JP2508967Y2 - Data input circuit - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a data input circuit capable of reliably diagnosing ignition circuits parallel to each other.

[Prior Art] An airbag system that inflates and protects an occupant in the event of a collision connects a detonator element called a squib to an impact sensor that operates by sensing an impact, and the squib is ignited when the impact sensor operates. It is configured such that an electric current is applied to cause ignition and detonation, and the airbag is inflated directly or indirectly to be deployed. Such an airbag system
In order to ensure reliable operation in the event of a collision,
It is desirable to monitor or diagnose whether or not the ignition circuit is broken or short-circuited regularly or at room temperature.

The data input circuit shown in FIG. 2 is a circuit for inputting data for in-vehicle airbag system diagnosis.
Specifically, the first ignition circuit 11 including the first impact detection sensor 13 and the second ignition circuit 21 including the second impact detection sensor 23 are connected in parallel to the power supply 1, and the third It has a circuit configuration in which it is commonly grounded via the impact detection sensor 31.

In the case of the present example, the first ignition circuit 11 is composed of a first sneak-in prevention diode 12, a parallel connection circuit of a contact 13a that senses a shock on the driver's side and is closed, and a diagnostic resistor 13b for conducting a diagnostic current. The first impact detection sensor 13 and the squib 14 which is ignited by a predetermined ignition current are connected in series. The second ignition circuit 21 includes a second sneak-in prevention diode 22, a contact 23a that senses an impact on the passenger side and closes, and a parallel connection circuit of a diagnostic resistor 23b for conducting a diagnostic current. The detection sensor 23 and a squib 24 which is ignited by a predetermined ignition current to explode and ignite are connected in series, and basically have the same circuit configuration as the first ignition circuit 21. The third impact detection sensor 31 includes a contact 31a that closes by sensing an impact outside the vehicle compartment and a diagnostic resistor 3 for conducting a diagnostic current.
It consists of a parallel connection circuit of 1b.

When each impact detection sensor 13, 23, 31 detects the additional speed associated with the collision and the contacts 13a, 23a, 31a are closed, the squibs 14, 24 are energized with an ignition current that brings the required ignition energy, and the squib 14, The airbag is activated with the ignition and detonation of 24. Even if the above-mentioned emergency does not occur, the diagnostic current, which is less than the ignition current, is always applied to the squibs 14 and 24 for the purpose of diagnosis, and the voltage difference generated in the circuit is detected by the comparator based on this diagnostic current. It is configured to monitor at 41 and detect the presence or absence of a circuit abnormality.

Specifically, since the squibs 14 and 24 are connected at the connection point B on the downstream side and commonly connected to the third impact detection sensor 31, this connection point B is used as a comparison input terminal (inversion input terminal) of the comparator 41. ), While the connection point (reference voltage input point 25) between the second sneak-in prevention diode 22 and the second impact detection sensor 23 is connected to the reference input terminal (non-inverting input terminal) of the comparator 41. . When there is no abnormality in the first ignition circuit 11 and the second ignition circuit 21, the voltage at the reference voltage input point 25 is higher than the voltage at the connection point B, in which case the output of the comparator 41 is at high level. . Usually diagnostic resistance
A diagnostic current of several mA is constantly applied to 13b and 23b, and there is a voltage drop of the value obtained by multiplying the diagnostic current by the series combined resistance of diagnostic resistor 23b and squib 24, so the reference input voltage of comparator 41 is compared. It exceeds the input voltage and the comparator 41
Output becomes high level. On the other hand, for example, when an abnormality such as a disconnection or a short circuit occurs between the reference voltage input point 25 and the connection point B, the voltage relationship between the reference voltage input point 25 and the connection point B is reversed, and the comparison input voltage becomes As a result of exceeding the reference input voltage, the output of the comparator 41 is inverted from the high level to the low level, and the abnormality is detected.

[Problems to be Solved by the Invention] In the conventional data input circuit described above, the same standard diode is used for the first sneak-proof diode 12 and the second sneak-proof diode 22, but the voltage may vary due to variations between products. There may be a difference in the drop characteristics, the voltage drop in the second sneak prevention diode 22 is larger than the voltage drop in the first sneak prevention diode 12, and the difference may reach a considerable value. In such a case, the first ignition circuit 11
There is a problem that the voltage at the connection point B is raised due to the small voltage drop at the line B, and the comparator 41 may output a low-level abnormality detection signal although the ignition circuits 11 and 21 have no abnormality. there were.

The present invention has been made in view of the above circumstances, and data that prevents erroneous judgment of a comparator even if there are variations in a plurality of circuits that are originally connected in parallel and should have the same characteristics and have the same characteristics. An object is to provide an input circuit.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a shock-sensing sensor including a parallel connection circuit of a contact that senses and closes a shock and a diagnostic resistor for conducting a diagnostic current. A plurality of ignition circuits that are connected in series to a squib that is ignited by an ignition current and ignites to explode, and that are connected in parallel to a power source through a sneak-off prevention diode, and a common ground circuit that grounds the plurality of ignition circuits in common.
A comparator having a reference input terminal commonly connected to the cathode of each of the sneak-through prevention diodes via a resistor and a comparator having a comparison input terminal connected to a connection point of each of the ignition circuits and the common ground circuit. It is a thing.

