JP2014089233A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a uniform temperature distribution in an axial direction of a fixing member or a pressure member by suppressing an increase in temperature of a non-paper-feed part while achieving space saving and cost reduction with a simple configuration.SOLUTION: A fixing device 20 includes a fixing belt 24, and a pressure roller 23 that forms a nip part between the fixing belt 24 and the pressure roller 23, and heatingly fixes a toner image T on a recording medium P. The fixing member 20 further has: pressure application/release means 30 (such as a pressure application/release cam 34) for bringing the pressure roller 23 into a pressure application state or a pressure release state relative to the fixing belt 24; a heat pipe roller 25 that comes into contact with at least one of the fixing belt 24 and pressure roller 23 to make a temperature in an axial direction uniform; and temperature uniformization member contact/separation means (such as a temperature uniformization cam 28) for bringing the heat pipe roller 25 into a contact state or a separation state relative to the fixing belt 24 or the pressure roller 23. The temperature uniformization member contact/separation means is controlled to be driven by the same driving means as that of the pressure application/release means.

Description

  The present invention relates to a fixing device and an image forming apparatus. More specifically, the present invention relates to a fixing device mounted on an electrophotographic image forming apparatus such as a copying machine, a facsimile, or a printer.

  Various image forming apparatuses using an electrophotographic system have been devised as image forming apparatuses such as copying machines, facsimiles, and printers, and are well-known techniques. In the image forming process, for example, an electrostatic latent image is formed on the surface of a photosensitive drum as an image carrier, and the electrostatic latent image on the photosensitive drum is developed with a toner or the like as a developer to be visualized. The developed image is transferred to a recording medium (also referred to as paper, recording paper, or recording material) by a transfer device to carry the image, and a toner image on the recording paper is transferred by a fixing device (thermal fixing device) that uses pressure, heat, or the like. It is established by the process of establishment.

  In recent years, image forming apparatuses are required to save energy, increase speed, and increase image quality. In order to achieve these required performances, it is important to improve the thermal efficiency of the fixing device used in the image forming apparatus and to finely control the heat of various members such as rollers and belts provided in the fixing device.

  As a fixing device provided in an image forming apparatus, a contact heating type fixing device such as a heat roller method, a film heating method, and an electromagnetic induction heating method is widely known.

  For example, a heat roller type fixing device has a rotation roller pair consisting of a fixing roller that has a heat source such as a halogen lamp inside and is adjusted to a predetermined temperature, and a pressure roller that is in pressure contact with the fixing roller. Yes. A recording material is introduced and conveyed to a fixing nip portion that is a contact portion of these rotating roller pairs, and an unfixed toner image is melted and fixed by heat and pressure from the fixing roller and the pressure roller.

  In addition, the fixing device of the film heating method is such that a recording material is brought into close contact with a heating body fixedly supported by a supporting member through a thin fixing film having heat resistance, and the fixing film is slid with respect to the heating body. The heat of the heating body is supplied to the recording material through the film material (for example, Patent Documents 1 and 2).

  In this film heating type fixing device, for example, a ceramic heater having a resistance layer on a ceramic substrate such as alumina or aluminum nitride having characteristics such as heat resistance, insulation, and good thermal conductivity is used as a heating element. . Since this fixing device can use a thin film having a low heat capacity as the fixing film, it has high heat transfer efficiency, shortens the warm-up time, and enables quick start and energy saving.

  As an electromagnetic induction heating type fixing device, an induction overheating fixing device is also known in which an eddy current is induced in a metal layer (heat generation layer) of a fixing sleeve by magnetic flux and heat is generated by the Joule heat. This fixing device can generate heat directly from the fixing film by utilizing the generation of induced current, and achieves a highly efficient fixing process.

  Further, as an electromagnetic induction heating type fixing device, a fixing sleeve having a release layer, an elastic layer, a metal layer (heat generation layer), an elastic layer included in the fixing sleeve, and a support (core metal) There is known a configuration in which a pressure nip portion is formed by having a roller and mutually pressing the fixing roller and the pressure roller through a fixing sleeve.

  Further, a fixing device is known in which a fixing sleeve is disposed on the outer periphery of a fixing member that is fixedly supported, and the recording material is conveyed by sliding on the outer periphery of the fixing member as the pressure roller rotates. The fixing sleeve is heated by induction heating or other heating method from inside or outside the fixing member.

