JP4532715B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus that forms an image on a sheet such as a copying machine, a printer, or a facsimile, and particularly has a feature in sheet conveyance.
[0002]
[Prior art]
Examples of the image forming apparatus using the electrophotographic system include a copying machine, a printer, and a facsimile machine. A copying machine generally has a function of reading an image such as an original, and forms an image on a sheet based on the read image information. In recent years, a copying machine has a communication function or the like to send image information sent from the outside. Some have the ability to input. The printer generally forms an image on a sheet based on image information sent from an external device such as a computer. The facsimile apparatus generally has a function of reading an image such as a document and a communication function, sends the read image information to the outside, and forms an image on a sheet based on the information sent from the outside.
[0003]
A conventional image forming apparatus will be described with reference to FIG. The figure shows an example of a laser printer. A toner image is formed by a developing device 101 on a photosensitive drum 100 as an image carrier, and a transfer means 104 is transferred to a sheet fed by a pair of registration rollers 102 and a pair of pre-transfer rollers 103. To transfer the toner image. The sheet on which the toner image has been transferred is guided to a fixing device 106 by a conveyance guide 105, which is a conveyance guide, and the image is fixed after being heated and pressurized, and then discharged outside the apparatus, thereby forming an image. Is called.
[0004]
In the above apparatus, it is necessary to remove a jammed sheet such as a paper jam during conveyance, and it is necessary to secure a space for jamming between the photosensitive drum 100 and the fixing device 106. Therefore, particularly when the distance between the photosensitive drum 100 and the fixing device 106 is short, the transfer unit 104 and the conveyance guide 105 are supported by the conveyance frame 107, and a rotation fulcrum 107a is provided on the upstream side of the conveyance frame 107 in the sheet conveyance direction, It is known to secure the space by rotating the conveyance frame 107 by rotating the handle 108.
[0005]
[Problems to be solved by the invention]
However, when the conveyance guide 105 is fixedly formed on the conveyance frame 107 as shown in the drawing, the leading end portion 105a of the conveyance guide 105 passes the locus F shown in the drawing when the conveyance frame 107 rotates. Become. Here, the conveyance guide 105 and the fixing device 106 need to be separated to some extent so that the front end portion 105a does not come into contact with the fixing stay 106a that supports the fixing device 106. An interval L is generated between the leading end portion 105a and the entrance guide 109 that guides the sheet to the fixing device 106.
[0006]
Due to the presence of the interval L, when the lower curled sheet is conveyed, the leading end of the sheet collides with the entrance guide 109, and there is a possibility that the sheet skews or a jam occurs. Therefore, the front end portion 105a of the conveyance guide is arranged higher than the front end portion of the entrance guide 109 by a height H so that even the lower curled sheet is not caught. However, since the transfer portion between the conveyance guide 105 and the entrance guide 109 is stepped, there is a possibility that an image defect such as transfer deviation may occur due to the impact of the leading end portion of the sheet coming into contact with the entrance guide 109.
[0007]
Although it is conceivable to extend the ribs of the inlet guide 109 in order to reduce the distance L, when the transport frame 107 is attached to the main body, it easily interferes with the ribs of the inlet guide 109 and may be damaged. It is difficult to extend to a certain extent. In order to reduce the distance L, there is a method of moving the rotation fulcrum 107a of the conveyance frame 107 to the fixing device side. In this case, it is necessary to secure a space for jam processing between the registration roller pair 102 and the pre-transfer roller pair 103. There is a problem that becomes difficult.
