JP3209451B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to an image forming apparatus, and more particularly, to an image forming apparatus in which one or both of an image carrying means and a transfer material conveying means is constituted by a belt holding mechanism and an endless belt member. The present invention relates to an image forming apparatus which forcibly applies a biasing force to an endless belt member so that the endless belt member can be reliably driven within a certain moving range.

[0002]

2. Description of the Related Art As is well known, various types of image forming apparatuses employing an electrophotographic system or an electrostatic recording system for an image forming process have been developed. In these various types of image forming apparatuses, a photosensitive drum is used as an image carrying means, and a charger, an exposing means, peripheral devices such as a developing device, a transfer material transport mechanism, etc. are arranged around the photosensitive drum. There is a thing of the form. In recent years, in order to further improve the functions of the photosensitive drum and the transfer material transporting mechanism, an endless belt member carrying a photoreceptor has been employed in place of the photosensitive drum, and the transfer material transporting mechanism has also been provided with an endless belt. An image forming apparatus employing a belt member has been developed. As described above, in an image forming apparatus that employs an endless belt member for a photoconductor, a transfer material transport mechanism, and the like, it is possible to improve a number of functions. Some means for suppressing the belt shift during driving and the occurrence of snake motion, which are disadvantages of (1), are indispensable. In other words, the drawbacks such as deviation and meandering during belt driving are caused by the belt driving mechanism, the mechanical accuracy of the belt itself, changes in the characteristics of the belt, and the transfer material entering the transfer material transport belt from the transfer material supply mechanism. Since it is generated by various external forces such as the vibration of the conveyor belt that occurs, it is impossible to prevent the belt from shifting or meandering without providing any means. Met.

Conventionally, the following method has been employed as a means for correcting such inconveniences when the belt is shifted or meandering. (A) A method in which the diameter of the roller member holding the endless belt member is made larger at the center portion than at both end portions so that the roller member has a crown shape as a whole. (B) A method in which a guide groove is provided in each roller member, and a guide rib is provided in a portion on the inner peripheral side of the endless belt member corresponding to the groove. (C) A method of writing a registration mark on a belt member and correcting the relative positional deviation of the mark by optically feeding back. (D) A method in which a registration mark is written on a belt member, and the relative position of the belt holding member is changed based on the relative positional deviation of the mark. (E) A method in which a biasing force is forcibly applied to the belt member to intentionally generate a bias, and the image forming timing is adjusted according to the amount of belt deviation.

[0004]

However, according to each of the above conventional examples, there are problems as described below.

First, the conventional methods for correcting the belt deviation shown in (a) to (e) above have the following problems. That is, the above method (a) is the most widely used correction means. However, the belt member is formed by distorting the endless belt member by forming the roller member into a crown shape to generate an internal stress difference. Therefore, it is necessary to use a belt made of a material having sufficient elasticity. Furthermore, since the so-called permanent deformation of the belt member due to creep strain is prevented while utilizing the strain generated in the belt member, for example, when a rubber belt is used, a material with a low rubber hardness and a material having high elasticity is used. It is necessary to adopt it and to set its thickness so as to satisfy the mechanical strength. Therefore, when the method (a) is applied to a photosensitive belt or the like, an image is deformed due to distortion of the belt surface, which is not suitable. Since the thickness of the belt must be increased, the transfer current must be set to a large value, which is still unsuitable.

Next, in the above method (b), the bias of the belt member is suppressed by receiving the thrust force generated in the belt member at the end surface of the guide rib. The accuracy of the ribs determines the accuracy of the control of the moving speed of the belt member. However, since it is technically very difficult to attach the guide rib to the inner peripheral side of the belt member with high accuracy, the movement speed of the belt member cannot be controlled with high accuracy, and it is not suitable for mass production. Absent.

In the method (c), it takes a long time to provide feedback for adjusting the optical system, so that it is difficult to provide feedback every time an image is formed. The problem of offset and belt destruction cannot be solved by this method.

Next, the above method (d) aims to make the belt travel substantially straight near the target position as shown by the two-dot chain line curve in FIG. However, there is a problem that the shift direction and the shift degree do not follow the delay of the response of the shift of the belt to the change of the belt and the delicate change of the relative position of the belt.

