JPH11304604A - Sensor and sensor device using magnetostrictor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable to detect a permeability-change of a magnetostrictor by external force pressed to an inductance-change of a coil to realize small size and cost reduction by eliminating a magnetic circuit including a permanent magnet. SOLUTION: A magnetostrictor 1 and at least one coil 2 placed at the surroundings of the magnetostrictor 1 is housed in a casing 30, and strike plates 11, 14, which are concave surface shaped members located at both sides of the magnetostrictor 1 so that weighting is exerted in the center axis direction of the magnetostrictor 1, are placed in the casing 30. Then, a permeability- change of the magnetostrictor 1 by the weighting is detected as an inductance- change of the coil 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor using a magnetostrictive element capable of detecting pressure by measuring a load-inductance characteristic with a slight displacement during pressurization by using a magnetostrictive element and a sensor using the same. The present invention relates to a single sensor device.
Uses include a vibration detecting device, a load (pressure) detecting device, and the like.

[0002]

2. Description of the Related Art A conventional sensor using a magnetostrictive element is disclosed in JP-A-8-320337. A magnetic circuit element using a permanent magnet, a magnetostrictive element and a coil are combined, and the magnetic permeability of the magnetostrictive element is increased by applying an external force. The external force is detected by measuring the induced voltage generated in the coil in the structure with the change.

[0003]

Incidentally, the structure sensor having a magnetic circuit element using a permanent magnet has a problem that the shape becomes large and the cost becomes high.

[0004] A first object of the present invention is to solve the above problems,
Provided is a sensor using a magnetostrictive element, which is capable of detecting a change in the magnetic permeability of the magnetostrictive element due to the application of an external force by converting it into a change in the inductance of a coil, eliminating the need for a magnetic circuit including a permanent magnet, and reducing the size and cost. It is in.

A second object of the present invention is to convert a change in the magnetic permeability of the magnetostrictive element due to the application of an external force into a change in the inductance of a coil, and to convert the change in the inductance into an electric signal (voltage, It is an object of the present invention to provide a sensor and a sensor device using a magnetostrictive element capable of outputting as a current or the like.

[0006] Other objects and novel features of the present invention will be clarified in embodiments described later.

[0007]

In order to achieve the above object, a sensor using a magnetostrictive element according to the present invention comprises a magnetostrictive element and at least one coil disposed around the magnetostrictive element housed in a casing. Then, concave shaped members located at both ends of the magnetostrictive element are provided in the casing so that the weight is applied in the direction of the central axis of the magnetostrictive element, and the change in the magnetic permeability of the magnetostrictive element due to the load is defined as the change in the inductance of the coil. It is configured to detect.

In the sensor using the magnetostrictive element, a preload adjusting mechanism for applying a preload to the magnetostrictive element may be provided in the casing.

Further, a load is applied by bringing spherical or hemispherical members into contact with concave-shaped members on both ends of the magnetostrictive element, respectively, so that the load direction and the central axis direction of the magnetostrictive element coincide with each other. It is good to do so.

The sensor using the magnetostrictive element further includes means for converting a change in inductance of the coil into an output electric signal to the outside, the means comprising: a pulse generating circuit for applying a pulse to the coil; A configuration may be provided that includes a sampling circuit that samples a voltage value at both ends of the coil at a timing delayed by a predetermined time from the application of the pulse, and a circuit that converts the sampled voltage value to an external output electric signal.

The oscillation frequency of the pulse generating circuit is set to 100
Hz to 50 kHz and the number of samplings is 10
A configuration in which the weight change is detected in real time at 0 to 50,000 times / sec can be adopted.

The sensor device according to the present invention is characterized in that the magnetostrictive element and at least one coil disposed around the magnetostrictive element are housed in a casing, and the magnetostrictive element is applied so that a load is applied in the direction of the central axis of the magnetostrictive element. Provided in the casing are concave-shaped members located at both ends of the sensor, and having two sensors using magnetostrictive elements for detecting a change in the magnetic permeability of the magnetostrictive elements due to a load as a change in inductance of the coil, and including these two sensors. The configuration has a differential circuit that outputs the differential output of the sensor as an output electric signal to the outside.

In the above-described sensor device, one of the two sensors may be used as a reference for temperature characteristic compensation without applying an external load.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a sensor and a sensor device using a magnetostrictive element according to the present invention will be described below with reference to the drawings.

