JPH10115964A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an image having excellent image quality by preventing an adverse effect given to the image such as the sticking of fixing releasing agent to an intermediate transfer belt and a photoreceptor at the time of both-face transfer and the cause of electrification unevenness or the like. SOLUTION: When the both-face transfer is performed a certain number of sheets, the fixing releasing agent stuck to a secondary transfer belt 31 is removed by bringing a fixing releasing agent absorbing member 35 into contact with the secondary transfer belt 31, so that the dispersion of the resistance values of the secondary transfer belt 31 and the intermediate transfer belt 21 and the electrification unevenness of the photoreceptor 11 because the large amount of the fixing releasing agent is stuck to the secondary transfer belt 31 and runs to the intermediate transfer belt 21 and the photoreceptor 11 are prevented.

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 for forming a full-color image, and more particularly to a high-quality image without defects.

[0002]

2. Description of the Related Art In an image forming apparatus for forming a full-color image, toner images of a plurality of colors formed on a photosensitive member are transferred onto an intermediate transfer belt, and the toner images transferred onto the intermediate transfer belt are transferred. An apparatus employing a transfer method based on an intermediate transfer belt system for transferring an image onto transfer paper is disclosed in, for example, Japanese Patent Application Laid-Open No. 2-28.
JP-A-2491, JP-A-5-210316, JP-A-5-3135
No. 25, etc. As shown in FIG. 6, this transfer method employs a medium resistance (surface resistance; 1 × 10 ⁷ to 10 ¹³ Ω).
A secondary transfer roller 26 having a medium resistance is provided in contact with the inside of the intermediate transfer belt 21 and a paper transfer roller 41 is provided at a position outside the intermediate transfer belt 21 opposed to the secondary transfer roller 26.
When the toner image 9 transferred to the intermediate transfer belt 21 is transferred to the transfer paper 8, the transfer roller 41 is in contact with the secondary transfer roller 26 while applying a transfer bias to the paper transfer roller 41. The toner image 9 is transferred onto the transfer paper 9 passing between the intermediate transfer belt 21 and the paper transfer roller 41 by bringing the paper transfer roller 41 into pressure contact with the position of the intermediate transfer belt 21.

[0003]

As described above, when the toner image is transferred to the transfer paper by bringing the paper transfer roller into pressure contact with the intermediate transfer belt, the toner transferred to the intermediate transfer belt is transferred. The layer is compressed by the local pressure of the paper transfer roller, the releasability between the toner and the belt surface is reduced, and a part of the toner remains on the intermediate transfer belt, and the transfer paper or the like is removed. There is a possibility that a so-called insect-eating image in which a part of the transferred image is defective, that is, there is a defect.

Further, an air gap exists near the paper transfer entrance, and as shown in FIG. 4, an electric line of force (electric field) φ is formed by this paper transfer bias, and the toner is transferred to the transfer paper before the nip. However, there is a disadvantage in that transfer dust is generated on the transfer paper, and a defect occurs in the image transferred on the transfer paper.

Further, when transferring to both sides of the transfer paper,
When the second surface passes through the transfer roller, the previously transferred first surface is pressed against the transfer roller, so that continuous double-side transfer results in a large amount of the fixing release agent. Adheres to the surface of the rubber. The fixing release agent adhered to the transfer roller adheres to the intermediate transfer belt, causing the resistance value of the intermediate transfer belt to vary, and the fixing release agent adhered to the intermediate transfer belt adheres to the photosensitive member. There is also a disadvantage that an image is adversely affected due to uneven charging or the like.

SUMMARY OF THE INVENTION It is an object of the present invention to improve such disadvantages and to provide an image forming apparatus capable of forming a high quality image without defects.

