JPH09174975A - Stricture of drive transmission gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the transmission and resonance of vibration and prevent image wise pitch irregularity by molding a transmission gear from a resin and making the wall thickness of a gear bottom part or a rib part non-uniform. SOLUTION: A speed reducing gear consists of the large gear meshed with a motor pinion gear and the small gear meshed with a transmission gear 38. The small gear transmits rotatory power to the driving gear of a driving roller through the transmission gear 38 to rotationally drive the transfer belt of a transfer device. The transmission gear 38 of a driving transmission device is constituted of a cylindrical hub 40, a gear edge circle 41a, a pitch circle 41b, a gear bottom circle 41c and ribs 42. The number of the ribs is six and the ribs 42 are laid out at an equal interval in a peripheral direction. Vibration is generated six times during one rotation of the gear but all of the wall thiknesses A, B, C of the gear bottom parts positioned between the ribs are different and a difference is generated in the intensity of vibration generated by the distortion of the gear bottom parts. By this constitution, the cyclicity of vibration is eliminated and the propagation of cyclical vibration to a photosensitive body is presented and the resonance with other part to prevent the lowering of image quality.

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 printer, a copying machine, a facsimile and a printing machine using an electrophotographic method, and more particularly, charging, optical writing, developing, transferring,
By repeating each process such as fixing, cleaning, and charge removal, an image is formed on the image carrier, and the image is sequentially transferred to a transfer paper.
The present invention relates to an improvement in the structure of a gear that can be applied to an image forming apparatus that fixes and records on transfer paper.

[0002]

2. Description of the Related Art In a conventional image forming apparatus using an electrophotographic system, for example, a printer, a toner image formed on a photoconductor is transferred onto a transfer paper while a transfer belt is in contact with the photoconductor which is an image carrier. There is something to transfer to. For example, FIG.
Shows a drive mechanism in a conventional image forming apparatus,
This drive mechanism rotates the transfer device 2 by the drive transmission device 1 and sequentially transmits the rotational force of the drive motor (not shown) of the drive transmission device 1 from the transmission gear 3 to the drive gear 4 to drive the transfer device 2. A drive roller 5 coaxial with the gear 4 is rotationally driven to drive a transfer belt 7 that is stretched between the drive roller 5 and a driven roller 6. Then, while being in contact with the photoconductor 8, the photoconductor 8 is rotated in the clockwise direction, and the transfer belt 7 of the transfer device 2 is also rotated in the direction of the arrow in the figure. By the way, the drive gear 4 constituting the drive transmission device 1 of this type is manufactured by injection molding or the like using a resin material. FIG. 8 is a diagram showing an example of this type of drive gear. The gear 4 includes a cylindrical hub portion 4a provided at the center and a plurality of radially extending radial portions from the hub portion 4a (see FIG. (6 in FIG. 8) and a gear portion 4 concentric with the hub portion 4a formed by connecting the outer ends of the hub portions 4b in a circular shape.
with c.

[0003]

[Problems to be solved by the invention]

<Purpose corresponding to claim 1> By the way, when molding a gear using a resin material, it is customary to make the wall thickness uniform in order to ensure gear accuracy (prevention of sink marks). As shown in FIG. 8, the gear has a tooth portion and a tooth bottom portion (gear portion) 4 on the outer periphery.
c, a small cylindrical hub portion 4a at the central portion, and a rib portion 4b connecting the outer peripheral portion and the central portion to each other. If this gear meshes with a counterpart gear (not shown), the rib 4
In the outer peripheral tooth portion / bottom portion (gear portion) 4c corresponding to the outer diameter side end portion of b, the rib 4b supports the radial force (force generated in the gear center direction) when transmitting the meshing driving force. However, in the tooth portion / bottom portion 4c corresponding to the portion where the rib does not exist, the tooth portion / bottom portion 4c is bent toward the center by the radial force. Rib 4b
If there are six, the flexure occurs six times for one rotation of the gear 4, and the flexure and the original shape restoration operation of the flexure serve as a vibration source. For example, if the gear 4 is rotating at 200 rpm, vibration of 200 rpm × 6 times ÷ 60 seconds = 20 Hz is generated. In order to reduce the bending, it is effective to make the thickness of the tooth bottom as thick as possible or to increase the number of ribs, but there is a limit to such processing for ensuring the gear accuracy. When vibration occurs due to such bending of the gear, periodic vibration occurs in the electrophotographic image forming system, and uneven pitches at equal intervals occur on the image, which is not preferable. In particular, the periodic vibration from the gear that drives the transfer belt 7 or the like that is in contact with the photoconductor has a great adverse effect on image quality. In the present invention, in order to eliminate such a problem, bending of the tooth bottom portion of the gear without ribs, the cycle of periodic vibration caused by the deformation is randomized, vibration transmission, resonance is eliminated, The purpose is to prevent pitch unevenness on an image.

