JPH04338059A - Curl correcting device for image forming device - Google Patents

Abstract

PURPOSE:To form a sheet into a loop between a fixing device and a curl removing device disposed at the downstream part of the fixing device and adjust the direction and size of this loop optionally to correct the curl of the sheet by the curl removing device in the image forming device of an electronic copying machine or the like. CONSTITUTION:A curl removing device 10 is disposed with a specified space at the downstream part of a fixing device 1, and a curl generated to a sheet is corrected by this curl removing device 10. The curl removing device 10 is formed in such a way that the quantity of pressing a pressure roller 15 to a belt 11 can be regulated optionally by a cam member 18. Between both devices 1, 10, a loop setting gate 5 and a loop escape gate 6 are disposed to control the loop of the sheet. Meanwhile, the loop state of the sheet is detected by a sensor 8 so as to control the sheet carrier speed in the curl removing device 10.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an apparatus such as an electronic copying machine using an electrophotographic method, in which when passing through a fixing device,
In particular, regarding a device for correcting curl that occurs in copies,
When a mechanism is provided to correct curl by pressing a pressure roll against a belt, the paper conveyance speed of the curl removal device is configured to be variable, and a loop of a fixed shape is formed in the paper between both devices. The present invention relates to a device that allows curl correction to be performed in a state in which the curl is corrected.

0002

2. Description of the Related Art In an image forming apparatus such as an electronic copying machine using an electrophotographic method, a toner image is formed on an image bearing member such as a photoreceptor drum, and after the toner image is transferred to paper, it is transferred to a fixing device. A method is used to apply heat and pressure to fix the image and make copies. However, when the paper carrying the toner image is fixed through a fixing device, heat and pressure are applied to the paper, causing the paper to curve to one side, resulting in curled paper. Further, conditions such as the image density of the toner image carried by the paper also influence the state of curling, and there is a tendency that the higher the image density, the more curling occurs.

As mentioned above, when paper curls occur, when the curled paper is conveyed through the paper path,
It may get caught on the edge of the guide plate in the paper path or be stopped by a gate member or the like. The curled paper may impede the conveyance in the paper path, or
This may cause a jam to occur during the process. Also,
Even when curled paper is sorted and stored in the tray of the sorter, since the paper is not stored before it is ready, a full detection information is output before the tray reaches the number of copies set for the tray, and copies are not made correctly. There may be cases where it is not possible to accommodate the In addition, other problems occur, such as the next copy hitting the leading end of the copy housed in the tray, making it impossible to properly accommodate copies.

In order to solve the above-mentioned problems caused by curled paper, a curl correction device is disposed downstream of the fixing device, as shown in, for example, Japanese Patent Application Laid-open No. 59-167450. In a modified state, the paper is ejected onto an ejection tray or the like. In the curl correction device shown in the conventional example, a pressure roll is disposed on a belt that conveys paper discharged from a fixing device, and the paper is passed through a portion of the belt pressed by the pressure roll. It consists of When a sheet of paper passing between the belt and the pressure roll is detected, a predetermined range of the leading edge of the paper is suddenly bent while the rotation of the pressure roll is stopped. A squeezing action is added to remove curls from the paper. By using the above-mentioned curl correction device, even if the paper ejected from the fixing device has a large curl, a certain part of the leading edge of the copy will not be curled. To,
Copy capacity can be improved. Further, there is an advantage that jams can be prevented from occurring even when copies are transported within the paper path.

[0005]

[Problems to be Solved by the Invention] The curl removing device as described above is generally placed downstream of the fixing device, and if the paper is pulled against the fixing device, the belt This causes problems such as scratching the image surface. Therefore, in conventional apparatuses, the curl removal device is arranged at a distance greater than the length of the paper from the fixing device, so as to prevent the paper from being pulled between the two devices. Therefore, although relatively large devices such as electronic copiers have sufficient space inside the device and can be equipped with a conventional curl removal device, small devices cannot be equipped with a curl removal device. The problem is that it can't be done.

In order to solve the above problem, it is conceivable to arrange the curl removing device close to the fixing device and to set the paper transport speed of the curl removing device to be smaller than the paper transport speed of the fixing device. . However, when setting the paper to form a loop between both devices, the loop becomes very large for large-sized paper, and the paper slides strongly against the guide plate in the paper path, causing the image to Problems such as damage may occur. Furthermore, if the paper loop becomes large, an inconvenient condition such as the paper being bent within the paper path may occur. Therefore, although it is necessary to accurately set the paper transport speed in both devices and form an appropriate amount of loops on the paper, it is necessary to accurately set the paper feed speed in each device depending on the type of paper, etc. Difficult to control.

