Airbag deployment monitor and sensing electronics

• US 20040207388A1
• Filed: 05/14/2004
• Published: 10/21/2004
• Est. Priority Date: 03/07/2003
• Status: Active Grant

• Current Assignee: Breed Automotive Technology, Inc. (Ningbo Junsheng Investment Group Co., Ltd.)
• Original Assignee: Breed Automotive Technology, Inc. (Ningbo Junsheng Investment Group Co., Ltd.)
• Inventors: Pettypiece, Robert P. Jr., Ilyes, Timothy, Monroe, Tex K.
• Granted Patent: US 6,838,870 B2
• Time in Patent Office: Days
• US Class Current: 324/178
• CPC Class Codes: B60R 2021/01095 optical
• CPC Class Codes: B60R 21/01504 detecting bag displacement
• CPC Class Codes: G01D 5/147 influenced by the movement of a third element, the position of Hall device and the source of magnetic field being fixed in respect to each other
• CPC Class Codes: G01D 5/2405 by varying dielectric
• CPC Class Codes: G01D 5/25 Selecting one or more conductors or channels from a plurality of conductors or channels, e.g. by closing contacts
• CPC Class Codes: G01P 3/66 using electric or magnetic means G01P3/80 takes precedence; measuring short time intervals G04F8/00, G04F10/00
• CPC Class Codes: G01P 3/68 using optical means, i.e. using infrared, visible, or ultraviolet light G01P3/80 takes precedence ; by reflection of waves G01S17/58

Abstract

An airbag deployment sensor has a cartridge containing a quantity of tape one end of which is attached to the inside surface of an airbag cushion. Deployment of the cushion pulls tape from the cartridge at a rate that is monitored by transmitting light through the tape, or by detecting the presence of metalized, or magnetic shielding portions, of the tape.

Claims

1. An airbag deployment monitor comprising:

a cartridge containing a length of tape, the tape having a first end attached to an inside surface of an airbag cushion, wherein the tape has first portions which allow a passage of light, and second portions which are substantially opaque, and wherein the first portions alternate with the second portions;

a light source positioned on the cartridge to illuminate one side of the tape; and

a light sensor positioned on the cartridge opposite the light source to receive light when a tape first portion is between the light source and the light sensor, the light sensor positioned to be shielded from the light source when the tape second portion is between the light source and the light sensor.

2. The airbag deployment monitor of claim 1 wherein the light source is a light emitting diode, and the light sensor is a phototransistor.

3. The airbag deployment monitor of claim 2 further comprising a comparator circuit with hysteresis connected to the phototransistor to provide a digital output each time a first tape portion alternates with a second tape portion.

4. The airbag deployment monitor of claim 2 wherein the light emitting diode is of the type which emits infrared light.

5. The airbag deployment-monitor of claim 1 wherein the tape is comprised of a black plastic film, and the first portions of the tape define holes through which light from the light source can pass.

6. An airbag deployment monitor comprising:

a cartridge containing a length of tape, the tape having a first end attached to an inside surface of an airbag cushion, wherein the tape has first portions which conduct electricity, and second portions which are substantially non-conductive, and wherein the first portions alternate with second portions;

a sensor mounted to the cartridge so that as the tape is drawn from the cartridge a first portion is positioned opposite the sensor, followed by a second portion, wherein the sensor provides an output which varies depending on whether the first portion, or the second portion is positioned opposite the sensor, so that the sensor output varies with time as tape is withdrawn from the cartridge.

7. The airbag deployment monitor of claim 6 wherein the sensor mounted to the cartridge forms a capacitor with the first portions that conduct electricity.

8. The airbag deployment monitor of claim 7 wherein the capacitor is part of an oscillator circuit having a frequency which varies in proportion to a capacitance value of the capacitor, so that as tape is drawn from the cartridge and conductive portions are successively brought opposite the sensor mounted to the cartridge the oscillator circuit produces a frequency modulated output.

