JP2005091725A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively prevent the occurrence of image deviation due to impact by dispersing the impact caused due to the abutting of a transfer roller to individual sides. <P>SOLUTION: The image forming apparatus is provided with: an intermediate transfer body to which a toner image developed on a photoreceptor is transferred with a prural times of rotation; and a transfer roller arranged so as to be freely pressed into contact with/separated from the intermediate transfer body and capable of transferring the toner image on the intermediate transfer body to a sheet material while transporting the sheet material in a state of pressurized contact with the intermediate transfer body. The image forming apparatus further has a shaft to be freely rotated, two cams fitted to the shaft and a push arm of which one end side is abutted to the cams and the other end side is abutted to a rotating bearing arranged on one end side of the transfer roller. When the phases of the two cams are shifted, the transfer roller is abutted on the intermediate transfer body so that the one-end side in the longitudinal direction of the transfer roller precedes the other end side as to timing for moving the transfer roller from the separated state to the abutted state to the intermediate transfer body. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a color copying machine, and more particularly to a transfer mechanism for transferring a toner image from an intermediate transfer member to transfer paper.

  For example, in a color copying machine as shown in FIG. 8, a photoconductor 4 inside the copier body 1 and a charging device 4a and a developing device 5 (5Y, 5M, 5C, 5B) arranged around the photoconductor 4 are provided. ), And the developing devices 5Y, 5M, 5C, and 5B are filled with toners of yellow, magenta, cyan, and black, respectively.

  A document reading device 2 is disposed on the upper portion of the copying machine main body 1. The document reading device 2 is provided with a document table for placing a document, scans the document placed on the document table below the document table, and the reflected light is converted into an electrical signal by the CCD. The The electrical signal from the CCD is guided as a laser beam onto the photoconductor 4 by the laser transmitter 9 to form an electrostatic latent image. A belt-like intermediate transfer member (intermediate transfer belt) 6 is disposed for contacting the photosensitive member 4 and superimposing toner images of a plurality of colors. Around the intermediate transfer belt 6, a primary transfer device 6a for transferring the toner image on the photoreceptor 4 to the intermediate transfer belt 6, and a roller for transferring the toner image on the intermediate transfer belt 6 to a sheet material A transfer device (secondary transfer outer roller 8) 80 and a transfer belt cleaning device 6b are provided.

  In FIG. 8, 10 is a paper cassette, 11 is a paper feed roller, 14 is a registration roller, 17 is a fixing device, 19 is a discharge roller, and 20 discharge sheet tray.

  As shown in FIG. 9, the roller transfer device 80 includes a secondary transfer outer roller 8 that is pressed against and separated from the intermediate transfer belt 6, an end side that rotatably supports an end of the secondary transfer outer roller 8, and an image. A swaying bearing 32 constituted by the other end side supported slidably by the forming apparatus main body 1 and a press for fixing the secondary transfer outer roller 8 to the intermediate transfer belt 6 in pressure contact with the swaying bearing 32. It is composed of a pressure spring 33. FIG. 9 shows one end side of the secondary transfer outer roller, and the other end side has the same configuration.

  In addition, a shaft 30 rotatably supported by a driving source (not shown) in the copying machine main body 1, a cam 34 disposed on the shaft 30, one end abuts against the outer peripheral surface of the cam 34, and the other end side A push arm 31 is provided so as to be in contact with the dynamic bearing 32 and slidable as indicated by an arrow in FIG.

  In the above-described configuration, the document placed on the document reading device 2 is scanned, and the photosensitive member 4 is exposed by the laser light emitted from the laser transmitting device 9 by an electrical signal from the CCD. Sequentially, a toner image is formed by the developing device 5. The toner image formed on the photoreceptor 4 is transferred to the intermediate transfer belt 6 by the primary transfer device 6a. In this way, the toner images of the respective colors are sequentially superimposed on the intermediate transfer belt 6 with the image positions thereof aligned. The three-color toner images are transferred to the sheet material fed from the paper cassette 10 by the secondary transfer outer roller 8, fixed by the fixing device 17, and discharged from the copying machine main body 1 onto the discharge sheet tray 20. As a result, a color image is formed.

  The secondary transfer outer roller 8 during the image forming process has a cam 34 at the illustrated rotational position as shown in FIG. 10 when the toner images are sequentially superimposed on the intermediate transfer belt 6. The secondary transfer outer roller 8 is moved to a position retracted from the intermediate transfer belt 6 by the pushing of the swing bearing 32. Further, when the toner image on the intermediate transfer belt 6 is transferred to the sheet material, the cam 34 is rotated in the direction shown in the figure by the rotation of the shaft 30 as shown in FIG. At this time, the swing bearing 32 is pushed back together with the push arm 31 and the secondary transfer outer roller 8 by the extension of the pressure spring 33, and the secondary transfer outer roller 8 contacts the intermediate transfer belt 6 with a predetermined contact pressure.

