JP2001083770A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an image defect such as the scattering and the passing- through of a toner image transferred to transfer material. SOLUTION: Distance relation between a transfer belt 12, a resist unit 7 for aligning the toner image with the transfer material P in a batch transfer stage and a pre-transfer guide 8 regulating the posture of the material P and the center line L2 of a photoreceptor drum 1 parallel with a tangent L1 passing through a transfer nip T in a carrying path for the material P from a resist nip R to the transfer nip T is set as follows. Assuming that a distance to the nip T from the center line L2 is A, a distance to the edge of the guide 8 therefrom is B and a distance to the nip R therefrom is C, the values are set so that relation A>=B and A>C may be established.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic color image forming apparatus such as a copying machine, a laser beam printer, and a facsimile.

[0002]

2. Description of the Related Art FIG. 6 partially shows an example of a conventional electrophotographic color image forming apparatus.

The color image forming apparatus of this embodiment is of a system in which toner images of a plurality of colors sequentially superimposed on the image carrier 101 are collectively transferred to a transfer material P, and the toner images are transferred. The transfer material P is transferred to a transfer roller 1 serving as a contact transfer unit.
10 to be conveyed.

In such an image forming apparatus, a charging roller (transfer roller) 110 is used at a portion where batch transfer is performed, and a transfer bias power source (in synchronization with a plurality of color toner images on the image carrier 101) is used. (Not shown) to apply a predetermined transfer bias.

The transfer roller 110 is separated from the image carrier 101 until a plurality of color toner images are superimposed on the image carrier 101, and the plurality of color toner images are collectively transferred to the transfer material P. The transfer nip (hereinafter, referred to as “transfer nip”) T is formed by being brought into contact with the image carrier 101 in accordance with the timing at which the transfer is performed thereon.

[0006] The registration unit 107 includes the image carrier 1
Roller 118 located in parallel with the axis
And the registration lower roller 119, the registration nip R
Is formed. The registration unit 107 is disposed upstream of the transfer roller 110 in the transport direction of the transfer material P, and transfers a plurality of color toner images on the image carrier 101 to predetermined positions on the transfer material P. The transfer material P is conveyed at a predetermined timing in synchronization with the image carrier 101 as described above. The distance between the center line L2 of the image carrier 101 parallel to the tangent line L1 passing through the transfer nip T and the center line L2 of the image carrier 101 Is arranged so as to be larger than the distance from the transfer nip T to the transfer nip T.

The above-mentioned image carrier is a photosensitive drum in an image forming apparatus of a multi-developing system, and is an intermediate transfer member in an image forming apparatus of a multi-transfer system.

[0008]

However, the above conventional example has the following problems.

With reference to FIG. 7, the cause of the problem in the conventional electrophotographic color image forming apparatus will be schematically described.

The transfer material P started to be conveyed at a predetermined timing by the registration unit 7 (see FIG. 6) is conveyed to the transfer nip T by a transfer material conveyance guide 108 provided immediately before the transfer section. When the toner image on the image carrier 101 is collectively transferred to the transfer material P, the transfer roller 110
The transfer member P is in contact with the image carrier 101 via the transfer material P. Thereafter, a transfer bias synchronized with the toner image is applied to the transfer roller 1.
10, the toner image is transferred from the image carrier 101 to the transfer material P. When the transfer bias is applied, an electric field is generated due to a potential difference between the image carrier 101 and the transfer material P in a minute space between the image carrier 101 and the transfer material P immediately before the transfer nip T. The toner t charged negatively and electrostatically attracted to the image carrier 101 moves electrostatically to the transfer material P side in the minute space, and the toner image is disturbed (scattered) on the transfer material P. There was a problem.

This phenomenon is a state in which the toner t is scattered around the originally drawn line. In an extreme example, in fine kanji, blank portions are filled with the scattered toner t, and it is difficult to identify characters. become.

Further, when the transfer material P has a high resistance (such as an OHP sheet), an electric field is generated between the transfer material P and the image carrier 101, and the toner image is not transferred normally and partially comes off (penetration). ).

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a color image forming apparatus capable of preventing a toner image transferred to a transfer material from scattering and piercing.