[0008]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus in which the distance between the conveyance guide and the entrance guide of the fixing device is eliminated, and the conveyance performance and jam handling performance are improved.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, a typical configuration of an image forming apparatus according to the present invention includes an image carrier that carries a toner image, a transfer unit that transfers the toner image to a sheet, and the toner image that is transferred to the sheet. A fixing unit for fixing the toner image to the fixing unit, a conveyance guide for guiding the sheet onto which the toner image has been transferred to the fixing unit, and supporting the transfer unit and the conveyance guide, and having a fulcrum on the upstream side in the sheet conveyance direction so as to be rotatable. In the image forming apparatus having the transport frame disposed, the transport guide has a pivot point on the upstream side in the sheet transport direction, is pivotally disposed on the transport frame, and has an urging unit. a sheet conveying direction downstream side of the conveying guide are biased in a direction away from the conveyor frame, the pivot point of the conveyance guide, under the sheet conveying direction than the supporting point of the conveyor frame Located side, when in the sheet at a position where the conveying frame is closed to the conveying guide to guide, the mount position of the conveying guide said by the conveying guide defines means and abutment of said fixing means near Stipulated against the urging force of the urging means, and when the downstream side of the conveying frame in the sheet conveying direction is rotated downward, the rotation fulcrum is lowered, and the urging force of the urging means causes the rotation fulcrum to be centered. When the conveyance guide is rotated while being in contact with the defining means, and further when the rotation fulcrum is lowered, the conveyance guide is rotated by the urging force of the urging means until it comes into contact with the protrusion of the conveyance frame, When the conveyance guide separated from the defining means and urged by the urging means comes into contact with the protrusion, the conveyance guide is brought into a stationary open state at a predetermined angle, It characterized in that the can state can be rotated against the conveyance guide the biasing force of the biasing means.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings. 1 is a schematic configuration diagram of an image forming apparatus according to the present embodiment, FIG. 2 is a schematic configuration diagram illustrating an operation of lowering a conveyance frame, FIG. 3 is a schematic configuration diagram illustrating a state where the conveyance frame is lowered, and FIG. It is a top view explaining the structure of a conveyance guide. It should be noted that the dimensions, materials, shapes, relative positions, and the like of the components described in the following description are examples unless otherwise specified, and are not intended to limit the scope of the present invention.
[0011]
In this embodiment, a laser printer is used as the image forming apparatus. The laser printer shown in FIG. 1 emits a laser beam from a laser scanner (not shown) based on image information obtained from an external device, and irradiates the photosensitive drum 1 as an image carrier. As a result, a latent image is formed on the photosensitive drum 1, and the latent image is developed by the developing device 3 to form a toner image.
[0012]
On the other hand, sheets stored in a cassette (not shown) are separated and fed one by one, conveyed by the registration roller pair 4 and the pre-transfer roller pair 5, and sent to the nip between the photosensitive drum 1 and the transfer roller 6. The transfer roller 6 is supported by the transfer arm 7 and is urged against the photosensitive drum 1 by a spring 8 with a predetermined pressure. In this way, the transfer roller 6 is urged to the photosensitive drum 1 to form a transfer portion, and the toner image is transferred from the photosensitive drum 1 to the sheet at the transfer portion. Further, the photosensitive drum 1 is provided with a cleaner 2 to remove a toner image remaining on the photosensitive drum 1 after transfer, and the photosensitive drum 1 is used for the next image formation.
[0013]
A conveyance guide 9 to be described later is disposed on the downstream side of the transfer portion, and guides the sheet to a fixing device 11 as fixing means. In the fixing device 11, the sheet is heated and pressed to fix the toner image. The sheet is further conveyed and discharged outside the apparatus by a pair of discharge rollers (not shown), and image formation is completed.
Here, by setting the distance between the fixing device 11 and the transfer roller 6 to be smaller than the minimum paper size postcard that can be conveyed, it is necessary to provide a roller pair between the fixing device 11 and the transfer roller 6 or to provide a conveyance fan. Absent.
[0014]
Here, the transfer roller 6, the transfer arm 7, and the conveyance guide 9, which are transfer means, are supported by the conveyance frame 12, and the conveyance frame 12 is rotated with respect to the apparatus main body by a rotation fulcrum 12 a provided on the upstream side in the sheet conveyance direction. It is arranged to be movable. The conveyance frame 12 is fixed in contact with a positioning portion (not shown) of the cleaner 2 by a pressure plate 13, and the transfer roller 6 and the conveyance guide 9 are arranged at predetermined positions with respect to the photosensitive drum 1. The pressure plate 13 is supported by a cam 15 fixed to the handle 14, and supported or released by rotating the handle 14.
