JP4854010B2 - Charging device and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a charging device having a cleaning mechanism for cleaning a discharge wire, and an image forming apparatus including the charging device.

  2. Description of the Related Art A charging device using corona discharge is known in electrophotographic image forming apparatuses such as copying machines and printers. There are corotron and scorotron types of charging devices. The former is a shield with a cross-sectional "U" shape, with its opening facing the surface of the photoreceptor, and in the vicinity of the opening. In addition to this, the latter is provided with a grid in the opening of the shield. These charging devices charge the surface of the photoreceptor uniformly (uniformly) to a predetermined polarity and potential by corona discharge generated by applying a high voltage to the discharge wire.

  In the above-described charging device, discharge products such as NOx generated by corona discharge and foreign matters such as paper dust are gradually attached to the discharge wire, and uneven resistance occurs in the longitudinal direction due to the attached foreign matter. For this reason, uneven charging occurs on the surface of the photoreceptor during charging, and as a result, uneven density of the toner image occurs.

  In order to prevent the occurrence of such uneven charging and uneven toner image density, there has been proposed a technique for wiping off foreign matter adhering to the discharge wire (see, for example, Patent Document 1).

  In this case, the discharge wire is sandwiched by the cleaning pad held by the holding member, and the holding member is moved by the driving mechanism, so that the discharge wire is rubbed by the cleaning pad, thereby removing the foreign matter adhering to the discharge wire. To wipe away. In particular, in this example, the cleaning pad is positively inclined with respect to the discharge wire so that the cleaning pad rubs 50% or more of the circumferential length of the cross section of the discharge wire.

JP 2002-268342 A

  However, according to the above-described conventional example, the frictional resistance between the discharge wire and the cleaning pad is increased. Therefore, the increase in the frictional resistance is an increase in load resistance when the holding member is moved by the driving mechanism, and thus the discharge wire. Causes uneven wiping. In particular, when a screw is employed as the drive mechanism, an appropriate margin (play) is provided between the screw and the holding member, so that the holding member is conveyed while generating a large swell according to the pitch of the screw. For this reason, the strength of the cleaning of the cleaning pad is generated according to this pitch, and cleaning unevenness corresponding to the pitch is generated on the surface of the discharge wire. As described above, uneven cleaning of the discharge wire causes uneven charging and uneven toner image density.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a charging device having a cleaning mechanism that suppresses uneven cleaning of the discharge wire and prevents uneven charging and uneven density, and an image forming apparatus including the charging device. Is.

The invention according to claim 1 includes a shield having a back surface portion and two side portions, the cross-sectional shape orthogonal to the longitudinal direction being formed in a “U” shape, and the length of the shield in the vicinity of the opening of the shield. The present invention relates to a charging device including a discharge wire stretched along a direction and a cleaning mechanism for cleaning the discharge wire. In the charging device according to the present invention, the cleaning mechanism is loosely fitted to the transport screw disposed along the discharge wire between the back surface portion and the discharge wire inside the shield. And a moving base that moves along the discharge wire as the conveying screw rotates, a cleaning member that is held by the moving base and sandwiches the discharge wire, and that is held by the moving base and the moving base with the movement are Bei Ete and a load member that imparts a load to the moving base by being rubbed on the inner surface of said side of.
In the present invention, the load member is elastically deformed by contacting the inner surface of the side portion.
The base end side that is formed by a plate-like member that is held by the moving base is in relation to the back surface portion.
They are held in parallel.
In the present invention, the two side portions of the shield are defined as a first side portion and a second side portion.
Both end portions of the load member along the direction perpendicular to the conveying screw are the first end portion,
A load generated by the first end portion being rubbed against the first side portion;
When the load generated when the two end portions are rubbed against the second side portion is the second load, the load member
When the moving base moves in the forward direction due to forward rotation of the conveying screw,
2 load is larger than the first load, and by reverse rotation of the conveying screw
When the moving base moves in the reverse direction, the first load is larger than the second load.
It is characterized by being formed.

The invention according to claim 2 is the charging device according to claim 1, wherein the load member is formed into asymmetrical with respect to a center line corresponding to the discharge wire, it is formed in point symmetry with respect to the center point It is characterized by that.

According to a third aspect of the invention, in the charging device according to the first or second aspect , the load member is detachable from the moving base.

