JP2838854B2 - Vehicle safety device control system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control system for a vehicle safety device such as an air bag.

[0002]

2. Description of the Related Art As disclosed in Japanese Utility Model Application Laid-Open No. 2-3571, a system for controlling a vehicle safety device such as an air bag includes an acceleration detecting means and a vehicle collision based on a deceleration signal from the acceleration detecting means. It comprises a collision determining means for determining the presence or absence and a drive circuit incorporating a squib as a basic configuration. The drive circuit includes a transistor (main switching means) connected in series with the squib. The collision determining means sends an ON command signal to the transistor of the drive circuit when the collision is determined to turn on the transistor, ignites the squib and inflates the airbag, thereby ensuring the safety of the occupant.

In the above-mentioned control system, a microcomputer is used to make a collision determination with high accuracy, and it is necessary to consider runaway of the microcomputer.
If the microcomputer runs out of control, an ON command signal may be output even though no collision has actually occurred, and the airbag malfunctions. Therefore, a safing switch is used. This safing switch is turned on by an inertial force at the time of a collision, and is connected in series with the transistor and the squib. When a collision does not actually occur, the safing switch is turned off, so even if the transistor is turned on due to runaway of the microcomputer as described above, current does not flow through the squib, and the malfunction of the airbag may occur. Can be prevented. The control system does not include a means for checking whether the safing switch is normal. Therefore, if a failure occurs while the safing switch remains off, even if the microcomputer operates normally and determines that a collision has occurred and turns on the transistor, no current is supplied to the squib and the airbag does not expand. Also,
If a malfunction occurs while the safing switch is on, malfunction of the airbag cannot be prevented when the microcomputer runs away.

[0004] The safing switch includes, for example, a reed switch, a permanent magnet movable in a traveling direction, and a spring for urging the permanent magnet in a direction opposite to the traveling direction. At the time of collision, the reed switch is turned on by the permanent magnet moving against the spring. Means for detecting such a failure of the safing switch is known. Specifically, an electromagnet is provided near the permanent magnet. A test pulse is supplied from the test pulse output means to the drive circuit of the electromagnet, whereby an exciting force is generated in the electromagnet, and the exciting force causes the permanent magnet to temporarily move against the spring and turn on the reed switch. . The failure determination means determines that the reed switch is turned on in response to the test pulse to determine that the reed switch is normal, and otherwise determines that a failure has occurred.

[0005]

However, in the case of confirming whether the safing switch is normal or not as described above, the size of the safing switch becomes large because an electromagnet is required. In addition, the core of the electromagnet is magnetized, and due to the repulsive or attractive force between this core and the permanent magnet,
The dynamic characteristics of the permanent magnet may change slightly. Further, since the above test involves the actual movement of the permanent magnet and the actual ON operation of the safing switch, the microcomputer may run away during this ON and turn on the transistor, and the airbag may expand. JP-A-63-241467 discloses means for supplying a test pulse to a piezo element of an acceleration sensing circuit to detect a failure.

[0006]

The control system according to the present invention includes a drive circuit 2 for a vehicle safety device 1 as shown in FIG. The drive circuit 2 has a main switching means 2a connected in series to the vehicle safety device, and a safing switch 2b. The safing switch 2b is turned on by inertia at the time of a vehicle collision, and one end thereof is grounded. When both are on, the vehicle safety device 1 operates. The control system further
An acceleration detecting means 3 for detecting the deceleration of the vehicle, and the presence or absence of a collision is determined on the basis of the deceleration signal from the acceleration detecting means 3, and an ON command signal is output to the main switching means 2a when the collision is determined. A collision determination unit 4 is provided. The control system according to the present invention is characterized by including the following configuration in addition to the above basic configuration. That is, there are provided an inductance 5 for generating a high voltage and an auxiliary switching means 6 for controlling the supply of current to the inductance 5. One end of the inductance 5 is connected to the battery, and the other end is connected to an end of the safing switch 2b on the opposite side to the ground. Further, a test pulse output means 7 and a failure determination means 8 are provided. The test pulse output means 7 supplies a current to the inductance 5 by outputting a test pulse to the auxiliary switching means 6 and turning on the test pulse, and supplies the current to the inductance 5 when the current supply corresponding to the end of the test pulse is stopped. Generate a back electromotive voltage. The failure determining means 8 determines whether or not a minute current due to discharge flows through the safing switch 2b when the back electromotive voltage of the inductance 5 is applied to the safing switch 2b. It is determined that the safing switch 2b has failed.

