Method and system for seat belt retraction speed control

• US 9,008,916 B2
• Filed: 02/28/2012
• Issued: 04/14/2015
• Est. Priority Date: 02/28/2011
• Status: Active Grant

• Current Assignee: Polestar Performance AB (Polestar Automotive Holding UK Plc)
• Original Assignee: Volvo Car Corporation (AB Volvo)
• Inventors: Adolfsson, Peter, Aldeborg, Gert
• Primary Examiner(s): Jen, Ian
• Application Number:
  US13/406,894
• Publication Number:
  US 20120221210A1
• Time in Patent Office: 1,141 Days
• Field of Search: 701/45
• US Class Current: 701/45
• CPC Class Codes: B60R 2022/444 the additional retraction device being an electric actuator
• CPC Class Codes: B60R 2022/4466 the additional retraction device being an electric actuator
• CPC Class Codes: B60R 22/44 with means for reducing belt tension during use under normal conditions not included in the retractor B60R22/19; B60R22/3405 takes precedence

Abstract

A seat belt is wound around a spool and a spring biases the spool to rotate in a belt retraction direction. A sensor detects a retraction speed of the belt when the spool rotates in the belt retraction direction and generating a belt speed signal. An electrical drive unit receives the belt speed signal and applies a torque to the spool in a belt extension direction (opposite to the belt retraction direction) if the retraction speed exceeds a threshold value. The torque is of a magnitude sufficient to maintain the retraction speed below the threshold value. The electric motor and/or electrical control unit may be part of or otherwise integrated with a safety belt pre-tensioning system.

Claims

1. A method for controlling a retraction speed of a seat belt wound around a spool, the spool rotatable in a belt extension direction and in an opposite belt retraction direction, the method comprising:

applying, by a retraction spring, a first torque rotating the spool in the belt retraction direction;

detecting if a connector attached to the seat belt is engaged with a seat belt latch;

monitoring a retraction speed of the seat belt caused by the retraction spring when the connector is disengaged from the seat belt latch; and

if the retraction speed exceeds a predetermined non-zero threshold value, activating an electric motor to apply a second torque to the spool in the belt extension direction to limit the retraction speed to the threshold value.

2. The method according to claim 1 further comprising:

monitoring an elapsed time since disengagement of the connector from the latch; and

stopping the electric motor if the elapsed time exceeds a predetermined period of time.

3. The method according to claim 1, wherein the retraction speed is monitored by measuring a rotational speed of the spool.

4. The method according to claim 1 further comprising:

detecting if the spool reaches a belt end position; and

stopping the electric motor if the belt end position is reached.

5. The method according to claim 1 further comprising:

monitoring if the retraction speed is approaching zero; and

stopping the electric motor in response to the retraction speed approaching zero.

6. The method according to claim 1, wherein the electric motor is controlled by an electrical control unit receiving signals from a retraction speed sensor.

7. The method according to claim 6, wherein the electrical control unit comprises at least a portion of a seat belt pre-tensioner safety system.

8. Apparatus for extending and retracting a seat belt comprising:

a spool around which the seat belt is wound, the spool rotatable in a belt extension direction and in an opposite belt retraction direction;

a retraction spring biasing the spool in the belt retraction direction;

a sensor detecting a retraction speed of the belt when the spool is rotated by the retraction spring in the belt retraction direction and generating a belt speed signal;

a latch condition sensor detecting if a connector on the seat belt is engaged with a seat belt latch and generating a latch condition signal; and

an electrical drive unit receiving the belt speed signal and the latch condition signal and applying a torque to the spool in the belt extension direction if the latch is disengaged and the retraction speed exceeds a non-zero threshold value, the torque sufficient to maintain the retraction speed below the threshold value.

9. The apparatus of claim 8 wherein the sensor further detects if the spool reaches a belt end position and the electrical drive unit stops rotation of the spool if the belt end position is reached.

10. The apparatus of claim 8, wherein the sensor measures a rotational speed of the spool.

11. The apparatus of claim 8, wherein the electrical drive unit is arranged to control the rotational speed of the spool.

12. The apparatus of claim 8, wherein the electrical drive unit comprises at least a portion of a seat belt pre-tensioner safety system.

13. The apparatus of claim 8, wherein the electrical drive unit comprises at least one electrical motor controlled by an electrical control unit.

14. Apparatus for limiting a rotational speed of a spool around which a seat belt is wound, the spool biased by a spring mechanism to rotate in a belt retraction direction, the apparatus comprising:

a sensor detecting the rotational speed of the spool in the belt retraction direction caused by the spring mechanism;

a latch condition sensor detecting if a connector on the seat belt is engaged with a seat belt latch and generating a latch condition signal;

an electrical control unit receiving an indication of the rotational speed in the retraction direction caused by the spring mechanism from the sensor and the latch condition signal; and

an electric motor controlled by the electrical control unit to apply a torque to the spool counter to the belt retraction direction if the rotational speed in the retraction direction exceeds a non-zero threshold value and the latch is disengaged, the torque sufficient to maintain the rotational speed in the retraction direction below the threshold value.

15. The apparatus of claim 14, wherein the electrical control unit comprises at least a portion of a seat belt pre-tensioner safety system.

16. The apparatus of claim 14 wherein the sensor further detects if the spool reaches a belt end position and the electrical control unit stops the motor if the belt end position is reached.