JPH10293481A - Transfer member and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always stably output an excellent image without sand mark or image irregularity by executing optimum transfer voltage control in an interpaper stage without extending an interval between paper and paper in a continuous printing mode, consequently, without lowering throughput in the image forming device of a transfer system using a contact and rotary type transfer member. SOLUTION: The transfer member 9 is an ion conductive system member, and its resistance value distribution is <=1.5 in a rotating direction, and its surface roughness Ra is <=5 μm. Impressed transfer voltage control that the resistance value of the transfer member 9 is measured and voltage impressed on the transfer member 9 is controlled in accordance with the measured result of the resistance value is properly executed in the interpaper stage where the leading edge of the next material to be recorded P reaches a transfer part after the trailing edge of the first material to be recorded P passes through the transfer part when the material to be recorded P is continuously fed to the transfer part T and the image is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image bearing device in which a recording material (paper or the like) is held in contact with an image carrier, a voltage is applied, and a recording material (paper, etc.) is nipped and conveyed at a transfer portion which is a nip portion with the image carrier. The present invention relates to a contact-type / rotation-type transfer member for electrostatically transferring a transferable image on a body side to a recording material side, and an image forming apparatus including the transfer member.

[0002]

2. Description of the Related Art For example, an image forming apparatus such as a transfer type electrophotographic copying machine or an LBP (laser beam printer)
An electrophotographic photoreceptor (hereinafter, referred to as a photoreceptor drum) as an image carrier, generally a rotating drum type, is used as a transferable image corresponding to target image information by an image forming process means of charging, image exposure and development. The toner image is formed and carried, and the toner image is transferred to a recording material side by a transfer unit, and the recording material is introduced into a fixing unit, and the toner image is thermally fixed as a permanently fixed image on the surface of the recording material. Image formation (copy, print)
Output. After the transfer of the toner image onto the recording material, the surface of the photoreceptor drum is subjected to removal of residual contaminants such as transfer residual toner and paper dust, is cleaned, and is repeatedly subjected to image formation.

As a means for transferring a toner image from a photosensitive drum to a recording material, there is an advantage that the conveyance path of the recording material is simplified and can be stabilized. A contact / rotational type in which a voltage is applied and a recording material is nipped and conveyed at a transfer portion which is a nip portion with the photoconductor drum, and a toner image on the photoconductor drum is electrostatically transferred to the recording material side. The transfer member using a transfer member, in general, a transfer roller has been widely used.

As a transfer roller proposed in recent years, generally, an elastic layer is provided on a metal core, the elastic layer is made conductive, and a bias having a polarity opposite to that of toner is applied to the metal core. The toner image on the photosensitive drum is sequentially and electrostatically transferred to the surface of the recording material which is nipped and conveyed at the transfer portion.

The transfer roller has a resistance value of 1 × 10 ⁶ to 1
Although it is adjusted to a value of about × 10 ¹⁰ Ω, it is known that the resistance of the transfer roller tends to fluctuate in accordance with the temperature and humidity of the atmospheric environment. Cause the occurrence of.

Therefore, in order to prevent the occurrence of transfer failures and paper marks due to fluctuations in the resistance of the transfer roller, the resistance of the transfer roller is measured, and the transfer applied to the transfer roller according to the resistance measurement result. “Applied transfer voltage control” for appropriately controlling the voltage is adopted.

An example of such an applied transfer voltage control is ATVC control (Active Transfer Voltage Control) disclosed in Japanese Patent Application Laid-Open No. 2-123385.

The ATVC control is a means for optimizing a transfer bias applied to a transfer roller at the time of transfer, and prevents transfer failure and occurrence of paper marks. The transfer bias applies a desired constant current bias to the photosensitive drum from the transfer roller during the pre-rotation process of the image forming apparatus, detects the resistance of the transfer roller from the bias value at that time, and performs the transfer during the printing process. A transfer bias according to the resistance value is applied to the transfer roller.

[0009] The above control is made more sophisticated by Japanese Patent Application Laid-Open No. 2-264278.
This is TVC control. This is a voltage obtained by multiplying the hold voltage obtained at the time of constant current control before the recording material arrives at the transfer portion by a certain coefficient R, and intends to perform constant voltage control when the recording material reaches the transfer portion. By selecting this coefficient R, it is intended to obtain a more appropriate transfer current.

