JPH0926432A - Acceleration detection equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize the miniaturization and the cost reduction of an acceleration detection equipment. SOLUTION: For checking the sensor output from the electrodes 28, 32 of an acceleration sensor, an analog switch 9 is turned off, and an analog switch 10 is turned on. An electric signal is delivered to electrodes 27, 33 from a microcomputer 5. Since the electrodes 27, 33 and the electrodes 28, 32 vibrate at the same time, the failure check of the sensor output of the electrodes 28, 32 can be performed. The sensor output check of the electrodes 27, 33 is perormed in the manner opposite to the case of the sensor output check of the electrodes 28, 32. In the case of collision detection, the analog switches 9, 10 are turned off, and the input signals to the electrodes 28, 32 and the electrodes 27, 33 are cut off. The outputs of electrodes 28, 32 and the electrodes 27, 33 which are caused by collision are inputted in an A/D converter of the microcomputer 5. The collision detection is performed by the AND of the two signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration detecting device used in an airbag system or the like which detects a collision of an automobile or the like and inflates the airbag.

[0002]

2. Description of the Related Art Conventionally, an acceleration sensor for detecting a collision of an automobile is built in an air bag controller, and since it is an electronic type, it is represented by a system such as a relay in order to prevent malfunction due to an electrical cause. Mechanical sensors were inserted in series.

FIG. 3 shows the structure of a conventional airbag controller. As shown in FIG. 3, the output of the electronic acceleration sensor 1 is AD-converted and fetched by the microcomputer 2, and the microcomputer 2 determines whether or not there is a collision and turns on the switch 3. A safing sensor 4 is arranged in series with the switch 3, and the safing sensor 4 is of a mechanical type and is set to be turned on at a smaller acceleration than that of the electronic acceleration sensor 1.

As described above, even the acceleration detecting device in which the electronic type acceleration sensor 1 and the mechanical type acceleration sensor 4 in the conventional example described above are combined can detect a collision without malfunction.

Next, self-check of the electronic acceleration sensor 1 will be described. 4 to 9 show an electronic acceleration sensor 1, FIG. 4 is a plan sectional view, and FIG. 5 is A of FIG.
-A arrow sectional view, FIG. 6 is a BB arrow sectional view of FIG. 4, FIG.
7A is a plan view of the diaphragm, FIG. 7B is a cross-sectional view of the central portion of the diaphragm, FIG. 8 is a plan view of one piezoelectric ceramic element,
FIG. 9 is a plan view of the other piezoelectric ceramic element.

As shown in FIGS. 4 to 6, the mounting base 11
A metal shield case 13 is fixed to the inside of the frame-shaped portion 12 by adhesion or the like, a base 14 is fixed to the inside of the bottom of the shield case 13 by adhesion, or the like. Are subjected to ring projection welding at a welded portion 16 to form a housing 17. A sub base 18 is integrally formed inside the housing 14 so as to project inside the central portion of the base 14.
An annular protrusion 19 is provided at the protruding end of the.

The vibration plate 20 has a circular positioning hole 2 at the center thereof.
1 is formed, positioning annular projections 22 and 23 are formed concentrically on the outer periphery of the positioning hole 21 and have large diameters on the back surface and the front surface in order, and a terminal 24 is provided by cutting and raising at a part of the edge of the positioning hole 21. (See FIGS. 7A and 7B).

A circular hole 26 is formed in the center of the piezoelectric ceramic element 25, a positive electrode 27 and a positive electrode 28 are annularly divided into two, and a negative electrode 29 is provided on the entire back surface. (See Figure 8). The piezoelectric ceramic element 30 has a circular hole 31 formed in the center, a positive electrode 32 provided on the front surface, and a negative electrode 3 on the back surface.
3 are provided (see FIG. 9).

The hole 26 of the piezoelectric ceramic element 25 is fitted and fixed to the positioning annular projection 23 on the surface side of the diaphragm 20, and the piezoelectric ceramic element 30 has the hole 3 thereof.
1 is an annular projection 2 for positioning on the back surface side of the diaphragm 20.
2 is fitted and fixed, the negative electrode 29 on the back surface of the piezoelectric ceramic element 25 is electrically connected to the front surface of the diaphragm 20,
The positive electrode 32 on the front surface of the piezoelectric ceramic element 30 is electrically connected to the back surface of the diaphragm 20. In the vibration plate 20 to which the piezoelectric ceramic elements 25 and 30 are attached in this way, the hole 21 is fitted into the annular projection 19 of the sub base 18, and is electrically insulated and fixed from the base 14. .

