JP2002258672A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus which deals with time changes by the wear of a roller or the like, and stably rotates a photoreceptor by a comparatively simple mechanism. SOLUTION: The image forming apparatus is provided with a photoreceptor 1, an electrifying roller 2 which uniformly charges the surface of the photoreceptor 1, an exposure device which irradiates the photoreceptor 1 with light to form an electrostatic latent image, a developing device 5 which develops an electrostatic latent image on the basis of gray scale information on image data, and a transfer roll 8 which transfers the electrostatic latent image of the photoreceptor 1 on transfer paper. The image forming apparatus has further a driving motor 23 which rotationally drives the rotary shaft of the photoreceptor 1, and a deceleration device which transmits driving force from the driving motor 23 to the rotary shaft of the photoreceptor 1. A driving mechanism different from gear driving is provided at the rotary shaft of the driving motor 23 which turns the photoreceptor 1, and the photoreceptor 1 is rotationally driven by gear driving and the driving mechanism different from the gear driving.

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 such as a copying machine, a printer, and a facsimile, and more particularly, to an image forming apparatus having a driving device for uniformly rotating a photosensitive member.

[0002]

2. Description of the Related Art In an image forming apparatus using a photoreceptor, rotation fluctuation of the photoreceptor affects writing and transfer of a latent image, resulting in uneven density of an output image. There is known a means for increasing a moment of inertia by attaching a flywheel to a rotating shaft and reducing uneven rotation of a photosensitive member.

However, the conventional flywheel mounted on the rotating shaft of the photoconductor responds to fluctuations in the rotation of gears and pulleys of the photoconductor drive system and fluctuations in the load on the photoconductor due to the transfer paper entering the developing unit and the transfer unit. Therefore, a large moment of inertia is required. Since the moment of inertia is proportional to the square of the radius, it is necessary to increase the outer diameter of the flywheel in order to increase the moment of inertia, and increasing the outer diameter of the flywheel increases the size of the apparatus.
Also, by attaching a heavy flywheel, it is necessary to increase the steel properties of the shaft and the device, and there is also a problem in maintainability.

[0004]

As another method, there is known a means for reducing the uneven rotation of the photosensitive member by bringing a brake material into contact with the surface of the photosensitive member or a gear on a rotating shaft or the like. Japanese Patent Application Laid-Open No. 75065 proposes a method in which a rotational load material is brought into contact with an outer peripheral surface of a photosensitive drum, and Japanese Patent Application Laid-Open No. H11-7205 proposes a method in which a rotational load material is brought into contact with an outer peripheral surface of an intermediate transfer member or a photosensitive member shaft. . However, in this case, the contact surface between the roller and the photosensitive drum has a problem in rotation stability due to abrasion of the roller, pressure adjustment at the time of mounting, and pressure fluctuation due to aging of the brake material.

Accordingly, the present invention aims at eliminating the above-mentioned problem with a relatively simple mechanism, and provides an image forming apparatus capable of coping with a change over time due to abrasion of a roller and stably rotating a photosensitive member. Is what you do. In addition, even when the speed of the photosensitive member fluctuates, the drive shaft and the photosensitive member shaft are connected and driven by the belt, thereby eliminating the problem that the drive transmission becomes unstable due to the backlash of the gear drive. The present invention provides an image forming apparatus having improved image quality.

[0006]

