JP2001312148A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device where a cleaning function and a destaticizing function for an intermediate transfer belt are secured, furthermore, a cleaning function for a driving roller is also provided and where image quality deterioration can be prevented with a simple constitution. SOLUTION: In the device, a destaticizing roller 21 is installed so that it is abutted to a back surface of the intermediate transfer belt 11 to be able to be rotated in a forward direction and brought into contact with the driving roller 19. Rotating speed of the intermediate transfer belt 11 is increased to 160 mm/sec that is faster than 120 mm/sec which is processing speed when forming an image and a charge of -3 kV is impressed to the destaticizing roller 21 simultaneously.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic or electrostatic recording type image forming apparatus such as a copying machine or a printer.

[0002]

2. Description of the Related Art Conventionally, various types of image forming apparatuses have been developed. In an image forming apparatus such as a copying machine or a laser beam printer, a toner image is formed on the surface of a photosensitive drum as an image carrier. In the method of transferring the toner image onto a transfer material such as paper, the residual toner remaining on the surface of the photosensitive drum after the transfer of the toner image is removed by a cleaning device.

On the other hand, in a color image forming apparatus of a type having an intermediate transfer member for improving the selectivity of a transfer material, untransferred toner remaining on the intermediate transfer member is removed by a cleaning device for the intermediate transfer member. I have.

The above-described cleaning device has a cleaning blade in which an elastic member such as urethane rubber is formed in a plate shape, and the edge of the cleaning blade is brought into contact with the surface of the photosensitive drum or the surface of the intermediate transfer member at a predetermined pressure. In this way, the residual toner adhering to the surface of the photosensitive drum or the surface of the intermediate transfer member is scraped off.

A cleaning device using this cleaning blade has a relatively simple structure, is small in size, has an advantage in terms of cost, and has an advantage of excellent toner removal performance. I have.

In a high-quality color image forming apparatus that requires high-speed and high-quality images, a simpler and lighter pressure type than a cleaning blade is used in order to minimize vibration and damage to the intermediate transfer member. Some models have introduced brush cleaners and cleaning-less types.

[0007] On the other hand, in recent years, the pursuit of high-quality images has become remarkable, and it has been inevitable that the particle size of toner as a developer is reduced. The reduction in the particle size of the toner causes the toner to scatter inside the machine more than ever, due to the speeding up of the image forming apparatus and the sliding operation by the cleaning member. Up to now, improvements in airflow in the apparatus and electrostatic aggregation by increasing the amount of electrostatic charge of toner have been common solutions.

[0008] However, there is a limit to the improvement of the airflow in the machine. That is, if the suction force is increased, the toner scattered from the developing device and the waste toner from the waste toner box in the cleaning device are sucked out, and the photosensitive drum and the intermediate transfer member, particularly the belt-like intermediate transfer member are sucked. (The non-image forming material carrying surface: inside) is contaminated, and there is a problem that image defects due to poor transfer electrification are likely to occur. In particular, contamination by scattered toner in the belt system also contaminates the belt driving roller, which is a belt driving unit, and accumulates and fuses on the surface layer of the belt driving roller, which hinders rotation of the belt itself. Specifically, the slip, skew, wrinkles, etc. of the belt.

[0009]

Further, with the demand for higher speed, recently, a belt type intermediate transfer member has been frequently used, and the inner surface of the belt due to scattered toner (rear surface: non-image forming material carrying surface). Conventionally, the problem of image contamination and the occurrence of image defects due to the contamination have been generally dealt with by disposing a belt back surface cleaning member.

However, in order to reduce the damage to the belt itself, the belt back surface cleaning member cannot expect a high contact pressure to increase the removal force, and the belt has a poor contact with the unevenness of the belt itself. However, there remains a problem that the cleaning ability of the back surface of the belt cannot be made so strong.