[Operation] According to the present invention, the impact detection sensor is connected in series to the squib, and a plurality of ignition circuits connected in parallel to the power source through the sneak-in prevention diode are connected to the common ground via the common ground circuit and the comparator reference. By connecting the input terminal to the cathode of each sneak prevention diode via a resistor in common, and connecting the comparator's comparison input terminal to the connection point between each ignition circuit and the common ground circuit, the comparator detects whether there is an abnormality in the ignition circuit. Can be monitored more accurately.

[Embodiment] An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a circuit diagram showing an embodiment of the data input circuit of the present invention.

The data input circuit is basically one that is connected in parallel to the first and second ignition circuits between the power supply 1 and the third impact detection sensor 31, which is a common ground circuit, and is used to detonate the airbag. The basic part directly involved in ignition has the same circuit configuration as the conventional one. Further, the connection point B of the squibs 14, 24 and the third impact detection sensor 31 is directly connected to the comparison input terminal of the comparator 41 without a resistor or the like.

However, the point that is greatly different from the conventional one is that the first branch circuit 16 is connected to the first reference voltage input point 15 between the first wraparound prevention diode 12 and the first impact detection sensor 13, and the second sneak path A second branch circuit 26 is connected to a second reference voltage input point 25 between the prevention diode 22 and the second impact detection sensor 23, and both branch circuits 16 and 26 are respectively connected to comparators via branch resistors 16a and 26a. Commonly connected to 41 reference input terminals.

Here, the resistance values of the branch resistors 16a and 26a are set to R1 and R2, respectively.
The cathode voltage of the sneak-in prevention diode 12 is set to E1, the second
Let the cathode voltage of the sneak-in prevention diode 22 be E2,
When the voltage applied to the comparison input terminal of the comparator 41 is E, it is expressed by E = (R2E1 + R1E2) / (R1 + R2) from the principle of internal division. In the embodiment, branch resistors 16a and 26a having the same resistance values R1 and R2 are used. Since R1 = R2, E = (E1 + E2) / 2.

That is, the comparison input voltage E of the comparator 41 is
The cathode voltage E1, of the second sneak-proof diode 12,22
It can be seen that the arithmetic mean is E2. Therefore, when there is no abnormality in the first ignition circuit 11 and the second ignition circuit 21, the reference input voltage of the comparator 41 is always higher than the comparison input voltage, and the output of the comparator 41 is high level.

In addition, the first and second sneak-proof diodes 12, 22
Even if the voltage drop characteristics at the
A point A indicating the average voltage E of the cathode voltages E1 and E2 of 12,22,
Impact sensor 13 and squib 1 compared to cathode voltages E1 and E2
At the voltage drop at 4 or at the connection point B which is lower by the voltage drop at the shock sensor 23 and the squib 24, there is a strict voltage difference, so that the comparator 41 outputs a low level signal even though there is no abnormal point. There is no output.

Also, if there is an abnormality such as a disconnection or a short circuit between the first reference voltage input point 15 or the second reference voltage input point 25 and the point B,
The relationship between the voltage E at point A and the voltage at point B is reversed and the comparator
A low-level signal is output from 41, and an error is displayed on the indicator lamp.

In the above embodiment, the data input circuit constituted by connecting the first and second two series of ignition circuits 11 and 21 in parallel between the power supply 1 and the impact detection sensor 31 is taken as an example. It is also possible to connect ignition circuits of a series or more in parallel to the power source 1 and commonly connect the cathodes of the sneak prevention diodes of the ignition circuits to the reference input terminal of the comparator.

[Effects of the Invention] As described above, according to the present invention, the impact detection sensor is connected in series to the squib, and a plurality of ignition circuits connected in parallel to the power source via the sneak prevention diode are connected via the common ground circuit. In addition to common grounding, the reference input terminal of the comparator is commonly connected to the cathode of each sneak prevention diode via a resistor, and the comparison input terminal of the comparator is connected to the connection point of each ignition circuit and the common ground circuit. Therefore, the cathode voltage of the sneak prevention diode in each ignition circuit can be weighted and added according to the resistance ratio of the resistor that passes to the comparator, and can be used as the reference input voltage of the comparator. However, if there is no abnormality in each ignition circuit, erroneous output of the comparator can be surely prevented. It has an excellent effect such as that

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a data input circuit of the present invention, and FIG. 2 is a circuit diagram showing an example of a conventional data input circuit. (Explanation of the symbols in the drawings showing the main parts) 1 …… Power supply 11,12 …… Ignition circuit 12,22 …… Diversion prevention diode 13,23 …… Impact detection sensor 14,24 …… Squib 15,25 …… Reference Voltage input point 16,26 …… Branch circuit 16a, 26a …… Resistance 31 …… Impact sensor 41 …… Comparator B …… Connection point

Claims (1)

(57) [Scope of utility model registration request] 1. A shock detection sensor comprising a parallel connection circuit of a contact for detecting a shock and closing and a diagnostic resistor for energizing a diagnostic current is connected in series to a squib which is ignited by a predetermined ignition current and wraps around. A plurality of ignition circuits connected in parallel to the power supply via the prevention diode, a common ground circuit for common grounding the plurality of ignition circuits, a reference input terminal commonly connected to the cathode of each of the sneak prevention diodes via a resistor, and A data input circuit comprising: a comparator having a comparison input terminal connected to a connection point of each of the ignition circuits and the common ground circuit.