Stationary Tubing Variable Displacement Oil Pump, Its Usage Method and Special Locking Mechanism

Abstract

The present invention discloses a displacement-variable sucker rod pump without pulling the tubing string, its usage method and a special locking mechanism, which includes a pump barrel, an outer plunger and an inner plunger. The outer plunger is arranged inside the pump barrel, and the inner plunger is arranged inside the outer plunger. It also includes a plunger locking mechanism, which includes a fixing frame and a plunger anti-rotation mechanism. The outer plunger and the inner plunger are connected and fixed through the fixing frame, and the plunger anti-rotation mechanism is connected with the fixing frame. The present invention can change the working system through the tubing string without pulling according to the change of formation energy, achieving the purpose of lifting liquid with a large-diameter plunger in the initial stage and maintaining stable production with a small-diameter plunger after the formation energy drops. By adjusting the working system through the tubing string without pulling, the pump replacement operation after the energy drops is avoided, thus reducing the maintenance cost.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield and gas field development and production, and specifically to a displacement-changing sucker rod pump without pulling out the production string, its using method and a special locking mechanism. Background Art

[0002] In the initial stage of low-permeability reservoir development, the formation energy is relatively high, but the low-permeability characteristics lead to a rapid decline in energy in the later stage. To make better use of the formation energy, large-diameter sucker rod pumps are generally used in the initial production stage, and when the energy drops, the sucker rod pump is replaced by a small-diameter sucker rod pump through a workover method. For coalbed methane fields after fracturing, there is a lot of fracturing fluid in the initial stage, and large pumps are generally used for rapid liquid drainage, but soon there will be a phenomenon of insufficient liquid supply for large-diameter sucker rod pump production. In this case, it is necessary to replace the original production string in the well with a small pump for production. Since the small pump is replaced through operations during the service life of the sucker rod pump, the original sucker rod pump is scrapped artificially and the operation cost is increased.

[0003] Currently, there is no technology that can effectively realize the conversion from pumping with a large-diameter sucker rod pump to pumping with a small-diameter sucker rod pump without pulling out the production string.

[0004] In order to achieve clean production and efficient production, there is an urgent need to develop a method that can achieve efficient production without pulling out the production string.

[0005] Publication (Announcement) No.: CN106593836B, Publication (Announcement) Date: June 1, 2018 provides a multi-stage plunger displacement-changing sucker rod pump, including a pump barrel, a fixed valve pair, a traveling valve pair, a biasing valve pair, a plunger, etc.; among them, the hollow cavity of the pump barrel is divided into a first cylindrical pump cavity and a second cylindrical pump cavity that are connected and communicated, and the inner diameter of the first cylindrical pump cavity is smaller than that of the second cylindrical pump cavity. The fixed valve pair is connected to one end of the first cylindrical pump cavity, the plunger is arranged in the pump barrel, and its shape matches the hollow cavity of the pump barrel; the traveling valve pair is arranged at the liquid inlet of the plunger in the first cylindrical pump cavity, the biasing valve pair is arranged on the plunger in the first cylindrical pump cavity and is close to the traveling valve pair; the oil outlet valve cover is connected to the top end of the plunger in the second cylindrical pump cavity, and the pull rod is connected to the oil outlet valve cover and extends outside the pump barrel. Both the plunger and the pump barrel adopt a two-stage structure, corresponding to different pump diameters respectively, and different strokes are used to realize the switching between different pump diameters, corresponding to two displacements respectively, greatly expanding the displacement range of the sucker rod pump.

[0006] When the device is in large-displacement production, when the lower plunger enters the small pump barrel during the downward movement, there is no pressure relief channel for the well fluid between the two-stage plungers, which will inevitably cause the polished rod not to move downward.

[0007] Publication (Announcement) Number: CN109812407B, Publication (Announcement) Date: March 24, 2020. An automatic variable displacement lifting device is provided, which includes a pump barrel and a basic plunger, and also includes an outer sleeve plunger. The outer sleeve plunger is sleeved outside the basic plunger. The outer sleeve plunger is provided with at least one stage. That is, the outer sleeve plunger sleeved outside the basic plunger is regarded as the first-stage outer sleeve plunger, and the outer sleeve plunger sleeved outside the first-stage outer sleeve plunger is the second-stage outer sleeve plunger, and so on. A first-stage snap ring is arranged between the basic plunger and the first-stage outer sleeve plunger, a last-stage snap ring is arranged between the pump barrel and the last-stage outer sleeve plunger, and corresponding intermediate-stage snap rings are also arranged between the outer sleeve plungers of each stage. The displacement of this lifting device is automatically adjusted according to the liquid supply situation of the oil well without manual intervention. It adopts a concentric nested structure, and the working body length is similar to that of a conventional oil pump, and it is convenient for transportation and installation.

