JPH10254256A - Image forming apparatus and process cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of a deviation in transfer by freely turnably supporting an upper pretransfer guide with a pair of floating pins and regulating/ keeping the upper pretransfer guide to/at a fixed position with an elastic member and a butting position regulating member. SOLUTION: The upper pretransfer guide 501 is freely turnably supported by a pair of the floating pins 508, in such a manner that the center of turning is provided in the vicinity of an image carrier 1 and regulated to the fixed position by an energizing spring 503 having a spring pressure (light pressure) of irreducible minimum strength required for regulating/keeping the upper pretransfer guide 501 to/at a normal position and a position regulating floating pin 507. Therefore, even if the bottom end of a transfer sheet such as a cardboard passes through resist rollers 505 and 506, the upper pretransfer guide 501 is pushed up by the stiffness of the bottom end of the transfer sheet, to reduce the frictional resistance between the transfer sheet S and the upper pretransfer guide 501, so that the transfer sheet S can be carried by electrostatic attracting force to the image carrier 1, without any problems. Further, even if the transfer sheet such as a thin paper that is not sufficiently stiff is carried, the transfer sheet can be guided/carried without any problems, and the deviation in the transfer never occurs.

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 an electrostatographic copying machine and an electrostatic printing apparatus, and a process cartridge, and particularly to a process cartridge for transferring an object to an image transfer section for transferring an image on an image carrier. It relates to a pre-transfer guide.

[0002]

2. Description of the Related Art A conventional image forming apparatus of this type forms an electrostatic latent image on an image carrier, develops the electrostatic latent image with a developer, and uses the developed image as a transfer object. Transfer to a transfer sheet. The transferred image is fixed on a transfer sheet via a fixing device.

In a transfer step of transferring an image to a transfer sheet in this series of processes, the transfer sheet is usually sent to a transfer section by a registration roller in synchronization with a developed image on an image carrier, and the image is transferred by a transfer charger. This is performed by transferring an image on a carrier onto a transfer sheet.

[0004] A pre-transfer guide for regulating the advancing direction of the transfer sheet is provided immediately before the transfer unit in order to feed the transfer sheet to a normal position of the transfer unit. The pre-transfer guide is a pair of upper and lower guides, and is usually formed in a wedge shape with a wide entrance and a narrow feed regulating portion at the tip.

Further, in order to facilitate the process of removing paper jams in the transfer section, a transfer separation charger, a lower guide before transfer, and a transfer table for transferring a transfer sheet after transfer are integrally formed.
In many cases, the sheet is retracted from the image carrier during a paper jam removal process.

However, the upper guide before transfer is usually fixed to the image carrier support member in order to ensure the accuracy of regulating the position of the leading end and to simplify the apparatus. In addition, the upper and lower guides before the transfer, the potential in the transfer process before and after the transfer,
In order not to fall to the ground through the lower guide, it is fixed to the supporting member via a float pin made of a normal resin having high electric resistance.

In this case, as the transfer sheet, a paper type usually used is 60 (g / m ² ) paper to 80 (g / m ² ) paper, but recently, 200 (g) has been requested due to the diversification of the paper type. / M
² ) Strong paper such as paper is often used.

[0008]

However, in the above-mentioned conventional example, the upper and lower guides are fixed during the image forming operation before the transfer, and the paper conveyed to the transfer section comes off the registration roller at the rear end of the paper. Then, the conveying force is reduced. Further, in the case of thick paper, due to its stiffness, the trailing end of the paper is curved and rubs on the upper guide surface before transfer, resulting in rubbing resistance in conveyance. When the rubbing resistance exceeds the conveying force, a slight difference occurs between the moving speed of the surface of the image carrier and the moving speed of the transfer sheet, so that the image transferred on the transfer sheet is disturbed. "Transfer misalignment" will occur. If the distance between the upper and lower guides before transfer is increased in order to reduce the rubbing resistance, there has been a problem that the leading edge of the paper cannot be guided to the normal transfer position.

