JP5286819B2 - Belt unit and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a belt unit and an image forming apparatus including the belt unit.

  In general, image forming apparatuses are classified into a tandem system and a four-rotation system. In the tandem system, an intermediate transfer member or a transfer belt is used for conveying a sheet. The transfer belt generally rotates in response to a rotational force from at least one drive roller that supports the belt. On the other hand, in the four-rotation system, a transfer belt is often used as an intermediate transfer member, and this also uses a number of methods in which a large tension is applied to the belt and the belt is rotated by an included drive roller.

  When performing transfer using this transfer belt, if the alignment between the included rollers is twisted, there is a problem that a so-called deviation occurs in which the transfer moves in a direction perpendicular to the rotation direction. As a means for preventing the deviation of the transfer belt, a method of restricting the deviation by bringing a flange into contact with the end face of the transfer belt is generally used.

  Further, as another means for preventing the deviation, there is one using a steering roller as one of the rollers for stretching the transfer belt (see, for example, Patent Documents 1 and 2). According to this, since the steering roller is provided, when the transfer belt is shifted, the transfer belt can be moved and corrected in the reverse direction by tilting one of the roller shafts by the motor.

JP 2005-292480 A JP 2006-65056 A

  All of the conventional methods described above have problems with belt durability and component costs. In the method in which the flange is brought into contact with the belt end surface, the end of the belt always keeps sliding with the flange, so that the end of the belt is worn and the durability is lowered. In addition, when the belt offset force increases, wear and cracks (breaks) occur at the end of the transfer belt, which may cause unevenness in rotation of the transfer belt and image defects. In order to reduce the deviation force of the belt, it is necessary to manage the difference in the circumferential length and thickness of the belt and the alignment between the rollers with high accuracy. For this reason, the price of parts has increased, which has been an obstacle to cost reduction.

  On the other hand, the method of providing the steering roller requires a sensor for detecting the position of the belt end, a motor for tilting the roller shaft, a controller for controlling the motor based on information detected by the sensor, and the like. For this reason, the number of parts increases, leading to an increase in size and cost of the apparatus.

  The object of the present invention is to solve the above-mentioned problems, and without increasing the number of parts, the belt offset force is reduced with a low-cost configuration, the belt end is cracked, and image defects occur. It is an object of the present invention to provide a hard belt unit and an image forming apparatus including the belt unit.

  In order to achieve the above object, the present invention provides a belt unit having a side plate frame having a fitting groove and a regulating wall for regulating the belt so as not to be shifted to one side, and a boss having a taper on the regulating wall. And the boss rides on the fitting groove of the side plate frame when the belt approaches one side.

  Further, a side plate frame having a belt for transferring a toner image formed on a photosensitive member to a sheet, a large roller, a small roller, a tension roller for suspending the belt, and a fitting groove for supporting the large roller and the small roller. And a belt unit having a regulating wall that is arranged on both sides of the large roller or the small roller and regulates the belt so as not to be shifted to one side, and a tapered boss is provided on the regulating wall, When the transfer belt is close to one side, the boss rides on the fitting groove of the side plate frame.

  Further, the restriction wall is capable of rotating in a thrust radial direction independently of the roller.

  The taper angle γ of the boss is γ> 6 °.

  In addition, the curvature of the corner of the fitting groove of the side plate frame that supports the roller on which the restriction wall is provided is 1 mm or more.

  Further, the restriction wall is made of a resin having slidability.

  The belt unit is a transfer belt unit, and the transfer belt is characterized in that the base material is a resin containing PC, PI, or PTFE.

  The image forming apparatus includes the belt unit.

  According to the present invention, it is possible to provide a belt unit and an image forming apparatus that can reduce the shifting force of the belt by a simple method and have few image defects without increasing the number of parts.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. First, an outline of an electrophotographic apparatus according to the present invention will be described with reference to FIG.

