JP3597817B2 - Charging device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a charging device that is used in an electrophotographic image forming apparatus such as a copying machine, a facsimile, and a printer, and that charges a surface of a photosensitive member to a predetermined potential.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus such as a copying machine is provided with a charging device that charges a photosensitive drum to a predetermined potential in order to enable formation of an electrostatic latent image on the surface of the photosensitive drum. ing. As shown in FIG. 12, in the charging device 3 ′, the charging wire 31 facing the photoconductor drum 4 and extending in the width direction thereof (that is, the rotation axis direction of the photoconductor drum 4) opens the photoconductor drum 4 side. It is housed in a shield case 32 ', and has a structure in which a grid 33 is provided at an open portion of the shield case 32'. Then, a high voltage is applied to the charging wire 31 to charge the surface of the photosensitive drum 4, and a bias voltage is applied to the grid 33 to reduce uneven charging potential on the surface of the photosensitive drum 4.
[0003]
As shown in FIG. 13, the grid 33 is held in a state where a required tension is applied by a holding member 35 ′ attached to a longitudinal end of the shield case 32. This is because, in order to uniformly control the charging potential of the photosensitive drum 4, it is necessary to prevent the photosensitive drum 4 from sagging due to its own weight and to set the positional accuracy within a predetermined range. The holding member 35 'is often formed of a leaf spring so as to reduce a change in tension at the time of assembly, transportation, environmental change, and the like. A base portion 35b 'attached to and fixed to the case 32' and an elastic portion 35c 'for applying tension to the grid 33 locked by the locking portion 35a' by being elastically deformed like a bow are provided. I have.
[0004]
[Problems to be solved by the invention]
In the holding member 35 ', the vertical length l of the elastic portion 35c' is formed to be somewhat longer in order to obtain elasticity for applying a required tension to the grid 33. Therefore, the holding member 35 'becomes large, which is a factor that hinders the miniaturization of the charging device 3'. In addition, when trying to obtain the required tension by the holding member 35 ′ having a reduced length 1 of the elastic portion 35 c ′, the amount of deformation of the elastic portion 35 c ′ must be increased, so that an appropriate tension is obtained. It is difficult to set the elastic portion 35c 'in the first position.
[0005]
The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a charging device in which a holding member is miniaturized and which can apply a required tension stably to a grid. And
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 provides a grid in which a predetermined voltage is applied by applying a high voltage to a charging wire extending in the width direction of the photoreceptor to generate a corona discharge. A charging device for charging the photoreceptor surface to a predetermined voltage via
A shield case for opening the photoconductor side and housing the charging wire,
A holding member attached to a longitudinal end of the shield case and holding the grid,
The holding member has an elastic portion having a shape bent and protruded in the longitudinal direction of the shield case, and the elastic portion elastically deforms and holds the grid in a state where tension is applied to the grid. is there.
[0007]
According to this configuration, since the elastic portion of the holding member is bent and formed so as to protrude in the longitudinal direction of the shield case, when the elastic portion is elastically deformed, the amount of bending is reduced instead of its length in the vertical direction. And the adjustment and setting of the elastic part for obtaining the required tension can be easily performed. Accordingly, an error between the required tension of the grid and the tension applied to the grid from the elastic portion can be reduced, so that a relatively stable tension can be applied to the grid even if the holding member is configured to be small. it can.
[0008]
The invention according to claim 2 is the charging device according to claim 1, wherein the holding member has a shape in which the elastic portion is bent so as to protrude inward in a longitudinal direction of the shield case. Is what it is.
[0009]
According to this configuration, since the elastic portion protrudes inward in the longitudinal direction of the shield case and is bent, and the bent portion of the elastic portion does not protrude outward in the longitudinal direction of the shield case, the shield required for attaching the holding member is provided. The space in the longitudinal direction of the case can be reduced.
[0010]
According to a third aspect of the present invention, there is provided the charging device according to the first or second aspect, wherein the holding member includes a locking portion for locking the grid, and a longitudinal direction of the shield case. And a support portion extending in the longitudinal direction of the shield case and having a lower portion in contact with the bottom of the shield case.