According to a fourth aspect of the invention, the photosensitive member is charged and exposed to form an electrostatic latent image, the electrostatic latent image is developed as a toner image, and the toner image is transferred from the photosensitive member to another member. The present invention relates to an image forming apparatus. The image forming apparatus according to the present invention is the charging device according to any one of claims 1 to 3, wherein the means for charging the photoconductor is disposed so as to face the photoconductor. It is a feature.

  According to invention of Claim 1, the wiping unevenness of the discharge wire by a cleaning member can be suppressed. That is, the cleaning member that sandwiches the discharge wire is held by the moving base, and the moving base is loosely fitted to the conveying screw and moves along the discharging wire as the conveying screw rotates. Therefore, the cleaning member can perform an operation (hereinafter referred to as “wiping operation” as appropriate) of rubbing the discharge wire by the rotation of the conveying screw and wiping the discharge product adhering to the discharge wire. By the way, since the holding member is loosely fitted to the conveying screw, the cleaning member held by the holding member tends to generate wiping unevenness corresponding to the pitch of the conveying screw during the wiping operation. However, in the invention according to the present invention, the load member held by the moving base is rubbed against the inner surface of the side portion of the shield to apply an appropriate load to the holding member. Since the play (the margin part, the play) when the moving base moves can be eliminated by this, the wiping unevenness of the discharge wire corresponding to the pitch of the conveying screw by the cleaning member can be suppressed.

According to the invention of claim 1 , since the load member is formed by a plate-like member that is elastically deformed by contacting the inner surface of the side portion, the shape, size, and size of the load member are appropriately selected. Thus, it is possible to generate a suitable (minimum necessary) load resistance to prevent wiping unevenness and to suppress an increase in driving force caused by the load resistance being too large.

Further , according to the invention of claim 1 , since the base end side where the moving base is held is held parallel to the back surface portion, for example, compared with the case where the load member is held at a right angle, The posture when the load member is rubbed against the inner surface of the side portion of the shield can be stabilized.

According to the first aspect of the present invention, when the conveying screw rotates in the forward direction and the moving base moves in the forward direction, the load member has a second end portion with a large load at the time of rubbing. On the other hand, when the conveying screw is reversely rotated and the moving base moves in the reverse direction, the first end portion having a large load during rubbing is more than the second end portion having a small load. I feel late. With such a load member, regardless of whether the moving base moves in the forward direction or the reverse direction, the moving base moves in a state twisted in the same direction with respect to an axis orthogonal to the discharge wire. Accordingly, the cleaning member performs a wiping operation in a twisted state, and can further suppress wiping unevenness. Furthermore, since the direction of twisting of the cleaning member is the same when the moving base moves in the forward direction and when it moves in the reverse direction, the wiping operation is performed in a stable posture regardless of the moving direction of the moving base. It can be carried out.

The invention of claim 2 specifically defines the shape of the load member. Unlike the invention of this claim, when the load member is formed symmetrically with respect to the center line corresponding to the discharge wire, both ends of the load member are rubbed against the inner surface of the side portion of the shield. In this case, since the same load resistance acts on both ends, it is impossible to generate a force in the direction of twisting the moving base. On the other hand, when the load member is formed asymmetrically with respect to the center line corresponding to the discharge wire as in the invention according to claim 2, both ends of the load member are side portions of the shield. When rubbed against the inner surface, load resistances of different magnitudes act on both ends, so that a force in the direction of twisting the moving base is generated. Furthermore, when the load member is formed symmetrically with respect to the center point, the direction and magnitude of the force that twists the moving base when the moving base moves in the positive direction and when it moves in the negative direction. Since the height can be made substantially constant, the posture of the moving base when moving in the forward direction and the reverse direction can be stabilized, and the wiping operation of the cleaning member can be stabilized.

According to the invention of claim 3 , since the load member is detachable from the moving base, it can be easily attached to the existing moving base, and can be easily replaced when it deteriorates. it can.

According to the fourth aspect of the present invention, since the means for charging the photosensitive member in the image forming apparatus is the above-described charging apparatus, it is possible to prevent uneven image density due to uneven wiping of the discharge wire.

  Hereinafter, the best embodiment of the present invention will be described in detail with reference to the drawings. In addition, in each drawing, the member etc. which attached | subjected the same code | symbol are the same structures, The duplication description about these shall be abbreviate | omitted suitably. Moreover, in each drawing, members and the like that are not necessary for the description are omitted as appropriate.

