JPH05100599A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain an inexpensive image forming device capable of obviating the need for a dedicated inverting mechanism by providing sheet ejection roller pairs and a sheet ejection tray along the direction of the tangent of a nip part between a heat roller and a pressure roller positioned downstream in the carrying direction of transfer paper. CONSTITUTION:The first and second pressure rollers 43 and 44 are energized to the side of the heat roller 42 by spring members 45 and 46. In the direction of the tangent of the nip part between the heat roller 42 and the second pressure roller 43 positioned downstream in the carrying direction of the transfer paper P1, the sheet ejection tray 49 is provided in addition to a first sheet ejection roller pair 47 and a second sheet ejection roller pair 48. The transfer paper P1 held between the heat roller 42 and the second pressure roller 44 is linearly ejected onto the sheet ejection tray 49 via the first and second sheet ejection roller pairs 47 and 48. Therefore, the transfer sheet is prevented from curling. Thus, the sheets of transfer paper can be stacked on the sheet ejection tray neatly and the stack performance can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus,
More specifically, the present invention relates to an image forming apparatus including a two-stage pressure fixing device.

[0002]

2. Description of the Related Art Generally, an image forming apparatus such as a laser printer is provided with a fixing device for fixing a visible image formed on a transfer sheet to the transfer sheet.
As shown in, there are a one-stage pressure system and a two-stage pressure system. Figure 2
In (a) and (b), the one-step pressing method is a method in which the heat rollers 3 and 4 contacting the transfer paper surfaces 1a and 2a of the transfer papers 1 and 2 on which the visible images are formed, and the heat rollers 3 and 4, It is composed of pressure rollers 5 and 6 that press the transfer sheets 1 and 2 toward the heat rollers 3 and 4 while sandwiching the transfer sheets 1 and 2. It should be noted that FIG. 2A is used for a lower conveyance type image forming apparatus, and FIG. 2B is used for an upper conveyance type image forming apparatus.

On the other hand, in FIGS. 2 (c) and 2 (d), the two-stage pressurizing method includes heat rollers 9 and 10 which come into contact with transfer sheet surfaces 7a and 8a of transfer sheets 7 and 8 on which a visible image is formed, A pressure roller 11 for pressing the transfer papers 7 and 8 toward the heat rollers 9 and 10 while sandwiching the transfer papers 7 and 8 together with the heat rollers 9 and 10.
a, 11b, 12a, 12b. In addition,
FIG. 2C is used for a lower conveyance type image forming apparatus,
(D) is used for an upper conveyance type image forming apparatus. This 2
In the stepwise pressing method, since two pressing rollers 11a, 11b, 12a, 12b are arranged in the circumferential direction of the heat rollers 9, 10,
Compared with the one-stage pressure method, the transfer images 7 and 8 have a better fixability of visible images and have been widely used in recent years.

An example of an image forming apparatus equipped with such a two-stage pressure type fixing device is shown in FIG. Incidentally, FIG. 3 is provided with the upper conveyance type fixing device of FIG. In FIG. 3, 21
Is a laser printer as an image forming apparatus, and paper feed cassettes 22a and 22b accommodating recording papers P are detachably provided on the side of a main body 21a of the printer 21.
The recording paper P in the paper feed cassettes 22a and 22b is fed by a paper feed roller.
After the paper is fed by 23a and 23a, the photosensitive drum 25 is fed by the registration roller 24 at a predetermined timing.
Is supplied to.

The photosensitive drum 25 is driven to rotate in a counterclockwise direction, and the surface of the photosensitive drum 25 is charged by a charging charger 26 in accordance with the rotation of the photosensitive drum 25.
Is irradiated with the laser beam L from the laser to form an electrostatic latent image on the surface thereof. This electrostatic latent image is developed by the developing device 28.
The toner stored in the apparatus 28 visualizes the visible image when passing through the sheet. This visible image is transferred by the transfer charger 29 to the transfer sheet P conveyed from the sheet feeding cassettes 22a and 22b. A visible image is transferred and then a fixing device 30
Is established by.

