JPH06194244A - Pressure sensor using magnetostrictive device - Google Patents

Abstract

PURPOSE:To improve the reliability and integrate a pressure regulating actuator so as to simplify its system in a pressure sensor for detecting a fluid pressure by using a magnetostrictive device. CONSTITUTION:A magnetostrictive device 3 is placed inside a housing 2 and fluid routes 10, 13 and 15 are prepared to communicate the space 2b within the housing 2 with a pressure control chamber 11 and a reserve tank 16. Further the space 2b is connected with the magnetostrictive device 3 while it is separated from a space 2a for arranging the magnetostrictive device 3, and a piston 5 is prepared in a manner to be slidable in the housing 2. in addition, a Hall element 20 is provided to detect the magnetizing condition in the longitudinal direction of the magnetostrictive device 3 and a coil 22 for applying a magnetic field is also provided to apply to the magnetostrictive device 3 the magnetic field having the same direction as that for making the piston 5 to slide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor using a magnetostrictive element, and more particularly to a pressure sensor for detecting a fluid pressure using the magnetostrictive element.

[0002]

2. Description of the Related Art Conventionally, as a pressure sensor for detecting a pressure of a fluid, an amorphous magnetic alloy is fixed to a portion which is deformed by the pressure, and the pressure is changed by paying attention to a change in magnetic permeability of the amorphous magnetic alloy. A pressure sensor for detecting is known (Japanese Patent Application Laid-Open No. HEI-2
No. 21233).

In the pressure sensor described in the above publication, an amorphous magnetic alloy is fixed to an axis whose longitudinal direction is the direction to which the pressure to be detected is applied, and the strain corresponding to the applied pressure is applied to the amorphous magnetic alloy. It is generated in the alloy. Then, a predetermined magnetic field is applied to the amorphous magnetic alloy, and the applied pressure is detected by detecting the magnetic permeability of the amorphous magnetic alloy that exhibits a change according to the strain generated in itself.

[0004]

However, in the pressure sensor having the above-mentioned conventional structure, the portion (the shaft) that is deformed by pressure is used.
And the amorphous magnetic alloy are fixed, and as long as some pressure is applied to the sensor,
Stress is applied to the fixed portion between the shaft and the amorphous magnetic alloy. Therefore, there is a problem in that the adhered portion is likely to be peeled off, and there is a problem in reliability as a sensor.

When such a sensor is used, for example, in a hydraulic system for maintaining the belt tension at an appropriate value, it is necessary to provide an actuator for adjusting the hydraulic pressure separately from the pressure sensor. For this reason, many systems using such a pressure sensor conventionally have a configuration in which a pressure sensor and a pressure adjusting actuator are independently provided, and the cost is increased due to the complexity of the system.

The present invention has been made in view of the above-mentioned points, and aims to improve reliability by eliminating a fixed portion that may cause peeling due to stress applied during pressure detection, and for pressure adjustment. It is an object of the present invention to provide a pressure sensor using a magnetostrictive element that integrates an actuator and enables simplification of the above system.

[0007]

A pressure sensor using a magnetostrictive element having the following structure can eliminate a fixed portion having a possibility of peeling.

According to the first aspect of the invention, the magnetostrictive element is arranged inside the housing.

Further, a communication port for establishing communication between the internal space of the housing and the fluid chamber or the fluid path is provided.

Further, a piston is provided so as to separate the inner space of the housing into a side provided with a communication port and a side on which the magnetostrictive element is arranged, while being connected to the magnetostrictive element and slidable in the housing. .

Then, a magnetization state detecting means for detecting the magnetization state of the magnetostrictive element is provided. In this case, as in the invention of claim 2, by providing the magnetic field applying means for applying the magnetic field in the same direction as the direction in which the piston can slide to the magnetostrictive element,
A pressure adjusting actuator can be integrated.

According to the third aspect of the invention, the magnetostrictive element is arranged inside the housing.

Further, a communication port and a discharge port for communicating the internal space of the housing with the fluid chamber or the fluid path are provided.

Further, a magnetization state detecting means for detecting the magnetization state of the magnetostrictive element is provided.

Furthermore, magnetic field applying means for applying a magnetic field to expand and contract the magnetostrictive element is provided.

Further, a valve portion which is opened and closed by contraction of the magnetostrictive element is arranged between the communication port and the discharge port.

[0017]

In the pressure sensor using the magnetostrictive element according to the first aspect of the present invention, the fluid whose pressure is to be detected is introduced into the internal space of the housing through the communication port. The fluid thus introduced is blocked by the piston and does not enter the space in the housing where the magnetostrictive element is disposed.

