JP4559199B2 - Image forming apparatus - Google Patents

Description

The present invention is a copying machine provided with a cam drive Organization utilizing the displacement of the movable member by the rotation of the cam, a printer, a facsimile, an image forming apparatus such as a plotter.

Japanese Patent Application Laid-Open No. 2004-084729 discloses a contact / separation clutch that contacts and separates a transfer belt with respect to a photosensitive drum.
The transfer belt is always pressed against the photosensitive drum by a spring member. When the transfer belt is separated, the cam is rotated, and the arm provided rotatably around one fulcrum is used to apply the biasing force of the spring member. It is designed to be displaced in a decreasing direction.
When the cam rotates in the reverse direction from the separated position, the arm is returned by the urging force of the spring member, and the transfer belt contacts the photosensitive drum. In the contact process of the transfer belt, the cam receives an urging force in the rotation direction via the arm, and is accelerated more than normal rotation.
When the acceleration of the cam occurs, the control timing of the contact / separation clutch cannot be achieved from the rotation time of the motor that is the driving source of the cam, and it becomes difficult to stop at the target position.
If a cam stopper or the like is provided in order to prevent this, the impact when hitting it becomes too large, and problems such as noise and durability arise.

In order to cope with such a problem, in the above-described conventional technology, a brake means is provided that abuts against the cam in the contact process of the transfer belt and decelerates the rotation of the cam by sliding resistance. In other words, the angular acceleration of the cam is canceled by the brake action.
The brake means is fixed at a predetermined position and is provided independently of the arm as the movable member.

JP 2004-084729 A

In the above-described prior art, since the brake means is fixed, the cam may be locked if the braking action of the brake part (sliding resistance developing part) is too great. On the other hand, if the setting of the brake part is weakened in order to reliably prevent the cam from being locked, the deceleration action may be insufficient.
For this reason, conventionally, there is a concern that there is a sensitivity in the setting of the brake unit, and the deceleration action changes greatly due to the superiority or inferiority of the set skill (adjustment skill), and a constant deceleration function cannot be obtained.

  It is an object of the present invention to provide a cam drive mechanism capable of obtaining a substantially constant deceleration function and reducing cam lock regardless of the setting skill of the brake unit, and an image forming apparatus including the cam drive mechanism. To do.

In order to achieve the above object, according to the first aspect of the present invention, an image carrier, an endless transfer belt facing the image carrier, a transfer member provided inside the transfer belt, a cam, and a movable member having a Rutotomoni the transfer member is urged in a direction to abut the cam, cam drive for displacing the movable member in a direction to and away from the above image carrier by rotation of the cam comprising a mechanism, a, by the cam drive mechanism by displacing the movable member and the transfer member, with respect to the image carrier, the image forming apparatus contacting and separating the transfer belt, the cam drive mechanism, the Brake means for decelerating the cam by coming into contact with the cam in the course of displacement in which the abutting portion of the movable member approaches the rotation center of the cam is provided integrally with the movable member. The features.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect , the brake means is provided on a vertical wall of the movable member, and the vertical wall is substantially parallel to a displacement direction of the movable member. The surface of the brake means that contacts the cam is substantially parallel to the displacement direction of the movable member.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the brake means has a two-layer structure of an elastic member and a sliding member that contacts the cam.

According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the sliding member is in the form of a film and is adhered to the elastic member with an adhesive or a double-sided tape.

According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, the elastic member is urethane foam, and the sliding member is a polyethylene terephthalate film or a urethane foam film.

According to a sixth aspect of the present invention, in the image forming apparatus according to the first or second aspect, the brake means is a cantilever using an elastic restoring force of a leaf spring.

According to a seventh aspect of the present invention, in the image forming apparatus according to the first or second aspect, the brake means is a doubly supported beam using an elastic restoring force of a leaf spring.

According to an eighth aspect of the present invention, in the image forming apparatus according to the first or second aspect, the brake means includes a belt that contacts the cam and a biasing member that applies tension to the belt. Features.

According to a ninth aspect of the present invention, in the image forming apparatus according to the first or second aspect, the brake means is an elastic belt.

