JP2011197027A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of improving the quality of an image by reducing a rotation transmission error by meshing a gear for driving an image carrier with a rotation transmission gear in the tooth surface center.SOLUTION: The image forming apparatus includes an image carrier 2, an image carrier drive shaft 600, a motor 610 having an output shaft 611 parallel to the image carrier driving shaft 600, the resin-made gear 620 for driving the image carrier fixed to the image carrier drive shaft 600, and the rotation transmission gear 640 that is fixed to an output shaft 611 or an intermediate shaft 630 of the motor 610 and meshes with the gear 620 for driving the image carrier. The image carrier 2 is driven and rotated by the transfer of the rotation of the output shaft 611 of the motor 610 from the rotation transmission gear 640 to the gear 620 for driving the image carrier. In the gear 620 for driving the image carrier, the tooth surface 622 of the gear 620 for driving the image carrier is formed in a crowning shape having a crowning amount of 0.0075±0.0035 mm along the tooth muscle direction so that the rotation transmission error from the rotation transmission torque is 0.8 μm or smaller.

Description

  The present invention relates to an image forming apparatus including an image carrier such as a photosensitive drum and a drive mechanism that drives the image carrier by meshing gears, such as a printer or a copier.

  As an image carrier driving gear for driving an image carrier such as a photosensitive drum, a resin is used to suppress rotation unevenness of the image carrier due to minute vibration generated by the meshing of the gear, and consequently pitch unevenness appearing on the image. It is common to use a large-diameter resin gear formed from

  Then, in order to stabilize the meshing at the central portion of the tooth width between the large-diameter image carrier driving gear and the rotary transmission gear fixed to the output shaft of the motor or the intermediate shaft interlocking with the output shaft, 2. Description of the Related Art There is known a body driving gear whose tooth surface is formed in a crowning shape along the tooth trace direction (see, for example, Patent Documents 1 and 2).

JP 2004-258353 A JP 2005-292634 A

  However, the image carrier driving shaft connected to the image carrier and the output shaft or intermediate shaft of the motor can maintain axial parallelism due to the accumulation of the assembly error of the image carrier and the deflection of the output shaft of the motor. There may be no (does not come out). When the axial parallelism cannot be maintained, the gears mesh with each other in an inclined state and hit each other at the end of the tooth surface. As a result, a rotation transmission error is likely to occur, and jitter (image signal swaying within a minute range) occurs in the image, which tends to cause deterioration in image quality.

  Even if the axial parallelism cannot be maintained, the present invention can reduce the rotation transmission error by meshing the image carrier driving gear and the rotation transmission gear at the center of the tooth surface, thereby improving the image quality. It is an object of the present invention to provide an image forming apparatus that can be used.

  The present invention includes an image carrier, an image carrier drive shaft connected to the image carrier, a motor having an output shaft parallel to the image carrier drive shaft, and a resin. An image carrier driving gear fixed to a shaft, and a rotation transmission gear fixed to an output shaft of the motor or an intermediate shaft interlocking with the output shaft, and meshing with the image carrier driving gear, The image carrier is configured such that rotation of the output shaft of the motor is transmitted from the rotation transmission gear to the image carrier driving gear to rotate the image carrier, and the image carrier driving gear transmits rotation. The tooth surface of the image carrier driving gear is formed in a crowning shape having a crowning amount of 0.0075 ± 0.0035 mm along the tooth trace direction so that the maximum rotation transmission error with respect to torque is 0.8 μm or less. Related image forming apparatus To do.

  The crowning amount is preferably 0.0075 ± 0.0025 mm.

  The rotation transmission torque is preferably set to 5 kgf · cm or less.

  The image carrier driving gear is preferably formed by injection compression molding.

  Moreover, it is preferable that the said rotation transmission gear consists of a metal gear formed from the metal material.

  According to the present invention, even if the axial parallelism cannot be maintained, the image carrier driving gear and the rotation transmission gear are engaged with each other at the center of the tooth surface to reduce the rotation transmission error and improve the image quality. It is possible to provide an image forming apparatus capable of performing the above.

