JP3339274B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In recent years, there has been a remarkable improvement in image quality and personalization of an image forming apparatus using an electrophotographic system. In particular, optical printers having a mainstream resolution of 300 dpi have been increased to 600 dpi and 1200 dpi. It is progressing. Under these circumstances, it has become an important technical issue to achieve both high image quality, low cost and improved operability.

Hereinafter, a conventional image forming apparatus will be described. 4 is a configuration diagram of a conventional image forming apparatus, FIG. 5 is a configuration diagram of a process unit of the conventional image forming apparatus, FIG. 6 is a detailed view of a driving unit of the process unit of the conventional image forming apparatus, and FIG. FIG. 3 is a configuration diagram of a main body of a forming apparatus and a driving unit of a process unit.

In FIG. 4, reference numeral 1 denotes a main body of a printer, which is an image forming apparatus, and reference numeral 2 denotes a paper cassette in which paper 3 is stored. The paper 3 is fed one by one from a paper cassette 2 by a paper feed roller 4,
The paper is sent to the paper transport path 6 while being sandwiched therebetween. Reference numeral 10 denotes a leading end detection sensor arm that transmits the leading end of the sheet 3 to an optical sensor (not shown), and controls the time for writing an image in the image transfer section downstream of the sheet 3 in the transport direction.
Reference numeral 11 denotes a process unit which is configured so that main components for image formation described below are integrated with each other and can be attached to and detached from the main body 1.

In FIGS. 5 and 6, the structure of the process cartridge 11 includes an upper frame 11a and a lower frame 11b. Reference numeral 12 denotes a photosensitive drum having a photosensitive layer, such as selenium (Se) or an organic photoconductor (OPC), applied on the outer peripheral surface thereof in a thin film form. Reference numeral 12a denotes a gear provided at an end of the photosensitive drum 12, Lower frame 11b by fixed shaft 12b
Are rotatably supported. Photoconductor drum 12
A charger 13, an exposure optical system 14 (FIG. 4), a developing roller 15, a transfer roller 16 (FIG. 4), and a cleaning blade 17 are provided on the peripheral surface of the photosensitive drum 12 in the order indicated by the arrow A in the rotation direction. I have.

The charger 13 is composed of a charging brush 13a made of conductive rayon or the like and a charging plate 13b made of a metal plate. A voltage of about -1.2 kV is applied to the charger 13 by a high voltage power supply (not shown) inside the main body 1. Is applied, the surface of the photosensitive drum 12 is uniformly charged to about -700V. Reference numeral 14a denotes a laser beam emitted from the exposure optical system 14, and an electrostatic latent image corresponding to an image signal is formed on the photosensitive drum 12 by the laser beam 14a.

As shown in FIG. 6, the developing roller 15 has a conductive member 15b such as urethane formed on the outer peripheral surface of a developing roller shaft 15a, and is supported by the lower frame 11b so as to be movable in the direction of arrow B. The bearing 24 is rotatably supported by a bearing 24. Since the bearing 24 is pushed toward the photosensitive drum 12 by the coil spring 25, the developing roller 15 is in contact with the photosensitive drum 12 with a constant load. A gear 27 is provided at an end of the developing roller shaft 15a via an Oldham type shaft coupling 26. The gear 27 is rotatably supported by a fixed shaft 27a provided on the lower frame 11b. Since the developing roller 15 is in contact with the photosensitive drum 12 by the coil spring 25, the photosensitive drum 12,
The center position of the developing roller 15 is not at a fixed position due to a radial error of the developing roller 15 or a center-to-center error of the lower frame 11b, and needs to be corrected by the Oldham type joint 26. An intermediate gear 28 is rotatably supported by a fixed shaft 28a provided on the lower frame 11b and drives the gear 27.

As shown in FIG. 5, the developing blade 18
A conductive member 18 such as silicon is attached to the tip of the blade plate 18a.
The fixing roller 18b is fixed to a fixing plate 18c fixed to the lower frame 11b by a leaf spring 18d, and presses the surface of the developing roller 15 via toner 19 as a developer. The replenishing roller 20 has a conductive member 20b such as urethane formed on the outer peripheral surface of a replenishing roller shaft 20a, is rotatably supported by the lower frame 11b, and has the toner 19 on the surface of the developing roller 15. Supplying.

