JP2005014497A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of readily ensuring alignment between a photosensitive body and an LED print head in a simple structure. <P>SOLUTION: A support member 30 having a coil spring 29 as an urging means attached thereto is fixed to a body frame 2. As the coil spring 29 urges the LED print head 10M downwardly (toward a photosensitive drum 4M), an abutment pin 21 is always in press contact with a receptive groove 28. A through-hole 31 into which a rotating tool for rotating the abutment pin 21 is to be inserted, is formed on the support member 30. As the rotating tool is inserted into a through-hole 33 formed on the body frame 2 and the through-hole 31 from the external section, and then the abutment pin 21 is rotated by the rotating tool, the LED print head 10M is swung in the longitudinal direction of the abutment pin 21, thereby aligning the relative position between the LED print head 10M and the photosensitive drum 4M. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus using an LED print head as exposure means for an electrophotographic printer, facsimile, copying machine, or the like.
[0002]
[Prior art]
2. Description of the Related Art In recent years, an electrophotographic image forming apparatus using an LED array as an exposure unit has attracted attention in order to reduce the size and simplification of the apparatus. In this electrophotographic image forming apparatus, an LED print head used for exposure of a photoconductor as an image carrier has an LED array formed by arranging a plurality of LED elements in a line, and is based on image data. Each LED element is made to selectively emit light individually.
[0003]
Unlike the laser scanner unit, this LED print head is compact because it does not require a polygon mirror, a motor, or the like. From the viewpoint of miniaturization of the apparatus, it has been attracting attention as an exposure means in an electrophotographic image forming apparatus. In particular, it can be said that the effect is particularly great in a so-called tandem type color image forming apparatus including a plurality of image forming units.
[0004]
In the LED exposure method, an LED array composed of a plurality of LEDs and a lens array (selfoc lens array) that is an imaging unit are usually unitized, but an LED print head that is an exposure unit (exposure unit). In order to manage the optical path length within a predetermined range, it is necessary to strictly adjust the position on the order of several tens of microns in the depth direction with respect to the photoconductor as the image carrier. That is, in order to obtain a stable image, it is necessary to make the relative position between the photoconductor and the LED print head constant.
[0005]
Therefore, a method of positioning the LED print head with respect to the photoconductor in order to increase the accuracy of the relative position between the photoconductor and the LED print head to be constant and form a more stable image has been proposed. More specifically, an abutting pin that is a positioning means that projects downward is disposed at each of both ends of the LED print head, and the photosensitive drum is pivotally supported by each of the abutting pins. The LED print head is positioned with respect to the photosensitive drum by being brought into pressure contact with the receiving groove of the positioning member provided in the frame unit. Then, by rotating the eccentric cam that contacts the positioning member in a predetermined direction, the receiving groove portion of the positioning member is moved in the vertical direction (the direction in which the LED print head contacts and separates from the photosensitive drum), and the LED print head and the photosensitive member are moved. It is the structure which adjusts the relative position between body drums (for example, refer patent document 1).
[0006]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-173881 (page 6-7, FIG. 5)
[0007]
[Problems to be solved by the invention]
Here, when using the butting pin as a means for positioning the LED print head, in order to obtain a more stable image, the focal points of all LED elements in the main scanning direction coincide with the peripheral surface of the photosensitive drum. Therefore, it is necessary to adjust the focal length of the LED element to match the distance from the LED element to the center of the tip portion of the abutting pin.
