JP2014174370A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device with a simple configuration capable of achieving energy saving and a reduction in first print time, preventing thermal deterioration for various types of sheets, and improving productivity.SOLUTION: A fixing device includes a rotatable fixing member, a heat source that heats the fixing member, a non-rotatable nip forming member that is brought into contact with the fixing member inside the fixing member, and a pressure member that forms a nip with the nip forming member with the fixing member therebetween. The fixing device further includes a heat transfer assisting member that is brought into contact with the fixing member to assist heat transfer of the fixing member; and the heat transfer assisting member is formed to extend in a rotation shaft direction of the fixing member centering around a central part in the rotation shaft direction of the fixing member, and has a large heat conductance in end part areas than in a central part area in the rotation shaft direction of the fixing member.

Description

  The present invention relates to a fixing device used in an image forming apparatus such as a copying machine, a printer, and a facsimile, and an image forming apparatus including the same.

  In recent years, market demands for energy saving and speeding up of image forming apparatuses such as copying machines, printers, and facsimiles have increased. In an image forming apparatus, an image is formed by an image forming process such as electrophotographic recording, electrostatic recording, or magnetic recording, and an unfixed toner image is recorded on a recording material sheet, printing paper, photosensitive paper, electrostatic It is formed on a recording material such as recording paper. As a fixing device for fixing an unfixed toner image, a contact heating method fixing device such as a heat roller method, a film heating method, or an electromagnetic induction heating method is widely used.

  As an example of such a fixing device, a belt-type fixing device (see, for example, Patent Document 1) is known.

  However, in such a belt-type fixing device, the temperature stability in the belt is poor, the heat capacity is large, and the temperature rise is slow. Therefore, the time required for warm-up and first printing in the fixing device reaches a predetermined temperature. There is a problem that it is long. Therefore, shortening of warm-up time and first print time is desired. The warm-up time refers to the time required from a normal temperature state to a predetermined printable temperature (reload temperature) such as when the power is turned on. The first print time is a time period from when a print request is received to when a print operation is performed through print preparation and paper discharge is completed.

  In order to shorten the warm-up time and the first print time, a surf fixing type (film fixing type) fixing device using a ceramic heater has been proposed (see, for example, Patent Document 2). This surf-fixing type fixing device can be reduced in heat capacity and size as compared with a belt-fixing type fixing device.

  However, this fixing device locally heats only the fixing nip portion. For this reason, the other portions are not heated, and there is a problem that the belt is in the coldest state in the vicinity of the carry-in entrance of the sheet or the like in the fixing nip portion, so that fixing failure is likely 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 fixing nip increases.

  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. For this reason, a so-called temperature drop in which the amount of heat is insufficient at the beginning of continuous printing is a problem.

  In order to solve the problems as described above, in the configuration using an endless belt, it is possible to warm the entire belt, shorten the first print time from the heating standby time, and insufficient heat amount during high-speed rotation There has been proposed a fixing device that eliminates the above problem and can obtain good fixability even when mounted in a highly productive image forming apparatus (see, for example, Patent Document 3).

  As shown in FIG. 9, the fixing device described in Patent Document 3 is provided with an endless belt 100, a pipe-shaped metal heat conductor 200 disposed inside the endless belt 100, and a metal heat conductor. The heat source 300 and the pressure roller 400 that abuts against the metal heat conductor 200 via the endless belt 100 to form the nip portion N are provided. The endless belt 100 is rotated by the rotation of the pressure roller 400. At this time, the metal thermal conductor 200 guides the movement of the endless belt 100. Further, the endless belt 100 is heated by the heat source 300 in the metal heat conductor 200 via the metal heat conductor 200. With such a configuration, the entire endless belt constituting the fixing device can be warmed. For this reason, the first print time from the heating standby time can be shortened, and the shortage of heat during high-speed rotation can be solved to some extent.

  However, such a fixing device is required to further save energy and improve the first print time.

  In order to further save energy and improve the first print time, a configuration in which an endless belt is directly heated without using a metal heat conductor has been proposed (for example, see Patent Document 4).

  As shown in FIG. 10, the fixing device described in Patent Document 4 removes the pipe-shaped metal heat conductor from the inside of the endless belt 100, and instead includes a plate-shaped nip forming member 500. Then, a pressure roller 400 that forms a nip portion N in contact with the nip forming member 500 via the endless belt 100 is provided. In the case of this configuration, the endless belt 100 can be directly heated by the heat source 300 at a place other than where the nip forming member 500 is disposed. Therefore, heat transfer efficiency is greatly improved and power consumption is reduced. Thereby, it is possible to further shorten the first print time from the heating standby time. Moreover, the cost reduction by not providing a metal heat conductor can also be anticipated. In this fixing device, the nip forming member 500 is supported by a support member 600 such as stainless steel, and the strength of the nip forming member 500 against the pressure applied by the pressure roller 400 is increased.

  However, this type of fixing device that directly heats the endless belt 100 has an endless belt in the axial direction of the endless belt when a sheet having a width smaller than the heating width of the heat source 300 that heats the endless belt 100 is passed. The temperature rise (edge temperature rise) in the area outside the sheet passing range becomes remarkable. Specifically, when the sheet passes through the nip portion N, the area in the endless belt 100 in the sheet passing area continues to be deprived of heat, while the area outside the sheet passing area is less likely to be deprived of heat. Therefore, the temperature of the endless belt 100 in the region outside the sheet passing range rapidly increases as shown in FIG. Further, in the case of a fixing belt having a low heat capacity, such a problem is particularly noticeable.

  Therefore, when such a sheet is continuously passed, the temperature of members constituting the fixing, such as a fixing member and a pressure member, reaches or exceeds the heat resistance temperature of these members. As a result, in order to protect the member, the temperature in the area outside the sheet passing range has to be suppressed, and the productivity has to be reduced by performing CPM down. In particular, since the demand for shortening the warm-up time and the reduction of power consumption in recent years has caused the temperature fluctuation of the fixing belt to occur easily due to the low heat capacity of the fixing belt, such a problem becomes significant.

