JPH0720140A - Angular speed sensor - Google Patents

Abstract

PURPOSE:To allow precise angular speed detection by applying a magnetic field to an oscillator made of a supermagnetostrictive material to generate oscillation through magnetostriction and detecting the variation in the magnetization upon application of angular speed to the oscillator. CONSTITUTION:An oscillation circuit 14 applies a voltage to a drive coil 12 wound around a C-shaped oscillator 11 made of a magnetostrictive material to generate an exciting field which is applied to the oscillator 11 thus causing a bending oscillation. The oscillator 14 also delivers a phase reference signal directly to a synchronism detection circuit 17. Since the oscillator 11 is oscillating, the leg part of the oscillator 11 is magnetized by reverse magnetostrictive effect. Signals corresponding to the magnetization are amplified by amplifiers 15a, 15b connected with detection coils 13a, 13b and detected. The difference between both signals is amplified by a differential amplifier 16 and rectified by the synchronism detection circuit 17. Consequently, the variation of impedances at the detection coils 13a, 13b is obtained as an output corresponding to the rotational angular speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angular velocity sensor using a giant magnetostrictive material as a vibrating body.

[0002]

2. Description of the Related Art Conventionally, many methods have been put into practical use for detecting angular velocity. For example, methods such as a piezoelectric type, a conductive type, a strain gauge type, and a semiconductor gauge type can be mentioned. Among these, the angular velocity sensor using the piezoelectric ceramic is widely used for detecting vibration of various machines because of its simple structure.

A conventional piezoelectric type angular velocity sensor will be described with reference to FIG. This angular velocity sensor has a structure in which strip-shaped piezoelectric elements 2 are bonded to the four side surfaces of a quadrangular prism vibrating body 1 made of a highly elastic metal material. In this angular velocity sensor, a driving signal is applied to one pair of piezoelectric elements 2 of the two pairs of piezoelectric elements 2 facing each other, and thereby the vibrating body 1 is flexibly vibrated. When a rotational angular velocity is applied about the axis of the vibrating body 1 as indicated by an arrow in the figure, Coriolis force is generated in a direction orthogonal to the vibrating direction of the vibrating body 1. As a result, the vibration direction of the vibrating body 1 is deviated by the action of new vibration corresponding to the rotational angular velocity, as compared with the vibration direction when there is no rotation. This new vibration component is detected by the other pair of piezoelectric elements. Note that FIG.
In addition to those shown in FIG. 1, there are angular velocity sensors such as a spay tuning fork type or a Watson tuning fork type.

[0004]

However, the conventional piezoelectric type angular velocity sensor has various drawbacks as described below. That is, since this angular velocity sensor is a structure in which a piezoelectric element is bonded to a vibrating body, it is difficult to miniaturize, poor reproducibility, and due to a difference in thermal expansion coefficient between the vibrating body and the piezoelectric element. There are problems such as temperature fluctuations. Also, since it is necessary to apply a voltage from the lead wire connected to the piezoelectric element to operate it, vibration leakage occurs through the lead wire,
The angular velocity cannot be detected accurately. Further, regarding the piezoelectric element itself, there are problems that a high voltage is required to operate the piezoelectric element, a complicated process is required for manufacturing the electrode, and the material is fragile. The present invention has been made to solve the above problems, and an object of the present invention is to provide a small-sized and practical angular velocity sensor capable of accurately detecting an angular velocity.

[0005]

The angular velocity sensor of the present invention comprises a vibrating body made of a giant magnetostrictive material having an intermetallic compound of a rare earth metal and a transition metal as a main phase, and a magnetostriction by applying a magnetic field to the vibrating body. And a means for detecting a change in magnetization corresponding to a change in vibration when an angular velocity is applied to the vibrating body.

As the rare earth metal-transition metal intermetallic compound constituting the giant magnetostrictive material used in the present invention, a rare earth / iron Laves phase intermetallic compound having a large magnetostriction is preferable. The rare earth / iron Laves type intermetallic compound is 100
It has been reported to have a saturation magnetostriction (λ _s ) of more than 0 ppm (Japanese Patent Publication No. 61-33892, etc.). Such a giant magnetostrictive material is generally represented by the following formula (I).

