JP2002328499A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of the quality of a toner image by stably supplying toner to a photoreceptive drum from a developing roller by stably maintaining an engaged state between a gear for the photoreceptive drum and a gear for the developing roller. SOLUTION: The photoreceptive drum 5 on which an electrostatic latent image is formed and the gear 11 for the photoreceptive drum fixed at one end part 10 of the photoreceptive drum 5 in an axial direction are freely rotatably supported at one side plate 3 of a housing 2 by a first bearing 4. The gear 12 for the developing roller freely rotatably supported by one side plate 3 of the housing 2 is engaged with the gear 11 for the photoreceptive drum, an Oldham's coupling 14 intervenes between the other end part 70 of the gear 12 for the developing roller and the developing roller 9 by which the electrostatic latent image is developed with the toner by coming into press- contact with the surface of the photoreceptive drum 5. The motive power of a driving source 15 with which the photoreceptive drum 5 and the developing roller 9 are driven is transmitted to one end part 10 of the photoreceptive drum 5 by a spline 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer and a facsimile machine.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, light corresponding to image information is irradiated from a light source onto the surface of an image carrier, and an electrostatic latent image is formed on the surface of the image carrier by exposure to light irradiation.
The electrostatic latent image is developed with the toner supplied from the developing roller to form a toner image, the formed toner image is transferred onto a recording sheet conveyed by a conveying unit, and the toner image transferred onto the recording sheet is fixed. Thus, an image is formed on the recording paper.

Among the above-described image forming apparatuses, an image forming apparatus that employs a contact developing method of developing an electrostatic latent image by resiliently contacting an elastic developing roller with an image carrier is disclosed.
The rotation speed of the developing roller is set to be higher than the rotation speed of the image carrier, so that the supply of toner from the developing roller to the electrostatic latent image on the surface of the image carrier is not interrupted.

When the image carrier is formed of an endless belt, the pressing force for bringing the developing roller into contact with the image carrier is absorbed by the displacement of the endless belt, so that the developing roller slides on the surface of the image carrier. The frictional force at the time is reduced. However, when the image carrier is a drum having a cylindrical or cylindrical shape, when the developing roller is pressed against the image carrier, the image carrier can hardly be displaced.
The pressing force of the developing roller against the image carrier is not reduced, and the developing roller slides on the surface of the image carrier with a large frictional force.

At this time, when the driving means for the image carrier and the developing roller are different, and a gear is used for transmitting the power of the driving means, for example, the gear has a backlash, so that the friction between the image carrier and the developing roller is caused. The rotation may follow the rotation of the developing roller due to the force. Irregular rotation in which the image carrier follows the developing roller and rotates following the developing roller, so that the image carrier rotates instantaneously faster than the originally set rotational speed, and then returns to the original set rotational speed. When this phenomenon occurs, in a toner image developed on the surface of the image carrier, so-called banding, which exhibits irregular stripes in the circumferential direction of the image carrier, occurs, thereby deteriorating the image quality.

[0006]

As a countermeasure for this problem, the drive source for the image carrier and the developing roller are made the same, and the image carrier follows the rotation speed of the developing roller by friction with the developing roller. I try not to rotate.

However, in an image forming apparatus which develops an electrostatic latent image by pressing a developing roller against an image carrier, when transmitting rotational power from a gear provided on the image carrier to a gear provided on the developing roller, The axial distance between the rotation axis of the gear provided on the image carrier and the rotation axis of the gear provided on the developing roller varies depending on the pressing force of pressing the developing roller against the image carrier. As a result, the meshing state between the gear provided on the image carrier and the gear provided on the developing roller changes, so that the developing roller or the image carrier rotates irregularly, and the banding occurs in the toner image. Sometimes.

As a technique for solving this problem, for example, Japanese Patent Application Laid-Open No. 9-31552 discloses that an Oldham coupling is provided between a rotating shaft of a developing roller and a gear transmitting power to the rotating shaft of the developing roller. Have been. The Oldham coupling is a coupling that can transmit power even when there is a deviation between the axis of the rotating shaft of the developing roller and the axis of the gear that transmits power to the rotating shaft of the developing roller. Yes, to the extent permitted by Oldham couplings,
Since the developing roller can be displaced in response to the reaction force of the pressing force, the contact state between the developing roller and the image carrier can be stably maintained by the displacement of the developing roller.

This prior art has the following problems. In this prior art, a support member that supports a gear provided on an image carrier and a support member that supports a gear provided on a developing roller are mounted on different members. The Oldham coupling can transmit power even when there is a deviation between the axis of the developing roller and the axis of the gear that transmits power to the developing roller. If the distance between the two supporting members changes accordingly, power cannot be transmitted smoothly.

The distance between the axis of the support member for supporting the gear provided on the image carrier and the axis of the support member for supporting the gear provided on the developing roller varies depending on the pressing force of the developing roller. That is, when the distance between the axis of the gear provided on the image carrier and the axis of the gear provided on the developing roller changes, the meshing state between the gear provided on the image carrier and the gear provided on the developing roller changes. As a result, the developing roller or the image carrier may rotate irregularly, so that the toner supply from the developing roller to the image carrier becomes unstable, and the quality of the toner image developed on the image carrier surface deteriorates. Occurs.

SUMMARY OF THE INVENTION It is an object of the present invention to maintain the distance between the axis of a gear provided on an image carrier and the axis of a gear provided on a developing roller constant with high accuracy, and to provide the gear provided on the image carrier with a developing roller. An object of the present invention is to provide an image forming apparatus capable of stably supplying toner from a developing roller to an image carrier by maintaining a stable meshing state with a gear provided in the image forming apparatus and preventing a deterioration in quality of a toner image. .

[0012]

According to the present invention, there is provided a photosensitive drum on which an electrostatic latent image is formed rotatably supported by a first bearing on one side plate of a housing, and (b) a photosensitive drum mounted on the housing. A developing roller supported by a case by second and third bearings, wherein toner adheres to the surface and is pressed against the surface of the photosensitive drum to visualize the electrostatic latent image on the photosensitive drum with the toner. (C) a photosensitive drum gear fixed to one end in the axial direction of the photosensitive drum, and (d) a photosensitive drum rotatably supported by one side plate of the housing near the one end of the photosensitive drum. A developing roller gear meshing with the body drum gear, (e) an Oldham coupling interposed between one end of the developing roller and the developing roller gear, (f) a driving source, and (g) driving Source power in front of photoreceptor drum On the other hand an image forming apparatus which comprises a spline that transmits the end.

