JPH06175424A - Image formation device - Google Patents

Abstract

PURPOSE:To automatically adjust pressurizing force between a photosensitive body drum and a roller pressurized against the photosensitive body drum in a copying machine and others. CONSTITUTION:Facing a photosensitive body drum 10, an electric charge roller and a transfer roller are provided, and a drum gear 12 integrated with the drum and a roller gear 22 integrated with the rollers are engaged with each other. Driving force of a motor 50 is transmitted to a drive gear 70 through an intermediate gear. Torque of the drive gear 70 generates a torque in a constant direction in an arm 80, and the rollers are pressurized by the photosensitive body drum 10 by this torque, and a nip is formed. Simultaneously when the motor 50 stops and driving force of the drive gear 70 is lost the torque of the arm 80 is also lost, and the rollers are returned to their initial states by their elasticity restoring force.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a facsimile and a computer.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus of this type includes a photosensitive drum and a pressure roller which is pressure-bonded to the photosensitive drum, and is integrally formed with the photosensitive drum provided on the rotation shaft of the photosensitive drum. The rotating gear and power from a motor, which is a driving unit (hereinafter referred to as a drum gear), are brought into mesh with the drum gear via the driving gear, and the photosensitive drum is driven. In addition, the driving force is transmitted to the roller by meshing the power with a gear that rotates integrally with the pressure roller (hereinafter referred to as a roller gear) and a drum gear.

FIG. 5 shows an example of a conventional drive mechanism disclosed in, for example, Japanese Patent Application Laid-Open No. 2-17376.
The photosensitive drum 10 and the pressure roller 20, which are image bearing members, are arranged so as to rotate in contact with each other. A drum gear 12 that rotates integrally with the photoconductor drum 10 is attached to one end of the photoconductor drum 10.
A roller gear 22 that rotates integrally with the drum 0 is provided and meshes with the drum gear 22. The motor 30, which is a drive source, has an appropriate speed reducer, etc., and drives the drive gear 32. Drive gear 3
Reference numeral 2 meshes with a roller gear 22 to form a pressure roller 20.
And the photosensitive drum 10 is driven.

The photosensitive drum 10 is a rigid drum made of, for example, an aluminum alloy. On the other hand, the pressure roller 20 is made of an elastic material such as urethane foam. A transfer is inserted between the pressure roller 20 and the photosensitive drum 10 and is passed between the roller and the roller while applying an appropriate pressure, and a process such as transfer proceeds. When the pressure roller 20 made of an elastic material is pressed against the photoconductor drum 10, the pressure roller 20 changes its elasticity to form a so-called nip portion. Good quality transfer can be achieved by adjusting the amount and pressure of the nip portion. The tracking rollers 24a and 24b provided on both sides of the pressure roller 20 are made of a rigid material, and when the tracking rollers 24a and 24b come into contact with the photosensitive drum 10, the pressure roller 20 The amount of deformation (nip amount) is adjusted.

In another conventional drive mechanism shown in FIG. 7, the drive gear 32 of the motor 30 drives the drum gear 12 of the photosensitive drum 10, and the rotational force thereof is a pressure roll.
It is transmitted to the roller gear 22 of the la 20. In these conventional devices, the pressure roller 20 is constantly in pressure contact with the photosensitive drum 10 and is in an elastically deformed state. Even when the pressure roller is stopped, it remains elastically deformed and its position is fixed, so that part is flattened, and as a result unevenness in the roller curvature causes deterioration of transferability. Becomes

[0006]

SUMMARY OF THE INVENTION According to the present invention, the roller does not press against the photosensitive drum when the photosensitive drum is stopped in order to improve the above-mentioned conventional drawbacks. Or
By retreating, the quality of the photosensitive drum changes,
Further, it is intended to prevent the deformation of the roller.

[0007]

In the image forming apparatus of the present invention, the drive gear and the roller gear are integrally formed with the arm, and the arm is configured to be rotatable around the axis of the drive gear. When the drive is transmitted to the drive gear, the arm and the roller gear are rotated around the shaft center of the drive gear due to the torque, and the arm and the roller gear are coupled to the drum gear and the driving force of the drive gear is transmitted to the drum gear.

[0008]

The torque generated in the arm by the rotation of the drive gear acts in the direction of pressing the roller against the photosensitive drum to form the nip portion. When the drive gear is stopped, the torque disappears and the nip is not pressed.

[0009]

FIG. 1 is a perspective view showing a first embodiment of the present invention,
FIG. 2 is an explanatory diagram showing the operation of the drive mechanism. Motor 50
The output gear 52 provided on the output shaft of the
Meshes with the first intermediate gear 60 and the second intermediate gear 62
Mesh with. The second intermediate gear 62 drives the gear 70 via the shaft 64. The shaft 64 is rotatably supported by a proper bearing, and one end of the arm 80 is rotatably supported by the bearing 82 with respect to the shaft 64. The drive gear 70 meshes with the pressure gear 22 of the pressure roller 20 and rolls.
The Lagia 22 is driven. The roller gear 22 is rotatably supported by the arm 80 via a bearing 84. The roller gear 22 meshes with the drum gear 12 of the photosensitive drum 10 and drives the photosensitive drum 10.

