JPH0672280A - Ignition control device of safety device for vehicle - Google Patents

Abstract

PURPOSE:To determine the current feeding time to a squib in consideration a chattering of a mechanical switch. CONSTITUTION:When a CPU 9 recognizes a collision depending on the input of a G sensor 10, FETs 3 and 4 are turned ON. When a mechanical switch 5 is turned ON, and the FETs 3 and 4 are operated ON, a current is fed to a squib 2 so as to operate an air bag. When the current was fed to the squib 2 in a scheduled time, the FETs are turned OFF by deciding that a sufficient energy has been given to ignite the squib 2. The measuring value of the time of feeding the current to the squib 2, that is the ON time, is cleared by the interruption by an interrupt circuit 11. This interruption is generated when the mechanical switch 5 is turned ON. As a result, the FETs can be turned OFF depending on the continued current feeding time, except for a chattering time of the mechanical switch.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition control device for a safety device for a vehicle, and more particularly to an ignition control device for a safety device for a vehicle capable of controlling the on-time of a safety device ignition circuit.

[0002]

2. Description of the Related Art There is known a system in which an acceleration of a vehicle or the like is detected based on an output signal of an acceleration sensor, a collision is determined from the detected signal, and a safety device is operated. In this system, the ignition means (squib) is ignited based on the collision determination, the airbag is inflated rapidly, and the pretensioning device for the seat belt is operated.

For example, the device described in Japanese Patent Laid-Open No. 3-208749 is constructed as follows. In FIG. 7, when the evaluation circuit 10 determines that a collision has occurred, the evaluation circuit 10 outputs a trigger signal to the ignition circuit 20. The trigger signal is input to the one-shot circuit 21, which is a component of the ignition circuit 20, to turn on the field effect transistor 22 and ignite the squib 30 connected to the field effect transistor 22. When the squib 30 is ignited, the airbag 40 is inflated.

By the way, in the above-mentioned device, it is necessary to construct an extremely safe system in which the airbag 40 does not inflate when it is unnecessary or does not inflate when it is needed. . Therefore, in order to sufficiently bring out the performance of the semiconductor switch (field effect transistor 22) which is generally considered to be weak against electric noise, the mechanical switch 5 may be connected in series with the semiconductor switch. That is, the mechanical switch 5 and the semiconductor switch 2
The current is supplied to the squib 30 only when both of the two operate.

The mechanical switch 5 has, for example, a ball-shaped or roller-shaped moving body and an opened contact, and closes the opening contact when the moving body is deviated due to acceleration. The configured one is used. An example of a mechanical switch configured to close a contact by a ball is shown in Japanese Patent Application No. 3-339466.

[0006]

The above-mentioned conventional device has the following problems. In order to ignite the squib, it is necessary to turn on the field effect transistor for a predetermined time to supply sufficient electrical energy to the squib. That is, the turn-on time of the field effect transistor is set so that the energy determined by the current and the energization time determined by the resistance of the squib and the circuit configuration is sufficient to ignite the squib.

However, it is generally known that a mechanical switch, that is, a mechanical operation type switch, has a so-called chattering phenomenon in which a contact repeatedly turns on and off for a certain time during its operation. Since the current flows through the squib only when both the mechanical switch and the semiconductor switch are in the on-operation, the chattering does not always supply the current to the squib for the duration of the on-operation of the semiconductor switch. Not necessarily. That is, no current is supplied to the squib when the contacts are opened by chattering. Moreover, it is not possible to judge the time when this current continues to flow to the squib.

Therefore, conventionally, the turn-on time is set with a sufficient margin, so that it tends to be unnecessarily long. If the turn-on time, that is, the squib energization time is long, circuit components having durability against temperature rise are required, and it is necessary to increase the capacity of a capacitor provided as an auxiliary power supply. As a result, the size of the device becomes large, and more expensive components than necessary must be used.

The object of the present invention is to solve the above problems,
An object of the present invention is to provide an ignition control device for a vehicle safety device that can set a minimum necessary squib ignition time while considering chattering of a mechanical switch.

