JP2012108195A - Belt device, transfer device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a belt device capable of reducing collision noise occurring in bringing into contact/separating actions of an abutting member as well as obtaining a small sized device.SOLUTION: The belt device includes: a moving member 28 which can be moved between a first position for bringing an abutting member 11 into an abutted state to a belt 8 and a second position for bringing the abutting member 11 into a separated state which is being separated from the belt 8; driving means for moving the moving member 28; an abutting/pressing member 32 for pressing the moving member 28 toward the first position; and a separating/pressing member 34 for pressing the moving member 28 toward the second position. In this case, the abutting/pressing member 32 and the separation/pressing member 34 have the pressing forces increased/reduced along with the movement of the moving member 28. In the abutted state, the pressing force of the separating/pressing member 34 is composed to be greater than the pressing force of the abutting/pressing member 32 and in the separated state, the pressing force of the abutting/pressing member 32 is composed to be greater than the pressing force of the separating/pressing member 34.

Description

  The present invention relates to a belt device, a transfer device using the belt device, and an image forming apparatus including the transfer device.

  In an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a complex machine of these, a plurality of photosensitive members as an image carrier that carries an image on a surface, and a plurality of image forming units that perform image forming processing are arranged in parallel. A so-called tandem type is known. In this tandem type image forming apparatus, images on each photosensitive member are sequentially transferred to an intermediate transfer belt used as an intermediate transfer member by a primary transfer device, and then images on the intermediate transfer belt are transferred by a secondary transfer device. There are an intermediate transfer type that batch-transfers onto a transfer paper such as a sheet, and a direct transfer type that sequentially transfers images on each photoconductor sequentially onto a transfer paper conveyed by a transfer belt by a transfer device.

  Further, in an image forming apparatus provided with a belt such as the intermediate transfer belt or the conveyor belt, the belt is prevented from waiting for printing in order to prevent permanent deformation of the belt due to the same portion of the belt coming into contact with the photosensitive member for a long time. In order to suppress wear of the color photoreceptor and the color developing device during monochrome image formation, the belt is made to be separated from all the photoreceptors (see Patent Document 1). Some are configured to be separated from the body (see Patent Document 2).

FIG. 7 is a schematic diagram showing the configuration of a conventional transfer apparatus in which the intermediate transfer belt is configured to be able to contact and separate from the photosensitive member.
As shown in FIG. 7, the transfer apparatus 100 includes four photoreceptors 200Y, 200C, 200M, and 200Bk that carry yellow, cyan, magenta, and black images, and an intermediate transfer belt 300 that is stretched by two rollers. And four transfer rollers (primary transfer rollers) 400Y, 400C, 400M, 400Bk and the like that face the photoconductors 200Y, 200C, 200M, 200Bk via the intermediate transfer belt 300. Here, of the four transfer rollers, three transfer rollers 400Y, 400C, and 400M facing the photoconductors 200Y, 200C, and 200M for color (yellow, cyan, and magenta) images are brought into contact with and separated from the intermediate transfer belt 300. It is configured as possible. Specifically, as the contact / separation means, a rotatable arm member 500 that holds the three transfer rollers 400Y, 400C, and 400M, a pressure spring 600 that pressurizes each arm member 500, and a horizontally movable member. A moving member 700, an eccentric cam 800 that moves the moving member 700, a drive device 900 that rotates the eccentric cam 800, and the like are provided.

  In the state shown in FIG. 7, the three transfer rollers 400Y, 400C, and 400M for color images are in contact with the intermediate transfer belt 300, whereby the intermediate transfer belt 300 is in contact with the respective photoreceptors 200Y for color images. , 200C, 200M. When the eccentric cam 800 rotates 180 ° from this state, as shown in FIG. 8, the eccentric cam 800 moves the moving member 700 to the right side of the figure, and this movement causes each arm member 500 to rotate counterclockwise in the figure. The transfer rollers 400Y, 400C, and 400M are separated from the intermediate transfer belt 300 by rotating. As a result, the position of the intermediate transfer belt 300 is lowered, and the intermediate transfer belt 300 is separated from the color photoconductors 400Y, 400C, and 400M.

FIG. 9 is a graph showing the rotational torque for each rotational position (rotational angle) of the eccentric cam in the conventional transfer apparatus shown in FIGS.
In FIG. 9, points A to D indicate rotational torque when one point Q on the circumference of the eccentric cam 800 shown in FIG. 7 reaches point A to point D in the figure during rotation. That is, point A indicates the rotational torque when the transfer roller is in contact with the intermediate transfer belt (the state shown in FIG. 7), and point C indicates the state where the transfer roller is separated from the intermediate transfer belt (shown in FIG. 8). Rotational torque in the state).

