JP2008216969A - Belt unit, transfer belt unit, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent collision noise from being caused by contact-separation operation between contact members such as a photoreceptor and primary transfer rollers and a belt and to suppress the increase in torque due to contact between an eccentric cam and a braking member. <P>SOLUTION: A braking member 12 that comes into contact with the outer circumference of an eccentric cam 10 is provided to control the accelerating force applied to the eccentric cam 10 from a pressure member, and thus, collision noise caused by contact-separation operation of primary transfer rollers 4a to 4d is reduced. The braking member 12 is arranged to control the accelerating force applied to the eccentric cam 10 only by a predetermined angle, whereby the space occupied by the braking member 12 is minimized. Since a braking force is not applied to the eccentric cam 10 in a range where the braking member 12 does not come into contact with the eccentric cam 10, the eccentric cam 10 does not rotate beyond the maximum rotation torque without the braking member 12, whereby the increase in cost and enlargement of space can be minimized. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a belt device used in an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine having at least two of these functions, and in particular, when used in a transfer belt device, a belt photoreceptor. And a mechanism having an abutment / separation mechanism.

  Among the prior art documents disclosing this kind of technology, for example, Patent Document 1 mentions a contact / separation mechanism using a cam. Further, Patent Document 2 mentions that a pinion gear configuration is added as a braking member that relieves an impact during operation of the contact / separation mechanism. Further, Patent Document 3 describes a technique in which a transfer belt device having a drive device (main motor) for rotating an eccentric cam is provided with a braking member (buffer material) that contacts the outer periphery of the cam. In this technique, since the braking member is provided on a lever that swings, the cam and the braking member always come into contact with each other. Therefore, the drive torque of the cam increases, leading to an increase in cost and an increase in the size of the entire apparatus.

JP 2003-186313 A JP 2001-337497 A JP-A-8-339129

    According to the present invention, when a member, such as a primary transfer roller, or a device and a belt are brought into contact with or separated from each other, a collision sound is not generated so much and torque increase due to contact between a cam and a braking member can be suppressed. An object of the present invention is to provide a belt device and a device using the belt device, and to solve the conventional problems described above.

  According to a first aspect of the present invention, there is provided a belt device comprising: a contact member that can contact the belt; a movable member that is movable; and the movement of the movable member based on rotation of an eccentric cam. And a contact / separation mechanism that enables contact between the belt and the belt. The belt device includes a braking unit that brakes the rotation of the eccentric cam by a predetermined angle.

  According to a second aspect of the present invention, in the belt device according to the first aspect, the braking means includes an elastic member provided in a housing provided at a constant interval with a maximum rotation diameter of the eccentric cam. To do.

  A transfer belt device according to a third aspect of the present invention is the transfer belt device for an image forming apparatus using the belt device according to the first or second aspect, wherein the contact member is an image carrier, and the movable member. And a transfer member provided at a position facing the image carrier with the belt interposed therebetween, and the contact / separation mechanism is configured such that the transfer member is moved in the direction of the image carrier by the movement of the movable member. The image carrier and the belt can be brought into contact with and separated from each other by moving in a direction opposite to the image carrier.

  According to a fourth aspect of the present invention, in the transfer belt device according to the third aspect, the maximum value of the eccentric cam driving torque when the transfer member is separated when the braking member is not provided is A, and the braking is performed. When the maximum value of the driving torque in the upper fulcrum equilibrium region of the eccentric cam when the transfer member is separated when there is no member is B, and the torque acting around the center of the eccentric cam by the braking force of the braking member is C The braking force C is set so as to satisfy the relationship of A ≧ B + C.

  According to a fifth aspect of the present invention, in the image forming apparatus using the transfer belt device according to the third or fourth aspect, an image is formed using the belt as an intermediate transfer belt.

  According to a sixth aspect of the present invention, the transfer belt device according to the third or fourth aspect is used, and an image is formed using the belt as a recording medium conveyance belt.

  According to a seventh aspect of the present invention, an image is formed using the transfer belt device according to the third or fourth aspect.

  According to the present invention, when the contact member such as the photosensitive member and the belt are brought into contact with and separated from each other, little or no collision noise is generated, and further, torque increase due to contact between the eccentric cam and the braking member can be suppressed. effective.

  The present invention achieves the above-mentioned object by adopting a configuration in which a braking member, for example, an elastic body such as rubber or sponge is provided on the outer peripheral surface of the eccentric cam so as to contact only a certain range of the rotation angle of the eccentric cam. The present invention will be described below with reference to the embodiments shown in the drawings.