In recent years, the copy speed has been increased due to a demand for improvement in productivity. However, in order to obtain a normal image, a developing device for developing an electrostatic latent image on an image carrier is driven at a high speed. Accordingly, there is a problem that the amount of the developer scattered in the machine from the developing sleeve carrying the developer increases. In order to address this problem, an attempt has been made to collect a scattered developer by providing a suction duct at the lower part of the developing device. However, at present, cleaning is performed by maintenance without solving the problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has as its object to provide an image forming apparatus which conveys a transfer sheet smoothly and is easy to maintain.
It is another object of the present invention to provide a configuration excellent in user-friendly handling.

[0011]

According to the present invention, there is provided an image forming apparatus and a process cartridge having the following constitution.

(1) A pair of pre-transfer upper and lower guides for guiding the transfer sheet to the image transfer section, a pair of float pins for rotatably supporting the pre-transfer upper guide, and the pre-transfer upper guide at a predetermined position. An image forming apparatus, comprising: an elastic member for regulating the pressure; and an abutting position regulating member.

(2) The float pin for supporting the upper guide before transfer and the abutting position regulating member are made of an electrically insulating member.
The image forming apparatus according to (1), wherein the elastic member is supported so as to be electrically insulated on the upper guide contact side or the opposite side before the transfer.

(3) The image forming apparatus according to (1) or (2), wherein a rotation center for rotatably supporting the pre-transfer upper guide is provided near the image carrier.

(4) The image forming apparatus according to (1) or (2), wherein the center of rotation for rotatably supporting the pre-transfer upper guide is provided at a position far from the image carrier.

(5) The strength of the elastic member for regulating the position of the pre-transfer upper guide is necessary and minimum for regulating and maintaining the pre-transfer upper guide at the proper position. The image forming apparatus according to any one of (1) to (3).

(6) A pair of upper and lower guides before transfer, which guide the transfer sheet to the image transfer section, and a long engagement length foot which supports the pre-transfer upper guide at a position far from the image carrier as a center of rotation. A pair of float pins having a long engagement length foot and a short engagement length foot for engaging and supporting a position of the pre-transfer upper guide near the image carrier at a predetermined position. An image forming apparatus comprising:

(7) When the float pin having a long engagement length for supporting and supporting the position of the upper guide before the transfer near the image carrier is removed, the upper guide before the transfer is rotated to a position farther from the image carrier. The float pin is supported by the pair of float pins supported as the center so as to be movable in the thrust direction and cannot be disengaged, and the amount of movement in the thrust direction is equal to the float pin having a long engagement length and the float pin having a short engagement length. (6) The image forming apparatus according to (6), wherein the engagement amount with the guide before transfer is larger than the engagement amount.

(8) When the pre-transfer upper guide is rotated close to the image carrier about a pair of float pins which support the position of the upper guide before transfer far from the image carrier, the upper pre-transfer guide is rotated. (6) The abutting portion of the upper guide before transfer contacts the image carrier protection guide before the leading end of the image carrier facing surface position of the guide comes into contact with the image carrier. Or the image forming apparatus according to (7).

(9) The image forming apparatus according to any one of (6) to (8), wherein the float pin supporting the upper guide before transfer is an electric insulator.

(10) The transfer / separation charger, the lower guide before transfer, and the transfer table for transferring the transfer sheet after transfer are integrally formed, and are retracted from the image carrier during a paper jam removal process. The image forming apparatus according to any one of (1) to (9).

(11) A cleaner, a pre-exposure section, a pre-transfer charger and a pre-transfer upper guide are formed as one unit on a frame supporting the image carrier, and any one of (1) to (9) is provided. A process cartridge which is detachably mounted on the image forming apparatus main body according to claim 1.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below.

Embodiment 1 FIG. 1 is a schematic sectional view showing an image forming apparatus main body according to Embodiment 1 of the present invention, and FIG. 2 is a sectional view of a process kit.

