JP6205764B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device that fixes an image on a recording medium, and an image forming apparatus including the fixing device.

  In image forming apparatuses such as copiers, printers, facsimiles, or multi-function machines having these functions, image fixing methods such as electrophotographic recording, electrostatic recording, magnetic recording, etc. are not fixed by image transfer method or direct method. A toner image is formed on a recording medium such as paper. A copy or recorded matter can be obtained by heating and fixing the unfixed toner image transferred and carried on the recording medium. During fixing, the unfixed image is heated while the recording medium carrying the unfixed image is sandwiched and conveyed by the fixing member and the pressure member, so that the toner of the unfixed image is melted and softened and penetrates into the recording medium. As a result, the toner is fixed to the recording medium.

  In recent years, market demands for energy saving and high speed are increasing for image forming apparatuses. Among them, a fixing device for fixing an unfixed toner image consumes a large amount of energy, so that many proposals have been made from the viewpoint of energy saving. As such a fixing device, a heating roller method, a belt method, a film heating method (surf fixing) using a ceramic heater, a contact heating method fixing device such as an electromagnetic induction heating method, etc. are widely adopted.

  In the belt-type fixing device, in recent years, further reduction in warm-up time and first print time has been desired (Problem 1). The warm-up time is the time required from a normal temperature state to a predetermined printable temperature (reload temperature), such as when the power is turned on, and the first print time is the print operation after receiving a print request and preparing for printing. This is the time until the paper discharge is completed. Further, as the speed of the image forming apparatus increases, the number of sheets to be passed per unit time increases and the required heat amount increases, so that there is a problem that the heat amount is insufficient at the beginning of continuous printing (so-called temperature drop). (Problem 2).

  As a method for solving the problem of problem 1, surf fixing using a very thin film as a fixing member has been proposed. Compared to the belt method, this method can be reduced in heat capacity and reduced in size, but it is difficult to endure, and since only the nip part is heated locally, other parts are not heated, and the nip part is not heated. There is a problem that the belt is in the coldest state at the entrance, and fixing failure tends to occur. In particular, in a high-speed machine, there is a problem that fixing failure is more likely to occur because the belt rotates fast and the heat radiation of the belt outside the nip increases (problem 3).

  In order to solve the above problems 1 to 3, the present applicant has made a proposal in Patent Document 1. This makes it possible to heat the entire belt in a configuration that uses an endless belt, shortens the first print time from the standby time of heating, and eliminates the lack of heat during high-speed rotation, resulting in high production. Even if it is mounted on a compatible image forming apparatus, good fixability is obtained.

  FIG. 9 schematically shows the fixing device proposed in Patent Document 1. A pipe-shaped metal heat conductor 22 is fixed inside the endless fixing belt 21 so as to be able to guide the movement of the fixing belt 21, and metal heat is generated by a halogen heater 23 in the metal heat conductor 22. The fixing belt 21 is heated via the conductor 22. Further, a pressure roller 24 that forms a nip portion N in contact with the metal heat conductor 22 via the fixing belt 21 is provided, and the fixing belt 21 is moved in the circumferential direction as the pressure roller 24 rotates. Let With such a configuration, the entire endless belt constituting the fixing device can be warmed, the first print time from the heating standby time can be shortened, and the shortage of heat at the time of high-speed rotation can be solved.

  However, in order to further save energy and improve the first print time, it is necessary to further improve the thermal efficiency, and the applicant further describes a configuration in which an endless belt is directly heated without using a metal heat conductor, for example, in Patent Document 2 Proposed. In this configuration, it is possible to reduce the power consumption by greatly improving the heat transfer efficiency and to further shorten the first print time from the heating standby time. In addition, the cost can be reduced without using a metal heat conductor.