The residual toner adhering to the surface of the photosensitive drum 25 after the transfer of the visible image is removed by the cleaning device 31 having the cleaning blade 31a. Is collected in the toner collection tank 31b. A double-sided entrance guide 32 is rotatably provided downstream of the fixing device 30 in the transfer paper conveyance direction, and the transfer paper P discharged from the fixing device 30 is guided to the double-sided conveyance roller pair 33 by the double-sided entrance guide 32. A reversing roller pair 34 is provided downstream of the double-sided conveying roller pair 33 in the transfer paper conveying direction so as to be able to rotate in the forward and reverse directions. It is led to the outside of the main body 21a by being guided to the paper 34 so that its tip end side is located above the paper feed cassette 22a. In addition, a reversing sensor is installed near the reversing roller pair 34.
35 is provided, and this sensor 35 detects that the transfer paper P is guided to the reversing roller pair 34. Then, the reversing roller pair 34 rotates counterclockwise after a predetermined time elapses after the reversing sensor 35 detects the transfer sheet P, and is conveyed again to the registration roller pair 24 by the rotatable reversing guide 36.

The transfer sheet P is conveyed to the photosensitive drum 25 at a predetermined timing by the registration roller pair 24, and then the toner is fixed through the procedure as described above. At this time, the transfer surface of the transfer paper P is reversed to the side opposite to the transfer surface when the paper is fed from the paper feed cassettes 22a and 22b, so that a visible image is formed on both surfaces of the recording paper P. .. Then, the transfer paper P having visible images formed on both sides
After passing through the fixing device 30, the paper is guided to the rotating double-sided entrance guide 32 and discharged to the paper discharge unit 37. Reference numeral 38 in FIG. 3 indicates a double-sided entrance guide 32 by correcting the transfer paper P after fixing in the horizontal direction.
It is a pair of conveyance rollers for conveying to the side.

[0008]

However, in such a conventional image forming apparatus, the fixing device 30 is of the two-stage pressure type, that is, the fixing device 30 is shown in FIG.
Since the pressure rollers 12a and 12b are arranged in the circumferential direction of the heat roller 10 as shown in (d), the angle at which the transfer paper P is wound around the heat roller 10 becomes large, and the transfer paper P is discharged from the fixing device 30. The recording paper P to be discharged has been ejected considerably downward.

For this reason, after the recording paper P is temporarily corrected in the horizontal direction by the conveying roller pair 38 after the paper is discharged, the conveying direction of the recording paper P is switched by the double-sided entrance guide 32. There is a problem that the recording paper P is curled when passing through the pair of transport rollers 38 because it is bent. This has been clarified by an experiment, and even in the lower-conveying two-stage pressurizing type fixing device shown in FIG. 2C, the transfer paper 7 is ejected in a considerably upward direction. Experiments have revealed that curl occurs when the trajectory is corrected by the pair of transport rollers.

When the curled recording paper P is conveyed by the pair of double-sided conveying rollers, the recording sheet P is caught by a guide plate or the like constituting the conveying path and causes edge folds or jams. Not only does it deteriorate, but when it is ejected to the paper ejection unit 37, it is stacked in pieces and falls from the paper ejection unit 37, which causes a problem such as deterioration of stackability. I got it.

When a reversing mechanism such as a reversing roller pair 34 provided above the paper feeding cassette 22a is used to change the conveying direction of the recording paper P to form a visible image on both sides of the recording paper P, When the sheet P is conveyed to the reversing roller pair 34, the operator has intentionally pulled the recording paper P out of the main body 21a so that the front end portion thereof is located above the sheet feeding cassette 22a.
The paper cassette 22a
There was a problem that it was caught in and jam occurred.
Further, since the dedicated reversing mechanism is provided above the main body 21a, there is a problem that the cost of the device increases.

Therefore, an object of the present invention is to provide an image forming apparatus capable of improving the stack performance by preventing the recording paper from curling after fixing the visible image. Further, in the invention according to the second aspect, by providing the function of changing the direction of the transfer paper in the paper discharge section, it is possible to surely prevent the situation in which the transfer paper is intentionally pulled out at the time of changing the direction. ,
An object of the present invention is to provide a low-cost image forming apparatus that does not require a dedicated reversing mechanism.

