JP2001117390A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the discharge drop-out of a toner image transferred onto a recording medium and to prolong the life of a contact transfer member. SOLUTION: This image forming device has an image carrying member 1 on which the toner image T meeting image information is formed and carried, the contact transfer member 2 which is arranged to face this image carrying member 1 and a transfer bias impressing means 3 which impresses a transfer bias to transfer the toner image T on the image carrying member 1 to the recording medium K via the contact transfer member 2. The contact transfer member 2 described above is composed of a material including ion conductivity. The image forming device described above includes a transfer bias control means 4 which controls the bias impressing quantity of the transfer bias impressing means 3 in accordance with the ion dissociation quantity information relating to the ion quantity dissociating from the contact transfer member 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for transferring a toner image formed on an image carrier onto a recording medium, and more particularly, to a method for transferring a toner image from the image carrier to a recording medium. The present invention relates to an image forming apparatus of a type performed by transfer.

[0002]

2. Description of the Related Art Conventionally, for example, as an intermediate transfer type image forming apparatus, a photosensitive drum on which a toner image corresponding to an electrostatic latent image is formed, and a toner image on the photosensitive drum are intermediately transferred. An intermediate transfer belt, a primary transfer device for transferring the toner image on the photosensitive drum to the intermediate transfer body, and a secondary transfer device for collectively secondary transferring the toner image transferred on the intermediate transfer belt to paper A device provided with a transfer device is known. Here, as the primary transfer device, for example, a transfer roll or the like that is arranged in contact with the intermediate transfer belt is used. The transfer roll forms an electric field between the photosensitive drum and the intermediate transfer belt to move the toner image on the photosensitive drum toward the intermediate transfer belt.

[0003] As such a transfer roll,
An electron conductive filler such as carbon or metal oxide dispersed in a base material made of resin or rubber, or an ion conductive material such as a polar rubber such as hydrin rubber or a metal ion salt is dispersed in the base material. One is known (see JP-A-7-248669).

[0004] Here, the former type in which the electron conductive type filler is dispersed has an advantage that the change in electric resistance due to environmental changes is small, but the electric conductive type filler is liable to agglomerate. There is a problem that it varies. On the other hand, the latter type, in which the ion conductive substance is dispersed, has an advantage that the dispersion of the electric resistance can be extremely reduced because the ion conductive substance can be dispersed at the molecular level with respect to the base material. However, there is a problem that it is difficult to set the transfer parameters and the like because the amount of change in the electrical resistance due to the environment, particularly the humidity, is large.

Therefore, a transfer roll (hereinafter referred to as a hybrid transfer roll) has been proposed in which an electron conductive filler and an ion conductive material are dispersed in a base material to obtain preferable characteristics of both. (See JP-A-10-254215).

[0006]

However, even if the above-described hybrid transfer roll is employed, the electric resistance increases with time, and the voltage applied to the hybrid transfer roll, that is, the transfer voltage, increases, so that the intermediate transfer is performed. There has been a technical problem that a phenomenon in which toner on the belt scatters (so-called discharge omission) occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned technical problems, and suppresses an increase in electric resistance of a contact transfer member with time to thereby transfer a toner image transferred onto a recording medium. An object of the present invention is to provide an image forming apparatus capable of preventing the discharge of the contact transfer member and extending the life of the contact transfer member.

[0008]

The present inventor studied various parameters to prevent the resistance of the contact transfer member from increasing over time. The inventors examined the amount of ions detached from the contact transfer member and the electric current. The present inventors have found out that there is a correlation between the increase in resistance and that there is a condition under which ions are easily detached from the contact transfer member, and have devised the present invention.

That is, in a first embodiment of the present invention, as shown in FIG. 1, an image carrier 1 on which a toner image T corresponding to image information is formed and carried, and the image carrier 1 is disposed to face the image carrier 1. A contact transfer member; and a transfer bias applying unit for applying a transfer bias for transferring the toner image on the image carrier to the recording medium via the contact transfer member; In the image forming apparatus in which the material 2 has ion conductivity, the bias application amount of the transfer bias applying unit 3 is controlled based on the ion detachment amount information relating to the ion detachment amount from the contact transfer member 2. And a transfer bias control unit 4.

