Fixation device and image formation apparatus

Abstract

To equalize the heat distribution of multiple heating elements that are independently controllable.SOLUTION: A fixation device 200 includes: a heating element 620-1 and a heating element 620-2 which heat a region 1, a region 21, and a region 22 on the inner side in a longitudinal direction and are continuously provided in the longitudinal direction; a heating element 620-31 and a heating element 620-32 which are provided at different positions from those of the heating element 620-1 and the heating element 620-2 of a substrate 207 in a conveyance direction, heat a region 31, a region 32, a region 41 and a region 42 on the outer side relative to the region 1, the region 21 and the region 22 heated by the heating element 620-1 and the heating element 620-2 in the longitudinal direction and are divided in a region overlapping the heating element 620-1 and the heating element 620-2; and a heating element 620-41 and a heating element 620-42.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a fixing device that fixes a toner image formed on a recording material to the recording material by heat and pressure, and to an image forming apparatus equipped with the fixing device. [Background technology]

[0002] In recent years, there has been a demand for a fixing device provided in an image forming apparatus to shorten the warm-up time due to rapid temperature rise and to be able to handle a variety of sizes of paper. One possible way to shorten the warm-up time is to reduce the thermal capacity of the fixing heater. However, in a fixing heater that has only a heating element with a length that matches the maximum width of the paper, if the thermal capacity of the fixing heater is reduced, the temperature of the non-paper passing area becomes too high compared to the paper passing area.

[0003] In response to this, Patent Document 1 discloses a heater (hereinafter referred to as a "split heater") that has heat generating regions that can be independently controlled according to the width of the paper. In the split heater of Patent Document 1, multiple heat generating elements with different lengths in the longitudinal direction are arranged in parallel in the lateral direction, and the power supply to each is controlled according to the width of the paper to suppress the temperature rise in the non-paper passing area. In such a split heater, it is necessary to make the heat amount per unit length uniform in order to make the heat distribution of the heater uniform. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-86277 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in conventional split heaters, the heating elements are connected in parallel to a power source, and the longitudinal lengths of the heating elements are significantly different, so the resistance value per unit length of each heating element is significantly different. Specifically, when the longitudinal length of the heating element is short, the resistance value per unit length is large, and when the longitudinal length of the heating element is long, the resistance value per unit length is small. When the resistance values ​​per unit length of each heating element are significantly different in this way, the composition of the materials constituting each heating element is different, so that the TCR (temperature coefficient of resistance) is different, and there is a problem that the heat distribution of each heating element within the paper passing width is not uniform.

[0006] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a fixing device and an image forming apparatus capable of uniformizing the heat distribution of a plurality of independently controllable heat generating elements. [Means for solving the problem]

[0007] The fixing device of the present invention is a fixing device that fixes a toner image formed on a recording material to the recording material by heat and pressure, and is characterized in that it has a fixing belt, a pressure roller that is pressed against the fixing belt to form a fixing nip portion that, together with the fixing belt, pinches and transports the recording material, a substrate whose longitudinal direction is perpendicular to the transport direction of the recording material, and a fixing heater that heats the toner image in the fixing nip portion, and the multiple heating elements are provided on the substrate and have different lengths along the longitudinal direction, and the multiple heating elements include an inner heating element that heats an inner region in the longitudinal direction and is provided continuously in the longitudinal direction, and an outer heating element that is provided at a position different from the inner heating element on the substrate in the transport direction, heats a region outer than the inner heating element in the longitudinal direction, and is divided at intervals in the region overlapping with the inner heating element. Effect of the Invention

[0008] According to the present invention, it is possible to make the heat distribution of a plurality of independently controllable heating elements uniform. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of an image forming apparatus according to an embodiment of the present invention; [Diagram 2] 1 is a schematic cross-sectional view of a fixing device according to an embodiment of the present invention. [Diagram 3] 2 is a schematic plan view of a fixing device according to an embodiment of the present invention; [Figure 4] 5 is a diagram showing characteristics of a fixing heater of the fixing device according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0011] <Configuration of Image Forming Apparatus> The configuration of an image forming apparatus 100 according to an embodiment of the present invention will be described in detail with reference to FIG.

[0012] Here, a printer is exemplified as the image forming apparatus 100. The image forming apparatus 100 includes photoconductor drums 101y, 101m, 101c, and 101k, primary charging rollers 102y, 102m, 102c, and 102k, and laser units 103y, 103m, 103c, and 103k. The image forming apparatus 100 also includes developing sleeves 104y, 104m, 104c, and 104k, primary transfer rollers 105y, 105m, 105c, and 105k, photoconductor cleaners 106y, 106m, 106c, and 106k, and an intermediate transfer belt 107.

