JP3235657B2 - Occupant detection system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an occupant detection system and an occupant detection method and, more particularly, to deploying an airbag of an airbag device in accordance with the occupant's seating status in a passenger seat of an automobile having the airbag device. The present invention relates to an improvement in an occupant detection system and an occupant detection method that can be set to a state or an undeployable state.

[0002]

2. Description of the Related Art The applicant of the present invention has previously proposed an occupant detection system in which antenna electrodes are arranged on a sheet and an electric field generated by the antenna electrodes is disturbed. The basic principle of the occupant detection system will be described with reference to FIG. First, as shown in FIG. 2A, when a high-frequency low voltage from the oscillation circuit OSC is applied to the antenna electrode E, a weak electric field is generated around the antenna electrode E. The current I flows. In this state, if an object OB is present near the antenna electrode E as shown in FIG.
It flows different currents I ₁ and.

[0003] Therefore, depending on whether the object OB is on or off the vehicle seat, the antenna electrode E
A change occurs in the current flowing to the side of the vehicle, and by utilizing this phenomenon, it is possible to detect the occupant's seating state on the seat and the like. In addition, an object (occupant) O
When B is riding, the current flowing toward the antenna electrode E increases, and when the object OB is not riding on the sheet, the current flowing toward the antenna electrode E decreases.

A specific example of an occupant detection system utilizing this principle will be described with reference to FIGS. FIG. 8 shows a passenger seat (or driver seat) sheet.
1 is mainly composed of a seating portion 1a and a backrest portion 1b. The seating portion 1a includes, for example, a seat frame 3 fixed to a base 2 which can be slid forward and backward, a cushion material disposed on the upper portion of the sheet frame 3, and an exterior material covering the cushion material. It is composed of This seating part 1
For example, as shown in FIG. 9, an insulating base member 5 and a plurality of antenna electrodes 4a to 4d spaced apart from the base member 5 are provided between the cushion member and the exterior member.
And an antenna electrode 4 composed of lead wires (6) 6a to 6d derived from the antenna electrodes 4a to 4d. In particular, the antenna electrodes 4a to 4d
Is made of a conductive cloth in consideration of, for example, the occupant's comfort, but a thread-like metal wire or a conductive fiber is woven into a sheet cloth surface, or a conductive paint is applied to the cloth surface. Or a metal plate having a small thickness and flexibility can be arranged.

[0005] A control unit 10 is disposed in or near the sheet frame 3 of the sheet 1, and the control unit 10 includes a plurality of switching means 11a to 11a as shown in FIG. Switching circuit 1 having 11d
1, electric field generating means 12 for generating a weak electric field around the plurality of antenna electrodes 4a to 4d, and switching means 11 in switching circuit 11
Connectors (or terminals) connected to the output sides of a to 11d
13a to 13d and the switching circuit 1
1, antenna electrode 4a via connectors 13a to 13d
A current detection circuit 19 for detecting a current flowing through
A control circuit 16 including a PU, an external memory (for example, an EEPROM) and the like, and a connector (or terminal) 17 disposed in the housing and connected to a battery power supply (not shown)
And a power supply circuit 18 connected to the connector 17 and generating a Vcc power supply.

In this control unit 10, the selective switching of the switching means 11a to 11d in the switching circuit 11 is performed based on the signal from the control circuit 16, whereby the antenna electrodes 4a to 4d are appropriately connected to the high frequency and low frequency. A voltage is applied. Further, the electric field generating means 12 is configured to generate a high frequency low voltage having a frequency of about 120 KHz and a voltage of about 5 V, for example. The current detection circuit 19 includes, for example, a resistor connected in series to a transmission system circuit,
It comprises an amplifier such as a differential amplifier for amplifying the terminal voltage of the resistor, and its output side is an AC-DC conversion circuit,
It is connected to the control circuit 16 via an amplifier or the like. Further, a DC Vcc power supply (for example, 5 V) generated by the power supply circuit 18 is a
It is supplied to circuit elements that require cc power.

Further, the control circuit 16 of the control unit 10 is connected to the control circuit 16 via a communication means (not shown), for example, as shown in FIG.
Is connected. The airbag device 20 includes, for example, a safety sensor S
A squib circuit on the driver's seat side comprising a series circuit of switching elements SW1 such as S1, squib SQ1 and field effect transistors, and a passenger side side comprising switching elements SW2 such as safety sensors SS2, squib SQ2 and field effect transistors. , The electronic acceleration sensor GS, and the presence or absence of a collision is determined based on the output signal of the electronic acceleration sensor GS, and the switching element SW
1 and a control circuit CC having a function of supplying a signal to the gate of SW2.

[0008] The occupant detection system thus configured operates as follows. First, the high frequency low voltage from the electric field generating means 12 is applied to the antenna electrodes 4a to 4d via the current detection circuit 19, the switching circuit 11, and the connectors 13a to 13d.
As a result, a weak electric field is generated around the antenna electrodes 4a to 4d. At this time, the switching circuit 11 performs opening / closing control by a signal from the control circuit 16.
That is, first, only the switching means 11a is closed,
Next, only the specific switching means is sequentially closed in the same manner so that only the switching means 11b is closed. Therefore, when the specific switching means is closed, the high-frequency signal is supplied to the specific antenna electrodes (4a to 4d) via the current detection circuit 19, the specific switching means, and the specific connector. An electric field is generated around a specific antenna electrode, and different levels of current flow depending on whether or not an occupant is seated. This current is detected by the current detection circuit 19 and input to the control circuit 16 one after another.

