Heating member, fixing device, and image forming apparatus

Abstract

To provide a heating member, a fixing device, and an image forming apparatus that can reduce the number of heat generating blocks in which temperature unevenness occurs due to passage of an end of a recording medium in a width direction orthogonal to a conveyance direction of the recording medium, and thereby can improve the durability of the heating member.SOLUTION: A heating member 42 for heating a fixing member (41) comprises a plurality of heat generating blocks B(1)-B(n) generating heat upon energization. The plurality of heat generating blocks B(1)-B(n) are arranged in parallel along a width direction W orthogonal to a conveyance direction T of a recording medium P. A length e1 in the width direction W of at least one of the plurality of heat generating blocks B(1)-B(n) is equal to or less than the minimum difference in the length in the width direction W between recording media P, P of standard sizes [S(1), S(2)]-[S(m-1), S(m)] adjacent to each other in the order of length in the width direction W, of recording media P of a plurality of types of standard sizes S(1)-S(m) to be conveyed.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a heating member, a fixing device, and an image forming apparatus such as a copier, a multifunction machine, a printer, or a facsimile machine. [Background technology]

[0002] Electrophotographic image forming apparatuses are capable of forming high-quality images with good reproducibility and operability at low cost, and therefore are widely used as devices such as copiers, printers, facsimile machines, and multifunction machines having two or more of these functions.

[0003] An electrophotographic image forming apparatus includes, for example, a photoconductor (image carrier), a charging device, an exposure device, a developing device, a transfer device, and a fixing device.

[0004] The fixing device provided in the image forming apparatus includes a fixing device having a heating member (e.g., a heating member including a heating element having a positive temperature characteristic) for heating a fixing member (e.g., a fixing roller or a fixing belt). For example, a fixing device having a heating member, a fixing member, and a pressure roller is generally used. The fixing member is heated by the heating member, and heats and melts the toner constituting the unfixed toner image on a recording medium (recording material) such as a recording paper, thereby fixing the toner to the recording medium. The pressure roller is provided so as to be in pressure contact with the fixing member, and by pressing the recording medium, promotes the fixing of the melted toner to the recording medium. The recording medium carrying the unfixed toner image is introduced into the fixing nip portion, which is the contact portion between the fixing member and the pressure roller, so that the carrying surface of the toner image contacts the surface of the fixing member, and the unfixed toner image is fixed by heating and pressurizing it.

[0005] In recent years, in order to protect the environment, there has been a demand for energy-saving fixing devices, and there has been active development of fixing devices that have a short warm-up time from when the power is turned on until printing is possible. Methods for shortening the warm-up time include increasing the efficiency of heat conversion by the heating member and reducing the heat capacity of the fixing member.

[0006] For example, heater lamps such as conventional halogen lamps have been used as a means for improving the thermal efficiency of the heating member, but since the energy loss during heat conversion is unavoidable in the case of heater lamps, sheet heaters in which a resistance heating layer is formed on an insulating substrate have come to be used. Furthermore, thin fixing belts are sometimes used to reduce the thermal capacity of the fixing member.

[0007] In this way, by combining a fixing member with a low heat capacity and a highly efficient heat source, the temperature rise characteristics of the fixing member are improved, but this also requires highly accurate temperature control in the longitudinal direction of the heating member.

[0008] In this regard, a heating member having a heat generating portion made up of a plurality of heat generating blocks that generate heat when electricity is applied thereto has been conventionally known (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2005-221575 A Summary of the Invention [Problem to be solved by the invention]

[0010] In detail, Patent Document 1 describes a configuration in which multiple magnetic cores (heat generating blocks) are composed of magnetic core A made of a material whose Curie temperature is higher than the temperature of the magnetic core during image fixing and lower than the heat resistance temperature of the excitation coil, and magnetic core B made of a material whose Curie temperature is higher than that of magnetic core A, and magnetic core A and magnetic core B are regularly and repeatedly arranged in the same straight line.

[0011] However, the conventional configuration has the following disadvantages, which will be explained below with reference to FIG.

[0012] 13 is a plan view showing a schematic configuration of multiple heat generating blocks B(1) to B(n) (n is an integer of 2 or more, n=14 in this example) in a conventional heating member 42X. Note that the following description will be given taking as an example a case where recording media of m types (m is an integer of 2 or more, m=6 in this example) of standard sizes [S(1) to S(m)] in the centimeter system are transported with the center in the width direction W as the reference (center reference C).

[0013] Here, the lengths [L(1) to L(m) (m=6)] in the width direction W perpendicular to the transport direction T of the recording media of m standard sizes [S(1) to S(m) (m=6)] are as follows:

[0014] That is, the first length L(1) is the length (100 mm) in the width direction W of a postcard-sized recording medium when it is passed vertically (postcard vertical size S(1)). The second length L(2) is the length (148 mm) in the width direction W of an A5-sized recording medium when it is passed vertically (A5 vertical size S(2)). The third length L(3) is the length (182 mm) in the width direction W of a B5-sized recording medium when it is passed vertically (B5 vertical size S(3)). The fourth length L(4) is the length (210 mm) in the width direction W of an A5-sized recording medium when it is passed horizontally (A5 horizontal size) and an A4-sized recording medium when it is passed vertically (A4 vertical size S(4)). The fifth length L(5) is the length (257 mm) in the width direction W of a B5-sized recording medium when it is passed horizontally (B5 horizontal size) and a B4-sized recording medium when it is passed vertically (B4 vertical size S(5)). In addition, the sixth length L (m) is the sixth length (297 mm) in the width direction W when an A4 size recording medium is passed horizontally (A4 horizontal size) and when an A3 size recording medium is passed vertically (A3 vertical size S (m) (m = 6)).

[0015] 13, among the heat generating blocks B(1)-B(14) in the heating member 42X, the four heat generating blocks B(6)-B(9) in the center have only a pass area α for recording media of all m types (six types in this example) of standard sizes S(1)-S(6) in each heat generating block B(6)-B(9). Meanwhile, in the five heat generating blocks B(1)-B(5) on one side in the width direction W and the five heat generating blocks B(10)-B(14) on the other side, the pass area α and non-pass area β for recording media of standard sizes S(1)-S(6) are mixed in each heat generating block B(1)-B(5), B(10)-B(14), and temperature unevenness (heat rise at the end portions) occurs in the heat generating blocks B(1)-B(5), B(10)-B(14).

[0016] This will increase the thermal damage caused by the temperature difference (heat bias, temperature unevenness) between the recording medium passing area α and non-passing area β in each of the heat generating blocks B(1)-B(5), B(10)-B(14), resulting in a decrease in the durability of heating member 42X and damage and decrease in durability of the fixing member.

[0017] Therefore, the present disclosure aims to provide a heating member, a fixing device, and an image forming apparatus that can reduce the number of heat generating blocks that cause temperature unevenness when the ends of the recording medium pass through in the width direction perpendicular to the transport direction of the recording medium, thereby improving the durability of the heating member. [Means for solving the problem]

[0018] In order to solve the above problem, the heating member of the present disclosure is a heating member for heating a fixing member, and is provided with a plurality of heat generating blocks that generate heat when electricity is applied thereto, the plurality of heat generating blocks are arranged side by side along a width direction perpendicular to the transport direction of the recording medium, and the length in the width direction of at least one of the plurality of heat generating blocks is less than or equal to the minimum difference in length in the width direction between adjacent recording media of the standard sizes in length order in the width direction among the recording media of the plurality of types of standard sizes being transported.

[0019] A fixing device according to the present disclosure is characterized by including the heating member according to the present disclosure.

[0020] An image forming apparatus according to the present disclosure is characterized by including the fixing member according to the present disclosure. Effect of the Invention

[0021] According to the present disclosure, it is possible to reduce the number of heat generating blocks that become uneven in temperature when the ends of the recording medium pass through in the width direction perpendicular to the transport direction of the recording medium, thereby improving the durability of the heating member. [Brief description of the drawings]

