JPH05323711A - Image forming device - Google Patents

Abstract

PURPOSE:To improve accuracy in the mutual rotation of three cylinder-like members, etc., in a recording system in which the primary and secondary transfers using an adhesive intermediate transfer body are carried out in sequence. CONSTITUTION:In an image forming device which makes the intermediate transfer body 8 adhere to a toner image carrier 2, creates a potential difference therebetween to transfer a toner image on the toner image carrier 2 to the intermediate transfer body 8, and further transfers the toner image to a recording material by making the recording material in pressure-contact with the intermediate transfer body 8 by the use of a pressure cylinder 27 after heating the toner image and the recording material or while heating them, is provided with: drive means 43, 44 and 45 for driving the toner image carrier 2, the intermediate transfer body 8, and the pressure cylinder 27, respectively, the rotating position detectors 49, 50 and 51 being provided on the shafts of the driving means 43, 44 and 45, respectively; and a cylinder control means 55 for carrying out mutual positioning of the toner image carrier 2, the intermediate transfer body 8 and the pressure cylinder 27, and the control of their phases by having the encoder pulse of one of the rotating position detectors 49-51 as a reference.

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 digital copying machine, a digital color copying machine, a printer or the like, which records image information on a recording material such as paper with toner.

[0002]

2. Description of the Related Art Generally, this type of image formation is performed by utilizing electrophotographic technology. That is, an electrostatic latent image is formed on a photoconductor by image exposure, this is developed with toner, and then electrostatic force is applied to the toner by a corona charger, a bias roller, etc., and transferred to a recording material such as paper, I try to get it by fixing it.

However, such an image forming apparatus has a problem that density unevenness and toner scattering occur in a transferred image, and resolution and dot reproducibility are deteriorated. This is because the paper and the photoconductor do not completely adhere due to the unevenness of the surface of the paper,
It is considered that this is because a non-uniform gap appears, the electric field is disturbed, and Coulomb repulsion between the toners is caused, and the non-uniform force acts on the toner. Therefore,
This is a problem especially in the case of color recording.

From this point of view, the one in which the toner image is not directly transferred from the photoconductor to the recording paper, but the superposed transfer is realized by the corona method using the intermediate transfer member, is disclosed in JP-A-59-59.
It is disclosed in Japanese Patent No. 17572.

[0005]

However, since the system using such an intermediate transfer body also employs the corona system in the secondary transfer, it causes uneven transfer of toner and toner scattering. As a result, there is a problem in that the shape of the dots forming the image is broken and stable color reproduction cannot be performed in the case of color recording.

However, an intermediate transfer member having adhesiveness and elasticity such as silicon rubber is provided, and the photosensitive member having the developed toner image and the intermediate transfer member are brought into pressure contact with each other, and the toner image is adhesively transferred or statically transferred. Primary transfer to the intermediate transfer body by an electric potential difference and secondary transfer to the recording material by the pressure of the pressure cylinder and heating of the toner and the recording material prevent uneven transfer and toner scattering. What you have done is proposed.

However, since the three cylindrical members are used, if the rotational accuracy and the alignment between them are not performed with high accuracy, uneven exposure pitch may occur during latent image formation.
Bleeding of the toner image due to the relative speed difference between the cylindrical members at the time of the primary and secondary transfer, and in particular, dot position deviation in the color image may occur, and further improvement can be said to be necessary.

[0008]

According to a first aspect of the present invention, a cylindrical intermediate transfer member having an adhesive surface is brought into close contact with a cylindrical toner image carrier, and the intermediate transfer member and the toner image carrier are supported. A toner image on the toner image carrier is transferred onto the intermediate transfer member by forming a potential difference between the toner image carrier and the intermediate transfer member, and the toner image on the intermediate transfer member and the recording material are heated or heated. However, in the image forming apparatus in which the recording material is pressed against the intermediate transfer member by a pressure cylinder to transfer the toner image on the intermediate transfer member onto the recording material, Three drive means for individually driving the transfer body and the pressurizing cylinder are provided, and three rotary position detectors are provided by being directly connected to the drive shafts of these respective drive means, and any one of these rotary position detectors is provided. Or one rotation position The toner image bearing member encoder pulses by the detector as a reference, provided cylinder control means for performing an intermediate transfer member and the alignment and phase control between the pressure cylinder each other.

