JP2000231229A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device that can solve such problem on an image failure such as a reversed transfer by carrying out output control of not only potential of an image carrier but also of a transfer charge imparting means corresponding to an image forming mode. SOLUTION: The intermediate transfer type image forming device that primarily transfers a visual image formed on a photoreceptor drum 10 on an intermediate transfer belt 221 by imparting electric charge to the intermediate transfer belt 221 to forme a transfer electric field and then secondarily transfers the primarily transferred image on the intermediate transfer belt 221 to a transfer material, is provided with a transfer electric field control means 1 controlling output of the primary transfer power source 128 according to potential information of the photoreceptor drum 10 and image forming mode information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile, a printer and the like. More specifically, the present invention relates to a transfer area where an image carrier and an intermediate transfer body are opposed to and contact with each other. A transfer electric field is formed by applying a charge to the transfer body, the toner image formed on the image carrier is transferred onto the intermediate transfer body, and the toner image transferred on the intermediate transfer body is transferred to a transfer material. The present invention relates to an image forming apparatus for transferring images onto an upper side.

[0002]

2. Description of the Related Art A conventional image forming apparatus is disclosed in
The one shown in -20679 is known. This image forming apparatus is an image forming apparatus of an intermediate transfer system in which a visible image formed on an image carrier is primarily transferred to an intermediate transfer body, and a primary transfer image on the intermediate transfer body is secondarily transferred to a transfer material. A relationship between a predetermined potential of the image carrier that does not cause a discharge between the intermediate transfer body portion after the primary transfer and the image carrier and a transfer bias potential applied to the intermediate transfer body, and an image carrier Control means for controlling the transfer bias voltage based on the potential information.

In this conventional image forming apparatus, the charging potential of the image carrier and the output value of the transfer charge applying means are adjusted so that the potential of the image carrier and the output voltage of the transfer charge applying means become constant. Was controlled at a fixed value corresponding to one-to-one.

However, in the control in which the potential of the image carrier and the output value of the transfer charge applying means correspond only to one body as in the prior art, the change in the image forming mode is dealt with. I can't do it. For example, when the image forming mode is the full color mode, when transferring the second and subsequent colors of toner, a sequentially larger transfer bias is applied in consideration of the potential of the already transferred toner and the charging potential of the intermediate transfer body. If not, there is a problem that insufficient transfer occurs.

In the case where the image forming mode is a mode in which the intermediate transfer body performs the idle rotation operation which does not include the image transfer processing after the transfer process to the intermediate transfer body is completed, the output of the transfer charge applying means during the idle rotation is output. If there is no contrivance such as controlling the
There has been a problem that image defects such as reverse transfer occur.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to solve image defects such as reverse transfer by controlling output of a transfer charge applying means corresponding to not only the potential of an image carrier but also an image forming mode. By controlling the output of the transfer charge applying unit corresponding to not only the potential of the image carrier but also the image forming mode, which provides an image forming apparatus capable of performing image formation, it is possible to solve an image defect such as reverse transfer. An object of the present invention is to provide a forming apparatus.

[0006]

According to a first aspect of the present invention, a visible image formed on an image carrier is transferred to an intermediate transfer member by applying a charge to the intermediate transfer member to form a transfer electric field. In the intermediate transfer type image forming apparatus for performing primary transfer to an intermediate transfer member and secondary transfer of a primary transfer image on the intermediate transfer member to a transfer material, the potential information of the image carrier and the image forming mode information are used. An image forming apparatus, further comprising a control unit for controlling an output of the charge applying unit in response to the request. With this configuration, image defects such as reverse transfer can be solved by controlling the output of the transfer charge applying means corresponding to the image forming mode as well as the potential of the image carrier.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the image forming mode is a mode corresponding to the number of transfers.

