JP2018081251A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can separate a plurality of transfer members from photoreceptors with a driving force of a motor, and when some of the transfer members are separated from the photoreceptors, can inhibit an intermediate transfer body from contacting the transfer members, while ensuring a torque margin of the motor.SOLUTION: An image forming apparatus A of an intermediate transfer system comprises a contact/separation mechanism 100 that can move a plurality of primary transfer rollers 8 to contact positions to be brought into contact with a plurality of photoreceptor drums 1 with a driving force of a motor Mo with an intermediate transfer belt 4 therebetween, and separation positions to be separated from the plurality of photoreceptor drums 1. When moving the primary transfer rollers 8Y, 8M, and 8C for color printing from the contact positions to the separation positions, the contact/separation mechanism 100 increases the amount of separation per one primary transfer roller 8 compared with that when moving all the primary transfer rollers 8, and makes the total amount of separation equal to or less than that when moving all the primary transfer rollers.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image forming apparatus such as an electrophotographic copying machine or an electrophotographic printer (for example, a laser beam printer, an LED printer).

  As an electrophotographic image forming apparatus, an intermediate transfer tandem that transfers toner images of each color on the surface of an intermediate transfer belt as an intermediate transfer member in sequence, and then transfers a full color toner image to a recording material in a batch. There is a type of image forming apparatus.

  In such an intermediate transfer tandem type image forming apparatus, in a monochrome mode in which only a black toner image is transferred to a recording material to form an image, a primary transfer roller (transfer member) provided in a color image forming unit is provided. A configuration in which the belt is separated from the intermediate transfer belt is known. As a result, wear of the primary transfer roller and the photosensitive member can be suppressed, and the life of the parts can be extended. Further, a configuration is known in which all the primary transfer rollers can be separated from the intermediate transfer belt in order to replace the photosensitive drum and the intermediate transfer belt.

  However, in the configuration in which the primary transfer roller for color is separated in the monochrome mode, the tension for stretching the intermediate transfer belt is lowered, and the primary transfer unit that transfers the black toner image is bent to reduce the image quality. There is a fear.

  In view of this, a configuration that suppresses the bending of the primary transfer portion due to such a decrease in tension of the intermediate transfer belt has been conventionally proposed. For example, in Patent Document 1, an intermediate transfer belt in the primary transfer unit is provided by providing an auxiliary roller for stretching the intermediate transfer belt on the upstream side in the moving direction of the intermediate transfer belt from the primary transfer unit that transfers the black toner image. A configuration for suppressing the bending of the belt is described.

JP 2011-33739 A

  FIG. 6 is a schematic cross-sectional view of an intermediate transfer unit showing the configuration described in Patent Document 1 in which an auxiliary roller 109 is arranged upstream of the primary transfer portion N that transfers a black toner image in the moving direction of the intermediate transfer belt 104. It is. As shown in FIG. 6, in the configuration described in Patent Document 1, the bending of the intermediate transfer belt 104 is suppressed at the primary transfer portion N formed from the photosensitive drum 101K and the primary transfer roller 108K. However, in the primary transfer rollers 108Y, 108M, and 108C (hereinafter referred to as 108) for color that are separated from the photosensitive drums 101Y, 101M, and 101C, sagging occurs in the intermediate transfer belt 104, and a part of the primary transfer roller 108 for color is used. May come into contact. In this way, when the intermediate transfer belt 104 rotates in a state where the primary transfer roller 108 for color and the intermediate transfer belt 104 are in contact with each other, the primary transfer roller 108 for color cannot be driven to rotate and the surface is scraped, resulting in image defects or This leads to shorter life of the members.

  It is conceivable to deal with such a problem by simply increasing the separation amount of the primary transfer roller for color in the monochrome mode. However, in the configuration in which the primary transfer roller is separated by the driving force of the motor, the load torque of the motor at the time of separation increases, leading to an increase in size of the motor due to torque increase.

