Fixing device and image forming apparatus

Abstract

The fixing device (30) includes a fixing belt (1), a pressure roller (20), and a heating unit (10). The heating unit (10) includes a heater (11), a plurality of temperature sensors (13A, 13B), a heater holding member (12), and a sensor holding member (15). The sensor holding member (15) holds the temperature sensors (13A, 13B) between it and the heater holding member (12). The heater holding member (12) has observation holes (12c, 12d) that expose the heater. The heater holding member (12) has guide portions (12x, 12y) for positioning the sensor holding member (15). The sensor holding member (15) has engaging portions (15x, 15y). The sensor holding member (15) holds the plurality of temperature sensors (13A, 13B) at positions corresponding to each of the plurality of observation holes (12c, 12d) respectively by the engagement of the engaging portions with the guide portions.

Description

Technical Field

[0001] The present invention relates to a fixing device and an image forming device. Background Art

[0002] A fixing device of a heating film type or a fixing belt type mounted on an electrophotographic image forming apparatus is known. The fixing device disclosed in Patent Document 1 includes a fixing assembly as a heating portion and a pressure roller that presses the fixing assembly to form a fixing nip.

[0003] The fixing assembly includes a cylindrical fixing belt (fixing film), a flat heater in contact with the inner surface of the fixing belt, a heater holder for holding the heater, and a metal stay for pressing the heater holder and the heater toward the pressure roller. In addition, a thermistor is provided as a temperature sensor for measuring the temperature of the heater.

[0004] The thermistor is disposed on the heater holder. Specifically, in order to accurately measure the temperature of the heater, the thermistor is disposed so as to contact one surface of the heater at a predetermined pressure through a through hole (observation hole or measurement hole) provided in the heater holder.

[0005] [Prior art literature]

[0006] [Patent Document]

[0007] Patent Document 1: Japanese Patent Publication No. 2017-97143 Summary of the invention

[0008] [Technical problem to be solved by the invention]

[0009] In addition, the fixing device is used to fix the toner on sheets of various widths ("lateral width" orthogonal to the conveying direction) such as B5 to A3. At this time, when the width of the passing sheet is narrower than the width of the heater, there is a case where the temperature of the heater in the "non-paper passing area" at both ends of the sheet width direction that does not participate in the fixing of the toner rises. Among them, the sheet width (lateral width) direction is a direction parallel to the length direction or axis (rotation axis) direction of the pressure roller used for toner pressure contact in the fixing device.

[0010] To address this problem, in the fixing device, in order to enable detailed temperature control in the sheet width direction, multiple strip or block heaters with relatively short lengths in the sheet width direction are arranged in the sheet width direction (axial direction of the pressure roller) for use.

[0011] However, in order to perform appropriate temperature control, a temperature sensor must be provided on each of the plurality of heaters, and the number of temperature sensors assembled in the heating part, also called a fixing assembly or fixing unit, increases. As a result, the assembly work of the heating part becomes complicated, and the cost of the fixing device as a whole increases due to the increase in man-hours.

[0012] An object of the present invention is to provide a fixing device and an image forming apparatus capable of suppressing a cost increase due to an increase in the number of parts and working man-hours.

[0013] [Technical solutions for solving technical problems]

[0014] The fixing device of the present invention has a fixing belt, a pressure roller and a heating part. The fixing belt has a pressing surface. The pressure roller is in contact with the pressing surface. The heating part heats the fixing belt. The heating part includes a heater, a plurality of temperature sensors, a heater holding member and a sensor holding member. The heater extends in the axial direction of the pressure roller. The plurality of temperature sensors measure the temperature of the heater. The heater holding member holds the heater in a manner in contact with the back side of the pressing surface of the fixing belt. The sensor holding member holds the plurality of temperature sensors in a manner separated along the axial direction between the sensor holding member and the heater holding member. The heater has a first surface facing the heater holding member. The heater holding member has observation holes for exposing the first surface of the heater at a plurality of predetermined locations separated along the axial direction. The heater holding member has a guide portion for positioning the sensor holding member relative to the heater holding member. The sensor holding member has an engagement portion that engages with the guide portion. The sensor holding member holds the plurality of temperature sensors at positions corresponding to the plurality of observation holes, respectively, by the engagement between the engagement portion and the guide portion.

