Heater-equipped electrostatic capacitance sensor and heater-equipped electrostatic capacitance sensor unit

Abstract

A heater-equipped electrostatic capacitance sensor unit 2 comprises a first electrically conductive portion 23 that forms an electrostatic capacitance with an object being detected, and generates heat by means of electrical resistance, and a second electrically conductive portion 24 that forms an electrostatic capacitance with the object being detected, and is connected to the first electrically conductive portion 23, wherein the second electrically conductive portion 24 is configured such that a current does not flow to the second electrically conductive portion 24 when the first electrically conductive portion 23 is generating heat by means of electrical resistance.

Description

Heated capacitance sensor and heated capacitance sensor unit

[0001] The present invention relates to a heater-equipped capacitance sensor and a heater-equipped capacitance sensor unit. For designated countries where incorporation by reference of literature is permitted, the content of Japanese Patent Application No. 2024-117010, filed in Japan on July 22, 2024, is incorporated herein by reference and made a part of the present specification.

[0002] A known grip sensor that can be attached to a steering wheel includes a sensor unit, a control circuit unit, and a harness that electrically connects the sensor unit and the control circuit unit (see, for example, Patent Document 1).

[0003] In the grip sensor disclosed in Patent Document 1, the sensor unit includes a substrate made of nonwoven fabric and a sensor wire made of metal wire. The control circuit includes a power supply unit and a sensor circuit. The power supply unit causes the sensor wire to generate heat by passing a current through it (see, for example, Patent Document 1, paragraph

[0047] ). The sensor circuit passes an AC current through the sensor wire and detects changes in capacitance in the sensor wire (see, for example, Patent Document 1, paragraph

[0048] ).

[0004] Japanese Patent Application Laid-Open No. 2018-142411

[0005] In the grip sensor of the above-mentioned conventional technology, the sensor wire that functions as a heater is also used as a capacitance sensor electrode. However, because the sensor wire is thin, the area of ​​the sensor electrode formed by the sensor wire is small, which causes a problem of reduced sensitivity of the capacitance sensor.

[0006] An object of the present invention is to provide a heater-equipped capacitance sensor that can improve sensitivity.

[0007] [1] Aspect 1 of the present invention is a heater-equipped capacitance sensor comprising a first conductive part that forms a capacitance between itself and a detected object and generates heat due to electrical resistance, and a second conductive part that forms a capacitance between itself and the detected object and is connected to the first conductive part, wherein the second conductive part is configured so that no current flows through the second conductive part when the first conductive part generates heat due to electrical resistance.

[0008] [2] A second aspect of the present invention may be the heater-equipped capacitance sensor of the first aspect, wherein the first conductive portion includes a linear pattern extending linearly.

[0009] [3] Aspect 3 of the present invention may be a heater-equipped capacitance sensor according to aspect 2, wherein the second conductive portion includes a planar pattern connected to the linear pattern at only one point.

[0010] [4] A fourth aspect of the present invention may be the heated capacitance sensor of the second or third aspect, wherein the linear pattern has a meandering shape with a plurality of folded portions.

[0011] [5] A fifth aspect of the present invention may be a heated capacitance sensor according to the fourth aspect, wherein the second conductive portion includes a first intervening portion disposed inside the folded portion.

[0012] [6] A sixth aspect of the present invention may be a heated capacitance sensor according to any one of the second to fifth aspects, wherein the linear pattern includes a first serpentine shape having a plurality of first folded portions, and a second serpentine shape having a plurality of second folded portions and adjacent to the first serpentine shape with a gap therebetween, and the second conductive portion includes a second intervening portion arranged between the first folded portion and the second folded portion.

[0013] [7] A seventh aspect of the present invention may be the heated capacitance sensor according to any one of the fourth to sixth aspects, wherein the folded-back portion is folded back in a curved shape.

[0014] [8] Aspect 8 of the present invention may be a heated capacitance sensor according to any one of aspects 1 to 3, wherein the first conductive portion includes a mesh pattern formed by a plurality of linear patterns intersecting each other.

