JP3044992B2 - Vehicle collision detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a collision detecting device for detecting a collision of a vehicle.

[0002]

2. Description of the Related Art There is known a collision detecting device which integrates a deceleration of a vehicle detected by a deceleration sensor by an integrator, and compares the integrated value with a predetermined value by a comparator to determine a collision of the vehicle (see, for example). For example, see JP-A-63-503531).

In this type of apparatus, a high-pass filter is provided between the deceleration sensor and the integrator to correct the zero point drift of the deceleration sensor. The zero point drift of the deceleration sensor mainly occurs due to the temperature fluctuation of the detection element and the detection circuit, and the deceleration sensor used for vehicle collision detection generates a drift of about 0.1 to 0.5 G. A high-pass filter installed between the deceleration sensor and the integrator removes this drift component from the output signal of the deceleration sensor.

[0004] The cut-off frequency of the high-pass filter is desirably 1 Hz or more in consideration of, for example, a drift frequency component due to a current collecting effect of the piezoelectric body. On the other hand, the output signal of the deceleration sensor at the time of the actual collision varies depending on the rigidity of the vehicle body and the situation at the time of the collision, but the frequency component of about 3 to 7 Hz is often the main component. The cutoff frequency is desirably 1 Hz or less so that the influence of the frequency component of 3 to 7 Hz on the gain is reduced.

[0005]

However, an occupant restraint device such as an air bag activated by a collision detection device is required to operate even at about 5 to 6G.
The zero point drift of the 0.5 G deceleration sensor is a value that has a great influence on accurate collision determination. In the conventional collision detection device described above, a high-pass filter is provided between the deceleration sensor and the integrator to correct the zero point drift of the deceleration sensor, but this causes an error in the deceleration signal at the time of collision. Therefore, there is a problem that it is necessary to adjust each collision determination circuit so as to reduce the influence of the error, or to use a complicated collision determination method in consideration of the influence of the error.

SUMMARY OF THE INVENTION An object of the present invention is to provide a collision detection device capable of removing a drift of a deceleration sensor and accurately determining a collision, without relying on complicated adjustment and complicated determination methods.

[0007]

The first and second aspects of the present invention will be described with reference to FIG. 1 showing the configuration of the first embodiment. The present invention is applied to a vehicle collision detection device including a speed detection unit 1 and a collision determination circuit 7 that determines a vehicle collision based on a deceleration signal output from the deceleration detection unit 1. A drift component extraction circuit 2 for extracting a drift component from the deceleration signal output from the deceleration detection means 1 and a holding circuit for holding the signal output from the drift component extraction circuit 2 at the time when the holding command is input 4, 6, C1, a holding command output circuit 5, R1, R2 for detecting a collision start and outputting a holding command to the holding circuits 4, 6, C1, and a holding command from the holding command output circuits 5, R1, R2. Until is output, the drift component extracted by the drift component extracting means 2 is subtracted from the deceleration signal output from the deceleration detecting means 1, and the holding command is output from the holding command output circuit 5, R1, R2. After that, a subtraction circuit 3 for subtracting the holding signals of the holding circuits 4, 6, and C1 from the deceleration signal output from the deceleration detecting means 1 is provided. From determining the collision of the vehicle based on the result deceleration signal, to achieve the above object. Further, in the vehicle collision detecting device according to the second aspect, the holding command output circuit 5, R
1, the holding command is output when the deceleration signal output from the subtraction circuit 3 exceeds a predetermined value by R2. The third embodiment of the present invention will be described with reference to FIG. 3 showing the configuration of the second embodiment. The holding command output circuit of the vehicle collision detecting device according to the third embodiment detects a predetermined impact applied to the vehicle. Means 11 for outputting a holding command when a predetermined impact is detected by the impact detection means 11.

[0008]

A drift component is extracted from the deceleration signal detected by the deceleration detecting means, and the drift component is subtracted from the deceleration signal until the collision start is detected and a holding command is output, thereby starting the collision. When the holding command is output upon detection, the immediately preceding drift component is held, the held drift component is subtracted from the deceleration signal, and a collision of the vehicle is determined based on the resulting deceleration signal. This allows
Accurate collision determination can be performed by removing the drift of the deceleration detecting means 1 without using a complicated adjustment or a complicated determination method.

In the means and means for solving the above problems which explain the constitution of the present invention, the drawings of the embodiments are used to make the present invention easy to understand. However, the present invention is not limited to this.

[0010]

【Example】

-First Embodiment- FIG. 1 is a functional block diagram showing a configuration of a first embodiment. A deceleration sensor (hereinafter, referred to as a G sensor) 1 detects the deceleration of the vehicle, and outputs a voltage signal v0 corresponding to the deceleration to a low-pass filter (hereinafter, referred to as an LPF) 2 and a subtractor 3. LPF2 has a cutoff frequency of 1-2
Hz, the high frequency component of the deceleration signal detected by the deceleration sensor 1 is removed, and the voltage signal v1 of only the low frequency drift component is output to the switch 4.
This switch 4 controls the control signal v5 from the comparator 5
, And is closed when the control signal v5 is at the Hi level to connect the LPF 2 with the buffer amplifier 6 and the capacitor C1. The capacitor C1 is charged by the output voltage v1 of the LPF 2 while the switch 4 is closed, and the terminal voltage changes with the output voltage v1.
When the switch 4 is opened, the terminal voltage of the capacitor C1 holds the output voltage v1 of the LPF 2 immediately before the switch C1 is opened. The buffer amplifier 6 outputs the terminal voltage of the capacitor C1 as it is to the subtractor 3 as a voltage signal v2.