[0015] The image forming apparatus of the present invention comprises the above-mentioned fixing device and an image forming unit. The image forming unit is used to form a toner image on a sheet. The fixing device fixes the toner image to the sheet.

[0016] [Effects of the invention]

[0017] According to the present invention, it is possible to suppress a cost increase due to an increase in the number of parts and working man-hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a diagram showing the structure of an image forming apparatus including a fixing device according to an embodiment of the present invention.

[0019] Figure 2AIt is a perspective view showing a fixing device according to an embodiment of the present invention.

[0020] Figure 2B It is a perspective view showing a heating unit of the fixing device according to the embodiment of the present invention.

[0021] Figure 3 It is an exploded perspective view showing a heating unit of the fixing device according to the embodiment of the present invention.

[0022] Figure 4A is a top view of the sensor holder of the heating unit.

[0023] Figure 4B is a top view of the heater holder.

[0024] Figure 4C This is a diagram of the heater as viewed from the heater holder side.

[0025] Figure 4D This is a diagram showing a structure in which a heater holder holds a heater.

[0026] Figure 5A is a perspective view of the sensor holder of the heating unit.

[0027] Figure 5B is a bottom view of the sensor holder.

[0028] Figure 5C It is a diagram showing the state of the electric wiring accommodated in the sensor holder of the heating unit. DETAILED DESCRIPTION

[0029] Next, refer to the attached Figure 1 The embodiment of the present invention is described in detail. In the drawings, the same or corresponding parts are marked with the same reference numerals and the description thereof will not be repeated. In addition, the X-axis, Y-axis, and Z-axis shown as a reference for directions in the drawings are three-dimensional orthogonal coordinates that are orthogonal to each other, and the Z-axis is parallel to the pressing direction (clamping direction) of the pressure roller 20 that presses the heating unit 10 as the heating portion of the fixing device 30.

[0030] Reference Figure 1 , the structure and operation of the image forming apparatus 100 including the fixing device 30 will be described. Figure 1 1 is a diagram showing a configuration of an image forming apparatus 100 having a fixing device 30. The image forming apparatus 100 processes image data stored in a storage medium or image data transmitted from an external device, and forms an image on a sheet S. An image read from a document may be used as image data.

[0031] The image forming apparatus 100 is, for example, a copier, a printer, a facsimile machine, or an integrated machine having these functions. Hereinafter, an embodiment in which the image forming apparatus 100 is a black-and-white printer will be described.

[0032] like Figure 1 As shown, the image forming apparatus 100 includes a feeding section 40 , a conveying section 50 , an image forming section 60 , a fixing device 30 , and a discharging section 70 .

[0033] The feed section 40 accommodates a plurality of sheets S and feeds the sheets S one by one to the conveying section 50. The sheets S are, for example, sheets of paper or synthetic resin. The conveying section 50 includes a plurality of conveying roller pairs and conveys the sheets S fed from the feed section 40 to the discharge section 70 through the image forming section 60 and the fixing device 30.

[0034] The image forming unit 60 forms a toner image on the sheet S by an electrophotographic method. Specifically, the image forming unit 60 includes a photosensitive drum, a charging device, an exposure device, a developing device, a replenishing device, a transfer device, a cleaning device, and a static eliminating device.

[0035] The charging device charges the photosensitive drum. The exposure device outputs laser to expose the photosensitive drum, thereby forming an electrostatic latent image. The developing device supplies toner to form a toner image on the photosensitive drum. The replenishing device replenishes toner to the developing device. The transfer device transfers the toner image on the photosensitive drum to the sheet S. The cleaning device removes the residual toner remaining on the photosensitive drum after the transfer. The de-static device removes the charge remaining on the photosensitive drum.