[0010]

SUMMARY OF THE INVENTION To solve the above problems and to achieve the object, the present invention comprises means for detecting the on / off state of a mechanical switch, and means for measuring the on time of the mechanical switch. And a means for clearing an on-time of the mechanical switch in response to detection of an on-state of the mechanical switch, and means for detecting an on-operation of a semiconductor switch connected in series with the mechanical switch, It is characterized in that the timing for turning off the semiconductor switch is determined by a parameter including at least the on time of the mechanical switch when the switch is on.

[0011]

According to the present invention having the above characteristics, the contact of the mechanical switch is continuously closed while the semiconductor switch is on, that is, the mechanical switch and the semiconductor switch are connected in series. The continuous supply time of current to the squib is detected. Then, the semiconductor switch can be turned off according to the parameter based on the continuous supply time of the current.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. FIG. 1 is a diagram showing a configuration of an ignition control device according to an embodiment of the present invention. In the figure, the drive circuit 1 is provided with an activation element or squib 2 for activating a safety device such as an airbag (not shown). In the event of a collision,
A mechanical switch and a semiconductor switch, which will be described later, operate to supply a current to the squib 2, and when the squib 2 ignites, the safety device is activated.

A P channel FE is provided at one end of the squib 2.
The source of T3 is connected and the N channel FET4 is connected to the other end.
The drain of is connected. These two FETs 3, 4
Is a semiconductor switch for supplying a current to the squib 2. A mechanical switch 5 is connected between the drain of the FET 3 and the power supply.

The resistor 6 connected in parallel to the mechanical switch 5 is for limiting the current flowing when the squib 2 is tested. Further, the drive circuit 1 is provided with a capacitor 7 as an auxiliary power source for storing electric power. One of the outputs of the CPU 9 is inverted by the inverter 8 and supplied to the gate of the FET 3 while the other is inverted by the FET 4
Is supplied to the gate.

The FETs 3 and 4 which are semiconductor switches detect the acceleration and convert it into an electric signal.
It operates based on the output signal of. For example, a piezoresistive element can be used as the G sensor 10. G sensor 10
Is supplied to the CPU 9 and compared with a comparison value preset in the CPU 9. When a collision determination is made based on the comparison result, the CPU 9 outputs a collision determination signal. This collision determination signal is supplied to the gates of the FETs 3 and 4, and as a result, the FETs 3 and 4 are turned on.

When the contacts of the mechanical switch 5 are closed and the FETs 3 and 4 are turned on, a current is supplied to the squib 2 from a power source or an auxiliary power source, that is, a capacitor 7.

In the present embodiment, in the above configuration, the current supply time, that is, the on-time of the collision determination signal output from the CPU 9 is controlled. For this control, the potentials Vs1 and Vs2 at both ends of the squib 2 are taken into the CPU 9.

The cold side of the mechanical switch 5, that is, the side opposite to the power source, is connected to the comparison signal input terminal of the comparator 11, and the reference potential input terminal of the comparator 11 is supplied with a reference potential for comparison. Power 12
Are connected. This comparator 11 constitutes an interrupt circuit, and its output is the interrupt terminal IN of the CPU 9.
Connected to T. The on-time control of the collision determination signal will be described in detail below.

First, the operation timings of the mechanical switch and the semiconductor switch will be described with reference to FIG. FIG. 3A shows the interrupt circuit input voltage input to the comparison signal input terminal of the interrupt circuit, that is, the comparator 11.
This voltage indicates a high level voltage V1 when the contact is closed by the mechanical switch 5, and indicates a low level voltage V0 when the contact is open. The figure shows that the voltage changes to high and low due to chattering and stabilizes to the high level voltage V1 after the chattering ends.

