JPH01179967A - Transfer device for image output device - Google Patents

Abstract

PURPOSE:To accurately match respective positions of each color to one another in case of the use of plural photosensitive bodies by elastically pressing a flexible sheet as a transfer body to the photosensitive body to always keep positional relations between a transfer drum and the photosensitive body in the contacting state. CONSTITUTION:A transfer drum 7 consists of a hollow roll, and a notch is formed on the outside surface, and flexible and elastic meshes 16 are stuck to this notch part throughout except the part of a gripper 9, and the surface of meshes 16 of the transfer drum 7 is always brought into contact with a photosensitive body 1. Meshes 16 are elastically deformed inward and are pressed to the photosensitive body 1 in this state, and the distance from the center of the transfer drum 7 to the photosensitive body 1 is always kept constant and a sufficient nip width is secured. Thus, positions of images transferred from respective photosensitive bodies 1 accurately coincide with one another.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transfer device used in an electrophotographic copying machine and the like, and particularly to a transfer device that prevents image distortion during transfer.

[Conventional technology]

For example, in a color image output device such as a color electrophotographic copying machine, a color image is obtained by successively transferring images of different colors onto the same sheet of paper.

Conventionally, as one of the color image output devices using such an electrophotographic method, there is one that uses a transfer drum to convey and transfer paper.

This is yellow and magenta around one photoreceptor.

Three-color cyan or four-color developer (black plus cyan) is arranged, and the latent image formed on the photoreceptor is developed in turn by each developer.Then, the paper is placed on the transfer drum. The paper is gripped by a gripper or adsorbed to a mesh or film made of a material such as polyethylene terephthalate, and the transfer drum is rotated to transport the paper to the photoreceptor, and a transfer device such as a corotron transfers the toner image on the photoreceptor. A common method is to repeat this process for each color to transfer the color image onto the paper.

However, this method has a problem in that the speed is slow because development and transfer are repeated for each color.

To solve this problem, multiple photoreceptors are arranged around the transfer drum, each color is developed in advance on each photoreceptor, and each color toner image on each photoreceptor is developed during one rotation of the transfer drum. A method called a tandem type in which full-color copying is performed by transferring to paper has been proposed in Japanese Patent Application Laid-open No. 122067/1983.

FIG. 10 shows an example of this tandem type color image output device.

In the figure, numeral 1 indicates a photoreceptor, and around the photoreceptor 1 there is a charger 4. Scanning exposure system such as RO3 (rusk output scanner) using LED (light emitting diode) as a light source 3. Developing device5. A cleaner 2 and the like are arranged to constitute an image forming section. A plurality of image forming sections are arranged around the transfer drum 7 in correspondence to the number of colors to be combined. In the example of FIG. 2, two image forming sections S, , S, are provided. The image forming section itself has the same structure as a normal monochrome digital electrophotographic copying machine, and a toner image is formed on the photoreceptor 1 in accordance with an image signal supplied to the scanning exposure system 3.

Further, a deflector 6 is disposed on the paper supply side of the transfer drum 7 to regulate the adsorption posture of the paper, and a screen tack corotron 8 is disposed inside the transfer drum 7 facing the deflector 6. Ru. In addition, the transfer drum 7
A transfer device 10 is disposed at a location corresponding to each photoreceptor 1 inside the paper, and a peeling corotron 11 is disposed on the paper discharge side.

The transfer drum 7 has a part of its surface cut out and a flexible sheet such as a screen mesh or polyethylene terephthalate film attached, as shown in Japanese Patent Laid-Open No. 59-24869. Charging and the like are performed via the flexible sheet.