  In order to solve such a problem, there is known a fixing device in which a longitudinal width of a heater is set to a length corresponding to various transfer sheets in a fixing upper unit that can be detachably attached to an image forming apparatus main body. (For example, refer to Patent Document 5).

  However, there are various sizes of paper such as A4Y, A4T, A5T, B4, B5T, and postcards, and optimizing the heat generation length of the heater leads to an increase in size and cost of the apparatus.

  A fixing device that solves such a problem is not yet known at the time of the present application, but has been proposed in, for example, Japanese Patent Application No. 2012-284663.

  In the content of this proposal, the above-mentioned problem can be solved because the region unnecessary for heating is shielded by providing a light-shielding member adapted to each paper width.

  However, a fixing device that solves the above-described problems with a simpler configuration is desired.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device having a simple configuration capable of saving energy and improving a first print time, preventing thermal deterioration corresponding to various sheets, and improving productivity.

In order to solve the above-described problem, a fixing device according to a first aspect of the present invention includes:
A rotatable fixing member;
A heat source for heating the fixing member;
A non-rotating nip forming member in contact with the fixing member inside the fixing member;
A pressure member that forms a nip with the nip forming member via the fixing member, and a fixing device comprising:
A heat transfer auxiliary member that contacts the fixing member and assists the heat transfer of the fixing member;
The heat transfer assisting member is formed to extend in the rotation axis direction of the fixing member around a central portion in the rotation axis direction of the fixing member,
The heat transfer assisting member has a thermal conductance larger in an end region than in a central region in the rotation axis direction of the fixing member.

  According to the present invention, it is possible to provide a fixing device having a simple configuration capable of saving energy and improving the first print time, preventing thermal deterioration corresponding to various papers, and improving productivity.

1 is a configuration diagram schematically illustrating an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing a fixing device of the image forming apparatus shown in FIG. 1. FIG. 2 is an explanatory diagram illustrating a reflecting member of the fixing device of the image forming apparatus illustrated in FIG. 1. FIG. 2 is an explanatory diagram illustrating a fixing member of the fixing device of the image forming apparatus illustrated in FIG. 1. It is explanatory drawing explaining the heat equalization member of the 1st aspect of the image forming apparatus shown in FIG. It is explanatory drawing explaining the heat equalization member of the 2nd aspect of the image forming apparatus shown in FIG. It is explanatory drawing explaining the heat equalization member of the 3rd aspect of the image forming apparatus shown in FIG. It is explanatory drawing explaining the heat equalization member of the 4th aspect of the image forming apparatus shown in FIG. It is sectional drawing which shows the conventional fixing device. It is sectional drawing which shows the conventional fixing device. It is explanatory drawing explaining the relationship between the width | variety of a paper, and the temperature of an endless belt.

  Next, an embodiment according to the present invention will be described below with reference to the drawings. In each drawing for explaining the present embodiment, constituent elements such as members or components having the same function or shape are given the same reference numerals as much as possible, and once explained, the explanation will be given. Is omitted.

  FIG. 1 is a schematic sectional view showing an example of an image forming apparatus as a color printer 10 provided with a fixing device of the present invention. The image forming apparatus 10 shown here includes a fixing device 50 to be described later and an electrophotographic image forming unit, and the image forming unit includes a plurality of (four in the illustrated example) image forming means 1a, 1b, 1c and 1d are provided. Although the first to fourth image forming units 1a, 1b, 1c and 1d have the same configuration, only the corresponding toner colors are different. Therefore, for example, a black toner image, a magenta toner image, a cyan toner image, and a yellow toner image are formed in these image forming units. Since these image forming units have the same configuration except for the difference in developer (toner) color, in the following description, the subscripts a, b, c, and d in the reference numerals are omitted as appropriate. To do.

  The image forming unit 1 is provided with a drum-shaped photoconductor 2 that is an electrostatic latent image carrier. A charging member 3, a developing device 4, and a cleaning unit 5 are provided around the photoconductor 2. Yes. The photoreceptor 2 can be driven to rotate clockwise, and a charging member 3 is pressed against the surface of the photoreceptor 2. The charging member 3 is driven to rotate as the photosensitive member 2 rotates. In addition, a predetermined bias voltage is applied to the charging member 3 from a high voltage power source (not shown) so that the surface of the photoconductor 2 to be rotationally driven can be uniformly charged. The charging member 3 shown here employs a roller-shaped member that contacts the photosensitive member 2, but a non-contact type utilizing corona discharge or the like can also be employed.

  Further, in the image forming apparatus 10 shown in FIG. 1, an exposure device 6 is provided obliquely downward in parallel with the four image forming means. The exposure apparatus 6 has appropriate components such as a light source, a polygon mirror, an f-θ lens, and a reflection mirror. Then, each photoreceptor 2 charged by the charging member 3 is exposed based on image information formed according to the image data of each color toner. And it is provided in order to create an electrostatic latent image on each photoconductor 2. The electrostatic latent image formed on the photosensitive member 2 using the exposure device 6 is developed and visualized by applying toner of each color when passing through the developing device 4 by the rotation of the photosensitive member 2. The In addition, toner bottles 20a, 20b, 20c, and 20d filled with black, magenta, cyan, and yellow toners are disposed above the image forming apparatus 10. A predetermined replenishment amount of toner is replenished from the toner bottles 20a, 20b, 20c and 20d to the color developing devices 4a, 4b, 4c and 4d via a conveyance path (not shown).