[0008] Since the two-stage plungers are softly connected by the radial force of the spring between the two-stage plungers, the complex force on the plunger pull rod causes friction between the plunger and the pump barrel, reducing the service life of the oil pump. In addition, the liquid column load borne by the snap ring between the two-stage plungers is in the vertical direction, while the bonding force is in the radial direction, so it is difficult to disconnect the two-stage plungers.

[0009] The technical solutions, the technical problems to be solved and the beneficial effects generated by the above disclosed technologies are all different from those of the present invention, or the technical fields or application scenarios are different. For more technical features, the technical problems to be solved and the beneficial effects of the present invention, there is no technical inspiration in the above disclosed technical documents. Summary of the Invention

[0010] Aiming at the above-mentioned defects existing in the prior art, the purpose of the present invention is to provide a displacement-changing oil pump with a fixed pipe string, a use method and a special locking mechanism, which can realize large-displacement liquid drainage in the initial stage, and realize stable production in the later stage by means of a fixed pipe string when the formation energy drops. It truly realizes the effective separation between the inner and outer plungers, thus ensuring the normal production of the small plunger.

[0011] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0012] A displacement-changing oil pump with a fixed pipe string includes a pump barrel, an outer plunger, and an inner plunger. The outer plunger is arranged inside the pump barrel, and the inner plunger is arranged inside the outer plunger;

[0013] It also includes a plunger locking mechanism, and the plunger locking mechanism includes a fixing frame and a plunger anti-rotation mechanism;

[0014] The outer plunger and the inner plunger are connected and fixed through the fixing frame, and the plunger anti-rotation mechanism is connected to the fixing frame.

[0015] Further, the fixing frame includes a small fixing frame, a large fixing frame, and a reverse-threaded screw;

[0016] The small fixing frame is fixedly connected to the inner plunger, and the large fixing frame is fixedly connected to the outer plunger. The center of the small fixing frame has a reverse-threaded screw, and a threaded hole for fitting the reverse-threaded screw is provided at the center of the large fixing frame.

[0017] Further, the plunger anti-rotation mechanism includes an upper anti-rotation combination body and a lower anti-rotation combination body;

[0018] The upper end of the upper anti-rotation combination body is fixedly connected to the large fixing frame; the upper anti-rotation combination body is of a cylindrical structure, and there are vertical convex strips on the inner wall;

[0019] The lower end of the lower anti-rotation combination body is fixedly connected to the fixed valve assembly at the lower port of the pump barrel; the lower anti-rotation combination body is of a cylindrical structure, and there are vertical grooves on the outer wall corresponding to the vertical convex strips; the vertical convex strips and the vertical grooves can be inserted into each other.

[0020] Further, the top end of the vertical groove of the lower anti-rotation combination body is of a conical structure, which can introduce the vertical convex strip into the vertical groove.

[0021] An upper traveling valve assembly is installed at the upper port of the inner plunger, and a lower traveling valve assembly is installed at the lower port of the inner plunger; a valve cover is installed at the upper end of the upper traveling valve assembly.

[0022] Further, the upper end of the pump barrel is connected to an upper joint, and the lower end of the pump barrel is connected to a lower joint.

[0023] In order to achieve the above object, the present invention adopts the following technical solutions:

[0024] The using method of the fixed string variable displacement oil pump includes the following steps:

[0025] After the fixed string variable displacement oil pump is lowered into the well, a sucker rod with a releasing joint is lowered, and the rod string is lifted to determine the lower dead point of the polished rod, and then normal production can be carried out;

[0026] Since the inner and outer plungers are connected into one body by a fixing frame with a reverse-threaded screw, during production, the inner plunger's traveling valve assembly is used for liquid intake, and the outer plunger moves up and down to lift the liquid;

[0027] When it is necessary to switch to inner plunger production, the rod string is lowered to make the vertical convex strip enter the vertical groove and connect into one body. At this time, the rod string is rotated forward, the inner plunger rotates accordingly, the outer plunger does not rotate, and the reverse-threaded screw disengages from the large fixing frame, that is, the inner and outer plungers are separated from each other. At this time, the inner and outer plungers are no longer integrated. Lifting the rod string drives the inner plunger, and inner plunger production can be achieved, and finally variable displacement oil pumping production is realized.

