JP2010243804A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which allows the surface of an image carrier to be uniformly and stably charged to a desired state, allows a charging member to be cleaned and made compact, and prevents creep deformation of the charging member. <P>SOLUTION: A charging device 2A includes: a cleaning roller 22; an elastic charging member 21 in the form of a sleeve, which is disposed between a photoreceptor 1 and the roller 22; and a regulating member 23 which holds the charging member 21 with the roller 22 and brings the member 21 into pressure-contact with the surface of the photoreceptor 1. An arm member 24 is connected so as to be swingable around the rotation center line of the roller 22, and the regulating member 23 is supported by the arm member 24. When the charging device is not in use, the charging member 21 is separated and retreated from the surface of the photoreceptor 1 by reverse rotation of the roller 22 and the like. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multifunction machine that combines two or more of these.

  There are various types of image forming apparatuses such as a copying machine, a printer, a facsimile machine, and a multifunction machine combining two or more of these. At least an image forming unit capable of forming a toner image by charging the surface of the latent image carrier) with a charging device, performing image exposure on the charged area to form an electrostatic latent image, and developing the electrostatic latent image. And an image forming apparatus that can transfer a toner image formed by the image forming unit to a transfer target.

  Various types of charging devices in this type of image forming apparatus are also known. As a charging device that has been known for a long time, there is a charging device using corona discharge. Further, a contact charging type charging device using a charging roller or a charging brush is also well known as one that generates less ozone than a charging device using corona discharge.

  Recently, as a type of contact-type charging device, a roller-type charging member that can be elastically deformed is used to form a wide charging nip, and the surface of the image carrier is stably stabilized under the charging nip. There has also been proposed a charging device for obtaining a charged state.

  For example, in Japanese Patent Laid-Open No. 2006-163197, a charging roller formed of a conductive elastic material is pressed against a surface of a photosensitive drum while being rotatably held by a conductive block, and has a width in the moving direction of the photosensitive drum. The formation of a wide charging nip is described.

  Japanese Patent Application Laid-Open No. 10-333400 describes that an elastically deformable sleeve-shaped charging member is brought into contact with the surface of an image carrier with a wide nip width using a plurality of rollers.

JP 2006-163197 A Japanese Patent Laid-Open No. 10-333400

  However, the charging devices described in Japanese Patent Application Laid-Open Nos. 2006-163197 and 10-333400 are still large enough to meet the demand for downsizing of today's image forming apparatuses, and a charging member cleaning unit is provided. Then, it will further increase in size.

  Further, the elastically deformable charging member, whether it is in the form of a solid roller or a sleeve, remains pressed against the image carrier as when the image forming apparatus is not used for a long period of time. If left unattended, creep deformation occurs on the surface of the charging member, and if the surface of the image carrier is charged while the deformation is present, charging failure occurs, and as a result, image failure occurs. This phenomenon is particularly likely to occur in a sleeve-shaped charging member.

  Therefore, the present invention charges the surface of the image carrier that is rotationally driven in a certain direction with a charging device, forms an electrostatic latent image by exposing the charged area to an image, and develops the electrostatic latent image. An image forming apparatus comprising one or more image forming units capable of forming a toner image and capable of transferring a toner image formed by the image forming unit to a transfer target, wherein at least one image forming unit In the charging device, a wide charging nip is formed between the charging member and the image carrier, and the surface of the image carrier can be uniformly and stably charged to a desired charging state. The image forming apparatus is capable of forming a good image while reducing the size of the entire image forming apparatus when the charging apparatus is not used, and can prevent the creep deformation of the charging member when the charging apparatus is not used. The It is an object of the present invention to provide.