Therefore, a pressure difference corresponding to the fluid pressure is generated on both sides of the piston. Therefore, the piston is
The magnetostrictive element is moved in the housing toward the magnetostrictive element, and the magnetostrictive element is pressed by a force corresponding to the pressure of the fluid. And
Due to its characteristic, the magnetostrictive element exhibits magnetization according to the force applied to the piston.

Therefore, the magnetized state detecting means detects the pressure of the fluid by detecting the magnetized state of the magnetostrictive element. At this time, the pressure of the fluid acts only in the direction in which the piston is pressed against the magnetostrictive element to compress the magnetostrictive element, and does not cause peeling of component members or the like.

Further, the magnetic field applying means of claim 2 applies a magnetic field to the magnetostrictive element in the same direction as the direction in which the piston can slide. Therefore, magnetostriction is generated in the magnetostrictive element according to the magnetic field, and the magnetostrictive element expands and contracts in the same direction as the direction in which the piston can slide. As the piston expands and contracts, the piston slides in the housing to change the volume of the space including the communication port. Therefore, the pressure in the system using the fluid is adjusted.

In the pressure sensor using the magnetostrictive element according to the third aspect of the present invention, the fluid whose pressure is to be detected is introduced into the housing through the communication port. Then, the magnetostrictive element is pressed by a force corresponding to the pressure of the introduced fluid, and exhibits magnetization according to the pressing force. Further, the pressure of the fluid is detected by detecting the magnetized state of the magnetostrictive element by the magnetized state detecting means. Further, by applying / non-applying the magnetic field to the magnetostrictive element by the magnetic field applying means, the magnetostrictive element expands and contracts to open / close the valve portion, and the pressure in the system using the fluid is adjusted.

Therefore, the fluid pressure acts only in the direction of compressing the magnetostrictive element, and the fluid pressure is maintained at a predetermined pressure value.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of an embodiment of a pressure sensor using a magnetostrictive element according to the present invention. In FIG. 1, reference numeral 2 indicates a housing of the pressure sensor 1 of this embodiment. Inside the housing 2, a magnetostrictive element 3, a permanent magnet 4, and a piston 5 are arranged.

When a magnetic field is applied, the magnetostrictive element 3 causes magnetostriction in the same direction as the direction of the magnetic field, and when a mechanical stress is applied, the magnetostrictive element 3 changes the magnetization state of the element to change the stress direction. It is an element that changes the magnetic flux generated in the same direction. The magnetostrictive element 3 is connected to the housing 2 and the piston 5 via a permanent magnet 4 arranged at the end in the longitudinal direction. In this embodiment, the positive magnetostrictive material Tb _0.3 which is known to have a particularly large magnetostriction rate is used.
A giant magnetostrictive element made of Dy _0.7 Fe _1.9 or a negative magnetostrictive material SmFe ₂ is used.

The piston 5 can slide inside the housing 2 in the same direction as the longitudinal direction of the magnetostrictive element, and divides the internal space of the housing 2 into two spaces. Of the divided spaces, the magnetostrictive element 3 and the permanent magnet 4 are disposed in one space 2a as described above. The other space 2b communicates with a fluid chamber or a fluid path through a fluid inlet 6, an outlet 7, and a supply port 8 provided in the housing 2. The fluid inlet 6, the fluid outlet 7, and the replenishment port 8 correspond to the above-mentioned communication port.

The fluid inlet 6 communicates with a pressure control chamber 11 via a fluid passage 10 having an on / off valve 9, and the fluid outlet 7 communicates with a pressure control chamber 11 via a fluid passage 13 having a check valve 12. ing. The check valve 12 is a one-way valve that allows only the flow from the space 2b in the housing 2 to the pressure control chamber 11.

The fluid supply port 8 is provided with a fluid reserve tank 16 through a fluid passage 15 having a check valve 14.
Is in communication with. This check valve 14 is used for the reserve tank 1
This is a one-way valve that allows only the flow from 6 to the space 2b in the housing 2.

The reserve tank 16 is connected to the pressure control chamber 11 via a fluid passage 18 having a constant pressure release valve 17. The constant pressure release valve 17 is opened when the internal pressure of the pressure control chamber 11 exceeds a predetermined pressure, and the constant pressure release valve 17 is opened.
By discharging the fluid in the reserve tank 16,
This is a valve for maintaining the internal pressure of the pressure control chamber 11 at an appropriate value.

Therefore, when the on / off valve 9 is opened, the fluid can freely flow back and forth between the space 2b in the housing 2 and the pressure control chamber 11 through the fluid passage 10 and those spaces. Are held in conduction with each other. On the other hand, when the on / off valve 9 is closed,
The direction in which the fluid can flow is restricted by the action of the check valves 12 and 14, and the fluid can only flow from the reserve tank 15 to the space 2b and from the space 2b to the pressure control chamber 11 unless the constant pressure release valve 17 is opened. is there.