According to the present invention, even if the axis of the developing roller pressed against the photosensitive drum as the image bearing member is curved due to the pressing force between a pair of bearings supporting the developing roller, Oldham is The power of the developing roller gear can be reliably transmitted to the developing roller by the function of the joint. Even if the axis of the developing roller is curved, there is no problem in meshing the gear for the developing roller and the gear for the photosensitive drum.

Further, since the power of the driving source is transmitted by a spline having an axis extending from the axis of the photosensitive drum, there is no possibility that an undesired reaction force due to the power from the driving source is generated on the photosensitive drum. There is no problem that the axis of the photosensitive drum is curved. Further, by providing the photosensitive drum and the spline for transmitting the power of the drive source to the photosensitive drum gear on the same axis, the volume occupied by the power transmitting member can be reduced, so that the size of the image forming apparatus can be reduced. It can contribute to the conversion.

Further, the present invention is characterized in that one side plate of the housing on which the gear for the developing roller is supported and one side plate of the housing on which the photosensitive drum is supported by the first bearing.

According to the present invention, the one end of the photosensitive drum and the gear for the photosensitive drum are supported by the first bearing on one side plate of the housing so as to have a linear axis.
The developing roller gear is also supported by one side plate of the housing. Thus, even when the state of the developing roller pressed against the photosensitive drum changes, the fluctuation in the axial distance between the photosensitive drum gear and the developing roller gear is suppressed. The displacement of the axis of the developing roller due to the pressing force against the drum can be prevented.

Further, the invention is characterized in that the photosensitive drum and the developing roller are detachably provided on the housing.

According to the present invention, since the photosensitive drum and the developing roller are detachably provided in the housing, the photosensitive drum and the developing roller can be individually exchanged. Thus, only the members that need to be replaced can be easily replaced, so that the maintenance cost of the image forming apparatus can be reduced. Further, since the first bearing for supporting the photosensitive drum gear and the developing roller gear are mounted on one side plate of the integral housing, the axis of the developing roller gear and the first bearing for supporting the photosensitive drum are provided. There is no need to adjust the distance, and the time for replacing the developing roller and the photosensitive drum can be reduced.

According to the present invention, there is provided an Oldham coupling of the Oldham coupling, wherein a locking projection is formed at one end of the Oldham coupling, and the locking projection has a dovetail shape. The power is transmitted from the gear for the developing roller to the Oldham coupling by engaging with the locking concave portion formed at the other end of the near side.

According to the present invention, the developing roller gear and the Oldham coupling are connected by engaging the locking projection formed on the Oldham coupling with the locking concave formed on the developing roller gear. Since the locking projection has a dovetail shape, the rotation driving force can be reliably transmitted from the developing roller gear to the developing roller.

In the present invention, a fitting projection extending in the axial direction is formed at one end of the Oldham coupling, and the fitting projection and the other end of the developing roller gear near the Oldham coupling are formed. When the fitting recess is fitted, the developing roller gear and the Oldham coupling are positioned in a connected state.

According to the present invention, the Oldham coupling is formed with a fitting protrusion extending in the axial direction, the developing roller gear is formed with a fitting recess, and the fitting protrusion and the fitting recess are fitted. By doing so, the developing roller gear and the Oldham coupling are positioned in a connected state. By this, when the Oldham coupling is connected to the developing roller gear, the mutual axis of the developing roller gear and the Oldham coupling can be easily matched, so that the time required for replacing the developing roller can be reduced. it can.

[0023]

FIG. 1 is a cross-sectional view showing a simplified configuration of an image forming apparatus 1 according to an embodiment of the present invention, and FIG. 2 is a sectional view showing a main part of the image forming apparatus 1 shown in FIG. FIG. 3 is an exploded cross-sectional view showing a portion, and FIG. 3 is an image forming apparatus 1 shown in FIG.
FIG. 4 is a schematic cross-sectional view showing the entire configuration of the image forming apparatus 1 shown in FIG.

The image forming apparatus 1 as a printer includes a photosensitive drum 5 rotatably supported by a first bearing 4 on one side plate 3 of a housing 2 on which an electrostatic latent image is formed, and a second photosensitive drum 5 mounted on the housing 2. And a developing roller 9 supported by a case 8 by third bearings 6 and 7, wherein toner adheres to the surface and is pressed against the surface of the photosensitive drum 5 to expose the electrostatic latent image on the photosensitive drum 5 with the toner. A developing roller 9 for forming an image, a gear 11 for a photosensitive drum fixed to one end 10 of the photosensitive drum 5 in the axial direction, and one side plate 3 of the housing 2 near the one end 10 of the photosensitive drum 5 are provided. A developing roller gear 12 rotatably supported and meshing with the photosensitive drum gear 11; an Oldham coupling 14 interposed between the one end 13 of the developing roller 9 and the developing roller gear 12; Source 1 When, and a spline 16 for transmitting power of the driving source 15 to the one end portion 10 of the photosensitive drum 5.

The housing 2 is a hollow container made of a metal or a hard synthetic resin, and connects one side plate 3, another side plate (not shown) provided opposite to the one side plate 3, and one side plate 3 and the other side plate. And first and second connecting plates 17 and 18.

The photosensitive drum 5 is made of aluminum and has a cylindrical shape, and its outer peripheral surface is coated with selenium (Se) or an organic photoconductor (Organic Photo-Conductor) to form a photosensitive receiving layer. ing. FIG. 5 is a cross-sectional view schematically showing the configurations of the photosensitive drum 5 and the developing roller 9. A photoconductor drum gear 11 is fixed to one end 10 of the photoconductor drum 5, and a flange portion 20 is fixed to the other end 19. First and second through holes 21 and 22 are formed in the photosensitive drum gear 11 and the flange portion 20, respectively, and a photosensitive drum shaft 23 is provided through the first and second through holes 21 and 22. .