  However, when the endless belt, which is a fixing member, is heated directly from the inside, the radiant heat from the heat source also heats the components inside the endless belt. There is a risk of malfunction. The applicant of the present application devised a configuration in which a fixed nip forming member is used to abut the flexible endless belt against the pressure rotating body, and the nip forming member is supported inside the endless belt using a support member. However, the fixed nip forming member rubs against the endless belt. Therefore, a heat resistant resin having a relatively low frictional resistance is used as the base material of the nip forming member, or a rubbing sheet made of PFA is wound around the base material, and further, a lubricant made of silicone oil or fluorine grease is impregnated. However, due to the radiant heat from the heat source, there is a problem of failure due to thermal deformation of the base material or the rubbing sheet or volatilization of the lubricant or deterioration of durability.

  An object of the present invention is to avoid strength reduction and thermal deformation due to heating of a nip forming member and its supporting member in addition to a heat source on the inner peripheral side of the fixing belt.

The above-mentioned problem is that an endless belt, a pressure rotator that abuts on the outer peripheral surface of the belt, and a fixing nip portion that is disposed inside the belt and that forms the fixing nip portion via the belt. In a fixing device including a nip forming member, a support member disposed inside the belt and supporting the nip forming member, and a heat source disposed inside the belt, the fixing device is equal to or more than the support member. The heat transfer member having high thermal conductivity is disposed between the support member and the nip forming member, is attached to the support member, and is connected to the frame of the apparatus main body.

  According to the present invention, the heat transfer member having high heat conductivity is attached to the support member that is disposed inside the fixing belt and supports the nip formation member, and this is connected to the frame of the apparatus main body. Further, the heat applied to the support member is released to the frame of the apparatus main body through the heat transfer member, and is radiated to avoid overheating of the nip forming member and the support member.

1 is a front view showing an entire image forming apparatus. 1 is a cross-sectional view of a fixing device according to an embodiment of the present invention. It is a figure which shows the attachment state in the both ends of the heat transfer member which is the characteristic structure of this invention. FIG. 6 is a cross-sectional view of a fixing device according to another embodiment. FIG. 6 is a cross-sectional view of a fixing device according to another embodiment. It is sectional drawing of the fixing device which concerns on another embodiment provided with the light-shielding member. It is an expanded view of the light-shielding member which has the light-shielding width match | combined with each paper width. It is a figure explaining the operation position of the light-shielding member with respect to different paper widths. It is a schematic sectional drawing which shows the basic composition of the fixing device which concerns on a prior art.

  First, the overall configuration and operation of an image forming apparatus equipped with a fixing device according to the present invention will be described with reference to FIG. The image forming apparatus 1 is a tandem color laser printer. As a matter of course, the image forming apparatus according to the present invention is not limited to this method, and includes a copying machine, a facsimile, and the like.

  In FIG. 1, four image forming units 4Y, 4M, 4C, and 4K are provided in the center of the printer main body. Each of the image forming units 4Y, 4M, 4C, and 4K contains developers of different colors of yellow (Y), magenta (M), cyan (C), and black (K) corresponding to the color separation components of the color image. Since the configuration is the same except for the configuration, only the configuration of the black image forming unit 4K will be described. The other image forming units 4Y, 4M, and 4C omit the symbol display.

  The image forming unit 4K includes a drum-shaped photosensitive member 5 as a latent image carrier, a charging device 6 that charges the surface of the photosensitive member 5, a developing device 7 that supplies toner to the surface of the photosensitive member 5, and a photosensitive member. And a cleaning device 8 for cleaning the surface of 5.

  Under the image forming units 4Y, 4M, 4C, and 4K, an exposure device 9 that exposes the surface of the photoreceptor 5 is disposed. The exposure device 9 includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates the surface of each photoconductor 5 with laser light based on image data.

  A transfer device 3 is disposed above the image forming units 4Y, 4M, 4C, and 4K. The transfer device 3 includes an intermediate transfer belt 30 as a transfer body, four primary transfer rollers 31 as primary transfer means, a secondary transfer roller 36 as secondary transfer means, and a secondary transfer backup roller 32. ing. Further, a cleaning backup roller 33, a tension roller 34, and a belt cleaning device 35 are also provided.