[0015] [9] A ninth aspect of the present invention may be a heated capacitance sensor according to the eighth aspect, wherein the mesh pattern includes an opening surrounded by the plurality of linear patterns, and the second conductive portion includes a third intervening portion disposed within the opening.

[0016]

[10] Aspect 10 of the present invention may be a heated capacitance sensor according to any one of aspects 1 to 9, wherein the heated capacitance sensor further comprises an electrically insulating substrate, and the first and second conductive portions are provided on a main surface of the substrate.

[0017]

[11] Aspect 11 of the present invention may be a heated capacitance sensor according to any one of aspects 1 to 10, wherein the second conductive portion is integrally formed with the first conductive portion.

[0018]

[12] A twelfth aspect of the present invention may be a heater-equipped capacitance sensor according to any one of aspects 1 to 11, wherein the thickness of the first conductive portion is greater than the thickness of the second conductive portion.

[0019]

[13] Aspect 13 of the present invention is a heated capacitance sensor unit comprising: a heated capacitance sensor of any one of aspects 1 to 12; a heater circuit that causes the first conductive portion to generate heat by passing a current through the first conductive portion; and a sensor circuit that applies a voltage to the first and second conductive portions and detects a change in the capacitance.

[0020] In the present invention, the first conductive part forms a capacitance with the object to be detected and generates heat due to electrical resistance, and the second conductive part forms a capacitance with the object to be detected and is configured so that no current flows to the second conductive part when the first conductive part generates heat due to electrical resistance, so that the detection area of ​​the capacitance sensor can be increased, thereby improving the sensitivity of the capacitance sensor.

[0021] Furthermore, in the present invention, the heat generated by the first conductive portion is diffused by the second conductive portion, so that the heater can be uniformly heated.

[0022] Fig. 1 is a plan view showing an example of a steering wheel to which a heated capacitance sensor unit according to an embodiment of the present invention is attached. Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1. Fig. 3 is an enlarged developed view of a wiring board of a heated capacitance sensor unit according to an embodiment of the present invention, which is an enlarged developed view of the wiring board at part III in Fig. 1. Fig. 4 is an enlarged cross-sectional view of a first modified wiring board according to an embodiment of the present invention. Fig. 5 is an enlarged cross-sectional view of a second modified wiring board according to an embodiment of the present invention. Fig. 6 is an enlarged developed view of a third modified wiring board according to an embodiment of the present invention, which is an enlarged developed view corresponding to part III in Fig. 1.

[0023] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0024] Fig. 1 is a plan view showing an example of a steering wheel 1 to which a heated capacitance sensor unit 2 according to this embodiment is attached. Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1. Fig. 3 is an enlarged development view of a wiring board 20a of the heated capacitance sensor unit 2 according to this embodiment, and is an enlarged development view of the wiring board 20a at part III in Fig. 1.

[0025] Although not particularly limited, the heated capacitance sensor unit 2 in this embodiment is attached to a vehicle steering wheel 1. As shown in Fig. 1, the heated capacitance sensor unit 2 includes a wiring board 20a and a control circuit 30.

[0026] The wiring board 20a functions as a heater and also as a capacitance sensor. That is, the wiring board 20a is a capacitance sensor with a heater. More specifically, the wiring board 20a can function as a capacitance sensor that detects the grip of the rim portion 11 by a detection object (e.g., the driver's hand), and can also function as a heater that heats the rim portion 11 and the detection object.

[0027] As shown in FIG. 2, the wiring board 20a is attached to the rim portion 11 of the steering wheel 1 and is covered with a cover layer 4 made of, but not limited to, resin, leather, or the like.

[0028] 1, the rim portion 11 has a circular ring shape. The wiring board 20a is arranged in a first circumferential direction D of the rim portion 11 (the direction of rotation of the steering wheel 1). １ In this case, the wiring boards 20a may be attached around the entire periphery of the rim portion 11, or may be attached to only a part of the rim portion 11. When the wiring boards 20a are attached to only a part of the rim portion 11, a pair of wiring boards 20a may be attached to both sides of the rim portion 11, respectively.

