Submersible electrically driven plunger pump

Abstract

A kind of electric drive plunger pump of electric submersible motor.The electric submersible motor, protector assembly, transmission device, plunger oil pump of the present application are connected in order from bottom to top;The motor shaft of electric submersible motor is connected with the planetary roller screw of transmission device, the planetary roller screw nut matched with planetary roller screw is connected with the plunger of plunger oil pump, and drives the plunger to reciprocate up and down along the pump barrel;The upper protector compensates the amount of lubricating oil of transmission device;The lower protector compensates the amount of motor oil of electric submersible motor, and prevents well fluid from entering the inside of motor;The planetary roller screw pair of transmission device converts the rotary motion of electric submersible motor into linear reciprocating motion of plunger.Its beneficial effects are that the structure is reasonable, the rotary power is provided by permanent magnet synchronous electric submersible motor, the rotary motion of motor is converted into linear motion by transmission device, the plunger is driven to reciprocate, well fluid is lifted to ground, and rotary motor drives plunger pump to reciprocate to drive oil, with the advantages of low failure rate, high efficiency, high lift and long service life.

Description

Technical Field

[0001] This invention relates to a plunger pump, and more particularly to a submersible electric plunger pump, belonging to the field of oil and gas development technology. Background Technology

[0002] With the continuous advancement of oil drilling technology, horizontal wells and cluster wells have become dominant, and rodless oil production technology compatible with horizontal and cluster wells urgently needs development. Currently, rodless oil production mainly relies on submersible centrifugal pumps, electric submersible direct-drive screw pumps, and electric submersible direct-drive plunger pumps. However, for oil production in wells with complex well structures such as low-yield wells, highly deviated wells, and unevenly ground wells, the above-mentioned rodless oil production equipment has shown its own inadequacies. These are mainly manifested in the following ways: submersible centrifugal pumps suffer from low energy efficiency and high losses in small-displacement, low-yield wells; electric submersible direct-drive screw pumps use a rotary motor directly connected to the screw pump to drive oil, but due to the high price and short lifespan of screw pumps, they are difficult to promote in oil production; electric submersible direct-drive plunger pumps use a linear motor directly connected to the plunger pump, which suffers from low efficiency, high power consumption, and high failure rate of the linear motor, thus restricting its widespread application. Summary of the Invention

[0003] In order to overcome the above-mentioned shortcomings of existing rodless oil production pumps in oil production of wells with complex well structures such as low-yield wells, highly deviated wells, and unevenly ground wells, this invention provides a submersible electric-driven plunger pump.

[0004] The technical solution adopted by this invention to solve its technical problem is: a submersible electric piston pump, including a submersible motor and a protector, characterized in that: the submersible motor, the protector assembly, the transmission device, and the piston pump are connected in sequence from bottom to top; the motor shaft of the submersible motor is connected to the planetary roller screw of the transmission device, driving the planetary roller screw to rotate; the planetary roller screw nut that cooperates with the planetary roller screw is connected to the piston of the piston pump, driving the piston to reciprocate up and down along the pump barrel.

[0005] The submersible motor is a permanent magnet synchronous motor, which adopts a direct torque control mode.

[0006] The protector assembly includes an upper protector and a lower protector; the upper protector compensates for the amount of lubricating oil in the transmission device; the lower protector compensates for the amount of motor oil in the submersible motor and prevents well fluid from entering the motor.

[0007] The planetary roller screw pair of the transmission device converts the rotational motion of the submersible motor into the linear reciprocating motion of the plunger of the plunger oil pump.

[0008] During the upstroke of the plunger oil production pump, the plunger moves upward to lift the well fluid, which then enters the pump through the screen tube; during the downstroke, the plunger moves downward, and the well fluid enters the pump through the traveling valve of the plunger oil production pump.

[0009] The motor shaft of the submersible motor, the drive shaft of the protector assembly, the connecting shaft of the transmission device, and the planetary roller screw are connected sequentially from bottom to top.

