Method for controlling the speed of an electric motor of a belt retractor

• US 10,093,275 B2
• Filed: 06/11/2015
• Issued: 10/09/2018
• Est. Priority Date: 06/16/2014
• Status: Active Grant

• Current Assignee: TRW Automotive Safety Systems GmbH & Co. KG
• Original Assignee: TRW Automotive Safety Systems GmbH & Co. KG
• Inventors: Stegmann, Volker, Staudt, Norbert
• Primary Examiner(s): Lee, Tyler J
• Application Number:
  US15/314,957
• Publication Number:
  US 20170197581A1
• Time in Patent Office: 1,216 Days
• Field of Search: 701 45
• CPC Class Codes: B60R 2022/4473 using an electric retraction device combined with a spring B60R2022/444, B60R2022/4466
• 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 method of controlling the motor speed of an electric retractor motor (18) of a belt retractor (10) for reducing a belt slack in the comfort mode comprises the following steps of:

• • a) measuring the motor current (I_M) applied to the retractor motor (18) as well as the voltage applied to the retractor motor (18),
  • b) estimating the motor speed taking the time curve of the motor current (I_M) applied to the retractor motor (18), the curve of the voltage as well as plural motor parameters (R_M, I_M, K_M) into account,
  • c) adapting the motor current (I_M) in response to the estimated motor speed, and
  • d) repeating the steps a) to c) until the estimated motor speed has reached a defined value.

Claims

1. A method of controlling a motor speed of an electric retractor motor (18) of a belt retractor (10) for reducing belt slack in a comfort mode, comprising the following steps of:

a) measuring a motor current (I_M) applied to the retractor motor (18) as well as a voltage applied to the retractor motor (18),

b) estimating the motor speed by taking a time curve of the motor current (I_M) applied to the retractor motor (18), a time curve of the voltage as well as plural motor parameters (R_M, I_M, K_M) into account,

c) modifying the motor current (I_M) in response to the estimated motor speed, and

d) repeating the steps a) to c) until the estimated motor speed has reached a defined value.

2. The method according to claim 1, wherein a pulse-width modulated operating voltage (U_B) is established from the voltage curve.

3. The method according to claim 1, wherein the motor parameters (K_M) are the motor resistance (R_M) and the motor inductivity (L_M) of the retractor motor as well as a motor-dependent constant (K_M).

4. The method according to claim 1, wherein the motor speed is estimated by the following formula: