Pressure sensor and pressure detection device

Abstract

A pressure sensor (1) comprises a detection unit that has a shape which is elongate in one direction, and that has a flexible structure capable of being expanded / contracted and bent. The detection unit has different values in a plurality of sections in the longitudinal axis direction as conversion factors, which are each an indicator of the degree of ease with which the characteristic impedance changes in accordance with the shape of the cross-section of the detection unit as viewed from the longitudinal axis direction.

Description

Pressure sensor and pressure detection device

[0001] The present disclosure relates to pressure sensors and the like.

[0002] Time domain reflectometry (hereinafter referred to as TDR) is used as a method for checking the wiring condition of cables such as HDMI (registered trademark). TDR is a measurement method in which a voltage pulse is applied to one end of a cable, and the amplitude of the reflected wave and the time until the reflected wave is measured (i.e., the time width of the reflected wave) are measured to calculate the distribution of the characteristic impedance of the cable. TDR will be explained using FIG. 1. FIG. 1 is a diagram for explaining the principle of TDR.

[0003] Fig. 1(a) is a schematic diagram showing a configuration for performing TDR measurement. As shown in Fig. 1(a), TDR measurement can be performed using a cable 5 and a vector network analyzer (VNA) 6. The cable 5 is a cable in which a conductor, a dielectric, and another conductor are concentrically layered in this order from the inside. The cable 5 has a characteristic impedance of the conductor located inside, Z ０ and the cable 5 has a wiring length of Tp. The vector network analyzer 6 is a measuring instrument that inputs a signal to the measurement target and measures the reflected signal reflected inside the measurement target and the transmitted signal passing through the measurement target. One end of the cable 5 and the vector network analyzer 6 are electrically connected by two wirings. The upper wiring connects the conductor located inside the cable 5 to the vector network analyzer 6, and is an electrical path through which the vector network analyzer 6 inputs a signal to the cable 5 and measures the reflected signal and transmitted signal. The lower wiring connects the conductor located outside the cable 5 to the vector network analyzer 6 and is connected to ground. The wiring connected to the other end of the cable 5 is a wiring through which the transmitted signal flows, and the end of this wiring is switched between short-circuited and open-circuited.

[0004] 1(b) is a diagram showing the results of measuring the amplitude and time width of the reflected wave when the end of the wiring connected to the other end of the cable 5 is short-circuited. The diagram shown in FIG. 1(b) is a graph in which the horizontal axis represents time and the vertical axis represents voltage. Note that the voltage V shown in FIG. 1(b) ０ is the characteristic impedance Z of the cable 5 ０ is the voltage corresponding to

[0005] As shown in FIG. 1(b), when the voltage is V ０ The time width of the reflected wave is a time width corresponding to 2Tp, which is twice the wiring length Tp of the cable 5. This is because the signal travels back and forth through the cable 5. Furthermore, since the wiring connected to the other end of the cable 5 is short-circuited, the resistance of this wiring is 0 Ω, and therefore the voltage in the time width corresponding to the reflected wave from this wiring is 0 V.

[0006] Fig. 1(c) is a diagram showing the results of measuring the amplitude and duration of the reflected wave when the termination of the wiring connected to the other end of the cable 5 is left open. Similar to Fig. 1(b), Fig. 1(c) is a graph in which the horizontal axis represents time and the vertical axis represents voltage.

[0007] As shown in FIG. 1(c), when the voltage is V ０ The time width of the reflected wave is the time width corresponding to 2Tp, which is twice the wiring length Tp of the cable 5. This is for the same reason as explained in FIG. 1B. Also, since the wiring connected to the other end of the cable 5 is open, the resistance of this wiring is infinite, so the voltage in the time width corresponding to the reflected wave from this wiring is 2V. ０ This becomes:

[0008] Fig. 2 shows the results of measuring the amplitude and time width of the reflected wave when the cable 5 in Fig. 1(a) is changed to a cable having the characteristic impedance distribution shown in the upper part of Fig. 2. The diagram shown in the upper part of Fig. 2 is a schematic diagram showing the relationship in magnitude between the characteristic impedances inside the cable. The graph shown in the lower part of Fig. 2 is a graph in which the horizontal axis is time and the vertical axis is voltage, similar to Fig. 1(b). Note that the voltage V shown in Fig. 2 ０ is the characteristic impedance Z０ is the voltage corresponding to the voltage V １ is the characteristic impedance Z １ is the voltage corresponding to the voltage V ２ is the characteristic impedance Z ２ is the voltage corresponding to

[0009] As shown in the upper diagram of Figure 2, the characteristic impedance inside the cable changes along the way. The largest characteristic impedance is Z １ and the characteristic impedance of the intermediate magnitude is Z ０ and the smallest characteristic impedance is Z ２ is.

[0010] As shown in the lower graph of FIG. 2, each voltage is obtained at a time interval corresponding to the wiring length of each characteristic impedance. Specifically, the characteristic impedance Z １ The time width t corresponding to the wiring length １ and voltage V １ is obtained, and the characteristic impedance Z ２ The time width t corresponding to the wiring length ２ and voltage V ２ has been obtained.

[0011] As described above, the TDR method can be used to measure the distribution of characteristic impedance in a cable. For example, a pressure sensor has been disclosed that applies the measurement of the distribution of characteristic impedance using the TDR method to identify the position and magnitude of an external force applied to a sensing member from the distribution of characteristic impedance (see Patent Document 1). Specifically, the pressure sensor described in Patent Document 1 measures a change in characteristic impedance from a change in the winding angle of the coil wound around the sensing member when the sensing member expands or contracts, and identifies the position and magnitude of the external force.

[0012] Patent No. 5406662

[0013] However, in the pressure sensor described in Patent Document 1, the winding angle of the coil wound around the sensing member changes not only when the sensing member expands and contracts, but also when the sensing member is bent, etc. As a result, the pressure sensor cannot distinguish between a change in characteristic impedance caused by an external force applied when the sensing member is pressed, and a change in characteristic impedance caused by a change in the shape of the sensing member, such as bending.

[0014] Therefore, the present disclosure aims to provide a pressure sensor or the like that can distinguish between a change in characteristic impedance caused by an external force applied when the sensing member is pressed and a change in characteristic impedance caused by a change in the shape of the sensing member, such as bending.

[0015] In order to achieve the above goal, a pressure sensor according to one embodiment of the present disclosure includes a detection unit that has a long shape in one direction and a flexible structure that is capable of stretching and bending, and the detection unit has different values ​​in multiple sections in the longitudinal axis direction as a conversion coefficient, which is an index that indicates the ease of change when the characteristic impedance changes depending on the cross-sectional shape of the detection unit when viewed from the longitudinal axis direction.

[0016] In order to achieve the above goal, a pressure detection device according to one embodiment of the present disclosure includes the above pressure sensor and a measurement unit that inputs an arbitrary voltage wave to the detection unit and measures the time width and amplitude of the reflected wave from the detection unit.

[0017] The present disclosure provides a pressure sensor and the like that can distinguish between a change in characteristic impedance caused by an external force applied when the sensing member is pressed and a change in characteristic impedance caused by a change in shape of the sensing member, such as bending.

[0018] FIG. 1 is a diagram illustrating the principle of the TDR method. FIG. 2 is a diagram illustrating the results of measuring the amplitude and time width of a reflected wave when the cable in FIG. 1(a) is replaced with a cable having the characteristic impedance distribution shown in the upper part of FIG. 2. FIG. 3 is a perspective view of a pressure sensor according to embodiment 1. FIG. 4 is a cross-sectional view of the pressure sensor shown in FIG. 3. FIG. 5 is a schematic diagram illustrating a load state of the pressure sensor shown in FIG. 3 and a diagram illustrating measurement results when the pressure sensor is subjected to the load. FIG. 6A is a diagram illustrating a calculation model prepared before simulating a change in characteristic impedance due to an external force being applied to the first section. FIG. 6B is a diagram illustrating a calculation model obtained when a simulation is performed using the calculation model prepared in FIG. 6A in which the first section is not subjected to a load. FIG. 6C is a diagram illustrating a calculation model obtained when a simulation is performed using the calculation model prepared in FIG. 6A in which the first section is subjected to a load. FIG. 7 is a diagram illustrating calculation results obtained by simulation using the calculation model prepared in FIG. 6A. FIG. 8 is a diagram illustrating the relationship between voltage and characteristic impedance in the TDR method. FIG. 9A is a diagram showing a first step in manufacturing the pressure sensor shown in FIG. 3 . FIG. 9B is a diagram showing a second step in manufacturing the pressure sensor shown in FIG. 3 . FIG. 9C is a diagram showing a third step in manufacturing the pressure sensor shown in FIG. 3 . FIG. 9D is a diagram showing a fourth step in manufacturing the pressure sensor shown in FIG. 3 . FIG. 9E is a diagram showing a fifth step in manufacturing the pressure sensor shown in FIG. 3 . FIG. 10 is a perspective view of a pressure sensor according to embodiment 2. FIG. 11 is a cross-sectional view of the pressure sensor shown in FIG. 10 . FIG. 12A is a diagram showing a first step in manufacturing the pressure sensor shown in FIG. 10 . FIG. 12B is a diagram showing a second step in manufacturing the pressure sensor shown in FIG. 10 . FIG. 12C is a diagram showing a third step in manufacturing the pressure sensor shown in FIG. 10 . FIG. 12D is a diagram showing a fourth step in manufacturing the pressure sensor shown in FIG. 10 . FIG. 13 is a diagram showing the stress distribution obtained in the simulation of FIG. 6C . FIG. 14 is a perspective view of a pressure sensor according to embodiment 3. FIG. 15 is a cross-sectional view of the pressure sensor shown in FIG. 14 .Fig. 16A is a diagram showing a first process for manufacturing the pressure sensor shown in Fig. 14. Fig. 16B is a diagram showing a second process for manufacturing the pressure sensor shown in Fig. 14. Fig. 17 is a block diagram showing the configuration of a pressure detection device. Fig. 18 is a flowchart showing how the pressure detection device identifies the magnitude of an external force from data related to reflected waves. Fig. 19 is a diagram showing an example of analysis of waveform data obtained in step S2 of Fig. 18.

