Radio wave transmissive heater

Abstract

To provide a radio wave transmissive heater having radio wave transmissivity and capable of causing a temperature to uniformly rise.SOLUTION: A radio wave transmissive heater includes: a substrate; a first interdigital electrode disposed on the substrate and comprising a first main electrode and a plurality of first sub electrodes; a second interdigital electrode disposed on the substrate and comprising a second main electrode and a plurality of second sub electrodes; and PTC resistors disposed between the first sub electrodes and the second sub electrodes. The first sub electrodes and the second sub electrodes are disposed alternately and in parallel and in a radio wave transmissive region, the PTC resistors are disposed linearly so as to form lattices with the first sub electrodes and the second sub electrodes.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a radio wave transparent heater. [Background technology]

[0002] Radar devices that transmit and receive radio waves have been put to practical use. The radar device is mounted on, for example, a vehicle and detects obstacles around the vehicle by transmitting and receiving radio waves from an antenna. If snow, rain, or other obstructions adhere to an antenna cover such as a radome that covers the antenna, the radio waves may be attenuated, and the propagation of the radio waves may be impeded and attenuated.

[0003] Therefore, as a technology to suppress the adhesion of obstructing objects to the antenna cover, for example, Patent Document 1 proposes an antenna device that prevents the deterioration of electrical performance during snowfall and eliminates the need for regular maintenance. In this antenna device, a heater installed inside increases the temperature of the radome surface. As a result, snow adhering to the radome surface is removed, ensuring reliable propagation of radio waves.

[0004] Here, heaters used in conventional antenna devices have generally been heaters in which a metal heating wire is arranged on a substrate (also referred to as "metal heaters" in this specification). Metal heaters do not require a complicated configuration because their temperature rises when electricity is passed through the metal heating wire. Furthermore, metal heaters used in antenna devices can allow radio waves to pass through by setting the intervals between the metal heating wires widely. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6804966 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the above-mentioned metal heater, if the intervals between the metal heating wires are set wide, there is a problem in that it is difficult to increase the temperature in areas far from the metal heating wires, and it is difficult to make the temperature of the entire heater uniform.

[0007] On the other hand, a planar heating element having a PTC characteristic (positive temperature coefficient) is also known as a planar heater. A planar heating element having a PTC characteristic usually has a pair of electrodes and a resistor having a PTC characteristic (also referred to as a "PTC resistor" in this specification) disposed between the electrodes. A PTC resistor usually contains a crystalline resin and conductive particles. When a voltage is applied to such a planar heating element, electricity is conducted through the conductive particles in the PTC resistor, and the temperature rises. On the other hand, when the temperature of the planar heating element (PTC resistor) rises, the crystalline resin in the PTC resistor thermally expands. Then, the distance between the conductive particles increases, the resistance value rises sharply, and it becomes difficult to conduct electricity. It is possible to use such a planar heating element as a heater for an antenna device, but a PTC resistor has a property of easily attenuating radio waves. Therefore, it has been difficult to use a conventional planar heating element as a heater for an antenna device.

[0008] An object of the present disclosure is to provide a radio wave transparent heater that has radio wave transparency and can be used for, for example, an antenna cover, and is capable of raising the temperature uniformly. [Means for solving the problem]

[0009] The present disclosure provides a radio wave transparent heater having a radio wave transparent region for transmitting radio waves, the heater including a substrate, a first comb electrode arranged on the substrate, the first comb electrode having a first main electrode and a plurality of first sub-electrodes, a second comb electrode arranged on the substrate, the second comb electrode having a second main electrode and a plurality of second sub-electrodes, and a PTC resistor arranged between the first sub-electrode and the second sub-electrode, the first sub-electrodes and the second sub-electrodes being arranged alternately and in parallel, and in the radio wave transparent region, the PTC resistor is arranged in lines so as to form a lattice with the first sub-electrode and the second sub-electrode. Effect of the Invention