[0036] The fixing device 30 heats and pressurizes the toner image to fix the toner image to the sheet S. The sheet S to which the toner image is fixed is conveyed by the conveying unit 50 to the discharge unit 70 . The discharge unit 70 discharges the sheet S to the outside of the image forming apparatus 100 .

[0037] The fixing device 30 is installed in the image forming apparatus 100. Figure 2A , Figure 2B and Figure 3 The fixing device 30 according to the present embodiment will be described.

[0038] Figure 2A 2 is a perspective view showing a fixing device 30 according to the present embodiment. Figure 2B It is a perspective view showing the heating unit 10 of the fixing device 30 .

[0039] like Figure 2A and Figure 2BAs shown, the fixing device 30 includes a fixing belt 1, belt holding members 22A and 22B, a pressure roller 20, and a heating unit 10. The heating unit 10 includes a flat heater 11, two temperature sensors 13A and 13B, a heater holder 12, and a sensor holder 15.

[0040] The heating unit 10 is disposed in the cylindrical fixing belt 1. The heating unit 10 is an example of a heating portion of the present invention. The heater holder 12 is an example of a heater holding member of the present invention, and the sensor holder 15 is an example of a sensor holding member of the present invention.

[0041] The pressure roller 20 rotates around the rotation axis Ax and contacts the outer peripheral surface of the fixing belt 1 to push the fixing belt 1. The pressure roller 20 has a shaft 21 as a core rod, a release layer on the outermost surface (outer peripheral surface), and a cylindrical elastic layer inside the shaft 21. In the present embodiment, the rotation axis Ax extends in the Y-axis direction.

[0042] The shaft 21 is a shaft member extending along the rotation axis Ax. The shaft 21 is formed of, for example, stainless steel or aluminum. The elastic layer is formed of, for example, silicone rubber. The mold release layer is formed of, for example, fluororesin.

[0043] The fixing belt 1 is heated by the heater 11 to fix the toner image on the sheet S. The fixing belt 1 has a substantially cylindrical shape. The fixing belt 1 is an endless belt that rotates in the circumferential direction. In addition, the fixing belt 1 has a plurality of layers. The fixing belt 1 has, for example, a polyimide layer and a release layer. The release layer is, for example, a heat-resistant film made of a fluorine resin.

[0044] The fixing belt 1 is rotatably supported at both ends of the pressure roller 20 in the direction of the rotation axis Ax (Y-axis direction) by the belt holding members 22A and 22B. Therefore, the fixing belt 1 rotates synchronously with the rotation of the pressure roller 20 along the support shape (here, semicircular) of the belt holding members 22A and 22B.

[0045] like Figure 2B As shown in FIG. 1 , the heating unit 10 is covered by the fixing belt 1. Specifically, the heating unit 10 and the flat heater 11 face the pressure roller 20 via the fixing belt 1. The portion of the outer peripheral surface of the fixing belt 1 facing the pressure roller 20 is the pressing surface 1a. Figure 2B In FIG. 1 , the pressing surface 1 a is a surface hidden under the fixing belt 1 .

[0046] The pressing surface 1a of the fixing belt 1 and the pressure roller 20 form a nip for applying heat and pressure while sandwiching the sheet S. When the pressure roller 20 rotates, the fixing belt 1 is driven by the pressure roller 20 to rotate. Then, the sheet S passes through the nip, and the toner image is melted and fixed on the sheet S.

[0047] Next, refer to Figure 3 The structure of the heating unit 10 of the fixing device 30 according to the present embodiment will be described. In addition, the heating unit 10 of the present embodiment is assembled in a process different from the assembly process of the image forming apparatus 100. After being assembled into a unit, as shown in FIG. Figure 2B As shown in FIG. 1 , the fixing belt 1 is inserted into the inner side (inner circumference) of the cylindrical fixing belt 1 and is ready to be incorporated into the image forming apparatus 100 .

[0048] Figure 3 1 is a perspective exploded view showing a heating unit 10 of the fixing device 30 of the present embodiment. The heating unit 10 disposed on the inner side (inner periphery) of the fixing belt 1 includes, in addition to a heater 11, a heater holder 12, temperature sensors 13A and 13B, and a sensor holder 15, electric wiring 14A, 14B, and 14C, four coil springs 16, and a stay 17.