[0007]

A discharge is generated in the safing switch 2b by the back electromotive voltage of the inductance 5, and a very small current flowing at that time is detected, whereby the safing switch 2b is detected.
Since it is determined whether the switch is normal or faulty, components such as an electromagnet are not required, and the safing switch 2b can be downsized. Further, the normal operation characteristics of the safing switch 2b are not affected. Further, since the test of the safing switch does not involve an actual ON operation, even if the main switching means 2a is accidentally closed during the test, a large current does not flow through the safing switch 2b, and the vehicle safety device 1 malfunctions. Can be prevented.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 2 schematically shows a control system for controlling the squib 10 of the airbag (vehicle safety device). The control system basically includes an acceleration sensing circuit 20 (acceleration detecting means) for detecting acceleration and deceleration of the vehicle, a microcomputer 30, and a drive circuit 40 for the squib 10.

The acceleration sensing circuit 20 includes an acceleration sensor such as a piezo element for outputting a voltage signal corresponding to acceleration and deceleration, and a necessary amplifier circuit.
Voltage signals representing acceleration or deceleration from the acceleration sensing circuit 20 are sent to analog / digital converters ADC incorporated in the microcomputer 30 to be converted into digital data and supplied to the microcomputer 30.

[0010] The drive circuit 40, the transistor 41 of the PNP type and (main switching means) and safing switch 42, constituted by sequentially connected in series toward the ground from the battery V _B. An airbag squib 1 is provided between the transistor 41 and the safing switch 42.
0 is connected. Transistor 41 and battery V
Between the _B, and order from the transistor 41 to the battery V _B, the energy reservoir comprising a large-capacity capacitor (not shown), the step-up circuit for a voltage of the energy reservoir higher than the power supply voltage (not shown) Is interposed. Only when both the transistor 41 and the safing switch 42 are turned on, the squib 10 is ignited by receiving the current supply from the energy reservoir, and executes the expansion of the airbag. The output port O _{1 of the} microcomputer 30 is connected to the base of the transistor 41.
Is connected.

FIG. 3 shows a known configuration of the safing switch 42. Safe switch 42
Are an elongated reed switch 42a, a spring 42b disposed on the outer periphery of the reed switch 42a, and an annular permanent magnet 4 disposed at one end of the spring 42b and slidably mounted on the reed switch 42a.
2c. The reed switch 42a has an elongated container 42x, and an elongated reed piece 42 is provided at both ends thereof.
y and 42z penetrate. These lead pieces 42y, 4
One end of 2z is arranged outside the container 42x, and the other end is arranged inside the container 42x and is radially opposed to each other at the center of the container 42x. An inert gas such as argon, neon, or helium is sealed in the container 42x. The reed switch 42a is installed on the vehicle in a state parallel to the traveling direction. At the time of vehicle collision, the permanent magnet 42c
Is moved against the spring 42b by the inertia force, so that the lead pieces 42y, 42 of the reed switch 42a are moved.
Turn on by touching z.