[0022] [Figure 1] 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus including a fixing device according to an embodiment of the present invention. [Diagram 2] 1 is a cross-sectional view showing a schematic configuration of an example of a fixing device according to an embodiment of the present invention. [Diagram 3] 11 is a chart showing the widthwise lengths of standard-sized recording media in centimeters and the minimum difference in length in the widthwise direction between adjacent standard-sized recording media in order of length in the widthwise direction. [Figure 4] 4 is a plan view (top) and a side view (bottom) showing a configuration example (first embodiment) in which the arrangement pitch of the heat generating blocks is 14 mm when the minimum difference in length in the width direction of the recording medium shown in FIG. 3 is 14 mm. [Figure 5A] 4 is an enlarged front view showing a portion of a heat generating block of the heating member. FIG. [Figure 5B] 4 is an enlarged side view showing a portion of a heat generating block of the heating member. FIG. [Figure 5C] 4 is an enlarged plan view showing a portion of a heat generating block of the heating member. FIG. [Figure 6A] 5A and 5B are a plan view (top) and a side view (bottom) showing another example (second embodiment) of the heat generating block shown in FIG. [Figure 6B]5 is a plan view (top) and a side view (bottom) showing an example (third embodiment) of the heating member shown in FIG. 4 in which the length in the width direction of the heat generation block that is equal to or less than the minimum difference is set to 5 mm or more. [Figure 6C] 6C is a plan view (top) and a side view (bottom) showing an example (fourth embodiment) in which heat generating blocks are provided on both ends in the width direction of the recording medium in the heating member shown in FIG. 6B. [Figure 6D] 6D is a plan view (top) and a side view (bottom) showing an example (fifth embodiment) in which the Curie temperature of the second heat generation block is set higher than the Curie temperature of the first heat generation block in the heating member shown in FIG. 6C. [Figure 6E] 6E is a graph showing a temperature distribution when the heating member shown in FIG. 6D generates heat. [Figure 7A] 5A and 5B are a plan view (top) and a side view (bottom) showing a configuration example (first embodiment) in which the arrangement pitch of the heat generating blocks in the example shown in FIG. 4 is 10 mm. [Figure 7B] 7B is a plan view (top) and a side view (bottom) showing another example (second embodiment) of the heat generating block shown in FIG. 7A. [Figure 7C] 7C is a plan view (top) and a side view (bottom) showing an example (third embodiment) of the heating member shown in FIG. 7B in which the length in the width direction of the heat generation block that is equal to or less than the minimum difference is set to 5 mm or more. [Figure 7D] 7D is a plan view (top) and a side view (bottom) showing an example (fourth embodiment) in which heat generating blocks are provided on both ends in the width direction of the recording medium in the heating member shown in FIG. 7C. [Figure 7E] 7B is a plan view (top) and a side view (bottom) showing an example (fifth embodiment) in which the Curie temperature of the second heat generation block is set higher than the Curie temperature of the first heat generation block in the heating member shown in FIG. 7D. [Figure 8] This is a chart showing the minimum difference when a fixed size in inches (11×17 vertical x 8.5×11 horizontal) is included in the chart shown in FIG. 3. [Figure 9A] 9A and 9B are a plan view (top) and a side view (bottom) showing a configuration example (first embodiment) in which the arrangement pitch of heat generating blocks is 9 mm when the minimum difference in length in the width direction of the recording medium shown in FIG. 8 is 9 mm. [Figure 9B] 9B is a plan view (top) and a side view (bottom) showing another example (second embodiment) of the heat generating block shown in FIG. 9A. [Figure 9C] 9C is a plan view (top) and a side view (bottom) showing an example (third embodiment) in which the difference in the length of each heat generation block in the width direction is set to 5 mm or more in the heating member shown in FIG. 9B. [Figure 9D] 9D is a plan view (top) and a side view (bottom) showing an example (fourth embodiment) in which heat generating blocks are provided on both ends in the width direction of the recording medium in the heating member shown in FIG. 9C. [Figure 9E] 9E is a plan view (top) and a side view (bottom) showing an example (fifth embodiment) in which the Curie temperature of the second heat generation block is set higher than the Curie temperature of the first heat generation block in the heating member shown in FIG. 9D. [Figure 10] This is a chart showing the minimum difference when a fixed size in inches (8.5×11 vertical x 5.5×8.5 ​​horizontal, 5.5×8.5 ​​vertical) is included in the chart shown in FIG. 8. [Figure 11A] 11A and 11B are a plan view (top) and a side view (bottom) showing a configuration example (first embodiment) in which the arrangement pitch of the heat generating blocks is 3 mm when the minimum difference in length in the width direction of the recording medium shown in FIG. 10 is 3 mm. [Figure 11B] 11B is a plan view (top) and a side view (bottom) showing another example (second embodiment) of the heat generating block shown in FIG. 11A. [Figure 11C] 11C is a plan view (top) and a side view (bottom) showing an example (third embodiment) in which heat generating blocks are provided on both ends in the width direction of the recording medium in the heating member shown in FIG. 11B. [Figure 11D] 11C, showing an example (fourth embodiment) in which the Curie temperature of the second heat generation block is set higher than the Curie temperature of the first heat generation block. FIG. [Figure 12] 1A and 1B are a plan view (top) and a side view (bottom) showing a schematic configuration of a single heat generating part in a heating member according to a reference example. [Figure 13] FIG. 11 is a plan view showing a schematic configuration of a plurality of heat generating blocks in a conventional heating member. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. In the following description, the same components are denoted by the same reference numerals. The names and functions of the components are also the same. Therefore, detailed description thereof will not be repeated.

[0024] [Image forming device] FIG. 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus 100 including a fixing device 4 according to the present embodiment.

[0025] Image forming apparatus 100 according to this embodiment is a multifunction machine having a copy function, a scanner function, a facsimile function and a printer function, and includes an image reading device 6. Image forming apparatus 100 transmits an image of an original document read by image reading device 6 to the outside, and forms an image of an original document read by image reading device 6 or an image received from the outside on a recording medium P such as recording paper. Note that image forming apparatus 100 is a monochrome image forming apparatus, but may also be a color image forming apparatus (specifically, a color multifunction machine).

[0026] The image reading device 6 scans a scanning optical system (not shown) to read an original placed on an original placement table (not shown), or reads an original conveyed by an original conveying device (not shown) to generate image data.

[0027] The image forming apparatus 100 includes an image forming section 1, a transfer device 2, a recording medium supplying device 3, a fixing device 4, and a discharge device 5, and the unfixed toner image is fixed onto the recording medium P by the fixing device 4.

[0028] The image forming unit 1 includes a photoconductor drum 11 (image carrier), a charging device 12, an exposure device 13 (optical scanning unit), a developing device 14, a toner supply container 15, a drum cleaning device 16, and a photoconductor discharge device 17.

[0029] An electrostatic latent image corresponding to image information is formed on the surface of photoreceptor drum 11. Photoreceptor drum 11 is supported by image forming apparatus main body 101 so as to be rotatable about an axis by a drive unit (drive motor) not shown. Photoreceptor drum 11 has a photosensitive layer, and acts as an image carrier that carries the electrostatic latent image, and therefore a toner image, on the surface of the photosensitive layer.

[0030] The photoreceptor drum 11 may be made of, for example, a conductive substrate made of aluminum or the like and a photosensitive layer formed on the surface of the conductive substrate. The conductive substrate may be cylindrical, columnar, or sheet-shaped, and among these, a cylindrical conductive substrate is preferably used. The photosensitive layer may be an organic photosensitive layer or an inorganic photosensitive layer.

[0031] The charging device 12 uniformly charges the surface of the photoconductor drum 11. The exposure device 13 irradiates the surface of the charged photoconductor drum 11 with laser light (signal light) corresponding to image information consisting of a digital signal, and forms an electrostatic latent image corresponding to the image information on the surface of the photoconductor drum 11. The developing device 14 supplies toner to the surface of the photoconductor drum 11 and develops the electrostatic latent image on the surface of the photoconductor drum 11 to form a toner image. The toner supply container 15 stores toner, and supplies toner to the developing tank in the developing device 14 depending on the toner consumption status in the developing device 14.

[0032] The transfer device 2 includes a transfer member 21 (a transfer roller in this example) that is rotatably driven around an axis by a drive unit (drive motor) not shown. The transfer member 21 transfers the toner image formed on the surface of the photosensitive drum 11 onto a recording medium P supplied by a recording medium supply device 3. The transfer device 2 transports the recording medium P bearing the toner image (unfixed toner image) to the fixing device 4.

[0033] The recording medium supplying device 3 includes recording medium cassettes 31a, 31b, and 31c, a pickup roller 32, a transport roller 34, and a registration roller 35. The recording medium cassettes 31a, 31b, and 31c store recording media P. Examples of the recording media P include plain paper, coated paper, paper for color copying, OHP film, and postcards. Here, the standard sizes of the recording media P in the centimeter system (for example, Japanese specifications, European specifications) include sizes defined in the A series and B series of ISO 216, such as A3, A4, B4, and B5, as well as sizes such as postcards. In addition, standard sizes of the recording medium P in inches (e.g., US specifications) include, for example, double letter size: 11 x 17 inches (279 x 432 mm), letter size: 8.5 x 11 inches (216 x 279 mm), half letter size: 5.5 x 8.5 inches (140 x 216 mm), etc.

[0034] The pickup roller 32 feeds the recording medium P one by one to the transport roller 34. The recording medium P stored in the recording medium cassette 31a is fed to the transport roller 34 by the pickup roller 32. The recording medium P stored in the recording medium cassette 31b is fed to the transport roller 34 through the recording medium receiving port 33a. The recording medium P stored in the recording medium cassette 31c is fed to the transport roller 34 through the recording medium receiving port 33b or the recording medium receiving port 33c. The transport roller 34 feeds the recording medium P to the registration roller 35. The registration roller 35 feeds the recording medium P to the transfer nip portion in synchronization with the timing at which the toner image on the photosensitive drum 11 is transported to the transfer nip portion, which is the contact portion between the photosensitive drum 11 and the transfer member 21.

[0035] The drum cleaning device 16 removes and collects the toner remaining on the surface of the photoreceptor drum 11 after the toner image on the surface of the photoreceptor drum 11 is transferred to the recording medium P. The photoreceptor charge eliminating device 17 eliminates charge on the surface of the photoreceptor drum 11 after the toner has been collected by the drum cleaning device 16.

[0036] The fixing device 4 heats and melts the unfixed toner image on the recording medium P conveyed from the transfer device 2, while applying pressure to fix the toner image to the recording medium P. The fixing device 4 also conveys the recording medium P with the fixed toner image to a discharge device 5.

[0037] The fixing device 4 includes a fixing belt 41 (an example of a fixing member), a heating member 42, and a pressure roller 43. The fixing belt 41, the heating member 42, and the pressure roller 43 will be described in detail later.

[0038] The discharge device 5 includes a conveying roller 51, a discharge roller 52, storage sections 53a and 53b, and a switching gate 54. The conveying roller 51 conveys the recording medium P conveyed from the fixing device 4 to the discharge roller 52. The discharge roller 52 discharges the recording medium P conveyed from the conveying roller 51 to the storage section 53a or the storage section 53b. The storage sections 53a and 53b store the recording medium P on which the toner image is fixed. The switching gate 54 selectively switches the discharge destination of the recording medium P conveyed by the discharge roller 52 to either the storage section 53a or the storage section 53b.

[0039] [Fixing device] FIG. 2 is a cross-sectional view showing a schematic configuration of an example of the fixing device 4 according to the present embodiment.

