Fixing device and image forming apparatus

Abstract

To provide a fixing device that can accurately detect a fixing temperature even when the printing speed is accelerated, and an image forming apparatus.SOLUTION: A fixing device comprises: a heater (60) that has resistance heating elements (62) arranged on a substrate (61); a first temperature detection member (81) that detects the temperature of a center part in a longitudinal direction of the heater (60); and a second temperature detection member (82) that detects the temperature at a position closer to an end in the longitudinal direction than the first temperature detection member (81). The second temperature detection member (82) is arranged outside 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 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 detection element that detects the heater's temperature. The fixing temperature of the heater is controlled based on the temperature detection element's detection results. Furthermore, in order to accommodate the minimum and maximum widths of sheets that can be used with the fixing device, it has been proposed to provide two thermistors (temperature detection elements) in the heater's longitudinal direction, facing the center and end portions of the resistance heating element, respectively (see, for example, Patent Document 1 below). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-169413 Summary of the Invention [Problem to be solved by the invention]

[0004] In the conventional fixing device as described above, when the printing speed is increased, it is sometimes impossible to detect the fixing temperature with high accuracy during the fixing operation. Specifically, in the conventional fixing device, when the printing speed is increased, particularly when the printing speed is increased with a minimum width sheet, it is sometimes impossible to prevent the temperature detected by the temperature detecting member provided at the end from becoming too high, and therefore it is sometimes impossible to detect the fixing temperature with high accuracy.

[0005] 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 even when an attempt is made to increase the printing speed. [Means for solving the problem]

[0006] In order to solve the above problems, 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 first temperature detection member that detects the temperature of the center of the heater in the longitudinal direction, and a second temperature detection member that detects the temperature on the end side of the first temperature detection member in the longitudinal direction, and the second temperature detection member is arranged outside the resistance heating element in the longitudinal direction.

[0007] According to the above configuration, the second temperature detection member is disposed outside the resistance heating element in the longitudinal direction of the heater to detect the temperature, so the second temperature detection member can detect the temperature while suppressing the influence of excessive temperature rise at the longitudinal end portion. This makes it possible to configure a fixing device that can detect the fixing temperature with high accuracy even when attempting to increase the printing speed.

[0008] A second aspect of the present disclosure is the fixing device of the first aspect, wherein the second temperature detection member may be disposed within an installation range of the belt in the longitudinal direction.

[0009] According to the above configuration, the second temperature detection member can be brought closer to the resistance heating element, and temperature detection can be performed with higher accuracy while suppressing the effects of excessive temperature rise at the longitudinal end portions.

[0010] A third aspect of the present disclosure is a fixing device of the first or second aspect, further comprising a holder that holds the heater and a heat conduction member arranged between the heater and the holder, and the second temperature detection member may be in contact with the heat conduction member.

[0011] According to the above configuration, the second temperature detection member can quickly and accurately detect the temperature via the heat conduction member.

[0012] A fourth aspect of the present disclosure is a fixing device according to any one of the first to third aspects, wherein the heater includes a power supply terminal arranged at one end of the longitudinal direction and connected to the resistance heating element, and the second temperature detection member may be arranged on the other end side of the longitudinal direction.

[0013] According to the above configuration, the second temperature detection member is provided at an end side different from the end where the power supply terminal is provided in the longitudinal direction, so that the degree of freedom in arranging the second temperature detection member can be increased.

[0014] A fifth aspect of the present disclosure is a fixing device according to any one of the first to third aspects, wherein the heater includes a power supply terminal arranged at one end of the longitudinal direction and connected to the resistance heating element, and the second temperature detection member may be arranged on the one end side of the longitudinal direction.

[0015] According to the above configuration, the second temperature detection member is provided on the same end side as the power supply terminal in the longitudinal direction, so that the wiring connected to the second temperature detection member and the wiring connected to the power supply terminal can be provided on the same end side, improving the workability of routing and arranging these wirings, and making it easy to simplify the manufacture of the fixing device.

[0016] A sixth aspect of the present disclosure is a fixing device according to any one of the first to fifth aspects, further comprising a current interrupting member that cuts off current to the resistance heating element when the heater abnormally rises in temperature, and the current interrupting member may be positioned in the longitudinal direction within a range that allows a sheet of the smallest width that can be used in the fixing device to pass through.

[0017] 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.

[0018] A seventh aspect of the present disclosure is a fixing device according to any one of the first to fifth 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 arranged on one end side in the longitudinal direction.

