阅读说明：本技术 定影带和定影装置 (Fixing belt and fixing device ) 是由 佐伯谅太 于 2020-09-08 设计创作，主要内容包括：提供一种定影带和定影装置,能够同时实现抑制定影带的带电以及确保定影带的次级部件和加热器的绝缘耐压。实施方式的定影带是筒状环形带,从内周侧起依次具有基层、弹性层和脱模层。所述定影带从所述基层侧测量的表面电阻率为7[LOGΩ/sq.]以上且10[LOGΩ/sq.]以下。(Provided are a fixing belt and a fixing device capable of simultaneously achieving suppression of electrification of the fixing belt and securing of an insulation withstand voltage of a secondary member of the fixing belt and a heater. The fixing belt of the embodiment is a cylindrical endless belt, and includes a base layer, an elastic layer, and a release layer in this order from the inner peripheral side. The fixing belt has a surface resistivity of 7[ LOG Ω/sq ] or more and 10[ LOG Ω/sq ] or less as measured from the base layer side.)

1. A fixing belt, characterized in that,

the fixing belt is a cylindrical endless belt having a base layer, an elastic layer, and a releasing layer in this order from the inner peripheral side,

a surface resistivity measured from the base layer side is 7 or more and 10 or less, wherein a unit of the surface resistivity is: LOG omega/sq.

2. A fixing belt, characterized in that,

the fixing belt is a cylindrical endless belt having a base layer, an elastic layer, a primer layer, and a release layer in this order from the inner periphery side,

a volume resistivity measured from the base layer side is 14 or more, wherein a unit of the volume resistivity is: LOG Ω. cm.

3. The fixing belt according to claim 2,

the elastic layer is formed using Si rubber, and the releasing layer is formed using PFA tube,

the surface resistivity of the elastic layer is less than the surface resistivity of the release layer.

4. A fixing device is characterized by comprising:

the fixing belt according to claim 1 or 2;

a pressure roller forming a nip portion with the fixing belt; and

a heating portion that heats the fixing belt from an inner side of the fixing belt.

5. A fixing device according to claim 4,

the heating section has: a substrate; an insulating layer laminated on the substrate; a heating element formed on a surface of the insulating layer opposite to the substrate; and a protective layer that is laminated on the insulating layer so as to cover the heat generating body, and that forms the nip portion with the protective layer interposed therebetween.

Technical Field

Embodiments of the present invention generally relate to a fixing belt and a fixing device.

Background

Conventionally, there is a fixing device that heats a fixing belt from inside the cylindrical fixing belt by a planar heater. In such a fixing device, a metal material is often used for a base material of the fixing belt in a high-speed machine, and a non-metal material is often used for a fixing belt in a medium-speed machine or a low-speed machine. This is because the high-speed machine takes a lot of heat away from the paper, and the temperature of the fixing belt cannot be maintained unless the fixing belt has a certain thermal capacity. In addition, it is difficult to use an expensive metal fixing belt for an inexpensive low-speed machine. Therefore, if there is no problem in the heat capacity, it is desirable to use a fixing belt made of a nonmetal.

However, when a non-metallic fixing belt is used, static electricity generated by the sliding between the fixing belt and the heater may adversely affect the operation of the fixing device. Specifically, there is a problem that the surface of the fixing belt is charged, and the charged unfixed toner image may be disturbed. As a countermeasure, a resin having conductivity is generally used for a resin constituting a base material of the fixing belt. However, in this measure, if the heating surface of the planar heater is brought into direct contact with the inside of the fixing belt, there is a possibility that the withstand voltage between the fixing belt and the heater cannot be sufficiently secured.

Disclosure of Invention

The present invention provides a fixing belt and a fixing device, which can simultaneously realize the suppression of the electrification of the fixing belt and the guarantee of the insulation and voltage resistance of a secondary component of the fixing belt and a heater.

The fixing belt of the embodiment is a cylindrical endless belt, and includes a base layer, an elastic layer, and a release layer in this order from the inner peripheral side. The fixing belt has a surface resistivity of 7[ LOG Ω/sq ] or more and 10[ LOG Ω/sq ] or less as measured from the base layer side.

The fixing device of the embodiment comprises: the above-described fixing belt; a pressure roller forming a nip portion with the fixing belt; and a heating unit that heats the fixing belt from an inner side of the fixing belt.

Drawings

Fig. 1 is a diagram showing an outline of the configuration of an image forming apparatus according to a first embodiment.

Fig. 2 is a diagram showing a specific example of the hardware configuration of the image forming apparatus according to the first embodiment.

Fig. 3 is a front sectional view of the heating device of the first embodiment.

Fig. 4 is a front sectional view of the heater unit of the first embodiment.

Fig. 5 is a bottom view of the heater unit of the first embodiment.

Fig. 6 is a front sectional view of the heat conductive member, the heater unit, and the tubular belt according to the first embodiment.

Fig. 7 is a top view of the heater thermometer and thermostat of the first embodiment.

Fig. 8 is a circuit diagram of the heating device of the first embodiment.

Fig. 9 is a diagram showing a detailed configuration example of the fixing device of the first embodiment.

Fig. 10 is a flowchart showing a flow of the state control process in the first embodiment.

Fig. 11 is a flowchart showing a flow of the state control process in the second embodiment.

Description of the reference numerals

100: an image forming apparatus; 1: a display; 2: a scanning section; 3: an image forming unit; 4: a sheet feeding section; 5: a conveying section; 6: a control unit; 7: a paper discharge tray; 8: a control panel; 9: a turning unit; 10: a housing; 20: a sheet accommodating portion; 21: a pickup roller; 23: a conveying roller; 24: aligning rollers; 25. 25Y, 25M, 25K: an image forming section; 25 d: a photosensitive drum; 26: a laser scanning unit; 27: an intermediate transfer belt; 28: a transfer section; 30: a fixing device; 30 h: a membrane unit; 30 p: a pressure roller; 31: a flange; 32: a core rod; 33: an elastic layer; 34: a release layer; 35: a fixing film; 36: a support member; 38: a support; 40: a heater unit; 41: a substrate; 43: an insulating layer; 45: a heat generating body group; 45 a: a central heating element; 45b 1: a first end heating element; 45b 2: a second end heating element; 46: a protective layer; 49: a heat conductive member; 52 a: a central portion contact; 52 b: an end contact; 53 a: a central portion wiring; 53b 1: a first end wiring; 53b 2: a second end wiring; 55: a wiring group; 57: a common wiring; 58: a common junction; 62: a heater thermometer; 62 a: a central portion heater thermometer; 62 b: an end heater thermometer; 64: a film thermometer; 64 a: a central part film thermometer; 64 b: an end film thermometer; 68: a thermostat; 68 a: a center thermostat; 68 b: an end thermostat; 90: a communication unit; 92: a memory; 93: a secondary storage device; 95: a power source; 96 a: a central portion triac; 96 b: and a bidirectional thyristor at the end part.

