KR19990063007A - Photosensitive belt position sensing device for image forming apparatus - Google Patents

Abstract

For detecting the position in the width direction of the photosensitive belt so as to determine the widthwise direction skew of the photosensitive belt wound on the plurality of rollers and turned in the sub scanning direction and / or the scanning timing of the light scanned by the laser scanning unit A photosensitive belt position sensing device is disclosed.

The disclosed photosensitive belt position sensing device comprises: a base; A guide member having a guide surface which is in contact with one side of the photosensitive belt and which is rotated in accordance with the widthwise displacement of the photosensitive belt; A lever member hinged to both ends of the base and the guide member such that the guide member is pivotable with respect to the base; Elastic bias means for elastically biasing the guide member to contact one side of the photosensitive belt; And sensing means for sensing a widthwise displacement of the photosensitive belt by detecting a movement amount of the guide member.

Therefore, when there is a local defect on the edge of the photosensitive belt, the guide surface of the guide member comes into line contact with one side of the photosensitive belt, thereby preventing malfunction of the steering device and deformation of the image front end start position due to local defects.

Description

Photosensitive belt position sensing device for image forming apparatus

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a photosensitive belt position sensing apparatus for an image forming apparatus that senses a positional change in a main scanning direction of a photosensitive belt running in a sub-scan direction, To a photosensitive belt position sensing apparatus for an image forming apparatus having an improved structure.

Generally, in an image forming apparatus such as a laser printer or a copying machine, a latent electrostatic image is formed by scanning a photosensitive medium with a laser beam, developed with a toner of a predetermined color using a developing unit, .

1, a general image forming apparatus includes a photosensitive belt 10 wound around a driving roller 12, a transfer backup roller 14, and a steering roller 31 provided in a main body thereof and rotating in a predetermined orbit.

An erasing lamp 15 for erasing the surface potential formed on the photosensitive belt 10, a charger 17 for charging the photosensitive belt 10 whose surface potential has been reset to a predetermined potential, A plurality of laser scanning units (LSU) 20 for scanning the belt 10 with a laser beam to form electrostatic latent images corresponding to the respective colors, and a plurality of developing units 19 for developing the electrostatic latent image formed portion do.

In the image forming apparatus having such a configuration, the photosensitive belt 10 is wound around the rollers 12, 14, and 31 so that the rollers 12, 14, LSU 18 in the main scanning direction. Therefore, the image forming apparatus employing the photosensitive belt 10 includes a photosensitive belt steering device 30 for correcting the skew of the photosensitive belt 10, And a photosensitive belt position sensing device 40 for determining the photosensitive belt position.

Referring to FIG. 2, the conventional photosensitive belt position sensing device allows the light scanned by the laser scanning unit 20 to pass through the edge of the photosensitive belt 10 in the main scanning direction, And detects a change in position in the main scanning direction. Here, the laser scanning unit 20 includes a light source 21 for irradiating a laser beam to an edge portion of the photosensitive belt and a region corresponding to the electrostatic latent image, a beam deflector 23 such as a rotary polygonal mirror for deflectively scanning the irradiated light, A lens element 25 for adjusting the line width of the scanning beam and correcting the aberration, and a reflection mirror 27 for causing the scanned light to be incident substantially perpendicularly to the plane of the photosensitive belt 10. [

The light scanned by the laser scanning unit 20 passes through the edge of the photosensitive belt 10 and is scanned to the one non-image area 10b and the image area 10a.

The photosensitive belt position sensing means 40 includes a refraction prism 41 for refracting the scanning light directed to the edge of the photosensitive belt 10 so as to be incident substantially perpendicularly to the edge portion of the photosensitive belt 10, And a photodetector 43 which is disposed on the rear surface of the photoreceptor belt 10 and refracted through the prism 41 to receive light incident on one side of the edge of the photoreceptor belt 10 to sense the position of the photoreceptor belt 10.

The photosensitive belt position sensing means 40 configured as described above can detect the position of the photosensitive belt 10 in the main scanning direction of the photosensitive belt 10 according to the amount of light received by the photodetector 43 when there is no defect in the edge portion of the photosensitive belt 10 Can be detected normally. Accordingly, when the meandering in the main scanning direction occurs, the steering device 30 can be operated to correct the meandering.

On the other hand, the photosensitive belt 10 is subject to local defects D1 and D2 at the edges, as shown in Fig. 3A, due to contact between peripheral components during manufacture and use. In this case, even when the photosensitive belt 10 travels in a normal orbit without a skew, if the photosensitive belt 10 is moved to the position of the local defect D1 of the edge as shown in Fig. 3B, As shown in FIG. Accordingly, when the steering device 30 is in the & There is a problem in that skew correction is performed in the direction

The start position of the image area 10a of the photosensitive belt 10 after a predetermined time from when the light scanned by the laser scanning unit 20 and received by the photodetector 43 is shielded by the photosensitive belt 10 (SP). This effective start position SP becomes a boundary between the image area 10a and the non-image area 10b, and in a normal case, it forms a straight line in the sub-scan direction. On the other hand, when there is a local defect D1 of the edge of the photosensitive belt 10 as described above, the start position SP1 is changed and the image edge deformation occurs.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an image forming apparatus capable of preventing skew correction of a photosensitive belt due to local defects of a photosensitive belt edge and image edge deformation at an effective optical scanning start position from occurring, And an object of the present invention is to provide a photosensitive belt position sensing device.

