JPH09145495A - Temperature correcting device for magnetostrictive sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the detection accuracy of a sensor by adding the output voltage having a positive temperature characteristic from a temperature correcting means and the output voltage having a nagative temperature characteristic from a rectifying means with an adding means, and offsetting the temperature characteristics. SOLUTION: A constant current with the prescribed frequency is fed to the exciting coil 5a of a sensor 1 from an AC exciting power source 19 through an exciting amplifier 17. When compressive stress is applied to a magnetostrictive element 3, the magnetic flux crossing a detecting coil 5b vertically crossing the coil 5a is generated on the element 3, the voltage proportional to the stress is generated on the coil 5b and rectified by a rectifying circuit 21, and the voltage VIN having a negative temperature characteristic is outputted. A constant DC voltage is fed to a diode 33 from a constant DC voltage source 29. The output voltage V1 of the cathode terminal of the diode 33 has a positive temperature characteristic. The voltage VIN and the voltage V1 are added at a connecting point 24 and inputted to a voltmeter 39 via an arithmetic amplifier 25. The voltage faithfully indicates the stress applied to the sensor 1, and the stress can be known from the indicated value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention excites a magnetostrictive sensor in which a coil is wound around a magnetostrictive element made of a magnetic material, and the magnetization characteristic of the magnetic material changes when a force is applied to the magnetostrictive element. The present invention relates to a magnetostrictive sensor for detecting an applied force by utilizing a temperature correction element, in particular, a decrease in accuracy of a sensor detected value caused by a change in a detected value of the magnetostrictive sensor depending on a temperature change. The present invention relates to a temperature compensating device for a magnetostrictive sensor which is suppressed by using the temperature characteristic of the above.

[0002]

2. Description of the Related Art Generally, in order to measure the force applied to a certain substance, various means are known for detecting the magnitude of the force by utilizing the fact that the physical properties change due to the application of the force. . Among them, the magnetostrictive sensor has features that the structure is simple and the mechanical strength is high, it is difficult to be affected by disturbance noise, and the output of the magnetostrictive sensor is low because the impedance of the detection element is low. It is used for applications such as the weight of trucks. This magnetostrictive sensor
The magnitude of the applied force is measured using the principle that a magnetostrictive sensor made by winding a coil around a magnetostrictive element made of a magnetic material is excited, and the magnetic characteristics of the magnetic material change when a force is applied to the magnetostrictive element. I'm trying to detect.

More specifically, the conventional magnetostrictive sensor is made of a magnetic material having four through holes aligned in a square shape in its central portion, as disclosed in, for example, Japanese Patent Laid-Open No. 6-313740. And a pair of coils in which electric wires are wound around the pair of through-holes located diagonally among these four through-holes in a peg shape through these through-holes. . One of the coils is an exciting coil, and the ends of the pair of lead wires drawn from this coil are connected to an alternating-current exciting power supply that supplies a constant voltage having a predetermined frequency to the exciting coil. The other coil is a detection coil, and the ends of the pair of lead wires pulled out from this coil pass through an appropriate amplifier that amplifies the voltage generated in the detection coil due to the stress applied to the magnetostrictive sensor. Connected to a display instrument such as a voltmeter.

Here, the principle of stress detection of the magnetostrictive sensor will be described. When mechanical strain is applied to the magnetic substance, the magnetization characteristics of the magnetic substance, particularly the transparent property, are increased between the lengthwise extending direction and the lengthwise contracting direction. There is a big difference in magnetic susceptibility. For example, considering a case where a compressive stress is applied to a magnetostrictive element from a certain direction, the magnetic permeability decreases in the stressed direction, while the magnetic permeability increases in the direction perpendicular to the stressed direction. As a result, in the state where no compressive stress is applied, the magnetic flux distribution in the magnetostrictive element maintains symmetry, and there is no magnetic flux that intersects the detection coil and no voltage is generated in the detection coil, whereas when compressive stress is applied, The symmetry of the magnetic flux distribution collapses to generate a magnetic flux that intersects the detection coil, and a voltage proportional to the applied compressive stress occurs in the detection coil.
Therefore, it is possible to know the compressive stress applied to the magnetostrictive element by measuring this voltage value.

[0005]

However, in the above-mentioned conventional magnetostrictive sensor, the sensor detection value includes an error due to the fluctuation of the ambient temperature around the sensor, and the detection accuracy of the sensor is affected by the error. There was a problem that it was difficult to improve.