[0008]
However, in the above-described conventional technology, the abutting pin is moved up and down by moving the receiving groove of the positioning member instead of advancing and retracting the abutting pin in the contact / separation direction, and the abutting pin is moved. The LED print head is moved in the vertical direction in conjunction with this. Therefore, in the configuration in which the relative position of the LED print head and the photosensitive drum is adjusted by the advancement / retraction of the receiving groove, the center of the abutting pin tip portion is displaced from the peripheral surface of the photosensitive drum by the advancement / retraction of the receiving groove. In addition, even if the center of the abutting pin tip is aligned with the peripheral surface of the photosensitive drum, the angle of the LED print head with respect to the positioning member provided with the receiving groove may vary. In this case, since the focal length of the LED element in the main scanning direction changes, it becomes difficult to make the focal length coincide with the distance from the LED element to the center of the tip portion of the abutting pin. Therefore, it becomes difficult to make the relative position between the photosensitive member and the LED print head constant, and there arises a disadvantage that a more stable image cannot be formed.
[0009]
SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that solves the above-described problems and can accurately and easily adjust the position between a photoconductor and an LED print head with a simple configuration.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides an image carrier, an LED print head that is provided close to the surface of the image carrier and exposes image information to the image carrier by light irradiation, and image formation A first positioning unit that is fixedly provided on the apparatus main body side and supports the image carrier and an LED print head, and abuts on the first positioning unit to make a distance between the image carrier and the LED print head. In an image forming apparatus including a second positioning unit that regulates, an elasticity for biasing the second positioning unit in a predetermined direction away from the LED print head between the second positioning unit and the LED print head. Means are provided.
[0011]
Here, the present invention biases the LED print head in the direction of the image end holder, and also biases the second positioning means so as to be always in pressure contact with the receiving groove formed in the first positioning means. Can be provided.
[0012]
In the present invention, the second positioning means is rotatably attached to the LED print head, and the LED print head is moved in the longitudinal direction of the second positioning means by rotating the second positioning means. The relative position between the LED print head and the image carrier can be adjusted.
[0013]
Further, according to the present invention, a support member to which a biasing means is attached is fixedly provided on the main body frame, and a rotating tool for rotating the second positioning means is provided on each of the support member and the main body frame. It is assumed that an insertion hole for inserting is inserted.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. In the image forming apparatus shown in FIG. 1, 1 is a color printer as an example of the image forming apparatus, 2 is a main body frame of the color printer 1, and four image forming units are provided in the main body of the image forming apparatus 1. That is, 3M, 3C, 3Y, and 3B are disposed in order from the upstream side. These image forming portions are magenta, cyan, yellow, and black image forming portions, respectively, and form images of four different colors by respective processes of charging, exposure, development, and transfer.
[0015]
The image forming units 3M, 3C, 3Y, and 3B are provided with photosensitive drums 4M, 4C, 4Y, and 4B as dedicated image carriers, respectively. The toner images formed on 4M, 4C, 4Y, and 4B are transferred onto the sheet 6 conveyed from the sheet feeding cassette 5, and then the sheet 6 on which the toner image is transferred is heated and fixed by the fixing unit 7. Pressure is applied, the toner image is fixed, and then the discharge is guided to the discharge unit 8. In this embodiment, the processes for the photosensitive drums 4M, 4C, 4Y, and 4B while rotating the photosensitive drums 4M, 4C, 4Y, and 4B, which are image carriers, clockwise in FIG. Is done.
[0016]
Next, the image forming unit will be described. In the four image forming units 3M, 3C, 3Y, and 3B disposed in the main body of the image forming apparatus 1, the photosensitive drums 4M, 4C, 4Y, and 4B are rotatably disposed above the photosensitive drums 4M, 4C, 4Y, and 4B. Are provided with charging devices 9M, 9C, 9Y, and 9B, and LED print heads 10M, 10C, 10Y, and 10B that expose image information to the photosensitive drums 4M, 4C, 4Y, and 4B by light irradiation. Is provided close to the surface of each of the photoconductive drums 4M, 4C, 4Y, and 4B. First, the surfaces of the photoconductive drums 4M, 4C, 4Y, and 4B are charged by the charging devices 9M, 9C, 9Y, and 9B. Is charged to a uniform charge, and then exposed by light irradiation by the LED print heads 10M, 10C, 10Y, and 10B, and the photosensitive drums 4M, 4C, 4Y, and 4B are exposed. The electrostatic latent image corresponding to the image signal is formed.