<Embodiment 1>
An image forming apparatus 11 including a charging device 10 according to the present invention will be described with reference to FIG. An image forming apparatus 11 shown in FIG. 1 is an electrophotographic image forming apparatus 11, and an image is formed on a sheet (for example, plain paper, envelope, transparent film, etc.) P as a recording medium (other member) with powder toner. (Toner image) is formed. FIG. 1 is a left side view schematically showing the schematic configuration. That is, in the image forming apparatus 11, the right side in FIG. 1 is the front (front) side, and the left side is the rear (back) side. Here, as the image forming apparatus 11, a copier, a printer, a facsimile, and a multifunction machine of these are equivalent to this.

  As shown in FIG. 1, the image forming apparatus 11 includes a sheet feeding unit 12, an image forming unit 13, a fixing unit 14, and a sheet from the upstream side to the downstream side along the conveyance direction (arrow K direction) of the sheet P. A P discharge unit 15 is provided.

  The sheet feeding unit 12 feeds the sheet P stored in the sheet feeding cassette 16 by the sheet feeding roller 17 and conveys it downstream by the conveying roller 20 while preventing the double feeding by the retard roller 18. Further, after the conveyed sheet P is corrected in skew by the registration roller pair 21, the sheet P is supplied to the image forming unit 13 by the rotation of the registration roller pair 21 synchronized with the operation of the image forming unit 13.

  The image forming unit 31 includes a drum-type electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) 22 that is rotationally driven in the direction of an arrow (clockwise in FIG. 1). The photosensitive layer of the photosensitive drum 22 is made of, for example, amorphous silicon (a-Si). Around the photosensitive drum 22, a charging device 10, an exposure device 23, a developing device 24, a transfer device 25, a cleaning device 26, and the like are disposed almost in order along the rotation direction. The surface of the photosensitive drum 22 is uniformly (uniformly) charged to a predetermined polarity and potential by the charging device 10. The surface of the photosensitive drum 22 after charging is subjected to exposure L based on image information by the exposure device 23, and the charge of the exposed portion is removed to form an electrostatic latent image. This electrostatic latent image is developed as a toner image by the developing device 24. The toner image thus formed on the photosensitive drum 22 is transferred by the transfer roller (transfer device) 25 to the sheet P supplied by the above-described registration roller pair 21.

  The fixing unit 14 includes a fixing roller 27 with a built-in heater (not shown) and a pressure roller 28 pressed against the fixing roller 27. The fixing unit 14 heats the sheet P at a fixing nip formed between the two rollers. While applying pressure. As a result, the toner image is fused and fixed on the sheet P.

  The sheet discharge unit 15 discharges the fixed sheet P onto the discharge tray 31 by the discharge roller pair 30.

  Thus, image formation on one side of one sheet P is completed.

  Next, the charging device 10 will be described with reference to FIGS. Of these figures, FIG. 2 is an enlarged view taken along line AA in FIG. The left side in FIG. 2 is the left side of the charging device 10, and the right side in FIG. 2 is the right side of the charging device 10. Further, FIG. 2 illustrates a case in which one moving base 55 to be described later is located at a right end side home position P1, a left end side folded portion P2, and an intermediate portion P3 therebetween. FIG. 3 is an enlarged view taken along line BB in FIG. In the following, for convenience of explanation, the upper and lower sides and the front and rear sides of the charging device 10 in FIGS. 2 and 3 are the far side from the photosensitive drum 22 and the side closer to the photosensitive drum 22 is the lower side of the charging device 10. Further, the right side in FIG. 3 is described as the front side of the charging device 10 and the left side is described as the rear side of the charging device 10. FIG. 4 is a perspective view showing a state where the charging device 10 shown in FIG. 3 is turned upside down and a part of the front side portion 41 and the rear side portion 42 of the shield 33 is removed. FIG. 5 is a diagram illustrating a configuration in the vicinity of the left end portion of the conveying screw 54.

  As shown in FIG. 2, the entire charging device 10 is formed long in the left-right direction along the bus bar 32 of the photosensitive drum 22. As shown in FIG. 3, the charging device 10 is stretched in the left-right direction in the vicinity of the shield 33 having a “U” -shaped cross section in the direction orthogonal to the longitudinal direction (left-right direction) and the opening 34 of the shield 33. And a cleaning mechanism 36 for cleaning the discharge wire 35.

