JPH04269768A - Drum driving device for image forming device - Google Patents

Abstract

PURPOSE:To eliminate deformation of a formed image by controlling unevenness in rotation due to tooth contact of gears and rotating the drum without unevenness. CONSTITUTION:A driving gear 4 is attached to a rotational shaft of a driving motor 2. A fixing gear 5 constituting a reduction gear in cooperation with the driving gear 4 is attached to the drum 1, and a mobile gear 6 is coaxially attached relatively rotatable against the fixing gear 5. Then, this mobile gear 6 is elastically energized by a spring 11 in the direction rotating the drum 1 in a forward direction. That is, the direction of the elastic energization is reversed to that of the conventionally used scissors gear, rotational drive is first received by the mobile gear 6 by the driving gear 4, and rotational force is transmitted to a fixed gear 5 elastically supported against the mobile gear 4 through the spring 11.

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 that forms an image on a photosensitive drum or on photosensitive paper held by the drum, and more specifically, the present invention relates to an image forming apparatus that forms an image on a photosensitive drum or on photosensitive paper held by the drum. The present invention relates to a drum drive device for rotationally driving.

0002

2. Description of the Related Art Conventional image forming apparatuses have a structure in which a photoreceptor drum or a drum holding photosensitive paper is rotated, and a laser beam that is main-scanned in the axial direction is applied to the drum using a known structure such as a polygon mirror for exposure. It is being Therefore, the rotational speed unevenness of the drum greatly affects the quality of the image formed by exposure. Therefore, a driving force transmission mechanism with less backlash and the like is required.

Conventionally, as this driving force transmission mechanism, a structure using scissor gears as shown in FIGS. 3 and 4 is known.

FIG. 3 shows the configuration near the drive gear.
A deceleration drive gear 4 is rotatably fixed to a drive shaft 3 of a drive motor 2 that drives the drum 1 so as to be integral with the drive shaft 3. On the other hand, a fixed gear 5 is fixed to the drum 1 so as to be able to rotate integrally with the drum 1 and abut the driving gear 4. Furthermore, a movable gear 6 is rotatably supported by the fixed gear 5. The fixed gear 5 and the movable gear 6 are each provided with openings 7 and 8 at two locations.

FIG. 4 is a side view of the three reduction gears 4, 5, and 6. A hook 9 is fixed to each of the two openings 7 provided in the fixed gear 5 on the front side in the rotational direction, and a hook 9 is fixed to each of the two openings 8 provided on the movable gear 6 on the rear side in the rotational direction. 10 is fixed. A spring 11 is stretched between the hooks 9 and 10, and controls the movement of the movable gear 6.

The teeth of the movable gear 6 are connected to the fixed gear 5 by the spring 11 from the rear side in the direction of rotation.
It is pressed forward in the direction of rotation by the teeth of.

Next, the operation of the conventional example will be explained. The drum drive motor 2 rotates, and the drive gear 4 also rotates in the direction of the arrow in the figure by the drive shaft 3. One tooth of the driving gear 4 collides with one tooth of the corresponding fixed gear 5, pushes the one tooth of the fixed gear 5, and rotates the fixed gear 5 in the direction of the arrow in the figure.
Accordingly, the next tooth of the drive gear 4 is set to the fixed gear 5.
The fixed gear 5 collides again with the next tooth of the fixed gear 5 and pushes the next tooth of the fixed gear 5, causing the fixed gear 5 to further rotate in the direction of the arrow in the figure. This is repeated to rotate the fixed gear 5. As a result, the drum 1 also rotates in the direction of the arrow in the figure together with the fixed gear 5.

At this time, vibrations are generated every time the teeth of the drive gear 4 collide with the teeth of the fixed gear 5. However, since the teeth of the drive gear 4 are pressed against the teeth of the fixed gear 5 from behind by the teeth of the movable gear 6, the amplitude of the vibrations due to this collision is reduced.

