ANTI-SKID SYSTEM HAVING IMPROVED SENSOR

• US 3,854,556 A
• Filed: 12/27/1973
• Issued: 12/17/1974
• Est. Priority Date: 12/27/1973
• Status: Expired due to Term

• Current Assignee: Thomas A. Gee
• Original Assignee: Thomas A. Gee
• Inventors: Gee, Thomas A.
• Primary Examiner(s): Reger, Duane A.
• Application Number:
  US05/428,709
• Time in Patent Office: 355 Days
• Field of Search: 188/181R 310/156 317/5 324/161,162,163,166 340/262,263
• US Class Current: 188/181.00R
• CPC Class Codes: B60T 8/171 Detecting parameters used in the regulation; Measuring values used in the regulation
• CPC Class Codes: G01P 3/488 delivered by variable reluctance detectors

Abstract

An anti-skid system is disclosed having an improved wheel speed sensor. The sensor provides a frequency signal proportional to wheel velocity. The anti-skid circuit operates in dependency upon the value of the velocity signal to provide an anti-skid signal which is supplied to a brake control system for relieving brake forces applied to the wheel. The improved sensor is a variable reluctance voltage generator comprising a stator and a rotor. The rotor is mounted on the vehicle wheel so as to rotate therewith in close proximity to the stator. The rotor is made of ferromagnetic material and is provided with an annular array of rotor teeth. The stator includes three members defining a source of magnetic flux and a split magnetic path therefor. Two of the members are mounted so as to face the rotor to define a magnetic air gap therebetween. The members are oriented and configured such that a reluctance change in the first and second members caused by rotation of the rotor is essentially 180* out of phase while the reluctance change caused by like changes in the air gap spacing is essentially in phase. A coil has winding portions located on the stator to provide an output voltage having its maximum value when the reluctance changes are 180* out of phase.

Claims

1. An anti-skid system for relieving brake forces applied to at least one independently rotatable wheel in response to a skid signal comprising:

anti-skid control circuit means for providing a said skid signal in dependence upon a received wheel speed signal representative of the wheel speed of a said wheel;

wheel speed signal generating means including a variable reluctance wheel speed sensor, said sensor including a stationary stator and a rotor adapted to be mounted on said wheel for rotation therewith in close proximity to said stator and cooperating with said stator to define an air gap therebetween;

said rotor including an annular ferromagnetic member having an annular array of teeth with adjacent teeth being separated by a recess, each said tooth extending toward said stator and terminating in a pole face having a width in the direction of rotation corresponding with the width in the same direction of each said recess;

said stator comprising means for defining a magnetic flux source and a split magnetic flux path, said defining means including spaced apart first and second leg members which define, at least in part, first and second magnetic circuits and a third member which defines a common magnetic path for said first and second magnetic circuits, each said first and second leg member having a pole face which faces said rotor and being spaced therefrom to define an air gap, said first and second leg members being oriented and configured such that the reluctance change in said first and second leg members caused by rotation of said rotor is essentially 180* out of phase and the reluctance change in said first and second leg members caused by a like change in said air gap spacing is essentially in phase, coil means for providing an output signal in dependence upon said reluctance changes such that essentially no output signal is provided when said reluctance changes are in phase.

2. An anti-skid system as set forth in claim 1 wherein said leg members are oriented such that when the pole face of said first leg member is in registry with a said rotor tooth the pole face of the second leg member is in registry with a rotor recess.

3. An anti-skid system as set forth in claim 2 wherein said means defining said magnetic flux source includes said third member, said first and second leg members being constructed of ferromagnetic material and serving as portions of said split magnetic path for said source.

4. An anti-skid system as set forth in claim 3 wherein said third member is a permanent magnet.

5. An anti-skid system as set forth in claim 3 wherein said coil means includes a first winding portion wound about a portion of the length of said first leg member and a second winding portion wound about a portion of the length of said second leg member, said winding portions being connected together in series such that induced voltages of opposite sense across said winding portions are additive whereas induced voltages of the same sense across said winding portions are subtractive.

6. An anti-skid system as set forth in claim 5 wherein said first and second leg members are circular in cross section to assist in tightly winding said winding portions thereabout.

7. An anti-skid system as set forth in claim 6 wherein said third member is a permanent magnet.

8. An anti-skid system as set forth in claim 7 wherein said members are supported in place by an encapsulating layer of non-conductive material.

9. An anti-skid system as set forth in claim 3 including a strap member constructed of ferromagnetic material and is included in said split magnetic path.

10. An anti-skid system as set forth in claim 9 wherein said strap member interconnects said first and second leg members.

11. An anti-skid system as set forth in claim 10 wherein said means defining said magnetic flux source includes first and second permanent magnets located proximate to the pole faces of said first and second leg members and serving as extentions thereof, said first, second, and third members being constructed of ferromagnetic material for defining first and second magnetic circuits such that said third member provides a common flux path for both circuits.

12. An anti-skid system as set forth in claim 11 wherein said coil means includes first and second winding portions respectively wound on said first and second leg members and interconnected such that induced voltages in said winding portions are additive when of opposite sense and are substractive when of the same sense.

13. An anti-skid system as set forth in claim 12, including a strap member of ferromagnetic material interconnecting said first, second and third members and included in said first and second magnetic circuits.

14. A wheel speed signal generator for providing a wheel speed signal representative of angular velocity of a wheel and including a stationary stator and a rotor adapted to be mounted on a said wheel for rotation therewith in close proximity to said stator and cooperating with said stator to define an air gap therebetween;

said rotor including an annular ferromagnetic member having an annular array of teeth with adjacent teeth being separated by a recess, each said tooth extending toward said stator and terminating in a pole face;

said stator comprising means for defining a magnetic flux source and a split magnetic path, said defining means including spaced apart first and second leg members and a common flux path third member, said first and second leg members being oriented so that each has a pole face which faces said rotor and spaced therefrom by said air gap;

said leg member pole faces being oriented and configured such that when the pole face of said first leg is in registry with a said rotor pole face, the pole face of said second leg member is in registry with a said rotor recess so that during rotation of the rotor the reluctance change in said first and second leg members is 180* out of phase and when the said air gap is changed, the said reluctance change is in phase; and

means for providing an output signal having a maximum value only when the reluctance change in said first and second legs is out of phase by essentially 180*.