FIG. 2 is a diagram for explaining an arrangement of each component of a printer 1 as an image forming apparatus in the present embodiment. FIG. 2 is a longitudinal sectional view illustrating a schematic configuration of a rotation driving unit of a photosensitive drum 2 in the printer 1 of the present embodiment. FIG. 2 is a perspective view illustrating a configuration of a main part of a rotation driving unit of a photosensitive drum 2 in the printer 1 of the present embodiment. FIG. 3 is a perspective view illustrating a main part of a rotation driving unit of a photosensitive drum 2 in the printer 1 of the present embodiment. FIG. 3 is an enlarged perspective view illustrating a photosensitive drum driving gear that is a main element of a rotation driving unit of the photosensitive drum 2 in the printer 1 of the present embodiment. FIG. 5 is an enlarged perspective view illustrating an initial shape of a tooth portion of a photosensitive drum driving gear 620 in the printer 1 of the present embodiment. FIG. 6 is an enlarged perspective view illustrating a final shape of a tooth portion of a photosensitive drum driving gear 620 in the printer 1 of the present embodiment. FIG. 6 is an enlarged plan view for explaining a final shape of a tooth portion of a photosensitive drum driving gear 620 in the printer 1 of the present embodiment. It is a graph which shows the experimental result of the comparative example 1 in case axial parallelism is 0 degree. It is a graph which shows the experimental result of Example 1 in case an axial parallelism is 0 degree. It is a graph which shows the experimental result of Example 2 in case axial parallelism is 0 degree. It is a graph which shows the experimental result of the comparative example 2 in case axial parallelism is 0 degree. It is a graph which shows the result of the comparative example 3 in case an axial parallelism is 0 degree. It is a graph which shows the experimental result of the comparative example 1 in case axial parallelism is 0.1 degree. It is a graph which shows the experimental result of Example 1 in case an axial parallelism is 0.1 degree. It is a graph which shows the experimental result of Example 2 in case an axial parallelism is 0.1 degree. It is a graph which shows the experimental result of the comparative example 2 in case axial parallelism is 0.1 degree. It is a graph which shows the experimental result of the comparative example 3 in case axial parallelism is 0.1 degree.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
With reference to FIG. 1, the overall structure of a printer 1 as an image forming apparatus in the present embodiment will be described. FIG. 1 is a diagram for explaining the arrangement of each component of the printer 1.

As shown in FIG. 1, a printer 1 as an image forming apparatus includes an apparatus main body M and an image forming unit GK that forms a predetermined toner image on a sheet T as a sheet-like transfer material based on predetermined image information. And a paper supply / discharge unit KH that supplies the paper T to the image forming unit GK and discharges the paper T on which the toner image is formed.
The outer shape of the apparatus main body M is configured by a case body BD as a casing.

  As shown in FIG. 1, the image forming unit GK includes a photosensitive drum 2 as an image carrier (photosensitive member), a charging unit 10, a laser scanner unit 4 as an exposure unit, a developing device 16, and a toner cartridge. 5, a toner supply unit 6, a drum cleaning unit 11, a static eliminator 12, a transfer roller 8, and a fixing unit 9.

  As shown in FIG. 1, the paper feed / discharge unit KH includes a paper feed cassette 52, a manual paper feed unit 64, a transport path L for paper T, a registration roller pair 80, and a paper discharge unit 50.

Hereinafter, each configuration of the image forming unit GK and the paper supply / discharge unit KH will be described in detail.
First, the image forming unit GK will be described.
In the image forming unit GK, in order from the upstream side to the downstream side along the surface of the photosensitive drum 2, charging by the charging unit 10, exposure by the laser scanner unit 4, development by the developing device 16, transfer by the transfer roller 8. Then, static elimination by the static eliminator 12 and cleaning by the drum cleaning unit 11 are performed.

The photosensitive drum 2 is made of a cylindrical member and functions as a photosensitive member or an image carrier. The photosensitive drum 2 is disposed so as to be rotatable in the direction of an arrow about an axis extending in a direction orthogonal to the conveyance direction of the paper T in the conveyance path L. An electrostatic latent image can be formed on the surface of the photosensitive drum 2.
The configuration of the rotational drive unit of the photosensitive drum 2 will be described in detail later.

  The charging unit 10 is disposed to face the surface of the photosensitive drum 2. The charging unit 10 uniformly charges the surface of the photosensitive drum 2 to be negative (minus polarity) or positive (plus polarity).

  The laser scanner unit 4 functions as an exposure unit, and is disposed away from the surface of the photosensitive drum 2. The laser scanner unit 4 includes a laser light source (not shown), a polygon mirror, a polygon mirror driving motor, and the like.

  The laser scanner unit 4 scans and exposes the surface of the photosensitive drum 2 based on image information input from an external device such as a PC (personal computer). By scanning exposure with the laser scanner unit 4, the charge on the exposed portion of the surface of the photosensitive drum 2 is removed. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 2.

  The developing device 16 is provided corresponding to the photosensitive drum 2 and is disposed to face the surface of the photosensitive drum 2. The developing device 16 attaches a single color (usually black) toner to the electrostatic latent image formed on the photoconductive drum 2 to form a single color toner image on the surface of the photoconductive drum 2. The developing device 16 includes a developing roller 17 disposed opposite to the surface of the photosensitive drum 2, a stirring roller 18 for stirring the toner, and the like.

