JP2008082712A - Pressure sensor element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure sensor element simple in constitution, and easy in manufacturing. <P>SOLUTION: The pressure sensor element 10 is provided with an insulation substrate 11, a wire conductor 12 of copper laid down on the insulation substrate 11, and the like. The wire conductor 12 is laid down while meandering on the insulating substrate 11. On the rear surface of the insulating substrate 11, the ground plate 14 of copper etc., is bonded. On the insulating substrate 11, a medium 16 forming the conductor periphery medium to the wire conductor 12 is bonded. The medium 16 is constituted of a base material 17 of dielectric elastic resign or elastomer, and the minute coiled carbon dispersed in the base material 17 and fibers 18. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pressure sensor element for detecting, for example, a position where a pressure is applied and an intensity of the pressure when a pressure is applied to the planar pressure detection surface from the outside.

Conventionally, a planar pressure sensor element capable of simultaneously detecting a position where pressure is applied and its strength as described above is configured by two-dimensionally arraying a plurality of pressure detectors (for example, Patent Documents 1, 2, 3, etc.). And the output signal of each pressure detection part is taken out outside through the some wiring formed in matrix form, in order to pinpoint the position.
JP-A-8-327474 Japanese Patent Laid-Open No. 10-38720 JP 2001-287189 A

  However, in the conventional pressure sensor element described above, it is necessary to increase the number of pressure detection units in order to increase the pressure detection area or increase the detection resolution. Not only that, but the number of wires for taking out the output signal of each pressure detection unit to the outside also increases, making the configuration complicated and making it difficult to manufacture.

  The present invention has been made paying attention to such problems existing in the prior art. The object is to provide a pressure sensor element that is simple in construction and easy to manufacture.

  In order to achieve the above object, an invention according to claim 1 is provided with a line conductor and a peripheral medium provided around the line conductor so as to form a conductive path together with the line conductor. When at least one of the line conductor and the surrounding medium is deformed by an external pressure in a state where a drive signal is applied to the input end, depending on the position and degree of deformation at the input end and the output end of the line conductor. It is characterized in that it is configured to output a signal having a different waveform.

  In this invention, when pressure is applied from the outside to any position of the sensor element so that at least one of the line conductor and the surrounding medium is deformed, the deformation of at least one of the line conductor and the surrounding medium At least one of the primary distribution constants (inductance, capacitance, resistance, and conductance per unit length) at the deformation position varies depending on the degree of deformation. This change is reflected in the signals at the input end and the output end with respect to the drive waveform applied to the input end of the line conductor. Then, the position where the pressure is applied and its strength are obtained from the measured values of the signals at the input end and the output end. Therefore, the position where the pressure is applied and the strength of the pressure can be detected by the pressure sensor element having a simple configuration in which the line conductor and the peripheral medium are combined. Therefore, a pressure sensor that is simple in configuration and easy to manufacture is realized.

  The invention according to claim 2 has a distributed constant line composed of a line conductor and a peripheral medium of the line conductor, and the line conductor by pressure applied to at least one of the line conductor and the peripheral medium, and It is characterized in that at least one of the primary distributed constants on the line conductor is changed at a position where the same pressure is applied by deformation of at least one of the surrounding media. Here, the primary distribution constant means an inductance L, a capacitance C, a resistance R, and a conductance G per unit length.

  In the present invention, when pressure is applied to an arbitrary position, at least one of the first-order distribution constants of the line conductor at that position changes. The position on the line conductor in which at least one of the primary distributed constants is changed can be obtained based on the input end signal and the output end signal of the line conductor with respect to a predetermined drive signal. Therefore, it is possible to grasp the position where the pressure is applied from the change position of the primary distribution constant. Further, by grasping in advance the relationship between the intensity of the pressure, that is, the amount of change of at least one of the primary distribution constants with respect to the degree of deformation, the intensity of the actually applied pressure is grasped. The first-order distributed constant along the line conductor may be a lossless line that does not include resistance and conductance as loss, or may be a loss line that includes at least one of resistance and conductance as loss. Good.