The photosensitive drum shaft 23 has an outer diameter of approximately 6 mm.
It is an iron shaft. One end 2 of photoconductor drum shaft 23
4 is inserted through a first through hole 21 formed in the photoconductor drum gear 11, and is prevented from being removed by a first retaining pin 25 outside the photoconductor drum gear 11. The other end 26 of the photosensitive drum shaft 23 is rotatably supported by a photosensitive drum case 28 by a fourth bearing 27. The photoconductor drum case 28 is a housing made of a hard synthetic resin that houses the photoconductor drum 5. The photoconductor drum 5 can be attached to and detached from the housing 2 by attaching and detaching the photoconductor drum case 28 to and from the housing 2. Done by

An earth member 29 is attached to the flange portion 20 by a screw 30 so as to contact the inner peripheral surface of the photosensitive drum 5 and the photosensitive drum shaft 23.
, The photosensitive drum 5 is grounded via the photosensitive drum shaft 23.

The first bearing 4 comprises a bearing body 31 and a bearing body 3
1 is mounted on one side plate 3 of the housing 2 by the bearing member 32. The drive source 15
Power transmission shaft 33 for transmitting the power of
The first bearing 4 rotatably supports the one side plate 3 of the housing 2. The outer diameter of the power transmission shaft 33 is approximately 10 mm.
It is an iron shaft. The power transmission shaft 33 is provided with a first ring member 35 on one end 34 side in contact with the bearing body 31, and receives a thrust force in the power transmission direction by the first ring member 35. The power transmission shaft 33 has one end 34.
In the vicinity, the fifth bearing 36 also rotatably supports the frame member 37 of the image forming apparatus 1. A power transmission gear 38 is attached to the power transmission shaft 33 on the inner side of the image forming apparatus 1 with respect to the fifth bearing 36, and the power transmission gear 3
8 is fixed at a predetermined position by a second retaining pin 39.

The drive source 15 is, for example, an electric motor, and is mounted on the frame member 37 of the image forming apparatus 1 such that the drive shaft 41 of the drive source 15 projects inward of the image forming apparatus 1. A drive gear 42 is formed on the drive shaft 41, and the drive gear 42 meshes with the power transmission gear 38 to transmit the power of the drive source 15 to the power transmission shaft 33. Power transmission shaft 3
An insertion hole 44 extending in the axial direction is formed in the end surface of the other end 43 of the third member 3. When the photoconductor drum 5 is supported by the first bearing 4 by fitting the support hole 46 formed at one end 45 of the photoconductor drum case 28 with the bearing member 32, the insertion hole 44 One end 24 of the photoconductor drum shaft 23 is inserted, and the axis of the power transmission shaft 33 matches the axis of the photoconductor drum 5.

At the other end 43 of the power transmission shaft 33, a spline shaft 47 having a plurality of projecting protrusions extending along the axis is mounted. The spline shaft 47 is predetermined by a third retaining pin 49. Fixed in position. In the present embodiment, the spline shaft portion 47 is a spur gear. A spline boss portion 48 having a plurality of concave grooves extending along an axis is formed in a concave portion formed in the photosensitive drum gear 11. In the present embodiment, the spline boss portion 48 is an internal gear. The spline 16 having an axis extending from the axis of the photosensitive drum 5 is formed by a spline shaft 47 provided on the other end 43 of the power transmission shaft 33 and a spline boss 48 formed on the gear 11 for the photosensitive drum. Is configured. The spline shaft portion 47 and the spline boss portion 48 constituting the spline 16 mesh with each other, and the drive source 15
Is transmitted to the photosensitive drum 5. As described above, the photosensitive drum 5 is supported by the one side plate 3 of the housing 2 by the first bearing 4, and is rotated by the power of the drive source 15 being transmitted by the spline 16.

Since the power of the drive source 15 is transmitted by a spline 16 having an axis extending from the axis of the photosensitive drum 5, an undesired reaction force is generated in the photosensitive drum 5 by the power from the drive source 15. There is no danger and there is no problem such as the axis of the photosensitive drum 5 being curved. The drive source 1 is connected to the photosensitive drum 5 and the photosensitive drum gear 11.
By providing the power transmission spline 16 and the power transmission spline 16 on the same axis, the volume occupied by the power transmission member can be reduced, which can contribute to downsizing of the image forming apparatus 1.

The other end 26 of the photosensitive drum shaft 23 is supported by a fourth bearing 27 on the photosensitive drum case 28, but one end 24 of the photosensitive drum shaft 23 is supported by the photosensitive drum case 28. Without housing 2
Is supported by a first bearing 4 on one side plate 3. Therefore, the photosensitive drum shaft 23 is not excessively restrained by the photosensitive drum case 28, and can rotate smoothly.

A developing device 91 having the developing roller 9 is provided adjacent to the photosensitive drum 5. The developing roller 9
A roller having an outer diameter of approximately 16 mm and an outer periphery of a cored bar 52 covered with an elastic rubber layer 53 is provided so as to rotate around an axis parallel to the axis of the photosensitive drum 5 in the same plane. The developing roller 9 transports the toner by adhering the toner to the elastic rubber layer 53 forming the surface, and presses against the photosensitive drum 5 to visualize the electrostatic latent image formed on the surface of the photosensitive drum 5 by the toner. I do. The developing roller 9 includes a developing device 9
The spring 1 is urged in the direction of arrow 51 by a spring member (not shown) suspended on the photosensitive drum 5. The pressing force is
It is often selected within the range of 700 to 2000 g, and in this embodiment, 1000 g is selected.

The vicinity of both ends of the core 52 of the developing roller 9 is
The elastic rubber layer 53 is formed to have an outer diameter smaller than the vicinity of the central portion covered by the elastic rubber layer 53, and forms a rotation shaft of the developing roller 9. The developing roller 9 is rotatably supported by the developing device case 8, which is the case 8, by second and third bearings 6 and 7 on the rotation shafts at both ends. A second ring member 55 is provided on the rotating shaft of the developing roller 9, that is, on the metal core 52, in contact with the second bearing 6 on one end 54 side of the developing roller 9, and an axial thrust force is applied by the second ring member 55. Is receiving.