1 is a schematic view showing a general image forming apparatus;

2 is a schematic perspective view showing a laser scanning unit and a photosensitive belt position detecting device of a conventional image forming apparatus.

FIGS. 3A and 3B are schematic views for explaining image edge deformation according to a local defect of a photosensitive belt edge when a conventional photosensitive belt position sensing device is employed. FIG.

4 is a schematic perspective view showing a photosensitive belt position sensing apparatus for an image forming apparatus according to an embodiment of the present invention.

5 is a schematic view showing an operation state of a photosensitive belt position sensing apparatus for an image forming apparatus according to an embodiment of the present invention.

6 is a schematic perspective view showing a photosensitive belt position sensing apparatus for an image forming apparatus according to another embodiment of the present invention.

FIG. 7 is a schematic plan view showing an example of the lever rotation angle detecting sensor shown in FIG. 6. FIG.

DESCRIPTION OF THE REFERENCE NUMERALS

10 ... photosensitive belt 20 ... laser scanning unit 30 ... steering device

51, 71 ... bases 53, 73 ... guide member 53a ... guide groove

53b ... Guide surface 55 ... Detection projection 57,77 ... Lever member

58,78 ... Torsion spring 60 ... Photodetector 80 ... Rotation angle sensor

81 ... first electrode 83 ... resistor 85 ... second electrode

In order to achieve the above-mentioned object, the present invention is characterized in that in order to determine the widthwise skew of the photosensitive belt wound around a plurality of rollers and turned in the sub-scanning direction and / or the scanning period of light scanned by the laser scanning unit, The photosensitive belt position sensing device for an image forming apparatus comprising: a base; A guide member having a guide surface that contacts one side of the photosensitive belt and is rotated in accordance with a widthwise displacement of the photosensitive belt; A lever member having both ends hinged to the base and the guide member such that the guide member is pivoted relative to the base; Elastic bias means for elastically biasing the guide member to contact one side of the photosensitive belt; And sensing means for sensing a widthwise displacement of the photosensitive belt by detecting a movement amount of the guide member.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of a photosensitive belt position sensing apparatus for an image forming apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

4 and 5, an apparatus for detecting the position of a photosensitive belt for an image forming apparatus according to an embodiment of the present invention includes a base 51, a guide member 53 rotated according to a widthwise displacement of the photosensitive belt 10 A lever member 57 for causing the guide member 53 to rotate with respect to the base 51 and an elastic bias member for elastically biasing the guide member 53 to contact one side of the photosensitive belt 10, And sensing means for sensing the widthwise displacement of the photosensitive belt 10 by detecting the amount of movement of the guide member 53.

The photosensitive belt 10 is wound around a plurality of rollers 12, 14 and 31 in FIG. 1 to be turned in the sub scanning direction and is driven in the main scanning direction of light scanned by the laser scanning unit 20 10 in the width direction.

The guide member 53 includes a guide groove 53a formed to be inserted into a portion of the side of the photosensitive belt 10. The inner side surface of the guide groove 53a is a guide surface 53b which is in contact with one side of the photosensitive belt 10. Since the guide surface 53b is in line contact with the edge of the photosensitive belt 10, even if there are local defects D1 and D2 at the edge, it is not affected by the local defect.

Both ends of the lever member 57 are hinged to the base 51 and the guide member 53 so that the guide member 53 is rotated according to the widthwise displacement of the photosensitive belt 10.

The elastic bias means elastically biases the guide member 53 such that the guide member 53 is rotated while being in contact with one side of the photosensitive belt 10. A torsion spring 58 may be employed as the elastic bias means so as to be engaged with the stoppers 51a and 77a formed in the base 51 and the lever member 57, respectively. As the elastic bias means, a tension spring, a compression spring, or the like may be employed.

