Fixing equipment and image forming apparatus equipped with heaters

Abstract

A fixing apparatus and an image forming apparatus equipped with a heater are disclosed. The fixing apparatus includes a substrate, a first heat generator, a second heat generator with a length equal to the length of the first heat generator in the longitudinal direction of the substrate, a third heat generator with a length shorter than the lengths of the first and second heat generators, and a heat-spreading member having a positioning portion in the longitudinal direction. In the short-side direction of the substrate, the first heat generator is arranged at one end, the second heat generator at the other end, and the third heat generator is arranged between the first and second heat generators. The heat-spreading member is arranged between the heater and a holder in the thickness direction. When viewed in the short-side direction, the positioning portion is positioned outside the region corresponding to the third heat generator and inside the region corresponding to the first heat generator.

Description

Technical Field

[0001] The present invention relates to a fixing device and an image forming apparatus provided with a fixing device. Background Technology

[0002] Conventionally, image forming apparatuses include fixing devices that fix toner images transferred onto recording materials by heating and pressurizing them. Furthermore, some fixing devices include multiple heating members of different lengths to heat the recording material according to its width. For example, Japanese Patent Application Publication (JP-A) 2020-115189 discloses a fixing device with multiple heating members of different lengths in the longitudinal direction, configured as follows: In the fixing device disclosed in JP-A 2020-115189, to suppress thermal deformation of the heater plate, long heating members in the longitudinal direction are arranged symmetrically with respect to the center in the transverse direction near the two ends of the heater plate, while short heating members in the longitudinal direction are arranged between the long heating members. Additionally, for example, Japanese Patent 6242181 proposes a configuration that reduces temperature non-uniformity of the heater plate by arranging a heat-soaking member with high thermal conductivity on the back surface of the heater plate.

[0003] In configurations where a heat-spreading member, such as an aluminum plate, is arranged to contact a heater plate to reduce temperature non-uniformity of the heater, which serves as a heating element, a positioning portion can be provided on the heat-spreading member to secure it to a heater holder that holds the heater. For example, the positioning portion is formed by a process such as bending a portion of the aluminum plate used as the heat-spreading member, and the position of the heat-spreading member is secured by embedding the bent portion into a recess formed in the heater holder.

[0004] In this situation, because the volume of the heat spreader increases, the heat capacity of the bent portion, which serves as the positioning part, is greater than that of the portion where bending is not performed. As a result, since the area of ​​the heater plate opposite the positioning part of the heat spreader is less likely to experience a temperature rise compared to other areas excluding the positioning part, regions with different temperatures are generated in the heater plate, and localized temperature gradients appear, which may then cause the heater plate to deform. Summary of the Invention

[0005] According to an aspect of the present invention, a fixing apparatus is provided for fixing an unfixed toner image on a recording material onto the recording material, the fixing apparatus comprising: a heater having an elongated substrate, a first heat-generating member, a second heat-generating member having a length in the longitudinal direction of the substrate substantially equal to the length of the first heat-generating member; and a third heat-generating member having a length in the longitudinal direction shorter than the lengths of the first and second heat-generating members; a heat-monopolating member configured to homogenize the temperature of the substrate; and a holder configured to hold the heater and the heat-monopolating member, wherein the first heat-generating member, the second heat-generating member, and the third heat-generating member... Components are arranged on a substrate, wherein, relative to the short side direction of the substrate perpendicular to the longitudinal direction and the thickness direction of the substrate, a first heat-generating component is arranged on one end side, a second heat-generating component is arranged on the other end side, and a third heat-generating component is arranged between the first heat-generating component and the second heat-generating component, wherein a heat-spreading component is arranged between a heater and a holder relative to the thickness direction of the substrate, wherein the heat-spreading component includes a positioning portion of the holder positioned relative to the longitudinal direction of the heat-spreading component, wherein, when viewed in the short side direction, the positioning portion is positioned outside the region corresponding to the third heat-generating component, and at least a portion of the positioning portion is positioned inside the region corresponding to the first heat-generating component.

[0006] Other features of the invention will become clear from the following description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0007] Figure 1 This is a cross-sectional view showing the configuration of an image forming apparatus according to the first embodiment, the second embodiment, and the third embodiment.

[0008] Figure 2 This is a block diagram showing the configuration of the control section of the image forming apparatus according to the first embodiment, the second embodiment, and the third embodiment.

[0009] Figure 3 This is a cross-sectional schematic diagram illustrating the configuration of a fixing device according to the first embodiment and the second embodiment.

[0010] Figure 4 Parts (a) and (b) are schematic diagrams illustrating the configuration of the heater according to the first embodiment and the second embodiment.

[0011] Figure 5 This is a circuit diagram of the power control circuit according to the first embodiment.

[0012] Figure 6Parts (a), (b), and (c) are schematic diagrams illustrating the current path to the heating member according to the first embodiment.

[0013] Figure 7 Parts (a) and (b) are schematic diagrams illustrating the configuration of the heat-spreading member according to the first embodiment.

[0014] Figure 8 This is a view illustrating the positional relationship between the positioning portions of the heating member and the heat spreader according to the first embodiment.

[0015] Figure 9 This is a circuit diagram of the power control circuit according to the second embodiment.

[0016] Figure 10 Parts (a), (b), (c), and (d) are diagrams illustrating the configuration of the heating member according to the second embodiment.

[0017] Figure 11 This is a schematic diagram showing the configuration of the heat-spreading member according to the second embodiment.

[0018] Figure 12 This is a view illustrating the positional relationship between the positioning portions of the heating member and the heat spreader according to the second embodiment.

[0019] Figure 13 This is a circuit diagram of the power control circuit according to the third embodiment. Detailed Implementation

[0020] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following embodiments, the recording material passing through the fixing clamp portion of the fixing device is referred to as passing through the sheet.

[0021] <First Embodiment>

[0022] [Overall Structure of the Image Forming Apparatus]

[0023] Figure 1 This is a cross-sectional view showing the configuration of a serial system color image forming apparatus, which is an image forming apparatus equipped with the fixing device of the first embodiment. (The last sentence appears to be incomplete and possibly refers to a technical description of the apparatus.) Figure 1 This describes the configuration of an electrophotographic color image forming apparatus. Incidentally, the first station is for forming a yellow (Y) toner image, and the second station is for forming a magenta (M) toner image. Furthermore, the third station is for forming a cyan (C) toner image, and the fourth station is for forming a black (K) toner image.

[0024] In the first station, the photosensitive drum 1a, serving as the image-carrying component, is an OPC photosensitive drum. The photosensitive drum 1a is composed of multiple layers of functional organic materials, including a charge-generating layer that generates charge through exposure on a metal cylinder and a charge-transfer layer that transports the generated charge. The outermost layer of the photosensitive drum 1a has low conductivity and is essentially insulating. A charging roller 2a, serving as a charging unit, abuts against the photosensitive drum 1a and, as the photosensitive drum 1a rotates, is driven rotatably to uniformly charge the surface of the photosensitive drum 1a. A voltage consisting of a DC voltage or an AC voltage superimposed is applied to the charging roller 2a, and discharge is generated from the clamping portion between the charging roller 2a and the surface of the photosensitive drum 1a in tiny air gaps upstream and downstream of the photosensitive drum 1a relative to the direction of rotation. In this way, the photosensitive drum 1a is charged. A cleaning unit 3a cleans any remaining toner on the photosensitive drum 1a after one transfer, as will be described below. The developing unit 8a, which is a developing unit, contains a non-magnetic single-component toner 5a and includes a developing roller 4a and a developer coating blade 7a. The photosensitive drum 1a, charging roller 2a, cleaning unit 3a, and developing unit 8a are housed in an integrated processing cartridge 9a (image forming section) that can be detached from the image forming apparatus.

[0025] The exposure device 11a, serving as an exposure unit, comprises a scanner unit or an LED (light-emitting diode) array that reflects a laser beam through a rotatable multifaceted mirror and scans the surface of the photosensitive drum 1a, and emits a scanning beam 12a modulated according to an image signal onto the photosensitive drum 1a. Additionally, the charging roller 2a is connected to a high-voltage charging power supply 20a, which serves as the voltage supply unit for the charging roller 2a. The developing roller 4a is connected to a high-voltage developing power supply 21a, which serves as the voltage supply unit for the developing roller 4a. The primary transfer roller 10a is connected to a high-voltage primary transfer power supply 22a, which serves as the voltage supply unit for the primary transfer roller 10a. The configuration of the first station has been described above, and the second, third, and fourth stations include the same configuration. For the second, third, and fourth stations, the parts having the same function as those in the first station are given the same reference numerals, and for each station, the reference numerals are prefixed with b, c, and d. Incidentally, in the following description, the subscripts a, b, c, and d are omitted except when describing a specific station.

[0026] The intermediate transfer belt 13 is supported by three rollers: a secondary transfer opposing roller 15, a tension roller 14, and an auxiliary roller 19, which serve as the tensioning member of the intermediate transfer belt 13. The force in the direction of tension of the intermediate transfer belt 13 by a spring (not shown) is applied only to the tension roller 14, and appropriate tension on the intermediate transfer belt 13 is maintained. The secondary transfer opposing roller 15 receives power from the main motor 99 (see...). Figure 2The intermediate transfer belt 13, driven by the rotation of the photosensitive drums 1a to 1d, rotates and is wound around the outer periphery 13 of the secondary transfer opposing roller 15. The intermediate transfer belt 13 rotates relative to the photosensitive drums 1a to 1d (e.g., in...). Figure 1 In the counter-clockwise direction) in the direction of the arrow (e.g., in Figure 1 The primary transfer roller 10 moves at substantially the same speed (clockwise) across the intermediate transfer belt 13 and opposite the photosensitive drum 1, and is rotated along with the movement of the intermediate transfer belt 13. The position where the photosensitive drum 1 abuts against the primary transfer roller 10 across the intermediate transfer belt 13 is called the primary transfer position. The auxiliary roller 19, tension roller 14, and secondary transfer opposing roller 15 are electrically grounded. Incidentally, the primary transfer rollers 10b to 10d in the second, third, and fourth stations have the same configuration as the primary transfer roller 10a in the first station, and therefore their description is omitted.