[0007]

OBJECTS OF THE INVENTION The curl correcting device for an image forming apparatus of the present invention solves the problems of the conventional curl removing device as described above. It is an object of the present invention to provide an apparatus that is configured to be able to adjust the paper conveyance speed in the apparatus, and that is provided with means for forming an appropriate loop between both apparatuses.

[0008]

SUMMARY OF THE INVENTION The present invention relates to an image forming apparatus that transfers a toner image formed using an electrophotographic method onto a sheet of paper and fixes it through a fixing device to create a copy. In the apparatus of the present invention, a curl removal device is disposed downstream of the fixing device, and the paper conveyance speed by the curl removal device and the paper conveyance speed in the fixing device are set to different speeds, and both members Means for forming a loop on the paper and means for controlling the size of the loop are provided between the two.

With the above-described configuration, the curl removing device can be placed close to the fixing device, and it is possible to provide the curl removing device even in a small image forming apparatus. Further, the curl correction device of the image forming apparatus of the present invention can form an appropriate amount of loop between the fixing device and the curl removal device, so that it is possible to prevent the loop portion from being rubbed by the guide plate. , damage to the image surface is prevented. Further, in the apparatus of the present invention, since the speed of the curl removal device can be changed depending on the state of the paper loop, problems such as the paper being pulled together between the two devices do not occur.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS A curl correction device for an image forming apparatus according to the present invention will be explained according to an illustrated example. As shown in FIG. 1, the curl correction device of the image forming apparatus according to the present invention includes a curl removal device 10 disposed downstream of a fixing device 1, and copies ejected from the fixing device by a belt 11 and a pressure roll 1.
5, a sharp bending action is added to provide an action to correct the curl. Figure 1 above
In the curl correction device for an image forming apparatus shown in FIG. It is placed. The paper path between the fixing device 1 and the curl removing device 10 is formed by upper and lower guide plates 3.
, 4, but in the device of the present invention, a loop setting gate 5 is arranged in correspondence with the upper guide plate 3, a loop release gate 6 is arranged in correspondence with the lower guide plate 4, and the loop A setting gate 5 and a loop release gate 6 are each swingably provided. Further, an actuator 7 and a sensor 8 are provided corresponding to the loop release gate 6, and the actuator 7 is swung by the loop of the paper via the shaft 7a, and the information is used to convey the paper by the curl removal device. It is configured so that the speed can be changed.

[0011] A curl removal device 10 disposed downstream of the fixing device applies a sharp bending action to the paper when passing the paper between the belt 11 and the pressure roll 15, and also bends the paper. It is configured to apply a squeezing action to correct curls. Figure 1 above
The decurling device 10 shown in FIG. 3 uses a device configured as shown in FIG. In the curl removal device 10 shown in FIG. 3, the belt 11 is stretched around a drive shaft 12 and a driven shaft 13, and a predetermined tension is applied to the belt 11. Further, the press roll 15 that is 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 is engaged with a cam member 18. combined,
A pressing action is applied to the pressing roll 15. The cam member 18 is provided with an indexing disk 22 on its support shaft 19, and a locking pawl member 21 operated by a solenoid 20 is attached to a protrusion 23 of the disk 22.
By engaging, the rotational position of the cam member 18 is controlled.

Then, the cam shaft 19 is driven by the motor 25, the cam member 18 is rotated, and the pressure roll 15 is rotated.
By setting the amount by which the belt 11 is pressed by the belt 11, the paper curl correction performance can be changed. In other words, the size of curl that occurs on a copy that passes through the fixing device varies depending on conditions such as the quality of the paper and the density of the toner image, so the curl correction performance of the curl removal device depends on the amount of curl that occurs on the copy. It is necessary to set the setting according to the degree of curl. Therefore, in the curl removing device of the present invention, the curl correction performance of the curl removing device is changed depending on the case of plain paper and tracing paper, and the copying mode such as monochrome copying and color copying. using an apparatus configured to obtain

In the apparatus shown in FIG. 1, the curl removing device having the configuration shown in FIG. . Further, as shown in FIG. 1, in the apparatus of the present invention, paper sensors S1 and S2 are arranged between the fixing device 1 and the curl removal device 10 to detect paper, and to monitor the movement of the paper. It is configured so that the state can be detected. Of course, the paper sensor is
Even if only one is provided, it is possible to detect copying and control the operation of each member as described below.