  Accordingly, the present invention provides a configuration in which a plurality of transfer members can be separated from the photosensitive member by a driving force of the motor, while ensuring a torque margin of the motor, the intermediate transfer member becomes the transfer member when some of the transfer members are separated. An object of the present invention is to provide an image forming apparatus capable of suppressing contact.

  A typical configuration of the image forming apparatus according to the present invention for achieving the above object is that a plurality of photosensitive members and a developer image formed on the surface of the plurality of photosensitive members are temporarily transferred and transferred. The intermediate transfer member on which the developer image is transferred to a recording material, and the intermediate transfer member disposed at a position corresponding to the plurality of photosensitive members below the intermediate transfer member and in contact with the intermediate transfer member. A plurality of transfer members that transfer the developer image to a body; a contact position where the plurality of transfer members abut on the plurality of photoconductors via the intermediate transfer body by a driving force of a motor; and the plurality of photosensitive members Moving means movable to a separated position separated from the body, and the moving means moves the plurality of transfer members when moving a part of the plurality of transfer members from the contact position to the separated position. Than when moving all of the Increasing the spacing amount per member one, and, characterized in that the same or less than the spacing of total.

  According to the present invention, in a configuration in which a plurality of transfer members can be separated from the photosensitive member by the driving force of the motor, the intermediate transfer member is transferred to the transfer member when a part of the transfer members is separated while ensuring a torque margin of the motor. It can suppress that it contacts.

1 is a schematic cross-sectional view of an image forming apparatus. 2 is a schematic cross-sectional view of an image forming unit in a monochrome mode. FIG. FIG. 3 is a schematic cross-sectional view of an image forming unit in a full-desorption mode. FIG. 3 is a schematic cross-sectional view of a separation / contact mechanism and a primary transfer roller. FIG. 3 is a schematic cross-sectional view of a separation / contact mechanism and a primary transfer roller. FIG. 10 is a schematic cross-sectional view of a conventional intermediate transfer unit.

(First embodiment)
<Image forming apparatus>
First, the overall configuration of the image forming apparatus A according to the first embodiment of the present invention will be described with reference to the drawings together with the operation during image formation.

  The image forming apparatus A primarily transfers four-color toner images (developer images) of yellow Y, magenta M, cyan C, and black K onto an intermediate transfer belt, and then secondarily transfers the image onto a sheet as a recording material. Is a color image forming apparatus of an electrophotographic system and an intermediate transfer tandem system.

  As shown in FIG. 1, an image forming apparatus A includes an image forming unit B that transfers a toner image to a sheet, a sheet feeding unit that supplies the sheet to the image forming unit, and a fixing unit that fixes the toner image to the sheet. Prepare.

  The image forming unit B includes a plurality of photosensitive drums 1 (1Y, 1M, 1C, and 1K) that are rotatably provided, and a charging roller 50 (50Y, 50M, 50C, and 50K) that charges the photosensitive drum 1. . Further, the image forming apparatus includes an intermediate transfer unit 60, a laser scanner unit 2 (2Y, 2M, 2C, 2K), a developing device 3 (3Y, 3M, 3C, 3K).

  The intermediate transfer unit 60 includes a plurality of primary transfer rollers 8 (8Y, 8M, 8C, 8K) as transfer members, a secondary transfer roller 10, a secondary transfer counter roller 7, an intermediate transfer belt 4, and a belt driving roller 5. . Further, a first tension roller 6, an idler roller 62, and auxiliary rollers 9 (9a, 9b) for applying tension to the intermediate transfer belt 4 are provided. The auxiliary rollers 9a and 9b are configured to be movable in the vertical direction by an auxiliary roller moving mechanism (not shown), and are arranged at positions separated from the positions in contact with the intermediate transfer belt 4 in accordance with each mode described later.