  By the way, in order to finely control the temperature of the pressure member composed of a pressure roller, a pressure belt, and the like in accordance with the above-described demand for high image quality in the image forming apparatus, a fixing roller, a fixing belt, There has also been proposed a fixing device having a pressing / depressurizing unit that completely separates from a fixing member such as a fixing sleeve.

  Conventionally, as a pressurizing / depressurizing means, a lever (pressure lever) operated by a cam mechanism is hung on a bearing of a pressure member (pressure roller) to press the pressure member against the fixing member. Yes. At this time, the pressure lever operated by the cam mechanism applies a load by a spring with the cam follower as a fulcrum, or a separate lever also applies a load by the spring using the pressure lever operated by the cam mechanism as a base. Mechanisms are known.

  It is also known that in a fixing device, a small amount of toner and paper powder gradually accumulate on a fixing member or a pressure member, and develop into sticking as a lump. Accordingly, a fixing device having a cleaning member for cleaning the fixing member and / or the pressure member is also known (for example, Patent Document 3). Thereby, the durability of the fixing device can be improved.

  However, if the cleaning unit is always in contact with the fixing member or the pressure member, there is a problem that the fixing member or the pressure member is deteriorated and the life of the member of the cleaning unit is shortened. For this reason, it is conceivable that the cleaning means is provided with a contact / separation mechanism for contacting and separating as necessary.

  Further, in order to achieve energy saving and speeding up of the image forming apparatus, the fixing member and the pressure member have been reduced in heat capacity. In the fixing member and pressure member having a reduced heat capacity, the axial direction (longitudinal direction, Since the heat conduction in the sheet passing width direction does not proceed, the temperature rise at the non-sheet passing portion on the axial end side outside the sheet passing region becomes a problem.

  Various means for preventing the temperature rise of the non-sheet passing portion have been devised. For example, it is considered that the heat pipe roller is brought into contact with the fixing member or the pressure member to assist the heat transfer in the axial direction. A heat pipe roller is used as a temperature uniformizing member in the axial direction.

  For example, Patent Document 4 includes a contact / separation mechanism that contacts and separates a roller (second roller) formed of a heat pipe from a belt, and the heat pipe is applied to a fixing member or a pressure member as necessary. A fixing device for making contact and separation is disclosed.

  However, in order to realize a means for bringing the temperature equalizing member into contact with or separating from the fixing member or the pressure member, the driving means and the drive transmission mechanism take up space for the fixing device, which is costly. .

  In addition to the means for contacting and separating the temperature equalizing member, it is desirable to provide other means such as a means for pressurizing / depressurizing the pressure member toward the fixing member, or a cleaning means. There arises a problem that the space for the fixing device is taken up by the driving means and the drive transmission mechanism, respectively, and the cost is increased.

  Therefore, the present invention saves space with a simple configuration by driving the means for contacting and separating the temperature equalizing member from the fixing member or the pressure member and the other means by the same driving means. It is an object of the present invention to provide a fixing device capable of achieving a uniform temperature distribution in the axial direction of a fixing member or a pressure member by suppressing a temperature increase in a non-sheet passing portion while reducing costs.

  In order to achieve such an object, a fixing device according to the present invention includes a fixing member, a pressure member that is disposed so as to be able to press at least a part of the fixing member, and that forms a nip portion between the fixing member, A fixing device that heats a toner image on a recording medium and fixes the toner image on the recording medium at the nip portion, wherein the pressure member is pressed against the fixing member or is depressurized. Pressurizing / depressurizing means to be in a state; a temperature equalizing member that is in contact with at least one of the fixing member or the pressing member and uniformizes the temperature in the axial direction of the fixing member or the pressing member; Temperature uniformizing member contacting / separating means for bringing the temperature uniformizing member into contact with or separated from the fixing member or the pressure member, and the temperature uniformizing member contacting / separating means includes: Same drive as pressurizing / depressurizing means It is intended to be driven and controlled by stage.

  According to the present invention, the temperature equalizing means and the other means are driven by the same driving means, thereby suppressing the temperature rise of the non-sheet passing portion while saving space and reducing the cost with a simple configuration. Thus, the temperature distribution in the axial direction of the fixing member or the pressure member can be made uniform.

