JPH10221968A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image forming device provided with a color smear preventing function suitable for a driven-driving system belt driving device by making a transfer material carrier made of an anisotropic raw material whose elastic degree is different in a direction. SOLUTION: A carrying belt 103 has two-layer structure, the lower layer (first layer 301) of the belt is made of a material which has flexibility and a small elastic degree such as chloroprene rubber and the upper layer (second layer 302) of the belt having elasticity such as urethane foam is stuck to the first layer 301. Then, the first layer 301 made of a rigid material has resistance to the difference between tensile forces being different at each place of the belt, in the tensile force generated in the direction of carrying the carrying belt 103, so that the occurrence of strain, deformation and waving is suppressed to prevent the color smear of a recording sheet. Further, the second layer 302 having the elasticity comes into soft close contact with the periphery of a press- contact roller, to prevent transfer unevenness, in press-contact parts where the second layer 302 is brought into press-contact with photoreceptor drums 41Y and 41C and 41K and 41M by the press-contact roller.

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, and more particularly to an improvement in a transport belt used for transporting a recording sheet in a tandem type full color image forming apparatus.

[0002]

2. Description of the Related Art At present, in a color copying system, a plurality of image forming units including a photosensitive drum, a charging charger, a developing device, a transfer charger and the like are arranged, and an image is formed by superimposing images of respective colors. The tandem type image forming apparatus performing the above is becoming mainstream. In this tandem type image forming apparatus, it is said that the difference in the peripheral speed between the photosensitive drums in each image forming unit has a great effect on the color shift of the recording sheet. As a simple transport belt driving method for preventing this problem, a transport belt composed of an endless belt stretched over a plurality of rollers is pressed against each photosensitive drum, and the transport belt or the photosensitive drum is contacted through the pressed portion. There has been proposed a system in which one of the driving forces is transmitted to the other to be driven and driven.

[0003]

However, in the conveyor belt driving system, a plurality of photosensitive drums must be installed in a state where the photosensitive drums are pressed in parallel with their axial directions aligned with the width direction of the conveyor belt. Further, since the pressure contact portion has a structure in which pressure contact plates are provided at both ends of the conveyance belt to press the belt against the photoconductor drum, tension generated in the conveyance direction of the belt due to the traveling load of the photoconductor drum at the time of driving is caused by the belt. It differs at both ends in the width direction and at the center.

Therefore, the transport belt is deformed and loses its flatness in an extreme case, so that the pressure contact property between the recording sheet and the photosensitive drum at each color transfer position becomes non-uniform and the toner belt becomes uneven. -Non-uniformity (hereinafter referred to as "transfer non-uniformity") appears at the time of image transfer. Further, in the belt driving method, since a plurality of photosensitive drums are continuously installed in pressure contact with the transport belt, the traveling load is accumulated on the transport belt as it goes upstream (hereinafter simply referred to as upstream) in the transport direction. Is done. As a result, the waving and distortion of the transport belt increase toward the upstream side, so that the position of the recording sheet gradually moves during transport as the transport belt deforms, and there is a possibility that a significant color shift occurs.

In order to solve these problems, if the deformation of the conveyor belt is suppressed by increasing the rigidity of the conveyor belt, the adhesion between the drive roller and the conveyor belt becomes poor, and the drive roller slips during driving. As a result, the conveyor belt cannot be driven smoothly. Further, as is clear from the nature of the rigid belt, the non-uniformity of the material during the production of the belt is notably reflected as it is as the performance of the belt.

On the other hand, if the rigidity of the conveyor belt is reduced and the adhesion is improved by using a stretchable material, there is a risk of increasing the deformation of the conveyor belt. The accurate transfer position of the recording sheet to the image forming unit is shifted. Further, when an elastic material is used for the conveyance belt, the surface of the conveyance belt excessively sinks in the thickness direction of the belt at the pressure contact portion between the conveyance belt and the photosensitive drum, and the recording sheet passing through the pressure contact portion
This causes the sheet to be turned up in close contact with the photosensitive drum.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a novel and useful transport belt capable of withstanding deformation due to a partial difference in tension, and a driven belt drive device. It is an object of the present invention to provide an image forming apparatus having a color misregistration preventing function, which is suitable for the above.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention comprises an image carrier and a transfer material carrier for transporting a transfer material. In an image forming apparatus for transferring and forming an image on a transfer material at an opposing portion, the transfer material transport body is made of an anisotropic material whose expansion ratio varies depending on a direction.

Here, the transfer material transporting body may have a small stretchability in the transport direction of the transfer material and a large stretchability in the thickness direction. Further, the transfer material transporting body is a laminate, and the non-stretchable portion may be a lower layer, and a stretchable portion having stretchability in a thickness direction may be an upper layer. Further, the transfer material transporting body may be knitted by using non-stretchable fibers for knitting in the transfer direction of the transfer material and using stretchable fibers for knitting in the width direction.