[0010] The planetary roller screw nut, guide rod, push rod, and plunger of the oil pump in the transmission device are connected in sequence from bottom to top.

[0011] The upper pump barrel, pump barrel, and screen pipe of the plunger oil pump are connected in sequence from top to bottom, and the plunger moves up and down along the pump barrel.

[0012] A fixed valve is installed inside the upper pump cylinder. The valve seat I, the closed valve cover I, and the fixed valve cover are fixedly connected in sequence from bottom to top. The valve seat I is fixedly connected to the upper pump cylinder.

[0013] A traveling valve is fixedly installed on the upper end of the plunger, and the plunger, the valve seat II of the traveling valve, and the closed valve cover II are fixedly connected in sequence from bottom to top.

[0014] The lower end of the plunger, the open valve cover, and the push rod of the transmission device are fixedly connected from top to bottom, and the push rod drives the plunger to move up and down reciprocally.

[0015] When the plunger moves upward, the fixed valve opens and the traveling valve closes, lifting the well fluid in the cavity between the traveling valve and the fixed valve. At the same time, the well fluid in the wellbore enters the plunger oil pump through the screen pipe.

[0016] When the plunger moves downward, the stationary valve closes and the traveling valve opens, allowing well fluid to enter the cavity between the traveling and stationary valves via the traveling valve.

[0017] The sealing device, outer cylinder, and protector connector of the transmission device are fixedly connected in sequence from top to bottom.

[0018] The outer cylinder contains, from top to bottom, an anti-torsion assembly to prevent the guide rod from rotating, a planetary roller screw pair, and a connecting shaft connecting the planetary roller screw and the protector assembly.

[0019] The upper and lower ends of the planetary roller screw nut of the planetary roller screw pair are respectively fixedly installed with anti-collision mechanisms to eliminate the reversing impact.

[0020] A thrust-reducing mechanism is installed at the connecting shaft to reduce axial thrust.

[0021] The sealing device seals and isolates the cavity of the plunger oil pump from the cavity of the transmission device.

[0022] The upper and lower protectors are capsule-type protectors.

[0023] The upper protector is coaxially arranged with an upper protective shaft tube, an upper breathing capsule, and an upper protector housing outside the drive shaft. The upper protective shaft tube has a radial through hole. The upper and lower ends of the upper breathing capsule are fixedly connected to the upper protective shaft tube. The annular space between the drive shaft and the upper protective shaft tube and the upper breathing capsule are filled with lubricating oil.

[0024] The lower protector is coaxially arranged with a lower shaft guard tube, a lower breathing capsule, and a lower protector housing outside the motor shaft. The lower shaft guard tube has a radial through hole. The upper and lower ends of the lower breathing capsule are fixedly connected to the lower shaft guard tube. The annular space between the motor shaft and the lower shaft guard tube and the lower breathing capsule are filled with motor oil.

[0025] When the plunger moves upward, the volume of the transmission device increases, the upper breathing capsule of the upper protector contracts, and lubricating oil enters the annulus between the transmission shaft and the upper protective shaft tube. At the same time, well fluid enters the annulus between the upper breathing capsule and the upper protector housing from the radial through hole of the upper protector housing.

[0026] When the plunger moves downward, the volume of the transmission device decreases, the upper breathing capsule of the upper protector expands, and the lubricating oil flows back to the upper breathing capsule through the radial through hole of the upper shaft tube. The well fluid in the annulus between the upper breathing capsule and the upper protector housing is discharged into the wellbore.

[0027] The motor oil of the submersible motor, which expands or contracts due to temperature changes, is compensated by the lower protector.

[0028] When the submersible motor is lowered to the bottom of the well, the temperature rises, and motor oil enters the lower breathing capsule of the lower protector.

[0029] When the submersible motor starts, the temperature continues to rise, and more motor oil enters the lower breathing capsule. When the motor oil temperature reaches its maximum value, the lower breathing capsule is full of motor oil.

