First, CJT13 type radial piston pump structure and working principle shown in Figure 1, the pump by the radial piston pump (also known as the main oil pump, the drum 15, the reaction ring 16, the plunger 17, the slider 18 , The rotor 19, the oil distribution shaft 20 and other components), the servo control mechanism (by the reset small plunger 8, the adjustment screw 9, the positioning of the movable plate 10, the control plunger 11, the servo slide valve 12, the zero slide valve 13, servo Piston 14, a small piston 21 and other components), gear pump (auxiliary pump) 2, safety valve 7, the valve 6, the suction check valve 5, back pressure valve 4 and other components. Sliding seat 18 in the gear pump 2 under the pumping control can move left and right, resulting in eccentric, to achieve the main oil pump bi-directional variables. The pressure oil of the gear pump 2 is divided into two paths from the outlet c to the port e, all the way to the oil chamber g of the small piston 21 via the oil path f, and the other path (see FIG. 2) is connected via the oil path h → d → r . When the servo spool 12 is moved to the right by a distance e, the oil port a is opened and the oil in the oil chamber r enters the left chamber j of the servo piston 14 through the oil port a. Since the area of ​​the servo piston 14 is larger than the area of ​​the smaller piston 21 (FIG. 1) (the area ratio is 2: 1), the pressure of the gear pump urges the servo piston 14, carriage 18, drum 15 and reaction ring 16 to the right, The oil port a is closed, the movement stops, and its moving distance is equal to the distance e that the servo slide valve 12 moves to the right. When the servo spool 12 moves to the left for a distance e, the port b is opened, and the oil in the chamber j passes through the port b → t → the oil sump. The pressure oil in the oil chamber g pushes the small piston 21 to drive the carriage 18, the drum 15 and the reaction ring 16 to move to the left until the oil port b is closed and the movement is stopped by the distance e that the servo spool moves to the left. The axial displacement of the servo slide valve 12 is controlled by three control plungers 11 uniformly distributed around it (FIG. 2). Under the action of the pressure oil of the gear pump, the control plunger 11 moves left to the end face of the corresponding adjustment screw 9 , The adjustment screw 9 can control the stroke of the maneuvering plunger 11. The left end of the maneuvering plunger 11 is also in contact with the edge of the positioning movable plate 10 fixed on the left end of the servo sliding valve 12. Therefore, when the maneuvering plunger 11 is moved to the left, the movable plate 10 is driven to move the servo slide valve 12 to the left to make the radial piston The pump carriage 18 generates an eccentric movement. The center of the servo slide valve 12 has a small φ12mm reset plunger 8 (smaller than the maneuvering plunger 11) with its left end resting on the fixed cover. The reset small plunger s cavity s 8 always through the gear pump pressure oil 2, the servo slide valve 12 has a rightward force, so that the servo slide valve 12 on the movable plate 10 close to the end face of the manipulating plunger 11 on. When the right end of the maneuvering plunger 11 is connected to return oil, the servo slide valve 12 moves to the right. As can be seen from FIG. 3, the "zero" maneuvering plunger 11a is controlled by the two-position three-way solenoid valve 26 and the "return" maneuvering plunger 11b controlled by the two-position three-way solenoid valve 27. The "working" maneuvering plunger 11c is always supplied with high pressure oil. The actual position of the two-position three-way solenoid directional control valve 26, 27 is shown in FIG. 4. 1. Oil filter 2. Gear pump 3. Relief valve 4. Back pressure valve 5. Suction check valve 6. Directional valve 7. Safety valve 8. Reset small plunger 9. Adjusting screw 10. Positioning movable plate 11 Pilot plunger 12. Servo slide valve 13. Zero slide valve 14. Servo piston 15. Drum 16. Reaction ring 17. Plunger 18. Carriage 19. Rotor 20. Oil distribution shaft 21. Small piston Figure 1 8 . Reset the small plunger 9. Adjust the screw 10. Positioning the movable plate 11. Manipulate the plunger 12. Servo slide valve 13. Zero slide valve 14. Servo piston Figure 2 Second, the main problems and improvements 1. Large energy consumption 1) Cause The reason for large energy consumption is that the oil output from the gear pump 2 is overflowed by the relief valve 3. The first gear pump pressure oil into the servo control mechanism, changing the eccentric main pump to achieve its variables, the required pressure p1 = 1.2 ~ 1.5MPa. The second is through the relief valve 3 overflow oil (see Figure 1) through the port k → filter 1 → port l → port m → port n, into the main suction pump suction chamber, the suction chamber to maintain 0.2 to 0.3 MPa pressure (set by the back pressure valve 4), the plunger in the suction chamber 17 and the reaction ring 16 is pressed. The gear pump and main pump are driven by a single motor. As soon as the motor is started, it generates an overrun, which reduces only when the main pump is changed to an eccentric position. Now CJT13-400E (E on behalf of low-noise type) radial piston pump as an example for analysis. The power required to drive gear pump P1 is calculated as follows: P1 = Q (p1 + p2) / (61.2η1), kW (1) Where Q - gear pump flow, Q = 80L / min p1 - change the main pump Eccentric required pressure p1 = 1.2 ~ 1.5MPa p2 - the main pump suction chamber pressure p2 = 0.2 ~ 0.3MPa η1 - gear pump efficiency, take η1 = 0.7 Substitution into (1) Formula: P1 = 80 〔 1.5) + (0.2 ~ 0.3)] / (61.2 × 0.7) = 2.6 ~ 3.36kW