[0010] The radio wave transparent heater of the present disclosure has radio wave transparency and is capable of uniformly increasing the temperature. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a plan view of a radio wave transparent heater according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a partial enlarged view of the area enclosed by the dotted line in FIG. [Diagram 3] FIG. 3 is a schematic cross-sectional view showing the configuration of a radar device including an antenna cover equipped with a radio wave transparent heater according to the present disclosure. [Figure 4] 4A is a front view of the antenna cover, FIG. 4B is a plan view of the antenna cover, FIG. 4C is a cross-sectional view along line AA in FIG. 4B, FIG. 4D is a side view of the antenna cover, and FIG. 4E is a bottom view of the antenna cover. [Diagram 5] FIG. 5 is a diagram showing a state in which a radio wave transparent heater is disposed on a cover main body. [Figure 6] FIG. 6 is a diagram showing a radar device mounted on a vehicle. [Figure 7] FIG. 7 is a diagram showing a step in a method for manufacturing an antenna cover. [Figure 8] FIG. 8 is a diagram showing a step in a method for manufacturing an antenna cover. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. The radio wave transparent heater of this embodiment is used, for example, in an in-vehicle antenna cover, and is capable of transmitting millimeter waves (radio waves). Hereinafter, a radio wave transparent heater capable of transmitting millimeter waves will be described, but the radio waves transmitted by the radio wave transparent heater are not limited to millimeter waves.

[0013] The radio wave transparent heater of this embodiment is used by being arranged so that the electric field direction of the radio wave is parallel to its surface. In other words, the heater is used by being arranged so that the radio wave is incident perpendicularly to the surface of the radio wave transparent heater. However, "parallel" in this specification does not only mean a case where the two are completely parallel, but also includes a case where there is a deviation that does not impede the purpose and effect of the invention, for example, a case where the angle between the two is within 0±5°.

[0014] 1 shows a plan view of a radio wave transparent heater according to an embodiment of the present disclosure. The radio wave transparent heater 100 has a substrate 21, a first comb electrode 8 arranged on the substrate 21, a second comb electrode 9 arranged on the substrate 21, and a PTC resistor 10. The radio wave transparent heater 100 of this embodiment further has two terminals 14 for electrically connecting the first comb electrode 8 and the second comb electrode 9 to an external power source or the like. The radio wave transparent heater 100 of this embodiment has a rectangular shape in plan view, but the radio wave transparent heater 100 does not need to be rectangular and may have any shape, such as a circular shape, an elliptical shape, or a polygonal shape.

[0015] The first comb electrode 8 has a first main electrode 8a and a plurality of first sub-electrodes 8b connected thereto. The second comb electrode 9 also has a second main electrode 9a and a plurality of second sub-electrodes 9b connected thereto. The first sub-electrodes 8b and the second sub-electrodes 9b are arranged alternately and at equal intervals when the radio wave transparent heater 100 is viewed in plan. The PTC resistor 10 is arranged between the first sub-electrode 8b and the second sub-electrode 9b in a predetermined pattern. In this embodiment, the PTC resistor 10 is arranged not only between the first sub-electrode 8b and the second sub-electrode 9b but also so as to cover them, but the PTC resistor 10 does not necessarily have to cover the first sub-electrode 8b and the second sub-electrode 9b. The pattern of the PTC resistor 10 will be described later.

[0016] In the radio wave transparent heater 100 of this embodiment, when a voltage is applied between the first comb electrode 8 and the second comb electrode 9, the temperature of the PTC resistor 10 rises. On the other hand, when the temperature reaches a predetermined temperature, the electrical resistance of the PTC resistor 10 increases rapidly, making it difficult for electricity to pass through. Therefore, it is possible to maintain the temperature of the radio wave transparent heater 100 within a desired range.

[0017] Here, the radio wave transparent heater 100 of this embodiment has a radio wave transparent region 15 for transmitting radio waves from an antenna or the like, and a heating promotion region 16 arranged around it for more efficiently increasing the temperature of the radio wave transparent heater 100.

