Forklift: Function and Composition of Transmission System

The transmission components between the power unit and the driving wheels are collectively referred to as the transmission system. It transfers the power output from the power unit to the drive wheels, so that the power output characteristics of the power unit can meet the requirements of the mechanical running mechanism as much as possible. The requirements for the transmission system of the forklift: one is to ensure that the machine has high power and economy; the other is to work reliably and operate conveniently; third, light weight and small size; fourth, high transmission efficiency; fifth, less noise.

Type of transmission system

Forklift transmission systems are generally divided into three types: mechanical transmission, hydro mechanical transmission and hydraulic transmission.

1) Mechanical transmission

The mechanical transmission system generally consists of clutch parts, a transmission, a universal transmission, a main reducer, a differential and an axle shaft. The power from the engine is transmitted to the drive axle through the clutch, transmission and universal transmission. At the drive axle, the power is transmitted to the driving wheels through the final gear, differential and half shafts.

The advantages of mechanical transmission are: high transmission efficiency, simple structure and reliable operation.

2) Hydro mechanical transmission

Hydro mechanical transmission is also called dynamic hydraulic transmission, which uses the change of kinetic energy of the liquid medium in the process of circulating between the active element and the driven element to transmit power. It can realize step-less speed change, so it is widely used. However, the ratio of the output torque to the input torque of the torque converter cannot meet the requirements of various driving conditions of the forklift. Generally, a stepped mechanical transmission is connected in series at the back. Such a transmission is called a hydro mechanical transmission. The hydro-mechanical transmission can automatically realize step-less speed change within several thousand vehicle speed ranges according to the change of road resistance.

The main advantages of the hydrodynamic transmission are: because the crankshaft of the engine and the drive wheel are not rigidly connected, the engine can be protected from overload or flame out when the external load suddenly increases; it can achieve smooth automatic shifting without interrupting the power. , This greatly simplifies the operation, improves the work efficiency, and reduces the labor intensity of the driver (operator) for the forklift that needs to start, stop and shift frequently during operation. The disadvantage is: the transmission efficiency is lower than that of the mechanical type, and the cost is higher.

3) Hydraulic transmission

Hydraulic transmission transfers energy through changes in the static pressure of the liquid transmission medium. It is mainly composed of an engine-driven oil pump, a hydraulic motor and a control device. The mechanical energy output by the engine is converted into hydraulic energy by the oil pump, and then the hydraulic energy is converted into mechanical energy by the hydraulic motor. The oil supply of the oil pump can be continuously changed within a certain range under the control of the hydraulic control device, and the rotational speed of the hydraulic motor will also change continuously within a certain range.