[0029] The shape of the rim portion 11 is not limited to a circular ring shape, but may be a polygonal ring shape. Alternatively, the shape of the rim portion 11 may not be a ring shape, but may be a shape in which a portion of the ring is missing.

[0030] 2, the rim portion 11 has a substantially circular cross-sectional shape. The rim portion 11 includes a core 12 made of metal or the like, and a resin layer 13 that covers the core 12. Examples of the resin material that makes up the resin layer 13 include polyurethane resin. The cross-sectional shape of the rim portion 11 is not limited to a substantially circular shape, and may be an elliptical or polygonal shape.

[0031] In this embodiment, the wiring board 20a is oriented in a second circumferential direction D, which is the circumferential direction of the circular cross section of the rim portion 11. ２ In the second circumferential direction D, the wiring board 20a is arranged to cover the entire outer peripheral surface of the rim portion 11. ２In this case, the mounting member 12 may be attached only to a part of the outer peripheral surface of the rim portion 11 .

[0032] The wiring board 20a of the heater-equipped capacitance sensor unit 2 in this embodiment includes a first base material 21, a conductive layer 22, a first adhesive layer 26, and a second adhesive layer 27. The first base material 21 corresponds to an example of a "base material" in the aspects of the present invention. Note that in this embodiment, the conductive layer 22 and the second adhesive layer 27 are in direct contact with each other, but this is not limiting. The wiring board 20a may further include, for example, an insulating protective layer provided on the first base material 21 so as to cover the conductive layer 22. This insulating protective layer is a layer that protects the conductive layer 22. An example of a material constituting the insulating protective layer is a resist material. Specific examples of the resist material include resist materials containing polyester, epoxy, acrylic, polyimide, polyurethane, etc.

[0033] The first base material 21 is bent along the outer peripheral surface of the resin layer 13 of the rim portion 11 and attached to the outer peripheral surface via a first adhesive layer 26. The first base material 21 is made of a resin material that is electrically insulating and flexible. Examples of such a resin material include, but are not limited to, polyimide (PI), liquid crystal polymer (LCP), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyetherimide (PEI), polyether ether ketone (PEEK), and aramid.

[0034] In this embodiment, the first base material 21 is oriented in the first circumferential direction D in accordance with the outer shape of the rim portion 11 along the annular shape. １ Although not particularly shown, the first base material 21 may be provided with a slit so that it can be easily bent along the outer peripheral surface of the rim portion 11.

[0035] As shown in Figures 2 and 3, a conductive layer 22 is formed on the main surface (outer peripheral surface) 21a of the first substrate 21. In this embodiment, the conductive layer 22 is made of a conductive material. Specifically, although not particularly limited, the conductive layer 22 can be formed by printing a conductive paste on the main surface 21a of the first substrate 21 and solidifying (curing) it. Examples of methods for printing the conductive paste include screen printing, gravure offset printing, flexographic printing, and inkjet printing. The conductive paste is composed of conductive particles and a binder resin mixed with water or a solvent and various additives.

[0036] Specific examples of conductive particles include silver, copper, nickel, tin, bismuth, zinc, indium, palladium, alloys thereof, metal salts thereof, carbon, conductive polymers such as PEDOT / PSS, etc. Specific examples of binder resins include acrylic resin, polyester resin, epoxy resin, vinyl resin, urethane resin, phenolic resin, polyimide resin, silicone resin, and fluororesin. Examples of solvents contained in the conductive paste include α-terpineol, butyl carbitol acetate, butyl carbitol, 1-decanol, butyl cellosolve, diethylene glycol monoethyl ether acetate, and tetradecane. The binder resin may be omitted from the conductive paste. Alternatively, a conductive ink may be used instead of the conductive paste.

[0037] Alternatively, the conductive layer 22 may be made of a metal material such as copper, aluminum, etc. When the conductive layer 22 is made of such a metal material, the conductive layer 22 can be formed on the main surface 21 a of the first base material 21 using a subtractive method, an additive method (either a full-additive method or a semi-additive method), or the like.

