JPH07239601A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device which forms high quality image by preventing the surface to be electrified of a belt-like photoreceptor from being deflected and soiled by the electrifying member at the time of drive, thereby keeping electrification performance uniform, in the case of electrifying the surface to be electrified of the belt-like photoreceptor by the contact of the electrifying member. CONSTITUTION:The image forming device equipped with the electrifying member 2 for electrifying the electrification surface of the belt-like photoreceptor 1 in contact with it is provided with a backup roller 3 arranged opposite to the electrifying member 2 with the belt-like photoreceptor 1 between them, a pressure means 4 for pressing the electrifying member 2 against the backup roller 3 via the photoreceptor 1, a drive roller 6 arranged immediately downstream from the backup roller 3 which drives the photoreceptor 1, and a drive means for driving the backup roller 3 by the driving force of the drive roller 6.

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 an electrophotographic copying apparatus, a facsimile apparatus, a printer apparatus, a printing apparatus, an image scanner, or a multifunction machine in which all or a part of them is integrated. More specifically, the present invention relates to an image forming apparatus including a charging member that contacts and charges a charging surface of a belt-shaped photoreceptor.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine, a facsimile machine, a printer, a printing machine, an image scanner, or a multi-function machine in which all or a part of them is integrated, a surface of a photoconductor is used. Toner obtained by irradiating the surface of the photoconductor with image information consisting of light in a state where the toner is uniformly charged to form an electrostatic latent image, and applying toner from the developing device to the electrostatic latent image. An image is formed by transferring and fixing the image on a transfer paper.

A contact charging device in a conventional electrophotographic image forming apparatus will be described with reference to FIG. The unit composed of the charging roller 102 and the drum photosensitive member 101 in the electrophotographic copying machine is provided on the left and right sides as shown in the figure in order to avoid wear due to constant contact between the two before being assembled to the copying machine body. It is separated by a spacer 120. The spacer 120 is provided between the charging unit 10 and the charging roller 10 during the period from the shipment of the unit made into a cartridge from the manufacturing factory to the mounting of the unit on the copying apparatus body.
2 and the drum photoconductor 101 are prevented from contacting with each other. After being mounted on the body of the copying apparatus, the left and right spacers 120 shown in the figure are removed so that the charging roller 102 and the drum photoconductor 101 are always in contact with each other. (See Japanese Patent Laid-Open No. 2-39169). Further, as shown in FIG. 8, in a device using a solenoid 121 and a lever 122 for moving the charging roller 102a, the charging roller 102a and the drum photosensitive member are rotated by rotating the lever 122 about a fulcrum 122a by the solenoid 121. A configuration is also known in which contact with and separation from 101a is performed.

Further, a non-elastic charging member is provided on the surface of a flexible endless belt-shaped member to be charged, and an elastic pressing member is provided on the back surface for charging, so that a softening agent is not included. There is also known a contact charging device in which an inelastic charging member does not contaminate an object to be charged, does not cause deformation and does not repeat deformation (see JP-A-5-107869).

Further, a belt holding member for rotatably supporting the latent image bearing member is provided on the side opposite to the charging member at a position slightly displaced from the contact portion between the belt-shaped latent image bearing member and the charging member. A contact charging type image forming apparatus is also known in which the nip width between the image carrier and the charging member is maintained (see Japanese Patent Laid-Open No. 4-157484). However, in the conventional contact charging type image forming apparatus, when the charging surface of the belt-shaped photosensitive member is contacted and charged by the charging member, the charging surface of the belt-shaped photosensitive member may be deformed by driving or due to the charging member. There is a problem in that the consideration for preventing the generation of contamination is not sufficient and the charging performance cannot be kept uniform.

[0006]

In the above-mentioned conventional image forming apparatus, when the charging member is brought into contact with the charging surface of the belt-shaped photosensitive member to charge it, the charging surface of the belt-shaped photosensitive member is driven at the time of driving. There is a problem that it is not possible to prevent the bending of the photoconductor and the occurrence of contamination of the photoconductor by the charging member, and it is not possible to maintain uniform charging performance.

