JPH07157129A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device which is small in size, low in cost, and excellent in durability and prevents the meandering of a transfer belt surely. CONSTITUTION:In an image processing device which is provided with an endless feeding belt 1 to feed loaded sheets in a feeding direction, the feeding belt is installed tensely by a drive roller 3 and a driven roller 2 movable in tensed direction, and brake pads 4a to 4c to give a braking force in contact with the outer circumferential surface of the driven roller are installed at both ends of the driven roller in axial direction. Also at least each one of meandering detection sensors 5a and 5b to detect the meandering of each feeding belt are positioned near the driven roller or at both ends of the feeding belt in lateral direction. The brake pads can be pressed alternatively by pressing cams 6a to 6c connected symmetrically with each other. A selective drive means which drives by selecting a pressing cam corresponding to one or the other of the brake pad drives the pressing cams selectively based on the detected results of the meandering detection sensor. Thus the meandering can be prevented by adjusting the tension of the feeding belt.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an image forming apparatus such as a transfer sheet for an electrophotographic copying machine, a facsimile, a printer, a printing machine or the like, and more particularly to a conveyor belt for placing a sheet and conveying it in a conveying direction. The present invention relates to an image forming apparatus having the same.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine, a facsimile machine, a printer, a printing machine or the like, a transfer is endlessly run between rollers, and a regulation is made in contact with an end edge of a conveyor belt to prevent the belt from being offset A device in which belt meandering is prevented by a member is known (Shokai 57-724).
42, Japanese Utility Model Laid-Open No. 64-36863, etc.). Further, in electrophotographic copying machines, facsimiles, printers, printing machines, etc., the tensile strength at both edges outside the image area of the transfer / transport belt may be made stronger than that at the central portion, or the thickness at both edges may be increased. A configuration for preventing meandering by forming a step is also known (JP-A-2-103).
89).

However, in these conventional examples, since members made of different materials are stuck or adhered to both edges of the transfer / conveying belt, the manufacturing cost is high, and the difference in expansion / contraction ratio between the members due to temperature rise is high. As a result, there has been a problem that the transfer / conveyor belt meanders due to slack, twisting, and uneven strength due to the quality of the adhesive state. Further, the regulation member is constantly rubbed with the belt, and in the transfer / transport belt having a stepped shape in which the thickness of both ends is increased, it is constantly rubbed with the stepped part side surface of the transport roller that stretches the transfer / transport belt. Was causing the.

[0004]

An image forming apparatus having a conveyor belt for placing a sheet and conveying the sheet in the conveying direction is expensive in manufacturing cost, causes uneven conveyance of the conveyor belt, and prevents the conveyor belt from meandering. There was a problem that the ability to do was insufficient.

[0005]

SUMMARY OF THE INVENTION Therefore, the present invention is intended to solve such a problem. That is, it is an object of the present invention to provide an image forming apparatus that is small in size, excellent in durability, and reliably prevents the meandering of a conveyor belt.

[0006]

In order to achieve the above object, the present invention is an image forming apparatus having an endless conveyor belt for conveying a placed sheet in a conveying direction, wherein the conveyor belt is a drive roller. And a driven roller that is movable in the stretching direction, and a brake pad that applies a braking force to the outer peripheral surface of the driven roller is provided at both ends of the driven roller in the axial direction. At least one meandering detection sensor for detecting the meandering of the conveyor belt is disposed at both ends of the conveyor belt in the width direction, and the brake pads are connected to each other by pressing cams which are connected in a target shape. Selective drive means configured to be alternately pressable and for selecting and driving the pressing cam corresponding to one or the other of the brake pads is detected by the meandering detection sensor. A cleaning pad that slides in contact with the driven roller to adjust the tension of the conveyor belt to prevent meandering by selecting and driving the pressing cam based on the result is arranged so as to apply tension to the conveyor belt. The brake pads are arranged on both sides of the cleaning pad in the axial direction.
The brake pad is pressed against the surface of the conveyor belt wound around the peripheral surface of the driven roller.