[0049] The coil spring 16 is an example of a biasing member in the present invention. The stay 17 is an example of a reinforcing member in the present invention. Figure 3 In the figure, the upper surface of the flat plate-shaped heater 11 facing the heater holder 12 is a first surface 11 a , and the lower surface facing the fixing belt 1 (not shown) is a second surface 11 b .

[0050] The heater 11 is, for example, a slender thin plate-shaped heating element, and extends along the rotation axis direction (Y-axis direction) of the pressure roller 20. The heater 11 is connected to a power source (not shown) to generate heat, and the toner image on the sheet S is melted and fixed via the fixing belt 1 on the second surface 11b side. The heater 11 is, for example, a ceramic heater, and includes a ceramic substrate and a plurality of resistance heating elements arranged on the second surface 11b side of the ceramic substrate. The thickness of the heater 11 is, for example, 1 mm.

[0051] The heater holder 12 holds the flat heater 11 in contact with the inner side of the cylindrical fixing belt 1. The heater holder 12 faces the fixing belt 1 via the heater 11. In other words, the heater holder 12 presses the fixing belt 1 heated by the heater 11 against the sheet S conveyed between the fixing belt 1 and the pressure roller 20.

[0052] The heater holder 12 is made of, for example, a heat-resistant resin, and extends along the axis (Y axis) of the pressure roller 20. The heater holder 12 is engaged with a stay 17 as a reinforcement member.

[0053] The temperature sensors 13A and 13B measure the temperature of the heater 11 as the surface temperature of the ceramic substrate. The temperature sensors 13A and 13B are, for example, thermistors. The image forming apparatus 100 controls the heating by the heater 11 based on the temperatures measured by the temperature sensors 13A and 13B. By using thermistors as the temperature sensors 13A and 13B, the accuracy of controlling the temperature of the heater 11 can be improved.

[0054] In addition, the temperature sensors 13A and 13B may be thermal cutoff devices or thermostats. In the case of thermal cutoff devices, when the temperature of the heater 11 is above a threshold value, the power supply to the heater 11 is cut off. In the case of thermostats, when the temperature of the heater 11 is above a threshold value, the power supply to the heater 11 is cut off, and when the temperature drops below the threshold value, the power supply to the heater 11 is restored.

[0055] The electrical wirings 14A, 14B, and 14C electrically connect the temperature sensors 13A and 13B or the temperature sensors 13A and 13B to the image forming apparatus 100. The image forming apparatus 100 also includes a temperature controller for the heater 11 or a control unit capable of controlling the temperature of the heater 11. The electrical wirings 14A, 14B, and 14C will be described later.

[0056] The sensor holder 15 is disposed between the heater holder 12 and the stay 17, and holds the temperature sensors 13A and 13B at a predetermined position. In addition, the electrical wiring 14A, 14B, and 14C are stored in a space-saving and compact manner. The holding of the temperature sensors 13A and 13B will be described later.

[0057] The stay 17 is used to suppress outward deflection of the heater holder 12 and to strengthen the pressing of the heater holder 12 toward the pressure roller 20. The stay 17 is, for example, a slender metal stay member.

[0058] The stay 17 overlaps with the heater holder 12 along its length direction (Y-axis direction), and a space (hereinafter referred to as wiring accommodation space) capable of accommodating the temperature sensors 13A, 13B or the electrical wiring 14A, 14B, 14C, etc. is formed between the stay 17 and the heater holder 12.

[0059] The four coil springs 16 are respectively inserted into the through holes 15d (15d1 to 15d4) of the sensor holder 15 and are arranged between the stay 17 and the heater holder 12. In addition, at a predetermined position of the heater holder 12 where the coil springs 16 are arranged, Figure 3As shown, the temperature sensors 13A and 13B are placed. Therefore, substantially, the four coil springs 16 are located between the stay 17 and the temperature sensors 13A and 13B. Thus, each coil spring 16 urges the temperature sensors 13A and 13B toward the heater holder 12 and the heater 11.

