JP4876786B2 - Charging device, process unit and image forming apparatus - Google Patents

Description

  The present invention relates to a charging device having a grid for controlling a charging potential on the surface of an image carrier, a process unit including the charging device, and an image forming apparatus, and more particularly to improvement of a technique for cleaning the grid.

An electrophotographic image forming apparatus exposes a uniformly charged image bearing member such as a photosensitive drum to form an electrostatic latent image, and develops the formed electrostatic latent image with a developer such as toner. The image is formed by transferring the developed image onto a sheet.
The charging device for charging the image carrier is located in a space between the discharge electrode and the image carrier, which is a long discharge electrode made of a wire or a sawtooth, etc. that generates a discharge. In many cases, the so-called scorotron system is provided with a long grid for controlling the charging potential of the image carrier to be constant.

The grid is usually held at both ends by a pair of holders, and the distance from the image carrier is a predetermined distance that is predetermined as an optimum distance for potential control, for example, about 1.0 to 1.5 [mm]. So that it is positioned.
In the case of such a scorotron method, for example, when the grid surface is partially contaminated by dust in the apparatus or toner particles leaking from the developing device, the potential distribution on the grid due to discharge between the contaminated part and the unstained part. Becomes non-uniform and the surface of the image carrier cannot be uniformly charged.

Therefore, conventionally, a cleaning member that cleans the grid is provided in the charging device. For example, there exists a structure which cleans a grid by making a cleaning member contact the surface at the side of the discharge electrode of a grid, and sliding in a longitudinal direction.
JP 2002-311691 A

However, the conventional configuration has a problem that the dirt on the grid cannot be effectively removed.
This is because when the cleaning member is slid to remove the dirt on the grid, it is necessary to press the cleaning member against the grid with a certain force.
However, the grid is made of a long thin metal plate or metal wire, and is stretched so as to be pulled in the longitudinal direction by an urging force such as a spring. . On the other hand, the prescribed interval is extremely narrow as about 1.0 to 1.5 [mm] as described above.

For this reason, if the cleaning member is pressed against the grid by applying a certain amount of pressing force, the grid is likely to be bent and contact the surface of the image carrier to damage the image carrier. A scratch on the image carrier directly leads to image quality degradation.
Therefore, the cleaning member can be cleaned only in a state where it slightly touches the grid surface, and dirt is likely to remain.

  The present invention has been made in view of the above problems, and has a simple configuration that can effectively clean a grid without damaging the image carrier, and a process including the charging device. An object is to provide a unit and an image forming apparatus.

In order to achieve the above object, a charging device according to the present invention is a charging device for charging an image carrier, which is a discharge member and a long space, and a space between the discharge member and the image carrier. Are arranged in a state where tension is applied in the longitudinal direction, and the distance d between the grid for controlling the charging potential of the surface of the image carrier and the grid and the image carrier is a prescribed distance d0. And at least one positioning member that contacts a surface of the grid facing the discharge member in a state in which a pressing force acts between the grid and determines a position of the grid with respect to the image carrier. The positioning member is a cleaning member that cleans the grid, and is configured to be movable in the longitudinal direction of the grid while being in contact with the grid.

The second holder for holding the first holder holding the first part before Symbol grid, the grid, a second portion separated by a predetermined distance from said first portion in the longitudinal direction The first holder holds the first portion of the grid such that the distance d is the specified distance d0, and the second holder is a second portion of the grid. The portion is held at a position farther from the image carrier than the holding position of the first portion by the first holder, and the positioning member is located between the first and second holders during non-cleaning. The grid is positioned so that the distance d becomes the specified distance d0 at the home position, and when cleaning, the grid is moved by moving between the first and second holders. And

  The second holder protrudes toward the image carrier in the interval direction at a position closer to the first holder than a holding position for holding the second portion of the grid. A convex portion is provided, and the position of the tip of the convex portion is located between the holding position of the second end portion and the contact position of the grid by the positioning member in the interval direction, and the positioning When the member is located at the home position, the convex portion and the grid do not come into contact with each other, and when the member moves away from the home position due to movement during cleaning, the convex portion and the grid come into contact with each other. It is characterized by being.