More specifically, in the peripheral equipment connected to the conventional magnetostrictive sensor, for example, in an AC excitation power source for exciting the excitation coil, a predetermined frequency is exhibited with respect to the excitation coil. It supplies a constant voltage,
When the resistance value of the exciting coil changes due to the change in ambient temperature around the magnetostrictive sensor, the current value flowing in the exciting coil also changes, which in turn changes the magnetic flux generated by the exciting coil. Is detected by the detection coil, and as a result, the detected value of the compressive stress applied to the magnetostrictive element includes an error. Therefore, in order to eliminate the error in the sensor detection value caused by such a change in the ambient temperature, it is proposed to use an AC excitation power supply of a form that supplies a constant current having a predetermined frequency to the excitation coil. Has been done. According to this proposal, even if the resistance value of the exciting coil changes due to the change of the ambient temperature around the sensor, the value of the current flowing through the exciting coil does not change, and the displacement of the magnetic flux generated by the exciting coil is reduced. Can be suppressed. However, even if this proposal is adopted,
Experiments have shown that the error in the sensor detection value cannot be completely removed. That is, when no stress is applied to the magnetostrictive sensor, a constant current having a predetermined frequency is supplied to the exciting coil to detect when the ambient temperature around the sensor is changed. When the output voltage of the coil for observation was observed, it was found that the output voltage of the coil for detection exhibits a so-called negative temperature characteristic in which the voltage value decreases in response to the rise in temperature. It is presumed that this is because the magnetization characteristics of the magnetic substance that constitutes the magnetostrictive element are displaced by fluctuations in the ambient temperature, but the current situation is that no countermeasures have been taken against this. There was a strong demand among the parties concerned to solve these problems.

The present invention has been made in view of the above situation, and corrects the output voltage of the detection coil, which includes an error due to the fluctuation of the ambient temperature around the magnetostrictive sensor, using a temperature correction element. Accordingly, it is an object of the present invention to provide a temperature correction device for a magnetostrictive sensor that can improve the detection accuracy of the sensor by removing the error in the sensor detection value.

[0008]

In order to solve the above-mentioned problems, the invention of claim 1 is such that a coil is wound around a magnetostrictive element made of a magnetic material, and this magnetostrictive element is excited,
A magnetostrictive sensor configured to detect the magnitude of the applied stress by utilizing the fact that the magnetization characteristics of the magnetic body change when stress is applied to the magnetostrictive element exhibits a predetermined frequency. An alternating-current excitation power supply that supplies a constant current, an excitation coil that is supplied with a constant current from the alternating-current excitation power supply, and excites the magnetostrictive element, and is disposed so as to intersect the excitation coil vertically. A detection coil for detecting a change in the magnetization characteristics when stress is applied to the element, a rectifying means for rectifying an AC voltage generated in the detection coil, and a temperature correction in series with the positive electrode of the DC constant voltage source. Temperature compensating means in which the elements are connected and the output voltage of the temperature compensating element exhibits a positive temperature characteristic; and adding means for adding the output voltage from the temperature compensating means and the output voltage from the rectifying means. Be equipped with It is the gist of.

According to the first aspect of the invention, first, a constant current having a predetermined frequency is supplied to the exciting coil of the magnetostrictive sensor from the AC exciting power source. At this time, if no stress is applied to the magnetostrictive element, the magnetic flux distribution in the magnetostrictive element maintains symmetry with respect to the exciting coil, and as a result, there is no magnetic flux that intersects the detecting coil, and there is no voltage across the detecting coil. Does not occur. On the other hand, for example, when compressive stress is applied to the magnetostrictive element, the magnetic permeability decreases in the stressed direction, while the magnetic permeability increases in the direction perpendicular to the stressed direction, and the magnetic flux generated by the exciting coil is increased. The symmetry of the distribution is broken, and as a result, a magnetic flux intersecting the detection coil is generated in the magnetostrictive element, and a voltage proportional to the applied compressive stress is generated in the detection coil. The AC voltage from the detection coil is rectified by the rectifying means, and the rectifying means outputs a voltage exhibiting a negative temperature characteristic according to the temperature characteristic of the magnetostrictive element.

