JPH05116813A - Transfer-paper feed method for image forming apparatus - Google Patents

Abstract

PURPOSE:To provide a transfer-paper feed method capable of preventing a toner image transferred onto a transfer paper sheet from being shrunk in the transfer paper sheet conveyance direction or preventing any void from being produced in the toner image, in a transfer paper sheet feed method for a copying machine arranged to feed a transfer paper sheet to a resist roller via a relay roller and feed it through rotation of a resist roller to photosensitive body with a specified timing. CONSTITUTION:In a specified time period after reaching of a front end edge of a transfer paper sheet 10 conveyed by a relay roller 12 to a resist roller 13, the rotation of the relay roller 12 is stopped. Thereafter, the resist roller 13 is rotated to start sending the transfer paper sheet to a photosensitive body 1. In a specified time length thereafter, the relay roller 12 is again rotated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer paper feeding method for an image forming apparatus.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electronic copying machine, a printer or a facsimile, which forms a toner image on the surface of an image carrier and transfers the toner image onto a transfer paper to obtain a recorded image, it is fed from a paper feeding unit. The transferred transfer paper is conveyed by a relay roller to a pair of registration rollers, and after the leading edge of the transfer paper reaches the registration rollers, the registration rollers start rotating at a predetermined timing to transfer the toner image on the image carrier to the transfer paper. The transfer paper is fed to the image carrier so that and are aligned.

At that time, the relay roller is continuously driven for a predetermined time even after the front end of the transfer paper sent to the registration roller hits the registration roller, and after the transfer paper has a slack, the drive of the relay roller is stopped. After that, the rotation of the registration roller is started at a predetermined timing. In this way, when the leading edge of the transfer paper is brought into contact with the registration roller so that the transfer paper has a slack, when the registration roller starts rotating, the leading edge of the transfer paper can be correctly aligned and fed to the image carrier. This makes it possible to prevent the problem that the transfer sheet is skewed.

In the transfer sheet feeding method as described above, conventionally, when the transfer sheet is fed by the rotation of the registration roller, the driving of the relay roller is turned off, and the relay roller moves around by the movement of the transfer sheet. It is configured to (follow). This is based on the idea that the transfer roller does not need to be transported if the transfer roller starts feeding the transfer sheet.

However, according to the above-mentioned structure, there is no particular problem when the load when the relay roller circulates is small, but when this load becomes large, the transfer paper is conveyed by the registration rollers. The relay roller acts as a resistance force to prevent this, the pair of registration rollers reliably grips the transfer sheet and makes it impossible to convey the transfer sheet, and the transfer sheet may slip with respect to the registration roller. In this case, the toner image transferred from the image carrier on the transfer paper shrinks in the carrying direction.

Therefore, the present inventor conducted an experiment in which the driving of the relay roller is restarted at the same time as the driving of the registration roller is started, and the driving timing of both rollers is controlled so that the load of the relay roller is not applied to the transfer sheet. I tried. However, according to this configuration, although the above-mentioned problems can be prevented, it has been found that, as will be described in detail later, the transfer paper can be curled, which causes a new problem of deterioration in image quality.

[0007]

SUMMARY OF THE INVENTION The present invention is based on the above-mentioned novel recognition, and provides a transfer paper feeding method for an image forming apparatus capable of eliminating the above-mentioned conventional problems with a simple structure. To aim.

[0008]

In order to achieve the above object, the present invention conveys a transfer sheet sent from a sheet feeding section to a registration roller by a relay roller, and the front end of the transfer sheet reaches the registration roller. After that, the driving of the relay roller is stopped after a lapse of a predetermined time, and then the rotation of the registration roller is started at a predetermined timing to feed the transfer sheet to the image carrier. In the above, a configuration is proposed in which the relay roller is re-driven after a lapse of a predetermined time after the rotation of the registration roller is started.

At this time, it is desirable to set the feeding speed of the transfer paper by the relay roller higher than the feeding speed of the transfer paper by the registration roller.

It is also advantageous to set the feed speed of the transfer paper by the relay roller and the feed speed of the transfer paper by the registration roller to be equal.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an electronic copying machine. A drum-shaped photoreceptor 1 which is an example of the configuration of an image carrier is rotationally driven in the clockwise direction, and at this time, the surface is uniformly made by a charger 2. Be charged. Image exposure is performed on the charged surface at the exposure position indicated by reference numeral 3, whereby an electrostatic latent image is formed on the photoconductor 1. This latent image is developed by the developing device 4.
When it passes through, it is visualized as a toner image.