In such technical means, the image carrier 1 includes not only a latent image carrier such as a photosensitive drum but also an intermediate transfer member such as an intermediate transfer belt. The recording medium K includes not only a final recording medium such as paper, but also an intermediate transfer member such as an intermediate transfer belt.

As for the ion detachment amount, the amount of ions detached from the contact transfer member 2 may be actually measured. However, from the viewpoint of simplification of the configuration, the ion detachment amount and the image carrier and the image carrier may be measured. It is preferable to use the fact that there is a correlation with the amount of the recording medium passing between the contact transfer member and estimate the ion detachment amount based on the amount of the recording medium.

Further, from the same viewpoint, utilizing the fact that there is a correlation between the ion detachment amount and the transfer bias application time to the contact transfer member 2, the ion transfer is performed based on the transfer bias application time. The withdrawal amount may be estimated. Further, from the same viewpoint, the fact that there is a correlation between the ion detachment amount and the resistance value of the contact transfer member 2 may be used, and the ion detachment amount may be estimated based on this resistance value.

The amount of ions released from the contact transfer member 2 is correlated with the surrounding environmental conditions, and increases particularly when a high voltage is applied in a high temperature and high humidity environment. Therefore,
According to a second aspect of the present invention, as shown in FIG. 1, an image carrier 1 on which a toner image T corresponding to image information is formed and carried, and a contact transfer member 2 arranged to face the image carrier, Transfer bias applying means 3 for applying a transfer bias for transferring the toner image T on the image carrier 1 to the recording medium K via the contact transfer member 2; and the contact transfer member 2 has ion conductivity. In the image forming apparatus made of a material having a different material, the amount of bias applied by the transfer bias applying unit 3 is controlled based on environmental information on the surrounding temperature and humidity so that the detachment of ions from the contact transfer member 2 is suppressed. And a transfer bias control unit 4.

In such technical means, the image carrier 1 includes not only a latent image carrier such as a photosensitive drum but also an intermediate transfer member such as an intermediate transfer belt. The recording medium K includes not only a final recording medium such as paper, but also an intermediate transfer member such as an intermediate transfer belt.

The transfer bias control means 4 may be appropriately selected as long as it controls the amount of bias applied by the transfer bias application means 3 so that the detachment of ions from the contact transfer member 2 is suppressed. For example, there is a method in which constant current control is performed under a condition where both humidity and temperature are less than a predetermined value, and constant voltage control is performed under a condition where at least one of humidity or temperature is equal to or more than the predetermined value. No. Further, as another method,
For example, the constant current control is performed under the condition that both the humidity and the temperature are less than a predetermined value, and the voltage applied to the contact transfer member under the condition that at least one of the humidity and the temperature is a predetermined value or more. May be provided with an upper limit.

In the first and second embodiments of the present invention, the contact transfer member 2 may be appropriately selected as long as it has ion conductivity. It does not exclude those having the type. In consideration of the stability of the electrical resistance over time, the contact transfer member 2 may be formed of a mixture of a material having ion conductivity and a material having electron conductivity. Is preferred.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the accompanying drawings. First Embodiment FIG. 2 shows a first embodiment of a color image forming apparatus to which the present invention is applied. In the figure, a color image forming apparatus according to the present embodiment includes a plurality of image forming units 100 (specifically, 100K, 100Y, 100M, and 100C) on which respective color component toner images are formed by an electrophotographic method.
And an intermediate transfer belt 110 as a recording medium for sequentially transferring (primary transfer) each color component toner image formed by each image forming unit 100, and an intermediate transfer belt 110
A collective transfer device 120 for collectively transferring (secondarily transferring) the superimposed image transferred thereon to the sheet 117;
Cleaner 140 for removing residual toner on the belt 10
And a fixing device 150 for fixing the batch-transferred images on the sheet 117.

In the present embodiment, the image forming unit 100 for each color component (specifically, 100K, 100Y,
00M, 100C) are a uniform charger 102 on which the photosensitive drum 101 is charged, and a laser exposure device on which an electrostatic latent image is written on the photosensitive drum 101, around the photosensitive drum 101 as an image carrier. 103, a developing device 104 in which each color component toner is stored and the electrostatic latent image on the photosensitive drum 101 is visualized, and a contact in which each color component toner image on the photosensitive drum 101 is transferred to the intermediate transfer belt 110 An electrophotographic device such as a primary transfer roll 105 as a transfer member and a cleaner 106 for removing residual toner and the like on the photosensitive drum 101 are sequentially arranged. And
As shown in FIG. 3, a transfer bias power supply 107 (specifically, a positive DC bias is applied to the primary transfer roll 105 (specifically, 105K, 105Y, 105M, 105C) of each image forming unit 100. Has 107
K, 107Y, 107M, 107C). Each of these transfer bias power supplies 107 can change an applied voltage, and can be used as a current source and also as a constant voltage source.