According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the image forming mode is a mode in which the intermediate transfer body is idlely rotated after the transfer step to the intermediate transfer body is completed. It is characterized by:

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a full-color electrophotographic copying machine to which the present invention is applied will be described. FIG. 1 is a schematic configuration diagram of a main part of the printer unit according to the first embodiment. The printer unit is provided with a photoreceptor drum 10 as an image carrier. Around the photoreceptor drum, a writing optical unit as an exposure unit (not shown) and a photoreceptor cleaning device 111 as a cleaning unit When,
A charging charger 13 as charging means, and a revolver developing unit 110 which is a rotary developing device as developing means
And an intermediate transfer unit 120 as an intermediate transfer unit. The printer unit also includes a transfer unit 130 as a transfer unit, a fixing unit 145 as a fixing unit, and a paper supply unit and a control unit (not shown) similar to those in the first embodiment.

The photoconductor cleaning device 111 includes a fur brush 111 b and a photoconductor cleaning blade 11.
1c to clean the surface of the photosensitive drum 10 after the primary transfer. Further, the fixing unit 145 includes:
It has a fixing roller pair 145a and a discharge roller pair (not shown). In addition, around the fur brush 111b,
A solid lubricant 111d as a lubricant is arranged so as to contact the brush tip. As the solid lubricant 111d, for example, as in the first embodiment, for example, zinc stearate composed of fine particles molded into a plate shape can be used.

The revolver developing unit 110 has a Bk
Developing unit 115, C developing unit 116, and M developing unit 117
And a Y developing device 118, and by rotating the revolver developing unit, a developing position of the developing device of each color which faces the photosensitive drum 10 can be determined.

The intermediate transfer unit 120 includes an intermediate transfer belt 121 serving as an intermediate transfer member, a primary transfer bias roller 122 serving as a charge applying means, a primary transfer power supply 128 serving as a power supply connected thereto, and a primary transfer power supply 128 serving as a power supply. An earth roller 123 as a pre-transfer charge removing unit, a driving roller 124 as a belt driving unit, a tension roller 125,
The configuration is such that the secondary transfer opposing roller 126 and the cleaning opposing roller 127 are stretched. All the rollers that are stretched over the intermediate transfer belt 121 are formed of a conductive material, and each roller other than the primary transfer bias roller 122 is grounded. The primary transfer bias roller 122 is supplied with a predetermined primary transfer bias controlled by a primary current or a constant voltage by a primary transfer power supply 128. The intermediate transfer belt 121 has the same configuration as that of the first embodiment, but is formed so that its volume resistivity is 10 ¹² to 10 ¹⁴ Ωcm, preferably 10 ¹³ Ωcm. Further, the surface resistivity of the intermediate transfer belt 121 on the surface layer side is configured to be 10 ⁷ to 10 ¹⁴ Ωcm. Around the intermediate transfer belt 121, a lubricant applying brush 129a as a lubricant applying means and a belt cleaning blade 129 are provided.
b and a transfer unit 130, which can be brought into contact with and separated from the intermediate transfer belt 121 by a contact / separation mechanism (not shown).

The transfer unit 130 includes a secondary transfer belt 134 as a transfer material carrier, and a transfer cleaning blade 132 for cleaning the surface of the secondary transfer belt.
, A secondary transfer bias roller 131 facing the secondary transfer facing roller 126 of the intermediate transfer unit 120, a secondary transfer power supply 139 connected to the secondary transfer bias roller 131, and a first support located at an end on the paper feed unit side. Roller 135a and fixing unit 1
There is a second support roller 135b located at the end on the 45 side, a third support roller 135c facing the transfer cleaning blade 132, a transfer paper charge removal charger 136, and a transfer belt charge removal charger 137. The secondary transfer belt 134 has a volume resistivity of 10 which is made of PVDF.
It is formed to have a high resistance of ¹³ Ωcm or more. still,
The transfer unit 130 is not limited to this configuration, and may have a configuration in which a member having another shape such as a drum is used instead of the secondary transfer belt 134, for example.