An Oldham coupling 14 is interposed between the one end 13 of the developing roller 9 and the developing roller gear 12.
The Oldham coupling 14 can be used even when a shift exists between the power input axis and the output axis in the same plane.
It is a joint that can transmit power. FIG. 6 is an exploded front view showing a simplified configuration of the Oldham coupling 14 and the developing roller gear 12.

The Oldham coupling 14 includes first to third coupling members 61, 62, 63 having a circular cross section perpendicular to the axis, and is provided in this order from the developing roller 9 side to the developing roller gear 12 side. . The first joint member 61 is slidable in the axial direction of the developing roller 9, but is not slidable in the rotating direction.
Is attached to the one end 54. First and third joint members 6
The first and second projecting pieces 64, which have a dovetail shape and extend in the radial direction, are provided on
65 are formed respectively. On the surface of the second joint member 62 facing the first joint member 61, a first concave groove portion 66 is formed corresponding to the first projection piece 64, and on the surface of the second joint member 62 facing the third joint member 63. Corresponds to the second projection 65,
A concave groove 67 is formed. The first groove 66 and the second groove 67 formed in the second joint member 62 extend in directions orthogonal to each other.

The first projection 64 and the first groove 66 are engaged, and the second projection 65 and the second groove 67 are engaged. First and second projection pieces 64, 65 and first and second projection pieces
The concave grooves 66 and 67 can slide in the radial direction in a plane perpendicular to the axis of the Oldham coupling 14 in the engaged state. As a result, the Oldham coupling 14 can transmit power from the input shaft to the output shaft without changing the angular velocity even when there is a deviation between the input axis and the output axis of power in the same plane. it can.

FIG. 7 shows a third example of the Oldham coupling 14 shown in FIG.
FIG. 8 is a right side view of the developing roller gear 12 shown in FIG. 6. Third joint member 63
Has a dovetail-shaped locking projection 69 at one end 68.
Is formed. A cylindrical protrusion 71 extending in the axial direction is formed at the other end 70 of the developing roller gear 12 near the Oldham coupling 14. A locking recess 72 having a shape corresponding to the locking protrusion 69 is formed on the protrusion 71 of the developing roller gear 12.

The length L1 of the end of the locking projection 69 facing the developing roller gear 12 in the vertical direction in FIG.
6, the engaging projection 69 of the third joint member 63 is inserted into the engaging recess 72 of the developing roller gear 12 because the length L2 of the third joint member 63 faces the third joint member 63. Can be engaged. The locking projection 69 has a dovetail shape,
Since the locking recess 72 is formed in a shape corresponding to the locking projection 69, when the developing roller gear 12 is rotated in the direction of the arrow 73, the locking recess 72 and the locking projection 69 are separated. The third joint member 6 is removed from the developing roller gear 12
3, that is, the rotational power can be reliably transmitted to the Oldham coupling 14.

Further, a fitting protrusion 74 extending in the axial direction is formed at one end 68 of the third joint member 63. The fitting protrusion 74 has a cylindrical shape having an outer diameter d1. The vicinity of the tip of the fitting protrusion 74 facing the developing roller gear 12 is formed in a truncated cone shape, and the outer diameter d2 of the tip 75 is the outer diameter. It is formed in a size smaller than the diameter d1. The other end 70 of the developing roller gear 12
The inner diameter d3 of the cylindrical projection 71 formed is equal to or slightly larger than the outer diameter d1 of the fitting projection 74, and the internal recess of the projection 71 becomes the fitting recess 76. As described above, the vicinity of the distal end of the fitting projection 74 is formed in a truncated cone shape, so that the Oldham coupling 14 and the developing roller gear 12 are formed.
When the connection is made, the fitting protrusion 74 can be easily inserted into the fitting recess 76, and the fitting between the fitting protrusion 74 and the fitting recess 76 is performed smoothly. Thus, when the developing device 91 including the developing roller 9 is mounted on the housing 2, the axes of the developing roller gear 12 and the Oldham coupling 14 can be easily matched with each other. Work time can be reduced.

When the developing device 91 is mounted on the housing 2, the Oldham coupling 14 is connected to the first coupling member 61 and the second coupling member 61.
Washer 7 provided outside and adjacent to ring member 55
8 is pressed against the developing roller gear 12 by a spring member 77 provided between the housing 2 and the housing 2.
In the state of being separated from the developing device, the spring member 77 presses against the developing device cover 79. Since the Oldham coupling 14 is sandwiched between the developing roller 9 and the developing roller gear 12 or between the developing roller 9 and the developing device cover 79, the Oldham coupling 14 is held without falling off from the developing device 91.

The developing roller gear 12 is connected to the Oldham coupling 14 at the other end 70, is rotatably supported at one end 79 on the one side plate 3 of the housing 2, and meshes with the photosensitive drum gear 11. Developing roller gear 12
Includes a developing roller gear body 80, a sixth bearing 81, and a support member 82. The developing roller gear body 80 is rotatably supported by a support member 82 by a sixth bearing 81, and the support member 82 is screwed by one side plate 3 of the housing 2.
Attached to.

As described above, the power of the drive source 15 is first transmitted from the drive shaft 41 to the power transmission gear 38, and then the power transmission gear 38 and lower power transmission shaft 33, the spline 16, and the photosensitive drum And transmitted to the developing roller 9 from the developing roller gear 12 via the Oldham coupling 14.

Since the developing roller gear 12 and the developing roller 9 are connected by the Oldham coupling 14, the developing roller 9 is pressed against the photosensitive drum 5 so that the axis of the developing roller gear 12 and the axis of the developing roller 9 Power can be transmitted even when a deviation occurs between the two. Therefore, even if the axis of the developing roller 9 pressed against the photosensitive drum 5 is curved due to the pressing force between the pair of second and third bearings 6 and 7 supporting the developing roller 9, the Oldham coupling 14 Thus, the power from the developing roller gear 12 can be reliably transmitted to the developing roller 9. Even if the axis of the developing roller 9 is curved, the developing roller gear 1
There is no hindrance to the meshing of the gear 2 with the photosensitive drum gear 11.