On the other hand, recently, a cleaning device has been newly arranged in order to positively clean the back surface (inner surface) of the intermediate transfer member. However, the cleaning device itself is expensive and complicated, and maintenance is required. The variability and difficulty of the cleaning setting itself are common, and the load on the belt drive is increased, and the displacement (color misregistration) of the pixels is caused due to the deformation of the belt during the belt conveyance, such as the deflection and the displacement of the belt. The problem of hindering image quality formation has also been raised.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a simple structure having a cleaning function for an intermediate transfer member, which secures a cleaning property for the intermediate transfer member, and at the same time, ensures a neutralization property of the intermediate transfer member. An object of the present invention is to provide an image forming apparatus capable of preventing deterioration.

[0013]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
An image bearing member having a movable surface on which a toner image is formed, an intermediate transfer member onto which the toner image is transferred and further transferred to a transfer material, and a charge eliminator for contacting the intermediate transfer member to remove charge And a driving speed of the intermediate transfer member and a driving speed of the charge removing unit have a relative speed difference.

According to one embodiment of the present invention, there is provided an intermediate transfer member driving unit for driving the intermediate transfer member, and the charge removing unit is in contact with the intermediate transfer member driving unit.

According to another embodiment of the present invention, when the driving speed of the intermediate transfer member and the driving speed of the charge eliminating means have a relative speed difference, the driving of the intermediate transfer member and the charge eliminating means is performed. At least one of the speeds is higher than each drive speed when transferring the toner image formed on the image carrier to the transfer material.

According to another embodiment of the present invention, the intermediate transfer member and the charge eliminating means are arranged so that the predetermined distance between the drive speed of the intermediate transfer member and the drive speed of the charge eliminating means is a predetermined value. Has a speed difference.

According to another embodiment of the present invention, the driving of the intermediate transfer member is performed while there is a relative speed difference between the driving speed of the intermediate transfer member and the driving speed of the charge removing means. Has been stopped.

According to another embodiment of the present invention, when the driving speed of the intermediate transfer member and the driving speed of the discharging unit have a relative speed, the driving speed of the discharging unit is The transfer speed is higher than the drive speed of the charge removing unit when the toner image formed on the image carrier is transferred to the transfer material.

According to another embodiment of the present invention, when there is a relative speed difference between the driving speed of the intermediate transfer member and the driving speed of the charge removing means, the drive of the charge removing means is stopped. Have been.

According to another embodiment of the present invention, the driving speed of the intermediate transfer member when there is a relative speed difference between the driving speed of the intermediate transfer member and the driving speed of the static elimination means, The transfer speed is higher than the drive speed of the intermediate transfer member when transferring the toner image formed on the image carrier to the transfer material.

According to another embodiment of the present invention, a period in which there is a relative speed difference between the driving speed of the intermediate transfer member and the driving speed of the charge removing means is a latent image on the image carrier. , And the period during which the toner image is transferred to the transfer material.

According to another embodiment of the present invention, the intermediate transfer member is an endless belt.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

Embodiment 1 A first embodiment of the present invention will be described with reference to FIGS.

The image forming apparatus of the present embodiment shown in FIG. 1 is a four-color full-color copying machine,
Inside the “apparatus main body”) 100, four image forming units, that is, a first image forming unit 4a in order from the upstream side to the downstream side along the rotational conveyance direction A of the photosensitive drum 1 as an image carrier. , Second image forming unit 4b, third image forming unit 4
c, and a fourth image forming section 4d.

The photosensitive drum 1 is provided with a drum type electrophotographic photosensitive member, and a photosensitive layer having a carrier generation layer (CGL) and a carrier transport layer (CTL) is formed on a surface of a cylindrical aluminum substrate. Rz having a JIS surface roughness (B0601) coated so as to have a thickness of 40 μm
(Average of 10 points) having an initial state of 2 μm or less is used.

The photosensitive drum 1 is rotatably supported by the apparatus main body 100, and is driven to rotate by a driving means (not shown) at a process speed of 120 mm / sec in the direction of arrow A. The outer diameter of the photosensitive drum 1 of this embodiment is 80 mm.

Above the photosensitive drum 1, a primary charger 2 is disposed in close proximity, and the surface of the photosensitive drum 1 is uniformly charged by the primary charger 2. The charged surface of the photosensitive drum 1 is exposed to an optical system (latent image forming means) disposed above the first image forming unit 4a to form an electrostatic latent image. Receive exposure.

