JP5533009B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a laser printer.

  There is a color laser printer as an example of an image forming apparatus in which each side wall facing the width direction of the main body frame is configured by a sheet metal frame and a resin frame. In the width direction, the sheet metal frame is disposed relatively outside, and the resin frame is disposed relatively inside.

  Between the resin frames facing in the width direction, a belt unit for conveying paper is disposed. Above the belt unit, four photosensitive drums are arranged in parallel along the sheet conveyance direction by the belt unit. Each color toner formed on the surface of each photosensitive drum is transferred onto the sheet conveyed by the belt unit, whereby a color image is formed on the sheet by superimposing the respective color toner images.

JP 2007-148142 A

  As the material of the resin frame, a resin having a low linear expansion coefficient is employed. However, a resin having a low linear expansion coefficient is generally more expensive than a resin having a high linear expansion coefficient. Therefore, there is a problem that the cost of the color laser printer is high.

  If an inexpensive resin material having a high linear expansion coefficient is used as the material of the resin frame, the cost of the color laser printer can naturally be reduced. However, the difference in the coefficient of linear expansion between the sheet metal frame and the resin frame becomes large, and the relative position between the member held on the sheet metal frame and the belt unit held on the resin frame is increased as the heat changes. Deviation occurs. If such a relative displacement occurs, the operation of the color laser printer may be affected.

  An object of the present invention is to provide an image forming apparatus capable of preventing a relative displacement between a member held by a first frame and a member held by a second frame while reducing costs. Is to provide.

  In order to achieve the above object, the present invention provides an image forming apparatus, comprising a metal main frame, a first frame made of a resin having a higher linear expansion coefficient than the main frame, and attached to the main frame. A transport mechanism that transports at least the sheet that is held by the first frame and onto which the developer image is transferred; a second frame that is made of a resin having a higher linear expansion coefficient than the main frame and is attached to the main frame; Relative positioning means for positioning the first frame and the second frame relative to each other in a direction orthogonal to the sheet conveyance surface by the conveyance mechanism is provided.

  According to the present invention, the first frame and the second frame made of resin having a high linear expansion coefficient are attached to the metal main frame.

  Further, the first frame and the second frame are positioned relative to each other in a direction perpendicular to the sheet conveyance surface by the conveyance mechanism by the relative positioning means. Accordingly, it is possible to prevent relative displacement between the conveyance mechanism held by the first frame and the member held by the second frame in a direction orthogonal to the sheet conveyance surface. That is, even if an inexpensive material having a high coefficient of linear expansion is used for the first frame and the second frame, it is possible to prevent displacement.

FIG. 1 is a side sectional view of a color printer according to an embodiment of the present invention. FIG. 2 is a perspective view showing an internal structure of the main casing. FIG. 3 is a side view of the main frame, the first frame, and the second frame shown in FIG. FIG. 4 is a side view of the first frame and the second frame shown in FIG. 2 viewed from the outside in the left-right direction. FIG. 5 is a plan view showing the internal structure of the main casing. FIG. 6 is a cross-sectional view of the first frame, the second frame, and the belt unit taken along the cutting line VI-VI shown in FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
1. Overall Configuration of Printer A printer 1 as an example of an image forming apparatus is a tandem type color printer. As shown in FIG. 1, a drum unit 3 is mounted in a main body casing 2 as an example of an apparatus main body of the printer 1. The drum unit 3 is detachable from the main casing 2 by opening a front cover 4 provided on one side wall of the main casing 2.

  In the following description, the side where the front cover 4 is provided (left side in FIG. 1) is the front side (front side), and the opposite side (right side in FIG. 1) is the rear side (back side). In addition, when the printer 1 is viewed from the front side, the left and right reference is used.

  The drum unit 3 includes four photosensitive drums 5. The four photosensitive drums 5 are provided corresponding to the respective colors of black, yellow, magenta, and cyan, and are arranged in parallel at equal intervals in the order of black, yellow, magenta, and cyan from the front side in the front-rear direction.

  The drum unit 3 includes a scorotron charger 6 as an example of a charger and a developing cartridge 7 corresponding to each photosensitive drum 5. The developing cartridge 7 includes a developing roller 8 for supplying toner (developer) to the photosensitive drum 5. Each developing cartridge 7 is detachably attached to the drum unit 3.

  Above the drum unit 3, an exposure unit 9 that emits four laser beams corresponding to each color is arranged.