According to the second aspect of the present invention, the intermediate transfer body, in which the intermediate transfer sheet having adhesiveness is wound around the cylinder rotating body, is brought into close contact with the cylindrical toner image carrier, and the intermediate transfer body and the toner image carrier are carried. A toner image on the toner image carrier is transferred onto the intermediate transfer member by forming a potential difference between the toner image carrier and the intermediate transfer member, and the toner image on the intermediate transfer member and the recording material are heated or heated. However, in the image forming apparatus in which the recording material is pressed against the intermediate transfer body by a pressure cylinder to transfer the toner image on the intermediate transfer body onto the recording material, the toner image carrier, the cylinder Form the outer diameter of the rotating body and pressure cylinder equal,
The clamp part for the intermediate transfer sheet is retracted inside the outer diameter position of the cylinder rotating body, and the clamp part of the pressure cylinder for the recording material is projected outside the outer diameter position of the pressure cylinder. Let me arrange.

In this case, according to the third aspect of the invention, ring-shaped elastic bodies having a thickness equal to or less than the thickness of the intermediate transfer sheet are attached to both ends of the intermediate rotating body, and the distance between these ring-shaped elastic bodies is set to the intermediate transfer sheet and The length was set longer than the axial length of the clamp portion of the recording material.

Further, in the invention of claim 4, the surface layer of the ring-shaped elastic body is formed of a heat resistant and low friction coefficient material such as fluorine-based, silicon-based, polyimide or polyamide-imide.

Further, in the invention of claim 5, a developing means of a wet developing system and a cleaning device are provided so as to face the toner image carrier, and the entire circumference of the toner image carrier is L _p , and the maximum image length is When L _i , the developing electrode length is L _d , the surface potential is V _p , the developing bias is V _d , and the cleaning bias is V _c , the relation L _p −L _i > L _d is set,
When a non-image portion having a length (L _p −L _i ) passes through the developing electrode in opposition to the developing electrode, a bias voltage satisfying the relationship of V _c > V _p > V _d is applied to the developing electrode to adhere to the developing electrode. After the toner is once attached to the toner image carrier, only the non-image portion is operated by the cleaning device.

Further, according to the present invention, the toner is held in a state in which the contact position between the toner image carrier and the intermediate transfer sheet on the cylinder rotary member is shifted with respect to the vertical line passing through the axis of the toner image carrier. The image carrier, the cylinder rotator, and the pressure cylinder are arranged substantially vertically, and the cleaning device is also provided for the intermediate transfer member, so that the toner attached to the developing electrode is once attached to the toner image carrier. After that, the intermediate transfer sheet was made to adhere again to the intermediate transfer sheet by the adhesive force of the intermediate transfer sheet, and the cleaning device was operated.

[0014]

According to the invention described in claim 1, the three cylindrical members of the toner image bearing member, the intermediate transfer member and the pressure cylinder are driven by individual driving means, respectively, and
A rotary position detector is provided for each drive shaft, and alignment and phase control between these three cylindrical members are performed with reference to an encoder pulse from one of the rotary position detectors. Therefore, it is possible to improve the rotation accuracy between the three rotating cylindrical members. Therefore, especially in the case of color recording, the dot position shift is reduced, the color matching accuracy is high, and the image quality can be improved.

According to the invention described in claims 2 and 3,
In the case where the three cylindrical members of the toner image carrier, the intermediate transfer member and the pressure cylinder are all made equal in diameter, and even if there is a clamp part, it is mounted on the outer peripheral cam to escape the clamp part. It is possible to drive with high accuracy without such a load fluctuation component. In particular, since the surface layer of the ring-shaped elastic body is formed of the heat resistant and low friction coefficient material as in the invention described in claim 4, the phase matching can be performed by using a slip with a low load.

