JP3408931B2 - Detonator for side airbag - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition device for a side air bag which can reliably diagnose an ignition circuit without causing an explosive element to explode. 2. Description of the Related Art The importance of the role of an airbag system as an occupant restraint for protecting a vehicle occupant from an impact in a collision has been recognized. Vehicles equipped with both frontal airbags and side airbags to protect occupants are becoming widespread. In the case of a frontal airbag that buffers the impact of a frontal collision, the engine room functions as a cushion that absorbs the impact to some extent, so that the collision determination time required from the occurrence of the collision to the deployment of the airbag can have some allowance. In the case of a side airbag that protects an occupant from a side impact in which an impact may harm the occupant due to deformation of a door, etc., for example, in the case of a high-speed side impact, a collision determination is made within a very short time of about 5 ms. Therefore, it has been found that the collision determination algorithm also requires an operation considering an event specific to the side collision. However, both frontal airbags and side airbags operate on the same principle in that a squib called a squib is used as a deployment trigger for the airbag. Basically, an ignition circuit having substantially the same configuration has been adopted as an ignition circuit for supplying an ignition current to initiate ignition. [0003] A detonator 1 for a side airbag shown in FIG.
Is a detonating switching element Qu, which conducts in response to a deployment command from an arithmetic unit (not shown) that calculates an acceleration signal detected by the acceleration sensor and determines a threshold value to determine a collision.
Qd is connected to both ends of a detonating element 2 that is detonated when an ignition current is supplied to form an ignition circuit, and connected to a battery power source 3. The side airbag detonating device 1 shown in the present embodiment separately ignites and detonates the driver's side airbag and the passenger's side airbag, so that a pair of ignition circuits 4 and 5 are provided for each side airbag. And the parallel connection circuit of the ignition circuits 4 and 5 is connected to the battery power supply 3. That is, the ignition circuits 4 and 5
Each of the upstream switching elements Qu is connected to the battery power supply 3 via a reverse blocking diode D, and the downstream switching element Qd is grounded. [0004] The detonating switching elements Qu and Qd include:
FETs having different channel structures are used. In this case, a gate resistance R is used as the upstream switching element Qu.
A P-channel FET having g and a source-gate resistance Rsg is used, and an N-channel FET having a gate resistance Rg and a gate-source resistance Rgs is used as a downstream switching element Qd. Further, current limiting resistors Ru and Rd for bypassing the source and the drain are connected in parallel to the detonating switching elements Qu and Qd, and a safe diagnostic current less than the detonation level is always supplied to the detonating element 2. Is responsible for [0005] In addition, the upstream detonating switching element Q
u, the connection point of the diode D, the connection point of the upstream switching element Qu and the element 2, and the element 2
And the connection point between the switching element Qd on the downstream side and
When the diagnostic circuit 6 supplies a safe diagnostic current less than the ignition current to the detonating element 2, the voltages V1, V2 and V3 at the three connection points are checked. It is configured to check for the presence or absence of a circuit abnormality. However, at the time of diagnosis, of the pair of detonating switching elements Qu, Qd connected in series with the detonating element 2 to the battery power source 3, only one detonating switching element Qu or Qd is selectively made conductive, and Care has been taken to avoid an explosion caused by simultaneous energization of the switching elements Qu and Qd. [0006] The above-mentioned conventional side airbag detonating device 1 is used when the detonating element 2 is out of order,
When the ground short-circuit occurs between the detonating element 2 and the downstream switching element Qd, when the upstream switching element Qu is closed and a fault diagnosis is performed, a safe diagnostic current for the detonating element 2 can be obtained. There is a danger that an ignition current of several A flows and the detonating element 2 is exploded. For this reason, like a frontal airbag detonator, a mechanical G sensor as a safing sensor is interposed between the ignition circuits 4 and 5 and the battery power supply 3 or between the downstream switching prevention Qd and the ground to cause an explosion. Safety measures to prevent this were considered. However, in the case of a mechanical G sensor having a structure in which the movable part is displaced to close the reed switch, a response from the detection of deceleration to the generation of a collision detection signal is currently required for the side collision determination. 5ms
At present, there is almost no sensor capable of meeting such a high-speed demand, and there is no choice but to expect the emergence of a mechanical G sensor that can withstand practical use as a safing sensor. The present invention has been made to solve the above-mentioned problem, and uses an electronic switching element instead of a mechanical G sensor as a safing sensor so that an ignition circuit can be diagnosed without explosion of a detonating element. It is an object of the present invention to provide a side airbag detonating device. [0008] In order to achieve the above object, the present invention is directed to an explosion element which, when supplied with an ignition current exceeding an explosion level, causes ignition and explosion, serves as a deployment trigger for a side airbag. connected to the upstream side and the downstream side of the squib, and a pair of initiator switching element to conduct receiving inflation instruction, connected in parallel to each of the pair of initiator switching element, safe diagnosis less than the detonation level A current limiting resistor that constantly supplies a current, an explosion avoiding switching element that is connected between the upstream detonating switching element and the battery power supply and that conducts in response to the deployment command; A current limiting resistor that is connected in parallel and constantly supplies a safe diagnostic current less than the detonation level; A diagnostic circuit that issues a diagnostic command in place of the deployment command to the avoidance switching element to selectively conduct, and determines a threshold value of a voltage at a diagnostic location to diagnose the presence or absence of a circuit abnormality. It is. Further, the present invention is characterized in that the explosion avoiding switching element is formed of a transistor that conducts with at least one of the pair of detonating switching elements upon receiving a deployment command having a reverse polarity. Things. An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a schematic circuit configuration diagram showing an embodiment of the side airbag detonating device of the present invention. In FIG. 1, a side airbag detonating device 11 is shown.