[0011]
According to this configuration, since the holding member is supported by the contact between the lower portion of the support portion and the bottom of the shield case, the elastic portion of the holding member is elastically deformed and the holding member is pulled inside the shield case. In addition, the inclination of the holding member in the pulling direction is reduced, and the attachment state of the holding member to the shield case is stabilized.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a charging device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a schematic configuration of an image forming apparatus provided with the charging device of the present invention. As shown in FIG. 1, in a copying machine 1 which is an example of an image forming apparatus according to the present invention, a photoconductor drum (photoconductor or image) rotated in a direction A in FIG. The carrier 4 is uniformly charged, and an electrostatic latent image is formed on the photosensitive drum 4 by a laser beam from an exposure device (laser scanning unit or the like) 6 based on the document image read by the document reading device 5. Then, a developer (hereinafter, referred to as toner) is attached to the electrostatic latent image by the developing device 7 to form a toner image. The supply of the toner to the developing device 7 is performed from the toner container 8.
[0013]
The paper is conveyed from the paper feeding mechanism 9 via the paper conveyance path 10 toward the photoconductor drum 4 on which the toner image is formed as described above, and the toner image on the surface of the photoconductor drum 4 is transferred by the transfer roller 11 to the paper. Is transferred to Then, the sheet on which the toner image has been transferred is separated from the photosensitive drum 4, and is conveyed to a fixing device 12 having a pair of fixing rollers, where the toner image is fixed. The sheet that has passed through the fixing device 12 is sent to a sheet conveying path 13 branched in a plurality of directions, and the conveying direction is divided by a branching member at a branch point of the sheet conveying path 13, and is sent as it is (or sent to the sheet conveying path 17). The sheet is then ejected from the sheet ejection section of the upper sheet tray 102a, the lower sheet tray 102b, or the sheet tray 103.
[0014]
The present invention relates to the charging device 3 described above, and particularly relates to mounting of the charging device 3 on a shield case of a grid (details will be described later).
[0015]
Reference numeral 16 denotes a cleaning unit that removes residual toner and the like on the photoconductor drum 4, and a rubbing roller 160 refines the surface of the photoconductor drum 4. The paper feeding mechanism 9 is detachably attached to the copying machine main body 2 and includes paper feeding cassettes 91 and 92 for storing paper, and a stack bypass (bypass tray) 93 provided above the paper feeding cassettes 91 and 92. Is connected to an image forming unit including the photosensitive drum 4 and the developing device 7 by a paper transport path 10.
[0016]
The charging device 3 will be described with reference to FIG. 2 and FIG. FIG. 2 is a perspective view showing the charging device 3. The charging device 3 includes a charging wire 31 for corona discharge, which extends in the width direction of the charging device 3 facing the photoconductor drum 4, and a shield of a long box body in which the charging wire 31 is stored and the photoconductor drum 4 side is opened. The case 32 has a grid 33 attached to the opening 32 a of the shield case 32 so as to be interposed between the charging wire 31 and the photosensitive drum 4. The charging device 3 applies a high voltage to the charging wire 31 to generate corona discharge, and charges the surface of the photosensitive drum 4 to a predetermined potential via the grid 33. A bias voltage is applied to the grid 33 so as to reduce uneven charging potential on the surface of the photosensitive drum 4.
[0017]
The charging wire 31 is stretched inside the shield case 32 in the width direction of the photoconductor drum 4, that is, in the rotation axis direction of the photoconductor drum 4. The grid 33 is a conductive thin plate in which a mesh-like hole 33 e is opened in a control area for controlling the charging potential, and is locked at both ends in the longitudinal direction of the shield case 32. A notch 32b is provided on the side wall (front side in FIG. 2) of the longitudinal end of the shield case 32 in order to improve the convenience of attaching the charging wire 31 to the shield case 32 and a holding member described later. Has been.
[0018]
Next, a holding member used to attach the grid 33 to the longitudinal end of the shield case 32 will be described. FIG. 3 is a perspective view showing the holding member, and FIG. 4 is a perspective view showing the holding member viewed from a different angle from FIG. The holding member 35 is attached to the inside of the side wall at the longitudinal end of the shield case 32, and plays a role of locking the grid 33 and locking the grid 33 to the shield case 32.