The control system further includes an inductor 50 and a transistor 51 connected in series for generating a high voltage.
(Auxiliary switch means). One end of the inductance 50 and the other end is connected to the battery V _B is connected to the collector of the transistor 51. Transistor 51
The base is connected to the output port O ₂ of the microcomputer. Between the collector of the transistor 51 and the end of the safing switch 42 on the squib 10 side,
A series circuit of a diode 53 and a large resistor 54 is connected. The diode 53 has an anode connected to the transistor 51.
For collectors. The voltage between both ends of the resistor 54 is detected by a voltage detection circuit 55. The output stage of the voltage detection circuit 55 is connected to the input port I of the microcomputer 30. The detection output of the voltage detection circuit 55 is, for example, a low level when a current does not flow through the resistor 54 and the voltage across the resistor 54 is substantially zero, and a small current described later flows through the resistor 54 to cause a voltage drop. High level when The connection point between the resistor 54 and the safing switch 42 is connected to the squib 10 via a diode 56. Diode 56 points the anode to squib 10. The control system further
An alarm lamp 60 controlled by a transistor 61 is provided. The base of the transistor 61 is connected to the output port O ₃ of the microcomputer 30.

In the configuration described above, the microcomputer 30 determines the presence or absence of a collision based on a signal from the acceleration sensing circuit 20. That is, when a signal representing the deceleration is input from the acceleration sensing circuit 20, the integration is performed and compared with the threshold level. Then, the integral value when it is determined that exceeds the threshold level, outputs an ON command signal from the output port O ₁ to the transistor 41 as a collision. If the safing switch 42 is normal, it is turned on at the time of deceleration due to the vehicle collision, so that current is supplied to the squib 10 from the energy reservoir, and the airbag is expanded. When the microcomputer 30 goes out of control is sometimes ON command signal is output from the output port O ₁ of the microcomputer 30 to the transistor 41. However, since the safing switch 42 remains off unless a collision occurs, malfunction of the airbag can be prevented.

Next, a test routine executed by the microcomputer 30 at the time of power-on will be described with reference to FIG. After the initialization, a high-level test pulse is output from the output port O ₂ to the transistor 5.
1 and the transistor 51 is turned on (step 100). Thus, a current is supplied to the inductance 50 in synchronization with the test pulse. Next, the output state of the test pulse is maintained for a predetermined time T ₀ (for example, 100 msec) (step 101). It stops outputting the test pulse after the predetermined time T ₀ has elapsed (step 102). Thereby, the transistor 51 is turned off, and the current supply to the inductance 50 is stopped. When the current supply is stopped, a back electromotive voltage is generated in the inductance 50, and the back electromotive voltage is applied to the safing switch 42.

The lead piece 42 of the safing switch 42
If y and 42z are normal, when the back electromotive voltage of the inductance 50 exceeds the discharge level as shown in FIG. 5, a discharge occurs between the two and a small current should flow through the resistor 54. Then, when the back electromotive voltage drops and falls below the discharge level, the discharge ends. Therefore, the time T when the detection output of the voltage detection circuit 55 for detecting the voltage between both ends of the resistor 54 becomes high level falls within a certain time range, and T ₁ ≦ T
≦ T ₂ should hold. Safe switch 4
If the second lead piece 42y, 42z breaks down and remains off due to damage or the like, no discharge is performed even if a back electromotive voltage is applied, and the detection output remains at a low level. Therefore, in this case T is and T <T ₁ is zero. Further, when the lead pieces 42y and 42z are in contact with each other, that is, when the failure occurs while being turned on, the detection output remains at the high level even if the back electromotive voltage is lower than the discharge level, and T> T
It becomes ₂ .

After the step 102, the microcomputer 30 determines whether the detection output of the voltage detection circuit 55 is high or low (step 103). If it is determined to be high, time measurement by the timer is started (step 104). Next, at step 105, the measurement time T
Is equal to or upper limit value T ₂ following the allowable range. In the case of a negative determination, that is, when it is determined that T> T ₂ due to the on failure of the safing switch 42, a high-level signal is output from the output port O ₃ to the transistor 61 to turn on the alarm lamp 60. The test routine is turned on (step 106), and the test routine ends. Step 105
If the determination is affirmative, the process returns to step 103. Then, while the timer determines that the detection output is at the high level in step 103, the timer continues the time measurement (step 104).

