JPH0881119A - Sheet carrier device - Google Patents

Abstract

PURPOSE: To prevent paper powder from cumulating on the surface of a frictional rotator by making the periphery speed of the frictional rotator of a first carrier means slower than the speed of a sheet moved by a second carrier means so as to provide a relative speed between the sheet and the surface of the frictional rotator. CONSTITUTION: When a paper feed roller 1 is driven to start paper feeding and the tip of a sheet 4 mounted on a sheet supporting base 5 is detected by a first paper end sensor 8, a carrier roller 2 is turned while timing t1 is set after a time T1 by which the tip of the sheet reaches the carrier roller 2. The paper feed roller 1 is turned at its periphery speed a little slower than the moving speed of the sheet 4 carried by a paper discharge roller 2 when the priority of carriage is allotted only to the carrier roller 2. When the transport of the sheet 4 is advanced and the terminal of the sheet 4 is detected by a second paper end sensor 9, the clutch of the paper feed roller 1 is cut off. Cumulation of paper powder on a roller surface is prevented by turning the paper feed roller 1 in accordance with movement of the sheet 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying device used in a sheet conveying system of an image forming apparatus such as a printer or a copying machine.

[0002]

2. Description of the Related Art A conventional sheet conveying apparatus of this type has a structure as shown in FIG.

That is, the sheet 103 picked up by the paper feed roller 100 and the separation pad 102 is fed to the transport roller 104 on the downstream side, and the transport roller 104.
After the conveyance is started by, the power transmission to the sheet feeding roller 100 is cut off, the sheet feeding roller 100 is in a freely rotatable state, and is driven to rotate as the sheet 103 moves.

The sheet 103 conveyed by a certain amount by the sheet feeding roller 100 is sensed by the sheet edge sensor 105 immediately before the conveying roller 104, the presence or absence of the sheet 103 is confirmed, and the timing of conveyance is determined. Laura 100
Becomes free to rotate, and only the conveying roller 104 is driven to convey the sheet 103. That is, the drive timing is as shown in FIG. 12, and the paper feed roller 100 does not have a rotation command when the transport roller 104 is driven.

[0005]

Paper is fed by the difference between the coefficient of friction between the stacked sheets 103 and the coefficient of friction between the sheets 103 and the paper feed roller 100.

However, when the paper feed roller 100 is used for a long period of time, the coefficient of friction between the sheet 103 and the paper feed roller 100 decreases due to the change of the surface layer with time. Further, when the paper is continuously fed, paper dust is accumulated on the surface of the paper feed roller 100,
The friction coefficient between the sheet 103 and the paper feed roller 100 is reduced. This reduction in the friction coefficient between the sheet 103 and the paper feed roller 100 causes a paper feed failure, which causes a problem in the reliability of the apparatus.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and an object thereof is to reduce the friction between the sheet and the first conveying means arranged on the upstream side. An object of the present invention is to provide a sheet conveying device that can be reduced as much as possible and an image forming apparatus using the same.

[0008]

In order to achieve the above object, in the present invention, there is provided a first conveying means provided with a friction rotating body which comes into contact with the sheet and sends the sheet by a frictional force, and the first conveying means. In the sheet conveying apparatus, which is arranged downstream of the first conveying means and further conveys the sheet sent by the first conveying means to the further downstream side, the sheets are the first and second sheets. While straddling the conveying means, the second
The peripheral speed of the friction rotating body of the first conveying means is set to be slower than the sheet conveying speed of the conveying means, and the sheet is conveyed with a speed difference between the sheet conveying speed and the peripheral speed of the friction rotating body. Is characterized by.

Further, the first conveying means is for selecting and feeding sheets.

It is characterized in that it has means for setting or recognizing the sheet type, and controls the drive time of the first conveying means in accordance with the sheet type.

It is characterized in that a means for detecting the trailing edge of the sheet is provided upstream of the first conveying means, and the first conveying means is drive-controlled based on the detected data.