Then, when the paper in the tray 14 is conveyed toward the transfer drum 7 by the feed roll 15, the paper is attracted to the transfer drum 7 by the deflector 6 and the screen tack corotron 8. When this paper reaches the image forming section S1, the toner image on the photoreceptor 1 is transferred by the transfer device 10 to the paper on the transfer drum 7. Next, the paper is transferred to the image forming section S2.
Then, the toner image on the photoreceptor 1 is similarly transferred by the transfer device 10 so as to be superimposed on the toner image formed in the image forming section S1. After the transfer, the sheet of paper is peeled off from the transfer drum 7 by a peeling corotron 11, and sent to a fixing device 13 by a conveying device 12, where the toner image is fixed on the sheet. In this way, an image in which multiple colors are combined is obtained on the paper.

According to this tandem-type color image output device, a color image can be obtained with one rotation of the transfer drum 7, so there is an effect that the copying speed can be increased.

[Problem to be solved by the invention]

However, in this tandem type color image output device, a plurality of photoreceptors 1 are arranged around one transfer drum 7.
Since a separate photoreceptor 1 is used for each color, it is difficult to transfer the toner images on the photoreceptor 1 to the same position on the paper on the transfer drum 7 in an overlapping manner.

When a plurality of photoreceptors are used, the outer dimensions and eccentricity of each photoreceptor 1 are different. In addition, since a common transfer drum 7 is used for a plurality of photoreceptors 1, the outer dimensions of the transfer drum 7 become large, which makes it easily deformed, and the shape of the transfer drum 7 is distorted or eccentricity occurs. Inevitable. Further, since the paper comes into contact with the photoreceptor, the distance from the transfer drum to the photoreceptor and the length of the contact area between the mesh and the photoreceptor change depending on the diameter difference and eccentricity of the photoreceptor, and the speed of the paper changes.

If there is a difference in diameter or eccentricity of the photoconductors, the image will expand or contract during image writing, and as a result, the positions of the images transferred from each photoconductor 1 will not match accurately, resulting in color misregistration. The disadvantage is that it is easy to occur. Furthermore, if the dimensional accuracy of the transfer drum 7 is low, the gap between the transfer drum 7 and the photoreceptor 1 cannot be maintained accurately, and good transfer cannot be performed. Since a sufficient contact width, ie, nip width, between the sheet or mensch and the photoreceptor 1 cannot be ensured, toner scattering occurs during transfer, resulting in a problem in that the image quality of the transfer (image quality) deteriorates.

In an image output device in which a plurality of photoreceptors are arranged around one transfer drum, in order to maintain good registration, it is necessary to satisfy the following two conditions.

The first condition is to keep the distance from the center of the transfer drum to the photoreceptor constant at all times in order to keep the paper feeding speed, that is, the circumferential speed of the transfer drum constant. The second condition is to keep the amount of nimp between the flexible sheet and the photoreceptor constant in order to suppress variations in the position where the flexible sheet of the transfer drum contacts the photoreceptor.

However, to directly satisfy these conditions,
The accuracy of the photoreceptor, the transfer drum, and the tensioning accuracy of the flexible sheet must be extremely high, resulting in a problem of high manufacturing costs.

The present invention was devised to solve the above-mentioned problems, and even when a plurality of photoreceptors are used, the relative positions of each color can be accurately determined without increasing the dimensional accuracy of the parts. The objective is to obtain a color image with good matching and registration.

[Means to solve the problem]

In order to achieve the above object, the transfer device of the image output device of the present invention is characterized in that a flexible sheet that elastically presses against the photoreceptor is attached to the peripheral surface of the transfer member that conveys the paper. do.

The surface speed of the transfer body is set to 0 from the surface speed of the photoreceptor.
．． It is desirable to increase the speed by 1 to 1% in order to correct distortion of the image formed on the photoreceptor.

[Effect]

In the present invention, a flexible sheet of a transfer body such as a transfer drum is elastically pressed against the photoreceptor, so that the positional relationship between the transfer drum and the photoreceptor is always maintained in a state of contact. Accordingly, when the photoreceptor contacts the transfer member and the toner image on the photoreceptor is transferred to the paper of the transfer member, the accuracy of the transfer member and the flexible sheet itself becomes irrelevant. In other words, the pressure contact position between the flexible sheet and the photoconductor is not determined by the dimensions of the transfer body;
Automatically determined by the elastic deformation of the flexible sheet.