<Purpose Corresponding to Claim 2> The resin gear generates its own vibration depending on the number of rotations and the number of ribs. For example, when there is a gear that produces a vibration of 20 Hz as in the above calculation, in order to prevent the vibration from being amplified by the resonance of another adjacent gear, the other gear meshing with the gear that produces a vibration of 20 Hz It goes without saying that it is necessary to devise so that the gear vibration of the
It is also highly necessary to prevent resonance from occurring at high frequencies such as Hz and 80 Hz. Further, when gears having periodicity in vibration are in mesh, each gear also shares the vibration of the other gear in mesh, resulting in a gear having two types of vibration. Defect occurs. For example, if one gear is vibrating at 20 Hz and the other gear is vibrating at 27 Hz, two peaks of 20 Hz and 27 Hz are present in the vibration frequency of each gear. The occurrence of such a situation must be strictly prevented in the electrophotographic image forming process, and the present invention intends to prevent such a situation from occurring. That is, it is an object of the invention of claim 1 to prevent the vibration generated in the resin gear from expanding and deteriorating the vibration caused by sharing the vibration of other parts, and the resulting deterioration of the image quality.

[0005]

In order to achieve the above-mentioned object, the invention of claim 1 is a contact type discharge device which rotationally drives the rotational force of a drive motor through a transmission gear while contacting the image carrier. In a drive transmission device for transmitting to an electric appliance, the transmission gear is formed of resin, and the tooth bottom portion or rib portion has a non-uniform wall thickness. According to a second aspect of the present invention, in the drive transmission device for transmitting the rotational force of the drive motor to the contact type discharger which is rotationally driven while being in contact with the image carrier through the transmission gear, the transmission gear is made of resin. Along with
The feature is that the intervals between the plurality of ribs are made non-uniform.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 applies the present invention to 2
FIG. 3 is an overall schematic configuration diagram of an image forming unit of a color printer. Reference numeral 10 in the drawing denotes a drum-shaped photosensitive member as an image bearing member. The photoconductor 10 rotates in the clockwise direction in the drawing, the outer peripheral surface of the photoconductor 10 is uniformly charged by the first charger 11 with the rotation, and the laser light L, for example, is irradiated by the first writer 12 to generate image data. Is written to form an electrostatic latent image, and the first developing device 13
The toner of the color is attached and the electrostatic latent image is visualized to form a black image, for example. Then, the second charger 14
Then, the second writing device 15 performs writing again, and then the second developing device 16 attaches the toner of the second color to form a red image, for example. Then, the charge is removed by the pre-transfer charge remover 17. On the other hand, below the photoconductor 10,
A transfer device 21 as a contact-type discharge device is located, and the transfer paper 20 is fed to the transfer device 21 while the timing is adjusted by a pair of registration rollers 18 and guided by a guide plate 19. Then, the two-color image formed on the photoconductor 10 as described above is transferred to the transfer paper 20 by the transfer device 21.

The transfer device 21 includes a driving roller 22, a driven roller 23, and a transfer belt 24 wound between them.
A bias roller 25 that is in contact with the back surface of the transfer belt 24 in proximity to the surface of the photoconductor 10 and a belt cleaner 26 that cleans the surface of the transfer belt 24.
Then, as the drive roller 22 rotates, the transfer belt 2
4 is rotated counterclockwise in the figure to convey the transfer paper 20, and a bias voltage is applied to the bias roller 25 to transfer the image on the photoconductor 10 to the transfer paper 20. The belt cleaning device 26 cleans the surface of the transfer belt 24 by removing toner and paper powder adhering to the transfer belt 24 with a cleaning blade 27. The transfer paper 20 after the image transfer is
This is conveyed by the transfer belt 24 and sent to a fixing device (not shown), the transferred image is fixed by the fixing device, and the sheet is discharged to a sheet discharging stack portion (not shown). The surface of the photoconductor 10 after transfer is cleaned by removing the residual toner by the photoconductor cleaner 29, and then discharged by the charge remover 30. Then, charging, writing and development are performed again to form an image on the photoconductor 10 and the same process is repeated. By the way, in the illustrated printer,
As the transfer device 21, an image carrier contact type discharge device that rotates while contacting the transfer belt 24 to the photoconductor 10 is used. The transfer device 21 according to the present invention is as shown in FIG. 33 is used to transmit the driving force.

