JPH08194395A - Image forming device - Google Patents

Abstract

PURPOSE: To provide an image forming device capable of maintaining an excellent state by detecting resistance and its unevenness in the cylindrical direction of a transfer belt, for facilitating its selection and correcting a resistance value, for reducing the resistance unevenness, in an image forming device using a contact type transfer system. CONSTITUTION: The image forming device is provided with the transfer belt which is constituted of a dielectric and capable of coming into contact with the outer periphery of an image carrier, a means driving the transfer belt, a charge applying means for directly applying a charge to the transfer belt, a destaticization member 7 for destaticizing the belt and means 24 for detecting a current flowing in the destaticization member 7. In the image forming device constituted in such a manner that the destaticization member 7, the current detecting means 24 and the charge applying means are arranged in a direction perpendicular to the rotational direction of the transfer belt, plural insulators extended in the peripheral direction of the destaticization member 7 are provided in the cylindrical direction, so that the member 7 is divided into plural destaticization parts and the current detecting means 24 are provided in the destaticization parts respectively, to detect the current of the each destaticization part, at the time of stopping a driving belt.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly to a transfer / conveying system for an electrophotographic image forming apparatus used in copying machines, printers, facsimiles and the like.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus using an electrophotographic method, a transfer belt or the like is used in a state of contacting the transfer paper as a means for transferring toner on a transfer paper to directly transfer the toner onto the transfer paper. A contact type transfer means for applying an electric charge has been proposed. Compared with the corona transfer method that has been used conventionally, this type of method (1) produces less ozone, (2) requires less power supply voltage,
(3) It has advantages such as easy size reduction and cost reduction of the apparatus, and has been applied to various image forming apparatuses in recent years. Generally, a transfer belt that performs transfer using a contact electrode uses a medium resistance region (10 ⁶ to 10 ¹² Ω). A belt having a resistance value in this region is a belt mounted state,
For example, it has a characteristic that the resistance easily changes depending on the presence or absence of tension and the ambient temperature.

However, the change in the resistance value of the transfer belt as described above causes a change in the transferability, and the discharge between the transfer paper and the sensitizer easily occurs, and the peeling discharge between the transfer paper and the transfer belt easily occurs. If the resistance value of the transfer belt is lowered, pre-transfer is likely to occur immediately before the transfer nip, and the periphery of the image is bleeded, or white spots due to pre-discharge are likely to occur. On the other hand, if the resistance value of the transfer belt increases, the current does not flow easily even when a high voltage is applied, resulting in a transfer failure. Further, in the case of constant current control, the applied voltage becomes high and the risk of leakage easily occurs. There is a point. Such a problem is remarkable especially when there is unevenness in resistance in the cylindrical direction of the transfer belt, as shown in FIG. 20, and unevenness in resistance occurs in the cylindrical direction of the transfer belt (resistance unevenness occurs due to secular change or the like). (Including cases), there is a problem that an abnormal image is locally generated.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and in an image forming apparatus using a contact type transfer system, detects resistance in the cylindrical direction of a transfer belt and uneven resistance,
By detecting the state of the belt, it is possible to easily select the belts that can be used in the device, and if the resistance unevenness in the cylindrical direction of the belt is large, correct the resistance value to reduce the resistance unevenness. In addition to expanding the usable range of resistance of the transfer belt and improving the yield,
An object of the present invention is to provide an image forming apparatus capable of maintaining a good condition by correcting the resistance value of the belt in maintenance such as replacement of the transfer belt. Further, after detecting the resistance unevenness of the transfer belt, the charge supply means is controlled so as to supply an optimum transfer current, and an image having good image quality can be obtained regardless of variations in the resistance value of the transfer belt. The purpose is to provide a device.

