JP2009300806A - Charger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a charger avoiding accumulation of a foreign matter on a regulation member for positionally regulating a shaft-less charging roller made of hollow elastic material with simple constitution. <P>SOLUTION: The charger is equipped with the charging roller 4 having no rotary supporting shaft and made of the hollow elastic material. The charging roller 4 comes in contact with a surface of a photoreceptor drum 2 and rotates to follow the rotation of the photoreceptor drum 2. The regulation member 5 is equipped with a sliding member 5a on which the charging roller 4 slides. The sliding member 5a where a groove or a hole for scraping off the foreign matter such as toner adhering to a surface of the charging roller 4 is formed moves back and forth in a direction skewing to a following rotating direction (e), and a direction orthogonal to the following rotating direction (e) in predetermined timing. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a charging device, and more particularly to a charging device mounted on an electrophotographic image forming apparatus such as a copying machine or a printer.

  In an electrophotographic image forming apparatus, as a charging means for charging a photosensitive drum that is rotationally driven in one direction to a predetermined potential, conventionally, a charging roller in which a conductive rubber material is wound around a metal support shaft. Was used. The support shaft is rotatably held by a bearing member and is pressed by a spring. As a result, the charging roller comes into contact with the surface of the photosensitive drum and rotates following the rotation of the photosensitive drum.

  However, in the charging roller with a shaft, the cost is increased by attaching the shaft, and a bearing member and a spring for press contact are required, so that the cost is further increased and the configuration is complicated.

  Therefore, Patent Document 1 proposes a charging roller made of a shaftless and hollow elastic member. The charging roller is surrounded by a regulating member and is positionally regulated, and is driven to rotate with the rotation of the photosensitive drum, thereby applying a charge to the photosensitive drum. The charging roller is slidably brought into contact with the regulating surface of the regulating member at the time of driven rotation, and the position is regulated.

However, foreign matters such as toner adhering to the surface of the photosensitive drum, post-processing agent contained in the toner, and paper dust adhere to the regulating surface (sliding contact surface) of the regulating member via the charging roller and accumulate. Has a defect. When these deposits are reattached to the surface of the charging roller, uneven charging or abnormal discharge of the photosensitive drum is induced, causing image noise.
JP 2006-163197 A

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a charging device capable of avoiding accumulation of foreign matters on a regulating member for regulating the position of a shaftless charging roller made of a hollow elastic material with a simple configuration.

In order to achieve the above object, a charging device according to one embodiment of the present invention is provided.
In a charging device that charges a photosensitive drum rotated in one direction to a predetermined potential,
A charging roller that is made of a hollow elastic material having no rotation support shaft and that is in contact with the surface of the photosensitive drum and is rotated by the rotation of the photosensitive drum;
A regulating member for determining the driven rotation position of the charging roller;
With
The regulating member includes a sliding contact member that the charging roller is in sliding contact with, and a moving unit that moves the sliding contact member at a predetermined timing.
A groove or hole for scraping off foreign matter adhering to the surface of the charging roller is formed in the sliding contact member;
It is characterized by.

  In the charging device, the charging roller rotates following the sliding contact with the sliding member. The sliding contact member is moved at a predetermined timing by the moving means, so that the foreign matter adhering to the charging roller from the surface of the photosensitive drum is scraped into a groove or a hole to avoid the accumulation of the foreign matter. As a result, deposits are not reattached to the surface of the charging roller, and as a result, it is possible to prevent uneven charging of the photosensitive drum and abnormal discharge.

  Embodiments of a charging device according to the present invention will be described below with reference to the accompanying drawings.

(Schematic configuration of image forming apparatus, see FIG. 1)
First, an image forming apparatus equipped with a charging device according to the present invention will be described with reference to FIG. FIG. 1 shows a schematic configuration of an electrophotographic printer. A process unit 1 includes a photosensitive drum 2, a charging device 3, a developing device 6, a residual toner cleaning blade 7, and a toner collection unit that are rotationally driven in the direction of arrow E. 8, a transfer roller 9 and a laser scanning optical unit 10 are provided.

