Power transmission

A variable displacement rotary hydraulic machine comprising:

• a housing;
• a shaft mounted within said housing for rotation about a shaft axis;
• cylinder means having a cylinder cavity within said housing;
• piston means dispose din said cavity, one of said piston means and said cylinder means being coupled to said shaft;
• valve means including fluid inlet and outlet ports in said housing and means from selectively connecting said cavity to said fluid inlet and outlet ports;
• means coupled to one of said piston means and said cylinder means within said housing for varying displacement of said piston means within said cylinder cavity as said shaft rotates about said axis;
• microprocessor-based electronic control means mounted on said valve means and including means for receiving and storing electronic control signals from an external source, and means responsive to said control signals for controlling piston of said displacement-varying means within said housing;
• and sensor means for sensing operating conditions of said machine and providing electronic sensor signals as functions thereof, including a first sensor coupled to said displacement-varying means within said housing and providing a corresponding first signal to said electronic control means;
• said valve means comprising a valve block, said housing including a base mounted on said valve block to form an internal cavity in which said shaft, said cylinder means, said piston means and said displacement-varying means are positioned;
• said sensor means further comprising a speed sensor coupled to said shaft for providing an electronic signal as a function of speed of rotation of said shaft, and said microprocessor-based control means including means responsive to said speed signal for controlling operation of said machine;
• said speed sensor comprising a rotor coupled to said shaft within said cavity and a stator carried by said block adjacent to said rotor, said rotor comprises a sprocket of ferromagnetic construction mounted on said shaft, and wherein said stator comprises an inductive sensor carried by said block radially adjacent to said sprocket;
• said sensor means further comprising a pressure sensor coupled to said one of said ports for providing an electronic signal as a function of fluid pressure at said one of said ports, and said microprocessor-based control means including means responsive to said pressure signal for controlling operation of said machine;
• said microprocessor-based control means comprising a printed circuitboard assembly mounted externally of said block, said stator of said speed sensor, said pressure sensor and said first sensor being mounted on said block, and a cover mounted on said block to enclose said circuitboard assembly.

A system for controlling operation of a variable displacement hydraulic pump that includes a pump shaft, means responsive to hydraulic fluid for controlling pump displacement, an electrohydraulic valve responsive to a valve control signal for variably applying hydraulic fluid to said displacement-controlling means, means responsive to speed of rotation of said shaft for providing a continuing series of electronic signal cycles at a frequency that varies with shaft speed, and means responsive to speed of rotation of said shaft as a function of said electronic signal cycles for controlling said valve control signal comprising:

• a control microprocessor, means responsive to said control microprocessor for initiating a speed-measurement cycle and means for measuring time duration over a preselected number of said signal cycles during a speed measurement cycle, said microprocessor being responsive to said time duration for determining speed of shaft rotation,
• said duration-measuring means comprising a down-counter having data inputs for preloading a count corresponding to said preselected number of signal cycles, a count input responsive to said signal cycles and an enable input responsive to said measurement initiating means, and a latch having an input coupled to said microprocessor for receiving and storing said count and an output coupled to said counter data inputs, said cycle-initiating means including means responsive to said microprocessor for selectively loading said count from said latch into said counter.