Fixing device and image forming apparatus

Abstract

The present invention relates to a fixing device and an image forming apparatus, which can appropriately perform temperature detection of a temperature detection member even if an electrically conductive support member is miniaturized in order to miniaturize a fixing member. A fixing device (30) includes a hollow fixing member (31) that heats and fixes an image onto a recording material (P); an opposing member (32) that forms a fixing nip with the fixing member; an electrically conductive support member (33) that is disposed in a hollow portion of the fixing member and supports a fixing nip portion of the fixing member; and a temperature detection member (40) that detects a temperature, a recess or an opening portion (33d) being provided in a portion of the electrically conductive support member that opposes an exposed conductive portion of the temperature detection member.

Description

Technical Field

[0001] This invention relates to a fixing apparatus and an image forming apparatus. Background Technology

[0002] Previously, a fixing device was known, which included a hollow fixing member for heating and fixing an image onto a recording material, an opposing member forming a fixing clamping portion between itself and the fixing member, a conductive support member disposed in the hollow portion of the fixing member and supporting the fixing clamping portion of the fixing member, and a temperature detection member for detecting temperature.

[0003] For example, the fixing apparatus disclosed in Patent Document 1 includes an annular fixing belt as a fixing component, a pressure roller as an opposing component, and a metal support bar (conductive support member) disposed on the inner circumference (hollow portion) of the fixing belt. The support bar has an upstream conductive support portion and a downstream conductive support portion in the recording material transport direction. The front ends of these support portions support a heater holder that holds a planar heater, and the heater holder supports the fixing clamping portion of the fixing belt. While holding the heater on one side of the fixing clamping portion, the heater holder also holds a temperature sensing component made of a thermistor on the opposite side of the fixing clamping portion. This temperature sensing component is disposed inside the support bar and detects the temperature of the heater through a through hole provided in the heater holder.

[0004] In recent years, miniaturization of the fixing unit has been required in fixing devices, particularly of the conductive support component housed within its hollow portion. However, miniaturizing the conductive support component makes it difficult to perform proper temperature detection using a temperature sensing component, potentially hindering the proper operation of the fixing device.

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2020-098311 Summary of the Invention

[0006] To address the aforementioned issues, the present invention provides a fixing apparatus comprising: a hollow fixing member for heating and fixing an image onto a recording material; an opposing member forming a fixing clamping portion with the fixing member; a conductive support member disposed in the hollow portion of the fixing member and supporting the fixing clamping portion of the fixing member; and a temperature detection member for detecting temperature. The fixing apparatus is characterized in that a recess or opening is provided in the conductive support member at a portion opposite to the exposed conductive portion of the temperature detection member.

[0007] According to the present invention, even if the conductive support member is miniaturized in order to miniaturize the fixing member, the temperature of the temperature detection member can be appropriately detected, and the fixing device can be appropriately operated. Attached Figure Description

[0008] Figure 1 The diagram shown is a schematic configuration diagram of the printer according to the embodiment.

[0009] Figure 2 The diagram shown illustrates the configuration of the printer's fusing unit.

[0010] Figure 3 The diagram shown is an explanatory diagram of the state after the fixing device has been decomposed and the fixing belt has been removed.

[0011] Figure 4 The image shown is a perspective view of the fixing device with its components.

[0012] Figure 5 The diagram shown is an explanatory diagram of the state of the component decomposed (excluding the state of the fixing belt).

[0013] Figure 6 The diagram shown is an illustration of an example of the configuration of the heater (with a coating) in the fixing device.

[0014] Figure 7 The diagram shown is an illustration of another example of the configuration of the heater (with a coating) in the fixing device.

[0015] Figure 8 The diagram shown is a schematic representation of the internal structure of the fixing belt in the fixing device.

[0016] Figure 9(a) shows a perspective view of an example of the thermostat in the fixing device, and Figure 9(b) shows an explanatory diagram of the thermostat arranged in the internal space of the support bar, as seen from the detection section side of the thermostat.

[0017] Figure 10(a) shows a side view of the thermostat before it is placed inside the support bar, and Figure 10(b) shows a side view of the thermostat after it is placed inside the support bar. Detailed Implementation

[0018] Hereinafter, an embodiment of the present invention will be described for application to a printer, which is an image forming apparatus of an electrophotographic method.