  The shield 33 has a back surface portion 40 on the upper side, a front side portion (first side portion) 41 on the front side, and a rear side portion (second side portion) 42 on the rear side. The front side portion 41 and the rear side portion 42 are respectively extended so as to extend downward from the front end edge and the rear end edge in the width direction (front-rear direction) of the back surface portion 40 toward the photosensitive drum 22. A belt-like slit 43 that is long in the left-right direction is formed in the back surface portion 40 at the center in the front-rear direction. A pair of guide portions 44 and 45 are formed in the back portion 40 so as to face each other at the slit 43 so as to face each other. These guide portions 44 and 45 guide movement in a direction along the discharge wire 35 of a movement base 55 described later. In the present embodiment, the front side portion 41 and the rear side portion 42 are divided into two. The base end side portions 46 and 47 of the front side portion 41 and the rear side portion 42 are configured by bending the front end and rear end of the back surface portion 40 downward, and the base end side portions 46 and 47 include lower ends. Engaging portions 48 and 50 are formed, and front side portions 51 and 52 of the front side portion 41 and the rear side portion 42 are formed in a plate shape that is long in the left-right direction, and the upper end edge is engaged with the engaging portion. By combining, the front side part 41 and the rear side part 42 are comprised with the base end side part. The present invention can be similarly applied to the front side portion 41 and the rear side portion 42 even if the front side portion 41 and the rear side portion 42 are divided into two as described above or integrally formed.

  As described above, the shield 33 is formed in a cross-sectional “U” shape by the rear surface portion 40 positioned on the upper side, the front side portion 41 positioned on the front side, and the rear side portion 42 positioned on the rear side, The opening 34 is disposed so as to face the surface of the photosensitive drum 22 with an appropriate gap. Further, the charging device 10 of the present embodiment is of a so-called scorotron type, and a grid wire 53 is stretched on the opening 34 of the shield 33. The present invention can be similarly applied to a corotron type that does not have the grid wire 53.

  The discharge wire 35 is stretched along the left-right direction, that is, the longitudinal direction of the shield 33, slightly above the opening 34 inside the shield 33. The left and right end portions of the discharge wire 35 are attached to attachment portions (not shown) respectively disposed on the left and right end portions of the shield 33. As described above, the grid wire 53 is disposed in the opening 34 of the shield 33.

  Here, when charging the surface of the photosensitive drum 22 by the charging device 10, a voltage is applied to the discharge wire 35 and the grid wire 53 by a charging bias application power source (not shown). Charged uniformly (uniformly) to the potential.

  In the charging device 10 described above, the charging time increases as the number of images formed increases, and foreign substances such as discharge products generated during charging adhere to the discharge wire 35, resulting in uneven charging and thus uneven toner image density. Cause.

  Therefore, in this embodiment, the charging device 10 is provided with a cleaning mechanism 36 to clean the discharge wire 35. In addition, at this time, the occurrence of uneven wiping of the discharge wire 35 is suppressed to prevent uneven charging and uneven toner image density.

  The cleaning mechanism 36 will be described with reference to FIGS. 2 is an enlarged view taken along line AA in FIG. 1 as described above, and FIG. 3 is an enlarged view taken along line BB in FIG. FIG. 4 is a perspective view showing a state where the charging device 10 in FIG. 2 is turned upside down and a part of the side portions 41 and 42 (tip side portions 51 and 52) is removed.

  As shown in these drawings, the cleaning mechanism 36 includes a conveying screw 54 disposed in the left-right direction, a moving base 55 loosely fitted to the conveying screw 54, and a cleaning member 56 held by the moving base 55. And a load member 57.

  As shown in FIG. 4, the conveying screw 54 is configured by a shaft 58 and a screw portion 60 that protrudes spirally on the outer peripheral surface of the shaft 58, and as shown in FIGS. 2 and 3, Between the back surface portion 40 and the discharge wire 35 inside the shield 33, it is disposed along the longitudinal direction of the shield 33, that is, along the discharge wire 35. Both end portions in the axial direction of the conveying screw 54 are supported rotatably (forward and reverse rotation) by bearings (not shown) respectively disposed on the left and right end portions of the shield 33, and further, the right end side is It is connected to a drive unit 61 having a speed reduction mechanism (not shown) and a motor (not shown) as drive means (drive source). The conveying screw 54 rotates forward and backward in response to forward and reverse rotation of the motor. The right end portion of the conveying screw 54 is a home position P1 of the moving base 55 described later, while the left end portion of the conveying screw 54 is a folded portion P2 of the moving base 55.

