JP6065675B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device and an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine having at least two functions thereof.

In recent years, market demands for energy saving and shortening of start-up time have been increasing for image forming apparatuses such as printers, copiers and facsimiles.
In an image forming apparatus, an unfixed toner image is transferred to a recording medium sheet, printing paper, photosensitive paper, electrostatic recording paper, etc. by an image transfer method or a direct method by an image forming process such as electrophotographic recording, electrostatic recording, or magnetic recording. It is formed on a recording medium. 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, and an electromagnetic induction heating method is widely used.

  Among them, the startup time of the fixing device (effects such as shortening the time required for the fixing member to reach a predetermined printable temperature (reload temperature) such as when the power is turned on, and reducing energy consumption) Various devices have been devised in order to obtain the fixing device, among which fixing devices that rapidly raise the temperature of the fixing member using radiant heat from a heating source as described in Patent Documents 1 and 2 are known. In such a fixing device, the heat transfer efficiency from the heating source to the fixing member can be improved by concentrating the radiant heat from the heating source at a specific place using the reflecting member.

  In this type of fixing device, the reflecting member reflects the radiant heat from the heating source to the fixing member, but not all of the radiant heat that reaches the reflecting member is reflected and part of the radiant heat is absorbed by the reflecting member. ing. As a result, when the heating source continuously radiates heat, such as during continuous paper feeding, the reflective member gradually becomes high temperature, which may cause thermal deterioration or thermal breakage of the reflective member. For this problem, it is conceivable to take measures to cool the reflecting member by moving heat from the reflecting member by some method. At this time, if heat is transferred from the reflecting member to the fixing member, it is desirable that the reflecting member can be cooled while improving the heat transfer efficiency from the heating source to the fixing member.

  However, on the other hand, there is a fixing device configured to transfer heat from an image passing range (an unfixed toner image passing range) of the fixing member to a reflecting member or the like when starting up. In this type of fixing device, the amount of heat radiated from the heating source increases in order to raise the surface temperature of the image passing range of the fixing member from the normal temperature to the reload temperature when starting up. As a result, the start-up time of the fixing device is extended and the energy consumption is also increased. For this reason, it is desirable that the fixing device has a configuration in which heat is not transferred from the image passing range of the fixing member to the reflecting member or the like when the fixing device is started up.

  In order to satisfy both of these two demands, the amount of heat transferred from the image passing range of the fixing member to the reflecting member is suppressed at the start-up, and heat is transmitted from the reflecting member to the fixing member during continuous paper passing. A structure that conducts heat is required.

  In response to such a request, in Patent Document 3, a heat radiation film is formed on the surface of the reflecting member that faces the fixing member, and heat is radiated from the reflecting member that becomes high temperature during continuous paper passing to the fixing member. Thus, it is described that the maximum temperature of the reflecting member is lowered. According to this configuration, it is possible to achieve the above problem. However, in this method, in addition to the cost for forming the heat radiation film on the reflecting member, the heat transfer rate from the reflecting member to the fixing member is high at the member temperature of the fixing device (about 200 ° C.) under normal use conditions. There was a problem of being slow.

  The present invention eliminates the above-described problems, suppresses the amount of heat transferred from the fixing rotator to the reflecting member in the contact area at startup, and slows the temperature rise of the fixing rotator in the range through which the unfixed image passes. It is an object of the present invention to provide a fixing device and an image forming apparatus using the fixing device.

  In order to solve the above problems, the present invention provides a fixing rotator, a pressure rotator that presses against the fixing rotator to form a fixing nip, a heating source that heats the fixing rotator, and the heating source Fixing means for fixing the toner image to the recording medium when the recording medium carrying the unfixed toner image passes through the fixing nip and has a heating member having a reflecting member that reflects radiant heat toward the fixing rotator. In the apparatus, a heat transfer member that contacts the reflecting member of the heating means and the fixing rotator and transfers heat between the two is provided, and a contact area of the heat transfer member to the fixing rotator is the recording area. The present invention proposes a fixing device characterized in that it is set at a position where it does not overlap with the image passing range through which the unfixed toner image carried by the medium passes in the rotational axis direction of the fixing rotator.

