JPWO2020138105A1 - Heater and fixing device - Google Patents

Abstract

The heater is located on the substrate (30) extending from the first end (30a) to the second end (30b) and on the first end (30a) side or the second end (30b) side in the longitudinal direction of the substrate (30). It has a plurality of terminals (61 to 63) and a plurality of heat generating parts located side by side along the longitudinal direction of the substrate (30), and the plurality of heat generating parts are connected to the same terminal (61 to 63). The group (41) and the group (41) are provided. Further, in the heat generating portion group (41), the heat generating portion located at the central portion has a smaller electric resistance than the heat generating portion located at the end portion.

Description

The disclosed embodiments relate to heaters and fixing devices.

Conventionally, there is known a fixing heater in which a plurality of heat generating parts are provided side by side and the plurality of heat generating parts are integrally provided to generate heat (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2016-115512

However, in the conventional fixing heater, since the current is concentrated in the central portion of the heat generating portion group, there is a problem that the temperature varies in a plurality of heat generating portions in the heat generating portion group.

One aspect of the embodiment is made in view of the above, and an object of the present invention is to provide a heater and a fixing device having less variation in temperature in a plurality of heat generating portions.

The heater according to one aspect of the embodiment includes a substrate extending from the first end to the second end, a plurality of terminals located on the first end side or the second end side in the longitudinal direction of the substrate, and the substrate. It has a plurality of heat generating parts arranged side by side along the longitudinal direction of the above, and includes a group of heat generating parts in which the plurality of heat generating parts are connected to the same terminal. Further, in the heat generating portion group, the heat generating portion located at the central portion has a smaller electric resistance than the heat generating portion located at the end portion.

Further, in the fixing device according to one aspect of the embodiment, a pressure region is formed between the fixing member that heats the toner on the medium while rotating around the axis and the fixing member while rotating around the axis. A pressurizing member that pressurizes the toner on the medium that passes through the pressurizing region, and a heater that is located corresponding to the pressurizing region with the fixing member interposed therebetween and heats the fixing member. Be prepared. The heater includes a substrate extending from a first end to a second end, a plurality of terminals located on the first end side or the second end side in the longitudinal direction of the substrate, and along the longitudinal direction of the substrate. It has a plurality of heat generating parts located side by side, and includes a group of heat generating parts in which the plurality of heat generating parts are connected to the same terminal. Further, in the heat generating portion group, the heat generating portion located at the central portion has a smaller electric resistance than the heat generating portion located at the end portion.

In the heater and the fixing device of one aspect of the embodiment, there is little variation in temperature in a plurality of heat generating portions.

FIG. 1 is a schematic view (front view) showing a printer according to an embodiment. FIG. 2 is a cross-sectional view schematically showing the fixing device according to the embodiment. FIG. 3 is a bottom view schematically showing the heater according to the embodiment. FIG. 4 is a cross-sectional view taken along the line AA shown in FIG. FIG. 5 is a diagram for explaining the factors of temperature variation in the heater according to the embodiment. FIG. 6 is a diagram for explaining an arrangement example of a resistance heating element in the heater according to the embodiment. FIG. 7 is a bottom view schematically showing the heater according to the first modification of the embodiment. FIG. 8 is a diagram for explaining the factors of temperature variation in the heater according to the first modification of the embodiment. FIG. 9 is a bottom view schematically showing the heater according to the second modification of the embodiment.

Hereinafter, embodiments of the heater and the fixing device disclosed in the present application will be described with reference to the accompanying drawings. In each figure, "Fr" indicates "front", "Rr" indicates "rear", "L" indicates "left", "R" indicates "right", and "U" indicates "right". "Upper" indicates "upper" and "D" indicates "lower".

[Overall configuration of printer]
First, the overall configuration of the printer 1 in which the fixing device 7 according to the embodiment is used will be described with reference to FIG. FIG. 1 is a schematic view (front view) showing the printer 1. The printer 1 includes a device main body 2, a paper cassette 3, a paper output tray 4, a paper feed device 5, an image drawing device 6, a fixing device 7, and a control device (not shown).

The apparatus main body 2 constitutes a substantially rectangular parallelepiped appearance in the printer 1. The paper cassette 3 is located at the lower part of the apparatus main body 2 and accommodates the sheet S before the image is formed. Such a sheet S is an example of a medium, for example, plain paper. The sheet S is not limited to paper, but may be made of resin or the like.

The output tray 4 is located at the upper part of the apparatus main body 2 and accommodates the sheet S after the image is formed. The paper feed device 5 is located at the upstream end of the transport path 8 extending from the paper feed cassette 3 to the paper output tray 4.

The image-forming device 6 is located in the middle of the transport path 8, and has a toner container 10, a drum unit 11, and an optical scanning device 12.

The toner container 10 contains, for example, black toner (developer). The toner contained in the toner container 10 may be a two-component developer in which the toner and the carrier are mixed, or a one-component developer composed of magnetic toner.

The drum unit 11 includes a photoconductor drum 13, a charging device 14, a developing device 15, and a transfer roller 16. The transfer roller 16 contacts the photoconductor drum 13 from below to form a transfer nip.

The fixing device 7 is located on the downstream side of the transport path 8. Details of the fixing device 7 will be described later.

The control device appropriately controls each of the above-mentioned devices, and performs the image forming process according to the following procedure. First, the charging device 14 charges the surface of the photoconductor drum 13. Then, the photoconductor drum 13 receives the scanning light emitted from the optical scanning device 12 and carries an electrostatic latent image.

Next, the developing device 15 develops the electrostatic latent image on the photoconductor drum 13 into a toner image using the toner supplied from the toner container 10. Then, the paper feed device 5 feeds the sheet S from the paper feed cassette 3 to the transport path 8. As a result, the toner image on the photoconductor drum 13 is transferred to the sheet S passing through the transfer nip.

Next, the fixing device 7 fixes the toner image on the sheet S. Finally, the sheet S on which the toner image is fixed is discharged to the paper ejection tray 4.