  The intermediate transfer belt 30 is an endless belt and is stretched by a secondary transfer backup roller 32, a cleaning backup roller 33, and a tension roller 34. Here, when the secondary transfer backup roller 32 is driven to rotate, the intermediate transfer belt 30 runs (rotates) in the direction indicated by the arrow in the figure.

  Each of the four primary transfer rollers 31 sandwiches the intermediate transfer belt 30 from each photoconductor 5 to form a primary transfer nip. Further, a power source (not shown) is connected to each primary transfer roller 31 so that a predetermined DC voltage (DC) and / or AC voltage (AC) is applied to each primary transfer roller 31. .

  The secondary transfer roller 36 sandwiches the intermediate transfer belt 30 with the secondary transfer backup roller 32 to form a secondary transfer nip. Similarly to the primary transfer roller 31, a power source (not shown) is connected to the secondary transfer roller 36, and a predetermined DC voltage (DC) and / or AC voltage (AC) is applied to the secondary transfer roller 36. It has become so.

  The belt cleaning device 35 includes a cleaning brush and a cleaning blade disposed so as to contact the intermediate transfer belt 30. A waste toner transfer hose (not shown) extending from the belt cleaning device 35 is connected to an entrance of a waste toner container (not shown).

  A bottle container 2 is provided in the upper part of the printer main body, and four toner bottles 2Y, 2M, 2C, and 2K containing replenishing toner are detachably attached to the bottle container 2. A replenishment path (not shown) is provided between each toner bottle 2Y, 2M, 2C, 2K and each developing device 7, and each developing device is connected from each toner bottle 2Y, 2M, 2C, 2K via this replenishment path. 7 is supplied with toner.

  On the other hand, at the bottom of the printer main body, a paper feed tray 10 that stores paper P as a recording medium, a paper feed roller 11 that carries the paper P out of the paper feed tray 10, and the like are provided. Here, the concept of the recording medium includes, in addition to plain paper, thick paper, postcard, envelope, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheet, and the like. Although not shown, a manual paper feed mechanism may be provided.

  In the printer main body, a transport path R is provided for discharging the paper P from the paper feed tray 10 through the secondary transfer nip to the outside of the apparatus. In the transport path R, on the upstream side of the secondary transfer roller 36 in the paper transport direction, a timing adjusting roller 12 called a pair of registration rollers is disposed as a transport means for transporting the paper P to the secondary transfer nip. ing.

  Further, the fixing device 20 is disposed downstream of the secondary transfer roller 36 in the sheet conveyance direction. Further, a pair of paper discharge rollers 13 for discharging the paper to the outside of the apparatus is provided downstream of the fixing device 20 in the paper conveyance direction of the conveyance path R. In addition, a paper discharge tray 14 for stocking paper discharged outside the apparatus is provided on the upper surface of the printer main body.

  Next, the basic operation of the printer according to this example will be described. When the image forming operation is started, each photoconductor 5 in each of the image forming units 4Y, 4M, 4C, and 4K is rotationally driven clockwise by a driving device (not shown), and the surface of each photoconductor 5 is charged by a charging device. 6 is uniformly charged to a predetermined polarity. The surface of each charged photoconductor 5 is irradiated with laser light from the exposure device 9 to form an electrostatic latent image on the surface of each photoconductor 5. At this time, the image information to be exposed on each photoconductor 5 is single-color image information obtained by separating a desired full-color image into color information of yellow, magenta, cyan, and black. In this way, toner is supplied to each electrostatic latent image formed on each photoconductor 5 by each developing device 7, whereby the electrostatic latent image is visualized (visualized) as a toner image. .

  When the image forming operation is started, the secondary transfer backup roller 32 is driven to rotate counterclockwise in the figure, and the intermediate transfer belt 30 is caused to run in the direction indicated by the arrow in the figure. Then, a constant voltage or a constant current controlled voltage having a polarity opposite to the charging polarity of the toner is applied to each primary transfer roller 31. As a result, a transfer electric field is formed in the primary transfer nip between each primary transfer roller 31 and each photoconductor 5.