[0014]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
In a color image forming apparatus that sequentially forms images of a plurality of colors on an image carrier and collectively transfers the transfer material to a transfer material using a contact transfer unit, a registration unit that positions the image and the transfer material during the batch transfer step A transfer material transport guide that regulates the orientation of the transfer material, and a center line of the image carrier that is parallel to a tangent passing through a transfer nip formed by the image carrier and the contact transfer unit. When the distance to the tangent passing through the transfer nip is A, the transfer material separation position to the tip of the pre-transfer guide is B, and the distance to the resist nip formed by the resist unit is C, A ≧
The color image forming apparatus is characterized in that the value of the distance is set so that the relationship of B, A> C is established.

It is preferable that the contact transfer means is a transfer belt. According to another aspect, the contact transfer unit is preferably a transfer roller. Further, it is preferable that the image carrier is a drum-type electrophotographic photosensitive member.
According to another aspect, it is preferable that the image carrier is a drum-type intermediate transfer body.

According to another aspect of the present invention, there is provided a color image forming apparatus for sequentially forming images of a plurality of colors on a belt-shaped image carrier and collectively transferring the images to a transfer material using contact transfer means. Transfer nip formed by the belt-shaped image carrier and the contact transfer means, comprising a registration unit for aligning the image and the transfer material at the time of transfer, and a transfer material transport guide for regulating the posture of the transfer material. Stretching the belt-shaped image carrier parallel to a tangent passing through,
The distance from the center line of the opposing roller in contact with the contact transfer unit via the belt-shaped image carrier to the tangent line passing through the transfer nip is A, and the distance from the transfer material transport guide to the transfer material separation position is B. When the distance to the resist nip formed by the resist unit is C, A ≧
A color image forming apparatus is provided, wherein the value of the distance is set such that the relationship of B, A> C is satisfied.

Preferably, the belt-shaped image carrier is a belt-type electrophotographic photosensitive member. According to another aspect, it is preferable that the belt-shaped image carrier is a belt-type intermediate transfer body.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a color image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

Embodiment 1 FIG. 1 shows a laser printer as a first embodiment of a color image forming apparatus according to the present invention. The laser printer shown in FIG. 1 performs full-color printing (image formation) by performing four-color multiplex development.

The printer of this embodiment includes a drum-type electrophotographic photosensitive member (hereinafter, referred to as "photosensitive drum") 1 as an image carrier. The photosensitive drum 1 is driven to rotate at a predetermined process speed (peripheral speed) in the direction of arrow R1 by a driving unit (not shown).

In the course of rotation, the photosensitive drum 1 is uniformly charged to a predetermined polarity and a predetermined potential by the primary corona charger 2, and then subjected to image exposure means (for example, color separation / imaging exposure of a color original). A first color in a target color image by receiving image exposure 3 by an optical system or a scanning exposure system using a laser scanner that outputs a laser beam modulated in accordance with a time-series electric digital pixel signal of image information. An electrostatic latent image corresponding to the component image (for example, a yellow component image) is formed.

Next, the electrostatic latent image is transferred to the first
Developing unit (yellow developing unit) 4Y develops with yellow toner Y as the first color.

The yellow, magenta, cyan, and black developing units 4Y, 4M, 4C, and 4BK are mounted on a rotary 4a rotatable in the direction of arrow R4. By rotation in the R4 direction, the photosensitive drum 1 is arranged at a developing position D facing the photosensitive drum 1.

The above-mentioned yellow toner image is not transferred to the transfer material P in the next step, and the photosensitive drum 1 is again brought to a predetermined polarity and a predetermined potential by the primary corona charger 2 in order to develop the next toner image. The image is uniformly charged, an electrostatic latent image corresponding to a second color component image (for example, a magenta component image) of the color image is formed, and is developed with the magenta toner M of the second color.

Similarly, the third color (for example, cyan) and the fourth color (for example, black) are sequentially superimposed and developed on the photosensitive drum 1 to form a composite color toner image corresponding to a target color image.

The toner used in this embodiment is a non-magnetic toner having an average particle diameter of 8 μm and a normal environment (temperature: 25 ° C., relative humidity: 5 μm).
(0%) is about −25 μC / g.

The registration unit 7 is arranged on the upstream side of the transfer nip T in the transfer material P transport direction, and aligns the image and the transfer material P in the transfer nip T during the batch transfer process. The resist unit 7 presses two rollers, that is, a resist upper roller 18 and a resist lower roller 19, arranged in parallel with the axis of the photosensitive drum 1 with a resist pressing spring (not shown), thereby forming a resist nip R. Has formed. The registration upper roller 18 and the registered roller 19 can be repeatedly rotated and stopped by an electromagnetic clutch (not shown). A resist upper roller 18 that moves up and down in accordance with the thickness of the transfer material P, and a resist upper guide 22 and a resist lower guide roller 19 that move following the resist roller 18 are sintered bearings (not shown).
, And is supported by a resist lower guide 21, and is configured so that the resist upper roller 18 is pressurized by bridging a resist pressure spring over a bearing.

