JP3453538B2 - Image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrostatic copying machine, a facsimile and a printer.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrostatic copying machine, an electrostatic latent image is formed on a photosensitive drum, the electrostatic latent image is visualized with toner, and the visualized toner image is transferred. Transfer to paper as body. For this reason, there are some which are provided with a transfer roller facing the peripheral surface of the photosensitive drum. A sheet of paper passes between the peripheral surfaces of the transfer roller and the photoconductor drum, and a predetermined voltage is applied to the transfer roller during that time, and the toner image formed on the photoconductor drum is transferred onto the paper.

By the way, the transfer roller is positioned at a predetermined position with respect to the photosensitive drum in order to stably obtain a clean image. On the other hand, the transfer roller can be displaced with respect to the photosensitive drum for maintenance such as jam clearance. For example, the photosensitive drum is rotatably supported while being positioned with respect to the base member, and the transfer roller is rotatably supported while being positioned with respect to a transport base that forms a transport path around the photosensitive drum. It is supported. The transport base and the base member are connected to each other.
The transport base is rotatably supported with respect to the base member, and the transport path can be opened and closed by rotating the transport base. When the conveyance path is closed, the transfer roller can be arranged at the above-mentioned predetermined position with respect to the photosensitive drum via the base member, the conveyance base, etc., and image formation is possible. Further, when the conveyance path is opened, the transfer roller comes to be arranged apart from the photosensitive drum.

[0004]

However, when the conveying path is opened and closed, the transfer roller may not be returned to the predetermined position with respect to the photosensitive drum when the conveying path is closed. As a result, it is expected that the images will vary. Therefore, an object of the present invention is to solve the above-described technical problem and to position the transfer roller with respect to the photoconductor drum without misalignment when the transport path is opened and closed to return to the image-formable state. It is to provide an image forming apparatus capable of performing the same.

[0005]

According to another aspect of the present invention, there is provided an image forming apparatus including: a photosensitive drum which forms a toner image on the surface while rotating; and a photosensitive drum which rotates while facing the photosensitive drum. A transfer roller that transfers the toner image on the surface of the body drum to the paper, a casing that supports both ends of the photosensitive drum in the axial direction, a base member that detachably supports the casing, and the conveyance of the paper between the casing. And a conveyance base that holds the transfer roller while forming a path. The conveyance base closes the conveyance path so that an image can be formed, and has a first position where the transfer roller approaches and faces the photosensitive drum. In an image forming apparatus that is supported by a base member so as to be displaceable with respect to the casing at a second position where the transfer path is opened and the transfer roller is separated from the photosensitive drum, the transfer path is closed. That when placing the conveying base in the first position, the positioning member for positioning the shaft end located in the vicinity of both end portions of the axial direction of the transfer roller against the photosensitive drum is provided in the casing, the base member, Provided is an image forming apparatus characterized in that an image forming unit including a photosensitive drum, a casing, and a positioning member is detachably supported, and a transfer unit including a transfer roller and a conveyance base is displaceably supported.

According to the present invention, since the positioning member is attached to the casing, the transfer roller can be positioned stably with respect to the photosensitive drum when the transport path is opened and closed and the photosensitive drum is not displaced. As a result, it is possible to stably convey the sheet and obtain an image without variation. The positioning member is provided on the image forming unit.
Even when the imaging unit is detached and returned,
Stabilize the image transfer roller with respect to the photosensitive drum
Can be positioned. An image forming apparatus according to a second aspect is the image forming apparatus according to the first aspect, wherein the casing is provided with a guide member for guiding the sheet between the transfer roller and the photosensitive drum. The image forming apparatus is characterized in that the and the positioning member form an integral unit, and the unit is positioned at a predetermined position with respect to the photosensitive drum.

According to the present invention, when the conveying path is opened and closed, the guide member can also be stably positioned with respect to the photosensitive drum and the transfer roller, so that an even image can be obtained. You can In particular, since the positioning member and the guide member form a unit, positioning with respect to the photosensitive drum is easy.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings using a copying machine as an example.
FIG. 1 is a front view showing a schematic configuration of the copying machine of this embodiment. The copying machine 1 has an apparatus main body 2 in which the image forming apparatus 8 and the like are housed, and a document feeding section 6 provided on the upper surface of the apparatus main body 2. The device body 2 includes an upper part 3 and a lower part 4.
And a paper discharge section 5 that is partitioned between the upper portion 3 and the lower portion 4 and discharges the paper. The paper discharge unit 5 is exposed through a window 7 defined between the upper portion 3 and the lower portion 4.

