JP2009300965A - Belt driving device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a belt driving device and an image forming apparatus capable of reducing the relative difference of the belt winding angle of the steering roller within the range of adjusting the inclination of the steering roller and accurately controlling the belt shift of the endless belt.
A distance between the centers of a roller from a steering roller to a first suspension roller disposed immediately upstream of the steering roller and a distance from the steering roller to a second suspension roller disposed immediately downstream of the steering roller. Each roller was disposed so that the ratio of the other when the short one of the two as a reference was 1.2 or less, and the amount of tilt of the steering roller was changed at equal intervals. The endless belt wrapping angle of the steering roller, which changes according to the tilt amount of the steering roller, is set so that the relative difference is within 1% within the adjustment range.
[Selection] Figure 2

Description

  The present invention relates to a belt driving device and an image forming apparatus, and more particularly, to a belt driving device including a belt shift control unit that performs endless belt shift control, and an image forming apparatus including the belt drive device.

  2. Description of the Related Art Conventionally, as an image forming apparatus such as a copying machine or a printer, an apparatus using an endless belt, an intermediate transfer belt, a photosensitive belt, or a transfer conveyance belt is known. These endless belts are biased or meandered in a direction orthogonal to the moving direction (rotating direction) due to the rotation thereof. When such a belt shift phenomenon of an endless belt occurs, for example, in an image forming apparatus that transfers an image on a photosensitive drum onto a recording sheet using an intermediate transfer belt, the position of the toner image on the photosensitive drum is an intermediate transfer. The belt meanders and shifts on the recording paper, causing deterioration in image position accuracy. For this reason, in a belt driving device having such an endless belt, particularly in an image forming apparatus that transfers an image onto the belt as described above, it is necessary to appropriately control the bias and meandering of the endless belt.

  There are several methods for controlling the belt shift of such an endless belt. One of the methods is to adjust the inclination of one of a plurality of stretching rollers that stretch the endless belt, and A method for controlling the belt end of an endless belt is known. This method is applied to the endless belt as compared with a method for forcibly eliminating the belt end of the endless belt, such as providing a rib on the belt edge of the endless belt or guiding the belt edge. There are advantages that the strength is weak and the durability and reliability of the belt is high.

  By the way, as a specific method for controlling the belt shift of the endless belt as described above, conventionally, as described in Patent Document 1, for example, the belt edge shape of the endless belt is stored, and this belt edge is stored. There is a method in which the shape and the detection result of the belt position of the endless belt are compared, and the inclination of the steering roller of the endless belt is changed from the difference to control the belt shift.

Further, as shown in Patent Document 2, there is a method of adjusting and controlling the amount of inclination of the steering roller in proportion to the amount of change in the belt edge position.
JP-A-11-295948 JP 2002-287527 A

  However, any of these methods has the following problems.

  The belt slip speed or slip sensitivity depends on the tilt amount of the steering roller and the belt winding angle on the steering roller, but the belt winding angle does not become constant when the steering roller tilt amount is changed at equal intervals. A problem arises, and the belt shift speed differs by an arbitrary amount of tilt, and high-precision control cannot be performed.

  In particular, the above-described problem is likely to be manifested in a configuration in which adjustment control is performed on the premise of proportional control.

  Depending on the roller arrangement described above, the difference in belt shift speed between the front and back is particularly large, and when mounted on a highly productive image forming device that rotates the belt at a high speed, the belt position due to the difference in front and back response. Deviation appears prominently.

  Even if the home position of the steering roller tilt is detected and the cam shape is devised so that the belt wrap angle is the same at an arbitrary tilt from the initial roller arrangement, the steering stop position is not always the same, so continuous control The accuracy of is reduced.

  The present invention has been made in view of the above problems, and the object of the present invention is to reduce the relative difference of the belt winding angle of the steering roller within the steering roller tilt adjustment range, and to reduce the belt shift of the endless belt. It is an object to provide a belt driving device and an image forming apparatus that can be controlled with high accuracy.