According to a tenth aspect of the present invention, in the image forming apparatus according to any one of the first to ninth aspects, the transfer belt is an intermediate transfer belt, and the cleaning device cleans the toner on the intermediate transfer belt. characterized in that it comprises a.

According to an eleventh aspect of the present invention, in the image forming apparatus according to the tenth aspect, the intermediate transfer belt is rotatably supported by a support member, and the movable member is supported by the support member inside the intermediate transfer belt. The intermediate transfer belt is supported and moved away from the image carrier by displacement of the movable member.

  According to the first, tenth, or eleventh aspects of the present invention, in the cam drive mechanism that includes a cam and a movable member that is biased in a direction in contact with the cam, the cam drive mechanism displaces the movable member by the rotation of the cam. A brake means for decelerating the cam by contacting the cam in a displacement process in which the abutting portion of the movable member approaches the rotation center of the cam; and the brake means is provided integrally with the movable member; Therefore, it is possible to reduce the locking of the cam even if the braking action of the brake portion is too great, and to facilitate the adjustment of the brake function (including the selection of materials).

  According to the invention of claim 2, 10 or 11, in the cam drive mechanism of claim 1, the surface of the brake means that contacts the cam is substantially parallel to the displacement direction of the movable member. Therefore, the brake function can be obtained efficiently.

  According to a third, tenth, or eleventh aspect of the present invention, in the cam drive mechanism according to the first or second aspect, the brake means has a two-layer structure of an elastic member and a sliding member that contacts the cam. As a result, the brake function can be easily adjusted.

  According to the invention of claim 4, 10 or 11, in the cam drive mechanism of claim 3, the sliding member has a film shape and is adhered to the elastic member with an adhesive or a double-sided tape. Therefore, the brake means can be easily configured and can be easily attached to the movable member.

  According to the invention described in claim 5, 10 or 11, in the cam drive mechanism described in claim 4, the elastic member is urethane foam, and the sliding member is a polyethylene terephthalate film or a urethane foam film. Therefore, the brake means can be easily configured and the brake function can be easily adjusted.

  According to the invention of claim 6, 10 or 11, in the cam drive mechanism of claim 1 or 2, the brake means is a cantilever beam using the elastic restoring force of the leaf spring. A good braking function can be obtained with a simple configuration.

  According to the invention of claim 7, 10 or 11, in the cam drive mechanism of claim 1 or 2, the brake means is a doubly supported beam using the elastic restoring force of the leaf spring. A good braking function can be obtained with a simple configuration.

  According to the invention of claim 8, 10 or 11, in the cam drive mechanism of claim 1 or 2, the brake means has a belt contacting the cam and a biasing member for applying tension to the belt. Therefore, a good brake function can be obtained with a simple configuration.

  According to the invention of claim 9, 10 or 11, in the cam drive mechanism of claim 1 or 2, since the brake means is an elastic belt, a good brake function can be obtained with a simple configuration. Can do.

Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
First, an outline of the configuration of a color printer as an image forming apparatus in the present embodiment will be described with reference to FIG. A transfer belt unit 10 having an intermediate transfer belt (endless belt) 11 as an intermediate transfer member and four image stations are disposed in the center of the apparatus main body. The transfer belt unit 10 is based on a frame 14 as a support member.
Each image station has photosensitive drums 20Y, 20C, 20M, and 20Bk as image carriers, around which are dedicated charging devices 30Y, 30C, 30M, and 30Bk, developing devices 50Y, 50C, 50M, and 50Bk, Cleaning devices 40Y, 40C, 40M, and 40Bk are arranged.
A toner bottle group 9 for replenishing toner is provided at the upper part of the apparatus main body. Each toner bottle is filled with toners of yellow (Y), cyan (C), magenta (M), and black (Bk) from the left in the drawing. Each color developing device 50Y, 50C, 50M, 50Bk is replenished.