[0007]

SUMMARY OF THE INVENTION Therefore, the present invention is intended to solve such a problem. That is, the present invention prevents the charging surface of the belt-shaped photosensitive member from being bent during driving or from being contaminated due to the charging member when the charging member is brought into contact with and charged by the charging surface of the belt-shaped photosensitive member. It is an object of the present invention to provide an image forming apparatus in which a high quality image is formed by maintaining uniform charging performance.

[0008]

In order to achieve the above object, the present invention provides an image forming apparatus including a charging member that contacts a charging surface of a belt-shaped photoreceptor to charge it.
A backup roller that is arranged so as to face the belt-shaped photosensitive member so as to be sandwiched between the charging member and the charging member, a pressing unit that presses the charging member to the backup roller via the belt-shaped photosensitive member, and a backup roller of the backup roller. Immediately after that, it has a driving roller which is arranged on the downstream side and drives the belt-shaped photosensitive member, and a driving means which drives the backup roller by the driving force of the driving roller, and the charging member is interlocked with the backup roller. A roller-shaped charging roller that is rotatably driven via a means,
The outer peripheral speed (Vb) of the drive roller is the same as or faster than the outer peripheral speed (Va) of the backup roller (Va).
b ≧ Va), the charging roller is configured to separate from the charging surface of the belt-shaped photoconductor when the belt-shaped photoconductor is driven in the direction opposite to the traveling direction during image recording. It is characterized by

[0009]

In the image forming apparatus having the above-described structure, the image forming apparatus is provided downstream of the backup roller disposed in a position facing the charging member that comes in contact with and separated from the belt-shaped photoconductor, and is located downstream in the driving direction of the belt-shaped photoconductor. When the charging roller contacts the charging surface of the belt-shaped photoreceptor to charge it by driving the belt-shaped photoreceptor and the backup roller, the charging surface of the belt-shaped photoreceptor is driven. Therefore, it is possible to provide an image forming apparatus in which high-quality images are formed by preventing the bending of the sheet and the occurrence of contamination by the charging member and uniformly maintaining the charging performance.

[0010]

Embodiments of the present invention will now be described with reference to the drawings. In FIG. 1, the surface potential of the charged surface of the belt-shaped photosensitive member 1 that is charged becomes a reference potential of 0V to 150V by being irradiated with light from the static elimination lamp 8 located on the downstream side. Next, the belt-shaped photoreceptor 1 is charged by the charging member 2 located further downstream so that the surface potential of the charged surface of the belt-shaped photoreceptor 1 becomes around -1100V. The backup roller 3 is arranged at a position facing the charging member 2 with the belt-shaped photosensitive member 1 interposed therebetween, and the charging member 2 is pressed against the backup roller 3 by the pressing means 4 composed of a spring.

The driving roller 6 is arranged downstream of the backup roller 3 in the driving direction A of the belt-shaped photosensitive member 1 and drives the belt-shaped photosensitive member 1 to rotate in the traveling direction indicated by an arrow A. It is like this. Further, the drive roller 6 drives the backup roller 3 by the drive force transmission means 5 such as a timing belt. The drive roller 6
The outer peripheral speed (Vb) is the same as or faster than the outer peripheral speed (Va) of the backup roller 3 (Vb ≧ Va).

Since the backup roller 3 and the charging member 2 sandwich the belt-shaped photosensitive member 1 at a predetermined pressure, the outer peripheral speed (Vb) of the drive roller 6 is greater than the outer peripheral speed (Va) of the backup roller 3. Slow speed (Vb <
Va) causes a phenomenon in which the belt-shaped photoconductor 1 is loosened between the charging member 2 and the drive roller 6 due to the driving force that conveys the belt-shaped photoconductor 1, and the drive roller 6 and the belt-shaped photoconductor 1 are separated from each other. Looseness occurs between them, the linear velocity at which the belt-shaped photosensitive member 1 is conveyed is changed, and there is a problem that the formed image is disturbed.

