JPH07122643B2 - Acceleration detection device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, a semiconductor-type acceleration-type detection device that is effectively used in an anti-skid control device for an automobile, for example.

[Prior Art] An anti-skid control device for a vehicle is configured for the purpose of preventing a locked state of wheels that occurs when sudden braking is applied on a road with poor road conditions. For this reason,
In this control device, the rotation speed sensor of the wheel is used to monitor the rotation state of the wheel, and the acceleration detection device is used to monitor the state of acceleration acting on the vehicle. Then, the actual vehicle speed when the braking operation is executed is calculated.

That is, if the vehicle body slips and the wheels are locked when braking is applied, the vehicle body does not have the deceleration predicted in advance. The acceleration detection device detects the deceleration of the vehicle body in such a case, and when it is determined that the predetermined deceleration operation is not executed while the braking hydraulic pressure that applies the braking force is increased. Then, the wheel lock is determined. Then, when such a determination is made, the control for reducing the braking hydraulic pressure is performed to increase the rotational speed of the wheels and release the locked state of the wheels.

That is, the acceleration detection device is effectively used in the traveling control of a vehicle such as the automobile as described above,
The sensor for detecting the acceleration state is generally formed by a beam having a weight that is bent by the action of acceleration, and is configured to electrically detect the bending state of the beam.

As such an acceleration detection sensor, a semiconductor chip shaped into a beam is used.
A semiconductor type acceleration detection sensor is known in which a piezoresistive element is attached to a portion of the semiconductor chip where bending occurs.

The piezoresistive element that constitutes such an acceleration sensor is
For example, it is designed to be used as a part of a resistance element that constitutes a bridge circuit, and a detection signal of a voltage level corresponding to the acceleration applied from this bridge circuit is output. When this acceleration detection sensor is installed and set on the body of an automobile, the acceleration (G) in the opposite direction acts during acceleration and deceleration. For example, let's detect positive and negative accelerations corresponding to the front-back direction. In this case, if it is attempted to detect ± 1G as an analog output in the range of 1 to 3V, the relationship between the output and the acceleration G is as shown in FIG. Therefore, the output per 1 G is 1 V (1 V / G), and if a resolution of 1% is required, a minimum resolution of 10 mV is required on the circuit. Further, in the case where a comparison circuit is set in the rear circuit to which the detection output signal is supplied, it is necessary to set two sets of comparison circuits corresponding to positive and negative accelerations, respectively.

[Problems to be Solved by the Invention] The present invention has been made in view of the above points, and it is possible to easily improve the accuracy of the detected acceleration and use the comparison circuit to calculate the acceleration amount. An object of the present invention is to provide, for example, a semiconductor-type acceleration detection device in which one set of comparison circuits may be used in the case of performing reference determination.

[Means for Solving the Problems] That is, the acceleration detection device according to the present invention uses an absolute value circuit to output an output signal from an acceleration detection sensor that generates an electrical detection signal at a level corresponding to the amount of acceleration applied. In this absolute value circuit, for example, the detection signal on the positive side, which is lower than the signal level corresponding to zero acceleration, is inverted and amplified and output as an acceleration detection signal.

[Operation] In the acceleration detecting device as described above, a detection signal corresponding to each acceleration amount can be obtained both positively and negatively with reference to the state of zero acceleration.
Both positive and negative accelerations can be expressed in a predetermined voltage range. Therefore, the output per 1 G is set to be large, and the resolution is effectively improved. In addition, since the front-rear acceleration is expressed as an absolute value, when performing control using a comparison circuit, it is possible to perform a front-rear acceleration determination operation with one set of comparison circuits. Become.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 shows its schematic configuration. For example, a detection signal from a semiconductor type acceleration detection sensor 11 is generated by an amplifier 12
After being appropriately amplified by, the signal is supplied to a filter circuit 13 that cuts a DC component contained in the detection signal, for example. Then, the output signal from the filter circuit 13 is supplied to an absolute value circuit 14 to form an acceleration detection signal which is an absolute value signal corresponding to each of the positive and negative accelerations.

Then, the acceleration signal from the absolute value circuit 14 is
The signal is appropriately amplified by 15 and supplied to the comparison circuit 16, and the control operation corresponding to the detected acceleration is executed by comparing with the set reference level or the like.