On the other hand, a paper feed section 5 is provided in the lower part of the main body of the copying machine, and the paper feed section illustrated here includes a paper feed cassette 6 and
It has a paper feed table 8 arranged therein and a paper feed roller 9 supported on the copying machine main body side.
It is rotatably supported with respect to the paper feed cassette 6 centering on the side. Transfer sheets 10 are stacked and set on the paper feed table 8, and the free end side of the paper feed table 8 is lifted by a pressure member (not shown).

When the paper feed signal is generated, a one-rotation paper feed roller clutch (not shown) is actuated as shown in FIG. 2A, and the motor causes the paper feed roller 9 to make one revolution. It is driven to rotate counterclockwise. At this time, the cylindrical surface of the paper feed roller 9 contacts the uppermost transfer sheet 10, and the frictional force causes the uppermost transfer sheet 10 to be fed in the direction of arrow A. At this time, the separation claws (not shown) prevent double feeding of the transfer sheets, and only the uppermost transfer sheet is fed.

The transfer sheet 10 sent from the sheet feeding section 5 as described above is sent to the pair of relay rollers 12, and as shown in FIG. 2B, a clutch (not shown) of the relay roller 12 is provided. Also turns on at the same time when the feed roller 9 starts rotating,
The relay roller 12 is rotationally driven. Therefore, the relay roller 10 sent out is conveyed by the pair of relay rollers 12 while being nipped by the pair of relay rollers 12, and is guided by the guide member 11 while being paired with the pair of registration rollers 1.
Reach the nip portion of 3.

At this time, the registration roller 13 is stopped without rotating. On the other hand, the relay roller 12 continues to be driven even after the leading end of the transfer paper 10 hits the nip portion of the pair of registration rollers 13, and the relay roller 12 also stops rotating after a predetermined time. As a result, a slack is formed on the transfer paper 10 as shown in FIG.
In this state, the entire length of the front end of the transfer paper hits the nip portion of the registration roller 13. As shown in FIG. 1, the registration sensor 1 is provided in front of the registration roller 13 in the transfer paper conveyance path.
4 is provided, and as shown in FIGS. 2B and 2C, the relay roller clutch is turned off after a predetermined time t ₁ has elapsed since the sensor 14 detected the leading edge of the transfer paper 10. Then, the driving of the roller 12 is stopped.

In this way, after the leading edge of the transfer paper 10 reaches the registration roller, the drive of the relay roller 12 is stopped after a predetermined time has elapsed.
At a predetermined timing, the registration roller clutch (not shown) is turned on as shown in FIG. 2D, and the registration roller 13 starts rotating in the direction shown by the arrow in FIG. As a result, the transfer paper 10 is fed to the photoconductor 1 at the timing matched with the toner image formed on the photoconductor 1 as described above.

At the start of feeding of the transfer paper, the transfer paper 10 has a slack, and the leading end of the transfer paper 10 is aligned with the registration roller 13. Therefore, after the registration roller 13 starts rotating, the transfer paper 10 is rotated. Are fed to the photoconductor 1 without causing skew.

The transfer paper 10 sent to the photoconductor 1 has a structure shown in FIG.
As shown in FIG. 5, the toner image on the photoconductor 1 is transferred by the action of the transfer charger 15, and after the transfer, the transfer paper leaves the photoconductor 1 and passes through the fixing device 16 where the toner image is fixed, and The sheet is ejected to the outer sheet ejection tray 17. The cleaning device 18 removes the residual toner from the surface of the photoconductor after the transfer of the toner image, and is subjected to a neutralizing action.

The above-mentioned structure is the same as that of the conventional copying machine.
In such a conventional copying machine, as described above, when the registration roller 13 starts rotating and the transfer paper is fed to the photoconductor 1, the relay located upstream of the registration roller 13 is used. The roller 12 is not driven, and the roller 12 is configured to be driven to rotate (roll around) by the transfer sheet being conveyed. Therefore, when the load of the relay roller 12 is large, the roller 12 gives resistance to the transfer paper 10 in the direction opposite to the conveying direction, whereby the transfer paper slips and transfers to the registration roller 13. There is a risk that the paper conveyance speed becomes slow and the toner transferred to the transfer paper contracts in the transfer paper conveyance direction.

Therefore, as described above, in order to prevent the load of the relay roller 12 from acting on the transfer sheet, an experiment was conducted in which the drive of the relay roller 12 was restarted at the same time as the rotation of the registration roller 13 was started. The slack of the transfer paper 10 formed as shown in FIG. 3A before the rotation of the roller 13 is changed after the rotation of the registration roller 13 and the relay roller 12 is changed as shown by the solid line in FIG. Finally, as shown by the chain line in FIG. 4, the transfer paper 10 can be curled, and as shown in FIG. 5, the curl portion of the transfer paper 10 cannot be brought into close contact with the photoconductor 1 during the transfer of the toner image, and the toner image is formed on this portion. The so-called blank image was generated.