  According to FIG. 9, from the point A to the point B, the repulsive force increases as the pressure spring 600 is compressed, so that the rotation of the eccentric cam 800 is opposite to the rotation direction. Torque increases. In the process from point B to point C, the compression amount of the pressure spring 600 is further increased and the repulsive force is increased, but during this time, the point of contact of the eccentric cam 800 with the moving member 700 is the eccentric cam 800. The rotational torque gradually decreases as the axis approaches. On the other hand, from the point C to the point D, the moving member 700 is pushed in the moving direction by the pressure applied by the pressure spring 600, so that the eccentric cam 800 accelerates the rotation in addition to the rotational torque of the driving device 900. Since the force is applied, the rotational torque in the opposite direction is increased. Further, from point D to point A, the compression force of the pressure spring 600 decreases, and the acceleration force that the moving member 700 receives from the pressure spring 600 gradually weakens, so the rotational torque decreases.

  As described above, in the conventional transfer device, when going from the point A to the point B, the rotational torque in the direction opposite to the rotational direction of the eccentric cam 800 gradually increases and becomes the maximum near the point B. In order to place the intermediate transfer belt 300 in the separated state, it is necessary to move the moving member 700 with a large force. For this reason, it is necessary to apply a large driving torque to the eccentric cam 800, and it is difficult to reduce the size of the driving device 900.

  Further, since the force for accelerating the rotation of the eccentric cam 800 increases from the point C to the point D, the back of the drive transmission means such as a gear and a pulley for transmitting the driving force to the eccentric cam 800 is provided. In the rush, the meshing of gears and pulleys becomes unstable and a collision noise is generated. Further, when the acceleration force to the eccentric cam 800 becomes maximum near the point D, the collision sound between the eccentric cam 800 and the moving member 700, the collision sound between the moving member 700 and the arm member 500, the transfer roller 400Y. , 400C, 400M and the intermediate transfer belt 300 also generate a collision sound, resulting in a significant reduction in commercial value.

  Further, as shown in FIG. 7, the center positions of the transfer rollers 400Y, 400C, 400M, and 400Bk deviate from the vertical lines drawn toward the intermediate transfer belt 300 from the center positions of the photoconductors 200Y, 200C, 200M, and 200Bk. When the so-called offset transfer method is employed, the separation amount of the transfer rollers 400Y, 400C, and 400M increases, so that the compression amount of the pressure spring 600 at the time of separation increases, and the eccentric cam 800 rotates. The rotational torque acting in the direction opposite to the direction is also increased. Therefore, in particular, in such an offset transfer type transfer device, it is necessary to increase the driving torque, and it becomes more difficult to reduce the size, and the rotational torque acting on the eccentric cam 800 also increases. Is also likely to occur.

  In view of such circumstances, the present invention can reduce a collision sound generated in the contact and separation operation of a transfer roller or the like with respect to the belt and can reduce the size of the device, and uses the belt device. It is an object of the present invention to provide a transfer device and an image forming apparatus provided with the transfer device.

  The invention of claim 1 is a belt device comprising a belt, an abutting member that abuts against the belt, and contact / separation means for contacting and separating the abutting member with respect to the belt. A movable member movable between a first position for contacting the belt and a second position for separating the contact member from the belt; and the movement A driving unit that moves the member; a contact pressure member that pressurizes the moving member toward the first position; and a separation pressure member that pressurizes the moving member toward the second position. The contact pressure member and the separation pressure member increase and decrease with the movement of the moving member. In the contact state, the pressure of the separation pressure member is increased. It is larger than the pressing force of the contact pressure member, and in the separated state, In which pressure of SeKKa member is configured to be greater than the pressure of the separation pressure member.

  With the configuration as described above, the load applied to the driving means due to the pressurization of the contact pressure member or the separation pressure member is the difference in the applied pressure between the contact pressure member and the separation pressure member. As a result, the load on the driving means can be significantly reduced.

  According to a second aspect of the present invention, in the belt device according to the first aspect, the pressing force of the separation pressure member in the contact state and the pressing force of the contact pressure member in the separation state are: While setting to the same magnitude | size, the applied pressure of the said contact pressure member in the said contact state and the applied pressure of the said separation pressure member in the said separation state are set to the same magnitude | size. .

  This makes it possible to equalize the load generated in the drive means in the process of transition between the contact state and the separation state, and to effectively reduce the load.

  According to a third aspect of the present invention, in the belt device according to the first or second aspect, the difference in the applied pressure between the contact pressure member and the separation pressure member is maximized in the contact state or the separation state. In the middle of the transition between the contact state and the separated state, it becomes zero.

  As a result, the load on the driving means can be effectively reduced.

  According to a fourth aspect of the present invention, in the belt device according to any one of the first to third aspects, the driving means includes a rotatable eccentric cam that contacts a pair of cam receiving portions provided on the moving member. And in the contact state, the eccentric cam is in contact with one of the cam receiving portions by the pressure of the separation pressure member, and the moving member is held, and in the separation state, the contact pressure The eccentric cam is brought into contact with the other cam receiving portion by the pressing force of the member, and the moving member is held.

  Accordingly, it is not necessary to separately provide a holding member for holding the moving member in the contact state or in the separated state, so that reduction in size and cost can be achieved.

  According to a fifth aspect of the present invention, in the belt device according to any one of the first to fourth aspects, the separation pressure member is a tension applying member for applying tension to the belt.

