JP2000153749A - Occupant detection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an occupant detection system which is able to accurately detect the occupant seating state even if the drift occurs in the system circuit, and to appropriately control an airbag system based on the detected results. SOLUTION: An occupant detection system contains an antenna electrode arranged in a seat, an electric field generation means 11 which generates a feeble electric field around the periphery of the antenna electrode, and information detection circuits 21 (21a to 21d) which detect information related to the current that flows to the antenna electrode based on a signal provided from the electric field generation means. The occupant detection system also contains a control circuit 18 in which information data Sin from the information detection circuit is corrected by using signal data Hin in an operating state and basic value data D that is set using an initial-state output signal of the electric field generation means or a plurality of output signals that correspond in advance to the initial-state output signal of the electric field generation means, which judges the occupant seating state based on the corrected data. In addition, an airbag system 30 is provided which has a function enabling the airbag to be set to the predetermined operation mode based on the judgement results of the control circuit.

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 more particularly, to a state in which an airbag of an airbag device can be deployed or not depending on the occupant's seating status in a passenger seat of an automobile equipped with the airbag device. The present invention relates to an improvement in an occupant detection system that can be set to a possible state.

[0002]

2. Description of the Related Art Generally, an airbag device is a device for reducing the impact received by an occupant at the time of a collision of an automobile.
It has become indispensable to the safety of automobiles, and has recently been installed not only in the driver's seat but also in the passenger seat.

[0003] As shown in FIG. 7, for example, this airbag device includes a self-service sensor SS1, a squib SQ1, and a squib SQ1.
Switching element SW1 such as a field effect transistor
A squib circuit on the driver's seat side composed of a series circuit of the following, a squib circuit on the passenger's seat side composed of a safety sensor SS2, a squib SQ2, and a switching element SW2 such as a field effect transistor, and an electronic acceleration sensor (collision detection sensor). GS and the output signal of the electronic acceleration sensor GS to determine the presence or absence of a collision,
And a control circuit CC having a function of supplying a signal to the gate of SW2.

According to this airbag device, when an automobile collides for some reason, the switching contacts of the safety sensors SS1 and SS2 are closed in response to a relatively small acceleration, and the safety sensors SS1 and SS2 are closed. The squib circuit on the passenger 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 switching element S
A signal is supplied to the gates of W1 and SW2, and the switching elements SW1 and SW2 are turned on. As a result, a current flows through each squib circuit. As a result, the driver and passenger side airbags are deployed due to the heat generated by the squibs SQ1 and SQ2, and the occupant is protected from the impact due to the collision.

[0005] By the way, this airbag device is configured so that the airbag is deployed by the collision of the vehicle irrespective of whether or not the occupant is seated on the seat.
For example, when an adult occupant is seated in the passenger seat, the above-mentioned occupant protection effect can be expected at the time of collision, but when the occupant is a child, the sitting height is lower than that of an adult. Because the head position is low, there is a concern that the deployment of the airbag may affect children. Therefore, if the occupant is a child, it may be desirable not to deploy the airbag even if the vehicle collides.

Therefore, conventionally, in order to cope with such a problem, an airbag device as shown in FIG. 8 has been proposed. This airbag device is provided with a sensor SD for detecting whether or not an occupant is seated in a passenger seat, and a control circuit C based on a detection signal of the sensor SD.
C is configured to determine the occupant's seating state in the passenger seat, and set the airbag to one of a deployable state and an undeployable state when the vehicle collides. In particular, a weight sensor is used as the sensor SD,
An adult or a child is determined based on the weight of the occupant measured by the weight sensor, or an occupant sitting on a sheet is photographed by a camera to determine an adult or a child by image processing. Things have been suggested.

[0007] According to the former method, it is possible to roughly determine whether the occupant is an adult or a child, and based on the result, the airbag is set to one of a deployable state and an undeployable state. Although it is possible to avoid an unexpected situation at the time of a collision of a car, there is a problem that accuracy is lacking because the weight varies greatly among individuals and even a child may be heavier than an adult.

Further, according to the latter method, although the occupant's seating state and the judgment of whether the occupant is an adult or a child can be made fairly accurately, image data taken by a camera is image-processed and various patterns are obtained. However, there is a problem that the processing device becomes complicated and expensive because it is necessary to make a comparison judgment with the processing.

[0009]

SUMMARY OF THE INVENTION Accordingly, the applicant has
Earlier, an occupant detection system shown in FIG. 9 was proposed. This occupant detection system basically utilizes the disturbance of a weak electric field (Electric Field) generated in an antenna electrode arranged on a sheet. 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. Current I
Flows. In this state, when the object OB is present near the antenna electrode E as shown in FIG.
The electric field is disturbed, and a current I ₁ different from the current I flows on the antenna electrode E side. Most objects OB are electrically represented by conductance and capacitance, and are coupled to ground (vehicle body) via capacitance.

Therefore, when the object OB is on the vehicle seat and when it is not, the antenna electrode E
Changes occur 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 particular, by increasing the number of antenna electrodes, it becomes possible to obtain a lot of information about an object including an occupant on a sheet,
It is possible to more accurately detect the occupant's seating status on the seat. When the object OB is on the sheet, the current flowing to the antenna electrode E increases, and when the object OB is not on the sheet, the current flowing to the antenna electrode E decreases. I do.

An occupant detection system according to the prior art utilizing this principle will be described with reference to FIGS. 10 to 11 show the arrangement of a passenger seat (or driver's seat) sheet and antenna electrodes. The sheet 1 is composed of a seating portion 1a and a backrest portion 1b, for example. ing. 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. The backrest portion 1b is configured by disposing a cushion material on the front side of a sheet frame and covering the cushion material with an exterior material, for example. In particular, a plurality of antenna electrodes 4 (4) formed in substantially the same shape (for example, square) are formed in the seating portion 1a.
a to 4d) are arranged symmetrically apart from each other, but may be arranged on the backrest 1b or on both.

As shown in FIG. 11, the antenna electrode 4 basically includes at least a base member 5 made of an insulating member such as a nonwoven fabric and a base member 5 on one surface thereof. And conductive antenna electrode portions 4a to 4d which are symmetrically spaced apart from each other, and are arranged inside the exterior material of the seating portion 1a. In particular, the antenna electrode portions 4a to 4d are made of, for example, conductive cloth, but are formed of a thread-like metal wire or conductive fiber.
The seat member 1a may be constructed by weaving the sheet surface of the seat member 1a as a base member and weaving the sheet member with a conductive paint. Lead wires 6 (6a to 6d) such as shielded wires are electrically connected to desired portions of the antenna electrode portions 4a to 4d, and the leading ends of the lead wires 6a to 6d are described later. Connected to the connectors 14 a to 14 d of the control unit 10.

A control unit 10 is incorporated in the sheet 1 described above.
As shown in FIG. 2, an electric field generating means (oscillation circuit) 11 for outputting a sine wave alternating current to generate a weak electric field around the antenna electrode portions 4a to 4d, and a transmission signal output from the electric field generating means 11 A resistor 12 connected to the transmission system, and a plurality of switching means 13 connected to the output side of the resistor 12
a switching circuit 13 for the antenna electrode portions 4a to 4d having a to 13d, connectors 14a to 14d connected to the switching means 13a to 13d of the switching circuit 13 at the time of closing operation and arranged in the housing of the control unit; 1
2 that is connected to the output side of the antenna 2 and converts an AC line voltage related to a current flowing through the antenna electrode 4 into a DC.
5, a CPU, an A / D converter, and an external memory (for example, EE
Control circuit 18 including a PROM, a RAM, etc., a connector 19 disposed in the housing and connected to a battery power supply (not shown), and a power supply circuit 2 connected to the connector 19.
0. These components are housed in the same housing to form the control unit 10. For example, the seat frame in the seat 1a of the seat 1 is provided.
The vehicle 3 is fixed so as not to be exposed to the occupant's seat. The control circuit 18 of the control unit 10 is connected to, for example, an airbag device 30 having a configuration shown in FIG. The switching means 13a in the switching circuit 13
13d is selectively switched based on a signal from the control circuit 18.

In the control unit 10 described above, the electric field generating means 11 is constituted by, for example, a quadrature oscillation circuit, and outputs a sine wave high frequency low voltage.
As the oscillating circuit, an appropriate oscillating circuit such as a weir bridge oscillating circuit other than a quadrature oscillating circuit can be used. In the output of the oscillation circuit, the frequency is, for example, about 120 KHz, and the voltage is, for example, 5 V _PP , but can be changed to an appropriate value as needed.

In the control unit 10, a receiving circuit
Reference numeral 15 denotes an AC-DC conversion circuit as shown in FIG.
(A full-wave rectifier circuit) 16 and a smoothing circuit 17.
Have been. The AC-DC conversion circuit 16 includes first and second
Operational amplifier 16a₁, 16a _Two And the first and second dio
-16b₁, 16b_Two And the resistor 16c₁~ 16c_ThreeWhen
The smoothing circuit 17 includes a resistor 17a and a resistor 17a.
And a capacitor 17b. In addition, this reception time
The output side of the path 15 is connected to a control circuit 18.

Further, in the control unit 10, the power supply circuit 20 is configured to generate a single Vcc power supply by stepping down the battery power supply (12V) to, for example, 5V, and is configured by, for example, a three-terminal regulator. Have been. The single Vcc power generated by the power supply circuit 20 is supplied to all the components that require a power supply among the components configuring the control unit 10. Note that this Vc
It is desirable to use a single c power supply, but it is also possible to set different voltages.

Next, the operation of the occupant detection system thus configured will be described with reference to FIGS. First, when the electric field generating means 11 in FIG.
A high frequency low voltage of a sine wave as shown in FIG. This high-frequency output is supplied to a resistor 12, a transmission system, and a switching circuit 13.
(Switching means 13a to 13d), connector 14a
１４14d to the antenna electrode 4 (4a〜4d). As a result, a weak electric field is generated around the antenna electrode 4 (4a〜4d). At this time, the switching circuit 13 is controlled to open and close by a signal from the control circuit 18, and only the switching means 13 a is closed first, then only the switching means 13 b is closed, and so on. The switching control is performed so that only the switching means is closed and the other switching means are opened at the same time. Therefore, the specific switching means (13a-1)
When 3d) is closed, the high frequency output is
Transmission system (transmission line), specific switching means (13
a to 13d), supplied to specific antenna electrodes 4 (4a to 4d) via specific connectors (14a to 14d),
As a result, a weak electric field is generated around the specific antenna electrodes 4 (4a to 4d), and the occupant is seated on the seat 1, and the occupant is identified (adult or child). Different levels of current flow depending on the current.

For example, when an occupant is seated on the seat 1, a large capacitance component is present around a specific antenna electrode as compared with the stray capacitance in a vacant state, and the level is high. Since a current flows, the voltage drop across the resistor 12 also increases. For this,
Since the capacitance component of the occupant is larger in an adult than in a child, the level of the current flowing through the antenna electrode also increases, and the voltage drop at the resistor 12 increases. Accordingly, the line voltage of the transmission system is as shown in FIG. 15 (a), and the line voltage V is different in the case of an adult because the capacitance component differs between the adult and the child and the current flowing through the antenna electrode differs. Is small and large for children. On the other hand, when the occupant is not occupied in the seat 1, a low-level current flows based on the stray capacitance existing around the specific antenna electrode, but the voltage drop at the resistor 12 is small. It becomes extremely small, and the line voltage V becomes a value close to the output voltage of the electric field generating means 11.

As described above, the AC line voltage at the output side of the resistor 12 is taken into the receiving circuit 15. This AC line voltage is first subjected to full-wave rectification in the AC-DC conversion circuit 16 as shown in FIG. 15B, and then to direct current (Vd) in the smoothing circuit 17 as shown in FIG. ). Specifically, of the line voltage of the AC, a positive voltage half cycle is input to the AC-DC converter circuit 16, a first output of the operational amplifier 16a ₁ is inverted to the negative, the second diode - de 16b ₂ is to be cut off, the voltage of the second operational amplifier 16a ₂ to the applied positive half cycle is output to the second output of the operational amplifier 16a ₂ via a resistor 16c _2. Then, when the voltage of the negative half cycle is input to the AC-DC converter circuit 16, a first output of the operational amplifier 16a ₁ is inverted to the positive, the second diode - de 16b ₂ is turned on for, the voltage of the inverted state is output to the positive to the second output of the operational amplifier 16a _2. Therefore, an output voltage as shown in FIG. 15B is obtained as the output of the AC-DC conversion circuit 16.

As described above, the level of the DC output Vd of the receiving circuit 15 differs according to the output of the AC-DC converting circuit 16. In FIG. 15C, the dashed 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. There is a discernable level difference between the two. ing. This DC conversion level depends on the magnitude of the capacitance component existing around the antenna electrode if the resistance value of the resistor 12 in the transmission system is set to be constant. For example, when the capacitance is large like an adult, On the other hand, when the capacitance is small like a child, it becomes large, and when the sheet 1 is vacant, it becomes the largest. The DC output of the receiving circuit 15 is taken into the control circuit 18 one after another, A / D converted, and stored in the memory.