  According to the present invention, the heat that is radiated from the heating source and absorbed without being reflected by the reflecting member is transferred to the fixing rotator, so that the reflecting member can be used even when the heating source is continuously lit, such as during continuous paper feeding. While being able to prevent high temperature, the heat transfer efficiency can be improved by indirectly transferring the heat from the heating source to the fixing rotator.

FIG. 1 is a schematic sectional view showing an example of a color printer as an image forming apparatus provided with the fixing device of the present invention. FIG. 3 is a cross-sectional explanatory view of the fixing device cut along a cross section perpendicular to the rotation axis direction of the fixing rotator within the image passing range showing the first embodiment of the present invention. FIG. 3 is a cross-sectional explanatory view of the fixing device cut along a cross section perpendicular to the rotation axis direction of the fixing rotator outside the image passing range, showing Embodiment 1 of the present invention. FIG. 6 is an explanatory diagram of the fixing device as viewed in a state where the rotation axis direction of the fixing rotator is horizontal. It is a graph which shows the temperature distribution of the outer peripheral surface of the fixing rotation body in the position along a contact region and a rotation direction. 6 is a graph showing the temperature of the outer peripheral surface of the fixing rotator along the rotation axis direction of the fixing rotator. It is a graph which shows the temperature of the outer peripheral surface of a reflection member and a fixing rotary body when heat is continuously radiated from a heating source such as during continuous paper feeding. FIG. 9 is a cross-sectional explanatory view of the fixing device cut along a cross section perpendicular to the rotation axis direction of the fixing rotator within the image passing range showing Embodiment 2 of the present invention. FIG. 10 is a cross-sectional explanatory view of the fixing device cut along a cross section perpendicular to the rotation axis direction of the fixing rotator outside the image passing range, showing Embodiment 2 of the present invention. FIG. 6 is an explanatory diagram of the fixing device as viewed in a state where the rotation axis direction of the fixing rotator is horizontal.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each of the drawings for explaining the embodiments of the present invention, components such as members and components having the same function or shape are given the same reference numerals as much as possible to simplify the explanation. To do.

  FIG. 1 is a schematic sectional view showing an example of a color printer as an image forming apparatus 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. It touches. 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 an alignment roller 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 alignment roller 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 alignment roller 35 that has not yet started to rotate and forms a so-called loop, thereby registering the recording medium. . Thereafter, rotation of the alignment roller 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.

  The above description is a printing operation when a full-color image is formed on a recording medium. The image forming apparatus forms a single color image using any one of the four image forming units 1a, 1b, 1c, and 1d, or uses two or three image forming units to form two colors or three colors. It is of course possible to form a color image.

  2 to 4 show an outline of the fixing device according to the first embodiment of the present invention, and FIG. 2 is an explanatory cross-sectional view of the fixing device cut along a cross section perpendicular to the rotation axis direction of the fixing rotator within the image passing range. . 3 is an explanatory cross-sectional view of the fixing device taken along a section perpendicular to the rotation axis direction of the fixing rotator outside the image passing range, and FIG. 4 is viewed so that the rotation axis direction of the fixing rotator is horizontal. 2 is an explanatory diagram of a fixing device. FIG.

  2 to 4, the fixing rotator 51 and the pressure rotator 61 are disposed opposite to each other in the fixing device so as to be relatively pressurized, so that the fixing rotator 51 and the pressure rotator 61 are interposed. A fixing nip 71 is formed on the substrate. In the fixing nip 71, a frictional force is generated between the fixing rotator 51 and the pressure rotator 61. When one of the fixing rotator 51 and the pressure rotator 61 is driven to rotate, the other rotates together. To do. The sheet-like recording medium P carrying the unfixed toner image T is sandwiched between the fixing rotator 51 and the pressure rotator 61 in the fixing nip 71, and is conveyed along with the respective rotations. Simultaneously with this conveyance, the toner image T is fixed to the recording medium P by applying heat and pressure to the toner image T on the recording medium P from the fixing rotator 51 and the pressure rotator 61 at the fixing nip 71. 4 indicates the image passing range of the recording medium.

  The fixing device 50 in this embodiment is provided such that a heating source 81 covered with a reflection member 82 is positioned on the outer peripheral surface of the fixing rotator 51 as a heating unit, and the heating unit defines a heating region A1 of the fixing rotator 51. Heated from outside by radiant heat. By directly heating the outer peripheral surface of the fixing rotator 51 in contact with the toner image T at the fixing nip 71, the start-up time can be shortened compared to the type in which the inner peripheral surface of the fixing rotator 51 is heated. It becomes possible.

