Planar unit with linear body

Abstract

To provide a planar unit which can be used for a steering heater or an interior heater and in which the linear bodies have the same functions on the main surface and the other main surface of a substrate.SOLUTION: A planar unit includes a substrate made of a polymer foam and a linear body fixed to the substrate, the linear body is either a heater wire or a sensor wire, or both, and the linear body is exposed on both a main surface and the other main surface of the substrate, and the substrate is divided by the linear body in a cross section perpendicular to the main surface, and the periphery of the linear body has two straight lines that are approximately parallel to the main surface of the substrate in a cross section perpendicular to the main surface, and the linear body has a core material in which a conductor wire is wound around the outer periphery of a fiber core, and in which the diameter of the substrate perpendicular to the main surface and the wire diameter of the core material are approximately the same, resulting in a generally flat shape in a cross section perpendicular to the main surface.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a planar unit including a heater unit for warming the wheel portion of a steering wheel used in, for example, an automobile or a ship, a sensor unit for detecting the temperature or grip of the steering wheel, and a heater unit installed in the interior of a vehicle, such as an armrest or door trim. [Background technology]

[0002] It has been proposed to install a heater unit on the wheel portion of a steering wheel to warm the driver's hands in cold weather. A steering wheel consists of a wheel portion, spokes, and a boss portion. The wheel portion is formed from a wheel core material made of a metal core covered with urethane resin or the like, and a covering material made of synthetic resin, textile products, leather, or the like. The heater unit is installed between the wheel core material and the covering material, and is connected to lead wires that pass through the spokes and boss portion to receive power.

[0003] Known heater units installed on steering wheels include those in which cord-shaped heaters are arranged in a predetermined pattern on a substrate, as shown in Patent Document 1. Various types of foamed resin sheets, foamed rubber sheets, rubber sheets, nonwoven fabrics, woven fabrics, etc. are disclosed as substrates. Patent Documents 2 to 5, for example, are particularly relevant technologies. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4202071: Kurabe [Patent Document 2] Patent Publication 2014-143175: Kurabe [Patent Document 3] Patent Publication No. 2014-209444: Kurabe [Patent Document 4] International Publication WO2014 / 104000: Toyoda Gosei, Kurabe [Patent Document 5] International Publication WO2017 / 026217: Kurabe DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0005] For example, in the heater units described in Patent Documents 2 to 5, the thickness of the base material at the location where the cord-shaped heater is disposed is thinned to conform to the shape of the cord-shaped heater, resulting in a flat shape. When such a heater unit is incorporated into a steering wheel, the cord-shaped heater typically does not cause any irregularities, and the user does not experience any discomfort when steering. However, recently, the heater units described above have also been used as interior heaters by installing them in vehicle interiors such as armrests and door trims. In this case, depending on the installation location, both the front and back surfaces of the heater may come into contact with the user, and in such locations, it is necessary for the heater's temperature to be uniform. Furthermore, to reduce design and manufacturing man-hours, heater units incorporated into steering wheels and interior heaters installed in vehicle interiors are required to have a common basic structure.

[0006] The present invention has been made to solve the problems of the prior art, and its purpose is to provide a planar unit that can be used for a steering heater or an interior heater, and in which the linear bodies on one main surface of the substrate have the same functionality as the linear bodies on the other main surface. [Means for solving the problem]

[0007] In order to achieve the above object, the planar unit of the present invention is a planar unit comprising a substrate made of a polymer foam and a linear body fixed to the substrate, the linear body being either a heater wire or a sensor wire, or both, and the linear body being exposed on the main surface and the other main surface of the substrate. It is also conceivable that the substrate is divided by the linear members in a cross section perpendicular to the main surface. In addition, in a cross section perpendicular to the main surface, the periphery of the linear body may have two straight line portions that are approximately parallel to the main surface of the substrate. In addition, the linear body has a core material in which a conductor wire is wound around the outer periphery of a fiber core, and in a cross section perpendicular to the main surface, the diameter of the substrate perpendicular to the main surface and the wire diameter of the core material are approximately the same, and it is considered to have a generally flat shape. [Effects of the Invention]

[0008] According to the present invention, since there is no substrate on the front or back side of the linear body in the planar unit, the linear body functions equally on the main surface of the substrate and the other main surface.