A printing operation will be described. The transfer paper 2 as a recording medium is fed from the paper feed cassette 1 by the paper feed roller 3, and when the leading edge of the transfer paper 2 reaches the registration roller pair 4, it is detected by a sensor (not shown), and timing is determined by this detection signal. The transfer sheet 2 is conveyed to the nip portion between the secondary transfer roller 5 and the intermediate transfer belt 11 by the registration roller pair 4.
The photosensitive drums 20Y, 20C, 20M, and 20Bk uniformly charged in advance by the charging devices 30Y, 30C, 30M, and 30Bk are exposed and scanned with laser light by the optical writing device 8, and the photosensitive drums 20Y, 20C, and An electrostatic latent image is created on 20M and 20Bk.

The electrostatic latent images are developed by developing devices 50Y, 50C, 50M, and 50Bk for the respective colors, and yellow, cyan, magenta, and black toner images are formed on the surfaces of the photosensitive drums 20Y, 20C, 20M, and 20Bk. .
Next, a primary transfer voltage is applied to the primary transfer rollers 12Y, 12C, 12M, and 12Bk, and the toner on the photosensitive drums 20Y, 20C, 20M, and 20Bk is sequentially transferred onto the intermediate transfer belt 11. At this time, the image forming operation for each color is executed while shifting the timing from the upstream side toward the downstream side so that the toner image is transferred to the same position on the intermediate transfer belt 11.

The image formed on the intermediate transfer belt 11 is conveyed to the position of the secondary transfer roller 5 and is secondarily transferred to the transfer paper 2 at once. The transfer paper 2 onto which the toner images of the respective colors have been transferred is conveyed to the fixing device 6 and fixed by heat and pressure, and is discharged by a paper discharge roller pair 7 onto a paper discharge tray 15 that forms the upper surface of the apparatus main body.
The residual toner on the photoconductive drums 20Y, 20C, 20M, and 20Bk is cleaned by the respective cleaning devices 40Y, 40C, 40M, and 40Bk, and then the charging device 30Y, in which the bias of the AC component is superimposed and applied to the direct current. 30C, 30M, and 30Bk are charged simultaneously with static elimination to prepare for the next image formation.
The residual toner on the intermediate transfer belt 11 is cleaned by the intermediate transfer belt cleaning device 13 to prepare for the next image forming process.

  The intermediate transfer belt 11 guides the transfer paper 2 from the registration roller pair 4 to the nip portion of the drive roller 21, the drive roller 21 facing the intermediate transfer belt cleaning device 13, the secondary transfer roller 5 and the intermediate transfer belt 11. Thus, the intermediate transfer belt 11 is substantially supported by an inlet roller 23 that forms the inlet shape of the intermediate transfer belt 11. The driving roller 21, the driving roller 21, and the entrance roller 23 are all supported by the frame 14.

As shown in FIG. 1, inside the intermediate transfer belt 11, a cam drive mechanism 60 that is integrally provided with primary transfer rollers 12Y, 12C, and 12M corresponding to the photosensitive drums 20Y, 20C, and 20M is provided. .
In FIG. 1, only the photosensitive drums 20Y, 20C, 20M, and 20BK are displayed. However, as described above, the photosensitive drums 20Y, 20C, 20M, and 20BK are actually configured as a process unit including a charging device, a developing device, and the like. Therefore, hereinafter, they are also referred to as “process units 20Y, 20C, 20M, 20BK”.

At the time of full color image formation, as shown in FIG. 1, four color process units 20Y, 20C, 20M, and 20BK of yellow, cyan, magenta, and black are in contact with the intermediate transfer belt 11.
At the time of monochrome image formation, as shown in FIG. 2, the intermediate transfer belt 11 is separated from the process units 20Y, 20C, and 20M by the operation of a cam drive mechanism 60 described later. That is, the intermediate transfer belt 11 is in contact with only the black color process unit 20BK.