  FIG. 1 is a schematic cross-sectional view showing the configuration of an example of an image forming apparatus that can be implemented by the present invention. This image forming apparatus is a general tandem color image forming apparatus, and each of the yellow, cyan, magenta, and black process cartridges 102a, 102b, 102c, and 102d is detachably attached to the image forming apparatus main body 100. In the image forming apparatus main body 100, an exposure device 103, an intermediate transfer unit 101, a paper feed tray 104, a fixing device 110, and the like are disposed.

  The process cartridges 102a, 102b, 102c, and 102d are set at predetermined positions of the image forming apparatus main body 100, toner images are formed in the process cartridges 102a, 102b, 102c, and 102d, and the intermediate transfer belt 121, which is a transfer target member. The primary transfer. When the process proceeds to the image forming and transfer process, the transfer paper held on the paper supply tray 104 is conveyed to the registration roller pair 107 by the paper supply roller 105, and the toner image formed on the intermediate transfer belt 121 is the leading edge of the transfer paper. Is adjusted by the registration roller pair 107 so as to coincide with the position of the secondary transfer roller 109, and the toner image is secondarily transferred onto the transfer paper. Thereafter, the transfer sheet is conveyed between the rollers of the fixing device 110, and the toner image transferred by heat and pressure is fused to the transfer sheet, and is discharged to a discharge tray 106 outside the apparatus.

  On the other hand, the waste toner remaining without being transferred on the intermediate transfer belt 121 after the secondary transfer is scraped off by the cleaning blade 123 in contact with the belt in the intermediate transfer belt cleaning device 122, and is stored in the intermediate transfer belt cleaning device 122. The screw 124 is carried in the axial direction of the screw 124. The waste toner conveyed to the end of the intermediate transfer belt cleaning device 122 passes through the joint portion 125 that is a connecting member and is collected in a waste toner bottle 126 that is a waste toner container. At the same time, the agitating plate 127 for agitating the waste toner in the waste toner bottle 126 is swung in order to fill the waste toner bottle 126 with waste waste collected without waste. The stirring plate 127 is in contact with the stirring shaft 128 penetrating from the inside of the waste toner bottle 126 to the outside, and meshes with the stirring gear 129 assembled at the end of the stirring shaft 128 and the main body gear 10 installed in the image forming apparatus main body 100. The power at the time of swing is obtained.

  FIG. 2 is a conceptual cross-sectional view showing a typical configuration of a main part of a transfer belt apparatus configured using the belt apparatus according to the present invention and an image forming apparatus using the transfer belt apparatus, and FIGS. 6 is a conceptual cross-sectional view showing movement of a transfer member and contact / separation operation of a contact member and a belt in the apparatus of FIG.

  In the figure, reference numeral 1 denotes an intermediate transfer belt. The intermediate transfer belt 1 is stretched between a driving roller 2 and a driven roller 3, and is rotated in the direction of arrow A in the figure by rotating the driving roller 2 by a driving device (not shown). Driven by rotation. Inside the intermediate transfer belt 1, primary transfer rollers 4 a to 4 d as transfer members are disposed, and are supported rotatably by arms 5 and 6. That is, the arms 5 and 6 can be rotated in the left-right direction in the drawing around the central rotation axis, support the primary transfer rollers 4a to 4d at the tip, and the spring 7 is disposed at the lower end. The transfer rollers 4a to 4d are pressed and biased in a direction in which the transfer rollers 4a to 4d are brought into contact with the photoconductors 8a to 8d as image carriers.

  The photoconductor 8a is for forming a black image, and the photoconductors 8b, 8c, and 8d are for forming a color image (for example, any one of magenta, yellow, and cyan), and a single color or a color image is formed by combining these colors.

  Around each of the photoconductors 8a to 8d (hereinafter, simply referred to as the photoconductor 8 unless otherwise necessary), a charging unit, an exposure unit, a developing unit, a cleaning unit, and the like used in a known electrophotographic process are clocked. It is provided in the direction of rotation. Although not shown, the charging means uniformly charges the surface of the photoconductor 8. The exposure unit forms a latent image corresponding to the read image on the surface of the photoconductor 8 by the LED or LD. The developing means forms a toner image (developed image) by adhering powder such as toner to the latent image on the photoconductor 8. Then, the toner image on the photoconductor 8 is primarily transferred to the intermediate transfer belt 1, and the transfer residual toner remaining on the photoconductor 8 after the transfer is collected and discarded by a cleaning unit (not shown). In addition, there is a cleanerless system in which the transfer unit toner is collected by the developing unit without providing the cleaning unit on the photosensitive member 8, and various known cleaning units can be employed in the present invention.

