Patent Application
20150030358
This application is based on and claims the benefit of priority from Japanese Patent application No. 2013-156246 filed on Jul. 29, 2013, the entire contents of which are incorporated herein by reference.
The present disclosure relates to a fixing device configured to fix a toner image on a recording medium and an image forming apparatus provided with the fixing device.
An electrographic image forming apparatus, such as a copying machine and a printer, is provided with a fixing device configured to fix a toner image on a recording medium such as a sheet . The fixing device includes a fixing member (for example, a fixing roller or a fixing belt) and a pressing member (for example, a pressing roller or a pressing belt) configured to come in pressure-contact with the fixing member. By heating and pressing the recording medium and the toner image at a fixing nip formed between the fixing member and the pressing member, the toner image is fixed on the recording medium.
For example, a fixing deice having the fixing member, the pressing member which comes in pressure-contact with the fixing member to form the fixing nip and a separating member which separates the recording medium passed through the fixing nip from the fixing member is provided. The above separating member has a separating plate which faces a sheet passing region (a region through which the recording medium is passed) of the fixing member with an interval and a restricting piece which comes in contact with a non-sheet passing region (a region outside the sheet passing region).
In the above-mentioned fixing device, when foreign substances (for example, toner, paper powder, shaving chips of a surface coating of the fixing member) are deposited on a space between the non-sheet passing region of the fixing device and the restricting piece of the separating member, the fixing member would be damaged or the foreign substances would adhere on the recording medium to contaminate the recording medium. Alternatively, when the foreign substances are sandwiched between the non-sheet passing region of the fixing member and the restricting piece of the separating member, the interval between the sheet passing region of the fixing member and the separating plate of the separating member would be varied.
In accordance with an embodiment of the present disclosure, a fixing device includes a fixing member, a pressing member and a separating member. The fixing member is configured to be rotatable. The fixing member is provided with a sheet passing region and a non-sheet passing region. Through the sheet passing region, a recording medium is passed. The non-sheet passing region is arranged outside the sheet passing region. The pressing member is configured to come in pressure-contact with the fixing member to form a fixing nip. The separating member is configured to separate the recording medium passed through the fixing nip from the fixing member. The separating member has a separating plate and a restricting piece. The separating plate faces the sheet passing region with an interval. The restricting piece is configured to restrict the interval between the sheet passing region and the separating plate. The restricting piece is provided with a contacting surface which comes in contact with the non-sheet passing region. The contacting surface has a width which becomes wider from an upstream side to a downstream side in the rotation direction of the fixing member.
In accordance with an embodiment of the present disclosure, an image forming apparatus includes a fixing device. The fixing device has a fixing member, a pressing member and a separating member. The fixing member is configured to be rotatable. The fixing member is provided with a sheet passing region and a non-sheet passing region. Through the sheet passing region, a recording medium is passed. The non-sheet passing region is arranged outside the sheet passing region. The pressing member is configured to come in pressure-contact with the fixing member to form a fixing nip. The separating member is configured to separate the recording medium passed through the fixing nip from the fixing member. The separating member has a separating plate and a restricting piece. The separating plate faces the sheet passing region with an interval. The restricting piece is configured to restrict the interval between the sheet passing region and the separating plate. The restricting piece is provided with a contacting surface which comes in contact with the non-sheet passing region. The contacting surface has a width which becomes wider from an upstream side to a downstream side in the rotation direction of the fixing member.
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.
FIG . 5 is a perspective view showing a front end portion and its peripheral portion of the fixing unit, in the fixing device of the color printer according to the embodiment of the present disclosure.
First, with reference to
The color printer 1 includes a box-shaped printer main body 2. In a lower part of the printer main body 2, a sheet feeding cartridge 3 storing sheets (recording mediums) is provided and, on an upper surface of the printer main body 2, a sheet ejecting tray 4 is provided.
In a middle part of the printer main body 2, an intermediate transferring belt 6 is bridged over a plurality of rollers and, below the intermediate transferring belt 6, an exposure device 7 consisting of a laser scanning unit (LSU) is arranged. Under the intermediate transferring belt 6, four image forming units 8 are provided for respective colors (for example, four colors of magenta, cyan, yellow and black) of toners (developers). Hereinafter, one of the four image forming units 8 will be described. In each image forming unit 8, a photosensitive drum 9 is rotatably provided. Around the photosensitive drum 9, a charger 10, a development device 11, a first transferring unit 12, a cleaning device 13 and a static eliminator 14 are arranged in order of a first transferring process. Above the development device 11, four toner containers 15 corresponding to the image forming units 8 are provided for different colors (for example, four colors of magenta, cyan, yellow and black) of toners, respectively.