  Thereafter, when each color toner image on the photoconductor 5 reaches the primary transfer nip as each photoconductor 5 rotates, the toner image on each photoconductor 5 is generated by the transfer electric field formed in the primary transfer nip. Are successively superimposed and transferred onto the intermediate transfer belt 30. Thus, a full color toner image is carried on the surface of the intermediate transfer belt 30. The toner on each photoconductor 5 that has not been transferred to the intermediate transfer belt 30 is removed by the cleaning device 8. Thereafter, the surface of each photoconductor 5 is neutralized by a neutralizing device (not shown), and the surface potential is initialized.

  In the lower part of the image forming apparatus, the paper feed roller 11 starts to rotate, and the paper P is sent out from the paper feed tray 10 to the transport path R. The sheet P sent to the transport path R is timed by the registration roller 12 and sent to the secondary transfer nip between the secondary transfer roller 36 and the secondary transfer backup roller 32. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the intermediate transfer belt 30 is applied to the secondary transfer roller 36, thereby forming a transfer electric field in the secondary transfer nip. .

  Thereafter, when the toner image on the intermediate transfer belt 30 reaches the secondary transfer nip as the intermediate transfer belt 30 rotates, the transfer electric field formed in the secondary transfer nip causes the toner image on the intermediate transfer belt 30 to move. The toner images are transferred onto the paper P all at once. At this time, the residual toner on the intermediate transfer belt 30 that has not been transferred to the paper P is removed by the belt cleaning device 35, and the removed toner is conveyed to a waste toner container (not shown) and collected.

  Thereafter, the paper P is conveyed to the fixing device 20, and the toner image on the paper P is fixed to the paper P by the fixing device 20. Then, the paper P is discharged out of the apparatus by the paper discharge roller 13 and stocked on the paper discharge tray 14.

  The above description is an image forming operation when a full-color image is formed on a sheet. A single color image can be formed using any one of the four image forming units 4Y, 4M, 4C, and 4K. Of course, it is possible to form a two-color or three-color image using two or three image forming units.

  Next, the fixing device according to this embodiment will be described with reference to FIG. The fixing device 20 includes a fixing belt 21 that is a flexible endless belt, a pressure roller 24 that is a pressure rotating body (pressure member) that abuts on the outer peripheral surface thereof, and a halogen heater 23 that is a heat source. The fixing belt 21 is directly heated from the inner peripheral side by the halogen heater.

  A nip forming member 26 that forms a fixing nip portion N and a pressure roller 24 that is opposed to each other via the fixing belt 21 is disposed on the inner peripheral side of the fixing belt 21, and directly on the inner surface of the fixing belt or a low friction (not shown). The sheet is rubbed indirectly through the sheet. The nip forming member 26 is made of a heat-resistant member, and is arranged in a long length in the axial direction of the fixing belt 21 or the axial direction of the pressure roller 24.

  In FIG. 2, the shape of the fixing nip portion N is flat, but may be a concave shape in which the nip forming member 26 or the pressure roller 24 side is depressed or other shapes. If the nip forming member 26 has a concave shape, the discharge direction at the front end of the paper is closer to the pressure roller, so that the separation property is improved and the occurrence of jam can be suppressed.

  The fixing belt 21 is composed of a thin and flexible endless belt or film using a metal material such as nickel or SUS or a resin material such as polyimide. The outer peripheral surface of the belt has a release layer such as PFA, PTFE, etc., and has a release property so that toner does not adhere. There may be an elastic layer formed of silicone rubber or the like between the base material of the fixing belt 21 and the release layer. When there is no elastic layer, the heat capacity is reduced and the fixability is improved, but when the unfixed image is crushed and fixed, the minute irregularities on the belt surface are transferred to the image and the image has a crusty skin shape. There is a possibility of causing a defect in which gloss unevenness (zudder skin image) remains. In order to improve this, it is preferable to provide an elastic layer of silicone rubber of 100 [μm] or more. Due to the deformation of the silicone rubber, minute irregularities are absorbed.