Next, the operation of the copying machine when the order of development is Bk, C, M, and Y will be described. Before starting the image forming cycle, the photosensitive drum 10 is rotationally driven in the direction of arrow C in FIG. 1, that is, counterclockwise, and the charging charger 13 starts corona discharge. At this time, for example, the photosensitive drum 10 is uniformly charged to a predetermined potential with a negative charge. The intermediate transfer belt 121 of the intermediate transfer unit 120 is driven at the same speed as the photosensitive drum 10, and rotates in the direction of arrow D in FIG. 1, that is, clockwise.

In the scanner section, as in the first embodiment, color image information of a document is read at a predetermined timing, and a laser beam is written by the writing optical unit based on Bk image data obtained from the image information. Optical writing (for example, raster exposure) with light is performed. Thereby, the B corresponding to the Bk image data is displayed on the photosensitive drum 10.
A k latent image is formed. Thereafter, the Bk latent image formed on the photosensitive drum 10 is transferred to the revolver developing unit 110.
Is reversely developed with negatively charged toner. As a result, a Bk toner image is formed on the photosensitive drum 10.

The Bk toner image thus formed on the photosensitive drum 10 is primarily transferred to the surface of the intermediate transfer belt 121 by the transfer electric field in the primary transfer area. This transfer electric field is formed by electric charges applied to the intermediate transfer belt 121 by the primary transfer bias roller 122. At this time, for example, 1.5 kV for the first color Bk toner image and 1.6 to 1 for the second color C toner image are applied to the primary transfer bias roller 122 by the primary transfer power supply 128. An appropriate primary transfer bias of 1.8 kV to 1.8 kV for the third color M toner image and 2.0 to 2.2 kV for the fourth color Y toner image is applied. . The primary transfer residual toner remaining on the photoconductor drum 10 after development is removed from the photoconductor drum by the photoconductor cleaning device 111.

The image surface on the intermediate transfer belt 121 on which the Bk toner image has been primarily transferred is returned to the primary transfer area again as in the first embodiment. At this time, similarly to the first embodiment, the lubricant application brush 129a and the belt cleaning blade 129b are separated from the intermediate transfer belt 121 by the respective contact / separation mechanisms so that the toner image is not disturbed. Further, the transfer unit 1
The first support roller 135a and the secondary transfer bias roller 131 in 30 are moved by a transfer contact / separation mechanism (not shown) to separate the secondary transfer bias roller from the intermediate transfer belt 121. At this time, the voltage application by the secondary transfer power supply 139 connected to the secondary transfer bias roller 131 is stopped. The above state is maintained until the toner image primarily transferred on the intermediate transfer belt 121 is secondarily transferred onto transfer paper.

On the other hand, after the above-described Bk process is completed, the C process is started on the photosensitive drum 10 side, and the color image information of the original is read again at a predetermined timing, and the C image data obtained from this image information is read. , A C latent image is formed on the photosensitive drum 10 by a laser beam, and a C toner image is formed by a C developing device 116. In the present embodiment, the rotation operation of the revolver developing unit 110 is started immediately after the rear end portion of the Bk latent image has passed. This rotation operation is completed before the leading end portion of the C latent image formed on the photosensitive drum 10 reaches the developing position of the C developing device 116. This allows
The C developing device 116 is positioned at the developing position, and develops the C development moving to the developing position with the C toner.

Thereafter, in the M step and the Y step, the latent image formation, development, and primary transfer are performed based on the respective image data in the same manner as in the above-described C step. In this way, on the same image surface on the intermediate transfer belt 121,
Bk, C, sequentially formed on the photosensitive drum 10
The primary transfer of each of the M and Y toner images forms a toner image in which these four colors overlap on the intermediate transfer belt.

