JPH04176752A - Collision detecting device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a collision detection device used in a system for detecting a vehicle collision and activating an air pack to ensure the safety of occupants.

BACKGROUND OF THE INVENTION A conventional collision detection device for an air pack system uses a mechanical device in which a spring is attached to a cylindrical roller and the switch is turned on by the roller that moves against the elastic force of the spring in the event of a collision. was.

Problems to be Solved by the Invention However, since the conventional device described above is a purely mechanical collision detection device, there is a problem in that the detection accuracy of detection parameters such as acceleration generated at the time of a collision is low.

The present invention solves the above-mentioned conventional problems, and provides a collision detection device with high detection accuracy and fewer false detections.

Means for Solving the Problems In order to achieve the above object, the present invention provides a differentiating means for differentiating the output of an acceleration sensor, a first comparison means for comparing the output of the differentiating means with a predetermined level, and the above-mentioned acceleration sensor. a charging/discharging means that charges and discharges according to the output level of the charging/discharging means, a second comparing means that compares the charging voltage of the charging/discharging means with a predetermined level, and a collision is detected based on the comparison results of the first and second comparing means. This is a special feature characterized by comprising a means for determining.

Operation The present invention has the above-mentioned configuration, in which the pulse-like characteristic waveform included in the output of the acceleration sensor at the initial stage of a collision is detected by the differentiating means and the first comparison means, and the high level signal of the acceleration sensor is The rain detection means and the second comparison means detect the rain, and if the rain detection results match, it is determined that a collision has been detected.

EXAMPLE An example of the present invention will be described below with reference to the drawings. FIG. 1 shows a collision detection device in one embodiment of the present invention. In Fig. 1, 1 is an acceleration sensor using a piezoelectric element, 2 is a low-pass filter for cutting high frequency components (for example, 1KH2 or more) in the output signal of the acceleration sensor 1, and 3 is the output signal level of the low-pass filter 2. This comparator 3 outputs a high level -H'' when the output level of the low-pass filter 2 is higher than vl. 4 is an AND circuit, 5
, 6 are a capacitor and a resistor that constitute a differential circuit,
The differentiating circuit outputs a high level -H'' when the output of the AND circuit 4 changes from -L to -H. Reference numeral 7 designates a timer portion. Next, the configuration of this timer portion 7 will be explained. 71 is a resistor, 72 is a transistor, and when the output of the differential circuit becomes "H", the transistor 72 is turned on.If the transistor 72 is off, the capacitor 74 is charged via the resistor 73, or the transistor 7
2 turns on, the charge accumulated in the capacitor 74 is discharged through the transistor 72, and the capacitor 74
The charging voltage of will decrease. A comparator 75 compares the charging voltage of the capacitor 74 with a predetermined voltage v4, and this comparator 75 outputs a high level output "H" when the charging voltage of the capacitor 74 is higher than v4. 76 and 77 are resistors and capacitors forming a delay circuit, the output of the comparator 75 is delayed by the delay circuit, and the signal delayed by this delay circuit is applied to the other input terminal of the AND circuit 4. In FIG. 1, while no shock is applied to the acceleration sensor 1, the output of the AND circuit 4 is "L-", so the transistor 72 is off, and the capacitor 74
is charged and its charging voltage is higher than the voltage v4, so the output of the comparator 75 becomes "H", and °H" is applied to the other input terminal of the AND circuit 4.

In this state, when an impact is applied to the acceleration sensor 1 and a signal with a level higher than the voltage v1 is output from the acceleration sensor 1, the two input outputs of the AND circuit 4 become "H". The output changes from "-L" to "H".The output of the AND circuit 4 is differentiated by a differentiating circuit consisting of a capacitor 5 and a resistor 6, so when the output of the AND circuit 4 changes from -L° to "H-" A high level pulse is output to
This pulse turns on the transistor 72 and discharges the charge accumulated in the capacitor 74. Next, the output of the differentiator circuit changes from "H-" to "L", so the transistor 72 changes from on to off, charging of the capacitor 74 starts, and the charging voltage of the capacitor 74 becomes equal to the resistance value of the resistor 73. It rises with a time constant determined by the capacitance value of the capacitor 74. When the charging voltage of the capacitor 74 becomes larger than the voltage v4, the output of the comparator 75 changes from "°L" to "H", and this change is delayed and the AND It is applied to the input terminal of the circuit 4. As described above, the first timer of the timer part 7 is activated by turning on the transistor 72, discharging the charge in the capacitor 74, and reducing the charging voltage of the capacitor 74 to below v4, and then turning off the transistor 72 and discharging the charge in the capacitor 74.
This is to prohibit the output of the acceleration sensor 1 from passing through the AND circuit 4 until the charging voltage becomes greater than V4 (period TI in FIG. 2A). Note that the delay circuit consisting of the resistor 76 and the capacitor 77 mainly prevents the transistor 72 from turning off and charging of the capacitor 74 to start while the transistor 72 is turned on and the capacitor 74 is not sufficiently discharged. 78 compares the charging voltage of the capacitor 74 with a predetermined voltage v5, and determines that the charging voltage of the capacitor 74 is v5.
This comparator 78 outputs a high level -H" while the output voltage of the acceleration sensor 1 is higher than v.
After the transistor 72 is turned on and the capacitor 74 is discharged, the capacitor 74 charging voltage becomes larger than the voltage ■5.
''.The output of the second timer is applied to one input terminal of the AND circuit 9 via the input 10. 8 is a differentiating circuit consisting of a capacitor 81 and a resistor 82. This differential circuit 8 is the acceleration sensor 1
The differential circuit 8 outputs a signal corresponding to the sharpness of the rise of the output of the acceleration sensor 1. 11 sets the output level of the differentiating circuit 8 to a predetermined voltage v2.
This is a comparator that outputs a high level -H" when the output of the differentiating circuit 8 is higher than a predetermined voltage V2. The output of this comparator 11 is input to the AND circuit 9. 12 is the AND circuit 9 13 is a mono-multivibrator activated by the output of acceleration sensor 1. 13 compares the output level of acceleration sensor 1 with a predetermined voltage v3,
When the output of the comparator 13 is "H-", the transistor 16 is turned off and the charge accumulated in the capacitor 17 is discharged through the resistor. When the output becomes -L, the transistor 16 is turned on and the capacitor 17 is charged by the current flowing through the resistor 15. 19 is a comparator, and this comparator 19 sets the charging voltage of the capacitor 17 to a predetermined voltage V6. When the charging voltage becomes higher than v6, it outputs "H". 20 is a monomulti/<ibrator activated by the output of the comparator 19, and 21 is an ant circuit.