[0013] The image forming apparatus 100 also has a secondary transfer roller 108, an intermediate transfer belt cleaner 110, a paper cassette 111, a pickup roller 112, a paper feed roller 113, and a registration roller 114. The image forming apparatus 100 also has a conveying roller 115, a conveying roller 116, a conveying roller 117, a conveying roller 118, an operation unit 119, and a fixing device 200.

[0014] The photoconductor drum 101y, the primary charging roller 102y, the laser unit 103y, the developing sleeve 104y, and the primary transfer roller 105y constitute a yellow image forming section. The photoconductor drum 101m, the primary charging roller 102m, the laser unit 103m, the developing sleeve 104m, and the primary transfer roller 105m constitute a magenta image forming section. The photoconductor drum 101c, the primary charging roller 102c, the laser unit 103c, the developing sleeve 104c, and the primary transfer roller 105c constitute a cyan image forming section. The photoconductor drum 101k, the primary charging roller 102k, the laser unit 103k, the developing sleeve 104k, and the primary transfer roller 105k constitute a black image forming section.

[0015] The photoconductor drums 101y, 101m, 101c, and 101k rotate in a counterclockwise direction in FIG.

[0016] The primary charging rollers 102y, 102m, 102c, and 102k uniformly charge the surfaces of the photoconductor drums 101y, 101m, 101c, and 101k.

[0017] The laser units 103y, 103m, 103c, and 103k irradiate and expose the uniformly charged surfaces of the photoconductor drums 101y, 101m, 101c, and 101k with a laser. The laser units 103y, 103m, 103c, and 103k expose the surfaces of the photoconductor drums 101y, 101m, 101c, and 101k to light, thereby drawing latent images on the surfaces of the photoconductor drums 101y, 101m, 101c, and 101k.

[0018] The developing sleeve 104y develops the latent image on the photoconductor drum 101y with yellow toner as the surface of the photoconductor drum 101y passes over it. The developing sleeve 104m develops the latent image on the photoconductor drum 101m with magenta toner as the surface of the photoconductor drum 101m passes over it. The developing sleeve 104c develops the latent image on the photoconductor drum 101c with cyan toner as the surface of the photoconductor drum 101c passes over it. The developing sleeve 104k develops the latent image on the photoconductor drum 101k with black toner as the surface of the photoconductor drum 101k passes over it.

[0019] When a voltage is applied to the primary transfer roller 105y, the yellow toner that was on the surface of the photoconductor drum 101y is transferred to the surface of the intermediate transfer belt 107. When a voltage is applied to the primary transfer roller 105m, the magenta toner that was on the surface of the photoconductor drum 101m is transferred to the surface of the intermediate transfer belt 107. When a voltage is applied to the primary transfer roller 105c, the cyan toner that was on the surface of the photoconductor drum 101c is transferred to the surface of the intermediate transfer belt 107. When a voltage is applied to the primary transfer roller 105k, the black toner that was on the surface of the photoconductor drum 101k is transferred to the surface of the intermediate transfer belt 107.

[0020] The photoconductor cleaners 106y, 106m, 106c, and 106k scrape and collect the toner remaining on the photoconductor drums 101y, 101m, 101c, and 101k.

[0021] The intermediate transfer belt 107 rotates in a clockwise direction in Fig. 1. On the intermediate transfer belt 107, a full-color image is formed by yellow, magenta, cyan and black toners transferred from the photoconductor drums 101y, 101m, 101c and 101k.

[0022] The secondary transfer rollers 108 pinch and transport the recording material P that is contained in the paper cassette 111 and fed and transported, thereby transferring the full-color image formed on the intermediate transfer belt 107 onto the surface of the recording material P. The secondary transfer rollers 108 transport the recording material P with the full-color image transferred thereto to the fixing device 200.

[0023] The paper cassette 111 accommodates the recording material P.

[0024] A pickup roller 112 feeds a recording material P stored in a paper cassette 111 to a paper feed roller 113 at a predetermined timing.

[0025] The paper feed roller 113 is provided to prevent double feeding of the recording materials P. The paper feed roller 113 separates the recording materials P fed by the pickup roller 112 one by one and feeds them to the registration roller 114.

[0026] The registration roller 114 is provided to prevent skewing of the recording material P. The registration roller 114 conveys the recording material P fed by the paper feed roller 113 to the secondary transfer roller 108 in accordance with the timing at which the four-color toner image conveyed by the intermediate transfer belt 107 passes through the secondary transfer roller 108.

[0027] The conveying roller 115 conveys the recording material P conveyed by the fixing device 200 to the conveying roller 116 .

[0028] The conveying roller 116 conveys the recording material P conveyed by the conveying roller 115 to the conveying roller 117 .

[0029] The conveying roller 117 conveys the recording material P conveyed by the conveying roller 116 to the conveying roller 118 .

[0030] The conveying roller 118 discharges the recording material P conveyed by the conveying roller 117 to the outside of the image forming apparatus 100. In this way, the recording material P on which a color image is formed can be obtained.