[0007]

An image forming apparatus according to the present invention comprises: a primary transfer unit for transferring toner images of a plurality of colors formed on a photosensitive member onto an intermediate transfer belt having a medium resistance;
An image forming apparatus comprising: a secondary transfer unit having a secondary transfer belt for transferring a toner image transferred to an intermediate transfer belt to a transfer material, wherein a fixing release agent adhered to the secondary transfer belt is removed. A fixing release agent removing means for removing is provided along a non-transfer portion of the secondary transfer belt.

It is preferable that the fixing release agent removing means is brought into contact with the secondary transfer belt when a predetermined number of double-sided transfers have been performed to remove the fixing release agent adhered to the secondary transfer belt.

Further, the fixing release agent removing means includes an absorbing member or a second member for absorbing the fixing release agent attached to the secondary transfer belt.
It is desirable to use a scraping means for scraping off the fixing release agent adhered to the next transfer belt.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to the present invention has an image forming unit, a primary transfer unit, a secondary transfer unit, and a fixing unit. The image forming unit forms a plurality of toner images on the photoreceptor surface. The primary transfer unit has an intermediate transfer belt having a medium resistance, a primary transfer unit, and a secondary transfer unit. The secondary transfer section has two medium-resistance secondary transfer rollers disposed in the intermediate transfer belt at regular intervals in the direction of movement of the transfer material. Then, the toner image formed on the surface of the photoreceptor is primarily transferred to an intermediate transfer belt at a primary transfer section.

The secondary transfer unit has a medium resistance secondary transfer belt wound along a transfer material moving path, a bias applying unit provided inside the secondary transfer belt, and a non-transfer unit of the secondary transfer belt. And a fixing release agent removing means including an absorbing member for absorbing the fixing release agent attached to the secondary transfer belt or a scraping means for scraping off the fixing release agent attached to the secondary transfer belt. . When the toner image transferred to the intermediate transfer belt is secondarily transferred to a transfer material, the secondary transfer belt is pressed against the intermediate transfer belt between the two secondary transfer rollers of the primary transfer unit, The secondary transfer belt and the intermediate transfer belt are brought into contact with each other with a relatively large area, the pressure applied to the contact surface between the secondary transfer belt and the intermediate transfer belt is reduced, and the toner of the toner image formed on the intermediate transfer belt is contacted. Prevents excessive pressure.

A bias applying section is provided in a secondary transfer belt opposed to a secondary transfer roller provided downstream of the two secondary transfer rollers in the moving direction of the transfer material. When the toner image transferred to the intermediate transfer belt is secondarily transferred to the transfer material, the lines of electric force (electric field) generated on the upstream side of the contact area between the intermediate transfer belt and the secondary transfer belt are suppressed. It is prevented from being generated and adhering to the transfer material.

Further, the bias applying section is formed integrally with the driving section of the secondary transfer belt so that the position of the bias applying section with respect to the secondary transfer belt is always kept constant, and the distance between the bias applying section and the secondary transfer belt at the time of transfer is increased. Prevents the resistance from fluctuating due to fluctuations in the resistance.

Further, when a predetermined number of double-sided transfers have been performed, the fixing release agent removing means is brought into contact with the secondary transfer belt to remove the fixing release agent adhered to the secondary transfer belt. Is attached to the secondary transfer belt in large quantities and reaches the intermediate transfer belt and the photoreceptor, thereby preventing the resistance value of the secondary transfer belt and the intermediate transfer belt from fluctuating and causing uneven charging.

[0015]

FIG. 1 is a block diagram showing an embodiment of the present invention. As shown in the figure, the image forming apparatus includes an image forming unit 1, a primary transfer unit 2, a secondary transfer unit 3, a transport unit 4, a fixing unit 5, a duplex transport path 6, and a duplex bank unit 7. The image forming unit 1 includes a charging charger 12 disposed around a photoreceptor 11 and a laser.
It has an irradiation section of the beam 13, a color developing section 14 composed of yellow (Y), magenta (M), cyan (C) and black (BK), and a drum cleaning section 15.