In order to achieve the above-mentioned object, the invention of claim 1 comprises an endless belt suspended between a plurality of rollers and moved by a predetermined driving source, and the plurality of rollers are constituted by three or more.
At least one steering roller arranged to be adjustable in alignment;
A first suspension roller disposed immediately upstream of the steering roller with respect to the belt movement direction of the endless belt, and a second suspension roller disposed immediately downstream of the steering roller with respect to the belt movement direction of the endless belt. Belt position detecting means for detecting the belt position of the endless belt in the direction perpendicular to the belt moving direction, and the inclination of the steering roller is within a predetermined range based on the belt position detected by the belt position detecting means. In the belt drive device for controlling the belt shift of the endless belt by adjusting the endless belt, the endless belt of the steering roller that changes according to the amount of tilt of the steering roller when the amount of tilt of the steering roller is changed at equal intervals Make sure that the winding angle is within 1% of the adjustment range. The suspension roller and the second suspension roller are arranged.

  In this belt driving device, even when the steering roller inclination amount is adjusted and controlled in proportion to the belt position fluctuation amount, the belt winding angle of the steering roller is within 1% within the adjustment range. Since the first suspension roller and the second suspension roller are arranged so that the belt end of the endless belt is accurately controlled.

  According to a second aspect of the present invention, the distance between the rollers from the steering roller to the first suspension roller disposed immediately upstream of the steering roller, and the second suspension disposed from the steering roller immediately downstream of the steering roller. Each roller is arranged such that the relationship between the distance to the center of the roller and the distance between the rollers is 1.2 or less when the shorter one of the two is used as a reference.

  In this belt drive device, the ratio of the inter-roller distance that greatly affects the difference in winding angle generated when the angle of the steering roller is swung is set to 1.2 or less so that it is not easily affected by other restrictions and has a simple configuration. Within 1% can be realized. As a result, for example, the degree of freedom of design such as the rotation center arrangement of the steering roller is increased, and the belt shift is accurately controlled with a compact configuration.

  According to a third aspect of the present invention, in the image forming apparatus provided with the belt driving device for driving the endless belt, the belt driving device according to the first or second aspect is used as the belt driving device. is there.

  In this image forming apparatus, since the belt driving device according to claim 1 or 2 is used as the belt driving device, it is possible to form an image with good image quality.

  As described above, in the present invention, the steering roller 32 that is highly sensitive to changes in the winding angle so that the winding angle of the intermediate transfer belt 31 is within 1% regardless of the amount of inclination of the steering roller 32 within the steering adjustment movable range. The distance from the first roller 38 to the second roller 39 is arranged within a certain ratio. Therefore, the shifting speed at the time of switching between the front side and the back side can be kept constant, and the side shift can be controlled with high accuracy.

  Further, the next shift control can be stably restarted irrespective of the stop state at the end of the control such as the stop position of the intermediate transfer belt 31 and the stop angle of the steering roller 32.

  Further, it is not necessary to perform control such as differentiation and integration for reducing an error caused by the winding angle difference using a complicated arithmetic processing circuit, and the belt shift amount can be proportionally controlled with a simple configuration.

  Next, details of the present invention will be described in accordance with the description of the embodiments.

  The image forming apparatus of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of a main part of an image forming apparatus. The illustrated image forming apparatus is a color image forming apparatus in which a plurality of image forming units are arranged in parallel. The illustrated color image forming apparatus is provided with an image output unit 1P. The image output unit 1P is roughly divided into an image forming unit 10 (four stations a, b, c, and d arranged in parallel. The configuration is the same), and includes a feeding unit 20, an intermediate transfer unit 30, and a fixing unit 40.