[0013]

The invention according to claim 1 is
In order to achieve the above-mentioned object, a heat roller with which the paper surface side of the transfer paper on which a visible image is formed by the image forming means is in contact, and a heat roller that is arranged along the transport direction of the transfer paper and sandwiches the transfer paper together with the heat roller. While the image forming apparatus includes a fixing device including a pair of pressure rollers that press the transfer sheet toward the heat roller, a nip portion between the heat roller and the pressure roller located on the downstream side in the transfer sheet conveyance direction. It is characterized in that a paper discharge roller pair and a paper discharge tray are provided along the tangential direction of.

According to a second aspect of the present invention, in order to achieve the above object, two paper discharge roller pairs are provided, and a transfer paper is discharged to a paper discharge tray between the paper discharge roller pairs. A switching claw capable of switching to a switching position and a second switching position for transporting the transfer paper to the return path for returning the transfer paper to the image forming means is provided, and a paper discharge roller pair on the paper discharge tray side of the two paper discharge roller pairs. It is characterized in that a drive motor for rotating the motor is provided.

[0015]

According to the first aspect of the invention, the transfer paper having the visible image fixed by the fixing device is discharged straight to the paper discharge tray. Therefore, the transfer sheets are not curled, and the sheets are regularly stacked on the sheet discharge tray to improve the stacking performance. According to the second aspect of the present invention, the transfer paper having the visible image fixed on one surface by the fixing device is conveyed straight to the paper discharge tray, and is directed by the paper discharge roller on the paper discharge tray side. After the conversion, the visible image is formed on the other surface by being conveyed again to the image forming means through the return path. Therefore, when a visible image is formed on both sides of the transfer paper, the transfer paper does not curl, and when the paper is returned to the return path, the transfer paper does not have a fold or a jam. .. As a result, workability of the image forming work is improved.

In addition to this, since a mechanism for changing the direction of the transfer paper is provided in the paper discharge section, there is no possibility that the transfer paper is intentionally pulled out when the direction is changed.
No error occurs. Further, the dedicated inversion mechanism as in the prior art is not required, and the cost of the image forming apparatus can be reduced.

[0017]

EXAMPLES The present invention will be described below based on examples.
FIG. 1 is a diagram showing an embodiment of an image forming apparatus according to the present invention. It should be noted that in the present embodiment, the paper discharge unit and the return path of the transfer paper are different from those of the image forming apparatus shown in FIG. 3, but the other configurations are substantially the same as those of the conventional example, and therefore only the paper discharge unit and the return path are provided. , And other configurations are not shown.

First, the structure will be described. In FIG. 1, 41
Is a fixing device, and the fixing device 41 is a heat roller with which the paper surface side of the transfer paper P1 on which a visible image is formed by an image forming means including a photoconductor drum, a charging charger, a developing device, a transfer charger and the like (not shown) is in contact. 42 and transfer paper P
1. The transfer paper P1 is arranged along the conveyance direction of the first transfer roller P1 while holding the transfer paper P1 together with the heat roller 42.
It is composed of a pair of a first pressure roller 43 and a second pressure roller 44 that apply pressure to the side.
3 and 44 are heat rollers 42 by spring members 45 and 46.
Biased to the side.

Further, in the tangential direction of the nip portion of the heat roller 42 and the second pressure roller 43 located on the downstream side of the transfer paper P1 in the conveying direction, two first paper discharge roller pairs 47 and two second paper discharge roller pairs are provided. In addition to 48, a paper discharge tray 49 is provided, and the transfer paper P1 nipped by the heat roller 42 and the second pressure roller 44 is linearly moved through the first and second paper discharge roller pairs 47, 48. The paper is discharged to the paper discharge tray 49.

A switching claw 50 is rotatably provided between the first and second conveying roller pairs 47, 48.
Conveys the transfer paper P1 discharged from the fixing device 41 to the paper discharge tray 49 as it is to the first switching position (shown by a solid line) and the transfer paper P1 discharged from the fixing device 41 to the return path 51. It can be switched to the second switching position (shown by a broken line).