That is, the bias applied to the transfer member is calculated from a voltage generated when a constant current is applied to the transfer member by the constant current control from the power supply when the recording material does not exist at the transfer portion, by a control formula set in advance. So-called ATV
This is a voltage value determined by the C control method.

FIG. 7 is a view showing a general image forming process operation process of the image forming apparatus.

A. Pre-multi-rotation process When the main power switch of the image forming apparatus is turned on, the main motor of the apparatus is driven to rotate the photosensitive drum, and the heater of the fixing apparatus is energized to start heating, thereby preparing necessary process equipment. This is a start-up (start-up) operation period (warming period) of the apparatus for executing the operation.

When the temperature of the fixing device rises to a predetermined temperature at which a toner image can be fixed, the driving of the main motor is temporarily stopped, the rotation of the photosensitive drum is stopped, and the apparatus receives a print start signal. Until the standby state is maintained. During this time, the temperature of the fixing device is adjusted to a predetermined temperature.

B. Pre-rotation process This is a period in which the main motor is driven again by the input of a print (print) start signal to drive the photosensitive drum again, and the apparatus performs a predetermined pre-print operation for a while.

C. Printing Process When a predetermined pre-rotation process is completed, a printing process (image forming process, image forming process) of a predetermined sequence, such as charging, image exposure and development on the rotating photosensitive drum, and transfer of a toner image to a recording material, is performed. Then, the printing process for the first sheet is performed.

In the case of the continuous printing (continuous printing) mode, the recording material is continuously fed to the transfer portion, and a printing process for a predetermined set number n is sequentially performed.

D. Paper interval In the continuous printing mode, after the trailing edge of one recording material passes through the transfer portion, and before the leading edge of the next recording material arrives at the transfer portion, the non-recording material at the transfer portion is removed. This is a paper passing state period.

E. Post-rotation process This is a period in which the main motor is continued to be driven for a while to drive the photosensitive drum to rotate and perform a predetermined post-operation of the apparatus even after the last n-th printing process is completed.

When the post-rotation process is completed, the drive of the main motor is stopped, the rotation of the photosensitive drum is stopped, and the apparatus is kept in the standby state again until the next print start signal is input.

In the above description, if a print start signal is input immediately after the previous multi-rotation process, the printing process is subsequently executed through the pre-rotation process. In the case of printing only one sheet, after the end of the printing process, the apparatus enters a standby state via a post-rotation process.

[0021]

In order to accurately detect the resistance value of a transfer roller as a transfer member and determine an optimum applied transfer voltage, the resistance value for one round of the transfer roller is monitored and the average value thereof is determined. At the same time, since the resistance value of the transfer roller has a voltage dependency, it is necessary to set a constant current value such that a value as close as possible to the voltage applied at the time of transfer is generated.

For this reason, in the conventional image forming apparatus, the ATVC control is generally performed during a "pre-rotation step", which has a relatively long time on the image forming operation of the apparatus. After the ATVC control, the primary charging for one rotation or more of the photosensitive drum was performed before the start of the first sheet printing process in order to remove the transfer charging memory of the photosensitive drum as the image bearing member.

However, in the above method, the AT is performed only during the pre-rotation stroke.
Since the VC control is performed, there is no means for compensating for a change in the resistance value of the transfer roller even when the resistance value of the transfer roller fluctuates due to the temperature rise in the apparatus during the continuous printing mode.

In the "paper interval" during continuous printing, the ATV
C control is performed when the paper interval is generally 30 to
Since the interval is as small as 100 mm, it is difficult to execute the same accurate ATVC control during the “pre-rotation stroke” in such a small interval time.

In recent years, as the image processing capability of computers has been improved, there has been a demand for outputting a large amount of halftone images. When such images are printed continuously, the transfer roller resistance during continuous printing is reduced. An adverse effect due to a change in the value is likely to appear in an output image.

The demand for printing various types of recording materials, from thin paper to thick paper, is also increasing. Some types of recording materials are sensitive to changes in the resistance value of the transfer roller, and are always optimal during continuous printing. It has become necessary to perform a transfer voltage control in an appropriate manner.

As a countermeasure, it is conceivable to widen the interval between the paper strokes in continuous printing to the extent that the same accurate ATVC control as in the preceding rotation stroke can be performed. The decrease in throughput is remarkably impractical.