The control circuit 20 includes thresholds (threshold data) relating to whether or not the occupant is seated, the occupant's seating posture, identification of the occupant (discrimination between adults and children, etc.), and seating patterns. Are stored (stored). For example, regarding whether or not the occupant is seated, the level of the current flowing through the antenna electrode in the seated state of the occupant is higher than that in the unseat state, so it is determined whether or not the signal data relating to the current exceeds a certain value. Although it is set as a reference, a characteristic pattern also appears in the current pattern flowing through each antenna electrode, so that it is also possible to use that pattern. Regarding the identification of the occupant, for example, FIG.
As shown in (a) and (b), when an adult and a child are seated on a sheet, the areas facing the antenna electrodes are different, so that a characteristic current flows through each antenna electrode. Since a high-level current flows in the case of an adult P as shown in FIG. 11A and a low-level current flows in a case of a child SP as shown in FIG. The current is set based on the characteristic current.
It is also possible to use a service.

Accordingly, various kinds of arithmetic processing are performed on the actual signal data relating to the current flowing through the plurality of antenna electrodes 4a to 4d taken into the control circuit 16. For example, actual signal data is compared with threshold data relating to the presence / absence of an occupant, identification of the occupant, and the like, which are stored in advance.
It is determined whether the occupant is seated, whether the occupant is an adult or a child, and the like. Based on the result of this determination, the airbag device 20 shown in FIG. 11 is set so that the airbag can be deployed or cannot be deployed by the transmission signal from the control circuit 16. That is, the transmission signal from the control circuit 16 is input to the control circuit CC of the airbag device 20, and when the occupant is a child, the occupant does not supply a signal to the gate of the switching element SW2 on the passenger seat side. In the case of an adult, it is set so as to supply a signal to the gate of the switching element SW2. Therefore, even if the car collides, the passenger side airbag will not be deployed in the case of a child,
It is expanded in the case of an adult.

[0011]

According to the occupant detection system, a current flows through the plurality of antenna electrodes 4a to 4d disposed on the seat 1 according to the occupant's seating state. The presence / absence of an occupant, the identification of the occupant, and the like can be accurately determined based on the signal data regarding the current, and based on the determination result, the airbag device 20 can be determined.
Can be appropriately controlled.

However, as the number of antenna electrodes (4a to 4d) arranged on the sheet 1 increases, the number of data taken into the control circuit 16 increases, and the accuracy of judgment is improved. In some cases, the antenna electrodes 4a to 4d move between the cushion material and the exterior material due to movement on the ground, and the antenna electrodes may come into contact (short).

For example, the antenna electrode 4a and the antenna electrode 4
When b contacts (short), the output of the current detection circuit 19 when only the switching means 11a of the switching circuit 11 is closed has a higher level than in the normal state, and the switching is performed. When only the means 11b is closed,
The output of the current detection circuit 19 has a higher level than in the normal state. Therefore, if a child is seated on sheet 1,
Since the detection level is high, there is a concern that the occupant may be erroneously determined to be an adult.

Therefore, during the use of the system, a problem occurs that the antenna electrodes come into contact (short) with each other, so that a signal different from the signal to be detected is detected. The judgment result in the circuit 16 does not reflect the actual seating state. For this reason, there is a problem that the accuracy and reliability of the judgment are impaired.

Therefore, an object of the present invention is to accurately detect a short state even when an antenna electrode moves and shorts among the antenna electrodes in association with an occupant sitting on a seat. An occupant detection system is provided.

[0016]

SUMMARY OF THE INVENTION Accordingly, in order to achieve the above-mentioned object, the present invention provides a plurality of antenna electrodes arranged on and / or around a sheet and a weak electric field around the antenna electrodes. A plurality of interface circuits including an electric field generating means for detecting the electric current flowing through the antenna electrode based on power supply from the electric field generating means, and a plurality of interface circuits. The electric field generating means is operated, a switching circuit having a plurality of switching means for selectively generating an electric field at the plurality of antenna electrodes, and a signal output from each interface circuit are taken in. A control circuit for judging an occupant's seating state or the like based on the signal data, wherein an electric field is selectively generated by a switching circuit among the plurality of antenna electrodes. A DC potential or an earth potential is applied to an antenna electrode other than the antenna electrode described above, an output signal from an interface circuit relating to the applied potential is taken into a control circuit, and based on the signal data, It is characterized in that the presence or absence of a short between the antenna electrodes is determined.

Further, a second invention of the present invention provides a sheet and / or
Or, a plurality of antenna electrodes disposed therearound, an electric field generating means for generating a weak electric field around the antenna electrodes, and information related to a current flowing through the antenna electrodes based on power supply from the electric field generating means. A plurality of interface circuits including circuits, and a plurality of switching means for selectively operating an electric field generating means of the plurality of interface circuits to generate an electric field at the plurality of antenna electrodes. Switching circuit and each interface
A control circuit which takes in a signal output from the control circuit and judges a seating state of the occupant based on the signal data;
An airbag device having a function of setting the airbag to a predetermined operation mode based on a determination result of the control circuit, wherein an electric field is selectively generated by a switching circuit among the plurality of antenna electrodes. A DC potential or an earth potential is applied to antenna electrodes other than the specific antenna electrode, and an output signal from an interface circuit relating to the applied potential is taken into a control circuit, and the signal data is stored in the signal data. It is characterized in that the presence or absence of a short between the antenna electrodes is determined on the basis of this.