  The intermediate transfer belt 4 (intermediate transfer body) has an endless shape composed of a resin base layer and a rubber or elastomer rubber elastic layer (layer formed of an elastic body) having a thickness of about 200 to 400 μm. The elastic belt is excellent in transferability even on rough paper such as embossed paper. The intermediate transfer belt 4 is stretched by a primary transfer roller 8, a belt driving roller 5, a first tension roller 6, an idler roller 62, a secondary transfer counter roller 7, and an auxiliary roller 9a when a full color image is formed. . The intermediate transfer belt 4 rotates in the direction of arrow R2 following the rotation of the belt driving roller 5 that receives driving force from a driving source (not shown) in the direction of arrow R1.

  The primary transfer roller 8 is disposed at a position corresponding to each of the photosensitive drums 1 below the intermediate transfer belt 4, and is urged toward the photosensitive drum 1 by a spring (not shown). Further, the primary transfer roller 8 is rotated by the rotation of the intermediate transfer belt 4 and performs primary transfer described later in a state where the primary transfer roller 8 is in contact with the intermediate transfer belt 4. In addition, the primary transfer roller 8 has a contact position that contacts the photosensitive drum 1 via the intermediate transfer belt 4 in accordance with each mode to be described later, and a photosensitive member by a separation / contact mechanism 100 (see FIG. 4) as a moving unit. It is configured to be movable to a separated position separated from the drum 1. The arrangement of the primary transfer roller 8 and the separation / contact mechanism 100 in each mode will be described in detail later.

  Next, an image forming operation when forming a full-color image will be described. First, when a control unit (not shown) receives an image forming job signal, the sheet P stacked and stored in the sheet stacking unit 61 by the feeding roller 74 and the conveying roller 81 is sent to the registration roller 75. Thereafter, the sheet P is subjected to skew correction and timing correction by the registration roller 75 and then sent to the image forming unit B.

  On the other hand, in the image forming unit B, first, the surface of the photosensitive drum 1 is charged by the charging roller 50. The laser scanner unit 2 emits laser light from a light source (not shown) provided inside, and irradiates the photosensitive drum 1 with laser light according to image information. As a result, an electrostatic latent image corresponding to the image information is formed on the surface of the photosensitive drum 1. A toner image is formed on the surface of the photosensitive drum 1 by developing the electrostatic latent image with the developing device 3 by attaching toner.

  The toner image formed on the surface of the photosensitive drum 1 is subjected to a primary transfer bias applied to the primary transfer roller 8 at a primary transfer nip portion formed by the photosensitive drum 1 and the primary transfer roller 8, thereby causing the intermediate transfer belt 4. Each is first-transferred.

  The primary transferred toner image reaches the secondary transfer portion formed by the secondary transfer counter roller 7 and the secondary transfer roller 10 which are downstream in the rotation direction due to the rotation of the intermediate transfer belt 4. Transferred to the sheet P. That is, the toner image formed on the surface of the photosensitive drum 1 is temporarily transferred to the intermediate transfer belt 4, and the transferred toner image is subsequently transferred to the sheet P.

  The sheet P on which the toner image has been transferred is sent to the fixing device 90 where it is heated and pressurized to fix the toner image on the sheet P and then discharged onto the discharge tray 65.

<Arrangement of primary transfer roller>
Next, the arrangement of the primary transfer roller 8 and the auxiliary roller 9 in each mode will be described.

  The image forming apparatus A has a full color mode for forming a full color image and a monochrome mode for forming a monochrome image by transferring only a black toner image to the sheet P as modes for image formation. Further, the image forming apparatus A has a full removal mode that is executed when the photosensitive drum 1, the intermediate transfer belt 4, and the like are replaced.

  As shown in FIG. 1, in the full color mode, all the primary transfer rollers 8 are arranged at the contact positions. The auxiliary roller 9 a is in contact with the intermediate transfer belt 4 at the same height as the primary transfer roller 8, and the auxiliary roller 9 b is disposed at a position separated from the intermediate transfer belt 4.

