JP2560779B2 - Paper loop amount controller - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for controlling a loop of a sheet at a sheet introducing portion of a fixing device, and particularly to a portion for introducing a sheet to a heating roller type fixing device. The present invention relates to a device that keeps the amount of paper loops constant and prevents image misalignment and the like from occurring on paper that has passed through a fixing device.

(Prior Art) Conventionally, a heating roller type fixing device is often used in a copying machine. In this heating roller type fixing device, a heating roller and a pressure roller are arranged in parallel, and pressure and heat are applied to a sheet nipped between the two rollers, and the sheet is carried by the sheet. It is an apparatus configured so that an unfixed toner image is melted and pressed against a sheet to form a copy.

Generally, in a copying machine, an apparatus having a structure as shown in FIG. 3 is used. In the apparatus shown in FIG. 3, the paper P on which the toner image is transferred from the photosensitive drum is conveyed by the conveying device 3 and the heating roller 11
It is introduced into a fixing device 10 composed of a pressure roller 12 and a pressure roller 12 to make a copy.

In the heating roller type fixing device as described above, at a stage before the nip part of the roller, a loop as a certain margin part is formed on the sheet, and the image transfer part of the photoconductor drum passes through the conveying device. The paper fed out is nipped between both rollers so that the fixing operation can be performed.

As described above, as a method for forming a loop on the sheet with respect to the upstream portion of the fixing device, means for setting the driving speed of the roller of the fixing device to be slightly slower than the sheet conveying speed of the conveying device. Is used.

Then, by controlling the drive as described above, by pulling the paper too much by the roller of the fixing device, image misalignment or rubbing at the nip portion of the roller,
Alternatively, it is possible to prevent the paper from wrinkling.

(Problems to be Solved by the Invention) However, in a sheet conveying device of a copying machine, the sheet conveying speed is kept constant due to various causes such as variations in processing accuracy of parts constituting the device and slipping of the sheet. It is difficult to maintain.

Also, in a device such as A4 size or B5 size that is commonly used for copying using small size cut paper, after the leading edge of the paper is nipped between both rollers, Then, the trailing edge of the paper separates from the image copying portion of the photoconductor drum in a short time, and after that, the paper is subjected to the conveyance action at the nip portion by the rollers, so that it is pulled by the fixing device. Therefore, it is possible to prevent the toner image from being stretched or rubbed at the image transfer portion of the photosensitive drum.

However, in an apparatus that makes a copy using a large size sheet such as AO size, while the sheet is nipped by the roller of the fixing device, the fixing and transport operations are performed. The operation of transferring the image from the photosensitive drum is continued behind the paper, and the driving of the roller of the fixing device and the feeding of the paper by the rotation of the photosensitive drum are simultaneously performed in parallel.

Then, as described above, when the conveyance speed in the front and rear portions of the sheet cannot be controlled to be constant, the loop amount in the upstream portion of the fixing device cannot be properly maintained, and the loop amount cannot be maintained. When the amount is small, the sheet may be pulled by the fixing device and the toner image may be displaced.

On the contrary, when the amount of the loop is too large, the side carrying the toner image on the paper slides on the structure 8, which causes the toner image to be rubbed and the copy is damaged. There are drawbacks such as being cut.

(Object of the Invention) The present invention solves the above-mentioned drawbacks of the conventionally used apparatus, and in order to keep the loop at the inlet of the fixing apparatus constant, the roller of the fixing apparatus is fixed. It is an object of the present invention to provide a device capable of controlling driving and obtaining a good copy.

(Means and Actions for Solving Problems) A sheet loop amount control device of the present invention is a heating roller system in which a sheet on which a toner image is transferred by an image forming unit such as a photosensitive drum is conveyed by a conveying device. In a device configured to feed the toner to the fixing device and perform fixing, a paper loop detection unit is provided on the upstream side of the fixing device, and a detection signal from the detection unit is input to the control device of the fixing device. An apparatus configured to control the drive mechanism of the sheet conveying means of the fixing device by using the detection signal so that the amount of the sheet loop in the upstream portion of the fixing device can be maintained constant. .

Therefore, in the paper loop amount control device of the present invention, the drive speed of the drive motor is controlled according to the value of the loop detected by the paper sensor, and the conveyance speed of the paper by the fixing device is controlled. As a result, an appropriate amount of loops will be formed in the part in front of the fixing device.

(Example) The structure of the apparatus of the present invention will be described according to the illustrated example.

As shown in FIG. 1, in the photoconductor drum of the present invention, the transfer corotron 2 is arranged at the image transfer portion of the photoconductor drum 1 so as to convey the paper from the image transfer portion. The transport device 3 is provided between the transport device 3 and the fixing device 10.

A guide plate 5 is arranged at the connecting portion between the conveying device 3 and the fixing device 10, and the paper P is conveyed by the guide plate.
It can be inserted into the nip portion of both rollers at a predetermined angle.

The fixing device 10 of the present invention is configured as a heating roller type device, and nips a sheet carrying an unfixed toner image between the heating roller 11 and the pressing roller 12 to perform heating and pressing. By doing so, it is supposed to make a copy. The pressure roller 12 of this fixing device is a drive motor.
The drive motor 13 is driven by the drive motor 13. The drive motor 13 controls the number of rotations thereof by a drive signal from the control device 18.

Further, in order to detect a loop formed on the sheet P at the portion of the guide plate 5, sheet sensors 15 and 16 are arranged above and below the sheet conveying path. In this paper sensor, the lower paper sensor 15 is provided in the hole 6 formed in the guide plate 5, and the upper paper sensor 16 is provided in a predetermined position with respect to the structure 8.

Then, the state of the loop formed on the sheet P is detected by the two sheet sensors 15 and 16 provided at the upper and lower portions of the sheet conveying path, and the detection information from the sheet sensor is input to the control device 18 for control. A drive speed signal is output from the device to the drive motor 13 to adjust the paper conveyance speed in the fixing device 10.

In the embodiment of the present invention shown in FIG. 2, only one sheet sensor 15 is used, and the sheet sensor 15 can detect the loop state of the sheet. Then, the detection information from the paper sensor 15 is input to the control device 18 to control the drive speed of the pressure roller 12 so that the paper loop can be adjusted.

In the device of the present invention configured as described above, the first
As shown in the figure, when the two paper sensors are arranged in the upper and lower portions of the paper conveyance path, when the loop formed on the paper P reaches the position B by these paper sensors, Detection is performed by the upper paper sensor 16, and a command for increasing the drive speed of the fixing device drive motor 13 is output, and the pressure roller 12 is driven at a high speed to lower the overly large loop. Thus, the control is performed so as to prevent the unfixed toner image bearing surface of the sheet from coming into contact with the structure 8.

When the paper sensor 15 detects that the paper approaches the point A, the conveyance speed of the fixing device is high, and the paper pulled by the fixing device leaves the conveyance surface of the conveyance device 3, It shows a linear state from the nip portion of the fixing device to the image transfer portion of the photosensitive drum.

Therefore, when the above-described state occurs, the conveyance speed of the fixing device is higher than the rotation speed of the photoconductor drum 1, so that the paper pulled by the fixing device is not transferred to the image transfer portion of the photoconductor drum. The operation is such as sliding the paper. When the above-described phenomenon occurs, the toner image on the photoconductor drum is rubbed against the paper, which causes a problem such as an unclear image.

Therefore, when the tension of the paper becomes large as described above and a state where the paper is attracted between the fixing device and the photoconductor drum occurs, the control device 18 controls the speed of the drive motor according to the detection information from the paper sensor 15. Is output, and the fixing device adjusts the sheet conveyance speed to reduce the loop of the sheet until it reaches a predetermined value.

Further, as shown in FIG. 2, when only one sheet sensor is used, the sheet sensor 15 detects the upper and lower positions of the loop of the sheet, and the drive motor 13 is driven by the detected information. Make the speed adjustment operation.

In the above-described apparatus of the present invention, as shown in FIG. 1, when the paper sensors are arranged to face each other at the upper and lower portions of the paper transport path, a photo sensor is used as the paper sensor and a loop sensor is used. The state is the position of point A and B
It is possible to detect the loop when approaching each of the positions and the switch device equipped with a detection arm that comes into direct contact with the paper. is there.

Further, as shown in FIG. 2, when a single paper sensor is used, a sensor that can directly measure the distance between the sensor and an object is desirable, such as an ultrasonic sensor. It is possible to use various devices.

In the apparatus shown in FIG. 2, two photosensors having different focal lengths are combined and configured as a paper sensor 15 so that the upper limit and the lower limit can be measured, respectively, and a paper loop detection operation is performed. It is also possible to configure so that it can be performed accurately.

In the embodiment of the present invention described above, the copying machine is
The case of a large-sized device such as AO size that makes a copy on a large-sized paper has been described. However, the paper loop amount control device of the present invention can be applied to a relatively small copying machine. When the copying operation is performed on a sheet longer than the distance between the photoconductor drum and the fixing device, the control operation as described above can be performed.

In addition to the copying machine, the paper loop amount control device of the present invention is also applied to a device of a system in which a toner image is transferred onto a paper and fixed by a fixing device, for example, a device such as a printer. In addition, it can be used as a device for controlling the loop of the paper in the paper transport path in the device using the normal paper.

(Effect of the Invention) Since the device of the present invention is configured as described above,
Just before being nipped between both rollers of the fixing device,
The paper loop can be controlled arbitrarily, and the loop detection device can be easily incorporated in the paper transport path.

Further, by using the apparatus of the present invention, the action of adjusting the amount of loop of the paper caused by slip of the paper or the like is performed at any time, and the loop at the introduction portion of the fixing device is changed, so that the unfixed toner image is formed. It is possible to prevent the phenomenon of being rubbed by a structure or being pulled while being in contact with the photosensitive drum.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the configuration of a sheet loop amount control device of the present invention, and FIG. 2 is an explanatory diagram of another embodiment of the present invention.
FIG. 3 is an explanatory diagram showing the configuration of a conventional device. Reference numeral 1 in the figure: 1 photoconductor drum, 3 transport device, 5 guide plate, 8 structure, 10 fixing device, 11 heating roller, 12 pressure roller, 13 … Drive motor, 15 ・ 16 ……
Paper sensor, 18 ... Control device.

Claims (1)

(57) [Claims] 1. An apparatus configured so that a sheet on which a toner image has been transferred by an image forming means such as a photoconductor drum is conveyed by a conveying device and fed to a heating roller type fixing device to perform fixing. A paper loop detection unit is provided on the upstream side of the fixing device, and a detection signal from the detection unit is input to the control device of the fixing device.
The detection signal is used to control the drive mechanism of the sheet conveying means of the fixing device, and the amount of paper loops in the upstream portion of the fixing device can be maintained constant. Paper loop amount control device.