JP4844217B2 - Image forming apparatus and transfer unit - Google Patents

Description

  The present invention relates to an image forming apparatus using an electrophotographic system such as a copying machine, a printer, a facsimile machine, and a multifunction machine of these, and a transfer unit used in the image forming apparatus.

  In an image forming apparatus such as a copying machine or a printer to which an electrophotographic system is applied, for example, an electrostatic latent image formed on a photosensitive drum is developed by a developing device (developing device) using a developer, and is then exposed to light. A toner image is formed on the photosensitive drum, and the toner image formed on the photosensitive drum is transferred and fixed onto a recording medium conveyed from the paper feeding unit, thereby forming an image. Yes. Such an image forming apparatus includes, for example, an endless intermediate transfer belt, a belt conveyance device such as a photosensitive belt or a paper conveyance belt. More specifically, some tandem-type color image forming apparatuses each having an image forming unit corresponding to each color of yellow, magenta, cyan, and black include an intermediate transfer belt.

  In general, in a belt drive device that supports an endless belt with a predetermined number of rolls and travels the endless belt using one of the rolls as a driving roll, the traveling endless belt moves in the width direction (direction perpendicular to the belt traveling direction). A so-called belt walk (meandering belt) occurs. Such a belt walk phenomenon causes a relative positional shift of the images of the respective colors when the images of the respective colors are transferred onto the intermediate transfer belt in the tandem type color image forming apparatus described above. That is, it causes color misregistration and color unevenness of the image. Therefore, in order to obtain a high-quality output image, it is necessary to suppress the belt walk. Various proposals have been made as a configuration for suppressing such a belt walk (see, for example, Patent Document 1).

  This patent document 1 has an object of providing an image forming apparatus capable of obtaining a high-quality image by absorbing a belt shift or distortion. Then, as a configuration for achieving this object, a shift guide is disposed at the position of one side end of at least one roller in a region that does not affect the application band of the toner image of the intermediate transfer belt, and the shift guide is It is disclosed to provide a shift guide restricting member that is sandwiched and pressed between rollers.

JP-A-5-333707

  However, in the configuration disclosed in Patent Document 1, since the shift guide is always sandwiched between the shift guide restricting member and the roller, a force in a direction perpendicular to the belt surface of the intermediate transfer belt is likely to be generated. There is a problem that the transfer belt is easily dropped from the roller. When the direction of the belt walk is on the roller side, there is a concern that the shift guide will ride on the roller, which may cause damage to the intermediate transfer belt due to excessive stress.

The present invention has been made to solve the technical problems as described above, and an object of the present invention is to make it possible to reduce the stress applied to the belt accompanying the belt walk.
Another object is to make it possible to suppress the amount of displacement of the belt accompanying the belt walk.

For this purpose, an image forming apparatus to which the present invention is applied is provided with a belt-like member configured to be capable of circulating movement, a plurality of stretch members that stretch the belt-like member, and the belt-like member. and rib members but extending in a direction circularly moved, is disposed adjacent to at least one of the plurality of stretching members, movably configured in the width direction of the belt-shaped member, a guide member for guiding the rib member, the guide member A first elastic member that is positioned between the belt member and the tension member adjacent to the guide member and elastically biases the guide member in a direction away from the tension member in the width direction of the belt-shaped member; And a second elastic member that is positioned between the guide member and elastically biases the guide member in a direction that comes into contact with the image forming apparatus main body and approaches the stretching member in the width direction of the belt-like member .

From another point of view, the transfer unit to which the present invention is applied is provided with a transfer belt that can be circulated, a plurality of rolls that stretch the transfer belt, and the transfer belt. A rib member extending in the moving direction and a pulley arranged adjacent to at least one of the plurality of rolls, configured to be movable in the width direction of the transfer belt , and having a flange portion formed at both ends for guiding the rib member A guide member having a shape, a first elastic member positioned between the guide member and a roll adjacent to the guide member, and elastically biasing the guide member in a direction away from the roll in the width direction of the transfer belt; those containing positioned between the unit body and the guide member, a second elastic member elastically urging the guide member toward the width direction of the roll of the transfer belt in contact with the transfer unit body, a That.

Draft inner member may be characterized in that Ru pulley shape der the flange portion formed at both ends.