In order to solve the above problems, the present invention provides:
The surface of the image carrier that is rotationally driven in a certain direction can be charged by a charging device, image exposure can be performed on the charging area to form an electrostatic latent image, and the electrostatic latent image can be developed to form a toner image. An image forming apparatus that includes one or more image forming units and is capable of transferring a toner image formed by the image forming unit to a transfer target.
The charging device in at least one image forming unit includes a cleaning roller arranged in parallel to the image carrier, an elastic charging member in the form of a sleeve arranged between the image carrier and the cleaning roller, and the charging member A charging member position regulating member disposed in parallel with the cleaning roller and sandwiching the charging member between the cleaning roller,
An arm member is connected to the cleaning roller so as to be swingable about a rotation center line of the roller, and the restriction member is supported by the arm member,
By rotating the cleaning roller in the same rotational direction as the image carrier, the charging member sandwiched between the cleaning roller and the regulating member is brought into pressure contact with the surface of the image carrier to move the surface of the image carrier. A charging nip having a width in the direction is formed and the arm member swings to a position where it comes into contact with the first stopper,
An image forming apparatus is provided in which the charging member is separated and retracted from the image carrier by swinging the arm member in the opposite direction from the state where the arm member is in contact with the first stopper.

  The image forming apparatus according to the present invention may be a monochrome image forming apparatus having one image forming unit or a color image forming apparatus having a plurality of image forming units each capable of forming a toner image of the assigned color.

  The “transfer object” to which the toner image is transferred is generally a recording medium such as a recording paper in a monochrome image forming apparatus, and the toner image on the image carrier is different from that in a color image forming apparatus. When an intermediate transfer body that performs primary transfer is employed, it can be said that both the intermediate transfer body and the recording medium on which the toner image is secondarily transferred from the intermediate transfer body are transferred. Some color image forming apparatuses also use a direct transfer method in which a toner image on an image carrier is directly transferred to a recording medium. The present invention can also be applied to such an image forming apparatus.

  According to the image forming apparatus of the present invention, in at least one image forming unit, the image carrier applies an image carrier charging voltage to a sleeve-shaped elastic charging member that contacts the image carrier (for example, a charging member position regulating member). The charging member can be charged by applying a charging voltage to the charging member.

  Thus, when charging the image carrier with the elastic charging member in the form of a sleeve, the cleaning roller is rotationally driven in the same rotational direction as the image carrier so that it is sandwiched between the cleaning roller and the charging member position regulating member. The charging member is swung together with the arm member supporting the regulating member until the arm member comes into contact with the first stopper, thereby stably pressing the charging member against the surface of the image carrier. It is possible to stably form a charging nip having a width in the moving direction of the image carrier surface.

  Thus, the surface of the image carrier can be uniformly and stably charged to a desired potential via the charging nip.

  Further, since the cleaning roller is in contact with the charging member, contamination of the charging member can be suppressed, and in this respect as well, the surface of the image carrier can be favorably charged to a desired potential.

  When it is not necessary for the charging member in the form of a sleeve to contact the image carrier, such as when the image forming apparatus is not used, the arm member is swung in the opposite direction from the state where the arm member is in contact with the first stopper. By moving the charging member, the charging member is moved away from the image bearing member, thereby preventing creep deformation of the charging member.

  Thus, even when a charging device including a charging member in the form of a sleeve is not used for a long period of time, creep deformation of the charging member can be prevented, and when the surface of the image carrier is then charged using the charging member, the image carrier Can be satisfactorily charged, and the surface of the image bearing member can be uniformly and stably charged at a desired potential, and a good image can be formed.

  Thus, in the charging device including the sleeve-shaped elastic charging member and its cleaning roller, the surface of the image carrier can be uniformly and stably charged to a desired potential, and the charging member can be cleaned, and the charging device is used. In this case, the charging member can be prevented from being creep-deformed, and can be reduced in size with a simple structure including a cleaning roller, a charging member, a regulating member, and a support arm. As a result, the entire image forming apparatus can be reduced in size. A good image can be formed.

In the image forming apparatus according to the present invention, the swinging of the arm member in the opposite direction for moving the charging member away from the image carrier can be performed, for example, as follows.
(1) The cleaning roller is rotated in the reverse direction.
(2) The charging roller is moved away from the image bearing member by the reverse rotation of the cleaning roller, and the arm member is in contact with the second stopper.

(3) In the above (1) and (2), the charging member is moved away from the image carrier by rotating the cleaning roller in the reverse direction, and the arm member is swung in the opposite direction from the state where the arm member is in contact with the first stopper. In addition, the spring is assisted by the spring acting on the arm member. In this case, the operation of rotating the cleaning roller in the same rotational direction as that of the image carrier to bring the charging member into contact with the image carrier and swinging the arm member to the position in contact with the first stopper is the elasticity of the spring. Made against resilience.

