Created on:2021-04-21 10:07

Variable mechanism of radial piston motor

Variable mechanism of radial piston motor

① The variable displacement of single acting variable displacement motor is realized by changing the eccentricity of eccentric wheel. Figure t shows the variable structure of the radial moving eccentric sleeve. A variable slip ring 1 is arranged between the valve housing and the cylinder block, and is fixed together with screws. The eccentric part of the crankshaft is provided with large and small piston cavities. The control oil is introduced by the variable slip ring into the small piston cavity, and pushes the small piston 3 against the eccentric sleeve 5 to the maximum eccentricity position. At this time, the motor displacement is the maximum, which is the low-speed and high torque condition; when the control oil pushes the large piston 4 against the eccentric sleeve to the minimum eccentricity, the motor displacement is the minimum, which is the high-speed and low torque condition. By properly designing the stroke of large and small pistons, the variable displacement motors with different eccentricities can be obtained.


The control oil circuit with stage variable is shown in Figure U. The shuttle valve 3 is set in the oil circuit to ensure that the control oil pressure in the piston chamber of variable cylinder 1 is always high pressure when the hydraulic motor 2 is in forward and reverse rotation. In Figure u, the variable cylinder L is a combination of large and small pistons, and the throttle valve 4 is used to adjust the variable process time. The two position four-way manual directional valve 5 can be either manual or hydraulic. When the main engine requires free wheel operation, the motor can be designed as a step variable with zero eccentricity and maximum eccentricity.


② The stage variable control of the multi action hydraulic motor is usually realized by changing any one of the action number x, row number y and plunger number Z when the plunger diameter D and plunger stroke h are fixed.

a. Changing the variable of action number x to divide the guide surface number of the motor into two or three groups is equivalent to dividing a motor into several motors in parallel, and using the variable speed directional valve and the corresponding port shaft structure to realize the variable. Figure V shows the variable principle of changing the action number X. the action number of the motor is divided into Xa and XB motors, x = XA + XB. When the hydraulic control directional valve is in the right position as shown in Figure V, the pressure oil enters motor A and B at the same time, which is a low-speed full torque condition. When the reversing valve is switched to the left position, all the pressure oil enters into motor a, and the oil inlet and outlet of motor B are connected back to the oil circuit. It is a high-speed half torque working condition, and B is driven to rotate by A. With proper allocation of XA and XB, the motor can get different variable adjustment range.

b. Changing the variable of plunger number Z, this method is to divide the plunger of motor into two groups or arrays, a and B, corresponding to the distribution window group of valve distributor. Figure w shows the expansion diagram of variable plunger number variable for x = 6 and z = 10 motors. The left side is the expansion diagram of the port window of the valve distributor, and the right side is the port window of the cylinder bore. When the directional valve is in the lower position as shown in Fig. W, the two groups of plunger A and B are all filled with pressure oil, which is the low-speed full torque working condition. When the reversing valve is switched to the upper position, the plunger of group B is supplied with pressure oil, and the plunger of group A is supplied with return oil, which is a high-speed half torque condition.


c. When the hydraulic motor is designed as a double or three row plunger structure, the displacement can be changed by changing the number of rows. This variable method does not need special variable design, so there is no pulsation before and after the variable. Figure x shows the variable method of two rows of plugs in series or in parallel. The variable speed directional valve makes two rows of plugs in parallel or in series to realize variable. As shown in figure x, two groups A and B are respectively connected with the oil inlet and outlet, which is the low-speed full torque working condition. The outlet of group A is connected with the inlet of group B, which is high-speed half torque condition.


It should be pointed out that the above step variable method will reduce the efficiency and shorten the service life of roller and guide rail when reversing the variable. Reasonable design of variable directional valve can avoid this situation. The oil return back pressure of the system should be selected according to the high speed condition.

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