Next, the above method (e) is based on the above (a) to (b)
It has many advantages over the method (d), and is more practical in terms of belt deviation control. However,
The above (e) also has the following problems.

First, depending on the environment in which the device is placed,
The device body is twisted. Since the torsion also involves torsion of the belt supporting portion, the belt deviates from the deviation control amount set at the time of assembling the apparatus, and the belt moves only in one direction, and eventually breaks.

Secondly, due to the durability, the belt is deformed due to plastic deformation and the like, which causes a change in the shift of the belt. There is a problem of control deviation.

SUMMARY OF THE INVENTION An object of the present invention is to prevent an image forming apparatus having an endless belt member from deviating from belt shift control due to twisting or temporal change of the image forming apparatus main body, and to prevent breakage of the belt member. It is an object of the present invention to provide an image forming apparatus capable of performing the above.

[0013]

According to the present invention, there is provided a transfer material conveying belt for carrying and transferring a transfer material,
An image forming means for forming an image on the transfer material carried on said transfer material conveying belt, the support for supporting the transfer material conveyance belt
And moving means for moving the position of the support,
Moving means reciprocate the position of the support within a predetermined range.
In this way, the transfer material transport belt is
Intersecting alternately in a first direction and a second direction opposite to the first direction
In the image forming apparatus to be swung in response to the swinging speed of the transfer material conveyance belt, to change the predetermined range
This is achieved by having control means for controlling the amount of movement of the support by the moving means .

According to the invention of the present application, the above object is
Supporting an image bearing belt that carries and conveys an image, and an image forming means for forming an image on said image bearing belt, said image bearing belt
A support, and moving means for moving the position of the support.
Then, the moving means moves the position of the support within a predetermined range.
By moving backward, the image bearing belt is moved straight in the image transport direction.
Intersecting alternately in a first direction and a second direction opposite to the first direction
In the image forming apparatus to be swung in response to the swinging speed of the image carrier belt, on to change the predetermined range
It is also achieved by having control means for controlling the amount of movement of the support by the moving means .

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 and 2 of the present invention will be described with reference to the drawings.

<First Embodiment> First, a first embodiment of the present invention will be described with reference to FIGS. The image forming apparatus according to the present invention is configured such that at least one of the image carrying means and the transfer material conveying means provided in the apparatus has a belt holding mechanism and an endless belt member. An image forming process from latent image formation to visible image formation is performed by the means, and the transfer material conveying means conveys a transfer material to which a visible image on the image bearing means is transferred. is there. Since the functions of the above-described units are already well known, detailed description thereof will be omitted.

FIG. 1 is a schematic perspective view showing an image forming apparatus according to a first embodiment of the present invention. In the image forming apparatus according to the present embodiment, only the transfer material conveying means has a belt holding mechanism and an endless belt member. Although the configuration is the same, it goes without saying that only the image bearing unit may have the same configuration, or both units may have the same configuration. In addition, since the color image forming apparatus is provided with image carrying means at four positions, the present invention is not limited to this, and the present invention can be applied to an image forming apparatus having an arbitrary number of image carrying means. is there.

Since the image forming apparatus shown in FIG. 1 employs an electrophotographic image forming apparatus process, a rotating polygon mirror 1 is provided on four uniformly charged photosensitive drums 161 to 164.
A latent image of an image to be copied is formed by the image forming apparatus 30 and the reflecting mirrors 141 to 152, and is converted into a visible image by a developing device (not shown). ) 101 so as to be transferred onto a transfer material (not shown) conveyed by 101. The belt 101 includes a driving roller 104, a tension roller 105, and a correction roller 10 that constitute a belt holding mechanism.
6 and the driven roller 107 to move in the direction of the arrow Z shown in the figure.

Next, the image forming apparatus according to the present invention shown in FIG. 1 will be described in detail with reference to FIG. 2 showing a detailed structure of a belt and a belt holding mechanism which is the gist of the present invention.