The return path 51 comprises a space defined by a guide plate 51a, and the return path 51 is provided with a plurality of double-sided conveying roller pairs 52 to 54 along the extending direction thereof. Then, the transfer sheet P1 conveyed to the return path 51 is guided to the registration roller pair 55 by these roller pairs 52 to 54, and then is again conveyed to the image forming means at a predetermined timing by the registration rollers 55. ..

On the other hand, the second paper discharge roller pair 48 is connected to a drive motor (not shown), and the second paper discharge roller pair 48 is driven to rotate in the forward and reverse directions by this drive motor. Note that FIG.
In the figure, 56 is a separation claw for separating the transfer paper from the heat roller 42, and 57 and 58 are paper feed rollers for feeding the transfer paper stored in a paper feed cassette (not shown). Next, the operation will be described.

The transfer paper P1 on which a visible image is formed by the image forming means is introduced into the nip portion between the heat roller 42 and the first pressure roller 43 and fixed there, and then the heat roller 42 and the second pressure roller 43. It is introduced to the nip portion of 44 and re-fixed.
At this time, since the switching claw 50 is in the first switching position shown by the solid line, the transfer sheet P1 is moved along the tangential direction between the heat roller 42 and the second pressure roller 44 by the first and second sheet discharging roller pairs 47 and 48. The paper is conveyed straight and discharged to the paper discharge tray 49. In addition,
At this time, the second paper discharge roller pair 48 rotates in the direction of arrow a by the normal rotation of the drive motor.

On the other hand, when a visible image is formed on both sides of the transfer sheet P1, the visible image is fixed on the transfer sheet P1 by the fixing device 41 as described above, and then the transfer sheet P1 is ejected from the discharge tray 49.
To be transported to. Then, the rear end of the transfer paper P1 is the second
When it is pinched by the discharge roller pair 48, the switching claw 50 is switched to the second switching position shown by the broken line, and the drive motor is reversely driven to move the second discharge roller pair 48 in the direction opposite to the arrow a direction. Rotate.

Therefore, the transfer paper P1 is changed in direction, the transfer paper is supplied to the return path 51, and the pair of double-sided conveyance rollers 52 is supplied.
It is conveyed to the registration roller pair 55 by. Then, the registration rollers 55 supply the image forming apparatus at a predetermined timing. At this time, the surface of the transfer paper P1 on which the visible image is formed is opposite to the surface on which the visible image is first formed, so that the visible images are formed on both surfaces of the transfer paper P1.

As described above, in this embodiment, the heat roller 42 is used.
Since the pair of conveying rollers 47 and 48 and the discharge tray 49 are provided along the tangential direction of the nip portion of the second pressure roller 44, the transfer sheet P1 on which the visible image is fixed by the fixing device 41 is straight. The paper is output to the output tray. Therefore, the transfer paper P
It is possible to prevent curl from occurring and to stack the sheets neatly on the paper discharge tray 49 to improve stacking performance.

A first switching position for discharging the transfer sheet P1 to the discharge tray 49 between the pair of discharge rollers 47 and 48, and a first transporting path 51 for returning the transfer sheet P1 to the image forming means again. The transfer pawl P on which the visible image is fixed by the fixing device 41 is provided because the switching pawl 50 that can be switched to the two switching positions is provided and the drive motor that rotates the second paper discharge roller pair 48 in the forward and reverse directions is provided.
1 can be discharged straight to the discharge tray 49, and curling of the transfer paper P1 can be prevented. Therefore, the transfer sheets P1 can be stacked on the discharge tray 49 in an orderly manner, and the stacking performance can be improved.

Further, the transfer paper P1 on which the visible image is fixed on one surface by the fixing device 41 is straightened to the paper discharge tray.
In addition to being able to convey the image toward the sheet 49, the second sheet discharging roller pair 48 changes the direction, and then conveys it again to the image forming means via the return path 51 to form a visible image on the other surface. You can Therefore, it is possible to prevent the transfer sheet P1 from curling when a visible image is formed on both surfaces of the transfer sheet P1, and to transfer the transfer sheet P1 to the return path 51.
It is possible to prevent the ear 1 from causing an ear break or causing a jam, and it is possible to improve the workability of the image forming work.