One end 10 of the photosensitive drum 5 and the photosensitive drum gear 11 are supported on the one side plate 3 of the housing 2 by a first bearing 4 and have an axis in a straight line. 12 is also supported by the one side plate 3 of the housing 2. As a result, even when the state of pressing the developing roller 9 against the photosensitive drum 5 changes, the fluctuation of the distance between the axes of the photosensitive drum gear 11 and the developing roller gear 12 is suppressed, so that the developing Developing roller 9 caused by the pressing force of roller 9 against photosensitive drum 5
Can be prevented from shifting.

Oldham coupling 14 and developing roller gear 12
Is connected or disconnected, the developing unit 91 provided with the developing roller 9 and the Oldham coupling 14 and the housing 2 become detachable from each other. By connecting or disconnecting the photosensitive drum gear 11 and the photosensitive drum 5 from the first bearing 4, the photosensitive drum 5 and the photosensitive drum case 28 accommodating the photosensitive drum 5 and the housing 2 are connected to each other. It becomes removable. Thus, only the members that need to be replaced can be easily replaced, so that the maintenance cost of the image forming apparatus 1 can be reduced. Since the first bearing 4 and the developing roller gear 12 that support the photosensitive drum gear 11 are mounted on the one side plate 3 of the housing 2 that is integrally formed, the developing roller gear 12 and the photosensitive drum Gear 1
There is no need to adjust the distance between the axes of the first bearing 4 and the first bearing 4, and the time for replacing the developing roller 9 and the photosensitive drum 5 can be reduced.

The image forming apparatus 1 of the present embodiment employs a non-magnetic one-component contact development system using a developer composed of one toner component. Therefore, by making the rotation speed of the developing roller 9 higher than the rotation speed of the photosensitive drum 5, a portion where the toner supplied from the developing roller 9 to the photosensitive drum 5 is not interrupted is generated. Specifically, the number of teeth of the photosensitive drum gear 11 is 37,
The number of teeth of the developing roller gear 12 is set to 16. Since the outer diameter of the photosensitive drum 5 is 30 mm and the outer diameter of the developing roller 9 is 16 mm, the rotation speed of the developing roller 9 is
This is 1.23 times the rotation speed of the photosensitive drum 5. In many cases, in the image forming apparatus employing the contact developing method, the rotation speed of the developing roller is 1.1 times the rotation speed of the photosensitive drum.
The range is selected to be 1.5 times.

Next, the spline 16 for transmitting the power of the driving source 15 from the power transmission shaft 33 to the photosensitive drum gear 11 will be described. FIG. 9 is a cross-sectional view of the spline 16 perpendicular to the axial direction. In the present embodiment, as described above, the spline shaft portion 47 is formed as a spur gear, and the spline boss portion 48 is formed as an internal gear having the same number of teeth as the spur gear formed on the spline shaft portion 47. . A backlash is set between the spur gear formed on the spline shaft portion 47 and the internal gear formed on the spline boss portion 48. The spline 16 has a backlash so that the spline shaft portion 47 and the spline boss portion 48 can smoothly move even when a slight displacement occurs between the spline shaft portion 47 and the spline boss portion 48. Linked to

FIG. 10 is a sectional view perpendicular to the axial direction of the spline 111 having no backlash. If the spline 111 has no backlash,
If a slight misalignment occurs between the spline shaft portion 112 and the spline boss portion 113, the spline shaft portion 11
2 and the spline boss 113
The sliding resistance between the teeth of the internal gear formed on the inner gear increases, which may result in damage to the gear.

The power transmission shaft 3 using the spline 16
By transmitting power from the gear 3 to the gear 11 for the photosensitive drum, the following advantages can be obtained. FIG. 11 is a cross-sectional view perpendicular to the axial direction showing a simplified configuration for transmitting power to the photosensitive drum gear 11 in the present embodiment, and FIG. 12 is a conventional photosensitive drum gear 1.
FIG. 4 is a cross-sectional view perpendicular to the axial direction, showing a simplified configuration for transmitting power to the motor. It is.

In the conventional example shown in FIG. 12, a power transmission relay gear 115 for transmitting power is provided on the side opposite to the developing roller 12 with respect to the photosensitive drum gear 114. The power transmission relay gear 115 is a photosensitive drum gear 114.
And rotates in the direction of arrow 116 to transmit power to the photosensitive drum gear 114. Power transmission relay gear 11
When 5 transmits power to the photosensitive drum gear 114,
From the power transmission relay gear 115 to the photosensitive drum gear 11
4, a force f0 based on power is applied.

The photoreceptor drum gear 114 receives power from the power transmission relay gear 115, rotates in the direction indicated by an arrow 117, and meshes with the developing roller gear 12 to supply power to the developing roller gear 12. introduce. The photosensitive drum gear 114 applies a force f1 based on power to the developing roller gear 12, and conversely, the photosensitive drum gear 1
14 also receives the reaction force f2 of the force f1. Accordingly, the rotating shaft 118 of the photosensitive drum gear 114 receives the forces f0 and f2 directed downward in FIG.

In the present embodiment shown in FIG.
The power of 5 is transmitted to the photosensitive drum gear 11 by a spline 16 having an axis extending from the axis of the photosensitive drum 5. When the spline shaft 47 is rotated in the direction of arrow 84 to transmit power to the spline boss 48, that is, the photosensitive drum gear 11, the rotation directions of the spline shaft 47 and the spline boss 48 are the same. The force applied to the spline boss portion 48 by the spline shaft portion 47 and the reaction force generated in the spline boss portion 48 cancel each other.
The gear 11 for the photoreceptor drum rotates in the direction of the arrow 84 and engages with the gear 12 for the developing roller to transmit power to the gear 12 for the developing roller, thereby causing the gear 1 for the developing roller to rotate.
Rotating 2 in the direction of arrow 85 is the same as in the conventional example. Therefore, the photosensitive drum gear 11 applies a force f1 based on power to the developing roller gear 12, and conversely, the photosensitive drum gear 11 also receives a reaction force f2 of the force f1.

