Fixing device and image forming apparatus

Abstract

To provide a fixing device and an image forming apparatus that prevent deformation of a heat conduction member.SOLUTION: A fixing device comprises: a cylindrical rotating body; a pressure member that forms, with the rotating body, a fixing nip at which a toner image is fixed to a sheet; a heater that is arranged in an internal space of the rotating body, and that has a substrate and a heating element provided on the substrate and heating the rotating body upon energization; a heater holder that holds the heater; and a heat conduction member that is arranged between the heater and the heater holder. The fixing nip conveys the sheet in a direction parallel to a short direction orthogonal to a longitudinal direction of the heater. The heater has projections that extend toward the heater holder from a surface of the heater provided on the opposite side of the fixing nip. The projections face the heat conduction member in the longitudinal direction, and are arranged not to overlap the heat conduction member when seen in the short direction.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a fixing device that fixes a toner image on a sheet and an image forming apparatus including the fixing device. [Background technology]

[0002] According to Patent Document 1, a fixing device is proposed that includes a cylindrical film, a heater that contacts the film, a support member that supports the heater, and a pressure roller that forms a nip portion with the heater through the film, and fixes a toner image to a sheet. A heat-conducting member with high thermal conductivity is attached to the surface of the heater opposite to the surface that contacts the film, and this heat-conducting member equalizes the temperature of the heater in the longitudinal direction. The heat-conducting member repeatedly expands and contracts in accordance with changes in the heater temperature, so that it is displaced in the longitudinal direction relative to the heater. Patent Document 1 also proposes a configuration in which a bent portion is provided in the heat-conducting member, and the outer bent portion is inserted into a hole in the support member to lock the heat-conducting member to the support member.

[0003] Also, Patent Document 2 proposes a fixing device that includes a heater having protrusions on its back surface and a heat conductive member having grooves that fit with the protrusions. The protrusions of the heater fit with the grooves of the heat conductive member, restricting the heat conductive member from moving in the longitudinal direction relative to the heater. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-049618 A [Patent Document 2] Patent Publication No. 2022-102905 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Documents 1 and 2, the bent portions and grooves of the heat conductive member are fitted to the support member or heater, thereby preventing the heat conductive member from being displaced. However, when the bent portions and grooves of such a heat conductive member become hot, excessive thermal expansion occurs in the fitted bent portions and grooves, which may cause deformation of the heat conductive member. In addition, when the heat conductive member is subjected to bending or punching, there is a risk that the heat conductive member may be deformed or damaged when the heat conductive member thermally expands due to residual stress caused by the processing.

[0006] SUMMARY OF THE PRESENT DISCLOSURE In view of the above, an object of the present invention is to provide a fixing device and an image forming apparatus in which deformation of a heat conductive member is suppressed. [Means for solving the problem]

[0007] The present invention is characterized in that a fixing device comprises a cylindrical rotating body, a pressure member which forms a fixing nip together with the rotating body to fix a toner image to a sheet, a heater arranged in the internal space of the rotating body, the heater having a substrate and a heating element which is provided on the substrate and heats the rotating body when electricity is passed through it, a heater holder which holds the heater, and a heat conductive member which is arranged between the heater and the heater holder, wherein the fixing nip transports a sheet in a direction parallel to a short direction which is perpendicular to the longitudinal direction of the heater, and the heater has a protrusion which extends from a surface of the heater on the opposite side to the fixing nip towards the heater holder, and the protrusion faces the heat conductive member in the longitudinal direction and is arranged so as not to overlap the heat conductive member when viewed in the short direction. Effect of the Invention

[0008] According to the present invention, deformation of the heat conducting member can be suppressed. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing an image forming apparatus according to a first embodiment. [Diagram 2] FIG. [Diagram 3]FIG. 4 is a cross-sectional view showing a cross section parallel to the longitudinal direction of the peripheral configuration of the heater. [Figure 4] 4A is a cross-sectional view showing the CS1-CS1 cross section shown in FIG. 3, and FIG. 4B is a cross-sectional view showing the CS2-CS2 cross section or the CS3-CS3 cross section shown in FIG. [Diagram 5] 4A is a plan view showing the heat conductive member and the protrusions in the first embodiment, FIG. 4B is a plan view showing a modified example of the protrusions, and FIG. 4C is a plan view showing another modified example of the protrusions. [Figure 6] 5 is a cross-sectional view illustrating thermal expansion of a heater and a heat conductive member. FIG. [Figure 7] 6 is a graph showing the change in the longitudinal length of the gap when the heater and the thermally conductive member thermally expand. [Figure 8] FIG. 4 is a cross-sectional view showing a cross section parallel to the longitudinal direction of the peripheral configuration of the heater according to the first modified example of the first embodiment. [Figure 9] 1A is a plan view showing a protrusion according to Modification 2 of Example 1, FIG. 1B is a plan view showing a modification of the protrusion, and FIG. 1C is a plan view showing another modification of the protrusion. [Figure 10] FIG. 10A is a front view showing the front surface of a heater according to a second embodiment, and FIG. [Figure 11] FIG. [Figure 12] FIG. 4 is a front view showing the rear surface of the heater with a thermally conductive member disposed on the heater. [Figure 13] FIG. 13 is a cross-sectional view showing the cross section 13A-13A of FIG. [Figure 14] FIG. 13 is a front view showing the rear surface of the heater according to the first modified example of the second embodiment. [Figure 15] FIG. 15 is a cross-sectional view showing the cross section 15A-15A of FIG. [Figure 16] FIG. 13 is a front view showing the rear surface of the heater according to Modification 2 of Example 2. [Figure 17] FIG. 17 is a cross-sectional view showing the cross section 17A-17A of FIG. [Figure 18] FIG. 11A is a front view showing the front surface of a heater in Example 3, and FIG. [Figure 19] FIG. 4 is a front view showing the rear surface of the heater with a thermally conductive member disposed on the heater. [Figure 20] FIG. 4 is a cross-sectional view showing a cross section parallel to the longitudinal direction of the peripheral configuration of the heater. [Figure 21] FIG. 13 is a front view showing the rear surface of the heater according to the first modified example of the third embodiment. [Figure 22] FIG. 4 is a front view showing the rear surface of the heater with a thermally conductive member disposed on the heater. [Figure 23] FIG. 13 is a front view showing the rear surface of the heater according to Modification 2 of Example 3. [Figure 24] FIG. 4 is a front view showing the rear surface of the heater with a thermally conductive member disposed on the heater. [Diagram 25] FIG. 4 is a cross-sectional view showing a cross section parallel to the longitudinal direction of the peripheral configuration of the heater. [Figure 26] FIG. 11 is a perspective view showing a heater holder according to a fourth embodiment. [Figure 27] 27(a) is a plan view showing the adhesive joint, (b) is a cross-sectional view showing the 27B-27B cross section of FIG. 27(a), and (c) is a cross-sectional view showing the 27C-27C cross section of FIG. 27(a). [Figure 28] FIG. 1A is a plan view showing an adhesive portion according to variant example 1 of embodiment 4; FIG. 1B is a plan view showing an oval-shaped adhesive portion; FIG. 1C is a plan view showing a square-shaped adhesive portion; FIG. 1D is a plan view showing a rectangular-shaped adhesive portion; and FIG. 1E is a plan view showing another rectangular-shaped adhesive portion. [Figure 29] 29(a) is a plan view showing an adhesive portion relating to variant example 2 of embodiment 4, (b) is a cross-sectional view showing the 29B-29B section of FIG. 29(a), (c) is a cross-sectional view showing the 29C-29C section of FIG. 29(a), and (d) is a cross-sectional view showing the 29D-29D section of FIG. 29(a). [Diagram 30] 30(a) is a plan view showing an adhesive portion relating to variant example 3 of embodiment 4, (b) is a cross-sectional view showing the 30B-30B section of FIG. 30(a), (c) is a cross-sectional view showing the 30C-30C section of FIG. 30(a), and (d) is a cross-sectional view showing the 30D-30D section of FIG. 30(a). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] <Example 1> [Overall Configuration of Image Forming Apparatus] First, a first embodiment of the present invention will be described. FIG. 1 is a schematic diagram showing an image forming apparatus 100. The image forming apparatus 100 according to the first embodiment is an electrophotographic laser beam printer. As shown in FIG. 1, the image forming apparatus 100 has a feed cassette 35 that is provided so as to be insertable and removable from the main body of the image forming apparatus 100, and a feed roller 10. The image forming apparatus 100 also has an image forming section 36 that forms an image (toner image) on a sheet P fed by the feed roller 10, a fixing device 6, and a pair of discharge rollers 9. In this embodiment, the sheet as the recording material includes paper such as paper and envelopes, plastic film such as an overhead projector sheet (OHP), cloth, and the like.

[0011] When an image formation command is output to the image forming apparatus 100, an image forming process is started by the image forming unit 36 ​​based on image information input from an external computer connected to the image forming apparatus 100 or an image reading device connected as an option. The image forming unit 36 ​​has a process cartridge having a photosensitive drum 1, a charging roller 2, a developing roller 4, a cleaning blade 7, etc., a laser scanner 33, and a transfer roller 5. The photosensitive drum 1 rotates in the direction of arrow r1 by a driving force transmitted from a driving motor (not shown).

[0012] The image forming apparatus 100 is provided with a video controller 31 that converts image information input from an external personal computer or the like into image creation information. A laser scanner 33 receives a light emission instruction from a control unit 32 based on the image creation information received from the video controller 31, and irradiates a laser beam L toward the photosensitive drum 1. At this time, the photosensitive drum 1 is charged in advance by a charging roller 2, and an electrostatic latent image is formed on the photosensitive drum 1 by irradiating it with the laser beam L. Thereafter, the electrostatic latent image is developed by a developing roller 4, and a toner image is formed on the photosensitive drum 1.

[0013] In parallel with the above-mentioned image forming process, a sheet P stacked in a feeding cassette 35 is sent out by a feeding roller 10. The sheet P fed by the feeding roller 10 is conveyed by a pair of conveying rollers 37 toward a transfer nip NT formed by the photosensitive drum 1 and a transfer roller 5. A transfer bias is applied to the transfer roller 5, so that the toner image formed on the photosensitive drum 1 is transferred to the sheet P at the transfer nip NT. Toner remaining on the photosensitive drum 1 is collected by a cleaning blade 7.

[0014] The sheet P onto which the toner image has been transferred by the transfer nip NT is subjected to a heat and pressure treatment by a fixing nip NF of the fixing device 6, whereby the toner image is fixed. Then, the sheet P onto which the toner image has been fixed is discharged onto a discharge tray 38 by a pair of discharge rollers 9.

[0015] [Configuration of the fixing device] Next, the configuration of the fixing device 6 will be described with reference to FIG. 2. FIG. 2 is a cross-sectional view showing the fixing device 6. As shown in FIG. 2, the fixing device 6 has a fixing film unit 19, a pressure roller 17, and the like. The fixing film unit 19 is pressed toward the pressure roller 17 by a pressure unit (not shown), and forms a fixing nip NF together with the pressure roller 17. Note that the pressure roller 17 may be pressed toward the fixing film unit 19. The sheet P holding the unfixed toner image T on its upper surface is introduced into the fixing nip NF by being conveyed in the sheet conveying direction p0, and is heated and pressurized in the fixing nip NF, where the unfixed toner image is fixed.

[0016] The fixing film unit 19 has a fixing film 13 formed in a flexible cylindrical shape, and a heater 11 that contacts the inner surface of the fixing film 13 and heats the fixing film 13. The fixing film unit 19 also has a heater holder 12 that holds the heater 11, and a heat conductive member 18 that is arranged between the heater 11 and the heater holder 12. The fixing film 13 as a rotating body and a film can rotate in the direction of an arrow r13 while contacting the sheet P transported in the sheet transport direction p0. Note that instead of the fixing film 13, a flexible endless belt or the like may be used. The heater 11 and a pressure roller 17 sandwich the fixing film 13.