The image forming apparatus further includes a plurality of image carriers arranged in a row at a predetermined interval, and a transfer material carrier for transporting a transfer material to a position facing an image forming area of the image carrier. In a tandem-type image forming apparatus that forms an image by driving one of the image carrier and the transfer material transporter while the body is pressed against the image carrier, the other is driven, The transfer material transport member has a small expansion and contraction ratio in the transfer direction of the transfer material, a large expansion and contraction ratio in the thickness direction due to contact with and release from the image carrier, and until the transfer material reaches the next image carrier. Further, the transfer material transporting body may have a temporal restoring property of returning to the original thickness.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION

[Embodiment 1] A tandem color digital copying machine 1 (hereinafter simply referred to as a copying machine 1), which is an example of a tandem image forming apparatus according to the present invention, will be described below. FIG. 1 is a front view showing the entire configuration of the copying machine 1. As shown in FIG. 1, the copying machine 1 includes an image reader unit 10 for reading a document image, and a printer unit 20 for printing the read image on a recording sheet S and reproducing it.

The image reader section 10 is composed of a transparent original placing plate (not shown) and an image sensor (not shown) such as a CCD disposed immediately below the original placing plate. Reading by a CCD is a well-known method in which a document image is separated into three colors of red (R), green (G), and blue (B), and R, G, and The image data for each color component B undergoes various data processing in the control unit 30 and is further converted into image data of each reproduction color of cyan (C), magenta (M), yellow (Y), and black (K). (Hereinafter, each of the reproduced colors of cyan, magenta, yellow, and black is simply represented as C, M, Y, and K, and the numbers of the components related to each reproduced color are represented by subscripts of C, M, Y, and K. This is temporarily stored in the image memory of the control unit 30 and then read out in synchronism with the supply of the recording sheet S, and modulated for laser light to be used for image formation.

The printer section 20 includes a recording sheet transport section 100 (hereinafter, simply referred to as a transport section 100) having a transport belt 103 stretched thereon, and an upstream side in the recording sheet transport direction (hereinafter, referred to as the transport section 100) facing the transport belt 103. Cyan (C), magenta (M), cyan (C), and magenta (M) arranged at predetermined intervals from the upstream in the transport direction to the downstream in the transport direction (hereinafter, simply referred to as the downstream).
Yellow (Y) and black (K) color image forming units 40C-4
0K, and a sheet feeding unit 50 disposed upstream of the conveying unit 100.
And a well-known heat fixing unit 80 arranged downstream, and a well-known paper discharge tray 90 further arranged downstream.

Each of the image forming units 40C to 40K includes an exposure scanning unit 70C to 70K and an image processing unit 60C to 60K.
It is composed of The exposure scanning units 70C to 70K
The laser beam modulated by the original image is applied to the photosensitive drum 4
Laser diodes 46C to 46K and polygon mirrors 47C to scan in the main scanning direction on 1C to 41K.
47K or the like.

The image processing units 60C to 60K include photosensitive drums 41C to 41K, charging chargers 42C to 42K disposed around the photosensitive drums 41C to 41K, and a developing unit 4C.
3C to 43K, cleaners 44C to 44K, and transfer chargers 45C to 45K. The paper supply unit 50 includes a paper supply cassette 51 for storing the recording sheets S, a paper supply roller 52 for supplying the recording sheets S from the paper supply cassette 51, and a timing for setting a timing for supplying the recording sheets S to the transport belt 103. And a roller 53. On the upstream side of the timing roller 53, there is provided a recording sheet position detection sensor SE1 for detecting the leading end of the recording sheet S, and taking the timing of transporting the recording sheet S on the transport unit and the timing of each image formation. I have. Further, a sensor SE2 for detecting a paper jam is provided upstream of the heat fixing unit 80.

FIG. 2 is a perspective view showing the configuration of the transport section 100 in detail. As shown in FIG.
The conveyor belt 103, a pair of rollers 101 and 102 around which the belt is stretched, a motor 109 for driving one of the rollers 101, and the conveyor belt 103 are connected to the photosensitive drum 41C.
Rollers 104a-107a, 1 which press against 4K-41K
04b to 107b.

The pressing rollers 104a to 107b are rotatably supported by a frame (not shown), and a portion of the roller peripheral surface near the end of the conveying belt 103 outside the conveying area of the recording sheet S is connected to the photosensitive drums 41C to 41K. We are in pressure contact.
FIG. 3 is a sectional view of the transport belt 103 in the transport direction. As shown in this figure, the transport belt 103 has a two-layer structure. That is, the lower layer of the belt (hereinafter referred to as the first layer 30)
1) is made of a flexible and less stretchable material such as chloroprene rubber (CR).
An upper layer (hereinafter, referred to as a second layer 302) having elasticity such as urethane foam is attached to 01. The surface of the second layer 302 is coated with silicon rubber or the like so that toner does not easily adhere.

