Fixing device and image forming apparatus

Abstract

To provide a fixing device and an image forming apparatus that can prevent displacement of the relative position of a temperature sensor and a sheet with which the temperature sensor is in contact.SOLUTION: A fixing device comprises: a heater (60) that has a resistance heating element (62) arranged on a substrate (61); a holder (75) that is formed with a hole (75A1) and holds the heater (60); a metal sheet (70) that is in contact with the substrate (61); and a first temperature sensor (81) that detects the temperature of the heater (60). The first temperature sensor (81) is in contact with the metal sheet (70) through the hols (75A1), and by inserting an end in a short direction of the metal sheet (70) into the hole (75A1) locates the metal sheet (70) with respect to the heater (60).SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a fixing device and an image forming apparatus. [Background technology]

[0002] Known image forming devices, such as electrophotographic printers, include a fixing device that heats a sheet on which an image is formed to fix a developer image. Such fixing devices typically include a heater having a resistance heating element and a temperature sensor that detects the heater's temperature. The fixing temperature is controlled by the heater based on the temperature sensor's detection results. A conventional fixing device has been proposed in which a graphite sheet, a sheet-like thermally conductive member, is provided between the heater and the temperature sensor, and a spring presses the graphite sheet toward the heater via the temperature sensor to bring the heater and the graphite sheet into close contact with each other (see, for example, Patent Document 1 below). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-169413 Summary of the Invention [Problem to be solved by the invention]

[0004] In the conventional fixing device described above, the temperature detection by the temperature sensor was sometimes unstable. Specifically, in the conventional fixing device, the pressing force (biasing force) of the spring against the graphite sheet could change instantaneously or over time, which made it easy for the relative positions of the temperature sensor and the graphite sheet to shift.

[0005] An object of the present disclosure is to provide a fixing device and an image forming apparatus that can suppress displacement of the relative position between a temperature sensor and a sheet with which the temperature sensor comes into contact. [Means for solving the problem]

[0006] In order to solve the above problems, the fixing device of the present disclosure comprises a substrate, a heater having a resistive heating element arranged on the substrate, an endless belt having an inner surface that contacts the heater and rotates around the heater, a holder with a hole formed therein that holds the heater, a metal sheet that contacts the substrate, and a temperature sensor that detects the temperature of the heater, wherein the temperature sensor contacts the metal sheet through the hole, and the metal sheet is positioned relative to the heater by inserting an end of the metal sheet into the hole in the short direction of the substrate.

[0007] According to the above configuration, the metal sheet is positioned relative to the heater, so that it is possible to suppress misalignment of the metal sheet relative to the temperature sensor.

[0008] In the fixing device of the present disclosure, the metal sheet may be bent such that both ends in the short side direction intersect with the substrate.

[0009] According to the above configuration, the metal sheet to be inserted into the hole can be easily configured.

[0010] In the fixing device of the present disclosure, the metal sheet may have a central portion that contacts the substrate, a pair of first extension portions that extend from both ends of the central portion in the short side direction in perpendicular directions that are perpendicular to the longitudinal direction and the short side direction of the substrate, and a pair of second extension portions that extend in the short side direction from the ends of the pair of first extension portions.

[0011] According to the above configuration, the metal sheet can be reliably positioned relative to the heater.

[0012] In the fixing device of the present disclosure, the holder may include a wall having the hole, and the metal sheet may be positioned in the longitudinal direction by abutting an end surface of the metal sheet in the longitudinal direction against the wall.

[0013] According to the above configuration, the metal sheet can be reliably positioned in the longitudinal direction.

[0014] In the fixing device of the present disclosure, the metal sheet may have an opening formed in the center in the longitudinal direction of the metal sheet at a portion that is inserted into the hole.

[0015] According to the above configuration, the heat capacity of the metal sheet can be reduced while the positioning accuracy of the metal sheet can be easily improved.

[0016] In the fixing device of the present disclosure, the metal sheet may have an end portion in the short side direction that protrudes beyond the hole on the side opposite to the substrate.

[0017] According to the above configuration, the strength of the metal sheet can be increased and the metal sheet can be easily assembled.

[0018] In the fixing device of the present disclosure, the end portion of the metal sheet in the short side direction may be bent to the outside of the hole.

[0019] According to the above configuration, the strength of the metal sheet can be reliably increased.

[0020] In the fixing device of the present disclosure, the end portion of the metal sheet in the short side direction may be bent in a direction away from the substrate and toward the outside of the hole.

[0021] According to the above configuration, the metal sheet can be easily assembled.

[0022] In the fixing device of the present disclosure, the contact area between the substrate and the metal sheet may be smaller than the contact area between the substrate and the holder.

[0023] According to the above configuration, the heat capacity of the metal sheet can be reliably reduced, and the temperature of the heater can be raised quickly.

[0024] In the fixing device of the present disclosure, the thermal conductivity of the metal sheet may be greater than the thermal conductivity of the substrate.