  Image formation is performed by a known electrophotographic method. That is, the photosensitive drum 2 is rotationally driven in the direction of arrow E at a predetermined speed, and the surface thereof is charged to a predetermined potential by the charging device 3 and is electrostatically latentized by a laser beam LB modulated based on image data. An image is formed and developed by the developing device 6. On the other hand, the transfer material S is conveyed in the direction of arrow F through the nip portion between the photosensitive drum 2 and the transfer roller 9, and the toner image is transferred. Thereafter, the transfer material S is fixed with toner by a fixing device (not shown) and discharged to the outside of the process unit 1.

  The printer is provided with a control unit 11. The controller 11 controls the state and operation of each part of the printer including the process unit 1, and in particular controls the operation of the charging device 3 described below.

(Refer to basic form of charging device, FIG. 1 and FIG. 2)
The charging device 3 includes a charging roller 4 and a regulating member 5. The charging roller 4 is made of a hollow elastic material that does not have a rotation support shaft (shaftless), contacts the surface of the photosensitive drum 2, and rotates following the rotation of the photosensitive drum 2. Specifically, the charging roller 4 is made of a conductive resin such as PA, PI, PFA, PTEE, or a tube obtained by applying a conductive coating to a non-conductive resin, or a conductive rubber, and has a surface resistance of 10 ⁵ to. 10 ⁸ Ω, the outer diameter is 8.5 mm (relative to the photosensitive drum 2 having an outer diameter of 30 mm), and the wall thickness is 0.1 mm. Of course, these numerical values are only examples.

  The charging roller 4 is placed on the surface of the photosensitive drum 2, and a regulating member 5 for determining the driven rotation position is disposed. Further, the regulating member 5 has conductivity so that a predetermined voltage can be supplied to the charging roller 4 and is formed of iron or stainless steel plated with Ni. A voltage supplied from the regulating member 5 is applied to the photosensitive drum 2 via the charging roller 4. Note that a voltage may be supplied to the charging roller 4 by another conductive member.

  The regulating member 5 has a space larger than the free shape of the charging roller 4 and has a regulating surface (sliding contact surface) 5a that regulates the position of the charging roller 4 during driven rotation. The regulating member 5 holds the charging roller 4 on the photosensitive drum 2 when in the free state (when the photosensitive drum 2 is not rotating). As shown in FIG. 2, the charging roller 4 is driven to rotate in the direction of arrow e as the photosensitive drum 2 rotates, and the regulating surface 5 a regulates the charging roller 4 during the driven rotation. As a result, the charging roller 4 is deformed into a slightly crushed shape, and is pressed against the surface of the photosensitive drum 2 with an appropriate pressure by the sliding reaction force G.

(Refer to the first and second embodiments of the charging device, FIGS. 3 and 4)
In the charging device 3 according to the first embodiment, as shown in FIG. 3, a regulating member 5 that regulates the position of the charging roller 4 includes a sliding contact member 5a (regulating surface) and fixing members 5b and 5c. In the charging device 3 according to the second embodiment, as shown in FIG. 4, a regulating member 5 for regulating the position of the charging roller 4 is composed of a sliding contact member 5a (regulating surface), a fixing member 5c, and a light pressure contacting member 5d. ing. The light pressure contact member 5d is lightly pressed against the charging roller 4 by a torsion spring (not shown), and elastically biases the charging roller 4 toward the sliding contact member 5a.

  On the surface of the charging roller 4, foreign matters such as toner adhering to the surface of the photosensitive drum 2, a post-processing agent contained in the toner, paper dust, and the like are transferred, and these foreign matters further move in the driven rotation direction e of the sliding contact member 5 a. It adheres and deposits from the upstream side. In the first and second embodiments, therefore, a moving means 20 (see FIGS. 5 to 9) for moving the sliding contact member 5a at a predetermined timing is provided, and the sliding contact member 5a adheres to the surface of the charging roller 4. Grooves and holes for scraping off foreign matter were formed.

  Further, the scraped foreign matter goes around to the back side of the sliding contact member 5a through the grooves and holes and falls downward. In order to collect the falling foreign matter, a collecting member 5e is installed.

