This application is based on and claims the benefit of priority from Japanese Patent application No. 2018-034891 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 photosensitive drum, an exposure device, a supporting member and a main adjustment member. The photosensitive drum is provided for each of a plurality of colors forming a color image. The exposure device is configured to emit a laser light on each of the photosensitive drums to form an electrostatic latent image. The supporting member is configured to support end portions of rotation shafts of all the photosensitive drums. The main adjustment member is configured to shift the supporting member in a vertical plane 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. The left flange member 37 and a right end portion of the rotation shaft 39 are each inserted in a pressing lever 41. Between the left pressing lever 41 and the left flange member 37 and between the right pressing lever 41 and the right end portion of the rotation shaft 39, respective springs 43 are interposed. The spring 43 is a biasing member which biases each of the left flange member 37 and the right end portion of the rotation shaft 39 downward.
The drum unit 23 further includes a charge device 33 charging the photosensitive drum 31 and a cleaning device removing the toner remaining on the surface of the photosensitive drum 31. The charge device 33 and the cleaning device 35 are arranged along the rotation direction (the clockwise direction 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 (a parallel direction). The four attachment sections S correspond to yellow, magenta, cyan and black in the order from the front side to the rear side of the main frame 29. In the present embodiment, the black color is defined as a reference color.
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 flange member 37 of the photosensitive drum 31 of each drum unit 23 is inserted.
The right side plate 29d has an axis hole 52 and a groove 53 as shown in
The outer side plate 32 will be described with reference to
The outer side plate 32 is formed with four attachment sections S to which the respective drum units 23 and the respective development units 25 are attached. The four attachment sections S corresponds to the respective attachment sections S of the right side plate 29d. In each attachment section S, a hollow portion 55 recessed from an outside to an inside is formed. In the hollow portion 55, a vertical groove 57 is formed. The vertical groove 57 is cut out from an upper edge of the outer sideplate 32 downward. Into the vertical groove 57, the right end portion of the rotation shaft 39 of the photosensitive drum 31 is inserted. In each attachment section S, a lower opening 59 and a side opening 61 are formed at a lower position and an oblique front lower position of the vertical groove 57, respectively. When the drum unit 23 and the development unit 25 are attached to the attachment section S, the charge device 33 of the drum unit 23 and the development device of the development unit 25 are respectively exposed through the lower opening 59 and the side opening 61. Both the openings 59 and 61 are communicated with the hollow portion 55.
Next, the main adjustment mechanism 30 will be described with reference to
The main adjustment mechanism 30 is supported by the right side plate 29d. On an outer face (a face facing the outer side plate 32) of the right side plate 29d, a first shaft 29g, a second shaft 29h and a protrusion 29i are formed. The first shaft 29g is protruded rightward at an obliquely lower position of a lower end portion of the groove 53. The second shaft 29h is protruded rightward at an obliquely lower position of the first shaft 29g. The protrusion 29i extends rearward horizontally from the second shaft 29h.
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
The adjustment plate 65 is supported by the first shaft 29g of the right side plate 29d with the rib 83 facing the outer side plate 32. 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 groove 53 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 through the lower end portion of the groove 53.
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 through the lower end portion of the groove 53. 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.
When the drum unit 23 is attached to the above described attachment section S, as shown in
In the image forming unit 17 having the above described configuration, a skew adjustment way of a first embodiment will be described with reference to
As shown in
When the movable shaft 63 is pushed up, as shown in
When the photosensitive drum 31 is inclined upward to the right side as shown in
Additionally, as shown in
The skew amount of each photosensitive drum 31 will be described with reference to
Conventionally, the photosensitive drum 31 (the drum unit 23) corresponding to black, which is the reference color, is positioned with high precision, and the positioning precision becomes low as the distance from the drum unit 23 corresponding to black becomes long. Accordingly, the skew amount increases in proportion to the distance from the photosensitive drum 31 corresponding to black. That is, as shown in the graph of
As described above, according to the present disclosure, the right end portions of the rotation shafts 39 of all the photosensitive drums 31 are supported by the outer side plate 32 so that color shift of the toner image of each color is reduced. Additionally, by turning the outer side plate 32 in the vertical plane by the main adjustment mechanism 30, it becomes possible to correct the skew for all the photosensitive drums 31. That is, one adjustment work allows the skew adjustment for all the photosensitive drums 31 and it becomes possible to carry out the skew adjustment work effectively using a simple structure.