  The toner cartridge 5 is provided corresponding to the developing device 16 and stores toner supplied to the developing device 16.

  The toner supply unit 6 is provided corresponding to the toner cartridge 5 and the developing device 16, and supplies the toner contained in the toner cartridge 5 to the developing device 16. The toner supply unit 6 and the developing device 16 are connected by a toner supply path (not shown).

  The transfer roller 8 transfers the toner image developed on the surface of the photosensitive drum 2 to the paper T. A transfer bias for transferring the toner image formed on the photosensitive drum 2 to the paper T is applied to the transfer roller 8 by a transfer bias applying unit (not shown). The transfer roller 8 is configured to be rotatable while being in contact with the photosensitive drum 2.

  A sheet T conveyed on the conveyance path L is sandwiched between the photosensitive drum 2 and the transfer roller 8. The sandwiched paper T is pressed against the surface of the photosensitive drum 2. A transfer nip N is formed between the photosensitive drum 2 and the transfer roller 8. In the transfer nip N, the toner image developed on the photosensitive drum 2 is transferred onto the paper T.

  The static eliminator 12 is disposed to face the surface of the photosensitive drum 2. The static eliminator 12 irradiates the surface of the photosensitive drum 2 with light, thereby neutralizing the surface of the photosensitive drum 2 after the transfer is performed (removing the electric charge).

  The drum cleaning unit 11 is disposed to face the surface of the photosensitive drum 2. The drum cleaning unit 11 removes toner and deposits remaining on the surface of the photosensitive drum 2, and transports the removed toner and the like to a predetermined recovery mechanism for recovery.

  The fixing unit 9 melts and presses the toner constituting the toner image transferred to the paper T and fixes the toner on the paper T. The fixing unit 9 includes a heating rotator 9a heated by a heater and a pressure rotator 9b pressed against the heating rotator 9a. The heating rotator 9a and the pressure rotator 9b sandwich and pressurize the paper T on which the toner image has been transferred, and convey the paper T. By transporting the paper T while being sandwiched between the heating rotator 9a and the pressure rotator 9b, the toner transferred onto the paper T is melted and pressurized, and is fixed to the paper T.

Next, the paper supply / discharge unit KH will be described.
As shown in FIG. 1, in the lower part of the apparatus main body M, a single paper feed cassette 52 that stores paper T is disposed. The paper feed cassette 52 is configured to be drawable in the horizontal direction from the right side (the right side in FIG. 1) of the apparatus main body M. In the paper feed cassette 52, a placement plate 60 on which the paper T is placed is disposed. In the paper feed cassette 52, the paper T is stored in a state of being stacked on the placement plate 60. The paper T placed on the placement plate 60 is sent out to the transport path L by the cassette paper feed unit 51 arranged at the paper feed side end of the paper feed cassette 52 (the right end in FIG. 1). The cassette paper feed unit 51 includes a forward feed roller 61 for taking out the paper T on the placement plate 60 and a paper feed roller pair 63 for feeding the paper T one by one to the transport path L. Is provided.

  On the right side (right side in FIG. 1) of the apparatus main body M, a manual paper feed unit 64 is provided. The manual paper feed unit 64 is provided mainly for supplying the apparatus main body M with a paper T of a size and type different from the paper T set in the paper feed cassette 52. The manual paper feed unit 64 includes a manual feed tray 65 that forms a part of the front surface of the apparatus main body M in the closed state, and a paper feed roller 66. The lower end of the manual feed tray 65 is attached to the vicinity of the paper feed roller 66 so as to be rotatable (openable and closable). The paper T is placed on the open manual feed tray 65. The paper feed roller 66 feeds the paper T placed on the open manual feed tray 65 to the manual feed path La.

  A paper discharge unit 50 is provided on the upper side of the apparatus main body M. The paper discharge unit 50 discharges the paper T to the outside of the apparatus main body M by the third roller pair 53. Details of the paper discharge unit 50 will be described later.

  The conveyance path L for conveying the paper T is a first conveyance path L1 from the cassette paper feeding unit 51 to the transfer nip N, a second conveyance path L2 from the transfer nip N to the fixing unit 9, and a discharge from the fixing unit 9. A third conveyance path L3 to the section 50, a manual conveyance path La that joins the paper supplied from the manual sheet feeding unit 64 to the first conveyance path L1, and a third conveyance path L3 from the downstream side to the upstream side. And a return transport path Lb that reverses the front and back and returns the sheet to the first transport path L1.