  In the image forming apparatus having the above-described mechanism, the pressure spring 33 is compressed to the maximum when the secondary transfer outer roller 8 is separated, and the push arm 31 is sufficiently loaded. The secondary transfer outer roller 8 rotates the sway bearing 32 at a very high speed because the spring 40 is in the extending direction at the moment when it is pressed against the intermediate transfer belt 6. For this reason, a large impact force is generated when the secondary transfer outer roller 8 contacts the intermediate transfer belt 6. Due to this impact, when the toner image is transferred from the photosensitive member to the intermediate transfer belt, the image may be displaced or blurring may occur. Further, when the photosensitive member is irradiated with laser light, the latent image itself may be displaced or blurred.

  On the other hand, there are the following technologies. A contact / separation cam is fixed to one end of the rotating shaft, an anti-phase cam is fixed to the other end, and a spring clutch is provided in the center. The antiphase cam is 180 ° out of phase with the contact cam. An arm is provided in relation to the contact / separation cam, and a load arm is provided in relation to the antiphase cam. The transfer roller moves in accordance with the movement of the arm, and moves toward and away from the intermediate transfer belt. The anti-phase cam and the load arm are configured to reduce the impact by applying a braking force to the rotation of the contact / separation cam (see Patent Document 1).

There are also the following technologies. As a transfer roller contact / separation mechanism, a swinging plate having a rotating shaft at one end and holding the secondary transfer roller at the other end, and the other end 2 of the swinging plate are biased toward the intermediate transfer member. A spring, a cam that moves the other end of the swing plate away from the intermediate transfer member against the biasing force of the spring, and a swing when the other end of the swing plate moves toward the intermediate transfer member. It is the structure provided with the damper means which relieve | moderates the moving speed of the other end part of a moving plate (refer patent document 2).
JP 2000-268410 A JP 2000-155473 A

  However, in any of the configurations described above, a means for urging the secondary transfer outer roller to the intermediate transfer belt with a predetermined pressure necessary for image formation, and a damper as a means for suppressing the urging force. Etc. need to be separately provided, and the number of components to be formed is increased, which is expensive in cost. There is also a problem that the mechanism becomes complicated.

  Accordingly, the present invention provides an intermediate transfer member to which a toner image developed on a photosensitive member is transferred while being rotated a plurality of times, and is provided so as to be capable of being pressed against and separated from the intermediate transfer member, whereby the sheet material is pressed against the intermediate transfer member. In an image forming apparatus provided with a transfer roller for transferring a toner image on an intermediate transfer member to a sheet material while being conveyed, a shaft provided rotatably, two cams provided on the shaft, and one end side of the cam And a push arm that contacts the rotary bearing provided at one end of the transfer roller, and the transfer roller moves away from the intermediate transfer member by shifting the phase of the two cams. The timing of moving from the state to the contact state is characterized in that one end side in the longitudinal direction of the transfer roller comes into contact with the intermediate transfer member before the other end side.

  According to the present invention, since the impact at the time of contact of the transfer roller can be dispersed one by one, image shift due to the impact can be effectively prevented.

(First embodiment)
FIG. 1 is a sectional view of a color copying machine showing an embodiment equipped with the transfer roller device of the present invention, and FIG. 2 is a top sectional view of the transfer roller device, in which the intermediate transfer belt and the secondary transfer outer roller are separated from each other. Show. FIG. 3 is a top sectional view for explaining the operation in which the secondary transfer outer roller contacts the intermediate transfer member, and FIG. 4 is a top sectional view in which the intermediate transfer member and the secondary transfer outer roller are in contact with each other. . In addition, the same code | symbol is attached | subjected in the component which has a function similar to the past.

  The color copying machine of this embodiment is an improved structure of a conventional roller transfer device. Therefore, the detailed description of the same components as those in the past will be omitted, and the roller transfer device that is a feature of the present invention will be described.

  As shown in FIGS. 1 and 2, the roller transfer device 80 described above includes a secondary transfer outer roller 8 that is pressed against and separated from the intermediate transfer belt 6, and swing bearings 26 and 27 that are rotatably received by the secondary transfer outer roller 8. A pressure spring 28 provided between the swing bearings 26 and 27 and the roller transfer device main body 80 biases the secondary transfer outer roller 8 to the intermediate transfer belt 6 with a predetermined force. As shown in FIG. 4, the pressure spring 28 is arranged so that a predetermined load is applied to the intermediate transfer belt when the secondary transfer outer roller 8 is in contact, and is compressed in the separated state of FIG. Further, the rotary shaft 21 rotatably supported by the image forming apparatus main body 1, the cams 22 and 23 attached integrally with the rotary shaft 21, and the cam surfaces of the cams 22 and 23, one end side of which is a swing bearing 26. , And 27 are provided as push arms 24 and 25, respectively. The rotation shaft 21 is connected to a gear train 29 disposed in the image forming apparatus main body 1 and a drive source M that supplies a drive force to the gear train 29 to obtain a rotational force.