The toner image transferred on the intermediate transfer belt 121 as described above is sent to the secondary transfer area for secondary transfer onto the transfer paper 100. At this time, the secondary transfer bias roller 131 of the transfer unit 130
Is pressed against the intermediate transfer belt 121 by a transfer contact / separation mechanism (not shown). Thereafter, a predetermined secondary transfer bias is applied to the secondary transfer bias roller 131 to form a secondary transfer electric field in the secondary transfer area. Thus, the toner image on the intermediate transfer belt 121 is transferred onto the transfer paper 100. The transfer paper 100 conveyed to the secondary transfer area is transferred to the intermediate transfer belt 12.
The sheet is fed at the timing when the leading end of the toner image on the sheet 1 reaches the secondary transfer area.

As described above, the intermediate transfer belt 121
The transfer paper 100 on which the toner images formed by overlapping the four colors are collectively transferred is then transferred to the transfer unit 13.
At 0, the sheet is conveyed to a portion opposite to the transfer sheet discharging charger 136. When passing through the facing portion, the transfer paper is
The transfer paper is neutralized by the transfer paper neutralization charger 136 in the operating state, and is separated from the secondary transfer belt 134. Then, the separated transfer paper is sent between the rollers of the fixing roller pair 145a of the fixing unit 145. In the fixing roller pair 145a, the unfixed toner image on the transfer paper 100 is melted in a fixing area formed by a nip formed between the rollers, and the unfixed toner image is fixed.
Then, the transfer paper is carried out to a copy tray (not shown) and stacked.

On the other hand, the intermediate transfer belt 121 after the secondary transfer
The belt cleaning blade 129b presses the intermediate transfer belt 121 by a belt cleaning contact / separation mechanism (not shown) to remove the secondary transfer residual toner remaining on the surface of the intermediate transfer belt 121. Further, in order to improve the cleaning property and the secondary transfer property, the lubricant accommodated in the lubricant accommodating portion 129c by the lubricant applying brush 129a pressed against the intermediate transfer belt 121 by a contact / separation mechanism (not shown). Is applied. As the lubricant, for example, zinc stearate composed of plate-shaped fine particles can be used. After the transfer paper is peeled off, the charges remaining on the surface of the secondary transfer belt 134 are discharged by the transfer belt discharging charger 137. The surface of the secondary transfer belt 134 is further cleaned by the belt cleaning blade 129b.

FIG. 2 is a schematic structural view of a main part of the printer section according to the second embodiment, and the same reference numerals are given to the same components as those in the first embodiment. This copier mainly aims at cost reduction, and the structure and operation of the printer section are only slightly different from those of the first embodiment. Therefore, the copier is configured in the same manner as the first embodiment. The description of the operating part will be omitted.

In this embodiment, the intermediate layer of the intermediate transfer belt 221 in the intermediate transfer unit 220 is a medium resistance layer having a volume resistivity of 10 ⁸ to 10 ¹¹ Ωcm. Further, the intermediate transfer belt 221 has 10 ¹⁰
It has a volume resistivity of 〜１０10 ¹² Ωcm. The surface resistivity of the intermediate transfer belt 221 on the surface layer side is:
It is configured to be 10 ⁷ to 10 ¹⁴ Ωcm. By using the intermediate transfer belt 221 having such a medium resistance,
It is possible to prevent charging unevenness occurring on the surface of the intermediate transfer belt 221 after the primary transfer. In the present embodiment, the driving roller 224 in the intermediate transfer unit 220 is used.
Are disposed downstream of the secondary transfer area in the belt rotation direction and upstream of the primary transfer area in the belt rotation direction. By arranging the belt cleaning blade 129b so as to face the drive roller 224, the drive roller also serves as the cleaning counter roller 127 in the second embodiment.

In the present embodiment, the transfer unit is replaced by the secondary transfer opposing roller 12 of the intermediate transfer unit 220 instead of the transfer unit in the first embodiment.
6 is used. Accordingly, the number of components required for the secondary transfer process is reduced, and the cost can be reduced as compared with the first embodiment. At the time of paper feeding in this embodiment, the fed transfer paper 100 is directly sandwiched between the secondary transfer bias roller 231 and the intermediate transfer belt 221, and between the rollers of the fixing roller pair 145 a of the fixing unit 145. Sent to.

