JP3430781B2 - Toner image transfer device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner image transfer device, and more particularly to a toner image transfer device for transferring a toner image on a photoconductor onto a recording sheet by applying a transfer voltage to a transfer roll arranged to face the photoconductor. Regarding the device.

[0002]

2. Description of the Related Art A corotron system and a transfer roll system are known as a transfer system in a printer or the like for transferring a toner image formed on a photoconductor onto a recording paper. The corotron system is a system in which a transfer voltage is applied to a conductive wire to remove toner from a photoconductor and move it to a recording sheet. On the other hand, the transfer roll method is a method in which a transfer voltage is applied to a conductive rubber roll that also has a recording paper conveyance function to separate the toner from the photoconductor and move it to the recording paper.

The corotron system has disadvantages in that the transfer efficiency is lower than that of the transfer roll system and that a recovery device (tank) for residual toner and a device for countering generated ozone are required. Therefore, the transfer roll method has been increasing in recent years because the size of the apparatus can be reduced and the overall economic efficiency is high.

However, in the transfer roll method, it is important that the recording paper is pressed against the photoconductor with a uniform contact pressure. If the contact pressure is not uniform, it is judged that an image defect occurs due to missing pixels. Will be done. In particular, in an apparatus that uses a long transfer roll so that it can accommodate wide recording paper, when the transfer roll is supported only at its both ends, there is a problem that the contact pressure is insufficient at the central portion in the length direction of the transfer roll. is there.

Therefore, various measures have been taken to eliminate such problems and to uniformly press the recording paper.
FIG. 10 shows an example of a transfer roll for compensating for the contact pressure that tends to decrease at the center of the transfer roll. The transfer roll 100
Has a so-called crown shape in which the diameter of the central portion is larger than the diameters of both ends. An example of a crown-shaped transfer roll is described in JP-A-3-236080.

Further, especially when a transfer roll having a wide width is used, or when the transfer roll is provided immediately below the photosensitive member due to the layout, the transfer roll is bent due to its own weight. As a result, , Sufficient pressing force cannot be obtained in the central part. Although it is conceivable to increase the diameter of the transfer roll in order to reduce the bending, there is a problem that the weight is increased and the amount of conductive rubber constituting the transfer roll is increased. Therefore, a support member that presses the central portion of the transfer roll toward the photoconductor may be provided.

[0007]

The crown-shaped transfer roll described in the above publication has the following problems. That is, the transfer roll needs to have not only the function of transferring the toner image onto the recording paper but also the function of conveying the recording paper, and it is necessary to devise a method that does not cause the recording paper to be skewed or wrinkled during the conveyance. . However, in the case of a so-called crown-shaped transfer roll, the peripheral speed at the central portion in the recording paper width direction becomes high, which causes wrinkles on the recording paper.

In order to prevent the occurrence of wrinkles, conversely, the diameter of both ends of the transfer roll is increased to increase the peripheral speed at both ends.
It is advisable to generate a force that pulls the recording paper to both sides.
However, in this case, it is apparent that the contact pressure at the central portion of the transfer roll is insufficient, the contact state between the recording paper and the photoconductor deteriorates in the recording paper width direction, and transfer failure occurs.

Further, when the center portion of the transfer roll is pressed and held by the support member, the support member itself also bends. Therefore, in order to prevent this deflection, the same problem as when the transfer roll bends occurs. There is.

As described above, the conventionally studied methods and apparatuses do not satisfy both the transfer function and the transfer function of the transfer roll. Therefore, it is desired to realize a toner image transfer apparatus that satisfies these functions. It had been.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a toner image transfer device capable of simultaneously satisfying a recording paper transport function and a transfer function.

[0012]

SUMMARY OF THE INVENTION The present invention for solving the above problems and achieving the object is to provide a toner image transfer device for transferring a toner image formed on a surface of a photoconductor to a recording sheet by a transfer roll. In order to support the transfer roll, a plurality of support rolls arranged along the axial direction of the transfer roll and a pressing means for pressing the support roll against the transfer roll are provided, and the plurality of support rolls are provided. Among them, the support roll arranged in the central part of the transfer roll is biased to the upstream side in the recording paper conveyance direction with reference to the straight line connecting the centers of the transfer roll and the photoconductor, and the support arranged in the central part of the transfer roll. A support roll other than the roll is located on the downstream side in the recording paper conveyance direction with respect to the support roll arranged at the center of the transfer roll, and Without even have a first feature in that biases the recording sheet conveyance direction downstream side straight line connecting the centers of the support roll disposed in the transfer roll endmost nearer the transfer roll and the photoreceptor as a reference.