  According to the present invention, it is possible to reduce the stress applied to the belt along with the belt walk.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram showing an image forming apparatus according to the present embodiment.
The image forming apparatus 10 shown in FIG. 1 is a so-called tandem type in which four color process cartridges (image forming units, drum cartridges) 11a, 11b, 11c, and 11d are sequentially arranged in a vertical direction in a main body 10a. In addition, a conveyance path 12 through which a sheet (recording medium) P is conveyed from a substantially vertical lower side to an upper side is disposed at a corresponding position in each of the process cartridges 11a to 11d. Further, a paper feed cassette 13 for storing the paper P that is transported through the transport path 12 and to which the toner images are sequentially transferred is disposed further below (upstream) of the lowermost (uppermost) process cartridge 11a. Has been. In addition, due to the size of the paper P stored in the paper feed cassette 13, a part of the paper feed cassette 13 protrudes to the back side (rear side, in side) of the main body 10a. If it is a small size, it does not protrude from the main body 10a.

  The process cartridges 11 a to 11 d form toner images for yellow (Y), magenta (M), cyan (C), and black (K) in order from the upstream side of the conveyance path 12. Each of the process cartridges 11a to 11d is a cartridge in which a photosensitive drum (image holding member) 14 and various electrophotographic devices sequentially arranged around the photosensitive drum 14 are integrally formed. It is. The device includes a charging roller that precharges the photosensitive drum 14, a developing device that develops the electrostatic latent image formed on the photosensitive drum 14 charged by the charging roller with each corresponding toner, and And a cleaning device that removes waste toner on the photosensitive drum 14.

  An exposure device (ROS) 15 common to the process cartridges 11a to 11d is disposed on the opposite side of the transport path 12 of the process cartridges 11a to 11d. The exposure device 15 drives and drives four semiconductor lasers (not shown) based on image data corresponding to each color. The light from the four semiconductor lasers is deflected and scanned by a polygon mirror (not shown) and guided to an exposure point on the photosensitive drum 14 through an fθ lens (not shown) and a plurality of reflection mirrors, thereby the photosensitive drum 14. It is configured to draw a light image on top.

  A transport belt (band member, transfer belt) 16 that circulates and moves along the transport path 12 is disposed at a position corresponding to each photosensitive drum 14 of the process cartridges 11a to 11d. The transport belt 16 is made of a belt material capable of electrostatically adsorbing the paper P, and is stretched around a pair of driven rollers (stretching members) 17A and driving rollers (stretching members) 17B. Further, an adsorption roller 18 for electrostatically adsorbing the paper P to the conveyance belt 16 is disposed in the conveyance path 12.

  A transfer roller 19 is disposed on the back side of the conveyance belt 16 corresponding to each photosensitive drum 14 of the process cartridges 11a to 11d. The transfer roller 19 is for transferring the toner image formed on the photosensitive drum 14 onto the paper P by bringing the photosensitive drum 14 and the paper P on the transport belt 16 into close contact with each other.

  A fixing device 20 is provided in the conveyance path 12 further above (downstream side) of the uppermost (most downstream) process cartridge 11d. On the upper part of the main body 10a, a paper discharge unit 21 is provided integrally with the main body 10a for storing the paper P discharged after the toner image is fixed by the fixing device 20. The main body 10 a is provided with a reversing conveyance path 22 for reversing the paper P, one side of which has been fixed by the fixing device 20, and sending it again to the conveyance path 12.

FIG. 2 is a diagram for explaining the manual feed tray 23.
As shown in FIG. 2, the main body 10a of the image forming apparatus 10 is provided with a manual feed tray 23 that is rotatable about a rotation fulcrum J provided at the lower end. That is, the manual feed tray 23 is configured to be openable and closable on the front side (front side and out side). When the manual feed tray 23 is rotated in the opening direction, a desired paper P can be set in an insertion window (not shown). As described above, the image forming apparatus 10 is configured to feed paper P other than the paper P stored in the paper feed cassette 13 from the manual feed tray 23.

  Here, in a state where the paper P on which the toner image is to be transferred is set, either one of the paper P in the paper feed cassette 13 and the paper P in the manual feed tray 23 is instructed by a user to a control device (not shown). Are sent at a predetermined timing. The sent paper P is transported to the transport path 12 via a plurality of transport rollers 24 and sent to the transfer positions of the process cartridges 11 a to 11 d via the transport belt 16.