Reference numeral 34 in FIG. 2 is a drive motor, and 35 is a drive motor.
Is a motor pinion gear attached to the drive shaft.
The motor pinion gear 35 includes two reduction gears 36, 3
7 mesh with each other. One reduction gear 36 transmits the driving force to the developing devices 13 and 16 shown in FIG. 1 and a fixing device (not shown). The other reduction gear 37, as shown in FIG.
A large gear 37a that meshes with the tapinion gear 35, and a small gear 37b that meshes with the transmission gear 38 coaxially therewith. The small gear 37b transmits a rotational force to the drive gear 39 coaxial with the above-mentioned drive roller 22 through meshing with the transmission gear 38, and rotationally drives the transfer belt 21 of the transfer device 21. In the invention described in claim 1, the transmission gear 38 of the drive transmission device 33 is configured as shown in the enlarged front view of FIG. That is, reference numeral 40 is a cylindrical hub,
Reference numeral 41a is a tip circle, 41b is a pitch circle, 41c is a root circle, and 42 is a rib. Rib 4 of the gear in FIG.
The number of 2 is 6, and the rib 42 is equally divided in the circumferential direction (60
The gears 38 are
6 times of vibration is generated during one rotation of, but by making all (or at least part of) the wall thicknesses A, B, C of the tooth bottom portions (gear portions) located between the ribs different, The strength of the vibration generated by the flexure becomes strong and weak, and periodic vibration can be prevented from occurring.

FIG. 3 shows only the wall thicknesses A, B and C of the tooth bottom portions at three places located between the ribs, but the wall thicknesses of the remaining three tooth bottom portions may be made thicker or thinner. Of course, if different from the others, the effect of preventing periodic vibration occurrence is enhanced. The gear to which the present invention is applied is not limited to the transmission gear 38, and may be the drive gear 39 or the reduction gear 37. Therefore, in the claims, these gears are collectively referred to as a transmission gear. This also applies to the claims corresponding to the following embodiments.

FIG. 4 and FIG. 5 are a partial structural view and a partial detailed view of another embodiment of the present invention. This gear (transmission gear) 3
8 has the same thickness at the tooth bottom portion between the ribs 42a, 42b, 42c ..., However, the diameter of one rib 42a is configured to be thicker than the other adjacent ribs 42b, 42c. By doing so, a sink mark is generated at a portion of the pitch circle 41b as shown in FIG. In addition to the vibration due to the bending generated at the tooth bottom portion between the ribs, the depression caused by the sink mark a makes it possible to generate vibration of a specific cycle when the gear 38 meshes with another gear. With respect to the other ribs of the gear, if the rib diameter is made thick like the rib 42a, it is possible to apply vibrations of different cycles due to the sink marks, and if the rib diameter is made thin, there is no sink mark and the vibration is reduced. Lost. Therefore, by adjusting the diameters of the plurality of ribs included in one gear to be thicker or thinner, the vibration generated during one rotation of the gear 38 loses its periodicity, and other vibrations occur. Resonance with parts can be prevented. as a result,
When this gear is applied to the drive system of the image forming unit of the image forming apparatus, it is possible to prevent deterioration of image quality due to resonance. This form example may be combined with the form example. That is, by changing the thickness of the root portion between the ribs and the diameter of the ribs at the same time, a more excellent resonance preventing effect can be exhibited.