(4) By stopping the rotation of the cleaning roller and making the roller rotatable, the charging member, the charging member position restricting member, and the arm member supporting the restricting member are caused to move in the opposite direction. By swinging, the charging member is moved away from the image carrier.
(5) In (4), a spring for assisting the separation and retraction operation is provided when the charging member is separated and retracted from the image carrier, and the spring is performed with the assistance of the spring. Also in this case, the operation of rotating the cleaning roller in the same rotational direction as the image carrier to bring the charging member into contact with the image carrier and swinging the arm member to the position in contact with the first stopper is performed by the spring. Made against the elastic restoring force.

As explained above, according to the present invention,
The surface of the image carrier that is rotationally driven in a certain direction can be charged by a charging device, image exposure can be performed on the charging area to form an electrostatic latent image, and the electrostatic latent image can be developed to form a toner image. An image forming apparatus that includes one or more image forming units and is capable of transferring a toner image formed in the image forming unit to a transfer target, wherein the charging device in at least one image forming unit includes: By forming a wide charging nip between the charging member and the image carrier, the surface of the image carrier can be uniformly and stably charged to a desired charging state, and the charging member can be cleaned. Further, it is possible to reduce the size of the image forming apparatus, and further to prevent the occurrence of creep deformation of the charging member when the charging apparatus is not used, and to provide an image forming apparatus capable of forming a good image while reducing the size of the entire image forming apparatus. so That.

1 is a diagram schematically illustrating a configuration of an example of an image forming apparatus according to the present invention. FIG. 2 is a view of a charging device and a photoreceptor in the image forming apparatus of FIG. 1 as viewed from the right side in FIG. FIG. 2 is a diagram illustrating a state in which a charging device in the image forming apparatus of FIG. 1 is disposed at a position for charging a photosensitive member. FIG. 2 is a diagram illustrating a state in which a charging member of a charging device in the image forming apparatus of FIG. 1 is disposed at a position separated and retracted from a photoreceptor. It is a figure which shows the other example of a charging device, and is a figure which shows a mode that this charging device is arrange | positioned in the position which charges a photoreceptor. FIG. 6 is a diagram illustrating a state in which a charging member of the charging device illustrated in FIG. 5 is disposed at a position separated and retracted from the photosensitive member. It is a figure which shows the other example of a charging device, and is a figure which shows a mode that this charging device is arrange | positioned in the position which charges a photoreceptor. It is a figure which shows a mode that the charging member of the charging device shown in FIG. 7 is arrange | positioned in the position which separated and evacuated from the photoconductor.

Hereinafter, an example of an image forming apparatus according to the present invention will be described with reference to the drawings.
FIG. 1 shows an example of an image forming apparatus according to the present invention.
An image forming apparatus 10 in FIG. 1 includes a drum-type photosensitive member 1 that is driven to rotate counterclockwise in the figure as an image carrier. Around the photoconductor 1, a charging device 2A, an image exposure device 3, a developing device 4, a transfer device 5, and a cleaning device 6 are arranged in this order in the photoconductor rotation direction.

  The image forming apparatus 10 is a monochrome image forming apparatus, and the photoreceptor 1, the charging device 2A, the image exposure device 3, and the developing device 4 constitute a toner image forming unit.

  In addition, the image forming apparatus 10 transfers a recording medium supply unit (not shown) and a recording medium S such as recording paper supplied from the recording medium supply unit at a predetermined timing to the transfer member (the transfer member (the transfer member 5) of the photosensitive member 1 and the transfer device 5 In this example, a pair of timing rollers supplied to the transfer roller 51) is included, and a fixing device 7 disposed on the downstream side of the transfer roller 51 in the recording medium conveyance direction is also included.

  Although not limited thereto, the photoreceptor 1 is a negatively chargeable drum type organic photoreceptor in this example, and the surface layer is formed of a resin mainly composed of polycarbonate. The photoreceptor 1 has an outer diameter of 30 mm, and is driven to rotate counterclockwise in FIG. 1 at a predetermined peripheral speed by a photoreceptor drive motor M1 (see FIG. 2).