A reading section 20 is provided on the upper portion 3 of the apparatus main body 2. A document placing plate 21 is provided on the upper surface of the upper portion 3, and a document feeding unit 6 is rotatably and openably attached to the upper surface. The document feeding section 6 automatically feeds out one document placed on the upper surface thereof, and feeds it to the upper surface via the document placing plate 21. The reading unit 20 exposes a document passing on the transparent document placing plate 21 by the document feeding unit 6,
Alternatively, an original placed on the original placing plate 21 is exposed and scanned, reflected light from the original is guided to a light receiving element 24 by an optical system such as a mirror 22, a lens 23, etc. Convert to. The signal from the reading unit 20 is subjected to predetermined processing by a signal processing unit (not shown) and output.

The lower part 4 of the apparatus main body 2 has a housing 3
The following parts are included in 0. That is, a light irradiation unit (LSU) 9 that obtains a predetermined light beam by scanning laser light emitted from a semiconductor laser or the like with a polygon mirror or the like in accordance with a signal from a signal processing unit.
A photoconductor drum 41 for forming a latent image according to the light from the light irradiation unit 9, a charger 42 for charging the photoconductor drum 41, and an electrostatic latent image formed on the photoconductor drum 41 for a developing roller. An image forming unit 40 including a developing device 43 that visualizes with toner supplied by using a toner 44, and a cleaner 45 for cleaning the surface of the photosensitive drum 41 after the toner image is transferred. In order to transfer the image visualized by the image forming unit 40 onto a sheet, the transfer unit 4 includes a transfer roller 47 provided to face the photosensitive drum 41 and conveys the sheet in a predetermined direction.
6. A fixing unit 48 that heats and fixes the toner image transferred onto the sheet. A sheet is fed from a sheet feeding cassette 51 by a sheet feeding roller 52, passes through the image forming unit 40 and the fixing section 48 from the pre-stage portion 11 including a pair of registration rollers 53,
The sheet conveying unit 10 that discharges to the sheet discharging unit 5 by the rear stage portion 12 including the conveying roller 54. A transport path 13 that is partitioned inside the paper transport unit 10, between the image forming unit 40 and the transfer unit 46, inside the fixing unit 48, and the like to pass the paper. Each of these parts is provided in the housing 30. The image forming unit 40 and the transfer unit 46 form an image forming apparatus 8 that forms a toner image on a sheet.

The photosensitive drum 41 has a cylindrical shape and is arranged so that its central axis extends in the front-rear direction. The photosensitive drum 41 forms a toner image on the surface while rotating in the clockwise rotation direction in FIG. 1, for example. Further, the transfer roller 47 described above is arranged so as to approach the peripheral surface of the photoconductor drum 41 and face it. A predetermined voltage is applied to the transfer roller 47, and when the conveyed sheet comes into contact with the transfer roller 47, the sheet is charged. While the transfer roller 47 rotates, the paper is passed between the transfer roller 47 and the photoconductor drum 41, and the charged toner image adhering to the photoconductor drum is electrostatically transferred onto the charged paper.

Further, in the portion of the conveying path 13 near the photosensitive drum 41 and the transfer roller 47, the conveyed sheet is guided to a transfer area formed between the transfer roller 47 and the photosensitive drum 41. A pair of guide members 56, 57
Is provided. The pair of guide members 56 and 57 are plate-like members that are arranged on the upstream side of the photoconductor drum 41 in the paper transport direction and can follow the transported paper, and are in the axial direction of the photoconductor drum 41. And a part of the transport path 13 is defined between them. The guide member 56 is provided on the casing 35 which is a part of the image forming unit 40, and the guide member 57 is a conveyance base 33 which is a part of the transfer unit 46.
It is fixed to. The sheet is guided by the guide members 56 and 57, reaches between the photosensitive drum 41 and the transfer roller 47, and passes between them (see arrow H in FIG. 2).

By the way, the image forming unit 40 including the photosensitive drum 41 and the transfer roller 47 are arranged so that the transfer roller 47 is arranged at a predetermined position with respect to the photosensitive drum 41.
Each of the transfer units 46 including is positioned and attached to the base member 32 of the housing 30. On the other hand, in order to facilitate maintenance such as jam clearance, the image forming unit 40 can be attached to and detached from the base member 32 of the housing 30, and the transfer unit 46 can be rotationally displaced. .

In the present embodiment, when the image forming unit 40 is attached or detached or the transfer unit 46 is rotated, the transfer roller 47 is attached to the photosensitive drum 41 so that the transfer roller 47 can be returned to its original position. A pair of positioning members 61 for positioning with respect to each other are provided in the casing 35 of the image forming unit 40 including the photosensitive drum 41. This allows
Positioning of the transfer roller 47 with respect to the photoconductor drum 41 can be realized with high accuracy so that the positioning position does not change when the image forming unit 40 or the like is displaced and returned to the original position.