The primary transfer unit 2 includes an intermediate transfer belt 21
And a primary transfer section 22 having a bias application roller 23 and an earth roller 24; a secondary transfer section having a tension roller 25 and two secondary transfer rollers 26 and 27; And a roller 29 facing the cleaning section 28. The intermediate transfer belt 21 has a surface resistance of 1 × 10 ⁸ to 10 ¹⁰ Ω
Formed of a material having medium resistance electrical characteristics
Roller 24, bias applying roller 23, tension roller 25, secondary transfer rollers 26 and 27, and opposing roller 2.
It is wound around 9. The intermediate transfer belt 21 is separated from the surface of the photoconductor 11 by a contact / separation mechanism (not shown) except when the toner image on the photoconductor 11 is primarily transferred, and the surface of the photoconductor 11 is only used for the primary transfer to the intermediate transfer belt 21. Is pressed against. The two secondary transfer rollers 26 and 27 provided inside the intermediate transfer belt 21 are 0.3 m thick on a metal roller.
m of hydrin rubber and has a surface resistance of 1 × 10 ⁷ to 1
It is formed to about ⁰⁹ Ω. These two secondary transfer rows
The rollers 26 and 27 are arranged in the intermediate transfer belt 21 at regular intervals along the moving direction of the transfer material 8.

The secondary transfer unit 3 includes a secondary transfer belt 31 wound around a driving roller 32 and a driven roller 33 provided along a moving path of the transfer material 8, and a secondary transfer belt 31.
Is provided outside the secondary transfer belt 31 at a position facing the drive roller 32 and opposed to the drive roller 32 so as not to hinder the transfer of the transfer material 8, and is attached to the secondary transfer belt 31. A fixing release agent absorbing member 35 which is a fixing release agent removing means for removing the fixing release agent, an image detection sensor 36 provided inside the secondary transfer belt 31, and a driven roller 33.
And a transfer belt cleaner 37 provided outside the secondary transfer belt 31 at a position facing the transfer belt. Secondary transfer belt 3
Numeral 1 is formed of a material having a medium resistance electrical characteristic having a surface resistance of 1 × 10 ⁸ to 10 ¹⁰ Ω. Bias applying unit 34
Is composed of corona transfer means, two secondary transfer rollers 2
6 and 27, which are provided in a secondary transfer belt 31 facing a secondary transfer roller 27 provided downstream of the transfer material 7 in the moving direction of the transfer material 7, and always have a fixed position with respect to the secondary transfer belt 31. It is configured integrally with the driving unit of the secondary transfer belt 31 so as to hold it. The fixing release agent absorbing member 35 is attached to a separating mechanism 38 as shown in the partial configuration diagram of FIG.
The secondary transfer belt 31 rotates in a direction opposite to the rotation direction.

The secondary transfer unit 3 is provided rotatably in the direction of the primary transfer unit 2 around a driving roller 32 as shown in the partial configuration diagram of FIG. When the image is subjected to the secondary transfer, the secondary transfer belt 31 is pressed against the intermediate transfer belt 21, and when the secondary transfer is not performed, the secondary transfer belt 31 is separated from the intermediate transfer belt 21.