[0007]

In the image forming apparatus constructed as described above, when the conveyance belt to be conveyed is deviated (meandering) in the width direction, it is detected and the conveyance belt is placed between the drive roller and the driving roller. Since the tension of the conveyor belt is adjusted by selecting either of the plurality of brake pads that apply the braking force provided at both ends of the driven roller that is stretched and conveyed,
It is possible to provide an image forming apparatus that is small in size, excellent in durability, and reliably prevents the meandering of the conveyor belt.

[0008]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a plan view showing a main configuration of an image forming apparatus to which the present invention is applied, FIG. 2 is a front view of FIG. 1, and FIG.
FIG. 1 to 3, in, for example, a color image forming apparatus having an endless conveyor belt 1 such as a transfer paper conveyor belt, a plurality of photosensitive drums 9 are provided for each color. In this embodiment, Four black photosensitive drums 9a, yellow photosensitive drums 9b, magenta photosensitive drums 9c, and cyan photosensitive drums 9d are arranged in parallel in this order. The conveyor belt 1 is arranged immediately below each drum along the transfer position of each drum, and a transfer sheet (not shown) placed on the belt is conveyed from the right side to the left side in the direction of arrow A, and the above-mentioned photosensitive sheets are interposed therebetween. Body drums 9a-9d
The toner image for each color formed individually on the transfer sheet is transferred onto the transfer sheet by discharge of a transfer charger (not shown) located below the transport belt 1 on which the transfer sheet is placed.

The conveyor belt 1 is stretched between a driven roller 2 and a driving roller 3 which can move forward and backward in the stretching direction (left and right direction in FIG. 2) and is driven by the driving roller 3. The tension of the conveyor belt 1 is given by applying a pressing force to the driven roller 2 in the arrow B direction by the arm member 8a holding the cleaning pad 8 and the tension coil spring 8b shown in FIGS. . Therefore, the bearing portion of the shaft 2a of the driven roller 2 has an elongated hole shape as shown in the drawing.

As shown in the drawing, on the driven roller 2 side, the front meandering detection sensor 5a and the back meandering detection sensor 5a are provided as the meandering detection sensors 5 provided at the positions facing the widthwise both ends of the conveyor belt 1, respectively. The meandering of the conveyor belt 1 is detected by 5b. That is, when the conveyor belt 1 is conveyed in the direction of arrow A and approaches the front side in the figure, the front meandering detection sensor 5a of the meandering detection sensor 5 is changed from ON to OFF. Each of the front meandering detection sensor 5a and the back meandering detection sensor 5b is composed of, for example, a photo interrupter, and has a structure in which a light emitting element and a light receiving element are arranged to face each other with a belt edge being sandwiched therebetween. Here, the width direction refers to a direction orthogonal to the belt conveying direction.

When either the meandering detection sensor 5a or the back meandering detection sensor 5b is turned from ON to OFF, the motor 7a as the selection driving means 7 rotates to rotate the worm 7b and the worm wheel 7c. Brake pads 4 (front brake pad 4a, rear brake) that are alternately pressed against the peripheral surface of the driven roller 2 to provide braking force at both ends of the driven roller 2 in the axial direction and on both sides of the cleaning pad 8. Pads 4b) are arranged. Brake pad 4a or the other back brake pad 4
b is selectively pressed by the front pressing cam 6a as the pressing cam 6 driven by the worm 7b and the worm hole 7c or the other back pressing cam 6b. The front pressing cam 6a or the other rear pressing cam 6b is arranged so as to have a symmetrical shape.

The brake pads 4a and 4b are arm members 4c and 4c extending in the vertical direction shown in FIGS. 1 and 2, respectively.
Is held by the upper ends of the tension coil springs 4d, 4
A pressing force is constantly applied in the pressing direction indicated by arrow B by d. This pressing force is set equal to the pressing force of the cleaning pad 8. A shaft 6c for integrally supporting the one front pressing cam 6a and the other rear pressing cam 6b by coupling them is also used as a rotating shaft of the worm wheel 7c, and the shaft 6c is provided with a side plate 10 as shown in FIG. Front side plate 10a
A positioning plate 7d rotatably supported by the rear side plate 10b and fixed to one end of the shaft 6c as shown in the figure is provided corresponding to a sensor (photointerrupter) 7e fixed to the main body.