[0009] In other words, when the linear body is a heater wire, the substrate does not function as a heat insulator, and the main surface and the other main surface have the same heat transfer or radiation function. Also, when the linear body is a sensor wire, the substrate does not function as a shielding material, and the detection accuracy of the main surface and the other main surface is the same. In addition, when incorporating the planar unit as a steering heater or interior heater, there is no need to worry about the front and back sides, which increases the degree of design freedom. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a plan view showing the configuration of a planar unit according to the present invention; [Figure 2] FIG. 2 is a rear view of a plan view showing the configuration of a planar unit according to the present invention. [Figure 3] 1 is an enlarged cross-sectional view schematically illustrating a main part of a planar unit according to a first embodiment of the present invention. [Figure 4] FIG. 1 is a diagram showing the configuration of a hot press type planar unit manufacturing device used in the present invention. [Figure 5] FIG. 10 is a partial perspective view showing how linear bodies are arranged in a predetermined pattern in the planar unit of the present invention. [Figure 6] 1 is a partially cutaway side view showing an example of a linear body used in the present invention. [Figure 7] 1 is a partially cutaway side view showing an example of a linear body used in the present invention. [Figure 8] 1 is a partially cutaway side view showing an example of a linear body used in the present invention. [Figure 9] 1 is a partially cutaway side view showing an example of a linear body used in the present invention. [Figure 10] 1 is a partially cutaway side view showing an example of a linear body used in the present invention. [Figure 11] 1 is a partially cutaway perspective view showing a state in which a planar unit according to the present invention is embedded in a steering wheel. [Figure 12] 1 is a schematic diagram showing an example of the use of a planar unit according to the present invention embedded in the interior of a vehicle. [Figure 13] FIG. 10 is a diagram showing an SEM photograph of a cross section of a planar unit. BEST MODE FOR CARRYING OUT THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. These embodiments show examples in which the planar unit of the present invention is applied to a steering heater.

[0012] First, a first embodiment will be described with reference to FIGS. 1 to 3. The configuration of the linear body 1 in this first embodiment will be described. The linear body 1 in this first embodiment has a configuration as shown in FIGS. 6 and 7. In this embodiment, the linear body 1 functions as a heater wire. The core wire 3 is formed of an aromatic polyamide fiber bundle having an outer diameter of approximately 0.2 mm. Five conductor wires 5a, which are hard tin-containing copper alloy wires having an element diameter of 0.08 mm, are wound helically around the core wire 3 at a pitch of approximately 1.0 mm. As shown in FIGS. 6 and 7, an insulating coating 5b is formed around the conductor wires 5a. The insulating coating 5b is formed of an inner layer 5c made of polyurethane resin and an outer layer 5d made of polyamideimide resin. The inner layer 5c of the insulating coating 5b is formed by applying polyurethane varnish around the conductor wires 5a and drying it to form a layer with a thickness of 4 μm. Next, the outer layer 5d is formed by applying polyamideimide varnish to the outer periphery of the inner layer 5c and drying it to form a layer with a thickness of 4 μm. The outer periphery of the core wire 3 around which the conductor wire 5a is wound is covered with an insulating layer. The insulating layer is formed by extrusion coating polyethylene resin containing a flame retardant to a thickness of 0.2 mm. In this embodiment, the polyethylene resin of the insulating layer also functions as the heat-sealed portion 9. The finished outer diameter of the linear body 1 is 0.8 mm, and the outer diameter excluding the heat-sealed portion 9 is approximately 0.4 mm. The core wire 3 is effective in terms of high flexibility and tensile strength. It is also possible to use multiple conductor wires by pulling them together or twisting them together without using the core wire 3.

[0013] Next, the configuration of substrate 11 to which linear body 1 having the above configuration is adhered and fixed will be described. Substrate 11 in the first embodiment has an apparent density of 40 kg / m 3 The base material 11 is made of a foamed polyurethane resin having a hardness of 220N (JIS K6400) and a thickness of 2 mm (JIS K7222 compliant). Such a base material 11 is cut into a desired shape by a known method such as die cutting.

[0014] Next, a configuration for arranging, adhering, and fixing linear body 1 to substrate 11 in a predetermined pattern will be described. FIG. 4 shows the configuration of hot-press heater manufacturing apparatus 13 for heating and pressurizing a substrate on which linear body 1 is arranged. First, there is hot-press jig 15, on which multiple locking mechanisms 17 are provided. As shown in FIG. 5, locking mechanism 17 includes pin 19, which is inserted from below into hole 21 drilled in hot-press jig 15. Locking member 23 with a needle-shaped tip is attached to the top of pin 19 so as to be movable in the axial direction and is constantly biased upward by coil spring 25. Then, as shown by phantom lines in FIG. 5, linear body 1 is arranged in a predetermined pattern by hooking it onto locking members 23 of multiple locking mechanisms 17.

