch circle radius of the separation gear portion 17a. As a result, the pressure of the transfer spring 15 is released at once when the separated state between the photosensitive drum 6 and the transfer roller 7 is released without adding another component such as a damper member, and the transfer roller 7 and the photosensitive drum 6 Can be prevented from abruptly contacting. Alternatively, even when a damper member is used, it can be replaced with an inexpensive damper member or a small damper member. Alternatively, when it is necessary to use a plurality of damper members, the number can be reduced. Further, as a result of suppressing the abrupt contact between the transfer roller 7 and the photosensitive drum 6, it is possible to reduce the operation sound generated when the transfer roller 7 and the photosensitive drum 6 contact each other. In addition, it is possible to reduce damage to the surface of the transfer roller 7 and peripheral components due to an impact when the transfer roller 7 and the photosensitive drum 6 are abutted suddenly.

  Further, by suppressing the impact when the transfer roller 7 and the photosensitive drum 6 abruptly contact each other, it is possible to prevent the surface of the photosensitive drum 6 and the surface of the transfer roller 7 from rubbing. Here, when the photoconductive drum 6 and the transfer roller 7 are rubbed, the photoconductive drum 6 is locally charged, and the contact mark of the transfer roller 7 on the image (toner image) formed on the photoconductive drum 6. Such a belt-like image defect may occur. On the other hand, in this embodiment, the photosensitive drum 6 and the transfer roller 7 are not easily rubbed, so that it is possible to suppress the occurrence of the image defect as described above. Therefore, the image quality can be further improved.

[Example 2]
Next, another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the first embodiment. Therefore, in the image forming apparatus of this embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of Embodiment 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 7 is a side view of the separation gear 17 in this embodiment, and FIG. 8 is a side view showing the separation release operation between the photosensitive drum 6 and the transfer roller 7 in the transfer portion N in this embodiment.

In Example 1, apart from the gear 17, spaced gear portion 17a is adjacent to the variable Pitchigia portion 17c, the pitch circle radius _{R c} of the variable Pitchigia portion 17c is, teeth 17b missing from the portion adjacent to the spaced gear portions 17a It is comprised so that it may become small gradually to the part adjacent to.

In the present embodiment, as shown in FIG. 7, the separation gear 17 is arranged on both sides of the separation gear portion 17 a in the circumferential direction of the separation gear 17, and a separation fixed gear portion 17 d (17 d 1, 17 d 2) as a third gear portion. Have That is, in the circumferential direction of the separation gear 17, one separation fixing gear portion 17d1 is provided on the variable pitch gear portion 17c side of the separation gear portion 17a, and the other separation fixing gear portion 17d2 is provided on the chipped portion 17b side. Yes. Pitch circle radius _{R d1, R d2} of spaced stationary gear unit 17d1,17d2 is larger than the pitch circle radius _{R a} of spaced gear portion 17a. A variable pitch gear portion 17c is provided between the missing tooth portion 17b and the separation fixed gear portion 17d1. The variable Pitchigia unit 17c, a pitch circle radius _{R c} are spaced a fixed gear portion 17d1 (i.e., spaced gear portion 17a side) is gradually decreased from the pitch circle radius _{R d1} up to the pitch circle radius _{R b} of the release portion immediately before 17c1 It is comprised so that it may become.

Thus, when the spaced gear 17 is rotated in the arrow C or C 'direction, the pitch circle radius of the separation gear 17 in the meshing portion between the drum gear 16, spaced fixed gear section from the pitch circle radius R _a of spaced gear portions 17a pitch circle radius _R d1 of _17d1,17d2, changes to the _{R d2.} At this time, since R _d1 and R _d2 are larger than R _a , the separation gear 17 is moved in a direction away from the drum gear 16 (in the direction of arrow D in FIG. 8). Here, in a state where the transfer roller 7 and the photosensitive drum 6 are separated from each other, the urging force F of the transfer spring 15 is applied to the separation gear 17, so that the separation gear 17 is separated from the drum gear 16 as described above. In order to move in the direction, a force against this biasing force F is required.