The pressure control chamber 11 communicates with the space inside the pressure sensor 1 as described above, and the hydraulic system 25 is required to have a stable fluid pressure via the fluid passage 19.
For example, it is connected to a hydraulic chamber such as a tensioner of various drive belts.

Further, in FIG. 1, reference numeral 20 indicates a Hall element corresponding to the above-mentioned magnetized state detecting means. The Hall element 11 is arranged so as to detect the magnetic flux density in the same direction as the longitudinal direction of the magnetostrictive element 3, and the detected value is the Gauss meter 2
Output to 1.

Reference numeral 22 indicates a magnetic field applying coil corresponding to the above-mentioned magnetic field applying means. This magnetic field applying coil 2
2 is such that the magnetostrictive element 3 is located at the center,
It is arranged so that its axial direction coincides with the longitudinal direction of the magnetostrictive element 3. Therefore, the magnetic field generated by passing a current through the magnetic field applying coil 22 acts on the magnetostrictive element 3 to cause longitudinal magnetostriction.

Here, the magnetic field applying coil 22 and the on / off valve 9 are both connected to the drive circuit 23, and generate a predetermined magnetic field according to the drive signal supplied from the drive circuit 23, or the fluid passage 10. Control the continuity of.

The operation of the apparatus of this embodiment described above will be described below. In the initial stage, the space 2b in the housing 2 and the pressure control chamber 11 are filled with fluid at an appropriate pressure, and the on / off valve 9 is open.

When the space 2b is filled with fluid, the pressure of the piston 5 pushes the piston 5 toward the space 2a. Since the piston 5 can slide in the housing 2 in the predetermined direction as described above, it is displaced in the direction in which the magnetostrictive element 3 is compressed by this pressing force and reaches the position where the fluid pressure and the reaction force of the magnetostrictive element 3 are balanced. Moving.

That is, a stress corresponding to the pressure of the fluid is applied to the magnetostrictive element 3, and a strain corresponding to the stress is generated in the longitudinal direction of the magnetostrictive element 3. On the other hand, as described above, the magnetostrictive element 3 is an element that changes the magnetization state according to the strain generated in itself. Therefore, when such strain occurs, the magnetic flux density in the longitudinal direction emitted from the magnetostrictive element 3 changes according to the applied stress.

FIG. 2 is a graph showing the relationship between the compressive stress applied to the magnetostrictive element 3 and the result of measuring the change in the magnetic flux density emitted from the magnetostrictive element 3 with the Hall element 20 and the Gauss meter 21 in this embodiment. Show. As shown in the figure, when the compressive stress is in the range of 0 to 2.0 kgf / mm ² , the compressive stress applied to the magnetostrictive element 3 and the Hall element 20
Shows a nearly linear relationship with the magnetic flux density detected, and the magnetic flux density shows a change of about 0 to 2.0 G.

In the permanent magnet 4 of this embodiment, a bias magnetic field is applied to the magnetostrictive element 3 in advance so that the compressive stress and the change in magnetic flux density have a good relationship as shown in FIG. It is provided.

That is, as can be seen from the initial magnetization characteristics of the magnetostrictive element 3 shown in FIG. 3, the magnetic flux density generated from the magnetostrictive element 3 changes slowly when the bias magnetic field is near zero. On the other hand, the magnetic flux density near the appropriate bias magnetic field Hm shows a sudden change.

Therefore, in order to greatly change the magnetization state of the magnetostrictive element 3 and improve the accuracy as a pressure sensor,
It is necessary to apply an appropriate bias magnetic field Hm in advance, and in this embodiment, this bias magnetic field is generated by the permanent magnets 4 arranged at both ends of the magnetostrictive element 3.
Therefore, the magnetostrictive element 3 increases the magnetic flux density substantially linearly in response to a slight change in compressive stress, and exhibits good characteristics as shown in FIG.

As described above, in the present embodiment, by opening the on / off valve 9, the pressure in the pressure control chamber 11 is guided to the space 2b in the housing 2, and the pressure is applied to the magnetostrictive element 3 as well. The Hall element 20 and the Gauss meter 21 enable accurate measurement.

Further, as described above, the present embodiment has a structure in which the magnetostrictive element 3 is compressed by the fluid through the piston 5 and the permanent magnet 4, which causes a problem in reliability such as shear stress in any part. Such stress does not occur. Therefore, in the above-described pressure sensor of the conventional configuration, peeling is likely to occur between the shaft that generates strain due to pressure and the amorphous magnetic alloy that is fixed to the shaft. It is possible to avoid such a defect.