[0038] 2 and 3, the conductive layer 22 includes a first conductive portion 23 and a second conductive portion 24. In this embodiment, the first conductive portion 23 and the second conductive portion 24 are made of the same material and are integrally formed with each other. Therefore, the first conductive portion 23 and the second conductive portion 24 are electrically connected to each other. However, the first conductive portion 23 and the second conductive portion 24 may be made of different materials.

[0039] The first conductive portion 23 forms a capacitance between itself and the object to be detected, and generates heat due to electrical resistance in response to a current from a heater circuit 31 (see FIG. 3 ), which will be described later. That is, the first conductive portion 23 functions as a capacitance sensor and also as a heater.

[0040] As shown in FIG. 2, the thickness T １ is the thickness T of the second conductive portion 24 ２ Although not particularly limited, when the first conductive portion 23 is made using a conductive paste with a relatively high resistance value, the thickness T １ is the thickness T of the second conductive portion 24 ２ By making the thickness thicker than the thickness of the first conductive portion 23, the resistivity of the first conductive portion 23 can be adjusted to a range in which a current can flow, and the amount of heat generated as a heater can be controlled.

[0041] 3, the first conductive portion 23 includes a first meandering shape 231 that meanders linearly and a second meandering shape 233 that meanders linearly. The first meandering shape 231 and the second meandering shape 233 are arranged in a first circumferential direction D. １ , and extend parallel to each other along the line 31. Although not particularly shown, in this embodiment, the first serpentine shape 231 and the second serpentine shape 233 are electrically connected to each other in series, and the first serpentine shape 231 and the second serpentine shape 233 form a single serpentine linear pattern. However, the first serpentine shape 231 and the second serpentine shape 233 may also be arranged electrically in parallel to each other. In this case, for example, the first serpentine shape 231 and the second serpentine shape 233 may be electrically connected to the heater circuit 31 independently of each other.

[0042] As shown in FIG. 3, the first serpentine shape 231 is ２ A third circumferential direction D parallel to ３ a plurality of folded portions 232a curved to protrude toward the third circumferential direction D ３ A fourth circumferential direction D opposite to the ４ The first serpentine shape 231 in this embodiment includes a plurality of folded portions 232b that are curved so as to protrude toward the first circumferential direction D. In this embodiment, the folded portions 232a and 232b are generally U-shaped and are connected to each other and are curved in the first circumferential direction D. １ It is composed of tiles arranged alternately along the line.

[0043] The folded portion 232a has a vertex V １ In the third circumferential direction D ３ from the fourth circumferential direction D ４ On the other hand, the folded portion 232b is bent in a curved shape toward the vertex V ２ In the fourth circumferential direction D ４ from the third circumferential direction D ３ It is folded back in a curve towards the

[0044] The second serpentine shape 233 is ３ a plurality of folded portions 234a curved to protrude toward the fourth circumferential direction D ４ The second serpentine shape 233 in this embodiment includes a plurality of folded portions 234b that are curved so as to protrude toward the first circumferential direction D. In this embodiment, the folded portions 234a and 234b are generally U-shaped and are connected to each other. １ It is composed of tiles arranged alternately along the line.

[0045] The folded portion 234a has a vertex V ３ In the third circumferential direction D ３ from the fourth circumferential direction D ４ The folded portion 234a is folded back in a curved shape toward the third circumferential direction D ３2, the folded portion 234b is disposed adjacent to the folded portion 232a of the first meandering shape 231 with a gap therebetween. On the other hand, the folded portion 234b, in contrast to the folded portion 234a, has a vertex V ４ In the fourth circumferential direction D ４ from the third circumferential direction D ３ The folded portion 234b is folded back in a curved shape toward the third circumferential direction D ３ , the folded portion 232b of the first meandering shape 231 is disposed adjacent to the folded portion 232b with a gap therebetween.