[0027] Next, the following will describe Figure 1 The image forming apparatus shown in the figure is in image forming operation. When the image forming apparatus receives a print command during standby mode, the image forming operation begins. The photosensitive drum 1, intermediate transfer belt 13, etc., are connected by the main motor 99 (see [reference]). Figure 2 The system begins rotating at a predetermined processing speed in the direction of the arrow in the diagram. The photosensitive drum 1a is uniformly charged by the charging roller 2a, which receives a charging voltage from the charging high-voltage power supply 20a. Then, an electrostatic latent image is formed based on image information by the scanning beam 12a emitted from the exposure device 11a. The toner 5a in the developing unit 8a is negatively charged by the developing agent coating doctor blade 7a and coated onto the developing roller 4a. A predetermined developing voltage is applied to the developing roller 4a by the developing high-voltage power supply 21a. As the photosensitive drum 1a rotates and the electrostatic latent image formed on it reaches the developing roller 4a, the latent image is visualized by the adhesion of the negative polarity toner, and a toner image of the first color (e.g., Y (yellow)) is formed on the photosensitive drum 1a. Each station for other colors M (magenta), C (cyan), and K (black) operates in the same manner. At a timing corresponding to the distance between the primary transfer positions for each color, while delaying the write signal from the controller (not shown), an electrostatic latent image is formed on each of the photosensitive drums 1a to 1d by scanning beams 12a to 12d from exposure devices 11a to 11d. A high DC voltage opposite to the polarity of the toner is applied to each of the primary transfer rollers 10a to 10d from primary transfer high-voltage power supplies 22a to 22d. As a result, the toner images on the photosensitive drums 1a to 1d are sequentially transferred to the intermediate transfer belt 13 (hereinafter referred to as primary transfer), and multiple toner images are formed on the intermediate transfer belt 13.

[0028] Subsequently, based on the toner image formation, paper P, which is recording material stacked in cartridge 16 (paper feed section), is fed into feed channel Y via feed roller 17, which is rotatably driven by paper feed solenoid (not shown). The fed paper P is fed to alignment roller 18 (hereinafter referred to as alignment roller) via feed roller (not shown). Paper P is synchronized with the toner image on intermediate transfer belt 13 and fed to transfer clamping section where intermediate transfer belt 13 abuts against secondary transfer roller 25 via alignment roller 18. A voltage opposite to the polarity of the toner is applied to secondary transfer roller 25 by secondary transfer high voltage power supply 26, and multiple toner images of four colors carried on intermediate transfer belt 13 are transferred to paper P (recording material) at once (hereinafter referred to as secondary transfer). On the other hand, after secondary transfer is completed, residual toner on intermediate transfer belt 13 is cleaned by cleaning unit 27. After the secondary transfer is completed, the paper P is fed to the fixing device 50, which is the fixing unit, and the paper P with the toner image fixed is discharged into the discharge tray 30 as an image forming item (printing, copying). From the start of the image forming operation until the paper P reaches the fixing clamping part N, which will be described below (see... Figure 3 The time from the start of the image forming operation to the discharge of the paper P is, for example, approximately 9 seconds, and the time from the start of the image forming operation to the discharge of the paper P is, for example, approximately 12 seconds. Incidentally, the fixing film 51, heater holder 52, pressure roller 53, and heater 54 of the fixing device 50 will be described below.

[0029] The printing mode in which images are continuously printed on multiple sheets of paper P is hereinafter referred to as continuous printing or continuous operation. In continuous printing, the interval between the rear end of the previously printed sheet of paper P (hereinafter referred to as the previous sheet) and the front end of the next sheet of paper P printed after the previous sheet (hereinafter referred to as the subsequent sheet) is called the sheet spacing. In this embodiment, in the continuous printing of A4-sized sheets of paper P, the toner image on the intermediate transfer belt 13 and the sheet P are synchronized and fed, such that the sheet spacing is set to, for example, 30 mm, and printing is performed. The image forming apparatus in this embodiment is a center-based image forming apparatus, which performs the printing operation by aligning the center position of each component relative to the direction perpendicular to the feed direction of the sheet P (the longitudinal direction described below). Therefore, the center position of each sheet of paper P is the same, whether the printing operation is for a sheet of paper P with a larger length relative to the direction perpendicular to the feed direction or for a sheet of paper P with a smaller length relative to the direction perpendicular to the feed direction.

[0030] [Control block of the image forming apparatus]

[0031] Figure 2 This is a block diagram showing the configuration of the control section of an image forming apparatus, and will be referenced... Figure 2This describes the printing operation of the image forming apparatus. The PC 110, acting as the host computer, sends print commands, including image data and printing information for the image to be printed, to the video controller 91 inside the image forming apparatus.

[0032] The video controller 91 converts the image data received from the PC 110 into exposure data and transmits it to the exposure control device 93 in the engine controller 92. Simultaneously, the video controller 91 transmits a print command to the CPU 94 in the engine controller 92. The exposure control device 93, controlled by the CPU 94, controls the exposure device 11, which turns the laser beam on and off according to the exposure data. The size of the exposure data is determined by the image size. When the CPU 94, acting as the control unit, receives a print command from the video controller 91, it begins the image forming operation.

[0033] A CPU 94, a memory 95, and other components are mounted on the engine controller 92. The CPU 94 operates according to a program pre-stored in the memory 95. Additionally, the CPU 94 includes a timer for measuring time, and the memory 95 stores various information controlling the fixing device 50, which will be described below. The high-voltage power supply 96 consists of the charging high-voltage power supply 20, the developing high-voltage power supply 21, the primary transfer high-voltage power supply 22, and the secondary transfer high-voltage power supply 26 described above. Furthermore, the power control section 97 includes a bidirectional thyristor 56 (hereinafter referred to as a bidirectional silicon controlled rectifier) ​​as a supply control section. In addition, the power control section 97 also includes a heating element switching device 57, which switches the heating element switching unit by switching the power supply path. The power control section 97 selects the heating element supplied with power in the fixing device 50 and determines the amount of power to be supplied. In this embodiment, the heating element switching device 57 is, for example, an arc contact relay.

[0034] The drive unit 98 consists of a main motor 99, a fixing motor 100, etc. Additionally, the sensor 101 consists of a fixing temperature sensor 59, which is a temperature detection unit for detecting the temperature of the fixing unit 50, and a paper sensor 102, which includes a marker to detect the presence or absence of paper P, etc. The detection result of the sensor 101 is transmitted to the CPU 94. The CPU 94 acquires the detection result of the sensor 101 and controls the exposure unit 11, the high-voltage power supply 96, the power control unit 97, and the drive unit 98 based on the detection result. Therefore, the CPU 94 forms an electrostatic latent image, transfers the developed toner image onto the paper P, fixes the transferred toner image onto the paper P, etc., and controls the image data received from the PC 110 to be printed onto the paper P as an image forming process for the toner image. Incidentally, the image forming apparatus of the present invention is not limited to its configuration. Figure 1The image forming apparatus described herein, however, may be an image forming apparatus capable of printing paper P of different widths and may be equipped with a fixing device 50 including a heater 54, which will be described below.

[0035] [Components of a fixing device]

[0036] Next, we will use Figure 3 This describes the configuration of a fixing device 50 that controls the heating device (heater) used to heat the toner image on paper P by means of a heating element. Here, "longitudinal direction" refers to the direction of rotation of the pressure roller 53, which is substantially perpendicular to the feed direction of paper P, as described below. Furthermore, the length of paper P in the direction substantially perpendicular to the feed direction of paper P (longitudinal direction) is called the paper width.

[0037] Figure 3 This is a schematic cross-sectional view illustrating the configuration of the fixing device 50. In the fixing device 50, a sheet P carrying an unfixed toner image T is fed from the left side toward the fixing clamping portion N in the direction of the arrow in the figure. The fixing clamping portion N is configured to abut against the fixing film 51 (hereinafter referred to as "film 51") using a pressure roller 53. In the fixing clamping portion N, the fixing film 51 is clamped between the pressure roller 53 and the heater 54. Furthermore, when the sheet P is fed from the left to the right side in the fixing clamping portion N, the sheet P is heated and the toner T is fixed onto the sheet P. The fixing device 50 includes a cylindrical film 51, a heater holder 52 that holds the film 51, a pressure roller 53 that forms the fixing clamping portion N together with the film 51, and a heater 54 (heater portion) that serves as a heating device for heating the sheet P. In addition, the fixing device 50 includes an aluminum plate 60, which is a heat equalization component arranged between the heater 54 and the heater holder 52.

[0038] Membrane 51 is a fixing film serving as a rotatable heating element. Membrane 51 is made of, for example, polyimide as a base layer, and an elastic layer made of silicone rubber and a release layer made of PFA are formed on the base layer. The inner diameter of membrane 51 is 18 mm, and the outer circumference of membrane 51 is approximately 58 mm. To reduce the friction between heater holder 52 and membrane 51, and between heater 54 and membrane 51, caused by the rotation of membrane 51, lubricating oil is applied to the inner surface of membrane 51.