  The movement unit 20 is controlled in operation by the control unit 11 and moves in a direction in which the sliding contact member 5a is skewed with respect to the direction e in which the charging roller 4 is driven to rotate or in a direction perpendicular to the driven rotation direction e. Move or reciprocate. Further, the moving means 20 may move the sliding contact member 5a according to the cumulative driving time of the photosensitive drum 2 or the cumulative number of printed sheets.

(Refer to Fig. 5 for the first example of moving means and groove or hole)
In the first example, as shown in FIG. 5, the cam plate 22 attached to the output shaft of the motor 21 and one end of the sliding contact member 5a are coupled by a link 23, and the guide hole 25 formed in the sliding contact member 5a is formed. The headed guide pin 26 is engaged. The guide hole 25 is formed in a direction orthogonal to the driven rotation direction e of the charging roller 4. Further, the sliding member 5a is formed with a plurality of grooves 31 that are inclined with respect to the driven rotation direction e so as to penetrate in parallel to each other and to the front and back.

  In this moving means 20, when the motor 21 is driven to rotate by a predetermined angle in the direction of arrow a, for example, the sliding contact member 5 a is urged to the right via the link 23 and driven along the guide hole 25. It moves in a direction orthogonal to e (arrow b direction). Every time the cumulative driving time of the photosensitive drum 2 reaches a predetermined time or every time the cumulative number of printed sheets reaches a predetermined number, the motor 21 is rotated forward by a predetermined angle in the direction of arrow a and reversely rotated by a predetermined angle. As a result, the sliding contact member 5a reciprocates at a predetermined timing in the directions of the arrows b and b '. Here, the predetermined cumulative drive time means, for example, 5 to 10 minutes or 1 hour, and the predetermined cumulative print number means, for example, 10 to 100 sheets or 10,000 sheets.

  As described above, the sliding contact member 5a reciprocates in the directions of the arrows b and b ', so that foreign matters such as toner adhering to the charging roller 4 are scraped into the groove 31 and stay as deposits is avoided. . As a result, deposits are not reattached to the surface of the charging roller 4, and as a result, occurrence of uneven charging of the photosensitive drum 2 and abnormal discharge are prevented.

  The groove 31 penetrates the front and back of the sliding contact member 5a, and the scraped foreign matter falls from the back surface of the sliding contact member 5a and is collected by the collecting member 5e (see FIGS. 3 and 4). In addition, the groove | channel 31 does not necessarily need to penetrate the front and back of the sliding contact member 5a, it is opened only in the surface facing the charging roller 4, and a foreign substance may only stay. Further, the sliding contact member 5a may be controlled to move in one direction at a pitch of about 0.1 mm for every predetermined cumulative driving time or for every cumulative number of printed sheets. Even in this case, the foreign matter can be scraped off from the surface of the charging roller 4. Such a modification is the same in the second to fifth examples described below.

(Refer to the second example of moving means and groove or hole, see FIG. 6)
In the second example, as shown in FIG. 6, a headed guide pin 26 is engaged with a guide hole 27 formed in a direction oblique to the driven rotation direction e of the charging roller 4. The drive mechanism is the same as in the first example. Further, the sliding contact member 5a is formed with a plurality of holes 32 penetrating the front and back.

  In this moving means 20, when the motor 21 is driven to rotate by a predetermined angle, for example, in the direction of arrow a, the sliding contact member 5 a is urged to the right via the link 23 and is driven along the guide hole 27. It moves in an oblique direction (arrow c direction) that is opposite to e. Every time the cumulative driving time of the photosensitive drum 2 reaches a predetermined time or every time the cumulative number of printed sheets reaches a predetermined number, the motor 21 is rotated forward by a predetermined angle in the direction of arrow a and reversely rotated by a predetermined angle. As a result, the sliding contact member 5a reciprocates at a predetermined timing in the directions of arrows c and c '.

