JPH11316532A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent faulty cleaning from occurring even when a reference pattern for controlling toner density is transferred to a transfer body. SOLUTION: This device is provided with a speed control part 900 capable of varying the circumferential speed of an intermediate transfer belt 501 so that the upper side of the belt 501 may be perfectly cleaned even when the reference pattern for controlling the toner density is always developed and transferred on the same place, and the circumferential speeds of a photoreceptor 10 and the belt 501 are controlled to be varied between when the reference pattern for controlling the toner density exists at a primary transfer position and when the ordinary toner image exists at a transfer position. The circumferential speeds are controlled to be lower when the reference pattern for controlling the toner density exists at the transfer position of the belt 501 than when the ordinary toner image exists at the transfer position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer and a facsimile, and more particularly to an image forming apparatus for transferring a toner image formed on an image carrier to a transfer body by a transfer means.

[0002]

2. Description of the Related Art As an image forming apparatus of this type, an image carrier driven so that the surface moves in one direction, a toner image forming means for forming a toner image on the image carrier, an image carrier 2. Description of the Related Art There is known an image forming apparatus that includes a transfer unit that transfers a toner image on a body to a transfer body that moves in the same direction as an image carrier.
In this image forming apparatus, a reference pattern for toner density control for controlling toner density on an image carrier is developed at the time of installation of the apparatus (for example, installation of the apparatus upon delivery, etc.) or at the time of power-on accompanying use of the apparatus. Some have an operating mode for controlling the image processing conditions thereby.

[0003]

In the conventional image forming apparatus as described above, the toner density control reference pattern is developed on the image carrier because of the toner supply condition of the developing device and the charging condition of the charging device. This is for controlling the image processing conditions such as. Therefore, there is a possibility that the above-described reference pattern for toner density control is transferred to the transfer body in addition to the desired toner image. Then, the toner density control reference pattern transferred to the transfer body in this manner causes a cleaning failure when entering a cleaning process.

For example, a toner image formed on a photosensitive drum as an image carrier is transferred to an intermediate transfer belt as a transfer body at a primary transfer unit, and the toner image on the intermediate transfer belt is transferred at a secondary transfer unit. In an image forming apparatus configured to transfer to a paper, it is not necessary to transfer a toner image other than a normal toner image to a transfer paper. Therefore, the toner density control reference pattern transferred onto the intermediate transfer belt is completely removed. Needs cleaning.

Further, in order to control the toner density, there is a type in which the current toner density on the photoreceptor is detected by using a reflection type sensor or the like at a certain position in the axial direction on the photoreceptor. It is necessary to always create a reference pattern for controlling the toner density at the position where is read. For this reason,
The intermediate transfer belt has a toner image (pattern image) more than necessary, and it has to be always cleaned.

That is, in the above-described conventional image forming apparatus, when cleaning the intermediate transfer belt,
At the position where the toner density control reference pattern is transferred, a state in which the toner cannot be completely cleaned due to a large amount of toner adhesion occurs, and eventually the cleaning becomes defective, and the toner density control reference pattern remains on the intermediate transfer belt. In the next secondary transfer step, the poor cleaning image was transferred to the transfer paper.

In order to solve the above-mentioned conventional problems, the present invention provides an image forming apparatus which does not cause a cleaning failure even when a toner density control reference pattern other than a desired toner image is transferred onto an intermediate transfer belt. The purpose is to provide.

[0008]

According to a first aspect of the present invention, there is provided an image forming apparatus comprising: an image carrier which is driven so that a surface moves in one direction; An image forming apparatus includes: a toner image forming unit that forms a toner image on the image carrier; and a transfer unit that transfers the toner image on the image carrier to a transfer body that moves in the same direction as the image carrier. And a speed controller for variably controlling a peripheral speed between the image carrier and the transfer body based on an image pattern formed on the image carrier, in a driving unit of the transfer body.

According to a second aspect of the present invention, in order to achieve the above object, the speed control means controls a toner density control reference pattern required for controlling a toner density formed on the image carrier. Is controlled so that the peripheral speed between the image carrier and the transfer member is changed between when the transfer unit is at the transfer position and when the normal toner image is at the transfer position.