[0017] When the detected output in step 103 is determined to be low level, it is determined whether a measurement by the timer time T is allowable range lower limit above T ₁ of (step 107), if the determination is affirmative i.e. If it is determined that T ₁ ≦ T ≦ T ₂ because the safing switch 42 is normal, the test routine ends. Also,
If the determination is negative, that is, if the safing switch 42 is determined to have become to T <T ₁ off failure, the alarm lamp 60 from the output port O ₃ outputs a high level signal to the transistor 61 The test routine is turned on (step 108), and the test routine ends.

As is clear from the above description, the microcomputer 30 has a collision judging means. Steps 100 to 100 executed by the microcomputer 30
Reference numeral 102 denotes a test pulse output unit. Further, steps 103, 104, 105, and 103 executed by the resistor 54, the voltage detection circuit 55, and the microcomputer 30.
107 constitutes failure determination means.

In the test of the safing switch 42, the movement of the permanent magnet 42c and the lead pieces 42y, 42
Since the contact of z is not involved, even if the transistor 41 is turned on due to runaway of the microcomputer 30 during the test,
Since a large current does not flow between the lead pieces 42y and 42z separated from each other, erroneous ignition of the squib 10 can be prevented.

The role of the diode 53 is as follows.
That is, during the test in which the transistor 51 is on, the microcomputer 30 runs away and the transistor 41
Is turned on, it is prohibited to form a current circuit by the transistor 41, the squib 10, and the transistor 51. The diode 56 has a role of preventing the back electromotive voltage of the inductance 50 from being applied to the transistor 41.

The present invention is not limited to the above-described embodiment, and various embodiments are possible. For example, the test routine may be performed every time the vehicle stops. The safing switch includes all switches having one or two lead pieces. As the inductance, a transformer of a booster circuit can be used. The control system of the present invention can be applied not only to airbags but also to tightening control of seat belts.

[0022]

As described above, according to the present invention, since no electromagnet is required for testing the safing switch, the safing switch can be downsized, and the normal operating characteristics of the safing switch can be reduced. Has no effect. Furthermore, since the safing switch test does not involve the actual turning on of the safing switch, even if the main switching means is accidentally closed during the test, a large current does not flow through the safing switch, and the vehicle safety device is erroneously turned on. Operation can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of a control system according to the present invention.

FIG. 2 is a circuit diagram schematically showing an embodiment of a control system according to the present invention.

FIG. 3 is a cross-sectional view illustrating an example of a safing switch.

FIG. 4 is a flowchart illustrating a test routine executed by the microcomputer of FIG. 2;

FIG. 5 is a time chart for explaining the operation of the control system of FIG. 2;

[Explanation of symbols]

 1,10 Vehicle safety device 2,40 Drive circuit 2a, 41 Main switching means 3,20 Acceleration detecting means 2b, 42 Safing switch 5,50 Inductance 6,51 Auxiliary switching means 7 Test pulse output means 8 Failure judgment means

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B60R 21/32 H01H 9/54-9/56 G01P 15/135 G01P 15/11 G01P 21/00

Claims (1)

(57) [Claims] (1) A drive circuit for a vehicle safety device. This drive circuit has a main switching means and a safing switch connected in series to the vehicle safety device. The safing switch is turned on by an inertial force at the time of a collision, and one end thereof is grounded. When both are on, the vehicle safety device operates. (B) acceleration detection means for detecting the deceleration of the vehicle. (C) Collision judging means for judging the presence or absence of a collision based on the deceleration signal from the acceleration detecting means, and outputting an ON command signal to the main switching means when it is determined that the collision is occurring. The control system for a vehicle safety device having the above configuration further includes the following configuration. (D) Inductance for generating high voltage. One end of this inductance is connected to the battery, and the other end is connected to the end of the safing switch opposite to the ground. (E) auxiliary switching means for controlling current supply to the inductance; (F) By outputting a test pulse to the auxiliary switching means and turning it on, a current is supplied to the inductance, and a counter electromotive voltage is generated in the inductance when the current supply corresponding to the end of the test pulse is stopped. Pulse output means. (G) When the back electromotive voltage of the inductance is applied to the safing switch, it is determined whether or not a small current due to discharge flows through the safing switch. Failure determination means for determining