  Thereby, since it is not necessary to provide a separate pressurizing member separately, it becomes possible to achieve downsizing and cost reduction.

  The invention of claim 6 is a transfer device for transferring an image formed on an image carrier to a recording medium using a belt device provided with an endless belt that is wound around a plurality of support members and driven to rotate. The belt device according to any one of claims 1 to 5 is used as the belt device.

  Since the transfer device uses the belt device according to any one of claims 1 to 5, the above-described effects by these belt devices can be obtained.

  According to a seventh aspect of the present invention, in the transfer device according to the sixth aspect, the image forming apparatus further comprises a transfer member facing the image carrier through the belt, and the transfer member is brought into contact with and separated from the image carrier. The transfer device is configured such that the belt can contact and separate from the image carrier, and the transfer member is the contact member.

  The configuration of the present invention can also be applied to such a transfer apparatus.

  The invention according to claim 8 is the transfer apparatus according to claim 6 or 7, wherein the belt is an intermediate transfer belt onto which an image on the image carrier is transferred.

  The configuration of the present invention can also be applied to a transfer device using an intermediate transfer belt.

  According to a ninth aspect of the present invention, in the transfer apparatus according to the sixth or seventh aspect, the belt is a conveyance belt that conveys a recording medium.

  The configuration of the present invention can also be applied to a transfer device using a conveyance belt.

  A tenth aspect of the present invention is an image forming apparatus including the transfer device according to any one of the sixth to ninth aspects.

  Since the image forming apparatus includes the transfer device according to any one of claims 6 to 9, the above effect of the belt device used in these transfer devices can be obtained.

  According to the present invention, the load generated in the driving means can be greatly reduced, so that an unpleasant sound (collision sound) at the time of contact / separation operation can be reduced, a contact / separation mechanism is small, and a low-cost belt device is provided. It becomes possible to provide.

1 is a schematic cross-sectional view illustrating an overall configuration of an image forming apparatus to which the present invention is applied. FIG. 2 is a schematic diagram illustrating a configuration of a transfer device mounted on the image forming apparatus. FIG. 2 is a schematic diagram illustrating a configuration of a transfer device mounted on the image forming apparatus. It is a graph which shows the rotational torque for every rotation position (rotation angle) of the eccentric cam in the transfer apparatus of this embodiment. It is a figure for demonstrating the rotation position of an eccentric cam. 1 is a schematic view showing the configuration of a direct transfer type transfer apparatus to which the configuration of the present invention is applied. It is the schematic which shows the structure of the conventional transfer apparatus. It is the schematic which shows the structure of the conventional transfer apparatus. It is a graph which shows the rotational torque for every rotation position (rotation angle) of the eccentric cam in the conventional transfer apparatus.

  Hereinafter, the present invention will be described with reference to the accompanying drawings. In the drawings for explaining the present invention, components such as members and components having the same function or shape are denoted by the same reference numerals as much as possible, and once described, the description will be given. Omitted.

First, an overall configuration and operation of an image forming apparatus to which the present invention is applied will be described with reference to FIG.
The image forming apparatus shown in FIG. 1 is a color laser printer, and four process units 1Y, 1C, 1M, and 1Bk as image forming units are detachably attached to the apparatus main body 99. Each process unit 1Y, 1C, 1M, 1Bk contains toner of different colors of yellow (Y), cyan (C), magenta (M), and black (Bk) corresponding to the color separation components of the color image. Other than that, the configuration is the same. In the following description, the alphabet (Y, C, M, Bk) indicating each color is omitted unless particularly required.

  Each process unit 1 includes a drum-shaped photoconductor 2 as an electrostatic latent image carrier (or image carrier), a charging roller 3 as a charging means for charging the surface of the photoconductor 2, and the surface of the photoconductor 2. A developing roller 4 serving as a developing unit that supplies toner to the surface, and a cleaning blade 5 serving as a cleaning unit that removes toner remaining on the surface of the photoreceptor 2 are provided. The cleaning blade 5 may not be provided, and the developing roller 4 may remove the residual toner on the photoconductor 2. Various other known cleaning means can also be employed.

  In FIG. 1, an exposure device 6 as an exposure means for exposing the surface of the photoreceptor 2 is disposed above each process unit 1Y, 1C, 1M, 1Bk. On the other hand, a transfer device 7 is disposed below the process units 1Y, 1C, 1M, and 1Bk. The transfer device 7 has an intermediate transfer belt 8 as a transfer body composed of an endless belt. The intermediate transfer belt 8 is stretched around a driving roller 9 and a tension roller 10 as support members. When the driving roller 9 rotates counterclockwise in the figure, the intermediate transfer belt 8 is in a direction indicated by an arrow in the figure. It is comprised so that it may run around (rotate).

  Four primary transfer rollers 11 as primary transfer means are disposed at positions facing the four photoconductors 2. Each primary transfer roller 11 is in contact with the inner peripheral surface of the intermediate transfer belt 8 at each position. As a result, the intermediate transfer belt 8 and each photoconductor 2 come into contact with each other, and a primary transfer nip is formed at the contact portion. Each primary transfer roller 11 is connected to a power source (not shown), and a predetermined direct current voltage (DC) and / or alternating current voltage (AC) is applied to the primary transfer roller 11. The primary transfer means is not limited to a roller, and may be a conductive member such as a brush.

