This application is based on and claims the benefit of priority from Japanese Patent application No. 2018-034892 filed on Feb. 28, 2018, which is incorporated by reference in its entirety.
The present disclosure relates to an image forming apparatus provided with a photosensitive drum on which an electrostatic latent image is formed.
In an electrophotographic type image forming apparatus, a photosensitive drum is exposed with laser light emitted from an optical element of an exposure device to form an electrostatic latent image on the photosensitive drum. If the exposure device is slightly displaced from the photosensitive drum, a skew (a distortion) occurs on the image (the electrostatic latent image) on the photosensitive drum. This causes a color shift. Because plural elements are conventionally arranged between the optical element and the photosensitive drum, it is difficult to position the optical element and the photosensitive drum with a high precision.
For example, the image forming apparatus is sometimes provided with an exposure device arranged obliquely with respect to a rotation shaft of the photosensitive drum. In the image forming apparatus, a rotation speed of the photosensitive drum is finely adjusted such that an inclination of the toner image is the same as the inclination of the exposure device. Alternatively, another image forming apparatus is provided with an exposure device in which a mirror is finely adjusted by using a stepping motor.
However, in a case where the optical element of the exposure device is finely adjusted, the structure and the control process of the exposure device may be complicated and the exposure device may be made large in size.
In accordance with an aspect of the present disclosure, an image forming apparatus includes a groove, an exposure device and an adjustment member. In the groove, each of both end portions of a rotation shaft of a photosensitive drum is inserted. The exposure device is configured to emit a laser light on the photosensitive drum to form an electrostatic latent image. An adjustment member is configured to shift each of both the end portions of the rotation shaft to adjust a skew of the laser light.
The above and other objects, features, and advantages of the present disclosure will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present disclosure is shown byway of illustrative example.
Hereinafter, with reference to the attached drawings, an image forming apparatus according to one embodiment of the present disclosure will be described.
First, with reference to
An apparatus main body 2 of the color printer 1 includes a sheet feeding cassette 3 storing a sheet P, a sheet feeding device 5 feeding the sheet P from the sheet feeding cassette 3, an image forming part 7 forming a full color toner image on the sheet P, a fixing device 9 fixing the toner image on the sheet P, and a sheet ejecting device 13 ejecting the sheet P, having a fixed toner image, on an ejected sheet tray 11. In the apparatus main body 2, a conveying path for the sheet P is formed from the sheet feeding device 5 to the sheet ejecting device 13 through the image forming part 7 and the fixing device 9.
The image forming part 7 is provided with an image forming unit 17, an exposure device 19 arranged below the image forming unit 17 and four toner containers 21 arranged above the image forming unit 17.
Next, with reference to
The image forming unit 17 includes four drum units 23, four development units 25, an intermediate transferring unit 27 and an image forming frame 28 (refer to
Next, with reference to
The drum unit 23 includes a photosensitive drum 31 on which an electrostatic latent image is formed. To both end openings of the photosensitive drum 31, flange members 37 are fixed. Between the flange members 37, a rotation shaft 39 is penetrated along an axial center of the photosensitive drum 31, and the photosensitive drum 31 is rotated around the rotation shaft 39.
As shown in
As shown in
With reference to
The intermediate transferring unit 27 includes an endless intermediate transferring belt 47 and four primary transferring rollers 49 disposed in a hollow space of the intermediate transferring belt 47. Each primary transferring roller 49 is arranged between the development unit 25 and the cleaning device 35 of the drum unit 23 along the rotation direction of the photosensitive drum 31, and faces the photosensitive drum 31 via the intermediate transferring belt 47. The apparatus main body 2 is provided with a secondary transferring roller 48 disposed at a rear side of the intermediate transferring unit 27 so as to face the intermediate transferring belt 47.
The four toner containers 21 store the respective toners of the four colors (yellow, magenta, cyan and black). The toners are supplied from the four toner containers 21 to the respective development units 25.