With the above configuration, the separation gear 17 is also applied by the biasing force F of the transfer spring 15 even when a force that rotates the separation gear 17 from the phase of the separation state due to vibration or impact applied to the cartridge 5 during the transportation of the product or the like. Can be prevented from rotating to the phase in the released state. That is, it is possible to more reliably maintain the separation state between the transfer roller 7 and the photosensitive drum 6 during product distribution. The pitch circle radii R _d1 and R _d2 of the separation fixed gear portions 17d1 and 17d1 are sufficiently larger than the pitch circle radius R _a of the separation gear portion 17a for this purpose.

Further, when the separation gear 17 rotates when the power of the apparatus main body 110 is turned on, the separation gear 17 is moved once in the direction away from the drum gear 16 (direction of arrow D in FIG. 8) by the driving force of the drum gear 16. Thereafter, in the same manner as in Example 1, the pitch circle radius R _c of the variable Pitchigia portion 17c along with the decrease, the distance gradually transfer roller 7 in accordance with the rotation of the drum gear 16 and the photosensitive drum 6 It can be shortened.

  As described above, in this embodiment, the separation gear 17 is adjacent to the first gear portion 17a in the circumferential direction, on at least one side of the first gear portion 17a, from the pitch circle radius of the first gear portion 17a. A third gear portion (separate fixed gear portion) 17d having a larger pitch circle radius. In particular, in this embodiment, the separation gear 17 includes third gear portions 17d1 and 17d2 adjacent to both sides of the first gear portion 17a in the circumferential direction. The separation fixing gear portion 17d is provided adjacent to at least one side of the separation gear portion 17a in the circumferential direction of the separation gear 17, so that the above-described effect can be obtained accordingly. It is preferable to provide it on both sides.

  As described above, according to the present embodiment, the same effects as those of the first embodiment can be obtained, and the separation state between the photosensitive drum 6 and the transfer roller 7 can be more surely released when the product is transported. Can be suppressed.

[Example 3]
Next, still another embodiment of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the first embodiment. Therefore, in the image forming apparatus of this embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of Embodiment 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 9 is a perspective view showing the transfer portion N in this embodiment, and FIG. 10 is a side view showing a separated state between the photosensitive drum 6 and the transfer roller 7 in the transfer portion N in this embodiment.

  In the first and second embodiments, the transfer roller 7 and the photosensitive drum 6 are separated from each other when the meshing portions of the drum gear 16 and the separation gear 17 are in contact with each other.

  In the present embodiment, as shown in FIG. 9, a separation cam 30 is provided as a separation member that can rotate together with the separation gear 17 at a position shifted from the separation gear 17 in the rotation axis direction of the separation gear 17. . In this embodiment, the separation cam 30 is formed integrally with the separation gear 17. The transfer roller 7 and the photosensitive drum 6 are separated from each other by the contact between the separation cam 30 and the photosensitive drum 6.

  Here, in this embodiment, the separation cam 30 is located on the photosensitive drum 6 outside the image carrying range (image forming area: area where the toner image can be carried) in the rotational axis direction of the photosensitive drum 6. It arrange | positions so that it may contact | abut. Thereby, even if the photosensitive drum 6 is damaged due to the contact of the separation cam 30, it can be prevented that the image affects the image.

In the separated state between the photosensitive drum 6 and the transfer roller 7 shown in FIG. 10, the distance from the rotation center of the separation gear 17 to the cam surface of the separation cam 30 is R _cam . At this time, the length Lc obtained by adding the distance R _cam and the radius r _{dr of the} photosensitive drum 6 is larger than the length l obtained by adding the radius r _tr of the transfer roller 7 and the radius r _dr of the photosensitive drum 6. ing. As a result, when the cartridge 5 is used as the apparatus main body 110, the cam surface of the separation cam 30 abuts on the photosensitive drum 6, and the separation state in which the transfer roller 7 is not pressed against the photosensitive drum 6 can be achieved.

Further, in this embodiment, in a separated state of the transfer roller 7 and the photosensitive drum 6, the length Lc, the pitch circle radius R of a pitch circle radius R _a and drum gear 16 of spaced gear portions 17a of the separation gear 17 _The distance b is larger than the length La obtained by adding _dr . This distance b is set to a small distance such as the backlash of the meshing portion between the drum gear 16 and the separation gear 17. That is, the distance b can be transmitted by driving the drum gear 16 and the separation gear 17 in mesh with each other, but in a state where they are completely in contact with each other (a state where the drum gear receives a biasing force applied to the separation gear in the drum gear direction). ).