According to the first feature, the transfer roll is supported by the plurality of support rolls, and the bending in the gravity direction is prevented. On the other hand, since the support rolls themselves can be shortened in length, the occurrence of bending is suppressed. Further, the support roll arranged in the central portion of the transfer roll causes the central portion of the transfer roll to be pushed in the recording paper conveyance direction, so that the transfer roll is bent. Due to the bending of the transfer roll, a vector of the conveying force acts on the recording paper passing between the transfer roll and the photoconductor so as to pull the recording paper to both sides, and wrinkles occur on the recording paper. Can be prevented.

Further, according to the present invention, in order to support the transfer roll, the transfer roll is arranged along the axial direction of the transfer roll, and the straight line connecting the centers of the transfer roll and the photoconductor is used as a reference on the upstream side in the recording paper conveying direction. A plurality of biased support rolls, a pressing means for pressing the support roll against the transfer roll, a pressing force varying means for varying the pressing force by the pressing means for each support roll, and the recording If the skew of the recording paper is detected by the skew sensor means for detecting the skew of the paper and the skew sensor means, among the plurality of support rolls,
A second feature is that a control means for urging the pressing force varying means is provided in order to increase the pressing force of the support roll provided in the direction opposite to the skew direction.

According to the second feature, the deflection of the transfer roll increases at the position of the support roll on the side where the pressing force is increased. Therefore, the vector of the conveying force is changed so that the recording paper is pulled toward the transfer roll, and the skew is corrected.

[0016]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below with reference to the drawings. FIG. 3 is a diagram showing a main configuration of an electrophotographic apparatus according to an embodiment of the present invention. In the figure, the photoreceptor 1 is a so-called photosensitive drum having a cylindrical shape.
Around the photoconductor 1, a charger 2 for uniformly charging the surface of the photoconductor 1, a laser scanner 3 for writing an image,
A developing device 4 for developing the latent image formed by the laser scanner 3 with toner is arranged.

A transfer roll 5 is arranged below the photoconductor 1. The transfer roll 5 is made of conductive rubber and has a shaft 5
A transfer voltage is supplied via a and a bearing of the shaft 5a. The shaft 5a is driven by a motor. The bearing, the bias control device for supplying the transfer voltage, the driving motor for the shaft 5a, and the like are not shown because they are not directly related to the present invention. A support roll 6 is provided below the transfer roll 5. A plurality of the support rolls 6 are arranged around the transfer roll 5. Details of the structure and arrangement of the support roll 6 will be described later with reference to FIGS. 1 and 2.

A skew sensor 7 for detecting the skew of the recording paper is provided upstream of the recording paper conveyance direction. The skew sensor 7 is composed of a plurality of optical sensors arranged at positions corresponding to the widths of various recording papers so that the skews of the recording papers P of various sizes can be detected. Skew correction based on the output signal of the skew sensor 7 will be described later.

The recording paper P is fed between the transfer roll 5 and the photosensitive member 1, passes through the transfer portion while being skew-corrected based on the detection result of the skew sensor 7, and is conveyed in the direction of arrow F. . Then, the toner image formed on the photoconductor 1 by the transfer voltage is transferred onto the recording paper P.

An example of the arrangement of the skew sensor 7 is shown in FIG.
In the same figure (a), the skew sensor 7R, which is separated from the recording paper P by a distance X in the width direction according to the width of the recording paper P,
7L is provided. Further, in the example of FIG. 4B, one side edge of the recording paper P is used as a reference, and the recording sheet P is separated by a distance X.
The two skew sensors 7R and 7L are arranged separately.

