Heating device and heating processing system using the same

Abstract

To suppress excessive temperature rise around a contact region without increasing a pressure load to the contact region when forming the contact region for heating between belt-like means to be heated and heat generating means.SOLUTION: A heating device includes: heat generating means 2 for heating means 1 to be heated; pressure means 4 for making the means 1 to be heated and the heat generating means 2 contact with each other in a pressurized state; and pressure adjustment means 5 for adjusting the pressurized state by the pressure means 4 so as to change a shorter direction width of a contact region CN. The heat generating means 2 includes a plurality of heating resistors 3 (3a, 3b) extending along a longer direction. When a minimum contact region CNS is formed in which the shorter direction width of the contact region CN is minimum by the pressure means 4, regarding at least two heating resistors (3a, 3b) of the plurality of heating resistors 3, a high heat generating part 6 is wholly contained in the minimum contact region CNS; part of a low heat generating part 7 is contained in the minimum contact region CNS; and a remaining part of the low heat generating part 7 is deviated from the range of the minimum contact region CNS.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a heating device and a heat treatment system using the same. [Background technology]

[0002] As a conventional heating device, for example, the device described in Patent Document 1 has already been provided. Patent Document 1 discloses a fixing device comprising a cylindrical belt, a heater having a first heating resistor and a second heating resistor formed along the longitudinal direction of a thin substrate, in contact with the inner surface of the belt, and a backup roller which, together with the heater, forms a nip portion via the belt for transporting and heating a recording material carrying a toner image, wherein the resistance value per unit length of the first heating resistor is lower at the ends in the longitudinal direction of the substrate than at the central portion, and the fixing device has a first fixing process mode in which all of the first heating resistor and the second heating resistor are within the contact area where the heater and the belt are in contact, and a second fixing process mode in which, in the transport direction of the recording material, all of the first heating resistor is within the contact area and at least a portion of the second heating resistor protrudes from the contact area. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5618771 (Form for carrying out the invention, Figure 4) Summary of the Invention [Problem to be solved by the invention]

[0004] The technical problem that the present invention aims to solve is to provide a heating device and a heat treatment system using the same that, when forming a heating contact area between a belt-shaped heated means and a heat generating means, suppresses excessive temperature rise around the contact area without increasing the pressure load on the contact area. [Means for solving the problem]

[0005] A first technical feature of the present invention is a method for heating a heated means comprising: a belt-like heated means that rotates in a circular manner; a heat generating means that is provided in contact with the rear side of the heated means and extends in a direction intersecting the direction of rotation of the heated means to heat the heated means; a pressure applying means that brings the heated means and the heat generating means into contact with each other under pressure and forms a contact area that contacts the heated means and extends along the longitudinal direction of the heat generating means; and a pressure adjusting means that adjusts the pressure applied by the pressure applying means so as to change the lateral width of the contact area. The heat generating means has a plurality of heat generating resistors that extend along the longitudinal direction, and the plurality of heat generating resistors The heating device is characterized in that narrow high heat generating portions and wide low heat generating portions are formed in series on the antibody, and for at least two of the multiple heating resistors, the high heat generating portions are formed in different regions in the longitudinal direction of the contact area, and when the pressure means forms a minimum contact area in which the short-side width of the contact area is the smallest, for the at least two heating resistors, all of the high heat generating portions are included within the range of the minimum contact area, part of the low heat generating portions are included within the range of the minimum contact area, and the remainder of the low heat generating portions are outside the range of the minimum contact area.

[0006] A second technical feature of the present invention is a heating device having the first technical feature, characterized in that the heating means has a first heating resistor and a second heating resistor extending along the longitudinal direction, the first heating resistor has a narrow high heating portion having a high heat generation amount and a wide low heating portion having a low heat generation amount formed in series, the second heating resistor has the high heating portion and the low heating portion formed in series in an area different from the first heating resistor, and when a minimum contact area having a minimum width in the short side direction of the contact area is formed by the pressure means, all of the high heating portions of the first heating resistor and the second heating resistor are included in the range of the minimum contact area, a part of the low heating portion is included in the range of the minimum contact area, and the remainder of the low heating portion is outside the range of the minimum contact area. A third technical feature of the present invention is a heating device having the first technical feature, characterized in that the pressurizing means has a pressurizing member that is rotatably arranged opposite the heat generating means, sandwiching the heated means therebetween. A fourth technical feature of the present invention is a heating device having the first technical feature, characterized in that the pressurizing means has a pressing member that presses the heat generating means against the heated means.

[0007] A fifth technical feature of the present invention is a heating device having the first technical feature, characterized in that the heated means contacts the medium to be heated moving in the contact area or downstream of the contact area in the direction of rotation to heat the medium to be heated, and the heat generating means has the plurality of heating resistors arranged to include a maximum width area in a cross direction that crosses the direction of movement of the medium to be heated. A sixth technical feature of the present invention is a heating device having the fifth technical feature, characterized in that the heat generating means has the plurality of heat generating resistors that heat the medium to be heated that moves around a center reference line that passes through the center of a cross direction that intersects with the rotation direction of the heated means. A seventh technical feature of the present invention is a heating device having the second technical feature, characterized in that the heated means heats a medium to be heated that moves around a center reference line that passes through the center of a cross direction that intersects with the rotation direction of the heated means, and the first heating resistor, which is one of the multiple heating resistors, forms the high heat generation portion in an area that includes the longitudinal center of the contact area, and forms the low heat generation portion near the longitudinal ends on either side of the high heat generation portion. An eighth technical feature of the present invention is a heating device having the seventh technical feature, characterized in that the second heating resistor forms the low heat generating portion in an area corresponding to the high heat generating portion of the first heating resistor, and forms the high heat generating portion in an area corresponding to the low heat generating portion of the first heating resistor. A ninth technical feature of the present invention is a heating device having the first technical feature, characterized in that the heated means heats a medium to be heated that moves around a center reference line that passes through a cross-directional center that crosses the rotation direction of the heated means, the heating means has first to third heating resistors, the first heating resistor forms the high heat generation portion in an area including the longitudinal center of the contact area, and forms the low heat generation portion toward the longitudinal ends sandwiching the high heat generation portion, the second heating resistor forms the low heat generation portion in an area corresponding to the high heat generation portion of the first heating resistor, and forms the high heat generation portion in an area corresponding to the low heat generation portion of the first heating resistor, and the third heating resistor forms the high heat generation portion in an area including the longitudinal center of the contact area and narrower than the high heat generation portion of the first heating resistor, and forms the low heat generation portion toward the longitudinal ends sandwiching the high heat generation portion.

[0008] A tenth technical feature of the present invention is a heating device having the first technical feature, characterized in that the high heat generation portion and the low heat generation portion are connected via a connecting heat generation portion whose width dimension gradually changes. An eleventh technical feature of the present invention is a heating device having the tenth technical feature, characterized in that the connected heat generating portion is formed in a mountain shape whose width dimension changes linearly. A twelfth technical feature of the present invention is a heating device having the first technical feature, characterized in that the heat generating means has an elongated substrate and the plurality of heat generating resistors formed along the longitudinal direction of the substrate. A thirteenth technical feature of the present invention is a heating device having the twelfth technical feature, characterized in that the heat generating means forms the plurality of heat generating resistors along the longitudinal direction on the surface of the substrate facing the heated means, and covers the plurality of heat generating resistors with a heat-resistant protective layer. A fourteenth technical feature of the present invention is a heating device having the first technical feature, characterized in that the heated means contacts the medium to be heated moving in the contact area or downstream of the contact area in the rotational direction to heat the medium to be heated, and when heating the heated means without passing the medium to be heated, the pressurizing means forms the minimum contact area, and the heating means heats at least two heating resistors among the multiple heating resistors, the high heating portion of which is included within the range of the minimum contact area. A fifteenth technical feature of the present invention is a heating device having the fourteenth technical feature, characterized in that when the medium to be heated is passed through the heated means to heat the heated means, the pressurizing means forms a contact area wider than the minimum contact area, and the heat generating means generates heat by combining the multiple heat generating resistors depending on a width dimension in a cross direction intersecting the movement direction of the medium to be heated. A 16th technical feature of the present invention is a heat treatment system comprising a treatment means for performing a predetermined treatment on a medium to be heated, and a heating device having any of the 1st to 15th technical features for heating the medium to be heated that has been treated by the treatment means. A 17th technical feature of the present invention is a heat processing system having the 16th technical feature, characterized in that the processing means is an image creating means for creating an unfixed image on the medium to be heated, and the heating device is a fixing device for fixing the unfixed image created on the medium to be heated. Effect of the Invention