The resist lower guide 21 is grounded via a varistor or resistor 23 to the ground, and is configured to prevent the transfer current from flowing out of the transfer nip T via the transfer material P.

The transfer material P is transferred by the resist unit 7
The paper is fed in time with the toner image on the photosensitive drum 1 and sent to the transfer unit 5.

The transfer unit 5 is located below the photosensitive drum 1.
They are arranged to form a transfer unit. The transfer unit 5 includes
The photo belt 12 rotates (moves) in the direction of arrow R12.
Are located in As shown in FIG.
Are two rows arranged in parallel with the axis of the photosensitive drum 1.
A transfer roller (driven roller) 10 and a transfer bell
Drive roller (drive roller) 11
You. The transfer roller 10 and the drive roller 11 are made of SUS or the like.
Core metal and a surface layer of conductive urethane rubber (resistance 10 ^Four~
10⁷Ω) and the overall resistance
Is 10^FourΩ or less, and the transfer bell
A predetermined transfer bias is applied to both rows by a power supply (not shown).
Applied to the

The transfer belt 12 has a two-layer structure in which a base layer is made of a thermosetting urethane elastomer and a surface layer is made of vinylidene fluoride rubber, has a thickness t = 0.3 mm, and has an overall resistance of 10 ^10.
Ω. The degree of elongation when the transfer belt 12 is stretched over the transfer roller 10 and the transfer belt driving roller 11 is about 5%.
It is.

The transfer unit 5 has a transfer frame 9 in which a transfer roller 10 and a transfer belt driving roller 11 are supported via bearings (not shown), and the transfer roller 10 side can swing substantially vertically. Have been.

One end of the transfer frame 9 is supported by a pressure piece 15 via a pressure spring (compression spring) 14, and the pressure piece 15 moves vertically by rotation of a cam member 16. As a result, the entire transfer unit 5 performs a contact / separation operation with respect to the photosensitive drum 1. That is, when the cam member 16 is rotated clockwise in the figure around the shaft 16a, the pressure piece 15 descends,
Transfer roller 10 of transfer frame 9 via pressure spring 14
As a result, the transfer belt 12 is separated from the surface of the photosensitive drum 1.

On the other hand, when the cam member 16 is rotated to the position shown in FIG.
4, the transfer frame 9 is pushed up on the transfer roller 10 side, whereby the transfer belt 12 is brought into contact with the surface of the photosensitive drum 1 to form a transfer nip T. The contact pressure (transfer pressure) at this time is set to be 4 kg in total pressure.

Incidentally, the contact and separation operation of the transfer unit 5 is performed at a predetermined timing by an electromagnetic clutch (not shown) and a pressing cam 16 provided in the image forming apparatus.

A transfer material transport guide (hereinafter referred to as a “pre-transfer guide”) 8 is transferred by a transfer frame 9 to the transfer roller 1.
The transfer member P is supported at a predetermined interval on the upstream side of the transfer roller 10 at a predetermined interval, and stabilizes the transport path of the transfer material P sent from the registration unit 7. The pre-transfer guide 8 swings up and down following the transfer roller 10, approaches the photosensitive drum 1 at a predetermined interval in accordance with the timing at which the transfer material P enters the transfer unit T, and Is ensured. Further, the pre-transfer guide 8 is connected to the resist unit 7 via a contact plate 25, and has the same potential as the resist unit 7.

The multicolor developed four-color toner image on the photosensitive drum 1 is transferred to a transfer material P at a transfer nip T by applying a transfer bias to a transfer roller 10 and a drive roller 11.

In FIG. 1, a cleaning device 6 is disposed on the left side of the photosensitive drum 1. The cleaning device 6
The cleaning blade 6a is disposed so as to be able to contact and separate from the photosensitive drum 1 in the direction of the arrow, and the cleaning blade 6a is brought into contact with the surface of the photosensitive drum 1 to remove the transfer residual toner remaining on the surface of the photosensitive drum 1 after the toner image is transferred. I do.

