JPH06160418A - Acceleration sensor - Google Patents

Abstract

PURPOSE:To provide an acceleration sensor which can highly accurately detect not only constant acceleration, but also acceleration within a frequency range from a low frequency to a high frequency, with a less number of parts at a low cost. CONSTITUTION:A weight 1 formed of a large-diameter column body 1A and small-diameter sections 1a and 1b protruded from both sides of the body 1A is supported with coil springs 2a and 2b press-contacted with both sides of the body 1A and the sections 1a and 1b are loosely inserted into the springs 1a and 1b. The springs 2a and 2b are connected in series with an AC power source 8. When the weight 1 is accelerated, the weight 1 and springs 2a and 2b are displaced and a reactance change occurs between the springs 2a and 2b. The change is fetched from the voltage VOUT across both ends of the spring 2a as an acceleration detecting signal. Since the springs 2a and 2b are constituted not only as an acceleration detecting section, but also as the supporting bodies of the weight 1, the number of parts used in this acceleration sensor and, therefore, the cost of the sensor can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor using a weight.

[0002]

2. Description of the Related Art FIGS. 3 and 4 show a conventional acceleration sensor using a weight. 3 shows a piezoelectric type acceleration sensor using the piezoelectric body 3, and FIG. 4 shows a strain gauge type acceleration sensor system using the strain gauge 4.
In FIG. 3A, the beam 7 integrally formed with the base 6 portion of the case 5 is used as the center axis, and the piezoelectric bodies 3a, 3
b is fixed, and the weights 1a and 1b are fixed to the outside of the beam. When acceleration occurs in the left-right direction in the drawing, the weights 1a and 1b arranged on the left and right of the beam 7 are moved to move the beam 7b. Is bent, and the stress is applied to the piezoelectric bodies 3a and 3b.
And the piezoelectric bodies 3a and 3b are deformed (distorted), and a voltage corresponding to the amount of deformation can be extracted as an acceleration detection signal.

In FIG. 3B, the weight 1 is integrally formed on the base 6 portion of the case 5 via the piezoelectric body 3, and when acceleration occurs in the vertical direction of the figure, the weight 1 moves up and down. As a result, the piezoelectric body 3 expands and contracts in the same manner as described above, and a voltage corresponding to this deformation amount can be taken out as an acceleration detection signal.

In FIG. 4, when acceleration is generated in the left-right direction, the weight 1 moves left and right, and the strain gauges 4a and 4b are distorted by the deflection of the beam 7, and a voltage corresponding to this distortion amount is used to detect the acceleration. Take out as a signal.

[0005]

However, in the case of the piezoelectric type acceleration sensor as shown in FIG. 3, in the case of a constant acceleration or in the case of an acceleration change at an extremely low frequency close to it,
Since the amount of deformation of the piezoelectric body 3 hardly changes with time, acceleration cannot be detected. In addition, since an expensive charge amplifier is required to convert the current generated by the deformation amount of the piezoelectric body 3 into a voltage and extract it as a voltage, there is a problem that the cost of the acceleration sensor becomes high. Further, in this case, there is a problem that the detection accuracy is poor because the hysteresis during signal processing is large and the reproducibility is poor.

Further, in the case of the strain gauge type acceleration sensor of FIG. 4, it is small and lightweight and can detect from a constant acceleration to a large acceleration, but since the detection voltage is small, an amplifier circuit is required and the cost is reduced. There was a problem that it was difficult. Further, the strain gauge 4 has a drawback that it is easily affected by temperature changes.

Further, in the case of FIGS. 3 and 4, a charge amplifier and an amplifier circuit are required to increase the number of parts, and moreover, the center position of the weight 1 needs to be determined with high accuracy, resulting in high manufacturing cost. The acceleration sensor has been made more expensive.

The present invention has been made to solve the above-mentioned conventional problems, and its object is to detect not only constant acceleration but also acceleration in a low frequency range to a high frequency range with high accuracy and the number of parts. The object is to provide an acceleration sensor that can reduce the cost and reduce the cost.

[0009]

In order to achieve the above object, the present invention is constructed as follows. That is, the acceleration sensor of the present invention includes a weight that is displaced by acceleration, a coil spring that holds the weight from both sides, and a detection unit that detects a change in reactance of the coil spring due to the displacement of the weight as an acceleration signal. It is characterized by that.

[0010]

When the weight is displaced by acceleration, one side of the coil spring holding the weight is compressed and the other side is expanded, so that the reactance of each coil spring changes, and the change amount of this reactance is converted into an acceleration signal by the detecting means. Take it out.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of an acceleration sensor according to the present invention, and FIG. 2 shows an equivalent circuit diagram thereof.

In these drawings, a weight 1 made of a magnetic material is provided with a small diameter portion 1a having a small diameter from both sides of a large diameter column 1A.
The weight 1 is formed in a protruding shape, and the weight 1 is held in pressure contact with the coil springs 2a and 2b from both sides of the column 1A in the housing 9. The coil springs 2a and 2b are electrically compatible. When the weight 1 moves in the acceleration direction indicated by the arrow in the figure, the small diameter portion 1 of the weight 1
The diameters of the small diameter portions 1a and 1b are such that the a and 1b portions move in the coil springs 2a and 2b in a loosely inserted state.
It is formed sufficiently smaller than the inner diameter of 2b.