[0025] According to the above configuration, the metal sheet can easily distribute the heat from the heater from the substrate uniformly, thereby improving the accuracy of temperature detection by the temperature sensor.

[0026] In the fixing device of the present disclosure, the metal sheet may be made of aluminum, phosphor bronze, stainless steel, or titanium.

[0027] According to the above-mentioned configuration, the metal sheet can reliably ensure uniform distribution of the heat from the heater from the substrate, and the accuracy of temperature detection by the temperature sensor can be reliably improved.

[0028] In the fixing device of the present disclosure, the temperature sensor may include a first temperature sensor that detects the temperature of the center of the heater in the longitudinal direction, and a second temperature sensor that detects the temperature closer to the end of the longitudinal direction than the first temperature sensor, and the two metal sheets may be arranged to correspond to the first temperature sensor and the second temperature sensor, respectively.

[0029] According to the above configuration, it is possible to stabilize the temperature detection of each of the first and second temperature sensors.

[0030] The fixing device of the present disclosure may further include a current interrupting member that cuts off the flow of electricity to the resistance heating element when the heater abnormally rises in temperature, and the current interrupting member may contact the surface of the substrate opposite to the surface that contacts the belt.

[0031] According to the above configuration, the current interrupting member can ensure the responsiveness of the heater to the temperature, and can interrupt the current flow when the heater temperature rises abnormally.

[0032] In the fixing device of the present disclosure, the current interrupting member may be disposed at a center portion in the longitudinal direction of the heater.

[0033] According to the above configuration, the current interrupting member can interrupt the current when the heater temperature rises abnormally, regardless of the size of the sheet in the width direction.

[0034] The image forming apparatus of the present disclosure includes the fixing device, and can be configured to suppress displacement of the relative position between the temperature sensor and the sheet with which the temperature sensor comes into contact. [Effects of the Invention]

[0035] According to one aspect of the present disclosure, it is possible to provide a fixing device and an image forming apparatus that can suppress displacement of the relative position between a temperature sensor and a sheet with which the temperature sensor comes into contact. [Brief explanation of the drawings]

[0036] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus according to a first embodiment of the present disclosure. [Figure 2] (A) is a plan view showing a heater of a heating unit provided in a fixing device according to embodiment 1 of the present disclosure, and (B) is a plan view showing a first temperature sensor, a second temperature sensor, and a current interrupting member of the heating unit. [Figure 3] FIG. 2(A) is a perspective view showing the first temperature sensor and the second temperature sensor, and FIG. 2(B) is a perspective view showing the current interruption member. [Figure 4] 3 is a schematic diagram illustrating the relationship between a metal sheet and a temperature sensor in the holder shown in FIG. 2. FIG. [Figure 5] FIG. 4 is a cross-sectional view showing the first temperature sensor and the metal sheet of the heating unit. [Figure 6] FIG. 2 is a perspective view showing a specific configuration example of the metal sheet. [Figure 7] FIG. 3 is a perspective view illustrating a hole formed in the holder and a wall surrounding the hole. [Figure 8] 10A and 10B are diagrams illustrating the relationship between the metal sheet and the holder. [Figure 9] FIG. 4 is a cross-sectional view showing the current interruption member of the heating unit. [Figure 10] (A) is a plan view showing a heater of a heating unit provided in a fixing device according to a second embodiment of the present disclosure, and (B) is a plan view showing a first temperature sensor, a second temperature sensor, and a current interrupting member of the heating unit. [Figure 11] FIG. 4 is a cross-sectional view showing the first temperature sensor and the metal sheet of the heating unit. DETAILED DESCRIPTION OF THE INVENTION

[0037] [Embodiment 1] A first embodiment of the present disclosure will be described below with reference to Figures 1 to 6. In this embodiment, a laser printer that forms an image on a sheet S1 using toner will be described as an example of an image forming apparatus 1.

[0038] [Configuration of image forming apparatus 1] 1 is a diagram illustrating a schematic configuration of an image forming apparatus 1 according to a first embodiment of the present disclosure. In the following description, a monochrome printer that performs image formation processing for monochrome images is exemplified as the image forming apparatus 1, but the present embodiment is not limited to this, and the image forming apparatus 1 may also be, for example, a color printer that performs image formation processing for full-color images.

[0039] 1, the image forming apparatus 1 includes a housing 2, a paper feed unit 3, an image forming unit 4, a discharge roller 5, and a discharge tray 6. As shown in FIG. 1, the housing 2 forms the outer container of the image forming apparatus 1 and houses the main components of the image forming apparatus 1.

[0040] As shown in Fig. 1, the paper feed unit 3 supplies sheets S1. The paper feed unit 3 includes a paper feed tray 31, a feed roller 32, a pressure plate 33, a transport roller 34, and a registration roller 35. The paper feed tray 31 is a box-shaped member with an open top, and stores a predetermined amount of sheets S1. The sheets S1 are recording media on which an image formation process is performed, and are made of paper, plastic, or the like.

