JPH04369446A - Pressure sensor - Google Patents

Abstract

PURPOSE:To obtain a pressure sensor with reliability improved which detects occurrence of a failure such as peeling of a fixed amorphous magnetic alloy regarding the pressure sensor with a magnetostrictive effect of the amorphous magnetic alloy applied. CONSTITUTION:When a failure such as peeling of amorphous magnetic alloy 5 occurs, its magnetic permeability varies. A sensor detects a defect when magnetic permeability at a steady state of the amorphous magnetic alloy 5 fixed to a deformed part 4 of a body 5 or difference from that of amorphous magnetic alloy 27 fixed to a nondeformed part 25 is not within guaranteed accuracy compared with initial characteristics. Thus a hiqhly reliable pressure sensor can be realized.

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 the magnetostrictive effect of an amorphous magnetic alloy.

0002

2. Description of the Related Art In recent years, pressure sensors using the magnetostrictive effect of amorphous magnetic alloys have been proposed. (FIG. 4) is a cross-sectional view schematically showing an example of such a pressure sensor.

1 is made of titanium and has a diameter of 10 mm and a height of 50 m.
2 is a pressure inlet with a diameter of 6 mm, and 3 is a pressure chamber for transmitting pressure. Reference numeral 4 denotes a cylindrical deformation part due to pressure, and a part of the main body 1 is processed to have a wall thickness of 2 mm.

[0004] 5 is a Fe-Si-B-Cr-based amorphous magnetic material with a thickness of 0.03 mm fixed on the outer periphery of the main body 1 with an imide adhesive at 250° C. for 1 hour so as to cover the deformed portion 4. It is an alloy. 6 is a pressure detection coil formed by winding the coil 100 times as a magnetic permeability detection element of the amorphous magnetic alloy 5, and a phenol resin bobbin is attached to the outside of the amorphous magnetic alloy 5 fixed on the outer periphery of the deformed portion 4. 7.

The pressure detection coil 6 is connected in series with a fixed resistor and driven at a constant voltage. 8 is a yoke made of 48% Ni-Fe alloy, and is attached to the outer periphery of the bobbin 7. 9 is main body 1
The fixing screw part is machined to a pitch of PF3/8. 10 is a detection circuit.

[0006] Pressure is transmitted from the pressure introduction port 2 to the pressure chamber 3, and applies stress in the direction of expanding the pressure chamber 3.

As a result, the deformed portion 4 changes, and the magnetic permeability of the amorphous magnetic alloy 5 bonded to its surface changes. In accordance with this change, the inductance of the pressure detection coil 6 changes. Since the pressure detection coil 6 is connected in series with a fixed resistor and driven at a constant voltage, when the inductance of the pressure detection coil 6 changes, the voltage across it also changes. This is detected as a change in pressure.

[0008]

[Problems to be Solved by the Invention] The pressure sensor configured as described above has a problem in that the reliability of the sensor output is poor because it does not have a means for detecting failures such as peeling of the fixed amorphous magnetic alloy. Ta.

[0009]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention utilizes the fact that when an amorphous magnetic alloy undergoes exfoliation, its magnetic permeability changes, so that the magnetic permeability in a steady state can be reduced. The structure is such that when the pressure sensor changes beyond its guaranteed accuracy, it is detected as a failure.

0010

[Operation] According to the above configuration, if there is a change in output that exceeds the guaranteed accuracy due to peeling, etc., it is output as a failure.
It is possible to always obtain highly accurate output and improve reliability.

[0011]

【Example】

(Example 1) Hereinafter, an example of the present invention (Figure 1)
This will be explained with reference to. In the configuration of the present invention, parts that are the same as those in the conventional example are given the same numbers, detailed explanations are omitted, and only parts that are the features of the present invention will be described.

That is, the feature of the present invention lies in the output signal processing after the detection circuit 10 in (FIG. 1). 11 is a thermistor for measuring the temperature near the amorphous magnetic alloy 5;
12 is a microprocessor for signal processing, and 13 is a sensor operating temperature range of 1°C (-30 to 100°C in this example).
This is reference data in which the initial output of the pressure detection coil 6 in a steady state (described later) is stored in a semiconductor memory.

The operation of the characteristic portion of the present invention will be explained below. When this pressure sensor is used to measure the brake pressure of an automobile, for example, the steady state is a state in which the brakes are not applied. When the pressure sensor is under steady state,
The microprocessor 12 reads the temperature of the amorphous magnetic alloy 5 from the thermistor 11 and the voltage across the pressure detection coil 6 (a function of the magnetic permeability of the amorphous magnetic alloy 5), and stores them in the reference data 13. It is compared with the initial output of the pressure detection coil 6 at a certain current temperature.

As a result, if the voltage across the pressure detection coil 6 is not within the guaranteed accuracy (within ±2.5% of the full scale ratio in this embodiment) with respect to the initial output, a failure signal is output. . Note that the temperature is read because the magnetic permeability of the amorphous magnetic alloy 5 also changes depending on the temperature.

With the above-described configuration and operation, failures such as peeling of the amorphous magnetic alloy can be detected, and a pressure sensor that is more reliable than conventional pressure sensors can be obtained.

(Embodiment 2) FIG. 2 is a sectional view schematically showing a pressure sensor according to a second embodiment of the present invention. 21 is made of titanium and has a diameter of 10 mm.
, a cylindrical main body with a height of 70 mm, 22 a pressure introduction port with a diameter of 6 mm, and 23 a pressure chamber for transmitting pressure. Reference numeral 24 denotes a portion deformed by pressure, which is formed by processing a portion of the main body 21 to a thickness of 2 mm.