[0019] In addition to printers, image forming apparatuses can also be copiers, fax machines, or their multi-functional peripherals. Furthermore, this embodiment describes a single-drum type image forming apparatus with one photosensitive drum, but a tandem type image forming apparatus with multiple photosensitive drums is also possible. Additionally, this embodiment describes a direct transfer type image forming apparatus where the photosensitive drum directly transfers the image to the paper, but an intermediate transfer type image forming apparatus where the image is transferred from the photosensitive drum to the paper via an intermediate transfer unit is also possible.

[0020] Figure 1 The diagram shown is a schematic diagram of the printer involved in this embodiment.

[0021] The printer of this embodiment includes a paper feeding device 4, a pair of positioning rollers 6, a photosensitive drum 8 serving as an image carrier, a transfer device 10, a fixing device 30, etc. The paper feeding device 4 includes a paper feeding tray 14 in which stacked sheets of paper P are stored, and a paper feeding roller 16 that sequentially separates and feeds the top sheet of paper stored in the paper feeding tray 14 one by one. The paper P fed by the paper feeding roller 16 is stopped and its posture deviation is corrected by the pair of positioning rollers 6. Then, the paper P is transported to the transfer unit N by the pair of positioning rollers 6 at a time that is synchronized with the rotation of the photosensitive drum 8, that is, at a time when the tip of the toner image formed on the photosensitive drum 8 is at a predetermined position with the tip of the paper P in the transport direction.

[0022] Around the photosensitive drum 8, in the order of rotation shown by the arrows in the figure, are arranged a charging roller 18 as a charging mechanism, a reflector 20 which forms part of an exposure apparatus that is a latent image forming mechanism, a developing apparatus 22 which is a developing mechanism and has a developing roller 22a, a transfer apparatus 10 which is a transfer mechanism, and a cleaning apparatus 24 which is a cleaning mechanism and has a cleaning blade 24a. Exposure light Lb, which is irradiated by the reflector 20, irradiates and scans the exposure section 26 on the photosensitive drum 8 located between the charging roller 18 and the developing apparatus 22.

[0023] When the photosensitive drum 8 begins to rotate, its surface is uniformly charged by the charging roller 18, and the exposure light Lb is irradiated and scanned in the exposure section 26 according to the image information. As a result, an electrostatic latent image corresponding to the image information is formed on the surface of the photosensitive drum 8. This electrostatic latent image moves toward the developing apparatus 22 by the rotation of the photosensitive drum 8, where it is supplied with toner and visualized, forming a toner image.

[0024] The toner image formed on the photosensitive drum 8 is transferred by the transfer device 10 through a transfer bias applied to the paper P that enters the transfer section N at a predetermined time. Afterward, the paper P carrying the toner image is conveyed toward the fixing device 30, and after being fixed in the fixing device 30, it is discharged toward the paper tray and stacked.

[0025] Residual toner that was not transferred at the transfer clamping section N and remained on the photoreceptor 8 reaches the cleaning device 24 as the photoreceptor 8 rotates, and is scraped off by the cleaning scraper 24a during its passage through the cleaning device 24. Afterwards, the residual potential on the photosensitive drum 8 is removed by the static elimination mechanism, and it is ready for the next imaging process.

[0026] Next, the configuration and operation of the fixing device 30 in this embodiment will be explained.

[0027] Figure 2 The diagram shown is an explanatory diagram of the configuration of the fixing device 30 in this embodiment.

[0028] Figure 3 The diagram shown is an explanatory diagram of the fixing device of this embodiment after disassembly and removal of the fixing belt.

[0029] like Figure 2 As shown, the fixing device 30 of this embodiment has an annular fixing belt 31 as a fixing component, and a pressure roller 32 as an opposing component that forms a fixing clamping portion SN with the fixing belt 31. The fixing device 30 has a first frame 30A and a second frame 30B that are joined to each other by screws or the like, and the fixing belt 31 and the pressure roller 32 are disposed in these frames 30A and 30B.

[0030] like Figure 3 As shown, the first frame 30A consists of two side plates at both ends 32f of the mandrel 32a supporting the pressure roller 32 and a bridging plate connecting these side plates. The first frame 30A can be formed by bending a sheet of metal, or the two side plates and the bridging plate can be formed as different components and fastened together with screws or the like.