[Fixing device and heater]
Next, the details of the fixing device 7 and the heater 23 according to the embodiment will be described with reference to FIGS. 2 to 6. FIG. 2 is a cross-sectional view schematically showing the fixing device 7 according to the embodiment, FIG. 3 is a bottom view schematically showing the heater 23 according to the embodiment, and FIG. 4 is A shown in FIG. It is a cross-sectional view taken along the line A.

As shown in FIG. 2, the fixing device 7 includes a fixing belt 21, a pressure roller 22, and a heater 23. The fixing belt 21 is an example of a fixing member, the pressure roller 22 is an example of a pressure member, and the heater 23 is an example of a heater.

The fixing belt 21 is an endless belt and has a substantially cylindrical shape that is long in the front-rear direction (hereinafter, also referred to as an axial direction). The surface layer of the fixing belt 21 is made of, for example, a heat-resistant and elastic synthetic resin material such as a polyimide resin.

The fixing belt 21 is arranged above the inside of the housing 20 (see FIG. 1). A pair of substantially cylindrical caps (not shown) are attached to both ends of the fixing belt 21 in the axial direction. A belt guide (not shown) for holding the substantially cylindrical shape of the fixing belt 21 may be located inside the fixing belt 21.

The pressing member 24 is located inside the fixing belt 21. The pressing member 24 has a substantially square cylinder shape that is long in the axial direction. The pressing member 24 penetrates the fixing belt 21 (and the cap) in the axial direction and is supported by the housing 20. The fixing belt 21 described above is rotatably supported by the pressing member 24. The pressing member 24 is made of, for example, a metal material.

The pressure roller 22 has a substantially cylindrical shape that is long in the front-rear direction (that is, the axial direction). The pressure roller 22 is arranged below the inside of the housing 20. The pressure roller 22 has a metal core metal 22a and an elastic layer 22b such as a silicone sponge laminated on the outer peripheral surface thereof.

Both ends of the core metal 22a in the axial direction are rotatably supported by the housing 20. A drive motor (not shown) is connected to the core metal 22a via a gear train or the like, and the pressurizing roller 22 is rotationally driven by the drive motor.

The fixing device 7 includes a pressure adjusting unit (not shown) that raises and lowers the pressure roller 22 to adjust the contact pressure of the pressure roller 22 with respect to the fixing belt 21. When the pressure roller 22 is pressed against the fixing belt 21, a pressure region N is formed between the fixing belt 21 and the pressure roller 22.

Further, the pressure region N is from the position on the upstream side of the sheet S having a pressure of 0 Pa in the transport direction to the position on the downstream side of the sheet S having a pressure of 0 Pa again via the position where the maximum pressure is reached. Refers to the area of.

Further, in the present disclosure, the "passing direction" refers to a direction orthogonal to the axial direction and a direction in which the sheet S passes through the pressurizing region N of the fixing device 7 (the direction in which the sheet S is conveyed). Further, in the following description, "upstream" and "downstream" and similar terms refer to "upstream" and "downstream" in the passing direction and similar concepts.

The heater 23 is a heat source for heating the fixing belt 21. The heater 23 is fixed to the lower surface of the pressing member 24 via the holding member 25. The holding member 25 has a semicircular cross section orthogonal to the axial direction and a long shape in the axial direction. It is curved along the lower inner surface of the fixing belt 21. The holding member 25 is made of, for example, a heat-resistant resin material.

As shown in FIG. 4, the heater 23 has a substrate 30, a heat insulating layer 31, and a heat generating contact portion 32. The substrate 30 is fixed to the lower surface of the holding member 25. The heat insulating layer 31 is located on the lower surface of the substrate 30. The heat generating contact portion 32 is located on the lower surface of the heat insulating layer 31.

The heater 23 is held on the lower surface of the holding member 25. The heat generating contact portion 32 in the heater 23 is a portion that faces the pressure roller 22 and comes into contact with the inner surface of the fixing belt 21. The contact portion between the fixing belt 21 and the pressure roller 22 is the pressure region N.

That is, the heater 23 is provided so as to correspond to the pressure region N with the fixing belt 21 interposed therebetween. A temperature sensor (not shown) for detecting the surface temperature of the fixing belt 21 or the temperature of the heater 23 may be provided in the housing 20 shown in FIG.

As shown in FIGS. 3 and 4, the substrate 30 has a substantially rectangular plate shape that is long in the front-rear direction (axial direction). In other words, the substrate 30 has an axial direction in the longitudinal direction and a passing direction in the lateral direction, and extends from the first end 30a to the second end 30b in the longitudinal direction. The substrate 30 is made of a material having electrical insulation such as ceramics.

Here, the first end 30a of the substrate 30 is the end on the side where the individual electrodes 51 to 53, which will be described later, are drawn out, and the second end 30b is the end on the side opposite to the first end 30a. Further, both the upper and lower surfaces of the substrate 30 are substantially smooth.

The heat insulating layer 31 is laminated (deposited) on one surface (entire lower surface) of the substrate 30. The heat insulating layer 31 is made of a material having electrical insulation and low thermal conductivity, such as ceramic or glass. The heat insulating layer 31 has a function of restricting the heat generated in the heat generating contact portion 32 from being transferred to the substrate 30 side.

The heat generating contact portion 32 is laminated on one surface (lower surface) of the heat insulating layer 31. As shown in FIG. 3, the heat-generating contact portions 32 include a plurality of (for example, three) heat-generating parts groups 41, the same number of individual electrodes 51 to 53 as the heat-generating parts groups 41, a common electrode 54, and a coat layer 60. (See FIG. 4).

The plurality of heat generating unit groups 41 are made of a conductive material such as a metal having a higher electric resistance than the individual electrodes 51 to 53 and the common electrode 54, for example. Further, the plurality of heat generating unit groups 41 are located side by side in a row in the longitudinal direction of the substrate 30 on the lower surface of the heat insulating layer 31.