A means for detecting the presence / absence of a sheet is arranged between the first conveying means and the second conveying means, and the first conveying means is drive-controlled based on the detected data.

In an image forming apparatus incorporating the sheet conveying device according to any one of claims 1 to 5, the driving of the first conveying means is terminated before the sheet moves to the image forming portion. And

In the image forming apparatus incorporating the sheet conveying device according to any one of claims 1 to 5, the first conveying means is reversed before the sheet moves to the image forming portion. .

In the image forming apparatus incorporating the sheet conveying device according to any one of claims 1 to 5, the speed of the second conveying means located upstream of the sheet moving speed in the image forming section from the image forming section. Is set to a high speed so that tension does not act on the roller between the image forming unit and the second conveying unit located upstream of the image forming unit.

[0016]

According to the present invention, in the portion where the paper feed roller is conventionally driven, there is a speed difference between the upstream first transport means and the downstream second transport means. The peripheral speed of the friction rotating body of the first conveying means is set to be lower than the conveying speed of the sheet by the second conveying means, and the sheet and the surface of the friction rotating body are forced to slip. As a result, the surface of the friction rotator is abraded and the friction coefficient is prevented from lowering due to aging of the surface layer. Further, by positively giving a relative speed, the paper dust is released to maintain the friction coefficient.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to illustrated embodiments. [Embodiment 1] FIG. 1 shows a drive timing chart of a roller of Embodiment 1 of the present invention, and FIG. 2 shows an outline of the configuration. The upper part of FIG. 1 shows the drive timing of the paper feed roller, and the lower part shows the drive timing of the transport roller.

First, the structure will be described. In FIG.
Reference numeral 1 denotes a sheet feeding roller which is a friction rotating member of the first conveying means, and is driven through a clutch, though not shown. Reference numeral 2 is a carrying roller which is a second carrying means. Denoted at 3 is a separation pad, and the conveyed sheet 4 is the paper feed roller 1.
It is arranged on the back side of the part that contacts with. Reference numeral 5 denotes a sheet support, on which a plurality of sheets 4 are stacked. Reference numeral 6 denotes a preload spring, which is arranged below the sheet table 5 and presses the separation pad 3 against the sheet feeding roller 1. Reference numeral 7 is a sheet guide. 8
Is a first paper edge sensor, and includes a paper feed roller 1 and a conveyance roller 2
Placed between. A second paper edge sensor 9 is arranged upstream of the paper feed roller 1. Although not shown, the first
The paper edge sensor and the second paper edge sensor are connected to a controller that controls the paper feed roller 1 and the transport roller 2.

Next, the operation will be described.

The paper feed roller 1 is driven as shown in FIG.
After the time T ₁ at which the leading edge of the sheet 4 is recognized by the first paper edge sensor 8 and then reaches the transport roller 2, the transport roller 2 is rotated at a timing (t ₁ ).

Next, the main body of the transfer moves to the transfer roller 2,
As shown in FIG. 1C, the paper feed roller 1 is the conveyance roller 2
Is rotated in the sheet travel direction slightly slower peripheral speed v ₂ than the moving speed v ₁ of the sheet 4 conveyed by the. When the conveyance of the sheet 4 progresses and the trailing edge of the sheet 4 is recognized by the second sheet edge sensor 9 (t _{2 in the} figure), the clutch of the sheet feeding roller 1 is disengaged and the sheet 4 moves thereafter. Thus, the paper feed roller 1 is driven. That is, the paper feed roller 1 ends the drive before the end of the conveyance of the sheet 4 currently being conveyed. This relationship is the driving timing as shown in FIG. 1, and the driving time is adjusted and driven by the sheet 4 which conveys the sheet feeding roller 1 while the conveying roller 2 is being driven.

In this embodiment, as shown in FIG. 3, two first and second paper edge sensors 8 and 9 are provided to control the paper feed roller 1 and the transport roller 2 via the controller 20. . As a result, the trailing edge of the sheet 4 can be recognized before the sheet feeding roller 1. Therefore, by controlling the sheet feeding roller 1, only the sheet 4 currently conveyed is conveyed.