1 is a cross-sectional view illustrating an embodiment of an image forming apparatus. FIG. 2 is a side cross-sectional view illustrating a configuration of an embodiment of a fixing device. It is a cam lift diagram which shows the relative motion of the pressurization / decompression cam with respect to a common cam shaft, and a temperature equalization cam. FIG. 6 is a side cross-sectional view illustrating a configuration of another embodiment of the fixing device. FIG. 6 shows a cam lift diagram showing relative movement of a cleaning cam and a temperature equalizing cam with respect to a common cam shaft.

  Hereinafter, the configuration according to the present invention will be described in detail based on the embodiment shown in FIGS.

[First Embodiment]
The fixing device according to the present embodiment is arranged so that at least a part of the fixing member (fixing belt 24) and the fixing member can be pressed, and a pressure member (pressure roller) that forms a nip portion with the fixing member. 23), and in the fixing device (fixing device 20) for heating the toner image (toner image T) on the recording medium (recording medium P) and fixing the toner image on the recording medium in the nip portion. Pressurizing / depressurizing means (pressurizing / depressurizing means 30 including the pressurizing / depressurizing cam 34) for bringing the pressure member into a pressurized state or a depressurizing state with respect to the fixing member, and the fixing member or the pressure member A temperature uniformizing member (heat pipe roller 25) for making the temperature in the axial direction of the fixing member or the pressure member uniform, and the temperature equalizing member to the fixing member or the pressure member , Temperature uniformity to contact or separate Of a member moving means (including temperature leveling cam 28) has, temperature equalizing member moving means is intended to be driven and controlled by pressure and depressurizing means of the same drive means. In addition, the code | symbol in embodiment and the example of application are shown in a parenthesis.

(Image forming device)
FIG. 1 is a schematic configuration diagram illustrating the overall configuration of a tandem type color copier that is an embodiment of an image forming apparatus according to the present invention. The outline and operation of the internal configuration of the image forming apparatus will be described with reference to FIG.

  In FIG. 1, 1 is an image forming apparatus main body, 2 is a writing unit that emits laser light based on input image information, 3 is a document conveying unit that conveys a document D to a document reading unit 4, and 4 is image information of the document D. A document reading unit to be read, 7 is a paper feed unit that accommodates a recording medium P such as transfer paper, 9 is a registration roller that adjusts the conveyance timing of the recording medium P, and 11Y, 11M, 11C, and 11BK are each color (yellow, magenta, Cyan and black) on which the toner image is formed, 12 is a charging unit for charging the photosensitive drums 11Y, 11M, 11C, and 11BK, and 13 is the photosensitive drums 11Y, 11M, 11C, and 11BK. A developing unit 14 for developing the formed electrostatic latent image is a transfer-by unit that transfers the toner images formed on the photosensitive drums 11Y, 11M, 11C, and 11BK in an overlapping manner on the recording medium P. Surora (primary transfer bias roller), 15 denotes the photosensitive drums 11Y, 11M, 11C, a cleaning unit for collecting the untransferred toner on 11BK.

  Reference numeral 16 denotes an intermediate transfer belt cleaning unit that cleans the intermediate transfer belt 17, 17 an intermediate transfer belt on which toner images of a plurality of colors are transferred and superimposed, and 18 a color toner image on the intermediate transfer belt 17 on the recording medium P. A secondary transfer bias roller 20 for transferring the toner image onto the recording medium P indicates a fixing device for fixing the toner image on the recording medium P.

  Hereinafter, an operation during normal color image formation in the image forming apparatus will be described. First, the document D is transported from the document table in the direction of the arrow in the drawing by the transport rollers of the document transport unit 3 and placed on the contact glass 5 of the document reading unit 4. Then, the document reading unit 4 optically reads the image information of the document D placed on the contact glass 5. Specifically, the document reading unit 4 scans the image of the document D on the contact glass 5 while irradiating light emitted from an illumination lamp. Then, the light reflected by the document D is imaged on the color sensor via the mirror group and the lens. The color image information of the document D is read for each RGB (red, green, blue) color separation light by the color sensor, and then converted into an electrical image signal. Further, color conversion processing, color correction processing, spatial frequency correction processing, and the like are performed by the image processing unit based on the RGB color separation image signals to obtain yellow, magenta, cyan, and black color image information.

  Then, the image information of each color of yellow, magenta, cyan, and black is transmitted to the writing unit 2. The writing unit 2 emits laser light (exposure light) based on the image information of each color toward the corresponding photosensitive drums 11Y, 11M, 11C, and 11BK.

