JPS6161325B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure or displacement sensor that converts pressure or displacement into internal stress of an amorphous magnetic alloy having magnetostriction and detects this as a change in inductance that is included as a part of a magnetic core.

In recent years, amorphous amorphous magnetic alloys have become available at low cost and in large quantities using the ultra-quenching method, and their high magnetic permeability,
Due to its high saturation magnetic flux density, it has many practical applications, and in some cases it is already being used as a product material. Furthermore, microprocessors are rapidly developing and becoming widespread due to their many advantages, and are beginning to bring about major changes in production systems and social life. However, among the various sensors that serve as input to this microprocessor, there are still none that are sufficiently inexpensive and accurate, and there is a particularly high need for pressure/displacement sensors.

Under these circumstances, the present invention uses an amorphous magnetic alloy, which is an inexpensive and inherently excellent magnetic material, and provides a pressure or displacement sensor that utilizes its magnetostriction.

An embodiment of the present invention will be described below based on the drawings. FIG. 1 is a pressure or displacement sensor with an astable multivibrator circuit including an inductance. 1 is the standard inductance for measurement, and the value is
Let it be l ₁ . 2 is an inductance having a magnetic core using a magnetic material having magnetostriction at least in part, and having a mechanism by which pressure or displacement is transmitted to the magnetic material, and its value is l ₂ . 3 and 4 are feedback capacitors for oscillation, and their values are C ₁ and C ₂ . 5 and 6 are feedback resistors for oscillation, and their values are r ₁ and r ₂ . 7 and 8 are switching transistors, and 9 and 10 are emitter current backflow blocking diodes. The unstable multivibrator section is thus configured. Reference numeral 11 denotes a circuit for measuring the length of time _T1 during which the collector voltage is at a low level when the transistor 7 is conductive, and numeral 12 is a circuit for measuring the length of time _T2 during which the collector voltage is at a low level when the transistor 8 is conductive. 13 is time length measurement circuit 1
This circuit detects the change in l ₂ using the time lengths T ₁ and T ₂ sent from 1 and 12, and calculates and outputs pressure or displacement from the change. i ₁ and i ₂ are inductances 1 and 2
is the current flowing through. In this unstable multivibrator section, during oscillation, capacitors 3 and 4 have smaller impedance than inductances 1 and 2, and resistors 5 and 4 have lower impedance than inductances 1 and 2.
6, the discharge time constant of capacitors 3 and 4 is set longer than their oscillation period.

Various types of inductance 2 in FIG. 1 can be considered. FIGS. 2 and 3 show an example in which the invention is applied to a pressure sensor, and FIG. 4 shows an example in which the invention is applied to a displacement sensor.

In FIG. 2, 21 is a thin disk made of an amorphous magnetic alloy having magnetostriction, and 22 is a brim-shaped soft ferrite having a cylindrical protrusion 22b in the center so as to be flush with the outer ring wall 22a. 23 is a coil wound around the cylindrical protrusion 22b, and 24 is a small hole through which the lead wire is taken out. The space surrounded by 21 and 22 is evacuated, and the small hole 24 and 21 and 2
The bonded part 2 is made airtight with adhesive and filler, and treated so as not to break the vacuum. 21 and 22 constitute a magnetic circuit, which is excited by a coil 23. At this time, 21 is strained due to the pressure difference between the external pressure and the internal vacuum, and internal stress changes, and the inductance value changes due to the magnetostrictive effect.

In FIG. 3, 31 is a cylinder made of an amorphous magnetic alloy having magnetostriction, and 32 is a coil formed by winding a part of the peripheral wall of the cylinder 31 in the axial direction. 33 is a non-magnetic airtight plug, which secures the shape of both ends of the cylinder 31. The space surrounded by 31 and 32 is evacuated and vacuumed. 31 constitutes a cylindrical magnetic circuit, and the coil 3
It is excited at 2. At this time, the internal stress of 31 changes due to the pressure difference between the external pressure and the internal vacuum, and the value of this inductance changes due to the magnetostrictive effect.