The control circuit 18 has, for example, a
Threshold value (threshold data) relating to the seating status of the occupant seated in the
) Are stored. Specifically, the threshold value regarding the presence or absence of the occupant is set as follows. For example, as shown in FIGS.
When an adult occupant P and a child occupant SP are seated on the vehicle 1 respectively, a difference occurs in capacitance components existing around each antenna electrode due to a difference in an area facing each antenna electrode or the like. As a result, the level of the current flowing through the antenna electrode is different, the level of the current is higher in the case of an adult occupant P than in the case of a child occupant SP, and the voltage drop at the resistor 12 is also different. The DC level output from is also different. Therefore, the level between the DC output related to the current level in the case of the child SP and the DC output in the vacant state shown by the dotted line in FIG. 15C is set as the threshold value regarding the presence or absence of the occupant. In addition, DC output data
If the value is smaller than the threshold value, it is determined that the occupant is seated, and if the value is larger than the threshold value, it is determined that the occupant is not seated. In particular, it is desirable to set this threshold value for the sum of the DC output from the receiving circuit 15 related to the current flowing through each antenna electrode, but it is also possible to set this threshold value for each antenna electrode.

The threshold value for the identification of the occupant is set as follows. For example, as shown in FIG. 16 (a), when an adult occupant P is seated on the seat 1, the level of the current flowing through each antenna electrode becomes large, and transmission is performed due to a voltage drop at the resistor 12. The line voltage of the system decreases, and the DC level output from the receiving circuit 15 becomes the level (Vd) shown by the solid line in FIG. On the other hand, as shown in FIG. 16B, when the child occupant SP is seated on the seat 1, the level of the current flowing through each antenna electrode becomes small, and the voltage drop at the resistor 12 causes The line voltage of the transmission system decreases,
The DC level output from the receiving circuit 15 is as shown in FIG.
At a level between the levels indicated by the solid and dotted lines.
Therefore, a DC output related to an intermediate current level between the adult P and the child SP is set as a threshold for identification. If the DC conversion data is smaller than the threshold value, it is determined to be an adult P, and if it is larger, it is determined to be a child SP. In particular, it is desirable to set this threshold value for the sum of the DC output from the receiving circuit 15 related to the current flowing through each antenna electrode, but it is also possible to set this threshold value for each antenna electrode.

Therefore, the signal data relating to the occupant's seating state taken into the control circuit 18 is compared with threshold data relating to the occupant's sitting state stored in the control circuit 18 in advance. As shown in (a), when the DC output from the receiving circuit 15 is low and lower than the threshold value for discrimination of seating in relation to the high current levels of all the antenna electrodes 4a to 4d, -It is determined that the occupant seated in G1 is an adult P. As a result, the airbag device 30 shown in FIG.
Is set so that the airbag can be deployed by the transmission signal from. Conversely, as shown in FIG.
If the DC output from the receiving circuit 15 is high in relation to the low current level of all the antenna electrodes 4a to 4d and is higher than the threshold value for identification of seating, the seat 1 is seated. The occupant is determined to be a child SP.
As a result, the airbag device 30 shown in FIG. 14 is set such that the airbag cannot be deployed by the transmission signal from the control circuit 18. That is, the transmission signal from the control circuit 18 is input to the control circuit CC of the airbag device 30, and in the latter case, the gate signal is set so as not to supply the gate signal to the switching element SW2 on the passenger seat side in the event of a car collision. You. A gate signal is supplied to the switching element SW1 on the driver's seat side. In the former case, it is set so that the gate signal is supplied to the switching elements SW1 and SW2.

As described above, according to the prior art, the antenna electrode 4 (4a to 4a) is transmitted by the transmission signal from the electric field generating means 11.
In 4d), a current corresponding to a capacitance component or the like existing around the antenna electrode flows. At this time, a voltage drop occurs according to the current in the resistor 12 connected to the transmission system, and the line voltage of the transmission system becomes It becomes a voltage related to the current flowing through the antenna electrode. In particular, the current flowing through the antenna electrode is
Since this voltage varies depending on whether or not the driver is seated in the vehicle 1 and whether or not the occupant is an adult, the receiving circuit 15 converts this voltage from AC to DC to obtain identifiable DC data. This data is taken into the control circuit 18, and the seating status of the occupant in the seat 1 can be appropriately determined based on the signal data relating to the DC data. Therefore,
The main problem in the conventional example shown in FIG. 8 can be solved.

In addition, the control circuit 18 determines the seating status of the occupant in the seat 1 based on the signal data on the DC output from the receiving circuit 15, and communicates the determination result to the airbag device 30. In relation to being transmitted via means,
The airbag device 30 can be appropriately controlled according to the occupant's seating status.

However, in the prior art, the electric field generating means 11 and the receiving circuit 15 constituting the control unit 10
Such components tend to exhibit a drift phenomenon in which characteristics gradually change due to self-heating or an increase in ambient temperature accompanying operation. For example, the resistance value and the capacitance of a resistance component and a capacitor component increase or decrease due to a rise in temperature, and the switching characteristics of a semiconductor component such as a transistor and a diode change. Therefore, the signal level related to the current flowing through the antenna electrode 4 is also affected.

In particular, when the electric field generating means 11 is constituted by a circuit component mainly composed of a semiconductor component such as a quadrature oscillation circuit, a Wien bridge oscillation circuit, etc., the electric field generating means 11 outputs. The amplitude of the signal fluctuates. The AC-DC conversion circuit 16 in the receiving circuit 15 includes, for example, first and second operational amplifiers 16a ₁ and 16a ₂ , first and second diode amplifiers.
De 16b _1, 16b _2, are constituted by resistance 16c ₁ ~16c _3, first, second diode - de 16b _1, 1
Since the forward voltage of 6b ₂ has a negative temperature coefficient,
The forward voltage also varies depending on the ambient temperature. For this,
The output voltage of the AC-DC converter circuit 16 becomes a voltage corresponding to the cycle is reversed by the first operational amplifier 16a ₁ varies, also varies the level of the DC output from the smoothing circuit 17.

The DC output of the smoothing circuit 17 is supplied to the control circuit 1
The control circuit 18 determines the seating state of the occupant based on a comparison between threshold data stored in advance and the received signal data, for example. If a change occurs only in the DC output of the smoothing circuit 17 irrespective of the occupant's seating status, a determination is made that the current output does not match the actual seating status. For example, sheet 1 has child occupant SP
Is seated, an adult may be determined to be seated due to a change in the level of the DC output, making it difficult to appropriately control the airbag device 30. Therefore, there is a problem that not only the accuracy of the judgment in the control circuit 18 is impaired, but also the reliability is lowered.