The exposure device 19 emits laser light toward the photosensitive drum 31 of each drum unit 23. An angle of incidence of the laser light with respect to a tangential direction T on the surface of the photosensitive drum 31 is zero, as described later with reference to
Next, an image forming operation will be described. In the image forming part 7, the photosensitive drum 31 of each drum unit 23 is charged by the charge device 33 and then exposed by the exposure device 19 according to an image date to form the electrostatic latent image on the photosensitive drum 31. The electrostatic latent image is developed to the toner image by the development device of each development unit 25. Each toner image is transferred from the photosensitive drum 31 to the intermediate transferring belt 47 by the primary transferring roller 49 of the intermediate transferring unit 27. Thereby, a full color toner image is formed on the intermediate transferring belt 47. The full color toner image is transferred from the intermediate transferring belt 47 to the sheet P by the secondary transferring roller 48. The toner remaining on the photosensitive drum 31 is removed by the cleaning device 35 of the drum unit 23. The sheet P on which the full color toner image is transferred is conveyed to the fixing device 9. The fixing device 9 fixes the full color toner image on the sheet P. The sheet P on which the full color toner image is fixed is ejected to the ejected sheet tray 11 by the sheet ejecting device 13.
Next, the image forming frame 28 will be described with reference to
The main frame 29 includes a front side plate 29a and a rear side plate 29b which face each other in the front-and-rear direction and a left sideplate 29c and a right side plate 29d which face each other in the left-and-right direction. Between the left sideplate 29c and the right side plate 29d, four attachment sections S to which the four drum units 23 and the four development units 25 are attached are formed in parallel along the front-and-rear direction. The four attachment sections S are arranged corresponding to yellow, magenta, cyan and black in the order from the front side to the rear side of the main frame 29.
In each attachment section S of the left side plate 29c, a flange receiving groove 51 is formed. The flange receiving groove 51 is cut out from an upper edge of the left side plate 29c downward. Into the flange receiving groove 51, the left side flange member 37 of the photosensitive drum 31 of each drum unit 23 is inserted.
The flange receiving groove 51 will be described with reference to
Each attachment section S of the right side plate 29d will be described with reference to
As shown in
As shown in
As shown in
Next, the adjustment mechanism 30 will be described with reference to
The adjustment mechanism 30 includes an adjustment plate 65 and a dial gear 67 as shown in
The adjustment mechanism 30 to shift the right end portion of the rotation shaft 39 of the photosensitive drum 31, which is provided in each attachment section S of the right side plate 29d, will be described. The adjustment plate 65 is supported in a rotatable manner between the right sideplate 29d and a first inner plate 29e disposed inside the right side plate 29d. The dial gear 67 is supported in a rotatable manner between the right side plate 29d and a second inner plate 29f disposed inside the right side plate 29d.
As shown in
Next, the adjustment plate 65 will be described with reference to
The adjustment plate 65 is a disk-shaped member, and includes a cylindrical axial hole part 71, an approximately semicircular adjustment part 73 and an approximately semicircular gear part 75. The adjustment part 73 is provided at one side (the rear side) of the axial hole part 71 and the gear part 75 is provided at the other side (the front side) of the axial hole part 71. Around an outer circumferential edge of the adjustment part 73, a first arc-shaped edge 77, a second arc-shaped edge 78 and a third arc-shaped edge 79 are formed in the order in the circumferential direction. The first arc-shaped edge 77, the second arc-shaped edge 78 and the third arc-shaped edge 79 have different radius, and the radius becomes large in a stepwise manner in the order. For example, a difference in the radius between the adjacent arc-shaped edges is 0.1 mm. The adjacent arc-shaped edges are connected via a stepped portion 80 extending radially. Around an outer circumferential edge of the gear part 75, gear teeth 81 are formed at predetermined intervals. On one face of the gear part 75, an arc-shaped rib 83 along the circumferential direction is formed. A tip end face of the rib 83 is formed in a semi-circular cross section.
The adjustment plate 65 is formed by preparing a member A formed with the axial hole part 71 and the adjustment part 73 integrally and a member B formed with the gear part 75 and an axial hole 85 integrally, overlapping them with aligning the axial hole part 71 and the axial hole 85 coaxially and then coupling them, as shown in
As shown in
Next, the dial gear 67 will be described with reference to
The dial gear 67 is a disk-shaped member, and includes an axial hole part 91, a gear part 93 and a rack part 95 which are provided coaxially with the axial hole part 91. The rack part 95 has an outer diameter larger than that of the gear part 93. Along an outer circumferential edge of the gear part 93, gear teeth 97 engageable with the gear teeth 81 of the gear part 75 of the adjustment plate 65 are formed. Along an outer circumferential edge of the rack part 95, rack teeth 99 are formed at predetermined intervals.