[0017]
The developing devices 11M, 11C, 11Y, and 11B are filled with a developer (toner) for magenta, cyan, yellow, and black, respectively, and the amount of toner in the developing devices 11M, 11C, 11Y, and 11B is filled. When the shortage is detected by a toner sensor (not shown), the toner is supplied from the toner hoppers 12M, 12C, 12Y, and 12B to the developing devices 11M, 11C, 11Y, and 11B. The developer of each color is supplied onto the photosensitive drums 4M, 4C, 4Y, and 4B by the developing devices 11M, 11C, 11Y, and 11B, and is visible according to the electrostatic latent image formed by the exposure. An image is formed.
[0018]
The paper 6 serving as a transfer destination of the toner image is accommodated in the paper feed cassette 5, and the paper 6 delivered from the paper feed cassette 5 is guided by the paper feed guide 13 and rotated counterclockwise. It is attracted to the upper surface of the conveying belt 14 and is conveyed toward the respective photosensitive drums 4M, 4C, 4Y, and 4B. Here, the conveyance belt 14 uses a sheet made of a dielectric resin, and a belt having an endless shape in which both ends thereof are overlapped with each other or a seamless belt having no seam is used.
[0019]
When the rotation of the transport belt 14 is started, the paper 6 is guided by the paper feed guide 13 and transported onto the transport belt 14. At this time, an image is formed in the most upstream image forming unit 3M at a predetermined timing, and an image is formed on the photosensitive drum 4M constituting the image forming unit 3M. Next, when the sheet 6 passes just below the image forming unit 3M, the image (magenta toner image) formed on the photosensitive drum 4M is transferred to the sheet 6 by the transfer roller 15M. Next, the sheet 6 is conveyed to the next image forming unit 3C by the conveying belt, and, like the image forming unit 3M, when the sheet 6 passes directly below the image forming unit 3C, it is transferred by the transfer roller 15C. An image (cyan toner image) formed on the photosensitive drum 4 </ b> C is transferred to the paper 6. In the same manner, images of respective colors (yellow and black toner images) are sequentially transferred onto the paper 6 by the transfer rollers 15Y and 15B when passing just below the image forming units 3Y and 3B. The four color images (magenta, cyan, yellow, and black) transferred to the paper 6 are formed with a predetermined positional relationship that is predetermined with respect to the paper 6 in order to form a full-color image.
[0020]
The sheet 6 on which the four-color toner images are transferred is separated from the transport belt 14 and transported to the fixing unit 7, and the four-color toner that forms a full-color image on the sheet 6 is transported by the sheet 6 through the fixing unit 7. The paper 6 is fixed when passing, and then the paper 6 is guided to the paper discharge unit 8 by the paper discharge guide 16. The toner remaining on the photosensitive drums 4M, 4C, 4Y, and 4B after the transfer is removed by the cleaning devices 17M, 17C, 17Y, and 17B to prepare for the subsequent latent image formation. It has a configuration.
[0021]
Next, an LED print head in the image forming apparatus according to the present embodiment will be described with reference to the drawings. FIG. 2 is a schematic diagram illustrating a schematic configuration of an LED print head in the image forming apparatus according to the embodiment of the present invention. FIG. 3 is a schematic diagram when the LED print head is incorporated in the image forming apparatus. 4 is a partially enlarged view for explaining a mounting configuration of a butting pin which is a positioning means of the LED print head shown in FIG. In the present embodiment, the above-described four image forming units 3M, 3C, 3Y, and 3B differ only in the color of the toner to be used, and the others are substantially the same in configuration. Only the section 3M will be described, and the description of the other image forming sections 3C, 3Y, and 3B will be omitted. This is exactly the same in the description related to FIGS.
