JPH1111256A - Occupant detection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an occupant detection system capable of accurately detect only the presence or absence of seating of an occupant and also reducing a cost. SOLUTION: An occupant detection system is provided with a seat 1B, a substantially one antenna electrode 5 arranged approximately through the entire surface of a seating part 1a at least on the front side of the seat 1B, an oscillating circuit to generate a minute electric field around the antenna electrode 5, an amplitude control circuit to control the voltage amplitude of transmission signals transmitted from the oscillating circuit from the antenna electrode so that it is set approximately at a constant, a current detection circuit to detect, based on the minute electric field, a current flowing from the oscillating circuit to the antenna electrode through the amplitude control circuit, and a control circuit to detect, based on output signals from the current detection circuit, the presence or absence of the seating of an occupant on the seat 1B. Also the oscillating circuit, amplitude control circuit, current detection circuit, and control circuit are stored in the same housing so as to form a control unit 20, and the control unit 20 is arranged under the seat 1B.

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 an improvement in an occupant detection system capable of simply detecting the occupant's seating state in a passenger seat of a vehicle equipped with a seat belt.

[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.

As shown in FIG. 8, for example, this airbag device has a self-service sensor SS1, a squib SQ1,
A driver-side squib circuit comprising a series circuit of semiconductor switching elements SW1 such as field-effect transistors;
The output signal of the squib circuit on the passenger side, which is composed of the semiconductor sensor SW2 such as the safety sensor SS2, the squib SQ2, and the field effect transistor, the electronic acceleration sensor (collision detection sensor) GS, and the electronic acceleration sensor GS The control circuit CC has a function of determining the presence or absence of a collision based on the signal and supplying a signal to the gates of the semiconductor switching elements SW1 and 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, a signal is supplied to the gates of the semiconductor switching elements SW1 and SW2, and the switching elements SW1 and SW2 are turned on. Becomes ON state. As a result, current flows through each squib circuit,
Due to the heat generated by the squibs SQ1 and SQ2, the airbags on the driver's seat side and the passenger's seat side are deployed, and the occupant is protected from the impact due to the collision.

By the way, according to this airbag device,
For example, as shown in FIG. 9 (a), when an adult P is seated on the seat 1, the above-described occupant protection effect can be expected at the time of collision. However, as shown in FIG. (B), the passenger seat sheet - Child and fixed on sheet 1 sheet - if bets 1A infant SP is sitting backward (R ear F acing I nfant S eat: less, (Referred to as RFIS), since the deployment of the airbag may adversely affect the infant SP, it is desirable that the airbag should not be deployed even if the vehicle collides. Also, FIG.
As shown in (1), when the infant SP is sitting forward on the child seat 1A fixed on the seat 1 in the passenger seat ( F
orward F acing C hild S eat: less, since the air bag by the deployment of the air bag there is a concern that covers the face of the child SP to called FFCS), RFI
As in the case of S, it is desirable that the airbag should not be deployed even if the vehicle collides.

Therefore, conventionally, in order to cope with such a problem, for example, an airbag apparatus as shown in FIG. 10 has been proposed. In this airbag device, a sensor SD for detecting whether or not an occupant is seated in a passenger seat is installed, and a control circuit CC determines the seating status of the occupant in the passenger seat based on a detection signal of the sensor SD. When an automobile collides, the airbag is set to one of a deployable state and an undeployable state. In particular, as the sensor SD, a sensor using a weight sensor for measuring the weight, and a sensor SD that determines whether the child is an adult P or a child SP by photographing an occupant sitting on a sheet with a camera and performing image processing are proposed. Have been.

[0007] According to the former method, it is possible to roughly determine whether the occupant is an adult P or a child SP, and based on the result, the airbag is deployed in one of a state in which it can be deployed and a state in which it cannot be deployed. Although it can be set to avoid an unexpected situation in the event of a car collision, the weight varies greatly between individuals and even if a child is heavier than an adult, it is not only inaccurate, but also RFIS, FFCS
However, there is a problem that it is not possible to determine which of the above states.

According to the latter method, the occupant is seated, the occupant is determined to be an adult P or a child SP, and a child seat is provided.
It is possible to determine whether the child is in the state of RFIS or FFCS with high accuracy, but it is necessary to perform image processing on image data taken by a camera and make comparison judgments with various patterns. In addition, there is a problem that the processing apparatus becomes complicated and expensive.

[0009]

SUMMARY OF THE INVENTION Accordingly, the applicant has
Previously, an occupant detection system as shown in FIGS. 11 to 15 has been proposed. This occupant detection system basically has a weak electric field (Ele) generated between two electrodes arranged on a sheet.
ctric field). First, as shown in FIG. 11A, when the oscillation circuit 10 for generating a high-frequency low voltage is connected to the electrode E1 and the electrode E2 is connected to the ground, the electrodes E1 and E2 are connected based on the potential difference between the electrodes. An electric field is generated, and the displacement current I
d flows. In this state, when the object OB is present in the electric field, the electric field is disturbed and a displacement current Id1 different from the displacement current Id flows on the electrode E2 side, as shown in FIG. Become. Most objects OB are electrically represented by conductance and capacitance, and are coupled to ground via capacitance.