While the toner image on the photosensitive drum 1 is being developed, the transfer unit 5 and the cleaning device 6 are separated from the surface of the photosensitive drum 1.

The transfer material P to which the toner image has been transferred is conveyed to a fixing device 17, where it is heated and pressed by a fixing roller 17a and a pressure roller 17b to fix a toner image on the surface. It is discharged outside the main body.

Hereinafter, the transfer step will be described in more detail.

The photosensitive drum 1 facing the transfer belt 12 is a contact transfer means, charged areas V _D and toner has a region V _L to be developed, typically 300~500V
Potential difference. At the time of transfer, unless the transfer is performed with a voltage sufficient to absorb these potential differences, in other words, the difference in load impedance, the toner on the paper as the transfer material P scatters after the transfer.

[0043] When this transfer voltage is low, since much the V _D portion by the difference of the load impedance, less transfer charge to the V _L portion from being supplied, unevenness of locally transferring charge to the paper backing occurs, the toner on the paper after transfer, caused by thus scattered in the V _D portion from V _L portion. Therefore, it is necessary to use a transfer belt having a somewhat high resistance, which generates a transfer voltage high enough to absorb the difference in load impedance.

When a composite color toner image of four colors (yellow, magenta, cyan, and black) is formed on the photosensitive drum 1, the transfer material P is adjusted by the registration unit 7 to the toner image on the photosensitive drum 1. The transfer unit 5 is conveyed to the transfer unit via the pre-transfer guide 8, and at this time, the transfer unit 5 is also brought into contact with the photosensitive drum 1 in timing with the toner image on the photosensitive drum 1.

That is, the pressure cam 16 rotates, and the pressure unit 15 in the transfer unit 5 is pushed up to rotate the transfer unit 5 upward, so that the transfer belt 12 and the transfer roller 10 come into contact with the photosensitive drum 1. . However, at the moment when the transfer belt 5 and the transfer roller 10 come into contact with the photosensitive drum 1, the pressure spring 14 is hardly compressed.
A transfer belt 12 and a transfer roller 10
There is almost no contact shock. Therefore, since there is no adverse effect such as vibration or displacement due to a shock applied to the photosensitive drum 1 during the exposure / development process, the toner images of four colors without pitch unevenness on the photosensitive drum 1 can be accurately shifted. Therefore, a synthesized color toner image having high resolution and high color reproducibility is formed.

When the pressure cam 16 is further rotated and the top is fixed by contacting the pressure piece 15, the pressure spring 14 is also gradually compressed, and finally the transfer belt 12 is set at a set pressure of 4 kg.
Then, the transfer roller 10 is brought into contact with the photosensitive drum 1. When the contact operation is completed, the transfer material P conveyed by the registration unit 7 is transferred to the photosensitive drum 1 and the transfer belt 12.
The four-color toner image on the photosensitive drum 1 is transferred by the transfer bias in the transfer nip T, which is a contact portion with the transfer roller 10.

The transfer material P after the transfer is separated from the photosensitive drum 1 by the transfer belt 12 having a large capacitance.
Adsorbed and transported. In this embodiment, the photosensitive drum 1 is operated under a normal environment (temperature: 25 ° C., relative humidity: 50%).
The charged areas V _D -500-550 V, toner and -170~-180V regions V _L to be developed, the transfer bias during the collective transfer step, the constant voltage control +200
+ 300V.

The transfer material P sucked and conveyed to the transfer belt 12 is subjected to curvature separation downstream of the transfer belt 12, and is fixed to the fixing device 1.
7 for heat fixing.

In this embodiment, as shown in FIG. 2, the transfer belt 12 of the transfer unit 5 and the toner image (at the time of the batch transfer step) in the transfer path of the transfer material P from the above-described registration nip R to the transfer nip T. A registration unit 7 for aligning the image P) with the transfer material P, a pre-transfer guide 8 for regulating the posture of the transfer material P, and a center line L2 of the photosensitive drum 1 parallel to a tangent L1 passing through the transfer nip T. Are set as follows. That is, the center line L
A is the distance from the transfer nip T to the transfer nip T, B is the distance from the pre-transfer guide 8 to the transfer material separation position, and C is the distance from the resist nip R. The relationship of A ≧ B and A> C holds. These values are set so that

By maintaining the above relationship, as shown in FIG. 3, the pre-transfer guide 8 allows the transfer material P to reliably enter the transfer nip T along the photosensitive drum 1. As a result, the electric field generated between the photosensitive drum and the transfer material immediately before the transfer nip T, that is, the electrostatic movement of the toner t in the region where the electrostatic attraction is generated can be suppressed, and scattering and penetration can be prevented.