[0022]
In FIG. 2, an LED print head 10M includes a board 18M having wiring, an LED array 19M that is arranged in a row on the board 18M, and includes a plurality of LED elements that are controlled to be turned on according to image data. And a lens array 20M that is arranged above the LED array 19M and forms an erecting equal-magnification image.
[0023]
Here, the LED array 19M and the lens array 20M, which is an imaging means, are unitized, and the lens array 20M is projected from the surface of the LED array 19M as shown in FIG. The lens array 20M and the like are held by a holding member (not shown). Further, an LED array control unit (not shown) for driving and controlling the LED print head 10M is provided outside.
[0024]
In FIG. 3, reference numeral 4M denotes a photosensitive drum having a drum shape. The lens array 20M receives light from the LED element 19M ′ constituting the LED array 19M, refracts it, and passes it on the surface of the photosensitive drum 4M. The state of image formation is indicated by a wavy line. Note that F in the figure indicates the focal point of the LED element 19M ′, and shows that the focal point F exists on the peripheral surface of the photosensitive drum 4M.
[0025]
At both ends of the LED print head 10M, abutting pins 21 as positioning means (“second positioning means” in claims) are provided so as to protrude downward. Here, as shown in FIG. 4, the abutting pin 21 has a screw portion 22, the screw portion 21 is screwed into a screw hole 23 formed in the substrate 18 </ b> M, and the abutting pin 21 is attached to the substrate. By engaging with 18M, the abutting pin 21 is rotatably attached to the LED print head 10M.
[0026]
As shown in FIGS. 2 and 4, an elastic member 25 is provided between the abutting pin 21 and the LED print head 10M as elastic means for urging the abutting pin 21 in a predetermined direction. ing. The elastic member 25 is held between the screw head 24 and the substrate 18M in a state where the elastic member 25 is in contact with the screw head 24 and the upper side 18M ′ of the substrate 18M. By this, it is urged in a predetermined direction (the direction of arrow A in the figure) moving away from the LED print head 10M. With this configuration, it is possible to prevent looseness and rattling of the screw portion 22 and the screw hole 23. For the elastic member 25, for example, rubber, resin, coil spring, leaf spring, wave washer, spring washer and the like can be used. The screw head 24 is provided with a slit (not shown) so that the rotation of the butting pin 21 can be adjusted using a screwdriver or the like.
[0027]
Next, a positioning mechanism for the image forming unit in the image forming apparatus according to the present embodiment will be described with reference to the drawings. FIG. 5 is a front sectional view for explaining the positioning mechanism of the image forming unit in the image forming apparatus according to the embodiment of the present invention. FIG. 6 shows the positioning of the image forming unit in the image forming apparatus according to the present embodiment. FIG. 7 is a side sectional view for explaining the mechanism, and FIG. 7 is an enlarged view of a contact portion between the abutting pin and the receiving groove of the positioning mechanism.
[0028]
As shown in FIGS. 5 and 6, the photosensitive drum 4M has a rotating shaft 4M ′, and positioning means (fixed) provided on both ends of the shaft 4M ′ on the image forming apparatus main body side. The photosensitive drum 4M is supported by the image carrier support member 26 by being inserted into a bearing hole 27 formed in the image carrier support member 26, which is the “first positioning means” described in the claims. Positioned.
[0029]
The abutting pin 21 is in contact with the image end support member 26 and regulates the distance between the photosensitive drum 4M and the LED print head 10M. More specifically, the image carrier support member 26 is formed with receiving grooves 28 that come into contact with the abutting pins 21 attached to both ends of the LED print head 10M. The LED print head 10M is positioned by being brought into pressure contact with the head.