[0015] Returning to Figure 4, press hot plate 27 is arranged above the plurality of locking mechanisms 17 so that it can be raised and lowered. That is, linear body 1 is arranged in a predetermined pattern while being hooked onto locking members 23 of the plurality of locking mechanisms 17, and substrate 11 is placed on top of it. In this state, press hot plate 27 is lowered to apply heat and pressure to linear body 1 and substrate 11. Note that when press hot plate 27 is lowered to apply heat and pressure, locking members 23 of the plurality of locking mechanisms 17 move downward against the biasing force of coil spring 25. When press hot plate 27 is lowered, it is preferable to design it so that the amount of compression of substrate 11 is at least equal to the outer diameter of linear body 1 excluding heat-sealed portion 9; in this embodiment, it is preferable to compress it to 0.4 mm. As a result, the substrate 11 is compressed, and the substrate 11 breaks in the areas corresponding to the arrangement pattern shape of the linear body 1, and the heat-sealed portions 9 on the outer periphery of the linear body 1 are fused, thereby adhering and fixing the linear body 1 and the substrate 11 together.

[0016] By performing the above steps, planar unit 31 as shown in FIGS. 1 to 3 can be obtained. FIG. 3 is an enlarged cross-sectional view of the main portion of FIGS. 1 and 2. Since base material 11 is compressed by press hot plate 27 to a diameter equal to the outer diameter of linear body 1 excluding heat-sealed portion 9, the portion where linear body 1 is disposed is pressed by linear body 1 and fractures. At this time, heat-sealed portion 9 is melted by press hot plate 27 and impregnated into base material 11. As a result, linear body 1 in base material 11 is exposed on both the main surface and the other main surface of base material 11. Since planar unit 31 thus obtained has no obstruction to linear body 1 on the main surface and the other main surface of base material 11, the linear body functions equally on both the main surface and the other main surface of the base material. That is, the base material does not function as a heat insulator, and the main surface and the other main surface can perform equivalent heat transfer or radiation functions.

[0017] In planar unit 31 obtained by embodiment 1, the thickness of substrate 11 in the area where linear body 1 is not disposed is 0.4 mm. Moreover, the outer diameter of linear body 1 excluding heat-sealed portion 9 is actually measured to be 0.4 mm.

[0018] Furthermore, heat-sealed portion 9 on the periphery of linear body 1 deformed and flowed due to the application of heat and pressure, and some of it penetrated into the gaps (pores) in substrate 11. Furthermore, the area where linear body 1 was fixed was generally flat, with no irregularities compared to the surrounding thickness. Here, a thickness variation within a range of about ±10% can be said to be generally flat, and is essentially a nearly constant thickness. Furthermore, if the degree of thickness variation is within a range in which the user does not perceive any irregularities visually or tactilely, it can also be said to be generally flat.

[0019] In planar unit 31 obtained as described above, both ends of linear body 1 are drawn out and connected to lead wires 35, which connect linear body 1, temperature control device 39, and a connector (not shown). The temperature control device is disposed on linear body 1 and controls the temperature of planar unit 31 using heat generated by linear body 1. The temperature control device is then connected to the vehicle's electrical system (not shown) via the connector. Planar unit 31 configured as described above is installed on steering wheel 71 in the state shown in FIG. 11. Steering wheel 71 includes a wheel portion 72, spoke portions 73, and a boss portion 74, and planar unit 31 is installed between a wheel core material 77 and a covering material 78 of wheel portion 72. In this state, planar unit 31 functions as a heater unit.

[0020] An adhesive layer (not shown) is formed on the substrate 11 to bond the planar unit 31 and the covering material 78 of the steering wheel, or the heater unit 31 and the wheel core material 77 of the steering wheel. The adhesive layer is preferably formed by first forming an adhesive layer consisting only of an adhesive on a release sheet, and then transferring the adhesive layer from the release sheet to the surface of the substrate 11. In this way, the adhesive does not penetrate into the interior of the substrate 11, and the adhesive layer is formed only on the surface of the substrate 11.