As described above, the transfer material P is made to follow the photosensitive drum 1 before the area where the electrostatic attraction is generated, thereby preventing scattering and punch-through. Scattering and punch-through due to the material and size are reduced, and a clear color output image can be always obtained.

In this embodiment, the distance A from the center line L2 of the photosensitive drum 1 parallel to the tangent line L1 passing through the transfer nip T to the transfer nip T is 92.7 mm. Set the distance B to the transfer material separation position at 9
Very good results could be obtained by setting the distance C from the center line L2 to the resist nip R to 1.7 mm and the distance C to 90.7 mm.

Embodiment 2 Next, a second embodiment of the present invention will be described with reference to FIG.

In the present embodiment, unlike the first embodiment, the toner images sequentially formed on the photosensitive drum 1 are temporarily primary-transferred to an intermediate transfer drum (intermediate transfer member) 20 as an image carrier, and the intermediate transfer is performed. A plurality of toner images are superimposed on the transfer drum 20,
Thereafter, the plurality of toner images are transferred to the intermediate transfer drum 20.
The present invention is applied to a color image forming apparatus (for example, a copying machine or a laser printer) using an electrophotographic process of a type in which secondary transfer is collectively performed on a transfer material P from above.
In the following description, the same members as those of the first embodiment are denoted by the same reference numerals, and the repeated description will be appropriately omitted.

The image forming apparatus shown in FIG. 4 has a photosensitive drum 1 substantially at the center thereof, and the photosensitive drum 1 is rotated at a predetermined process speed (peripheral speed) in the direction of arrow R1 by driving means (not shown). Driven.

In the course of rotation, the photosensitive drum 1 is uniformly charged to a predetermined polarity and a predetermined potential by the primary charging roller 2A, and then exposed by an exposure unit (for example, a color separation / imaging exposure optical system for a color original). Or a scanning exposure system using a laser scanner that outputs a laser beam modulated according to a time-series electric digital pixel signal of image information.
(For example, a yellow component image) is formed.

Then, the electrostatic latent image is transferred to the first
The developing unit (yellow developing unit) 4Y develops with the yellow toner Y as the first color.

The yellow, magenta, cyan, and black developing units 4Y, 4M, 4C, and 4BK are mounted on a rotary 4a rotatable in the direction of arrow R4. Is disposed at a developing position D facing the photosensitive drum 1.

In this embodiment, under normal environment (temperature 25 ° C., relative humidity 50%), the potential V _D of the charged area of the photosensitive drum 1 is −500 to −550 V, and the toner is developed. The potential _VL of the region is -170 to -180V.

An intermediate transfer drum 20 is disposed in contact with the photosensitive drum 1, and is driven to rotate in the direction of arrow R20 at the same speed as the rotation of the photosensitive drum 1 in the direction of arrow R1.

The first color yellow toner image formed and carried on the photosensitive drum 1 passes through a primary transfer nip T 1 between the photosensitive drum 1 and the intermediate transfer drum 20.
Primary transfer bias power supply (not shown) for intermediate transfer drum 20
The primary transfer is performed on the surface of the intermediate transfer drum 20 by the electric field and pressure generated by the primary transfer bias applied from the first transfer bias. Hereinafter, this step is referred to as primary transfer.

Hereinafter, similarly, the magenta toner image of the second color,
The cyan toner image of the third color and the black toner image of the fourth color are sequentially superimposed and transferred on the intermediate transfer drum 20, and a composite color toner image corresponding to a target color image is formed on the surface of the intermediate transfer drum 20.

The primary transfer bias in this embodiment is +3 in a normal environment (temperature: 25 ° C., relative humidity: 50%).
00V.

The transfer belt 12 is disposed below the intermediate transfer drum 20. The transfer belt 12 is supported in parallel with the intermediate transfer drum 20 and is
0 contacts from below. The transfer belt 12 is supported by a transfer roller (bias roller) 10 and a transfer belt drive roller (tension roller) 11, and a desired secondary transfer bias is applied to the transfer roller 10 by a secondary transfer bias source (not shown). Have been.

The secondary transfer bias in this embodiment is +20 μA under constant voltage control, and a voltage of +1200 to +1500 V is generated in a normal environment (temperature: 25 ° C., relative humidity: 50%).

