A cylindrical submersible linear motor with an external rotor

Abstract

The invention discloses an outer-mover submersible linear motor, comprising an upper coupling, an outer motor rotor and a motor stator, wherein the motor stator comprises an upper stator joint, a stator core, an outer stator cylinder, a lower stator joint and a centralizer; the outer motor rotor is arranged on the outer side of the motor stator and supported by the upper stator joint, the centralizer and the lower stator joint; the upper coupling is directly connected to an oil pipe column used for oil field production; the outer motor rotor comprises an upper retaining ring of the rotor, an outer rotor cylinder, a magnetic ring, a permanent magnet ring and an upper joint of a pump barrel, the outer motor rotor fixes the pump barrel through the upper joint of the pump barrel, and the upper retaining ring of the rotor provides a pre-tightening force for the magnetic ring and the permanent magnet ring; the efficiency of the outer-mover and inner-stator submersible linear motor of the invention is greatly improved, the whole equipment is more compact, the structural rigidity is good and the reliability is high.

Description

Technical Field

[0001] The invention belongs to the technical field of linear motors, and in particular, relates to an outer-mover cylindrical submersible linear motor. Background Art

[0002] The submersible electric plunger pump is an artificial lifting device that uses a submersible linear motor to directly drive the plunger pump underground in the oil and gas well to achieve oil and gas extraction. The cylindrical linear motor is a linear power device that can directly drive the plunger pump by using its reciprocating motion in a linear direction. It is widely used in artificial lifting of oil and gas. The submersible linear motor is limited by the size of the oil well casing. The linear motor has a small diameter and a slender structure. Due to the high DC copper loss of the linear motor, the submersible linear motor has a low operating efficiency. The current highest level of submersible linear motor efficiency can only reach about 40%.

[0003] The existing submersible linear motor has a small diameter and a structure of an outer stator and an inner rotor. The ratio of the diameter of the air gap to the average diameter of the winding is very small. According to Maxwell's equations, the magnetic flux of the magnetic field formed in the air gap after the current is passed through the stator winding is only related to the sum of the currents passing through a certain cross section of the stator winding. When the above ratio is smaller, the relative length of the stator winding is longer, and the relative resistance increases, that is, the DC copper loss under the same air gap magnetic field conditions increases, resulting in lower efficiency of the linear motor.

[0004] In a permanent magnet submersible linear motor, the ratio of the average diameter of the rotor magnet to the diameter of the air gap is also very small, and the magnetic induction intensity of the magnetic field generated by the rotor magnet in the air gap is also small. Since the electromechanical energy conversion of the motor is located in the air gap between the stator and the rotor, the greater the magnetic induction intensity of the excitation magnetic field in the air gap, the smaller the current requirement for the stator under the same output thrust. Under the same stator conditions, the smaller the current, the lower the DC copper loss.

[0005] The existing patent publication number CN107276364A discloses a submersible linear motor, including a stator assembly, a mover assembly and a spring, wherein the mover assembly is sleeved in the stator assembly, the spring is sleeved in the stator assembly and is located below the mover assembly, and the stator assembly includes an inlet terminal assembly, a plurality of stator short sections, a bearing, an upper extension tube, a lower extension tube and an outer tube. The structure of the invention is reasonably designed, so that the mover can work normally for a long time, but the mover of the submersible linear motor is arranged on the inner side of the stator, resulting in a very small ratio of the diameter of its air gap to the average diameter of the winding, a relatively long stator winding, a large relative resistance, and an increase in the DC copper loss under the same air gap magnetic field conditions, resulting in a low efficiency of the linear motor. Summary of the invention

[0006] The present invention is mainly aimed at the submersible linear motor in the prior art, which has a small diameter and a structure of an outer stator and an inner mover. The ratio of the diameter of the air gap to the average diameter of the winding is very small; the ratio of the average diameter of the mover magnetic steel to the diameter of the air gap is also very small, and the magnetic induction intensity of the magnetic field generated by the mover magnetic steel in the air gap is also relatively small; increasing the ratio of the diameter of the air gap to the average diameter of the winding, and the ratio of the average diameter of the magnetic steel to the diameter of the air gap can effectively reduce the copper loss of the motor, and proposes an outer mover cylindrical submersible linear motor.