[0039] The heater holder 52 guides the film 51 from the inside and simultaneously forms a fixing clamping portion N between the film 51 and the pressure roller 53. The heater holder 52 is a rigid, heat-resistant, and thermally insulating component, formed of a liquid crystal polymer or the like. The film 51 is embedded in the heater holder 52. The pressure roller 53 is a roller that serves as a rotatable pressure component and is composed of a core metal 53a, an elastic layer 53b, and a release layer 53c. The pressure roller 53 is rotatably held at both ends relative to the longitudinal direction and is controlled by the fixing motor 100. Figure 2 The film 51 is rotatably driven, and rotates due to the rotation of the pressure roller 53. Incidentally, the fixing motor 100 is arranged in... Figure 3 The pressure roller 53 is driven from the front side of the pressure roller 53. Hereinafter, the side of the pressure roller 53 on which the fixing motor 100 is arranged is referred to as the driving side, and the opposite side of the pressure roller 53 on which the fixing motor 100 is arranged is referred to as the non-driving side.

[0040] The heater 54, serving as a heating element, is arranged and held within the internal space of the fixing film 51, with one end of the heater 54 abutting against a heater holder 52 relative to the longitudinal direction. A protrusion is formed at the location where the heater holder 52 abuts against the heater 54, thus restricting the longitudinal position of the heater 54. The heater 54, held in the heater holder 52, contacts the inner surface of the film 51. The heater plate 54a, heating elements 54b1 (54b1a, 54b1b), 54b2 and 54b3, protective glass layer 54e, and fixing temperature sensor 59 will be described below. Figure 3 (Not shown in the image).

[0041] [Overview of the heater section]

[0042] Next, the heater 54, which is the heating part, will be described. Figure 4 Part (a) shows when from Figure 3 This is a schematic diagram showing the configuration of the heater 54, with heating elements arranged on one side of the pressure roller 53. Figure 4 In part (a), reference line a is the center line of heating members 54b1a, 54b1b, 54b2, and 54b3 relative to the longitudinal direction, and is also the center line of the paper P fed to the fixing clamping part N of the fixing device 50 relative to the longitudinal direction (paper width direction). Figure 4 As shown in part (a), heater 54 includes heater plate 54a, heating elements 54b1a, 54b1b, 54b2 and 54b3, conductor 54c, contacts 54d1 to 54d4, and protective glass layer 54e. Conductor 54c is the part painted black in the figure. Hereinafter, heating elements 54b1a, 54b1b, 54b2 and 54b3 are collectively referred to as heating element 54b.

[0043] In this embodiment, the heater plate 54a is elongated and is made of alumina (Al2O3), a ceramic material. Alumina (Al2O3), aluminum nitride (AlN), zirconium oxide (ZrO2), and silicon carbide (SiC) are known ceramic plates, and among them, alumina (Al2O3) is inexpensive and readily available. Alternatively, the heater plate 54a can be made of a metal with excellent strength. Stainless steel (SUS) is preferred due to its excellent price and strength when using metal plates. Furthermore, if both the ceramic plate and the metal plate are conductive, an insulating layer can be provided and applied to both. Heating elements 54b1a, 54b1b, 54b2, and 54b3, conductor 54c, and contacts 54d1 to 54d4 are arranged on the heater plate 54a, and a protective glass layer 54e is coated on top of each heating element to ensure insulation between it and the membrane 51.

[0044] The positional relationship of heating element 54b in the longitudinal direction will be described below. The length of each heating element in the longitudinal direction ( Figure 4 The lengths in the transverse direction of part (a) are different, and the lengths L1 of heating elements 54b1a and 54b1b in the longitudinal direction are 222 mm, the length L2 of heating element 54b2 in the longitudinal direction is 188 mm, and the length L3 of heating element 54b3 in the longitudinal direction is 154 mm. The order of lengths L1, L2, and L3 in the longitudinal direction is L1 > L2 > L3. In addition, each heating element in the short side direction (in Figure 4 In part (a), the heating members 54b1a, 54b2, 54b3, and 54b1b are arranged in the vertical direction. The heating members 54b1 (54b1a, 54b1b), 54b2, and 54b3 are arranged such that the centers of the heating members relative to the longitudinal direction are aligned on the heater plate 54a. Furthermore, the maximum paper width (hereinafter referred to as "maximum paper width") of the paper P that can be used in the image forming apparatus of this embodiment is 216 mm, and the minimum paper width (hereinafter referred to as "minimum paper width") is 76 mm. Therefore, the heating member 54b1, with a length of length L1 (222 mm) in the longitudinal direction, is long enough to fix an image size (206 mm) of the maximum paper width (216 mm).

[0045] like Figure 4As shown in part (a), heating elements 54b1a and 54b1b are electrically connected to contact 54d2 (first contact) at one end via conductor 54c and to contact 54d4 (fourth contact) at the other end, respectively. Additionally, heating element 54b2 (third heating element) is electrically connected to contact 54d2 at one end via conductor 54c and to contact 54d3 (third contact) at the other end. Similarly, heating element 54b3 (fourth heating element) is electrically connected to contact 54d1 (second contact) at one end via conductor 54c and to contact 54d3 at the other end. Incidentally, as... Figure 4 As shown in part (a), heating elements 54b1a and 54b1b have the same length as length L1 in the longitudinal direction, and the two heating elements 54b1a and 54b1b are always used simultaneously. Hereinafter, the pair of heating elements 54b1a and 54b1b are collectively referred to as heating element 54b1. Heating element 54b1a (the first heating element) is arranged at one end of the heater plate 54a relative to its short side, and heating element 54b1b (the second heating element) is arranged at the other end of the heater plate 54a in the short side direction. Heating elements 54b2 and 54b3 are arranged symmetrically between heating elements 54b1a and 54b1b in the short side direction of the heater plate 54a relative to its center in the short side direction.

[0046] [Heating Vaporizer]

[0047] In this embodiment, such as Figure 3 As shown, an aluminum plate 60, serving as a heat equalization member for equalizing the temperature of the heater plate 54a, is arranged between the heater holder 52 and the heater 54. The aluminum plate 60 is positioned on the opposite side of the heating member 54b and the protective glass layer 54e via the heater plate 54a.

[0048] The aluminum plate 60 has a thickness of 0.3 mm, a length of 7 mm in the short side direction, and a length of 222 mm in the longitudinal direction, the same as that of the heating element 54b1. At a location on the aluminum plate 60 in the longitudinal direction, a positioning portion 60a (also referred to as the bent portion) is formed that bends toward the heater holder 52 side (see [reference]). Figure 7 The positioning portion 60a restricts the longitudinal position of the aluminum plate 60 by being embedded in a positioning recess formed on the heater holder 52. In this embodiment, the shape of the positioning portion 60a of the aluminum plate 60 is formed by bending the aluminum plate 60; however, this is not a limitation, and it can also be formed by, for example, casting, cutting, or drawing.

[0049] [Fixing Temperature Sensor]

[0050] exist Figure 4In part (a), the area surrounded by the dashed line is the fixing temperature sensor 59. The dashed line indicates that the fixing temperature sensor 59 is arranged on the back side of the heater plate 54a (opposite to the surfaces on which the heating elements 54b1, 54b2, and 54b3 are arranged), and also indicates the position where the fixing temperature sensor 59 abuts against the heater plate 54a. The main thermistor 59a, which detects the temperature of the fixing temperature sensor 59, is arranged on the center line of the heating elements 54b1, 54b2, and 54b3 relative to their short sides and on reference line a, which is the center line of the paper P fed to the fixing device 50.

[0051] Figure 4 Part (b) shows the situation when the heater 54 is in the direction of the paper P being fed to the fixing device 50 relative to the longitudinal direction. Figure 4 A schematic diagram of the cross-section when the center line of reference line a) in part (a) is cut. The fixing temperature sensor 59, which is a temperature detection unit for detecting the temperature of the heater 54, includes the following components: The fixing temperature sensor 59 includes a main thermistor 59a, a holder 59b, a ceramic paper 59c for heat conduction between the holder 59b and the main thermistor 59a, and an insulating resin sheet 59d that physically and electrically protects the main thermistor 59a. The main thermistor 59a is a temperature detection element whose resistance value changes according to the temperature of the heater 54 and whose output voltage changes according to the temperature of the heater 54, and is connected to the CPU 94 via a Dumet wire (not shown) and wiring. The main thermistor 59a detects the temperature of the heater 54 via an aluminum plate 60 and outputs a voltage corresponding to the temperature of the heater 54 to the CPU 94. The CPU 94 controls the temperature of the heater 54 during the fixing process based on the temperature detection result of the fixing temperature sensor 59 (main thermistor 59a).

[0052] like Figure 4 As shown in part (a), the fixing temperature sensor 59 is positioned at a reference line a in the longitudinal direction of the heating element 54b and is in contact with the aluminum plate 60. Furthermore, the fixing temperature sensor 59 is positioned at the center of the heater plate 54a relative to its short side. That is, the fixing temperature sensor 59 is positioned at substantially equal distances from the heating elements 54b2 and 54b3 in the short side direction. Therefore, when either the heating element 54b2 or the heating element 54b3 is heated, the temperature of the heater plate 54a can be detected, and this also applies to the two heating elements in the heating element 54b1.