FIG. 3B shows the output of the result of comparing the input voltage of the interrupt circuit with the reference potential, that is, the output of the interrupt circuit. When the interrupt circuit input voltage is higher than the reference potential, the interrupt circuit output is high "H", and when the interrupt circuit input voltage is lower than the reference potential, the interrupt circuit output is low "L". The rising edge of the output of the interrupt circuit causes (d) in FIG.
The "interrupt by the interrupt circuit" shown in is generated.

Further, FIG. 7C shows the interrupt timing by the timer at regular intervals. Collision determination is performed at this timer interruption. FIG. 6E shows the operation of the semiconductor switch.

As shown in FIG. 2, when both the mechanical switch and the semiconductor switch are turned on, the squib is energized. In this embodiment, the energization time is measured, and the timing for turning off the semiconductor switch is determined based on this energization time and the current supplied to the squib at that time. However, when chattering was performed, the energization time measured up to that point was reset and not considered as the actual energization time for operating the squib.

Next, the operation of this embodiment will be described with reference to the flow chart. First, in the timer interrupt of FIG. 3, a collision determination process is performed in step S1. In this collision determination process, for example, it is determined whether the integrated value of the output waveform of the G sensor 10 has exceeded a predetermined value.

In step S2, it is determined whether or not a collision has occurred based on the result of the collision determination process. If the determination in step S2 is affirmative, the process proceeds to step S3 to issue an ON operation command to the semiconductor switch. Specifically, FET3,
A predetermined voltage is applied to the gate of No. 4.

At step S4, the ON time is measured, that is, the continuous energization time for the squib 2 is measured. The details of this will be described later with reference to FIG. In step S5, the current supplied to the squib is calculated. This calculation is based on the potential difference (Vs1−Vs2) across the squib 2 and the resistance value of the squib 2.

In step S6, it is determined whether or not the ON operation command to the semiconductor switch is stopped. This judgment is made based on whether or not the product of the on-time measurement result and the supply current has reached a predetermined value. Note that this determination is not limited to this, and may be performed based on whether or not the on-time has reached the scheduled value, or the product of the amount of power supplied to the squib 2 and the on-time has reached the scheduled value. It may be done depending on whether or not. In short, it may be determined by whether or not a predetermined parameter obtained based on the continuous energization time to the squib 2 has reached a predetermined value.

When it is determined that the ON operation command for the semiconductor switch is stopped, the process proceeds to step S7, and the ON operation command is stopped. That is, the semiconductor switch is turned off.

Next, details of the on-time measurement will be described with reference to the flowchart of FIG. In the figure, in step S10, it is determined whether the semiconductor switch is on. If the semiconductor switch is off, the process proceeds to step S14 and the parameter t indicating the on time is cleared.

On the other hand, if the semiconductor switch is on, the process proceeds to step S11 to determine whether the on flag is "1". This on-flag is set by an interrupt by the interrupt circuit, and if this on-flag is set (= 1), it is determined that there is a rapid deceleration such that the mechanical switch 5 is turned on.

If the ON flag is not "1", the process proceeds to step S14. If the ON flag is "1", the process proceeds to step S12, and it is determined whether or not the mechanical switch 5 is ON. Whether or not the mechanical switch 5 is turned on can be determined by monitoring the interrupt circuit input voltage connected to the comparison signal input terminal of the interrupt circuit, that is, the comparator 11.

If the mechanical switch 5 is on, step S1
3, the value t of the free-run counter for on-time measurement
Read _n, and the value t of the free-run counter at the time of the previous processing
_A new on-time t is calculated by adding the difference from _n-1 to the on-time t at the time of the previous measurement, and stored in a predetermined storage means.

Next, the interrupt by the interrupt circuit will be described with reference to the flowchart of FIG. In FIG.
In step S20, the free run counter is reset. This reset resets the on time when chattering occurs. In step S21, the ON flag is set (“1” is set).

As described above, in this embodiment, when both the semiconductor switch and the mechanical switch are on, the counter is started to measure the on-time. Since the on-time t is reset when the interrupt circuit interrupts, the continuous on-time, that is, the time when the current is continuously supplied to the squib without chattering can be measured.

