JPH02108972A - Acceleration sensor - Google Patents

Abstract

PURPOSE:To improve the detection sensitivity to impressed acceleration by using a beam which is nearly corrugated lengthwise as a beam which bends with the impressed acceleration. CONSTITUTION:The beam 12 is formed by cutting a nonmagnetic, elastic plate material and the part between the fixation part for a silicon substrate 25 and the fixation part for a permanent magnet 2 is corrugated lengthwise. Then when the acceleration is impressed in the thickness direction as shown by an arrow, the beam bends toward a magneto-resistance element 301 or 3-2. The quantity of the bending varies with the impressed acceleration and the operation of moving the magnet 2 is detected from the output of the addition part to which the elements 3-1 and 3-2 are connected.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a sensor that electromagnetically detects acceleration, and aims to increase the sensitivity of an acceleration sensor that combines a magnetoresistive element and a permanent magnet, and has a sensor that deflects due to applied acceleration. A beam, a permanent magnet supported at a predetermined portion of the beam, and at least a pair of magnetoresistive elements provided at symmetrical positions on both sides of the permanent magnet, the beam being bent substantially in a waveform in its length direction. It is characterized by becoming.

[Industrial application field]

The present invention relates to a sensor that generates acceleration electromagnetically, and particularly to a configuration that increases sensitivity.

Conventional acceleration sensors that detect the displacement of a weight due to applied acceleration or the strain of a cantilever beam supporting the weight have a drawback of low sensitivity. Therefore, a permanent magnet is attached to a predetermined position of a beam that bends due to applied acceleration, and at least two magnetoresistive elements are provided on both sides of the permanent magnet at symmetrical positions sandwiching it, and the outputs of the magnetoresistive elements are reversed. An acceleration sensor equipped with an addition section that performs addition using magnetism has appeared.

[Conventional technology]

FIG. 7 is a basic configuration diagram (A) of an acceleration sensor (Patent Application No. 110882-1982) filed by the present applicant on May 7, 1988, and a perspective view (A) showing an example of the configuration of its acceleration detection section.
0).

In Fig. 7 (a), ■ is a beam that bends due to applied acceleration, 2 is a permanent magnet with N and S poles, 3-1.3
−, z are two barber pole magnetoresistive elements, 4-7
and 4-t are the output signal lines of the magnetoresistive element, 5 is the addition section, 5
-1 is an output signal terminal of the addition section 5, and 6 is a detection section.

In FIG. 7 (II) showing the detection unit 6, 7 is a silicon substrate, 8 is a hole provided in the silicon substrate 7, 9 to 9-4 are magnetoresistive elements 3-+ formed on the upper surface of the silicon substrate 7,
A beam l, which is a connection pad between 3-z and the adder 5 and is made of non-magnetic phosphor bronze, has one end fixed to the silicon substrate 7 and the other end fixed to the permanent magnet 2. .

In the acceleration sensor configured in this way, the mass of the magnet 2 is m
1. When the acceleration applied to magnet 2 is G, and the amount by which magnet 2 is displaced from its initial position relative to, for example, magnetoresistive element 3-2 is X, the acceleration G is G = kx/m, where k is a proportional constant. is given by That is, from the initial position where no acceleration G is applied to the magnet 2, the beam 1 is deflected in the direction of the arrow due to the applied acceleration G, and when the magnet 2 approaches the magnetoresistive element 3 = 2, the magnetoresistive element 3 The amount of positional displacement can be read out from the change in the electrical signal due to the voltage fluctuation on the -2 output signal line 4-t, and the value of acceleration can be determined from the amount of displacement.

Even if the direction of application of acceleration is reversed and the magnet 2 is displaced in a direction approaching the magnetoresistive element 3-0, the value of the acceleration at that time can be similarly known.

[Problem to be solved by the invention]

As explained above, the conventional acceleration sensor that combines a magnetoresistive element and a permanent magnet can easily obtain a larger output than the previous one, and has the effect of realizing high precision and miniaturization. Therefore, if you want to make the acceleration sensor even more sensitive, you can make the beam longer or thinner. There is a problem in that it is difficult to realize this method due to limitations in the mechanical strength and manufacturing of the beams that support the magnets.