Subsequently, the toner in the developer is attached to the electrostatic latent image by the first to fourth image forming units 4a to 4d, and is developed as a toner image. As a developer, a two-component developer mainly composed of a silicon-based toner and a ferrite-based carrier is used.

This toner image has a photosensitive drum 1 and a linear pressure (a value obtained by dividing the member pressure applied in the thrust direction by the length in the drum thrust direction) of 5 gr / c.
m (= 0.49 N / m), when the photosensitive drum 1 and the intermediate transfer belt 11, which is an intermediate transfer body rotating in the forward direction, arrive at the transfer portion T 1 where the photosensitive drum 1 comes into contact with and comes into contact with the photosensitive drum 1. The surface of the photosensitive drum 1 is electrostatically attracted to the intermediate transfer belt 11 and transferred by the action of the electric field formed by the transfer belt 11.

The intermediate transfer belt 11 is a primary transfer bias roller 8 facing the photosensitive drum 1, a support roller 9, an opposing roller 10 opposing the secondary transfer bias roller 12, and an intermediate transfer member driving means opposing the cleaning blade 16. It is wrapped around a certain drive roller 19 and can be transported and rotated in the direction of arrow B.

The intermediate transfer belt 11 uses EPDM rubber, chloroprene rubber, epichlorohydrin rubber, silicon rubber, NBR rubber, or a modified rubber thereof as a base layer material.

As the material of the surface layer, a material containing a fluororesin (for example, a material containing PVDF, PTFE, tetrafluoroethylene, etc.) is used from the viewpoint of high releasability and low friction coefficient.

FIG. 2 is a partially enlarged sectional view of the intermediate transfer belt 11 shown in FIG. In this embodiment, the base layer 11a of the intermediate transfer belt 11 is
Using PDM rubber, the base layer 11a was coated with a coating material in which a PVDM resin was dispersed to form a surface layer 11b.

As shown in FIG. 1, a charge eliminating roller 21 serving as a charge eliminating means is disposed so as to abut on the back surface of the intermediate transfer belt 11 and contact the drive roller 19. A roller-like grounding member 22 facing the static elimination roller is arranged so as to contact the surface of the transfer belt 11. Here, when the contact pressure of the discharging roller 21 against the intermediate transfer belt 11 during image formation is P1 and the contact pressure during non-image formation is P2, P1 = P2> 0 is satisfied.

The base layer constituting the charge removing roller 21 includes
EPDM rubber was used, and carbon was dispersed and added as a conductive filler to the base layer to form a surface layer that was in contact with the intermediate transfer belt 11. The electric resistance is 1.0 × 10 ⁵
１．０1.0 × 10 ⁶ Ω or less.

The roller surface layer of the grounding member 22 facing the static elimination roller was made of the same material, and the charge by static elimination was set to earth. Both rollers have an outer diameter of 16 mm and a thrust length of 306 mm, and the contact pressure of the neutralizing roller 21 with the intermediate transfer belt 11 is 400 gf (= 3.92 N) in total pressure.
And

A drive roller 19 connected to a drive source (not shown) for driving the intermediate transfer belt 11 has an electric resistance 10.
The core material is Al material of Ω · cm or less, and the surface layer is BIE
(Butadiene isoprene EPDM) material was used and had an electric resistance of 10 ⁵ to 10 ⁶ Ωcm or less. Note that a rubber hardness of 50 ° or more according to JIS-A was used. The core was grounded. The driving roller 1
9 is 5 gr / cm (=
0.49 N / m).

Further, a cleaning blade 16 as cleaning means for the intermediate transfer belt 11 was brought into contact with the drive roller 19 in the forward direction with respect to the transport rotation direction of the intermediate transfer belt 11. Note that polyurethane rubber was used as a material of the cleaning blade 16.

After the transfer of the toner image, the residual toner remaining on the surface of the photosensitive drum 1 that has not been transferred to the transfer material P is scraped off by the cleaning blade 17 of the cleaning device 5 and is removed. As a result, the residual charge is removed, and the resultant is provided for the next image formation.