  In FIG. 1, an intermediate transfer device 17 is disposed at the center of the device, and around the intermediate transfer device 17, a photoreceptor 1, a transfer roller 10, and an intermediate transfer device cleaning unit 12 are disposed. A charger 2 is disposed around the photoreceptor 1. Developers 4K, 4Y, 4M, and 4C in which toners that are finely colored powders of four different colors are encapsulated are arranged in a stacked manner, below which are exposure devices 3, and further below that are paper sheets. A paper holding means 8 for storing the paper and a paper supply device 9 are arranged. Above the electrophotographic apparatus, a fixing device 11 and a paper discharge device 18 are arranged.

  In such a configuration, the charger 2 charges the surface of the photoreceptor 1 uniformly. Next, image and character information by a personal computer, an image scanner or the like is exposed in dot units by the exposure device 3 to form an electrostatic latent image on the surface of the photoreceptor 1. Thereafter, the electrostatic latent image is visualized as a toner image by being supplied and developed by any of the developing devices 4K, 4Y, 4M, and 4C, and is conveyed to the intermediate transfer device 17.

  The above process is repeated as many times as necessary by each of the developing devices 4K, 4Y, 4M, and 4C, and a toner image corresponding to image and character information is formed on the surface of the intermediate transfer device 17. Thereafter, the toner image is transferred to the paper supplied from the paper holding means 8 by the paper supply device 9 by the transfer roller 10. The toner remaining in the intermediate transfer device 17 is cleaned by the intermediate transfer device cleaning means 12. The sheet on which the toner image has been transferred is conveyed to the fixing device 11, where the toner image is fixed on the sheet, and is discharged by the sheet discharge device 18.

  Next, an intermediate transfer device that is a belt unit in the electrophotographic apparatus of the present invention will be described with reference to FIGS.

  FIG. 2 is an overall perspective view of the intermediate transfer device 17 according to the present invention. The intermediate transfer device 17 includes a large roller 5, a tension roller 6, a small roller 7, a large roller shaft 30 that supports the large roller, a small roller shaft 31 that supports the small roller, a transfer belt 22, a regulation wall 23, a tension arm 24, It is composed of a tension spring 25. The transfer belt 22 rotates in the direction of arrow C in the figure.

  FIG. 3 is a detailed perspective view of the regulating wall 23 in the present invention, wherein γ indicates the taper angle of the boss 23a, and r indicates the curvature of the boss tip. When the transfer belt 22 shown in FIG. 2 is shifted to one side, the boss 23a comes into contact with the small roller support fitting groove 41 of the side plate frame 32 shown in FIG.

  FIG. 4 is a cross-sectional view of the small roller 7 in the present invention. The small roller 7 is supported by the small roller shaft 31 via a ball bearing 26. The large roller 5 shown in FIG. 2 is supported by the large roller shaft 30 shown in FIG. 2 via a ball bearing 26.

  In FIG. 2, in this embodiment, the transfer belt 22 is made of PC alloy, the thickness is 0.15 mm, the transfer belt 22 has a width of 250 mm, and the transfer belt 22 has a peripheral length of 380 mm. The large roller 5 is made of aluminum and has a diameter of φ = 104.8 mm. The small roller 7 is made of aluminum and has a diameter of φ = 30 mm. The large roller shaft 30, the small roller shaft 31, and the tension arm 24 are supported by a side plate frame 32 shown in FIG. Since the large roller shaft 30 and the small roller shaft 31 support the large roller 5 and the small roller 7 via the ball bearings 26 shown in FIG. 3, they do not rotate with respect to the side plate frame 32 shown in FIG. The tension roller 6 is made of aluminum and has a diameter of φ = 12 mm. The restricting wall 23 is made of polyacetal, the outer diameter of the flange for preventing misalignment of the transfer belt 22 is φ = 33 mm, the base diameter of the boss is φ = 9.0 mm, and the taper angle γ of the boss is 10 °. Yes, the curvature r of the tip of the boss is 1.0 mm. The tension spring 25 is made of SWPB and has a spring constant of 0.7 N / mm.

