JP4957744B2 - Image forming apparatus - Google Patents

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 a sleeve-shaped charging member that can be elastically deformed 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.

  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. It is an object of the present invention to provide an image forming apparatus capable of forming a good image while reducing the size of the entire image forming apparatus.

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. The image forming apparatus includes one or more image forming units and can transfer a toner image formed in the image forming unit to a transfer target. The charging device in at least one image forming unit is an image forming unit. A cleaning roller disposed in parallel with the carrier, an elastic charging member in the form of a sleeve disposed between the image carrier and the cleaning roller, and disposed in the charging member in parallel with the cleaning roller. Charging member position regulation in which the charging member is sandwiched between the cleaning roller and the cleaning roller so as to be driven to rotate (in other words, the circumferential speed of the charging member can be controlled by the cleaning roller). The charging member is pressed against the surface of the image carrier while being sandwiched between the cleaning roller and the regulating member to form a charging nip having a width in the moving direction of the image carrier. The position regulating member is arranged on either the upstream side or the downstream side in the moving direction of the image carrier surface with respect to the line connecting the rotation center line of the image carrier and the rotation center line of the cleaning roller. And the charging member is disposed closer to the one side. When the image carrier and the cleaning roller are driven to rotate, the cleaning roller is driven in the same rotational direction as the image carrier, and the image carrier. The image carrier and the cleaning member are arranged such that a difference is generated between the surface moving speed and the charging member surface moving speed to prevent the charging member from biting into the other side and deforming. To provide an image forming apparatus respectively over la is rotated.

  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 regulating member is installed). The charging member can be charged by applying a charging voltage to the charging member.

  At this time, the charging member is pressed against the surface of the image carrier while being sandwiched between the cleaning roller and the charging member regulating member to form a large charging nip having a width in the moving direction of the image carrier. The body surface can be charged to the desired potential uniformly and stably.

  The charging member regulating member arranged in the charging member is either upstream or downstream in the moving direction of the image carrier surface from the line connecting the rotation center line of the image carrier and the rotation center line of the cleaning roller. The charging member is arranged on one side and the charging member is arranged on the one side. Further, when the image carrier and the cleaning roller are driven to rotate, the cleaning roller is driven in the same rotational direction as the image carrier. In addition, the image carrier and the charging member surface moving speed and the charging member surface moving speed may be different from each other so that the charging member is prevented from biting and deforming from the one side to the other side. Each cleaning roller is driven to rotate.

  Thus, the position of the sleeve-shaped elastic charging member is stable even when the cleaning roller and the image carrier are driven to rotate. Therefore, the charging nip between the charging member and the image carrier is also located at the same position. In addition, the nip state such as the width in the moving direction of the image carrier surface is stabilized, so that the surface of the image carrier can be more uniformly and stably charged to a desired potential, and a good image can be formed accordingly.

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

  As described above, the charging device in at least one image forming unit can stably and stably charge the surface of the image carrier to a desired potential, can clean the charging member, and further includes a cleaning roller, a charging member, and a regulating member. Therefore, it is possible to reduce the size of the image forming apparatus. As a result, it is possible to form a good image while reducing the size of the entire image forming apparatus.

  In the image forming apparatus according to the present invention, either the upstream side or the downstream side in the moving direction of the image carrier surface from the line where the charging member position regulating member connects the rotation center line of the image carrier and the rotation center line of the cleaning roller. When the image bearing member and the cleaning roller are driven to rotate in a state where the charging member is disposed on one side and the charging member is disposed on the one side, the charging member bites and deforms from the one side to the other side. In order to suppress this, an example in which each of the image carrier and the cleaning roller is driven as follows can be given.

That is, the position restricting member is arranged on the upstream side (or downstream side) in the moving direction of the image carrier surface with respect to the line connecting the rotation center line of the image carrier and the rotation center line of the cleaning roller, and the charging member is also upstream. Placed near the side (or downstream side),
When rotating the image carrier and the cleaning roller, the cleaning roller is driven in the same rotational direction as the image carrier, and the surface of the image carrier is moved between the image carrier surface moving speed and the charging member surface moving speed. Since each of the image carrier and the cleaning roller is rotationally driven so as to generate a relationship of moving speed <charging member surface moving speed (or image carrier surface moving speed> charging member surface moving speed). is there.