[0007] RFe _z (I) (R is a rare earth metal other words La containing Y, Ce, Pr,
Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, E
It is at least one selected from the group consisting of r, Tm, Yb, Lu, and Y, and satisfies 1.5 ≦ z ≦ 2.5). In the giant magnetostrictive material used in the present invention, a part of Fe may be replaced with Co. When a part of Fe is replaced with Co, it can be used at a low temperature and the corrosion resistance can be improved. However, from the viewpoint of magnetostrictive properties, the substitution amount of Fe by Co is preferably 95 at% or less.

Further, part of Fe may be replaced with Mn. When a part of Fe is replaced with Mn, a large magnetostriction value is exhibited in a wide magnetic field region from a high magnetic field to a low magnetic field. The substitution amount of Fe with Mn is preferably 0.5 to 50 at%. If the amount of substitution is less than 0.5 at%, there is no effect of addition, and if the amount of substitution exceeds 50 at%, the Curie temperature decreases and the magnetostrictive characteristics deteriorate in the practical temperature range.

Further, part of Fe is replaced with Ni, Mg, A
l, Ga, Zn, V, Zr, Hf, Ti, Nb, Cu,
Ag, Sn, Mo, Cr, Ta, Pd, In, Sb, I
You may substitute by elements, such as r, Pt, Au, Pb, Si, Ge, B, P, and C. These elements are added for the purpose of improving the material strength, corrosion resistance, saturation magnetostriction, electromechanical coupling coefficient, or adjusting the elastic modulus. The substitution amount of Fe with these elements is 0.5 to 5 in total with the substitution amount with Mn.
It is preferably 50 at%. Replacement amount is 0.5 at
If the amount of substitution is less than 50 at%, characteristics such as magnetostriction deteriorate.

The atomic ratio z of rare earth metal and Fe is 1.5.
≦ z ≦ 2.5 is set. If it is less than 1.5 or more than 2.5, the Laves phase responsible for the magnetostrictive properties is reduced, and sufficient magnetostrictive properties cannot be obtained. The range of z is more preferably 1.7 ≦ z ≦ 2.2. Among the giant magnetostrictive materials represented by the formula (I), those having large magnetostriction and small coercive force are represented by the following formula (II).

[0011] _{R 1-x Zr x (Fe} 1-y Mn y) z (II) (R is at least one kind of rare earth elements including Y, 0.
005 ≦ x ≦ 0.5, 0.005 ≦ y ≦ 0.5, 1.5
≦ z ≦ 2.5). Zr has the effect of lowering the coercive force. Even if Sc and Hf are used, the same effect as that of Zr can be obtained, and thus the same amount may be added. If x is less than 0.005, the effect of addition cannot be obtained, and if x exceeds 0.5, the amount of magnetostriction decreases. The action of Mn and the reasons for limiting y and z are as described above.

Table 1 shows a giant magnetostrictive material represented by the formula (II) (N
o. 1 to 10) and a giant magnetostrictive material (No.
11 to 16), characteristics such as coercive force are collectively shown.

[0013]

[Table 1]

Among the giant magnetostrictive materials represented by the formula (I), those having particularly good magnetostrictive properties are described in the following (III).
It is represented by a formula. _{Tb 1-a Dy a (Fe} 1-y Mn y) z (III) wherein, more preferably 0.3 ≦ a ≦ 0.7 0.5 ≦ a
≤0.6, 0.005 ≤ y ≤ 0.5 is more preferable, y is in the vicinity of 0.1, and 1.5 ≤ z ≤ 2.5 is more preferable, 1.7.
≦ z ≦ 2.2, more preferably 1.9 ≦ z ≦ 1.95.

In the present invention, the vibrating body made of a giant magnetostrictive material may have a cylindrical shape or a prismatic shape such as a triangular prism, a quadrangular prism, or a polygonal prism. Molds or crosses are preferred. The U-shaped vibrator is
It can be considered that the two legs are connected by providing a node (coupling part) so as to flexurally vibrate. The cross-shaped vibrating body has nodes (coupling points, intersections) so that bending vibrations occur on two axes.
Can be regarded as a connection.