[0018] The radio wave transparent region 15 may have any shape as long as it can transmit the desired radio waves, and in this embodiment, only one rectangular radio wave transparent region 15 is arranged on the central side of the radio wave transparent heater 100. However, the planar shape of the radio wave transparent region 15 is not limited to a rectangular shape, and may be any shape, such as a circular shape, an elliptical shape, or a polygonal shape. In addition, the position of the radio wave transparent region 15 is not limited to the central side of the radio wave transparent heater 100, and may be arranged on the end side. Furthermore, the number of radio wave transparent regions 15 in the radio wave transparent heater 100 is not limited to one, and may be multiple.

[0019] In the radio wave transmission region 15, the first sub-electrode 8b, the second sub-electrode 9b, and the linear PTC resistor (hereinafter, the linear PTC resistor 10 is also referred to as the linear PTC resistor 10a) are arranged to form a lattice. FIG. 2 shows a partial enlarged view of the region surrounded by the dotted line in FIG. 1. In this embodiment, the first sub-electrode 8b and the second sub-electrode 9b arranged alternately and in parallel, and the multiple linear PTC resistors 10a are arranged so as to be perpendicular to each other. In addition, in the region A surrounded by the first sub-electrode 8b, the multiple second sub-electrodes 9b, and the two linear PTC resistors 10a, the substrate 21 is exposed. In this embodiment, since the region A where the substrate 21 is exposed is provided, the propagation of radio waves is not easily hindered, and radio waves can be efficiently transmitted.

[0020] Here, when the radio wave transparent heater 100 is driven, the temperature of the linear PTC resistor 10a rises in the radio wave transparent region 15. At this time, the heat of the PTC resistor 10a is transferred to the first sub-electrode 8b and the second sub-electrode 9b, which also function as a heat ray. Therefore, the heat is easily transferred to the region A where the PTC resistor 10a and the first sub-electrode 8b and the second sub-electrode 9b are not arranged, and the temperature is less likely to be uneven in the radio wave transparent region 15.

[0021] In this embodiment, as shown in Fig. 2, the radio wave transparent heater 100 is installed so that the extension direction of the first sub-electrode 8b and the second sub-electrode 9b is perpendicular to the polarization direction of the radio wave. At this time, the interval between the first sub-electrode 8b and the second sub-electrode 9b, i.e., the distance X from the end of the adjacent first sub-electrode 8b to the end of the second sub-electrode 9b, may be longer than the wavelength of the radio wave passing between them. More specifically, it may be longer than the wavelength of the radio wave in the member (e.g., the substrate 21) immediately before entering the lattice. The width w1 of the first sub-electrode 8b and the second sub-electrode 9b is appropriately selected within a range that does not affect the transmission of the radio wave through the radio wave transparent heater 100.

[0022] On the other hand, the number of the linear PTC resistors 10a arranged in the radio wave transmitting region 15 is appropriately selected according to the area of ​​the radio wave transmitting region 15, the number of desired lattices, etc., and may be only one or more. When there are multiple linear PTC resistors 10a, they are preferably arranged at equal intervals. The interval between the multiple linear PTC resistors 10a, i.e., the distance Y from one end to the other end of the adjacent linear PTC resistors 10a, is appropriately selected within a range that does not affect the passage of radio waves, but a smaller interval is preferable from the viewpoint of easily increasing the temperature of the radio wave transmitting region 15. In addition, the width w2 of the linear PTC resistors 10a is preferably thicker from the viewpoint of efficiently increasing the temperature of the radio wave transmitting region 15. On the other hand, a thinner width is preferable from the viewpoint of easily transmitting radio waves through the radio wave transmitting heater 100 (easiness to reduce the amount of attenuation of radio waves). Therefore, the width is appropriately set in consideration of the allowable value of the attenuation in the radio wave transmitting heater 100, etc. In this specification, the width w2 of the linear PTC resistor 10a refers to the length of the linear PTC resistor in the direction in which the first sub-electrode 8b and the second sub-electrode 9b extend. The width w2 of the linear PTC resistor 10a may be constant or may vary continuously or intermittently, but is preferably constant from one end to the other end in order to avoid affecting the radio wave transmission.

