Pressure-sensitive sensor using pressure-sensitive conductor

Abstract

To provide a pressure-sensitive sensor with which, when a skin is used on a sensor, it is possible to discriminate a pressure due to winding or engagement of the skin from a pressure due to grasping or contact, and possible to indicate a change in electrical resistance for only the pressure due to grasping or contact.SOLUTION: A pressure-sensitive sensor comprises: a pressure-sensitive conductor whose electrical resistance value changes by application of pressure; an electrode disposed on both sides of the pressure-sensitive conductor; and a spacer installed between the pressure-sensitive conductor and the electrode, and having an opening in the spacer. The pressure-sensitive sensor is installed on a curved section, and has a shortest width W of the spacer opening having the following relationship between a radius curvature r and a spacer thickness t: W<√(8rt+4 t^2), where W represents a shortest width (mm) of the spacer opening, r represents a radius of curvature (mm), and t represents a spacer thickness (mm). The pressure-sensitive sensor is installed in a vehicle interior or on a steering wheel. The pressure-sensitive conductor contains barium titanate powder and metal powder that are mixed in a matrix composed of a high polymer material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive sensor that uses a pressure-sensitive conductor whose electrical resistance value changes when pressure is applied, and in particular to a grip sensor in which, when a skin is wrapped around the sensor and used, such as in a steering wheel of an automobile, the sensor does not show a change in electrical resistance in response to the pressure generated on the sensor when the skin is wrapped around the sensor's outer circumference, but shows a change in electrical resistance in response to pressure from the user's grip; and to a contact sensor in which, when a skin is engaged with the sensor and used, such as in the interior of a car, the sensor does not show a change in electrical resistance in response to pressure generated when the skin is placed on the sensor and the sensor is squeezed by the skin, particularly in a part of the interior that is not flat, but the sensor can show a change in electrical resistance in response to pressure from the user's contact. [Background technology]

[0002] Conventionally, pressure-sensitive conductors have been known in which conductive particles, such as graphite particles or positive temperature coefficient thermistor powder, are dispersed in a matrix such as silicone rubber. Pressure deforms the elastic matrix, causing the dispersed conductive particles to come into contact with each other, reducing the resistance and establishing electrical continuity. When the pressure is released, the conductive particles separate and return to their original state of non-contact, increasing the resistance and restoring the electrical insulation state. Examples of such technologies include Patent Document 1. References to such technologies include Patent Document 2.

[0003] The applicant has also already proposed a pressure-sensitive conductor in which barium titanate and metal particles are dispersed in a polymer matrix, and which exhibits a large change in resistance, particularly in response to low-pressure contact, and a method for manufacturing the same (Patent Application No. 2023-187407). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 9-245937 A: Riken [Patent Document 2] Patent No. 6221863: Denso DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0005] When a pressure-sensitive sensor is used as a grip sensor for an automobile steering wheel, because a skin is wrapped around the outermost surface of the steering wheel, it is necessary to distinguish between pressure generated when the skin is wrapped around the steering wheel and pressure generated by gripping. In other words, the sensor's electrical resistance must not change in response to the skin's wrapping pressure, but must only show a change in electrical resistance in response to gripping pressure. Furthermore, even when a pressure-sensitive sensor is used on a curved surface with a skin, not just a steering wheel, pressure generated by the skin's engagement is constantly applied from the skin to the pressure sensor. Therefore, the sensor's electrical resistance must not change in response to pressure from the skin when the user is not touching the sensor, but must only show a change in electrical resistance in response to pressure applied when the user is in contact with the sensor. While the pressure-sensitive conductors described in Patent Documents 1 and 2 can detect pressure, they cannot distinguish between pressure generated by wrapping or engaging the skin and pressure generated by gripping or contacting the sensor, and the sensor always shows a change in electrical resistance in response to pressure.