(Means for Solving the Problems) FIG. 1 is a schematic diagram of a basic configuration example showing a detection section of an acceleration sensor according to the present invention, and FIG. , an acceleration detection section 11 corresponding to the conventional detection section 6 includes, for example, a beam 12 fixed at one end so as to be bent by applied acceleration; a permanent magnet fixed to the other end (predetermined portion) of the beam 12; A pair of magnetoresistive elements 3-1 provided at symmetrical positions on both sides of the magnet 2
and 3-2, and is characterized in that the beam 12 is bent in a waveform in its length direction (in the direction of the arrow in the figure).

[Effect]

In the present invention, a beam that is deflected by applied acceleration is
By using beams that are approximately wave-shaped in the length direction, the deflection due to applied acceleration is greater than that of conventional beams that use straight beams, and this also increases the amount of movement of the permanent magnets fixed to the beam. Become. Therefore, the amount of change in the magnetic field of the permanent magnet is increased relative to the magnetoresistive element, and the detection sensitivity of applied acceleration is improved.

〔Example〕

EMBODIMENT OF THE INVENTION Below, the acceleration sensor by the Example of this invention is demonstrated using drawing.

FIG. 2 is a perspective view showing the basic configuration of a beam used in the acceleration detection section according to the present invention.

In FIG. 2(a), the cantilever beam 12-1 is cut out and molded from a plate material such as phosphor bronze that has non-magnetic and spring properties, and is fixed to a silicon substrate, for example.
The space between the I and the fixed part 134 that fixes the permanent magnet is formed in a waveform in the length direction, and the amount of movement of the fixed permanent magnet due to deflection when acceleration is applied is determined by the waveform as long as the flexible length ( Therefore, it is larger than the conventional beam l, which is a straight rectangular shape.

In Fig. 2 (o), the cantilever dyer 2-2 is cut out and molded from a plate material such as phosphor bronze, and includes a fixed part 13-I that is fixed to a silicon substrate, etc., and a fixed part that fixes a permanent magnet. 134 is formed in the same waveform as the cantilever beam 12-1, and an elongated through hole 13 is provided at the center in the width direction. The deflection of the beam 12-2 provided with such a through hole 13-1 is greater than that of the beam 12-1, and the stability against torsion and the like is equivalent to that of the beam 12-1.

In FIG. 2(c), the cantilever 12-3 is cut out and molded from a plate material such as phosphor bronze, and includes a fixed part 13-1 fixed to a silicon substrate, etc., and a fixed part 13 fixed to a permanent magnet. -2 is formed in the same waveform as the cantilever beam 12-1, and has an elongated through hole 13-4 in the center in the width direction and
3-3 is provided. However, the crosspiece 13-6 between the through-hole 13-4 and the pair of through-holes 13-3 is located at a position that has little influence on the deflection of the beam 124, that is, at a position that coincides with the peak of the waveform. The deflection of the beam 12-3 provided with such through holes 13 and 134 is almost the same as that of the beam 12-2, and the stability against torsion etc. is superior to that of the dyework 2-2. .

FIG. 3 is an exploded perspective view showing a detection section of an acceleration sensor according to an embodiment of the present invention.

In FIG. 3, a detection unit 21 according to the present invention corresponds to the conventional detection unit 6, and a cap 22 and a base 23 that constitute a sealed case are made of a magnetic material such as silicon steel, and their surfaces are coated with nickel plating. It has been subjected. The cap 22 has a sealing port 22 that is sealed by injecting anti-vibration oil into the case.
-I is attached to the base 23 by glass sealing.
and external terminals 24-1 to 24 fixed in an electrically insulated state.
-6 and fixed terminals 2L, 24-6 are provided.

Then, the cap 22 is placed over the base 23 on which the silicon substrate 25 and the like are mounted, and the joints are sealed by welding or the like to form a magnetically shielded case, and then the anti-vibration oil is poured into the case from the filling port 22-1. After injecting the filling port 22-
Block I.

This completes the detection section 21 that can be mounted on a printed board.

Cantilever beam 12 (or 12-1, 12-z, 12-i)
The silicon substrate 25 supporting one end of the square rod-shaped part 25
-I and the recess 25. which accommodates the beam 12 between 25-7. ．．
3, and has a rectangular bar-shaped portion 25. ,, and 25. A pair of barber pole type magnetic resistance elements 3 and 3-2 formed on the upper surface of one end of each are provided at symmetrical positions with the permanent magnet 2 in between, and for example, four resistance elements are connected in a full bridge configuration. The external connection pads of the magnetoresistive elements 3-i and 3-z are connected to the corresponding external terminals 24-8 to 24-2.
Connected to 4-b.