Further, in the present embodiment, as shown in FIG. 5, a staying mechanism 62 for the moving base 55 is provided at the folded portion P <b> 2 at the left end of the conveying screw 54. The staying mechanism 62 is provided at the left end of the conveying screw 54 with a non-threaded portion (a portion of only a shaft having no threaded portion) 63 having a length of one pitch or more of the threaded portion, and the non-threaded portion 63 penetrates the inside. A compression spring (biasing member) 64, a stopper member 65 that is fixed to the non-threaded portion 63 and restricts the position of the proximal end side of the compression spring 64, and is attached to the distal end of the compression spring 64 to fit the moving base 55 And a washer 66 that contacts the left end surface of the joint portion 67. This staying mechanism 62 mechanically turns the moving base 55 when the conveying screw 54 is continuously rotated in the state in which the moving base 55 is arranged at the turning portion P2 by the normal rotation of the conveying screw 54. To keep in P2,
Further, when the conveying screw 54 is rotated in the reverse direction with the moving base 55 in the folded portion P2, the moving base 55 starts to move rightward . In the above description, the case where the staying mechanism 62 is provided on the folding part 62 side of the conveying screw 54 has been described as an example, but a similar staying mechanism is also provided on the home position P1 side. The specific operation of the staying mechanism 62 will be described later.

  As shown in FIGS. 3 and 4, the moving base 55 has a fitting portion 67 that is loosely fitted to the above-described conveying screw 54, and a holding portion 68 that holds the cleaning member 56 and the load member 57. . The fitting portion 67 is formed in a cylindrical shape, and a screw portion (not shown) corresponding to one pitch of the screw portion 60 on the outer peripheral surface of the shaft 58 of the conveying screw 54 is formed on the inner peripheral surface thereof. Yes. In the loosely fitted state with respect to the conveying screw 54, the fitting portion 67 is provided with play (backlash) by approximately one pitch along the axial direction of the conveying screw 54. That is, it is possible to move in the axial direction by a distance corresponding to approximately one pitch. In addition, the fitting portion 67 is provided with appropriate play between the conveying screw 54 in the radial direction. In this way, by providing play, the transfer screw 54 can be rotated by a motor with a small output, and the moving base 55 can be moved smoothly.

  A pair of guide grooves 70 and 71 are formed at the upper end of the moving base 55 in FIG. A pair of guide portions 44 and 45 of the back surface portion 40 of the shield 33 are fitted into the guide grooves 70 and 71 with appropriate play. As a result, the movement base 55 is roughly maintained in its posture when moving in the left-right direction along the discharge wire 35 by the rotation of the conveying screw 54.

  The holding portion 68 is provided below the fitting portion 67 in the moving base 55 in FIG. 3, that is, on the side close to the opening portion 34 of the shield 33. The holding portion 68 has a bifurcated portion corresponding to the discharge wire 35 on the lower end side. The bifurcated portions 72 and 73 have appropriate attachment surfaces 74 and 75 for attaching a cleaning member 56 described below. They face each other through a gap. The bifurcated portions 72 and 73 can be elastically deformed in the direction of the arrow (substantially in the front-rear direction) with reference to the base end portions 76 and 77. This facilitates attachment of the cleaning member 56 to the attachment surfaces 74 and 75, and the cleaning member 56 presses each other after attachment, so that the discharge wire 35 can be sandwiched with an appropriate force from the front-rear direction. Accordingly, the cleaning effect of the discharge wire 35 can be enhanced. The lower surface 78 of the moving base 55, that is, the lowermost end of the holding portion 68 is formed in a planar shape parallel to the back surface portion 40 described above.

  The cleaning member 56 is attached to the attachment surfaces 74 and 75 of the bifurcated portions 72 and 73 of the moving base 55 described above. The cleaning member 56 is formed of, for example, a non-woven fabric, and sandwiches the discharge wire 35 in a state in which the cleaning member 56 is appropriately pressed and compressed by the bifurcated portions 72 and 73 described above. When the conveying screw 54 is rotated in this sandwiched state, the cleaning member 56 can rub the discharge wire 35 as the moving base 55 moves in the left-right direction along the discharge wire 35.