[0017] The pressure roller 17 as a pressure member has a metal core and a rubber layer, and contacts the outer peripheral surface of the fixing film 13. It can be said that the pressure roller 17 forms a fixing nip NF that sandwiches and conveys the sheet P together with the heater 11 via the fixing film 13. The pressure roller 17 is rotated in the direction of arrow r17 by a motor (not shown) via a gear. When the pressure roller 17 rotates, the fixing film 13 rotates following the rotation of the pressure roller 17.

[0018] Each member constituting the fixing device 6 extends in a longitudinal direction LD (see FIG. 3), which is a direction perpendicular to the sheet conveying direction p0 and the thickness direction TD of the sheet P, that is, a direction from the front to the back in FIG. 2. The dimension of each member constituting the fixing device 6 in the longitudinal direction LD is set corresponding to the size of the sheet P that can be passed through the fixing device 6, and in the fixing device 6 of this embodiment, the length is set to correspond to the longitudinal feed (215.9 mm x 279.4 mm) of an LTR size sheet. The details of the dimension of the longitudinal direction LD of each member will be described later. In addition, the direction perpendicular to the longitudinal direction LD and the thickness direction TD is the transverse direction SD (see FIG. 4(a)), and the transverse direction SD is a direction parallel to the sheet conveying direction p0 of the sheet P in the fixing nip NF.

[0019] [Heater peripheral configuration] Next, the detailed configuration of the periphery of the heater 11 will be described. FIG. 3 is a cross-sectional view showing a cross section parallel to the longitudinal direction of the peripheral configuration of the heater 11. FIG. 4(a) is a cross-sectional view showing the CS1-CS1 cross section shown in FIG. 3. FIG. 4(b) is a cross-sectional view for explaining protrusions 11d and 11e described later, and is a cross-sectional view showing the CS2-CS2 cross section or the CS3-CS3 cross section shown in FIG. 3. In each figure, the upper side of the figure is the back side of the member, and the lower side is the front side of the member. In addition, for convenience of explanation, each member in the figure is displayed in an expanded form, but in the actual fixing device 6, as shown in FIG. 2, the heater holder 12 to the fixing film 13 are configured in close contact with each other.

[0020] As shown in FIG. 3, the heater 11 has a substrate 11a, a resistance heating element 11b as a heating element, and a protective layer 11c, and is disposed in the internal space of the fixing film 13. The substrate 11a is made of a highly insulating ceramic substrate such as alumina (aluminum oxide) or AlN (aluminum nitride), or a heat-resistant resin substrate such as polyimide. The resistance heating element 11b is a layer of heat-generating paste such as Ag / Pd (silver palladium), RuO2 (ruthenium dioxide), or Ta2N (tantalum nitride) printed in an arbitrary shape. The protective layer 11c is made of a highly insulating material such as glass or polyimide, and covers the resistance heating element 11b for protection and insulation of the resistance heating element 11b. The heater 11 of this embodiment is configured by laminating the Ag / Pd resistance heating element 11b and the glass protective layer 11c on the alumina ceramic substrate 11a. The resistance heating element 11b generates heat when an AC current is passed through it from a power supply unit (not shown).

[0021] The dimensions of the substrate 11a are 270 mm in the longitudinal direction, 10 mm in the lateral direction, and 1.0 mm in the thickness direction. The longitudinal dimension of the resistance heating element 11b is 218 mm. The thickness (thickness direction dimension) of the protective layer 11c including the resistance heating element 11b is approximately 60 μm, which is much smaller than the thickness of the substrate 11a.

[0022] The surface of the heater 11 comes into contact with the back surface of the fixing film 13 via heat-resistant grease 22 as a lubricant, and the heater 11 heats the fixing film 13. The heat-resistant grease 22 is intended to reduce friction between the surface of the fixedly supported heater 11 and the back surface of the rotating fixing film 13, and to reduce friction between the surface of the heat conductive member 18 and the back surface of the heater 11, and is made by dispersing fluororesin in fluorine-based oil.

[0023] The back surface of the heater 11 comes into contact with the heat conducting member 18 via heat resistant grease 22. The heat conducting member 18 is made of a metal plate made of a metallic material, and in this embodiment, a flat aluminum material (JIS standard: A5052) with a thickness of 0.3 mm is used. The thermal conductivity of the heat conducting member 18 is 140 W / m·K, which is higher than the thermal conductivity of the substrate 11a of the heater 11, which is 20 W / m·K. By having the heat conducting member 18 with high thermal conductivity come into contact with the back surface of the heater 11, the temperature difference occurring in the longitudinal direction LD of the heater 11 can be leveled out.

[0024] The thermal expansion coefficient of the heat conductive member 18 is 24×10 -6 [1 / K], and the thermal expansion coefficient of the substrate 11a of the heater 11 is 7.6×10 -6 [1 / K], and the difference is large. Meanwhile, the heat conductive member 18 and the heater 11 are held in close contact with each other. Therefore, the rear surface of the heater 11 may hinder the dimensional change caused by thermal expansion of the heat conductive member 18 due to frictional force, which may cause deformation or damage to the heat conductive member 18. To avoid such a problem, heat-resistant grease 22 is applied between the rear surface of the heater 11 and the front surface of the heat conductive member 18 to reduce friction. The heat-resistant grease 22 is the same as the heat-resistant grease 22 applied to the front surface of the heater 11, but it is not necessarily required that they are the same.

[0025] A thermistor 20 serving as a temperature detection element is in contact with the back surface of the heat conductive member 18, and the thermistor 20 detects the temperature of the heater 11 via the heat conductive member 18. The thermistor 20 is connected to a control unit 32 (see FIG. 1) by lead wires 21, and provides the detected temperature information to the control unit 32. The control unit 32 controls the AC current passed through the resistance heating element 11b via the power supply unit so that the heater 11 reaches a desired temperature. In this embodiment, the temperature of the thermistor 20 (or heater 11) is controlled to be 200° C. when LTR size paper is fed at a conveying speed of 50 ppm.

[0026] Similarly to the thermistor 20, a thermoswitch (not shown) serving as a safety element is in contact with the heater 11 via a heat conductive member 18. The thermoswitch is arranged in series with the resistance heating element 11b on the electric circuit of the power supply unit, and when the temperature of the heater 11 exceeds the operating temperature of the thermoswitch, it physically cuts off the electric circuit and stops the flow of electricity to the resistance heating element 11b. The operating temperature of the thermoswitch in this embodiment is 270°C. The thermoswitch is intended to prevent the fixing device 6 from becoming particularly hot under irregular operating conditions, such as when an unexpected sheet P, such as cardboard, is fed into the image forming apparatus 100, and does not operate during normal use.

[0027] In addition, the longer the length of the heat conductive member 18 in the longitudinal direction LD (hereinafter referred to as the longitudinal length), the greater the effect of leveling the temperature of the heater 11, but if the length is too long, the temperature in the fixing nip NF will decrease, and the fixability of the unfixed toner image T will decrease. Therefore, the longitudinal length of the heat conductive member 18 is appropriately set in accordance with the characteristics of the image forming apparatus 100 and the fixing device 6. In this embodiment, the longitudinal length of the heat conductive member 18 is 218 mm, which is the same as the length of the resistance heating element 11b. The length of the heat conductive member 18 in the transverse direction SD (hereinafter referred to as the transverse length) is 7 mm, and the thickness is 0.3 mm.

[0028] The heater holder 12 supports a heat conductive member 18 and a heater 11. The heater holder 12 has a heater holder surface 12d, a second seating surface 12c disposed at a position recessed above the heater holder surface 12d, and a first seating surface 12b disposed at a position recessed above the second seating surface 12c. As shown in Fig. 3 and Fig. 4(a), the heat conductive member 18 is supported by the first seating surface 12b, and the heater 11 is supported by the second seating surface 12c.

[0029] It is desirable that the step (distance) in the thickness direction TD between the first seating surface 12b and the second seating surface 12c is equal to or smaller than the thickness of the heat conductive member 18. This is to avoid impeding the contact between the heater 11 and the heat conductive member 18. In this embodiment, the step is set to 0.3 mm, which is equal to the thickness of the heat conductive member 18.

[0030] Furthermore, the heater holder surface 12d contacts the rear surface of the fixing film 13 together with the surface of the heater 11. Therefore, when the heater 11 and the heat conductive member 18 are housed in the heater holder 12, it is preferable that the position of the heater holder surface 12d in the thickness direction TD is approximately the same as the surface of the heater 11. Therefore, in this embodiment, the step between the heater holder surface 12d and the second seating surface 12c has a thickness of 1.1 mm.

[0031] Next, the positional relationship of peripheral members of the heater 11 in the longitudinal direction LD will be described with reference to Fig. 3. The heater holder 12 has a heater positioning portion 12a against which the heater 11 abuts in the longitudinal direction LD. The heater 11 contacts a second seating surface 12c of the heater holder 12 in a state in which the heater 11 abuts against the heater positioning portion 12a. One end of the heater 11 in the longitudinal direction LD does not contact the rear surface of the fixing film 13, and the heater 11 is held by the heater holder 12 by the one end being held by a holding structure such as a clip. The resistance heating element 11b may be connected to the power supply unit via a connector, and the connector may be provided with a clip function for holding the heater 11 to the heater holder 12.

[0032] 3, the right end of the heater 11 contacts the heater positioning portion 12a, but the left end of the heater 11 does not contact the heater holder 12 in the longitudinal direction LD. That is, a gap GH is provided between the left end of the heater 11 and the heater holder 12 in the longitudinal direction LD.

[0033] On the other hand, the heat conductive member 18 contacts the first seating surface 12b in the thickness direction TD. In addition, the left and right ends of the heat conductive member 18 do not contact the heater holder 12 in the longitudinal direction LD. The heater 11 is provided with protrusions 11d and 11e, which will be described later, and both ends of the heat conductive member 18 are separated from the protrusions 11d and 11e by gaps GR and GL, respectively, in the longitudinal direction LD. In this embodiment, when the heater 11 is not heated (for example, when the heater 11 is at room temperature) and the heat conductive member 18 is disposed at the center of the protrusions 11d and 11e, the length of the gaps GR and GL in the longitudinal direction LD is set to 0.5 mm.

[0034] [Protrusion configuration] Next, the protrusions 11d and 11e will be described in detail. As shown in Fig. 3 and Fig. 4(b), the protrusions 11d and 11e extend in the thickness direction TD from the back surface 11m of the substrate 11a of the heater 11 toward the heater holder 12. These protrusions 11d and 11e are disposed outside the heat conductive member 18 in the longitudinal direction LD. The back surface 11m is the surface of the heater 11 that is provided on the opposite side to the fixing nip NF. In other words, the heat conductive member 18 is disposed between the back surface 11m of the heater 11 and the first seating surface 12b of the heater holder 12.

[0035] More specifically, the heat conductive member 18 has one end 18d and the other end 18e in the longitudinal direction LD, and the protrusion 11d as a first protrusion faces the one end 18d in the longitudinal direction LD and is disposed on the opposite side of the one end 18d from the other end 18e. Moreover, as shown in Fig. 3 and Fig. 5(a), the protrusion 11d is disposed so as not to overlap the heat conductive member 18 when viewed in the short-side direction SD.

[0036] The protrusion 11e as a second protrusion faces the other end 18e in the longitudinal direction LD and is disposed on the opposite side of the one end 18d with respect to the other end 18e. As shown in Fig. 3 and Fig. 5(a), the protrusion 11e is disposed so as not to overlap the heat conductive member 18 when viewed in the short direction SD. The heat conductive member 18 is disposed between the protrusions 11d, 11d in the longitudinal direction LD, and the distance DS1 between the protrusions 11d, 11e is longer than the length DS2 of the heat conductive member 18.