In order to correct the negative temperature characteristic of the output voltage, the invention of claim 1 employs temperature correcting means in which the output voltage of the temperature correction element exhibits a positive temperature characteristic. That is, the adding means adds the output voltage having the positive temperature characteristic from the temperature correcting means and the output voltage having the negative temperature characteristic from the rectifying means to correct the negative temperature characteristic by offsetting. The output voltage can be obtained. The output voltage obtained here is a value that faithfully reflects the stress applied to the corrected magnetostrictive element due to the temperature characteristics of the magnetostrictive element, and as a result, the error in the sensor detection value is eliminated and the sensor The detection accuracy of can be improved.

The invention of claim 2 is characterized in that the temperature correction element is a diode.

Further, the invention of claim 3 further comprises an amplifying means for amplifying the output voltage from the adding means.

The invention according to claim 4 further comprises a display means for displaying the output voltage from the amplifying means.

According to the invention of claim 4, the output voltage displayed on the display means is a value that faithfully reflects the stress applied to the magnetostrictive sensor. Therefore, the output voltage added by reading the indication value on the display means. You can know the applied stress.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a temperature compensating device for a magnetostrictive sensor according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic block diagram showing a temperature compensating device for a magnetostrictive sensor according to the present invention, and FIGS. 2 to 6 are diagrams for explaining the temperature compensating device for a magnetostrictive sensor according to the present invention. As shown in FIG. 1, a magnetostrictive sensor 1 according to the present invention
Includes a magnetostrictive element 3 made of a magnetic material such as permendur, and a coil 5 wound around the magnetostrictive element 3. As the magnetic material forming the magnetostrictive element 3, for example, permalloy or soft iron can be used. More specifically, four through holes 7 are formed in the substantially central portion of the magnetostrictive element 3, and these through holes 7 are arranged in a square shape and their bottom sides are parallel to the bottom surface of the magnetostrictive element 3.
With such an arrangement of the through holes 7, the compressive or tensile stress on the magnetostrictive element 3 can be efficiently detected.
In these four through holes 7, an electric wire is wound around each of a pair of diagonally located through holes through the through holes, and the pair of coils 5a and 5b are formed with this. To do. The coil 5a is an exciting coil, and a pair of lead wires 9a and 9b of the coil 5a are provided with an AC exciting power source 19 for supplying a constant current having a predetermined frequency through the exciting side terminals 13a and 13b, respectively. It is connected to an exciting amplifier 17 that amplifies the output power from 19 to an appropriate value. On the other hand, the coil 5b is a detection coil, and the pair of lead wires 11a of the coil 5b,
11b via respective detecting terminals 15a, 15b and a rectifier circuit 21 for rectifying an AC output voltage from the detecting coil 5b, described below temperatures perform temperature compensation for the output voltage V _in from the rectifier circuit 21 The correction circuit 22, the operational amplifier 25 that amplifies the voltage after temperature correction to an appropriate value, and the voltmeter 3 that displays the output voltage V _out from the operational amplifier 25.
9 is connected to. The voltage value displayed on the voltmeter 39 has its temperature characteristic corrected by the temperature correction circuit and is a value that faithfully reflects the stress applied to the magnetostrictive sensor 1. You can know the applied stress by reading.

Next, the circuit structure after the rectifier circuit 21 will be described in more detail. The output voltage V _in from the rectifier circuit 21 is the inversion of the operational amplifier 25 through the first resistor 23 and the first connection point 24 in series. It is input to the input terminal. Also,
The non-inverting input terminal of the operational amplifier 25 is grounded. The output terminal of the operational amplifier 25 is connected to the inverting input terminal via the second resistor 27 and the first connection point 24. As a result, part of the output voltage V _out is generated by the operational amplifier 25 by the first and second resistors 23 and 27 that function as negative feedback resistors.
It is returned to the input side of and stabilizes the circuit operation by the negative feedback operation. Furthermore, in order to correct the temperature characteristic of the output voltage V _in from the rectifier circuit 21, the first connection point 24 is
It is connected to the temperature correction circuit 22 via the fifth resistor 37. The temperature correction circuit 22 has a DC constant voltage source 29 having its negative electrode side grounded and its positive electrode side connected to a second connection point 32, and its anode terminal connected to the second connection point 32 and its cathode terminal connected. A diode 33 connected to the third connection point 34, a third resistance 31 connected in parallel to the diode 33, and a fourth resistance having one end connected to the third connection point 34 and the other end grounded. And 35.

The circuit operation of the temperature compensating device for the magnetostrictive sensor according to the present invention having the above-described structure will be described with reference to FIGS.