Moreover, the 1st junction part P1 and the 2nd junction part P2 are provided in the middle of the 1st conveyance path L1. A first branch portion Q1 is provided in the middle of the third transport path L3.
The first joining part P1 is a joining part where the manual feed path La joins the first transport path L1. The second junction P2 is a junction where the return conveyance path Lb merges with the first conveyance path L1.
The first branch portion Q1 is a branch portion where the return transport path Lb branches from the third transport path L3, and includes a first roller pair 54a and a second roller pair 54b. One roller of the first roller pair 54a and one roller of the second roller pair 54b are combined.

  In the middle of the first transport path L1 (specifically, between the second junction P2 and the transfer roller 8), a sensor for detecting the paper T, correction of skew (oblique paper feeding) of the paper T, and image A registration roller pair 80 is arranged to match the timing of toner image formation in the forming unit GK. The sensor is disposed immediately before the registration roller pair 80 in the transport direction of the paper T (upstream in the transport direction). The registration roller pair 80 conveys the paper T by performing the above-described correction and timing adjustment based on detection signal information from the sensor.

The return conveyance path Lb is a conveyance path that is provided so that the opposite surface (unprinted surface) to the surface that has already been printed faces the photosensitive drum 2 when performing duplex printing on the paper T.
According to the return conveyance path Lb, the sheet T conveyed from the first branching section Q1 to the paper discharge section 50 side by the first roller pair 54a is reversed and returned to the first conveyance path L1 by the second roller pair 54b. , And can be conveyed to the upstream side of the registration roller pair 80 disposed on the upstream side of the transfer roller 8. A predetermined toner image is transferred onto the unprinted surface at the transfer nip N on the paper T that is reversed upside down by the return conveyance path Lb.

  A paper discharge unit 50 is formed at the end of the third transport path L3. The paper discharge unit 50 is disposed on the upper side of the apparatus main body M. The paper discharge unit 50 opens toward the right side of the apparatus main body M (the right side in FIG. 1, the manual paper feed unit 64 side). The paper discharge unit 50 discharges the paper T conveyed on the third conveyance path L3 to the outside of the apparatus main body M by the third roller pair 53.

On the opening side of the paper discharge unit 50, a paper discharge stacking unit M1 is formed. The paper discharge stacking unit M1 is formed on the upper surface (outer surface) of the apparatus main body M. The paper discharge stacking unit M1 is a part formed by the upper surface of the apparatus main body M being depressed downward. The bottom surface of the paper discharge stacking unit M1 constitutes a part of the top surface of the apparatus main body M. In the paper discharge stacking unit M1, sheets T formed with a predetermined toner image and discharged from the paper discharge unit 50 are stacked and stacked.
A paper detection sensor is disposed at a predetermined position on each conveyance path.

Next, the operation of the printer 1 of the present embodiment will be briefly described with reference to FIG.
First, a case where single-sided printing is performed on the paper T stored in the paper feed cassette 52 will be described.
The paper T accommodated in the paper feed cassette 52 is sent out to the first transport path L1 by the forward feed roller 61 and the paper feed roller pair 63, and then the registration rollers via the first junction P1 and the first transport path L1. Transported to pair 80.
In the registration roller pair 80, skew correction of the paper T and timing adjustment with the toner image are performed.

The paper T discharged from the registration roller pair 80 is introduced between the photosensitive drum 2 and the transfer roller 8 (transfer nip N) via the first conveyance path L1. A toner image is transferred onto the paper T between the photosensitive drum 2 and the transfer roller 8.
Thereafter, the paper T is discharged from between the photosensitive drum 2 and the transfer roller 8 and is fixed to the fixing nip between the heating rotator 9a and the pressure rotator 9b in the fixing unit 9 via the second conveyance path L2. To be introduced. Then, the toner TN is melted in the fixing nip, and the toner TN is fixed on the paper T.

Next, the paper T is conveyed to the paper discharge unit 50 through the third conveyance path L3 by the first roller pair 54a, and is discharged from the paper discharge unit 50 to the paper discharge stacking unit M1 by the third roller pair 53.
In this way, single-sided printing of the paper T stored in the paper feed cassette 52 is completed.

  When single-sided printing is performed on the paper T placed on the manual feed tray 65, the paper T placed on the manual feed tray 65 is sent out to the manual feed path La by the paper feed roller 66, and then the first joining portion. It is conveyed to the registration roller pair 80 via P1 and the first conveyance path L1. Subsequent operations are the same as the one-side printing operation of the paper T accommodated in the paper feed cassette 52 described above, and a description thereof will be omitted.