  On the other hand, the four photosensitive drums 11Y, 11M, 11C, and 11BK are rotated clockwise in FIG. First, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK are uniformly charged at a portion facing the charging unit 12 (charging process). Thus, a charged potential is formed on the photosensitive drums 11Y, 11M, 11C, and 11BK. Thereafter, the charged surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK reach the irradiation positions of the respective laser beams.

  In the writing unit 2, laser light corresponding to the image signal is emitted from the four light sources corresponding to each color. Each laser beam passes through a different optical path for each color component of yellow, magenta, cyan, and black (exposure process).

  Laser light corresponding to the yellow component is irradiated on the surface of the first photosensitive drum 11Y from the left side of the drawing. At this time, the yellow component laser light is scanned in the rotation axis direction (main scanning direction) of the photosensitive drum 11Y by a polygon mirror that rotates at high speed. Thus, an electrostatic latent image corresponding to the yellow component is formed on the photosensitive drum 11Y charged by the charging unit 12.

  Similarly, the laser beam corresponding to the magenta component is irradiated onto the surface of the second photosensitive drum 11M from the left side of the paper, and an electrostatic latent image corresponding to the magenta component is formed. The cyan component laser light is applied to the surface of the third photosensitive drum 11C from the left side of the paper, and an electrostatic latent image of the cyan component is formed. The black component laser beam is applied to the surface of the fourth photosensitive drum 11BK from the left side of the paper, and an electrostatic latent image of the black component is formed.

  Thereafter, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK on which the electrostatic latent images of the respective colors are formed reach the positions facing the developing unit 13, respectively. Then, the respective color toners are supplied from the developing units 13 onto the photosensitive drums 11Y, 11M, 11C, and 11BK, and the latent images on the photosensitive drums 11Y, 11M, 11C, and 11BK are developed (developing step).

  Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK after the development process reach the opposed portions to the intermediate transfer belt 17, respectively. Here, a transfer bias roller 14 is installed at each facing portion so as to contact the inner peripheral surface of the intermediate transfer belt 17. Then, the toner images of the respective colors formed on the photosensitive drums 11Y, 11M, 11C, and 11BK are sequentially superimposed and transferred onto the intermediate transfer belt 17 at the position of the transfer bias roller 14 (primary transfer process). .

  Then, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK after the transfer process reach positions facing the cleaning unit 15, respectively. Then, the untransferred toner remaining on the photosensitive drums 11Y, 11M, 11C, and 11BK is collected by the cleaning unit 15 (cleaning process).

  Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK pass through a static elimination unit (not shown), and a series of image forming processes on the photoconductive drums 11Y, 11M, 11C, and 11BK is completed.

  On the other hand, the intermediate transfer belt 17 on which the toners of the respective colors on the photoconductive drums 11Y, 11M, 11C, and 11BK are transferred (carried) are run in the clockwise direction in the drawing and are connected to the secondary transfer bias roller 18. Reach the opposite position. The color toner image carried on the intermediate transfer belt 17 is transferred onto the recording medium P at a position facing the secondary transfer bias roller 18 (secondary transfer step).

  Thereafter, the surface of the intermediate transfer belt 17 reaches the position of the intermediate transfer belt cleaning unit 16. Then, the untransferred toner adhered on the intermediate transfer belt 17 is collected by the intermediate transfer belt cleaning unit 16, and a series of transfer processes in the intermediate transfer belt 17 is completed.

  Here, the recording medium P conveyed between the intermediate transfer belt 17 and the secondary transfer bias roller 18 (secondary transfer nip) is conveyed from the paper supply unit 7 via the registration roller 9 and the like. is there.

  Specifically, the recording medium P fed by the paper feeding roller 8 from the paper feeding unit 7 that stores the recording medium P is guided to the registration roller 9 after passing through the conveyance guide. The recording medium P that has reached the registration roller 9 is conveyed toward the secondary transfer nip at the same timing.

  Then, the recording medium P on which the full-color image is transferred is guided to the fixing device 20 by the transport belt. In the fixing device 20, the color image (toner) is fixed on the recording medium P at the nip between the fixing roller and the fixing belt and the pressure roller.

  Then, the recording medium P after the fixing process is discharged as an output image outside the main body of the image forming apparatus 1 by a paper discharge roller, and a series of image forming processes is completed.

(Fixing device)
Next, the configuration and control of the fixing device 20 included in the image forming apparatus 1 will be described. FIG. 2 shows an example of the fixing device 20 and is a schematic sectional view in the axial direction of the fixing roller 22.