  Of the four primary transfer rollers 11Y, 11C, 11M, and 11Bk, the three primary transfer rollers 11Y, 11C, and 11M that face the photoconductors 2Y, 2C, and 2M for color (yellow, cyan, and magenta) images are: The intermediate transfer belt 8 is configured to be able to contact and separate. As indicated by a two-dot chain line in FIG. 1, when the primary transfer rollers 11Y, 11C, and 11M are separated from the intermediate transfer belt 8, the intermediate transfer belt 8 is separated from the color image photoreceptors 2Y, 2C, and 2M. It is supposed to be.

  In the present embodiment, the center positions of the primary transfer rollers 11Y, 11C, 11M, and 11Bk are shifted from the center positions of the photoreceptors 2Y, 2C, 2M, and 2Bk from the perpendicular drawn toward the intermediate transfer belt 8. Although a so-called offset transfer method is employed, the center positions of the primary transfer rollers 11Y, 11C, 11M, and 11Bk may be arranged on the perpendicular line.

  A secondary transfer roller 12 as a secondary transfer unit is disposed at a position facing the drive roller 9. The secondary transfer roller 12 is in contact with the outer peripheral surface of the intermediate transfer belt 8, and a secondary transfer nip is formed at the contact portion. Similar to the primary transfer roller 11, the secondary transfer roller 12 is connected to a power source (not shown) so that a predetermined direct current voltage (DC) and / or alternating current voltage (AC) is applied to the secondary transfer roller 12. It has become.

  A belt cleaning device 13 for cleaning the surface of the intermediate transfer belt 8 is disposed on the outer peripheral surface of the intermediate transfer belt 8 on the right end side in the drawing. A waste toner transfer hose (not shown) is attached from the belt cleaning device 13, and the tip of the toner transfer hose is connected to an inlet portion of a waste toner container 14 disposed below the transfer device 7. In the waste toner container 14, a stirring plate 23 for stirring the waste toner is provided in order to fill the waste toner without waste. The stirring plate 23 is configured to be swingable by contacting with a stirring shaft 24 penetrating from the inside of the waste toner container 14 to the outside. Further, the stirring shaft 24 obtains power at the time of swinging by meshing the stirring gear 25 assembled at its end with the main body gear 26 installed in the apparatus main body 99.

  A paper feed cassette 15 that accommodates a sheet-like recording medium P such as paper or OHP is disposed below the apparatus main body 99. The paper feed cassette 15 is provided with a paper feed roller 16 for feeding out the stored recording medium P. On the other hand, a pair of paper discharge rollers 17 for discharging the recording medium to the outside and a paper discharge tray 18 for stocking the discharged recording medium are disposed on the upper portion of the apparatus main body 99.

  In the image forming apparatus main body 99, a conveyance path R for guiding the recording medium from the lower paper feed cassette 15 to the upper paper discharge tray 18 is formed. A pair of registration rollers 19 is disposed on the conveyance path R in the middle from the paper feed roller 16 to the secondary transfer roller 12. A fixing device 20 for fixing the image on the recording medium is provided on the way from the secondary transfer roller 12 to the paper discharge roller 17. The fixing device 20 includes a fixing roller 21 as a fixing member that is heated by a heat source, and a pressure roller 22 as a pressure member that presses the fixing roller 21. A fixing nip as a fixing unit is formed at a position where the fixing roller 21 and the pressure roller 22 are in pressure contact with each other.

The basic operation of the image forming apparatus will be described below with reference to FIG.
First, when forming a full-color image, the image forming operation is started in a state where the four primary transfer rollers 11Y, 11C, 11M, and 11Bk are in contact with the intermediate transfer belt 8. When the image forming operation is started, the photosensitive members 2 of the four process units 1Y, 1C, 1M, and 1Bk are driven to rotate clockwise by a driving device (not shown), and the surface of each photosensitive member 2 is charged by the charging roller 3. It is uniformly charged to a predetermined polarity. The surface of each charged photoconductor 2 is irradiated with laser light from the exposure device 6 to form an electrostatic latent image on the surface of each photoconductor 2. At this time, the image information to be exposed on each photoconductor 2 is monochromatic image information obtained by separating a desired full-color image into color information of yellow, cyan, magenta, and black. The electrostatic latent image formed on the photoreceptor 2 in this way is supplied with toner by each developing roller 4 so that the electrostatic latent image is visualized (visualized) as a toner image.

  Further, when the driving roller 9 is driven to rotate counterclockwise in the figure, the intermediate transfer belt 8 is driven to rotate in the direction indicated by the arrow in the figure. Further, a constant voltage or a constant current controlled voltage having a polarity opposite to the toner charging polarity is applied to each primary transfer roller 11. As a result, a transfer electric field is formed at the primary transfer nip between each primary transfer roller 11 and each photoconductor 2. The toner images of the respective colors formed on the photoreceptors 2 of the process units 1Y, 1C, 1M, and 1Bk are sequentially transferred onto the intermediate transfer belt 8 by the transfer electric field formed in the primary transfer nip. The Thus, the intermediate transfer belt 8 carries a full-color toner image on its surface. After the transfer of the toner image, the toner remaining on the surface of each photoconductor 2 is removed by the cleaning blade 5. Next, the surface of the photoconductor 2 is subjected to a static elimination action by a static eliminator (not shown), and the surface potential is initialized to prepare for the next image formation.

