Patent Application
20200192255
This application is based on and claims the benefit of priority from Japanese patent application No. 2018-233800 filed on Dec. 13, 2018, which is incorporated by reference in its entirety.
The present disclosure relates to a fixing device which fixes a toner on a sheet and an image forming apparatus including the fixing device.
An electrophotographic type printer is provided with a fixing device which fixes a toner on a sheet. The fixing device includes a fixing member (a fixing roller, a fixing belt or the like), a pressing roller and a heating part (a halogen heater, a ceramic heater, an induction heating heater or the like), and a pressing area through which the sheet is held and conveyed is formed between the fixing member and the pressing roller. The heating part heats the fixing member, and the toner is heated and pressed at the pressing area to be fixed on the sheet.
The fixing device including a separation claw which assists a separation of the sheet from the fixing member is known. The separation claw has a wedge-shaped tip end portion, and is disposed on the downstream side of the pressing area in the sheet conveyance direction. The tip end portion of the separation claw is pressed against the outer circumferential face of the fixing member to separate the adhered sheet from the fixing member.
However, in some cases, a part of the toner is transferred to the fixing member from the sheet without being fixed on the sheet, then to the separation claw from the fixing member and is accumulated on the separation claw. The accumulated toner may become a lump of the toner to cause a deterioration of the sheet conveyance performance and a contamination of the sheet.
Then, a technique for suppress the accumulation of the toner on the separation claw is discussed. For example, a sheet separation claw is discussed, which has a body part through which a supporting shaft is inserted, a recessed part extending from the upper portion of the body part and a sliding part extending on the tip side of the recessed part and having a tip edge sliding on a surface of a roller, and the upper face of the recessed part is formed in a mountain-like shape. Additionally, the separation claw having a tip width of 1 mm or smaller is also discussed. Furthermore, it is discussed to provide a step portion on an opposite face to a separation claw guide face, in which the step portion is recessed in a direction far from a rotational body at a position separated rearward by a predetermined distance from the tip portion of the separation claw.
However, in the above described sheet separation claw, because a wide portion remains near the sliding part, the lump of toner formed on this portion may remain as it is and then grow. Furthermore, if the tip width of the separation claw is made to be narrow as described above, a contact force on the fixing roller becomes high to shorten a life of the fixing member owing to a surface abrasion. Additionally, if the step portion is formed on the separation claw guide face, the toner gone around from the tip of the separation claw fills the step portion and then grows, and then the grown toner lump may be held between the separation claw and the fixing member.
In accordance with an aspect of the present disclosure, a fixing device includes a fixing member, a separation craw. The fixing member heats a toner image on a sheet while rotating around an axis. The separation claw comes into contact with a surface of the fixing member and separates the sheet from the surface of the fixing member. The separation claw has an opposing face facing the sheet. The opposing face has a tip end portion coming into contact with the surface of the fixing belt. The opposing face is formed to be asymmetry with respect to a conveyance direction along which the sheet is conveyed from the tip end portion.
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 by way of illustrative example.
Hereinafter, an embodiment of the present disclosure will be described with reference to the attached figures. In the figures, “Fr” shows “front”, “Rr” shows “rear”, “L” shows “left”, “R” shows “right”, “U” shows “upper” and “D” shows “lower”. “Upstream”, “downstream” and these similar terms show “upstream”, “downstream” and their similar concept in a conveyance direction (a passing direction) of a sheet S.
[Outline of the color printer] With reference to
The color printer 1 includes an apparatus main body 2 constituting an approximately parallelepiped appearance. In the lower portion of the apparatus main body 2, a sheet feeding cassette 3 which stores a paper sheet S (a medium) is provided in an attachable and detachable manner. On the upper face of the apparatus main body 2, a discharge tray 4 is provided.
The color printer 1 is provided with a sheet feeding device 5, an image forming device 6 and a fixing device 7 which are stored in the apparatus main body 2. The sheet feeding device 5 is disposed at an upstream end portion of a conveyance path 8 extending from the sheet feeding cassette 3 to the discharge tray 4. The fixing device 7 is disposed in the downstream side portion of the conveyance path 8. The image forming device 6 is disposed between the sheet feeding device 5 and the fixing device 7 on the conveyance path 8.