[0009]

However, although scissor gears have a great effect on backlash, they do not have a sufficient effect on damping vibrations. The vibrations here are generated between the drive gear and the fixed gear, so the vibrations are transmitted to the drum via the fixed gear, causing uneven rotation, which causes uneven exposure, etc., and the formed image. The problem was that it had a negative impact.

[0010] Furthermore, there is another problem in that the vibrations are transmitted to an image forming apparatus, such as a laser scanner, and cause a deflection of the scanning beam light.

The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to prevent the vibrations generated by the tooth contact of the reduction gear for driving the rotation of the drum from being transmitted to the drum. Accordingly, it is an object of the present invention to provide a drum drive device that can prevent deterioration of image quality such as exposure unevenness.

0012

[Means for Solving the Problems] In order to achieve this object, the drum drive device of the image forming apparatus of the present invention rotates the drum whose rotation angle corresponds to the sub-scanning position by a drive source via a gear train. In the drum drive device, the gear train includes a first gear, a second gear meshing with the first gear,
a third gear that meshes with the second gear, is coaxial with the first gear, and is rotatable relative to the first gear;
urging means for rotationally urging the third gear relative to the second gear, and the rotational force from the drive source is directed in a direction that resists the urging force of the urging means. Features.

[0013]

[Operation] In the drum drive device of the present invention configured as described above, for example, if the first gear is on the drum side and the second gear is on the drive source side, the third gear is configured to rotate the drum in the image forming direction. Since the second gear is attached in a direction that pushes the third gear when the second gear rotates, the second gear generates vibration between the teeth and the third gear. while rotating the third gear.

As described above, the third gear rotates while generating vibrations as in the conventional case, but since the first gear is connected to the third gear via the biasing means, the first gear is connected to the third gear. It is possible to rotate at an instantaneous peripheral speed different from the instantaneous peripheral speed of .

[0015] Therefore, the vibrations are not transmitted because the inertia force caused by the mass of the first gear and the drum rotates at a constant speed. In other words, the rotation of the drum remains constant without being affected by the vibrations.

Conversely, the same thing can be done if the first gear is placed on the drive source side and the second gear is placed on the drum side.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment embodying the present invention will be described below with reference to the drawings. In the description, parts similar to those of the conventional example shown in FIGS. 3 and 4 are given the same reference numerals, and the description thereof will be omitted.

FIG. 1 shows the configuration near the drive gear.
FIG. 2 is a side view of the three reduction gears 4, 5, and 6.

Similar to the conventional example, a fixed gear 5 is provided on the drum 1 in contact with a driving gear 4, and a movable gear 6 is rotatably supported on the fixed gear 5. The fixed gear 5 and the movable gear 6 are each provided with openings 7 and 8 at two locations.

Two openings 7 provided in the fixed gear 5
A hook 101 is fixed to the rear side in the rotation direction, respectively, and a hook 102 is fixed to each of the two openings 8 provided in the movable gear 6 on the front side in the rotation direction. A spring 11 is stretched between the hooks 101 and 102,
It controls the movement of the movable gear 6.

The teeth of the movable gear 6 press the teeth of the drive gear 4 from the front side in the rotational direction, and the teeth of the fixed gear 5 from the rear side in the rotational direction by the spring 11. That is, in this embodiment, the movable gear 6 is one of the reduction gears,
is rotatably attached to the drum-side fixed gear by a spring, and is provided so as to sandwich the teeth of a motor-side drive gear fixed to the drive motor between the teeth of the drum-side fixed gear; Further, the movable gear is attached in a direction such that the motor-side drive gear pushes the movable gear when the drum rotates in the image forming direction.

Next, the operation of this embodiment will be explained. The drum drive motor 2 rotates, and the drive gear 4 also rotates in the direction of the arrow in the figure by the drive shaft 3. One tooth of the drive gear 4 collides with one tooth of the corresponding movable gear 6, pushes the one tooth of the movable gear 6, and rotates the movable gear 6 in the direction of the arrow in the figure.
Accordingly, the next tooth of the drive gear 4 is set to the movable gear 6.
The movable gear 6 collides again with the next tooth of the movable gear 6, and pushes the next tooth of the movable gear 6, causing the movable gear 6 to further rotate in the direction of the arrow in the figure. This is repeated to rotate the movable gear 6.