In the above structure, the conveyor belt 1 is stretched between the driven roller 2 movable in the stretching direction and driven by the driving roller 3 to cause a bias toward the inner side, The back meandering detection sensor 5b is turned off from ON.
In this state, the control unit (not shown) starts the rotation drive of the motor 7a as the selection drive means 7 based on the detection signal. When the motor 7a rotates, one front pressing cam 6a rotates a predetermined angle via the worm 7b and the worm wheel 7c, and the arm portion 4c of the arm member 4c is rotated.
Since c'is pushed down, the front side brake pad 4a of the brake pad 4 can be further pressed against the driven roller 2. In this case, the rotation direction and the rotation amount of the motor for rotating the front pressing cam 6a at the initial position (weak force pressing position) to the strong force pressing position are stored as control information in the memory of the control unit. Therefore, the control unit controls the rotation direction and the rotation amount of the motor according to the control information. Alternatively, the sensor 7e may be configured to detect the pressing position of a strong force for each of the cams 6a and 6b.

When the front brake pad 4a is further pressed, the balance of the force applied to the right side (B direction) of the driven roller 2 is lost, that is, the conveyor belt 1 in FIG.
The tension on the front side becomes stronger, the axial distance from the drive roller 3 becomes longer, and the force to move the conveyor belt 1 to the front side acts, so that the deviation to the back side is surely corrected. . Therefore, the material of the conveyor belt 1 may be the same, and it is cheaper and does not cause slack, and the front brake pad 4a and the other rear brake pad 4b are arranged at both ends of the cleaning pad 8. Therefore, the space can be effectively used, the size can be reduced, and the meandering of the conveyor belt 1 can be reliably corrected or the occurrence of the meandering can be surely prevented.

FIG. 4 is an enlarged view showing the mechanism for pressing the pad. Either the meandering detection sensor 5a (not shown) or the deep meandering detection sensor 5b (not shown) is turned on.
In this state, the control unit rotationally drives the motor 7a as the selection driving unit 7 to select the pressing cam 6a or the other inner pressing cam 6b via the worm 7b, the worm wheel 7c, and the shaft 6c. Driven by the above, the one front brake pad 4a or the other back brake pad 4b that applies a braking force at both ends of the driven roller 2 is operated.

The brake pad 4 is the arm member 4
It is held by the upper end of c and the arm member 4c is rotatably supported about the rotation shaft 4A, so that the pad 4 is constantly pressed in the direction of arrow B by the tension coil spring 4d. This pressing force is equal to the pressing force of the cleaning pad 8 not shown. However, the front brake pad 4
a or the other back brake pad 4b is used for each arm member 4
When c is pressed in the direction of arrow B in the drawing by one of the front pressing cam 6a of the pressing cam 6 or the other rear pressing cam 6b, it is further pressed. The shaft 6c that connects and supports one front pressing cam 6a and the other back pressing cam 6b is rotatably supported by a front side plate 10a (not shown) and a back side plate 10b (not shown) of the side plate 10 (not shown). The sensor 7e fixed to the main body of the image forming apparatus is provided below the positioning plate 7d fixed to the front end of the shaft 6c.

The sensor 7e is provided on the front side pressing cam 6 on one side.
One slit hole 7f and two slit holes 7g provided at 180 ° intervals in the positioning plate 7d corresponding to a and the other back pressing cam 6b are detected. The sensor 7e detects either one slit hole 7f or two slit holes 7g, so that either one of the front pressing cam 6a or the other rear pressing cam 6b pushes down the arm portion 4c 'with a strong force. You can see By using the sensor 7e in this way,
One of the front brake pad 4a and the other rear brake pad 4b can be selected.

FIG. 5, FIG. 6 and FIG. 7 are a plan view, a front view and a right side view showing the essential structure of another embodiment of the present invention. The cleaning pad 8 of this embodiment is the first embodiment. Brake pad 4
However, a characteristic is that the driven roller 2 is sandwiched and pressed against the surface of the position conveying belt 1 opposite to the cleaning pad 8. Brake pad 4 in this case
May be a roller member as shown.