[0006] The present invention has been made to solve the problems of the prior art, and its purpose is to provide a pressure-sensitive sensor that, when a skin is used on the sensor, can distinguish between pressure caused by wrapping or engaging the skin and pressure caused by gripping or contact, and that can show a change in electrical resistance only in response to pressure caused by gripping or contact. [Means for solving the problem]

[0007] In order to achieve the above object, the pressure-sensitive sensor of the present invention comprises a pressure-sensitive conductor whose electrical resistance value changes when pressure is applied, electrodes installed on both sides of the pressure-sensitive conductor, and a spacer installed between the pressure-sensitive conductor and the electrodes, and the spacer has an opening. Furthermore, it is considered that the shortest width W of the spacer opening placed on the curved surface satisfies the following relationship with the radius of curvature r and the thickness t of the spacer. W<√(8rt+4t^2) W: Shortest width of spacer opening (mm) r: radius of curvature (mm) t: spacer thickness (mm) It may also be installed in the interior of the car or on the steering wheel. The pressure-sensitive conductor may be a mixture of barium titanate powder and metal powder in a matrix made of a polymer material. [Effects of the Invention]

[0008] The pressure-sensitive sensor of the present invention has a spacer between the pressure-sensitive conductor and the electrode. When the user is not in contact with the sensor, the spacer prevents electrical continuity between the pressure-sensitive conductor and the electrode. When the user is in contact with the sensor, the pressure-sensitive conductor or the electrode flexes, establishing electrical continuity. The sensor also exhibits a change in electrical resistance in response to the user's contact pressure. This allows the sensor to detect pressure due to the user's grip or contact, without detecting pressure due to constant wrapping or engagement of the skin. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a partially cutaway plan view showing the configuration of a pressure-sensitive sensor using a pressure-sensitive conductor according to the present invention. [Figure 2] 1 is a cross-sectional view showing a state in which a grip sensor using a pressure-sensitive sensor according to the present invention is installed on a steering wheel. [Figure 3] 1 is a partially cutaway perspective view showing a state in which a grip sensor using a pressure-sensitive sensor according to the present invention is embedded in a steering wheel. [Figure 4] 1 is a schematic diagram showing an example of use of a contact sensor using a pressure-sensitive sensor according to the present invention; BEST MODE FOR CARRYING OUT THE INVENTION

[0010] In the examples of this application, a pressure-sensitive conductor with a thickness of approximately 0.2 mm is used, in which metal powder and barium titanate powder are dispersed in a silicone matrix. Any insulating material can be used as the spacer, and in the examples, a piece of paper with a thickness of 0.08 mm and perforated by punching is used.

[0011] In Example 1, a pressure-sensitive sensor was created in which a pressure-sensitive conductor 1 and a spacer 2 with an opening were placed between two flexible electrodes 51 and 52. In this case, the top and bottom of the pressure-sensitive conductor 1 and spacer 2 can be determined arbitrarily. If it is desired to avoid the unevenness caused by the opening of the spacer 2 appearing on the epidermis, it is preferable to place the spacer 2 on the bottom, but this is not necessary as long as the unevenness of the opening is hidden by the tension of the outer electrode 52.

[0012] A 2 mm thick rubber sheet (not shown) was fitted onto the pressure-sensitive sensor of Example 1 in a predetermined manner, and a contact detection test was conducted. When the user was not in contact with the sensor, the spacer prevented electrical continuity between the pressure-sensitive conductor and the electrode, and no change in electrical resistance was observed. When the user was in contact with the sensor, the pressure-sensitive conductor or the electrode flexed, establishing electrical continuity and causing a change in electrical resistance.

[0013] The spacer of the present invention can be made of any insulating material, such as paper, plastic, or rubber. However, it is preferable that the thickness of the spacer does not change due to pressure from the outer sheath. If the thickness changes due to pressure from the outer sheath, the distance between the electrode and the sensor cannot be maintained properly, and the pressure from the outer sheath may cause the electrode and the sensor to come into contact, resulting in malfunction. Furthermore, the shape is not limited to ribbon or band, but may also be linear, lattice, or strip-like. Specifically, possible materials include paper with openings formed using a hole punch, or loosely woven threads to maintain a consistent thickness. Examples of possible threads include monofilaments, multifilaments, or spun organic fibers such as cotton thread or glass fiber, polyester fibers such as polyethylene terephthalate, aliphatic polyamide fibers, aromatic polyamide fibers, and wholly aromatic polyester fibers, as well as the organic polymer materials that make up these fiber materials. Furthermore, from the standpoint of being able to form the spacer to a consistent thickness and durability, plastic sheets or rubber sheets with openings are also suitable.