The present invention has been proposed in view of the above, and a transfer type image forming apparatus using a contact type / rotary type transfer member has the same structure as that of the related art without increasing the paper interval in the continuous printing mode. The optimal transfer voltage control can be performed in the paper interval process with the paper interval set as it is, so that the throughput is not reduced, and a good image with no sand or uneven image is stably output. The purpose is to let them.

[0029]

According to the present invention, there is provided a transfer member and an image forming apparatus having the following constitutions.

(1) A voltage is applied to the image bearing member, a voltage is applied, and the recording material is nipped and conveyed at a transfer portion which is a nip portion between the image bearing member and the transferable image on the image carrier side to form a recording material. Contact type / rotation type transfer member for electrostatically transferring to the side, the transfer member is an ion conductive member, and its resistance value distribution in the rotation direction is 1.5 or less, and its surface roughness Ra
Is 5 μm or less.

(2) The transferable image is formed and held on the image carrier, and the transferable image is brought into contact with the image carrier and a voltage is applied to the nip between the contact / rotational transfer member and the image carrier. In an image forming apparatus in which an image is electrostatically transferred to a recording material that has been nipped and conveyed at a transfer portion, the transfer member is an ion conductive member, and its resistance value distribution is 1.
5 or less, the surface roughness Ra is 5 μm or less, an applied transfer voltage control for measuring a resistance value of the transfer member, and controlling a voltage applied to the transfer member according to the resistance value measurement result, When the recording material is continuously fed to the transfer portion to form an image, after the rear end of one recording material passes through the transfer portion, and until the leading end of the next recording material reaches the transfer portion. An image forming apparatus, which is appropriately performed in the paper interval process.

(3) The voltage applied to the transfer member at the time of measuring the resistance value of the transfer member is controlled with a constant current to the image carrier, and the transfer is performed according to the voltage value at the time of transferring the next transferable image to the recording material. The image forming apparatus according to (2), wherein the voltage applied to the member is determined.

(4) The first or first transferable image is transferred, and the recording material that has passed through the heat fixing device is re-fed to the transfer portion to transfer the second or second transferable image. The image forming apparatus according to (3), wherein when performing double-sided printing or multiplex printing continuously, the constant current value controlled at the time of measuring the resistance value of the transfer member is smaller than that at the time of single-sided printing.

<Operation> 1) The ionic conductive member as the contact / rotation type transfer member in the present invention is obtained by adding an ionic conductive material to an elastic layer to impart conductivity. Examples thereof include a material in which a material such as urethane itself has conductivity, a material in which a surfactant is dispersed in an elastic layer, and a material in which NBR rubber and a surfactant are reacted to have conductivity.

As a transfer member provided with conductivity, there is an electronic conductive type transfer member. This is to give conductivity by dispersing a conductive filler in the elastic layer, as an example,
Rollers in which conductive fillers such as metal oxides such as carbon, tin oxide, and titanium oxide are dispersed.

In the present invention, when the transfer member is energized, the transfer member is of the ionic conduction type because the ionic conduction type has less resistance unevenness in the longitudinal and circumferential directions than the electronic conduction type. .

2) In the present invention, the resistance value distribution in the rotation direction of the transfer member is obtained by sampling the current value when the transfer member is rotated one or more times, and determining the maximum value and the minimum value of the sampling current value as I _MAX and I _MIN. In this case, I _MAX / I _MIN was defined as the resistance value distribution in the rotation direction of the transfer member, that is, the resistance circumference unevenness.

3) In the present invention, the surface roughness Ra of the transfer member is called a center line average roughness, and the value obtained by integrating the measured surface from the center line of the measured roughness surface and dividing it by the measured length is obtained. Ra is defined.

4) As a contact-type / rotation-type transfer member, an ion conductive member having a resistance value distribution of 1.5 or less in the rotational direction and a surface roughness Ra of 5 μm or less is used. By using a certain material, there is little unevenness in the electric conduction characteristics of the transfer member, and the resistance value of the transfer member is detected even during a short time between sheets during continuous printing, and the image on the next recording material is detected. The transfer bias to be applied to the transfer member at the time of transfer can be optimally determined similarly to the transfer voltage control during the pre-rotation process, and applied to the transfer member.