Therefore, the displacement current flowing on the side of the electrode E2 changes depending on whether the object OB is on or off the seat of the vehicle. By utilizing this phenomenon, It is possible to detect the occupant's seating status on the seat. In particular, by increasing the number of electrodes, it becomes possible to obtain a lot of information about an object including an occupant on the sheet, and it is possible to more accurately detect the occupant's seating state on the sheet.

A specific occupant detection system utilizing this principle will be described with reference to FIGS. still,
The same parts as those of the conventional example shown in FIGS. 8 to 10 are denoted by the same reference numerals, and detailed description thereof will be omitted. FIG. 12 shows a sheet according to the prior art, in which a plurality of electrodes are arranged on the front side of the sheet 1 in the passenger seat. Specifically, for example, rectangular electrodes E1 and E2 are arranged in the seating portion 1a, and electrodes E3 and E4 having substantially the same shape are arranged in the backrest portion 1b. These electrodes are formed of a conductive cloth in consideration of the occupant's comfort, but weaving a thread-like metal on the sheet cloth surface, applying conductive paint to the cloth surface, It can also be configured by arranging plates. These electrodes E1 to E4 are connected to and incorporated in the circuit shown in FIG. 13 (FIG. 14).

In FIG. 13, the occupant detection system has a frequency of about 100 KHz and a voltage of 10 to 12 V, for example.
An oscillation circuit 10 for generating a high-frequency low voltage of about the same level, a load current detection circuit 11, a transmission / reception switching circuit 12, a current / voltage conversion circuit 13 having an amplification function, a bandpass function (unnecessary noise removal function), A detection circuit (demodulation circuit) 14 having an AC-DC conversion function, an amplification circuit 15, an offset conversion circuit 16, and a control circuit 17 such as an MPU
And an airbag device 18. FIG.
13 is a further embodiment of the circuit of FIG. 13. The amplifier circuit 15 is composed of a first amplifier circuit 15A and a second amplifier circuit 15B having a gain G of 1 × and 100 ×, for example. An analog selection circuit 19 for selecting output signals of the second amplifier circuits 15A and 15B is provided.
The analog selection circuit 19 is controlled by the control circuit 17.

In this system, the load current detecting circuit 11 comprises, for example, an impedance element such as a resistor 11a connected in series to the circuit, and an amplifier 11b for amplifying a terminal voltage of the resistor 11a. 10
The current (load current) supplied to the specific electrode selected from is detected. The transmission / reception switching circuit 12 includes, for example, switching means Aa to Ad for connecting one selected electrode (referred to as a transmission electrode) among the electrodes E1 to E4 to the output side of the oscillation circuit 10; The switching circuits Ba to Bd for connecting the other electrodes (referred to as receiving electrodes) to the current / voltage conversion circuit 13 are controlled by the control circuit 17. It is desirable that the transmission / reception switching circuit 12 be constituted by a multiplexer circuit. The current / voltage conversion circuit 13 includes, for example, an impedance element such as a resistor 13a for converting a displacement current flowing on the receiving electrode side into a voltage, and an amplifier 13 for amplifying the converted voltage.
b, and are provided corresponding to the respective electrodes E1 to E4. The analog selection circuit 19 includes, for example, four switching means 19a which are simultaneously selected and connected to the output side of the second amplification circuit 15B, and four switching means 19 which are simultaneously selected and connected to the output side of the first amplification circuit 15A. And a switching means 19b.

The system configured as described above operates as follows. First, based on a signal from the control circuit 17, only the switching means Aa of the transmission / reception switching circuit 12 is connected to the output side of the oscillation circuit 10, and the switching means Bb to Bd are connected to the current / voltage conversion circuit 13. ,
A high-frequency low voltage is applied from the oscillation circuit 10 to the transmission electrode E1, and a displacement current flows through the reception electrodes E2 to E4. This current is converted to a voltage by the resistor 13a, amplified by the amplifier 13b, and output to the detection circuit 14. On the other hand, the load current flowing through the transmission electrode E1 is detected by the load current detection circuit 11 and output to the detection circuit 14 as data R (1, 1) described later. In the detection circuit 14, for example, a signal of about 100 KHz is band-passed, unnecessary noise components are removed, and the first and second amplification circuits 15A and 15A are removed.
B. The first and second amplifier circuits 15A, 15A
The output signal of 5B is appropriately selected by the operation of the offset conversion circuit 16 and the analog selection circuit 19, and is output to the control circuit 17. For example, when the output signal from the detection circuit 14 can be measured in the full range, only the four switching means 19b of the analog selection circuit 19 are simultaneously selected and connected to the output side of the first amplification circuit 15A.
When it is difficult to measure a subtle change in a full range due to a small output signal, only the four switching means 19a of the analog selection circuit 19 are simultaneously operated by the second amplification circuit 15B.
Is selected and connected to the output side. Then, in the control circuit 17, the output signals from the first and second amplifier circuits 15A and 15B are A / D converted and then stored in the memory.