In the conventional example, the rotating shaft 118 of the photosensitive drum gear 114 receives the forces f0 and f2 in the downward direction in FIG. 12, while in the present embodiment, the photosensitive drum shaft 2
No. 3 only receives the force f2 in the downward direction on the paper of FIG.
As described above, in the present embodiment, the force applied to the photosensitive drum shaft 23 is reduced as compared with the conventional example, and there is a possibility that an undesired reaction force may be generated on the photosensitive drum 5 by the power from the drive source 15. In addition, it is possible to prevent a problem that the axis of the photosensitive drum 5 is curved.

Hereinafter, preferred modes of the spur gear formed on the spline shaft portion 47 and the internal gear formed on the spline boss portion 48 will be described. When the gears are engaged with each other, if the number of teeth of the gear is small, a down phenomenon occurs in which the root of the gear is cut off by the tip of the counterpart gear. When used as a spline composed of a spur gear and an internal gear, a phenomenon in which the gears are cut down hardly occurs. However,
When a gear having a small number of teeth is manufactured with high precision by cutting, a downcut phenomenon may occur. Therefore, it is not preferable to reduce the number of teeth without limitation. The limit of the number of teeth that does not cause the reduction phenomenon is 17 when the pressure angle of the gear is 20 degrees regardless of the gear module. However, in practice, it is said that even if the number of teeth is reduced to 14, the devaluation phenomenon hardly occurs. Therefore, although it is possible to prevent the occurrence of the devaluation phenomenon by setting the number of teeth to 14 or more, it is preferable to set the number of teeth to 17 or more. In the present embodiment, the spline gear of the spline shaft portion 47 has 18 teeth.

Further, it is preferable that the tooth profile of the spur gear formed on the spline shaft portion 47 is formed according to an involute curve. As a result, the spline shaft portion 47
Power can be reliably transmitted from the power transmission shaft 33 to the photoreceptor drum gear 11 even if there is a slight displacement between the axis of the spline boss 48 and the spline boss 48. Here, the tooth profile of the spur gear formed on the spline shaft portion 47 is
Formed according to the involute curve of module 0.8.

In order to smoothly mesh and rotate the spur gear of the spline shaft portion 47 having the same number of teeth and the internal gear formed on the spline boss portion 48, at least one of the gears is displaced, and It is necessary to form backlash. Here, the shift coefficient of the internal gear formed on the spline boss portion 48 is +0.3, and the shift coefficient of the spur gear formed on the spline shaft portion 47 is +0.2. If the absolute value of the difference between the dislocation coefficients of the spur gear of the spline shaft portion 47 and the internal gear formed on the spline boss portion 48 exceeds 0.15, the backlash becomes excessive and rotation unevenness occurs. It is preferable to set the value to be equal to or less than .15.

As a means for forming an appropriate backlash, it is conceivable to shift the spur gear formed on the spline shaft portion 47 so that the shift coefficient becomes negative. However, the thickness of the tooth root of the spur gear is reduced. Alternatively, since the power transmission shaft 33 must be thin, there is a problem in strength, which is not preferable. Therefore, it is preferable to form a backlash by shifting the internal gear formed on the spline boss portion 48 so that the shift coefficient becomes positive as described above.

Returning to FIG. 4, image formation by the printer, which is the image forming apparatus 1 of the present embodiment, will be described. The printer 1 includes four sets of visible image forming means 86K (black), 86C (cyan), and 86 for forming a visible image on recording paper.
M (magenta), 86Y (yellow), a recording paper tray 87 for storing recording paper, and conveyance means 8 for conveying recording paper
8 and a printer body case 89. The four sets of visible image forming means 86K, 86C, 86M, 86Y are indicated by arrows 90.
Are provided along the conveying means 88 in this order from the upstream side to the downstream side in the conveying direction of the recording paper shown in FIG. The visible image forming means 86K includes a developing device 91, an optical unit 92, a photosensitive drum 5, a charger 93, and a cleaner unit 94.
And a transfer device 95.

The photosensitive drum 5 is mounted on the housing 2 and is arranged so as to be in contact with a transport belt 99 of a transport means 88 described later. The charger 93, the optical unit 92, the developing unit 91, the transfer unit 95, and the cleaner unit 94 surround the photoconductor drum 5 and extend in the circumferential direction.
Are arranged in this order from the upstream side to the downstream side in the rotation direction.

The charger 93 is a charger for uniformly charging the surface of the photosensitive drum 5 to a predetermined potential. The optical unit 92 includes a laser irradiation unit and a reflecting mirror,
A laser scanning unit (LSU) of the printer 1 is configured. The optical unit 92 irradiates the surface of the photosensitive drum 5 uniformly charged with laser light to form an electrostatic latent image corresponding to image information. The developing device 91 includes the developing roller 9, and presses the developing roller 9 against the photosensitive drum 5 to supply toner to the photosensitive drum 5, and forms an electrostatic latent image formed on the surface of the photosensitive drum 5. Visualize.

The transfer unit 95 is a roller made of a metal such as stainless steel and having an outer diameter of 8 to 10 mm. The surface of the transfer unit 95 is made of a material having conductivity and elasticity, such as urethane foam or ethylene propylene rubber (EPDM). ). Thus, the transfer device 95 can uniformly apply a high voltage to the recording paper. The transfer unit 95 is provided to face the photosensitive drum 5 via the transport belt 99 of the transport unit 88, and applies a bias voltage opposite to that of the toner to transfer the toner image formed on the surface of the photosensitive drum 5. Transfer to recording paper. Cleaner unit 94
After the toner image is transferred from the photosensitive drum 5 onto the recording paper, the toner remaining on the surface of the photosensitive drum 5 is removed and collected, and the surface of the photosensitive drum 5 is cleaned for the next development. Other visible image forming means 86C, 86
M and 86Y have the same configuration as that of the visible image forming unit 86K except that the color of the toner is different, and thus the description is omitted.

The conveying means 88 includes a driving roller 96, a stretching roller 97, a plurality of driven rollers 98, and a driving roller 9.
Endless conveying belt 99 which is stretched and rotatable by the roller 6 and the stretching roller 97, and a belt cleaner unit 10
0 is included. The driving roller 96 is driven to rotate by an electric motor or the like about an axis perpendicular to the plane of FIG.
The stretching roller 97 is arranged to have an axis parallel to the axis of the driving roller 96 in a plane including the axis of the driving roller 96. Although the stretching roller 97 does not have a driving source, the power of the driving roller 96 is transmitted by the conveyor belt 99 and is driven to rotate in the same direction as the driving roller 96. The endless transport belt 99 stretched between the driving roller 96 and the stretching roller 97 is a film having a thickness of about 100 μm, and rotates in the direction of the arrow 90 with the rotation of the driving roller 96. The recording paper is conveyed by being electrostatically attracted.