  As shown in FIG. 2, the fixing device 20 according to the present embodiment has a heating roller 21 heated by a heat source (not shown) such as induction heating means and a halogen heater, and an elastic layer on the outer periphery of the metal core. A fixing roller 22, a heating belt 21, a fixing belt 24 stretched around the fixing roller 22, and a pressure roller 23 disposed on the outer peripheral side of the fixing belt 24 and forming a nip portion with the fixing roller 22. It is equipped with.

  The fixing device 20 includes a recording medium P (paper) that carries a toner image (unfixed toner image) T at a nip portion between the fixing belt 24 and the pressure roller 23 formed by pressure contact between the fixing roller 22 and the pressure roller 23. ) Through the paper and heat fixing. The recording medium P is guided to the nip portion by an entrance guide plate 26 provided in the transport path.

  Further, the fixing device 20 includes a temperature equalizing member that prevents a temperature rise in a non-sheet passing portion on the axial end side outside the sheet passing region. In the present embodiment, the heat pipe roller 25 is provided as a temperature equalizing member, and the heat pipe roller 25 provided on the outer peripheral side of the pressure roller 23 is in contact with and separated from the pressure roller 23. It is provided to be switchable.

  The contact / separation of the heat pipe roller 25 is controlled by driving the temperature equalizing cam 34 and the temperature equalizing link mechanism 27. The temperature equalizing cam 34 and the temperature equalizing link mechanism 27 function as temperature equalizing member contacting / separating means.

  In this embodiment, the heat pipe roller 25 is used as the temperature equalizing member, but the temperature equalizing member is not limited to this. Further, although the temperature equalizing member is provided on the pressure roller 23 side, it may be provided on the fixing belt 24 side or on both the pressure roller 23 side and the fixing belt 24 side.

  The heating roller 21, the fixing roller 22, and the pressure roller 23 are rotatably supported in a longitudinal direction (depth / front direction in the drawing) of a housing (not shown) of the fixing device 20, and driving means for each roller (not shown). Etc. are fixedly held in the housing.

  The heating roller 21 has, for example, an axial length of 320 mm and an outer diameter of 40 mm, and includes a conductive heat generating layer, an elastic layer, and a cored bar layer, which are heat generating member bodies, in this order.

  The fixing belt 24 is wound around the fixing roller 22 and the heating roller 21, and is in close contact with the heating roller 21 and the fixing roller 22. A nip portion is configured by pressing the pressure roller 23 against the fixing belt 24 configured as described above at a position corresponding to the fixing roller 22.

  Further, the fixing belt 24 is composed of, for example, a PI belt which is an endless film of a heat-resistant resin having a thickness of 90 μm, and the surface layer has an anti-offset agent such as PFA (tetrafluoroethylene barfluoroalkyl vinyl ether copolymer resin). Is coated.

  The fixing roller 22 does not have a heat source, and a highly rigid core material (core metal) such as metal (iron or aluminum) is covered with a thick elastic layer such as silicon rubber.

  The fixing roller 22 and the pressure roller 23 are rubber rollers arranged to face each other. When the pressure roller 23 is pressed toward the center of the fixing roller 22 via the fixing belt 24, the pressure roller 23. And a fixing belt 24 form a nip portion.

  Further, the driving unit drives the fixing roller 22 to rotate in the clockwise direction. As the fixing roller 22 rotates, the pressure roller 23 and the fixing belt 24 that are in pressure contact with the fixing roller 22 rotate at the same speed.

  The heating roller 21 is heated by the heat source, and the recording medium P is conveyed while the toner image T is heated and melted at the nip portion by the reverse rotation of the pressure roller 23 and the fixing belt 24.

  Further, the heating roller 21 is controlled based on a temperature signal from a temperature detecting means (not shown) such as a thermistor so as to maintain a fixing possible temperature at which the fixing belt 24 can be fixed favorably.

  According to the fixing device 20 having this configuration, the recording medium P on which the toner image T is formed is conveyed from the inlet guide plate 26 disposed on the upstream side of the fixing belt 24 in the sheet conveying direction, and the toner image on the recording medium P is recorded. The toner image T is fixed by heating and melting T at the nip portion. Thereafter, the recording medium P is separated by a separation plate (not shown) or the like, and is discharged from the paper discharge unit on the downstream side in the paper transport direction.

