Variable pump and hydraulic control system thereof

Abstract

The invention discloses a variable pump and a hydraulic control system thereof. The variable pump comprises a shell, and a pump body, a variable control oil cylinder, a pressure control valve and a flow control valve are arranged in the shell; the hydraulic control system based on the variable pump further comprises a pilot-operated overflow valve and an oil tank, and an oil outlet formed in a shell of the variable pump is communicated with an oil inlet of the pilot-operated overflow valve through a pipeline; a one-way rotating mechanism is arranged at the end of a rod column of the screw pump and is in transmission connection with a transmission shaft of the variable pump. The variable pump is applied to a screw pump well, the braking effect of the variable pump is automatically adjusted according to the braking requirements of the screw pump and a rod string, the rotating speed of the rod string is prevented from being too high, meanwhile, the reverse rotation energy of the rod string is consumed as much as possible, safety protection is provided for the screw pump well, and safety guarantee is provided for underground production.

Description

Technical Field

[0001] The present invention relates to a variable pump and its hydraulic control system, belonging to the technical field of hydraulic control. Background Art

[0002] In recent years, due to the advantages of less one-time investment, small floor area, energy conservation, etc., the screw pump oil production technology has been widely applied in the oilfield exploitation field. Although the advantages are obvious, the screw pump also has deficiencies in actual application. For example Figure 1 As shown, a structural schematic diagram of a surface-driven screw pump well is given. The casing 501 extends into the well, and the tubing 502 is placed inside the casing; the rod string 503 is placed inside the tubing 502. A polished rod component is provided at the upper end of the rod string 503, and the lower end is connected to the screw pump 504. The motor 505 is installed on the fixed bracket 507 and drives the screw pump 504 to extract the oil in the casing 501 through the transmission device 506 and the rod string 503, and outputs it through the tubing 502. When the screw pump 504 stops operating, due to factors such as the elastic potential energy stored in the deformation of the rod string 503 during operation and the liquid level difference between the tubing 502 and the casing 501, the rod string 503 may rotate at high speed, which is likely to cause a series of problems endangering the safe production operation, such as damage to the surface drive device, rupture of the pulley, and the polished rod being thrown out.

[0003] Regarding this phenomenon, the prior art mostly uses a ratchet and pawl mechanism to control the reverse rotation of the screw pump well, but this mechanism may fail under the conditions of rain, snow, freezing weather, and cannot guarantee the safety of production. Summary of the Invention

[0004] Aiming at the problems existing in the above-mentioned prior art, the present invention provides a variable pump and its hydraulic control system. The variable pump can adjust its own displacement according to its output flow rate, and the hydraulic control system can prevent the reverse rotation of the sucker rod string of the screw pump, providing a safety guarantee for downhole production.

[0005] To achieve the above object, the present invention provides a variable pump, including a housing. Inside the housing, a pump body, a variable control cylinder, a pressure control valve, and a flow control valve are provided. An inclined plate is hinged inside the pump body, and one end of the inclined plate is connected to the variable control cylinder; the oil outlet of the pump body is communicated with the oil outlet provided on the variable pump housing through a pipeline 1, and a throttle hole is opened on the pipeline 1;

[0006] A return spring is sleeved outside the piston rod section in the rodless cavity of the variable control cylinder. The end of the piston rod is connected to one end of the inclined plate close to its side; the piston rod of the variable control cylinder is also connected to the valve sleeve of the flow control valve through a feedback rod;

[0007] When the flow control valve is working in the right position, its P port is connected to the B port, and the A port is connected to the T port; when it is working in the left position, the P port is connected to the A port, and the B port is connected to the T port; the left control port of the flow control valve is provided with a pipeline 2, which is connected to the oil outlet of the pump body through a pipeline 1; the right control port of the flow control valve is provided with a pipeline 3, which is connected to the oil outlet on the variable pump housing through a pipeline 1; the T port of the flow control valve drains oil to the housing through a pipeline 4; the A port of the flow control valve is connected to the rod chamber of the variable control oil cylinder through a pipeline 5;