Further, the second holder is provided with a holding portion that holds the positioning member when the positioning member is positioned at the home position and restricts the position in the interval direction. When it is located at the home position, it is held by the holding portion of the second holder.
A first holder for holding the first portion of the grid; and a second holder for holding a second portion of the grid that is a predetermined distance away from the first portion in the longitudinal direction. And when the two positioning members are arranged as the first and second positioning members, the first and second positioning members are each of the first and second positioning members when not being cleaned. The grid is positioned so as to be positioned at the home position between the second holders so that the distance d becomes the specified distance d0. During cleaning, the grid is moved between the first and second holders. And the first and second holders are arranged such that the first and second portions of the grid are positioned more than the position where the grid is positioned by the first and second positioning members. Position away from And wherein the holding.

A process unit according to the present invention includes the above-described charging device as a charging device for charging an image carrier for image formation.
An image forming apparatus according to the present invention includes the above charging device as a charging device for charging an image carrier.

  According to the above configuration, the positioning member, which is an indispensable member for determining the position of the grid, can move in a state of receiving a pressing force from the grid. It is also possible to clean the grid, and there is no need to arrange a cleaning member separately from the positioning member as in the prior art, and the grid can be effectively cleaned with a simple configuration.

Hereinafter, embodiments of a charging device, a process unit, and an image forming apparatus according to the present invention will be described using a tandem color digital printer (hereinafter simply referred to as “printer”) as an example.
FIG. 1 is a diagram illustrating an overall configuration of a printer 1 according to an embodiment.
As shown in the figure, the printer 1 includes an image processing unit 10, a feeding unit 20, a fixing unit 30, a control unit 50, and the like. The printer 1 is connected to a network, here a LAN, and is connected to an external terminal device (not connected). When a print job execution instruction is received from (shown), the print job is executed based on the instruction.

The image processing unit 10 includes image forming units (process units) 2Y, 2M, 2C, and 2K corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (K), and an endless shape. Intermediate transfer belt 11 and the like.
The image forming unit 2Y includes a photosensitive drum 3, a charging unit 4, an exposure unit 5, a developing unit 6, a primary transfer roller 7, a cleaning unit 8, and the like. The charging unit 4 is a scorotron charging device, has a grid 52 (FIG. 3) as a control electrode, and uniformly charges the surface of the photosensitive drum 3. Further, as will be described later, the charging unit 4 has a member that combines a positioning function for determining the position of the grid 52 with respect to the photosensitive drum 3 and a cleaning function for cleaning the grid 52 (hereinafter referred to as “cleaning member”). 56 (FIG. 3).

The image forming unit 2 </ b> Y is configured to be insertable / removable with respect to the apparatus main body, and can be replaced by a user of the printer 1. The other image forming units 2M to 2K have the same configuration as the image forming unit 2Y.
The intermediate transfer belt 11 is stretched around a driving roller 12, a driven roller 13, and a tension roller 14, and is driven to rotate in the direction of arrow B. The cleaning unit 16 cleans residual toner on the surface of the intermediate transfer belt 11.

The feeding unit 20 includes a sheet feeding cassette 21 that accommodates the sheets S, a feeding roller 22 that feeds the sheets S in the sheet feeding cassette 21 one by one, a conveyance roller pair 23 that conveys the fed sheet S, and two A timing roller pair 24 for taking the timing of feeding the sheet S to the next transfer position 15 and a secondary transfer roller 25 are provided.
The control unit 50 receives an image signal transmitted from an external terminal device, converts the image signal into a digital image signal for Y to K colors, and controls the image processing unit 10, the feeding unit 20, and the like. The print operation is executed.