[0030]
Here, as shown in FIG. 7, the tip of the abutting pin 21 forms a circumferential surface (or spherical surface) having a radius R, and is located at the center C of the circumference (or spherical surface). The distance from the LED element 19M ′ to the peripheral surface of the photosensitive drum 4M (ie, the peripheral surface of the photosensitive drum 4M) is determined by locking the photosensitive drum 4M to the image carrier supporting member 26 and positioning the photosensitive drum 4M so that the peripheral surface of the photosensitive drum 4M is located. The distance from the LED element 19M ′ to the center C of the tip of the abutting pin 21) can be kept constant. At this time, the center C always maintains the same position with respect to the receiving groove 28.
[0031]
Further, as shown in FIGS. 5 and 6, a support member 30 to which a coil spring 29 as an urging means is attached is fixed to the main body frame 2. As shown in FIGS. 2 and 5, the coil spring 29 is disposed so as to contact the upper side 18M ′ of the substrate 18M so as to surround the spring head 24 and the elastic member 25 of the abutting pin 21, and the LED print head. 10M is biased downward (that is, in the direction of the photosensitive drum 4M). Accordingly, the abutting pin 21 attached to the LED print head 10M is given a biasing force via the LED print head 10M, and therefore the abutting pin 21 is always in pressure contact with the receiving groove 28. The abutting pin 21 is inserted through an insertion hole 32 formed in the support member 30.
[0032]
Next, adjustment of the relative position of the LED print head 10M and the photosensitive drum 4M will be described. In the present embodiment, by rotating the abutting pin 21 attached to the LED print head 10M, the LED print head 10M is swung in the longitudinal direction of the abutting pin 21, and the LED print head 10M and the photosensitive drum are rotated. It is characterized in that the relative position of 4M is adjusted.
[0033]
That is, as shown in FIGS. 5 and 6, the support member 30 is formed with an insertion hole 31 for inserting a rotation tool (for example, a driver) for rotating the abutting pin 21. When adjusting the relative position between the print head 10M and the photosensitive drum 4M, first, a rotation tool is inserted from the outside into the insertion hole 33 formed in the main body frame 2 and the insertion hole 31, and then the rotation is performed. By rotating the abutting pin 21 with a tool for use, the LED print head 10M is swung in the longitudinal direction of the abutting pin 21.
[0034]
At this time, as described above, the abutting pin 21 is urged by the elastic member 25 in a predetermined direction (in the direction of arrow A in FIG. 4) away from the LED print head 10M, and at the same time, the coil spring 29 as an urging means. Thus, an urging force is applied through the LED print head 10M and is always in pressure contact with the receiving groove 28, so that the abutting pin 21 rotates but does not advance or retreat, and the LED print head 10M is not in contact with the abutting pin 21. It will swing in the longitudinal direction.
[0035]
That is, even if the abutting pin 21 is rotated, the abutting pin 21 always remains in pressure contact with the receiving groove 28, and therefore the center of the circumference (or the spherical circumference) of the tip portion of the abutting pin 21. While maintaining the state where C is positioned on the peripheral surface of the photosensitive drum 4M, the LED print head 10M is swung in the longitudinal direction of the abutting pin 21, and the relative position between the LED print head 10M and the photosensitive drum 4M is adjusted. It becomes possible.
[0036]
Therefore, in the present embodiment, there is no fear that the center C of the tip portion of the abutting pin 21 is displaced from the circumferential surface of the photosensitive drum 4M, and the center C is kept on the circumferential surface of the photosensitive drum 4M. Since the LED print head 10M can be swung in the longitudinal direction of the abutting pin 21, the angle of the LED print head 10M with respect to the image carrier support member 26 provided with the receiving groove 28 does not vary. The change in the focal length of the LED element 19M ′ in the main scanning direction can be prevented. Therefore, the focal length is made equal to the distance from the LED element 19M ′ to the center C of the tip portion of the abutting pin, and adjustment for making the relative position between the photosensitive drum 4M and the LED print head 10M constant is easy. As a result, a more stable image can be formed.
