JPH06308840A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device which is extremely small by miniaturizing a photosensitive body and an intermediate transfer body. CONSTITUTION:The speed at which a transfer material 28 is carried at the time of transferring a toner image to the transfer material 28 is set higher than the peripheral speed of the photosensitive body 102 for forming a latent image and the peripheral speed of the intermediate transfer body 103 for synthesizing and holding developed toner images. Thereby, the latent image compressed from a requested size in the direction in which it is carried on the photosensitive body 102 is formed on the photosensitive body 102. Each latent image is developed with each color toner and the developed color images are synthesized on the intermediate transfer body 103, and the image of the requested size can be obtained by stretching the image when transferring it to the transfer material 28.

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 using an intermediate transfer member for temporarily holding a toner image formed on a photosensitive member.

[0002]

2. Description of the Related Art Conventionally, image forming apparatuses have been used as output devices for computers and the like. The conventional image forming apparatus will be described below.

FIG. 5 is a block diagram of a conventional image forming apparatus. In FIG. 5, reference numeral 1 is a loop belt type photoconductor. The photoconductor 1 is supported by the photoconductor conveying roller 2 and the photoconductor supporting rollers 3 and 4, and is rotated in the direction of arrow d1 by a drive motor or the like. Reference numeral 5 denotes a photosensitive member position detection mark, which is arranged at one end of the photosensitive member 1. Reference numeral 6 denotes a photoconductor position detection sensor that detects the photoconductor position detection mark 5. The photoreceptor 1 has a seam 7, and the seam 7 must be avoided when forming an image. At this time, the output of the photoconductor position detection sensor 6 is referred to.

On the peripheral surface of the photosensitive member 1, a charger 8, an exposure optical system 9, a black (K), a yellow (Y), a magenta (M), and a cyan (C) are developed in the rotational direction indicated by an arrow d1. Device 10K, 10Y, 10M, 10C, pre-intermediate charge eliminator 11, intermediate transfer roller 12, photoconductor cleaning device 1
3, and a static eliminator 14 are provided.

When a negative high voltage is applied to the charging wire provided inside the charger 8, the charging wire causes corona discharge,
When a voltage of, for example, -700V is applied to the grid plate, the surface of the photoconductor 1 is uniformly charged to a negative potential of about -700V.

Reference numeral 15 denotes an exposure light beam emitted from the exposure optical system 9. The exposure light beam 15 is light emitted from a laser diode or the like in which the image signal sent from the gradation converting device 100 is pulse-width modulated by the laser driving circuit 101 and corresponds to image data of a specific color on the photoconductor 1. Form an electrostatic latent image.

Each developing device 10K, 10Y, 10M, 1
0C stores toners of black, yellow, magenta, and cyan, respectively, and also has sleeve rollers 16K, 16Y, 16M, and 16C made of conductive rubber or the like. These sleeve rollers 16K, 1
When 6Y, 16M, and 16C are rotated in the forward direction with respect to the driving direction of the photoconductor 1 indicated by the arrow d1, each developing device 10 is rotated.
Toner thinned from inside K, 10Y, 10M, 10C is supplied to the surface of the sleeve rollers 16K, 16Y, 16M, 16C. This toner is negatively charged due to friction when it is thinned. To develop each color, a negative voltage (developing bias) is applied to the sleeve rollers 16K, 16Y, 16M, 16C, and the sleeve rollers 16K, 16Y,
Separation cam 17 for each color while rotating 16M and 16C
Dedicated motors corresponding to K, 17Y, 17M and 17C are driven to move the selected black developing device 10K in the direction of arrow d3 to bring the sleeve roller 16K into contact with the photoconductor 1. That is, in this example, contact development using a non-magnetic one-component toner is adopted.