[0053] [Power Control Section]

[0054] Figure 5This is a circuit diagram of the power control circuit of the power control section 97 of the fixing unit 50, which controls the power supply from the AC power supply 55 to the heater 54, which includes heating elements 54b1, 54b2, and 54b3. The power control circuit of the fixing device 50 consists of bidirectional thyristors 56a, 56b, and 56c and a heating element switching device 57. The contact 54d1 of the heater 54 is connected to the bidirectional thyristor 56c (third switch) and is connected to the first terminal of the AC power supply 55 via the bidirectional thyristor 56c. Additionally, the contact 54d2 of the heater 54 is connected to the heating element switching device 57 and the second terminal of the AC power supply 55. Furthermore, the contact 54d3 of the heater 54 is connected to the bidirectional thyristor 56b (second switch) and the heating element switching device 57, and is connected to the first terminal of the AC power supply 55 via the bidirectional thyristor 56b. Furthermore, the contacts 54d4 of the heater 54 are connected to the bidirectional thyristor 56a (first switch), and are connected to the first pole of the AC power supply 55 via the bidirectional thyristor 56a. Incidentally, the heating element 54b supplied with power from the AC power supply 55 is switched by switching the power supply path using the heating element switching device 57. Therefore, in this embodiment, "switching the power supply path" is also referred to as "switching the heating element 54b".

[0055] In this embodiment, the heating element switching device 57 is specifically an electromagnetic relay configured with moving contacts. When the bidirectional thyristors 56a, 56b, and 56c are set to an on or off state, the power supply from the AC power supply 55 to the heating elements 54b1, 54b2, and 54b3 is interrupted or blocked. The CPU 94 calculates the amount of power required to set the heater 54 to a predetermined temperature (the target temperature required for fixing) based on the temperature information of the heater 54 obtained from the main thermistor element 59a. Furthermore, the CPU 94 instructs the power control section 97 to set the on / off state of the bidirectional thyristors 56a, 56b, and 56c. Through setting instructions from the CPU 94 of the engine controller 92, the heating element switching device 57 is set to a state where contacts 54d2 and 54d3 are connected or a state where contacts 54d2 and 54d3 are disconnected.

[0056] [Power Supply Path]

[0057] Next, a method for supplying power from AC power source 55 to the heating elements by alternately switching between "heating elements 54b1 and 54b2" and "heating elements 54b1 and 54b3" will be described. Figure 6 This shows that power is supplied from AC power source 55. Figure 5 The supply path is shown in the circuit diagram described in [the diagram]. Figure 6In the heater 54, which is arranged with heating elements 54b1, 54b2, and 54b3 of three different lengths relative to the longitudinal direction, three different current paths (which are both electrical paths and power supply paths) to each of the heating elements 54b1, 54b2, and 54b3 are shown in thick solid lines. Incidentally, Figure 6 The current paths shown are merely examples, and other current paths can be constructed.

[0058] (Power supply to heating element 54b1)

[0059] When electricity is supplied from AC power source 55 to heating element 54b1, current flows through... Figure 6 The thick line in section (a) shows the current path. Fixing temperature sensor 59 ( Figure 6 (Not shown) The temperature of heater 54 is detected, and based on the temperature information obtained from fixing temperature sensor 59, CPU 94 operates bidirectional thyristor 56a to change the temperature of heater 54 to a predetermined temperature. In this way, the power supply from AC power supply 55 to heating element 54b1 is controlled. The power supply to heating element 54b1 only requires bidirectional thyristor 56a to be in the ON state, and does not depend on the states of bidirectional thyristors 56b and 56c or the state of heating element switching device 57 (OFF or Short Circuit). That is, when power is supplied to heating element 54b1, heating element switching device 57 can be in the OFF or Short Circuit state, and as an example, in Figure 6 In part (a), the heating component switching device 57 is in the off state.

[0060] In this embodiment, when the bidirectional thyristors 56a and 56b are set to the ON state, the bidirectional thyristor 56c is set to the OFF state, and the heating element switching device 57 is set to the OFF state, power can be supplied to heating elements 54b1 and 54b2 simultaneously from the AC power supply 55. Similarly, when the bidirectional thyristors 56a and 56c are set to the ON state, the bidirectional thyristor 56b is set to the OFF state, and the heating element switching device 57 is set to the OFF state, power can be supplied to heating elements 54b1 and 54b3 simultaneously from the AC power supply 55. Furthermore, when power is supplied only to heating element 54b1 from the AC power supply 55, the bidirectional thyristor 56a is set to the ON state, and the bidirectional thyristors 56b and 56c are set to the OFF state.

[0061] (Power supply to heating element 54b2)

[0062] When power is supplied from AC power source 55 to heating element 54b2, current flows through... Figure 6The current path is shown by the thick line in section (b). When power is supplied to the heating element 54b2, the bidirectional thyristor 56b is set to the ON state, and the contacts of the heating element switching device 57 are set to the OFF state. When the heating element switching device 57 is in the OFF state, the impedance of the contacts of the heating element switching device 57 is sufficiently greater than the impedance of the heating element 54b2. Therefore, current from the AC power supply 55 flows to the heating element 54b2, and almost no current flows to the heating element switching device 57, resulting in heating only the heating element 54b2. The power supplied to the heating element 54b2 is controlled by the bidirectional thyristor 56b, and when power is supplied only to the heating element 54b2, the bidirectional thyristors 56a and 56c are set to the OFF state.

[0063] (Power supply to heating element 54b3)

[0064] When power is supplied from AC power source 55 to heating element 54b3, current flows through... Figure 6 The current path is shown in bold in section (c). When power is supplied to heating element 54b3, the bidirectional thyristor 56c is set to the ON state, and the contacts of heating element switching device 57 are set to the OFF state. Therefore, almost all the current from AC power supply 55 flows to heating element 54b3. When heating element switching device 57 is in the OFF state, the impedance of the contacts of heating element switching device 57 is sufficiently less than the impedance of heating element 54b2, so almost no current flows to heating element 54b2, and only heating element 54b3 can be heated. The power supplied to heating element 54b3 is controlled by bidirectional thyristor 56c, and when power is supplied only to heating element 54b3, bidirectional thyristors 56a and 56b are set to the OFF state.

[0065] [Switching power supply path]

[0066] As described above, when power is supplied from AC power source 55 to heating element 54b1, heating element switching device 57 can be in an open or short-circuited state. However, when power is supplied to heating element 54b2, the contacts of heating element switching device 57 need to be set to an open state. Therefore, when switching... Figure 6 The power supply path to the heating element 54b1 shown in part (a) (hereinafter referred to as "power supply path 1") is similar to... Figure 6When the power supply path to heating element 54b2 (hereinafter referred to as "power supply path 2") is shown in part (b), the contacts of heating element switching device 57 are pre-set to be in the open state. In this way, the power supply path can be switched by independently controlling the bidirectional thyristors 56a and 56b, which act as contactless switches. That is, by controlling the power supply path 1 ( Figure 6 Part (a)) and power supply path 2 ( Figure 6 The bidirectional thyristors 56a and 56b can be switched between their on and off states in part (b) to achieve seamless state transitions, and power supply path 1 and power supply path 2 can be used simultaneously.

[0067] Alternatively, the power supply path 1 of the heating element 54b1 can also be switched. Figure 6 Part (a) and Figure 6 The power supply path to the heating element 54b3 (hereinafter referred to as "power supply path 3") is shown in section (c). As described above, in power supply path 1, which supplies power to the heating element 54b1, the heating element switching device 57 can be in an open state or a short-circuit state. On the other hand, when supplying power to the heating element 54b3, the contacts of the heating element switching device 57 need to be set to a short-circuit state. Therefore, when switching between power supply path 1 and power supply path 3, subsequent operations can be performed as long as the contacts of the heating element switching device 57 are in a short-circuit state beforehand. That is, by switching between power supply path 1 ( Figure 6 Part (a)) and power supply path 3 ( Figure 6 The bidirectional thyristors 56a and 56c can be switched between their on and off states in parts (c) to achieve seamless state transitions, and power supply path 1 and power supply path 3 can be used simultaneously.

[0068] On the other hand, when power is supplied to heating element 54b2, the contacts of heating element switching device 57 need to be set to an open state, and when power is supplied to heating element 54b3, the contacts of heating element switching device 57 need to be set to a short-circuit state. Therefore, when switching the power supply path 2 for heating element 54b2 ( Figure 6 Part (b)) and power supply path 3 for heating component 54b3 Figure 6 When using part (c), it is necessary to switch the state of the heating component switching device 57. That is, only the power supply path 2 can be used. Figure 6 Part (b)) and power supply path 3 ( Figure 6One of the parts (c)), and they are exclusive. In addition, unlike the bidirectional thyristors 56a, 56b and 56c which are non-contact switches, the heating element switching device 57 formed by the moving contact takes time to stabilize when the state of the contact is switched.

[0069] Therefore, in power supply path 2 ( Figure 6 Part (b)) and power supply path 3 ( Figure 6 In the case of a transition between parts (c)), it can be performed as described below. For example, a transition from power supply path 2 ( Figure 6 Part (b)) to power supply path 1 ( Figure 6 Part (a)) to power supply path 3 ( Figure 6 Part (c)) or from power supply path 3 ( Figure 6 Part (c)) to power supply path 1 ( Figure 6 Part (a)) to power supply path 2 ( Figure 6 The state transition in part (b)). Any state transition can occur in power supply path 2 ( Figure 6 Part (b)) and power supply path 3 ( Figure 6 Part (c)) through power supply path 1 ( Figure 6 Part (a)) routing. When using power supply path 1 ( Figure 6 In part (a), that is, when power is supplied to the heating element 54b1, the state of the heating element switching device 57, which is composed of moving contacts, changes from an open state to a short-circuit state or from a short-circuit state to an open state. By inserting power supply path 1, a period of time is prepared for stabilizing the state of the heating element switching device 57 composed of moving contacts. Therefore, the following situation can be avoided: the power supply from AC power source 55 to heater 54 stops due to the unstable state of heating element switching device 57, resulting in no heat required to heat the heating paper P.