[0046] In this embodiment, the folded portions 232a, 232b, 234a, and 234b have a curved shape, but are not limited to this and may have a bent shape. Furthermore, in this embodiment, a case has been described in which two serpentine shapes are arranged adjacent to each other, but this is not limited to this and the number of serpentine shapes may be one or three or more. Furthermore, when multiple serpentine shapes are provided, both curved serpentine shapes and bent serpentine shapes may be provided. Alternatively, a single serpentine shape may include both curved and bent folded portions.

[0047] As shown in Figures 2 and 3, the second conductive portion 24 is connected to the first conductive portion 23. This second conductive portion 24 forms a capacitance with the object to be detected, but does not generate heat because almost no current flows through it from the heater circuit 31 (see Figure 3). In other words, the second conductive portion 24 functions as a capacitance sensor but does not actually function as a heater. More precisely, when the heater circuit 31 starts to supply current to the conductive layer 22, an inrush current flows into the second conductive portion 24, but after the inrush current flows in, almost no current flows through the second conductive portion 24. Therefore, the second conductive portion 24 generates almost no heat while the first conductive portion 23 continues to generate heat as a heater.

[0048] 3, the second conductive portion 24 includes a plurality of intervening portions 240a, a plurality of intervening portions 240b, a plurality of intervening portions 240c, and a plurality of intervening portions 240d. The intervening portion 240a is connected to the first serpentine shape 231 at only one point, and the intervening portion 240b is connected to the first serpentine shape 231 at only one point. The intervening portion 240c is connected to the second serpentine shape 233 at only one point, and the intervening portion 240d is connected to the second serpentine shape 233 at only one point. The intervening portions 240a to 240d correspond to an example of a "first intervening portion" in this aspect of the present invention, and the intervening portions 240b and 240d also correspond to an example of a "second intervening portion" in this aspect of the present invention.

[0049] The intervening portion 240a is formed inside the folded portion 232a and between the folded portions 232b. The intervening portion 240a includes a connecting portion 241a and a planar portion 242a. The connecting portion 241a is oriented in the fourth circumferential direction D. ４ The interposing portion 240a has a linear shape extending from the folded portion 232a toward the folded portion 232a, and connects the folded portion 232a and the planar portion 242a. As a result, the interposing portion 240a is connected to the folded portion 232a at only one point.

[0050] The planar portion 242a is connected to the connecting portion 241a and is spaced apart from the folded portions 232a and 232b. The planar portion 242a fills most of the space inside the folded portion 232a and most of the space between the folded portions 232b.

[0051] The intervening portion 240b is disposed inside the folded portion 232b and is formed between the folded portion 232b and the folded portion 234b. The intervening portion 240b includes a connecting portion 241b and a planar portion 242b. The connecting portion 241b is oriented in the third circumferential direction D. ３ The fold portion 232b has a linear shape extending from the folded portion 232b toward the plane portion 242b, and connects the folded portion 232b and the plane portion 242b.

[0052] The planar portion 242b is connected to the connecting portion 241b and is spaced apart from the folded portions 232b and 234b, filling the space between the folded portions 232b and 234b.

[0053] The intervening portion 240c is formed from the inside of the folded portion 234b of the second serpentine shape 233 to extend between the folded portions 234a. The intervening portion 240c has a shape obtained by inverting the shape of the intervening portion 240a in the left-right direction of the paper in the figure. The intervening portion 240c includes a connecting portion 241c and a planar portion 242c. The connecting portion 241c extends from the folded portion 234b in the third circumferential direction D3 and connects the folded portion 234b and the planar portion 242c.

[0054] The planar portion 242c has a shape obtained by mirror-inverting the planar portion 242a. The planar portion 242c is connected to the connecting portion 241c and is spaced apart from the folded portions 234a and 234b. The planar portion 242c fills most of the space inside the folded portion 234b and most of the space between the folded portions 234a.

[0055] The interposed portion 240d is disposed inside the folded portion 234a and is formed between the folded portion 232a and the folded portion 234a. The interposed portion 240d includes a connecting portion 241d and a planar portion 242d. The connecting portion 241d extends from the folded portion 234a in the fourth circumferential direction D2 and connects the folded portion 234a and the planar portion 242d.