  FIG. 2 is a schematic cross-sectional view of the image forming unit B in the monochrome mode. As shown in FIG. 2, in the monochrome mode, the primary transfer rollers 8Y, 8M, and 8C for color other than the primary transfer roller 8K that transfers the black toner image are arranged at separated positions. The auxiliary roller 9a contacts the intermediate transfer belt 4 at a position lower than the height of the primary transfer roller 8K, and the auxiliary roller 9b contacts the intermediate transfer belt 4 at the same height as the primary transfer roller 8K.

  FIG. 3 is a schematic cross-sectional view of the image forming unit B in the full removal mode. As shown in FIG. 3, in the full removal mode, all the primary transfer rollers 8 are disposed at a separated position away from the photosensitive drum 1. Further, both auxiliary rollers 9a and 9b are disposed at a position lower than the height of the photosensitive drum 1. As a result, the photosensitive drum 1 and the intermediate transfer belt 4 can be replaced.

<Movement means>
Next, the movement of the primary transfer roller 8 by the separation / contact mechanism 100 as a moving unit will be described.

  FIG. 4 is a schematic cross-sectional view of the separation / contact mechanism 100 and the primary transfer roller 8. Here, FIG. 4A shows a state in the full color mode, FIG. 4B shows a state in the monochrome mode, and FIG. 4C shows a state in the full removal mode. As shown in FIG. 4, the separation / contact mechanism 100 includes a drive gear 12, a motor Mo that rotates the drive gear 12 by applying a drive force, and a guide member 13 that regulates the position of the primary transfer roller 8. The guide member 13 is provided with a rack gear portion 13c (gear) that meshes with the drive gear 12. The guide member 13 is moved in the left-right direction by the rotation of the drive gear 12.

  When the primary transfer roller 8 moves from the full color mode to the monochrome mode, as shown in FIG. 4B, first, the driving gear 12 is rotated in the direction of the arrow R3 by the driving force of the motor Mo. As a result, the guide member 13 moves in the direction of arrow K1 (one side) via the rack gear portion 13c. When the guide member 13 moves in the direction of the arrow K1, the rotation shafts 8Ya, 8Ma, and 8Ca of the primary transfer rollers 8Y, 8M, and 8C move downward along the inclined surface 13a of the guide member 13, thereby the primary transfer rollers 8Y and 8M. , 8C are separated from the photosensitive drum 1.

  When shifting from the full color mode to the full removal mode, as shown in FIG. 4C, the motor Mo rotates in the opposite direction to that when shifting to the monochrome mode, and the drive gear 12 is moved to the arrow by the driving force of the motor Mo. Rotate in R4 direction. As a result, the guide member 13 moves in the direction of the arrow K2 (the other side) via the rack gear portion 13c. When the guide member 13 moves in the direction of the arrow K2, the rotation shafts 8Ya, 8Ma, 8Ca, and 8Ka of all the primary transfer rollers 8 move downward along the inclined surface 13b of the guide member 13, whereby all the primary transfer rollers 8 are moved. Move from the contact position to the separation position.

  Here, the separation distances of the primary transfer rollers 8Y, 8M, and 8C at the time of transition to the monochrome mode are L1, and the separation distances of the primary transfer rollers 8Y, 8M, 8C, and 8K at the time of the transition to the full release mode are L2. At this time, the separation distance of the primary transfer roller 8 (separation amount per primary transfer member) is set to L1> L2, and with respect to the total separation distance of the primary transfer roller 8, the separation distance at the time of transition to the monochrome mode is It is set to be the same as or less than the separation distance at the time of transition to the full release mode. In the present embodiment, L1: L2 = 3: 4 is set, and the total amount of separation of the primary transfer roller 8 is set to be the same when the monochrome mode shifts and when the full release mode shifts.

