Created on:2021-05-14 09:34

Working principle of swing hydraulic motor

Working principle of swing hydraulic motor

(1) Vane type swing motor

① The blade of single blade swing motor [Fig. Q (a)] divides the working chamber into two chambers. When the pressure oil enters one of the cavities, the volume of the cavity increases, the blades rotate, and the volume of the other cavity decreases to drain the oil. When the load reverses, the blade is driven to rotate reversely through the output shaft. The advantages of single blade swing motor are simple and compact structure, small axial size, light weight, easy installation, good for overall layout and high mechanical efficiency. The disadvantages are that the sealing is difficult, the processing is complex, the compression area of the two end covers is large, the stiffness is not easy to guarantee, and the output shaft is subject to unbalanced radial force.

② Multi blade swing motor [Fig. Q (b) and (c)] two (or three) a cavities of multi blade swing motor must be filled with pressure oil at the same time, and two (or three) B cavities must also return oil at the same time. Compared with the single blade swing motor, the output torque of the multi blade swing motor can be increased by one or two times, the output shaft is free of radial force, and the mechanical efficiency is higher. But the angle is small, the internal leakage is large, and the volumetric efficiency is low.

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(2) Piston rack and pinion swing motor

① The working principle of single cylinder single acting rack and pinion swing motor is shown in Figure R (a). When the pressure oil flows into the left chamber of the hydraulic cylinder, the piston rod with the rack moves to the right under the push of the pressure oil, and the load on the output shaft is driven to rotate through the rack and gear. The pressure oil reverses and the output shaft reverses. The advantages of this kind of motor are simple structure, easy sealing, high transmission efficiency, smooth transmission of torque and angular velocity, and easy position control. The disadvantage is that the manufacturing and installation requirements are high.

② The single cylinder double acting type is shown in the figure R (b). When the pressure oil enters the left and right cavities of the hydraulic cylinder at the same time, the upper and lower pistons move relatively to drive the gear to rotate and output torque. If the pressure oil enters the middle chamber, the gear will rotate in the opposite direction. Compared with the single acting type, the output torque is larger. But the stroke is short, the angle is small, and the manufacturing and installation accuracy is higher.

③ The double cylinder double acting type is shown in Figure R (c), and the upper and lower hydraulic cylinders are independent of each other. When the pressure oil enters from ports a and D, the piston of the upper cylinder moves to the right and the piston of the lower cylinder moves to the left, which jointly drives the gear to rotate clockwise to output torque. At this time, ports B and C discharge oil; when the pressure oil reverses, the gear rotates counterclockwise. Compared with the single cylinder double acting swing motor of the same size, the double cylinder double acting swing motor has longer stroke and larger angle.

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(3) Figure s (a) shows the working principle of a piston screw swing motor. The piston and the screw form a screw pair, and the left and right half of the screw are right-handed and left-handed threads, which are respectively rotated with the left and right pistons. When the pressure oil flows in from the middle of the two pistons, the two pistons move in opposite directions to drive the screw to rotate and output torque. If the pressure oil reverses, the screw rotates reversely. The output torque is large and the screw is free of axial force. However, it can only be used for low pressure because of its short stroke, small angle and large leakage at the screw. Figure s (b) shows another kind of piston spiral swing motor. Its principle is the same as that in figure s (a), but the motor in figure s (b) uses a sealing ring to separate the left and right cavities of the piston, and there is no need to set another seal at the screw pair, so the internal leakage is greatly reduced, which can be used for high pressure.

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(4) The piston chain swing motor is shown in Figure T. the large and small pistons of the piston chain swing motor are fixed with the chain. The chain wheel is installed on the output shaft, and the chain wheel is meshed with the chain wheel. When passing through the pressure oil, the big piston will move in a straight line along the pressure direction because of the large thrust, and the output shaft will rotate through the transmission of chain and sprocket. If the pressure oil reverses, the output shaft also reverses. Madaco drives two loads with a certain distance to rotate at the same speed. The load acting on the shaft is small and the work is reliable. But the chain is easy to wear, and the transmission is not stable enough at high speed.

(5) The piston crank connecting rod type swing motor is shown in Figure U. the hydraulic cylinder of the piston crank connecting rod type swing motor can swing. The piston rod is connected with the crank, and the crank is connected with the output shaft. When the pressure oil passes into the piston cavity, the piston rod pushes the crank to move, drives the output shaft to rotate, and outputs the torque. When returning, the piston is pushed back by external force. This kind of motor has the advantages of simple structure and easy manufacture; the longer the crank is, the greater the output torque is, and it is easy to realize the angle adjustment.

(6) The piston to compound swing motor is shown in Fig. v. in the piston to compound swing motor, when the pressure oil enters from port a and pushes the piston to move in a straight line to the left, port B discharges the oil. In Figure V, the main shaft is fixed, and the connecting cylinder block and the connecting rod are forced to rotate by the connecting screw pair. If port B is filled with oil and port a is drained, the cylinder block will be reversed. The size of the motor angle depends on the piston stroke. The motor has the advantages of compact structure, small volume, stable and reliable operation and easy sealing. The disadvantage is that the processing cost is high.

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This kind of motor can also be designed as a double screw pair at the inner and outer diameters of the piston. At this time, the structure is more compact and the work is more stable, but the processing and assembly requirements are correspondingly improved.

In addition to some of the above hydraulic motors, recently a kind of bag swing hydraulic motor has been introduced abroad. A pair of bags which can fill or discharge hydraulic medium are symmetrically arranged inside the motor. Through the expansion and contraction of the bags, the output shaft of the motor can be driven to swing. When one bag is filled with pressure liquid, it pushes an annular lever arm to swing the motor output shaft, while the other bag discharges liquid. The liquid in and out of the two bags is controlled by a four-way reversing valve, so that the motor can change the swing direction. The motor has the advantages of high motion accuracy, small leakage, low pollution sensitivity and wide adaptability to liquid medium. The output angle of the motor is 100 ° and the torque is 31On · M.

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