Next, based on a signal from the control circuit 17, the switching means Aa of the transmission / reception switching circuit 12 is opened, only the switching means Ab is connected to the output side of the oscillation circuit 10, and the switching means Ba, Bc, Bd
When connected to or changed to the voltage conversion circuit 13, a high-frequency low voltage is applied from the oscillation circuit 10 to the transmission electrode E2, and the reception electrode E
A displacement current flows through 1, 1, 3 and E4. This current is converted to a voltage by the resistor 13a, amplified by the amplifier 13b, and output to the detection circuit 14. The load current flowing through the transmission electrode E2 is detected by the load current detection circuit 11 and output to the detection circuit 14 as data R (2, 2) described later. The data is processed in the same manner as described above and stored in the control device 17 as data. Next, the switching means Ac
Only to the output side of the oscillation circuit 10 and the switching means Ba, Bb, Bd to the current / voltage conversion circuit 13.
When changed, a high-frequency low voltage is applied from the oscillation circuit 10 to the transmission electrode E3, and a displacement current flows to the reception electrodes E1, E2, and E4. The load current flowing through the transmission electrode E3 is detected by the load current detection circuit 11, and the data R described later is used.
The signal is output to the detection circuit 14 as (3, 3). further,
When only the switching means Ad is connected to the output side of the oscillation circuit 10 and the switching means Ba, Bb, Bc is connected or changed to the current / voltage conversion circuit 13, a high-frequency low voltage is applied from the oscillation circuit 10 to the transmission electrode E4, Receiving electrode E1,
A displacement current flows through E2 and E3. These displacement currents are converted into voltages by the resistor 13a, amplified by the amplifier 13b, and output to the detection circuit 14. The transmission electrode E
4 is detected by a load current detection circuit 11 and is detected as data R (4, 4) to be described later.
4 is output. The processing is performed in the same manner as described above, and the control device 17
Is stored as data.

The control circuit 17 calculates the seating pattern by arithmetically processing these data. Various types of seating patterns are stored in the control circuit 17 in advance, and the seating patterns calculated by data based on various combinations of the transmitting electrodes and the receiving electrodes in the electrodes E1 to E4 are stored in advance. The stored seating pattern is compared with the stored seating pattern, and the corresponding seating pattern is extracted and determined. In the control circuit 17, for example, various seating patterns described below are provided.
Is the target of the determination. Specifically, an empty seat pattern where no occupant is seated on the seat, an FFCS pattern where the child is seated in the child seat in the FFCS state, and a child seat where the child is in the RFIS state. R sitting at
The FIS pattern is a person pattern in which an adult is seated on a sheet. Each of the electrodes E1 to E4 is appropriately selected, and various combinations of transmission electrodes and reception electrodes are used.
The data represented by the general formula R (i, j) is obtained. In the general formula R (i, j), i = j indicates transmission data, and i ≠
j indicates reception data, i indicates a transmission electrode, and j indicates a reception electrode. In the control circuit 17, arithmetic processing is performed using, for example, 16 pieces of data for each pattern, and the characteristics of the seated pattern are extracted.

When the seating pattern is detected and specified by the control circuit 17, a signal based on the detected pattern is transmitted to the airbag device 18. For example, the seating pattern is vacant, FFC
In the case of S, RFIS, a signal is sent to the airbag device 18 to set the airbag so that the airbag will not be deployed even if the vehicle collides. In other patterns, the airbag is deployed. Is transmitted to set the value. These signals are inputted to the control circuit CC of the airbag device 18, and in the case of the former pattern, the gate signal is set so as not to be supplied to the semiconductor switching element SW2 on the passenger seat side at the time of collision. A gate signal is supplied to the semiconductor switching element SW1 on the driver's seat side. In the latter case, it is set so that a gate signal is supplied to the semiconductor switching elements SW1 and SW2.

According to this prior art, a plurality of electrodes E1 to E4 are arranged on the front surface side of the sheet 1, and between one selected transmitting electrode and a receiving electrode other than the transmitting electrode. Since a weak electric field is generated by the application of the high-frequency low voltage, a displacement current relating to the seating pattern of the occupant on the sheet 1 flows on the receiving electrode side. Therefore, the occupant's seating pattern can be accurately detected by determining the characteristic pattern of the displacement current. For this reason, the airbag of the airbag device 18 can be set to any of a deployable state and an undeployable state according to the seating pattern of the occupant.