Reference numeral 21 denotes a toner storage unit which is constituted by the lower frame 11b and stores the toner 19. The agitator 22 has a blade 22b formed on an agitator shaft 22a.
The toner 19 in the toner storage unit 21 is rotatably supported by the lower frame 11 b, and is supplied onto the developing roller 15 by the agitator 22 and the replenishing roller 20. The toner is conveyed onto the photosensitive drum 12 by friction charging in a state. A negative potential of about -300 V is applied to the developing roller 15 having the toner 19 on the surface,
By applying a negative charge to the toner 19 in advance, the toner 19 adheres only to the portion of the photosensitive drum 12 where the laser beam 14a has been irradiated and the charge has disappeared, and the development is performed by a so-called negative-positive process. Reference numeral 23 denotes an opening / closing lid which is opened / closed when replenishing the toner 19 to the toner storage unit 21, and is slidably supported by the upper frame 11a.

In FIG. 7, reference numeral 11c denotes a projection provided on the process cartridge 11, and 1a denotes a rail provided on the main body 1, which guides and positions the process cartridge 11 when it is mounted on the main body 1. 29, 30, 31, 3
Reference numeral 2 denotes a gear provided on the main body 1 and driven by a motor 33. After the process cartridge 11 is mounted, the gears 29 and 30 engage the gear 12a and the intermediate gear 28 to drive the photosensitive drum 12 and the developing roller 15, respectively.

In FIG. 4 and FIG. 5, the transfer roller 16 has a conductive member 1 such as urethane on the outer periphery of a transfer roller shaft 16a.
6b is formed and is rotatably supported by the main body 1. Toner 19 adhered to photoreceptor drum 12 and developed
By applying a high voltage of about +1 KV to the transfer roller 16, the image is transferred by the transfer roller 16 onto the surface of the sheet 3 conveyed by the sheet feed roller 4. The cleaning blade 17 cannot transfer the image onto the sheet 3 and the photosensitive drum 1
2 is to remove the toner 19 remaining on the surface 2.

A photosensitive drum 12, a charger 13, a developing roller 15,
Since the cleaning blade 17 and the like generally have a shorter service life than the main body 1 and need to be replaced periodically, the cleaning blade 17 and the like are integrated into the process cartridge 11 and replaced collectively to save labor for maintenance.

Reference numeral 28 denotes a fixing unit for fixing the sheet 3 on which the image has been transferred. The fixing unit 28 includes a heat roller 28a having a heat source therein and a pressure roller 28b, and applies an image formed by the toner 19 on the sheet 3 to the heat roller 28a. The fixing is performed by the pressure and the heat with the rotation of the pressure roller 28b. Reference numeral 29 denotes a switching claw that switches the discharge direction of the sheet 3 on which the image is fixed, and switches the discharge direction to the face-down roller 30 at the position of the solid line and to the face-up roller 31 at the position of the dotted line.

The operation of the image forming apparatus configured as described above will be described below. First, in FIG. 7, the process cartridge 11 is inserted in the direction of arrow A along the rail 1a. By driving the motor 33, the gears 29, 3
0 rotates in the directions of arrows B and C, respectively. Thus, the gear 12a and the intermediate gear 28 in the process cartridge 11
Applies a load in the directions of arrows D and E. Therefore, the process cartridge 11 is pushed in the mounting direction (arrow A) to ensure the positioning between the process cartridge 11 and the main body. Here, if the gear 27 is directly driven by the gear on the main body 1 side without passing through the intermediate gear 28, a load is applied in a direction for detaching the process cartridge 11. Therefore, an extra mechanism such as a means for fixing the process cartridge 11 is required. Required.

