Fixing device and image forming apparatus

Abstract

To provide a fixing device that can accurately detect a fixing temperature regardless of a sheet size, and an image forming apparatus.SOLUTION: A fixing device comprises: a heater (60) that has resistance heating elements (62); a holder (75) that holds the heater (60); a heat conduction member (70) that is arranged between the heater (60) and the holder (75); and a second temperature detection member (82) that detects the temperature at an end in a longitudinal direction of the heater (60). The heat conduction member (70) has a first heat conduction member (71) and a second heat conduction member (72) arranged such that their end faces face each other in the longitudinal direction, and the second temperature detection member (82) is in contact with the first heat conduction member (71). An opposite position being a position between the first heat conduction member (71) and the second heat conduction member (72) is located closer to the second temperature detection member (82) than the middle position of the resistance heating elements (62) in the longitudinal direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Known image forming apparatuses, 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 detection element that detects the heater's temperature. The fixing temperature is controlled based on the temperature detection element's detection results. It has also been proposed that a conventional fixing device include a heat conductive element between the heater and a holder that supports the heater, and that the temperature is detected by bringing a temperature detection element into contact with the heat conductive element (see, for example, Patent Document 1 below). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-99190 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the conventional fixing device described above, a long heat conductive member corresponding to the maximum width of the sheet that can be used in the fixing device is used, and therefore, depending on the sheet size, the fixing temperature during the fixing operation cannot be detected with high accuracy.

[0005] Specifically, in a conventional fixing device, for example, when fixing a sheet of the smallest width that can be used with the fixing device, the temperature detection member provided on the end of the heater may detect a temperature including the temperature of the low temperature region in the center of the heater in the longitudinal direction. As a result, the conventional fixing device may not be able to detect the temperature on the end of the heater in the longitudinal direction with high accuracy.

[0006] An object of the present disclosure is to provide a fixing device and an image forming apparatus that can detect the fixing temperature with high accuracy regardless of the sheet size. [Means for solving the problem]

[0007] In order to solve the above problem, a fixing device of a first aspect of the present disclosure comprises a heater having a substrate and a resistance heating element arranged on the substrate, an endless belt having an inner surface in contact with the heater and rotating around the heater, a holder for holding the heater, a heat conduction member arranged between the heater and the holder, and a temperature detection member for detecting the temperature of the longitudinal end of the heater, wherein the heat conduction member has a first heat conduction member and a second heat conduction member arranged closely together so that their end faces face each other in the longitudinal direction, the temperature detection member contacts the first heat conduction member, and the opposing position between the first heat conduction member and the second heat conduction member is closer to the temperature detection member than the center position of the resistance heating element in the longitudinal direction.

[0008] According to the above configuration, the temperature detection member is in contact with the first heat conduction member or the second heat conduction member, which is located closer to the temperature detection member than the center of the resistance heating element. Therefore, unlike conventional examples, when performing a fixing operation on a sheet with the minimum width usable in the fixing device, the temperature detection member can detect the temperature at the longitudinal end portion while suppressing the influence of temperatures including the temperature in the low-temperature region at the longitudinal center. This makes it possible to configure a fixing device that can detect the fixing temperature with high accuracy regardless of the sheet size.

[0009] A second aspect of the present disclosure is the fixing device of the first aspect, wherein the opposing position may be located inside, in the longitudinal direction, an end in the width direction of a sheet having a minimum width that can be used in the fixing device.

[0010] According to the above configuration, when performing the fixing operation on a sheet with the smallest width that can be used in the fixing device, it is possible to easily increase the temperature on the first heat conductive member side, while enhancing the heat transfer effect of the heat conductive member when performing the fixing operation on a sheet with a width other than the smallest, thereby more reliably detecting the fixing temperature with high accuracy regardless of the sheet size.

[0011] A third aspect of the present disclosure is a fixing device of the first aspect, wherein the opposing position may be, in the longitudinal direction, outside the widthwise end of a sheet of a minimum width that can be used in the fixing device, and inside the widthwise end of a sheet of an intermediate width that can be used in the fixing device.