Next, the arrangement of the support rolls 6 will be described. FIG. 1 shows a support roll 6 for a transfer roll 5.
3 is a bottom view of the main part of the transfer portion showing the arrangement of FIG. 2, and FIG. 2 is a side view of the main part. 1 and 2, the transfer roll 5
A plurality of (five in this example) support rolls (hereinafter, each support roll is indicated by reference numeral 6 below)
a, 6b, 6c, 6d, 6e) are provided. The transfer roll 5 includes these five support rolls 6a-
It is supported from below by 6e. The support roll 6a
6e have metal shafts 60a to 60e, and the roll body 6
a to 6e are made of epoxy resin for insulation. In addition,
The roll bodies 6a to 6e are made of metal, and the shafts 60a to 60 are
e may be made of an insulating material.

Of the support rolls 6a to 6e, the support rolls 6a, 6e and 6c are the photoconductor 1 and the transfer roll 5.
It is arranged so as to deviate from the line L connecting with. Transfer roll 5
While the support roll 6c located at the central portion in the longitudinal direction of the recording paper P is displaced upstream in the transport direction of the recording paper P, the support rolls 6a and 6e located at the longitudinal end portions of the transfer roll 5 are transported in the transport direction of the recording paper P. It is shifted to the downstream side.

Although the support rolls 6b and 6d are arranged on the line L, the support rolls 6b and 6d may be slightly displaced to the support roll 6c side, that is, to the upstream side in the conveying direction. Further, the support rolls 6b and 6d may be omitted, and the support rolls 6a, 6c and 6e may be supported. What is essential is that the transfer roll 5 is supported at both ends, and the holding force of the transfer roll 5 is generated upward while the central portion is pushed out to the downstream side in the recording paper conveyance direction.

Each of the support rolls 6a to 6e is configured to elastically support the transfer roll 5. That is, the support rolls 6a to 6e are supported by the support plate 8 having the leaf spring portion 8a and the bearing portion 8b, and are pressed against the transfer roll 5 by the elastic force of the leaf spring portion 8a.
The leaf spring portion 8a may be rotatably supported by a hinge, and the leaf spring portion 8a may be pressed by a coil spring or the like to apply a pressing force. In this case, the leaf spring portion 8a does not necessarily have a spring property, but may be a flat plate having the bearing portion 8b. Although all the support rolls are provided with similar support plates, the reference numerals are omitted to avoid complexity of the drawings.

When the transfer roll 5 is elastically pressed by the support plate 8, the central portion thereof is pushed out in the recording paper conveyance direction, and as shown by the dotted line in FIG. The curved state is exaggerated for easy understanding. When the transfer roll 5 bends in this way, the conveyed recording paper P is first sandwiched between the transfer roll 5 and the photoconductor 1 at both ends. Then, the central portion of the recording paper P is gradually sandwiched and the transfer of the image is executed. The symbol F indicates the transport direction.

At this time, since the transfer roll 5 is curved, the transport force vector vs of the transfer roll 5 acting on the recording paper P is different in each part of the transfer roll 5 in the longitudinal direction. That is, at the end of the transfer roll 5, the vector vs is slightly outward. Due to such vector orientation, the recording paper P is conveyed while receiving a tensile force on both sides to transfer an image.

In the above description, the center reference system, that is, the center registration in which the widthwise center of the recording paper P passes through the center of the transfer roll 5, the recording paper P is also transferred. There is also an electrophotographic apparatus constituted by a side edge reference system, that is, a side register, which is arranged so as to be moved toward one side. When the present invention is applied to this side registration method, when transferring to a recording paper of a small size, it is preferable that the position where the bending of the transfer roll 5 is the largest is closer to the end than the center of the transfer roll 5. For example, the support roll 6b is arranged on the upstream side in the transport direction of the recording paper P similarly to the support roll 6c. By doing so, the position where the bending of the transfer roll 5 is the largest can be brought closer to one side of the transfer roll 5, that is, closer to the support roll 6b.

Next, another embodiment of the present invention will be described. In this embodiment, attention is paid to the fact that the vector at each part of the transfer roll 5 that conveys the recording paper P is different depending on the position where the amount of bending of the transfer roll 5 is maximum, and this vector is changed to change the recording paper P. Correct skew.