In FIG. 1, reference numeral 1 denotes an image carrier for forming a latent image in an image forming unit; 2, a developing device for developing a latent image formed on the image carrier; 3, a developer is supplied to the developing device 2; A hopper section 4, a pre-transfer charger for equalizing the charge amount of the developer on the image carrier 1 before transfer, 5 a resist roller for guiding the transfer sheet S to the transfer section, 6 a transfer separation charger, 7 Is a cleaner for collecting the developer remaining on the image carrier 1, 8 is a pre-exposure section for removing the residual potential on the image carrier, 9 is a primary charger for charging the image carrier 1, and 10 is a document. An optical system for reading an image, which has an exposure unit 10 a for writing a latent image on the image carrier 1. 11 is a document processing device for guiding a document to a reading unit, 12 is a sheet feeding unit for feeding a transfer sheet S to an image forming unit, 13 is a conveyance table, and 14 is an image on the transfer sheet formed by the image forming unit. A fixing unit 15 for fixing, a sheet discharging unit 15 for discharging the transfer sheet S on which image formation has been completed, an intermediate tray 17 for temporarily storing the transfer sheet S on which an image has been formed and fed to the image forming unit again, and a reference numeral 16 A re-feeding sheet guiding section 18 for guiding a transfer sheet to be re-feeded to the intermediate tray 17 is a sheet re-feeding section for feeding the transfer sheets stored in the intermediate tray 17 to the image forming section again.

Next, the operation will be described.

When a copy operation button (not shown) is pressed, the image carrier 1 rotating in the direction of the arrow is charged to a predetermined potential by the primary charger 9. On the other hand, the original in the original processing device 11 is guided to a reading unit, an image of the original is read by the optical system 10, and a latent image is written on the image carrier 1 by the exposure unit 10a.

The latent image formed on the image carrier 1 by writing the image is developed by the developing device 2. At this time, when the developer remaining amount is detected by a developer remaining amount detection sensor (not shown) in the developing device 2, the developer is appropriately replenished to the developing device 2 from the hopper 3.

When the transfer sheet S is fed from the sheet feeding section 12 to the image forming section, the image on the image carrier 1 is transferred onto the transfer sheet S by the transfer / separation charger 6, and the fixing section 14 is transferred by the transport table 13. And the image on the transfer sheet S is fixed.

In the case of one-sided copying, the sheet is directly discharged to the sheet discharge unit 15, but in the case of the double-sided mode or the multiplex mode, the sheet is not discharged as it is, but is stacked and stored on the intermediate tray 17 by the sheet re-feeding sheet guiding unit 16. When the predetermined number of sheets have been stored, the transfer sheets S are separated and fed one by one by the sheet re-feeding unit 18 and fed again to the image forming unit. Then, when the next document is placed on the platen by the document exchange device 11, a second image is formed, and then the image is fixed by the fixing unit 14 and then discharged to the sheet discharge unit 15.

The residual developer remaining on the image carrier 1 that has not been transferred onto the transfer sheet S by the transfer / separation charger 6 is scraped off by the cleaner 7 and collected by cleaning.

Next, the configuration around the image carrier 1 will be described.

In the first embodiment, the cleaners 7, the pre-exposure section 8, the pre-transfer charger 4 and the pre-transfer are provided on the frames 102 and 103 (see FIGS. 2, 9 and 10) supporting the image carrier 1. This is in the form of a so-called process kit (hereinafter, referred to as a P kit) in which the upper guide 501 is configured as one unit.

The image carrier 1 includes a front plate 102 and a rear plate 10.
3 is rotatably supported. When the image carrier 1 is mounted on the P kit, the mounting position is guided by the resin image carrier rear guide 101 and the front guide (front guide not shown) attached to the non-image area. The surface of the image carrier 1 does not come into contact with other parts and is not damaged.

The cleaner 7 includes a cleaning blade 7
01, magnet roller 704, discharge screw 70
6, a separation claw 707 and the like. Cleaning blade 7
01 has one end supported by a support member 702 and the other end contacted to the image carrier 1 by a pressure spring 703 at a predetermined contact pressure. The magnet roller 704 is applied with a predetermined thickness of collected developer by a layer thickness regulating roller 705, and is brought into contact with the image carrier 1 at a position in front of the cleaning blade 701 to apply a predetermined amount of developer to the image carrier 1. . With this developer, the frictional resistance between the cleaning blade 701 and the image carrier 1 is reduced.

The discharge screw 706 discharges the residual developer collected from the image carrier 1 by the cleaning blade 701 to a waste toner bottle (not shown). The image carrier separation claw 707 separates the transfer sheet S that has not been completely separated from the image carrier 1 by the separation operation of the transfer / separation charger 6 from the image carrier 1.