FIG. 2 shows a more concrete form of the acceleration detecting device as described above. The acceleration detecting sensor 11 is composed of a bridge circuit including a piezoresistive element attached to a semiconductor chip. The power supply of the bridge circuit is configured by the constant current circuit 17 including the operational amplifier A1. That is, a voltage output according to the amount of acceleration acting on the sensor 11 can be obtained between the output terminals of the bridge circuit. Then, the detected output voltage is amplified in an analog manner by the amplifier 12 including the operational amplifiers A2 and A3.

The filter circuit 13 is composed of a low-pass filter 131 that cuts a detection signal component due to, for example, the inclination of the vehicle body, and a high-pass filter 132 that cuts a DC component. The low-pass filter 131 includes a resistor R1 and a capacitor C1.
Composed by. The high-pass filter 132 is composed of a differentiating circuit including the capacitor C2 and the resistor R2, and the output side of the capacitor C2 is set to the reference potential set by the resistors R3 and R4 via the resistor R2. Then, the AC component of the signal on the input side of the capacitor C2 is taken out as a detection signal, and the operational amplifier A4 lowers this impedance.

The acceleration detection signal from the high pass filter 132 is further supplied to the absolute value circuit 14. The absolute value circuit 14 is composed of an op amp A5 and is designed to invert and amplify an input signal higher than the reference potential set by the resistors R3 and R4. Then, the output signal from the absolute value circuit 14 is output by the amplifier circuit 15 including the op amp A6, and the output per 1 G is 2 V
Therefore, the output signal is processed and output by a comparison circuit or the like.

Here, it is assumed that the absolute value circuit 14 does not exist, and the output signal from the high-pass filter 132 is directly supplied to the amplifier circuit 15, and the output per 1 G is 1 V, and the output at 0 G is 2 V. Then, the relationship between acceleration and output is
It becomes like the figure.

In the absolute value circuit 14, when the potential of the (−) side terminal of the operational amplifier A5 is lower than the potential of the (+) side terminal (in the case of negative acceleration), the negative feedback (NF) of the operational amplifier A5 is It is "-1". When the above case is reversed, the operational amplifier A5 is in a non-operating state,
The input signal is inverted and amplified and output. That is,
The input signal corresponding to the negative acceleration is non-inverted amplified, and the input signal corresponding to the positive acceleration is determined and amplified and output.

Therefore, the input signal is inverted and amplified based on the positive / negative state of the input signal to the absolute value circuit 14 with respect to the reference potential set at the (+) side terminal of the operational amplifier A5. By making the reference potential match the input signal level when the acceleration is 0 G, the absolute value circuit 14 can obtain the output signal with the 0 G being the apex as shown in FIG. Is.

That is, for example, ± 1G is set to 1 by the absolute value circuit 14 described above.
If analog output is made in the range of ~ 3V, it will be as shown in Fig. 3, and the output per 1G will be 2V. Therefore, for example, if the resolution on the circuit is 10 mV, 0.5%
The resolution will be improved, and the accuracy will be substantially doubled as compared with the conventional one.

Further, front and rear accelerations are detected and output as absolute values. Therefore, the reference potentials of the front G comparison circuit and the rear G comparison circuit can be set to be the same, so that the front and rear acceleration detection processing can be executed by one comparison circuit. .

As described above, according to the acceleration detecting device of the present invention,
The resolution of the acceleration detection signal is easily improved, and the acceleration detection accuracy is easily improved. Further, when this acceleration detecting device is used for anti-skid control for an automobile, for example, the acceleration in the front-rear direction of the vehicle body can be detected by an absolute value, and processing such as comparison of detection signals can be performed. It will be executed in a simplified manner.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram illustrating an acceleration and detection device according to an embodiment of the present invention, FIG. 2 is a circuit configuration diagram showing the above embodiment in more detail, and FIG. 3 is the above embodiment. FIG. 4 is a diagram showing a state of an output signal from the device, and FIG. 4 is a diagram showing a state of a conventional acceleration detection output. 11 ... Acceleration detection sensor, 12, 15 ... Amplifier, 13 ... Filter circuit, 14 ... Absolute value circuit, 16 ... Comparison circuit.

Claims (1)

[Claims] 1. An acceleration detection sensor that generates an electrical detection signal of a level corresponding to the amount of acceleration applied, and an absolute value circuit to which a signal corresponding to the acceleration amount based on the detection signal from this sensor is supplied. A reference signal corresponding to zero acceleration is supplied and set to the absolute value circuit. In this absolute value circuit, the input signal is divided by the reference signal, and one of the input signals is inverted and output. An acceleration detecting device characterized in that