JP2007033383A - Pressure detection element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure detection element based on a new principle that has improved pressure sensitivity and can be used even under high temperature and high pressure. <P>SOLUTION: The pressure detection element comprises a first conductor having one surface to which pressure operates and the other surface that opposes the surface; a second conductor, having a first surface to which pressure operates and the other surface that opposes the surface and adheres to the other surface of the first conductor; electrodes provided on the other surfaces of the first and second conductors; and a conductor connected to the electrode. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pressure detection element, and particularly to a pressure detection element suitable for use under high pressure and high temperature.

  Conventionally, a metal strain gauge or a semiconductor element is generally used as a pressure detection element or a load detection element. In particular, semiconductor pressure sensing elements using silicon single crystals have a wide range of applications because their sensitivity is several orders of magnitude better than metal strain gauges. However, the semiconductor pressure detection element using a silicon single crystal has a problem that the pressure cannot be measured at 150 ° C. or higher because the detection characteristic with respect to the temperature of the silicon single crystal deteriorates at a high temperature. In addition, the semiconductor pressure sensing element is weak in mechanical strength and cannot be used as a single unit under high pressure, so measurements are incorporated into a pressure-resistant container, which complicates the structure of the pressure sensing device and increases costs. There was a problem.

In order to solve this problem, many researches have been made on pressure detecting elements that can withstand use under high temperature and high pressure, and an example thereof is disclosed in Patent Document 1. The pressure detection element disclosed in Patent Document 1 is a semiconductor pressure detection element using a polycrystalline ceramic material mainly composed of Si ₃ N _{4 on} which SiC is deposited, and an SiC whose electric resistance changes when pressure is applied. The pressure is detected using the piezoresistive effect. This pressure detection element is manufactured by sintering Si ₃ N ₄ and C to precipitate SiC.

According to such a pressure detection element, Si ₃ N ₄ which is a high-strength ceramic material is a main component, so that a high pressure can be measured without being incorporated in a pressure vessel or the like, and the pressure can be measured even at a high temperature of 150 ° C. or higher. There is an advantage that the detection element can be measured without deterioration of performance due to oxidation or the like. However, according to the fact that the inventor created and confirmed this pressure detection element, this pressure detection element has a problem that the amount of change in electrical resistance with respect to the pressure change, that is, the pressure sensitivity is low.
JP 2004-20355 A

    The present invention has been made by the inventor's earnest study in order to solve the above-described conventional problems. The first object of the present invention is to provide a pressure detection element based on a new principle having excellent pressure sensitivity. A second object is to provide a pressure detecting element that can be used even under high temperature and high pressure.

Hereinafter, the present invention will be described with reference to FIGS.
As shown in FIG. 1A, the pressure detection element according to the first aspect of the present invention includes at least a pressure receiving surface (one surface) 111 on which pressure acts and a close contact surface (other surface) 112 facing the pressure receiving surface 111. A pressure-sensitive surface (one surface) 121 on which pressure acts, and a contact surface (other surface) 122 that is opposed to the pressure-receiving surface 121 and is in close contact with the contact surface 112 of the first conductor 11. A second conductor 12 provided; electrodes 14 provided on the pressure-receiving surfaces 111 and 121 of the first conductor 11 and the second conductor 12; and a conductor 15 connected to the electrode 14. ing. Note that the close contact refers to a state in which the first conductor 11 and the second conductor 12 are mechanically in close contact with each other. According to the pressure detection element 1 of the first aspect, the contact interface 13 formed by bringing the contact surfaces 112 and 122 between the first conductor 11 and the second conductor 12 into close contact has an electrical resistance, that is, a contact resistance. It is formed. When the pressure P acts on the pressure receiving surfaces 111 and 121 of the first conductor 11 and the second conductor 12, the contact resistance changes depending on the magnitude of the pressure P.

  Here, in the pressure detection element 1 of the first aspect, the principle that the electric resistance changes with pressure will be described based on FIG. 1B which is an electrical equivalent circuit diagram of the pressure detection element 1 of the first aspect. . In the figure, symbol R1 indicates the electrical resistance of the first conductor 11, symbol R2 indicates the electrical resistance of the second conductor 12, symbol R3 indicates the resistance at the contact interface 13, and the resistors R1 and R2 are the first conductor. The resistance R3 is a variable resistance whose resistance value varies with the magnitude of the pressure P as described above. Since this resistance R3 depends on the contact state between the first conductor 11 and the second conductor 12, it shows a very large change with respect to the pressure change. Assuming that the overall resistance in this circuit is R4, the resistance value of the resistor R4 is the sum of the R1 to R3 resistance values because the resistors R1 to R3 are arranged in series. Here, in the pressure detection element 1 configured as described above, the resistance value of the resistor R3 is high when the pressure P is low, and decreases as the pressure increases. Therefore, the resistance R4 of the entire circuit changes based on a change in the resistance value of the resistance R3 as the pressure P increases or decreases. Therefore, the pressure detecting element 1 having the above-described configuration having the contact interface 13 in which the first conductor 11 and the second conductor 12 are in close contact with each other has a principle that the resistance R3 of the contact interface 13 changes due to the change of the pressure P. It will have a pressure sensitivity based on it.