[0023] On the other hand, the heating promotion region 16 is disposed near the radio wave transparent region 15, and is a region for efficiently increasing the temperature of the radio wave transparent heater 100. In this embodiment, the heating promotion region 16 is disposed so as to surround the radio wave transparent region 15 disposed at the center of the radio wave transparent heater 100. However, the position and shape of the heating promotion region 16 are not limited to these positions and shapes.

[0024] In the heating promotion area 16, the above-mentioned first sub-electrode 8b and second sub-electrode 9b and a planar PTC resistor 10 (hereinafter, the PTC resistor 10 in the heating promotion area 16 is also referred to as a "planar PTC resistor 10b"). When the heating promotion area 16 is viewed from above, in the heating promotion area 16 in which such a planar PTC resistor 10 is arranged, the planar PTC resistor 10b efficiently generates heat when the radio wave transparent heater 100 is driven. Therefore, the temperature of the radio wave transparent heater 100 is likely to increase more efficiently. The area of ​​the heating promotion area 16 is not particularly limited. In addition, depending on the type, size, and use of the radio wave transparent heater 100, the heating promotion area 16 does not necessarily have to be arranged.

[0025] Hereinafter, each member constituting the radio wave transparent heater 100 will be described. The substrate 21 is not particularly limited in type as long as it has insulating properties, is not deformed or melted by the heat of the radio wave transparent heater 100, and can support the first comb electrode 8, the second comb electrode 9, and the PTC resistor 10. For example, it may be a resin film or a polyester film. The planar shape and thickness of the substrate are also not particularly limited, and are appropriately selected according to the application. For example, the planar shape of the substrate may be any shape, such as a rectangle, a circle, or an ellipse.

[0026] The first comb electrode 8 may have a first main electrode 8a and a first sub-electrode 8b, and the second comb electrode 9 may have a second main electrode 9a and a second sub-electrode 9b. The shapes of the first sub-electrode 8b and the second sub-electrode 9b are as described above. On the other hand, the shapes of the first main electrode 8a and the second main electrode 9a are not particularly limited and are appropriately selected according to the shape of the radio wave transparent heater 100, etc. The first main electrode 8a and the second main electrode 9a may have a linear shape in a plan view, or may have any shape such as a curved shape or a semicircular shape.

[0027] The first comb electrode 8 and the second comb electrode 9 are preferably made of a material having high thermal conductivity as well as electrical conductivity. Specific examples of materials constituting the first comb electrode 8 and the second comb electrode 9 include silver, copper, gold, aluminum, and alloys thereof.

[0028] On the other hand, the PTC resistor 10 may be any material having PTC characteristics, and may be, for example, a resistor having the same composition as a known PTC resistor, for example, a resistor containing conductive particles and a crystalline resin. On the other hand, the PTC resistor is more preferably a resistor containing conductive particles, a binder resin, and a wax. In this case, the wax is preferably a naturally occurring wax and / or a polyolefin wax. The PTC resistor containing wax will be described later.

[0029] Furthermore, the terminal 14 is not particularly limited in structure or type as long as it has a structure that can electrically connect the first comb electrode 8 and the second comb electrode 9 to an external power source. Furthermore, the radio wave transparent heater 100 of this embodiment may have a structure other than the above as long as it does not impair the object and effect of this embodiment.

[0030] (About the manufacturing method of radio wave transparent heater) The manufacturing method of the radio wave transparent heater 100 described above is not particularly limited. For example, the first comb electrode 8, the second comb electrode 9, and the PTC resistor 10 may be formed in this order on the substrate 21. For example, the first comb electrode 8 and the second comb electrode 9 can be formed by bonding a metal foil or the like formed in a pattern to the substrate 21. The PTC resistor 10 can be formed by printing a composition containing the PTC resistor by screen printing or the like and solidifying it.