The subtractor 3 subtracts the output voltage v2 of the buffer amplifier 6 from the output voltage v0 of the G sensor 1, and outputs a voltage signal v3 (= v0−v2) to the collision determination circuit 7 and the comparator 5. The comparator 5 compares the output voltage v3 of the subtractor 3 with a reference voltage v4 set by dividing the power supply voltage Vcc by the resistors R1 and R2. If the output voltage v3 of the subtracter 3 is smaller than the reference voltage v4. Hi
The level control signal v5 is output to the switch 4. At this time, the switch 4 is closed. When a collision occurs and the output voltage v3 of the subtractor 3 exceeds the reference voltage v4, the comparator 5 outputs a control signal v5 of Lo level to the switch 4. The Lo level control signal v5 is the above-described holding command, and the switch 4 opens according to the holding command, and the capacitor C1 holds the terminal voltage. The collision determination circuit 7 has an integrator and integrates the voltage signal v3 output from the subtractor 3. If the integrated value exceeds a predetermined value, it is determined that a collision has occurred, and a collision detection signal v6 is output.

FIG. 2 is a time chart showing waveforms at various parts of the collision detection device shown in FIG.
(B) shows the output voltage v2 of the buffer amplifier 6, and (c) shows the output voltage v3 of the subtractor 3.
Is shown. The operation of the first embodiment will be described with reference to these drawings. Before the collision, the output voltage v0 of the G sensor 1 is shown in FIG.
It is assumed that the offset is offset to the + side due to the zero point drift as shown in FIG. This voltage signal v
0 is supplied to the LPF 2 and the subtractor 3. G before collision
Since the output voltage v0 of the sensor 1 includes only a low-frequency drift component, the LPF 2 outputs the low-frequency voltage signal v1 (≒ v0) to the switch 4 as it is.

As described above, since the output voltage v3 of the subtractor 3 is smaller than the reference voltage v4 before the collision, the Hi-level control signal v5 is supplied from the comparator 5 to the switch 4, and the switch 4 is closed. I have. The low-frequency voltage signal v1 (≒ v0) output from the LPF 2 is
Is input to the buffer amplifier 6 and the capacitor C1 through the capacitor C1, and the capacitor C1 is charged. At this time, the terminal voltage of the capacitor C1 is equal to the output voltage v1 (≒
v0), and the terminal voltage is directly output to the subtractor 3 as the voltage signal v2 by the buffer amplifier 6. That is, when the switch 4 before the collision is closed, the output voltage v2 of the buffer amplifier 6 is substantially equal to the output voltage v1 of the LPF2, that is, the output voltage v0 of the G sensor 1, as shown in FIG. Become. As a result, a voltage signal v3 resulting from the subtraction of the output voltage v0 of the G sensor 1 and the output voltage v2 of the buffer amplifier 6 by the subtractor 3 is performed.
Becomes almost 0 V as shown in FIG.

Assuming that a collision has occurred in the vehicle at time t1, the output voltage v0 of the G sensor 1 starts from this time.
Increase. This voltage signal v0 includes a low-frequency drift component and a high-frequency collision component.
Is supplied to the subtractor 3. LPF2 receives the voltage signal v
0, the high frequency collision component is removed, and only the low frequency drift component is passed through the switch 4 to the capacitor C.
1 and the buffer amplifier 6. Therefore, the output voltage v2 of the buffer amplifier 6 immediately after the collision start time t1
As shown in FIG. 2B, the output voltage v0 of the G sensor 1 is a voltage of only a drift component obtained by removing a high-frequency collision component. This voltage v2 is supplied to the subtractor 3. On the other hand, a voltage signal v0 including a drift component and a collision component is supplied from the G sensor 1 to the subtractor 3, and a voltage signal v0 including only the drift component is supplied from the voltage signal v0.
2 is subtracted. The voltage signal v3 resulting from this subtraction is shown in FIG.
As shown in (c), only high frequency collision components are included. The voltage signal v3 including the collision component is supplied to the comparator 5, and is compared with the reference voltage v4.

At time t2 after the occurrence of the collision, the subtractor 3
When the output voltage v3 of only the collision component exceeds the reference voltage v4, the control signal v5 of the comparator 5 changes to Lo level. That is, the holding command is input to the switch 4,
The switch 4 opens. At this time, as shown in FIG.
The output voltage v1 of the PF2 is held. This output voltage v1 is a voltage obtained by extracting a drift component from the output voltage v0 of the G sensor 1, and this voltage is output as a voltage signal v2 'by the buffer amplifier 6. That is, the voltage signal v2 'is used as a drift component of the G sensor 1 after time t2. The subtractor 3 calculates the drift component voltage v2 ′ from the voltage signal v0 detected by the G sensor 1 after time t2.
Is subtracted, and only the collision component is extracted and output to the collision determination circuit 7. The collision determination circuit 7 integrates only this collision component,
If the integrated value exceeds a predetermined value, it is determined that a collision has occurred, and a collision detection signal v6 is output.