  Since the intermediate transfer device 17 does not have a driving source and is driven to rotate by receiving the rotational force from the photoconductor 1, a wide nip width of the first transfer portion that is a contact portion with the photoconductor 1 is secured. ing. In order to obtain an optimum operation, it is preferable to secure a nip width of 10 mm or more at the first transfer portion. In this embodiment, the nip width is set to about 24 mm. One of at least two rollers that suspend and support the transfer belt 22 so as to easily secure the nip width has a large radius of curvature and is configured to be suspended by the large roller 5 and the small roller 7. ing. Since the transfer belt 22 that is an intermediate transfer member is driven to rotate by contact with the photoreceptor 1, a tension roller 6 that applies a tension that does not sag the transfer belt 22 is disposed. The tension roller 6 is supported by a tension arm 24, and a load is applied to the tension roller 6 by a tension spring 25 that supports the tension arm 24. Details of the configuration will be described later.

  Next, a method for reducing the deviation of the transfer belt according to the present invention will be described with reference to FIGS.

  First, the small roller shaft twist (hereinafter referred to as the small roller shaft twist) and the belt shift with respect to the large roller shaft will be described with reference to FIG. The large roller support fitting groove 40 of the side plate frame 32 supports the large roller shaft 30. The small roller support fitting groove 41 of the side plate frame 32 supports the small roller shaft 31. An arrow C indicates the rotation direction of the transfer belt 22. HL indicates a distance between the large roller support fitting groove 40 on the side plate frame 32L side and the small roller support fitting groove 41 on the side plate frame 32L side. HR indicates the distance between the large roller support fitting groove 40 on the side plate frame 32R side and the small roller support fitting groove 41 on the side plate frame 32R side. ΔH indicates a difference in height between the left and right grooves of the side plate frame 32 (= HR−HL). In this embodiment, ΔH <0.3 mm.

  ΔT is a small roller shaft twist amount. In a state where the large roller shaft 30 and the small roller shaft 31 are supported by the fitting grooves of the side plate frame 32, ΔT = ΔH.

  When ΔT = ΔH> 0 (HR> HL), when the transfer belt 22 is rotated so as to be driven by the photoreceptor 1, the transfer belt 22 rotates while causing out-of-plane deformation. At this time, a force toward the L side is generated with respect to the transfer belt 22, and the transfer belt 22 moves to the L side. On the other hand, when ΔT = ΔH <0 (HR <HL), a force toward the R side is generated with respect to the transfer belt 22, and the transfer belt 22 moves to the R side.

  FIG. 6 is an enlarged view of a part A in FIG. 5 and shows a state in which the transfer belt 22 is in contact with the regulation wall 23 toward the L side. l indicates a tangent at a contact point between the boss of the regulating wall 23 and the small roller supporting fitting groove 41. β represents an angle formed between the tangent line 1 and the fitting groove surface of the side plate frame. r indicates the curvature of the boss tip of the regulating wall 23. e indicates the curvature of the small roller shaft support fitting groove 41B.

  FIG. 7 is a view showing a state in which the boss 23a of the regulating wall 23 rides on the small roller supporting fitting groove 41. FIG.

  Δε represents an amount by which the boss of the restriction wall 23 rides on the small roller support fitting groove 41 (hereinafter referred to as a boss ride amount). When the boss of the restriction wall 23 rides on the small roller support fitting groove 41, it can be expressed as ΔT = ΔH−Δε.

  In this embodiment, when ΔH> 0, the transfer belt 22 moves to the L side and contacts the regulation wall 23. Thereafter, the regulating wall 23 moves to the L side together with the transfer belt 22 and comes into contact with the small roller supporting fitting groove 41. When F is the force of the transfer belt 22 and F is the frictional force between the boss of the regulating wall 23 and the fitting groove 41 for supporting the small roller, and Fcosβ> M, the regulating wall 23 is fitted for supporting the small roller. Get on the groove 41. As the boss ride amount Δε increases, ΔT decreases and the belt offset force F decreases. The shift of the transfer belt 22 toward the L side is subsided when Fcos β = M.