[0015]
The conveyance guide 9 has a rotation fulcrum 9a on the upstream side in the sheet conveyance direction, and is rotatably disposed on the conveyance frame 12. Further, an urging means 10 is attached to the rotation fulcrum 9a and urges the conveyance guide 9 in a direction separating from the conveyance frame 12 (clockwise direction in the figure) as shown in FIG. Further, a rib 9b protrudes from the lower portion of the conveyance guide 9 and the rib 9b abuts on a fixing stay 16 (regulating means) that supports the fixing device 11, whereby the conveyance guide 9 The position is defined against the biasing force.
[0016]
Further, an inlet guide 17 as a guide member is disposed on the upstream side of the fixing device 11 in the transport direction, and is opposed to the leading end portion 9c of the transport guide. As shown in FIG. 4, a plurality of protrusions 9 d extending toward the downstream side in the transport direction are provided on the leading end portion 9 c of the transport guide, and a plurality of protrusions 17 a extending toward the upstream side in the transport direction are provided on the inlet guide 17. Is provided. These protrusions 9d and 17a are alternately arranged, and are positioned so as to overlap on the same plane in a state where the protrusions 9d and 17a can be conveyed.
[0017]
With the configuration described above, since the protrusions 9d and 17a of the conveyance guide 9 and the inlet guide 17 can overlap in the sheet conveyance direction, there is no gap between the conveyance guide 9 and the inlet guide 17, and a high The step in the vertical direction can be set small. Therefore, even the lower curled sheet can be smoothly conveyed, and the conveyed sheet may collide with the entrance guide 17 to cause jamming or skew feeding, and image defects such as transfer deviation due to impact may occur. It is possible to improve transportability.
[0018]
Next, the operation at the time of jam processing will be described. When a jam occurs, as shown in FIG. 2, the handle 15 is rotated in the counterclockwise direction in the drawing, so that the cam 15 is also rotated in the counterclockwise direction, and the pressure plate 13 is dropped accordingly. As a result, the support of the transport frame 12 is released and rotation about the rotation fulcrum 12a is started. At this time, even if the conveyance frame 12 starts to fall, the conveyance guide 9 tries to rotate in a direction away from the conveyance frame 12 by the urging force of the urging means 10, so that the lower rib 9 b is attached to the fixing stay 16. The rotating fulcrum 9a side falls while being in contact. Therefore, the transport frame 12 can be rotated without the front end portion 9c of the transport guide interfering with the inlet guide 17.
[0019]
As shown in FIG. 3, when the conveying frame 12 is completely dropped, the sheet conveying path between the photosensitive drum 1 and the fixing device 11 is opened, and the jam processing can be performed. At this time, the conveyance guide 9 is rotated in a direction (clockwise direction) away from the conveyance frame 12 by the urging means 10, and comes to rest at a predetermined angle by coming into contact with the protrusion 12 b on the conveyance frame 12. When the jam processing is performed in this state, the conveyance guide 9 can freely rotate to a position along the conveyance frame 12 (broken line 9e) by drawing a trajectory F when touched by an operator. Sufficient space is provided for the
[0020]
After the jam processing is completed, by rotating the handle 14 in the clockwise direction in the figure, the transport frame 12 can be rotated and supported again in the transportable state.