On one side (the right upper side in the figure) in the printer main body 2, a sheet conveying path 16 extending in the upper and lower directions is provided. At an upper stream end of the conveying path 16, a sheet feeder 17 is provided. At an intermediate stream part of the conveying path 16, a second transferring unit 18 is provided at one end (the right end in the figure) of the intermediate transferring belt 6. At a lower stream part of the conveying path 16, a fixing device 20 is provided. At a lower stream end of the conveying path 16, a sheet ejecting port 21 is provided.
Next, the operation of forming an image by the color printer 1 having such a configuration will be described. When the power is supplied to the color printer 1, various parameters are initialized and initial determination, such as temperature determination of the fixing device 20, is carried out. Subsequently, when image data is inputted and a printing start is directed from a computer or the like connected with the color printer 1, the image forming operation is carried out as follows .
First, the surface of the photosensitive drum 9 is electrically charged by the charger 10. Then, the surface of the photosensitive drum 9 is irradiated with a laser (refer to an arrow P) by the exposure device 7, thereby forming an electrostatic latent image on the surface of the photosensitive drum 9. The electrostatic latent image is then developed to a toner image having a correspondent color by the developing device 11 with a toner supplied from the toner container 15. The toner image is first-transferred onto the surface of the intermediate transferring belt 6 in the first transferring unit 12. The above-mentioned operation is repeated in order by the image forming units 8, thereby forming the toner image having full color on the intermediate transferring belt 6. Toner and electric charge remained on the photosensitive drum 9 are eliminated by the cleaning device 13 and static eliminator 14.
On the other hand, a sheet fed from the sheet feeding cartridge 3 or a manual bypass tray (not shown) by the sheet feeder 17 is conveyed to the second transferring unit 18 in a suitable timing for the above-mentioned image forming operation. Then, in the second transferring unit 18, the toner image having full color on the intermediate transferring belt 6 is second-transferred onto the sheet. The sheet with the second-transferred toner image is conveyed to a lower stream side on the conveying path 16 to enter the fixing device 20, and then, the toner image is fixed on the sheet in the fixing device 20. The sheet with the fixed toner image is ejected from the first sheet ejecting port 21 on the sheet ejecting tray 4.
Next, the fixing device 20 will be described. Hereinafter, for convenience of explanation, the near side viewed from the paper plane of
As shown in
First, the fixing unit 22 will be described. As shown in
As shown in
As shown in
At the left bottom corner of the movable frame part 41, a rotatable detected member 46 is provided. On the left side of the detected member 46, a first sensor 47 is provided. The first sensor 47 is composed of a PI sensor (a Photo Interrupter Sensor). As shown in
The heating roller 25 (refer to
The heating roller 25 has a first rotating shaft 50. As shown in
To each of the front and back ends of the heating roller 25, a disk-shaped belt flange 52 (refer to
The fixing roller 26 (refer to
The fixing roller 26 faces the pressing roller 30 via the fixing belt 28. The fixing roller 26 has a second rotating shaft 54. As shown in
The tension roller 27 (refer to
The fixing belt 28 is formed into a flexible endless belt. The fixing belt 28 is composed of a substrate layer, an elastic layer provided around the substrate layer and a release layer coating the elastic layer, for example. The substrate layer of the fixing belt 28 is made from metal such as nickel and stainless steel or resin such as PI (polyimide). The elastic layer of the fixing belt 28 is made from silicon rubber, for example. The release layer of the fixing belt 28 is made from fluoroethylene resin such as PFA (Perfluoro alkoxy alkane), for example. In this embodiment, the front and back directions (the depth direction of the paper plane in
The fixing belt 28 is rotatably supported by the movable frame part 41 via the heating roller 25, the fixing roller 26 and the tension roller 27. As shown in
As shown in
The pressing roller 30 is composed of a cylindrical core metal, an elastic layer provided around the core metal and a release layer coating the elastic layer, for example. The core metal of the pressing roller 30 is made from metal such as stainless steel or aluminum, for example. The elastic layer of the pressing roller 30 is made from silicon rubber or silicon sponge, for example. The release layer of the pressing roller 30 is made from fluoroethylene resin such as PFA, for example.
The pressing roller 30 comes in pressure-contact with the fixing belt 28 to form a fixing nip 60 between the fixing belt 28 and the pressing roller 30. The front and back end portions of the pressing roller 30 are rotatably supported by the front and back walls 42 of the fixed frame part 40 via third bearings 61 (refer to
As shown in
As shown in
The driving motor 64 is arranged on the front side of the front wall 42 of the fixed frame part 40. The driving motor 64 has a motor shaft 71 extending downward. To the motor shaft 71, a warm gear 72 is fixed concentrically.