Detailed Description

Next, a fixing belt and a fixing device according to an embodiment will be described with reference to the drawings.

(first embodiment)

Fig. 1 is a diagram showing an outline of the configuration of an image forming apparatus according to a first embodiment. The image forming apparatus 100 of the first embodiment is, for example, a multifunction device. The image forming apparatus 100 includes a housing 10, a display 1, a scanner portion 2, an image forming unit 3, a sheet feeding portion 4, a conveying portion 5, a paper discharge tray 7, a reversing unit 9, a control panel 8, and a control portion 6. Note that the image forming unit 3 may be a device for fixing a toner image or an inkjet device.

The image forming apparatus 100 forms an image on a sheet S using a developer such as toner. The sheet S is, for example, paper or label paper. The sheet S may be any object as long as the image forming apparatus 100 can form an image on its surface.

The housing 10 forms the outer shape of the image forming apparatus 100. The display 1 is an image display device such as a liquid crystal display, an organic EL (Electro Luminescence) display, or the like. The display 1 displays various information related to the image forming apparatus 100.

The scanner unit 2 reads image information of a reading target in the form of light and shade. The scanner unit 2 records the read image information. The scanner unit 2 outputs the generated image information to the image forming unit 3. It is to be noted that the recorded image information may be transmitted to other information processing apparatuses via a network.

The image forming unit 3 forms an output image (hereinafter, referred to as a toner image) with a recording agent such as toner based on image information received from the scanner unit 2 or image information received from the outside. The image forming unit 3 transfers the toner image onto the surface of the sheet S. The image forming unit 3 heats and pressurizes the toner image on the surface of the sheet S, and fixes the toner image on the sheet S. Details of the image forming unit 3 are described later. Note that the sheet S may be a sheet fed by the sheet feeding portion 4 or a manually fed sheet.

The sheet feeding portion 4 feeds the sheets S one by one to the conveying portion 5 in accordance with the timing at which the image forming unit 3 forms the toner image. The sheet feeding portion 4 includes a sheet accommodating portion 20 and a pickup roller 21.

The sheet accommodating portion 20 accommodates sheets S of a prescribed size and type. The pickup roller 21 takes out the sheets S one by one from the sheet accommodating portion 20. The pickup roller 21 feeds the taken out sheet S to the conveying portion 5.

The conveying portion 5 conveys the sheet S supplied from the sheet supply portion 4 to the image forming unit 3. The conveying section 5 includes a conveying roller 23 and a registration roller 24. The conveying roller 23 conveys the sheet S fed from the pickup roller 21 to the registration roller 24. The conveying roller 23 abuts the leading end of the sheet S in the conveying direction against the nip portion N of the registration roller 24.

The registration rollers 24 adjust the leading end position of the sheet S in the conveying direction by bending the sheet S at the nip portion N. The registration rollers 24 convey the sheet S in accordance with the timing at which the image forming unit 3 transfers the toner image onto the sheet S.

The image forming unit 3 will be explained. The image forming unit 3 includes a plurality of image forming portions 25, a laser scanning unit 26, an intermediate transfer belt 27, a transfer portion 28, and a fixing device 30. The image forming portion 25 includes a photosensitive drum 25 d. The image forming unit 25 forms a toner image corresponding to image information from the scanner unit 2 or the outside on the photosensitive drum 25 d. The plurality of image forming units 25Y, 25M, 25C, and 25K form toner images based on yellow, magenta, cyan, and black toners, respectively.

A charger, a developer, and the like are disposed around the photosensitive drum 25 d. The charger charges the surface of the photosensitive drum 25 d. The developer contains developer containing yellow, magenta, cyan, and black toners. The developer develops the electrostatic latent image on the photosensitive drum 25 d. As a result, toner images based on the toners of the respective colors are formed on the photosensitive drum 25 d.

The laser scanning unit 26 scans the charged photosensitive drum 25d with the laser beam L to expose the photosensitive drum 25 d. The laser scanner unit 26 exposes the photosensitive drums 25d of the image forming portions 25Y, 25M, 25C, 25K of the respective colors with different laser lights LY, LM, LC, LK. Thereby, the laser scanner unit 26 forms an electrostatic latent image on the photosensitive drum 25 d.

The toner image on the surface of the photosensitive drum 25d is primarily transferred onto the intermediate transfer belt 27. The transfer portion 28 transfers the toner image primarily transferred onto the intermediate transfer belt 27 onto the surface of the sheet S at the secondary transfer position. The fixing device 30 heats and pressurizes the toner image transferred onto the sheet S, and fixes the toner image onto the sheet S. Details of the fixing device 30 are described later.

The reversing unit 9 reverses the sheet S to form an image on the back side of the sheet S. The reversing unit 9 reverses the sheet S discharged from the fixing device 30 through the switchback portion. The reversing unit 9 conveys the reversed sheet S toward the registration rollers 24.

The sheet discharge tray 7 is used to place the sheet S on which the image is formed and discharged. The control panel 8 has a plurality of buttons. The control panel 8 receives a user operation. The control panel 8 outputs a signal corresponding to an operation performed by the user to the control section 6 of the image forming apparatus 100. Note that the display 1 and the control panel 8 may be constituted as an integrated touch panel. The control unit 6 controls each unit of the image forming apparatus 100. Details of the control section 6 are described later.