  FIG. 8 shows the small roller shaft twist amount ΔT and the stress σ (hereinafter referred to as belt end stress) generated at the end of the transfer belt 22 when the end of the transfer belt 22 collides with the regulating wall 23. Showing the relationship.

  σk indicates the allowable stress that the transfer belt 22 can satisfy the specified life. σmax indicates the belt end stress σ when the small roller shaft twist amount ΔT is maximum.

  In this embodiment, | ΔT | <0.3 mm. σmin indicates the stress σ of the transfer belt 22 when Fcosβ = M.

According to this configuration, even when the left-right height difference ΔH occurs in the small roller support fitting groove 41 and the belt end stress σ is equal to or greater than σk, the restriction wall 23 has a tapered boss. The boss of the restriction wall 23 rides on the small roller support fitting groove 41, and when Fcosβ = M and the shift of the transfer belt 22 is cured, σ <σk. Accordingly, it is possible to prevent the transfer belt 22 from being worn or cracked (broken), uneven rotation of the transfer belt, and image defects. Details of the relationship between the end stress σ of the transfer belt 22 and the small roller shaft twist amount ΔT, the boss shape of the restriction wall 23, and the frictional force M between the boss of the restriction wall 23 and the small roller support fitting groove 41 will be described later. To do.
<Relationship between twisting amount of small roller and end stress of transfer belt>
The relationship between the small roller shaft twist amount ΔT and the belt end stress σ will be described with reference to FIG.

  FIG. 8 is a diagram illustrating the relationship between the small roller shaft twist amount ΔT and the belt end stress σ.

  The horizontal axis indicates the small roller shaft twist amount ΔT, and the case where the R side of the small roller shaft is higher than the large roller shaft is + (plus), and the case where the L side is high is − (minus). The vertical axis represents the end stress σ of the transfer belt 22.

In the case of ΔT = 0 [mm], the belt offset force F = 0 [N], and the belt end stress σ = 0 [MPa]. However, when ΔT ≠ 0 [mm], a belt shifting force is generated. For example, when ΔT = 0.06 [mm], the belt end stress σ = 2.1 [MPa]. When ΔT = 0.1 mm or more, the belt end stress σ> belt allowable stress σk = 2.5 [MPa], and the end of the transfer belt 22 is worn or cracked (broken). In addition to unevenness in rotation, image defects may occur.
<Regarding the taper angle of the boss of the restriction wall>
The relationship between the taper angle γ of the boss of the regulating wall 23 and the offset force F of the transfer belt 22 will be described with reference to FIG.

  In the case of the offset force F [N] of the transfer belt 22, when the boss of the restriction wall 23 collides with the small roller support fitting groove 41, a force of Fcosβ [N] acts in the tangential l direction. On the other hand, when the boss of the restriction wall 23 rides on the small roller support fitting groove 41, a frictional force M is generated between the boss of the restriction wall 23 and the small roller support fitting groove 41. When Fcos β> M, the boss of the restriction wall 23 rides on the small roller supporting fitting groove 41.

  In this embodiment, the frictional force M between the boss of the regulating wall 23 and the small roller support fitting groove 41 is 9 [N]. The restriction wall 23 has a boss taper angle γ = 10 [°] and a boss tip curvature r = 1 [mm]. The curvature k of the small roller support fitting groove B is k = 3 [mm]. In this case, the angle β formed by the surface of the small roller support fitting groove 41 and the tangent line 1 at the point where the tip end of the boss of the restriction wall 23 and the small roller support fitting groove 41B contact each other is 40 °. When the belt offset force F> 12.7 [N], the boss of the restriction wall 23 rides on the small roller support fitting groove 41. Further, when the boss of the regulating wall 23 rides on the small roller support fitting groove 41, the belt offset force F decreases, and when the belt offset force F = 12.7 [N], the belt offset is stopped. At that time, ΔT = 0.06 mm.