According to a third aspect of the present invention, in order to achieve the above object, the transfer body is formed of a belt material, and the speed control means switches a peripheral speed between the image carrier and the transfer body. In this case, the peripheral speed is controlled to be lower when the toner density control reference pattern is at the transfer position of the transfer unit than when a normal toner image is at the transfer position.

According to a fourth aspect of the present invention, in order to achieve the above object, the transfer means is constituted by using a charge applying means for applying a transfer charge to the transfer body, and the speed control means is provided by the toner When the density control reference pattern is at the transfer position of the transfer unit, control is performed such that the normal toner image is slower than when it is at the transfer position, and no charge is applied from the charge applying unit or the toner is It is characterized in that it is set so as to give charges of the same polarity.

The present invention is also applicable to a case where the image carrier is a photosensitive member and the transfer body is an intermediate transfer body, and a case where the image carrier is an intermediate transfer body and the transfer body is a transfer material such as paper. it can.

[0013]

Embodiments and examples of the present invention will be described below with reference to the drawings. Hereinafter, an embodiment will be described in which the present invention is suitable for an electrophotographic color copying machine (hereinafter, referred to as a color copying machine) as an image forming apparatus, but the present invention is not limited to this. Further, the present invention is not limited to the following embodiments and examples. For example, the present invention can be applied to a case where a belt-shaped photoconductor is used and a case where an intermediate transfer body having another shape is used.

FIG. 1 is a schematic configuration diagram of an image forming unit which is a main part of a color copying machine according to an embodiment of the present invention. In the figure, reference numeral 100 denotes a photoconductor, 200 denotes a charging charger, 300 denotes a photoconductor cleaning device, 400 denotes a developing device, 500 denotes an intermediate transfer unit, 600 denotes a secondary transfer roller, 700 denotes a fixing roller, and 900 denotes a speed control unit. The color copying machine includes an image forming unit shown in FIG. 1, a color image reading unit (hereinafter, referred to as a scanner) (not shown), a paper feeding unit, a control unit, and the like, and performs image processing on image data read by the scanner. Black (hereinafter BK), C
yan (same C), Magenta (same M), Yellow
The w (same Y) color image data is sent to the photoconductor 100 as image data.

In the image forming section shown in FIG.
00, the photoconductor 100 is charged, the image data is exposed to form a latent image on the photoconductor 100, and Bk, C, M,
The Y image data is transferred to the Bk developing device 401
The developing is performed by the developing unit 402, the M developing unit 403, and the Y developing unit 404.

The intermediate transfer unit 500 includes an intermediate transfer belt 501, an earth roller 502, a primary transfer bias roller 507 as a primary transfer charge applying means, a belt driving roller 508 also serving as a cleaning opposite roller, a belt tension roller 509, Secondary transfer facing roller 51
0. Each roller is formed of a conductive material,
Primary transfer bias roller 507 and belt drive roller 50
Each roller other than 8 is grounded. The primary transfer bias roller 507 is supplied with a transfer bias controlled by a primary transfer power source 801 controlled by a constant current or a constant voltage to a current or voltage of a predetermined magnitude according to the number of superimposed toner images. I have. The intermediate transfer belt 501 is driven to rotate in a direction indicated by an arrow in the figure by a belt drive roller 508 that is driven to rotate by a drive motor (not shown).

A neutralizing brush 513 is in contact with the inner peripheral surface of the intermediate transfer belt 501 at a primary transfer nip formed by the photosensitive drum 100, the primary transfer bias roller 507 and the ground roller 502. .

In the figure, reference numeral 504 denotes a cleaning blade, which comes into contact with the intermediate transfer belt 501, which is wrapped around a belt driving roller 508 also serving as a cleaning opposing roller, in a trailing manner. The intermediate transfer belt 50 is
1 is performing a contact / separation operation. The ON / OFF control of the belt cleaning blade 504 is performed as follows. For example, when forming a full-color image, after the completion of the secondary transfer, the belt cleaning blade 504 is brought into contact at least until the intermediate transfer belt 501 makes one rotation. When a monochrome image is formed, after the primary transfer is completed, the belt cleaning blade 504 is brought into contact with at least until the intermediate transfer belt 501 makes one rotation. In the drawing, reference numeral 505 denotes a lubricant application brush, and 506 denotes a lubricant.