[0031] like Figure 3 As shown, each side plate of the first frame 30A has a cutout 30a for inserting the ends 32f of the mandrel 32a of the pressure roller 32. Pressure bearings 32d, which are made of sliding bearings, are embedded in these cutouts 30a. In this embodiment, the pressure bearing 32d is a sliding bearing, but it could also be a ball bearing. Figure 3 As shown, a pressure gear 32e is provided at one end of the pressure roller 32. The pressure gear 32e is connected to a drive gear provided on the side of the printer body and is driven to rotate.

[0032] The fixing device 30 inserts the pressure roller 32 into the cutout 30a of the first frame 30A, such that each end 32f of the spindle 32a of the pressure roller 32 engages with the pressure bearing 32d. Thus, the pressure roller 32 is supported on the first frame 30A and can rotate. Next to the pressure roller 32, a belt assembly containing the fixing belt 31 is inserted into the cutout 30a of the first frame 30A. Then, the second frame 30B is positioned onto the first frame 30A by blocking the inlet of the cutout 30a, and the first frame 30A and the second frame 30B are secured.

[0033] like Figure 3 As shown, a compression spring 35, serving as a force-applying mechanism, is provided between the second frame 30B and the belt assembly. The force exerted by this compression spring 35 applies force to the belt assembly (fixing belt 31) towards the pressure roller 32, thereby forming a fixing clamping portion between the fixing belt 31 and the pressure roller 32. The compression spring 35 can apply force directly to the belt assembly, or it can apply force to the belt assembly via a lever member. By using the lever member, based on the lever principle, even a weak force can achieve a large applied force.

[0034] Figure 4 The image shown is a perspective view of the fixing device 30 with components according to this embodiment.

[0035] Figure 5 The diagram shown is an explanatory diagram of the state of the tape component in this embodiment (without the fixing tape).

[0036] The belt assembly of this embodiment has a heater holder 36, a heater 37 held on the heater holder 36, left and right flanges 38 provided at both ends of the belt assembly, and a support bar 33 supporting the heater holder 36 on the inner peripheral side (hollow part) of the fixing belt 31.

[0037] like Figure 5 As shown, a recess with a shape substantially the same as that of the heater 37 is formed in the heater holder 36, and the heater 37 is embedded in this recess. Since the heater holder 36 is in contact with the heater 37 and is prone to high temperatures, it is preferably formed of a heat-resistant material. Furthermore, the heater holder 36 is preferably insulating and has the lowest possible thermal conductivity. Therefore, the heater holder 36 is suitable to be formed of, for example, a heat-resistant resin material such as LCP or PEEK. If the heater holder 36 is formed of such a heat-resistant resin, heat transfer from the heater 37 to the heater holder 36 can be suppressed, and this portion of the heat from the heater 37 can be effectively transferred to the fixing belt 31.

[0038] The support bar 33, used to support the back side of the heater holder 36 (the side opposite to the side where the heater 37 is disposed), is a component with higher rigidity than the heater holder 36. For example... Figure 2 As shown, the two ends of the support bar 33 are supported by cutouts 30a provided in the side plates of the first frame 30A. The support bar 33 firmly bears the pushing force and supports the heater holder 36 in such a way that the heater holder 36 will not bend due to the pushing force from the pressure roller 32. Thus, the belt portion of the fixing clamping part SN of the fixing belt 31 is supported by the support bar 33 by means of the heater holder 36, and the fixing clamping part SN with the desired pressure can be formed.

[0039] like Figure 5 As shown, the support bar 33 in this embodiment consists of an upstream side foot 33a disposed upstream in the conveying direction of the paper P, a downstream side foot 33b disposed downstream in the conveying direction of the paper P, and a connecting portion 33c connecting these feet 33a and 33b. The support bar 33 is formed, for example, by bending a sheet of metal so that the shape of the cross section orthogonal to the length direction is groove-shaped or U-shaped. The support bar 33 is configured such that the front ends of the upstream side foot 33a and the front ends of the downstream side foot 33b abut against the back of the heater holder 36 throughout the length direction, and supports the heater holder 36 so that the heater holder 36 does not flex due to the pushing force from the pressure roller 32.

[0040] Flanges 38 located at both ends of the belt assembly abut against and support the inner circumferential surfaces near the sides of the fixing belt 31. Furthermore, the flanges 38 abut against the sides of the fixing belt 31 to limit belt serpentination that may occur during the movement (rotation drive) of the fixing belt 31.