[0005]

To achieve the above object, a first means of an image forming apparatus according to the present invention is a transfer belt which is formed of a dielectric material and can be brought into contact with the outer peripheral surface of an image carrier, and this transfer belt. A means for driving the transfer belt, a charge supplying means directly applied to the transfer belt, a charge removing member for removing charge from the belt, and a means for detecting a current flowing through the charge removing member,
Further, in the one in which the charge eliminating member, the current detecting means, and the charge supplying means are arranged in a direction orthogonal to the rotation direction of the transfer belt, a plurality of insulators extending in the circumferential direction of the charge eliminating member are provided in the cylindrical direction of the charge eliminating member. Thus, the static elimination member is divided into a plurality of static elimination portions, each static elimination portion is provided with a current detecting means, and the current of each static elimination portion is detected when the drive belt is stopped. A second means of the image forming apparatus according to the present invention is characterized in that, in the first means, a current is detected in each charge eliminating portion when the transfer belt is rotated. The third means of the image forming apparatus according to the present invention is, in addition to the above-mentioned first means, provided with a variable resistor in each of the plurality of divided charge eliminating members so that the detected currents of the respective charge eliminating portions have substantially the same value. The variable resistance is controlled. The fourth means of the image forming apparatus according to the present invention is, in addition to the above-mentioned second means, provided with a variable resistor in each of the plurality of divided charge eliminating members so that the detected currents of the respective charge eliminating portions have substantially the same value. It is characterized in that the variable resistance is controlled. Fifth of the image forming apparatus according to the present invention
In addition to the above-mentioned second means, the means of dividing the charge supply means into a plurality of charge supply portions by providing a plurality of insulators extending in the circumferential direction of the charge supply means in the cylindrical direction of the charge supply means. In addition, the plurality of charge supply units are arranged so as to be displaced in the transport direction of the transfer belt. A sixth means of the image forming apparatus according to the present invention is characterized in that, in addition to the fifth means, the transfer bias supplied from the charge supplying means to the transfer belt is controlled for each charge supplying means. A seventh means of the image forming apparatus according to the present invention is characterized in that, in addition to the sixth means, the charge eliminating member detects the current of the transfer belt and changes the transfer bias of the charge supplying means.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on the embodiments shown in the drawings. 1 and 2 are schematic configuration diagrams of an image forming apparatus according to an embodiment of the present invention, in which 1 is a registration roller, 2 is a photoconductor drum, 3 is a driven roller, and 4 is a transfer belt 8 from a photoconductor. A belt push-up lever for contacting and separating, 5 for supplying electric charge, 6 for a cleaning blade for cleaning the surface of the photosensitive drum 2, 7 for a charge removing member for flowing the current from the transfer belt 8 to the ground, 8 for the transfer belt, and 9 for the driven member. A drive roller that stretches and drives the transfer belt with the roller 3, 10 is a transfer belt unit, 11 is a cleaning blade that cleans the surface of the transfer belt, and 12 is toner that receives scraped toner and paper dust. A receiver, 13 is a collecting coil that conveys toner and paper powder to a collecting bottle provided on the apparatus main body side, 14 is a discharge roller,
Reference numeral 15 is a static elimination lamp that lowers the surface potential of the photoconductor.

In the image forming apparatus thus configured, the transfer sheet P fed to the registration roller 1 and waiting is fed from the registration roller 1 at the image timing on the photosensitive drum 2. Further, the transfer belt 8 is also pushed up by the push-up lever 4 at the same time when the front end of the transfer paper P comes close to the contact portion between the photoconductor drum 2 and the transfer belt 8, and hits the photoconductor drum 2 as shown in FIG. Contact. At this time, a nip portion having a width of 4 mm to 8 mm is formed at the contact portion.

As described above, the transfer belt unit 10 includes a transfer belt 8 made of an elastic material, a driving roller 9 for driving the transfer belt, and a downstream side of the photosensitive drum 2 and arranged inside the transfer belt 8. Charge supplying means 5 for applying a transfer bias while maintaining the nip width W with the photosensitive drum.
A driven roller 3 for preventing deviation of the belt by tapering both ends of the roller, a static eliminator 7 for flowing the current from the transfer belt 8 to the ground, and a DC solenoid operated by a signal from the control plate. A belt unit push-up lever 4 for bringing the belt into and out of contact with the photosensitive member, and a cleaning blade 11 for cleaning the surface of the transfer belt 8.
A toner receiver 13 for receiving the toner and paper dust scraped off by the cleaning blade 11, and a collecting coil 12 for conveying the toner and paper powder to a collecting bottle of the main body.
Is provided.