Therefore, close contact between the flexible sheet and the photoreceptor is ensured.

Furthermore, since the paper is conveyed in synchronization with the transfer body rather than the photoconductor, when the surface speed of the transfer body is made 0.1 to 1% faster than the surface speed of the photoconductor, the photoconductor and the paper are Transfer is always performed in a slippery state, and the image quality during writing is caused by dimensional errors of the photoreceptor! Misalignment is corrected during transfer. Therefore, there is no positional shift when multiple transfer is performed from a plurality of photoreceptors to a common transfer member.

〔Example〕

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, features of the present invention will be specifically described based on examples with reference to the drawings.

FIG. 1 shows a schematic sectional view of a transfer device according to an embodiment of the present invention. Note that parts corresponding to the configuration of the conventional example shown in FIG. 10 are denoted by the same reference numerals, and explanations thereof will be omitted.

The transfer drum 7 is a hollow roll, and has a notch formed on its outer surface. A mesh 16 having flexibility and elasticity, such as polyester, is attached to this cutout. This message 251
6 is pasted on the entire circumference except for the gripper 9 portion.

As can be seen from FIG. 1, the positional relationship between the transfer drum 7 and the photoreceptor 1 is such that the surface of the mesh 16 of the transfer drum 7 is placed on the photoreceptor 1.
be in constant contact with the The amount of 1,000/3) at this time varies depending on the rigidity of the mesh 16, but is up to 30
0 to 600 Iin interference.

This amount of interference is set so that the contact pressure is approximately 7 g/am. Note that the amount of interference here means the distance in the radial direction that the photoreceptor 1 bites into the mesh 16.

Next, the operation of this embodiment will be explained. The basic configuration is the same as that of the conventional example shown in FIG. 10, so it will be explained with reference to the same figure.

In this embodiment as well, like the conventional example shown in FIG. 10, paper is fed from the tray 14 by the feed roll 15 and is gripped by the gripper 9 of the transfer drum 7. A mesh 16 formed on the outer periphery of the transfer drum 7 is charged with electric charge by the screen tack corotron 8 and the deflector 6, and the paper is attracted to the mesh 16. and,
The toner image on the photoreceptor 1 is transferred at the first image forming section S1, and then the same transfer is carried out at the second image forming section S2.

At this time, the positional relationship between the transfer drum 7 and the photoreceptor 1 is such that, as described above, the surface of the mesh 16 is placed on the photoreceptor 1 by a maximum of 3
Since the mesh 16 has flexibility and elasticity, the mesh 2:L
16 is in pressure contact with the photoreceptor 1 in a state in which it is elastically deformed inward as shown in FIG. That is, the mesh 16 comes into elastic contact with the photoreceptor 1.

Therefore, the accuracy of the transfer drum 7 itself or the mesh 1
Regardless of the mounting accuracy of the transfer drum 6, the distance from the center of the transfer drum 7 to the photoreceptor 1 is always kept constant, and a sufficient nip width is ensured.

Note that when the paper is conveyed by the transfer drum 7, the paper 17 is attracted to the mesh 16 and conveyed, but especially when the rigidity of the mesh 16 is small, the paper is The tip of the gripper 9 is gripped by the gripper 9.

At this time, the gripper 9 is placed at a position slightly lower than the surface of the transfer drum 7, as shown in FIG. 1, so as not to interfere with the photoreceptor 1.

Next, the relationship between the peripheral speeds of the transfer drum and the photoreceptor in this embodiment will be explained.

In this embodiment, the speed at which the transfer drum 7 conveys the paper 17 is set to be slightly lower than the surface speed of the photoreceptor 1, for example, 0.
．． Speed it up by 1-1%.