  As shown in FIG. 2A, the pressure detection element according to the second aspect of the present invention includes a pressure receiving surface (one surface) 211 on which pressure acts and a close contact surface (other surface) 212 opposite to the pressure receiving surface. A second conductor having a first conductor 21, a pressure-receiving surface (one surface) 221 on which pressure acts, and a contact surface (other surface) 222 that faces the pressure-receiving surface and contacts the contact surface 212 of the first conductor. A body 22, a pair of electrodes 24 provided in a portion of the first conductor 21 other than the pressure-receiving surface 211 and the close contact surface 212 of the first conductor 21, and a conductive wire 25 connected to the electrode 24. This is the pressure detection element 2. According to the pressure detection element 2 of the second aspect, the contact interface 23 formed by bringing the contact surfaces 212 and 222 between the first conductor 21 and the second conductor 22 into close contact has an electrical resistance, that is, a contact resistance. It is formed. When the pressure P acts on the pressure receiving surfaces 211 and 221 of the first conductor 21 and the second conductor 22, the contact resistance changes depending on the magnitude of the pressure P.

Here, in the pressure detection element of the second aspect, the principle that the electric resistance changes depending on the pressure will be described based on FIG. 2B which is an electrical equivalent circuit of the pressure detection element 2. In the figure, symbol R1 indicates the electrical resistance of the first conductor 21, symbol R2 indicates the electrical resistance of the second conductor 22, and symbol R3 indicates the contact resistance at the contact interface 23. In this circuit, if the overall resistance is R4, the resistance value of R4 can be expressed by the following equation: 1 / R4 = 1 / R1 + 1 / (R2 + R3).
In this circuit, the resistors R1 and R2 are specific electric resistances of the first conductor 21 and the second conductor 22, respectively, and are constant values. The resistor R3 has a large resistance value when the pressure P is small, and the pressure increases. This is a variable resistor whose resistance value decreases as the time passes. The value of the resistance R3 depends on the contact state of the contact interface 23 and shows a very large resistance change with respect to the pressure change. That is, in the state where the pressure P is close to 0, the contact resistance R3 is larger as it approaches infinity, so most of the current flows through the route through the resistor R1 (that is, the first conductor 21), and the value of the resistance R4 of the entire circuit is It becomes almost the same as the resistor R1. On the other hand, when the pressure P acts on the pressure receiving surfaces 111 and 121, the contact interface 23 is brought into close contact with and the resistance R3 is reduced. Therefore, not only the resistance R1 but also the resistances R3 and R2 (that is, the contact interface 23 and the second conductor 22). The current also flows in parallel with the other route (hereinafter referred to as a bypass circuit). When the pressure P increases, the contact resistance R3 decreases and the current flowing through the bypass circuit increases, so the electrical resistance (1 / (R2 + R3)) of the bypass circuit on the right side of the formula changes, and therefore the resistances R1 to R3 The electrical resistance R4 of the entire circuit, which is a combined resistance, varies greatly. Therefore, the pressure detection element 2 having the above-described configuration having the contact interface 23 in which the first conductor 21 and the second conductor 22 are in close contact with each other has a resistance value of the bypass circuit formed by the action of the pressure P. It has pressure sensitivity based on the principle that it changes with the change of.

  In the pressure detection elements 1 and 2 of the first aspect or the second aspect, it is preferable that the first conductors 11 and 21 are made of ceramics and the second conductors 12 and 22 are made of metal. By using ceramics as the first conductors 11 and 21, it becomes possible to measure up to a high pressure, and by using a metal having high conductivity as the second conductors 12 and 22, pressure detection with excellent pressure sensitivity. This is because the elements 1 and 2 can be obtained. Here, the ceramic materials of the first conductors 11 and 21 are carbon, silicon carbide, tin oxide, indium oxide, silver oxide, copper oxide, carbides, nitrides and borides of group IV, V and VI transition metal elements. , Silicides, oxides, and composite compounds composed of these compounds, or those containing two or more of them can be used. Furthermore, the conductive ceramics or metal is added to an insulating compound containing at least one of silicon nitride, sialon, aluminum nitride, alumina, yttria, mullite, zirconia, magnesia, cordierite, and aluminum titanate. Conductive ceramics in which particles are dispersed can be used. As the metal element of the second conductors 12 and 22, any one of transition metal elements, indium and tin, or an alloy containing two or more of them can be used.