On one face (a face at the side of the gear part 93) of the dial gear 67, an annular groove 101 is formed around the axial hole part 91. As shown in
As shown in
When the dial gear 67 is rotated in one direction, the adjustment plate 65 is rotated in a counter direction to the rotation direction of the dial gear 67. Then, the outer circumferential edge of the adjustment plate 65 exposed through the lower end portion of the shaft receiving groove 57 is changed. That is, by rotating the dial gear 67, one of the first arc-shaped edge 77, the second arc-shaped edge 78 and the third arc-shaped edge 79 is exposed thorough the lower end portion of the shaft receiving groove 57.
Additionally, the dial gear 67 is prevented from being rotated with respect to the right side plate 29d at a position where one of the first arc-shaped edge 77, the second arc-shaped edge 78 and the third arc-shaped edge 79 is exposed thorough the lower end portion of the shaft receiving groove 57. In detail, when the dial gear 67 is rotated, one inclined side face of the recess 105 engaged with the protrusion 29i comes into contact with the protrusion 29i, the inclined side face is guided in a direction away from the protrusion 29i against the biasing force of the spring 111, and then the rib 103 runs on the protrusion 29i. When the dial gear 67 is further rotated, the dial gear 67 is biased by the spring 111 in a direction close to the protrusion 29i, and then the adjacent recess 105 is engaged with the protrusion 29i. At this time, a click feeling is offered on the dial gear 67.
The adjustment mechanism 30 to shift the left flange member 37 includes the adjustment plate 65 and the dial gear 67 which are the same as those of the adjustment mechanism 30 to shift the right end portion of the rotation shaft 39. That is, a part of the outer circumferential edge of the adjustment part 73 of the adjustment plate 65 is exposed through a lower end portion of the flange receiving groove 51 obliquely from the front lower side. The dial gear 67 is engaged with the gear part 93 of the adjustment plate 65, and partially exposed through an opening formed in the left side plate 29c.
When the drum unit 23 is attached to the above described attachment section S, as shown in
With reference to
As described above, through the lower end portion of the shaft receiving groove 57, the outer circumferential edge (for example, the first arc-shaped edge 77) of the adjustment part 73 of the adjustment plate 65 is exposed obliquely from the front lower side. When the right end portion of the rotation shaft 39 is inserted in the shaft receiving groove 57, the first arc-shaped edge 77 comes into contact with the right end portion of the rotation shaft 39 obliquely from the front lower side and presses the right end portion of the rotation shaft 39 to the rear side edge 57a of the shaft receiving groove 57. For example, an angle θ2 of a line passing through a contact position of the first arc-shaped edge 77 of the adjustment part 73 with the rotation shaft 39 and the axial center of the rotation shaft 39 with respect to a vertical line passing through the axial center of the rotation shaft 39 is 45 degrees.
Additionally, the pressing lever 41 is engaged with the right side plate 29d, and the right end portion of the rotation shaft 39 is biased downward by the spring 43 (refer to a white blank arrow in
The flange member inserted into the flange receiving groove 51 is biased downward by the spring 43, is pressed against the rear side edge 51a of the flange receiving groove 51 by the first arc-shaped edge 77 of the adjustment part 73 to be positioned, in the same manner as the right end portion of the rotation shaft 39.
Next, a skew adjustment way of a first embodiment will be described.
As shown by a solid line in
If the right end portion of the rotation shaft 39 is further shifted upward, the dial gear 67 is further rotated in the clockwise direction in
When the right end portion of the rotation shaft 39 is shifted downward, the dial gear 67 is rotated in the counterclockwise direction in
As described above, when the dial gear 67 is operated to rotate the adjustment plate 65, the contact position of the outer circumferential edge of the adjustment part 73 of the adjustment plate 65 with the rotation shaft 39 is varied. Then, depending on the radius of the adjustment part 73 at the contact position, the right end portion of the rotation shaft 39 is shifted vertically along the rear side edge 57a so that it becomes possible to shift the right end portion of the rotation shaft 39 of the photosensitive drum 31 vertically. In the embodiment, because the difference in the radius between the adjacent arc-shaped edges is constant, the right end portion of the rotation shaft 39 is shifted by the same distance.
