JP2007192895A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify a moving means that carries the attitude switching of a brush electrifier, consequently, to attain the reduction of the manufacturing cost of an image forming apparatus with a function of moving the brush electrifier. <P>SOLUTION: The moving means M comprises a permanent magnet 46 loaded to the brush electrifier 11, and an electromagnet 47 facing the moving track of the permanent magnet 46 so as to impart magnetic attraction force and magnetic repulsive force to the permanent magnet 46. Consequently, as compared with a conventional planet gear type or solenoid type moving means, the structure of the moving means is drastically simplified, and the number of the components and the time and labor for the assemblage are reduced, consequently, the reduction of the manufacturing cost of the image forming apparatus with the function of moving the brush electrifier 11 is attained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In the present invention, the brush charger for charging the photosensitive drum can be switched between a contact position where it contacts the outer peripheral surface of the photosensitive drum and a non-contact position where it is not in contact with the outer peripheral surface of the photosensitive drum. The present invention relates to an image forming apparatus.

  The present applicant has proposed an image forming apparatus having a brush charger moving function of this type in Japanese Patent Application Laid-Open No. 2000-29280 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2000-66481 (Patent Document 2). In the former, a planetary gear mechanism is employed as a moving means for switching the attitude of the brush charger. In the latter, a solenoid mechanism is adopted as the moving means.

In this way, the brush charger can be switched from the contact position to the non-contact position, and after the printing operation is completed, the brush charger can be separated from the photosensitive drum. Since the brush tip is strongly pressed against the photosensitive drum over time, it is possible to reliably prevent the so-called standby hook from being attached to the bent posture of the brush tip. As a result, the occurrence of uneven charging of the photosensitive drum due to non-uniform pressure contact with the photosensitive drum can be prevented, thereby contributing to the improvement of the print image quality of the image forming apparatus.
JP 2000-29280 A JP 2000-66481 A

  The problem of Patent Document 1 is that since a planetary gear mechanism is employed as the moving means, there is a lot of trouble in properly assembling a large number of gears such as a sun gear and a planetary gear, and the manufacture of the image forming apparatus The cost is increased. In the configuration according to Patent Document 2, since an expensive electromagnetic solenoid is employed as the moving unit, it is inevitable that the overall cost of the image forming apparatus increases.

  The present invention has been made in order to solve the above problems, and in an image forming apparatus having a brush charger moving function, the moving means for switching the posture of the brush charger is simplified. The purpose is to reduce the manufacturing cost by as much.

  According to a first aspect of the present invention, there is provided a photosensitive drum and a brush charger for charging the photosensitive drum, and the brush charger is in contact with an outer peripheral surface of the photosensitive drum; In the image forming apparatus configured to be switchable between a non-contact position and a non-contact position that is non-contact with the outer peripheral surface of the body drum, a moving unit that performs posture switching of the brush charger is attached to the brush charger. The permanent magnet is composed of a permanent magnet and an electromagnet that applies a magnetic attraction force and a magnetic repulsion force to the permanent magnet along the movement path of the permanent magnet.

  According to a second aspect of the present invention, when the brush charger reaches the contact position from the non-contact position, a transmission gear provided on the photosensitive drum is connected to a driven gear provided on the brush charger. It is comprised so that the rotational drive force from may be transmitted.

  According to a third aspect of the present invention, the photoconductor and the brush charger are accommodated and held in a housing including two vertical walls arranged opposite to each other, and each of the vertical walls has a long hole shape. The guide holes are opposed to each other, and both end portions of the brush charger in the longitudinal direction of the brush charger are guided and supported through the bearing tools. The bearing device is assembled so as to be slidable along the guide hole but is not rotatable. The permanent magnet is attached to the bearing device, and the brush shaft is attached to the bearing device. On the other hand, the structure can be supported so as to be freely rotatable.

  According to the first aspect of the present invention, since the moving means is composed of a permanent magnet and an electromagnet, the structure of the moving means is greatly simplified as compared with conventional planetary gear type and solenoid type moving means, It is possible to reduce the number of components and the time and effort of assembly. Thereby, it is possible to reduce the manufacturing cost of the image forming apparatus having the function of moving the brush charger.