More specifically, the position restricting member is disposed upstream of the line connecting the rotation center line of the image carrier and the rotation center line of the cleaning roller in the image carrier surface movement direction, and the charging member is also upstream of the upstream side. When placed on the side,
When rotating the image carrier and the cleaning roller, the cleaning roller is driven in the same rotational direction as the image carrier, and the surface of the image carrier is moved between the image carrier surface moving speed and the charging member surface moving speed. Each of the image carrier and the cleaning roller is rotationally driven so as to generate a relationship of moving speed <charging member surface moving speed.

When the position restricting member is arranged on the downstream side in the moving direction of the image carrier surface with respect to the line connecting the rotation center line of the image carrier and the rotation center line of the cleaning roller, and the charging member is arranged closer to the downstream side. ,
When rotating the image carrier and the cleaning roller, the cleaning roller is driven in the same rotational direction as the image carrier, and the surface of the image carrier is moved between the image carrier surface moving speed and the charging member surface moving speed. Each of the image carrier and the cleaning roller is rotationally driven so that a relationship of moving speed> charge member surface moving speed is generated.

  In any case, the surface moving speed of the image carrier usually governs the image forming speed of the image forming apparatus, in other words, the recording medium conveyance speed, that is, the so-called system speed. Rotating and driving the surface movement speed constant without being constrained by the arrangement positions of the member and the charging member, and the cleaning roller is moved between the image carrier surface movement speed and the charging member surface movement speed. An example can be given in which the rotational drive is performed so that the relationship of <the charging member surface moving speed (or the image carrier surface moving speed> the charging member surface moving speed) occurs.

  The position restricting member may be a member that rotates as the sleeve-shaped charging member rotates or a member that does not rotate. For example, a shaft rod-shaped member that can rotate around a rotation center line parallel to the rotation center line of the cleaning roller, or a fixed member that does not rotate and extends parallel to the rotation center line of the cleaning roller can be exemplified.

  As described above, according to the present invention, the surface of the image carrier that is rotationally driven in a certain direction is charged by a charging device, and image exposure is performed on the charging area to form an electrostatic latent image. An image forming apparatus that includes one or more image forming units that can develop a toner image to form a toner image, and that can transfer a toner image formed by the image forming unit to a transfer target, at least A charging device in one image forming unit can form a wide charging nip between the charging member and the image carrier to charge the surface of the image carrier uniformly and stably in a desired charged state. In addition, the charging member can be cleaned and the size can be reduced, and an image forming apparatus capable of forming a good image while reducing the size of the entire image forming apparatus can be provided.

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. It is a figure which shows the outline of a structure of the other example of the image forming apparatus concerning this invention. FIG. 6 is a diagram illustrating an example in which the position of a charging member in the form of a sleeve changes due to the rotation of the image carrier and the cleaning roller, or the charging nip by the charging member changes. FIG. 10 is a diagram illustrating another example in which the position of a charging member in the form of a sleeve changes due to the rotation of the image carrier and the cleaning roller, or the charging nip by the charging member changes. FIG. 10 is a diagram showing still another example in which the position of a charging member in the form of a sleeve changes due to the rotation of the image carrier and the cleaning roller, or the charging nip by the charging member changes.

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 10A 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 10A 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 to this, the image forming apparatus 10A also 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 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 </ b> A together with the photoreceptor 1.
Both ends of the restricting member 23 are rotatably supported by the frame F.

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 photoreceptor 1 (counterclockwise in the example of FIG. 1) by the motor M2.

In this example, the regulating member 23 is a conductive shaft rod having a circular cross section, and as described above, both end portions thereof are rotatably supported by the frame F so that a charging voltage can be applied from the power source PW. .
The regulating member 23 may not be rotated and may be a fixed type, and the cross-sectional shape does not need to be circular.

The charging member 21 is sandwiched between the cleaning roller 22 and the regulating member 23 and can be driven and rotated by the cleaning roller 22 that is rotationally driven (in other words, the charging member 21 is driven by the cleaning roller 22. In a state in which the peripheral speed can be controlled) , a charging nip having a width in the moving direction of the surface of the photoconductor 1 is formed in pressure contact with the surface of the photoconductor 1.
Thus, the surface of the photoreceptor 1 can be charged by applying a charging voltage from the power source PW to the charging member 21 via the regulating member 23.

  It should be noted here that the regulating member 23 and the charging member 21 are moved in the direction of movement of the surface of the photoconductor 1 from a line L connecting the rotation center of the photoconductor 1 and the rotation center line of the cleaning roller 22 as shown in FIG. The photosensitive member 1 and the cleaning roller 22 are rotationally driven as follows when the surface of the photosensitive member 1 is charged by the charging member 21.