Therefore, it is an object of the present invention to accurately detect an occupant's seating state on a seat even if a drift phenomenon or the like occurs in a system circuit, and to appropriately set an airbag device based on the detection result. And a controllable occupant detection system.

[0030]

SUMMARY OF THE INVENTION Therefore, in order to achieve the above-mentioned object, the present invention provides an antenna electrode disposed on a sheet and / or its periphery, and a method for generating a weak electric field around the antenna electrode. An electric field generating means, an information detection circuit for detecting information related to a current flowing through the antenna electrode based on a signal supply from the electric field generating means, and an output signal in an initial state of the electric field generating means or a plurality of signals corresponding thereto in advance. The information data from the information detecting circuit is corrected based on the reference value data set using the output signal and the output signal from the electric field generating means in the actual operation state, and based on the corrected data. It is characterized by comprising a control circuit for judging the occupant's seating status, comprising a half-wave rectifier circuit for half-wave rectification of the in-voltage, and a smoothing circuit for smoothing the output of the half-wave rectifier circuit. .

The second invention of the present invention relates to a sheet and / or
Or an antenna electrode disposed therearound, and an electric field generating means for generating a weak electric field around the antenna electrode,
An information detection circuit that detects information related to a current flowing through the antenna electrode based on a signal supply from the electric field generation unit,
From the information detection circuit based on the reference value data set using the output signal in the initial state of the electric field generating means or a plurality of output signals corresponding thereto in advance and the output signal from the electric field generating means in the working state. And a function for setting the airbag to a predetermined operation mode based on the result of the judgment by the control circuit. And an airbag device having:

The third invention of the present invention relates to a sheet and / or
Or a plurality of antenna electrodes disposed therearound, electric field generating means for generating a weak electric field around the antenna electrodes, and selectively switching the electric field generating means to a specific antenna electrode among the plurality of antenna electrodes. A first switching circuit to be connected, and an output side of the first switching circuit connected to a plurality of antenna electrodes corresponding to the plurality of antenna electrodes and related to a current flowing through a specific antenna electrode selected by the first switching circuit. An information detection circuit for detecting information, a second switching circuit for selectively switching and outputting information output from each information detection circuit, and an output from the second switching circuit,
A receiving circuit for DC conversion, an output signal in an initial state of the electric field generating means or a reference value data set in advance using a plurality of output signals corresponding thereto and an information detecting circuit from the electric field generating means in a working state. The information data from the information detection circuit is corrected based on the signal data directly output via the first and second switching circuits without passing through, and based on the corrected data. And a control circuit for judging a seating state of the occupant.

The fourth invention of the present invention relates to a sheet and / or
Or a plurality of antenna electrodes disposed therearound, electric field generating means for generating a weak electric field around the antenna electrodes, and selectively switching the electric field generating means to a specific antenna electrode among the plurality of antenna electrodes. A first switching circuit to be connected, and an output side of the first switching circuit connected to a plurality of antenna electrodes corresponding to the plurality of antenna electrodes and related to a current flowing through a specific antenna electrode selected by the first switching circuit. An information detection circuit for detecting information, a second switching circuit for selectively switching and outputting information output from each information detection circuit, and an output from the second switching circuit,
A receiving circuit for DC conversion, an output signal in an initial state of the electric field generating means or a reference value data set in advance using a plurality of output signals corresponding thereto and an information detecting circuit from the electric field generating means in a working state. The information data from the information detection circuit is corrected based on the signal data directly output via the first and second switching circuits without passing through, and based on the corrected data. A control circuit for judging the seating state of the occupant, and an airbag device having a function of setting the airbag to a predetermined operation mode based on the judgment result of the control circuit are provided.

According to a fifth aspect of the present invention, the information detecting circuit comprises an impedance element, preferably a resistor, connected in series to a transmission system of an output signal from the electric field generating means. A sixth invention is characterized in that the first and second switching circuits are constituted by analog switches, and a seventh invention is characterized in that the reception circuit converts the AC line voltage of a transmission system to DC. AC-DC conversion circuit and AC-
An eighth invention is characterized in that a buffer circuit is connected between the information detecting circuit and the electric field generating means.

Further, according to a ninth aspect of the present invention, the control circuit is characterized in that the control circuit includes at least an output signal in an initial state of the electric field generating means or a reference value data set in advance using a plurality of output signals corresponding thereto. Information from the information detecting circuit based on the reference value data and signal data directly output from the electric field generating means in the working state without passing through the information detecting circuit. It is characterized by having a correction unit for correcting data and a determination unit for determining the occupant's seating state based on the correction data of the correction unit.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a first 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. 10 to 14 are denoted by the same reference numerals, and detailed description thereof will be omitted.
In the figure, the characteristic part of this embodiment is that the first switching circuit 13A is connected to the transmission system of the electric field generating means 11 and the output terminals Oa to Od of the first switching circuit 13A and the connectors 14a to 14d are connected. The information detection circuit 21 (21a
To 21d) and a second output system for information detection.
Of the information detection circuit 21 (21a
To 21d) and selectively output the signal from the electric field generating means 11 to the output terminal Oe of the first switching circuit 13A without passing through the information detecting circuit 21. That is, the transmission is performed to the input terminal Ie of the second switching circuit 13B. Although analog switches are recommended for the first and second switching circuits 13A and 13B, other switching circuits can be applied.

In the first switching circuit 13A, the selective connection between its input terminal I and output terminals Oa to Oe is performed based on a switching signal from the control circuit 18, and for example, I-Oa , I-Ob, I-Oc... I-Oe. On the other hand, in the second switching circuit 13B, the selective connection between its input terminals Ia to Ie and the output terminal O is performed based on a switching signal from the control circuit 18, and for example, Ia-O, Ib- O, Ic-O... Ie-O are connected. In particular, IO of the first switching circuit 13A
a is connected to the antenna electrode portion 4a (connector 14a).
Is selected, the input terminal Ia and the output terminal O of the second switching circuit 13B are connected such that the output from the information detecting circuit 21a is input to the receiving circuit 15. That is,
The first switching circuit 13A and the second switching circuit 13B are controlled such that their switching and connection correspond to each other. Therefore, when the I-Oe of the first switching circuit 13A is connected, the Ie-O of the second switching circuit 13B is connected, and the output signal of the electric field generating means 11 is output to the information detection circuits 21 (21a to 21a).
The signal is directly input to the receiving circuit 15 without going through d).