FIG. 3 is a view for explaining the front cover 25.
As shown in FIG. 3, the main body 10a of the image forming apparatus 10 is provided with a front cover 25 that is rotatable about a rotation fulcrum J provided at the lower end. The front cover 25 functions as an external cover together with the main body 10a in the closed state. That is, the front cover 25 constitutes a side wall portion on the upper side of the paper feed cassette 13 and on the front side of the image forming apparatus 10.

  A transport belt 16, a driven roller 17 </ b> A, a driving roller 17 </ b> B, a suction roller 18, a transfer roller 19, and a reverse transport path 22 are attached to the front cover 25. Therefore, when the front cover 25 is opened, these components are accompanied and separated from the main body 10a side. Therefore, the process cartridges 11a to 11d are exposed by opening the front cover 25, and the user can easily access the transport path 12.

  Here, each of the process cartridges 11a to 11d is detachably attached to the main body 10a in a substantially horizontal direction. Therefore, the process cartridges 11a to 11d can be attached and detached by opening the front cover 25 of the main body 10a. A set detection sensor (not shown) detects the set state of each of the process cartridges 11a to 11d and outputs the detection result to a control device (not shown).

  Thus, by opening the front cover 25, the process cartridges 11a to 11d can be exposed and replaced. Further, it is possible to deal with a paper jam (jam clear) with the photosensitive drum 14 exposed. Thus, the maintainability of the image forming apparatus 10 is improved.

FIG. 4 is a view for explaining a pulled-out state of the paper feed cassette 13.
The paper feed cassette 13 is accommodated in a cassette accommodating portion 26 provided in the main body 10a, and is configured to be drawable from the front side of the main body 10a. More specifically, the paper feed cassette 13 can be pulled out and inserted into the cassette housing portion 26 with the manual feed tray 23 and the front cover 25 closed.
The paper feed cassette 13 is provided with an insertion window in which the paper P for the manual feed tray 23 is set. Further, the paper feed cassette 13 is provided with a part of a plurality of transport rollers 24 for transporting the paper P on the manual feed tray 23. Thus, the paper feed cassette 13 is formed with a delivery path through which the paper P set in the insertion window is delivered to the transport path 12.

[First Embodiment]
FIG. 5 is a perspective view for explaining the transfer unit 30 according to the first embodiment. The transfer unit 30 referred to here includes the above-described conveyance belt 16, a driven roller 17 </ b> A stretched below the conveyance belt 16, and a drive that stretches above the conveyance belt 16 and drives the conveyance belt 16. A driving roller 17B as a unit, a suction roller 18 (see FIGS. 1 to 4), and a transfer roller 19 (see FIGS. 1 to 4) are integrally configured. The transfer unit 30 is replaced during maintenance or maintenance, and is handled separately from the image forming apparatus. In FIG. 5, the suction roller 18 and the transfer roller 19 are not shown.
As shown in FIG. 5, the conveying belt 16 constituting a part of the transfer unit 30 is formed with a single rib (rib member) 31 along the moving direction of the conveying belt 16 near the one end 16 a. Yes. The rib 31 is affixed to the inner peripheral surface of the transport belt 16 in an endless manner.

  Further, the angle of the driven roller 17A with respect to the conveyor belt 16 is set so that the conveyor belt 16 moves in the direction of the arrow X. In other words, the conveyor belt 16 is configured so as not to endlessly walk in the direction opposite to the direction of the arrow X. Note that, instead of setting the angle of the driven roller 17A with respect to the conveyance belt 16, it is also conceivable that the angle of the driving roller 17B with respect to the conveyance belt 16 is set.

FIG. 6 is a cross-sectional view for explaining the periphery of the end of the driving roller 17B in the transfer unit 30. FIG.
As shown in FIG. 6, the transfer unit 30 includes a guide member (guide member) 32 for guiding the rib 31 of the transport belt 16. The guide member 32 has flange portions 32a at both ends. In other words, the guide member 32 is formed such that the intermediate portion 32b has a smaller diameter than both ends. As described above, the guide belt 32 formed in the pulley shape guides the transport belt 16 in the circulating movement state via the ribs 31 located in the intermediate portion 32b, thereby restricting the belt walk.