[0012] According to the above configuration, when performing fixing operation on a sheet of the smallest width that can be used in the fixing device, it is easier to increase the temperature on the first heat conduction member side, and the temperature detection member can detect the temperature with higher accuracy.

[0013] A fourth aspect of the present disclosure is the fixing device according to any one of the first to third aspects, wherein the temperature detection member may be disposed at an end position of the resistance heating element in the longitudinal direction.

[0014] According to the above configuration, the temperature detecting member can detect the temperature at the longitudinal end of the resistance heating element where the temperature rises more easily, and the detection accuracy of the fixing temperature can be more reliably improved.

[0015] A fifth aspect of the present disclosure is a fixing device according to any one of the first to fourth aspects, wherein the temperature detection member may be positioned within a width-wise range of an intermediate-width sheet that can be used in the fixing device.

[0016] According to the above configuration, when a fixing operation is performed on a sheet with the smallest width that can be used in the fixing device, the temperature detection member can detect the temperature rise in the first heat conduction member with high accuracy.

[0017] A sixth aspect of the present disclosure is a fixing device according to any one of the first to fourth aspects, wherein an end of the first heat conduction member opposite the second heat conduction member is positioned outside the resistance heating element in the longitudinal direction, and the temperature detection element may be arranged outside the longitudinal end of the resistance heating element.

[0018] According to the above configuration, the heat resistance temperature of the temperature detection member can be reduced.

[0019] A seventh aspect of the present disclosure is a fixing device according to any one of the first to sixth aspects, further comprising a current interrupting member that interrupts current to the resistance heating element when the heater abnormally rises in temperature, and the current interrupting member may be positioned at the opposing position and in contact with the substrate.

[0020] According to the above configuration, the current interrupting member comes into contact with the substrate, so that the current interrupting member can easily ensure responsiveness to the temperature of the heater.

[0021] An image forming apparatus according to an eighth aspect of the present disclosure includes the fixing device according to any one of the first to seventh aspects.

[0022] According to the above configuration, it is possible to configure an image forming apparatus that can detect the fixing temperature with high accuracy regardless of the sheet size. [Effects of the Invention]

[0023] According to one aspect of the present disclosure, it is possible to provide a fixing device and an image forming apparatus that can detect the fixing temperature with high accuracy regardless of the sheet size. [Brief explanation of the drawings]

[0024] [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, (B) is a plan view showing a heat conduction member of the heating unit, and (C) is a plan view showing 6, a second temperature detection member, and a current interruption member of the heating unit. [Figure 3] FIG. 2(A) is a perspective view showing the first temperature detecting member and the second temperature detecting member, and FIG. 2(B) is a perspective view showing the current interrupting member. [Figure 4] FIG. 3 is a cross-sectional view showing the first temperature detection member of the heating unit. [Figure 5] FIG. 4 is a cross-sectional view showing the current interruption member of the heating unit. [Figure 6] FIG. 4 is a cross-sectional view showing the second temperature detecting member of the heating unit. [Figure 7] (A) is a side view showing the main configuration of the heating unit of the comparative example, (B) is a diagram explaining the temperature distribution during the fixing operation of the maximum width sheet in the comparative example, and (C) is a diagram explaining the temperature distribution during the fixing operation of the minimum width sheet in the comparative example. [Figure 8] (A) is a side view showing the main configuration of the heating unit of embodiment 1, (B) is a diagram explaining the temperature distribution during the fixing operation of a maximum width sheet in embodiment 1, (C) is a diagram explaining the temperature distribution during the fixing operation of a minimum width sheet in embodiment 1, and (D) is a diagram explaining the temperature distribution during the fixing operation of a medium width sheet in embodiment 1. [Figure 9] 1A is a side view showing the configuration of the main part of a heating unit according to a first modification of the present disclosure, and FIG. 1B is a diagram illustrating the temperature distribution during the fixing operation of a sheet with the minimum width according to the first modification. [Figure 10] 10A is a side view showing the configuration of the main part of a heating unit according to a second modification of the present disclosure, and FIG. 10B is a diagram illustrating the temperature distribution during the fixing operation of a sheet with the minimum width according to the second modification. [Figure 11] FIG. 10 is a side view showing the configuration of a main part of a heating unit according to a second embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0025] [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.