However, in the present invention, the outer peripheral speed (Vb) of the drive roller 6 is set to the outer peripheral speed (Va) of the backup roller 3.
By setting the same speed or a higher speed (Vb ≧ Va), it is possible to stabilize the linear velocity at which the belt-shaped photosensitive member 1 is conveyed and prevent the occurrence of defects that cause the formed image to be disturbed. Digital recording image information sent from an image reading device (not shown) or the like is received by a line driver circuit (not shown) and then amplified by a laser driver circuit (not shown). This digital recording image information is a 1-bit (recording / non-recording) binary signal per pixel,
The laser driver circuit activates the laser diode 9 in response to the binarized signal.

The laser light emitted from the laser diode 9 is applied to the belt-shaped photosensitive member 1 to form an image. The surface potential of the belt-shaped photoconductor 1 in the image portion irradiated with the laser light is 0V to -290V, and the developing roller 10a is biased by the developing roller 10a in the next developing unit 10 to the image portion. Therefore, the developing unit 10
The toner 10b inside adheres to form a toner image 10c. On the other hand, the background portion of the non-image portion remains around -1100V, so that the toner 10b does not adhere.

The surface of the belt-shaped photosensitive member 1 on which the toner image 10c is formed is rotated by a driving roller 6 and is rotated to move the front end portion of the transfer paper 12 conveyed from the paper feeding device 11 and the image portion. The toner image 1 on the surface of the belt-shaped photoconductor 1 is conveyed at the same timing at the transfer unit 13 and is conveyed.
0c is transferred to the transfer paper 12, and the transfer paper 12 is separated by the curvature of the separating portion 13a. The separated transfer paper 12 is sent to the fixing unit 14, and the toner image 10c is fused to the transfer paper 12 by heat and pressure to form an image.
Are discharged and stored.

On the other hand, remaining on the surface of the belt-shaped photosensitive member 1,
The residual toner 10b is scraped off by the cleaning blade 15a of the cleaning unit 15, the surface of the belt-shaped photosensitive member 1 is completely free of the toner 10b, and the process proceeds to the next image forming step again. The belt-shaped photosensitive member 1 and the charging member 2 may be mounted in one cartridge as a minimum unit. The charging member 2 may have any shape such as a roller, a blade, or a brush as long as it maintains the charging performance uniformly, but the following description will be made in more detail particularly in the case of a roller shape. explain. However, since the other shapes are similar, detailed description thereof will be omitted.

2 and 3 are a partial cross-sectional perspective view and a DD cross-sectional view showing a main structure of an image forming section to which the present invention is applied. The charging roller 2a as the charging member 2 is made of metal. It has a structure in which a conductive elastic member 2c is wound around the outer periphery of a cored bar 2b, and a voltage is applied by a power source (not shown) to charge the charging surface of the belt-shaped photoreceptor 1. The backup roller 3 is arranged at a position facing the charging roller 2a via the belt-shaped photosensitive member 1, and when the charging roller 2a is pressed by the pressing unit 4, the backup roller 3 and the belt-shaped photosensitive member 1 of the elastic member 2c on the outer periphery are provided. The contact portion is slightly depressed to form a uniform nip portion in the axial direction.

The dent amount of the elastic member 2c is 0.3 m.
Since it is m or less, the position of the charging roller 2a does not greatly vary, and the interlocking means 7 for driving the charging roller 2a is used.
Since the gears 7a and 7b are tooth height gears, the rotational force is reliably transmitted, and the gears 7a and 7b do not interfere with each other. The gear 7a has its shaft center fixed by the shaft end of the backup roller 3a, and the gear 7b has its shaft center fixed by the shaft end of the charging roller 2a.
Further, both gears 7a and 7b are in mesh with each other.