[0021] When the planar unit 31 was installed on the steering wheel, one of the following manufacturing methods 1 to 4 was used. (Method 1) In manufacturing method 1, the planar unit 31 and the covering material 78 are bonded together, with the surface side on which the heater wire 11 is disposed being bonded to the covering material 78. Thereafter, the covering material 78 to which the planar unit 31 is bonded is used to cover the wheel core material 77. (Method 2) In manufacturing method 2, the planar unit 31 and the covering material 78 are bonded together, and at that time, the surface side on which the heater wire 11 is not disposed is bonded to the covering material 78. Thereafter, the covering material 78 to which the planar unit 31 is bonded is used to cover the wheel core material 77. (Method 3) In manufacturing method 3, the planar unit 31 and the wheel core material 77 are bonded together, with the surface side on which the heater wire 11 is disposed being bonded to the wheel core material 77. Thereafter, the wheel core material 77 to which the planar unit 31 is bonded is covered with a covering material 78. (Method 4) In manufacturing method 4, the planar unit 31 and the wheel core material 77 are bonded together, with the surface side on which the heater wire 11 is not disposed being bonded to the wheel core material 77. Thereafter, the wheel core material 77 to which the planar unit 31 is bonded is covered with a covering material 78.

[0022] (Embodiment 2) In the above-described embodiment 1, the thickness of the base material 11 was set to 2 mm before compression and 0.4 mm after compression, and the planar unit 31 according to embodiment 2 was produced and installed on the steering wheel 71 by the above-described manufacturing methods 1 to 4. (Comparative form 1) In the above-described first embodiment, the apparent density of the substrate 11 before compression is set to 40 kg / m 3 , thickness 4mm, apparent density after compression 80kg / m 3 The heater unit 31 according to the second embodiment was fabricated using a material having a thickness of 2 mm and a hardness after compression of ASKER C 4, and was installed on the steering wheel 71 by the above manufacturing methods 1 to 4.

[0023] The planar units 31 according to the first and second embodiments and the comparative embodiment 1 obtained as described above were installed on steering wheels 71 as shown in Fig. 11 using the methods shown in manufacturing methods 1 to 4. In this state, the steering wheels were put into actual use and a check was made to see if they felt any discomfort. To check, 10 users gripped the steering wheel and performed steering operations on the left and right 10 times each, and were asked whether they felt any unevenness caused by the linear bodies 1, and the number of people who answered that they felt discomfort was investigated.

[0024] For the planar units of Embodiments 1 and 2, no user responded that they felt uncomfortable when they were installed on the steering wheel using any of the manufacturing methods. However, for Comparative Example 1, some users responded that they felt uncomfortable depending on the manufacturing method.

[0025] The present invention is not limited to the above-described embodiment. First, the configuration of the linear body 1 may be, for example, as in the above-described embodiment, a configuration in which a plurality of conductor element wires 5a covered with an insulating coating 5b are twisted or aligned and wound around a core wire 3, with a thermally fused portion 9 formed on the outer periphery (see FIG. 8), a configuration in which a plurality of conductor element wires 5a covered with an insulating coating 5b are twisted together without using a core wire 3 (see FIG. 9), or a configuration in which an insulating coating 7 is formed on the inner periphery of the thermally fused portion 9 (see FIG. 10).

[0026] Furthermore, the linear body 1 may be used not only as a heater wire but also as a sensor wire. If the linear body 1 is used as a heater wire, the planar unit 31 becomes a heater unit, and if it is used as a sensor wire, the planar unit 31 becomes a sensor unit. The sensor wire can be used as a capacitance sensor or other sensors such as a temperature sensor. As a type of temperature sensor, the linear body can be made into a solder wire and used as an abnormal temperature detection unit. In terms of detecting radio waves, the linear body can also be used as an antenna wire and as an antenna unit. It is also possible to use a single linear body that includes both a conductor that performs a heater function and a conductor that performs a sensor function, or to use the linear body 1 as a shielded wire.

[0027] Furthermore, the conductor wires 5a may not be coated with the insulating coating 5b. For example, various configurations are conceivable, including a configuration in which no insulating coating 5b is coated on any of the conductor wires 5a, a configuration in which conductor wires 5a coated with the insulating coating 5b and conductor wires 5a not coated with the insulating coating 5b are alternately arranged, and a configuration in which only some of the conductor wires 5a are coated with the insulating coating 5b or are not coated at all. Furthermore, it is also conceivable to twist the core wire 3 and the conductor wires 5a together.

[0028] Examples of the core wire 3 include monofilaments, multifilaments, and spun organic fibers such as inorganic fibers like glass fibers, polyester fibers like polyethylene terephthalate, aliphatic polyamide fibers, aromatic polyamide fibers, and wholly aromatic polyester fibers, or fibers having a core made of these fiber materials or an organic polymer material constituting these fiber materials and a thermoplastic organic polymer material covering the periphery. Furthermore, when a heat-shrinkable and heat-fusible core wire 3 is used, if a conductor wire 5a breaks and abnormal heating occurs, the core wire 3 melts and is cut, and also shrinks. When the core wire 3 shrinks, the conductor wires 5a wound around the core wire 3 follow the movement of the core wire 3, causing the ends of the broken conductor wire 5a to separate. This prevents the ends of the broken conductor wire 5a from repeatedly coming into contact and separating. Furthermore, the ends of the broken conductor wire 5a do not come into contact with each other over a small area, such as a point contact. This prevents abnormal heat generation. Furthermore, if the conductor wires 5a are insulated by the insulating coating 5b, the core wire 3 does not need to be made of an insulating material. For example, a stainless steel wire or a titanium alloy wire can be used as the core wire 3. However, since there is a possibility that the conductor wires 5a may break, it is preferable that the core wire 3 be made of an insulating material.