Next, the main functions of this embodiment will be described with reference to the block diagram of FIG. In the figure, the collision determination unit 1
3 determines the collision based on the output signal of the G sensor 10, and if the collision is recognized, the semiconductor switch-on command unit 1
4 outputs a collision detection signal. The semiconductor switch ON command unit 14 outputs an ON operation command to the semiconductor switch 15 in response to the collision detection signal.

The semiconductor switch-on detector 16 detects the on / off state of the semiconductor switch 15 and outputs a detection signal when it is on. Similarly, the mechanical switch ON detection unit 17 detects the ON / OFF state of the mechanical switch 5 and outputs a detection signal when the mechanical switch 5 is ON. Detection signals from the semiconductor switch-on detector 16 and the mechanical switch-on detector 17 are input to the timer means 18. When the two detection signals are supplied, the timer means 18 starts measuring time. This timer means can consist of a free-run counter,
The counter value is incremented by the clock signal CK. When the chattering detector 19 detects chattering of the mechanical switch, the timer means 18 is reset by the detection signal.

The counter value of the timer means 18 is supplied to the semiconductor switch-on command judging section 20 and it is judged whether or not the counter value has reached a predetermined value. The semiconductor switch-on command determination unit 20 outputs an on-command stop signal if the counter value has reached the predetermined value. This ON command stop signal is supplied to the semiconductor switch ON command unit 14, and the supply of the ON operation command to the semiconductor switch 15 is stopped.

The semiconductor switch-on command determining section 20 is not limited to determining whether to turn off the semiconductor switch based only on the counter value from the timer means 18. As described above, the electric current supplied to the squib and the electric power supplied can be used as a judgment factor.

In the present embodiment, the example in which the FET is used as the semiconductor switch has been described, but this is not limited to the FET, and another transistor may be used.

[0039]

As is apparent from the above description, according to the present invention, an unnecessarily long time is set as the squib ignition time even when using a mechanical switch in which chattering must be taken into consideration. You can avoid that.

Therefore, the squib can be ignited by supplying the electric current only for the minimum necessary time, and the components for forming the squib starting circuit are those whose temperature specifications are suppressed to the minimum necessary. become able to.

As a result, it is not necessary to provide a heat dissipation plate for preventing a temperature rise or to use a large component, and the entire control device can be downsized and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a hardware configuration of an ignition control device.

FIG. 2 is a timing chart showing the operation of the ignition control device.

FIG. 3 is a flowchart showing a timer interrupt operation.

FIG. 4 is a flowchart showing an on-time measuring operation.

FIG. 5 is a flowchart showing an interrupt operation by an interrupt circuit.

FIG. 6 is a block diagram showing a main function of the ignition control device.

FIG. 7 is a block diagram showing a configuration of a conventional safety device.

[Explanation of symbols]

2 ... Squib, 3, 4 ... FET, 5 ... Mechanical switch, 7 ... Auxiliary power supply, 1 ... Interrupt circuit

Front Page Continuation (72) Inventor Yutaka Yoshima 1-4-1 Chuo 1-4-1 Wako-shi, Saitama Stock Research Institute Honda Technical Research Institute

Claims (2)

[Claims] 1. An ignition system for a vehicle safety device configured to supply an ignition current to a squib by turning on a semiconductor switch and a mechanical switch that is connected in series to the semiconductor switch and that operates by acceleration. In the control device, means for detecting ON / OFF state of the mechanical switch, means for measuring ON time of the mechanical switch, and ON of the measured mechanical switch in response to the ON state detection signal of the mechanical switch. Means for clearing time, means for detecting an ON operation of the semiconductor switch, and a semiconductor switch when a parameter including at least an ON time of the mechanical switch when the semiconductor switch is in an ON state reaches a predetermined value And an ignition control device for a vehicle safety device. . 2. The ignition control device for a vehicle safety device according to claim 1, wherein the parameters are an on-time of the mechanical switch and a current supplied to the squib.