The toner supplied from the developing roller 9 to the photosensitive drum 5 is transferred from the photosensitive drum 5 to recording paper,
Further, although the toner remaining without being transferred to the recording paper is removed and collected by the cleaner unit 94, part of the toner on the surface of the photosensitive drum 5 adheres to the transport belt 99. The toner adhering to the transport belt 99 becomes a cause of soiling the rear surface opposite to the surface on which the image of the recording paper is recorded, and thus is removed and collected by the belt cleaner unit 100.

The recording paper tray 87 is a container for storing recording paper used for recording an image, and is provided below the printer 1. The upper plate 10 of the printer body case 89
Reference numeral 1 functions as a discharge tray on which recording paper on which an image discharged from a discharge port 102 formed in an upper portion of the printer 1 is placed is placed.

The printer 1 further includes a pickup roller 103, a registration roller 104, a fixing device 105
And a plurality of transport rollers 106 and a plurality of transport rollers 10
6, the recording paper transport paths 107a, 107
7b.

The pickup roller 103 is provided at one end of the recording paper tray 87, extracts recording paper one by one from the recording paper tray 87, and supplies the recording paper to the transport path 107a. The registration roller 104 temporarily holds the recording paper extracted from the recording paper tray 87 and conveyed along the conveyance path 107a, and performs recording in response to the output of a detection sensor (not shown) provided upstream of the registration roller 104 in the recording paper conveyance direction. The position where the image recording of the paper is started and the position of the toner image formed on the surface of the photosensitive drum 5 are matched, and the toner image is sent to the visible image forming means 86K, 86C, 86M and 86Y. The transport roller 106 is a small-diameter roller for promoting the transport of the recording paper, and a plurality of the transport rollers 106 are provided along the transport paths 107a and 107b.

The fixing device 105 includes a heating roller 108, a pressure roller 109, and release agent applying rollers 110a, 110
b. The heating roller 108 is a metal-made roller having a cylindrical shape, and has a conductive layer serving as a heating member provided therein, and is heated by, for example, induction heating means (not shown). The surface temperature of the heating roller 108 is detected by a temperature sensor, and is maintained at a predetermined fixing temperature by a control unit that controls the temperature in response to the output of the temperature sensor. The pressure roller 109 is a metal roller having a cylindrical shape. The pressure roller 109 is provided so as to have an axis parallel to the axis of the heating roller 108 in a plane including the axis of the heating roller 108, and is heated by a spring member (not shown). It is pressed against the roller 108. The heating roller 108 and the pressure roller 109 nip and convey the recording paper on which the toner image has been transferred, and heat and pressurize the toner, thereby melting, mixing and pressing the toner on the recording paper to fix the toner on the recording paper.

On the surface of the heating roller 108, a release layer for preventing the heated and softened toner from fusing to the surface of the heating roller 108, for example, a layer made of polytetrafluoroethylene (PTFE) is provided. . The release agent applying rollers 110a and 110b are rolls for applying a release agent such as oil to a release layer provided on the surface of the heating roller 108. The recording paper on which the multicolor toner image is fixed is conveyed along the conveyance path 107b, and is discharged from the discharge port 102 to the upper plate portion 101 of the printer main body case 89 functioning as a discharge tray.

In the printer 1, an image is formed as follows. The recording paper fed one by one from the recording paper tray 87 to the transport path 107 a by the pickup roller 103 is further transported by the transport belt 99 in the arrow 90 direction. First, in the visible image forming means 86K, the photosensitive drum 5 is uniformly charged by the charger 93, and then the surface of the photosensitive drum 5 is laser-exposed by the optical unit 92 according to image information to form an electrostatic latent image. Is done. The developing device 91 supplies toner to the electrostatic latent image on the photosensitive drum 5 to perform development, and the developed toner image is transferred to the recording paper on the transport belt 99 by the transfer device 95.

While the recording paper is being conveyed in the direction indicated by the arrow 90, the toners of the respective colors are successively multiplex-transferred by other visible image forming means 86C, 86M, 86Y arranged downstream in the conveyance direction. Is done. Four sets of visible image forming means 8
After the development and the transfer by 6K, 86C, 86M, and 86Y are completed, the recording paper is separated from the conveyance belt 99 by the curvature formed on the driving roller 96, and the fixing device 105
Transported to In the fixing device 105, a recording roller carrying a toner image is provided with a heating roller 108 and a pressure roller 109.
And a suitable temperature and pressure are applied between them, and the toner is fixed on the recording paper to form a robust image. The recording paper after fixing is fed to the transport path 107b,
Is discharged to the upper plate portion 101 of the printer main body case 89, and a series of image forming processes is completed.

In the printer 1 according to the present embodiment, even if the pressure contact state between the developing roller 9 and the photosensitive drum 5 changes as described above, it is possible to prevent the displacement of the axis of the developing roller 9. Also, there is no problem such as the curvature of the axis of the photosensitive drum 5. This prevents defects such as banding from occurring in the toner image, so that image formation of good quality can be stably performed.

As described above, in the embodiment of the present invention, the photosensitive drum 5 and the developing roller 9 are detachably provided on the housing 2, but are not limited thereto. Alternatively, one of the developing rollers 9 may be detachably provided in the housing 2, and the photosensitive drum 5 and the developing roller 9
May be left mounted on the housing 2. Further, the photosensitive drum gear 11 and the developing roller gear 12 are spur gears, but are not limited thereto, and may be helical gears. Similarly, the drive shaft gear 42 and the power transmission gear 38 may be helical gears. The image forming apparatus 1 is configured to form a multi-color image, but is not limited to this, and may be configured to form a single-color image.

