Patent Grant
9639035
This application claims priority from Japanese Patent Application No. 2015-114192 filed Jun. 4, 2015. The entire content of the priority application is incorporated herein by reference.
The present disclosure relates to a fixing device including a resin frame supporting a pressure roller.
Japanese Patent Application publication No. 2015-068907 discloses a fixing device provided in an image forming device. The fixing device includes a heat unit, a pressure roller for nipping a conveyed sheet in cooperation with the heat unit, and a frame supporting the pressure roller. The heat unit is urged toward the pressure roller to provide a pressure contact therebetween. The pressure roller is supported to the frame made from resin through a bearing.
According to the disclosed structure, heat transmitted to the pressure roller is transmitted to the frame through the bearing. Thus, the portion of the frame near the bearing becomes high temperature to generate a steep temperature gradient in the frame. The temperature gradient is generated in the printing operation, and the temperature gradient disappears in non-printing operation during which the frame is cooled. In the fixing device, as a result of repetition of such two states, creep deformation may occur in the frame when force is applied from the pressure roller to the frame.
It is therefore an object of the present disclosure to provide a fixing device capable of restraining deformation of the frame.
According to one aspect, a fixing device includes a heat unit, a pressure roller configured to nip a conveyed sheet in cooperation with the heat unit, the pressure roller having a shaft defining an axial direction, a bearing configured to support the shaft, a frame configured to support the bearing and made from resin, and a heatsink made from metal, and in surface contact with the frame and at least one of the shaft and the bearing.
The particular features and advantages of the disclosure as well as other objects will become apparent from the following description taken in connection with the accompanying drawings, in which:
A fixing device 100 according to an embodiment will be described while referring to
As shown in
Directions in the following description will be based on an orientation of the laser printer 1 shown in
The sheet supply unit 3 is positioned in a lower portion of the main housing 2, and includes a sheet supply tray 31, a lifter plate 32 for lifting up a leading end portion of the sheet P, a sheet supply roller 33, a sheet supply pad 34, a paper dust removing rollers 35, 36, and registration rollers 37. The sheet P in the sheet supply tray 31 is moved toward the sheet supply roller 33 by the lifter plate 32, and each one of the sheets P is separated from remaining sheets by the sheet supply roller 33 and the sheet supply pad 34, and is conveyed toward the process cartridge 5 by way of the paper dust removing rollers 35, 36 and the registration rollers 37.
The exposure unit 4 is provided in an upper portion of the main housing 2. The exposure unit 4 includes a laser light-emitting unit (not shown), a polygon mirror 41 rotationally driven, lenses 42, 43, and reflecting mirrors 44, 45, 46. As indicated by a dotted chain line in
The process cartridge 5 is positioned below the exposure unit 4. The main housing 2 has an opening which is opened or closed by a front cover 21. The process cartridge 5 can be attached to and detached from the main housing 2 through the opening when the front cover 21 is open. The process cartridge 5 includes a drum unit 6 and a developing unit 7.
The drum unit 6 includes the photosensitive drum 61, a charger 62, and a transfer roller 63. The developing unit 7 is configured to be attached to and detached from the drum unit 6, and includes a developing roller 71, a supply roller 72, a layer thickness regulation blade 73, and a toner chamber 74 for accommodating toner therein.
In the process cartridge 5, the charger 62 performs discharge to apply a uniform charge to the surface of the photosensitive drum 61, after which the exposure unit 4 irradiates laser beams to expose the surface of photosensitive drum 61 to light for forming an electrostatic latent image thereon on a basis of image data. Further, the toner in the toner chamber 74 is supplied to the developing roller 71 via the supply roller 72. Toner on the developing roller 71 is subjected to toner layer thickness regulation by the layer thickness regulation blade 73, and such toner layer is carried on the developing roller 71.
The toner carried on the developing roller 71 is then supplied to the electrostatic latent image formed on the surface of the photosensitive drum 61 to produce a toner image on the photosensitive drum 61. Then, the toner image on the photosensitive drum 61 is transferred to the sheet P when the sheet P is moved past the photosensitive drum 61 and the transfer roller 63.
