JPH10319034A - Acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize the outer shape, reduce the cost and detect acceleration in a wide range by providing an elastic body formed of a shape memory alloy and fixed in one end to a base, and a permanent magnet fixed to the free end thereof. SOLUTION: This acceleration sensors comprises an elastic body 7 formed of a shape memory alloy and fixed in one end to a base 2, and a permanent magnet 3 fixed to the free end of the elastic body 7. At least two magnetic detecting elements 5 are arranged facing the moving route of the permanent magnet 4 moved when an acceleration is applied. Even if the elastic body 7 is deformed by applying a large acceleration, the elastic body 7 can be reused as an acceleration sensor having the characteristic equal to that before deformation by leaving the elastic body 7 in an environment restorable to the original form. The elastic body 7 can be reacted to a relatively feasible acceleration without requiring a high safety ratio to deformation. Thus, this sensor can detect accelerations widely ranging from a feasible acceleration to an acceleration of about 10 G.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor mounted on an automobile and used for speed control or mounted on various devices and used for detecting earthquakes. The present invention relates to an acceleration sensor capable of detecting a wide range of acceleration up to a certain acceleration.

In recent years, acceleration sensors have been used in a wide range of fields as means for converting acceleration due to vibration or impact into electric signals. For example, in a moving body such as a vehicle or an aircraft, safety is maintained and riding comfort is improved. Therefore, an acceleration sensor is used.

[0003] In the case of buildings and structures fixed on the ground, the destruction of facilities such as chemical plants and computers due to earthquakes is prevented, and explosions and leakages caused by the destruction of such facilities are prevented. An acceleration sensor is used as a means to prevent a secondary disaster.

Various types of acceleration sensors have already been developed as means for converting acceleration into an electric signal. However, the acceleration sensor used in such applications has a small external shape, is inexpensive, and can detect a wide range of acceleration from a weak acceleration to an acceleration of about 10 G. Must be something.

Therefore, it is desired to develop an acceleration sensor that has a small external shape, is inexpensive, and can detect a wide range from a weak acceleration to an acceleration of about 10 G.

[0006]

2. Description of the Related Art FIG. 5 is a perspective view showing a conventional acceleration sensor. Acceleration sensors built into driving assistance equipment and various devices that detect acceleration and control the speed of automobiles and that are used for earthquake detection, etc. can be downsized and are inexpensive and detect a wide range of acceleration from weak acceleration to about 10 G acceleration. It is required to be able to do it.

In FIG. 1, a conventional acceleration sensor comprises an elastic body 3 made of a phosphor bronze plate or the like and having one end fixed to a base 2 via a fixing member 1, and an elastic body 3 fixed to the free end side of the elastic body 3. And a permanent magnet 4 supported so as to be swingable in a direction perpendicular to the surface.

Further, two magnetic sensing elements 5 arranged facing the moving path of the permanent magnet 4 are mounted on the base 2 made of a printed wiring board or the like, and the elastic body 3 to which the permanent magnet 4 is fixed is provided. The magnetic sensing element 5 is covered and protected by a cap 6 fixed to the base 2.

In this acceleration sensor, the permanent magnet 4 is located in the middle of the magnetic detecting element 5 and does not output a voltage in a stationary state, but when an acceleration in a direction perpendicular to the surface of the elastic body 3 is applied, the permanent magnet 4 4 oscillates and its amplitude is almost proportional to the magnitude of the acceleration.

As a result, the output voltage of the magnetic detecting element 5 in the moving direction of the permanent magnet 4 increases, the output voltage of the other magnetic detecting element 5 decreases, and the voltage output from the two magnetic detecting elements 5 becomes Each increases or decreases substantially in proportion to the magnitude of the acceleration applied to the permanent magnet 4.

Therefore, by previously verifying the relationship between the magnitude of the applied acceleration and the voltage output from the magnetic detecting element 5, such an acceleration sensor can be mounted on an automobile and used for speed control or various devices. It can be used to detect earthquakes.

[0012]

However, a conventional acceleration sensor miniaturized for detecting a weak acceleration has a thin elastic body made of a phosphor bronze plate or the like, and is hard due to careless handling, for example. When dropped on the floor, an acceleration of about 100 G may be applied, and may become unusable thereafter.

Further, even after being attached to various devices, an acceleration much higher than originally expected may be applied due to an accident or the like. There is a problem that the base is deformed and the detection accuracy thereafter is reduced.

An object of the present invention is to provide an acceleration sensor which has a small external shape, is inexpensive, and can detect a wide range from a weak acceleration to an acceleration of about 10 G.

[0015]

FIG. 1 is a perspective view showing an acceleration sensor according to the present invention. The same object is denoted by the same symbol throughout the drawings.