Further, as shown in FIG. 2, the intermediate transfer belt 110 is stretched over a plurality of (six in the present embodiment) support rolls 131 to 136. Here, the support roll 131 is a drive roll of the intermediate transfer belt 110, the support rolls 132 and 135 are driven rolls, and the support roll 133 is a correction roll (a steering roll) for regulating meandering in a direction substantially perpendicular to the moving direction of the intermediate transfer belt 110. : Provided so as to be tiltable with one end in the axial direction as a fulcrum), support roll 1
Reference numeral 34 denotes a backup roll of the collective transfer device 120 and a support roll 136 denotes an idler roll used for positioning the intermediate transfer belt 110 and forming a flat secondary transfer surface, as described later.

The intermediate transfer belt 110 is made of a resin such as polyimide, polycarbonate, polyester, polypropylene, polyethylene terephthalate or various rubbers containing an appropriate amount of carbon black or the like, and has a volume resistivity of 10 ⁶ to 10 ¹⁵ Ω · cm. And its thickness is set to 0.1 mm.

Further, the collective transfer device 120 includes a secondary transfer roll 113 which is disposed in pressure contact with the toner carrying surface of the intermediate transfer belt 110 and a secondary transfer roll 113 which is disposed on the back side of the intermediate transfer belt 110. A backup roll 114 (also used as a support roll 134) serving as an electrode is provided, and a power supply roll 115 to which a bias having the same polarity as the charged polarity of the toner is stably applied is abutted on the backup roll 114. On the exit side of the nip area of the secondary transfer roll 113, a peeling member 121 is disposed.

In the present embodiment, the backup roll 114 is made of EPDM (ethylene propylene diene rubber) having a two-layer structure in which a foamed elastic material layer and an outer conductive layer are coated on the outer periphery of a metal core material. Was. The outer conductive layer is a semiconductive EPDM foam rubber in which carbon black is dispersed at 15 to 35% by weight, and the thickness of the conductive layer is 0.5 to 1.5.
mm, and its surface resistivity is 10 ⁷ to 10
It is controlled in the resistance area of ¹⁰ Ω / □.

Further, the secondary transfer roll 113 is provided with a carbon black having a thickness of 5 to 20 μm via a skin layer on a core layer made of a metal core material and a carbon black dispersed and foamed EPDM material fixed around the metal core material. One having a coating layer made of a dispersed fluororesin-based material was used. The volume resistivity between the metal core and the coating layer is 1
0 ⁴ [Omega] cm is to 10 ⁶ [Omega] cm, also roll hardness is 45 ° to 20 ° in Asker C hardness.

The secondary transfer roll 113 is provided with a cleaning blade 122 made of, for example, urethane rubber, and removes stains attached to the secondary transfer roll 113 to prevent the back surface of the paper 117 from being stained. Further, between the collective transfer device 120 and the belt cleaner 140, there is provided a static eliminator 112 for removing residual charges of the intermediate transfer belt 110 before the cleaning process.

Further, in the present embodiment, the paper transport system feeds the paper 117 from the paper tray 116 to the secondary transfer position at a predetermined timing, and transports the paper 117 after the secondary transfer. The sheet is guided to a belt 118, and is conveyed to the fixing device 150 by the conveyance belt 118.

Next, the primary transfer roll 105 will be described in detail. In the present embodiment, the primary transfer roll 1
Reference numeral 05 denotes a conductive core material whose outer periphery is coated with a conductive foamed elastic body. The conductive foamed elastic body has a sea-island structure of three types of rubbers having different solubility parameter values, and two types of carbon blacks having different oil absorbing properties are dispersed therein. In the present embodiment, the three types of rubbers having different solubilities are NBR (nitrile butadiene rubber), EPDM (ethylene propylene diene rubber), and rubber having a solubility parameter value intermediate between those rubbers. For example, CR (chloroprene) or SBR (styrene butadiene rubber). Ketjen black and thermal black are particularly preferable as the carbon blacks having different oil absorbing properties. As described above, in the present embodiment, the primary transfer roll 105 has ion conductivity by the NBR rubber (polar rubber) and electron conductivity by the carbon black.