The image forming device 6 includes four toner containers 10, an intermediate transferring belt 11, four drum units 12 and an optical scanning unit 13. The four toner containers 10 store toners (developers) of four colors (yellow, magenta, cyan and black). The drum unit 12 includes a photosensitive drum 14, a charge device 15, a development device 16, a primary transferring roller 17 and a cleaning device 18. The primary transferring roller 17 is disposed such that the intermediate transferring belt 11 is put between the photosensitive drum 14 and the primary transferring roller 17. With the right side portion of the intermediate transferring belt 11, a secondary transferring roller 19 comes into contact. Between the secondary transferring roller 19 and the intermediate transferring belt 11, a transferring nip is formed.
The color printer 1 is provided with a controller 9 which controls the above devices suitably to perform the following image forming operation. The charge device 15 charges the surface of the photosensitive drum 14. The photosensitive drum 14 is received with a scanning light emitted from the optical scanning unit 13 to carry an electrostatic latent image. The development device 16 employs the toner supplied from the corresponding toner container 10 and develops the electrostatic latent image on the photosensitive drum 14 in a toner image. The primary transferring roller 17 primarily transfers the toner image on the photosensitive drum 14 to the rotating intermediate transferring belt 11. The intermediate transferring belt 11 carries a full color toner image formed by overlapping the four color toner images while rotating. The sheet S is fed from the sheet feeding cassette 3 to the conveyance path 8 by the sheet feeding device 5. The secondary transferring roller 19 secondarily transfers the toner image on the intermediate transferring belt 11 to the sheet S passing through the transferring nip. The fixing device 7 heat-fixes the toner image on the sheet S. Then, the sheet S is discharged on the discharge tray 4. The cleaning device 18 removes the toner remaining on the photosensitive drum 14.
[The fixing device] Next, with reference to
As shown in
<The casing> The casing 20 is formed in an approximately parallelepiped shape long in the front-and-rear direction, and made of plate metal or heat resistant resin, for example. As shown in
<The fixing roller> As shown in
<The pressing roller> The pressing roller 22 as an example of a pressing member is formed in an approximately cylindrical shape long in the front-and-rear direction (the axial direction), and disposed on the right side of the fixing roller 21. The pressing roller 22 includes a pressing core metal 22A, a pressing elastic layer 22B provided on the outer circumferential face of the pressing core metal 22A and a pressing release layer 22C which covers the pressing elastic layer 22B. Both the front and rear end portions of the pressing roller 22 (the pressing core metal 22A) are supported by a pair of movable frames 34 in a rotatable manner (refer to
When the pressure adjustment part turns the movable frames 34 to a side of the fixing roller 21, the pressing roller 22 is pressed against the fixing roller 21 to form the compressed pressing area N between the fixing roller 21 and the pressing roller 22. On the other hand, when the pressure adjustment part turns the movable frames 34 in a direction separate from the fixing roller 21, the pressing of the pressing roller 22 against fixing roller 21 is released to form the decompressed pressing area N. The pressing area N shows an area from an upstream position where the pressure is 0 Pa through a position where the pressure is maximum to a downstream position where the pressure is 0 Pa again.
<The halogen heater> As shown in
Inside the casing 20, a temperature sensor (not shown), such as a thermopile and a thermistor, which detects a surface temperature of the fixing roller 21 (or a temperature of the halogen heater 23) is provided. To the controller 9 of the color printer 1, the drive motor 32, the halogen heater 23, the temperature sensor and the others are electrically connected. The controller 9 controls the drive motor 32, the halogen heater 23, the temperature sensor and the others via various drive circuits.
<The separation unit> As shown in
(The separation claw) As shown in
As shown in
In other words, the non-vertical portion 40N extends in a direction crossing to an imaginary face P (shown by a two-dotted chain line in
That is, the opposing face 40F is formed in an asymmetrical shape when viewed from a direction perpendicular to the axial direction of the fixing roller 21 (with respect to the conveyance direction along which the sheet is conveyed from the tip end portion 40E).