The backup roller 3 is made of a conductive material, and a voltage of about -150 V is applied by a power source (not shown). The backup roller 3 is preferably a conductive elastic material and at the same time has a hardness of 70 degrees or more, and is preferably made of metal.
By doing so, the charging roller 2a does not largely invade the backup roller 3, a proper nip is formed, and normal charging performance can be kept uniform. Therefore, the backup roller 3 can suppress the change in the nip amount, which largely changes the position of the charging roller 2a due to the difference in the circumferential length of the belt-shaped photosensitive member 1, the tension roller pressure, and the like, and the normal charging performance can be kept uniform.

A bearing member 2d for supporting both ends of the charging roller 2a supports both ends of the charging roller 2a and is held by the unit side plate 16 so as to be vertically movable.
The compression spring 4a functions to press the shaft end of the charging roller via the bearing members 2d that support both ends of the charging roller 2a to form an appropriate nip in the charging roller 2a. The cover member 4b supports the compression spring 4a from above, and is detachable so that the charging roller 2a can be detached from the unit side plate 16.

The drive means 5 is located at the shaft end opposite to the interlocking means 7, and has a timing belt 5a fixed to the drive shaft 6b of the drive roller 6 and a timing pulley 6c and a backup roller shaft 3a of the backup roller 3. By being stretched between the timing pulley 3b fixed to the
The rotational force of the drive shaft roller 6 is transmitted to the backup roller 3. The driving roller 6 is arranged immediately downstream of the backup roller 3 in the driving direction of the belt-shaped photoconductor 1 and drives the belt-shaped photoconductor 1 by the driving means 5 for driving the backup roller 3. Therefore, the belt-shaped photosensitive member 1 is pulled on the upstream side immediately before the driving roller 6. Therefore, as compared with the case where the driving roller 6 is arranged on the upstream side of the charging position, the belt-shaped photosensitive member 1 is prevented from sagging on the upstream side immediately before the charging roller 2a, and no waviness is generated, so that it is always appropriate. Since such a nip is obtained, normal charging performance can be kept uniform.

The coupling member 6a is fixed to one end of the drive shaft 6b of the drive roller 6, and the rotational force sent from a drive source (not shown) from the coupling member 17b fixed to the drive shaft 17a of the apparatus main body 17 side. Is transmitted. The drive source (not shown) is configured to be controlled to perform a rotation operation opposite to the rotation operation of the drive of the normal image formation for a predetermined time after completion of the drive operation of the normal image formation,
The charging roller 2a is rotated by the opposite rotation operation when the belt-shaped photoconductor 1 is driven in the opposite direction.
It is designed to be separated from the charged surface of. Such an operation is realized by the cam 18.

That is, the cam 18 attached to the shaft portion at the other end of the charging roller 2a includes a one-way bearing 18a and a convex portion 18
b, and the one-way bearing 18 has a charging roller 2a.
Is press-fitted and fixed to the other end of the. The above one-way bearing 1
8a is configured to be in a free state with the charging roller 2a, that is, the rotational force of the charging roller 2a is not transmitted to the cam 18 during a normal image forming driving operation. Also, after the normal driving operation of image formation is completed, when the charging roller 2a is rotated in the reverse direction, the rotational force of the charging roller 2a is transmitted to the cam 18.

The main body of the cam 18 at the time of the drive operation of the normal image formation can bring the charging roller 2a close to the charging surface of the belt-shaped photoreceptor 1 and separate it by the reverse operation after the completion of the normal image formation. It is shaped like this. That is, cam 1
By supporting the outer peripheral surface of the main body of 8 on the upper surface of the cam receiving member E so as to be rollable, the charging roller 2a can be moved up and down according to the rotation angle of the cam 18. The tension spring 19 connects the charging roller 2a to the belt-shaped photoreceptor 1
When the cam 18 operates so as to move from a position separated from the charging surface (upper surface) of
Rotational force in the same direction as the rotation direction of the charging roller 2a (reversed in FIG. 2) so that the cam 18 can surely return to the predetermined position when the charging roller 2a takes a position close to the charging surface of the belt-shaped photoreceptor 1. A clockwise rotating force) is applied to the cam 18.