  As described above, the separation / contact mechanism 100 allows the separation amount per primary transfer roller 8 to move a part of the primary transfer roller 8 from the contact position to the separation position rather than to move all of the primary transfer rollers 8. And the total distance is the same or less. As a result, the amount of separation of the primary transfer roller 8 in the monochrome mode is increased, and the total force that the separation / contact mechanism 100 resists the pressure applied to the primary transfer roller 8 during the transition to the monochrome mode, that is, the load torque of the motor Mo is reduced. It can be the same as or less than that in the transition mode. Therefore, with a simple configuration, while securing the torque margin of the motor Mo included in the separation / contact mechanism 100, the separation amount of the primary transfer roller 8 in the monochrome mode is increased, and the intermediate transfer belt is moved to the primary transfer rollers 8Y, 8M, and 8C. It can suppress that 4 contacts. For this reason, it is possible to prevent the surface of the primary transfer rollers 8Y, 8M, and 8C from being scraped by the rotation of the intermediate transfer belt 4 while preventing the motor Mo from becoming large, thereby preventing image defects and shortening of the member life. .

  As shown in FIG. 3, since the tension of the intermediate transfer belt 4 is particularly low in the full removal mode, the intermediate transfer belt 4 is slackened and comes into contact with the primary transfer roller 8. However, as described above, since the full removal mode is executed when the photosensitive drum 1, the intermediate transfer belt 4 and the like are replaced, the intermediate transfer belt 4 is not driven and the surface of the primary transfer roller 8 is not scraped. That is, in the full removal mode, the primary transfer roller 8 only needs to be separated from the photosensitive drum 1, and a separation amount L2 smaller than the separation amount L1 at the time of transition to the monochrome mode is sufficient. By executing the full release mode with such a small separation amount, the load on the separation mechanism 100 is reduced, and the motor Mo can be reduced in size.

  When an elastic belt having an elastic layer is used as the intermediate transfer belt 4, sagging tends to occur when the weight increases and the tension of the intermediate transfer belt 4 decreases. However, according to the above configuration, the intermediate transfer belt 4 is prevented from coming into contact with the color primary transfer roller 8 in the monochrome mode, so that the surface of the color primary transfer roller 8 is secured while securing the advantage of the elastic belt. It can suppress that it cuts.

  Further, when the primary transfer roller 8 position in the monochrome mode is set to the home position during standby (standby) of the image forming apparatus A, the first copy time can be set to the fastest. On the other hand, when the primary transfer roller 8 position in the full release mode is set to the home position, the photosensitive drum 1 and the intermediate transfer belt 4 can be replaced even when the power is turned off, so that serviceability can be improved.

<Modification>
Next, as a modification of the present embodiment, a configuration in which the primary transfer roller 8 is moved by the rotation of a cam driven by a motor Mo will be described.

  FIG. 5 is a schematic cross-sectional view of the separation mechanism 100 and the primary transfer roller 8 according to a modification. Here, FIG. 5A shows a state in the full color mode, FIG. 5B shows a state in the monochrome mode, and FIG. 5C shows a state in the full removal mode. As shown in FIG. 5, the separation / connection mechanism 100 includes a cam 14 having a cam shaft 14a and a cam surface 14b having different distances from the cam shaft 14a. The motor Mo rotates the camshaft 14a by applying a driving force, a guide member 15 that regulates the position of the primary transfer roller 8, and a biasing member (not shown) that biases the guide member 15 in the arrow K1 direction.

  When the primary transfer roller 8 moves, when shifting from the full color mode to the monochrome mode, as shown in FIG. 5B, the cam 14 is first rotated in the direction of the arrow R5 by the driving force of the motor Mo. As a result, the guide member 15 is moved in the direction of the arrow K1 by the biasing force of the biasing member (not shown) in the direction of the arrow K1. When the guide member 15 moves in the direction of the arrow K1, the rotation shafts 8Ya, 8Ma, and 8Ca of the primary transfer rollers 8Y, 8M, and 8C move downward along the inclined surface 15a of the guide member 15, and thereby the primary transfer rollers 8Y and 8M. , 8C move from the contact position to the separated position.