  When the image forming operation is started, the sheet feeding roller 16 starts rotating, and the recording medium P stored in the sheet feeding cassette 15 is sent out to the transport path R by the sheet feeding roller 16. The recording medium P sent to the transport path R is temporarily stopped by the registration roller 19. Thereafter, the driving of the registration roller 19 is resumed, and the recording medium P is sent to the secondary transfer nip between the secondary transfer roller 12 and the drive roller 9 in synchronization with the toner image on the intermediate transfer belt 8. . At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the intermediate transfer belt 8 is applied to the secondary transfer roller 12, thereby forming a transfer electric field in the secondary transfer nip. When the recording medium P and the toner image on the intermediate transfer belt 8 reach the secondary transfer nip, the toner image on the intermediate transfer belt 8 is transferred onto the recording medium P by the transfer electric field formed in the secondary transfer nip. Are collectively transferred. Alternatively, the toner image on the intermediate transfer belt 8 may be transferred to the recording medium P by applying a transfer voltage having the same polarity as the toner charging polarity to the driving roller 9 by bias applying means. Further, the toner remaining on the intermediate transfer belt 8 after the transfer is removed by the belt cleaning device 13, and the removed toner is conveyed to the waste toner container 14 and collected.

  The recording medium P to which the toner image has been transferred is conveyed to the fixing unit 20, and the recording medium P is heated and pressed by the fixing roller 21 and the pressure roller 22 to fix the toner image. Thereafter, the recording medium P is discharged to the paper discharge tray 18 by the paper discharge roller 17. In addition, fixing may be performed simultaneously with the transfer by adopting a configuration in which heat can be applied in the secondary transfer nip.

Next, an operation for forming a monochrome image will be described.
When forming a monochrome image, the three primary transfer rollers 11Y, 11C, and 11M for color images are separated from the intermediate transfer belt 8, and the intermediate transfer belt 8 is placed on the color image photoreceptors 2Y, 2C, and 2M. They are separated from each other (see the two-dot chain line in FIG. 1). When the image forming operation is started, an image is formed only on the black image photoreceptor 2Bk, and the image is transferred to the recording medium P via the intermediate transfer belt 8 in the same manner as described above. Fix at 20 and eject out of machine. In this way, when forming a monochrome image, the color image photoreceptors 2Y, 2C, and 2M are separated from the intermediate transfer belt 8, thereby consuming and deteriorating color toner, and the color image photoreceptors 1Y, 1Y, 1C and 1M wear and the like can be suppressed.

Hereinafter, the configuration of the transfer device will be described in detail.
2 and 3 are schematic views showing the configuration of the transfer device 7. 2 shows a state in which a full color image is formed in which all the primary transfer rollers 11Y, 11C, 11M, and 11Bk are in contact with the intermediate transfer belt 8, and FIG. 3 shows three primary transfer rollers 11Y, 11C for color images. , 11M show a state when forming a monochrome image separated from the intermediate transfer belt 8.
Each primary transfer roller 11Y, 11C, 11M for color images is rotatably held by an arm member 27 as a rotation holding member. Specifically, each arm member 27 is formed in a substantially L shape, and primary transfer rollers 11Y, 11C, and 11M are attached to the upper end portions (one end portions) 27a thereof. Each arm member 27 is configured to be rotatable about a rotation shaft 27c disposed in the horizontal direction, and the primary transfer roller held by each arm member 27 as it rotates. 11Y, 11C, and 11M are in contact with and separated from the intermediate transfer belt 8.

  Below each arm member 27, a moving member 28 that is movable in the horizontal direction is disposed. The moving member 28 is configured to be able to reciprocate between a first position moved to the left as shown in FIG. 2 and a second position moved to the right as shown in FIG. As drive means for moving the moving member 28, a drive device 29, an eccentric cam 30, and a drive transmission means 31 for transmitting the driving force of the drive device 29 to the eccentric cam 30 are provided. The eccentric cam 30 is disposed between a pair of cam receiving portions (receiving surfaces) 28a, 28b provided on the moving member 28, and the eccentric cam 30 rotates to rotate the pair of cam receiving portions 28a, 28b. It abuts on one of 28b. The drive transmission means 31 is composed of, for example, a gear train, a timing belt, and a pulley.