[0040] 2, the fixing device 4 includes a fixing member (e.g., a fixing roller or a fixing belt, fixing belt 41 in this example) supported rotatably about a rotation axis, a pressure member (pressure roller 43 in this example) that rotates in parallel with the fixing member while being pressed against it, a heating member 42 (heat source) that heats the fixing member (41), a power supply device (not shown) that supplies power to the heating member 42, a control device (not shown) that controls the power supply device, and a temperature detection unit 44 that detects the temperature of the surface of the fixing member (41). The fixing device 4 sandwiches the recording medium P to which the toner image has been transferred between the fixing member (41) and the pressure member (43) and applies heat and pressure to fix the toner image to the recording medium P.

[0041] Specifically, the fixing member is a fixing belt 41. The fixing belt 41 is an endless (annular) flexible belt. The fixing belt 41 is rotatable about a rotation axis along a direction (width direction W) perpendicular to the conveying direction T of the recording medium P.

[0042] An example of the fixing belt 41 is one in which an elastic layer (e.g., a silicone rubber layer) of a predetermined thickness (e.g., about 100 μm to 500 μm) is provided on a base material of a predetermined thickness (e.g., about 30 μm to 200 μm) made of a flexible heat-resistant material such as polyimide, and a release layer (e.g., a fluororesin layer) of a predetermined thickness (e.g., about 10 μm to 50 μm) is further formed thereon. Specifically, the fixing belt 41 can be one in which a PFA tube is provided on a silicone rubber layer, or one in which a fluororesin is applied. In this example, a 300 μm-thick silicone rubber layer is provided on a base material of an inner diameter of 30 mm and a thickness of 50 μm, and a 30 μm-thick PFA tube is further applied thereon.

[0043] The fixing belt 41 is heated by the heating member 42 to a predetermined fixing temperature (for example, 180° C.).

[0044] The heating member 42 includes a heat generating portion 421 (heater portion), a holding portion 422 (heater holder) that holds the heat generating portion 421, a reinforcing portion 423 (stay) that reinforces the holding portion 422, and a belt guide member 424. The heat generating portion 421, the holding portion 422, the reinforcing portion 423, and the belt guide member 424 are provided on the inner side of the fixing belt 41.

[0045] The fixing device 4 further includes a temperature detection unit 44 (thermistor) that detects the surface temperature of the fixing belt 41. The fixing device 4 controls the power supply to the heat generation unit 421 based on the detection result of the surface temperature of the fixing belt 41 by the temperature detection unit 44 so that the surface temperature of the fixing belt 41 becomes a predetermined fixing temperature (for example, 180° C.). The detailed configuration of the heat generation unit 421 will be described later.

[0046] The holding portion 422 is formed in a long plate shape extending in a width direction W (the direction of the rotation axis of the fixing belt 41) along the surface of the recording medium P perpendicular to the transport direction T of the transported recording medium P. The holding portion 422 is made of a heat-resistant material. The length of the holding portion 422 is longer than the length of the fixing belt 41 in the width direction W. The holding portion 422 is provided with a heat generating portion 421 that heats the fixing belt 41.

[0047] In detail, a seat for holding heat generating part 421 is provided on the heater mounting surface side of holding part 422, and heat generating part 421 is fitted into said seat for positioning. Examples of materials that can be used for holding part 422 include heat-resistant and insulating materials such as polyphenylene sulfide (PPS) and liquid crystal polymer (LCP).

[0048] The reinforcing portion 423 supports the holding portion 422 while pressing the heat generating portion 421 against the inner circumferential surface of the fixing belt 41. Both ends of the reinforcing portion 423 in the width direction W are fixed to a fixing frame (not shown). The reinforcing portion 423 is a substantially U-shaped stay provided on the surface of the holding portion 422 opposite to the attachment side of the heat generating portion 421, since the holding portion 422 is subjected to pressure from the pressure roller 43. The holding portion 422 is made of a metal member such as stainless steel.

[0049] The pressure roller 43 is disposed at a position facing the heat generating unit 421 with the fixing belt 41 interposed therebetween. The pressure roller 43 rotates about a rotation axis parallel to the rotation axis of the fixing belt 41 and extends parallel to the fixing belt 41. The pressure roller 43 presses the fixing belt 41 toward the heat generating unit 421 to form a fixing nip FN between the pressure roller 43 and the fixing belt 41. The pressure roller 43 may be configured as a roller member in which the surface of a cylindrical core material formed of a metal such as aluminum is covered with an elastic material such as rubber. The outer diameter of the pressure roller 43 is not limited to this, but is set to 25 mm in this example.

[0050] The pressure roller 43 is rotationally driven by a drive unit (drive motor) not shown. The pressure roller 43 is rotationally driven by receiving a driving force from the drive unit. The fixing belt 41 is rotated in accordance with the rotational drive of the pressure roller 43 in a predetermined rotation direction M. In other words, the pressure roller 43 forms a fixing nip portion FN by contacting with the surface of the fixing belt 41, and transmits a driving force to the fixing belt 41 via the fixing nip portion FN, thereby rotating the fixing belt 41.

[0051] The belt guide member 424 is disposed in an area of ​​the fixing belt 41 opposite to the fixing nip portion FN, and guides the area of ​​the fixing belt 41 opposite to the fixing nip portion FN.

[0052] Heat generating section 421 is provided so as to be in sliding contact with the inner circumferential surface of fixing belt 41. Fixing belt 41 is rotated in accordance with the rotational drive of pressure roller 43, and thereby slides against heat generating section 421. A lubricant may be applied between the surface of heat generating section 421 and the inner circumferential surface of fixing belt 41 to reduce frictional force.

[0053] The pressure roller 43 is supported at both ends in the direction of the rotation axis and is rotatably provided in a state in which a pressure mechanism (not shown) presses the fixing belt 41. The pressure roller 43 is rotated by receiving a driving force from a drive unit (drive motor) (not shown).

[0054] In this embodiment, the pressure roller 43 has a core metal, an elastic layer, and a surface layer. The core metal can be made of metal materials such as aluminum and iron. The elastic layer is provided on the outer peripheral surface of the core metal, and can be made of an elastic material such as silicone rubber or silicone sponge. The surface layer is provided on the outer peripheral surface of the elastic layer, and can be made of the same material as that of the surface layer of the fixing belt 41. In this example, the pressure roller 43 is a roller having an outer diameter of 25 mm, in which a silicone sponge layer having a thickness of 6 mm is provided as an elastic layer on the outer peripheral surface of a core metal having an outer diameter of 13 mm, and a PFA tube layer having a thickness of 30 μm is provided as a surface layer on the outer peripheral surface of the elastic layer.

[0055] (First embodiment) (First embodiment-1) Fig. 3 is a chart showing the lengths [L(1) to L(m)] (m is an integer of 2 or more, in this example m=6) in the width direction W of a recording medium P of a standard size in centimeters, and the minimum difference in length [d(3)=(L(4)-L(3)) / 2)=14mm] in the width direction W between recording media P, P of standard sizes [S(1),S(2)] to [S(m-1),S(m)] adjacent in length order in the width direction W. Fig. 4 is a plan view (top) and a side view (bottom) showing a configuration example (first embodiment) in which the arrangement pitch PT of heat generating blocks B(1) to B(n) (n is an integer of 2 or more) is 14mm when the minimum difference in length [L(1) to L(m)] in the width direction W of the recording medium P shown in Fig. 3 is 14mm [=d(3)=(L(4)-L(3)) / 2]. 5A to 5C are respectively a front view, a side view, and a plan view showing an enlarged portion of the heat generating blocks B(1) to B(n) in the heating member .

[0056] In this example, the image forming apparatus 100 transports the recording medium P based on the center in the width direction W of the standard size recording medium P (center reference C). Note that the image forming apparatus 100 may also transport the recording medium P based on one end of the standard size recording medium P in the width direction W (one-side reference).

[0057] The heating member 42 for heating the fixing member (in this example, the fixing belt 41) includes a plurality of heat generating blocks B(1) to B(n) that generate heat when energized. The plurality of heat generating blocks B(1) to B(n) are arranged in parallel along the width direction W.

[0058] In this embodiment, the heat generating blocks B(1) to B(n) have a positive temperature coefficient (PTC). That is, the heat generating blocks B(1) to B(n) are capable of self-temperature control, with resistance values ​​increasing when the temperature exceeds the Curie point, and a representative example is a PTC heater. In this example, the heat generating blocks B(1) to B(n) are made of a barium titanate (BaTiO3) base to which strontium titanate (SrTiO3) and lead titanate (PbTiO3) are added. The heat generating blocks B(1) to B(n) are shaped like a rectangular parallelepiped.

[0059] Here, there is a need to ensure safety in the event of runaway, such as by preventing the flow of electricity to the heating member 42 from being cut off. As a safety measure in the event of runaway, it is effective to use a heat generating block (PTC heater) that has a positive temperature coefficient and is capable of self-temperature control. Since the resistance value of a PTC heater increases significantly near the Curie temperature, it is not heated above the Curie temperature, so that safety in the event of runaway can be ensured, such as by preventing the flow of electricity to the heating member 42 from being cut off.

[0060] In this embodiment, the length in the width direction W of at least one (all or a part) of the multiple heat generating blocks B(1) to B(n) (in this example, all of the heat generating blocks B(1) to B(n)) is less than the minimum difference in length [L(1) to L(m)] in the width direction W between recording media P, P of adjacent standard sizes [S(1), S(2)] to [S(m-1), S(m)] in the order of length [L(1) to L(m)] in the width direction W among the multiple types of standard size recording media P being transported (d(3) = (L(4) - L(3)) / 2 = 14 mm in this example). In the example shown in FIG. 4, the lengths (1) to L(6) of each of the heat generating blocks B(1) to B(n) in the width direction W are all 13.5 mm [gap f (see FIG. 5B) = 0.5 mm], which is less than the minimum difference [d(3)] of 14 mm, and the number n of heat generating blocks B(1) to B(n) is 22.

