JPH05289549A - Image forming device - Google Patents

Abstract

PURPOSE:To improve the ability of peeling and separating a non-image sheet by controlling a transfer output at the initial stage in the feeding of the sheet to a transfer part and at a stage in the course of the passing of the sheet through the transfer part, so that when a carrying force is exerted on the non-image sheet by a sheet feed roller, the sheet is not electrostatically attracted, and when the carrying force is not exerted thereon, it is electrostatically attracted. CONSTITUTION:In a transfer part 4, when a sheet 100 does not have an image thereon, the transfer output is set to OFF at the initial stage in the feeding of the sheet to the transfer part 4 and is set to ON at the stage in the course of the passing of the sheet 100 through the transfer part 4. Therefore, by setting the transfer output to OFF at the initial stage in the feeding of the sheet 100 to the transfer part 4, the sheet 100 is not attoracted to a photosensitive drum 1 at the stage, so that the ability of the sheet 100 to be separated from the photosensitive drum 1 is improved. Since the transfer output is set to ON at the stage in the course of the passing of the sheet 100 through the transfer part 4, an electrostatic attracting action is generated accompanying that, between the photosensitive drum 1 and the sheet 100, and a force for carrying the sheet 100 is exerted by this action and the rotating action of the photosensitive drum 1. Thus, the occurrence of a jam can be suppressed.

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, and more particularly, to an electrostatic image forming apparatus having a function of improving the peeling performance of image-free paper passing through a transfer portion from a photosensitive drum.

[0002]

2. Description of the Related Art In an electrostatic image forming apparatus shown in FIG. 2, a charging unit 2 having a corona charger 2a, a developing unit 3 having a developing unit 3a, and a transfer unit 4a are provided around a photosensitive drum 1. The transfer unit 4 having the charge removing unit 5a and the charge removing unit 5 having the charge removing unit 5a are arranged in this order in the rotation direction X of the photoconductor drum 1, and the transfer unit 4 is additionally provided with the sheet charge removing unit 6. A cleaner 7 is installed between 6 and the static eliminator 5. In addition, a paper feed unit 8 having a paper feed roller (registration roller) 8a, a paper transport unit 9, and a fixing unit 10 are provided.

In this image forming apparatus, the surface of the photosensitive drum 1 charged by the corona charger 2a is exposed with an original image by the action of an optical system (not shown) to form an electrostatic latent image. Toner is attached at the developing section 3 to form a toner image on the surface of the photosensitive drum 1. Then, the transfer unit 4 electrostatically transfers the toner image onto the sheet 100 fed from the sheet feeding unit 8. The sheet 100 on which the toner image is transferred is sent to the fixing unit 10 via the sheet conveying unit 9, and the toner image is thermally fixed. In addition, the photosensitive drum 1
After the dust has been removed by the cleaner 7, the charge is removed by the charge removing unit 5, whereby one cycle is completed.

As shown in FIG. 3, the paper feed roller 8a of the paper feed unit 8
A sheet entrance guide 11 is provided between the transfer section 4 and the transfer section 4. The distance between the front end of the approach guide 11 and the photosensitive drum 1 is set to a narrow interval of 1.5 mm or less in order to prevent image bleeding due to transfer. Paper 1 to move to 4
It is unavoidable that a resistance is generated at the time of the shift to 0, and the resistance at that time becomes a factor that deteriorates the transportability of the paper 100.

Therefore, as can be inferred from the time chart of FIG. 4, the trailing edge of the sheet 100, to which the feeding force is applied by the sheet feeding roller 8a, is before the trailing edge of the sheet 100 leaves the sheet feeding roller 8a. The transfer output of the transfer unit 4 is turned on before the front end reaches the front end of the toner image on the photosensitive drum 1, and even after the rear end of the paper 100 separates from the paper feed roller 8a. The sheet 100 is stably conveyed by the electrostatic attraction action generated between the sheet 100 and the sheet 100 and the rotation action of the photosensitive drum 1. The ON state of the transfer output is maintained until the rear end of the sheet 100 separates from the front end of the entrance guide 11. After that, the above resistance to the sheet 100 disappears, and thus the sheet 100 is sent to the fixing unit 10 by the carrying force of the carrying unit 9. On the other hand,
The separation output of the paper static eliminator 6 is 0 immediately after the transfer output is turned on.
When the separation output is turned on, the sheet 100 electrostatically attracted to the photosensitive drum 1 is set.
Is removed, and the waist (rigidity, stiffness) of the paper 100 causes the paper 100 to be separated from the photosensitive drum 1 without difficulty.