  The photoreceptor 1 does not need to be negatively charged, and may be positively charged depending on the charging polarity of the toner used in the developing device 4.

  The charging device 2 </ b> A includes a cleaning roller 22 disposed in parallel with the photoreceptor 1, a sleeve-shaped elastic charging member 21 disposed between the photoreceptor 1 and the cleaning roller 22, and a cleaning roller 22 within the charging member 21. And a charging member position regulating member 23 that sandwiches the charging member 21 between the cleaning roller 22 and the cleaning roller 22.

As shown in FIG. 2, the cleaning roller 22 is rotatably supported by the left and right frames F in the image forming apparatus 10 together with the photoreceptor 1.
Arm members 24 are swingably connected to the left and right shaft portions of the cleaning roller 22, and both ends of the regulating member 23 are supported by the left and right arm members 24.

The charging member 21 is not limited thereto, but in this example, the charging member 21 has a sleeve shape (cylinder shape) made of conductive polyamide containing a conductive material (conductive carbon in this example), and has an outer diameter of 8 mm and a thickness of It is in the range of about 0.05 mm to 0.8 mm.
The charging member 21 has elasticity and can be elastically deformed. Furthermore, the elastic member can be elastically deformed so that the diameter of the cross section perpendicular to the longitudinal direction of the charging member 21 changes.

  The charging member 21 is mainly composed of polyamide (PA) as in this example, and is mainly composed of a resin such as polyimide (PI), PFA, PTFE, and mixed with a conductive material to impart conductivity. It may be made of a resin material. Moreover, what consists of rubber | gum which provided electroconductivity may be sufficient.

The cleaning roller 22 is not limited thereto, but in this example, urethane foam (polyurethane foam) is provided around a shaft rod having a diameter of 4 mm and the outer diameter is 8 mm.
As shown in FIG. 2, the cleaning roller 22 can be driven to rotate in the same direction as the photosensitive member 1 (counterclockwise in the example of FIG. 1) by the motor M2.

In this example, the regulating member 23 is an elongated member having a cross-sectional shape that forms a convex arc toward the roller 22, and both end portions are fixedly supported by the arm member 24 so as not to rotate, so that a charging voltage can be applied from the power source PW. It has become.
The restricting member 23 may be a shaft rod having a circular cross section, or may be rotatably supported by the arm member 24.

  The charging member 21 can be pressed against the surface of the photosensitive member 1 as shown in FIG. 1 while being sandwiched between the cleaning roller 22 and the regulating member 23 and has a width in the direction of movement of the photosensitive member 1 surface. Nips can be formed. In this state, a charging voltage can be applied to the charging member 21 from the power source PW via the regulating member 23 to charge the surface of the photoreceptor 1.

  More specifically, in the charging device 2A, as shown in FIG. 3, the cleaning roller 22 and the regulating member are driven by rotating the cleaning roller 22 in the same rotational direction as the photoreceptor 1 (counterclockwise in FIG. 1) by the motor M2. The charging member 21 sandwiched between 23 and 23 is pressed against the surface of the photoconductor 1 to form a wide charging nip having a width in the direction of movement of the surface of the photoconductor 1 and the arm member 24 contacts the first stopper 25. Thus, the charging member 21 is stably disposed at a position for charging the photosensitive member 1, and the surface of the photosensitive member 1 can be uniformly and stably charged to a desired potential.

  Further, when the arm member 24 is in contact with the first stopper 25, the motor M2 is reversed and the cleaning roller 22 is reversed, so that the charging member 21 is opposed to the regulating member 23 and the arm member 24 as shown in FIG. The charging member 21 can be moved away from the surface of the photoreceptor 1 by swinging in the direction until the arm member contacts the second stopper 26. In this way, when the charging member 21 is not used, the charging member 21 can be separated and retracted from the photoreceptor 1 to prevent creep deformation that occurs if the charging member 21 remains in contact with the photoreceptor 1.