Means for Solving the Problems In order to eliminate the above problem, the invention according to claim 1 comprises a photosensitive member, a charger for uniformly charging the surface of the photosensitive member, and irradiating the photosensitive member with light. An exposure device that forms an electrostatic latent image on the basis of image data, a developing device that develops the electrostatic latent image based on the gradation information of the image data, and a transfer device that transfers the electrostatic latent image of the photoconductor to transfer paper. ,
In an image forming apparatus having a motor that rotationally drives a rotating shaft of a photosensitive drum and a speed reducer that transmits a driving force from the motor to the rotating shaft of the photosensitive member, a gear is driven by a rotating shaft of a motor that rotates the photosensitive member. A separate drive mechanism is provided,
An image forming apparatus in which a photoreceptor is rotationally driven by a gear drive and a drive mechanism different from the gear drive. According to a second aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein the driving mechanism different from the gear driving directly drives the rotating shaft of the photoconductor from the rotating shaft of the motor. According to a third aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein the drive mechanism different from the gear drive is a belt drive without teeth. According to a fourth aspect of the present invention, there is provided the image forming apparatus according to any one of the first to third aspects, wherein a reduction ratio of the rotation axis of the photosensitive member by the gear drive mechanism and a drive mechanism different from the gear drive is different. .

According to a fifth aspect of the present invention, there is provided the image forming apparatus according to any one of the first to fourth aspects, wherein the rotation speed of the photosensitive member by the gear drive mechanism is faster than that of a drive mechanism different from the gear drive. I do. According to a sixth aspect of the present invention, in the belt according to any one of the first to fourth aspects, a tension roller is provided on a belt that is a drive mechanism of the photoconductor by a drive mechanism different from the gear drive mechanism. An image forming apparatus is used. The invention according to claim 7 is the image forming apparatus according to claim 6, wherein the tension roller is pressed against the belt by a spring. The invention according to claim 8 is
The image forming apparatus according to any one of claims 1 to 6, wherein a rotation speed of the motor for driving the photoconductor is controlled by a rotation speed detecting unit provided on the photoconductor or the photoconductor shaft.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. As shown in FIG. 1, a drum-shaped photoconductor 1 is fixed to a rotating shaft 2 via a support member described later, and rotates in an arrow (clockwise) direction.
A charging roller (charging device) 3 comes into contact with the periphery of the photoconductor drum 1, and the surface of the photoconductor 1 is uniformly charged to a predetermined polarity. A laser beam 4 from an exposed portion (not shown)
The image exposure is performed by the writing scan, and a predetermined electrostatic latent image is formed on the surface of the photoconductor 1. The electrostatic latent image thus formed is visualized as a toner image by the toner conveyed by the developing roller 6 rotating in the direction of the arrow (counterclockwise) in the developing device 5. The toner image formed on the surface of the photoconductor 1 is sent from the registration roller 7 between the photoconductor 1 and a transfer roller (transfer device) 8 and is transferred to a transfer paper 9. The toner image transferred to the transfer paper 9 is the paper guide plate 1
2, the toner image is guided and conveyed to the fixing device 13, and the toner image transferred onto the transfer paper 8 by the fixing device 13 is fixed. On the other hand, after the transfer of the toner image, the toner and fine paper powder remaining on the surface of the photoconductor 1 are neutralized by the fur brush 11 of the cleaning device 10, and the photoconductor 1 is rotated by the contact rotation of the fur brush 11. Removed from When the surface of the photoconductor is neutralized after the cleaning process, the static elimination means (not shown) is used.

FIG. 2 is a schematic cross-sectional view showing a conventional photoreceptor driving section, showing a photoreceptor and a supporting structure thereof. As shown in FIG. 2, the photoreceptor 1 is integrated with the rotating shaft 2 by engaging a pin 14, and the rotating shaft 2 is a bearing 16 fixed to a right side plate 15.
And a bearing 18 fixed to the left side plate 17 so as to be rotatable. A driven gear 19 is fixed to the rotation shaft 2 on the right side of the rotation shaft 2 of the right side plate 15 by engaging a pin 20.
A bearing 21 for supporting the rotating shaft 2 is fixed to a motor mounting plate 22, and a driving motor 23 for driving the photoconductor 1, for example, a DC brushless motor is fixed to the motor mounting plate 22. An integrated gear 23a is fixed to the output shaft of the drive motor 23. The gear 23a rotationally drives an idle gear 25a rotatably inserted into a stud 24 fixed to a motor mounting plate 22. An idle gear 25b having a smaller diameter than the idle gear 25a is integrated with the idle gear 25a. The idle gear 25b meshes with a driven gear 19 fixed to the rotating shaft 2 of the photoconductor 1, and the idle gear 25b The photoconductor 1 is driven to rotate. Photoconductor 1
A flywheel 26 is fixed to an end of the rotating shaft 2 on the drive mechanism side in order to reduce the rotation fluctuation of the rotating shaft 2 by inertia force.