Further, since a plurality of electrodes are arranged on the sheet 1 at a distance from each other, the number of combinations of transmitting electrodes and receiving electrodes can be increased, and the number of obtained data can be increased. -It is possible to more accurately determine the pattern in which the occupant is seated.

The control circuit of the system includes, for example, an RF
Since the current pattern characterized by the current flowing through each electrode based on the seating pattern of IS, FFCS, Person, Empty is stored in advance as the seating pattern, the transmitting electrode and the receiving electrode are appropriately set. By comparing received signal data obtained by combining the above with various kinds of seating patterns stored in advance and extracting the corresponding stored seating pattern, the actual seating pattern can be accurately detected.
It is possible to obtain excellent effects such as the ability to detect noise.

However, recently, depending on the type of automobile, an occupant detection system having only a function of simply determining whether or not the occupant is seated in the passenger seat may be required. When the above-described occupant detection system according to the prior art is applied to such a vehicle, RFIS, FFCS,
Although the various seating patterns of Person and Empty have the function of accurately identifying and detecting the seating, only the function of detecting the presence or absence of the occupant is used, resulting in excessive quality and unnecessarily high cost. There is a problem.

On the other hand, for example, as shown in FIG.
Sensor S for detecting whether or not an occupant is seated in the passenger seat
If a weight sensor is used as D, the cost of the system can be effectively reduced, but the weight sensor only detects the weight of the object located in the passenger seat, and discriminates between a person and an object other than a person by weight. And there is a problem that another means must be adopted.

Therefore, recently, depending on the type of vehicle, there is a demand for an occupant detection system which can not only reliably detect the presence or absence of an occupant sitting on a seat, but also can be configured at a low cost.

Therefore, an object of the present invention is to provide an occupant detection system capable of reliably detecting only the presence or absence of an occupant in a seat and reducing the cost.

[0025]

SUMMARY OF THE INVENTION Accordingly, in order to achieve the above objects, the present invention provides a seat and substantially at least a seating portion on at least the front side of the seat. One antenna electrode, an oscillation circuit for generating a weak electric field around the antenna electrode, and a current detection circuit for detecting a current flowing from the oscillation circuit to the antenna electrode based on the weak electric field generated around the antenna electrode A control circuit for detecting the presence or absence of an occupant in the seat based on an output signal of the current detection circuit,
According to a second aspect of the present invention, the oscillation circuit, the current detection circuit,
The control unit includes a control circuit, and these circuits are housed in the same housing to form a control unit.
It is characterized in that it is arranged at

A third aspect of the present invention provides a sheet, substantially one antenna electrode disposed at least over substantially the entire seating portion on the front side of the sheet, and a peripheral portion of the antenna electrode. An oscillation circuit for generating a weak electric field at
An amplitude control circuit that controls the voltage amplitude of a transmission signal transmitted from the oscillation circuit to the antenna electrode to be substantially constant,
A current detection circuit for detecting a transmission current flowing from the oscillation circuit to the antenna electrode via the amplitude control circuit based on the weak electric field, and detecting whether or not the occupant is seated on the sheet based on an output signal of the current detection circuit. A fourth invention is characterized in that the oscillation circuit, the amplitude control circuit,
It is characterized in that it includes a current detection circuit and a control circuit, and these circuits are housed in the same housing to form a control unit, and this control unit is arranged on a sheet.

According to a fifth aspect of the present invention, the amplitude control circuit comprises at least an amplitude variable circuit capable of varying the voltage amplitude of the transmission signal, and an amplitude detection circuit detecting the voltage amplitude of the transmission signal. According to a sixth aspect of the present invention, the oscillation circuit controls a high frequency low voltage based on an output signal of the amplitude detection circuit so that a voltage amplitude of the transmission signal is controlled to be substantially constant. The antenna is characterized in that a weak electric field is generated around the antenna electrode by applying the high frequency low voltage to the antenna electrode.

Further, according to a seventh aspect of the present invention, the antenna electrode is formed so as to extend over substantially the entire surface of the seating portion of the sheet and to extend a part of the antenna portion. An eighth aspect of the present invention is characterized in that the antenna section includes a conductive section and a connector provided on the conductive section. The eighth invention is characterized in that the width of the conductive section of the antenna electrode is formed smaller than the width of the antenna section. The tenth invention is characterized in that a connector connected to an oscillation circuit via at least a current detection circuit is provided in a housing of the control unit, and a connector of an antenna electrode is electrically connected to the connector. The control circuit compares the occupant's seating pattern stored in advance with a seating pattern calculated based on the output signal of the current detection circuit to detect whether or not the occupant is seated. Control In the eleventh aspect, the control circuit displays a warning light based on a result of determining whether or not the occupant is seated on the seat and a result of detecting the state of seat belt attachment. Control as described above.