Further, it is not necessary to draw out the signal line, which is required when using a piezoelectric element such as lead zirconate titanate (PZT) which has been widely applied to pressure sensors from the inside of the housing 2. Therefore, as compared with the configuration using PZT, a mechanism for preventing fluid leakage in the lead-out hole of the signal line is not required, and the configuration is simplified and epoch-making assembly can be facilitated.

By the way, when the environmental temperature of the pressure sensor 1 and the hydraulic system 25 of this embodiment rises, the fluid existing in the system of the pressure sensor 1 and the hydraulic system 25 thermally expands. When the fluid present inside expands, the pressure in the pressure control chamber 11 and the space 2b rises. And
When this pressure exceeds the opening pressure of the constant pressure release valve 17, it passes through the fluid passage 18 from the pressure control chamber 11 to the reserve tank 16
The fluid is discharged toward.

When the pressure in the pressure control chamber 11 drops due to the discharge of the fluid and becomes lower than the opening pressure of the constant pressure release valve 17, the fluid passage 18 is cut off again and the pressure control chamber 11 and the space 2 are closed.
b is separated from the reserve tank 16.

When the environmental temperature of the pressure sensor 1 and the hydraulic system 25 decreases from this state, the fluid existing in the pressure control chamber 11 and the space 2b contracts, and the fluid pressure supplied to the hydraulic system 25 decreases. Become.

By the way, in many cases, the pressure sensor 1 is provided in such a hydraulic system 25 in order to monitor the pressure in the system and increase the fluid pressure when a pressure drop is detected. Is. Therefore, conventionally, in such a system, an actuator for increasing pressure is provided separately from the pressure sensor.

By the way, in the magnetostrictive element 3 of this embodiment, a magnetic field is applied by the magnetic field applying coil 22 as described above, so that distortion occurs in the longitudinal direction. At this time, the magnetostrictive element 3
A bias magnetic field Hm is applied to each of them as shown in FIG. Therefore, if the magnetic field applying coil 22 alternately applies a magnetic field in a direction in which the bias magnetic field Hm is strengthened and a magnetic field in a direction in which the bias magnetic field Hm is weakened, the magnetostrictive element 3 is centered on the entire length when the bias magnetic field Hm is applied. As a result, it expands and contracts in the longitudinal direction.

That is, when an alternating current is supplied from the drive circuit 23 to the magnetic field applying coil 22, the magnetostrictive element 3 repeats expansion and contraction according to the cycle of the alternating current. Therefore, assuming that the amplitude is ΔL and the diameter of the piston 5 is d, the expansion / contraction of the magnetostrictive element 3 for one cycle causes ΔV.
= Volume change represented by ΔL · π · d ^2/4 is, space 2a
Occur in.

In this embodiment, the diameter d of the piston 5 is
= 10 mm, total length L = 50 mm, and magnetostriction λ = 1000 ppm due to application of an alternating magnetic field (ΔL = L.
λ), the volume of 3 mm ³ changes in the space 2b due to expansion and contraction for one cycle.

Therefore, the pressure sensor 1 constitutes a pump by utilizing this volume change, and the pressure control chamber 11 and the space 2b.
When the internal pressure of is decreased, the pressure can be increased. That is, the drive circuit 23 monitors the pressure of the fluid from the magnetized state of the magnetostrictive element 3 using the Hall element 20 and the Gauss meter 21, and when detecting the decrease in the pressure, first closes the on / off valve 9. Next, a predetermined alternating current is supplied to the magnetic field applying coil 22. Along with this, the magnetostrictive element 3 begins to expand and contract as described above.

When the magnetostrictive element 3 shifts from the contracted state to the extended state, the space 2 is moved as described above as the piston 5 moves.
The volume of b is reduced by 3 mm ³ . At this time, 3 mm ³ of fluid needs to be discharged from the space 2b, but the fluid passage 10 is shut off by the on / off valve 9. Further, due to the action of the check valve 14, the fluid cannot flow out from the space 2b to the fluid passage 15. Therefore, the volume reduction of the space 2b is 3
All mm ³ will flow into the pressure control chamber 11 through the fluid passage 13.

When the magnetostrictive element 3 shifts from the extended state to the contracted state, the volume of the space 2b increases by 3 mm ³ contrary to the above case. Therefore, in this case, 3 mm ³ of fluid needs to be introduced into the space 2b.

This time, the check valves 12 and 14 act in reverse to the above cases. That is, since the check valve 12 prevents the fluid from flowing from the pressure control chamber 11 to the space 2b,
The fluid flows through the fluid passage 15 into the space 2b only from the reserve tank 16. Therefore, the fluid in the pressure control chamber 11 does not flow out to the outside, and its internal pressure is maintained in a state of being increased by the inflow of 3 mm ³ .