  Here, each unit will be described in detail. In the image forming unit 10, photosensitive drums 11a, 11b, 11c, and 11d as image carriers that are rotationally driven in the direction of the arrow shown in the drawing are pivotally supported at the center and face the outer peripheral surfaces of the photosensitive drums 11a to 11d. The primary charger 12 (12a, 12b, 12c, 12d), the optical system 13 (13a, 13b, 13c, 13d), and the developing device 14 (14a, 14b, 14c, 14d) are arranged in the rotation direction. .

  Then, the primary chargers 12a to 12d give a uniform charge amount to the surfaces of the photosensitive drums 11a to 11d, and then sensitize light beams such as laser beams modulated by the optical systems 13a to 13d according to the recording image signal. The photosensitive drums 11a to 11d are exposed to form electrostatic latent images on the photosensitive drums 11a to 11d. Then, each electrostatic latent image is visualized as a toner image by developing devices 14a to 14d each containing developer (toner) of four colors of yellow, cyan, magenta, and black. The photosensitive drums 11a to 11d are not transferred to the recording material P on the downstream side of the image primary transfer areas Ta, Tb, Tc and Td where the visualized toner image is transferred to the intermediate transfer belt 31 as a belt member. The remaining toner is scraped off by the cleaning device 15 (15a, 15b, 15c, 15d), and the surfaces of the photosensitive drums 11a to 11d are cleaned. Through the above-described process, image formation with each toner is sequentially performed.

  On the other hand, the feeding unit 20 is a pickup for feeding the recording material P one by one from the cassette 21 (21a, 21b) and the manual feed tray 27 for storing the recording material P, the cassette 21a, 21b, or the manual feed tray 27. Rollers 22a, 22b, 26, a pair of feeding rollers 23 and a feeding guide 24 for feeding the recording material P fed from the pickup rollers 22a, 22b, 26 to the registration rollers 25a, 25b. It is composed of registration rollers 25a and 25b for sending the recording material P to the secondary transfer region Te in accordance with the image formation timing.

  The intermediate transfer unit 30 includes an intermediate transfer belt 31 as an intermediate transfer member. The intermediate transfer belt 31 includes a driving roller 33 that transmits a driving force to the intermediate transfer belt 31, and a belt traveling direction to the intermediate transfer belt 31. Steering roller 32 that swings in order to apply a shifting force in the orthogonal direction, a secondary transfer inner roller 34 that faces the secondary transfer region Te across the intermediate transfer belt 31, and a steering in the conveyance direction (arrow direction). A first roller 38 provided upstream of the roller 32 and restricts the height of the primary transfer region Td, and provided downstream of the steering roller 32 in the transport direction (arrow direction) and restricts the height of the entrance of the secondary transfer region Te. The second roller 39 is wound around. The steering roller 32 is pivotally fixed by a pivot arm 61 about a support shaft 37, and a cam follower 62 is connected to the other end of the pivot arm 61. A steering cam 63 attached to the outer peripheral surface of the cam follower 62 so as to be able to control the rotation angle by the pulse motor 64 is in contact with the steering roller. The amount of inclination of 32 is variable.

  As the material of the intermediate transfer belt 31, for example, PET (polyethylene terephthalate), PVdF (polyvinylidene fluoride), or the like is selected.

  A primary transfer plane A is formed between the drive roller 33 and the first roller 38. The drive roller 33 is formed by coating the surface of a metal roller with rubber (urethane or chloroprene) having a thickness of several millimeters. And slip. The drive roller 33 is rotationally driven by a pulse motor (not shown).

  Primary transfer devices 35 a to 35 d as primary transfer means are disposed behind the intermediate transfer belt 31 in the primary transfer regions Ta to Td where the photosensitive drums 11 a to 11 d and the intermediate transfer belt 31 face each other. A secondary transfer device 36 is arranged to face the secondary transfer inner roller 34 to form a secondary transfer region Te.