Further, according to the invention of claim 5, the cleaning of the developing electrode in the developing means of the wet developing system can be easily carried out without using mechanical means.

According to the sixth aspect of the invention, the degree of freedom of arrangement of the cleaning device is increased, and the reliability is improved. In particular, the liquid receiver for preventing liquid dripping in the developing means can be arranged so as to overlap to a position beyond the vertical line of the axis of the toner image carrier.

[0018]

An embodiment of the present invention will be described with reference to the drawings. First, as shown in FIG. 2, in the upper part of the apparatus main body 1, a photosensitive member 2 as a toner image bearing member formed in a cylindrical shape is provided. The shaft 3 of the photoconductor 2 has a face plate 4
It is rotatably supported by and driven to rotate in a counterclockwise direction. Around it, a charging charger 5, an optical writing section 6, a developing device (developing means) 7 by a wet developing system, an intermediate transfer member 8 and a cleaner ( A cleaning device 9 is arranged in order. Here, the optical writing unit 6 forms a laser beam modulated according to an image signal on the photoconductor 2 through an imaging lens 11 and a reflection mirror 12 by rotating and deflecting the laser beam by a polygon mirror 10, thereby performing main scanning. It is something to do.

Although the developing device 7 will be described in detail later, the developing device 7 is generally pumped by the developing solution 14 in the developing solution tank 13.
5 is pumped up and supplied onto the developing electrode 16 arranged facing the photoconductor 2 for development, and the residual developing solution 14 is collected in the developing solution tank 13 using the reverse roller 17. It is configured.

Next, the intermediate transfer member 8 is a cylindrical member provided in place of a transfer charger or the like in a normal electrophotographic process, and as shown in FIG. 2, it is not vertically below the shaft 3 of the photosensitive member 2. The photoconductor 2 is arranged slightly offset to the downstream side in the rotation direction. As shown in FIG. 3, the intermediate transfer body 8 is formed of a cylinder rotary body 18 made of an aluminum tube and an intermediate transfer sheet 20 wound around the cylinder rotary body 18 and supported by a clamp portion 19. .. The intermediate transfer sheet 20 is formed of a material having adhesiveness and elasticity such as silicon rubber. Here, in the cylinder rotating body 18, the clamp portion 19 is formed by cutting out a part of the cylinder rotating body 18 so as to have a substantially D-shaped cross section, so that the leading end of the clamp portion 19 holds the intermediate transfer sheet 20 in a wound state. The height is set so that it does not protrude beyond the outer peripheral surface. The shaft 21 of the intermediate transfer member 8 is supported by a swing lever 23 that is swingable about the shaft 22, and the urging force of a pressure spring 24 locked to a part of the swing lever 23. Thus, the photosensitive member 2 is configured to come into pressure contact with an appropriate pressure contact force. In order to adjust the pressure contact force, the other end of the pressure spring 24 is locked to the pressure adjusting eccentric cam 25, and the eccentric cam 26 for releasing the pressure may interfere with the swing lever 23. It is provided in the position.

Such an intermediate transfer member 8 is driven to rotate in a clockwise direction, and a pressure cylinder 27 is provided in a pressure contact state directly below the intermediate transfer member 8 and is positioned upstream in the rotation direction. A cleaner (cleaning device) 28 and a heater 29 are provided (downstream of the photoconductor 2). Further, a horizontal conveyance path is set between the intermediate transfer body 8 and the pressure cylinder 27, and the transfer paper (recording material) 30
Paper feeding section 31 for feeding paper to the pressure cylinder 27
And a paper ejection unit 32 for receiving the recording paper 30 after recording.

