JPH09114278A - Transferring device for image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transferring device for an image forming device capable of effectively preventing the dirt of a recording paper trailing end. SOLUTION: The transferring device of the image forming device for transferring the toner image on a photoreceptor drum 1 to a recording paper P by the transferring roll 6, is provided with re-contact preventive means for energizing the trailing end of the recording paper P in the direction distanced from a surface of the transferring roll 6 right after the recording paper is allowed to pass through a nip part of the transferring roll 6. For instance, the re-contact preventive means is, a transporting device 9 for transporting the recording paper P 10 allowed to pass through the nip part toward the fixing device, and its transporting velocity VT is set quicker than the surface velocity VR of the transferring roll 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer device used in a transfer device of an image forming apparatus such as a copying machine,
In particular, the present invention relates to a transfer device of an image forming apparatus that prevents stains on recording paper during transfer.

[0002]

2. Description of the Related Art For example, in an electrophotographic copying machine, the surface of a photosensitive drum, which is an image carrier, is uniformly charged and exposed to light corresponding to the image of an original to form an electrostatic latent image. Then, the electrostatic latent image is developed to form a toner image, and the toner image is transferred to the recording paper by the transfer device.

A transfer device, for example, a transfer roll, is arranged adjacent to the photosensitive drum, and is applied with a voltage having a polarity opposite to the charge of the toner. The photoconductor drum and the transfer roll rotate while being in pressure contact with each other. The recording paper is conveyed while being sandwiched between the photoconductor drum and the transfer roll,
At this time, the toner on the photosensitive drum is electrostatically attracted toward the transfer roll via the recording paper, and the toner is transferred to the recording paper. The recording paper after the transfer comes out from between the photoconductor drum and the transfer roll, and is conveyed by a belt or the like for the subsequent fixing process. In such a transfer device, a part of the toner on the photosensitive drum or a part of the toner floating in the device is attracted to the potential of the transfer roll and adheres to the surface of the transfer roll, so that the transfer roll is contaminated. There is.

In the transfer step, it is desirable that only the toner on the photosensitive drum is transferred to the recording paper. However, in reality, dirt due to toner adheres due to various causes.

For example, when the recording paper passes between the photosensitive drum and the photosensitive drum, the toner adhering to the front surface of the transfer roll may adhere to the back surface of the recording paper to stain the back surface of the recording paper. .

Further, when the recording paper comes out of the nip portion between the photosensitive drum and the transfer roll, for example, the trailing end of the recording paper hangs downward due to curl or its own weight and comes into contact with the surface of the transfer roll again. The toner that has adhered to the surface of the transfer roll may adhere to the trailing edge of the recording paper and stain the trailing edge of the recording paper.

In order to solve such a problem, in JP-A-55-153973, a gap about the thickness of the recording paper is provided between the image carrier and the transfer roll to prevent the transfer roll from being soiled. By doing so, it is disclosed that the back surface of the recording paper is prevented from being soiled. However, since the gap between the image carrier and the transfer roll in the magnetic roll development is 200 to 300 μm, the thickness of the recording paper as described in the above publication, that is, 1
With a gap of about 100 μm, it is difficult to prevent the toner from flying from the image carrier to the transfer roll.

Further, as described in Japanese Patent Laid-Open No. 1-269967, when the recording paper is placed along the transfer roll for the purpose of preventing the image disturbance after the transfer, one layer of the trailing edge of the recording paper is formed. The dirt gets worse.

Further, it has been proposed that the surface speed of the transfer roll is made higher than the speed of the recording paper in order to prevent the characters from being missing when the transfer roll is used. At the moment the trailing edge leaves the transfer nip, the trailing edge of the recording paper is pushed out by the transfer roll.
Contamination at the trailing edge is accelerated and the image quality is significantly deteriorated.

[0010]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a transfer device of an image forming apparatus capable of effectively preventing the rear end of the recording paper from being soiled.

[0011]

SUMMARY OF THE INVENTION The present invention is a transfer device of an image forming apparatus for transferring a toner image of an image carrier to a recording paper by a contact transfer means, wherein the recording paper is a contact transfer portion of the contact transfer means. Re-contact preventing means for urging the rear end of the recording paper in a direction of separating from the contact transfer means immediately after passing is provided.