[0030] When the submersible motor stops running, the motor oil shrinks in volume as the temperature decreases, the lower breathing capsule contracts, and the well fluid enters the annulus between the lower breathing capsule and the lower protector housing through the radial through-hole.

[0031] The beneficial effects of this invention are that it has a reasonable structural design, with a permanent magnet synchronous submersible motor providing rotational power. The transmission device converts the rotational motion of the motor into linear motion, driving the plunger to reciprocate and lift the well fluid to the surface. This realizes the rotary motor driving the plunger pump to reciprocate and drive oil, which has the advantages of low failure rate, high efficiency, high head and long service life. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the submersible electric-driven plunger pump structure of the present invention.

[0033] Figure 2 This is a schematic diagram of the protector structure in this invention.

[0034] Figure 3 This is a schematic diagram of the transmission device structure in this invention.

[0035] Figure 4 This is a schematic diagram of the plunger oil pump structure in this invention.

[0036] In the diagram: 1. Oil drainer, 2. Fixed valve, 3. Cavity, 4. Floating valve, 5. Plunger, 6. Open valve cover, 7. Screen tube, 8. Push rod, 9. Sealing device, 10. Guide rod, 11. Anti-torsion assembly, 12. Outer cylinder, 13. Planetary roller screw pair, 14. Planetary roller screw nut, 15. Planetary roller screw, 16. Connecting shaft, 17. Protector connector, 18. Upper breathing capsule, 19. Upper protector housing, 20. 21. Drive shaft, 22. Lower breathing capsule, 23. Lower protector housing, 24. Motor shaft, 25. Pump barrel, 26. Upper pump barrel, 27. Connector, 28. Coupling, 29. Pipe body, 200. Anti-collision mechanism, 21. Upper shaft guard tube, 22. Lower shaft guard tube, 23. Submersible motor, 200. Protector assembly, 201. Upper protector, 202. Lower protector, 300. Transmission device, 400. Plunger oil pump. Detailed Implementation

[0037] The present invention will be further described below with reference to the accompanying drawings and embodiments. However, those skilled in the art should understand that the present invention is not limited to the specific embodiments listed, and any embodiment that conforms to the spirit of the present invention should be included within the scope of protection of the present invention.

[0038] In the description of this invention, it should be noted that the terms "vertical", "up", "down", "left", "right", "horizontal", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing or simplifying the description of this invention, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0039] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," "link," and "seal" should be interpreted broadly. For example, a connection can be a fixed connection or a detachable connection; it can be a direct connection or an indirect connection, or an integral connection; it can be a mechanical connection or an indirect connection through an intermediate medium, or it can be a connection between the internal parts of two components. A seal can be an oil seal, a packing seal, or other forms of seal. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0040] See appendix Figure 1-4This invention discloses a submersible electric-driven plunger pump, comprising a submersible motor 100, a protector assembly 200, a transmission device 300, and a plunger pump 400, which are connected sequentially from bottom to top. The motor shaft 23 of the submersible motor 100 is connected to the planetary roller screw 15 of the transmission device 300, driving the planetary roller screw 15 to rotate. The planetary roller screw nut 14, which mates with the planetary roller screw 15, is connected to the plunger 5 of the plunger pump 400, driving the plunger 5 to reciprocate up and down along the pump barrel 24. The upper end of the submersible electric-driven plunger pump is connected to an oil pipe via an oil drainer 1, and the lower end is connected to a centralizer or a scale inhibitor.

[0041] The submersible motor 100 is a permanent magnet synchronous motor.

[0042] The protector assembly 200 includes an upper protector 201 and a lower protector 202, which are axially connected in sequence. Both the upper protector 201 and the lower protector 202 are capsule-type protectors. The upper protector 201 compensates for the amount of lubricating oil in the transmission device 300; the lower protector 202 compensates for the amount of motor oil in the submersible motor 300 and prevents well fluid from entering the motor.