[0006]

In the above-described image forming apparatus, one of the sheets 100 is selected from a sheet bundle in which non-image sheets such as slip sheets and cover sheets and sheets on which images are formed (normal sheets) are mixed. When the image forming process described above is performed by feeding the sheets one by one to the sheet feeding unit 8, the image exposure is not performed on the surface of the photoconductor drum 1 (no electrostatic latent image is formed) on the non-image sheet, and thus the charging unit is not used. Charge output at 2 is OF
The charge on the surface of the photoconductor drum 1 is erased by setting F or by turning on the blank lamp 12. Therefore, the toner is not attached to the image-free paper in the developing unit 3.

In this case, in the transfer section 4, no toner is present between the surface of the photosensitive drum 1 and the non-image paper. Therefore, the electrostatic attraction between the photoconductor drum 1 and the non-image paper due to the transfer output being turned on becomes too strong, and even if the separation output of the paper discharging section 6 is turned on, the non-image paper is turned on. Depending on the waist, a situation occurs in which the image-free paper is less likely to be peeled off from the photosensitive drum 1, which leads to the occurrence of jams.

In order to eliminate such a situation, in the image forming process when the non-image paper is sent to the transfer section 4, the transfer output of the transfer section 4 is turned off and the above electrostatic attraction action occurs. Although it may be considered not to do so, doing so eliminates the carrying force applied to the image-free paper due to its electrostatic attraction action, so that the trailing edge of the image-free paper remains untouched from the moment it leaves the feed roller 8a. The image paper may not be conveyed, which may cause a jam.

As described above, in the conventional image forming apparatus, the transfer output of the transfer unit is turned on at a constant timing regardless of whether the paper fed to the transfer unit is normal paper or non-image paper. Since an attempt was made to convey the paper by using the electrostatic attraction force between the photoconductor drum and the paper that is generated along with it, it may be difficult to peel off the non-image paper from the photoconductor drum well. However, there is a problem in that the conveyance state of non-image paper is unstable.

The present invention has been made in view of the above problems. That is, according to the present invention, when the conveying force of the sheet feeding roller of the sheet feeding unit is applied to the non-image paper, the electrostatic attraction action does not occur between the photosensitive drum and the non-image paper. When the non-image paper is prevented from being attracted to the photoconductor drum and the conveyance force of the paper feed roller of the paper feed section is no longer applied to the non-image paper, the electrostatic attraction action described above is generated and An object of the present invention is to provide an image forming apparatus capable of imparting a conveying force by an electroadhesive action and a photosensitive drum rotation action.

[0011]

According to another aspect of the present invention, there is provided an image forming apparatus in which a charging section, a developing section, a transfer section and a charge eliminating section are arranged around a photosensitive drum in this order in the rotational direction of the photosensitive drum. In the image forming apparatus, in which the sheet fed from the sheet feeding section is fed to the fixing section via the transfer section, the transfer section is an initial stage of feeding the sheet to the transfer section when the sheet is a non-image sheet. Then, the transfer output is set to OFF, and the transfer output is set to ON in the middle of the sheet passing through the transfer section.

In the image forming apparatus according to the second aspect of the present invention, the transfer output of the transfer section in the image forming apparatus is set to ON before the trailing edge of the sheet leaves the sheet feeding roller of the sheet feeding section. It is configured.

[0013]

In the first aspect of the invention, since the paper is a non-image paper, it is not necessary to transfer the toner image on the photosensitive drum to the paper. Therefore, even if the transfer output is OFF, there is no hindrance to the execution of the image forming process. On the other hand, when the transfer output is set to OFF at the initial stage of feeding the sheet to the transfer unit, the sheet is not adsorbed to the photosensitive drum at that stage, and the separability of the sheet from the photosensitive drum is improved. Then, the transfer output is set to ON while the paper is passing through the transfer portion, and accordingly, electrostatic attraction occurs between the photoconductor drum and the paper, which action and the photoconductor drum. By the rotation action of, the conveying force is applied to the paper.

In the invention of claim 2, the transfer output is turned on before the trailing edge of the paper leaves the paper feed roller of the paper feed section.
Is set to, the feeding force is applied to the paper by the paper feed roller in the initial stage of feeding the paper to the transfer unit, and the trailing edge of the paper is fed by the paper feed roller in the middle of the sheet passing through the transfer unit. Before being separated from the sheet, the conveying force by the electrostatic attraction action and the rotation action of the photosensitive drum is applied to the sheet.
Therefore, the conveyance force is always applied to the paper.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a time chart showing transfer output, paper feed roller drive clutch and separation output in an image forming apparatus according to an embodiment of the present invention. The image forming apparatus according to the embodiment of the present invention has the same components as the image forming apparatus described in FIG.