In the present invention, the re-contact preventing means is a conveying means for conveying the recording paper having passed through the contact transfer section toward a fixing device, and the conveying speed is the surface speed of the contact transfer means. It is characterized in that the conveying means is set faster.

Further, the present invention is characterized in that the conveying means is a suction type conveying means for sucking the recording paper by negative pressure.

Further, in the present invention, the re-contact preventing means is arranged so that the rear end of the recording paper is separated from the contact transfer means by the air flow immediately after the recording paper passes through the contact transfer portion of the contact transfer means. It is characterized in that it is an air blowing means for energizing.

Further, according to the present invention, the re-contact preventing means is a conveying means for conveying the recording paper having passed through the contact transfer section toward a fixing device, and the position of the end portion on the contact transfer section side is It is characterized in that the recording paper is a movable type conveyance means that is movable in a direction away from the contact transfer means immediately after passing through the contact transfer portion of the contact transfer means.

According to the present invention, the contact transfer means is arranged above the image carrier, and the re-contact preventing means has a fixing nip position between the contact transfer means and the image carrier. The fixing device is arranged closer to the image carrier than the horizontal line passing through the transfer nip position.

Further, in the present invention, the re-contact preventing means is arranged such that the rear end of the recording paper is separated from the contact transfer means by an electrostatic force immediately after the recording paper passes through the contact transfer portion of the contact transfer means. It is characterized by being an electric field applying means for energizing.

The present invention is also a transfer device in which the electric field applying means is included in the contact transfer means, and the recording paper is located at the position of the end portion on the contact transfer portion side of the contact transfer portion of the contact transfer means. The transfer device is characterized in that the transfer electric field is strengthened immediately after passing.

Further, according to the present invention, there is provided a static eliminator for removing static electricity from the recording paper after the electric field applying means has transferred, wherein the recording paper is the contact transfer portion of the contact transfer means at an end position on the contact transfer portion side. The static eliminator is characterized in that the static elimination electric field is weakened immediately after passing through.

[0020]

1 is a schematic diagram showing a schematic configuration of an image forming apparatus to which a transfer device of the present invention is applied.

Around the photosensitive drum 1 which is an image carrier, a charger 2, an exposure device 3, a developing device 4, a paper guide 5, a transfer roll 6 which is a transfer device, a charge eliminating electrode 7, a cleaning device 8 and the like are provided. They are arranged in sequence. Further, a suction conveyance device 9 that conveys the transfer recording paper, and a fixing device 10 that includes a pair of fixing rolls 10a and 10b that performs a fixing process on the recording paper are provided. 2a, 6a and 7a are
It is a power source that applies a voltage of a predetermined polarity and a predetermined magnitude to the charger 2, the transfer roll 6, and the charge eliminating electrode 7.

In the image forming apparatus shown in FIG. 1, the surface of the photosensitive drum 1 is charged by the charger 2 and exposed by the exposing device 3 to form an electrostatic latent image, and the electrostatic latent image is developed by the developing device. 4 is developed to form a toner image T. On the other hand, in synchronization with the formation of the toner image T, the recording paper P is sent to the nip portion between the photosensitive drum 1 and the transfer roll 6 via the paper guide 5. The recording paper P is conveyed while being sandwiched between the photosensitive drum 1 and the transfer roll 6,
At this time, the toner image T on the photoconductor drum 1 is transferred to the recording paper P.
The toner image T is electrostatically attracted toward the transfer roll 7 via the transfer roller 7, and the toner image T is transferred to the recording paper. The recording paper P after transfer is
After being discharged from between the photoconductor drum 1 and the transfer roll 6 and being neutralized by the static elimination electrode 7, it is transported to the fixing device 10 by the suction transport device 9. The toner remaining on the surface of the photosensitive drum 1 after the transfer is removed by the cleaning device 8 to prepare for the next image forming cycle.

[0023]

【Example】

[First Embodiment] FIG. 2 is a schematic view of the essential portions of a first embodiment of the present invention.