[0007] In view of the above technical problems, the technical solutions of the present invention are as follows:

[0008] A cylindrical submersible linear motor with an outer rotor comprises an upper coupling, an outer rotor and a stator, wherein the stator comprises an upper stator joint, a stator core, an outer stator tube, a lower stator joint and a centralizer; the outer motor rotor is arranged on the outside of the motor stator and supported by the upper stator joint, the centralizer and the lower stator joint; the upper coupling is directly connected to an oil pipe column used for oil field production; the outer motor rotor comprises an upper rotor retaining ring, an outer rotor tube, a magnetic ring, a permanent magnet ring and an upper pump barrel joint, the outer motor rotor fixes the pump barrel through the upper pump barrel joint, and the upper rotor retaining ring pre-tightens the magnetic ring and the permanent magnet ring.

[0009] Furthermore, the upper retaining ring of the mover is connected to the outer cylinder of the mover via threads.

[0010] Furthermore, the outer cylinder of the mover is made of non-magnetic material.

[0011] Furthermore, the magnetizing direction of the permanent magnetic ring is an axial direction, and the magnetizing directions of adjacent permanent magnetic rings are opposite.

[0012] Furthermore, the stator upper joint, the centralizer and the stator lower joint are all provided with a wear-resistant layer, and the wear-resistant alloy is set at the current position by metallurgical bonding, namely the stator upper joint wear-resistant layer, the centralizer wear-resistant layer and the stator lower joint wear-resistant layer.

[0013] Furthermore, the diameter of the wear-resistant layer is larger than the outer diameter of other parts of the motor stator.

[0014] Furthermore, the stator upper joint is provided with a plurality of holes, on which motor lead wires can be installed, so as to connect the motor windings with the motor external cables.

[0015] Furthermore, the magnetic conductive ring is made of wear-resistant magnetic conductive material, and its inner diameter is smaller than the inner diameter of the permanent magnetic ring.

[0016] Furthermore, it also includes a plunger, which is directly connected to the lower joint of the stator through threads, and a fixed valve is installed at the other end of the plunger.

[0017] Furthermore, one end of the pump barrel is connected to a traveling valve, and one end of the traveling valve is provided with a traveling valve lower joint.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The present invention includes an upper coupling, an outer motor mover and a motor stator, wherein the motor stator includes an upper stator joint, an electronic core, an outer stator cylinder, a lower stator joint, a centralizer and an oil pipe; the outer motor mover is arranged on the outside of the motor stator, and the submersible linear motor of the outer mover and the inner stator can greatly improve the ratio of the air gap diameter of the moving stator to the average diameter of the winding, and the ratio of the average diameter of the magnetic steel to the diameter of the air gap, effectively reduce the copper loss of the motor, thereby achieving a significant improvement in the efficiency of the cylindrical linear motor. According to analysis, the efficiency of the motor of the present invention can reach about 70%, which is 75% higher than the efficiency of existing products of 40%.

[0020] 2. The inner stator is directly connected to the plunger, and the outer mover is directly connected to the pump barrel, making the entire equipment more compact, with short structural dimensions, good rigidity and high reliability; and the inner stator is directly set on the oil pipe, which reduces the manufacturing cost of the motor.

[0021] 3. The pump is located at the bottom of the motor, so there is no need to consider reserving space for external cables. A larger diameter pump can be selected to increase production. The motor lifts the pump from the top, which is more stable than lifting the pump from the bottom. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of the outer mover submersible linear motor of the present invention;

[0023] Figure 2 It is a schematic diagram of the upper part of the structure of the outer mover submersible linear motor of the present invention;

[0024] Figure 3 It is a schematic diagram of the lower half structure of the extra-motor submersible linear motor of the present invention.