The primary transfer bias for sequentially superimposing and transferring the toner images of the first to fourth colors from the photosensitive drum 1 to the intermediate transfer drum 20 has a polarity (+) opposite to that of the toner and has a primary transfer bias power supply (not positive). (Shown). In the process of sequentially transferring the toner images of the first to fourth colors from the photosensitive drum 1 to the intermediate transfer drum 20, the transfer belt 12 and the intermediate transfer body cleaning roller 24
It can be moved away from.

The secondary transfer of the composite color toner image superimposedly transferred onto the intermediate transfer drum 20 to the transfer material P is performed as follows. That is, while the transfer belt 12 is in contact with the intermediate transfer drum 20, the transfer material P passes through the registration unit 7 and the pre-transfer guide 8 from the paper feed cassette 13 and is transferred between the intermediate transfer drum 20 and the transfer belt 12. At a predetermined timing, and at the same time, a secondary transfer bias is applied to the transfer roller 10 from a bias power supply (not shown). The composite transfer toner image is collectively and secondarily transferred from the intermediate transfer drum 20 to the transfer material P by the secondary transfer bias.

The transfer material P to which the toner image has been transferred is introduced into the fixing device 17 and is fixed by heating. After the image transfer to the transfer material P is completed, the secondary transfer residual toner on the intermediate transfer drum 20 is cleaned by the intermediate transfer member cleaner roller 24 contacting the intermediate transfer drum 20.

Hereinafter, the transfer step of this embodiment will be described in detail.

The intermediate transfer drum 20 used in this embodiment is
For example, it has a roller shape having at least an elastic layer made of rubber, elastomer, or resin on a cylindrical conductive support, and further has a roller shape having one or more coating layers above the elastic layer.

As the cylindrical conductive support, metals and alloys such as aluminum, iron, copper and stainless steel, conductive resins in which carbon and metal particles are dispersed, and the like can be used. Such a cylinder or a cylinder having a reinforced interior.
The core metal used in the present embodiment is obtained by reinforcing the inside of an aluminum cylinder having a thickness of 3 mm.

The thickness of the elastic layer used for the intermediate transfer drum 20 is preferably 0.5 to 7 mm in consideration of the formation of the primary transfer nip T1 and the secondary transfer nip T2, color shift due to rotation, material cost, and the like. The thickness of the surface is preferably made thin so as to further convey the flexibility of the lower elastic layer to the upper layer or the surface of the photosensitive drum 1, and specifically, 20 to 200 μm.

In this embodiment, the thickness of the elastic layer is 5 mm, the surface layer thickness is 30 μm, and the total outer diameter of the intermediate transfer drum 20 is 186 mm.

In the elastic layer, Ketjen black is dispersed as a conductive material in acrylonitrile-butadiene rubber (NBR) by giving importance only to the resistance value, and the volume resistivity is set to 10 ⁵ to 1.
It was used as the control to 0 ⁸ [Omega] cm. In this embodiment, it is set to 10 ⁷ Ωcm.

The surface layer of the intermediate transfer drum 20 was formed by dispersing 200 parts of PTFE powder using a urethane resin as a binder. The molding method is a method of spray-coating and polishing on the above-mentioned elastic layer.

The resistance value of the intermediate transfer drum 20 manufactured as described above was 2 × 10 ⁷ Ω.

The four colors (yellow,
When a composite color toner image (magenta, cyan, black) is formed, the transfer material P is adjusted by the registration unit 7 to the toner image on the intermediate transfer drum 20 via the pre-transfer guide 8 at the secondary transfer nip. At this time, the transfer unit 5 applies a predetermined transfer pressure (in this embodiment, the total transfer pressure) to the intermediate transfer drum 20 by the same process as that of contacting / pressing the photosensitive drum in the first embodiment. Pressure 4k
g), the four-color toner image is transferred onto the transfer material P.

In this embodiment, as in the first embodiment, FIG.
As shown in FIG. 5, the transfer unit 5 in the transfer path of the transfer material P from the above-described registration nip R to the transfer nip T is provided.
Transfer belt 12, a registration unit 7 for aligning the toner image and the transfer material P during the batch transfer process, a pre-transfer guide 8 for regulating the posture of the transfer material P, and a tangential line passing through the secondary transfer nip T2. The distance relationship between L1 and the center line L2 of the intermediate transfer drum 20 parallel to L1 is set as follows. That is, from the center line L2, the secondary transfer nip T
2, the distance to the transfer material separation position of the pre-transfer guide 8 is B, and the distance to the resist nip R is C, so that the relations A ≧ B and A> C hold. Set the value of.

