JPH08146685A - Image forming device - Google Patents

Abstract

PURPOSE: To attain reduction in the cost and miniaturization by dispensing with a pair of resist rollers in an image forming device. CONSTITUTION: The nip part of a photoreceptor 1 and a transfer roller 5a is substituted for the resist rollers. Therefore, for making a transfer paper P butt against the nip part of the photoreceptor 1 and the transfer roller 5a, to sag the paper P, a carrying roller 11 is temporarily stopped with prescribed timing. The roller 11 is rotated again after a short time not for absorbing and elongating the sag of the transfer paper P.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a fax machine or a printer, which uses a transfer roller.

[0002]

2. Description of the Related Art FIG. 9 shows a conventional image forming apparatus. In the figure, reference numeral 1 denotes a photoconductor, and a cleaning unit 7 having a charger 2, an optical unit 3 for emitting a laser beam L for writing or exposure, a developing unit 4, a transfer charger 5, and a cleaning blade 6 around the photoconductor 1. Is provided, the transfer paper fed from the paper feed unit 8 by the paper feed roller 9 is the intermediate roller 10,
The transfer roller 11 is sent to the registration roller 15 via the transfer roller 11 and the transfer sheet detection unit 13, and the transfer roller 11 is stopped at a predetermined timing to abut the tip of the transfer sheet against the nip portion of the registration roller pair 15 to transfer the transfer sheet. The flexure prevents the occurrence of skew and wrinkles. In the figure, 12 is a guide part.

However, although it is important to provide the pair of registration rollers 15 in order to prevent the occurrence of skew and wrinkle, the number of constituent elements of the apparatus is increased and the cost is increased. In the technique disclosed in Japanese Patent Laid-Open No. 59-68765, this problem is solved by using the transfer roller as either one of the pair of registration rollers, but one registration roller must be provided, which results in cost reduction. I wasn't trying to go down.

In view of the above points, an object of the present invention is to provide an image forming apparatus capable of reducing the cost and downsizing by eliminating the registration roller pair.

[0005]

In order to achieve the above object, an image forming apparatus according to the present invention is provided with a photoconductor, a transfer roller,
Includes a conveyance roller and transfer paper detection means, but abuts the transfer paper so as to slacken the nip portion of the photoconductor and the transfer roller, temporarily stops the conveyance roller at a predetermined timing, and stops the transfer roller at this time. It is configured to be made to.

The image forming apparatus according to the present invention may have a structure in which a guide member is provided to prevent the slack portion of the transfer paper from coming into contact with the photoconductor.

In the image forming apparatus according to the present invention, the distance L1 between the detection position of the transfer paper detection means and the nip portion between the photoconductor and the transfer roller, and the distance L2 between the writing or exposure position and the nip portion are Ll. The configuration may be such that> L2.

The image forming apparatus according to the present invention may be arranged such that the linear velocity Vr of the conveying roller is equal to or higher than the linear velocity Vk of the photosensitive member.

The image forming apparatus according to the present invention is configured such that the friction coefficient μk of the photoconductor, the friction coefficient μp of the transfer paper, and the friction coefficient μr of the transfer roller are μk <μp <μr. be able to.

The image forming apparatus according to the present invention may have a configuration in which the direction of the polishing grain of the transfer roller is the same as the direction of the transfer paper entering.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a main part of an embodiment of an image forming apparatus according to the present invention. Since the basic structure is the same as that of the apparatus of FIG. 8, common parts are designated by the same reference numerals and overlapped. Although not described, the apparatus of this embodiment does not include a registration roller or a registration roller pair as is apparent from the drawing.

Next, the image forming process operation of the apparatus of this embodiment will be described. The photoconductor 1 rotates in the direction of arrow A, is charged by the charger 2, forms a latent image with the laser light L for writing or exposure, is formed by the developing unit 4, and is transferred onto the transfer paper P by the transfer roller 5a. To be done. Excess toner on the photoconductor 1 is cleaned by the cleaning blade 6 and collected in the cleaning unit 7. On the other hand, the transfer paper P is conveyed in the direction of arrow B, and the image is fixed by a fixing device (not shown).

The operation of feeding and conveying the transfer paper P will be described. Transfer paper P fed from the paper feeding unit 8 by the paper feeding roller 9
Is transported by the intermediate roller 10 and the transport roller 11,
The leading end is conveyed along the guide portion 12 to the nip portion N between the photoconductor 1 and the transfer roller 5a. When the leading edge of the transfer sheet P detected by the transfer sheet detecting unit 13 reaches the nip portion N between the photoconductor 1 and the transfer roller 5a, the transport roller 1 is slackened at a predetermined timing.
1 stops once. As a result, even if either the left or right end of the transfer paper P arrives first, the conveyance force from the rear end of the transfer paper P eliminates the displacement of the left and right front end positions and prevents the occurrence of skew and wrinkles (FIG. 2A). , B and FIGS. 3A, B).