A sensor body SR1 of a sensor using a magnetostrictive element will be described with reference to FIGS. In these figures,
Reference numeral 1 denotes a columnar magnetostrictive element such as an Fe—Ni-based magnetostrictive material,
A coil 2 in which a winding 4 is applied to a bobbin 3 is provided around the magnetostrictive element 1. In this case, the cavity 5 is provided between the inner periphery of the bobbin 3 and the magnetostrictive element 1 so that the magnetostrictive element 1 and the coil 2 maintain a non-contact state. Alternatively, no stress is applied to the bobbin 3.

A disc-shaped elastic plate 10 made of phosphor bronze or the like and a pressure receiving seat 11 made of hardened steel are provided on one end face of the magnetostrictive element 1 and the coil 2, and a contact member made of stainless steel is provided on the other end face. 12, a bottom block 13 made of stainless steel or the like, and a pressure seat 14 made of hardened steel or the like are arranged, and other than the pressure seat 11 are housed in a cylindrical magnetic yoke 20 which also serves as a magnetic shield together with the magnetostrictive element 1 and the coil 2. You. Here, the both ends of the magnetic yoke 20 are swaged to form the disc-shaped elastic plate 10.
Then, the pressure receiving seat 14 is integrated so as not to fall off.

The pressure receiving seat 11 is formed by fitting a cylindrical outer casing 30 made of aluminum or the like to the outside of the cylindrical magnetic yoke 20 and fixing it by bonding or the like. Is held so as to abut against the end face.

The O-ring 35 is used for waterproof and dustproof purposes.
Are provided between the pressure receiving seat 11 and the casing 30, between the bobbin 3 and the elastic plate 10, between the contact member 12 and the bottom block 13, and between the bottom block 13 and the magnetic yoke 20, respectively.

The bottom block 13 is provided with a male screw member 15 made of stainless steel or the like for adjusting a preload so as to apply a load (preload; prestress) to the magnetostrictive element as necessary even when no external load is applied. The distal end surface of the male screw member 15 abuts on the bottom of the abutting member 12, and the amount of protrusion of the male screw member 15 is adjusted to eliminate play at both ends of the magnetostrictive element 1, and 1 constitutes a preload adjusting mechanism capable of adjusting the preload applied to 1. In addition,
The male screw member 15 is formed with an engagement recess 15 a so that the male screw member 15 can be rotated by a jig through a through hole of the receiving seat 14.

The pressure receiving seats 11 and 14 come into planar or linear contact with the spherical surface of a spherical body 40 as a pair of spherical members to which a measuring load from the outside is applied, and a load is applied in the axial direction of the magnetostrictive element 1. Such concave portion (for example, spherical shape, conical shape, etc.) 11
a, 14a are formed. Sphere 4
When it comes into contact with the spherical surface of 0 in a planar manner, the concave portions 11a and 14a are partial spherical surfaces that match the spherical surface of the spherical body 40 and are in circular contact with the spherical body 40 with a predetermined width. When the spherical surface of the spherical body 40 is in linear contact with the spherical surface, the concave portions 11a and 14a are conical surfaces and contact the spherical body 40 with a circle.

The lead 6 of the coil 2 is led out of the cutout 31 of the casing 30 as shown in FIG. 3, and is connected to the sensor circuit SR2 described with reference to FIG. 5 or FIG. Details of the sensor circuit unit SR2 will be described later.

As shown in FIG. 1, when a measurement load (measurement pressure) is applied between the spheres 40 from the outside, the magnetostrictive element 1 passes through the pressure receiving seat 11 on one end surface, the elastic plate 10 and the other end. A load is applied in the axial direction of the magnetostrictive element 1 via the pressure receiving seat 14, the bottom block 13, the male screw member 15, and the contact member 12 on the end face side, and the magnetic permeability of the magnetostrictive element 1 decreases with an increase in the load. . As a result, as shown in FIG. 4, when the weight increases, the inductance of the coil 2 decreases. That is, in the sensor body SR1, the change in the magnetic permeability of the magnetostrictive element 1 is
Is detected as a change in inductance.

A pair of spheres 40 to which a measurement load is applied from the outside, and a concave portion (for example, a concave portion (for example, a sphere) which comes into contact with the spherical surface of the sphere 40 in a planar or linear manner so that the load is applied in the axial direction of the magnetostrictive element 1 The reason why the pressure receiving seats 11 and 14 having spherical and conical surfaces 11a and 14a are interposed is to prevent the shear pressure from being applied to the magnetostrictive element 1.

The sensor circuit portion SR2 shown in FIG.
Is output as a change in the electric signal, for example, a change in the output voltage.