In FIG. 4, 41 is a rectangular plate with a square hole made of amorphous magnetic alloy having magnetostriction, and 42 is a rectangular plate 41.
43 is a fixture that fixes one end of 41, and 44 is a transmitter that transmits the displacement to be measured. 41 constitutes a magnetic circuit, which is excited by a coil 42. At this time, the square plate 41 undergoes strain and changes in internal stress due to the displacement transmitted by the transmitter 44, and the inductance value changes due to the magnetostrictive effect.

Next, the operation of the multivibrator section shown in FIG. 1 will be described. The state where the transistor 7 is conductive and the transistor 8 is non-conductive is designated as A, and the state where the transistor 7 is non-conductive and the transistor 8 is conductive is designated as B. As mentioned above, each time length is T ₁ for A,
B is _T2 . At this time, the value of capacitance 3 and 4 is C ₁ ,
C ₂ and the values of resistors 5 and 6 are r ₁ and r ₂ . As shown in FIG. 5, in the A state, the base current of the transistor 7 is supplied via the capacitor 4 and the resistor 6 by the magnetic energy stored in the B state immediately before the inductance 2, and during this time the inductance 1 is connected to the power source. It stores magnetic energy by receiving current supply from the magnet. When the magnetic energy of the inductance 2 disappears, the base current of the transistor 7 is no longer supplied, and the transistor 7 becomes non-conductive. As a result, the magnetic energy stored in the inductance 1 begins to be supplied to the base of the transistor 8 as a current through the capacitor 3 and the resistor 5, and the transistor 8 enters the B state. The B state continues until the magnetic energy of the inductance 1 is exhausted, and during that time, current is supplied to the inductance 2 from the power supply and magnetic energy is accumulated. When the magnetic energy of the inductance 1 disappears, the base current of the transistor 8 is no longer supplied, and the transistor 8 becomes non-conductive. As a result, a current begins to flow through the base of the transistor 7 due to the release of magnetic energy in the inductance 2, and the transistor 7 enters the A state. The same process is repeated and the oscillation continues.

According to the above operating principle, the time length T ₁ of the A state and the time length T ₂ of the B state can be determined by l ₁ , l ₂ , r ₁ , and r ₂ . That is, assume that the state enters the A state from the B state at t=0. Since the capacitors 3 and 4 and the resistors 5 and 6 are set to the above setting conditions, i ₁ and i ₂ are expressed by the following equations.

A state i ₁ = (Vcc / l ₁ ) t ... (1) i ₂ = i ₀₂ + [(Vcc - V ₀₂ ) / l ₂ ] t ... (2) B state i ₁ = i ₀₁ + [( Vcc- _V01 )/ _l1 ](t- _T1 )...(3) _i2 =(Vcc/ _l2 )(t- _T1 )...(4) Here, Vcc is the power supply voltage, _V01 , i ₀₁ is the voltage between the terminals of the capacitor 3 and the value of i ₁ at the time when the inductance 1 starts to emit magnetic energy, that is, in the B state. V ₀₂ and i ₀₂ are the voltage across the terminals of the capacitor 4 and the value of i ₂ at the time when the inductance 2 begins to emit magnetic energy, that is, in the A state. FIG. 6 shows the changes in i ₁ and i ₂ and the changes in the collector and base voltages of the transistors 7 and 8. (1)
The following four equations are derived from equation (4) and the continuous repetition of state A and state B.

(Vcc/l ₁ )T ₁ =i ₀₁ ……(5) (Vcc/l ₂ )T ₂ = i ₀₂ ……(6) (Vcc/l ₁ )T ₁ + [(Vcc−V ₀₁ )/l ₂ ]T ₂ ……(7) (Vcc/l ₂ )T ₂ + [(Vcc−V ₀₂ )/l ₁ ]T ₁ =0 ……(8) Furthermore, charging by inductance 1, 2 of capacity 3, 4 The following equation is derived from the fact that the electric charge and the electric charge discharged by the resistors 5 and 6 match.

1/2 (Vcc/l ₁ )T ₁ T ₂ = (V ₀₁ /r ₁ ) (T ₁ +T ₂ ...(9) 1/2 (Vcc/l ₂ )T ₂ T ₁ = (V ₀₂ /r ₂ ) (T ₁ + T ₂ ) ...(10) From equations (5) to (10) above, if Vcc, V ₀₁ , V ₀₂ , i ₀₁ , and i ₀₂ are eliminated, T ₁ and T ₂ can be calculated using the following equations. expressed.