  That is, the rotation driving of the photosensitive member 1 by the motor M1 and the rotation driving of the cleaning roller 22 by the motor M2 are performed so that both the photosensitive member 1 and the roller 22 rotate in the same direction (counterclockwise in the case of FIG. 1). In addition, the rotation of the photosensitive member 1 by the motor M1 is driven at a predetermined constant peripheral speed, whereas the rotational driving of the cleaning roller 22 by the motor M2 is performed by the rotation speed of the surface of the photosensitive member 1 and the charging member. 21 is performed so that a difference between the surface moving speed and the charging member 21 is prevented from biting into the downstream side of the connection L and being deformed.

Specifically, both the photosensitive member 1 and the cleaning roller 22 are driven in the same rotation direction, and accordingly, in the portion where the charging member 21 and the photosensitive member 1 are in contact with each other, that portion of the charging member 21 and that of the surface of the photosensitive member 1 are the same. Driven so that the part moves in the same direction (forward direction),
The photosensitive member 1 and the cleaning roller are arranged such that a relationship of V ₁ <V ₂₁ occurs between the photosensitive member 1 surface moving speed V ₁ (a predetermined constant speed) and the charging member 21 surface moving speed V _21. 22 are each driven.

  The image exposure apparatus 3 forms an electrostatic latent image by performing image exposure on the photoreceptor 1 using a laser beam modulated by an image signal supplied from a personal computer (not shown), an image reading apparatus, or the like. is there.

  In this example, the developing device 4 can reversely develop the electrostatic latent image on the photosensitive member 1 by the developing roller 41 using a so-called one-component developer mainly composed of toner. The developing roller 41 is rotationally driven by a developing roller drive motor (not shown) at least during electrostatic latent image development, and a developing bias is applied from a power supply (not shown).

  The developing device 4 may perform development with a so-called two-component developer mainly composed of toner and carrier.

  According to the image forming apparatus 10A described above, the photosensitive member 1 is rotated by the motor M1, the cleaning roller 22 is rotated by the motor M2, and a charging voltage is applied from the power source PW to the charging member 21 via the regulating member 23. The surface of the photosensitive member 1 is charged by the charging member 21, an image exposure device 3 performs image exposure on the charged area to form an electrostatic latent image, and the latent image is developed by a developing device to form a toner image. Then, the toner image is transferred to a recording medium S conveyed from a recording medium supply unit (not shown) by a transfer roller 51 to which a transfer voltage is applied, and the transferred toner image is heated and pressed by a fixing device 7 under a recording medium. It can be fixed to S and discharged out of the apparatus. Transfer residual toner and the like on the photoreceptor 1 after the toner image transfer is cleaned by a cleaning device 6.

  When charging the surface of the photoreceptor 1 by the charging device 2A, the charging member 21 is pressed against the surface of the photoreceptor 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 photoreceptor 1 surface. Since a large charging nip is formed, the surface of the photoreceptor 1 can be uniformly and stably charged to a desired potential.

Further, the regulating member 23 and the charging member 21 arranged in the charging member 21 are arranged on the upstream side in the moving direction of the photoconductor surface from the line L connecting the photoconductor rotation center line and the cleaning roller rotation center line. Furthermore, between the constant peripheral speed chestnut training roller 22 against the photosensitive member 1 driven, the photosensitive member 1 surface movement speed V ₁ (predetermined constant speed) and the charging member 21 surface movement speed V _21, It is rotationally driven so that the relationship of V ₁ <V ₂₁ occurs.

Here, if each of the photosensitive member 1 and the cleaning roller 22 is rotationally driven so that a relationship of V ₁ ≧ V ₂₁ occurs, the charging member 21 is connected to the photosensitive member 1 as shown in FIG. It deforms so as to bite into the downstream side where the gap with the cleaning roller 22 becomes narrower, and further deforms so as to reciprocate between the downstream side and the upstream side, and between the photosensitive member 1 and the charging member 21. The charging nip fluctuates, and charging failure such as uneven charging of the photosensitive member 1 occurs, resulting in image failure.

Further, as shown in FIG. 4, if the charging member 21 and the regulating member 23 are arranged so as to be positioned on the line L, the cleaning roller 22 has either the magnitude relationship or the same relationship between V ₁ and V _21. The charging member 21 is unstablely deformed between the upstream side and the downstream side even if it is driven so that charging failure such as charging unevenness of the photosensitive member 1 occurs, resulting in image failure.