The surface potential (bright potential) of the photosensitive member 1 in the portion where the latent image is formed has risen to around -50 to -100V, and when a negative potential of about -300V is applied to the sleeve roller 16K, the photosensitive member 1 is exposed. An electric field is generated from the body 1 in the direction of the sleeve roller 16K. As a result, the negatively charged toner on the sleeve roller 16K is opposite to the electric field, that is, a Coulomb force acts in the direction of the photoconductor 1, and the toner adheres to the latent image portion formed on the photoconductor 1. On the other hand, since the surface potential (dark potential) of the photoconductor 1 in the portion where the latent image is not formed remains −700 V, the electric field is generated from the sleeve roller 16K toward the photoconductor 1 even when the developing bias is applied. Therefore, the toner does not adhere to the photoconductor 1. The development process as described above
It is generally called a negative-positive process or a reversal phenomenon because toner adheres to a portion irradiated with light.

The pre-intermediate transfer static eliminator 11 has a plurality of red LEDs arranged on a line, and transfers the toner image formed on the photoconductor 1 to an intermediate transfer body 18 which is a synthetic medium for synthesizing images of respective colors. Immediately before, the surface of the photoconductor 1 is discharged. In principle, the pre-intermediate charge eliminator 11 does not operate during transfer of the first color, but operates during transfer of the second and subsequent colors. In the pre-transfer charge elimination, the toner image is transferred to the intermediate transfer member 18, and the photosensitive member 1
When there is no toner on the upper side, there is an effect of preventing the toner image on the intermediate transfer member 18 from being reversely transferred to the photosensitive member 1.

The intermediate transfer roller 12 is a photoconductor supporting roller 3.
Is located in the vicinity of the photoconductor 1 with the intermediate transfer member 18 interposed therebetween. Since some layers of the photoconductor 1 are grounded, when a positive voltage is applied to the intermediate transfer roller 12, an electric field is generated from the intermediate transfer roller 12 toward the photoconductor 1. Therefore, the Coulomb force acts on the negatively charged toner on the photosensitive member 1 in the direction of the intermediate transfer member 18, and the toner is transferred to the intermediate transfer member 1.
8 is transferred.

The intermediate transfer member 18 is a medium for synthesizing single color images to form a full color image. Intermediate transfer body 1
8 is supported by three conveying rollers 19, 20, 21 and is rotated in the direction of arrow d2 by the same drive motor as the photosensitive member 1. 22 is an intermediate transfer member position detection mark,
Eight of them are arranged at the end of the intermediate transfer body 18. An intermediate transfer member position detection sensor 23 detects the intermediate transfer member position detection mark 22. When forming an image, one is selected from the plurality of intermediate transfer member position detection marks 22 and used as a reference for the image forming position.

On the peripheral surface of the intermediate transfer member 18, a pre-transfer charger 24, a density sensor 25, a transfer material transfer roller 26, and an intermediate transfer member cleaning device 27 are arranged in the rotational direction indicated by arrow d2.
Are arranged.

When the pre-transfer charger 24 applies a negative high voltage to the charging line, the charging line causes corona discharge, and the intermediate transfer member 1
The toner image composited on 8 is forcibly recharged. The pre-transfer charge eliminator 24 is activated only for the image area on the intermediate transfer member 18 immediately before the toner image on the intermediate transfer member 18 is transferred onto the transfer material 28, and is stopped for other periods. The density sensor 25 is an application of a reflection type sensor, and detects the toner density on the intermediate transfer member 18.

The transfer material transfer roller 26 is pressed against the intermediate transfer body 18 and rotates when transferring the toner image synthesized on the intermediate transfer body 18 to the transfer material 28.

The intermediate transfer member cleaning device 27 is a device for removing the residual toner on the intermediate transfer member 18 after transferring the toner image on the intermediate transfer member 18 onto the transfer material 28. Intermediate transfer body 1 during synthesis
It is separated from No. 8 and contacts only when cleaning.

Next, the structure of the paper feeding system will be described. The paper feeding system includes a transfer material cassette 29, a paper feeding roller 30, and a transfer material conveying path 3
1, a slip roller 32, a registration roller 33a and a driven roller 33b thereof.