[0019] Embodiments of the present disclosure will be described below with reference to the drawings. Each of the embodiments described below represents a specific example of the present disclosure. The numerical values, components, component placement and connection, steps, step order, and display examples shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, the present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims. Furthermore, the technical features described in each embodiment can be combined with each other. Furthermore, each drawing is not necessarily an exact representation. In each drawing, substantially identical components are designated by the same reference numerals, and redundant explanations are omitted or simplified.

[0020] (Embodiment 1) [Configuration] The configuration of the pressure sensor 1 according to embodiment 1 will be described with reference to FIGS. 3 and 4. FIG. 3 is a perspective view of the pressure sensor 1 according to embodiment 1. Note that the dots drawn in the second section 12 shown in FIG. 3 are patterns for emphasis in the description and do not indicate a cross section, and this also applies to FIG. 3 and subsequent drawings. Also, in FIG. 3, the detailed cross-sectional shape of the first section 11 located at the far left is not shown, and this also applies to the subsequent perspective views. FIG. 4 is a cross-sectional view of the pressure sensor 1 shown in FIG. 3. (a) of FIG. 4 is a cross-sectional view of the first section 11 as viewed from the X-axis direction in FIG. 3, and (b) of FIG. 4 is a cross-sectional view of the second section 12 as viewed from the X-axis direction in FIG. 3.

[0021] The pressure sensor 1 is a sensing element whose characteristic impedance value changes depending on the cross-sectional shape. The pressure sensor 1 is, for example, a cable made up of multiple conductors and one or more dielectrics. In this specification, a conductor is defined as a material having a resistivity of 10 ―８ Ωcm to 10 ３ A material with a resistivity of 10 Ωcm is called a dielectric. ７ Ωcm to 10 １８ This refers to a material with a resistivity of Ωcm.

[0022] As shown in Figure 3, the pressure sensor 1 has a detection unit that is elongated in one direction (i.e., the X-axis direction) and has a flexible structure that allows expansion and contraction and bending in the X-axis direction (i.e., the longitudinal axis direction). The detection unit is a structure that has multiple conversion coefficients in the X-axis direction, whose characteristic impedance changes depending on the cross-sectional shape of the pressure sensor when viewed from the X-axis direction. Here, the conversion coefficient is an index that indicates the ease of change when the characteristic impedance changes depending on the cross-sectional shape. Note that in embodiment 1, the detection unit refers to the first section 11 and the second section 12.

[0023] The first sections 11 and the second sections 12 have structures with different conversion coefficients. While Fig. 3 illustrates a detection unit in which four first sections 11 and four second sections 12 are alternately arranged, this is not necessarily limited to this. The detection unit may be composed of at least one first section 11 and at least one second section 12.

[0024] As shown in FIG. 4A , the cross section of the first section 11 has a concentric circular shape. The first section 11 includes, from the inside out, a first conductor 111 made of the above-described conductor, a dielectric 112 made of the above-described dielectric, and a second conductor 113 made of the above-described conductor, stacked concentrically. The first conductor 111 and the second conductor 113 may be made of the same conductor or different conductors. The first conductor 111, the dielectric 112, and the second conductor 113 may be made of elastic materials. The material with the smallest Young's modulus in the cross section of the first section 11 is included in the dielectric 112. In this specification, an elastic material refers to a material with a Young's modulus of 10 MPa or less. The detailed constituent materials of the first section 11 will be described later.

[0025] Also, r shown in FIG. １ denotes the radius of the outer periphery of the first conductor 111, and r ２ indicates the radius of the inner periphery of the second conductor 113.

[0026] As shown in FIG. 4B , the cross section of the second section 12 has a concentric circular shape. The second section 12 includes, from the inside out, a first conductor 121 made of the conductor described above, a dielectric 122 made of the dielectric described above, and a second conductor 123 made of the conductor described above, stacked concentrically. The first conductor 121 is made of metal, the dielectric 122 is made of resin, and the second conductor 123 is made of an elastic material. The material with the smallest Young's modulus in the cross section of the second section 12 is included in the second conductor 123. The Young's modulus of the metal and resin is preferably 100 MPa or more, and more preferably 1 GPa or more. The detailed constituent materials of the second section 12 will be described later.

[0027] Also, r shown in FIG. １ denotes the radius of the outer periphery of the first conductor 121, and r ２ indicates the radius of the inner periphery of the second conductor 123.

[0028] Here, the characteristic impedance will be explained. The characteristic impedance of the concentric sensing member (i.e., the first section 11 and the second section 12) as in the first embodiment is expressed by the following formula (1). In the following formula (1), R is the resistance value, j is an imaginary number, ω is the angular frequency, L is the inductance, G is the conductance, and C is the capacitance.

[0029]

[0030] When the signal input to the sensing member becomes high frequency, that is, when the value of ω increases, the above equation (1) can be expressed as the following equation (2).

[0031]

[0032] Furthermore, L and C are expressed by the following formulas (3) and (4), respectively. １ is the radius of the outer periphery of the internal conductor, and r ２ is the radius of the inner circumference of the external conductor, μ is the magnetic permeability, and ε is the permittivity.

[0033]

[0034]

[0035] Using the above equations (2), (3), and (4), the following equation (5) is obtained.

[0036]

[0037] From the above equation (5), the characteristic impedance of the concentric sensing member is r １ and ２ and (i.e., radius ratio).

[0038] Next, the conversion coefficient will be explained. The value of the conversion coefficient of the first section 11 is larger than the value of the conversion coefficient of the second section 12. Specifically, when the first section 11 and the second section 12 are subjected to the same magnitude of external force from the surroundings, the cross-sectional shape of the second section 12 is closer to a concentric shape than the cross-sectional shape of the first section 11. This is achieved by the difference in materials constituting the first section 11 and the second section 12. Since each component of the first section 11 is made of an elastic body, when the first section 11 is subjected to an external force, the cross-sectional shapes of the first conductor 111, the dielectric 112, and the second conductor 113 are likely to change. As a result, the r １ and ２ The radius ratio of the first conductor 121 to the dielectric 122 changes from the radius ratio before the external force is applied. On the other hand, the second section 12 is configured with the first conductor 121 being metal, the dielectric 122 being resin, and the second conductor 123 being elastic. The Young's modulus of the metal and the resin is at least 10 times that of the elastic body, and the metal and the resin are materials that are less likely to deform than the elastic body. Therefore, when the second section 12 is subjected to an external force, the cross-sectional shapes of the first conductor 121 and the dielectric 122 are less deformed than the cross-sectional shape of the second conductor 123. As a result, the r in the second section 12 １ and ２ The radius ratio of the radius of the sphere to the radius of the sphere remains almost unchanged from the radius ratio before the external force is applied.

[0039] Furthermore, from the above-mentioned formula (5), the characteristic impedance of the first section 11 (second section 12) is expressed as the radius r of the outer periphery of the first conductor 111 (first conductor 121). １ and the radius r of the inner periphery of the second conductor 113 (second conductor 123) ２ The characteristic impedance of the first section 11 is determined by the radius ratio between the first section 11 and the second section 12. In other words, the first section 11 has a large conversion coefficient and the radius ratio is easily changed, so it is a structure in which the characteristic impedance is easily changed by an external force. On the other hand, the second section 12 has a small conversion coefficient and the radius ratio is not easily changed, so it is a structure in which the characteristic impedance is not easily changed by an external force. Therefore, the magnitude of the conversion coefficient is an index showing the ease with which the characteristic impedance is changed.

[0040] The characteristic impedance values ​​of the first section 11 and the second section 12 are the same when the cross-sectional shape is concentric (that is, under normal conditions).

[0041] [Operation Example] An operation example of the pressure sensor 1 will be described with reference to FIG. 5 . FIG. 5 is a schematic diagram showing the load state of the pressure sensor 1 shown in FIG. 3 and a diagram showing measurement results when the pressure sensor 1 is subjected to the load. In this specification, the load includes an external force that presses the pressure sensor 1 from the periphery so as to reduce the cross-sectional area of ​​the pressure sensor 1, and distortion (or an external force that causes the distortion) caused by deformation of the shape of the pressure sensor 1, such as bending. FIG. 5(a) is a schematic diagram showing the pressure sensor 1 when not subjected to a load, and a diagram showing the results of measuring the amplitude and time width of the reflected wave in this state. FIG. 5(b) is a schematic diagram showing the pressure sensor 1 when distortion due to bending occurs in the pressure sensor 1, and a diagram showing the results of measuring the amplitude and time width of the reflected wave in this state. As shown in the right diagram of FIG. 5(b), the pressure sensor 1 is deformed into a curved shape. FIG. 5(c) is a schematic diagram showing the pressure sensor 1 when pressed from the periphery, and a diagram showing the results of measuring the amplitude and time width of the reflected wave in this state. As shown in the right diagram of Fig. 5(c), the pressure sensor 1 is subjected to external forces pressing from above and below. In Fig. 5, the connection at one end of the pressure sensor 1 is shown as being disconnected.

[0042] As shown in FIG. 5A, since the pressure sensor 1 is in a state where no load is applied (that is, in a normal state), the pressure sensor 1 can obtain a graph showing a constant characteristic impedance.

[0043] 5B, when the pressure sensor 1 is curved, the shape of the pressure sensor 1 itself is deformed. That is, the cross sections of the curved first section 11 and second section 12 are deformed from concentric circles to ellipses, and the radii r of the first section 11 and second section 12 are deformed. １ and radius r ２ is the normal radius r １ and radius r ２Therefore, the radius ratio when curved changes from the radius ratio when normal, and the value of the characteristic impedance changes in both the first section 11 and the second section 12. For example, if the radius ratio when curved in the first section 11 and the second section 12 becomes larger than the radius ratio when normal, the pressure sensor 1 can obtain a graph in which the voltage increases in a time width corresponding to the curved positional relationship, as shown in the right diagram of (b) of Figure 5.

[0044] As shown in (c) of Figure 5, the pressure sensor 1 is subjected to external forces pressing from above and below. As described above, when the first section 11 and the second section 12 are subjected to external forces of the same magnitude, the radius ratio of the first section 11 is more likely to change than that of the second section 12. Therefore, the value of the characteristic impedance in the first section 11 changes more than the value of the characteristic impedance in the second section 12. For example, the pressure sensor 1 can obtain a graph, as shown on the right in (c) of Figure 5, in which the voltage rises in the time width corresponding to the positional relationship of the first section 11 and the voltage does not change much in the time width corresponding to the positional relationship of the second section 12. This allows the pressure sensor 1 to identify the position where the external force is applied.

[0045] Comparing Figure 5(b) and Figure 5(c), the amplitude and time width waveforms of the obtained reflected waves are different, so the pressure sensor 1 can determine whether the change in characteristic impedance is a change caused by an external force pressing from the surroundings, or a change caused by the shape, such as bending.

[0046] [Relationship between Characteristic Impedance Value and External Force] The relationship between the characteristic impedance value of the pressure sensor 1 and the magnitude of the external force will be described with reference to Figures 6A, 6B, 6C, and 7. Figure 6A is a diagram showing a calculation model used in the simulation, and Figures 6B, 6C, and 7 are diagrams showing results obtained by the simulation using Figure 6A.

[0047] FIG. 6A is a diagram showing a calculation model (i.e., a calculation model in a cross-sectional view) prepared before calculating, by simulation, a change in characteristic impedance due to the first section 11 being subjected to an external force.

[0048] The calculation conditions for the calculation model shown in FIG. 6A were as follows. The calculation environment used was "Ansys 2022 R2 Analysis System Static Structure." The boundary conditions were: no friction in contact between the first section 11 and the metal 7; the contact points of the first conductor 111, the dielectric 112, and the second conductor 113 do not separate; the first section 11 is in contact with the two metals 7 in the initial state; and the point where the first section 11 and the metals 7 initially contact does not move in the Y-axis direction (i.e., does not shift in the Y-axis direction). The deformation conditions were such that the upper and lower metals 7 sandwiching the first section 11 approach each other by 5 μm (i.e., the distance between the metals 7 in the Z-axis direction approaches each other by 5 μm). The physical properties of each material were set as follows: The first conductor 111 had a diameter of 1 mm, a Young's modulus of 6 MPa, and a Poisson's ratio of 0.49. The dielectric 112 had a diameter of 3 mm, a Young's modulus of 3 MPa, and a Poisson's ratio of 0.49. The second conductor 113 had a diameter of 4 mm, a Young's modulus of 3 MPa, and a Poisson's ratio of 0.49. The metal 7 had a Young's modulus of 0.2 GPa and a Poisson's ratio of 0.3.

[0049] FIG. 6B is a diagram showing a calculation model (i.e., a calculation model in a cross-sectional view) obtained when a simulation is performed using the calculation model prepared in FIG. 6A in which the first section 11 is not subjected to a load (i.e., the movement distance of the metal 7 is 0 mm). FIG. 6B (a) is a diagram showing the distribution of stress generated in the first section 11 and the two metals 7. As shown in FIG. 6B (a), the magnitude of the stress is displayed according to the type of hatching. Note that this method of displaying stress is the same in the drawings subsequent to FIG. 6B. FIG. 6B (b) shows only the first section 11 shown in FIG. 6B (a), and displays the boundaries between the first conductor 111, the dielectric 112, and the second conductor 113 so that they can be seen.

[0050] 6B(a), since the first section 11 is divided into a number of regions by lines in order to precisely calculate the stress distribution in the first section 11, the first section 11 appears to be displayed in black, but when enlarged, each region is hatched (not shown). Also, the lines drawn on the metal 7 indicate the division into multiple regions, and stress is calculated for each region.

[0051] As shown in (a) of Fig. 6B, the metal 7 has not moved from the initial state set in the calculation model shown in Fig. 6A, so the first section 11 is not subjected to an external force from the metal 7. Therefore, each region of the first section 11 and the metal 7 is shown with hatching indicating that the stress is small. Also, as shown in (b) of Fig. 6B, the shape of the first section 11 is concentric because the first section 11 is not subjected to an external force from the metal 7.

[0052] 6C is a diagram showing a calculation model obtained when a simulation is performed using the calculation model prepared in FIG. 6A in which the first section 11 is subjected to a load (the movement distance of the metal 7 is 0.33 mm). In other words, the distance between the metals 7 shown in FIG. 6C is 3.33 mm. FIG. 6C (a) is a diagram showing the distribution of stress generated in the first section 11 and the two metals 7. FIG. 6C (b) shows only the first section 11 shown in FIG. 6C (a), and illustrates the boundaries between the first conductor 111, the dielectric 112, and the second conductor 113.

[0053] 6C (a), the first section 11 receives an external force from the metal 7 in the vertical direction, and the shape of the first section 11 is deformed from a concentric shape to an elliptical shape with the Y-axis direction as the major axis and the Z-axis direction as the minor axis. This shows that large stress is generated in the first section 11 in the part where the amount of deformation from the original shape is large, that is, in the contact surface with the metal 7 and its surrounding area. It can be seen that the metal 7 receives a reaction force from the contact surface with the first section 11, and stress of the same magnitude is generated uniformly.

[0054] As shown in (b) of Fig. 6C, the shape of the first section 11 is changed from a concentric circle to an ellipse with the Y-axis direction as the major axis and the Z-axis direction as the minor axis. Compared with (b) of Fig. 6B, the radius r １ and the radius r of the second conductor 113 parallel to the Z-axis direction ２ As a result, the r １ and ２ Since the radius ratio of the first section 11 to the second section 12 changes, the characteristic impedance of the first section 11 changes.

[0055] 7A and 7B are diagrams showing calculation results obtained by simulation using the calculation model prepared in Fig. 6A. In Fig. 7A, the horizontal axis represents the magnitude of the external force applied to the first section 11 when the moving distance between the metals 7 is set per 1 mm length, and the vertical axis represents r １ and ２ The solid line in (a) of FIG. ２ The dashed line indicates the value of radius r １ 7B is a graph in which the horizontal axis represents the magnitude of the external force applied to the first section 11 when the moving distance between the metals 7 is set per 1 mm length, and the vertical axis represents the average characteristic impedance, which is the average value of the characteristic impedances obtained by performing the simulation of FIG.

[0056] As shown in FIG. 7A, when the first section 11 is subjected to an external force of 1 N / mm, the radius r １ is shortened by about 0.05 mm, and the radius r ２ 6A, the Young's modulus of the first conductor 111 is 6 MPa, and the Young's modulus of the dielectric 112 is 3 MPa. Therefore, when the first conductor 111 and the dielectric 112 are subjected to an external force of the same magnitude, the dielectric 112 deforms more than the first conductor 111. As a result, the radius r ２ is the radius r １ Therefore, as the magnitude of the external force applied to the first section 11 increases, the value of r １ and ２ Since the radius ratio to the radius of the first section 11 becomes smaller, it is expected that the value of the characteristic impedance of the first section 11 will become smaller according to the above formula (5).

[0057] As shown in Fig. 7(b), as the magnitude of the external force applied to the first section 11 increases, the value of the average characteristic impedance of the first section 11 decreases. This result is consistent with the assumption in Fig. 7(a). Here, Fig. 8 will be used to explain the meaning of the dashed line and arrow line shown in Fig. 7(b).

[0058] FIG. 8 is a diagram for explaining the relationship between voltage and characteristic impedance in the TDR method. FIG. 8 differs from FIG. 1 in that two pressure sensors (i.e., pressure sensor 1c and pressure sensor 1d) are used. In FIG. 8, the characteristic impedances of pressure sensor 1c and pressure sensor 1d when no external force is applied are respectively Z ０ and Z Ｌ 8, it is assumed that when pressure sensor 1c and pressure sensor 1d are subjected to an external force, the value of the characteristic impedance of pressure sensor 1c does not change, and only the value of the characteristic impedance of pressure sensor 1d changes. Furthermore, if pressure sensor 1c and pressure sensor 1d are considered to be one pressure sensor, and pressure sensor 1c is considered to be in the second section 12 and pressure sensor 1d is considered to be in the first section 11, the following description can be applied to pressure sensor 1 according to embodiment 1.

[0059] In FIG. 8, the vector network analyzer 6 measures the voltage of the incident wave incident on the pressure sensor 1c and the pressure sensor 1d as V ｉｎ , the minimum voltage of the reflected wave that the vector network analyzer 6 can measure is V ｒｅｆ Then, the characteristic impedance Z ０ and Z Ｌ and is expressed by the following equation (6).

[0060]

[0061] For example, V ｉｎ is 1V, V ｒｅｆ If ΔZ is 10 mV, the above equation (6) can be expressed as the following equation (7). Ｌ is the characteristic impedance Z Ｌ The change in

[0062]

[0063] The above equation (7) is the characteristic impedance Z of the pressure sensor 1d. Ｌ This equation indicates that the vector network analyzer 6 can measure the change in voltage if V changes by at least 2%. ｉｎ is 1V, V ｒｅｆis 10 mV, the strength of the reflected wave obtained by the vector network analyzer 6 is equivalent to 40 dB. Some commonly available vector network analyzers have specifications that provide a reflected wave resolution of 60 dB or more, so the assumptions in this explanation are fully realizable.

[0064] Returning to the explanation of Figure 7(b), the dashed line shown in Figure 7(b) indicates a 2% change in characteristic impedance value (approximately 32.20Ω) from the average characteristic impedance value in the initial state (approximately 38.95Ω). Furthermore, in Figure 7(b), the magnitude of the external force indicated at the intersection of the solid line and dashed line is the magnitude of the external force required to change the characteristic impedance value of the first section 11 by 2%. In other words, the pressure sensor 1 generates a reflected wave with an amplitude of 10 mV when the first section 11 is subjected to an external force of 0.64 N / mm.

[0065] 9A to 9E, a manufacturing example of the pressure sensor 1 will be described. Note that the numerical values ​​shown in the description of Fig. 9A to 9E are merely examples, and even a structure manufactured by appropriately changing the numerical values ​​is included in the pressure sensor 1 of the present disclosure.

[0066] Fig. 9A is a diagram showing a first step in manufacturing the pressure sensor 1 shown in Fig. 3. (a) of Fig. 9A is a perspective view of the thin metal wire 21. (b) of Fig. 9A is a cross-sectional view taken along line B-B in (a) of Fig. 9A. (c) of Fig. 9A is a cross-sectional view taken along line CC in (a) of Fig. 9A. Note that the thin metal wire 21 on line B-B in (a) of Fig. 9A is used as the first conductor 111 of the first section 11, and the thin metal wire 21 on line CC is used as the first conductor 121 of the second section 12.

[0067] 9A(a) is, for example, a copper wire. Specifically, a copper wire having a thickness of 0.06 mm, a Young's modulus of 130 GPa, and a Poisson's ratio of 0.34 is used as the thin metal wire 21. In order to make the pressure sensor 1 a structure that can expand and contract in the longitudinal axis direction, a coil-shaped copper wire having an inner diameter of 0.6 mm is used as the thin metal wire 21.

[0068] 9A(b) and 9A(c) show cross-sectional views of the thin metal wire 21, but for ease of understanding, the thin metal wire 21 is shown without showing any cavity therein, and this also applies to the subsequent drawings. Also, as shown in FIG. 9A(c), the thin metal wire 21 corresponds to the first conductor 121 of the second section 12.

[0069] FIG. 9B is a diagram showing a second step in manufacturing the pressure sensor 1 shown in FIG. 3. FIG. 9B is a diagram showing a step performed after the step described in FIG. 9A. FIG. 9B (a) is a perspective view of the thin metal wire 21 placed on a mold. FIG. 9B (b) is a perspective view of the mold shown in FIG. 9B (a) after the conductive rubber 22 is poured into the mold to form the first conductor 111 of the first section 11. FIG. 9B (c) is a cross-sectional view taken along line CC shown in FIG. 9B (b). FIG. 9B (d) is a cross-sectional view taken along line DD shown in FIG. 9B (b). Note that line CC shown in FIG. 9B (b) is the same position as line BB shown in FIG. 9A (a), and line DD shown in FIG. 9B (b) is the same position as line CC shown in FIG. 9A (a).

[0070] 9B(a), the mold has two forming portions with recesses for forming the first conductors 111 and one non-forming portion provided for not forming the conductive rubber 22. The length of the forming portion and the non-forming portion in the longitudinal direction is 2 mm. The cross section of the forming portion when viewed in the longitudinal direction is a semicircle with a diameter of 1 mm.

[0071] As shown in (b) of Fig. 9B, conductive rubber 22 with a diameter of 1 mm is formed in two locations. The conductive rubber 22 is, for example, silicone rubber containing a filler. The filler is, for example, carbon black or metal powder. Specifically, silicone rubber with a Young's modulus of 6 MPa and a Poisson's ratio of 0.49 is used as the conductive rubber 22.

[0072] 9B(c), the conductive rubber 22 is formed on the thin metal wire 21. The thin metal wire 21 and the conductive rubber 22 in FIG.

[0073] As shown in (d) of Fig. 9B, the thin metal wires 21 were located in the non-formation area, so no conductive rubber 22 was formed. Therefore, the cross-sectional view shown in (d) of Fig. 9B is the same as the cross-sectional view shown in (c) of Fig. 9A.

[0074] 9C is a diagram showing a third step in manufacturing the pressure sensor 1 shown in FIG. 3. FIG. 9C is a diagram showing a step performed subsequent to the step described in FIG. 9B. FIG. 9C (a) is a perspective view after a dielectric coating 23 has been formed on the structure shown in FIG. 9B (b). FIG. 9C (b) is a cross-sectional view taken along line B-B in FIG. 9C (a). FIG. 9C (c) is a cross-sectional view taken along line C-C in FIG. 9C (a). Note that line B-B in FIG. 9C (a) is the same as line B-B in FIG. 9A (a), and line C-C in FIG. 9C (a) is the same as line C-C in FIG. 9A (a).

[0075] As shown in (a) of Figure 9C, there is no significant difference in appearance from (b) of Figure 9B. This is because, as shown in (b) and (c) of Figure 9C, only a small amount of the dielectric coating 23 is formed on the first conductor 111 of the first section 11 and the first conductor 121 of the second section 12. For example, the thickness of the dielectric coating 23 is 0.12 mm. The dielectric coating 23 is made of, for example, polyimide or polyethylene. Specifically, polyimide with a Young's modulus of 3 to 5 GPa and a Poisson's ratio of 0.35 is used as the dielectric coating 23.

[0076] As shown in (c) of FIG. 9C, the dielectric coating 23 corresponds to the dielectric 122 of the second section 12.

[0077] FIG. 9D is a diagram showing a fourth step in manufacturing the pressure sensor 1 shown in FIG. 3. FIG. 9D is a diagram showing a step performed after the step described in FIG. 9C. FIG. 9D (a) is a perspective view of the structure shown in FIG. 9C (a) when placed on a mold. FIG. 9D (b) is a perspective view of the mold shown in FIG. 9D (a) after the dielectric rubber 24 has been poured into the mold to form the dielectric 112 of the first section 11. FIG. 9D (c) is a cross-sectional view taken along line CC shown in FIG. 9D (b). FIG. 9D (d) is a cross-sectional view taken along line DD shown in FIG. 9D (b). Note that line CC shown in FIG. 9D (b) is the same position as line BB shown in FIG. 9A (a), and line DD shown in FIG. 9D (b) is the same position as line CC shown in FIG. 9A (a).

[0078] 9D(a), the mold has two forming portions provided with recesses for forming the dielectric 112 and one non-forming portion provided so that the dielectric rubber 24 is not formed. The length of the forming portion and the non-forming portion in the longitudinal direction is 2 mm. The cross section of the forming portion when viewed in the longitudinal direction is a semicircle with a diameter of 3 mm.

[0079] 9D(b), dielectric rubber 24 having a diameter of 3 mm is formed in two locations. The dielectric rubber 24 is, for example, silicone rubber. Specifically, silicone rubber having a Young's modulus of 3 MPa and a Poisson's ratio of 0.49 is used as the dielectric rubber 24.

[0080] As shown in (c) of Fig. 9D, the dielectric rubber 24 is formed on the dielectric coating 23. The dielectric coating 23 and the dielectric rubber 24 in (c) of Fig. 9D correspond to the dielectric 112 of the first section 11.

[0081] As shown in (d) of Fig. 9D, the dielectric rubber 24 is not formed because the dielectric 122 is located in the non-forming portion. Therefore, the cross-sectional view shown in (d) of Fig. 9D is the same as the cross-sectional view shown in (c) of Fig. 9C.

[0082] FIG. 9E is a diagram showing a fifth step in manufacturing the pressure sensor 1 shown in FIG. 3. FIG. 9E is a diagram showing a step performed after the step described in FIG. 9D. (a) of FIG. 9E is a perspective view of the structure shown in (a) of FIG. 9D placed on a mold. (b) of FIG. 9E is a perspective view of the mold shown in (a) of FIG. 9E after pouring conductive rubber 25 into the mold to form the second conductors 113 of the first section 11 and the second conductors 123 of the second section 12. (c) of FIG. 9E is a cross-sectional view taken along line CC shown in (b) of FIG. 9E. (d) of FIG. 9E is a cross-sectional view taken along line DD shown in (b) of FIG. 9E. Note that line CC shown in (b) of FIG. 9E is the same position as line BB shown in (a) of FIG. 9A, and line DD shown in (b) of FIG. 9E is the same position as line CC shown in (a) of FIG. 9A.

[0083] 9E(a), the mold has one forming portion provided with a recess for forming the conductive rubber 25. The length of the forming portion in the longitudinal direction is 6 mm. The cross section of the forming portion when viewed in the longitudinal direction is a semicircle with a diameter of 4 mm.

[0084] 9E(b), a conductive rubber 25 having a diameter of 4 mm is formed over the entire surface. The conductive rubber 25 is, for example, silicone rubber containing a filler. Specifically, silicone rubber having a Young's modulus of 3 MPa and a Poisson's ratio of 0.49 is used as the conductive rubber 25.

[0085] 9E(c), the conductive rubber 25 is formed on the dielectric 112. The conductive rubber 25 in FIG.

[0086] 9E(d), the conductive rubber 25 is formed on the dielectric 122. The conductive rubber 25 in FIG.

[0087] From the above description, it is possible to form a pressure sensor 1 having a first section 11 and a second section 12 with different conversion coefficients.

[0088] [Effect] As described above, the pressure sensor 1 according to the first embodiment has a detection section that has a long shape in one direction and a flexible structure that is capable of expansion, contraction, and bending, and the detection section has different values ​​in multiple sections in the longitudinal direction as a conversion coefficient, which is an index showing the ease of change when the characteristic impedance changes depending on the cross-sectional shape of the detection section when viewed from the longitudinal direction.

[0089] With this configuration, when the pressure sensor 1 is subjected to an external force, the characteristic impedance changes according to the conversion coefficient for each section having a different conversion coefficient, making it possible to identify the position where the external force, such as pressure, is being applied. Furthermore, when the pressure sensor 1 is deformed, for example by bending, the cross-sectional shape of the conversion coefficient also changes, so the value of the characteristic impedance changes regardless of the difference in conversion coefficient. Therefore, the pressure sensor 1 can distinguish between a change in characteristic impedance caused by an external force applied when the sensing member is pressed and a change in characteristic impedance caused by a change in shape, such as bending, of the sensing member.

[0090] In addition, in the pressure sensor 1 according to embodiment 1, the detection section has a first section 11 and a second section 12 having different conversion coefficients, and both the first section 11 and the second section 12 are composed of a plurality of conductors and one or more dielectrics, and the Young's modulus of the dielectric in the first section 11 is smaller than the Young's modulus of the dielectric in the second section 12.

[0091] With this configuration, the dielectric 112 of the first section 11 is more easily deformed than the dielectric 122 of the second section 12, so when the first section 11 and the second section 12 are subjected to an external force of the same magnitude, the cross section of the first section 11 is deformed more than the cross section of the second section 12. As a result, the pressure sensor 1 has the first section 11, in which the value of the characteristic impedance is more likely to change, and the second section 12, in which the value of the characteristic impedance is less likely to change, and therefore can identify the position where an external force is applied.

[0092] Furthermore, in the pressure sensor 1 according to embodiment 1, in both the cross section in the first section 11 and the cross section in the second section 12, a first conductor which is a conductor, a dielectric, and a second conductor which is a conductor are stacked concentrically from the inside.

[0093] With this configuration, when the first section 11 and the second section 12 are subjected to an external force of the same magnitude, the dielectric 112 of the first section 11 is more likely to deform than the dielectric 122 of the second section 12. １ and ２ The radius ratio of r in the second section 12 is １ and ２ The characteristic impedance of the concentric sensing element is more likely to change than the radius ratio of r １ and ２ Since the characteristic impedance is determined by the radius ratio, the pressure sensor 1 has a first section 11 where the value of the characteristic impedance is likely to change and a second section 12 where the value of the characteristic impedance is unlikely to change. This allows the pressure sensor 1 to identify the position where an external force is applied.

[0094] Furthermore, in the pressure sensor 1 according to embodiment 1, the material with the smallest Young's modulus in the cross section of the first section 11 is included in the dielectric 112, and the material with the smallest Young's modulus in the cross section of the second section 12 is included in the second conductor 123.

[0095] With this configuration, the dielectric 112 is the material that is most easily deformed in the first section 11. On the other hand, the second conductor 123 is the material that is most easily deformed in the second section 12. In other words, when the first section 11 and the second section 12 are subjected to an external force of the same magnitude, the radius r ２ is the radius r in the first section 11 １ , radius r in the second section 12 １ , and the radius r in the second section 12 ２ The characteristic impedance of the concentric sensing element varies more than r １ and ２ Since the characteristic impedance is determined by the radius ratio, the pressure sensor 1 has a first section 11 where the value of the characteristic impedance is likely to change and a second section 12 where the value of the characteristic impedance is unlikely to change. This allows the pressure sensor 1 to identify the position where an external force is applied.

[0096] (Embodiment 2) [Configuration] The configuration of a pressure sensor 1a according to embodiment 2 will be described with reference to Figures 10 and 11. Figure 10 is a perspective view of the pressure sensor 1a according to embodiment 2. Figure 11 is a cross-sectional view of the pressure sensor 1a shown in Figure 10. (a) of Figure 11 is a cross-sectional view of the pressure sensor 1a in the third section 13. (b) of Figure 11 is a cross-sectional view of the pressure sensor 1a in the fourth section 14. Below, only the differences between the pressure sensor 1a according to embodiment 2 and the pressure sensor 1 according to embodiment 1 will be described, and the same points will be omitted. Note that, like the pressure sensor 1 according to embodiment 1, the pressure sensor 1a is a sensing member whose characteristic impedance value changes depending on the cross-sectional shape, and is a cable composed of a plurality of conductors and one or more dielectrics.

[0097] As shown in Figure 10, the pressure sensor 1a has a third section 13 corresponding to the first section 11 of the pressure sensor 1 according to embodiment 1 and a fourth section 14 corresponding to the second section 12 of the pressure sensor 1 according to embodiment 1.

[0098] The fourth section 14 is the structure of the pressure sensor 1a at a location bound by a tungsten wire 26, which is a thin tungsten wire. The fourth section 14 is the structure at a location where the radius obtained from the cross section when viewed from the X-axis direction is smallest. The third section 13 is the structure of the pressure sensor 1a other than the fourth section 14. The radius obtained from the cross section when viewed from the X-axis direction (longitudinal axis direction) in the third section 13 is larger than the radius obtained from the cross section when viewed from the X-axis direction in the fourth section 14.

[0099] 11(a), in the third section 13, from the inside out, a first conductor 131 made of the above-mentioned conductor, a dielectric 132 made of the above-mentioned dielectric, and a second conductor 133 made of the above-mentioned conductor are concentrically stacked. Note that the first conductor 131 and the second conductor 133 may be made of the same conductor or different conductors. Furthermore, the first conductor 131, the dielectric 132, and the second conductor 133 are made of elastic materials. The elastic material with the smallest Young's modulus in the cross section of the third section 13 is the elastic material making up the dielectric 132.

[0100] 11(b), the fourth section 14 includes, from the inside out, a first conductor 141 made of the above-described conductor, a dielectric 142 made of the above-described dielectric, and a second conductor 143 made of the above-described conductor, all stacked concentrically. Note that the first conductor 141 and the second conductor 143 may be made of the same conductor or different conductors. The first conductor 141, the dielectric 142, and the second conductor 143 are made of elastic materials.

[0101] The fourth section 14 is a structure bound by tungsten wire 26, and the diameter of the second conductor 143 of the fourth section 14 is smaller than the diameter of the second conductor 133 of the third section 13. Furthermore, when the third section 13 and the fourth section 14 are subjected to the same magnitude of external force from the surroundings, the elastic body constituting the fourth section 14 is already subjected to the external force from the tungsten wire 26, so the elastic body constituting the fourth section 14 is less likely to deform than the elastic body constituting the third section 13. In other words, the r １ and ２ The radius ratio of r １ and ２ The radius ratio of the second conductor 143 to the radius of the second conductor 133 is more likely to change than the radius ratio of the second conductor 13 to the radius of the second conductor 133. Therefore, the value of the characteristic impedance in the third section 13 changes more significantly than the value of the characteristic impedance in the fourth section 14. The diameter of the second conductor 143 shown in Fig. 11(b) is preferably 80% or less, and more preferably 50% or less, of the diameter of the second conductor 133 shown in Fig. 11(a).

[0102] [Manufacturing Example] Next, a manufacturing example of the pressure sensor 1a will be described with reference to Fig. 12A to Fig. 12D. Note that the numerical values ​​shown in the description of Fig. 12A to Fig. 12D are merely examples, and a structure manufactured by appropriately changing the numerical values ​​is also included in the pressure sensor 1a of the present disclosure.

[0103] FIG. 12A is a diagram showing a first step in manufacturing the pressure sensor 1a shown in FIG. 10. (a) of FIG. 12A is a perspective view of a mold for forming the first conductors 131 of the third section 13 and the first conductors 141 of the fourth section 14. (b) of FIG. 12A is a perspective view after pouring conductive rubber 22 into the mold shown in (a) of FIG. 12A to form the first conductors 131 of the third section 13 and the first conductors 141 of the fourth section 14. (c) of FIG. 12A is a cross-sectional view taken along line CC shown in (b) of FIG. 12A. (d) of FIG. 12A is a cross-sectional view taken along line DD shown in (b) of FIG. 12A. Note that the conductive rubber 22 on line CC shown in (b) of FIG. 12A is used as the first conductors 131 of the third section 13, and the conductive rubber 22 on line DD is used as the first conductors 141 of the fourth section 14.

[0104] 12A (a), the mold has one forming portion provided with recesses for forming the first conductors 131 of the third section 13 and the first conductors 141 of the fourth section 14. The forming portion has a cross section that is semicircular with a diameter of 1 mm when viewed from the longitudinal axis direction.

[0105] 12A(b), a conductive rubber 22 having a diameter of 1 mm is formed. Note that the conductive rubber 22 used in the second embodiment is the same as the conductive rubber 22 used in the first embodiment, and therefore a description thereof will be omitted.

[0106] As shown in (c) of FIG. 12A , the conductive rubber 22 corresponds to the first conductor 131 of the third section 13 .

[0107] As shown in (d) of FIG. 12A , the conductive rubber 22 corresponds to the first conductor 141 of the fourth section 14 .

[0108] In the cross-sectional views shown in (c) of FIG. 12A and (d) of FIG. 12A, the cross-sectional views of the first conductor 131 of the third section 13 and the first conductor 141 of the fourth section 14 are the same.

[0109] FIG. 12B is a diagram showing a second step of manufacturing the pressure sensor 1a shown in FIG. 10. FIG. 12B is a diagram showing a step performed after the step described in FIG. 12A. FIG. 12B (a) is a perspective view of the structure shown in FIG. 12A (b) when placed on a mold. FIG. 12B (b) is a perspective view after dielectric rubber 24 has been poured into the mold shown in FIG. 12A (a) to form the dielectric 132 of the third section 13 and the dielectric 142 of the fourth section 14. FIG. 12B (c) is a cross-sectional view taken along line CC shown in FIG. 12B (b). FIG. 12B (d) is a cross-sectional view taken along line DD shown in FIG. 12B (b). Note that the CC line shown in (b) of Figure 12B is at the same position as the CC line shown in (b) of Figure 12A, and the DD line shown in (b) of Figure 12B is at the same position as the DD line shown in (b) of Figure 12A.

[0110] 12B(a), the mold has one forming portion provided with recesses for forming the dielectric 132 of the third section 13 and the dielectric 142 of the fourth section 14. The forming portion has a cross section in the shape of a semicircle with a diameter of 3 mm when viewed from the longitudinal axis direction.

[0111] 12B(b), a dielectric rubber 24 having a diameter of 3 mm is formed. Note that the dielectric rubber 24 used in the second embodiment is the same as the dielectric rubber 24 used in the first embodiment, and therefore a description thereof will be omitted.

[0112] As shown in (c) of Fig. 12B, the dielectric rubber 24 is laminated on the conductive rubber 22. The dielectric rubber 24 shown in (c) of Fig. 12B corresponds to the dielectric 132 of the third section 13.

[0113] As shown in (d) of Fig. 12B, the dielectric rubber 24 is laminated on the conductive rubber 22. The dielectric rubber 24 shown in (d) of Fig. 12B corresponds to the dielectric 142 of the fourth section 14.

[0114] In the cross-sectional views shown in (c) of FIG. 12B and (d) of FIG. 12B, the cross-sectional views of the dielectric 132 in the third section 13 and the dielectric 142 in the fourth section 14 are the same.

[0115] 12C is a diagram showing a third step of manufacturing the pressure sensor 1a shown in FIG. 10. FIG. 12C is a diagram showing a step performed after the step described in FIG. 12B. FIG. 12C (a) is a perspective view of the structure shown in FIG. 12B (b) when placed on a mold. FIG. 12C (b) is a perspective view of the mold shown in FIG. 12C (a) after the conductive rubber 25 has been poured into the mold to form the second conductors 133 of the third section 13 and the second conductors 143 of the fourth section 14. FIG. 12C (c) is a cross-sectional view taken along line CC shown in FIG. 12C (b). FIG. 12C (d) is a cross-sectional view taken along line DD shown in FIG. 12C (b). Note that the CC line shown in (b) of Figure 12C is at the same position as the CC line shown in (b) of Figure 12A, and the DD line shown in (b) of Figure 12C is at the same position as the DD line shown in (b) of Figure 12A.

[0116] 12C (a), the mold has one forming portion provided with recesses for forming the second conductors 133 of the third section 13 and the second conductors 143 of the fourth section 14. The forming portion has a cross section that is semicircular and has a diameter of 4 mm when viewed from the longitudinal axis direction.

[0117] 12C(b), a conductive rubber 25 having a diameter of 4 mm is formed. Note that the conductive rubber 25 used in the second embodiment is the same as the conductive rubber 25 used in the first embodiment, and therefore a description thereof will be omitted.

[0118] 12C (c), the conductive rubber 25 is laminated on the dielectric rubber 24. The conductive rubber 25 shown in FIG. 12C (c) corresponds to the second conductor 133 of the third section 13.

[0119] As shown in (d) of Fig. 12C, the conductive rubber 25 is laminated on the dielectric rubber 24. The conductive rubber 25 shown in (d) of Fig. 12C corresponds to the second conductor 143 of the fourth section 14.

[0120] In addition, in the cross-sectional views shown in (c) of FIG. 12C and (d) of FIG. 12C, the cross-sectional views of the second conductor 133 of the third section 13 and the second conductor 143 of the fourth section 14 are the same.

[0121] Fig. 12D is a diagram showing a fourth step in manufacturing the pressure sensor 1a shown in Fig. 10. Fig. 12D(a) is a perspective view of the structure shown in Fig. 12C(b) after binding with tungsten wire 26. Fig. 12D(b) is a cross-sectional view of the third section 13 shown in Fig. 12D(a). Fig. 12D(c) is a cross-sectional view of the fourth section 14 shown in Fig. 12D(a).

[0122] As shown in (a) of Fig. 12D, the pressure sensor 1a is formed by binding the structure shown in (b) of Fig. 12C with tungsten wire 26. The location where the tungsten wire 26 is bound includes the location on line D-D shown in (b) of Fig. 12C.

[0123] The cross-sectional view shown in (b) of FIG. 12D is the same as the cross-sectional view shown in (c) of FIG. 12C.

[0124] As shown in (c) of Figure 12D, the diameters of the first conductor 141, the dielectric 142 and the second conductor 143 are smaller than the diameters of the first conductor 141, the dielectric 142 and the second conductor 143 shown in (d) of Figure 12C.

[0125] [Stress Applied to Tungsten Wire] The following describes the stress generated in the tungsten wire 26 when binding the fourth section 14, using FIG. 13 . FIG. 13 is a diagram showing the stress distribution obtained by the simulation of FIG. 6C . FIG. 13 is a diagram showing the stress distribution generated around the first section 11. Note that the fourth section 14 before being bound with the tungsten wire 26 has the same structure as the first section 11.

[0126] 13, the largest stress occurs in the upper and lower regions where the diameter of the first section 11 is smallest, and the magnitude of the stress obtained by the simulation is about 1.1 MPa. In other words, from the results shown in FIG. 13, it is possible to reduce the diameter of the fourth section 14 by using a thin tungsten wire with a wire diameter of 1.1 μm and a tensile strength of about 3.7 MPa as the tungsten wire 26.

[0127] [Effect] As described above, the pressure sensor 1a according to the second embodiment has a detection unit that has a shape that is long in one direction and has a flexible structure that is capable of expansion, contraction, and bending, and the detection unit has different values ​​in multiple sections in the longitudinal direction as a conversion coefficient, which is an index that indicates the ease of change when the characteristic impedance changes depending on the cross-sectional shape of the detection unit when viewed from the longitudinal direction.

[0128] With this configuration, when pressure sensor 1a is subjected to an external force, the characteristic impedance changes according to the conversion coefficient for each section having a different conversion coefficient, making it possible to identify the position where external force such as pressure is being applied. Furthermore, when pressure sensor 1a is deformed, such as by bending, the cross-sectional shape of the conversion coefficient also changes, so the value of the characteristic impedance changes regardless of the conversion coefficient. Therefore, pressure sensor 1a can distinguish between changes in characteristic impedance caused by an external force applied when the sensing member is pressed and changes in characteristic impedance caused by a change in shape, such as bending, of the sensing member.

[0129] In addition, in the pressure sensor 1a of embodiment 2, the detection section has a third section 13 and a fourth section 14 with different conversion coefficients, and both the third section 13 and the fourth section 14 are composed of a plurality of conductors and one or more dielectrics, and in both the cross section of the third section 13 and the cross section of the fourth section 14, a first conductor which is a conductor, a dielectric, and a second conductor which is a conductor are stacked concentrically from the inside, and the radius obtained from the cross section of the third section 13 is larger than the radius obtained from the cross section of the fourth section 14.

[0130] With this configuration, r １ and ２ The radius ratio of r １ and ２ Since the characteristic impedance in the third section 13 changes more easily than the radius ratio of the pressure sensor 1a to the radius of the pressure sensor 1a, the value of the characteristic impedance in the third section 13 changes more greatly than the value of the characteristic impedance in the fourth section 14. This allows the pressure sensor 1a to identify the position where an external force is applied.