  Further, an endless belt-shaped intermediate transfer belt 7 configured as an intermediate transfer member is disposed opposite to the photoreceptor 2 of each image forming unit, and each photoreceptor 2 is applied to the surface of the intermediate transfer belt 7. Touching. The intermediate transfer belt 7 shown in FIG. 1 is configured by being wound around a plurality of support rollers (for example, support rollers 15a and 15b). In the illustrated example, the support roller 15a is coupled to a drive motor as a drive source (not illustrated). By driving this drive motor, the intermediate transfer belt 7 is rotated counterclockwise in the drawing, and the support roller 15b that can be driven and rotated is rotated. Further, on the back surface of the intermediate transfer belt 7, a primary transfer roller 8 is disposed so as to face the photoconductor 2 with the belt interposed therebetween. A primary transfer bias is applied to the primary transfer roller 8 from a high voltage power source (not shown), and the toner image visualized by the developing device 4 is primarily transferred to the intermediate transfer belt 7. The primary transfer residual toner that is left on the photosensitive member 2 without being primarily transferred is removed by the cleaning unit 5 in preparation for the next image forming operation by the photosensitive member 2, and the toner on the photosensitive member 2 is completely removed. Removed.

  Further, in the illustrated image forming apparatus 10, a secondary transfer roller 18 as a secondary transfer device is provided downstream of the primary transfer roller 8 in the driving direction of the intermediate transfer belt 7. The secondary transfer roller 18 faces the support roller 15b with the intermediate transfer belt 7 interposed therebetween. The secondary transfer roller 18 and the support roller 15b form a secondary transfer nip portion via the intermediate transfer belt 7. Further, the image forming apparatus 10 includes a registration roller pair (positioning roller pair) 35 and the like in addition to a paper feeding cassette 30 and a feeding roller 31 as a recording medium stacking unit. A fixing device 50 and a paper discharge roller pair 36 are provided on the downstream side in the conveyance direction of the recording medium when viewed from the secondary transfer roller 18.

  Next, an image forming operation will be described. Also in this image forming operation, the configuration in which a toner image is formed on each photoconductor 2 and the toner image is transferred to the intermediate transfer belt 7 is substantially the same except that the color of the toner image is different. , A, b, c, and d are omitted as necessary.

  First, the above-described photoconductor 2 is rotated in a clockwise direction by a drive source (not shown), and at this time, light from a static eliminator (not shown) is irradiated on the surface of the photoconductor to initialize the surface potential. The surface of the photoreceptor 2 having the surface potential initialized is uniformly charged to a predetermined polarity by the charging member 3 this time. The charged photoconductor surface is irradiated with laser light from the exposure device 6, whereby an electrostatic latent image is formed on the photoconductor surface. At this time, the image information exposed on each photoreceptor 2 is single-color image information obtained by separating a desired full-color image into yellow, cyan, magenta, and black toner color information. The electrostatic latent image formed on the photosensitive member in this way is visualized as a visualized toner image by being supplied with each color toner (developer) from the developing device 4 when passing through the developing device 4. .

  The intermediate transfer belt 7 is driven to run counterclockwise in the drawing. The primary transfer roller 8 is applied with a primary transfer voltage having a polarity opposite to the toner charging polarity of the toner image formed on the photoreceptor. As a result, a transfer electric field is formed between the photosensitive member 2 and the intermediate transfer belt 7. Then, the toner image on the photoreceptor 2 is electrostatically primary-transferred onto the intermediate transfer belt 7 that is rotationally driven in synchronization with the photoreceptor 2. In this manner, the color toner images that are primarily transferred are superimposed on the intermediate transfer belt 7 sequentially at the same timing from the upstream side in the transport direction of the intermediate transfer belt 7 to form a desired full-color image.

  On the other hand, the recording medium on which an image is to be formed is separated one by one from the recording medium bundle loaded in the paper feeding cassette 30 to the registration roller pair 35 by the action of an appropriate conveying member such as the feeding roller 31. To be fed. At that time, the leading edge of the conveyed recording medium comes into contact with the nip portion of the registration roller pair 35 that has not yet started to rotate and forms a so-called loop, thereby registering the recording medium. . Thereafter, rotation of the registration roller pair 35 is started at the timing of the full-color toner image carried on the intermediate transfer belt 7. Then, the recording medium is sent out toward the secondary transfer nip portion constituted by the support roller 15b and the secondary transfer roller 18 facing the support roller 15b via the intermediate transfer belt 7. In this embodiment, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the surface of the intermediate transfer belt is applied to the secondary transfer roller 18. As a result, the full color toner image formed on the surface of the intermediate transfer belt 7 is collectively transferred onto the recording medium. The recording medium to which the toner image is transferred is further conveyed to the fixing device 50. Then, when passing through the fixing device 50, heat and pressure are applied, and the toner image is fixed on the recording medium as a permanent image. The recording medium after image formation with the image fixed is discharged to a recording medium discharge section such as a discharge tray via a pair of discharge rollers 36, thereby completing the image forming operation. The residual toner remaining on the intermediate transfer belt 7 without being transferred at the secondary transfer nip portion where the secondary transfer roller 18 is disposed is removed and collected by the intermediate transfer belt cleaning means 19.

Next, the configuration of the fixing device 50 will be described below with reference to FIG.
As shown in FIG. 2, the fixing device 50 includes a fixing belt 51 as a rotatable fixing member, a pressure roller 52 as a pressing member rotatably provided facing the fixing belt 51, and a fixing belt. Radiated from the halogen heater 53 as a heat source for heating 51, a nip forming member 54 disposed inside the fixing belt 51, a stay 55 as a support member for supporting the nip forming member 54, and the halogen heater 53. Fixing a reflecting member 56 that reflects light to the fixing belt 51, a temperature sensor 57 as temperature detecting means for detecting the temperature of the fixing belt 51, a separating member 58 that separates the paper from the fixing belt 51, and the pressure roller 52. An urging means (not shown) for urging the belt 51, a heat equalizing member (heat transfer assisting member) 60, and the like are provided.

  The fixing belt 51 is composed of a thin and flexible endless belt member (including a film). Specifically, the fixing belt 51 includes a base material on the inner peripheral side formed of a metal material such as nickel or SUS, or a resin material such as polyimide (PI), and a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA). Or it is comprised by the mold release layer of the outer peripheral side formed with polytetrafluoroethylene (PTFE) etc. Further, an elastic layer made of a rubber material such as silicone rubber, foamable silicone rubber, or fluorine rubber may be interposed between the base material and the release layer.