[0070] [Positioning part of the heat spreader]

[0071] Here, the positional relationship between the positioning portion 60a of the aluminum plate 60 relative to the heater holder 52 and the heating member 54b of the heater 54 will be described. The aluminum plate 60 is a heat-spreading member characteristic of this embodiment. First, it will be described by using... Figure 7 To describe the shape of aluminum plate 60. Figure 7 Part (a) is a top view showing the shape of the aluminum plate 60 when viewed from the heater holder 52 side, and the arrow on the right indicates Figure 3 The direction of the paper feed P described in the text. Figure 7 Part (b) is when from the drive side ( Figure 3A side view of the aluminum plate 60 when viewed from one side of the fixing motor 100 that drives the pressure roller 53. Figure 7 In part (b), the surface of the aluminum plate 60 that contacts the heater holder 52 is the upper surface in the figure, and surface 60b is the contact surface that contacts the heater plate 54a.

[0072] exist Figure 7 In part (a), the positioning part 60a is embedded in a positioning recess formed on the heater holder 52 and restricts (defines) the position of the aluminum plate 60 in the longitudinal direction. The width H1 of the positioning part 60a in the longitudinal direction is... Figure 7 Part (a) is 5mm, and the height h1 of the positioning part 60a is 5mm. Figure 7 Part (b) is 3 mm in diameter and has a height h1 perpendicular to the contact surface 60b. The aluminum plate 60 is positioned in the longitudinal direction by embedding the positioning part 60a into the recess formed on the heater holder 52. Furthermore, as described above, the position of the heater 54 relative to the heater holder 52 in the longitudinal direction is determined by abutting the drive side surface of the heater 54 against the heater abutting portion formed on the heater holder 52. Therefore, the positional relationship between the aluminum plate 60 and the heater 54 in the longitudinal direction is limited by the heater holder 52.

[0073] [Positional relationship between the heat spreader and the heating element of the heater]

[0074] Figure 8 This is a view showing the positional relationship between the heater 54 and the aluminum plate 60 in this embodiment. Figure 8 The diagram at the top shows... Figure 4 The diagram above shows a view of the arrangement of heating elements 54b1 (54b1a, 54b1b), 54b2, and 54b3 of the heater 54 described herein. On the other hand, the lower diagram is a view of an aluminum plate 60 arranged on the surface opposite to the surface of the heating element 54b of the heater 54, as viewed from the side where the heating element 54b is arranged. The area enclosed by the dashed line indicates the location where the positioning portion 60a is set. Incidentally, Figure 8 The position of the positioning portion 60a shown is an example, and as described below, when viewed from the short side direction of the heater plate 54a, at least a portion of the positioning portion 60a is arranged in the area corresponding to the longest heating member 54b1.

[0075] As described above, heating members 54b1 (54b1a, 54b1b), 54b2, and 54b3 are arranged such that the centers of the heating members relative to the longitudinal direction are aligned on the heater plate 54a. Heating members 54b1 (54b1a, 54b1b) have a length of 222 mm in the longitudinal direction. Heating member 54b2 has a length of 188 mm in the longitudinal direction, and its end in the longitudinal direction is arranged such that heating member 54b2 is located 17 mm (=(222mm-188mm) / 2) inward from the end of heating member 54b1 in the longitudinal direction. Furthermore, heating member 54b3 has a length of 154 mm in the longitudinal direction, and its end in the longitudinal direction is arranged such that heating member 54b3 is located 34 mm (=(222mm-154mm) / 2) inward from the end of heating member 54b1 in the longitudinal direction.

[0076] On the other hand, the end of the aluminum plate 60 is positioned substantially at the same location as the end of the heating member 54b1. Furthermore, the positioning portion 60a of the aluminum plate 60 is formed with a length of 5 mm in the longitudinal direction to the left, extending from a position 5 mm from the driving-side end (right side end of the aluminum plate 60) in the figure. That is, as shown... Figure 8 As shown, the positioning portion 60a of the aluminum plate 60 is arranged in the region where heating members 54b1 are arranged symmetrically at the ends of the heater plate 54a in the short side direction. Figure 8 The positioning portion 60a of the aluminum plate 60 is not arranged at a position corresponding to the heating element 54b2 and heating element 54b3 which are not arranged at the end side of the heater plate 54a in the short side direction (arranged in the center portion in the short side direction). That is, the positioning portion 60a of the aluminum plate 60 is arranged at a position corresponding to the outside of the area where the heating element 54b2 and heating element 54b3 are arranged.

[0077] Here, when a temperature gradient is formed in the short side direction of the heater plate 54a, strain occurs in the heater plate 54a due to the difference in thermal expansion. Furthermore, in the event of a partial malfunction of the fixing device 50 and excessive power being supplied to the heating element 54b, the heater plate 54a may deform. Without heating elements (e.g., heating elements 54b2 and 54b3 in this embodiment) symmetrically arranged at the two ends of the heater plate 54a in the short side direction, the deformation of the heater plate 54a is significant.

[0078] When heating elements are arranged at asymmetrical positions at the two ends of the heater plate 54a in the short-side direction relative to the centerline of the heater plate 54a in the short-side direction, the temperature of the heater plate 54a at the location where the heating elements are arranged becomes higher. On the other hand, at the ends of the heater plate 54a in the short-side direction, the amount of heat radiation is greater due to the larger surface area of ​​the heater plate 54a. This is particularly noticeable at the end of the heater plate 54a on the side where the heating elements are not arranged asymmetrically at the two ends of the heater plate 54a in the short-side direction. As a result, the temperature of the heater plate 54a decreases, and the temperature gradient in the short-side direction of the heater plate 54a increases. Therefore, when electricity is supplied to the heating elements (heating elements 54b2 and 54b3 in this embodiment) arranged near the center of the heater plate 54a in the short-side direction, the difference in thermal expansion caused by the temperature difference in the heater plate 54a results in a larger deformation of the heater plate 54a. In particular, compared to the case where the heating element is arranged asymmetrically off-center from the center of the heater plate 54a, the deformation of the heater plate 54a is more significant when the heating element is arranged at the center of the heater plate 54a. On the other hand, when the heating elements (heating element 54b1 in this embodiment) are symmetrically arranged at the two ends of the heater plate 54a in the short side direction, the ends with the heating elements in the short side direction are less affected by the amount of heat radiation, and the temperature gradient of the heater plate 54a in the short side direction is unlikely to be large.

[0079] As described above, in this embodiment, the positioning portion 60a of the aluminum plate 60, which serves as a heat-absorbing member with a large heat capacity and readily absorbs heat from the heater plate 54a, is provided at the following location: The positioning portion 60a is not arranged at a position where the heating members 54b2 and 54b3, which are arranged asymmetrically relative to the centerline of the heater plate 54a in the short-side direction, overlap via the heater plate 54a. Furthermore, the positioning portion 60a is arranged at a position where at least a portion of the positioning portion 60a overlaps with the heating member 54b1, which is symmetrically arranged at the end of the heater plate 54a in the short-side direction, via the heater plate 54a. In this way, the increase in the thermal gradient when the heating member 54b is heated can be reduced, and deformation due to strain of the heater plate 54a can be suppressed.

[0080] As described above, according to this embodiment, deformation of the heater plate caused by the positioning portion of the heat spreader can be suppressed.

[0081] <Second Embodiment>

[0082] In the second embodiment, a power control circuit with a configuration different from that of the first embodiment, and heating and heat-spreading components with shapes different from those of the first embodiment, will be described. Incidentally, the image forming apparatus used in the second embodiment has a configuration similar to that of the first embodiment; therefore, the same reference numerals are used for the same components and descriptions are omitted.

[0083] [Power Control Section]

[0084] Figure 9 This is a circuit diagram of the power control circuit 97 of the fixing device 50 in this embodiment, which controls the power supply from the AC power source 55 to the heater 154, which includes heating elements 154b1, 154b2, and 154b3. Figure 9 In the heater 154, there are heater plate 154a, heating elements 154b1a, 154b1b, 154b2 and 154b3, conductor 154c, contacts 154d1 to 154d4, and protective glass layer 154e. Figure 9 (Not shown in the image). Additionally, heating members 154b1 (154b1a, 154b1b), 154b2, and 154b3 are arranged such that the centers of the heating members relative to the longitudinal direction are aligned on the heater plate 154a. Incidentally, in this embodiment, as described below, the shapes of the two ends of the heating member 154b1 in the longitudinal direction differ from those of the first embodiment.

[0085] Furthermore, the power control circuit of the fixing device 50 in this embodiment is composed of bidirectional thyristors 156a and 156b and a heating element switching device 157, which serves as a switching contact relay. The contact 154d1 of the heater 154 is connected to the bidirectional thyristor 156b (second switch) and the first contact of the heating element switching device 157, and is connected to the first terminal of the AC power supply 55 via the bidirectional thyristor 156b. Additionally, the contact 154d2 of the heater 154 is connected to the second terminal of the heating element switching device 157 and the AC power supply 55. Furthermore, the contact 154d3 of the heater 154 is connected to the heating element switching device 157. And, the contact 154d4 of the heater 154 is connected to the bidirectional thyristor 156a (first switch), and is connected to the first terminal of the AC power supply 55 via the bidirectional thyristor 156a.