FIGS. 2(a) to 2(g) are diagrams for explaining the operation of the embodiment shown in FIG. 1. FIG. 2(a) shows the output waveform of the acceleration sensor 1. The above embodiment describes the characteristics of the rising part of the output of the acceleration sensor 1 in the case of a strong collision, that is, in the case of a strong collision, a level fluctuation or a large pulse-like waveform occurs in the rising part of the output of the acceleration sensor 1, and a signal with a high output level. Collision detection is performed by detecting pulse-like waveforms and high-level waveforms, focusing on the occurrence of collisions. After an impact is applied to the acceleration sensor 1 and the output level of the acceleration sensor 1 becomes equal to or higher than V1, the second timer outputs a gate signal of a predetermined time width (T2) as shown in FIG. 2(b). do. This gate signal is input to the AND circuit 9 via the inverter 10. FIG. 2(C) shows the output waveform of the differentiating circuit 8, and the differential output from the comparator 1
1 is compared with V2, and the comparator 11 outputs the pulse shown in FIG. 2(d). FIG. 2(e) shows the output of the mono multivibrator 12. It can be seen that by outputting "H" from the mono-multivibrator 12, a sharp pulse-like signal peculiar to the time of a collision was generated at the initial rise of the acceleration sensor output. FIG. 2(f) shows the output of the comparator 13. Figure 2 (g) shows capacitor 1
7, and the output of comparator 13 is “L”.
When , the transistor 16 is turned on and the capacitor 17 is charged, and when the output of the comparator 13 is -H, the transistor 16 is turned off and the capacitor 17 is discharged. resistance 1
Since the resistance value of the resistor 5 is sufficiently smaller than the resistance value of the resistor 18, the charging voltage of the capacitor 17 increases each time the transistor 16 is turned on. FIG. 2(h) shows the output of the comparator 19, and FIG. 2(i) shows the output of the mono multivibrator 20. FIG. 2(j) shows the output of the NAND circuit 21, and the mono multivibrators 12 and 20 are both "
Outputs the H- period 'H'.

As described above, in the above embodiment, the sharp pulse-like signal that occurs at the initial stage of a collision is detected, the height of the level is detected, and the collision is detected based on the rain detection result, so that accurate collision detection without errors is possible. is possible.

Effects of the Invention The present invention has the above-described configuration, and detects characteristic vibrations and high-level vibrations of the acceleration sensor output at the initial stage of a vehicle collision, thereby enabling accurate collision detection.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a collision detection device according to an embodiment of the present invention, and FIGS. 2(a) to 2(j) are explanatory diagrams of the operation of the device. 1... Acceleration sensor, 2... Low pass filter, 3
...Comparator, 4...Ant circuit, 5...Capacitor, 6...Resistor, 7...Part of timer, 8...Differential circuit, 9...Ant circuit, 10...・Inverter, 1
1... Comparator, 12... Mono multivibrator,
13... Comparator, 14.15... Resistor, 16...
Transistor, 17... Capacitor, 18... Resistor, 19... Comparator, 20... Mono multivibrator, 21... AND circuit, 22... Output terminal. Name of agent: Patent attorney Akira Koyaharu and 2 others9
9 wheel 9 i 6 6
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Claims (1)

[Claims] a differentiating means for differentiating the output of the acceleration sensor; a first comparison means for comparing the output of the differentiating means with a predetermined level;
A charging/discharging means for charging and discharging according to the output level of the acceleration sensor, a second comparing means for comparing the charging voltage of the charging/discharging means with a predetermined level, and a comparison result of the first and second comparing means. A collision detection device comprising means for determining a collision based on the above.