FIG. 3 shows a photosensitive member driving section of the present invention,
FIG. 2 is an enlarged schematic cross-sectional view illustrating a photoconductor and a support structure thereof. FIG. 4 is a right side view of FIG. The bearing 27 rotatably supports a rotating shaft 28 in which the photosensitive member 1 is engaged with the pin 14,
A driven gear 30a and a belt pulley 30b, which are integrated on the right side of the right side plate 29 to which the bearing 27 is fixed, are fixed to the rotating shaft 28 by engaging a pin 31. A bearing 32 for supporting the rotating shaft 28 is fixed to a motor mounting plate 33, and a driving motor 34 for driving the photoconductor 1, for example, a DC brushless motor is fixed to the motor mounting plate 33. An integrated gear 34a is fixed to the output shaft of the drive motor 34, and the gear 34a is a stud 35 fixed to the right side plate 29.
The idle gear 36, which is rotatably inserted into the motor, is driven to rotate. The idle gear 36 is formed by integrating an idle gear 36a meshing with a gear 34a of a drive motor 34 and an idle gear 36b having a smaller diameter than the idle gear 36a. The idle gear 36b is a driven gear The photoreceptor 1 is rotated by the rotation of the driven gear 30a. On the other hand, a belt 37 is wound around a belt pulley 30b fixed to the rotation shaft 34b of the drive motor 34 and the rotation shaft 28 of the photoconductor 1, and a tension is applied between the drive motor 34 and the belt pulley 30b. A roller 38 is provided. The tension roller 38 is rotatably inserted into a roller shaft 40 of a roller bracket 39, and the roller bracket 42 is rotatably inserted into a bracket shaft 41. The roller bracket 39 is provided with a spring 39 for urging the belt 37 with a constant pressing force. Although the present embodiment describes a compression coil spring as the pressing force of the tension roller 38, a tension coil spring or a torsion coil spring may be used. A pulse encoder 43 for detecting the rotation speed of the photoconductor 1 and controlling the rotation speed of the drive motor 34 is attached to an end of the rotation shaft 28.

FIG. 5 is a block diagram showing the configuration of the feedback drive control device. The drive control device 44 is mainly executed by the microcomputer, and the output of the pulse encoder 43 for detecting the rotation speed is output from the drive control device 4.
The rotation speed of the photoconductor 1 is calculated by the rotation speed calculation unit 45. The rotation speed of the drive motor 34 is calculated from the difference between the target rotation speed and the rotation speed of the photoconductor 1 by the arithmetic control unit 46 based on the calculated rotation speed. The motor drive unit 47 drives the drive motor 34 at the calculated rotation speed.