[0031] An operation unit 119 outputs a signal corresponding to a user's operation to a control unit (not shown).

[0032] The fixing device 200 heats the recording material P conveyed by the secondary transfer roller 108 at a high temperature to melt the toner on the recording material P, and then applies pressure to the recording material P to fix the toner image formed on the surface of the recording material P to the recording material P. The fixing device 200 conveys the recording material P with the fixed toner image toward the outside of the image forming apparatus 100. The configuration of the fixing device 200 will be described in detail later.

[0033] In the image forming apparatus 100 having the above-mentioned configuration, a control unit (not shown) controls the image forming operation in accordance with a signal input from the operation unit 119 or via a network.

[0034] <Configuration of the fixing device> The configuration of the fixing device 200 according to the embodiment of the present invention will be described in detail with reference to FIGS.

[0035] The fixing device 200 includes a fixing heater unit 201, a pressure roller 202, a switch 622-1, a switch 622-2, a switch 622-3, a switch 622-4, and a power source 623.

[0036] The fixing heater unit 201 is provided above the pressure roller 202 , and includes a fixing heater 203 , a heater holder 204 , a reinforcing metal plate 205 , a fixing film 206 , a thermistor 211 , and a thermostat 212 .

[0037] The fixing heater 203 is a heat source and heating element for heating the recording material P. The fixing heater 203 is supported and fixed by a heater holder 204. The fixing heater 203 has a lower surface which is pressed against the pressure roller 202 with a predetermined pressing force through a fixing film 206 against the elastic force of the elastic layer of the pressure roller 202, thereby forming a fixing nip portion N of a predetermined width required for fixing a toner image. The configuration of the fixing heater 203 will be described in detail later.

[0038] The heater holder 204 has a semicircular barrel-shaped cross section and is a support that supports the fixing heater 203. The heater holder 204 is made of a liquid crystal polymer resin with high heat resistance, and plays a role of holding the fixing heater 203 and guiding the fixing film 206. Both ends of the heater holder 204 in the longitudinal direction are urged in the axial direction of the pressure roller 202 with a total pressure of 90 to 320 N by a pressure mechanism (not shown). By being urged in the axial direction of the pressure roller 202, the heater holder 204 presses the lower surface of the fixing heater 203 with a predetermined pressure against the elastic force of the elastic layer of the pressure roller 202 via the fixing film 206.

[0039] The reinforcing sheet metal 205 has an inverted U-shaped cross section, and is provided to prevent the fixing heater unit 201 from being deformed when the fixing heater unit 201 is pressed by the pressure roller 202 .

[0040] The fixing film 206 serving as a fixing belt has a cylindrical shape. Grease is applied to the inner surface of the fixing film 206 to improve the sliding property between the heater holder 204 and the inner surface of the fixing film 206. The fixing film 206 is formed by providing a silicone rubber layer (elastic layer) having a thickness of about 300 μm by ring coating on a cylindrical stainless steel substrate having a thickness of 30 μm. The fixing film 206 covers the silicone rubber layer with a PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) resin tube having a thickness of 20 μm.

[0041] As the pressure roller 202 rotates, the fixing film 206 slides against the fixing heater 203 while being in close contact with it, and rotates around the heater holder 204. Note that the base material of the fixing film 206 is not limited to stainless steel, and may be a nickel-based metal material or a heat-resistant resin such as polyimide.

[0042] The thermistor 211 is disposed on the upper surface in FIG. 2, which is the non-heated surface, as opposed to the lower surface in FIG. 2, which is the heated surface of the fixing heater 203, and serves the function of detecting the temperature of the fixing heater 203.

[0043] The thermostat 212 is a switch in which the bimetal is reversed and the contacts are opened when a predetermined temperature is reached, and has the function of cutting off the power supply to the fixing heater 203 when the temperature of the fixing heater 203 exceeds the predetermined temperature.

[0044] The pressure roller 202 is a pressure member provided below the fixing heater unit 201, and has a multi-layer structure in which an elastic silicone rubber layer 213 and a PFA resin tube 214 are laminated in this order on a stainless steel core 210. Both ends of the core 210 in the longitudinal direction of the pressure roller 202 are rotatably supported by bearings between side plates of an apparatus frame (not shown). The pressure roller 202 is driven to rotate in the counterclockwise direction in FIG. 2, which is the conveying direction of the recording material P, by a drive system (not shown).

[0045] The switch 622-1 opens and closes under the control of a control unit (not shown) to connect or disconnect the power source 623 and an electrode 621-1 (described later) of the fixing heater 203.

[0046] The switch 622-2 opens and closes under the control of a control unit (not shown) to connect or disconnect the power source 623 and an electrode 621-2 (described later) of the fixing heater 203.

[0047] The switch 622-3 opens and closes under the control of a control unit (not shown) to connect or disconnect the power source 623 and an electrode 621-3 (described later) of the fixing heater 203.

