View Full Version : Cấu tạo các hệ thống trên động cơ
28-06-2012, 08:32 AM
MỘT ĐỘNG CƠ ĐỐT TRONG THÔNG THƯỜNG BAO GỒM CÁC HỆ THỐNG SAU ĐÂY:
1. hệ thống phát lực.
2. hệ thống phân phối khí.
3. hệ thống cố định
4. hệ thống bôi trơn
5. hệ thống làm mát.
6. hệ thống điện và điều khiển động cơ
7. hệ thống nhiên liệu "động cơ xăng và hệ động cơ diesel"
i. HỆ THỐNG PHÁT LỰC.
Píttông chuyển động thẳng đứng bên trong xylanh, do áp suất được tạo ra bởi sự cháy của hỗn hợp không khí - nhiên liệu.
bao kin pittong và xylanh hạn chế mức thấp nhất không khí trong buồng cháy lọt xuống catte
Trục khuỷu biến chuyển động thẳng của píttông thành chuyển động quay thông qua thanh truyền.
Bánh đà được chế tạo ở dạng một đĩa thép nặng, biến chuyển động quay của trục khuỷu thành quán tính. Do đó, nó có thể tạo ra lực chuyển động quay ổn định
28-06-2012, 08:32 AM
Xin bổ sung thêm một hệ thống trên động cơ đốt trong cho mọi người tham khảo.
Hệ thống này được sử dụng trên các xe tải off-highway. Sử dụng động cơ để giảm tốc cho xe khi xe đang xuống dốc vì nếu rà thắng quá lâu sẽ làm nóng các chi tiết hệ thống thắng và giảm tuổi thọ.
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 engine's exhaust valves. 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.
(1) Slave pistons
(2) Solenoid valve
(3) Valve connector
(4) Master cylinders
The CAT compression brake consists of three 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 is 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, two, or all three of the compression brake housing assemblies. This provides progressive braking capabilities with the retarding effect of two cylinders, of four cylinders, or of all six cylinders in the engine.
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 the actuator spool
The CAT compression brake is operated by engine oil from engine oil pan (15) . The engine oil is pressurized by engine oil pump (14) . The engine oil supply for the CAT compression brake is supplied through rocker arm shaft oil passage (13) . Actuator valve (5) controls the flow of the supply oil in the compression brake housing. When the actuator valve is activated by a signal from the ECM, low pressure oil passes from the actuator spool supply port (P) to actuation port (A) . The oil flow opens check valve (1) and flows into high pressure oil passage (2) . Oil is supplied to slave piston (7) and master piston (4) .
This engine oil pressure overcomes master piston spring (8) . The piston is forced downward toward fuel injector rocker arm (12) . Oil fills the cylinder for the master piston and the high pressure oil passage between the master piston and the slave piston. The master piston follows the movement of the fuel injector rocker arm. The master piston moves upward with the fuel injector rocker arm. The movement of the master piston causes a flow of high pressure oil that closes the circuit's check valve. The closed check valve causes pressure to increase in the hydraulic circuit of the master piston, the slave piston, and the high pressure oil passage.
As the oil pressure in the high pressure oil passage is increased by the movement of the master piston, the slave piston is forced downward in the bore. This compresses spring (9) for the slave piston. As the slave piston moves downward, the slave piston makes contact with exhaust valve rocker arm (10) . The slave piston continues to apply a force to the exhaust valve rocker arm. This force causes exhaust valves (16) to open. As the exhaust valves open, the cylinder pressure that is created by the engine's piston during the compression stroke is relieved through the open exhaust valves.
During compression brake operation, the ECM disables the signal to each of the fuel injectors that are selected for braking. The power stroke of the engine will not occur for the selected cylinders during the application of the compression brake. This creates a net braking force at the flywheel.
As the fuel injector rocker arm moves downward, the master piston is allowed to retract into the bore. As the master piston retracts, the hydraulic pressure in the circuit is decreased. This allows the slave piston to retract and control of the exhaust valves is returned to the engine's valve train.
De-energizing the actuator valve allows the oil to drain from port (T1) and (T2) to the engine oil pan through oil drain passage (6) .
28-06-2012, 08:32 AM
nói gì chả hiểu @@
28-06-2012, 08:32 AM
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