  As the photosensitive drum 5 rotates, the surface of the photosensitive drum 5 is uniformly charged by the discharge from the scorotron charger 6 and then selectively exposed by the laser beam from the exposure unit 9. By this exposure, electric charges are selectively removed from the surface of the photosensitive drum 5, and an electrostatic latent image is formed on the surface of the photosensitive drum 5. When the electrostatic latent image faces the developing roller 8, toner is supplied from the developing roller 8 to the electrostatic latent image. As a result, a toner image is formed on the surface of the photosensitive drum 5.

  Instead of the exposure device 9, four LED arrays may be provided corresponding to each photosensitive drum 5.

  A paper feed cassette 10 that accommodates the paper P is disposed at the bottom of the main casing 2. The paper P stored in the paper feed cassette 10 is transported onto the transport belt 11 by various rollers. The conveyor belt 11 is disposed facing the four photosensitive drums 5 from below. A transfer roller 12 is disposed at each position facing the photosensitive drum 5 with the upper portion of the transport belt 11 interposed therebetween. The paper P transported on the transport belt 11 sequentially passes between the transport belt 11 and each photosensitive drum 5 as the transport belt 11 travels. The toner image on the surface of the photosensitive drum 5 is transferred to the paper P by the transfer bias applied to the transfer roller 12 when facing the paper P.

  A fixing device 13 is provided on the downstream side in the conveyance direction of the paper P with respect to the conveyance belt 11. The sheet P on which the toner image is transferred is conveyed to the fixing device 13. In the fixing device 13, the toner image is fixed on the paper P by heating and pressing. The paper P on which the toner image is fixed is discharged to a paper discharge tray 14 on the upper surface of the main body casing 2 by various rollers.

  A cleaning unit 15 as an example of a cleaner is provided below the conveyor belt 11. The cleaning unit 15 includes a collection box 16 and a pair of cleaning rollers 17.

As the cleaning roller 17 rotates and the conveyor belt 11 travels, toner that is not transferred to the paper P and adheres to the outer peripheral surface of the conveyor belt 11 is captured by the cleaning roller 17. Thereafter, the toner captured by the cleaning roller 17 is collected in the collection box 16.
2. Configuration in Main Body Casing As shown in FIG. 2, a pair of main frames 21 are opposed to the main body casing 2 with an interval in the left-right direction. Each main frame 21 is made of a sheet metal made of a galvanized steel sheet and is formed in a substantially rectangular shape in a side view. In FIG. 2, only the left main frame 21 of the pair of main frames 21 is illustrated, and the right main frame 21 is not illustrated.

A first frame 23 and a second frame 24 are attached to the inner side surface of each main frame 21 (the right side surface of the left main frame 21). The first frame 23 and the second frame 24 are formed of a resin (for example, ABS resin) having a higher linear expansion coefficient than the main frame 21 and a relatively high linear expansion coefficient among the resins. More specifically, as the material of the first frame 23 and the second frame 24, a resin having a linear expansion coefficient higher than that of the material of the frame side plate 55 described later and being inexpensive is used.
(1) First frame The first frame 23 is formed in an elongated rectangular plate shape that is long in the front-rear direction. The dimension of the first frame 23 in the front-rear direction is, for example, about three-quarters of the dimension of the main frame 21 in the front-rear direction. In addition, the vertical dimension of the first frame 23 is, for example, about half of the vertical dimension of the main frame 21.

  A drum unit 3 (see FIG. 1) is disposed in a space between the left and right first frames 23.

  The first frame 23 is formed with four first through holes 30 and four second through holes 31 penetrating the first frame 23 in the left-right direction.

  The first through holes 30 are arranged at equal intervals in the front-rear direction in the upper portion of the first frame 23, and a development coupling (not shown) for transmitting driving force to the development roller 8 (see FIG. 1). ) To the left and right. A developing drive input portion (not shown) provided in the main body casing 2 is inserted into the first through hole 30, and the driving force is transmitted from the developing drive input portion to the developing coupling, whereby the developing roller 8 is rotationally driven. Is done.

  The four second through holes 31 are arranged at positions below the rear side with respect to the first through holes 30, and drum couplings (not shown) for transmitting driving force to the photosensitive drum 5 (see FIG. 1). ) To the left and right. A drum drive input portion (not shown) provided in the main body casing 2 is inserted into the second through hole 31 and the driving force is transmitted from the drum drive input portion to the drum coupling, so that the photosensitive drum 5 is rotationally driven. Is done.