Next, the operation of the printer 1 when performing duplex printing will be described.
In the case of single-sided printing, as described above, the paper T on which single-sided printing has been performed is discharged from the paper discharge unit 50 to the paper discharge stacking unit M1, and the printing operation is completed.
On the other hand, when performing double-sided printing, the paper T on which single-sided printing has been performed is reversed from the time of single-sided printing and conveyed again to the registration roller pair 80 via the return conveyance path Lb. Then, double-sided printing is performed on the paper T.

  More specifically, the operation is the same as the above-described single-sided printing operation until the paper T on which single-sided printing is performed is discharged from the paper discharge unit 50 by the third roller pair 53. Thus, in the case of double-sided printing, the rotation of the third roller pair 53 is stopped and rotated in the reverse direction in a state where the paper T on which single-sided printing has been performed is held by the third roller pair 53. Thus, when the third roller pair 53 is rotated in the reverse direction, the paper T held by the third roller pair 53 moves in the reverse direction (from the paper discharge unit 50 to the first branching unit Q1) along the third conveyance path L3. Transported in the direction of heading).

  As described above, when the paper T is transported in the reverse direction on the third transport path L3, it is introduced into the second roller pair 54b (not the first roller pair 54a). Then, the paper T joins the first transport path L1 via the return transport path Lb and the second joining portion P2. Here, the paper T is turned upside down from the one-side printing.

  Further, the paper T is corrected or adjusted by the registration roller pair 80 and is introduced between the photosensitive drum 2 and the transfer roller 8 through the first conveyance path L1. Since the unprinted surface of the sheet T passes through the return conveyance path Lb and faces the photosensitive drum 2, the toner image is transferred to the unprinted surface, and as a result, duplex printing is performed.

Next, with reference to FIG. 2 to FIG. 8, the details of the configuration of the rotation drive unit of the photosensitive drum 2 which is a characteristic part of the present invention will be described.
FIG. 2 is a longitudinal sectional view illustrating a schematic configuration of the rotation driving unit of the photosensitive drum 2 in the printer 1 of the present embodiment. FIG. 3 is a perspective view illustrating a configuration of a main part of the rotation driving unit of the photosensitive drum 2 in the printer 1 of the present embodiment. FIG. 4 is a perspective view showing a main part of the rotation driving unit of the photosensitive drum 2 in the printer 1 of the present embodiment.

  FIG. 5 is an enlarged perspective view showing a photosensitive drum driving gear which is a main element of the rotation driving unit of the photosensitive drum 2 in the printer 1 of the present embodiment. FIG. 6 is an enlarged perspective view for explaining the initial shape of the teeth of the photosensitive drum driving gear 620 in the printer 1 of the present embodiment. FIG. 7 is an enlarged perspective view for explaining the final shape of the teeth of the photosensitive drum driving gear 620 in the printer 1 of this embodiment. FIG. 8 is an enlarged plan view for explaining the final shape of the teeth of the photosensitive drum driving gear 620 in the printer 1 of this embodiment.

  As shown in FIG. 2, the rotation driving unit 200 of the photosensitive drum 2 includes a photosensitive drum driving shaft 600 connected to the photosensitive drum 2 and a motor 610 having an output shaft 611 parallel to the photosensitive drum driving shaft 600. A photosensitive drum driving gear 620 fixed to the photosensitive drum driving shaft 600, an intermediate shaft 630 interlocking with the output shaft 611 of the motor 610, and a photosensitive drum driving gear 620 fixed to the intermediate shaft 630. A meshing gear 640 for rotation transmission and a drive unit frame 650 are provided.

  As shown in FIGS. 2 and 3, the motor 610 is fixed to the outer surface of the drive unit frame 650. The photosensitive drum drive shaft 600 is rotatably supported by the drive unit frame 650 via a bearing 651 on one end side in the axial direction. The photosensitive drum drive shaft 600 is connected (directly connected) to the drum through shaft 680 via the coupling 670 on the other end side in the axial direction.

  As shown in FIG. 4, the drum penetrating shaft 680 rotates integrally with the photosensitive drum 2 via a flange 681 positioned and fixed to the end of the photosensitive drum 2 in the cylindrical axis direction. 2 is fixed.

  In the rotation driving unit 200 configured as described above, the rotation of the output shaft 611 of the motor 610 is transmitted from the rotation transmission gear 640 to the photosensitive drum driving gear 620. As a result, the photosensitive drum drive shaft 600 is driven to rotate. The rotation of the photosensitive drum driving shaft 600 is transmitted to the drum penetrating shaft 680 via the coupling 670, so that the photosensitive drum 2 is driven and rotated integrally with the flange 681.