[0014] The method of providing the openings in the spacer may be appropriately selected from perforations by punching, openings provided from the time of spacer molding, lattice-like woven spacers so as to maintain a uniform thickness, etc. Furthermore, if the openings are provided during molding, material loss due to perforations can be reduced.

[0015] The shape of the spacer opening can be selected from various shapes such as circle, square, triangle, etc. Furthermore, the shortest width of the spacer opening is the same as the diameter when the opening shape is a perfect circle, but when the opening shape is an oval, square, triangle, etc., the shortest width is measured as appropriate.

[0016] The electrodes are preferably made of a flexible material rather than a rigid metal plate, and may be appropriately selected from commonly known conductors such as conductive cloth, metal foil, conductive polymers, etc.

[0017] As for the pressure-sensitive conductor, it is preferable to use a pressure-sensitive conductor, which is the applicant's application (Patent Application No. 2023-187407), in which barium titanate and metal particles are dispersed in a polymer matrix and which shows a large change in resistance, particularly in response to low-pressure contact.

[0018] It is difficult to constantly maintain the distance between the electrodes using a spacer, and if the pressure-sensitive conductor or electrode becomes wrinkled due to the application of contact pressure, the pressure-sensitive conductor or electrode may remain bent even when the contact pressure is released. However, in this embodiment, a pressure-sensitive conductor is used in the pressure-sensitive sensor, so there is no conductivity even if the conductor is bent when not in contact with the user, and the conductor is only conductive when contact pressure is applied by the user.

[0019] Specifically, a one-component curing silicone rubber known as RTV was used as the matrix. This reacts with moisture in the air at room temperature to harden and become a rubbery elastic body. Aluminum powder with an average particle size of 98 μm was used as the metal powder dispersed in the matrix. Barium titanate ceramic particles before sintering were used as the barium titanate powder dispersed in the matrix. This barium titanate powder had a Curie temperature of 40°C, and when the geometric mean diameter was calculated using an optical microscope, the average primary particle size was 2.0 μm.

[0020] The aluminum powder and barium titanate powder were mixed to form a mixed powder. This mixed powder was mixed with a fluidized RTV and thoroughly kneaded to form a paste. This paste was then applied to a pair of aluminum foils measuring 20 mm in length, 50 mm in width, and 20 μm in thickness at a predetermined thickness, and then left at room temperature to cure the RTV.

[0021] It has been confirmed that when the compounding ratio of the matrix and each powder is 100 parts by weight of matrix to 10-67 parts by weight of barium titanate powder and 20-133 parts by weight of metal powder, a significant decrease in resistance value is observed even with a small pressure. Furthermore, when the thickness of the pressure-sensitive conductor is equal to or greater than the sum of the average particle diameters of the barium titanate powder and the metal powder, and is less than three times the sum of the average particle diameters of the barium titanate powder and the metal powder, a significant decrease in resistance value is observed even with a small pressure. Furthermore, when the average particle diameter of the metal powder is 98 μm or more and 300 μm or less, a significant decrease in resistance value is observed even with a small pressure. It has also been confirmed that even when urethane rubber is used as the matrix instead of silicone rubber, or magnesium powder is used as the metal powder instead of aluminum powder, a sufficient decrease in resistance value is observed with a small pressure, and detection is possible even with a pressure equivalent to contact pressure. When copper powder is used as the metal powder, the pressure at which resistance value decreases tends to be greater than when aluminum powder or magnesium powder is used.

[0022] Conventionally, it has been difficult to form an ohmic contact between barium titanate and an electrode, requiring the formation of a special ohmic electrode, such as a multilayer electrode primarily composed of nickel or silver. In this pressure-sensitive conductor, by adding aluminum powder or magnesium powder to barium titanate powder, an ohmic contact is formed between the electrode layer and barium titanate without the need for a special ohmic electrode.