The coil springs 2a and 2b are connected in series via a lead wire 10, and those connected in series are connected to the AC power source 8 side. Circuits including an AC power supply 8 and terminals 11 and 12 are formed so that terminals 11 and 12 for extracting the voltage across both ends of the coil spring 2a are formed, and the output voltage V _{OUT of the} acceleration sensor is extracted from these terminals 11 and 12. The detecting means 13 is configured by the above.

This embodiment is constructed as described above,
When the weight 1 moves upward in the drawing due to acceleration, for example, the coil spring 2b is compressed, the small diameter portion 1b portion enters the inside of the coil spring 2b, and the number of windings of the coil around the small diameter portion 1b increases. On the other hand, since the coil spring 2a is stretched, the number of turns of the coil winding the small diameter portion 1a is reduced. Therefore, the inductance L _b of the coil spring 2b decreases and the inductance L _a of the coil spring 2a increases. The changes in the inductances L _a and L _b due to the displacement of the coil springs 2 a and 2 _b are proportional to the acceleration.

The coil spring 2a, each of the reactance X _a of 2b, X _b, if the frequency of the AC power source 8 is f,

X _a = zπf · L _a

X _b = 2πf · L _b

Since the effective value of the voltage of the AC power supply 8 is V _IN , the output voltage V _OUT is

V _OUT = V _IN · X _a / (X _a + X _b ) = V
_IN・ L _a / (L _a + L _b )

Thus, the displacement amount of the coil springs 2a and 2b is converted into reactance, which is taken out as an acceleration signal.

When the acceleration is constant, the displacement of the coil spring 2 is kept constant, so that the inductances L _a and L _b of the coil springs 2a and 2b do not change and a constant voltage is output from the acceleration sensor. .

As described above, according to this embodiment, the coil spring 2 functions as a structure for supporting the weight 1 and also as an acceleration detecting section for generating an inductance that changes with acceleration. Therefore, since the number of parts is small, the parts cost is reduced, manufacturing is facilitated, and a low-cost acceleration sensor can be provided.

Furthermore, since the coil spring 2 also when the acceleration is constant to maintain the displacement state, because it is always caused constant inductance L _a, a L _b, the acceleration sensor and to be able to detect and output a constant voltage V _{OU T} Become. Therefore, it is possible to detect not only constant acceleration but also acceleration in a low frequency range to a high frequency range.

Further, the output voltage V of the acceleration sensor
_{Since OUT} is taken out by utilizing the difference between the inductances L _a and L _b of the coil springs 2a and 2b, the electrical characteristics of the coil springs 2a and 2b, which cause the detection error, cancel each other out, resulting in a highly accurate acceleration. Become a sensor. Further, even if there is a change in temperature, the physical characteristics due to the expansion of the coil springs 2a and 2b also cancel each other out, so there is no problem with the strain gauge type acceleration sensor, and highly accurate and stable acceleration is achieved. A sensor can be provided.

Further, unlike the conventional case, since it is not necessary to position the weight 1 with high accuracy, the manufacturing is further facilitated and the cost of the acceleration sensor can be further reduced.

The present invention is not limited to the above-mentioned embodiments, and various embodiments can be adopted. For example, although the weight 1 is made of a magnetic material in the above embodiment, it may be made of a non-magnetic material such as aluminum or copper. Also in this case, when the weight 1 moves due to the acceleration, the coil springs 2a and 2b expand and contract, and the reactance of the coil springs 2a and 2b changes. Therefore, by detecting this, the acceleration can be similarly detected.

Although the output voltage V _OUT of the acceleration sensor is taken from the voltage across the coil spring 2a, it may be taken from the voltage across the coil spring 2b. Also, the difference between the voltage across each of the coil spring 2a and the coil spring 2b is calculated,
You may extract the difference as an acceleration signal.

Further, by changing the spring constant of the coil spring 2 and the size of the weight 1, it is possible to provide an acceleration sensor of arbitrary sensitivity.

Further, although the coil springs 2a and 2b are electrically compatible, they are not necessarily the same.

[0030]

According to the present invention, since the weight is supported by the coil spring from both sides and the change in the inductance generated in the coil spring due to the acceleration is used for the acceleration detection, the number of parts constituting the acceleration sensor can be reduced. The acceleration sensor can be provided at low cost.

Further, since the acceleration is detected by using the difference between the inductances generated in the two coil springs, the electrical characteristics of the coil springs causing the detection error and the physical characteristics due to the temperature cancel each other out. Accurate and stable acceleration sensor.

Furthermore, since the positioning accuracy of the weight is not required, the manufacturing becomes easy and the cost can be further reduced.

Further, since the coil spring keeps a constant displacement amount even when the acceleration is constant, it is possible to detect not only the constant acceleration but also the low frequency region to the high frequency region.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an acceleration sensor according to the present invention.

FIG. 2 is an equivalent circuit diagram of the embodiment.

FIG. 3 is a configuration diagram showing a conventional acceleration sensor using a piezoelectric body.

FIG. 4 is a configuration diagram showing a conventional acceleration sensor using a strain gauge.

[Explanation of symbols]

 1 Weights 2a, 2b Coil spring 13 Detection means

Claims (1)

[Claims] 1. An acceleration sensor comprising a weight that is displaced by acceleration, a coil spring that holds the weight from both sides, and a detection unit that detects a change in reactance of the coil spring due to the displacement of the weight as an acceleration signal.