[0025] In the above figure, 1. upper coupling; 2. oil pipe; 3. outer motor of the motor; 4. motor stator; 5. plunger; 6. upper joint of the pump barrel; 7. pump barrel; 8. fixed valve; 9. floating valve; 11. oil pipe thread; 31. upper retaining ring of the mover; 311. stopper of the upper retaining ring of the mover; 32. outer cylinder of the mover; 33. magnetic ring; 34. permanent magnetic ring; 41. motor lead wire; 42. upper joint of the stator; 421. wear-resistant layer of the upper joint of the stator; 422. stopper of the upper joint of the stator; 43. stator core; 44. outer cylinder of the stator; 45. centralizer; 451. wear-resistant layer of the centralizer; 46. lower joint of the stator Head; 461. Wear-resistant layer of stator lower joint; 462. Snap end of stator lower joint; 47. Inner cavity of stator; 48. Cavity between mover and stator; 491. Weld between stator upper joint and oil pipe; 492. Weld between stator upper joint, stator outer tube and stator core; 493. Weld between stator core, stator outer tube and centralizer; 494. Weld between stator lower joint, stator outer tube and stator core; 495. Oil pipe thread between stator lower joint and oil pipe; 61. Oil guide hole; 62. Snap end of pump barrel upper joint; 71. Inner pump barrel; 72. Outer pump barrel; 91. Upper joint of traveling valve; 92. Lower joint of traveling valve. DETAILED DESCRIPTION

[0026] In order to clearly illustrate the technical features of the application scheme of the present invention, the present invention is described in detail below through specific implementation methods and in conjunction with the accompanying drawings.

[0027] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0028] In addition, in the description of the present invention, it should be understood that the terms "center", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first" and "second" are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0029] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0030] In the present invention, unless otherwise clearly specified and limited, the first feature "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. In the description of this specification, reference terms: "one embodiment", "some embodiments", "example", "specific example" or "some examples" and the like are intended to mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in an appropriate manner in any one or more embodiments or examples.

[0031] Example 1

[0032] like Figure 1 , Figure 2 and Figure 3 As shown, an outer rotor cylindrical submersible linear motor comprises an upper coupling 1, a motor outer rotor 3 and a motor stator 4, wherein the motor stator 4 comprises a stator upper joint 42, an electronic core 43, a stator outer cylinder 44, a stator lower joint 46 and a centralizer 45; the motor outer rotor 3 is arranged on the outside of the motor stator 4, and is supported by the stator upper joint 42, the centralizer 45 and the stator lower joint 46; the upper coupling 1 is directly connected to the oil pipe column used for oil field production; the motor outer rotor 3 comprises a rotor upper retaining ring 31, a rotor outer cylinder 32, a magnetic ring 33, a permanent magnet ring 34 and a pump barrel upper joint 6, the motor outer rotor 3 fixes the pump barrel 7 through the pump barrel upper joint 6, and the rotor upper retaining ring 31 pre-tightens the magnetic ring 33 and the permanent magnet ring 34.

[0033] like Figure 2As shown, in this embodiment, the submersible linear motor is mainly composed of a motor outer rotor 3 and a motor stator 4. The motor stator 4 includes a stator upper joint 42, a stator core 43, a stator lower joint 46, a stator outer tube 44, a stabilizer 45 and an oil pipe 2. The motor stator 4 can be directly set on the oil pipe 2, or other steel pipes that meet the requirements can be selected according to the motor design requirements. The oil pipe 2 is connected to the upper coupling 1 and the stator lower joint 46 through the oil pipe thread 11. The oil pipe thread 495 between the stator lower joint and the oil pipe can provide good load-bearing and sealing effects, thereby increasing the stability and reliability of the submersible linear motor. The upper coupling 1 is directly connected to the oil field production oil pipe column, and some downhole tools such as a check valve, a sand settling pipe, an oil unloading valve, etc. can be added below it to improve the versatility of the equipment.

[0034] The motor outer mover 3 is arranged outside the motor stator 4 and supported by the stator upper joint 42, the centralizer 45 and the stator lower joint 46 to prevent the motor outer mover 3 from directly rubbing against the weak part of the motor stator 4 and causing wear. The stator upper joint 42, the centralizer 45 and the stator lower joint 46 are all provided with a wear-resistant layer, specifically, as Figure 2 As shown, it includes a stator upper joint straightening wear-resistant layer 421, a straightener wear-resistant layer 451 and a stator lower joint wear-resistant layer 461. The wear-resistant alloy is set at the current position by metallurgical bonding, and the diameter of each wear-resistant layer is larger than the outer diameter of the corresponding part of the motor stator 4.