[0026] [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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 1, the pressure roller 51 is driven to rotate clockwise in accordance with instructions from the control unit. In other words, the pressure roller 51 rotates while sandwiching the sheet S1, which is being transported to the discharge tray 6 side, between the pressure roller 51 and a belt 53 (described later) provided in the heating unit 52, so that the belt 53 is driven to rotate in a predetermined rotation direction by the frictional forces between the pressure roller 51, the belt 53, and the sheet S1, as illustrated by R in FIG. 4 (described later). As a result, in the fixing device 45, the sheet S1, on which the toner image has been transferred, is transported between the pressure roller 51 and the heating unit 52, and the toner image is thermally fixed onto the sheet S1.

[0039] [Configuration of heating unit 52] Here, the heating unit 52 of this embodiment will be specifically described with reference to FIGS. 2 to 6. 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. FIG. 2(B) is a plan view showing the heat conduction member 70 of the heating unit 52. FIG. 2(C) is a plan view showing the first temperature detection member 81, the second temperature detection member 82, and the current interruption member 83 of the heating unit 52. FIG. 3(A) is a perspective view showing the first temperature detection member 81 and the second temperature detection member 82. FIG. 3(B) is a perspective view showing the current interruption member 83. FIG. 4 is a cross-sectional view showing the first temperature detection member 81 of the heating unit 52. FIG. 5 is a cross-sectional view showing the current interruption member 83 of the heating unit 52. FIG. 6 is a cross-sectional view showing the second temperature detection member 82 of the heating unit 52.

[0040] 2(A) to 2(C), the heating unit 52 of this embodiment includes a heater 60, a holder 75 that holds the heater 60, and a heat conduction member 70 that is disposed between the heater 60 and the holder 75. The heater 60 is a heating member that is rectangular in plan view, and includes a substrate 61 and, for example, two resistance heating elements 62 that are disposed on the substrate 61.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 2A, in the heater 60, the resistance heating element 62 has a longitudinal dimension that 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 be able to accommodate a plurality of types of sheets S1 with different widths. Specifically, the fixing device 45 performs a fixing operation on sheets S1 of a plurality 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.

[0045] 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.

[0046] 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.

[0047] 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 accommodates heater 60, heat conduction member 70, holder 75, first temperature detection member 81, second temperature detection member 82, and current-cutting member 83 therein, and rotates around heater 60, heat conduction member 70, holder 75, first temperature detection member 81, second temperature detection member 82, and current-cutting member 83.

[0048] Furthermore, the inner peripheral surface of the belt 53 is in contact with 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. In addition, the longitudinal dimension of the belt 53 is larger than the dimension of the resistance heating element 62, as shown in Fig. 8(A) below.

[0049] The holder 75 is made of, for example, a synthetic resin material. As shown in Fig. 2(C), the holder 75 has a support portion 75A that supports the heater 60. That is, the support portion 75A abuts against the heat conductive member 70 and supports the substrate 61 of the heater 60, shown by the dotted line in Fig. 2(C), with the heat conductive member 70 interposed therebetween. 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.

[0050] The heat conduction member 70 is made of a metal material with high thermal conductivity, such as aluminum, an aluminum alloy, or copper, and functions as a heat equalizer plate for conducting heat in the longitudinal direction of the heater 60 and uniformizing the temperature of the heater 60 in the longitudinal direction. The heat conduction member 70 can also be made of an anisotropic heat conduction member such as a graphite sheet. When using such an anisotropic heat conduction member, it is desirable to make the heat conductivity in the longitudinal direction greater than the heat conductivity in the thickness direction.

[0051] 2(B), the heat conduction member 70 has a first heat conduction member 71 and a second heat conduction member 72 that are arranged closely together so that their end faces face each other in the longitudinal direction of the heater 60. Here, "arranged closely together so that their end faces face each other" refers to a state in which the end face of the first heat conduction member 71 and the end face of the second heat conduction member 72 are in contact with each other in the longitudinal direction, or a state in which they are separated by a predetermined gap.