In a third aspect of the present invention, the interface circuit includes an electric field generating means for generating a weak electric field at least around the antenna electrode, and generating the electric field around the antenna electrode. An AC-DC conversion circuit for converting an AC line voltage of a transmission system related to a current flowing through the antenna electrode into a DC based on the electric field, and a fourth invention including the electric field generating means. A fifth aspect of the present invention is characterized in that a resistor is connected in series to the transmission system, and a CR time constant circuit is formed by the resistor and a capacitance component present around the antenna electrode. Between the transmission system of the transmission signal output from the generating means and the AC-DC conversion circuit.
A sixth aspect of the present invention is characterized in that a dance conversion circuit is interposed. The sixth invention is characterized in that the impedance conversion circuit is constituted by an operational amplifier having an amplification factor of about 1 times. The circuit includes at least a means for storing in advance a threshold value relating to a short between the antenna electrodes, a means for capturing a signal output from the interface circuit, and a threshold for the captured signal data. A determination unit for determining the presence or absence of a short between the antenna electrodes by comparing with the value data.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of an occupant detection system according to the present invention will be described with reference to FIGS. The same parts as those in the prior art shown in FIGS. 8 to 12 are denoted by the same reference numerals, and detailed description thereof will be omitted. In the figure, reference numeral 10A denotes a control unit arranged in the sheet frame 3 of the sheet 1 or in the vicinity thereof, for example, a switching circuit 11 having a plurality of switching means 11a to 11d.
, A plurality of interface circuits Aa to Ad, a control circuit 16, and a power supply circuit 18. Switching of the switching means 11a to 11d in the switching circuit 11 is performed based on a signal from the control circuit 16, whereby gate signals are selectively supplied to the interface circuits Aa to Ad. Interface circuits Aa to A
Connectors (or terminals) 13a to 13d are connected to the transmission system of the high-frequency output of the connector d.
Antenna electrodes 4a to 4d are connected to 3a to 13d using lead wires or the like. The output system of the interface circuits Aa to Ad is connected to the control circuit 16. Note that an airbag device 20 is connected to the control circuit 16. Further, the power supply circuit 18 is configured to reduce the battery power supply (12 V) to, for example, 5 V to generate a single Vcc power supply, and is configured by, for example, a three-terminal regulator. The Vcc power generated by the power supply circuit 18 is supplied to all the circuit elements that require the Vcc power among the circuit elements constituting the control unit 10A.

In the above-mentioned control unit 10A, the plurality of interface circuits Aa to Ad have the same configuration as shown in FIG. These interface circuits (Aa) include, for example, an electric field generating means 12, an impedance conversion circuit (buffer circuit) 14 connected to a transmission system of a high frequency output of the electric field generating means 12, and an impedance conversion circuit. An AC-DC conversion circuit 15 converts the output of the circuit 14 into a direct current.

In the above-described interface circuit (Aa), the electric field generating means 12 is connected to, for example, a resistor 12 with respect to a Vcc power supply (a constant DC voltage) from a power supply circuit 18.
a and a switching means (for example, a field effect transistor) 12b are connected in series, a gate signal of which is given from a control circuit 16 to the gate thereof, a transmission system from a drain, and a connector (13a). And a high frequency low voltage of a square wave is outputted to the antenna electrode (4a) through the antenna. This high-frequency output is determined by a gate signal controlled by PWM (Pulse Wide Modulation) output from the control circuit 16, and its frequency is, for example, 12
It is configured to generate a high frequency low voltage of about 0 KHz. The duty ratio (ON duty) of the gate signal is set to, for example, about 10%, but can be changed to an appropriate duty ratio depending on circuit constants, frequencies, and the like. The high-frequency low voltage output from the electric field generating means 12 to the transmission system is output when the switching means 12b is in the OFF operation, and the duty ratio (ON duty) thereof is approximately 9.
It is about 0%.

In the interface circuit Aa,
The impedance conversion circuit 14 is composed of, for example, an operational amplifier 14a whose amplification factor is set to 1. Therefore, the output side of the impedance conversion circuit 14 has a low impedance, and the current required for the CPU of the control circuit to read can be taken out without affecting the input side. An AC-DC conversion circuit 15 is connected to the output side of the impedance conversion circuit 14, and is constituted by, for example, a smoothing circuit including a resistor 15a and a capacitor 15b. The AC-DC conversion circuit 15
Is connected to the control circuit 16.

