JP2000211477A - Sear belt wear detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a seat belt wear detecting device difficult to generate wear/tear, even when connection/disconnection between a tongue plate and a buckle is repeated. SOLUTION: This detecting device detects the wear of a seat belt 15 of an occupant seated on a seat of a vehicle. In this case, the device is provided with a tongue plate 16 and a freely connectable buckle 18 mounted on the seat belt 15, non-contact detecting means 34, 35 generating outputs corresponding to existence/non-existence of the tongue plate 16 at a connecting location within the buckle 18 without contacting the tongue plate 16 and a judging means judging presence or absence of the wear of the seat belt 15 from outputs of the non-contact detecting means 34, 35.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seat belt wearing detecting device for detecting whether or not an occupant seated in a vehicle seat wears a seat belt.

[0002]

2. Description of the Related Art Conventionally, detection of seat belt wearing is performed by using a mechanical switch. That is, when the tongue plate of the seat belt is inserted into the buckle, the actuator of the detection switch disposed in the buckle is depressed, and the contact of the switch is switched to obtain a signal indicating that the seat belt is worn.

[0003]

However, due to the structure of the detection switch, mechanical contact between the tongue plate and the actuator is repeated, so that mechanical wear cannot be avoided. Also, the mechanical contacts are consumed.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a seat belt wearing detecting device which is less likely to be worn or worn even when the mounting and dismounting of the tongue plate and the buckle are repeated.

[0005]

According to the present invention, there is provided a seat belt wearing detecting device for detecting the wearing of a seat belt of an occupant seated in a vehicle seat, the seat belt wearing detecting device comprising: A buckle that can be connected to the tongue plate attached to the buckle; non-contact detection means that generates an output corresponding to the presence / absence of the tongue plate at the connection position in the buckle without contacting the tongue plate; Determining means for determining the presence or absence of the seat belt from the output of the detecting means.

[0006] With this configuration, it is possible to detect the wearing of the seat belt without contacting the tongue plate, and it is possible to extend the life of the seat belt wearing detecting device.

[0007] Preferably, the non-contact detecting means includes an ultrasonic sensor, a capacitance sensor, a magnetic sensor, and an optical sensor.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows a seat belt device. After sitting on the seat 12 of the vehicle, the occupant pulls out the seat belt 15 via the support portion 14 from the seat belt winding portion 13 attached to the side wall of the vehicle body. And the tongue plate 1 attached to the seat belt 15
6 is connected to one end of the buckle 18 so that the seat belt 15
Attach. The other end of the buckle 18 is attached to the floor of the vehicle body on the side of the seat or the lower part of the side of the seat via an attachment member such as a belt. Inside the buckle 18, a non-contact type sensor for detecting seat belt wearing is provided. The front end side of the seat belt 15 is attached to a lower portion of a side wall of the vehicle body by an anchor plate 19.

FIG. 2 schematically shows an example in which an ultrasonic sensor is used as a non-contact type sensor. In the figure, a tongue plate 16 through which a seat belt 15 is inserted is inserted into a buckle 18 and locked by a connecting mechanism 18a. On the inner side wall of the buckle 18, a transmitter 34 and a receiver 35 constituting a pickup portion of the ultrasonic sensor are provided. In a state where the tongue plate 16 is inserted into the buckle 18 (seat belt wearing state),
Ultrasonic wave radiated from the transmitter 34 (shown by a solid line in the figure)
Is reflected by the tongue plate 16 and returns to the receiver. In the state where the tongue plate 16 is not inserted into the buckle 18 (the state in which the seat belt is not fastened), the ultrasonic waves radiated from the transmitter 34 are reflected by the inner side wall opposite to the buckle 18 (indicated by a dotted line in the figure) and received. It returns to the wave device 35. Therefore, the propagation path length of the ultrasonic wave differs depending on whether the seat belt is worn or not.

FIG. 3 is a block diagram showing a control system of a seat belt wearing detecting device using the ultrasonic sensor.
FIG. 4 is an explanatory diagram for explaining a signal on the way.

The signal processing / control section 31 is constituted by a microcomputer system mounted on a vehicle, and supplies a pattern signal in which pulses having a constant period are continuous as shown in FIG. The modulator 32 is supplied from the carrier generator 33 by a pattern signal.
A 0 KHz carrier signal is modulated to form a modulation signal in which a 100 KHz carrier pulse is intermittent as shown in FIG. This modulated signal is provided to the transmitter 34 and is converted into intermittent ultrasonic waves. The ultrasonic waves radiated from the transmitter 34 are reflected by the tongue plate 16 or the inner wall and return to the receiver 35. The ultrasonic wave is converted into an electric signal by the receiver 35, and the level is amplified by the amplifier 36.
For example, noise is removed by a band-pass filter 37 having a center frequency of 100 KHz. This received signal is supplied to the demodulation unit 38, where it is subjected to level detection, demodulated into the original pattern signal as shown in FIGS. 4C and 4D, and supplied to the signal processing / control unit 31.