[0048] The switch 622-4 opens and closes under the control of a control unit (not shown) to connect or disconnect the power source 623 and an electrode 621-4 (described later) of the fixing heater 203.

[0049] A power supply 623 supplies power to electrodes 621-1, 621-2, 621-3, 621-4, and 621-5 of the fixing heater 203, which will be described later.

[0050] <Configuration of the fixing heater> The configuration of the fixing heater 203 of the fixing device 200 according to the embodiment of the present invention will be described in detail with reference to FIGS.

[0051] The fixing heater 203 includes a substrate 207, a protective glass 209, a heating element 620-1, a heating element 620-2, a heating element 620-31, a heating element 620-32, a heating element 620-41, a heating element 620-42, and an electrode 621-1. The fixing heater 203 also includes an electrode 621-2, an electrode 621-3, an electrode 621-4, and an electrode 621-5. In addition, in FIG. 2, the heating elements 620-1, 620-2, 620-31, 620-32, 620-41, and 620-42 are collectively referred to as a heating element 620.

[0052] Here, the fixing heater 203 is provided with four systems of heat elements, namely, a heat element 620-1, a heat element 620-2, a heat element 620-31 and a heat element 620-32, and a heat element 620-41 and a heat element 620-42.

[0053] The substrate 207 has a longitudinal direction perpendicular to the conveying direction of the recording material P (perpendicular to the paper surface in FIG. 2 and left-right direction in FIG. 3). The substrate 207 is made of a material having insulating, heat-resistant and low heat capacity properties, such as ceramics such as alumina or aluminum nitride. The substrate 207 may be provided with a polyimide layer having a thickness of about 10 μm as a sliding layer on the contact surface side with the fixing film 206 in order to reduce the sliding resistance between the fixing film 206 and the fixing heater 203, reduce the driving torque, and prevent wear on the inner surface of the fixing film 206. The polyimide layer provided as a sliding layer on the substrate 207 is not necessary when a heat-resistant resin such as polyimide is used as the base material of the fixing film 206.

[0054] The protective glass 209 has a thickness of 60 to 90 μm. The protective glass 209 covers the heating elements 620-1, 620-2, 620-31, 620-32, 620-41, and 620-42. The protective glass 209 ensures insulation of the heating elements 620-1, 620-2, 620-31, 620-32, 620-41, and 620-42.

[0055] Heating element 620-1 as a first inner heating element is provided by printing and baking on one surface of substrate 207, and is made of silver palladium (Ag / Pd) or the like. Heating element 620-1 is provided continuously in the longitudinal direction, and has a symmetrical shape with respect to central cross section AA, which is the central position in the longitudinal direction of substrate 207 shown in FIG.

[0056] The length of the heat generating element 620-1 in the longitudinal direction is equal to the sum of the length of the heat generating element 620-41 and the length of the heat generating element 620-42 in the longitudinal direction. The length of the heat generating element 620-1 in the longitudinal direction is different from the length of the heat generating element 620-2 in the longitudinal direction, and is different from the sum of the length of the heat generating element 620-31 and the length of the heat generating element 620-32 in the longitudinal direction. The heat generating element 620-1 heats an inner region 1 in the longitudinal direction. Here, the region 1 is a region that needs to be heated when heating the recording material P of width W1, width W2, width W3, or width W4.

[0057] Heating element 620-2 as the second inner heating element is provided by printing and baking on one surface of substrate 207, and is made of silver palladium (Ag / Pd) or the like. Heating element 620-2 is provided continuously in the longitudinal direction, and has a shape symmetrical with respect to central cross section AA shown in FIG.

[0058] The length of the heat generating element 620-2 in the longitudinal direction is different from the length of the heat generating element 620-1 in the longitudinal direction, the sum of the longitudinal lengths of the heat generating elements 620-31 and 620-32, and the sum of the longitudinal lengths of the heat generating elements 620-41 and 620-42. The heat generating element 620-2 heats the region 1, region 21, and region 22 on the inside in the longitudinal direction, and also heats the region 21 and region 22 on the outside in the longitudinal direction of the region 1 heated by the heat generating element 620-1. Here, the region 21 and region 22 are regions that need to be heated when heating the recording material P of width W2, width W3, or width W4.

[0059] The heating element 620-31 is provided on one surface of the substrate 207 by printing and baking, and is made of silver palladium (Ag / Pd) or the like. The longitudinal length of the heating element 620-31 is the same as the longitudinal length of the heating element 620-32. The heating element 620-31 heats the region 21 and the region 31 outside the region 1 heated by the heating element 620-1 in the longitudinal direction, and heats the region 31 outside the region 1 and the region 21 heated by the heating element 620-2 in the longitudinal direction. Here, the region 31 is a region that needs to be heated when heating the recording material P having the width W3 or the width W4.

