Hydraulic control system for a continuously variable transmission

A hydraulic control system for a continuously variable transmission (CVT) to control a primary pulley and a secondary pulley linked by a chain or belt, the hydraulic control system comprising:

• a pressure regulator subsystem providing a pressurized oil;
• a selection valve in downstream fluid communication with the pressure regulator subsystem, the selection valve configured to control a flow of pressurized oil from the pressure regulator subsystem to a primary pulley circuit and a secondary pulley circuit, the primary pulley circuit in fluid communication with the primary pulley and the secondary pulley circuit in communication with the secondary pulley, wherein the selection valve is configured to communicate the flow of pressurized oil from the pressure regulator subsystem to whichever of the primary pulley circuit and the secondary pulley circuit has less oil pressure;
• a ratio control pump disposed in fluid communication between the primary pulley circuit and the secondary pulley circuit, wherein rotation of the ratio control pump in a first direction pumps pressurized oil from the secondary fluid line to the primary fluid line and rotation of the control pump in a second direction pumps pressurized oil from the primary pulley circuit to the secondary pulley circuit to change a ratio of the CVT, and a speed of rotation of the ratio control pump controls a rate of change of the ratio of the CVT;
• a secondary accumulator in fluid communication with the secondary pulley circuit, wherein the secondary accumulator is configured to maintain a pressure in the secondary pulley circuit when the ratio control pump is not rotating;
• and
• an electric motor for controlling a rotation direction and rotation speed of the ratio control pump.

A hydraulic control system for a continuously variable transmission (CVT) to control a primary pulley and a secondary pulley linked by a chain or belt, the hydraulic control system comprising:

• a pressure regulator subsystem providing a pressurized oil;
• a selection valve in downstream fluid communication with the pressure regulator subsystem, the selection valve configured to control a flow of pressurized oil from the pressure regulator subsystem to a primary pulley circuit and a secondary pulley circuit, the primary pulley circuit in fluid communication with the primary pulley and the secondary pulley circuit in communication with the secondary pulley, wherein the selection valve is configured to communicate the flow of pressurized oil from the pressure regulator subsystem to whichever of the primary pulley circuit and the secondary pulley circuit has less oil pressure;
• a ratio control pump disposed in fluid communication between the primary pulley circuit and the secondary pulley circuit, wherein rotation of the ratio control pump in a first direction pumps pressurized oil from the secondary fluid line to the primary fluid line and rotation of the control pump in a second direction pumps pressurized oil from the primary pulley circuit to the secondary pulley circuit to change a ratio of the CVT, and a speed of rotation of the ratio control pump controls a rate of change of the ratio of the CVT;
• an electric motor interconnected to the ratio control pump for controlling a rotation direction and rotation speed of the ratio control pump;
• an anti-drive back mechanism connected between the electric motor and the ratio control pump to selectively prevent the ratio control pump from rotating due to pressure in the primary fluid line or the secondary fluid line when the electric motor is off;
• a primary accumulator in fluid communication with the primary pulley circuit, wherein the primary accumulator is configured to maintain a pressure in the primary pulley circuit when the electric motor is off;
• and
• a secondary accumulator in fluid communication with the secondary pulley circuit, wherein the secondary accumulator is configured to maintain a pressure in the secondary pulley circuit when the electric motor is off.