Further, each heating element group 41 is composed of a plurality of resistance heating elements 40 arranged in a row in the longitudinal direction of the substrate 30. The resistance heating element 40 is an example of a heating element. Each of the plurality of resistance heating elements 40 has a substantially rectangular shape elongated in the passing direction (that is, the lateral direction of the substrate 30).

The plurality of heat-generating unit groups 41 include a first heat-generating unit group 41A, a second heat-generating unit group 41B, and a third heat-generating unit group 41C in order from the first end 30a side of the substrate 30. That is, the second heat generating portion group 41B is located in the center in the axial direction, the first heat generating portion group 41A is located on the first end 30a side in the axial direction, and the third heat generating portion group is located on the second end 30b side in the axial direction. 41C is located.

The second heating element group 41B located at the center in the axial direction has a plurality of (8 in the figure) resistors arranged in a range corresponding to the front-rear width of a small-sized (for example, A5 size) sheet S passing through the pressurizing region N. It is composed of a heating element 40.

The first heating element group 41A and the third heating element group 41C located on both sides of the second heating element group 41B correspond to the front-rear width of the normal size (for example, A4 size) sheet S passing through the pressurizing region N. It is composed of a plurality of (4 in the figure) resistance heating elements 40 arranged in a range.

Here, in the embodiment, the second heating element group 41B located at the center in the axial direction has more resistance heating elements 40 than the first heating element group 41A and the third heating element group 41C located on both sides in the axial direction. Have.

The plurality of individual electrodes 51 to 53 and the common electrode 54 are located on the lower surface of the heat insulating layer 31. The plurality of individual electrodes 51 to 53 and the common electrode 54 are made of, for example, a conductive material such as a metal having an electric resistance smaller than that of the resistance heating element 40.

The individual electrode 51 connects one side of the first heat generating portion group 41A to the terminal 61. The individual electrode 52 connects one side of the second heat generating portion group 41B to the terminal 62. The individual electrode 53 connects one side of the third heat generating portion group 41C to the terminal 63.

Further, the common electrode 54 connects to the same terminal 64 as the other side of all the heat generating parts group 41. Terminals 61 to 64 are connection terminals for electrically connecting to an external device such as a power supply.

The individual electrode 51 has a connecting portion 51a and a drawing portion 51b. The connection portion 51a is a portion for connecting the resistance heating elements 40 of the first heating unit group 41A in parallel. The drawer portion 51b is a portion extending from the connection portion 51a toward the terminal 61 along the longitudinal direction of the substrate 30.

The individual electrode 52 has a connecting portion 52a and a drawing portion 52b. The connection portion 52a is a portion for connecting the resistance heating elements 40 of the second heating unit group 41B in parallel. The drawer portion 52b is a portion extending from the connection portion 52a toward the terminal 62 along the longitudinal direction of the substrate 30.

The individual electrode 53 has a connecting portion 53a and a drawing portion 53b. The connection portion 53a is a portion for connecting the resistance heating elements 40 of the third heating unit group 41C in parallel. The drawer portion 53b is a portion extending from the connection portion 53a toward the terminal 63 along the longitudinal direction of the substrate 30.

The common electrode 54 has a connecting portion 54a and a drawing portion 54b. The connecting portion 54a is a portion for connecting each resistance heating element 40 of all the heating unit groups 41 in parallel. The drawer portion 54b is a portion extending from the connection portion 54a toward the terminal 64 along the longitudinal direction of the substrate 30.

As shown in FIG. 4, the coat layer 60 covers a plurality of heat generating portions 41, a plurality of individual electrodes 51 to 53, and a common electrode 54. The coat layer 60 is made of a material having electrical insulation such as ceramic and having a small sliding frictional force with respect to the fixing belt 21.

The coat layer 60 constitutes a surface that comes into contact with the inner surface of the fixing belt 21. The coat layer 60 is also laminated on the portion where the plurality of heat generating portions 41, the individual electrodes 51 to 53, and the common electrode 54 are not laminated.

For the production of the heater 23 described above, for example, a film forming technique such as sputtering, a printed circuit board manufacturing technique, a screen printing technique, or a combination of these techniques can be used.

For example, the heat insulating layer 31 and the heat generating contact portion 32 may be formed on the substrate 30 by sputtering. Further, the heat insulating layer 31 and the heat generating contact portion 32 may be formed on the substrate 30 by repeating steps such as exposure, development, etching, peeling, and laminating using a photomask, which is a technique for manufacturing a printed circuit board.

Further, the heat insulating layer 31 and the heat generating contact portion 32 may be formed by applying an electrically insulating paint or a conductive paint on the substrate 30 (screen printing). With these manufacturing methods, the heat insulating layer 31 and the heat generating contact portion 32 can be accurately formed on the substrate 30.

Further, the terminals 61 to 64 of the heater 23, the drive motor, and the like are electrically connected to the power supply (not shown) via various drive circuits (not shown). Further, the heater 23, the drive motor, the temperature sensor, and the like are electrically connected to the control device of the printer 1 via various circuits. Such a control device controls an electrically connected device or the like.

Here, the details of the fixing process performed by the fixing device 7 will be described mainly with reference to FIG.

First, the control device drives and controls the drive motor and the heater 23. The pressure roller 22 rotates under the driving force of the drive motor, and the fixing belt 21 rotates in accordance with the pressure roller 22 (see the solid line thin arrow in FIG. 2).

Each resistance heating element 40 (see FIG. 3) passes between the individual electrodes 51 to 53 (see FIG. 3) and the common electrode 54 (see FIG. 3) sandwiching the plurality of heating unit groups 41 (see FIG. 3). Heat is generated by passing an electric current along the direction (that is, the lateral direction of the substrate 30). As a result, the pressure region N of the fixing belt 21 is heated.

At this time, the control device changes the heat generating unit group 41 that generates heat according to the size of the seat S. For example, when the normal size sheet S passes through the pressurizing region N, the control device supplies electric power to all the heat generating parts groups 41 to heat all the heat generating parts groups 41.