First, the exciting coil 5a of the magnetostrictive sensor 1
A constant exciting current having a predetermined frequency is supplied from an AC exciting power source 19 via an exciting amplifier 17. At this time, if no stress is applied to the magnetostrictive element 3,
The magnetic flux distribution in the magnetostrictive element 3 maintains symmetry with respect to the exciting coil 5a, and as a result, there is no magnetic flux crossing the detecting coil 5b and no voltage is generated in the detecting coil 5b. On the other hand, when compressive stress as shown in FIG. 1 is applied to the magnetostrictive element 3, the magnetic permeability decreases in the stressed direction, while the magnetic permeability increases in the direction perpendicular to the stressed direction. The symmetry of the magnetic flux distribution by the exciting coil 5a is destroyed, and as a result, a magnetic flux intersecting the detecting coil 5b is generated in the magnetostrictive element 3, and a voltage proportional to the applied compressive stress is generated in the detecting coil 5b. To do. The AC output voltage from the detection coil 5b is rectified in the rectifier circuit 21, and the rectifier circuit 21 outputs the voltage V _in exhibiting the negative temperature characteristic shown _in FIG.

[0020] In order to correct the negative temperature characteristic of the output voltage V _in, the present invention employs a diode 33 which exhibits a negative temperature characteristic. This will be described with reference to FIG.
Includes a DC constant voltage source 29, which is a main part of the temperature correction circuit 22.
And a diode 33 is shown in a series circuit. In this series circuit, a DC constant voltage V _R is supplied from a DC constant voltage source 29.
Is supplied to the diode 33, the inter-terminal voltage V _F of the diode 33 exhibits a negative temperature characteristic of decreasing the inter-terminal voltage V _F as the temperature rises, as shown in FIG. As a result, the output voltage V _{1 at} the cathode terminal of the diode 33 exhibits a positive temperature characteristic of increasing the output voltage V ₁ as the temperature rises, as shown in FIG. In the present invention, by adding the output voltage V ₁ exhibiting the positive temperature characteristic and the output voltage V _in exhibiting the negative temperature characteristic, as shown in FIG.
The negative temperature characteristic is used to obtain the output voltage V _out corrected by the cancellation. At the time of this correction, the temperature correction ratio by the diode 33 is adjusted by appropriately adjusting the distribution ratio of the resistance values of the third resistor 31 and the fourth resistor 35, and the output voltage at the cathode terminal of the diode 33 is adjusted. The potential level of V ₁ can be adjusted. Further, the potential level of the output voltage V ₁ at the cathode terminal of the diode 33 can be adjusted by setting the voltage V _R of the DC constant voltage source 29 to an appropriate value.

The output voltage V _in and the output voltage V ₁ are added at the first connection point 24 via the first and fifth resistors 23 and 37, respectively, and the added voltage is added to the operational amplifier 25. It is input to the inverting input terminal. In addition, when adding the output voltage V ₁ and the output voltage V _in , the first
In order to make the potentials of the two at the connection point 24 equal,
If the resistance values of the third, fourth, and fifth resistors 23, 31, 35, 37 are set to appropriate values, circulation of circulating current can be blocked. Then, the first and fifth resistors 23 and 37
When the output voltage V _{ou t} amplified in accordance with the distribution ratio of the resistance value of the second resistor 27 is output from the output terminal of the operational amplifier 25. This output voltage V _out is input to the voltmeter 39, and the temperature characteristic of the output voltage V _out displayed on the voltmeter 39 is corrected by the temperature correction circuit 22, so that the stress applied to the magnetostrictive sensor 1 is faithful. Since the value is reflected on, the applied stress can be known by reading the indicated value of the voltmeter 39.

In this embodiment, the diode 3
The arrangement position of 3 can be arranged close to the magnetostrictive element 3 so as to receive a temperature equivalent to the ambient temperature around the magnetostrictive element 3.

Further, in the present embodiment, the form of the magnetostrictive sensor which is preferable for detecting the compressive or tensile stress is illustrated, but the present invention is not limited to this, and the four through holes formed in the magnetostrictive element. The arrangement can also be applied to a magnetostrictive sensor having a square shape and one side of which is positioned at an angle of 45 ° with the bottom surface of the magnetostrictive element to detect shear stress on the magnetostrictive element.

Lastly, in the present embodiment, the diode has been described as an example of the temperature correction element, but the present invention is not limited to this, and the output thereof when a DC constant voltage source and a series circuit are formed. Appropriate elements whose voltage exhibits a positive temperature characteristic can be employed.