Next, the operation of the occupant detection system will be described with reference to FIGS. First, the control circuit 16
The detection modes A to D shown in FIG. 3 are sequentially selected by the switching operation of the switching circuit 11 based on the signal from the control circuit. For example, when the detection mode A is selected, in the switching circuit 11, only the switching means 11a is closed, and the other switching means 11b to 11d are opened. For this purpose, a gate signal as shown in FIG. 4A is applied to the switching means 12b of the electric field generating means 12 in the interface circuit Aa. Each time the gate signal goes high, the switching means 11b is turned on,
Its drain is at the ground level and is not output to the transmission system. At this time, the electric charge charged in the capacitance component existing around the antenna electrode 4a is discharged via the switching means 12b. On the other hand, when the gate signal goes low, the switching means 12b is turned off, and the transmission system has a substantially square wave high-frequency low voltage (for example, 120 KHz, +5) as shown in FIG.
V) is output. This high frequency output is supplied to the antenna electrode 4a via the transmission system and the connector 13a, and a weak electric field is generated around the antenna electrode 4a. As a result, different levels of current flow depending on whether or not the occupant is seated on the seat 1, identification of the occupant (discrimination as an adult or a child), and the occupant's seating state such as the seating posture.

For example, when the seat 1 is not occupied by an occupant, a low-level current flows based on the stray capacitance existing around the antenna electrode 4a. At this time, the rising of the high frequency and low voltage of the transmission system is shown in FIG.
As shown in (1), the resistance is slightly reduced based on the CR time constant caused by the capacitance component of the stray capacitance and the resistance 12a of the electric field generating means 12. On the other hand, when an occupant is seated on the seat 1, a large capacitance component exists around the antenna electrode 4a as compared with the stray capacitance in the vacant state, and a high-level current flows. Will be. It should be noted that the capacitance component of the occupant is larger in adults than in children, and the level of current flowing through the antenna electrode is also higher. At this time, the rising of the high frequency and low voltage of the transmission system is
As shown in FIG. 4 (c), it becomes exponential based on the CR component due to the capacitance component larger than the stray capacitance and the resistance 12a of the electric field generating means 12, and becomes largely dull. Incidentally, the manner in which the rise is slowed is large for an adult and small for a child because the capacitance component differs between an adult and a child.

As described above, the high frequency low voltage (voltage waveform) of the transmission system including the electric field generating means 12 and the transmission system exhibiting various patterns based on the CR time constant in the antenna electrode system.
Is subjected to impedance conversion in an impedance conversion circuit (buffer circuit) 14 comprising an operational amplifier 14a set to a single amplification factor. That is, the input side is high impedance.
The dance and the output side (AC-DC conversion circuit 15 side) have low impedance, so that the current required for reading by the control circuit 16 can be appropriately taken in as needed. The output (high-frequency low voltage) of the impedance conversion circuit 14 is A
It is input to the C-DC conversion circuit 15. In this circuit 15, the AC line voltage is divided into a resistor 15a and a capacitor 15b.
Are smoothed by a smoothing circuit including the following, and are converted into direct current as shown in FIG. In the figure, the dotted line indicates the DC conversion level when the seat is vacant, and the solid line indicates the DC conversion level when the occupant is seated, and there is a discernible level difference between the two. Note that this DC conversion level depends on the magnitude of the capacitance component existing around the antenna electrode if the resistance value of the resistor 12a is set to be constant in the above-mentioned CR time constant. For example, the capacitance is large like an adult. In the case where the capacitance is small like a child, it becomes large, and when the sheet 1 is vacant, the size becomes large. The DC output of the AC-DC conversion circuit 15 is taken into the control circuit 16, A / D converted, and stored in the memory. Each time the detection mode A is switched to the detection modes B, C and D, the respective antenna electrodes 4b to 4b
Data relating to d is output from the respective interface circuits and taken into the control circuit 16 one after another.

On the other hand, in the detection mode A, the gate of the switching means 12b of the electric field generating means 12 in the interface circuits Ab to Ad is gated from the control circuit 16.
Antenna signals 4b to 4d
Is applied with a DC voltage of a Vcc power supply via a resistor 12a of the electric field generating means 12, a transmission system, and connectors 13b to 13d. This Vcc voltage is input to the AC-DC conversion circuit 15 via the impedance conversion circuit 14, and the AC-DC
It is output from the conversion circuit 15 as the Vcc voltage. Vcc
Is 5 V, for example, a DC voltage indicated by a solid line in FIG. 5 is output. Each time the detection mode A is switched to the detection modes B, C, and D, the information from the respective antenna electrodes to which the Vcc voltage is applied is output from the corresponding interface circuit. It is output and taken into the control circuit 16 one after another.

For example, assuming that the antenna electrodes 4a and 4b are short-circuited in the detection mode A, the transmission systems of the interface circuits Aa and Ab are connected to each other. , Interface circuit A
The same DC output is output from a and Ab, and this DC output is at a level lower than the Vcc voltage shown by the solid line in FIG. Then, the detection mode A includes the detection modes B, C,
Each time the switch is switched to D, a DC output of a level lower than the Vcc voltage is output by the combination of the antenna electrode to which the high-frequency low voltage is applied and the antenna electrode 4a or the antenna electrode 4b, and is taken into the control circuit 16 one after another.