  As shown in FIGS. 3 and 4, a first boss 32, which is an example of an absolute positioning means, is formed at a substantially central portion of the first frame 23 in the front-rear direction and the vertical direction. The first boss 32 protrudes from the first frame 23 toward the main frame 21 (outside in the left-right direction). A through hole (not shown) having substantially the same size as the first boss 32 is formed in the main frame 21. Then, by inserting the first boss 32 into the through hole of the main frame 21, the first frame 23 is attached to the main frame 21 while being positioned in the front-rear direction and the vertical direction.

As shown in FIG. 4, a second boss 33 is formed at the rear end of the first frame 23. The second boss 33 is formed in a columnar shape that protrudes outward from the first frame 23 in the left-right direction.
(2) Second Frame As shown in FIG. 2, the second frame 24 is formed in an elongated rectangular plate shape that is long in the vertical direction when viewed from the side. The dimension of the second frame 24 in the front-rear direction is, for example, about one quarter of the dimension of the main frame 21 in the front-rear direction. The vertical dimension of the second frame 24 is substantially the same as the vertical dimension of the first frame 23.

  The second frame 24 is attached to the main frame 21 at a position behind the first frame 23 by a plurality of bosses 35 projecting toward the main frame 21. In this state, the front end portion of the second frame 24 overlaps the rear end portion of the first frame 23 so as to face in the left-right direction.

  At the front end portion of the second frame 24, an oblong hole 36 that is elliptical in a side view in the front-rear direction is provided at a position facing the second boss 33 of the first frame 23 in the left-right direction. It is formed as a through hole that penetrates. The size of the long hole 36 in the vertical direction is substantially the same as the outer diameter of the second boss 33. Therefore, the second boss 33 is positioned in the vertical direction with respect to the long hole 36 in a state where the second boss 33 is inserted inside the long hole 36. Thus, the second boss 33 and the long hole 36 constitute relative positioning means for positioning the first frame 23 and the second frame 24 in the vertical direction, and the first frame 23 and the second frame 24 are the second boss. A relative positional shift in the front-rear direction is allowed while being positioned in the up-down direction via the 33 and the long hole 36.

  Further, a third through hole 37 and a fourth through hole 38 are formed in the second frame 24 so as to penetrate the second frame 24 in the left-right direction.

  The third through hole 37 is formed in the upper part of the second frame 24. A fixing drive input section (not shown) for driving the fixing device 13 (see FIG. 1) is inserted into the third through hole 37. In a state where the fixing device 13 is disposed between the pair of second frames 24, the fixing device 13 is attached to the second frame 24 by an attachment member (not shown). Then, the fixing drive input unit is connected to the fixing device 13 through the third through hole 37, so that the driving force is transmitted to the fixing device 13.

The fourth through hole 38 is formed in the lower portion of the second frame 24. A belt driving input gear 39 for driving the belt unit 25 (see FIG. 2) is inserted into the fourth through hole 38. The belt driving input gear 39 is connected to a driving roller 51 of the belt unit 25 described later, so that driving force is transmitted to the belt unit 25.
(3) Belt Unit As shown in FIG. 2, the belt unit 25 includes a pair of frame side plates 55 that face each other at an interval in the left-right direction. The frame side plate 55 is made of a resin material (for example, Multilon (registered trademark) to which a predetermined amount of filler is added) having a linear expansion coefficient higher than that of the main frame 21 and lower than that of the first frame 23 and the second frame 24. .

  On the outer side surface of the frame side plate 55, a holding projection 56 that protrudes outward in the left-right direction is formed. Each of the left and right holding projections 56 of the frame side plate 55 is supported by the first frame 23 on the same side in the width direction. Specifically, in each first frame 23, a holding hole 57 (see FIG. 3) that is recessed outward in the width direction at a portion that matches the corresponding holding protrusion 56 (on the same side in the width direction) when viewed from the width direction. ) And the corresponding holding projection 56 is fitted into the holding hole 57. In this state, the holding projection 56 is urged forward by an urging member (not shown), so that it is pressed against the surface defining the front side of the holding hole 57 in the first frame 23 and can move back and forth. Can not. That is, the belt unit 25 is positioned in the front-rear direction with respect to the first frames 23 by the holding projections 56.