Then, when the transfer paper enters the nip width W, a transfer bias is applied to the bias roller 5 and an electric charge having a polarity opposite to that of the toner on the photoconductor is imparted to the transfer belt, so that the transfer is performed. Be seen. In this embodiment, the surface is −
A positive toner is developed on the photoconductor charged to 800V, and the surface potential of the photoconductor is lowered by the pre-transfer charge eliminating lamp (PTL) 15.
A current of about μA is passed to transfer the toner onto the transfer paper.
Further, the electric charges applied to the belt and the transfer paper are discharged by the discharging member 7 as they move to the downstream side (traveling direction).

FIG. 3 is a diagram showing an embodiment of the static eliminating member 7 used in the transfer belt unit 10, and FIG. 4 is an example of a detection circuit. As shown in FIG. 20, if the resistance unevenness of the transfer belt in the cylindrical directions A and B is different, the resistance unevenness causes deterioration in image quality. Therefore, it is necessary to first measure the resistance unevenness of the transfer belt. Therefore, a charge removing member and a detection circuit described later are installed, and the resistance value of the transfer belt is measured without rotating the transfer belt. That is, the resistance unevenness in the cylindrical direction of the belt is measured at several places for one belt. The static eliminator 7 is provided with a plurality of insulators 20 extending in the circumferential direction of the cylindrical static eliminator in the cylindrical direction of the static eliminator to divide the static eliminator into a plurality of static eliminators. n) is connected to the ammeter 24 via the connector 22.

The discharging member 7 is installed together with the detection circuit, a certain bias is applied from the charge supplying means 5, and the discharging member 7 is placed at an arbitrary position on the inner peripheral surface of the transfer belt 8.
Is installed, the current value flowing into the divided static elimination portions (1) to (n) is measured, analog / digital conversion is performed, and a digital signal is supplied to the CPU, whereby the belt is rotated in the cylindrical direction (rotational direction). Resistance unevenness in the (orthogonal direction) is measured, and the transfer belt that does not satisfy the standard value is displayed as NG,
It is possible to sort the drive belt.

In the above-described embodiment, the resistance unevenness in the cylindrical direction of the belt is measured while the transfer belt is stopped, but it is also possible to measure the resistance unevenness in the same manner as described above while the transfer belt is rotated. is there. At that time, if current values at all points of each static elimination portion (1) to (n) are measured, it becomes possible to obtain a plurality of outputs as shown in FIG. By plotting the change of, the current value as shown in FIG. 6 can be obtained. That is, by measuring the resistance unevenness while rotating the transfer belt, it is possible to simultaneously measure the resistance unevenness in the circumferential direction and the cylindrical direction of the transfer belt. Even in this case, the resistance value of the transfer belt is less than the standard value. When it comes off, NG is displayed by the CPU of the detection circuit, and it is possible to avoid the use of the transfer belt in which an abnormal image is likely to occur.

More specifically, in order to measure the resistance unevenness in the cylindrical direction of the transfer belt, as shown in FIG. 5, the resistance values A to A of the static elimination portions at a certain point in the circumferential direction are measured.
In order to obtain the resistance unevenness in the circumferential direction of the transfer belt from Z, the current values a to z at arbitrary rotational positions can be obtained as shown in FIG.

FIG. 7 is a view showing another embodiment of the charge eliminating member used in the transfer belt unit 10 according to the present invention. The difference from the embodiment shown in FIG. 3 is that each charge eliminating portion (1)- The point is that the ammeter 24 is provided from (n) via the variable resistor 26 and the connector 22. That is, a variable resistor 26 is provided in each of the divided static elimination portions (1) to (n), and the current value flowing into the static elimination portion can be made constant by changing the value of the variable resistor 26. Variable resistance 2 when the resistance unevenness of the belt in the cylindrical direction is large.
By controlling the value of 6, the resistance unevenness can be reduced and corrected, the usable range of the resistance of the transfer belt can be widened, and it is effective for the correction when the belt is replaced.