The sensing means senses the amount of movement of the guide member (53) and senses the widthwise displacement of the photosensitive belt (10). To this end, the sensing means includes a sensing protrusion 55 formed on one side of the guide member 53 and a photodetector 60. The sensing protrusion 55 is formed on one side of the guide member 53 and moves together with the guide member 53. The sensing protrusion 55 cuts off the light L scanned by the laser scanning unit 20 according to the widthwise displacement of the photosensitive belt 10, as shown in the figure. The sensing protrusion 55 may further include a reflective coating or a reflective member on the surface facing the light L so as to reflect the incident light. The photodetector 60 is fixed to the upper portion of the sensing protrusion 55. The photodetector 60 receives the light incident through the periphery of the sensing protrusion 55 after being partly blocked by the sensing protrusion 55 . Here, the widthwise displacement of the photosensitive belt 10 can be determined according to the amount of light received through the photodetector 60. The photodetector 60 is fixed to the lower portion of the sensing protrusion when sensing the widthwise displacement of the photosensitive belt 10 using light reflected from one surface of the sensing protrusion 55.

5, when the photosensitive belt 10 is not warped in the width direction, the edge of the photosensitive belt 10 is locally engaged with the edge of the photosensitive belt 10, (D1, D2), the guide member 53 is not rotated. Therefore, the amount of light received by the photodetector 60 is not changed, and the optical scanning start position SP for the image area 10a of the photosensitive belt 10 is not changed. Therefore, the straightness in the sub-scanning direction of the leading end position SP of the scanning line can be remarkably improved.

On the other hand, when the photosensitive belt 10 is meandering as shown by the dotted line in FIG. 5, the guide member 53 is rotated in accordance with the degree of skew of the photosensitive belt 10, The amount of light to be changed changes. In this case, the steering apparatus (30 in Fig. 1) is operated to move the vehicle in the maze correction direction .

6 and 7, the photosensitive belt position sensing apparatus for an image forming apparatus according to another exemplary embodiment of the present invention includes a base 71, a guide member 73 rotated in accordance with the widthwise displacement of the photosensitive belt 10 A lever member 77 for causing the guide member 73 to rotate relative to the base 71 and an elastic bias member for elastically biasing the guide member 73 to contact one side of the photosensitive belt 10, And sensing means for sensing the widthwise displacement of the photosensitive belt 10 by detecting the amount of movement of the guide member 73. Here, the base 71, the guide member 73, the lever member 77, and the elastic bias means are the same as those of the base 51, the guide member 53, The lever member 57, and the elastic bias means, respectively, detailed description thereof will be omitted.

The present embodiment is characterized in that the structure of the sensing means is changed. That is, the sensing means according to the present embodiment includes a lever rotation angle detection sensor 80 for sensing the rotation angle of the lever member 77 according to the rotation of the guide member 73.

The lever rotation angle sensor 80 senses the rotation angle of the lever member 77 with respect to the base 71 and can calculate the widthwise displacement of the photosensitive belt 10 from the rotation angle detection sensor 80.

As an example of the lever rotation angle detecting sensor 80, a variable resistor as shown in FIG. 7 may be employed. The variable resistor includes a fixed first electrode 81 and a second electrode 85 provided so as to be movable in conjunction with rotation of a protrusion 77a protruding from one end of the lever member 77, And a resistor 83 positioned between the second electrodes 81 and 85. The position of the contact between the second electrode 85 and the resistor 83 varies depending on the rotation angle of the lever member 77. Therefore, the resistance value between the first electrode 81 and the second electrode 85 is varied, and the voltage value between them v _o ) Changes. The lever rotation angle detection sensor 80 may be a semiconductor sensor using a conventional photoelectric rotation angle sensor or a Hall IC, A pressure sensor using a pressure change according to the angle may be employed.

As described above, the photosensitive belt position sensing apparatus for an image forming apparatus according to the present invention employs a guide member provided movably in accordance with the movement of the photosensitive belt in the width direction while being in line contact with one side of the photosensitive belt, It is possible to prevent the malfunction of the steering device and the deformation of the start position of the image due to the local defect even if there is a local defect on the photosensitive belt edge.

Claims (3)

An image forming apparatus for detecting a position in the width direction of the photosensitive belt so as to determine a widthwise jaggedness of a photosensitive belt wound on a plurality of rollers and turned in a sub scanning direction and / or a scanning timing of light scanned by the laser scanning unit A photosensitive belt position sensing device for a photosensitive belt, A base; A guide member having a guide surface that contacts one side of the photosensitive belt and is rotated in accordance with a widthwise displacement of the photosensitive belt; A lever member having both ends hinged to the base and the guide member such that the guide member is pivoted relative to the base; Elastic bias means for elastically biasing the guide member to contact one side of the photosensitive belt; And sensing means for sensing a widthwise displacement of the photosensitive belt by detecting a movement amount of the guide member. 2. The apparatus according to claim 1, A sensing protrusion formed on one side of the guide member and moved together with the guide member; And a photodetector fixed to the periphery of the sensing protrusion and receiving light that is scanned by the laser scanning unit and partially reflected by the sensing protrusion and / or light incident on the periphery of the sensing protrusion And the position of the photosensitive belt is detected. 2. The apparatus according to claim 1, And a lever rotation angle detection sensor for detecting a rotation angle of the lever member according to the rotation of the guide member.