  With the above configuration, even when the urging force of the transfer spring 15 is applied to the separation gear 17 when the photosensitive drum 6 and the transfer roller 7 are separated from each other, the separation gear 17 and the drum gear 16 are not completely in contact with each other. A small gap with a distance b is formed in the meshing portion. As a result, vibrations and impacts during product transportation or the like are not directly transmitted to the meshing portion of the drum gear 16 and the separation gear 17, and scratches and damage to the tooth surfaces of the drum gear 16 and the separation gear 17 can be reduced.

Also, the profile of the cam surface of the separation cam 30 is configured to have a gradual radius becomes smaller portions with a pitch circle radius R _c and the phase of the variable Pitchigia portion 17c of the separation gear 17. In this configuration, when the drum gear 16 is driven, the separation cam 30 rotates in the direction of arrow C in the drawing due to the engagement between the separation gear 17 and the drum gear 16. Then, while keeping the cam surface of the separation cam 30 and the photosensitive drum 6 in contact with each other, the separation distance between the transfer roller 7 and the photosensitive drum 6 is reduced following the rotation of the photosensitive drum 6. I can go. At this time, in this embodiment, the distance b is maintained at the meshing portion of the separation gear 17 and the drum gear 16. In this embodiment, after the transfer roller 7 contacts the photosensitive drum 6, the contact of the separation cam 30 with the photosensitive drum 6 is released.

  Note that the same phase includes not only the completely same phase but also a case where the phase is shifted within an allowable error range. For example, an error of about ± 30% may be allowed. In this embodiment, it is only necessary that the separation gear 17 and the drum gear 16 are engaged with each other without being completely in contact with each other to transmit the drive, and the separation cam 30 can be rotated while being in contact with the photosensitive drum 6.

  As described above, in this embodiment, the image forming apparatus 100 can be rotated together with the separation gear 17 and has the separation cam 30 that contacts the photosensitive drum 6 and separates the transfer roller 7 from the photosensitive drum 6. Then, in a state where the photosensitive drum 6 and the transfer roller 7 are separated from each other, the urging force of the transfer spring 15 is received by the photosensitive drum 6 via the separation cam 30. In the present embodiment, the separation cam 30 has a first cam surface 30 a that abuts on the photosensitive drum 6 in a state where the first gear portion 17 a of the separation gear 17 is engaged with the drum gear 16. Further, the separation cam 30 has a contact release portion 30b that releases contact with the photosensitive drum 6 in a state where the separation gear 17 is disengaged from the drum gear 16 in the release portion 17b. The separation cam 30 is formed between the first cam surface 30a and the contact release portion 30b along the direction opposite to the rotation direction of the separation cam 30 accompanying the rotation of the separation gear 17 in the predetermined direction. It has the 2nd cam surface 30c located in between. The second cam surface 30c has a radius adjacent to the contact release portion 30b that is smaller than the radius of the first cam surface 30a. The second cam surface 30c is released from contact with the first cam surface along the direction opposite to the rotation direction of the separation cam 30 accompanying the rotation of the separation gear 17 in the predetermined direction. A portion whose radius gradually decreases toward the portion adjacent to the portion.

  As described above, according to the present embodiment, the same effects as those of the first embodiment can be obtained, and it is possible to prevent the tooth surfaces of the drum gear 16 and the separation gear 17 from being damaged or damaged during the transportation of the product.

  In addition, when using the separation gear 17 of Example 2, it is good also as a structure which provides the separation cam 30 similarly to a present Example. Also in this case, the cam profile of the cam surface of the separation cam 30 is engaged with the separation gear 17 and the drum gear 16 in a state where the separation gear 17 and the drum gear 16 are not completely in contact with each other, and is transmitted while the separation cam 30 contacts the photosensitive drum 6. It can be set as the structure which can be rotated. More specifically, the cam profile of the cam surface of the separation cam 30 can be configured so that the radius of the cam surface changes in the same phase as the separation cam 17. That is, in this case, at least one side of the first cam surface 30a in the circumferential direction of the separation cam 30 than the first cam surface 30a in the circumferential direction of the separation cam 30 corresponding to the separation fixed gear portion 17d of the separation gear 17 in the second embodiment. A third cam surface having a large radius may be provided.