As described above, the first image forming section 4a
The photosensitive drum 1 on which the first toner image is formed is conveyed and rotated, and the second image forming unit 4b and the third image forming unit 4
c, and the toner image is multiply developed by the fourth image forming unit 4d in the same manner as in the first image forming unit 4a. However, the first to fourth image forming units 4a to 4d
Are different from each other in the toner color of the toner image to be developed.

The four color toner images are collectively transferred onto the intermediate transfer belt 11 by the primary transfer bias roller 8 at the primary transfer portion T1, and further conveyed to the secondary transfer portion T2. On the other hand, the transfer material P is conveyed to the secondary transfer portion T2 so as to be synchronized with the toner image on the intermediate transfer belt 11, and the toner image is collectively transferred onto the transfer material P by the secondary transfer bias roller 2. You. The transfer material P is conveyed to the fixing unit 14 via the transfer material conveying path 18, and is subjected to heat and pressure by the fixing unit 14 so that the toner image is fixed to obtain a copy image.

At this time, the fixing roller 14 of the fixing means 14
For example, silicone oil is applied as a release agent to the surface of the fixing roller 14a to prevent the toner on the transfer material P from adhering to the surface of the fixing roller 14a.

The transfer material P having a toner image formed on the front surface (first surface) is discharged outside the apparatus after passing over a flapper (not shown) when the image is formed on one side. On the other hand, when the image formation is performed on both sides, the transfer material P having the toner image fixed on the first surface is guided to the lower re-feeding unit without being discharged out of the apparatus by switching the flapper.

Then, after the toner image is transferred to the second surface again after being turned upside down by a reversing device (not shown), the toner image is fixed by the fixing means 14 and passes over the flapper to the outside of the machine. The sheet is discharged, and the image formation is completed.

Thereafter, the photosensitive drum 1 performs a three-rotation idle rotation operation (post-rotation), and at the same time, the intermediate transfer belt 11 rotationally contacted with the photosensitive drum 1 in the forward direction also performs a predetermined rotation operation.

Here, the characteristic portion of the present invention will be described with reference to FIG.
This will be described with reference to FIG. FIG. 3 shows an operation sequence of the present embodiment.

The rotation speed (process speed: P.S.) of the photosensitive drum 1, the intermediate transfer belt 11, and the charge removing roller 21 at the time of image formation is 120 mm / sec. Static elimination roller 21
And the rotational speed of the intermediate transfer belt 11 is changed from 120 mm / sec to 160 mm.
/ Sec.

Further, a charge of -3 kV was applied to the discharging roller 21 during the idling operation (post-rotation). The charge removing roller 21 is in contact with the intermediate transfer belt 11 in a forward rotation.

Due to the relative speed difference generated in this manner, a frictional force is generated between the intermediate transfer belt 1 and the charge eliminating roller 21, and an operation occurs in which the intermediate transfer belt 11 and the charge eliminating roller 21 mutually grind each other. It is possible to remove foreign matters such as residual toner, belt shavings, dust and the like that accumulate on the intermediate transfer belt 11 and the surface of the charge removing roller 21 due to the accumulation of the number of image formation, thereby achieving high-quality and stable image formation. We were able to.

Incidentally, in this embodiment, the contact pressure of the cleaning blade 16 contacting the intermediate transfer belt 11 is set to 200 gr / cm (= 19.6 N / m). %, As a result of an endurance test in an environmental test chamber, it was found that, at 100,000 sheets in the past, adhesion rubbing and toner fusing
It was confirmed that the toner image was stuck on the surface of the intermediate transfer member drive roller 19 and the toner was stuck, but still maintained a good state even after 150,000 sheets had passed. In this endurance experiment,
In the endurance mode, evaluation was performed by continuously copying an image having an image ratio of about 25% in an A4 size landscape mode.

Embodiment 2 Next, a second embodiment of the present invention will be described with reference to FIG.

In the present embodiment, the sequence as in the first embodiment at the time of non-image formation is avoided from being constantly executed.
At an interval of a certain number of copies, high image quality and high stability are achieved by utilizing an increase in polishing ability using a relative speed difference, which is the main feature of the first embodiment.