[0019] According to the above configuration, the current interrupting member can detect the temperature of the end portion in the width direction of the sheet, and can interrupt the current when the heater temperature rises abnormally.

[0020] 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.

[0021] According to the above configuration, it is possible to configure an image forming apparatus that can detect the fixing temperature with high accuracy even when the printing speed is increased. [Effects of the Invention]

[0022] 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 even when an attempt is made to increase the printing speed. [Brief explanation of the drawings]

[0023] [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 a first temperature detection member, 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 detecting 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 sheet of the maximum width in embodiment 1, and (C) is a diagram explaining the temperature distribution during the fixing operation of a sheet of the minimum width in embodiment 1. [Figure 9] (A) is a plan view showing a heater of a heating unit provided in a fixing device relating to embodiment 2 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 a first temperature detection member, a second temperature detection member, and a current interruption member of the heating unit. DETAILED DESCRIPTION OF THE INVENTION

[0024] [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.

[0025] [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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] [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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 2(B), the heat conduction member 70 is provided so as to have a dimension larger than the range including the entire maximum width H1 in the longitudinal direction of the heater 60. In other words, the heat conduction member 70 extends in the longitudinal direction beyond the other end 62B of the resistance heating element 62 toward the other end of the substrate 61, and a second temperature detection member 82 that detects the temperature of the end of the heater 60 in the longitudinal direction is in direct contact with the extended portion of the heat conduction member 70, as will be described in detail later.

[0051] Furthermore, as will be described in detail later, openings 70A and 70B are formed in the heat conduction member 70 at the center and one end of the heater 60 in the longitudinal direction, respectively, and the first temperature detection member 81 and the current interruption member 83 are in direct contact with the back surface 61A of the substrate 61 via openings 70A and 70B, respectively.

[0052] 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.

[0053] 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.

[0054] 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 70A of the heat conduction member 70, 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.

[0055] In addition to this description, the first temperature detection member 81 may be configured to contact the heat conduction member 70 by contacting the protruding member 80B with the back surface of the heat conduction member 70 without forming the opening 75A1 of the holder 75 and the opening 70A of the heat conduction member 70.

[0056] As shown in Fig. 2(C), the second temperature detection member 82 is provided on the holder 75 so as to be positioned outside the resistance heating element 62 in the longitudinal direction, and detects the temperature at the end portion in the longitudinal direction relative to 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 heat conduction member 70, thereby detecting the temperature at the end portion in the longitudinal direction. 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 end portion in the longitudinal direction using the detection result of the second temperature detection member 82.

[0057] 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.

[0058] 2(C), 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 side in the longitudinal direction of the heater 60. Specifically, in the current interrupting member 83, as shown in FIG. 5, the temperature detecting unit 83B is inserted successively through the opening 75A3 of the holder 75 and the opening 70B of the heat conducting member 70, and the temperature detecting unit 83B comes into contact with the rear surface 61A of the substrate 61, thereby detecting the temperature of the one end side.

[0059] 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 disposed on the substrate 61, the first temperature detection member 81 that detects the temperature of the heater 60 at the longitudinal center, and the second temperature detection member 82 that detects the temperature at the longitudinal end of the heater 60 relative to the first temperature detection member 81. The second temperature detection member 82 is disposed outside the resistance heating element 62 in the longitudinal direction. Thus, in this embodiment, the second temperature detection member 82 is disposed outside the resistance heating element 62 in the longitudinal direction of the heater 60 to detect the temperature of the heater 60. This allows temperature detection to be performed while suppressing the effects of excessive temperature rise at the longitudinal end, compared to when the second temperature detection member 82 is disposed within the range of the resistance heating element 62. As a result, this embodiment can configure the fixing device 45 and image forming apparatus 1 that can detect the fixing temperature with high accuracy even when increasing the printing speed.

[0060] Furthermore, this embodiment further includes 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, and the second temperature detection member 82 is in contact with the heat conduction member 70. This allows the second temperature detection member 82 to quickly and accurately detect temperature via the heat conduction member 70.

[0061] 2, in this embodiment, the power supply terminal 63 of the heater 60 is disposed at one end in the longitudinal direction of the heater 60, and the second temperature detection member 82 is disposed at the other end in the longitudinal direction. As a result, in this embodiment, the second temperature detection member 82 can be disposed regardless of the power supply terminal 63 and the wiring connected thereto, and the degree of freedom in disposing the second temperature detection member 82 can be increased.

[0062] In addition, in this embodiment, the current interrupting member 83 is arranged on one end side of the heater 60 in the longitudinal direction, so that the current interrupting member 83 can detect the temperature on the end side of the sheet S1 in the width direction and can interrupt the flow of current to the resistance heating element 62 if the heater 60 becomes abnormally hot.