[0031] (Modification) In the above, it has been described that the radio wave transparent heater 100 is arranged so that the first sub-electrode 8b and the second sub-electrode 9b are perpendicular to the polarization direction of the radio wave. However, the radio wave transparent heater 100 may be configured so that the first sub-electrode 8b and the second sub-electrode 9b are arranged parallel to the polarization direction of the radio wave.

[0032] In the above embodiment, the first sub-electrode 8b and the second sub-electrode 9b are perpendicular to the linear PTC resistor 10a. However, the angle between the first sub-electrode 8b and the second sub-electrode 9b and the linear PTC resistor 10a is not limited to 90° and may be any angle as long as the desired radio wave can be transmitted.

[0033] (About PTC resistors) A PTC resistor 10 including conductive particles, binder resin, and wax that can be used in the radio wave transparent heater 100 described above will be described. The PTC resistor 10 includes polyolefin wax or naturally derived wax along with the conductive particles and binder resin. In the PTC resistor 10, the wax melts near its melting point when the temperature rises. The volume increase due to melting of the wax is much larger than the volume increase of a general resin. In addition, since they melt easily, the resistance value increases significantly in a short time. Therefore, in the radio wave transparent heater 100 using the PTC resistor 10, the temperature can be easily controlled.

[0034] The conductive particles in the PTC resistor 10 are not particularly limited as long as they are conductive particles, and examples thereof include carbon-based particles such as graphite, carbon black, carbon nanotubes, and graphene; metal-based particles such as nickel powder, copper powder, silver powder, and tungsten powder; and the like.

[0035] The binder resin in the PTC resistor 10 may be any resin capable of binding conductive particles and wax, and binding them to the substrate 21, etc. Examples of the binder resin include known thermoplastic resins. Specific examples include thermoplastic polyurethane resins, polyester resins, polyacrylate resins, polysiloxane resins, vinyl halide resins, vinylidene resins, polyimide resins, phenoxy resins, polyether resins, polyketone resins, polyvinyl butyral resins, polyvinylpyrrolidone resins, polyacrylate resins, SEBS resins (styrene-ethylene-butylene-styrene copolymers) and hydrogenated products thereof, SEPS resins (styrene-ethylene-propylene-styrene copolymers) and hydrogenated products thereof, etc.

[0036] Examples of waxes include polyolefin waxes (waxes containing 50% by mass or more of olefin-derived components). In this specification, wax refers to an organic material that is solid or semi-solid at room temperature (25°C) and melts without decomposition when heated. Examples of polyolefin waxes include olefin homopolymers, copolymers of two or more olefins, copolymers of olefins and monomers other than olefins, etc. More specific examples of polyolefin waxes include polyethylene waxes such as low-density polyethylene wax, medium-density polyethylene wax, and high-density polyethylene wax, polypropylene wax, polybutene wax, ethylene-propylene copolymer wax, and ethylene-propylene-butene copolymer wax. In addition, these may be oxidized polyolefin waxes obtained by oxidizing them by a known method. Among these, polyethylene waxes are preferred from the viewpoints of availability and PTC properties.

[0037] The weight average molecular weight of the above-mentioned polyolefin wax is preferably 1,000 to 1,500,000, more preferably 3,000 to 20,000. The weight average molecular weight is a polystyrene equivalent value measured by gel permeation chromatography (GPC). When the weight average molecular weight of the polyolefin wax is within this range, it is easy to exhibit PTC properties in a desired temperature range.