  When the brush charger reaches the contact position from the non-contact position, the rotational driving force from the transmission gear provided on the photosensitive drum is transmitted to the driven gear of the brush charger. If the brush charger is rotated, a special mechanism for rotating the brush charger is not required, and the structure of the brush charger can be simplified. This also contributes to a reduction in manufacturing cost of an image forming apparatus having a brush charger moving function.

  As in the third aspect of the present invention, the bearing device is configured to be slidable with respect to the guide hole provided in the vertical wall, but is not rotatable, and the brush shaft is supported on the bearing device so as to be freely rotatable. As a result, even when the brush charger is rotationally driven or slid along the guide hole, the permanent magnet mounted on the bearing tool is not displaced from the position facing the electromagnet. As a result, the energization control on the electromagnet can always properly apply a magnetic attraction force and a magnetic repulsion force to the permanent magnet, so that the brush charger is reliably moved between the contact position and the non-contact position. Therefore, it is possible to obtain a moving means having excellent reliability.

Hereinafter, a first embodiment in which an image forming apparatus according to the present invention is applied to a copying machine will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram schematically showing the configuration of a copier, and FIG. 2 is a side sectional view of an image forming unit constituting the copier. In FIG. 1, this copier is an apparatus for forming an image by an electrophotographic process. In a casing 1, an image forming unit 2 responsible for exposure, development and transfer processes, a fixing device 3 responsible for a toner fixing process, and the like. Is provided. The image forming unit 2 and the fixing device 3 are provided along a paper conveyance path R formed in the casing 1 from the paper feeding device 5 in which the paper P is accommodated to the paper discharge tray 6.

  1 and 2, the image forming unit 2 includes a drum cartridge 7 and a developing cartridge 9 that can be attached to and detached from the drum cartridge 7. The drum cartridge 7 forms an electrostatic latent image by irradiating light on the photosensitive drum 10 on which a print image is formed as an electrostatic latent image, a brush charger 11 for charging the photosensitive drum 10, and the photosensitive drum 10. An exposure device 12, a transfer roller 13 for transferring a toner image corresponding to the electrostatic latent image to the paper P, an eraser brush 15 for collecting the transferred toner, and the like are assembled in a plastic housing 16. . As shown in FIG. 6B, the brush charger 11 is in contact with the outer peripheral surface of the photosensitive drum 10 as shown in FIG. 6B, and the outer peripheral surface of the photosensitive drum 10 as shown in FIG. The position can be switched between a non-contact position near the front that is in contact. In the present embodiment, the downstream side of the sheet conveyance path R in the periphery of the drum cartridge 7 is the front side, and the upstream side is the rear side.

The developing cartridge 9 includes a developing roller 17 that sends toner toward the photosensitive drum 10, a toner container 19 that stores toner supplied to the developing roller 17, a supply roller 20 that frictionally charges toner supplied to the developing roller 17, and the like. Is provided. An agitator 21 for stirring the toner is assembled in the toner container 19.
The photosensitive drum 10 and the transfer roller 13 are arranged to face each other with the paper transport path R interposed therebetween. When the paper P passes between these 10 and 13, the supply drum 20 and the developing roller 17 are interposed. The toner sent from the toner container 19 to the photosensitive drum 10 is transferred to the paper P.

  A fixing device 3 is arranged on the downstream side of the image forming unit 2. The fixing device 3 includes a heating roller 22 as a heat fixing unit and a pressure roller 23 as a pressing unit, and both the rollers 22 and 23 are arranged to face each other with the sheet conveyance path R in between. The toner transferred onto the paper P by the image forming unit 2 is heated and pressurized when passing between the rollers 22 and 23 and is fixed on the paper P.

  On the downstream side of the fixing device 3, a pair of upper and lower discharge rollers 25, 25 are arranged to face each other across the paper transport path R, and the paper P conveyed by being nipped by both the discharge rollers 25, 25. , And is discharged onto the discharge tray 6.

  As shown in FIG. 2, the brush charger 11 and the photosensitive drum 10 are assembled in a square box-shaped housing 16 constituting the drum cartridge 7. FIG. 3 is a plan sectional view of the drum cartridge 7. As shown in the figure, the housing 16 has left and right vertical walls 26 and 26 arranged to face each other, and between the vertical walls 26 and 26, the photosensitive drum 10 and the brush charger 11 are parallel and horizontal. It is assembled in a posture.