Therefore, in the inter-paper process in the continuous printing, the transfer voltage control such as the ATVC control is executed without any problem without reducing the throughput, and the optimum transfer bias according to the transfer member resistance fluctuation in the continuous printing is determined. Switching application (correction application) could be applied to the transfer member, and a good image without any sand or image unevenness could be stably output.

5) When the image forming apparatus can perform image formation in a double-sided printing mode or a multiple printing mode and performs transfer voltage control by ATVC control, and when performing double-sided continuous printing or multiple continuous printing, the transfer member By making the constant current value controlled when measuring the resistance value smaller than that for single-sided printing, the first-side printed material or the first-time printed recording material once heated through the heating and fixing means passes through the transfer area. The two-sided printed image or the second-time printed image, which is caused by a further decrease in the resistance of the transfer member, is prevented from being sandy or uneven in image, and a good double-sided printed image or a multi-printed image is formed without lowering the throughput. Could be output.

[0042]

BEST MODE FOR CARRYING OUT THE INVENTION

<Embodiment 1> (FIGS. 1 to 4) (1) Example of Image Forming Apparatus FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus according to the present invention. The image forming apparatus according to the present embodiment is a laser beam printer capable of performing double-sided and multiple printing using a transfer type electrophotographic process.

Reference numeral 1 denotes an electrophotographic photosensitive drum as an image carrier, which is driven to rotate at a predetermined peripheral speed (process speed) in a clockwise direction indicated by an arrow.

Reference numeral 2 denotes charging means such as a contact charging roller.
The charging means uniformly charges (primarily charges) the surface of the rotating photosensitive drum 1 to a predetermined polarity and potential.

Reference numeral 3 denotes a laser beam scanner as an image exposing means, which is turned on / off in accordance with a time-series electric digital pixel signal of target image information input from an external device such as an image scanner / computer (not shown). The laser beam L is output to scan and expose (irradiate) the charged surface of the rotating photosensitive drum 1. By this scanning exposure, the charge of the exposed light portion on the surface of the rotating photosensitive drum 1 is eliminated, and an electrostatic latent image corresponding to the target image information is formed on the surface of the rotating photosensitive drum 1.

Reference numeral 4 denotes a developing device. A developer (toner) is supplied from the developing sleeve 4a to the surface of the rotating photosensitive drum 1 so that the electrostatic latent image on the rotating photosensitive drum 1 is converted into a transferable image. Developed sequentially. In the case of LBP, a reversal development method is generally used in which toner is adhered to the exposed portion of an electrostatic latent image and developed.

Reference numeral 5 denotes a paper feed cassette in which recording materials P (hereinafter, referred to as transfer materials) are loaded and stored. The paper feed roller 6 is driven based on the paper feed start signal, and the transfer material P in the paper feed cassette 5 is separated and fed one by one. It is introduced at a predetermined timing into a transfer portion T which is a contact nip portion with a transfer roller 9 as a contact-type / rotation-type transfer member. That is, when the leading end of the toner image on the rotating photosensitive drum 1 reaches the transfer site T, the registration roller 7 moves the transfer material P so that the leading end of the transfer material P also reaches the transfer site T. The transport is controlled.

The transfer material P introduced into the transfer portion T is conveyed while nipping the transfer portion T. During this time, a transfer voltage (transfer bias) controlled in a predetermined manner from a transfer bias applying power source (not shown) is applied to the transfer roller 9. Applied. The transfer roller 9 as a transfer member and transfer voltage control will be described in detail in the following section (2). When a transfer bias having a polarity opposite to that of the toner is applied to the transfer roller 9, the toner image on the surface of the rotating photosensitive drum 1 at the transfer portion T is electrostatically transferred to the surface of the transfer material P.

The transfer material P to which the toner image has been transferred at the transfer portion T is separated from the surface of the rotating photosensitive drum 1 and conveyed to the fixing device 11 through the sheet path 8b, where the toner image is heated and pressed and fixed. Receive processing.

On the other hand, after the transfer material is separated (after the transfer of the toner image to the transfer material P), the surface of the rotating photosensitive drum 1 is cleaned by the cleaning device 10 to remove transfer residual toner, paper dust, and the like. Provided for imaging.

When the “single-sided printing mode” is selected, the transfer material P that has passed through the fixing device 11 is guided to the sheet path 8c by the first flapper 12 that has been switched to the first position. From the paper output port 13 to the paper output tray 14
Is discharged on top.