[0060] The heating element 620-32 is provided on one surface of the substrate 207 by printing and baking, and is made of silver palladium (Ag / Pd) or the like. The longitudinal length of the heating element 620-32 is the same as the longitudinal length of the heating element 620-31. The heating element 620-32 has a shape symmetrical to the heating element 620-31 with respect to the central cross section AA shown in Fig. 3. The heating element 620-32 is connected to the heating element 620-31 via a conductive pattern of silver (Ag) or the like.

[0061] The heating element 620-32 heats the region 22 and the region 32 which are located outside the region 1 heated by the heating element 620-1 in the longitudinal direction, and also heats the region 32 which is located outside the region 1 and the region 22 heated by the heating element 620-2 in the longitudinal direction. Here, the region 32 is a region which needs to be heated when the recording material P having the width W3 or the width W4 is heated.

[0062] Heating element 620-31 and heating element 620-32 constitute a first outer heating element that is provided at a position different from heating elements 620-1 and 620-2 of substrate 207, which are inner heating elements, in the transport direction of recording material P. The sum of the longitudinal lengths of heating element 620-31 and heating element 620-32 is different from the longitudinal length of heating element 620-1, the longitudinal length of heating element 620-2, and the sum of the longitudinal lengths of heating element 620-41 and heating element 620-42.

[0063] Heating element 620-41 is provided by printing and firing on one surface of substrate 207, and is made of silver palladium (Ag / Pd) or the like. The length of heating element 620-41 in the longitudinal direction is the same as the length of heating element 620-42 in the longitudinal direction.

[0064] The heating element 620-41 heats the regions 21, 31, and 41 which are outside the region 1 heated by the heating element 620-1 in the longitudinal direction. The heating element 620-41 heats the regions 31 and 41 which are outside the region 1 and region 21 heated by the heating element 620-2 in the longitudinal direction. The heating element 620-41 heats the region 41 which is outside the region 21 and region 31 heated by the heating element 620-31 in the longitudinal direction. Here, the region 41 is a region which needs to be heated when heating the recording material P having a width W4.

[0065] The heating element 620-42 is provided on one surface of the substrate 207 by printing and baking, and is made of silver palladium (Ag / Pd) or the like. The length of the heating element 620-42 in the longitudinal direction is the same as the length of the heating element 620-41 in the longitudinal direction. The heating element 620-42 is connected to the heating element 620-41 via a conductive pattern of silver (Ag) or the like.

[0066] The heating element 620-42 heats the regions 22, 32, and 42 which are outside the region 1 heated by the heating element 620-1 in the longitudinal direction. The heating element 620-42 heats the regions 32 and 42 which are outside the region 1 and region 22 heated by the heating element 620-2 in the longitudinal direction. The heating element 620-42 heats the region 42 which is outside the region 22 and region 32 heated by the heating element 620-32 in the longitudinal direction. Here, the region 42 is a region that needs to be heated when heating the recording material P having a width W4.

[0067] Heating element 620-41 and heating element 620-42 constitute a second outer heating element that is provided at a position different from heating element 620-1 and heating element 620-2 of substrate 207, which are inner heating elements, in the conveying direction of recording material P. The sum of the longitudinal lengths of heating element 620-41 and heating element 620-42 is the same as the longitudinal length of heating element 620-1. In addition, the sum of the longitudinal lengths of heating element 620-41 and heating element 620-42 is different from the longitudinal length of heating element 620-2 and the sum of the longitudinal lengths of heating element 620-41 and heating element 620-42.

[0068] The electrode 621-1 is an independent electrode, and is connected to one end in the longitudinal direction of the heating element 620-1 via a conductive pattern of silver (Ag) etc. The electrode 621-1 is connected to the H side of the power source 623 via a switch 622-1.

[0069] The electrode 621-2 is an independent electrode, and is connected to one end of the heating element 620-2 in the longitudinal direction via a conductive pattern of silver (Ag) etc. The electrode 621-2 is connected to the H side of the power source 623 via a switch 622-2.

[0070] The electrode 621-3 is an independent electrode, and is connected to one end in the longitudinal direction of the heating element 620-31 via a conductive pattern of silver (Ag) etc. The electrode 621-3 is connected to the H side of the power source 623 via a switch 622-3.

[0071] The electrode 621-4 is an independent electrode, and is connected to one end in the longitudinal direction of the heating element 620-41 via a conductive pattern of silver (Ag) etc. The electrode 621-4 is connected to the H side of the power source 623 via a switch 622-4.

[0072] The electrode 621-5 is a common electrode, and is connected to the other end in the longitudinal direction of the heating element 620-1, the other end in the longitudinal direction of the heating element 620-2, the other end in the longitudinal direction of the heating element 620-32, and the other end in the longitudinal direction of the heating element 620-42 via a conductive pattern such as silver (Ag). The electrode 621-5 is connected to the N side of the power source 623.

