Controlling current supplied to electric motor of a seat belt retractor

• US 20050083000A1
• Filed: 08/04/2004
• Published: 04/21/2005
• Est. Priority Date: 08/06/2003
• Status: Active Grant

• Current Assignee: Key Safety Systems, Inc. (Ningbo Junsheng Investment Group Co., Ltd.)
• Original Assignee: Key Safety Systems, Inc. (Ningbo Junsheng Investment Group Co., Ltd.)
• Inventors: Liedl, Christian, Specht, Martin, Heckmayr, Alexander
• Granted Patent: US 7,180,258 B2
• Time in Patent Office: Days
• US Class Current: 318/432
• 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 and a device for adjusting a supply current, which feeds an electric motor, the torque of which is transferred to a belt reel of a seat belt retractor of a motor vehicle, whereby the motor current of the electric motor is measured during the torque generation and compared as a controlled variable with a command variable, which is adjusted depending on at least one driving situation or at least one driving condition of the vehicle, for controlling the supply current for the electric motor situated in the control circuit.

Claims

1. A method for adjusting a supply current to an electric motor that is situated in a control circuit and produces torque that is transferred to a belt reel of a seat belt retractor of a motor vehicle in dependence on at least one driving situation or a driving condition of the vehicle, comprising the steps of:

(a) measuring a motor current of the electric motor during the torque generation;

(b) comparing the motor current measured in step (a) as a controlled variable with a command variable; and

(c) adjusting the torque transferred to the belt reel by controlling the supply current for the electric motor situated in the control circuit.

2. The method according to claim 1, wherein the command variable is adjusted depending on an amount of slack that is to be removed from a belt webbing of the seat belt.

3. The method according to claim 1, wherein the command variable is adjusted depending on a reference position into which, in a potential crash situation, a vehicle occupant restrained by the seat belt is to be brought by means of the motor torque acting upon the seat belt.

4. The method according to claim 1, wherein due to the adjusted command variable, a constant restraint force on the seat belt or a constant supply current for the electric motor is achieved after a pretensioning of the seat belt.

5. The method according to claim 2, wherein due to the adjusted command variable, a constant restraint force on the seat belt or a constant supply current for the electric motor is achieved after a pretensioning of the seat belt.

6. The method according to claim 3, wherein due to the adjusted command variable, a constant restraint force on the seat belt or a constant supply current for the electric motor is achieved after a pretensioning of the seat belt.

7. The method according to claim 1, wherein the command variable is adjusted depending on an unlocking process that is to performed in which the retensioned belt reel of the belt retractor is unlocked out of a locked or blocked position by applying an additional motor torque in the tightening direction.

8. The method according to claim 1, wherein the command variable is adjusted depending on the weight of a vehicle occupant restrained by the seat belt.

9. A device for adjusting a supply current in the supply current circuit of an electric motor, the torque of which is to be transferred to a belt reel of a seat belt retractor, whereby an adjustment device for the torque is connected to a sensor device for detecting a driving situation or a driving condition of the vehicle, wherein the electric motor is arranged in a current control circuit that comprises:

(a) a current measuring device for measuring the motor current in a generated torque,

(b) a comparator connected to the current measuring device, whereby the comparator is connected to a command variable generator, which for generating a command variable is connected to a sensor device and generates the command variable depending on the sensor signals supplied, and in that a supply current circuit is connected to the comparator the supply current of which is adjusted depending on the deviation detected in the comparator.