JP2893555B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus such as an electrophotographic copying machine using an electrophotographic system, which can be used when passing through a fixing device.
With regard to an apparatus for correcting curl generated in copying, in particular,
When a mechanism for correcting the curl by pressing the pressing roll against the belt is provided, the paper conveying speed of the curl removing device is configured to be variable, and a loop of a predetermined shape is formed on the paper between the two devices. The present invention relates to an apparatus that can perform curl correction in a state.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine using an electrophotographic system, a toner image is formed on an image carrier such as a photosensitive drum, and the toner image is transferred to a sheet. A means for applying heat and pressure to fix the paper and make a copy is used. However, when the paper carrying the toner image is fixed through a fixing device, there is a problem that the paper is curved to one side by applying heat or pressure to the paper, thereby forming a curled paper. Further, conditions such as the image density of the toner image carried on the sheet also affect the state of curl, and the higher the image density, the greater the tendency for curl to occur.

As described above, when a sheet is curled, when the curled sheet is conveyed in a sheet path,
It may be caught on the end of the guide plate in the paper path or locked by a gate member or the like. Then, the curled paper may interfere with the transport operation in the paper path,
A jam may occur on the way. Also,
Even when curled paper is sorted and stored in the sorter tray, the paper is not stored neatly, so full detection information is output before the number of copies set in the tray is reached, and normal copying is performed. The case where it cannot be accommodated occurs. In addition, there arises a problem that the next copy collides with the leading end of the copy accommodated in the tray, and the operation of accommodating the copy is not normally performed.

In order to solve the above-mentioned problem caused by the curled paper, for example, as shown in JP-A-59-167450, a curl correction device is arranged downstream of a fixing device to curl a copy. Are corrected and discharged toward a discharge tray or the like. In the curl correction device shown in the conventional example, a pressing roll is arranged on a belt that conveys the paper discharged from the fixing device, and the paper is passed through a portion where the belt is pressed by the pressing roll. Make up. When a sheet passing between the belt and the pressing roll is detected, the sheet is rapidly bent in a state where the rotation of the pressing roll is stopped with respect to a predetermined range of the leading end of the sheet. By adding an extraordinary effect, the curl of the paper is removed. By using the above-described curl correction device, even if the paper discharged from the fixing device has a large curl, a certain portion of the leading end of the copy is not curled. To
Copy accommodation can be improved. Another advantage is that jamming can be prevented even when a copy is conveyed in a paper path.

[0005]

The above-described curl removing device is generally disposed downstream of the fixing device, and when a state in which the sheet is pulled against the fixing device occurs, a belt is removed. This causes a problem of rubbing the image surface. Therefore, in the conventional device, the curl removing device is arranged at a larger interval than the length of the sheet with respect to the fixing device so that the sheet does not have a pulling action between the two devices. Therefore, in a relatively large apparatus such as an electronic copier, there is sufficient room inside the apparatus, so that a conventional curl removing apparatus can be provided, but in a small apparatus, a curl removing apparatus can be provided. There is a problem that can not be done.

In order to solve the above-mentioned problem, it is conceivable to dispose the curl removing device close to the fixing device and set the transport speed of the curl removing device to be smaller than the paper transport speed of the fixing device. . However, when a loop is formed on the paper between the two devices, the loop becomes very large for large-size paper, and the paper slides strongly on the guide plate in the paper path, and the image surface Problems such as damage to the device. In addition, when the paper loop becomes large, an inconvenient state such as folding of the paper in the paper path occurs. Therefore, it is necessary to accurately set the paper transport speed in both devices and form an appropriate amount of loop for the paper, but the feed speed in each device is accurately adjusted according to the type of paper and the like. Difficult to control.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems of the conventional curl removing device. In this case, the fixing device and the curl removing device are arranged close to each other, and the paper conveying speed of the curl removing device is adjusted. It is an object of the present invention to provide a device which is configured to perform the above-mentioned steps and is provided with means for forming an appropriate loop between the two devices.

[0008]

SUMMARY OF THE INVENTION The present invention relates to an image forming apparatus for forming an unfixed image through a fixing device. The invention according to claim 1 of the present invention is provided at a downstream side of the fixing device, and conveys the sheet after fixing, and curls the sheet to remove the curl of the sheet by holding the sheet, and the fixing device. A sensor that comes into contact with a paper loop generated by a paper conveyance speed difference from the curl removing unit and turns on / off according to the size of the loop; and the fixing device and the curl removal based on on / off by the sensor. Control means for controlling the transport speed relationship of the means. The invention of claim 2 is
The control means switches the transport speed of the curl removing means between high speed and low speed in accordance with an output of the sensor.

