1. Power and transmission system
The power unit of hydraulic excavator mostly adopts vertical multi cylinder, water-cooled and 1-hour power calibrated diesel engine. The transmission system transmits the output power of the diesel engine to the working device, rotary device and walking mechanism through the hydraulic system.
2. Slewing mechanism
The rotary mechanism of the hydraulic excavator can realize the left or right rotation of the working device and the upper turntable for excavation and loading and unloading. The slewing mechanism must be able to support the turntable on the frame without tilting and make the slewing light and flexible. Therefore, hydraulic excavators are equipped with rotary support device and rotary transmission device, which are collectively referred to as rotary mechanism.
(1) Slewing support
The hydraulic excavator uses the slewing support to realize the slewing of the upper platform. According to the structural form, the slewing support is divided into two types: rotating column type and rolling bearing type.
(2) Rotary drive
The rotary mechanism of hydraulic excavator can be driven directly or indirectly:
Direct transmission is to install the driving pinion on the output shaft of the low-speed high torque hydraulic motor to mesh with the rotary gear ring. Now hydraulic excavators generally do not adopt this structural form.
Indirect transmission is an indirect transmission structure in which the high-speed hydraulic motor drives the rotary gear ring through the gear reducer. This transmission form has compact structure, large transmission ratio and good stress condition of gear. The structure of the axial piston hydraulic motor is basically the same as that of the same type of hydraulic oil pump. Many parts can be used in general to facilitate manufacturing and maintenance, so as to reduce the cost.