T ₁ = (2l ₁ / r ₁ ) (1 + l ₂ r ₁ / l ₁ r ₂ ) ² ... (11) T ₂ = (2l ₂ / r ₂ ) (1 + l ₁ r ₂ / l ₂ r ₁ ) ² ... ...(12) From equations (11) and (12), T ₁ and T ₂ change depending on the value of l ₂ .

From the above, it is understood that the inductances 1 and 2 shown in FIG. 2, FIG. 3, or FIG. By using an inductance having , a change in the value of the inductance 2 due to pressure or displacement causes a change in the oscillation period of the multivibrator section shown in FIG. 1, making it possible to measure pressure or displacement.

As a specific example, assume that the inductance shown in FIG. 2 is used as the inductance 2 to measure pressure.
First, the values of the resistors 5 and 6 are made the same, and a correspondence table between the inductance value l ₂ and the pressure shown in FIG. 2 is prepared in advance. Next, apply measuring pressure to the outside of the inductance amorphous disk shown in Fig. 2, measure T ₁ and T ₂ , calculate l 2 from l ₁ (l ₂ = (T ₁ / T ₂ ), and calculate _{l 2 to} Just output the corresponding pressure.

FIG. 7 shows another embodiment of the invention. 71,7
2 is the same inductance as shown in FIG. 2, FIG. 3, or FIG. , let its value be l. 73 and 74 are feedback capacitors for oscillation, and their values are C ₁ ' and C ₂ '. Reference numerals 75 and 76 indicate oscillation feedback resistors whose values are (r ₁ )' and (r ₂ )'. 7
7, 78 are switching transistors, 79,
80 is an emitter current backflow blocking diode.
81 is a circuit for measuring the time T ₁ ' when the collector voltage becomes low level when the transistor 77 is conductive, and 82 is a circuit for measuring the time T ₂ ' when the collector voltage is low level when the transistor 78 is conductive. 83 is 81,8
This is a circuit that detects a change in l using T ₁ ' and T ₂ ' sent from 2, and calculates and outputs pressure or displacement from this. Here, in the unstable multivibrator section of FIG. 7, the impedance of the capacitances 73 and 74 during oscillation operation is smaller than that of the inductances 71 and 72.
The discharge time constant of the resistors 75 and 76 is set to be longer than the cycle of the capacitors 73 and 74. The operation of this embodiment is the same as the case where l ₁ =l ₂ =l in the previous embodiment. Therefore, in the unstable multivibrator section of FIG. 7, transistor 77 becomes conductive and transistor 78 becomes conductive.
Let T ₁ ' be the time during which the transistor 77 is non-conductive and the time during which the transistor 78 is non-conductive is T ₂ ', then T ₁ '=(2l/ _r1 ')・(1+ _r1 '/ _r2 ') ² ... (13) T ₂ ′=(2l/r ₂ ′)・(1+r ₂ ′/r ₁ ′) ² ...(14) Therefore, from equations (13) and (14), T ₁ ′ and T ₂ ′ change depending on the value of l. From the above, if at least a part of the magnetic core is made of a magnetic material having magnetostriction as shown in FIG. 2, FIG. 3, or FIG. A change in value due to pressure or displacement causes a change in the oscillation period of the multivibrator section shown in FIG. 7, making it possible to measure pressure or displacement.

As a specific example, assume that the inductances shown in FIG. 2 are used as the inductances 71 and 72 to measure pressure. First, a correspondence table between T=T ₁ '+T ₂ ' and pressure is prepared in advance, and then measurement pressures are applied to the outside of the two inductance amorphous disks shown in FIG. 2. It is sufficient to measure T ₁ ′ and T ₂ ′, obtain T=T ₁ ′+T ₂ ′, and output the corresponding pressure.