With the above arrangement, according to the first aspect of the present invention, a sensor is provided between the fixing device and the curl removing means for detecting the contact with the paper loop. Since the control of the sheet transport speed is performed, the loop amount of the sheet can be reliably controlled. Further, according to the second aspect of the present invention, since the sheet conveying speed of the curl removing unit is switched between high speed and low speed based on the detection information from the sensor, the operation of the sheet loop control can be simplified. In the present invention, since a loop of a proper amount of paper can be formed between the fixing device and the curl removing means, the loop portion can be prevented from being rubbed by the guide plate, and the image surface is damaged. Is prevented. Therefore, in the apparatus of the present invention, since the speed of the curl removing device can be changed according to the state of the loop of the sheet, there is no problem such as pulling the sheet between the two apparatuses.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A curl correction device of an image forming apparatus according to the present invention will be described with reference to the illustrated example. As shown in FIG. 1, a curl correction device of an image forming apparatus according to the present invention includes a curl removing device 10 disposed downstream of a fixing device 1, and a copy discharged from the fixing device is transferred to a belt 11 and a pressing roll 1.
In addition, a function of correcting a curl is provided by adding an action of sharply bending the sheet between the first and second positions. FIG. 1
In the curl correction device of the image forming apparatus shown in (1), the discharge roller 2 is disposed downstream of the fixing roller of the fixing device, and the curl removal device 10 is disposed at a predetermined interval downstream of the discharge roller 2. Have been placed. The paper path between the fixing device 1 and the curl removing device 10 is regulated by upper and lower guide plates 3 and 4, but in the apparatus of the present invention, the loop setting gate 5 corresponds to the upper guide plate 3. And a loop relief gate 6 corresponding to the lower guide plate 4.
And the loop setting gate 5 and the loop release gate 6 are provided so as to be swingable. Further, an actuator 7 and a sensor 8 are provided in correspondence with the loop relief gate 6, and the actuator 7 is oscillated by the loop of the paper via the shaft 7a. It is configured so that the speed can be changed.

A curl removing device 10 arranged downstream of the fixing device imparts a sharp bending action to the sheet when passing the sheet between the belt 11 and the pressing roll 15, and also removes the sheet. It is configured to perform an action of correcting curl by adding an intense action. FIG. 1
As shown in FIG. 3, the curl removing apparatus 10 uses an apparatus configured as shown in FIG. In the curl removing device 10 shown in FIG. 3, the belt 11 is set to a state in which a predetermined tension is applied to the belt 11 by extending the belt 11 around a drive shaft 12 and a driven shaft 13. The pressing roll 15 pressed against the belt 11 supports a small-diameter member on the rod by a link 17, and a cam follower 16 disposed at the other end of the link 17 engages with a cam member 18. Combined
A pressing action on the pressing roll 15 is provided. The cam member 18 has an indexing disk 22 provided on its support shaft 19, and a locking claw member 21 actuated by a solenoid 20 against a projection 23 of the disk 22.
Is engaged to control the rotational position of the cam member 18.

Then, the cam shaft 19 is driven by a motor 25 to rotate the cam member 18 so that the pressing roll 15
By setting the amount by which the belt 11 is pressed, the curl correction performance of the paper can be changed.
In other words, the size of the curl that occurs in a copy that has passed through the fixing device depends on conditions such as the paper quality of the paper and the density of the toner image. It is necessary to set in accordance with the degree of curling to be performed. Therefore, in the curl removing device of the present invention, for example, the curl correction performance of the curl removing device is changed in accordance with the copy mode such as plain paper and tracing paper, monochrome copy, and color copy. The device is configured to obtain.

The apparatus shown in FIG. 1 employs a curl removing apparatus having the structure shown in FIG. 3 and has a mechanism capable of adjusting the sheet conveying speed in the curl removing apparatus. . Further, as shown in FIG. 1, in the apparatus of the present invention, paper sensors S1 and S2 are disposed between the fixing device 1 and the curl removing device 10 in order to detect the paper, It is configured so that the state can be detected. Of course, the paper sensor
Even if only one is provided, it is possible to detect copy and control the operation of each member as described below.

Next, the operation of each member when removing the curl of the sheet in the apparatus of the present invention will be described. First, when a copy is discharged from the fixing device 1, each device is set to the position shown in FIG.
4 and the leading end of the paper is
The nip position is set to zero. At this time, the belt 11 of the curl removing device 10 is driven at a speed V lower than the paper transport speed V1 by the fixing device 1 and the discharge roller 2.
2 is driven. Then, the leading end of the copy is nipped between the belt 11 of the curl removing device and the pressing roll 15, and after a certain period of time, a loop is formed in the copy between the two devices. Therefore, after a predetermined time has passed since the paper sensor disposed in the paper path has detected the paper, the loop setting gate 5 and the loop release gate 6 are operated by a driving unit (not shown) as shown in FIG. Rock to the position shown in. Then, the copy paper P is pressed by the loop setting gate 5 to form a loop downward, and this state is continued until the loop swings the actuator 7 and is detected by the sensor 8. .