  The guide member 32 is disposed adjacent to one end of the drive roller 17B. In other words, the guide member 32 is disposed on the shaft portion 17 </ b> C on the side where the rib 31 of the transport belt 16 is located. More specifically, the guide member 32 is disposed on the shaft portion 17C of the drive roller 17B so as to be movable in the width direction of the transport belt 16, that is, in the axial direction of the drive roller 17B.

  Between the drive roller 17B and the guide member 32, a rubber member (elastic member) 33 for applying an urging force in the axial direction to the guide member 32 is disposed. The guide member 32 is elastically movable in the width direction of the transport belt 16 by the rubber member 33. That is, when the guide member 32 tries to move in the direction approaching the drive roller 17B, the rubber member 33 is deformed and allowed to move. On the other hand, the rubber member 33 causes the guide member 32 to apply a biasing force that biases the guide member 32 in a direction away from the drive roller 17B in accordance with the amount of deformation.

Next, a behavior when the straightness of the rib 31 with respect to the circulating movement direction of the transport belt 16 is poor will be described.
7 is a view for explaining the relationship between the rib 31 of the transport belt 16 and the drive roller 17B and the guide member 32. FIG. 8 is a view for explaining the periphery of the end of the drive roller 17B in the transfer unit 30. It is sectional drawing.
As shown in FIG. 7, when the rib 31 formed on the conveyor belt 16 has a portion bent in the direction of the arrow X, if the dimension of the bent portion is L, the conveyor belt 16 has a drive An external force that moves by L in the direction opposite to the direction of the arrow X acts on the roller 17B. With respect to such an external force, if the rib 31 is deformed by a deformation amount corresponding to L, the conveying belt 16 does not move. However, if the amount of deformation of the rib 31 is too large, the deformation of the rib 31 may cause excessive stress on the joint surface between the conveyance belt 16 and the rib 31, which may cause damage to the conveyance belt 16.

In this regard, in this embodiment, as described above, the guide member 32 is configured to be movable in the width direction of the transport belt 16, and the rubber member 33 is disposed between the guide member 32 and the drive roller 17B. It is installed. For this reason, the guide member 32 moves in the direction of arrow X as shown in FIG. The amount of movement thereof when the guide member 32 and L _1. Also, the rib 31 itself is deformed. The deformation amount of the rib 31 of the case and L _2. That is, L = L ₁ + L ₂ .
Thus, although the rib 31 is deformed, the amount of deformation is L ₂ which is smaller than the dimension L of the bent portion of the rib 31. Therefore, the stress on the joint surface between the conveyor belt 16 and the rib 31 can be reduced, and the product life of the conveyor belt 16 can be extended.

More specifically, as shown in FIG. 8, when the guide member 32 moves by L _{1 in} the direction of arrow X, the rubber member 33 is pressed by the guide member 32, and the dimension in the direction of arrow X is shortened by L _1. Become. An elastic force that pushes back the guide member 32 is generated inside the rubber member 33. For this reason, if the rib 31 comes to be guided by the guide member 32 by the portion having good straightness, the original state is restored.
In the present embodiment, the rubber member 33 is used as an elastic member, but the present invention is not limited to this. For example, a urethane member or a spring member can be used.

As described above, according to the present embodiment, even when the rib 31 is not straight, the conveyance belt 16 can be guided and maintained in a predetermined route while absorbing the irregularities by the rubber member 33. That is, it is possible to suppress the influence of the straightness of the rib 31 from being transmitted to the conveyance belt 16. Therefore, the belt walk can be effectively prevented without concentrating stress on the adhesion surface between the conveyance belt 16 and the rib 31.
Even if the straightness of the ribs 31 is poor, the displacement amount in the width direction of the transport belt 16 can be suppressed, so that color registration shift (color registration shift) that occurs between different colors can be suppressed. And color registration can be improved.

  Further, the rubber belt 33 is disposed between the end portion of the driving roller 17 </ b> B and the guide member 32, so that the transport belt 16 is walked on the side opposite to the rib 31. That is, since the conveying belt 16 is always acted in the direction in which the conveying belt 16 is stretched, the undulation of the conveying belt 16 can be prevented, and the deterioration of the color registration due to the undulating can be prevented.