  In this embodiment, the load member 57 is attached to the holding portion 68 of the moving base 55. The load member 57 is formed of a plate-like elastic member, for example, a plate-like (sheet P-like) synthetic resin having a thickness of about 0.5 mm, and as shown in FIG. ) Is attached to the lower surface 78 of the holding portion 68 of the moving base 55 and is parallel to the back surface portion 40 of the shield 33. As a method for attaching the load member 57, for example, sticking with a double-sided tape having adhesive portions on both front and back surfaces can be employed. In the present embodiment, the load member 57 is formed in a substantially track shape. In other words, the central portion (base end portion) attached to the lower surface of the holding portion 68 is formed in a rectangular shape that is long in the front-rear direction, and has a shape in which a semicircle is attached to the front and rear short sides thereof, that is, a track It is formed in a shape. The load member 57 is in the natural state shown in FIG. 4, that is, its front end portion (first end portion) 81 and rear end portion (second end portion) 82 do not contact the inner surfaces of the front side portion 41 and the rear side portion 42 described above. In the non-contact state, the length in the front-rear direction is set longer than the distance between the front side portion 41 and the rear side portion 42 described above. Therefore, as shown in FIG. 3, the load member 57 is elastically deformed when the front end portion 81 and the rear end portion 82 are in contact with the inner surfaces of the front side portion 41 and the rear side portion 42, respectively, in an actual mounting state. And bends. At this time, as shown in FIG. 3, the bending direction may be upward or vice versa, but it is preferable that the bending directions of the front end portion 81 and the rear end portion 82 coincide. By matching the bending direction, the posture of the moving base 55 can be further stabilized when the moving base 55 moves in the left-right direction as the conveying screw 54 rotates, as will be described later.

  Next, the operation of the charging device 10 having the above-described configuration, that is, the charging device 10 including the cleaning mechanism 36 having the load member 57 will be described.

  When the discharge wire 35 is not cleaned, the cleaning mechanism 36 is disposed at the home position P1 at the right end of the conveying screw 54 so as not to prevent charging of the photosensitive drum 22 by the discharge wire 35 and the like.

  When cleaning the discharge wire 35, when the motor is rotated forward, the transport screw 54 is rotated forward, and the moving base 55 loosely fitted on the transport screw 54 is turned along the discharge wire 35 from the home position P1 to the folded portion P2. Move left toward As a result, the cleaning member 56 holding the discharge wire 35 is rubbed against the discharge wire 35 to wipe off foreign matters such as discharge products adhering to the discharge wire 35. At this time, the front end portion 81 and the rear end portion 82 of the load member 57 held by the moving base 55 are rubbed against the inner surface of the front side portion 41 and the inner surface of the rear side portion 42 of the shield 33, respectively. The base 55 is preceded by the fitting portion 67 side to which the conveying force from the conveying screw 54 is applied, and the lower end side serving as a resistance is slightly fed, that is, the lower end side is inclined toward the upstream side in the movement direction (the right end side in FIG. 2). Move in a stable posture. That is, since the moving base 55 is moved to the left in a stable posture in which play between the fitting portion 67 and the conveying screw 54 is eliminated, the cleaning member 56 is attached to the discharge wire 35. The foreign matter can be wiped off evenly.

  When the conveying screw 54 continues to rotate forward, the moving base 55 approaches the turn-back portion P2, and the fitting portion 67 of the moving base 55 moves to a position corresponding to the last one pitch of the screw portion 60 of the conveying screw 54. The left end of the joining portion 67 contacts the washer 66 of the staying mechanism 62 and starts to be urged to the right by the compression spring 64. The moving base 55 is moved to the left against the urging force of the compression spring 64 by the forward rotation of the conveying screw 54 while the fitting portion 67 is engaged with the screw portion 60 of the conveying screw 54. . The moving base 55 is 1 until the screw portion of the fitting portion 67 comes off from the screw portion 60 of the conveying screw 54 and at the same time comes into contact with the screw portion 60 of the conveying screw 54 by the urging force of the compression spring 64. Moves to the right by the pitch. As described above, the moving base 55 that has reached the turn-back portion P2 repeats the staying operation of moving left and right by one pitch in the turn-back portion P2 while the conveying screw 54 continues to rotate forward.

  Here, in a state where the moving base 55 stays in the turn-back portion P2, if the motor is reversely rotated to reversely rotate the conveying screw 54, the moving base 55 is quickly moved rightward toward the home position P1. . That is, as described above, the moving base 55 during the dwelling operation is in a state where the left end of the screw portion 60 of the conveying screw 54 and the right end of the screw portion of the fitting portion 67 are always overlapped in the axial direction. When the transport screw 54 is rotated in the reverse direction, the rightward movement is started immediately after the play is eliminated. When the movement base 55 moves in the right direction, the movement in the left direction is caused by the resistance of the front end portion 81 and the rear end portion 82 of the load member 57 due to rubbing against the front side portion 41 and the rear side portion 42. It moves in a stable posture inclined in the opposite direction to the time. Therefore, the cleaning member 56 can wipe the foreign matter adhering to the discharge wire 35 without wiping.