FIG. 2 shows the rotation direction of each gear, and the drive gear 70 rotates in the direction of arrow R1. In response to this rotational force, the roller gear 22 rotates in the arrow R2 opposite to the rotational direction R1 of the drive gear 70. The drum gear 12 meshing with the roller gear 22 rotates in the same direction as the drive gear 70 in the direction of arrow R3. When the drive gear 70 drives the roller gear 22, the arrow F1 is attached to the arm 80 that supports the roller gear 22.
Torque is applied in the direction indicated by. This force F1 acts as a force for pressing the pressure roller 20 toward the photoconductor drum 10.

Due to this pressing force, the pressure roller 20 made of an elastic material is pressed against the photosensitive drum 10 to form the nip portion 40. The nip amount of the nip portion 40 is adjusted by tracking rollers provided on both sides of the pressure roller 20. Further, by providing the bearing 84 with a torque limiter, the nip amount can be controlled. When the driving of the motor 50 is stopped, the driving of the driving gear 70 to the roller gear 22 is also stopped, and the torque F1 is also lost. The pressure roller 20 is
Due to its elasticity, it returns to a cylindrical shape as shown in FIG.
The nip portion is simply in contact. By this action,
The pressure roller 20 maintains a cylindrical shape at rest and does not impair the accuracy of the shape. In addition, no extra pressure is applied when the photosensitive drum 6 is stopped, and the life is improved.

FIG. 3 shows another embodiment of the present invention. In this embodiment, the drive gear 7 that transmits power from the motor
The axis center of 0 is the axis center of the roller gear 22 and the photoconductor gear 12
Is disposed above the center of the axis. The shaft center of the drive gear 70 and the shaft center of the roller gear 22 are the bearing 1 with respect to the arm 100.
It is rotatably supported via 02 and 104. When power is not transmitted to the drive gear 70, the roller gear 2
The gear 2 is disengaged from the drum gear 12 and is hung by its own weight at the position indicated by the solid line in FIG. By providing the bearing 104 with a torque limiter, when the drive gear 70 rotates in the direction of the solid line R5, the torque F2 causes the arm 100 to rotate and the roller gear 22.
Meshes with the drum gear 12.

In this state, the rotational force of the drive gear 70 is
Rotate the lager 22 in the direction of arrow R6 to
Rotates the drum gear 12 to the arrow R7. Torque F2
As a result, the pressure roller 20 is pressed against the photosensitive drum 10 to form a nip portion. When the motor 50 is turned off and the rotational force of the drive gear 70 is cut off, the torque F2 disappears and the roller gear 22 automatically disengages from the mesh with the drum gear 12 together with the arm 100. As a result, the roller 20 is disengaged from the photoconductor drum 10, and the joining pressure between the two is lost. Therefore, the photosensitive drum 10 and the pressure roller 20 are completely released, and the life is extended.

[0014]

As described above, the present invention provides a mechanism for driving a drum and a roller while pressing a charging roller or a transfer roller against a photosensitive drum to form a nip portion. The drum and the gears provided on the rollers are meshed with each other, and the roller gear side is driven by a drive gear to which power is transmitted from the motor. The axes of the drive gear and the roller gear are supported by a common arm. When the drive gear rotates, a force acts in the direction of pressing the roller against the photosensitive drum. Therefore, the nip pressure is automatically generated while the drive gear is rotating, and the nip pressure is reduced when the motor is stopped. The elastic force of the roller returns to the initial state, and deformation of the outer peripheral surface is prevented. As a result, deterioration of the dimensional accuracy of the cylindrical shape of the roller is prevented, and good image formation is achieved.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

2 is an explanatory view showing the drive mechanism of FIG. 1. FIG.

FIG. 3 is an explanatory view showing another embodiment of the present invention.

FIG. 4 is an explanatory view showing the operation of the present invention.

FIG. 5 is an explanatory view showing the operation of the present invention.

FIG. 6 is an explanatory view showing a conventional drive mechanism.

FIG. 7 is an explanatory view showing another conventional drive mechanism.

[Explanation of symbols]

10 photoconductor drum, 12 drum gear, 20 low
La, 22 Roller gear, 50 motor 70 Drive gear, 80 arm

Claims (4)

[Claims] 1. An image forming apparatus comprising: an image bearing drum for bearing an image; and a roller which is in pressure contact with the image bearing drum and which is constituted by an elastic body; a driving gear; and a roller meshing with the driving gear. It has an integral roller gear, an image carrying drum meshing with the roller gear, an integral drum gear, and an arm for rotatably indicating the shaft of the drive gear and the shaft of the roller gear. An image forming apparatus characterized in that a drive gear is rotated in a direction in which generated torque presses a roller toward an image bearing drum. 2. The image forming apparatus according to claim 1, wherein the roller is configured to be retractable with respect to the image carrier drum. 3. The image forming apparatus according to claim 1, wherein the roller is a charging roller. 4. The image forming apparatus according to claim 1, wherein the roller is a transfer roller.