Specifically, for each of the image forming units 2Y to 2K, the photosensitive drum 3 rotating in the direction of arrow A is uniformly charged by the charging unit 4, and the surface of the charged photosensitive drum 3 is exposed by the exposure unit 5. Thus, an electrostatic latent image is formed. The formed electrostatic latent image is developed by the developing unit 6 and visualized as a toner image.
The developed color toner images are primarily transferred from the photosensitive drum 3 onto the intermediate transfer belt 11 by the action of electrostatic force by the primary transfer rollers 7. At this time, the image forming operations for the respective colors are executed at different timings so that the toner images are primarily transferred at the same position on the intermediate transfer belt 11. Each color toner image on the intermediate transfer belt 11 is moved to the secondary transfer position 15 by the rotation of the intermediate transfer belt 11.

  On the other hand, the sheet S is fed from the feeding unit 20 via the timing roller pair 24 in accordance with the movement timing of each color toner image on the intermediate transfer belt 11, and the sheet S rotates. The toner image is sandwiched between the intermediate transfer belt 11 and the secondary transfer roller 25 and conveyed, and the toner image on the intermediate transfer belt 11 is secondarily transferred onto the sheet S by the electrostatic force at the secondary transfer position 15.

The sheet S that has passed the secondary transfer position 15 is conveyed to the fixing unit 30, where the toner image is heated and pressed to be fixed on the sheet S, and then onto the discharge tray 41 via the discharge roller pair 40. Discharged.
Hereinafter, a method for cleaning the grid 52 of the charging unit 4 will be outlined with reference to FIG. 2, and a specific configuration of the charging unit 4 will be described with reference to FIGS. 3 to 7.

FIG. 2 is a diagram schematically showing how the grid 52 is cleaned, in which FIG. 2A shows a state during non-cleaning, and FIGS. 2B and 2C show a state during cleaning. Is shown.
As shown in FIG. 2A, the grid 52 is located in a space between the photosensitive drum 3 and the discharge electrode 51, and tension is applied in the X direction (corresponding to the axial direction of the photosensitive drum 3). It is arranged by.

One end 522 of the grid 52 in the X direction is held by a holder 54, and the other end 521 is held by a holder 53.
Specifically, the end portion 522 of the grid 52 is a portion 540 of the holder 54, and the Y direction (a direction orthogonal to the X direction) between the portion 524 of the grid 52 facing the photosensitive drum 3 and the photosensitive drum 3. The distance d (corresponding to the distance direction between the photosensitive drum 3 and the grid 52) is held at a specified distance d0, for example, 2 [mm]. Here, the prescribed interval d0 is a predetermined interval by experiment or the like as an optimum interval for potential control.

On the other hand, the end portion 521 of the grid 52 is held in the portion 530 of the holder 53 at a position farther from the photosensitive drum 3 than the portion 540 in the Y direction. In other words, the holder 53 holds the end 521 of the grid 52 at a position where the distance d is wider than the specified distance d0.
The cleaning member 56 moves in the X direction between the holders 53 and 54 in a state where the cleaning member 56 is in contact with the surface 520 of the grid 52 facing the discharge electrode 51 to clean the grid 52.

  Further, the cleaning member 56 is located at the home position shown in the figure at the time of non-cleaning, and is held by the holder 53 at the home position, and the portion 523 in contact with the cleaning member 56 in the grid 52 is The interval d is held so as to be a specified interval d0. As a result, the distance d between the portion 524 of the grid 52 and the photosensitive drum 3 is maintained at the specified distance d0. In this sense, the cleaning member 56 functions as a positioning member that determines the position of the grid 52 in the Y direction with respect to the photosensitive drum 3 in addition to the cleaning function of the grid 52.

The cleaning member 56 starts to move from the home position, and when it reaches the position shown in FIG. 2C, it cleans the grid 52 by a reciprocating operation that reverses and returns to the home position.
Since the grid 52 is tensioned in the X direction as described above, the end 521 of the grid 52 is held at a position farther from the photosensitive drum 3 in the Y direction than the end 522 and the portion 523. Thus, the pressing force from the grid 52 acts on the cleaning member 56.