[0052] 2(B), the first heat conducting member 71 is provided to correspond to an area including almost the entire end region H3 at one end of the heater 60 in the longitudinal direction. As will be described in detail later, the first heat conducting member 71 is in direct contact with a second temperature detecting member 82 serving as a temperature detecting member for detecting the temperature of the end of the heater 60 in the longitudinal direction.

[0053] 2(B), second heat conduction member 72 is provided so as to correspond to a range including minimum width H2 and the entire end region H4 at the center and the other end of heater 60 in the longitudinal direction. As will be described in detail later, second heat conduction member 72 has openings 72A and 72B formed in the center, and first temperature detection member 81 and current interruption member 83 are in direct contact with rear surface 61A of substrate 61 via openings 72A and 72B, respectively.

[0054] 2(B), the opposing position between first heat conducting member 71 and second heat conducting member 72 is set closer to second temperature detecting member 82 in the longitudinal direction than the center position of resistance heating element 62. Specifically, the opposing position is within end region H3 as shown in FIG.

[0055] The first temperature detecting member 81 and the second temperature detecting member 82 are configured using, for example, a thermistor. In the following description, the first temperature detecting member 81 and the second temperature detecting member 82 will be collectively referred to as the temperature detecting member 80.

[0056] 3(A), the temperature detection member 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 detection member 80, by pressing the temperature detection element 80D with the protruding member 80B, the temperature detection element 80D can be reliably brought into contact with the object to be detected, thereby enabling accurate temperature detection.

[0057] As shown in Fig. 2(C), the first temperature detection member 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. 4, the protruding member 80B of the first temperature detection member 81 is inserted successively through the opening 75A1 of the holder 75 and the opening 72A of the second thermal conductive member 72, and the temperature detection element 80D comes into contact with the rear surface 61A of the substrate 61, thereby detecting the temperature of the central portion. The first temperature detection member 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 detection member 81.

[0058] In addition to this description, the first temperature detection member 81 may be configured to contact the second heat conduction member 72 by contacting the protruding member 80B with the back surface of the second heat conduction member 72 without forming the opening 75A1 of the holder 75 and the opening 72A of the second heat conduction member 72.

[0059] As shown in Fig. 2(C), the second temperature detection member 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 detection member 81. Specifically, as shown in Fig. 6, the protruding member 80B of the second temperature detection member 82 is inserted into the opening 75A2 of the holder 75, and the temperature detection element 80D comes into contact with the back surface of the first heat conduction member 71, thereby detecting the temperature of the longitudinal end. The second temperature detection member 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 detection member 82.

[0060] 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 detecting unit 83B that protrudes upward from the container 83A and detects the temperature. The container 83A is connected to the temperature detecting 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.

[0061] 2(C), the current interrupting member 83 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, in the current interrupting member 83, as shown in FIG. 5, the temperature detecting portion 83B is inserted successively through the opening 75A3 of the holder 75 and the opening 72B of the second thermal conductive member 72, and the temperature detecting portion 83B comes into contact with the rear surface 61A of the substrate 61, thereby detecting the temperature of the central portion.

[0062] As described above, the fixing device 45 of this embodiment and the image forming apparatus 1 using the same include the heater 60 having the resistance heating element 62, the holder 75 that holds the heater 60, the heat conducting member 70 arranged between the heater 60 and the holder 75, and the second temperature detection member 82 that detects the temperature of the longitudinal end of the heater 60. The heat conducting member 70 has a first heat conducting member 71 and a second heat conducting member 72 that are arranged close to each other so that their end faces face each other in the longitudinal direction, and the second temperature detection member 82 is in contact with the first heat conducting member 71. The opposing position between the first heat conducting member 71 and the second heat conducting member 72 is located closer to the second temperature detection member 82 than the center position of the resistance heating element 62 in the longitudinal direction. As a result, in this embodiment, when performing a fixing operation on a sheet S1 having the minimum width H2 usable in the fixing device 45, the second temperature detection member 82 can detect the temperature at the end in the longitudinal direction while suppressing the influence of temperatures including the temperature of the low-temperature region in the central portion in the longitudinal direction, unlike when there is no opposing position between the first heat conductive member 71 and the second heat conductive member 72. Therefore, in this embodiment, it is possible to configure a fixing device 45 and an image forming apparatus 1 that can detect the fixing temperature with high accuracy regardless of the sheet size.