The signal processing / control unit 31 determines whether the time Δt from transmitting the pattern signal to receiving the reflected wave is within a predetermined time. Further, it is determined whether the transmission pattern of the pattern signal matches the reception pattern. The transmission and reception patterns match, and the response time Δt is within a first predetermined range, for example, 40 to 70 μs.
, It is determined that the tongue plate is in the connected state (seat belt wearing state). The signal processing / control unit 31 outputs a wearing signal or sets a seat belt wearing flag. Further, the respective patterns of the transmission and reception signals match, and the response time Δt is within a second predetermined range, for example, 100 to 130 μs.
, It is determined that the tongue plate is not connected (the seat belt is not fastened). The signal processing / control unit 31 outputs a wearing signal or sets a seat belt wearing flag.

Further, the signal processing / control unit 31 determines that the influence of disturbance noise is present when the patterns of the transmission and reception signals do not match or when the response time is not within a predetermined range.
The pattern signal is transmitted again to perform the detection operation. If the received signal cannot be obtained even after transmitting the pattern signal, it is determined that the seatbelt fastening detection device has failed, and a warning display of the failure of the seatbelt fastening detection device is displayed on the console panel or maintenance display of the vehicle. I do.

FIGS. 5 to 7 are explanatory diagrams for explaining the second embodiment. In this example, a capacitance type sensor is used.

FIG. 5 shows an example of a capacitance type sensor provided in a buckle. When the tongue plate 16 through which the seat belt 15 is inserted is inserted into the buckle 18, it is locked by the connecting mechanism 18a. Buckle 1
A plate-like electrode 41a is arranged on one side wall inside 8 through an insulator (not shown). A plate-like electrode 41b is also arranged on the other side wall via an insulator (not shown).
The electrodes 41a and 41b face each other and constitute a capacitor. In the state where the tongue plate 16 is not inserted into the buckle 18 (the state in which the seat belt is not fastened), the electrode 41 a
And 41b constitute a first capacitor. In a state where the tongue plate 16 is inserted into the buckle 18 (seat belt wearing state), the electrode 41a and the tongue plate 1
6, the tongue plate 16 and the electrode 41b constitute a second capacitor. Therefore, whether the seat belt is worn or not can be determined by discriminating the capacitance of the capacitor.

FIG. 6 shows an example of a device configuration for determining the capacitance of a capacitor. The capacitance detection unit 42 includes an electrode 41
Outputs corresponding to the capacitances of a and 41b are generated. This output is discriminated by the determination unit to determine whether or not the seat belt is worn, to output a seat belt wearing signal, or to set a flag indicating the seat belt wearing state in a status register of the computer system.

FIG. 7 shows an example of the configuration of the capacitance detecting section 42. In this example, a change in the capacitance is detected as a change in the cutoff frequency of the low-pass filter.

In FIG. 1, a resistor 42b and an electrode 41a
A low-pass filter (LPF) is constituted by the capacitor 41 formed by the capacitor 41 and the capacitor 41b. A high frequency signal having a frequency fo near the cutoff frequency is supplied from the high frequency oscillator 42a to the low pass filter. The output of the low-pass filter is converted into a level signal by a level detector (DET) formed by a diode 42c and a capacitor 42d, and is provided to a level comparator 43 as a determination unit. A predetermined reference voltage Vth is supplied to a comparison reference input of the level comparator 43.

The low-pass filter is a tongue plate 16
Is inserted between the two electrodes to increase the capacitance of the capacitor 41, the cutoff frequency is lowered, and the level of the passing high-frequency signal is greatly reduced. Further, when the capacitance of the capacitor 41 decreases, the cutoff frequency increases, and the decrease in the level of the passing high-frequency signal is reduced. When the comparison reference voltage Vth is set to an intermediate value between the two outputs of the level detector when the tongue plate 16 is inserted into the buckle 18 and when the tongue plate 16 is not inserted, the output of the level comparator 43 indicates whether the seat belt is fastened. The seat belt wearing signal shown is obtained.

FIGS. 8 to 10 are explanatory diagrams for explaining the third embodiment. In this example, a magnetic sensor is used.

FIG. 8 shows an example of a magnetic sensor provided in the buckle 18. When the tongue plate 16 through which the seat belt 15 is inserted is inserted into the buckle 18,
Locked by the coupling mechanism 18a. An excitation coil (electromagnet) 51 is provided on one side wall inside the buckle 18, and a magnetic sensor 52 is arranged on the other side wall. The magnetic sensor 52 indicates a resistance value according to the strength of the surrounding magnetic field. When the magnetic tongue plate 16 is inserted between the exciting coil 51 and the magnetic sensor 52, the tongue plate 1
6 is a kind of magnetic shield, and reduces the influence of the magnetic field by the exciting coil 51 on the magnetic sensor 52. Therefore,
By discriminating the output level of the magnetic sensor 52, it is possible to determine whether the seat belt is worn or not.

FIGS. 9 and 10 show an example of the configuration of a control system of a seatbell attachment detection device using a magnetic sensor. In the figure, a signal processing / control unit 54 includes an excitation coil 51
, An exciting current in an intermittent pattern is supplied to generate a magnetic field intermittently as shown in FIG. The signal processing / control unit 54 is configured by an on-board microcomputer system. When the tongue plate 16 is not inserted into the buckle 18, the output of the magnetic sensor 52 is relatively large and exceeds the determination reference voltage Vth. When the tongue plate 16 is inserted into the buckle 18, the radiated magnetic field of the exciting coil 51 is blocked by the tongue plate 16. The output of the magnetic sensor 52 becomes relatively small and falls below the determination reference voltage Vth. The output of the magnetic sensor 52 is A / D output by an interface (not shown) of the signal processing / control unit 54.
It is converted and written to the data memory by the DMA operation.

The signal processing / control unit 54 includes an exciting coil 51
If the output of the magnetic sensor 52 exceeds the determination value Vth as shown in FIG. The seat belt signal is not worn or the seat belt wearing flag of the status register is reset. The output of the magnetic sensor 52 is
As shown in FIG. 10C, when it does not exceed the determination value Vth, it is determined that the seat belt is worn. Set the seat belt signal to the seat belt signal or set the seat belt seat flag in the status register.

Further, the signal processing / control section 54 detects the seat belt attachment when the output cannot be obtained from the magnetic sensor 52 even when the exciting current is applied to the exciting coil 51 or when an abnormally high level is detected. Judging that the device is out of order, an error warning is displayed on the console panel. If the exciting current pattern to the exciting coil 51 does not match the output pattern of the magnetic sensor, or if the response time of the magnetic sensor to the supply of the exciting current is not within a predetermined range, it is determined that disturbance has been mixed and detection is performed again. Do.

The excitation coil 51 and the magnetic sensor 51
May be replaced with a light emitting diode and a phototransistor, respectively, to similarly configure a seat belt wearing detection device.

[0026]

As described above, the seatbelt fastening detection device of the present invention can determine seatbelt fastening without mechanically contacting the tongue plate, and therefore, high reliability of the sensor can be expected.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating an outline of a seat belt device.

FIG. 2 is an explanatory diagram illustrating an example of a sensor that detects seat belt wearing by ultrasonic waves.

FIG. 3 is an explanatory diagram illustrating a signal processing system when an ultrasonic sensor is used.

FIG. 4 is a signal waveform diagram illustrating some signals of the signal processing system shown in FIG. 3;

FIG. 5 is an explanatory diagram illustrating an example of a sensor that detects seat belt wearing by capacitance.

FIG. 6 is an explanatory diagram illustrating a signal processing system when an electrostatic capacitance type sensor is used.

FIG. 7 is a circuit diagram illustrating a configuration example of a capacitance detection unit 42;

FIG. 8 is an explanatory diagram illustrating an example of a sensor that detects seatbelt attachment by magnetism.

FIG. 9 is an explanatory diagram illustrating a signal processing system when a magnetic sensor is used.

10 is an explanatory diagram illustrating an example of a signal waveform in the signal processing system illustrated in FIG. 9;

[Explanation of symbols]

15 Seat belt 16 Tongue plate 18 Buckle 31, 54 Signal processing / control unit (microcomputer)

Claims (1)

[Claims] 1. A seat belt wearing detection device for detecting the wearing of a seat belt by an occupant seated in a vehicle seat, comprising: a buckle connectable to a tongue plate attached to the seat belt; and a connection in the buckle. Non-contact detecting means for generating an output corresponding to the presence / absence of the tongue plate at the position without contacting the tongue plate; and determining means for judging the presence or absence of the seat belt from the output of the non-contact detecting means. Equipped with a seat belt wearing detection device.