  In the pressure detection elements 1 and 2 of the first aspect or the second aspect, it is preferable that the first conductors 11 and 21 and the second conductors 12 and 22 are made of ceramics. By configuring both the first conductors 11 and 21 and the second conductors 12 and 22 with ceramics, it becomes possible to detect pressure even under high pressure, and the ceramics are chemically stable and altered even at high temperatures. This is because it is difficult to obtain a pressure detection element capable of detecting pressure even at high temperatures. Here, the ceramic materials of the first conductors 11 and 21 and the second conductors 12 and 22 are carbon, silicon carbide, tin oxide, indium oxide, silver oxide, copper oxide, IV, V, and VI group transition metals. Elemental carbides, nitrides, borides, silicides, oxides, and composite compounds composed of these compounds or those containing two or more of them can be used. Further, the ceramics and metal particles that are electrically conductive to an insulating compound containing one or more of silicon nitride, sialon, aluminum nitride, alumina, yttria, mullite, zirconia, magnesia, cordierite, and aluminum titanate. It is possible to use conductive ceramics in which is dispersed.

  In the pressure detection elements 1 and 2 of the first aspect or the second aspect, it is preferable that the first conductors 11 and 21 have a property that the electric resistance changes with pressure, that is, a piezoresistance effect. By selecting a material having a piezoresistance effect, such as silicon single crystal, silicon carbide, or the like, as the first conductors 11 and 21, depending on the contact resistance and bypass circuit of the pressure detecting elements 1 and 2 of the first aspect or the second aspect. This is because the change in the electric resistance with respect to the pressure synergizes with the change in the electric resistance with respect to the pressure of the first conductors 11 and 21 itself, and the pressure detecting elements 1 and 2 having further excellent pressure sensitivity can be obtained.

  In the pressure detection element of the first aspect or the second aspect, it is desirable that the contact surface of the second conductor is configured to be in close contact with the contact surface of the first conductor only at both ends. The pressure detection element 3 of the third aspect is shown in FIG. The pressure detecting element 3 has the same first conductor 31, electrode 34 and conductive wire 35 as the pressure detecting element 2, and the central portion is removed in a concave shape in the energizing direction of the current flowing through the conductive wire 35 in the horizontal direction on the paper surface. The contact surface 33 is formed by bringing the contact surface 322 formed at both ends of the second conductor 32 into close contact with the contact surface 312 of the first conductor 31. It has become. According to the pressure detection element 3 having such a structure, the contact area between the first conductor 31 and the second conductor 32 is reduced as compared with the pressure detection elements 1 and 2 of the first aspect and the second aspect. Since the contact surface pressure at the interface 33 is increased, the amount of change in electrical resistance with respect to the change in pressure at the close contact surface 33 is increased (that is, the rate of change of the variable resistor R3 is increased). An element can be obtained.

  Furthermore, the pressure detecting element according to the second aspect includes a pressure receiving surface (one surface) on which pressure acts and a close contact surface (other surface) opposite to the pressure receiving surface and in close contact with the pressure receiving surface of the first conductor. A structure having three conductors is desirable. The pressure detection element 4 of the fourth aspect is shown in FIG. The pressure detection element 4 includes a first conductor 21, a second conductor 2, an electrode 24, and a conductor 25 having the same configuration as the pressure detection element of the second aspect, a pressure receiving surface 431 on which the pressure P acts, and the pressure receiving surface. And a third conductor 43 provided with a close contact surface 432 that is in close contact with the pressure receiving surface 211 of the first conductor 21. In this way, by providing the third conductor 43 similar to the second conductor 22 via the first conductor 21, the bypass circuit described above is interposed between the first conductor 21 and the third conductor 43. As a result, the amount of change in electrical resistance with respect to a pressure change is further increased, so that a pressure detection element having higher pressure sensitivity can be obtained.

  As described above, according to the present invention, it is possible to provide a novel pressure detection element that detects a pressure using mechanical contact between the first conductor and the second conductor. Such a pressure detection element has a relatively simple structure, and can provide a pressure detection element having excellent pressure sensitivity by constituting either the first conductor or the second conductor with a metal, and the first conductor. And the pressure detection element which has the comparatively high pressure sensitivity which can be used also under high temperature and a high pressure can be provided by comprising a 2nd conductor with ceramics.