The configuration is such that a switching element Q for avoiding an explosion is interposed between the battery power supply 3 and a parallel connection circuit of a pair of ignition circuits 4 and 5 provided on the driver's seat side and the passenger's seat side. The explosion avoiding switching element Q uses a P-channel FET having a gate resistance Rg and a source-gate resistance Rsg, and a current limiting resistance R bypassing the source and drain is connected in parallel. Safe diagnostic current less than the detonation level
A current of about mA is always supplied. As in the prior art, the diagnostic circuit 6 comprises a voltage V1 at the connection point between the upstream detonating switching element Qu and the diode D, and a voltage V2 at the connection point between the upstream detonation switching element Qu and the detonating element 2. Then, the voltage V3 at the connection point between the detonating element 2 and the downstream switching element Qd is detected to diagnose the abnormality. In the diagnostic circuit 6, the voltages V1, V
2, a voltage dividing circuit for dividing V3, and a comparator (comparator) or a window comparator (window comparator) for discriminating the output of the voltage dividing circuit or its AD conversion value as a threshold value, and operating an ignition key Immediately after the start of the engine, the switching elements Q, Qu, and Qd are sequentially turned on selectively in accordance with a series of diagnosis programs to execute diagnosis. In the diagnosis, a safe diagnostic current of, for example, about several tens mA, which is lower than the detonation level, is supplied to the detonating element 2, and at that time, the voltages V1, V2, and V3 at the connection points are checked. Is checked. The diagnostic current flowing through the detonating element 2 is suppressed to a safe value that does not cause the detonating element 2 to ignite. Therefore, a potential difference of several tens of mV is generated between both ends of the detonating element 2 having a resistance of several Ω. Therefore, the potential difference V2-
By determining the threshold value of V3 in the diagnostic circuit 6, it is possible to diagnose whether the firing element 2 is short-circuited or open. Further, when the switching element Q for explosion avoidance is turned on, if it is determined that the voltages V1 and V2 are the same voltage, it is detected that the switching element Qu for upstream detonation is short-circuited, and the one-sided voltage is detected. If it is determined that V3 is at the ground level, it is detected that the downstream switching element Qd is short-circuited. Also,
When a voltage difference substantially equal to the potential difference between both ends of the current limiting resistor Ru is recognized between the voltages V1 and V2 when the upstream switching element Qu is turned on, it is detected that the switching element Qu is open. Is done. When such a circuit abnormality such as a short circuit or an open circuit is detected, the diagnosis circuit 6 issues an abnormality detection signal, and the abnormality is notified to a console panel or the like. By the way, at the time of the above-mentioned diagnosis, if the squib 2
Suppose that the upstream-side detonation switching element Qu is turned on without noticing that the cold side of the switch is ground short-circuited. In this case, in the case of the conventional side airbag detonating device 1 having no explosive avoidance switching element Q, an ignition current of several A flows through the detonating element 2 together with the conduction of the upstream detonating switching element Qu. As described above, the explosion of the detonating element 2 could not be avoided. However, in the case of the side airbag detonating device 11 in which the explosive avoiding switching element Q is provided between the upstream detonating switching element Qu and the battery power supply 3, the current connected in parallel to the explosive avoiding switching element Q Since the limiting resistor R limits the current, the squib 2
The ignition current exceeding the safe value does not flow through the switch, and unnecessary explosion can be avoided. [0015] Further, the detonating device 1 for a side airbag.