When the “double-sided printing mode” is selected, the transfer material P with the first side printed after passing through the fixing device 11 is selected.
Is the first flapper 12 that has been switched to the second position.
The path is guided to the sheet path 8d by the second path, and further guided to the sheet path 8e by the second flapper 15 which is switched to the first position, and the sheet path 8g ( To the switchback section). At a point shortly before the rear end of the loaded transfer material passes through the second flapper 15 and passes through the switchback roller pair 8f, the switchback roller pair 8
f is switched to the reverse drive, the second flapper 15 is switched to the second position, the transfer material in the sheet path 8g is pulled out and conveyed, and is introduced from the sheet path 8h to the sheet path 8i in a reversed state. . Then, the toner image is re-introduced into the transfer portion T in a reversed state on the path of the sheet path 8i, the registration roller 7, and the sheet path 8a, and the toner image is transferred to the second side of the transfer material. By being introduced, the transfer toner image on the second side is subjected to a fixing process, and the path is guided to the sheet path 8c side by the first flapper 12 which is switched to the first position. The print is discharged onto the discharge tray 14 as a print.

When the “multiple printing” mode is selected, the transfer material P after the first printing through the fixing device 11
Is the first flapper 12 that has been switched to the second position.
Is guided to the sheet path 8d side, and further guided to the sheet path 8j side by the second flapper 15 which is switched to the third posture, and is introduced into the sheet path 8i without being turned upside down. Then, the toner image is re-introduced to the transfer portion T along the path of the sheet path 8i, the registration roller 7, and the sheet path 8a, thereby receiving the second transfer of the toner image on the surface on which the first printing has been performed. The first flapper 12 that has undergone the second transfer toner image fixing process by being re-introduced into the first position has been switched to the first position.
The sheet is guided to the sheet path 8c side by the sheet ejection tray 13 as a multiple printed product (multiple print) from the paper ejection port 13.
4 is discharged.

(2) Transfer Roller 9 and Transfer Voltage Control a) Transfer Roller 9 The transfer roller 9 as a contact type / rotary type transfer member is an ion conductive member, and its resistance value distribution (resistance Peripheral unevenness) is 1.5 or less, and the surface roughness is 5 μm or less in Ra.

[0055] Resistance value of transfer roller 9 The ion conductive transfer roller 9 of the present example reacts NBR rubber and a surfactant or the like concentrically and integrally around the outer periphery of the core bar 9b,
A roller having a resistance value of 2 × 10 ⁷ to 2 × 10 ⁹ Ω in which a conductive elastic layer 9a is formed into a roller shape is used.

FIG. 2 is a schematic diagram of the resistance measuring device of the transfer roller 9. That is, the transfer roller 9 is pressed against the rotatably driven aluminum drum 1A with a contact pressure of 1.5 kg and is driven to rotate, and 1 kV is applied between the cored bar 9b and the earth from the bias applying power supply E to flow to the aluminum drum 1A. The resistance was calculated by measuring the current with the ammeter A. The measurement was carried out by leaving the transfer roller 9 in an environment of 20 ° C. and 60% RH, and under the same environment.

In the above measurement, the transfer roller 9
The current value at the time of rotation or more was sampled, and the roller resistance was calculated from the average value of the sampled values.

[0058] In accordance with the resistance circumference unevenness of the transfer roller 9, the maximum value and the minimum value of the sampling current value are set to I
_Assuming that _MAX and I _MIN are _satisfied , the transfer roller 9 that _satisfies I _MAX / I _MIN ≦ 1.5, that is, the transfer roller 9 whose resistance value distribution (resistance circumferential unevenness) in the rotation direction is 1.5 or less was used.

The reason will be described below. First, I _MAx
/ I _MIN is defined as the resistance circumference unevenness of the transfer roller 9 and when the resistance circumference unevenness is larger than 1.5, a short timing between papers (for example, about 10 mm width in the transfer roller circumferential direction).
When the transfer bias is applied based on the result, and the ATVC control is performed in the portion of the maximum value R _MAX of the transfer roller resistance, the minimum value R _{MIN of the} transfer roller resistance is obtained.
The transfer voltage is too high in the part where the drum memory,
Sand tends to be generated, which appears in the next print image.