The fixing device 100 is disposed rearward of the process cartridge 5. The toner image that has been transferred onto the sheet P is thermally fixed to the sheet P when the sheet P is moved past the fixing device 100. The sheet P is then discharged on to a discharge tray 22 by conveyer rollers 24.
As shown in
The heat unit 200 includes a fixing belt 110, a halogen lamp 120, a nip plate 130, a reflection plate 140, and a stay 160 those provided in an internal space of the fixing belt 110.
The fixing belt 110 is a tubular film member extending in leftward/rightward direction, and providing heat resistivity and flexibility. The fixing belt 110 has a left end portion and a right end portion each being guided by each guide member 170 (
The halogen lamp 120 is disposed in the internal space of the fixing belt 110 and is spaced apart at a prescribed distance from inner surfaces of the fixing belt 110 and the nip plate 130. The halogen lamp 120 is a heater configured to heat the nip plate 130 and the fixing belt 110 to heat toner carried on the sheet P.
The nip plate 130 is a plate-like member and is configured to receive radiant heat from the halogen lamp 120. The nip plate 130 is disposed in the internal space of the fixing belt 110, and has a surface in relative sliding contact with an inner circumferential surface of the fixing belt 110. The nip plate 130 is configured to receive radiant heat from the halogen lamp 120 and to transmit the heat to the toner carried on the sheet P through the fixing belt 110. The nip plate 130 is made from metal such as aluminum having heat conductivity higher than that of the stay 160.
The reflection plate 140 is configured to reflect radiant heat from the halogen lamp 120 toward the nip plate 130. The reflection plate 140 is disposed to cover the halogen lamp 120 and is spaced away from the halogen lamp 120 by a predetermined distance.
The reflection plate 140 is provided by a metal plate such as an aluminum plate having a high reflection ratio with respect to infrared ray and far infrared ray. The reflection plate 140 is shaped into U-shape in cross-section by bending the metal plate. More specifically, the reflection plate 140 is constituted by a reflection portion 141 having generally U shape in cross-section, a front flange portion 142a extending frontward from a lower front end portion of the reflection portion 141 and a rear flange portion 142b extending rearward from a lower rear end portion of the reflection portion 141.
The pressure roller 150 is disposed below the heat unit 200. The pressure roller 150 includes a shaft portion 151 extending in leftward/rightward direction, and a roller body 152 disposed over the shaft portion 151 and rotated about an axis of the shaft portion 151 along with the shaft portion 151. The roller body 152 is resiliently deformable. Upon resilient deformation of the roller body 152, the pressure roller 150 nips the fixing belt 110 in cooperation with the nip plate 130 thereby forming a nip region N with respect to the fixing belt 110.
A motor (not shown) is provided in the main housing 2 for rotationally driving the pressure roller 150. Rotation of the pressure roller 150 causes circular movement of the fixing belt 110 through frictional force with the surface of fixing belt 110 or via the sheet P.
Thus, the toner image carried on the sheet P is thermally fixed to the sheet P when the sheet P is conveyed between the pressure roller 150 and the heated fixing belt 110.
The stay 160 is adapted to support a front end portion and a rear end portion of the nip plate 130 via the front and rear flange portions 142a, 142b of the reflection plate 140 to ensure rigidity of the nip plate 130. The stay 160 is U-shaped in conformance with an outer shape of the reflection portion 141 of the reflection plate 140 for covering the reflection plate 140. The stay 160 has a rigidity higher than that of the reflection plate 140. For example, the stay 160 is formed of a metal plate bent into U-shape.
As shown in
The guide member 170 is made from an electrically insulating material such as resin. Further, each one guide member 170 is provided at each end of the fixing belt 110 for regulating position of a lateral end face of the fixing belt 110. More specifically, as shown in
The restricting portion 172 is a rib protruding inward in leftward/rightward direction from the regulation surface 171, and is C-shaped opening downward. The restricting portion 172 is inserted into the fixing belt 110 for restricting radially inward deformation of the fixing belt 110.
The recessed portion 173 is a groove like configuration opening downward and is also open inward in leftward/rightward direction. The lateral end portion of the stay 160 is fitted within the recessed portion 173 while the stay 160 presses against the nip plate 130 and the reflection plate 140. Thus, the stay 160 is supported to the guide member 170.
The frame 180 is made from resin and has side walls 181.