The stopper 20 holds the cam 18 so as not to rotate further so that the charging roller 2a can maintain a predetermined position close to the charging surface of the belt-shaped photosensitive member 1. The support member 21 is the tension spring 1 described above.
The other end of 9 is fixed. Incidentally, in the one-component developing method in which the charging surface of the belt-shaped photoreceptor 1 and the developing roller 10a are in contact,
When the image formation is completed, charging by the charging roller 2a,
When the voltage application to the developing roller 10a is turned off, the potential of the belt-shaped photosensitive member 1 and the potential on the charging roller 2a become 0 V, and the toner 10b of the developing roller 10a is contacted by the contact pressure.
However, there is a problem in that it adheres to the belt-shaped photoreceptor 1. However, if a voltage is applied to the substrate on the back side of the belt-shaped photosensitive member 1 and a potential difference is provided between the belt-shaped photosensitive member 1 and the developing roller 10a, the toner on the developing roller 10a easily adheres to the belt-shaped photosensitive member 1. Can be prevented.

FIG. 4 is a perspective view showing a concrete structure of the interlocking means. Gears 7a and 7b are formed on the shaft end side protruding from the respective ends of the gear 7a and the gear 7b constituting the interlocking means 7. A coaxial circular flange portion 7c is integrally formed.
The two flange portions 7a may be dimensioned so that they are always in contact with each other, or may be dimensioned so that they are in contact only when the other end of the charging roller is lifted. As described above, this structure is configured such that when one end of the charging roller 2a is used as a fulcrum and the other end is lifted to separate from the charging surface of the belt-shaped photoreceptor 1, the gear 7a and the gear 7b are separated from each other. When the tooth surface is used as the fulcrum, the flange portions 7c can be used as fulcrums in order to eliminate the problem that the tooth surface is flawed due to concentrated load and normal drive transmission cannot be performed.

FIG. 5 is a front view showing the structure of the cam portion.
During a normal image forming drive operation, the charging roller 2a rotates in the direction of arrow B shown in the figure. At this time, since the one-way bearing 18a is free from the charging roller 2a, the cam 18 is positioned by the protrusion 18b of the cam 18 contacting the stopper 20 only by the pulling force of the tension spring 19. The roller 2a is the belt-shaped photoreceptor 1
Maintain a position close to the charged surface of.

FIG. 6 is a front view showing the operation of the cam portion.
When the charging roller 2a performs a reverse rotation operation after the end of normal image formation, the rotational force is transmitted to the cam 18 via the one-way bearing 18a and rotates clockwise in the direction of arrow C shown in the drawing, and the charging roller 2a is rotated. One side 2a is lifted with the flange portion 7c as a fulcrum, and is separated from the charging surface of the belt-shaped photoreceptor 1.

Therefore, the state in which the charging roller 2a of the apparatus main body 17 and the charging surface of the belt-shaped photosensitive member 1 are kept in contact with each other is automatically avoided. Therefore, a part of the material of the charging roller 2a or a substance in the air The compound of (3) contaminates the charged surface of the belt-shaped photosensitive member 1, reduces the adhesive force of the toner 10b, and prevents the occurrence of abnormal images such as white spots in the formed image. It is possible to provide an image forming apparatus in which a high-quality image is formed by preventing the bending during driving and the occurrence of contamination by the charging roller 2a and keeping the charging performance uniform.

