JPH0763779A - Acceleration sensor - Google Patents

Abstract

PURPOSE:To obtain an acceleration sensor which is free from characteristic changes and output drifts by providing a section which absorbs bending stresses which are generated when the sensor is fixed to an object to be measured. CONSTITUTION:When V-grooves 9 are provided as stress absorbing sections between the stage section 4a and fixing flange sections 4b of a stem 4, by pressing, etc., strains generated when the flange sections 4b of the stem 4 are fixed to an object to be measured are absorbed by the grooves 9 and the propagation of the strains to the stage section 4a of the stem 4 can be prevented. While the grooves 9 are only formed on one surface of the stem 4 in this example, they can be formed on both surfaces of the stem 4. In addition, the cross sections of the grooves 9 can be formed in U-shapes, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor used in a vehicle air bag system, a suspension control system and the like.

[0002]

2. Description of the Related Art FIGS. 5A and 5B are configuration diagrams showing a conventional acceleration sensor. FIG. 5A is a top view, FIG. 5B is a side view, and FIG. In the figure,
1 is an acceleration detecting element (G chip) for detecting acceleration, 2
Is an electronic component that constitutes a signal processing circuit that processes an output signal of the acceleration detection element 1, 3 is a signal processing circuit board on which the acceleration detection element 1 and the electronic component 2 are arranged, and 4 is a signal processing circuit board 3 bonded. The stem is composed of a stage portion 4a for holding the signal processing circuit board 3 and a fixing flange portion 4b for fixing to the object to be measured which generates acceleration. Further, 5 is a cap for protecting the signal processing circuit board 3, 6 is a lead terminal protruding from the signal processing circuit board 3, 7 is a screw for fixing the stem 4, 8 is a stem 4
Is a fixing jig for fixing an object to be measured to an automobile or the like.

Next, the operation will be described. The acceleration sensor is used for an air bag system, a suspension control system, etc. of an automobile, and is fixed to the automobile etc. by a screw 7 and a fixing jig 8. The acceleration detection element 1 used in the acceleration sensor is generally a semiconductor type sensor made by a silicon micromachining technology. A strain detection type using a diffusion semiconductor strain gauge and a capacitance type detecting a change in capacitance. However, these acceleration detection elements 1 are sensitive to external stress. Further, when the cap 5 is welded to the stem 4, the stem 4 may be deformed as shown in (c), and when the acceleration sensor is fixed to the object to be measured, a bending moment (as shown in the drawing) ( M) may be added to the entire acceleration sensor.

[0004]

Since the conventional acceleration sensor is constructed as described above, when fixing the acceleration sensor to an object to be measured such as an automobile, the flatness of the fixing flange portion of the stem 4 or If the flatness of the sensor fixing surface of the object to be measured is not sufficiently secured, a bending moment is generated in the stem 4 at the time of fixing, and distortion due to this moment is transmitted from the stem 4 to the acceleration detecting element 1 via the signal processing circuit board 3. There is a problem that the characteristics of the acceleration detecting element 1 are transmitted and the output of the acceleration detecting element 1 drifts.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to obtain an acceleration sensor which does not change its characteristics or drift its output when it is fixed to an object to be measured. To do.

[0006]

According to another aspect of the present invention, there is provided an acceleration sensor, wherein a bending occurs between a stage portion of a stem and a fixing flange portion when the fixing flange portion is fixed to an object to be measured. A stress absorbing portion is provided to prevent the stress from propagating to the stage portion.

[0007]

In the acceleration sensor of the first aspect of the present invention, the bending stress generated when the fixing flange portion is fixed to the object to be measured is propagated to the stage portion between the stage portion of the stem and the fixing flange portion. By providing the stress absorbing portion for preventing the above, it is possible to prevent the characteristics from changing and the output from drifting.