  FIG. 2 shows the separated state of the secondary transfer outer roller, and the push arms 24 and 25 are protruded in the direction of the secondary transfer outer roller 8 by the cams 22 and 23 fixed to the rotating shaft 21. Yes. The distal ends of the push arms 24 and 25 are in contact with the swing bearings 26 and 27, respectively, and the pressurizing spring 28 is further compressed to separate the secondary transfer outer roller 8 from the intermediate transfer member.

  The secondary transfer outer roller contact operation when the intermediate transfer belt 6 transfers the toner image from the photoconductor 4 in a predetermined rotation and then performs secondary transfer to the sheet material will be described with reference to FIG.

  When it is time to bring the secondary transfer outer roller 8 into contact with the intermediate transfer belt 6, the rotating shaft 21 rotates 180 ° at a constant angular velocity. As the cams 22 and 23 rotate together with the rotation shaft, the cam surfaces that are in contact with the push arms 24 and 25 are displaced. Accordingly, the push arms 24 and 25 and the swing bearings 26 and 26 are moved from the cams 22 and 23. The pressurizing spring 28 that has been compressed via 27 extends, and the push arms 24 and 25 move in the direction of the arrow shown in FIG. At this time, the cam 22 and the cam 23 are attached with the angle (phase) shifted from the rotation shaft 21. For example, if the cam 22 is attached to the cam 23 with a phase shift so as to precede the rotational direction of the rotary shaft 21, as shown in FIG. 3, the swing bearing 26 and the swing bearing 27 deviate at the timing of starting movement. Occurs. Since the secondary transfer outer roller 8 is supported only by the swing bearings 26 and 27 at both ends, the secondary transfer outer roller 8 comes into contact with the intermediate transfer belt 6 first from the swing bearing 26 side. For this reason, the impact by the pressure springs provided at both ends of the transfer roller can be dispersed one by one. Therefore, a simple configuration that only shifts the phase to which the cam is attached prevents deterioration in image quality such as image shift.

(Second embodiment)
In the present embodiment, the shapes of the cam 22 and the cam 23 described in the first embodiment are different. FIG. 11 shows a state where the cams 22 and 23 are viewed from the direction of the cam 22 in a plane perpendicular to the rotating shaft 21.

  11 shows a state in which the secondary transfer outer roller 8 moves from the separated position to the contact position with respect to the intermediate transfer belt 6, and the rotation shaft 21 and the cams 22, 23 are driven by a drive source (not shown). It is rotating in the direction indicated by the arrow. The cam 22 and the cam 23 come into contact with the P3 position of the push arms 24 and 25 near the P2 position when the P1 position comes into contact with the push arms 24 and 25 at the P3 position. Therefore, the secondary transfer outer roller 8 is in a separated state. At this time, since the cam surface profiles of the cam 22 and the cam 23 are formed as shown in FIG. 11, the position where the push arm 25 and the cam 23 abut is the position of the push arm 25 a. On the other hand, in the push arm 24, the cam surface of the cam 22 is at the position shown in FIG. 11, so the surface where the push arm 24 and the cam 22 abut is at the position 24a. Accordingly, the secondary transfer outer roller 8 operates such that the swaying bearing 26 side comes into contact with the intermediate transfer belt 6 ahead of the swaying bearing 27 side as shown in FIG. Further, when the outer secondary transfer roller is moved away from the intermediate transfer belt 6, the rotation shaft 21 rotates in the direction of the arrow in the drawing, and the P2 position in contact with the P3 position of the push arms 24 and 25 is displaced to the P1 position. I will do it. At this time, since the shapes of the cam 22 and the cam 23 from the P2 position to the P1 position are the same, the secondary transfer outer roller 8 is configured to be separated in parallel to the intermediate transfer belt 6. .

(Third embodiment)
In the present embodiment, the shapes of the cams 22 and 23 are changed with respect to the first and second embodiments. FIG. 5 shows a state where the secondary transfer outer roller 8 and the intermediate transfer belt 6 are separated from each other in the third embodiment, and FIG. 6 shows that the secondary transfer outer roller 8 moves from the separation position to the contact position with respect to the intermediate transfer belt 6. The middle of movement is shown. FIG. 7 shows a state where the secondary transfer outer roller 8 and the intermediate transfer belt 6 are in contact with each other.