The transfer material cassette 29 is a cassette for storing the transfer material 28. A transfer material cassette presence / absence sensor, a transfer material size determination sensor, a transfer material presence / absence sensor, a transfer material remaining amount sensor, and the like are arranged around the cassette.

The paper feed roller 30 is a half-moon roller.
The transfer material 28 is sent from the transfer material cassette 29 to the transfer material transport path 31 one by one.

A slip roller 32 is arranged in the transfer material conveying path 31, and the transfer material 28 picked up by the paper feed roller 30 is conveyed by the slip roller 32 to the registration roller 33a. At the time when the leading end of the transfer material 28 reaches the registration roller 33a, the registration roller 33a is not rotating, the transfer material 28 cannot move forward, and stops at the position of the registration roller 33a.

Registration roller 33a and driven roller 33b
Is for temporarily stopping and waiting the transfer material 28 in order to match the positions of the transfer material 28 and the composite image on the intermediate transfer body 18, and they are rotated together during operation to transfer the transfer material 28 to the transfer material transfer roller. It is conveyed in the direction of 26.

In FIG. 5, V1 is the peripheral speed of the photosensitive member 1, V2 is the peripheral speed of the intermediate transfer member 18, and V3 is the transfer material 28.
Represents the transport speed of, and these are the same speed.

Next, FIG. 6 is a detailed view of a transfer device which constitutes a conventional image forming apparatus. In FIG. 6, reference numeral 26 is a transfer material transfer roller. The transfer material transfer roller 26 is attached to the swing plate 35 via a bearing 34 so as to face the transport roller 21 of the intermediate transfer member 18. The oscillating plate 35 rotates about a shaft 36 as a fulcrum when the oscillating plate arm portion 37 is pushed by a cam 41. A spring 38, a solenoid 39, a clutch 40, a cam 4 are provided around the swing plate arm portion 37.
There is one. The cam 41 has a cam convex portion 41a and a cam concave portion 41.
There is b. Further, the rocking plate 35 is urged toward the cam 41 by a spring 38 with a shaft 36 as a fulcrum.

The clutch 40 has claws 42 at 180 ° intervals.
a, 42b are formed, and a cam 41 and a rotation shaft 43 are provided coaxially, so that the transfer material 28 is transferred to the registration roller 33.
When it reaches a, the cam 41 rotates 180 ° and stops until the claw 42a hits the amateur of the solenoid 39. Therefore, the oscillating plate arm portion 37 rotates until it abuts the cam concave portion 41b, and the oscillating plate 35 rotates about the shaft 36 as a fulcrum. The rotation of the swing plate 35 causes the transfer material transfer roller 26 to nip with the conveyance roller 21 of the intermediate transfer member 18,
By sandwiching the transfer material 28 and applying a positive voltage to the transfer material transfer roller 26, the toner on the intermediate transfer body 18 is transferred to the transfer material 28.

Around the transfer material transfer roller 26, there are transfer material guides 50 and 51 for guiding the transfer material 28, a discharge toner tray 44 and a cleaning frame 45. The cleaning frame 45 is supported by a shaft 46 so as to be rotatable at a constant angle, and an arm portion 48 is supported by a spring 47 so as to move the arm portion 48.
The bearing 34 of No. 6 is brought into contact with either of the cam portions 34a and 34b. A cleaning blade 49 is adhered to the cleaning frame 45.

The cleaning frame 45 rotates in the clockwise direction as the transfer material transfer roller 26 rises about the shaft 46 by the spring 47 as a fulcrum, and the contact point of the arm portion 48 is from the cam portion 34a of the bearing 34 to the cam portion 34b side. The transfer material transfer roller 26 rotates and stops until it comes into contact with the intermediate transfer member 18.