[0009] According to a first technical feature of the present invention, a plurality of heating resistors are used as a heating means, and when a heating contact area is formed between a belt-shaped heated means and the heating means, excessive temperature rise around the contact area can be suppressed without increasing the pressure load on the contact area. According to a second technical feature of the present invention, two heating resistors are used as the heating means, and when a heating contact area is formed between the belt-shaped heated means and the heating means, excessive temperature rise around the contact area can be suppressed without increasing the pressure load on the contact area. According to a third technical feature of the present invention, in a configuration in which a medium to be heated is heated in the contact area between the heated means and the heat generating means, excessive temperature rise around the contact area can be suppressed without increasing the pressure load on the contact area. According to a fourth technical feature of the present invention, in a configuration in which the medium to be heated is heated downstream in the rotation direction of the heated means from the contact area between the heated means and the heat generating means, excessive temperature rise around the contact area can be suppressed without increasing the pressure load on the contact area. According to the fifth technical feature of the present invention, the heating means can efficiently heat the medium to be heated of the maximum size that can be used. According to the sixth technical feature of the present invention, the heating means can efficiently heat the medium to be heated that moves about the center reference line. According to the seventh technical feature of the present invention, it is possible to efficiently heat the medium to be heated of various sizes as well as the medium to be heated that moves around the center reference line. According to an eighth technical feature of the present invention, in an embodiment in which the heating means has two heating resistors, media to be heated of various sizes can be efficiently heated. According to a ninth technical feature of the present invention, in an embodiment in which the heating means has three heating resistors, media to be heated of various sizes can be efficiently heated. According to the tenth technical feature of the present invention, the distribution of the amount of heat generated by the high heat generating portion and the low heat generating portion in the longitudinal direction of the contact area can be made more uniform, compared to a case in which there is no connected heat generating portion. According to the eleventh technical feature of the present invention, the connecting heating part can be configured more simply than a connecting heating part that changes in a curved shape. According to a twelfth technical feature of the present invention, an existing planar heating means can be used as the heating means. According to the thirteenth technical feature of the present invention, compared to an embodiment in which multiple heating resistors are formed on the opposite side of the substrate to the heated means, it is possible to bring multiple heating resistors closer to the heated means, thereby obtaining a more appropriate distribution of heat generation while avoiding friction with the heated means. According to the fourteenth technical feature of the present invention, the heating process of the heating device can be appropriately carried out without passing the medium to be heated. According to the fifteenth technical feature of the present invention, the heating process of the heating device can be appropriately carried out by passing the medium to be heated. According to a 16th technical feature of the present invention, a heat treatment system can be constructed that includes a heating device that uses multiple heating resistors as a heat generation means and that can suppress excessive temperature rise around the contact area without increasing the pressure load on the contact area when forming a heating contact area between a belt-shaped heated means and the heat generation means. According to the seventeenth technical feature of the present invention, it is possible to provide a heat processing system capable of appropriately heating a heating target medium on which an unfixed image has been formed. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1A is an explanatory diagram showing an overview of an embodiment of a heat treatment system including a heating device to which the present invention is applied, and FIG. 1B is an explanatory diagram showing details of the heat generating means shown in FIG. [Diagram 2] FIG. 1 is an explanatory diagram showing an overall configuration of an image forming system according to a first embodiment. [Diagram 3] FIG. 2 is an explanatory diagram illustrating a configuration example of the fixing device and the periphery of the fixing device according to the first embodiment. [Figure 4] FIG. 1A is an explanatory diagram showing an example of the configuration of a heat generating component of a fixing device according to embodiment 1, and FIG. 1B is an explanatory diagram showing the layout of the heat generating resistors of the heat generating component in the width direction of the contact area when a narrow contact area is used. [Diagram 5] 3 is an explanatory diagram showing the pattern and heat generation amount of a plurality of heating resistors of the heat generating component in the first embodiment. FIG. [Figure 6]FIG. 4 is an explanatory diagram showing an example of a contact area variable mechanism used in the first embodiment. [Figure 7] FIG. 1A is an explanatory diagram showing the operating state when a wide normal contact area is set by the contact area variable mechanism, and FIG. 1B is an explanatory diagram showing the operating state when a narrow minimum contact area is set by the contact area variable mechanism. [Figure 8] 5 is a flowchart showing a heating and pressurizing process of the fixing device according to the first embodiment. [Figure 9] FIG. 1A is an explanatory diagram showing a layout of a heat generating component of a fixing device according to a first comparative example in a narrow contact area, and FIG. 1B is an explanatory diagram showing a solution to the technical problem shown in FIG. [Figure 10] FIG. 13 is an explanatory diagram showing a main part of a contact area varying mechanism according to modified embodiment 1-1. [Figure 11] 11 is an explanatory diagram showing an example of a pattern of heating resistors of a heat generating component when a side reference method is adopted as a medium transport method in which one side in a width direction intersecting with the moving direction of the medium is used as a reference. [Figure 12] 10 is an explanatory diagram showing the pattern and heat generation amount of a plurality of heat generating resistors of a heat generating component of a fixing device according to a second embodiment. FIG. [Figure 13] FIG. 1A is an explanatory diagram showing the layout of the heating resistors of a heat-generating component in the width direction of the contact area when a wide normal contact area is used, and FIG. 1B is an explanatory diagram showing the layout of the heating resistors of a heat-generating component in the width direction of the contact area when a narrow minimum contact area is used. [Figure 14] FIG. 11 is an explanatory diagram showing a main part of a fixing device according to a third embodiment. [Figure 15] 13 is an explanatory diagram showing details of a peripheral structure of a heat generating component of a fixing device according to a third embodiment. FIG. [Figure 16] FIG. 2A is an explanatory diagram showing the layout of a heat generating component when a narrow minimum contact area is used, and FIG. 2B is an explanatory diagram showing the layout of a heat generating component when a wide normal contact area is used. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Overview of the embodiment FIG. 1(a) shows an overview of a heat treatment system including a fixing device according to a first embodiment of the present invention. In the figure, the heat treatment system includes a treatment means 10 that performs a predetermined treatment on a medium S to be heated, and a heating device 11 that heats the medium S to be heated that has been treated by the treatment means 10. In this type of heat processing system, for example, the processing means 10 is an image forming means that creates an unfixed image on the medium S to be heated, and the heating device 11 is a fixing device that fixes the unfixed image created on the medium S to be heated.

[0012] In this example, the heating device 11 includes a belt-like heated means 1 that rotates in a circular manner, a heat generating means 2 that is provided in contact with the back side of the heated means 1 and extends in a direction intersecting the direction of rotation of the heated means 1 to heat the heated means 1, a pressure applying means 4 that brings the heated means 1 and the heat generating means 2 into contact with each other under pressure and forms a contact area CN that contacts the heated means 1 and extends along the longitudinal direction of the heat generating means 2, and a pressure adjusting means that adjusts the pressure applied by the pressure applying means 4 so as to change the lateral width of the contact area CN. 1(b), the heat generating means 2 has a plurality of heat generating resistors 3 (3a, 3b) extending along the longitudinal direction, and the plurality of heat generating resistors 3 are formed with narrow high heat generating portions 6 having a high heat generation amount and wide low heat generating portions 7 having a low heat generation amount in a continuous manner, and for at least two of the plurality of heat generating resistors 3 (3a, 3b), the high heat generating portions 6 are formed in different regions in the longitudinal direction of the contact area CN, and the width of the contact area CN in the lateral direction is made smallest by the pressure applying means 4, i.e., the minimum contact area CN S When forming the minimum contact area CN, for at least two heating resistors (3a, 3b) of the plurality of heating resistors 3, all of the high heat generating portions 6 are S and a part of the low heat generating portion 7 is within the minimum contact area CN S The remaining part of the low heat generating part 7 is included in the range of the minimum contact area CN S This is to ensure that the value does not fall within the range of .

[0013] In this example, when the heating means 2 has three or more heating resistors 3, two of the heating resistors (3a, 3b) are within the minimum contact area CNS In this case, the minimum contact area CN S When using the above, the two heating resistors (3a, 3b) should be used for the heating process. For this reason, for heating resistors other than the two heating resistors (3a, 3b), the pattern (the pattern of the high heat generating portion 6 and the low heat generating portion 7) should be appropriately selected in consideration of the size of the medium S to be heated, etc. In contrast, in an embodiment in which the heat generating means 2 has two heat generating resistors 3, specifically a first heat generating resistor 3a and a second heat generating resistor 3b extending along the longitudinal direction, a narrow high heat generating portion 6 that generates a high amount of heat and a wide low heat generating portion 7 that generates a low amount of heat are formed in series in the first heat generating resistor 3a, and the high heat generating portion 6 and the low heat generating portion 7 are formed in series in a region different from the first heat generating resistor 3a in the second heat generating resistor 3b, and the short-side width of the contact area CN is made smallest by the pressure means 4, i.e., a minimum contact area CN S When forming the minimum contact area CN, all of the high heat generating portions 6 of the first heating resistor 3a and the second heating resistor 3b are S and a part of the low heat generating portion 7 is within the minimum contact area CN S The remaining part of the low heat generating part 7 is included in the range of the minimum contact area CN S It is sufficient to make the value fall outside the range of

[0014] In such technical means, the heated means 1 may be a belt-like object that rotates in a circular manner. As a circular rotation method for the heated means 1, for example, one of the tensioning means that tensions the heated means 1 may be used as a driving source to rotate the heated means 1, or the heated means 1 may be driven to rotate by the pressure means 4 as a driving source. Furthermore, the heat generating means 2 may be disposed in contact with the rear surface of the heated means 1, and is not necessarily limited to being disposed opposite the pressure applying means 4. Furthermore, a representative example of the heat generating means 2 is one that uses a sheet heating element, but it is also possible to apply means other than a sheet heating element. Furthermore, the pressurizing means 4 may be appropriately selected as long as it brings the heated means 1 and the heat generating means 2 into contact with each other under pressure. Furthermore, the pressure adjustment means 5 may be any means that adjusts the pressure applied by the pressure means 4. In this example, the width dimension of the contact area CN is made variable by changing the pressure load, and the minimum contact area CN S It is sufficient that the contact area CN has at least a plurality of contact areas CN having different widths, including the above.

