JPH04172257A - Acceleration sensor - Google Patents

Abstract

PURPOSE:To obtain a rugged, highly accurate acceleration sensor by providing a plurality of pressure detecting means for detecting the pressure distribution of fluid with acceleration on the inner wall surface of a cavity wherein liquid is tightly sealed. CONSTITUTION:Piezoelectric elements 1a and 1b which are arranged at the right and left sides so as to face each other are electrically connected to leads 4 through metal thin wires 3. The inside of a case 10 is used as a cavity 11. The elements 1a and 1b are attached to the inner wall surface of the cavity. The inside of the cavity 11 is filled with fluid 12 in a tightly sealed state. By this constitution, when an acceleration sensor is subject to the accelerations in the components in the right and left directions, the pressure distribution corresponding to the accelerations is generated in the fluid 12. The different pressures are applied on the elements 1a and 1b, respectively, and the difference occurs between the generated voltages. The acceleration is computed based on the voltage difference. Namely, e.g. when the pressure in the rightward direction is applied, the fluid 12 is pushed to the left wall surface by the law of inertia, and the pressure on the left wide becomes larger than the right side. The fact is detected with the elements 1a and 1b.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an acceleration sensor.

[Prior Art] FIG. 6 shows a conventional acceleration sensor. In the figure, a groove (2) is formed in a semiconductor element (1) that is distorted due to deformation, and the above-mentioned groove (2) is formed on the upper surface of the groove (2). A circuit for detecting distortion is provided. The thin metal wire (3) electrically connects the semiconductor element (1) and the lead (4). A weight (5) is attached to the end of the semiconductor element (1).

The semiconductor element (1) is attached to the pedestal (6), and the pedestal (6)
) is fixed to the substrate (7). A space sealed by the substrate (7) and the cap (8) is filled with a viscous fluid (9).

With the above configuration, the semiconductor element (1) is fixed to the pedestal (6) in a cantilever state, so when the acceleration sensor receives acceleration in a direction perpendicular to the cantilever, the tip of the cantilever The attached weight (5) receives an inertial force, and the semiconductor element (1) receives a bending force. Semiconductor element (
1) is provided with the groove (2), so the strain caused by the bending force is concentrated in the groove (2), and the amount of strain is detected by a circuit provided on the upper surface of the groove (2). The acceleration received by the sensor is determined from the detected amount of distortion.

The viscous fluid (9) acts as a vibration suppressor to prevent the semiconductor element (1) from being deformed beyond the destruction limit due to excessive vibration when the acceleration sensor receives a shockingly large acceleration.

[Problems to be Solved by the Invention] Since the conventional acceleration sensor is configured as described above, there is a problem in that when a large acceleration is applied, stress concentrates on the groove portion of the semiconductor element, causing the groove portion to break. In order to prevent this, it is necessary to fill the inside of the sensor case with viscous fluid, which causes problems such as a decrease in the sensitivity of the sensor.

This invention was made to solve the above-mentioned problems.The purpose of this invention is to obtain an acceleration sensor that does not break even when a large acceleration is applied, does not require damping by viscous fluid, and has high sensitivity. shall be.

[Means for Solving the Problems] An acceleration sensor according to the present invention includes a fluid-tight cavity and a plurality of pressure detection means for measuring the pressure distribution of the fluid inside the cavity.

[Function] In this invention, the fluid sealed in the cavity acts as a weight, and generates a pressure distribution in the cavity according to the acceleration received by the sensor, which is then detected by the pressure detection means installed in the cavity. Detected by.

[Example] An embodiment of the present invention will be described below with reference to FIG.

Fig. 1 shows an acceleration sensor using a piezoelectric element as a pressure detection means. electrically connected to.

Inside the case (10) is a cavity (11),
Piezoelectric elements (la) and (lb) are attached to the inner wall surface of the cavity. Further, the cavity (11) is filled with a fluid (12) in a sealed manner.

In addition, the same reference numerals as in FIG. 6 indicate the same or corresponding parts.

Next, the operation will be explained. When the acceleration sensor receives acceleration in the left-right direction component as shown in the figure, a pressure distribution is generated in the fluid (12) sealed inside the cavity (11) according to the acceleration, and the piezoelectric elements (Ia) and (Ib) respectively Different pressures are applied, resulting in a difference in the voltage generated. The acceleration applied due to the voltage difference is calculated. For example, in Fig. 1, when pressure is applied in the right direction, the fluid (12) is pressed against the left wall surface due to the law of inertia, and the pressure on the left side becomes larger than that on the right side (the piezoelectric element (la) ,
Acceleration is calculated by detecting (lb).

FIG. 2 shows another embodiment in which a semiconductor element having a pressure sensitive surface is used as the pressure detection means.
) and (6b), respectively.

(14a) and (14b) are diaphragm sections that operate as pressure-sensitive surfaces, and a circuit is provided above them to detect distortion when the diaphragm section is deformed by pressure. A cavity (1) formed by the diaphragm portions (14a), (14b) and the pedestals (6a), (6b).
5a).

The inside of (15b) is sealed with a vacuum or with gas at the same pressure and 2 volumes.

In addition, the same reference numerals as in FIG. 1 indicate the same or corresponding parts.

With the above configuration, the acceleration sensor receives acceleration from the fluid (
12), the diaphragm part (14a
) and (14b), and the acceleration is detected accordingly.

FIG. 3 shows yet another embodiment, in which six piezoelectric elements are used to detect acceleration in three-dimensional directions. That is, the piezoelectric elements (1a) to (1d) are attached to each surface of the cubic cavity (11).

In addition, the same reference numerals as in FIG. 1 indicate the same or corresponding parts.

With the above configuration, the piezoelectric elements (la) and (Ib) cause acceleration in the left and right direction, and the piezoelectric elements (lc) and (ld)
Due to the acceleration in the vertical direction, it is not shown in the figure, but it is the front.

Three-dimensional acceleration is detected by detecting acceleration in the front-rear direction using a piezoelectric element attached to the rear surface.

Further, FIGS. 4 and 5 show another embodiment, in which four piezoelectric elements are used to detect acceleration in three-dimensional directions. Piezoelectric elements (la) and (lb
), Ub) and (lc), and (Ic) and (1d) to detect acceleration in three-dimensional directions.

Although a piezoelectric element is used as the pressure detection means in the embodiment shown in FIG. 3 and the embodiment shown in FIG. 4, it goes without saying that similar effects can be obtained by using a semiconductor element having a pressure-sensitive surface.

[Effects of the Invention] As described above, according to the present invention, since acceleration is detected by detecting the pressure distribution of the fluid within the cavity, it is possible to obtain a robust and highly accurate acceleration sensor. .

[Brief explanation of drawings]

1 to 4 are longitudinal cross-sectional views of embodiments of the present invention, and FIG. 5 is a cross-sectional view taken along the line V-v in FIG. 4.
FIG. 6 is a longitudinal sectional view of a conventional acceleration sensor. (la), (lb), (lc), (ld)...Piezoelectric element (pressure detection means'), (10)...Case, (1
1) Capity, (12)-Fluid, (13a),
(13b)...Semiconductor element (pressure detection means), (14
a), (14b)...Diaphragm part. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] An acceleration sensor comprising a fluid-sealed cavity and a plurality of pressure detection means attached to the inner wall surface of the cavity to detect pressure distribution of the fluid due to acceleration.