  When the taper angle γ of the boss of the restriction wall 23 is 6 ° or less, the value of the angle β becomes large, and the force Fcosβ that the boss of the restriction wall 23 tries to ride on the small roller support fitting groove 41 becomes small. . In this case, Fcosβ <M, and the boss of the restriction wall 23 cannot ride over the small roller support fitting groove 41. When ΔT> 0.1 mm, the belt end stress σ> the belt allowable stress σk, and therefore, it becomes impossible to prevent the transfer belt from being worn or cracked (broken), transfer belt rotation unevenness, and image defects.

  If the taper angle γ of the boss of the restriction wall 23 is 6 ° or more, the boss of the restriction wall 23 can be easily ridden and the belt shifting force can be reduced.

From the above, in this embodiment, by setting the angle γ> 6 °, the shift of the transfer belt 22 is reduced, and the transfer belt 22 is worn or cracked (broken), the transfer belt 22 is unevenly rotated, and image defects are generated. It becomes possible to prevent.
<When the intermediate transfer device is driven>
In this embodiment, the intermediate transfer device 17 is driven. However, even when the large roller 5 or the small roller 7 of the intermediate transfer device 17 is driven, by adopting the same configuration, the shifting force of the transfer belt 22 is reduced. In addition, it is possible to prevent the transfer belt 22 from being worn or cracked (broken), the transfer belt 22 from rotating unevenness, and image defects.
<Tandem method>
The color image forming apparatus in this embodiment is a four-rotation system, and the transfer belt 22 is used as an intermediate transfer body. However, in the tandem system, the transfer belt 22 is used for conveying an intermediate transfer body or paper. However, by adopting the same configuration, it is possible to reduce the deviation of the transfer belt 22 and prevent the transfer belt 22 from being worn or cracked (breakage), the rotation unevenness of the transfer belt 22, and the occurrence of image defects. is there.

  Next, a case where the belt unit of the present invention is used in the fixing device as another embodiment will be described with reference to FIGS. Although the regulating wall 23 in the above embodiment is used in the intermediate transfer device 17, even a fixing device using a belt has the same configuration, so that the belt is worn, cracked (broken), and image defects are generated. It is possible to prevent.

  FIG. 9 is a perspective view of the fixing device. The fixing device includes a heating roller 51, a pressure belt 52, a shift regulating wall 53, a pressure frame 54, and a plate 55. FIG. 9 shows the arrangement of the fixing device. Yes. The heating roller 51 is rotatably supported by the plate 55 and is rotated by a gear (not shown). The pressure belt 52 is rotated by the rotational driving force of the heating roller 51.

  The pressure belt 52 is suspended by pressure means, and is in contact with the heating roller 51 with a shaft provided on the plate 55 as a base point by a pressure spring or the like.

  FIG. 10 shows the arrangement of the pressure belt 52, the deviation regulating wall 53 and the pressure frame 54. The offset regulating wall 53 that contacts the end surface of the pressure belt 52 has a substantially cylindrical guide portion that guides the inner surface of the pressure belt 52 on one end surface, and a boss K on the other end surface. It is the structure supported by this fitting groove J.

  FIG. 11 shows the arrangement of the boss K, the pressure belt 52, the pressure frame 54, and the plate 55 of the shift regulating wall 53. The pressure belt 52 moves in the direction of arrow G due to the distortion of the plate 55. It is shown that.

  FIG. 12 shows a state where the boss K of the shift regulating wall 53 rides on the fitting groove J of the pressure frame 54 due to the belt shift force of the pressure belt 52. Thereby, it is possible to reduce the belt offset force of the pressure belt 52 due to the distortion of the plate 55.