[0043] The planetary roller screw pair 13 of the transmission device 300 converts the rotational motion of the submersible motor 100 into the linear reciprocating motion of the plunger 5 of the plunger pump 400.

[0044] During the upstroke of the plunger oil pump 400, the plunger 5 moves upward to lift the well fluid, which enters the pump through the screen pipe 7; during the downstroke, the plunger 5 moves downward, and the well fluid enters the pump through the traveling valve 4.

[0045] The motor shaft 23 of the submersible motor 100, the transmission shaft 20 of the protector assembly 200, the connecting shaft 16 of the transmission device 300, and the planetary roller screw 15 are fixedly connected from bottom to top to form the transmission shaft for the motor's rotational power.

[0046] The planetary roller screw nut 14, guide rod 10, push rod 8, and plunger 5 of the plunger oil pump 400 of the transmission device 300 are fixedly connected from bottom to top to complete the linear reciprocating motion.

[0047] In the embodiments,

[0048] The submersible motor 100 is a permanent magnet synchronous motor that generates a synchronous rotating magnetic field through permanent magnet excitation, providing rotational power for the submersible electric piston pump. The permanent magnet synchronous motor is controlled using direct torque control (DTC) mode, which enables starting under no-load and load conditions, and achieves precise control of frequent commutation and speed.

[0049] The permanent magnet synchronous motor includes a motor shaft 23, a rotor, and stator windings. Multiple permanent magnet synchronous motors can be connected in series to meet different power requirements depending on the needs of oil production conditions. Alternatively, the motor power can be increased by lengthening the rotor and stator windings.

[0050] See appendix Figure 2 The upper protector 201 and lower protector 202 of the protector assembly 200 have the same structure, including a breathing capsule, a shell, a protective shaft tube, a seal, a drive shaft 20 or a motor shaft 23, etc. The drive shaft 20 / motor shaft 23 is set inside the protective shaft tube, and there is an annular space between the protective shaft tube and the shell.

[0051] The breathing capsule is cylindrical and installed in the annular space between the protective shaft tube and the shell. It is used to store the lubricating oil of the transmission device 300 or the motor oil of the submersible motor 100. The breathing capsule has flanges at both ends and is fixedly connected to the protective shaft tube by clamps.

[0052] The breathing capsule is made of natural rubber and fiber reinforcement layer after vulcanization, and has good tensile strength and aging resistance, as well as elasticity and flexibility.

[0053] The upper protector 201 compensates for the amount of lubricating oil in the transmission device 300 through the breathing motion of the upper breathing capsule 18; the lower protector 202 compensates for the amount of motor oil in the submersible motor 100 through the breathing motion of the lower breathing capsule 21, balances the pressure between the motor and the wellbore, compensates for the thermal expansion and contraction of the motor oil caused by temperature changes, prevents well fluid from entering the submersible motor 100, and avoids motor burnout.

[0054] Furthermore, the upper protector 201 is coaxially arranged with an upper protective shaft tube 27, an upper breathing capsule 18, and an upper protector housing 19 on the outside of the drive shaft 20. The upper protective shaft tube 27 is provided with a radial through hole connecting the upper breathing capsule 18 and the drive shaft 20. The upper and lower ends of the upper breathing capsule 18 are fixedly connected to the upper protective shaft tube 27. The annular space between the drive shaft 20 and the upper protective shaft tube 27 and the upper breathing capsule 18 are filled with lubricating oil.

[0055] When the plunger 5 moves upward, the volume of the transmission device 300 increases, the upper breathing capsule 18 of the upper protector 201 contracts, and lubricating oil enters the annulus between the transmission shaft 20 and the upper protective shaft tube 27. At the same time, well fluid enters the annulus between the upper breathing capsule 18 and the upper protector housing 19 from the radial through hole of the upper protector housing 19.