Each of the rollers constituting the above-described belt holding mechanism is rotatably supported by a shaft, and the driving roller 104 and the driven roller 107 are arranged in a corresponding relationship.
In addition, each is fixed at a predetermined position. A drive motor 108 for rotating the drive roller 104 in the direction of arrow B shown in the figure is connected to the rotation shaft of the drive roller 104. The correction roller 106 as a support for supporting the belt corrects a problem such as a deviation or meandering generated on the belt 101. One end of the rotation shaft of the correction roller 106 is provided by a pivot bearing 112, The other ends are each supported by a bearing 109. The bearing 109 is a rod 1 coaxially connected to an operating shaft of an actuator 110 as a moving means for performing variable adjustment.
2, the operating shaft of the actuator 110 reciprocates along the belt 101 as shown by X in FIG.
1 and along with the correction roller 106, as shown by AA 'in FIG. That is, the correction roller 106 is a pivot bearing 1
Since the pivot 12 is fixed, the other end (that is, the bearing 109 side) of the pivot bearing 112 is actuated by the operation of the actuator 110 in FIG.
As indicated by A ′, the bearing 110 is moved in an operating axis direction (along the belt 101) in an arc and drawn.
Thus, the rotation center axis of the correction roller 106 can be at an arbitrary angle with respect to the original position of the correction roller 106 in the direction along the belt 101. In the present embodiment, a linear stepping motor is used as the actuator 110, and the movement amount of the rotation center axis of the correction roller 106 is set by a drive command signal (pulse signal) output to the linear stepping motor.
Can be easily performed by changing the number of pulses.

An appropriate mark 102 such as a registration mark is provided on the belt 101, and the mark 102 is formed on the belt 101 in a direction transverse to the moving direction of the belt 101. It is detected by the belt position detecting means 131 which detects the sign. In this embodiment,
The belt position detecting means 131 includes an illuminating means 113 for illuminating the belt 101 along a direction crossing the moving direction of the belt 101, and a CCD (electric charge detecting means) which detects reflected light from the marker 102 and converts the reflected light into an electric signal. Coupling element) array 11
And 4.

In the above configuration, the actuator 11
For example, as shown in FIG. 3, when the rotation center axis of the correction roller 106 is moved from the original position C indicated by the dotted line to the position C ′ indicated by the solid line in the moving direction of the belt 101 as shown in FIG. + Direction), unlike the case where the correction roller 106 is at the original position, a twist angle occurs between the correction roller 106 and the other rollers. Therefore, the winding position of the belt 101 is shifted from the position indicated by the broken line in FIG. The belt 101 moves to the position indicated by the solid line (indicated by the distance α), and the belt 101 is shifted. Conversely, when the rotation center axis of the correction roller 106 is moved from the original position C indicated by a dotted line in a direction opposite to the moving direction of the belt 101 (this moving direction is defined as a negative direction), the correction roller 106 is similarly moved to the original position. 3, a twist angle occurs between the roller 101 and the other rollers. Therefore, the winding position of the belt 101 shifts from the position shown by the broken line in FIG. 3 to the outside (to the right) in FIG. The belt 101 is shifted in the opposite direction. Therefore, the first direction in the belt movement range
From the maximum offset position in the + direction as the
Belt 1 between the maximum offset positions in two directions-direction
01 is always forcibly moved (oscillated) , that is, when one end of the belt 101 reaches the maximum offset position in the + direction, the correction roller is inclined to move the belt in the-direction. When the opposite end of the belt 101 reaches the maximum offset position in the negative direction, the correction roller is tilted in the reverse direction to move the belt in the positive direction, so that the belt position is constantly forcibly zigzag at a predetermined offset speed. If you move to
As shown by the solid line, the belt 101 can always be driven within a certain range, and an accident such as breakage of the belt can be prevented.

