Forklift engine can be divided into reciprocating piston type and rotary piston type according to the piston movement mode, and can be divided into four stroke and two stroke according to the working stroke, but can be divided into gasoline engine and diesel engine according to the fuel used; According to the cooling mode, it can be divided into water cooling and air cooling; According to the cylinder arrangement, it can be divided into in-line type, in-line type and horizontal opposed type; It can be divided into single cylinder type and multi cylinder type according to the number of cylinders; It can be divided into positive ignition type and compression ignition type according to fuel ignition mode; According to speed, it can be divided into high-speed internal combustion engines (above 1000r/min), medium speed internal combustion engines (600-1000r/min) and low-speed internal combustion engines (below 600r/min).

The engine parts of the whole forklift are mainly composed of two mechanisms and four systems: crank linkage, valve train, supply system, lubrication system, cooling system and starting system.

1. Crank linkage

Crank connecting rod mechanism is mainly used to generate output power, which is mainly composed of cylinder block crankcase group, piston connecting rod group and crankshaft flywheel group. It usually has the characteristics of high temperature, high pressure and high-speed movement. Whether it works normally will directly affect the power, economy and working reliability of the engine.

2. Valve train

The valve distribution mechanism is a control mechanism for intake and exhaust. It regularly opens and closes the intake and exhaust valves of each cylinder according to the work order of each cylinder of the engine and the requirements of each cylinder's working cycle, so that the combustible mixture (gasoline engine) or air (diesel engine) can enter and enter the cylinder in time, and exhaust gases can be discharged from the cylinder in time. It is mainly composed of valve group and valve transmission group.

3. Supply system

The fuel supply system of forklift engine can be divided into two parts: gasoline engine and diesel engine. The fuel supply system of gasoline engine is mainly composed of gasoline tank, gasoline filter, gasoline pump, air filter, carburetor, intake and exhaust pipe and exhaust muffler. Its function is to prepare a certain amount of fuel and air into a certain amount and concentration of combustible mixture for the cylinder according to the requirements of various working conditions of the engine, and to lead the exhaust gas after combustion work out of the cylinder.

The fuel supply system of diesel engine can be divided into four parts: fuel supply device, air supply device, mixture forming device and exhaust emission device. Its function is to complete the storage, filtering and transmission of diesel oil, and according to the requirements of various working conditions of diesel engines, diesel oil is injected into the combustion chamber regularly, quantitatively and at constant pressure, so that it can be quickly and well mixed with air before combustion, and exhaust gas is discharged into the big gas after combustion.

4. Lubrication system

The main function of the lubrication system is to ensure the normal operation of the forklift engine, separate the two contact surfaces, improve the power of the forklift engine, and extend the life of the forklift accessories of the entire engine. It is mainly composed of oil pump, oil radiator, pressure limiting valve, coarse/fine oil filter, oil pipe and passage, oil pressure sensor, oil pressure gauge, crankshaft, oil temperature gauge, piston, camshaft, valve rocker arm, timing gear, dipstick and other accessories.

5. Cooling system

The main function of the cooling system is to ensure that the running engine can work continuously at the most appropriate temperature (80-90 ℃). The cooling water path shall be unblocked to avoid dead corners or stagnant water flow; The cooling of all parts shall be uniform as far as possible. The flow rate of cooling water shall be appropriately increased at places with high heat load, such as the bottom of the cylinder head and the upper part of the cylinder liner; The multi cylinder engine shall distribute the cooling water evenly to maintain the same cooling intensity. It is mainly composed of water pump, water jacket, radiator, louver, fan, water distribution pipe, thermostat, coolant thermometer and other forklift accessories.

6. Starting system

When the forklift engine changes from static state to working state, external force (human or mechanical force) must be used to drive the crankshaft to rotate. The starting system is used to drive the crankshaft to rotate and start the engine. The starting system consists of point switch, starter, starting switch, starting relay, etc.