[0037] The heat conductive member 18 expands and contracts in the longitudinal direction LD in response to a change in temperature, and as a result, moves in the longitudinal direction LD relative to the heater 11. However, the protrusions 11d and 11e, together with the first seating surface 12b and the rear surface 11m of the heater 11, surround the heat conductive member 18 and restrict the movement of the heat conductive member 18 in the longitudinal direction LD. Therefore, it is not necessary to provide the heat conductive member 18 with an uneven shape for fitting the heat conductive member 18 to the heater 11 or the heater holder 12, and the heat conductive member 18 can be configured to have a simple shape, reducing the risk of deformation or damage during thermal expansion. In addition, the protrusions 11d and 11e allow the heat conductive member 18 to be thermally expandable and movable in the longitudinal direction LD within the range of the gaps GR and GL, while restricting movement beyond the gaps GR and GL, thereby suppressing misalignment of the heat conductive member 18 in the longitudinal direction LD.

[0038] In this embodiment, the two protrusions 11d and 11e are provided on the rear surface 11m of the heater 11, but the present invention is not limited to this. For example, only one of the protrusions 11d and 11e may be provided, but it is preferable to provide two of them in terms of the functionality of the protrusions 11d and 11e, which will be described later.

[0039] 5(a) is a plan view showing the heat conductive member 18 and the protrusions 11d, 11e in this embodiment. As described above, the protrusions 11d, 11e are disposed outside the one end 18d and the other end 18e of the heat conductive member 18 in the longitudinal direction LD and extend in the short side direction SD. In this embodiment, the protrusions 11d, 11e extend parallel to the sheet conveying direction p0 and the short side direction SD.

[0040] The shape of the protrusions 11d and 11e is not limited to that shown in Fig. 5(a). For example, the protrusions 11d and 11e may extend at an angle with respect to the sheet conveying direction p0 and the short-side direction SD as shown in Fig. 5(b). This allows the stress generated in the heat conductive member 18 to be released in the short-side direction SD and the deformation of the heat conductive member 18 to be suppressed even if one end 18d or the other end 18e of the heat conductive member 18 hits the protrusions 11d and 11e. In addition, the protrusions 11d and 11e may have a shape extending in the longitudinal direction LD to the end of the heater 11 in the longitudinal direction LD as shown in Fig. 5(c).

[0041] In this embodiment, the protrusions 11d and 11e are formed of the same glass material as the protective layer 11c, but are not limited to this. For example, the protrusions 11d and 11e may be formed integrally with the substrate 11a of the heater 11, or the protrusions 11d and 11e may be formed by disposing a small member on the back surface 11m of the heater 11 and then coating the small member with the same material as the protective layer 11c.

[0042] 3 and 4(b), the protrusions 11d and 11e are disposed at positions corresponding to the first seating surface 12b of the heater holder 12 in the longitudinal direction LD and the lateral direction SD. That is, the protrusions 11d and 11e face the first seating surface 12b in the thickness direction TD.

[0043] Moreover, in order to prevent the protrusions 11d, 11e from hitting the first seating surface 12b, the thickness of the protrusions 11d, 11e is equal to or less than the thickness of the heat conductive member 18. On the other hand, if the thickness of the protrusions 11d, 11e is significantly thin, the effect of restricting the movement of the heat conductive member 18 is weakened, so the thickness of the protrusions 11d, 11e is preferably in the range of 65 to 100% of the thickness of the heat conductive member 18. In this embodiment, the thickness of the protrusions 11d, 11e is set to 0.25 mm.

[0044] Furthermore, due to thermal expansion of heat conduction member 18, protrusions 11d, 11e may come into contact with ends of heat conduction member 18 in the longitudinal direction LD. In order for heat conduction member 18 to stably come into contact with protrusions 11d, 11e, it is preferable that the length of protrusions 11d, 11e in the short-side direction SD be equal to or greater than the length of heat conduction member 18 in the short-side direction SD. In this embodiment, the length of protrusions 11d, 11e in the short-side direction SD is set to 8 mm.

[0045] [Effect of protrusion] Next, the effect of the protrusions 11d, 11e will be described in detail with reference to Fig. 6. Fig. 6 is a cross-sectional view for explaining thermal expansion of the heater 11 and the heat conductive member 18. Fig. 6 shows a cross section parallel to the longitudinal direction LD and the thickness direction TD.

[0046] As shown in FIG. 6, the right end (one end in the longitudinal direction LD) of the heater 11 abuts against the positioning portion 12a of the heater holder 12, and a gap GH exists between the left end (the other end in the longitudinal direction LD) of the heater 11 and the heater holder 12. Therefore, when the heater 11 heats up and thermally expands, the protrusion 11d of the heater 11 facing one end 18d of the heat conductive member 18 expands in the direction of the arrow E11R from the position Z11. Similarly, the protrusion 11e of the heater 11 facing the other end 18e of the heat conductive member 18 expands in the direction of the arrow E11L from the position Z11. The position Z11 is the position in the longitudinal direction LD of the contact portion where the right end of the heater 11 and the positioning portion 12a contact each other.

[0047] On the other hand, although the heat conducting member 18 is disposed between the rear surface 11m of the heater 11 and the first seating surface 12b of the heater holder 12, it is not fixed in the longitudinal direction LD. Therefore, the heat conducting member 18 is movable relative to the heater 11 between the protrusions 11d, 11e. Also, the heat conducting member 18 thermally expands from an arbitrary point as a starting point. In FIG. 6, it is assumed that the heat conducting member 18 thermally expands from a starting point Z18, which is the center position of the heat conducting member 18 in the longitudinal direction LD. That is, one end 18d of the heat conducting member 18 expands in the direction of the arrow E18R, and the other end 18e of the heat conducting member 18 expands in the direction of the arrow E18L.

[0048] As described above, when the heater 11 and the heat conductive member 18 thermally expand in accordance with the operation of the fixing device 6, the protrusion 11d moves leftward and one end 18d of the heat conductive member 18 moves rightward in Fig. 6, so that the gap GR decreases. On the other hand, when the heater 11 and the heat conductive member 18 thermally expand, the protrusion 11e moves leftward and the other end 18e of the heat conductive member 18 also moves leftward in Fig. 6, so that the gap GL decreases at a slower pace than the gap GR.

[0049] 7 is a graph showing the change in the length of the gaps GL, GR in the longitudinal direction LD when the heater 11 and the heat conductive member 18 thermally expand. The data in the graph are calculated values, and the longitudinal length and thermal conductivity of each member involved in the calculation are as described above. In the graph shown in FIG. 7, the horizontal axis indicates the temperature of the heater 11 and the heat conductive member 18, and the vertical axis indicates the longitudinal length of the gaps GL, GR. In FIG. 7, the heater 11 and the heat conductive member 18 are assumed to be at the same temperature, and the temperature detected by the thermistor 20 at this time (hereinafter also simply referred to as the detected temperature) is also assumed to be the same temperature as the heater 11 and the heat conductive member 18.

[0050] The longitudinal lengths of the gaps GL and GR are both 0.5 mm when the temperature detected by the thermistor 20 is 20° C., and shorten with the thermal expansion of the heater 11 and the heat conductive member 18. When the ends 18d and 18e of the heat conductive member 18 abut against the protrusions 11d and 11e, the longitudinal lengths of the gaps GL and GR become 0 mm, that is, the vertical axis in FIG. 7 becomes 0 mm. The horizontal axis at that point indicates the temperature when the ends 18d and 18e of the heat conductive member 18 abut against the protrusions 11d and 11e (hereinafter, referred to as the abutment temperature). In other words, the abutment temperature is the temperature detected by the thermistor 20 when the distance DS1 between the protrusions 11d and 11e shown in FIG. 3 becomes equal to the length DS2 of the heat conductive member 18.

[0051] In Fig. 7, data for gap GR is indicated by a black circle. The longitudinal length of gap GR is 0 mm when the detected temperature is 196°C, at which point one end 18d of heat conductive member 18 abuts against protrusion 11d. Also, in Fig. 7, data for gap GL is indicated by a black circle. The longitudinal length of gap GL does not become 0 mm even when the detected temperature is 350°C, and the other end 18e of heat conductive member 18 does not abut against protrusion 11e unless heater 11 is heated to a higher temperature than on the gap GR side.

[0052] As described above, the starting point Z18 of the expansion of the heat conductive member 18 is not a point that is structurally strongly fixed, but is a starting point of temporary expansion of the heat conductive member 18 that can move relatively freely in the longitudinal direction LD. Therefore, when the detected temperature is 196°C, one end 18d of the heat conductive member 18 hits the protrusion 11d, and then when the temperature of the heater 11 further increases, the heat conductive member 18 thermally expands from the protrusion 11d toward the other end 18e in the longitudinal direction LD. Therefore, the longitudinal length of the gap GL decreases more rapidly when the detected temperature is 196°C or higher than when the detected temperature is less than 196°C (the data at that time is indicated by □ in FIG. 7).

[0053] If the detected temperature rises to 300° C., the gaps GR and GL will both be 0 mm, and both ends 18d and 18e of the heat conductive member 18 will abut against the protrusions 11d and 11e. If the detected temperature exceeds 300° C. and the heater 11 rises in temperature, the one end 18d and the other end 18e of the heat conductive member 18 will increase their pressing force against the protrusions 11d and 11e due to thermal expansion of the heat conductive member 18, which may cause the heat conductive member 18 to deform or break.

[0054] On the other hand, as described above, in this embodiment, the control unit 32 controls the heater 11 so that the detected temperature of the thermistor 20 is 200°C, and the temperature of the heater 11 and the heat conductive member 18, including temperature variations, does not exceed the operating temperature of the thermoswitch, 270°C. Therefore, the gaps GR and GL do not both become 0 mm, and one end 18d and the other end 18e of the heat conductive member 18 are not excessively pressed against the protrusions 11d and 11e and deformed or damaged. In other words, when the sheet P is conveyed by the fixing nip NF, the protrusions 11d and 11e do not abut against the heat conductive member 18 at the same time. Therefore, if the protrusions 11d and 11e and the heat conductive member 18 are arranged in the longitudinal direction LD so that the detected temperature is 300°C and the gaps GR and GL are 0 mm, deformation or damage of the heat conductive member 18 can be reliably avoided.

[0055] In the fixing device 6 of this embodiment, the longitudinal lengths of the gaps GR and GL are both set to 0.5 mm when the temperature detected by the thermistor 20 is 20° C., as described above. Increasing the longitudinal lengths of the gaps GR and GL can increase the abutment temperature. However, in that case, the movable range of the heat conductive member 18 in the longitudinal direction LD increases, so that the heat conductive member 18 may become significantly closer to the protrusion 11d side or the protrusion 11e side in the longitudinal direction LD.

[0056] For example, when the heat conductive member 18 is close to the protrusion 11d, one end 18d of the heat conductive member 18 moves outward in the longitudinal direction LD from the resistance heating element 11b, and the temperature is leveled out to a range where the resistance heating element 11b is not present by the heat conductive member 18. This causes the temperature in the fixing nip NF to drop, and the fixability of the toner to the sheet P to deteriorate. In addition, because a part (the left end) of the resistance heating element 11b is located outward in the longitudinal direction LD from the other end 18e of the heat conductive member 18, the temperature in the fixing nip NF rises in that range, and the left end of the resistance heating element 11b becomes overheated relative to the sheet P and the toner.

[0057] On the other hand, the image writing position accuracy of an image forming apparatus such as a printer or a copier is generally ±2 mm. This variation in accuracy is caused by variation in the transport position of the sheet P in the image forming apparatus 100. The arrangement of each member in the longitudinal direction LD of the fixing device 6 is designed so that stable fixing performance can be obtained even if such variation in the transport position of the sheet P occurs. In contrast, the positional deviation of the heat conductive member 18 in the longitudinal direction LD caused by the longitudinal length of the gaps GR and GL is ±0.5 mm, which is sufficiently smaller than the variation in the transport position of the sheet P. Therefore, even if the heat conductive member 18 is misaligned in the longitudinal direction LD within the range of the gaps GR and GL set to 0.5 mm, it does not affect the fixability of the toner to the sheet P.