  As described above, in the fixing device, the pressure frame is configured as the side plate frame, thereby reducing the belt shifting force of the pressure belt 52, wear and cracking (breaking) of the pressure belt 52, and the pressure belt 52. It is possible to prevent paper wrinkles that occur due to the movement in the thrust direction, paper jams that are likely to occur due to wear or cracking (breaking) of the pressure belt 52, and the like.

  According to the present invention, it is possible to provide a high-quality image forming apparatus that can regulate a belt shift, can be configured at a low price without increasing the number of components of an intermediate transfer device and a fixing device, and has no image unevenness.

1 is a schematic cross-sectional view of an image forming apparatus according to the present invention. 1 is a perspective view of an intermediate transfer device according to the present invention. It is a perspective view of the control wall in this invention. It is sectional drawing of the small roller in this invention. It is explanatory drawing which shows arrangement | positioning of the fitting groove | channel of each roller and side plate frame in this invention. It is a figure which shows arrangement | positioning of the boss | hub of a control wall, and a side-plate frame fitting groove | channel. It is a figure which shows the state which the boss | hub of the control wall got on the fitting groove of the side plate frame. It is a figure which shows the relationship between a small roller shaft twist amount and a belt edge part stress. It is a perspective view of the fixing device in the present invention. It is a figure which shows arrangement | positioning of the pressurization belt in this invention, a shift | offset | difference regulation wall, and a pressurization flame | frame. It is a figure which shows arrangement | positioning of the boss | hub of a deviation control wall, a pressure belt, a pressure frame, and a board. It is a figure which shows the state which the boss | hub of the deviation control wall got on the fitting groove of the pressurization frame.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging device 3 Exposure apparatus 4 Developer 5 Large roller 6 Tension roller 7 Small roller 8 Paper holding means 9 Paper supply device 10 Transfer roller 11 Fixing device 12 Intermediate transfer device Cleaning means 17 Intermediate transfer device 18 Paper discharge device 22 Transfer belt 23 Restriction wall 24 Tension arm 25 Tension spring 26 Ball bearing 30 Large roller shaft 31 Small roller shaft 32 Side plate frame 40 Side plate frame large roller support fitting groove 41 Side plate frame small roller support fitting groove 51 Heating roller 52 Pressure belt 53 Shift regulating wall 54 Pressure frame 55 Plate

Claims (7)

A side plate frame having a fitting groove, in a belt unit having a regulating wall for regulating for the belt is prevented depend piece, together with the regulating wall is provided at the end of the roller for suspending the belt, a tapered having a boss, the roller is supported on a shaft, said shaft being supported in a fitting groove of the side frames through the boss, when the belt went displaced in one, the belt is the regulation The belt unit is characterized in that the regulating wall moves in contact with a wall, the boss rides on the fitting groove of the side plate frame, and the roller is tilted in a direction to eliminate the shifting force of the belt. 2. The belt unit according to claim 1, wherein a taper angle [gamma] of the boss is [gamma]> 6 [deg .]. 3. The belt unit according to claim 1, wherein a corner curvature of the fitting groove of the side plate frame that supports the roller on which the restriction wall is provided is 1 mm or more . 4. The belt unit according to any one of claims 1 to 3, wherein the restriction wall is made of a sliding material.
A belt unit characterized by being a resin having mobility . The belt unit according to any one of claims 1 to 4, wherein the belt unit is
A transfer belt unit, wherein the substrate includes PC, PI, or PTFE.
Belt unit, which is a non-resin. In a belt unit having a frame having a fitting groove and a regulating wall for regulating the belt so as not to be displaced , the regulating wall is provided at an end portion of a roller for suspending the belt, and the belt is provided at one end surface. A substantially cylindrical guide portion for guiding an inner surface; a boss having a taper on the other end surface; and the boss is supported by a fitting groove of the frame; The belt unit is configured to move in contact with the restriction wall, the boss moves onto the fitting groove of the frame, and the roller is tilted in a direction to cancel the shifting force of the belt. An image forming apparatus comprising the belt unit according to claim 1.

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