Next, FIG. 6 shows another embodiment of the present invention.
The characteristic is that the intervals (angles) between the plurality of ribs 42a, 42b, 42c ... Are made non-uniform. Normally, the ribs of a transmission gear made of resin are laid out at equal intervals, but if the thickness of the teeth and roots between the ribs is constant and evenly spaced, there is periodic vibration. Occurs. That is,
At the outer peripheral teeth and bottom corresponding to the outer diameter side end of the rib, the rib can support the radial force (the force generated in the gear center direction) when transmitting the meshing driving force. As described above, in the tooth portion / bottom portion corresponding to the nonexistent portion, the radial portion causes the tooth portion / bottom portion to bend toward the center. When there are six ribs, the transmission gear 38 is bent six times for one rotation, and this bending and the original shape restoring operation of the bending serve as a vibration generation source. When the rib interval is constant and the root thickness between ribs is also constant, the vibrations generated from the roots are the same, so the vibrations obtained are periodic and the image formation It will have an adverse effect. On the other hand, if the ribs are arranged at unequal intervals, the periodicity of vibration disappears, and resonance of vibration with other components can be prevented, as in the case where the thickness of the tooth bottom between ribs is different. It will be possible.

The embodiment shown in FIG. 6 may be combined with the embodiment shown in FIG. 3 or 4. That is, it is possible to make the rib intervals uneven, and at the same time, make various combinations such as varying the thickness of the tooth bottom portion between the ribs or varying the diameter of the ribs, and the effect of preventing resonance with other parts, respectively. Can be demonstrated. Further, when a gear with ribs laid out at equal intervals and a gear with ribs laid out at unequal intervals mesh with each other, transmission of periodic vibrations from the gears with unequal ribs to the gears with unequal ribs may be weakened. understood. It is considered that this is because the periodic vibrations from the equally-spaced gears are attenuated by the bending of the tooth bottom portion between the ribs of the gears that are not equally-spaced.

[0013]

As described above, according to the invention of claim 1,
In a resin gear including a plurality of ribs radially extending from the hub in the outer radial direction and a gear portion that connects the outer diameter side end portions of the ribs in a circular shape, a tooth bottom portion of the gear used for driving force transmission,
Alternatively, since the diameters of the ribs are made non-uniform, it is possible to eliminate the periodicity of vibration caused by the bending of each gear portion (root portion) located between the ribs, and as a result, It is possible to prevent periodic vibration propagation and further prevent resonance with other components, and prevent deterioration in image quality due to vibration. According to the second aspect of the present invention, by making the intervals of the plurality of ribs different from each other, it is possible to prevent the occurrence of periodic vibration, and further to engage another gear (a gear having an even rib interval) with which the gear meshes. ) From the periodic vibration propagation can be canceled.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an image forming unit of an image forming apparatus to which the present invention is applied.

FIG. 2 is a diagram showing a configuration of a main part of FIG.

FIG. 3 is a diagram showing a configuration of a transmission gear according to one embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a transmission gear according to another embodiment of the present invention.

5 is an operation explanatory view of the transmission gear of FIG.

FIG. 6 is a diagram showing a configuration of a transmission gear according to another embodiment of the present invention.

FIG. 7 is an explanatory diagram of an example of a conventional drive transmission device.

8 is a configuration diagram of an example of the drive gear of FIG.

[Explanation of symbols]

10 image carrier (photoreceptor), 11 first charger, 12
First writing device, 13 first developing device, 14 second charging device,
15 second writing device, 16 second developing device, 20 transfer paper,
21 Contact Discharger (Transfer), 22 Drive Roller, 2
3 driven roller, 24 transfer belt, 25 bias roller, 26 belt cleaning device, 29 photoconductor cleaning device, 30 static eliminator, 33 drive transmission device, 34
Drive motor, 35 Motor pinion gear, 36, 37
Reduction gear, 38 transmission gear, 39 drive gear, 40 cylindrical hub, 41a tip circle, 41b pitch circle, 41
c root circle, 42, 42a, 42b, 42c rib,

Claims (2)

[Claims] 1. A drive transmission device for transmitting the rotational force of a drive motor to a contact type discharger which is rotationally driven while being in contact with an image carrier through a transmission gear, wherein the transmission gear is formed of resin. In addition, the structure of the drive transmission gear is characterized in that the tooth bottom portion or rib portion has a non-uniform thickness. 2. In a drive transmission device for transmitting a rotational force of a drive motor to a contact type discharger which is rotationally driven while being in contact with an image carrier through the transmission gear, the transmission gear is made of resin. In addition, the structure of the drive transmission gear is characterized in that the intervals between the plurality of ribs are made uneven.