[0041] In the belt assembly of this embodiment, the heater 37 and the heater holder 36, the heater holder 36 and the left flange 38, and the left flange 38 and the first frame 30A have positioning shapes for positioning each other in the longitudinal direction. The support bar 33 is inserted with some play (wobbling) relative to the left and right flanges 38. In the right flange 38, no positioning shape is provided relative to the heater holder 36. This is because the heater holder 36 will not protrude relative to the first frame 30A even if thermal expansion occurs.

[0042] Figure 6 The diagram shown is an explanatory diagram of an example of the configuration of the heater 37 (with the covering coating 39 formed) in this embodiment.

[0043] Figure 7 The diagram shown is an explanatory diagram of another example of the configuration of the heater 37 (with the covering coating 39 formed) in this embodiment.

[0044] The heater 37 of this embodiment has heating element patterns 37a1 to 37a8 disposed on the heater substrate material 37b, conductor patterns 37d with a resistance value smaller than these heating element patterns, and electrodes 37e and 37f. A cover coating 39 as an insulating layer is formed on the heater 37 to cover them.

[0045] As the material for the heater substrate 37b, ceramics such as alumina or aluminum nitride, glass, and mica are preferred due to their excellent heat resistance and insulation properties. Alternatively, an insulating material can be laminated onto a conductive material such as a metal. From a cost perspective, aluminum or stainless steel are preferred. Furthermore, materials with high thermal conductivity, such as copper, graphite, or graphene, are more preferred because they can homogenize the temperature of the entire heater through high thermal conductivity, thus improving image quality by enhancing fixing uniformity. In this embodiment, the heater substrate 37b is, for example, an alumina substrate material with a short side length of 8 mm, a long side length of 270 mm, and a thickness of 1.0 mm.

[0046] The heating element patterns 37a1 to 37a8 are formed, for example, by screen printing or applying a paste made of silver-palladium (AgPd) or glass powder, followed by firing. The resistance of each of the heating element patterns 37a1 to 37a8 is 80 Ω at room temperature. In addition to the materials mentioned above, resistive materials such as silver alloy (AgPt) or ruthenium oxide (RuO2) can also be used for the heating element patterns 37a1 to 37a8. In this embodiment, the heating element patterns 37a1 to 37a8 are formed, for example, by screen printing silver (Ag) or silver-palladium (AgPd) to create the conductor pattern 37d or electrodes 37e and 37f.

[0047] As the material for the overlay coating 39, a heat-resistant glass with a thickness of 75 μm can be used. The overlay coating 39 is formed by covering the heating element patterns 37a1 to 37a8 and the conductor pattern 37d on the heater substrate material 37b, and ensures the insulation of the heating element patterns 37a1 to 37a8 from the heater surface. In addition, the overlay coating 39 also serves to ensure sliding movement with the inner circumferential surface of the fixing belt 31.

[0048] The heater 37 contacts the fixing belt 31 on the side of the cover coating 39 to heat it, and raises the temperature of the fixing belt 31 by heat transfer, thereby heating and fixing the unfixed image that is transported to the fixing clamping part SN onto the paper P.

[0049] like Figure 6 and Figure 7As shown, heating element patterns 37a1 to 37a8 are divided along their length and electrically connected in parallel. Furthermore, heating element patterns 37a1 to 37a8 are made of a material with PTC (positive temperature resistivity) characteristics, exhibiting a characteristic that the resistance increases (heater output decreases) as the temperature rises. When fixing a piece of paper P that is narrower than the range of heating element patterns 37a1 to 37a8, in the portion of the heating element pattern further outward in the paper's width direction (outward in the direction of the long side of the heater 37), the temperature rises because heat is not lost to the paper, and therefore the resistance increases due to the aforementioned characteristic. At this time, since the voltage applied to the heating element patterns 37a1 to 37a8 is constant, the output of the heating element pattern portion outside the paper is relatively reduced, thereby suppressing the temperature rise of that heating element pattern portion.

[0050] When the heating element patterns 37a1 to 37a8 are connected in series, in order to suppress the temperature rise of the heating element pattern portion opposite to the outer side of the paper width direction, it is necessary to reduce the image forming speed (printing speed) during continuous image formation. In contrast, by adopting the configuration of this embodiment, it is no longer necessary to reduce the image forming speed in order to suppress the temperature rise of the heating element pattern portion, so it is possible to improve productivity.