In the following, the first sheet and the third sheet fed from the sheet feeding section 8 to the fixing section 10 via the transfer section 4 are normal sheets, and the second sheet is a non-image sheet. A case will be described.

As shown in FIG. 1, the first regular paper is the paper feed section 8.
Inserted into the paper feed roller 8a within a time period from t1 to t2.
Is applied to the normal paper. t1 is the time when the drive clutch of the paper feed roller 8a is turned on, and t2
Is the time immediately after the trailing edge of the normal paper has passed the paper feed roller 8a. Then, the plain paper inserted in the paper feed unit 8 is temporarily stopped when the leading end reaches the paper feed roller 8a, and the leading end of the image on the photosensitive drum 1 and the leading end of the plain paper are transferred to the transfer unit 4. Are timed to match. Then, at that timing, the drive clutch of the paper feeding roller 8a is turned on, the normal paper is sent out from the paper feeding unit 8 by the conveying force of the paper feeding roller 8a, and is fed to the transfer unit 4 via the entry guide 11 (see FIG. 3). Will be sent.

In the case of the first sheet of normal paper, the transfer output of the transfer section 4 is a little before the leading edge of the paper reaches the transfer section 4 (t.
It is turned on within the time of 1 to t2), and the rear end of the paper is transferred to the transfer unit 4
It is turned off shortly after the sheet has passed through (after the time of t2), and by such control, sufficient transfer performance over the entire sheet surface can be obtained. Then, the separation output of the sheet charge eliminator 6 is controlled to be turned on immediately after the transfer output is turned on and turned off immediately after the transfer output is turned off.

The same applies to the third normal paper to which the feeding force is applied by the paper feed roller 8a within the time period from t5 to t6.

When the second non-image paper is inserted into the paper feed section 8, the feeding force by the paper feed roller 8a is applied to the non-image paper within the time period of t3 to t4. t3 is the time when the drive clutch of the paper feed roller 8a is turned on, and t4 is the time immediately after the trailing edge of the non-image paper passes through the paper feed roller 8a. Then, the non-image paper inserted in the paper feed unit 8 is temporarily stopped when the leading end reaches the paper feed roller 8a,
Timing is set so that the position corresponding to the image front end of the photoconductor drum 1 and the front end of the non-image paper coincide with each other in the transfer unit 4. Then, at that timing, the drive clutch of the paper feed roller 8a is turned on, the non-image paper is sent out from the paper feed unit 8 by the conveying force of the paper feed roller 8a, and is transferred to the transfer unit 4 via the entry guide 11 (see FIG. 3). Be delivered.

In the case of non-image paper, the transfer output of the transfer section 4 is
The first half of the paper is controlled to be OFF in the initial stage of passing through the transfer unit 4, and even if it is controlled in this way, it is originally unnecessary to transfer the toner image for the non-image paper, so that the image forming process is not performed. It does not hinder the execution.
When the transfer output is controlled to be OFF in this way, the electrostatic attraction action does not occur between the photoconductor drum 1 and the paper 100 in the transfer portion 4, so that the non-image paper is kept on the photoconductor drum 1. There is no electroadsorption and the separation performance is improved. However, if the transfer output is kept in the OFF state until the trailing edge of the non-image paper passes through the transfer section 4, the conveyance force by electrostatic attraction does not occur, so that the trailing edge of the non-image paper is When it is separated from the paper feed roller 8a, conveyance failure occurs.

Therefore, in the transfer section 4, the sheet is transferred to the transfer section 4.
The transfer output is controlled to be turned on during the passage of the sheet, i.e., at the stage where the latter half of the non-image sheet passes in this embodiment. Then, the timing at which the transfer output is controlled to be ON is set slightly before the timing (indicated by symbol T in FIG. 1) at which the rear end of the non-image paper leaves the paper feed roller 8a.

According to the image forming apparatus having the transfer section 4 controlled as described above, when the front half of the non-image paper passes through the transfer section 4, the feeding force by the paper feed roller 8a causes the non-image paper to move. When the latter half of the sheet passes through the transfer unit 4, the electrostatic attraction between the photoconductor drum 1 and the imageless paper and the transporting force by the rotation of the photoconductor drum 1 are applied to the imageless paper, respectively. When the first half of the above passes the transfer unit 4, the electrostatic attraction action does not occur. Therefore, stable conveyance (sheet passing) is performed even on non-image paper, and the occurrence of jam due to poor separation is also suppressed.