[0015] Next, a representative or preferred embodiment of the heating device 11 according to the present embodiment will be described. In this example, a representative embodiment of the pressurizing means 4 is one having a pressurizing member rotatably provided opposite the heat generating means 2 across the heated means 1. Another embodiment is one having a pressurizing member that presses the heat generating means 2 against the heated means 1. In addition, in a configuration in which the heated means 1 contacts the medium to be heated S moving in the contact area CN or downstream of the contact area CN in the rotational direction to heat the medium to be heated S, the heat generating means 2 must have a plurality of heating resistors 3 arranged so as to include the widest area in the intersecting direction that intersects with the moving direction of the medium to be heated S. In this case, the heating means 2 may have a plurality of heating resistors 3 that heat the medium to be heated S moving around a center reference line Lc passing through the center of the intersecting direction that intersects with the rotation direction of the heated means 1, as shown in Figure 1(b).

[0016] In addition, in an embodiment in which the heating means 2 has two heating resistors 3 (3a, 3b), when the heated means 1 heats the medium to be heated S moving around a center reference line Lc passing through the center of the intersecting direction that intersects the rotation direction of the heated means 1, as shown in Figure 1 (b), the first heating resistor 3a, which is one of the multiple heating resistors 3, may form a high heat generation portion 6 in an area including the longitudinal center of the contact area CN, and form a low heat generation portion 7 near the longitudinal ends sandwiched between the high heat generation portion 6. Furthermore, the second heating resistor 3b may have a low heat generation portion 7 formed in an area corresponding to the high heat generation portion 6 of the first heating resistor 3a, and a high heat generation portion 6 formed in an area corresponding to the low heat generation portion 7 of the first heating resistor 3a.

[0017] In addition, in a case where the heated means 1 heats the medium to be heated S moving around the center reference line Lc, in an embodiment in which the heating means 2 has three heating resistors 3 (specifically, a first heating resistor 3a, a second heating resistor 3b, and a third heating resistor not shown), from the viewpoint of efficiently heating the medium to be heated S of each size, as shown in FIG. 1(b), the first heating resistor 3a forms a high heat generating portion 6 in an area including the center of the contact area CN in the longitudinal direction, and the high heat generating portion 6 is sandwiched between the first heating resistor 3a and the second heating resistor 3b. The second heating resistor 3b forms the low heat generating portion 7 in an area corresponding to the high heat generating portion 6 of the first heating resistor 3a and forms the high heat generating portion 6 in an area corresponding to the low heat generating portion 7 of the first heating resistor 3a. The third heating resistor (not shown) forms the high heat generating portion 6 in an area including the longitudinal center of the contact area CN and narrower than the high heat generating portion 6 of the first heating resistor 3a, and forms the low heat generating portion 7 near the longitudinal end between the high heat generating portion 6. In this embodiment, the third heating resistor (not shown) may be used mainly when a small-sized medium S is to be heated, and the first heating resistor 3a and the second heating resistor 3b may be used during the start-up operation and when a medium S of a size other than the small size is to be heated. The combination of the patterns of the first heating resistor 3a to the third heating resistor may be selected as appropriate.

[0018] In addition, from the viewpoint of preventing a sudden change in the heat generation pattern between the high heat generation portions 6 and the low heat generation portions 7, a preferred pattern for the heating resistor 3 is one in which the high heat generation portions 6 and the low heat generation portions 7 are connected via a connecting heat generation portion 8 whose width dimension changes gradually, as shown in FIG. 1(b). In this embodiment, a preferred embodiment of the heat generating connection part 8 is one in which the width dimension is formed in a mountain shape that changes linearly. A representative embodiment of the heat generating means 2 includes an elongated substrate (not shown) and a plurality of heat generating resistors 3 formed along the longitudinal direction of the substrate. In this example, a preferred embodiment of the heating means 2 is one in which multiple heating resistors 3 are formed along the longitudinal direction on the surface of the substrate facing the heated means 1, and the multiple heating resistors 3 are covered with a heat-resistant protective layer not shown.

[0019] In addition, in a mode in which the heated means 1 contacts the medium S to be heated that moves in the contact area CN or downstream of the contact area CN in the rotation direction to heat the medium S, when the heated means 1 is heated without passing the medium S to be heated, the pressurizing means 4 is set to the minimum contact area CN. S The heating means 2 has a minimum contact area CN S It is preferable to heat at least two heating resistors 3 (3a, 3b) whose high heat generating portion 6 is included in the range. Furthermore, in this embodiment, when the heated medium S is passed through the heated means 1 to heat the heated means 1, the pressurizing means 4 is pressed against the medium S in the minimum contact area CN S and the heat generating means 2 generates heat by combining a plurality of heat generating resistors 3 depending on the width dimension in the intersecting direction intersecting the moving direction of the medium S to be heated.

[0020] Hereinafter, the present invention will be described in more detail based on the embodiments shown in the accompanying drawings. First embodiment -Overall configuration of image forming system- FIG. 2 is an explanatory diagram showing the overall configuration of the heat treatment system according to the first embodiment. In the same figure, the heating processing system is configured as an image forming system 20 equipped with an image creating means as a processing means for creating an unfixed image on a medium S to be heated (hereinafter referred to as medium S in the embodiment), and a fixing device as a heating device for fixing the unfixed image created on the medium S. In this example, the image forming system 20 is a so-called tandem type image forming system of an intermediate transfer type, and is equipped with each component as an image forming means and a fixing device in a common unit (not shown). Of course, the image forming means and the fixing device may be configured as separate units, and multiple units may be combined.

[0021] In this example, the image forming system 20 has a plurality of image forming units 22 (22a to 22d) in which toner images of each color component (four colors, yellow (Y), magenta (M), cyan (C), and black (K) in this example) are formed by electrophotography. A belt-shaped intermediate transfer body 23 is disposed at a location corresponding to each image forming unit 22. A primary transfer device 24 (a primary transfer roll in this example) is disposed on the back of the intermediate transfer body 23 corresponding to each image forming unit 22. Furthermore, a secondary transfer device 25 (a secondary transfer roll in this example) 25 is disposed at a part of the intermediate transfer body 23, which secondary transfers each color component toner image, which has been primarily transferred from each image forming unit 22 to the intermediate transfer body 23 by the primary transfer device 24, onto a medium S such as paper. A fixing device 60 is disposed downstream in the transport direction of the medium S to which the color component toner image has been transferred, and fixes an unfixed toner image (corresponding to an unfixed image) on the medium S. In this embodiment, the image forming units 22, the intermediate transfer body 23, the primary transfer device 24, and the secondary transfer device 25 correspond to an image forming unit that forms an unfixed image on the medium S.

[0022] <Image forming section> Here, each image forming unit 22 has a drum-shaped photoconductor 30 that rotates in a predetermined direction, and around this photoconductor 30, there are provided a charging device 31 that charges the photoconductor 30, an exposure device 32 such as a laser scanning device that writes an electrostatic latent image on the photoconductor 30 charged by the charging device 31, a developing device 33 that develops the electrostatic latent image written on the photoconductor 30 by the exposure device 32 with a corresponding color toner, and a cleaning device 34 that cleans off any residue on the photoconductor 30 after the toner image developed by the developing device 33 is primarily transferred onto the intermediate transfer body 23 by the primary transfer device 24. <Around the intermediate transfer body> The intermediate transfer body 23 is stretched over a plurality of tension rolls 41 to 45, and is rotated in a predetermined direction, for example with the tension roll 41 as a drive roll. The tension roll 44 also serves as an opposing roll to the secondary transfer roll of the secondary transfer device 25, and generates a secondary transfer electric field required for secondary transfer between the secondary transfer roll and the opposing roll. Furthermore, an intermediate transfer cleaning device 46 is disposed on the surface of the intermediate transfer body 23 corresponding to the tension roll 45.

[0023] <Media transport system> Furthermore, a medium supplying device 50 is provided below the intermediate transfer body 23, and the medium S supplied from this medium supplying device 50 is transported along a transport path 51 that passes through a secondary transfer device 25 and reaches a fixing device 60. The transport path 51 is also provided with an appropriate number of transport rolls 52, a transport belt 53 that transports the medium S from the secondary transfer device 25 to the fixing device 60, guide plates 54 and 55 that guide the medium S to a secondary transfer portion by the secondary transfer device 25 and a fixing portion of the fixing device 60, and discharge rolls 56 for discharging the medium S to a medium discharge portion (not shown). In this example, a method is adopted in which the medium S moves about a center reference line Lc (see FIG. 5) that passes through the center in a cross direction (typically the width direction) that crosses the transport direction.

[0024] -Overall configuration of the fixing device- Next, the fixing device 60 used in the present embodiment will be described with reference to FIG. In the figure, the fixing device 60 has a width dimension necessary for fixing the medium S moving in the conveying direction. The fixing device 60 includes a fixing belt 61 as a heated means that rotates in a circulating manner, a heat generating component 62 as a heat generating means that heats the fixing belt 61 and is provided in contact with the back side of the fixing belt 61, a pressure roll 63 that is provided in contact with a portion facing the heat generating component 62 across the fixing belt 61 and applies pressure to form a contact area CN between the fixing belt 61 and the pressure roll 63, an upstream tension roll 64 that stretches the fixing belt 61 so as to be circulating and rotatable on the upstream side of the contact area CN of the fixing belt 61 in the movement direction, and a downstream tension roll 65 that stretches the fixing belt 61 so as to be circulating and rotatable on the downstream side of the contact area CN of the fixing belt 61 in the movement direction.