The invention described in claim 3 is characterized in that, in addition to the invention described in claim 1 or 2, the line conductor is sandwiched between an insulating substrate and the peripheral medium.
In the present invention, it is only necessary to sandwich the line conductor between the insulating substrate and the peripheral medium, and the pressure sensor element can be easily manufactured with a simple configuration.

  According to a fourth aspect of the present invention, in addition to the first aspect of the present invention, the peripheral medium includes an inductance (L) component, a capacitance (C) component, and a capacitance based on a coil shape. A coiled carbon fiber that has a resistance (R) component and functions as an LCR resonance circuit is dispersed in a dielectric base material.

  In this invention, when the medium is compressed by pressure, the medium and the coiled carbon fiber in the medium are deformed. For this reason, the electrical constant (magnetic permeability μ, dielectric constant ε, conductivity σ) in the medium changes, and as a result, out of the primary distribution constants (inductance L, capacitance C, resistance R, and conductance G per unit length). At least one changes. Therefore, the position where the pressure is applied and its strength are detected by detecting the change of the first-order distribution constant on the line conductor.

  The present invention has an effect that the structure is simple and the manufacture is easy as the pressure sensor element.

(First embodiment)
Next, a first embodiment embodying the present invention will be described with reference to FIGS.
As shown in FIG.1 and FIG.2, the pressure sensor element 10 of this 1st Embodiment has comprised flat form as a whole. On a flat insulating substrate 11 made of ceramic or synthetic resin, a single line conductor 12 made of bare copper or aluminum is laid in a meandering manner. Both ends of the line conductor 12 are drawn out of the insulating substrate 11 and connected to the first input terminal 13a and the first output terminal 13b, respectively.

  A ground plate 14 made of a conductor such as copper or aluminum is bonded and fixed to the lower surface of the insulating substrate 11. A second input terminal 15a and a second output terminal 15b are connected to the side surfaces of the ground plate 14, respectively.

  A peripheral medium (hereinafter simply referred to as a medium) 16 that forms a conductive path and a distributed constant line together with the line conductor 12 is bonded and fixed to the upper surface of the insulating substrate 11. The medium 16 is composed of a base material 17 made of dielectric elastic resin or elastomer, and minute coiled carbon fibers 18 dispersed in the base material 17.

  As the elastic resin forming the base material 17, for example, a silicone resin, a urethane resin, an epoxy resin, a copolymer resin of styrene and a thermoplastic elastomer, or the like can be used. As the coiled carbon fiber 18, at least one of a single-winding coil, a double-winding coil, and a superelastic coil is used. The content of the coiled carbon fiber 18 in the base material 17 is 1 to 20% by mass.

  The single-winding coiled carbon fiber 18 is configured to have, for example, a wire diameter of 1 nm to 1 μm, a coil diameter of 1 nm to 100 μm, a coil helical pitch of 1 nm to 100 μm, and a coil length of 100 μm to 10 mm. ing. From the viewpoint of ease of manufacture and the like, the diameter of the coil is preferably 1 nm to 10 μm, and the helical pitch is preferably 10 nm to 10 μm. Furthermore, the length of the coil is preferably 150 μm or less in order to ensure dispersibility in the base material 17. The double-winding coiled carbon fiber 18 has, for example, a wire diameter of 0.1 to 1 μm, a coil diameter of 0.1 to 50 μm, a helical pitch of almost 0, and a coil length of 0.1 to 10 mm. It is comprised so that it may become. The superelastic coil has a diameter larger than the wire diameter, the coil diameter is 5 to 100 μm, the coil pitch is 0.1 to 10 μm, and the coil length is 0.3 to 5 mm. It is comprised so that. That is, the coiled carbon fiber 18 includes not only a structure in which the carbon fiber is spirally wound but also a structure in which the carbon fiber is simply twisted. In addition, the winding direction of the coiled carbon fiber 18 wound spirally may be either clockwise (right-handed) or counterclockwise (left-handed) around the axis of the coil. In addition, the twisted direction of the coiled carbon fiber 18 having a twisted structure may be either clockwise (right-handed) or counterclockwise (left-handed) around the axis of the wire.

  An equivalent circuit of the medium 16 is shown in FIG. Each coiled carbon fiber 18 has an impedance based on the coil shape. This impedance consists of an inductance (L) component, a capacitance (C) component, and a resistance (R) component. Accordingly, each coiled carbon fiber 18 constitutes an LCR resonance circuit. The coiled carbon fibers 18 are capacitively coupled to each other in the dielectric base material 17. Therefore, the medium 16 is a complex resonance circuit in which a number of LCR resonance circuits are capacitively coupled.

Next, the detection principle of the position where the pressure is applied in the pressure sensor element 10 and the strength of the pressure will be described using a model shown in FIGS. 4 and 5 in which the pressure sensor element 10 is simplified.
4 and 5 show the pressure sensor element 10 having a configuration in which the linear line conductor 12 is formed on the band-shaped insulating substrate 11 and the line conductor 12 is covered with the band-shaped medium 16. . That is, in the pressure sensor element 10, the upper surface of the medium 16 is the pressure detection surface 19. Therefore, the pressure sensor element 10 is configured to detect the position and strength when pressure is applied to the linear region along the line conductor 12. In other words, the pressure sensor element 10 is configured by a uniform loss line having a constant primary distribution constant (inductance L, capacitance C, resistance R, conductance G per unit length) on the linear line conductor 12. . The primary distribution constant on the line conductor 12 includes the structure (width, thickness, etc.) and electric constant (conductivity σ) of the line conductor 12, and the structure (cross-sectional shape, medium 16 and line conductor 12) of the medium 16. And the electric constants (permeability μ 1, permittivity ε, conductivity σ) of the medium 16.

  The pressure sensor element 10 is applied with a drive signal (for example, a step signal) S0 from the drive device 20 between the first and second input terminals 13a and 15a in the electrical configuration as shown in FIG. Then, between the first and second input terminals 13a and 15a in the pressure sensor element 10, an input end signal S1 based on the drive signal in the line conductor 12 and its reflection appears. An output terminal signal S2 that has passed through the line conductor 12 appears between the first and second output terminals 13b and 15b. The input terminal signal S1 is measured by a measuring instrument 21 connected between the first and second input terminals 13a and 15a. The output terminal signal S2 is measured by the measuring instrument 22 connected between the first and second output terminals 13b and 15b. Then, when pressure is applied to the pressure detection surface 19 (illustrated in FIG. 5) on the upper surface of the medium 16, the pressure sensor element 10 determines from the measured values indicating the waveform patterns of the input end signal S1 and the output end signal S2. The position where the pressure is applied and the strength of the pressure can be detected.

  More specifically, as shown in FIG. 6, when pressure is applied to an arbitrary position x on the pressure detection surface 19 on the medium 16 in the pressure sensor element 10, the line conductor 12 at the position x is shown. At least one of the first-order distribution constants of. This is because, when the medium 16 is compressed at the position x, the medium 16 and the coiled carbon fiber 18 at the position x are deformed, and the electric constants of the medium 16 (permeability μ, dielectric constant ε, conductivity σ). This is because of changes. In the medium 16, the coiled carbon fiber 18 is deformed according to the degree of deformation of the medium 16, that is, the amount of compression. This deformation changes the electrical constant, and as a result, the primary distribution constant (inductance L, capacitance C, resistance R, and conductance G per unit length) changes. Since this pressure sensor only needs to detect a change in at least one of the primary distribution constants, attention is paid to the resistance R (x) here. The electrical conductivity σ of the electrical constant is significantly increased. Therefore, in the pressure sensor element 10, the resistance R (x) of the primary distribution constant is remarkably reduced with respect to the applied pressure, and the conductance G (x) is remarkably increased. The graph of FIG. 6 shows a state in which the resistance R (x) at the position x is changed by the pressure applied to the position x of the pressure sensor element 10. Therefore, pressure was applied by determining the position x where the resistance R (x) changed from the input terminal signal S1 between the input terminals 13a and 15a and the output terminal signal S2 between the output terminals 13b and 15b. The position x is known. Furthermore, the strength of the applied pressure can be grasped by obtaining in advance the relationship between the strength of the pressure indicating the degree of deformation and the amount of change in the resistance R (x).

  Next, from the input terminal signal S1 between the first and second input terminals 13a and 15a and the output terminal signal S2 between the first and second output terminals 13b and 15b, the primary on the line conductor 12 of the medium 16 is obtained. A method for obtaining the distribution constant will be described.

  As described above, the pressure sensor element 10 causes the line conductor 12 to meander on the insulating substrate 11. As a result, the line conductor 12 is arranged in a substantially planar shape, and the position and strength can be accurately detected regardless of the pressure applied to any position on the pressure detection surface 19 of the medium 16. .

  In the loss non-uniform line modeled as shown in FIG. 7, primary distribution constants L (x), C (x), R (x), G that change depending on the position of the line conductor 12 in the length direction are different. (X) is incorporated into the relational expressions (1) and (2) by using the position V on the line conductor 12, the voltage V (x, t) at the time t, and the current I (x, t).

また、その境界条件は、関係式（３），（４）のように表される。

The boundary condition is expressed as in relational expressions (3) and (4).

ここで、ｅ_ｓ（ｔ）は、第１及び第２入力端子１３ａ，１５ａ間に印可される駆動電圧である。また、ｒ_ｓは、駆動電源の内部抵抗であり、ｒ_ｌは、第１出力端子１３ｂと第２出力端子１５ｂとの間の出力端抵抗である。なお、駆動電圧ｅ_ｓ（ｔ）は、前記駆動信号Ｓ０を表している。また、第１及び第２入力端子１３ａ，１５ａ間の電圧Ｖ（０，ｔ）は、前記入力端信号Ｓ１の電圧を表し、第１及び第２出力端子１３ｂ，１５ｂ間の電圧Ｖ（ｌ，ｔ）は、前記出力端信号Ｓ２の電圧を表している。

Here, e _s (t) is a drive voltage applied between the first and second input terminals 13a and 15a. Further, _{r s} is an internal resistance of the driving power source, _{r l} is the output resistance between the first output terminal 13b and the second output terminal 15b. The drive voltage e _s (t) represents the drive signal S0. The voltage V (0, t) between the first and second input terminals 13a, 15a represents the voltage of the input terminal signal S1, and the voltage V (l, l) between the first and second output terminals 13b, 15b. t) represents the voltage of the output terminal signal S2.

By the way, deriving an expression for obtaining each primary distribution constant L (x), C (x), R (x), G (x) from the above relational expressions (1) to (4) is related to the relational expression (1 ) To (4) are difficult because they cannot be solved analytically. Therefore, as shown in FIGS. 8A to 8C, the voltages V (0, t) and V (l, t) when the predetermined drive voltage e _s (t) is actually input are input. An approximate value of the primary distribution constant (L (x), C (x), R (x), G (x)) on the line conductor 12 is obtained by using a measurement value with time (for example, every δt). That is, when the measured values of the voltages V (0, t) and V (l, t) are substituted into the relational expressions (1) and (2), the relational expressions (1) and (2) are established. The approximate values are assumed to be primary distribution constants.

  And by the said method, the approximate value of the primary distribution constant on the line conductor 12 in the state where the pressure is not applied to the pressure detection surface 19 of the pressure sensor element 10, and the same primary distribution in the state where the pressure is applied Find the approximate value of the constant. Next, a position x where the value of the primary distribution constant has changed is determined from the approximate values of the two primary distribution constants on the line conductor 12. Further, by knowing in advance the correspondence between the position x on the line conductor 12 and the two-dimensional position on the pressure detection surface 19, the position where pressure is applied on the pressure detection surface 19 can be obtained. it can. Furthermore, the actual strength of the pressure can be obtained by obtaining in advance the relationship between the strength of the pressure applied to the pressure detection surface 19 and the amount of change in the primary distribution constant with respect to this strength.

The embodiment described above in detail has the following effects.
(1) In the pressure sensor element 10, when pressure is applied to the medium 16 at an arbitrary position x, at least one of the first-order distribution constants on the line conductor 12 changes at the position x. The position x of the line conductor 12 at which at least one of the primary distributed constants is changed, that is, the position in the length direction of the line conductor 12 is a change in the input end signal and the output end signal with respect to application of a predetermined drive signal. It is requested from. From this position x, the position where pressure is actually applied on the pressure detection surface 19 is grasped. Furthermore, by grasping in advance the relationship of the change amount of the primary distribution constant to the strength of the pressure, the strength of the pressure can be grasped from the change amount of the primary distribution constant. Accordingly, a pressure sensor having a simple configuration in which a position where pressure is applied on the plane and the strength of the pressure are combined with a single line conductor 12 made of copper or the like and a medium 16 made of a dielectric material. It can be detected by the element 10. Therefore, the pressure sensor element 10 having a simple configuration and easy manufacture can be realized. The pressure sensor and the sensor element 10 can be used for an input device of a computer, for example.

  (2) One line conductor 12 meandered on the insulating substrate 11, and the pressure sensor element 10 was formed in a planar shape as a whole. Then, the position where the pressure is applied on the plane where the line conductor 12 is laid is obtained from the position x where the pressure is applied on the line conductor 12. Therefore, unlike a conventional planar pressure sensor, it does not have a configuration in which a large number of pressure detection units are arrayed, so that the configuration becomes complicated even if the pressure detection area is increased or the detection resolution is increased. There is no. Therefore, manufacture of the pressure sensor element 10 becomes easy.

(3) Since the line conductor 12 has a simple configuration in which the line conductor 12 is simply sandwiched between the insulating substrate 11 and the medium 16, the pressure sensor element 10 can be easily manufactured.
(4) The medium 16 was formed by dispersing the coiled carbon fiber 18 functioning as an LCR resonance circuit in a dielectric base material 17. For this reason, the electric constant changes due to deformation based on the pressure applied to the medium 16, and as a result, the primary distribution constants (inductance L, capacitance C, resistance R, and conductance G per unit length) change. Focusing on the conductivity σ of the electrical constant, the conductivity σ changes, and as a result, the resistance R and the conductance G change. Therefore, by detecting the change of the resistance R on the line conductor 12, it is possible to detect the position where the pressure is applied and its strength.

(Second Embodiment)
Next, a second embodiment embodying the present invention will be described with reference to FIG. A description will be given centering on differences from the first embodiment.

  As shown in FIG. 9, the line conductor 12 is laid in a spiral shape on the upper plane of the insulating substrate 11. The first end of the line conductor 12 is connected to the first input terminal 13 a, and the second end of the line conductor 12 passes through the insulating substrate 11 and the ground plate 14 from the center of the spiral line conductor 12 and is below the ground plate 14. To the first output terminal 13b. The line conductor 12 and the ground plate 14 are insulated by, for example, an insulating film formed on the inner peripheral surface of the through hole of the ground plate 14.

This embodiment configured as described above also exhibits the same operations and effects as the first embodiment.
(Third embodiment)
Next, a third embodiment embodying the present invention will be described with reference to FIG. 10 focusing on differences from the first embodiment.

  As shown in FIG. 10, the line conductor 12 is laid so as to meander in the upper plane of the insulating substrate 11 as in the first embodiment. A ground line 30 that snakes in a positional relationship parallel to the line conductor 12 is laid on the upper plane of the insulating substrate 11. The ground line 30 replaces the ground plate 14, and the ground plate 14 is abolished.

  In this embodiment configured as described above, similarly to the first embodiment, the medium 16 is elastically deformed by the pressure applied to the pressure detection surface 19, and the electric constant is changed by this elastic deformation. , Primary distribution constants (inductance L, capacitance C, resistance R, and conductance G per unit length) change. Focusing on the electrical conductivity σ of the electrical constant, the electrical conductivity σ changes significantly, and the resistance R (x) and the conductance G (x) change significantly as the electrical conductivity σ changes. Therefore, by detecting the change in the resistance R (x) or the conductance G (x), the position where the pressure is applied and the strength thereof can be obtained.

This embodiment has the following effects in addition to the effects (1) to (4) of the first embodiment.
(5) Instead of providing the ground plate 14 below the insulating substrate 11, the ground line 30 was similarly laid along the line conductor 12 laid on the insulating substrate 11. For this reason, less material is used as the ground.