5 and 6 are views showing the arrangement of support rolls for skew correction. In the figure,
Reference numeral 1 is a photoconductor. The transfer roll 5 arranged to face the photoconductor 1 has support rolls X and Y near the center thereof.
Supported by. The support rolls X and Y have independent pressing means. In FIG. 5, the support plate 9 for the support rolls X and Y is provided so as to be rotatable around a shaft 10 fixed to a frame (not shown). One end of the tension spring 11 is coupled to one end of the support plate 9, and the other end of the tension spring 11 is coupled to the plunger 13 of the solenoid 12. The solenoid 12 is fixed to the frame similarly to the shaft 10. The support rolls X and Y are pressed in the direction of arrow B by the support roll pressing means. Here, when the solenoid 12 is excited, the pressing force of the tension spring 11 can be further strengthened.

With the above configuration, the skew sensor 7
When the skew of the recording paper P is detected by, the pressing force of the support roll in the direction opposite to the skew direction of the support rolls X and Y is strengthened. That is, the solenoid 12 is excited. By increasing the pressing force of one of the support rolls, the position where the deflection of the transfer roll becomes maximum changes in the direction opposite to the skew, and the vector of the conveying force of the transfer roll 5 changes in the direction to correct the skew.

The change in the vector will be described with reference to FIG. In the figure, the dotted line shows the transfer roll in a state where the support rolls X and Y are pressed and bent. The size of the flexure is exaggerated for ease of understanding. In the same figure (a), the pressing forces of the support rolls X and Y are equal, and in this case, the composite v of the vectors v1 and v2 of the conveying force by the transfer roll 5 is orthogonal to the axis of the transfer roll 5 in the state without any bending. It is the direction to do. When no skew occurs, such a vector state is maintained.

When it is detected that a skew (arrow C) on the right side in the drawing as shown in FIG. 7B is generated, the pressing force of the support roll X is strengthened. As a result, the position where the deflection of the transfer roll 5 is maximum is shifted to the left in the figure, and the vector v1 and the composite v of the vectors v1 and v2 are changed.
Changes to the left and the skew is corrected.

FIG. 8 is a block diagram showing the configuration of a drive control device for the solenoid 12 for skew correction. In the figure, the skew sensor 7 is arranged on the conveyance path of the recording paper as described above. The size sensor 13 is a sensor that detects the size of the recording paper, and the arrangement position can be arbitrarily selected on the recording paper conveyance path upstream of the skew sensor 7. Detection signals from the skew sensor 7 and the size sensor 13 are sent to the CPU 15 via the input / output circuit (I / O) 14.
Entered in.

A plurality of sets of skew sensors 7 are provided, and only the set of output signals corresponding to the size of the recording paper detected by the size sensor 13 is fetched by the CPU 15.
When the skew of the recording paper occurs, the detection signal from the skew sensor 7 is input to the CPU 15, and the CPU 15
Discriminates the direction of the skew to determine the support rolls X, Y
Of which of the solenoids 12 is to be excited is determined, and an excitation command is supplied to the solenoid 12. ROM1
6 is a memory for storing programs and system data, and RAM 17 is a memory for storing processing results. The operation unit 18 includes keys and buttons for inputting operator's instructions, a liquid crystal screen for displaying processing results, and the like.

Instead of detecting the size of the recording paper with the size sensor 13, the operator may input the recording paper size from the operating section 18 prior to printing. If the electrophotographic apparatus prints the image data supplied from the host computer, the size of the recording paper may be recognized from the size instruction information included in the image data.

Next, the skew correction will be described with reference to a flowchart. In FIG. 9, in step S1, the recording paper size is read from the size sensor 13. In step S2, a set of skew sensors 7 to be used is determined based on the detected recording paper size. Here, it is assumed that a recording sheet corresponding to the skew sensors 7R and 7L passes, and a case where the skew sensors 7R and 7L are selected will be described. In step S3, it is determined whether the right sensor, that is, the skew sensor 7R is on. If the skew sensor 7R is off, the process proceeds to step S4, and it is determined whether or not the left sensor, that is, the skew sensor 7L is on.

