JPS63132171A - Semiconductor type acceleration detector - Google Patents

Abstract

PURPOSE:To recognize the abnormal state of an acceleration sensor by receiving the output of the acceleration sensor which uses a semiconductor chip, and outputting, for example, an absolute value in a front-rear direction and comparing it with the signal of a predictive abnormal area. CONSTITUTION:The signal of potential difference corresponding to acceleration which is generated between output terminals (a) and (b) of the acceleration sensor of a bridge circuit composed of a semiconductor chip is amplified A1 and A2 differentially, the output (c) is applied to one terminal of a differential amplifier A3, and a reference voltage is applied to the plus terminal. This circuit 14 inverts the input (c) when the input (c) is smaller than a reference value to obtain an output (e), which is further amplified A4 to obtain an acceleration detection signal. An abnormality detecting circuit 15 applies a reference voltage Vr1 to the plus terminal of a comparator C1, Vr2 to the minus terminal of C2, and the signal (c) to the other-terminal sides, and both outputs are applied together to the input side of an amplifying circuit 16. When the sensor 11 is destroyed, c>Vr1 and when the sensor is in fault, c<Vr2, and an output signal is at 'L' in both cases and the abnormality of the sensor 11 is securely discriminated and recognized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor acceleration detection device which allows for effective and reliable use, for example, in an anti-skid control device of a motor vehicle.

[Prior Art] It is known to use a semiconductor as an acceleration detection element. FIG. 4 shows a configuration example of an acceleration detecting element using a semiconductor. A semiconductor cantilever 51 is formed by cutting a semiconductor substrate such as silicon into a beam shape, and a piezoresistive film is formed on a thin part 511 of the cantilever 51. 52 is attached.

Here, a weight 5 is attached to the free vibration end of the cantilever 51.
3, the cantilever 51 bends when acceleration is applied, and the resistance value of the piezoresistive film 52 changes depending on the degree of bending.

The piezoresistance element [52] is used, for example, as a resistance element constituting a bridge circuit connected to a constant current power supply, and it generates an electrical signal corresponding to the amount of acceleration acting on the cantilever 51, specifically Specifically, a highly linear voltage signal as shown in FIG. 5, which corresponds to the amount of acceleration, is extracted.

Acceleration detection elements using such semiconductors have the advantage of high strain sensitivity output compared to, for example, metal wire strain meters, but it is difficult to improve the breaking strength and mechanical There is a risk of destruction if a strong impact is applied.

Such an acceleration detection element is effectively used, for example, when constructing an anti-skid detection device for an automobile. Such a control device is used, for example, to prevent a wheel lock phenomenon that occurs when sudden braking is applied on a road with poor road surface conditions. This device calculates the actual vehicle speed during the braking operation using detection information from the wheel rotational speed sensors and the acceleration sensor that detects the acceleration acting on the vehicle body. Here, if a wheel slips during the braking operation and becomes locked, the previously predicted deceleration of the vehicle body will not occur.

The acceleration sensor detects the deceleration state of the vehicle body, and if the predicted deceleration is not acting even though braking is in progress, it indicates that the deceleration is acting on the wheels. To release a locked state of a wheel by reducing braking force and making the wheel easily rotate. That is, the locked state of the wheels is monitored by the acceleration sensor, and the occurrence of slip is detected and the braking force is controlled to ensure that the most effective braking operation is performed.

When configuring such an anti-skid control device, if a failure occurs in the sensors that observe the operating state of the vehicle body, for example, if the cantilever of the semiconductor acceleration detection element breaks, this will be immediately recognized and safety measures will be taken. It is important to let it be processed.

The detection signal processing circuit in a conventional acceleration detection device of this type is generally configured to amplify the detection signal from the acceleration sensor, and is used to distinguish between excessive input and a broken state of the sensor element, for example. It was impossible.

[Problems to be Solved by the Invention] This invention has been made in view of the above-mentioned points. Therefore, it is an object of the present invention to provide a semiconductor acceleration detection device that can reliably distinguish between an excessive input state and this destruction, and which can be used to configure a highly reliable anti-skid control device for an automobile. be.

[Means for Solving the Problems] That is, in the semiconductor acceleration detection device according to the present invention, an acceleration sensor is configured in an acceleration detection element made of a semiconductor, and from this sensor. The detection signal is supplied to an absolute value circuit so that, for example, acceleration in the longitudinal direction is output as an absolute value. Then, this detection signal is compared with a signal of a previously predicted abnormal area, and the abnormal state of the sensor is recognized.

[Operation] In other words, for example, if the acceleration detection element is destroyed by mechanical impact, etc., the acceleration detection sensor will
An abnormal state signal outside the range of normal acceleration detection signals is output as a detection signal. When such a state occurs, an abnormal state is detected based on a set value predicted in advance, and with the detection of such an abnormal state, the output of the acceleration detection signal is set to a blocked state, for example. This is what happens.

[Embodiment of the Invention] An embodiment of the invention will be described below with reference to 14 drawings. FIG. 1 shows its schematic configuration. The acceleration sensor 11 is composed of a bridge circuit including a resistive element made of the semiconductor acceleration detection element described above, and this bridge circuit is connected to a constant current power supply from a constant current circuit 12. Supply is set.