At the bottom of the housing 17, the terminal 3
4, 35, 36, a sensor output terminal 37, a power supply terminal 38, and a ground terminal 39.
The drive terminal 40 is attached in a penetrating state. The circuit board 41 has pins 4 in the housing 17.
2, the upper ends of the terminals 34 to 40 penetrate the circuit board 41 and are connected by soldering. Positive electrode 2 of piezoelectric ceramic element 25
7 and the negative electrode 33 of the piezoelectric ceramic element 30 are connected to the sensor output terminal 37 via the lead frames 43 and 44 and the circuit board 41, respectively.
The terminal 24 of the diaphragm 20 is connected to the terminal 35 via the lead frame 45. Piezoelectric ceramic element 2
The drive electrodes 28 and 32 of 5 and 30 are connected via a lead frame 46 to a drive terminal 40 for applying and vibrating a voltage for the purpose of self-checking the sensor characteristics.

The acceleration sensor 1 thus constructed is attached to the vehicle body by utilizing a pair of attachment holes 47 formed on both sides of the attachment base 21.

Then, the acceleration generated by the traveling of the automobile is transmitted to the diaphragm 20 via the mount 11, the base 14, the sub-base 18, etc., and the diaphragm 20 is bent. The bending of the vibration plate 20 alternately applies a tensile force and a compressive force to the piezoelectric ceramic elements 25 and 30, so that electric charges are generated in the piezoelectric ceramic elements 25 and 30. This charge is converted into a voltage by the impedance conversion circuit of the circuit board 41 and output through the filtering circuit and the amplification circuit so as to have a required band and an optimum output level, and a sensor output is obtained.

In the acceleration sensor 1, a self-check is performed by applying a voltage to the drive terminal 40, and applying the voltage to the drive electrodes 28 and 32 by the voltage ceramic elements 25 and 30 and the diaphragm 20. Vibrate the configured oscillator. On the other hand, as a matter of course, since the sensor output electrodes 27 and 33 are also baked on the same piezoelectric ceramic elements 25 and 30, an output can be obtained from the sensor even when a voltage is applied, and a failure check of the entire sensor including the vibrator, that is, Self-check is possible.

[0014]

However, in the above-described acceleration detecting device of the conventional example, since the two types of acceleration sensors 1 and 4 are used, it is difficult to reduce the cost, and the air bag in which these acceleration sensors 1 and 4 are incorporated. There is a problem that it is difficult to reduce the size of the controller.

The present invention solves such a conventional problem, and an object of the present invention is to provide an acceleration detecting device which can be reduced in size and cost.

[0016]

In order to achieve the above object, the present invention has a piezoelectric type acceleration sensor having a divided electrode and capable of outputting a voltage proportional to a vibration acceleration and an input voltage, and a failure. Control means for inputting an electric signal to the electrode at the time of checking and for cutting off the electric signal to the electrode to obtain a plurality of sensor outputs by using the electrode as a sensor at the time of detecting acceleration. Is.

Then, in the above technical means, based on a sensor output using an electrode capable of inputting an electric signal,
It can be configured to turn on at any applied acceleration and continue to turn on for any time.

[0018]

According to the present invention configured as described above, since a plurality of sets of electrodes of the piezoelectric type acceleration sensor can be used both as a drive and as a sensor output, one acceleration sensor can be used as a plurality of acceleration sensors. You can get the output.

[0019]

An embodiment of the present invention will be described below with reference to the drawings.

1 and 2 show an acceleration detecting device according to an embodiment of the present invention. FIG. 1 is a schematic block diagram of the whole, and FIG. 2 is a schematic block diagram of a main part.