Here, if the switch 4 is not opened after the time t2, the output voltage v2 of the buffer amplifier 6 increases as shown by the broken line in FIG. 2B. This is G
The low-frequency component is included in the deceleration signal at the time of collision detected by the sensor 1, and the LPF 2 outputs the low-frequency component in addition to the drift component.
Is output via the Such a problem is solved by opening the switch 4 after time t2, holding the drift component of the immediately preceding deceleration signal and assuming that the drift component is after time t2. The drift component of the G sensor 1 fluctuates with time even after time t2, but the drift due to temperature fluctuates slowly.
Since the time from the start of the collision to the detection of the collision is extremely short, even if the fluctuation of the drift during this period is ignored, the error becomes extremely small and there is no problem.

Second Embodiment FIG. 3 is a functional block diagram showing a configuration of a second embodiment. FIG. 1 shows the configuration of the first embodiment in FIG.
The same reference numerals are given to the same devices as the devices described above, and the description will focus on the differences. In the first embodiment described above, the output voltage v3 of the subtractor 3 is compared with the reference voltage v4 and the switch 4
The control signal v5 is set to determine the opening timing of the switch 4. In the second embodiment, the opening timing of the switch 4 is determined using the G switch 11 that closes upon receiving a predetermined impact. Before the collision, the G switch 11 is open, and the power supply voltage Vcc is supplied to the switch 4 via the resistor R3. That is, the high-level control signal v5
Is supplied to the switch 4, and the switch 4 is closed. When a predetermined impact is applied to the G switch 11 due to the collision, the G switch 11 closes, the Lo level control signal v5, that is, the holding command is supplied to the switch 4, and the switch 4 opens. The operation other than the opening timing of the switch 4 in the second embodiment is the same as the operation of the first embodiment described above, and the description is omitted.

In the configuration of the above embodiment, the deceleration sensor 1 functions as a deceleration detecting means, the collision determination circuit 7 performs a collision determination circuit, the low-pass filter 2 performs a drift component extraction circuit, the switch 4, the buffer amplifier 6, and the capacitor. C1 is the holding circuit, the comparator 5 and the resistor R
1, R2, the G sensor 11, and the resistor R3, the holding command output circuit, the subtractor 3, the subtraction circuit, and the G sensor 11
Constitute the impact detection means.

[0019]

As described above, according to the present invention, the drift component is extracted from the deceleration signal detected by the deceleration detection means, and the deceleration is detected until the start of collision is detected and the holding command is output. The drift component is subtracted from the signal, and when the collision start is detected and the holding command is output, the immediately preceding drift component is held, and the held drift component is subtracted from the deceleration signal. Since the collision of the vehicle is determined on the basis of the signal, the drift of the deceleration detecting means can be removed and accurate collision determination can be performed without using a complicated adjustment or a complicated determination method.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a configuration of a first embodiment.

FIG. 2 is a time chart showing operation waveforms of each unit of the first embodiment.

FIG. 3 is a functional block diagram showing a configuration of a second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 G sensor 2 Low pass filter (LPF) 3 Subtractor 4 Switch 5 Comparator 6 Buffer amplifier 7 Collision judgment circuit 11 G switch C1 Capacitor R1, R2, R3 Resistor

Claims (3)

(57) [Claims] 1. A vehicle collision detection system comprising: deceleration detection means for detecting a deceleration of a vehicle; and a collision determination circuit for determining a collision of the vehicle based on a deceleration signal output from the deceleration detection means. In the apparatus, a drift component extraction circuit for extracting a drift component from a deceleration signal output from the deceleration detection means, and a holding circuit for holding a signal output from the drift component extraction circuit when a holding command is input A holding command output circuit for detecting the start of collision and outputting a holding command to the holding circuit; and a deceleration signal output from the deceleration detecting means until the holding command is output from the holding command output circuit. Is subtracted from the drift component extracted by the drift component extracting means, and after the holding command is output from the holding command output circuit, the drift component is output from the deceleration detecting means. A subtraction circuit for subtracting the holding signal of the holding circuit from the obtained deceleration signal, wherein the collision determination circuit determines a vehicle collision based on the deceleration signal resulting from the subtraction by the subtraction circuit. Vehicle collision detection device. 2. The vehicle collision detection device according to claim 1, wherein the holding command output circuit outputs a holding command when a deceleration signal output from the subtraction circuit exceeds a predetermined value. Characteristic vehicle collision detection device. 3. The vehicle collision detection device according to claim 1, wherein the holding command output circuit has an impact detection unit that detects a predetermined impact applied to the vehicle, and the predetermined impact is detected by the impact detection unit. A collision detection device for a vehicle, which outputs a holding command when the collision is detected.