[0008] When the pressure control valve is working in the right position, the P port is closed and the A port is connected to the T port; when it is working in the left position, the P port is connected to the A port and the T port is closed; the P port of the pressure control valve is connected to the left control port of the pressure control valve through a pipeline 6; the A port of the pressure control valve is connected to the rodless chamber of the variable control oil cylinder through a pipeline 7; an adjustable spring is provided on the right side of the pressure control valve;

[0009] The P port of the flow control valve is connected to the left control port of the pressure control valve via pipeline 8. Pipeline 8 connects the P port of the flow control valve and the left control port of the pressure control valve in parallel to pipeline 1 via pipeline 9. A damper is connected in series to pipeline 9. The flow area of the damper is smaller than the flow area of the throttle hole. Pipeline 8 is connected to pipeline 6.

[0010] The B port of the flow control valve is connected to the T port of the pressure control valve through pipeline ten.

[0011] Furthermore, a limit stopper is provided inside the pump body, and the limit stopper is close to the oil outlet 1 of the pump body; when the swash plate rotates to its highest stroke, it contacts and cooperates with the limit stopper.

[0012] A hydraulic control system based on the above variable displacement pump further includes a pilot-operated relief valve and an oil tank;

[0013] The variable pump housing is also provided with an S port and an L port for leaked oil to flow back to the oil tank. The S port and the L port are respectively connected to the oil tank. The oil outlet provided on the variable pump housing is connected to the oil inlet of the pilot-operated relief valve through a pipeline 11.

[0014] A one-way rotation mechanism is provided at the end of the rod column of the screw pump, and the one-way rotation mechanism is in driving connection with the transmission shaft of the variable displacement pump.

[0015] Furthermore, it also includes a controller, which is connected to the pilot-operated relief valve.

[0016] Furthermore, it also includes a safety valve, the oil inlet P of the safety valve is connected between the variable pump and the pilot relief valve, the T ports of the safety valve and the pilot relief valve are both connected to the oil tank, and the set pressure of the safety valve is higher than the set pressure of the pressure control valve.

[0017] Further, the one-way rotation mechanism is a ratchet structure or a one-way clutch; the transmission connection is a belt or gear connection.

[0018] In the present invention, a variable control oil cylinder, a pressure control valve, and a flow control valve are arranged in the variable pump housing. An inclined disk is hinged inside the pump body, and one end of the inclined disk is connected to the variable control oil cylinder. According to the working positions of each control valve, the inclined disk swings driven by the variable control oil cylinder, thereby realizing the adjustment of the flow displacement of the variable pump. This variable pump can adjust its own displacement within a certain range according to its own flow rate. The larger the flow rate, the larger the displacement. When this variable pump is applied to a progressing cavity pump well, according to the braking requirements of the progressing cavity pump and the rod string, it automatically adjusts its own braking effect, avoiding too high a rotational speed of the rod string and consuming its reverse energy as much as possible, providing safety protection for the progressing cavity pump well and ensuring safety for downhole production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic diagram of the structure of a progressing cavity pump well in the prior art;

[0020] Figure 2 is a schematic diagram of the structure of the progressing cavity pump well of the present invention;

[0021] Figure 3 is a schematic structural diagram of the variable pump of the present invention;

[0022] Figure 4 is a hydraulic schematic diagram of applying the variable pump to a progressing cavity pump well in the present invention.

[0023] In the figure: 1, variable pump; 2, housing; 3, pump body; 4, variable control oil cylinder; 5, pressure control valve; 6, flow control valve; 7, inclined disk; 8, pipeline one; 9, throttle hole; 10, return spring; 11, piston rod; 12, feedback rod; 13, pipeline two; 14, pipeline three; 15, pipeline four; 16, pipeline five; 17, pipeline six; 18, pipeline seven; 19, adjustable spring; 20, pipeline eight; 21, pipeline nine; 22, damping; 23, pipeline ten; 24, limit stop; 25, pilot-operated relief valve; 26, oil tank; 27, pipeline eleven; 28, one-way rotation mechanism; 29, safety valve;

[0024] 501, casing; 502, tubing; 503, rod string; 504, progressing cavity pump; 505, motor; 506, transmission device; 507, fixed support. DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention will be further described below with reference to the accompanying drawings.