The volume resistivity of the primary transfer roll 105 is from 10 ^7.5 Ωcm ( ^7.5 log Ωcm) to 10 ⁹ Ωcm.
(9 log Ωcm). The present inventors investigated the relationship between the volume resistivity of the primary transfer roll 105 and the obtained image, and obtained the results shown in FIG. According to this, when the volume resistance value is less than 7.5 log Ωcm, the applied voltage is too low, and a transfer failure occurs.
From the above, it can be seen that the applied voltage is too high and the discharge phenomenon occurs due to the discharge phenomenon. Therefore, the primary transfer roll 105
Is preferably selected from the above range.

Further, using the primary transfer roll 105,
The paper P was passed through while applying a transfer bias by each transfer bias power supply 107, and the temporal change in the volume resistivity of the primary transfer roll 105 was examined. The result shown in FIG. 5 was obtained. Here, the applied current from each transfer bias power supply 107 is always constant irrespective of the number of sheets passed and environmental fluctuations. According to this, it was confirmed that the volume resistivity of the primary transfer roll 105 was increased by approximately one digit by passing 200 kpv (200,000 sheets). Therefore, even if the volume resistivity of the primary transfer roll 105 at the start of running, that is, at the initial stage, is 9 log Ωcm, the volume resistivity exceeds 9 log Ωcm with the passage of time, and a discharge phenomenon occurs due to a discharge phenomenon. Will do. Therefore, in the present embodiment, 7.5 lo
The primary transfer roll 105 having a volume resistivity of gΩcm is used.

This is because the NBR component having ion conductivity is ion-exchanged as the number of sheets passed increases, and the volume resistivity increases due to the characteristics of carbon black having electron conductivity as the number of sheets passed increases. It is estimated that In this embodiment, since such ion exchange is actively performed when the transfer bias applied to the primary transfer roll 105 is a high voltage under a high-temperature and high-humidity environment, FIG. As shown, a control device 200 for controlling the transfer bias of each transfer bias power supply 107 according to the environmental conditions is provided. In the figure, the temperature detection signal from the temperature sensor 161 and the humidity detection signal from the humidity sensor 162 are transmitted through the input interface 201 to C.
PU 202, CPU 202 then, RO
After executing a control program stored in advance in M203 and appropriately performing data processing with the RAM 204, the black transfer bias power supply 107K, the yellow transfer bias power supply 107Y,
A bias control signal is sent to each of a magenta transfer bias power supply 107M and a cyan transfer bias power supply 107C.

Next, an image forming process of the color image forming apparatus according to the present embodiment will be described. Now, when a start switch (not shown) is turned on, a predetermined image forming process is executed. More specifically, for example, when the color image forming apparatus is configured as a digital color copying machine, a document set on a document table (not shown) is read by a color image reading device, and the read signal is read by an image signal processing unit. , And temporarily store the digital image signals in a memory. Based on the stored digital image signals of four colors (K, Y, M, and C), toner images of each color are formed. .

That is, the image forming unit 1 according to the digital image signal of each color inputted from the image signal processing means.
00 (specifically, 100K, 100Y, 100M, 10
0C) are respectively driven. Then, each image forming unit 1
At 00, an electrostatic latent image corresponding to the digital signal is written on the photosensitive drum 101 uniformly charged by the uniform charger 102 by the laser exposure device 103, respectively. And
Each of these electrostatic latent images is developed by the developing device 104 containing the toner of each color to form a toner image of each color. When this color image forming apparatus is configured as a device such as a printer, it is only necessary to form toner images of each color based on an image signal input to the image signal processing means from the outside.

The toner image formed on each photosensitive drum 101 is transferred to a primary transfer roll 10 at a primary transfer position where each photosensitive drum 101 contacts the intermediate transfer belt 110.
5, the image is sequentially transferred from the photosensitive drum to the surface of the intermediate transfer belt 110.