In the state shown in FIG. 2, when the copy loop becomes larger than a predetermined value while the copy is being conveyed, and the actuator 7 swings to the position shown by the imaginary line, the sensor 8 outputs the detection information, and the information is input to the control device. Then, the control device changes the drive speed of the drive shaft 12 of the curl removing device 10 at high speed,
An operation for eliminating the loop is performed, and after a certain period of time has elapsed after the detection information of the sensor 8 disappears, the paper conveying speed of the curl removing device is returned to the constant speed again. By driving the paper transport speed of the curl removing device 10 in accordance with the information from the sensor 8 and the low speed mode set in the control device, the operation of transporting the copy while adjusting the amount of loop generated in the copy. Can be performed.

The operation of controlling the loop for copying in the apparatus of the present invention as described above can be explained as follows. First, assuming that the paper transport speed in the fixing device is V1, the tolerance of the paper transport speed by members constituting the fixing device and the like is ± a%, the paper transport speed in the curl removing device is V2, and the tolerance is ± b%, The paper conveyance speed in the curl removing device is V2 = V1 · (100−a) / (1
00 + b). This does not cause a problem when the distance between the fixing device and the curl removing device is larger than the maximum paper size used for the image forming apparatus, but such a problem occurs in a general copying machine. It is difficult to obtain a large space. Therefore,
When the curl removing device is placed very close to the fixing device, the speed of the curl removing device is equal to the paper transport speed of the fixing device to prevent the paper from being pulled by the curl removing device. Or lower.

When the paper transport speed of the curl removing device is set as described above, the paper sent from the fixing device to the curl removing device is used for a predetermined time by using the information detected by the paper sensor S2. Then, after the leading end of the sheet is securely nipped by the curl removing device, the two gates 5 and 6 are lowered to form a sheet loop toward the lower part and to release the loop. To do. Then, when the loop of the paper is sufficiently large and the loop portion of the paper is in a state of operating the actuator 7, the control device sets the paper transport speed of the curl removing device to V.
Output a command to make 2 ≧ V1 · (100 + a) / (100-b). Then, if the operation of transporting the sheet is continued as it is, the loop of the sheet is eliminated, and the curl removing device pulls the sheet. Therefore, when the sensor 8 is turned off while the curl removing device is being driven at a high speed,
The speed of the curl removing device is returned to the original low speed, and an operation of forming a loop on the sheet is performed. The effect of changing the speed of the decurling device continues throughout the transport of the sheet. Further, when the interval between sheets conveyed in the sheet path is narrow, there is a concern that a situation may occur in which a subsequent sheet collides with a sheet in which a loop is formed in the preceding sheet. You. Therefore, in the apparatus of the present invention, immediately after the trailing edge of the preceding sheet has passed through the fixing device, the curl removing device is driven at a high speed using the detection information of the sheet sensor S1, and the succeeding sheet collides. Control that does not occur can be performed.

[0018]

As described above, according to the first aspect of the present invention, the sensor for detecting the contact between the fixing device and the curl removing means in contact with the paper loop is provided. Is arranged, and the paper conveyance speed is controlled by the curl removing means, so that the loop amount of the paper can be reliably controlled. According to the second aspect of the present invention, the paper transport speed of the curl removing unit is switched between high speed and low speed based on the detection information from the sensor.
The operation of paper loop control can be simplified. In the present invention, a proper amount of paper loop can be formed between the fixing device and the curl removing unit.
The loop portion can be prevented from being rubbed against the guide plate, and the image surface can be prevented from being damaged. Therefore,
In the apparatus of the present invention, since the speed of the curl removing device can be changed according to the state of the loop of the sheet, there is no problem such as pulling the sheet between the two apparatuses.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a configuration of a curl correction device in an image forming apparatus of the present invention.

FIG. 2 is an explanatory diagram of a state in which a loop is formed on a sheet.

FIG. 3 is an explanatory diagram showing a configuration of a curl removing device of the present invention.

[Explanation of symbols]

1 fixing device, 5 loop setting gate, 6
Loop relief gate, 7 actuators, 8 sensors, 10 curl remover, 11 belt, 1
5 Press roll.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B65H 29/00-29/70

Claims (2)

(57) [Claims] An image forming apparatus that forms an image on an unfixed image through a fixing device is provided downstream of the fixing device and conveys a sheet after fixing.
At the same time, hold the paper and remove the curl of the paper.
A decurling unit that supports, in contact with the sheet of loop caused by the sheet conveying speed difference between the fixing device and the curl eliminating means, a sensor which is turned on / off by the size of the loop, the on / off by the sensor An image forming apparatus comprising: a control unit configured to control a transport speed relationship between the fixing device and the curl removing unit based on the control information. 2. The control means according to an output of the sensor.
The image forming apparatus according to claim 1, wherein a transport speed of the curl removing unit is switched between a high speed and a low speed.