In the present invention, as a means for applying a magnetic field to the vibrating body to vibrate by magnetostriction, for example, a drive coil provided in a non-contact manner around a part of the vibrating body and an AC power source connected to the drive coil. Is used. The vibrating body may be driven by the orbiting magnetic field generated by the line current. In the present invention, as means for detecting a change in magnetization corresponding to a change in vibration when an angular velocity is applied to the vibrating body, for example, a detection coil provided in a non-contact manner around a part of the vibrating body and connected to this detection coil The detected detection circuit is used.

As the drive coil and the detection coil, a solenoid coil, a plane coil or the like is used. The detection circuit is composed of circuits such as a synchronous detection circuit, a bridge circuit, and a rectification circuit. For the U-shaped vibrating body, for example, the drive coil is arranged around the joint (connecting portion) and the detection coil is arranged around the leg portion. In addition, two U-shaped vibrators are stacked on each other so that the vibration is transmitted, and a drive coil is provided around one U-shaped vibrator and a detection coil is provided around the other U-shaped vibrator. You may arrange. For the cross-shaped vibrator, for example, a drive coil is arranged around one axis and a detection coil is arranged around the other axis.

The operation of the angular velocity sensor of the present invention will be described below. First, the vibrating body is excited by applying an alternating current of a predetermined frequency to a drive coil arranged in a non-contact manner around a part of the vibrating body. Since the vibrating body made of a giant magnetostrictive material undergoes bending vibration due to the magnetostrictive effect, this is referred to as basic vibration. Now, when the rotational angular velocity is applied to the vibrating body, Coriolis force is generated correspondingly, and the vibration of the vibrating body deviates from the basic vibration. When such a vibration change occurs, an impedance change occurs in the detection coil arranged around a part of the vibrating body in a non-contact manner due to the inverse magnetostrictive effect. This amount of change is converted into an electric signal by the detection circuit. The magnitude or direction of the angular velocity can be identified by the amplitude and phase difference of the signal obtained here.

In the angular velocity sensor of the present invention, a magnetic bias may be applied to the U-shaped or cross-shaped vibrating body by a rare earth magnet, a ferrite magnet, a metal magnet or the like.
In such a configuration, since the relationship between the magnetostriction and the magnetic field (current) is linear and the vibrating body can be operated in the region exhibiting the maximum magnetostriction rate, the linearity of the sensor characteristics and the sensor sensitivity are improved.

The angular velocity sensor of the present invention can easily avoid various problems that occur in the piezoelectric type angular velocity sensor as described below. First, the angular velocity sensor of the present invention has the advantages that the resonance frequency during flexural vibration can be reduced and the vibrator can be made smaller. Here, the resonance frequency when the rod-shaped vibrating body vertically vibrates is given by the following formula.

Ω = (iπ / l) × (E / ρ) ^{1/2 In the} above equation, ω is the frequency, i is the order of vibration, l is the length, E is the elastic modulus of the material, and ρ is the density. is there. The elastic modulus of the giant magnetostrictive material (E = 2 to 3 × 10 ¹⁰ N / m ² ) is about 1/2 to 1 as compared with the elastic modulus of the piezoelectric material (E = 7 × 10 ¹⁰ N / m ² ).
It is a small value of / 3. As can be seen from the above equation, if E is small, the frequency can be reduced, and it can be operated in a practical frequency band. Conversely, if the frequency is constant,
Since the length of the rod-shaped vibrating body can be shortened, the overall size can be reduced.

Further, since the coil having the low impedance is used to generate the vibration, it can be driven at a low voltage. Since the drive coil and the detection coil are not in contact with the vibrating body, vibration leakage through the lead wire can be insulated and detection accuracy can be improved. Since the step of bonding the piezoelectric element to the vibrating body is eliminated, the manufacturing process can be simplified and the reproducibility is high. As in the case of the piezoelectric element, the temperature fluctuation caused by the difference in thermal expansion from the vibrating body can be eliminated. Furthermore, the giant magnetostrictive material is superior to the piezoelectric material in mechanical strength.