The toner image primarily transferred onto the intermediate transfer belt 110 in this manner is superimposed on the intermediate transfer belt 110, and is conveyed to the secondary transfer position as the intermediate transfer belt 110 rotates. On the other hand, the paper 117 is supplied to the secondary transfer position at a predetermined timing, and the secondary transfer roll 113 is
Nip.

Then, at the secondary transfer position, the transfer electric field formed between the secondary transfer roll 113 as the batch transfer device 120 and the backup roll 114 causes
The toner image carried on the intermediate transfer belt 110 is
17 are collectively transferred. The sheet 117 to which the toner image has been transferred is conveyed to the fixing device 150 by the conveyance belt 118, and the toner image is fixed. Further, the intermediate transfer belt 110 after the secondary transfer has a residual charge removed by the charge eliminator 112, and the intermediate transfer belt 11 after the secondary transfer.
The toner remaining on 0 is cleaned by the belt cleaner 140.

Next, the control of the transfer bias for each primary transfer roll 105 by the control device 200 will be described in detail with reference to the flowchart shown in FIG. When image formation is started, first, constant current control is started. For example, a constant current of 25 μA is supplied to each primary transfer roll 105. When the temperature detection signal from the temperature sensor 161 and the humidity detection signal (temperature and humidity sensor information) from the humidity sensor 162 are input, and the temperature is 26 ° C. or more,
Alternatively, if the humidity is 55% or more, it is determined that the environment is such that ions are easily detached from the primary transfer roll 105, and a high voltage is not applied to the primary transfer roll 105.
Specifically, each transfer bias power supply 107 is controlled so that the upper limit (voltage limiter) of the voltage applied to each primary transfer roll 105 is set to 3 kV. That is, the voltage is 3 k
The constant current control is executed until the voltage reaches V, and when the voltage becomes 3 kV, the control is switched to the constant voltage control for applying 3 kV. On the other hand, when the temperature and the humidity do not satisfy the above conditions, each transfer bias power supply 107 is controlled to continue the constant current control.

After the voltage limiter is set, the temperature detection signal from the temperature sensor 161 and the humidity detection signal (temperature and humidity sensor information) from the humidity sensor 162 are input again, and the temperature is lower than 26 ° C. 55% humidity
The control of the transfer bias is continued in a state where the voltage limiter is set until the value becomes less than the value, that is, until the environment in which the ions are not easily detached from the primary transfer roll 105 is set. on the other hand,
When the above condition is satisfied, the control is switched to the constant current control again.

In the present embodiment, by avoiding a situation in which a high voltage is applied to the primary transfer roll 105 under high temperature or high humidity conditions, it is possible to prevent a large amount of ions from being detached from the primary transfer roll 105. With this configuration, it is possible to avoid an increase in resistance of the primary transfer roll 105 and a discharge omission associated with the increase, and at the same time, to extend the life of the primary transfer roll 105.

In this embodiment, the temperature and humidity at which the voltage limiter is operated are set to 26 ° C. and 55%, respectively. However, the present invention is not limited to this. It may be changed as appropriate depending on the situation. Further, in the present embodiment, the voltage limiter is set to 3 kV. However, the present invention is not limited to this. The voltage limiter may be appropriately changed depending on the material of the primary transfer roll 105 and the like. Also, the value of the voltage limiter is not limited to one, and it is a matter of course that a plurality of values may be set according to temperature, humidity, and the like. When the secondary transfer roll 113 is made of a material having ion conductivity, the transfer bias applied to the secondary transfer roll 113 may be controlled similarly to the primary transfer roll 105. Of course.

Embodiment 2 The present embodiment is almost the same as Embodiment 1, but as shown in the flowchart of FIG. 8, under the condition that the temperature is 26 ° C. or more or the humidity is 55% or more. This is to switch to complete constant voltage control. At this time, the transfer bias from each transfer bias power supply 107 is uniformly set to, for example, 2.5 kV. Also in the present embodiment, it is possible to avoid a situation in which a high voltage is applied to the primary transfer roll 105 under high temperature or high humidity conditions, so that a large amount of ions are prevented from being detached from the primary transfer roll 105. Therefore, it is possible to avoid an increase in resistance of the primary transfer roll 105 and a discharge omission associated with the increase, and at the same time, to extend the life of the primary transfer roll 105.

Embodiment 3 The present embodiment is almost the same as Embodiment 1, except that the number of sheets 117 (the number of sheets passed) passing through the collective transfer device 120 is counted. The control of the transfer bias applied to the primary transfer roll 105 is started from the time when the predetermined number of sheets is reached.