Fig. 2 is a diagram showing a specific example of the hardware configuration of the image forming apparatus 100 according to the first embodiment. The image forming apparatus 100 includes a CPU (Central Processing Unit) 91, a memory 92, and an auxiliary storage device 93 connected by a bus, and executes programs. The image forming apparatus 100 functions as an apparatus including the scanner section 2, the image forming unit 3, the sheet feeding section 4, the conveying section 5, the reversing unit 9, the control panel 8, and the communication section 90 by executing a program. All or part of the functions of image forming apparatus 100 may be implemented by hardware such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array). The program may be recorded in a computer-readable recording medium. The computer-readable recording medium is, for example, a removable medium such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, or a storage device such as a hard disk incorporated in a computer system. The program may be transmitted via a telecommunication line.

The CPU91 functions as the control unit 6 by executing programs stored in the memory 92 and the auxiliary storage device 93. The control unit 6 controls the operation of each functional unit of the image forming apparatus 100. The auxiliary storage device 93 is configured using a storage device such as a magnetic hard disk device or a semiconductor storage device. The auxiliary storage device 93 stores various information related to the image forming apparatus 100. The communication section 90 includes a communication interface for connecting the present apparatus to an external apparatus. The communication section 90 communicates with an external device via a communication interface.

The fixing device 30 is explained in detail. Fig. 3 is a front sectional view of the heating device of the first embodiment. The heating device of the first embodiment is a fixing device 30. The fixing device 30 includes a pressure roller 30p and a film unit 30 h.

The nip portion N is formed between the pressing roller 30p and the film unit 30 h. The pressure roller 30p presses the toner image t of the sheet S entering the nip portion N. The pressure roller 30p conveys the sheet S by self-rotation. The pressing roller 30p includes a core bar 32, an elastic layer 33, and a releasing layer 34. In this way, the pressure roller 30p can press the surface onto the fixing film 35, and can be rotationally driven.

The mandrel 32 is formed in a cylindrical shape from a metal material such as stainless steel. Both axial ends of the mandrel 32 are rotatably supported. The mandrel 32 is rotationally driven by a motor (not shown). The core rod 32 abuts against a cam member (not shown). The cam member causes the core rod 32 to approach and separate from the film unit 30h by rotating.

The elastic layer 33 is formed of an elastic material such as silicone rubber. The elastic layer 33 is formed with a constant thickness on the outer peripheral surface of the mandrel bar 32. The releasing layer 34 is formed of a resin material such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer). The release layer is formed on the outer peripheral surface of the elastic layer 33. The hardness of the outer circumferential surface of the pressure roller 30p is preferably 40 ° to 70 °, as measured using an ASKER-C durometer under a load of 9.8N. Thereby, the area of the nip portion N and the durability of the pressure roller 30p are ensured.

The pressing roller 30p can approach and separate from the film unit 30h by the rotation of the cam member. When the pressing roller 30p approaches the film unit 30h and is pressed by the pressing spring, the nip portion N is formed. On the other hand, when a sheet S is jammed in the fixing device 30, the sheet S can be removed by separating the pressure roller 30p from the film unit 30 h. In addition, in a state where the fixing film 35 stops rotating, such as at a standstill, the pressure roller 30p is separated from the film unit 30h, thereby preventing plastic deformation of the fixing film 35.

The pressure roller 30p is rotationally driven by a motor. When the pressure roller 30p rotates in a state where the nip portion N is formed, the fixing film 35 of the film unit 30h is driven to rotate. The pressing roller 30p rotates in a state where the sheet S is arranged at the nip portion N, thereby conveying the sheet S in the conveying direction W.

The film unit 30h heats the toner image t of the sheet S entering the nip portion N. The membrane unit 30h includes: the fixing film 35, the heater unit 40, the heat conduction member 49, the support member 36, the holder 38, the heater thermometer 62, the thermostat 68, and the film thermometer 64.

The fixing film 35 is formed in a cylindrical shape. The fixing film 35 includes, in order from the inner peripheral side: a base layer, an elastic layer, and a release layer. The base layer is formed in a cylindrical shape. The elastic layer is laminated and arranged on the outer peripheral surface of the base layer. The elastic layer is formed of an elastic material such as rubber. The release layer is laminated and disposed on the outer peripheral surface of the elastic layer. The releasing layer is formed of a material such as PFA resin.

Fig. 4 is a front sectional view of the heater unit taken along line IV-IV of fig. 5. Fig. 5 is a bottom view (view viewed from the + z direction) of the heater unit. The heater unit 40 includes: a substrate (heat-generating body substrate) 41, a heat-generating body group 45, and a wiring group 55.

The substrate 41 is made of a metal material such as stainless steel, a ceramic material such as aluminum nitride, or the like. The substrate 41 is formed in an elongated rectangular plate shape. The substrate 41 is disposed radially inward of the fixing film 35. The substrate 41 has the fixing film 35 with its longitudinal direction as the axial direction.

In the present application, the x-direction, y-direction, and z-direction are defined as follows. The y direction is the longitudinal direction of the substrate 41. The y direction is parallel to the width direction of the fixing film 35. As described later, the + y direction is a direction from the center heating element 45a toward the first end heating element 45b 1. The x direction is the short side direction of the substrate 41, and the + x direction is the conveyance direction (downstream direction) of the sheet S. The z direction is a normal direction of the substrate 41, and the + z direction is a direction in which the heating element group 45 is disposed with respect to the substrate 41. On the surface of the substrate 41 in the + z direction, an insulating layer 43 is formed of a glass material or the like.

The heating element group 45 is disposed on the substrate 41. As shown in fig. 4, the heat generating element group 45 is formed on the surface of the insulating layer 43 in the + z direction. The heat generating element group 45 is formed of a TCR (temperature coefficient of resistance) material. For example, the heating element group 45 is formed of a silver-palladium alloy or the like. The heating element group 45 is formed in a rectangular shape having a longitudinal direction in the y direction and a short side in the x direction.

As shown in fig. 5, the heat-generating element group 45 includes a first end heat-generating element 45b1, a center heat-generating element 45a, and a second end heat-generating element 45b2 arranged in parallel in the y direction. The central heating element 45a is disposed in the center of the heating element group 45 in the y direction. The central heating element 45a may be configured by combining a plurality of small heating elements arranged in parallel in the y direction. The first end heating element 45b1 is disposed at the end of the heating element group 45 in the + y direction of the center heating element 45 a. The second end heating element 45b2 is disposed at the-y direction end of the center heating element 45a and the-y direction end of the heating element group 45. The boundary line between the center heating element 45a and the first end heating element 45b1 may be arranged parallel to the x direction or may intersect the x direction. The same applies to the boundary line between the center heating element 45a and the second end heating element 45b 2.