  In the present embodiment, a bias is applied to the primary transfer rollers 4a to 4d by a bias applying unit (not shown) to perform primary transfer electrostatically. The primary transfer member is not limited to a roller, and may be a brush. In this embodiment, as can be seen from FIGS. 2 to 5, a line passing through the center of the photosensitive member 8 and connecting the center of the driving roller 2 and the driven roller 3, in other words, both rollers 2, 3 In the middle of the state where it is passed around the drive roller 2 and the driven roller 3 through the perpendicular line drawn down on the surface formed by the intermediate transfer belt 1 that has just been wound around and the center of the primary transfer rollers 4a to 4d. The perpendicular line down on the surface formed by the transfer belt 1 is displaced. The primary transfer roller 4 pushes up the intermediate transfer belt 1 and can be wound around a part of the surface of the photoreceptor 8. In such a configuration, the so-called offset transfer system, the amount of movement of the primary transfer roller 4 increases, and the amount of eccentricity of the eccentric cam 10 also increases. If the amount of eccentricity of the eccentric cam 10 is large, the frictional force between the eccentric cam 10 and the slider 9 also increases, so that it is easy to increase the torque. That is, it can be considered that the offset transfer method can more easily exert the above-described effects of the present invention.

  Then, the toner images sequentially primary-transferred from the photoreceptor 8a are superposed on the intermediate transfer belt 1 to form a color toner image. A counter roller 20 is provided at a position facing the driving roller 2 around which the intermediate transfer belt 1 is wound, and a sheet conveyed from a sheet feeding / conveying means (not shown) between the driving roller 2 and the counter roller 20. The recording medium P such as is passed through. The color toner images superimposed on the intermediate transfer belt 1 are carried and conveyed to a position between the driving roller 2 and the opposing roller 20 in accordance with the timing of passage of the recording medium P, and collectively onto the recording medium P. Secondary transfer.

  The drive roller 2 is electrostatically subjected to secondary transfer by applying a bias of toner charging polarity and dynamic polarity by bias applying means (repulsive transfer). However, the toner charging polarity is applied to the opposing roller 20. Secondary transfer (attractive transfer) may be performed by applying a bias having a reverse polarity.

  After the secondary transfer, the recording medium P such as paper passes through a fixing unit (not shown), and the toner is fixed to form a final image. However, simultaneous transfer and fixing may be performed by applying heat at the secondary transfer portion.

  Further, as shown in the figure, the slider 6 and the eccentric cam 10 are connected to the arm 6 and the primary transfer rollers 4b, 4c, and 4d, and the arm 6 is rotated in one direction by the drive device 11 connected to the eccentric cam 10. And the primary transfer rollers 4b, 4c, and 4d are reciprocated to move the primary transfer rollers 4b to 4d in the direction of the photoconductors 8b to 8d or in the direction opposite to the photoconductors 8b to 8d. -8d contact / separation is performed.

  FIG. 6 is an enlarged view showing a shape example of the eccentric cam 10. The eccentric cam 10 rotates around the rotation center 10r, and the rotation radius continuously increases from the lower fulcrum 10a to the part 10b. In the parts 10b to 10d including the upper fulcrum 10c, the rotation radius is the same as the maximum rotation diameter. Even if a force is received from the slider 9, an equilibrium region is set in which a force for rotating the eccentric cam 10 does not work. Since the rotation radius is constant, the rotational drive torque is also constant. When the primary transfer rollers 4b to 4d are in the separated state, the rotation of the eccentric cam 10 is stopped in the equilibrium regions 10b to 10d, and the separated state is maintained.

  Since the primary transfer rollers 4b to 4d are always pressed in the direction in contact with the photoreceptors 8b to 8d at the time of color printing, it is necessary to move the slider 9 with a force larger than the applied pressure in order to separate them. . The rotational torque of the eccentric cam 10 gradually increases from the lower fulcrum 10a to the portion 10b where the equilibrium region begins at the contact point between the eccentric cam 10 and the slider 9, and becomes maximum near the portion 10b as shown in FIG. .

  In the equilibrium regions 10b to 10d, the rotational torque is constant and rotates with a force smaller than the maximum value. The rotational torque gradually decreases from the portion 10d where the equilibrium region ends to the lower fulcrum 10a. The slider 9 is pushed by the pressure, and a force for accelerating the rotation is applied to the eccentric cam 10 in addition to the rotational torque of the drive device 11.