In the present embodiment, in addition to the temperature detection signal from the temperature sensor 161 and the humidity detection signal from the humidity sensor 162, the controller 200 includes a batch transfer device 120 as shown by a broken line in FIG. Paper passing through
A print number signal is input from a print counter 163 that counts the number of prints. This print number signal is for transmitting the cumulative number of sheets since the last time the primary transfer roll 105 was replaced.

In the present embodiment, the number-of-prints signal from the print counter 163 is 100 kpv (10
Constant current control until 10k
After that, control similar to that of the first embodiment, that is, control for setting the voltage limiter (3 kV) under high temperature or high humidity conditions is performed.

The inventor of the present invention carried out paper passing at 200 kpv using the image forming apparatus according to the present embodiment, and examined the change over time in the volume resistivity of the primary transfer roll 105.
The result shown by the solid line in FIG. 10 was obtained. Here, the broken line portion shows the result (shown in FIG. 5) in the comparison mode. From the figure, it is understood that in the image forming apparatus according to the present embodiment, the increase in the resistance of the primary transfer roll 105 is suppressed from the time when it exceeds 100 kpv, that is, when the control of the transfer bias is started.

In the present embodiment, constant current control is always performed until the number of sheets P passed is 100 kpv, so that a very good image can be obtained in this range. Then, from the point of time exceeding 100 kpv, the primary transfer roll 10 is heated under high temperature or high humidity conditions.
5 can be avoided, so that a large amount of ions can be prevented from detaching from the primary transfer roll 105, and the primary transfer roll 10
5 can be avoided and the discharge omission associated with the increase in resistance can be avoided, and at the same time, the life of the primary transfer roll 105 can be extended.

Instead of the print number signal from the print counter 163, as shown by a dashed line in FIG.
The control may be performed based on an energization time signal from an energization time counter 164 that integrates the energization time to the primary transfer roll 105.

Embodiment 4 This embodiment is almost the same as Embodiment 1, except that the amount of desorbed ions is estimated by measuring the resistance of the primary transfer roll 105 at the start of image formation. The transfer bias is controlled.

In the control device 200 according to the present embodiment, as shown in FIG. 11, a resistance detection signal from a resistance measuring device 165 for measuring the resistance of the primary transfer roll 105 is taken into the CPU 202 via the input interface 201. Next, the CPU 202 executes a control program stored in the ROM 203 in advance, performs appropriate data processing with the RAM 204, and outputs
A bias control signal is sent to each of the black transfer bias power supply 107K, the yellow transfer bias power supply 107Y, the magenta transfer bias power supply 107M, and the cyan transfer bias power supply 107C via the control unit 05.

Next, the control of the transfer bias for each primary transfer roll 105 by the control device 200 will be described in detail with reference to the flowchart shown in FIG. When image formation is started, first, the resistance detection mode is started. Specifically, a predetermined current (2 in this embodiment) is applied to the primary transfer roll 105 by each transfer bias power supply 107.
5 μA) is applied, and a voltage induced in the primary transfer roll 105 is measured, and this voltage is input to the control device 200 as a resistance detection signal. And the voltage is 1.5
If the voltage is equal to or higher than kV, it is determined that ions have been detached from the primary transfer roll 105 and the resistance has been increased (see FIG. 4), and specifically, a high voltage is not applied to the primary transfer roll 105. Each transfer bias power supply 107 is controlled so that the upper limit (voltage limiter) of the voltage applied to the primary transfer roll 105 is set to 3 kV. That is, the constant current control is performed until the voltage becomes 3 kV, and the voltage becomes 3 kV.
At this point, the control is switched to the constant voltage control of applying 3 kV. On the other hand, when the voltage does not satisfy the above condition, each transfer bias power supply 107 is controlled so as to always execute the constant current control.

In this embodiment, the primary transfer roll 105
As the resistance is increased, the voltage applied to the primary transfer roll 105 is limited.
05, the resistance of the primary transfer roll 105 can be extended.

[0050]

As described above, according to the present invention,
By delaying the escape of ions from the contact transfer member as much as possible, the increase in the electrical resistance of the contact transfer member with time is suppressed, so that the discharge of the toner image transferred onto the recording medium is prevented, and The life of the contact transfer member can be extended.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating an outline of an image forming apparatus according to the present invention.