The giant magnetostrictive material used in the present invention is
Generally, the anisotropy of magnetostriction is large. Therefore, in order to obtain a high-performance element, it is preferable to control the crystal orientation of the giant magnetostrictive material so that the operating direction of the element and the crystal orientation capable of obtaining a large magnetostriction value coincide with each other. The element of the present invention is preferably operated so that the vibration generation direction is within the range of <111> to <110> of the giant magnetostrictive material. This means that the direction of the easy axis of magnetization of the giant magnetostrictive material and the direction of deformation due to magnetostriction are <1.
11>. In order to control the crystal orientation of the giant magnetostrictive material, the floating zone melting method (Floating Zo) is used.
ne method) (JP-A-62-109946, US Pat. No. 4,609,402) and the improved Bridgman method (JP-A-63-242442, European published patent 2).
A method of manufacturing a rod using 82059) is known.

However, the giant magnetostrictive rod manufactured by these methods has a large coercive force (Hc) and a large hysteresis of the displacement characteristic when incorporated in an element, so that it is inferior in the controllability of minute displacement and the frequency characteristic. ing. The cause of the increase in coercive force in this material system is pinning by inclusions such as grain boundaries and different phases. Further, the maximum rod diameter of the giant magnetostrictive alloy obtained by the floating zone melting method is limited to 10 mm, and it is difficult to increase the size. Further, since the Bridgman method melts the alloy in the crucible, it is difficult to avoid the reaction between the alloy and the crucible, and is not suitable for mass production.

In order to solve the above problems, it is conceivable to subject the giant magnetostrictive material to an optimum heat treatment. For example, a method in which the giant magnetostrictive material is heated to a temperature equal to or higher than the eutectic temperature and lower than the melting point, held for a predetermined time, and then gradually cooled at a cooling rate of 500 ° C./h or less can be preferably used. This heat treatment method will be further described.

First, each constituent element is mixed so as to obtain a desired composition, and is melted by high frequency induction melting or the like. The obtained ingot, or a sample processed from the ingot into a suitable shape by cutting or the like, is rapidly heated to a temperature equal to or higher than the eutectic temperature of the alloy and lower than the melting point, and held for a predetermined time. The holding time at this time is preferably 0.01 to 500 hours. Then, it is gradually cooled at a cooling rate of 500 ° C./h or less. The cooling rate is more preferably 200 ° C./h or less. These heat treatments are preferably performed in vacuum or in an atmosphere of an inert gas such as nitrogen or argon.

The coercive force of the giant magnetostrictive material subjected to such heat treatment is significantly reduced. This is because inclusions such as different phases that cause an increase in coercive force can be removed and the crystal grain boundaries can be reduced by crystal grain growth, as described below. First, inclusions such as different phases can be removed by heating above the eutectic temperature. If the heating temperature is lower than the eutectic temperature, inclusions such as different phases cannot be removed. Moreover, even in the subsequent slow cooling step, these inclusions hinder the crystal grain growth, so that the desired effect cannot be obtained. Next, 500 ° C / h
Gradually cooling at the following cooling rate causes crystal grains to grow, so that the crystal grain boundaries that cause an increase in coercive force are relatively reduced. In addition, when the cooling rate is higher than 500 ° C./h, sufficient crystal grain growth does not occur.

A specific example of this heat treatment method will be described below. First, high frequency induction melting was performed in an argon atmosphere using an alumina crucible, and the eutectic temperature was 890 ° C.
Fe ₂ was produced. This alloy was heated to 1000 ° C., which is a temperature higher than the eutectic temperature, in argon gas and held for 1 hour, after which 100 ° C./h, 200 ° C./h, 500 ° C./h,
Alternatively, it was cooled at a cooling rate of 1000 ° C./h. After this, 5
A sample having a diameter of 1 mm and a thickness of 1 mm was cut out to prepare a sample for measuring coercive force. The coercive force of each sample was measured by measuring the magnetization-magnetic field curve using a vibrating sample magnetometer. The results are shown in FIG. From FIG. 9, the cooling rate is 500 ° C./h
It can be seen that in the following cases, a low coercive force of 10 to 30 Oe is exhibited. For comparison, the same experiment as described above was performed, except that the heating temperature of the DyFe ₂ alloy was 750 ° C., which was a temperature lower than the eutectic temperature. The results are shown in FIG.
From FIG. 10, when the heating temperature is lower than the eutectic temperature,
It can be seen that the coercive force is as high as 80 to 120 Oe regardless of the cooling rate.