As described above, according to the present embodiment, in the color image forming apparatus using the intermediate transfer drum 20, as in the first embodiment, the transfer material transport path
The secondary transfer nip T2 can be caused to enter the secondary transfer nip T2 with the transfer material along the intermediate transfer drum 20, and the electric field generated between the intermediate transfer drum 20 and the transfer material P immediately before the secondary transfer nip T2 can be used. It is possible to suppress electrostatic movement of the toner, to prevent the toner image transferred to the transfer material P from scattering and piercing, and to reduce scattering and piercing due to the material and size of the transfer material P, and to always obtain a stable output image. Can be.

In the above-described embodiment, the structure including the transfer belt which comes into contact with or separates from the photosensitive drum or the intermediate transfer drum has been described. However, instead of the transfer belt, the structure shown in the conventional example described with reference to FIG. A transfer roller can also be used.

Embodiment 3 Next, a third embodiment of the present invention will be described with reference to FIG.

In the present embodiment, the entire configuration except that the image carrier uses a photosensitive belt instead of a photosensitive drum is as follows.
This is the same as the first embodiment.

The photosensitive belt 30 is rotatably stretched around the rotating rollers 32 and 33 and the opposing roller 31, and the transfer roller 10 contacts the opposing roller 31 via the transfer belt 12 and the photosensitive belt 30, and the transfer nip T To form

In the same way as in the first embodiment, the transfer belt 12 of the transfer unit 5 and the toner image and the transfer material P during the batch transfer process in the transfer path of the transfer material P from the above-described registration nip R to the transfer nip T. The distance relationship between the registration unit 7 for performing the position adjustment, the pre-transfer guide 8 for regulating the posture of the transfer material P, and the center line L2 of the opposing roller 31 parallel to the tangent line L1 passing through the transfer nip T is as follows. Set as follows. That is, when the distance from the center line L2 to the transfer nip T is A, the distance from the pre-transfer guide 8 to the transfer material separation position is B, and the distance from the resist nip R is C, A ≧ B, A> These values are set so that the relationship of C 1 is established.

As described above, according to the present embodiment, in the color image forming apparatus using the photosensitive belt 30, the transfer material is transferred onto the photosensitive belt 30 in the transfer material transport path, as in the first embodiment. It is possible to cause the toner to enter the transfer nip T along the transfer nip T, suppress electrostatic toner movement due to an electric field generated between the photosensitive belt 30 and the transfer material P immediately before the transfer nip T, and transfer the toner to the transfer material P. It is possible to prevent the toner image from scattering and abutting, and reduce scattering and penetration due to the material and size of the transfer material P, so that a stable output image can always be obtained.

Embodiment 4 Next, a fourth embodiment of the present invention will be described with reference to FIG.

In this embodiment, the entire configuration is the same as that of the second embodiment except that an intermediate transfer belt is used instead of the intermediate transfer drum.

The intermediate transfer belt 40 includes rotating rollers 42, 4
The transfer roller 10 is rotatably extended between the transfer roller 3 and the opposing roller 41, and the transfer roller 10 abuts on the opposing roller 41 via the transfer belt 12 and the intermediate transfer belt 40 to form a secondary transfer nip T2.

As in the second embodiment, the transfer belt 12 of the transfer unit 5 and the toner image and the transfer material P during the collective transfer process in the transfer path of the transfer material P from the registration nip R to the secondary transfer nip T2. Distance between the registration unit 7 for performing the positioning of the transfer material P, the pre-transfer guide 8 for regulating the posture of the transfer material P, and the center line L2 of the opposed roller 41 parallel to the tangent line L1 passing through the secondary transfer nip T2 Is set as follows. That is, from the center line L2 to 2
When the distance to the next transfer nip T2 is A, the distance to the transfer material separating position of the pre-transfer guide 8 is B, and the distance to the resist nip R is C, the relationship of A ≧ B and A> C holds. Set these values as follows.