On the other hand, as shown in FIG. 4, in a digital electrophotographic technique of forming an electrostatic latent image by scanning a photosensitive drum 12 with a laser beam 14a as in the above-described conventional image forming apparatus, the photosensitive If the rotation speed of the body drum 12 fluctuates, the speed of the latent image formation in the sub-scanning direction fluctuates, causing a slight shift in the interval between one line and causing a significant deterioration in image quality. As a countermeasure, as shown in Japanese Patent Application Laid-Open No. 6-133122, the rigidity of the drive transmission unit to the photosensitive drum 12 is reduced to prevent resonance and reduce the transmission gain of the drive system, thereby reducing the transmission gain. There is a technology for reducing speed fluctuations.

In FIG. 6, the developing roller 15 having the largest load torque is driven in the image forming apparatus, and the meshing portion of the gear 27 which is most decelerated, that is, the intermediate gear 2 is used.
The loads C and E applied to the gear at the meshing portion with the gear 8 become maximum. When a load is applied to the gear, bending of the gear teeth and bending of the gear supporting portion occur, causing fluctuations in the rotational speed. This variation is caused by the development roller 15 and the gears 30, 31, 29, 12
a, the speed of the photosensitive drum 12 fluctuates, and the image quality is reduced. As a countermeasure against this, the gear 27,
The intermediate gear 28 may be a helical gear, or the lower frame 11 of the shaft 27a, 28a for supporting the gear 27 and the intermediate gear 28.
The fluctuation of the rotation speed is suppressed by strengthening the support rigidity to the b.

[0017]

However, in the conventional configuration, since there are two gear engagement portions between the main body 1 and the process cartridge 11, the gear engagement and the gear center distance when the process cartridge 11 is attached and detached are set. There was a problem that it was difficult to ensure accuracy.

Further, in order to strengthen the support rigidity of the shaft 28a, the thickness of the lower frame 11b must be increased and ribs for reinforcement are required, so that the volume and cost are increased.

Further, in a system in which the speed fluctuation of the photosensitive drum 12 is reduced by lowering the rigidity of the drive transmitting portion to the photosensitive drum 12, a factor that directly causes the speed fluctuation of the photosensitive drum 12, for example, the developing roller 15 In addition, the fluctuation due to the transfer roller 16 and the cleaning blade 17 lowers the rigidity of the photosensitive drum 12 in the rotation direction, so that there is a problem that a speed fluctuation occurs.

Accordingly, it is an object of the present invention to provide an image forming apparatus having high image quality, low cost, and good operability.

[0021]

According to the present invention, a first gear supported on one end of a photosensitive drum and transmitting a driving force to the photosensitive drum is provided on a side of a process cartridge detachably formed from a main body; A second gear that transmits driving force to the developing roller coaxially with the first gear, a third gear that meshes with the second gear coaxially with the developing roller and transmits driving force to the developing roller, and a frame of the process cartridge. The first gear and the second gear are rotatably supported by the body, and the shaft is formed of an integral member. , A fourth gear and a fifth gear.

A third gear for transmitting a driving force to the developing roller coaxially with the developing roller except for a driving force transmitting path between the motor as a driving source and the photosensitive drum, and a third gear for transmitting the driving force to the third gear. An elastic portion is provided in the drive transmission path on the motor side from the meshing portion with the second gear, and an elastic portion is provided between the meshing portion and the developing roller.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to a first aspect of the present invention is directed to a first gear supported on one end of a photosensitive drum for transmitting a driving force to the photosensitive drum, and a first gear coaxial with the first gear. A second gear for transmitting a driving force to the developing roller, and a process cartridge that incorporates the photosensitive drum, the developing roller, and the second gear and that is detachably attached to the main body. The first gear and the second gear that transmit the driving force to the photosensitive drum and the developing roller, and the fourth gear and the fifth gear that mesh with the respective gears and transmit the driving force are provided coaxially. The gear engagement between the main body and the process cartridge is performed between the same parallel shafts. Therefore, it is easy to engage the gears when attaching and detaching the process cartridge and to ensure the accuracy of the distance between the gear centers.
Furthermore, the shaft supporting the second gear can be shared with the shaft supporting the photosensitive drum, and the shaft and the supporting portion of the shaft are not required exclusively for supporting the second gear, thereby achieving high image quality. Both low cost and good operability can be achieved.

The invention described in claim 2 is the first invention.
A third gear that meshes with the second gear coaxially with the developing roller and transmits a driving force to the developing roller, and transmits the driving force to a developing roller that is a source of speed fluctuation. By providing an engagement portion between a third gear and a second gear for transmitting drive to the third gear and an elastic portion between the photosensitive drums, the speed fluctuation of the photosensitive drum is reduced, and the photosensitive drum is reduced. Since the rigidity of the drive transmission unit to the photosensitive drum is not reduced, it is possible to make the speed fluctuation less likely to occur even when the speed is directly changed on the photosensitive drum.

Hereinafter, an embodiment of the present invention will be described. FIG. 1 is a configuration diagram of a main body of an image forming apparatus and a driving unit of a process unit according to an embodiment of the present invention. FIG. 2 is a perspective view of gears of the image forming apparatus according to an embodiment of the present invention. FIG. 3 is a perspective view of an elastic portion of the image forming apparatus according to the embodiment. Here, the same reference numerals are given to the same components as in FIGS. 4 to 7 showing the conventional image forming apparatus, and the detailed description is omitted.

In FIG. 1, reference numeral 34 denotes an intermediate gear for driving a gear 27, which is rotatably supported on a shaft 12b which rotatably supports the photosensitive drum 12 coaxially with the photosensitive drum 12. A gear 35 provided on the main body 1 is rotatably supported on a shaft 36 provided on the main body 1. The gear 35 includes gears 35a, 35b, and 35c. The driving force from the motor 33 is transmitted to the gear 35c, and the gears 35a and 35b rotate.

FIG. 2 is a perspective view of the gears 27 and 35b.
b and 35d are teeth, 27c and 35e are flanges, 27
d and 35f are teeth 27b and 35d and a flange 27c,
It is easy to be elastically deformed by the rib connecting 35e, and the teeth 27b, 35
d and the torsional rigidity between the flange portions 27c and 35e is reduced.

In FIG. 3, reference numeral 37 denotes an Oldham type shaft coupling 2
An elastic portion that connects the developing roller 6 and the developing roller 15 has a plurality of cuts and is easily elastically deformed, so that the torsional rigidity between the Oldham type joint 26 and the developing roller 15 is reduced.

The operation of the image forming apparatus configured as described above will be described below. First, in FIG.
The gears 35 a and 35 b driven by the motor 33 are the gears 12 a and the intermediate gear 34 in the process cartridge 11.
By rotating the photosensitive drum 12, the developing roller 1
Rotate 5 Here, the gears 27 and 35b have elastic portions. Of these, the elastic portion of the gear 27 may be provided between the Oldham type shaft coupling 26 and the developing roller 15 as shown in FIG.

As described above, according to the present embodiment, a driving force is transmitted to the photosensitive drum 12 by being supported by one end of the photosensitive drum 12 on the side of the process cartridge 11 which is configured to be detachable from the main body 1. Gear 12a and gear 12a
Intermediate gear 3 for transmitting driving force to developing roller 15 coaxially with
4, a gear 27 that is coaxial with the developing roller 15 and meshes with the intermediate gear 34 to transmit a driving force to the developing roller 15, and a gear 1 supported by the lower frame 11b of the process cartridge 11.
The main body 1 includes a shaft 12b rotatably supporting the intermediate gear 2a and the intermediate gear 34, and a gear 35a and a gear 35b that are coaxial with each other to transmit the driving force by meshing with the gear 12a and the intermediate gear 34, respectively. ing. Therefore,
Since the meshing portion of the gear between the main body 1 and the process cartridge 11 is formed between the same parallel shafts, it is easy to engage the gear when attaching and detaching the process cartridge 11 and to ensure the accuracy of the gear center distance. Further, the shaft supporting the intermediate gear 34 is a shaft 12b supporting the photosensitive drum 12.
Since the shaft and the supporting portion of the shaft are not required exclusively for supporting the intermediate gear 34, it is possible to achieve both high image quality, low cost, and good operability.