The heat generating element group 45 generates heat by energization. The resistance value of the center heating element 45a is smaller than the resistance values of the first end heating element 45b1 and the second end heating element 45b 2. The sheet S having a small width in the y direction passes through the center portion in the y direction of the fixing device 30. In this case, the control unit 6 causes only the central heating element 45a to generate heat. On the other hand, in the case of the sheet S having a large width in the y direction, the control unit 6 causes the entire heat-generating body group 45 to generate heat. Therefore, the center heating element 45a, the first end heating element 45b1, and the second end heating element 45b2 are controlled to generate heat independently of each other. The first end heating element 45b1 and the second end heating element 45b2 are controlled to generate heat in the same manner.

The wiring group 55 is formed of a metal material such as silver. The wiring group 55 includes: the center portion contact 52a, the center portion wiring 53a, the end contact 52b, the second end portion wiring 53b1, the second end portion wiring 53b2, the common contact 58, and the common wiring 57.

The center contact 52a is arranged in the-y direction of the heating element group 45. The central wiring 53a is arranged in the + x direction of the heating element group 45. The center wiring 53a connects the end side of the center heating element 45a in the + x direction and the center contact 52 a.

The end contact 52b is arranged in the-y direction of the center contact 52 a. The first end portion wiring 53b1 is arranged in the + x direction of the heating element group 45 and in the + x direction of the center portion wiring 53 a. The first end wiring 53b1 connects the end edge of the first end heating element 45b1 in the + x direction and the end edge of the end contact 52b in the + x direction. The second end portion wiring 53b2 is arranged in the + x direction of the heat generating element group 45 and in the-x direction of the center portion wiring 53 a. The second end wiring 53b2 connects the end edge of the second end heating element 45b2 in the + x direction and the end edge of the end contact 52b in the-x direction.

The common contact 58 is disposed in the + y direction of the heating element group 45. The common wiring 57 is arranged in the-x direction of the heat generating element group 45. The common wiring 5 connects the edges of the center heating element 45a, the first end heating element 45b1, and the second end heating element 45b2 in the-x direction to the common contact 58.

In this way, the second end wiring 53b2, the center wiring 53a, and the first end wiring 53b1 are arranged in the + x direction of the heating element group 45. In contrast, only the common wiring 57 is disposed in the-x direction of the heating element group 45. Therefore, the center 45c of the heating element group 45 in the x direction is arranged at a position closer to the x direction than the center 41c of the substrate 41 in the x direction.

As shown in fig. 3, a straight line CL connecting the center pc of the pressure roller 30p and the center hc of the film unit 30h is defined. The center 41c of the x direction of the substrate 41 is arranged in the + x direction compared to the straight line CL. Thereby, the substrate 41 extends in the + x direction of the nip portion N, and thus the sheet S having passed through the nip portion N is easily peeled from the film unit 30 h.

The center 45c of the heating element group 45 in the x direction is arranged on the straight line CL. The entire heat generating element group 45 is included in the region of the nip portion N and is disposed at the center of the nip portion N. Thereby, the heat distribution of the nip portion N becomes uniform, and the sheet S passing through the nip portion N is uniformly heated.

As shown in fig. 4, the heating element group 45 and the wiring group 55 are formed on the surface of the insulating layer 43 in the + z direction. The protective layer 46 is formed of a glass material or the like so as to cover the heating element group 45 and the wiring group 55. The protective layer 46 improves the slidability of the heater unit 40 and the fixing film 35.

As shown in fig. 3, the heater unit 40 is disposed inside the fixing film 35. The inner peripheral surface of the fixing film 35 is coated with a lubricant (not shown). The heater unit 40 is in contact with the inner peripheral surface of the fixing film 35 via a lubricant. When the heater unit 40 generates heat, the viscosity of the lubricant decreases. Thereby, the slidability of the heater unit 40 and the fixing film 35 is ensured. Thus, the fixing film 35 is a belt-like film having one face in contact with the heater unit 40 while sliding on the surface of the heater unit 40.

The heat-conducting member 49 is formed of a metal material having high thermal conductivity such as copper. The heat-conducting member 49 has the same outer shape as the substrate 41 of the heater unit 40. The heat conduction member 49 is disposed in contact with the surface of the heater unit 40 in the-z direction.

The support member 36 is formed of a resin material such as a liquid crystal polymer. The support member 36 is disposed to cover both sides of the heater unit 40 in the-z direction and the x direction. The support member 36 supports the heater unit 40 via the heat conductive member 49. Rounded chamfers are formed at both ends of the support member 36 in the x direction. The supporting members 36 support the inner peripheral surface of the fixing film 35 at both ends in the x direction of the heater unit 40.

When the sheet S passing through the fixing device 30 is heated, a temperature distribution is generated in the heater unit 40 according to the size of the sheet S. If the heater unit 40 locally becomes high temperature, the temperature may exceed the heat-resistant temperature of the support member 36 formed of the resin material. The heat conduction member 49 uniformizes the temperature distribution of the heater unit 40. This ensures heat resistance of the support member 36.

Fig. 6 is a front sectional view of the heat conductive member, the heater unit, and the cylindrical belt. The heat conduction member 49 is disposed on a surface of the heater unit 40 that is not in contact with the fixing film 35. The heat-conducting member 49 is configured not to contact the heater unit 40 at a position where the heat generation distribution in the heater unit 40 is a peak. Specifically, as shown in fig. 6, the heater unit 40 and the heat conduction member 49 are in contact in the regions a1 and a 2. Further, the non-contact portion forms a groove portion of the heat conductive member 49. The width of the groove portion is set to be wider than the width of the heat generating element group 45 of the heater unit 40 by a length d1 and a length d2, respectively. For example, the width of the heating element group 45 of the heater unit 40 is 4.5[ mm ] to 4.9[ mm ], and the width of the groove portion is about 5[ mm ].