The pressure cylinder 27 rolls and holds the transfer paper 30 fed from the paper feed unit 31, and a clamp portion 33 for holding the leading end of the transfer paper 30 is provided on a part of the outer circumference. It is provided. More specifically, the pressurizing cylinder 2
7 is also made of an aluminum tube similar to the cylinder rotating body 18, and the clamp portion 33 having a clamp claw structure is used for the transfer paper 3
It is provided so as to project outward from the outermost diameter in order to easily clamp 0.

The pressurizing cylinder 27 is rotated counterclockwise about the shaft 34. At both ends of the shaft 34, there are long holes vertically formed in a part of the swing lever 23. A slide bearing 36 guided by 35 is provided,
The intermediate transfer body 8 is held so as to be movable in and out of the axial direction. The slide bearing 36 is rotatably supported by a shaft 37 provided upright on a part of the swing lever 23.
A substantially V-shaped pressure lever 38 having a pressure portion 38a that contacts the lower end of the pressure lever 38 is provided. A pressure spring 39 is locked between the other end of the pressure lever 38 and a part of the swing lever 23, and the pressure lever 38 causes the pressure cylinder 27 to come into pressure contact with the intermediate transfer member 8. Is configured. Here, one end of the pressure spring 39 is locked to the pressure adjustment eccentric cam 40, and the pressure can be adjusted.

A heater 41 is also provided on the outer circumference of the pressure lever 38. These heaters 29, 41
Is an infrared lamp, for example, and is arranged at substantially symmetrical positions when viewed from the nip portion of the intermediate transfer body 8 and the pressure cylinder 27.

The operation of this basic structure will be described. First, when a laser beam modulated according to an image signal is irradiated and image-formed on the photoconductor 2 by the optical writing unit 6, an electrostatic latent image is formed on the photoconductor 2 uniformly charged by the charging charger 5. It is formed. This electrostatic latent image is developed by the developing device 7 by a wet developing method to form a toner image. When this toner image is pressed against the intermediate transfer sheet 20 of the intermediate transfer body 8 while rotating in the counterclockwise direction, the toner image is primarily transferred onto the intermediate transfer sheet 20 by its adhesive force and electrostatic force.

On the other hand, the transfer paper 30 is fed from the paper feed unit 31 to the pressure cylinder 27 at a predetermined timing, and the pressure cylinder 27 is clamped while the leading end is clamped by the clamp unit 33.
It is wound around the outer peripheral surface and further heated by the heater 41 toward the nip portion with the intermediate transfer sheet 20. At this time, the intermediate transfer sheet 20 to which the toner image is primarily transferred is also heated by the heater 29, and the toner is in a semi-melted state, and moves toward the nip portion with the transfer paper 30 on the pressure cylinder 27. As a result, the toner in a semi-molten state in this nip flows on the transfer paper 30 and permeates into the fibers of the paper. At this time, since the releasability works between the intermediate transfer sheet 20 and the intermediate transfer sheet 20, the toner once permeating into the transfer sheet 30 is not offset to the intermediate transfer sheet 20, and the secondary transfer of the toner image onto the transfer sheet 30 is performed. Done.

In the case of color recording, as will be described later, the writing by the color-separated image signal color-separated into Y (yellow), M (magenta), C (cyan), and Bk (black) is performed optically. A color image is obtained by repeating the writing section 6 and correspondingly repeating the above-described steps of development, transfer and the like on the same transfer paper 30.

Therefore, in this embodiment, the intermediate transfer member 8 is used.
In, the ring-shaped elastic bodies 42 are fitted to both ends of the outer peripheral surface of the cylinder rotating body 18. This ring-shaped elastic body 4
2 has a surface layer formed of a heat-resistant and low friction coefficient material such as fluorine-based, silicon-based, polyimide or polyamide-imide, and its thickness is equal to the thickness of the intermediate transfer sheet 20, but is an intermediate transfer sheet. The thickness is equal to or less than 20 so that the thickness is not greater than 20.