[0035] In this embodiment, the stator upper connector 42 is provided with a plurality of evenly distributed wiring holes, and the motor lead wires 41 are installed by using the wiring holes to connect the motor windings with the motor external cables, thereby saving the installation space of the motor. The stator core 43 includes the motor windings, core, and punching sheets.

[0036] The installation process of the motor stator 4 is as follows: the stator lower joint 46 is tightened with the oil pipe 2 through the oil pipe thread 11 to achieve better connection and sealing, and the connection and sealing effect are further strengthened after welding; the stator outer tube 44 is sleeved on the outside of the stator core 43, and the prepared stator core 43 and the centralizer 45 are alternately sleeved on the stator outer tube 44 from the other end of the oil pipe 2, and the end of the stator core 43 is welded to the oil pipe 2 to prevent loosening; after the windings between the segments of the stator core 43 are connected, the stator inner cavity 47 is completely sealed by using the weld 491 between the stator upper joint and the oil pipe, the weld 492 between the stator upper joint, the stator outer tube and the stator core, the weld 493 between the stator core, the stator outer tube and the centralizer, and the weld 494 between the stator lower joint, the stator outer tube and the stator core, and the stator inner cavity 47 is filled with insulating oil for further insulation and sealing.

[0037] Example 2

[0038] like Figure 2 and Figure 3As shown, in this embodiment, the outer rotor 3 of the motor includes a retaining ring 31 on the rotor, an outer barrel 32 of the rotor, a magnetic ring 33, a permanent magnet ring 34 and a joint 6 on the pump barrel. In the outer rotor 3 of the motor, the magnetic ring 33 is made of wear-resistant and magnetically conductive material, and its inner diameter is slightly smaller than the outer diameter of the permanent magnet ring 34. The inner circles of the magnetic ring 33 and the permanent magnet ring 34 are uniformly processed and chrome-plated to strengthen the surface, so as to achieve long-term direct friction between them and the wear-resistant layer on the stator side. The stopper 311 of the retaining ring on the rotor and the stopper 422 of the joint on the stator are matched to prevent the outer rotor 3 of the motor from moving downward and out of the range of the motor. The stopper 62 of the joint on the pump barrel is matched with the stopper 462 of the lower joint of the stator to prevent the outer rotor 3 of the motor from moving upward and out of the range of the motor. During the reciprocating operation of the motor, the volume of the cavity 48 between the moving and stator will change. The oil guide hole 61 is used to connect the cavity 48 between the moving and stator with the external environment of the motor to avoid a sudden change in pressure in the cavity 48 between the moving and stator, which would cause the well fluid to quickly enter and exit the motor through the air gap between the moving and stator, flush and wear the inside of the motor, and cause damage to the motor.

[0039] The joint 6 on the pump barrel is used to connect the outer rotor 3 of the motor and the pump barrel 7. The upper retaining ring 31 of the rotor is installed in cooperation with the outer barrel 32 of the rotor through threads. A small flat surface can be processed on the exposed end to facilitate tightening it with a wrench; the upper retaining ring 31 of the rotor provides pre-tightening force for the magnetic ring 33 and the permanent magnet ring 34 to avoid loosening; the outer barrel 32 of the rotor is made of non-magnetic material, and the magnetization direction of the permanent magnet ring 34 is along the axial direction, and the magnetization directions of two adjacent permanent magnet rings 34 are opposite.

[0040] like Figure 2 and Figure 3 As shown, in this embodiment, the installation process of the motor outer rotor 3 is as follows: install the pump barrel upper joint 6 and the rotor outer cylinder 32 in place, and use the high-precision match between the pump barrel upper joint stop 62 at the front end of the pump barrel upper joint 6 and the rotor outer cylinder 32 to ensure the installation accuracy, and then install the magnetic ring 33 and the permanent magnet ring 34 from the other end of the rotor outer cylinder 32 to the inside, and finally install the rotor upper retaining ring 31, and pre-tighten the entire motor outer rotor 3, and anti-loosening measures must be taken at all threaded connections.