[0041] The feed roller 32 feeds out the sheet S1 stored in the paper feed tray 31. That is, when the sheet S1 is fed out, the sheet S1 on the paper feed tray 31 is brought toward the feed roller 32 by the pressure plate 33, and is fed to the conveyance roller 34 as the feed roller 32 rotates. The conveyance roller 34 conveys the sheet S1 toward the registration roller 35. The registration roller 35 aligns the position of the leading edge of the sheet S1, and then conveys the sheet S1 toward the image forming unit 4.

[0042] The image forming unit 4 forms an image by performing an image forming process on the sheet S1 delivered by the paper feed unit 3. As shown in Fig. 1, the image forming unit 4 includes an exposure unit 41, a transfer unit 42, a charger 43, a developing unit 44, a fixing device 45 of the present disclosure, and a photosensitive drum 46. The exposure unit 41 includes a laser light source (not shown), a polygon mirror 41G, a scanning lens 41L, a polygon motor 41M, and a reflecting mirror 41R.

[0043] The polygon mirror 41G is a rotary polygonal mirror having six reflective surfaces on the side surfaces of a regular hexagonal prism. The polygon mirror 41G deflects the light beam L1 emitted from the laser light source in a direction toward the photosensitive drum 46. The polygon motor 41M is driven by a motor driver (not shown) to rotate the polygon mirror 41G.

[0044] The exposure unit 41 deflects a light beam L1 using a polygon mirror 41G, and emits the light beam L1 from the polygon mirror 41G via a scanning lens 41L and a reflecting mirror 41R onto the surface of the photosensitive drum 46. The exposure unit 41 scans the surface of the photosensitive drum 46 with the light beam L1 to expose the photosensitive drum 46. As a result, an electrostatic latent image that constitutes a toner image (described later) is formed on the photosensitive drum 46. The polygon motor 41M is, for example, a brushless DC motor.

[0045] The transfer unit 42 includes a transfer roller that sandwiches the sheet S1 between itself and the photosensitive drum 46, and transfers the toner image from the photosensitive drum 46 to the sheet S1. The charger 43 includes, for example, a scorotron charger having a charging wire and a grid portion (not shown). In this charger 43, a charging voltage is applied to the charging wire by a high-voltage generating circuit (not shown), and a grid voltage is applied to the grid portion, thereby generating a corona discharge and uniformly charging the surface of the photosensitive drum 46. The developing unit 44 includes a developing roller 44R and a toner cartridge 44A that contains a developer, such as toner.

[0046] In addition to the above description, for example, the transfer device 42 may include a transfer belt instead of the transfer roller. Also, for example, the charger 43 may include a charging roller instead of the scorotron charger.

[0047] In the image forming unit 4, the surface of the photosensitive drum 46 is uniformly charged by the charger 43, and then a light beam L1 from the exposure unit 41 forms an electrostatic latent image based on print data on the surface of the photosensitive drum 46. The developing roller 44R supplies toner from inside the toner cartridge 44A to the surface of the photosensitive drum 46 on which the electrostatic latent image has been formed. This makes the electrostatic latent image visible, and a toner image is formed on the surface of the photosensitive drum 46. Thereafter, a sheet S1 fed from the paper feed unit 3 is transported to a transfer position between the photosensitive drum 46 and the transfer unit 42, whereby the toner image formed on the surface of the photosensitive drum 46 is transferred onto the sheet S1.

[0048] The sheet S1 onto which the toner image has been transferred is transported to the fixing device 45 by the photosensitive drum 46 and the transfer device 42. The fixing device 45 fixes the toner image formed on the sheet S1. Specifically, the fixing device 45 uses heat generated by the heater 60 to thermally fix the toner image on the sheet S1 transported from the photosensitive drum 46 and the transfer device 42. The sheet S1 onto which the toner image has been thermally fixed is discharged onto a discharge tray 6 by discharge rollers 5.

[0049] The fixing device 45 includes a pressure roller 51 that applies pressure to the sheet S1 on which the toner image is formed, and a heating unit 52 that comes into contact with the sheet S1 and heats the sheet S1. One of the pressure roller 51 and the heating unit 52 is pressed against the other by a pressing unit (not shown). In the fixing device 45, the pressing unit is controlled in accordance with instructions from a control unit (not shown), so that the toner image is fixed to the sheet S1 with a predetermined pressure being applied between the pressure roller 51 and the heating unit 52.

[0050] 1, the pressure roller 51 is driven to rotate clockwise in accordance with instructions from the control unit. That is, the pressure roller 51 rotates while sandwiching the sheet S1, which is conveyed toward the discharge tray 6, between the pressure roller 51 and a belt 53 (described later) provided in the heating unit 52. As a result, the belt 53 is configured to rotate in a predetermined rotation direction due to the frictional forces between the pressure roller 51, the belt 53, and the sheet S1, as illustrated by R in FIG. 5 (described later). As a result, in the fixing device 45, the sheet S1, on which the toner image has been transferred, is conveyed between the pressure roller 51 and the heating unit 52, and the toner image is thermally fixed onto the sheet S1.