The bracket 38 shown in fig. 3 is formed of a steel plate material or the like. The cross section of the bracket 38 perpendicular to the y direction is formed in a U shape. The holder 38 is mounted in the-z direction of the support member 36 so as to close the U-shaped opening portion by the support member 36. The support 38 extends in the y-direction. Both ends of the holder 38 in the y direction are fixed to a housing of the image forming apparatus 100. Thereby, the film unit 30h is supported by the image forming apparatus 100. The support 38 improves the bending rigidity of the membrane unit 30 h. Flanges 31 for restricting the movement of the fixing film 35 in the y direction are attached to the holders 38 near both ends in the y direction.

The heater thermometer 62 is disposed in the-z direction of the heater unit 40 via the heat conductive member 49. For example, the heater thermometer 62 is a thermistor. The heater thermometer 62 is mounted and supported on the-z surface of the support member 36. The temperature sensing element of the heater thermometer 62 passes through a hole penetrating the support member 36 in the z direction, and is in contact with the heat conductive member 49. The heater thermometer 62 measures the temperature of the heater unit 40 via the heat conductive member 49.

The thermostat 68 is configured in the same manner as the heater thermometer 62. The thermostat 68 is installed in a circuit described later. When the temperature of the heater unit 40 detected via the heat conductive member 49 exceeds a predetermined temperature, the thermostat 68 cuts off the energization to the heat generating element group 45.

Fig. 7 is a plan view (view viewed from the-z direction) of the heater thermometer and the thermostat. In fig. 7, the description of the support member 36 is omitted. The following description of the arrangement of the heater thermometer 62, the thermostat 68, and the film thermometer 64 is a description of the arrangement of the respective temperature sensing elements.

The plurality of heater thermometers 62 (the center heater thermometer 62a and the end heater thermometer 62b) are arranged in parallel in the y direction. The plurality of heater thermometers 62 are disposed within the y-direction range of the heat generating element group 45. The plurality of heater thermometers 62 are disposed at the center of the heating element group 45 in the x direction. That is, the plurality of heater thermometers 62 and the heat generating body group 45 at least partially overlap when viewed from the z direction. The plurality of thermostats 68 (center portion thermostat 68a, end portion thermostat 68b) are also arranged in the same manner as the plurality of heater thermometers 62 described above.

The plurality of heater thermometers 62 includes a center heater thermometer 62a and an end heater thermometer 62 b. The center heater thermometer 62a measures the temperature of the center heating element 45 a. The center heater thermometer 62a is disposed within the range of the center heating element 45 a. That is, the central portion heater thermometer 62a and the central portion heating element 45a overlap when viewed from the z direction.

The end portion heater thermometer 62b measures the temperature of the second end heat-generating body 45b 2. As described above, the first end heating element 45b1 and the second end heating element 45b2 are controlled to generate heat in the same manner. Therefore, the temperature of the first end heating element 45b1 is the same as the temperature of the second end heating element 45b 2. The end heater thermometer 62b is disposed within the range of the second end heating element 45b 2. That is, the end heater thermometer 62b and the second end heat-generating body 45b2 overlap when viewed from the z direction.

The plurality of thermostats 68 includes a center thermostat 68a and an end thermostat 68 b. When the temperature of the center portion heating element 45a exceeds a predetermined temperature, the center portion thermostat 68a cuts off the energization to the heating element group 45. The center thermostat 68a is disposed within the range of the center heating element 45 a. That is, the center thermostat 68a and the center heat-generating element 45a overlap each other when viewed from the z direction.

When the temperature of the first end heating element 45b1 exceeds a predetermined temperature, the end thermostat 68b cuts off the current to the heating element group 45. As described above, the first end heating element 45b1 and the second end heating element 45b2 are controlled to generate heat in the same manner. Therefore, the temperature of the first end heating element 45b1 is the same as the temperature of the second end heating element 45b 2. The end thermostat 68b is disposed within the range of the first end heating element 45b 1. That is, the end thermostat 68b and the first end heat-generating body 45b1 overlap when viewed from the z direction.

As described above, the center heater thermometer 62a and the center thermostat 68a are disposed within the range of the center heat-generating body 45 a. Thereby, the temperature of the central portion heating element 45a is measured. When the temperature of the central heating element 45a exceeds a predetermined temperature, the current supply to the heating element group 45 is cut off. On the other hand, the end heater thermometer 62b and the end thermostat 68b are disposed within the range of the first end heating element 45b1 and the second end heating element 45b 2. Thus, the temperatures of the first end heat-generating body 45b1 and the second end heat-generating body 45b2 were measured. When the temperatures of the first end heating element 45b1 and the second end heating element 45b2 exceed the predetermined temperature, the current supply to the heating element group 45 is cut off.

The plurality of heater thermometers 62 and the plurality of thermostats 68 are alternately arranged in parallel along the y direction. As described above, the first end heating element 45b1 is disposed in the + y direction of the center heating element 45 a. An end thermostat 68b is disposed within the first end heating element 45b 1. The center heater thermometer 62a is disposed in the + y direction with respect to the center of the center heating element 45a in the y direction. The center thermostat 68a is disposed at a position closer to the y direction than the center of the center heating element 45a in the y direction. As described above, the second end heating element 45b2 is disposed in the-y direction of the center heating element 45 a. An end heater thermometer 62b is disposed within the second end heating element 45b 2. Thus, the end thermostat 68b, the center heater thermometer 62a, the center thermostat 68a, and the end heater thermometer 62b are arranged in parallel in this order from the + y direction to the-y direction.

Generally, the thermostat 68 connects and disconnects the circuit by utilizing the bending deformation of the bimetal plate accompanying the temperature change. The thermostat is formed to be elongated according to the shape of the bimetal plate. The terminals extend outward from both ends of the thermostat 68 in the longitudinal direction. The connector of the external wiring is connected to the terminal by crimping. Therefore, a space needs to be secured on the outer side in the longitudinal direction of the thermostat 68. Since the fixing device 30 has no extra space in the x direction, the long side direction of the thermostat 68 is arranged along the y direction. At this time, if a plurality of thermostats 68 are disposed adjacently in the y direction, it is difficult to secure a connection space for external wiring.