In addition to this, since a mechanism for changing the direction of the transfer sheet P1 is provided in the discharge section, it is possible to prevent the situation in which the transfer sheet P1 is intentionally pulled out at the time of changing the direction. Therefore, it is possible to prevent an error or the like from occurring. Further, it is possible to eliminate the need for a dedicated reversing mechanism as in the related art, and it is possible to reduce the cost of the image forming apparatus. Further, the space having the reversing mechanism as in the prior art can be utilized for other functions, for example, a space for mounting an envelope feeder or a space for newly providing a paper feeding mechanism of a paper feeding cassette.

[0030]

According to the first aspect of the invention, the transfer paper having the visible image fixed by the fixing device can be discharged straight to the paper discharge tray, and the transfer paper is curled. Can be prevented. For this reason, the transfer sheets can be regularly stacked on the sheet discharge tray, and the stacking performance can be improved.

According to the second aspect of the present invention, the transfer sheet having the visible image fixed on one surface thereof by the fixing device can be conveyed straight toward the discharge tray, and the transfer sheet can be conveyed. After the sheet is turned by the sheet discharge roller on the sheet discharge tray side, it is conveyed again to the image forming means through the return path, so that a visible image can be formed on the other surface. Therefore, it is possible to prevent the transfer paper from curling when forming a visible image on both sides of the transfer paper,
When the paper is returned to the return path, it may cause tears on the transfer paper,
It is possible to prevent the occurrence of jam and improve the workability of the image forming work.

In addition to this, since a mechanism for changing the direction of the transfer paper is provided in the paper discharge section, it is possible to prevent the situation in which the transfer paper is intentionally pulled out when the direction of the transfer paper is changed. Therefore, it is possible to prevent an error or the like from occurring. Further, it is possible to eliminate the need for a dedicated reversing mechanism as in the related art, and it is possible to reduce the cost of the image forming apparatus.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a fixing device, a paper discharge mechanism, and a return path that are mounted on an image forming apparatus according to the present invention.

2A and 2B are configuration diagrams of a general fixing device, FIG. 2A is a schematic configuration diagram of a one-stage pressure type fixing device applied to a lower conveyance type image forming apparatus, and FIG. 1 is a schematic configuration diagram of a one-stage pressure type fixing device applied to the image forming apparatus of FIG. 1, (c) is a schematic configuration diagram of a two-stage pressure type fixing device applied to the lower conveyance type image forming apparatus, FIG. 3D is a schematic configuration diagram of a two-stage pressure type fixing device applied to an upper conveyance type image forming apparatus.

FIG. 3 is a configuration diagram of a conventional image forming apparatus.

[Explanation of symbols]

 41 Fixing device 42 Heat roller 43 First pressure roller (pressure roller) 44 Second pressure roller (pressure roller) 47 First paper discharge roller pair (paper discharge roller pair) 48 Second paper discharge roller pair (paper discharge) (Paper roller) 49 Output tray 50 Switching claw 51 Return path

Claims (2)

[Claims] 1. A heat roller on which a paper surface side of a transfer sheet on which a visible image is formed by an image forming means comes into contact, and a heat roller which is arranged along the conveyance direction of the transfer sheet and holds the transfer sheet together with the heat roller. In an image forming apparatus including a fixing device including a pair of pressure rollers that press the paper toward the heat roller, a tangential direction of a nip portion between the heat roller and the pressure roller located on the downstream side in the transfer paper conveyance direction. An image forming apparatus characterized in that a pair of paper discharge rollers and a paper discharge tray are provided along the line. 2. A pair of discharge rollers is provided, and
A switching claw capable of switching between a first switching position for discharging the transfer sheet to the discharge tray and a second switching position for transporting the transfer sheet to the return path for returning the transfer sheet to the image forming means is provided between the pair of discharge rollers. 2. The image forming apparatus according to claim 1, further comprising a drive motor that rotates the pair of discharge rollers on the side of the discharge tray of the two pairs of discharge rollers in the forward and reverse directions.