[0025] -Example of fixing belt configuration- In this embodiment, the fixing belt 61 is an endless heat conductive belt having flexibility and heat resistance. As the fixing belt 61, a belt formed into a cylindrical original shape using a material such as a synthetic resin, for example, polyimide or polyamide, is used. In this example, either the upstream tension roll 64 or the downstream tension roll 65 (the downstream tension roll 65 in this example) functions as a drive roll that is driven and rotated by a drive motor (not shown). The other (the upstream tension roll 64 in this example) functions as a tension applying roll that applies tension to the fixing belt 61. From the viewpoint of preventing the fixing belt 61 from being shifted to one side, the upstream tension roll 64 may of course be supported so as to be tiltable and function as a steering roll.

[0026] -Heat generating parts- In this example, the heat generating component 62 directly heats the rear surface of the fixing belt 61, and heats the medium S, which is clamped and pressurized and transported in the contact area CN between the fixing belt 61 and the pressure roll 63, via the fixing belt 61. In this example, the heat generating component 62 is arranged on the back side corresponding to the contact area CN of the fixing belt 61, and comprises a long, plate-shaped planar heater 70 extending in a width direction intersecting the transport direction of the medium S, and a heater holder 75 that holds the planar heater 70, and the heater holder 75 is fixed at a predetermined position via a support bracket 78.

[0027] <Example of sheet heater configuration> 4(a), the sheet heater 70 is positioned and accommodated in a recess 76 formed in a heater holder 75 and fixed via a fixture. The sheet heater 70 includes a long substrate 71, a plurality of heating resistors 72 provided on the surface of the substrate 71 that contacts the inner circumferential surface of the fixing belt 61 and extending along the longitudinal direction of the substrate 71, wiring electrodes (not shown) provided on the substrate 71 near both longitudinal ends of the heating resistors 72 for supplying power to the heating resistors 72, and an insulating layer 73 laminated on the surface of the substrate 71 facing the fixing belt 61 so as to cover the heating resistors 72 and the wiring electrodes. Here, the substrate 71 is a rectangular plate-like member whose length dimension in the width direction intersecting with the transport direction of the medium S is longer than the maximum size. The substrate 71 is made of an electrically insulating material, and for example, a ceramic substrate is used. Furthermore, the insulating layer 73 may be made of any suitable material, for example glass.

[0028] <Example of heating resistor configuration> In this example, the heating resistor 72 is a strip-shaped heating resistor having a predetermined resistance value, which is formed by printing and firing a metal paste whose main component is, for example, a silver (Ag) / palladium (Pd) alloy. In addition, in this example, the heating resistor 72 has multiple (two in this example) heating wire portions 72a, 72b extending linearly along the longitudinal direction of one side of the substrate 71, and these heating wire portions 72a, 72b are arranged at intervals in the short direction of the substrate 71. Here, assuming that the heating wire portion 72a of the heating resistor 72 is the first heating resistor R1 and the heating wire portion 72b is the second heating resistor R2, as shown in FIG. 5, the first and second heating resistors R1, R2 are configured in the following pattern. The longitudinal length d0 of the first and second heating resistors R1, R2 is selected so as to include, for example, the width dimension of the medium size used that intersects with the transport direction (for example, the short-side dimension of JIS standard A4 size paper). The line widths of the first and second heating resistors R1 and R2 are set as follows according to the longitudinal areas. The first heating resistor R1 is set as a high heat generation portion 721 in which the line width of the heat generation material in this region is narrow and the electrical resistance is large, so that a region of length d1 (for example, the short side dimension of a JIS standard A5 size paper) on the left and right sides of the center (center reference line Lc) of the heat generation region along the longitudinal direction generates heat with a high amount of heat. Also, the regions located at both ends of the heat generation region of the high heat generation portion 721 are set as low heat generation portions 722 in which the line width of the heat generation material is wide and the electrical resistance is small, so that they do not generate heat.

[0029] The second heating resistor R2 is set as a low heat generating portion 722 in which the line width of the heat generating material is wide and the electrical resistance is low so that the regions of length d1 on the left and right sides of the center (center reference line Lc) of the heat generating region along the longitudinal direction do not generate heat. Also, the regions located at both ends of the heat generating region of the low heat generating portion 722 are set as high heat generating portions 721 in which the line width of the heat generating material is narrow and the electrical resistance is high so that the regions generate heat with a high amount of heat. Furthermore, in this example, the first and second heating resistors R1, R2 are configured such that the high heat generation portion 721 and the low heat generation portion 722 are connected to each other via a connecting heat generation portion 723 whose width dimension changes gradually, so that the heat generation pattern does not change suddenly between the high heat generation portion 721 and the low heat generation portion 722. Here, the connecting heat generation portion 723 is configured, for example, to have a mountain shape whose width dimension changes linearly. In this way, in this example, the first and second heating resistors R1, R2 are both formed with the high heat generation portion 721 and the low heat generation portion 722 connected together, but the positional relationship between the high heat generation portion 721 and the low heat generation portion 722 is reversed in the longitudinal direction. Therefore, when the heat generation amounts of the first and second heating resistors R1, R2 in the longitudinal direction are added together, a substantially uniform heat generation amount is obtained, as shown in FIG.

[0030] -Pressure roll- As shown in FIG. 3, the pressure roll 63 is made of a metal roll 63a with an elastic material 63b such as urethane rubber laminated therearound, and a protective layer 63c is laminated on the surface of the elastic material. In this embodiment, the pressure roll 63 is rotatable through bearings 67 at both ends of the metal roll 63a. It is a supporter of Noh. Furthermore, in this example, the pressure roll 63 is adapted to move between a set position where it contacts the fixing belt 61 and a retract position where it is not in contact with the fixing belt 61 via a retract mechanism 80. In this example, the retract mechanism 80 has a swinging support arm 81 that swings about a swinging support shaft 82, and this swinging support arm 81 is formed with a U-shaped groove 83 in which the bearings 67 located at both ends of the pressure roll 63 are received, so that the pressure roll 63 is brought into contact with and separated from the fixing belt 61.

[0031] - Variable contact area mechanism - In this example, as shown in FIG. 3, a contact area varying mechanism 90 is provided which varies the width dimension of the contact area CN along the transport direction of the medium S. FIG. 6 shows an example of the contact area varying mechanism 90 used in the first embodiment. In the figure, the contact area varying mechanism 90 is configured by utilizing the retraction mechanism 80 of the pressure roll 63 . In this example, the retract mechanism 80 has a contact and separation mechanism 85 for contacting and separating the pressure roll 63 with respect to the fixing belt 61. This contact and separation mechanism 85 projects a protruding piece 851 on the free end side of the swing holding arm 81, disposes an eccentric cam 852 in contact with the lower side of the protruding piece 851, and provides a biasing spring 853 for biasing the protruding piece 851 toward the eccentric cam 852 on the side opposite to the eccentric cam 852 of the protruding piece 851, and the eccentric cam 852 is switched and rotated to the major diameter position RL and the minor diameter position RS by a drive motor 854. In this example, when the minor diameter position RS of the eccentric cam 852 abuts against the protruding piece 851 in the retract mechanism 80, the pressure roll 63 is retracted to the retract position, and when the major diameter position RL of the eccentric cam 852 abuts against the protruding piece 851, the pressure roll 63 is arranged at the set position.

[0032] In this example, the contact area variable mechanism 90 utilizes a middle diameter position other than the major diameter position RL and the minor diameter position RS of the eccentric cam 852 in the contact and separation mechanism 85 of the retract mechanism 80, rotates the pressure roll 63 around the swing support shaft 82 of the swing holding arm 81, and makes the width dimension of the contact area CN variable. In this example, when the major diameter position RL of the eccentric cam 852 abuts against the protruding piece 851, the pressure roll 63 is arranged at the set position. In this state, as shown in FIG. 7, the pressure roll 63 has a wide contact area CN used during normal printing L is assumed to be arranged so as to be ensured (see FIG. 4(a)). Note that the posture position of the swing holding arm 81 is indicated by Q1 in the figure. On the other hand, as shown in FIG. 7, when the drive motor 854 is stopped at a position where the middle diameter position RM (RS < RM < RL) of the eccentric cam 852 abuts against the protruding piece 851, the posture position of the swing holding arm 81 is inclined by ΔQ from Q1 to Q2. As a result, the pressure roll 63 has a narrow minimum contact area CN having the minimum width dimension S is arranged so as to be ensured (FIG. 4(b)). Note that in this example, the contact area CN is a wide normal contact area CN L and a narrow minimum contact area CN SHowever, the present invention is not limited to these two changes, and it goes without saying that a contact area CN that is intermediate between these two changes may be more appropriately selected depending on the physical properties and size of the medium.

[0033] -Relationship between change in contact area and heating resistor pattern- As described above, the contact area CN between the fixing belt 61 and the pressure roll 63 is changed by the contact area changing mechanism 90 to a wide normal contact area CN L and narrow minimum contact area CN S It changes to. In this state, the high heat generating portions 721 of the first and second heating resistors R1 and R2 are in contact with each other over a wide contact area CN L , or narrow minimum contact area CN S In either case, the position is adjusted so as to be included within the contact area CN.