As described above, the plurality of heater thermometers 62 and the plurality of thermostats 68 are alternately arranged in parallel along the y direction. Thus, the heater thermometer 62 is disposed in the vicinity of the thermostat 68 in the y direction. Therefore, a connection space for external wiring of the thermostat 68 can be secured. In addition, the degree of freedom in layout of the thermostat 68 and the heater thermometer 62 in the y direction is improved. This enables the thermostat 68 and the heater thermometer 62 to be arranged at the optimum positions, and the temperature of the fixing device 30 to be controlled. Further, it is easy to separate the ac wiring connected to the plurality of thermostats 68 and the dc wiring connected to the plurality of heater thermometers 62. This suppresses the generation of noise in the circuit.

As shown in fig. 3, the film thermometer 64 is disposed inside the fixing film 35 and in the + x direction of the heater unit 40. The film thermometer 64 is in contact with the inner peripheral surface of the fixing film 35 to measure the temperature of the fixing film 35. Hereinafter, the temperature detected by the film thermometer 64 is referred to as "first detection temperature".

Fig. 8 is a circuit diagram of the heating device of the first embodiment. In fig. 8, the bottom view of fig. 5 is arranged above the paper surface, and the top view of fig. 7 is arranged below the paper surface. In fig. 8, a cross section of the fixing film 35 and a plurality of film thermometers 64 are shown above a lower plan view. The plurality of film thermometers 64 includes a central film thermometer 64a and an end film thermometer 64 b.

The center film thermometer 64a is in contact with the y-direction center portion of the fixing film 35. The center film thermometer 64a is in contact with the fixing film 35 in the y-direction range of the center heat-generating element 45 a. The center film thermometer 64a measures the temperature of the center portion of the fixing film 35 in the y direction.

The end portion film thermometer 64b is in contact with the end portion of the fixing film 35 in the-y direction. The end film thermometer 64b is in contact with the fixing film 35 in the range of the y direction of the second end heat-generating body 45b 2. The end portion film thermometer 64b measures the temperature of the end portion of the fixing film 35 in the-y direction. As described above, the first end heating element 45b1 and the second end heating element 45b2 are controlled to generate heat in the same manner. Therefore, the temperature of the end of the fixing film 35 in the-y direction is the same as the temperature of the end of the fixing film 35 in the + y direction.

The power source 95 is connected to the center portion contact 52a via a center portion TRIAC (TRIAC)96 a. The power source 95 is connected to the end contact 52b via an end triac 96 b. The controller 6 controls on/off of the center triac 96a and the end triac 96b independently of each other.

When the control unit 6 turns on the center triac 96a, the power source 95 supplies power to the center heating element 45 a. Thereby, the central heating element 45a generates heat. When the controller 6 turns on the end triac 96b, the first end heating element 45b1 and the second end heating element 45b2 are energized by the power source 95. Thereby, the first end heating element 45b1 and the second end heating element 45b2 generate heat. As described above, the center heating element 45a, the first end heating element 45b1, and the second end heating element 45b2 are controlled to generate heat independently of each other. The center heating element 45a, the first end heating element 45b1, and the second end heating element 45b2 are connected in parallel to the power supply 95.

The power source 95 is connected to the common junction 58 via the center thermostat 68a and the end thermostat 68 b. The center thermostat 68a and the end thermostat 68b are connected in series. If the temperature of the center portion heating element 45a abnormally rises, the detected temperature of the center portion thermostat 68a exceeds a predetermined temperature. At this time, the central thermostat 68a cuts off the power supply from the power source 95 to the entire heating element group 45.

If the temperature of the first end heating element 45b1 abnormally rises, the detected temperature of the end thermostat 68b exceeds the prescribed temperature. At this time, the end thermostat 68b cuts off the current from the power source 95 to the entire heating element group 45. As described above, the first end heating element 45b1 and the second end heating element 45b2 are controlled to generate heat in the same manner. Therefore, when the temperature of the second end heat-generating element 45b2 abnormally increases, the temperature of the first end heat-generating element 45b1 also increases similarly. Therefore, when the temperature of the second end heating element 45b2 abnormally increases, the end thermostat 68b similarly cuts off the current from the power supply 95 to the entire heating element group 45.

The control unit 6 measures the temperature of the center heating element 45a by the center heater thermometer 62 a. The control section 6 measures the temperature of the second end heating element 45b2 using the end heater thermometer 62 b. The temperature of the second end heating element 45b2 is the same as the temperature of the first end heating element 45b 1. The control section 6 measures the temperature of the heat generating element group 45 by the heater thermometer 62 at the time of startup (warm-up) of the fixing device 30 and at the time of recovery from the temporary stop state (sleep state).

When the fixing apparatus 30 is started up and when it is resumed from the temporary stop state, the control unit 6 causes the heat generating element group 45 to generate heat in a short time when the temperature of at least one of the center heat generating element 45a and the second end heat generating element 45b2 is lower than a predetermined temperature. After that, the control section 6 starts the rotation of the pressure roller 30 p. Due to the heat generation of the heat generation element group 45, the viscosity of the lubricant applied on the inner peripheral surface of the fixing film 35 decreases. Thereby, the slidability of the heater unit 40 and the fixing film 35 at the start of rotation of the pressure roller 30p is ensured.

The control section 6 measures the temperature of the center portion of the fixing film 35 in the y direction by the center portion film thermometer 64 a. The control section 6 measures the temperature of the end portion of the fixing film 35 in the-y direction using the end portion film thermometer 64 b. The temperature of the end of the fixing film 35 in the-y direction is the same as the temperature of the end of the fixing film 35 in the + y direction. The control unit 6 measures the temperature of the center portion and the end portion of the fixing film 35 in the y direction when the fixing device 30 is in operation.

The control unit 6 performs phase control or frequency control of the power supplied to the heating element group 45 by the center triac 96a and the end triac 96 b. The control section 6 controls the energization of the center portion heating element 45a based on the temperature measurement result of the center portion of the fixing film 35 in the y direction. The control section 6 controls the energization to the first end heat-generating body 45b1 and the second end heat-generating body 45b2 based on the temperature measurement result of the end portion of the fixing film 35 in the y direction.