The shift distance of the right end portion of the rotation shaft 39 of the photosensitive drum 31 increases in proportion to the distance from the supporting shaft 62. Because the supporting shaft 62 is arranged near the attachment section S to which the drum unit 23 corresponding to the reference color (black) is attached, the skew amount increases in proportion to the distance from the drum unit 23 corresponding to black owing to positioning precision. As described, an increasing tendency for the skew amount is the same as an increasing tendency for the shift distance of the right end portion of the rotation shaft 39 of the photosensitive drum 31 so that the displacement distance of the writing position can be adjusted according to the skew amount.
Additionally, because the right end portions of the rotation shafts 39 of all the photosensitive drums 31 are supported by the outer side plate 32, if the skew is adjusted for any one of the photosensitive drums 31, the skew can be automatically adjusted for the other photosensitive drums 31. In this case, because the photosensitive drum 31 corresponding to yellow, which has a largest adjustment width, in other words, a longest shift distance of the rotation shaft 39, is adjusted for its skew, the skew adjustment work can be easily carried out.
In the present embodiment, the attachment section S of the drum unit 23 corresponding to the reference color (black) is arranged at the end portion (the rear end portion) in the parallel direction (the front-and-rear direction). If the reference color is a color other than black, the shaft 62 is preferably provided near the attachment section S of the drum unit 23 corresponding to the reference color.
The mechanism to shift the movable shaft 63 of the outer side plate 32 is not limited to the mechanism of the present embodiment.
Next, a skew adjustment way of a second embodiment will be described with reference to
In the second embodiment, each attachment section S corresponding to colors (cyan, magenta and yellow) other than black is provided with a sub adjustment mechanism 40. The sub adjustment mechanism 40 includes the adjustment plate 65 as a sub adjustment plate and the dial gear 67. The adjustment plate 65 and the dial gear 67 have the same structures as those of the main adjustment mechanism 30. That is, the adjustment plate 65 and the dial gear 67 are supported in a rotatable manner on an inner face of the hollow portion 55 of each attachment section S of the outer side plate 32. A part of the outer circumferential edge (for example, the first arc-shaped edge 77) of the attachment part 73 of the attachment plate is exposed through a lower end portion of the vertical groove 57 obliquely from the front lower side. The right end portion of the rotation shaft 39 of the photosensitive drum 31 is pressed on the rear side edge of the vertical groove 57 by the first arc-shaped edge 77 of the adjustment part 73. When the dial gear 67 is operated to rotate the adjustment plate 65, the right end portion of the rotation shaft 39 is shifted vertically along the rear side edge of the vertical groove 57.
In the second embodiment, not only by turning the outer side plate 32 to which the right end portions of the rotation shafts 39 of all the photosensitive drums 31 in the vertical plane, but also by shifting the right end portions of the rotation shafts 39 of the photosensitive drums 31 corresponding to cyan, magenta and yellow, individually, the writing positions are adjusted. The shift distance of the right end portion of the rotation shaft 39 and the displacement distance of the writing position are described above with reference to
The rotation shaft 39 of the photosensitive drum 31 corresponding to black is positioned with high precision as described above. Additionally, when the outer side plate 32 is turned so as to adjust the skew of the photosensitive drum 31 corresponding to black, the skew of the photosensitive drum 31 corresponding to each of another colors is automatically adjusted. However, even if the outer side plate 32 is turned so as to adjust the skew of the photosensitive drum 31 corresponding to black, when the skew of the photosensitive drum 31 corresponding to each of the other colors is not be adjusted suitably, by performing fine adjustment using the sub adjustment mechanism 40, it becomes possible to adjust the skew of the photosensitive drum 31 corresponding to each of the other colors surely.
The sub adjustment mechanism 40 may be provided in the attachment section S of the drum unit 23 corresponding to black. In this case, it becomes possible to surely adjust the skew of the photosensitive drum 31 corresponding to the reference color (black).
The sub adjustment mechanism 40 may be provided in the attachment section S of the drum unit 23 corresponding to all colors. In this case, it becomes possible to surely adjust the skew of the photosensitive drum 31 corresponding to all colors.
In the first and second embodiments, the outer side plate 32 is supported by the right side plate 29d in a turnable manner around the supporting shaft 62. On the other hand, in the other embodiments, the outer side plate 32 may be supported in a movable manner in the upper-and-lower direction or the right-and-left direction in the vertical plane. Alternatively, the outer side plate 32 may support the left end portion of the rotation shaft 39.
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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2018-034891 | Feb 2018 | JP | national |