Reference numeral 25 denotes a non-deformable portion that does not undergo distortion due to pressure, and a hollow portion 26 of the same size as the pressure chamber 23 is provided inside. 27 is a deformed portion 24 of the main body 21
2 with imide adhesive so as to cover the non-deformed part 25.
Fe-S with a thickness of 0.03mm fixed in 1 hour at 50℃
It is an i-B-Cr based amorphous magnetic alloy.

28 is a magnetic permeability detecting element for the amorphous magnetic alloy 27, which is arranged around a phenol resin bobbin 30.
A pressure detection coil 29 formed by winding a coil once is a dummy coil having the same configuration as the pressure detection coil 28.

The bobbin 30 having these coils is attached to the outer periphery of the amorphous magnetic alloy 27. 31 is 48% Ni-
The yoke is made of Fe alloy and is attached to the outer periphery of the pressure detection coil 28 and the dummy coil 29. 32 is a screw part for fixing the main body, which is machined to a pitch of PF3/8. 33 is a detection circuit, a block diagram of which is shown in FIG. 3. The pressure detection coil 28 and the dummy coil 29 are each connected in series with a fixed resistor 41 to form a bridge circuit, and are driven by an excitation circuit 42 at a constant voltage. The outputs of these coils are input to a differential circuit 43, and a comparison circuit 45 with an initial voltage 44 outputs pressure.

The operation of the above-mentioned pressure sensor will be explained below. The pressure is transmitted from the pressure introduction port 22 to the pressure chamber 23, and applies stress in the direction of expanding the pressure chamber 23. As a result, the deformed portion 24 moves and the amorphous magnetic alloy 27 fixed to its surface deforms. Due to this deformation, the magnetic permeability of the amorphous magnetic alloy 27 changes due to the inverse magnetostriction effect.

This change is detected by the pressure detection coil 28 as a change in inductance. On the other hand, dummy coil 29
Since the output is not dependent on pressure, the differential between the two is detected by the detection circuit
Get pressure by taking 3.

Failure detection is performed as follows. When this pressure sensor is used to measure the brake pressure of an automobile as in Example 1, the output difference between the pressure detection coil 28 and the dummy coil 29 is measured by a differential circuit under steady state, that is, when the brake is not applied. (see (Figure 3)). The output difference at this time is compared with the initial voltage by a comparator, and if it is not within the guaranteed accuracy (same as in the first embodiment), a failure signal is output.

With this configuration, the dummy coil 2
By taking a differential with the output of 9, it is possible to cancel the effect of changes in magnetic permeability due to temperature. There is no need to keep it in place, making the fault detection circuit extremely simple.

[0024] Furthermore, if the state where pressure is applied is a steady state, such as the pressure of an automobile suspension,
If a steady state pressure is applied to the hollow portion 26, a failure can be detected in an equivalent manner. That is, for example, assuming that the steady state is 10 atm, a pressure medium such as gas is sealed in advance so that a pressure of 10 atm is constantly applied to the hollow portion 26.

When the pressure sensor is in a steady state, 10 atm is applied to the pressure chamber 23, so the differential between the pressure detection coil 28 and the dummy coil 29 at this time is taken, and a failure is detected using the same method as above. can be detected. In this way, this configuration has the advantage that failures can be easily detected even in any steady state.

With the above configuration and operation, it was possible to obtain a pressure sensor with higher reliability than the conventional one with a simple failure detection circuit.

[0027]

[Effects of the Invention] As is clear from the above explanation, according to the present invention, when a failure occurs due to peeling of an amorphous magnetic alloy, the magnetic permeability changes, and the magnetic permeability of the amorphous magnetic alloy changes. A highly reliable pressure sensor can be provided by detecting a failure when the change in magnetic permeability of the amorphous magnetic alloy exceeds guaranteed accuracy.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a pressure sensor according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a pressure sensor according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a detection circuit according to a second embodiment of the present invention.

FIG. 4 is a sectional view of a conventional pressure sensor.

[Explanation of symbols]

1, 21 Main body 2, 22 Pressure inlet 3, 23 Pressure chamber 4, 24 Deformed part 5, 27 Amorphous magnetic alloy 6, 28 Pressure detection coil 7, 30 bobbin 8, 31 York 9, 32 Fixing screw 10, 33 Detection circuit 11 Thermistor 12 Microprocessor 13 Reference data 25 Non-deformed part 26 Hollow part 29 Dummy coil

Claims (2)

[Claims] 1. A pressure introduction port and a deformable portion that is distorted by the pressure introduced from the pressure introduction port, an amorphous magnetic alloy having magnetostriction is fixed to the deformation portion, and the amorphous magnetic alloy is bonded to the amorphous magnetic alloy. In a pressure sensor that has a configuration in which a magnetic permeability detection element is arranged in the deformed part to form a magnetic circuit, and detects pressure from a change in magnetic permeability of the magnetic permeability detection element as pressure is applied, the magnetic permeability in a steady state is equal to the pressure A pressure sensor characterized by detecting a change in accuracy beyond the guaranteed accuracy of the sensor as a failure. 2. A pressure introduction port, a deformable portion that is distorted by the pressure introduced from the pressure introduction port, and a non-deformable portion that is not distorted by the pressure, and the deformable portion and the non-deformable portion have magnetostriction. Fix the amorphous magnetic alloy,
It has a configuration in which magnetic permeability detection elements are respectively arranged in the deformed part and the non-deformed part so as to form a magnetic circuit with the amorphous magnetic alloy, and from the magnetic permeability difference between the two magnetic permeability detection elements due to pressure application. 1. A pressure sensor for detecting pressure, which detects a failure when a magnetic permeability difference in a steady state changes beyond the guaranteed accuracy of the pressure sensor.