Reference Signs List 5 Process Cartridge 6 Photosensitive Drum 7 Transfer Roller 14 Transfer Roller Bearing 15 Transfer Spring 16 Drum Gear 17 Separation Gear 17a Separation Gear Portion 17b Missing Teeth 17c Variable Pitch Gear Unit 17d Separation Fixed Gear Unit 30 Separation Cam

Claims (10)

An image carrier capable of rotating and carrying a toner image;
A first gear that rotates with the image carrier;
The image carrier and the transfer member are provided so as to be movable between a contact position that contacts the image carrier and a separated position that is separated from the image carrier, and arranged in the contact position. A transfer member for transferring a toner image from the image carrier to a transfer medium sandwiched between
Biasing means for biasing the transfer member in a direction from the separation position toward the contact position;
A second gear which is provided so as to be movable together with the transfer member along a moving direction between the separation position and the contact position of the transfer member, and which can rotate in mesh with the first gear;
Have
The second gear is
A first gear portion that meshes with the first gear in a state where the transfer member is disposed at the separated position and the image carrier is stopped;
A release portion that is disengaged from the first gear in a state where the transfer member is disposed at the contact position;
When the rotation direction of the second gear is rotated in accordance with the rotation of the first gear in the rotation direction during image formation, the rotation direction of the second gear is a predetermined direction. A second gear portion positioned between the first gear portion and the release portion along a reverse direction;
Have
In the second gear portion, a pitch circle radius of a portion adjacent to the release portion is smaller than a pitch circle radius of the first gear portion, and the first gear is along a direction opposite to the predetermined direction. An image forming apparatus comprising a portion having a pitch circle radius that gradually decreases from a portion side toward a portion adjacent to the release portion.   After the second gear rotates in the predetermined direction and the transfer member comes into contact with the image carrier, the meshing of the second gear portion of the second gear with the first gear is released. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The sum of the pitch circle radius of the portion adjacent to the release portion of the second gear portion and the pitch circle radius of the first gear is the radius of the roller-shaped transfer member and the radius of the drum-shaped image carrier. The image forming apparatus according to claim 2, wherein the image forming apparatus is substantially equal to a sum of.   The second gear has a pitch circle radius larger than the pitch circle radius of the first gear portion on at least one side of the first gear portion adjacent to the first gear portion in the circumferential direction. The image forming apparatus according to claim 1, further comprising three gear portions.   The image forming apparatus according to claim 4, wherein the second gear includes the third gear portion adjacent to both sides of the first gear portion in a circumferential direction.   The second gear rotates in the predetermined direction to release the mesh with the first gear, and then rotates by its own weight to release the mesh with the first gear at the release portion. The image forming apparatus according to claim 1, wherein the image forming apparatus is in a state.   The urging force of the urging means is received by the first gear via the second gear in a state where the image carrier and the transfer member are separated from each other. The image forming apparatus described in the item. A separation member that is rotatable together with the second gear and that contacts the image carrier to separate the transfer member from the image carrier;
7. The urging force of the urging means is received by the image carrier through the separation member in a state in which the image carrier and the transfer member are separated from each other. The image forming apparatus described in 1. The spacing member is
A first cam surface that contacts the image carrier in a state where the first gear portion of the second gear meshes with the first gear;
A contact release portion that releases contact with the image carrier in a state where the engagement of the second gear with the first gear is released in the release portion;
A second position located between the first cam surface and the contact release portion along the direction opposite to the rotation direction of the separation member accompanying the rotation of the second gear in the predetermined direction. The cam surface,
Have
In the second cam surface, a radius of a portion adjacent to the contact release portion is smaller than a radius of the first cam surface, and the separation member is accompanied by the rotation of the second gear in the predetermined direction. 9. The device according to claim 8, further comprising a portion whose radius gradually decreases from the first cam surface side to a portion side adjacent to the contact release portion along a direction opposite to the rotation direction. Image forming apparatus. A cartridge including the image carrier and the first gear is detachable from an apparatus main body of the image forming apparatus including the transfer member and the second gear.
In a state before the cartridge is mounted on the apparatus main body and the use of the image forming apparatus is started, the first gear portion of the second gear is engaged with the first gear, and the transfer member is The image forming apparatus according to claim 1, wherein the image forming apparatus is separated from the image carrier.

Images