As described above, the static eliminating member provided with the variable resistor 26 is used, and the value of the variable resistor is set so that the current value flowing through each static eliminating portion of the static eliminating member becomes constant with the transfer belt being rotated. By controlling, it is also possible to compensate for the local uneven resistance of the belt. Further, by providing a means for connecting at least two or more of the plurality of charge eliminating parts and the charge supplying means from the detected current value, it becomes possible to control the detected current value to a constant value, and the resistance value of the transfer belt can be controlled. It is also possible to enable stable transcription without dependence.

A specific control example for correcting the resistance value of the transfer belt by using the charge eliminating member having the variable resistance will be described below. First, there is no abnormal image, the resistance value is within the normal range, and the current value flowing into the static elimination portion corresponding to a certain portion of the belt that enables stable transfer is used as a reference and other Calculate the ratio of the current value flowing into the static elimination part and determine (control) the variable resistance so that the current value to each static elimination part is constant, or the environmental fluctuation or the resistance of the transfer material If different, the output of the high-voltage power supply may be variable. That is, as shown in FIG. 8, the transfer belt is divided into a cylindrical direction and a circumferential direction, and it is possible to detect whether the resistance value in each region is higher or lower than the reference value, and it is indicated by a diagonal line. As described above, since it is possible to know whether the local resistance value is high or low, it is possible to adjust the variable resistance according to the resistance value and maintain a predetermined resistance value.

FIG. 9 is a diagram showing an example in which the inflow current to each charge eliminating portion is controlled according to the resistance value of the predetermined area of the transfer belt as described above. Control is performed so that the inflow currents of the charge eliminating portions (1) to (n) are constant with respect to the rotation time t (circumferential position) of the transfer belt. That is, by sequentially varying the value of the variable resistance connected to each charge eliminating portion along with the rotation of the belt, it is possible to control the resistance unevenness of the belt and prevent a white spot image or an abnormal image that occurs locally. It will be possible. Further, even when the resistance value of the transfer belt greatly changes due to aging or the like, the resistance value of the transfer belt can always be kept constant, so that stable transfer can be always performed.

In particular, by controlling the value of the variable resistance to be high in a region where image whiteout is likely to occur due to pre-discharge, the occurrence thereof is prevented, and the charge easily escapes at the edge of the paper. Although an abnormal image (scale-like shape or black spot-like shape) is likely to occur due to the shortage, the occurrence of the abnormal image is reduced by setting the variable resistance of the static elimination member near the end portion to a low value. Further, as described above, the value of the variable resistance is not changed according to the resistance value of the transfer belt, but the charge supply means is divided into a plurality of parts according to the resistance value of the transfer belt, and the transfer bias value of each is changed. The transfer belt may be charged with a substantially constant amount by controlling the resistance.

FIG. 10 is a view showing another embodiment of the present invention. The difference from FIG. 4 described above is that a plurality of charge supplying means are arranged in the transfer belt conveying direction so as to be displaced from each other. FIG. 11 is a diagram showing an embodiment of a plurality of charge supplying means used in the transfer belt unit 10. As an example, FIG. 11 shows a case where the charge supplying means is composed of three bias rollers.

In the above-described embodiment, since the insulator is provided in the circumferential direction of the static eliminating member and a plurality of the insulators are provided in the cylindrical direction of the static eliminating member, the rotation unevenness of the rotating belt in the cylindrical direction and the circumferential direction are caused by the rotation of the transfer belt. It is possible to detect the uneven resistance. Therefore, it is possible to grasp the local resistance unevenness of the transfer belt, and in the present embodiment, control is performed so that an appropriate charge supply amount is obtained from the local resistance value of the belt. That is, the divided charge supply portions (1) to (1) among the charge supply means A, B, C according to the resistance value of the belt.
Determine which of (n) to use.

The charge supplying means A is used when the resistance value R of the transfer belt is smaller than the standard belt resistance value r (R <r), and the charge supplying means B is used as the resistance value R of the transfer belt. It is used when the standard belt resistance value r is substantially equal (R≈r). Similarly, when the transfer belt resistance value R is smaller than the standard belt resistance value r (R≈r) ( R> r).