[0060] Reference Figure 4A to Figure 4D , the relationship between the arrangement positions of the temperature sensors 13A and 13B and the heater 11 will be described. Figure 4A is a top view of the sensor holder 15, Figure 4B It is a top view of the heater holder 12. Figure 4C FIG. 1 is a diagram showing the flat heater 11 as viewed from the upper side (heater holder 12 side). Figure 4D This is a diagram showing a structure in which the heater holder 12 holds the flat heater 11 .

[0061] In addition, Figure 4C In the figure, the rectangle drawn by imaginary lines (double-dotted lines) on the resistance heating elements R1 and R2 (indicated by dotted lines) located on the back side (second surface 11b side) of the ceramic substrate represents the portion where the thermistor portion of each temperature sensor 13A and 13B abuts against the first surface 11a of the heater 11.

[0062] like Figure 4B As shown, the heater holder 12 forms an upward U-shaped sensor accommodation space 12S. The heater holder 12 has an inner bottom surface 12a of the sensor accommodation space 12S, two observation holes 12c, 12d and convex protrusions 12x, 12y. In addition, the protrusions 12x, 12y are an example of the guide portion of the present invention.

[0063] In addition, if Figure 4D As shown, the heater holder 12 has an outer bottom surface 12b for holding the heater 11 on the back side of the inner bottom surface 12a. The observation holes 12c and 12d are rectangular openings that penetrate from the inner bottom surface 12a side of the sensor accommodation space 12S toward the outer bottom surface 12b. When the heater holder 12 holds the heater 11, the observation holes 12c and 12d expose the upper surface (first surface 11a) of the heater 11 to the inner side of the sensor accommodation space 12S.

[0064] In addition, if Figure 4B As shown, each observation hole 12c, 12d is offset in a direction orthogonal to the axial center line of the heater holder 12 shown by the single dotted line in the figure. This is because the resistance heating elements R1, R2 arranged on the lower surface (second surface 11b) of the heater 11 are offset relative to the center line of the heater holder 12.

[0065] In other words, the offset arrangement of the observation holes 12c, 12d corresponds to Figure 4C The position of each resistance heating element R1, R2 is offset as shown. With this structure, the thermosensitive portion (probe portion) of the temperature sensors 13A, 13B placed on the observation holes 12c, 12d can contact the positions corresponding to the front and back sides of the resistance heating elements R1, R2 when inserted through the observation holes 12c, 12d. As a result, each temperature sensor 13A, 13B can accurately measure the temperature of each resistance heating element R1, R2.

[0066] Then, if Figure 4B As shown in FIG. 1 , the projections 12x and 12y as guides are cylindrical or conical and protrude upward from the inner bottom surface 12a of the sensor housing space 12S. The projections 12x and 12y engage with the engagement portions 15x and 15y on the sensor holder 15 side.

[0067] The engaging portions 15x and 15y of the sensor holder 15 are Figure 4A The through-hole shape shown is formed in a round hole or an elongated hole shape. The engaging portions 15x and 15y are fitted into the protrusions 12x and 12y of the heater holder 12, respectively.

[0068] Next, refer to Figure 5A to Figure 5C The arrangement positions of the temperature sensors 13A and 13B and the structure for applying force to the temperature sensors 13A and 13B will be described. Figure 5A is a three-dimensional diagram of the sensor holder 15, Figure 5B is a bottom view of the sensor holder 15, Figure 5C It is a cross-sectional view showing a state of the electric wiring accommodated in the sensor holder 15 of the heating unit 10 .

[0069] like Figure 5C As shown, each temperature sensor 13A, 13B is assembled to the sensor holder 15 in a state where wiring, biasing members, etc. are added to function as a sensor, and in this state is assembled at a predetermined position between the heater holder 12 and the stay 17 .

[0070] As a result, the thermosensitive parts of the temperature sensors 13A and 13B contact the first surface 11a of the flat heater 11 through the observation holes 12c and 12d of the heater holder 12, and can respectively measure the temperatures of the resistance heating elements R1 and R2 constituting the heater 11.