The cam drive mechanism 60 is supported by a shaft 61 supported by the frame 14 on the process unit 20BK side, and a movable member 62 provided so as to be rotatable in a direction in which the process unit 20BK is in contact with or separated from the process units 20Y, 20C, 20M. The movable member 62 includes an eccentric cam 63 that displaces (moves) the movable member 62 in the contact / separation direction, a drive unit 64 that will be described later, and the like.
The movable member 62 is formed in the shape of an arm that extends along the direction in which the process units 20Y, 20C, and 20M are disposed as a whole, and is integrally provided with primary transfer rollers 12Y, 12C, and 12M. The movable member 62 can also be called a YCM station.
As shown in FIG. 1, a spring 65 is installed in the vicinity of the eccentric cam 63 (on the right side in the figure) as an urging means for urging the movable member 62 in a direction to contact the eccentric cam 63. The upper end portion of the spring 65 is hung on a locking piece 14 a formed on the frame 14, and the lower end portion is hung on a locking piece 62 a formed on the lower end of the movable member 62.
Due to the biasing force of the spring 65, the movable member 62 comes into contact with the cam surface of the eccentric cam 63 by the contact portion 62b.

Brake means 66 for decelerating the rotation of the eccentric cam 63 is provided on the left side of the eccentric cam 63 in the drawing. In FIG. 1, the eccentric cam 63 and the brake means 66 are hatched for easy understanding (the same applies to FIGS. 2 and 5).
As shown in FIG. 3, the brake means 66 is installed in a state of being flush with the bottom surface 62 c of the movable member 62 and the vertical wall 62 d.
The brake means 66 has a two-layer structure of foamed urethane (foamed PUR) 66a as an elastic member and a PET (polyethylene terephthalate) film 66b as a sliding member having a low friction coefficient that comes into contact with the cam surface, and has a plate shape. The double-sided tape 67 is attached to the vertical wall 62d.
As a fixing method, an adhesive may be used. In addition, a foamed urethane film (PUR film) or the like may be employed as the surface layer sliding member.
By providing the PET film 66b on the surface, moderate slipperiness can be ensured, and the brake function can be easily controlled by the amount of the urethane foam 66a biting into the eccentric cam 63 and the foam density.
From the viewpoint of the coefficient of friction, it is desirable to use a PET film 66b as a surface layer in order to obtain a light brake function, and a PUR film as a surface layer to obtain a heavy brake function.

  The brake means 66 is installed so that the PET film 66 b as a surface that contacts the eccentric cam 63 is substantially parallel to the displacement direction (substantially vertical direction) of the movable member 62. That is, the movable member 62 is disposed at a substantially right angle with respect to the longitudinal direction.

As shown in FIG. 4, the eccentric cam 63 is rotationally driven by a drive unit 64 provided on the apparatus main body side. 4 is a perspective view seen from the opposite side of FIG.
The eccentric cam 63 operates by being driven by the drive unit 64. However, due to the structure like a one-way clutch of the coupling (clutch) 68 located in the middle, when the angular acceleration moment is applied, the eccentric cam 63 It may turn ahead of the angular position determined by the rotation.
Such a problem can be improved by changing the structure of the coupling 68, but the structure using the half-rotation clutch as disclosed in Patent Document 1 inevitably allows the cam to advance in advance. Therefore, it is desirable to install a brake. Also in this embodiment, the brake means 66 is provided from the same viewpoint.

As described above, FIG. 1 shows a state during full-color image formation, and the intermediate transfer belt 11 is pressed by the cam drive mechanism 60 and is in contact with the process units 20Y, 20C, and 20M. At this time, the maximum diameter region of the cam surface of the eccentric cam 63 is located at the contact portion 62 b of the movable member 62.
The movable member 62 is urged by the urging force of the spring 65 and the tension of the intermediate transfer belt 11 and is in contact with the eccentric cam 63.
If this position is the home position of the eccentric cam 63, during monochrome image formation, a command signal is output from the control unit (not shown) (for example, the main controller of the image forming apparatus) to the drive unit 64, and the eccentric cam 63 is rotated clockwise (arrow). Rotation starts in direction A).

As shown in FIG. 5, when the eccentric cam 63 rotates in the clockwise direction, the movable member 62 is displaced (moved) upward so that the contact portion 62 b approaches the rotation center 63 a of the eccentric cam 63. The intermediate transfer belt 11 is also reduced in tension and is separated from the process units 20Y, 20C, and 20M.
In the separation process of the intermediate transfer belt 11, the urging force of the spring 65 and the tension of the intermediate transfer belt 11 act on the eccentric cam 63 in the same direction as the rotation direction, and an acceleration moment that generates angular acceleration is generated.
However, this angular acceleration is canceled out by the brake means 66. The principle will be described below.