[0029] The conductor wires 5a may be conventionally known, such as copper wire, copper alloy wire, nickel wire, iron wire, aluminum wire, nickel-chromium alloy wire, and iron-chromium alloy wire. Examples of copper alloy wires include tin-copper alloy wire, copper-nickel alloy wire, and silver-bearing copper alloy wire in which a copper solid solution and a copper-silver eutectic are fibrous. Among these, copper wire or copper alloy wire is preferred from the viewpoint of cost-performance balance. These copper wires and copper alloy wires are available in both soft and hard varieties. From the viewpoint of flex resistance, hard wires are particularly preferred over soft wires. Hard copper wires and hard copper alloy wires are formed by elongating individual metal crystal grains in the processing direction through cold processing such as wiredrawing, resulting in a fibrous structure. When such hard copper wires or hard copper alloy wires are heated above their recrystallization temperature, the processing strain generated within the metal crystals is eliminated, and crystal nuclei that serve as starting points for new metal crystals begin to appear. These crystal nuclei develop, and recrystallization occurs, successively replacing the old crystal grains, leading to further growth of the crystal grains. A soft copper wire or soft copper alloy wire is a wire in this state of crystal grain growth. Although these soft copper wires or soft copper alloy wires have higher elongation and electrical resistance than hard copper wires or hard copper alloy wires, they have lower tensile strength, and therefore lower bending resistance than hard copper wires or hard copper alloy wires. As such, hard copper wires or hard copper alloy wires become soft copper wires or soft copper alloy wires with low bending resistance through heat treatment, so it is preferable to carry out processing with as little thermal history as possible. Hard copper wires are defined in JIS-C3101 (1994), and soft copper wires are defined in JIS-C3102 (1984). Soft copper wires are defined as those with an elongation of 15% or more for an outer diameter of 0.10 to 0.26 mm, 20% or more for an outer diameter of 0.29 to 0.70 mm, 25% or more for an outer diameter of 0.80 to 1.8 mm, and 30% or more for an outer diameter of 2.0 to 7.0 mm. Tin-plated copper wires are also included. Tin-plated hard copper wires are defined in JIS-C3151 (1994), and tin-plated soft copper wires are defined in JIS-C3152 (1984). Various cross-sectional shapes can be used for the conductor wires 5a, and they are not limited to the commonly used circular cross-sections; so-called rectangular wires may also be used.

[0030] When a temperature-sensing sensor wire is used as the linear body, the conductor wire 5a is preferably made of a material whose resistance value changes significantly with temperature. Examples include various metal wires such as copper wire, copper alloy wire, nickel wire, iron wire, aluminum wire, nickel-chromium alloy wire, copper-nickel alloy, and iron-chromium alloy wire, as well as carbon fiber wire and conductive resin wire. Among these, those with a positive characteristic temperature coefficient are preferred. Nickel wire and platinum wire, which have particularly large coefficients, are preferred. Materials with a positive characteristic temperature coefficient increase their resistance value as the temperature rises. Therefore, an increase in resistance value is deemed to be an abnormal temperature, and the control method stops the flow of current. Therefore, if the conductor wire 5a breaks, the resistance value becomes infinite, and the flow of current is stopped, just as if an abnormal temperature occurred. This is an extremely reliable method when viewed as a safety device.

[0031] When winding the conductor wires 5a around the core wire 3, among the above-mentioned materials for the conductor wires 5a, those with a small amount of springback when wound are preferred. For example, a silver-copper alloy wire, in which a copper solid solution and a copper-silver eutectic are fibrous, has excellent tensile strength and bending strength, but is prone to springback when wound. Therefore, when winding the conductor wires 5a around the core wire 3, the conductor wires 5a are likely to lift or break due to excessive winding tension. Furthermore, they are prone to twisting after processing, making them undesirable. In particular, when the conductor wires 5a are coated with an insulating coating 5b, the insulating coating 5b also exerts a restoring force. Therefore, it is important to select a conductor wire 5a with a small restoring rate to compensate for the restoring force of the insulating coating 5b.

