MANIFOLD 4N8467 - Caterpillar

The CAT compression brake is controlled by the Engine Control Module (ECM). The CAT compression brake helps the operator to slow the vehicle speed on grades, or for a necessary speed reduction. The service brakes should not be used continuously on long descending grades. The service brakes are assisted by the CAT compression brake.The engine crankshaft is turned by the drive train during downhill operation or during any slow down condition. The engine uses the rotation of the components of the drive train to dictate vehicle speed. A braking torque can be applied to the drive train of the vehicle in order to reduce the speed of the vehicle.When the CAT compression brake is activated, braking power is accomplished by opening the exhaust valves of the engine. The exhaust valves are opened near the top of the compression stroke in order to release the highly compressed air into the exhaust system. The CAT compression brake can only be activated when the engine is in the no-fuel position. Thus, combustion does not occur and no positive force is produced on the piston. The compressed air pressure that is released to the atmosphere prevents the energy from returning to the engine piston on the power stroke. The result is a loss of energy since the work that is done by the compression of the cylinder charge is not returned by the expansion process. This loss of energy is taken from the drive train. The drive train provides the braking action for the vehicle.
Illustration 1 g01165931
(1) Slave pistons (2) Solenoid valve (3) Valve connector (4) Master cylindersThe CAT compression brake consists of identical housing assemblies. Each housing assembly is positioned over two cylinders. The housing assembly is mounted to the supports for the rocker arm shaft with studs and nuts. The rocker arm and the exhaust bridge assembly are used to transfer force from slave pistons (1) to the exhaust valves. Master cylinders (4) transfer lifting force from the fuel injector rocker arm to hydraulic force for the brake. The brake logic signal for the CAT compression brake is carried to solenoid valve (2) by signal wires that connects at valve connector (3) . This is done in order to activate the CAT compression brake on the two cylinders of the engine.The control circuit for the CAT compression brake permits the operation of either one or multiple compression brake housing assemblies. This provides progressive braking capabilities with the retarding effect of numerous cylinders in the engine.Operation of the CAT Compression Brake
Illustration 2 g01103105
Schematic for master-slave circuit (1) Check valve (2) High-pressure oil passage (3) Slave piston adjustment screw (4) Master piston (5) Actuator valve (6) Oil drain passage (7) Slave piston (8) Master piston spring (9) Spring for the slave piston (10) Exhaust rocker arm (11) Exhaust bridge (12) Fuel injector rocker arm (13) Rocker arm shaft oil passage (14) Engine oil pump (15) Engine oil pan (16) Exhaust valve (A) Actuation port (T1) Drain port (T2) Drain port (P) Supply port for