[0071] The structure of the sensor holder 15 will be described. Figure 5A and Figure 5BThe sensor holder 15 shown holds two temperature sensors 13A and 13B. Engagement parts 15x and 15y that engage with the protrusions 12x and 12y are formed at both ends of the sensor holder 15 in the axial direction (Y-axis direction). The engagement with the protrusions 12x and 12y enables accurate positioning.

[0072] The detailed structure of the sensor holder 15 is described. The sensor holder 15 as a whole is a double-layer structure consisting of a lower wiring space 15L and an upper wiring space 15U, wherein the lower wiring space 15L accommodates the temperature sensors 13A, 13B and the electrical wirings 14A, 14B, 14C at the lower side, and the upper wiring space 15U accommodates the electrical wirings 14A, 14B at the upper side.

[0073] like FIG. 5A to FIG. 5C As shown, the sensor holder 15 has a partition plate portion 15a, first to fourth sensor holding portions 15b1 to 15b4, a notch portion 15c, and first to fourth through holes 15d1 to 15d4 between the engaging portions 15x and 15y at both ends in the axial direction (length direction).

[0074] The partition plate portion 15 a has a plate shape extending in the longitudinal direction (Y-axis direction), and partitions an upper wiring space 15U and a lower wiring space 15L in the up-down direction.

[0075] The four sensor holding parts 15b1 to 15b4 are in the shape of a wall extending in a direction (X-axis direction) perpendicular to the longitudinal direction. The temperature sensors 13A and 13B are held between the first sensor holding part 15b1 and the second sensor holding part 15b2 and between the third sensor holding part 15b3 and the fourth sensor holding part 15b4.

[0076] In addition, if Figure 5B As shown, notches are formed on the walls constituting the sensor holding portions 15b1 to 15b4 so that leads (terminals) of the sensors protruding from the temperature sensors 13A and 13B in the longitudinal direction (Y-axis direction) can be inserted.

[0077] In addition, if Figure 5C As shown, the temperature sensors 13A and 13B are held in a state where the heat-sensitive portions are protruding downward from the sensor holder 15 so that the heat-sensitive portions can contact the flat heater 11. Furthermore, the temperature sensor 13A (left in the figure) and the temperature sensor 13B (right in the figure) are arranged so that the polarities of the leads (terminals) are opposite.

[0078] The notch 15c is disposed between the left and right temperature sensors 13A and 13B at the center of the partition plate 15a in the length direction (X-axis direction). In order to quickly assemble the electrical wiring 14A, 14B, and 14C connected to the temperature sensors 13A and 13B to the sensor holder 15, the notch 15c is not a hole (through shape) but a notch opened in the X-axis direction.

[0079] Four through holes 15d1 to 15d4 through which four coil springs 16 are inserted are provided two each at predetermined intervals between the first sensor holding portion 15b1 and the second sensor holding portion 15b2 and between the third sensor holding portion 15b3 and the fourth sensor holding portion 15b4.

[0080] In addition, if Figure 5C As shown in FIG. 1 , through holes 15d1 and 15d2 are arranged in pairs on both sides of the Y-axis direction of the thermosensitive portion of one temperature sensor 13A. In addition, through holes 15d3 and 15d4 are arranged in pairs on both sides of the Y-axis direction of the thermosensitive portion of the temperature sensor 13B. Therefore, when assembled between the heater holder 12 and the stay 17, the thermosensitive portions of the temperature sensors 13A and 13B can be pushed toward one side (the first side 11a) of the heater 11 in an even and evenly pressurized manner.

[0081] In addition, the engaging parts 15x and 15y of the sensor holder 15 that engage with the protrusions 12x and 12y are preferably through holes in the shape of a circular hole or a long hole. In particular, when one engaging part 15x is a circular hole and the other engaging part 15y is a long hole, it is preferable because both the accuracy of positioning and the ease of embedding the heater holder 12 into the guide part can be taken into account. In addition, the long hole can allow for shape errors of the protrusions 12x and 12y.