Due to the overflow of the pressure oil output from the gear pump 2 through the overflow valve 3, the energy consumption is converted into heat energy to increase the oil temperature of the machine tool . (2) Improvement Method Clogged gear pump outlet c, cancel the relief valve 3, so that the gear pump only 0.2 ~ 0.3MPa pressure to the main pump suction chamber for oil. In addition, the servo control valve inlet e then a pressure-limiting variable pump, such as Qinchuan Machine Tool Plant produced 1PV2V4-type pressure-limiting variable displacement vane pump (flow selected 80L / min), the main pump to change the moment of eccentricity, The pump discharges high-pressure high flow, the rest of the pump only discharge high-pressure to maintain the leakage of small flow, thus greatly saving energy consumption. After increasing the pressure limiting variable pump, gear pump energy consumption P2 = 80 × 0.3 / (61.2 × 0.7) = 0.56kW. Pressure limiting variable vane pump in the main oil pump to the moment of energy conversion P3 = Qp1 / (61.2 × η2), take Q = 80L / min, p1 = 1.5MPa (whichever is greater), η2 0.9, substituted: P3 = 80 × 1.5 / (62.1 × 0.9) = 2.18kW. Radial piston pump reversing (time is very short) after the end of pressure-limiting variable pump as long as the pressure (p1 = 1.5MPa), to supplement the required flow of system leakage can be. It is known that the pump volumetric efficiency η3 = 0.95, the amount of leakage Q bleed = 80 × (1-0.95) = 4L / min. At this point, the pressure limiting variable pump drive power P4 = Q vent × p1 / (61.2 × η2) = 4 × 1.5 / (61.2 × 0.9) = 0.11kW. This shows that the use of pressure-limiting variable pump, you can reduce the drive power = P1-P2-P4 = (2.6 ~ 3.36) -0.56-0.11 = (1.93 ~ 2.69) kW. (Due to the main pump reversing time is short, ignoring its instantaneous energy consumption P3) 2. Noise (1) causes One of the reasons for noise is the main pump self-absorption ability is poor, the suction chamber must be supplied by the gear pump 2 , The hydraulic pressure set by the back pressure valve 4 0.2 ~ 0.3MPa, the plunger in the suction chamber 17 and the reaction ring 16 compression (because of the friction between the plunger and the rotor hole, the centrifugal force alone can not be the plunger Thrown). However, the gear pump displacement is much smaller than the main pump displacement, resulting in poor self-absorption due to the noise generated. Now CJT13-400E radial piston pump on the L6140B type broaching machine (Figure 3) as an example to analyze. The hydraulic system of the broaching machine is a closed loop when working and returns a differential loop. Known: broaching cylinder diameter D = 280mm, piston rod diameter d = 90mm, working speed v workers = 1.5 ~ 7.2m / min, the maximum return speed v back = 20m / min. The maximum flow rate required for work Q max is calculated according to the following formula: Q max = v max x F1 / 1000 (2) where max max - max working speed v max = 7.2 m / min F1 - Work pressure of the piston area, F1 = π (D2-d2) / 4 Substitution (2) Type: Q workers max = 7.2π (2802-902) / (4 × 1000) = 397.5L / min CJT13-400E type Radial piston pump rated displacement of 400L / min, to meet the requirements. The maximum working speed, the oil return chamber row Q row according to the following formula: Q row = V workers maxF / 1000 (3) where F = πD2 / 4 into (3) Type: Q row = 7.2π × 2802 /(4×1000)=443.3L/min Because the closed-loop work, the displacement into the main pump suction chamber, coupled with the displacement of the gear pump to the suction chamber flow greater than 400L / min, the suction chamber excess Oil through the back pressure valve 4 back to the pool. At this point, the suction chamber to ensure that there is 0.2 ~ 0.3MPa hydraulic pressure, no noise. Return to the required maximum flow Q return max calculated as follows: Q return max = V return F2 / 1000 (4) Where V return - return to the maximum speed, V return = 20m / min F2 - piston rod area, F2 = πd2 / 4 Substituting into equation (4), Q returns max = 20π × 902 / (4 × 1000) = 127L / min In this cycle, the oil discharged from the main oil pump enters the left chamber (rodless chamber) The oil in the right chamber (rod chamber) enters the rodless chamber through the pilot operated check valve 22, and the one-way valve 23 closes to form a differential circuit. Calculated by the above, return to the maximum speed, the main pump displacement of 127L / min, while the gear pump displacement of only 80L / min, less than the main pump displacement, the main pump must be drawn through the check valve 5 from the oil Therefore, the suction chamber can not guarantee a pressure of 0.2 ~ 0.3MPa, resulting in poor self-absorption due to the noise generated, the noise up to 90dB or more. 1. Oil filter 2. Gear pump 3. Relief valve 4. Back pressure valve 5. Suction check valve 6. Directional valve 7. Safety valve 8. Resetlet plunger 11a. . Manipulate plunger 11b. "Return" maneuvering plunger 11c. "Work" maneuver plunger 12. Servo slide valve 13. Zero slide valve 14. Servo piston 22. Pilot operated check valve 23. Check valve 24. Pressure Table 25. Pressure Gauge Switches 26, 27. 2/3-Way Solenoid Directional Valves (23E1-10B) Figure 3 9a. Zero Adjustment Screw 9b. Return Adjustment Screw 9c. Operating Adjustment Screws 26, 27 Two-way three-way solenoid valve (23E1-10B) Figure 4 28. Two two-way solenoid valve (diameter φ10mm) Figure 5 (2) Solution ①Increase the gear pump flow can be parallel to a gear Pump; ② The return speed is controlled at 12.5m / min or less, so that the displacement of the main oil pump gear pump displacement. 3. Zero valve work is not reliable (1)
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