[0034] - Peripheral structure of the fixing device - 3 and 5, a surface temperature sensor SN is provided to detect the temperature of the surface of the fixing belt 61 upstream of the contact area CN in the rotation direction. As the surface temperature sensor SN, a known sensor using a thermistor, a resistance temperature detector, or the like may be appropriately selected. In this example, two surface temperature sensors are used as the surface temperature sensor SN. One of the surface temperature sensors, SN1, detects the temperature of the surface of the fixing belt 61 corresponding to the medium passing area. In this example, the surface temperature sensor SN1 detects the temperature of the surface of the fixing belt 61 in the vicinity of the center reference line Lc. The other surface temperature sensor SN2 detects the temperature of the surface of the fixing belt 61 corresponding to the medium non-passage area.

[0035] Furthermore, a position sensor 110 that detects the position of the medium S is provided on the transport path 51 upstream of the entrance of the fixing device 60 in the transport direction of the medium S. This position sensor 110 is used to start counting in a timer counter by detecting the leading or trailing end of the transported medium S, thereby determining the position of the medium S. Furthermore, the medium type indication unit 120 indicates physical property information such as the size and thickness of the medium S being transported, but it is also possible to detect the size and physical property information of the medium S while the medium S is being transported and use this detected information as indication information.

[0036] - Control system of fixing device - In Fig. 3, reference numeral 100 denotes a control device made up of a microcomputer including various processors. The term "processor" here refers to a processor in a broad sense, including general-purpose processors (e.g., CPU: Central Processing Unit, etc.) and dedicated processors (e.g., GPU: Graphics Processing Unit, ASIC: Application Specific Integrated Circuit, FPGA: Field Programmable Gate Array, programmable logic device, etc.). In this example, the control device 100 has a heating and pressure processing program (see FIG. 8) for the fixing device pre-installed in a memory not shown, and inputs operation signals from an operation panel not shown, information from the position sensor 110, the surface temperature sensor SN, and the media type indication unit 120 into a processor, which executes various programs and controls predetermined control signals to the planar heater 70, the retraction mechanism 80, the contact area variable mechanism 90, etc.

[0037] - Heating and pressurizing the fixing device - Now, assuming that a print instruction is given from an operation panel (not shown), the control device 100 executes a series of image forming processes. When the fixing device 60 receives a print command but the heating conditions of the fixing device and the pressure conditions of the pressure roll 63 are not yet ready, a start-up operation is performed for the fixing device 60. Here, when the control device 100 judges that it is the start-up time, the contact area CN is narrowed by using the contact area variable mechanism 90. In other words, the contact area CN is narrowed to the minimum contact area CN S (See FIG. 4(b) and FIG. 5). In this state, the control device 100 monitors the temperature information from the surface temperature sensor SN1 and simultaneously energizes the first and second heating resistors R1, R2 to heat the fixing belt 61 until the fixing belt 61 reaches a predetermined specified value Tm (corresponding to the temperature required for fixing operation). This type of start-up operation is performed when the high heat generating portions 721 of the first and second heating resistors R1 and R2 are in contact with the minimum contact area CN S Since the fixing belt 61 is heated with a large amount of heat generated inside the fixing belt 61, the heating process of the fixing belt 61 is performed efficiently in a short time. At this time, the high heat generating portions 721 of the first and second heating resistors R1 and R2 are in contact with each other within the minimum contact area CN S Since the contact area does not deviate from the range of CN S The surrounding area will not be excessively heated.

[0038] Next, when the start-up operation of the fixing device 60 is completed, the control device 100 makes the contact area CN in a wide state. In other words, the contact area CN is made the normal contact area CN during printing. L is set to. In this state, the control device 100 performs a fixing process suitable for printing. That is, to ensure a good fixing state in the longitudinal medium passing area, the temperature acquired by the surface temperature sensor SN1 is kept constant, while the temperature acquired by the surface temperature sensor SN2 is controlled as follows so that the longitudinal medium non-passing area does not exceed the heat resistance temperature of various members and does not exceed the threshold temperature Tth. ■When printing on a medium of a small size (for example, JIS standard A5 size) or smaller, the first heating resistor R1 is controlled to be turned on and off, and the second heating resistor R2 is turned off. ■ When printing on media larger than small size (i) When the temperature acquired by the surface temperature sensor SN2 is equal to or lower than the threshold value Tth, the first and second heating resistors R1 and R2 are controlled to be turned on and off. (ii) In cases other than (i), the first heating resistor R1 is controlled to be turned on and off, and the second heating resistor R2 is turned off.

[0039] Comparison form 1-1 In evaluating the performance of the fixing device according to this embodiment, a fixing device according to comparative example 1-1 will be described. Now, as shown in FIG. 9(a), a pressure load P1 is applied to the pressure roll 63 to change the contact area CN to a narrow minimum contact area CN S For example, the first heating resistor R1 of the first and second heating resistors R1 and R2 is set to a minimum contact area CN S Assume that the sensor is placed outside the range of the sensor. At this time, the minimum contact area CN S When the first heating resistor R1, which is out of the contact area, heats up, the minimum contact area CN S The fixing belt 61 other than the first heating resistor R1 is disposed in a non-contact state with the pressure roll 63. Therefore, the heat of the fixing belt 61 heated by the first heating resistor R1 is not transferred to the pressure roll 63, and the minimum contact area CN S This will lead to abnormal heating of the surrounding area. In order to solve this problem, the first and second heating resistors R1 and R2 should be connected to each other over a wide contact area CN as shown in FIG. L In order to make the pressure load P1 on the pressure roll 63 fall within the range of P2 (>P1), it is necessary to increase the pressure load P1 to P2 (>P1). Therefore, it is difficult to reduce the pressure load.

[0040] ◎Transformation form 1-1 In this embodiment, the contact area variable mechanism 90 adopts a method of moving the pressure roll 63 relative to the fixing belt 61, but this is not limited to this, and it is possible to configure the contact area variable mechanism 90 as shown in, for example, FIG. 10. In this example, the contact area variable mechanism 90 has D-cut guide protrusions 91 protruding from both longitudinal ends of the support bracket 78 of the heat-generating component 62, and has support frames (not shown) disposed on both sides of the guide protrusions 91. The contact area variable mechanism 90 has elongated holes (not shown) formed in the support frames that extend in the width direction of the contact area CN along the transport direction of the medium S, and the guide protrusions 91 are fitted into the elongated holes so as to be slidable (slidably movable), and the heat-generating component 62 is disposed so as to be linearly movable along the width direction of the contact area CN (x direction in the figure). Furthermore, the contact area variable mechanism 90 has a protruding piece 92 extending in a direction perpendicular to the width direction of the contact area CN provided on a part of the support bracket 78, and an eccentric cam 93 is arranged in contact with this protruding piece 92. The contact area variable mechanism 90 has a biasing spring 94 arranged on the opposite side of the protruding piece 92 to the eccentric cam 93, which biases the protruding piece 92 toward the eccentric cam 93, and a drive motor 95 is used to rotate the eccentric cam 93 between the major axis position RL and the minor axis position RS.

[0041] In this example, as shown in FIG. 10, when the minor axis position RS of the eccentric cam 93 abuts against the protruding piece 92, the heat generating component 62 contacts the wide contact area CN L are arranged so as to ensure On the other hand, as shown in FIG. 10, when the long axis position RL of the eccentric cam 93 abuts against the protruding piece 92, the heat generating component 62 moves toward the inlet side of the medium S along the width direction of the contact area CN (x direction in the figure), and the narrowest width of the minimum contact area CN S are arranged so as to ensure

[0042] ◎Transformation form 1-2 In this embodiment, the planar heater 70 of the heat generating component 62 has a pattern of first and second heating resistors R1, R2 (high heat generating portion 721, low heat generating portion 722) set on the premise that the medium S is transported based on the center of the width of the medium S (center reference line Lc) (center reference method). However, as shown in FIG. 11, when assuming a method (side reference method) in which the medium S is transported based on one widthwise side (side reference line Ls) of the medium S as a reference, the passing area of ​​media S of different sizes relative to the fixing belt 61 is different from that in the center reference method. Therefore, in the side reference method shown in FIG. 11, since the small-sized medium S passes close to the side reference line Ls of the fixing belt 61, the patterns of the first and second heating resistors R1, R2 are configured as follows.

[0043] 11, the first heating resistor R1 is set as a high heat generation portion 721 in which the line width of the heat generation material in this region is narrow and the electrical resistance is large, so that an area of ​​length d1 (for example, the short-side dimension of a JIS standard A5 size paper) based on one side (side reference line Ls) of the heat generation region along the longitudinal direction generates a high amount of heat. Also, the area on the opposite side of the heat generation region of the high heat generation portion 721 is set as a low heat generation portion 722 in which the line width of the heat generation material is wide and the electrical resistance is small, so that the area does not generate heat. The second heating resistor R2 is set as a low heat generation portion 722 in which the line width of the heat generation material in this region is wide and the electrical resistance is small so that a region of length d1 based on one side (side reference line Ls) of the heat generation region along the longitudinal direction does not generate heat. Also, the region located on the opposite side of the heat generation region of the low heat generation portion 722 is set as a high heat generation portion 721 in which the line width of the heat generation material is narrow and the electrical resistance is large so that a high amount of heat is generated. In this example, the first and second heating resistors R1 and R2 each have a high heat generating portion 721 connected to a low heat generating portion 722 via a connecting heat generating portion 723. In this way, in this example, both the first and second heating resistors R1, R2 are formed with the high heat generation portion 721 and the low heat generation portion 722 connected together, but the positional relationship between the high heat generation portion 721 and the low heat generation portion 722 is reversed in the longitudinal direction. Therefore, the total heat generation amount of the first and second heating resistors R1, R2 in the longitudinal direction is approximately uniform.