[0073] In the above configuration, each of the heating elements 620-1, 620-2, 620-31 and 620-32, and 620-41 and 620-42 has a longitudinal length corresponding to the widths W1, W2, W3, and W4 of the recording material P.

[0074] Further, there is no region where the heating element 620-1, the heating element 620-2, the heating element 620-31 and the heating element 620-32, and the heating element 620-41 and the heating element 620-42 all overlap in the longitudinal direction. Specifically, the region 1 is a region where the heating element 620-31, the heating element 620-32, the heating element 620-41, and the heating element 620-42 do not overlap. The regions 21 and 22 are regions where the heating element 620-1 does not overlap. The regions 31 and 32 are regions where the heating element 620-1 and the heating element 620-2 do not overlap. The regions 41 and 42 are regions where the heating element 620-1, the heating element 620-2, the heating element 620-31, and the heating element 620-32 do not overlap.

[0075] Furthermore, there is a region where two or more of the heating elements 620-1, 620-2, 620-31 and 620-32, and 620-41 and 620-42 overlap in the longitudinal direction. Specifically, region 1 is a region where the heating elements 620-1 and 620-2 overlap. Region 21 is a region where the heating elements 620-2, 620-31, and 620-41 overlap. Region 22 is a region where the heating elements 620-2, 620-32, and 620-42 overlap. Region 31 is a region where the heating elements 620-31 and 620-41 overlap. Region 32 is a region where the heating elements 620-32 and 620-42 overlap.

[0076] <Characteristics of heating element> The characteristics of the heat generating element 620-1, the heat generating element 620-2, the heat generating element 620-31 and the heat generating element 620-32, and the heat generating element 620-41 and the heat generating element 620-42 of the fixing device 200 according to the embodiment of the present invention will be described in detail with reference to FIG.

[0077] FIG. 4 shows the required power, resistance, required power per unit length, and resistance per unit length of heating elements 620-1, 620-2, 620-31 and 620-32, and 620-41 and 620-42 connected in parallel to a power supply 623 having a voltage of 100V.

[0078] A certain amount of heat is required to melt and fix the unfixed toner image on the recording material P. For this reason, the required power per unit length in each of the heating elements 620-1, 620-2, 620-31 and 620-32, and 620-41 and 620-42 is 4.9 W / mm.

[0079] Heating elements 620-1, 620-2, 620-31, 620-32, 620-41, and 620-42 are manufactured by kneading materials such as silver palladium (Ag / Pd) in a predetermined ratio. In this case, the resistance value per unit length of each of heating elements 620-1, 620-2, 620-31 and 620-32, and 620-41 and 620-42 differs greatly when the longitudinal length differs.

[0080] Furthermore, when the resistance value per unit length of the heating elements 620-1, 620-2, 620-31 and 620-32, and 620-41 and 620-42 is significantly different, the ratio of the material is significantly different. In this case, the characteristics such as the temperature coefficient of resistance (TCR) of the heating elements 620-1, 620-2, 620-31 and 620-32, and 620-41 and 620-42 are different. As a result, the temperature distribution of each region heated by the heating elements 620-1, 620-2, 620-31, 620-32, 620-41, and 620-42 becomes non-uniform, and there is a risk of image defects occurring due to non-uniform fixed images.

[0081] In consideration of this problem, heating elements 620-31 and 620-32 are divided in the longitudinal center of the region overlapping with heating elements 620-1 and 620-2 in the longitudinal direction. Heating elements 620-41 and 620-42 are divided in the longitudinal center of the region overlapping with heating elements 620-1 and 620-2 in the longitudinal direction. On the other hand, heating elements 620-1 and 620-2 are not divided in the longitudinal center, but are formed continuously in the longitudinal direction.

[0082] As a result, the longitudinal lengths of the heating elements 620-1, 620-2, 620-31 and 620-32, and 620-41 and 620-42 do not differ significantly as shown in Fig. 4. Therefore, the characteristics of the heating elements 620-1, 620-2, 620-31 and 620-32, and 620-41 and 620-42 do not differ significantly. As a result, the heat distribution of each of the heating regions of the heating elements 620-1, 620-2, 620-31 and 620-32, and 620-41 and 620-42 can be made uniform.

[0083] <Operation of the fixing device> The operation of the fixing device 200 according to the embodiment of the present invention will be described in detail with reference to FIGS.

[0084] In the fixing device 200, when the fixing film 206 is rotated by the pressure roller 202 as the pressure roller 202 is rotated, electricity is applied to the fixing heater 203. Then, when the temperature of the fixing heater 203 is raised to the target temperature and is adjusted, the recording material P carrying the unfixed toner image is guided and introduced into the fixing nip portion N along an entrance guide (not shown).

[0085] In the fixing nip portion N, the recording material P moves together with the fixing film 206 while the toner image bearing surface side is in close contact with the outer surface of the fixing film 206 .