[Second Embodiment]
FIG. 9 is a perspective view for explaining a transfer unit according to the second embodiment.
Since the basic configuration of the transfer unit shown in FIG. 9 is the same as that of the transfer unit according to the first embodiment, different parts will be described. The same reference numerals are used for the same portions, and the description thereof is omitted.
As shown in FIG. 9, in this embodiment, a rubber member 34 is disposed on the opposite side of the guide member 32 from the rubber member 33. That is, the guide member 32 is sandwiched between a rubber member 33 as a first elastic member and a rubber member 34 as a second elastic member. More specifically, the guide member 32 is disposed between the end portion of the driving roller 17 </ b> B and the housing 35. A rubber member 33 is disposed between the end of the drive roller 17 </ b> B and the guide member 32, and a rubber member 34 is disposed between the housing 35 and the guide member 32. Therefore, when the guide member 32 moves in the direction of the arrow X, the guide member 32 receives an external force from the rubber member 33 to return to the original position, and when it moves in the direction of the arrow Y, the external force to return to the original position. It is received by the rubber member 34.
In the first embodiment, as described above, the angle of the driven roller 17A with respect to the conveyor belt 16 is set so that the conveyor belt 16 moves in the direction of the arrow X. Since the rubber member 34 is also provided, it is not necessary to perform such setting.

In the present embodiment, the rubber member 34 is also arranged outside the pulley-shaped guide member 32, so that even when the belt walk is in the belt outer direction, the conveyance belt 16 is fixed while absorbing the irregularities of the ribs 31. You can guide and maintain the route.
Further, since the guide member 32 can be moved by an elastic member made of rubber, the various effects described above can be obtained at low cost and space saving.

1 is a schematic configuration diagram illustrating an image forming apparatus according to an exemplary embodiment. It is a figure for demonstrating a manual feed tray. It is a figure for demonstrating a front cover. FIG. 6 is a diagram for explaining a drawer state of a paper feed cassette. It is a perspective view for demonstrating the transfer unit which concerns on 1st Embodiment. FIG. 5 is a cross-sectional view for explaining the periphery of an end portion of a driving roller in a transfer unit. It is a figure for demonstrating the relationship between the rib of a conveyance belt, a drive roller, and a guide member. FIG. 5 is a cross-sectional view for explaining the periphery of an end portion of a driving roller in a transfer unit. It is a perspective view for demonstrating the transfer unit which concerns on 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 16 ... Conveyance belt, 16a ... One end part, 17A ... Driven roller, 17B ... Drive roller, 17C ... Shaft part, 18 ... Adsorption roller, 19 ... Transfer roller, 30 ... Transfer unit, 31 ... Rib, 32 ... Guide member, 33 , 34 ... Rubber member, 35 ... Housing

Claims (3)

An image forming apparatus for forming an image on a recording medium,
A belt-shaped member configured to be capable of circulating movement;
A plurality of stretching members that stretch the belt-shaped member;
A rib member provided in the belt-like member and extending in a direction in which the belt-like member circulates;
A guide member that is disposed adjacent to at least one of the plurality of stretching members, is configured to be movable in the width direction of the belt-shaped member, and guides the rib member;
A first elasticity which is located between the guide member and the tension member adjacent to the guide member and elastically biases the guide member in a direction away from the tension member in the width direction of the belt-shaped member. A member,
The guide member is located between the image forming apparatus main body and the guide member, and elastically biases the guide member in a direction that comes into contact with the image forming apparatus main body and approaches the stretching member in the width direction of the belt-shaped member. Two elastic members;
The including image forming apparatus. A transfer unit attached to an image forming apparatus for transferring a toner image to a recording medium,
A transfer belt configured to be capable of circulating movement;
A plurality of rolls that stretch the transfer belt;
A rib member provided on the transfer belt and extending in a direction in which the transfer belt circulates;
A pulley-shaped guide member disposed adjacent to at least one of the plurality of rolls, configured to be movable in the width direction of the transfer belt, and guiding the rib member;
A first elastic member that is positioned between the guide member and the roll adjacent to the guide member and elastically biases the guide member in a direction away from the roll in the width direction of the transfer belt;
A second elastic member that is located between the transfer unit main body and the guide member and elastically biases the guide member in a direction that comes into contact with the transfer unit main body and approaches the roll in the width direction of the transfer belt. When,
Including a transfer unit. The guide member, a transfer unit according to claim 2, wherein the Ru pulley shape der the flange portion formed at both ends.

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