[0051] Furthermore, when the heating element patterns 37a1 to 37a8 are arranged side by side along the length direction, a distance needs to be maintained between the heating element patterns to ensure insulation between them, which reduces heat generation in the area between the heating element patterns. Therefore, as Figure 6 and Figure 7 As shown, it is preferable that the patterns of each heating element are arranged in an overlapping manner along the long side, thereby suppressing the reduction of local heating in the long side.

[0052] Alternatively, the heating element patterns 37a1 to 37a8 can also be formed by folding the heating element material back to obtain the desired output (resistance value).

[0053] The fixing device 30 of this embodiment will be described in more detail below.

[0054] Figure 8 The diagram shown is a schematic representation of the internal structure of the fixing belt 31 in the fixing device 30 of this embodiment.

[0055] The fixing device 30 of this embodiment has an annular fixing belt 31 as a fixing component, and a pressure roller 32 as an opposing component that forms a fixing clamping portion SN with the fixing belt 31.

[0056] The fixing belt 31 is a component that heats and fixes the toner image onto paper P. In this embodiment, the fixing belt 31 has a hollow substrate made of polyimide (PI) with an outer diameter of 25 mm and a thickness of 40 μm to 120 μm. To improve durability and ensure release properties, a release layer with a thickness of 5 μm to 50 μm, formed of a fluorinated resin such as PFA or PTFE, is formed in the outermost peripheral layer of the fixing belt 31. An elastic layer made of rubber or the like with a thickness of 50 μm to 500 μm may also be provided between the substrate and the release layer. The substrate of the fixing belt 31 is not limited to polyimide; it may also be a heat-resistant resin such as PEEK, or a metal substrate such as nickel (Ni) or SUS. Alternatively, a layer of polyimide or PTFE may be provided on the inner peripheral surface of the fixing belt 31 as a sliding layer.

[0057] In this embodiment, the pressure roller 32 has an outer diameter of 25 mm and is composed of a solid iron core rod 32a, an elastic layer 32b formed on the surface of the core rod 32a, and a release layer 32c as the outermost peripheral layer. The elastic layer 32b is formed of silicone rubber, for example, and has a thickness of 3.5 mm. In order to improve the release properties, a fluoropolymer layer with a thickness of about 40 μm can be used in the release layer 32c formed on the surface side of the elastic layer 32b.

[0058] like Figure 2 As shown, the heater holder 36 abuts against the back of the heater substrate material 37b at two locations that avoid the heating element patterns 37a1 to 37a8, in order to suppress heat transfer from the heater 37 to the heater holder 36.

[0059] like Figure 8 As shown, in this embodiment, the fixing device 30 has a thermistor 34, which serves as a temperature detection mechanism, disposed inside the heater holder 36 to detect the temperature of the heater 37. Specifically, the thermistor 34 is disposed on the back side of the heater substrate material 37b of the heater 37 (the side opposite to the side where the heating element patterns 37a1 to 37a8 are disposed). The temperature detected by the thermistor 34 is sent to the temperature control unit 50.

[0060] The temperature control unit 50 controls the heater power supply 51 that supplies power to the heater 37 based on the temperature detected by the thermistor 34, and performs fixing temperature control to ensure that the temperature of the fixing belt 31 reaches the target temperature. The temperature control unit 50 can be configured as a microcomputer including a CPU, ROM, RAM, I / O interface, etc. Furthermore, the temperature control unit 50 can perform temperature control based solely on the temperature detected by the thermistor 34, or it can consider other parameters.

[0061] In addition, such as Figure 8As shown, the fixing device 30 of this embodiment, as an additional temperature detection component for detecting the temperature of the heater 37, also includes a thermostat 40. The thermostat 40 is disposed within the internal space of the support bar 33 (the space enclosed by the upstream leg 33a, downstream leg 33b, connecting portion 33c of the support bar 33, and the back surface of the heater holder 36). The thermostat 40 is positioned in the longitudinal direction by embedding the temperature detection portion 40a into the opening 36a provided on the heater holder 36. Furthermore, the thermostat 40 is positioned in the paper transport direction by clamping it between the upstream leg 33a and downstream leg 33b of the support bar 33.