[0038] Examples of waxes include naturally derived waxes. Naturally derived waxes refer to plant-based waxes derived from plants or animal-based waxes derived from animals. Furthermore, plant-based waxes refer to waxes made from plants. Animal-based waxes refer to waxes derived from animals. The type of naturally derived wax contained in the PTC resistor is not particularly limited, but the PTC resistor is usually required to increase in resistance value at 40°C or higher and 100°C or lower. Therefore, the melting point of the naturally derived wax is preferably 40°C or higher and 100°C or lower, more preferably 50°C or higher and 90°C or higher.

[0039] Examples of the plant-based wax, which is one type of naturally occurring wax, include candelilla wax, carnauba wax, rice wax, Japan wax wax, hydrogenated jojoba wax, etc. Among these, carnauba wax, candelilla wax, and rice wax are preferred from the viewpoints of availability and ease of increasing the PTC multiplier.

[0040] On the other hand, examples of animal waxes, which are a type of naturally derived wax, include beeswax and lanolin wax.

[0041] (Applications of radio wave transparent heaters) Hereinafter, an example in which the radio wave transparent heater 100 described above is used as an antenna cover will be described, but the use of the radio wave transparent heater 100 described above is not limited to this use. Fig. 3 shows a schematic cross-sectional view of the configuration of a radar device equipped with an antenna cover including the radio wave transparent heater 100 described above. The radar device has a support part 1, an antenna substrate 2, an antenna 3, an antenna control part 4, and an antenna cover 5.

[0042] The support part 1 is a member for supporting each part of the radar device, and together with the antenna cover 5 forms an accommodation chamber R for accommodating the antenna substrate 2 and the antenna 3. The support part 1 is made of, for example, a resin material. The antenna substrate 2 is a member for supporting the antenna 3, and is fixed to the support portion 1 in the accommodation chamber R. The antenna substrate 2 is made of, for example, a resin material.

[0043] The antenna 3 is disposed on the antenna board 2, and is configured to transmit radio waves W of a predetermined frequency, for example millimeter waves, toward the front in response to a control signal from the antenna control unit 4. The antenna 3 also receives reflected waves that are the transmitted radio waves W reflected back by an external object, and outputs a received signal to the antenna control unit 4 according to the intensity of the reflected waves.

[0044] The antenna control unit 4 is configured to control the antenna 3, and is electrically connected to the antenna 3. The antenna control unit 4 outputs a preset control signal to the antenna 3 so that radio waves W are transmitted from the antenna 3 at a predetermined timing. The antenna control unit 4 also receives a reception signal from the antenna 3 according to the intensity of the reflected wave. The antenna control unit 4 calculates the position of an object present outside based on the change in the frequency of the reflected wave relative to the frequency of the transmitted radio waves W, and the like.

[0045] The antenna cover 5 has a cover body (so-called radome) 6 that protects the antenna 3, and a heating device (the radio wave transparent heater described above) 100 that removes obstructions such as snow and rain that adhere to the radar device by heating. Figures 4A to 4E show the structure of the antenna cover 5. Figure 4A is a front view of the antenna cover 5, Figure 4B is a plan view, Figure 4C is a cross-sectional view taken along line AA in Figure 4B, Figure 4D is a side view, and Figure 4E is a bottom view.

[0046] The cover body 6 is disposed so as to completely cover the antenna substrate 2 and the antenna 3. The cover body 6 is disposed in front of the antenna 3, i.e., on the transmitting side of the radio waves W, and is therefore formed to be transparent to the radio waves W. In this case, the cover body 6 is formed so as to be curved convexly in the transmitting direction with a thickness according to the frequency of the radio waves W so as not to impede the propagation of the radio waves W. The cover body 6 can be made of a material having radio wave transparency, such as a resin material.

[0047] On the other hand, the radio wave transparent heater 100 is disposed on the bottom side of the antenna cover 5, and disposed so as to curve along the cover body 6. As shown in Fig. 4D, the radio wave transparent heater 100 includes the first comb electrode 8, the second comb electrode 9, and a plurality of linear PTC resistors 10, and heats the cover body 6 when electricity is applied.

