Patent Application
20180039208
This application is based on and claims the benefit of priority from Japanese Patent application No. 2016-155487 filed on Aug. 8, 2016, which is incorporated by reference in its entirety.
The present disclosure relates to a transfer unit which transfers a toner image formed on an image carrier to a sheet and to an image forming apparatus including the transfer unit.
In an image forming apparatus, such as a copying machine and a printer, a toner image formed on an image carrier, such as a photosensitive drum and an intermediate transferring belt, is transferred to a sheet from the image carrier at a transferring nip formed between the image carrier and a transfer member.
The sheet is guided to the transferring nip along a guide. The guide is configured to guide the sheet to the transferring nip with a constant conveying posture. When the sheet is guided with the constant conveying posture, the guide receives a load from the sheet. As the size of the image forming apparatus is reduced in recent years, a curvature of a conveying path of the sheet becomes large. As a result, a stiffness of the sheet has a large effect on the conveying posture. In a case of a sheet having a large rigidity such as a thick paper, the load received by the guide increases because of its strong stiffness.
There is an image forming apparatus provided with a lever which is turned to press the transfer member against the image carrier. The lever is pressed by a turnable conveying unit and then turned to press the transfer member against the image carrier.
An example in which the transfer member is pressed by the lever will be described with reference to
When the conveying unit is turned, the levers 104 are turned around the bosses 107 and presses the rotating shaft 101b of the transfer roller 101 such that the transfer roller 101 is pressed against the intermediate transferring belt 106 to form the transferring nip 111. The holder 103 and the lever 104 respectively have turning stoppers 113 and 114 both of which are engaged with each other to prevent the holder 103 from being turned with respect to the lever 104.
In a case of the example shown in
However, depending on sizes and shapes of the holder 103 and the levers 104, it is necessary to form the turning stoppers 113 and 114 near an axial center of the rotating shaft 101b. Then, if the turning stoppers 113 and 114 may have dimension errors, a turning angle of the holder 103 until the tuning stoppers 113 and 114 are engaged with each other becomes large, and thus the holder 103, that is, the guide 102 is considerably displaced. In addition, because the load received by the guide 102 is transferred to the levers 104 through the holder 103, dimension error and rigidity of the holder 103 is also affected on the displacement of the guide 102.
If the guide 102 may be displaced, the conveying posture of the sheet is varied such that it becomes difficult to guide the sheet to the transferring nip 111 stably. As a result, image failure may be occurred. Alternatively, if the guide 102 and the holder 103 may be made using high rigid material in order to withstand the increased load, the size of each member may become large and a material cost may be increased.
In accordance with an aspect of the present disclosure, a transfer unit includes a transfer roller, a guide, a holder and a lever. The transfer roller is configured to be pressed against an image carrier to form a transferring nip and to transfer a toner image from the image carrier to a sheet at the transferring nip. The guide is configured to guide the sheet to the transferring nip. The holder is configured to support a rotating shaft of the transfer roller in a rotatable manner and to support the guide. The lever is configured to support the holder in a turnable manner around the rotating shaft so as to press the transfer roller against the image carrier. The guide has an engaged part. The lever has an engagement part which is engaged with the engaged part. An engagement of the engagement part with the engaged part prevents a turning of the guide with respect to the lever.
In accordance with an aspect of the present disclosure, an image forming apparatus includes a conveying unit and the above described transfer unit. The conveying unit is supported by an apparatus main body in a tunable manner and configured to form a sheet conveying path with the apparatus main body. The conveying unit has a storage recess in which the transfer unit is stored. The storage recess has a supporting shaft and a biasing member. The supporting shaft supports the lever in a tunable manner. The biasing member is configured to bias the lever in a direction in which the transfer roller is pressed against the image carrier when the conveying unit is turned in a direction in which the conveying path is formed.
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, a transfer unit and an image forming apparatus according to one embodiment of the present disclosure will be described.
With reference to
An apparatus main body 2 of the color printer 1 includes a sheet feeding cassette 3 in which a sheet S is stored, an image forming part 4 configured to form a full color toner image on the sheet S, a fixing device 5 configured to fix the toner image to the sheet S, a sheet ejection device 6 configured to eject the sheet S having the fixed toner image, an ejected sheet tray 7 configured to receive the ejected sheet S, a cover unit 8 and a conveying unit 9 both of which form a conveying path of the sheet S.
The image forming part 4 includes an exposing device 11, an image forming unit 12 provided for each toner of four colors (yellow, magenta, cyan and black), an intermediate transfer unit 13 disposed above the image forming units 12 and four toner containers 14 each containing the toner of each color.
Each image forming unit 12 includes a photosensitive drum 16 on which an electrostatic latent image is formed, a charger 17 which charges the photosensitive drum 16, a development device 18 which develops the electrostatic latent image formed on the photosensitive drum 16 with the toner supplied from the toner container 14 and a cleaning device 19 which removes the toner remained on a surface of the photosensitive drum 16.