[0063] Here, the effects of the fixing device 45 and image forming apparatus 1 of this embodiment will be specifically described with reference to Figures 7 and 8. Figure 7(A) is a side view showing the configuration of the main parts of a heating unit of a comparative example, Figure 7(B) is a diagram illustrating the temperature distribution during the fixing operation of a maximum-width sheet in the comparative example, and Figure 7(C) is a diagram illustrating the temperature distribution during the fixing operation of a minimum-width sheet in the comparative example. Figure 8(A) is a side view showing the configuration of the main parts of a heating unit of embodiment 1, Figure 8(B) is a diagram illustrating the temperature distribution during the fixing operation of a maximum-width sheet in embodiment 1, and Figure 8(C) is a diagram illustrating the temperature distribution during the fixing operation of a minimum-width sheet in embodiment 1.

[0064] 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 heat conducting member 170, and a temperature detecting member 182 that contacts the heat conducting member 170 and detects the temperature of an end portion of the heater 160 in the longitudinal direction. In the comparative example, the temperature detecting member 182 is disposed within the range of the resistance heating element 162, rather than outside the resistance heating element 162.

[0065] 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.

[0066] 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.

[0067] 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).

[0068] In this way, in the comparative example, when performing a fixing operation on a sheet S1 with the 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 fixing temperature of a sheet S1 with the minimum width H2 with high accuracy.

[0069] Furthermore, in the comparative example, when the printing speed is increased, the temperature of the heater 160 rises. In particular, in the comparative example, when the printing speed is increased for a sheet S1 with a minimum width H2, the temperature at the edge rises significantly as the printing speed increases. For this reason, in the comparative example, the accuracy of detecting the edge temperature of the temperature detection member 182 decreases as the printing speed increases, or it becomes necessary to use a temperature detection member 182 with high heat resistance.

[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 heat conduction member 70, and a second temperature detection member 82 that contacts the heat conduction member 70 and detects the temperature of the longitudinal end of the heater 60.

[0071] 8B, when a fixing operation is performed on a sheet S1 having a maximum width H1 usable by the heating unit 52, the longitudinal dimension of the sheet S1 having the maximum width H1 is slightly smaller than the heat generation area HA1 of the resistance heating element 62. As a result, a non-paper passing area is generated outside the maximum width H1, and the temperature of the heater 60 rises in the non-paper passing area. Furthermore, because the resistance heating element 62 is not present outside the heat generation area HA1, the temperature of the heater 60 is lower outside the heat generation area HA1 than inside the heat generation area HA1.

[0072] Therefore, the temperature distribution of the heater 60 is shown by waveform G1. As shown in Fig. 8(B), the second temperature detection member 82 detects the temperature outside the resistance heating element 62 as the temperature of the end portion, so the heat resistance temperature of the second temperature detection member 82 does not need to be high.

[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 area HA1 generated by the resistance heating element 62. This results in a relatively large non-paper passing area, and the temperature in this non-paper passing area rises relatively significantly. Furthermore, because the resistance heating element 62 is not present outside the heat generation area HA1, the temperature of the heater 60 is lower outside the heat generation area HA1 than inside the heat generation area HA1.

[0074] Therefore, the temperature distribution of the heater 60 is uniformed by the heat conduction member 70 to the temperature of the center of the relatively low-temperature region, so the temperature in the non-paper passing region is slightly lower, as shown by waveform G2. The second temperature detection member 82 detects the temperature outside the resistance heating element 62, as shown in FIG. 8(C). If the second temperature detection member 82 were positioned inside the heat generation range HA1, there is a risk that an abnormal temperature rise in the heater 60 may not be detected due to the temperature difference between the non-paper passing region and the paper passing region and changes in the temperature distribution of the heater 60. However, in this embodiment, the second temperature detection member 82 detects the temperature outside the resistance heating element 62, so it is less affected by the temperature difference between the non-paper passing region and the paper passing region and changes in the temperature distribution of the heater 60, and can therefore accurately detect the temperature at the end.

[0075] Furthermore, in this embodiment, the second temperature detection member 82 is positioned outside the resistance heating element 62, so even when an attempt is made to increase the printing speed, unlike the comparative example, it is possible to reduce the decrease in the detection accuracy of the temperature at the end of the second temperature detection member 82 as the printing speed increases, and to easily reduce costs by lowering the heat resistance temperature of the second temperature detection member 82.