That is, when an alternating current is supplied to the magnetic field applying coil 22 with the on / off valve 9 closed, a fluid of 3 mm ³ flows from the reserve tank 16 to the pressure control chamber every time the magnetostrictive element 3 expands or contracts in accordance with the alternating cycle. As a result, the pressure in the hydraulic system is gradually increased.

As described above, the pressure sensor 1 of this embodiment can detect the pressure of the fluid with high reliability and high accuracy, and when the internal pressure of the hydraulic system 25 decreases, It also functions as an actuator for increasing the pressure, and it is not necessary to separately provide an actuator for increasing pressure as in a system using a conventional pressure sensor.

When the magnetostrictive element 3 is used as a pressure increasing actuator, that is, the magnetic field applying coil 2 is used.
When an AC magnetic field is emitted from 2, the Hall element 2
The magnetic flux generated by the magnetostrictive element 3 and the magnetic flux generated by the magnetic field applying coil are applied to 0 in a superposed state.

Therefore, in this case, correction is made by subtracting the magnetic flux generated from the magnetic field applying coil 22 from the magnetic flux detected by the Hall element 20 and the Gauss meter 21, and at the preset time such as the maximum extension of the magnetostrictive element 3. By taking in the magnetic flux density, the pressure inside the pressure control chamber 11 can be detected.

At this time, the magnetic flux generated from the magnetic field applying coil 22 is generated based on the value of the current flowing in the magnetic field applying coil 22, and is further outside the magnetic field applying coil 22 to further pick up a magnetic field detecting pickup coil. May be provided, and it may be performed based on the magnetic flux detected by the pickup coil.

If such a mechanism is not provided, the magnetic field applying coil 22 may apply a magnetic field slightly different from the Hall element 20 in detecting magnetic flux, or the magnetic field may be applied at predetermined intervals. The Hall element 20 and the Gauss meter 2 are stopped by stopping the magnetic field and detecting the magnetic flux.
The magnetic field emitted from the magnetic field applying coil 22 may be prevented from being superimposed on the magnetic flux detected by 1.

Even if the pressure increasing operation and the pressure detecting operation are separately performed in this manner, the pressure control chamber 11
When the internal pressure reaches a predetermined pressure, the constant pressure release valve 17
Since the valve is opened, the system internal pressure of the hydraulic system does not become excessive and reliability problems do not occur.

FIG. 4 is a block diagram of another embodiment of the pressure sensor according to the present invention. The pressure sensor 31 of the present embodiment has a pickup coil 32 as the above-mentioned magnetized state detecting means.
It is characterized by using. In FIG. 4, the same components as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

In FIG. 4, reference numeral 32 indicates a pickup coil which is an essential part of this embodiment. Pickup coil 32
Is arranged between the housing 2 and the magnetic field applying coil 22 such that the magnetostrictive element 3 is located at the center thereof. Therefore, when the longitudinal component of the magnetic flux emitted from the magnetostrictive element 3 changes, the pickup coil 32 changes in accordance with the change.
Induced electromotive force is generated.

Both ends of the winding wire constituting the pickup coil 32 are connected to an integrator / voltmeter 33. The integrator / voltmeter 33 integrates the induced electromotive force v (v = −dB / dt) generated in the pickup coil 32 and sets the integrated value as a voltage value V (V = −∫dB / dt · dt). ) This is the output circuit.

That is, the pressure in the space 2b in the housing 2 is
As the force changes, the magnetization state of the magnetostrictive element 3 in the longitudinal direction changes to B.₀
→ B₁Change to V = B in the integrator / voltmeter 33.₀
-B ₁= Voltage corresponding to ΔB (∫dB) will appear
It Therefore, the change of the Gauss meter 21 in FIG.
By monitoring the output of the integrator / voltmeter 33,
It is possible to detect the magnetization state of the strain element 3.

Note that the fluid pressure increasing mechanism operates exactly as in the case of the embodiment shown in FIG. 1, and in this embodiment as well, the pressure of the fluid supplied to the hydraulic system 25 can be increased appropriately. .

As described above, according to this embodiment, it is possible to perform pressure detection with high reliability and high accuracy as in the above embodiments, and the pressure boosting actuator can be integrally formed. it can. However, when the function as the actuator for boosting pressure is not required, that is, when it is sufficient to simply detect the pressure in the system, the magnetic field applying coil in FIGS. 1 and 4 may be omitted.

Further, in the above embodiment, the bias magnetic field Hm is created by sandwiching the magnetostrictive element 3 between the two permanent magnets 4, and the Hall element 20 is limited to the side surface of the magnetostrictive element 3. , But not limited to this.