[0062] The thermostat 40 is connected to the power path from the heater power supply 51 to the heater 37. When the temperature of the heater 37 rises above the specified upper limit temperature, the thermostat 40, which detects this temperature, switches off the power supply from the heater power supply 51 to the heater 37. This ensures temperature control so that the heater 37 does not exceed the specified upper limit temperature, thus guaranteeing safety.

[0063] To miniaturize the fixing belt 31, it is necessary to miniaturize the conductive support member, namely the support bar 33, disposed in the hollow portion of the fixing belt 31 (the space surrounded by the inner circumferential surface of the annular fixing belt 31). If the paper transport direction of the support bar 33 can be... Figure 8 (left-right direction) or the pressure direction of the fixing clamp ( Figure 8 By miniaturizing the size of the fixing belt 31 in the vertical direction, the circumference of the fixing belt 31 can be shortened, thus miniaturizing the fixing belt 31.

[0064] Here, as shown in Figures 9(a) and (b), the thermostat 40 is typically configured with the detection part 40a and two terminals 40b exposed to the outside. Furthermore, as shown in Figure 9(b), the thermostat 40 is installed within the internal space of the support bar 33 with the wiring 40c connected to the two terminals 40b via soldering or the like. At this time, the two terminals 40b of the thermostat 40 are conductors, and because they are exposed, they become exposed conductive parts.

[0065] Since the thermostat 40 is disposed within the internal space of the support bar 33, when the conductive support member, i.e., the support bar 33, is miniaturized, the distance between the exposed conductive portion (terminal 40b) of the thermostat 40 and the opposing portion of the support bar 33 becomes shorter. For example, in this embodiment, the gap between the upstream leg 33a and the downstream leg 33b of the support bar 33 is narrowed, thereby miniaturizing the size of the support bar 33 in the paper transport direction. At this time, as shown in FIG9(b), the distance L between the exposed conductive portion (terminal 40b) of the thermostat 40 and the upstream leg 33a and the downstream leg 33b of the support bar 33 becomes shorter. In particular, when the thermostat 40 is sandwiched between the upstream side foot 33a and the downstream side foot 33b of the support bar 33, the exposed conductive part (terminal 40b) of the thermostat 40 is closest to the upstream side foot 33a and the downstream side foot 33b of the support bar 33, and the distance L is very short.

[0066] Therefore, when the support bar 33 is miniaturized, short circuits or other issues can easily occur between the support bar 33 and the exposed conductive portion (terminal 40b) of the thermostat 40, making it difficult to perform proper temperature detection using the thermostat 40. As a result, it may hinder the proper operation of the fixing device 30 (such as temperature control to ensure that the heater 37 does not exceed the specified upper limit temperature).

[0067] Furthermore, if the insulating component is positioned between the exposed conductive portion (terminal 40b) of the thermostat 40 and the opposing portion of the support bar 33, the occurrence of short circuits can also be suppressed. However, since the thickness of the insulating component would correspondingly hinder the miniaturization of the support bar 33, the miniaturization requirement cannot be fully met.

[0068] Therefore, in this embodiment, as shown in Figures 10(a) and (b), an opening 33d is provided in the portion of the support bar 33 opposite to the exposed conductive portion (terminal 40b) of the thermostat 40. Specifically, when the thermostat 40 is disposed in the internal space of the support bar 33, an opening 33d is provided in the portions of the upstream leg 33a and the downstream leg 33b of the support bar 33 opposite to the exposed conductive portion (terminal 40b) of the thermostat 40.

[0069] By providing such an opening 33d, even if the support bar 33 is miniaturized, the distance (closest distance) between the exposed conductive part (terminal 40b) of the thermostat 40 and the support bar 33 can be increased. Therefore, even if the support bar 33 is miniaturized, the occurrence of the aforementioned short circuits can be suppressed.

[0070] Furthermore, an opening 33d serving as a through hole is provided in the opposing portion of the support bar 33 opposite to the exposed conductive portion (terminal 40b) of the thermostat 40, but this is not a limitation; for example, a recess may also be provided in this opposing portion. Specifically, when the thermostat 40 is placed in the internal space of the support bar 33, recesses (recesses) may be provided in the inner wall surfaces of the upstream leg 33a and downstream leg 33b of the support bar 33 opposite to the exposed conductive portion (terminal 40b) of the thermostat 40, respectively.