[0058] As described above, the fixing device 6 of this embodiment has the heat conductive member 18 disposed on the back surface 11m of the heater 11, and also has the protrusions 11d, 11e on the back surface 11m of the heater 11. The protrusions 11d, 11e face one end 18d and the other end 18e of the heat conductive member 18 with gaps GR, GL of appropriate longitudinal length, so that the movement of the heat conductive member 18 in the longitudinal direction LD can be restricted between the protrusions 11d, 11e. And, since the heat conductive member 18 is not processed into a shape that fits the heater 11, deformation or damage due to residual stress caused by processing does not occur. With this configuration, stable fixing performance can be obtained without causing deformation or damage to the heat conductive member 18, and image defects can be reduced.

[0059] Next, the longitudinal lengths of the gaps GR and GL when the detected temperature is 20° C. are changed, and the temperatures of the heater 11 or the detected temperatures at which the gaps GR and GL become 0 mm in each case are shown in Table 1 below. [Table 1]

[0060] The temperature values ​​in Table 1 are calculated values ​​as in the above description. In this embodiment (embodiment 1), the longitudinal length of the gaps GR and GL is 0.5 mm when the detected temperature is 20°C, and the detected temperature when the gap GR is 0 mm, i.e., when one end 18d of the heat conductive member 18 abuts against the protrusion 11d, is 196°C. Also, when the gap GL is 0 mm, i.e., when the other end 18e of the heat conductive member 18 abuts against the protrusion 11e, is 300°C.

[0061] In Comparative Example 1, the longitudinal lengths of the gaps GR and GL when the detected temperature is 20° C. are changed to 0.25 mm, and in Comparative Example 2, the longitudinal lengths of the gaps GR and GL when the detected temperature is 20° C. are changed to 0.8 mm. In Comparative Example 1, the protrusions 11d and 11e of this embodiment are each moved 0.25 mm inward in the longitudinal direction LD. In Comparative Example 2, the protrusions 11d and 11e of this embodiment are each moved 0.3 mm outward in the longitudinal direction LD.

[0062] In Comparative Example 1, the gap GR is 0 mm, i.e., the detected temperature at which one end 18d of the heat conductive member 18 abuts against the protrusion 11d is 108°C. Also, the gap GL is 0 mm, i.e., the detected temperature at which the other end 18e of the heat conductive member 18 abuts against the protrusion 11e is 160°C. In the fixing device 6 of this embodiment, the target temperature of the heater 11 in the image forming job is set to 200°C, so that one end 18d and the other end 18e of the heat conductive member 18 abut against the protrusions 11d and 11e, respectively, during the image forming job. This is not preferable because it is likely that the heat conductive member 18 will be deformed or damaged.

[0063] In Comparative Example 2, the gap GR is 0 mm, i.e., the detected temperature at which one end 18d of the heat conductive member 18 hits the protrusion 11d is greater than 300°C. Also, the gap GL is 0 mm, i.e., the detected temperature at which the other end 18e of the heat conductive member 18 hits the protrusion 11e is greater than 300°C. Therefore, there is no possibility that one end 18d and the other end 18e of the heat conductive member 18 hit the protrusions 11d and 11e during an image forming job. On the other hand, the movable range of the heat conductive member 18 in the longitudinal direction LD is larger by 0.3 mm on the gap GR side and the gap GL side than in this embodiment. Therefore, the heat conductive member 18 is displaced in the longitudinal direction LD, which may cause the temperature of the fixing nip NF to become unstable, and the fixing property of the toner to deteriorate.

[0064] Therefore, it is preferable that the longitudinal lengths of the gaps GR and GL are as small as possible within the range while ensuring that the thermal conductive member 18 does not abut against the protrusions 11d and 11e even if the thermal conductive member 18 thermally expands during an image forming job. In Table 1 above, this embodiment (Example 1) is more preferable than Comparative Examples 1 and 2. Next, it was confirmed in Table 2 below whether the above-mentioned effects could be obtained in the same manner when the expansion starting point Z18 of the heat conductive member 18 was displaced in the longitudinal direction LD. [Table 2]

[0065] Example 1 in Table 2 is the condition of the present embodiment described above, and the starting point Z18 of the expansion of the heat conductive member 18 coincides with the center position in the longitudinal direction LD of the heat conductive member 18. On the other hand, Examples 1-1 to 1-4 are conditions in which the starting point Z18 is displaced 30 mm or 60 mm to the left or right in the longitudinal direction LD of FIG. 3 from the center position in the longitudinal direction LD of the heat conductive member 18. The temperature at which the gaps GR and GL become 0 mm under each condition is a calculated value, as in Table 1. This confirmation was performed because the starting point Z18 of the expansion is easily displaced in the longitudinal direction LD due to minute load unevenness in the fixing nip NF when the sheet P is conveyed to the fixing device 6. Therefore, in Table 2, a significantly large displacement of up to 60 mm is assumed for calculation.

[0066] Under the conditions of Examples 1-1 to 1-3, the detected temperature when the longitudinal length of the gap GL is 0 mm is 300° C. In the fixing device 6, the target temperature of the heater 11 is set to 200° C., and the operating temperature of the thermoswitch 270° C. is 270° C., so that when the image forming apparatus 100 is actually used, one end 18d and the other end 18e of the heat conductive member 18 do not both abut against the protrusions 11d, 11e.

[0067] Under the conditions of Example 1-4, one end 18e of heat conductive member 18 abuts against protrusion 11e before the other end 18d of heat conductive member 18 abuts against protrusion 11d, but the abutment temperature at which one end 18d and the other end 18e of heat conductive member 18 both abut against protrusions 11d, 11e is 300° C. Therefore, during actual use of image forming apparatus 100, one end 18d and the other end 18e of heat conductive member 18 do not both abut against protrusions 11d, 11e, as in the conditions of Examples 1-1 to 1-3.

[0068] Therefore, by appropriately setting the longitudinal lengths of the gaps GR and GL, deformation and damage of the heat conductive member 18 can be reduced even when the starting point Z18 of the expansion of the heat conductive member 18 is biased to the left or right in the longitudinal direction LD.

[0069] <Modification 1 of Example 1> Next, Modification 1 of Example 1 will be described, in which the longitudinal length of heat conduction member 18 is configured to be shorter than that of Example 1. For this reason, the same configuration as in Example 1 will be omitted from the illustrations or will be described with the same reference numerals in the drawings.

[0070] In the first embodiment, the longitudinal length of the heat conducting member 18 is set to be the same as that of the resistance heating element 11b, but is not limited thereto. Fig. 8 is a cross-sectional view showing a cross section parallel to the longitudinal direction LD of the peripheral configuration of the heater 11 according to a first modified example of the first embodiment. As shown in Fig. 8, the heat conducting member 118 in this first modified example is shorter than the resistance heating element 11b in the longitudinal direction LD and is disposed closer to the left side of the heater 11.

[0071] In addition, in this modified example 1, the sheet P is transported with one end in the width direction parallel to the longitudinal direction LD as a reference position ZP. That is, regardless of the size of the sheet P, the sheet P is transported with one side (one end in the width direction) of the sheet P coinciding with the reference position ZP. For example, the sheet P is transported with the one side in frictional contact with a reference surface provided on a transport guide (not shown), so that the sheet P is transported with one side as a reference along the reference position ZP.

[0072] In such a configuration, the non-paper passing area in the fixing nip NF when a narrow sheet P is conveyed is only the left side in Fig. 8, and by arranging the heat conductive member 118 in correspondence with such a non-paper passing area, the heat conductive member 118 can be configured to be short. Furthermore, by shortening the longitudinal length of the heat conductive member 118, the change in length of the heat conductive member 118 during thermal expansion can be reduced, and therefore the gaps GR and GL can be set narrower than in the above-described first embodiment.

[0073] In addition, in a configuration such as the present modified example 1, the starting point (Z18) of the expansion of the heat conductive member 118 is often on the one end 118d side of the heat conductive member 118. This is because the position of the starting point (Z18) is affected by the pressure distribution and temperature distribution in the longitudinal direction LD of the fixing nip NF. For example, when the one end 118d of the heat conductive member 118 is the starting point (Z18) of the expansion, the heat conductive member 118 thermally expands only on the other end 118e side. For this reason, the heater 11 may be provided with only the protrusion 11e without the protrusion 11d.

[0074] Moreover, it is preferable that the heater holder 12 has a first seating surface 12b corresponding to the heat conductive member 118 having a length shorter than that of the first embodiment, and a second seating surface 12c having a length longer than that of the first embodiment. In Fig. 8, the heater 11 may be bonded to the area CP of the second seating surface 12c with a heat-resistant adhesive.

[0075] <Modification 2 of Example 1> Next, a second modified example of the first embodiment will be described, in which protrusions 11f and 11g are provided on the rear surface 11m of the heater 11 in addition to the protrusions 11d and 11e. Therefore, the same configuration as in the first embodiment will be described by omitting illustrations or by assigning the same reference numerals in the drawings.

[0076] 9(a), a protrusion 11f as a third protrusion arranged on one side in the short-side direction SD of the heat conductive member 18 and a protrusion 11g as a fourth protrusion arranged on the other side in the short-side direction SD extend from the rear surface 11m of the heater 11. In other words, the heat conductive member 18 is arranged in the short-side direction SD with a gap between the protrusions 11f and 11g. The protrusions 11f and 11g are arranged on opposite sides to each other in the short-side direction SD with the heat conductive member 18 therebetween, facing the heat conductive member 18, and arranged so as not to overlap the heat conductive member 18 when viewed in the longitudinal direction LD.

[0077] A configuration is known in which the load applied to the fixing film unit 19 is lightened to facilitate the user's removal of the jammed sheet when the sheet P is stuck and stopped in the fixing nip NF, i.e., a jam occurs. In such a light-pressure state, if the jammed sheet is pulled out and removed in a direction or angle different from the normal sheet conveyance direction p0 of the sheet P, the heat conductive member 18 may be displaced in the short-side direction SD relative to the heater 11. This is because the heat conductive member 18 is not fixed to the first seating surface 12b of the heater holder 12 or the back surface 11m of the heater 11. The protrusions 11f and 11g of this modification have the effect of preventing such displacement of the heat conductive member 18 in the short-side direction SD.

[0078] The change in the short-side length of the heat conductive member 18 during thermal expansion is not as large as the change in the long-side direction LD. Therefore, the gap between the heat conductive member 18 and the protrusions 11f, 11g in the short-side direction SD can be set narrower than the gaps GR, GL. In addition, the thickness of the protrusions 11f, 11g is set to be equal to or smaller than the thickness of the heat conductive member 18 in order to prevent the protrusions 11f, 11g from hitting the first seating surface 12b. On the other hand, if the thickness of the protrusions 11f, 11g is significantly thin, the effect of restricting the movement of the heat conductive member 18 is weakened, so the thickness of the protrusions 11f, 11g is preferably set to be in the range of 65 to 100% of the thickness of the heat conductive member 18. In this embodiment, the thickness of the protrusions 11f, 11g is set to 0.25 mm, the same as that of the protrusions 11d, 11e.

[0079] Furthermore, if the protrusions 11f, 11g and the protrusions 11d, 11e are structurally connected, this will affect the displacement of the protrusions 11d, 11e when the heater 11 thermally expands, so it is preferable to have a configuration in which these are not connected.

[0080] Furthermore, as shown in FIG. 9(b), the protrusions 11f and 11g may be discontinuous in the longitudinal direction LD, as long as the effect of restricting the movement of the heat conductive member 18 is not lost.

[0081] Furthermore, as shown in FIG. 9(c), when the protrusions 11f, 11g are provided only at the longitudinal ends, they have almost no effect on the displacement of the protrusions 11d, 11e, so that the protrusions 11f, 11g may be connected to the protrusions 11d, 11e.