On the other hand, after being detected by the transfer paper detecting means 13, a latent image is formed on the photosensitive member 1 by the laser light L for writing or exposing at a predetermined timing, and the developing unit 4
The image formed in (1) is transferred to the transfer paper P by the transfer roller 5a. Depending on the configuration in the vicinity of the transfer portion, when the front end of the transfer paper P sags, the slack portion X may come into contact with the photoconductor 1 to cause image rubbing. The guide member 14 prevents this. However, since a white spot may be usually provided at the front end of the transfer paper P, a few mm may be in contact (Fig. 3).
(See A).

If the distance between the position of the transfer paper detecting means 13 and the nip portion N between the photoconductor 1 and the transfer roller 5a is L1, and the distance between the writing or exposure position and the nip portion N is L2, then L1> L2 in this embodiment. With such a configuration, writing or exposure is started immediately after the transfer paper detection unit 13 detects the leading end of the transfer paper P, and the transfer paper P is formed on the photoconductor 1 immediately after the transfer paper P stops with a slack in the transfer portion. Good timing is obtained in which the imaged image is transferred with almost no time lag (see FIG. 4). In this embodiment, the position of the transfer sheet detecting means 13 is arranged on the upstream side of the transport roller 11, but it may be on the downstream side of the transport roller 11 as long as the positional relationship is L1> L2.

The above-mentioned various operations will be described with reference to the timing chart of FIG. First, the transport roller 11 is turned on, the photoconductor 1 is turned on for charging, and then the charger 2 is turned on. After the transfer sheet P has passed the position of the transfer sheet detecting means 13, a predetermined timing (L1 + α−L2:
However, α is the slack amount of the transfer paper P. ), The optical unit 3 for writing or exposure is turned on, and the transfer roller 1 is temporarily transferred at the timing (L1 + α) at which the transfer paper P strikes the nip portion N between the photoconductor 1 and the transfer roller 5a with a slack.
1 turns off. Almost at the same time, the transfer roller 5 is used so that the image formed on the photoconductor 1 is transferred to the transfer paper P.
a turns on.

Next, the conveyance roller 11 which has been stopped is immediately turned on. At this time, the stop time is set such that the slack amount α is absorbed and the transfer paper P does not extend completely. This prevents jitter such as image blurring. The OFF timing of each operation thereafter is different depending on the length of the transfer paper P.
Further, the above timing is an example in which there is almost no time lag between the transfer paper conveyance and the process steps.

By the way, the transfer sheet P is conveyed at a speed of the photosensitive member 1.
If it is not equal to the linear velocity Vk of, the image expansion or contraction on the transfer paper P occurs. Since the transport speed of the transfer paper P is influenced by the linear velocity Vr of the transport roller 11, at least regarding the image expansion on the transfer paper P, the linear velocity Vr of the transport roller 11 that pulls the transfer paper P is problematic, so Vr ≧ Vk. To do. Further, the conveying roller 11 which has been stopped is immediately turned to O so that the slack amount α of the transfer paper P is absorbed and the transfer paper P is not fully extended.
Combined with the timing of N, the effect of preventing the image stretching and the image blurring can be obtained.

Further, the friction coefficient of the photoconductor 1 is μk, the friction coefficient of the transfer paper P is μp, and the friction coefficient of the transfer roller 5a is μ.
When r is set, μk <μp <μr.
With such a relationship, if the friction coefficient of the transfer paper P is smaller than the friction coefficient of the transfer paper P, the transfer paper P is not conveyed, and if it is larger, the transfer paper P is conveyed. Therefore, since the friction coefficient μk of the photoconductor 1 which is the counterpart member is small, the photoconductor 1 does not convey the transfer paper P even when it is rotating.
Further, since the friction coefficient μr of the transfer roller 5a, which is a counterpart member, is large, the transfer sheet P is conveyed by the rotation of the transfer roller 5a. As a result, misregistration of the leading edge of the transfer paper P is prevented as much as possible.

As an example, considering the friction coefficient of the transfer paper, the friction coefficient μk of the photoconductor 1 is 0.3 or less, the friction coefficient μp of the transfer paper P is about 0.6, and the friction coefficient μ of the transfer roller 5a.
When r was set to 0.7 or more, the registration deviation of the front end of the transfer paper P was prevented as expected.

Further, when the leading end of the transfer sheet P comes into contact with the nip portion N between the photosensitive member 1 and the transfer roller 5a, it may be possible to come into contact with the transfer roller 5a first in some cases.
As shown in FIG. 3, if the polishing eye direction of the transfer roller 5a is set to be the same as the approach direction of the transfer paper P (the direction of the arrow in the figure), the leading end of the transfer paper P is caught by the transfer roller 5a and the nip portion N is formed.
It is possible to prevent a non-feeding jam (see FIG. 8B) that does not reach the end of the transfer sheet P and reach the nip portion N without catching the leading end of the transfer sheet P on the transfer roller 5a (see FIG. 8A).