For example, as shown in FIG. 5, a permanent magnet 4 and a magnetostrictive element 3 are sandwiched between a permanent magnet 4 and a magnetostrictive element 3, and a soft magnetic material 42 made of a silicon steel sheet for magnetic core, permalloy, pamenjour, etc. is sandwiched between the permanent magnet 4 and the permanent magnet 4. The magnetic flux may be efficiently guided to the magnetostrictive element 3. Furthermore, this permanent magnet 4 is not always 2
It is not necessary to provide one, and it may be provided only at one end of the magnetostrictive element 3.

By the way, in the case of the structure including the magnetic field applying coil 22 like the pressure sensor 51 shown in FIG. 6, instead of disposing the permanent magnets 4 at both ends of the magnetostrictive element 3, the bias magnetic field Hm is applied. The coil 22 may apply the voltage. That is, the bias current Ib is constantly supplied to the magnetic field applying coil 22, and when the magnetostrictive element 3 is expanded or contracted, a current that fluctuates with a predetermined amplitude centered on the bias current Ib may be supplied.

It is sufficient for the Hall element 20 to be able to detect the longitudinal component of the magnetic field emitted from the magnetostrictive element 3. Therefore, if the Hall element 20 is arranged in consideration of the directivity, it may be arranged on the extension of the magnetostrictive element as shown in FIG.

FIG. 7 is a constitutional view of still another embodiment of the pressure sensor according to the present invention. In FIG. 7, the same components as those in FIGS. 1 and 2 are designated by the same reference numerals and the description thereof will be omitted.

Reference numeral 60 in FIG. 7 denotes a pressure sensor according to this embodiment, and reference numeral 61 in the figure denotes a cylindrical housing made of a non-magnetic material.

An inflow port 62 corresponding to a communication port is formed in the upper part of the housing 61. This inlet 62
Are connected to, for example, a pressure control chamber (not shown) via a fluid passage (not shown). Further, at the bottom of the housing 61, a base portion 63 that constitutes a part of the housing 61 is provided.
Is provided.

A plurality of outlets 64 corresponding to discharge ports are formed in the vicinity of the peripheral edge of the base 63 so as to penetrate the base 63 at equal intervals in the circumferential direction. The plurality of outlets 64 communicate with, for example, a reserve tank (not shown) via fluid passages (not shown).

In the vicinity of the center of the upper surface of the base 63,
Via the permanent magnet 5, a giant magnetostrictive material such as Tb-Dy-F
A columnar magnetostrictive element 3 made of an e-based material is arranged so that, for example, the central axis of the magnetostrictive element 3 (vertical axis in FIG. 3) and the central axis of the housing 61 coincide with each other.

On the inner peripheral surface of the housing 61 facing the outer peripheral surface near the central portion of the magnetostrictive element 3 in the central axis direction, a triangular cross section made of an elastic material such as rubber is provided over the entire inner peripheral surface. The valve portion 70 constituted by the projection body is disposed. The tip portion of the valve portion 70 (the apex portion facing the magnetostrictive element 3 in FIG. 7) has a curvature of the circumference formed by the tip portion so that the fluid is not introduced into the housing 61. It is formed so as to correspond to the curvature of the outer peripheral surface of the magnetostrictive element 3 when the magnetostrictive element 3 is contracted in the central axis direction. Therefore, when the fluid is not introduced into the housing 61, that is, when the magnetostrictive element 3 is contracted, the valve portion 70 is magnetostrictive over the entire circumference of the tip portion of the valve portion 70 as shown in FIG. The outer peripheral surface of the element 3 is in contact with and closed. On the other hand, the valve section 7
0 indicates that when the magnetostrictive element 3 extends in the central axis direction and the curvature of the outer peripheral surface of the magnetostrictive element 3 is smaller than the curvature, the tip portion of the valve portion 70 has the magnetostrictive element 3 The valve is configured to be separated from the outer peripheral surface of the valve and closed.

Further, similarly to the above-described embodiment (see FIG. 4), the outer side of the housing 61 facing the magnetostrictive element 3 corresponds to a magnetized state detecting means for detecting the magnetized state of the magnetostrictive element 3. A pickup coil 32 is provided, and the pickup coil 32 includes an integrator / voltmeter 3
3 is connected to the pickup coil 32.
A magnetic field applying coil 22 corresponding to a magnetic field applying means for applying a magnetic field so as to expand and contract the magnetostrictive element 3 is arranged on the outer side of the magnetic field applying coil 22. Connected to the integrator / voltmeter 33.

The pickup coil 32, the integrator / voltmeter 33, the magnetic field applying coil, and the drive circuit 23 have the same functions as the above-described embodiments.

The operation of this embodiment will be described below with reference to FIG. FIG. 8 is an operation explanatory view for explaining the operation of the present embodiment.