  The photosensitive drum 10 has a horizontal shaft 30 extending in the left-right horizontal direction, a hollow cylindrical drum body 31 attached to a central portion of the horizontal shaft 30, and a ring shape that seals openings at both left and right ends of the drum body 31. Cover member 32. Both left and right ends of the horizontal shaft 30 are supported by the vertical walls 26 and 26 in a cantilevered manner. Reference numeral 33 denotes a bearing device mounted at a position opposite to the vertical walls 26 and 26, and the horizontal shaft 30 is supported by the vertical walls 26 and 26 so as to be freely rotatable via the bearing tools 33 and 33. ing. Reference numeral 34 denotes a ground terminal interposed between the horizontal shaft 30 and the drum body 31.

  The brush charger 11 includes a brush shaft 35 extending in the horizontal direction and a brush body 36 attached to the center of the brush shaft 35. The brush body 36 is configured by implanting and fixing a group of brush hairs 39 on the peripheral surface of a columnar holder 37 made of a conductive material. In order to configure the brush charger 11 to be displaceable between a contact position and a non-contact position, a sliding mechanism for the brush charger 11 is provided in the housing 16. 3 to 6, the slide mechanism has long-hole-shaped guide holes 40, 40 that are opposed to the vertical walls 26, 26, respectively, and is slidably movable in the guide holes 40, 40, but can rotate. It consists of bearing tools 41 and 41 that are mounted immovably and hold the left and right ends of the brush shaft 35 so as to be freely rotatable. These guide holes 40 and 40 are formed long in the front-rear horizontal direction.

  The bearing tools 41 and 41 include a hollow elliptical columnar bearing portion 42 that is inserted into the guide holes 40 and 40, and a retaining collar portion 43 that protrudes outward from the left and right inner surfaces of the bearing portion 42. A plastic molded product formed integrally is mainly formed, and a bearing 45 is assembled therein. As shown in FIG. 3, it is inserted into the guide holes 40, 40 from the inner surface side of the vertical walls 26, 26. Installed. In this mounted state, as shown in FIG. 5, the bearing tool 41 cannot rotate with respect to the guide hole 40 by engaging the upper and lower surfaces of the bearing portion 42 long in the front-rear direction with the upper and lower inner surfaces of the guide hole 40. Has been. As described above, the bearing 45 for the brush shaft 35 is fixed in an embedded state inside the bearing portion 42, and both ends of the brush shaft 35 are connected to the bearing tool 41 via the bearing 45. Thus, the structure is supported so as to be freely rotatable.

  On both the left and right outer surfaces of the housing 16, there is a moving means M responsible for switching the posture of the brush charger 11 between a contact position (see FIG. 6B) and a non-contact position (see FIG. 6A). Is provided. As shown in FIG. 3, the moving means M faces the permanent magnets 46 and 46 attached to the left and right bearings 41 and the movement trajectory of the permanent magnets 46. It is comprised with the left-right paired electromagnet 47 which gives a magnetic repulsive force. These permanent magnets 46 have their N poles at the rear (photosensitive members) at positions facing the photosensitive drums 10 of the respective bearing tools 41, more specifically, near the rear end portion of the bearing portions 42 protruding outward from the vertical walls 26. It is fixed in a semi-embedded posture toward the drum 10 (see FIG. 5).

  In FIG. 3, reference numeral S denotes an internal space that is formed inside the copying machine and in which the image forming unit 2 is removably assembled. Reference numeral 50 denotes left and right partition walls that partition the internal space S, and the electromagnet 47 is embedded and fixed in the partition wall 50 facing the guide hole 40. That is, in the mounted state in which the image forming unit 2 is mounted in the internal space S, each electromagnet 47 is assembled to each partition wall 50 that faces each guide hole 40.

  Inside the drum cartridge 7, a brush transmission system D for applying a rotational driving force to the brush charger 11 is configured. As shown in FIGS. 3 and 4, the brush transmission system D includes a transmission gear 51 fixed at a position adjacent to the drum body of the horizontal shaft 30 of the photosensitive drum 10, and a small-diameter meshingly engaged with the transmission gear 51. The reversing gear 52 and a driven gear 53 fixed to the brush shaft 35 corresponding to the reversing gear 52 are included. The reversing gear 52 is mounted on a gear shaft 54 that is supported between the vertical walls 26 and 26 so as to be supported at both ends. Then, as shown in FIG. 6B, when the brush charger 11 reaches a contact state, the driven gear 53 meshes with the reversing gear 52, and the rotational driving force from the transmission gear 51 causes the brush charger 11 to rotate. It is a specification transmitted to.