By providing a speed difference in this way, the paper 17 is always
Transfer is performed while the photoreceptor 1 is sliding. At this time, since the speed at which the transfer drum 7 conveys the paper 17 is faster than the surface speed of the photoreceptor 1, the paper 17 pulled by the gripper 9 is always under tension, and the paper 17 is not bent. It won't sag or wrinkle. Thereby, during exposure of the photoreceptor 1, that is, when writing an image, the positional deviation of the image caused by eccentricity of the photoreceptor 1 can be corrected during transfer.

Note that if the above-mentioned speed difference is less than 0.1%, sufficient tension cannot be obtained and control becomes impossible, and if it is greater than 1%, the toner is dragged in the process direction during transfer, resulting in large smears and poor visibility. This has the disadvantage that the quality of the upper image deteriorates.

Here, the positional deviation of the image that occurs when the image is written from the scanning exposure system 3 onto the photoreceptor 1 will be explained.

If the drum of the photoreceptor 1 is eccentric, even if the rotational speed of the photoreceptor 1 itself is constant, its circumferential speed will vary depending on the distance from the axis to the surface.

At this time, in a portion where the radius from the center to the surface of the photoreceptor 1 is short, the position of the image is aligned, but the length of the image is short with respect to the conveyance direction of the paper. On the other hand, even in a portion where the radius from the center to the surface of the photoreceptor 1 is long, the image position I is the same, but the length of the image becomes long. In a portion where the radius from the center to the surface of the photoreceptor l is intermediate, the length of the image is accurate, but the position shifts back and forth.

Therefore, in this state, if the paper is closely rotated in synchronization with the rotation of the photoreceptor 1 and the image on the photoreceptor 1 is transferred to the paper,
The image after transfer will also be distorted.

Since the eccentricity of each photoreceptor is different, the positions of multiple transferred images are shifted. Particularly when forming a color image, color shift occurs and the image quality is significantly degraded.

However, in this embodiment, the paper 17 is not conveyed in synchronization with the photoreceptor 1, but is conveyed in synchronization with the transfer drum 7. The opposite phenomenon occurs between the two. Therefore, the position of the image is corrected to return to its original position. In other words, the image is compressed and recorded in the small-diameter portion of the photoreceptor 1, and expanded and recorded in the large-diameter portion, but since the circumferential speed of the small-diameter portion is slow and the circumferential speed of the large-diameter portion is fast, the image remains constant. When the image is transferred to a sheet of paper moving at a high speed, the image in the small diameter portion is expanded, and the image in the large diameter portion is compressed and transferred.

Next, another example of the transfer device will be described with reference to FIGS. 2 and 3. In this embodiment, an elastic roll 18 is provided inside the transfer drum 7 at a position facing each photoreceptor 1.
are arranged respectively. In this case, since the mesh 16 is pressed against the photoreceptor 1 by the roll 18 made of an elastic body, the contact between the photoreceptor 1 and the mesh 16 becomes more reliable.

At this time, it is preferable to bring the mesh 16 into contact with the photoreceptor for a maximum of about 300 to 600 degrees so that the contact pressure is about 7 g/am, although it varies depending on the mesh rigidity.

FIG. 3 shows a 2-layer system using the elastic roll 18 shown in FIG.
A color image output device is shown. Note that parts corresponding to those in the conventional example in FIG. 10 are given the same reference numerals, and explanations thereof will be omitted.

In addition, instead of the roll 18 shown in FIG. 2, a tower-shaped elastic guide 19 shown in FIG. 4 is provided, and the mesh 16 of the transfer drum 7 (
The same effect can be obtained with a configuration in which the photoreceptor (see FIG. 2) is pressed against the photoreceptor 1.