The flange member 37 inserted into the flange receiving groove 51 is shifted by the adjustment mechanism 30 in the same manner as the right end portion of the rotation shaft 39. That is, when the dial gear 67 is operated to rotate the adjustment plate 65, the contact position of the flange member 37 with the outer circumferential edge of the adjustment part 73 of the adjustment plate 65 is varied. Then, depending on the radius of the adjustment part 73 at the contact position, the flange member 37 is shifted vertically along the rear side edge 51a.
When the right end portion of the rotation shaft 39 of the photosensitive drum 31 is shifted vertically, the photosensitive drum 31 is inclined upward in the right side as shown in
Next, with reference to
As shown in the center figure in
As described above, because the shift distance D becomes large from the left side to the right side along the axial direction of the rotation shaft 39, the displacement distance α of the writing position becomes large from the left side to the right side. As a result, the writing position is displaced obliquely with respect to the axial direction of the rotation shaft 39 so that a skew can be adjusted.
Like the exposure device 19 of the present embodiment, in a case where the laser light is incident from the approximately lower side along the vertical direction (the Y direction), the amount of the displacement distance of the writing position responds to the shift distance of the rotation shaft 39 in the X direction more sensitively than in the Y direction. In other words, a ratio (an adjustment sensitivity) of the amount of the displacement distance of the writing position to the amount of the shift distance of the rotation shaft 39 is smaller in the Y direction than in the X direction. Conventionally, the low adjustment sensitively makes a fine adjustment easy. On the other hand, when the skew is remarkably large and it is required to shift the photosensitive drum 31 largely, the high adjustment sensitivity is preferable.
In a case of the angle φ of 45 degrees, the amount of the displacement distance of the writing position is equal between when the rotation shaft 39 is shifted in the X direction and when the rotation shaft 39 is shifted in the Y direction. In a case of the angle φ of 0 degree, the writing position is not displaced even if the rotation shaft 39 is shifted in the Y direction. Accordingly, the angle φ is set to be larger than 0 degree and 45 degrees or smaller.
As described above, in the color printer 1 of the present disclosure, it becomes possible to shift the right end portion of the rotation shaft 39 of the photosensitive drum 31 and the left flange member 37, that is, the left end portion of the rotation shaft independently. By shifting the left and right end portions of the rotation shaft 39 independently, it becomes possible to displace the writing position of the laser light independently at the left and right end portions. The skew is generated obliquely with respect to the axial direction of the rotation shaft 39, an amount and the direction of the skew are different from depending on characteristics of the exposure device 19 or the like. Then, depending on the amount and the direction of the skew, it becomes possible to shift the left and right end portions of the rotation shaft independently so that the writing position can be effectively adjusted for various types of skew. Additionally, because the rotation shaft 39 is shifted vertically, an adjustment sensitivity is set to be low so that fine adjustment becomes possible.
Owing to adjustment error of the exposure device 19, a displacement where the writing position is curved in an arc shape along the width direction, which is called “bow”, may be generated. When the skew and the bow are generated at the same time, a displacement distance of the writing position is increased. In this case, only by adjusting the skew, it becomes possible to reduce the displacement distance of the writing position.
Next, the skew adjustment way of a second embodiment will be described. In the second embodiment, the left end portion and the right end portion of the rotation shaft 39 are shifted in different shift ranges.
In the second embodiment, the right adjustment plate 65 (the adjustment plate 65 at the side of the right end portion of the rotation shaft 39) is formed such that the radiuses of the first arc-shaped edge 77, the second arc-shaped edge 78 and the third arc-shaped edge 79 of the adjustment part 73 become large in the order by 0.2 mm, for example. On the other hand, the left adjustment plate 65 (the adjustment plate 65 at the side of the left flange member 37) are formed such the radiuses of the first arc-shaped edge 77, the second arc-shaped edge 78 and the third arc-shaped edge 79 of the adjustment part 73 become large in the order by 0.1 mm, for example.