Hereinafter, a characteristic configuration of the present embodiment will be described. FIG. 3 is a view showing the vicinity of the photosensitive drum and the intermediate transfer belt of the image forming apparatus described above.

As shown in FIG. 3, a primary transfer power supply 128 is connected to a primary transfer bias roller 221 (121) that stretches the intermediate transfer belt, and the primary transfer power supply 128 and the surface of the photosensitive drum 10 are connected. A transfer electric field control unit 1 that controls a transfer bias in accordance with the surface potential of the photosensitive drum 10 and the image forming mode is provided between the surface potential detection sensor that detects the potential.

FIG. 4 is a block diagram showing the structure of the transfer electric field control means. The transfer electric field control means includes a CPU,
It has a ROM, a RAM, and an I / O interface. This I / O interface has a primary transfer power supply 12
8, the surface potential detection sensor 6, and the imaging mode signal unit.

FIG. 5 is a diagram showing the relationship between the photoconductor potential and the transfer bias. The charging potential of the photoreceptor is normally controlled to a value of about -400 volts to about -800 volts. The relationship between the charging potential value of the photoreceptor and the optimum transfer bias at that time is as shown in FIG. From FIG. 5, it can be seen that the optimum transfer bias changes in accordance with the photoconductor potential, and that the lower the photoconductor potential, the higher the transfer bias is optimal.

FIG. 6 shows the relationship between the transfer bias and the image density at the time of idling in a mode in which the idling operation of the intermediate transfer member not including the image transfer process is performed after the transfer step to the intermediate transfer member. FIG. 6 also shows that the lower the transfer bias during the idling operation, the smaller the reverse transfer amount.

In the prior art, as shown in FIG. 5, the relationship between the photoconductor potential and the transfer bias is one-to-one.
For example, when the photoconductor potential is -600 volts, 1500 volts is selected as the transfer bias. However, according to this prior art, the transfer bias in the mode including the idling operation and the potential of the photoconductor is -600 volts is also 1500 V.
Will be selected. This is a bias area where the reverse transfer amount is large, as shown in FIG.

In consideration of the prevention of reverse transfer, it is desirable to select a lower bias during idling, and since the image transfer process is not performed during idling, the transfer bias can be set low.

Tables 1 to 5 show transfer bias control values when the transfer bias control according to the present invention is performed. Table 1 shows the transfer bias T1 * according to the photoconductor potential Vd * in the single-color mode, Table 2 shows the transfer bias T1 according to the photoconductor potential Vd in the two-color mode, and Table 3 shows three colors. Transfer bias T1 corresponding to the photoconductor potential Vd in the mode
Table 4 shows the transfer bias T1 according to the photoconductor potential Vd in the four-color mode, and Table 5 shows the bias T1 according to the photoconductor potential Vd in the idling mode.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

[0037]

[Table 4]

[0038]

[Table 5]

As shown in FIG. 6, the image density decreases as the primary transfer bias during idling increases. That is, reverse transcription increases. The mechanism of adhesion of the transplanted dust is, for example, when two toner layers are stacked, when a mechanical force is applied and the toner layer is crushed, and when the toner layer falls, the height of the potential (the potential difference between the upper layer toner and the background portion of the belt) is high. May fall.

Although a high-resistance belt is used as the intermediate transfer belt, the reason why this high-resistance belt is used is to suppress transplant dust. In the case of a medium resistance belt or a low resistance belt, the background has almost no potential. Even if it has a potential, it attenuates immediately and becomes a small value such as -100V. However, when a high resistance belt is used, the potential of the background portion is large. For this reason, the potential difference between the toner and the toner becomes small, and it is difficult to cause dust.

