JP2006003567A - Photoreceptor drive unit and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoreceptor drive unit for suppressing image defect due to vibration of a gear engagement cycle and rotation irregularity by reducing the rotation irregularity due to gear engagement vibration by an inexpensive structure easy to assemble in a photoreceptor drive unit. <P>SOLUTION: In the photoreceptor drive unit capable of being used for an image forming apparatus such as a digital copy machine and a laser printer, two gears 3 and 4 of which modules, the numbers of teeth, pitch circle diameters, pressure angles and torsion angles are equal to each other are on a coax at a position where a tooth bottom of one gear and a tooth edge correspond, and a double gear is used as a gear reduction system having a region in which a diameter of a width being equal to or more than a tooth width of a counterpart engaged between the two gears 3 and 4 is equal to or less than a tooth circle diameter. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photoreceptor driving device that can be used in an image forming apparatus such as a digital copying machine or a laser printer, which can simplify a bearing structure and form a photoreceptor driving system at low cost.

2. Description of the Related Art Conventionally, a drive means for driving a photosensitive member and a drive transmission means for transmitting a driving force of the drive means to the photosensitive member are provided, and a damping member is provided between the two helical gears whose torsion directions are opposite to each other. There is known a photosensitive member driving device in which at least one pair of gear pairs each having a sandwiched gear body is provided, or the teeth of two helical gears of the gear body are shifted from each other by a half pitch phase (for example, Patent Documents). 1).
FIG. 10 is a schematic sectional view showing an example of a conventional photosensitive member driving device. In FIG. 10, a photosensitive drum 21 is supported on a frame body 20 by a shaft 21a in order to reduce uneven rotation due to gear meshing vibration with an inexpensive configuration.
From a gear body 33 having a structure in which a damping member 32 is sandwiched between two helical gears 30 and 31 whose torsion directions are opposite to each other, to a drive transmission means 24 for transmitting the driving force of the photosensitive body drive motor 23 to the photosensitive drum 21. At least one gear pair is provided.
Using the helical gears 30 and 31 reduces the meshing vibration by increasing the meshing rate, and cancels the thrust force caused by the meshing of the helical gears by combining the two helical gears 30 and 31 whose torsion directions are opposite to each other. Accordingly, the vibration in the thrust direction is reduced, and the damping member 32 sandwiched between the two helical gears 30 and 31 is also used to reduce the vibration caused by the molding error and assembly error between the helical gears 30 and 31. Yes.
Japanese Patent Laid-Open No. 10-161477

The vibration of the gear meshing frequency and the rotation unevenness cause image defects. By using the two gears shifted by a half pitch and overlapping on the same axis, the high frequency side shift of the vibration frequency and the reduction of the rotation unevenness amplitude can be achieved.
However, in the prior art method, it is difficult to move the gear in the axial direction when the gear is attached / detached, so that the bearing mechanism and the like become complicated, resulting in a problem of cost increase.
FIG. 10 shows an example in which two helical gears 30 and 31 having different twist directions are aligned in the coaxial direction. However, when these gears 30 and 31 are attached and detached, these gears 30 and 31 are shown. Since the movement of the shaft in the axial direction is regulated by the mutual gears 30 and 31, a complicated mechanism such as changing the distance between the shafts becomes necessary, and an inexpensive drive device can be obtained if the bearing structure is included. Becomes difficult.
The object of the present invention is to reduce the rotation unevenness due to gear meshing vibration and to reduce the image defect due to the gear meshing cycle vibration and rotation unevenness in the photosensitive member driving device in consideration of the above-mentioned situation by an easy and inexpensive structure. It is an object of the present invention to provide a photoconductor driving device that suppresses the above.