  Hereinafter, the present invention will be specifically described with reference to examples. In addition, Example 1 described below is the above-described Embodiment 1, Examples 2 to 13 and Comparative Examples 2 and 3 are the above Embodiment 2, Example 14 is the above Embodiment 3, and Examples 15 and 16 are the above. It is the example which implemented the pressure detection elements 1-4 of Embodiment 4. FIG.

(Example 1): Embodiment 1
Example 1 is an example in which SiC, which is ceramic, is used for both the first conductor 11 and the second conductor 12.
A method for manufacturing the first conductor 11 and the second conductor 12 will be described. As the 1st conductor 11 and the 2nd conductor 12, what processed the SiC tablet (product made from high purity chemical, purity 2N) in the shape of a 3 mm x 3 mm x 12 mm square bar was prepared. In each of the first conductor 11 and the second conductor 12, one surface of 3 mm × 12 mm was used as pressure receiving surfaces 111 and 121, and the Cu electrode 14 was brazed to the pressure receiving surfaces 111 and 121. Next, a Cu lead wire 15 having a diameter of 0.6 mm was connected to the Cu electrode 14 with solder. Thereafter, the contact surface 122 of the second conductor 12 was brought into close contact with the contact surface 112 of the first conductor 11 to complete the pressure detecting element 1.
Next, a milliohm meter is connected to the copper lead wire 15 of the completed pressure detection element 1, a predetermined pressure change is applied to the pressure receiving surfaces 111 and 121, and the rate of change in electrical resistivity is measured. Pressure sensitivity was evaluated. The measurement conditions are 1) pressure change: 0 to 20 MPa, 2) measurement temperature: 25 ° C., 200 ° C. The measurement results are shown in Table 1. In the following Examples 2 to 16 and Comparative Examples 1 to 3, the completed pressure detection elements 2 and 3 were evaluated by the same method.

(Example 2): Embodiment 2
Example 2 is an example in which SiC as ceramic is used as the first conductor 21 and Cu as metal is used as the second conductor 22.
The first conductor 21 was prepared as follows. 45 g of β-SiC powder (manufactured by high purity chemical, model number: SII01FA), 3.5 g of Al ₂ O3 (manufactured by high purity chemical, model number: ALO05PA) as a sintering aid and Y2O3 (manufactured by high purity chemical, model number: YYO01PA) ) Was weighed and ball milled in ethanol to obtain a mixed powder. The mixed powder was dried to obtain a dried powder, and then the dried powder was molded to form a molded body having a diameter of 36 mm and a thickness of 10 mm. The compact was subjected to hot press sintering in a nitrogen atmosphere at a sintering temperature of 1800 ° C., a holding time of 2 hours, and an applied pressure of 50 MPa to prepare a sintered body. The sintered body was processed into a 3 mm × 3 mm × 12 mm square bar shape, and this was used as the first conductor 21.
The 2nd conductor 22 used what processed Cu tablet (product made from high purity chemical, model number: CUE01CA) in the shape of a square bar of 3 mm x 3 mm x 12 mm.
The first conductor 21 and the second conductor 22 were assembled to produce the pressure detection element 2. In the case of this embodiment, one surface of the first conductor 21 is a pressure receiving surface 211 and a surface opposite to the pressure receiving surface 211 is a contact surface 212, and the surface does not include the pressure reception surface 211 and the contact surface 212. Were brazed with 1 mm thick Cu electrodes 24 on two surfaces of 3 mm × 3 mm. Next, a lead wire 25 having a diameter of 0.6 mm, which is a conductive wire, was connected to the Cu electrode 24 with solder. Thereafter, the close contact surfaces 212 and 222 of the first conductor 21 and the second conductor 22 were brought into close contact with each other to complete the pressure detection element 2, and the pressure sensitivity was measured in the same manner as described above. The method for assembling the pressure detection element 2 is the same in the following Examples 3 to 14 and 16 and Comparative Examples 2 and 3.

(Example 3): Embodiment 2
Example 3 is an example in which SiC is used as the first conductor 21 and Al which is a metal is used as the second conductor 22.
A SiC sintered body produced by the same method as in Example 2 was used as the first conductor 21. As the 2nd conductor 22, what processed Al tablet (product made from high purity chemical, model number: AlE01CA) in the shape of a square bar of 3 mm x 3 mm x 12 mm was used. As in the second embodiment, the Cu electrode 24 is brazed to the first conductor 21, the lead wire 25 is connected to the Cu electrode 24, and then the first conductor 21 and the second conductor 22 are brought into close contact with each other. Then, the pressure detection element 2 was assembled and the pressure sensitivity was evaluated. The measurement results are shown in Table 1.

(Example 4): Embodiment 2
Example 4 is an example in which SiC is used as the first conductor 21 and Ni which is a metal is used as the second conductor 22.
A SiC sintered body produced by the same method as in Example 2 was used as the first conductor 21. As the 2nd conductor 22, what processed Ni tablet (product made from high purity chemical, model number: NiE01CA) in the shape of a square bar of 3 mm x 3 mm x 12 mm was used. As in the second embodiment, the Cu electrode 24 is brazed to the first conductor 21, the lead wire 25 is connected to the Cu electrode 24, and then the first conductor 21 and the second conductor 22 are brought into close contact with each other. Then, the pressure detection element 2 was assembled and the pressure sensitivity was evaluated. The measurement results are shown in Table 1.

Example 5: Embodiment 2
Example 5 is an example in which SiC is used as the first conductor 21 and Au, which is a metal, is used as the second conductor 22.
A SiC sintered body produced by the same method as in Example 2 was used as the first conductor 21. As the 2nd conductor 22, what processed Au tablet (product made from high purity chemical, model number: AuE01CA) in the shape of a 3 mm x 3 mm x 12 mm square bar was used. As in the second embodiment, the Cu electrode 24 is brazed to the first conductor 21, the lead wire 25 is connected to the Cu electrode 24, and then the first conductor 21 and the second conductor 22 are brought into close contact with each other. Then, the pressure detection element 2 was assembled and the pressure sensitivity was evaluated. The measurement results are shown in Table 1.

Example 6: Embodiment 2
Example 6 is an example in which Si ₃ N ₄ , which is a ceramic provided with conductivity by C, is used as the first conductor 21, and Cu is used as the second conductor 22.
The first conductor 21 was prepared as follows. α-Si ₃ N ₄ powder (average particle size 2 μm) 38.0 g, C powder (manufactured by high purity chemical, model number: CCE01PA) 3.0 g, Al ₂ O ₃ (manufactured by high purity chemical, Model No .: ALO05PA) 6.0 g, Y ₂ O ₃ (manufactured by Koyo Chemical Co., Ltd. model number: YYO01PA) was weighed and ball milled in ethanol. After drying, a molded product having a diameter of 36 mm and a thickness of 10 mm was prepared, and sintered by a hot press in a sintering temperature of 1650 ° C., a holding time of 2 hours, a pressing force of 50 MPa, and a nitrogen atmosphere. The obtained sintered body was processed into the same dimensions as in Example 2 and used as the first conductor 21.
As the 2nd conductor 22, what processed Cu tablet (product made from high purity chemical, model number: CUE01CA) in the shape of a square bar of 3 mm x 3 mm x 12 mm was used. As in the second embodiment, the Cu electrode 24 is brazed to the first conductor 21, the lead wire 25 is connected to the Cu electrode 24, and then the first conductor 21 and the second conductor 22 are brought into close contact with each other. Then, the pressure detection element 2 was assembled and the pressure sensitivity was evaluated. The measurement results are shown in Table 1.

Example 7: Embodiment 2
Example 7 is an example in which SiC is used as the first conductor 21 and Si ₃ N ₄ is used as the second conductor 22.
A SiC sintered body produced by the same method as in Example 2 was used as the first conductor 21. Further, a Si ₃ N ₄ sintered body produced by the same method as in Example 6 was used as the second conductor 22. As in the second embodiment, the Cu electrode 24 is brazed to the first conductor 21, the lead wire 25 is connected to the Cu electrode 24, and then the first conductor 21 and the second conductor 22 are brought into close contact with each other. Then, the pressure detection element 2 was assembled and the pressure sensitivity was evaluated. The measurement results are shown in Table 1.

Example 8: Embodiment 2
In Example 8, SiC is used as the first conductor 21 and WC, which is ceramic, is used as the second conductor 22.
A SiC sintered body produced by the same method as in Example 2 was used as the first conductor 21. As the second conductor 22, a WC tablet (manufactured by Koyo Chemical Co., Ltd., purity 2N) processed into a square bar shape of 3 mm × 3 mm × 12 mm was used. As in the second embodiment, the Cu electrode 24 is brazed to the first conductor 21, the lead wire 25 is connected to the Cu electrode 24, and then the first conductor 21 and the second conductor 22 are brought into close contact with each other. Then, the pressure detection element 2 was assembled and the pressure sensitivity was evaluated. The measurement results are shown in Table 1.