[0023] The pressure-sensitive conductor is not limited to the above-described form and various selections are possible. The polymer material serving as the matrix may be selected from various resins, rubbers, thermoplastic elastomers, and the like, including rubber materials such as polyurethane rubber, chloroprene rubber, silicone resin, silicone rubber, neoprene rubber, diene rubber, nitrile rubber, butyl rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, isoprene rubber, fluororubber, and natural rubber, resin materials such as polyurethane resin, polyethylene resin, polypropylene resin, vinyl chloride resin, ethylene-vinyl acetate copolymer, fluororesin, ABS resin, PPS resin, polycarbonate resin, polyester resin, acrylic resin, polystyrene resin, polyamide resin, polyacetal resin, polyimide resin, phenolic resin, alkyd resin, urea resin, melamine resin, and epoxy resin, and thermoplastic elastomer materials such as polyurethane-based thermoplastic elastomer, polyolefin-based thermoplastic elastomer, polyester-based thermoplastic elastomer, and polystyrene-based thermoplastic elastomer. The material can be selected appropriately depending on various applications, such as the heating temperature of the heating element, the environment in which it is used, the desired hardness and flexibility, etc. In particular, the more flexible the material, the more sensitive it can be to detecting even small pressures, so it is preferable to select it from rubber materials and thermoplastic elastomer materials.

[0024] Examples of metal powders include aluminum powder, magnesium powder, copper powder, zinc powder, tin powder, iron powder, silver powder, gold powder, titanium powder, chromium powder, cobalt powder, and nickel powder (including alloys of these metals). Among these, aluminum powder or magnesium powder is preferred due to its high pressure sensitivity. Because magnesium powder has issues with water resistance, aluminum powder is particularly preferred. It is also possible to mix multiple types of metal powders. For example, mixing nickel powder with various metal powders can improve contact between the metal powder and the barium titanate powder. This is particularly effective when using metal powders that are prone to forming an oxide film. Furthermore, the average particle size of the metal powder is preferably 98 to 300 μm. When the average particle size of the metal particles is less than 98 μm, ohmic contact tends to be difficult to achieve. This is presumably because metal powders such as aluminum and magnesium are easily oxidized, resulting in a large proportion of an oxide layer on the surface, which impairs their conductive properties as metallic aluminum or metallic magnesium. Furthermore, the number of contact points between the metal powder and the barium titanate powder between the electrodes increases, increasing the probability of insufficient contact between the metal powder and the barium titanate powder. If the average particle size of the metal powder exceeds 500 μm, it cannot be formed into a thin sheet shape for use as a heating element, limiting its applications. The average particle size is calculated using the geometric mean diameter measured under an optical microscope. The shape of the metal powder is not particularly limited, and various shapes obtained by various powder production methods, such as pulverization, electrolysis, atomization, chemical reduction, plasma rotating electrode, and droplet spraying, can be used. It is also possible to use metal powders with randomly rolled shapes, such as thin strips of metal foil rolled up in a mortar and pestle. In such cases, the metal powder has elasticity, and when an external force is applied, the metal powder deforms, increasing the number of contact points with the barium titanate powder. The amount of metal powder is preferably 20 to 133 parts by weight per 100 parts by weight of the polymer matrix material. If the amount is less than 20 parts by weight, the metal powder and the barium titanate powder will not be in sufficient contact with each other, which may result in the inability to detect pressure.If the amount exceeds 133 parts by weight, the metal powder particles tend to come into contact with each other, which can easily cause short circuits.

[0025] Barium titanate powder can be used in various forms. It can be made by pulverizing sintered ceramic PTC powder, or it can be calcined barium titanate powder. Calcined barium titanate powder is particularly preferable. Barium titanate can have its Curie temperature changed by adding additives, but any Curie temperature can be used. The average particle size of the primary particles is preferably 1 to 5 μm, but this is not limited to this. For example, pressure-sensitive properties are exhibited even with an average particle size of 1 mm, but particles exceeding 1 mm tend to cause roughness and uneven dispersion on the pressure-sensitive conductor surface. The average particle size is calculated using the geometric mean diameter measured with an optical microscope. Furthermore, it is preferable that the barium titanate powder be 10 to 67 parts by weight per 100 parts by weight of the polymer matrix material. If the amount is less than 10 parts by weight, the metal powder and barium titanate powder will not be in sufficient contact, potentially making it impossible to detect pressure. If the amount is more than 67 parts by weight, the low polymer component content reduces flexibility and flexibility, which tends to reduce sensitivity to small pressures.

[0026] It is also considered that the surface of the aluminum powder is covered with barium titanate powder. This can prevent short circuits due to contact between the aluminum powder particles. However, even if the surface of the aluminum powder is not completely covered with barium titanate powder, an ohmic contact between the electrode layer and the barium titanate powder can be obtained, so it is not essential that the surface of the aluminum powder is covered with barium titanate powder.