In this embodiment, the peripheral speed of the paper feed roller 1 is set to be slower than the process speed of a printer, a copying machine or the like, that is, the moving speed of the sheet 4 conveyed by the conveying rollers 2 in advance. Therefore, the drive motor is set to the transport roller 2
Also, the drive time of the paper feed roller 1 can be controlled only by the clutch. [Embodiment 2] In Embodiment 1, the description was given of driving the paper feed roller 1 via the clutch. However, an independent motor is provided for the paper feed roller 1 and a direct paper feed roller is provided separately from the carry roller 2. You may drive. In this case, it is not necessary to set the rotation speed of the paper feed roller 1 to be constant, but the rotation speed can be made variable, and finer control is possible. Further, it is not necessary to set the paper feed speed lower than the process speed, and the overall image forming time can be shortened. [Third Embodiment] By providing the paper type sensor 21 on the sheet table 5, the second paper edge sensor 9 disposed upstream of the paper feed roller 1 is removed, and the second paper edge sensor 9 is provided between the paper feed roller 1 and the transport roller 2. One first paper edge sensor 8 is used. Instead of the information of the removed paper edge sensor 9, as shown in FIG. 4, the paper type sensor 2 and the first paper edge sensor 8 are used to feed the paper feed roller 1 and the transport roller 2.
May be controlled.

That is, the paper type sensor 21 recognizes the paper type, and the drive time of the paper feed roller 1 is controlled based on the recognized information on the length of the sheet. As a result, the number of paper edge sensors can be one, and the sheet 4
Can be conveyed sheet by sheet. [Fourth Embodiment] In the third embodiment, instead of the paper type sensor 21, the paper type information F may be obtained by some means as shown in FIG. For example, as the acquisition means 22,
There is information directly supported by the device and a higher-level controller (such as a computer in the case of a printer). [Fifth Embodiment] The second paper edge sensor 9 may be omitted from FIG. 2 of the first embodiment and may be controlled only by the first paper edge sensor 8 between the paper feed roller 1 and the transport roller 2.

The operation is almost the same as that shown in the first embodiment. The paper feed roller 1 is driven, then the main body of the conveyance roller 2 is moved, and the paper feed roller 1 is rotated in the sheet movement direction at a peripheral speed slightly lower than the movement speed of the sheet 4 conveyed by the conveyance roller 2. To do. After the sheet 4 is conveyed, the trailing edge of the sheet 4 passes through the sheet feeding roller 1 and further passes through the first sheet edge sensor 8, and then the sheet feeding roller 1 is stopped. The next sheet is conveyed and the leading edge is between the paper feed roller 1 and the conveyance roller 2.

That is, as shown in FIG. 6, the paper feed roller 1 and the carry roller 2 are controlled via the controller by one piece of paper edge sensor information. As a result, the number of parts can be reduced. [Embodiment 6] An embodiment incorporated in an image forming apparatus will be described.

A timing chart is shown in FIG. 7, and a schematic diagram of the configuration is shown in FIG.

In FIG. 8, 10 is an image forming unit.
In this embodiment, the sheet feeding roller 1 is freely rotatable before the conveyed sheet 4 reaches the image forming unit 10.

In FIG. 9, the sheet 4 is being conveyed by the conveying roller 2, and the sheet feeding roller 1 is being driven.

In FIG. 10, the sheet 4 has passed through the image forming section 10, and at this time, the sheet feeding roller 1 is freely rotatable. A point A in FIG. 7 is a point at which the sheet 4 reaches the image forming unit 10, and the feed roller 1 is controlled to be freely rotatable before that point. The timing at which the paper feed roller 1 is allowed to rotate freely may be determined by providing a paper edge sensor or by determining the mounting position and speed.