[0037]
In the present embodiment, since the insertion hole 31 is formed in the support member 30 and the insertion hole 33 is formed in the main body frame 2, the abutting pin 21 is rotated using a rotation tool, It is possible to adjust the relative position of the LED print head 10M and the photosensitive drum 4M by swinging the LED print head 10M in the longitudinal direction of the abutting pin 21 from the outside.
[0038]
Further, since adjustment from the outside is possible in this way, it is not necessary to take out the LED print head when performing the adjustment, and it is not necessary to turn off the power for ensuring safety. Therefore, the above adjustment can be performed while the power is on, and printing can be performed immediately even after the adjustment.
[0039]
In addition, this invention is not limited to the said embodiment, Based on the meaning of this invention, it is possible to change suitably the structure of each part, a shape, etc., and excludes them from the scope of the present invention. is not.
[0040]
【The invention's effect】
As described above, in the present invention, the LED print head is abutted while keeping the center of the circumference (or sphere) of the tip of the abutting pin on the circumferential surface of the photosensitive drum. Since it can be swung in the longitudinal direction of the contact pin, the change in the focal length of the LED element in the main scanning direction is prevented without causing variations in the angle of the LED print head with respect to the positioning member provided with the receiving groove. it can. Therefore, adjustment for making the relative position between the photosensitive drum and the LED print head constant is facilitated.
[0041]
In addition, the present invention makes it possible to adjust the relative position of the LED print head and the photosensitive drum from the outside using a rotating tool. Even after adjustment, printing can be performed immediately.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic diagram illustrating a schematic configuration of an LED print head in the image forming apparatus according to the embodiment of the present invention.
FIG. 3 is a schematic diagram when an LED print head is incorporated in an image forming apparatus.
4 is a partially enlarged view for explaining a mounting configuration of a butting pin which is a positioning means of the LED print head shown in FIG. 2; FIG.
FIG. 5 is a front sectional view for explaining the positioning mechanism of the image forming unit in the image forming apparatus according to the embodiment of the present invention.
FIG. 6 is a side sectional view for explaining the positioning mechanism of the image forming unit in the image forming apparatus according to the present embodiment.
FIG. 7 is an enlarged view of a contact portion between an abutting pin and a receiving groove of the positioning mechanism.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Color printer 2 Main body frame 3B, 3C, 3M, 3Y Image formation part 4B, 4C, 4M, 4Y Photosensitive drum 5 Paper feed cassette 6 Paper 9B, 9C, 9M, 9Y Charger 10B, 10C, 10M, 10Y LED printing Head 11B, 11C, 11M, 11Y Developing device 19M LED array 20M Lens array 21 Abutting pin 22 Screw part 23 Screw hole 24 Screw head 25 Elastic member 26 Positioning member 28 Receiving groove 29 Coil spring 30 Support member 31, 33 Insertion hole

Claims (4)

An image carrier, an LED print head that is provided close to the surface of the image carrier, and exposes image information to the image carrier by light irradiation, and is fixed to the image forming apparatus main body, A first positioning means for supporting the image carrier; and a second positioning means provided on the LED print head, for regulating a distance between the image carrier and the LED print head in contact with the first positioning means. In an image forming apparatus comprising positioning means,
An elastic means for urging the second positioning means in a predetermined direction away from the LED print head is provided between the second positioning means and the LED print head. Image forming apparatus. And urging means for urging the LED print head in the direction of the image end-carrying body and always bringing the second positioning means into pressure contact with a receiving groove formed in the first positioning means. The image forming apparatus according to claim 1. The second positioning means is rotatably attached to the LED print head. By rotating the second positioning means, the LED print head is moved in the longitudinal direction of the second positioning means. The image forming apparatus according to claim 2, wherein the relative position between the LED print head and the image carrier is adjusted by swinging. A support member to which the urging means is attached is fixed to the main body frame, and a rotation tool for rotating the second positioning means is inserted into each of the support member and the main body frame. The image forming apparatus according to claim 2, wherein an insertion hole for forming the image is formed.

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