As another heat treatment, a polycrystalline giant magnetostrictive alloy ingot having a desired composition is produced, and the alloy ingot and the heating furnace are heated in a furnace having a temperature gradient of 20 ° C./cm or more in a temperature range below the melting point. It is also possible to use a method in which the moving speed is set to 5 to 400 mm / h, and the moving speed is relatively moved to cool. The reasons for defining the heat treatment conditions are as follows. If the heating temperature is above the melting point, a reaction with the crucible occurs. When the temperature gradient is less than 20 ° C / cm, the relative moving speed between the alloy ingot and the heating furnace is 5 mm / cm.
The speed must be lower than h, which causes a problem in productivity. The relative moving speed between the alloy ingot and the heating furnace is 5
If it is less than mm / h, there is a problem in productivity, while 400 mm
If it exceeds / h, the crystal orientation cannot be controlled. In this method, one end or both ends of the alloy ingot may be fixed and held in the heating furnace without using the crucible, or an inexpensive crucible material may be selected or the crucible may be reused.

As the alloy ingot, an alloy ingot which has been subjected to plastic deformation processing such as extrusion processing, drawing processing and rolling in the temperature range of 500 ° C. or higher and lower than the melting point may be used. Alternatively, the alloy ingot may be put into a metal pipe, and both may be plastically deformed at the same time. In this case, a metal or alloy (for example, stainless steel) having a melting point equal to or higher than the processing temperature is used as the coating metal pipe. Regarding the temperature of the plastic deformation process, if the temperature is lower than 500 ° C, sufficient plastic deformability cannot be obtained, and if the temperature is higher than the melting point, the shape of the alloy cannot be maintained. A more preferable temperature range is 800 to 1200 ° C.
Is. When the plastic deformation process is performed in this way, the crystal grains become fine, and when the heat treatment is subsequently performed, the crystal grains become coarse, so that the control of the crystal orientation becomes easy. Further, by performing the plastic deformation process a plurality of times, it becomes possible to manufacture a thin wire rod from a large-shaped ingot.
The plastic deformation process and the heat treatment are preferably performed in a vacuum or in an atmosphere of an inert gas such as argon or helium.

A specific example of this heat treatment method will be described below. Example 1: Tb _0.4 Dy _0.6 (Fe _0.95 Mn _0.05 ) in atomic ratio
Each element was blended so as to be _1.93, and high-frequency induction melting was performed using an alumina crucible in an argon atmosphere, and then cast into a quartz crucible to give an outer diameter of 15 mm and a length of 20.
A 0 mm alloy rod was obtained. The obtained alloy rod was held in an alumina crucible, and the temperature gradient in the range of 1130 ° C to 980 ° C was set to 50 ° C / cm in a heating furnace at 70 mm /
It was lowered at a speed of h. 7mm of alloy rod after heat treatment
Was processed into a cube, and the magnetostrictive properties in the rod axial direction and its orthogonal direction were evaluated using a strain gauge at room temperature. The magnetic field is generated by a counter pole type magnet and the magnetostriction (λ
_{2 kOe} ) was measured. As a result, the rod axial direction is 950
ppm, which is a low value of 380 ppm in the orthogonal direction, and an alloy rod having large magnetostriction anisotropy could be obtained.

Example 2: Tb _0.5 Dy _0.5 (Fe in atomic ratio
_0.9 Mn _0.1 ) _1.95 , each element was mixed, and after high frequency induction melting using an alumina crucible in an argon atmosphere, cast into an alumina mold having an inner diameter of 30 mm heated to 1100 ° C. by a carbon heater, Further, a water-cooled copper plate was used as a cooling plate and furnace cooling was performed to obtain an alloy ingot. The obtained giant magnetostrictive ingot is hot extruded at a processing temperature of 1080 ° C. and a pressure of 4 ton / cm ² ,
A giant magnetostrictive alloy rod having a diameter of 10 mm was obtained. The lower end of the obtained alloy rod was held and the temperature gradient in the range of 1150 ° C to 1000 ° C was set to 70 ° C / cm in a heating furnace at 100 ° C.
It was lowered at a speed of mm / h. The alloy rod after the heat treatment was processed into a cube of 6 mm, and the magnetostrictive characteristics in the extrusion axis direction and the direction orthogonal thereto were evaluated using a strain gauge at room temperature.
The magnetic field was generated by a counter-pole magnet, and the magnetostriction (λ _2kOe ) in a 2kOe magnetic field was measured. As a result, it was possible to obtain an alloy rod having a large magnetostriction anisotropy, which was a low value of 1050 ppm in the extrusion axis direction and 350 ppm in the orthogonal direction.