[0063] Furthermore, in this embodiment, the second temperature detection member 82 is positioned at the longitudinal end of the resistance heating element 62, so that the second temperature detection member 82 can detect the temperature at the longitudinal end of the resistance heating element 62, where the temperature rises more easily, thereby more reliably improving the detection accuracy of the fixing temperature.

[0064] Here, the effects of the fixing device 45 and the image forming apparatus 1 of this embodiment will be specifically described with reference to FIGS. 7 and 8. FIG. 7(A) is a side view showing the configuration of the main components of a heating unit of a comparative example, FIG. 7(B) is a diagram illustrating the temperature distribution during the fixing operation of a maximum-width sheet in the comparative example, and FIG. 7(C) is a diagram illustrating the temperature distribution during the fixing operation of a minimum-width sheet in the comparative example. FIG. 8(A) is a side view showing the configuration of the main components of a heating unit of the first embodiment, FIG. 8(B) is a diagram illustrating the temperature distribution during the fixing operation of a maximum-width sheet in the first embodiment, FIG. 8(C) is a diagram illustrating the temperature distribution during the fixing operation of a minimum-width sheet in the first embodiment, and FIG. 8(D) is a diagram illustrating the temperature distribution during the fixing operation of a medium-width sheet in the first embodiment.

[0065] As shown in Figure 7(A), in the comparative example, the heating unit 152 includes a heater 160 having a resistance heating element 162, a holder 175, a belt 153, a single heat conduction member 170, and a temperature detection member 182 that contacts the heat conduction member 170 and detects the temperature of the longitudinal end of the heater 160.

[0066] In the comparative example, as shown in Fig. 7(B), when a fixing operation is performed on a sheet S1 of maximum width H1 usable by the heating unit 152, the longitudinal dimension of the sheet S1 of maximum width H1 is slightly smaller than the heat generation range HA1 of the resistance heating element 162. As a result, a non-paper passing area occurs outside the maximum width H1, and the temperature of the heater 160 rises in the non-paper passing area, and the temperature distribution of the heater 160 is shown by waveform g1. Then, as shown in Fig. 7(B), the temperature detection member 182 detects a temperature slightly higher than the temperature at the center as the temperature at the edge.

[0067] 7C, in the comparative example, when a fixing operation is performed on a sheet S1 having a minimum width H2 that can be used by the heating unit 152, the longitudinal dimension of the sheet S1 having the minimum width H2 is smaller than the maximum width H1 of the heat generation range HA1 of the resistance heating element 162. As a result, a relatively large non-paper passing area occurs, causing a relatively large rise in temperature at the edge.

[0068] However, in the comparative example, the temperature of the end portion is equalized with the temperature of the central portion, which is a relatively low-temperature region, by the heat conduction member 170, and therefore, the temperature distribution of the heater 160, as shown by waveform g2, shows a reduced increase in temperature at the end portion compared to waveform g3, which shows the temperature distribution when the heat conduction member 170 is not provided.Then, the temperature detection member 182 detects the temperature reduced by the temperature of the central portion as the temperature of the end portion, as shown in Fig. 7(C).

[0069] In this way, in the comparative example, when performing a fixing operation on a sheet S1 with a minimum width H2, the temperature detection member 182 detects a temperature at the edge that is lower than the actual temperature. As a result, in the comparative example, it is not possible to detect the temperature of the sheet S1 with a minimum width H2 with high accuracy.