An example of controlling the charge supplying means will be described below. Now, when the charge supply control of the transfer belt as shown in FIG. 12 is performed, the hatched area X1 of the transfer belt
The belt resistance RL of 1, X2, 1, X2, 2, Xn, 1 is lower than the standard belt resistance r, and the belt resistance RH of the cross-hatched regions X1 and X2 is the standard belt resistance r. The belt resistance RA is higher than r, and the belt resistance RA in other areas of the transfer belt shown in white is approximately equal to the standard belt resistance r.

The charge supply control of the transfer belt is as follows.
At a certain time t1, of the divided charge supply portions (1) to (n) in the charge supply means A, (1) corresponding to X1,1 is selected and activated in the region X1,1. That is, since the belt resistance value of the region X1,1 is lower than the standard resistance r, the charge supplying means A corresponding to it is used.
Further, at the same time t1, in the regions X1 and X2, the resistance value is larger than the standard resistance r, so that (2) in the charge supply means C is selected. Further, in the regions X1,3 to X1, n, since the belt resistance is substantially equal to the standard resistance, each charge supply portion of the charge supply means B is selected and the charge is supplied.

Next, at time t2 (t2 = t1 + t),
In the regions X2,1 and X2,2, the resistance value is larger than the standard resistance r, so (1) in the charge supply means C,
(2) is selected, and in other regions, the electric charge is supplied by each electric charge supplying portion of the electric charge supplying means B. In this way, the charge supply means for sequentially applying the bias is determined according to the resistance value of the belt. For example, some arbitrary time t
FIG. 13 shows an example of selection of the charge supply means at 1 and t2 (= t1 + T).
14), and FIG. 14 shows ON / OFF of the bias of the charge supply means B shown in FIG.

As shown in FIG. 13, at the time t1, the charge supplying portion (1) of the charge supplying means A operates, and the time t1
In the charge supplying portion (1) in 2, the charge supplying means C is operating. That is, the resistance value of the transfer belt corresponding to the charge supply portion (1) is smaller than the standard resistance value r at an arbitrary time t1, but the belt whose resistance value is a standard at the arbitrary time t2. Since the resistance value is smaller than the resistance value r, such control is performed.

As for the charge supplying means B, as shown in FIG. 14, only the charge supplying portion (3) operates at an arbitrary time t1 to t2, and the charge supplying portion (3) at the time t2. Bias application is turned off,
The charge supply portions (2) and (4) are biased. The transfer bias of each divided portion is constant.

Next, another embodiment according to the present invention will be described. In the above-described embodiment, each charge supply portion (1)-
Although the transfer bias value supplied to the transfer belt is constant from (n), it is possible to set an arbitrary transfer bias. That is, in the conventional control method, as shown in FIG. 15, I1-I2 = Iout (where Iout: current value (constant) flowing through the photoconductor, I1: current value output from high-voltage power supply, I2: feedback current) The value of I1 is controlled so that the relationship of (value) can be obtained. However, in this method, the output current I1 is set so that the optimum drum current Iout is obtained according to the local resistance of the belt. is there.

FIG. 16 shows an arbitrary portion Xn, 1 of the belt.
Corresponding to the output currents In and 1 and the drum current Ioutn,
17 is a diagram showing the relationship with FIG. 1, FIG. 17 shows the output current In2 and the drum current Io corresponding to an arbitrary portion Xn, 2 of the belt.
It is a figure which shows the relationship with utn and 2. That is, instead of keeping the drum current Iout constant as in the conventional case, the optimum drum current (transfer current) I is set according to the resistance value of the transfer belt.
The current I supplied from the charge supply means so as to be out
1 is variably controlled.

FIG. 18 is a diagram showing an example in which the output current I1 of the charge supply means B shown in FIG. 14 is variable. Charge supply portion (3) that is turned on at time t1
The value of the bias current supplied by the device is 50 μA, and the time is t2.
The bias current values supplied from the charge supply portions (2) and (4) that are turned on at 55 μA and 45 μA, respectively.
The bias current difference is A, and the resistance value of the transfer belt is different, so that the optimum drum current is set. It should be noted that the bias current value supplied from each charge supply portion is constant until the resistance of the transfer belt is detected again.