[0026] As Figure 3As shown, a variable pump 1 includes a housing 2. Inside the housing 2, a pump body 3, a variable control cylinder 4, a pressure control valve 5, and a flow control valve 6 are provided. Inside the pump body 3, a swash plate 7 is hinged. One end of the swash plate 7 is connected to the variable control cylinder 4. The oil outlet of the pump body 3 is communicated with the oil outlet provided on the housing 2 of the variable pump 1 through a pipeline 1 8, and a throttle hole 9 is opened on the pipeline 1 8.

[0027] An external part of the piston rod section in the rod chamber of the variable control cylinder 4 is sleeved with a return spring 10. The end of the piston rod 11 is connected to one end of the swash plate 7 close to the side where it is located. The piston rod 11 of the variable control cylinder 4 is also connected to the valve sleeve of the flow control valve 6 through a feedback rod 12.

[0028] When the flow control valve 6 works in the right position, its P port is communicated with the B port, and the A port is communicated with the T port. When it works in the left position, the P port is communicated with the A port, and the B port is communicated with the T port. A pipeline 2 13 is provided at the left control port of the flow control valve 6. The pipeline 2 13 is communicated with the oil outlet of the pump body 3 through the pipeline 1 8. A pipeline 3 14 is provided at the right control port of the flow control valve 6. The pipeline 3 14 is communicated with the oil outlet on the housing 2 of the variable pump 1 through the pipeline 1 8. The T port of the flow control valve 6 discharges oil to the housing 2 through a pipeline 4 15. The A port of the flow control valve 6 is communicated with the rod chamber of the variable control cylinder 4 through a pipeline 5 16.

[0029] When the pressure control valve 5 works in the right position, the P port is closed, and the A port is communicated with the T port. When it works in the left position, the P port is communicated with the A port, and the T port is closed. The P port of the pressure control valve 5 is communicated with the left control port of the pressure control valve through a pipeline 6 17. The A port of the pressure control valve 5 is communicated with the rodless chamber of the variable control cylinder 4 through a pipeline 7 18. An adjustable spring 19 is provided on the right side of the pressure control valve 5 to change its pressure setting value.

[0030] The P port of the flow control valve 6 is communicated with the left control port of the pressure control valve 5 through a pipeline 8 20. The pipeline 8 20 and the pipeline 9 21 connect the P port of the flow control valve 6 and the left control port of the pressure control valve 5 in parallel to the pipeline 1 8. A damper 22 is connected in series on the pipeline 9 21. The flow area of the damper 22 is smaller than the flow area of the throttle hole 9. The pipeline 8 20 is communicated with the pipeline 6 17.

[0031] The B port of the flow control valve 6 is communicated with the T port of the pressure control valve 5 through a pipeline 10 23.

[0032] In order to facilitate the control of the minimum angle between the swash plate 7 and the oil outlet of the pump body, and further achieve the control of the minimum displacement of the variable pump 1, a limit stop 24 is also provided inside the pump body 3, and the limit stop 24 is close to the oil outlet of the pump body 3; when the swash plate 7 rotates to its minimum angle with the vertical direction, it is in contact and cooperation with the limit stop 24; the limit stop 24 in the present invention is an adjustable bolt.

[0033] As Figure 2 and Figure 4 shown, a hydraulic control system based on the above variable pump further includes a pilot-operated relief valve 25 and a fuel tank 26;

[0034] An S port and an L port for the leakage oil to flow back to the fuel tank are also opened on the housing 2 of the variable pump 1, and the S port and the L port are respectively communicated with the fuel tank 26; the oil outlet opened on the housing 2 of the variable pump 1 is communicated with the oil inlet of the pilot-operated relief valve 25 through pipeline eleven 27;

[0035] A unidirectional rotation mechanism 28 is provided at the end of the rod string 503 of the screw pump, and the unidirectional rotation mechanism 28 is in transmission connection with the transmission shaft of the variable pump 1.

[0036] In order to facilitate the automatic control of the screw pump control system, a controller is further included, and the controller is connected to the pilot-operated relief valve 25; the pilot-operated relief valve 25 in the present invention can be an electro-hydraulic proportional relief valve or a non-electro-controlled type relief valve (in this case, the controller is no longer required), and it is used as a load. According to different specific situations, the pilot-operated relief valve 25 can be replaced by a direct-acting relief valve.