[0056] The planar portion 242d has a shape obtained by flipping the planar portion 242b left and right. The planar portion 242d is connected to the connecting portion 241d and is spaced apart from the folded portions 232a and 234a. The planar portion 242d fills the space between the folded portions 232a and 234a.

[0057] In this way, the intervening portions 240a to 240d are connected at only one point to either the first serpentine shape 231 or the second serpentine shape 233. Therefore, when the first conductive portion 23 generates heat as a heater, no current flows through the intervening portions 240a to 240d, and the intervening portions 240a to 240d do not function as heaters. On the other hand, when the sensor circuit 32 applies a voltage to the first conductive portion 23, the intervening portions 240a to 240d have substantially the same potential as the potential of the first conductive portion 23, and therefore can function as sensor electrodes of the capacitance sensor.

[0058] In this embodiment, the planar shapes of the planar portions 242a to 242d are triangular, but are not limited to this. The planar shape of the planar portion 242a can be changed depending on the shape of the space inside the folded portion and the shape of the space between the first and second serpentine shapes 231, 233.

[0059] 2, the first adhesive layer 26 is interposed between the first substrate 21 and the rim portion 11, and fixes the first substrate 21 to the rim portion 11. Examples of materials that form the first adhesive layer 26 include an acrylic resin adhesive, a urethane resin adhesive, and a polyester resin adhesive.

[0060] The second adhesive layer 27 is formed on the first substrate 21 so as to cover the conductive layer 22. The second adhesive layer 27 fixes the cover layer 4 to the first substrate 21 and the conductive layer 22. Examples of materials constituting the second adhesive layer 27 include the materials constituting the first adhesive layer 26 described above.

[0061] 1, the control circuit 30 of the heated capacitance sensor unit 2 is provided in, but is not limited to, the spoke portion 14 of the steering wheel 1. The control circuit 3 is a circuit board that applies current and voltage to the conductive layer 22. The control circuit 30 is supplied with power from, for example, an auxiliary battery (not shown) of the vehicle.

[0062] As shown in FIG. 3 , the control circuit 30 includes a heater circuit 31 and a sensor circuit 32. As shown in FIG. 1 , the control circuit 30 is electrically connected to the wiring board 20a by, for example, a wire harness 5, although this is not particularly limited. Note that in this embodiment, the wire harness extends only in one direction, the −X direction, from the control circuit 30 and connects to the wiring board 20a, but this is not limiting. For example, the wire harness 5 may extend from the control circuit 30 in the +X direction or the −Y direction. Furthermore, multiple electric wires included in the wire harness 5 may extend in different directions to connect to the wiring board 20a. For example, some electric wires may extend in the −X direction to connect to the wiring board 20a, and the remaining electric wires may extend in the +X direction to connect to the wiring board 20a.

[0063] 3 , the heater circuit 31 causes the first conductive portion 23 to generate heat by passing a current through the first conductive portion 23. Meanwhile, the sensor circuit 32 applies a voltage to the first and second conductive portions 23, 24 to form capacitance between the object to be detected and the first and second conductive portions 23, 24. The sensor circuit 32 can detect the change in capacitance by, for example, outputting an AC signal to the first and second conductive portions 23, 24 and detecting a change in the frequency of the AC signal due to the approach or contact of the object to be detected.

[0064] In the heater-equipped capacitance sensor unit 2 of this embodiment as described above, the second conductive part 24, which functions only as a capacitance sensor, is connected to the first conductive part 23, which functions as both a heater and a capacitance sensor. This makes it possible to increase the detection area of ​​the capacitance sensor and improve the sensitivity of the heater-equipped capacitance sensor unit 2. This makes it possible to strengthen the signal against noise, improve the S / N ratio, and suppress false detection.