In particular, in the present embodiment, the pair of positioning members 61 and the one guide member 56 constitute an integral guide unit 60, and the guide unit 60 is positioned with respect to the photoconductor drum 41 and the casing. It is attached to 35. The details will be described below. In the explanation below,
The direction will be described with reference to the front view when the image forming unit 40 and the transfer unit 46 are arranged at predetermined positions on the base member 32. In addition, an arrow X indicating the left-right direction is illustrated in FIG. 1 and each of the drawings described below.

First, the image forming unit 40 and the transfer unit 4
The attachment of 6 will be described. Please refer to FIG. The housing 30 is a base member 32 as a structural member that supports the image forming apparatus 8, the light irradiation unit 9, the paper transport unit 10, and the like.
A plate-shaped transport base 33 that is rotatably attached to the left side surface of the base member 32 and forms a part of the transport path 13 and constitutes a part of the transfer unit 46;
A metal frame composed of an exterior member 31 that is attached to surround 2 to form an exterior of the copying machine 1 and a plurality of metal plate members fixed to a base member 32 to support the upper portion 3 of the apparatus body 2 (see FIG. (Not shown) and the image forming unit 4
And a casing 35 that constitutes a part of 0 and supports each part thereof.

The casing 35 is made of resin and is formed in a box shape elongated in the front-rear direction. The casing 35 directly supports bearings 71 (see FIG. 3) at both ends in the longitudinal direction. The portions near the both ends of the drum 41 in the axial direction are supported. The casing 35 is detachably supported by the base member 32. The casing 35 can be attached to the accommodation chamber portion 62 of the base member 32 from the front along the front-rear direction and can be pulled out to the front. Also, the casing 3
5 is positioned at a predetermined position of the base member 32 when attached to the accommodation chamber portion 62.

The transfer base 33 is supported by the base member 32 so as to be rotatable around a support shaft 34. In FIG. 1, a first position in which the outer surface portion of the transport base 33 is arranged along the left side surface of the housing 30 and the transport base 33 is opened so that the inner surface portion of the transport base 33 is opened.
The transport base 33 can be rotationally displaced to a second position in which it is tilted with respect to the left side surface of 0. At the first position, the transport path 13 is defined between the right side surface of the transport base 33 and the left side surface of the base member 32 and the casing 35 attached thereto, and the transport path 13 is closed to the outside. Then, the transfer roller 47 approaches and opposes the photosensitive drum 41 supported by the casing 35, thereby enabling image formation. At the second position, the conveyance path 13 is opened to the outside, the peripheral surfaces of the photosensitive drum 41 and the transfer roller 47 are separated from each other,
Jam processing is possible.

Although only a part of the base member 32 is shown, the main plate portion 61 supporting the light irradiation unit 9 is shown.
And the image forming unit 4 provided on the left side of the main plate portion 61.
It has the above-mentioned accommodating chamber portion 62 that surrounds 0, and a support portion (not shown) that is provided at the left end of the accommodating chamber portion 62 and that supports the support shaft 34. An opening for inserting and removing the casing 35 is provided on the front surface of the accommodation chamber portion 62. The above-mentioned respective parts of the base member 32 are made of resin and are integrally formed.

Next, each part of the image forming unit 40 and the transfer unit 46 will be described based on the state during image formation.
Please refer to FIG. 2 and FIG. FIG. 3 is a sectional view of the photosensitive drum 41 and the transfer roller 47 in the vicinity of the rear side as viewed in the direction of arrow A. The image forming unit 40 includes a casing 35, a positioning member 61, and a guide member 56, in addition to the above-described parts such as the photosensitive drum 41. A positioning ring 72 that is integrally rotatable and a bearing 71 that is rotatably supported by the casing 35 are provided on both sides of the photosensitive drum 41 in the axial direction, and one end is integrally rotatable. A drive gear 73 is provided. The drive gear 73 is driven by a motor (not shown) to rotate the photosensitive drum 41, and at the same time, transmits the rotation to the transfer roller 47 via the driven gear 83 meshing with each other.

The transfer roller 47 has a rotatable central shaft 84 extending integrally from both ends in the axial direction. A rotation center shaft 84 on both sides of the transfer roller 47 in the axial direction is provided with a positioning ring 82 that can rotate integrally with the transfer roller 47 and a bearing 81 that rotatably supports the rotation center shaft 84. , The shaft end 8 on the outer side in the axial direction than these
5 is protruding. Further, on the rear side of the transfer roller 47,
The driven gear 83 described above is fixed to the rotation center shaft 84 so as to be integrally rotatable.