[0044] ◎Embodiment 2 FIG. 12 is an explanatory diagram showing the pattern and heat generation amount of a plurality of heat generating resistors of a heat generating part of a fixing device according to the second embodiment. In the figure, the heat generating component 62 is substantially the same as in embodiment 1, with a planar heater 70 held by a heater holder 75, but the number and pattern of the heat generating resistors 72 of the planar heater 70 are different from those in embodiment 1. Note that the same components as in embodiment 1 are denoted by the same reference numerals and detailed description thereof will be omitted here. In this example, the heating resistor 72 has multiple (three in this example) heating wire portions 72a, 72b, 72c extending linearly along the longitudinal direction of one side of the substrate 71, and these heating wire portions 72a, 72b, 72c are arranged at intervals in the short direction of the substrate 71.

[0045] Here, if the heating wire portion 72a of the heating resistor 72 is defined as the first heating resistor R1, the heating wire portion 72b is defined as the second heating resistor R2, and the heating wire portion 72c is defined as the third heating resistor R3, then, as shown in FIG. 12, the first to third heating resistors R1, R2, and R3 are configured in the following pattern. The longitudinal lengths of the first to third heating resistors R1, R2, and R3 are set to a length d0 (for example, the short side dimension of a JIS standard A3 size) corresponding to a predetermined maximum size of the medium S. The line widths are set as follows according to the longitudinal regions of each. The first heating resistor R1 is set as a high heat generation portion 721 in which the line width of the heat generation material in this region is narrow and the electrical resistance is large, so that a region of length d1 (for example, the short side dimension of a JIS standard A5 size paper) on the left and right sides of the center (center reference line Lc) of the heat generation region along the longitudinal direction generates heat with a high amount of heat. Also, the regions located at both ends of the heat generation region of the high heat generation portion 721 are set as low heat generation portions 722 in which the line width of the heat generation material is wide and the electrical resistance is small, so that they do not generate heat.

[0046] The second heating resistor R2 is set as a high heat generation portion 721 in which the line width of the heat generation material in this region is narrow and the electrical resistance is large, so that a region of length d2 (for example, the short side dimension of JIS standard B4 size paper) on the left and right sides of the center (center reference line Lc) of the heat generation region along the longitudinal direction generates heat with a high amount of heat. Also, the regions located at both ends of the heat generation region of the high heat generation portion 721 are set as low heat generation portions 722 in which the line width of the heat generation material is wide and the electrical resistance is small, so that they do not generate heat. The third heating resistor R3 is set as a low heat generating portion 722 in which the line width of the heat generating material is wide and the electrical resistance is low so that the left and right regions of length d2 on the left and right of the center (center reference line Lc) of the heat generating region along the longitudinal direction do not generate heat. Also, the regions located at both ends of the heat generating region of the low heat generating portion 722 are set as high heat generating portions 721 in which the line width of the heat generating material is narrow and the electrical resistance is high so that the regions generate a high amount of heat. In this example, the first to third heating resistors R1, R2, and R3 each have a high heat generating portion 721 connected to a low heat generating portion 722 via a connecting heat generating portion 723. In this way, in this example, the second and third heating resistors R2, R3 are both formed with the high heat generation portion 721 and the low heat generation portion 722 connected together, but the positional relationship between the high heat generation portion 721 and the low heat generation portion 722 is reversed in the longitudinal direction. Therefore, when the heat generation amounts of the second heating resistor R2 and the third heating resistor R3 in the longitudinal direction are added together, a substantially uniform heat generation amount is obtained, as shown in FIG.

[0047] In this embodiment, a contact area variable mechanism 90 (FIGS. 3 and 5) is provided for varying the width of the contact area CN, as in the first embodiment. S and the wide contact area CN selected for normal printing. L However, it goes without saying that the contact area CN may be changed more finely depending on the physical properties and size of the medium S. Furthermore, in this embodiment, three surface temperature sensors SN (see FIG. 3) for detecting the temperature of the surface of the fixing belt 61 are used. One of the surface temperature sensors, SN1, detects the temperature of the surface of the fixing belt 61 corresponding to the medium passing area. In this example, the surface temperature sensor SN1 detects the temperature of the surface of the fixing belt 61 in the vicinity of the center reference line Lc. Another surface temperature sensor SN2 detects the temperature of an area on the surface of the fixing belt 61 corresponding to the medium passing area, the area being outside the short side dimension of letter size paper and inside the short side dimension of JIS standard B4 size. Another surface temperature sensor SN3 detects the temperature of the surface of the fixing belt 61 corresponding to the media non-passage area.

[0048] - Heating and pressurizing the fixing device - Now, assuming that a print instruction is given from an operation panel (not shown), the control device 100 executes a series of image forming processes. When the fixing device 60 receives a print command but the heating conditions of the fixing device 60 and the pressure conditions of the pressure roll 63 are not yet ready, a start-up operation for the fixing device 60 is performed. Here, when the control device 100 judges that the start-up operation is in progress, the contact area CN is narrowed by using the contact area variable mechanism 90. In other words, the contact area CN is narrowed to the minimum contact area CN S (See FIG. 12 and FIG. 13(b)). In this state, the control device 100 monitors the temperature information from the surface temperature sensor SN1 and simultaneously energizes the second heating resistor R2 and the third heating resistor R3 to heat the fixing belt 61 until the fixing belt 61 reaches a predetermined specified value Tm (corresponding to the temperature required for fixing operation).

[0049] In this embodiment, as shown in FIG. 12, the high heat generating portions 721 of the second and third heating resistors R2 and R3 are located at the minimum contact area CN S is included in the range. This type of start-up operation is performed when the high heat generating portions 721 of the second and third heating resistors R2 and R3 are in contact with the minimum contact area CN S Since the fixing belt 61 is heated with a large amount of heat generated inside the fixing belt 61, the heating process of the fixing belt 61 is performed efficiently in a short time. At this time, the high heat generating portions 721 of the second and third heating resistors R2 and R3 are in contact with each other within the minimum contact area CN S Since the contact area does not deviate from the range of CN S The surrounding area will not be excessively heated. In this example, since the first heating resistor R1 is not used during the start-up operation, the high heat generating portion 721 of the first heating resistor R1 is in the minimum contact area CN S It is acceptable if the value is not included in the range.

[0050] Next, when the start-up operation of the fixing device 60 is completed, the control device 100 makes the contact area CN in a wide state. In other words, the contact area CN is made to be in the wide normal contact area CN during printing. L In this example, the high heat generating portions 721 of the heat generating resistors R1, R2, and R3 are set to the wide normal contact area CN L is included. In this state, the control device 100 performs a fixing process suitable for printing. That is, to ensure a good fixing state in the longitudinal medium passing area, the temperature acquired by the surface temperature sensor SN1 is kept constant, while the temperature acquired by the surface temperature sensor SN2 or SN3 is controlled as follows so that the longitudinal medium non-passing area does not exceed the heat resistance temperature of various members and the temperature acquired by the surface temperature sensor SN2 or SN3 does not exceed the threshold value Tth.

[0051] ■ When printing on media of B4 size or larger (i) When the temperature acquired by the surface temperature sensor SN3 is equal to or lower than a certain threshold value Tth, the second and third heating resistors R2, R3 are simultaneously controlled to be turned on and off. (ii) In cases other than (i) The third heating resistor R3 is turned off, and the second heating resistor R2 is controlled to be turned on and off. ■ When printing on media smaller than B4 size (i) When the temperature acquired by the surface temperature sensor SN2 is equal to or lower than a certain threshold value Tth, the first and second heating resistors R1, R2 are simultaneously controlled to be turned on and off. (ii) In any case other than (i), the second heating resistor R2 is always off, and the first heating resistor R1 is on / off controlled.

[0052] Third embodiment FIG. 14 shows a main part of a fixing device according to the third embodiment. In the same figure, the basic configuration of the fixing device 60 includes a fixing belt 61, a pressure roll 63 that is arranged opposite the front side of the fixing belt 61 and pressurizes the fixing belt 61, an opposing pad 130 that is arranged opposite the pressure roll 63 across the fixing belt 61 and forms a first contact area CN1 through which the medium S passes between the fixing belt 61 and the pressure roll 63, a heat-generating component 140 that is arranged in contact with the back surface of the fixing belt 61 at a location different from the first contact area CN1 and heats the back surface of the fixing belt 61, a spring 150 as a pressing means that presses the heat-generating component 140 toward the fixing belt 61, and a pressure adjustment mechanism 160 that changes the pressure state of the second contact area CN2 between the heat-generating component 140 and the fixing belt 61.

[0053] In this example, the fixing belt 61 is made of a cylindrical belt member, and is rotatably sandwiched between the pressure roll 63 and the opposing pad 130 in a first contact area CN1. The pressure roll 63 is rotated by a driving force from a driving mechanism 170 , and the fixing belt 61 rotates following the pressure roll 63 . Furthermore, in this example, the second contact area CN2 is provided at a position displaced from the first contact area CN1 relative to the fixing belt 61 by approximately 180°. 15, the heat generating component 140 has a curved substrate 141 that extends along the width direction of the fixing belt 61 and has a curved cross section. A radius of curvature r1 (not shown) of the surface side of the curved substrate 141 is set to be shorter than a radius of curvature r2 (not shown) of the inner surface of the fixing belt 61 in a free state. A plurality of (two in this example) heat generating resistors 142 (specifically, 142a and 142b) are formed on the surface of the curved substrate 141, and an insulating protective layer 143 is laminated on the surface of the curved substrate 141 so as to cover the heat generating resistors 142. The heat generating component 140 is supported by a support member 145 , and a biasing spring 150 biases the support member 145 to press the heat generating component 140 against the fixing belt 61 .