  Further, the moving member 28 is provided with a contact portion 28 c that contacts the lower end portion (other end portion) 27 b of each arm member 27, and the lower end portion 27 b of each arm member 27 is moved by the pressure spring 32. Pressure is applied to the contact portion 28 c side of the member 28. Note that the end of each pressurizing spring 32 opposite to the end contacting the arm member 27 is supported by a spring support 33 provided on the main body frame of the transfer device 7. Further, the moving member 28 is provided with a spring receiving portion (receiving surface) 28d for receiving one end portion of a tension spring 34 as a tension applying member. The tension member 34 presses the moving member 28 to the right side in FIG. 2 or FIG. On the other hand, the other end portion of the tension spring 34 presses the shaft portion of the tension roller 10 toward the intermediate transfer belt 8 (the left side in FIG. 2 or FIG. 3), whereby tension is applied to the intermediate transfer belt 8. ing.

The transfer device 7 configured as described above operates as follows.
When the eccentric cam 30 is rotated 180 ° from the state shown in FIG. 2, the eccentric cam 30 comes into contact with the cam receiving portion 28 b on the right side of the drawing, and moves the moving member 28 to the right side of the drawing. Along with this movement, the abutting portion 28c of the moving member 28 pushes the lower end portion 27b of the arm member 27 to the right side in the figure, and each arm member 27 rotates counterclockwise in the figure. As a result, as shown in FIG. 3, the color image primary transfer rollers 11Y, 11C, and 11M are separated from the intermediate transfer belt 8, and the intermediate transfer belt 8 is moved to the color image photoreceptors 2Y, 2C, and 2M. It will be in the state spaced apart.

  Further, when the eccentric cam 30 is further rotated 180 ° from the state shown in FIG. 3, the eccentric cam 30 comes into contact with the cam receiving portion 28a on the left side of the drawing and moves the moving member 28 to the left side of the drawing. Along with this movement, the lower end portion 27b of the arm member 27 is pushed by the pressure spring 32 and moves to the left side of the figure, and each arm member 27 rotates clockwise in the figure. As a result, as shown in FIG. 2, the color image primary transfer rollers 11Y, 11C, and 11M abut against the intermediate transfer belt 8, and the intermediate transfer belt 8 contacts the color image photoreceptors 2Y, 2C, and 2M. It will be in the state contact | abutted with respect.

  In the present embodiment, the primary transfer roller 11Bk for black image is held by the arm member 35 as a rotation holding member, but is always in contact with the intermediate transfer belt 8 by the pressure of the pressure spring 36. It is not configured to be able to contact and separate.

  The pressurizing direction of each pressurizing spring 32 and the pressurizing direction of the tension spring 34 are opposite to each other. In this case, the pressurizing direction of the pressurizing spring 32 pressurizes the moving member 28 to the left first position (via the arm member 27), and the tension spring 34 causes the moving member 28 to move to the right first position. The pressure is applied in the direction of movement to position 2. That is, the pressure spring 32 functions as a contact pressure member that presses the primary transfer rollers 11Y, 11C, and 11M toward the first position where the primary transfer rollers 11Y, 11C, and 11M contact the intermediate transfer belt 8, and the tension spring 34 functions as the primary transfer roller 11Y. , 11C, 11M function as a separation pressure member that pressurizes the intermediate transfer belt 8 toward the second position.

  Further, in the contact state shown in FIG. 2, when the resultant force of the pressure force fa of each pressure spring 32 is Fa and the pressure force of the tension spring 34 is Fb, Fb> Fa (= fa + fa + fa) is set. ing. On the other hand, in the separated state shown in FIG. 3, assuming that the resultant force of the pressure force fc of each pressure spring 32 is Fc and the pressure force of the tension spring 34 is Fd, Fd <Fc (= fc + fc + fc) is set. Yes.

  Since each pressing force is set as described above, in the contact state shown in FIG. 2, the pressing force Fb of the tension spring 34 is larger than the pressing force Fa of the pressing spring 32, and the moving member 28 is on the right side of the drawing. Is in a state of being energized. For this reason, the eccentric cam 30 is held in a state where the cam receiving portion 28a on the left side of the drawing is in contact. Then, when the eccentric cam 30 is rotated from the state shown in FIG. 2, the moving member 28 follows the eccentric cam 30 because it is pushed to the right in the drawing by the pressure of the tension spring 34. During this time, the moving member 28 moves to the right side of the drawing, so that the tension spring 34 is gradually extended, and accordingly, the applied pressure decreases. On the other hand, since the pressure spring 32 is gradually compressed, the pressure increases accordingly. During the transition from the contact state to the separation state, the pressure force of the tension spring 34 and the pressure force (composite force) of the pressure spring 32 become the same value, and the difference between them becomes zero.

  After the difference in the applied pressure between the tension spring 34 and the pressure spring 32 becomes zero, the eccentric cam 30 comes into contact with the cam receiving portion 28b on the right side of the figure to move the moving member 28 to the right side of the figure. Along with this movement, the tension spring 34 is further extended to reduce the applied pressure. On the other hand, the pressure spring 32 is further compressed to increase the pressure. In the separated state shown in FIG. 3, the pressing force (combined force) of the pressure spring 32 exceeds the pressing force of the tension spring 34, and as described above, the relationship Fd <Fc (= fc + fc + fc) is established. Therefore, in this state, the moving member 28 is urged to the left side in the figure by the pressure Fc of the pressure spring 32, and the eccentric cam 30 is in contact with the right cam receiving part 28b in the figure. Retained.