Reference numeral 501 denotes a pre-transfer upper guide, which is a pair of float pins 50 made of a resin (for example, PP) having a high electric resistance.
At 8, a rotation center is provided in the vicinity of the image carrier 1 and is rotatably supported, and is regulated to a predetermined position by an elastic biasing force of a biasing spring 503 and a float pin 507 for abutting position regulation. I have.

Further, since the biasing spring 503 is supported on the opposite side to the guide contact side by the support member 504 made of high electric resistance resin, the upper guide 501 before transfer is electrically floated with respect to the frame 103. It is supported in the state. This prevents the potential from dropping to the ground through the pre-transfer guide in the transfer operation and causing a transfer image defect.
Further, the urging spring 503 is set to a spring pressure (light pressure) having a minimum and necessary strength to regulate and maintain the pre-transfer upper guide 501 at a regular position.

Next, the transfer operation will be described.

FIGS. 3 and 4 are cross-sectional views of the periphery of the image carrier during the transfer operation. When the transfer sheet S is nipped and conveyed by the registration rollers 505 and 506, the leading end of the upper guide 501 before transfer is transferred. Is guided to a predetermined image carrier position, and is conveyed to a transfer unit. Then, while being subjected to a transfer operation, it is conveyed to a fixing device 14 by a conveyance table 13. At this time, as shown in FIG. 3, while being nipped and conveyed by the registration rollers 505 and 506, the transfer speed of the transfer sheet S is synchronized with the moving speed of the image carrier, so that a so-called transfer deviation does not occur. . However, as shown in FIG.
When the trailing end of the transfer sheet S comes off the registration rollers 505 and 506, the transfer sheet S is conveyed only by the electrostatic attraction force to the image carrier 1.

Here, 60 (g / m) which is usually used is used.
² ) In the case of a transfer sheet such as paper to 80 (g / m ² ) paper, the stiffness of the paper is small, and the rubbing force with the pre-transfer guide 501 is small and weak. As a result, the sheet is conveyed without any problem, and no transfer deviation occurs. However, in the case of a thick transfer sheet such as 200 (g / m ² ) paper, the stiffness of the transfer sheet is considerably strong, and the sliding resistance between the upper guide 501 before transfer and the rear end of the transfer sheet becomes large.

Therefore, in the first embodiment, the upper guide 501 before transfer is transferred to the image carrier 1 by a pair of float pins 508.
, A biasing spring having a minimum required spring pressure (light pressure) for regulating and maintaining the pre-transfer upper guide 501 at a proper position. 503
And, it is regulated to a predetermined position by a float pin 507 for regulating the abutting position.

Therefore, when the rear end of the transfer sheet passes through the registration rollers 505 and 506, the rear end of the upper guide 501 before transfer is pushed up by the stiffness of the rear end of the transfer sheet, and the downward inclination angle with the front end down is reduced. Make it sudden (Fig. 4). In this state, the sliding resistance between the transfer sheet and the pre-transfer upper guide 501 is reduced, and does not become the resistance for conveying the transfer sheet. Further, since the position of the lower guide 502 before transfer remains fixed at the center of rotation near the image carrier 1, the transfer sheet S
Is not changed, and the sheet conveying force due to the electrostatic attraction force does not change at all. Therefore, the transfer sheet S can be conveyed without any problem by the electrostatic attraction force of the image carrier 1, and no transfer deviation occurs.

As described above, according to the first embodiment, the pre-transfer upper guide is rotatably supported by the pair of float pins with the center of rotation provided near the image carrier. Is regulated and maintained at a predetermined position by an urging spring having a necessary and minimum strength of a spring pressure (light pressure) and a float pin for regulating an abutting position. Even if the transfer sheet comes off, the upper guide before transfer is pushed up by the waist force of the rear end of the transfer sheet, and the friction between the transfer sheet and the upper guide before transfer is reduced. Can be transported without any problem, and no transfer deviation occurs. Further, since it is not necessary to change the leading end position of the upper guide before transfer, even if a transfer sheet such as a thin paper sheet is conveyed, the transfer sheet can be guided and conveyed to a predetermined position of the image carrier without any problem.