Next, the operation of each member in the apparatus of the present invention when removing curls from paper will be explained. First, when a copy is ejected from the fixing device 1, each device is set at the position shown in FIG.
4, and the leading edge of the paper is placed in the curl removing device 1.
0 to reach the nip position. At this time, the belt 11 of the curl removing device 10 moves at a speed V2 that is slower than the paper conveyance speed V1 by the fixing device 1 and the discharge roller 2.
It is driven by. Then, the leading end of the copy is nipped between the belt 11 of the curl removal device and the pressure roll 15, and after a certain period of time, a loop is formed in the copy between the two devices. Therefore, after a certain period of time has passed since the paper sensor placed in the paper path detects the paper, the loop setting gate 5 and the loop relief gate 6 are opened.
is swung to the position shown in FIG. 2 by operating a drive means (not shown). 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 certain value while the copy is being conveyed and the actuator 7 is swung to the position shown by the imaginary line, the sensor 8 outputs 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 removal device 10 at high speed,
An operation is performed to eliminate the loop, and when a certain period of time has elapsed since the sensor 8 no longer detects information, the paper conveyance speed by the curl removal device is returned to a constant speed. By driving the paper conveyance speed by the curl removal device 10 based on information from the sensor 8 and a low speed mode set in the control device, the copy is conveyed while adjusting the amount of loops that occur in the copy. can be made to do so.

The loop control operation for copying in the apparatus of the present invention as described above can be explained as follows. First, let the paper conveyance speed in the fixing device be V1, the tolerance of the paper conveyance speed due to the members constituting the fixing device be ±a%, the paper conveyance speed in the curl removal device be V2, and the tolerance be ±b%. The paper conveyance speed in the curl removing device is V2=V1・(100-a
)/(100+b). This problem does not occur if the distance between the fixing device and the curl removal device is greater than the maximum paper size used in the image forming device, but in general copying machines, etc. It is difficult to obtain a large space. Therefore, in order to prevent the paper from being pulled by the curl removing device when the curl removing device is placed very close to the fixing device, the speed of the curl removing device should be set to the paper transport speed of the fixing device. It is necessary to set it equal to or lower than .

When the paper conveyance speed of the curl removal device is set as described above, the paper sent from the fixing device toward the curl removal device is detected by the paper sensor S2 when a predetermined period of time elapses. After the leading edge of the paper is securely nipped by the curl removal device, the two gates 5 and 6 are lowered to form a loop of paper toward the bottom and to release the loop. do it like this. Then, when the loop of the paper becomes sufficiently large and the loop portion of the paper is in a state where the actuator 7 is actuated, the control device changes the paper conveyance speed of the curl removal device to V.
Outputs a command to set 2≧V1・(100+a)/(100−b). Then, if the paper continues to be conveyed in this state, the loop of the paper disappears and the curl removing device becomes in a state where it pulls the paper. Therefore, if the sensor 8 turns off while the curl removal device is being driven at high speed, the speed of the curl removal device is returned to the original low speed to form a loop in the paper. The effect of changing the speed of the decurler continues throughout the paper transport. In addition, if the distance between sheets conveyed in the paper path is narrow, there is a concern that a situation may occur in which the following sheet collides with the preceding sheet in which a loop has been formed. Ru. Therefore, in the apparatus of the present invention, immediately after the trailing edge of the preceding sheet passes through the fixing device,
Using the detection information of the paper sensor S1, the curl removal device can be driven at high speed, and control can be performed to prevent the following paper from colliding with the curl removal device.

[0018]

[Effects of the Invention] By configuring the curl correcting device for an image forming apparatus according to the present invention as described above, the curl removing device can be placed close to the fixing device, and curl correction can be performed even in a small image forming device. It becomes possible to provide a removal device. Further, the curl correction device of the image forming apparatus of the present invention can form an appropriate amount of loop between the fixing device and the curl removal device, so that the loop portion is not rubbed by the guide plate or the image surface can be prevented from being damaged. Further, in the apparatus of the present invention, since the speed of the curl removal device can be changed depending on the state of the paper loop, problems such as the paper being pulled together between the two devices do not occur.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the 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 of paper.

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

[Explanation of symbols]

1 Fixing device, 5 Loop setting gate, 6 Loop release gate, 7 Actuator, 8 Sensor, 10 Curl removal device, 11 Belt, 15 Press roll.

Claims (1)

[Claims] 1. An image forming apparatus that transfers a toner image formed on a photoreceptor using an electrophotographic method onto a sheet of paper and fixes it through a fixing device to create a copy, comprising: a curl removal device provided downstream of the fixing device; the paper transport speed by the curl removing device and the paper transport speed in the fixing device are set to different speeds, and a loop is formed for the paper between the fixing device and the curl removing device. 1. A curl correction device for an image forming apparatus, comprising: a means for controlling the size of the loop; and a means for controlling the size of the loop.