JPH08194389A - Image forming device - Google Patents

Abstract

PURPOSE: To prevent the occurrence of a failure and void in a transfer, irrespective of the variance of the resistance value at the time of manufacturing an intermediate transfer body or a transfer roller and an environmental fluctuation. CONSTITUTION: A DC bias controlled to be a prescribed value I1 with a constant current is applied from a high-voltage power source 9 to the intermediate transfer body 5, when an image is not formed and simultaneously, a DC voltage value V1 at this time is detected by a bias detecting means 10. Moreover, the DC bias controlled to be a prescribed value I2 with the constant current is applied from the high-voltage power source 9 to the transfer roller 8 and simultaneously, a DC voltage value Vt at this time is detected by the bias detecting means 10. At the time of forming the image, the biases of the above-mentioned detected values V1 and Vt are applied to the intermediate transfer body 5 and the transfer roller 8 respectively, when primary and secondary transfers are performed.

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 printer or a copying machine which employs an electrophotographic system or an electrostatic recording system, and more particularly to an image forming apparatus equipped with an intermediate transfer member. Is.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus using an intermediate transfer member as shown in FIG. 5 has been proposed for the purpose of obtaining a color image free from color misregistration. In FIG. 5, the image forming apparatus is provided with a photosensitive drum 101 as a first image carrier which is rotationally driven in a direction of an arrow at a predetermined peripheral speed, and its surface is first uniformly charged by a charging unit 102. It Next, ON / OFF according to the first image information
Scanning is performed by the controlled exposure unit 103, and a first electrostatic latent image is formed.

This first electrostatic latent image is developed and visualized by a first developing means 104a containing a first color developer. The visualized first toner image is brought into pressure contact with the photosensitive drum 101 with a predetermined pressing force, and is rotationally driven in the direction of the arrow at a speed substantially equal to the peripheral speed of the photosensitive drum 101. Intermediate transfer member 105 as
At the nip portion between and, primary transfer is performed on the surface of the intermediate transfer member 105. At this time, a voltage that is opposite to the charging polarity of the toner and is uniquely set is applied to the intermediate transfer member 105.

Then, the above steps are repeated a plurality of times, and the second developing means 104b and the third developing means 104 are carried out each time.
c, toner images of different color developers contained in the fourth developing means 104d are sequentially electrostatically transferred and laminated on the surface of the intermediate transfer body 105 to form a color image, and then the intermediate transfer body 105 and A transfer material that is pressed against this with a predetermined pressing force and is conveyed to a nip portion with the transfer roller 106 as a transfer means that is rotated at a speed substantially equal to the peripheral speed of the intermediate transfer body 105 in the direction of the arrow. 107
Secondary transfer is performed collectively on the surface. At this time, the transfer roller 1
To 06, a voltage having a polarity opposite to the charging polarity of the toner and uniquely set in advance is applied.

[0005]

However, in order to adjust the resistance value of the intermediate transfer member 105 and the transfer roller 106 as shown in the above-mentioned conventional example, carbon is contained in an elastic member such as rubber. It has a form in which a conductive material such as a metal oxide is dispersed. It is generally known that the resistance value of such a material fluctuates at the time of manufacturing, and the resistance value of the material greatly changes due to a change in the surrounding environment.

Under these circumstances, the intermediate transfer member 10
When the primary transfer bias applied to No. 5 and the secondary transfer bias applied to the transfer roller 106 are constant voltage control uniquely set in advance as in the conventional case, for example, in a low temperature and low humidity environment. As described above, when the resistance of the intermediate transfer body 105 and the transfer roller 106 becomes high, a transfer failure easily occurs.

On the other hand, when the resistance of the intermediate transfer body 105 and the transfer roller 106 is lowered, such as in a high temperature and high humidity environment, an excessive bias is applied, which causes a part of excess charge. The toner is converted into the same polarity as the transfer bias, and it becomes difficult for the toner to be transferred to the surfaces of the intermediate transfer member 105 and the transfer material 107, so-called transfer omission easily occurs.