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

FIG. 3 is an enlarged view of a primary transfer device of the image forming apparatus according to the first embodiment.

FIG. 4 is a graph showing a relationship between an applied current applied to a primary transfer roll and an induced voltage.

FIG. 5 is a graph showing the relationship between the number of sheets passed and the volume resistivity of the primary transfer roll.

FIG. 6 is a block diagram of a control device according to the first to third embodiments.

FIG. 7 is a flowchart showing a control flow according to the first embodiment.

FIG. 8 is a flowchart showing a control flow according to the second embodiment.

FIG. 9 is a flowchart showing a control flow according to the third embodiment.

FIG. 10 is a graph showing a relationship between a primary transfer roll and a volume resistivity in an image forming apparatus according to a third embodiment.

FIG. 11 is a block diagram of a control device according to a fourth embodiment.

FIG. 12 is a flowchart showing a control flow according to the third embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image carrier, 2 ... Contact transfer member, 3 ... Transfer bias application means, 4 ... Transfer bias control means, K ... Recording medium, 1
01 photoconductor drum, 105 primary transfer roll, 107
... Transfer bias power supply, 110 ... Intermediate transfer belt, 113
... secondary transfer roll, 114 ... backup roll, 12
0: Batch transfer device, 161: Temperature sensor, 162: Humidity sensor, 163: Print counter, 164: Power-on time counter, 165: Resistance measuring device, 200: Control device

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masao Okubo 2274 Hongo, Fuji Xerox Co., Ltd., Ebina City, Kanagawa Prefecture (72) Inventor Masaaki Takahashi 2274 Hongo, Ebina City, Kanagawa Prefecture, Fuji Xerox Co., Ltd. (72) Inventor Yoko Miyamoto 2274 Hongo, Ebina-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Makoto Katayama 2274 Hongo, Ebina-shi, Kanagawa Prefecture Fuji Xerox Co., Ltd.F-term (reference) ED24 EE07 EF09 2H032 AA05 AA15 BA09 BA18 CA02 CA14

Claims (8)

[Claims] An image carrier on which a toner image corresponding to image information is formed and supported; a contact transfer member arranged to face the image carrier; and a toner on the image carrier via the contact transfer member. An image forming apparatus comprising: a transfer bias applying unit for applying a transfer bias for transferring an image to a recording medium; wherein the contact transfer member is made of a material having ion conductivity; An image forming apparatus comprising: a transfer bias control unit configured to control a bias application amount of the transfer bias application unit based on ion detachment amount information regarding an amount of ions to be transferred. 2. The image forming apparatus according to claim 1, wherein the ion detachment amount is estimated based on an amount of a recording medium passing between the image carrier and the contact transfer member. Image forming apparatus. 3. The image forming apparatus according to claim 1, wherein the ion detachment amount is estimated based on a transfer bias application time to the contact transfer member. 4. The image forming apparatus according to claim 1, wherein the ion detachment amount is estimated based on a resistance value of the contact transfer member. 5. An image carrier on which a toner image corresponding to image information is formed and carried; a contact transfer member disposed to face the image carrier; and a toner on the image carrier via the contact transfer member. An image forming apparatus comprising: a transfer bias applying unit for applying a transfer bias for transferring an image to a recording medium; wherein the contact transfer member is made of a material having ion conductivity. An image forming apparatus comprising: a transfer bias control unit that controls a bias application amount of the transfer bias application unit so as to suppress detachment of ions from the contact transfer member based on information. 6. The image forming apparatus according to claim 5, wherein the transfer bias control unit performs a constant current control under a condition that both the humidity and the temperature are less than a predetermined value. An image forming apparatus, wherein constant voltage control is performed under a condition where one of them is equal to or more than the predetermined value. 7. The image forming apparatus according to claim 5, wherein the transfer bias control unit performs a constant current control under a condition that both the humidity and the temperature are less than a predetermined value. An image forming apparatus, wherein an upper limit is set for a voltage applied to the contact transfer member under a condition that one of them is equal to or more than a predetermined value. 8. The image forming apparatus according to claim 1, wherein the contact transfer member is made of a mixture of a material having ion conductivity and a material having electron conductivity. An image forming apparatus comprising: