JPH07160095A - Roller positioning device for image forming apparatus - Google Patents

Abstract

(57) [Abstract] [Purpose] Cost reduction of the roller member positioning mechanism around the photoconductor. [Structure] Bearings 7 and 8 for supporting a charging roller 3 are supported by elongated holes 9 and 10 provided in a side plate so that they can move back and forth with respect to a photoconductor 2. The bearing 8 is pulled by a spring 12 toward the center of the photoreceptor, and the bearing 7 is pulled radially by a spring 11. The elongated hole 9 is formed in an arc shape centering on the gear 14, and the gears 13 and 14 are engaged at any position. When the gear 14 is rotationally driven, the tangential force F moves the bearing 7 downward, and the charging roller 3 approaches the photoconductor. When the driving is stopped, the bearing 7 is lifted by the force of the spring 11, and the charging roller 3 tilts and separates from the photoconductor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile or a laser printer, and more particularly to positioning of a roller member arranged around a photosensitive member.

[0002]

2. Description of the Related Art An image forming apparatus such as a copying machine, a facsimile, a laser printer, etc., includes a photoconductor for forming an image and a charging device, an exposure device, a developing device, a transfer device, a cleaning device arranged around the photoconductor. And so on. As the charging device, a corona discharger is generally installed, but a charging roller that contacts the photoconductor to charge it may be provided. Similarly, the developing device may be provided with a developing roller, and the transfer device may be provided with a transfer roller.

Roller members such as this type of charging roller, developing roller, and transfer roller are in direct contact with the photoconductor or very close to the photoconductor, so that the roller members are At least the surface layer portion has to be made of an elastic body such as rubber. However, such a rubber as the elastic member generally contains a softening agent, a cross-linking agent, etc., and if the same portion of the roller member and the photoconductor is left in contact for a long time. ,
Substances such as a softening agent and a cross-linking agent exude from the elastic member of the roller member, which contaminates the photoreceptor. As a result, the next time an image is formed, only the portion of the photoconductor that was in contact with the charging member becomes difficult to develop, and white spots occur on the image.

Further, in this type of image forming apparatus, the transfer paper may be jammed while passing between the photoconductor and the transfer roller. If the gap between the photoconductor and the transfer roller is narrow, the transfer paper is removed. Is difficult. Further, if the developing roller is constantly in contact with the photoconductor, the reversely charged toner is adsorbed to the photoconductor when the image forming operation is not performed, and the background stain occurs on the photoconductor.

Therefore, it is desirable that the roller members such as the charging roller, the developing roller and the transfer roller are separated from the photoconductor when the image forming operation is not performed.

For example, in the technique disclosed in Japanese Patent Laid-Open No. 4-140769, the photosensitive member and the contact member are rotated at predetermined intervals to prevent the same portion from being left in contact for a long time.

Further, in Japanese Patent Laid-Open No. 2-39169,
It has been proposed to install a spacer to prevent the contact between the charging roller and the photoconductor from the time the device is manufactured to the time it is actually used.

Further, Japanese Patent Laid-Open No. 182679/1983 proposes that a contacting / separating mechanism for a cleaning roller is composed of a solenoid, a return spring, a cam member and the like.

[0009]

However, in the technique disclosed in Japanese Unexamined Patent Publication No. 4-140769, the photoconductor is operated even when the copying operation is not performed, and it is inevitable that the photoconductor is wasteful. Further, if the main power supply of the apparatus is turned off, the operation cannot be performed, and therefore it is impossible to completely prevent the photoconductor and the contact member from being left in contact with each other for a long time.

Further, according to the technique disclosed in Japanese Patent Laid-Open No. 2-39169, a human is forced to attach / detach the spacer. Therefore, it has been found in advance that the device will not be used for a long period of time in practice. The spacer cannot be mounted unless it is present, and contact between the photoconductor and the roller member cannot be prevented after the apparatus starts operating.

Further, in order to position the roller member,
When a drive device such as a solenoid is added as in JP-A-58-182679, it is inevitable that the cost of the device becomes considerably high.

Therefore, an object of the present invention is to realize the positioning of the roller member toward and away from the photoconductor with a low-cost device.

[0013]

In order to solve the above-mentioned problems, in the present invention, image forming is provided with a photoreceptor (2) for forming an image and at least one roller member (3) arranged around the photoreceptor. In a roller positioning device of the device: while supporting the roller member rotatably,
A shaft supporting means (7) for movably supporting at least one end of the shaft of the roller member between a position close to the photoconductor and a position separated from the photoconductor in a direction substantially perpendicular to the shaft. , 9); separating means (1) for applying a force to the roller member in a direction in which the roller member moves away from the photosensitive member.
1); a driving means (14) for giving a force for rotationally driving the roller member and a force for moving the roller member to a position close to the photoconductor during a predetermined operation, and eliminating or reducing the force when the operation is stopped. Set up.

According to a second aspect of the present invention, the driving means is provided with a driven rotary member (13) mounted on the shaft of the roller member and a drive rotary member (14) which is constantly engaged with the driven rotary member.
The shaft support means is provided with a guide hole (9) formed in an arc shape around the rotation center of the drive rotation member.

According to a third aspect of the present invention, the separating means is composed of a spring member (11) having one end connected to the fixed member and the other end connected to the bearing of the roller member.

Further, in the present invention, the roller member is at least one of a charging roller of a charging device, a transfer roller of a transfer device, and a developing roller of a developing device.

The symbols shown in the parentheses are reference numerals of corresponding elements in the embodiments described later, but each constituent element of the present invention is a specific element in the embodiments. It is not limited to only.

[0018]

In the present invention, the roller member (3) is supported by the shaft supporting means (7, 9) and is rotatable.
Moreover, at least one end of the shaft is movable in a direction substantially perpendicular to the shaft between a position close to the photoconductor (2) and a position separated from the photoconductor (2). A force in the direction of moving to a position away from the photoconductor is constantly applied to the roller member by the separating means (11). In addition, drive means (1
In 4), during a predetermined operation (for example, during an image forming operation), a force for rotationally driving the roller member and a force for moving it to a position close to the photoconductor are applied to the roller member, and the force disappears when the operation is stopped or Reduce.

Therefore, during a predetermined operation, the roller member is positioned at a position close to the photosensitive member by the force generated by the driving means, and when the operation is stopped, one end of the shaft of the roller member is lifted by the force of the separating means, and the like. The roller member is separated from the photoconductor because it is inclined with the end as a fulcrum.

In the second aspect, when the driving means rotationally drives the driving rotary member (14) during a predetermined operation, the tangential force of the engaging portion between the driving rotary member (14) and the driven rotary member (13) causes the roller member to rotate. One end of the shaft moves in the circumferential direction of the drive rotation member along the guide hole (9) and approaches the photoconductor.
When the operation is stopped, one end of the shaft of the roller member is lifted by the force of the separating means and tilts with the other end as a fulcrum, so that the roller member is separated from the photoconductor.

Further, in the third aspect, since the spring member (11) is provided as the separating means, even when the roller member is arranged above the photoconductor, the force in the direction of separating from the photoconductor is applied to the roller. It can be reliably applied to the member.

According to the present invention, when the roller member is a charging roller, the photoconductor is prevented from being contaminated by the material contained in the charging roller. When the roller member is the transfer roller, the contamination of the photoconductor is prevented, and when the paper jam of the transfer paper occurs at that portion, the transfer paper can be easily removed. When the roller member is the developing roller, the background stain of the photoreceptor due to the oppositely charged toner on the developing roller is prevented.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of the main part of an image forming apparatus according to an embodiment.
Shown in. This will be described with reference to FIG. During the image forming operation, the photosensitive drum 2 rotates clockwise as shown by the arrow. The surface of the photoconductor drum 2 is first subjected to the irradiation of light from the charge eliminating lamp 1 to eliminate the charge, and the surface potential of the photoconductor is zero.
It becomes the reference potential of -150V. Next, the photosensitive drum 2
An electric charge is supplied to the photoconductor drum 2 by the charging roller 3 arranged so as to come into contact with the surface of the photoconductor drum 2.
Has a surface potential of about -1100V. After that, image light is irradiated by the exposure unit EXP located downstream of the charging roller 3 in the rotation direction of the photosensitive drum 2.

In the portion of the surface of the photosensitive drum irradiated with the image light (hereinafter referred to as the image portion), the surface potential is 0 to -29.
It will be about 0V. When the image portion on the surface of the photoconductor drum passes the next developing unit 4, a bias voltage of about −800 V is applied to the developing roller 41, so that the toner T in the developing unit 4 is applied to the image portion on the surface of the photoconductor drum. Adhere to. Since the non-image portion (background portion) of the photosensitive drum 2 is around −1100V, toner does not adhere to that portion. The photoconductor drum 2 on which the toner image is formed further rotates and moves.

Then, a transfer sheet is supplied from a sheet feeding unit (not shown) so as to be aligned with the toner image at the image forming timing, and the transfer sheet is superposed on the toner image on the surface of the photoreceptor at the transfer unit. To be done. The toner image on the surface of the photoconductor is electrostatically transferred onto the transfer paper by the transfer roller 5. The transfer paper on which the toner image has been transferred is separated from the photoconductor drum 2, the toner image is fixed by a fixing unit (not shown), and then discharged to the outside of the apparatus. On the other hand, the residual toner remaining on the photoconductor drum 2 is scraped off by the cleaning blade 6 in the cleaning unit, the toner is left on the photoconductor, and the process proceeds to the next image forming step again.

The structure around the charging roller 3 of FIG. 1 is shown in FIG. The components shown in FIG. 2 are incorporated in one cartridge as a minimum unit. This will be described with reference to FIG. The charging roller 3 has a structure in which a conductive elastic member (rubber) is wound around a metal cored bar. A power source (not shown) is connected to the cored bar, and a voltage applied to the cored bar causes a current to flow through the photosensitivedrum 2 through an elastic member that is in contact with the surface of the photosensitivedrum 2, thereby causing the photosensitivedrum to rotate. 2 becomes charged.

Both ends of the shaft of the charging roller 3 are rotatably supported by bearings 7 and 8, respectively. The front side plate Pf and the rear side plate Pr (see FIG. 4) of the cartridge are
Slotted holes 10 and 9 are formed respectively, the bearing 7 penetrates the slotted hole 9, and the bearing 8 penetrates the slotted hole 10. The elongated hole 9 is formed in an arc shape as shown in FIG. 3, and the bearing 7 is movable along the elongated hole 9 in the up-down direction, that is, in the direction of advancing and retracting with respect to the photosensitive drum 2. The elongated hole 10 on the front side is shorter than the elongated hole 9, and the bearing 8 is movable along the elongated hole 10 in the vertical direction, that is, in the direction of advancing and retracting with respect to the photosensitive drum 2. .

The tension spring 11 has one end fixed to the cartridge side plate and the other end fixed to the rear bearing 7. The spring 11 constantly applies a force in a direction away from the photosensitive drum 2 to the bearing 7. Further, the tension spring 12 has one end fixed to the cartridge side plate,
The other end is fixed to the bearing 8 on the front side. The spring 12 constantly applies a force that pulls the bearing 8 toward the center of the photosensitive drum 2 to the bearing 8.

A gear 13 is mounted on the shaft of the charging roller 3, and another gear 1 is provided at a position where the gear 13 is constantly meshed with the gear 13.
4 is rotatably installed. The gear 14 is connected to a drive source (not shown), is continuously driven clockwise in FIG. 2 during the image forming operation, and stops when the image forming operation is completed.

FIG. 3 shows a state in which the vicinity of the rear end of the charging roller 3 is viewed from the axial direction, and FIG. 4 shows a state in which the vicinity of the charging roller 3 is viewed from a direction perpendicular to the axis (direction A in FIG. 1). Show. 3 and 4, (a) shows a state where the charging roller 3 is stopped, and (b) shows a state where the charging roller 3 is rotating.

Referring to FIG. 3, the elongated hole 9 for guiding the bearing 7 is formed in an arc shape centered on the rotation center of the gear 14. Therefore, no matter where the bearing 7 moves along the long hole 9, the distance from the center of the gear 14 to the center of the bearing 7 is constant, and the gear 13 mounted on the shaft of the charging roller 3 is always The gear 14 is maintained in a meshed state.

When the gear 14 is not driven, the bearing 7 is pulled up by the force of the spring 11 and stops at the position where it abuts the upper end of the slot 9. Therefore, as shown in FIG. 4A, the charging roller 3 supported by the bearing 7 has its rear end side lifted and tilted. In this state, the lower end of the bearing 8 in contact with the lower end of the elongated hole 10 on the front side serves as a fulcrum, and all the portions of the charging roller 3 located on the inner side of the bearing 8 on the front end side are lifted up to the photoconductor drum. 2. Make sure to move to a position away from the surface of 2.

On the other hand, when the gear 14 is driven clockwise in FIG. 3, a tangential force F acts on the meshing portion between the gear 13 and the gear 14, as shown in FIG. 5B. Force F
Is larger than the lifting force of the spring 11,
The force F causes the gear 13 to move downward. That is, the bearing 7 that supports the charging roller 3 moves in the circumferential direction of the gear 14 along the elongated hole 9, and the charging roller 3 moves to the photosensitive drum 2.
Move toward. Then, the movement of the bearing 7 stops when the outer periphery (lower end) of the bearing 7 reaches the lower end of the elongated hole 9. In this state, the slot 9 is formed so that the positional relationship between the charging roller 3 and the photosensitive drum 2 is optimized (for example, the charging roller 3 is pressed against the photosensitive drum 2 with a predetermined pressure).
The lower end position of is predetermined. Therefore, at this time,
The charging roller 3 is arranged at a position where the entire image area on the photosensitive drum 2 can be charged, as shown in FIG.

When the lower end of the bearing 7 reaches the lower end of the elongated hole 9, the movement of the gear 13 is stopped, so that a counterclockwise rotational force is applied to the gear 13 as the gear 14 rotates. . In this case, the charging roller 3 receives the rotational force of the photosensitive drum 2 in contact therewith and rotates so as to rotate with it, but the rotation of the gear 13 causes the charging roller 3 to rotate more reliably.

When the image forming operation is completed, the driving of the gear 14 is stopped, so that the elastic force of the spring 11 causes
The bearing 7 is lifted, and the charging roller 3 moves again to the position retracted from the photosensitive drum 2.

In the above embodiment, only the positioning of the charging roller 3 has been described, but the transfer roller 5 and the developing roller 41 are also positioned by the same structure as the positioning mechanism of the charging roller 3 shown in the above embodiment. can do. The transfer roller 5 is normally the photosensitive drum 2
When it is applied to the transfer roller 5, it can be configured to be separated from the photoconductor 2 by its own weight, so that the spring 11 becomes unnecessary. Further, when applied to a developing roller, it is difficult to prevent toner leakage with a configuration in which the roller unit moves, so it is necessary to configure the entire developing unit to move.

[0037]

As described above, according to the first and second aspects of the present invention, the roller member is provided at a position close to and away from the photoconductor with a contact / separation mechanism having a low cost and a simple structure. It can be positioned reliably. Therefore, according to the invention of claim 3, since the spring member (11) is further provided as the separating means, even if the roller member is arranged above the photoconductor, A force in the separating direction can always be reliably applied to the roller member.

Further, according to the invention of claim 4, when the roller member is the charging roller, the same portion of the charging roller and the photosensitive member is not left in contact with each other, and the photosensitive member is not left. Of pollution is prevented. Further, when the roller member is a transfer roller, the same portion of the transfer roller and the photoconductor is not left in contact with each other, and the photoconductor can be prevented from being contaminated. If the transfer paper becomes jammed while passing between the transfer rollers, the transfer paper can be easily removed. When the roller member is the developing roller, it is possible to prevent the background charge from being generated on the image bearing member by the reversely charged toner on the developing roller while the operation is stopped (at the time of non-developing).

[Brief description of drawings]

FIG. 1 is a front view showing a main part of an image forming apparatus according to an embodiment.

FIG. 2 is a perspective view showing the periphery of the charging roller 3 of FIG.

FIG. 3 is a partially enlarged front view showing the vicinity of the rear end of the charging roller shaft.

FIG. 4 is a side view showing the periphery of the charging roller 3 of FIG.

[Explanation of symbols]

1: Static elimination lamp 2: Photosensitive drum 3: Charging roller 4: Developing unit 5: Transfer roller 6: Cleaning blade 7: Bearing behind unit side plate 8: Bearing on front side of unit side plate 9: Long hole behind unit side plate 10: Unit Side Plate Front Side Long Hole 11, 12: Spring 13, 14: Gear T: Toner Pf: Front Side Plate Pr: Rear Side Plate EXP: Exposure Section

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location G03G 15/16 103 21/14

Claims (4)

[Claims] 1. A roller positioning device for an image forming apparatus, comprising: a photoconductor for forming an image; and at least one roller member disposed around the photoconductor; wherein the roller member is rotatably supported and A shaft supporting means for supporting at least one end of the shaft of the roller member so as to be movable in a direction substantially perpendicular to the shaft between a position close to the photosensitive member and a position separated from the photosensitive member; A separating means for applying a force in a direction in which it moves to a position away from the photoconductor; a force for rotationally driving the roller member and a force for moving it to a position close to the photoconductor at a predetermined operation. A roller positioning device for an image forming apparatus, which is provided with a driving means for giving or reducing the force when the operation is stopped. 2. The driving means includes a driven rotating member mounted on a shaft of the roller member and a driving rotating member constantly engaged with the driven rotating member, and the shaft supporting means includes the driving rotating member. The roll of the image forming apparatus according to claim 1, further comprising a guide hole formed in an arc shape centered on a rotation center of the image forming apparatus.
La positioning device. 3. The roller positioning device for an image forming apparatus according to claim 1, wherein the separating means is a spring member having one end connected to a fixing member and the other end connected to a bearing of the roller member. apparatus. 4. The roller of the image forming apparatus according to claim 1, wherein the roller member is at least one of a charging roller of a charging device, a transfer roller of a transfer device, and a developing roller of a developing device. Positioning device.