[0041] Example 3

[0042] like Figure 3As shown, the external mover submersible linear motor also includes a plunger 5, a floating valve 9 and a fixed valve 8. The plunger 5 is fixedly connected to the stator lower joint 46, and the other end of the plunger 5 is connected to the fixed valve 8. The fixed valve 8 can adopt a fixed valve seat sealing connection structure to achieve a threaded screw-on sealing connection, extend the service life of the valve seat, and is suitable for stable and efficient operation under deep well conditions. The floating valve 9 is arranged at the lower end of the pump barrel 7 and connected to the pump barrel 7. The floating valve 9 includes a floating valve upper joint 91 and a floating valve lower joint 92. The end is provided with an oil pipe thread 11 interface, which can be hung with other downhole tools, such as: a sand and scale precipitation prevention fixed valve, a downhole safety valve or a packer, which can achieve sand prevention, air release, anti-scaling and other functions, and improve the service life of the submersible linear motor.

[0043] In this embodiment, the lower part of the pump barrel upper joint 6 is connected to the pump barrel 7, and the pump barrel 7 can adopt a double-layer structure of an inner pump barrel 71 and an outer pump barrel 72, such as Figure 3 As shown, the overall structural rigidity can be improved, and the outer pump barrel 72 may not be added.

[0044] Example 4

[0045] In this embodiment, the electric plunger pump is arranged at the lower end of the motor, so there is no need to consider reserving space for external cables, and a larger diameter pump can be selected to increase production. The motor lifts the plunger pump from the upper end, and the force pattern is more stable compared to lifting the pump from the lower end.

[0046] Obviously, the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A cylindrical submersible linear motor with an outer rotor, characterized in that: It comprises an upper coupling, an outer motor mover and a motor stator, wherein the motor stator comprises an upper stator joint, a stator core, an outer stator cylinder, a lower stator joint and a centralizer; the outer motor mover is arranged on the outside of the motor stator and supported by the upper stator joint, the centralizer and the lower stator joint; the upper coupling is directly connected to the oil pipe column used for oil field production; the outer motor mover comprises an upper mover retaining ring, an outer mover cylinder, a magnetic ring, a permanent magnet ring and an upper pump barrel joint, the outer motor mover fixes the pump barrel through the upper pump barrel joint, and the upper mover retaining ring pre-tightens the magnetic ring and the permanent magnet ring.

2. The outer rotor cylindrical submersible linear motor according to claim 1, characterized in that: The upper retaining ring of the mover is connected to the outer cylinder of the mover through threads.

3. The outer rotor cylindrical submersible linear motor according to claim 2, characterized in that: The outer cylinder of the mover is made of non-magnetic material.

4. The outer rotor cylindrical submersible linear motor according to claim 1, characterized in that: The magnetizing direction of the permanent magnetic ring is the axial direction, and the magnetizing directions of adjacent permanent magnetic rings are opposite.

5. The outer-motor cylindrical submersible linear motor according to claim 1, characterized in that: The stator upper joint, the centralizer and the stator lower joint are all provided with a wear-resistant layer, and the wear-resistant layer is a wear-resistant alloy.

6. The outer-motor cylindrical submersible linear motor according to claim 5, characterized in that: The diameter of the wear-resistant layer is larger than the outer diameter of other parts of the motor stator.

7. The outer-motor cylindrical submersible linear motor according to claim 1, characterized in that: The stator upper joint is provided with a plurality of holes, on which the motor lead wires can be installed, and are used to connect the motor windings with the motor external cables.

8. The outer-motor cylindrical submersible linear motor according to claim 1, characterized in that: The magnetic conductive ring is made of wear-resistant magnetic conductive material, and its inner diameter is smaller than the inner diameter of the permanent magnetic ring.

9. The outer-motor cylindrical submersible linear motor according to claim 1, characterized in that: It also includes a plunger, which is directly connected to the lower joint of the stator through threads, and a fixed valve is installed at the other end of the plunger.

10. The outer rotor cylindrical submersible linear motor according to claim 1, characterized in that: One end of the pump barrel is connected with a traveling valve, and one end of the traveling valve is provided with a traveling valve lower joint.

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