On the other hand, if the ATVC control is performed at the portion of the transfer roller resistance minimum value R _MIN , the transfer current becomes insufficient at the transfer roller resistance maximum portion R _MAX in the rotation period of the transfer roller, resulting in poor transfer at the time of printing the next page. .

In the case where the ATVC control is performed in the sheet interval process, for example, when a drum memory is generated. In the next image forming step, when the photosensitive drum 1 is charged by the charging roller 2, the portion receiving the drum memory is sufficient. The memory cannot be removed by charging the photosensitive drum 1 one more round, and the memory can be removed. Therefore, at the time of development, when the non-image portion of the uneven charging portion is developed, a fog image and a black spot image (sand image) are generated.

According to the study by the present inventors, it has been found that this sandy image is remarkably generated when the resistance circumferential unevenness of the transfer roller 9 described above is larger than 1.5. Even when V _MAX is applied, the flowing current is small, no drum memory is generated, and no sand image is generated.

[0063] When the surface roughness of the transfer roller 9 was measured along with the surface roughness Ra of the transfer roller 9,
When a> 5 μm, sand was generated, and when Ra ≦ 5 μm, no sand was generated.

When Ra> 5 μm, the transfer current flowing through the photosensitive drum 1 is concentrated near the convex portion on the surface of the transfer roller, so that a drum memory is generated and a sand image is formed.

Conversely, when Ra ≦ 5 μm, the transfer current flows uniformly from the roller surface to the photosensitive drum, so that no sand image is generated.

In this phenomenon, since the ATVC control is performed between the sheets, the print image of the next page is easily affected.

B) Transfer Voltage Control This example uses the above-described ion conductive roller as a transfer roller, and has a resistance circumference unevenness of 1.5 or less and a surface roughness Ra of 5 μm.
using the following m, perform ATVC control to determine the transfer bias V _T, is applied to the transfer bias V _T to the transfer roller 9 in the transfer step. The ATVC control means will be described below.

In continuous printing, first, when printing is started,
A constant current bias V _TO of a constant current I _O is applied during the pre-multi-rotation process or the pre-rotation process, and the constant current bias V _TO is held.

Here, the ion conductive roller is as shown in FIG.
Generally, it shows a good VI characteristic and a VR characteristic as shown in FIG.
It is a target. Therefore, the constant current bias V_TOLow when applied
From the resistance of the image forming device (printer)
Current I suitable for the load_T (See VI characteristic graph in FIG. 3).
Rough A), transfer bias without transfer failure, paper marks, etc.
Transfer bias V_T Is applied to the transfer roller. next
If the transfer roller resistance decreases during continuous printing (see V in FIG. 3).
-I characteristic graph B), the transfer bias V_TApply
And I_T ′ Current flows and defective images such as sandy areas and image unevenness
Occur. This is because I _TExcess current I
_T Occurs because the 'flows. Therefore, during continuous printing
Same as during the multi-rotation process before or during the pre-rotation process
Constant current I_O A bias is applied and the constant current
Ass V_O1Hold. Next, as a transfer bias, V_T1
Is applied to prevent sand and image unevenness, and
You can print good and bad images.

In the ATVC control in the sheet interval, the control frequency may be arbitrarily defined according to the number of prints. For example, when the number of printed sheets is 10, every 5 sheets, when it is 100, every 2 sheets, and the like. However, since the resistance of the ion-conductive transfer roller 9 changes due to a slight change in temperature and humidity, during continuous printing, the ATVC control is performed in every inter-paper process, and an optimum transfer bias is determined for each printing process. Is desirable for outputting a good image.

Using the transfer roller 9 described above,
A good image can be output by applying an appropriate transfer bias during the pre-rotation by the VC control.

In addition, even when the resistance of the transfer roller 9 greatly changes (decreases) during continuous printing due to an increase in the temperature inside the apparatus, the optimal transfer bias can be detected by the ATVC control in the sheet-to-sheet process, so that sand and image unevenness can be detected. Can be prevented.

Further, the resistance circumference unevenness is 1.5 or less, and the surface roughness R
By using the ion conductive transfer roller 9 having a ≦ 5.0 μm or less, since the electron conduction characteristics during energization are excellent, even during the inter-paper stroke at a small interval (30 to 100 mm) during continuous printing.
The transfer roller resistance can be detected by the ATVC control without changing the throughput.