[0086] During the process of being sandwiched and conveyed in the fixing nip portion N, the recording material P is subjected to heat from the fixing heater 203 via the fixing film 206, so that the unfixed toner image is melted and fixed.

[0087] At this time, the fixing device 200 controls the opening and closing of the switches 622-1, 622-2, 622-3, and 622-4 in accordance with the width of the recording material P passing through the fixing nip portion N. The fixing device 200 controls the duty of power supply to each of the heating elements 620-1, 620-2, 620-31 and 620-32, and 620-41 and 620-42 in accordance with the width of the recording material P passing through the fixing nip portion N.

[0088] Specifically, when the fixing device 200 heats the recording material P of width W1, it turns on the switch 622-1 and controls the duty of the power supply to the heating element 620-1 to make the heating element 620-1 generate heat. In addition, the fixing device 200 turns off the switches 622-2, 622-3, and 622-4 to prevent the heating elements 620-2, 620-31 and 620-32, and 620-41 and 620-42 from generating heat, or controls the temperature of the non-paper passing portion to a desired temperature. This makes it possible to suppress the temperature rise of the non-paper passing portion of the recording material P of width W1 and to prevent the temperature drop in the paper passing portion.

[0089] When the fixing device 200 heats the recording material P of width W2, it turns on the switch 622-2 and controls the duty of the power supply to the heating element 620-2 to make the heating element 620-2 generate heat. The fixing device 200 also turns off the switches 622-1, 622-3 and 622-4 to prevent the heating elements 620-1, 620-31 and 620-32, and 620-41 and 620-42 from generating heat, or controls the temperature of the non-paper passing portions to a desired temperature. This makes it possible to suppress a rise in temperature of the non-paper passing portions of the recording material P of width W2, and to prevent a drop in temperature in the paper passing portions.

[0090] In addition, the fixing device 200 may generate heat from the heat generating element 620-1 included in the width W2 in the longitudinal direction, in addition to the heat generating element 620-2, as necessary.

[0091] When heating the recording material P having a width W3, the fixing device 200 turns on the switches 622-1 and 622-3 and controls the power supply duty to each of the heating elements 620-1, 620-31, and 620-32. For example, the fixing device 200 controls the power supply to the heating elements 620-31 and 620-32 with a power supply duty that is a predetermined ratio to the power supply duty that keeps the temperature of the center in the longitudinal direction constant by the heating element 620-1. As a result, the heating elements 620-1, 620-31, and 620-32 generate heat.

[0092] Furthermore, the fixing device 200 controls the switches 622-2 and 622-4 to turn off the heating elements 620-2, 620-41, and 620-42 so that they do not generate heat, or controls the temperature of the non-paper passing portion to a desired temperature. This makes it possible to suppress a rise in temperature of the non-paper passing portion of the recording material P of width W3, and to prevent a drop in temperature in the paper passing portion.

[0093] In addition to the heat generating elements 620-1, 620-31, and 620-32, the fixing device 200 may also generate heat from the heat generating element 620-2 that is included in the width W3 in the longitudinal direction, as necessary.

[0094] When the fixing device 200 heats the recording material P having a width W4, the fixing device 200 turns on the switches 622-1, 622-3, and 622-4 to control the duty of the power supply to each of the heating elements 620-1, 620-31 and 620-32, and 620-41 and 620-42. As a result, the heating elements 620-1, 620-31, 620-32, 620-41, and 620-42 generate heat. In addition, the fixing device 200 turns off the switch 622-3 to prevent the heating elements 620-31 and 620-32 from generating heat, or controls the temperature of the non-paper passing portion to a desired temperature. As a result, it is possible to suppress the temperature rise of the non-paper passing portion of the recording material P having a width W4, and to prevent the temperature drop in the paper passing portion.

[0095] If necessary, the fixing device 200 may be configured so that the heating elements 620-31 and 620-32 do not generate heat.

[0096] Further, the power supply duty of each of the heating elements 620-2, 620-31 and 620-32, and 620-41 and 620-42 is set to a predetermined ratio with respect to the power supply duty of the heating element 620-1. However, this is not limited to the above, and each of the heating elements 620-2, 620-31 and 620-32, and 620-41 and 620-42 may be provided with a temperature detection means and controlled individually.

[0097] Then, the recording material P that has passed through the fixing nip portion N is separated from the fixing film 206 and discharged to the outside of the image forming apparatus 100.

[0098] In the above operation, the resistance value per unit length of each of the heating elements 620-1, 620-2, 620-31 and 620-32, and 620-41 and 620-42 does not differ significantly, so that heat is generated uniformly in each region, and a uniform fixed image can be obtained.