[0086] When power is supplied to heating element 154b1, power is supplied from AC power supply 55 by setting bidirectional thyristor 156a to the ON state. When power is supplied to heating element 154b2, in addition to setting bidirectional thyristor 156b to the ON state, power is also supplied from AC power supply 55 by connecting a first contact at heating element switching device 157. Furthermore, when power is supplied to heating element 154b3, in addition to setting bidirectional thyristor 156b to the ON state, power is also supplied from AC power supply 55 by connecting a second contact at heating element switching device 157. In this way, as... Figure 9 As shown, in this embodiment, the configuration is designed to connect the bidirectional thyristor 156a to the heating element 154b1, and to select the heating element 154b2 or the heating element 154b3 by means of a switching contact relay constituting the heating element switching device 157.

[0087] [Components of the heater]

[0088] Figure 10 Parts (a) to (d) are in Figure 9 The image shows an enlarged view of the heater 154 in this embodiment near the right side of its end relative to the longitudinal direction, and a view showing the positional relationship between the heating elements as a standard-sized sheet of paper (sheet) P passes through the fixing device 50. Figure 10 Part (a) is an enlarged view of the heater 154 near the right side of its end relative to the longitudinal direction, and a view showing the shape of heating elements 154b1a and 154b1b. Figure 10 Part (b) is a view illustrating the area near the ends of heating members 154b1a and 154b1b relative to the longitudinal direction. Additionally, Figure 10 Part (c) is an illustration of when LTR paper (letter paper) passes through... Figure 10 A view showing the positional relationship of heating members 154b1a and 154b1b in part (a). Furthermore, Figure 10 Part (d) is an illustration of when an A4-sized sheet of paper (described as A4 paper in the figure) passes through... Figure 10 A view showing the positional relationship of heating elements 154b1a and 154b1b in part (a).

[0089] like Figure 10 As shown in parts (a) and (b), in the ends of heating members 154b1a and 154b1b relative to the longitudinal direction, a region having a shape whose width gradually narrows from width H2 to width H3 relative to the short side direction is defined as region F. Figure 10Part (b)). Furthermore, a region adjacent to region F, having a shape whose width gradually increases from width H3 to width H4 relative to the short side direction, is defined as region G. Figure 10 Part (b)). Furthermore, a region having a shape with a width H4 that is constant relative to the shorter side direction is defined as region H( Figure 10 Part (b)).

[0090] In region F of heating elements 154b1a and 154b1b, the width relative to the short side gradually narrows from width H2 to width H3 towards the center relative to the longitudinal direction, and in this embodiment, width H2 is 1.0 mm and width H3 is 0.7 mm. Incidentally, in Figure 10 In part (a), the width of region F narrows linearly; however, it can, for example, be configured to narrow in a curved manner. Additionally, the length L4 of region F relative to the longitudinal direction is 6 mm. Next, region G will be described. In region G of heating members 154b1a and 154b1b, the width relative to the short side gradually widens from width H3 to width H4 towards the center relative to the longitudinal direction, and in this embodiment, width H4 is 0.8 mm. Therefore, the size relationship between widths H2, H3, and H4 is width H2 > width H4 > width H3. Incidentally, in Figure 10 In the middle, the width of region G increases linearly; however, for example, it can be configured to increase in a curved manner. The length L5 of region G relative to the longitudinal direction is 22 mm. Furthermore, the width H4 (first length) of region H of heating member 154b1a relative to the short side direction is a constant 0.8 mm, and the length L6 from the center of region H relative to the longitudinal direction is 83 mm (=(222mm / 2)-6mm-22mm). Therefore, the relationship between lengths L4, L5, and L6 is length L6>length L5>length L4. Additionally, as... Figure 10 As shown in part (a), heating elements 154b1a and 154b1b are symmetrical (vertically symmetrical) with respect to the center (middle) of the heater plate 154a in the short-side direction, and have the same dimensions as heating element 154b1a. Furthermore, Figure 10 Part (a) is in Figure 9 The image shows an enlarged view of the heater 154 near its right end relative to the longitudinal direction, and the heating elements 154b1a and 154b1b (not shown) on the left side of the heater 154 relative to the longitudinal direction have shapes similar to... Figure 10 The shape on the right side shown in part (a) is symmetrical. That is, the shapes of heating members 154b1a and 154b1b relative to the longitudinal direction are symmetrical with respect to the center (middle) of the heater plate 154a in the longitudinal direction. Figure 10 (The shape is symmetrical on both sides).

[0091] The heating elements 154b1a and 154b1b are shaped as described above because when a voltage is applied to the heating elements 154b1a and 154b1b from the AC power supply 55, the heat generated per unit length (energy density P) increases in the order of regions G, H, and F. That is, when the energy densities in regions F, G, and H are defined as P1, P2, and P3 respectively, the order is P2>P3>P1. Here, the average width of region F relative to the short side direction (the average of width H2 and width H3) is defined as width H23 (third length) (=(width H2 (1.0 mm) + width H3 (0.7 mm) / 2=0.85 mm)). Furthermore, the average width of region G relative to the short side direction (the average of width H3 and width H4) is defined as width H34 (second length) (=(width H3 (0.7 mm) + width H4 (0.8 mm) / 2=0.75 mm)). In this case, within heating elements 154b1a and 154b1b, the size relationship is: width H23 (0.85 mm) of region F > width H4 (0.8 mm) of region H > width H34 (0.75 mm) of region G. Here, the resistance value per unit length in region F, which is the region at the very end of heating elements 154b1a and 154b1b relative to the longitudinal direction, is defined as R1; the resistance value in region G near region F is defined as R2; and the resistance value in region H, which is the central portion relative to the longitudinal direction, is defined as R3. The resistance in each region is directly proportional to the length of that region and inversely proportional to the cross-sectional area of ​​that region (in this case, the width relative to the shorter side). Therefore, the size relationship between the values ​​of resistances R1, R2, and R3 is: resistance value R2 > resistance value R3 > resistance value R1, and the resistance value per unit length in each region increases in the order of region G, region H, and region F. In this way, when a voltage is applied to the heating elements 154b1a and 154b1b, the heat generated per unit length (energy density) can be increased in the order of regions G, H, and F. Furthermore, the energy density in each region is in the following order: energy density P2 (heat generated P2) in region G > energy density P3 (heat generated P1) in region H > energy density P1 (heat generated P3) in region F.

[0092] [Positional relationship between paper and heating element]

[0093] Figure 10 Part (c) is a view illustrating the positional relationship between the LTR paper, which is the longest sheet of paper P relative to the longitudinal direction, and regions F, G, and H of the heating elements 154b1a and 154b1b. Additionally, Figure 10Part (d) is a view illustrating the positional relationship between an A4 sheet of paper, P (which is the second longest sheet of paper after the LTR paper in the longitudinal direction), and regions F, G, and H of the heating elements 154b1a and 154b1b. Figure 10 In parts (c) and (d), the top of the paper indicates the leading edge of the paper in the feed direction. The area within 5 mm of the leading edge and the right edge in the figure is the margin, and the black area excluding the margin indicates the image area to be printed. Incidentally, the rear edge of the paper and the left edge in the figure are not shown, and their margins are 5 mm. Figure 10 As shown in part (c), the image area of ​​the LTR paper passes through the fixing clamping part N, which corresponds to the region G with high energy density of the heating members 154b1a and 154b1b, relative to the end in the longitudinal direction. Additionally, as... Figure 10 As shown in (d), region F of the heating members 154b1a, 154b1b corresponding to the non-feed area of ​​the fixing clamping portion N that does not pass through the longitudinal edge of the A4 paper is a low energy density region. Therefore, the temperature rise of the non-passing portion of the paper in the non-passing area (non-passing portion) of the fixing clamping portion N corresponding to region F is suppressed, and in addition, the temperature drop at the ends relative to the longitudinal direction, where the amount of heat radiation is greater than that at the center portion relative to the longitudinal direction, can be reduced, where the temperature is more easily reduced.

[0094] [The shape and positioning components of the heat spreader]

[0095] Figure 11 This is a top view of the shape of the aluminum plates 161 and 162, which are heat-spreading components in this embodiment, as viewed from the heater holder 52 side, with the arrow on the right indicating... Figure 3The paper P is shown in the feed direction. The aluminum plate 60, serving as the heat-spreading member in this embodiment, is a single body, while the heat-spreading member in this embodiment consists of two bodies, aluminum plates 161 and 162. The aluminum plate 161 on the drive side (first heat-spreading member) and the aluminum plate 162 on the non-drive side (second heat-spreading member) are arranged symmetrically in the longitudinal direction with respect to the heater 154 of the fixing device 50. That is, aluminum plate 161 is arranged at one end of the heater 154 in the longitudinal direction relative to the heater 154, and aluminum plate 162 is arranged at the other end of the heater 154 in the longitudinal direction relative to the heater 154. The opposite ends of aluminum plates 161 and 162, relative to the central ends in the longitudinal direction, are arranged at positions substantially the same as the positions of the two ends of the heating member 154b1. A gap is provided between aluminum plates 161 and 162 to prevent them from interfering with each other during thermal expansion. Positioning portions 161a (first positioning portion) and 162a (second positioning portion) for positioning relative to heater holder 152 (not shown) are formed on aluminum plates 161 and 162, respectively. Positioning portions 161a and 162a are formed by bending the aluminum plates, for example, in a manner similar to positioning portion 60a in the first embodiment, and have a longitudinal width H1 (length) of 5 mm and a height of 3 mm in the direction of heater holder 152. Positioning holes are formed on heater holder 152 into which the positioning portions 161a and 162a formed on aluminum plates 161 and 162 are respectively inserted. When the positioning portions 161a and 162a of aluminum plates 161 and 162 are respectively inserted into the positioning holes of heater holder 152, the positions of aluminum plates 161 and 162 relative to heater holder 152 in the longitudinal direction are restricted.