[0054] In this example, the two heating resistors 142 (142a, 142b) extend along the longitudinal direction on the surface of the curved substrate 141 and are arranged side by side with a gap between them. The two heating resistors 142 (142a, 142b) are configured as strip-shaped heating wire parts having the same width. 15, in this example, the pressure adjustment mechanism 160 has the base end of the urging spring 150 attached to a movable plate 161 that can be raised and lowered, and an eccentric cam 162 arranged in contact with the lower part of the movable plate 161. The eccentric cam 162 has a long diameter position RL and a short diameter position RS. The eccentric cam 162 can be rotated by a drive motor 163, and when the movable plate 161 rises, the position of the base end of the urging spring 150 rises accordingly, and the heat generating component 140 is pressed against the fixing belt 61.

[0055] In this example, the pressure adjustment mechanism 160 changes the pressure state during start-up operation of the fixing device 60 and during printing, thereby changing the contact area of ​​the second contact area CN2 between the heat generating component 140 and the fixing belt 61. That is, when the fixing device 60 is started up, the pressure adjustment mechanism 160 brings the minor axis position RS of the eccentric cam 162 into contact with the movable plate 161, lowering the position of the movable plate 161. Therefore, as shown in Fig. 16(a), the urging force of the urging spring 150 on the heat generating component 140 becomes weaker, and the contact area between the heat generating component 140 and the fixing belt 61 at the second contact area CN2 becomes narrower. Therefore, at the time of start-up, in order to raise the temperature of the fixing belt 61 to a predetermined temperature at high speed, the contact area is narrowed so as not to take heat away from the fixing belt 61, while the heat generated by the heating resistor 142 is stored in the fixing belt 61, making it possible to raise the temperature of the fixing belt 61.

[0056] On the other hand, during normal printing, the pressure adjustment mechanism 160 brings the long diameter position RL of the eccentric cam 162 into contact with the movable plate 161, and raises the position of the movable plate 161. Therefore, as shown in Fig. 16(b), the urging force of the urging spring 150 on the heat generating component 140 becomes stronger, and the contact area between the heat generating component 140 and the fixing belt 61 at the second contact area CN2 becomes wider. In this way, during normal printing, the contact area of ​​the second contact area CN2 becomes wider. Therefore, in addition to the heat generated by the heating resistor 142, the heat stored in the heat generating component 140 is supplied to the fixing belt 61 in large amounts. Therefore, when the medium S passes through the first contact area CN1, heat is taken from the fixing belt 61, but the temperature of the fixing belt 61 immediately rises due to the heat supplied from the heat generating component 140. In this example, the pressure adjustment mechanism 160 presses the heat generating component 140 upward, but this is not limited to this, and the design may be modified as appropriate, for example, to press the heat generating component 140 sideways against the fixing belt 61.

[0057] In addition, in this embodiment, an example is given in which the multiple heating resistors 142 (142a, 142b) are configured as band-shaped heating wire sections of the same width, but this is not limited to this. As in embodiments 1 and 2, it is also possible to provide high heat generation sections and low heat generation sections of different line widths for the heating resistor 142, and control the heat generation state from the heating resistor 142 to the fixing belt 61 by changing the contact area of ​​the second contact area CN2.

[0058] (Additional Note) (((1))) A belt-like heated means that rotates in a circular manner; a heat generating means provided in contact with a rear surface side of the heated means, extending in a direction intersecting a rotation direction of the heated means, and heating the heated means; a pressurizing means for contacting the heated means and the heat generating means under pressure to form a contact area that contacts the heated means and extends along the longitudinal direction of the heat generating means; a pressure adjusting means for adjusting a pressure applied by the pressure applying means so as to change a width of the contact area in a lateral direction; Equipped with the heat generating means has a plurality of heat generating resistors extending along a longitudinal direction, the plurality of heat generating resistors are formed with narrow high heat generating portions and wide low heat generating portions in series, and the high heat generating portions of at least two of the plurality of heat generating resistors are formed in different regions in the longitudinal direction of the contact area, A heating device characterized in that when the pressure applying means forms a minimum contact area having the smallest short-side width of the contact area, for the at least two heating resistors, all of the high heat generating portions are included within the range of the minimum contact area, part of the low heat generating portions are included within the range of the minimum contact area, and the remainder of the low heat generating portions are outside the range of the minimum contact area. (((2))) In the heating device according to (((1))), the heat generating means has a first heat generating resistor and a second heat generating resistor extending along a longitudinal direction, the first heat generating resistor has a narrow high heat generating portion and a wide low heat generating portion which are connected to each other, the second heat generating resistor has the high heat generating portion and the low heat generating portion connected to each other in an area different from that of the first heat generating resistor, A heating device characterized in that when the pressure applying means forms a minimum contact area having a minimum short-side width of the contact area, all of the high heat generating portions of the first heating resistor and the second heating resistor are included within the range of the minimum contact area, a portion of the low heat generating portions are included within the range of the minimum contact area, and the remainder of the low heat generating portions are outside the range of the minimum contact area. (((3))) In the heating device according to (((1))) or (((2)), The heating device according to claim 1, wherein the pressurizing means has a pressurizing member rotatably provided opposite the heat generating means with the heated means therebetween. (((4))) In the heating device according to (((1))) or (((2)), The heating device according to claim 1, wherein the pressure applying means has a pressing member for pressing the heat generating means against the heated means. (((5))) In the heating device according to any one of (((1))) to (((4))), The heated means contacts a medium to be heated that moves in the contact area or downstream of the contact area in the rotation direction to heat the medium to be heated, A heating device, characterized in that the heat generating means has the plurality of heat generating resistors arranged so as to include a maximum width area in a direction intersecting a moving direction of the medium to be heated. (((6))) In the heating device according to (((5))), A heating device characterized in that the heat generating means has a plurality of heat generating resistors that heat the medium to be heated that moves around a center reference line that passes through the center of a direction intersecting the rotation direction of the heated means. (((7))) In the heating device according to (((2))), The heated means heats a medium to be heated that moves about a center reference line that passes through the center of a direction intersecting a rotation direction of the heated means, A heating device characterized in that the first heating resistor, which is one of the multiple heating resistors, forms the high heat generation portion in an area including the longitudinal center of the contact area, and forms the low heat generation portion toward the longitudinal ends sandwiched between the high heat generation portion. (((8))) In the heating device according to (((7))), A heating device characterized in that the second heating resistor forms the low heat generation portion in an area corresponding to the high heat generation portion of the first heating resistor, and forms the high heat generation portion in an area corresponding to the low heat generation portion of the first heating resistor. (((9))) In the heating device according to (((1))), The heated means heats a medium to be heated that moves about a center reference line that passes through the center of a direction intersecting a rotation direction of the heated means, the heat generating means has first to third heat generating resistors, the first heating resistor forms the high heat generating portion in a region including a longitudinal center of the contact area, and forms the low heat generating portion near the longitudinal end portions sandwiching the high heat generating portion; the second heating resistor forms the low heat generating portion in an area corresponding to the high heat generating portion of the first heating resistor, and forms the high heat generating portion in an area corresponding to the low heat generating portion of the first heating resistor; A heating device characterized in that the third heating resistor includes the longitudinal center of the contact area, forms the high heat generation portion in an area narrower than the high heat generation portion of the first heating resistor, and forms the low heat generation portion closer to the longitudinal ends sandwiched between the high heat generation portion. (((10))) In the heating device according to any one of (((1))) to (((9))), The heating device is characterized in that the high heat generating portion and the low heat generating portion are connected via a connecting heat generating portion whose width dimension gradually changes. (((11))) In the heating device according to any one of (((1))) to (((10))), The heating device is characterized in that the connected heat generating portion is formed in a mountain shape whose width changes linearly. (((12)) In the heating device according to any one of (((1))) to (((11))), A heating device, wherein the heat generating means comprises an elongated substrate and the plurality of heat generating resistors formed along the longitudinal direction of the substrate. (((13))) In the heating device according to (((12))), The heating device is characterized in that the heat generating means is formed by forming a plurality of heat generating resistors along the longitudinal direction on the surface of the substrate facing the heated means, and covering the plurality of heat generating resistors with a heat-resistant protective layer. (((14))) In the heating device according to any one of (((1))) to (((13))), The heated means contacts a medium to be heated that moves in the contact area or downstream of the contact area in the rotation direction to heat the medium to be heated, When the heated means is heated without passing the medium to be heated, the pressurizing means forms the minimum contact area, The heating device is characterized in that the heat generating means generates heat from at least two of the plurality of heat generating resistors, the high heat generating portion of which is included within the range of the minimum contact area. (((15))) In the heating device according to (((14))), When the medium to be heated is passed through the heated means, the pressure means forms a contact area wider than the minimum contact area; The heating device is characterized in that the heat generating means generates heat by combining the plurality of heat generating resistors depending on a width dimension of the medium in a direction intersecting with a moving direction of the medium to be heated. (((16))) A processing means for performing a predetermined processing on the medium to be heated; A heating device according to any one of ((1)) to ((15))) that heats the medium to be heated that has been treated by the treatment means; A heat treatment system comprising: (((17))) In the heat treatment system according to (((16))), the processing means is an image forming means for forming an unfixed image on the heating target medium, The heat processing system is characterized in that the heating device is a fixing device that fixes an unfixed image formed on the medium to be heated.