This pressing force continues to act even if the cleaning member 56 moves from the home position in the X direction during cleaning, as shown in FIGS. 2 (b) and 2 (c). Therefore, the cleaning member 56 can clean the grid 52 in a state where a certain amount of pressing force is applied to the grid 52.
The pressing force is generated in a state where the grid 52 is held such that the distance d between the photosensitive drum 3 and the photosensitive drum 3 is a predetermined distance d0. The cleaning of the grid 52 by the cleaning member 56 is performed by the pressing force. It is executed as long as it continues to work. Therefore, it is possible to prevent the cleaning member 56 from being pressed against the grid 52 in order to prevent the photosensitive drum 3 from being scratched as in the prior art, and to prevent the grid 52 from being left behind, thereby improving the cleaning ability.

Next, a specific configuration example of the charging unit 4 will be described.
FIG. 3 is a side view showing the configuration of the charging unit 4, and FIG. 4 is a cross-sectional view taken along the line GG in FIG. 3 when the charging unit 4 is cut. FIG. 5A is a perspective view showing a state in which the grid 52 is held by the holder 53, and FIG. 5B is a perspective view showing a configuration example of the holder 53 with the grid 52 removed. is there. FIG. 6 is a diagram illustrating a state in which the cleaning member 56 is moved during cleaning, and FIG. 7 is another diagram illustrating a state in which the cleaning member 56 is moved.

FIG. 3 shows a non-cleaning state in which the cleaning member 56 is located at the home position, and a part of the shield electrode 55 is cut away so that the internal configuration can be easily understood.
As shown in FIG. 3 and the like, the charging unit 4 includes a discharge electrode 51, a grid 52, holders 53 and 54, a shield electrode 55, a cleaning member 56, a motor 57, a feed screw 58, a tension spring 59, and the like.

The discharge electrode (discharge member) 51 is a long electrode that performs corona discharge. Here, a sawtooth electrode in which a number of sharpened electrodes are arranged in the X direction is used. The discharge electrode is not limited to this, and for example, a wire electrode or a needle electrode may be used.
The grid 52 is formed by forming a thin metal plate into a long shape, and is provided with a number of slit-like grid holes (not shown). The distance d between the grid 52 and the photosensitive drum 3 is a specified distance d0.

The grid 52 is held at a predetermined potential by the control unit 50 and controls the corona ion flow from the discharge electrode 51 to uniformly charge the surface of the photosensitive drum 3.
The shield electrode 55 has a long shape and is a metal member having a U-shaped cross section as shown in FIG. 4 and the like, and shields the discharge of corona ions from the discharge electrode 51 to the outside.
Each of the holders 53 and 54 is a block-shaped member made of resin (FIG. 5). The holder 53 is attached to one end of the shield electrode 55 in the X direction, and the holder 54 is attached to the other end. Has been.

The holders 53 and 54 are provided with hooks 531 and 541. One end of the grid 52 is hooked on the hook 531, and the other end is hooked on the hook 532 via the tension spring 59. As a result, the grid 52 is held in a tensioned state so as to be pulled in the X direction.
The end portion 522 of the grid 52 is held by the holding portion 542 of the holder 54 so that the distance d between the grid 52 and the photosensitive drum 3 becomes d0. In this sense, the holding portion 542 can be said to correspond to the portion 540 in FIG. Further, the end portion 521 of the grid 52 is held by the hook 531 of the holder 53 at a position farther in the Y direction from the photosensitive drum 3 than the holding portion 542. In this sense, the hook 531 corresponds to the portion 530 in FIG.

The cleaning member 56 is a member that cleans the discharge electrode 51 in addition to the grid 52, and includes a holding member 561, cleaners 562, 563, and the like as shown in FIG. Hereinafter, in the description of the figure, the top, bottom, left, and right (vertical and horizontal) are defined based on the position of the discharge electrode 51.
The holding member 561 is a resin member integrally formed so that the first holding piece 565 and the second holding piece 566 are T-shaped when viewed from the front. A lower portion 5651 of the first holding piece 565 is engaged with a notch groove 551 (FIG. 5) provided in the back surface portion 552 of the shield electrode 55 and extending in the X direction, and is held movably in the X direction. .

A central portion 5562 of the first holding piece 565 is bifurcated to the left and right with the discharge electrode 51 in between, and a cleaner 562 that contacts the discharge electrode 51 so as to sandwich the discharge electrode 51 from the left and right inside the branched portion. , 562 are disposed.
The cleaner 562 is made of a velvet material (planted cloth) from the viewpoints of cleanability, durability, ozone resistance, and the like, and cleans toner particles, dust, and the like attached to the discharge electrode 51.

The second holding piece 566 is located on the opening 550 side of the shield electrode 55, and a cleaner 563 is disposed on the upper surface thereof.
The cleaner 563 contacts the surface 520 of the grid 52 and cleans toner particles, dust, and the like attached to the grid 52. Here, the cleaner 563 is made of a flocking cloth similar to the cleaner 562, and has a flocking height of about 0.5 to 1.0 [mm].

The lowermost end portion 5653 of the first holding piece 565 (the portion exposed to the outside through the notch groove 551 of the shield electrode 55) is screwed with the feed screw 58.
The feed screw 58 is connected to the rotating shaft of the motor 57 as shown in FIG. When the feed screw 58 is rotated by the rotation of the motor 57, the holding member 561 (that is, the cleaning member 56) is transferred in the X direction by an amount corresponding to the rotation amount. The charging unit 4 is provided with a sensor (not shown) for detecting the position of the cleaning member 56 in the X direction, and the control unit 50 grasps the position of the cleaning member 56 from the detection result of the sensor. Then, rotation control of the motor 57 is performed.

  A step portion 532 is provided on the portion of the holder 53 facing the holder 54 as shown in the enlarged view (circle) in FIG. The step 532 is provided to hold the cleaning member 56 at the home position. Specifically, when the cleaning member 56 returns to the home position, the second holding piece 566 of the cleaning member 56 stops in a state where the second holding piece 566 rides on the lower surface 533 of the step portion 532. Since the pressing force from the grid 52 is applied to the cleaning member 56 as described above, the second holding piece 566 and the cleaner 563 of the cleaning member 56 are in contact with the grid 52 on the surface 533 of the holder 53 at the home position. It is held in a state where it is pressed against the surface 533 by the pressing force from the grid 52 while being sandwiched between 533.

In this holding state (in the home position), the size of the second holding piece 566, the thickness of the cleaner 563, and the surface so that the distance d between the grid 52 and the photosensitive drum 3 coincides with d0. The height of 533 and the like is determined in advance from experiments and the like.
The cleaning member 56 is moved by a feed screw 58, and positional variation in the Y direction may occur due to movement such as screw backlash. Therefore, in the present embodiment, when the cleaning member 56 is positioned at the home position, the cleaning member 56 is also held by the step portion 532 of the holder 53 to restrict the position of the cleaning member 56 in the Y direction (interval direction). Thus, the position of the grid 52 in the Y direction can be held more securely. In this sense, it can be said that the stepped portion 532 functions as a holding portion that holds the cleaning member 56 at the home position and restricts the position in the interval direction.

  When the cleaning member 56 starts to move from the home position for cleaning, the second holding piece 566 of the cleaning member 56 has the surface 533 of the holder 53 by an amount corresponding to the variation due to the backlash or the like, as shown in FIG. It moves so that it may descend the slope 534 provided in and moves away from the holder 53, and starts the cleaning operation of the grid 52. When moving further in the X direction, the portion 525 of the grid 52 comes into contact with the top (convex portion) 536 of the holder 53 as shown in FIG. The top portion 536 is provided to maintain the pressing force of the grid 52 to the cleaning member 56 to a certain level even when the cleaning member 56 is away from the home position.