In this embodiment, the photoconductor is belt-shaped, but it may be a drum photoconductor. Similarly, the charger is a charger, but other charging methods such as rollers, brushes, blades, etc. may be used.

[0023]

As described above, in the image forming apparatus according to the first aspect of the present invention, the conveying roller is temporarily stopped at a predetermined timing in order to slacken the transfer paper against the nip portion between the photoconductor and the transfer roller. With this configuration, it is possible to provide a resist function of preventing skew and wrinkles of the transfer paper, and it is possible to achieve cost reduction and device miniaturization by removing the registration roller.

In the image forming apparatus according to the second aspect of the present invention, the guide member is provided so that the slack portion of the transfer paper does not come into contact with the photosensitive member side, so that the transfer paper can be prevented from being rubbed and the transfer paper can be prevented from being stained. The effect is that you will be able to.

In the image forming apparatus according to the third aspect, the transfer paper detection position, the nip distance L1 between the photosensitive member and the transfer roller, the writing or exposure position and the nip distance L2 are L1>
With the configuration of L2, writing or exposure is started immediately after the transfer paper is detected, and the image formed on the photoconductor is transferred immediately after the transfer paper has a slack in the transfer portion and is stopped. There is an effect that timing can be obtained and high speed can be coped with.

In the image forming apparatus according to the fourth aspect of the present invention, the conveying roller linear velocity Vr is set to be equal to or higher than the photosensitive member linear velocity Vk, so as to prevent jitter such as image extension and image blur caused by pulling the transfer paper. There is an effect that can be.

An image forming apparatus according to a fifth aspect of the present invention is configured such that μk <μp <μr, where μk is the friction coefficient of the photoconductor, μp is the friction coefficient of the transfer paper, and μr is the friction coefficient of the transfer roller. As a result, there is an effect that it is possible to prevent the registration deviation of the leading end of the transfer paper as much as possible due to the magnitude relationship of the friction coefficient with respect to the transfer paper.

In the image forming apparatus according to the sixth aspect of the present invention, since the direction of the grain of the transfer roller is set in the same direction as the direction of entry of the transfer paper, the leading end of the transfer paper is caught by the transfer roller and does not reach the nip portion. This has the effect of preventing undelivered jams.

[Brief description of drawings]

FIG. 1 is a sectional view showing a main part of an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a diagram showing how the leading edge of the transfer paper reaches the nip portion in the embodiment of FIG.

3 is a diagram showing how the leading edge of the transfer paper reaches the nip portion in the embodiment of FIG.

FIG. 4 is a diagram showing a relationship between a position of a transfer sheet detection unit and a distance of a nip portion and a writing or exposure position and a distance of a nip portion in the embodiment of FIG.

5 is a diagram showing the timing of the operation of each part of the embodiment of FIG.

FIG. 6 is a diagram showing a relationship among a friction coefficient of a photoconductor, a friction coefficient of a transfer sheet, and a friction coefficient of a transfer roller in the embodiment of FIG.

FIG. 7 is a diagram showing a relationship between a polishing grain direction of a transfer roller and an approach direction of a transfer sheet.

FIG. 8 is a diagram showing a state in which the leading end of the transfer paper is in contact with the nip portion between the photoconductor and the transfer roller.

FIG. 9 is a sectional view showing a conventional image forming apparatus.

[Explanation of symbols]

 1 Photoconductor 2 Charging Device 3 Optical Unit 4 Developing Unit 5a Transfer Roller 6 Cleaning Blade 7 Cleaning Unit 8 Paper Feeding Unit 9 Paper Feeding Roller 10 Intermediate Roller 11 Conveying Roller 12 Guide Part 13 Transfer Paper Detecting Means 14 Guide Member P Transfer Paper N Nip portion between photoconductor and transfer roller L Laser light for writing or exposure

Claims (6)

[Claims] 1. A photosensitive member, a transfer roller, a conveying roller, and a transfer paper detecting means are provided, and the transfer paper is abutted against the nip portion of the photosensitive member and the transfer roller so as to sag, and the transfer paper is conveyed at a predetermined timing. An image forming apparatus characterized in that a roller is once stopped, and at this time, the transfer roller is stopped. 2. The image forming apparatus according to claim 1, further comprising a guide member for preventing the slack portion of the transfer paper from coming into contact with the photosensitive member. 3. A distance L1 between the detection position of the transfer paper detecting means, the nip portion of the photoconductor and the transfer roller, and a distance L2 between the writing or exposure position and the nip portion are L
3. The image forming apparatus according to claim 1, wherein l> L2. 4. The image forming apparatus according to claim 1, wherein the linear velocity Vr of the conveying roller is set to be equal to or higher than the linear velocity Vk of the photoconductor. 5. The friction coefficient μk of the photoconductor, the friction coefficient μp of the transfer paper, and the friction coefficient μr of the transfer roller are μ
It is characterized in that k <μp <μr. 6. The image forming apparatus according to claim 1, wherein the transfer grain direction of the transfer roller is set in the same direction as the transfer paper entering direction.