When a full-color image is formed by the image forming apparatus constructed as described above, the charging charger 12 is used.
The surface of the photoreceptor 11 charged with the laser beam 13 is irradiated with a laser beam 13 to form an electrostatic latent image. The latent image on the photoreceptor 11 is visualized with toner attached to each color by a color developing unit 14 composed of yellow (Y), magenta (M), cyan (C), and black (BK). Toner on photoconductor 11
The image is primarily transferred onto the intermediate transfer belt 21 of the primary transfer unit 2 and then removed by the drum cleaning unit 15.
The toner image on the photoreceptor 11 is placed on the intermediate transfer belt 21 by one.
When performing the next transfer, the intermediate transfer belt 21 is
A primary transfer is performed for each toner of Y, M, C, and BK by contacting the surface and indirectly applying a charge in the primary transfer unit 22. That is, when the first toner image formed on the photoconductor 11 is primarily transferred onto the intermediate transfer belt 21, the intermediate transfer belt 21 is pressed against the surface of the photoconductor 11 by a contact / separation mechanism (not shown) to perform the first transfer. The first transfer of the toner image is performed. When the first primary transfer of the toner image is completed, the intermediate transfer belt 21 is separated from the surface of the photoconductor 11, and the rotation of the intermediate transfer belt 21 is controlled so that the next toner image is superimposed accurately.
The surface of the photoconductor 11 is again pressed against the surface to form
Next transfer. This primary transfer is sequentially repeated for each toner, and the Y, M, C, and BK toners are transferred onto the intermediate transfer belt 21.
The images are superimposed sequentially. The full-color toner image 9 transferred onto the intermediate transfer belt 21 is secondarily transferred to the transfer material 8 conveyed onto the secondary transfer unit 3.

When the full-color toner image 9 transferred onto the intermediate transfer belt 21 is secondarily transferred to the transfer material 8,
The secondary transfer unit 3 is rotated toward the primary transfer unit 2 to press the secondary transfer belt 31 against the intermediate transfer belt 21 between the secondary transfer rollers 26 and 27 as shown in FIG. A bias voltage is applied and charged by the bias applying unit 34,
Toner image 9 on intermediate transfer belt 21 is transferred onto transfer material 8 conveyed between intermediate transfer belt 21 and secondary transfer belt 31.
Next transfer. The transfer material 8 onto which the toner image 9 has been transferred is sent from the transport unit 4 to the fixing unit 5, where the fixing roller 5 coated with a silicone-based release agent in order to enhance the release property.
1 and a nip formed by the pressure roller 52, and is fixed and discharged to the discharge tray 101.

When the secondary transfer is performed as described above, the secondary transfer belt 31 is rotated around the driving roller and pressed against the intermediate transfer belt 21 between the secondary transfer rollers 26 and 27. Pressing can be performed with a small pressing force. Further, since the secondary transfer belt 31 and the intermediate transfer belt 21 are in contact with each other with a relatively large area, the pressure applied to the contact surface between the secondary transfer belt 31 and the intermediate transfer belt 21 can be reduced. Further, the bias applying section 34 is constituted by corona transfer means, and a bias voltage is applied directly to the secondary transfer belt 31 at a position facing the secondary transfer roller 27. The pressure applied to the contact surface between the transfer belt 31 and the intermediate transfer belt 21 can be further reduced. Therefore, it is possible to prevent an excessive pressure from being applied to the toner of the toner image 9 formed on the intermediate transfer belt 21, and to separate the toner image 9 formed on the intermediate transfer belt 21 from the belt surface. It is possible to prevent the moldability from being reduced. For this reason, the toner secondary-transferred to the transfer material 8
It is possible to prevent a so-called insect image from occurring in the image.

The bias applying unit 34 is a secondary transfer roller facing the secondary transfer roller 27 provided downstream of the two secondary transfer rollers 26 and 27 in the moving direction of the transfer material 8. The toner image 9 on the intermediate transfer belt 21 is transferred to the transfer material because a positive transfer bias having a polarity opposite to that of the toner charged negatively is applied to the secondary transfer belt 31 having a medium resistance. When the secondary transfer is performed on the transfer material 8, the lines of electric force (electric field) generated near the nip at the transfer entrance due to the transfer bias can be suppressed, and the generation of transfer dust and adherence to the transfer material 8 can be prevented. As a result, a high-quality image can be stably formed on the transfer material 8.

Further, the secondary transfer rollers 26 and 2 having a medium resistance are used.
7, the intermediate transfer belt 21 and the secondary transfer belt 31 are used and applied at a position facing the secondary transfer roller 27, so that the applied charges can be uniformly distributed and a uniform image can be stably formed. Can be formed.