[0019]
The holding member 35 includes a locking portion 35a to which the grid 33 is locked, a base portion 35b attached to and fixed to an end of the shield case 32, and an elastic portion 35c which elastically deforms and applies tension to the grid 33. have. The locking portion 35a locks with a hole 33a (FIG. 2) formed near the longitudinal end of the grid 33. The locking portion 35a is provided with a flange portion 35d for restricting the vertical movement of the grid 33 locked to the locking portion 35a.
[0020]
The elastic part 35c is provided so as to extend upward from the base part 35b, and the locking part 35a is provided at the upper end thereof. The elastic portion 35c is bent so as to protrude outward in the longitudinal direction of the shield case 32, and has a substantially “C” shape in side view. Thus, the elastic portion 35c is elastically deformed in the longitudinal direction of the shield case 32 and in a direction (vertical direction) perpendicular to the longitudinal direction. When the hole 33a of the grid 33 is locked by the locking portion 35a and the holding member 35 holds the grid 33, tension is applied to the grid 33 by the elastic force generated by the elastic deformation. I have.
[0021]
The base portion 35b is provided with a protruding piece 35e at the upper portion thereof, which is in contact with the side wall of the longitudinal end of the shield case 32. The protruding piece 35e has flexibility, and has a shape that is inclined outward and extends upward in the longitudinal direction of the shield case 32, and is pressed by a side wall 322a of the holding member mounting portion 322 (see FIG. 5 described later). The holding member 35 is prevented from coming off. Further, around the portion where the elastic portion 35c of the base portion 35b is provided, cutout portions 35f are provided on both sides of the elastic portion 35c. The notch 35f increases the relative amount of elastic deformation of the elastic portion 35c.
[0022]
Further, on the side of the base portion 35b, support portions 35g and 35h are provided at positions deviated from the locking portions 35b in the longitudinal direction of the shield case 32 and extend in the longitudinal direction of the shield case 32. In particular, a lower 35h ₁ of the support portion 35h, the contact between the bottom portion 32c of the shield case 32, the elastic portion 35c of the holding member 35 is elastically deformed, even when pulled toward the inside of the shield case 32, the holding member The inclination of the 35 in the pulling direction is reduced, and the attachment state of the holding member 35 to the shield case 32 is stabilized.
[0023]
The end portion 35i of the support portion 35h has a bifurcated shape, and is locked with a locking portion (not shown) provided on a side wall extending in the longitudinal direction in the shield case 32 to restrict the vertical movement of the holding member 35. The mounting condition is made more stable.
[0024]
The support portions 35g and 35h are formed so as to be orthogonal to the base portion 35b, and the side surfaces thereof are set to abut on both side walls extending in the longitudinal direction of the shield case 32. Accordingly, the holding posture of the holding member 35 is supported by the both side walls, so that the one side of the base 35b is prevented from being shifted toward the inside of the shield case 32, and the holding member in the shield case 32 is reduced. The mounting state of 35 is further stabilized.
[0025]
Next, an attachment portion of the holding member 35 to the longitudinal end of the shield case 32 will be described. FIG. 5 is a perspective view showing a longitudinal end of the shield case 32, and FIGS. 6 and 7 are perspective views showing a state in which the holding member 35 and the charging wire 31 are attached to the shield case 32 end. At a longitudinal end 321 of the shield case 32, a holding member attaching portion 322 in which the holding member 35 is housed and attached, and a wire fixing portion 323 to which one end of the charging wire 31 is attached and fixed are provided. I have.
[0026]
The holding member mounting portion 322 is formed by being surrounded by a side wall 322a at the longitudinal end of the shield case 32, a side wall 322b extending in the longitudinal direction, and a projection 322c. The lower portion of the elastic portion 35c of the holding member 35 is placed on the bottom 322d in the holding member mounting portion 322. A hole 322e into which the base 35b of the holding member 35 is inserted is provided between the bottom 322d and the protrusion 322c. The portion of the holding member 35 where the elastic portion 35c protrudes outward in the longitudinal direction of the shield case 32 is arranged between two protrusions 322f provided on the side wall 322a.