The above-mentioned problem has an elastic body 7 formed of a shape memory alloy and having one end fixed to the base 2 and a permanent magnet 4 fixed to a free end of the elastic body 7 when an acceleration is applied. At least two facing the movement path of the moving permanent magnet 4
This is achieved by the acceleration sensor according to the present invention in which the magnetic detection elements 5 are provided.

The acceleration sensor of the present invention having the elastic body formed of the shape memory alloy and having one end fixed to the base and the permanent magnet fixed to the free end of the elastic body has a suddenly large acceleration. Even if the elastic body is deformed by the application of the acceleration sensor, the elastic body can be used again as an acceleration sensor having the same characteristics as before the deformation by leaving it in an environment where the elastic body can be restored to its original shape. Purchase costs are reduced.

In addition, it is not necessary to take a large safety factor against deformation, and the elastic body is made to respond to relatively weak acceleration, and the relationship between the acceleration after the elastic body is deformed and the output voltage of the magnetic sensing element is checked in advance. By doing so, the acceleration can be detected from the output voltage of the magnetic detection element even when an acceleration larger than the expected acceleration is applied.

That is, it is possible to realize an acceleration sensor having a small external shape and being inexpensive and capable of detecting a wide range from a weak acceleration to an acceleration of about 10 G.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 2 is a perspective view showing another embodiment of the present invention, FIG. 3 is a diagram for explaining the operation of another embodiment of the present invention,
FIG. 4 is a view for explaining still another embodiment of the present invention.

One embodiment of the acceleration sensor according to the present invention is, as shown in FIG. 1, an elastic body 7 having one end fixed to a base 2 via a fixing member 1, and an elastic body 7 fixed to a free end side of the elastic body 7. The permanent magnet 4 is supported so as to be swingable in a direction perpendicular to the surface of the elastic body 7.

Further, two magnetic sensing elements 5 arranged facing the movement path of the permanent magnet 4 are mounted on the base 2 made of a printed wiring board or the like, and the elastic body 7 to which the permanent magnet 4 is fixed is provided. The magnetic sensing element 5 is covered and protected by a cap 6 fixed to the base 2.

In this acceleration sensor, the permanent magnet 4 is located in the middle of the magnetic detecting element 5 and does not output a voltage in a stationary state, but when an acceleration in a direction perpendicular to the surface of the elastic body 7 is applied, the permanent magnet 4 4 oscillates and its amplitude is almost proportional to the magnitude of the acceleration.

As a result, the output voltage of the magnetic detecting element 5 in the moving direction of the permanent magnet 4 increases, the output voltage of the other magnetic detecting element 5 decreases, and the voltage output from the two magnetic detecting elements 5 becomes Each increases or decreases substantially in proportion to the magnitude of the acceleration applied to the permanent magnet 4.

Therefore, by previously verifying the relationship between the magnitude of the applied acceleration and the voltage output from the magnetic detecting element 5, such an acceleration sensor can be mounted on an automobile and used for speed control or various devices. It can be used to detect earthquakes.

In the acceleration sensor of the present invention, unlike the conventional acceleration sensor, the elastic member 7 is made of, for example, a Nitinol (NiTi) -based shape memory alloy. It is set so that it can be restored by heating.

That is, even when the elastic body is deformed by suddenly applying a large acceleration, the elastic body is left in an environment where the elastic body can be restored, so that it can be used again as an acceleration sensor having the same characteristics as before the deformation. As a result, the purchase cost of the acceleration sensor is reduced.

In addition, since it can be easily restored, it is not necessary to take a large safety factor against deformation, so that it is possible to cope with relatively weak acceleration. In addition, the relationship between the acceleration after deformation and the output voltage is tested in advance to obtain a large acceleration. Can also be detected when is applied.

In another embodiment of the acceleration sensor according to the present invention, as shown in FIG. 2, an elastic body 7 having one end fixed to the base 2 via a fixing member 1, and an elastic body 7 fixed to the free end side of the elastic body 7. The permanent magnet 4 is supported so as to be swingable in a direction perpendicular to the surface of the elastic body 7.

Further, two magnetic detecting elements 5 arranged facing the moving path of the permanent magnet 4 are mounted on the base 2 made of a printed wiring board or the like, and the permanent magnet 4 is moved out of the set range. Stoppers 8 that contact the elastic body 7 when moved are disposed on both sides of the elastic body 7.

In this acceleration sensor, as shown by the solid line in FIG. 3, positive and negative voltages are output around 0 V before the elastic body 7 is deformed, but when the elastic body 7 reaches the point shown by the dashed line, the elastic body 7 The contact is deformed, and the output change of the voltage shifts to one of positive and negative.

In the case of the above-described embodiment, when a large acceleration is applied, the elastic body 7 is deformed from the root and the permanent magnet 4 is disengaged from the magnetic sensing element 5, and the acceleration after the deformation and the output voltage of the magnetic sensing element 5 are different. Even if the relationship is tested in advance, the detectable region is limited to a narrow range.