When the secondary transfer is not performed, the secondary transfer belt 31 is separated from the intermediate transfer belt 21. Therefore, it is necessary to prevent an abnormal image from occurring when a plurality of toner images are superimposed on the intermediate transfer belt 21. Can be.

Further, since the bias applying section 34 is formed integrally with the driving section of the secondary transfer belt 31, the secondary transfer belt 31 is rotated to contact the intermediate transfer belt 21 to perform secondary transfer. When this is done, the position of the bias applying unit 34 with respect to the secondary transfer belt 31 can always be kept constant. Therefore, it is possible to prevent the resistance or the like between the secondary transfer belt 31 and the bias applying unit 34 from fluctuating. Further, maintenance and the like of the secondary transfer unit 3 can be easily performed.

When performing double-side transfer with this image forming apparatus,
When performing double-sided transfer manually, the transfer material 8 discharged to the paper discharge tray 101 is set on the manual feed tray 102 with the previously transferred image side down and the blank side up, and Perform transcription. In the case where the double-sided transfer is automatically performed, the transfer material 8 discharged from the fixing unit 5 is sent from the double-sided conveyance path 6 to the double-sided bank unit 7, and the previously transferred image 10 is turned down and the blank side is turned upside down. The sheet is sent to the secondary transfer unit 3 after being turned upside down so as to be transferred again. When performing this double-sided transfer, the image detection sensor 36
By detecting the image of the first surface which has been transferred first, it is possible to detect the double-sided transfer and the number of double-sided transferred images.

During the double-side transfer, the first surface previously transferred is attracted to the secondary transfer belt 31, and if continuous double-side transfer is performed, a large amount of the fixing release agent is removed from the secondary transfer belt. 3
1 and the resistance value of the secondary transfer belt 31 varies. Further, the fixing release agent adhered to the secondary transfer belt 31 adheres to the intermediate transfer belt 21, and the intermediate transfer belt 2
1 and the intermediate transfer belt 2
The fixing release agent adhering to No. 1 adheres to the photoreceptor 11 and causes uneven charging, thereby adversely affecting the image.
Further, the transfer belt cleaner 37 is also adversely affected. Therefore, when the double-side transfer is performed, when the number of the double-side transfer reaches a predetermined fixed number, for example, 30 sheets, the fixing release agent absorbing member 35 is brought into contact with the secondary transfer belt 31 and the transfer operation is not performed. Then, the secondary transfer belt 31 is rotated about once to three times to absorb and remove the adhered fixing release agent. Thereafter, the transfer operation is performed with the fixing release agent absorbing member 35 separated from the secondary transfer belt 31. When the fixing release agent adhering to the secondary transfer belt 31 is removed as described above, the fixing release agent absorbing member 35 is moved to the secondary transfer belt 31 for a short time.
, It is possible to remove only the fixing release agent without cleaning the toner remaining on the secondary transfer belt 31, and the contact resistance of the secondary transfer belt 31 during the secondary transfer is reduced. It is possible to prevent the speed of the transfer belt 31 from being affected.

In the above embodiment, the fixing release agent absorbing member 3 is used.
Although the case where the transfer roller 8 is provided at a position facing the drive roller 32 has been described, the fixing release agent absorbing member 35 transports the transfer material 8 in the non-transfer area of the secondary transfer belt 31 as shown in FIG. May be arranged at any position as long as the position does not cause any trouble.

In the above embodiment, the case where the fixing release agent absorbing member 35 is used as the fixing release agent removing means has been described. However, as shown in FIG. 391 and the secondary transfer belt 31
The fixing release agent adhered to the secondary transfer belt 31 is scraped off by a scraping means 39 provided with a regulating means 392 and an oil pan 393 which are provided on the outside of the secondary transfer belt 31 and which can be freely attached to and detached from the secondary transfer belt 31. Is also good. If the fixing release agent attached to the secondary transfer belt 31 is scraped off by the scraping means 39 in this way, the fixing release agent attached to the secondary transfer belt 31 can be removed in a shorter time, and The number of maintenance can be reduced.

[0030]

As described above, according to the present invention, when the toner image transferred to the intermediate transfer belt is secondarily transferred to the transfer material, the secondary transfer belt is used for the two secondary transfer of the primary transfer unit. The secondary transfer belt and the intermediate transfer belt are brought into contact with a relatively large area by pressing against the intermediate transfer belt between the rollers,
The pressure applied to the contact surface between the secondary transfer belt and the intermediate transfer belt is reduced to prevent applying excessive pressure to the toner of the toner image formed on the intermediate transfer belt. It is possible to prevent the releasability between the formed toner image and the belt surface from deteriorating, and to prevent the occurrence of a worm image in the toner image secondary-transferred to the transfer material. An image can be formed.

The toner transferred to the intermediate transfer belt is
When the image is secondarily transferred to the transfer material, the lines of electric force (electric field) generated near the nip at the transfer entrance and upstream of the contact area between the intermediate transfer belt and the secondary transfer belt are suppressed, and transfer dust occurs. Adhesion to the transfer material can be prevented, and an image without defects can be formed on the transfer material.

Further, when a fixed number of double-sided transfers are performed, the fixing release agent adhering to the secondary transfer belt is absorbed or the fixing release agent adhering to the secondary transfer belt is scraped off. Since the fixing release agent adhering to the next transfer belt is removed, it is possible to prevent a large amount of the fixing release agent from adhering to the secondary transfer belt and circling to the intermediate transfer belt and the photoconductor, and to fix the toner. Variations in the resistance value and uneven charging of the secondary transfer belt and the intermediate transfer belt due to the release agent can be prevented, and a stable image can be formed.

Further, the fixing / release agent removing means is brought into contact with the secondary transfer belt only when removing the fixing / release agent adhering to the secondary transfer belt, so that the durability and transfer speed of the secondary transfer belt are affected. The fixing release agent can be removed without giving.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a partial configuration diagram illustrating a secondary transfer unit of the embodiment.

FIG. 3 is a partial configuration diagram illustrating a movable state of a secondary transfer unit of the embodiment.

FIG. 4 is a partial configuration diagram illustrating a secondary transfer unit according to a second embodiment.

FIG. 5 is a partial configuration diagram illustrating a secondary transfer unit according to a third embodiment.

FIG. 6 is a configuration diagram illustrating a secondary transfer unit of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming unit 2 Primary transfer unit 3 Secondary transfer unit 11 Photoconductor 14 Color developing part 21 Intermediate transfer belt 26 Secondary transfer roller 27 Secondary transfer roller 31 Secondary transfer belt 34 Bias applying part 35 Fixing release agent absorbing member 39

Claims (4)

[Claims] 1. A primary transfer unit for transferring a plurality of color toner images formed on a photoreceptor onto an intermediate transfer belt having a medium resistance, and a toner image transferred on the intermediate transfer belt to a transfer material. An image forming apparatus comprising: a secondary transfer unit having a secondary transfer belt for removing a fixing release agent attached to the secondary transfer belt; An image forming apparatus provided along a transfer section. 2. The fixing / release agent removing means according to claim 1, wherein said fixing / release agent removing means is brought into contact with a secondary transfer belt when a predetermined number of double-sided transfer operations are performed to remove the fixing / release agent adhered to the secondary transfer belt. Image forming device. 3. The image forming apparatus according to claim 2, wherein said fixing release agent removing means is an absorbing member for absorbing the fixing release agent attached to the secondary transfer belt. 4. The image forming apparatus according to claim 2, wherein said fixing release agent removing means is a scraping means for scraping off the fixing release agent attached to the secondary transfer belt.