Note that when the gripper 9 holding the leading edge of the paper 17 passes through the transfer area, the gripper 9
Although it is preferable not to come into contact with the elastic roll 18 or the elastic guide 19 (see FIG. 10), no particular problem will arise if the contact occurs with the elastic roll 18 or the elastic guide 19. In addition, the elastic roll 18 or the elastic guide 19. The magnitude of the force pressing on the photoreceptor 1 is 7 g
It has been confirmed through experiments that a value around / am is optimal.

FIGS. 5 and 6 show cross-sectional views of still another embodiment of the present invention, in which a belt-shaped elastic push-up material 20a made of a rigid resin or the like exhibiting elasticity is formed on the surface of the outer peripheral end of the transfer drum 7. ,
20b are laminated and a mesh 16 is attached thereon.

FIG. 7 shows still another embodiment using a ring-shaped elastic push-up member 20c, in which a mesh 16 is attached to the outer periphery of the transfer drum 7, and a small diameter portion is provided inside the transfer drum 7 in the axial direction. An elastic body push-up member 20c is interposed between this small-diameter portion and the mesh 16.

In the embodiments shown in FIGS. 5 to 7, the mesh 16 is pressed against the photoreceptor 1 by the elasticity of the mesh 16 and the elasticity of the elastic push-up members 20a, 20b, and 20c, and the two always come into contact with each other.

FIG. 8 shows an embodiment of a further arrangement for pressing the transfer drum 7 against the photoreceptor 1. As shown in FIG. In FIG. 8, reference numeral 22 indicates an electrostatic transfer roll, and a sliding member 23 supporting the electrostatic transfer roll 22 is housed in a slot 24 so as to be movable forward and backward. The base end of the sliding member 230 and the sleeve 2
A coil spring 2 as an elastic push-up member is installed between the bottom of the
5 are arranged. A high voltage of about 2 to 5 V, which is necessary for transfer, is applied to the electrostatic transfer roll 22 from a power source 26. In the example of FIG. 8, the sliding member 23.
Sleeve 24. Elastic push-up mechanism 2 by coil spring 25 etc.
7 is composed.

FIG. 9 shows a case where the elastic push-up mechanism 27 shown in FIG. 8 is applied to a four-color full-color copying apparatus. Note that parts corresponding to those in the conventional example in FIG. 10 are given the same reference numerals, and explanations thereof will be omitted.

This color copying apparatus includes a photoreceptor 1. Charger 4° scanning exposure system 3. Developing device5. yellow, magenta, consisting of cleaner 2nd grade;
Electrophotographic image forming apparatuses for each color, black and white, are arranged around the transfer drum 1, and toner images of each color are formed on the photoreceptor 1.

As shown in FIG. 9, the forward bending elastic push-up mechanism 27 is provided at a location corresponding to each photoreceptor 1 inside the transfer drum 7, and is adapted to press the transfer drum 7 against the photoreceptor 1. There is.

To explain in more detail, the transfer drum 7 has a structure in which a flexible sheet such as a screen mesh or polyethylene terephthalate film for adsorbing paper is stretched around a large-diameter hollow roll. , the electrostatic transfer roll 22 pushed up by the elastic push-up mechanism 27 elastically presses against the photoreceptor 1 .

Here, the operation of the color copying apparatus shown in FIG. 9 will be briefly explained.

The paper stored in the tray 14 is placed on the registration roll 3.
1 and the gripper of the transfer drum 7 (see FIG. 1) rotates and approaches, the registration roll 31 is released at the timing, passes through the paper chute 32, and is held by the sheet grip section. , rotates integrally with the transfer drum 7.

The electrostatic transfer roll 22 is supplied with 2 to 5 KV from a DC power source 26.
A relatively high voltage is applied thereto, and the photoreceptor 1 is pressed against the photoreceptor 1 by an elastic push-up mechanism 27 composed of a coil spring 25 and the like.