[0051] [Configuration of heating unit 52] 2 to 9, the heating unit 52 of this embodiment will be described in detail. FIG. 2(A) is a plan view showing the heater 60 of the heating unit 52 included in the fixing device 45 according to the first embodiment of the present disclosure, and FIG. 2(B) is a plan view showing the first temperature sensor 81, the second temperature sensor 82, and the current-cutting member 83 of the heating unit 52. FIG. 3(A) is a perspective view showing the first temperature sensor 81 and the second temperature sensor 82, and FIG. 3(B) is a perspective view showing the current-cutting member 83. FIG. 4 is a schematic diagram illustrating the relationship between the metal sheet 70 and the temperature sensor 80 in the holder 75 shown in FIG. 2. FIG. 5 is a cross-sectional view showing the first temperature sensor 81 and the metal sheet 70 of the heating unit 52. FIG. 6 is a perspective view showing a specific configuration example of the metal sheet 70. FIG. 7 is a perspective view illustrating a hole 75A1 formed in the holder 75 and a wall 75A11 surrounding the hole 75A1. Fig. 8 is a diagram illustrating the relationship between the metal sheet 70 and the holder 75. Fig. 9 is a cross-sectional view showing the current interruption member 83 of the heating unit 52.

[0052] [Configuration of heater 60] 2(A) and 2(B), the heating unit 52 of this embodiment includes a heater 60 and a holder 75 that holds the heater 60. The heater 60 is a heating member configured in a rectangular shape in a plan view, and includes a substrate 61 and, for example, two resistance heating elements 62 arranged on the substrate 61.

[0053] The substrate 61 is made of, for example, a ceramic material, and the two resistance heating elements 62 are formed on one surface of the substrate 61 by, for example, print patterning so that they are parallel to each other. In addition to this description, the substrate 61 can also be made of, for example, a metal material such as stainless steel. In this case, the two resistance heating elements 62 are formed on one surface of the substrate 61 with an insulating layer such as a glass material interposed therebetween.

[0054] The resistance heating element 62 is made of a conductive material with excellent heat generating properties, such as a nickel-chromium alloy or an iron-chromium alloy. A power supply terminal 63 is connected to one end 62A of the resistance heating element 62 via a conductor 64. A conductor 65 is connected to the other end 62B of the resistance heating element 62, so that the two resistance heating elements 62 are electrically connected via the conductor 65.

[0055] A connector (not shown) is detachably connected to the power supply terminal 63, and a power source (not shown) is connected to the power supply terminal 63 via the connector to supply power. In the heater 60, the resistance heating element 62 generates heat in accordance with instructions from the control unit. That is, the current supplied to the resistance heating element 62 is controlled, and further, the heat generated by the resistance heating element 62 is increased or decreased, thereby controlling the heating of the belt 53 from the heater 60.

[0056] 2A, the heater 60 has a resistance heating element 62 whose longitudinal dimension is larger than that of a sheet S1 having the maximum width H1 that can be used in the fixing device 45. The fixing device 45 is also configured to accommodate a variety of sheet S1 with different widths. Specifically, the fixing device 45 performs a fixing operation on sheets S1 of a variety of sheet sizes with their centers in the width direction aligned. For example, a sheet S1 having the minimum width H2 that can be used in the fixing device 45 is fixed by being heated by the center of the resistance heating element 62.

[0057] Furthermore, in the fixing device 45, when a fixing operation is performed on a sheet S1 of minimum width H2, edge regions H3 and H4 on the outer longitudinal sides of the minimum width H2 become non-paper passing regions where the sheet S1 of minimum width H2 does not exist. Therefore, in the edge regions H3 and H4, heat is not absorbed by the sheet S1 of minimum width H2 during the fixing operation, and the temperature of the heater 60 is more likely to rise than in the center of the resistance heating element 62, i.e., the region of minimum width H2.

[0058] 5, the heater 60 has a cover 66 provided on the substrate 61 so as to cover the resistance heating element 62. The cover 66 is made of an insulating material such as glass. The cover 66 also has a nip surface 66A that comes into contact with the inner circumferential surface of the belt 53.

[0059] [Configuration of belt 53] Belt 53 is an endless belt that is heat-resistant and flexible, and includes a base material made of a metal material such as stainless steel, and an insulating layer made of a synthetic resin material such as fluororesin that covers the base material (not shown). Belt 53 houses therein heater 60, metal sheet 70, holder 75, first temperature sensor 81, second temperature sensor 82, and current interrupting member 83. Belt 53 rotates around heater 60, metal sheet 70, holder 75, first temperature sensor 81, second temperature sensor 82, and current interrupting member 83.

[0060] Furthermore, the inner peripheral surface of the belt 53 abuts against the nip surface 66A of the heater 60, so that heat from the heater 60 is transferred to the sheet S1 via the belt 53. The longitudinal dimension of the belt 53 is larger than the dimension of the resistance heating element 62.