Thus, in the image forming apparatus that performs the ATVC control, the ATVC control is performed in the inter-paper stroke at the time of continuous printing, so that the optimum transfer bias is always determined regardless of the change in the transfer roller resistance without lowering the throughput. It is possible to stably output a good image in which sand and unevenness of the image are prevented.

<Second Embodiment> In the double-sided continuous printing mode or the multiple continuous printing mode, the transfer voltage control (ATVC control) performed in the above-described first embodiment is directly used. Sand and image unevenness occurred.

This is because, when printing is performed on the second side or the second time, the transfer material P that has been once passed through the fixing device 11 and passed through the transfer portion T in the execution of the first side or the first printing is further transferred to the transfer roller. The resistance is lowered, and the constant current bias for ATVC detection during the sheet-to-paper process causes an excess current to flow, including variations in the high-voltage unit, etc., during single-sided printing, thereby causing sand and image unevenness. This example prevents this.

That is, in the transfer voltage control, as in the first embodiment, the ATVC control is performed in the pre-multi-rotation process or the pre-rotation process, and the transfer bias V _T is determined by applying the constant current bias V _T0 . In addition as in Embodiment Example 1 Continuous sided printing mode is performed the ATVC control in the inter-sheet process, then applying a constant current I ₀ bias, it is optimum transfer bias V _T1 to hold the V ₀₁ at this time It is determined.

In the double-sided continuous printing mode or the multiple continuous printing mode, as shown in FIG. 5, the transfer roller resistance is large and decreases, and the characteristic shown in the VI characteristic graph C is shown. The constant current value is set to a value I _O2 smaller than I _O in the VI characteristic graph A in the inter-paper stroke during single-sided printing.

At the time of the above control, the latitude with respect to sand and image unevenness due to the high-pressure variation in the VI characteristic graph C is as shown by the arrow b at I _{O and} the arrow c at I _O2.
And spreads in the same direction as the arrow a shown in the graph A at the time of single-sided paper passing described in the first embodiment.

Therefore, even if the printing process (image forming process) immediately enters the printing process (image forming process) after the ATVC control during the paper interval process in the double-sided continuous printing mode or the multiple continuous printing mode, a good image is output without generating sand or image unevenness. it can.

At this time, as shown in FIG. 6, the transfer bias V _TO2 to be applied is a bias that can secure a current _{IT 2} that does not cause transfer failure and paper marks, as in the first embodiment. Here, the curves A 'and C' lie down in comparison with FIG. 5 because the VI characteristics are measured when the transfer material having high resistance of the transfer material is printed on the second surface or after the second printing. It is. In determining V _TO2 , V _TO2 can be arbitrarily determined in a sandy area, an area d where image unevenness and transfer failure do not occur. However, it is desirable to determine in consideration of the variation in the VI characteristics of the transfer roller.

As described above, in double-sided continuous printing or multiple continuous printing, an ion conductive transfer roller having a resistance circumference unevenness of 1.5 or less and a roller surface roughness Ra of 5.0 μm or less is used as a transfer member. By lowering (decreasing) the constant current value of the ATVC control performed in the inter-sheet process compared with the one-sided printing, it is possible to suppress the occurrence of sand and image unevenness due to the application of the constant current, and to set the optimum transfer bias, thereby achieving a good image quality. Can be output stably.

<Others> 1) The transfer member of the contact type and the rotary type is not limited to the roller type of the embodiment, but may be a rotating belt type. It may be used in the form of an intermediate transfer member.

2) The principle and process of forming a transferable image on the image carrier is not limited to the electrophotographic process of the embodiment.

The image exposing means as information writing means on the charged surface of the image carrier is not limited to the laser scanning exposing means for forming a digital latent image as shown in the embodiment, but may be an analog image exposing means. Any other light-emitting element such as exposure or LED may be used, and any light-emitting element such as a combination of a light-emitting element such as a fluorescent lamp and a liquid crystal shutter may be used as long as it can form an electrostatic latent image corresponding to image information.

The image carrier may be an electrostatic recording dielectric or the like. In this case, after the dielectric is uniformly charged to a predetermined polarity and potential, the charge is selectively removed by a charge removing means such as a charge removing needle head or an electron gun to write and form a target electrostatic latent image.

The toner developing method and means of the electrostatic latent image are arbitrary, and may be a reversal developing method or a regular developing method.