  The reflecting member 82 reflects the radiant heat radiated from the heating source 81 in all directions, thereby concentrating the radiant heat from the heating source 81 in the heating area A1 and improving the heat transfer efficiency from the heating source 81 to the heating area A1. . Of the reflecting member 82, at least the surface facing the heating source 81 needs to have a high reflectance with respect to the radiant heat from the heating source. Specifically, it is desirable that the reflecting member 82 be a material having a high surface reflectance in the air such as a metal material, or a member having a structure for improving the reflectance such as an aluminum vapor deposition film on the surface.

  In this embodiment, the fixing rotator 51 is formed by laminating a base material layer 51a, an elastic layer 51b, and a release layer (not shown) in order from the inner peripheral side. The base material layer 51a needs to be highly rigid in order to suppress deformation of the fixing rotator 51 due to the pressure from the pressure rotator 61. As a material, for example, a metal material such as nickel, stainless steel, and aluminum is desirable. In the present embodiment, the base material layer 51a has a hollow cylindrical shape, but it may be solid. The elastic layer 51b desirably has high elasticity and low thermal conductivity. For example, a highly elastic resin material such as silicone rubber or foamed silicone rubber is desirable. Due to the deformation of the elastic layer 51b, even when the recording medium P passing through the fixing nip 71 has a concavo-convex shape on the surface, it is possible to improve the non-uniform pressure and thermal conductivity on the toner image T, and the toner fixing quality Will improve. Further, the outer peripheral surface of the fixing rotator 51 heated in the heating region A1 is thermally insulated from the base material layer 51a by the elastic layer 51b, thereby preventing heat from escaping from the outer peripheral surface of the fixing rotator 51 to the base material layer 51a. it can. The release layer (not shown) is made of a material having a high releasability between the toner image T and the recording medium P. For example, PFA (tetrafluoroethylene perfluoroalkyl vinyl ether copolymer), PTFE (tetrafluoroethylene resin) Preferably, polyimide, polyetherimide, PES (polyether sulfide), or the like is used.

  The pressure rotator 61 includes a cored bar 61a formed of a metal material and an elastic layer 61b formed of an elastic material such as silicone rubber or foamed silicone rubber. Although not shown, by providing a release layer formed of a fluorine-based resin such as PFA or PTFE on the outer peripheral portion of the elastic layer, the peelability of the toner image T and the recording medium P can be improved.

  In this embodiment, the heat transfer member 83 is provided on both sides outside the image passage range W in the reflection member 82 of the heating means. The heat transfer member 83 is made of a metal material having a high thermal conductivity, and one end is fixed to the reflecting member 82 and the other end is a free end and is in contact with the surface of the fixing rotator 51. Reference numeral B <b> 1 is a contact region B <b> 1 where the heat transfer member 83 contacts the fixing rotator 51.

  As described above, the heat transfer member 83 having high thermal conductivity is also in contact with the fixing rotator 51 and the reflecting member 82, thereby generating heat transfer by heat conduction between the reflecting member 82 and the fixing rotator 51. I am letting. It is desirable that the heat transfer member 83 has a spring property with respect to a direction substantially perpendicular to the peripheral surface of the fixing rotating body 51 in the contact region B1 by a method such as a plate spring shape. That is, the heat transfer member 83 is brought into contact with the peripheral surface of the fixing rotator 51 by the elastic force of its plate spring. As a result, even when the position of the peripheral surface of the fixing rotator 51 in the contact area B1 varies due to the rotational shake of the fixing rotator 51, the contact between the fixing rotator 51 and the heat transfer member 83 in the contact area B1. Pressure and heat transfer characteristics can be stably maintained.