When the copying machine 1 having such a configuration is driven, the recording sheet S fed from the sheet feeding unit 50 on the upstream side in the transport direction is transported by the transport belt 103.
The respective color toner images are formed in the respective image forming units 40C to 40K while taking the transfer timing in accordance with the transport speed, and are recorded by the photosensitive drums 41C to 41K which are driven and rotated at the same peripheral speed as the transport speed of the transport belt 103. The image is transferred to a predetermined position on the sheet S. After that, the recording sheet S to which the toner of each color adheres is heat-fixed on the toner by the heat fixing unit 80, and is discharged to a discharge tray 90 downstream.

In this series of operations, the transport belt 103 having the two-layer structure solves the problem at the time of transfer. In other words, the first layer 301 made of a rigid material is resistant to a difference in tension at each point of the belt, against the tension generated in the transport direction of the transport belt 103 by driving, and the first layer 301 is made of a material having distortion, deformation, and the like. The occurrence of ripples is suppressed to prevent color shift of the recording sheet S. In addition, the second layer 302 having elasticity is formed by pressing rollers 104 a to 104 a.
a, 104b to 107b, and
At the press contact portion pressed against 41K, the press roller 104
a-107a and 104b-107b are flexibly adhered to the peripheral surfaces to prevent transfer unevenness. Accordingly, the copier 1 can form a color image with excellent reproducibility on the recording sheet S by the transport belt 103 having the two-layer structure.

As shown in FIG. 3P, the second layer 302, which has passed through the press contact portion by driving, gradually recovers at intervals from one press contact portion 303 to the next press contact portion 304. It is preferable to set the material to be completed and have a temporal recovery property. By doing so, the excessive pressure contact area between the peripheral surface of the photosensitive drum and the belt can be reduced, and the danger of the recording sheet S not being transported and being turned up while being in close contact with the photosensitive drum can be prevented.

[Embodiment 2] The present embodiment is the same as Embodiment 1 except for the structure of the conveyor belt. The conveyor belt is knitted with two types of fibers instead of a two-layer structure. Are different. That is, as shown in the enlarged view in the perspective view of the conveying belt in FIG. 4, the conveying belt uses non-stretchable fibers 401 such as aromatic polyamide in the conveying direction and highly elastic fibers 402 such as polyurethane in the width direction of the belt. It is knitted and therefore has an anisotropic structure that is non-stretchable in the transport direction and stretchable in the width and thickness directions. With this structure, similarly to the belt of the first embodiment, the present belt can be uniformly expanded and contracted in the thickness direction at the press contact portion, and the transfer unevenness can be suppressed to surely transfer the color image onto the recording sheet. Is possible. Further, this belt is Embodiment 1
On the contrary, since the belt also expands and contracts in the width direction, it can absorb the waving of the belt generated in the same direction. In the above two embodiments, the tandem type image forming apparatus has been described. However, it is needless to say that the present invention can be similarly applied to other types of image forming apparatuses.

[0022]

As is apparent from the above description, the image forming apparatus according to the present invention includes an image carrier and a transfer material transporter for transporting a transfer material, and includes the transfer material transporter and the image carrier. And an image transfer apparatus for transferring and forming an image on a transfer material at a portion opposed to the transfer material, and the transfer material transporting body is made of an anisotropic material whose expansion / contraction ratio varies depending on directions. Therefore, there is less distortion in the manner in which the tension is applied to the transfer material transporting body during driving as compared with a unidirectional transporting body, and the direction of the tension can be adjusted in one direction.

In the transfer material transporting body, if the expansion and contraction rate in the transfer direction of the transfer material is small and the expansion and contraction rate in the thickness direction is large,
The transfer material is resistant to the tension in the transport direction caused by the driving in the transport direction, and has an effect of preventing the transfer material from moving to an incorrect position due to distortion, deformation, or undulation caused by the tension. In addition, due to the pressing force received from the transfer carrier in the thickness direction at the time of driving, the transfer material transporter can flexibly adhere to the contact surface of the carrier and perform uniform transfer to the transfer material.

Further, if the transfer material transporting body is a laminate, and the non-stretchable portion is the lower layer and the stretchable portion having elasticity in the thickness direction is the upper layer, the lower layer shows the resistance to the tension and the transfer. While the material carrier is prevented from expanding and contracting or deforming, in the transfer image forming step by the image carrier and the transfer material carrier, the upper layer is flexibly deformed at the opposed portion, and the image carrier is closely attached to the transfer material. The advantage of the two-layer structure that the transferability is improved and effective transfer is ensured can be obtained.