An image forming apparatus for a magnetic recording process using a magnetic recording magnetic material may be used.

3) Double-sided continuous printing or multiple continuous printing
The first or first printed recording material is temporarily stacked and stored in the intermediate tray portion for a predetermined number of times, and the recording material is sequentially re-fed from the intermediate tray portion to the transfer portion to be transferred to the second or second surface.
The image forming apparatus may be configured to execute by performing the second printing.

In addition to forming a single color image, a plurality of toner images are sequentially superimposedly transferred onto an intermediate transfer member to form a multi-color or full-color image, and the toner images are collectively transferred to a recording material by a transfer unit. An image forming apparatus may be used.

A rotating belt type image carrier is used, a toner image corresponding to the target image information is formed on the image carrier by an appropriate image forming process, and the toner image forming section is positioned at the reading display section. There is also an image display apparatus in which an image is displayed, and if necessary, the toner image is transferred to a recording material to output a hard copy, and the image carrier is repeatedly used for image formation. In the present invention, the image forming apparatus includes such an image display device.

[0092]

As described above, according to the present invention,
Regarding a transfer type image forming apparatus using a contact type / rotary type transfer member, in continuous printing, the interval between papers is set to the same value as before without increasing the interval between papers, so that the interval between sheets is reduced without reducing the throughput. Optimal transfer voltage control can be performed during the process, and a good transfer image can be stably output without any sand or image unevenness regardless of the use environment.

Even in the case of double-sided continuous printing or multiple continuous printing, it is possible to stably output a constantly good transfer image free of sand, image unevenness, etc. regardless of the use environment.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram of a procedure for measuring the resistance of a transfer roller.

FIG. 3 is a VI characteristic diagram of a transfer roller.

FIG. 4 is a VR characteristic diagram of a transfer roller.

FIG. 5 is a diagram illustrating VI during ATVC control according to the second embodiment.
Characteristic diagram

FIG. 6 is a characteristic diagram of a transfer bias and a current value.

FIG. 7 is a process chart of an image forming operation of the image forming apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 image carrier (rotating photosensitive drum) 2 charging device 3 laser beam scanner 4 developing device 5 paper feed cassette 6 paper feed roller 7 registration roller 8a to 8j sheet path 9 transfer roller 10 cleaning device 11 fixing device 12.15 flapper 13 Paper discharge port 14 Paper discharge tray P Recording material (transfer material)

Claims (4)

[Claims] 1. A voltage is applied to an image bearing member,
A contact-type / rotation-type transfer member that sandwiches and conveys a recording material at a transfer portion that is a nip portion with the image carrier and electrostatically transfers a transferable image on the image carrier side to the recording material side; The transfer member is an ion conductive member, has a resistance value distribution of 1.5 or less in the rotation direction, and has a surface roughness Ra of 5 or less.
a transfer member having a thickness of not more than μm. 2. A transferable image is formed and carried on an image carrier.
The transferable image is electrostatically applied to the recording material side which is nipped and conveyed at a transfer portion which is a nip portion between a contact type / rotation type transfer member to which an image carrier is applied and a voltage is applied and the image carrier. The transfer member is an ion conductive member, has a resistance value distribution of 1.5 or less in the rotation direction, and has a surface roughness Ra of 5 μm.
m or less. The applied transfer voltage control for measuring the resistance value of the transfer member and controlling the voltage applied to the transfer member according to the resistance value measurement result continuously feeds the recording material to the transfer portion. When image formation is performed, it is appropriately performed in a paper interval process after the rear end of one recording material passes through the transfer site and before the front end of the next recording material reaches the transfer site. Characteristic image forming apparatus. 3. A voltage applied to the transfer member when the resistance value of the transfer member is measured is controlled with a constant current to the image carrier, and the transfer member is transferred at the time of transfer of a transferable image to the next recording material according to the voltage value at that time. The image forming apparatus according to claim 2, wherein a voltage applied to the image forming apparatus is determined. 4. The second or first transferable image is transferred by re-feeding the recording material having passed through the heat fixing device after the transfer of the first or first transferable image to the transfer portion. 4. The image forming apparatus according to claim 3, wherein when performing double-sided printing or multiplex printing continuously, a constant current value controlled at the time of measuring the resistance value of the transfer member is smaller than that at the time of single-sided printing.