Further, a current of a proper current value or more may flow into the photosensitive drum 101 to cause a photoconductor memory, or the resistance of the transfer material may be extremely reduced to cause punch-through.

Therefore, a first object of the present invention is to form an image which can prevent the occurrence of transfer failure without depending on the fluctuation of the resistance value at the time of manufacturing the second image carrier or the transfer means or the environmental change. It is to provide a device.

A second object of the present invention is to provide an image forming apparatus capable of preventing the occurrence of transfer dropout without depending on the fluctuation of the resistance value at the time of manufacturing the second image carrier or the transfer means or the environmental fluctuation. Is to provide.

A third object of the present invention is to provide a photosensitive member memory for the first image carrier without depending on fluctuations in resistance value during manufacturing of the second image carrier or transfer means or environmental fluctuations. An object of the present invention is to provide an image forming apparatus capable of preventing the occurrence of punch-through.

[0012]

The above object can be achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
The first electrostatic latent image formed on the surface of the rotatable first image carrier is visualized by the developer of the first color, and this is electrostatically transferred to the surface of the rotatable second image carrier. After that, by repeating the process a plurality of times, a color image is formed on the surface of the second image carrier by the developers of a plurality of colors, and the color images are collectively formed on the surface of the transfer material conveyed to the transfer site by the transfer means. In an image forming apparatus for transfer, at the time of non-image formation, a bias is applied between the first image carrier and the second image carrier, the voltage-current characteristic of the second image carrier is measured, and the voltage is measured. An image forming apparatus characterized by storing current characteristics.

The voltage applied to the second image carrier is determined based on the voltage-current characteristic of the second image carrier, and the determined voltage is applied to the second image carrier by constant voltage control during image formation. It is preferable to apply.

It is preferable that, while the voltage is applied to the second image carrier, a bias is applied to the transfer means to measure the voltage-current characteristics of the transfer means, and the voltage-current characteristics are stored.

It is preferable that the voltage applied to the second image carrier is determined based on the voltage-current characteristics of the second image carrier measured in advance.

The measurement of the voltage-current characteristic of the second image carrier is carried out for at least one revolution of the second image carrier,
The fluctuation of the voltage-current characteristic is measured, and a second value is measured according to the fluctuation.
It is preferable to vary the voltage applied to the image carrier.

The distribution of the voltage-current characteristic of the second image carrier for one round is measured in advance, the voltage-current characteristic of a part of the second image carrier is measured immediately before image formation, and the measurement is performed. It is preferable to change the voltage applied to the second image carrier according to the value and the voltage-current characteristic distribution.

According to another aspect of the present invention, the first electrostatic latent image formed on the surface of the rotatable first image carrier is visualized by the developer of the first color, and this can be rotated. Na second
After the electrostatic transfer to the surface of the image carrier, the step is repeated a plurality of times to form a color image by the developers of a plurality of colors on the surface of the second image carrier, and the color image is conveyed to the transfer site. In an image forming apparatus for collectively transferring to the surface of the transferred transfer material by transfer means, a conductor is provided in contact with the transfer means, a bias is applied between the transfer means and the conductor, and a voltage of the transfer means is applied. There is provided an image forming apparatus characterized by measuring current characteristics and also storing the voltage-current characteristics.

It is possible to determine the voltage to be applied to the second image carrier based on the voltage-current characteristics of the transfer means, and apply the determined voltage to the second image carrier by constant voltage control during image formation. preferable.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

First Embodiment A first embodiment of the image forming apparatus according to the present invention will be described with reference to FIG. In FIG. 1, the image forming apparatus includes a photosensitive drum 1 as a first image carrier. Photosensitive drum 1 is OPC, amorphous Se, amorphous S
A photosensitive material such as i is formed on the outer peripheral surface of a cylindrical substrate such as aluminum or nickel. The photosensitive drum 1 is rotationally driven in the direction of the arrow at a predetermined peripheral speed, and first, the charging roller 2 as a charging device uniformly charges its surface to −700 V as a dark portion potential V _D.