The intermediate transfer unit 13 includes an endless intermediate transferring belt 21 as an image carrier, four primary transferring rollers 22 disposed in a hollow space of the intermediate transferring belt 21 and a belt cleaning device 23. The intermediate transferring belt 21 is supported by a drive roller 24 and a driven roller 25 to be circulated by rotation of the drive roller 24. Each primary transferring roller 22 faces the photosensitive drum 16 via the intermediate transferring belt 21. Between the intermediate transferring belt 21 and the photosensitive drum 16, a primary transferring nip 26 is formed.
The cover unit 8 is supported in an opening 2a formed on a right side face of the apparatus main body 2 in a rotatable manner around its lower end. The conveying unit 9 is supported by an inner face of the cover unit 8 in a rotatable manner around its lower end. Between the conveying unit 9 and the apparatus main body 2, the conveying path 28 of the sheet S is formed such that the sheet S is conveyed from the sheet feeding cassette 3 to the sheet ejection device 6 through the image forming part 4 and the fixing device 5. On an inner face (a face facing the conveying path 28) of the conveying unit 9, a secondary transfer unit 30 is supported. The secondary transfer unit 30 is configured to form a secondary transferring nip 29 with the intermediate transferring belt 21. On the conveying path 28, a pair of registration rollers is provided at the upstream side of the secondary transferring nip 29 in the conveying direction. One of the registration rollers 32 is supported by the inner face of the conveying unit 9 in a rotatable manner. Between the cover unit 8 and the conveying unit 9, a conversion path 33 for a duplex printing is formed.
In each image forming unit 12, the photosensitive drum 16 is charged by the charger 17 and then exposed by the exposing device 11 according to an image data. This forms an electrostatic latent image on the photosensitive drum 16. The electrostatic latent image is developed into a toner image by the development device 18. The toner image is transferred to the intermediate transferring belt 21 from the photosensitive drum 16 at the primary transferring nip 26. By transferring the four toner images developed by the four image forming units 12 to the intermediate transferring belt 21, a full color toner image is formed on the intermediate transferring belt 21. The toner remained on each photosensitive drum 16 is removed by the cleaning device 19.
On the other hand, the sheet S fed from the sheet feeding cassette 3 is conveyed along the conveying path 28. Then, the full color toner image formed on the intermediate transferring belt 21 is transferred to the sheet S at the secondary transferring nip 29. The sheet S having the full color toner image is conveyed to the fixing device 5. The fixing device 5 fixes the full color toner image on the sheet S. The sheet S having the fixed full color toner image is ejected on the ejected sheet tray 7 by the sheet ejection device 6.
Next, the secondary transfer unit 30 will be described with reference to
As shown in
The transfer roller 41 has a roller body 41a and a rotating shaft 41b. The roller body 41a is made of electrical conductive elastic material. The transfer roller 41 is electrically connected to a transfer bias power source. When the full color toner image transferred on the intermediate transferring belt 21 is transferred on the sheet S at the secondary transferring nip 29, a predetermined bias voltage is applied to the transfer roller 41.
The guide 42 has a guide plate 47 facing the conveying path 28 and a side plate 48 provided on both ends of the guide plate 47 in a width direction (the front-rear direction) perpendicular to the conveying direction. As shown in
As shown in
Each shaft supporting part 54 has a bearing opening 59 configured to support one end portion of the rotating shaft 41b of the transfer roller 41 in a rotatable manner. The bearing opening 59 has a diameter larger than a diameter of the rotating shaft 41b of the transfer roller 41. The bearing opening 59 is formed by cutting a part of a side edge of the shaft supporting part 54 inward.
As shown in
The bearing part 61 is formed into a cylindrical shape. Through the bearing part 61, the one end portion of the rotating shaft 41b of the transfer roller 41 is passed. In addition, the bearing part 61 is configured to be passed through the bearing opening 59 of the shaft supporting part 54 of the holder 43.
The turning fulcrum part 63 is formed into a recess having an inverted U-shape and recessed outward from an inner face of the lever 44, as shown in
The spring receiving part 62 is formed into a circular recess. The hook part 65 is located at the tip portion further separated from the bearing part 61 than the spring receiving part 62.
On the inner face of the lever 44, a pin 67 is stood at a position further separated away from the bearing part 61 than the turning fulcrum part 63. The pin 67 is an example of an engagement part capable of being fitted into the long hole 50 of the guide 42.