  A cleaning device 50 for cleaning the image forming surface of the intermediate transfer belt 31 is disposed downstream of the secondary transfer region Te on the intermediate transfer belt 31, and the cleaning device 50 removes the cleaner blade 51 and waste toner. The waste toner box 52 is housed. As the material of the cleaner blade 51, polyurethane rubber or the like is used.

  The fixing unit 40 includes a fixing roller 41a having a heat source such as a halogen heater therein, a pressure roller 41b to which pressure is applied to the fixing roller 41a (the pressure roller 41b may also have a heat source), a fixing roller A conveyance guide 43 for guiding the recording material P to the nip portion between 41a and the pressure roller 41b, a fixing roller 41a, an inner discharge roller 44 for further guiding the recording material P discharged from the pressure roller 41b to the outside of the apparatus, It consists of an outer discharge roller 45 and the like.

  Next, a characteristic configuration of the present embodiment will be described. 2 to 4 are views showing angles at which the intermediate transfer belt 31 is wound around the steering roller 32 when the steering roller 32 is rotated within the steering adjustment movable range.

  The angle at which the intermediate transfer belt 31 is wound around the steering roller 32 is determined by the arrangement of the movable steering roller 32 and the first roller 38 fixedly arranged upstream of the steering roller 32 with respect to the conveying direction of the intermediate transfer belt 31. It is determined by the relationship with the second roller 39 fixedly arranged downstream.

  FIG. 2 is a schematic diagram when the turning arm 61 is at the center of the steering adjustment movable range, and the steering angle at this time is indicated by α. In this initial state, in this embodiment, the inter-axis distance x between the steering roller 32 and the first roller 38 is set to 60 mm, and the inter-axis distance y between the steering roller 32 and the second roller 39 is set to 50 mm. The inter-axis distance y is shorter than the inter-axis distance x, and the relationship is x / y = 1.2.

  FIG. 3 is a diagram when the alignment of the steering roller 32 is controlled to the lowest limit of the steering adjustment movable range. The steering angle at this time is indicated by Β, and the relative difference from the steering angle α in the initial state is 0.5% or less.

  FIG. 4 is a view when the alignment of the steering roller 32 is controlled to the upper limit of the steering adjustment movable range. The steering wrap angle at this time is indicated by γ, and the relative difference from the steering wrap angle α in the initial state described above is 0.5% or less, and the steering wrap angle 制 御 when controlled to the lowest limit of the steering adjustment movable range Β The relative difference is 1% or less.

  Therefore, when the tilt amount of the steering roller 32 is changed at equal intervals at any position in the steering adjustment movable range, the winding angle of the intermediate transfer belt 31 that changes according to the tilt amount of the steering roller 32 is 1% or less. Arranged to fit.

  A belt edge sensor 92 serving as a detecting unit including a light emitting unit and a light receiving unit is provided on the back side of the primary transfer plane that receives the transfer from the photosensitive drum 11 in the drawing. FIG. 5 is a top view for explaining the operation of the belt edge sensor 92. The light receiving portion 91 is provided with a slit 91a. A predetermined voltage is output by detecting the amount of light that has passed through the slit 91a out of the light emitted by the light emitting unit 90 (not shown).

FIG. 6A is a diagram showing the relationship between the position shift amount of the edge portion 31 a of the intermediate transfer belt 31 and the output voltage of the belt edge sensor 92. Now, considering the case where the edge portion 31a is moved to X ₁ by shifting from the predetermined position X _0, the amount of the edge portion 31a blocks the slit 91a is reduced, so that the amount of light detected by the light receiving unit 91 is increased To do. At this time, the voltage V ₁ is output from the belt edge sensor 92. Based on the information of the output voltage V _1, the number of drive pulses of the pulse motor 64 is determined by the control device 70 shown in FIG.