[0037] In order to prevent the pressure from being too high in extreme cases and further improve the safety performance of the system, a safety valve 29 is further included. The oil inlet P of the safety valve is connected between the variable pump 1 and the pilot-operated relief valve 25. The T ports of the safety valve 29 and the pilot-operated relief valve 25 are both communicated with the fuel tank 26, and the set pressure of the safety valve 29 is higher than the set pressure of the pressure control valve 5.

[0038] As a preferred embodiment, the unidirectional rotation mechanism 28 is a ratchet structure or a one-way clutch; the transmission connection is a belt or a gear connection.

[0039] The working principles of the present invention under different control modes are as follows:

[0040] I. Flow control mode

[0041] As Figure 3As shown, when the system pressure has not reached the set pressure of the pressure control valve 5, the pressure control valve 5 always operates in the right position under the action of the adjustable spring 19 provided on its right side. Its P port is closed, and the A port is in communication with the T port. At this time, the flow control valve 6 controls the movement of the variable control cylinder 4 through the pipeline 23 and the pipeline 18 to achieve flow control. Specifically:

[0042] When the system operates in the flow control mode, the displacement of the variable pump 1 is proportional to the flow rate of the pump body 3. The controller is used to set the pressure of the pilot-operated relief valve 25. When the variable pump 1 operates stably, the flow control valve 6 operates stably in the balanced position.

[0043] Since all the oil discharged from the pump body 3 flows through the throttle orifice 9, the pressure difference before and after the throttle orifice 9 represents the flow rate of the variable pump 1. The flow control valve 6 senses the oil pressure before flowing through the throttle orifice 9 through the pipeline 13 on the left side and senses the oil pressure after flowing through the throttle orifice 9 through the pipeline 14 on the right side. The pressure difference between the left and right sides determines the working position of the flow control valve 6. When the flow rate of the pump body 3 decreases, the oil pressure difference before and after the throttle orifice 9 becomes smaller, and the flow control valve 6 switches from the balanced position to the right position. Its P port is in communication with the B port, and the A port is in communication with the T port. The oil from the pump body 3 passes through the pipeline 21, the damper 22, the pipeline 20, the P port of the flow control valve 6 to the B port, the pipeline 23, the T port of the pressure control valve 5 to the A port, and the pipeline 18, and then enters the rodless cavity of the variable control cylinder 4, pushing the oil in the rod chamber of the variable control cylinder 4 through the pipeline 16, the A port of the flow control valve 6 to the T port, and the pipeline 15, flowing into the housing 2, and finally flowing back to the fuel tank 26 through the L port; at the same time, the variable control cylinder 4 compresses the return spring 10 and moves to the left. The leftward movement of the piston rod 11 drives the swash plate 7 in the pump body 3 to swing clockwise, gradually reducing the displacement of the variable pump 1; at the same time, the feedback rod 12 also moves to the left under the drive of the variable control cylinder 4, dragging the valve sleeve of the flow control valve 6 to move to the left until the flow control valve 6 reaches the balanced position again, and the variable control cylinder 4 stabilizes at a new position, and the displacement of the variable pump 1 is re-stabilized;

[0044] When the flow rate of the pump body 3 increases, the hydraulic pressure difference across the throttle orifice 9 becomes larger. The flow control valve 6 switches from the balanced position to the left position. Its P port is connected to the A port, and the B port is connected to the T port. The oil from the pump body 3 passes through pipeline nine 21, damper 22, pipeline eight 20, the P port to the A port of the flow control valve 6, and pipeline five 16, and then enters the rodless cavity of the variable control cylinder 4. It pushes the oil in the rodless cavity of the variable control cylinder 4 to flow through pipeline seven 18, the A port to the T port of the pressure control valve 5, pipeline ten 23, the B port to the T port of the flow control valve 6, and pipeline four 15, and then flows into the housing 2, and finally returns to the fuel tank 26 through the L port; at the same time, under the action of the return spring 10, the rightward movement of the piston rod 11 drives the swash plate 7 in the pump body 3 to swing counterclockwise, causing the displacement of the variable pump 1 to gradually increase; meanwhile, the feedback rod 12 also moves to the right under the drive of the variable control cylinder 4, dragging the valve sleeve of the flow control valve 6 to move to the right until the flow control valve 6 reaches the balanced position again, the variable control cylinder 4 stabilizes at a new position, and the displacement of the variable pump 1 stabilizes again.