FIG. 6 shows the angular acceleration component force acting on the eccentric cam 63 from the spring 65 through the movable member 62. In Figure, P ₀ is the force transmitted from the movable member 62 to the eccentric cam 63, P ₁ is the angular acceleration component force. P ₂ is the component of force directed to the rotating shaft 63b of the eccentric cam 63, which is canceled by the reaction force generated in the rotation shaft 63b which is fixed the other direction of rotation.
Angular acceleration component force P _1, by the cam surface of the eccentric cam 63 abuts on the brake means 66, offset by the sliding resistance, so that the preceding rotation of the eccentric cam 63 is suppressed.

Figure 7 shows the relationship between the acceleration moment and angular position occurring eccentric cam 63 by the angular acceleration component force P ₁ shown in FIG.
When the highest portion (maximum diameter region) and the lowest portion (shortest diameter region) of the cam face each other at approximately 180 ° as in the eccentric cam 63, the acceleration moment as described above may be highest near the substantially right angle portion. I understand.
Therefore, it is effective to operate the brake function (deceleration function) by the brake means 66 within the range. If the brake function is applied at an acute angle or an obtuse angle position instead of a substantially right angle range, the load on the drive unit 64 increases.

As described above, when the surface layer of the brake means 66 is a sliding member having a low friction coefficient, the wear resistance can be increased and high durability can be obtained. Further, since the function as a brake is obtained from the elastic deformation energy of the elastic member, it can be freely controlled by the density and the amount of biting of the elastic member (foamed urethane 66a).
Assuming that the brake means 66 is fixed separately and independently in relation to the movable member 62 as in the prior art disclosed in Patent Document 1, if the braking action of the brake means 66 is too great, the eccentric cam 63 is locked. (The load on the drive unit 64 becomes abnormally large).

However, in this embodiment, since the brake means 66 is provided integrally with the movable member 62, the force that the brake means 66 receives from the eccentric cam 63 is a force that displaces the movable member 62.
That is, even if there is some force that causes the lock to be received by the braking means 66 from the eccentric cam 63, the extra force is consumed as it is for displacement (movement) of the movable member 62.
This means the degree of freedom of setting of the brake means 66, that is, the degree of freedom (ease of setting of the brake means) of the elastic member density, the amount of biting, and the selection of the material of the sliding member.

A second embodiment will be described with reference to FIG. In addition, the same part as the said embodiment is shown with the same code | symbol, The description on the structure and function which were already demonstrated is abbreviate | omitted as long as there is no special need, and only the principal part is demonstrated (the same is the following other embodiment).
The brake means 70 in this embodiment is configured by bending a leaf spring into a V shape, and is fixed to the movable member 62 in a cantilever manner by fixing the base end portion 70a to the vertical wall 62d of the movable member 62. Is attached to.
When the cam surface of the eccentric cam 63 comes into contact with the free end portion 70b, the free end portion 70b is elastically displaced, and the same braking function as in the first embodiment (sliding resistance and elastic restoring force of the free end portion 70b) ( (Deceleration function).
As shown in FIG. 10, it is good also as the brake means 71 of the both-ends beam type which consists of a leaf | plate spring in which both ends were each fixed to the bottom face 62c and the vertical wall 62d of the movable member 62 (3rd Embodiment).

FIG. 11 shows a fourth embodiment. The brake means 72 in the present embodiment has a belt 73 that contacts the eccentric cam 63 and a spring 74 as a biasing member that applies tension to the belt 73.
One end of the spring 74 is fixed to the vertical wall 62 d of the movable member 62, and the other end is connected to the upper end of the belt 73. The lower end side of the belt 73 is fixed to the bottom surface 62 c of the movable member 62.
In the present embodiment, the brake function can be easily adjusted by changing the spring constant of the spring 74.
As shown in FIG. 12, it is good also as the brake means 75 which consists of an elastic belt with both ends fixed to the bottom surface 62c of the movable member 62 and the vertical wall 62d, respectively (fifth embodiment).