A sensor body S using the magnetostrictive element 1 of FIG.
The relationship between the weight of R1 and the inductance is such that the inductance decreases as the weight increases, as shown in FIG. The method of extracting the inductance change as an electric signal uses a coil as an element that constitutes an LC oscillation circuit,
A method of extracting the change as the oscillation frequency and converting this to a voltage or current signal, a method of exciting the coil with a sine wave and converting the AC impedance to an electric signal according to the same principle as the LC meter, and the inductance and resistance of the coil A method of converting the signal into an electric signal by using it as a part of an LR charge / discharge circuit is conceivable.

The low coil Q makes it difficult to form a stable oscillating circuit, and is not suitable for high-speed pressure change detection. Requires a sinusoidal oscillator, synchronous detector, etc., and is expensive.
High-speed measurement is also difficult. Can be configured with relatively inexpensive circuit components, and the measurement speed can be increased.

FIG. 5 is a principle diagram of a sensor circuit section SR2 which converts a change in inductance of a coil of a sensor body SR1 using a magnetostrictive element according to the method into an electric signal and outputs the electric signal. In this figure, E: DC power supply voltage, R ₁ : series resistor, R ₂ : resistance of coil 2, L: inductance of coil 2, S: switch circuit. Voltage V ₁ : voltage applied to a series circuit of series resistor R ₁ and coil 2, Voltage V ₂ : voltage (output voltage) across coil 2, current I ₁ : series circuit of series resistor R ₁ and coil 2 Is the current flowing through

[0028] FIG. 6 is a time chart of the circuit of each part of the voltage, current in Figure 5, on the switch circuit S, a step voltage of voltages V ₁ shown in FIG. 6 off (A) of the sensor body SR1 When applied to the L-R discharge circuit including the coil 2, the current I ₁ is gradually increasing waveform of FIG. (B), the voltage V ₂ across the coil 2 in FIG (C) becomes gradually decreasing waveform, yet these transients The phenomenon waveform changes depending on the inductance of the coil 2. In other words, the coil 2
Of the voltage V _{2 as the} pressure increases, as is apparent from FIG. 7 in which FIG. 6 (C) is enlarged.
The degree of decrease becomes steep. Therefore, by sampling at a sampling pulse for generating a waveform of the voltage V ₂ for a period of time elapsed from step voltage application, can be known from the sampled output voltage value inductance of the coil 2, i.e. the measurement weight.

FIG. 8 shows that the inductance L of the coil 2 is 10
An example of a current I ₁ and simulation waveforms of the voltage V ₂ when the change to 0% to 60%, change in waveform of the voltage V ₂ caused by the inductance change is found to be sufficiently large.

FIG. 9 is a specific circuit configuration of the sensor circuit section SR2 using the measurement principle of FIGS. 5 and 6, and FIG. 10 is a time chart thereof. In these figures, the pulse generator 50 is intended to generate a square wave of FIG. 10 (A), the switching circuit 51 is the square wave when the switch-on an internal series resistor R ₁ of Figure 5 L -Apply to the coil 2 of the sensor body SR1 which is an R series circuit. Sensor body S
The terminal voltage (V ₂ ) of R1 is applied to the buffer circuit 52.

On the other hand, the sampling pulse generator 53
As shown in FIG. 10B, the sampling and holding circuit 54 generates a sampling pulse that is delayed for a predetermined time from the rise of the square wave (provided that the delay amount is less than 1/2 cycle).
Add to The sample and hold circuit 54 holds the output of the buffer circuit 52 when the sampling pulse arrives. The buffer circuit 52, the sampling pulse generator 53 and the sample and hold circuit 54
It functions as a sampling circuit that samples a voltage value at both ends of the coil at a timing delayed by a predetermined time from application of a pulse voltage to the coil.

When the inductance of the coil 2 changes as shown in FIG. 10 (C), the terminal voltage (V ₂ ) of the sensor main body SR1, that is, the coil 2 has a voltage gradually decreasing with the change of the inductance. The voltage waveform is as shown in FIG. Therefore, the output voltage of the sample and hold circuit 54 obtained by sampling at a timing delayed by a certain time from the application of the square wave pulse to the coil 2 is shown in FIG.
The voltage waveform decreases as the inductance decreases and increases as the inductance increases, as shown in FIG. This is amplified by the output amplifier circuit 55, whereby the output signal (voltage or current) shown in FIG. Here, the output amplifier circuit 55 outputs a waveform obtained by inverting and amplifying the waveform of FIG. 10E, but may output a non-inverted output. The signal from the zero point adjusting circuit 56 is added to the output amplifying circuit 55 so that the output signal can be zero point adjusted.