In the first embodiment, the suction conveyance device 9
The transport speed V _T of the recording paper P due to is set to be higher than the peripheral speed of the transfer roll 6, that is, the surface speed V _R. As a result, the recording paper P is transferred between the photosensitive drum 1 and the transfer roll 6,
That is, immediately after the recording paper P exits from the transfer nip portion, the conveyance speed of the recording paper P changes from V _R to V _T, and the conveyance speed of the recording paper P increases, so that the trailing edge of the recording paper P is the transfer roll 6. Leaves the surface rapidly. Therefore, the toner on the surface of the transfer roll 6 does not adhere to the rear end of the recording paper P, and the rear end of the recording paper P can be reliably prevented from being soiled. Also,
Since the recording paper P is stably conveyed by the suction conveyance device 9 while being pulled by the negative pressure, the rear end of the recording paper P and the surface of the transfer roll 6 are surely brought into contact with each other regardless of the size of the recording paper P. Can be prevented.

[Second Embodiment] FIG. 3 is a schematic view showing a second embodiment of the present invention. Members corresponding to those shown in FIG. 1 are designated by the same reference numerals.

In the second embodiment, an air duct 13 having a fan motor 11 at one end and an outlet 12 at the other end is provided, and the outlet 12 of the air duct 13 conveys the recording paper P. Regarding the direction, the photosensitive drum 1
It is arranged immediately downstream of the transfer nip portion between the transfer roller 6 and the transfer roller 6. In addition, in the vicinity of the transfer nip portion, the recording paper P
A paper sensor 14 for detecting the passage of the paper is disposed, and the control circuit 15 is based on the output of the paper sensor 14.
The fan motor 11 is controlled accordingly.

FIG. 4 is a timing chart of fan motor control in the second embodiment. When the front end of the recording paper P reaches the position of the paper sensor 14, the paper sensor 14 is turned on, and when the rear end of the recording paper P reaches the position of the paper sensor 14, the paper sensor 14 is turned off. The fan motor 11 is turned on for a short period of time after the paper sensor 14 is turned on, and air is sent out from the air outlet 12 of the air duct 13, and the trailing edge of the recording paper P is transferred by the air flow. Away from the surface of. As a result, the trailing edge of the recording paper P that has slipped out of the transfer nip portion is transferred to the transfer roll 6
Therefore, the rear end of the recording paper P can be prevented from being soiled. The fixed time is set so that the fan motor 11 is turned on when the trailing edge of the recording paper P leaves the transfer nip portion or immediately after the trailing edge.
For example, if the distance between the paper sensor 14 and the transfer nip portion is L
1. When the length of the recording paper P is L2 and the process speed is V, the above-mentioned fixed time is (L1 + L2) / V. When the rear end of the recording paper P is no longer in contact with the surface of the transfer roll 6 again, the fan motor 11 is turned off and the recording paper P is turned off.
Are normally transported by the suction transport device 9. The fan motor 11 may be turned on for a short time after the trailing edge of the sheet is detected and after a certain time corresponding to the distance L1. Further, the resist generally provided on the upstream side of the transfer nip portion may also be used as the paper sensor 14.

[Third Embodiment] FIG. 5 is a schematic view showing a third embodiment of the present invention. Members corresponding to those shown in FIG. 1 are designated by the same reference numerals.

In the third embodiment, a movable guide 16 tiltably provided about a shaft 15a is used as a device for conveying the recording paper after transfer to the fixing device. Although not shown in FIG. 5, in the third embodiment, a tiltable transfer device is provided, and the movable guide 16 is attached to this transfer device. It should be noted that this transfer device does not have to be a suction type. One end of a drive lever 18 rotatably provided about a shaft 17 is in contact with the bottom surface of the movable guide 16,
The other end of the drive lever 18 is connected to a solenoid 20 via a link 19. This solenoid 20
Also, similarly to the second embodiment, it is controlled by the control circuit 15 to which the output of the paper sensor 14 is supplied (not shown in FIG. 5).