FIG. 6B shows the relationship between the output voltage of the belt edge sensor 92 and the number of drive pulses of the pulse motor 64. When the voltage V ₁ is output from the belt edge sensor 92, the control device 70 determines P ₁ as the number of driving pulses of the pulse motor 64. The drive pulse signal P ₁ is sent to the pulse motor 64, and the pulse motor 64 rotates in a predetermined direction by the number of pulses P ₁ . Along with this, the cam follower 62 is pushed down following the profile of the steering cam 63, and the turning arm 61 is turned around the support shaft 37, thereby raising the steering roller 32. As a result, the alignment on the front side of the steering roller 32 shifts upward, and the intermediate transfer belt 31 that has been moved forward moves in the direction toward the back at a shift direction and a shift speed corresponding to a predetermined number of pulses. . Thus, the intermediate transfer belt 31 is returned to the predetermined position X _0.

1 is a cross-sectional view of a main part of an image forming apparatus. It is a schematic diagram showing a steering wrap angle when the steering position is at the center of the adjustable movable range. It is a schematic diagram showing a steering wrap angle when the steering position is at the lowest limit of the adjustable movable range. It is a schematic diagram showing a steering wrap angle when the steering position is at the upper limit of the adjustable movable range. It is a top view explaining the effect | action of a belt edge sensor. FIG. 4A is a diagram illustrating a relationship between a position shift amount of an edge portion of an intermediate transfer belt and an output voltage of a belt edge sensor. (B) It is a figure which shows the relationship between the output voltage of a belt edge sensor, and the number of drive pulses of a steering motor. It is a flowchart explaining steering control.

Explanation of symbols

A Primary transfer plane P Recording material Ta to Td Image primary transfer area Te Secondary transfer area 1P Image output section 10 Image forming section 11 Photosensitive drum 12 Primary charger 13 Optical system 14 Developing device 15 Cleaning device 20 Feeding unit 21 Cassette 22a Pickup roller 22b Pickup roller 23 Feed roller pair 24 Feed guide 25a Registration roller 25b Registration roller 26 Pickup roller 27 Manual feed tray 30 Intermediate transfer unit 31 Intermediate transfer belt 31a Edge portion 32 Steering roller 33 Drive roller 34 Secondary transfer inner roller 35 Primary transfer device 36 Secondary transfer device 37 Support shaft 38 First roller 39 Second roller 40 Fixing unit 41a Fixing roller 41b Pressure roller 43 Transport guide 44 Inner discharge roller 45 Outer discharge Over La 50 cleaning device 51 cleaning blade 52 a waste toner box 60 side plate 61 pivot arm 62 the cam follower 63 steering cam 64 pulse motor 70 control board 90 light emitting portion 91 light receiving portion 91a slit 92 belt edge sensor

Claims (3)

An endless belt suspended between a plurality of rollers and moved by a predetermined drive source;
The plurality of rollers are composed of three or more,
At least one steering roller arranged to be adjustable in alignment;
A first suspension roller disposed immediately upstream of the steering roller with respect to the belt movement direction of the endless belt;
A second suspension roller disposed immediately downstream of the steering roller with respect to the belt movement direction of the endless belt,
Belt position detecting means for detecting the belt position of the endless belt in a direction perpendicular to the belt moving direction, and adjusting the tilt of the steering roller within a predetermined range based on the belt position detected by the belt position detecting means In the belt drive device for controlling the belt shift of the endless belt,
When the tilt amount of the steering roller is changed at equal intervals, the steering roller endless belt wrapping angle that changes according to the tilt amount of the steering roller is within 1% of the relative difference within the adjustment range. And a first suspension roller and a second suspension roller.   Roller center distance from the steering roller to the first suspension roller disposed immediately upstream of the steering roller, and roller center distance from the steering roller to the second suspension roller disposed immediately downstream of the steering roller 2. The belt driving device according to claim 1, wherein each of the rollers is arranged so that a ratio of the other of the two is 1.2 or less when the shorter one is used as a reference.   3. An image forming apparatus comprising a belt driving device for driving an endless belt, wherein the belt driving device according to claim 1 is used as the belt driving device.

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