For example, as shown in FIGS. 5 and 6, the forcible zigzag movement of the belt 101 is performed by storing the maximum offset position information in the + direction and the maximum offset position information in the-direction of the belt movement range in advance. 121, and the correction roller is moved by a predetermined amount with respect to the original position C as a center by − and +.
The direction is alternated. That is, when S ₁ moves the correcting roller 106 from the original position in the + direction, the belt starts to move in the + direction. At this time, the position and moving direction of the belt are
It is detected by the array 114. As shown in FIG.
D represents a number of light receiving elements a to
k (actually, more light receiving elements are arranged)
As can be easily understood from FIGS. 7A and 7B, the elements a to k that receive the light reflected from the marker 102 on the belt 101 according to the movement of the belt position are provided. Because it changes, the belt position can be accurately detected by detecting from which element the output is generated,
By comparing which element the output is generated every other rotation of the belt, it also serves as a belt shift speed detecting means for detecting the belt movement direction and the shift speed (shift amount / time of one belt rotation). . Also, the maximum deviation position information such as the + direction is stored in the memory 121 by the comparison operation circuit 120.
Reading the, compared to the position information of the label 102 on the belt 101 detected by the CCD 114, continues to hold the S ₁ position of the correction roller 106 until the result of the comparison is zero.

As shown in FIG. 6A, when one end of the belt reaches the maximum offset position in the + direction, the comparison operation circuit 1
20 is 0, the driver 123 moves the correction roller 106 in the negative direction by S ₁ + S ₂ from the current position, and at the same time, the maximum deviation position information in the negative direction from the memory 121 is read out to the comparison operation circuit 120. It is. On the other hand, the belt changes its moving direction and starts moving in the + direction.
When the opposite end of the belt reaches the maximum offset position in the negative direction, the comparison result becomes 0, and the driver 123 moves the correction roller 6 in the positive direction from the current position by S as shown in FIG.
₁ + S ₂ , and the above operation is repeated. Thus, as shown in FIG. 4, the belt 101 reciprocates zigzag between the maximum offset position in the + direction and the maximum offset position in the-direction within the movable range. At this time, the correction roller 106 alternately moves between + S ₁ (first position) and −S ₂ (second position) from the original position.

However, if the device body is twisted or the belt is plastically deformed due to endurance, this relationship is broken, and even if the correction roller 6 is alternately moved between + S ₁ and −S ₂ , the reciprocation occurs. It does not move and moves only in the negative direction. Then, at that time, it was confirmed that the deviation speed of the belt was changed as a sign of deviating from the zigzag reciprocating motion control.

In the present embodiment, as shown in FIG. 8, the amount of movement of the correction roller 106 is corrected. When the belt shift speed (oscillation speed) is detected and calculated by the above-described belt shift speed detecting means, the belt shift speed ( the slope of the straight line in FIG. 8 ) is calculated as shown by R3 → R4 in FIG. , Normal R1
→ It is determined that the speed is significantly higher than the speed to R2. At this time, until now, + S _1, once the correction roller 106 which has been moved between the -S ₂ to + direction S ₁ + S ₂ + ΔS ₁
Just move. Note that this ΔS ₁ is obtained from ΔS ₁ = K · Δv (K: a coefficient obtained from an experiment) with respect to the variable amount Δv of the deviation speed, and is automatically given to the driver 123 from the variable amount of the deviation speed. It is set and added to the amount of movement of the actuator 110.

With this correction, the belt also returns to the normal shift speed, and this time, as if the apparent original position of the correction roller 106 was shifted by ΔS, + (S ₁ + ΔS ₁ )
And the correction roller 106 repeatedly moves between −S ₂ + ΔS ₁ . The deviation of the deviation control is avoided by this correction.

The displacement of the visible image transferred from each image bearing means (photosensitive drum in this embodiment) to the transfer material caused by forcibly moving the belt position as described above (in the transport direction of the belt 101). Position deviation of each color in a direction substantially perpendicular to the direction), the deviation speed of the belt 101 is obtained from the amount of deviation of the belt 101 read by the CCD 114 and the time required for the belt 101 to make one revolution. The correction can be made by adjusting the image timing for the image carrier.

However, the positional deviation between the photosensitive drums is significantly smaller than the amount of deviation of the belt, so that the correction can be ignored.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIGS. The same parts as those in the first embodiment are denoted by the same reference numerals, and the description is omitted.