Further, when the small-sized sheet S passes through the pressurizing region N, the control device generates heat only in the central second heating unit group 41B (see FIG. 3). As a result, only the necessary portion of the fixing belt 21 (pressurized region N) can be heated according to the size of the sheet S. As a result, it is possible to suppress excessive temperature rise at both ends of the fixing belt 21 in the axial direction.

The temperature sensor detects the surface temperature of the fixing belt 21 and transmits a detection signal to the control device via the input circuit. When the control device receives a detection signal indicating that the set temperature (for example, 150 to 200 ° C.) has been reached from the temperature sensor, the control device starts the above-mentioned image forming process while controlling the heater 23 so as to maintain the set temperature. do.

The sheet S on which the toner image is transferred enters the housing 20, and the fixing belt 21 heats the toner (toner image) on the sheet S passing through the pressure region N while rotating forward about the axis. The pressurizing roller 22 pressurizes the toner on the sheet S passing through the pressurizing region N while rotating around the axis. Then, the toner image is fixed on the sheet S. Then, the sheet S on which the toner image is fixed is sent out to the outside of the housing 20 (see FIG. 1) and discharged to the paper ejection tray 4 (see FIG. 1).

FIG. 5 is a diagram for explaining the factors of temperature variation in the heater 23 according to the embodiment. In the heater 23 having the above configuration, as shown in FIG. 5, in one heat generating unit group 41, the current is concentrated in the central portion of the heat generating unit group 41. As a result, the current flowing through the drawer portion 52b increases, and the wiring resistance of the drawer portion 52b increases.

As a result, the resistance heating element 40 located at the center of the heating element group 41 becomes colder than the resistance heating element 40 located at the end. This is because the wiring resistance of the lead-out portion 52b becomes high, and the voltage supplied to the resistance heating element 40 located in the central portion becomes small due to the wiring loss of the lead-out portion 52b.
Q = V ² / R ・ t ・ ・ (1)
Q = I ²・ R ・ t ・ ・ (2)

In the above equation (1), V is a voltage value, R is an electric resistance, and t is a time for passing a current. Further, in the above equation (2), I is a current value.

In particular, in the heating unit group 41 (second heating unit group 41B) having the largest number of resistance heating elements 40, from the other heating unit group 41 (first heating unit group 41A, third heating unit group 41C) to the central portion. Since the degree of concentration of the current is large, the wiring loss of the lead-out portion 52b is large, the voltage supplied to the central portion is smaller than that of the end portion, and the temperature of the central portion becomes lower.

As described above, when the temperature of the resistance heating element 40 located at the center of the heating unit group 41 is lowered, the temperature varies in the longitudinal direction in the heater 23, so that the toner image can be fixed on the sheet S. There is a risk of adverse effects.

Therefore, in the embodiment, the electric resistance of the resistance heating element 40 located at the center of the same heating element group 41 is made smaller than the electric resistance of the resistance heating element 40 located at the end. As a result, the current supplied to the resistance heating element 40 located in the central portion increases, and as shown by the above equation (2), the Joule heat Q of the resistance heating element 40 located in the central portion increases. On the other hand, although the current flowing through the extraction portion 52b increases and the wiring loss of the extraction portion 52b increases, the influence of the wiring loss of the extraction portion 52b on the increase in Joule heat Q becomes small, and the resistance heat generated at the end portion is generated. It can approach the Joule heat Q of the body 40.

Therefore, according to the embodiment, the temperature variation of the plurality of resistance heating elements 40 in the heater 23 is small.

Specifically, in the case of the second heating element group 41B in which the degree of current concentration in the central portion is large, the electric resistance of the resistance heating element 40 located in the central portion is changed to the electric resistance of the resistance heating element 40 located in the end portion. It may be smaller by a more predetermined ratio, for example, 10%.

Further, the electric resistance of the resistance heating element 40 located between the central portion and the end portion may be adjusted stepwise according to the distance from the resistance heating element 40 of the central portion and the end portion. Thereby, the variation in temperature within the second heat generating portion group 41B can be effectively reduced.

Even in the case of the heating element group 41 (first heating element group 41A, third heating element group 41C) in which the number of resistance heating elements 40 is small and the degree of current concentration in the central portion is small, the heating element 40 is located in the central portion. The electric resistance of the resistance heating element 40 may be made smaller than the electric resistance of the resistance heating element 40 located at the end. Thereby, the variation in temperature within the heat generating unit group 41 (first heat generating unit group 41A, third heat generating unit group 41C) can be effectively limited.

Further, in the heater 23 having the above configuration, as shown in FIG. 5, the individual electrode 52 of the second heating element group 41B having the largest number of resistance heating elements 40 has a larger current than the other individual electrodes 51 and 53. It flows. This is because, in order to generate all of the many resistance heating elements 40, a large amount of current must be passed through the individual electrodes 52.

Further, in the individual electrode 52, since the width of the drawer portion 52b is narrower than that of the connection portion 52a, the electric resistance per unit length is large. This is because the heater 23 has a limitation on the width of the substrate 30 in the lateral direction (that is, the passing direction of the sheet S), so that the drawer portions 51b to 53b arranged side by side in the lateral direction are widened. Is difficult.

Therefore, in the heater 23 having the above-described configuration, when a large amount of current flows through the extraction portion 52b of the individual electrode 52, heat is generated in the extraction portion 52b.

When the drawer portion 52b generates heat, the temperature of the heat generating portion group 41 (first heat generating portion group 41A) adjacent to the drawer portion 52b is higher than that of the other heat generating portion group 41 due to thermal interference. Within 23, the temperature varies in the longitudinal direction.

Therefore, in the embodiment, the resistance heating element 40 of the heating element group 41 (first heating element group 41A) adjacent to the drawer portion 52b where heat is generated is replaced with another heating element group 41 (second heating element group 41B, first). It was decided to make the electric resistance larger than the resistance heating element 40 of the 3 heating unit group 41C). Here, the resistance heating element 40 adjacent to the drawer portion 52b is a resistance heating element 40 located directly below the drawer portion 52b on the illustrated surface, and according to FIG. 5, it is located in the first heating unit group 41A. It is a resistance heating element 40.