Such an acceleration sensor 11 outputs a voltage signal having a value corresponding to the amount of applied acceleration, and this detection signal is supplied to an absolute value circuit 14 by an amplifier circuit 13. Further, the output signal from the acceleration sensor 11 is constantly monitored by an abnormality detection circuit 15. When the abnormality detection circuit 15 detects an abnormality in the detection signal from the sensor 11, a command is given to the absolute value circuit 14 to set the acceleration detection signal to a specified level, and detect the sensor abnormality. This is to make people aware of this.

FIG. 2 shows the above-mentioned device in more detail, with the output terminal a of the bridge circuit constituting the acceleration sensor 11.
A signal with a potential difference corresponding to the amount of acceleration is generated between points A1 and B, and this detection signal is amplified by an instrument differential amplifier circuit 13 constituted by amplifiers A1 and A2. Then, the output portion C from this amplifier circuit 13
The acceleration detection signal from is supplied to an absolute value circuit 14 constituted by a differential amplifier A3. Here, the amplified detection signal is supplied to the (-) terminal of the amplifier A3, and the (+) terminal of the amplifier A3 is
A reference voltage set by resistors R1 and R2 is supplied and set. The absolute value circuit 14 inverts and amplifies the input signal when the input signal is lower than the reference voltage.
By setting the basic r$ lightning voltage in accordance with the input signal level to the absolute value circuit I4 based on the detection signal from the sensor in the state, the detection signal in the negative direction is inverted and appears at the output e. That is, the relationship between the applied acceleration and the detected output from the absolute value circuit 14 is as shown in FIG. It will be output as an acceleration detection signal via the .

The abnormality detection circuit 15 includes first and second comparators C
1 and C2. First and second base voltages Vrl and Vr2 set by resistors R3 to R5 are supplied to the comparators C1 and C2, and the (+)
The first reference voltage Vrl is supplied to the terminal, and the second reference voltage Vr2 is supplied to the (-) terminal of the second comparator C2. The detection signal from the amplifier circuit 13 is supplied to the (-) and (+) terminals of the first and second comparators C1 and C2, and the output signals from the comparators C1 and C2 are , are collectively supplied to the input terminal of the amplifier circuit 16.

That is, in the first comparator C1, the terminal C
When the signal of the second comparator C is higher than the first reference voltage Vrl, its output becomes low level.
2, the output becomes low level when the potential of the terminal C is lower than the second reference voltage Vr2. Therefore, in an abnormal state where the voltage at terminal C does not exist between the first and second reference voltages Vrl and Vr2,
Either of the outputs of the first and second comparators C1 and C1 becomes low level. Here, the output of the comparator is configured with an oven collector of an NPN h transistor.

That is, if the semiconductor detection element constituting the acceleration sensor 11 is destroyed and, for example, the output a becomes low level, the output C of the instrument differential amplifier circuit 13
but! The signal on the output line d from the abnormality detection circuit 15 becomes low level. Furthermore, if a fault occurs in the sensor 11 and its output terminal a goes to an abnormally high level, the output C of the instrument differential amplifier circuit 13 goes to a low level, and this potential becomes a value lower than the second reference voltage Vr2. Therefore, the output d from the abnormality detection circuit 15 becomes low level.

Therefore, when the detection element of the acceleration detection sensor 11 is damaged, the output signal from the abnormality detection circuit 15 becomes low level, and the destruction of the sensor 11 is recognized. This allows the output signal from the device to be set in the abnormal voltage range.

[Effects of the Invention] As described above, according to the semiconductor acceleration detection device according to the present invention, for example, in the case where a semiconductor acceleration sensor is damaged, the abnormal state of the sensor can be reliably and easily detected. This enables identification and recognition, and for example, when this acceleration detection device is used in an anti-skid control device for an automobile, its reliability can be ensured.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic configuration of a semiconductor acceleration detection device according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing the above device in more detail, and FIG. 3 is a diagram showing the above detection device. FIG. 4 is a diagram illustrating the configuration of a semiconductor acceleration detection element, and FIG. 5 is a diagram illustrating the state of a detection signal from the detection element. 11... Acceleration detection sensor, 12... Constant current circuit,
13...Amplification circuit, 14...Absolute value circuit, 15...
- Abnormality detection circuit, C'l, C2... comparator. Applicant's agent Patent attorney Takeshi Suzue 3 Figure 1 Figure 2 Figure 3 Section 4 Figure yyn4shi1 input Figure 5

Claims (1)

[Claims] An acceleration sensor that includes a detection element in which a strain detection element is set on a detection piece made of a semiconductor chip, and that generates an electrical output signal corresponding to acceleration, and a detection output signal from the acceleration sensor is supplied. an absolute value circuit that inverts and outputs a signal on one side of the set reference value, and an abnormality detection circuit that detects a signal generated when the acceleration sensor is in an abnormal state. A semiconductor acceleration detection device comprising: means for setting the output from the absolute value circuit to an abnormal region in a state in which the absolute value circuit is detected.