Next, the laser beam 3 on / off-controlled on the surface of the photosensitive drum 1 according to the first image information.
Scanning exposure is performed, and the light potential V _L is -100.
A first electrostatic latent image of V is formed.

The electrostatic latent image thus formed is developed and visualized by the developing device 4. The developing device 4 is
The first developing device 4a containing yellow toner as the first color toner, the second developing device 4b containing magenta toner as the second color toner, and the cyan toner as the third color toner. Third developing device 4
c, a fourth developing device 4d containing black toner as the fourth color toner is integrated.

First, the first electrostatic latent image is developed and visualized by the first developing device 4a containing yellow toner as the first color toner. As a developing method, a jumping developing method, a two-component developing method, an FEED developing method, or the like is used, and image exposure and reversal developing are often used in combination.

The visualized first toner image is pressed against the photosensitive drum 1 with a predetermined pressing force, and is rotated in the direction of the arrow at a speed substantially equal to the peripheral speed of the photosensitive drum 1. Electrostatic transfer (primary transfer) is performed on the surface of the intermediate transfer member 5 at the first transfer portion 6a that comes into contact with the intermediate transfer member 5 as the image carrier.

The intermediate transfer member 5 has a peripheral length slightly longer than the length of the transfer material, and the toner image formed on the surface of the photosensitive drum 1 is transferred to the intermediate transfer member 5 by a high voltage power source 9 to transfer the toner. By applying a voltage having a polarity opposite to the charging polarity, electrostatic transfer (primary transfer) is performed on the surface of the intermediate transfer member 5.

The high-voltage power supply 9 can be controlled by constant current or constant voltage. Then, the toner slightly remaining on the surface of the photosensitive drum 1 after the primary transfer is removed by the cleaning device 7a.

Subsequently, the above-mentioned steps are repeated three times, and the second toner image developed with magenta toner each time,
The third toner image developed with cyan toner and the fourth toner image developed with black toner are sequentially transferred and laminated on the surface of the intermediate transfer member 5.

After that, the transfer roller 8 as the transfer means, which is in a state of being separated from the surface of the intermediate transfer body 5, is pressed, driven or driven to rotate on the surface of the intermediate transfer body 5 with a predetermined pressing force, and the transfer roller 8 is rotated. On the other hand, a voltage having a polarity opposite to the charging polarity of the toner is applied by the high-voltage power supply 9 to collectively transfer (secondary transfer) to the surface of the transfer material P that is conveyed to the second transfer portion 6b at a predetermined timing. The transfer material P is conveyed to a fixing device (not shown), fixed as a permanent image, and then ejected to the outside of the apparatus.

Incidentally, a small amount of residual toner on the surface of the intermediate transfer body 5 after the secondary transfer is operated to the surface of the intermediate transfer body 5 at a predetermined timing by the cleaning device 7.
removed by b.

Further, the structures of the photosensitive drum, the intermediate transfer member, and the transfer roller according to the present embodiment will be described in detail with reference to FIG.

In FIG. 2, the photosensitive drum 1 has a wall thickness of 1 m.
An organic photosensitive layer 12 having polycarbonate as a main binder is formed on the outer peripheral surface of a cylindrical base body 11 made of aluminum having a diameter of 30 mm.
It is rotationally driven at a peripheral speed of 0 mm / sec.

On the other hand, the intermediate transfer member 5 has a thickness of 3 mm.
By dispersing carbon as conductive particles in silicon rubber on the outer peripheral surface of the cylindrical base body 51 made of aluminum, the resistance value is 10 ⁵ to 10 ¹⁰ Ωc.
The elastic resistance layer 52 having a wall thickness of 5 mm and having an outer diameter of 100 mm and a hardness of 30 ° (JI
S A), which is rotationally driven at a peripheral speed substantially equal to the peripheral speed of the photosensitive drum 1. The photosensitive drum 1 and the intermediate transfer member 5 are pressed against each other at a total pressure of 500 g by a pressing means (not shown).

Further, the transfer roller 8 has conductive cores 81 having an outer diameter of 6 mm, on which carbon as conductive particles is dispersed, and the resistance value thereof is adjusted to 10 ⁷ to 10 ¹⁰ Ωcm. A foamed EPDM layer is formed as the layer 82, which has an outer diameter of 20 mm and a hardness of 45 ° (ASKER C), and is applied to the surface of the intermediate transfer member 5 at a predetermined timing with a total pressure of 800 g by a pressing means (not shown). While being pressed, the intermediate transfer member 5 is driven or rotated at a peripheral speed substantially equal to the peripheral speed of the intermediate transfer member 5.

The transfer bias control means according to the present invention will be described in detail below.

(1) The photosensitive drum 1 which rotates by separating the transfer roller 8 from the intermediate transfer member 5 during non-image formation
The surface of the intermediate transfer body 5 is uniformly charged by the charging roller 2 to a dark potential of −700 V, and a high-voltage power supply 9 applies a direct current bias controlled to a predetermined current value I ₁ [μA] to the intermediate transfer body 5 while applying a bias. The detection means 10 detects the DC voltage value V ₁ [kV] generated at this time.

The voltage value V ₁ may be determined by one-time detection, but there are various methods such as an average value, a maximum value and a minimum value obtained by performing it a plurality of times. In this embodiment, the detection was performed for one round of the intermediate transfer member, sampling was performed 50 times in the detection, and the average value was set to V ₁ . Above constant current value I ₁
[ΜA] is a preset value necessary for good primary transfer of the toner image formed on the surface of the photosensitive drum 1 to the surface of the intermediate transfer body 5, and in the present embodiment, 3 μA.
Set to A.

(2) At the time of non-image formation, the transfer roller 8 is brought into contact with the intermediate transfer body 5, and the intermediate transfer body 5 is brought into a grounded state. The surface of the rotating photosensitive drum 1 is uniformly charged by the charging roller 2 to a dark portion potential of −700 V, and a predetermined current value I ₂ [μ is applied to the transfer roller 8 by the high voltage power source 9.
A DC voltage value V _t [kV] generated at this time is detected by the bias detection means 10 while applying a constant-current-controlled DC bias to A]. In order to determine this voltage value V _t [kV], V ₁ [kV] may be determined in the same manner as in the case of determining it, but a plurality of samplings are performed and the average value thereof is
Various methods such as the maximum value and the minimum value may be adopted. However, the accuracy is further improved by performing sampling for at least one round of the transfer roller 8, and preferably for one round of the intermediate transfer body 5.

The constant current value I _t [μA] is such that the toner image formed on the surface of the intermediate transfer member 5 can be well transferred to the surface of the transfer material P.
It is a preset value required for the next transfer,
In this example, it was set to 5 μA.

(3) At the time of primary transfer in the image forming process, by applying a low-voltage-controlled primary transfer bias to the previously detected V ₁ [kV], 1 formed on the surface of the photosensitive drum 1 A toner image of a color, for example, a yellow image is primarily transferred onto the surface of the intermediate transfer member 5.

(4) Similar to (3) above, the photosensitive drum 1
A toner image of the second color formed on the surface, for example, a magenta image, a toner image of the third color formed on the surface of the photosensitive drum 1, for example, a cyan image, and a toner image of the fourth color formed on the surface of the photosensitive drum 1. For example, even when the black image is primarily transferred to the surface of the intermediate transfer body 5, a predetermined voltage V _s is applied to the intermediate transfer body 5 by the high-voltage power supply 9 to V ₁ [kV] at each stage. Voltage added to the step voltage V ₂ = V ₁ + V _S , V ₃ = V ₂ + V _S , V ₄ = V ₃ +
By applying a constant-voltage-controlled primary transfer bias to V _S , a large amount of current flows in the portion where the toner image does not exist between the surface of the photosensitive drum 1 and the surface of the intermediate transfer member 5, and the voltage drops. The electric field strength necessary for transfer is not lost, and good primary transfer is performed in each case.

In the present embodiment, a good transferred image could be obtained by setting the predetermined voltage V _S to 0.3 kV.

(5) At the time of secondary transfer in the image forming process, the DC voltage values V ₁ [kV] and V _t [kV] detected in (1) and (2) above are converted into a constant a shown below.
_The secondary transfer bias V _T [kV] is calculated according to the secondary transfer bias calculation formula (A) in which ₁ , b ₁ and c ₁ are preset, and the obtained voltage value V _T [kV] is applied to the transfer roller 8. By applying the high voltage power source 9 to the surface, the color image formed on the surface of the intermediate transfer member 5 is secondarily transferred to the surface of the transfer material P.

V _T = a ₁ · V ₁ + b ₁ · V _t + c ₁ + 3V _S (A) In this embodiment, the constants a ₁ , b ₁ , and c ₁ are 1.1 and 0, respectively. By setting the ratio to 0.8 or 1.2, it became possible to obtain a good transferred image.

Here, c ₁ is a value determined in consideration of the voltage drop due to the resistance of the transfer material P when the color image formed on the surface of the intermediate transfer member 5 is secondarily transferred to the surface of the transfer material P. .

In the present embodiment, the secondary transfer bias calculation formula (A) has the form of the primary formula, but the present invention is not limited to this.

Further, in the present embodiment, constant current control is performed to measure the resistance of the intermediate transfer member 5 and the transfer roller 8, and the voltage value at the constant voltage control is determined by the voltage generated at this time. The current flowing at this time is detected,
It is also possible to determine the voltage value during constant voltage control based on this current value.

Further, in this embodiment, the voltage-current characteristic was measured by passing a current through the photosensitive drum 1. However, the intermediate transfer member when a constant current flows through a roller made of a conductor, which is installed so as to come into contact with the intermediate transfer member 5. Alternatively, the bias voltage applied to the intermediate transfer member may be determined based on the measured voltage applied to the intermediate transfer member 5 or the current flowing when a constant voltage is applied to the intermediate transfer member.

By using the control method as described above, good transfer can be performed even when the resistance value changes due to resistance fluctuation during manufacturing of the intermediate transfer member 5 or the transfer roller 8 and environmental changes. You can

Second Embodiment A second embodiment according to the present invention will be described below. However, since the structure of the image forming apparatus in this embodiment is the same as that of the first embodiment, the description thereof will be omitted.

[0051] In the first embodiment, the generated voltage at the time current flows to the intermediate transfer member 5 has taken as a single value as V _1, a plurality of times sensing the voltage generated at that time subjected to constant current control in this embodiment Then, the respective values are continuously recorded together with the recording by the position detecting means of the intermediate transfer body 5 (not shown). These values can be represented as shown in the graph of FIG. 3 by plotting the position of the intermediate transfer member 5 on the horizontal axis and the voltage on the vertical axis. It is characterized in that when actually transferring from the photosensitive drum 1 to the intermediate transfer member 5 based on the recorded value, the voltage is applied while changing the voltage in synchronization with the rotation and position of the intermediate transfer member 5.

The control means of the bias of the intermediate transfer member according to this embodiment will be described in detail below.

(1) The photosensitive drum 1 that rotates by separating the transfer roller 8 from the intermediate transfer member 5 during non-image formation
The surface is uniformly charged by the charging roller 2 to a dark part potential of −700 V, and a bias is applied to the intermediate transfer body 5 while applying a constant-current-controlled DC bias to a predetermined current value I ₄ [μA] by the high-voltage power supply 9. The detection means 10 detects the DC voltage value generated at this time.

At this time, the DC voltage value was continuously recorded, and a curve W ₁ shown in the graph of FIG. 3 was obtained. Above constant current value I ₄
[ΜA] is a preset value necessary for good primary transfer of the toner image formed on the surface of the photosensitive drum 1 to the surface of the intermediate transfer member 5, and in this embodiment, it is set to 3 μA.