Further, as shown in FIGS. 3 and 4, when the distance between the ring-shaped elastic bodies 42 is L ₁ and the axial length of the clamp portion 33 of the pressure cylinder 27 is L ₂ (the clamp portion). 19 is also the same as the axial length), and L ₁ > L ₂ is set, and the ring-shaped elastic body 42 includes the transfer paper 30 and the clamp portion 33.
It is set so that it can contact the pressurizing cylinder 27 itself without contacting.

In practice, the three cylindrical members 2, 8, 2
When assembling 7, the concave portion (clamper portion 19) of the intermediate transfer body 8 and the clamp portion 33 of the pressure cylinder 27 are always in mesh with each other.

Under these conditions, in the present embodiment, the photosensitive member 2, the intermediate transfer member 8 (in which the intermediate transfer sheet 20 is wound) and the pressure cylinder 27 are all formed to have the same outer diameter. Has been made equal in diameter (with respect to the image area). That is, although there is a protruding portion such as the clamp portion 33, since the ring-shaped elastic member 42 is fitted in the intermediate transfer body 8, there is no contact interference between the clamp portion 33 and the intermediate transfer body 8,
It is not necessary to provide a cam-shaped projection or the like for escaping the clamp portion 33. Therefore, load fluctuation is reduced,
Smooth and highly accurate drive is possible. Further, regarding the phase matching in the color superposition in the case of color recording, the photoconductor 2 and the intermediate transfer sheet 20 are also out of the image area, that is, at the position where the toner image does not contact the intermediate transfer sheet 20 as shown in FIG. The transfer paper 3
Even in the secondary transfer for 0, the secondary transfer is performed by performing phase alignment at a position where the intermediate transfer sheet 20 does not contact the transfer sheet 30 as shown in FIG. 5B. In this operation, since the surface layer of the ring-shaped elastic body 42 is made of a material having a low friction coefficient, slipping is possible with a small torque even if the phases are deviated.

Next, the drive system for the photoconductor 2 and the like in this embodiment will be described with reference to FIG. In this example,
Three DC servo motors (driving sources) 43 for individually driving the photoconductor 2, the intermediate transfer body 8, and the pressure cylinder 27,
44 and 45 are provided and are of a direct drive type. Here, the DC servo motor 43 is connected to the shaft 3 of the photoconductor 2 via the coupling 46, but the intermediate transfer member 8 and the pressure cylinder 27 are displaced in position, so that the shafts 21 and 34 are connected to each other. For universal joint 4
The DC servomotors 44 and 45 are connected via 7 and 48. Further, rotary encoders (rotational position detectors) 49, 50, 51 are directly connected to the shafts 3, 21, 34. These rotary encoders 49, 5
0 and 51 are held by brackets 52, 53 and 54, and output a predetermined pulse and a home position pulse corresponding to the rotation of each shaft 3, 21, and 34. The detection outputs of these rotary encoders 49, 50, 51 are passed through a phase control circuit 55 and a motor driver 56, which constitute cylinder control means, to the DC servo motors 43, 4 respectively.
It is fed back to 4,45. In the phase control circuit 55, since the outer diameters of the cylindrical members are equal,
With reference to the encoder pulse output of one of the rotary encoders 49, 50, 51, the photoconductor 2 and the intermediate transfer member 8
The position adjustment and phase control between the pressure cylinders 27 and the pressure cylinders 27 are performed by the PLL method.

Therefore, it is possible to control the mutual accurate alignment and the like. That is, when assembling the three cylindrical members, the home position pulse may be aligned with a predetermined position to perform mutual alignment. In particular, when the length of the entire circumference common to each cylindrical member is L _p and the maximum image length is L _i , there is a relationship of L _p > L _i , and each rotary encoder 4
The DC servo motors 43, 4 are set so that the detection timing (area) for the phase comparison of encoder pulses by 9, 50, 51 is set outside the image area and the phase shift is corrected instantly.
By controlling 4 and 45, it is possible to prevent the occurrence of an abnormal image due to the deviation between the writing and the transfer timing.