FIG. 6 is a timing chart of solenoid control in the third embodiment. When the front end of the recording paper P reaches the position of the paper sensor 14, the paper sensor 14 is turned on, and when the rear end of the recording paper P reaches the position of the paper sensor 14, the paper sensor 14 is turned off. After the paper sensor 14 is turned on, the solenoid 20 is turned on for a short period of time after a certain period of time. As a result, the drive lever 18 is pulled by the solenoid 20 and rotated clockwise, and the movable guide 16 is pushed up by the tip of the drive lever 18. Since the end of the movable guide 16 on the fixing device 10 side is rotatably supported by the shaft 15a, the end of the movable guide 16 on the transfer nip side is lifted. Therefore, the recording paper P on the movable guide 16
The rear end is separated from the surface of the transfer roll 6. This allows
The trailing edge of the recording paper P that has come out of the transfer nip does not come into contact with the surface of the transfer roll 6, and the trailing edge of the recording paper P can be prevented from being soiled. When there is no risk of the trailing edge of the recording paper P coming into contact with the surface of the transfer roll 6 again, the solenoid 2
When 0 is turned off, the movable guide 16 is placed in a horizontal state, and the recording paper P is smoothly slid along the surface of the movable guide 16 to be conveyed as usual.

The above-mentioned fixed time is, for example, the paper sensor 1
4 is L1 and the length of the recording paper P is L1.
2. When the process speed is V, (L1 + L2) / V
And

[Fourth Embodiment] FIG. 7 is a schematic view showing a fourth embodiment of the present invention. Members corresponding to those shown in FIG. 1 are designated by the same reference numerals.

In the fourth embodiment, the photosensitive drum 1
The charging device 2 is disposed below the transfer roller 6 and the transfer roller 6 is disposed on the information of the photoconductor drum 1. The transfer nip portion between the photoconductor drum 1 and the transfer roll 6 (intersection point of the vertical line a and the horizontal line b). The position of the nip portion (shown by the intersection of the vertical line c and the horizontal line d) of the fixing device 10 is on the side of the photoconductor drum 1 rather than the horizontal line b passing through (shown by the position). Also,
Between the transfer nip portion and the nip portion of the fixing device 10, there is provided a suction type conveying device 21 which is inclined slightly downward.

In the fourth embodiment, the recording paper P passing through the transfer nip portion is conveyed to the fixing device 10 via the suction type conveying device 21, but the trailing end of the recording paper P passes through the transfer nip portion. Immediately after that, the trailing edge of the recording paper P moves in the direction away from the surface of the transfer roll 6 by its own weight. This allows
The trailing edge of the recording paper P that has come out of the transfer nip does not come into contact with the surface of the transfer roll 6, and the trailing edge of the recording paper P can be prevented from being soiled. The recording paper P that has come out of the transfer nip portion is fixed by the suction type conveyance device 21 to the fixing device 1.
Transported to zero.

In the fourth embodiment, since the recording paper P is ejected with the image side facing down, it is possible to output copies or prints of a plurality of pages from the first sheet and arrange the page order, thus improving the productivity. Has the advantage of being high.

[Fifth Embodiment] FIG. 8 is a schematic view showing a fifth embodiment of the present invention. Members corresponding to those shown in FIG. 1 are designated by the same reference numerals.

In the fifth embodiment, the power source 6a for applying a voltage to the transfer roll 6 is a variable output voltage power source,
The voltage applied to the transfer roll 6 can be controlled by the control circuit 15 to which the output of the paper sensor 14 is supplied.

FIG. 9 is a timing chart of the transfer device control in the fifth embodiment. When the front end of the recording paper P reaches the position of the paper sensor 14, the paper sensor 14 is turned on, and when the rear end of the recording paper P reaches the position of the paper sensor 14, the paper sensor 14 is turned off. When the paper sensor 14 is turned on, a voltage is applied to the transfer roll 6 from the power source 6a, and an electric field (relatively low electric field) required for transfer is obtained. Next, after the paper sensor 14 is turned on, the power source 6
The output voltage of a is increased for a short time. As a result, when the trailing edge of the recording paper P passes through the transfer nip, or immediately after passing, the transfer electric field becomes high (relatively high electric field), and the electrostatic attraction force to the photosensitive drum 1 side becomes strong. The trailing edge of the recording paper P follows the photosensitive drum 1 side. For example,
In the case of reversal development in which the surface of the photoconductor drum 1 is negatively charged, toner having a negative charge adheres to the exposed portion (discharged portion). On the other hand, a positive charge is supplied to the recording paper P from the transfer roll 6, and the toner is attracted to the recording paper P. At this time, the electrostatic attraction force also acts between the photosensitive drum 1 and the recording paper P, and the recording paper P receives a force in the direction of the photosensitive drum 1,
It becomes easy to follow the surface of the photoconductor drum 1. As a result, the balance between the electrostatic attraction force and the waist strength of the recording paper P changes,
The recording paper P is separated from the surface of the photosensitive drum 1 on the downstream side. As a result, the trailing edge of the recording paper P that has come out of the transfer nip portion does not come into contact with the surface of the transfer roll 6, and the trailing edge of the recording paper P can be prevented from being soiled. When there is no risk of the trailing edge of the recording paper P coming into contact with the surface of the transfer roll 6 again, the application of the transfer electric field is stopped.