The control circuit 16 has, for example, a
The seating status of the occupant seated in the port 1 (presence or absence of seating, identification of adult or child, etc.) and a threshold value (threshold data) relating to the short of the antenna electrodes are stored in a memory (storage means). ) Is stored. Specifically, the threshold value regarding the presence or absence of the occupant is set as follows. For example, as shown in FIG. 9 (a) or FIG. 9 (b), when an adult occupant P or a child occupant SP is seated on the sheet 1, the area opposed to the antenna electrodes 4a to 4d, etc. Although the capacitance components existing around the antenna electrodes 4a to 4d are different due to the difference, when the sheet 1 is vacant, the capacitance becomes considerably larger than the stray capacitance existing around the antenna electrodes 4a to 4d. As a result,
There is also a significant difference in the level of the current flowing through the antenna electrodes 4a to 4d. When the occupant is seated, not only does a higher level of current flow than when the occupant is vacant,
In relation to the difference in the CR time constant, the rise of the rising of the voltage waveform of the line voltage (high-frequency low voltage) of the transmission system increases, and the DC level output from the AC-DC conversion circuit 15 also decreases. Accordingly, when the occupant is seated, the DC level is reduced as shown by the solid line in FIG. 4D, and when the occupant is vacant, the DC level is increased as shown by the dotted line in FIG. . Therefore, the DC level between the solid line and the dotted line is set as a threshold value regarding the presence or absence of the occupant. If the DC output data is smaller than this threshold, it is determined that the occupant is seated,
If it is larger, it is determined that the driver is not seated.

The threshold value for the identification of the occupant is set as follows. For example, as shown in FIG. 12 (a) or FIG. 12 (b), when an adult occupant P or a child occupant SP is seated on the sheet 1, the difference in the area opposed to the antenna electrode and the like is caused. A difference occurs in the capacitance component existing around the antenna electrode. As a result,
The level of the current flowing through the antenna electrode is different. In the case of the adult occupant P, the current level is higher than that of the child occupant SP. The rise in the voltage waveform of the line voltage (high-frequency low voltage) also becomes large, and the DC level output from the AC-DC conversion circuit 15 also becomes low. Therefore, an intermediate DC output level between the adult P and the child SP is set as a threshold value for identification. If the DC output data is smaller than the threshold value, it is determined that the adult is P,
If it is larger, it is determined to be a child SP.

Further, the threshold value regarding the presence or absence of the short between the antenna electrodes is set as follows.
In any of the detection modes, there is no short circuit between the antenna electrodes, and in a normal state, no high-frequency low voltage is applied and all antenna electrodes to which a DC voltage (5 V) is applied are connected. The DC output from the interface circuit becomes 5 V (Vcc) as shown by the solid line in FIG. When there is a short between the antenna electrodes, a high-frequency low voltage is applied to one of the antenna electrodes, and when a DC voltage is applied to the other antenna electrode, a signal from the corresponding interface circuit is applied. DC output drops below 5V. Therefore, as shown in the figure, the level of the dotted line slightly lower than the solid line is set as the threshold value SH1 regarding the presence / absence of a short between the antenna electrodes. If the DC output data is larger than the threshold value SH1, it is determined that there is no short-circuit, and if the DC output data is smaller, it is determined that there is a short-circuit between the antenna electrodes.

Accordingly, the signal data relating to the occupant's seating status, the short-circuit between the antenna electrodes, and the like taken into the control circuit 15 are stored in the control circuit 15 in advance. This is compared with threshold data relating to a shot or the like. For example, the actual output data from the interface circuit corresponding to the antenna electrode to which the Vcc voltage is applied is compared with the threshold value SH1, and when the actual output data is higher than the threshold value SH1, Since there is no short between the antenna electrodes, it is determined that the antenna is normal, and the occupant's seating status is determined. When the actual output data is lower than the threshold value SH1, it is determined that there is a short between the antenna electrodes, and the fact is displayed on a display device or notified by a buzzer or the like. In particular,
In the case of the short determination, if only one data is used, it is conceivable that an erroneous determination is made due to noise or the like. Therefore, the data is fetched a plurality of times, for example, five times for the same detection mode. For example, when the same result is obtained three or more times, it is recommended to make a final determination based on the result.
If it is determined that there is a short between the antenna electrodes, the occupant's seating status may not be determined.

If it is determined that there is no short between the antenna electrodes and that the antenna is normal, it is determined that the occupant is seated. For example, as shown in FIG.
AC-DC associated with the high current levels of
If the DC output from the conversion circuit 15 is low and lower than the threshold value for discrimination of seating, it is determined that the occupant seated on the seat 1 is an adult P. As a result, FIG.
The airbag device 20 shown in FIG. 1 is set so that the airbag can be deployed by a transmission signal from the control circuit 16. Conversely, as shown in FIG. 12 (b), AC- related to the low current level of the antenna electrodes 4a to 4d.
If the DC output from the DC conversion circuit 15 is high and higher than the threshold value for discriminating seating, it is determined that the occupant seated on the seat 1 is a child SP. As a result, the airbag device 20 shown in FIG. 11 is set by the transmission signal from the control circuit 16 so that the airbag cannot be deployed.

In this state, when an automobile collides, the safety sensors SS1 and SS2 have their switch contacts closed in response to relatively small acceleration, and the squib circuits on the driver's seat side and the passenger's seat side. Becomes operable. When the control circuit CC determines that the vehicle has definitely collided based on the signal from the electronic acceleration sensor GS, the gates of the switching elements SW1 and SW2 output a signal corresponding to the determination result of the control circuit 16 described above. Is supplied. That is, when the result of the determination by the control circuit 16 is an adult P, the switching elements SW1 and SW2 are turned on, and when the result is a child SP, only the switching element SW2 is turned off. In these operation modes, a current flows in an appropriate squib circuit, and as a result, the squib SQ1 and the squib SQ2 or the squib SQ1 generates heat so that the driver's seat side and the passenger's seat side, or the driver's seat side airbag. Is deployed, and the occupant is properly protected from the impact of the collision.