  Between a pair of frame side plates 55, a driving roller 51 and a driven roller 52 as an example of a conveying roller, and four transfer rollers are rotatably held.

  The drive roller 51 is installed between the rear end portions of the frame side plate 55. As shown in FIG. 6, the driving roller 51 includes a driving roller shaft 60 as an example of a shaft extending in the left-right direction. Then, both end portions of the drive roller shaft 60 are inserted into the frame side plate 55 and project outside the frame side plate 55.

  Further, the drive roller shaft 60 is opposed from the inside to a portion where the first frame 23 and the second frame 24 overlap in the left-right direction. The drive roller shaft 60 is pressed toward one side (for example, the left side) by a biasing member (not shown). Accordingly, the first frame 23 is pressed toward the right side by the drive roller shaft 60. Since the first frame 23 and the second frame 24 overlap in the left-right direction, the second frame 24 is pressed toward the right side by the first frame 23. That is, the drive roller shaft 60 presses the second frame 24 toward the right side via the first frame 23.

  As shown in FIG. 2, the driven roller 52 is installed between the front end portions of the frame side plate 55.

  The four transfer rollers 12 (see FIG. 1) are arranged at equal intervals in the front-rear direction between the drive roller 51 and the driven roller 52.

An endless conveyance belt 11 is wound around the driving roller 51 and the driven roller 52.
(4) Sensor unit A sensor unit 53 as an example of a sensor is disposed at a position separated rearward from the belt unit 25.

  The sensor unit 53 faces the surface of the conveyor belt 11 in the left-right direction. Inside the sensor unit 53, a detection unit (not shown) for detecting a toner image formed on the surface of the conveyor belt 11 is provided.

  A toner image (patch data) having a predetermined pattern is formed on the surface of the conveyor belt 11, and the toner image is detected by the detection unit of the sensor unit 53, and is formed by the four photosensitive drums 5 (see FIG. 1). The positional deviation of the toner image can be detected.

Further, holding projections 65 projecting outward in the left-right direction are formed at both ends in the left-right direction of the sensor unit 53. The sensor unit 53 is held by the second frame 24 by inserting the holding protrusion 65 into the holding hole 66 (see FIG. 3) of the second frame 24.
(4) Cleaning Unit As described above, the cleaning unit 15 includes the collection box 16 and the pair of cleaning rollers 17.

  As shown in FIG. 2, the collection box 16 is formed in a box shape extending in the front-rear direction and the left-right direction, and includes a pair of box side plates 70 facing in the left-right direction.

  Each cleaning roller 17 is installed in the center part of the box side plate 70 in the front-rear direction.

Further, a columnar box support protrusion 71 is formed on the front end portion and the rear end portion of the box side plate 70 so as to protrude outward in the left-right direction from the outer surface. Each box support protrusion 71 is inserted into the box support hole 72 of the first frame 23, whereby the cleaning unit 15 is held by the first frame 23.
3. As described above, even if the first frame 23 and the second frame 24 are made of a resin having a high linear expansion coefficient (inexpensive), the first frame 23 and the second frame 24 are positioned relative to each other in the vertical direction. By doing so, positional accuracy can be maintained.

  The first frame 23 is attached to the main frame 21 by a first boss 32. The second frame 24 is attached to the main frame 21 by a plurality of bosses 35. The first frame 23 and the second frame 24 are positioned relative to each other in the vertical direction by the second boss 33 and the long hole 36. Therefore, when the environmental temperature changes, the first frame 23 expands and contracts around the first boss 32, and the second frame 24 extends and contracts around the boss 35.

  On the other hand, play is provided in the front-rear direction between the long hole 36 and the second boss 33. Therefore, when the first frame 23 and the second frame 24 expand and contract, the expansion and contraction can be absorbed by the movement of the second boss 33 in the long hole 36. Thereby, it is possible to prevent relative displacement between the belt unit 25 held by the first frame 23 and the sensor unit 53 held by the second frame 24 in the vertical direction.

  In addition, since the conveyance belt 11 held by the first frame 23 and the sensor unit 53 held by the second frame 24 can be accurately positioned, a toner image (for detecting positional deviation) by the sensor unit 53 can be obtained. Detection accuracy of patch data) can be improved.

  The cleaning unit 15 is held by the first frame 23. The toner image transferred onto the conveyance belt 11 is removed by the cleaning unit 15. Both the cleaning unit 15 and the transport belt 11 are held by the first frame 23. Therefore, the positional accuracy between the cleaning unit 15 and the conveyance belt 11 can be improved.