  Next, the posture switching operation of the brush charger 11 by the moving means M configured as described above will be described with reference to FIG. FIG. 6A shows a standby state in which the printing operation is off. In this state, the photosensitive drum 10 is in a stopped state, and the potential of the brush charger 11 is also off. Further, an electric current is passed through the electromagnet 47 of the moving means M so that the side facing the permanent magnet 46 (here, the front side) has the same polarity (N pole) as the permanent magnet 46. As a result, a magnetic repulsive force acts between the electromagnet 47 and the permanent magnet 46, so that the bearing tool 41 slides forward along the guide hole 40 away from the photosensitive drum 10, and the brush charger 11 is moved. The bristles of the bristles 39 are in a non-contact position where they are not in contact with the outer peripheral surface of the photosensitive drum 10.

  When the copy start button of the copier is turned on from the standby state (non-contact position) and the printing operation is turned on, the photosensitive drum 10 starts to rotate in the clockwise direction in FIG. 6, and the potential of the brush charger 11 is also changed. Turn on. In addition, as shown in FIG. 6B, a current is passed through the electromagnet 47 so that the front side of the electromagnet 47 facing the permanent magnet 46 becomes the south pole. As a result, since a magnetic attractive force acts between the electromagnet 47 and the permanent magnet 46, the bearing tool 41 slides backward along the guide hole 40 toward the photosensitive drum 10, and the brush charger. No. 11 reaches a contact position where the bristles of the bristles 39 come into contact with the outer peripheral surface of the photosensitive drum 10. At this contact position, as shown in FIG. 4, the driven gear 53 meshes with the reversing gear 52, and the rotational driving force from the transmission gear 51 is transmitted to the brush charger 11. The photosensitive drum 10 can be efficiently charged by rotating in the opposite direction of the body drum 10.

  When the printing operation is turned from on to off, the potential of the brush charger 11 is turned off, and a current in a direction in which a magnetic repulsive force acts on the permanent magnet 46 is caused to flow again to the electromagnet 47, whereby the brush The charger 11 returns to the non-contact state as shown in FIG. Thus, the brush charger 11 can be brought into contact with the photosensitive drum 10 only when the printing operation is on, and the brush charger 11 can be brought into a non-contact state in which the brush charger 11 is separated from the photosensitive drum 10 during printing standby. Since the tip of the bristle 39 is strongly pressed against the photosensitive drum 10 for a long time while waiting for printing, it is possible to reliably prevent the bristle 39 from sticking to the standby.

  As described above, according to the image forming apparatus according to the present embodiment, since the moving means M responsible for switching the posture of the brush charger 11 is configured by the permanent magnet 46 and the electromagnet 47, a conventional planetary gear type or solenoid is used. Compared to the type of moving means, the structure of the moving means M can be simplified, and the number of components and assembly work can be greatly reduced. Accordingly, an increase in manufacturing cost associated with the addition of the moving function of the brush charger 11 can be effectively suppressed, and an image forming apparatus having the function can be provided at low cost.

  As shown in FIG. 4, when the brush charger 11 reaches the contact position, the rotational driving force from the transmission gear 51 provided on the photosensitive drum 10 is transmitted to the driven gear 53 of the brush charger 11, If the brush charger 11 is rotated, a special mechanism for rotating the brush charger 11 is not required, and the structure of the brush charger 11 can be simplified. This can also contribute to a reduction in manufacturing cost of the image forming apparatus. In particular, if the reversing gear 52 is interposed between the driven gear 53 and the transmission gear 51, the photosensitive drum 10 and the brush charger 11 can be moved in the opposite directions at their contact portions with a simple configuration. Since it can be moved, the charging property of the brush charger 11 can be improved while ensuring a good frictional contact force of the brush charger 11 with respect to the photosensitive drum 10.