  In FIG. 5, the cams 22 and 23 fixed to the rotating shaft 21 are in contact with the push arms 24 and 25 at a position having a radius R0 from the center of rotation. At this time, the separation distance between the secondary transfer outer roller 8 and the intermediate transfer belt 6 is L (2 to 3 mm). The cams 22 and 23 are rotated by a drive source (not shown) in the direction of the arrow shown in FIG. Next, as shown in FIG. 6, when the position of the radius R1 from the rotation center of the cams 22 and 23 comes into contact with the push arms 24 and 25, R0> R1, and therefore the secondary transfer outer roller 8 The distance between the intermediate transfer belt 6 and the intermediate transfer belt 6 is S (0 to 2 mm). When the cams 22 and 23 further rotate in the direction of the arrow, the cams 22 and 23 move to the positions of the push arms 24 and 25 and the radius R2 until they come into contact. At this time, since the R1 and R2 of the cams 22 and 23 are formed with the same radius, the positions of the push arms 24 and 25 are changed by the rotation of the cams 22 and 23 during this time. The separation distance from the transfer belt 6 remains S. Further, when the cams 22 and 23 are rotated, as shown in FIG. At this time, the secondary transfer outer roller 8 and the intermediate transfer belt 6 are already in contact with each other. Since the rotary shaft 21 is connected by a gear train so as to rotate at a constant angular velocity, the push arms 24 and 25 and the secondary transfer outer roller 8 are separated while the cams 22 and 23 rotate at a constant angular velocity. The operation stops once in the middle of reaching the contact state. As a result, the separation distance L between the secondary transfer outer roller 8 and the intermediate transfer belt 6 is not brought into contact at once by the extension force of the pressure spring 28, but the secondary transfer outside by the pressure spring extension force of the separation distance S. The roller can be brought into contact. Therefore, since the impact of contact is suppressed, an effect of preventing a decrease in image quality such as an image shift can be obtained.

Sectional view showing a color copier equipped with the transfer device of the present invention FIG. 3 is a top sectional view showing the separated state of the main part of the transfer apparatus according to the first embodiment of the present invention. FIG. 3 is a top sectional view showing the operating state of the main part of the transfer apparatus according to the first embodiment of the present invention. FIG. 3 is a top sectional view showing the contact state of the main part of the transfer apparatus according to the first embodiment of the present invention. Sectional drawing which shows the separation state of the principal part of the transfer apparatus which is the 3rd Example of this invention Sectional drawing which shows the operation state of the principal part of the transfer apparatus which is the 3rd Example of this invention. Sectional drawing which shows the contact state of the principal part of the transfer apparatus which is 3rd Example of this invention Sectional view showing a conventional color copier Sectional drawing which shows the contact state of the conventional transfer apparatus principal part Sectional drawing which shows the separation state of the principal part of the conventional transfer device Sectional drawing which shows the operation state of the principal part of the transfer apparatus which is 2nd Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 80 Roller transfer apparatus 6 Intermediate transfer belt 7 Secondary transfer inner roller 8 Secondary transfer outer roller 21 Rotating shaft 22, 23 Cam 24, 25 Push arm 26, 27 Shaft bearing 28 Pressure spring 29 Gear train M Driving source

Claims (3)

  An intermediate transfer member to which a toner image developed on the photosensitive member is transferred while being rotated a plurality of times, and an intermediate transfer member that is provided so as to be able to be pressed and separated from the intermediate transfer member while being pressed and conveyed to the intermediate transfer member In an image forming apparatus comprising a transfer roller for transferring the toner image on a sheet material, a shaft provided rotatably, two cams provided on the shaft, and one end side of which is in contact with the cam and the other end And a push arm that abuts a rotary bearing provided at one end of the transfer roller, and the transfer roller is moved from a separated state to a contact state with respect to the intermediate transfer member by shifting the phase of the two cams. An image forming apparatus characterized in that the moving timing is such that one end side in the longitudinal direction of the transfer roller comes into contact with the intermediate transfer body before the other end side.   When the transfer roller moves from the separated state to the contact state with respect to the intermediate transfer member, one end side in the longitudinal direction of the transfer roller contacts the intermediate transfer member before the other end side, and the transfer roller is moved to the separate state. 2. The image forming apparatus according to claim 1, wherein when the roller moves, the shape of the two cams is formed so that one end side and the other end side in the longitudinal direction of the transfer roller move simultaneously.   The stop position where the transfer roller temporarily stops the movement while the transfer roller moves from the separated state to the contact state with respect to the intermediate transfer member is provided. Image forming apparatus.

Images