  The fixing device 20 according to the present embodiment includes a pressurizing / depressurizing unit 30 that is a mechanism for controlling a pressurizing state in which the pressure roller 23 is pressed toward the fixing roller 22 and a non-pressurizing depressurizing state. ing. A known configuration can be used as the pressurizing / depressurizing means 30. In this embodiment, a pressure lever (spring) 31, a pressure spring 32, a pressure lever (cam) 33, and a pressure / decompression cam 34 are provided.

  Here, the camshaft 35 that is the rotation shaft of the pressurizing / decompressing cam 34 is rotationally driven by an actuator (not shown) such as a stepping motor to rotationally drive the pressurizing / decompressing cam 34. The pressure lever 33 and the pressure lever 31 are operated by the rotation of the pressure / decompression cam 34 to realize the pressure / decompression operation of the pressure roller 23. The pressurizing / depressurizing means 30 may be any mechanism that can pressurize and depressurize the pressure roller 23 toward the fixing roller 22, and is not limited to the example shown in FIG.

  The camshaft 35 is also a common camshaft that is also the rotation shaft of the temperature equalizing cam 28, and the temperature equalizing cam 28 is also rotationally driven by the rotational drive of the camshaft (hereinafter referred to as “common camshaft”) 35.

  By operating the temperature equalizing link mechanism 27 by the rotational drive of the temperature equalizing cam 28, the heat pipe roller 25 can be brought into contact with and separated from the pressure roller 23.

  FIG. 3 is a cam lift diagram showing the relative movement of the pressurizing / depressurizing cam 34 and the temperature equalizing cam 28 with respect to the common camshaft 35.

  The pressurization / decompression cam 34 has a home position in the vicinity of the bottom dead center (lift amount / small) in the decompression state, and gradually increases the pressurization lift amount along with the rotation operation, in the top dead center (lift amount / large) range. A normal nip (maximum pressure state) capable of passing paper is obtained. At this time, a special mode may be provided in which an arbitrary point in the cam lift is selected and the paper is passed.

  Immediately after the pressurization / decompression cam 34 reaches the top dead center range, the heat pipe roller 25 is in a separated state with respect to the pressurization roller 23, and even if the common cam shaft 35 is rotated, the pressurization / decompression is performed. Since the cam 34 has reached the top dead center, there is no change in the amount of pressurization at the nip portion.

  Here, by further rotating the common cam shaft 35, the temperature equalizing cam 28 operates the temperature equalizing link mechanism 27, and the heat pipe roller 25 comes into contact with the pressure roller 23. It comes to show.

  Thus, in the top dead center range of the pressure / decompression cam 34, both the range in which the lift amount of the temperature equalizing cam 28 abuts the heat pipe roller 25 on the pressure roller 23 and the range in which the heat pipe roller 25 abuts are included. It seems to be.

  The cams of both the pressurizing / decompressing cam 34 and the temperature equalizing cam 28 are in the relationship of the cam lift amount as shown in FIG. It is possible to control the contact and separation states of the heat pipe roller 25 in the depressurization operation and the normal nip state (pressure state of the pressure roller 23).

  When the heat pipe roller 25 is provided on both the pressure roller 23 side and the fixing belt 24 side, a temperature equalizing cam and a temperature equalizing link mechanism are provided for each, and the two temperature equalizing cams are shown in FIG. The cam lift amount of the temperature equalizing cam 28 shown in FIG.

  As described above, according to the fixing device according to the present embodiment, while using a mechanism for pressing and depressurizing the pressure member toward the fixing member, it is possible to save space more easily and at low cost. Further, it is possible to achieve uniform axial temperature distribution by the axial temperature uniformizing member of the fixing member and / or the pressure member. Further, since the temperature equalizing member can be separated, the energy saving performance can be maintained.

  Here, the temperature equalizing member is useful only when the temperature of the non-sheet passing portion is increased. Since the temperature rise in the non-sheet passing portion occurs when the pressure roller 23 is pressurized and the sheet is passing, it is desirable that the temperature equalizing member is in contact with the pressure roller 23 in the pressurized state. According to the fixing device according to the present embodiment, it is possible to achieve contact and separation of the temperature equalizing member in the normal nip state (pressure state of the pressure roller 23).

  Further, by using a heat pipe as the temperature uniformizing member, it is possible to efficiently achieve uniform temperature in the axial direction.