[0027]
A notch 32b is provided in the side wall 322a. The cutout portion 32b is provided on the extension of the charging wire 31 attached to the wire fixing portion 323, and is provided so as to allow the inside and outside of the shield case 32 to pass through the side wall 322a to which the holding member 35 is attached. ing. Further, the notch 32b has a shape cut out below a position (a vertical position) of the charging wire 31 attached to the wire fixing portion 323.
[0028]
When the holding member 35 is attached to the holding member attaching portion 322, the base portion 35b of the holding member 35 comes into contact with the projection 322c, and the tip of the protruding piece 35e comes into contact with the inner wall 322g with a predetermined pressure. I have.
[0029]
The support portion 35g of the holding member 35 comes into contact with the side wall 322b on the near side of the shield case 32 in FIG. 5 and FIG. Supporting portion 35h of the holding member 35, abuts against the bottom portion 32c of the lower 35h ₁ is the shield case 32, the side surface portions are adapted to abut against the inner side of the side wall 322b in FIG. 5 and FIG. The distal end 35i of the support 35h is sandwiched between the side wall 322b and the second side wall 322h. The distal end portion 35i is attached so as to sandwich an engaging portion (not shown) provided between the side wall 322b and the second side wall 322h, and is attached to the shield case 32 (holding member attaching portion 322). The holding member 35 is positioned in the up-down direction to stably conduct electricity.
[0030]
The housing 325 of the shield case 32 is adapted to be attached to the side 324 of the end 321 of the shield case 32, and is formed on the housing 325 on a protrusion 324 a provided on the side 324. By fitting the hole 325a, the housing 325 is positioned with respect to the end 321 in the up, down, left, and right directions.
[0031]
The attachment of the charging wire 31 to the shield case 32 will be further described with reference to FIG. FIG. 8 is a perspective view schematically showing a state in which the charging wire 31 is assembled to the wire fixing portion 323. First, the charging wire 31 is made to extend in the longitudinal direction of the shield case 32, and is placed in a wire mounting groove 323 a provided in the wire fixing portion 323. From outside the shield case 32. Then, holding the leading end of the charging wire 31 outside the shield case 32, pulling the charging wire 31 to apply a required tension to the charging wire 31, and further pressing the charging wire 31 against the bottom of the wire mounting groove 323a. The charging wire 31 is pushed down. As described above, since the cutout portion 32b is cut out below the position of the charging wire 31 attached to the wire fixing portion 323, the work of pushing down the charging wire 31 can be performed. I have.
[0032]
In this way, a predetermined tension is applied to the charging wire 31, and after the charging wire 31 is pressed against the wire mounting groove 323a, the MC pin 323c is fitted into the fitting hole 323b of the wire fixing portion 323 from above. The charging wire 31 is fixed to the wire fixing part 323. Although not particularly shown, a mounting groove having a position and a shape corresponding to the wire mounting groove 323a is also provided below the MC pin 323c, and the charging wire 31 is sandwiched between the mounting groove and the wire mounting groove 323a. The charging wire 31 is fixed to the wire fixing portion 323. The other end of the charging wire 31 is fixed to the other end in the longitudinal direction of the shield case 32 by a spring member as an elastic member.
[0033]
As a result, the charging wire 31 is fixed in the shield case 32 while being stretched with a required tension over the width direction of the photosensitive drum 4. After the holding member 35 is attached to the holding member attachment portion 322, the holding member 35 is interposed between the wire fixing portion 323 and the notch portion 32b, and the work of attaching the charging wire 31 cannot be performed. The attachment of the charging wire 31 is performed before the attachment of the holding member 35.