The cleaning blade 49 comes into contact with the transfer material transfer roller 26 when the cam 41 rotates about 60 ° to 70 °, and when the cam 41 rotates about 30 ° from this, the cleaning function is completely fulfilled. . The timing at which the cleaning blade 49 completely fulfills the cleaning function is such that the intermediate transfer body 18 and the transfer material transfer roller 26 transfer the transfer material 28 by nipping the transfer material 28, and the rear end of the transfer material 28 to which the toner has been transferred is the transfer material transfer. Roller 26 and intermediate transfer member 1
It is when the transfer material transfer roller 26 is separated from the intermediate transfer member 18 again after passing through the nip portion of No. 8.

[0027]

However, in the above conventional structure, the length of the photosensitive member 1 for forming a latent image and the intermediate transfer member 18 for synthesizing the visualized toners of a plurality of colors is at least as long as the transfer material. 28 sizes are required. For example, in the image forming apparatus shown in the conventional example, the legal size long side (3
The length of the intermediate transfer member 18 is about 400 mm when a margin is taken into consideration. Further, since the photoconductor 1 has a seam and the seam is controlled so as not to enter the image area, it is convenient that the photoconductor 1 has the same length as the intermediate transfer member 18. Looking at the configuration of the image forming apparatus of FIG.
The intermediate transfer member 18 and the photosensitive member 1 are largely located in the center of the apparatus. Since the size of the image forming apparatus is greatly influenced by the sizes of the photoconductor 1 and the intermediate transfer member 18, it is a cause of hindering the overall size reduction.

[0028]

In order to solve the above problems, the present invention sets the transfer material conveyance speed to be higher than the peripheral speed of the intermediate transfer member.

[0029]

With the above setting, the toner image formed in a reduced size with respect to the rotation direction of the intermediate transfer member can be expanded and restored to its original size when transferred to the transfer material.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of an image forming apparatus according to an embodiment of the present invention. In FIG. 1, the photoconductor 10
2 and the length of the intermediate transfer member 103 are shorter than those of the structure of the conventional example, the structure of the transfer device, and the photosensitive member 1.
02 and peripheral speed of the intermediate transfer member 103 and the transfer material 28
Since the configuration is the same as that of the conventional example except that the relation with the transport speed of No. 1 is different from that of the conventional example, description of these same configurations will be omitted.

The relationship between the peripheral speed V4 of the photosensitive member 102, the peripheral speed V5 of the intermediate transfer member 103, and the conveying speed V3 of the transfer material 28 will be described below. The relationship between these speeds is (Equation 1), and here the relationship of (Equation 2) is used to simplify the description.

[0032]

[Equation 1]

[0033]

[Equation 2]

Next, FIG. 2 which is a detailed view of the transfer device constituting the image forming apparatus in one embodiment of the present invention will be described.

In this transfer device, the intermediate transfer member 103 and the transfer material transfer roller 26 are not in contact with each other, the transfer material transfer roller 26 is located at a position facing the transfer roller 21, and the transfer material 28 is transferred by a motor or the like. Rotate in the direction that does not interfere with.
Transfer material guides 50 and 51 are arranged on the carry-out side of the registration roller 33a, and a transfer material guide sheet 52 made of polyester is attached to the transfer material guide 50.

The operation of the image forming apparatus configured as described above will be described below with reference to FIG. A photoconductor that forms a latent image so that the size of the latent image on the photoconductor 102 drawn by the exposure light beam 15 emitted from the exposure optical system 9 with respect to the moving direction of the photoconductor 102 is half the size of the actual image. If the peripheral speed of the intermediate transfer member 103 that combines and holds the toner image 102 and the toner image that visualizes this latent image is set to 1/2 of the peripheral speed at which the actual image size is drawn, the photosensitive member 102 and the intermediate transfer member 103 are set. The toner image formed on the upper part of the image area is contracted to a size of 1/2 with respect to the moving direction of the photoconductor 102. When the composite image is formed on the intermediate transfer member 103, the transfer material 28 is sent from the transfer material cassette 29 to the transfer material transport path 31. The transfer material 28 is the slip roller 3
2 is conveyed to the registration roller 33a by the transfer material 2
8 and the rotation of the registration roller 33a and the driven roller 33b in order to match the position of the composite image on the intermediate transfer member 103 are temporarily stopped when the tip of the transfer material 28 reaches the registration roller 33a. The material 28 is in a standby state. During operation, the registration roller 33a and the driven roller 33b rotate together to convey the transfer material 28 toward the transfer material transfer roller 26. Here, the transfer material transfer roller 26
Keeps rotating in the conveying direction of the transfer material 28 until the transfer material 28 is discharged from the paper feed. 1 on the intermediate transfer member 103
The toner image formed in the size of / 2 has the transfer material 28 passing between the intermediate transfer body 103 and the transfer material transfer roller 26 at a speed twice as fast as the peripheral speed of the intermediate transfer body 103. It is doubled and transferred to the transfer material 28.