By the way, when the image forming process is executed on the non-image paper, generally, the transfer output of the transfer unit 4 is turned off until the entire non-image paper passes through the transfer unit 4.
By doing so, electrostatic attraction of the image-free paper to the photosensitive drum 1 is prevented. So in this one,
The releasability of the image-free paper from the photosensitive drum 1 becomes extremely good. However, if the transfer output is kept in the OFF state until the rear end of the non-image paper passes through the transfer unit 4 in this way, the conveyance force due to electrostatic attraction does not occur.
When the trailing edge of the image-free paper leaves the paper feed roller 8a, conveyance failure occurs. On the other hand, as in the above-described embodiment, the transfer output of the transfer unit 4 is turned off in the initial stage of feeding the sheet to the transfer unit 4, and turned on in the stage where the sheet is passing through the transfer unit 4. With such a structure, after the rear end of the image-free paper is separated from the paper feed roller 8a, the electrostatic attraction action with the image-free paper of the photoconductor drum 1 and the rotation of the photoconductor drum 1 are performed as described above. The image-free paper is stably conveyed by the conveying force of the action.

Further, as shown in FIG. 3, the transport unit 9 is often provided with a sheet suction section 9a, and the sheet suction section 9a is provided.
When the image-free paper is adsorbed on a, the image-free paper is reliably conveyed by the conveyance unit 9. However, in the case of an image forming apparatus that employs the transport unit 9 that does not include the paper suction unit 9a, such a transport state cannot be expected. Further, since the non-image paper is small in size, the rear end of the non-image paper may be separated from the paper feed roller 8a before the suction action of the paper suction unit 9a is exerted. When the rear edge of the non-image paper leaves the paper feed roller 8a, conveyance failure occurs. On the other hand, as in the above-described embodiment, if the image-free sheet is separated from the photoconductor drum 1 due to the strength of its waist at the initial stage of feeding the image-free sheet to the transfer portion 4, the image-free sheet is Even when electrostatically attracted to the photosensitive drum 1 during the course of passing through the transfer section 4, reliable peeling is performed, and at the same time, stable electrostatic force is obtained by the electrostatic attraction at the transfer point.

[0026]

According to the first aspect of the invention, the transfer force is applied to the non-image paper by adsorbing the transfer force to the photoconductor drum only when the transfer force is required to be applied to the non-image paper. The image-free paper that has passed through is more likely to be peeled off from the photoconductor drum, which leads to an improvement in the separability of the image-free paper from the photoconductor drum, which is effective in preventing the occurrence of jams.

According to the second aspect of the invention, the carrying force of the paper feed roller and the carrying force of the non-image paper adsorbed to the photosensitive drum are continuously applied to the non-image paper. This leads to an improvement in the separability of the image-free paper from the body drum and suppresses the occurrence of jam when the image forming process is performed on the image-free paper.

[Brief description of drawings]

FIG. 1 is a time chart showing a paper feed roller clutch, transfer output, and separation output in an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of an image forming apparatus.

FIG. 3 is an enlarged configuration diagram of a main part of FIG.

FIG. 4 is a time chart showing a paper feed roller clutch, transfer output, and separation output in a conventional image forming apparatus.

[Explanation of symbols]

 1 Photoreceptor Drum 2 Charging Section 3 Developing Section 4 Transfer Section 5 Electrification Section 8 Paper Feeding Section 100 Paper X Rotating Direction of Photoreceptor Drum

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshikazu Harada 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka

Claims (2)

[Claims] 1. A charging unit, a developing unit, a transfer unit, and a charge eliminating unit are arranged around a photosensitive drum in this order in the rotation direction of the photosensitive drum, and a sheet fed from a paper feeding unit is transferred to the transfer unit. In the image forming apparatus that is fed to the fixing unit via the transfer unit, when the sheet is a non-image sheet, the transfer output is set to OFF in the initial stage of sheet feeding to the transfer unit.
An image forming apparatus, characterized in that the transfer output is set to ON while a sheet is passing through a transfer section. 2. The image forming apparatus according to claim 1, wherein the transfer output is set to ON before the trailing edge of the sheet leaves the sheet feeding roller of the sheet feeding section.