[0082] Here, the assembly of the temperature sensors 13A and 13B and the harnesses 14A to 14C connecting them to the sensor holder 15 will be described.

[0083] First, the temperature sensors 13A, 13B and the electrical wirings 14A to 14C are supplied in a connected state in a process different from the heating unit 10. Furthermore, when it is desired to connect the lead wires of the temperature sensors 13A, 13B to the electrical wirings 14A to 14C by an automatic machine, a space of several centimeters or more is required between the temperature sensor 13A and the temperature sensor 13B (remaining electrical wiring) due to process constraints such as component handling and clamping.

[0084] Thus, even when there is a surplus of electrical wiring between the temperature sensor 13A and the temperature sensor 13B, in the sensor holder 15 of the heating unit 10 of the present embodiment, as shown in FIG. Figure 5C As shown, the harnesses 14A to 14C can also be housed in the holding member in a simple and compact manner.

[0085] For example, in Figure 5C In the example, first, the left temperature sensor 13A is embedded between the specified first sensor holding part 15b1 and the second sensor holding part 15b2, the left electrical wiring 14A is arranged from the lower wiring space 15L to the upper wiring space 15U, and the right electrical wiring 14B is arranged in the lower wiring space 15L.

[0086] Next, the upper harness 14A and the lower harness 14B are fitted into the cutout 15c from the side of the sensor holder 15 so that they vertically cross each other at the cutout 15c.

[0087] Next, the left temperature sensor 13B is embedded in the specified position between the third sensor holding part 15b3 and the fourth sensor holding part 15b4, the upper electrical wiring 14A is pulled out directly from the end of one side of the sensor holding frame 15, and the lower electrical wiring 14C connected to the lead of the temperature sensor 13B is pulled out from the same end.

[0088] Next, using the sensor holder 15 that is assembled with the temperature sensors 13A, 13B and the electrical wiring 14A to 14C, the snap-fitting portion 15x of the sensor holder 15 is embedded in the protrusion 12x of the heater holder 12, and the snap-fitting portion 15y of the sensor holder 15 is embedded in the protrusion 12y of the heater holder 12, thereby completing the arrangement and positioning of multiple temperature sensors in the heater holder 12.

[0089] Thus, in the fixing device 30 of the present embodiment, the temperature sensors 13A and 13B can be positioned at once. In addition, the temperature sensors 13A and 13B can be assembled to the heating unit 10 in one operation, so that the fixing device 30 can be constructed simply.

[0090] Therefore, in the fixing device 30 of the present embodiment, even when a temperature sensor must be provided on each heater, the increase in the number of parts and the working hours can be suppressed, thereby suppressing the increase in the total cost of the fixing device 30 and the image forming device 100 having the fixing device 30.

[0091] Above, the embodiments of the present invention have been described with reference to the accompanying drawings. However, the present invention is not limited to the above-mentioned embodiments, and can be implemented in various ways without departing from the scope of its main purpose. For example, several structural elements can be deleted from all the structural elements shown in the embodiments. In the accompanying drawings, for ease of understanding, the respective structural elements are schematically represented as the main body, and the thickness, length, number, interval, etc. of the structural elements shown in the drawings are different from the actual situation from the perspective of the situation of the drawings. In addition, the material, shape, size, etc. of the structural elements shown in the above-mentioned embodiments are examples, and are not particularly limited. Various changes can be made within the scope of the structure of the present invention without departing substantially.

[0092] The image forming apparatus 100 is a black and white integrated machine, but the present invention is not limited thereto. The image forming apparatus 100 only needs to be an electrophotographic machine. For example, the image forming apparatus 100 may also be a color integrated machine.

[0093] The type and number of temperature sensors and the type and number of heaters held by the sensor holding member (sensor holding frame) of the fixing device of the present invention are not limited to the examples in the embodiments. In the present invention, the more the number of heaters and temperature sensors for measuring the temperature of each heater, the more the increase in the number of parts and working hours can be suppressed, thereby suppressing the increase in total cost.

