Wheel speed sensor for drive axle

An anti-wheel lock brake control system for controlling the brakes of a pair of wheels mounted on the ends of a drive axle of a vehicle, said drive axle including a housing and a pair of axle shafts and a differential mechanism therein for operationally rotating each said axle shaft which is respectively associated with one of said wheels, said axle shafts being joined to said differential mechanism in a manner which allows movement thereof during said rotating which is transverse with respect to said housing, said system comprising:

• a valve capable of delivering operating air pressure to said both brakes;
• a computer capable of receiving an input voltage signal for controlling said valve by issuing commands thereto to cause said valve to deliver a proportional amount of said operating air pressure to said both brakes for preventing either of said wheels from locking;
• a wheel speed sensor mounted on said drive axle at each side of said differential mechanism inwardly of each said wheel in alignment with its corresponding said axle shaft;
• said wheel speed sensor including an electromagnetic sensing device, an excitor rotor and means for maintaining within predetermined limits a predetermined distance therebetween during rotational and transverse movement of said axle shaft;
• said excitor rotor being mounted for rotation in response to said rotational movement of its respective said axle shaft without responding to said transverse movement thereof;
• and
• said electromagnetic sensing device being aligned with said excitor rotor for sensing its said rotation and providing said input voltage signal to said computer which is unaffected by said transverse movement of said axle shaft and thus indicative of the speed of its respective said wheel.