[Second Embodiment]
Hereinafter, other embodiments of the image forming apparatus according to the present invention will be described. In addition, the description about the same point as the said embodiment is abbreviate | omitted.

  FIG. 4 is a schematic sectional view in the axial direction of the fixing roller 22, showing another example of the fixing device 20. The fixing device 20 according to the present embodiment does not include the pressurizing / depressurizing unit 30 and includes a cleaning unit 40 including a cleaning cam (cleaning mechanism contacting / separating cam) 41 and a cleaning member 42.

  A known structure can be used as the cleaning member 42 for cleaning the surface of the abutting member. In this embodiment, the cleaning member is provided on the pressure roller 23 side, but may be provided on the fixing belt 24 side or on both the pressure roller 23 side and the fixing belt 24 side.

  A camshaft 35 that is a rotating shaft of the cleaning cam 41 is rotationally driven by an actuator (not shown) such as a stepping motor to rotate the cleaning cam 41. The cleaning member 42 is operated by the rotation of the cleaning cam 41 to switch between a state of contact with the pressure roller 23 (during cleaning) and a state of separation (during non-cleaning). That is, the cleaning cam 41 functions as a cleaning member contacting / separating means.

  The camshaft 35 is also a common camshaft that is also the rotation shaft of the temperature equalizing cam 28, and the temperature equalizing cam 28 is also rotationally driven by the rotational drive of the camshaft (hereinafter referred to as “common camshaft”) 35.

  By operating the temperature equalizing link mechanism 27 by the rotational drive of the temperature equalizing cam 28, the heat pipe roller 25 can be brought into contact with and separated from the pressure roller 23.

  FIG. 5 is a cam lift diagram showing the relative movement of the cleaning cam 41 and the temperature equalizing cam 28 with respect to the common cam shaft 35.

  The cleaning cam 41 uses the vicinity of the bottom dead center where the cleaning member 42 is separated from the pressure roller 23 as a home position, and gradually increases the contact / separation lift amount along with the rotation operation, and matches the pressure amount of the pressure roller 23. Stopping at the position results in a contactable state (cleaning cam 41 top dead center).

  Further, the bottom dead center range of the cleaning cam 41 includes both a range in which the lift amount of the temperature equalizing cam 28 is in contact with the pressure roller 23 and a range in which the heat pipe roller 25 is in contact with the pressure roller 23 and can be selected and controlled. It has become.

  As described above, in the range of the bottom dead center of the cleaning cam 41 in which the cleaning member 42 is in the separated state, when the temperature equalizing cam 28 is at the top dead center, the temperature equalizing link mechanism 27 operates and the heat pipe roller 25 is added. By abutting against the pressure roller 23, the effect of uniforming the temperature is exhibited. In the range of the bottom dead center of the cleaning cam 41, when the temperature equalizing cam 28 is also at the bottom dead center, the heat pipe roller 25 is also separated from the pressure roller 23.

  By making the cams of both the cleaning cam 41 and the temperature equalizing cam 28 have a cam lift amount relationship as shown in FIG. 5 and controlling the rotation angle of the common cam shaft 35, the contact and separation operations of the cleaning member 42, In the separated state of the cleaning member 42, the contact and separated state of the heat pipe roller 25 can be controlled.

  When the cleaning member 42 is provided on both the pressure roller 23 side and the fixing belt 24 side, a cleaning cam (cleaning member contacting / separating means) is provided for each, and the two cleaning cams are shown in FIG. What is necessary is just to make it equal to the cam lift amount of the cam 41.

  According to the fixing device according to the present exemplary embodiment, the fixing member is fixed in a simpler and lower cost space while using a mechanism for bringing the cleaning member into contact with and / or away from the fixing member and / or the pressure member. Uniform temperature distribution in the axial direction can be achieved by the temperature uniformizing member in the axial direction of the member and / or the pressure member. Further, since the temperature equalizing member can be separated, the energy saving performance can be maintained.

  Here, when the cleaning member is configured to be capable of contacting and separating, the cleaning operation is not always necessary, and is an operation that is not prioritized when the temperature rise of the non-sheet passing portion exceeds the allowable range. Therefore, in the present embodiment, it is possible to perform a selective operation in which the cleaning operation and the temperature equalizing operation in the axial direction do not function simultaneously.