Embodiment 2 5 and 6 are cross-sectional views of a P kit according to Embodiment 2 of the present invention. The same parts as those in Embodiment 1 are denoted by the same reference numerals, and redundant description is omitted.

In recent years, the copy speed has been increased due to a demand for improvement in productivity. However, in order to obtain a normal image, it is necessary to drive a developing device for developing an electrostatic latent image on an image carrier at a high speed. This necessitates a problem that the developer is scattered into the machine from the developing sleeve carrying the developer. In particular, the scattered dirt below the developing device is severe, and if the dirt is increased, the scattered developer may adhere to the transfer sheet S when the transfer sheet S comes into contact with a guide or the like, and may stain the transfer sheet S. Therefore, at present, the upper and lower guides before transfer are regularly cleaned and maintained.

Therefore, in the second embodiment, the pre-transfer upper guide 501 is pivoted to a position separated from the image carrier 1 by a pair of float pins 507 made of a resin (for example, PP) having high electric resistance. Is provided so as to be rotatable, and is regulated and maintained at a predetermined position by an elastic biasing force of a biasing spring 509 and a float pin 508 for abutting position regulation. The biasing spring 509 supports the opposite side of the guide abutment side by a support member 510 made of a high electric resistance resin, and electrically supports the upper guide 501 before transfer with respect to the frame 103 in a floating state. ing.

According to this configuration, in the transfer operation, the potential is prevented from dropping to the ground through the upper guide before transfer and causing a transfer image defect. In addition, the biasing spring 509 is
Since the spring pressure (light pressure) having the minimum and necessary strength to regulate and maintain the pre-transfer upper guide 501 at the normal position is set, during maintenance, the state shown in FIG. In addition, the leading end of the upper guide 501 before transfer can be pushed down to easily retreat from the surface of the image carrier 1, and the scattered developer adhered on the upper guide before transfer can be easily cleaned. Further, when the upper guide before transfer is moved in the thrust direction when the upper guide before transfer is rotated and retracted from the image carrier 1, the upper guide 501 before transfer is held so as not to rotate by being hooked on an engaging portion (not shown). In addition, the cleaning operation becomes easier.

Embodiment 3 7 and 8 are sectional views of a P kit according to Embodiment 3 of the present invention, and FIGS.
9 is a view showing the relationship between the float pin and the upper guide before transfer when the P kit of FIGS. 7 and 8 is viewed from below, and the same parts as those in the first embodiment are denoted by the same reference numerals and are duplicated. Description is omitted.

The pre-transfer upper guide 501 is composed of a pair of float pins 507 made of a resin (for example, PP) having a high electric resistance.
With this arrangement, a rotation center is provided at a position distant from the image carrier 1 so as to be rotatably supported, and a float pin 511 having a short foot is attached to the rear side plate 103 at a position near the image carrier 1. Long float pin 5 paired with
12 is attached to the front side plate 102, and the upper guide 501 before transfer.
Is held at the regular position (FIGS. 7 and 9).

After performing the image forming operation in this state, the following operation is performed when performing cleaning maintenance of the upper guide 501 before transfer. First, the float pin 512 is removed and the pre-transfer upper guide 501 is pulled out to the near side.
11 is disengaged from the pre-transfer upper guide 501 (FIG. 1).
0), the upper guide 501 before transfer is turned from the normal posture state by its own weight, as shown in FIG. 8, around the float pin 507 as a fulcrum and retracted from the surface of the image carrier.

Since the float pin 507 is sufficiently far from the image carrier 1, the scattered developer adhering to the upper guide before transfer can be easily cleaned. After cleaning, push the upper guide 501 before transfer upward while pushing it up.
The float pin 511 is guided by the tapered end of the float pin 511 and can be easily attached to the engagement position. Further, when the float pin 512 is inserted into the front side plate, the tapered end portion is easily inserted into the upper guide before transfer, and the position of the upper guide 501 before transfer can be easily regulated.