[0096] [Positional relationship between the heating element and the heat spreader of the heater]

[0097] Figure 12 This is a view showing the positional relationship between the heater 154 and the aluminum plates 161 and 162 in this embodiment. Figure 12 The diagram at the top shows... Figure 9 The first view shows the positional relationship between the heating elements 154b1 (154b1a, 154b1b), 154b2, and 154b3 of the heater 154 described herein. The second view, on the other hand, shows aluminum plates 161 and 162 arranged on opposite sides of the surfaces of the heating elements 154b1, 154b2, and 154b3 of the heater plate 154, as viewed from the side where the heating elements are arranged. The area enclosed by the dashed line indicates the location of the positioning portions 161a and 162a.

[0098] The positioning portion 161a of the aluminum plate 161 arranged on the drive side has a length of 5 mm extending from a position 5 mm from the drive-side end of the aluminum plate 161 (the right end of the aluminum plate 161 in the figure) in the left direction relative to the center in the longitudinal direction. Similarly, the positioning portion 162a of the aluminum plate 162 arranged on the non-drive side has a length of 5 mm extending from a position 5 mm from the non-drive-side end of the aluminum plate 162 (the left end of the aluminum plate 161 in the figure) in the right direction relative to the center in the longitudinal direction.

[0099] As described above, the centers of heating elements 154b1 (154b1a, 154b1b), 154b2, and 154b3 relative to the longitudinal direction are aligned and arranged on the heater plate 154a. The length of heating element 154b1 (154b1a, 154b1b) relative to the longitudinal direction is 222 mm. The length of heating element 154b2 in the longitudinal direction is 188 mm, and the end of heating element 154b2 in the longitudinal direction is arranged such that heating element 154b2 is located 17 mm (=(222mm-188mm) / 2) inside the end of heating element 154b1 in the longitudinal direction. In addition, the length of the heating member 154b3 in the longitudinal direction is 154mm, and the end of the heating member 154b3 in the longitudinal direction is arranged such that the heating member 154b3 is located 34mm (=(222mm-154mm) / 2) inside the end of the heating member 154b1 in the longitudinal direction.

[0100] That is, in this embodiment, the positioning portions 161a and 162a of the aluminum plates 161 and 162, which are divided into two main bodies relative to the longitudinal direction, are arranged in the following positions. The positioning portions 161a and 162a are not arranged at positions where heating members 154b2 and 154b3, which are arranged asymmetrically relative to the centerline of the heater plate 154a in the short-side direction, overlap with the heater plate 154a. Furthermore, the positioning portions 161a and 162a are arranged at positions where at least a portion of the positioning portions 161a and 162a overlaps with heating members 154b1, which are symmetrically arranged at the ends of the heater plate 154a in the short-side direction. In this way, the increase in the thermal gradient when the heating members are heated can be reduced and deformation due to strain of the heater plate 154a can be suppressed.

[0101] Furthermore, in this embodiment, when the aluminum plates 161 and 162, which serve as heat-spreading members, arranged on the back side of the heater 154a (opposite to the contact surface of the membrane 51), are not a single part but are divided into two main bodies (two members), the following advantages are provided. That is, the heat-spreading members arranged on the back side of the heater plate 154a are heated and thermally expanded by the heat generated by the heater 154. When the heater 154 has finished heating and the temperature drops, the aluminum plates 161 and 162, as heat-spreading members, attempt to shrink back to their original size; however, because the aluminum plates 161 and 162 are forcefully pressed between the heater 154 and the heater holder 152 due to the pressure of the pressure roller 53, they do not completely return to their original size. Repeating this process can change the size of the heat-spreading members. This phenomenon is significant when the heat-spreading members are made of a metal such as aluminum, whose thermal expansion is different from that of the heater plate 154a. Therefore, in a configuration where the aluminum plate, which serves as a heat-spreading component, is divided into multiple components, this dimensional change can be reduced due to the small amount of thermal expansion.

[0102] As described above, according to this embodiment, deformation of the heater plate caused by the positioning portion of the heat spreader can be suppressed.

[0103] <Third Embodiment>

[0104] In the third embodiment, the configuration of the heating element and the power control circuit differ from those in the first and second embodiments. Incidentally, the configuration of the image forming apparatus used in the third embodiment is similar to that in the first embodiment, and descriptions are omitted by using the same reference numerals for the same components.

[0105] [Components of the heater]

[0106] Figure 13 This is a circuit diagram of the power control section 97 of the fixing device 50, which controls the power supply from the AC power source 55 to the heater 254, including heating elements 254b1 (254b1a, 254b1b) and 254b2. Figure 13 In the heater 254, there are heater plate 254a, heating elements 254b1a, 254b1b and 254b2, conductor 254c, contacts 254d1 to 254d4 and protective glass layer 254e. Figure 13(Not shown in the image). Heating members 254b1a and 254b1b have a length L1 of 222 mm relative to the longitudinal direction, similar to heating members 54b1a and 54b1b in the first embodiment. Heating member 254b2 has a length L2 of 188 mm relative to the longitudinal direction. The centers of heating members 254b1 (254b1a, 254b1b) and 254b2 relative to the longitudinal direction are aligned on the heater plate 254a and arranged thereon. Heating members 254b1a and 254b1b are respectively arranged near each end of the heater plate 254a relative to its short side. On the other hand, heating member 254b2 is arranged at the center of the heater plate 254a relative to its short side.

[0107] Furthermore, the shapes of the aluminum plates 261 and 262 (not shown) as heat-spreading components, and their arrangement positions on the heater plate 254a, are similar to those of the aluminum plates 161 and 162 as heat-spreading components in the second embodiment described above. That is, the heat-spreading component in this embodiment is composed of two main bodies, aluminum plates 261 and 262. The aluminum plate 261 on the drive side and the aluminum plate 262 on the non-drive side are arranged symmetrically with respect to the heater 254 of the fixing device 50 in the longitudinal direction. A gap is provided between the aluminum plates 261 and 262 to prevent interference during thermal expansion. Positioning portions 261a and 262a for positioning relative to the heater holder 252 (not shown) are formed on the aluminum plates 261 and 262, respectively. The positioning portion 261a of the aluminum plate 261 on the drive side has a length of 5 mm from a position 5 mm from the drive-side end of the aluminum plate 261 towards the center in the longitudinal direction. In addition, the positioning portion 262a of the aluminum plate 262 arranged on the non-driving side is formed with a length of 5 mm from a position 5 mm from the non-driving side end of the aluminum plate 262 toward the center relative to the longitudinal direction.

[0108] [Power Control Section]

[0109] In addition, the power control circuit of the fixing device 50 in this embodiment is composed of a bidirectional thyristor 256a (first switch) and a bidirectional thyristor 256b (second switch). One terminal of the heating elements 254b1a, 254b1b, and 254b2 is connected to the contact 254d1 via a conductor 254c. The other terminal of the heating elements 254b1a and 254b1b (first heating elements) is connected to the contact 254d2 via a conductor 254c. The other terminal of the heating element 254b2 (second heating element) is connected to the contact 254d3 via a conductor 254c.

[0110] The heater 254's contact 254d1 (first contact) is connected to the second terminal of the AC power supply 55. Additionally, the heater 54's contact 54d4 is connected to the triac 56a (first switch), and via the triac 56a, is connected to the first terminal of the AC power supply 55. Furthermore, the heater 254's contact 154d3 (second contact) is connected to the triac 256b (second switch), and via the triac 256b, is connected to the first terminal of the AC power supply 55.

[0111] Subsequently, in this embodiment, the temperature gradient appearing in the heater plate 254a when each heating element is powered and heated will be described. In this embodiment, as... Figure 13 As shown, the heating element 254b2 is arranged at the center of the heater plate 254a relative to its short side. Therefore, when power is supplied to the heating element 254b2, a temperature gradient occurs in the heater plate 254a, where the temperature is higher in the central portion relative to its short side and lower near the ends relative to its short side. Thus, when the positioning portions 261a and 262a of the aluminum plates 261 and 262 are arranged in the region where the heating element 254b2 is arranged relative to the longitudinal direction, the heat capacity of the positioning portions 261a and 262a contributes to the temperature gradient relative to its short side. Then, when the temperature gradient is large, the deformation of the heater plate 254a is greater due to the strain caused by the uneven thermal expansion of the heater plate 254a. That is, not only in the case of heating elements arranged asymmetrically relative to the short side of the heater plate 254a, but also in the case of symmetrically arranged heating elements, the temperature gradient of the heater plate 254a during heating is greater than the temperature gradient when heating elements are arranged at the two ends of the heater plate 254a relative to its short side.