Rotation transmission gear 640 is made of a metal gear formed of a metal material such as carbon steel.
On the other hand, the photosensitive drum driving gear 620 shown in FIG. 5 is made of a resin gear formed by injection compression molding of resin. In forming the photosensitive drum driving gear 620 by injection compression molding, first, in each of the plurality of tooth portions 621, as shown in FIG. 6, tooth surfaces 622 on both sides along the tooth trace direction x1-x2, 622 are parallel or substantially parallel to each other, and the tooth roots (downward from the pitch circle) such that the surfaces 622a and 622a of the tooth tips (the height of the teeth above the pitch circle) approach each other toward the tooth tips. It is molded into a shape inclined with respect to the surface 622b of the tooth height).

  In the photosensitive drum driving gear 620 injection-molded as described above, among the tooth surfaces 622, 622 on both sides of each tooth portion 621, the tooth surface 622a, in particular, is formed on the tooth surface 622a. In addition, along the tooth trace direction x1-x2, there is a shape error such that both end portions in the tooth width direction are convex due to sink marks (dents) in the center portion in the tooth width direction.

  Therefore, in each tooth portion 621 after injection compression molding into an initial shape as shown in FIG. 6, the tooth tip surfaces 622a of the tooth surfaces 622 on both sides are shown as tooth traces as shown in FIGS. Along the direction x1-x2, the central part in the tooth width direction is formed into a crowning shape having a bulge (secondary processing).

  As a crowning method, for example, a total shape grindstone (not shown) having teeth formed in a reverse crowning shape is engaged with each tooth 621 of the photosensitive drum driving gear 620, and the total shape grindstone. A method of grinding each tooth portion 621 into a predetermined crowning shape by rotating the shaft and oscillating in the axial direction is employed.

  Specifically, the rotation transmission torque from the rotation transmission gear 640 to the photosensitive drum driving gear 620 is set to 5 kgf · cm or less (in the printer 1 of the present embodiment, set to about 1 to 3 kgf). Under such conditions, the crowning shape is formed so that the rotation transmission error with respect to the set rotation transmission torque (maximum 5 kgf · cm) is within 0.8 μm or less. The crowning shape is such that the crowning amount C in the meshing region b in the center portion in the tooth width direction of the tooth tip surface 622a of each tooth portion 621 of the photosensitive drum driving gear 620 is 0 along the tooth trace direction x1-x2. .0075 ± 0.0035 mm. In particular, the crowning amount C is preferably 0.0075 ± 0.0025 mm.

Further, in the tooth tip surface 622a of each tooth portion 621, a region b1 corresponding to 0.8 × h (total tooth height dimension) at both ends in the tooth width direction is slightly so as to release the meshing of the tooth portion 621. It is so-called end relief that reduces the wall thickness.
The relationship (effect) between the crowning amount and the rotation transmission error will be described in detail in a later embodiment.

According to this embodiment, the following effects are produced, for example.
The printer 1 of this embodiment includes a photosensitive drum 2, a photosensitive drum driving shaft 600 connected to the photosensitive drum 2, a motor 610 having an output shaft 611 parallel to the photosensitive drum driving shaft 600, and a resin. The photosensitive drum driving gear 620 formed and fixed to the photosensitive drum driving shaft 600 and the intermediate shaft 630 interlocking with the output shaft 611 of the motor 610 and meshing with the photosensitive drum driving gear 620 for rotation transmission. A gear 640. Further, in the present embodiment, the photosensitive drum 2 is configured so that the rotation of the output shaft 611 of the motor 610 is transmitted from the rotation transmission gear 640 to the photosensitive drum driving gear 620 to be rotated. The body drum driving gear 620 has the tooth surface 622 (tooth surface 622a) of the photosensitive drum driving gear 620 along the tooth trace direction so that the maximum rotation transmission error with respect to the rotation transmission torque is 0.8 μm or less. And a crowning shape having a crowning amount of 0.0075 ± 0.0035 mm.

  Therefore, it is possible to stabilize the meshing of the rotation transmission gear 640 and the photosensitive drum driving gear 620 at the center portion of the tooth width. Further, the parallelism between the output shaft 611 of the motor 610 and the photosensitive drum driving shaft 600 cannot be maintained due to the assembly error of the photosensitive drum 2 and the shake of the output shaft 611 of the motor 610, and both gears 640 and 620 are not maintained. Even if they are engaged with each other in an inclined state, it is possible to prevent the end portion of the tooth surface 622 from hitting one piece. For this reason, the maximum rotation transmission error when the rotational torque is transmitted from the rotation transmission gear 640 to the photosensitive drum driving gear 620 can be reduced to 0.8 μm or less. Therefore, it is possible to suppress the occurrence of jitter that causes the image signal to fluctuate within a minute range and improve the image quality.