In the first embodiment, the CCD array and the marker 102 are used as the belt position detecting means and the belt deceleration speed detecting means, as shown in FIGS. 9 and 10.
End surface sensors 131a and 131b (preferably a groove type photo interrupter, or a mechanical sensor formed by a combination of a lever and a groove type photo interrupter, which are preferably used) are disposed at both ends of the belt 101 in the direction in which the belt 101 is shifted. By judging which of the end face sensors 131a and 131b detects the belt end face, the shift direction and position of the belt are detected. Further, the belt reciprocates zigzag, and the end face sensors 131a, 131b
Are detected alternately, and the detection time interval T is measured by a timer. Since the positions of the end face sensors 131a and 131b are fixed, the shift speed of the belt is calculated by the following equation using α ₁ and α ₂ in FIG.

Belt deceleration speed = (α ₁ + α ₂ ) / T The other components and the correction method are the same as those of the above-described embodiment, and therefore the description thereof will be omitted.

With this configuration, in the above-described embodiment, the direction and speed of the shift of the belt are not determined until the belt makes a circuit and the mark reaches the CCD. However, since the belt end surface is continuous, the maximum There is an advantage that there is no delay in responsiveness near the offset position, and an advantage that it can be easily configured as compared with the CCD.

In the above embodiment, the case where the present invention is applied to an electrophotographic image forming apparatus has been described, but the present invention is also applicable to an electrostatic recording type image forming apparatus. Further, in the image forming apparatus of the above embodiment, only the transfer material conveying means has the belt holding mechanism and the endless belt member, but only the image bearing means may have the same structure, or Both the support means and the transfer material transport means may be configured to have a belt holding mechanism and an endless belt member. Further, the present invention is not limited to a color image forming apparatus. Further, it goes without saying that the arrangement position of the correction roller, the moving means of the rotation center axis of the correction roller, the moving direction, and the like can be variously changed as necessary.

[0035]

As described in the foregoing, according to the present invention, a transfer material conveying belt for bearing and conveying a transfer material, and an image forming means for forming an image on the transfer material carried on said transfer material conveyance belt, A support for supporting the transfer material transport belt;
Moving means for moving the position of the support,
Moves back and forth within the predetermined range of the support.
The transfer material transport belt is perpendicular to the transfer material transport direction.
Swing alternately in a first direction and a second direction opposite to the first direction
In the image forming apparatus causes, in response to the swinging speed of the transfer material conveyance belt, to change the predetermined range described above
Since the control means for controlling the amount of movement of the support by the moving means is provided , even if the apparatus main body is twisted or the transfer material transport belt changes due to durability, the transfer material transport belt is damaged. Can be prevented.

According to the present invention, an image is carried and conveyed.
And the image bearing belt that includes an image forming means for forming an image on said image bearing belt, a support for supporting the image bearing belt, said supporting
Moving means for moving the position of the holding body, wherein the moving means
Reciprocating the position of the support within a predetermined range
The image bearing belt is moved in a first direction orthogonal to the image conveying direction.
The like in image <br/> image forming apparatus for swinging alternately and a second direction opposite to the first direction, in response to the swing speed of the image carrier belt, to change the predetermined range By means of transportation
The structure has a control means for controlling the amount of movement of the support, so that even if the apparatus main body is twisted or the image carrying belt changes due to durability, the image carrying belt is prevented from being damaged. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a detailed configuration of a belt and a belt holding mechanism in the apparatus of FIG. 1;

FIG. 3 is a view for explaining the movement of a correction roller in the apparatus in FIG. 1;

FIG. 4 is a diagram illustrating a relationship between a movement amount of a correction roller and a movement range of a belt in a normal case in the apparatus in FIG. 1;

FIG. 5 is a block diagram showing a schematic configuration of a control unit of an actuator for moving a correction roller in the apparatus of FIG. 1;

FIG. 6 is a view showing a state in which a belt is biased in the apparatus shown in FIG. 1;

FIG. 7 is a diagram showing a relationship between a CCD constituting a belt position detecting means in the apparatus of FIG. 1 and a mark on the belt.