[0032] The insulating coating 5b covering the conductor wires 5a may be formed of two layers, an inner layer 5c and an outer layer 5d, as in the above embodiment, or may be formed of three or more layers, or may be a single layer. When a multi-layer structure is used, the thermal decomposition temperature of the material constituting the inner layer is preferably lower than the lower of the melting point and thermal decomposition temperature of the material constituting the outer layer. Here, the inner layer refers to a layer formed on the conductor wires 5a. The outer layer may be any layer located outside the inner layer, and therefore, it is possible to form another outer layer outside the outer layer or another intermediate layer between the inner and outer layers.

[0033] Examples of materials for the insulating coating 5b include polyurethane resin, polyamide resin, polyimide resin, polyamideimide resin, polyesterimide resin, nylon resin, polyesternylon resin, polyethylene resin, polystyrene resin, polypropylene resin, polyester resin, polybenzimidazole resin, vinyl chloride resin, fluororesin, and silicone resin. These materials may be used in combination, or may contain various known additives such as flame retardants and antioxidants. By combining these resins, the thermal decomposition temperature of the material constituting the inner layer 5c is lower than the lower of the melting point and thermal decomposition temperature of the material constituting the outer layer 5d. Materials for the inner layer 5c include polyurethane resin, vinyl chloride resin, polyacetal resin, polystyrene resin, polypropylene resin, polyester resins such as polymethyl methacrylate and polyethylene terephthalate, and polyvinyl alcohol. It is particularly preferable that the material for the inner layer 5c be a thermosetting resin and that the material for the outer layer 5d be a thermosetting resin. Here, thermosetting resins also include crosslinkable materials. From the viewpoints of heat generation characteristics as a heater wire and ease of terminal processing such as soldering, it is preferable that the material of the inner layer 5c is polyurethane resin or polyester resin, and the material of the outer layer 5d is any one of polyimide resin, polyamide-imide resin, and silicone resin. In particular, it is preferable that the material of the inner layer 5c is polyurethane resin, and the material of the outer layer 5d is polyamide-imide resin. This polyurethane resin may be variously modified or compounded, such as imide-containing polyurethane.

[0034] The thickness of the insulating coating 5b is preferably 3 to 30% of the diameter of the conductor wires 5a. If the thickness is less than 3%, sufficient voltage resistance characteristics cannot be obtained, which may result in the omission of individually coating the conductor wires 5a. If the thickness is more than 30%, it becomes difficult to remove the insulating coating 5b when crimping a connection terminal, and the heater wire becomes unnecessarily thick.

[0035] When the conductor wires 5a are wound around the core wire 3 by being paralleled or twisted, it is preferable to parallelize the conductor wires 5a rather than twist them. This is because the diameter of the heater wire becomes smaller and the surface becomes smoother. In addition to parallelizing or twisting the conductor wires 5a, it is also possible to braid the conductor wires 5a around the core wire 3.

[0036] The linear body 1 according to the present invention may also have an insulating coating 7 formed around the outer periphery of the conductor wires 5a (see, for example, FIG. 10). This insulating coating 7 insulates other components from electrical current even if the conductor wires 5a break, and also insulates against high-temperature heat generation in the event of a spark. The insulating coating 7 may be formed by extrusion molding or the like, or a pre-formed tubular insulating coating 7 may be applied, and there are no particular limitations on the method of formation. Forming the insulating coating 7 by extrusion molding is preferable because it fixes the position of the conductor wires 5a, preventing friction and bending of the conductor wires 5a due to misalignment, thereby improving bending resistance. The material constituting the insulating coating 7 may be appropriately selected depending on the manner of use and environment of the heater wire. Examples of suitable materials include polyolefin resins, polyester resins, polyurethane resins, aromatic polyamide resins, aliphatic polyamide resins, vinyl chloride resins, modified Noryl resins (polyphenylene oxide resins), nylon resins, polystyrene resins, fluororesins, synthetic rubber, fluororubber, ethylene-based thermoplastic elastomers, urethane-based thermoplastic elastomers, styrene-based thermoplastic elastomers, and polyester-based thermoplastic elastomers. In particular, flame-retardant polymer compositions are preferably used. Here, a flame-retardant polymer composition refers to a polymer composition having an oxygen index of 21 or higher in the flammability test according to JIS-K7201 (1999). A polymer composition having an oxygen index of 26 or higher is particularly preferred. To achieve such flame retardancy, a flame retardant or the like may be blended into the material constituting the insulating coating 7. Examples of the flame retardant include metal hydrates such as magnesium hydroxide and aluminum hydroxide, antimony oxide, melamine compounds, phosphorus compounds, chlorine-based flame retardants, bromine-based flame retardants, etc. These flame retardants may be subjected to appropriate surface treatment by known methods.