The information detection circuits 21 (21a to 21d) in the control unit 10A are all configured identically. For example, the information detection circuit 21a is connected to an operational amplifier 21P for a buffer and the output side of the operational amplifier 21P. Impedance element (for example, a resistor) 21R. The operational amplifier 21P is configured to have an amplification factor of approximately 1 times. The output terminal Oa of the first switching circuit 13A is connected to the non-inverting input terminal (+), and the output side of the operational amplifier 21P is connected to the inverting input terminal (-). Have been. The output side of the resistor 21R is connected to the second switching circuit 13
B is connected to the input terminal Ia.

The control unit 10A includes, for example, the electric field generating means 11, the first switching circuit 13A, the second switching circuit 13B, the information detecting circuits 21 (21a to 21d), the receiving circuit 15, the control circuit 18, It comprises a power supply circuit 20 and is incorporated in the sheet 1 as shown in FIG. In particular, the control circuit 18 of the control unit 10A is connected to, for example, an airbag device 30 having a configuration shown in FIG.

Next, the operation of the occupant detection system will be described with reference to FIGS. The basic operation is almost the same as the operation of the prior art shown in FIGS. First, the ignition switch is turned on, the system is started up, and the seat 1 is vacant (not necessarily vacant). In this state, when the terminal I-Oe of the first switching circuit 13A and the terminal Ie-O of the second switching circuit 13B are closed, FIG. 15A output from the electric field generating means 11 composed of a quadrature oscillation circuit. High frequency low voltage of sine wave shown in (for example, 5V _PP , 120KHz)
Is directly input from the I-Oe of the first switching circuit 13A to the receiving circuit 15 via the Ie-O of the second switching circuit 13B. The high frequency low voltage input to the receiving circuit 15 is AC
The DC conversion circuit 16 performs full-wave rectification as shown in FIG. 15B, and the smoothing circuit 17 performs smoothing as shown in FIG. The output voltage Vd of the smoothing circuit 17 is
8 and are subjected to A / D conversion and stored in the storage unit as initial data representing the initial state of the electric field generating means 11 and the receiving circuit 15. Incidentally, threshold data described later is also stored. In particular, the initial data is such that, for a plurality of systems, the output signal from the receiving circuit 15 in the same state is taken into the control circuit 18 and the average value is used as the reference value data.
It is recommended to use it as data (D).

Next, in a working state in which an occupant is seated on the seat 1, first, the first and second switching circuits 13A, 13A
When only the terminals I-Oa and Ia-O in 3B are closed, the output signal of the electric field generating means 11 (high-frequency low voltage)
Is input to the information detection circuit (voltage detection circuit) 21a via the first switching circuit 13A (terminal I-Oa). This signal is amplified by a buffer operational amplifier 21P whose amplification factor is set to approximately 1 times, and is amplified by a resistor 21R and a connector 14R.
a, is applied to the antenna electrode section 4a via the lead wire 6a. As a result, a weak electric field is generated around the antenna electrode portion 4a, and depending on whether the occupant is seated on the seat 1, and whether the occupant is an adult or a child, the antenna electrode portion 4a is generated.
Since different capacitance components are present around a, currents of different levels flow, and this current is generated by the resistor 21R.
Is converted into a voltage as shown in FIG. Note that the detection voltage on the output side of the resistor 21R is higher for a child occupant than for an adult occupant, and is highest when the seat is vacant. This detection voltage is applied to the terminal Ia of the second switching circuit 13B.
The signal is input to the receiving circuit 15 via -O. Receiver circuit 15
In FIG. 1, the AC detection voltage is applied to the AC-DC conversion circuit 16.
5 (b), full-wave rectification is performed, and smoothing is performed by the smoothing circuit 17 as shown in FIG. 5 (c). The DC output of the smoothing circuit 17 is taken into the control circuit 18, A / D converted, and stored in an external memory or the like as signal data Sin from the antenna electrode section 4a.

Next, the first and second switching circuits 13A, 13A
When only the terminals I-Ob and Ib-O at B are closed, the output signal of the electric field generating means 11 becomes the first switching circuit 1
It is input to the information detection circuit (voltage detection circuit) 21b via 3A (terminal I-Ob). This signal is amplified by an operational amplifier 21P for a buffer, and a resistor 21R, a connector 1
4b, and is applied to the antenna electrode portion 4b via the lead wire 6b. As a result, a weak electric field is generated in the vicinity of the antenna electrode portion 4b, and different levels of current flow depending on whether the occupant is seated on the seat 1, and whether the occupant is an adult or a child, This current is generated by the resistor 21R as shown in FIG.
The voltage is converted into a voltage as shown in FIG. This detection voltage is input to the receiving circuit 15 via the terminal Ib-O of the second switching circuit 13B. In the receiving circuit 15, the AC detection voltage is full-wave rectified by the AC-DC conversion circuit 16 as shown in FIG.
Is smoothed as shown in FIG. The DC output of the smoothing circuit 17 is taken into the control circuit 18, A / D converted, and stored in an external memory or the like as signal data Sin from the antenna electrode unit 4b. Hereinafter, similarly, by the switching connection of the corresponding terminals in the first and second switching circuits 13A and 13B, the voltage (information) related to the current flowing through the corresponding antenna electrode unit is detected by the information detection circuit, and the reception is performed. Circuit 15
Are successively taken into the control circuit 18.

Next, the first and second switching circuits 13A and 13A
When only the terminals I-Oe and Ie-O of B are closed,
The output signal of the electric field generating means 11 is supplied from the terminal I-Oe of the first switching circuit 13A to the terminal Ie-O of the second switching circuit 13B.
Is input directly to the receiving circuit 15 via the. This output signal is full-wave rectified by the AC-DC conversion circuit 16 as shown in FIG. 15B, and is smoothed by the smoothing circuit 17 as shown in FIG. The output voltage Vd of the smoothing circuit 17 is taken into the control circuit 18, subjected to A / D conversion, and stored in an external memory or the like as basic data Hin for correction.
Then, in the correction unit of the control circuit 18, the basic data Hin in the working state and the reference value data read from the storage unit are read.
Correction coefficient (D / Hi
n) is calculated. The actual operating signal data is added to this correction coefficient.
The electric field generating means 1 is multiplied by
1, the drift component in the receiving circuit 15 and the like is corrected,
True signal data TSin is obtained. Note that this true signal data (corrected signal data) TSin is TSin =
It is calculated by Sin × (D / Hin). The corrected signal data is compared with the threshold data read from the storage unit in the determination unit of the control circuit 18, and the occupant is seated depending on whether the data is larger or smaller than the threshold data. The presence or absence of the occupant and the identification of the occupant (whether the occupant is an adult or a child) are determined. For example, the threshold value relating to the presence or absence of the occupant is set between the dotted line level (vacant seat) and the solid line level in FIG. 15C. It is determined that the occupant is seated.