The operation sequence of this embodiment will be described with reference to FIG.

As described above, when the operation sequence is performed at an interval of a certain number of copies, the number of times of polishing is naturally smaller than that of the first embodiment, and this reduction must be covered by another means. Therefore, in the present embodiment, the rotation speed of the intermediate transfer belt 11 during non-image formation, that is, during post-rotation, is set to 120 mm / sec during image formation.
c, to 200 mm / sec, and at the same time, the rotation speed of the charge removing roller 21 is increased from 120 mm / sec to 150 mm.
mm / sec, and the number of times of polishing between the intermediate transfer belt 11 and the charge removing roller 21 is increased.

The configuration of this embodiment is particularly effective in an image forming apparatus having no double-sided continuous copy version.
In the executed sequence, the sequence of the present embodiment is input at a rate of once for every 5,000 copies, and the intermediate transfer belt 11 and the discharging roller 21 An attempt was made to achieve a longer life of the drive roller 19 and a longer life of the cleaning blade 16.

Incidentally, in the past, at 32 ° C. and 75% in a high-temperature and high-humidity environment, image blurring and toner fusion streaks and spots due to poor transfer electrification occurred on 100,000 sheets or less. In the examples, it was confirmed that the cleaning property was maintained up to 200,000 sheets by single-sided A4 size sideways feeding and one intermittent copy.

Embodiment 3 Next, a third embodiment of the present invention will be described with reference to FIG.

The purpose of this embodiment is the same as that of the second embodiment. However, the present embodiment is particularly effective for an image forming apparatus using a toner on the intermediate transfer belt 11 which is very easily fused. is there.

As an experimental evaluation of this embodiment, an external additive in the toner used in each of the first and second embodiments (particularly, as a cleaning aid, was added to serve as a lubricant and an abrasive). 2 strontium titanate
In the system in which the amount was doubled, a strong fusion substance (commonly called filming) was generated in a portion corresponding to a white background portion of the image forming portion as the number of copies was accumulated. The number of generated sheets was 50,000 or less in a high-temperature and high-humidity environment at 32 ° C. and 75%.

Therefore, as shown in the operation sequence of FIG. 5, in order to make the polishing property stronger than that of the second embodiment, the non-image formation before and after the image formation is performed.
The discharging roller 21 is stopped, and only the intermediate transfer belt 11 is rotated at a process speed of 120 mm / sec.
In addition, the polishing force of the static elimination roller to the intermediate transfer member as described in the second embodiment was generated, and the filming firmly adhered to the intermediate transfer drum could be removed. At this time, one side, A
It was a 4-size horizontal feed and one intermittent copy.

In this embodiment, in consideration of avoiding damage to the intermediate transfer belt 11 and the charge removing roller 21,
The sequence was activated every 5,000 sheets.

Embodiment 4 Next, a fourth embodiment of the present invention will be described with reference to FIGS.

In this embodiment, the process speed is 160 mm /
sec. The photosensitive drum 1 having an outer diameter of 180 mm was used in response to the increase in speed.

In this embodiment, the intermediate transfer belt 11 at the time of non-image formation, that is, at the time of post-rotation, is different from the process speed (V1 = 160 mm / sec) at the time of image formation.
Is set to V2 = 180 mm / sec, and the rotation of the charge removing roller 21 is stopped.

As an experimental evaluation, an evaluation mode similar to that of the third embodiment was performed. Conventionally, filming occurred at 50,000 copies. By doing so, it was possible to remove filming more firmly attached than in the third embodiment.

By the way, in the sequence of this embodiment, the intermediate transfer belt replacement target of 1.2 million sheets could be achieved by inserting every 5,000 sheets. At this time, it was A4 size horizontal feed and one intermittent copy.

As a modified example of the present embodiment, as shown in FIG.
Is stopped and the rotational speed of the charge removing roller 21 is set to V4 = 180 mm / sec, which is higher than the process speed (V3 = 160 mm / sec) at the time of image formation. . The used image had a duty ratio of 25%.