[0027] It is preferable that the thickness of the pressure-sensitive conductor be equal to or greater than the sum of the average particle size of the barium titanate powder and the average particle size of the metal powder, and be equal to or less than three times the sum of the average particle size of the barium titanate powder and the average particle size of the metal powder. If the thickness of the pressure-sensitive conductor is less than the sum of the average particle size of the barium titanate powder and the average particle size of the metal powder, the metal powder is more likely to come into contact with both of the electrodes, resulting in a short circuit. If the thickness of the pressure-sensitive conductor exceeds three times the sum of the average particle size of the barium titanate powder and the average particle size of the metal powder, the number of contact points between the metal powder and the barium titanate powder between the electrodes increases, increasing the likelihood of insufficient contact between the metal powder and the barium titanate powder. Furthermore, if the thickness of the heating element of the pressure-sensitive conductor exceeds three times the sum of the average particle size of the barium titanate powder and the average particle size of the metal powder, the sensitivity to small pressures decreases, but the pressure sensor functions by changing the amount of current flowing in response to the applied pressure. In this case, the more flexible the matrix material, the less pressure is required to conduct current. Furthermore, the thicker the pressure-sensitive conductor, the greater the force required to conduct current. The thickness here refers to the thickness in the same direction as the direction of the applied pressure.

[0028] As another example, we created a grip sensor that can distinguish between pressure caused by wrapping the skin and pressure caused by gripping or contact, even when installed on a curved surface such as a steering wheel core.

[0029] In the following Examples 2 to 5 and Examples a and b, a pressure-sensitive conductor approximately 0.2 mm thick, in which metal powder and barium titanate powder are dispersed in a silicone matrix, is used, as in Example 1. Any insulating material can be used as the spacer, and a 0.08 mm thick piece of paper with holes punched is used.

[0030] In Example 2, a steering wheel core 77 with a grip portion cross-sectional radius r (curvature radius in Table 1) of 16.5 mm was wound with a 30 mm wide conductive cloth as the inner electrode 51, a 30 mm wide, approximately 0.2 mm thick ribbon-shaped pressure-sensitive conductor 1 as the sensor, and a 30 mm wide, 0.08 mm thick spacer 2 with an opening of 1.5 mm diameter. In addition, a 30 mm wide conductive cloth was wound as the outer electrode 52, and finally a cover 78 was wound to create a steering wheel 71 with a grip sensor.

[0031] Further, steering wheels with grip sensors were produced in Example 2, with the diameter of the spacer opening changed to 2 mm, 2.5 mm, and 3 mm, and these were designated as Examples 3 to 5.

[0032] In all of Examples 2 to 5, when the user was not in contact, the sensor did not detect any pressure due to the wrapping pressure of the steering wheel skin, and only when the user was in contact did the sensor show a sudden change in electrical resistance from a high resistance value exceeding 10^6 Ω to a low resistance value of 10 Ω or less.

[0033] In Examples a to b, spacer openings with diameters of 3.5 mm and 4 mm were created and wrapped with a skin using the same manufacturing method as in Examples 2 to 5. The wrapping pressure of the skin caused the electrodes to contact the pressure sensor, resulting in conduction even when the user was not touching it, and a change in electrical resistance was observed. Therefore, in the configurations of Examples a to b, it is thought that it would be difficult to detect user contact when the sensor is installed on a shape with a small radius of curvature, such as the radius r of the cross section of the gripping portion of a steering wheel core. However, even in the configurations of Examples a to b, if the sensor is installed on a flat surface, no change in electrical resistance due to gripping or contact is observed when the user is not touching the sensor, but a change in electrical resistance due to gripping or contact can be detected when the user is touching the sensor.

[0034] In Examples 2 to 5 and Examples a to b, the opening shape is a perfect circle, so the diameter of the opening is the same as the shortest width of the opening.