[0070] In contrast, in this embodiment, as shown in Figure 8 (A), the heating unit 52 includes a heater 60 having a resistance heating element 62, a holder 75, a belt 53, a first heat conduction member 71, a second heat conduction member 72, and a second temperature detection member 82 that contacts the first heat conduction member 71 and detects the temperature of the longitudinal end of the heater 60.

[0071] 8(B), when a fixing operation is performed on a sheet S1 having a maximum width H1 that can be used by the heating unit 52, the longitudinal dimension of the sheet S1 having the maximum width H1 is slightly smaller than the heat generation range HA1 of the resistance heating element 62. As a result, a non-paper passing region occurs outside the maximum width H1, the temperature of the heater 60 rises in the non-paper passing region, and the temperature distribution of the heater 60 is uniformed with the temperature of the central portion of the relatively low temperature region by the first heat conducting member 71 and the second heat conducting member 72, as shown by waveform G1.

[0072] As shown in FIG. 8(B), the second temperature detecting member 82 can accurately detect a temperature slightly higher than the temperature at the central portion as the temperature at the end portion.

[0073] 8C, when a fixing operation is performed on a sheet S1 having a minimum width H2 that can be used by the heating unit 52, the longitudinal dimension of the sheet S1 having the minimum width H2 is smaller than the maximum width H1 of the heat generation range HA1 of the resistance heating element 62. This results in a relatively large non-paper passing area, causing a relatively large rise in temperature at the edge.

[0074] However, in this embodiment, the heat conduction member 70 is divided in the longitudinal direction into a first heat conduction member 71 and a second heat conduction member 72, and these first heat conduction member 71 and second heat conduction member 72 are arranged closely together so that their end faces face each other in the longitudinal direction. Furthermore, in this embodiment, the opposing position of these first heat conduction member 71 and second heat conduction member 72 is closer to the second temperature detection member 82 than the center position of the resistance heating element 62 in the longitudinal direction.

[0075] Therefore, in this embodiment, the temperature distribution of the heater 60 differs from that of the comparative example in that the influence of the temperature in the central portion of the heater 60, which is a relatively low-temperature region, is suppressed, as shown by waveform G2. Furthermore, the second temperature detection member 82 can accurately detect the temperatures of the longitudinal end portions, as shown in Fig. 8(C). Note that, in the temperature distribution when the first thermal conductive member 71 and the second thermal conductive member 72 are not installed, the temperature in the end portion H4 is not uniformized with the temperature in the central portion by the second thermal conductive member 72, so the temperature in the end portion H4 rises, as shown by waveform G3.

[0076] 8(D), when the heating unit 52 performs a fixing operation on a sheet S1 having an intermediate width H5 between the maximum width H1 and the minimum width H2, the longitudinal dimension of the sheet S1 having the intermediate width H5 is slightly smaller than the maximum width H1 with respect to the heat generation range HA1 of the resistance heating element 62. Therefore, a non-sheet passing area that is relatively smaller than that of the sheet S1 having the minimum width H2 is generated, and the temperature rise at the edge is relatively small.

[0077] However, in this embodiment, since the first heat conduction member 71 is provided as described above, the temperature distribution of the heater 60 is shown by waveform G4, as in the case of the sheet S1 with the minimum width H2, with the influence of the temperature in the central portion of the relatively low temperature region being suppressed. Furthermore, the second temperature detection member 82 can accurately detect the temperature at the end portions in the longitudinal direction, as shown in Fig. 8(D).

[0078] Furthermore, as in the comparative example, when a single, undivided heat conduction member is used instead of the first heat conduction member 71 and the second heat conduction member 72, during the fixing operation on the sheet S1 of medium width H5, the temperature distribution of the heater 60 is shown by waveform G5, as the influence of the temperature in the central part of the relatively low temperature region cannot be suppressed.

[0079] As described above, in this embodiment, the second temperature detection member 82 can accurately detect the temperature of the end portion in the longitudinal direction during the fixing operation, regardless of the sheet size.