The transfer roller 47 is held by the carrying base 33, and is elastically pushed upward through a bearing 81 by a coil spring 86 as an urging member attached to the carrying base 33. By being pushed in this direction, the transfer rollers 47 approach the photoconductor drum 41 and face each other (arrow B).
As a result, the peripheral surfaces of the positioning rings 72 and 82 come into contact with each other. Along with this, the transfer roller 47
Contacts the positioning member 61.

When the positioning ring 82 of the transfer roller 47 and the positioning ring 72 of the photosensitive drum 41 come into contact with each other at their peripheral surfaces, a predetermined gap is formed between the peripheral surfaces of both the transfer roller 47 and the photosensitive drum 41. Both of them 41 and 47 are positioned so as to face each other such that the above-mentioned center-to-center distance between them is a predetermined distance while ensuring the above. Positioning member 61
Are arranged corresponding to both axial ends of the transfer roller 47, and are fixed to the left side surface of the casing 35 near the transfer roller 47. The positioning member 61 is a bearing 71.
It is located near the.

The positioning member 61 is located on the left side of the photosensitive drum 41 and below the photosensitive drum 41 by a predetermined distance when the transport base 33 and the casing 35 are supported by the base member 32 so that an image can be formed. , Transfer roller 4
7 and the photosensitive drum 41 are positioned in the vertical direction, which is a direction intersecting with the direction in which the photosensitive drum 41 and the photoconductor drum 41 face each other (arrow B), and the shaft end portions 85 near both axial end portions of the transfer roller 47 are positioned. The positioning member 61 includes an upper surface 63 and a lower surface 62.
The upper surface 63 and the lower surface 62 face each other in the vertical direction, and the shaft end portion 85 of the transfer roller 47 is disposed between the upper surface 63 and the lower surface 62. The shaft end portion 85 of the transfer roller 47, which is pushed upward, is attached to the lower surface 62 of the positioning member 61.
Abut from below. In this way, the transfer roller 47
Since it is pressed against the positioning member 61, stable positioning is performed.

Further, the lower surface 62 of the positioning member 61 is in the direction in which the shaft end portion 85 of the transfer roller 47 is pushed when the transfer roller 47 receives a rotational driving force via the pair of gears 73 and 83. The direction is the direction in which the sheet is conveyed in the transfer area.), So that the transfer roller 47 that receives the rotational driving force can be positioned more stably. The space between the upper surface 63 and the lower surface 62 is open toward the left side, which is the side on which the transport base 33 is located, and the shaft end portion 85 of the transfer roller 47 moves in and out as the transport base 33 rotates. It is said to be the passage.

The guide member 56 is provided at both ends in the front-rear direction via the pair of positioning members 61, respectively, and the casing 35.
And is arranged at substantially the same position as the positioning member 61 in a front view. In addition, the pair of positioning members 61,
It may be fixed to the casing 35 via the guide member 56. During maintenance of the copying machine 1, first, the transport base 33 is tilted down, the shaft end portion 85 of the transfer roller 47 is separated from the positioning member 61, and the transfer roller 47 is separated from the photosensitive drum 41. At the same time, the guide members 56 and 57 are also separated from each other.

When replacing the image forming unit 40, the image forming unit 40 is removed from the accommodation chamber portion 62 of the base member 32, and then the replaced image forming unit 40 is attached to the base member 32. Next, when the transport base 33 is returned, the shaft end portion 85 of the transfer roller 47 is engaged with the lower surface 82 of the positioning member 61 while being pressed, and the transfer roller 47 is attached to the photosensitive drum 41 and to the photosensitive drum 41. The guide member 56 is positioned at a predetermined position. At this predetermined position, the central axes of the photosensitive drum 41 and the transfer roller 47 are parallel to each other by the positioning member 61 and the positioning rings 72 and 82.

As described above, according to the present embodiment, since the positioning member 61 is attached to the casing 35, the conveyance path 33 is rotated by rotating the conveyance base 33.
When the sheet is opened and closed, the transfer roller 47 can be positioned stably with respect to the photosensitive drum 41 without displacement. As a result, it is possible to stably convey the sheet and obtain an image without variation. In particular, the positioning member 61
Is provided in the image forming unit 40, so that the transfer roller 47 can be stably positioned with respect to the photosensitive drum 41 even when the image forming unit 40 is detached and then returned.