[0061] According to this embodiment, the length e1 in the width direction W of at least one (all in this example) of the heat generating blocks B(1) to B(n) is set to the minimum difference [d(3) = (L(4) - L(3)) / 2 = 14 mm] or less (13.5 mm in this example). By doing so, at least one of the heat generating blocks B(1) to B(n) [B(3), B(7), B(16), B(20) in this example] can be made to have only the passing area α of the recording medium P without including the non-passing area β. In addition, even if any of the heat generating blocks B(1) to B(n) includes a non-passing area β, the number of heat generating blocks including the non-passing area β [B(1) to B(2), B(4) to B(6), B(8) to B(15), B(17) to B(19), B(21) to B(22) in this example] can be reduced, and the durability of the heating member 42 can be improved accordingly. Moreover, uniformity of the fixed image in the width direction W can be achieved.

[0062] Here, at least one (all or part) of the heat generating blocks B(1) to B(7), B(1) to B(8), and B(16) to B(n), or B(15) to B(n), all or all and part of which are located outside the smallest size recording medium P, which has the shortest length in the width direction W, among the recording media P of multiple types of standard sizes S(1) to S(m) (m=6), may be equal to or less than the minimum difference. By doing so, it is possible to reliably improve the durability of the heating member 42 outside the smallest size recording medium P.

[0063] Furthermore, the heat generating blocks B(9) to B(14) or B(8) to B(15) through which the recording medium P of the smallest size in the width direction W among the recording media P of multiple types of standard sizes S(1) to S(m) (m=6) passes in whole or in whole and in part may be a single heat generating block. Furthermore, the number of heat generating blocks below the minimum difference may be ⅓ or more of the total number of heat generating blocks, or ½ or more, or the total number of heat generating blocks. These also apply to the second to fourth embodiments described below.

[0064] 5A to 5C, the heating member 42 includes heat generating blocks B(1) to B(n) (PTC panel portion), an insulating substrate 42a, a first electrode 42b, a second electrode 42c, a first conductive wire portion 42d, and a second conductive wire portion 42e. The heat generating blocks B(1) to B(n) of the heating member 42 form a heat generating portion 421 (PTC heater portion).

[0065] The insulating substrate 42a is an elongated substrate extending in the width direction W. The length of the insulating substrate 42a is longer than the length of the fixing belt 41 in the width direction W and shorter than the length of the holding portion 422.

[0066] In this embodiment, of the first conductive wire portion 42d and the second conductive wire portion 42e for generating heat in the heat generating blocks B(1) to B(n), the first conductive wire portion 42d extends in the width direction W on the back surface facing the insulating substrate 42a, and the second conductive wire portion 42e extends in the width direction W on the front surface opposite the insulating substrate 42a.

[0067] This allows each of the heat generating blocks B(1) to B(n) to generate heat uniformly in the thickness direction, thereby enabling more accurate temperature control.

[0068] A first electrode 42b and a second electrode 42c for supplying power from both sides of the heat generating blocks B(1) to B(n) are formed on the entire back surface of each of the heat generating blocks B(1) to B(n) facing the insulating substrate 42a and the surface opposite the insulating substrate 42a, respectively. This allows each of the heat generating blocks B(1) to B(n) to generate heat when current is applied via the first electrode 42b and the second electrode 42c.

[0069] The first conductive wire portion 42d extending in the width direction W is formed at an end position on the downstream or upstream side (in this example, the downstream side) in the transport direction T of the region on the insulating substrate 42a where the heat generating blocks B(1) to B(n) are to be arranged. The second conductive wire portion 42e extending in the width direction W is formed at an end position on the downstream or upstream side (in this example, the upstream side) in the transport direction T of the heat generating blocks B(1) to B(n).

[0070] A raised portion 42f extending in the width direction W is formed at the end position on the upstream or downstream side (upstream side in this example) in the transport direction T of the area on the insulating substrate 42a where the heat generating blocks B(1) to B(n) are to be arranged.

[0071] The heat generating blocks B(1) to B(n) have a first conductive wire portion 42d provided on the insulating substrate 42a at an end portion on the downstream or upstream side (downstream side in this example) in the transport direction T of the back surface of the insulating substrate 42a, and a downstream or upstream side (downstream side in this example) end portion in the transport direction T of the back surface of the insulating substrate 42a provided on a raised portion 42f of the insulating substrate 42a.

[0072] The raised portion 42f may be substituted with a bonding agent such as cement or a heat-resistant adhesive that fixes the heat generating blocks B(1) to B(n) to the insulating substrate 42a.

[0073] The size of the first conductive wire portion 42d and the second conductive wire portion 42e in the transport direction T does not need to be larger than necessary as long as the current flowing due to energization can be tolerated, and may be smaller than the size of the heat generating blocks B(1) to B(n) in the transport direction T (preferably half, more preferably 1 / 3, and even more preferably 1 / 4 of the heat generating blocks) under conditions that ensure an allowable current.

[0074] The first conductive wire portion 42d extends beyond the end of one side (the heat generating block B(n) side in this example) of the heat generating blocks B(1) to B(n) in the width direction W. The second conductive wire portion 42e extends beyond the end of one side (the heat generating block B(n) side in this example) of the heat generating blocks B(1) to B(n) in the width direction W, and is bent toward the insulating substrate 42a to further extend outward in the width direction W on the insulating substrate 42a.

[0075] In the heating member 42, when power is supplied from a power source (not shown) to the first conductive wire portion 42d and the second conductive wire portion 42e, the heat generating blocks B(1) to B(n) generate heat and heat the fixing belt 41.

[0076] For example, in a configuration in which the insulating substrate 42a is disposed between the heat generating blocks B(1) to B(n) and the fixing belt 41, in order to heat the fixing belt 41 stably over a long period of time with high efficiency using the heat generated by the heat generating blocks B(1) to B(n), a sliding layer (in this example, a thin glass protective layer) may be provided on the sliding surface (inner peripheral surface) of the insulating substrate 42a against the fixing belt 41 in order to obtain a small heat capacity and high slidability. Furthermore, it is effective to apply a lubricant or the like between them. However, this is not limited to this, and slidability may be ensured by providing a film or tape having slidability on the surface of the insulating substrate 42a that slides against the fixing belt.

[0077] In this example, a first conductive line portion 42d is formed on an alumina substrate constituting an insulating substrate 42a by screen printing or the like using a conductive material such as silver, and a plurality of heat generating blocks B(1) to B(n) having first electrodes 42b and second electrodes 42c formed on both sides thereof are fixed in parallel in the width direction W (longitudinal direction).

[0078] In this example, as shown in Figures 5A to 5C, the heat generating blocks B(1) to B(n) have an arrangement pitch PT (see Figure 5B) of 14 mm, a length e1 (see Figure 5B) in the width direction W (longitudinal direction) of 13.5 mm, a gap f (see Figure 5B) between adjacent heat generating blocks [B(1), B(2)], [B(2), B(3)] to [B(20), B(21)], [B(21), B(n) (n=22 in this example)] of 0.5 mm, a distance e2 (see Figure 5C) in the transport direction T (short direction) of 8 mm, and a thickness h (see Figure 5A) of 1 mm. As a result, the fixing device 4 has a heat generating area of ​​about 308 mm in the width direction W (longitudinal direction) and can handle recording media P up to A4 horizontal size / A3 vertical size S (m). The heat generating blocks B(1) to B(n) and the insulating substrate 42a can be fixed together with cement or a heat-resistant adhesive.

[0079] As shown in Figure 4, at least one of the heat generating blocks B(1) to B(n) (n = 22) that is equal to or smaller than the minimum difference [B(3), B(7), B(20), B(16) in this example] is located between the ends of the recording media P, P of adjacent standard sizes [S(4), S(5)] and [S(1), S(2)]. This makes it possible to reduce the number of heat generating blocks [B(3), B(7), B(20), B(16) in this example] through which the ends of the recording media P to P of each standard size [S(1) to S(m)] pass, causing the temperature to become uneven.

[0080] In this embodiment, as shown in Fig. 4, the minimum difference in length [L(1) to L(m)] in the width direction W between adjacent recording media P, P of standard sizes [S(1),S(2)] to [S(m-1),S(m)] in the width direction W among the conveyed recording media P, P of standard centimeter sizes [S(1) to S(m) (m=6)] is 14 mm (see the hatched area in Fig. 3). Therefore, the length in the width direction W of the heating blocks B(1) to B(n) (n=22) that is less than the minimum difference can be 14 mm or less, more preferably 10 mm or less.

[0081] Although the gap f is set to 0.5 mm, the heat generating blocks B(1) to B(n) may be disposed without any gap. This also applies to the second to fourth embodiments described later.

[0082] In the example shown in Fig. 4, the heating member 42 is not in contact with the adjacent heat generating blocks [B(1), B(2)] to [B(21), B(22)]. Therefore, the heating member 42 has a length e1 of 13.5 mm in the width direction W of the heat generating blocks B(1) to B(22), a gap f between the adjacent heat generating blocks [B(1), B(2)] to [B(21), B(22)] of 0.5 mm, and an arrangement pitch PT of the heat generating blocks B(1) to B(22) of 14 mm. The heat generating blocks B(1) to B(22) are connected in parallel between the first conductive wire portion 42d and the second conductive wire portion 42e in an equivalent circuit.

[0083] As shown in FIG. 4, when a recording medium P of a standard centimeter size is transported with the center in the width direction W as the reference (center reference C), the minimum difference is 14 mm. Therefore, by setting the lengths in the width direction W of the heat generating blocks B(1) to B(22) that are less than the minimum difference to 14 mm or less (13.5 mm in this example, with a gap f=0.5 mm), it can be suitably adapted to the image forming apparatus 100 that transports recording media P to P of standard centimeter sizes [S(1), S(2)] to [S(m-1), S(m) (m=6)] with the center reference C.

[0084] (First embodiment-2) FIG. 6A is a plan view (top) and a side view (bottom) showing another example (second embodiment) of the heat generating blocks B(1) to B(n) (n=26 in this example) shown in FIG.