When fluid is introduced into the housing 61 in which the magnetostrictive element 3 is contracted and the valve portion 70 is closed, for example, from a pressure control chamber (not shown) through a fluid passage (not shown) and an inflow port 62, magnetostriction occurs. A pressure corresponding to the fluid pressure P is applied to the element 3. Then, strain corresponding to this stress is generated in the magnetostrictive element 3 in the longitudinal direction, and the magnetostrictive element 3 further contracts in the longitudinal direction and expands in diameter, but in the magnetostrictive element 3, the outer peripheral surface of the magnetostrictive element 3 has a valve portion. Since the diameter of the valve portion 70 increases while making contact with the entire circumference of the tip portion of the valve 70, the valve closed state of the valve portion 70 is maintained. In this case, the increased diameter of the magnetostrictive element 3 is absorbed by the elastic deformation of the valve portion 70.

Further, since the magnetostrictive element 3 is an element that changes the magnetized state according to the strain generated by itself as described in the above-mentioned embodiment, when the strain in the longitudinal direction is generated, the magnetostrictive element is generated. The magnetic flux density in the longitudinal direction emitted from the element 3 changes according to the applied stress. An induced electromotive force U is generated in the pickup coil 32 according to a change in the longitudinal component of the magnetic flux generated from the magnetostrictive element 3, and the integrated value of the induced electromotive force U is generated in the integrator / voltmeter 33 as a voltage value. V
Is output as, the pressure P of the liquid is converted into a voltage value V and detected.

When the pressure value P of the fluid introduced into the housing 61 becomes a pressure value P ₁ higher than the reference pressure value P ₀ of the fluid due to thermal expansion or the like, induction is generated in the pickup coil 32. The electromotive force U becomes an electromotive force U ₁ higher than the induced electromotive force U ₀ corresponding to the reference pressure value P ₀ of the fluid, and the voltage value V output to the integrator / voltmeter 33 is the pressure of the fluid. wherein the high voltage V ₁ than the induced electromotive force U reference voltage V ₀ corresponding to ₀ when the reference pressure value P _0. Then, when the voltage value V of the integrated value / voltmeter 33 detects a voltage value V ₁ higher than the reference voltage value V ₀ , a signal is output from the integrated value / voltmeter 33 to the drive circuit 23 to cause the drive circuit 23 to operate. The magnetic field applying coil 22 is driven, and as a result, a predetermined alternating current is supplied to the magnetic field applying coil 22, and the magnetic field applying coil 22 is turned on.

On the other hand, the magnetostrictive element 3 is elongated in the longitudinal direction by the magnetic field applied by the magnetic field applying coil 22, and the outer peripheral surface of the magnetostrictive element 3 has a valve portion 70 as shown in FIG.
The valve portion 70 is opened apart from the tip of the valve. As a result, a part of the fluid flows to the downstream side of the valve portion 70,
It is discharged to, for example, a reserve tank (not shown) via the discharge port 64.

When the fluid pressure on the upstream side of the valve portion 70 becomes the reference pressure P ₀ due to the discharge of the fluid, that is, the induced electromotive force U of the pickup coil 32 becomes U _0, and the integrator / voltmeter When the voltage value V of 33 reaches V ₀ , the driving of the drive circuit 23 is stopped. Therefore, the application of the magnetic field from the magnetic field applying coil 22 to the magnetostrictive element 3 is stopped, so that the magnetostrictive element 3 expands while contracting in the longitudinal direction, and the outer peripheral surface of the magnetostrictive element 3 again causes the distal end of the valve portion 70 to reappear. The valve portion 70 is closed by coming into contact with the valve portion. As a result, the pressure of the liquid on the upstream side of the valve portion 70 is maintained at the reference pressure P ₀ again.

As described above, the pressure sensor 60 of this embodiment is
The pressure of the fluid can be accurately detected with high reliability as in the above embodiment. In addition, a magnetic field is applied to the magnetostrictive element 3 by the magnetic field applying coil 22 based on the detected pressure value of the fluid, and the magnetostrictive element 3 is expanded / contracted to open the valve portion 70 to maintain the fluid at a predetermined pressure. Therefore, it is not necessary to separately provide an actuator mechanism for pressure adjustment. Further, since the magnetostrictive element 3 receives the pressure of the fluid and is deformed by the magnetostrictive element 3 itself, it is possible to avoid the above-described inconvenience such as the separation between the shaft and the amorphous magnetic alloy, which is likely to occur in the conventional pressure sensor. it can.

In the present embodiment, the magnetized state detecting means is not limited to the pickup coil 22, but a Hall element 32 or the like as shown in FIG. 9 may be used as in the above embodiment (see FIG. 1). It may be. In this case, this Hall element is connected to the magnetization applying coil 22 via the Gauss meter 21 and the drive circuit 23 as in the above embodiment.

