Hydraulic hybrid powertrain system

A hydraulic hybrid powertrain system comprising:

• a power plant generating a high pressure fluid at an output;
• at least one variable displacement drive motor responsive to said high pressure fluid for generating rotary motion at an output;
• a mode selection means connected to said power plant output and said at least one drive motor for selecting a mode of operation of said at least one drive motor;
• and
• a control means connected to said power plant and said at least one drive motor for controlling a displacement of said at least one drive motor in response to an accelerator input and a brake input to said control means.

A hydraulic hybrid powertrain system, comprising:

• a power plant including an engine driving a pump connected to a low pressure fluid source to generate high pressure fluid at an output;
• at least one variable displacement pump/motor responsive to said high pressure fluid for generating rotary motion at an output;
• a mode selection means connected for fluid communication between said power plant output and said at least one pump/motor;
• a control means connected to said power plant outlet and said at least one pump/motor for selectively controlling a displacement of said at least one pump/motor in response to accelerator and brake inputs;
• a brake override means connected between said mode selection means and said at least one pump/motor, said brake override means being responsive to said brake input for preventing a flow of said high pressure fluid to said at least one pump/motor.