  As described above, according to the present embodiment, the moving base 55 is moved by the load screw 57 and the moving base 55 by the load member 57 both in the forward path moving from the home position P1 to the folded portion P2 and in the reverse path. Since the foreign material on the discharge wire 35 can be wiped off by the cleaning member 56 in a stable posture that is not affected by play between the toner and the toner, uneven wiping can be suppressed to prevent uneven charging and thus uneven toner image density. it can.

  Further, in the present embodiment, the stay mechanism 62 having the above-described configuration is provided on the folding portion P2 side and the home position P1 side of the conveying screw 54, thereby controlling the rotation direction of the motor in the normal rotation and reverse rotation, and the rotation thereof. The above-described cleaning operation and return operation of the moving base 55 can be performed by simple control such as control of the duration of the above. Here, the return operation is, for example, when the moving base 55 is stopped between the home position P1 and the turn-back portion P2 due to a power failure, jamming (paper jam) processing, or the like. The operation to return to the position P1.

  In the present embodiment, the time for the movement base 55 to move from the home position P1 to the turn-back portion P2 or the time to move from the turn-back portion P2 to the home position P1 by the forward / reverse rotation of the motor, including the margin time. Assuming T seconds, the moving base 55 can be returned to the home position P1 by rotating the motor in the reverse direction for T seconds or longer, regardless of the position on the conveying screw 54. Further, at the time of normal cleaning, the reciprocating cleaning operation of the moving base 55 can be performed by rotating the motor forward for T seconds or more and then rotating it reversely for T seconds or more. That is, the cleaning operation can be performed without complicated control of the sensor for detecting the position of the movement base 55 and the motor based on the output of the sensor.

  In the present embodiment, as described above, since the load member 57 is disposed at a position where the distance from the conveying screw 54 is farther than the discharge wire 35, the load resistance acting on the load member 57 is increased. Without this, the moment acting on the moving base 55 can be increased, so that the load on the motor due to the provision of the load member 57 can be reduced.

<Embodiment 2>
The present embodiment will be described with reference to FIGS. Of these, FIG. 6 is a diagram corresponding to FIG. 4 of the first embodiment. FIG. 7 is a diagram illustrating the shape of the load member 83 in a non-contact state. FIG. 8 is a diagram illustrating a state where the load member 83 is rubbed against the front side portion 41 and the rear side portion 42. In the present embodiment, the shape of the load member 83 is formed asymmetrically with respect to the center line C corresponding to the discharge wire 35 and is formed point-symmetrically with respect to the center point M. As a specific example, FIGS. 6, 7, and 8 show examples in which the load member 83 is formed in a parallelogram shape.

  As shown in FIGS. 6 and 7, in the natural state, the load member 83 has a pair of sides a and b perpendicular to the front side portion (first side portion) 41 and the rear side portion (second side portion) 42. Arrange as follows. Here, the load (friction resistance) generated by the sliding friction between the front end portion (first end portion) 84 of the load member 83 and the front side portion 41 of the shield 33 is the first load, while the rear end portion of the load member 83 ( A load (friction resistance) generated by sliding between the second end portion 85 and the rear side portion (second side portion) 42 of the shield 33 is defined as a second load. Further, the load member 83 in FIG. 7 moves in the direction of the arrow K1 with the movement of the moving base 55 toward the turn-back portion P2 due to the forward rotation of the transport screw 54, and conversely, the load member 83 is transported. As the moving base 55 moves toward the home position P1 due to the reverse rotation of the screw 54, it moves in the direction of the arrow K2. The other pair of sides c and d of the load member 83 is rubbed with the front end portion 84 in the forward direction and the rear end portion 85 in the counter direction when the load member 83 moves in the direction of the arrow K1, while the load member 83 When moving in the direction of arrow K2 of 83, the rear end portion 85 is slid in the forward direction and the front end portion 84 is rubbed in the counter direction. Therefore, when the load member 83 moves in the direction of the arrow K1, the second load is larger than the first load. Conversely, when the load member 83 moves in the direction of the arrow K2, the first load is greater than the second load. As a result, when moving in either the arrow K1 direction or the arrow K2 direction, as shown in FIG. 8, the load member 83 has a central point M in FIG. A moment in the direction of the arrow M1 acts, and the cleaning member 56 is rubbed against the discharge wire 35 in a state where the moving base 55 is twisted in the same direction. As a result, the discharge wire 35 is rubbed by the cleaning member 56 in an inclined state as shown in FIG. For this reason, compared with the case where it rubs straightly, it is rubbed still more favorably and a foreign material is also wiped off favorably. Therefore, the occurrence of uneven wiping is further suppressed.