[0029]

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. Incidentally, the basic principle of the present invention is to utilize the disturbance of a weak electric field generated around the antenna electrode basically in the same manner as the above-mentioned prior art, and specifically, it is arranged on a sheet. A weak electric field is generated around one antenna electrode, and the presence or absence of an occupant sitting on a seat is detected based on a transmission signal flowing through the antenna electrode based on electric characteristics of an object located around the antenna electrode. This is slightly different from the prior art in this respect.

FIG. 1 shows a passenger seat according to the present invention. The seat 1B is mainly composed of a seat 1a and a backrest 1b. This sheet 1B
For example, a sheet fixed to a base 2 that can slide back and forth
A toe frame 3; a cushion member 4 arranged on the upper part of the seat frame 3; an antenna electrode 5 arranged along the surface of the cushion member 4 and over substantially the entire seating portion 1a; Exterior material 6 arranged so as to cover electrode 5
It is composed of A control unit 20, which will be described later, is arranged inside the sheet 1B, for example, in the sheet frame 3. Although the antenna electrode 5 is arranged inside the exterior material 6, it can be arranged outside it, and the meaning of “at least on the surface side of the sheet... It includes both.

In particular, the antenna electrode 5 is formed of a conductive cloth in consideration of the occupant's sitting comfort. For example, a thread-like metal is woven into a sheet cloth surface, or a conductive paint is coated on the cloth surface. It can also be constructed by attaching it or arranging a metal plate. As shown in FIG. 2, the antenna electrode 5 is formed so as to extend over substantially the entire surface of the seating portion 1a and to extend from a part of the antenna portion 5a with a narrower width. Conductive part 5b and conductive part 5b
And a hook-type connector 5c which is caulked and fixed to the lead-out end of the connector so as to have an electrical connection relationship.
In particular, the conductive portion 5b of the antenna electrode 5 is arranged so as to extend from the front side of the cushion member 4 to the sheet frame side, and the connector 5c at the lead-out end is connected to the control unit 2 described later.
0 connector 28. The connector 5c
In addition to the hook type, any type such as a pin type and a jack-plug type can be applied.

A control unit 20 is fixed to the above-mentioned sheet 1B.
As shown in FIG. 1, an oscillation circuit 21 for generating a high-frequency low voltage having a frequency of about 100 KHz and a voltage of about 5 to 12 V, for example, and an amplitude control circuit 22 for controlling a voltage amplitude of a transmission signal from the oscillation circuit 21 to be substantially constant. A current detection circuit 25 for detecting a transmission current of a transmission signal; and a current detection circuit 25
AC-DC conversion circuit 26 for converting the output signal of
And an amplifier 27 for amplifying an output signal of the AC-DC conversion circuit 26, a connector 28 connected to the current detection circuit 25 and disposed in the housing, and a control circuit 29 such as an MPU.
A connector 30 disposed on the housing and connected to a battery power source (not shown);
9 and a power supply circuit 31 connected between them. The control circuit 29 of the control unit 20 is connected to, for example, a seat belt warning light 32 and a seat belt detection circuit 33 for detecting a seat belt wearing state.

In the control unit 20, the amplitude control circuit 22 includes, for example, an amplitude variable circuit 23 for varying the voltage amplitude of the transmission signal and an amplitude detection circuit 24 for detecting the voltage amplitude of the transmission signal. The variable amplitude circuit 23 includes, for example, a programmable gain amplifier (PG
A), the amplitude detection circuit 24 includes a voltage amplitude detection unit 24a such as an operational amplifier and an AC-DC conversion circuit 24b that converts an output signal of the detection unit 24a into a direct current. And an amplifier 24c for amplifying the output signal of the AC-DC conversion circuit 24b. The output signal of the amplifier 24c is supplied to the control circuit 29, and the variable amplitude signal for the variable amplitude section 23a is output from the control circuit 29.

In the control unit 20, the current detection circuit 25 includes, for example, an impedance element such as a resistor 25a connected in series to a circuit (transmission signal system), and a differential amplifier for amplifying the terminal voltage of the resistor 25a. Amplifier 2
5b. The output side of the current detection circuit 25 is connected to a control circuit 29 via an AC-DC conversion circuit 26 and an amplifier 27. And the current detection circuit 2
The output side of the resistor 25a at 5 is connected to a connector 28 arranged to be exposed on the outer surface of the housing.

The occupant detection system thus configured operates as follows. First, when a high frequency low voltage is transmitted from the oscillation circuit 21, the voltage amplitude thereof is detected by the detection unit 24a of the amplitude detection circuit 24, and the detection signal is A
It is converted to DC by the C-DC conversion circuit 24b, and
The signal is amplified at 4c and input to the control circuit 29. The control circuit 29 determines whether the detected voltage amplitude has a predetermined amplitude value, and outputs an amplitude variable signal for correcting the detected voltage amplitude to the predetermined voltage amplitude to the amplitude variable section 23a. Thereby, the voltage amplitude of the transmission signal is corrected to a predetermined amplitude,
Thereafter, the amplitude is controlled to be constant by the cooperative operation of the amplitude variable circuit 23 and the amplitude detection circuit 24.