In the image forming apparatus 10 </ b> A shown in FIG. 1, the cleaning roller 22 moves the photosensitive member 1 surface moving speed V ₁ (predetermined constant speed) and the surface of the charging member 21 with respect to the photosensitive member 1 driven at a constant circumferential speed. The charging member 21 is driven to rotate so that a relationship of V ₁ <V ₂₁ occurs with the moving speed V _21, and as a result, as shown in FIG. In addition, the charging nip between the charging member 21 and the photosensitive member 1 also stabilizes the position and the nip state such as the width in the moving direction of the photosensitive member, and the surface of the photosensitive member 1 is further uniformly stabilized at the desired potential. Therefore, a good image can be formed.

In the apparatus 10A, when the cleaning roller 22 is rotationally driven so that a relationship of V ₁ <V ₂₁ occurs between the photosensitive member 1 surface moving speed V ₁ and the charging member 21 surface moving speed V ₂₁ , If (V ₂₁ / V ₁ ) is too large, the charging member 21 is displaced from the proper position and charging failure is likely to occur. If it is too small, a difference is provided between V ₁ and V ₂₁ to stabilize the charging member position. The effect will be reduced. Therefore, an example in which (V ₂₁ / V ₁ ) is selected from a range of about 1.05 to 1.1 can be given.

  Further, since the charging roller 21 is in contact with the charging roller 21, the contamination of the charging member 21 can be suppressed, and the surface of the photoreceptor 1 can be well charged to a desired potential for a long time.

  Further, the charging device 2A can stably charge the surface of the photoconductor 1 uniformly to a desired potential, and has a simple structure that can clean the charging member 21, and can be downsized. As a result, a good image can be formed while reducing the size of the entire image forming apparatus 10A.

  FIG. 3 shows another example 10B of the image forming apparatus according to the present invention. The image forming apparatus 10B employs a charging device 2B instead of the charging device 2A in the image forming apparatus 10A of FIG. The other points are the same as those of the apparatus 10A, and the same reference numerals as those of the apparatus 10A are attached to the same parts, parts, etc.

  In the charging device 2B, as shown in FIG. 3, the regulating member 23 and the charging member 21 are downstream in the moving direction of the surface of the photoconductor 1 from the line L connecting the rotation center of the photoconductor 1 and the rotation center line of the cleaning roller 22. When the surface of the photosensitive member 1 is charged by the charging member 21, the photosensitive member 1 and the cleaning roller 22 are driven to rotate as follows.

  That is, the rotation driving of the photosensitive member 1 by the motor M1 and the rotation driving of the cleaning roller 22 by the motor M2 are performed so that both the photosensitive member 1 and the roller 22 rotate in the same direction (counterclockwise in the case of FIG. 1). In addition, the rotation of the photosensitive member 1 by the motor M1 is driven at a predetermined constant peripheral speed, whereas the rotational driving of the cleaning roller 22 by the motor M2 is performed by the rotation speed of the surface of the photosensitive member 1 and the charging member. 21 between the surface moving speed and the surface moving speed so as to cause a difference that prevents the charging member 21 from biting into the upstream side of the connection L and deforming.

Specifically, both the photosensitive member 1 and the cleaning roller 22 are driven in the same rotation direction, and accordingly, in the portion where the charging member 21 and the photosensitive member 1 are in contact with each other, that portion of the charging member 21 and that of the surface of the photosensitive member 1 are the same. Driven so that the part moves in the same direction (forward direction),
The photosensitive member 1 and the cleaning roller are arranged such that a relationship of V ₁ > V ₂₁ occurs between the photosensitive member 1 surface moving speed V ₁ (a predetermined constant speed) and the charging member 21 surface moving velocity V _21. 22 are each driven.

According to the image forming apparatus 10B, an image can be formed as in the case of the apparatus 10A.
In charging the surface of the photosensitive member 1 by the charging device 2B, the cleaning roller 22 moves the photosensitive member 1 surface moving speed V ₁ (predetermined constant speed) and the charging member 21 with respect to the photosensitive member 1 driven at a constant circumferential speed. It is rotationally driven so that a relationship of V ₁ > V ₂₁ occurs with the surface moving speed V ₂₁ .

Here, if each of the photosensitive member 1 and the cleaning roller 22 is rotationally driven so as to have a relationship of V ₁ ≦ V ₂₁ , the charging member 21 is connected to the photosensitive member 1 as shown in FIG. It is deformed so as to bite into the upstream side where the gap with the cleaning roller 22 becomes narrower, and further, deformed so as to reciprocate between the upstream side and the downstream side, and charging between the photosensitive member 1 and the charging member 21 is performed. The nip fluctuates, and charging failure such as charging unevenness of the photosensitive member 1 occurs, resulting in image failure.