  Also, when shifting from the separated state to the abutting state, the moving member 28 initially follows the eccentric cam 30 by the pressure of the pressure spring 32, contrary to the case of shifting to the separated state, Thus, the difference between the pressing force (combined force) of the pressure spring 32 and the pressing force of the tension spring 34 becomes zero, and thereafter, the moving member 28 is moved by the eccentric cam 30. Then, when returning to the separated state shown in FIG. 2, the pressure force of the tension spring 34 exceeds the pressure force (the resultant force) of the pressure spring 32, and Fb> Fa (= fa + fa + fa).

FIG. 4 is a graph showing the rotational torque for each rotational position (rotational angle) of the eccentric cam in the transfer apparatus of this embodiment.
In FIG. 4, points A to D indicate rotational torque when one point Q on the circumference of the eccentric cam 30 shown in FIG. 5 reaches point A to point D in the figure during rotation. Point A shows the rotational torque when the primary transfer roller is in contact with the intermediate transfer belt (shown in FIG. 2), and point C shows the state where the primary transfer roller is separated from the intermediate transfer belt (shown in FIG. 3). Rotational torque in the state).

  As shown in FIG. 4, in this embodiment, the acceleration force by the tension spring 34 is applied to the rotational torque of the eccentric cam 30 from the point A in the contact state to the point B rotated 90 °. Only the difference in pressure between the tension spring 34 and the pressure spring 32 is obtained. When the point B is reached, the pressure applied by the tension spring 34 and the pressure spring 32 becomes equal, and the rotation is performed only by the rotational torque of the eccentric cam 30. From point B to point C in the separated state, the pressure force of the pressure spring 32 is greater than the pressure force of the tension spring 34, and on the contrary, load torque is applied in a direction that prevents rotation of the eccentric cam 30. The magnitude is only the difference in the applied pressure between the pressure spring 32 and the tension spring 34. Further, an acceleration force by the pressure spring 32 is applied from the point C to the point D, and a load torque by the tension spring 34 is applied from the point to the point A. The magnitudes of the acceleration force and the load torque are as described above. Similarly, the difference between the pressure spring 32 and the tension spring 34 is obtained. As described above, in the present embodiment, the magnitude of the rotational torque applied to the eccentric cam 30 by the pressure spring 32 or the tension spring 34 is only the difference in the applied pressure between the pressure spring 32 and the tension spring 34. Therefore, it is significantly smaller than the rotational torque (see FIG. 9) generated in the conventional configuration shown in FIG.

  That is, in the conventional configuration shown in FIG. 7, since the pressing force 600 always applies a pressing force in one direction to the moving member 700, if the moving member 700 is moved in a direction against the pressing force, the pressing force is applied. As the pressure spring 600 is compressed, the applied pressure is increased, and a large load is applied to the eccentric cam 800 when the applied pressure becomes maximum.

  On the other hand, in the present embodiment, when the moving member 28 is moved in a direction against the pressure force of the pressure spring 32 in FIG. 2, the pressure force increases as the pressure spring 32 is compressed. Since the pressing force of the spring 34 acts in the opposite direction to the pressing force of the pressing spring 32, the load applied to the eccentric cam 30 by the pressing force of the pressing spring 32 is the pressing force and tension of the pressing spring 32. Only the difference from the applied pressure of the spring 34 is obtained. On the contrary, when the moving member 28 is moved in a direction against the pressure applied by the tension spring 34, the load applied to the eccentric cam 30 by the pressure applied by the tension spring 34 is similarly applied to the pressure applied by the pressure spring 32. And the difference between the pressure applied by the tension spring 34. As a result, the load applied to the eccentric cam 30, the drive device 20, and the drive transmission means 31 such as a gear train or timing belt for connecting them can be greatly reduced. Sound), a contact / separation mechanism is small, and a low-cost transfer device can be provided.

  Further, the pressure Fb of the tension spring 34 in the contact state and the pressure Fc of the pressure spring 32 in the separated state are set to the same magnitude (Fb = Fc), and in the contact state. By setting the pressure Fa of the abutting member and the pressure Fd of the tension spring 34 in the separated state to the same magnitude (Fa = Fd), as shown in FIG. It is possible to equalize the load generated in the eccentric cam 30 in the process of transition between the separated state and the separated state. That is, the difference in the applied pressure between the pressure spring 32 and the tension spring 34 can be made the same in the contact state or the separation state. In addition, the load on the eccentric cam 30 due to the pressure applied by the pressure spring 32 and the tension spring 34 can be made zero at an intermediate point between the contact state and the separation state. As a result, the load applied to the driving means such as the eccentric cam 30 can be effectively reduced.

  In this embodiment, the tension spring 34 for applying tension to the intermediate transfer belt 8 is used as a separation pressing member that presses the intermediate transfer belt 8 in a direction opposite to the pressing direction of the pressing spring 32. There is no need to provide a pressure member. For this reason, it is possible to achieve further miniaturization and cost reduction. Further, as in this embodiment, the moving member 28 is provided with a pair of cam receiving portions 28a and 28b, and the eccentric cam 30 is brought into contact with one of the cam receiving portions 28a and 28b in the contact state or the separated state. By holding the moving member 28, it is not necessary to separately provide a holding member for holding the moving member 28, and this can also reduce the size and cost.