The movable gear 6 is connected to the fixed gear 5 by a spring 11, and therefore the fixed gear 5 also rotates at the same rotation speed as the movable gear 6, rotating the drum 1 in the direction of the arrow in the figure. .

At this time, each time the teeth of the drive gear 4 collide with the teeth of the movable gear 6, vibrations, that is, vibrations between the teeth are generated. Since the teeth of the drive gear 4 are pressed against the teeth of the fixed gear 5 from the front side by the teeth of the movable gear 6, the amplitude of this vibration per tooth is suppressed to a minimum, but the amplitude Even if the vibration is kept small, vibration actually occurs. However, the generated vibration is generated between the drive gear 4 and the movable gear 6, and the frequency of the vibration due to tooth contact is as high as several tens to hundreds of Hz, so the vibration is caused by the fixed gear 5.
It is absorbed by the spring 11 connecting the movable gear 6 and the movable gear 6, and is not transmitted to the fixed gear. Therefore, the drum 1 is rotated at the same number of rotations as the movable gear 6 without being affected by vibrations on the teeth.

[0025] The same can be done when the first gear is placed on the drive source side. That is, a drive gear (first gear) is provided on the drive shaft of the drive motor, and a movable gear (third gear) is coaxially attached to this drive gear. However, this movable gear is rotatable relative to the shaft of the drive motor. The movable gear is biased by a spring (biasing means) in the same direction as the direction of rotation by the drive motor. A fixed gear (second gear) is provided that engages with both the drive gear and the movable gear and interlocks with the drum. If this is done, the driving force will be transmitted via the spring as in the above embodiment, and unnecessary vibrations will be absorbed by the spring.

Further, in this embodiment, a spring is used as the biasing means, but the effect as a damper may be enhanced by using rubber that easily absorbs the impact of contact with the teeth.

The drum drive device described in detail above is an image forming device in which the drum itself is photosensitive and which forms a toner image by electrostatic electricity on the drum and then transfers it to recording paper, or an image forming device in which recording paper having photosensitive characteristics is wound around the drum. It can be applied to an image forming apparatus, etc., which forms a toner image by static electricity on the recording paper. Further, as a means for forming an electrostatic latent image, it can be applied to a laser exposure device using a polygon mirror or the like, or a device using an optical fiber array. Furthermore, it can also be applied to devices using multi-stylus heads or the like.

[0028]

[Effect of the invention] As is clear from the detailed description above,
In the present invention, the drum can be rotated at a desired rotation speed without the vibration generated by the gear being transmitted to the drum, thereby preventing deterioration of image quality due to uneven exposure, etc. It is possible to provide a drum drive device that obtains.

[0029] Furthermore, the configuration is simply that the biasing direction of the auxiliary gear in the scissor gear is reversed, so that the number of parts and the assembly process are not increased.

[0030] Also, it has the same effect as a scissor gear on backlash.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing the configuration around a drive gear.

FIG. 2 is a side view of the reduction gear.

FIG. 3 is a configuration diagram showing the configuration around a drive gear in a conventional device.

FIG. 4 is a side view of a reduction gear in a conventional device.

[Explanation of symbols]

1 Drum 2 Drive motor 4 Drive gear 5 Fixed gear 6 Movable gear 11 Spring

Claims (1)

[Claims] 1. A drum drive device in which a drive source rotates a drum whose rotation angle corresponds to a sub-scanning position through a gear train, wherein the gear train includes a first gear and a first gear that meshes with the first gear. a second gear, a third gear that meshes with the second gear, is coaxial with the first gear, and is rotatable relative to the first gear; 1. A drum drive device for an image forming apparatus, comprising a biasing means for relatively rotationally biasing, and a rotational force from the drive source is applied in a direction that resists the biasing force of the biasing means.