[0021]
【The invention's effect】
As described above, in the image forming apparatus according to the present invention, the conveyance guide that guides the sheet to the fixing unit is disposed so as to be rotatable with respect to the conveyance frame that is rotatably disposed, and the biasing unit is provided. Since the conveyance guide and the inlet guide of the fixing unit can be overlapped in the sheet conveyance direction by having the biasing force in the direction away from the conveyance frame, a gap may be generated between the conveyance guide and the inlet guide. In addition, the step in the height direction can be set small. Therefore, even the lower curled sheet can be smoothly conveyed, and the conveyed sheet collides with the entrance guide to cause jamming and skewing, and an image defect such as transfer deviation due to the impact occurs. It is possible to improve transportability. In addition, it is possible to secure a sufficient space during the jam processing.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present invention.
FIG. 2 is a schematic configuration diagram illustrating an operation for lowering a transport frame.
FIG. 3 is a schematic configuration diagram illustrating a state in which a transport frame is lowered.
FIG. 4 is a plan view illustrating a configuration of a conveyance guide.
FIG. 5 is a diagram illustrating a conventional image forming apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum 2 ... Cleaner 3 ... Developing device 4 ... Registration roller pair 5 ... Pre-transfer roller pair 6 ... Transfer roller 7 ... Transfer arm 8 ... Spring 9 ... Conveyance guide 9a ... Rotation fulcrum 9b ... Rib 9c ... Tip part 9d ... projection
10… biasing means
11… Fixer
12… Conveying frame
12a… Rotating fulcrum
12b ... Protrusions
13… Pressure plate
14 ... handle
15… Cam
16… Fixing stay
17… Entrance guide
17a ... projection

Claims (4)

An image carrier for carrying a toner image;
Transfer means for transferring the toner image to a sheet;
Fixing means for fixing the toner image to the sheet;
A conveyance guide for guiding the sheet onto which the toner image has been transferred to a fixing unit;
An image forming apparatus that supports the transfer unit and the conveyance guide, and includes a conveyance frame that is pivotally disposed with a fulcrum on the upstream side in the sheet conveyance direction.
The conveyance guide has a rotation fulcrum on the upstream side in the sheet conveyance direction, is rotatably arranged on the conveyance frame, and has a biasing means, and the conveyance guide downstream side in the sheet conveyance direction is the conveyance frame. The rotation fulcrum of the conveyance guide is on the downstream side in the sheet conveyance direction with respect to the fulcrum of the conveyance frame,
When the conveyance frame is in a closed position for guiding the sheet by the conveyance guide, the conveyance guide is brought into contact with a defining means in the vicinity of the fixing means, so that the position of the conveyance guide is applied to the biasing means. Stipulated against the power,
When the downstream side of the conveyance frame in the sheet conveyance direction is rotated downward, the rotation fulcrum is lowered, and the conveyance guide is brought into contact with the defining unit around the rotation fulcrum by the urging force of the urging unit. Rotate,
When the rotation fulcrum is further lowered, the conveyance guide is rotated by the urging force of the urging means until it comes into contact with the protrusion of the conveyance frame, and the conveyance guide is separated from the defining means and is urged by the urging means. When the transport guide is in contact with the protrusion, the transport guide is brought into a stationary open state at a predetermined angle, and in the open state, the transport guide can be rotated against the biasing force of the biasing means. An image forming apparatus.   The fixing unit includes a guide member that guides a sheet on the upstream side in the sheet conveyance direction. The conveyance guide and the guide member are provided with a plurality of protrusions extending in the conveyance direction, and the plurality of protrusions of the conveyance guide and the guide member are alternately arranged. The image forming apparatus according to claim 1, wherein the image forming apparatuses are positioned and overlap on substantially the same plane.   The image forming apparatus according to claim 1, wherein a distance between the fixing unit and the transfer unit is shorter than a minimum sheet length that can be conveyed.   The fixing unit has a guide member for guiding a sheet upstream in the sheet conveying direction, and when the conveying frame is rotated in a direction away from the image carrier, the conveying guide is defined by a defining unit near the fixing unit. 2. The apparatus according to claim 1, wherein the biasing unit is separated from the transport frame while receiving a regulation, and a downstream end portion of the transport guide is maintained at a position near an upstream end portion of the guide member. Image forming apparatus.

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