  That is, when the cleaning member 56 is located at or near the home position, the grid 52 does not contact the top 536, and the portion 525 of the grid 52 is linear, but if the cleaning member 56 is separated from the home position by a certain distance, After that, it comes into contact and bends at the portion 525, and when the top portion 536 is not provided, the extension amount of the tension spring 59 becomes longer than when it remains linear (tensile tension). In this manner, a decrease in tension in the X direction of the grid 52 is suppressed. Since the pressing force of the grid 52 to the cleaning member 56 depends on the magnitude of the tension of the grid 52, the decrease in the pressing force is suppressed as much as the decrease in the tension is suppressed, and the size necessary for cleaning is maintained. .

For example, if the configuration is such that the tension of the grid 52 increases as the amount of movement of the cleaning member 56 from the home position increases, the top portion 536 may be omitted. However, it is sufficient if a necessary pressing force can be obtained during cleaning, and a tension spring having a somewhat large spring constant may be employed.
When the cleaning member 56 moves to the reverse position (FIG. 2C), the motor 57 reverses, the cleaning member 56 moves in the opposite direction, returns to the home position, and stops. The grid 52 is also cleaned until returning to the home position.

Immediately before the cleaning member 56 reaches the home position, the second holding piece 566 of the cleaning member 56 moves on the surface 533 by moving up the slope 534 provided on the surface 533 of the step portion 532. In this sense, the slope 534 can be said to have a function of smoothly guiding the cleaning member 56 that has returned to the home position to the step 532 of the holder 53.
As described above, in the present embodiment, the cleaning member 56 is configured to serve as a positioning member that is an essential member for determining the position of the grid 52 and a cleaning member that cleans the grid 52. Thus, there is no need to arrange a cleaning member separately from the positioning member. Further, the pressing force from the grid 52 acts on the cleaning member 56, and the cleaning member 35 can move and clean the grid 52 in a state in which the pressing force is acting. There is no need to adopt a configuration in which the member is pressed against the grid, and the grid 52 can be effectively cleaned.

In the above description, the cleaning member 56 is moved using a so-called screw feed mechanism. However, it is needless to say that the mechanism is not limited thereto as long as the cleaning member can be moved in the X direction. For example, a wire winding mechanism using a motor can be used.
Moreover, if the cleaning member 56 can be moved, it will not be restricted to electricity. For example, instead of the feed screw 57 and the motor 58, a rod-shaped member that is movable in the X direction is disposed, and the rod-shaped member and the cleaning member 56 are connected to each other. The cleaning member 56 may be moved by reciprocating in the direction.

(Modification)
As described above, the present invention has been described based on the embodiment. However, the present invention is not limited to the above-described embodiment, and the following modifications may be considered.
(1) In the above-described embodiment, one cleaning member 56 is disposed in the charging unit 4. However, the configuration is not limited to one, and a plurality of, for example, two may be disposed.

FIG. 8 is a diagram schematically illustrating how the grid 52 is cleaned by each cleaning member when two cleaning members 56 and 66 are provided. FIG. 8A shows a state during non-cleaning, and FIGS. 8B and 8C show a state during cleaning.
As shown in FIG. 8A, each of the cleaning members 56 and 66 is retracted to the home position shown in the figure when not being cleaned, and is held by the holders 53 and 54 at the home position, and the interval d is The grid 52 is held by coming into contact with the portions 523 and 526 of the grid 52 so as to have a predetermined interval d0.