[0065] Furthermore, although the second conductive portion 24 generates almost no heat due to electrical resistance, the heat generated by the heat generation of the first conductive portion 23 is diffused by the second conductive portion 24, thereby making it possible to achieve uniform heating of the heater-equipped capacitance sensor unit 2.

[0066] It should be noted that the above-described embodiments have been described to facilitate understanding of the present invention, and are not intended to limit the present invention. Therefore, the elements disclosed in the above embodiments are intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0067] For example, wiring board 20a in the above embodiment may include shielding layer 25. Fig. 4 is an enlarged cross-sectional view of a first modified example of wiring board a in the present embodiment, and Fig. 5 is an enlarged cross-sectional view of a second modified example of wiring board 20a in the present embodiment.

[0068] 4, wiring board 20b in the first modified example further includes shield layer 25 formed on main surface (inner peripheral surface) 21b of first substrate 21. This shield layer 25 electromagnetically shields conductive layer 22 from core 12, thereby suppressing the formation of electrostatic capacitance between conductive layer 22 and core 12. Examples of materials that can be used to form shield layer 25 include the conductive materials that form conductive layer 22 described above.

[0069] In this first modified example, the formation of capacitance between the conductive layer 22 and the core metal 12 is suppressed, thereby improving the sensitivity of the heater-equipped capacitance sensor unit 2.

[0070] In the first modified example, both the conductive layer 22 and the shield layer 25 are formed on the first substrate 21, but this is not limiting. As shown in the second modified example, the shield layer 25 may be formed on a second substrate 28 separate from the first substrate 21.

[0071] 5 , wiring board 20c in the second modified example further includes shielding layer 25, second substrate 28, and third adhesive layer 29. Second substrate 28 is attached to main surface 21b of first substrate 21 via third adhesive layer 29. Shielding layer 25 is formed on main surface (inner peripheral surface) 28b of second substrate 28. Shielding layer 25 may also be formed on main surface (outer peripheral surface) 28a of second substrate 28.

[0072] In this second modified example as well, the sensitivity of the heater-equipped capacitance sensor unit 2 can be improved by suppressing the formation of capacitance between the conductive layer 22 and the core metal 12.

[0073] Furthermore, in the above embodiment, first conductive portion 23 is composed of first and second serpentine shapes 231, 233, but is not limited to this. Fig. 6 is an enlarged development view of a third modified example of wiring board 20a in this embodiment, and corresponds to part III in Fig. 1. For example, in wiring board 20d in the third modified example, first conductive portion 23 is composed of mesh portion 235, and second conductive portion 24 is composed of interposed portion 240e. Mesh portion 235 corresponds to an example of a "mesh pattern" in this aspect of the present invention.

[0074] 6, the mesh portion 235 includes a plurality of first thin wires 236 and a plurality of second thin wires 237. The first and second thin wires 236 and 237 correspond to an example of a "linear pattern" in this aspect of the present invention.

[0075] The multiple first thin wires 236 extend substantially parallel to one another and are arranged at intervals along the circumferential direction of the rim portion 11. The multiple second thin wires 237 extend substantially parallel to one another and extend in a different direction from the first thin wires 236. The second thin wires 237 are arranged so as to intersect with the multiple first thin wires 236 and are electrically connected to the first thin wires 236. In this third modified example, the first and second thin wires 236, 237 of the mesh portion 235 generate resistance heat due to the current from the heater circuit 31 and function as a heater.

[0076] A plurality of openings 238 are formed in the mesh portion 235 and are surrounded by a plurality of first and second thin wires 236, 237 that intersect with each other. An intervening portion 240e of the second conductive portion 24 is provided inside the openings 238. The intervening portion 240e corresponds to an example of a "third intervening portion" in this aspect of the present invention.

[0077] The intervening portion 240e includes a connecting portion 241e and a planar portion 242e. The planar portion 242e is connected to the mesh portion 235 at only one point via the connecting portion 241e. Therefore, like the intervening portions 240a to 240d described above, the intervening portion 240e forms a capacitance with the object to be detected, but does not generate heat because almost no current flows from the heater circuit 31.