[0048] As shown in Figures 5 and 6, the radio wave transparent heater 100 is directly or indirectly connected to a power source 11 provided in a radar device or a vehicle V, a power source control unit 12 connected to the power source 11, and a detection unit 13.

[0049] The power supply 11 is configured to supply power to the first comb electrode 8 and the second comb electrode 9 of the radio wave transparent heater 100, and is configured to switch the power supply on and off according to the control of the power supply control unit 12.

[0050] The detection unit 13 is configured to detect obstructions such as snow and rain that adhere to the surface of the cover body 6. The detection unit 13 can be configured, for example, from a thermometer that measures the outside temperature, or a detector that directly detects outside snow, rain, etc. with a sensor.

[0051] The power supply control unit 12 is configured to switch the power supply 11 on and off based on the detection result of the detection unit 13 , and to control the heating of the cover body 6 by the radio wave transparent heater 100 .

[0052] This radar device can be mounted on a vehicle V as shown in Fig. 6, and can be arranged, for example, so that the cover body 6 is exposed to the outside from a front panel F of the vehicle V. An example of the vehicle V is a work vehicle such as a snowplow.

[0053] Next, a method for manufacturing the antenna cover 5 will be described.

[0054] The manufacturing method of the antenna cover 5 is not particularly limited. For example, the cover body 6 may be formed in advance, and the radio wave transparent heater 100 may be attached to the back surface of the cover body 6 by a known method (for example, adhesion with an adhesive, fusion, etc.). At this time, the substrate 21 may be attached to the cover body 6 so as to be in contact with the cover body 6, or the PTC resistor 10 may be attached to the cover body 6 so as to be in contact with the cover body 6.

[0055] 7, the first comb electrode 8, the second comb electrode 9, and the PTC resistor 10 may be formed on the surface of the substrate 21, and then the substrate 21 may be placed in a cavity C of a mold M and molten resin Ra may be poured therein to form the cover body 6, as shown in FIG. 8. At this time, the first comb electrode 8, the second comb electrode 9, and the PTC resistor 10 may be placed so as to be exposed in the cavity C, or may be placed so as to be located outside the cavity C. According to this method, no gap is generated between the cover body 6 and the radio wave transparent heater 100, and the radio wave transparent heater 100 can be placed at a desired position.

[0056] The operation of the above radar device will be described with reference to Fig. 6. The above radar device is disposed so that the cover body 6 of the antenna cover 5 is exposed to the outside from the front panel F of the vehicle V. Then, as shown in Fig. 3, when radio waves W of a predetermined frequency are transmitted from the antenna 3 under the control of the antenna control unit 4, the radio waves W propagate forward of the vehicle V via the antenna cover 5. The radio waves W propagated forward of the vehicle V are reflected by an object present in front of the vehicle V. Then, this reflected wave returns via the antenna cover 5 and is received by the antenna 3.

[0057] When the reflected wave is received by the antenna 3, the received signal is output from the antenna 3 to the antenna control unit 4. Then, the antenna control unit 4 calculates the frequency of the reflected wave based on the received signal, and calculates the position of the object with respect to the vehicle V based on the change in the frequency of the reflected wave relative to the frequency of the transmitted radio wave W, etc.

[0058] Next, when an obstruction such as snow adheres to the surface of the cover body 6, the detection unit 13 detects the adhesion of the obstruction to the cover body 6 as shown in Fig. 5. The detection unit 13 detects the adhesion of the obstruction by, for example, detecting it with a raindrop sensor or the like in the external environment of the vehicle V, or by predicting the adhesion by measuring the temperature. The detection unit 13 outputs the measured temperature to the power supply control unit 12.

[0059] The power supply control unit 12 determines whether an obstruction is attached to the cover body 6 based on the temperature measured by the detection unit 13. When the temperature measured by the detection unit 13 is higher than a predetermined value, the power supply control unit 12 determines that an obstruction is not attached and turns off the power supply 11.