  The contact area B1 is located between the downstream end of the fixing nip 71 and the upstream end of the heating area A1 with respect to the rotation direction R1 of the fixing rotating body 51. FIG. 5 shows an example of the temperature distribution on the outer peripheral surface of the fixing rotator 51 at the position along the contact area B1 and the rotation direction. The fixing rotator 51 rotating in the R1 direction receives a radiant heat from the heating source 81 in the heating region A1, and the temperature rises as it rotates. On the other hand, the heat moves to the pressure rotator 61 in the fixing nip 71. The temperature drops. As a result, the temperature of the region including the contact region B1 from the fixing nip 71 until reaching the heating region A1 is lower than the other positions along the rotation direction. By disposing the contact region B1 at such a position, the heat transfer rate from the reflecting member 82 to the fixing rotating body 51 is increased in the heat conduction between the reflecting member 82 and the fixing rotating body 51 via the heat transfer member 83. .

FIG. 4 also shows the positional relationship between the image passing range W and the contact area B1 with respect to the rotation axis direction of the fixing rotator 51.
The base material layer 51a of the fixing rotator 51 and the cored bar 61a of the pressure rotator 61 are rotatably supported by the side plates 91 and 92 and the support members 101 and 102 via bearings, respectively. The support members 101 and 102 move with respect to the side plates 91 and 92, so that the pressing rotator 61 is brought into and out of contact with the fixing rotator 51, and the area and pressure of the fixing nip 71 can be changed.

  In the present embodiment, the drive gear 111 is fixed to the cored bar 61 a of the pressure rotator 61, and the drive rotator 61 is rotated by driving the drive gear 111, and the drive torque is passed through the fixing nip 71. As a result, the fixing rotator 51 is driven and rotated.

  The distribution of the amount of heat radiated from the heating source 81 in the direction of the rotation axis is set as follows. First, the temperature of the outer peripheral surface of the fixing rotator 51 in the image passing range W is allowed to reach the reload temperature and the fixing temperature in a short time when the fixing device is started up. For this reason, in the image passing range W, the heat quantity distribution is set so that the radiant heat from the heating source 81 reaches with a substantially uniform heat quantity distribution. On the other hand, in a range other than the image passing range W, the temperature of the outer peripheral surface of the fixing rotator 51 is lowered due to heat conduction in the axial direction at the end of the image passing range W, and the fixing temperature may not be maintained. . The calorie distribution is such that the fixing rotator 51 is heated with the minimum calorie necessary to prevent such a problem. As a result, the temperature of the outer peripheral surface of the fixing rotator 51 at the position along the rotation axis direction of the contact area B1 and the fixing rotator 51 when the fixing device is started up from the room temperature is the contact as shown in FIG. The temperature in the region B1 is lower than the temperature in the image passing range W. On the other hand, the reflection member 82 is also averaged over the entire member with respect to the amount of heat absorbed in the image passing range W by the heat conduction inside the member. As a result, the entire member has a temperature distribution in which the temperature is raised substantially uniformly (overlapped in FIG. 6). Therefore, as in the present embodiment, the contact area B1 is arranged so as not to overlap the image passing range W with respect to the rotation axis direction of the fixing rotating body 51. With this configuration, the amount of heat transferred from the fixing rotator 51 to the reflecting member 82 via the heat transfer member 83 in the contact area B1 at the time of start-up is suppressed, and the image passing range W is contacted by the reflection member 82. It is possible to reduce the influence of the temperature increase of the fixing rotator 51 being delayed.

  FIG. 7 shows the temperatures of the reflecting member 82 and the outer peripheral surface of the fixing rotator 51 when heat is continuously radiated from the heating source 81, such as during continuous paper feeding. The reflecting member 82 absorbs part of the radiant heat from the heating source 81, and thus has a temperature higher than the temperature of the outer peripheral surface of the fixing rotating body 51 in the contact region B1. For this reason, the amount of heat is transferred from the reflecting member 82 to the fixing rotator 51 through the heat transfer member 83, and as a result, the temperature of the reflecting member 82 is lowered while maintaining the substantially uniform temperature as a whole due to heat conduction inside the member. Thereby, the temperature of the whole member of the reflection member 82 can be reduced. Further, the amount of heat transferred from the reflecting member 82 to the fixing rotator 51 in the contact area B1 acts in a direction in which the temperature of the fixing rotator 51 in the image passing range W is also increased by heat conduction in the rotation axis direction of the fixing rotator 51. . With this action, the heat transfer efficiency from the heating source 81 to the fixing rotator 51 can be increased.

