Lost motion exhaust rocker engine brake system with actuation solenoid valve and method of operation

A compression-release engine brake system for effectuating a compression-release engine braking operation in a diesel engine comprising an engine cylinder, at least one intake valve, at least one exhaust valve and at least one exhaust valve spring exerting a closing force on the at least one exhaust valve to urge the at least one exhaust valve into a closed position, the engine cylinder being associated with a four stroke piston cycle comprising an intake stroke, a compression stroke, an expansion stroke and an exhaust stroke, the brake system comprising:

• an exhaust rocker arm;
• an actuation device including an actuation piston slidably disposed in an actuation bore formed in the exhaust rocker arm and movable between retracted and extended positions, the actuation device configured to be operatively associated with the at least one exhaust valve to permit unseating thereof from the closed position;
• a reset device including a reset check valve and a slider assembly operatively connected to the reset check valve;
• and
• a hydraulic fluid circuit within the exhaust rocker arm;
• the actuation bore defining an actuation cavity delimited by the actuation piston within the actuation bore above the actuation piston,
• the reset check valve disposed in a reset bore formed in the exhaust rocker arm, the reset bore being in fluid communication with the actuation cavity through at least one connecting conduit of the hydraulic fluid circuit, the reset check valve operable between an open position and a closed position and biased toward the closed position thereof so that a hydraulic fluid is locked in the actuation cavity when the reset check valve is in the closed position thereof, and flows bi-directionally through the reset check valve when the reset check valve is in the open position;
• the slider assembly includes a slider-piston slidably disposed in the reset bore of the exhaust rocker arm, the slider-piston movable relative to the exhaust rocker arm between an extended position and a retracted position, the slider-piston biased toward the extended position, the slider assembly operatively associated with the reset check valve so that in the extended position the reset check valve is free to move toward the closed position, and in the retracted position the reset check valve is movable to the open position thereof by the slider-piston;
• and,
• the compression-release brake system actuated by a dual stage hydraulic solenoid valve, the solenoid valve including:
• a valve body having an intake port, an outlet port and an exhaust port;
• a solenoid coil disposed in the valve body;
• an armature rectilinearly reciprocating within the solenoid coil;
• a solenoid pin rectilinearly reciprocating within valve body and operatively associated with the armature;
• an intake valve disposed between the intake port and the outlet port;
• and
• a pressure regulating exhaust valve disposed between the outlet port and the exhaust port;
• wherein the pressurized hydraulic fluid supplied to the valve body through the intake port is regulated so as to flow through both the outlet port and the exhaust port via the pressure regulating exhaust valve when the solenoid coil is in a de-energized state and, when the solenoid coil is in an energized state, the pressure regulating exhaust valve is closed and the pressure regulating intake valve is opened so as to supply the pressurized hydraulic fluid only to the outlet port.

A method of operation of a compression-release engine brake system in a brake-on mode for operating at least one exhaust valve of an internal combustion engine during a compression-release engine braking operation, the compression-release brake system maintaining the at least one exhaust valve open during a portion of a compression stroke of the engine when performing the compression-release engine braking operation, the compression-release brake system comprising a lost motion exhaust rocker assembly comprising:

• an exhaust rocker arm;
• an actuation device including an actuation piston slidably disposed in a actuation bore formed in the exhaust rocker arm and movable between retracted and extended positions, the actuation device configured to be operatively associated with the at least one exhaust valve to permit unseating thereof from the closed position;
• a reset device including a reset check valve and a slider assembly operatively connected to the reset check valve;
• and
• a hydraulic fluid circuit within the exhaust rocker arm;
• the actuation bore defining an actuation cavity delimited by the actuation piston within the actuation bore above the actuation piston,
• the reset check valve disposed in a reset bore formed in the exhaust rocker arm, the reset bore being in fluid communication with the actuation cavity through at least one connecting conduit of the hydraulic fluid circuit, the reset check valve operable between an open position and a closed position and biased toward the closed position thereof so that a hydraulic fluid is locked in the actuation cavity when the reset check valve is in the closed position thereof, and flows bi-directionally through the reset check valve when the reset check valve is in the open position;
• the slider assembly including a slider-piston slidably disposed in the reset bore of the exhaust rocker arm, the slider-piston movable relative to the exhaust rocker arm between an extended position and a retracted position, the slider-piston biased toward the extended position thereof, the slider assembly operatively associated with the reset check valve so that in the extended position of the slider-piston the reset check valve is free to move toward the closed position thereof, and in the retracted position of the slider-piston the reset check valve is moved to the open position thereof by the slider-piston;
• the method comprising the steps of:
• mechanically and hydraulically biasing the reset check valve closed during a valve brake lift of the at least one exhaust valve during a compression stroke of the internal combustion engine;
• and
• resetting the at least one exhaust valve during an expansion stroke of the engine by opening the reset check valve and releasing hydraulic fluid from the actuation piston cavity to close the at least one exhaust valve.