The intermediate transfer belt 501 has a thickness of 150 μm.
And a material such as PVDF (polyvinylidene fluoride) having a volume resistivity of 10 ⁸ to 10 ¹³ Ωcm (JIS K69).
(Measurement method 100V described in 11, 10 seconds value)
The surface resistivity is 10 ⁸ to 10 ¹⁴ Ω / port (measured by Yuka Denshi's Hirester IP resistance measuring instrument at 500 V, 10 seconds value). Further, as shown in FIG. 2, the nip width Wn of the primary transfer portion is set to 10 mm, and the distance L from the downstream side of the nip portion in the belt moving direction to the contact position of the belt neutralizing brush 513 is set to 7 mm. . Belt neutralization brush 5
As 13, a conductive material in which carbon-containing resin fibers are implanted is used.

In the image forming apparatus having such a configuration, as described above, in order to control image processing conditions such as toner supply conditions of the developing device and charging conditions of the charging device, the toner density on the image carrier is controlled. The control reference pattern is developed. Therefore, there is a possibility that a reference pattern for toner density control is transferred to the intermediate transfer belt 501 in addition to a desired toner image. The reference pattern causes a cleaning failure in the next cleaning step. More specifically, since the toner density control reference pattern is developed and transferred to the same location in the axial direction when the apparatus is powered on, the cleaning load is always applied to the same location on the cleaning blade 504. More than the part of
As a result, as shown in FIGS. 3 and 4, toner adheres to only a certain portion of the cleaning blade 504 on the back side (portion indicated by T in FIGS. 3 and 4), and the toner gradually accumulates. Eventually, the cleaning performance is locally reduced, resulting in poor cleaning. Further, when the secondary transfer is performed in a state where the cleaning failure has occurred,
An abnormal image on which the toner density control reference pattern as shown in FIG. 5 is transferred.

Therefore, even if the toner density control reference pattern other than the desired toner image is always developed and transferred to the same place, the driving unit of the intermediate transfer belt 501 can be completely cleaned on the intermediate transfer belt 501. In addition, a speed control unit 90 as a speed control means capable of changing the peripheral speed
0 is provided. The speed control unit 900 controls the photoconductor 10
When the toner density control reference pattern required to control the toner density formed on the toner image 0 is at the primary transfer position and when the normal toner image is at the transfer position, the photosensitive member 1
00 and the peripheral speed of the intermediate transfer belt 501 are variably controlled.
The peripheral speed at the time of switching by the speed control unit 900 is controlled so that when the toner density control reference pattern is at the transfer position of the intermediate transfer belt 501, the peripheral speed is lower than when the normal toner image is at the transfer position. I do. As an example, when the toner density control reference pattern is at the primary transfer position, compared to when the desired toner image is at the primary transfer position,
When the peripheral speed was reduced to about half, the cleaning blade 50
4, good cleaning performance was obtained.

Further, when a desired toner image is at the primary transfer position, a primary transfer power source 801 is connected to the bias roller 507.
When a constant voltage of 1200 V is applied and the toner density control reference pattern is at the primary transfer position, the voltage is set to 0 V (no charge is applied), or a voltage of the same polarity as the toner is applied to apply the toner density control reference pattern. The pattern is prevented from being transferred to the intermediate transfer belt 501. As an example,
When negative polarity toner is used and the toner density control reference pattern is at the primary transfer position, the bias roller 5
When a voltage of −100 V was applied to the sheet No. 07, a very small amount of the toner density control reference pattern was transferred to the intermediate transfer belt 501. At the same time, when the toner density control reference pattern is at the primary transfer position, the intermediate transfer belt 50
When the peripheral speed of No. 1 was reduced to about half, a good image was obtained without occurrence of belt cleaning failure.