[0085] 6A shows an example in which the non-passage region β is not included in each of the heat generating blocks B(1) to B(n) (n=26) in the heating member 42 in the configuration shown in Fig. 4. Therefore, the end positions in the width direction W of the recording medium P of standard sizes S(1) to S(m) (m=6) coincide with the boundary positions of the heat generating blocks B(1) to B(26) and the end positions of the heat generating blocks B(1), B(26) at both ends.

[0086] In this embodiment, the length in the width direction W of at least one heat generating block [B(1), B(3), B(6), B(8), B(10), B(26), B(24), B(21), B(19), B(17)] among the multiple heat generating blocks B(1) to B(n) (n=26) is determined by the boundary position between adjacent heat generating blocks [B(1), B(2)], to [B(25), B(26)] and the heat generating blocks at both ends in the width direction W. The outer end positions of blocks B(1) and B(26) are located at the ends (both ends in this example) in the width direction W of recording media P of multiple standard sizes S(1) to S(m), so they differ from the constant (maximum) length (13.5 mm in this example) of the other heat generating blocks [B(2), B(4) to B(5), B(7), B(9), B(25), B(23) to B(22), B(20), B(18)] in the width direction W.

[0087] The length of the heat generating blocks in the constant width direction W between adjacent recording media P, P of standard sizes [S(1), S(2)] to [S(m-1), S(m)] is set as large as possible within the minimum difference [d(3)] (13.5 mm or less in this example). Also, the number of heat generating blocks with a constant (maximum) length (13.5 mm in this example) is set to be the greatest within each difference d(1) to d(m-1).

[0088] In the configuration shown in FIG. 6A, the ends in the width direction W of recording media P of standard sizes S(1) to S(m) are aligned with the joints between the heat generating blocks B(1) to B(26) and the ends of the heat generating blocks B(1), B(26) at both ends.

[0089] In this way, the heat generating blocks B(1) to B(26) can be made to have only the passing area α for the recording medium P without including the non-passing area β, thereby improving the durability of the heating member 42.

[0090] (First embodiment-3) However, if the length in the width direction W of the heat generating blocks B(1) to B(n) (n = 26) that is equal to or smaller than the minimum difference is less than 5 mm, it becomes difficult to assemble the heat generating blocks B(1) to B(n), and the assembly workability deteriorates.

[0091] In this regard, the heating member 42 according to the present embodiment (first embodiment-1) is configured as follows.

[0092] FIG. 6B is a plan view (top) and a side view (bottom) showing an example (third embodiment) of the heating member 42 shown in FIG. 6A in which the lengths in the width direction W of the heat generation blocks B(1) to B(n) (n=26) that are equal to or less than the minimum difference are set to 5 mm or more.

[0093] In the heating member 42 shown in Fig. 6B, the lengths in the width direction W of the heat generating blocks B(1)-B(26) that are equal to or smaller than the minimum difference are 5 mm or more. In this example, in the heating member 42 shown in Fig. 6A, the lengths in the width direction W of the heat generating blocks [B(6), B(7)], [B(21), B(20)] in the difference d(2) between recording media P, P including heat generating blocks whose lengths in the width direction W are smaller than 5 mm are made equal.

[0094] In the example shown in FIG. 6A, the lengths e1 of the heat generating blocks [B(6), B(7)], [B(21), B(20)] are 2.5 mm and 13.5 mm (gap f = 0.5 mm), respectively, whereas in the example shown in FIG. 6B, the lengths e1 of the heat generating blocks [B(6), B(7)], [B(21), B(20)] are all 8.0 mm (gap f = 0.5 mm), which is 5 mm or more.

[0095] This makes it possible to easily assemble the heat generating blocks B(1) to B(n), thereby improving the efficiency of the assembly work.

[0096] (First embodiment-4) Incidentally, like the heating member 42 shown in FIGS. 6A and 6B, it is possible not to provide heat generating blocks outside the heat generating blocks B(1) to B(n) (n=26) through which the recording medium P of the largest size (in this example, A4 horizontal size / A3 vertical size S(m)) that has the longest length in the width direction W among the recording media P of multiple types of standard sizes S(1) to S(m) (m=6) passes. In this case, however, the temperature at the end of the recording medium P in the width direction W is likely to decrease due to heat dissipation from the heat generating blocks B(1), B(n) (n=26) located at the end in the width direction W to the fixing member (fixing belt 41). This may result in poor fixing at the end of the recording medium P in the width direction W, making it difficult to ensure fixability.

[0097] In this regard, the heating member 42 according to this embodiment (first embodiment-2) is configured as follows.

[0098] FIG. 6C is a plan view (top) and a side view (bottom) showing an example (fourth embodiment) in which heat generating blocks B(1), B(n) (n=28) are provided at both ends in the width direction W of the recording medium P in the heating member 42 shown in FIG. 6B.

[0099] 4, 6A, and 6B (FIG. 6B in this example), one or more (one on each side in this example) heat generating blocks B(1), B(n) are present outside heat generating blocks B(2), B(n-1) (n=28) corresponding to the ends (at least one end, both ends in this example) in the width direction W of a recording medium P of a maximum size [S(m)] that has the longest length in the width direction W among recording media P of multiple types of standard sizes S(1) to S(m) (m=6). Here, the heat generating blocks B(2), B(n-1) corresponding to the ends in the width direction W of a recording medium P of a maximum size [S(m)] can be heat generating blocks through which more than half of a recording medium P of a maximum size [S(m)] passes.

[0100] This makes it possible to avoid a drop in temperature at the ends (both ends) in the width direction W of the recording medium P due to heat dissipation from the heat generating blocks B(1), B(n) located at the ends (both ends in this example) in the width direction W to the fixing member (fixing belt 41). Therefore, it is possible to effectively prevent poor fixing at the ends (both ends) in the width direction W of the recording medium P, thereby ensuring fixability.

[0101] (First embodiment-5) Fig. 6D is a plan view (top) and a side view (bottom) showing an example (fifth embodiment) in which the Curie temperatures of the second heat generating blocks [B(1)-B(10)] and [B(19)-B(n) (n=28)] are set higher than the Curie temperatures of the first heat generating blocks B(11)-B(18) in the heating member 42 shown in Fig. 6C. Fig. 6E is a graph showing the temperature distribution when the heating member 42 shown in Fig. 6D generates heat.

[0102] The heating member 42 shown in Fig. 6D is composed of first heat generating blocks B(11) to B(18) corresponding to the area through which a recording medium P of the smallest size (in this example, postcard length size S(1)) passes among the recording medium P of multiple types of standard sizes S(1) to S(m) (m = 6), and second heat generating blocks [B(1) to B(10)] and [B(19) to B(28)] other than the first heat generating blocks B(11) to B(18). Here, the first heat generating blocks B(11) to B(18) corresponding to the area through which the recording medium P passes refer to the heat generating blocks through which more than half of the recording medium P of the smallest size [S(1)] passes.

[0103] However, when the end (both ends in this example) of the recording medium P in the width direction W passes through the heating member 42 at the center reference C in the width direction W, a large temperature difference occurs between the first heat generating blocks B(11)-B(18) and the second heat generating blocks [B(1)-B(10)], [B(19)-B(28)]. When the temperature of the second heat generating blocks [B(1)-B(10)], [B(19)-B(28)] approaches the Curie temperature, the power is significantly reduced due to an increase in resistance. As a result, the temperature of the first heat generating blocks B(11)-B(18) on the inside adjacent to the second heat generating blocks [B(1)-B(10)], [B(19)-B(28)] also drops, making it difficult to stably maintain fixability in the width direction W.

[0104] In this regard, the heating member 42 according to this embodiment (first embodiment-3) is configured as follows.

[0105] In the heating member 42 shown in Figures 4, 6A, 6B, and 6C (Figure 6C in this example), the Curie temperature (e.g., 230°C to 270°C) of the second heat generating blocks [B(1) to B(10)] and [B(19) to B(28)] is higher than the Curie temperature (e.g., 220°C) of the first heat generating blocks B(11) to B(18) (see Figure 6E).

[0106] By doing so, even if the temperature of the second heat generating blocks [B(1)-B(10)], [B(19)-B(28)] rises to a certain degree, the increase in resistance value can be suppressed, and the supply of power can be maintained accordingly. Therefore, the temperature of the first heat generating blocks B(11)-B(18) can be maintained, and the fixability in the width direction W can be stably maintained.

[0107] 6D, the heat generation temperature of the second heat generation blocks [B(1)-B(10)], [B(19)-B(28)] may be 10°C to 50°C higher than the heat generation temperature of the first heat generation blocks B(11)-B(18). The heat generation temperature of the second heat generation blocks [B(1)-B(10)], [B(19)-B(28)] may actually be 30°C higher than the heat generation temperature of the first heat generation blocks B(11)-B(18). If the heat generation temperature exceeds 50°C, it is necessary to suppress the temperature of the high temperature region of the second heat generation blocks [B(1)-B(10)], [B(19)-B(28)] low when a recording medium P of a size [S(2)-S(m) (m=6)] wider than the recording medium P of the minimum size [S(1)] passes after the recording medium P of the minimum size [S(1)] passes.

[0108] 6D, it is preferable that the Curie temperature of the second heat generating blocks [B(1) to B(10)] and [B(19) to B(28)] is 10° C. or more higher than the Curie temperature of the first heat generating blocks B(11) to B(18). More preferably, it is 30° C. or more, and an upper limit of 50° C. can be exemplified as the upper limit of the temperature difference between the second heat generating blocks [B(1) to B(10)] and [B(19) to B(28)] and the first heat generating blocks B(11) to B(18).

[0109] By doing so, even if the temperatures of the second heat generating blocks [B(1)-B(10)], [B(19)-B(28)] rise to a certain degree, the increase in resistance value can be further suppressed, and the supply of power can be maintained accordingly. Therefore, the temperature of the first heat generating blocks B(11)-B(18) can be further maintained, and the fixability in the width direction W can be further stably maintained.