As shown in
At an approximate center portion of the driving member 66 in the upper and lower directions, a turning shaft 76 around which the driving member 66 is turnable is formed. At the lower end portion of the driving member 66, a driving gear 77 is formed. The driving gear 77 is meshed with the second gear 74 of the reduction gear mechanism 65. Thus, the driving motor 64 is connected to the driving member 66 via the reduction gear mechanism 65. In other words, the reduction gear mechanism 65 is installed between the driving motor 64 and the driving member 66.
At the upper end portion of the driving member 66, a driving piece 78 is formed. At the upper end portion of the driving member 66, a pressing piece 80 protruding leftward from the driving piece 78 is formed. The pressing piece 80 is formed into a long straight rod shape extending in the left and right directions. At the distal end portion (the left end portion) of the pressing piece 80, a disk-shaped collar part 81 is formed. In front of the driving member 66, a second sensor 82 configured to detect displacement of the driving piece 78 is formed. The second sensor 82 is composed of a PI (Photo Interrupter) sensor, for example.
The lever 67 extends in the upper and lower directions . At the lower end portion of the lever 67, a supporting shaft 83 around which the lever 67 is turnable is formed. At the upper end portion on the lever 67, a through hole 84 through which the pressing piece 80 of the driving member 66 is penetrated is formed. As shown in
As shown in
The left end portion of the second coil spring 69 comes in contact with the contacting piece 43 formed at each of the front and back walls 42 of the fixed frame part 40. The right end portion of the second coil spring 69 comes in contact with the upper portion of the lever 67. That is, the second coil spring 69 is installed between the fixed frame part 40 and the lever 67.
The nip pressure switching mechanism (not shown) provided on the back side has the same configuration as the above-mentioned nip pressure switching mechanism 31 provided on the front side except that the driving motor 64 is not provided. The nip pressure switching mechanism provided on the backside is coupled to the third gear 75 of the nip pressure switching mechanism 31 provided on the front side through a coupling shaft 86 (refer to
As shown in
The supporting plate 87 is formed in a long shape extending in the front and back directions. The supporting plate 87 is made from sheet metal, for example. The supporting plate 87 has a flat main body part 90, a bend part 91 bent in the left lower direction from the left upper end of the main body part 90 and attachment parts 92 bent in the left lower direction from the front and back ends of the main body part 90.
At each of the front and back end portions of the main body part 90 of the supporting plate 87, a positioning hole 93 is formed. At each of the front and back end portions of the main body part 90 of the supporting plate 87, a screw hole 94 is formed inside the positioning hole 93 in the front and back directions. At each of the front and back end portions of the main body part 90 of the supporting plate 87, a holding part 95 extending in the right lower direction is formed. At the distal end portion of the holding part 95, an L-shaped hook 96 protruding inwardly in the front and back directions is formed. As shown in
As shown in
As shown in
As shown in
Each restricting piece 89 is formed as a separated member from the supporting plate 87 and the separating plate 88. As shown in
As shown in
At the center portion of the fixed part main body 108 of the fixed part 106, a screw hole 110 is formed. The fixed part main body 108 is formed with positioning bosses 111 at the left and right side of the screw hole 110. While fitting each positioning boss 111 into each of the pair of positioning grooves 98 (refer to
On the distal end surface (a surface on the side of the movable part 107) of the first connecting portion 109 of the fixed part 106, an engaging protrusion 113 is formed. The engaging protrusion 113 is formed into a column shape coaxially with a rotation axis B. On the outer circumference of the engaging protrusion 113, a protrusion side thread 114 is formed.
The movable part 107 of each restricting piece 89 has an approximately fan-shaped movable part main body 115 and a square column-shaped second connecting portion 116 protruding in the left upper direction from the left upper portion of the movable part main body 115.
As shown in
As shown in
As shown in
Next, the IH unit 23 will be described. As shown in
In the fixing device 18 having the above-mentioned configuration, when the toner image is fixed to the sheet, the driving part (not shown) is driven to rotate the pressing roller 30. When the pressing roller 30 is rotated, the fixing belt 28 which comes in contact with the pressing roller 30 is rotated in the direction reverse to the pressing roller 30. Furthermore, when the toner image is fixed on the sheet, the IH coil 121 is applied with a high frequency current. Thus, the IH coil 121 generates a magnetic field which produces an eddy current in the fixing belt 28 to heat the fixing belt 28. Under this state, when the sheet is passed through the fixing nip 60, the sheet and the toner image are heated and pressed to fix the toner image on the sheet. The sheet passed through the fixing nip 60 is separated from the fixing belt 28 by the separating plate 88 of the separating member 32.