[0030]

Since the present invention is constructed as described above, the belt-shaped photosensitive member is driven immediately after the backup roller arranged at a position opposed to the charging member that comes in contact with and separates from the belt-shaped photosensitive member. Since the driving roller is arranged on the downstream side in the direction to drive the belt-shaped photosensitive member and the backup roller, when the charging member is brought into contact with the charging surface of the belt-shaped photosensitive member to charge it, It is possible to provide an image forming apparatus capable of forming a high-quality image by preventing the charging surface from being bent during operation and from being contaminated by the charging member, and thus uniformly maintaining the charging performance. It was

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating an outline of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a developed perspective view illustrating an outline of a main part of the image forming apparatus according to the embodiment of the present invention.

FIG. 3 is a cross-sectional view taken along line DD of the main part of the image forming apparatus showing the embodiment of the present invention in FIG.

FIG. 4 is a partially enlarged perspective view illustrating a main part of the image forming apparatus according to the exemplary embodiment of the present invention.

FIG. 5 is an explanatory diagram illustrating a state of another portion of a main part of the image forming apparatus according to the embodiment of the present invention.

FIG. 6 is an explanatory diagram illustrating another state of another part of the main part of the image forming apparatus according to the embodiment of the present invention.

FIG. 7 is an explanatory diagram illustrating a state of a part of a conventional contact charging device.

FIG. 8 is an explanatory diagram illustrating a state of a portion of another conventional contact charging device.

[Explanation of symbols]

1 ... Belt-shaped photoreceptor, 2 ... Charging member, 2a ...
-Charging roller, 2b ... core metal, 2c ... elastic member,
2d ... Bearing member, 3 ... Backup roller, 3
a ... backup roller shaft, 3b ... timing pulley, 4 ... pressurizing means, 4a ... compression spring, 4b ... cover member, 5 ... driving force transmitting means,
5a ... Timing belt, 6 ... Drive roller, 6
a: coupling member, 6b: drive shaft, 6c
..Timing pulley, 7 ... Interlocking means, 7a ...
Gear, 7b ... Gear, 7c ... Flange part, 8 ...
・ Static elimination lamp, 9 ... Laser diode, 10 ...
Developing unit, 10a ... Developing roller, 10b ...
Toner, 10c ... Toner image, 11 ... Paper feeding device,
12 ... Transfer paper, 13 ... Transfer part, 13a ... Separation part, 14 ... Fixing device, 15 ... Cleaning unit, 15a ... Cleaning roller, 16 ...
Unit side plate, 17 ... Device body, 17a ... Drive shaft, 17b ... Coupling member, 18 ... Cam,
18a ... One-way bearing, 18b ... Convex part, 19
... Tension spring, 20 ... Stopper, 21 ...
..Supporting member, 101 ... Drum photosensitive member, 102a
..Charging rollers, 120 ... Spacers, 121 ...
Solenoid, 122 ... Lever.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuhiro Shima 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (4)

[Claims] 1. An image forming apparatus provided with a charging member for contacting and charging a charging surface of a belt-shaped photoreceptor,
A backup roller that is arranged so as to face the belt-shaped photosensitive member so as to be sandwiched between the charging member and the charging member, a pressing unit that presses the charging member to the backup roller via the belt-shaped photosensitive member, and a backup roller of the backup roller. An image forming apparatus comprising: a driving roller which is disposed immediately downstream of the driving roller and drives the belt-shaped photosensitive member; and a driving unit which drives the backup roller by a driving force of the driving roller. 2. The image forming apparatus according to claim 1, wherein the charging member is a roller-shaped charging roller that is rotationally driven by the backup roller via interlocking means. 3. The peripheral velocity (Vb) of the drive roller is
The image forming apparatus according to claim 1, wherein the image forming apparatus is configured to have a speed equal to or higher than an outer peripheral speed (Va) of the backup roller (Vb ≧ Va). 4. The charging roller is configured to separate from the charging surface of the belt-shaped photoconductor when the belt-shaped photoconductor is driven in a direction opposite to the traveling direction during image recording. 2. The image forming apparatus according to 2.