When the adjustment parts 73 of the left and right adjustment plates 65 have different radiuses, a shift range of the right end portion of the rotation shaft 39 is different from that of the left end portion of the rotation shaft 39. In this case, a shift range of the right end portion is wider than that of the left end portion.
In the second embodiment, it becomes possible to shift the left end portion and the right end portion of the rotation shaft 39 of the photosensitive drum 31 independently and to make the shift ranges of the end portions different from each other. As described above, the skew is generated obliquely with respect to the axial direction of the rotation shaft 39. Additionally, the direction of the inclination (for example, an upward left direction and an upward right direction) is different depending on the characteristics of the color printer 1. Accordingly, the left and right shift ranges are changed depending on the characteristic so that the skew can be adjusted effectively.
According to the direction and the amount of the skew, the shift range and the shift distance (the difference in the radius between the adjacent arc-shaped edges of the adjustment part 73 of the adjustment plate 65) may be set.
Next, the skew adjustment way in a third embodiment will be described with respect to
In the third embodiment, as shown in
In the same manner as the first embodiment, a part of the outer circumferential edge (the first arc-shaped edge 77) of the adjustment part 73 of the adjustment plate 65 is exposed through the lower portion of the shaft receiving groove 57 obliquely from the front lower side.
In the third embodiment, the right end portion of the rotation shaft 39 of the photosensitive drum 31 is inserted into the shaft receiving groove 57 and comes into contact with the bottom edge 57b. Additionally, the pressing lever 41 is engaged with the right side plate 29d, and the right end portion of the rotation shaft 39 is biased downward by the spring 43. Between the spring 43 and the right end portion of the rotation shaft 39, a wedge member 44 is arranged. The wedge member 44 inverts the biasing direction of the spring 43 into an oblique front lower direction. Thereby, the right end portion of the rotation shaft 39 is biased in the oblique front lower direction, that is, the direction of the first arc-shaped edge 77 of the adjustment part 73 of the adjustment plate 65, as shown in white blank arrow in
As described above, the right end portion of the rotation shaft 39 is pressed to the bottom edge 57b and the first arc-shaped edge 77 by the spring 43 to be positioned.
When the right end portion of the rotation shaft 39 is shifted, the dial gear 67 is operated to rotate the adjustment plate 65 in a direction where the radius of the adjustment part 73 becomes large. Then, the right end portion of the rotation shaft 39 is shifted rearward along the bottom edge 57b while being pressed to the bottom edge 57b by the spring 43, as shown in a broken line and a two-dotted chain line in
On the other hand, the left flange member 37 is shifted vertically along the side edge 51a by the adjustment plate 65, in the same manner as the first embodiment.
In the third embodiment, it becomes possible to shift the left end portion and the right end portion of the rotation shaft 39 of the photosensitive drum 31 independently and to make the shift directions of the end portions different from each other. In detail, the right end portion is shifted horizontally and the left end portion is shifted vertically. That is, the adjustment sensitivities of the left end portion and the right end portion are different from each other, the adjustment sensitivity of the right end portion is high; the adjustment sensitivity of the left end portion is low. The shift direction of each end portion may be selected depending on the direction and amount of the skew. Therefore, it becomes possible to perform a skew adjustment such that the shift distance of the end portion at the side where the skew is larger than the other side is made long to provide a wide adjustment range.
In the third embodiment, it becomes possible to change the shift ranges of the left end portion (the left flange member 37) and the right end portion of the rotation shaft 39. Additionally, when the edges to which the right end portion of the rotation shaft 39 and the left flange member 37 are pressed are formed obliquely, the right end portion and the left end portion (the flange member 37) of the rotation shaft 39 are shifted obliquely.
While the above description has been described with reference to the particular illustrative embodiments of the image forming apparatus according to the present disclosure, a technical range of the disclosure is not to be restricted by the description and illustration of the embodiment.
Number | Date | Country | Kind |
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2018-034892 | Feb 2018 | JP | national |