[0094] In reference Figure 1 to Figure 5C In the embodiment described, the force applying member for applying force to the temperature sensors 13A and 13B is set as the coil spring 16, but the force applying member is not limited thereto. As the force applying member, other elastic members such as leaf springs may also be used. In addition, as long as the number of the members provided is multiple (more than 2), any number of members may be provided.

[0095] The positioning guide formed on the heater holding member and the engaging portion of the sensor holding member engaged therewith are not limited to Figure 1 to Figure 5C For example, the protrusions 12x and 12y of the heater holder 12 may be angular in shape in addition to being cylindrical or conical. The hole shape of the engaging portions 15x and 15y on the sensor holder 15 side may be appropriately changed in accordance with the outer peripheral shape of the protrusions 12x and 12y.

[0096] The present invention can be utilized in the fields of fixing devices and image forming apparatuses.

Claims

1. A fixing device, characterized in that, it has a fixing belt, a pressure roller and a heating unit, wherein, the fixing belt has a pressing surface; the pressure roller is in contact with the pressing surface; the heating unit heats the fixing belt, the heating unit includes a heater, a plurality of temperature sensors, a heater holding member and a sensor holding member, wherein, the heater extends along the axial direction of the pressure roller; the heater holding member holds the heater in contact with the back side of the pressing surface of the fixing belt; the sensor holding member holds the plurality of temperature sensors separated from each other along the axial direction between it and the heater holding member; the heater has a first surface facing the heater holding member; the heater holding member has observation holes exposing the first surface of the heater at a plurality of prescribed positions separated from each other along the axial direction; the heater holding member has a guiding portion for positioning the sensor holding member relative to the heater holding member; the sensor holding member has an engaging portion engaging with the guiding portion; the sensor holding member holds the plurality of temperature sensors at positions corresponding to each of the plurality of observation holes respectively through the engagement of the engaging portion with the guiding portion; the heating unit includes a first wiring and a second wiring connected to the plurality of temperature sensors; the sensor holding member forms a wiring accommodating space for accommodating the first wiring and the second wiring; the sensor holding member includes a partition portion and a notch portion, wherein, the partition portion divides the wiring accommodating space into an upper side wiring space and a lower side wiring space; the notch portion is for the first wiring and the second wiring to pass through; the first wiring includes a portion disposed in the upper side wiring space, a portion disposed in the lower side wiring space and a portion passing through the notch portion; the second wiring includes a portion disposed in the lower side wiring space, a portion disposed in the upper side wiring space and a portion passing through the notch portion.

2. The fixing device according to claim 1, characterized in that, in a state where the engaging portion is engaged with the guiding portion, the heat-sensitive portions of the plurality of temperature sensors are in contact with the first surface of the heater through the respective observation holes.

3. The fixing device according to claim 1, characterized in that, the heating unit includes a reinforcing member and a biasing member, wherein, the reinforcing member bears the pressing force received by the heater and the heater holding member from the pressure roller; the biasing member biases the temperature sensors; the sensor holding member has a through hole for the biasing member to penetrate along a direction orthogonal to the axial direction; the biasing member is disposed between the temperature sensors and the reinforcing member through the through hole.

4. The fixing device according to claim 3, characterized in that, a plurality of the biasing members are disposed on each of the temperature sensors.

5. The fixing device according to any one of claims 1 to 4, characterized in that, The heater has a second surface and a plurality of resistive heating elements, wherein, the second surface faces the fixing belt; the plurality of resistive heating elements extend along the axial direction, and the plurality of resistive heating elements are disposed on the second surface.

6. The fixing device according to any one of claims 1 to 4, wherein, the guiding portion is a protrusion, and the engaging portion is a hole for the protrusion to be engaged therewith.

7. The fixing device according to any one of claims 1 to 4, wherein, the plurality of temperature sensors are arranged such that the polarities of the terminals of adjacent temperature sensors are opposite.

8. An image forming apparatus, wherein, it has the fixing device according to any one of claims 1 to 7 and an image forming section, wherein, the image forming section is configured to form a toner image on a sheet, and the fixing device fixes the toner image on the sheet.

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