The transmission signal having a constant voltage amplitude is supplied to the antenna electrode 5 via the current detection circuit 25 and the connector 28. As a result, a weak electric field is generated around the antenna electrode 5, and the sheet 1B A different level of current flows from the oscillation circuit 21 to the antenna electrode 5 depending on whether or not a passenger is seated. This current is detected by a current detection circuit 25, converted into a direct current by an AC-DC conversion circuit 26, amplified by an amplifier 27, and input to a control circuit 29. The control circuit 29 previously stores a current pattern (or current level) flowing through the antenna electrode 5 when an occupant is seated on the seat 1B, and the control circuit 29 stores this current pattern. And the input current pattern (or current level) is compared and determined. The current detected by the current detection circuit 25 increases when the occupant is seated on the seat 1B, decreases when the occupant is not seated, and there is a clear level difference between the two. is there.

Next, when the control circuit 29 detects that the occupant is seated on the seat 1B, and the seat belt detection circuit 33 detects that the occupant does not wear the seat belt. The control circuit 29 outputs a warning signal to the seat belt warning light 32 to make the warning light blink. If the occupant wears the seat belt, no warning signal is output to the seat belt warning light 32, and the warning light does not blink. Further, if the occupant is not seated on the seat 1B, the seat belt warning lamp 32 does not operate regardless of the output signal from the seat belt detection circuit 33. When an object other than a person, for example, a luggage is placed in the passenger seat, since the dielectric constant is smaller than that of the person, the amount of current detected by the current detection circuit 25 is also reduced by the occupant. It is smaller than the case where there is no occupant, and it is not erroneously determined that the occupant is seated.

Next, the processing flow of the occupant detection system will be described.
Will be described with reference to FIG. In the figure, first, an ignition switch is turned on to start. Initialization is performed in step S1, and the process proceeds to step S2. In step S2, an initial diagnosis is performed on the communication system between the control circuit 29, the seat belt warning lamp 32, the seat belt detection circuit 33, and the like. In step S3, the oscillation circuit 21
The transmission current flowing from the antenna to the antenna electrode 5 is detected by the current detection circuit 2
5, and the detection signal is taken into the control circuit 29 via the AC-DC conversion circuit 26 and the amplifier 27. In step S4, the fetched current data is compared with current data stored in the control circuit 29 in advance to determine whether or not the occupant is seated. And see
A comprehensive judgment is made on the detection signal taken from the belt detection circuit 33 and a warning signal is output to the seat belt warning lamp 32 depending on the judgment. When step S4 ends, the process returns to step S3 again, and the same processing is repeated.

According to this embodiment, a weak electric field is generated around the antenna electrode 5 based on the high-frequency low voltage supplied from the oscillation circuit 21 to the antenna electrode 5, and the current flowing based on the weak electric field is generated. Varies depending on the object existing on the sheet 1B. In particular, when the object is a person, a current having a level difference that can be distinguished from the other objects flows. Therefore, by detecting the current flowing in the transmission signal system by the current detection circuit 25, it is possible to easily detect whether or not the occupant is seated on the seat 1B.

In particular, since the antenna electrode 5 is arranged over substantially the entire surface of the seat 1a of the sheet 1B, the antenna electrode 5 is disposed on the seat 1a of the sheet 1B for some reason as shown in FIG. Water wet (W) occurs, and the water wet part W
Even when the antenna portion is electrically connected to the antenna portion 5a, the area of the antenna electrode does not substantially increase and does not change at all. For this reason, the current level flowing in the transmission signal system does not change due to the water wetting, and the presence or absence of the occupant can be reliably detected regardless of whether the sheet 1B is wet.

In addition, since the antenna electrode 5 is composed of one, the circuit configuration is simplified as compared with the above-described prior art using a plurality of electrodes, and the system cost is reduced. Can be reduced.

Since the voltage amplitude of the transmission signal transmitted to the antenna electrode 5 is controlled by the amplitude control circuit 22 so as to be substantially constant, the judgment element in the control circuit 29 is specified only for the current element. Will be. Therefore, highly reliable and accurate detection is possible by a simple comparison between the current detected by the current detection circuit 25 and the current pattern stored in the control circuit 29.

Further, the control circuit 29 determines whether the occupant is in the seat 1B based on the detection result of the occupant and the state of the seat belt.
If the seat belt is not fastened despite the fact that the seat belt is not seated, a warning signal is output to the seat belt warning light 32, and the warning light flashes, so that the seat belt is urged to be worn. It is possible to expect safety during driving.