The embodiment of the present invention has been described above, but the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the present invention.
In the above-described embodiment, the case where the configuration of the present invention is applied to an indirect transfer type transfer apparatus using an intermediate transfer belt has been described as an example. For example, the direct transfer type transfer apparatus shown in FIG. It is also possible to apply a configuration. The transfer device shown in FIG. 6 includes a transport belt 37 that transports the recording medium P carried on the surface. In this configuration, the recording medium P is transported on the transport belt 37 from the right side to the left side of the drawing, and the toner images of the respective colors are directly transferred to the recording medium P when passing through the photoreceptors 2Y, 2C, 2M, 2Bk. The Other configurations and operations are basically the same as those of the above-described indirect transfer method, and thus description thereof is omitted. In the configuration shown in FIG. 6, the center positions of the transfer rollers 11Y, 11C, 11M, and 11Bk are arranged directly below the center positions of the photoconductors 2Y, 2C, 2M, and 2Bk. Such an offset transfer method may be adopted.

  In the above-described embodiment, the belt is brought into contact with and separated from the photosensitive member by moving the transfer roller without moving the photosensitive member. However, the belt is brought into contact with and separated from the belt by moving the photosensitive member. The configuration of the present invention can also be applied to the transfer device configured as described above. That is, the contact member that is brought into contact with and separated from the belt by the contact and separation means may be either a transfer member or a photosensitive member.

  In addition, the configuration of the present invention is not limited to the transfer device that brings some transfer members or photoconductors into contact with or separated from the belt as in the above-described embodiment, and all the transfer members or photoconductors come into contact with the belt. The present invention can also be applied to a transfer device that can be separated or a belt device other than the transfer device. Further, the image forming apparatus equipped with the belt device according to the present invention is not limited to the color laser printer as shown in FIG. 1, but may be other printers, copiers, facsimiles, or complex machines thereof. is there.

2 Photoconductor (image carrier)
7 Transfer device 8 Intermediate transfer belt 11 Primary transfer roller (contact member)
28 moving member 28a cam receiving portion 28b cam receiving portion 29 drive device 30 eccentric cam 31 drive transmission means 32 pressure spring (contact pressure member)
34 Tension spring (separating pressure member)
37 Conveyor belt P Recording medium

Japanese Patent No. 4068038 JP 2008-216969A

Claims (10)

In a belt device comprising a belt, a contact member that contacts the belt, and contact / separation means that contacts and separates the contact member from the belt,
A movable movement between a first position where the contact member is in contact with the belt and a second position where the contact member is separated from the belt. Members,
Driving means for moving the moving member;
A contact pressure member that pressurizes the moving member toward the first position;
A separation pressure member that pressurizes the moving member toward the second position;
The contact pressure member and the separation pressure member increase and decrease with the movement of the moving member. In the contact state, the contact pressure member applies the pressure force on the separation pressure member. A belt device configured to be larger than a pressing force of a contact pressure member, and in the separated state, a pressing force of the contact pressure member is larger than a pressing force of the separation pressure member.   The pressing force of the separation pressure member in the contact state and the pressing force of the contact pressure member in the separation state are set to the same magnitude, and the contact in the contact state The belt device according to claim 1, wherein the pressing force of the pressing member and the pressing force of the separation pressing member in the separated state are set to the same magnitude.   The difference in the applied pressure between the contact pressure member and the separation pressure member becomes maximum in the contact state or the separation state, and becomes zero during the transition between the contact state and the separation state. The belt device according to claim 1 or 2, wherein:   The drive means has a rotatable eccentric cam that contacts a pair of cam receiving portions provided on the moving member. In the contact state, the eccentric cam is one side by the pressure of the separation pressure member. The moving member is held in contact with the cam receiving portion, and in the separated state, the eccentric cam comes into contact with the other cam receiving portion by the pressure of the contact pressing member, and the moving member is The belt device according to any one of claims 1 to 3, wherein the belt device is configured to be held.   The belt apparatus according to any one of claims 1 to 4, wherein the separation pressure member is a tension applying member for applying tension to the belt. In a transfer device for transferring an image formed on an image carrier to a recording medium using a belt device provided with an endless belt that is wound around a plurality of support members and driven to rotate,
6. A transfer device using the belt device according to claim 1 as the belt device. A transfer member facing the image carrier via the belt is provided, and the belt can be brought into contact with and separated from the image carrier by bringing the transfer member into and out of contact with the image carrier. A transfer device,
The transfer device according to claim 6, wherein the transfer member is the contact member.   The transfer device according to claim 6, wherein the belt is an intermediate transfer belt to which an image on the image carrier is transferred.   The transfer device according to claim 6, wherein the belt is a conveyance belt that conveys a recording medium.   An image forming apparatus comprising the transfer device according to claim 6.

Images