In FIG. 1, reference numeral 1 denotes an electronic acceleration sensor, which has the same system and configuration as the conventional acceleration sensor 1 shown in FIGS. 4 to 9, and therefore, the same parts are designated by the same reference numerals. Although the description is omitted, the electrodes 28, 32 and 2
The configuration is different from that of the above-described conventional acceleration sensor in that the sensor output is obtained from each of 7 and 33. The microcomputer 5 is the electrode 2 of the acceleration sensor 1.
Self-checking power can be output to 8, 32 and 27, 33 to obtain sensor output from electrodes 27, 33 and 28, 32 for self-diagnosis, and electrodes 28, 32 and 27, 33 can be used. The sensor output of 1 is received by the A / D converter, collision detection is performed by AND from these two signals, and a large current is passed to the inflator via the switch 6.

Next, the interface between the electronic acceleration sensor 1 and the microcomputer 5 will be described in detail with reference to FIG.

The electronic acceleration sensor 1 has electrodes 28, 32.
, 27 and 33 respectively have circuits 7 and 8 for performing impedance conversion, amplification, filtering, and temperature characteristic correction in order to optimize the output thereof for collision detection.

To check the sensor output of the electrodes 28 and 32 in the self-check, first, the analog switch 9 is turned off and the analog switch 10 is turned on. For example, a rectangular wave of 0-5 V is output from the microcomputer 5 by the analog signal. It is applied to the electrodes 27 and 33 through the switch 10.
Then, the electrodes 27, 33 and 28, 32 vibrate at the same time, so that the failure of the sensor output of the electrodes 28, 32 can be checked. The check of the sensor output of the electrodes 27 and 33 is the reverse of the check of the sensor output of the electrodes 28 and 32.

On the other hand, when a collision is detected, the analog switches 9 and 10 are turned off, the input of electric signals to the electrodes 28 and 32 and 27 and 33 is cut off, and each pair of electrodes 28 and
The outputs of 32, 27, and 33 are A of the microcomputer 5.
A collision can be detected by inputting it to the / D converter as described above.

Then, an electrode 28 capable of inputting an electric signal,
Based on the sensor output using 32, 27, and 33, that is, the analog output, it can be configured to turn on at an arbitrary applied acceleration and continue to turn on for an arbitrary time.

As described above, according to the above-mentioned embodiment, it is possible to obtain the output of two acceleration sensors 1 by one, and it is possible to realize a small-sized and low-cost airbag controller.

[0028]

As described above, according to the present invention, it is possible to apply a voltage to a plurality of sets of electrodes by using the self-check electrodes of the piezoelectric type acceleration sensor.
Since the self-check can be performed and the outputs of the acceleration sensors for the number of electrodes can be obtained, it is possible to reduce the size and cost.

[Brief description of drawings]

FIG. 1 is a block diagram showing an acceleration detection device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a main part of the acceleration detection device.

FIG. 3 is a block diagram showing a conventional acceleration detection device.

FIG. 4 is a plan view showing an acceleration sensor used in an embodiment of the present invention and a conventional acceleration detection device.

5 is a cross-sectional view taken along the line AA of FIG.

6 is a sectional view taken along the line BB of FIG.

FIG. 7A is a plan view of a diaphragm used for the acceleration sensor, and FIG. 7B is a cross-sectional view of a central portion of the diaphragm used for the acceleration sensor.

FIG. 8 is a plan view of one piezoelectric ceramic element used for the acceleration sensor.

FIG. 9 is a plan view of the other piezoelectric ceramic element used for the acceleration sensor.

[Explanation of symbols]

 1 Acceleration Sensor 5 Microcomputer 7 Circuit 8 Circuit 9 Analog Switch 10 Analog Switch 20 Vibration Plate 25 Piezoelectric Ceramic Element 27 Positive Electrode 28 Positive Electrode 29 Negative Electrode 30 Piezoelectric Ceramic Element 32 Positive Electrode 33 Negative Electrode 41 Circuit Board

Claims (2)

[Claims] 1. A piezoelectric acceleration sensor having split electrodes, capable of outputting a voltage proportional to a vibration acceleration and an input voltage, and an electrode for inputting an electric signal to the electrode during a failure check and detecting the acceleration. And a control means for interrupting an electric signal to the electrode in order to obtain a plurality of sensor outputs using the sensor as a sensor. 2. Based on a sensor output using an electrode capable of inputting an electric signal, it is turned on at an arbitrary applied acceleration and kept on for an arbitrary time. The acceleration detection device described.