In the above-described embodiment, the bias current value is set at regular intervals such as when the image forming apparatus is powered on or when a certain number of sheets are passed, whereas in the other embodiments according to the present invention. For example, the bias current value supplied from each charge supply portion of the charge supply means may be set for each rotation of the transfer belt.

That is, while the transfer belt is rotating, the current is detected by each charge eliminating member, and the uneven resistance of the belt is detected based on the current value, and the drum current (transfer current) Iou is detected.
Set t according to the detected resistance unevenness. That is, by sequentially measuring the resistance value of the transfer belt, a local resistance value of the belt is obtained, and the drum current Iout set based on the resistance value is used as a drum current to be set at the time of the next belt rotation. It is possible to perform control closer to real-time control by giving it from the supply means.

When such control is carried out for the charge supplying means B shown in FIG. 14, for example, as shown in FIG. 19, when a current is supplied to the transfer belt by the same charge supplying portion, for example, (2). However, the current value is 55
There are cases where they differ from each other, such as μA and 57 μA, and it becomes possible to set an optimum output bias for each transfer.

[0033]

As described above, since the image forming apparatus according to the present invention can detect the resistance value and the resistance unevenness of the transfer belt in the cylindrical direction, it is possible to select the belt and rotate the transfer belt. By measuring the resistance value of the belt while it is being performed, it is possible to measure the resistance value in the circumferential direction in addition to the resistance value in the cylindrical direction, and it is possible to further improve the sorting accuracy of the belt.

Further, in the case where the resistance unevenness of the belt in the cylindrical direction is large, it is possible to widen the usable range of the belt by correcting the resistance unevenness by controlling the variable resistance provided in the charge eliminating member. In particular, it is effective in correcting the resistance value of the transfer belt to be constant when the belt is replaced at the time of manufacturing the image forming apparatus or during maintenance.

Further, since the resistance values of the transfer belt in the cylindrical direction and the circumferential direction can be detected, it is possible to grasp the resistance value of a certain area of the belt and change the resistance value according to the resistance value so that stable transfer can be performed. It is also possible to control the value of the resistance.

That is, by controlling so that the value of the variable resistance becomes high especially in the region where the white spots in the image are likely to occur due to the pre-discharge, the occurrence thereof is prevented, and the electric charge easily escapes at the edge of the paper. Although abnormal images (scales, black dots) due to insufficient transfer are likely to occur, it is possible to reduce the occurrence of abnormal images by setting the variable resistance of the static elimination member near the edges to a low value. In addition to obtaining good image quality, the usable range of the transfer belt is expanded to facilitate manufacturing cost and adjustment.

Further, it is possible to shift the position of the charge supplying means in accordance with the resistance unevenness of the transfer belt, and not only the transfer can be performed without being affected by the resistance unevenness, but also the resistance value of the belt changes with time. Even if it adapts, good image quality can be obtained. Furthermore, the transfer current can be finely controlled according to local resistance unevenness,
Since the control can be performed while sequentially detecting the current flowing into the charge eliminating member, a transfer bias current that is always in an optimum state can be obtained, and a remarkable effect is obtained in obtaining a good image quality.

[Brief description of drawings]

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

FIG. 2 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.

FIG. 3 is a diagram showing an example of a charge eliminating member used in a transfer belt unit.

FIG. 4 is a diagram showing an example of a detection circuit.

FIG. 5 is a diagram showing current values at all points of each static elimination portion (1) to (n).

FIG. 6 is a diagram plotting a change in current value with rotation of an arbitrary static elimination portion.

FIG. 7 is a view showing another embodiment of the charge eliminating member used in the transfer belt unit according to the present invention.

FIG. 8 is a diagram showing a state in which the transfer belt is divided into a cylindrical direction and a circumferential direction, and whether the resistance value in each region is higher or lower than a reference value is detected. (Figure showing uneven resistance)

FIG. 9 is a diagram showing an example of controlling an inflow current to a charge eliminating member.

FIG. 10 is a diagram showing an example in which a plurality of charge supply units are arranged in the image forming apparatus according to the present invention so as to be displaced in the transporting direction of the transfer belt.

FIG. 11 is a diagram showing an example of a plurality of charge supply units used in the transfer belt unit.