Each side wall 181 has a side surface 181A extending in a direction perpendicular to an axial direction of the pressure roller 150, i.e., leftward/rightward direction. The side surface 181A faces outward in the leftward/rightward direction. The side wall 181 is formed with a support groove 182 extending in vertical direction for guiding vertical movement of the guide member 170. The guide groove 182 has an upper open end. The side wall 181 is provided with the bearing 190, a coil spring 400 as an example of an urging member, a pivot arm 410 as an example of a second frame, a switching member 500, and a heatsink 300.
The bearing 190 is an antifriction bearing made from metal such as a roller bearing. As shown in
As shown in
More specifically, as shown in
In
The switching member 500 is adapted to release pressure contact between the heat unit 200 and the pressure roller 150 by acting on the pivot arm 410 upon pivotal movement of the switching member 500. More specifically, the switching member 500 includes an operation lever 510, a pivot shaft 520, and a cam portion 530.
The operation lever 510 has one end portion from which the pivot shaft 520 protrudes integrally. The pivot shaft 520 is supported to the side wall 181. Thus, the operation lever 510 is pivotally movable about an axis of the pivot shaft 520.
The cam portion 530 integrally extends radially outwardly from the pivot shaft 520, so that the cam portion 530 is pivotally movable along with the pivotal movement of the operation lever 510. By pivotally moving the operation lever 510 in clockwise direction in
The heatsink 300 is formed of a metal plate such as an aluminum plate. Here, the term aluminum implies pure aluminum as well as an aluminum alloy. The heatsink 300 is fixed to the side wall 181 of the frame 180 so as to be in surface contact with the side surface 181A of the frame 180 and a surface of the bearing 190.
More specifically, as shown in
As shown in
Accordingly, the flat plate portion 310 is in surface contact with the side surface 181A, and the contact portions 330 are in contact with a front end surface, a rear end surface and laterally outer surface of the bearing 190. Here the term “laterally” implies leftward/rightward direction. Further, an end face of the notched portion 320 is in contact with an outer peripheral surface of the bearing 190.
As shown in
More specifically, the heatsink 300 is in surface contact with the side surface 181A at regions upstream and downstream of the shaft portion 151 of the pressure roller 150 in a sheet conveying direction, i.e., at a front region and a rear region of the side surface 181A. Further, the heatsink 300 is in surface contact with the side surface 181A at regions frontward and rearward of the nip region N (
The front end portion of the heatsink 300 is positioned frontward of the pivot shaft 411 of the pivot arm 410. That is, the heatsink 300 is in contact with the side surface 181A at regions frontward and rearward of the pivot shaft 411.
Further, the rear end portion of the heatsink 300 is positioned rearward of a portion where the coil spring 400 acts on the frame 180, i.e., rearward of the spring support 183. In other words, the heatsink 300 is in contact with the side surface 181A at regions frontward and rearward of the spring support 183.
Next, advantages obtained by the above-described fixing device 100 will be described. Temperature of the heat unit 200 is elevated upon start of the image forming operation. In this case, temperature of the pressure roller 150 is also elevated because of heat transfer from the heat unit 200, and the heat from the pressure roller 150 is transmitted to the frame 180 through the bearing 190.
If the heatsink 300 were not provided, a temperature of a portion of the frame 180 positioned adjacent to the bearing 190 becomes higher than a remaining portion of the frame 180, so that steep temperature gradient is generated in the frame 180. In the fixing device 100, are repeated a state where the temperature gradient is generated in the frame 180 due to printing operation and another state where the temperature gradient disappears due to cooling to the frame 180 as a result of termination of printing operation. By such repetition, creep deformation may occur in the frame 180 due to pressure applied from the pressure roller 150 and biasing force from the coil spring 400. More specifically, vertical displacement of the guide member 170 in frontward/rearward direction may be degraded or restrained if a width of the support groove 182 is increased or decreased due to creep deformation of the frame 180.
According to the present embodiment, heat transmitted from the bearing 190 to the pressure roller 150 can be diffused to a wider region of the frame 180 by the heatsink 300. Therefore, temperature gradient generated in the frame 180 can be moderated in comparison with a case where the heatsink 300 is not provided. Further, heat dissipation efficiency of the heatsink 300 is higher than that of the frame 190 because the heatsink 300 is made from metal whereas the frame 190 is made from resin. Accordingly, generation of steep temperature gradient in the frame 180 can be restrained, which can restrain creep deformation of the frame 180.