  As shown in FIG. 3, the bearing tool 41 is configured to be slidable but not rotatable with respect to the guide holes 40 and 40 provided in the vertical walls 26 and 26, and the brush shaft 35 is allowed to play freely with the bearing tool 41. When the brush charger 11 is rotationally driven or slidably moved along the guide hole 40, the permanent magnet 46 mounted on the bearing tool 41 is opposed to the electromagnet 47. There is no misalignment. As a result, the energization control for the electromagnet 47 can always properly apply a magnetic attraction force and a magnetic repulsion force to the permanent magnet 46, so that the brush charger 11 can be reliably placed between the contact position and the non-contact position. Can be moved to. This contributes to improving the reliability of the moving means M.

  In the above embodiment, the electromagnet 47 is energized even in the standby state in which the printing operation is off. However, the present invention is not limited to this, and the electromagnet 47 may be deenergized in the standby state. Even in this case, since the brush charger 11 is not pressed against the photosensitive drum 10, it is possible to prevent the standby bristle from being attached to the brush bristles 39.

  In the above-described embodiment, the guide hole 40 is provided in the front-rear horizontal direction, but the present invention is not limited to this, and can be provided, for example, in a downwardly inclined shape. Thus, when the guide hole 40 is inclined downward, the brush charger 11 can be separated from the photosensitive drum 10 even in a non-operating state where no current flows through the electromagnet 47. Therefore, when the brush bristles 39 are pressed against the photosensitive drum 10 over a long period of time when the image forming apparatus is transported or sold, it is possible to effectively prevent the standby burr from being attached to the bristles 39.

  On the contrary, the guide hole 40 may be provided in a downwardly inclined shape. In this case, when the printing operation is turned on, in addition to the magnetic attraction force of the electromagnet 47, the driven gear 53 can be strongly pressed against the reversing gear 52 by the weight of the brush charger 11, so both gears As a result, it is possible to contribute to the improvement of the reliability of the transmission system D. However, in this case, for example, the brush charger 11 and the photosensitive drum are used for the purpose of preventing the tip of the bristle 39 and the photosensitive drum 10 from being in contact with each other for a long time during transportation and sales. It is necessary to take some measures such as interposing a cushion pad between the two.

1 is a schematic configuration diagram schematically showing a configuration of an image forming apparatus according to the present invention. FIG. 3 is a side sectional view of an image forming unit constituting the image forming apparatus. FIG. 3 is a plan sectional view of the drum cartridge. The block diagram for demonstrating the brush transmission system D which gives a rotational drive force to a brush charger. The block diagram for demonstrating the structure of the moving means M which bears the attitude | position switching of a brush charger. 4A and 4B are diagrams for explaining the switching of the posture of the brush charger by the moving means M. FIG. 4A is a non-contact state where the brush charger is not in contact with the photosensitive drum, and FIG. The contact state which contacts a drum is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Photosensitive drum 11 Brush charger 16 Housing 26 Vertical wall 35 Brush shaft 40 Guide hole 41 Bearing tool 46 Permanent magnet 47 Electromagnet 51 Transmission gear 53 Driven gear M Moving means

Claims (3)

A photosensitive drum and a brush charger for charging the photosensitive drum;
Image formation in which the brush charger is configured to be switchable between a contact position in contact with the outer peripheral surface of the photosensitive drum and a non-contact position in non-contact with the outer peripheral surface of the photosensitive drum. In the device
The moving means responsible for switching the posture of the brush charger is a permanent magnet mounted on the brush charger, and an electromagnet that applies a magnetic attraction force and a magnetic repulsion force to the permanent magnet facing the movement locus of the permanent magnet. An image forming apparatus comprising:   When the brush charger reaches the contact position from the non-contact position, the rotational driving force from the transmission gear provided on the photosensitive drum is transmitted to the driven gear provided on the brush charger. The image forming apparatus according to claim 1, which is configured as follows. The photosensitive drum and the brush charger are housed and held in a housing that includes two vertical walls disposed opposite to each other.
Each of these vertical walls is provided with a long hole-shaped guide hole facing each other, and both end portions of the brush charger in the longitudinal direction of the brush charger are guided and supported through the bearing tool. And
The bearing device is assembled so as to be slidable along the guide hole but not rotatable, and the permanent magnet is mounted on the bearing device,
The image forming apparatus according to claim 2, wherein the brush shaft is supported so as to freely rotate with respect to the bearing tool.

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