Problems Existing in CJT13 Radial Piston Pump and Improvement Methods

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 sliding valve 12 to the left to make the radial plunger 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 8 s cavity 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 steering 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 electromagnetic 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 the small plunger 9. Adjust the screw 10. Locate the movable plate 11. Manipulate the plunger 12. Servo slide valve 13. Zero-position slide valve
14. Servo piston 15. Drum 16. Reaction ring 17. Plunger 18. Slide 19. Rotor 20. With oil axis 21. Small piston Figure 1

8. Reset the small plunger 9. Adjust the screw 10. Locate the movable plate 11. Manipulate the plunger
12. Servo slide valve 13. Zero slide valve 14. Servo piston Figure 2
Second, there are major problems and improvements 1 large energy consumption (1) causes of energy consumption is due to the large gear 2 output of the oil overflow valve relief 3 caused. 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 pressure required p1 = 1.2 ~ 1.5MPa
p2 - main pump suction chamber pressure p2 = 0.2 ~ 0.3MPa
η1 - gear pump efficiency, take η1 = 0.7
Substitution (1) formula is:
P1 = 80 [(1.2-1.5) + (0.2-0.3)] / (61.2 × 0.7)
= 2.6 ~ 3.36kW
Due to the gear pump 2 output pressure oil overflow overflow valve 3 overflow, so more energy into heat, so that machine oil temperature rise.
(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 causes of noise is the main pump self-absorption ability is poor, the suction chamber must be supplied by the gear pump 2, hydraulic pressure set by the back pressure valve 4 at 0.2 ~ 0.3MPa, The plunger 17 in the suction chamber is pressed against the reaction ring 16 (because of the friction between the plunger and the rotor bore, the plunger can not be thrown out by centrifugal force alone). 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 required for work Q max is calculated as follows:
Q workers max = v workers max × F1 / 1000 (2)
Type v workers max - maximum working speed, v workers max = 7.2m / min
F1 - piston compression area when working, F1 = π (D2-d2) / 4
Substituting (2) into the formula:
Q work max = 7.2π (2802-902) / (4 × 1000) = 397.5L / min
CJT13-400E radial piston pump rated displacement of 400L / min, to meet the requirements.
The maximum working speed, the oil return chamber row Q row by the following formula:
Q row = V workers maxF / 1000 (3)
Where F = πD2 / 4
Substitution (3) is:
Q row = 7.2π × 2802 / (4 × 1000) = 443.3L / min
Because the work is closed loop, this displacement into the main pump suction chamber, coupled with gear pump displacement, 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.
The maximum flow required to return Q to 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
Substitution (4) is:
Q back to max = 20π × 902 / (4 × 1000) = 127L / min
During this cycle, the oil discharged from the main oil pump enters the left chamber (rodless chamber) of the cylinder and the oil in the right chamber (rod chamber) of the cylinder enters the rodless chamber through the pilot check valve 22. At this time, the check valve 23 is closed, 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. Inlet check valve 6. Directional valve
7. Safety valve 8. Reset the small plunger 11a. "Zero" manipulate the plunger 11. Operate the plunger
11b. "Return" maneuvering plunger 11c. "Work" maneuvering plunger 12. Servo slide valve
13. Zero Sliding Valve 14. Servo Piston 22. Hydraulic Check Valve 23. Check Valve 24. Pressure Gauge
25. Pressure gauge switch 26,27. Two three-way solenoid valve (23E1-10B)
image 3

9a. Zero adjustment screw 9b. Return adjustment screw
9c. "Working" adjustment screw
26,27. Two three-way solenoid valve (23E1-10B)
Figure 4

28. Two two-way solenoid valve (diameter φ10mm)
Figure 5
(2) solution â‘  increase the gear pump flow, a gear pump can be paralleled; â‘¡ return speed control in 12.5m / min or less, the main pump displacement is less than the gear pump displacement.
3. Zero valve work is not reliable (1) causes of the main zero eccentric piston manipulated by the control plunger 11, and manipulate the left end of the plunger position adjustment screw 9 set (Figure 2), because it is impossible to tune very Standard, so the main oil pump will have pressure oil output, for which set zero slide valve 13 (Figure 3). When the main oil pump eccentricity is "zero", the electromagnet YA1 is de-energized, and the gear pump pressure oil is manipulated by the solenoid valve 26 to "zero" to the left end of the plunger 11a and the zero-position slide valve 13 to connect the two chambers of the main oil pump x, y , So that the oil discharged from the main oil pump circulates inside it, without entering the system to stop the machine tool. However, due to the structure and size of the zero slide valve 13 (zero slide valve size is small, easy to get stuck), the throughput is not enough, although the two main oil pump oil chamber connected, but there are some pressure, pressure Oil enters the system so that the machine can not stop.
(2) solution with a diameter of 10mm two two-way solenoid valve 28 instead of zero slide valve 13. Specific practices are as follows: Remove the tube shown in Figure 5, B, blocking the oil port a2, b2, port a1, b1 received two two-way electromagnetic valve 28 port a3, b3.
Third, to improve the effect (1) reduce the heating hydraulic system, the maximum summer oil temperature can be lower than 60 ℃;
(2) the noise is obviously reduced, the noise can be controlled at about 85dB;
(3) with two two-way solenoid valve 28 instead of zero slide valve 13, the machine can stop and reliable.
Author: Yang Xiaohong (Hunan Institute of Industry and Technology, Shaoshan Road, Yuhua Pavilion, No. 102, 410007)
Zhao Xianqiong (Hunan Institute of Industry and Technology, Shaoshan Road, Yuhua Pavilion, No. 102, 410007)

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