[0110] <Second embodiment> <Second embodiment-1> In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

[0111] FIG. 7A is a plan view (top) and a side view (bottom) showing a configuration example (first embodiment) in which the arrangement pitch PT of the heat generating blocks B(1) to B(n) (n=30) in the example shown in FIG. 4 is 10 mm.

[0112] In the present embodiment, the length in the width direction W of the heat generating blocks B(1) to B(n) (n=30) that is equal to or less than the minimum difference is set to 10 mm or less.

[0113] In this way, by setting the length in the width direction W of the heat generating blocks B(1) to B(n) below the minimum difference to 10 mm or less, it can be suitably used with the image forming device 100 that transports recording media P of standard centimeter sizes with a center reference C.

[0114] In the example shown in Fig. 7A, the heat generating blocks B(1) to B(n) (n = 30) are all arranged with a pitch PT (see Fig. 5B) of 10 mm, a length e1 (see Fig. 5B) in the width direction W (longitudinal direction) of 9.5 mm, a gap f (see Fig. 5B) between adjacent heat generating blocks [B(1), B(2)] to [B(29), B(n)] of 0.5 mm, a distance e2 (see Fig. 5C) in the transport direction T (short direction) of 8 mm, and a thickness h (see Fig. 5A) of 1 mm. As a result, the fixing device 4 has a heat generating area of ​​about 300 mm in the width direction W (longitudinal direction) and can handle recording media P up to A4 horizontal size / A3 vertical size S (m).

[0115] 7A, the length e1 of the heat generating blocks B(1) to B(n) in the width direction W is set to the minimum difference [d(3) = (L(4) - L(3)) / 2 = 14 mm] or less (9.5 mm in this example) (gap f = 0.5 mm). By doing so, at least one of the heat generating blocks B(1) to B(n) [B(2), B(4), B(7), B(9) to B(10), B(21) to B(22), B(24), B(27), B(29) in this example] can be made to be only the passing area α of the recording medium P without including the non-passing area β.

[0116] As shown in Fig. 7A, at least one of the heat generating blocks B(1) to B(n) (n = 30) [B(2), B(4), B(7), B(9) to B(10), B(21) to B(22), B(24), B(27), B(29) in this example] is located between the ends of the recording media P, P of adjacent standard sizes [S(m-1), S(m)], [S(4), S(5)], [S(2), S(3)], [S(1), S(2)]. This reduces the number of heat generating blocks [B(2), B(4), B(7), B(9) to B(10), B(29), B(27), B(24), B(22) to B(21) in this example] through which the ends of the recording media P to P of each standard size [S(1) to S(m)] pass and the temperature becomes uneven.

[0117] Specifically, adjacent heat generating blocks [B(1), B(2)] to [B(29), B(30)] of the heating member 42 are not in contact with each other. The heat generating blocks B(1) to B(30) are connected in parallel in an equivalent circuit between the first conductive wire portion 42d and the second conductive wire portion 42e.

[0118] As shown in FIG. 7A, when a recording medium P of a standard centimeter size is transported with the center in the width direction W as the reference (center reference C), the minimum difference is 14 mm. Therefore, by setting the length in the width direction W of the heat generating blocks B(1) to B(30) to be less than the minimum difference, 14 mm or less (9.5 mm in this example, gap f=0.5 mm), it can be suitably adapted to the image forming device 100 that transports recording media P of standard centimeter sizes [S(1), S(2)] to [S(m-1), S(m) (m=6)] with the center reference C.

[0119] <Second embodiment-2> FIG. 7B is a plan view (top) and a side view (bottom) showing another example (second embodiment) of the heat generating blocks B(1) to B(n) (n=34) shown in FIG. 7A.

[0120] The configuration shown in Figure 7B shows an example in which the configuration shown in Figure 7A does not include a non-passage region β in each of the heat generating blocks B(1) to B(n) (n = 34) in the heating member 42. Therefore, the end positions in the width direction W of the recording medium P of standard sizes S(1) to S(m) (m = 6) coincide with the boundary positions of the heat generating blocks B(1) to B(34) and the end positions of the heat generating blocks B(1), B(34) at both ends.

[0121] The length of the heat generating blocks in the constant width direction W between adjacent recording media P, P of standard sizes [S(1), S(2)] to [S(m-1), S(m)] is set as large as possible within the minimum difference [d(3)] (9.5 mm or less in this example). Also, the number of heat generating blocks with a constant (maximum) length (9.5 mm in this example) is set to be the greatest within each difference d(1) to d(m-1).

[0122] In the configuration shown in FIG. 7B, the ends in the width direction W of recording media P of standard sizes S(1) to S(m) (m=6) are aligned with the joints between the heat generating blocks B(1) to B(34) and the ends of the heat generating blocks B(1), B(34) at both ends.

[0123] In this way, the heat generating blocks B(1) to B(34) can be made to have only the passing area α for the recording medium P without including the non-passing area β, thereby improving the durability of the heating member 42.

[0124] <Second embodiment-3> FIG. 7C is a plan view (top) and a side view (bottom) showing an example (third embodiment) of the heating member 42 shown in FIG. 7B in which the lengths in the width direction W of the heat generation blocks B(1) to B(n) (n=34) that are equal to or less than the minimum difference are set to 5 mm or more.

[0125] In the heating member 42 shown in Fig. 7C, the length in the width direction W of the heat generating blocks B(1) to B(34) that are equal to or smaller than the minimum difference is 5 mm or more. In this example, in the heating member 42 shown in Fig. 7B, the lengths in the width direction W of the heat generating blocks [B(3), B(4), B(5)], [B(32), B(31), B(30)], [B(6), B(7)], [B(29), B(28)], [B(10), B(11), B(12)], [B(25), B(24), B(23)] in the difference d(4), d(3), d(1) between the recording media P, P including heat generating blocks whose length in the width direction W is smaller than 5 mm are made equal.

[0126] This makes it possible to easily assemble the heat generating blocks B(1) to B(n), thereby improving the efficiency of the assembly work.

[0127] <Second embodiment-4> FIG. 7D is a plan view (top) and a side view (bottom) showing an example (fourth embodiment) in which heat generating blocks B(1), B(n) (n=36) are provided at both ends in the width direction W of the recording medium P in the heating member 42 shown in FIG. 7C.

[0128] In the heating member 42 shown in Figures 7A, 7B, and 7C (Figure 7C in this example), one or more (one on each side in this example) heat generating blocks B(1), B(n) are present outside the heat generating blocks B(2), B(n-1) (n = 36) that correspond to the ends (both ends in this example) in the width direction W of a recording medium P of the maximum size [S(m)] of multiple types of standard sizes S(1) to S(m) (m = 6).

[0129] This makes it possible to avoid a drop in temperature at the ends (both ends) in the width direction W of the recording medium P due to heat dissipation from the heat generating blocks B(1), B(n) located at the ends (both ends in this example) in the width direction W to the fixing member (fixing belt 41). Therefore, it is possible to effectively prevent poor fixing at the ends (both ends) in the width direction W of the recording medium P, thereby ensuring fixability.

[0130] (Second embodiment-5) FIG. 7E is a plan view (top) and a side view (bottom) showing an example (fifth embodiment) in which the Curie temperatures of the second heat generating blocks [B(1) to B(13)] and [B(24) to B(n) (n=36)] in the heating member 42 shown in FIG. 7D are made higher than the Curie temperatures of the first heat generating blocks B(14) to B(23).

[0131] In the heating member 42 shown in Figures 7A to 7D (in this example, Figure 7D), the Curie temperature (e.g., 230°C to 270°C) of the second heat generating blocks [B(1) to B(13)] and [B(24) to B(36)] is higher than the Curie temperature (e.g., 220°C) of the first heat generating blocks B(14) to B(23).

[0132] By doing so, even if the temperature of the second heat generating blocks [B(1)-B(13)], [B(24)-B(36)] becomes relatively high, the increase in resistance value can be suppressed, and the power supply can be maintained accordingly. Therefore, the temperature of the first heat generating blocks B(14)-B(23) can be maintained, and the fixability in the width direction W can be stably maintained.

[0133] <Third embodiment> <Third embodiment-1> In the third embodiment, the same components as those in the first and second embodiments are denoted by the same reference numerals, and the description thereof will be omitted.

[0134] FIG. 8 is a chart showing the minimum difference [d(m-1)=(L(m)-L(m-1)) / 2=9 mm] (m=7) when a fixed inch size (11×17 vertical x 8.5×11 horizontal) is included in the chart shown in FIG. 3.

[0135] For example, as shown in Fig. 8, when a recording medium P of standard centimeter and inch sizes [S(1) to S(m) (m = 7)] is further conveyed with the center in the width direction W as the reference (center reference C) as the standard centimeter and inch sizes, 11 x 17 vertical or 8.5 x 11 horizontal [L(6) = 279 mm], the minimum difference d(6) is d(6) = (L(7) - L(6)) / 2 = 9 mm (see the shading in Fig. 8). Therefore, it is more desirable for the minimum difference to be 9 mm or less.

[0136] FIG. 9A is a plan view (top) and a side view (bottom) showing a configuration example (first embodiment) in which the arrangement pitch PT of the heat generating blocks B(1) to B(n) (n=34 in this example) is 9 mm when the minimum difference in length [L(1) to L(m) (m=7)] in the width direction W of the recording medium P shown in FIG. 8 is 9 mm [=d(6)=(L(7)-L(6)) / 2].

[0137] In the present embodiment, the length in the width direction W of the heat generating blocks B(1) to B(n) (n=34) that is equal to or less than the minimum difference is set to 9 mm or less.

[0138] In this way, by setting the length in the width direction W of the heat generating blocks B(1) to B(n) equal to or less than the minimum difference to 9 mm or less, it can be suitably used with the image forming device 100 that transports recording media P of standard centimeter and inch sizes with a center reference C.