9. The airbag deployment monitor of claim 8 wherein the sensor comprises two spaced apart metal plates that formed one side of the capacitor, wherein a second side of the capacitor is formed by the first portions which conduct electricity.

10. The airbag deployment monitor of claim 7 wherein the sensor mounted to the cartridge comprises:

an oscillator connected to a first metal plate;

a second metal plate spaced from the first metal plate, and wherein the first conductive portions when positioned opposite the first metal plate and the second metal plate form a capacitive couple between the oscillator and an output connected to the second metal plate.

11. The airbag deployment monitor of claim 10 wherein the oscillator circuit has a frequency of operation of about 300 kHz to about 1 MHz.

12. The airbag deployment monitor of claim 6 further comprising a magnet mounted to the cartridge, and wherein the sensor is a magnetic field sensor mounted spaced from the magnet so that the tape is positioned to move between the magnet and a magnetic field sensor, and wherein the first conductive portions contain a magnetically impermeable material to block magnetic field lines, and withdrawal of the tape from the cartridge produces a time varying output from the magnetic field sensor.

13. The airbag deployment monitor of claim 12 wherein the magnetic field sensor is a Hall effect sensor.

14. The airbag deployment monitor of claim 6 wherein the tape comprises an oriented polyester film.

15. The airbag deployment monitor of claim 12 wherein the first portions further comprise a metal alloy containing an effective amount of at least one metal selected from the group consisting of iron, nickel, or cobalt.

16. The airbag deployment monitor of claim 6 wherein the sensor mounted to the cartridge comprises two spaced apart contacts positioned on the cartridge to contact the tape as tape is withdrawn from the cartridge, the two spaced apart contacts being positioned to form a current path with the first portions which conduct electricity when a first portion is opposite the two contacts.

17. The airbag deployment monitor of claim 6 wherein the first portions are substantially opaque to light, and wherein the second portions transmit at least one frequency of light, wherein the sensor comprises a light sensor, and further comprising a light source positioned on the cartridge to shine light through the second portions to the light sensor.

18. An airbag deployment monitor comprising:

a cartridge containing a length of tape, the tape extending from the cartridge and defining a direction along the length, the tape having a first end attached to an inside surface of an airbag cushion, wherein the tape has first portions which conduct electricity, and second portions which are substantially nonconductive, and wherein the first portions and the second portions are serially positioned in the direction of the tape; and

a means for detecting the passage of the first portions so that the rate at which tape is withdrawn from the cartridge can be monitored.

19. A method for detecting the rate at which an airbag cushion is deploying comprising the steps of:

inflating an airbag cushion;

drawing a tape by a first end connected to the airbag cushion from a tape cartridge; and

monitoring the rate at which the tape is withdrawn from the cartridge by detecting the passage of metalized regions on the tape past a sensor.

20. The method of claim 19 wherein the step of monitoring the rate at which tape is withdrawn from the cartridge further comprises the step of forming a capacitor between a first portion of the sensor and one of the metalized regions on the tape, the sensor monitoring the changing capacitance, as the metalized region moves past the first portion of the sensor.

21. The method of claim 20 further comprising the step of forming an oscillator with a capacitor, wherein the frequency of the oscillator changes as the capacitance of the capacitor changes so that a frequency modulated signal is produced by the withdrawing tape.

22. The method of claim 20 wherein an oscillator output is coupled to the sensor by the capacitor so that output of the sensor is an amplitude modulated signal.

23. The method of claim 19 wherein the metalized regions are rendered impermeable by selection of a material to form the metalized regions which is resistant to penetration of magnetic field lines and further comprising the step of positioning a magnet on a first side of the tape, and positioning a magnetic field sensor on a side of the tape opposite the magnet, wherein the step of monitoring the rate at which the tape is withdrawn from the cartridge is by detecting the change in magnetic field strength detected by the magnetic field sensor.