(The support frame) As shown in
(The metal plate member) Both the front and rear end portions of the metal plate member 42 are bent leftward (an opposite direction to the separation claw 40) to form a pair of bent pieces 43. To each bent piece 43, an approximately columnar support pin 44 extending from the rear side to the front side is fixed. The support pins 44 are disposed coaxially when viewed from the front side. The support pins 44 are supported by bearing portions (not shown) opened to the casing 20 in a slidable manner. The support frame 41 is provided in a slidable manner in the front-and-rear direction along the support pins 44 extending in the axial direction. The above described guide member 20B is disposed so as to cover the support frame 41 (refer to
As shown in
(The box-shaped member) The box-shaped member 45 has a projection 45A inserted into the through hole 42A of the metal plate member 42 and a pair of hooks 45B engaged with the pair of notches 42B of the metal plate member 42. The box-shaped member 45 is positioned to the metal plate member 42 by inserting the projection 45A into the through hole 42A and temporarily fixed to the metal plate member 42 by engaging the hooks 45B with the notches 42B. Then, the box-shaped member 45 is fastened to the metal plate member 42 by a screw (not shown). The two box-shaped members 45 are fastened to the front and rear end portions of the metal plate member 42 on both sides of the center portion in the front-and-rear direction (refer to
As shown in
As shown in
<The moving mechanism> As shown in
(The input gear) The input gear 50 is a warm wheel that a plurality of teeth is formed around an outer circumferential face of a disk. On the axial center of the input gear 50, a gear shaft portion 50A is formed so as to extend in the left-and-right direction (a direction perpendicular to the fixing roller 21). The gear shaft portion 50A is supported by the casing 20 in a rotatable manner. The input gear 50 (the teeth thereof) is connected to the drive motor 32 (the pinion gear thereof) via a drive force transmission mechanism 53. The drive force transmission mechanism 53 contains a plurality of circular gears 53A (a spur gear, a stepped gear or the like) and a warm gear 53B. The final gear of the drive force transmission mechanism 53 is the warm gear 53B which is meshed with the input gear 50.
(The eccentric cam) The eccentric cam 51 has an approximately cylindrical shape, and is protruded forward from the right end face of the input gear 50. The eccentric cam 51 is disposed at a position where its axial center is displaced from the gear shaft portion 50A of the input gear 50. That is, the eccentric cam 51 is a so-called disk cam that a distance (an eccentric radius) between the rotational center (the gear shaft portion 50A) and the outer circumferential face is not constant along the circumferential direction. The outer circumferential face of the eccentric cam 51 forms a continuous cam face 54 containing a first cam face 54A having the maximum radius and a second cam face 54B having the minimum radius (refer to
(The biasing member) The biasing member 52 is a compressed coil spring, and disposed between the rear face of the bent piece 43 formed in the front end portion of the support frame 41 and the casing 20. The biasing member 52 has a function to bias the separation claw 40 (the bent piece 43 of the separation unit 24) toward the cam face 54 of the eccentric cam 51.
<The biasing mechanism> As shown in
[An operation of the fixing device] Next, with reference to
Firstly, the controller 9 controls the drive motor 32 and the halogen heater 23 to be driven. The fixing roller 21 is driven by the drive force of the drive motor 32 to be rotated, and the pressing roller 22 is driven by the fixing roller 21 to be rotated (refer to a solid narrow line arrow in
[An operation of the separation claw] With reference to
[An operation of the moving mechanism] With reference to
The drive force of the drive motor 32 rotates the input gear 50 at almost a constant rotation speed via the drive force transmission mechanism 53. The moving mechanism 25 incorporates with the eccentric cam 51 rotating together with the input gear 50 and the biasing member 52 to reciprocate the separation unit 24 in the front-and-rear direction (the axial direction). In detail, the eccentric cam 51 rotates while bringing the cam face 54 indirectly contact with the separation claw 40 to reciprocate the separation claw 40 in the front-and-rear direction (the axial direction). Hereinafter, a case where the first cam face 54A comes into contact with the bent piece 43 of the support frame 41 is set to be “an initial state (0°)” (refer to the uppermost figure in
In the initial state, the eccentric cam 51 pushes out the separation unit 24 rearward against the biasing force of the biasing member 52, and the separation unit 24 is disposed at the rearmost position. When the eccentric cam 51 rotates from the initial state, the bent piece 43 is slid relatively from the first cam face 54A to the second cam face 54B. In this case, because the eccentric radius of the cam face 54 is gradually decreased, the separation unit 24 biases by the biasing member 52 and then moves forward gradually (refer to the second figure from the uppermost figure in
When the eccentric cam 4 rotates further and the bent piece 43 is slid relatively from the second cam face 54B to the first cam face 54A, because the eccentric radius of the cam face 54 is gradually increased, the separation unit 24 is gradually moved rearward against the biasing force of the biasing member 52 (refer to the lowermost figure in
As described above, when the eccentric cam 51 rotates once, the separation unit 24 reciprocates in the front-and-rear direction one time. When the eccentric cam 51 repeatedly rotates, the separation unit 24 (the separation claw 40) reciprocates repeatedly.