Next, the structure of the fixing film 35 is described in detail. As described above, the fixing film 35 includes the base layer, the elastic layer, and the releasing layer in this order from the inner peripheral side. For example, the base layer is formed of polyimide. The surface resistivity measured from the inside of the fixing film 35 is, for example, a value in the range of 7[ LOG/sq. ]to12 [ LOG/sq. ]. The conductivity, represented by the range of surface resistivities, is referred to herein as "micro-conductivity". The temperature of the measuring environment is 23 +/-3 ℃ and the humidity is 50 +/-10%. The probe used was UR type. As for the surface resistivity, the resistivity of the surface of the base layer on the upper side was measured with the base layer of the fixing film 35 facing the upper side and the release layer facing the lower side (base side of the measuring device). Here, as the measurement result of the surface resistivity, the average value of the measurement values of five positions in the longitudinal direction was used. The probe was fixed to UR, and the applied voltage was fixed to 500V. The reason why the probe is fixed and the voltage is applied is that the resistance value of the micro conductive region varies greatly depending on the measuring instrument, the probe, and the voltage applied.

In addition, when any of the following cases is not satisfied, the heater unit 40, the fixing film 35, and the secondary member close to the fixing film 35 are required to have a certain degree of dielectric breakdown voltage.

In the case where the surface of the protective layer 46 covering the heat-generating body group 45 and the inner surface of the fixing film 35 directly slide (for example, in the case of fig. 4), the thickness of the insulating layer 43 or the protective layer 46 is 0.4mm or more, or

The insulating layer 43 may slide on the surface opposite to the side on which the heating element group 45 is printed and the inside of the fixing film 35 (not shown), or

In the case where an insulator of 0.4mm or more is present between the protective layer 46 and the fixing film 35.

The insulation withstand voltage of the fixing film 35 and the secondary member needs to be about 1 minute at about 3 kV. In the case where this condition is not satisfied, it is necessary to keep a distance of at least about 2.4mm between the fixing film 35 and the secondary member. In particular, as the temperature sensor, a contact thermistor that is in contact with the inside of the fixing film 35 is often used. Therefore, the temperature sensor is desired to have a withstand voltage of 1 minute at 3 kV. On the other hand, a method of measuring the temperature of the fixing film 35 by a noncontact thermopile disposed outside the fixing film 35 instead of the contact thermistor described above is also conceivable. However, this method does not need to satisfy the condition of dielectric strength, but needs to be at the cost and space price.

Fig. 9 is a graph showing the results of measuring the dielectric breakdown voltage for fixing films having different conductivities. This measurement was performed by applying a high voltage between both end portions of a test piece 15mm long cut out from the fixing film. The column "determination result" in the figure indicates the determination result of whether or not each fixing film has a desired dielectric breakdown voltage. From the measurement results shown in fig. 9, it is understood that the insulating withstand voltage of the fixing film having a surface resistivity of 7.05[ LOG Ω/sq ] or less is as low as 3.8[ kV ] or less. The fixing film having a surface resistivity of 8.37[ LOG Ω/sq ] or more has an insulation withstand voltage of 9[ kV ] or more. From the measurement results, it is understood that the fixing film 35 may have a surface resistivity of at least 7.05[ LOG Ω/sq ] in order to satisfy a required dielectric breakdown voltage (about 3 kV).

Fig. 10 is a graph showing the results of measuring the amount of static electricity on the film surface for fixing films having different conductivities. This measurement is performed by averaging the surface static electricity amounts measured at five positions in the longitudinal direction for each fixing film in a state in which the charge amount is saturated. Here, a fixing device using a fixing film to be measured was mounted on an MFP (multifunction device), and was heated and driven for 10 minutes in a state where an ADU (automatic double-sided unit) was turned on, thereby saturating the surface static electricity amount of the fixing film. The electrostatic charge was measured in a state where the tip of the probe of the measuring device was brought close to a position of about 5cm from the surface of the fixing belt saturated with the charge amount. The measured value of the static electricity amount at each position was the maximum value of the static electricity amount measured in 10 seconds.

In addition, the measurement is preferably performed in a low humidity environment where static electricity is easily generated. Therefore, the measurement is performed here in an environment where the temperature is about 10 ℃ and the humidity is about 20%. The column "determination result" in the figure indicates the determination result of whether or not each fixing film has the desired non-charging property. From the measurement results shown in fig. 10, it is understood that if the surface resistivity is 9.87[ LOG Ω/sq ] or less, the surface static electricity amount is almost 0[ kV ].

On the other hand, with respect to the fixing film having a surface resistivity of 12.51[ LOG Ω/sq ], the surface electrification amount was 1.18[ kV ], which was at a low level, and the fixing condition of the image was also good. However, in this case, when the fixing film rotates, electrostatic noise is generated from the vicinity of the nip portion. In this case, static electricity generated on the fixing film leaks to the substrate 41, and there is a possibility that the substrate 41 is damaged. Therefore, the fixing film in this case may not necessarily have sufficient non-charging property.

In addition, with respect to the fixing film having a surface resistivity of 15[ LOG Ω/sq ] or more, electrostatic noise is large, and it is confirmed that the fixed image is also disturbed by static electricity (generally referred to as "electrostatic offset"). From the results, it is understood that the surface resistivity of the fixing film may be about 10[ LOG Ω/sq ] or less from the viewpoint of non-charging property. Note that the description of (OK) in the determination result indicates that it may be determined as OK from the viewpoint of convenience of adjustment, or may be determined as NG from the viewpoint of safety.

For this reason, the fixing device 30 in the first embodiment is configured using the fixing film 35 having a surface resistivity of 7[ LOG Ω/sq ] to 10[ LOG Ω/sq ] measured from the base layer side. According to the fixing film 35 thus configured, it is possible to simultaneously achieve suppression of electrification of the fixing film 35 and securing of the insulation withstand voltage of the secondary member of the fixing film 35 and the heater unit 40.

(second embodiment)

In the first embodiment, the case where the base layer of the fixing film 35 is made slightly conductive is described. In contrast, in the second embodiment, a case where a so-called pure polyimide material (hereinafter, referred to as "pure PI material") is used for the base layer of the fixing film 35 will be described. A pure PI material is a material that is electrically non-conductive. Here, as described above, the fixing film 35 is configured by laminating the base layer, the elastic layer (elastic rubber), and the release layer (PFA tube) in this order from the inside of the cylindrical shape. More specifically, a primer layer for improving the adhesion between the elastic rubber and the PFA tube is provided between the elastic rubber and the PFA tube. In the second embodiment, by using a non-conductive pure PI material with respect to the base layer, it is possible to simultaneously achieve suppression of electrification and securing of insulation withstand voltage by adjusting the conductivity of the elastic rubber, PFA tube or primer.