Therefore, the signal data relating to the occupant's seating state taken into the control circuit 18 is appropriately corrected by a correction coefficient based on the reference value data D and the signal data Sin in the actual state, and after the correction. Is compared with the threshold data on the occupant's seating status read from the storage unit of the control circuit 18 and, for example, as shown in FIG. If the DC output from the receiving circuit 15 is low in relation to the high current level of 4d and is lower than the threshold for discriminating seating, the occupant seated on the seat 1 is an adult P. Is determined. Thereby, the airbag device 3 shown in FIG.
0 is set so that the airbag can be deployed by a transmission signal from the control circuit 18. Conversely, FIG.
As shown in (b), all the antenna electrodes 4a to 4d
If the DC output from the receiving circuit 15 is high in relation to the low current level of the vehicle 1 and is higher than the threshold value for discrimination of seating, the occupant seated on the seat 1 has a child SP.
Is determined. As a result, the airbag device 30 shown in FIG. 14 is set such that the airbag cannot be deployed by the transmission signal from the control circuit 18.
That is, the transmission signal from the control circuit 18 is transmitted to the airbag device 3.
In the latter case, a gate signal is set so as not to be supplied to the switching element SW2 on the passenger seat side in the event of a collision of the vehicle. A gate signal is supplied to the switching element SW1 on the driver's seat side. In the former case, it is set so that the gate signal is supplied to the switching elements SW1 and SW2.

According to this embodiment, in the initial state, the high frequency output of the electric field generating means 11 is changed to the first and second switching circuits 1
Reference value data (or initial data) obtained by inputting directly to the receiving circuit 15 via 3A and 13B and taking in the output from the receiving circuit 15 into the control circuit 18.
D and the high-frequency output of the electric field generating means 11 in the working state are directly input to the receiving circuit 15 via the first and second switching circuits 13A and 13B, and the output from the receiving circuit 15 is taken into the control circuit 18. Correction coefficient (D / Hin) based on the basic data Hin in the actual operating state obtained as described above.
Is calculated, and the signal data Si in the working state is added to this correction coefficient.
By multiplying by n, drifts in the electric field generating means 11, the receiving circuit 15 and the like are corrected, and true signal data TSin is obtained. Therefore, since the corrected signal data has been corrected for the drift amount, it is possible to accurately determine the occupant's seating state based on the signal data.

In particular, the seating state of the occupant is determined on the basis of the output signal from the receiving circuit 15 taken into the control circuit 18.
(4a-4d) are arranged, and since these antenna electrodes are appropriately selected by the first switching circuit 13A, a large amount of signal data is taken into the control circuit 18. Therefore, since the judgment in the control circuit 18 is made based on a lot of signal data, the occupant can be detected with higher reliability.

Further, the control unit 10A includes circuits such as the electric field generating means 11, the first switching circuit 13A, the second switching circuit 13B, the receiving circuit 15, the control circuit 18, the power supply circuit 20, and the information detecting circuit 21 in the same housing. Since the components are housed in a compact structure, it can be easily incorporated into the sheet 1. In particular, seat flare in the seating section 1a.
Since the arrangement space is relatively easy to secure in or near the system 3, even if the control unit 10A becomes slightly large, it can be easily and easily incorporated.

Since the control unit 10A is incorporated in the sheet 1 on which the plurality of antenna electrodes 4 are arranged, the antenna electrodes 4 and the control unit 10A are connected to the lead wires 6 (6a to 6d). In making the electrical connection, the length of the wiring can be considerably shortened as compared with the case where the control unit 10A is arranged in a dashboard portion or an engine room. Therefore, not only the cost can be reduced, but also the influence of external noise can be reduced by shortening the wiring length, and the reliability of the occupant detection function of the system can be improved.

Further, the airbag of the airbag device 30 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, if it is determined that the occupant is a child SP based on the level of the DC output of the receiving circuit 15, the airbag of the airbag device 30 is set to a non-deployable state. Therefore, even if the vehicle collides, the airbag is not deployed, and the airbag device 30 can be appropriately controlled.

FIGS. 3 and 4 show a second embodiment of the occupant detection system according to the present invention. The basic configuration is the same as that of the embodiment shown in FIGS. The difference is
The receiving circuit 15A is used to perform half-wave rectification of the AC line voltage.
That is, the C-DC conversion circuit 16A and the smoothing circuit 17 are provided. In particular, the AC-DC conversion circuit 16A is configured by a circuit element including at least one operational amplifier 16a, and its non-inverting input terminal (+) has a second
The output terminal O of the switching circuit 13B is connected to the inverted input terminal (-).
Is applied with an appropriate reference voltage Vref, for example, 4V.

Next, the operation of the thus configured occupant detection system will be described. The basic operation is shown in FIG.
2 to FIG. 2, only different points will be described. First, in the initial state, when the electric field generating means 11 composed of a quadrature oscillation circuit is in an operating state, a high frequency low voltage of a positive bias side sine wave is output as shown in FIG. The output voltage of the electric field generating means 11 is set to 5 V _PP at a 4 V center, for example. This output voltage is input to the AC-DC conversion circuit 16A of the receiving circuit 15A via the terminal Ie-O of the second switching circuit 13B, that is, to the non-inverting input terminal (+) of the operational amplifier 16a. The inverting input terminal (-) of the operational amplifier 16a has a reference voltage Vre of +4 V (DC), for example.
Since f is applied, its output is
As shown in (b), a half-wave rectified voltage with the 4V center at 0V is output. This half-wave rectified voltage is
A DC output as shown in FIG. 4 (c) is obtained by smoothing by a smoothing circuit 17 comprising a capacitor 7a and a capacitor 17b.
In the figure, the DC output Vd indicated by a solid line indicates the DC conversion level when the seat is vacant, the DC output Vd ₁ indicated by a dotted line indicates the DC conversion level when the adult occupant P is seated, and the DC output level indicated by a two-dot chain line. The output Vd ₂ indicates the DC conversion level when the occupant SP of the child is in the seated state, and there is a discernible level difference between the three. This receiving circuit 1
The DC output from the 5A is successively taken into the control circuit 18 and A / D converted, and the average value is converted to a reference value data D.
Is stored in the storage unit of the control circuit 18.

Next, in the working state, the electric field generating means 1
1 high-frequency output is supplied to the first and second switching circuits 13A and 13B.
From the control circuit 18A.
The signal data taken in is used as basic data Hin for correction.
As an external memory. Then, the correction unit of the control circuit 18 calculates a correction coefficient (D / Hin) for the drift using the basic data Hin in the working state and the reference value data D read from the storage unit.
By multiplying the correction coefficient by the signal data Sin in the actual state, the drift in the electric field generating means 11 is corrected, and true signal data TSin is obtained.
Hereinafter, the seating status of the occupant is determined by comparing the signal data TSin with the threshold value. In addition, for example, the threshold value regarding the presence or absence of the occupant is set between the solid line and the two-dot chain line in FIG. As for the identification of the occupant, a threshold value is set between the dotted line and the two-dot chain line in FIG.