When the remounting operation is performed, the leading end 501b of the upper guide before transfer may come into contact with the surface of the image carrier 1, but in the third embodiment, the upper guide 501 before transfer is used.
The side projection 501a of the upper guide 50 comes into contact with the resin image carrier rear guide 101 and the front guide (the front guide is not shown) attached to the non-image area, and the pre-transfer upper guide tip 50.
1b is set so as not to hit the surface of the image carrier.
Thus, when performing maintenance for cleaning the upper guide 501 before transfer, the image carrier 1 is not damaged.

[0054]

As described above, according to the present invention, the pre-transfer upper guide of the pre-transfer guide for guiding the transfer sheet to the image transfer section is rotatably supported by a pair of float pins, and the transfer is performed. Since the upper front guide is configured to be maintained at a predetermined position by the elastic member and the abutting position restricting member,
Even if the trailing edge of the transfer sheet such as thick paper passes through the registration roller, the stiffness of the trailing edge of the transfer sheet pushes up the pre-transfer guide and reduces the sliding resistance between the transfer sheet and the pre-transfer upper guide. The transfer sheet can be conveyed without any problem by the electrostatic attraction force with the body, and there is an effect that transfer deviation does not occur. .

Since the upper transfer guide is configured to be electrically supported in a floating state, it is possible to reliably prevent a potential drop to the ground through the upper pre-transfer guide during the transfer operation, thereby causing a defective transfer image. There is.

Since the center of rotation for rotatably supporting the pre-transfer upper guide is provided near the image carrier, it is not necessary to change the tip position of the pre-transfer upper guide, and it is possible to use thin paper having a weak stiffness. There is an effect that even if a transfer sheet is conveyed, it can be guided and conveyed to a predetermined position of the image carrier without any problem.

Since the strength of the elastic member for regulating the position of the pre-transfer upper guide is set to the minimum necessary for regulating and maintaining the pre-transfer upper guide at the proper position, the tip of the pre-transfer upper guide is required during maintenance. The portion can be pushed down to easily retreat from the surface of the image carrier, and there is an effect that the developer scattered on the upper guide before transfer can be easily cleaned.

The pre-transfer upper guide is rotatably supported by a pair of float pins about a position distant from the image carrier, and the pre-transfer upper guide is located at a position closer to the image carrier. Since the float pin with a long engagement length with the front upper guide and the float pin with a short engagement length are configured to be supported at a predetermined position, during maintenance, the front end of the pre-transfer upper guide is detached from the float pin and the rear end is removed. Can be rotated by using a pair of float pins that support
Scattered developer adhered to the upper guide before transfer can be easily cleaned. Further, since the apparatus configuration is simple, there is an effect that the cost can be reduced.

When the float pin having a long engagement length with the pre-transfer upper guide is removed, the pre-transfer upper guide is supported by the pair of float pins so as to be freely movable in the thrust direction and not to be disengaged, and is moved in the thrust direction. The amount of engagement is greater than the amount of engagement between the float pin and the pre-transfer guide, which has a short engagement length, so that during maintenance, the upper guide before transfer can be easily disengaged from the float pin and removed from the surface of the image carrier. There is an effect that the evacuation can be performed and the cleaning operation can be easily performed.

When the pre-transfer upper guide is rotated close to the image carrier with the pair of float pins as the center of rotation, the pre-transfer upper guide is positioned before the front end of the upper surface of the upper guide facing the image carrier contacts the image carrier. Since the abutting portion of the upper guide before transfer abuts on the image carrier protection guide, there is an effect that the image carrier is not damaged.

The float pins for supporting the pre-transfer upper guide are made of a material having a high electrical resistance, and are configured to electrically support the pre-transfer upper guide in a floating state. This has the effect that the occurrence of transfer image defects can be reliably prevented with a simple configuration.

Since the transfer separation charger, the lower guide before transfer, and the transfer table for transferring the transfer sheet after transfer are integrally formed, and are configured to be retracted from the image carrier during paper jam removal processing, the image carrier is There is an effect that the paper jam removal processing can be performed quickly and easily without damaging the paper jam.

The cleaner, the pre-exposure section, the pre-transfer charger and the pre-transfer upper guide are configured as a single unit on the frame supporting the image carrier, and are configured to be detachable from the image forming apparatus main body. There is an effect that a configuration excellent in handling can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an image forming apparatus main body according to Embodiment 1 of the present invention.