Example 9: Embodiment 2
Example 9 is an example in which SiC is used as the first conductor 21 and TiN which is ceramics is used as the second conductor 22.
A SiC sintered body produced by the same method as in Example 2 was used as the first conductor 21. As the second conductor 22, a TiN tablet (manufactured by High Purity Chemical, purity 2N) processed into a square bar shape of 3 mm × 3 mm × 12 mm was used. As in the second embodiment, the Cu electrode 24 is brazed to the first conductor 21, the lead wire 25 is connected to the Cu electrode 24, and then the first conductor 21 and the second conductor 22 are brought into close contact with each other. Then, the pressure detection element 2 was assembled and the pressure sensitivity was evaluated. The measurement results are shown in Table 1.

Example 10: Embodiment 2
Example 10 is an example in which SiC is used for both the first conductor 21 and the second conductor 22.
A SiC sintered body produced by the same method as in Example 2 was used as the first conductor 21 and the second conductor 22. As in the second embodiment, the Cu electrode 24 is brazed to the first conductor 21, the lead wire 25 is connected to the Cu electrode 24, and then the first conductor 21 and the second conductor 22 are brought into close contact with each other. Then, the pressure detection element 2 was assembled and the pressure sensitivity was evaluated. The measurement results are shown in Table 1.

Example 11: Embodiment 2
Example 11 is an example in which Si ₃ N ₄ is used for both the first conductor 21 and the second conductor 22.
A Si ₃ N ₄ sintered body produced by the same method as in Example 6 was used as the first conductor 21 and the second conductor 22. As in the second embodiment, the Cu electrode 24 is brazed to the first conductor 21, the lead wire 25 is connected to the Cu electrode 24, and then the first conductor 21 and the second conductor 22 are brought into close contact with each other. Then, the pressure detection element 2 was assembled and the pressure sensitivity was evaluated. The measurement results are shown in Table 1.

Example 12: Embodiment 2
Example 12 is an example in which Si ₃ N ₄ ceramics containing SiC having a piezoresistance effect is used as the first conductor 21 and SiC is used as the second conductor 22.
The first conductor 21 was produced as follows. _α-Si 3 _{N 4} powder (average particle diameter 2 [mu] m) and 32.0 g, C powder (Wako Pure Chemical Industries, Ltd., model number: CCE01PA) was 9.0g weighed, 1500 ° C. × 2 hours placed in a carbon crucible, Ar It was calcined in the atmosphere. To the calcined powder, 6.0 g of high purity chemical Al ₂ O ₃ (ALO05PA) as a sintering aid and 3.0 g of Y ₂ O ₃ (high purity chemical, model number: YYO01PA) as a sintering aid are weighed. Then, ball mill mixing was performed in ethanol. After drying, a molded body having a diameter of 36 mm and a thickness of 10 mm was prepared, and sintered by a hot press in a sintering temperature of 1650 ° C., a holding time of 2 hours, a pressing force of 50 MPa, and a nitrogen atmosphere. This sintered body was processed into a 3 mm × 3 mm × 12 mm square bar shape and used as the first conductor 21.
A SiC sintered body produced by the same method as in Example 2 was used as the second conductor 22. As in the second embodiment, the Cu electrode 24 is brazed to the first conductor 21, the lead wire 25 is connected to the Cu electrode 24, and then the first conductor 21 and the second conductor 22 are brought into close contact with each other. Then, the pressure detection element 2 was assembled and the pressure sensitivity was evaluated. The measurement results are shown in Table 1.

Example 13: Embodiment 2
Example 13 is an example in which Cu is used for both the first conductor 21 and the second conductor 22.
As the 1st conductor 21 and the 2nd conductor 22, what processed Cu tablet (product made from high purity chemical, model number: CuE01CA) in the shape of a 3 mm x 3 mm x 12 mm square bar was used. As in the second embodiment, the Cu electrode 24 is brazed to the first conductor 21, the lead wire 25 is connected to the Cu electrode 24, and then the first conductor 21 and the second conductor 22 are brought into close contact with each other. Then, the pressure detection element 2 was assembled and the pressure sensitivity was evaluated. The measurement results are shown in Table 1.