[0056] When the plunger 5 moves downward, the volume of the transmission device 300 decreases, the upper breathing capsule 18 expands, and the lubricating oil flows back to the upper breathing capsule 18 through the radial through hole of the upper shaft tube 27. The well fluid in the annulus between the upper breathing capsule 18 and the upper protector housing 19 is discharged into the wellbore.

[0057] Furthermore, the motor shaft 23 extends axially through the lower protector 202. A lower shaft guard tube 28, a lower breathing capsule 21, and a lower protector housing 22 are coaxially arranged around the motor shaft 23. The lower shaft guard tube 28 has a radial through hole connecting the lower breathing capsule 21 and the motor shaft 23. The upper and lower ends of the lower breathing capsule 21 are fixedly connected to the lower shaft guard tube 28. The annular space between the motor shaft 23 and the lower shaft guard tube 28, and the lower breathing capsule 21, are filled with motor oil. The motor oil, which expands or contracts due to temperature changes, is compensated by the lower protector 202.

[0058] When the submersible motor 100 is lowered to the bottom of the well, the motor oil expands due to the increase in temperature, and some motor oil enters the lower breathing capsule 21 of the lower protector 202.

[0059] When the submersible motor 100 is started, as the temperature at the bottom of the well continues to rise, the motor oil continues to expand, and more motor oil enters the lower breathing capsule 21. When the motor oil temperature reaches its maximum value, the motor oil stops expanding, and the lower breathing capsule 21 is filled with motor oil.

[0060] When the submersible motor 100 stops running, the bottom hole temperature decreases, and the motor oil shrinks in volume as the temperature decreases. The lower breathing capsule 21 shrinks accordingly, and the well fluid enters the annulus between the lower breathing capsule 21 and the lower protector housing 22 through the radial through hole.

[0061] In this embodiment, the upper end of the permanent magnet synchronous motor is connected to the lower protector 202 via a spline sleeve and a flange.

[0062] See appendix Figure 3 The transmission device 300 uses a planetary roller screw pair 13 to convert the rotational motion of the submersible motor 100 into the linear reciprocating motion of the plunger 5 of the plunger pump 400 (the applicant has filed a separate patent for the transmission device, which is only briefly described in this application and will not be repeated).

[0063] The sealing device 9, outer cylinder 12, and protector connector 17 of the transmission device 300 are fixedly connected from top to bottom, and the outer cylinder 12 is provided with multiple components from top to bottom.

[0064] The outer cylinder 12 is provided with, from top to bottom, an anti-torsion assembly 11 to prevent the guide rod 10 from rotating, a planetary roller screw pair 13, and a connecting shaft 16 connecting the planetary roller screw 15 and the protector assembly 200.

[0065] The upper and lower ends of the planetary roller screw nut 14 of the planetary roller screw pair 13 are respectively fixedly installed with anti-collision mechanisms 26 for eliminating reversing impact.

[0066] The anti-torsion assembly 11 has a flat roller bearing mounted on the outer circumference of the guide rod 10.

[0067] The outer circle of the connecting shaft 16 is equipped with a thrust-resistant mechanism to reduce the axial thrust generated during the operation of the submersible electric piston pump.

[0068] The sealing device 9 seals and isolates the cavity of the plunger oil pump 400 from the cavity of the transmission device 300.

[0069] See appendix Figure 4 The upper pump barrel 25, pump barrel 24, and screen pipe 7 of the plunger oil pump 400 are connected in sequence from top to bottom. The plunger 5 moves up and down along the pump barrel 24 to lift the well fluid.

[0070] The upper pump cylinder 25 includes a connector 25-1, a coupling 25-2, and a pipe body 25-3. The connector 25-1, coupling 25-2, and pipe body 25-3 are fixedly connected from bottom to top. The upper end of the pipe body 25-3 is directly or indirectly connected to the oil drainer 1.