[0061] [Configuration of holder 75] The holder 75 is made of, for example, a synthetic resin material. As shown in Fig. 2(B), the holder 75 has a support portion 75A that supports the heater 60. That is, the support portion 75A supports the substrate 61 of the heater 60, which is shown by the dotted line in Fig. 2(B). As shown in Fig. 5, the holder 75 has a guide surface 75B1 that contacts the inner circumferential surface of the belt 53, and includes a guide portion 75B that guides the belt 53.

[0062] The holder 75 also has holes 75A1, 75A2, and 75A3 for installing the first temperature sensor 81, the second temperature sensor 82, and the current interruption member 83, respectively. These holes 75A1, 75A2, and 75A3 are formed by opening a rectangular shape in the support portion 75A of the holder 75, and the periphery of the hole 75A1 is surrounded by a wall 75A11, as illustrated in FIG. 7. The wall 75A11 has a thickness in the vertical direction in FIG. 5 that corresponds to the thickness of the support portion 75A. The metal sheets 70 are inserted into the holes 75A1 and 75A2, and the first temperature sensor 81 and the second temperature sensor 82 come into contact with the corresponding metal sheets 70 through the holes 75A1 and 75A2, respectively.

[0063] [Configuration of the first temperature sensor 81 and the second temperature sensor 82] The first temperature sensor 81 and the second temperature sensor 82 are configured using, for example, a thermistor. In the following description, the first temperature sensor 81 and the second temperature sensor 82 will be collectively referred to as the temperature sensor 80.

[0064] 3(A), the temperature sensor 80 includes a base material 80A, a protruding member 80B on which a temperature detection element 80D is mounted and which causes the temperature detection element 80D to protrude upward, and a film material 80C provided on the base material 80A so as to cover the protruding member 80B. The protruding member 80B is made of an elastic material such as a sponge material and is attached to the base material 80A. In the temperature sensor 80, the protruding member 80B presses the temperature detection element 80D, thereby ensuring that the temperature detection element 80D is in reliable contact with the object to be detected, thereby enabling accurate temperature detection.

[0065] As shown in FIG. 4, the temperature sensor 80 is attached to the hole 75A1 of the holder 75 with the metal sheet 70 interposed therebetween, with the base material 80A in contact with the support portion 75A.

[0066] As shown in Fig. 2(B), the first temperature sensor 81 is provided on the holder 75 so as to be located within the range of the minimum width H2, and detects the temperature of the central portion in the longitudinal direction of the heater 60. Specifically, as shown in Fig. 5, in the first temperature sensor 81, the protruding member 80B is inserted into the hole 75A1 of the holder 75, and the temperature detection element 80D comes into contact with the back surface of the substrate 61 via the central portion 70A of the metal sheet 70, thereby detecting the temperature of the central portion in the longitudinal direction. The first temperature sensor 81 is also connected to the control unit, and the control unit performs feedback control of the heater 60 using the detection result of the first temperature sensor 81.

[0067] As shown in FIG. 2(B), the second temperature sensor 82 is provided on the holder 75 at a position within the end region H3 and at a longitudinal end of the resistance heating element 62, and detects the temperature closer to the longitudinal end than the first temperature sensor 81. Specifically, in the second temperature sensor 82, like the first temperature sensor 81, the protruding member 80B is inserted through the hole 75A2 of the holder 75. The second temperature sensor 82 detects the temperature of the longitudinal end by contacting the temperature detection element 80D with the back surface of the substrate 61 via the central portion 70A of the metal sheet 70. The second temperature sensor 82 is also connected to the control unit, and the control unit determines the degree of temperature rise at the longitudinal end using the detection result of the second temperature sensor 82.

[0068] [Configuration of the current interruption member 83] The current interrupting member 83 cuts off the power supply to the resistance heating element 62 when the heater 60 abnormally rises in temperature. Specifically, the current interrupting member 83 is configured using, for example, a thermostat, and as shown in FIG. 3(B), includes a container 83A and a temperature detection unit 83B that protrudes upward from the container 83A and detects the temperature. The container 83A is connected to the temperature detection unit 83B and is provided with a cutoff mechanism (not shown) that uses, for example, a bimetal. The current interrupting member 83 cuts off the power supply to the resistance heating element 62 when the temperature of the heater 60 rises above a predetermined temperature. The current interrupting member 83 is not limited to a thermostat, and may be, for example, a thermal fuse or the like.

[0069] 2(B), the current interrupting member 83 is provided on the holder 75 so as to be located within the end region H4, and detects the temperature of one end in the longitudinal direction of the heater 60. Specifically, in the current interrupting member 83, as shown in FIG. 9, the temperature detecting section 83B is inserted through the hole 75A3 of the holder 75, and the temperature detecting section 83B comes into contact with the rear surface of the substrate 61, thereby detecting the temperature of the one end.