[0008]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to the drawings. 1 is a block diagram showing an embodiment of an acceleration sensor according to the invention of claim 1. In FIG. In the figure, the same reference numerals as those of the conventional one indicate the same or corresponding portions, and the explanation thereof will be omitted. Reference numeral 9 is a V-shaped groove (stress absorbing portion) provided between the stage portion 4a of the stem 4 and the fixing flange portion 4b.

Next, the operation will be described. The V-shaped groove 9 is formed by a press working method or the like. Such a V-shaped groove 9
By providing the, the strain generated when the fixing flange portion 4b of the stem 4 is fixed to the object to be measured is absorbed by the V-shaped groove 9, and the strain can be prevented from propagating to the stage portion 4a of the stem 4. Further, in this example, the V-shaped groove 9 is formed on one surface of the stem 4.
Although it is provided, it may be provided on both sides. In addition, the shape of the groove is V
Although the groove is formed in the shape of a letter, for example, a U shape may be used.

Embodiment 2. 2 is a configuration diagram showing another embodiment of the acceleration sensor according to the invention of claim 1. In FIG. Reference numeral 10 denotes a low-rigidity member (stress absorbing portion) such as resin provided between the stage portion 4a of the stem 4 and the fixing flange portion 4b.

Next, the operation will be described. By providing such a low-rigidity member 10 made of resin or the like as in the first embodiment, the strain generated when the fixing flange portion (4b) of the stem 4 is fixed to the object to be measured causes the low-rigidity member made of resin or the like. It is possible to prevent the strain from being absorbed by 10 and propagating to the stage portion (4a).

Embodiment 3. 3 is a block diagram showing another embodiment of the acceleration sensor according to the invention of claim 1. In FIG. Reference numeral 11 denotes a stage portion (4a) of the stem 4 and a fixing flange portion (4a).
It is a slit or a hole provided between (b) and b), and various shapes thereof can be considered from (a) to (d).

Next, the operation will be described. By providing such a slit 11 as in the first embodiment, the strain generated when the fixing flange portion 4b of the stem 4 is fixed to the object to be measured is absorbed by the stress absorbing portion near the slit 11, and the strain is reduced. It can be prevented from propagating to the stage portion 4a.

Example 4. FIG. 4 is a block diagram showing another embodiment of the acceleration sensor according to the invention of claim 1. As shown in the figure, by narrowing the entire width of the fixing flange portion of the stem 4 to have low rigidity, the strain generated when the fixing flange portion 4b of the stem 4 is fixed to the object to be measured is propagated to the stage portion 4a. Can be prevented.

[0015]

As described above, according to the invention of claim 1, between the stage portion of the stem and the fixing flange portion,
Since it is configured to provide a stress absorbing portion that prevents the bending stress generated when fixing the fixing flange portion to the measured object from propagating to the stage portion, the characteristics change when fixed to the measured object. There is an effect that an acceleration sensor can be obtained in which the acceleration and the output do not drift.

[Brief description of drawings]

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

FIG. 2 is a configuration diagram showing another embodiment of the acceleration sensor according to the invention of claim 1;

FIG. 3 is a configuration diagram showing another embodiment of the acceleration sensor according to the invention of claim 1;

FIG. 4 is a configuration diagram showing another embodiment of the acceleration sensor according to the invention of claim 1;

FIG. 5 is a configuration diagram showing a conventional acceleration sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Acceleration detecting element 2 Electronic component (signal processing circuit) 4 Stem 4a Stage part 4b Fixing flange part 5 Cap 9 V-shaped groove (stress absorbing part) 10 Low rigidity member such as resin (stress absorbing part)

Claims (1)

[Claims] 1. A signal processing circuit (2) for processing an output signal from an acceleration detecting element (1), and a stage portion (4a) and a fixing flange portion (4b) holding the signal processing circuit (2). In the acceleration sensor having a stem (4) and a cap (5) for protecting the signal processing circuit (2), the fixing part is provided between the stage part (4a) and the fixing flange part (4b). Flange (4
An acceleration sensor provided with a stress absorbing portion for preventing bending stress generated when attaching b) to an object to be measured from propagating to the stage portion (4a).