[0025]

As described above, according to the first aspect of the invention, first, a constant current having a predetermined frequency is supplied from the AC excitation power source to the exciting coil of the magnetostrictive sensor. At this time, if no stress is applied to the magnetostrictive element, the magnetic flux distribution in the magnetostrictive element maintains symmetry with respect to the exciting coil, and as a result, there is no magnetic flux that intersects the detecting coil, and there is no voltage across the detecting coil. Does not occur. On the other hand, for example, when compressive stress is applied to the magnetostrictive element,
While the magnetic permeability decreases in the stressed direction, the magnetic permeability increases in the direction perpendicular to the stressed direction, leading to the collapse of the symmetry of the magnetic flux distribution due to the excitation coil. A magnetic flux intersecting the working coil is generated, and a voltage proportional to the applied compressive stress is generated in the detecting coil. The AC voltage from the detection coil is rectified by the rectifying means, and the rectifying means outputs a voltage exhibiting a negative temperature characteristic according to the temperature characteristic of the magnetostrictive element.

In order to correct the negative temperature characteristic of the output voltage, the invention of claim 1 employs temperature correcting means in which the output voltage of the temperature correcting element exhibits a positive temperature characteristic. That is, the adding means adds the output voltage having the positive temperature characteristic from the temperature correcting means and the output voltage having the negative temperature characteristic from the rectifying means to correct the negative temperature characteristic by offsetting. The output voltage can be obtained. The output voltage obtained here is a value that faithfully reflects the stress applied to the corrected magnetostrictive element due to the temperature characteristics of the magnetostrictive element, and as a result, the error in the sensor detection value is eliminated and the sensor It has an extremely excellent effect that the detection accuracy of can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a temperature correction device for a magnetostrictive sensor according to the present invention.

FIG. 2 is a diagram for explaining a temperature correction device for a magnetostrictive sensor according to the present invention.

FIG. 3 is a diagram for explaining a temperature correction device for a magnetostrictive sensor according to the present invention.

FIG. 4 is a diagram for explaining a temperature correction device for a magnetostrictive sensor according to the present invention.

FIG. 5 is a diagram for explaining a temperature correction device for a magnetostrictive sensor according to the present invention.

FIG. 6 is a diagram for explaining a temperature correction device for a magnetostrictive sensor according to the present invention.

[Explanation of symbols]

 1 Magnetostrictive Sensor 3 Magnetostrictive Element 5a Excitation Coil 5b Detection Coil 7 Through Holes 9a, 9b, 11a, 11b Lead Wires 13a, 13b Excitation Side Terminal 15a, 15b Excitation Side Terminal 17 Excitation Amplifier 19 AC Excitation Power Supply 21 Rectification Circuit 22 Temperature correction circuit 23 First resistance 24 First connection point 25 Operational amplifier 27 Second resistance 29 DC constant voltage source 31 Third resistance 32 Second connection point 33 Diode 34 Third connection point 35 Fourth resistance 37 Fifth resistance 39 Voltage Total

Claims (4)

[Claims] 1. Utilizing the fact that a coil is wound around a magnetostrictive element made of a magnetic material, the magnetostrictive element is excited, and the magnetization characteristics of the magnetic material change when stress is applied to the magnetostrictive element. In the magnetostrictive sensor configured to detect the magnitude of the applied stress, an alternating current excitation power source for supplying a constant current exhibiting a predetermined frequency, and a constant current from the alternating current excitation power source are supplied, An exciting coil for exciting the magnetostrictive element, a detecting coil arranged to intersect the exciting coil perpendicularly, and detecting a change in the magnetization characteristic when stress is applied to the magnetostrictive element, and the detecting coil. Rectifying means for rectifying the AC voltage generated in the coil for temperature and a temperature correction element connected in series to the positive electrode of the DC constant voltage source, the temperature correction element having an output voltage exhibiting a positive temperature characteristic Means and The output voltage from the temperature compensation unit, the temperature correction unit of the magnetostrictive sensor, characterized by comprising and an adding means for adding the output voltage from said rectifying means. 2. The temperature correction device for a magnetostrictive sensor according to claim 1, wherein the temperature correction element is a diode. 3. The amplifying means for amplifying the output voltage from the adding means is further provided.
3. A temperature compensating device for a magnetostrictive sensor according to any one of claims 1 to 3. 4. The display means for displaying the output voltage from the amplifying means is further provided.
A temperature compensating device for the magnetostrictive sensor according to claim 1.