Further, since the guide unit 60 is arranged near the bearing 71 of the casing 35 that directly supports the bearing 71, the guide unit 60 can be reliably and stably positioned with respect to the photosensitive drum 41. Further, since the guide member 56 is provided as a unit together with the positioning member 61 in the casing 35, when the transport path 13 is opened and closed, the guide member 56 is also provided in the photosensitive drum 41 and the transfer roller 4.
As a result of stable positioning with respect to 7, it is possible to obtain an image with even more variation.

For example, the guide member 56 is connected to the photosensitive drum 4
1 can be arranged at a position suitable for guiding the paper with respect to the transfer area between the transfer roller 47 and the transfer roller 47. As a result, toner scattering in the transfer area due to the guided paper can be prevented, and A fine image can be formed. Also,
Since the casing 35, the guide unit 60, and the photoconductor drum 41 form the image forming unit 40, they can be arranged close to each other, and as a result, they can be accurately positioned at a predetermined position, and the positioning is easy. The configuration for can be simplified.

Particularly, the guide unit 60 is connected to the photosensitive drum 4
By positioning with respect to 1, the positioning member 61
The positioning of the guide member 56 and the photosensitive drum 41 by the three members can be realized more easily than in the case where the positioning is performed separately. The positioning member 61 is provided with a rotation center shaft 84 of the transfer roller 47 in an up-down direction which is a direction intersecting a direction in which the transfer roller 47 and the photosensitive drum 41 face each other.
Since both shaft end portions 85 are positioned, it is possible to prevent both rotation shafts of the transfer roller 47 and the photoconductor drum 41 from being inclined. In addition to this, the transfer roller 47 and the photosensitive drum 4
As a result of making the axial distance to 1 equal at both ends in the axial direction, the rotating shafts can be surely arranged in parallel with each other, and a clear image can be obtained.

Further, since the pair of guide members 56 and 57 are provided in separate units and can be separated from each other, it is easy to remove the jam. The casing 35 is formed by the base member 3
2 was attached and detached by inserting and removing in the front-rear direction, but is not limited to this. Further, although the transport base 33 rotates with respect to the base member 32, it is not limited to this. In short, if the transport base 33 and the casing 35 are displaceably connected to each other, the effects of the present invention can be obtained.

Further, the transfer roller 47 is the photosensitive drum 4
It may be in contact with 1, or may be arranged with a predetermined gap from the peripheral surface of the photosensitive drum 41.
In short, the present invention can be applied to the image forming apparatus 8 as long as it can displace and position the transfer roller 47 with respect to the photosensitive drum 41. Further, although the above-mentioned image forming apparatus is applied to a copying machine, it may be applied to a printer, a facsimile, or the like.

Besides, various design changes can be made within the scope of the present invention.

[Brief description of drawings]

FIG. 1 is a front sectional view of a schematic configuration of a copying machine showing an embodiment of the present invention.

FIG. 2 is an enlarged front sectional view of a portion near a transfer roller and a photosensitive drum shown in FIG.

FIG. 3 is a cross-sectional view of a portion in the vicinity of axial end portions of a transfer roller and a photosensitive drum when viewed in the direction A shown in FIG.

[Explanation of symbols]

8 image forming apparatus 13 transport path 32 base member 33 transport base 35 casing 40 image forming unit 41 photoconductor drum 46 transfer unit 47 transfer roller 56 guide member 60 guide unit 61 positioning member 85 shaft end

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) G03G 15/00 550 G03G 21/16-21/18 G03G 15/16-15/16 103

Claims (2)

(57) [Claims] 1. A photosensitive drum which forms a toner image on the surface while rotating, a transfer roller which transfers the toner image on the surface of the photosensitive drum to a sheet while rotating opposite to the photosensitive drum, and a photosensitive drum of the photosensitive drum. A casing that supports both ends in the axial direction, a base member that detachably supports the casing, and a conveying base that holds a transfer roller while forming a sheet conveying path between the casing and the casing are provided. The base is a first roller that closes a conveyance path so that an image can be formed, and a transfer roller approaches and faces the photosensitive drum.
And a second position where the transfer path is opened and the transfer roller is separated from the photosensitive drum, in the image forming apparatus supported by the base member so as to be displaceable with respect to the casing, the transfer path is closed. When the transport base is arranged at the first position, a positioning member that positions the shaft end portions near both end portions in the axial direction of the transfer roller with respect to the photosensitive drum,
The base member is provided in the casing and detachably supports the image forming unit including the photosensitive drum, the casing, and the positioning member, and displaceably supports the transfer unit including the transfer roller and the transport base. Image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the casing is provided with a guide member for guiding the paper between the transfer roller and the photosensitive drum, and the guide member and the positioning member are provided. An image forming apparatus, comprising an integrated unit, which is positioned at a predetermined position with respect to a photosensitive drum.