FIG. 12 is a diagram showing a state of a transfer belt.

FIG. 13 is a diagram showing an example of selection of charge supply means.

FIG. 14 is a diagram showing an example of an on / off state of a charge supply portion in the charge supply means B.

FIG. 15 is a diagram showing a relationship between an output current and a drum current in a conventional control method.

FIG. 16 is a diagram showing a relationship between an output current In1 and a drum current Ioutn, 1 corresponding to an arbitrary portion Xn, 1 of the belt.

FIG. 17 is a diagram showing a relationship between output currents In and 2 and drum currents Ioutn and 2 corresponding to arbitrary portions Xn and 2 of the belt.

FIG. 18 is a diagram showing an example in which the output current I1 of the charge supply unit B is variable.

FIG. 19 is a diagram showing an example in which the output current I1 of the charge supply unit B is variable for each rotation of the belt.

FIG. 20 is a diagram showing each direction of the transfer belt.

[Explanation of symbols]

1 ... Registration roller, 2 ... Photosensitive drum, 3
... Driven roller, 4 ... Belt lifting lever,
5 ... Charge supplying means, 6 ... Cleaning blade, 7 ... Static elimination member, 8 ... Transfer belt, 9.
..Drive rollers, 10 ... Transfer belt unit, 1
1 ... Cleaning blade, 12 ... Toner receiver, 13 ... Recovery coil, 14 ... Discharge roller,
15 ... Static elimination lamp, 20 ... Insulator, 22 ...
-Connector, 24 ... Ammeter, 26 ... Variable resistance.

Front page continuation (72) Inventor Joji Mizuishi Ricoh Co., Ltd. 1-3-6 Nakamagome, Ota-ku, Tokyo (72) Inventor Hajishi Ito 1-3-6 Nakamagome-Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Tadashi Matsuda 1-3-6 Nakamagome, Ota-ku, Tokyo, Ricoh Co., Ltd. (72) Inventor Yuko Harazawa 1-3-6 Nakamagome, Tokyo, Ota-ku, Tokyo (72) Inventor Masahide Nakatani 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd.

Claims (7)

[Claims] 1. A transfer belt formed of a dielectric material and capable of contacting an outer peripheral surface of an image carrier, a means for driving the transfer belt, a charge supplying means for directly applying a voltage to the transfer belt, and a transfer belt. An image forming apparatus comprising a charge removing member for removing charge and a means for detecting a current flowing through the charge removing member, wherein the charge removing member, the current detecting unit, and the charge supplying unit are arranged in a direction orthogonal to the rotational direction of the transfer belt. In the arranged ones, a plurality of insulators extending in the circumferential direction of the static eliminator are provided in the cylindrical direction of the static eliminator to divide the static eliminator into a plurality of static eliminators, and a current detector is provided in each static eliminator. An image forming apparatus, wherein the image forming apparatus is provided and detects a current of each charge eliminating portion when the transfer belt is stopped. 2. The image forming apparatus according to claim 1, wherein a current of each charge eliminating portion is detected when the transfer belt is rotated. 3. A variable resistance is further provided in each static elimination portion of the static elimination member divided into a plurality of parts, and the variable resistance is controlled so that the detection currents of the static elimination portions have substantially the same value. The image forming apparatus according to claim 1. 4. A variable resistor is further provided to each static elimination portion of the static elimination member divided into a plurality of parts, and the variable resistor is controlled so that the detection currents of the static elimination portions have substantially the same value. The image forming apparatus according to claim 2. 5. The charge supplying means is divided into a plurality of charge supplying portions by providing a plurality of insulators extending in the circumferential direction of the charge supplying means in a cylindrical direction of the charge supplying means, and a plurality of the charge supplying means. 3. The image forming apparatus according to claim 2, wherein the supply unit is arranged so as to be displaced in the conveying direction of the transfer belt. 6. The image forming apparatus according to claim 5, wherein the transfer bias supplied to the transfer belt by the charge supply unit is controlled for each charge supply unit. 7. The image forming apparatus according to claim 6, wherein the charge removing member detects the current of the transfer belt and changes the transfer bias of the charge supply unit.