(2) A curve W ₁ is applied to the intermediate transfer member 5 by the high voltage power source 9 during the primary transfer in the image forming process.
By applying a primary transfer bias whose voltage is controlled at a constant voltage in the same manner as the waveform of, the toner image of the first color, for example, a yellow image formed on the surface of the photosensitive drum 1 is transferred to the intermediate transfer member 5. Primary transfer is performed on the surface.

(3) Next, the second color toner image formed on the surface of the photosensitive drum 1, for example, a magenta image, and the third color toner image formed on the surface of the photosensitive drum 1, for example, a cyan image, are further exposed. 4 color toner images formed on the drum 1 surface, for example, a black image when each is primarily transferred to the intermediate transfer member 5 surface is given at each stage to the curve W ₁ as shown in the graph of FIG. 3 Curves V ₂ , W ₃ , W _{4 in} which the voltage V _S of each is added to the voltage of each preceding stage
By applying a constant-voltage-controlled primary transfer bias having
Good primary transfer is performed in each case.

In this embodiment, the predetermined voltage V _S is 0.
By setting the voltage to 3 kV, a good transferred image could be obtained.

As the control means for the secondary transfer thereafter, the same method as in Embodiment 1 can be used, but in this embodiment, the following control means was used.

(4) A bias is applied to the intermediate transfer member 5 by constant voltage control in which the constant voltage value is variable in accordance with the waveform of the curve W ₄ determined in (3) above when a non-image is created,
The transfer roller 8 is contacted to the intermediate transfer member 5, while applying a predetermined current value I _t2 [μA] to the constant current controlled DC bias to a high voltage power supply 9 for this case the transfer roller 8, the bias detection unit 10 DC voltage value V generated at this time
Detects _t2 [kV] more than one round of the transfer roller.

The voltage V _t2 [kV] obtained at this time is given a constant d ₁ shown below, and the secondary transfer bias V to be applied to the transfer roller 8 according to the following secondary transfer bias calculation formula (B) set in advance. _The voltage value V obtained by calculating _T2 [kV]
By applying _T2 [kV] to the transfer roller 8 by the high voltage power source 9 during the secondary transfer, the color image formed on the surface of the intermediate transfer member 5 is secondarily transferred onto the surface of the transfer material P.

V _T2 = V _t2 + d ₁ ... (B) In this embodiment, by setting the constant d ₁ to 1.2, a good transferred image can be obtained.

Here, the constant d ₁ is a value determined in consideration of the voltage drop due to the resistance of the transfer material P when the color image formed on the surface of the intermediate transfer member 5 is secondarily transferred to the surface of the transfer material P. is there.

In this embodiment, the secondary transfer bias calculation formula is an addition formula, but the present invention is not limited to this.

The curve W ₁ shown in (1) above may be detected even after the print signal arrives, but the print time becomes long, so the device is reset due to power-on or other reasons. Curve W measured when
₁ is recorded, or the curve W ₁ is recorded in a ROM etc. which is measured at the time of manufacture and only a part of the intermediate transfer member 5 is measured when a print signal is actually received. curve due to the difference in that part of the W ₁ W ₁
It is also possible to shorten the printing time by performing the correction by shifting.

By using the control method as described above, it is preferable even in the case where the resistance is changed due to resistance fluctuation during manufacturing of the intermediate transfer member 5 or the transfer roller 8 or environmental change as in the first embodiment. Transfer can be performed. Particularly, it is possible to obtain a good transferred image without being affected by resistance unevenness or the like that is produced during the manufacture of the intermediate transfer body 5, which has a large outer diameter and where it is difficult to make the resistance constant over the entire area.

In the present embodiment, as in the above embodiment, 1
Next, the voltage of each constant voltage control is determined based on the voltage value when the constant current control is performed in the secondary transfer, but the constant voltage control is performed and the voltage is determined based on the change of the current value at that time. It goes without saying that you can do it.

Third Embodiment Below, a third embodiment according to the present invention will be shown. However, the configuration of the image forming apparatus in this embodiment is the same as that of the first embodiment, and therefore will be omitted. However, it differs from the image forming apparatus of the above-described embodiment in that a conductive roller 14 is additionally provided as shown in FIG. The conductive roller 14 will be described later.

In this embodiment, the same control system as in Embodiment 1 or 2 is used up to the primary transfer from the photosensitive drum 1 to the intermediate transfer member 5, and during the secondary transfer from the intermediate transfer member 5 to the transfer material P. The method of controlling the bias applied to the transfer roller 8 will be described in detail.

(1) One color at a time from the photosensitive drum 1 to the surface of the intermediate transfer body 5 by the voltage determined in the same manner as in the first or second embodiment with the transfer roller 8 being separated from the intermediate transfer body 5. For example, primary transfer is performed in the order of yellow, magenta, cyan, and black.

(2) When the image is not formed or when the image is formed in (1) above, the transfer roller 8 separated from the intermediate transfer member 5 is made of aluminum having an outer diameter of 8 mm and a length equal to or greater than that of the transfer roller 8. the conductive roller 14 is brought into contact, with the application of a direct-current bias which is constant-current controlled to a predetermined value I _t3 [μA] the high voltage power supply 9, detects the DC voltage value V _t3 [kV] which is generated when the the bias detection unit 10 To do. At this time, both or one of the transfer roller 8 and the conductive roller 14 is driven and rotated so that the entire surface of the transfer roller 8 contacts the conductive roller 14.

Further, the detection voltage V _t3 [kV] can be freely determined in the number of times of sampling and the method of determination as in the above embodiment, depending on the situation. In this embodiment, sampling is performed 30 times over the entire circumference of the transfer roller 8 and the average value is detected voltage V.
_{It was set to t3} [kV].

The constant current value I _t3 [μA] is such that the toner image formed on the surface of the intermediate transfer member 5 can be well transferred to the surface of the transfer material P.
It is a preset value required for the next transfer,
In this example, it was set to 3 μA.

(3) The detection voltage V _t3 [kV] obtained in the above (2) and the DC voltage value V ₁ [kV] determined by the same method as in the first embodiment are set to the constant d ₁ shown below. The secondary transfer bias V _T3 [k to be applied to the transfer roller 8 according to a preset secondary transfer bias calculation formula (C).
V] is calculated, and the obtained voltage value V _T3 [kV] is applied to the transfer roller 8 by the high-voltage power supply 9 at the time of secondary transfer to transfer the color image formed on the surface of the intermediate transfer member 5 to the transfer material. Secondary transfer is performed on the surface of P.

V _T3 = V ₁ + V _t3 + d ₁ (C) In this embodiment, by setting the constant d ₁ to 1.2, a good transferred image can be obtained. . Here, d ₁ is a value determined in consideration of the voltage drop due to the resistance of the transfer material P when the color image formed on the surface of the intermediate transfer body 5 is secondarily transferred to the surface of the transfer material P.

By using the control method as described above, it is preferable even when the resistance changes due to resistance fluctuation during manufacturing of the intermediate transfer member 5 or the transfer roller 8 or environmental changes as in the above embodiment. In addition to the fact that the transfer can be performed, the resistance of the transfer roller 8 is measured, which is different from the above embodiment.
The current from the transfer roller 8 does not flow through the intermediate transfer body 5, which has unstable resistance and is not clear, but through a known resistance (especially, a resistance that is negligible compared to the resistance of the transfer roller is desirable). Since it is flown as a flow, there is an advantage that the resistance of the transfer roller 8 can be reliably measured.