FIG. 2 is a sectional view of a process kit.

FIG. 3 is a schematic cross-sectional view illustrating a configuration around an image carrier during a transfer operation.

FIG. 4 is a schematic sectional view showing a configuration around an image carrier during a transfer operation.

FIG. 5 is a sectional view of a process kit according to a second embodiment of the present invention.

FIG. 6 is a sectional view of a process kit according to a second embodiment in which the upper guide before transfer is retracted from the surface of the image carrier.

FIG. 7 is a sectional view of a process kit according to a third embodiment of the present invention.

FIG. 8 is a sectional view of a process kit according to a third embodiment in which the upper guide before transfer is retracted from the surface of the image carrier.

9 is a diagram showing a relationship between a float pin and an upper guide before transfer when the process kit of FIG. 7 is viewed from below.

10 is a diagram showing a relationship between a float pin and an upper guide before transfer when the process kit of FIG. 8 is viewed from below.

[Explanation of symbols]

 1 image carrier, 501 upper guide before transfer, 502 lower guide before transfer, 503, 509 biasing spring, 504, 510 support member, 507, 508, 511, 512 float pin.

Claims (11)

[Claims] A pair of pre-transfer upper and lower guides for guiding a transfer sheet to an image transfer unit; a pair of float pins rotatably supporting the pre-transfer upper guide; and a pre-transfer upper guide at a predetermined position. An image forming apparatus, comprising: an elastic member that regulates and a striking position regulating member. 2. A float pin for supporting an upper guide before transfer and an abutting position regulating member are made of an electric insulating member, and further support an elastic member so as to be electrically insulated on a contact side or an opposite side of the upper guide before transfer. The image forming apparatus according to claim 1, wherein: 3. The image forming apparatus according to claim 1, wherein a rotation center for rotatably supporting the pre-transfer upper guide is provided near the image carrier. 4. The image forming apparatus according to claim 1, wherein a rotation center for rotatably supporting the pre-transfer upper guide is provided at a position far from the image carrier. 5. The strength of the elastic member for regulating the position of the pre-transfer upper guide is a minimum and necessary strength for regulating and maintaining the pre-transfer upper guide at a regular position. The image forming apparatus according to any one of claims 1 to 3. 6. A pair of upper and lower guides before transfer, which guide a transfer sheet to an image transfer unit, and a long engagement length foot supporting a position of the upper guide before transfer far from the image carrier as a center of rotation. A pair of float pins having a long engagement length foot and a short engagement length foot for engaging and supporting a position of the pre-transfer upper guide near the image carrier at a predetermined position. An image forming apparatus characterized in that: 7. When the float pin having a long engagement length for engaging and supporting the position of the upper guide before transfer near the image carrier is removed, the position of the upper guide before transfer is farther from the image carrier as the rotation center. A pair of float pins having a short engagement length and a pair of the float pin having a long engagement length and the transfer pin are supported by a pair of float pins supported in a thrust direction so as to be freely movable and undetachably. 7. The image forming apparatus according to claim 6, wherein the amount of engagement is larger than the amount of engagement with the front guide. 8. The pre-transfer upper guide when the pre-transfer upper guide is rotated close to the image carrier about a pair of float pins that support the position of the pre-transfer upper guide far from the image carrier. 7. An abutting portion of said pre-transfer upper guide is set to abut against an image carrier protection guide before a front end of said image carrier facing surface position abuts on said image carrier. The image forming apparatus according to claim 7. 9. The image forming apparatus according to claim 6, wherein the float pin supporting the pre-transfer upper guide is an electrical insulator. 10. A transfer separation charging device, a lower guide before transfer, and a transfer table for transferring a transfer sheet after transfer, are integrated with each other, and are retracted from the image carrier during paper jam removal processing. Any one of claims 1 to 9
An image forming apparatus according to any one of the preceding claims. 11. The apparatus according to claim 1, wherein a cleaner, a pre-exposure section, a pre-transfer charger and a pre-transfer upper guide are formed as one unit on a frame supporting the image carrier. A process cartridge which is detachably attached to the image forming apparatus main body according to the above item.