[0028] In order to achieve the above object, the present invention adopts the following technical solutions:

[0029] Special plunger locking mechanism for non - moving string variable displacement oil pump, including a fixed frame and a plunger anti - rotation mechanism; the outer plunger and the inner plunger are connected and fixed through the fixed frame, and the plunger anti - rotation mechanism is connected with the fixed frame;

[0030] The fixed frame includes a small fixed frame, a large fixed frame and a reverse screw; the small fixed frame is connected and fixed with the inner plunger, the large fixed frame is connected and fixed with the outer plunger, the small fixed frame has a reverse screw at its center, and the large fixed frame is provided with a threaded hole at its center for assembling the reverse screw;

[0031] The plunger anti - rotation mechanism includes an anti - rotation upper combination body and an anti - rotation lower combination body; the upper end of the anti - rotation upper combination body is connected and fixed with the large fixed frame; the anti - rotation upper combination body is of a cylindrical structure with vertical convex strips on its inner wall; the lower end of the anti - rotation lower combination body is connected and fixed with the fixed valve assembly at the lower port of the pump barrel; the anti - rotation lower combination body is of a cylindrical structure with vertical grooves corresponding to the vertical convex strips on its outer wall; the vertical convex strips and the vertical grooves can be inserted into each other.

[0032] Furthermore, the top of the vertical groove of the anti - rotation lower combination body is of a conical structure, which can introduce the vertical convex strip into the vertical groove.

[0033] The present invention has the following beneficial effects compared with the prior art:

[0034] The two plungers are connected together through the fixed frame at the bottom. When changing to a small pump for production, after lowering the plunger, the plunger anti - rotation mechanism is combined and the rod string is rotated to complete the separation of the inner and outer plungers, truly realizing the effective separation between the inner and outer plungers. When using the small plunger for production, the large plunger acts as the pump barrel of the small plunger and is in a stable state under the action of gravity and liquid column, thus ensuring the normal production of the small plunger; during the production process of the large plunger, the traveling valve assembly of the small plunger can open and close normally, ensuring the smooth operation of the polished rod. Production is achieved through the variable displacement method, effectively solving the problem of needing to operate and replace the oil pump due to the rapid change of the dynamic liquid level. Due to the simple and effective use method of this tool and the remarkable use effect, it has good economic and social benefits and popularization and application value.

[0035] The present invention can change the working system through non - moving string according to the change of formation energy, achieving the purpose of lifting liquid with a large - diameter plunger in the initial stage and stable production with a small - diameter plunger after the formation energy drops. By adjusting the working system through non - moving string, the pump replacement operation after the energy drops is avoided, thus reducing the maintenance cost. Brief Description of the Drawings

[0036] Figure 1 It is a structural schematic diagram of the non - moving string variable displacement oil pump of the present invention;

[0037] Figure 2This is a schematic structural diagram of the fixed-string variable displacement oil pump of the present invention when the locking mechanism operates.

[0038] In the figure: upper joint 1, pump barrel 2, outer plunger 3, valve cover 4, upper traveling valve assembly 5, inner plunger 6, lower traveling valve assembly 7, reverse screw 8, large fixed frame 9, plunger anti-rotation lower combination body 10, vertical convex strip 11, vertical groove 12, fixed valve assembly 13, lower joint 14. Specific implementation mode

[0039] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0040] Embodiment 1:

[0041] Please refer to Figures 1 to 2 , the present invention provides a technical solution:

[0042] The fixed-string variable displacement oil pump includes a pump barrel 2, an outer plunger 3, and an inner plunger 6. The outer plunger is arranged inside the pump barrel, and the inner plunger is arranged inside the outer plunger;

[0043] It further includes a plunger locking mechanism, and the plunger locking mechanism includes a fixed frame and a plunger anti-rotation mechanism;

[0044] The outer plunger and the inner plunger are connected and fixed through the fixed frame, and the plunger anti-rotation mechanism is connected to the fixed frame.

[0045] Further, the fixed frame includes a small fixed frame, a large fixed frame 9, and a reverse screw 8;

[0046] The small fixed frame is connected and fixed to the inner plunger, the large fixed frame is connected and fixed to the outer plunger. The small fixed frame has a reverse screw at its center, and the large fixed frame has a threaded hole at its center for assembling the reverse screw.

[0047] Further, the plunger anti-rotation mechanism includes an anti-rotation upper combination body and an anti-rotation lower combination body 10;

[0048] The upper end of the anti-rotation upper combination body is connected and fixed to the large fixed frame; the anti-rotation upper combination body is of a cylindrical structure, and there is a vertical convex strip 11 on its inner wall;

[0049] The lower end of the anti-rotation lower combination body is connected and fixed to the fixed valve assembly 13 at the lower port of the pump barrel; the anti-rotation lower combination body is of a cylindrical structure, and there is a vertical groove 12 on its outer wall corresponding to the vertical convex strip; the vertical convex strip and the vertical groove can be inserted into each other.

[0050] Further, the top of the vertical groove of the anti-rotation combination is a conical structure, which can introduce the vertical convex strip into the vertical groove.