Further, the antenna section 5 is
Since the conductive portion 5b is formed to extend from a part of a, and the connector 5c provided on the conductive portion 5b is connected to the connector 28 of the control unit 20 disposed on the sheet 1B, The harness connecting the antenna unit 5a and the control unit 20 can be omitted completely. Therefore, the cost of the system can be effectively reduced in combination with the above-described unification of the antenna electrode 5 and simplification of the circuit configuration.

In this embodiment, when it is detected that the occupant is not seated in the passenger seat, the airbag is set in an airbag device (not shown) so that the airbag will not be deployed even if the vehicle collides. Control signal 29
It can also be configured to transmit from.

FIG. 6 shows a second embodiment of the occupant detection system according to the present invention, and the basic configuration is the same as that of the above-described embodiment. The difference is that one antenna electrode 5A is arranged on almost the entire surface of the seating portion 1a and the backrest portion 1b of the sheet 1C. Extending substantially an antenna unit 5a ₁ disposed over the entire surface, and the antenna portion 5a ₂ arranged on the backrest portion 1b, a narrow state width from the side of the antenna portion 5a ₁ of the antenna electrode 5A is seated portion 1a And a connector 5c provided at an end of the conductive portion 5b.
b is arranged from the side surface of the sheet 1C toward the control unit 20, and the connector 5c is connected to the control unit 20.

According to this embodiment, since the area of the antenna electrode 5A is significantly increased, it is expected that the occupant detection accuracy is further improved. The area of the antenna portion 5a ₁ and the antenna portion 5a ₂ is - can be changed and set as appropriate according to the area of the root section.

FIG. 7 shows a third embodiment of the occupant detection system according to the present invention.
This is the same as the embodiment. The difference is that the antenna section 5a and the conductive section 5b are composed of two pieces, and the antenna section 5a and the conductive section 5b are connected by connectors 5c provided respectively. Although this conductive portion 5b is disadvantageous in terms of cost, it can be replaced by a wire harness.

It should be noted that the present invention is not limited to the above-described embodiment, and the shape of the antenna electrodes arranged on the sheet may be rectangular, circular, elliptical, or polygonal except square. It can also be formed. Further, the output frequency of the oscillation circuit can be set to a value other than 100 KHz according to the detection target or the like, and the voltage can be used even when the voltage is outside the range of 5 to 12 V. Further, the oscillation circuit can be integrated and omitted in the control circuit to further reduce the cost, and in some cases, the amplitude control circuit can be omitted. Further, the interlocking with the seat belt mounting state can be omitted.

[0050]

As described above, according to the present invention, a weak electric field is generated around the antenna electrode based on the high-frequency low voltage supplied from the oscillation circuit to the antenna electrode. The current that flows depends on the objects present on the sheet. In particular, when the object is a person, a current having a level difference that can be distinguished from the other objects flows. Therefore, by detecting the current flowing in the transmission signal system by the current detection circuit, it is possible to easily detect whether or not the occupant is seated on the seat.

In particular, since the antenna electrode is disposed over substantially the entire seating portion of the sheet, the seating portion of the sheet may be wetted for some reason, and the wetted portion and the antenna portion may be separated from each other. Even if electrically connected, the area of the antenna electrode does not substantially increase and does not change at all. For this reason, there is no change in the level of the current flowing through the transmission signal system due to the water wetting, and it is possible to reliably determine whether or not the occupant is seated irrespective of the sheet being wet.

In addition, since the antenna electrode is composed of one, the circuit configuration is simplified and the system cost can be reduced as compared with the above-described prior art using a plurality of electrodes. .

Further, a conductive portion extends from a part of the antenna portion to the antenna electrode to be integrally formed, a connector is provided on the conductive portion, and the connector is connected to a connector of a control unit arranged on the sheet. By doing so, it is possible to completely omit the harness connecting the antenna unit and the control unit. Therefore, the cost of the system can be effectively reduced in combination with the above-described unification of the antenna electrodes and simplification of the circuit configuration.

[Brief description of the drawings]

1A and 1B show a seat of an occupant detection system according to the present invention, wherein FIG. 1A is a sectional view of a main part of the sheet, and FIG. .

FIGS. 2A and 2B are diagrams showing antenna electrodes of the occupant detection system according to the present invention, wherein FIG. 2A is a plan view and FIG.
FIG. 3 is a cross-sectional view of a connector portion in the conductive portion.

FIG. 3 is a circuit block diagram of a control unit of the occupant detection system according to the present invention.

FIG. 4 is an essential part cross-sectional view showing a connection state between the control unit and the antenna electrode shown in FIG. 3;

FIG. 5 is a flowchart of occupant detection by the occupant detection system according to the present invention.

6 (a) is a side view, and FIG. 6 (b) is a partially broken plan view of FIG. 6 (a), showing another embodiment of the sheet according to the present invention. FIG. 3C is a plan view of the antenna electrode.

FIG. 7 is a plan view showing still another embodiment of the antenna electrode according to the present invention.