By the way, the construction of the developing device 7 for performing color recording is shown in FIG. Y, M, C, B as shown
developer tanks 13 _Y , 13 _M , 1 containing the respective developer solutions of k
3 _C and 13 _Bk are provided, and individual pumps 15 _Y and 15 are provided.
Development electrode 1 by selectively pumping with _M , 15 _C , 15 _Bk
6 is configured so that it can be supplied on the above. A liquid receiving portion 55 is provided below the reverse roller 17. Also,
A bias power source 56 is connected to the developing electrode 16 and a developing bias V _d is applied.

As described above, the peripheral length of the photoconductor 2 is L _p , the maximum image length is L _i , the length of the developing electrode 16 is L _d , the surface potential of the photoconductor 2 is V _p , and the cleaning bias is Is set to V _c , a non-image portion is ensured by setting a relation of L _p −L _i > L _d, and when the non-image portion of L _p −L _i passes by facing the developing electrode 16, the developer electrode 16 V _c
A bias of> V _p > V _d is applied to once attach the toner adhering to the developing electrode 16 to the photoconductor 2, and then the cleaner 9 is applied only to the non-image portion to perform cleaning. Thereby, the developing electrode 16 itself can be easily cleaned without using a mechanical cleaning means. Incidentally, in the conventional case, particularly in the case of the image exposure method and the negative / positive developing method, the surface potential of the background portion of the photoconductor 2 is high, so that the Coulomb repulsive force with the toner causes the developing electrode 16
Since the toner easily adheres to the side, it needs to be cleaned by a mechanical cleaning means, which is mechanically complicated.

The charging to the non-image area may be turned off in a sequence, or the writing light source may be turned on in the non-image area to reduce the surface potential, and the above operation may be performed.

Further, since the present embodiment uses the intermediate transfer member 8, the toner image on the photosensitive member 2 is once transferred onto the intermediate transfer sheet 20, and then the cleaner 28 is actuated for cleaning. You may do it.

[0038]

Since the present invention is configured as described above, according to the first aspect of the invention, the three cylindrical members of the toner image carrier, the intermediate transfer member and the pressure cylinder are individually provided. It is to be driven by a driving means, and each drive shaft is provided with a rotational position detector individually, and between these three cylindrical members with reference to an encoder pulse by one rotational position detector among them. Since the position alignment and the phase control are performed, it is possible to improve the rotation accuracy between the three rotating cylindrical members, and thus to reduce the dot position deviation particularly in the case of color recording, It is possible to achieve high image quality with high color matching accuracy.

Further, according to the invention described in claims 2 and 3,
Since all three cylindrical members, the toner image carrier, the intermediate transfer member, and the pressure cylinder, have the same diameter, even if there is a clamp part, it is necessary to mount it on the outer peripheral cam to escape it. There is no load fluctuation component like
It is possible to drive with higher precision. Particularly, according to the invention of claim 4, since the surface layer of the ring-shaped elastic body is formed of the heat-resistant and low-friction coefficient material, phase adjustment is performed by using a slip with a low load. It can be carried out.

Further, according to the invention of claim 5, the cleaning of the developing electrode in the developing means of the wet developing system can be easily carried out without using mechanical means.

Further, according to the invention of claim 6, the degree of freedom of arrangement of the cleaning device is increased and the reliability is improved, and in particular, a liquid receiver for preventing liquid dripping in the developing means is used as a toner image carrier. It is possible to arrange them so as to overlap with each other until they extend beyond the vertical line of the axis.

[Brief description of drawings]

FIG. 1 is a side view including a drive control system showing an embodiment of the present invention.

FIG. 2 is a schematic front view.

FIG. 3 is a perspective view showing an intermediate transfer member.

FIG. 4 is a perspective view showing a pressure cylinder.

FIG. 5 is a front view showing a phase matching position.

FIG. 6 is a front view showing the vicinity of a developing unit.