[0045] II. Pressure control mode

[0046] When the pressure at the oil outlet of the pump body 3 reaches the set pressure of the pressure control valve 5, the high-pressure oil from the oil outlet of the pump body 3 acts on the left control port of the pressure control valve 5 through pipeline nine 21, damper 22, and pipeline eight 20 and overcomes the acting force of the spring on its right position, causing the spool of the pressure control valve 5 to move to the right. The pressure control valve 5 switches to the left position, and its P port and A port are connected, and the T port is blocked;

[0047] If the flow control valve 6 is in the right position at this time, the oil from the pump body 3 passes through pipeline nine 21, damper 22, pipeline eight 20, pipeline six 17, the P port to the A port of the pressure control valve 5, and pipeline seven 18, and then enters the rodless cavity of the variable control cylinder 4, pushing the piston rod 11 to move to the left, driving the swash plate 7 to swing clockwise, causing the displacement of the variable pump 1 to decrease; the oil compressed by the pump body 3 in the rod cavity of the variable control cylinder 4 flows out, passes through pipeline five 16, the A port to the T port of the flow control valve 6, and pipeline four 15, and then flows into the housing 2, and finally returns to the fuel tank 26 through the L port; at the same time, the oil from the pump body 3 passes through pipeline nine 21, damper 22, pipeline eight 20, the P port to the B port of the flow control valve 6, and pipeline ten 23, and then is blocked at the T port of the pressure control valve 5 and cannot enter the variable control cylinder 4;

[0048] If the flow control valve 6 is in the left position at this time, the rod chamber and the rodless chamber of the variable control cylinder 4 are connected. Since the effective area of the variable control cylinder 4 on the rodless chamber side is larger than the effective area of the rod chamber side, the oil in the rod chamber of the variable control cylinder 4 flows out, that is, the rod chamber of the variable control cylinder 4 passes through the pipeline 5 16, the A port to the P port of the flow control valve 6, and the pipeline 8 20, and then merges with the oil from the pump body 3 after being damped 22. Then, it passes through the pipeline 6 17, the P port to the A port of the pressure control valve 5, and the pipeline 7 18, and then enters the rodless chamber of the variable control cylinder 4. The variable control cylinder 4 compresses the return spring 10 and moves to the left, driving the swash plate 7 to swing in the clockwise direction, so that the displacement of the variable pump 1 is reduced;

[0049] In summary, the pressure control valve 5 realizes the pressure protection function for the variable displacement pump 1 .

[0050] 3. Application to prevent screw pump from reversing

[0051] like Figure 2 and Figure 4 As shown, combined with the working principle of the variable pump 1, it can be seen that the higher the reverse rotation speed of the rod 503, the higher the speed of the one-way rotating mechanism 28 at its end. Since the one-way rotating mechanism 28 is in driving connection with the drive shaft of the variable pump 1, the flow rate and displacement of the variable pump 1 are increased. The oil outlet provided on the housing 2 of the variable pump 1 is connected to the oil inlet of the pilot-operated relief valve 25 via the pipeline 11 27. Therefore, energy is consumed by the pilot-operated relief valve 25, thereby reducing the rotation speed of the rod 503. The lower the rotation speed of the rod 503, the smaller the flow rate and displacement of the variable pump 1. The pilot-operated relief valve 25 consumes less power, and the resistance effect on the rod 503 is reduced. In other words, the variable pump 1 and the system can automatically adjust their braking action according to the braking needs of the screw pump 504 and the rod 503, preventing the rod 503 from rotating too high while maximizing its reverse rotation energy, thus providing safety protection for the screw pump well.