[0080] 8(D), in this embodiment, the opposing positions of the first heat conductive member 71 and the second heat conductive member 72 are set within the edge region H3, outside the widthwise edge of the sheet S1 with the minimum width H2 and inside the widthwise edge of the sheet S1 with the intermediate width H5. As a result, in this embodiment, when performing a fixing operation on a sheet S1 with the minimum width H2, it is easier to increase the temperature on the side of the first heat conductive member 71, and the second temperature detection member 82 can detect the temperature with higher accuracy.

[0081] In the above description, the first heat conductive member 71 and the second heat conductive member 72 are positioned facing each other within the edge region H3. However, this embodiment is not limited to this. For example, the facing positions may be set inside the widthwise edge of the sheet S1 having the minimum width H2 in the longitudinal direction, i.e., within the range of the minimum width H2 in FIG. 2. This makes it easier to increase the temperature on the first heat conductive member 71 side when performing the fixing operation on the sheet S1 having the minimum width H2, while improving the heat transfer effect of the heat conductive member 70 when performing the fixing operation on a sheet other than the sheet S1 having the minimum width H2. As a result, the fixing temperature can be detected with high accuracy more reliably, regardless of the sheet size.

[0082] [Variation 1] Fig. 9(A) is a side view showing the configuration of the main part of the heating unit of Modification 1 of the present disclosure, and Fig. 9(B) is a diagram illustrating the temperature distribution during the fixing operation of a sheet of minimum width in Modification 1. For ease of explanation, members having the same functions as those described in the above embodiment are denoted by the same reference numerals, and their description will not be repeated.

[0083] In Modification 1, as shown in FIG. 9A, in the heating unit 52, the second temperature detection member 82 is disposed within the width direction of the sheet S1 having the intermediate width H5. As a result, in Modification 1, the second temperature detection member 82 is disposed further inward in the longitudinal direction than in Embodiment 1. Specifically, the second temperature detection member 82 shown by the dashed line in FIG. 9B is the position in Embodiment 1, and the second temperature detection member 82 shown by the solid line is the position in Modification 1. As a result, when performing a fixing operation on a sheet S1 having the minimum width H2, the second temperature detection member 82 can more accurately detect the temperature rise in the first heat conduction member 71 with respect to the temperature distribution of the heater 60 shown by waveform G2 in FIG. 9B.

[0084] [Variation 2] Fig. 10(A) is a side view showing the configuration of the main part of the heating unit of Modification 2 of the present disclosure, and Fig. 10(B) is a diagram illustrating the temperature distribution during the fixing operation of a sheet of minimum width in Modification 2. For ease of explanation, members having the same functions as those described in the above embodiment are denoted by the same reference numerals, and their description will not be repeated.

[0085] 10(A), in the heating unit 52, the end of the first heat conductive member 71 opposite the second heat conductive member 72 is positioned outside the resistance heating element 62 in the longitudinal direction of the heater 60. In addition, the second temperature detection element 82 is disposed outside the longitudinal end of the resistance heating element 62. As a result, in the present modification 2, when performing a fixing operation on a sheet S1 having a minimum width H2, the second temperature detection element 82 can more accurately detect the temperature rise in the first heat conductive element 71 with respect to the temperature distribution of the heater 60 shown by waveform G6 in FIG.

[0086] In addition, waveform G7 in Figure 10 (B) is the temperature distribution of the heater 60 when the first heat conduction member 71 is not extended outside the longitudinal direction of the heater 60, but is instead arranged inside the resistance heating element 62.

[0087] Furthermore, in Modification 2, second temperature detection member 82 detects a temperature lower than the peak in the temperature distribution of heater 60 shown in waveform G7, which is the same as waveform G2 in Figure 8(C), as the temperature of the end portion. That is, in Modification 2, the detected temperature of second temperature detection member 82 can be made lower than in Embodiment 1, in which the end portion of first heat conduction member 71 opposite second heat conduction member 72 is located more inward than resistance heating element 62.

[0088] As a result, in Modification 2, the heat resistance temperature of the second temperature detection member 82 can be reduced compared to Embodiment 1, making it easy to reduce costs. Also, in Modification 2, it is possible to reduce the threshold value in the control unit for determining the degree of temperature rise at the longitudinal end, making it easy to simplify the configuration and operation of the control unit.