[Sixth Embodiment] FIG. 10 shows the sixth embodiment of the present invention.
It is a schematic diagram which shows Example of this. Members corresponding to those shown in FIG. 1 are designated by the same reference numerals.

In the sixth embodiment, the power supply 7a for applying a voltage to the static elimination electrode 7 is a variable output voltage power source, and the voltage applied to the static elimination electrode 7 is supplied to the output of the paper sensor 14. It can be controlled by the circuit 15.

FIG. 11 is a timing chart for controlling the charger in the sixth embodiment. When the front end of the recording paper P reaches the position of the paper sensor 14, the paper sensor 14 is turned on, and when the rear end of the recording paper P reaches the position of the paper sensor 14, the paper sensor 14 is turned off. When the paper sensor 14 is turned on, a voltage is applied from the power source 7a to the static elimination electrode 7, and an electric field (relatively high electric field) required for static elimination is obtained. Next, after the paper sensor 14 is turned on, the power supply 7
The output voltage of a is lowered for a short time. As a result, when the trailing edge of the recording paper P passes through the transfer nip, or immediately after passing, the power removal becomes small (relatively low power removal), and the electrostatic charge between the photosensitive drum 1 and the recording paper is reduced. The suction power is maintained,
The trailing edge of the recording paper P follows the photosensitive drum 1 side.
As a result, the trailing edge of the recording paper P that has come out of the transfer nip portion does not come into contact with the surface of the transfer roll 6, and the trailing edge of the recording paper P can be prevented from being soiled. When there is no risk of the trailing edge of the recording paper P re-contacting the surface of the transfer roll 6,
The application of the transfer electric field is stopped.

[0042]

According to the present invention, the re-contact preventing means is provided for urging the rear end of the recording paper in the direction of separating from the contact transfer means immediately after the recording paper passes through the contact transfer portion of the contact transfer means. The trailing edge of the recording sheet will not come into contact with the surface of the contact transfer means again, and the trailing edge of the recording sheet can be prevented from being soiled.

Further, the recording paper after transfer can be stably carried by the suction-type carrying means having a carrying speed faster than the surface speed of the contact transfer means, so that regardless of the size of the recording paper.
It is possible to reliably prevent the trailing edge of the sheet from re-contacting the surface of the contact transfer unit.

When the trailing edge of the recording sheet is urged by the airflow in the direction away from the contact transfer means to prevent the trailing edge of the recording sheet from being soiled, the recording sheet conveying speed after passing through the transfer section is Since the surface velocities of the contact transfer means can be the same, it is possible to prevent image bleeding due to the speed difference.

Further, by providing movable conveying means, the leading edge of the recording paper is conveyed to the fixing device in a stable posture,
In addition, since only the trailing edge of the recording paper can be separated from the surface of the contact transfer means immediately after the recording paper passes through the contact transfer portion of the contact transfer means, the characteristics of the fixing device are adversely affected such as wrinkles. Therefore, the rear end of the recording paper can be effectively prevented from being soiled.

In order to prevent the trailing edge of the recording paper from being soiled by setting the position of the fixing nip portion closer to the image carrier than the horizontal line passing through the transfer nip portion, additional parts and movable parts are required. Therefore, the installation space can be reduced and the manufacturing cost can be reduced.
Further, since the copy and print can be output from the first page, the productivity is high.

Further, when the rear end of the recording paper is separated from the surface of the contact transfer means by using electrostatic force to prevent the rear end of the recording paper from being soiled, mechanical operation is not necessary, so mechanical vibration is not required. It is possible to prevent image disturbance such as banding due to the above, and to speed up the process. When controlling the transfer electric field, the trailing edge of the recording paper can be easily pulled to the image carrier side, and when controlling the static elimination electric field, the transfer performance of the trailing edge of the recording paper is not impaired. .