The communication port 62 and the discharge port 64 are each 1
And 2 or more, and may be 1 or 2 or more, respectively. When the plurality of outlets 64 are provided, the present invention is not limited to the case where each of the plurality of outlets 64 is formed in the base portion 63 as in the present embodiment. For example, as shown in FIG. It may be formed on the base portion 63 and also on the lower surface of the casing 61.

Further, the casing 61 may be made of a non-magnetic material, but a non-metallic material is desirable especially when high response is required.

Further, the shape of the valve portion 70 is not limited to the triangular shape in cross section, and the tip portion of the valve portion 70 is in contact with the outer peripheral surface of the magnetostrictive element 3 over the entire circumference. For example, the cross section may have a semicircular shape, and the valve portion 70 is not limited to the elastic body.

[0091]

As described above, according to the first aspect of the present invention, the pressure sensor of the conventional structure has a structure in which the fixed portion that causes the peeling due to the structure is eliminated, and the pressure can be detected with high accuracy. It can be performed. Therefore, the pressure sensor can detect the pressure with high accuracy and can ensure high reliability.

According to the second aspect of the invention, the pressure sensor and the fluid pressure increasing actuator can be integrally formed. In other words, when applied to a system that is required to maintain a constant pressure value with high reliability and high accuracy, it is necessary to separately provide a pressure sensor and a pressure adjustment actuator as in the conventional configuration. Disappear. Therefore, according to the present invention, such a system can be simplified, the cost can be reduced, and the assembling property of the system can be remarkably improved.

Further, according to the invention described in claim 3, as in the invention described in claim 1, since the fixing portion that causes structural peeling is eliminated, the pressure sensor having a high degree of accuracy is used. It is possible to detect and to secure high reliability. Further, since the fluid pressure can be maintained at a predetermined pressure, when the system is applied to a system in which the pressure is required to be accurately maintained at a constant value with high reliability, as in the invention according to claim 2, The system can be simplified and the cost can be reduced, and the assembling property of the system can be remarkably improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a pressure sensor using a magnetostrictive element according to the present invention.

FIG. 2 is a graph showing stress-flux change characteristics of the magnetostrictive element in this example.

FIG. 3 is a graph showing initial magnetization characteristics of a magnetostrictive element.

FIG. 4 is a configuration diagram of another embodiment of the pressure sensor using the magnetostrictive element according to the present invention.

FIG. 5 is a configuration diagram of a modified example (1) of the present embodiment.

FIG. 6 is a configuration diagram of a modified example (2) of the present embodiment.

FIG. 7 is a configuration diagram of still another embodiment of the pressure sensor using the magnetostrictive element according to the present invention.

FIG. 8 is an operation explanatory view for explaining the operation of the present embodiment.

FIG. 9 is a configuration diagram of a modified example (1) of the present embodiment.

FIG. 10 is a configuration diagram of a modified example (2) of the present embodiment.

[Explanation of symbols]

 1, 31, 41, 51, 60 Pressure sensor 2, 61 Housing 3 Magnetostrictive element 4 Permanent magnet 5 Piston 9 On-off valve 11 Pressure control chamber 12, 14 Check valve 16 Reserve tank 17 Constant pressure release valve 20 Hall element 21 Gauss meter 22 Magnetic field Applying coil 23 Drive circuit 25 Hydraulic system 32 Pickup coil 33 Integrator / voltmeter 42 Soft magnetic material 62 Communication port 64 Discharge port

Claims (3)

[Claims] 1. A housing having a communication port for communicating with a fluid chamber or a fluid path, a magnetostrictive element disposed in the housing, and a space in the housing provided with the communication port and the magnetostrictive element. A piston arranged to be in contact with the magnetostrictive element while being separated from the side on which the magnetostrictive element is disposed, and to be slidable in the housing, and a magnetization for detecting a magnetized state of the magnetostrictive element. A pressure sensor using a magnetostrictive element, comprising a state detecting means. 2. The pressure sensor using a magnetostrictive element according to claim 1, further comprising magnetic field applying means for applying a magnetic field in the same direction as the direction in which the piston can slide to the magnetostrictive element. 3. A housing having a communication port for communicating with a fluid chamber or a fluid path and a discharge port, a magnetostrictive element arranged in the housing, and a magnetized state detection for detecting a magnetized state of the magnetostrictive element. Means, a magnetic field applying means for applying a magnetic field so as to expand and contract the magnetostrictive element, and a valve portion which is disposed between the communication port and the discharge port and which is opened and closed by expansion and contraction of the magnetostrictive element. A pressure sensor using a magnetostrictive element.