FIG. 6 is a schematic sectional view showing a photoconductor driving unit according to another embodiment of the present invention, in which a photoconductor and a supporting structure thereof are enlarged. FIG. 7 is a right side view of FIG.
A driven gear 51a and a belt pulley 51b are integrated on the right side of the right side plate 50 on which the bearing 49 of the rotary shaft 48 fixing the photoreceptor 1 is fixed.
Fixed to. A bearing 53 that supports the rotating shaft 48 is held by the auxiliary plate 54 and holds the rotating shaft 48. A drive motor 55 for driving the photoconductor 1, for example, a DC brushless motor, is fixed to the right side plate 50. An integrated gear 55a and a pulley 55b are fixed to the output shaft of the drive motor 55, and the gear 55a is a stud 5 fixed to the auxiliary plate 54.
6 to rotate the idle gear 57 rotatably inserted therein. The idle gear 57 meshes with a driven gear 51 a fixed to the rotating shaft 48 of the photoconductor 1, and
When 5 rotates in the arrow (counterclockwise) direction, the driven gear 51a also rotates in the arrow (counterclockwise) direction, and the photoconductor 1 also rotates in the arrow (counterclockwise) direction. On the other hand, a belt driving pulley 55b is fixed to the rotating shaft of the driving motor 55, and a belt driven pulley 51b is fixed to the rotating shaft 44.
A belt 58 is wound around the belt driven pulley 51b. A tension roller 59 is disposed between the belt driving pulley 55b and the belt 58 wound around the belt driven pulley 51b, and is in contact with the belt 58. The tension roller 59 is rotatably inserted into a roller shaft 61 of a roller bracket 60, and the roller bracket 60 is rotatably inserted into a bracket shaft 62. The roller bracket 60 is provided with a spring 63 for urging the belt 58 with a constant pressing force. A pulse encoder 64 for detecting the rotation speed of the photoconductor 1 and controlling the rotation speed of the drive motor 55 is attached to the end of the rotation shaft 48.

As described above, the driving gear 34a and the driven gear 3
0a or separately from the driving of the driving gear 55a and the driven gear 51a, the belt 37 or 5 is attached to the rotating shaft 34b and the belt pulley 30b or the belt driving pulley 55b and the belt driven pulley 51b.
8, the photoreceptor 1 is driven so that the degree of freedom between gear teeth (backlash) is eliminated, and the belt drive rotates with a load generated in a direction opposite to the gear drive. The non-transmission of backlash caused by the load fluctuation and the motor driving speed change can be eliminated. As a result, the rotation speed of the motor can be reliably transmitted to the driven gear of the photosensitive member shaft, and the feedback control of the photosensitive member by the drive motor is executed faithfully.

[0014]

As described above, in the image forming apparatus according to the first aspect, in driving transmission to the photosensitive member, the speed of the photosensitive member is driven by a driving method different from the gear driving and the gear driving. Non-transmission (rattle) of backlash due to gear driving when fluctuation occurs can be eliminated, and the driving force of the driving motor can be smoothly transmitted to the photosensitive member shaft. In the image forming apparatus according to the second aspect, since a photoreceptor shaft coaxial with the gear drive is directly driven from the drive shaft by a drive mechanism different from the gear drive, the structure is simple and the assembly is simple. And the size of the device can be reduced. In the image forming apparatus according to the third aspect of the present invention, a speed difference between the gear drive and the belt drive is reduced by using a belt-less belt drive such as a flat belt or a round belt as a drive mechanism different from the gear drive. Therefore, meshing due to a difference in drive mechanism can be prevented. In the image forming apparatus according to the fourth aspect, since the reduction gear ratio between the gear drive and the belt drive is different, the gear on the driving side and the gear on the driven side are always in contact with each other. Rotation transmission corresponding to the speed of the drive motor can be performed.

In the image forming apparatus according to the fifth aspect, since the speed of the photosensitive member driven by the belt is made lower than that of the gear, the gear teeth always come into contact with each other in the driving side rotation direction.
Even when a load fluctuation occurs on the photoreceptor shaft, the rotation transmission drive following the drive speed of the motor can be performed. In the image forming apparatus according to the sixth aspect, the belt that directly drives the photosensitive member is provided with tension by the tension roller, so that stable drive transmission without speed fluctuation due to tension can be performed. In the image forming apparatus according to the seventh aspect, by pressing the tension roller against the belt with a constant pressure, the slip between the belt roller and the belt, which occurs due to the speed difference from the gear driving, can be kept constant. In the image forming apparatus according to the present invention, since the motor makes it possible to control the motor speed with high accuracy corresponding to the rotational speed fluctuation of the photoconductor by the contact between the driving gear and the driven gear by the belt, it is possible to eliminate the rotation unevenness of the photoconductor. .

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment of the invention.