[0099] In this embodiment, the heating elements 620-1 and 620-2 are provided to heat the regions 1, 21, and 22 and are continuously provided in the longitudinal direction. The heating elements 620-31, 620-32, 620-41, and 620-42 are provided at positions different from the heating elements 620-1 and 620-2 of the substrate 207 in the conveying direction of the recording material P. The heating elements 620-31, 620-32, 620-41, and 620-42 heat the regions 31, 32, 41, and 42 and are divided in the regions overlapping with the heating elements 620-1 and 620-2. This makes it possible to uniformize the heat distribution of the multiple heating elements 620-1, 620-2, 620-31, 620-32, 620-41, and 620-42 that can be controlled independently.

[0100] The present invention is not limited to the above-described embodiment, and it goes without saying that various modifications are possible without departing from the spirit and scope of the present invention.

[0101] Specifically, in the above embodiment, there are four systems: heating element 620-1, heating element 620-2, heating element 620-31 and heating element 620-32, and heating element 620-41 and heating element 620-42. However, this is not limited to this, and there may be three systems or five or more systems.

[0102] In the above embodiment, the mechanical switches 622-1, 622-2, 622-3, and 622-4 are provided, but the present invention is not limited to this and semiconductor elements such as triacs may be used.

[0103] In the above embodiment, the longitudinal lengths of the heating elements 620-1, 620-2, 620-31, 620-32, 620-41, and 620-42 are set to the lengths shown in Fig. 4. However, the present invention is not limited to this, and the longitudinal lengths of the heating elements 620-1, 620-2, 620-31, 620-32, 620-41, and 620-42 can be set to any length as long as they are not significantly different from each other. [Explanation of symbols]

[0104] 100 Image forming device 200 Fixing device 201 Fixing heater unit 202 Pressure roller 203 Fixing heater 204 Heater holder 206 Fixing film 207 Substrate 620-1 Heating element 620-2 Heating element 620-31 Heating element 620-32 Heating element 620-41 Heating element 620-42 Heating element 621-1 Electrode 621-2 Electrode 621-3 Electrode 621-4 Electrode 621-5 Electrode 622-1 Switch 622-2 Switch 622-3 Switch 622-4 Switch 623 Power supply

Claims

1. A fixing device that fixes a toner image formed on a recording material to the recording material by heat and pressure, Fixing belt and A pressure roller that, by pressing against the fixing belt, forms a fixing nip section that grips and transports the recording material together with the fixing belt, A fixing heater for heating a recording material comprises a substrate whose longitudinal direction is perpendicular to the transport direction of the recording material, and a plurality of heating elements provided on the substrate and having different lengths along the longitudinal direction, It has, The aforementioned multiple heating elements are The device comprises: a first inner heating element that heats the inner region in the longitudinal direction and is provided continuously in the longitudinal direction; a second inner heating element that heats the region in the longitudinal direction that is outside the region heated by the first inner heating element; and an outer heating element that heats the region in the longitudinal direction that is outside the region heated by the first inner heating element and is divided in the region that overlaps with the first inner heating element. A fixing device characterized by the following features.

2. The aforementioned external heating element is The device comprises a first outer heating element and a second outer heating element that heats a region outside the region heated by the first outer heating element in the longitudinal direction. The fixing device according to feature 1.

3. The aforementioned multiple heating elements are Having a length in the longitudinal direction corresponding to the width of the recording material, The fixing device according to feature 1.

4. In the longitudinal direction, there is no region where all of the multiple heating elements overlap. Two or more of the plurality of heating elements have overlapping regions in the longitudinal direction. The fixing device according to feature 1.

5. An image forming unit that forms a toner image on the recording material, A fixing device according to claim 1, which fixes a toner image formed on a recording material by the image forming unit onto the recording material, An image forming apparatus characterized by having the following features.

6. A fixing device for fixing a toner image formed on a recording material to the recording material by heat and pressure, Fixing belt and A pressure roller that, by pressing against the fixing belt, forms a fixing nip section that grips and transports the recording material together with the fixing belt, A fixing heater comprising a substrate whose longitudinal direction is perpendicular to the transport direction of the recording material, and a plurality of heating elements provided on the substrate and having different lengths along the longitudinal direction, for heating the recording material, It has, The aforementioned multiple heating elements are The device comprises: an inner heating element that heats the inner region in the longitudinal direction and is continuously provided in the longitudinal direction; a first outer heating element provided at a different position on the substrate in the transport direction from the inner heating element, which heats the region outside the region heated by the inner heating element in the longitudinal direction and is divided in a region overlapping with the inner heating element; and a second outer heating element that heats the region outside the region heated by the first outer heating element in the longitudinal direction. A fixing device characterized by the following features.

7. The plurality of heating elements are Having a length in the longitudinal direction corresponding to the width of the recording material, The fixing device according to feature 6.

8. There is no region in the longitudinal direction where all of the multiple heating elements overlap, Two or more of the plurality of heating elements have overlapping regions in the longitudinal direction. The fixing device according to feature 6.

Images