In other words, the heating element group 41 on the side where the individual electrode 52 of the second heating element group 41B having the largest number of resistance heating elements 40 is pulled out to the terminal 62 (that is, the first end 30a side) is on the opposite side (that is, that is). It was decided to make the electric resistance larger than that of the heating element group 41 on the second end 30b side).

Therefore, the current supplied to the resistance heating element 40 adjacent to the drawer portion 52b is reduced, and as shown in the above equation (2), the Joule heat Q of the resistance heating element 40 adjacent to the drawer portion 52b is reduced. Thereby, the sum of the Joule heat Q of the resistance heating element 40 adjacent to the drawer portion 52b and the heat generated from the drawer portion 52b can be brought close to the Joule heat Q of another resistance heating element 40. Therefore, according to the embodiment, it is possible to reduce the temperature variation in the plurality of resistance heating elements 40 in the heater 23.

For example, the electric resistance of the resistance heating element 40 on the first end 30a side may be made smaller than the electric resistance of the resistance heating element 40 on the second end 30b side by a predetermined ratio (for example, 35%).

Further, the electrical resistance of the resistance heating element 40 located between the first end 30a side and the second end 30b side depends on the distance from the resistance heating element 40 on the first end 30a side and the second end 30b side. It may be adjusted step by step. Thereby, the temperature variation in the plurality of heat generating unit groups 41 can be effectively reduced.

In the embodiment, as a means for making the electric resistance of the specific resistance heating element 40 smaller than the electric resistance of another resistance heating element 40, the length of the specific resistance heating element 40 is made shorter than that of another resistance heating element 40. Alternatively, the cross-sectional area (that is, width × thickness) may be increased. Further, the specific resistance heating element 40 may be made of a material having a smaller electric resistance than another resistance heating element 40.

For example, when the length of a specific resistance heating element 40 is made shorter than that of another resistance heating element 40, the centers of the respective resistance heating elements 40 provided in the heater 23 are aligned along the longitudinal direction of the substrate 30. It should be (ie, centered along the longitudinal direction of the center). As a result, the temperature distribution of the heater 23 in the passing direction of the sheet S (that is, the lateral direction of the substrate 30) can be made uniform. It should be noted that the fact that they are aligned along the longitudinal direction means that the centers of all the resistance heating elements 40 do not have to be aligned, and at least 80% of the total may be aligned. Further, for the center of the resistance heating element 40, a plan photograph may be taken and the area center of gravity of the resistance heating element 40 may be obtained by image processing.

Further, the length of the resistance heating element 40 (simply referred to as the resistance heating element 40a) adjacent to the extraction portion 52b of the individual electrode 52 is set to the length of another resistance heating element 40 (simply referred to as the resistance heating element 40b). To make it shorter, as shown in FIG. 6, the resistance heating element 40a adjacent to the extraction portion 52b may be arranged so as to be separated from the extraction portion 52b of the individual electrode 52 by the other resistance heating element 40b. FIG. 6 is a diagram for explaining an arrangement example of the resistance heating element 40 in the heater 23 according to the embodiment. Here, the fact that the resistance heating element 40a adjacent to the extraction portion 52b is separated from the extraction portion 52b of the individual electrode 52 from the other resistance heating element 40b means that the extraction portion 52b exists in the longitudinal direction of the substrate 30. In this case, the distances to the resistance heating element 40 in the lateral direction of the substrate 30 are compared.

As a result, the distance between the drawer portion 52b and the resistance heating element 40a adjacent to the drawer portion 52b is increased. In other words, the lines connecting the centers of the resistance heating elements 40a are closer to the common electrode 54 than the lines connecting the centers of the other resistance heating elements 40b. As a result, the heat generation region of the resistance heating element 40a constituting the first heat generation unit group 41A approaches the common electrode 54 side. As a result, in the temperature distribution on the line connecting the centers of the resistance heating element 40a (in other words, the temperature distribution on the pressurized region N in FIG. 2), in the lateral direction of the substrate 30 (that is, the passing direction of the sheet S). The temperature distribution of the heater 23 can be made uniform.

Further, in the embodiment, the terminals 61 to 64 to which the plurality of individual electrodes 51 to 53 and the common electrodes 54 are connected are all arranged on the first end 30a side of the substrate 30. As a result, the width of the heater 23 in the longitudinal direction can be reduced, so that the heater 23 can be miniaturized.

[Various variants]
Subsequently, various modifications of the heater 23 will be described with reference to FIGS. 7 to 9. FIG. 7 is a bottom view schematically showing the heater 23 according to the first modification of the embodiment. FIG. 8 is a diagram for explaining a factor of temperature variation in the heater 23 according to the first modification of the embodiment. In the following description, duplicate description will be omitted by assigning the same reference numerals to the same parts as those in the above-described embodiment.

In the first modification shown in FIG. 7, the individual electrodes 53 and the drawer portions 53b and 54b of the common electrode 54 extend toward the second end 30b side of the substrate 30 instead of the first end 30a side. different. The extraction portions 51b and 52b of the individual electrodes 51 and 52 extend toward the first end 30a side of the substrate 30 as in the embodiment.

As described above, both ends of the substrate 30 in the longitudinal direction, specifically, the individual electrodes 51 and 52 extend toward the first end 30a side, and the individual electrodes 53 and the common electrode 54 extend toward the second end 30b side, respectively. Due to the configuration, the spaces on both sides of the heater 23 in the longitudinal direction can be efficiently used.

On the other hand, as shown in FIG. 8, in the heater 23 according to the first modification, the current is concentrated in the central portion of the heat generating portion group 41 in one heat generating portion group 41 as in the embodiment.

As a result, as described above, the resistance heating element 40 located at the center of the heating unit group 41 becomes colder than the resistance heating element 40 located at the end.

Therefore, in the first modification, the electric resistance of the resistance heating element 40 located at the center of the same heating element group 41 is made smaller than the electric resistance of the resistance heating element 40 located at the end, as in the embodiment.