[0139] In the example shown in Fig. 9A, the heat generating blocks B(1) to B(n) are arranged with a pitch PT (see Fig. 5B) of 9 mm, a length e1 (see Fig. 5B) in the width direction W (longitudinal direction) of 8.5 mm, a gap f (see Fig. 5B) between adjacent heat generating blocks [B(1), B(2)] to [B(33), B(n) (n = 34)] of 0.5 mm, a distance e2 (see Fig. 5C) in the transport direction T (short direction) of 8 mm, and a thickness h (see Fig. 5A) of 1 mm. As a result, the fixing device 4 has a heat generating area of ​​about 306 mm in the width direction W (longitudinal direction) and can handle recording media P with a maximum size of A4 landscape / A3 portrait S (m) (m = 7).

[0140] Specifically, adjacent heat generating blocks B(1), B(2) to B(33), B(34) are not in contact with each other in the heating member 42. The heat generating blocks B(1) to B(34) are connected in parallel in an equivalent circuit between the first conductive wire portion 42d and the second conductive wire portion 42e.

[0141] <Third embodiment-2> FIG. 9B is a plan view (top) and a side view (bottom) showing another example (second embodiment) of the heat generating blocks B(1) to B(n) (n=38) shown in FIG. 9A.

[0142] The configuration shown in Figure 9B shows an example in which the configuration shown in Figure 9A does not include a non-passage region β in each of the heat generating blocks B(1) to B(n) (n = 38) in the heating member 42. Therefore, the end positions in the width direction W of the recording medium P of standard sizes S(1) to S(m) (m = 7) coincide with the boundary positions of the heat generating blocks B(1) to B(38) and the end positions of the heat generating blocks B(1), B(38) at both ends.

[0143] The length of the heat generating blocks in the constant width direction W between adjacent recording media P, P of standard sizes [S(1), S(2)] to [S(m-1), S(m)] is set as large as possible within the minimum difference [d(3)] (8.5 mm or less in this example). Also, the number of heat generating blocks with a constant (maximum) length (8.5 mm in this example) is set to be the greatest within each difference d(1) to d(m-1).

[0144] In the configuration shown in FIG. 9B, the ends in the width direction W of recording media P of standard sizes S(1) to S(m) (m=7) are aligned with the joints between heat generating blocks B(1) to B(38) and the ends of heat generating blocks B(1), B(38) at both ends.

[0145] In this way, the heat generating blocks B(1) to B(38) can be made to have only the passing area α for the recording medium P without including the non-passing area β, thereby improving the durability of the heating member 42.

[0146] <Third embodiment-3> FIG. 9C is a plan view (top) and a side view (bottom) showing an example (third embodiment) in which the lengths in the width direction W of heat generation blocks B(1) to B(38) that are equal to or less than the minimum difference among the differences d(1) to d(m-1) (m=7) in the heating member 42 shown in FIG. 9B are 5 mm or more.

[0147] In the heating member 42 shown in Fig. 9C, the lengths in the width direction W of the heat generating blocks B(1) to B(38) that are equal to or smaller than the minimum difference are 5 mm or more. In this example, in the heating member 42 shown in Fig. 9B, the lengths in the width direction W of the heat generating blocks [B(2), B(3)], [B(37), B(36)], [B(7), B(8)], and [B(32), B(31)] in the difference d(5), d(3) between recording media P, P including heat generating blocks whose lengths in the width direction W are smaller than 5 mm are made equal.

[0148] This makes it possible to easily assemble the heat generating blocks B(1) to B(n), thereby improving the efficiency of the assembly work.

[0149] <Third embodiment-4> FIG. 9D is a plan view (top) and a side view (bottom) showing an example (fourth embodiment) in which heat generating blocks B(1), B(n) (n=40) are provided at both ends in the width direction W of the recording medium P in the heating member 42 shown in FIG. 9C.

[0150] In the heating member 42 shown in Figures 9A, 9B, and 9C (Figure 9C in this example), one or more (one on each side in this example) heat generating blocks B(1), B(n) are present outside the heat generating blocks B(2), B(n-1) (n=40) that correspond to the ends (both ends in this example) in the width direction W of a recording medium P of the maximum size [S(m)] of multiple types of standard sizes S(1) to S(m) (m=7).

[0151] This makes it possible to avoid a drop in temperature at the ends (both ends) in the width direction W of the recording medium P due to heat dissipation from the heat generating blocks B(1), B(n) located at the ends (both ends in this example) in the width direction W to the fixing member (fixing belt 41). Therefore, it is possible to effectively prevent poor fixing at the ends (both ends) in the width direction W of the recording medium P, thereby ensuring fixability.

[0152] (Third embodiment-5) FIG. 9E is a plan view (top) and a side view (bottom) showing an example (fifth embodiment) in which the Curie temperatures of the second heat generating blocks [B(1) to B(15)] and [B(27) to B(40)] in the heating member 42 shown in FIG. 9D are made higher than the Curie temperatures of the first heat generating blocks B(16) to B(26).

[0153] In the heating member 42 shown in Figures 9A to 9D (in this example, Figure 9D), the Curie temperature (e.g., 230°C to 270°C) of the second heat generating blocks [B(1) to B(14)] and [B(27) to B(40)] is higher than the Curie temperature (e.g., 220°C) of the first heat generating blocks B(15) to B(26).

[0154] By doing so, even if the temperature of the second heat generating blocks [B(1)-B(14)], [B(27)-B(40)] becomes relatively high, the increase in resistance value can be suppressed, and the power supply can be maintained accordingly. Therefore, the temperature of the first heat generating blocks B(15)-B(26) can be maintained, and the fixability in the width direction W can be stably maintained.

[0155] <Fourth embodiment> <Fourth embodiment-1> In the fourth embodiment, the same components as those in the first to third embodiments are denoted by the same reference numerals, and the description thereof will be omitted.

[0156] FIG. 10 is a chart showing the minimum difference [d(5) = (L(6) - L(5)) / 2 = 3 mm] when including fixed inch sizes (8.5 x 11 vertical x 5.5 x 8.5 horizontal, 5.5 x 8.5 vertical) in the chart shown in FIG. 8.

[0157] For example, as shown in Fig. 10, when a recording medium P of standard centimeter and inch sizes [S(1) to S(m) (m = 9)] is further conveyed with the center in the width direction W as the reference (center reference C) as the standard centimeter and inch sizes, 11 x 17 vertical size or 8.5 x 11 horizontal size [L(8) = 279 mm], 8.5 x 11 vertical size or 5.5 x 8.5 horizontal size [L(6) = 216 mm], or 5.5 x 8.5 vertical size [L(2) = 140 mm], the minimum difference d(5) is d(5) = (L(6) - L(5)) / 2 = 3 mm (see the shaded area in Fig. 10). Therefore, it is more preferable that the minimum difference is 3 mm or less.

[0158] FIG. 11A is a plan view (top) and a side view (bottom) showing a configuration example (first embodiment) in which the arrangement pitch PT of the heat generating blocks B(1) to B(n) (n = 100 in this example) is 3 mm when the minimum difference in length [L(1) to L(m) (m = 9)] in the width direction W of the recording medium P shown in FIG. 10 is 3 mm [= d(5) = (L(6) - L(5)) / 2].

[0159] In the present embodiment, the length in the width direction W of the heat generating blocks B(1) to B(n) (n=100) that is equal to or less than the minimum difference is set to 3 mm or less.

[0160] In this way, by setting the length in the width direction W of the heat generating blocks B(1) to B(n) below the minimum difference to 3 mm or less, it can be suitably used with the image forming device 100 that transports recording media P of standard centimeter and inch sizes with a center reference C.

[0161] In the example shown in Fig. 11A, the heat generating blocks B(1) to B(n) are arranged with a pitch PT (see Fig. 5B) of 3 mm, a length e1 (see Fig. 5B) in the width direction W (longitudinal direction) of 2.5 mm, a gap f (see Fig. 5B) between adjacent heat generating blocks [B(1), B(2)] to [B(99), B(n) (n = 100)] of 0.5 mm, a distance e2 (see Fig. 5C) in the transport direction T (short direction) of 8 mm, and a thickness h (see Fig. 5A) of 1 mm. As a result, the fixing device 4 has a heat generating area of ​​about 300 mm in the width direction W (longitudinal direction) and can handle recording media P with a maximum size of A4 landscape / A3 portrait S (m) (m = 9).

[0162] Specifically, adjacent heat generating blocks [B(1), B(2)] to [B(99), B(100)] of the heating member 42 are not in contact with each other. The heat generating blocks B(1) to B(100) are connected in parallel in an equivalent circuit between the first conductive wire portion 42d and the second conductive wire portion 42e.

[0163] <Fourth embodiment-2> FIG. 11B is a plan view (top) and a side view (bottom) showing another example (second embodiment) of the heat generating blocks B(1) to B(n) (n=104) shown in FIG. 11A.

[0164] The configuration shown in Fig. 11B shows an example in which the non-passage area β is not included in each of the heat generating blocks B(1) to B(n) (n = 104) in the heating member 42 in the configuration shown in Fig. 11A. Therefore, the end positions in the width direction W of the recording medium P of standard sizes S(1) to S(m) (m = 9) coincide with the boundary positions of the heat generating blocks B(1) to B(104) and the end positions of the heat generating blocks B(1), B(104) at both ends.

[0165] The length of the heat generating blocks in the constant width direction W between adjacent recording media P, P of standard sizes [S(1), S(2)] to [S(m-1), S(m)] is set as large as possible within the minimum difference [d(5)] (2.5 mm or less in this example). Also, the number of heat generating blocks with a constant (maximum) length (2.5 mm in this example) is set to be the greatest within each difference d(1) to d(m-1).

[0166] In the configuration shown in FIG. 11B, the ends in the width direction W of recording media P of standard sizes S(1) to S(m) (m=9) are aligned with the joints between the heat generating blocks B(1) to B(104) and the ends of the heat generating blocks B(1), B(104) at both ends.

[0167] In this way, the heat generating blocks B(1) to B(104) can be made to have only the passing area α for the recording medium P without including the non-passing area β, thereby improving the durability of the heating member 42 accordingly.