When the paper is conveyed to the position of the photoreceptor 1 by the transfer drum 7, the paper is charged by the electrostatic transfer roll 22,
The toner image on the photoreceptor 1 is transferred onto paper. At this time, as described above, the flexible belt of the transfer drum 1 is pressed against the photoreceptor 1, so good transfer can be performed without increasing the tension accuracy of the hollow roll and flexible sheet. be exposed.

This step is image formation is,, s2. s3. After the process is repeated for each color in step s, the paper is released from the transfer drum 7, passes through the IJ/IJ-subber chute 33, is fixed by the fixing device 13, and is delivered onto the paper output tray 34 as a color copy.

In addition, in the above-mentioned embodiment, a case was described in which transfer was performed using a transfer drum in which a mesh was pasted on the cutout part of a hollow roll. Of course, similar effects can be obtained by using a transfer belt made of polyethylene terephthalate or the like.

In addition, instead of attaching a mesh to the transfer drum and transferring with a corotron, or using a transfer belt,
As shown in Publication No. 1-269176, a plurality of electrodes are arranged at predetermined intervals on a semiconductive resin film, and transfer is performed by selectively applying a predetermined voltage to these electrodes. It can also be applied to a transfer drum or a transfer belt.

Furthermore, it can also be applied to a transfer belt with a mesh attached to a chain tractor.

〔Effect of the invention〕

As described above, according to the present invention, a flexible sheet provided on a transfer body such as a transfer drum or a transfer belt is made to run along the photoreceptor while being pressed against the photoreceptor, thereby preventing distortion of the transfer body. Even if there is eccentricity, the paper speed can be kept constant regardless of eccentricity.

Therefore, images can be transferred without distortion in the transfer section, and registration will not deteriorate even when multiple images are transferred.

Furthermore, by making the peripheral speed of the transfer drum a little faster than the moving speed of the photoreceptor, any expansion/contraction or positional deviation of the image during writing caused by the diameter difference or eccentricity of the photoreceptor drum can be corrected during transfer. Therefore, good registration can be obtained.

Furthermore, according to the present invention, there is no need to increase the tension accuracy of the sheet conveyance drum and screen meningle in order to improve registration, so manufacturing costs can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a schematic sectional view of a transfer device according to an embodiment of the present invention, Fig. 2 is a schematic sectional view of a transfer device according to an embodiment of the present invention using an elastic roll, and Fig. 3 is a color image using the same transfer device. FIG. 4 is a schematic cross-sectional view of an output device, FIG. 4 is a schematic cross-sectional view of a transfer device using an elastic guide, and FIGS. 8 is a schematic sectional view of a transfer device using an electrostatic transfer roll as an elastic body pushing member; FIG. 9 is a schematic sectional view of a four-color image output device using the same transfer device; FIG. The figure is a schematic cross-sectional view of a conventional color image output device. 1: Photoreceptor 2. Cleaner 3: Scanning exposure system 4: Charger 5: Developing device 6. Deflector 7: Transfer drum 8; Screen tank corotron 9 Nigelippa 10: Transfer device 11: Peeling corotron 12: Conveyance device 13; Fixing device
14 Nidle 15; Feed roll 16: Mesh 17: Paper
18: Elastic body roll 19: Elastic body guides 19a, 20a, 20b, 20c: Elastic body push-up material 22: Electrostatic transfer roll 23: Sliding member 24 sleeve 25: Coil spring 26: DC power supply 2
7: Elastic push-up mechanism 31 resist roll 32; Vapor chute 33: Release paper chute 34: Paper ejection tray Patent applicant Fuji Xerox Co., Ltd. Agent Masu Kobori (and 2 others) Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure M9 @ Figure 10

Claims (1)

[Scope of Claims] 1. A transfer device for an image output device, characterized in that a flexible sheet that elastically presses against a photosensitive member is attached to the peripheral surface of a transfer member that conveys paper. 2. The transfer device for an image output device according to claim 1, wherein the surface speed of the transfer member is 0.1 to 1% faster than the surface speed of the photoreceptor.