  The pressure roller 52 includes a cored bar 52a, an elastic layer 52b made of foamable silicone rubber, silicone rubber, or fluorine rubber provided on the surface of the cored bar 52a, and PFA or PTFE provided on the surface of the elastic layer 52b. It is comprised by the mold release layer 52c which consists of etc. The pressure roller 52 is urged toward the fixing belt by an urging means (not shown) and is in contact with the nip forming member 54 via the fixing belt 51. At the place where the pressure roller 52 and the fixing belt 51 are in pressure contact, the elastic layer 52b of the pressure roller 52 is crushed to form a nip portion N having a predetermined width. The pressure roller 52 is configured to be rotationally driven by a drive source such as a motor (not shown) provided in the printer main body. When the pressure roller 52 is rotationally driven, the driving force is transmitted to the fixing belt 51 at the nip portion N, and the fixing belt 51 is driven to rotate.

  In the present embodiment, the pressure roller 52 is a solid roller, but may be a hollow roller. In that case, a heat source such as a halogen heater may be disposed inside the pressure roller 52. In addition, when there is no elastic layer, the heat capacity is reduced and the fixability is improved. However, when the unfixed toner is crushed and fixed, minute irregularities on the belt surface are transferred to the image and the solid portion of the image is glossy. Unevenness may occur. In order to prevent this, it is desirable to provide an elastic layer having a thickness of 100 μm or more. By providing an elastic layer having a thickness of 100 μm or more, minute unevenness can be absorbed by elastic deformation of the elastic layer, so that occurrence of uneven gloss can be avoided. The elastic layer 52b may be solid rubber, but if there is no heat source inside the pressure roller 52, sponge rubber may be used. Sponge rubber is preferable because the heat insulating property is increased and the heat of the fixing belt 51 is hardly taken away. In addition, the fixing member and the pressure member are not limited to being in pressure contact with each other, and may be configured to simply contact each other without applying pressure.

  Both ends of the halogen heater 53 are fixed to a side plate (not shown) of the fixing device 50. One halogen heater 53 is configured to generate heat by being output-controlled by a power supply unit (not shown) provided in the printer body. This output control is performed based on the detection result of the surface temperature of the fixing belt 51 by the temperature sensor 57. By such output control of the heater 53, the temperature of the fixing belt 51 (fixing temperature) can be set to a desired temperature. Needless to say, the halogen heater 53 is not limited to one as in the present embodiment. In addition to the halogen heater, an IH, a resistance heating element, a carbon heater, or the like may be used as a heat source for heating the fixing belt 51.

  The nip forming member 54 is disposed in a longitudinal shape along the rotation axis direction of the fixing belt 51 or the rotation axis direction of the pressure roller 52, and is fixedly supported by a stay 55. Thereby, the occurrence of bending of the nip forming member 54 due to the pressure by the pressure roller 52 is prevented. Therefore, a uniform nip width can be obtained over the rotation axis direction of the pressure roller 52. The stay 55 is preferably formed of a metal material having high mechanical strength such as stainless steel or iron in order to satisfy the function of preventing the nip forming member 54 from bending. The stay 55 can be made of resin.

  The nip forming member 54 is formed of a heat resistant member having a heat resistant temperature of 200 ° C. or higher. As a result, the nip forming member 54 is prevented from being deformed by heat in the toner fixing temperature range, and a stable state of the nip portion N is secured to stabilize the output image quality. For the nip forming member 54, polyether sulfone (PES), polyphenylene sulfide (PPS), liquid crystal polymer (LCP), polyether nitrile (PEN), polyamide imide (PAI), polyether ether ketone (PEEK), etc. It is possible to use a typical heat resistant resin.

  The nip forming member 54 has a low friction sheet (not shown) on its surface. When the fixing belt 51 rotates, the fixing belt 51 slides with respect to the low friction sheet, so that the driving torque generated in the fixing belt 51 is reduced and the load due to the frictional force on the fixing belt 51 is reduced.

  The reflection member 56 is disposed between the stay 55 and the halogen heater 53. In the present embodiment, the reflecting member 56 is fixed to the stay 55. Further, since the reflecting member 56 is directly heated by the halogen heater 53, it is desirable that the reflecting member 56 be formed of a high melting point metal material or the like. By arranging the reflecting member 56 in this way, the light emitted from the halogen heater 53 toward the stay 55 is reflected to the fixing belt 51. As a result, the amount of light applied to the fixing belt 51 can be increased, and the fixing belt 51 can be heated efficiently. Further, since it is possible to suppress the radiant heat from the halogen heater 53 from being transmitted to the stay 55 and the like, energy saving can be achieved.

  Instead of providing the reflecting member 56 as in the present embodiment, the surface of the stay 55 on the halogen heater 53 side may be subjected to mirror processing such as polishing or painting to form a reflecting surface. The reflectance of the reflecting surface of the reflecting member 56 or the stay 55 is preferably 90% or more.

  Further, the shape and material of the stay 55 cannot be freely selected to ensure its strength. Therefore, if the reflecting member 56 is separately provided as in the present embodiment, the degree of freedom of selection of the shape and material is increased, and the reflecting member 56 and the stay 55 can be specialized in their functions. Further, by providing the reflecting member 56 between the halogen heater 53 and the stay 55, the position of the reflecting member 56 with respect to the halogen heater 53 is reduced, so that the fixing belt 51 can be efficiently heated.

  Further, in order to further improve the heating efficiency of the fixing belt 51 by light reflection, it is necessary to examine the direction of the reflecting surface of the reflecting member 56 or the stay 55. For example, as shown in FIG. 3A, the reflection surface 56 a is disposed concentrically with the halogen heater 53 as the center. If it does so, since light will be reflected toward the halogen heater 53, a heating efficiency will fall correspondingly. On the other hand, as shown in FIG. 3B, a part or all of the reflection surface 56b is arranged in a direction in which light is reflected toward the fixing belt in a direction other than the halogen heater. As a result, the amount of light reflected in the direction of the halogen heater 53 is reduced, so that the heating efficiency by the reflected light can be improved.