<Embodiment 3>
This embodiment will be described with reference to FIG. FIG. 9 is a diagram corresponding to FIG. 4 of the first embodiment.

  In the present embodiment, as shown in FIG. 9, slits 87 and 88 for inserting the load member 86 are provided in the holding portion 68 of the moving base 55. The holding portion 68 is formed hollow inside, and slits 87 and 88 are formed at the front end portion and the rear end portion. The load member 86 can be attached to the moving base 55 by being inserted in the front-rear direction with respect to the slits 87 and 88. According to the present embodiment, the load member 86 can be easily attached to and detached from the moving base 55.

  In the above description, the case where the discharge wire of the charging device is cleaned according to the present invention has been described. However, the present invention is not limited to the charging device, and is generally applicable to the case where the wire is cleaned with a cleaning member to wipe off foreign matters. can do.

1 is a left side view schematically showing a schematic configuration of an entire image forming apparatus. It is an AA line arrow enlarged view in FIG. FIG. 3 is an enlarged view taken along line B-B in FIG. 2. FIG. 4 is a perspective view showing a state where the charging device shown in FIG. 3 is turned upside down and a part of a front side portion and a rear side portion are further removed. It is a figure explaining the return part vicinity in a conveyance screw. FIG. 5 is a diagram corresponding to FIG. 4 in the second embodiment. It is a figure explaining the contact state with respect to the shape of a load member, the front side part, and the rear side part in Embodiment 2. FIG. It is a figure explaining the state which a cleaning member twists and discharges a discharge wire by difference in contact resistance of a front end part and a rear end part of a load member. It is a perspective view explaining the structure of the movement base in which the attachment or detachment of a load member is easy in Embodiment 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Charging apparatus, 11 ... Image forming apparatus, 33 ... Shield, 34 ... Opening part, 35 ... Discharge wire, 36 ... Cleaning mechanism, 40 ... Back part, 41 ... Front side part (1st Side), 42 ...... Rear side (second side), 54 ... Conveying screw, 55 ... Moving base, 56 ... Cleaning member, 57,83,86 ... Load member, 81,84 ... Front end (first end), 82, 85 ... Rear end (second end), C ... Center line of load member, M ... Center point of load member, P ... Sheet (other member)

Claims (4)

A shield having a back portion and two side portions, the cross-sectional shape orthogonal to the longitudinal direction being formed in a “U” shape, and stretched in the vicinity of the opening of the shield along the longitudinal direction of the shield In a charging device comprising a discharge wire and a cleaning mechanism for cleaning the discharge wire,
The cleaning mechanism includes a conveying screw disposed along the discharge wire between the back surface portion and the discharge wire inside the shield,
A moving base that is loosely fitted to the conveying screw and moves along the discharge wire with the rotation of the conveying screw;
A cleaning member held by the moving base and sandwiching the discharge wire;
E Bei and a load member that imparts a load to the moving base by being rubbed on the inner surface of the side portion in accordance with movement of the moving base is held on the movable base,
The load member is formed by a plate-like member that is elastically deformed by contacting the inner surface of the side portion.
The base end side held by the moving base is held parallel to the back surface portion,
The two sides of the shield are the first side and the second side, and the load member has the side
Both ends along the direction orthogonal to the conveying screw are the first end and the second end,
A load generated when the first end portion is rubbed against the first side portion is a first load, and the second end portion is a front load.
When the load generated by rubbing against the second side portion is the second load,
In the load member, the moving base moves in the forward direction by the forward rotation of the conveying screw.
The second load is greater than the first load, and the conveying screw is
When the moving base moves in the reverse direction due to reverse rotation, the first load is the second load.
Formed to be larger than,
A charging device. The load member is formed asymmetrically with respect to a center line corresponding to the discharge wire.
Are formed symmetrically with respect to the center point,
The charging device according to claim 1. The load member is detachable from the moving base;
The charging device according to claim 1, wherein: Charging the photoreceptor, exposing it to form an electrostatic latent image, developing the electrostatic latent image as a toner image,
In the image forming apparatus for transferring the toner image from the photoconductor to another member,
  The means for charging the photoconductor is disposed so as to face the photoconductor.
It is a charging device of any one of thru | or 3.
  An image forming apparatus.

Images