[0034]
Next, attachment of the grid 33 to the holding member 35 will be described with reference to FIGS. 9 and 10 and FIG. 9 is a perspective view schematically showing a state where the holding member 35 is about to be pressed from the outside of the shield case 32, and FIG. 10 is a perspective view showing a state where the grid 33 is attached to the holding member 35. After the charging wire 31 and the holding member 35 are mounted in the shield case 32 as described above, first, a hole 33c provided in the rear end 33b of the grid 33 is provided in the end of the shield case 32. The projection 327 is engaged (FIG. 2).
[0035]
Then, as shown in FIG. 9, a driver or the like is inserted from the outside of the shield case 32 into the cutout portion 32b of the side wall 322a to press the holding member 35, and the elastic portion 35c of the holding member 35 is elastically inserted inside the shield case 32. Deform. When the holding member 35 is elastically deformed inside the shield case 32, the hole 33a provided in the tip portion 33d of the grid 33 is engaged with the locking portion 35a of the holding member 35 (FIG. 10). At this time, the flange 35d of the locking portion 35a protrudes from the hole 33a to the upper portion of the grid 33, restricts the vertical movement of the grid 33, and securely fixes the position of the grid 33 with respect to the locking portion 35a. In this way, the grid 33 is attached to the opening 32a (FIG. 12) of the shield case 32 so as to be interposed between the charging wire 31 and the photosensitive drum 4.
[0036]
The arrangement of the holding member 35 in the shield case 32 is set such that the elastic portion 35c is elastically deformed inside the shield case 32 when the grid 33 is attached as described above. Thus, by attaching the grid 33 to the shield case 32 by engaging the projection 327 and the locking portion 35a, a required tension is applied to the grid 33.
[0037]
As described above, according to the charging device 3 of the present invention, since the elastic portion 35c of the holding member 35 is bent and protruded in the longitudinal direction of the shield case 32, the grid 33 is attached to the holding member 35. When the elastic portion 35c of 35 is elastically deformed, the amount of flexure becomes large instead of the length of the elastic portion 35c in the vertical direction, and the adjustment and setting of the elastic portion 35c for obtaining a required tension can be easily performed. . Accordingly, an error between the required tension of the grid 33 and the tension applied to the grid 33 from the elastic portion 35c can be reduced, so that even if the holding member 35 (elastic portion 35c) is configured to be small, it is relatively stable. The applied tension can be applied to the grid 33.
[0038]
In addition, the leading end of the charging wire 31 is set to be outside the shield case 32 from the cutout portion 32b of the shield case 32, and the required tension is held by holding the leading end of the charging wire 31 outside the shield case 32. An operation of pulling the charging wire can be performed to provide the charging wire, and further, an operation of pressing the charging wire downward to press the charging wire against the wire fixing portion can be performed. This facilitates the operation of fixing the charging wire 31 to the wire fixing portion 323, and simplifies the operation of attaching the charging wire 31 to the shield case 32.
[0039]
Further, when attaching the grid 33 to the holding member 35, the holding member 35 can be pressed from the outside of the shield case 32 to the inside of the shield case 32 through the notch 32 b. Therefore, when attaching the grid 33 to the holding member 35, the operation of elastically deforming the holding member 35 to the inside of the shield case 32 can be easily performed. This facilitates the work of attaching the grid 33 to the holding member 35 and the work of assembling the grid 33 to the shield case 32.
[0040]
Note that the present invention is not limited to the configuration of the above embodiment, and various modifications are possible. For example, in the above-described embodiment, the holding member 35 has a shape in which the protruding piece 35e, the support portion 35g, and the support portion 35h are provided. It may be composed of the locking portion 35a and the base portion 35b. The holding member 35 has a shape in which the elastic portion 35c is bent so as to protrude outward in the longitudinal direction of the shield case 32. Instead of such a holding member 35, for example, as shown in FIG. Alternatively, a holding member 350 having an elastic portion 350c bent and formed to protrude inward in the longitudinal direction of the shield case 32 without the protruding piece 35e, the support portion 35g, and the support portion 35h described above may be applied.
[0041]
In the above embodiment, the notch 32b provided on the side wall 322a of the shield case 32 is cut out to a position lower than the position of the charging wire 31 attached to the wire fixing portion 323. However, the shape may be cut out only to the same position as the position of the charging wire 31 attached to the wire fixing portion 323. In the above-described embodiment, the cutout portion 32b is configured to be disposed on an extension of the charging wire 31 attached to the wire fixing portion 323, and is provided on the side wall 322a where the holding member 35 is attached. Although the configuration is adopted, a configuration satisfying only one of them may be adopted.