1 indicates that a pair of the detonating switching elements Q
As compared with the conventional detonator 1 in which u and Qd are simply connected to both ends of the detonating element 2, the switching element Q for preventing explosion that functions as a safing sensor is connected in series to the detonating element 2 together with a pair of detonating switching elements Qu and Qd. Due to the connection, the explosion avoidance ability due to runaway of the arithmetic unit is high, and the explosion avoidance switching element Q has a sufficient prompt conduction capability even for a collision judgment time of about 5 ms required for a high-speed side collision. Therefore, it is most suitable as a safing sensor for a side airbag. Further, a pair of switching elements Q for detonating
FETs having different channel structures are used as u and Qd,
In addition, since the switching element Q for preventing explosion uses an FET having a channel structure different from that of the switching element Qd for detonating on the downstream side, for example, noise generated due to electromagnetic interference even though no deployment command is issued is caused. Even if one of the detonating switching elements Q, Qu, or Qd conducts, the other detonating switching element Qd or Q, Qu remains non-conducting. The inconvenience of inadvertent simultaneous conduction can be eliminated. Therefore, a remarkable effect can be exhibited as a countermeasure against violence particularly in a place where electromagnetic interference is likely to occur, such as an engine room. In the above embodiment, the switching elements Q, Qu, Qd are constituted by FETs. However, these switching elements Q, Qu, Qd may be constituted by other transistors. As described above, according to the present invention,
Ignition current exceeding the detonation level is applied and ignition is detonated,
Upstream and downstream of the squib to be deployed triggering of the side airbag, as well as connecting a pair of initiator switching element to conduct receiving inflation instruction, the pair of detonators
Each current limiting resistor for energizing a safe diagnosis current of less than initiation level at all times of use switching elements connected in parallel, further between the detonator switching element and a battery power source on the upstream side, to conduct receiving inflation instruction Connect a switching element for explosion avoidance and connect a current limiting resistor that always supplies a safe diagnostic current less than the explosion level to this switching element for explosion avoidance in parallel. A diagnostic command in place of the deployment command is issued to the switching element for conduction, and the device is selectively made conductive, and the voltage at the diagnostic location is determined as a threshold to diagnose the presence or absence of a circuit abnormality. A conventional detonation device that simply connects a pair of detonating switching elements to both ends of the detonating element, even if the device causes a runaway In comparison, by the amount of explosion avoid switching element which functions as a safing sensor are connected in series squib with a pair of initiator switching element, outbursts evasion due to runaway of the arithmetic unit is high,
In addition, the switching device for avoiding an explosion has a sufficient responsive conduction capability even for a collision determination time of about 5 ms required for a high-speed side collision, so it is optimal for avoiding an explosion for a side airbag, and is diagnosed from a diagnostic circuit. When a command is issued to make the upstream detonating switching element conductive, even if the downstream detonating switching element and the detonating element are already short-circuited to the ground, the Since the current limiting resistors connected in parallel suppress the diagnostic current to a safe level that is lower than the detonation level, there is an excellent effect that it is possible to avoid explosion. Further, according to the present invention, since the switching element for avoiding explosion is constituted by a transistor which is conductive to at least one of the pair of switching elements for detonation upon receiving a deployment command having a reverse polarity, Even if one of the switching elements is turned on due to noise caused by electromagnetic interference, etc., despite the fact that the switching element is not emitted, the remaining switching elements remain non-conductive, so three switching elements are careless In addition, it is possible to eliminate the inconvenience of simultaneous conduction, and to provide a remarkable effect particularly as a countermeasure against violence in a place where electromagnetic interference is likely to occur, such as an engine room.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic circuit configuration diagram showing an embodiment of a side airbag detonating device of the present invention. FIG. 2 is a schematic circuit diagram showing an example of a conventional side airbag detonator. [Description of Signs] 11 Explosive device 2 for side airbag 2 Explosive element 3 Battery power supply 4, 5 Ignition circuit 6 Diagnosis circuit Q Switching device Qu for avoiding explosive switching device Qd for upstream explosion Switching device D for downstream explosion R, Ru, Rd Current limiting resistance Rg Gate resistance Rsg Source-gate resistance Rgs Gate-source resistance

Claims (1)

(57) [Claims] [Claim 1] An ignition element which is supplied with an ignition current exceeding an explosion level, initiates ignition, and serves as a deployment trigger of a side airbag, and an upstream and downstream side of the explosion element. A pair of detonation switching elements that are connected and conduct when receiving the deployment command, and a current limiting resistor that is connected in parallel to each of the pair of detonation switching elements and constantly supplies a safe diagnostic current less than the detonation level. An explosion avoiding switching element that is connected between the upstream detonating switching element and a battery power supply and that is conductive when receiving the deployment command, and that is connected in parallel to the explosion avoiding switching element and satisfies the detonation level. A current limiting resistor that constantly supplies a safe diagnostic current, and the pair of detonation switching element and explosion avoidance switching element are replaced with the deployment command. Issue a diagnostic command alternatively into conduction, the voltage of the diagnostic portion and the threshold value determination; and a diagnostic circuit for diagnosing the presence or absence of a circuit abnormality, the outbursts avoid switching element, for the pair of detonation
The polarity of at least one of the switching elements is mutually
It consists of a transistor that conducts in response to a reverse deployment command.
A detonator for a side airbag.