In the secondary transfer unit 30 having the above described configuration, the both end portions of the rotating shaft 41b of the transfer roller 41 are passed through the bearing parts 61 of the levers 44. The bearing parts 61 through which the end portions of the rotating shaft 41b are passed are supported by the bearing openings 59 of the shaft supporting parts 54 of the holder 43 in a rotatable manner. Thereby, as shown in
The secondary transfer unit 30 is supported by a storage recess 70 of the conveying unit 9. The storage recess 70 will be described with reference to
The storage recess 70 is recessed inward from the conveying path 28. At each end portion of the storage recess 70 in the width direction, a boss 71, a spring receiving part 74 and an engagement part 73 are formed. The boss 71 is an example of a supporting shaft which supports the lever 44 in a turnable manner. The boss 71 is stood at a left lower corner of the end portion of the storage recess 70 in parallel with the rotating shaft 41b of the transfer roller 41. The spring receiving part 74 is formed at a right upper corner of the end portion of the storage recess 70. The other end of a coil spring 72 is supported by the spring receiving part 74. The coil spring 72 is an example of a biasing member which biases the lever 44. The engagement part 73 is formed above the spring receiving part 74.
By inserting the turning fulcrum parts 63 of the pair of levers 44 onto the bosses 71 of the storage recess 70 from the upper side, the secondary transfer unit 30 is supported by the storage recess 70 in a slidable manner along the bosses 71 in the upper-lower direction and a turnable manner around the bosses 71. Then, when the hook parts 65 of the levers 44 are engaged with the engagement parts 73 of the storage recess 70, the one ends of the coil springs 72 come into pressure contact with the spring receiving parts 62 of the levers 44. The coil springs 72 bias the levers 44 in the counterclockwise direction in
When the conveying unit 9 to which the secondary transfer unit 30 is supported is turned in a direction in which the conveying path 28 is formed, the transfer roller 41 faces the drive roller 24 of the intermediate transfer unit 13. In addition, the levers 44 which are biased in the counterclockwise direction in
The sheet S conveyed from the sheet feeding cassette 3 along the conveying path 28 is guided to the secondary transferring nip 29 while curved along the guide plate 47 of the guide 42. Then, at the secondary transferring nip 29, the toner image is transferred to the sheet S from the intermediate transferring belt 21.
As shown in
As described above with reference to
However, in the present embodiment, as described above, the load F1 applied to the guide 42 from the sheet S is directly applied to the levers 44 without through the holder 43, and then applied to the bosses 71 from the levers 44. Thereby, the guide 42 is hardly affected by mounting backlash and rigidity of each member, and is hardly displaced accordingly. Thus, it becomes possible to guide the sheet S to the secondary transferring nip 29 with a constant conveying posture even if the sheet S has a strong stiffness.
As described above, in the color printer 1 according to the present disclosure, the load applied to the guide 42 from the sheet S is directly applied to the levers 44 through the pins 67 and the long holes 50 without being affected by the rigidity and the mounting backrush of the holder 43. Thus, the guide 42 is hardly displaced so that the sheet S can be guided to the secondary transferring nip 29 stably with a constant conveying posture even if the sheet S has a strong stiffness. In addition, increasing in rigidity of each member is eliminated and increasing in cost is accordingly eliminated.
Additionally, the load applied to the levers 44 is received by the bosses 71 of the conveying unit 9 so that the rigidity and the mounting backrush of the levers 44 have little effect on the guide 42. Accordingly, the displacement of the guide 42 can be restricted more surely.
Additionally, by a simple configuration in which the long holes 50 and the pins 67 which are engaged with each other are respectively formed on the guide 42 and the levers 44, the turning of the guide 42 and the levers 44 can be prevented surely. In addition, the pins 67 in the long holes 50 are allowed to be moved in the longitudinal direction but restricted from being moved in the lateral direction. Because the direction of the load F1 applied to the guide plate 47 from the sheet S is parallel with the lateral direction of the long holes 50, the pins 67 are restricted from being moved in the long holes 50 so that the load F1 can be directly transferred to the levers 44.
If the long holes 50 and the pins 67 may have dimension errors, the guide 42 may turn around the rotating shaft 41b until the side edge of the long holes 50 are engaged with the pins 67 of the levers 44 (until the guide 42 is prevented from being turned). Because the long holes 50 are located at the left lower corners of the side plates 48 of the guide 42, a distance between the long hole 50 and the axial center of the rotating shaft 41b becomes the farthest in a side view of the guide 42 and the holder 43. Thus, a turning angle of the guide 42 until the guide 42 is restricted from being turned can be made to be small so that the displacement of the guide 42 can be restricted.
While the preferable embodiment and its modified example of the image forming apparatus of the present disclosure have been described above and various technically preferable configurations have been illustrated, a technical range of the disclosure is not to be restricted by the description and illustration of the embodiment. Further, the components in the embodiment of the disclosure may be suitably replaced with other components, or variously combined with the other components. The claims are not restricted by the description of the embodiment of the disclosure as mentioned above.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-155487 | Aug 2016 | JP | national |