For example, a latent image is formed on the photoconductor 102 at 1 line / ms, and the photoconductor 102 and the intermediate transfer member 103 are formed by 8
It is considered that the lines are formed at the same intervals in the width scanning direction by driving at a peripheral speed of 5 μm / ms. At this time, the latent image forming speed for forming a latent image on the photoconductor 102 is set to 1 line / m.
The peripheral speed V of the photosensitive member 102 that forms a latent image and the intermediate transfer member 103 that combines the visualized toner image
When 4 and V5 are set to 1/2, the latent image is 1 line / ms
The photoconductor 102 and the intermediate transfer member 103 are formed by
Since it is driven at a peripheral speed of 42.5 μm / ms in the sub-scanning direction, the length of the toner image on the photoconductor 102 and the intermediate transfer member 103 is contracted to half the size. This is called image area contraction, and as shown in FIG. 3, the image on the intermediate transfer member 103 has a half of the length of the image formed area with respect to the image area.
Will be the size of. In order to transfer this image area contracted image to the transfer material 28 in the original size, while the peripheral speed V5 of the intermediate transfer body 103 is set to 1/2, the transport speed V3 of the transfer material 28 is set to the intermediate transfer body 103. When it is set to twice the peripheral velocity V5, the transfer material 28 passes at 85 μm / ms, so
The image whose length has been shrunk to the size of 2 is expanded to the original size, that is, expanded to twice the length of the image on the intermediate transfer member 103 and transferred. This is called image area expansion, and the image on the transfer material 28 is as shown in FIG.

According to the above operation, the length of the image on the photoconductor 102 and the intermediate transfer member 103 becomes shorter than the length of the image formed on the transfer material 28. When the relationship between the peripheral velocities V4 and V5 of the photoconductor 102 and the intermediate transfer member 103 and the transport velocity V3 of the transfer material 28 is set to 1: 1: 2 as in the present embodiment, the photoconductor 102 and the intermediate transfer member 103 have The length of the image is 1/2 with respect to the moving direction. Therefore, the length of the photosensitive member 102 and the intermediate transfer member 103 of the present invention is the same as the photosensitive member 10
2 and the peripheral velocities V4 and V5 of the intermediate transfer member 103 and the transfer material 28
The relationship with the transport speed V3 of 1 can be halved compared to the case of setting 1: 1: 1.

Next, the process of transferring the toner image on the intermediate transfer member 103 to the transfer material 28 will be described in detail with reference to FIG. When the toner image is transferred to the transfer material 28, if the intermediate transfer body 103 and the transfer material transfer roller 26 are nipped, there is a relative speed difference between the intermediate transfer body 103 and the transfer material 28. The toner image is rubbed on the transfer material 28 in the conveyance direction of, and the image becomes unclear.