[0037] By forming a heat-sealed portion 9 on the outer periphery of the linear body, the substrate 11 can be ruptured into the wiring pattern of the linear body 1 by heating and pressurizing, while simultaneously reconnecting the ruptured substrate 11. When an insulating coating 7 is formed, the heat-sealed portion 9 is formed on the outer periphery of the insulating coating 7. The material for the heat-sealed portion 9 can be the same as the material for the insulating coating 7. Among these, olefin-based resins, which have excellent adhesion to the substrate, are preferred. Examples of olefin-based resins include high-density polyethylene, low-density polyethylene, ultra-low-density polyethylene, linear low-density polyethylene, polypropylene, polybutene, ethylene-α-olefin copolymer, and ethylene-unsaturated ester copolymer. Among these, ethylene-unsaturated ester copolymers are particularly preferred. Because ethylene-unsaturated ester copolymers have a molecular structure containing oxygen within the molecule, they generate less heat of combustion than resins such as polyethylene, which have a molecular structure consisting only of carbon and hydrogen, thereby suppressing combustion. Furthermore, due to their inherently high adhesiveness, they also have good adhesion to the substrate. Furthermore, they are suitable for incorporating various flame retardants because their adhesiveness is not significantly reduced when inorganic powders or the like are incorporated. Examples of ethylene-unsaturated ester copolymers include ethylene-vinyl acetate copolymer, ethylene-methyl (meth)acrylate copolymer, ethylene-ethyl (meth)acrylate copolymer, and ethylene-butyl (meth)acrylate copolymer, and these may be used alone or in combination. Here, "(meth)acrylic acid" refers to both acrylic acid and methacrylic acid. While any of these may be selected, it is preferable to use a material that melts at a temperature below the decomposition onset temperature or melting point of the material constituting insulating coating 15b. Furthermore, polyester-based thermoplastic elastomers are examples of materials that have excellent adhesive properties with substrate 11. Polyester-based thermoplastic elastomers include polyester-polyester and polyester-polyether types, with polyester-polyether types being preferred due to their higher adhesive properties. When thermally fusing linear body 1 and substrate 11 together, the adhesive strength between linear body 1 and substrate 11 is extremely important.If the adhesive strength is insufficient, the linear body 1 will come off the substrate 11 during use, which will cause the linear body 1 to bend unexpectedly, increasing the possibility of the conductor wires 5a breaking. If the conductor wires 5a break, not only will the heater no longer function, but chattering may also cause sparks.

[0038] When forming the insulating coating 7, it is required that the melting point of the insulating coating 7 is higher than that of the heat-sealing portion 9. This prevents the shape of the insulating coating 7 from being substantially distorted when the heat-sealing portion 9 is fused by heating and pressurizing or the like, and allows sufficient insulating performance to be maintained. The melting point of the insulating coating 7 is preferably 215°C to 250°C, and the melting point of the heat-sealing portion 9 is preferably 100°C to 185°C. Furthermore, when forming the insulating coating 5b on the conductor wires 5a, it is preferable that the melting point of the insulating coating 7 is lower than that of the insulating coating 15b.

[0039] Furthermore, it is preferable that the material constituting the insulating coating 7 and the material constituting the heat-sealing portion 9 are the same polymer material. Here, the same polymer material refers to polymer materials having a common main chain structure, polymer materials having a common functional group, polymer materials differing only in molecular weight, copolymers having a common monomer unit, mixtures of common polymer materials, etc. Such materials ensure sufficient adhesion between the insulating coating 7 and the heat-sealing portion 9, preventing the heater wire from detaching from the substrate.

[0040] The conductor wires 5a may be formed with other layers as appropriate in addition to the two layers of the insulating coating 7 and the heat-sealed portion 9. Furthermore, the insulating coating 7 and the heat-sealed portion 9 are not limited to being formed continuously in the longitudinal direction, and may be formed in a straight or spiral line along the longitudinal direction of the linear body 1, in a dotted pattern, or intermittently. However, from the viewpoint of adhesive strength, it is preferable that the insulating coating 7 and the heat-sealed portion 9 be formed continuously in the longitudinal direction.

[0041] Furthermore, it is preferable that the linear body 1 obtained as described above can be bent 20,000 times or more before at least one of the conductor wires breaks in a bending test in which the linear body 1 is bent 90 degrees at a radius of curvature six times its own diameter.