  It should be noted that the second stopper 26 may be omitted as long as it is possible to determine the separation / retraction position of the charging member 21 without relying on the second stopper 26 by controlling the time during which the motor M2 is reversely rotated.

  In this example, the charging member 21 can be maintained at the separation retracted position shown in FIG. 4 by the cleaning roller 22 that stops rotating when the motor M2 is stopped. A device for maintaining the charging member 21 at the separate retreat position shown in FIG. 4 may be provided separately. For example, as shown in FIG. 4, the return swinging of the arm member 24 when the charging member 21 is in the separate retreat position can be prevented by a detent member 28 that can enter and leave the swinging track of the arm member 24. For example, a spring offset type solenoid that is turned on when the charging device 2A is used and retracts the member 28 from the arm member track, and is turned off when the charging member 21 is maintained at the separate retreat position to project the member 28 into the arm member track. The member 28 to be driven can be exemplified.

  According to the image forming apparatus 10 described above, the photosensitive member 1 is rotated by the motor M1, and the cleaning roller 22 is rotated by the motor M2 in the same direction as the photosensitive member 1, whereby the arm member 24 is moved as shown in FIG. The charging member 21 is stably brought into pressure contact with the surface of the photosensitive member 1 by being brought into contact with the stopper 25, and a charging voltage is applied from the power source PW to the charging member 21 through the regulating member 23. The surface is charged, image exposure is performed on the charged area by the image exposure device 3 to form an electrostatic latent image, the latent image is developed by a developing device to form a toner image, and the toner image is not shown. Is transferred to the recording medium S conveyed from the recording medium supply unit by the transfer roller 51 to which a transfer voltage is applied, and the transferred toner image is fixed on the recording medium S by heating and pressurization by the fixing device 7 and then out of the apparatus. Can be discharged That. Transfer residual toner and the like on the photoreceptor 1 after the toner image transfer is cleaned by a cleaning device 6.

  When performing image formation, the charging device 2A can stably press the charging member 21 against the surface of the photosensitive member 1 to form a stable wide charging nip, and the surface of the image carrier can be stably stabilized through the charging nip. Therefore, it can be charged to a desired potential.

  In addition, since the cleaning roller 22 is in contact with the charging member 21, it is possible to suppress contamination of the charging member, and in this respect as well, the surface of the image carrier can be favorably charged to a desired potential.

  When the charging device 2A is not used, such as when image formation by the image forming apparatus 10 is not performed (particularly when it is not performed for a long period of time), the arm member 24 is in contact with the first stopper 25 before that. By rotating the motor M2 in reverse and the cleaning roller 22 in reverse, the charging member 21 is moved in the opposite direction together with the regulating member 23 and the arm member 24 as shown in FIG. 4 until the arm member contacts the second stopper 26. The charging member 21 can be moved away from the surface of the photoreceptor 1 by swinging. In this way, when the charging member 21 is not used, the charging member 21 can be separated and retracted from the photoreceptor 1 to prevent creep deformation that occurs if the charging member 21 remains in contact with the photoreceptor 1.

  Thus, creep deformation of the charging member can be prevented, so that when the surface of the photosensitive member 1 is charged next by using the charging member 21, the photosensitive member 1 can be charged satisfactorily, and the surface of the photosensitive member 1 can be more uniformly desired. It can be stably charged to the potential, and a good image can be formed.

  As described above, in the charging device 2A including the elastic charging member 21 in the form of the sleeve and the cleaning roller 22 thereof, the surface of the photoreceptor 1 can be uniformly and stably charged at a desired potential, and the charging member 21 can be cleaned and charged. When the apparatus 2A is not used, creep deformation of the charging member 21 can be prevented, and the structure including the cleaning roller 22, the charging member 21, the regulating member 23, and the arm member 24 has a simple structure and can be downsized. Accordingly, a good image can be formed while reducing the size of the entire image forming apparatus 10.

5 and 6 show a charging device 2B that can be used instead of the charging device 2A.
The charging device 2B is obtained by providing an auxiliary spring 27 in the charging device 2A. As shown in FIG. 5, the auxiliary spring 27 is compressed by the arm member 24 when the charging member 21 is disposed at a position where the photosensitive member 1 is charged. As shown in FIG. 6, when the charging member 21 is retracted away from the photoreceptor 1, the arm member 24 is pushed by the elastic restoring force, and the movement of the charging member 21 to the separate retracting position can be assisted and facilitated. .