Where this potential is created,
It is believed that the discharge causes charging from the nip to the exit. Similarly, since a bias is applied even during idling, there is a potential difference, and a certain amount of discharge occurs to change the charged state. For this reason, if the bias at the time of idling is increased, the electric potential of the ground rises, and if it is increased, it is good for transplant dust. However, if it is too high, reverse transcription increases.

In the normal transfer, if the transfer bias is too large, the transfer becomes excessive, and the negative toner enters the nip due to charge injection or the like. In some cases, the negatively charged negative electrode may be reversely charged, or the polarity may be reversed, and may remain on the photoreceptor without being transferred. Also in this case, since the toner once transferred is returned, reverse transfer occurs.

In the case where reverse transfer occurs due to excessively increasing the transfer bias in both normal and idling cases, the transfer bias is controlled to prevent reverse transfer. The primary transfer bias is controlled by a table described later according to the potential of the photoconductor.
Since the amount of reverse transfer is experimentally determined based on the relationship between the photoconductor potential and the primary transfer bias, the amount is controlled using the tables in Tables 1 to 4. In the table, Vd is the photoconductor potential, and T1 is the primary transfer bias.

The difference between the potential at which the background is charged and the potential of the transferred toner at the end of the first color is controlled to be slightly increased in consideration of the increased potential. For example, when the photoconductor potential is -391 volts, the transfer bias is 1700 volts for the first color, whereas the transfer bias is 2700 for the second color.
Increase by 00 volts to 1900 volts. Each time a color is superimposed, a large bias is applied sequentially.

During idling, Tables 1 to 20 of Table 5 are used. Since the process of transferring the toner on the photosensitive member is not included during the idle rotation, the transfer bias is relatively small as compared with the case of the toner transfer. Since the potential of the photoconductor during idling also varies, the transfer bias is changed by selecting one of Tables 1 to 20 in Table 5 according to the variation of the potential of the photoconductor. By changing the transfer bias in this way, reverse transfer is prevented. When the idle rotation operation is performed, the developing unit has four developing sleeves, and the developing unit rotates while the toner is attached to the surface of the developing unit to perform development on the photoconductor.

During idle rotation, idle rotation is performed with the developing sleeve positioned on the surface of the photosensitive member. For example, when two repeat copies are made on thick paper,
At the time of entering the idle rotation mode with the color superimposed, the black developing device is at the developing position because the next black image is being prepared for writing. At this time, if the potential of the photoconductor drops, the toner on the developing device is electrically attached to the developing device, but the carrier and the toner are transferred to the photoconductor. This becomes abnormal and appears next.
Therefore, the potential of the photoconductor is changed. Depending on the state of the toner, the cause of the occurrence of carrier adhesion depending on whether the charge amount of the toner resin is large or small changes. To prevent this, the potential of the photoconductor changes depending on the toner state at that time.

For example, since the charge amount of the toner changes depending on the environment, when the density is desired, the photosensitive member potential Vd is raised to be deep. If the photoconductor potential is determined, the transfer bias for preventing reverse transfer is also determined from the table. The potential of the photoreceptor is from table 1 to table 20. Which one to select is determined by changing the potential of the photoreceptor so as to have the same density according to the charge amount of the toner. A transfer bias amount for preventing copying is selected from a table.

In the monochromatic mode (1C mode), the number of transfers is one.
Since the number of times, any one of Tables 1 to 20 in Table 1 is selected. In the two-color mode (2C mode), since the number of transfers is two, one of Tables 1 to 20 in Table 2 is selected. In the three-color mode (3C mode), since the number of transfers is three, one of Tables 1 to 20 in Table 3 is selected. In the four-color mode (4C mode), since the number of transfers is four, one of Tables 1 to 20 in Table 4 is selected.