In the present embodiment, the crowning amount is set to 0.0075 ± 0.0025 mm.
For this reason, it is possible to further reduce the rotation transmission error when the rotation torque is transmitted from the rotation transmission gear 640 to the photosensitive drum driving gear 620.

In the present embodiment, the rotation transmission torque is set to 5 kgf · cm or less.
Therefore, the rotation transmission error under the operating condition of the rotation transmission torque of 5 kgf · cm or less generally employed in the image forming apparatus can be suppressed to 0.8 μm or less, and the practical effectiveness can be exhibited.

Furthermore, in this embodiment, the photosensitive drum driving gear 620 is formed by injection compression molding.
Therefore, the shape error that is likely to occur in the tooth surface 622 of the photosensitive drum driving gear 620 due to sink marks or the like in the center of the tooth trace direction during injection compression molding is caused by crowning the tooth face 622 along the tooth trace direction. Can be absorbed and removed. Therefore, the rotation transmission error can be further reduced.

  Hereinafter, the present invention will be described in more detail using Examples (Examples 1 and 2) and Comparative Examples (Comparative Examples 1 to 3) of the present invention. However, the present invention is not limited to the following examples.

[Specimen]
Example 1: A tooth surface of a large-diameter gear formed by injection compression molding of a resin is formed into a crowning shape having a crowning amount of 5 μm along the tooth trace direction.
Example 2: A tooth surface of a large-diameter gear formed by resin injection compression molding is formed into a crowning shape having a crowning amount of 10 μm along the tooth trace direction.
Comparative Example 1: A tooth surface of a large-diameter gear formed by resin injection compression molding is not crowned along the tooth trace direction (crowning amount is 0 μm).
Comparative Example 2: A tooth surface of a large-diameter gear formed by resin injection compression molding is formed into a crowning shape having a crowning amount of 20 μm along the tooth trace direction.
Comparative Example 3: A tooth surface of a large-diameter gear formed by resin injection compression molding was formed into a crowning shape having a crowning amount of 25 μm along the tooth trace direction.

[Purpose of the experiment]
The presence or absence of the effect of crowning in each of Examples 1 and 2 and Comparative Examples 1 to 3, and the optimum crowning amount for large-diameter gears are ascertained.
〔experimental method〕
Using a single-tooth test machine, a large-diameter gear (corresponding to the photosensitive drum driving gear 620 of the present embodiment) and a gear fixed to the output shaft of the motor (corresponding to the rotational transmission gear 640 of the present embodiment). ). When the axis parallelism of the two axes (corresponding to the photosensitive drum driving shaft 600 and the intermediate shaft 630 of this embodiment) is 0 ° and when the axis parallelism is 0.1 °, the motor side gear is used. Rotational transmission torque in the range of 0 to 5 kgf · cm divided into 5 parts per 1 kgf · cm is sequentially applied. A rotation transmission error with respect to the inter-axis pitch (corresponding to the inter-center pitch between the photosensitive drum drive shaft 600 and the intermediate shaft 630 in this embodiment) is measured.

  Rotation transmission error is calculated by installing an encoder on the output side and input side of the large single-tooth tester, calculating the angle error (unit: “°”) from the output signals from both encoders, and calculating the calculated angle error. Is converted to “μm” so as to match the diameter (unit: “cm”) of the rotating body (photosensitive drum 2 of the present embodiment) to which the large-diameter gear transmits driving.

〔Experimental result〕
Each experimental result will be described with reference to FIGS. FIG. 9 is a graph showing the experimental results of Comparative Example 1 when the axial parallelism is 0 °. FIG. 10 is a graph showing experimental results of Example 1 when the axial parallelism is 0 °. FIG. 11 is a graph showing the experimental results of Example 2 when the axial parallelism is 0 °. FIG. 12 is a graph showing experimental results of Comparative Example 2 when the axial parallelism is 0 °.

  FIG. 13 is a graph showing the results of Comparative Example 3 when the axial parallelism is 0 °. FIG. 14 is a graph showing experimental results of Comparative Example 1 when the axial parallelism is 0.1 °. FIG. 15 is a graph showing the experimental results of Example 1 when the axial parallelism is 0.1 °. FIG. 16 is a graph showing the experimental results of Example 2 when the axial parallelism is 0.1 °. FIG. 17 is a graph showing experimental results of Comparative Example 2 when the axial parallelism is 0.1 °. FIG. 18 is a graph showing experimental results of Comparative Example 3 when the axial parallelism is 0.1 °.