Further, the transfer material transporting body is used for knitting the non-stretchable fibers in the transfer direction of the transfer material and the stretchable fibers for knitting in the width direction. Since elasticity is provided in two directions, the thickness direction and the thickness direction, deformation and distortion and waving can be absorbed by suppressing expansion and contraction due to tension in the transport direction and flexibly expanding and contracting in the width direction. In addition, expansion and contraction in the thickness direction increases the adhesion between the transfer material and the image carrier, and has the effect of improving the reproducibility of an image transferred to the transfer material.

The image forming apparatus further includes a plurality of image carriers arranged in a row at a predetermined interval, and a transfer material carrier for transporting the transfer material to a position facing the image forming area of the image carrier. In a tandem-type image forming apparatus that forms an image by driving one of the image carrier and the transfer material transporter while the body is pressed against the image carrier, the other is driven, The transfer material transport member has a small expansion and contraction ratio in the transfer direction of the transfer material, a large expansion and contraction ratio in the thickness direction due to contact with and release from the image carrier, and until the transfer material reaches the next image carrier. In addition, if the transfer material transporting body has a temporal restoring property that returns to the original thickness, the transfer material transporting body has a small expansion and contraction ratio in the transport direction, so it is resistant to deformation and waving due to the tension. In addition, it is possible to prevent the transfer position of the transfer material from being shifted. Further, since the transfer material transporting body has a large expansion and contraction rate in the thickness direction, there is an effect that the transfer material transporting member is uniformly brought into close contact with the image carrier in a pressure contact region with the image carrier, and the image can be reliably transferred to the transfer material. Further, the restoring property can reduce an excessive press-contact area between the transfer material conveying body and the image carrier in the press-contact area, thereby preventing a risk that the transfer material is turned up while keeping the transfer material in close contact with the peripheral surface of the image carrier. effective.

[Brief description of the drawings]

FIG. 1 is a front cross-sectional view illustrating an overall configuration of a tandem-type image forming apparatus as an example of the invention.

FIG. 2 is a perspective view of a transport unit of the tandem-type image forming apparatus.

FIG. 3 is a cross-sectional view of a conveyance belt of the conveyance section in a conveyance direction.

FIG. 4 is a cross-sectional view in the conveyance direction of the conveyance belt as one embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 copier 10 image reader unit 20 printer unit 30 control unit 40 image forming unit 41 photosensitive drum 42 charging charger 43 developing unit 44 cleaner 45 transfer charger 46 laser diode 47 polygon mirror 50 paper feed unit 51 paper feed cassette 52 paper feed roller 53 Timing roller 60 Image processing unit 70 Exposure scanning unit 80 Thermal fixing unit 90 Discharge tray 100 Transport unit 101, 102 Roller 103 Transport belt 104a to 107a, 104b to 107b Pressure contact roller 109 Motor 301 First layer 302 Second layer 401 Non Stretchable fiber 402 High stretchable fiber

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Hiroshi Murasaki 2-13-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka Inside Osaka International Building Minolta Co., Ltd. (72) Hideyuki Kurahashi Azuchi-cho, Chuo-ku, Osaka-shi, Osaka 2-3-13 Osaka International Building Minolta Co., Ltd.

Claims (5)

[Claims] 1. An image forming apparatus, comprising: an image carrier; and a transfer material carrier for transporting a transfer material, wherein an image is transferred to and formed on a transfer material at a portion where the transfer material carrier and the image carrier are opposed to each other. 2. The image forming apparatus according to claim 1, wherein the transfer material transporting body is made of an anisotropic material having a different expansion / contraction ratio depending on a direction. 2. The image forming apparatus according to claim 1, wherein the transfer material conveying body has a small expansion and contraction ratio in a transfer direction of the transfer material and a large expansion and contraction ratio in a thickness direction. 3. The image forming apparatus according to claim 2, wherein the transfer material transporting body is a laminate, wherein the non-stretchable portion is a lower layer, and the stretchable portion having elasticity in a thickness direction is an upper layer. apparatus. 4. The transfer material transporting body according to claim 2, wherein the non-stretchable fibers are knitted in the transfer direction of the transfer material, and the stretchable fibers are knitted in the width direction. The image forming apparatus as described in the above. 5. A transfer material transporter comprising: a plurality of image carriers arranged in a row at a predetermined interval; and a transfer material transporter for transporting a transfer material to a position facing an image forming area of the image carrier. In a tandem-type image forming apparatus that forms an image by driving one of the image carrier and the transfer material transporter while the body is pressed against the image carrier, the other is driven, The transfer material conveyance body has a small expansion and contraction rate in the transfer direction of the transfer material, and a large expansion and contraction rate in the thickness direction due to contact with and release from the image carrier, until the transfer material reaches the next image carrier. In addition, the transfer material transporting body has a temporal restoring property that returns to the original thickness, and is a tandem type image forming apparatus.