[0131] (Embodiment 3) [Configuration] The configuration of a pressure sensor 1b according to embodiment 3 will be described with reference to FIGS. 14 and 15. FIG. 14 is a perspective view of pressure sensor 1b according to embodiment 3. FIG. 15 is a cross-sectional view of pressure sensor 1b shown in FIG. 14. (a) of FIG. 15 is a cross-sectional view of the third section 13. (b) of FIG. 15 is a cross-sectional view of the fourth section 14. Pressure sensor 1b according to embodiment 3 differs from pressure sensor 1a according to embodiment 2 in that the periphery of pressure sensor 1a according to embodiment 2 is covered with heat-shrinkable material 27 and tungsten wire 26 is not used. Below, only the differences from pressure sensor 1a according to embodiment 2 will be described, and similarities will be omitted. Note that, like pressure sensor 1 according to embodiment 1, pressure sensor 1b is a sensing member whose characteristic impedance value changes depending on the cross-sectional shape, and is a cable composed of multiple conductors and one or more dielectrics.

[0132] 14, the pressure sensor 1b according to the third embodiment is a structure in which the periphery of the pressure sensor 1a according to the second embodiment is covered with a heat-shrinkable material 27. The heat-shrinkable material 27 is, for example, a resin such as polyolefin that uses conductive fibers inside, and has a tubular shape. The heat-shrinkable material 27 is a resin that shrinks irreversibly when heat is applied from the outside.

[0133] As shown in (a) of Figure 15, the third section 13 is formed by concentrically stacking, from the inside out, a first conductor 131 made of the above-mentioned conductor, a dielectric 132 made of the above-mentioned dielectric, a second conductor 133 made of the above-mentioned conductor, and a heat-shrinkable material 27.

[0134] As shown in (b) of Figure 15, the fourth section 14, like the third section 13, is formed by concentrically stacking, from the inside out, a first conductor 141 made of the above-mentioned conductor, a dielectric 142 made of the above-mentioned dielectric, a second conductor 143 made of the above-mentioned conductor, and a heat-shrinkable material 27.

[0135] In the pressure sensor 1b, the fourth section 14 is formed by applying heat to the heat-shrinkable material 27 at regular intervals. The diameter of the second conductor 143 in the fourth section 14 is smaller than the diameter of the second conductor 133 in the third section 13. Furthermore, when the third section 13 and the fourth section 14 are subjected to the same magnitude of external force from the surroundings, the elastic body constituting the fourth section 14 is already subjected to the external force from the heat-shrinkable material 27, so the elastic body constituting the fourth section 14 is less likely to deform than the elastic body constituting the third section 13. In other words, the r １ and ２ The radius ratio of r １ and ２ The radius ratio of the second conductor 143 to the radius of the second conductor 133 is more likely to change than the radius ratio of the second conductor 13 to the radius of the second conductor 133. Therefore, the value of the characteristic impedance in the third section 13 changes more significantly than the value of the characteristic impedance in the fourth section 14. The diameter of the second conductor 143 shown in Fig. 15(b) is preferably 80% or less, and more preferably 50% or less, of the diameter of the second conductor 133 shown in Fig. 15(a).

[0136] [Manufacturing Example] Next, a manufacturing example of the pressure sensor 1b will be described with reference to Figures 16A and 16B. Note that the numerical values ​​shown in the description of Figures 16A and 16B are just examples.

[0137] Fig. 16A is a diagram showing a first step in manufacturing the pressure sensor 1b shown in Fig. 14. The step shown in Fig. 16A is a step using the structure shown in Fig. 12C(b). Fig. 16A(a) is a perspective view of the structure before the heat-shrinkable material 27 is shrunk. Fig. 16A(b) is a cross-sectional view taken along line B-B shown in Fig. 16A(a). Fig. 16A(c) is a cross-sectional view taken along line CC shown in Fig. 12A(b). The structure on line B-B shown in Fig. 16A(a) is used as the third section 13, and the structure on line CC is used as the fourth section 14.

[0138] As shown in FIG. 16A(a), the structure shown in FIG. 12C(b) is covered with a tubular heat-shrinkable material 27.

[0139] As shown in FIG. 16A(b) and FIG. 16A(c), the heat shrinkable material 27 covers the conductive rubber 25.

[0140] FIG. 16B is a diagram showing a second step of manufacturing the pressure sensor 1b shown in FIG. 14. FIG. 16B is a diagram showing a step performed subsequent to the step described in FIG. 16A. (a) of FIG. 16B is a perspective view of the structure after the heat-shrinkable material 27 has been shrunk. (b) of FIG. 16B is a cross-sectional view of the third section 13 shown in (a) of FIG. 16B. (c) of FIG. 16B is a cross-sectional view of the fourth section 14 shown in (a) of FIG. 16B. Note that the cross-sectional view shown in (b) of FIG. 16B is a cross-sectional view taken along line B-B shown in (a) of FIG. 16A, and the cross-sectional view shown in (c) of FIG. 16B is a cross-sectional view taken along line CC shown in (a) of FIG. 16A.

[0141] As shown in (a) of Fig. 16B, pressure sensor 1b is formed by applying heat to the structure shown in (a) of Fig. 16A. Heat is applied to locations at regular intervals, including the locations on line CC shown in (a) of Fig. 16A.

[0142] [Effects] As described above, the pressure sensor 1b according to the third embodiment further includes the heat-shrinkable material 27 that covers the detection portion.

[0143] With this configuration, r １ and ２ The radius ratio of r １ and ２ Since the characteristic impedance in the third section 13 changes more easily than the radius ratio of the pressure sensor 1b to the radius of the pressure sensor 1b, the value of the characteristic impedance in the third section 13 changes more greatly than the value of the characteristic impedance in the fourth section 14. This allows the pressure sensor 1b to identify the position where an external force is applied.

[0144] (Fourth Embodiment) [Configuration] The configuration of a pressure detection device 4 according to a fourth embodiment will be described with reference to Fig. 17. Fig. 17 is a block diagram showing the configuration of the pressure detection device 4.

[0145] The pressure detection device 4 is a device that converts the time width and amplitude of the reflected wave from the pressure sensor 1 into the magnitude of the external force applied to the pressure sensor 1 .

[0146] As shown in Fig. 17, the pressure detection device 4 is a device that includes the pressure sensor 1 according to the first embodiment and a measurement device 3, and the pressure sensor 1 and the measurement device 3 are connected to each other. Specifically, the pressure detection device 4 is a device in which the cable 5 shown in Fig. 1(a) is replaced with the pressure sensor 1, and the vector network analyzer 6 is replaced with the measurement device 3. Note that the pressure detection device 4 may use the pressure sensor 1a according to the second embodiment or the pressure sensor 1b according to the third embodiment instead of the pressure sensor 1 according to the first embodiment. Note that the characteristic impedance of the first section 11 is set to Z ａ The characteristic impedance of the second section 12 is Z ｂ In addition, when the first section 11 and the second section 12 are not subjected to an external force, the amplitude of the reflected wave is V ０ is.

[0147] The measuring device 3 measures the time width and amplitude of the reflected wave from the pressure sensor 1 and converts it into the magnitude of the external force applied to the pressure sensor 1 .

[0148] The measurement device 3 includes a measurement unit 31 , a storage unit 32 , and an output unit 33 .

[0149] The measurement unit 31 is a control unit that inputs an arbitrary voltage wave to the pressure sensor 1 and measures the time width and amplitude of the reflected wave from the pressure sensor 1. The measurement unit 31 is realized by, for example, a processor. That is, the processor executes a program stored in a memory, thereby performing various functions of the measurement unit 31. The measurement unit 31 also includes a waveform output unit 311, an A / D conversion unit 312, and a processing unit 313.

[0150] The waveform output unit 311 inputs an arbitrary voltage wave (for example, a pulse voltage) to the pressure sensor 1 .

[0151] The A / D conversion unit 312 converts an analog signal indicating the time width and amplitude of the reflected wave from the pressure sensor 1 into a digital signal and measures it. The A / D conversion unit 312 also stores the converted digital signal in the storage unit 32.

[0152] The processing unit 313 generates waveform data indicating voltage fluctuations over time from the digital signal stored in the memory unit 32. The processing unit 313 determines whether the pressure sensor 1 is subjected to an external force based on whether the measured time width corresponds to the positional relationship of the conversion coefficient. Specifically, the processing unit 313 determines from the waveform data whether the voltage fluctuation is caused by an external force acting on the pressure sensor 1 or by a change in the shape of the pressure sensor 1, using the time width of the reflected wave calculated from the lengths of the first section 11 and the second section 12. Furthermore, if the processing unit 313 determines that the voltage fluctuation is caused by an external force, it calculates the magnitude of the external force acting on the pressure sensor 1 from the waveform data using a conversion table indicating the relationship between the magnitude of the voltage and the magnitude of the external force. The time width of the reflected wave calculated from the lengths of the first section 11 and the second section 12 and the conversion table are created in advance and stored in the memory unit 32.

[0153] The storage unit 32 stores various types of information and programs, and is realized by a memory or the like.

[0154] The output unit 33 outputs at least one of the results of the cause of the voltage fluctuation determined by the processing unit 313 and the magnitude of the external force calculated by the processing unit 313 to a display unit (not shown).