  The belt unit 25 includes a driving roller 51 and a driven roller 52. The drive roller 51 is rotatably provided around a drive roller shaft 60 that extends in the left-right direction. Thereby, the conveyance belt 11 stretched around the drive roller 51 and the driven roller 52 can be run in the front-rear direction.

  The first frame 23 and the second frame 24 partially overlap each other in the left-right direction. The drive roller shaft 60 presses the second frame 24 outward in the left-right direction via the first frame 23. Thereby, the drive roller shaft 60 can be positioned in the left-right direction.

  Further, the toner image transferred onto the paper P is fixed on the paper P by the fixing device 13. The fixing device 13 is held by the second frame 24. Since the first frame 23 and the second frame 24 are positioned in the vertical direction, the fixing device 13 held by the second frame 24 and the belt unit 25 held by the first frame 23 are accurately positioned. Can do.

  The first frame 23 is positioned in the front-rear direction and the vertical direction with respect to the main frame 21 by the first boss 32. For this reason, when the first frame 23 is thermally expanded / contracted due to a change in environmental temperature, it is possible to prevent a displacement between the first frame 23 and the main frame 21 in the vicinity of the first boss 32. it can.

  The first boss 32 is formed substantially at the center of the first frame 23 in the up-down direction and the front-rear direction. Therefore, with the first boss 32 as a reference, it is possible to predict the amount of displacement that occurs between the first frame 23 and the main frame 21 according to the distance from the first boss 32. Therefore, by arranging each member based on the predicted displacement amount, the influence of displacement caused between the first frame 23 and the main frame 21 can be reduced.

DESCRIPTION OF SYMBOLS 1 Printer 5 Photosensitive drum 11 Conveyance belt 13 Fixing device 15 Cleaning unit 21 Main frame 23 1st frame 24 2nd frame 25 Belt unit 32 1st boss 33 2nd boss 36 Long hole 50 Drive roller 51 Driven roller 53 Sensor unit 60 Drive Roller shaft

Claims (8)

A metal main frame,
A first frame made of a resin having a higher linear expansion coefficient than the main frame, and attached to the main frame;
A conveyance mechanism that conveys a sheet that is held on at least the first frame and onto which the developer image is transferred;
Made of a resin having a higher linear expansion coefficient than the main frame, and a second frame attached to the main frame;
A member held by the second frame;
Relative positioning means for positioning the first frame and the second frame relative to each other in a direction perpendicular to the sheet conveyance surface by the conveyance mechanism;
The second frame is located on one side in a direction parallel to the transport surface with respect to the first frame,
The relative positioning means positions the first frame and the second frame relative to each other in a direction parallel to the transport surface in a state where the first frame and the second frame are positioned in a direction perpendicular to the transport surface. An image forming apparatus configured to allow a general positional deviation.   The image forming apparatus according to claim 1, wherein the transport mechanism is regulated by the first frame.   The image forming apparatus according to claim 1, further comprising a plurality of image carriers that are arranged in parallel in a direction parallel to the conveyance surface and carry a developer image transferred to the sheet. The transport mechanism travels along the transport surface, and includes a transport belt for carrying and transporting the sheet,
It said member is a sensor for detecting a developer image transferred onto the transfer belt from the image bearing member, an image forming apparatus according to claim 3. A cleaner for removing the developer image transferred on the conveyor belt;
The image forming apparatus according to claim 4, wherein the cleaner is held by the first frame. The transport mechanism is disposed at intervals in a direction parallel to the transport surface, and is provided rotatably about an axis extending perpendicular to the direction and parallel to the transport surface, and the transport belt is stretched around the transport mechanism. A plurality of transport rollers,
The first frame and the second frame partially overlap each other in the direction in which the axis extends,
The image forming apparatus according to claim 4, wherein the shaft presses the second frame in a direction in which the shaft extends through the first frame. A fixing device for fixing the developer image transferred to the sheet conveyed by the conveyance mechanism to the sheet;
The image forming apparatus according to claim 1, wherein the fixing device is held by the second frame.   The absolute positioning means for positioning the first frame with respect to the main frame in a direction parallel to the transport surface and in a direction orthogonal to the transport surface, according to any one of claims 1 to 7. The image forming apparatus described.

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