Electrical power assisted steering mechanism

An electrically assisted power steering system for a vehicle having a steering wheel and a steering mechanism, said steering system comprising:

• a generally cylindrical housing;
• a shaft supported for rotation in said housing, said shaft having an input end adapted to be connected to the steering wheel and an output end adapted to be connected to the steering mechanism;
• torque sensor means responsive to a torque applied to said shaft for generating a torque signal having an amplitude component indicative of the magnitude of the torque applied between the input and output ends of said shaft and a direction component indicative of the direction of the applied torque;
• a power amplifier responsive to said torque signal for generating an amplified signal having a magnitude which varies as a function of the amplitude component of said torque signal and a direction component indicative of the direction of the applied torque;
• a low speed, high torque reversible electric motor disposed in said housing and circumscribing said shaft for generating a rotary output having a torque proportional to the magnitude of said amplified signal and a direction of rotation determined by the direction component of said amplified signal;
• and
• a gear train having a gear ratio between 1:1 and 10:1 for transmitting the rotary output of said electric motor to said shaft.

An electrically assisted power steering mechanism for a vehicle having a steering wheel for providing a rotary input to a steering gear box to turn the wheels of the vehicle;

• said power steering mechanism comprising:
• a housing;
• a shaft supported for rotation in said housing, said shaft including an input end adapted to be connected to said steering wheel and an output end adapted to be connected to said steering gear box;
• a torque sensor responsive to the torque applied between said input and output ends of said shaft for generating a torque signal indicative of the magnitude and direction of the applied torque;
• a power amplifier responsive to said torque signal for generating an amplified torque signal having a first component which is an anti-log function of the magnitude of the applied torque and a second component indicative of the direction of the applied torque;
• a low speed, high torque reversible electric motor disposed in said housing and concentric with said shaft for producing a rotary output having a torque corresponding to said first component of said amplified signal and a direction of rotation corresponding to said second component of said amplified signal;
• and
• a planetary gear train disposed in said housing having an input to output gear ratio between 1:1 and 10:1, said planetary gear train having an internal gear fixedly attached to said housing, a sun gear circumscribing said shaft and connected to the rotary output of said electric motor, a plurality of planet gears engaging said internal gear and said sun gear, and a planet gear carrier interconnecting said plurality of planet gears with the output end of said shaft.