  As described above, when the sliding contact member 5a reciprocates in the directions of the arrows c and c ′, foreign matters such as toner adhering to the charging roller 4 are scraped into the holes 32 and are prevented from staying as deposits. . As a result, deposits are not reattached to the surface of the charging roller 4, and as a result, occurrence of uneven charging of the photosensitive drum 2 and abnormal discharge are prevented.

(Third example of moving means and groove or hole, see FIG. 7)
As shown in FIG. 7, the third example includes the same moving means 20 as the first example, and a plurality of grooves 33 are formed in the sliding contact member 5a so as to penetrate the front and back in a zigzag shape. . The movement form of the sliding contact member 5a is the same as in the first example, and foreign matters such as toner adhered to the charging roller 4 are scraped off by the groove 33.

(Refer to Fig. 8 for the fourth example of moving means and groove or hole)
As shown in FIG. 8, the fourth example includes the moving means 20 similar to that of the first example, and a plurality of grooves 34 are formed in the sliding contact member 5a so as to penetrate the front and back in parallel to each other. Has been. The movement form of the sliding contact member 5a is the same as in the first example, and foreign matters such as toner adhering to the charging roller 4 are scraped off by the grooves 34.

(Refer to Fig. 9 for the fifth example of moving means and groove or hole)
As shown in FIG. 9, the fifth example includes the same moving means 20 as the first example, and the sliding contact member 5a has a plurality of grooves 35 crossing each other and penetrating front and back. Is formed. The movement form of the sliding contact member 5a is the same as in the first example, and foreign matters such as toner adhered to the charging roller 4 are scraped off by the groove 35.

(Other examples)
The charging device according to the present invention is not limited to the above embodiment, and can be variously modified within the scope of the gist thereof.

  In particular, the image forming apparatus equipped with the charging device is not limited to a monochrome printer, and may be a color printer, a copier or a multifunction machine with a facsimile. Further, a mechanism for supplying a voltage to the charging roller is arbitrary, and the configuration and shape of the regulating member are also arbitrary.

  Further, the moving means may use a solenoid or the like as a drive source in addition to the motor, and may be provided with a clutch means. Various mechanisms such as a combination of a pinion and a rack can be used instead of the cam. Of course, the timing for moving the sliding contact member may be controlled based on the cumulative number of rotations of the photosensitive drum.

1 is a schematic configuration diagram showing an image forming apparatus equipped with a charging device which is a basic form. It is explanatory drawing which shows the time of the driven rotation of a charging roller. 1 is an elevational view showing a first embodiment of a charging device according to the present invention. It is an elevation view showing a second embodiment of the charging device according to the present invention. It is a top view which shows the 1st example of a moving means and a groove | channel or a hole. It is a top view which shows the 2nd example of a moving means and a groove | channel or a hole. It is a top view which shows the 3rd example of a moving means and a groove | channel or a hole. It is a top view which shows the 4th example of a moving means and a groove | channel or a hole. It is a top view which shows the 5th example of a moving means and a groove | channel or a hole.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Process unit 2 ... Photosensitive drum 3 ... Charging device 4 ... Charging roller 5 ... Restriction member 5a ... Sliding contact member 20 ... Moving means 31, 33, 34, 35 ... Groove 32 ... Hole

Claims (3)

In a charging device that charges a photosensitive drum rotated in one direction to a predetermined potential,
A charging roller that is made of a hollow elastic material having no rotation support shaft and that is in contact with the surface of the photosensitive drum and is rotated by the rotation of the photosensitive drum;
A regulating member for determining the driven rotation position of the charging roller;
With
The regulating member includes a sliding contact member that the charging roller is in sliding contact with, and a moving unit that moves the sliding contact member at a predetermined timing.
A groove or hole for scraping off foreign matter adhering to the surface of the charging roller is formed in the sliding contact member;
A charging device.   The moving means moves the sliding member forward or reciprocally in a direction oblique to a direction in which the charging roller is driven to rotate or in a direction orthogonal to the driven rotation direction. Item 2. The charging device according to Item 1.   3. The charging device according to claim 1, wherein the moving unit moves the sliding member according to an accumulated driving time of the photosensitive drum or an accumulated number of printed sheets.

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