According to this embodiment, the same effects as in the first embodiment can be expected. In addition, the AC-DC conversion circuit 16A in the receiving circuit 15A has almost one operational amplifier 1A.
6a, the circuit configuration is significantly simplified as compared with the AC-DC conversion circuit 16 that performs full-wave rectification as in the first embodiment, and the cost can be reduced to about 30 to 50%.

The AC-DC conversion circuit 16A which performs full-wave rectification as in the first embodiment is provided in the AC-DC conversion circuit 16A.
Because no diode is used at all as in 6,
Fluctuations in the DC output of the receiving circuit 15A due to changes in the ambient temperature can be suppressed. Therefore, not only the accuracy of the determination regarding the seating state in the control circuit 18 based on the DC output can be improved, but also the reliability thereof can be improved.

FIG. 5 shows a third embodiment of the occupant detection system according to the present invention, which is basically the same as the embodiment shown in FIGS. The difference information detecting circuit 21A (21a to 21d), an operational amplifier 21P ₁ of buffer, a resistor 21R in series with the output of the operational amplifier 21P _1, the voltage associated with the current flowing in the antenna electrode 4a~4d is that the an amplifier 21P ₂ Metropolitan amplifying taken out (information) from both ends of the resistor 21R.

The basic operation of this embodiment is the same as that of the embodiment shown in FIGS.
The detected voltages in a to 21d) are large when the occupant is an adult, low when the occupant is a child, and further lower when the occupant is vacant. For this reason, the DC output from the receiving circuit 15 also has a value corresponding to the detected voltage, and the threshold value relating to the occupant's seating state stored in the control circuit 18 in advance is different from the embodiment shown in FIGS. Value. However, the drift amount of the signal data from the antenna electrodes 4a to 4d in the actual operation state is obtained by converting the output signal of the electric field generating means 11 in the initial state and the actual operation state to the information detection circuit 21A (21a to 21d).
The reference value data (or initial data) obtained by directly inputting the signal to the receiving circuit 15 and taking in the output from the receiving circuit 15 to the control circuit 18 without passing through 21d) is used. Therefore, the seating status of the occupant can be accurately determined.

FIG. 6 shows a fourth embodiment of the occupant detection system according to the present invention, which is basically the same as the embodiment shown in FIGS. The difference is that one antenna electrode is provided and arranged on the sheet 1 or the dash board, and the number of switching means that actually operates in the first and second switching circuits 13A and 13B is added to the antenna electrode. It is correspondingly reduced.

The basic operation of this embodiment and the effects obtained are the same as those of the first embodiment. However, since there is only one antenna electrode, the configuration of the system is simplified.
The cost can be reduced. In particular, if the antenna electrode is arranged on the dash board, it is possible to detect the distance between the occupant and the dash board based on the detection signal from the information detection circuit 21. Only when properly maintained, the airbag device 3
It can be controlled so that zero operation can be performed.

It should be noted that the present invention is not limited to the above-described embodiment at all.
In addition to the seat and the dashboard portion, it can be arranged on a door or a seat portion close to the door, or can be arranged on both the seat and the dashboard portion. When a plurality of antenna electrodes are arranged, the number of the antenna electrodes can be set as appropriate, and the form can be rectangular, band, loop or the like in addition to the square. In particular, when a plurality of antenna electrodes are arranged, it is recommended that the antenna electrodes be fixed to an insulating base member in advance. Also, the electric field generating means may be configured to generate a high frequency low voltage of a rectangular wave in addition to a sine wave. For example, the electric field generating means may be configured to appropriately divide a clock signal of a control circuit to generate a high frequency signal. Alternatively, it may be configured to generate a direct current by switching at a predetermined cycle, and the output frequency thereof may be one.
The voltage can be set to a value other than 20 KHz, and the voltage can be set to a voltage other than 5 V (for example, 3 to 20 V). Further, the buffer circuit in the information detection circuit can be omitted depending on the function and accuracy expected of the system. Further, a signal amplifying function can be given to the receiving circuit. The correction of the signal data in the working state in the control circuit is performed by the ratio between the reference value data (or the initial data) in the initial state and the signal data from the electric field generating means in the working state. In addition, it is also possible to configure so as to make a correction based on the difference between the two, and the correction can be made at appropriate intervals during running of the vehicle, continuously, or only at the start of running. . Based on the judgment result of the control circuit, the seat belt mounting state, the warning light, and the like can be controlled instead of the airbag device. Furthermore, in addition to comparing the threshold value stored in the control circuit in advance with the signal data related to the current flowing through the actual antenna electrode, the occupant determination is performed in addition to various seating patterns on the occupant seat. It is also possible to preliminarily store data relating to the seating position, the seating posture, and the like, and to determine whether or not the occupant is seated, whether or not the occupant is an adult, and the like, by comparison with the stored data.

[0060]

As described above, according to the present invention, in the initial state, the output signal of the electric field generating means is directly input to the receiving circuit without passing through the information detecting circuit, and the output signal from the receiving circuit is output. The reference value data (or initial data) obtained by taking the data into the control circuit and the output signal of the electric field generating means in the actual operating state are directly transmitted to the receiving circuit without passing through the information detecting circuit. By using the basic data in the active state obtained by inputting the output from the receiving circuit to the control circuit, the signal data in the active state is corrected. Accordingly, since the corrected signal data has been corrected for the drift, the seating status of the occupant can be accurately determined based on the signal data.

In particular, the seating state of the occupant is determined based on the output signal from the receiving circuit taken into the control circuit. When a plurality of antenna electrodes are arranged on the sheet, the control circuit is used. Captures more signal data. Therefore, since the determination in the control circuit is made based on a lot of signal data, the occupant can be detected with higher reliability.

Further, the airbag of the airbag device 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, if it is determined that the occupant is a child based on the level of the DC output of the receiving circuit, the airbag of the airbag device is set to a state where it cannot be deployed. Therefore, even if the vehicle collides, the airbag is not deployed, and appropriate control of the airbag device becomes possible.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram showing a first embodiment of an occupant detection system according to the present invention.

FIG. 2 is a specific electric circuit diagram of the information detection circuit shown in FIG.

FIG. 3 is an electric circuit diagram showing a second embodiment of the occupant detection system according to the present invention.

4A and 4B are diagrams for explaining the operation of the control unit shown in FIG. 1, wherein FIG. 4A is a waveform diagram of a line voltage of a transmission system, and FIG. 4B is an output of an AC-DC conversion circuit; FIG. 3C is a waveform diagram of a voltage, and FIG. 3C is a waveform diagram of an output voltage of the smoothing circuit.

FIG. 5 is an electric circuit diagram showing a third embodiment of the occupant detection system according to the present invention.

FIG. 6 is an electric circuit diagram showing a fourth embodiment of the occupant detection system according to the present invention.

FIG. 7 is an electric circuit diagram of an airbag device according to a conventional example.

FIG. 8 is an electric circuit diagram of an improved airbag device according to a conventional example.

9A and 9B are diagrams for explaining a basic operation of the occupant detection system according to the prior art, wherein FIG. 9A 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.

FIGS. 10A and 10B are diagrams showing an arrangement state of antenna electrodes on a sheet according to the prior art, wherein FIG. 10A is a side view and FIG. 10B is a plan view.

11A and 11B are configuration diagrams of the antenna electrode shown in FIG. 10, wherein FIG. 11A is a plan view and FIG.
FIG. 2C is a sectional view taken along the line X-Y, and FIG.

FIG. 12 is an electric circuit diagram of an occupant detection system according to the prior art.

13 is a specific electric circuit diagram of the receiving circuit shown in FIG.

14 is an electric circuit diagram of the airbag device in the occupant detection system shown in FIG.

15A and 15B are diagrams for explaining the operation of the control unit shown in FIG. 12, wherein FIG. 15A is a waveform diagram of a line voltage of a transmission system, and FIG. 15B is an output of an AC-DC conversion circuit; FIG. 3C is a waveform diagram of a voltage, and FIG. 3C is a waveform diagram of an output voltage of the smoothing circuit.

16A and 16B are views for explaining a seated state of an occupant in a sheet, wherein FIG. 16A is a view showing an adult seated state, and FIG. 16B is a view showing a child seated state.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 sheet 1a Seated part 1b Backrest part 5,5A Antenna electrode 10A, 10B, 10C Control unit 11,30 Electric field generation means 11a, 14a, 31a Resistance 11b Switching means 12,12A, 16 Connector 13 Impedance conversion circuit 13a Operational amplifier 14 AC-DC conversion circuit 14b Capacitor 15 Control circuit 17 Power supply circuit 20 Airbag device 31 Current detection circuit A, A _{1 to An} , AA Interface circuit for antenna electrode B, BB Correction interface Face circuit SS1, SS2 Surfing sensor SQ1, SQ2 Squib SW1, SW2 Switching element CC Control circuit GS Electronic acceleration sensor

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3D054 AA02 AA03 DD28 EE10 EE11 EE14 FF16

Claims (9)

[Claims] An antenna electrode 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 a signal supplied from the electric field generating means. An information detection circuit for detecting information related to a flowing current; an output signal in an initial state of the electric field generating means or a reference value data set in advance by using a plurality of output signals corresponding thereto; A control circuit for correcting information data from the information detection circuit based on the output signal from the generating means and judging a seating state of the occupant based on the corrected data. Detection system. 2. An antenna electrode 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 a signal supplied from the electric field generating means. An information detection circuit for detecting information related to a flowing current; an output signal in an initial state of the electric field generating means or a reference value data set in advance by using a plurality of output signals corresponding thereto; A control circuit that corrects information data from the information detection circuit based on the output signal from the generation means, and determines a seating state of the occupant based on the corrected data; and An occupant detection system, comprising: an airbag device having a function of setting an airbag in a predetermined operation mode. 3. A plurality of antenna electrodes disposed on and / or around the sheet, electric field generating means for generating a weak electric field around the antenna electrodes, and a specific antenna electrode among the plurality of antenna electrodes A first switching circuit for selectively switching and connecting the electric field generating means to the first switching circuit; and a first switching circuit connected to the output side of the first switching circuit so as to correspond to the plurality of antenna electrodes, and selected by the first switching circuit. An information detection circuit for detecting information related to a current flowing through a specific antenna electrode, a second switching circuit for selectively switching and outputting information output from each information detection circuit, and a second switching circuit. A receiving circuit for receiving the output of
Reference value data set using the output signal in the initial state of the electric field generating means or a plurality of output signals corresponding thereto in advance and the first and the second electric field generating means in the working state without passing through the information detecting circuit. The information data from the information detection circuit is corrected based on the signal data directly output via the second switching circuit, and the seating state of the occupant is determined based on the corrected data. An occupant detection system comprising a control circuit. 4. 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 electrodes, and a specific antenna electrode among the plurality of antenna electrodes A first switching circuit for selectively switching and connecting the electric field generating means to the first switching circuit; and a first switching circuit connected to the output side of the first switching circuit so as to correspond to the plurality of antenna electrodes, and selected by the first switching circuit. An information detection circuit for detecting information related to a current flowing through a specific antenna electrode, a second switching circuit for selectively switching and outputting information output from each information detection circuit, and a second switching circuit. A receiving circuit for receiving the output of
Reference value data set using the output signal in the initial state of the electric field generating means or a plurality of output signals corresponding thereto in advance and the first and the second electric field generating means in the working state without passing through the information detecting circuit. The information data from the information detection circuit is corrected based on the signal data directly output via the second switching circuit, and the seating state of the occupant is determined based on the corrected data. An occupant detection system, comprising: a control circuit; and an airbag device having a function of setting an airbag to a predetermined operation mode based on a result of determination by the control circuit. 5. The information detecting circuit according to claim 1, wherein the information detecting circuit is constituted by an impedance element connected in series to a transmission system of an output signal from the electric field generating means. The occupant detection system according to 1. 6. The apparatus according to claim 3, wherein said first and second switching circuits are constituted by analog switches.
The occupant detection system according to 1. 7. An AC-DC conversion circuit for converting an AC line voltage of a transmission system into a DC, and an AC-DC converter comprising:
5. The occupant detection system according to claim 3, further comprising a smoothing circuit for smoothing an output of the conversion circuit. 8. A buffer circuit is connected between the information detecting circuit and the electric field generating means.
4. The occupant detection system according to any one of 4. 9. A storage unit for storing at least an initial state output signal of the electric field generating means or reference value data set in advance using a plurality of output signals corresponding thereto, and A correction unit for correcting the information data from the information detection circuit based on the reference value data and the signal data directly output from the electric field generating means in the working state without passing through the information detection circuit; The occupant detection system according to any one of claims 1 to 4, further comprising: a determination unit configured to determine a seating state of the occupant based on the correction data of the correction unit.