Acceleration sensor pick-up with magnetic base stabilization

• US 4,900,925 A
• Filed: 08/04/1988
• Issued: 02/13/1990
• Est. Priority Date: 08/04/1987
• Status: Expired due to Fees

• Current Assignee: Daimler-Benz AG (Mercedes-Benz Group AG)
• Original Assignee: Daimler-Benz AG (Mercedes-Benz Group AG)
• Inventors: Knoll, Heinz W., Pfistner, Harald, Petri, Volker, Andres, Rudolf
• Primary Examiner(s): Nelms, David C.
• Application Number:
  US07/228,106
• Time in Patent Office: 558 Days
• Field of Search: 250/231 R, 73/517 R, 73/517 B, 73/517 A, 73/538
• US Class Current: 250/231.1
• CPC Class Codes: G01P 15/0891 with indication of predetermined acceleration values G01P15/135 takes precedence
• CPC Class Codes: G01P 15/093 by photoelectric pick-up
• CPC Class Codes: H03K 17/968 using opto-electronic devices

Abstract

An omnidirectional optoelectronic acceleration pick-up for the automatic actuation of passenger safety devices in motor vehicles during emergency conditions, utilizes an inertial body which is held in its rest position by an annular permanent magnetic. When a preset amplitude of acceleration is exceeded, a quasi digital switching behavior is achieved by a radially opening annular gap between the end face of the inertial body and the surface of the annular permanent magnet turned towards that face.

Claims

1. Acceleration pick-up for the automatic actuation of passenger safety devices in motor vehicles during an accident, comprising:

a housing with an interior space;

an elongated round and rotationally symmetric inertial body in said housing which functions as a seismic mass;

a transmitter means for sending signals to a receiver means;

said body means having a continuous longitudinal bore providing a signal path from said transmitter to said receiver in a rest position of the inertial body means;

said inertial body means having at an end face, a supporting base by which the body means is supported;

bearing means extending perpendicular to the longitudinal bore of said body means and having a through bore therein which is aligned with longitudinal bore of the body means when the body means is in a normal rest position;

the supporting base of the body means resting on the bearing means;

wherein when a preset amplitude of acceleration is exceeded, the body means is deflected along its supporting base so that an actuation control signal is initiated owing to interruption of the transmission means sending a signal to the receiver means along said signal path;

wherein the inertial body means has soft magnetic properties;

the bearing is constructed in the form of an annular permanent magnet;

the annular permanent magnet has a diameter that corresponds approximately to a diameter of the end face of the inertial body means;

the supporting base having a diameter which is smaller than the diameter of the end face; and

a radially opening annular gap being defined as the area starting from a center of the supporting base which abuts a flat surface on the annular permanent magnet to outwardly located spaces between the end face and the annular permanent magnet.

2. Acceleration pick-up according to claim 1, wherein the inertial body means consists of a non-magnetic material and is provided with a soft magnetic lining on at least its end face.

3. Acceleration pick-up according to claim 1, wherein the flat supporting base has a flat central portion and the end face of the inertial body means provides the radially opening annular gap in conjunction with the annular permanent magnet which itself is flat.

4. Acceleration pick-up according to claim 1, wherein, starting from the supporting base, the inertial body means is flat and a top face of the annular permanent magnet defines the radial annular gap.

5. Acceleration pick-up according to claim 1, wherein the inertial body means carries an impact absorber at its end located opposite its end face.

6. Acceleration pick-up according to claim 1, wherein an impact absorber is disposed in the interior space of the housing adjacent the end of the inertial body means opposite its end face.

7. Acceleration pick-up according to claim 1, wherein the housing consists of non-metallic elastic material.

8. Acceleration pick-up according to claim 1, wherein said transmitter and receiver are disposed opposite each other in the housing in line with the longitudinal bore.

9. Acceleration pick-up according to claim 1, wherein there is a reflector body means in line with the longitudinal bore at one end of the housing;

the transmitter and receiver being located at an opposite end of the housing from the reflector means; and

wherein the transmitter sends a signal through the bore to the reflector body means which reflects the signal back to the receiver.

10. Acceleration pick-up according to claim 1, wherein the ratio of the diameter of the supporting base to the diameter of the end face is approximately 1:

1.5 to 15.

11. Acceleration pick-up according to claim 1, wherein the annular gap has an aperture angle α

which is inversely proportional to the length of the inertial body.

12. Acceleration pick-up according to claim 1, wherein the inertial body has the shape of at least one of a frustum, double frustum and a barrel.

13. Acceleration pick-up according to claim 1, wherein at the lower end face, the inertial body means has a trough-shaped recess in the region of the longitudinal bore, into which projects a correspondingly shaped extension of the housing.

14. Acceleration pick-up according to claim 1, wherein evaluation electronics of the acceleration pick-up are integrated into the interior space of the housing.

15. Acceleration pick-up according to claim 1, wherein an acceleration output pick-up may be plugged into a printed circuit board.

16. Acceleration pick-up according to claim 1, wherein an acceleration output pick-up may be connected to a power supply of the safety device.