Control for shifting by a certain amount from a predetermined potential value is performed. The table of where to shift from is different for each mode. For example,
If the first C in the 4C mode is Bk, the B in the 1C mode
k and the transfer bias are different. The reason for this difference is that the potential of the intermediate transfer belt should not be excessively increased. In the 1C mode, there is only one pass, so the transfer margin is wide. If the first color is increased in the 4C mode, it becomes too high for the fourth color. Table 5 is selected in the idle rotation mode of the thick paper.

The image forming modes include a monochrome mode (1C mode), a color mode (2C mode, 3C mode, and 4C mode).
Mode) and idle rotation mode for thick paper. As described above, there are four modes from 1C to 4C for the number of colors to be transferred, and each mode has a mode of thick paper or plain paper. In the case of plain paper, since it does not re-enter the transfer section, there is no need to consider the bias during idle rotation.

In a state where an image is formed on the intermediate transfer member, for example, in a state where four-color images in a full-color mode are superimposed,
It may be necessary to pass the photoconductor again. Specifically, it is in the thick paper mode. In order to prevent reverse transfer in the case of thick paper, a transfer bias according to the photoconductor potential is selected from Tables 1 to 20 in Table 5.

When thick paper is used, idling is required. To prevent reverse transfer when idling, the primary transfer bias is determined by using the idling table in Table 5.

In the determination of the image forming mode, whether the image data forming the image is one color, two colors, three colors, or four colors is determined by, for example, a command. In the idle rotation mode, for example, it is determined whether the toner image primarily transferred on the intermediate transfer belt passes through the primary transfer area again. For example, the determination is made by detecting the deceleration of the intermediate transfer belt.

In the above-described embodiment, the case where the photosensitive drum is used as the image carrier has been described. However, for example, in addition to the photosensitive drum, a film-like photosensitive body, a transfer paper (for transfer from the intermediate transfer body to the transfer paper) may be used. The present invention can be applied to such cases. The present invention can be applied if the potential changes in a mode when the belt has a high resistance. Note that the present invention is not limited to the above embodiment. That is, various modifications can be made without departing from the gist of the present invention.

[0055]

As described above, according to the present invention, by controlling the output of the transfer charge applying means corresponding to not only the potential of the image carrier but also the image forming mode, an image such as reverse transfer can be obtained. An image forming apparatus capable of solving a defect can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a main part in a printer unit according to a first embodiment.

FIG. 2 is a schematic configuration diagram of a main part of a printer unit according to a second embodiment.

FIG. 3 is a diagram illustrating the vicinity of a photosensitive drum and an intermediate transfer belt of the image forming apparatus.

FIG. 4 is a block diagram illustrating a configuration of a transfer electric field control unit.

FIG. 5 is a diagram illustrating a relationship between a photoconductor potential and a transfer bias.

FIG. 6 is a diagram illustrating a relationship between a transfer bias and an image density during idling in a mode in which an idling operation of the intermediate transfer body is performed.

[Explanation of symbols]

 Reference Signs List 10 photoconductor drum (image carrier) 121 intermediate transfer belt 221 intermediate transfer belt 128 primary transfer power supply (charge applying means)

Continued on the front page (72) Inventor Shinji Kato 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (reference) 2H027 DA02 DA45 DE07 EA03 EC06 ED24 EF11 FA28 FA35 ZA01 2H032 AA05 BA09 BA23 BA25 BA30 CA02 CA12

Claims (3)

[Claims] 1. A transfer device according to claim 1, wherein the visible image formed on the image carrier is primarily transferred to the intermediate transfer member by applying a charge to the intermediate transfer member to form a transfer electric field. In an image forming apparatus of an intermediate transfer system for secondary transferring an image to a transfer material, according to the potential information of the image carrier and the image forming mode information,
An image forming apparatus, further comprising a control unit for controlling an output of the charge applying unit. 2. The image forming apparatus according to claim 1, wherein the image forming mode is a mode corresponding to a transfer count. 3. The image forming apparatus according to claim 1, wherein the image forming mode is a mode in which an idle rotation operation of the intermediate transfer body is performed after a transfer process to the intermediate transfer body is completed.