The reference pattern for controlling the toner density is constituted by a continuous pattern image having a gradation as shown in FIG. 6, and is developed at the axial center of the photosensitive member 100. Further, when the primary transfer bias applied to the bias roller 507 was shaken and the experiment was performed,
It was found that a good image could be obtained in the range of V to -300 V without occurrence of belt cleaning failure. Then, when a bias of -300 V or more is applied, a negative potential is generated on the intermediate transfer belt 501, and the next desired toner image comes to the primary transfer position in a state where the neutralization of the intermediate transfer belt 501 cannot be completely removed. Therefore, it has been found that the transfer efficiency of the next desired toner image is reduced.

[0024]

According to the image forming apparatus of the first aspect,
The provision of the speed control means for controlling the peripheral speeds of the image carrier and the transfer body according to the image pattern formed on the image carrier has an effect that good image quality without cleaning failure can be obtained.

According to the image forming apparatus of the present invention, the timing at which the peripheral speed is switched by the speed control means is defined by the image pattern, so that the cleaning can be effectively performed in addition to the common effect. It has the effect of becoming.

According to the image forming apparatus of the third aspect, the peripheral speed when the peripheral speed is switched by the speed control means is:
When the toner density control reference pattern required to control the toner density formed on the image carrier is located at the transfer position of the primary transfer means, it is easier than when the desired toner image is normally located at the transfer position. By controlling to be late, there is an effect that the cleaning property can be easily improved in addition to the above common effects.

According to the image forming apparatus of the fourth aspect, by using the same transfer applying means as the control means for switching the transfer conditions of the transfer means, in addition to the above-mentioned common effects, it is possible to ensure the cost at a low cost. Therefore, it is possible to prevent the transfer of the toner density control reference pattern, and to obtain an excellent image quality that does not completely cause cleaning failure by easy speed control.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming unit that is a main part of a color copying machine according to an embodiment.

FIG. 2 is an enlarged view of a primary transfer section of the color copying machine of FIG.

FIG. 3 is a side view illustrating occurrence of a defect in belt cleaning.

FIG. 4 is a cross-sectional view in which the back side of the cleaning blade is observed.

FIG. 5 is a plan view illustrating an abnormal image on transfer paper when a cleaning failure occurs.

FIG. 6 is a conceptual diagram showing a toner density control reference pattern.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 photoconductor 200 charging charger 300 photoconductor cleaning device 400 developing device 401 Bk developing device 402 C developing device 403 M developing device 404 Y developing device 500 intermediate transfer unit 501 intermediate transfer belt 502 ground roller 504 belt cleaning blade 505 lubricant applying brush 506 Lubricant 507 Bias roller 508 Belt drive roller 509 Belt tension roller 510 Secondary transfer opposing roller 513 Belt neutralizing brush 600 Secondary transfer roller 700 Fixing roller 801 Primary transfer power supply 802 Secondary transfer power supply 900 Speed control section T Toner adhesion section

Claims (4)

[Claims] An image carrier that is driven so that a surface moves in one direction; a toner image forming unit that forms a toner image on the image carrier; and a toner image formed on the image carrier. An image forming apparatus comprising: a transfer unit configured to transfer the image to a transfer member that moves in the same direction as the support. An image forming apparatus comprising a speed control unit for variably controlling a peripheral speed with a body. 2. A method according to claim 1, wherein the speed control means controls a toner density formed on the image carrier by controlling a toner density control reference pattern at a transfer position of the transfer means. 2. The image forming apparatus according to claim 1, wherein the control is performed such that the peripheral speed between the image carrier and the transfer body is changed between when the camera is at the transfer position. 3. The transfer member is formed of a belt material, and the speed control means determines a peripheral speed when switching a peripheral speed between the image carrier and the transfer member. 3. The image forming apparatus according to claim 1, wherein when the toner image is located at the transfer position, the control is performed so as to be slower than when the normal toner image is located at the transfer position. 4. The image forming apparatus according to claim 1, wherein the transfer unit includes a charge applying unit that applies a transfer charge to the transfer body, and the speed control unit determines when the toner density control reference pattern is at a transfer position of the transfer unit. Is controlled so as to be slower than when a normal toner image is at the transfer position, and is set so as not to apply a charge from the charge applying means or to apply a charge of the same polarity as the toner. 4. The image forming apparatus according to claim 1, wherein: