JP2913025B2 - Pressure sensing method and pressure sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor and a pressure sensor for accurately detecting pressure even in an environment where measurement was impossible in the past.

[0002]

2. Description of the Related Art Conventionally, as a pressure sensor, there is a device for detecting a pressure applied to an elastic body by measuring a resistance value of the elastic body mixed with metal powder, and is used for actual pressure measurement. ing.

[0003]

However, the resistance of the elastic body mixed with the metal powder is susceptible to the influence of the environmental temperature and is unstable, and it is necessary to connect lead wires to both ends of the elastic body. However, for example, when the measurement is performed in water, the contact resistance between the elastic body and the lead wire becomes a problem, and it is impossible to perform the measurement itself in a liquid having conductivity.

[0004]

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above-mentioned drawbacks, and has been proposed in view of the demands of the prior art. And an eddy current coil disposed adjacent to the pressure sensation section. When a high frequency signal is supplied to the eddy current coil to generate an eddy current in the pressure sensation section, the pressure sensation section is pressurized. And a pressure sense detection method for detecting the pressure required for the pressurization from the eddy current loss.

[0005] The present invention also provides a pressure sensation portion made of an elastic material that is an insulating material mixed with metal powder, an eddy current coil disposed adjacent to the pressure sensation portion, and a high frequency signal applied to the eddy current coil. A pressure sensor that detects a pressure required for the pressurization when the pressure sensation unit is pressurized from a change in eddy current loss generated in the pressure sensation unit by the transmission unit. To provide.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram illustrating a detection unit according to an embodiment of the present invention. In the drawing, reference numeral 1 denotes a sensor probe, 1a denotes an elastic body, and the elastic body 1a has a metal powder mixed therein, except for a part where one end protrudes from the case 1c as a pressure detecting surface 1a '. It is contained in case 1c. 1b is an eddy current coil, and the eddy current coil 1b is in contact with the elastic body 1a and the case 1c.
Wires 1 at both ends of the eddy current coil 1b
Only b 'is led out of case 1c.

The elastic body 1a has, for example, an appropriate viscoelasticity and a particle diameter of 10 to 100 in silicon rubber as an insulating member.
It is a compound in which nickel-iron magnetic alloy powder of about μm is mixed in about 10 to 40% by volume, and in particular, those containing 20% by volume of nickel-iron magnetic alloy powder are:
It turned out to be most suitable for practical use. The composition of the alloy is shown in Table 1, the physical properties of the elastic body 1a are shown in Table 2, and the properties of the sensor probe 1 are shown in Table 3.

[0008]

[Table 1]

[0009]

[Table 2]

[0010]

[Table 3]

The eddy current coil 1b receives a high-frequency signal from a transmitter, which will be described later, and the density of the metal particles in the elastic body 1a increases due to the contraction of the elastic body 1a due to the external pressure. And the impedance of the eddy current coil 1b increases and appears as an output signal. That is, an output corresponding to the load (pressure) on the elastic body 1a appears.

FIG. 2 shows the structure of a pressure sensor according to the present invention. A sensor probe 1 forms a part of a transmitter 2 to which a carrier wave of 300 KHz is constantly applied. , A signal component is extracted in the detector 3, and the output is further output by the linearizer 4.
The voltage is converted so that a voltage output proportional to the pressure applied to the sensor probe 1 is obtained. The DC offset component of the voltage is removed by the offset compensator 5, and the voltage is amplified by the amplifier 6 and output.

FIG. 3 shows an evaluation device of the pressure sensor according to the present embodiment. In FIG. 3, an elastic body 1a is disposed in contact with a spacer 9 mounted on a load cell 8 as a part of an evaluation device 7. , Shift adjuster 7 of evaluation device 7
By operating a, the load on the elastic body 1a is measured by the standard load cell 8. The elastic body 1a
The amount of length variation due to compression of the dial indicator 10
It is configured to be able to measure with.

FIG. 4 shows the characteristics of the elastic body 1a obtained by using the evaluation device 7 described above. FIG. 4 shows the pressure applied to the elastic body 1a and the amount of strain associated therewith. ● shows the value when the load is increased, and ○ shows the value when the load is reduced. . Note that the strain amount does not match when the load increases and when the load decreases, which is due to the hysteresis characteristic of the elastic body 1, and is a characteristic that is originally not preferable as a sensor.

FIG. 5 shows the output voltage of the pressure sensor when the elastic body 1a is incorporated into the sensor probe 1 and when the elastic body 1a is pressurized and depressurized. ○ indicates the characteristics at the time of pressure reduction.

At this time, the output voltage of the pressure sensor also has a hysteresis characteristic. However, the characteristic at the time of pressure reduction is not a problem since it is often unnecessary in view of the function required of the pressure sensor. When detecting a sense of pressure with a manipulator or the like, the hysteresis characteristic becomes a problem when grasping an object, and in this case, calibration of the linearizer 4 is performed based on the movement of the manipulator. What is necessary is just to prepare two types and to use properly according to operation.

As described above, the present invention has been described based on the embodiments described in the drawings. However, the present invention is not limited to the above-described embodiments, but may be modified in any manner unless the structure described in the claims is changed. But it can be implemented. For example, if an active sensor that bears a load and a dummy sensor that does not bear a load are provided and the output difference between the two sensors is obtained,
Temperature compensation can be easily performed.

[0018]

In summary, according to the present invention, since the pressure sensor is constituted by combining the elastic body containing the metal powder and the eddy current coil, the whole device is small and the sensitivity is good. It has excellent environmental resistance characteristics, fast response speed, low production cost and similar cost, and can be mass-produced, so it can be applied to, for example, a tactile sensor for the finger of a robot arm. High value.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a sensor probe in a pressure sensor according to an embodiment of the present invention.

FIG. 2 is a schematic block diagram illustrating a pressure sensor according to an embodiment of the present invention.

FIG. 3 is a schematic side view illustrating a configuration of an evaluation device for a pressure sensor according to an embodiment of the present invention.

FIG. 4 is a characteristic diagram showing pressure and strain applied to an elastic body in the pressure sensor according to the embodiment of the present invention.

FIG. 5 is a characteristic diagram showing input / output characteristics of the pressure sensor according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sensor probe 1a Elastic body 1a 'Pressure detection surface 1b Eddy current coil 1b' Wire 1c Case 2 Transmitter 3 Detector 4 Linearizer 5 Offset compensator 6 Amplifier 7 Pressure sensor evaluation device 7a Shift adjuster 8 Load cell 9 Spacer 10 Dial indicator

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-259834 (JP, A) JP-A-3-144329 (JP, A) JP-A-64-24622 (JP, A) JP-A-61- 240132 (JP, A) JP-A-60-58669 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01L 1/14 G01L 9/10

Claims (2)

(57) [Claims] 1. An eddy current coil comprising an elastic body, which is an insulating material mixed with metal powder, and an eddy current coil disposed adjacent to the pressure sensation section, and a high frequency signal is supplied to the eddy current coil. Generating an eddy current in the pressure sensation section, and detecting a pressure required for the pressurization from an eddy current loss when the pressure sensation section is pressurized. 2. A pressure sense portion made of an elastic material that is an insulating material mixed with a metal powder, an eddy current coil disposed adjacent to the pressure sense portion, and a transmitter for applying a high-frequency signal to the eddy current coil. A pressure sensor configured to detect a pressure required for the pressurization when the pressure sensation unit is pressurized from a change in eddy current loss generated in the pressure sensation unit by the transmission unit. .