In the heat treatment method as described above, even if a relatively large alloy ingot is used, it is not melted, so that the reaction with the crucible can be avoided and the crystal orientation can be controlled. In addition, you may use the foil body of the giant magnetostrictive material obtained by the ultraquenching technique. In this case, a composition containing B, P, C, Si or the like as an amorphizing element is preferable.

The giant magnetostrictive material obtained by the above method can be applied to various magnetic-mechanical displacement conversion devices in addition to the angular velocity sensor. For example, as a magnetostrictive vibrator, it is applied to speakers, sonar, parts feeders, ultrasonic processing machines, motor vibration isolation / vibration prevention mechanism, etc., as a displacement control actuator, precision positioning mechanism, valve control valve, mechanical switch, micro pump, printer. It can be applied to heads, magnetostrictive sensors such as pressure sensors, knock sensors, sound pressure sensors, and surface acoustic wave devices.

[0035]

EXAMPLES Examples of the present invention will be described below. Embodiment 1 FIG. 1 is a perspective view of an angular velocity sensor in this embodiment, and FIG. 2 is a block diagram of a circuit of this angular velocity sensor.

In FIG. 1, a U-shaped vibrating body 11 constituting an angular velocity sensor is made of a giant magnetostrictive material having a composition of Tb _0.3 Dy _0.7 Fe _1.9 , and has a rod shape of <112> orientation manufactured by the Bridgman method. The alloy is formed by diamond processing. A drive coil 12 is provided around the connecting portion that connects the two legs of the U-shaped vibrator 11.
However, the detection coils 13a and 13b are provided around the two legs.
However, they are wound in a non-contact manner.

As shown in FIG. 2, the drive coil 12 is connected to the oscillation circuit 14, and the oscillation circuit 14 is connected to the synchronous detection circuit 17
It is connected to the. The detection coils 13a and 13b are connected to the amplifiers 15a and 15b, respectively. These amplifiers 15a and 15b are connected to a differential amplifier 16, and the differential amplifier 16 is connected to a synchronous detection circuit 17.

The operation of this angular velocity sensor will be described. An alternating voltage of about 10 V is applied to the drive coil 12 by the oscillation circuit 14, and an exciting magnetic field generated by the drive coil 12 is applied to the vibrating body 11 to cause it to flexurally vibrate. Also, the oscillator 1
A reference signal serving as a phase reference is directly supplied from 4 to the synchronous detection circuit 17. Since the vibrating body 11 is vibrating in this way, the legs of the vibrating body 11 are magnetized by the inverse magnetostrictive effect. A signal corresponding to this magnetization is detected by the detection coil 13.
The signals are amplified and detected by the amplifiers 15a and 15b connected to a and 13b, the difference between the two signals is amplified by the differential amplifier 16, and this signal is synchronously rectified by the synchronous detection circuit 17.

As can be seen from the above description, the vibrating body 11
When the rotational angular velocity is not applied to, the signals from both detection coils 13a and 13b are canceled and no output is generated. On the other hand, when a rotational angular velocity around a vertical axis as indicated by an arrow in the figure is applied to the vibrating body 11 that is flexibly vibrating, a Coriolis force is generated in a direction orthogonal to the vibration direction of the legs of the vibrating body 11. As a result, the vibration direction of the leg portion deviates from the basic vibration direction, the stress acting on the leg portion changes due to this deviation, and the magnetization generated by the inverse magnetostriction effect changes. Therefore, the impedance change in the detection coils 13a and 13b is obtained as an output corresponding to the rotational angular velocity.

Although the solenoid coil is used as the drive coil in FIG. 1, the same effect can be obtained by using a circulating magnetic field generated by the line current 18 as shown in FIG. 3 instead. However, this configuration requires about 10 times the current as compared with the case where the solenoid coil is used.