[0076]

As is apparent from the above description, the image forming apparatus according to the present invention applies a bias between the first image carrier and the second image carrier during non-image formation,
By measuring the voltage-current characteristics of the second image carrier and storing the voltage-current characteristics, the resistance of the second image carrier or the transfer means at the time of manufacture does not depend on the fluctuation of the resistance value or the environmental fluctuation. To
It is possible to prevent the occurrence of transfer failure, the occurrence of transfer omission, and the occurrence of photoconductor memory or punch-through of the first image carrier. Therefore, a high-quality image can be obtained, the life of the first image carrier can be extended, and the running cost of the apparatus can be reduced.

In another embodiment of the image forming apparatus according to the present invention, the image forming apparatus has a conductor that contacts the transfer means, and a bias is applied between the transfer means and the conductor to obtain a voltage / current of the transfer means. By measuring the characteristics and also storing the voltage-current characteristics, the same effect as described above can be obtained.

[Brief description of drawings]

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

FIG. 2 is a configuration diagram of a photosensitive drum, an intermediate transfer member, and a transfer roller according to the present invention.

FIG. 3 is a detection voltage graph of Example 2.

FIG. 4 is a schematic configuration diagram showing a third embodiment of the image forming apparatus according to the present invention.

FIG. 5 is a schematic configuration diagram showing an example of a conventional image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum (first image carrier) 5 Intermediate transfer member (second image carrier) 8 Transfer roller (transfer means) 14 Conductive roller (conductor)

Front page continuation (72) Inventor Tatsunori Ishiyama 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroyuki Oba 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Kazuo Suzuki 1998-1 Yamada, Chichibu City, Saitama Prefecture

Claims (8)

[Claims] 1. A surface of a rotatable second image carrier, which visualizes a first electrostatic latent image formed on the surface of a rotatable first image carrier with a developer of a first color. After the electrostatic transfer to the surface, the process is repeated a plurality of times to form a color image by the developers of a plurality of colors on the surface of the second image carrier, and the color image is conveyed to the transfer site. In an image forming apparatus that performs a batch transfer by a transfer unit, a bias is applied between the first image carrier and the second image carrier during non-image formation so that the voltage-current characteristic of the second image carrier is An image forming apparatus, which measures and stores the voltage-current characteristic. 2. A voltage applied to the second image carrier is determined based on the voltage-current characteristic of the second image carrier, and the second image carrier is determined by constant voltage control during image formation. The image forming apparatus according to claim 1, wherein a voltage is applied. 3. A voltage-current characteristic of the transfer means is measured by applying a bias to the transfer means while the voltage is applied to the second image carrier, and the voltage-current characteristic is stored. The image forming apparatus according to claim 2. 4. The image forming apparatus according to claim 3, wherein the voltage applied to the second image carrier is determined based on a voltage-current characteristic of the second image carrier measured in advance. 5. The voltage-current characteristic of the second image carrier is measured for at least one revolution of the second image carrier, the fluctuation of the voltage-current characteristic is measured, and the second voltage is measured according to the fluctuation. 5. The image forming apparatus according to claim 1, wherein the voltage applied to the image carrier is changed. 6. The one of the voltage-current characteristics of the second image carrier.
The distribution of the circumference is measured in advance, the voltage-current characteristic of a part of the second image carrier is measured immediately before the image formation, and the second image carrier is measured by the measured value and the voltage-current characteristic distribution. The image forming apparatus according to claim 1, wherein the applied voltage is changed. 7. A surface of a rotatable second image carrier, which visualizes a first electrostatic latent image formed on the surface of a rotatable first image carrier with a developer of a first color. After the electrostatic transfer to the surface, the process is repeated a plurality of times to form a color image by the developers of a plurality of colors on the surface of the second image carrier, and the color image is conveyed to the transfer site. In the image forming apparatus for performing the batch transfer by the transfer unit, a conductor is provided in contact with the transfer unit, a bias is applied between the transfer unit and the conductor, and a voltage-current characteristic of the transfer unit is measured. An image forming apparatus, which also stores the voltage-current characteristic. 8. The voltage applied to the second image carrier is determined based on the voltage-current characteristic of the transfer means, and the determined voltage is applied to the second image carrier by constant voltage control during image formation. The image forming apparatus according to claim 7, characterized in that.