Preferably, the oscillation frequency of the pulse generator 50 is in the range of 100 Hz to 50 kHz, and the number of samplings is 100 to 50,000 times / second. If the oscillation frequency is less than 100 Hz, a time constant for generating a pulse becomes large, and a circuit element such as a CR becomes large. Also,
If the oscillation frequency is higher than 50 kHz, there is a problem that eddy current loss and the like of the coil 2 increase.

The sensor circuit part SR2 shown in FIG. 9 has the advantages that the circuit configuration is simple and compact, that it can follow a high-speed pressure change, and that a weight change can be detected in real time.

According to this embodiment, the following effects can be obtained.

(1) Pressure receiving seats 11 and 14 as concave members are provided at both ends of the magnetostrictive element 1 of the sensor main body SR1. Externally applied measurement loads are applied via a pair of spheres 40. By applying the pressure between the pressure receiving seats 11 and 14, the pressure can be measured such that the pressure in the shear direction is not applied to the magnetostrictive element 1 (the posture of the casing 30 coincides with the axial direction of the magnetostrictive element and the load direction). ), The reliability can be improved.

(2) A male screw member 15 for preload adjustment is screwed into the bottom block 13 to apply a load (preload) to the magnetostrictive element as required even when no external load is applied. A preload adjusting mechanism capable of adjusting the preload applied to the magnetostrictive element 1 is configured. By setting the preload to an appropriate value, a region having good linearity of the magnetostrictive element 1 can be used for external load measurement. The linearity can be improved.

(3) Using the inductance and resistance of the coil 2 of the sensor body SR1 as a part of the LR charging / discharging circuit, sampling the voltage values at both ends of the coil 2 at a timing delayed by a predetermined time from the pulse application. Thus, the change in inductance of the coil 2 caused by the external load can be extracted as an electric signal with a simple circuit configuration.

FIG. 11 shows a second embodiment of the present invention, in which two sensors using the magnetostrictive element of the first embodiment are combined. In this case, the sensor body SR1 and the sensor circuit SR2 described in the first embodiment are used.
The sensors X and Y are used, and the output signal of each sensor is differentially amplified by a differential amplifier 60 as a differential circuit, and the output is output to the outside. However, pulse generator 5
0, switch circuit 51, sampling pulse generator 53
Is shared by the sensors X and Y.

In the second embodiment, the sensor X
An external load for measurement is applied to the sensor main body SR1 including the magnetostrictive element 1 of FIG. When the differential amplifier 60 uses the difference between the outputs of the output amplifier circuits (or buffers) 55 of both sensors, the change due to the temperature of the magnetostrictive element 1 is canceled out, and a pressure sensor device having excellent temperature characteristics can be obtained. realizable.

Incidentally, the sensor body SR1 of the sensor X,
If a weight from a different pressure source is applied to the sensor body SR1 of the sensor Y, a difference between the weights of the two pressure sources can be detected. At this time, by taking the difference between the outputs of the two sensors, if the two sensors X and Y are under the same temperature condition, the change due to the temperature of the magnetostrictive element 1 can be removed.

The material of the constituent members of the sensor main body incorporating the magnetostrictive element can be changed as appropriate, but a member for transmitting pressure to the magnetostrictive element, that is, the elastic plate 10 and the pressure receiver 1
It is desirable that the contact members 1, 14, the contact member 12, the bottom block 13, and the male screw member 15 be made of a material that can sufficiently withstand the pressing force, that is, metal.

A spherical member 4 as a pair of spherical members abutting to apply an external load to the pressure receiving seats 11 and 14 is provided.
Although 0 is used, a hemispherical member may be used.

Although the embodiments of the present invention have been described above, it is obvious to those skilled in the art that the present invention is not limited to the embodiments and various modifications and changes can be made within the scope of the claims. There will be.

[0045]

As described above, according to the sensor using the magnetostrictive element according to the present invention, the magnetostrictive element and at least one coil disposed around the magnetostrictive element are housed in the casing, and the weight is applied. Is provided on the casing so as to be applied in the direction of the central axis of the magnetostrictive element, and a concave shape member located at both ends of the magnetostrictive element is provided on the casing, and a change in the magnetic permeability of the magnetostrictive element due to the load is detected as a change in inductance of the coil. This eliminates the need for a magnetic circuit using permanent magnets, reduces the number of components, and enables downsizing. Also,
The structure is such that no shear stress is applied to the magnetostrictive element due to an external load, and the reliability of the magnetostrictive element can be improved by avoiding destruction of the magnetostrictive element due to the shear stress.