  A support member 27 (stay) for supporting the nip forming member 26 is provided inside the fixing belt 21 to prevent the nip forming member 26 that receives pressure from the pressure roller 24 from being bent and uniform in the axial direction. The nip width can be obtained. The support member 27 made of a metal such as stainless steel, iron, or aluminum is positioned by being held and fixed to a holding member 28 with a flange at both ends (both ends in a direction perpendicular to the paper surface). Further, a reflection member 29 is provided between the halogen heater 23 and the support member 27, and wasteful energy consumption that the support member 27 is heated by radiant heat from the halogen heater 23 or the like is suppressed. The same effect can be obtained by performing heat insulation or mirror treatment on the surface of the support member 27 instead of providing the reflection member 29. The heat source may be the illustrated halogen heater, but may be IH, a resistance heating element, a carbon heater, or the like.

  In the pressure roller 24, an elastic rubber layer 24b is provided on a metal core 24a, and a release layer (PFA or PTFE layer) is provided on the surface in order to obtain releasability. The pressure roller 24 is rotated by a driving force transmitted through a gear from a driving source such as a motor provided in the image forming apparatus. The pressure roller 24 is pressed against the fixing belt 21 by a spring (not shown) and the elastic rubber layer is crushed and deformed to secure a predetermined nip width. The pressure roller 24 may be a hollow roller or a solid roller. In the case of a hollow roller, the pressure roller 24 may have a heat source such as a halogen heater. The elastic rubber layer may be solid rubber, but if there is no heat source in the pressure roller 24, sponge rubber may be used. Sponge rubber is more desirable because it improves heat insulation and makes it difficult for the fixing belt to lose heat.

  The fixing belt 21 rotates along with the pressure roller 24. As described above, the pressure roller 24 is rotated by a drive source (not shown), and the driving force is transmitted to the belt at the fixing nip portion N, whereby the fixing belt 21 is rotated. The fixing belt 21 is nipped and rotated by the pressure roller 24 and the nip forming member 26 at the fixing nip portion N, and travels while being guided by the flanges of the holding member 28 at both ends other than the fixing nip portion.

  In the fixing device 20, a heat transfer member 42 is further attached to the support member 27. The support member 27 in the vicinity of the halogen heater as a heat source is not only easily affected by the reflectance of the reflection member 29 and the ambient temperature, but also stainless steel, iron, aluminum, etc., in order to ensure rigidity to support the nip forming member 26. Such a metal material is generally used, and the endotherm is remarkable. When the support member 27 becomes high temperature, the nip forming member 26 supported by the support member 27 also becomes high temperature. The base material of the fixed nip forming member 26 that rubs against the fixing belt 21 is formed of a resin having a low frictional resistance, or is wound with a PFA rubbing sheet. There is a risk of doing. Therefore, the heat transmitted from the heat source to the support member 27 and the nip forming member 26 is released by the heat transfer member 42, thereby suppressing the temperature rise of these members. The heat transfer member 42 is made of, for example, the same material as the support member 27 such as copper or aluminum, or is more excellent in thermal conductivity, and is disposed between the nip forming member 26 and the support member 27. The nip forming member 26 is also used when the small-size paper is continuously passed by the high heat transfer member 42 extending in the belt width direction orthogonal to the sheet conveyance direction, that is, the longitudinal direction of the support member 27. In addition, local temperature rise of the support member 27 can be avoided, and uneven temperature distribution in the longitudinal direction can be eliminated. As shown in FIG. 3, the heat transfer member 42 extends over the entire width in the longitudinal direction of the support member 27, and both ends in the longitudinal direction are connected to a frame (side plate) 43 of the apparatus main body located further outside the holding member 28. ing. In most cases, the frame 43 that is not directly heated by the heat source is made of steel so that heat can be easily transmitted, has a larger surface area than the support member 47 and the nip forming member 26, and the transmitted heat spreads to the frame 43 and dissipates heat. As a result, overheating of the nip forming member 26 and the like can be avoided. It is conceivable to use a thin heat pipe, heat sink, or graphite sheet as the heat transfer member 42. Further, gold, silver, copper, or the like may be coated on the surface to obtain a high transferability of the heat transfer member 42.