When such the fixing operation is repeated, foreign substances (for example, toner, paper powder and shading chips of the surface coating layer of the fixing belt 28) may be deposited or sandwiched between the non-sheet passing region R2 of the fixing belt 28 and the restricting piece 89 of the separating member 32.
However, in the present embodiment, since the contacting surface 117 of the restricting piece 89 has the width which becomes wider from the upstream side to the downstream side in the rotation direction A of the fixing belt 28, the foreign substances are hardly deposited between the non-sheet passing region R2 of the fixing belt 28 and the restricting piece 89 of the separating member 32. Therefore, the fixing belt 28 is hardly damaged so as to prolong the lifetime of the fixing belt 28. Furthermore, since the foreign substances are hardly attached on the sheet, the sheet can be prevented from being contaminated.
Furthermore, by applying the above-mentioned configuration, the foreign substances are hardly sandwiched between the non-sheet passing region R2 of the fixing belt 28 and the restricting piece 89 of the separating member 32. Therefore, since the interval d between the sheet passing region R1 of the fixing belt 28 and the distal edge 88a of the separating plate 88 is prevented from being varied, a separating performance (a performance to separate the sheet from the fixing belt 28) of the separating member 32 can be stabilized.
The restricting piece 89 has the fixed part 106 configured to be fixed to the supporting plate 87 and the movable part 107 supported by the fixed part 106 in a turnable state around the rotation axis B and having the contacting surface 117. By applying such a configuration, when the fixing belt 28 is inclined relative to the separating member 32, for example, when the fixing belt 28 is undulated, since the movable part 107 of the restricting piece 89 is turned relative to the fixed part 106, it becomes possible to contact the contacting surface 117 of the restricting piece 89 to the non-sheet passing region R2 of the fixing belt 28 uniformly. Therefore, a sudden rise in the surface pressure of the fixing belt 28 caused by contacting the edge of the contacting surface 117 of the restricting piece 89 to the non-sheet passing region R2 of the fixing belt 28 can be prevented. Accordingly, the fixing belt 28 is more hardly damaged and therefore it becomes possible to more prolong the lifetime of the fixing belt 28.
The fixed part 106 of the restricting piece 89 is formed with the column-shaped engaging protrusion 113 coaxially with the rotation axis B, and the movable part 107 of the restricting piece 89 is formed with the engaging depression 118 formed into a column-shaped space coaxially with the rotation axis B and engageable with the engaging protrusion 113. By applying such a configuration, the movable part 107 can be rotatable relative to the fixed part 106 by using a simple structure.
On the outer circumference of the engaging protrusion 113, the protrusion side thread 114 is formed, and on the inner circumference of the engaging depression 118, a depression side thread 119 capable of screwing with the protrusion side thread 114 is formed. By applying such a configuration, the movable part 107 can be prevented from being fallen from the fixed part 106 by using a simple structure.
Since the fixing belt 28 formed into the flexible endless belt is used as the fixing member, it becomes possible to decrease a heat capacity of the fixing member compared with a case in which the fixing member is formed into a roller. Accordingly, it becomes possible to decrease a warming-up time and save energy.
The present embodiment shows a case in which the fixed part 106 of the restricting piece 89 is formed with the engaging protrusion 113 and the movable part 107 of the restricting piece 89 is formed with the engaging depression 118. On the other hand, in another embodiments, the fixed part 106 of the restricting piece 89 may be formed with the engaging depression and the movable part 107 of the restricting piece 89 may be formed with the engaging protrusion.
The present embodiment shows a case in which the configuration of the present disclosure is applied to the fixing device 20 configured such that the fixing belt 28 is wound around a plurality of rollers (the heating roller 25, the fixing roller 26 and the tension roller 27) installed inside the fixing belt 28. On the other hand, in another embodiments, the configuration of the present disclosure may be applied to a fixing device configured such that the fixing belt 28 is wound around one roller installed inside the fixing belt 28 and another fixing device configured such that the fixing belt 28 is slide relative to a pressing member installed inside the fixing belt 28.
In the present embodiment, a case in which the fixing member is formed into the fixing belt 28 is described. In another embodiments, the fixing member may be formed into a fixing roller.
In the present embodiment, a case in which the IH coil 121 is used as the heating source is described. In another embodiments, a heater such as a halogen heater and a ceramic heater may be used as the heating source.
In the embodiment, while the configuration of the disclosure is applied to the color printer 1, in another embodiment, the configuration of the disclosure may be applied to a monochrome printer, a copying machine, a facsimile, a multifunction peripheral or the like.
While the present disclosure has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments . It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-156246 | Jul 2013 | JP | national |