  By adopting the image forming apparatus (FIG. 1) including the fixing device 20 having the above-described configuration, the fixing can be performed while suppressing the increase in the temperature of the non-sheet passing portion while saving space and reducing the cost with a simple configuration. It is possible to provide an image forming apparatus including a fixing device that can achieve uniform temperature distribution in the axial direction of the member and / or the pressure member.

  The above-described embodiment is a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention. In the above embodiment, the belt fixing type fixing device in which the fixing belt stretched between the fixing roller and the heating roller forms a nip portion between the pressure roller and the fixing roller is described as an example. The present invention can also be applied to a roller fixing type fixing device in which a nip portion is formed between the roller and the pressure roller.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Writing part 3 Original conveyance part 4 Original reading part 5 Contact glass 7 Paper feed part 8 Paper feed roller 9 Registration roller 11Y, 11M, 11C, 11BK Photosensitive drum 12 Charging part 13 Developing part 14 Transfer bias roller ( Primary transfer bias roller)
15 Cleaning unit 16 Intermediate transfer belt cleaning unit 17 Intermediate transfer belt 18 Secondary transfer bias roller 20 Fixing device 21 Heating roller 22 Fixing roller 23 Pressing roller 24 Fixing belt 25 Heat pipe roller (temperature equalizing member)
26 Entrance guide plate 27 Temperature equalization link mechanism 28 Temperature equalization cam 30 Pressure / decompression means 31 Pressure lever 32 Pressure spring 33 Pressure lever 34 Pressure / decompression cam 35 Camshaft (common camshaft)
40 Cleaning means 41 Cleaning cam 42 Cleaning member D Document P Recording medium T Toner image

JP-A-63-313182 Japanese Patent Laid-Open No. 1-263679 JP-A-10-312130 JP 2005-181474 A

Claims (8)

A fixing member;
A pressure member that is arranged to be able to press at least a part of the fixing member and that forms a nip portion with the fixing member,
In the fixing device for heating the toner image on the recording medium and fixing the toner image on the recording medium in the nip portion,
Pressurizing / depressurizing means for bringing the pressurizing member into a pressurized state or a depressurizing state with respect to the fixing member;
A temperature uniformizing member that abuts on at least one of the fixing member or the pressure member and uniformizes the temperature in the axial direction of the fixing member or the pressure member;
Temperature uniformizing member contacting / separating means for bringing the temperature uniformizing member into contact with or separated from the fixing member or the pressure member;
The fixing device characterized in that the temperature equalizing member contacting / separating means is driven and controlled by the same driving means as the pressurizing / depressurizing means. A fixing member;
A pressure member that is arranged to be able to press at least a part of the fixing member and that forms a nip portion with the fixing member,
In the fixing device for heating the toner image on the recording medium and fixing the toner image on the recording medium in the nip portion,
A cleaning member that contacts at least one of the fixing member or the pressure member to clean the surface;
Cleaning member contacting / separating means for bringing the cleaning member into contact with or separated from the fixing member or the pressure member;
A temperature uniformizing member that abuts on at least one of the fixing member or the pressure member and uniformizes the temperature in the axial direction of the fixing member or the pressure member;
Temperature uniformizing member contacting / separating means for bringing the temperature uniformizing member into contact with or separated from the fixing member or the pressure member;
The fixing device characterized in that the temperature equalizing member contacting / separating means is driven and controlled by the same driving means as the cleaning member contacting / separating means. The temperature equalizing member contacting / separating means and the pressurizing / depressurizing means each have a cam,
The fixing device according to claim 1, wherein each cam has a common rotation shaft and is driven to rotate by one drive unit. When the pressurizing member is in a pressurized state with respect to the fixing member by the pressurizing / depressurizing means,
2. The temperature equalizing member contacting / separating means causes the temperature equalizing member to be in both a contact state and a separated state with respect to the fixing member or the pressure member. The fixing device according to 3. The temperature equalizing member contacting / separating means and the cleaning member contacting / separating means each have a cam,
The fixing device according to claim 2, wherein each cam has a common rotating shaft and is driven to rotate by one driving means. When the cleaning member is separated from the fixing member or the pressure member by the cleaning member contacting / separating means,
3. The temperature equalizing member contacting / separating means causes the temperature equalizing member to be in both a contact state and a separated state with respect to the fixing member or the pressure member. 5. The fixing device according to 5.   The fixing device according to claim 1, wherein the temperature equalizing member is a heat pipe roller.   An image forming apparatus comprising the fixing device according to claim 1.