Embodiment 2 FIG. 4 shows an exploded perspective view of the angular velocity sensor in this embodiment. In the angular velocity sensor of FIG. 4, first and second U-shaped vibrators 11 and 21 are sequentially stacked on a plate-shaped samarium-cobalt magnet 22. These U-shaped vibrators 11 and 21 have Tb _0.4 Dy _0.6 (F
e _0.9 Mn _0.1 ) _1.95 composed of a giant magnetostrictive material, which is formed by diamond processing from a <110> -oriented rod-shaped alloy produced by the Bridgman method. The drive coils 12a and 12b are wound around the two legs of the first U-shaped vibrator 11 in a non-contact manner.
Detection coils 13a and 13b are wound around the two legs of the U-shaped vibrating body 21 in a non-contact manner. The plate-shaped samarium-cobalt magnet 22 is provided to apply a magnetic bias to the vibrating body. The magnetic bias is set to an optimum value in advance so that the vibrating body operates in the region of maximum magnetostriction.

In this angular velocity sensor, the drive coil 12
a and 12b cause the first U-shaped vibrating body 11 to flexurally vibrate, and this vibration is transmitted to the second U-shaped vibrating body 21 to flexurally vibrate.
The detection coil 1 detects a vibration change occurring in the U-shaped vibrator 21.
3a, 13b and the detection circuit similar to that of the first embodiment, an output corresponding to the rotational angular velocity is obtained. Also, samarium
Since the bias magnetic field is applied to the vibrating body by the cobalt magnet 22, it is possible to operate in a region where the relationship between the magnetostriction and the magnetic field (current) is linear and the maximum magnetostriction rate is exhibited. The sensitivity is improved.

Embodiment 3 FIG. 5 is a perspective view of an angular velocity sensor in this embodiment, and FIG.
A block diagram of the circuit of this angular velocity sensor is shown in FIG. In FIG. 5, the cross-shaped vibrating body 31 forming the angular velocity sensor is
Tb _0.35 Dy _0.65 (Fe _0.9 Mn _0.05 Al _0.05 ), which is composed of a giant magnetostrictive material having a composition of _1.93 , is produced by the Bridgman method and sliced into a 0.1 mm-thick rod-shaped alloy having a <112> orientation. , Molded in a cross shape. Drive coils 32a and 32b are wound around one axis of the cross-shaped vibrating body 31, and detection coils 33a and 33b are wound around the other axis in a non-contact manner.

As shown in FIG. 6, the drive coils 32a, 3a
2b is connected to the oscillation circuit 34, and the oscillation circuit 34 is connected to the synchronous detection circuit 37. Detection coils 33a, 33
b is connected to the amplifiers 35a and 35b, respectively. These amplifiers 35a and 35b are connected to a differential amplifier 36, and the differential amplifier 36 is connected to a synchronous detection circuit 37.

In this angular velocity sensor, an oscillating circuit 34 applies an AC voltage of about 10 V to the drive coils 32a and 32b, and an exciting magnetic field generated by the drive coils 32a and 32b is applied to the vibrating body 31 to cause bending vibration. . Also,
A reference signal serving as a phase reference is directly supplied from the oscillator 34 to the synchronous detection circuit 37. Now, when a rotational angular velocity is applied to the vibrating body 31 that is flexibly vibrating, a Coriolis force is generated in a direction orthogonal to the vibration direction of the vibrating body 31. As a result, the vibration direction of the vibrating body 31 deviates from the basic vibration direction, the stress acting on the vibrating body 31 changes due to this deviation, and the magnetization generated by the inverse magnetostriction effect changes. Therefore, the impedance change in the detection coils 33a and 33b is obtained as an output corresponding to the rotational angular velocity.

Although the solenoid coil is used as the drive coil in FIG. 5, the same effect can be obtained by using a circulating magnetic field generated by the line current 38 as shown in FIG. However, this configuration requires about 10 times the current as compared with the case where the solenoid coil is used.

