Created on:2021-06-11 10:27

Non through shaft axial piston pump 1

Non through shaft axial piston pump 1

a. Figure f shows a non through shaft quantitative axial piston pump structure with large diameter cylinder bearing. A plunger 12 is arranged in the axial cylinder hole of the cylinder block 13, and a sliding shoe 11 is arranged on the spherical head of each plunger. The return mechanism is composed of central spring 6 and return plate 7, which presses the sliding shoe tightly on the inclined plane of swash plate 8, so that the pump has a certain self-priming capacity. When the cylinder block is driven to rotate by the transmission shaft 1, the plunger moves back and forth with respect to the cylinder block, and the oil hole at the bottom of the cylinder completes the oil suction and pressure work through the oil distribution window on the valve plate 14. The cylinder block is supported on the roller bearing 10, so that the radial force of the swash plate to the cylinder block can be borne by the roller bearing, so that the transmission shaft and the cylinder block are only subjected to torque without bending moment. The small hole between the plunger and the slipper can make the pressure oil in the cylinder hole flow to the contact plane between the slipper and the swashplate, forming a static pressure oil film, which reduces the wear between the slipper and the swashplate. A large diameter special short roller bearing 10 is arranged at the front end of the cylinder block to bear the lateral force directly, and the transmission shaft is only used to transmit the torque. Since the swash plate 8 is always fixed on the quantitative end cover 9, the stroke of the plunger cannot be changed, so the displacement of the pump is fixed.

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b. Variable pump figure g shows a non through shaft manual variable axial piston pump structure. The pump is composed of a variable head part on the basis of the structure of the quantitative pump shown in Fig. g. the former is called the main part of the pump here. The front end of the cylinder block is still provided with a short roller bearing 9 to bear the lateral force directly.

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The variable head is a manually controlled variable mechanism. Adjust the hand wheel 11 to make the adjusting screw 14 rotate and drive the variable piston 17 to move axially (the guide key is installed on the side to prevent rotation, which is not shown in the figure). Through the middle pin shaft 15, the swash plate supported on the housing of the variable mechanism rotates around the center of the ball hinge 7, thus changing the inclination angle of the swash plate, that is, changing the displacement of the hydraulic pump. The percentage value of the displacement adjustment can be roughly observed by the dial 16. After adjustment, it can be tightened by the lock nut 12. The structure of this variable mechanism is simple, but it is not easy to operate, and the adjustment variables must be unloaded during operation.

The domestic scy series pumps belong to this kind of pumps. The volumetric efficiency is as high as 95% and the rated pressure is 31.5Mpa. In addition to manual control, the variable control mechanism also includes hydraulic control, electro-hydraulic proportional control, DC motor servo control and stepping motor digital control. The main structure of these pumps is the same. As long as different variable mechanisms are replaced, they will become another variable pump.

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Figure h shows the structure of bcy14-1 electro-hydraulic proportional control variable axial piston pump. The main part of the pump is driven by the transmission shaft 1 to rotate the cylinder block 20, so that the seven plungers evenly distributed on the cylinder block rotate around the center line of the transmission shaft, and the slide shoe 18 in the column slide assembly is pressed on the inclined plane of the swash plate through the central spring 6. Thus, the plunger moves back and forth with the rotation of the cylinder block to complete the oil suction and pressure action. The variable mechanism adopts proportional electromagnet and external control oil pressure control, and works based on the principle of "flow displacement force feedback". The flow of the pump is changed by changing the current of the input proportional electromagnet 11. The input current is proportional to the flow of the pump. The principle of the electro-hydraulic proportional control variable is shown in Figure I. When the input current of the proportional electromagnet 1 is zero, the pilot spool 3 of the control slide valve is pushed to the upper end under the action of the feedback spring 6. At this time, the external control oil with pressure of PC and flow rate of QC enters the upper and lower cavities of the variable piston 7. Because the area of the upper cavity A1 is larger than the area of the lower cavity a, the variable piston is pushed to the lowest position, the deflection angle of the swash plate 8 is zero, and the displacement of the pump is zero. When the input current of the proportional electromagnet increases, the pilot spool 3 moves downward driven by the thrust of the proportional electromagnet, so that the upper port of the slide valve is opened, the upper chamber of the variable piston 7 is connected with the oil return chamber through the hydraulic resistance R and the control edge of the valve, the pressure of the upper chamber decreases, the variable piston moves upward, the swash plate deflection angle increases, and the displacement of the pump also increases The feed spring acts on the spool and pushes the spool to the balance position. The variable piston maintains a certain balance position and the pump displacement also maintains a certain value. On the contrary, when the input current decreases, the spool moves up under the action of the feedback spring, so that the valve port leading to the oil return chamber decreases and the valve port entering the upper chamber increases. As a result, the pressure PC1 in the upper chamber increases and the variable piston moves down. When the electromagnet thrust equals the feedback spring force, the spool returns to the balance position, so that pcla1 = PCA and the variable piston is flat in a new position Balance. Under the condition of constant input current, if the variable piston moves up or down due to load or other interference reasons, the displacement of the variable piston will change. Through the feedback spring acting on the spool of the slide valve, the opening of the slide valve will be changed, so that the upper chamber pressure of the variable piston will increase or decrease to resist the change of load, and finally the variable piston will return to the position corresponding to the input current Put it on, that is, keep the displacement unchanged. It can be seen that the proportional variable displacement pump can realize proportional control of displacement under the action of input current, and has strong anti load interference ability. Figure J shows the variable characteristic curve and hydraulic principle of the pump.

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Compared with other variable control methods, the electro-hydraulic proportional control variable piston pump has a series of advantages, such as flexible control, sensitive action, high repetition precision, good stability, and can easily realize the remote control, automatic control, stepless speed regulation, tracking feedback synchronization and computer control of the hydraulic system. It is suitable for mechanical equipment with higher automation requirements in the industrial field.

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