As a result, the current supplied to the resistance heating element 40 located in the central portion increases, and as shown by the above equation (2), the Joule heat Q of the resistance heating element 40 located in the central portion increases. On the other hand, although the current flowing through the extraction portion 52b increases and the wiring loss of the extraction portion 52b increases, the influence of the wiring loss of the extraction portion 52b on the increase in Joule heat Q becomes small, and the resistance heat generated at the end portion is generated. It can approach the Joule heat Q of the body 40. Therefore, according to the first modification, it is possible to reduce the temperature variation in the plurality of resistance heating elements 40 in the heater 23.

Further, in the heater 23 according to the first modification, as in the embodiment, a larger current flows through the individual electrodes 52 of the second heat generating unit group 41B, which has the largest number of heat generating unit groups 41, than the other individual electrodes 51 and 53. As a result, heat is generated at the extraction portion 52b of the individual electrode 52.

Therefore, in the first modification, the electric resistance of the heat generating portion group 41 on the first end 30a side is increased. Here, in the heat-generating portion group 41, the first heat-generating portion group 41A, the second heat-generating portion group 41B, and the third heat-generating portion group 41C are located in this order from the first end 30a side of the substrate 30. The first heat-generating part group 41A is connected to the individual electrode 51, the second heat-generating part group 41B is connected to the individual electrode 52, and the third heat-generating part group 41C is connected to the individual electrode 53. Therefore, in other words, the electric resistance of the first heat generating unit group 41A is increased.

As a result, the current supplied to the resistance heating element 40 adjacent to the drawer portion 52b is reduced, and as shown in the above equation (2), the Joule heat Q of the resistance heating element 40 adjacent to the drawer portion 52b is reduced. .. Thereby, the sum of the Joule heat Q of the resistance heating element 40 adjacent to the drawer portion 52b and the heat generated from the drawer portion 52b can be brought close to the Joule heat Q of another resistance heating element 40. Therefore, according to the first modification, it is possible to reduce the temperature variation in the plurality of resistance heating elements 40 in the heater 23.

Further, in the first modification, as shown in FIG. 8, there is a limitation on the length (distance in the axial direction) of the drawer portion 53b of the individual electrode 53 extending from the third heat generating portion group 41C toward the second end 30b side. .. Therefore, in the first modification, in the third heating element group 41C to which the individual electrodes 53 are connected, the electric resistance of the resistance heating element 40 on the second end 30b side is set from the electric resistance of the resistance heating element 40 on the first end 30a side. Enlarge.

As a result, even when the length of the extraction portion 53b of the individual electrode 53 is limited, it is possible to reduce the temperature variation in the plurality of resistance heating elements 40 in the heater 23.

FIG. 9 is a bottom view schematically showing the heater 23 according to the second modification of the embodiment. In the heater 23 shown in FIG. 9, the location where the individual electrodes 51 to 53 and the common electrode 54 are connected to the resistance heating element 40 is different from the above-described embodiment.

Specifically, the connecting portion 51a of the individual electrodes 51 has a protruding portion 51a1 that projects toward the common electrode 54 in a comb-teeth shape in the lateral direction of the substrate 30. The connecting portion 52a of the individual electrode 52 has a protruding portion 52a1 that projects in a comb-like shape in the lateral direction of the substrate 30 toward the common electrode 54.

The connecting portion 53a of the individual electrode 53 has a protruding portion 53a1 protruding toward the common electrode 54 in a comb-teeth shape in the lateral direction of the substrate 30. The connecting portion 54a of the common electrode 54 has a protruding portion 54a1 that projects in a comb-teeth shape in the lateral direction of the substrate 30 toward the individual electrodes 51 to 53.

Further, the resistance heating element 40 belonging to the first heat generating portion group 41A is arranged between the protruding portion 51a1 and the protruding portion 54a1, and the resistance heating element 40 belonging to the second heating portion group 41B is arranged between the protruding portion 52a1 and the protruding portion 54a1. The resistance heating element 40, which is arranged between the protrusions 54a1 and belongs to the third heating unit group 41C, is arranged between the protrusions 53a1 and the protrusions 54a1.

Then, all the resistance heating elements 40 are connected to the protrusions 51a1 to 54a1 on both sides in the longitudinal direction of the substrate 30. That is, the current flowing through the resistance heating element 40 flows not along the lateral direction of the substrate 30 as in the above-described embodiment, but along the longitudinal direction of the substrate 30.

In the heater 23 according to the second modification described so far, as a means for making the electric resistance of the specific resistance heating element 40 smaller than the electric resistance of another resistance heating element 40, a protrusion connected to the specific resistance heating element 40 is used. The distance between the portions 51a1 to 54a1 may be narrower than the distance between the protruding portions 51a1 to 54a1 connected to another resistance heating element 40.

For example, in the second modification, the protrusions 51a1 to 54a1 connected to the resistance heating element 40 located at the center of the same heating element group 41 are spaced apart from each other by the protrusions connected to the resistance heating element 40 located at the end. Make it smaller than the distance between the parts 51a1 to 54a1.

As a result, in the same heating element group 41, the length of the resistance heating element 40 located at the center (here, the length along the longitudinal direction of the substrate 30) is set from the length of the resistance heating element 40 located at the end. Can also be shortened.

Therefore, in the second modification, as in the embodiment, the electric resistance of the resistance heating element 40 located at the center of the same heating element group 41 is made smaller than the electric resistance of the resistance heating element 40 located at the end. Can be done.

Further, as shown in FIG. 9, the distance between the protrusions 51a1 to 54a1 connected to the resistance heating element 40 adjacent to the extraction portion 52b of the individual electrode 52 is set to the protrusion 51a1 connected to another resistance heating element 40. Make it narrower than the distance between ~ 54a1.

As a result, the length of the resistance heating element 40a adjacent to the extraction portion 52b of the individual electrode 52 (here, the length along the longitudinal direction of the substrate 30) is made shorter than the length of the other resistance heating elements 40b. Can be done. Therefore, according to the second modification, the electric resistance of the resistance heating element 40a adjacent to the extraction portion 52b of the individual electrode 52 can be made smaller than that of the other resistance heating elements 40b.