  Conventionally, the drive unit 11 and the eccentric cam 10 are connected by a link arm 11a, which is a transmission mechanism such as a gear train, a timing belt, and a pulley, but the gear and pulley have backlash, and the above-described eccentric cam. A collision sound between gears and pulleys is generated in the acceleration state after the 10 equilibrium regions are over. Further, since a collision sound between the slider 9 and the eccentric cam 10, a collision sound between the slider 9 and the arm 6, and a collision sound between the primary transfer rollers 4b, 4c, and 4d and the transfer belt 1 are also generated, the commercial value is greatly reduced. It was.

  In this embodiment, the braking member 12 is disposed in contact with the outer periphery of the eccentric cam 10, and the rotation of the eccentric cam 10 is not accelerated by constantly applying a braking force equal to or greater than the acceleration force by the spring 7 to the eccentric cam 10. Like that. The braking member 12 is not provided at a position where the eccentric cam 10 and the slider 9 are in contact with each other, but is provided on a housing 13 where a position for supporting the rotation shaft of the eccentric cam 10 is fixed. Thereby, the eccentric cam 10 and the braking member 12 do not always contact, and the driving torque of the eccentric cam 10 can be reduced.

  Examples of the housing 13 include a belt unit frame and a device body frame, but are not limited thereto, and various similar structures can be employed.

  Further, since the acceleration of the rotation of the eccentric cam 10 starts after passing the portion 10d of the equilibrium region, the braking member 12 is moved from an arbitrary position between the upper fulcrums 10c to 10d of the eccentric cam 10 to the lower fulcrum 10a of the eccentric cam 10. The braking member 12 is not in contact with the eccentric cam 10 in the vicinity of the starting portion 10b of the equilibrium region where the rotational torque is maximized, and the torque increase at the braking member 12 is rotated. It is possible to avoid adding to the maximum torque value. As a result, it is possible to achieve the maximum effect in a small space, and it is possible to minimize the cost increase due to the increase in the size of the motor of the drive device 11 and the increase in size of the device.

  A housing 13 is provided at a predetermined interval from the maximum rotation diameter 10e of the eccentric cam 10, and an elastic body such as sponge or rubber is used for the braking member 12, and the braking member 12 is compressed at an interval between the cam 10 and the housing 13. Since the amount is regulated, a change in the braking force can be suppressed, so that the braking force can be stabilized and the maximum braking effect can be exhibited. A resin sheet such as PET is attached to the surface of the braking member 12 that contacts the eccentric cam 10. This is to prevent the braking member 12 from being torn off by the frictional force with the eccentric cam 10.

  In this embodiment, the belt (intermediate transfer belt 1) is described as being in contact with the photoconductor 8. However, the photoconductor 8 may be in contact with the belt.

  That is, in the transfer belt device of the present invention, the acceleration force of the eccentric cam 10 received from the member for pressurization is limited by the provision of the braking member 12 that contacts the outer periphery of the eccentric cam 10, so that the primary transfer roller Or the collision sound accompanying the contact / separation operation of the transfer rollers 4a to 4d can be reduced. In addition, by disposing the braking member 12 by an angle that limits the acceleration force of the eccentric cam 10, it is possible to minimize the arrangement space of the braking member 12, and at an angle where the braking member 12 is not present, the braking force is applied to the eccentric cam 10. Therefore, the maximum rotation torque without the braking member 12 is not exceeded, and the cost of the device and the expansion of the space can be minimized.

  In the transfer belt device, the eccentric cam 10 is provided with a housing 13 having a certain distance from the maximum outer diameter of the eccentric cam 10, using an elastic body as the braking member 12, and compressing the elastic body with a constant thickness. The contact pressure with respect to can be made constant, so that the braking force is stabilized and the braking effect can be maximized.

  Further, the torque C around the center of rotation of the eccentric cam due to the braking force of the braking member 12 (friction force between the eccentric cam 10 and the braking member 12) and the rotational torque B (braking member in the upper fulcrum equilibrium region of the eccentric cam 10). The rotational torque obtained by adding the maximum transfer torque of the upper fulcrum equilibrium region of the eccentric cam 10 when the transfer member such as the primary transfer roller 12 or the transfer rollers 4a to 4d is separated when there is not 12 is the maximum rotational torque A (braking) (The maximum value of the driving torque of the eccentric cam 10 when the transfer member is separated when the member 12 is not present) is set so as not to exceed (the relation of A ≧ B + C). The torque may be the same as before the addition of the braking member 12, and it is possible to minimize the increase in cost and the size of the apparatus. Specifically, the torque C can be set by adjusting the hardness and thickness of the sponge or rubber as the braking member 12, the eccentric amount of the eccentric cam 10, and the spring force of the spring 7.