When the skew sensor 7L is turned on, the process proceeds to step S5, and the solenoid 12 connected to the support plate of the support roll Y is excited to strengthen the pressing force of the support roll Y. On the other hand, if it is determined in step S3 that the skew sensor 7R is turned on, the process proceeds to step S6, and in order to strengthen the pressing force of the support roll X, the solenoid 1 connected to the support plate of the support roll X is strengthened.
Energize 2.

[0038]

As is apparent from the above description, according to the first aspect of the invention, the transfer roll is prevented from bending in the direction of gravity, and the contact pressure between the transfer roll and the photoconductor is not reduced. Can be prevented.

Further, since the support rolls themselves can be shortened in length, the occurrence of bending is suppressed, and the reduction of the pressing force against the transfer roll can be prevented. Furthermore, the recording paper is pulled to both sides by the action of the vector due to the transfer roll being bent in the recording paper conveyance direction at its central portion, and the conveyance and transfer are performed without wrinkles, resulting in the occurrence of transfer defects. Can be prevented.

Further, according to the second aspect of the invention, when the skew occurs, the skew can be corrected by using the vector of the recording paper conveying force due to the bending of the transfer roll.

[Brief description of drawings]

FIG. 1 is a bottom view of a main part of a toner image transfer device showing an arrangement of support rolls according to an embodiment of the present invention.

FIG. 2 is a side view of essential parts of the toner image transfer device showing the arrangement of the support rolls according to the embodiment of the present invention.

FIG. 3 is a diagram showing a main configuration of an electrophotographic apparatus including a toner image transfer device according to an embodiment of the present invention.

FIG. 4 is a diagram showing an arrangement of skew rolls with respect to a recording sheet.

FIG. 5 is a side view showing a pressing force varying device for a support roll.

FIG. 6 is a diagram showing an arrangement of a support roll and a transfer roll for skew correction.

FIG. 7 is a diagram showing an operation of a support roll for skew correction.

FIG. 8 is a block diagram showing a configuration of a skew control device.

FIG. 9 is a flowchart showing an operation of skew correction.

FIG. 10 is a diagram showing a transfer roll of a conventional device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photoconductor, 5 ... Transfer roll, 5a ... Shaft of transfer roll, 6,6a, 6b, 6c, 6d, 6e ... Support roll, 7 ... Skew sensor, 8 ... Support plate, 8a ... Leaf spring part, 11 ... Tension spring, 12 ... Solenoid,
13 ... Size sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Norio Ogawara 2274 Hongo, Ebina-shi, Kanagawa Fuji Zerox Co., Ltd. (56) Reference JP-A-5-27613 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 15/16

Claims (2)

(57) [Claims] 1. A toner image transfer device for transferring a toner image formed on a surface of a photoconductor onto a recording sheet by a transfer roll, wherein a plurality of toner images are arranged along an axial direction of the transfer roll to support the transfer roll. And a pressing means for pressing the support roll against the transfer roll, and of the plurality of support rolls, the support roll disposed in the center of the transfer roll is Biased to the upstream side in the recording paper conveyance direction with reference to the straight line connecting the center of the body, the support rolls other than the support rolls arranged in the transfer roll central portion, than the support rolls arranged in the transfer roll central portion The support roll, which is located on the downstream side in the recording paper conveyance direction and is disposed at least near the end of the transfer roll, is used for the above-mentioned transfer. The toner image transfer apparatus being characterized in that a straight line connecting the center of the roll and the photoreceptor biases the recording sheet conveyance direction downstream side as a reference. 2. A toner image transfer device for transferring a toner image formed on a surface of a photoconductor onto a recording sheet by a transfer roll, wherein the toner image transfer device is arranged along the axial direction of the transfer roll to support the transfer roll, and A plurality of support rolls that are arranged offset toward the upstream side in the recording paper conveyance direction with reference to a straight line connecting the centers of the transfer roll and the photoconductor, a pressing means for pressing the support roll against the transfer roll, and A pressing force varying unit that varies the pressing force of the pressing unit for each support roll, a skew sensor unit that detects the skew of the recording paper, and a skew sensor unit that detects a skew of the recording paper. Of the support rolls, in order to increase the pressing force of the support rolls provided in the opposite direction to the skew direction, The toner image transfer apparatus characterized by comprising control means for energizing the serial pressing force varying means.