As described above, according to the present embodiment, in the color image forming apparatus using the intermediate transfer belt 40, as in the second embodiment, the transfer material transport path
It is possible to cause the transfer material to enter the secondary transfer nip T2 along the transfer material along the intermediate transfer belt 40, and the electric field generated between the intermediate transfer belt 40 and the transfer material P immediately before the secondary transfer nip T2 Electrostatic movement of the toner can be suppressed to prevent the toner image transferred to the transfer material P from being splattered or pierced, and scattered or pierced by the material or size of the transfer material P is reduced, and a stable output image is always obtained. be able to.

In the above-described embodiment, the structure including the transfer belt which comes in contact with and separates from the photosensitive belt or the intermediate transfer belt has been described. However, instead of the transfer belt, a structure similar to the conventional example described with reference to FIG. A transfer roller can also be used.

[0092]

As is apparent from the above description, according to the color image forming apparatus of the present invention, a registration unit for aligning an image and a transfer material in a batch transfer step,
A transfer material transport guide that regulates the posture of the transfer material,
The distance from the center line of the image carrier parallel to the tangent passing through the transfer nip formed by the image carrier and the contact transfer means to the tangent passing through the transfer nip is A, When the distance is B and the distance to the resist nip formed by the resist unit is C, A
By setting the value of the distance so as to satisfy the relationship of ≧ B, A> C, scattering and penetration of the toner image transferred to the transfer material can be prevented, and a high-quality image can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a color image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of a main part showing a transfer material transport path in the first embodiment.

FIG. 3 is an enlarged view of a main part for describing suppression of scattering and penetration according to the present invention.

FIG. 4 is a schematic configuration diagram illustrating a color image forming apparatus according to a second embodiment of the present invention.

FIG. 5 is an enlarged view of a main part showing a transfer material transport path in a second embodiment.

FIG. 6 is an enlarged view showing a main part of a conventional image forming apparatus.

FIG. 7 is an explanatory diagram showing a state of scattering and penetration in a conventional image forming apparatus.

FIG. 8 is an enlarged view of a main part showing a transfer material transport path in a third embodiment.

FIG. 9 is an enlarged view of a main part showing a transfer material transport path in a fourth embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum (image carrier) 7 registration unit 8 pre-transfer guide (transfer material transport guide) 12 transfer belt (contact transfer unit) 20 intermediate transfer drum (image carrier) 30 photosensitive belt (image carrier) 40 intermediate transfer belt (Image carrier) P transfer material R resist nip T transfer nip T2 secondary transfer nip

Claims (8)

[Claims] 1. A color image forming apparatus which sequentially forms images of a plurality of colors on an image carrier and collectively transfers the images to a transfer material by using a contact transfer unit, wherein the position of the image and the transfer material during the batch transfer step is adjusted. The image carrier parallel to a tangential line passing through a transfer nip formed by the image carrier and the contact transfer unit, the image carrier having a registration unit for performing the following, and a transfer material transport guide for regulating the posture of the transfer material. A, the distance from the center line to the tangent passing through the transfer nip to the transfer material separating position of the transfer material transport guide is B, and the distance from the resist nip formed by the resist unit is C, A color image forming apparatus, wherein the value of the distance is set such that a relationship of A ≧ B and A> C is satisfied. 2. The color image forming apparatus according to claim 1, wherein said contact transfer unit is a transfer belt. 3. The color image forming apparatus according to claim 1, wherein said contact transfer unit is a transfer roller. 4. The color image forming apparatus according to claim 1, wherein said image bearing member is a drum type electrophotographic photosensitive member. 5. The color image forming apparatus according to claim 1, wherein the image carrier is a drum-type intermediate transfer body. 6. A color image forming apparatus in which images of a plurality of colors are sequentially formed on a belt-shaped image carrier and are collectively transferred to a transfer material by using a contact transfer unit, the image forming apparatus comprising: A registration unit that performs alignment, and a transfer material transport guide that regulates the posture of the transfer material, and is parallel to a tangent passing through a transfer nip formed by the belt-shaped image carrier and the contact transfer unit. The distance between the center line of the opposing roller that contacts the contact transfer unit via the belt-shaped image carrier and the tangent line passing through the transfer nip is A, When the distance between the guide and the transfer material separation position is B, and the distance between the guide and the resist nip formed by the resist unit is C, the value of the distance is such that the relationship of A ≧ B and A> C holds. Setting the color image forming apparatus, characterized by. 7. The color image forming apparatus according to claim 6, wherein said belt-shaped image bearing member is a belt-type electrophotographic photosensitive member. 8. The color image forming apparatus according to claim 6, wherein said belt-shaped image carrier is a belt-type intermediate transfer body.