Further, it is possible to convert a change in inductance into an electric signal such as a voltage or a current with a simple circuit configuration.

According to the sensor device in which two sensors each using the magnetostrictive element are combined, the sensor using one magnetostrictive element is used as a reference for temperature characteristic compensation.
A more stable output can be obtained by offsetting the change due to temperature. Further, it can also be used for detecting a difference between two load pressures.

[Brief description of the drawings]

FIG. 1 is a front sectional view showing a sensor main body in a sensor using a magnetostrictive element according to a first embodiment of the present invention.

FIG. 2 is a plan view of the same.

FIG. 3 is a side view of the same.

FIG. 4 is a graph showing a relationship between a load applied to a magnetostrictive element and an inductance of a coil in the first embodiment.

FIG. 5 is a basic circuit diagram illustrating a principle of a sensor circuit unit that converts a change in inductance of a coil into an electric signal in the first embodiment.

FIG. 6 is a time chart of the circuit of FIG. 5;

7 is a time chart showing a change in terminal voltage of a coil and a timing of sampling after application of a step voltage in FIG. 6;

FIG. 8 is a simulation waveform diagram showing, in an enlarged manner, a change in terminal voltage of a coil accompanying a change in inductance.

FIG. 9 is a block diagram of a sensor circuit unit that converts a change in inductance of a coil into an electric signal in the first embodiment.

FIG. 10 is a time chart of the sensor circuit section of FIG. 9;

FIG. 11 is a block diagram of a sensor device in which two sensors each using the magnetostrictive element described in the first embodiment are combined.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylindrical magnetostrictive element 2 Coil 3 Bobbin 4 Winding 5 Cavity part 10 Elastic plate 11, 14 Pressure seat 12 Contact member 13 Bottom block 15 Male screw member 20 Magnetic yoke 30 Exterior casing 31 Notch part 40 Spherical SR1 sensor Main unit SR2 Sensor circuit unit 50 Pulse generator 51 Switch circuit 52 Buffer circuit 53 Sampling pulse generator 54 Sample hold circuit 55 Output amplifier circuit 56 Zero adjustment circuit 60 Differential amplifier X, Y sensor

Claims (7)

[Claims] 1. A magnetostrictive element and at least one coil disposed around the magnetostrictive element are housed in a casing, and are located at both ends of the magnetostrictive element so that a load is applied in a direction of a center axis of the magnetostrictive element. A sensor using a magnetostrictive element, wherein a concave-shaped member to be formed is provided in the casing, and a change in magnetic permeability of the magnetostrictive element due to the load is detected as a change in inductance of the coil. 2. The sensor according to claim 1, wherein a preload adjusting mechanism for applying a preload to the magnetostrictive element is provided in the casing. 3. A load is applied by bringing spherical or hemispherical members into contact with concave-shaped members on both ends of the magnetostrictive element, respectively, such that the load direction matches the central axis direction of the magnetostrictive element. A sensor using the magnetostrictive element according to claim 1. 4. A device for converting a change in inductance of the coil into an output electric signal to the outside, the device comprising: a pulse generating circuit for applying a pulse to the coil; and a timing delayed by a predetermined time from the application of the pulse. 4. The magnetostrictive element according to claim 1, further comprising a sampling circuit for sampling a voltage value at both ends of the coil, and a circuit for converting the sampled voltage value to an external output electric signal. Sensor. 5. An oscillation frequency of said pulse generating circuit is set to 10
0 Hz to 50 kHz, sampling frequency is 1
The sensor using the magnetostrictive element according to claim 4, wherein the weight change is detected in real time at a rate of 00 to 50,000 times / sec. 6. A magnetostrictive element and at least one coil disposed around the magnetostrictive element are housed in a casing, and are located at both ends of the magnetostrictive element such that a load is applied in a direction of a center axis of the magnetostrictive element. A sensor having a magneto-resistive element for detecting a change in magnetic permeability of the magnetostrictive element due to a load as a change in inductance of the coil, and a differential output of the two sensors. A differential circuit that outputs a signal as an output electric signal to the outside. 7. The sensor device according to claim 6, wherein one of the two sensors serves as a reference for temperature characteristic compensation without applying an external load.