(Other embodiments)
In addition, this embodiment can also be changed and embodied as follows.
-In 1st or 2nd embodiment, the pressure sensor element 10 whole is formed in the curved shape used as convex shape or concave shape. According to such a configuration, the pressure sensor element 10 having the curved pressure detection surface 19 can be obtained. Therefore, in such a configuration, it is possible to detect the position where the pressure is applied on the curved surface and its strength. Therefore, unlike the conventional flat pressure sensor, a configuration for detecting the pressure applied on the curved surface can be easily realized, and the range of use is expanded. For example, it can be used for a tactile sensor of a curved robot arm or a human body detection sensor of a care device such as a curved backrest of a wheelchair.

As shown in FIG. 5, the line conductor 12 is embodied in a pressure sensor element 10 having a linear shape.
The present invention is not provided with the coiled carbon fiber 18 and elastically deforms by pressure so that the dielectric constant of the electrical constant is largely changed, for example, a material such as a polytetrafluoroethylene foam is used as the medium 16. The pressure sensor element used is embodied. In this case, the capacitance C as the first-order distribution constant greatly changes due to the elastic deformation of the medium 16 with respect to the pressure.

The technical idea that can be grasped from the above embodiment will be described below.
(1) In the pressure sensor element according to claim 1 or 2, the line conductor is meandered. According to such a configuration, the line conductor is laid almost in a plane, and the detection area of the pressure sensor element can be expanded.

  (2) In the pressure sensor element according to claim 1 or 2, the line conductor is spirally wound. According to such a configuration, the line conductor is laid almost in a plane, and the detection area of the pressure sensor element can be expanded.

  (3) The pressure sensor element according to any one of claims 1 to 3, wherein the pressure sensor element is formed in a flat plate shape as a whole. According to such a configuration, the pressure sensor element configured in this way is suitable as a sensor installed on the flat surface portion.

  (4) The pressure sensor element according to any one of claims 1 to 3, wherein the pressure sensor element is formed in a curved plate shape as a whole. According to such a configuration, the pressure sensor element configured in this manner is suitable as a sensor installed on the curved surface portion.

The perspective view which shows the pressure sensor element of 1st Embodiment. Similarly disassembled perspective view. The equivalent circuit diagram of a medium. The schematic diagram which shows the electrical constitution of a pressure sensor element. The disassembled perspective view which shows the model which simplified the pressure sensor element. The graph which shows the change state of a primary distribution constant when a pressure is applied. Model showing non-uniform lossy line. (A) is a waveform of a drive signal, (b) is an input end waveform, and (c) is a graph showing an output end waveform. The disassembled perspective view which shows the pressure sensor element of 2nd Embodiment. The disassembled perspective view which shows the pressure sensor element of 3rd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Pressure sensor element, 11 ... Insulating substrate, 12 ... Line conductor, 14 ... Ground plate, 16 ... Peripheral medium, 17 ... Base material, 18 ... Coiled carbon fiber, R (x) ... Resistance as a primary distribution constant .

Claims (4)

A line conductor, and a peripheral medium provided around the line conductor so as to form a conductive path together with the line conductor;
In a state where a drive signal is applied to the input end of the line conductor, when at least one of the line conductor and the peripheral medium is deformed by an external pressure, the position deformed at the input end and the output end of the line conductor; A pressure sensor element configured to output a signal having a waveform corresponding to a degree of deformation. A distributed constant line composed of a line conductor and a surrounding medium of the line conductor;
At least one of the first order distributed constants on the line conductor at a position where the pressure is applied by deformation of at least one of the line conductor and the peripheral medium due to pressure applied to at least one of the line conductor and the peripheral medium. A pressure sensor element configured to change one of the two.   The pressure sensor element according to claim 1, wherein the line conductor is sandwiched between an insulating substrate and the peripheral medium.   The peripheral medium has an inductance (L) component, a capacitance (C) component, and a resistance (R) component based on a coil shape, and a coiled carbon fiber functioning as an LCR resonance circuit is dispersed in a dielectric base material. The pressure sensor element according to claim 1, wherein the pressure sensor element is configured as described above.

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