In the heater 23 according to the second modification, the means for reducing the electric resistance of the specific resistance heating element 40 to be smaller than the electric resistance of another resistance heating element 40 is the protruding portions 51a1 to connected to the specific resistance heating element 40. It is not limited to the case where the distance between 54a1 is narrowed.

For example, the cross-sectional area (that is, width × thickness) of a specific resistance heating element 40 may be larger than the cross-sectional area of another resistance heating element 40. The "width" described here is the length of the resistance heating element 40 along the lateral direction of the substrate 30. Also by this, the electric resistance of the specific resistance heating element 40 can be made smaller than the electric resistance of another resistance heating element 40.

Further, the specific resistance heating element 40 may be made of a material having a smaller electric resistance than another resistance heating element 40. Also by this, the electric resistance of the specific resistance heating element 40 can be made smaller than the electric resistance of another resistance heating element 40.

Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various changes can be made without departing from the spirit of the present disclosure. For example, in the above embodiment, the second heating element group 41B is provided with eight resistance heating elements 40, and the first heating element group 41A and the third heating element group 41C are provided with four resistance heating elements 40. However, the number of resistance heating elements 40 provided in each heating unit group 41 is not limited to the above example.

Further, in the above-described embodiment, the cross-sectional structure of the heater 23 is not limited to the example of FIG. For example, the individual electrodes 51 to 53 and the common electrode 54 may have a laminated structure made of different metal materials (for example, Ag, Al, etc.).

With such a laminated structure, the electric resistance of the individual electrodes 51 to 53 and the common electrode 54 can be reduced, so that the power consumption of the heater 23 can be reduced.

As described above, the heater (heater 23) according to the embodiment is located on the substrate 30 extending from the first end 30a to the second end 30b and on the first end 30a side or the second end 30b side in the longitudinal direction of the substrate 30. It has a plurality of terminals 61 to 63 located and a plurality of heat generating parts (resistive heating element 40) located side by side along the longitudinal direction of the substrate 30, and the plurality of heat generating parts (resistive heating element 40) are the same terminal. A heating element group 41 connected to 61 to 63 is provided. Further, in the heating element group 41, the heating element (resistive heating element 40) located at the center has a smaller electric resistance than the heating element (resistor heating element 40) located at the end. As a result, even when the current is concentrated in the central portion of the heating unit group 41, it is possible to reduce the temperature variation in the plurality of resistance heating elements 40 in the heater 23.

Further, in the heater (heater 23) according to the embodiment, a plurality of heat generating part groups 41, a common electrode 54 connecting all the heat generating parts groups 41 to the same terminal 64, and each heat generating part group 41 are connected to the same terminal. A plurality of individual electrodes 51 to 53 connected to 61 to 63 are provided. Further, when the side where the individual electrode 52 of the heat generating part group 41 (second heat generating part group 41B) having the largest number of heat generating parts (resisting heat generating part 40) is pulled out to the terminal 62 is the first end 30a side of the substrate 30. Of the plurality of heat generating parts groups 41, the heat generating part (resisting heat generating body 40) of the heat generating part group 41 located on the first end 30a side of the substrate 30 is the heat generating part group located on the second end 30b side of the substrate 30. The electric resistance is larger than that of the heat generating portion (resistance heating element 40) of 41. As a result, even when heat is generated from the extraction portion 52b of the individual electrode 52, it is possible to reduce the temperature variation in the plurality of resistance heating elements 40 in the heater 23.

Further, in the heater (heater 23) according to the embodiment, all the terminals 61 to 64 are located on the first end 30a side of the substrate 30. As a result, the width of the heater 23 in the longitudinal direction can be reduced, so that the heater 23 can be miniaturized.

Further, in the heater (heater 23) according to the embodiment, the first heat generating part group 41A, the second heat generating part group 41B, and the third heat generating part group 41C are located in order from the first end 30a side of the substrate 30. The individual electrode 51 connected to the first heat generating part group 41A and the individual electrode 52 connected to the second heat generating part group 41B are pulled out to the first end 30a side of the substrate 30 and are individually connected to the third heat generating part group 41C. The electrode 53 and the common electrode 54 are pulled out toward the second end 30b of the substrate 30. As a result, the spaces on both sides of the heater 23 in the longitudinal direction can be efficiently used.

Further, in the heater (heater 23) according to the embodiment, in the third heating unit group 41C, the heating element (resistor heating element 40) located on the second end 30b side of the substrate 30 is the first end 30a of the substrate 30. The electrical resistance is larger than that of the heating element (resistive heating element 40) located on the side. As a result, even when the length of the extraction portion 53b of the individual electrode 53 is limited, it is possible to reduce the temperature variation in the plurality of resistance heating elements 40 in the heater 23.

Further, in the heater (heater 23) according to the embodiment, the heating element (resistance) adjacent to the individual electrode 52 of the heating element group 41 (second heating element group 41B) having the largest number of heating elements (resisting element 40). The heating element 40) has a higher electrical resistance than the other heating elements (resistance heating element 40). As a result, even when Joule heat is generated from the extraction portion 52b of the individual electrode 52, it is possible to reduce the temperature variation in the plurality of resistance heating elements 40 in the heater 23.

Further, in the heater (heater 23) according to the embodiment, the heating element (resistor) adjacent to the individual electrode 52 of the heating element group 41 (second heating element group 41B) having the largest number of heating elements (resisting heating element 40). The heating element 40) is located so as to be separated from the individual electrode 52 by the other heating element (resistive heating element 40). As a result, the temperature distribution of the heater 23 in the passing direction of the sheet S can be made uniform.

Further, in the heater (heater 23) according to the embodiment, the heating element (resistor heating element 40) having a small electric resistance has a shorter length than the heating element (resistor heating element 40) having a large electric resistance. As a result, even when the same material is used for all the resistance heating elements 40, the resistance heating elements 40 having different electric resistances can be formed.