Example 14: Embodiment 3
Example 14 is an example in which SiC is used as the first conductor 31 and SiC is used as the second conductor 32.
A SiC sintered body produced by the same method as in Example 2 was processed into a square bar shape having the same dimensions as in Example 2, and used as the first conductor 31. As the second conductor 33, a SiC sintered body produced by the same method as in Example 2 was used, as shown in FIG. 3, from the center of the 3 × 12 mm surface to an area of 3 × 6 mm and a depth of 0.2 mm. Were used and processed into a U shape so that an area of 3 × 3 mm remained at both ends.
The Cu electrode 34 is brazed to the first conductor 31, the lead wire 35 is connected to the Cu electrode 34, and the close contact surface 311 of the first conductor 31 and the close contact surface 322 of the second conductor 32 are brought into close contact with each other. The detection element 3 was assembled and the pressure sensitivity was evaluated. Table 1 shows the measurement results.

Example 15: Embodiment 4
In Example 15, SiC is used as the first conductor 21, Cu is used as the second conductor 22, and Cu is used as the third conductor 43.
A SiC sintered body produced by the same method as in Example 2 was used as the first conductor 21. As the 2nd conductor 22 and the 3rd conductor 43, what processed Cu tablet (product made from high purity chemical, model number: CUE01CA) in the shape of a 3 mm x 3 mm x 12 mm square bar was used.
The first conductor 21, the second conductor 22, and the third conductor 43 were assembled to produce the pressure detection element 4. One surface of each of the first to third conductors 21, 22, 43 is 3 mm × 12 mm as pressure receiving surfaces 211, 221, 431, and surfaces facing the pressure receiving surfaces 211, 221, 431 are contact surfaces 212, 222, 432, Determined. Next, a Cu electrode 24 having a thickness of 1 mm was brazed to both end faces of 3 mm × 3 mm of the first conductor 21, and a Cu lead wire 25 having a diameter of 0.6 mm as a conducting wire was connected to the Cu electrode 24 with solder. Next, the contact surface 212 of the first conductor 21 and the contact surface 222 of the second conductor 22 are brought into close contact with each other, and the contact surface 432 of the third conductor 43 is brought into contact with the pressure receiving surface 211 of the first conductor 21. 4 was assembled. Then, the pressure sensitivity was measured in the same manner as in Example 2. Table 1 shows the measurement results.

Example 16: Embodiment 4
Example 16 is an example in which SiC is used for all of the first conductor 21, the second conductor 22, and the third conductor 43.
The SiC sintered body produced by the same method as in Example 2 was used as the first conductor 21, the second conductor 22, and the third conductor, and the pressure detecting element 4 was produced by the same method as in Example 15. The pressure sensitivity was measured. Table 1 shows the measurement results.

(Comparative Example 1)
Processing the _Si 3 _{N 4} sintered body was produced in the same manner as in Example 12 to square rod of 3mm × 3mm × 12mm, the electrode 24 is brazed to both end surfaces of 3 mm × 3 mm, to connect the lead wire 25 A pressure detection element was produced. Then, pressure was applied to a 3 mm × 12 mm surface under the same conditions as in Example 2 to evaluate pressure sensitivity. The measurement results are shown in Table 1.

(Comparative Example 2): Embodiment 2
Comparative Example 2 is an example in which SiC is used as the first conductor 21 and non-conductive Si ₃ N ₄ is used as the second conductor 22.
A SiC sintered body produced by the same method as in Example 2 was used as the first conductor 21. A second electrical conductor 22, using _Si 3 _{N 4} tablets (Wako Pure Chemical Industries, Ltd., purity 2N) those obtained by processing the square rod of 3mm × 3mm × 12mm.
As in the second embodiment, the Cu electrode 24 is brazed to the first conductor 21, the lead wire 25 is connected to the Cu electrode 24, and then the first conductor 21 and the second conductor 22 are brought into close contact with each other. Then, the pressure detection element 2 was assembled and the pressure sensitivity was evaluated. The measurement results are shown in Table 1.

(Comparative Example 3): Embodiment 2
Comparative Example 3 is an example in which SiC is used as the first conductor 21 and Si ₃ N ₄ having an electric resistance 177 times higher than that of the first conductor 21 is used as the second conductor 22.
A SiC sintered body produced by the same method as in Example 2 was used as the first conductor 21. A Si ₃ N ₄ sintered body produced by the same method as in Example 14 was used as the second conductor 22. As in the second embodiment, the Cu electrode 24 is brazed to the first conductor 21, the lead wire 25 is connected to the Cu electrode 24, and then the first conductor 21 and the second conductor 22 are brought into close contact with each other. Then, the pressure detection element 2 was assembled and the pressure sensitivity was evaluated. The measurement results are shown in Table 1.