FIG. 8 is a diagram for explaining correction control of a movement amount of a correction roller in the apparatus of FIG. 1;

FIG. 9 is a perspective view illustrating a schematic configuration of an apparatus according to a second embodiment of the present invention.

FIG. 10 is a block diagram illustrating an example of a control circuit of an actuator for moving a correction roller of the apparatus in FIG. 9;

[Explanation of symbols]

Reference Signs List 101 belt (endless belt member) 104 drive roller (belt holding mechanism (rotatable support)) 105 tension roller (belt holding mechanism (rotatable support)) 106 correction roller (belt holding mechanism (rotatable support) Body)) 107 driven roller (belt holding mechanism (rotatable support)) 110 actuator (moving means) 114 CCD (belt position detecting means, belt deceleration speed detecting means) 120 comparison operation circuit (belt deceleration speed detecting means) 121 Memory (belt shift speed detecting means) 123 Driver (movement amount correcting means) 131, 131a, 131b Belt position detecting means

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-153675 (JP, A) JP-A-4-55883 (JP, A) JP-A-4-50992 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G03G 15/16 B65H 5/02 G03G 15/01 114 G03G 21/00 370

Claims (8)

(57) [Claims] And 1. A transfer material conveying belt to transfer material carrying transport and a image forming means for forming an image on the transfer material carried on said transfer material conveying belt, supported for supporting the transfer material conveyance belt
Holding body, moving means for moving the position of the support,
The moving means reciprocates the position of the support within a predetermined range.
Moving the transfer material transport belt in the transfer material transport direction.
In a first direction orthogonal to and a second direction opposite to the first direction.
In the image forming apparatus, which oscillates alternately, in accordance with the oscillating speed of the transfer material conveying belt , the predetermined
Moving the support by the moving means to change the range
An image forming apparatus comprising control means for controlling a moving amount . 2. The image forming apparatus according to claim 1, wherein said image forming apparatus includes a counting means for counting a time required for the transfer material conveying belt to swing a predetermined distance in a direction orthogonal to the transfer material conveying direction. The image forming apparatus according to claim 1, wherein the movement amount is controlled according to the time counted by (1). Wherein said image forming apparatus, possess a first detection means and second detection means for detecting both ends of a direction perpendicular to the transfer material conveying direction of the transfer material conveyance belt, the counting means Means that the first detecting means conveys the transfer material
After the belt has been detected, the second detecting means
The image forming apparatus according to claim 2 , wherein a time until the detection of the transfer material transport belt is started is counted . 4. comprises a plurality of image bearing member for bearing the above image forming means an image of a plurality of colors, respectively, transfer material plural colors the image of on the plurality of image carriers is carried on the transfer material conveyance belt sequentially superimposed image forming apparatus according to any one of claims 1 to 3, characterized in that it is transferred to. 5. An image forming apparatus according to claim 4 , further comprising adjusting means for adjusting timing of forming images on said plurality of image carriers based on a swing speed of said transfer material conveying belt. . An image bearing belt that carries and conveys a 6. images, transfer moving an image forming means for forming an image on said image bearing belt, a support for supporting the image carrier belt, the position of the support
Moving means, and the moving means determines a position of the support body.
The image carrier belt is reciprocated within the range of
A first direction orthogonal to the transport direction and a second direction opposite to the first direction.
An image forming apparatus for swinging alternately in the direction according to the swing speed of the image carrier belt, the predetermined range
An image forming apparatus comprising: a control unit that controls an amount of movement of the support by the moving unit so as to change the image forming apparatus. 7. The image forming apparatus according to claim 1 , further comprising: counting means for counting a time required for the image bearing belt to swing a predetermined distance in a direction orthogonal to the image conveying direction, wherein the control means counts by the counting means. 7. The image forming apparatus according to claim 6 , wherein the amount of movement is controlled according to the time taken. 8. The image forming apparatus, possess a first detecting means and second detecting means for detecting the direction of the opposite end portions perpendicular to the image conveying direction of the image carrier belt, said counting means, The first detecting means is an image bearing bell.
After the detection of the image is completed, the second detecting means
The image forming apparatus according to claim 7 , wherein the time until the detection of the holding belt is started is counted .