  The heat equalizing member (heat transfer assisting member) 60 is disposed inside the fixing belt 51 as shown in FIG. The soaking member 60 is preferably made of carbon nanotubes having physical properties such as heat resistance and good thermal conductivity. In addition, the material of the soaking | uniform-heating member 60 is not limited to a carbon nanotube, What is necessary is just to have heat resistance and good thermal conductivity, such as silver, copper, aluminum.

  The fixing device 50 is devised in various ways in order to further improve energy saving and first print time. Specifically, the fixing belt 51 can be directly heated by a halogen heater 53 at a place other than the nip portion (direct heating method). In this embodiment, nothing is interposed between the halogen heater 53 and the fixing belt 51 in the left side portion in FIG. At that portion, the radiant heat from the halogen heater 53 is directly applied to the fixing belt 51.

  Further, in order to reduce the heat capacity of the fixing belt 51, the fixing belt 51 is thin and has a small diameter. Specifically, the thicknesses of the base material, the elastic layer, and the release layer constituting the fixing belt 51 are set in a range of 20 to 50 μm, 100 to 300 μm, and 10 to 50 μm, and the overall thickness is set. It is set to 1 mm or less. The diameter of the fixing belt 51 is set to 20 to 40 mm. In order to further reduce the heat capacity, the thickness of the entire fixing belt 51 is preferably 0.2 mm or less, and more preferably 0.16 mm or less. The diameter of the fixing belt 51 is desirably 30 mm or less.

  In this embodiment, the diameter of the pressure roller 52 is set to 20 to 40 mm, and the diameter of the fixing belt 51 and the diameter of the pressure roller 52 are configured to be equal. The diameter of the fixing belt 51 and the diameter of the pressure roller 52 are not limited to this configuration. For example, the fixing belt 51 may be formed so that the diameter thereof is smaller than the diameter of the pressure roller 52. In that case, since the curvature of the fixing belt 51 at the nip portion N is smaller than the curvature of the pressure roller 52, the recording medium discharged from the nip portion N is easily separated from the fixing belt 51.

  Next, the configuration of the end portion of the fixing belt will be described below with reference to FIG. In addition, illustration of a soaking | uniform-heating member is abbreviate | omitted for convenience of explanation. 4A is a perspective view, FIG. 4B is a plan view, and FIG. 4C is a side view of the fixing belt as viewed from the rotation axis direction. 4 (a) to 4 (c), only the configuration of one end is illustrated, but the opposite end also has the same configuration. Only the configuration of the end portion of this will be described.

  As shown in FIG. 4A or 4B, a belt holding member 40 is inserted into the end of the fixing belt 51, and the end of the fixing belt 51 can be rotated by the belt holding member 40. Is retained. As shown in FIG. 4C, the belt holding member 40 is formed in a C-shape that opens at a position where the nip forming member 54 is disposed. Further, as shown in FIG. 4A or FIG. 4B, the end portion of the stay 55 is fixed to the belt holding member 40 and positioned.

  Further, as shown in FIG. 4A or FIG. 4B, a protection for protecting the end portion of the fixing belt 51 between the end surface of the fixing belt 51 and the facing surface of the belt holding member 40 facing the fixing belt 51. A slip ring 41 as a member is provided. Therefore, when the fixing belt 51 is deviated in the rotation axis direction, the end portion of the fixing belt 51 does not directly contact the belt holding member 40 and is avoided from wear or damage. Further, the slip ring 41 is fitted to the belt holding member 40 with a margin. Therefore, when the end of the fixing belt 51 comes into contact with the slip ring 41, the slip ring 41 can be rotated with the fixing belt 51. Note that the slip ring 41 may be stationary without being rotated. As a material of the slip ring 41, it is preferable to apply a so-called super engineering plastic excellent in heat resistance, for example, PEEK, PPS, PAI, PEEK and the like.

  Although not shown, a shielding member that shields heat from the halogen heater 53 may be disposed between the fixing belt 51 and the halogen heater 53. Thereby, in particular, an excessive temperature rise in the non-sheet passing region of the fixing belt during continuous sheet feeding can be suppressed, and deterioration and damage of the fixing belt due to heat can be prevented. In addition, it becomes possible to aim at the further energy saving by using this shielding member in combination with the soaking | uniform-heating member mentioned later.

Hereinafter, the basic operation of the fixing device according to the present embodiment will be described with reference to FIG.
When the power switch of the printer body is turned on, power is supplied to the halogen heater 53 and the pressure roller 52 starts to rotate clockwise in FIG. As a result, the fixing belt 51 is driven to rotate counterclockwise in FIG. 2 by the frictional force with the pressure roller 52.

  Thereafter, the sheet P carrying the unfixed toner image T in the image forming process described above is conveyed in the direction of the arrow A1 in FIG. 2 while being guided by a guide plate (not shown), and the fixing belt 51 in the pressure contact state and It is fed into the nip N of the pressure roller 52. Then, the toner image T is fixed on the surface of the paper P by heat from the fixing belt 51 heated by the halogen heater 53 and pressure applied between the fixing belt 51 and the pressure roller 52.

  The paper P on which the toner image T is fixed is carried out from the nip portion N in the direction of the arrow A2 in FIG. At this time, the paper P is separated from the fixing belt 51 by the front end of the paper P coming into contact with the front end of the separation member 58. Thereafter, the separated paper P is discharged out of the apparatus by the paper discharge roller as described above, and stocked on the paper discharge tray.

Next, the heat equalizing member which is a characteristic configuration of the present invention will be described in more detail. The thermal conductance refers to the amount of heat that flows per fixed area and fixed time when the temperature difference between both sides of the solid is 1 ° C., and indicates the ease of heat transfer. The thermal conductance is expressed by the following equation.
C = λ / L
Here, the thermal conductance is represented by C [W / m ² · K], the thermal conductivity is represented by λ [W / m · K], and the length in the direction in which heat is transmitted is represented by L [m].