[0075]

According to the present invention, even if the axis of the developing roller pressed against the photosensitive drum is curved due to the pressing force between the pair of bearings supporting the developing roller, the function of the Oldham coupling works. As a result, the power from the gear for the developing roller can be reliably transmitted to the developing roller. Even if the axis of the developing roller is curved, there is no problem in meshing the gear for the developing roller and the gear for the photosensitive drum.

Further, since the power of the drive source is transmitted by a spline having an axis extending along the axis of the photosensitive drum, there is no possibility that an undesired reaction force is generated on the photosensitive drum by the power from the drive source. There is no problem that the axis of the photosensitive drum is curved. Further, by providing the photosensitive drum and the spline for transmitting the power of the drive source to the photosensitive drum gear on the same axis, the volume occupied by the power transmitting member can be reduced, so that the size of the image forming apparatus can be reduced. It can contribute to the conversion.

Further, according to the present invention, the one end of the photosensitive drum and the gear for the photosensitive drum are supported by the bearing on one side plate of the housing so as to have an axis in a straight line.
The developing roller gear is also supported by one side plate of the housing. Thus, even when the state of the developing roller pressed against the photosensitive drum changes, the fluctuation in the axial distance between the photosensitive drum gear and the developing roller gear is suppressed. The displacement of the axis of the developing roller due to the pressing force against the drum can be prevented.

Further, according to the present invention, since the photosensitive drum and the developing roller are detachably provided in the housing, the photosensitive drum and the developing roller can be individually exchanged. Thus, only the members that need to be replaced can be easily replaced, so that the maintenance cost of the image forming apparatus can be reduced. The first bearing for supporting the photosensitive drum gear and the developing roller gear are mounted on one side plate of the integrated housing, so that the distance between the axis of the developing roller gear and the first bearing for supporting the photosensitive drum is set. Need not be adjusted, and the time for replacing the developing roller and the photosensitive drum can be shortened.

According to the present invention, the engaging protrusion formed on the Oldham coupling engages with the retaining recess formed on the developing roller gear, thereby connecting the developing roller gear and the Oldham coupling. Since the locking projection has a dovetail shape, the rotational driving force can be reliably transmitted from the developing roller gear to the developing roller.

According to the present invention, the Oldham coupling is formed with a fitting protrusion extending in the axial direction, the developing roller gear is formed with a fitting recess, and the fitting protrusion and the fitting recess are fitted. As a result, the developing roller gear and the Oldham coupling are positioned in a connected state. By this, when connecting the Oldham coupling to the developing roller gear,
Since the axes of the developing roller gear and the Oldham coupling can be easily matched with each other, it is possible to reduce the time required for replacing the developing roller.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part schematically showing a configuration of an image forming apparatus 1 according to an embodiment of the invention.

FIG. 2 is an exploded sectional view showing a main part of the image forming apparatus 1 shown in FIG.

FIG. 3 is an exploded perspective view of a main part of the image forming apparatus 1 shown in FIG.

FIG. 4 is a schematic cross-sectional view illustrating an overall configuration of the image forming apparatus 1 illustrated in FIG.

FIG. 5 is a cross-sectional view showing a simplified configuration of a photosensitive drum 5 and a developing roller 9.

FIG. 6 is an Oldham coupling 14 and a developing roller gear 12;
FIG. 2 is an exploded front view showing a simplified configuration of FIG.

7 is a third joint member 6 of the Oldham coupling 14 shown in FIG.
3 is a left side view of FIG.

8 is a right side view of the developing roller gear 12 shown in FIG.

9 is a sectional view perpendicular to the axis of the spline 16. FIG.

FIG. 10 is a cross-sectional view perpendicular to the axial direction of a spline having no backlash.

FIG. 11 shows a photosensitive drum gear 1 according to the present embodiment.
FIG. 2 is a cross-sectional view perpendicular to the axial direction, showing a simplified configuration for transmitting power to the vehicle.

FIG. 12 is a cross-sectional view perpendicular to the axial direction showing a simplified configuration for transmitting power to a photosensitive drum gear 114 in a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 image forming apparatus 2 housing 3 one side plate 4 first bearing 5 photosensitive drum 9 developing roller 11 gear for photosensitive drum 12 gear for developing roller 14 Oldham coupling 16 spline

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H035 CA07 CB04 CD05 CD07 CD11 CD13 CE03 CG03 2H071 CA02 CA05 DA08 DA15 DA27 EA04 EA06 EA18 2H077 AD06 AD35 BA03 BA07 BA09 EA14 EA15 GA04 GA13 3J103 AA02 BA43 CA05 GA61 FA17 FA17 GA58 GA60

Claims (5)

[Claims] 1. A photoreceptor drum rotatably supported by a first bearing on one side plate of a housing to form an electrostatic latent image thereon, and (b) a case mounted on the housing by second and third bearings. A developing roller supported by the photosensitive drum, wherein the toner adheres to the surface and is pressed against the surface of the photosensitive drum to visualize the electrostatic latent image on the photosensitive drum with the toner; (c) the photosensitive drum And (d) a developing device rotatably supported on one side plate of the housing near the one end of the photosensitive drum and meshing with the photosensitive drum gear. A roller gear, (e) an Oldham coupling interposed between one end of the developing roller and the developing roller gear, (f) a drive source, and (g) a power source for the photosensitive drum. Supra to transmit to the one end An image forming apparatus comprising: 2. The device according to claim 1, wherein one side plate of the housing on which the gear for the developing roller is supported and one side plate of the housing on which the photosensitive drum is supported by the first bearing. Image forming device. 3. The image forming apparatus according to claim 1, wherein the photosensitive drum and the developing roller are detachably provided on the housing. 4. An Oldham coupling having a locking projection formed at one end thereof, the locking projection having a dovetail shape, and the locking projection and the developing roller gear being closer to the Oldham coupling. By engaging with the locking recess formed at the end,
The image forming apparatus according to claim 1, wherein power is transmitted from the developing roller gear to the Oldham coupling. 5. A fitting projection extending in the axial direction is formed at one end of the Oldham coupling, and a fitting recess formed at the other end of the Oldham coupling near the Oldham coupling of the developing roller gear and the developing roller gear. By mating with
The image forming apparatus according to any one of claims 1 to 4, wherein the positioning is performed in a state where the gear for the developing roller and the Oldham coupling are connected.