[Explanation of symbols]

 2 toner image carrier 7 developing means 8 intermediate transfer body 9 cleaning device 16 developing electrode 18 cylinder rotator 19 clamp part 20 intermediate transfer sheet 27 pressurizing cylinder 28 cleaning device 30 recording material 33 clamp part 43-45 driving means 49-51 Rotational position detector 55 Cylinder control means

Claims (6)

[Claims] 1. A cylinder-shaped intermediate transfer body having an adhesive property on the surface thereof is brought into close contact with a cylindrical toner image carrier to form a potential difference between the intermediate transfer body and the toner image carrier. After transferring the toner image on the toner image carrier onto the intermediate transfer member and heating the toner image on the intermediate transfer member and the recording material, or while heating the recording material, the recording material is transferred to the recording material by a pressure cylinder. In an image forming apparatus in which the toner image on the intermediate transfer body is transferred to the recording material by being pressed against the intermediate transfer body, the toner image carrier, the intermediate transfer body and the pressure cylinder are individually driven 3 Three driving means are provided, three rotational position detectors are directly connected to the drive shafts of the respective driving means, and an encoder pulse by any one rotational position detector among these rotational position detectors is provided. As a standard An image forming apparatus is provided with cylinder control means for performing positional adjustment and phase control among the toner image carrier, the intermediate transfer member and the pressure cylinder. 2. An intermediate transfer body, in which an intermediate transfer sheet having adhesiveness is wound around a cylinder rotating body, is brought into close contact with a cylindrical toner image carrier, and a potential difference between the intermediate transfer body and the toner image carrier. To transfer the toner image on the toner image bearing member onto the intermediate transfer member, and after heating the toner image on the intermediate transfer member and the recording material, or while heating, a pressure cylinder. In the image forming apparatus, wherein the recording material is brought into pressure contact with the intermediate transfer body to transfer the toner image on the intermediate transfer body onto the recording material, the toner image carrier, the cylinder rotating body, and the pressure cylinder. Have the same outer diameter, the clamp portion for the intermediate transfer sheet is retracted inside the outer diameter position of the cylinder rotating body, and the pressure cylinder for the recording material is provided. The image forming apparatus is characterized in that the clamp part is arranged so as to protrude outside the outer diameter position of the pressure cylinder. 3. A ring-shaped elastic body having a thickness equal to or less than the thickness of the intermediate transfer sheet is attached to both ends of the intermediate rotating body, and the distance between the ring-shaped elastic bodies is set to the axial length of the clamp section of the intermediate transfer sheet and the recording material. The image forming apparatus according to claim 2, wherein the image forming apparatus is set to be longer than the length. 4. The image forming apparatus according to claim 3, wherein the surface layer of the ring-shaped elastic body is formed of a heat resistant and low friction coefficient material such as fluorine-based, silicon-based, polyimide or polyamide-imide. 5. A wet developing type developing means and a cleaning device are provided so as to face the toner image carrier, and the entire circumference of the toner image carrier is L _p , the maximum image length is L _i , and the developing electrode length is L. _d , the surface potential is V _p , the developing bias is V _d , and the cleaning bias is V _c , the relationship is set to L _p −L _i > L _d , and the non-image part of length (L _p −L _i ). When passing through the developing electrode, V _c > V _p
A bias voltage satisfying a relation of> V _d is applied to temporarily attach the toner attached to the developing electrode to the toner image carrier, and then the cleaning device is operated only in the non-image portion. The image forming apparatus according to item 2, 3 or 4. 6. The toner image carrier and the cylinder rotator in a state in which a position where the toner image carrier and the intermediate transfer sheet on the cylinder rotator are in contact with each other is shifted with respect to a vertical line passing through the axis of the toner image carrier. The pressurizing cylinder and the intermediate transfer member are provided in a substantially vertical direction, and a cleaning device is also provided for the intermediate transfer member so that the toner attached to the developing electrode is once attached to the toner image carrier, and then the intermediate transfer sheet is further transferred. 6. The image forming apparatus according to claim 5, wherein the cleaning device is caused to adhere again onto the intermediate transfer sheet by the adhesive force of [1].