In this case, if the brake pad (or roller member) 4 on the side where the conveyor belt 1 is biased is pressed against the belt surface using the pressing cam 6, the first belt
As in the case of the embodiment, it is possible to correct the meandering of the conveyor belt 1 or to reliably prevent the meandering. Therefore,
Since the conveyor belt 1 does not need to be stretched strongly and the durability is improved, the meandering is surely prevented from occurring for a long period of time, and the one front brake pad (or roller member) is also provided.
4a and the other back brake pad (or roller member) 4b
A cleaning member 1b for cleaning the conveyor belt 1 and the front surface 1a is disposed between and along the axial direction. Therefore, it is possible to provide an image forming apparatus which is further downsized and which surely corrects the meandering of the conveyor belt 1 or surely prevents the meandering.

[0020]

As described above, the present invention detects the deviation in the width direction of the conveyor belt to be conveyed, and detects the deviation, and stretches the conveyor belt between the drive rollers. The tension of the conveyor belt is adjusted by selecting one of the multiple brake pads that provide braking force at both ends of the driven roller that is conveyed, and urging one end of the driven roller in the tension direction. Therefore, it is possible to provide an image forming apparatus that is small in size, inexpensive, excellent in durability, and surely prevents meandering of the conveyor belt.

[Brief description of drawings]

FIG. 1 is a plan view illustrating an outline of a main part of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a front view of FIG.

FIG. 3 is a right side view of FIG.

FIG. 4 is a partially enlarged front view illustrating a main part of the image forming apparatus according to the exemplary embodiment of the present invention.

FIG. 5 is a plan view illustrating an outline of a main part of an image forming apparatus according to another embodiment of the present invention.

6 is a front view of FIG.

7 is a right side view of FIG.

[Explanation of symbols]

1 ... Conveyor belt, 1a ... Surface, 1b ... Cleaning member, 2 ... Followed roller, 2a ... Shaft, 3
... Drive roller, 4 ... Brake pad (roller member), 4a ... Front brake pad (roller member),
4b ... Inner brake pad (roller member), 4c ...
Arm member, 4c '... arm portion, 4d ... tension coil spring, 5 ... meandering detection sensor, 5a ... front meandering detection sensor, 5b ... back meandering detection sensor, 6
... Pressing cam, 6a ... Front pressing cam, 6b ...
Back pressing cam, 6c ... Shaft, 7 ... Selection drive means, 7
a ... motor, 7b ... worm, 7c ... worm wheel, 7d ... positioning plate, 7e ... sensor, 7f ... one slit hole, 7g ... two slits Hole, 8 ... cleaning pad, 8a ... arm member, 8b ... tension coil spring, 9 ... photoconductor drum, 9a ... black photoconductor drum, 9b ...
-Yellow photoconductor drum, 9c ... Magenta photoconductor drum, 9d ... Cyan photoconductor drum, 10 ... Side plate, 10a ... Front side plate, 10b ... Back side plate.

Claims (4)

[Claims] 1. An image forming apparatus having an endless conveyor belt for conveying a placed sheet in a conveying direction, wherein the conveying belt is stretched by a driving roller and a driven roller movable in a stretching direction. Brake pads are provided at both ends of the driven roller in the axial direction so as to contact the outer peripheral surface of the driven roller to apply a braking force. The brake pads are provided at positions near the driven roller and at both ends of the conveyor belt in the width direction. At least one meandering detection sensor for detecting the meandering of the conveyor belt is arranged, and each of the brake pads is configured to be alternately pressable by a pressing cam connected to each other in a symmetrical shape, and to one or the other of the brake pads. The selection drive means for selecting and driving the corresponding pressing cam selects and drives the pressing cam based on the detection result of the meandering detection sensor. An image forming apparatus characterized by adjusting the tension of the above-mentioned conveying belt to prevent meandering. 2. The image forming apparatus according to claim 1, wherein a cleaning pad that is in sliding contact with the driven roller is arranged so as to apply tension to the conveyor belt. 3. The image forming apparatus according to claim 1, wherein the brake pads are arranged on both axial sides of the cleaning pad, respectively. 4. The image forming apparatus according to claim 1, wherein the brake pad is pressed against the surface of the conveyor belt wound around the peripheral surface of the driven roller.