[0082] As described above, by providing the protrusions 11f, 11g on the outer sides of the heat conductive member 18 in the short-side direction SD, it is possible to reduce misalignment of the heat conductive member 18 in the short-side direction SD.

[0083] <Example 2> Next, a second embodiment of the present invention will be described. The second embodiment is configured by using a heater 110 instead of the heater 11 of the first embodiment. Therefore, the same configuration as the first embodiment will be described by omitting illustrations or by assigning the same reference numerals in the drawings.

[0084] Fig. 10(a) is a front view showing the front surface of the heater 110 in this embodiment, and Fig. 10(b) is a front view showing the back surface 110m of the heater 110. As shown in Fig. 10(a), the front surface of the heater 110 is provided with a substrate 11a, a resistive heating element 11b, and a protective layer (not shown), similar to the heater 11 in Example 1. The resistive heating element 11b generates heat when an AC current is applied through a contact 11h by a power supply unit (not shown).

[0085] On the back surface of the heater 110, as shown in FIG. 10(b), a thermistor 200 as a temperature detector for detecting the temperature of the heater 110 and a printed wiring 201 for controlling the thermistor are directly provided on the substrate 11a by adhesion and printing. The printed wiring 201 as a wiring pattern is provided with a connection portion 201a, and provides detected temperature information to the control portion 32 (see FIG. 1) via a lead wire (not shown) electrically connected to the connection portion 201a. The thermistor 200 of this embodiment is a chip thermistor that can be mounted on the substrate 11a, so that the temperature of the heater 110 can be measured with high accuracy without using unnecessary members. At the same time, it is possible to save space compared to the configuration of the thermistor 20 of the first embodiment (see FIG. 3).

[0086] [Heater peripheral configuration] Next, the configuration around the heater 110 will be described. FIG. 11 is a cross-sectional view of the heater 110 disposed in the fixing device 206. In this embodiment, a fixing film unit 190 is used instead of the fixing film unit 19 of the first embodiment. The fixing film unit 190 has a fixing film 13 and a heater 110 disposed in the fixing film 13. The fixing film unit 190 also has a heater holder 12 that supports the heater 110, and an insulating layer 24 and a heat conductive member 180 that are disposed between the back surface 110m of the heater 110 and the heater holder 12. The insulating layer 24 is integrally provided on the back surface 110m of the heater 110 so as to cover at least a part of the thermistor 200 and the printed wiring 201, and is disposed between the back surface 110m and the heat conductive member 180. In this embodiment, the insulating layer 24 is integrally provided on the back surface 110m of the heater 110, but is not limited thereto. For example, the insulating layer 24 may be provided integrally with the heat conductive member 180. The basic operation of the fixing device 206 and the effect of the heat conductive member 180 are the same as those of the fixing device 6 described in the first embodiment.

[0087] Heat conductive member 180 is often made of a graphite sheet or a metal plate such as aluminum, iron, or copper, which has a high thermal conductivity, and if it is placed directly on the thermistor 200 or printed wiring 201, there is a risk of short circuit or leakage. To prevent this, in this embodiment, as described above, insulating layer 24 is provided on heater 110, and heat conductive member 180 does not directly contact the thermistor 200 or printed wiring 201. Note that heat conductive member 180 may be made of materials other than those described above, as long as it has a thermal conductivity of 80 [W / mK] or more. Also, for example, glass or polyimide is used for insulating layer 24.

[0088] [Thermistor and printed wiring peripheral configuration and operation] Next, the peripheral configuration and operation of thermistor 200 and printed wiring 201 will be described with reference to Figures 11, 12, and 13. Figure 12 is a front view showing rear surface 110m of heater 110 in a state in which heat conductive member 180 is disposed on heater 110. Figure 13 is a cross-sectional view showing cross section 13A-13A in Figure 12. In Figure 13, heater 110 and heat conductive member 180 are disposed in heater holder 12.

[0089] A lead wire 21 is joined to a connection portion 201a on the printed wiring 201 by means of welding, pressure welding, brazing, ultrasonic bonding or the like, and the lead wire 21 is connected to a control unit 32 (see FIG. 1). The control unit 32 applies an AC current to the resistance heating element 11b so that the heater 110 reaches a desired temperature.

[0090] The length (longitudinal length) and width (shortitudinal length) of the heat conductive member 180 are set to be the same as those of the heat conductive member 18 of the first embodiment. In addition, holes 180a are provided around the lead wire 21 and the connection portion 201a of the heat conductive member 180 so as to ensure an insulation distance from the lead wire 21 and the connection portion 201a. That is, the insulating layer 24 and the heat conductive member 180 respectively have holes 24a and 180a as openings through which the lead wire 21 serving as a conductor is wired. In addition, a hole 12e continuing to the hole 180a is provided in the heater holder 12 so that the lead wire 21 can be wired to the upper portion of the heater holder 12.

[0091] In addition, it is desirable to make the size of the hole 180a of the heat conductive member 180 as small as possible while ensuring the insulation distance in order to increase the temperature leveling effect of the paper passing portion, which is the area of ​​the heater 110 where the sheet P passes, and the non-paper passing portion, which is the area where the sheet P does not pass. In this embodiment, the insulating layer 24 is provided in the same range as the heat conductive member 180 in the longitudinal direction LD and the transverse direction SD so that there is no space between the heater 110 and the heat conductive member 180. However, in the range where the thermistor 200 and the printed wiring 201 are not present, there is no concern about short circuits or leaks, so a configuration without providing the insulating layer 24 may be acceptable. In this case, however, it is preferable to devise a shape such as making the heat conductive member 180 thick so that there is no space between the heater 110 and the heat conductive member 180.

[0092] As described above, in this embodiment, by using the heater 110 in which the thermistor 200 is disposed directly on the substrate 11a of the heater 110, it is possible to save space compared to the thermistor configuration of the first embodiment and to measure the temperature of the heater 110 with higher accuracy. In addition, by providing the insulating layer 24 and the heat conductive member 180 between the heater 110 and the heater holder 12, it is possible to level out the temperature difference in the non-paper passing area while suppressing leakage and short circuits.

[0093] <Modification 1 of Example 2> Next, a first modified example of the second embodiment will be described, in which a hole 180b for the thermistor 200 is formed in addition to the hole 180a in the heat conduction member 180 of the second embodiment. For this reason, the same configuration as in the second embodiment will be omitted from the drawings or will be described with the same reference numerals in the drawings.

[0094] Fig. 14 is a front view showing a rear surface 110m of the heater 110 in a state in which a thermally conductive member 180 is disposed on the heater 110. Fig. 15 is a cross-sectional view showing a cross section taken along line 15A-15A in Fig. 14. In Fig. 15, the heater 110 and the thermally conductive member 180 are disposed in a heater holder 12.

[0095] In the thermal conductive member 180 of this modification, in addition to the hole 180a around the connection portion 201a described in the second embodiment, a hole 180b is also formed around the thermistor 200. That is, the thermal conductive member 180 has a hole 180b as an opening at a position corresponding to the thermistor 200. This is to ensure an insulation distance between the thermistor 200 and the thermal conductive member 180. This eliminates the need to provide an insulating layer 240 on the thermistor 200, so that the insulating layer 240 can be made thinner than in the second embodiment. In other words, the insulating layer 240 has an opening 240a at a position corresponding to the thermistor 200.

[0096] In this modification, the area around thermistor 200 where insulating layer 240 is not provided is the same as hole 180b, but the size of the area is not important as long as it does not affect the insulation distance. In addition, since insulating layer 240 can be made thinner than in Example 2, insulating layer 240 may be a sheet-like material whose main material is polyimide, perfluoroalkoxy fluorine resin (PFA), polytetrafluoroethylene resin (PTFE), tetrafluoroethylene-hexafluoropropylene resin (FEP), or the like.

[0097] Furthermore, in the second embodiment, the insulating layer 24 is integral with the heater 110, but in the present embodiment, the insulating layer 24 may be integral with the heat conductive member 180, or the insulating layer 24 may simply be sandwiched between the heat conductive member 180 and the heater 110. In this modified example, similar to the second embodiment, the insulating layer 240 is provided in the same area as the heat conductive member 18 except for the periphery of the thermistor 200, but this is not limiting. For example, in an area where the printed wiring 201 is not present, there is no concern about short circuits or leaks, so the insulating layer 240 may not be provided.

[0098] <Modification 2 of Example 2> Next, a second modified example of the second embodiment will be described, in which a throttle shape that is retracted from the thermistor 200 is added to the heater holder 12 and the thermal conductive member 180 of the second embodiment. For this reason, the same configurations as those of the second embodiment will be omitted from the illustrations or will be described with the same reference numerals in the drawings.

[0099] Fig. 16 is a front view showing the rear surface 110m of the heater 110 in a state in which the heat conductive member 180 is disposed on the heater 110. Fig. 17 is a cross-sectional view showing the cross section taken along line 17A-17A in Fig. 16. In Fig. 17, the heater 110 and the heat conductive member 180 are disposed in a heater holder 12.

[0100] In the heat conductive member 180 of this modification, in addition to the hole 180a around the connection portion 201a described in the second embodiment, a tapered shape 180c is formed around the thermistor 200. That is, the heat conductive member 180 has the tapered shape 180c as a recessed portion recessed in a direction away from the thermistor 200 at a position corresponding to the thermistor 200. This is to ensure an insulation distance between thermistor 200 and the heat conductive member 180. This eliminates the need to provide an insulating layer 240 on the thermistor 200, and therefore it is possible to configure the insulating layer 240 to be thinner than in the second embodiment.

[0101] Furthermore, since holes 180b are not provided in heat conductive member 180 as in modified example 1 of embodiment 2, it is possible to suppress the blocking of heat transfer on heat conductive member 180, and it is possible to further improve the effect of leveling the temperature between the paper passing portion and the non-paper passing portion compared to modified example 1. Note that in this modified example, the range in which insulating layer 240 is not provided around the thermistor 200 is the same range as the drawn shape 180c, but the size does not matter as long as it does not affect the insulation distance. Also, as in modified example 1, insulating layer 240 may be sheet-shaped.

[0102] It goes without saying that, also in the configuration described in Example 2 (including Modifications 1 and 2), by providing the protrusions 11d, 11e described in Example 1 on the rear surface of the heater, the misalignment of the heat conductive member 18 in the longitudinal direction LD can be reduced.

[0103] <Example 3> Next, a third embodiment of the present invention will be described, in which holes for passing the lead wires 21 through the heater holder 12 are formed without performing hole processing or drawing on the insulating layer of the heater 110 or the heat conductive member 180 as in the second embodiment. For this reason, the same configurations as those in the second embodiment will be described with the same reference numerals or will be omitted from the drawings.

[0104] Fig. 18(a) is a front view showing the front surface of the heater 110 in this embodiment, and Fig. 18(b) is a front view showing the back surface of the heater 110. The front surface of the heater 110 has the same configuration as that shown in Fig. 10(a) described in the second embodiment.

[0105] 18(b), a thermistor 200 for detecting the temperature of the heater 110 and printed wiring 201 for controlling the thermistor are provided directly on the back surface of the heater 110 by adhesion and printing on the substrate 11a. A lead wire 21 (see FIGS. 19 and 20) is joined to a connection portion 201a on the printed wiring 201 by means of welding, pressure welding, brazing, ultrasonic bonding or the like, and the lead wire 21 is connected to the control portion 32 (see FIG. 1).

[0106] In this embodiment, the connection portion 201a of the printed wiring 201 is provided on the outside of the resistance heating element 11b provided on the surface of the heater 110 in the longitudinal direction LD. That is, the connection portion 201a and the resistance heating element 11b are arranged so as not to overlap each other in the thickness direction TD (see FIG. 20). In this embodiment, as shown in FIG. 18(a)(b), the contact 11h is provided on one end side (right side) of the heater 110 in the longitudinal direction LD, and the connection portion 201a is provided on the other end side (right side) of the heater 110 in the longitudinal direction LD. That is, the connection portion 201a is arranged on the opposite side of the contact 11h across the heat conductive member 18 in the longitudinal direction LD. This is configured so that the wiring connected to the contact 11h and the wiring connected to the connection portion 201a do not interfere with each other. Note that the contact 11h and the connection portion 201a may be arranged together on one end side or the other end side of the heater 110 as long as the wiring space can be secured.

[0107] 19 and 20, the lead wire 21 connected to the connection portion 201a of the printed wiring 201 is connected to the control unit 32 (see FIG. 1) through a hole 12h provided in the first seating surface 12b of the heater holder 12. Similar to the connection portion 201a, the hole 12h is disposed outside the resistance heating element 11b and the heat conductive member 18 in the longitudinal direction LD. Moreover, the hole 12h is disposed on the same side as the connection portion 201a with respect to the heat conductive member 18 in the longitudinal direction LD.

[0108] An insulating layer 24 is disposed between the heat conductive member 18 and the rear surface 11m of the heater 110, and the insulating layer 24 is integrally provided on the rear surface of the heater 110 so as to cover the thermistor 200 and the printed wiring 201. This allows the thermistor 200 and the printed wiring 201 to directly contact the heat conductive member 18, suppressing the occurrence of short circuits, leaks, and the like. In this embodiment, the connection portion 201a of the printed wiring 201 is disposed outside the insulating layer 24 and the heat conductive member 18 in the longitudinal direction LD.

[0109] In this embodiment, the insulating layer 24 is provided in the same range as the heat conductive member 18 in the longitudinal direction LD and the transverse direction SD so that there is no space between the heater 110 and the heat conductive member 18. However, in the range where the thermistor 200 and the printed wiring 201 are not present, there is no concern about short circuits or leaks, so it is possible to have a configuration without providing the insulating layer 24. In that case, however, it is preferable to devise a shape for the heat conductive member 18, such as by making it thicker, so that there is no space between the heater 110 and the heat conductive member 18.

[0110] As described above, in this embodiment, the connection portion 201a of the printed wiring 201, the lead wire 21 connected to the connection portion 201a, and the hole 12h of the heater holder 12 are disposed outside the resistance heating element 11b, the insulating layer 24, and the heat conductive member 18 in the longitudinal direction LD. This eliminates the need to perform hole processing or the like for passing the lead wire 21 through the heat conductive member 18 or the first seating surface 12b of the heater holder 12 in the heat generating region of the resistance heating element 11b, and improves the effect of leveling the temperature in the heat generating region of the heater 110 by the heat conductive member 18. In addition, since no processing is required for the heat conductive member 18 or the heater holder 12, costs can be reduced, and the possibility of deformation or damage occurring during thermal expansion of the heat conductive member 18 due to residual stress caused by processing can be reduced.

[0111] <Modification 1 of Example 3> Next, a first modified example of the third embodiment of the present invention will be described, in which a plurality of thermistors and printed wirings are provided on the rear surface of the heater 110. For this reason, the same configuration as in the second embodiment will be described with the same reference numerals in the drawings, or will be omitted from the drawings.

[0112] Fig. 21 is a front view showing the rear surface 110m of the heater 110 in this modified example, and Fig. 22 is a front view showing the rear surface 110m of the heater 110 in a state in which a thermally conductive member 180 is disposed on the heater 110. As shown in Fig. 21, in this modified example, a plurality of thermistors 200, 200L, 200R (three in this modified example) are provided on the rear surface 110m of the heater 110.

[0113] The fixing device 6 of this modified example (see FIG. 2) is a so-called center-based fixing device in which the conveyance reference position of the sheet P is the center in the longitudinal direction LD of the fixing device 6. The thermistor 200 is disposed in the center in the longitudinal direction LD of the fixing device 6, i.e., in the center in the longitudinal direction LD of the fixing nip NF, so as to overlap with the paper passing area of ​​the sheet P, regardless of the size of the sheet P.

[0114] On the other hand, thermistors 200L and 200R are arranged at positions 99 mm to the left and right of the sheet P transport reference position, i.e., the center of the fixing nip NF in the longitudinal direction LD, so as to overlap the non-paper passing area when A5 paper is printed.

[0115] The control unit 32 (see FIG. 1) energizes the resistance heating element 11b based on the temperature detected by thermistor 200 so that the heater 110 reaches the desired temperature. The thermistors 200L and 200R have the role of monitoring the temperature of non-paper passing areas when printing on narrow paper such as A5 paper. When either thermistor 200L or 200R reaches a predetermined temperature or higher, the control unit 32 performs control to stop printing or to increase the feeding interval of the sheet P.

[0116] The heat conductive member 18 has the same longitudinal length as the resistance heating element 11b, as in the example shown in Fig. 20. The connection parts 201a of the printed wiring 201 corresponding to the thermistors 200, 200L, 200R are disposed outside the resistance heating element 11b and the heat conductive member 18 in the longitudinal direction LD. The lead wires 21 connected to the connection parts 201a pass through holes 12h provided in the first seating surface 12b of the heater holder 12, as in the third embodiment, and are connected to the control unit 32 (see Fig. 1).

[0117] As described above, in this modified example, even in a configuration in which a plurality of thermistors 200, 200L, 200R are arranged, the connection portion 201a, the lead wire 21, and the hole 12h of the heater holder 12 are arranged outside the resistance heating element 11b and the heat conductive member 18 in the longitudinal direction LD. This eliminates the need to perform hole processing or the like for passing the lead wire 21 through the heat conductive member 18 or the first seating surface 12b of the heater holder 12 in the heat generating region of the resistance heating element 11b, and improves the effect of the heat conductive member 18 in leveling out the temperature in the heat generating region of the heater 110. This effect is greater in a configuration in which a plurality of thermistors and lead wires for each thermistor are provided.

[0118] In this modification, all of the connection parts 201a corresponding to thermistors 200, 200L, and 200R are disposed on the other end side (left side) in the longitudinal direction LD of heater 110. For example, the multiple connection parts 201a may be distributed and disposed on one end side (right side) and the other end side (left side) in the longitudinal direction LD of heater 110.

[0119] <Modification 2 of Example 3> Next, a second modification of the third embodiment of the present invention will be described, in which the longitudinal length of the heat conductive member 18 is shorter than that of the first modification of the third embodiment. For this reason, the same configuration as that of the first modification of the third embodiment will be omitted from the drawings or will be described with the same reference numerals in the drawings.

[0120] In this second modification, the sheet P is transported with one side (one end in the width direction) of the sheet P aligned with the reference position ZP, regardless of the size of the sheet, that is, transported with a so-called one-side reference. Fig. 23 is a front view showing the rear surface 110m of the heater 110 in this modification, and Fig. 24 is a front view showing the rear surface 110m of the heater 110 in a state in which the heat conductive member 18 and the insulating layer 24 are arranged on the heater 110. Fig. 25 is a side view showing the peripheral configuration of the heater 110. Fig. 25 is a cross-sectional view showing a cross section perpendicular to the short side direction SD, i.e., a cross section extending in the longitudinal direction LD and thickness direction TD.

[0121] In this embodiment, the sheet P is transported with one end (one side) in the width direction parallel to the longitudinal direction LD as a reference position ZP shown in Fig. 25. That is, regardless of the size of the sheet, the sheet P is transported with one side (one end in the width direction) of the sheet P coinciding with the reference position ZP. For example, the sheet P is transported with the one side in frictional contact with a reference surface provided on a transport guide (not shown), and is thereby transported with one side as a reference along the reference position ZP.

[0122] 23, in this modification, a plurality of thermistors 200, 200S (two in this modification) are provided on the rear surface 110m of the heater 110. Thermistor 200 is disposed in a position overlapping the paper passage area for all sizes of sheets that can be used by the fixing device 6, and control unit 32 (see FIG. 1) applies an AC current to resistance heating element 11b so that the temperature of thermistor 200 becomes a desired temperature.

[0123] On the other hand, thermistor 200S is positioned 198 mm to the left of reference position ZP of sheet P in the longitudinal direction LD so as to overlap with the non-paper passing area when A5 paper is printed. Thermistor 200S has the role of monitoring the temperature of the non-paper passing area when narrow paper such as A5 paper is printed. When thermistor 200S reaches or exceeds a predetermined temperature, control unit 32 stops printing or increases the feeding interval of sheet P.

[0124] In this modification, the non-paper passing area in the fixing nip NF when a narrow sheet P is conveyed is only the left side in FIGS. 23 to 25, and the heat conductive member 18 can be arranged to be short by arranging the heat conductive member 18 in such a non-paper passing area. Also, each connection portion 201a of the printed wiring 201 for supplying power to the thermistors 200 and 200S is arranged outside the resistance heating element 11b and the heat conductive member 18 in the longitudinal direction LD. A lead wire 21 is joined to each connection portion 201a by means of welding, pressure welding, brazing, ultrasonic bonding, or the like, and the lead wire 21 is connected to the control unit 32 (see FIG. 1). The lead wire 21 is connected to the control unit 32 (see FIG. 1) through a hole 12h provided in the first seating surface 12b of the heater holder 12. The hole 12h is arranged outside the resistance heating element 11b and the heat conductive member 18 in the longitudinal direction LD, similar to the connection portion 201a.

[0125] This eliminates the need to drill holes or the like in the heat conducting member 18 or the first seating surface 12b of the heater holder 12 in the heat generating area of ​​the resistance heating element 11b to pass the lead wires 21 through, thereby improving the effect of leveling out the temperature within the heat generating area of ​​the heater 110 by the heat conducting member 18.

[0126] In this modification, the insulating layer 24 is also provided in the longitudinal direction LD and the transverse direction SD in the range where the thermal conductive member 18 is not present. However, since there is no concern about short circuits or leaks in the range where the thermal conductive member 18 is not present, it is also possible to configure without providing the insulating layer 24. In this case, however, it is preferable to devise a shape of the second seating surface 12c of the heater holder 12 so that the thermistor 200 and the printed wiring 201 do not interfere with the heater holder 12.

[0127] As described above, in this modification, even in the fixing device 6 that transports the sheet P on one side, the connection portion 201a and the hole 12h are provided on the outside of the heat conductive member 18 in the longitudinal direction LD. This eliminates the need to perform hole processing or the like in the heat conductive member 18 or the first seating surface 12b of the heater holder 12 to pass the lead wire 21 through, and improves the effect of the heat conductive member 18 in leveling the temperature in the heat generating region of the heater 110.

[0128] It goes without saying that, also in the configuration described in Example 3 (including Modifications 1 and 2), by providing the protrusions 11d, 11e described in Example 1 on the rear surface 11m of the heater 11, the misalignment of the heat conductive member 18 in the longitudinal direction LD can be reduced.

[0129] <Example 4> Next, a fourth embodiment of the present invention will be described, in which an adhesive portion 12f is provided on the heater holder 12 of the first embodiment. Therefore, the same configurations as those of the first embodiment will be described by omitting illustrations or by assigning the same reference numerals in the drawings.

[0130] Conventionally, a configuration is known in which the load applied to the fixing film unit 19 is temporarily reduced in order to facilitate the processing of a jammed sheet. If the pressure of the fixing film unit 19 is reduced in the configuration of the first embodiment, the heater 11 may rise from the heater holder 12. This may cause the heat conductive member 18 to slip between the protrusions 11e, 11d or the protrusions 11f, 11g (see FIG. 9(a)) and the first seating surface 12b of the heater holder 12. In addition, if the pressure of the fixing film unit 19 is reduced in the configuration of the third embodiment, and the heater 11 rises from the heater holder 12, the position of the connection portion 201a moves, so that a load is applied to the lead wire 21, and there is a risk that the lead wire 21 may come off the connection portion 201a.