[0168] <Fourth embodiment-3> FIG. 11C is a plan view (top) and a side view (bottom) showing an example (third embodiment) in which heat generating blocks B(1), B(n) (n=106) are provided at both ends in the width direction W of the recording medium P in the heating member 42 shown in FIG. 11D.

[0169] In the heating member 42 shown in Figures 11A and 11B (Figure 11B in this example), one or more (one on each side in this example) heat generating blocks B(1), B(n) are present outside the heat generating blocks B(2), B(n-1) (n = 106) that correspond to the ends (both ends in this example) in the width direction W of a recording medium P of the maximum size [S(m)] of multiple types of standard sizes S(1) to S(m) (m = 9).

[0170] This makes it possible to avoid a drop in temperature at the ends (both ends) in the width direction W of the recording medium P due to heat dissipation from the heat generating blocks B(1), B(n) located at the ends (both ends in this example) in the width direction W to the fixing member (fixing belt 41). Therefore, it is possible to effectively prevent poor fixing at the ends (both ends) in the width direction W of the recording medium P, thereby ensuring fixability.

[0171] (Fourth embodiment-4) FIG. 11D is a plan view (top) and a side view (bottom) showing an example (fourth embodiment) in which the Curie temperatures of the second heat generating blocks [B(1) to B(36)] and [B(71) to B(106)] in the heating member 42 shown in FIG. 11C are made higher than the Curie temperatures of the first heat generating blocks B(16) to B(26).

[0172] In the heating member 42 shown in Figures 11A to 11C (in this example, Figure 11C), the Curie temperature (e.g., 230°C to 270°C) of the second heat generating blocks [B(1) to B(36)] and [B(71) to B(106)] is higher than the Curie temperature (e.g., 220°C) of the first heat generating blocks B(37) to B(70).

[0173] By doing so, even if the temperature of the second heat generating blocks [B(1)-B(36)], [B(71)-B(106)] becomes relatively high, the increase in resistance value can be suppressed, and the supply of power can be maintained. Therefore, the temperature of the first heat generating blocks B(37)-B(70) can be maintained, and the fixability in the width direction W can be stably maintained.

[0174] (Other embodiments) In the above-described example, a fixing belt is used as the fixing member, but a fixing roller may also be used.

[0175] <Example> Next, a durability experiment was carried out on the heating member 42 in the fixing device 4, and will be described below together with a reference example.

[0176] In Examples 1 to 3 and the reference example, the fixing device 4 used was equipped with a fixing belt 41 having a 300 μm thick silicone elastic layer on a 50 μm thick polyimide base material, and a 30 μm thick surface layer of PFA tubing, and a pressure roller 43 having a 6 mm thick silicone sponge layer as an elastic layer on the outer peripheral surface of a core metal with an outer diameter of 13 mm, and a 30 μm thick PFA tube layer as a surface layer further covering the outer peripheral surface of the elastic layer.

[0177] The paper feed conditions were A4 landscape / A3 portrait size [S(6)] and B5 landscape / B4 portrait size [S(5)], 1,000 sheets each, alternating for a total of 10,000 sheets.

[0178] <Example 1> 4, that is, a heating member 42 equipped with 22 heat generating blocks B(1) to B(22) arranged in a row (gap f: 0.5 mm, arrangement pitch PT: 14 mm) each having a width of 13.5 mm in the width direction W, was subjected to a paper passing aging test at a process speed of 180 mm / sec. The heat generating blocks B(1) to B(22) were made of barium titanate (BaTiO3) with lead titanate (PbTiO3) added.

[0179] <Reference example> FIG. 12 is a plan view (top) and a side view (bottom) showing a schematic configuration of a single heat generating portion 421Y in a heating member 42Y according to a reference example.

[0180] The heating member 42Y according to the reference example includes a single heat generating portion 421Y that generates heat when electricity is applied.

[0181] <Evaluation results of reference examples> In the reference example, a similar test was carried out using a single heat generating part 421Y shown in FIG. 12, and as a result, damage to the heating member 42Y, such as peeling off of the contact part of the heat generating part 421Y with the insulating substrate 42a, due to thermal damage was observed.

[0182] <Evaluation Results of Example 1> In contrast, in the case of the heating member 42 having the configuration shown in FIG. 4, no damage was observed in the members even after the end of the paper feed, and good images were obtained through aging.

[0183] Therefore, it was found that the durability of the heating member 42 could be improved compared to the heating member 42Y of the reference example.

[0184] <Example 2> In the heat generating blocks B(1) to B(22) shown in FIG. 4, although illustration is omitted, a paper passing test similar to that of Example 1 was conducted on a heating element 42 equipped with heat generating blocks B(1) to B(24), each of which was provided at both ends in the width direction W. As a result, an image similar to that of Example 1 was obtained through aging, and the heating element 42 after aging was in a better condition than that of Example 1.

[0185] In this way, by aligning the ends in the width direction W of the standard-size recording medium P with the joints between the heat generating blocks B(2) to B(23) and the ends of the heat generating blocks B(1), B(24) at both ends, it was found that it is possible to eliminate temperature unevenness within the heat generating blocks B(1) to B(24) and to realize a heating member 42 with higher durability.

[0186] <Example 3> Of the heat generating blocks B(1) to B(22) shown in FIG. 4, although not shown in the figure, one heat generating block B(1) and one heat generating block B(24) are provided at each end in the width direction W. Furthermore, the Curie temperature of the first heat generating blocks B(10) to B(15) are adjusted to 220°C, and by increasing the composition ratio of lead titanate (PbTiO3) in the second heat generating blocks B(1) to B(9), B(16) to B(24) on the outside, the Curie temperature of the second heat generating blocks B(1) to B(9), B(16) to B(24) is adjusted to 250°C.

[0187] When 100 sheets of postcard length size [S(1)], the smallest size [S(1)], were passed through heating member 42 equipped with second heat generating blocks B(1)-B(9), B(16)-B(24), which have a Curie temperature of 250°C higher than the Curie temperature of first heat generating blocks B(10)-B(15), 220°C, there were no problems. Furthermore, even when 1,000 sheets of A4 length size recording medium P were passed through, the temperature at the end of recording medium P in the width direction W could be maintained due to the effect of raising the Curie temperature of second heat generating blocks B(0)-B(8), B(15)-B(23), and good fixed images could be obtained.

[0188] The present disclosure is not limited to the above-described embodiments, and can be implemented in various other forms. Therefore, the embodiments are merely illustrative in all respects and should not be interpreted as being limited. The scope of the present disclosure is indicated by the claims, and is not restricted in any way by the text of the specification. Furthermore, all modifications and changes within the scope of the claims are within the scope of the present disclosure. [Explanation of symbols]

[0189] 100 Image forming device 4 Fixing device 41 Fixing belt 42 Heating element 421 Heating Part 422 Holding part 423 Reinforcement 424 Belt guide member 42a Insulating substrate 42b 1st electrode 42c 2nd electrode 42d First conductive wire section 42e Second conductive wire section 42f Raised section 43 Pressure roller 44 Temperature detection unit B Heating block C Center Standards P Recording medium PT arrangement pitch S Standard size T Transport direction W Width direction d difference e1 Length in the width direction e2 Distance in conveying direction f Gap h Thickness α passing region β non-passing region

Claims

1. A heating member for heating the fixing member, Equipped with multiple heat generating blocks that generate heat when electricity is applied, The plurality of heat generating blocks are arranged in parallel along a width direction perpendicular to a conveying direction of the recording medium, A heating member characterized in that the length in the width direction of at least one of the multiple heat generating blocks is less than or equal to the minimum difference in length in the width direction between adjacent recording media of the standard sizes in length order in the width direction among the multiple types of recording media of standard sizes being transported.

2. The heating element according to claim 1 , A heating member, characterized in that at least one of the heat generating blocks having a difference equal to or less than the minimum difference is located between ends of the adjacent recording media of the standard size.

3. The heating element according to claim 1 , A heating member, characterized in that the length in the width direction of the heat generating block that is equal to or smaller than the minimum difference is 14 mm or less.

4. The heating element according to claim 1 , A heating member characterized in that the length in the width direction of at least one of the multiple heat generating blocks is different from the constant length in the width direction of the other heat generating blocks so that the boundary positions between adjacent heat generating blocks and the outer end positions of the heat generating blocks at both ends in the width direction are positioned at the ends in the width direction of the recording media of the multiple types of standard sizes.

5. The heating element according to claim 1 , A heating member characterized in that the length in the width direction of the heat generating block that is equal to or smaller than the minimum difference is 5 mm or more.

6. The heating element according to claim 1 , A heating member characterized in that one or more heat generating blocks are present outside the heat generating block corresponding to the end in the width direction of a maximum size recording medium among the multiple types of standard sizes of recording media.

7. The heating element according to claim 1 , The plurality of heat generating blocks have a positive temperature characteristic, a first heat generating block corresponding to an area through which a recording medium of a smallest size, which has the smallest length in the width direction among the recording media of the plurality of types of standard sizes, passes, and a second heat generating block other than the first heat generating block, A heating member, characterized in that the Curie temperature of the second heat generating block is higher than the Curie temperature of the first heat generating block.

8. The heating element according to claim 7, A heating member, characterized in that the Curie temperature of the second heat generating block is 10° C. or more higher than the Curie temperature of the first heat generating block.

9. The heating element according to claim 1 , A heating member, characterized in that the length in the width direction of the heat generating block that is equal to or smaller than the minimum difference is 9 mm or less.

10. The heating element according to claim 1 , A heating member characterized in that at least one of the heat generating blocks, which is located entirely or entirely and partially outside the smallest size recording medium, which has the shortest length in the width direction, among the multiple types of standard sizes of recording media, is less than the minimum difference.

11. A fixing device comprising the heating member according to any one of claims 1 to 10.

12. An image forming apparatus comprising the fixing device according to claim 11.

Images