  The soaking member 60 is provided on the upstream side of the nip portion N as shown in FIG. The shape of the heat equalizing member 60 is a shape that approximates the arc shape of the fixing belt 51 to be contacted. The soaking member 60 is provided over the entire region of the fixing belt in the rotation axis direction. The soaking member 60 is responsible for heat transport in the longitudinal direction, and assists heat transfer in the rotation axis direction of the fixing belt 51. The soaking member 60 can obtain a soaking effect by increasing the contact area with the fixing belt 51 as much as possible. Here, it is conceivable that the contact area is increased as much as possible, for example, with respect to the fixing belt 51 of φ30 mm, the contact width in the fixing belt running direction is 20 mm, and the contact area in the longitudinal direction of the fixing belt 51 is the entire area. The heat equalizing member is not limited to an aspect provided on the upstream side of the nip portion N, and may be provided on the downstream side. Further, the range in which the soaking member contacts the fixing belt 51 is not limited to an aspect that covers the entire rotation axis direction of the fixing belt 51. For example, the heat equalizing member may be in contact with the fixing belt 51 in a range shorter than the length of the fixing belt 51 in the rotation axis direction with the central portion as the center. Further, the heat equalizing member may be in contact with at least one side end region of the fixing belt 51 from a part of the central region in the rotation axis direction of the fixing belt 51. With such a configuration, the member cost can be reduced.

  In addition, the surface roughness of the heat equalizing member 60 is set to a surface roughness Ra of about 6.3 μm or less, which is equal to or less than the surface roughness of the fixing belt 51, thereby improving the adhesion with the fixing belt 51. With such a configuration, when the surface of the heat equalizing member 60 and the fixing belt 51 are brought into contact with each other, it is possible to prevent an air layer from being present between them, and to prevent the heat transfer from being greatly impaired.

  The soaking member 60 may be coated with a fluororesin (for example, PFA, PTFE, ETFE) on the contact surface side that contacts the fixing belt 51 in an amount of about 5 to 50 μm to improve the slidability. Further, since the thermal conductivity of the fluororesin is inferior to that of the soaking member, the thickness of the fluororesin and the presence / absence of the fluororesin may be appropriately determined. Further, in order to further improve the slidability between the soaking member 60 and the fixing belt 51, a lubricant such as silicon oil, silicon grease, or fluorine-based grease may be applied.

  Although illustration is omitted, the heat equalizing member may be disposed outside the fixing belt. In this case, the shape of the heat equalizing member 60 is a shape that approximately approximates the arc shape of the fixing belt to be contacted. The soaking member 60 is provided over the entire region of the fixing belt in the rotation axis direction. Then, by increasing the contact area with the fixing belt as much as possible, it is possible to obtain a soaking effect. Therefore, it can respond to a flexible design. In addition, even when it is placed outside the fixing belt, the contact area of the heat equalizing member that contacts the fixing belt is made as large as possible, but it is recommended if there is a risk of scratching the surface of the fixing belt. Not. The heat equalizing member is not limited to an aspect provided on the upstream side of the nip portion N, and may be provided on the downstream side. Further, the range in which the soaking member contacts the fixing belt 51 is not limited to an aspect that covers the entire rotation axis direction of the fixing belt 51. For example, the heat equalizing member may be in contact with the fixing belt 51 in a range shorter than the length of the fixing belt 51 in the rotation axis direction with the central portion as the center. Further, the heat equalizing member may be in contact with at least one side end region of the fixing belt 51 from a part of the central region in the rotation axis direction of the fixing belt 51. With such a configuration, the member cost can be reduced.

  Next, the operation of the soaking member, which is a characteristic configuration of the present invention, will be described. Note that switching between contact and non-contact between the surface of the heat equalizing member 60 and the fixing belt 51 is performed by a solenoid (not shown) which is an external drive device, as shown in FIGS. The soaking member 60 is rotated around the axis.

  Further, the contact between the surface of the heat equalizing member 60 and the fixing belt 51 is executed when the temperature in the longitudinal direction of the fixing belt 51 is partially increased and the thermal uniformity in the longitudinal direction of the fixing belt 51 is impaired. Is done. In other words, if such a temperature deviation does not occur in the fixing belt 51, the soaking member 60 does not contact the fixing belt 51.

  Specifically, the temperature sensor 57 that detects the temperature detects the surface temperature of the fixing belt 51. Then, the detection information is transmitted to a processing unit (not shown). When the processing unit determines that the temperature increase in the longitudinal direction of the fixing belt 51 or the thermal uniformity is impaired, the information is transmitted to a control unit (not shown). Then, the control unit controls the soaking member 60 so as to contact the fixing belt 51 via a solenoid. On the other hand, when the processing unit determines that the thermal uniformity in the longitudinal direction of the fixing belt 51 has been recovered, the information is transmitted to the control unit. Then, the control unit controls the soaking member 60 ′ so as not to contact the fixing belt 51 via the solenoid. In this way, the heat equalizing member 60 can be switched between the state 60 in contact with the fixing belt 51 and the state 60 ′ in the non-contact state. A DC motor or the like may be used instead of the solenoid. Then, the heat equalizing member 60 can be contacted and separated depending on the temperature of the fixing belt 51. That is, the soaking member can contact the fixing belt 51 only when the soaking of the fixing belt 51 is required. Therefore, the fixing belt 51 can be efficiently heated and energy saving can be achieved.

Further, when the surface of the soaking member 60 and the fixing belt 51 come into contact with each other, an air layer is generated between them. In such a case, the thermal conductivity between the soaking member 60 and the fixing belt 51 is extremely lowered. In order to prevent this decrease in thermal conductivity, the heat equalizing member 60 is attached to the fixing belt 51 by an urging means (not shown) such as a spring so that the surface pressure becomes, for example, about 0.1 kgf / cm ² or less. Press it so that it is in close contact. As a result, when the surface of the heat equalizing member 60 and the fixing belt 51 are in contact with each other, it is possible to prevent an air layer from existing between them.

