Method for determining the rotational speed of a motor vehicle wheel rotating around a rotating axis

• US 6,237,403 B1
• Filed: 01/03/2000
• Issued: 05/29/2001
• Est. Priority Date: 07/03/1997
• Status: Expired due to Fees

• Current Assignee: Continental AG
• Original Assignee: Continental AG
• Inventors: Oldenettel, Holger, Ernst, Gerhard
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US09/462,314
• Time in Patent Office: 512 Days
• Field of Search: 73/146.2, 73/146.3, 73/146.4, 73/146.5, 340/442, 340/445, 340/446, 340/447, 200/61.22
• US Class Current: 73/146.5
• CPC Class Codes: B60C 23/0416 allocating a corresponding wheel position on vehicle, e.g. front/left or rear/right
• CPC Class Codes: G01P 15/09 by piezoelectric pick-up
• CPC Class Codes: G01P 3/44 for measuring angular speed G01P3/56 takes precedence

Abstract

The invention relates to a method for determining the rotational speed of a motor vehicle wheel (4), which rotates about a rotational axis (2), by an acceleration sensor (10). The acceleration sensor (10) is mounted on the motor vehicle wheel (4) at a spacing (r) to the rotational axis (2) in such a manner that the force-sensitive axis of the acceleration sensor (10) is perpendicular to the rotational axis and is perpendicular to the centrifugal force which acts on the acceleration sensor (10) with a rotation of the motor vehicle wheel (4) about the rotational axis (2). The rotational speed of the motor vehicle wheel (4) is measured in that the rotational axis (2) is aligned horizontally so that a periodic measurement signal is generated in the acceleration sensor (10) by the gravitational force. The frequency of the measurement signal corresponds to the rotational speed of the motor vehicle wheel (4) about the rotational axis (2). The invention also relates to an air pressure control system in which the rotational speed of the motor vehicle wheel is measured.

Claims

1. An air pressure control system for a motor vehicle having wheels with each wheel being rotatably journalled about a rotational axis and rotating at a number of revolutions per unit of time, the system comprising:

a plurality of air pressure control devices assigned to said wheels, respectively;

each of said air pressure control devices including an acceleration sensor to measure said number of revolutions;

said acceleration sensor being mounted at a spacing (r) to said rotational axis with said acceleration sensor being subjected to centrifugal force as the wheel rotates about said rotational axis;

said acceleration sensor defining a force-sensitive axis and exhibiting a high sensitivity to force along said force-sensitive axis;

said acceleration sensor being aligned so that said force-sensitive axis is substantially perpendicular to said rotational axis and substantially perpendicular to said centrifugal force so that said acceleration sensor generates a periodic measuring signal under the influence of the gravitational force when said wheel rotates about said rotational axis with said number of revolutions being determinable from the frequency of said periodic measuring signal;

said rotational axis and said centrifugal force conjointly defining a plane;

said acceleration sensor being a deflecting strip made of piezoelectric material and having a longitudinal length (l); and

,

said deflecting strip being so mounted on said wheel that said longitudinal length (l) is in said plane.

2. The air pressure control system of claim 1, wherein said deflecting strip has a height (h) and said length (l) and said height (h) defining a ratio of length (l)/height (h) greater than 2.

3. The air pressure control system of claim 2, wherein said length (l) is at least 3 mm.

4. The air pressure control system of claim 1, wherein said wheel includes a wheel rim defining a wheel rim base and said acceleration sensor being mounted in said wheel rim base.

5. A method of measuring the number of revolutions per unit of time of a wheel of a motor vehicle with said wheel being rotatably journalled about a rotational axis, the method comprising the steps of:

providing an acceleration sensor in the form of a deflecting strip made of piezoelectric material and mounting said acceleration sensor at a radial spacing (r) to said rotational axis with said acceleration sensor defining a force-sensitive axis along which said acceleration sensor exhibits a high sensitivity to force and with said acceleration sensor being subjected to centrifugal force as said wheel rotates about said rotational axis;

aligning said acceleration sensor so that said force-sensitive axis is substantially perpendicular to said is rotational axis and substantially perpendicular to said centrifugal force;

aligning said wheel so that said rotational axis extends almost horizontally;

imparting rotation to said wheel about said rotational axis and said rotational axis and said centrifugal force conjointly defining a plane;

determining said number of revolutions of said wheel from the frequency of a periodic measuring signal generated by said acceleration sensor under the influence of the gravitational force; and

,

mounting said deflecting strip on said wheel so that the longitudinal length of said deflecting strip lies in said plane so that said deflecting strip generates said periodic measuring signal because of the deformations produced by the gravitational force while said wheel rotates.