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

9A and 9B are diagrams showing various seating patterns, wherein FIG. 9A shows a state in which an adult occupant is seated on a sheet, and FIG. 9B shows an RFIS state. FIG.
9 is a diagram showing a state of FFCS.

FIG. 10 is a circuit block diagram of an improved airbag device according to a conventional example.

FIG. 11 is a diagram for explaining a basic operation of the occupant detection system according to the prior art which is a premise of the present invention, wherein FIG. 11 (a) is a diagram showing an electric field distribution between electrodes, and FIG. FIG. 4 is a diagram showing an electric field distribution when an object exists between electrodes.

FIG. 12 is a perspective view of a seat of the occupant detection system according to the prior art.

FIG. 13 is a circuit block diagram of an occupant detection system according to the prior art.

FIG. 14 is a specific circuit block diagram of FIG.

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

[Explanation of symbols]

1B, 1C sheet - DOO 1a seating portion 1b backrest 3 - Tofure - arm 4 cushion member 5, 5A, 5B antenna electrode 5a, 5a _1, 5a ₂ antenna portion 5b conductive portion 5c connector 6 exterior material 20 control unit 21 oscillation Circuit 22 Amplitude control circuit 23 Amplitude variable circuit 24 Amplitude detection circuit 25 Current detection circuit 26 AC-DC conversion circuit 27 Amplifier 28, 30 Connector 29 Control circuit 31 Power supply circuit 32 Seat belt warning light 33 Seat belt detection circuit

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Masahiro Ohto 1-1-25 Shinurashima-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Inside of NEC Robotics Engineering Co., Ltd.

Claims (11)

[Claims] 1. A sheet, substantially one antenna electrode disposed at least over substantially the entire seating portion on the front side of the sheet, and oscillation for generating a weak electric field around the antenna electrode. A circuit, a current detection circuit for detecting a current flowing from the oscillation circuit to the antenna electrode based on a weak electric field generated around the antenna electrode, and an occupant sitting on the seat based on an output signal of the current detection circuit. An occupant detection system, comprising: a control circuit for detecting presence / absence. 2. A control unit comprising the oscillating circuit, the current detecting circuit, and the control circuit, wherein these circuits are housed in the same housing to form a control unit, and the control unit is arranged on a sheet. Item 9. The occupant detection system according to item 1. 3. A sheet, substantially one antenna electrode disposed at least over substantially the entire seating portion on the front side of the sheet, and oscillation for generating a weak electric field around the antenna electrode. A circuit, an amplitude control circuit that controls the voltage amplitude of a transmission signal transmitted from the oscillation circuit to the antenna electrode to be substantially constant, and a transmission that flows from the oscillation circuit to the antenna electrode via the amplitude control circuit based on the weak electric field. An occupant detection system comprising: a current detection circuit for detecting a current; and a control circuit for detecting whether or not an occupant is seated on a sheet based on an output signal of the current detection circuit. 4. A control unit including the oscillation circuit, the amplitude control circuit, the current detection circuit, and the control circuit, wherein these circuits are housed in the same housing to constitute a control unit, and the control unit is arranged on a sheet. The occupant detection system according to claim 3, wherein: 5. The amplitude control circuit according to claim 1, wherein said amplitude control circuit includes at least an amplitude variable circuit capable of varying a voltage amplitude of a transmission signal and an amplitude detection circuit detecting a voltage amplitude of the transmission signal. 4. The occupant detection system according to claim 3, wherein the amplitude variable amount by the amplitude variable circuit is controlled so that the voltage amplitude of the transmission signal is substantially constant. 6. The oscillating circuit is configured to generate a high-frequency low voltage, and by applying the high-frequency low voltage to an antenna electrode, a weak electric field is generated around the antenna electrode. The occupant detection system according to claim 1 or 3, wherein 7. The antenna device according to claim 1, wherein the antenna electrode is provided on an antenna portion disposed over substantially the entire seating portion of the sheet, a conductive portion formed by extending a part of the antenna portion, and a conductive portion. 4. The connector according to claim 1, wherein said connector comprises a connector.
The occupant detection system described. 8. The antenna according to claim 7, wherein the width of the conductive portion of the antenna electrode is smaller than the width of the antenna portion.
The occupant detection system described. 9. The control unit according to claim 7, wherein a connector connected to an oscillation circuit via at least a current detection circuit is provided on a housing of the control unit, and a connector of an antenna electrode is electrically connected to the connector. The occupant detection system described. 10. The control circuit compares an occupant's seating pattern stored in advance with a seating pattern calculated based on an output signal of the current detection circuit to determine whether or not the occupant is seated. The occupant detection system according to claim 1, wherein the occupant detection system is controlled to detect the occupant. 11. The control circuit controls to display a warning light based on a determination result of presence or absence of an occupant in a seat and a detection result of a seat belt wearing state. The occupant detection system according to claim 1 or 3, wherein