In addition to the driving force transmission path between the motor 33 as a driving source and the photosensitive drum 12, the developing roller 15
Gear 27 for transmitting a driving force to developing roller 15 coaxially with
A rib 35f, which is an elastic portion, on the drive transmission path on the motor 33 side, and a rib 27d, which is an elastic portion between the meshing portion and the developing roller 15, than the meshing portion with the intermediate gear 34 that transmits the drive to the gear 27. Alternatively, an elastic portion 37 is provided. By providing an elastic portion between the meshing portion of the gear 27 and the intermediate gear 34, which is the source of the speed fluctuation, and the photoconductor drum 12, the speed fluctuation of the photoconductor drum 12 is reduced, and the speed of the photoconductor drum 12 is reduced. Since the rigidity of the drive transmission unit to the photosensitive drum 12 is not reduced, the speed fluctuation can be made less likely to occur even when the speed of the photoconductor drum 12 is directly changed.

[0032]

According to the present invention, a first gear supported on one end of a photosensitive drum and transmitting a driving force to the photosensitive drum, and a first gear are provided on a process cartridge side detachably formed from the main body. A second gear that transmits driving force to the developing roller coaxially with the third gear, a third gear that meshes with the second gear coaxially with the developing roller and transmits driving force to the developing roller, and is supported by the lower frame of the process cartridge The first gear and the second gear are rotatably supported, and the shaft is formed of an integral member. By providing the fourth gear and the fifth gear, the gear engagement between the main body and the process cartridge is performed between the same parallel shafts. It becomes easier. Furthermore, the shaft supporting the second gear can be shared with the shaft supporting the photosensitive drum, and the shaft and the supporting portion of the shaft are not required exclusively for supporting the second gear, thereby achieving high image quality. Both low price and good operability can be achieved.

A third gear for transmitting a driving force to the developing roller coaxially with the developing roller except for a driving force transmitting path between the motor as a driving source and the photosensitive drum, and a third gear for transmitting the driving force to the third gear. An elastic portion is provided in the drive transmission path on the motor side from the meshing portion with the second gear, and an elastic portion is provided between the meshing portion and the developing roller, and meshing between the third gear and the second gear, which are sources of speed fluctuation, is performed. By providing an elastic portion between the photoconductor drum and the photoconductor drum, the speed fluctuation of the photoconductor drum is reduced and the rigidity of the drive transmission unit to the photoconductor drum is not reduced. Can be made less likely to cause speed fluctuations.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main body of an image forming apparatus and a driving unit of a process unit according to an embodiment of the present invention.

FIG. 2 is a perspective view of a gear of the image forming apparatus according to the embodiment of the present invention;

FIG. 3 is a perspective view of an elastic portion of the image forming apparatus according to the embodiment of the present invention.

FIG. 4 is a configuration diagram of a conventional image forming apparatus.

FIG. 5 is a configuration diagram of a process unit of a conventional image forming apparatus.

FIG. 6 is a detailed view of a driving unit of a process unit of a conventional image forming apparatus.

FIG. 7 is a configuration diagram of a main body of a conventional image forming apparatus and a driving unit of a process unit.

[Description of sign]

 11 Process Cartridge 11b Lower Frame 12 Photoconductor Drum 12a Gear 12b Shaft 15 Developing Roller 27 Gear 27d Rib 33 Motor 35a Gear 35b Gear 35f Rib 37 Elastic Part

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/00 550 G03G 21/16-21/18 G03G 15/08-15/08 507 G03G 21/00 350 -352

Claims (3)

(57) [Claims] A first gear supported at one end of the photosensitive drum and transmitting a driving force to the photosensitive drum; a second gear transmitting a driving force to a developing roller coaxially with the first gear;
A process cartridge which contains the photosensitive drum, the developing roller, and the second gear and is detachably mounted to the main body; and the first gear and the second gear located on the main body side.
The fourth gear, which is coaxial with the gears
An image forming apparatus comprising: five gears . 2. A third gear for transmitting a driving force to the developing roller coaxially with the developing roller except for a driving force transmitting path between a motor as a driving source and a photosensitive drum, and a driving force to the third gear. An image forming apparatus comprising: an elastic portion provided in a drive transmission path on the motor side of a portion engaged with a second gear to be transmitted. Wherein the resilient unit, according to claim 2, characterized in that it is provided also between the developing roller and the engagement portion
The image forming apparatus as described in the above.