In the detection unit 21 configured in this way, the beam 12 receives acceleration applied in the thickness direction of the beam 12 (in the direction of the arrow in the figure), and the beam 12 is activated by either of the magnetoresistive elements 3-+ and 3-z. The magnetoresistive element 3
It is detected by the output of the adder (5) to which -1.3-z is connected.

4 and 5 are perspective views respectively showing beams according to other embodiments of the present invention, and the cantilever beam 26 in FIG.
3-8 and the fixed portion 13-2 are bent into a plurality of chevron shapes,
The cantilever beam 27 in FIG. As a modification of the beams 26 and 27, a through hole is provided in the center in the width direction to reduce the amount of deflection, similar to the beams 12-2 and 12-3. can be made larger.

FIG. 6 is a diagram showing the relationship between the amount of increase in the developed length of the beam and the amount of increase in deflection according to the present invention.

In Fig. 6, where the horizontal axis is the increase (%) in the developed length of the beam according to the present invention, and the vertical axis is the increase N (%) in the deflection of the beam according to the present invention, a phosphor bronze plate with a thickness of 0.05 mm is shown. Samples ■ to ■ made from
nv+ is constant, and sample ■ is the same straight rectangular shape as the conventional one.
Sample ■ has a waveform of 1 wavelength and an amplitude of 2 mm, and sample ■ has a waveform of 2 wavelengths and an amplitude of 21 mm. Sample ■ has a waveform of 1 wavelength and an amplitude of 4
n+n+ and sample (2) have a waveform with two wavelengths and an amplitude of 4ma+. Then, the amount of deflection of samples 1 to 2 compared with sample 2 increases in proportion to the amount of increase in the developed length.

In addition, in the above embodiment, the beam that is bent by applied acceleration is a cantilever beam, but instead of the cantilever beam, an acceleration detecting section in which a permanent magnet is fixed to the center of the double-support beam fixed at both ends is used. By applying the present invention, the same effect as using a cantilever beam can be obtained.

〔Effect of the invention〕

As explained above, in the acceleration sensor according to the present invention, the output of the magnetoresistive element is increased by increasing the deflection of the beam without changing the overall size, making it possible to provide an acceleration sensor with higher sensitivity than before. effective.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of an example of the basic configuration of the detection section of the acceleration sensor according to the present invention, Fig. 2 is a basic diagram of a beam used in the acceleration sensor of the present invention, and Fig. 3 is an acceleration sensor according to an embodiment of the present invention. FIG. 4 is a perspective view of a beam according to another embodiment of the present invention; FIG. 5 is a perspective view of a beam according to still another embodiment of the present invention; FIG. 6 is a perspective view of a beam according to another embodiment of the present invention; A diagram showing the relationship between the developed length of the beam and the amount of deflection according to the invention. Figure 7 is a conventional acceleration sensor. In the diagram, 2 is a permanent magnet, 3-x3-t is a magnetoresistive element, and 11.21 is an acceleration detection Section, 12.12-, . 12-2+ 12-3.26.27 is a beam, 13-,,13. , +3-s is a through hole provided in the beam,
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Hayabusa Makiri 9.] N Key Ebito No. 1 Illustrated wood reading Kabegai No. 7 / brunii staff's beam 0 Reimoto Zu No. Z
Figure 3: Exclusion part M and 93 Fig. 3 of the present invention (an actual drawing of the present invention)
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Claims (2)

[Claims] (1) Beam (12, 12
____1, 12_-_2, 12_-_3, 26, 27)
The beam includes a permanent magnet (2) supported at a predetermined portion of the beam, and at least a pair of magnetic resistance elements (3_-_1, 3_-_2) provided at symmetrical positions on both sides of the permanent magnet, An acceleration sensor characterized by being bent in a substantially waveform in the length direction. (2) The beam (12_-_2, 12_-_3) has a through hole (13_-_3, 13_-) having a length in the longitudinal direction thereof.
_4, 13_-_5) is formed in the center portion in the width direction.