  In the charging device 2 </ b> B, depending on the strength of the spring 27, the charging member 21 can be maintained at the separate retreat position even with the spring.

7 and 8 show another example 2C of the charging device.
In the charging device 2C, when the charging member 21 is brought into pressure contact with the surface of the photosensitive member 1, the cleaning roller 22 is driven in the same rotational direction as the photosensitive member 1 to swing the charging member 21 and the like counterclockwise CCW in the drawing to the stopper 25 '. However, when the charging member 21 is moved away from the photosensitive member 1, the driving of the motor M <b> 2 is stopped to enable free rotation, and the charging member 21, the regulating member 23, and the arm member 24 have their own weights as shown in FIG. 8. The charging member 21 and the like are swung clockwise CW in the drawing.

  In the case of the charging device 2C, when the charging member 21 is retracted to the position shown in FIG. 8, an auxiliary spring having the same function as the spring shown in FIGS.

  Although the image forming apparatus 10 described above is a monochrome image forming apparatus, the present invention can also be applied to a color image forming apparatus provided with a plurality of image forming units each capable of forming a toner image of the assigned color.

  In the present invention, a charging device in at least one image forming unit is configured to charge an image carrier at a wide charging nip using an elastic charging member in the form of a sleeve. The present invention can be used to provide an image forming apparatus that can be charged uniformly and stably in a state, can clean the charging member, and can prevent creep deformation of the charging member.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 1 Photoconductor M1 Photoconductor drive motor 2A, 2B, 2C Charging device 21 Charging member 22 Crime roller M2 Cleaning roller drive motor 23 Charging member position regulating member 24 Arm members 25, 25 ′ First stopper 26 Second stopper 27 Auxiliary spring 28 Detent member PW Charging power supply 3 Image exposure device 4 Developing device 41 Developing roller 5 Transfer device 51 Transfer roller 6 Cleek device 7 Fixing device S Recording medium

Claims (4)

The surface of the image carrier that is rotationally driven in a certain direction can be charged by a charging device, image exposure can be performed on the charging area to form an electrostatic latent image, and the electrostatic latent image can be developed to form a toner image. An image forming apparatus that includes one or more image forming units and is capable of transferring a toner image formed by the image forming unit to a transfer target.
The charging device in at least one image forming unit includes a cleaning roller arranged in parallel to the image carrier, an elastic charging member in the form of a sleeve arranged between the image carrier and the cleaning roller, and the charging member A charging member position restricting member disposed in parallel with the cleaning roller and sandwiching the charging member between the cleaning roller,
An arm member is connected to the cleaning roller so as to be swingable about a rotation center line of the roller, and the restriction member is supported by the arm member,
By rotating the cleaning roller in the same rotational direction as the image carrier, the charging member sandwiched between the cleaning roller and the regulating member is brought into pressure contact with the surface of the image carrier to move the surface of the image carrier. A charging nip having a width in the direction is formed and the arm member swings to a position where it comes into contact with the first stopper,
An image forming apparatus, wherein the charging member is moved away from the image carrier by swinging the arm member in the opposite direction from the state where the arm member is in contact with the first stopper.   The image forming apparatus according to claim 1, wherein the swinging of the arm member in the opposite direction for moving the charging member away from the image bearing member is performed by rotating the cleaning roller in the reverse direction.   The image forming apparatus according to claim 2, wherein the charging member is moved away from the image carrier and retreated by rotating the cleaning roller in the reverse direction, and the arm member can be brought into contact with the second stopper.   A spring is provided to assist the separation and retraction operation when the charging roller is separated and retracted from the image carrier by rotating the cleaning roller in the reverse direction from the state where the arm member is in contact with the first stopper. The operation of rotating the cleaning roller in the same rotation direction as that of the image carrier to bring the charging member into contact with the image carrier and swinging the arm member to a position in contact with the first stopper is elastic restoration of the spring. The image forming apparatus according to claim 1, 2 or 3, which is made against a force.

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