Further, in the heater (heater 23) according to the embodiment, the central portions (centers) of all the heat generating portions (resistive heating elements 40) are arranged so as to be aligned along the longitudinal direction. As a result, the temperature distribution of the heater 23 in the passing direction of the sheet S (that is, the lateral direction of the substrate 30) can be made uniform.

Further, in the heater (heater 23) according to the embodiment, the heating element (resistor heating element 40) having a small electric resistance has a larger cross-sectional area than the heating element (resistor heating element 40) having a large electric resistance. Thereby, even if the same material is used for all the resistance heating elements 40, the resistance heating elements 40 having different electric resistances can be formed.

Further, the fixing device 7 according to the embodiment includes a fixing member (fixing belt 21) that heats the toner on the medium (sheet S) while rotating around the axis, and a fixing member (fixing belt 21) that rotates around the axis. A pressure region N is formed between the two, and a pressure member (pressure roller 22) that pressurizes toner on a medium (sheet S) that passes through the pressure region N and a fixing member (fixing belt 21) are sandwiched between the two. It is located corresponding to the pressurizing region N and includes a heater (heater 23) for heating the fixing member (fixing belt 21). Further, the heater (heater 23) includes a substrate 30 extending from the first end 30a to the second end 30b, and a plurality of terminals 61 to 61 located on the first end 30a side or the second end 30b side in the longitudinal direction of the substrate 30. 63 and a plurality of heating elements (resisting heating elements 40) located side by side along the longitudinal direction of the substrate 30, and the plurality of heating elements (resisting heating elements 40) are connected to the same terminals 61 to 63. A group 41 and the like. The heating element (resisting heating element 40) located at the center of the heating element group 41 has a smaller electrical resistance than the heating element (resisting heating element 40) located at the end. As a result, it is possible to realize the fixing device 7 in which the temperature variation in the plurality of resistance heating elements 40 in the heater 23 is reduced.

The embodiments disclosed this time should be considered to be exemplary in all respects and not restrictive. Indeed, the above embodiments can be embodied in a variety of forms. Further, the above-described embodiment may be omitted, replaced or changed in various forms without departing from the scope of the appended claims and the purpose thereof.

1 Printer 7 Fixing device 21 Fixing belt (an example of fixing member)
22 Pressurizing roller (example of pressurizing member)
23 Heater (an example of a heater)
30 Substrate 30a 1st end 30b 2nd end 31 Insulation layer 32 Heat-generating contact part 40 Resistance heating element (example of heating part)
41 Heat-generating part group 41A 1st heat-generating part group 41B 2nd heat-generating part group 41C 3rd heat-generating part group 51 to 53 Individual electrodes 54 Common electrodes 61 to 64 terminals S sheet (example of medium)

Claims (13)

A substrate extending from the first end to the second end,
A plurality of terminals located on the first end side or the second end side in the longitudinal direction of the substrate, and
A group of heat generating parts having a plurality of heat generating parts arranged side by side along the longitudinal direction of the substrate and connecting the plurality of heat generating parts to the same terminal.
With
The heating element located at the center of the heating element group is a heater having a smaller electric resistance than the heating element located at the end. With the plurality of the heat generating parts group,
A common electrode that connects all the heat generating parts to the same terminal,
A plurality of individual electrodes connecting each of the heat generating parts to the same terminal,
With
When the side from which the individual electrodes of the heat generating part group having the largest number of heat generating parts are drawn out to the terminals is the first end side of the substrate.
Among the plurality of heat generating parts, the heat generating part of the heat generating part group located on the first end side of the substrate is from the heat generating part of the heat generating part group located on the second end side of the substrate. The heater according to claim 1, which has a large electrical resistance. The heater according to claim 2, wherein all the terminals are located on the first end side of the substrate. The first heat-generating part group, the second heat-generating part group, and the third heat-generating part group are located in this order from the first end side of the substrate.
The individual electrode connected to the first heat generating portion group and the individual electrode connected to the second heat generating portion group are pulled out to the first end side of the substrate.
The heater according to claim 2, wherein the individual electrode connected to the third heat generating portion group and the common electrode are pulled out to the second end side of the substrate. In the third heat generating part group,
The heater according to claim 4, wherein the heating element located on the second end side of the substrate has a higher electrical resistance than the heating element located on the first end side of the substrate. The heater according to any one of claims 2 to 5, wherein the heating portion adjacent to the individual electrode of the heating portion group having the largest number of heating portions has a higher electrical resistance than the other heating portions. The heat-generating portion adjacent to the individual electrode of the heat-generating portion group having the largest number of heat-generating portions is one of claims 2 to 6 located so as to be separated from the individual electrode by the other heat-generating portion. The heater described. The heater according to any one of claims 1 to 7, wherein the heat generating portion having a small electric resistance has a shorter length than the heat generating portion having a large electric resistance. The heater according to claim 8, wherein the central portions of all the heat generating portions are arranged so as to be aligned along the longitudinal direction. The heater according to any one of claims 1 to 9, wherein the heat generating portion having a small electric resistance has a larger cross-sectional area than the heat generating portion having a large electric resistance. The heater according to any one of claims 1 to 10, wherein a current flows through the heat generating portion along the lateral direction of the substrate. The heater according to any one of claims 1 to 10, wherein a current flows through the heat generating portion along the longitudinal direction of the substrate. A fixing member that heats the toner on the medium while rotating around the axis,
A pressure member that forms a pressure region with the fixing member while rotating about an axis and pressurizes the toner on the medium that passes through the pressure region.
A heater located across the fixing member and corresponding to the pressure region and heating the fixing member, and a heater.
With
The heater
A substrate extending from the first end to the second end,
A plurality of terminals located on the first end side or the second end side in the longitudinal direction of the substrate, and
A group of heat generating parts having a plurality of heat generating parts arranged side by side along the longitudinal direction of the substrate and connecting the plurality of heat generating parts to the same terminal.
With
The heating unit located at the center of the heat generating group is a fixing device having a smaller electric resistance than the heat generating unit located at the end.

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