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a schematic configuration of an image forming apparatus to which a transfer device of the present invention is applied.

FIG. 2 is a schematic view of an essential part showing a first embodiment of the present invention.

FIG. 3 is a schematic diagram showing a second embodiment of the present invention.

FIG. 4 is a timing chart of fan motor control in the second embodiment.

FIG. 5 is a schematic diagram showing a third embodiment of the present invention.

FIG. 6 is a timing chart of solenoid control in the third embodiment.

FIG. 7 is a schematic diagram showing a fourth embodiment of the present invention.

FIG. 8 is a schematic view showing a fifth embodiment of the present invention.

FIG. 9 is a timing chart of transfer device control in the fifth embodiment.

FIG. 10 is a schematic diagram showing a sixth embodiment of the present invention.

FIG. 11 is a timing chart of charger control in a sixth embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum, 2 ... Charging device, 3 ... Exposure device, 4 ... Developing device, 5 ... Paper guide, 6 ... Transfer roll, 7 ... Static elimination electrode, 8 ... Cleaning device, 9 ... Suction conveyance device, 10 ...
Fixing device 2a, 6a, 7a ... Power source, 11 ... Fan motor, 12 ... Blow-out port, 13 ... Air duct, 14 ... Paper sensor, 15 ... Control circuit, 15a ... Shaft, 16 ... Movable guide, 17 ... Shaft, 18 … Drive lever, 19… Link, 20
… Solenoid, 21… Paper guide

Claims (9)

[Claims] 1. A transfer device of an image forming apparatus for transferring a toner image of an image carrier onto a recording paper by a contact transfer means, wherein the recording paper is passed through the contact transfer part of the contact transfer means and immediately after the recording paper. A transfer device of an image forming apparatus, comprising re-contact preventing means for urging an end in a direction of separating from the contact transfer means. 2. The re-contact preventing unit is a conveying unit that conveys the recording paper that has passed through the contact transfer unit toward a fixing device, and the conveying speed is set to be higher than the surface speed of the contact transfer unit. The transfer device of the image forming apparatus according to claim 1, wherein the transfer device is a transporting unit. 3. The transporting means is a suction-type transporting means for sucking the recording paper sheet with a negative pressure.
A transfer device of the image forming apparatus described. 4. The re-contact preventing means urges the trailing edge of the recording paper in a direction away from the contact transfer means by an airflow immediately after the recording paper passes through the contact transfer portion of the contact transfer means. The transfer device of the image forming apparatus according to claim 1, wherein the transfer device is an air blowing unit. 5. The re-contact preventing unit is a conveying unit that conveys the recording paper, which has passed through the contact transfer unit, toward a fixing device, and the position of the end portion on the contact transfer unit side is the recording paper. 2. The transfer device for an image forming apparatus according to claim 1, wherein is a movable transfer unit that is movable in a direction away from the contact transfer unit immediately after passing through the contact transfer unit of the contact transfer unit. 6. The contact transfer means is disposed above the image carrier, and the re-contact preventing means has a fixing nip position at a transfer nip position between the contact transfer means and the image carrier. 2. The transfer device for an image forming apparatus according to claim 1, wherein the transfer device is a fixing device disposed closer to the image carrier than a horizontal line passing through. 7. The re-contact preventing means urges the rear end of the recording paper in a direction of separating from the contact transfer means by an electrostatic force immediately after the recording paper passes through the contact transfer portion of the contact transfer means. The transfer device of the image forming apparatus according to claim 1, wherein the transfer device is an electric field applying unit. 8. A transfer device in which the electric field applying unit is included in the contact transfer unit, and the position of the end portion on the contact transfer unit side is set immediately after the recording paper passes through the contact transfer unit of the contact transfer unit. 8. The transfer device of the image forming apparatus according to claim 7, wherein the transfer device is a transfer device capable of strengthening a transfer electric field. 9. A static eliminator for removing static electricity from the recording paper after the transfer by the electric field applying means, wherein the position of the end portion on the contact transfer portion side is immediately after the recording paper passes through the contact transfer portion of the contact transfer means. 8. The transfer device for an image forming apparatus according to claim 7, wherein the transfer device is a charge removing device that weakens the charge removing electric field.