[0071] For example, in this embodiment, the gap between the upstream side foot 33a and the downstream side foot 33b of the support bar 33 is narrowed, thereby reducing the size of the support bar 33 in the paper transport direction, but this is not a limitation. For example, the height (length in the pressing direction of the fixing clamp) of the upstream side foot 33a and the downstream side foot 33b of the support bar 33 can also be shortened to reduce the size of the support bar 33 in the pressing direction of the fixing clamp. In this example, since the connecting portion 33c of the support bar 33 is close to the exposed conductive portion (terminal 40b) of the thermostat 40, the opening 33d is provided on the connecting portion 33c.

[0072] In this embodiment, openings 33d are provided on both the upstream foot 33a and the downstream foot 33b of the support bar 33. However, openings 33d may be provided only in either foot 33a or 33b. For example, it is possible to arrange the thermostat 40 in the internal space of the support bar 33 with its orientation biased towards the upstream or downstream side of the paper transport direction, or to arrange the exposed conductive portion (terminal 40b) of the thermostat 40 with its orientation biased towards the upstream or downstream side of the paper transport direction. In this case, openings 33d may be provided only in the feet 33a or 33b that are closest to the exposed conductive portion (terminal 40b) of the thermostat 40.

[0073] Furthermore, in this embodiment, the temperature sensing component disposed within the internal space of the support bar 33 is a thermostat 40, which is separate from the thermistor 34 used to control the fixing temperature to the target temperature and is used to disconnect the power supply to the heater 37 when the upper limit temperature is exceeded. However, the temperature sensing component disposed within the internal space of the support bar 33 may also be a temperature sensing component used to control the fixing temperature to the target temperature.

[0074] Furthermore, in this embodiment, the opening 33d only needs to be of a size and shape sufficient to ensure that the distance (closest distance) between the exposed conductive part (terminal 40b) of the thermostat 40 and the support bar 33 does not cause a short circuit. However, when the opening 33d has other functions besides preventing short circuits, it may be larger than the required size or have a different shape depending on the other functions. Other functions may include, for example, recesses or openings used only when manufacturing the support bar 33, observation windows for observing and confirming the thermostat 40 disposed in the internal space of the support bar 33 from the outside of the support bar 33, and holes made for weight reduction.

[0075] The above explanation is just one example; the various methods below each have their own unique effects.

[0076] [First Method]

[0077] The first type of fixing device (30) includes a hollow fixing member (e.g., fixing belt 31) that heats and fixes an image onto a recording material (e.g., paper P); an opposing member (e.g., pressure roller 32) that forms a fixing clamping portion with the fixing member; a conductive support member (e.g., support bar 33) disposed in the hollow portion of the fixing member and supporting the fixing clamping portion of the fixing member; and a temperature detection member (e.g., thermostat 40) that detects temperature. A recess or opening (33d) is provided in the conductive support member at a portion opposite to the exposed conductive portion (e.g., terminal 40b) of the temperature detection member.

[0078] In conventional fixing devices, when the conductive support member disposed in the hollow portion of the fixing unit is miniaturized to achieve miniaturization, the distance between the exposed conductive portion of the temperature sensing member and the opposing portion of the conductive support member sometimes becomes shorter. For example, when the temperature sensing member is disposed inside the conductive support member, the smaller the conductive support member is, the shorter the closest distance between the exposed conductive portion of the temperature sensing member and the conductive support member becomes. Therefore, when the conductive support member is miniaturized, short circuits or similar issues can easily occur between the conductive support member and the exposed conductive portion of the temperature sensing member, making it difficult to perform proper temperature detection and potentially hindering the proper operation of the fixing device. In this case, if an insulating member is placed between the exposed conductive portion of the temperature sensing member and the opposing portion of the conductive support member, the occurrence of such short circuits can be suppressed. However, since the thickness of the insulating member correspondingly hinders the miniaturization of the conductive support member, the miniaturization requirements cannot be fully met.

[0079] In this method, by providing a recess or opening in the opposing portion of the conductive support member opposite the exposed conductive portion of the temperature sensing member, the closest distance between the exposed conductive portion of the temperature sensing member and the conductive support member can be extended even when the conductive support member is miniaturized. Therefore, even when the conductive support member is miniaturized, the occurrence of short circuits and the like can be suppressed. Thus, even when the conductive support member is miniaturized for the sake of miniaturizing the fixing member, temperature sensing by the temperature sensing member can be performed appropriately, and the fixing device can operate appropriately.