Next, the 1st aspect of the soaking | uniform-heating member which is the characteristic structure of this invention is demonstrated.
The thickness of the heat equalizing member 60a is a dimension t as shown in FIG. The width (length) of the heat equalizing member 60a in the rotation direction of the fixing belt 51 is such that the center region is in sliding contact with the fixing belt 51 with the dimension W1, and the end region has a dimension W2 larger than the dimension W1. Therefore, it slides in contact with the fixing belt 51. That is, the area of the heat equalizing member 60a that contacts the fixing belt 51 is larger in the end region than in the central region. Therefore, the heat equalizing member 60a has a larger thermal conductance in the end region than in the central region, and the heat of the heat equalizing member 60a moves greatly in the direction from the central region to the end region. That is, the soaking member 60a strongly assists the heat transfer of the fixing belt 51. As a result, the heat that has increased the end temperature of the fixing belt 51 moves toward the end. When a paper having a width smaller than the heating width of the halogen heater 53 is passed, an excessive temperature rise of the fixing belt 51 is suppressed, and continuous paper feeding can be performed without reducing productivity.

Next, the 2nd aspect of the soaking | uniform-heating member which is the characteristic structure of this invention is demonstrated.
As shown in FIG. 6, the thickness of the heat equalizing member 60b of the second mode is such that the central region is in contact with the fixing belt 51 with the dimension t1 in the rotational axis direction of the fixing belt 51, and the end region Is in sliding contact with the fixing belt 51 at a dimension t2 larger than the dimension t1. That is, the thickness of the heat equalizing member 60b that contacts the fixing belt 51 is greater in the end region than in the central region. Therefore, the heat equalizing member 60b has a larger thermal conductance in the end region than in the central region, and the heat of the heat equalizing member 60b moves greatly from the central region to the end region. For this reason, the heat at which the temperature of the fixing member has risen outside the sheet passing range is transferred to the end side. That is, the soaking member 60b strongly assists the heat transfer of the fixing belt 51. As a result, when a paper having a width smaller than the heating width of the halogen heater 53 is passed, an excessive temperature rise of the fixing belt 51 is suppressed, and continuous paper feeding can be performed without reducing productivity.

Next, the 3rd aspect of the soaking | uniform-heating member which is the characteristic structure of this invention is demonstrated.
As shown in FIG. 7, the material of the heat equalizing member 60 c of the third aspect is such that the central region of the fixing belt 51 is in contact with the fixing belt 51 with the material B in the direction of the rotation axis of the fixing belt 51. The region has a multi-layer structure composed of another member of the material A in addition to the member of the material B, and slides in contact with the fixing belt 51. That is, the total number of heat equalizing members 60c in contact with the fixing belt 51 is larger in the end region than in the central region. Therefore, the heat equalizing member 60c has a larger thermal conductance in the end region than in the central region, and the heat of the heat equalizing member 60c moves greatly from the central region to the end region. For this reason, the heat at which the temperature of the fixing member has increased in the area outside the sheet passing range is transferred to the end side. That is, the soaking member 60c strongly assists the heat transfer of the fixing belt 51. As a result, when a paper having a width smaller than the heating width of the halogen heater 53 is passed, an excessive temperature rise of the fixing belt 51 is suppressed, and continuous paper feeding can be performed without reducing productivity. The central region is not limited to a single layer made of only the material B, but may be a plurality of layers. However, the thermal conductance of the end portion is increased by making the number of layers in the end region larger than the number of layers in the central region. As an example of the materials A and B, the above-described heat-uniforming member material of a good heat conductor is preferable.

Next, the 4th aspect of the soaking | uniform-heating member which is the characteristic structure of this invention is demonstrated.
As shown in FIG. 8, the material of the soaking member 60d of the fourth aspect is a member B made of material B in the central region in the direction of the rotation axis of the fixing belt 51, and is in sliding contact with the fixing belt 51. The region slides in contact with the fixing belt 51 with another member of material A. The material A has a higher thermal conductivity than the material B. That is, the thermal conductivity of the heat equalizing member 60 c that contacts the fixing belt 51 is greater in the end region than in the central region. Therefore, the heat equalizing member 60c has a larger thermal conductance in the end region than in the central region, and the heat of the heat equalizing member 60d moves greatly from the central portion toward the end. For this reason, the heat at which the temperature of the fixing member has risen outside the sheet passing range is transferred to the end side. That is, the soaking member 60 d strongly assists the heat transfer of the fixing belt 51. As a result, when a paper having a width smaller than the heating width of the halogen heater 53 is passed, an excessive temperature rise of the fixing belt 51 is suppressed, and continuous paper feeding can be performed without reducing productivity. As an example of the materials A and B, the above-described good heat conductor soaking member material is preferable.

  In addition, it cannot be overemphasized that the 1st-4th aspect of the above-mentioned soaking | uniform-heating member is only a representative example, and can employ | adopt combining at least any one aspect. Needless to say, the thermal conductance of the heat equalizing member 60 is not limited to the above-described mode as long as the end region is larger than the central region in the rotation axis direction of the fixing belt 51.

Next, the operation of the image forming apparatus according to this embodiment will be described.
Regarding the thermal conductance in the direction of the rotation axis of the heat equalizing member 60, the end region is larger than the central region. Therefore, it becomes easy for the heat in the soaking member to move from the central region toward the end region. Then, when a sheet having a width narrower than the heating width of the heat source is passed, even if an area outside the end of the sheet width that is outside the sheet passing range in the rotation axis direction of the fixing belt 51 is about to rise in temperature, fixing is performed. The heat equalizing member 60 in contact with the belt 51 can strongly assist the heat transfer toward the end portion with respect to the rotation axis direction of the fixing belt 51. As a result, the temperature rise of the fixing belt can be suppressed, and continuous paper feeding can be performed without reducing productivity.