[0071] A fixed valve 2 is installed inside the upper pump cylinder 25. The valve seat I, the closed valve cover I, and the fixed valve cover of the fixed valve 2 are fixedly connected from bottom to top. The valve seat I is fixedly connected to the connector 25-1.

[0072] The upper end of the plunger 5 is fixedly installed with a traveling valve 4, and the plunger 5, the valve seat II of the traveling valve 4, and the closed valve cover II are fixedly connected from bottom to top.

[0073] Preferably, both the fixed valve 2 and the traveling valve 4 are ball valves.

[0074] The lower end of the plunger 5, the open valve cover 6, and the push rod 8 of the transmission device 300 are fixedly connected from top to bottom, and the push rod 8 drives the plunger 5 to move up and down.

[0075] When the plunger 5 moves upward, the fixed valve 2 opens and the traveling valve 4 closes, lifting the well fluid in the cavity 3 between the traveling valve 4 and the fixed valve 2. Simultaneously, the well fluid in the wellbore enters the plunger pump 400 through the screen pipe 7. When the plunger 5 moves downward, the fixed valve 2 closes and the traveling valve 4 opens, allowing the well fluid in the wellbore to enter the cavity 3 between the traveling valve 4 and the fixed valve 2 via the traveling valve 4. The reciprocating motion of the plunger 5 completes the lifting of the well fluid.

[0076] This invention relates to a submersible electric-driven plunger pump, which uses a permanent magnet synchronous motor to provide rotational power. The transmission device converts the rotational motion of the motor into linear motion, driving the plunger pump to reciprocate and lift the well fluid to the surface. It eliminates the need for a sucker rod, completely solving the problems of rod and tubing friction and tubing wear. It can meet the production requirements of wells with complex well structures such as horizontal and deviated wells, extend the pump inspection cycle, shorten the tripping time, improve lifting efficiency, save investment, reduce costs, reduce energy consumption, and broaden adaptability. It is especially suitable for rodless oil production operations in oil wells with low fluid supply and large well deviation in oilfields.

[0077] It should be noted that the above embodiments are examples and not limitations of the present invention, and those skilled in the art will be able to design many alternative embodiments without departing from the scope of the claims of this patent.

Claims

1. A submersible electric piston pump, comprising a submersible motor and a protector assembly, characterized in that: The submersible motor, protector assembly, transmission device, and plunger oil pump are connected in sequence from bottom to top; the motor shaft of the submersible motor is connected to the planetary roller screw of the transmission device, driving the planetary roller screw to rotate; the planetary roller screw nut that cooperates with the planetary roller screw is connected to the plunger of the plunger oil pump, driving the plunger to reciprocate up and down along the pump barrel. The submersible motor is a permanent magnet synchronous motor, which adopts a direct torque control mode. The protector assembly includes an upper protector and a lower protector; the upper protector compensates for the amount of lubricating oil in the transmission device; the lower protector compensates for the amount of motor oil in the submersible motor and prevents well fluid from entering the motor. The planetary roller screw pair of the transmission device converts the rotational motion of the submersible motor into the linear reciprocating motion of the plunger of the plunger oil pump; During the upstroke of the plunger oil production pump, the plunger moves upward to lift the well fluid, which enters the pump through the screen tube; during the downstroke, the plunger moves downward, and the well fluid enters the pump through the traveling valve of the plunger oil production pump. The upper and lower protectors are capsule-type protectors; The upper protector is coaxially arranged with an upper protective shaft tube, an upper breathing capsule, and an upper protector housing outside the drive shaft. The upper protective shaft tube has a radial through hole. The upper and lower ends of the upper breathing capsule are fixedly connected to the upper protective shaft tube. The annular space between the drive shaft and the upper protective shaft tube and the upper breathing capsule are filled with lubricating oil. The lower protector is coaxially arranged with a lower shaft guard tube, a lower breathing capsule, and a lower protector housing outside the motor shaft. The lower shaft guard tube has a radial through hole. The upper and lower ends of the lower breathing capsule are fixedly connected to the lower shaft guard tube. The annular space between the motor shaft and the lower shaft guard tube and the lower breathing capsule are filled with motor oil.