On the other hand, both end portions 521 and 522 of the grid 52 are held in positions 530 and 541 of the holders 53 and 54 at positions farther from the photosensitive drum 3 in the Y direction than the holding positions of the grid 52 by the cleaning members 56 and 66. ing. As a result, the distance d between the portion 524 of the grid 52 and the photosensitive drum 3 is maintained at the specified distance d0.
The cleaning members 56 and 66 are configured to perform a cleaning operation independently. Here, another notch groove similar to the notch groove 551 is provided on the back surface portion 552 of the shield electrode 55 in parallel, the cleaning member 56 is provided in one notch groove, and the cleaning member is provided in the other notch groove. 66 is engaged so as to be movable in the X direction. Further, another feed screw and a motor (not shown) are provided as a drive mechanism for the cleaning member 66.

The cleaning member 56 is connected to the motor 57 via the feed screw 58 as in the above embodiment, and is held by the holder 53 during non-cleaning.
On the other hand, the cleaning member 66 is connected to another motor via the another feed screw, and is configured to be driven independently of the cleaning member 56. Further, the holder 54 is provided with a step similar to the step 532 of the holder 53, and is configured to be held at the step when not cleaned.

As the cleaning operation, for example, as shown in FIG. 8B, the cleaning member 56 first moves to perform cleaning. The moving range of the cleaning member 56 can be, for example, up to the vicinity of the holder 54.
When the cleaning member 56 moves to the full movement range, it stops and reverses. In the middle of the cleaning member 56 returning to the home position, the movement of the cleaning member 66 is started as shown in FIG. The cleaning member 66 moves so as to follow the cleaning member 56, and the grid 52 is cleaned by the cleaning members 56 and 66.

The moving range of the cleaning member 66 can be, for example, up to the vicinity of the holder 53. When the cleaning member 66 moves to the full movement range, it stops, reverses and returns to its home position. Thereby, both the cleaning members 56 and 66 each reciprocate once, and the cleaning ability can be improved as compared with the case where there is one cleaning member.
Needless to say, the operations of the cleaning members 56 and 66 are not limited to those described above. For example, if both the cleaning members are moved from the home position at the same time and the operation of reversing at the substantially center position in the longitudinal direction of the grid 52 is performed, the cleaning time can be shortened compared with the case where the both ends of the grid 52 are reciprocated once. Can do.

Needless to say, the drive mechanism of each cleaning member is not limited to the above configuration. It is only necessary that each cleaning member can be driven. For example, a wire winding mechanism using a motor may be provided for each cleaning member. Further, the present invention is not limited to electric drive, and may be configured manually by the user as described above.
(2) In the above embodiment, an example in which a thin plate is used as the grid 52 has been described. However, the grid 52 is not limited to a thin plate as long as it functions as a control electrode. You can also. A drum-shaped photoconductor is used as the image carrier, but a belt-shaped or plate-shaped image may be used, for example.

  Furthermore, although the example using the cleaning member 56 as the positioning member has been described, it contacts with the grid 52 in a state where a pressing force is applied, and the position of the grid 52 with respect to the image carrier is determined during non-cleaning, and during cleaning. It goes without saying that the shape, size, drive mechanism, holding mechanism, material of the cleaner 563, thickness, etc. are not limited to the above as long as the member can move in the longitudinal direction of the grid 52 and clean the grid 52. Absent. Further, the cleaner 563 may not be provided. Even if there is no cleaner 563, if the positioning member moves in a state of receiving the pressing force from the grid 52, dirt such as toner adhering to the grid 52 is scraped or removed by the movement of the positioning member. This is because the substantial grid 52 can be cleaned. In that sense, the same effect as described above can be obtained by arranging a member configured to contact the grid in a state in which a pressing force is applied to determine the position of the grid and move in the longitudinal direction of the grid. Can be obtained.

Further, although an example in which the image forming apparatus is applied to the printer 1 has been described, the present invention can be applied to general image forming apparatuses such as a copying machine, a facsimile apparatus, and an MFP (Multiple Function Peripheral).
Further, the above embodiment and the above modification examples may be combined.

  The present invention is a charging device that charges an image carrier through a grid, and is useful as a technique for effectively cleaning the grid.