  As described above, the heat radiated from the heating source 81 and absorbed without being reflected by the reflecting member 82 is transferred to the fixing rotating body 51, so that it is reflected even when the heating source 81 is continuously lit, such as during continuous paper feeding. It can prevent that the member 82 becomes high temperature. Therefore, the heat transfer efficiency can be increased by indirectly transferring the heat from the heating source 81 to the fixing rotator 51. In the image passing range W through which the unfixed image passes in the fixing rotator 51, heat is transferred from the fixing rotator 51 to the reflecting member 82 in the contact area at the time of start-up by preventing the reflecting member 82 from contacting the fixing rotator 51. Reduce the amount of heat. Therefore, it is possible to reduce the influence of the temperature increase of the fixing rotator 51 in the image passing range W being delayed.

  In a state where the recording medium P is not expected to reach the fixing device 50 (non-sheet passing state), the fixing device 50 of the present embodiment stops heat radiation from the heating source 81. Further, in order to suppress consumption of energy necessary for driving the drive gear 111, the fixing device stops the rotation of the fixing rotating body 51 or reduces the rotation speed. However, the fixing device detects the temperature of the reflecting member 82 or the fixing rotator 51 by some temperature detection means (not shown), and controls the rotation speed of the fixing rotator 51 via the drive gear 111 according to the detected temperature. It is also possible.

  For example, when the reflecting member 82 is at a temperature higher than a certain temperature, the heat transfer speed from the fixing rotator 51 to the pressure rotator 61 in the fixing nip 71 is maintained by maintaining the rotation speed of the fixing rotator 51. Is maintained. Accordingly, the temperature of the outer peripheral surface of the fixing rotator 51 in the contact region B1 can be reduced as compared with the case where the rotational speed is reduced. As a result, it is possible to increase the rate of temperature decrease of the reflecting member 82 due to heat transfer to the fixing rotator 51 in the contact region B1, and to suppress thermal deterioration of the reflecting member 82. As described above, when the reflection member 82 is at a high temperature, the heat transfer efficiency from the reflection member 82 to the fixing rotator 51 is increased by increasing the rotation speed of the fixing rotator 51, thereby reducing the temperature of the reflection member. It is done. Further, when the reflecting member 82 is at a low temperature, the energy consumption for rotationally driving the fixing rotator 51 can be suppressed by reducing the rotation speed of the fixing rotator 51.

  When the temperature of the reflecting member 82 is higher than a certain value as compared with the temperature of the fixing rotator 51, the amount of heat received from the reflecting member 82 in the contact region B1 when the fixing rotator 51 rotates once. The amount of heat applied to the pressure rotator 61 at the fixing nip 71 is exceeded. In such a state, by maintaining the rotation speed of the fixing rotator 51, the temperature of the outer peripheral surface of the fixing rotator 51 can be increased by heat conduction from the reflecting member 82. Then, it is possible to reduce the amount of heat required to start up the fixing device 50 when the recording medium P reaches the fixing device again. At this time, the area of the fixing nip 71 can be reduced by separating the position of the pressure rotator 61 from the fixing rotator 51, and the amount of heat transferred from the fixing rotator 51 to the pressure rotator 61 can be reduced. It is. As a result, the amount of increase in the temperature of the outer peripheral surface of the fixing rotator 51 is increased.

  As described above, when the temperature of the reflecting member 82 is higher than the temperature of the fixing rotator 51, the fixing rotator 51 is increased by heat transfer from the reflecting member 82 to the fixing rotator 51 by increasing the rotation speed of the fixing rotator 51. Can be heated. Further, when the temperature of the reflecting member 82 is at the same level as or lower than the temperature of the fixing rotator 51, the energy consumption for rotationally driving the fixing rotator 51 is suppressed by slowing the rotation speed of the fixing rotator 51. be able to.

  8 and 9 are configuration diagrams showing an outline of the fixing device according to the second embodiment of the present invention. 8 is a cross-sectional view of the fixing device cut along a cross section perpendicular to the rotation axis direction of the fixing rotator at a position including the image passing range W illustrated in FIG. 10, and FIG. 9 is a position including the contact region B1 in FIG. FIG. 4 is a cross-sectional view of the fixing device cut along a cross section perpendicular to the rotation axis direction of the fixing rotator.