Therefore, the image resolution is maintained as follows. A specified gap is set so that the transfer material transfer roller 26 and the intermediate transfer member 103 do not nip. In this embodiment, when the transfer material 28 passes between the intermediate transfer body 103 and the transfer material transfer roller 26, a gap of 0.5 mm or less is formed between the intermediate transfer body 103 and the transfer material 28, and the transfer material guide The transfer material guide sheet 52 adhered to 50 always urges the transfer material 28 toward the transfer material transfer roller 26. The transfer material guide sheet 52 is effective in preventing the transfer material 28 from being unstablely transported between the transport roller 21 and the transfer material transfer roller 26, and stabilizing the image quality. Then, a high voltage of 1500 V, for example, is set on the transfer material transfer roller 26 to optimize the Coulomb force acting on the toner, and the transfer is performed in a cotton shape to form a clear image.

[0041]

As described above, according to the present invention, the conveyance speed of the transfer material is set to be higher than the peripheral speed of the intermediate transfer member so that the intermediate transfer member is reduced in the rotational direction. When the toner image is transferred to the transfer material, it can be expanded and restored to its original size, and the size of the photoconductor and intermediate transfer body, which had a large effect on the size of the image forming apparatus, can be made smaller than before. The image forming apparatus can be made ultra compact.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a detailed view of a transfer device that constitutes an image forming apparatus according to an embodiment of the present invention.

FIG. 3 is a diagram showing image area contraction of an image on an intermediate transfer member which constitutes an image forming apparatus according to an embodiment of the present invention.

FIG. 4 is a diagram showing image area expansion of an image on a transfer material used in an image forming apparatus according to an embodiment of the present invention.

FIG. 5 is a configuration diagram of a conventional image forming apparatus.

FIG. 6 is a detailed view of a transfer device that constitutes a conventional image forming apparatus.

[Explanation of symbols]

 1 photoconductor 2 photoconductor transport roller 3 photoconductor support roller 4 photoconductor support roller 5 photoconductor position detection mark 6 photoconductor position detection sensor 7 seam 8 charger 9 exposure optical system 10K developing device (black) 10Y developing device (yellow) ) 10M developing device (magenta) 10C developing device (cyan) 11 before intermediate transfer static eliminator 12 intermediate transfer roller 13 photoconductor cleaning device 14 static eliminator 15 exposure light beam 16K sleeve roller (black) 16Y sleeve roller (yellow) 16M sleeve roller ( Magenta) 16C Sleeve roller (cyan) 17K Separation cam (black) 17Y Separation cam (yellow) 17M Separation cam (magenta) 17C Separation cam (cyan) 18 Intermediate transfer member 19 Conveying roller 20 Conveying roller 21 Conveying roller 22 Intermediate transfer member position detection mark 23 Intermediate Transfer Body Position Detection Sensor 24 Pre-Transfer Charger 25 Density Sensor 26 Transfer Material Transfer Roller 27 Intermediate Transfer Body Cleaning Device 28 Transfer Material 29 Transfer Material Cassette 30 Paper Feed Roller 31 Transfer Material Conveying Path 32 Slip Roller 33a Registration Roller 33b Driven Roller 34 Bearing 34a Cam part 34b Cam part 35 Oscillating plate 36 Shaft 37 Oscillating plate arm part 38 Spring 39 Solenoid 40 Clutch 41 Cam 41a Cam convex part 41b Cam concave part 42a Claw 42b Claw 43 Rotating shaft 44 Discharge toner tray 45 Cleaning frame 46 Shaft 47 Spring 48 Arm Part 49 Cleaning Blade 50 Transfer Material Guide 51 Transfer Material Guide 52 Transfer Material Guide Sheet 102 Photosensitive Member 103 Intermediate Transfer Member

Claims (2)

[Claims] 1. A latent image forming means for forming a latent image on a photoreceptor, a developing means for developing the latent image on the photoreceptor with toner, and a toner image visualized by the developing means. An intermediate transfer member that synthesizes and holds the image, and a unit that transfers the image on the intermediate transfer member to a transfer material, and
An image forming apparatus characterized by being set at a speed higher than the peripheral speed of the intermediate transfer member. 2. The image forming apparatus according to claim 1, further comprising a biasing unit that biases the transfer material toward the transfer unit.