In order to solve the above problems, the invention according to claim 1 is a reduction gear system comprising a double gear in which two gears having the same module, the number of teeth, the pitch circle diameter, the pressure angle, and the torsion angle are coaxially stacked. In which the tooth bottom of one gear and the tooth tip of the other gear are in a positional relationship corresponding to the circumferential direction, and the opposite surfaces of the two gears are respectively provided with A spacer having a diameter equal to or smaller than the diameter is provided, and the total width of each spacer is equal to or greater than the tooth width of the mating gear with which the two gears mesh.
According to a second aspect of the present invention, in the first aspect, all the specifications of the two gears are equal.
A third aspect of the present invention is characterized in that, in the first or second aspect, the two gears have a structure that can be molded by the same mold.
According to a fourth aspect of the present invention, in the first, second, or third aspect, when the outer shape of the two gears is not a perfect circle but has a periodic shape error, the circumference is equal to a half period of the periodic shape error. It is characterized in that it is used by overlapping the direction position.
According to a fifth aspect of the present invention, in the first, second, third, or fourth aspect, the circumferential positional relationship between the two gears is such that the positions of a plurality of gates provided on one gear side face are on the other gear side face. It is assembled so that it may be located between the provided gates.
The invention of claim 6 is characterized in that, in claim 1, 2, 3, or 5, the positional relationship between the two gears is assembled such that one gear and the other gear are shifted by approximately 90 degrees. And The invention of claim 7 is the gear shaft hole diameter of claim 1, 2, 3, 5 or 6, when the opening diameters of the two axial ends of the gear shaft holes of the two gears are different. It is characterized in that two gears are assembled so that the large side faces each other.
According to an eighth aspect of the present invention, in the first to seventh aspects, the opposing surfaces of the spacers of the respective gears are provided with concave and convex portions at the same place, and the concave and convex portions are coaxially connected to one of the gears. The other gear is attached in a positional relationship shifted by a half pitch.
A ninth aspect of the invention is characterized in that the photoreceptor driving device according to any one of the first to eighth aspects is provided.

According to the present invention, the backlash of the gear is reduced to reduce the rotation unevenness of the gear meshing cycle, and the image defect phenomenon is reduced by shifting the meshing frequency, and the gear can be attached and detached in the axial direction. It is possible to realize a photosensitive member driving apparatus that can be used in an image forming apparatus such as a digital copying machine or a laser printer that can form a photosensitive member driving system at a low cost by simplifying the bearing structure.
Further, by forming double gears having shapes each having a width S that is equal to or greater than the width of each tooth of the mating gears on the side surfaces of the two gears, the frequency is shifted on the high frequency side and the rotation unevenness. Image defects can be reduced by reducing the amplitude, and gears can be attached and detached only by movement in the axial direction and rotational direction, and a low-cost drive system can be realized.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing a first embodiment of a photoreceptor driving device according to the present invention in a state before assembly. As shown in FIG. 1, in the first embodiment, two gears 3, 4 connected to the shaft 2 of the photosensitive drum 1 are provided.
Between these gears 3 and 4, there is a space (a portion having no teeth) S larger than the tooth widths of the counterpart gears 7 and 8. That is, the total width S of the spacers 3 a and 4 a provided on the opposing surfaces of the gears 3 and 4 is set to be larger than the tooth width of the mating gears 7 and 8. For this reason, it is possible to slide the gears 3 and 4 in the axial direction when mounting.
That is, the present invention is a photoreceptor driving device that uses a double gear in which two gears 3 and 4 having the same module, number of teeth, pitch circle diameter, pressure angle, and twist angle are coaxially stacked as a reduction system. The tooth bottom of one gear and the tooth tip of the other gear are in a positional relationship corresponding to the circumferential direction (a positional relationship shifted by a half pitch), and the diameters of the root circles are on the opposing surfaces of the two gears, respectively. The spacers 3a and 4a have the following diameters, and the total width S of each spacer is equal to or greater than the individual tooth widths of the mating gears 7 and 8 with which the two gears mesh.
FIG. 2 is a schematic view showing the first embodiment of the photosensitive member driving device according to the present invention in a state of an intermediate stage of assembly. As shown in FIG. 2, when the first gear 3 is slid to the space between the pinion gears 7 and 8 of the shaft 6 of the motor 5, the gear 3 is rotated by a half pitch.
That is, the counterpart gears 7 and 8 are fixed to the shaft 6 with the circumferential positions shifted so that the positions of the gears are shifted by a half pitch. On the other hand, the two gears 3 and 4 are similarly assembled in a state shifted by a half pitch. When assembling a double gear, which is a combination of two gears 3 and 4, from the state of FIG. 1 to the state of FIG. 2, after the gear 3 passes through the gear 8, the gear 3 and the gear 7, and the gear 4 and the gear In order to mesh the gears 8 at the same time, if the double gears are moved in the axial direction as they are, the gears cannot be meshed with each other because they are shifted by a half pitch. The double gear is rotated by a half pitch while the gear 8 is positioned in the space S. As a result, the gear 3 and the gear 7 and the gear 4 and the gear 8 can be meshed simultaneously.