In Example 1 of the present invention, it was shown that a pressure detecting element having excellent pressure sensitivity can be obtained by using the contact resistance between the first conductor and the second conductor. In Examples 2 to 15, it was shown that a pressure detection element having excellent pressure sensitivity can be obtained by using the contact resistance of the bypass circuit. In Examples 2 to 5, it was shown that a pressure detecting element having excellent pressure sensitivity at room temperature or lower can be obtained by combining SiC with a highly conductive metal. In Example 6, it was shown that a pressure detecting element having excellent pressure sensitivity can be obtained by combining not only SiC but also Si ₃ N ₄ with a highly conductive metal. In Examples 7 to 11, it was shown that by combining ceramics with each other, the contact interface was not oxidized even at a high temperature and a good contact interface was obtained, and a pressure detecting element having excellent pressure sensitivity was obtained even at a high temperature. In Example 12, it was shown that a pressure detecting element having better pressure sensitivity can be obtained by adopting an element whose electric resistance varies with pressure as the first conductor itself. In Example 13, it was shown that a pressure detecting element having excellent pressure sensitivity can be obtained even if both the first conductor and the second conductor are made of metal. In Example 14, the pressure sensing element having excellent pressure sensitivity is obtained by processing the second conductor into a U-shape, thereby reducing the contact area and increasing the pressure received by the surface forming the bypass circuit. It showed that it was obtained. In Examples 15 and 16, it was shown that a pressure detecting element having further excellent pressure sensitivity can be obtained by using two bypass circuits.
On the other hand, Comparative Example 1 is a sample prepared by the method disclosed in Patent Document 1, and the pressure dependency of electrical resistance is -0.02% / MPa, which means that a high pressure sensitivity cannot be obtained compared to the present invention. Indicated. In Comparative Examples 2 and 3, when a material having a high electrical resistance is used for the second conductor, even if the electrical resistance R3 at the contact interface is small, R2 is very large compared to the value of R1, so that The resistance was high, and the overall electrical resistance R4 was almost unchanged, indicating that excellent pressure sensitivity could not be obtained.

  The pressure sensor material of the present invention has a characteristic that the rate of change of electrical resistivity with respect to pressure is large, and can be measured even at high temperatures and pressures by changing the configuration, and has high mechanical strength and excellent durability and reliability. . Therefore, it is applicable to pressure measurement in a car engine (cylinder pressure sensor) and pressure measurement of a common rail that supplies fuel to an injector of a diesel engine.

It is the schematic diagram of the pressure detection element of the 1st aspect which concerns on this invention, and its electrical equivalent circuit schematic. It is the schematic diagram of the pressure detection element of the 2nd aspect which concerns on this invention, and its electrical equivalent circuit schematic. It is a schematic diagram of the pressure detection element of the 3rd aspect which concerns on this invention. It is a schematic diagram of the pressure detection element of the 4th aspect which concerns on this invention.

Explanation of symbols

1 (2, 3): Pressure detecting element 11 (21, 31): First conductor 12 (22, 31): Second conductor 13 (23, 33): Close contact surface 14 (24, 34): Electrode 15 (25, 35): Conductor 111 (211): Pressure receiving surface of the first conductor 112 (212): Close contact surface of the first conductor 121 (221): Pressure receiving surface of the second conductor 122 (222): Second Close contact surface of conductor

Claims (7)

A first conductor having a surface on which pressure is applied and another surface opposite to the one surface; a surface on which pressure is applied; and another surface facing the other surface and in close contact with the other surface of the first conductor. A pressure detection element comprising: a second conductor; an electrode provided on each of one surface of the first conductor and the second conductor; and a conductive wire connected to the electrode. A first conductor having a surface on which pressure acts and another surface opposite to the one surface; a surface on which pressure acts; and another surface facing the other surface and in close contact with the other surface of the first conductor. A pressure detection element comprising: a second conductor; a pair of electrodes provided on a portion of the first conductor other than one surface and the other surface of the first conductor; and a conductive wire connected to the electrode. The pressure detection element according to claim 2, wherein the first conductor is ceramics and the second conductor is metal. The pressure detection element according to claim 2, wherein the first conductor and the second conductor are ceramics. The pressure detection element according to claim 2, wherein the first conductor has a piezoresistive effect. The pressure sensing element according to claim 2, wherein the other surface of the second conductor is in close contact with the other surface of the first conductor only at both ends. The pressure detecting element according to claim 2, further comprising: a third conductor having one surface on which pressure acts and another surface facing the one surface and closely contacting one surface of the first conductor.

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