  In each of the above embodiments, application to a tandem type intermediate transfer type image forming apparatus has been described. However, a tandem type direct transfer type color image forming apparatus, a one-drum type color image forming apparatus, a monochrome image forming apparatus, etc. It can implement similarly as a mechanism (contact-separation mechanism).

FIG. 3 is a schematic front view showing the main part of the cam drive mechanism in the first embodiment of the present invention, and shows a state during full-color image formation. It is a general | schematic front view which shows the state at the time of the same monochrome image formation. It is an enlarged front view of a brake means. It is a perspective view which shows a drive unit. FIG. 10 is a front view of a main part showing a state immediately before the intermediate transfer belt separation operation is completed. It is a figure which shows the force relationship which acts on a cam. It is a graph which shows the relationship between the acceleration moment which arises in a cam by angular acceleration component force, and an angular position. 1 is a schematic front view of a color printer as an image forming apparatus. It is a principal part front view in 2nd Embodiment. It is a principal part front view in 3rd Embodiment. It is a principal part front view in 4th Embodiment. It is a principal part front view in 5th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Intermediate transfer belt as intermediate transfer member 20 Photosensitive drum as image carrier 62 Movable member 62b Abutting portion 63 Eccentric cam as cam 63a Rotation center 66, 70, 71, 72, 75 Brake means 66a Elastic member Urethane foam 66b Polyethylene terephthalate film as a sliding member 67 Double-sided tape 73 Belt 74 Spring as a biasing member

Claims (11)

An image carrier;
An endless transfer belt facing the image carrier,
A transfer member provided inside the transfer belt;
Cam and, and a movable member having a Rutotomoni the transfer member is urged in a direction to abut the cam, displaces the movable member in a direction to and away from the above image carrier by rotation of the cam a cam drive mechanism for,
An image forming apparatus that displaces the movable member and the transfer member by the cam drive mechanism to bring the transfer belt into contact with and separated from the image carrier .
The cam drive mechanism has a brake unit that abuts on the cam in a displacement process in which a contact portion of the movable member approaches the rotation center of the cam and decelerates the cam, and the brake unit is integrated with the movable member. An image forming apparatus provided in the apparatus . The image forming apparatus according to claim 1.
The brake means is provided on a vertical wall of the movable member, the vertical wall is substantially parallel to a displacement direction of the movable member, and a surface of the brake means that contacts the cam is a displacement direction of the movable member. An image forming apparatus characterized by being substantially parallel to the image forming apparatus . The image forming apparatus according to claim 1 or 2,
The image forming apparatus according to claim 1, wherein the brake means has a two-layer structure of an elastic member and a sliding member that contacts the cam. The image forming apparatus according to claim 3.
An image forming apparatus, wherein the sliding member is in the form of a film and is adhered to the elastic member with an adhesive or a double-sided tape. The image forming apparatus according to claim 4.
The image forming apparatus , wherein the elastic member is urethane foam, and the sliding member is a polyethylene terephthalate film or a urethane foam film. The image forming apparatus according to claim 1 or 2,
An image forming apparatus , wherein the brake means is a cantilever using an elastic restoring force of a leaf spring. The image forming apparatus according to claim 1 or 2,
An image forming apparatus , wherein the brake means is a doubly supported beam using an elastic restoring force of a leaf spring. The image forming apparatus according to claim 1 or 2,
The image forming apparatus , wherein the brake means includes a belt that contacts the cam and a biasing member that applies tension to the belt. The image forming apparatus according to claim 1 or 2,
An image forming apparatus wherein the brake means is an elastic belt. The image forming apparatus according to any one of claims 1 to 9,
The image forming apparatus, wherein the transfer belt is an intermediate transfer belt, and includes a cleaning device for cleaning toner on the intermediate transfer belt . The image forming apparatus according to claim 10.
Together with the intermediate transfer belt is rotatably supported by the support member, the movable member is supported by the support member in the inside of the intermediate transfer belt, the intermediate transfer belt the image carrier by the displacement of the movable member An image forming apparatus, wherein the image forming apparatus is brought into contact with or separated from the image forming apparatus.

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