[0131] To address this issue, it is effective to use, for example, a heat-resistant adhesive to bond the heater 11 to the heater holder 12. By bonding the heater 11 to the heater holder 12, the heater 11 does not float up from the heater holder 12, thereby suppressing the occurrence of the phenomenon described above.

[0132] Example 4 of the present invention will be described as an example of a configuration in which heater 11 is bonded to heater holder 12 using a heat-resistant adhesive. Fig. 26 is a perspective view showing heater holder 12 of this example, and is a perspective view showing the vicinity of region CP in Fig. 8.

[0133] In the heater holder 12 of this embodiment, as shown in Fig. 26, a plurality of adhesive portions 12f are provided on the second seating surface 12c. The heater 11 abuts against the second seating surface 12c as an abutment surface. The adhesive portions 12f are arranged in parallel in the longitudinal direction LD, and a heat-resistant adhesive is applied to adhere the back surface 11m (see Fig. 8) of the heater 11 to the second seating surface 12c of the heater holder 12.

[0134] The heat-resistant adhesive is a material that is heat-resistant, inexpensive, and easy to apply, such as moisture-curing silicone rubber or heat-curing silicone rubber. By using silicone rubber that retains elasticity even after curing, the adhesive surface can follow the repeated rise and fall in temperature and the heater 11 and heater holder 12 thermally expand and deform, preventing the adhesive from peeling off. In this embodiment, moisture-curing silicone rubber KE-3417 (manufactured by Shin-Etsu Silicone Co., Ltd.) was used as an example of a heat-resistant adhesive.

[0135] Next, the detailed shape of the adhesive portion 12f will be described with reference to Figs. 27(a) to (c). Since the adhesive portions 12f are all configured to have the same shape, only one adhesive portion 12f will be described. Fig. 27(a) is a plan view showing the adhesive portion 12f. Fig. 27(b) is a cross-sectional view showing the cross-section 27B-27B of Fig. 27(a), and Fig. 27(c) is a cross-sectional view showing the cross-section 27C-27C of Fig. 27(a). Fig. 27(b) shows a cross-section passing through the center CTR of the adhesive portion 12f and extending in the longitudinal direction LD and thickness direction TD, and Fig. 27(c) shows a cross-section passing through the center CTR of the adhesive portion 12f and extending in the transverse direction SD and thickness direction TD.

[0136] The adhesive portion 12f has an adhesive application surface 12f1 as an application surface, and grooves 12f2 and 12f3. The adhesive application surface 12f1 is a portion that is bonded to the heater 11 via a heat-resistant adhesive, and has a countersunk hole shape provided in the second seating surface 12c. In this embodiment, the adhesive application surface 12f1 is a circular countersunk hole with a diameter of 4 mm and a depth of 0.15 mm. The adhesive application surface 12f1 may be flush with the second seating surface 12c instead of being a countersunk hole.

[0137] The grooves 12f2 and 12f3 are provided so as to surround the periphery of the adhesive application surface 12f1. In this embodiment, the width of the grooves 12f2 and 12f3 is 1 mm, and the adhesive portion 12f is a circle having a diameter of 6 mm as a whole. The groove 12f2 as the first groove is provided near the center in the short direction of the second seating surface 12c, and the depth of the groove 12f2 is 0.6 mm from the second seating surface 12c. The groove 12f3 as the second groove is provided on the end side of the second seating surface 12c in the short direction SD with respect to the groove 12f2. The depth of the groove 12f3 is 1.0 mm from the second seating surface 12c, and is deeper than the groove 12f2. In other words, the groove 12f3 is disposed in a position closer to one end 12c1 as an end of the second seating surface 12c in the short direction SD than the groove 12f2, and is formed deeper than the groove 12f2. It can also be said that the volume of the groove 12f3 is larger than the volume of the groove 12f2.

[0138] Although a predetermined amount of heat-resistant adhesive is applied to the adhesive application surface 12f1, the heat-resistant adhesive may overflow from the adhesive application surface 12f1 due to the process capacity of the adhesive dispenser. If the overflowing heat-resistant adhesive overflows onto the second seating surface 12c, the heat-resistant adhesive may flow around from the end face (side face in the short-side direction SD) of the substrate 11a of the heater 11 onto the surface of the heater 11, which may hinder the sliding rotation of the fixing film 13. In particular, if the heat-resistant adhesive overflows onto the short-side direction SD of the heater 11, the distance to the end face of the substrate 11a is short, so there is a high possibility that the heat-resistant adhesive will flow around onto the surface of the heater 11.

[0139] In this manner, in this embodiment, grooves 12f2 and 12f3 are provided to surround adhesive application surface 12f1 in order to prevent the heat-resistant adhesive from flowing around onto the surface of heater 11. The heat-resistant adhesive that overflows from adhesive application surface 12f1 falls into grooves 12f2 and 12f3, making it less likely to overflow onto second seating surface 12c.

[0140] The deeper the grooves 12f2 and 12f3, the more space is created to allow the overflowing heat-resistant adhesive to escape, making it more difficult for the heat-resistant adhesive to overflow onto the second seating surface 12c. However, if the grooves 12f2 and 12f3 are made too deep, the rigidity of the heater holder 12 decreases, and there is a risk that the heater holder 12 will not be able to maintain the rigidity required for it.

[0141] Therefore, in this embodiment, the groove depth of groove 12f2, which is relatively far from the end face (side face in the longitudinal direction LD) of substrate 11a and is unlikely to cause the heat-resistant adhesive to wrap around to the surface of heater 11, is made shallow to ensure the rigidity of heater holder 12. On the other hand, the groove depth of groove 12f3, which is relatively close to the end face (side face in the transverse direction SD) of substrate 11a and is likely to cause the heat-resistant adhesive to wrap around to the surface of heater 11, is made deeper than groove 12f2. This allows the heat-resistant adhesive to overflow from adhesive portion 12f in the longitudinal direction LD to a certain extent, while preventing the heat-resistant adhesive from overflowing from adhesive portion 12f in the transverse direction SD, thereby suppressing the heat-resistant adhesive from wrapping around to the surface of heater 11.

[0142] As described above, by forming groove 12f3 deeper than groove 12f2, the rigidity of heater holder 12 can be ensured and the heat-resistant adhesive can be prevented from spreading onto the surface of heater 11.

[0143] <Modification 1 of Example 4> Next, a first modified example of the fourth embodiment will be described, in which the shape of the adhesive portion 12f of the fourth embodiment is changed. For this reason, the same configurations as those of the fourth embodiment will be described by omitting illustrations or by assigning the same reference numerals in the drawings.

[0144] In the fourth embodiment, the entire adhesive portion 12f is configured to be circular, but this is not limited thereto. Fig. 28(a) is a plan view showing an elliptical adhesive portion 12f. Fig. 28(b) is a plan view showing an oval adhesive portion 12f. Fig. 28(c) is a plan view showing a square adhesive portion 12f. Fig. 28(d) is a plan view showing a rectangular adhesive portion 12f. Fig. 28(e) is a plan view showing another rectangular adhesive portion 12f.

[0145] As shown in Fig. 28(a) to (e), the adhesive portion 12f may be configured in an elliptical shape, an oval shape, a square shape, a rectangular shape, or the like. In this case, the overall shape of the adhesive portion 12f does not necessarily have to match the shape of the adhesive application surface 12f1. For example, as shown in Fig. 28(e), the adhesive application surface 12f1 may be formed in a square shape, and the entire adhesive portion 12f may be formed in a rectangular shape.

[0146] As described above, by appropriately changing the shape of the adhesive portion 12f, it is possible to arrange the adhesive portion 12f in accordance with the shape of the surroundings in which the adhesive portion 12f is to be placed, thereby improving the degree of freedom in design.

[0147] <Modification 2 of Example 4> Next, a second modified example of the fourth embodiment will be described, in which the depth of the groove in the adhesive portion 12f of the fourth embodiment is divided into three. Therefore, the same configuration as that of the fourth embodiment will be omitted from the drawings or will be described by using the same reference numerals in the drawings.

[0148] Fig. 29(a) is a plan view showing the adhesive portion 12f, Fig. 29(b) is a cross-sectional view showing the cross-section 29B-29B of Fig. 29(a), Fig. 29(c) is a cross-sectional view showing the cross-section 29C-29C of Fig. 29(a), and Fig. 29(d) is a cross-sectional view showing the cross-section 29D-29D of Fig. 29(a).

[0149] 29(a)-(d), in this modification, a portion of the groove 12f2 of the fourth embodiment is replaced with a groove 12f4. The depth of the groove 12f4 is 0.8 mm from the second seating surface 12c, which is deeper than the groove 12f2 and shallower than the groove 12f3. That is, with the second seating surface 12c as the base, the adhesive application surface 12f1, the groove 12f2, the groove 12f4, and the groove 12f3 are deeper in this order.

[0150] In this modification, the groove depth of the adhesive portion 12f is divided into three parts, but it may be divided into four or more parts.

[0151] <Modification 3 of Example 4> Next, a third modification of the fourth embodiment will be described, in which the shape of the groove 12f3 of the adhesive portion 12f of the fourth embodiment is changed. For this reason, the same configurations as those of the fourth embodiment will be omitted from the drawings or will be described with the same reference numerals in the drawings.

[0152] Fig. 30(a) is a plan view showing the adhesive portion 12f, Fig. 30(b) is a cross-sectional view showing the cross-section 30B-30B of Fig. 30(a), Fig. 30(c) is a cross-sectional view showing the cross-section 30C-30C of Fig. 30(a), and Fig. 30(d) is a cross-sectional view showing the cross-section 30D-30D of Fig. 30(a).

[0153] As shown in Fig. 30(a) to (d), the groove 12f3 of the third modification has a gradient on the bottom surface 12f3a, and the depth of the groove changes continuously. In this modification, the bottom surface 12f3a slopes downward toward the outside in the short-side direction SD. In other words, the bottom surface 12f3a slopes downward in the short-side direction SD as it moves away from the center CTR of the adhesive portion 12f. The volume of the groove 12f3 is larger than the volume of the groove 12f2.

[0154] The groove depth of the groove 12f3 may be infinite, that is, the groove 12f3 may be a through hole. In the fourth embodiment, the adhesive application surface 12f1 is a smooth flat surface, but the adhesive application surface 12f1 may be textured or knurled to have irregularities. By forming irregularities on the adhesive application surface 12f1, the surface area of ​​the adhesive application surface 12f1 is increased, so that the adhesive strength using a heat-resistant adhesive can be improved. In the fourth embodiment, the adhesive portion 12f is provided near the region CP (see FIG. 8) of the second seating surface 12c of the heater holder 12, but is not limited thereto. The adhesive portion 12f may be located anywhere on the second seating surface 12c as long as it is a region where the heat conductive member 18 does not exist in the longitudinal direction LD and faces the heater 11 in the thickness direction TD.

[0155] It goes without saying that, also in the configuration described in Example 4 (including Modifications 1 to 3), by providing the protrusions 11d, 11e described in Example 1 on the rear surface 11m of the heater 11, the deviation in the longitudinal direction LD of the heat conductive member 18 can be reduced.

[0156] <Other embodiments> In any of the above-described embodiments, the heater 11 is in direct contact with the fixing film 13, but this is not limiting. For example, a sheet material having high thermal conductivity, such as an iron alloy or aluminum, may be provided between the heater 11 and the fixing film 13, and the heater 11 may contact the inner circumferential surface of the fixing film 13 via the sheet material. Even if such a sheet material is provided between the heater 11 and the fixing film 13, the pressure roller 17 sandwiches the fixing film 13 together with the heater 11.

[0157] In any of the above-mentioned embodiments, the heater is not limited to a ceramic heater, and a halogen heater or the like can also be used.

