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The composition and working principle of the excavator slewing mechanism

05-06, 2022 / in Bearing Knowledge / by LDB

Excavators, also known as excavators, are indispensable mechanical vehicles in engineering construction. The use of buckets to excavate earthwork and materials that need to be cleaned has greatly accelerated the construction progress and efficiency. When the hydraulic excavator is working, the slewing mechanism needs to be frequently the reciprocating action to make the bucket work.

It can be seen that the slewing mechanism is an important part of the hydraulic excavator. So, do you know the composition and working principle of the hydraulic excavator slewing mechanism?

The composition of the excavator slewing mechanism

Excavator slewing bearing

The excavator slewing mechanism is mainly composed of a slewing brake, a slewing reducer, a slewing bearing and a slewing hydraulic system.

1. Swing brake

The swing brake is set on the swing reducer and controlled by the swing hydraulic system. The structure of various excavator brakes is different, but the principle is basically the same. Taking a certain type of hydraulic excavator as an example, its rotary brake adopts normally closed, spring clamping, multi-disc, wet brake. When the excavator turntable stops rotating, the brake is applied to brake. When the turntable rotates, the hydraulic system pilot pressure oil pushes the brake. The moving piston compresses the spring to release the brake.

2. Rotary reducer

The slewing reducer is fixed on the turntable and is connected with the output shaft of the slewing motor. The output shaft of the slewing reducer is provided with a pinion, and the slewing bearing is provided with an inner gear ring. When the slewing motor drives the slewing reducer to rotate, the pinion mounted on the output shaft of the slewing reducer meshes with the ring gear of the slewing bearing. The revolving motion of the gear drives the turntable and the upper working device to rotate together.

3. Slewing bearing

The excavator slewing bearing is like a large rolling bearing, the outer ring is connected with the turntable by bolts, the inner ring is connected with the chassis by bolts, and there are rolling elements between the inner and outer rings. The vertical load, horizontal load and overturning moment of the excavator working device acting on the turntable are all transmitted to the chassis through the turntable, the outer ring, the rolling body and the inner ring of the slewing bearing.

4. Swing hydraulic system

Take a certain type of excavator as an example. The excavator is equipped with two main pumps, P1 and P2, and the P1 pump alone supplies oil when operating the rotation. The rotary motor is a swash plate type axial piston motor, and the pressure oil output by the P1 pump drives the rotary motor to rotate through the oil circuit of the rotary hydraulic system. The rotary motor is provided with an anti-reverse valve 2, a rotary relief valve 3, an oil replenishing check valve 4, and a delay brake valve 8. The delay brake valve 8 is composed of a pressure reducing valve 7 and a reversing valve 9. The main function of these valve groups is to protect the rotary oil circuit from overloading.

The working principle of the excavator slewing mechanism

Excavator slewing bearing

When the excavator is operated to rotate, the pressure oil output by the rotary pilot valve enters the side of the return switch to the spool, pushes the return switch valve 1 spool to move, and opens the return switch to the oil circuit. The pressure oil output from the main pump is converted back into the working oil circuit (ports A and B) of the rotary motor, and drives the rotary motor 5 to rotate.

The pilot pressure oil from the swing pilot valve enters the oil port of the delay brake at the same time, and the pilot pressure oil of the oil port pushes the reversing spool of the delay brake valve, so that the pressure oil (PG port) output by the pilot pump enters the swing Brake piston chamber. Lift the brake piston to separate the brake pads to release the brake, and the rotary motor can drive the turntable to rotate through the rotary reducer. When the excavator is controlled to stop turning, the spool of the turning pilot valve returns to the neutral position, the pilot oil is relieved of pressure, and the spool of the return switching direction returns to the neutral position.

The working oil circuit (A and B ports) of the rotary motor is cut off, and the rotary motor continues to rotate under the action of inertia, which increases the pressure on the oil return side of the rotary motor 5. This high-pressure oil becomes the main mechanism for the rotary motor to stop rotating. power. When the pressure reaches the pressure set by the swing relief valve, the swing relief valve opens to relieve pressure to prevent excessive pressure on the oil return side of the swing motor and protect the swing hydraulic system.

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