Therefore, in this embodiment, as shown in (b) and (d) of FIG. 2, the registration roller is moved at the timing when the leading edge of the toner image on the photoconductor 1 and the leading edge of the transfer paper 10 are substantially aligned with each other. Turn on the clutch of the roller 13
After the start of the driving, the slack of the transfer paper 10 on the upstream side of the registration roller 13 is eliminated, or after a predetermined time t ₂ when the slack is reduced, the relay roller clutch is turned on again. It is configured to redrive the relay roller 12.

According to this structure, the relay roller 12 does not give resistance to the transfer paper 10 in the direction opposite to the conveying direction, and therefore the toner image transferred to the transfer paper 10 is not likely to shrink. . Moreover, as shown in FIG. 3B, curl curling due to the slack of the transfer paper 10 does not occur, and it is possible to prevent a defect that a blank image occurs.

As described above, the relay roller 12 starts to be driven after a predetermined time has elapsed since the registration roller 13 started to rotate. At this time, the relay roller 12 is started.
If the transfer speed of the transfer paper 10 by the registration roller 13 is slower than the transfer speed of the transfer paper 10 by the registration roller 13, the relay roller 12
Are circulated by the transfer paper 10, and the load of the relay roller 12 is applied to the registration roller 13 due to this, and the transfer paper 10 may slip with respect to the registration roller 13. In this case, the transfer paper 1
The toner image transferred to 0 shrinks in the carrying direction.

In view of this, in this example, the transfer speed of the transfer paper 10 by the relay roller 12 is faster than the transfer speed of the transfer paper 10 by the registration roller 13, or the transfer speed of the transfer paper 10 by the relay roller 12 is the same. The diameters of the rollers 12 and 13 are set so that the registration rollers 13 feed the transfer paper at the same speed. With such a configuration, it is possible to prevent the relay roller 12 from rolling around and prevent the toner image from shrinking.

An image forming apparatus is also known in which a toner image is transferred onto one surface of a transfer sheet, the toner image is fixed, and then the toner image is transferred onto the same surface or the other surface and fixed again. In such an apparatus, a transfer sheet having a toner image formed on one surface thereof is once fed to an intermediate paper feeding unit, re-fed, and a toner image is formed on the transfer sheet again. The “paper feeding unit” in the present invention also includes such an intermediate paper feeding unit.

[0027]

According to the transfer paper feeding method of the first aspect of the invention, the registration roller starts rotating to absorb the slack of the transfer paper, and then the relay roller is driven again. It is possible to prevent the shrinkage of the toner image transferred to the transfer paper and the occurrence of a blank image.

According to the transfer paper feeding method of the second and third aspects, it is possible to prevent the relay roller from rolling around after the rotation of the relay roller is restarted, so that the shrinkage of the toner image is more surely generated. Can be stopped.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an electronic copying machine which is an example of an image forming apparatus.

FIG. 2 is a diagram showing an operation timing of one embodiment of the present invention.

FIG. 3 is an explanatory diagram showing the relationship between registration rollers and transfer paper.

FIG. 4 is an explanatory diagram showing a state of a transfer sheet when a relay roller is driven at the same time when a registration roller starts rotating.

FIG. 5 is a diagram for explaining a defect when the relay roller is driven at the same time when the registration roller starts rotating.

[Explanation of symbols]

 5 Paper Feeding Section 10 Transfer Paper 12 Relay Roller 13 Registration Roller

Claims (3)

[Claims] 1. A transfer roller fed from a paper feeding section is conveyed to a registration roller by a relay roller, and after the leading edge of the transfer paper reaches the registration roller, the drive of the relay roller is stopped after a lapse of a predetermined time. Then, in the transfer paper feeding method of the image forming apparatus that starts rotation of the registration roller at a predetermined timing to feed the transfer paper to the image carrier, a predetermined time has elapsed since the rotation of the registration roller started. A transfer paper feeding method, characterized in that the relay roller is re-driven later. 2. The transfer paper feeding method according to claim 1, wherein the transfer speed of the transfer paper by the relay roller is set higher than the transfer speed of the transfer paper by the registration roller. 3. The transfer paper feeding method according to claim 1, wherein the transfer paper feed speed by the relay roller and the transfer paper feed speed by the registration roller are set to be equal.