[0059] According to the heating device of (((1))), a plurality of heating resistors are used as a heating means, and when a contact area for heating is formed between the belt-shaped heated means and the heating means, excessive temperature rise around the contact area can be suppressed without increasing the pressure load on the contact area. According to the heating device of (((2))), two heating resistors are used as the heating means, and when a contact area for heating is formed between the belt-shaped heated means and the heating means, excessive temperature rise around the contact area can be suppressed without increasing the pressure load on the contact area. According to the heating device of (((3))), in a configuration in which a medium to be heated is heated in the contact area between the heated means and the heat generating means, it is possible to suppress excessive temperature rise around the contact area without increasing the pressure load on the contact area. According to the heating device of (((4))), in a configuration in which the medium to be heated is heated downstream in the rotation direction of the heated means from the contact area between the heated means and the heat generating means, excessive temperature rise around the contact area can be suppressed without increasing the pressure load on the contact area. According to the heating device of (((5))), the heating means can efficiently heat the medium to be heated that is the maximum size that can be used. According to the heating device of (((6))), the heating means can efficiently heat the medium to be heated that moves about the center reference line. According to the heating device of (((7))), it is possible to efficiently heat the medium to be heated of various sizes as the medium to be heated moves around the center reference line. According to the heating device of (((8))), in an embodiment in which the heat generating means has two heat generating resistors, media to be heated of various sizes can be efficiently heated. According to the heating device of (((9))), in an embodiment in which the heat generating means has three heat generating resistors, media to be heated of various sizes can be efficiently heated. According to the heating device of (((10))), the distribution of heat generated by the high heat generating portion and the low heat generating portion in the longitudinal direction of the contact area can be made more uniform, compared to a case in which there is no linked heat generating portion. According to the heating device of (((11))), the linked heat generating portion can be configured more simply than a linked heat generating portion that changes in a curved manner. According to the heating device of (((12))), an existing planar heating means can be used as the heating means. According to the heating device of (((13))), compared to an embodiment in which multiple heating resistors are formed on the opposite side of the heated means of the substrate, it is possible to bring the multiple heating resistors closer to the heated means, thereby avoiding friction with the heated means, and obtain a more appropriate distribution of heat generation. According to the heating device of (((14))), the heating process of the heating device can be appropriately performed without passing the medium to be heated. According to the heating device of (((15))), the medium to be heated can be passed through the heating device to appropriately perform the heating process. According to the heat treatment system of (((16))), a heat treatment system can be constructed that uses a plurality of heating resistors as a heat treatment means, and includes a heating device that can suppress excessive temperature rise around the contact area without increasing the pressure load on the contact area when forming a contact area for heating between the belt-shaped heated means and the heat treatment means. According to the heat processing system of (((17))), it is possible to provide a heat processing system capable of appropriately heating a heating target medium on which an unfixed image has been formed. [Explanation of symbols]

[0060] 1...Heated means, 2...Heat generating means, 3...Heat generating resistor (3a, 3b), 4...Pressure generating means, 5...Pressure adjusting means, 6...High heat generating section, 7...Low heat generating section, 8...Connected heat generating section, 10...Processing means, 11...Heating device, S...Medium to be heated, CN...Contact area, CN S …Minimum contact area, Lc…Center reference line

Claims

1. A belt-like heated means that rotates in a circular manner; a heat generating means provided in contact with a rear surface side of the heated means, extending in a direction intersecting a rotation direction of the heated means, and heating the heated means; a pressurizing means for contacting the heated means and the heat generating means under pressure to form a contact area that contacts the heated means and extends along the longitudinal direction of the heat generating means; a pressure adjusting means for adjusting a pressure applied by the pressure applying means so as to change a width of the contact area in a lateral direction; Equipped with the heat generating means has a plurality of heat generating resistors extending along a longitudinal direction, the plurality of heat generating resistors are formed with narrow high heat generating portions and wide low heat generating portions in series, and the high heat generating portions of at least two of the plurality of heat generating resistors are formed in different regions in the longitudinal direction of the contact area, A heating device characterized in that when the pressure applying means forms a minimum contact area having the smallest short-side width of the contact area, for the at least two heating resistors, all of the high heat generating portions are included within the range of the minimum contact area, part of the low heat generating portions are included within the range of the minimum contact area, and the remainder of the low heat generating portions are outside the range of the minimum contact area.

2. 2. The heating device according to claim 1, the heat generating means has a first heat generating resistor and a second heat generating resistor extending along a longitudinal direction, the first heat generating resistor has a narrow high heat generating portion and a wide low heat generating portion which are connected to each other, the second heat generating resistor has the high heat generating portion and the low heat generating portion which are connected to each other in an area different from that of the first heat generating resistor, A heating device characterized in that when the pressure applying means forms a minimum contact area having the smallest short-side width of the contact area, all of the high heat generating portions of the first heating resistor and the second heating resistor are included within the range of the minimum contact area, a portion of the low heat generating portions are included within the range of the minimum contact area, and the remainder of the low heat generating portions are outside the range of the minimum contact area.

3. 2. The heating device according to claim 1, The heating device according to claim 1, wherein the pressurizing means has a pressurizing member rotatably provided opposite the heat generating means with the heated means therebetween.

4. 2. The heating device according to claim 1, The heating device according to claim 1, wherein the pressure applying means has a pressing member for pressing the heat generating means against the heated means.

5. 2. The heating device according to claim 1, The heated means contacts a medium to be heated that moves in the contact area or downstream of the contact area in the rotation direction to heat the medium to be heated, A heating device, characterized in that the heat generating means has the plurality of heat generating resistors arranged so as to include a maximum width area in a direction intersecting a moving direction of the medium to be heated.

6. The heating device according to claim 5, A heating device characterized in that the heat generating means has a plurality of heat generating resistors that heat the medium to be heated that moves around a center reference line that passes through the center of a direction intersecting the rotation direction of the heated means.

7. The heating device according to claim 2, The heated means heats a medium to be heated that moves about a center reference line that passes through the center of a direction intersecting a rotation direction of the heated means, A heating device characterized in that the first heating resistor, which is one of the multiple heating resistors, forms the high heat generation portion in an area including the longitudinal center of the contact area, and forms the low heat generation portion toward the longitudinal ends sandwiched between the high heat generation portion.

8. The heating device according to claim 7, A heating device characterized in that the second heating resistor forms the low heat generation portion in an area corresponding to the high heat generation portion of the first heating resistor, and forms the high heat generation portion in an area corresponding to the low heat generation portion of the first heating resistor.

9. 2. The heating device according to claim 1, The heated means heats a medium to be heated that moves about a center reference line that passes through the center of a direction intersecting a rotation direction of the heated means, the heating means has first to third heating resistors, the first heating resistor forms the high heat generating portion in a region including a longitudinal center of the contact area, and forms the low heat generating portion near the longitudinal end portions sandwiching the high heat generating portion; the second heating resistor forms the low heat generating portion in a region corresponding to the high heat generating portion of the first heating resistor, and forms the high heat generating portion in a region corresponding to the low heat generating portion of the first heating resistor, A heating device characterized in that the third heating resistor includes the longitudinal center of the contact area, the high heat generation portion is formed in an area narrower than the high heat generation portion of the first heating resistor, and the low heat generation portion is formed closer to the longitudinal ends sandwiched between the high heat generation portion.

10. 2. The heating device according to claim 1, The heating device is characterized in that the high heat generating portion and the low heat generating portion are connected via a connecting heat generating portion whose width dimension gradually changes.

11. The heating device according to claim 10, The heating device is characterized in that the connected heat generating portion is formed in a mountain shape whose width changes linearly.

12. 2. The heating device according to claim 1, A heating device, wherein the heat generating means comprises an elongated substrate and the plurality of heat generating resistors formed along the longitudinal direction of the substrate.

13. 13. The heating device according to claim 12, The heating device is characterized in that the heat generating means is formed by forming a plurality of heat generating resistors along the longitudinal direction on the surface of the substrate facing the heated means, and covering the plurality of heat generating resistors with a heat-resistant protective layer.

14. 2. The heating device according to claim 1, The heated means contacts a medium to be heated that moves in the contact area or downstream of the contact area in the rotation direction to heat the medium to be heated, When the means to be heated is heated without passing the medium to be heated, the pressurizing means forms the minimum contact area, The heating device is characterized in that the heat generating means generates heat from at least two of the plurality of heat generating resistors, the high heat generating portion of which is included within the range of the minimum contact area.

15. 15. The heating device according to claim 14, When the medium to be heated is passed through the heated means, the pressure means forms a contact area wider than the minimum contact area; The heating device is characterized in that the heat generating means generates heat by combining the plurality of heat generating resistors depending on a width dimension of the medium in a direction intersecting with a moving direction of the medium to be heated.

16. A processing means for performing a predetermined processing on the medium to be heated; A heating device according to any one of claims 1 to 15, which heats the medium to be heated that has been treated by the treatment means; A heat treatment system comprising:

17. 17. The heat treatment system according to claim 16, the processing means is an image forming means for forming an unfixed image on the heating target medium, The heat processing system is characterized in that the heating device is a fixing device that fixes an unfixed image formed on the medium to be heated.

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