FIG. 2 is a schematic cross-sectional view of a conventional photoconductor driving unit, showing a photoconductor and a support structure thereof.

FIG. 3 is a schematic cross-sectional view showing, in an enlarged manner, a photoconductor driving unit of the present invention, which shows a photoconductor and a supporting structure thereof.

FIG. 4 is a right side view of FIG.

FIG. 5 is a block diagram illustrating a configuration of a feedback drive control device.

FIG. 6 is a schematic cross-sectional view illustrating a photoconductor driving unit according to another embodiment of the present invention, in which a photoconductor and a support structure thereof are enlarged.

FIG. 7 is a right side view of FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor 2 rotating shaft 3 charging roller 4 laser beam 5 developing device 6 developing roller 7 registration roller 8 transfer roller 9 transfer paper 10 cleaning device 11 fur brush 12 paper guide plate 13 fixing device 14 pin 15 right plate 16 bearing 17 left plate REFERENCE SIGNS LIST 18 bearing 19 driven gear 20 pin 21 bearing 22 motor mounting plate 23 drive motor 23a gear 24 stud 25 idle gear 25a idle gear 25b idle gear 26 flywheel 27 bearing 28 rotating shaft 29 right side plate 30a driven gear 30b belt pulley 31 pin 32 bearing 33 Motor Mounting Plate 34 Drive Motor 34a Gear 35 Stud 36 Idle Gear 36a Idle Gear 36b Idle Gear 37 Belt 38 Tension Roller 39 Roller Bracket 40 Roller Shaft 41B Ket shaft 42 Roller bracket 43 Pulse encoder 44 Drive controller 45 Rotation speed calculator 46 Calculation controller 47 Motor drive unit 48 Rotation shaft 49 Bearing 50 Right side plate 51a Follower gear 51b Belt pulley 52 Pin 53 Bearing 54 Auxiliary plate 55 Drive motor 55a Gear 55b Pulley 56 Stud 57 Idle gear 58 Belt 59 Tension roller 60 Roller bracket 61 Roller shaft 62 Bracket shaft 63 Spring 64 Pulse encoder

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/00 550 G03G 15/00 550

Claims (8)

[Claims] A photoreceptor; a charger for uniformly charging the photoreceptor surface; an exposure device for irradiating the photoreceptor with light to form an electrostatic latent image; A developing device that develops an electrostatic latent image on the transfer roller by using a developing device that transfers the electrostatic latent image of the photoconductor onto transfer paper; and a drive motor that rotationally drives a rotating shaft of the photoconductor. An image forming apparatus comprising: a speed reducer that transmits a driving force to a rotating shaft of the image forming apparatus; a driving mechanism different from the gear driving is provided on a rotating shaft of a motor that rotates the photoconductor, and the gear driving is different from the gear driving. An image forming apparatus characterized in that a photoreceptor is rotationally driven by the driving mechanism. 2. The image forming apparatus according to claim 1, wherein a drive mechanism different from the gear drive directly drives the rotation axis of the photoconductor from the rotation axis of the motor. 3. The image forming apparatus according to claim 1, wherein the driving mechanism other than the gear driving is a beltless belt driving. 4. The image forming apparatus according to claim 1, wherein a reduction ratio of the rotation axis of the photosensitive member by the gear drive mechanism and a drive mechanism different from the gear drive is different. 5. The image forming apparatus according to claim 1, wherein the rotation speed of the photoconductor by the gear driving mechanism is faster than that of a driving mechanism different from the gear driving. 6. A belt, which is a drive mechanism of a photosensitive member by a drive mechanism different from a gear drive mechanism, is provided with a tension roller.
The image forming apparatus according to any one of the above. 7. The image forming apparatus according to claim 6, wherein the tension roller is pressed against the belt by a spring. 8. A motor for driving a photoreceptor, the rotational speed of which is controlled by a rotational speed detecting means provided on the photoreceptor or the photoreceptor shaft. An image forming apparatus according to any one of the above.