During non-image formation, the intermediate transfer belt 11
V3> V4, where V3 is the transport rotation speed of the discharging roller 21 and V4 is the transport rotation speed at the time of image formation during the period when the rotation is stopped.

[0070]

As is apparent from the above description, according to the image forming apparatus of the present invention, since the driving speed of the intermediate transfer member and the driving speed of the charge removing means have a relative speed difference, the cleaning of the intermediate transfer member is performed. , And at the same time, the charge elimination property of the intermediate transfer body is ensured. Furthermore, the charge elimination means comes into contact with the intermediate transfer body drive means, which also has the cleaning property of the intermediate transfer body drive means. Can be prevented, and a high-quality image can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an embodiment of a color image forming apparatus according to the present invention.

FIG. 2 is a partial cross-sectional view illustrating an embodiment of an intermediate transfer belt.

FIG. 3 is a diagram showing one embodiment of an operation sequence according to the present invention.

FIG. 4 is a diagram showing another embodiment of the operation sequence according to the present invention.

FIG. 5 is a diagram showing another embodiment of the operation sequence according to the present invention.

FIG. 6 is a diagram showing another embodiment of the operation sequence according to the present invention.

FIG. 7 is a diagram showing a modification of the operation sequence shown in FIG.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 photosensitive drum (image carrier) 11 intermediate transfer belt (intermediate transfer member / endless belt member) 19 drive roller (intermediate transfer member driving means) 21 static elimination roller (static elimination means) P sheet material (transfer material)

Claims (10)

[Claims] An image bearing member having a movable surface on which a toner image is formed, an intermediate transfer member onto which the toner image is transferred and further transferred to a transfer material, and an image transfer member that contacts the intermediate transfer member. An image forming apparatus comprising: a charge removing unit configured to contact and remove a charge; wherein the driving speed of the intermediate transfer member and the drive speed of the charge removing unit have a relative speed difference. 2. The image forming apparatus according to claim 1, further comprising: an intermediate transfer member driving unit that drives the intermediate transfer member, wherein the charge removing unit contacts the intermediate transfer member driving unit. 3. When the driving speed of the intermediate transfer body and the driving speed of the charge removing means have a relative speed difference, at least one of the driving speeds of the intermediate transfer body and the charge removing means is the same as the above. 3. The image forming apparatus according to claim 1, wherein the driving speed is higher than the respective driving speeds when the toner image formed on the image carrier is transferred to the transfer material. 4. The method according to claim 1, wherein the intermediate transfer body and the charge removing unit have a predetermined speed difference between a drive speed of the intermediate transfer body and a drive speed of the charge removal unit at a predetermined time interval. The image forming apparatus according to claim 1, 2 or 3. 5. The driving of the intermediate transfer member is stopped while there is a relative speed difference between the driving speed of the intermediate transfer member and the driving speed of the charge removing means. The image forming apparatus according to claim 1. 6. The toner image formed on the image bearing member, wherein the driving speed of the discharging unit when the driving speed of the intermediate transfer member and the driving speed of the discharging unit have a relative speed. 6. The image forming apparatus according to claim 5, wherein a driving speed of the charge removing unit is higher than a driving speed when transferring the image to the transfer material. 7. The method according to claim 1, wherein when there is a relative speed difference between the drive speed of the intermediate transfer member and the drive speed of the charge removing unit, the drive of the charge removing unit is stopped. Item 3. The image forming apparatus according to item 1 or 2. 8. The driving speed of the intermediate transfer member when the driving speed of the intermediate transfer member has a relative speed difference between the driving speed of the intermediate transfer member and the driving speed of the charge removing means is formed on the image carrier. 8. The image forming apparatus according to claim 7, wherein the driving speed of the intermediate transfer body is higher than a driving speed of transferring the toner image onto the transfer material.
Image forming apparatus. 9. A period in which there is a relative speed difference between the driving speed of the intermediate transfer member and the driving speed of the charge removing means,
9. The image forming apparatus according to claim 1, wherein the period is a period other than a period during which a latent image is formed on the image carrier and a period during which the toner image is transferred to the transfer material. . 10. An image forming apparatus according to claim 1, wherein said intermediate transfer member is an endless belt.