[0112] In this embodiment, the positioning portions 261a and 262a of the aluminum plates 261 and 262 are positioned relative to the longitudinal direction without overlapping with the heating member 254b2 disposed in the central portion of the heater plate 254a relative to the short side direction via the heater plate 254a. Furthermore, the positioning portions 261a and 262a are arranged at positions where at least a portion overlaps with the heating member 254b1, which is symmetrically disposed at the end of the heater plate 254a relative to the short side direction, via the heater plate 254a. In this way, in this embodiment, the increase in the thermal gradient when the heating member is heated can be reduced and deformation due to strain of the heater plate can be suppressed.

[0113] As described above, according to this embodiment, deformation of the heater plate caused by the positioning portion of the heat spreader can be suppressed.

[0114] According to this embodiment, deformation of the heater plate caused by the positioning portion of the heat spreader can be suppressed.

[0115] <Other Embodiments>

[0116] One or more embodiments of the present invention can also be implemented by a computer that reads and executes computer-executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be more fully referred to as a "non-transient computer-readable storage medium") to perform the functions of one or more embodiments described above and / or includes one or more circuits (e.g., application-specific integrated circuits (ASICs)) for performing the functions of one or more embodiments described above, and by a method executed by a computer of a system or device, for example, by reading and executing computer-executable instructions from a storage medium to perform the functions of one or more embodiments described above and / or controlling one or more circuits to perform the functions of one or more embodiments described above. The computer may include one or more processors (e.g., a central processing unit (CPU), a microprocessor unit (MPU)) and may include a network of individual computers or individual processors to read and execute the computer-executable instructions. The computer-executable instructions may be provided to the computer, for example, from a network or storage medium. The storage medium may include, for example, a hard disk, random access memory (RAM), read-only memory (ROM), storage devices for distributed computing systems, optical discs (such as CDs, DVDs, or Blu-ray discs). TM One or more of the following: flash memory devices, memory cards, etc.

[0117] Although the invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the appended claims should be given the broadest interpretation to include all such modifications and equivalent structures and functions.

Claims

1. A fixing apparatus for fixing an unfixed toner image on a recording material onto the recording material, the fixing apparatus comprising: A heater having an elongated substrate, a first heat-generating member, and a second heat-generating member having a length in the longitudinal direction of the substrate substantially equal to the length of the first heat-generating member. And a third heat-generating member whose length in the longitudinal direction is shorter than that of the first heat-generating member and the second heat-generating member; A heat-equalizing component, the heat-equalizing component being configured to homogenize the temperature of the substrate; as well as A retainer, configured to hold the heater and the heat spreader, The first heat-generating component, the second heat-generating component, and the third heat-generating component are arranged on the substrate. Wherein, relative to the short side direction of the substrate which is perpendicular to the longitudinal direction and the thickness direction of the substrate, a first heat-generating member is arranged on one end side, a second heat-generating member is arranged on the other end side, and a third heat-generating member is arranged between the first heat-generating member and the second heat-generating member. The heat spreader is positioned between the heater and the holder relative to the thickness direction of the substrate. The heat-spreading component includes a positioning portion of a longitudinal direction positioning retainer relative to the heat-spreading component. The positioning portion overlaps with the regions of the first and second heat-generating components in the longitudinal direction and is located outside the region of the third heat-generating component.

2. The fixing device according to claim 1, wherein, The heat-spreading component is held by the retainer by engaging the positioning part with the recessed part provided on the retainer.

3. The fixing device according to claim 1, wherein, The heater is provided with a fourth heat-generating member whose length in the longitudinal direction is shorter than that of the third heat-generating member, and The first heat-generating component, the third heat-generating component, the fourth heat-generating component, and the second heat-generating component are arranged sequentially relative to the short side of the substrate.

4. The fixing device according to claim 3, wherein, The heater is equipped with: A first contact is electrically connected to one end of a first heat-generating component, a second heat-generating component, and a third heat-generating component. The second contact is electrically connected to one end of the fourth heat-generating component. The third contact is electrically connected to the other end of the third and fourth heat-generating components, and The fourth contact is electrically connected to the other end of the first heat-generating component and the second heat-generating component.

5. The fixing device according to claim 4, further comprising a switching unit configured to switch the power supply path from AC power to the first heat-generating component, the second heat-generating component, the third heat-generating component, and the fourth heat-generating component. in, The switching unit includes a first switch, a second switch, a third switch, and a relay. The first switch connects or disconnects the AC power supply and the fourth contact. The second switch connects or disconnects the AC power supply and the relay, and connects or disconnects the AC power supply and the third contact. The third switch connects or disconnects the AC power supply and the second contact, and The relay connects or disconnects the first contact and the third contact, and connects or disconnects the AC power supply and the third contact.

6. The fixing device according to claim 5, wherein, The first switch, the second switch, and the third switch include bidirectional thyristors.

7. The fixing device according to claim 6, wherein, The two ends of the heat-generating member in the longitudinal direction are arranged via a substrate at substantially the same positions as the two ends of the first heat-generating member or the second heat-generating member in the longitudinal direction.

8. The fixing device according to claim 4, further comprising a switching unit configured to switch the power supply path from AC power to the first heat-generating component, the second heat-generating component, the third heat-generating component, and the fourth heat-generating component. in, The switching unit includes a first switch, a second switch, and a relay. The first switch connects or disconnects the AC power supply and the fourth contact. The second switch connects or disconnects the AC power supply and the relay, and connects or disconnects the AC power supply and the second contact. The relay connects or disconnects the third contact and the second switch, or connects or disconnects the AC power supply and the third contact.

9. The fixing device according to claim 8, wherein, The first and second switches include bidirectional thyristors.

10. The fixing device according to claim 3, wherein, When the region including the first heat-generating member and the second heat-generating member relative to the center side in the longitudinal direction is the first region, the region closer to the end side of the first region relative to the longitudinal direction is the second region, and the region closer to the end side of the second region relative to the longitudinal direction is the third region, and... When the heat generation per unit length of the first and second heat-generating components corresponding to the first region is heat generation amount P1, the heat generation per unit length of the first and second heat-generating components corresponding to the second region is heat generation amount P2, and the heat generation per unit length of the first and second heat-generating components corresponding to the third region is heat generation amount P3, The condition P2>P1>P3 is satisfied.

11. The fixing device according to claim 3, wherein, When the region including the first heat-generating member and the second heat-generating member relative to the center side in the longitudinal direction is the first region, the region closer to the end side of the first region relative to the longitudinal direction is the second region, and the region closer to the end side of the second region relative to the longitudinal direction is the third region, and... When the first heat-generating component and the second heat-generating component corresponding to the first region have a shape with a length of H3 relative to the short side direction, The first heat-generating member and the second heat-generating member corresponding to the second region have a shape in which the length relative to the short side direction changes from H3 to H2, which is shorter than H3, toward the third region. When the first heat-generating member and the second heat-generating member corresponding to the third region have a shape where the length of the end in the longitudinal direction relative to the short side changes from H2 to H1, which is longer than H3, and When the average lengths of the first, second, and third regions relative to the shorter side are the first length, the second length, and the third length, respectively. The condition is satisfied that the third length > the first length > the second length.

12. The fixing device according to claim 11, wherein, The shapes of the first heat-generating member and the second heat-generating member are symmetrical with respect to the center of the substrate in the longitudinal direction and the center of the substrate in the short side direction.

13. The fixing device according to claim 12, wherein, The third region is the area that the image area on the recording material containing the image does not pass through.

14. The fixing device according to claim 1, wherein, The heater is equipped with: A first contact is electrically connected to one end of a first heat-generating component, a second heat-generating component, and a third heat-generating component. The second contact is electrically connected to the other end of the third heat-generating component, and The third contact is electrically connected to the other end of the first heat-generating component and the second heat-generating component.

15. The fixing apparatus of claim 14, further comprising a switching unit configured to switch the power supply path from AC power to the first heat-generating member, the second heat-generating member, and the third heat-generating member. in, The switching unit includes a first switch and a second switch. The first switch connects or disconnects the AC power supply and the third contact. The second switch connects or disconnects the AC power supply and the second contact.

16. The fixing device according to claim 15, wherein, The first and second switches include bidirectional thyristors.

17. The fixing device according to any one of claims 1 to 16, wherein, The heat spreader includes a first heat spreader and a second heat spreader, and The first heat-spreading member is arranged at one end of the heater relative to the longitudinal direction, and the second heat-spreading member is arranged at the other end of the heater relative to the longitudinal direction.

18. The fixing device according to claim 17, wherein, The first heat-spreading component includes a first positioning portion, and the second heat-spreading component includes a second positioning portion. Specifically, when viewed in the short-side direction, the first positioning portion of the first heat-generating member is positioned outside the region corresponding to the third heat-generating member, and at least a portion of the first positioning portion is positioned inside the region corresponding to the first heat-generating member. When viewed in the short side direction, the second positioning portion of the second heat-generating member is positioned outside the region corresponding to the third heat-generating member, and at least a portion of the second positioning portion is positioned inside the region corresponding to the first heat-generating member.

19. The fixing device according to claim 1, wherein, The positioning section is formed by bending the heat-spreading component.

20. An image forming apparatus, comprising: An image forming unit configured to form an unfixed toner image on a recording material; as well as According to claim 1, the fixing device fixes an unfixed toner image on a recording material.

21. The image forming apparatus according to claim 20, wherein, The fixing equipment includes a cylindrical film configured to be heated by a heater and a pressure roller that cooperates with the film to form a clamping portion. The heater is arranged in the internal space of the membrane, the heater and the pressure roller clamp the membrane, and the image on the recording material is heated through the membrane at the clamping part.

Images