[0070] [Configuration of metal sheet 70] The metal sheet 70 is made of a metal material with high thermal conductivity, such as aluminum, phosphor bronze, stainless steel, or titanium. The metal sheet 70 is provided in the holder 75 so as to be positioned relative to the heater 60 by being inserted into the hole 75A1 or 75A2. The metal sheet 70 has the function of minimizing displacement of the relative positions of the first temperature sensor 81 and the second temperature sensor 82 and the heater 60. The metal sheet 70 also has the function of uniformly distributing the heat of the heater 60 within the range of the metal sheet 70.

[0071] Specifically, the metal sheet 70 is made of the above-mentioned metal material, which has a thermal conductivity greater than that of the substrate 61. As a result, in this embodiment, the metal sheet 70 can easily uniformly distribute the heat from the heater 60 through the substrate 61. As a result, in this embodiment, the accuracy of temperature detection by the first temperature sensor 81 and the second temperature sensor 82, which are in contact with the metal sheet 70, can be improved.

[0072] Furthermore, because the metal sheet 70 is made of aluminum, phosphor bronze, stainless steel, or titanium, the metal sheet 70 can reliably ensure uniform distribution of heat from the heater 60 through the substrate 61. This allows the metal sheet 70 to reliably improve the accuracy of temperature detection by the first temperature sensor 81 and the second temperature sensor 82, which are in contact with the metal sheet 70.

[0073] 6, the metal sheet 70 has a rectangular central portion 70A. The metal sheet 70 is attached to the holder 75 so that the longitudinal and lateral directions of the central portion 70A coincide with the longitudinal and lateral directions of the heater 60 (and the substrate 61), respectively. The metal sheet 70 also has a pair of first extending portions 70B extending from both ends of the lateral direction of the central portion 70A in directions perpendicular to the longitudinal and lateral directions of the substrate 61, and a pair of second extending portions 70C extending in the lateral direction from the ends of the pair of first extending portions 70B, respectively.

[0074] 5, the central portion 70A contacts the rear surface of the substrate 61 and the temperature detection element 80D. The contact area of ​​the metal sheet 70 with the substrate 61, i.e., the contact area between the central portion 70A and the substrate 61, is smaller than the contact area between the substrate 61 and the holder 75. This ensures that the heat capacity of the metal sheet 70 is small in this embodiment. As such, in this embodiment, a metal sheet 70 is provided for each of the first temperature sensor 81 and the second temperature sensor 82.

[0075] Therefore, in this embodiment, compared to when a metal sheet is provided on the entire surface of the substrate 61, it is possible to significantly reduce the heat generated in the heater 60 from being absorbed by the metal sheet 70, and the temperature of the heater 60 can be raised more quickly. Therefore, in the image forming apparatus 1 of this embodiment, it is possible to quickly start up the fixing device 45, and image formation processing (printing processing) can be performed at high speed.

[0076] The first extending portions 70B constitute both ends of the metal sheet 70 in the short direction, and are bent in a direction intersecting the substrate 61 (i.e., the orthogonal direction, i.e., the up-and-down direction in FIG. 5). This makes it possible to easily configure the metal sheet 70 to be inserted into the hole 75A1 or 75A2 in this embodiment.

[0077] 5 to 7, the first extending portion 70B is configured such that its end face in the short-side direction is restricted by the wall 75A11 surrounding the hole 75A1. As a result, when the metal sheet 70 is attached to the holder 75, the end face in the short-side direction of the first extending portion 70B abuts against the wall 75A11, thereby positioning the metal sheet 70 in the short-side direction of the heater 60. As a result, in this embodiment, the metal sheet 70 can be reliably positioned in the short-side direction of the heater 60. Note that the positioning of the heater 60 in the short-side direction on the metal sheet 70 can be performed using the end face in the short-side direction of either one of the first extending portion 70B at both ends of the metal sheet 70 in the short-side direction.

[0078] 4 and 6 to 7, the first extending portion 70B is configured such that its longitudinal end face is restricted by the wall 75A11 surrounding the hole 75A1. As a result, when the metal sheet 70 is attached to the holder 75, the longitudinal end face of the first extending portion 70B abuts against the wall 75A11, thereby positioning the metal sheet 70 in the longitudinal direction of the heater 60. As a result, in this embodiment, the metal sheet 70 can be reliably positioned in the longitudinal direction of the heater 60. Note that the longitudinal positioning of the heater 60 on the metal sheet 70 can be performed using the longitudinal end face of either one of the first extending portion 70B at both longitudinal end portions of the metal sheet 70.

[0079] 5 to 6 and 8, the second extending portion 70C constitutes an end portion in the short direction of the metal sheet 70. The second extending portion 70C is bent in a direction intersecting the orthogonal direction so as to be parallel to the surface 75M of the support portion 75A toward the outside of the hole 75A1 or 75A2. In this way, in the metal sheet 70, the second extending portion 70C is bent toward the outside of the hole 75A1 or 75A2, so that the strength of the metal sheet 70 can be reliably increased in this embodiment.