Claims

1. A variable pump, comprising a housing (2), wherein a pump body (3), a variable control oil cylinder (4), a pressure control valve (5) and a flow control valve (6) are arranged inside the housing (2), a swash plate (7) is hinged inside the pump body (3), and is characterized in that, The oil outlet of the pump body (3) is connected to the oil outlet provided on the housing of the variable pump (1) through a first pipeline (8), and a throttle hole (9) is provided on the first pipeline (8); A return spring (10) is sleeved outside the piston rod section in the rodless cavity of the variable control cylinder (4), and one end of the piston rod (11) is connected to one end of the swash plate (7) close to the side where it is located; the piston rod (11) of the variable control cylinder (4) is also connected to the valve sleeve of the flow control valve (6) through a feedback rod (12); When the flow control valve (6) works in the right position, its P port is connected to the B port, and the A port is connected to the T port; when it works in the left position, the P port is connected to the A port, and the B port is connected to the T port; a second pipeline (13) is provided at the left control port of the flow control valve (6), and the second pipeline (13) is connected to the oil outlet of the pump body (3) through the first pipeline (8); a third pipeline (14) is provided at the right control port of the flow control valve (6), and the third pipeline (14) is connected to the oil outlet on the housing (2) of the variable pump (1) through the first pipeline (8); the T port of the flow control valve (6) discharges oil to the housing (2) through a fourth pipeline (15); the A port of the flow control valve (6) is connected to the rodless cavity of the variable control cylinder (4) through a fifth pipeline (16); When the pressure control valve (5) works in the right position, the P port is closed, and the A port is connected to the T port; when it works in the left position, the P port is connected to the A port, and the T port is closed; the P port of the pressure control valve (5) is connected to the left control port of the pressure control valve (5) through a sixth pipeline (17); the A port of the pressure control valve (5) is connected to the rodless cavity of the variable control cylinder (4) through a seventh pipeline (18); an adjustable spring (19) is provided on the right side of the pressure control valve (5); The P port of the flow control valve (6) is connected to the left control port of the pressure control valve (5) through an eighth pipeline (20), and the eighth pipeline (20) connects the P port of the flow control valve (6) and the left control port of the pressure control valve (5) in parallel to the first pipeline (8) through a ninth pipeline (21); a damper (22) is connected in series on the ninth pipeline (21); the flow area of the damper (22) is smaller than the flow area of the throttle hole (9); the eighth pipeline (20) is connected to the sixth pipeline (17); The B port of the flow control valve (6) is connected to the T port of the pressure control valve (5) through a tenth pipeline (23).

2. The variable displacement pump according to claim 1, characterized in that A limit stop block (24) is further provided inside the pump body (3), and the limit stop block (24) is close to the oil outlet of the pump body (3); when the swash plate (7) rotates to the minimum angle with the vertical direction, it is in contact and cooperation with the limit stop block (24).

3. A hydraulic control system for a variable displacement pump according to claim 1 or 2, characterized in that, It further includes a pilot-operated relief valve (25) and a fuel tank (26); An S port and an L port for the leaked oil to flow back to the fuel tank (26) are further provided on the housing (2) of the variable pump (1), and the S port and the L port are respectively connected to the fuel tank (26); the oil outlet provided on the housing (2) of the variable pump (1) is connected to the inlet port of the pilot-operated relief valve (25) through an eleventh pipeline (27); A one-way rotation mechanism (28) is provided at the end of the rod column of the screw pump, and the one-way rotation mechanism (28) is in driving connection with the transmission shaft of the variable displacement pump (1).

4. The hydraulic control system according to claim 3, characterized in that: The device also comprises a controller connected to the pilot-operated overflow valve (25).

5. The hydraulic control system according to claim 3, characterized in that, The invention also includes a safety valve (29), wherein the oil inlet P of the safety valve (29) is connected between the variable pump (1) and the pilot-operated relief valve (25), the T ports of the safety valve (29) and the pilot-operated relief valve (25) are both connected to the oil tank (26), and the set pressure of the safety valve (29) is higher than the set pressure of the pressure control valve (5).

6. The hydraulic control system according to claim 3, characterized in that, The one-way rotation mechanism (28) is a ratchet structure or a one-way clutch; the transmission connection is a belt or gear connection.

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