  When shifting from the full color mode to the full removal mode, as shown in FIG. 5C, the motor Mo rotates in the opposite direction to that when shifting to the monochrome mode, and the cam 14 is moved to the arrow R6 by the driving force of the motor Mo. Rotate in the direction. As a result, the guide member 15 moves to the arrow K2. When the guide member 15 moves in the direction of the arrow K2, the rotation shafts 8Ya, 8Ma, 8Ca, and 8Ka of all the primary transfer rollers 8 move downward along the inclined surface 15b of the guide member 15, whereby all the primary transfer rollers 8 are moved. Move from the contact position to the separation position.

  Thus, even if it is the structure which performs the movement of the primary transfer roller 8 based on rotation of the cam 14, it makes 1st Embodiment by making the separation amount of the primary transfer roller 8 in each mode the same as 1st Embodiment. The same effect can be obtained. In addition, by using the cam 14 for the separation / connection mechanism 100, the cam 14 can be further rotated in the direction of the arrow R6 after the full release mode to shift to the monochrome mode, and the degree of freedom of mode switching is improved. Downtime can be reduced.

  In the first embodiment and the modification, the primary transfer roller 8K that transfers the black toner image in the monochrome mode is described as not being separated from the photosensitive drum 1, but the present invention is not limited to this. In other words, the effect of the present invention can be achieved even in the case where the primary transfer roller 8 for transferring the color toner having high usage frequency to the intermediate transfer belt 4 is not separated or the primary transfer roller 8 for a plurality of colors is not separated. Can be obtained.

1 ... Photosensitive drum (photosensitive member)
4 ... Intermediate transfer belt (intermediate transfer member)
8 ... Primary transfer roller (transfer member)
13, 15 ... Guide member 13c ... Rack gear part (gear)
14 ... Cam 100 ... Separating mechanism (moving means)
A ... Image forming apparatus Mo ... Motor P ... Sheet (recording material)

Claims (6)

A plurality of photoreceptors;
An intermediate transfer member on which the developer images formed on the surfaces of the plurality of photosensitive members are temporarily transferred, and the transferred developer images are transferred to a recording material;
A plurality of transfer members disposed below the intermediate transfer member at positions corresponding to the plurality of photoconductors and transferring the developer image to the intermediate transfer member in a state of being in contact with the intermediate transfer member;
A moving means capable of moving to a contact position where the plurality of transfer members contact the plurality of photoconductors via the intermediate transfer body and a spaced position spaced apart from the plurality of photoconductors by a driving force of a motor;
With
In the case where a part of the plurality of transfer members is moved from the contact position to the separation position, the moving unit is configured to increase the separation amount per one transfer member as compared to the case where all of the plurality of transfer members are moved. An image forming apparatus characterized in that it is made large and the total distance is the same or less.   The moving means moves the plurality of transfer members from the contact position to the separated position by moving a guide member that regulates the positions of the plurality of transfer members via a gear by the driving force of the motor. The image forming apparatus according to claim 1.   The moving means moves the plurality of transfer members from the contact position to the separated position by rotating a cam by a driving force of the motor to move a guide member that regulates the positions of the plurality of transfer members. The image forming apparatus according to claim 1, wherein:   The moving means moves all of the plurality of transfer members by moving the guide member to one side, and moves a part of the plurality of transfer members by moving to the other side. The image forming apparatus according to claim 2 or 3.   The image forming apparatus according to claim 1, wherein the intermediate transfer body includes a layer formed of an elastic body.   The transfer means transfers the color developer image of the plurality of transfer members to the intermediate transfer member when the black developer image is transferred to the recording material to form a monochrome image. 6. The image forming apparatus according to claim 1, wherein a member is moved from the contact position to the separation position.

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