The adjustment of the conductivity is achieved by adjusting the amount of the conductive material added to the elastic rubber, the PFA tube, or the primer. Here, first, a case where only the conductivity of the elastic rubber is adjusted is studied. For example, an elastic rubber of a fixing film is obtained by adding a carbon-based conductive material to Si rubber and adjusting the surface resistivity to about 10[ LOG Ω/sq ]. The volume resistivity in this case is about 14[ LOG Ω · cm ] or more, and is substantially the same as the volume resistivity measured from the inner side (base layer side) of the fixing film using the ordinary PI in the base layer. Similarly, when the conductive material is added only to the primer, or when the conductive material is added only to the PFA tube, the volume resistivity of the fixing film is also about 14[ LOG Ω · cm ] or more. Fig. 11 is a diagram showing the results of such conductivity adjustment performed in a plurality of modes.

In the first embodiment, in order to suppress electrification of the fixing film by micro-conduction of the base layer, the surface resistivity of the fixing film needs to be about 10[ LOG Ω/sq ] or less. On the other hand, as shown in fig. 11, it is understood that the same effect can be obtained by adjusting the conductivity of the elastic rubber, the PFA tube or the primer. Specifically, the amount of static electricity on the surface of the fixing film can be suppressed as in the first embodiment.

Here, the layer thickness of the primer is as thin as several micrometers, and the contribution rate to the above effect is considered to be lower than those of the elastic rubber and the PFA tube. On the other hand, since the layer thickness of the Si rubber is about 200um, the contribution rate to the above effect is considered to be higher than the contribution rate of the PFA tube and the primer. Therefore, in view of cost and yield, it is desirable to configure to add the conductive material only to the Si rubber without adding the conductive material to the primer and the PFA tube. Specifically, in the measurement test of the electrical conductivity to obtain the measurement result shown in fig. 11, it was found that the surface resistivity of the Si rubber is preferably smaller than that of the PFA tube. In addition, as for the dielectric withstand voltage, the surface resistivity measured from the inside of the fixing film may be set within an allowable range of about 12[ LOG Ω/sq. ]to15 [ LOG Ω/sq. ]. This means that there is no problem even if a high voltage is applied to the fixing film 35. Note that the description of (OK) in the determination result indicates that it may be judged as OK from the viewpoint of convenience of adjustment, or may be judged as NG from the viewpoint of safety.

In this way, when the conductivity of the elastic layer, the primer layer, or the release layer is adjusted, a sufficient margin is obtained for the dielectric breakdown voltage. For this reason, the fixing film 35 of the second embodiment is made slightly conductive so that at least one of the elastic layer, the primer layer, and the releasing layer satisfies the following conditions. The condition is that the surface resistivity measured from the base layer side of the fixing film 35 is 12[ LOG Ω/sq ].

In general, PI is often provided as a pure material, and thus adjustment of its resistance value is expensive. However, in the fixing film 35 of the second embodiment, the resistance value of the layer other than the base layer can be adjusted, and the insulation withstand voltage also has a sufficient margin. Therefore, according to the fixing film 35 of the second embodiment, although the pure PI material is used in the base layer, it is possible to more easily and inexpensively achieve suppression of electrification of the fixing belt and securing of the withstand voltage of the secondary member of the fixing belt and the heater.

(modification example)

In the first and second embodiments, the structure of the fixing film of the so-called on-demand fixing device 30 is described as an example of the fixing device. The on-demand type fixing device refers to a fixing device in which a heater unit is provided in a nip portion formed by a fixing belt and a pressure roller. In the above-described embodiment, the fixing film 35 is shown as an example of the fixing belt of such an on-demand type fixing device. However, the fixing belt of the present embodiment is not limited to that of the on-demand type fixing device.

For example, the fixing belt of the present embodiment may be applied to a fixing device of a type in which the fixing belt is directly heated by a heater. Generally, a fixing device of this type includes a fixing belt, a pressure roller, a heating section, and a reflection section. In this case, the fixing belt follows the pressure roller, and a heat generating body such as a halogen lamp is disposed inside the fixing belt as a heating section. The reflecting portion is arranged inside the fixing belt in the same manner as the heating portion, and reflects heat generated by the heating portion toward the fixing belt. The fixing belt is heated by the heat condensed by the reflection portion (see, for example, japanese patent application laid-open No. 2019-124714). That is, in the fixing device of this aspect, the fixing belt and the heating section are arranged in non-contact.

For example, the fixing belt of the present embodiment may be applied to a roller fixing type fixing device. Generally, a roller fixing type fixing device includes a fixing belt, an elastic fixing roller, and a heating roller. In this case, the fixing belt is bridged by the elastic fixing roller and the heating roller, and is rotated by the driving of the elastic fixing roller or the heating roller. The heating roller is provided with a heat-generating body such as a halogen lamp therein, and heats the fixing belt by the heat thereof (see, for example, japanese patent application laid-open No. 2018-146895). Further, the roller fixing type fixing device may also include a fixing pressure pad that presses the fixing belt to the heating roller from an inner side thereof. The fixing pressure pad may be formed by disposing fluorine grease or the like as a sliding aid on a glass cloth containing a fluorine resin.

According to at least one embodiment described above, suppressing the electrification of the fixing belt and securing the insulation withstand voltage of the secondary member of the fixing belt and the heater can be simultaneously achieved by having the fixing belt: a fixing belt is a cylindrical endless belt formed by laminating a base layer, an elastic layer, and a releasing layer in this order from an inner peripheral side, and a surface resistivity measured from the base layer side is adjusted to be 7[ LOG Ω/sq ] or more and 10[ LOG Ω/sq ] or less; or a fixing belt which is a cylindrical endless belt formed by laminating a base layer, an elastic layer, a primer layer and a releasing layer in this order from the inner peripheral side, and whose volume resistivity measured from the base layer side is adjusted to 14[ LOG Ω · cm ] or more.

While several embodiments of the present invention have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. These embodiments can be implemented in other various manners, and various omissions, substitutions, and changes can be made without departing from the spirit of the present invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalent scope thereof.