[0042]
【The invention's effect】
As described above, according to the present invention, the elastic portion of the holding member has a shape that is bent by protruding in the longitudinal direction of the shield case. Instead, the amount of deflection increases, and adjustment and setting of the elastic portion for obtaining the required tension can be easily performed. Accordingly, an error between the required tension of the grid and the tension applied to the grid from the elastic portion can be reduced, so that a relatively stable tension can be applied to the grid even if the holding member is configured to be small. it can.
[0043]
Further, if the elastic portion is configured to be bent by protruding inward in the longitudinal direction of the shield case, the bent portion of the elastic portion does not protrude outward in the longitudinal direction of the shield case. The space in the longitudinal direction can be reduced.
[0044]
Further, the holding member is provided at a position where the holding member is locked to the grid and at a position deviated from the locking portion in the longitudinal direction of the shield case, extends in the longitudinal direction of the shield case, and has a lower portion corresponding to the bottom of the shield case. With a configuration having a supporting portion in contact with the supporting portion, the holding member is supported by the contact between the lower portion of the supporting portion and the bottom of the shield case. For example, when the holding member is pulled toward the shield case, the inclination of the holding member in the pulling direction is reduced, and the attachment state of the holding member to the shield case is stabilized.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating a schematic configuration of an image forming apparatus including a charging device according to the present invention.
FIG. 2 is a perspective view showing the charging device.
FIG. 3 is a perspective view of a holding member.
FIG. 4 is a perspective view of the holding member viewed from a different angle from FIG. 3;
FIG. 5 is a perspective view showing a longitudinal end of the shield case.
FIG. 6 is a perspective view showing a state where a holding member and a charging wire are attached to an end of the shield case.
FIG. 7 is a perspective view showing a state where a holding member and a charging wire are attached to an end of the shield case.
FIG. 8 is a perspective view schematically showing a state in which a charging wire is assembled to a wire fixing portion.
FIG. 9 is a perspective view schematically showing a state where the holding member is about to be pressed from the outside of the shield case.
FIG. 10 is a perspective view showing a state where a grid is attached to a holding member.
FIG. 11 is a perspective view showing another embodiment of the holding member.
FIG. 12 is a side sectional view showing a schematic configuration of a conventional charging device.
FIG. 13 is a perspective view showing a conventional holding member.
[Explanation of symbols]
1 Copier (image forming apparatus)
3 Charging Device 4 Photoconductor Drum 31 Charging Wire 32 Shield Case 32a Opening 32b Cutout 33 Grid 33a Hole 35,350 Holding Member 35b Base 35a Locking 35h Fixed 35g Fixed 35c Elastic 35e Projection 322 Holding Member Mounting part 323 Wire mounting part 323a Wire mounting groove 323c Pin 323b Fitting hole 350c Elastic part

Claims (3)

A charging device that applies a high voltage to a charging wire extending in the width direction of the photoconductor to generate corona discharge, and charges the surface of the photoconductor to a predetermined voltage through a grid to which a predetermined grid voltage is applied. So,
A shield case for opening the photoconductor side and housing the charging wire,
A holding member attached to a longitudinal end of the shield case and holding the grid,
The holding member has an elastic portion in a shape protruded and bent in the longitudinal direction of the shield case, and the elastic portion elastically deforms and holds the grid in a state where tension is applied to the grid. Characteristic charging device. The charging device according to claim 1, wherein the holding member has a shape in which the elastic portion is bent so as to protrude inward in a longitudinal direction of the shield case. The holding member is provided at a locking portion where the grid is locked, and at a position deviated from the locking portion in the longitudinal direction of the shield case, extends in the longitudinal direction of the shield case, and a lower portion is a bottom portion of the shield case. 3. The charging device according to claim 1, further comprising: a supporting portion that contacts the charging device. 4.

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