[Consideration of experimental results]
When the axis parallelism is 0 °, that is, when the two axes are parallel, in Example 1 in which the crowning amount is 5 μm and in Example 2 in which the crowning amount is 10 μm, compared to Comparative Example 1 in which the crowning amount is 0 μm, 0 Even in the rotation transmission torque in the range of 5 to 5 kgf · cm, the rotation transmission error is reduced. On the other hand, in both Comparative Example 2 with a crowning amount of 20 μm and Comparative Example 3 with a crowning amount of 25 μm, an increase in rotation transmission error was observed.
This is because if the amount of crowning is too large, the tooth surfaces contact each other only at the center in the tooth width direction of the crown surface of the crowning shape, so the contact width of the entire tooth surface decreases, and the meshing rate decreases accordingly. It is inferred that

Further, when the axis parallelism is 0.1 °, in Comparative Example 1 in which the crowning amount is 0 μm, the rotation transmission error is clearly increased when the rotation transmission torque is small. On the other hand, in Example 1 in which the crowning amount is 5 μm and Example 2 in which the crowning amount is 10 μm, the influence on the rotation transmission error due to the change in the parallelism is small.
This is presumed to be because the effect of one-sided contact due to the inclination of the gears is reduced by crowning.

[Conclusion]
In the large-diameter photosensitive drum driving gear 620 that transmits the driving rotation of the motor 610 to the photosensitive drum 2, forming the tooth surface 622 of each tooth portion 621 in a crowning shape is effective in reducing the rotation transmission error. It was confirmed that there was.
A suitable crowning amount along the tooth trace direction of the tooth surface 622 of each tooth portion 621 of the large-diameter photosensitive drum driving gear 620 that transmits the driving rotation of the motor 610 to the photosensitive drum 2 is 5 μm to 10 μm (0. 0075 ± 0.0035 mm). Further, it was confirmed that the optimum crowning amount was 0.0075 mm ± 0.0025 mm.

As mentioned above, although preferred embodiment of this invention was described, this invention can be implemented with a various form, without being limited to embodiment mentioned above.
For example, the rotation transmission gear 640 is fixed to the intermediate shaft 630 that is linked to the output shaft 611 of the motor 610 in the embodiment, but is not limited to this, and is directly fixed to the output shaft 611 of the motor 610. It may be.
In the present embodiment, a monochrome printer is described as the image forming apparatus. However, the present invention is not limited to this, and may be a color printer, a copier, a facsimile, or a complex machine of these.

  In the above-described embodiment, when the photosensitive drum driving gear 620 is formed by resin injection compression molding, it is initially molded into a shape as shown in FIG. Although what was formed next was demonstrated, it is not restrict | limited to this. For example, the photosensitive drum driving gear 620 having a crowned tooth portion may be formed only by injection compression molding.

  DESCRIPTION OF SYMBOLS 1 ... Printer (image forming apparatus), 2 ... Photoconductor drum (image carrier), 600 ... Photoconductor drum drive shaft (image carrier drive shaft), 610 ... Motor, 611 ... Output shaft, 620 ... photosensitive drum driving gear (image carrier driving gear), 630 ... intermediate shaft, 640 ... rotational transmission gear, 621 ... tooth portion, 622 ... tooth surface, x1-x2 ... tooth trace Direction, C ... Crowning amount

Claims (5)

An image carrier;
An image carrier drive shaft connected to the image carrier;
A motor having an output shaft parallel to the image carrier driving shaft;
An image carrier driving gear formed of resin and fixed to the image carrier driving shaft;
A rotation transmission gear fixed to an output shaft of the motor or an intermediate shaft interlocking with the output shaft, and meshing with the image carrier driving gear,
The image carrier is configured such that the rotation of the output shaft of the motor is transmitted from the rotation transmission gear to the image carrier driving gear and is rotated.
In the image carrier driving gear, the tooth surface of the image carrier driving gear is set to 0.0075 ± 0.00 mm along the tooth trace direction so that the maximum rotation transmission error with respect to the rotation transmission torque is 0.8 μm or less. An image forming apparatus formed into a crowning shape having a crowning amount of 0035 mm. The image forming apparatus according to claim 1, wherein the crowning amount is 0.0075 ± 0.0025 mm. The image forming apparatus according to claim 1, wherein the rotation transmission torque is set to 5 kgf · cm or less. The image forming apparatus according to claim 1, wherein the image carrier driving gear is formed by injection compression molding. The image forming apparatus according to claim 1, wherein the rotation transmission gear is formed of a metal gear formed of a metal material.

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