[0158] The disclosure of this embodiment also includes the following configuration examples and method examples. (Configuration 1) A cylindrical rotor; a pressure member that forms a fixing nip with the rotating body to fix a toner image onto a sheet; a heater disposed in an internal space of the rotating body, the heater including a substrate and a heating element provided on the substrate, the heating element heating the rotating body when energized; a heater holder for holding the heater; a thermal conductive member disposed between the heater and the heater holder, the fixing nip conveys the sheet in a direction parallel to a short side direction perpendicular to a long side direction of the heater, the heater has a protrusion extending from a surface of the heater opposite to the fixing nip toward the heater holder, the protrusion is disposed so as to face the heat conducting member in the longitudinal direction and not to overlap the heat conducting member when viewed in the lateral direction; A fixing device comprising: (Configuration 2) The heat conduction member abuts against the protrusion, so that movement in the longitudinal direction is restricted. 2. The fixing device according to claim 1, (Configuration 3) the protrusion is a first protrusion, the heater has a second projection extending from the surface toward the heater holder; the second protrusion is disposed on the opposite side of the heat conductive member from the first protrusion in the longitudinal direction, facing the heat conductive member, and not overlapping with the heat conductive member when viewed in the lateral direction. 3. The fixing device according to configuration 1 or 2. (Configuration 4) When a sheet is transported through the fixing nip, the first protrusion and the second protrusion do not contact the heat conductive member at the same time. 4. The fixing device according to configuration 3. (Configuration 5) the heat conducting member is movable in the longitudinal direction relative to the heater between the first protrusion and the second protrusion. 5. The fixing device according to configuration 3 or 4. (Configuration 6) the heater has a third protrusion and a fourth protrusion extending from the surface toward the heater holder, the third protrusion and the fourth protrusion are disposed on opposite sides to each other in the short-side direction with the heat conduction member therebetween, face the heat conduction member, and are disposed so as not to overlap the heat conduction member when viewed in the long-side direction. 6. The fixing device according to any one of configurations 3 to 5. (Configuration 7) The heat conductive member is made of a metal material. 7. The fixing device according to any one of configurations 1 to 6. (Configuration 8) In the longitudinal direction, the heat conducting member has the same length as the heating element. 8. The fixing device according to claim 1, wherein the fixing device is a fixing device having a fixing member. (Configuration 9) In the longitudinal direction, the heat conducting member is shorter than the heat generating element. 8. The fixing device according to claim 1, wherein the fixing device is a fixing device having a fixing member. (Configuration 10) The thermal conductivity of the heat conductive member is higher than the thermal conductivity of the substrate. 10. The fixing device according to any one of configurations 1 to 9. (Configuration 11) The heater is bonded to the heater holder by an adhesive. 11. The fixing device according to any one of configurations 1 to 10. (Configuration 12) a temperature detection unit provided on the surface of the heater and configured to detect a temperature of the heater; a wiring pattern provided on the surface of the heater and electrically connected to the temperature detection unit; an insulating layer disposed between the surface of the heater and the thermally conductive member. 12. The fixing device according to any one of configurations 1 to 11. (Configuration 13) the temperature detection unit and at least a part of the wiring pattern are covered with the insulating layer; 13. The fixing device according to configuration 12. (Configuration 14) The insulating layer has an opening at a position corresponding to the temperature detection unit. 13. The fixing device according to configuration 12. (Configuration 15) The heat conducting member has an opening at a position corresponding to the temperature detecting unit. 15. The fixing device according to configuration 14. (Configuration 16) The heat conducting member has a recess in a position corresponding to the temperature detecting portion and recessed in a direction away from the temperature detecting portion. 15. The fixing device according to configuration 14. (Configuration 17) A conductive wire connected to the wiring pattern is further provided. The insulating layer and the heat conductive member each have an opening through which the conductive wire is wired. 17. The fixing device according to any one of configurations 12 to 16. (Configuration 18) The insulating layer is formed in a sheet shape. 18. The fixing device according to any one of configurations 12 to 17. (Configuration 19) a temperature detection unit provided on the surface of the heater and configured to detect a temperature of the heater; a wiring pattern provided on the surface of the heater and electrically connected to the temperature detection unit; a conductor connected to the wiring pattern at a connection portion; The connection portion is disposed outside the heat conductive member in the longitudinal direction. 19. The fixing device according to any one of configurations 1 to 18. (Configuration 20) the heater holder has a hole through which the conductive wire passes, The hole is disposed on the same side as the connection portion with respect to the heat conducting member in the longitudinal direction. 20. The fixing device according to claim 19, (Configuration 21) the heater has a contact for energizing the heater, The connection portion is disposed on an opposite side of the thermal conductive member from the contact point in the longitudinal direction. 21. The fixing device according to configuration 19 or 20. (Configuration 22) the heater holder has a contact surface with which the heater comes into contact, and an adhesive portion provided on the contact surface and to which an adhesive is applied for adhering the heater and the heater holder, The adhesive portion has an application surface on which the adhesive is applied, and a first groove and a second groove surrounding a periphery of the application surface, The second groove is disposed outside the first groove in the short-side direction and has a volume larger than a volume of the first groove. 22. The fixing device according to any one of configurations 1 to 21. (Configuration 23) The second groove is formed deeper than the first groove with respect to the application surface. 23. The fixing device according to configuration 22. (Configuration 24) The second groove is closer to an end of the contact surface in the short side direction than the first groove. 24. The fixing device according to configuration 22 or 23. (Configuration 25) The adhesive has elasticity even after curing. 25. The fixing device according to any one of configurations 22 to 24. (Configuration 26) the rotating body is a film, the heater holds the film together with the pressure member, The toner image formed on the sheet is fixed to the sheet by being heated through the film in the fixing nip. 26. The fixing device according to any one of configurations 1 to 25. (Configuration 27) an image forming unit that forms a toner image on a sheet; and a fixing device according to any one of configurations 1 to 26, which fixes a toner image formed on a sheet by the image forming unit onto the sheet. 1. An image forming apparatus comprising: [Explanation of symbols]

[0159] 6: fixing device / 11,110: heater / 11a: substrate / 11b: heating element (resistance heating element) / 11d: protrusion, first protrusion / 11e: second protrusion (protrusion) / 11f: third protrusion (protrusion) / 11g: fourth protrusion (protrusion) / 11h: contact point / 11m,110m: surface (rear surface) / 12: heater holder / 12c: contact surface (second seat surface) / 12c1: end (one end) / 12f: adhesive part / 12f1: coating surface / 12f2: first groove (groove) / 12f3: second groove (groove) / 12h: hole / 13: rotating body, film (fixing film) / 17: pressure member (pressure roller) / 18, 118, 180: heat conductive member / 21: conductor (lead wire) / 24, 240: insulating layer / 24a: opening (hole) / 36: image forming section / 100: image forming device / 180a, 180b: opening (hole) / 180c: recess (aperture shape) / 200: temperature detection section (thermistor) / 201: wiring pattern (printed wiring) / 201a: connection section / 240a: opening / LD: longitudinal direction / NF: fixing nip / SD: longitudinal direction

Claims

1. A cylindrical rotor; a pressure member that forms a fixing nip with the rotating body to fix a toner image onto a sheet; a heater disposed in an internal space of the rotating body, the heater including a substrate and a heating element provided on the substrate, the heating element heating the rotating body when energized; a heater holder for holding the heater; a heat conductive member disposed between the heater and the heater holder, the fixing nip conveys the sheet in a direction parallel to a short side direction perpendicular to a long side direction of the heater, the heater has a protrusion extending from a surface of the heater opposite to the fixing nip toward the heater holder, the protrusion is disposed so as to face the heat conducting member in the longitudinal direction and not to overlap the heat conducting member when viewed in the lateral direction; A fixing device comprising:

2. The heat conduction member abuts against the protrusion, so that movement in the longitudinal direction is restricted.

2. The fixing device according to claim 1,

3. the protrusion is a first protrusion, the heater has a second projection extending from the surface toward the heater holder; the second protrusion is disposed on the opposite side of the heat conductive member from the first protrusion in the longitudinal direction, facing the heat conductive member, and not overlapping with the heat conductive member as viewed in the lateral direction; 2. The fixing device according to claim 1,

4. When a sheet is transported through the fixing nip, the first protrusion and the second protrusion do not contact the heat conductive member at the same time.

4. The fixing device according to claim 3.

5. the heat conducting member is movable in the longitudinal direction relative to the heater between the first protrusion and the second protrusion; 4. The fixing device according to claim 3.

6. the heater has a third protrusion and a fourth protrusion extending from the surface toward the heater holder, the third protrusion and the fourth protrusion are disposed on opposite sides to each other in the short-side direction with the heat conduction member therebetween, face the heat conduction member, and are disposed so as not to overlap the heat conduction member when viewed in the long-side direction.

4. The fixing device according to claim 3.

7. The heat conductive member is made of a metal material.

2. The fixing device according to claim 1,

8. In the longitudinal direction, the heat conducting member has the same length as the heating element.

2. The fixing device according to claim 1,

9. In the longitudinal direction, the heat conducting member is shorter than the heat generating element.

2. The fixing device according to claim 1,

10. The thermal conductivity of the heat conductive member is higher than the thermal conductivity of the substrate.

2. The fixing device according to claim 1,

11. The heater is bonded to the heater holder by an adhesive.

2. The fixing device according to claim 1,

12. a temperature detection unit provided on the surface of the heater and configured to detect a temperature of the heater; a wiring pattern provided on the surface of the heater and electrically connected to the temperature detection unit; an insulating layer disposed between the surface of the heater and the thermally conductive member.

2. The fixing device according to claim 1,

13. the temperature detection unit and at least a part of the wiring pattern are covered by the insulating layer; The fixing device according to claim 12 .

14. The insulating layer has an opening at a position corresponding to the temperature detection unit. The fixing device according to claim 12 .

15. The heat conducting member has an opening at a position corresponding to the temperature detecting unit. The fixing device according to claim 14 .

16. The heat conducting member has a recess in a position corresponding to the temperature detecting portion and recessed in a direction away from the temperature detecting portion. The fixing device according to claim 14 .

17. A conductive wire connected to the wiring pattern is further provided. The insulating layer and the heat conductive member each have an opening through which the conductive wire is wired. The fixing device according to claim 12 .

18. The insulating layer is formed in a sheet shape. The fixing device according to claim 12 .

19. a temperature detection unit provided on the surface of the heater and configured to detect a temperature of the heater; a wiring pattern provided on the surface of the heater and electrically connected to the temperature detection unit; A conductor connected to the wiring pattern at a connection portion, The connection portion is disposed outside the heat conductive member in the longitudinal direction.

2. The fixing device according to claim 1,

20. the heater holder has a hole through which the conductive wire passes, The hole is disposed on the same side as the connection portion with respect to the heat conducting member in the longitudinal direction. The fixing device according to claim 19 .

21. the heater has a contact for energizing the heater, The connection portion is disposed on an opposite side of the thermal conductive member from the contact point in the longitudinal direction. The fixing device according to claim 19 .

22. the heater holder has a contact surface with which the heater comes into contact, and an adhesive portion provided on the contact surface and to which an adhesive is applied for adhering the heater and the heater holder, The adhesive portion has an application surface on which the adhesive is applied, and a first groove and a second groove surrounding a periphery of the application surface, The second groove is disposed outside the first groove in the short-side direction and has a volume larger than a volume of the first groove.

2. The fixing device according to claim 1,

23. The second groove is formed deeper than the first groove with respect to the application surface.

23. The fixing device according to claim 22.

24. The second groove is closer to an end of the contact surface in the short direction than the first groove.

23. The fixing device according to claim 22.

25. The adhesive has elasticity even after curing.

23. The fixing device according to claim 22.

26. the rotating body is a film, the heater holds the film together with the pressure member, The toner image formed on the sheet is fixed to the sheet by being heated through the film in the fixing nip.

2. The fixing device according to claim 1,

27. an image forming unit that forms a toner image on a sheet; and a fixing device according to claim 1 , which fixes a toner image formed on a sheet by the image forming unit onto the sheet.

1. An image forming apparatus comprising:

Images