  In this embodiment, in order to shorten the start-up time of the fixing device 50, the fixing rotating body 51 is thinned to reduce the heat capacity. Further, since the heat conduction speed from the inner peripheral surface to the outer peripheral surface of the fixing rotator 51 is increased by the thinning, even if the heating source 81 is arranged inside the fixing rotator 51, the heating source 81 is installed outside. Compared to the case, the heating rate of the fixing rotator 51 can be made comparable. As a result, although the configuration of the second embodiment is more complicated than that of the first embodiment, when the diameters of the fixing rotator 51 and the pressure rotator 61 are substantially the same as those of the first embodiment, the configuration is small and the startup time is small. Short fixing device can be realized.

  In this embodiment, in order to form a fixing nip 71 between the fixing rotator 51 and the pressure rotator 61, a nip forming member 121 installed inside the fixing rotator 51 pressurizes and rotates the fixing rotator 51. The body 61 is pressurized. The nip forming member 121 is fixed to the fixing device so as not to rotate, and the fixing rotator 51 slides on the nip forming member 121.

  The thickness of the fixing rotating body 51 needs to be determined in consideration of flexibility and rigidity in addition to the heat capacity, and specifically, about 23 μm to 2 mm is desirable. The configuration of the fixing rotator 51 in the present embodiment is a configuration in which a base material layer, an elastic layer, and a release layer are laminated in order from the inner peripheral side, as in the first embodiment. However, when the performance requirement regarding image quality is not high, a two-layer structure including a base material layer and a release layer may be used except for the elastic layer.

  The base material layer is preferably a resin material such as polyimide or a metal material such as nickel or stainless steel having a thickness of 20 to 100 μm from the viewpoint of compatibility between flexibility and rigidity. Further, for the purpose of improving the slidability with the nip forming member 121 and the absorption rate of the radiant heat from the heating source 81, a coating material may be coated on the inner peripheral surface of the base material layer. For example, a fluorine resin or silicone oil coating is desirable for improving the slidability, and a black paint coating is desirable for improving the radiant heat absorption rate.

  The elastic layer is preferably 50 to 300 [mu] m in thickness and uses an elastic material such as silicone rubber. Due to the deformation of the elastic layer, even when the recording medium P passing through the fixing nip 71 has a concavo-convex shape on the surface, it is possible to improve non-uniform pressure and thermal conductivity on the toner image T, and the toner fixing quality is improved. improves.

  The release layer has a thickness of 3 to 50 μm and is made of a material having a high releasability between the toner image T and the recording medium P. For example, PFA (tetrafluoroethylene perfluoroalkyl vinyl ether copolymer), PTFE (4 fluorine It is desirable to use (Ethylene resin), polyimide, polyetherimide, PES (polyether sulfide) and the like. In particular, fluorine resin materials such as PFA and PTFE are desirable because they have a low coefficient of friction and good toner releasability. In this example, the release layer was made of PFA having a thickness of 20 μm.

  The material of the nip forming member 121 is preferably a highly heat-resistant resin material such as LCP (liquid crystal polymer), polyimide, or PAI (polyamideimide), but may be a metal material such as aluminum or stainless steel. Although not shown, the sliding frictional resistance of the fixing rotating body 51 with respect to the nip forming member 121 is reduced by means such as winding a material having a low friction coefficient around the nip forming member 121 as a sheet, or coating and coating. Can be made.

  In this embodiment, the reflecting member 82 is disposed at a position that shields the nip forming member 121 from the heating source 81. With this arrangement, it is possible to suppress a decrease in heat transfer efficiency to the fixing rotator 51 due to the radiant heat from the heating source 81 being absorbed by the nip forming member 121.

  In this embodiment, the heat transfer member 83 is in contact with the inner peripheral surface of the fixing rotator 51 in the contact region B1, and is also in contact with the reflection member 82 at the same time. With this configuration, heat transfer by heat conduction is generated between the reflecting member 82 and the fixing rotating body 51. The material of the heat transfer member 83 is preferably a material having high thermal conductivity such as a metal material, and the heat transfer member 83 and the inner peripheral surface of the fixing rotator 51 in the contact region B1 by a method such as making the heat transfer member 83 into a leaf spring shape. It is desirable that the heat transfer member 83 has a spring property with respect to a substantially vertical direction. As a result, even when the position of the inner peripheral surface of the fixing rotator 51 in the contact region B1 varies due to the rotational shake of the fixing rotator 51, between the fixing rotator 51 and the heat transfer member 83 in the contact region B1. Contact pressure and heat transfer characteristics can be stably maintained. Particularly in this embodiment, since the roundness of the fixing rotator 51 is likely to decrease due to the thinning, the positional variation of the contact region B1 increases, and therefore the spring property of the heat transfer member 83 is particularly useful.