  As shown in FIG. 4, the heat transfer member 42 is not disposed between the nip forming member 26 and the support member 27, but is disposed in a portion facing the heat source of the support member 27, and dissipates heat to the frame. As a result, the temperature rise of the nip forming member 26 may be suppressed.

  In this example, in order to suppress an increase in cost and a decrease in energy saving due to an increase in the size of the apparatus, each component is reduced in size, and a nip forming mechanism and a heat source are integrated inside the fixing belt 21. Therefore, a member close to the halogen heater as a heat source is easily affected by the reflectance of the reflecting member 29 and the ambient temperature, and is likely to become high temperature. When the support member 27 having high endothermic property, and hence the nip forming member 26, is exposed to high temperature, there is a problem that damage due to thermal deformation or the like and a reduction in the service life of components occur. By providing the heat transfer member 42 and radiating the heat of the support member 27 from the heat transfer member 42 through the frame 43 of the apparatus main body, it is possible to suppress the shortening of the service life of the components.

  FIG. 5 shows another example of the fixing device. In the example of FIG. 2, the heat source is composed of one halogen heater, whereas in this example, it is composed of three halogen heaters 23 </ b> A, 23 </ b> B, and 23 </ b> C to cope with various paper widths. By providing a plurality of heaters corresponding to various paper widths, an excessive amount of heat supply is suppressed, leading to improved energy saving. In addition, the same code | symbol is attached | subjected about the same member as the example of FIG. 2, and description is abbreviate | omitted.

  FIG. 6 shows still another example of the fixing device. In this example, in addition to the heat transfer member 42 and a plurality of heat sources (two) for accommodating a plurality of paper widths, a light shielding member 25 is provided. As shown in FIG. 7, the light shielding member 25 has a stepped shape having a plurality of light shielding widths in accordance with the respective paper widths. The light shielding member 25 is configured to rotate in a non-contact manner along the inner side of the fixing belt 21, and moves to a position corresponding to each paper width to shield an area unnecessary for heating. FIG. 8 shows the position of the light shielding member 25 when the A3 sheet is passed and when the postcard is passed. With such a configuration, even when narrow paper is continuously passed, it is possible to prevent the non-sheet passing area from becoming overheated, and control such as reducing productivity to cancel the overheated area. There is no need to do. Further, by using the light shielding member in combination, it is possible to reduce the number of heat sources required for dealing with a plurality of paper widths. Even in the fixing device configured as in this example, the heat of the support member 27 is transmitted to the fixing belt 21 by the heat transfer member 42 to avoid the problem due to overheating of the support member 27.

  As mentioned above, although this invention was demonstrated based on preferred embodiment, this invention is not limited to the demonstrated structure, In the range which does not deviate from the summary, it can change variously.

20 Fixing device 21 Fixing belt 23 Halogen heater (heat source)
24 Pressure roller 26 Nip forming member 27 Support member 28 Holding member 29 Reflecting member 42 Heat transfer member

JP 2007-334205 A JP 2009-42305 A

Claims (5)

An endless belt, a pressure rotator in contact with the outer peripheral surface of the belt, and a nip forming member that is disposed inside the belt and forms a fixing nip portion with the pressure rotator via the belt. In the fixing device, which is disposed inside the belt and supports the nip forming member, and a heat source disposed inside the belt, the heat conductivity is the same as or higher than that of the supporting member. A fixing device , wherein a high heat transfer member is disposed between the support member and the nip forming member, is attached to the support member, and is connected to a frame of the apparatus main body.   The fixing device according to claim 1, wherein the heat transfer member is provided over the entire longitudinal width of the support member. Or the heat transfer member is a heat pipe, the fixing device according to claim 1 or 2, characterized in that a graphite sheet. The fixing device according to claim 1 or 2, characterized in that said heat transfer member is surface-coated gold, silver or copper. An image forming apparatus including a fixing device according to any one of claims 1-4.

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