2. The submersible electric piston pump according to claim 1, characterized in that: The motor shaft of the submersible motor, the drive shaft of the protector assembly, the connecting shaft of the transmission device, and the planetary roller screw are connected in sequence from bottom to top. The planetary roller screw nut, guide rod, push rod, and plunger of the oil pump in the transmission device are connected in sequence from bottom to top.

3. The submersible electric piston pump according to claim 1, characterized in that: The upper pump barrel, pump barrel, and screen pipe of the plunger oil pump are connected in sequence from top to bottom, and the plunger moves up and down along the pump barrel; A fixed valve is installed inside the upper pump cylinder. The valve seat I, the closed valve cover I, and the fixed valve cover are fixedly connected from bottom to top. The valve seat I is fixedly connected to the upper pump cylinder. A traveling valve is fixedly installed on the upper end of the plunger, and the plunger, the valve seat II of the traveling valve, and the closed valve cover II are fixedly connected from bottom to top. The lower end of the plunger, the open valve cover, and the push rod of the transmission device are fixedly connected from top to bottom, and the push rod drives the plunger to move up and down reciprocally.

4. The submersible electric piston pump according to claim 3, characterized in that: When the plunger moves upward, the fixed valve opens and the traveling valve closes, lifting the well fluid in the cavity between the traveling valve and the fixed valve upward. At the same time, the well fluid in the wellbore enters the plunger oil pump through the screen pipe. When the plunger moves downward, the stationary valve closes and the traveling valve opens, allowing well fluid to enter the cavity between the traveling and stationary valves via the traveling valve.

5. The submersible electric piston pump according to claim 1, characterized in that: The sealing device, outer cylinder, and protector connector of the transmission device are fixedly connected from top to bottom in sequence. The outer cylinder contains, from top to bottom, an anti-torsion assembly to prevent the guide rod from rotating, a planetary roller screw pair, and a connecting shaft connecting the planetary roller screw and the protector assembly.

6. The submersible electric piston pump according to claim 5, characterized in that: The upper and lower ends of the planetary roller screw nut of the planetary roller screw pair are respectively fixedly installed with anti-collision mechanisms for eliminating reversing impact. A thrust-resistant mechanism to reduce axial thrust is installed at the connecting shaft. The sealing device seals and isolates the cavity of the plunger oil pump from the cavity of the transmission device.

7. The submersible electric piston pump according to claim 6, characterized in that: When the plunger moves upward, the volume of the transmission device increases, the upper breathing capsule of the upper protector contracts, and lubricating oil enters the annulus between the transmission shaft and the upper protective shaft tube. At the same time, well fluid enters the annulus between the upper breathing capsule and the upper protector housing from the radial through hole of the upper protector housing. When the plunger moves downward, the volume of the transmission device decreases, the upper breathing capsule of the upper protector expands, and the lubricating oil flows back to the upper breathing capsule through the radial through hole of the upper shaft tube. The well fluid in the annulus between the upper breathing capsule and the upper protector housing is discharged into the wellbore.

8. The submersible electric piston pump according to claim 7, characterized in that: because The motor oil of the submersible motor that expands or contracts due to temperature changes is compensated by a lower protector. When the submersible motor is lowered to the bottom of the well, the temperature rises, and motor oil enters the lower breathing capsule of the lower protector. When the submersible motor starts, the temperature continues to rise, and more motor oil enters the lower breathing capsule. When the motor oil temperature reaches its maximum value, the lower breathing capsule is full of motor oil. When the submersible motor stops running, the motor oil shrinks in volume as the temperature decreases, the lower breathing capsule contracts, and the well fluid enters the annulus between the lower breathing capsule and the lower protector housing through the radial through-hole.

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