  In the previous embodiment, the intermediate transfer tandem type image forming apparatus has been described. However, a direct transfer tandem type image forming apparatus may be used. The configuration in that case is shown in FIG. In this configuration, the transfer rollers 4 a to 4 d correspond to the primary transfer rollers 4 a to 4 d of the previous embodiment, and the conveyance belt 1 of the recording medium P also corresponds to the intermediate transfer belt 1. The recording medium P such as paper is conveyed in the direction of arrow A, passes between the photoconductor 8 and the transfer rollers 4a to 4d, and the toner images are sequentially transferred. Since other configurations and operations are the same as those in the first embodiment, description thereof is omitted. In the figure, the center positions of the primary transfer rollers 4a to 4d are shifted from the center position of the photoconductors 8a to 8d as image carriers from the perpendicular drawn toward the transport belt 1 (offset transfer is performed). However, the positions of the primary transfer rollers 4a to 4d may be provided directly below the photoconductors 8a to 8d, which are image carriers.

1 is a schematic cross-sectional view showing a configuration of an example of an image forming apparatus that can be an object of the present invention. 1 is a conceptual cross-sectional view showing a representative configuration of a main part of a transfer belt device configured using the belt device according to the first embodiment of the invention and an image forming apparatus using the same. FIG. 1 is a conceptual cross-sectional view showing a contact / separation operation of a primary transfer roller of the apparatus of FIG. FIG. 1 is a conceptual cross-sectional view showing a contact / separation operation of a primary transfer roller of the apparatus of FIG. FIG. 1 is a conceptual cross-sectional view showing a contact / separation operation of a primary transfer roller of the apparatus of FIG. Enlarged view showing examples of eccentric cam shapes Conceptual sectional view showing a representative configuration of a main part of a transfer belt device constituted by using a belt device according to Embodiment 2 of the present invention and an image forming apparatus using the same.

Explanation of symbols

1: Intermediate transfer belt 2: Drive roller 3: Driven roller 4a-4d: Primary transfer roller 5, 6: Arm 7: Spring 8a-8d: Photoconductor 9: Slider 10: Eccentric cam 10a: Lower fulcrum 10b of the eccentric cam 10d: Eccentric cam part 10c: Eccentric cam upper fulcrum 10e: Eccentric cam maximum rotation diameter 10r: Eccentric cam rotation center 11: Driving device 11a: Link arm 12: Braking member 13: Housing 20: Opposing roller 102a- 102d: Process cartridge 100: Image forming apparatus main body 103: Exposure apparatus 101: Intermediate transfer unit 104: Paper feed tray 110: Fixing device 105: Paper feed roller 107: Registration roller pair 109: Secondary transfer roller 110: Fixing device 106: Paper discharge tray 121: Intermediate transfer belt 122: Intermediate transfer belt cleaning device 123: Cleaning blade 124: Screw 125: Joint part 126: Waste toner bottle 127: Stirring plate 128: Stirring shaft 129: Stirring gear 130: Main body gear P: Recording medium

Claims (7)

A contact member that can contact the belt, a movable member that can move, and a contact member that allows the contact member and the belt to contact and separate by moving the movable member based on rotation of an eccentric cam. In a belt device comprising a mechanism,
A belt device comprising braking means for braking the rotation of the eccentric cam only by a certain angle. 2. The belt device according to claim 1, wherein the braking means is provided with an elastic member in a housing provided at a constant interval with a maximum rotation diameter of the eccentric cam. In the transfer belt device for an image forming apparatus using the belt device according to claim 1 or 2,
The contact member is an image carrier;
A transfer member connected to the movable member and provided at a position facing the image carrier with the belt interposed therebetween;
The contact / separation mechanism allows the image carrier and the belt to be contacted / separated by moving the transfer member in a direction of the image carrier or a direction opposite to the image carrier by the movement of the movable member. A transfer belt device characterized by that. In the transfer belt device according to claim 3,
The maximum value of the eccentric cam drive torque when the transfer member is separated when the brake member is not present is A, and the maximum drive torque of the upper cam balanced point of the eccentric cam when the transfer member is separated when the brake member is not present The braking force C is set such that A ≧ B + C, where B is a value and C is a torque acting around the center of the eccentric cam by the braking force of the braking member. Transfer belt device. 5. An image forming apparatus using the transfer belt device according to claim 3 or 4, wherein the belt is used as an intermediate transfer belt to form an image. An image forming apparatus using the transfer belt device according to claim 3 or 4 to form an image using the belt as a recording medium conveying belt. An image forming apparatus that forms an image using the transfer belt device according to claim 3.