According to this embodiment, a weak electric field is selectively generated around the plurality of antenna electrodes 4a to 4d spaced apart from the sheet 1, and a current flowing based on this electric field is generated by the electric field. The determination of the occupant's seating state or the like is performed by the arithmetic processing of the related signal data. A specific antenna electrode (for example, one of the antenna electrodes 4a to 4d) is determined.
When one is selected, the DC voltage is applied to all antenna electrodes other than the specific antenna electrode, so that the effects of external noise and the like can be reduced, and the electric field generated around the specific antenna electrode Becomes stable, and the current flowing based on this becomes stable. Therefore, it is possible to improve the accuracy and reliability of determining the occupant's seating status based on the signal data related to the current. In particular, when the airbag device 20 is mounted, it is possible to reliably set the airbag of the airbag device 20 to one of a deployable state and an undeployable state based on the determination result, which is undesirable. Deployment can be prevented beforehand.

In addition, a DC voltage is applied to all antenna electrodes other than the specific antenna electrode that generated the electric field by applying a Vcc power to these antenna electrodes.
2, the gate signal is not applied to the switching means 12b by the switching operation of the switching circuit 11, so that the operation of the electric field generating means 12 is stopped. , The Vcc voltage is automatically applied to the antenna electrode. Therefore, the circuit configuration for applying the DC voltage can be simplified.

In addition, the output signals from the interface circuits corresponding to all the antenna electrodes to which the DC voltage is applied are taken into the control circuit 16 and compared with the threshold value SH1. It is determined whether it is larger. In particular, when the antenna electrode to which the high-frequency low voltage is applied and the other antenna electrode are short-circuited, the output from the corresponding interface circuit becomes the same, and this output is originally a DC voltage. Is lower than the DC output from the interface circuit corresponding to the antenna electrode to which the voltage is applied, and lower than the threshold value SH1. Therefore, it can be detected that a short has occurred between the antenna electrodes.

In particular, when a short is generated between the antenna electrodes, the DC output from the interface circuit is different from the normal state, and the occupant determination result based on this data is obtained. Is less reliable. Therefore, it is desirable not to make a judgment on the occupant's seating status or the like when a short judgment is made, and even if it is judged, the airbag device 20 is not controlled based on the judgment result. Is desirable.

In the interface circuits Aa to Ad, the transmission system in which the high-frequency low voltage is output from the electric field generating means 12 is connected to the AC-
Since the DC conversion circuit 15 is connected, a line voltage (voltage waveform) having a relationship between the electric field generating means 12 and the current flowing through the antenna electrodes 4a to 4d via the transmission system is taken in and converted to direct current. Then, it is possible to appropriately determine the occupant's seating status on the sheet 1 based on the converted data.

Since an impedance conversion circuit 14 is connected between the transmission system and the AC-DC conversion circuit 15, the input side has a high impedance, and the output side has a low impedance. When the DC output of the AC-DC conversion circuit 15 is taken into the control circuit 16, even if the control circuit 16 takes out the current required for reading, it does not affect the transmission signal in the transmission system. Therefore,
Highly accurate occupant detection becomes possible.

Since the capacitance component existing around the antenna electrode differs depending on whether an adult occupant or a child occupant is seated on the sheet 1, the capacitance component and the electric field generating means are different. 12
By appropriately setting the CR time constant by the resistor 12a connected to the transmission system including the above, it is possible to cause the rising of the high-frequency low-voltage in the transmission line to have bluntness corresponding to each situation. Therefore, by discriminating signal data by converting an AC-DC conversion circuit from an alternating current to a direct current using a difference in waveform due to a slow rise, identifiable signal data is obtained based on the signal data. Can be accurately determined.

The antenna electrode 4 disposed on the sheet 1
a to 4d are applied to the electric field generating means 12
From the power supply circuit 1
In order to obtain a single-voltage Vcc power supply from step 8 by switching the switching means 12b with a gate signal of a desired frequency (for example, 120 KHz), for example, a direct current is converted into a high-frequency alternating current and then converted into a square wave. Compared with the oscillation circuit having a configuration for waveform shaping, the circuit configuration of the control unit as well as the electric field generating means 12 can be simplified, and the cost of the system can be effectively reduced.

Further, the airbag of the airbag device 20 is set to one of a deployable state and an undeployable state based on a determination whether the occupant is an adult or a child. For example, when it is determined that the occupant is a child SP based on the level of the DC output of the AC-DC conversion circuit 15, the airbag of the airbag device 20 is set to a non-deployable state. Therefore, even if the vehicle collides, the airbag is not deployed, so that the child can be prevented from being secondarily damaged by the airbag.

FIG. 6 shows another embodiment of the occupant detection system according to the present invention.
This is the same as the embodiment shown in FIG. The difference is that a switching circuit 11A is connected between the electric field generating means 12 and the connectors 13a to 13d in the interface circuits Aa to Ad. This switching circuit 11A has a plurality of pairs of switching means, one pair of two switching means. Terminals a and a are connected directly to terminals b and b, and terminals b and b are directly connected. Is connected to the earth through a resistor R. The switching control of these switching means is performed by a signal from the control circuit 16.

This occupant detection system operates as follows. The basic operation is the same as that of the embodiment shown in FIGS. 1 and 2, and the same operation is omitted. First, only the switching means 11a of the switching circuit 11 is closed by a signal from the control circuit 16, and the switching means 11b
To 11d, and the interface circuit Aa
Are connected to the terminals a and a, and the two switching means of the switching circuit 11A corresponding to the other interface circuits Ab to Ad are connected to the terminals b and b. Connecting. As a result, a gate signal is applied from the control circuit 16 to the switching means 12b of the electric field generating means 12 of the interface circuit Aa, and the switching circuit 12b is activated to apply a high-frequency low voltage to the antenna electrode 4a. A weak electric field is generated in the periphery. On the other hand, since the switching means of the switching circuit 11A corresponding to the interface circuits Ab to Ad is connected to the terminals b and b, the antenna electrodes 4b to 4d have an earth potential via the resistor R. Granted. To be precise, a potential distributed by the resistance ratio between the resistor 12a and the resistor R is applied. However, by setting the resistance value of the resistor R low, it is possible to approach the earth potential as much as possible. In particular, if there is no short between the antenna electrodes, the interface
The DC output from the switching circuits Ab to Ad has a low value. If there is a short between the antenna electrodes, the interface corresponding to the antenna electrode to which the high-frequency low voltage is applied
The DC output of the power circuit is also at a different level when the door is normal. Therefore, the presence or absence of a short between the antenna electrodes can be detected from these data. It should be noted that the threshold value for the presence / absence of a short has an inverse relationship to that shown in FIG.

According to this embodiment, the presence or absence of a short between the antenna electrodes can be accurately detected based on the output signals from the plurality of interface circuits as in the above embodiment. .

The present invention is not limited to the above-described embodiment. For example, the antenna electrode may be arranged on a dash board or the like in addition to a sheet, or may be arranged on both. However, the number of antenna electrodes can be appropriately increased or decreased. In addition to the oscillation circuit for generating a high-frequency low voltage, the electric-field generating means can directly use a high-frequency signal obtained by appropriately dividing a clock signal of a control circuit, and its output frequency is other than 120 KHz. Can be set to an appropriate frequency, and the voltage can be set to an appropriate low voltage other than 5V. Further, the internal configuration of the interface circuit can be appropriately changed. Furthermore, in addition to setting the operation mode of the airbag device to an appropriate mode based on the determination of the occupant, the airbag device may be configured to control a seat belt, an alarm device, and the like.

[0047]

As described above, according to the present invention, a weak electric field is selectively generated around the sheet and / or the plurality of antenna electrodes disposed around the sheet, and based on this electric field, Judgment of the occupant's seating state and the like is made based on signal data related to the current flowing through the antenna. All antenna electrodes other than the specific antenna electrode to which a high-frequency output is applied are applied with a DC potential or an arc. The influence of external noise and the like can be reduced because the potential is applied, and the electric field generated around the specific antenna electrode is stabilized, and the current flowing based on the electric field is also stabilized. Therefore, it is possible to improve the accuracy and reliability of determining the occupant's seating status based on the signal data related to the current. In particular, when the airbag device is mounted, the airbag of the airbag device can be reliably set to one of a deployable state and an undeployable state based on the determination result, and undesired deployment is performed. Can be prevented beforehand.

Further, when applying a DC voltage to all antenna electrodes other than the specific antenna electrode that generated the electric field, a Vcc power supply is applied to these antenna electrodes via the resistance and transmission system in the electric field generating means. The gate circuit is not connected, so that no gate signal is given to the electric field generating means by the switching operation of the switching circuit. When the operation of the electric field generating means stops, the Vcc voltage is automatically applied to the antenna electrode. Will be. Therefore, the circuit configuration for applying the DC voltage can be simplified.

In addition, the output signals from the interface circuits corresponding to all the antenna electrodes to which the DC voltage is applied are taken into the control circuit, compared with the threshold value, and determined whether the output signal is larger than the threshold value. Is determined. In particular, when an antenna electrode to which a high-frequency low voltage is applied and another antenna electrode are short-circuited, an interface corresponding to each antenna electrode is short-circuited.
The output from the interface circuit is the same, and this output is lower than the direct-current output from the interface circuit corresponding to the antenna electrode to which the direct-current voltage is applied. Will also be lower. Therefore, it can be detected that a short has occurred between the antenna electrodes.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of an occupant detection system according to the present invention.

FIG. 2 is a specific electric circuit diagram of the interface circuit in FIG.

FIG. 3 is a diagram showing a situation in which a high-frequency low voltage and a DC voltage are applied to a plurality of antenna electrodes in each detection mode.

4A and 4B are diagrams for explaining the operation of the control unit shown in FIGS. 1 and 2, wherein FIG. 4A shows a gate signal output from the control circuit, and FIG. In the figure, (c) shows a signal waveform of the transmission system (output waveform of the electric field generating means) when the seat is occupied, and (d) shows an AC-DC signal waveform. The figure which shows the DC output of a conversion circuit.

FIG. 5 is a graph showing AC voltage when a DC voltage is applied to an antenna electrode.
The figure which shows the DC output of the -DC conversion circuit.

FIG. 6 is a main part electric circuit diagram showing another embodiment of the occupant detection system according to the present invention.

7A and 7B are diagrams for explaining the basic operation of the occupant detection system according to the prior art, wherein FIG. 7A is a diagram showing an electric field distribution around an antenna electrode, and FIG. The figure which shows the electric field distribution when an object exists in the vicinity.

FIG. 8 is a view showing a sheet portion of the occupant detection system according to the prior art, wherein FIG. 8 (a) is a side view showing an arrangement state of antenna electrodes on the sheet, and FIG. The top view of figure (a).

9 (a) is a plan view, FIG. 9 (b) is a sectional view taken along line XX of FIG. 9 (a), and FIG. 9 (c) is a configuration diagram of the antenna electrode shown in FIG. FIG. 3 is a sectional view taken along line YY of FIG.

FIG. 10 is a circuit block diagram of an occupant detection system according to the prior art.

11 is a circuit block diagram of the airbag device shown in FIG.

12 is a plan view showing a seated state of an occupant on the sheet shown in FIG. 8, wherein FIG. 12 (a) shows a seated state of an adult, and FIG. 12 (b) shows a seated state of a child. FIG.

[Explanation of symbols]

 Reference Signs List 1 sheet 4 (4a to 4d) antenna electrode 10A control unit 11 switching circuit 11a to 11d switching means 12 electric field generating means 12a resistance 12b switching means 13a to 13d, 17 connector (terminal) 14 impedance conversion circuit 15 AC- DC conversion circuit 16 Control circuit 18 Power supply circuit 20 Air bag device Aa-Ad Interface circuit Vcc DC voltage R Resistance SS1, SS2 Safety sensor SQ1, SQ2 Squib SW1, SW2 Switching element CC Control circuit GS Electronic acceleration Sensor

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-270541 (JP, A) Table 9-509118 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01V 3/12 B60N 5/00 B60R 21/32 G01R 31/02 H01H 36/00

Claims (7)

(57) [Claims] A plurality of antenna electrodes disposed on a sheet and / or its periphery; an electric field generating means for generating a weak electric field around the antenna electrode; and an antenna electrode based on power supply from the electric field generating means. A plurality of interface circuits including a circuit for detecting information relating to a current flowing through the plurality of interface circuits, and an electric field generating means of the plurality of interface circuits in an operating state to selectively apply an electric field to the plurality of antenna electrodes. A switching circuit having a plurality of switching means for generating a signal, and a control circuit for taking in signals output from the respective interface circuits and judging an occupant's seating state or the like based on the signal data. A direct current potential or an earth potential is applied to antenna electrodes other than the specific antenna electrode for which an electric field is selectively generated by the switching circuit among the plurality of antenna electrodes. The control circuit receives an output signal from the interface circuit related to the applied potential and determines whether there is a short between the antenna electrodes based on the signal data. The occupant detection system. A plurality of antenna electrodes disposed on and / or around the sheet; an electric field generating means for generating a weak electric field around the antenna electrode; and an antenna electrode based on power supply from the electric field generating means. A plurality of interface circuits including a circuit for detecting information relating to a current flowing through the plurality of interface circuits, and an electric field generating means of the plurality of interface circuits in an operating state to selectively apply an electric field to the plurality of antenna electrodes. A switching circuit having a plurality of switching means for generating signals, a control circuit for taking in signals output from respective interface circuits, and judging a seating state of an occupant based on the signal data; An airbag device having a function of setting the airbag to a predetermined operation mode based on a determination result of the control circuit; A DC potential or an earth potential is applied to an antenna electrode other than a specific antenna electrode that selectively generates an electric field by a path, and an output signal from an interface circuit related to the applied potential is controlled by a control circuit. An occupant detection system, wherein the presence or absence of a short between the antenna electrodes is determined based on the signal data. 3. An interface circuit comprising: at least an electric field generating means for generating a weak electric field around the antenna electrode; and a current flowing through the antenna electrode based on the electric field generated around the antenna electrode. The occupant detection system according to claim 1, further comprising: an AC-DC conversion circuit configured to convert an AC line voltage of a transmission system related to the AC power supply into a DC power. 4. A configuration in which a resistor is connected in series to a transmission system including the electric field generating means, and a CR time constant circuit is formed by the resistor and a capacitance component existing around an antenna electrode. The occupant detection system according to claim 3, wherein: 5. An occupant detection system according to claim 3, wherein an impedance conversion circuit is interposed between a transmission system of a transmission signal output from said electric field generation means and an AC-DC conversion circuit. system. 6. The occupant detection system according to claim 5, wherein said impedance conversion circuit comprises an operational amplifier having an amplification factor of about 1. 7. The control circuit according to claim 1, wherein said control circuit stores at least a threshold value relating to a short-circuit between antenna electrodes, a means for receiving a signal output from an interface circuit, and Signal data is converted to threshold data.
By comparing the antenna electrode with the
The occupant detection system according to claim 1, further comprising: a determination unit configured to determine presence / absence of a vehicle.