[0080] [Second Method]

[0081] The second approach is characterized in that, in the first approach, the conductive support member has an upstream conductive support portion (e.g., upstream foot 33a) disposed on the upstream side of the transport direction of the recording material and a downstream conductive support portion (e.g., downstream foot 33b) disposed on the downstream side of the transport direction, and the recess or the opening is provided in one of the upstream conductive support portion and the downstream conductive support portion.

[0082] Therefore, even if the length of the recording material transport direction of the conductive support component is shortened to miniaturize the conductive support component, the temperature of the temperature detection component can be properly detected, and the fixing device can be properly operated.

[0083] [Third Method]

[0084] The third approach is characterized in that, in the second approach, the recess or the opening is provided only on the side of the upstream conductive support and the downstream conductive support closer to the temperature sensing component.

[0085] This reduces the number of recesses or openings formed in conductive support components.

[0086] [Fourth Method]

[0087] The fourth approach is characterized in that, in any of the first to third approaches, the exposed conductive portion is a terminal portion (e.g., terminal 40b) of the temperature sensing component.

[0088] Therefore, even if the conductive support component is miniaturized, short circuits between the terminals of the temperature sensing component and the conductive support component can be suppressed.

[0089] [Fifth Method]

[0090] The fifth method is characterized in that, in any of the first to fourth methods, the temperature detection component is a thermostat 40.

[0091] Because the thermostat 40 is relatively large compared to other temperature sensing components such as the thermistor 34, miniaturizing the conductive support component housed within its internal space can easily lead to short circuits between the conductive support component and the exposed conductive portion of the temperature sensing component. Therefore, according to this method, even if the temperature sensing component is such a thermostat, short circuits between the terminals of the temperature sensing component and the conductive support component can be suppressed.

[0092] [Sixth Method]

[0093] The sixth method is characterized in that, in any of the first to fifth methods, the recess or the opening is at least one of a recess or opening used during manufacturing, an observation window for external observation and confirmation of the temperature sensing component, and a hole opened for weight reduction.

[0094] Therefore, the recess or opening used to suppress short circuits between the terminal portion of the temperature sensing component and the conductive support component can also be used for other purposes.

[0095] [Seventh Method]

[0096] The seventh method is an image forming apparatus having a fixing mechanism for fixing an image formed on a recording material onto the recording material, characterized in that: the fixing mechanism is a fixing device using any one of the first to sixth methods.

[0097] Therefore, it is possible to provide an image forming apparatus that enables the fixing device to operate properly and to miniaturize the fixing device.

Claims

1. A fixing device, comprising: A hollow fixing component that heats and fixes the image onto the recording material; Opposite component forming a fixing clamping portion with the fixing component; A conductive support member disposed in the hollow portion of the fixing member and supporting the fixing clamping portion of the fixing member, and A temperature sensing component for detecting temperature, wherein the temperature sensing component is disposed within the internal space of the conductive support component. The fixing device is characterized in that a recess or opening is provided in the inner wall of the conductive support member at the location opposite the exposed conductive part of the temperature sensing member.

2. The fixing device according to claim 1, characterized in that: The conductive support member includes an upstream conductive support portion disposed on the upstream side of the transport direction of the recording material and a downstream conductive support portion disposed on the downstream side of the transport direction. The recess or the opening is provided on at least one of the upstream conductive support and the downstream conductive support.

3. The fixing device according to claim 2, characterized in that: The recess or the opening is provided only on the side of the upstream conductive support and the downstream conductive support that is closer to the temperature sensing component.

4. The fixing device according to any one of claims 1 to 3, characterized in that: The exposed conductive part is the terminal part of the temperature sensing component.

5. The fixing device according to any one of claims 1 to 3, characterized in that: The temperature detection component is a thermostat.

6. The fixing device according to any one of claims 1 to 3, characterized in that: The recess or the opening is at least one of the following: a recess or opening used during manufacturing, an observation window for external observation and confirmation of the temperature sensing component, and a hole opened for weight reduction.

7. An image forming apparatus having a fixing mechanism for fixing an image formed on a recording material onto the recording material, characterized in that: The fixing mechanism is the fixing device according to any one of claims 1 to 6.

Images