Typical structure of swing cylinder radial piston motor
Typical structure of swing cylinder radial piston motor
Figure B shows the structure of swing cylinder radial piston motor with end face distribution. The pressure oil enters the piston cylinder from the trunnion 13, and the cylinder body swings around the trunnion during operation. There is no lateral force between the plunger 12 and the swing cylinder, and there is almost no wear between them. The bottom of the plunger is designed as static pressure balance, and the force is transmitted between the plunger and crankshaft 3 through rolling bearing 11. These measures reduce the friction loss in the process of force transmission, thus improving the mechanical efficiency of the motor. The hydraulic mechanical efficiency of the motor, especially in the starting state, can reach 90%, so the starting torque is very large. In addition, the leakage is greatly reduced and the reliability is improved by using the end face flow distribution technology; the plastic piston ring seal is used between the piston and the swing cylinder, which can achieve almost no leakage and greatly improve the volumetric efficiency. This kind of motor has good stability at low speed and can run smoothly at very low speed (less than 1 R / min). The speed regulation range is also very large, and the speed regulation ratio (the ratio of the highest and the lowest stable speed) can reach 1000. Because of its simple structure, reasonable design and bearing with large load capacity, the motor has the advantages of small volume, light weight, reliable operation, long life and low noise. The figure below shows the physical shape of a swing cylinder fixed displacement radial piston motor.
③ Hydrostatic balance radial piston motor this kind of motor is also called hydrostatic balance motor, which belongs to no connecting rod motor, and its structure is shown in Figure C.
There are five plunger cylinders (numbered I-V) evenly distributed along the radial direction on the housing 4 of the motor, and the five plungers 2 are respectively installed in the plunger cylinders of the housing. This kind of motor cancels the connecting rod, and the five-star wheel 5, which is fitted on the eccentric 1 of the crankshaft 6, acts as the connecting rod. Each of the five radial holes of the five-star wheel is embedded with a pressure ring 7, and the upper end face of the pressure ring and the plunger are provided with corresponding middle through holes. Crankshaft 6 is supported by a pair of tapered roller bearings 8, one end of which is an extended output shaft, and the other end is provided with two annular grooves (C and D) which are respectively connected with the oil inlet and return ports a and B on the current collector 10. Two grooves are machined on the eccentric wheel in the middle of the crankshaft, and the two grooves are respectively connected with the oil inlet and outlet a and B through the axial hole and annular groove on the crankshaft.
When the motor is working, the high-pressure oil enters the current collector 10 from port a, passes through the annular groove D of the crankshaft, the axial hole and the port chamber on the left side of the eccentric, enters the through hole between the five star gear, the pressure ring and the plunger, and reaches the No. IV and V cylinders to form the high-pressure liquid chamber. The high-pressure oil acts directly on the eccentric of the crankshaft, and its resultant force forms a torque on the rotation center of the crankshaft through the center of the eccentric (eccentricity is e), so that the crankshaft rotates clockwise. After turning an angle, cylinder I is also connected with the high pressure chamber. In this way, two or three cylinders are fed with high pressure oil alternately. In the working process of the motor, the five-star wheel moves in a plane relative to the plunger, while the plunger moves up and down. During start-up or no-load, the elastic force of the spring 3 in the hollow plunger overcomes the friction between the plunger and the cylinder wall, so that the bottom surface of the plunger is in close contact with the pressure ring. When changing the flow direction of the inlet and outlet, the motor will reverse. This kind of motor has both crankshaft rotation type and shell rotation type. Because the crankshaft is fixed, the valve sleeve 9 can be omitted, which greatly simplifies the structure and reduces the cost. The motor with double extension shaft can bear more load than the motor with single extension shaft. In order to increase the torque, the hydrostatic balancing motor with double row plunger (two eccentric wheels) is sometimes made. In order to make the radial force on the crankshaft balance with each other, the eccentric directions of the two eccentric wheels are 180 ° different.
Compared with the connecting rod type motor, the hydrostatic balancing motor has the following characteristics: the crankshaft has the function of transmitting power and distributing shaft, so the axial dimension of the motor is smaller; replacing the connecting rod with five-star wheel can simplify the structure and process, and reduce the radial dimension; however, the cancellation of the connecting rod leads to the increase of the lateral force between the plunger and the cylinder bore, and the sliding between the five-star wheel and the bottom surface of the plunger, and between the five-star wheel and the eccentric wheel The relative motion friction loss between the moving surfaces is very large, which affects the mechanical efficiency of the motor. The pressure oil directly acts on the eccentric wheel of the crankshaft to form torque and make the crankshaft rotate. At this time, the hydraulic pressure on the plunger, the pressure ring and the five-star wheel is close to the static pressure balance. Therefore, in the work, the plunger, the pressure ring and the five-star wheel only play the sealing role of not making the pressure oil leak, so it is called static pressure Pressure balance motor.