According to the fixing device 7 of the present embodiment, when the transferring of the toner from the fixing roller 21 to the opposing face 40F of the claw main body 40B is repeated, the toner is pushed out in the direction F in
Additionally, according to the fixing device 7 of the present embodiment, because the separation claw 40 reciprocates in the axial direction by the moving mechanism 25, the separation claw 40 can scrape the sheet powder transferred to the fixing roller 21 from the sheet S within a wide range and then collect the sheet powder, so that a rate in amount of the sheet powder to the toner is increased. As a result, the toner accumulated on the opposing face 40F is easy to be broken. Then, according to the fixing device 7 of the present embodiment, compared with a case where the moving mechanism 25 is not provided, it becomes possible to inhibit the accumulation of the toner on the separation claw 40.
The above embodiment may be modified as follows.
That is, the opposing face 40F is formed so as to be asymmetry when viewed from a direction perpendicular to the axial direction of the fixing roller 21 (with respect to the conveyance direction).
According to the fixing device 7 of the modified example, when the transferring of the toner from the fixing roller 21 to the opposing face 40F of the claw main body 40B is repeated, the toner is pushed out in the direction F in
The above embodiment or the first modified example may be combined with the second modified example. That is, the opposing face 40F of the separation claw 40 may have the non-vertical portion 40N and the non-vertical portion 40N may have the inclined portion 40S.
The fixing device 7 of the above embodiments includes the four separation claws 40; however, a number of the claw is not limited to the above embodiment. The fixing device 7 may include one or more separation claws 40. The moving mechanism 25 reciprocates the separation claw 40 in the front-and-rear direction via the support frame 41; however, the moving mechanism is not limited to the embodiment. The moving mechanism may have a configuration to bring the eccentric cam 51 directly contact with the separation claw 40 and to reciprocate the separation claw 40.
In the fixing device 7 according to the above embodiments, the moving mechanism 25 employs a cam mechanism containing the eccentric cam 51; however, the present disclosure is not limited to the above moving mechanism 25. In place of the cam mechanism (the eccentric cam 51 and the others), for example, a solenoid or a rack-and-pinion mechanism (not shown) may be employed as the moving mechanism. In this case, the plunger of the solenoid or the rack gear may be coupled to the separation unit 24 or the separation claw 40 to reciprocate the separation claw 40, preferably.
In the fixing device 7 according to the above embodiments, the drive motor 32 drives the fixing roller 21 to be rotated; however, the present disclosure is not limited thereto. The drive motor 32 may drive the pressing roller 22 to be rotated. The pressure adjustment part displaces the pressing roller 22 to change the pressure of the pressing area N; however, the present disclosure is not limited thereto. The pressure adjustment part may displace the fixing roller 21 to change the pressure of the pressing area N.
In the fixing device 7 according to the above embodiments, the fixing roller 21 has a configuration where the fixing elastic layer 21B is provided around the fixing core metal 21A and the fixing belt 21C are wound around the fixing elastic layer 21B; however, the present disclosure is not limited thereto. For example, the fixing member may be an endless belt and a pad pressing the fixing belt against the pressing roller 22 from the inside may be provided (not shown).
The embodiments were described in a case of applying the configuration of the present disclosure to the color printer 1. On the other hand, in another embodiment, the configuration of the disclosure may be applied to another image forming apparatus, such as a monochromatic printer, a cloying machine, a facsimile or a multifunction peripheral.
Although the present disclosure described the specific embodiment, the present disclosure is not limited to the embodiment. It is to be noted that one skilled in the art can modify the embodiment without departing from the scope and spirit of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-233800 | Dec 2018 | JP | national |