[0080] Further, second extending portion 70C protrudes beyond hole 75A1 or 75A2 so as to be higher than wall 75A11 on the side opposite substrate 61. That is, as shown in Fig. 8, metal sheet 70 is attached to holder 75 with a distance K between the surface of second extending portion 70C facing substrate 61 and surface 75M of holder 75. As a result, in this embodiment, metal sheet 70 can be easily assembled to holder 75 while increasing the strength of metal sheet 70.

[0081] 4 and 6, the metal sheet 70 has an opening 70D formed in the center of the heater 60 in the longitudinal direction at the portion inserted into the hole 75A1 or 75A2. That is, the metal sheet 70 has a substantially rectangular parallelepiped opening 70D surrounded by the center 70A, a pair of first extension portions 70B facing each other in the longitudinal direction, and a pair of second extension portions 70C. This reduces the thermal capacity of the metal sheet 70 while easily improving the positioning accuracy of the metal sheet 70 using the pair of first extension portions 70B. Therefore, in the image forming apparatus 1 of this embodiment, the fixing device 45 can be started up more quickly and the image formation process (printing process) can be performed at a higher speed than when the metal sheet 70 does not have the opening 70D.

[0082] As described above, the fixing device 45 and image forming apparatus 1 of this embodiment include the heater 60 having the resistance heating element 62 disposed on the substrate 61, and the holder 75 having the hole 75A1 for holding the heater 60. The fixing device 45 and image forming apparatus 1 also include the metal sheet 70 in contact with the substrate 61 and the temperature sensor 80 for detecting the temperature of the heater 60. The temperature sensor 80 contacts the metal sheet 70 through the hole 75A1. In addition, the first extension portion 70B (the end portion in the short side direction) of the metal sheet 70 is inserted into the hole 75A1 in the short side direction of the substrate 61, thereby positioning the metal sheet 70 relative to the heater 60. In this way, in the fixing device 45 and image forming apparatus 1 of this embodiment, the metal sheet 70 is positioned relative to the heater 60, thereby preventing the metal sheet 70 from shifting in position relative to the temperature sensor 80.

[0083] Therefore, in the fixing device 45 and image forming apparatus 1 of this embodiment, unlike the conventional example, it is possible to minimize displacement in the relative positions of the temperature sensor 80 and the heater 60, thereby stabilizing the temperature detection of the temperature sensor 80. As a result, in the fixing device 45 and image forming apparatus 1 of this embodiment, it is possible to suppress a decrease in the accuracy of detection of the fixing temperature by the temperature sensor 80, and further, it is possible to appropriately control the temperature of the heater 60, thereby suppressing the occurrence of a decrease in image quality in the image formation process.

[0084] Furthermore, in the fixing device 45 and image forming apparatus 1 of this embodiment, the temperature sensor 80 has a first temperature sensor 81 that detects the temperature at the center of the heater 60 in the longitudinal direction, and a second temperature sensor 82 that detects the temperature at an end of the heater 60 in the longitudinal direction from the first temperature sensor 81. Furthermore, two metal sheets 70 are arranged corresponding to the first temperature sensor 81 and the second temperature sensor 80, respectively. This allows the fixing device 45 and image forming apparatus 1 of this embodiment to stabilize the temperature detection by the first temperature sensor 81 and the second temperature sensor 82.

[0085] Furthermore, in the fixing device 45 and image forming apparatus 1 of this embodiment, the current interrupting member 83 is disposed on one longitudinal end side of the heater 60, so that the current interrupting member 83 can detect the temperature of the end side in the width direction of the sheet S1. As a result, in the fixing device 45 and image forming apparatus 1 of this embodiment, the current interrupting member 83 can ensure the responsiveness of the heater 60 to the temperature, and can also interrupt the flow of electricity to the resistance heating element 62 if the temperature of the heater 60 rises abnormally.

[0086] [Embodiment 2] Other embodiments of the present disclosure will be described below. For ease of explanation, the same reference numerals will be used to designate components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0087] Fig. 10(A) is a plan view showing the heater 60 of the heating unit 52 included in the fixing device 45 according to the second embodiment of the present disclosure, and Fig. 10(B) is a plan view showing the first temperature sensor 81, the second temperature sensor 82, and the current interruption member 83 of the heating unit 50. Fig. 11 is a cross-sectional view showing the first temperature sensor 81 and the metal sheet 70 of the heating unit 52.

[0088] In the drawings, the difference between the present embodiment 2 and the above-described embodiment 1 is that the second extending portion 70C (the end portion in the short direction) of the metal sheet 70 is bent obliquely upward toward the outside of the hole 75A1 or 75A2 and away from the substrate 61. Another difference between the present embodiment 2 and the above-described embodiment 1 is that the current interrupting member 83 is arranged within a range through which the sheet S1 with the minimum width H2 can pass.

[0089] 10(A) and 10(B), in the heating unit 52 of the second embodiment, the current interrupting member 83 is disposed within a range through which the sheet S1 having the minimum width H2 can pass. That is, the current interrupting member 83, like the first temperature sensor 81, detects the temperature of the central portion in the longitudinal direction.