FIG. 3 is a schematic view showing a state in which the first embodiment of the photosensitive member driving device according to the present invention is assembled. As shown in FIG. 2, by rotating the gear 3 by a half pitch, it is possible to assemble the second gear 4 including the second gear 4 as shown in FIG.
FIG. 4 is a schematic view showing a combination of gears 3 and 4. FIG. 5 is a schematic view showing a state in which the gears 3 and 4 of FIG. 4 are combined. For example, a combination of the gears 3 and 4 in the first embodiment described above. The gears 3G of one gear 3 are assembled at different positions in the circumferential direction so that the tooth tips of the gear 4G of the other gear 4 are located at the tooth bottom of the gear 3G.
FIG. 6 is a schematic view showing an embodiment in the case of assembling so that the circumferential positions of a plurality of gates provided on the side surfaces of two gears do not overlap. FIG. 7 is a schematic view showing a state in which the two gears of FIG. 6 are assembled.
In many cases, tooth gaps of the gears 3 and 4 and roundness errors occur corresponding to the positions of the gates. However, as in this embodiment, the gate position of one gear is the same as the gate of the other gear. By assembling so as to be between the gates, it is possible to reduce the influence (rotational unevenness) of the gear shape error corresponding to the gate position.
FIG. 8 is a schematic view showing an embodiment of a concavo-convex shape for assembling two gears shifted by a half pitch. FIG. 9 is a schematic view showing a state in which the two gears of FIG. 8 are assembled.
As shown in the figure, the concave and convex portions 9 and 10 that can be fitted on the side surfaces of the disc-like spacers 3a and 4a to be the spacer portions are provided in a predetermined arrangement along a predetermined circumferential track. When the gears 3 and 4 that are shaped products are assembled while being concavo-convexly fitted, the teeth of the two gears 3 and 4 can be assembled in a positional relationship that is shifted by a half pitch.
As a result, the image defects can be reduced by shifting the frequency on the high frequency side and reducing the rotation unevenness amplitude, and the gears can be attached and detached only by movement in the axial direction and the rotational direction, thereby realizing a low-cost drive system.

In the photosensitive member driving device of the present invention, two gears having the same specifications are coaxially positioned so that the tooth bottom of one gear and the tooth tip of the other gear correspond to each other. A double gear having a region (joint of two spacers 3a and 4a) having a diameter equal to or larger than the tooth width of the gear of the other gear meshing with the other gear is used as a speed reduction system.
Therefore, it is possible to reduce image defects by shifting the meshing frequency on the high frequency side and reducing the rotation unevenness amplitude, and the gears can be attached and detached only by movement in the axial direction and the rotational direction, thereby realizing a low-cost drive system.
In addition, since two gears having the same specifications are used, rotation unevenness caused by a shape error can be canceled by appropriately combining gears processed in the same lot and having similar shape characteristics.
In the photoconductor driving device of the present invention, the gears used in an overlapping manner are formed by using the same mold and are shifted by a half pitch, so that the image frequency is reduced by shifting the meshing frequency on the high frequency side and reducing the rotation unevenness amplitude. The gears can be attached and detached only by movement in the axial direction and the rotational direction, and a low-cost drive system can be realized.
In the photosensitive member driving device of the present invention, the rotational unevenness caused by the periodic shape error of the gears can be canceled because the photoconductor driving devices of the present invention are overlapped and used in a positional relationship shifted by a half cycle of the periodic shape error of each gear. it can. In other words, when there is an error of one cycle during one rotation, the gears 3 and 4 having the same shape are assembled by shifting the circumferential position 180 degrees so that the two errors cancel each other.