As explained above, according to the present invention, since there are no moving parts, high dimensional accuracy is not required and the device is resistant to vibration. Additionally, since it utilizes magnetism itself, known as the magnetostrictive effect, it is possible to construct a highly accurate sensor. Furthermore, since no mechanical resonance is used, the structure can be made compact. Also, unlike bridge circuits and the like, it does not use minute electrical signals, so it is resistant to electrical disturbances.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
Figures 3 and 3 are a plan view and a sectional view of the inductance implemented in the pressure sensor, Figure 4 is a perspective view of the inductance implemented in the displacement sensor, and Figure 5 is a perspective view of the inductance implemented in the displacement sensor.
The figure is a diagram explaining the operating principle, Figure 6 is an operation waveform diagram, and Figure 7 is a diagram explaining the operating principle.
The figure is a configuration diagram showing another embodiment. 1, 2, 71, 72...Inductance, 3,
4, 73, 74...Oscillation feedback capacitor, 5, 6, 7
5, 76...Oscillation feedback resistor, 7, 8, 77, 7
8...Switching transistor, 9, 10,
79, 80... Emitter current backflow blocking diode, 11, 12, 81, 82... Voltage level time detection circuit, 13, 83... Pressure or displacement calculation circuit, 21, 31, 41... Amorphous magnetic alloy having magnetostriction. , 22... pot-shaped soft ferrite, 23, 32, 42... coil, 33... airtight plug, 43... fixture, 44... transmission tool.

Claims (1)

[Claims] 1. An unstable multivibrator including an inductance, in which at least a part of the magnetic core is made of an amorphous magnetic material having magnetostriction, and a means for transmitting pressure or displacement to the amorphous magnetic material is provided, and the oscillation period is In addition to detecting pressure or displacement, the unstable multivibrator
It consists of transistors Tr ₁ and Tr ₂ , inductances L ₁ and L ₂ connected to the respective collectors of Tr ₁ and Tr ₂ , capacitances C ₁ and C ₂ , and resistors R ₁ and R ₂ . , the L ₁ and L ₂ are connected to the power supply, the C ₁ and R ₁ are connected in parallel to each other, and the base of the Tr 2 is connected to the base of the Tr ₂ .
C ₂ and R ₂ are connected in parallel to each other and connected to the base of Tr ₁ , respectively, and in its oscillation state, the
The impedance of C ₁ and C ₂ is smaller than the impedance of L ₁ and L 2, and the impedance of C 1 and C ₂ is smaller than the impedance of L ₁ and L ₂ .
A pressure/displacement sensor configured so that the discharge time constant of C ₁ and C ₂ is longer than their oscillation period. 2. The pressure/displacement sensor according to claim 1, wherein the unstable multivibrator has means for preventing Zener breakdown between the emitter bases of Tr ₁ and Tr ₂ . 3. An inductance having a magnetic core made of an amorphous magnetic alloy having magnetostriction at least in part, a pot-shaped soft ferrite having an outer ring wall and a disc-shaped protrusion at the center, and an amorphous magnetic alloy covering the upper opening of the inductance. An inductance was used in which a magnetic core made of a thin disk and kept in a vacuum was used, a coil was wound around the cylindrical protrusion, and a lead wire was taken out from a small airtight hole drilled in the vase-shaped soft ferrite. A pressure/displacement sensor according to claim 1, characterized in that: 4. An inductance having a magnetic core using an amorphous magnetic alloy having magnetostriction at least in part, a cylindrical amorphous magnetic alloy, a coil having the cylindrical amorphous magnetic alloy as the magnetic core and a part of its peripheral wall wound in the axial direction, and the cylindrical amorphous magnetic alloy. 2. The pressure/displacement sensor according to claim 1, which is comprised of an airtight plug that covers both openings of the magnetic alloy, and uses an inductance that maintains a vacuum inside. 5. An amorphous magnetic alloy plate having a hole in an inductance having a magnetic core made of a magnetic alloy using an amorphous magnetic alloy having magnetostriction in at least a portion thereof, a coil wound through the hole using the amorphous magnetic alloy as a magnetic core, and the amorphous magnetic alloy plate having a hole in the inductance. The pressure/displacement sensor according to claim 1, characterized in that an inductance is used, which comprises a fixture that fixes one end of the alloy plate and a transmitter that transmits displacement to the other end.