Embodiment 4 FIG. 8 shows an exploded perspective view of the angular velocity sensor in this embodiment. In the angular velocity sensor of FIG. 8, a cross-shaped vibrating body 41 and a frame body 42 holding the cross-shaped vibrating body 41 are integrated on two plate-shaped samarium-cobalt magnets 43, 43, and the cross-shaped vibrating body 41. Corresponding to the planar drive coil 52
A polyimide film 44 on which a and 52b and flat type detection coils 53a and 53b are formed is sequentially stacked. The cross-shaped vibrating body 41 and the frame body 42 are Tb _0.5 Dy.
_0.5 (Fe _0.9 Mn _0.1 ) _1.95 composed of a giant magnetostrictive material and manufactured by Bridgman method <110
＞ 0.1mm by diamond processing of oriented rod-shaped alloy
After being sliced to a thickness, it is formed by laser processing. The shape of the planar drive coils 52a and 52b and the planar detection coils 53a and 53b may be any of spiral shape, rectangular shape, and meander shape, and are manufactured by a semiconductor process.

In this angular velocity sensor, the flat drive coils 52a and 52b oscillate the X-direction axis of the cross-shaped vibrating body 42, and the flat detection coils 53a and 53b and the detection circuit similar to that of the third embodiment detect the Y-direction. The change in shaft vibration is obtained as an output corresponding to the angular velocity of rotation. Also, samarium
Since the bias magnetic field is applied to the vibrating body 41 by the cobalt magnets 43, 43, the relationship between the magnetostriction and the magnetic field (current) can be linear, and the magnetic field can be operated in the region exhibiting the maximum magnetostriction. Performance and sensor sensitivity are improved. Furthermore, in this angular velocity sensor, the cross-shaped vibrating body 41 is used.
By optimizing the mass of the intersection point 41a, the vibration can be increased and the resonance frequency can be made variable.

[0049]

As described in detail above, according to the present invention, it is possible to provide a small-sized and practical angular velocity sensor capable of accurately detecting the angular velocity.

[Brief description of drawings]

FIG. 1 is a perspective view of an angular velocity sensor according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a circuit of the angular velocity sensor according to the first embodiment of the present invention.

FIG. 3 is a perspective view of a modification of the angular velocity sensor according to the first embodiment of the present invention.

FIG. 4 is an exploded perspective view of an angular velocity sensor according to a second embodiment of the present invention.

FIG. 5 is a perspective view of an angular velocity sensor according to a third embodiment of the present invention.

FIG. 6 is a block diagram showing a circuit of an angular velocity sensor according to a third embodiment of the present invention.

FIG. 7 is a perspective view of a modified example of the angular velocity sensor according to the third embodiment of the present invention.

FIG. 8 is an exploded perspective view of an angular velocity sensor according to a fourth embodiment of the present invention.

FIG. 9 is a characteristic diagram showing coercive force of a giant magnetostrictive alloy heat-treated by the heat treatment method according to the present invention.

FIG. 10 is a characteristic diagram showing the coercive force of a giant magnetostrictive alloy heat-treated by another heat treatment method.

FIG. 11 is a perspective view of a conventional piezoelectric angular velocity sensor.

[Explanation of symbols]

11, 21 ... U-shaped vibrator, 12, 12a, 12b,
32a, 32b ... Drive coil, 13a, 13b, 33
a, 33b ... Detection coil, 14, 34 ... Oscillation circuit, 15
a, 15b, 35a, 35b ... Amplifier, 16, 36 ... Differential amplifier, 17, 37 ... Synchronous detection circuit, 22, 43 ... Samarium-cobalt magnet, 31, 41 ... Cross-shaped vibrating body,
42 ... Frame body, 44 ... Polyimide film, 52a, 52
b ... Planar drive coil, 53a, 53b ... Planar detection coil.

Claims (3)

[Claims] 1. A vibrating body made of a giant magnetostrictive material having an intermetallic compound of a rare earth metal and a transition metal as a main phase, and means for applying a magnetic field to the vibrating body to generate vibration by magnetostriction.
An angular velocity sensor comprising: means for detecting a change in magnetization corresponding to a change in vibration when an angular velocity is applied to the vibrating body. 2. The angular velocity sensor according to claim 1, wherein the vibrating body has a U-shape. 3. The angular velocity sensor according to claim 1, wherein the vibrating body has a cross shape.