In the image forming apparatus 10B shown in FIG. 3, the cleaning roller 22 moves the photosensitive member 1 surface moving speed V ₁ (predetermined constant speed) and the surface of the charging member 21 with respect to the photosensitive member 1 driven at a constant circumferential speed. The charging member 21 is rotationally driven so that a relationship of V ₁ > V ₂₁ occurs with the moving speed V _21, and as a result, as shown in FIG. In addition, the charging nip between the charging member 21 and the photosensitive member 1 also stabilizes the position and the nip state such as the width in the moving direction of the photosensitive member, and the surface of the photosensitive member 1 is further uniformly stabilized at the desired potential. Therefore, a good image can be formed.

In the apparatus 10B, when the cleaning roller 22 is rotationally driven so that a relationship of V ₁ > V ₂₁ occurs between the photosensitive member 1 surface moving speed V ₁ and the charging member 21 surface moving speed V ₂₁ , If (V ₁ / V ₂₁ ) is too large, the charging member 21 will be displaced from the proper position and charging will be liable to occur. If it is too small, there will be a difference between V ₁ and V ₂₁ to stabilize the charging member position. Will become smaller. Therefore, (V ₂₁ / V ₁ ) can be given an example in which it is selected from a range of approximately 0.9 to 0.95.

  Although the image forming apparatuses 10A and 10B described above are monochrome image forming apparatuses, 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, and that the charging member can be cleaned and can be miniaturized.

10A, 10B Image forming apparatus 1 Photoconductor M1 Photoconductor drive motors 2A, 2B Charging device 21 Charging member 22 Crime roller M2 Cleaning roller driving motor 23 Charging member position regulating member PW Charging power source 3 Image exposure device 4 Developing device 41 Developing roller 5 Transfer Device 51 Transfer Roller 6 Crigue Device 7 Fixing Device L Line S Connecting Photoconductor Rotation Center and Clean Roller Rotation Center S Recording Medium

Claims (5)

  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. The image forming apparatus includes one or more image forming units and can transfer a toner image formed in the image forming unit to a transfer target. The charging device in at least one image forming unit is an image forming unit. A cleaning roller disposed in parallel with the carrier, an elastic charging member in the form of a sleeve disposed between the image carrier and the cleaning roller, and disposed in the charging member in parallel with the cleaning roller. A charging member position restricting member that is sandwiched between the cleaning roller and the cleaning roller so as to be driven to rotate. The charging member is sandwiched between the cleaning roller and the restricting member. In this state, a charging nip having a width in the direction of movement of the image carrier surface is formed by being pressed against the surface of the image carrier, and the position regulating member is configured to rotate the rotation center line of the image carrier and the cleaning roller. A charging member is also disposed closer to the one side of the image carrier surface moving direction than the line connecting the center line and either upstream or downstream, and the image carrier and the When rotating each cleaning roller, the cleaning roller is driven in the same rotational direction as the image carrier, and the charging member is moved from the one side between the image carrier surface moving speed and the charging member surface moving speed. An image forming apparatus, wherein each of the image carrier and the cleaning roller is rotationally driven so as to produce a difference that suppresses biting and deformation to the other side. The position regulating member is disposed on the upstream side (or downstream side) in the moving direction of the surface of the image carrier from the line connecting the rotation center line of the image carrier and the rotation center line of the cleaning roller, and the charging member is also upstream of the upstream side. It is arranged closer to the side (or downstream side)
When the image carrier and the cleaning roller are driven to rotate, the cleaning roller is driven in the same rotational direction as the image carrier, and the surface of the image carrier is moved between the image carrier surface movement speed and the charging member surface movement speed. The image carrier and the cleaning roller are each driven to rotate so as to generate a relationship of moving speed <charge member surface moving speed (or image carrier surface moving speed> charging member surface moving speed). Item 2. The image forming apparatus according to Item 1.   The image carrier is driven to rotate at a constant surface moving speed without being constrained by the arrangement positions of the regulating member and the charging member, whereas the cleaning roller moves the image carrier surface moving speed and the charging member surface. 3. The driving is performed so that the relationship between the moving speed and the image carrier surface moving speed <the charging member surface moving speed (or the image carrier surface moving speed> the charging member surface moving speed) is generated. The image forming apparatus described.   The image forming apparatus according to claim 1, wherein the position restricting member is a shaft bar-shaped member that is rotatable around a rotation center line parallel to the rotation center line of the cleaning roller.   4. The image forming apparatus according to claim 1, wherein the position restricting member is a fixed member that does not rotate and extends in parallel with a rotation center line of the cleaning roller.

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