  FIG. 10 is a schematic view of the fixing device according to the second embodiment observed in such a manner that the rotation axis direction of the fixing rotator 51 is horizontal, and the image passing area W and the contact area B1 with respect to the rotation axis direction of the fixing rotator 51. The positional relationship is also shown.

  The nip forming member 121 and the end flanges 131 and 132 are fixedly supported by the side plates 91 and 92, respectively. The end flanges 131 and 132 are inscribed in the rotation axis direction end of the fixing rotator 51, and the shape of the fixing rotator 51 is maintained by the fixing rotator 51 sliding around. The end flanges 131 and 132 also have an effect of stopping the fixing rotating body 51 from moving in the direction of the rotation axis.

  The pressure rotator 61 has a cored bar portion 61a rotatably supported by support members 101 and 102 via bearings and the like. As the support members 101 and 102 move relative to the side plates 91 and 92, the pressing and rotating body 61 is brought into and out of contact with the fixing rotating body 51.

  The drive gear 111 is fixed to the cored bar portion 61 a of the pressure rotator 61, and the drive rotator 61 is rotated by driving the drive gear 111, and the driving torque is transmitted to the fixing rotator via the fixing nip 71. By being transmitted to 51, the fixing rotator 51 is driven to rotate.

The temperature distribution of the outer peripheral surface of the fixing rotator 51 and the reflecting member 82 in the present embodiment is the same as the temperature distribution of the first embodiment illustrated in FIGS.
The reflection member 82 and the heat transfer member 83 are not necessarily separate members, and may be the same member as long as the conditions described in the two embodiments described above are satisfied.

50 fixing device 51 fixing rotator 61 pressure rotator 71 fixing nip 81 heating source 82 reflecting member 83 heat transfer member A1 heating area B1 contact area P recording medium T toner image W image passing range

JP 2010-020248 A JP 2005-234290 A JP 2009-180789 A

Claims (8)

A fixing rotator, a pressure rotator that presses against the fixing rotator to form a fixing nip, a heating source that heats the fixing rotator, and radiant heat from the heating source is reflected toward the fixing rotator. A fixing device for fixing a toner image on a recording medium when the recording medium carrying an unfixed toner image passes through the fixing nip and is conveyed, and includes a heating member having a reflecting member.
Providing a heat transfer member that contacts the reflecting member of the heating means and the fixing rotating body, and transfers heat between the two;
The contact area of the heat transfer member with the fixing rotator is set at a position where the image passing range through which an unfixed toner image carried by the recording medium passes does not overlap with the rotation axis direction of the fixing rotator. A fixing device.   The fixing rotator is provided with a heating area where the heating means is heated, and the contact area of the heat transfer member to the fixing rotator is from the downstream end of the fixing nip in the rotation direction of the fixing rotator. The fixing device according to claim 1, wherein the fixing device is located between the upstream end of the region.   The fixing device according to claim 1, wherein the heating source of the heating unit and the reflection member are located outside the fixing rotating body.   The fixing nip is formed by holding the fixing rotator between the nip forming member and the pressure rotator, and the heating source of the heating unit and the reflecting member are inside the fixing rotator. The fixing device according to claim 1, wherein the reflection member is disposed at a position that shields the nip forming member from the heating source.   5. The fixing device according to claim 1, wherein the heat transfer member has a spring property to press in a direction in contact with the fixing rotating body.   6. The fixing device according to claim 1, wherein a rotation speed of the fixing rotator is controlled in accordance with a temperature of the reflection member in a state where the recording medium is not conveyed.   The fixing device according to claim 1, wherein a rotation speed of the fixing rotator is controlled in accordance with a temperature difference between the reflecting member and the fixing rotator in a state where the recording medium is not conveyed.   An image forming apparatus comprising the fixing device according to claim 1.

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