1 is a diagram illustrating an overall configuration of a printer 1. FIG. FIG. 4 is a diagram schematically illustrating a state of cleaning of a grid 52 provided in the charging unit 4 of the printer 1. 3 is a side view showing a configuration of a charging unit 4. FIG. It is arrow sectional drawing when the charging part 4 is cut | disconnected by the GG line of FIG. (A) is a perspective view which shows the state in which the grid 52 is hold | maintained by the holder 53, (b) is a perspective view which shows the structural example of the holder 53 in the state from which the grid 52 was removed. It is a figure which shows a mode that the cleaning member 56 is moving at the time of cleaning. It is another figure which shows a mode that the cleaning member 56 is moving at the time of cleaning. In a modification, it is a figure showing typically a situation of cleaning of grid 52 by each cleaning member at the time of arranging two cleaning members 56 and 66.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Photosensitive drum 4 Charging part 51 Discharge electrode 52 Grid 53, 54 Holder 56, 66 Cleaning member 520 Grid discharge electrode side surface 521, 522 Grid edge part 532 Step part (holding part)
536 Top (convex)

Claims (7)

A charging device for charging an image carrier,
A discharge member;
A grid that is elongated and disposed in a state where tension is applied in a longitudinal direction to a space between the discharge member and the image carrier, and controls a charging potential of the surface of the image carrier;
The grid is in contact with the surface of the grid facing the discharge member in a state in which a pressing force acts between the grid and the image carrier so that a distance d between the grid and the image carrier is a predetermined distance d0. And at least one positioning member for determining the position of the grid with respect to the image carrier,
The positioning member is
A cleaning member for cleaning the grid;
The charging device is configured to be movable in a longitudinal direction of the grid while being in contact with the grid. A first holder for holding a first portion of the grid;
A second holder for holding a second portion of the grid that is separated from the first portion by a predetermined distance in the longitudinal direction;
The first holder is
Holding the first portion of the grid such that the spacing d is the specified spacing d0;
The second holder is
Holding the second portion of the grid at a position farther from the image carrier than the holding position of the first portion by the first holder;
The positioning member is
At the time of non-cleaning, the grid is positioned so that it is located at the home position between the first and second holders, and the distance d becomes the specified distance d0,
2. The charging device according to claim 1 , wherein the grid is cleaned by moving between the first and second holders during cleaning. In the second holder,
A convex portion protruding toward the image carrier in the interval direction is provided at a position closer to the first holder than a holding position for holding the second portion of the grid,
The position of the tip of the convex portion is located between the holding position of the second end portion and the contact position of the grid by the positioning member in the interval direction,
When the positioning member is located at the home position, the convex portion and the grid do not come into contact with each other, and when the positioning member moves away from the home position due to movement during cleaning, the convex portion and the grid are in contact with each other. The charging device according to claim 2 , wherein the charging device is in contact with the charging device. In the second holder,
A holding portion is provided for holding the positioning member when the positioning member is located at the home position and restricting the position in the interval direction;
The positioning member is
4. The charging device according to claim 2 , wherein the charging device is held by a holding portion of the second holder when positioned at the home position. 5. A first holder for holding a first portion of the grid;
A second holder for holding a second portion of the grid that is separated from the first portion by a predetermined distance in the longitudinal direction;
When the two positioning members are arranged, and these are the first and second positioning members,
The first and second positioning members are respectively
At the time of non-cleaning, the grid is positioned so as to be positioned at the home position between the first and second holders so that the distance d becomes the specified distance d0, and at the time of cleaning, the first and second Move between holders to clean the grid,
The first and second holders are
The first and second portions of the grid are held at positions farther from the image carrier than positions where the grid is positioned by the first and second positioning members. 2. The charging device according to 1 . A process unit comprising a charging device for charging an image carrier for image formation,
Process unit, characterized in that it comprises a charging device according to any one of claims 1 to 5 as the charging device. An image forming apparatus comprising a charging device for charging an image carrier,
An image forming apparatus comprising: a charging device according to any one of claims 1 to 5 as the charging device.

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