[0090] As shown in Fig. 11, the metal sheet 70 of the second embodiment is provided with a second extending portion 70E instead of the second extending portion 70C shown in Fig. 6. The second extending portion 70E constitutes an end portion in the short direction of the metal sheet 70 and is bent in a direction away from the substrate 61 toward the outside of the hole 75A1 or 75A2. In other words, the second extending portion 70E is provided continuously with the first extending portion 70B, similar to the second extending portion 70C. Furthermore, unlike the second extending portion 70C, the second extending portion 70E is bent at a predetermined angle greater than 0° with respect to the surface 75M (Fig. 8) of the support portion 75A.

[0091] With the above configuration, the second embodiment achieves the same effects as the first embodiment. Furthermore, in the second embodiment, the current cutoff member 83 is disposed within a range through which the sheet S1 with the minimum width H2 can pass. As a result, in the second embodiment, the current cutoff member 83 can cut off the current to the resistance heating element 62 when the heater 60 abnormally rises in temperature, regardless of the size of the sheet S1 in the width direction.

[0092] Furthermore, in the second embodiment, the metal sheet 70 is provided with a second extending portion 70E that is bent obliquely upward outside the hole 75A1 or 75A2. This makes it possible to easily assemble the metal sheet 70 to the holder 75 in the second embodiment.

[0093] In the above explanation, a configuration using a metal sheet 70 was described, but the present disclosure is not limited to any sheet that comes into contact with the temperature sensor 80, and sheets made of other materials may also be used.

[0094] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Configurations obtained by appropriately combining the technical means disclosed in each embodiment are also included in the technical scope of the present disclosure. [Explanation of symbols]

[0095] 1. Image forming device 45 Fixing device 53 Belt 60 Heater 61 PCB 62 Resistance heating element 70 Metal Sheets 70A central part 70B 1st extension part 70C, 70E 2nd extension 70D opening 75 Holder 75A1 hole 75A11 Wall 80 Temperature Sensor 81 First temperature sensor 82 Second temperature sensor 83 Current interrupting member S1 Seat

Claims

1. a heater having a substrate and a resistive heating element disposed on the substrate; an endless belt having an inner circumferential surface in contact with the heater and rotating around the heater; a holder having a hole formed therein and configured to hold the heater; a metal sheet in contact with the substrate; a temperature sensor that detects the temperature of the heater, the temperature sensor contacts the metal sheet through the hole; In the fixing device, the metal sheet is positioned relative to the heater by inserting an end of the metal sheet into the hole in the short-side direction of the substrate.

2. The metal sheet is The fixing device according to claim 1 , wherein both ends in the short side direction are bent in a direction intersecting with the substrate.

3. The fixing device of claim 2, wherein the metal sheet has a central portion that contacts the substrate, a pair of first extension portions that extend from both ends of the central portion in a direction perpendicular to the longitudinal direction and the lateral direction of the substrate, and a pair of second extension portions that extend in the lateral direction from the ends of the pair of first extension portions.

4. the holder includes a wall having the hole; 4. The fixing device according to claim 1, wherein the metal sheet is positioned in the longitudinal direction by abutting an end face of the metal sheet in the longitudinal direction against the wall.

5. The metal sheet is The fixing device according to claim 1 , wherein an opening is formed in the center of the metal sheet in the longitudinal direction at the portion to be inserted into the hole.

6. The metal sheet is The fixing device according to claim 1 , wherein the end in the short side direction protrudes beyond the hole on the side opposite to the substrate.

7. The metal sheet is The fixing device according to claim 6 , wherein the end portion in the short side direction is bent outward from the hole.

8. The metal sheet is The fixing device according to claim 7 , wherein the end portion in the short side direction is bent in a direction away from the substrate toward the outside of the hole.

9. The fixing device according to claim 1 , wherein a contact area between the substrate and the metal sheet is smaller than a contact area between the substrate and the holder.

10. The fixing device according to claim 1 , wherein the thermal conductivity of the metal sheet is greater than the thermal conductivity of the substrate.

11. The fixing device according to claim 1 , wherein the metal sheet is made of aluminum, phosphor bronze, stainless steel, or titanium.

12. The temperature sensor a first temperature sensor that detects the temperature of a central portion of the heater in the longitudinal direction; a second temperature sensor that detects a temperature closer to the end in the longitudinal direction than the first temperature sensor, The fixing device according to claim 1 , wherein the two metal sheets are arranged corresponding to the first temperature sensor and the second temperature sensor, respectively.

13. The heater further includes a current interrupting member that interrupts current to the resistance heating element when the heater temperature rises abnormally, The fixing device according to claim 1 , wherein the current interrupting member contacts a surface of the substrate opposite to a surface that contacts the belt.

14. The fixing device according to claim 13 , wherein the current interrupting member is disposed at a center portion in the longitudinal direction of the heater.

15. An image forming apparatus comprising the fixing device according to claim 1 .

Images