Further, the sheet feeding roller 1 may be reversed before the sheet 4 reaches the image forming section 10. This allows
It is possible to prevent the load variation on the sheet 4 by the sheet feeding roller 1 when the sheet 4 passes through the image forming member 10. [Embodiment 7] In the state shown in FIG. 10 of Embodiment 6, the peripheral speed of the conveying roller 2 is set slightly higher than the speed at which the sheet 4 passes through the image forming section 10 so that tension is not applied to the sheet 4. To As a result, similarly to the sixth embodiment, the load fluctuation on the sheet 4 by the sheet feeding roller 1 when the sheet 4 is passing through the image forming unit 10 is prevented.

As another embodiment, continuous operation may be performed without timing of conveyance.

[0033]

According to the present invention, the peripheral speed of the friction rotating body of the first conveying means is made slower than the moving speed of the sheet by the second conveying means so that the sheet and the surface of the friction rotating body have a relative speed. As a result, the surface of the friction rotator can always be in a good state, and the friction coefficient between the sheet and the friction rotator can be maintained. Further, it is possible to prevent paper dust from accumulating on the surface, and more stable sheet conveyance can be performed.

[Brief description of drawings]

FIG. 1 is a drive timing chart of the first embodiment.

FIG. 2 is a schematic diagram of the configuration of the first embodiment.

FIG. 3 is a block diagram of control according to the first embodiment.

FIG. 4 is a block diagram of control according to the third embodiment.

FIG. 5 is a block diagram of control according to the fourth embodiment.

FIG. 6 is a block diagram of control according to the fifth embodiment.

FIG. 7 is a drive timing chart of the sixth embodiment.

FIG. 8 is a schematic diagram of the configuration of the sixth embodiment.

FIG. 9 is an enlarged view of the sixth embodiment.

FIG. 10 is an enlarged view of the sixth embodiment.

FIG. 11 is a timing chart of a conventional example.

FIG. 12 is a schematic diagram of a configuration of a conventional example.

[Explanation of symbols]

 1 First Conveying Roller (Feeding Roller) 2 Second Conveying Roller (Conveying Roller) 3 Separation Pad 4 Sheet 8 First Paper Edge Sensor 9 Second Paper Edge Sensor 10 Image Forming Section

Claims (8)

[Claims] 1. A first conveying means provided with a friction rotator that comes into contact with the sheet and feeds the sheet by a frictional force, and is arranged downstream of the first conveying means and is fed by the first conveying means. In a sheet conveying device provided with a second conveying means for sending the received sheet further downstream, in a state where the sheet is straddling the first and second conveying means, The peripheral speed of the friction rotating body of the first conveying means is set to be slow,
A sheet conveying apparatus, which conveys a sheet in a state where there is a speed difference between the sheet conveying speed and the peripheral speed of the friction rotator. 2. The sheet conveying apparatus according to claim 1, wherein the first conveying means selects and feeds the sheet. 3. The sheet conveying according to claim 1, further comprising a unit for setting or recognizing a sheet type, and controlling the drive time of the first conveying unit according to the sheet type. apparatus. 4. A means for detecting the trailing edge of a sheet is provided upstream of the first conveying means, and the first conveying means is driven and controlled based on the detected data. The sheet conveying apparatus according to item 1. 5. A means for detecting the presence / absence of a sheet is arranged between the first conveying means and the second conveying means, and the first conveying means is drive-controlled based on the detected data. The sheet conveying device according to claim 1. 6. An image forming apparatus incorporating the sheet conveying device according to claim 1, wherein the driving of the first conveying unit is finished before the sheet moves to the image forming unit. An image forming apparatus characterized by. 7. An image forming apparatus incorporating the sheet conveying device according to claim 1, wherein the first conveying means is reversed before the sheet moves to the image forming portion. Image forming apparatus. 8. An image forming apparatus incorporating the sheet conveying device according to claim 1, further comprising a second conveying unit located upstream of a sheet moving speed in the image forming unit from the image forming unit. The image forming apparatus is characterized in that the tension is not applied to the roller between the image forming unit and the second conveying unit located upstream of the image forming unit.