[0155] [Operation] Next, the operation of the pressure detection device 4 will be described with reference to Figs. 18 and 19. Fig. 18 is a flowchart showing how the pressure detection device 4 identifies the magnitude of an external force from data related to reflected waves. Fig. 19 is a diagram showing an example of analysis of waveform data obtained in step S2 of Fig. 18. Fig. 19(a) is a diagram showing waveform data when the pressure sensor 1 is deformed. Fig. 19(b) is a diagram showing waveform data when the pressure sensor 1 is subjected to an external force.

[0156] First, the waveform output unit 311 inputs a pulse voltage to the pressure sensor 1, and the A / D conversion unit 312 measures the time width and amplitude of the reflected wave from the pressure sensor 1 by converting the analog signal into a digital signal, and stores the digital signal in the memory unit 32 (step S1).

[0157] The processing unit 313 generates waveform data from the digital signal stored in the storage unit 32 and analyzes the time width of the reflected wave indicated in the waveform data (step S2). The processing unit 313 analyzes the time width of the reflected wave indicated in the waveform data using a conversion table.

[0158] The processing unit 313 determines whether the voltage fluctuation is due to an external force, such as pressure from the surroundings, applied to the pressure sensor 1, or due to a change in the shape of the pressure sensor 1, such as bending, based on the time width of the reflected wave analyzed in step S2 (step S3). An example of the analysis performed by the processing unit 313 will now be described with reference to FIG. 19. Note that the 2T １ and 2T ２ Each of the double-headed arrows indicated by the arrows 11 and 12 indicates the time width of the reflected wave calculated from the lengths of the first section 11 and the second section 12.

[0159] As shown in FIG. 19(a), when the amplitude of the reflected wave is V ０ The time width of the section where the pressure sensor 1 is deviated from the reference value (i.e., the pressure sensor 1 is under load) is 2T １ and 2T ２ In other words, the waveform data indicates that the characteristic impedance in the first section 11 and the second section 12 is changing. Therefore, the waveform data corresponds to the measurement result shown in FIG. 5B. In such a case, the processing unit 313 analyzes that the time widths shown in the waveform data do not match the time widths indicated by the double arrows, and therefore determines that the voltage fluctuation is caused by a change in the shape of the pressure sensor 1, such as curvature.

[0160] As shown in FIG. 19(b), when the amplitude of the reflected wave is V ０ The time width of the section that is out of sync is 2T １ The amplitude of the reflected wave is V ０ The amplitude of the reflected wave is V ０ The time width of the section is 2T ２In other words, the waveform data indicates that the characteristic impedance in the first section 11 is changing, and that the characteristic impedance in the second section 12 is not changing. Therefore, the waveform data corresponds to the measurement result shown in FIG. 5(c). In such a case, the processing unit 313 analyzes that the time widths shown in the waveform data match the time widths indicated by the double-headed arrows, and therefore determines that the voltage fluctuations are caused by an external force, such as pressure from the surroundings, applied to the pressure sensor 1.

[0161] Returning to the explanation of FIG. 18, if the processing unit 313 determines in step S3 that the voltage fluctuation is caused by a change in the shape of the pressure sensor 1, such as bending, the measurement device 3 ends its operation.

[0162] If the processing unit 313 determines in step S3 that the voltage fluctuation is due to an external force such as pressure on the pressure sensor 1 from the surroundings, the processing unit 313 calculates the magnitude of the external force applied to the pressure sensor 1 by referring to the conversion table (step S4). １ The processing unit 313 converts the peak value of the amplitude into the magnitude of the external force over a time width of 1 / 2. When a plurality of first sections 11 are subjected to an external force, the processing unit 313 may output all of the magnitudes of the external force calculated for each first section 11 to the output unit 33, or may output only the largest value of the magnitudes of the external force calculated for each first section 11 to the output unit 33. Furthermore, the processing unit 313 may output information related to the position at which the pressure sensor 1 is subjected to the external force.

[0163] [Effects] As described above, the pressure detection device 4 according to this embodiment includes the pressure sensor described in any one of the first to third embodiments, and the measurement unit 31 that inputs an arbitrary voltage wave to the detection unit and measures the time width and amplitude of the reflected wave from the detection unit.

[0164] With this configuration, the pressure detection device 4 can measure the change in the characteristic impedance of the pressure sensor as the time width and amplitude of the reflected wave.

[0165] Furthermore, in the pressure detection device 4 according to this embodiment, the measurement unit 31 determines whether the detection unit is subjected to an external force based on whether the measured time width corresponds to the positional relationship of the conversion coefficients.

[0166] With this configuration, the pressure detection device 4 can determine whether the amplitude of the reflected wave from the pressure sensor is due to an external force such as pressure from the surrounding area on the pressure sensor, or due to a change in the shape of the pressure sensor, such as bending.

[0167] Furthermore, in the pressure detection device 4 according to this embodiment, the measurement unit 31 calculates the magnitude of the external force that the detection unit receives from the measured time width and amplitude.

[0168] With this configuration, the pressure detection device 4 can identify the magnitude of an external force, such as a pressure, that the pressure sensor receives from the surroundings.

[0169] [Modifications] While the pressure sensor and pressure detection device according to the present disclosure have been described above based on the above-described embodiment, the present disclosure is not limited to the above-described embodiment. As long as they do not deviate from the spirit of the present disclosure, various modifications conceivable by those skilled in the art to the above-described embodiment and configurations constructed by combining components of different embodiments may also be included within the scope of one or more aspects.

[0170] In addition, the present disclosure also includes forms obtained by applying various modifications to the above-described embodiments that would occur to those skilled in the art, and forms realized by arbitrarily combining the components and functions of the embodiments within the scope of the present disclosure. Furthermore, the present disclosure also includes any combination of two or more claims from among the multiple claims set forth in the claims at the time of filing, within the scope of technical compatibility. For example, when a dependent claim set forth in the claims at the time of filing is made into a multiple claim or multiple multiple claims that cite all of the superordinate claims within the scope of technical compatibility, the present disclosure also includes all combinations of claims included in that multiple claim or multiple multiple multiple claims.

[0171] In the above embodiments, each component may be configured with dedicated hardware, or may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

[0172] Furthermore, some or all of the functions of the pressure detection device according to the above-described embodiment may be realized by a processor such as a CPU executing a program.

[0173] Some or all of the components constituting each of the above devices may be configured as an IC card or a standalone module that can be attached to or detached from each device. The IC card or module is a computer system composed of a microprocessor, ROM, RAM, etc. The IC card or module may include a super multi-function LSI. The IC card or module achieves its functions when the microprocessor operates in accordance with a computer program. The IC card or module may be tamper-resistant.

[0174] A pressure sensor according to the present disclosure is useful, for example, as a sensor for identifying the magnitude of an external force.

[0175] 1, 1a, 1b, 1c, 1d Pressure sensor 11 First section 111, 121, 131, 141 First conductor 112, 122, 132, 142 Dielectric 113, 123, 133, 143 Second conductor 12 Second section 13 Third section 14 Fourth section 21 Thin metal wire 22, 25 Conductive rubber 23 Dielectric coating 24 Dielectric rubber 26 Tungsten wire 27 Heat shrinkable material 3 Measuring device 31 Measuring section 311 Waveform output section 312 A / D conversion section 313 Processing section 32 Memory section 33 Output section 4 Pressure detection device 5 Cable 6 Vector network analyzer 7 Metal

Claims

1. A pressure sensor comprising a detection unit that is elongated in one direction and has a flexible structure that is capable of stretching and bending, wherein the detection unit has a conversion coefficient that is an index showing the ease of change when the characteristic impedance changes depending on the cross-sectional shape of the detection unit when viewed from the longitudinal axis direction, and the conversion coefficient has different values ​​in multiple sections in the longitudinal axis direction.

2. A pressure sensor as described in claim 1, wherein the detection section has a first section and a second section having different conversion coefficients, the first section and the second section are both composed of a plurality of conductors and one or more dielectrics, and the Young's modulus of the dielectric in the first section is smaller than the Young's modulus of the dielectric in the second section.

3. The pressure sensor according to claim 2, wherein in both the cross section in the first section and the cross section in the second section, the first conductor, the dielectric, and the second conductor are concentrically stacked from the inside out.

4. The pressure sensor according to claim 3, wherein the material having the smallest Young's modulus in the cross section in the first section is included in the dielectric, and the material having the smallest Young's modulus in the cross section in the second section is included in the second conductor.

5. The pressure sensor according to claim 1, wherein the detection section has a third section and a fourth section having different conversion coefficients, each of the third section and the fourth section being composed of a plurality of conductors and one or more dielectrics, and in both the cross section in the third section and the cross section in the fourth section, the first conductor, the dielectric, and the second conductor are concentrically stacked from the inside out, and the radius obtained from the cross section in the third section is larger than the radius obtained from the cross section in the fourth section.

6. The pressure sensor according to claim 5, further comprising a heat shrink material covering the detection portion.

7. A pressure detection device comprising: a pressure sensor according to any one of claims 1 to 6; and a measurement unit that inputs an arbitrary voltage wave to the detection unit and measures the time width and amplitude of the reflected wave from the detection unit.

8. The pressure detection device according to claim 7, wherein the measurement unit determines whether the detection unit is subjected to an external force based on whether the measured time width corresponds to the positional relationship of the conversion coefficient.

9. The pressure detection device according to claim 8, wherein the measurement unit calculates the magnitude of the external force applied to the detection unit from the measured time width and amplitude.

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