[0078] In the wiring board 20d in the third modified example as described above, it is also possible to increase the detection area of ​​the capacitance sensor and improve the sensitivity of the heater-equipped capacitance sensor unit 2. It is also possible to achieve uniform heating of the heater-equipped capacitance sensor unit 2.

[0079] Although this modified example illustrates a case where one mesh portion 235 is formed, for example, a plurality of mesh portions 235 may be arranged so as to be electrically connected in parallel to the heater circuit 31. In this case, an intervening portion that is connected to the mesh portion 235 at only one point may be formed in the space between the plurality of mesh portions 235.

[0080] Furthermore, in the above embodiment, the first substrate 21 and the conductive layer 22 are attached to the outer peripheral surface of the rim portion 11, but this is not limited to this, and the first substrate 21 and the conductive layer 22 may be embedded in the resin layer 13 of the rim portion 11.

[0081] REFERENCE SIGNS LIST 1...Steering wheel 11...Rim portion 12...Core metal 13...Resin layer 14...Spoke portion 2...Heater-equipped capacitance sensor unit 20a to 20d...Wiring board (heater-equipped capacitance sensor) 21, 28...First and second substrates 22...Conductive layer 23...First conductive portion 231...First meandering shape 232a, 232b...Folded portion 233...Second meandering shape 234...Second folded portion 235...Mesh portion 236...First thin wire 237...Second thin wire 238...Opening 24...Second conductive portion 240a to 240e...Interposition portion 241a to 241e...Connecting portion 242a to 242e...Planar portion 25...Shield layer 26, 27, 29...First to third adhesive layers 30...Control circuit 31... heater circuit 32... sensor circuit 4... cover layer 5... wire harness

Claims

1. A heater-equipped capacitance sensor comprising: a first conductive part that forms capacitance with the object to be detected and generates heat due to electrical resistance; and a second conductive part that forms capacitance with the object to be detected and is connected to the first conductive part, wherein the second conductive part is configured so that no current flows through the second conductive part when the first conductive part generates heat due to electrical resistance.

2. A heater-equipped capacitance sensor according to claim 1, wherein the first conductive portion includes a linear pattern extending linearly.

3. A heater-equipped capacitance sensor according to claim 2, wherein the second conductive portion includes a planar pattern connected to the linear pattern at only one point.

4. A heater-equipped capacitance sensor according to claim 2 or 3, wherein the linear pattern has a meandering shape with a plurality of folded portions.

5. A heater-equipped capacitance sensor according to claim 4, wherein the second conductive portion includes a first interposed portion disposed inside the folded portion.

6. A capacitance sensor with a heater according to any one of claims 2 to 5, wherein the linear pattern includes a first serpentine shape having a plurality of first folded portions, and a second serpentine shape having a plurality of second folded portions and adjacent to the first serpentine shape with a gap therebetween, and the second conductive portion includes a second intervening portion arranged between the first folded portion and the second folded portion.

7. A heater-equipped capacitance sensor according to any one of claims 4 to 6, wherein the folded-back portion is folded back in a curved shape.

8. A capacitance sensor with a heater according to any one of claims 1 to 3, wherein the first conductive portion includes a mesh pattern formed by a plurality of linear patterns intersecting each other.

9. A heated capacitance sensor according to claim 8, wherein the mesh pattern includes an opening surrounded by the plurality of linear patterns, and the second conductive portion includes a third intervening portion disposed within the opening.

10. A heated capacitance sensor according to any one of claims 1 to 9, further comprising an electrically insulating substrate, and the first and second conductive portions are provided on a main surface of the substrate.

11. A heater-equipped capacitance sensor according to any one of claims 1 to 10, wherein the second conductive portion is formed integrally with the first conductive portion.

12. A capacitance sensor unit with a heater comprising: a capacitance sensor with a heater according to any one of claims 1 to 11; a heater circuit that causes the first conductive part to generate heat by passing a current through the first conductive part; and a sensor circuit that applies a voltage to the first and second conductive parts and detects a change in the capacitance.

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