In the photoconductor driving device of the present invention, the positional relationship of the overlapping gears is assembled so that the position of one gate is the position between the other gates, so that it is caused by the shape error of the gear corresponding to the position of the gate. Uneven rotation can be canceled.
In the photoreceptor driving device of the present invention, the positional relationship of the gears used in an overlapping manner is such that one gear and the other gear are shifted by approximately 90 degrees and are shifted by a half pitch. Uneven rotation due to the elliptical component shape error of the gear can be reduced. That is, when each gear 3, 4 is not a perfect circle but has an eccentricity close to, for example, an elliptical shape (when there is a shape error of two cycles in one rotation), the positions of the two error portions are The circumferential positions of both gears 3 and 4 are shifted and assembled so as to be shifted by 90 degrees. Of course, the pitch of each gear is shifted by a half pitch.
Therefore, it is possible to reduce image defects by reducing the high frequency side shift of the meshing frequency, the meshing cycle, and the rotation unevenness amplitude of the secondary component, and the gears can be attached and detached only by the movement in the axial direction and the rotational direction. The drive system can be realized.
In the photosensitive member driving device of the present invention, the positional relationship between the gears used in an overlapping manner is the positional relationship between one gear and the other gear, and the positional relationship in which the larger gear shaft hole diameter side faces. In addition, since they are assembled with a half-pitch shift, the diameters of both ends of the gear shaft hole tend to be small during the assembly, and it is possible to prevent the gears from being assembled in a tilted state. In other words, when the diameters of both axial openings of the shaft holes of the two gears 3 and 4 having the same shape are different, mounting with the large opening side being matched causes the rattling when the shaft is inserted. Is prevented. That is, since the outer opening of the shaft hole of the double gear has a small diameter, it can be in close contact with the shaft, and rattling is eliminated.
In the photoreceptor driving device of the present invention, the spacer portion of each gear has irregularities, and by fitting the irregularities, the other gear that is coaxial with one gear is assembled in a positional relationship shifted by a half pitch. Therefore, it is possible to easily position and fix the two gears with a positional relationship shifted by a half pitch.

1 is a schematic view showing a first embodiment of a photoreceptor driving device according to the present invention in a state before assembly. FIG. BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows 1st Embodiment of the photoconductor drive device by this invention in the state of an assembly | attachment intermediate process. 1 is a schematic view showing a state in which a first embodiment of a photoreceptor driving device according to the present invention is assembled. FIG. Schematic which shows the combination with a gear simple substance. Schematic which shows the state with which the gearwheel of FIG. 4 was combined. Schematic which shows embodiment in the case of assembling so that the gate position of two gears may not overlap. Schematic which shows the state which assembled | attached the two gearwheels of FIG. Schematic which shows embodiment of uneven | corrugated shape for assembling | attaching two gears shifted by half pitch. Schematic which shows the state which assembled | attached the two gearwheels of FIG. FIG. 6 is a schematic cross-sectional view showing an example of a conventional photoconductor driving device.

Explanation of symbols

  1 Photosensitive drum, 2 Photosensitive drum shaft, 3 Gear, 4 Gear, 5 Motor, 9 Convex part, 10 Concave part

Claims (9)

  A photosensitive member driving apparatus using a double gear in which two gears having the same module, the number of teeth, the pitch circle diameter, the pressure angle, and the torsion angle are coaxially overlapped as a reduction system. The tooth tips of the gears are in a positional relationship shifted by a half pitch corresponding to the circumferential direction, and the opposing surfaces of the two gears each have a spacer having a diameter equal to or less than the diameter of the root circle, The photosensitive member driving device is characterized in that the total width of the photosensitive member has a width equal to or greater than the tooth width of the mating gear with which the two gears mesh.   2. The photosensitive member driving device according to claim 1, wherein all the specifications of the two gears are equal.   3. The photosensitive member driving device according to claim 1, wherein the two gears have a structure that can be molded with the same mold. 4.   When the outer shape of the two gears is not a perfect circle but has a periodic shape error, the circumferential positions are shifted and overlapped by a half period of the periodic shape error. The photoreceptor driving device according to 1, 2, or 3.   The circumferential positional relationship between the two gears is assembled such that a plurality of gates provided on one gear side face are located between gates provided on the other gear side face. Item 5. The photoreceptor driving device according to Item 1, 2, 3, or 4.   6. The photosensitive member drive according to claim 1, wherein the two gears are assembled such that one gear and the other gear are shifted by approximately 90 degrees. apparatus.   2. The two gears are assembled such that when the opening diameters of both end portions in the axial direction of the gear shaft holes of the two gears are different, the larger gear shaft hole diameter faces each other. The photoreceptor driving device according to 2, 3, 5 or 6.   The opposing surfaces of the spacers of each gear are provided with a concavo-convex portion at the same location, and by fitting the concavo-convex portions, the other gear coaxial with one gear is shifted by a half pitch. 8. The photosensitive member driving device according to claim 1, wherein the photosensitive member driving device is assembled. An image forming apparatus comprising the photosensitive member driving device according to claim 1.

Images