[0076] 8(A), in this embodiment, the second temperature detection member 82 is disposed within the installation range of the belt 53 in the longitudinal direction of the heater 60. This allows the second temperature detection member 82 to be placed closer to the resistance heating element 62, thereby enabling more accurate temperature detection while suppressing the effects of excessive temperature rise at the longitudinal end portions.

[0077] [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.

[0078] 9A 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, FIG. 9B is a plan view showing a heat conduction member of the heating unit, and FIG. 9C is a plan view showing a first temperature detection member, a second temperature detection member, and a current interruption member of the heating unit. In the figures, the second embodiment differs from the first embodiment in that the second temperature detection member 82 and the power supply terminal 63 are disposed on one end side of the heater 60 in the longitudinal direction, and the current interruption member 83 is disposed within a range through which a sheet S1 having a minimum width H2 can pass.

[0079] 9(A) and 9(C), in the heating unit 52 of the second embodiment, the power supply terminal 63 and the second temperature detection member 82 are disposed on one longitudinal end side of the heater 60. Also, as shown in FIG. 9(C), the current interruption member 83 is disposed within a range through which the sheet S1 having the minimum width H2 can pass.

[0080] With the above configuration, the second embodiment achieves the same effects as the first embodiment. Furthermore, in the second embodiment, the second temperature detection member 82 is provided at the same end as the power supply terminal 63 in the longitudinal direction of the heater 60, so that the wires connected to the second temperature detection member 82 and the wires connected to the power supply terminal 63 can be provided at the same end. As a result, in the second embodiment, the workability of routing and arranging these wires is improved, and the manufacture of the fixing device 45 can be easily simplified.

[0081] Furthermore, in this embodiment 2, the current interrupting member 83 is positioned within a range through which the sheet S1 of minimum width H2 can pass, so the current interrupting member 83 can cut off the flow of electricity to the resistance heating element 62 when the heater 60 abnormally heats up, regardless of the widthwise size of the sheet S1.

[0082] In the above explanation, the heat conduction member 70 is provided between the heater 60 and the holder 75, and the second temperature detection member 82 is brought into contact with the heat conduction member 70. However, the present disclosure is not limited to this, and the heat conduction member 70 may be omitted, and the second temperature detection member 82 may be brought into contact with the rear surface 61A of the substrate 61.

[0083] Furthermore, in the above description, a configuration in which a single heat conduction member 70 is arranged between the heater 60 and the holder 75 is described, but the present disclosure is not limited to this, and for example, a configuration in which two heat conduction members are provided, each in contact with the first temperature detection member 81 and the second temperature detection member 82 individually, may also be used.

[0084] 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]

[0085] 1. Image forming device 45 Fixing device 53 Belt 60 Heater 61 PCB 62 Resistance heating element 70 Thermal Conduction Materials 75 Holder 81 First temperature detection member 82 Second temperature detection member 83 Current interrupting member S1 Seat H1 maximum width H2 minimum 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 first temperature detection member for detecting the temperature of a central portion of the heater in the longitudinal direction; a second temperature detection member that detects a temperature at an end side in the longitudinal direction relative to the first temperature detection member; a holder for holding the heater; a heat conducting member disposed between the heater and the holder, The second temperature detecting member is the heating element is disposed outside the resistance heating element in the longitudinal direction, a fixing device in contact with the heat-conducting member;

2. 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 first temperature detection member for detecting the temperature of a central portion of the heater in the longitudinal direction; a second temperature detection member that detects a temperature at an end side in the longitudinal direction relative to the first temperature detection member, the heater includes a power supply terminal disposed at one end in the longitudinal direction and connected to the resistance heating element, The second temperature detecting member is the heating element is disposed outside the resistance heating element in the longitudinal direction, a fixing device disposed on the other end side in the longitudinal direction;

3. 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 first temperature detection member for detecting the temperature of a central portion of the heater in the longitudinal direction; a second temperature detection member that detects a temperature at an end side in the longitudinal direction relative to the first temperature detection member, the heater includes a power supply terminal disposed at one end in the longitudinal direction and connected to the resistance heating element, The second temperature detecting member is the heating element is disposed outside the resistance heating element in the longitudinal direction, a fixing device disposed on one end side in the longitudinal direction;

4. 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 within a range in the longitudinal direction that allows a sheet having a minimum width that can be used in the fixing device to pass through.

5. 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 on one end side in the longitudinal direction.

6. The fixing device according to claim 1 , wherein the second temperature detection member is disposed within an installation range of the belt in the longitudinal direction.

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

Images