[0060] On the other hand, when the temperature measured by the detection unit 13 is equal to or lower than a predetermined value, the power supply control unit 12 determines that an obstruction is attached and turns on the power supply 11. When the power supply 11 is turned on, power is supplied from the power supply 11 to the radio wave transparent heater 100, which heats the cover body 6. This increases the temperature of the cover body 6, and obstructions such as snow attached to the surface of the cover body 6 can be melted or evaporated and removed. In addition, because the radio wave transparent heater 100 directly heats the cover body 6, obstructions can be removed with little power.

[0061] In this way, the radio wave transparent heater 100 heats the cover body 6 and suppresses the adhesion of obstructions, so that radio waves W can be transmitted smoothly to the front of the vehicle V regardless of changes in the external environment, and objects present in front of the vehicle V can be reliably detected.

[0062] According to this embodiment, the radio wave transparent heater 100 has the above-mentioned radio wave transparent region and is disposed so as not to impede the transmission and reception of the radio waves W, so that the radar device can be used stably.

[0063] In the above embodiment, it has been described that the radio wave transparent heater 100 is arranged on the bottom side (antenna 3 side) of the cover body 6, but the position of the radio wave transparent heater 100 may also be on the top side (outside) of the cover body.

[0064] In the above embodiment, the cover body 6 is disposed so as to be exposed to the outside from the front panel F of the vehicle V, but the present invention is not limited to this as long as obstructions can be removed. For example, the cover body 6 may be disposed so as to abut against the front panel F, and obstructions attached to the front panel F may be removed by heat conducted from the cover body 6 to the front panel F.

[0065] In addition, the above-mentioned embodiments are merely examples of the embodiment of the present invention, and the technical scope of the present invention should not be interpreted as being limited by these. That is, the present invention can be implemented in various forms without departing from the gist or main features of the present invention. For example, the disclosure of the shape and number of each part described in the above-mentioned embodiments is merely an example, and can be implemented by appropriately changing them. [Industrial Applicability]

[0066] The radio wave transparency according to the present disclosure can be used for a cover for an antenna that transmits and receives radio waves. [Explanation of symbols]

[0067] 1 Support part 2 Antenna Board 3 Antennas 4 Antenna control section 5 Antenna cover 6 Cover body 8 First comb-shaped electrode 8a 1st main electrode 8b 1st sub-electrode 9 Second comb-shaped electrode 9a 2nd main electrode 9b 2nd sub-electrode 10 PTC resistor 11 Power supply 12 Power supply control unit 13 Detection section 21 Substrate 100 Radio-transparent heater C Cavity F. Front Panel M mold R Containment Room Ra Molten Resin V Vehicle

Claims

1. A radio wave transparent heater having a radio wave transparent region for transmitting radio waves, A substrate; a first comb electrode disposed on the substrate, the first comb electrode including a first main electrode and a plurality of first sub-electrodes; a second comb electrode disposed on the substrate, the second comb electrode including a second main electrode and a plurality of second sub-electrodes; a PTC resistor disposed between the first sub-electrode and the second sub-electrode; Including, The first sub-electrodes and the second sub-electrodes are arranged alternately and in parallel, In the radio wave transmission region, The PTC resistors are arranged in lines so as to form a grid with the first sub-electrode and the second sub-electrode. Radio wave transparent heater.

2. The heating device further includes a heating promotion area disposed adjacent to the radio wave transmission area, In the heating promotion region, the PTC resistor is arranged in a planar shape. The radio wave transparent heater according to claim 1 .

3. the first comb electrode and / or the second comb electrode are made of a metal selected from the group consisting of silver, copper, gold, and aluminum, or an alloy thereof; The radio wave transparent heater according to claim 1 .

4. The PTC resistor includes conductive particles, a binder resin, and a wax, and the wax includes a naturally derived wax and / or a polyolefin wax. The radio wave transparent heater according to claim 1 .

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