In the present embodiment, the heatsink 300 is in surface contact with the side surface 181A of the frame 180. Therefore, an enlarged contact area between the frame 180 and the heatsink 300 can be obtained, and heat transmission to a wider region of the frame 180 can be achieved. Further, the heatsink 300 is made from aluminum, whose thermal conductivity is higher than iron which is a construction material of the laser printer 1.
Further, the heatsink 300 is fixed to the side surface 181A of the frame 180, which can reinforce the side wall 181 of the frame 180.
Particularly, in the present embodiment, the heatsink 300 is in surface contact with the front region of the side surface 181A frontward of the pivot shaft 411 of the pivot arm 410, and the rear region of the side surface rearward of the pivot shaft 411 of the pivot arm 410. With this structure, a portion of the frame 180 to which urging force from the pivot arm 410 is applied can be reinforced by the heatsink 300.
Further, the heatsink 300 is in surface contact with the front region of the side surface 181A frontward of the spring support 183 and the rear region of the side surface rearward of the spring support 183. With this structure a portion of the frame 180 to which urging force from the coil spring 400 is applied can be reinforced by the heatsink 300.
Further, the flat plate portion 310 of the heatsink 300 in surface contact with the side surface 181A extends in a direction perpendicular to the axial direction of the pressure roller 150. Because the flat plate portion 310 has high bending rigidity, deformation of the frame 180 can be restrained by the flat plate portion 310 against urging force applied to the frame 180 from the pressure roller 150 through the bearing 190 and from the coil spring 400.
Further, the heatsink 300 is solidly fixed to the frame 180, because the heatsink 300 is fixed to the frame 180 by the male threads S. Thus, heat transfer from the frame 180 to the heatsink 300 and mechanical reinforcement to the frame 180 can be ensured.
Various modifications may be conceivable. In the above-described embodiment, the bearing 190 of the pressure roller 150 is in contact with the heatsink 300. However, the shaft portion 151 of the pressure roller 150 can be in contact with the heatsink 300. For example, a contact portion 330 of the heatsink 300 can be in contact with the shaft portion 151.
In the above-described embodiment, the bearing 190 of the pressure roller 150 is a component different from the heatsink 300. However, as shown in
More specifically, the heatsink 300A is made from metal, and includes the bearing portion 340 which is a sliding bearing having a U-shape cross-section, and the flat plate portion 350 in surface contact with the side surface 181A of the frame 180 and extending outwardly in radial direction of the shaft portion 151. Front and rear end portions of the flat plate portion 350 are fixed to the frame 180 by male threads S to be in surface contact with the side surface 181A.
Because the flat plate portion 350 is integral with the bearing portion 340, the heatsink 300A is in contact with the shaft portion 151, so that the heat of the shaft portion 151 can be effectively transmitted to the heatsink 300A.
Further, as shown in
In the above-described embodiment, the heatsink 300 is in surface contact with the side surface 181A of the frame 180. However, the contacting region is not limited to this embodiment. For example, the heatsink 300 can be in surface contact with at least one of a lower surface, a rear surface, and a front surface of the frame 180 instead of the side surface 181A.
In the above-described embodiment, the heat unit 200 includes the fixing belt 110 and the nip plate 130. However, another structure is available. For example, a heat unit can be provided by a heat roller and a halogen heater provided in an internal space of the heat roller.
While the description has been made in detail with reference to specific embodiment(s) thereof, it would be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the above described embodiment(s).
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-114192 | Jun 2015 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5404214 | Yoshimoto et al. | Apr 1995 | A |
| 5442423 | Edmunds et al. | Aug 1995 | A |
| 20150093159 | Matsuno | Apr 2015 | A1 |
| Number | Date | Country |
|---|---|---|
| H06-202509 | Jul 1994 | JP |
| 2001-290386 | Oct 2001 | JP |
| 2009-237033 | Oct 2009 | JP |
| 2011-059359 | Mar 2011 | JP |
| 2015-068907 | Apr 2015 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20160357132 A1 | Dec 2016 | US |