However, in the present embodiment, since the elastic body 7 is deformed at the portion in contact with the stopper 8, the amount of displacement of the permanent magnet 4 is small, and the relationship between the acceleration after the deformation and the output voltage of the magnetic detecting element 5 is shown. By performing the test in advance, the detectable area can be expanded.

Further, since the elastic body 7 does not deform from the root, it returns to its original state after the deformation, and the permanent magnet 4 swings again in response to a weak acceleration. Can be considered, but the acceleration applied thereafter can be detected.

A Hall element or a magneto-resistive element can be considered as the magnetic detecting element 5 for detecting the magnetism of the permanent magnet 4 in the acceleration sensor. To reduce the size of the acceleration sensor, a magneto-resistive element, in particular, a barber pole type magneto-resistive element is used. Is more effective than the Hall element.

That is, as shown in FIG. 4B, the Hall element 51 applies a voltage between the opposing end faces 53 and 54 of the thin piece 52 made of an n-type semiconductor, and at the same time, the magnetic flux density B is perpendicular to the thin piece 52. The potential difference generated between the opposing electrodes 55 and 56 by applying such a magnetic field is used.

Assuming that the direction of movement of the permanent magnet 4 is parallel to the base 2 and a magnetic field parallel to the base 2 is formed by the permanent magnet 4, the Hall element 51 is formed of a thin piece 52 as shown in the figure. 2, the height of the acceleration sensor is hindered.

On the other hand, as shown in FIG. 4A, a barber pole type magnetoresistive element 57 has a magnetic detection pattern 59 formed on a substrate 58, and a magnetic detection pattern 59 made of a ferromagnetic thin film is formed on the substrate 58. Is formed in a zigzag shape inclined at an angle of 45 degrees with respect to the length direction.

The barber pole type magnetoresistive element 57
Indicates that a uniform magnetic field having a magnetic flux density B is applied in parallel to the surface of the substrate 58, and a meandering magnetic detection pattern 59 is formed.
When applied from a direction inclined by 45 degrees, the resistance value of the magnetic detection pattern 59 changes.

Therefore, when the magnetoresistive element 57 is mounted horizontally on the upper surface of the base 2, the magnetic field formed by the permanent magnet 4 can be detected. By arranging them between them, the size and height of the acceleration sensor can be reduced.

The acceleration sensor of the present invention having the elastic body formed of the shape memory alloy and having one end fixed to the base and the permanent magnet fixed to the free end of the elastic body has a suddenly large acceleration. Even if the elastic body is deformed by the application of the acceleration sensor, the elastic body can be used again as an acceleration sensor having the same characteristics as before the deformation by leaving it in an environment where the elastic body can be restored to its original shape. Purchase costs are reduced.

In addition, it is not necessary to take a large safety factor against deformation, and the elastic body is made to respond to relatively weak acceleration, and the relationship between the acceleration after the elastic body is deformed and the output voltage of the magnetic sensing element is checked in advance. By doing so, the acceleration can be detected from the output voltage of the magnetic detection element even when an acceleration larger than the expected acceleration is applied.

That is, it is possible to realize an acceleration sensor having a small outer shape and being inexpensive and capable of detecting a wide range from a weak acceleration to an acceleration of about 10 G.

[0044]

As described above, according to the present invention, it is possible to provide an acceleration sensor that has a small external shape, is inexpensive, and can detect a wide range from a weak acceleration to an acceleration of about 10 G.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an acceleration sensor according to the present invention.

FIG. 2 is a perspective view showing another embodiment of the present invention.

FIG. 3 is a diagram illustrating the operation of another embodiment of the present invention.

FIG. 4 is a diagram illustrating still another embodiment of the present invention.

FIG. 5 is a perspective view showing a conventional acceleration sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed member 2 Base 4 Permanent magnet 5 Magnetic detection element 6 Cap 7 Elastic body 8 Stopper 51 Hall element 52 Thin piece 53, 54 End face 55, 56 Electrode 57 Magnetic resistance element 58 Substrate 59 Magnetic detection pattern

Claims (4)

[Claims] 1. An elastic body formed of a shape memory alloy and having one end fixed to a base, and a permanent magnet fixed to a free end of the elastic body, wherein the permanent magnet moves when an acceleration is applied. An acceleration sensor, wherein at least two magnetic detection elements are provided facing a movement path of a magnet. 2. When the acceleration is applied and the permanent magnet moves out of a predetermined range, stoppers that contact the elastic body are provided on both sides of the elastic body. The acceleration sensor according to claim 1. 3. The acceleration sensor according to claim 1, wherein said magnetic detecting element is a magneto-resistive element. 4. The acceleration sensor according to claim 3, wherein said magnetoresistive element is a barber pole type magnetoresistive element.