[0089] [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.

[0090] 11 is a side view showing the configuration of a main part of a heating unit according to Embodiment 2 of the present disclosure. In the figure, the present embodiment differs from Embodiment 1 in that a current interruption member 83 is disposed at a position facing first heat conduction member 71 and second heat conduction member 72.

[0091] 11, in the heating unit 52 of the second embodiment, the first heat conductive member 71 and the second heat conductive member 72 are arranged with a predetermined gap therebetween. In addition, a current interrupting member 83 is provided in this gap in a state of contact with the rear surface of the substrate of the heater 60.

[0092] With the above configuration, the second embodiment achieves the same effects as the first embodiment. Furthermore, in the second embodiment, as in the first embodiment, the current interrupting member 83 is in contact with the rear surface 61A of the substrate 61 of the heater 60, so that the current interrupting member 83 can easily ensure responsiveness to the temperature of the heater 60. That is, because the current interrupting member 83 is in direct contact with the rear surface 61A of the substrate 61 of the heater 60, the current interrupting member 83 can quickly detect a rise in the temperature of the heater 60 and can also quickly detect whether the temperature of the heater 60 has reached the predetermined temperature as the cut-off temperature.

[0093] Furthermore, in this embodiment 2, unlike embodiment 1, the current interrupting member 83 is arranged at the above-mentioned opposing position, so that the installation of the opening 72B of the second heat conducting member 72 shown in Figure 5 can be omitted, and the current interrupting member 83 can be easily installed without performing processing on the second heat conducting member 72 for installation.

[0094] In the above explanation, the heat conduction member 70 is divided into a first heat conduction member 71 and a second heat conduction member 72. However, the present disclosure is not limited in any way to the number of divided parts of the heat conduction member 70 or their positions, as long as the configuration includes a second temperature detection member 82 as a temperature detection member that detects the temperature of the longitudinal end of the heater 60 and a first heat conduction member 71 that contacts this second temperature detection member 82, and the opposing position of the heat conduction member facing the first heat conduction member 71 is set closer to the second temperature detection member 82 than the center position of the resistance heating element 62 in the longitudinal direction.

[0095] 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]

[0096] 1. Image forming device 45 Fixing device 53 Belt 60 Heater 61 PCB 62 Resistance heating element 70 Thermal Conduction Materials 71 first heat conductive member 72 second heat conductive member 75 Holder 82 Second temperature detection member 83 Current interrupting member S1 Seat H1 maximum width H2 minimum width H5 Medium width

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 for holding the heater; a heat conducting member disposed between the heater and the holder; a temperature detection member for detecting the temperature of an end portion of the heater in the longitudinal direction, the heat conduction member includes a first heat conduction member and a second heat conduction member that are arranged close to each other so that end surfaces thereof face each other in the longitudinal direction; the temperature detection member is in contact with the first heat conduction member, a fixing device, wherein an opposing position between the first heat conducting member and the second heat conducting member is located closer to the temperature detecting member than a center position of the resistance heating element in the longitudinal direction;

2. 2. The fixing device according to claim 1, wherein the facing position is located inside, in the longitudinal direction, an end in the width direction of a sheet having a minimum width that can be used in the fixing device.

3. 2. The fixing device according to claim 1, wherein the opposing position is, in the longitudinal direction, outside the widthwise end of a sheet of a minimum width that can be used in the fixing device, and inside the widthwise end of a sheet of an intermediate width that can be used in the fixing device.

4. The fixing device according to claim 1 , wherein the temperature detection member is disposed at an end of the resistance heating element in the longitudinal direction.

5. The fixing device according to claim 1 , wherein the temperature detection member is disposed within a width direction range of a medium-width sheet that can be used in the fixing device.

6. an end of the first heat conducting member opposite to the second heat conducting member is located outside the resistance heating element in the longitudinal direction; The fixing device according to claim 1 , wherein the temperature detection member is disposed outside an end portion of the resistance heating element in the longitudinal direction.

7. 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 is disposed at the opposing position and is in contact with the substrate.

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

Images