[0042] The substrate 11 is not limited to foamed polyurethane resin; various polymer foams, such as foamed resin sheets or foamed rubber sheets made of other materials, are also possible. A porous, highly elastic foam is particularly preferred, and one with adjusted hardness is preferred to prevent the heater wire from appearing on the surface. Methods for adjusting hardness include adjusting the foaming rate, forming closed or open cells, or using a material with a suitable hardness. Materials may be selected from a variety of resins, rubbers, and thermoplastic elastomers, including polyurethane resin, chloroprene rubber, silicone resin, neoprene rubber, diene rubber, nitrile rubber, natural rubber, polyethylene resin, polypropylene resin, vinyl chloride resin, and ethylene-vinyl acetate copolymer. Other materials that can be used for the substrate 11 include nonwoven fabric, woven fabric, paper, aluminum foil, mica plate, resin sheet, and expanded porous material. Flame-retardant substrates are preferred, and flame-retardant fibers and flame retardants are preferably mixed into the substrate 11. Furthermore, a plurality of base materials 11 may be used by being stacked, and in this case, the respective base materials 11 may be made of different materials or have different porosities.

[0043] The planar unit according to the present invention can be stacked on top of other planar units. For example, a planar unit using a heater wire as the linear body can be created, and then a planar unit with a sensor wire attached can be stacked on top of this planar unit. This allows for parallelization of the manufacturing process and improved manufacturing speed compared to wiring heater wires and sensor wires on the front and back surfaces of a single substrate.

[0044] The planar unit 31 according to the present invention can be used for various purposes other than the steering wheel shown in FIG. 11 above. For example, the planar unit 31 having the above configuration can be embedded and installed in a vehicle interior as shown in FIG. 12. The planar unit 31 in FIG. 12 is installed in an interior component 80 such as an A-pillar, armrest, or door trim. Here, when the front and back surfaces of the interior component 80 are exposed to the interior of the vehicle, the planar unit 31 installed there may be required to provide equivalent heating functions to the front and back surfaces. In the planar units according to Cited Documents 1 to 5, the substrate covers one or both surfaces of the linear body, making it difficult to achieve equivalent heat transfer or radiation to the front and back surfaces, or resulting in attenuation of output. However, in the planar unit 31 according to the present invention, the linear body 1 is exposed on both the main surface and the other main surface of the substrate 11, so there is nothing blocking the linear body 1, and the linear body functions equivalently on both the main surface and the other main surface of the substrate. That is, the base material does not function as a heat insulating material, and the main surface and the other main surface can perform the same heat transfer or radiation function. [Industrial Applicability]

[0045] As described above, the present invention can prevent a user from feeling any discomfort when steering. Such a planar unit can be used in steering wheels and seats of automobiles, ships, various transport vehicles, various agricultural vehicles, and various heavy machinery for civil engineering and construction, and can be suitably used as a heater unit for heating the steering wheel or seat, a temperature sensor unit for detecting the temperature of the steering wheel or seat, or a capacitance sensor unit for detecting the temperature of the steering wheel or the seat occupancy. Furthermore, by taking advantage of the fact that the linear body portion is flat and without any irregularities, the planar unit of the present invention can be used for purposes other than steering wheels and seats. For example, it can be applied to electric blankets, electric carpets, heated toilet seats, heaters for anti-fog mirrors, heating appliances, heaters for floor heating, heaters for clothing, various planar temperature detectors, capacitance detectors, etc. [Explanation of symbols]

[0046] 1 linear body 3 Core material 5a Conductor wire 5b Insulation coating 5c Inner layer 5d outer layer 7 Insulation coating 9 Heat-sealed part 11 Base material 31 Planar unit 71 Steering wheel 77 Wheel core material 78 Covering material 80 Interior parts

Claims

1. A planar unit comprising a substrate made of a polymer foam and a linear body fixed to the substrate, the linear body being either a heater wire or a sensor wire, or both, and the linear body being exposed on both the main surface and the other main surface of the substrate.

2. 2. The planar unit according to claim 1, wherein the base material is divided by the linear members in a cross section perpendicular to the main surface.

3. 2. The planar unit according to claim 1, wherein the periphery of the linear body has two straight line portions that are substantially parallel to the main surface of the base material in a cross section perpendicular to the main surface.

4. A planar unit as described in any one of claims 1 to 3, wherein the linear body has a core material in which a conductor wire is wound around the outer periphery of a fiber core, and in a cross section perpendicular to the main surface, the diameter of the substrate perpendicular to the main surface and the wire diameter of the core material are approximately the same, and the linear body has a generally flat shape.

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