  Further, the width of the heat equalizing member 60a in the rotation direction of the fixing belt 51 is such that the end region is larger than the central region, so that the thermal conductivity in the longitudinal direction of the heat equalizing member 60a is centered at the end region. Can be larger than the area. Therefore, it becomes easy for the heat in the soaking member to move from the central region toward the end region. Then, when a sheet having a width narrower than the heating width of the heat source is passed, even if an area outside the end of the width of the sheet that is outside the sheet passing range in the rotation axis direction of the fixing belt 51 is about to rise in temperature, fixing is performed. The heat equalizing member 60a that is in contact with the belt 51 can strongly assist the heat transfer toward the end side with respect to the rotation axis direction of the fixing belt 51. As a result, the temperature rise of the fixing belt 51 can be suppressed, and continuous paper feeding can be performed without reducing productivity.

  Further, since the thickness of the end region of the heat equalizing member 60b that comes into contact with the fixing belt 51 is thicker than the central region, the end region is made larger than the central region for the thermal conductance in the longitudinal direction of the heat equalizing member 60b. it can. Therefore, it becomes easy for the heat in the soaking member to move from the central region toward the end region. Then, when a sheet having a width narrower than the heating width of the heat source is passed, even if an area outside the end of the sheet width that is outside the sheet passing range in the rotation axis direction of the fixing belt 51 is about to rise in temperature, fixing is performed. The heat equalizing member 60b in contact with the belt 51 can strongly assist the heat transfer toward the end portion with respect to the longitudinal direction of the fixing belt 51. As a result, the temperature rise of the fixing belt 51 can be suppressed, and continuous paper feeding can be performed without reducing productivity.

  Further, since the layer of the end region of the heat equalizing member 60c that comes into contact with the fixing belt is more multilayered than the central region, the end region is more than the central region with respect to the thermal conductance in the longitudinal direction of the heat equalizing member 60c. Can be bigger. Therefore, it becomes easy for the heat in the soaking member to move from the central region toward the end region. Then, when a sheet having a width narrower than the heating width of the heat source is passed, even if an area outside the end of the sheet width that is outside the sheet passing range in the rotation axis direction of the fixing belt 51 is about to rise in temperature, fixing is performed. The heat equalizing member 60c in contact with the belt 51 can strongly assist the heat transfer to the end side with respect to the rotation axis direction of the fixing belt 51. As a result, the temperature rise of the fixing belt 51 can be suppressed, and continuous paper feeding can be performed without reducing productivity.

  In addition, by using a member having a higher thermal conductivity in the end region of the heat equalizing member 60d that is in contact with the fixing belt 51 than in the central region, the thermal conductance in the longitudinal direction of the heat equalizing member 60d is greater than that in the central region. Can also enlarge the end region. Therefore, it becomes easy for the heat in the soaking member to move from the central region toward the end region. Then, when a sheet having a width narrower than the heating width of the heat source is passed, even if an area outside the end of the sheet width that is outside the sheet passing range in the rotation axis direction of the fixing belt 51 is about to rise in temperature, fixing is performed. The heat equalizing member 60d in contact with the belt 51 can strongly assist the heat transfer toward the end side with respect to the rotation axis direction of the fixing belt 51. As a result, the temperature rise of the fixing belt 51 can be suppressed, and continuous paper feeding can be performed without reducing productivity.

  In addition, since the heat equalizing member 60 is in contact with the entire length of the fixing belt 51, the contact area with the fixing belt 51 can be increased as much as possible, and a remarkable heat equalizing effect can be obtained.

  In addition, according to the image forming apparatus equipped with the fixing device as described above, an image forming apparatus corresponding to various papers capable of improving productivity by preventing energy deterioration and improving the first print time can be provided. it can.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this. Needless to say, the heat source is not limited to three heaters as in the present embodiment, and may be one or other modes.

  It should be noted that the materials and dimensions of each component introduced in the above-described embodiment are merely examples, and it is needless to say that various materials and dimensions can be selected within a range where the effects of the present invention can be exhibited.

1 Color printer (an example of an image forming apparatus)
50 fixing device 51 fixing belt (an example of a fixing member)
52 Pressure roller (an example of a pressure member)
53 Halogen heater (example of heat source)
54 Nip forming member 60 (60a, 60b, 60c, 60d) Heat equalizing member (heat transfer assisting member)
60 'heat equalizing member (heat transfer auxiliary member)
N fixing nip

JP 2004-286922 A Japanese Patent No. 2861280 JP 2007-334205 A JP 2011-186275 A Japanese Patent No. 3155066

Claims (8)

A rotatable fixing member;
A heat source for heating the fixing member;
A non-rotating nip forming member in contact with the fixing member inside the fixing member;
A pressure member that forms a nip with the nip forming member via the fixing member, and a fixing device comprising:
A heat transfer auxiliary member that contacts the fixing member and assists the heat transfer of the fixing member;
The heat transfer assisting member is formed to extend in the rotation axis direction of the fixing member around a central portion in the rotation axis direction of the fixing member,
The fixing device according to claim 1, wherein the heat transfer assisting member has a thermal conductance larger in an end region than in a central region in a rotation axis direction of the fixing member.   The fixing device according to claim 1, wherein the heat transfer auxiliary member can be contacted and separated according to a temperature of the fixing member.   The width in which the heat transfer auxiliary member contacts the fixing member in the rotation direction of the fixing member is larger in the end region than in the central region in the rotation axis direction of the fixing member. The fixing device according to 1 or 2.   The thickness of the portion where the heat transfer assisting member contacts the fixing member is thicker in the end region than in the central region in the direction of the rotation axis of the fixing member. The fixing device according to claim 1. The heat transfer auxiliary member is composed of a single layer or more layers,
The number of layers of the portion where the heat transfer assisting member comes into contact with the fixing member is larger in the end region than in the central region in the rotation axis direction of the fixing member. The fixing device according to claim 1. The heat transfer auxiliary member is composed of two or more kinds of materials,
The material of the portion where the heat transfer assisting member comes into contact with the fixing member has a thermal conductivity higher in the end region than in the central region in the rotation axis direction of the fixing member. The fixing device according to any one of 1 to 5.   The fixing device according to claim 1, wherein the heat transfer auxiliary member is in contact with the entire region of the fixing member in the rotation axis direction.   An image forming apparatus comprising the fixing device according to claim 1.

Images