[0035] From Examples 2 to 5 and Examples a to b, it is preferable that the shortest width of the opening formed in the spacer has the following relationship with the radius of curvature (radius r of the cross section of the gripping portion in the case of the configurations of Examples 2 to 5) and the thickness of the spacer. W<√(8rt+4t^2) W: Shortest width of spacer opening (mm) r: radius of curvature (mm) t: spacer thickness (mm)

[0036] By making the opening of the spacer have the above-mentioned minimum width, the pressure-sensitive conductor and either the inner electrode or the outer electrode do not come into contact when the user is not touching them, which is particularly preferable because it allows for the construction of a pressure-sensitive sensor that is not conductive to the pressure-sensitive sensor when the user is not touching it, but is able to detect user contact by bending the pressure-sensitive conductor or electrode to establish conduction and exhibiting a change in electrical resistance when the user is touching it.

[0037] In this example, the radius of the cross section of the steering wheel gripping portion was calculated as the radius of curvature, but when installing the pressure sensor of the present invention on a curved surface, a location corresponding to the radius of curvature can be selected as appropriate. The interior of a car does not have a fixed curved shape, but has a shape with multiple curved radii depending on the design and use, and even in such cases, the radius of curvature can be measured as appropriate.

[0038] In a shape where the radius of curvature changes gradually, it is practically difficult to measure all radii of curvature, so it is preferable to measure the radius of curvature at a predetermined point. This predetermined point may be, for example, a point with the smallest radius of curvature, a point with the largest radius of curvature, both, or neither, depending on the shape of the curved surface.

[0039] Furthermore, if the minimum width of the spacer opening, which is adapted to a portion with a large radius of curvature, is applied to a portion with a small radius of curvature, the pressure-sensitive conductor and the electrode will always be in contact, and pressure will be applied, resulting in a change in electrical resistance and false detection of user contact. Therefore, when adjacent portions have different radii of curvature but the minimum width of each spacer opening needs to be the same, it is preferable to set the minimum width of the spacer opening to match the portion with a small radius of curvature.

[0040] [Table 1]

[0041] The present invention can be installed in predetermined positions inside a vehicle, such as on spokes, door trim, instrument panel, or armrest, as indicated by the curved surface 80 shown in the shaded area in Figure 3. The curved surface may not have a constant radius of curvature, but may have multiple radii of curvature. In such cases, it is preferable to design the opening of the spacer to match the smallest radius of curvature, thereby achieving a uniform minimum opening width. However, the minimum width of each opening may also be designed for each radius of curvature, which would enable more sensitive contact detection. [Industrial Applicability]

[0042] As described above, the present invention makes it possible to create a pressure sensor that can distinguish between pressure caused by wrapping or engaging a skin and pressure caused by gripping or contact. Furthermore, by setting the minimum width of the spacer opening to a predetermined diameter relative to the radius of curvature and the thickness of the spacer, gripping or contact can be detected even when the sensor is installed on a curved surface. For example, the sensor can be used as a heat source that heats only upon contact, such as in home heaters, heating devices for automobile interiors, heating devices for motorcycles, industrial heating devices, various snow removal and ice melting devices, anti-fogging devices, cooking appliances, and thermotherapy devices. [Explanation of symbols]

[0043] 1: Pressure-sensitive conductor 2: Spacer 51: Inner electrode 52:Outer electrode W: Shortest width of spacer opening (mm) r: radius of curvature (mm) t: spacer thickness (mm) 71: Steering wheel 72: Skin (there are two skins in the drawing? 72 deleted from the drawing) 73: Steering wheel spokes 74: Steering wheel hub (hub?) 76: Steering wheel core material Slav 77: Steering wheel core material 78: Epidermis 80: Curved surface part

Claims

1. It consists of a pressure-sensitive conductor whose electrical resistance changes when pressure is applied, electrodes installed on both sides of the pressure-sensitive conductor, and a spacer installed between the pressure-sensitive conductor and the electrodes. A pressure sensor having an opening in the spacer.

2. 2. The pressure-sensitive sensor according to claim 1, wherein the spacer is disposed on a curved surface, and the minimum width W of the spacer opening satisfies the following relationship with the radius of curvature r and the thickness t of the spacer: W<√(8rt+4t^2) W: Shortest width of spacer opening (mm) r: radius of curvature (mm) t: spacer thickness (mm)

3. 3. The pressure sensor according to claim 2, wherein the pressure sensor is installed in the interior of a vehicle or in a steering wheel.

4. 4. The pressure-sensitive sensor according to claim 1, wherein the pressure-sensitive conductor is a mixture of barium titanate powder and metal powder in a matrix made of a polymer material.

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