[0051] Further, an upper traveling valve assembly 5 is installed at the upper port of the inner plunger, and a lower traveling valve assembly 7 is installed at the lower port of the inner plunger; a valve cover 4 is installed at the upper end of the upper traveling valve assembly.

[0052] Further, the upper end of the pump barrel is connected to an upper joint 1, and the lower end of the pump barrel is connected to a lower joint 14.

[0053] To achieve the above object, the present invention adopts the following technical solutions:

[0054] The using method of the non-moving string variable displacement oil pump includes the following steps:

[0055] After the non-moving string variable displacement oil pump is lowered into the well, a sucker rod with a disconnecting device is lowered, and the rod string is lifted to determine the lower dead point of the polished rod, and then normal production can be carried out;

[0056] Since the inner and outer plungers are connected into one body by a fixing frame with a reverse-threaded screw, during production, the liquid enters through the traveling valve assembly of the inner plunger, and the liquid is lifted by the up and down movement of the outer plunger;

[0057] When it is necessary to convert to inner plunger production, lower the rod string to make the vertical convex strip enter the vertical groove and connect into one body. At this time, rotate the rod string forward, the inner plunger rotates accordingly, the outer plunger does not rotate, and the reverse-threaded screw disengages from the large fixing frame, that is, the inner and outer plungers are disengaged from each other. At this time, the inner and outer plungers are no longer one body. Lifting the rod string drives the inner plunger, and inner plunger production can be achieved, and finally variable displacement pumping production is realized.

[0058] The double plungers are connected together through a fixing frame at the bottom. When changing to small pump production, after lowering the plunger, the plunger anti-rotation mechanism is combined and the rod string is rotated to complete the disengagement of the inner and outer plungers, truly realizing the effective separation between the inner and outer plungers. When using the small plunger for production, the large plunger acts as the pump barrel of the small plunger and is in a stable state under the action of gravity and liquid column, thus ensuring the normal production of the small plunger; during the production process of the large plunger, the traveling valve assembly of the small plunger can be opened and closed normally, ensuring the smooth operation of the polished rod. Production is achieved through variable displacement, effectively solving the problem of needing to operate and replace the oil pump due to the rapid change of the dynamic liquid level. Since the use method of this tool is simple and effective, and the use effect is remarkable, it has good economic and social benefits and popularization and application value. The present invention can adjust the working system through the non-moving string according to the formation energy change, achieving the purpose of lifting liquid with a large-diameter plunger in the initial stage and stable production with a small-diameter plunger after the energy drops. By adjusting the working system through the non-moving string, the pump replacement operation after the energy drops is avoided, thereby reducing the maintenance cost.

[0059] Embodiment 2:

[0060] Please refer to Figures 1 to 2 , the present invention provides a technical solution:

[0061] The fixed-tubing variable-displacement oil pump includes a pump barrel 2, an outer plunger 3, and an inner plunger 6. The outer plunger is arranged inside the pump barrel, and the inner plunger is arranged inside the outer plunger;

[0062] It further includes a plunger locking mechanism, and the plunger locking mechanism includes a fixing frame and a plunger anti-rotation mechanism;

[0063] The outer plunger and the inner plunger are connected and fixed through the fixing frame, and the plunger anti-rotation mechanism is connected to the fixing frame.

[0064] Further, the fixing frame includes a small fixing frame, a large fixing frame 9, and a reverse-threaded screw 8;

[0065] The small fixing frame is connected and fixed to the inner plunger, the large fixing frame is connected and fixed to the outer plunger. The small fixing frame has a reverse-threaded screw at its center, and the large fixing frame has a threaded hole at its center for fitting the reverse-threaded screw.

[0066] Embodiment 3:

[0067] Please refer to Figures 1 to 2 , the present invention provides a technical solution:

[0068] The special plunger locking mechanism for the fixed-tubing variable-displacement oil pump includes a fixing frame and a plunger anti-rotation mechanism;

[0069] The outer plunger and the inner plunger are connected and fixed through the fixing frame, and the plunger anti-rotation mechanism is connected to the fixing frame.

[0070] Further, the fixing frame includes a small fixing frame, a large fixing frame 9, and a reverse-threaded screw 8;

[0071] The small fixing frame is connected and fixed to the inner plunger, the large fixing frame is connected and fixed to the outer plunger. The small fixing frame has a reverse-threaded screw at its center, and the large fixing frame has a threaded hole at its center for fitting the reverse-threaded screw.

[0072] Further, the plunger anti-rotation mechanism includes an anti-rotation upper combination body and an anti-rotation lower combination body 10;

[0073] The upper end of the anti-rotation upper combination body is connected and fixed to the large fixing frame; the anti-rotation upper combination body is of a cylindrical structure with vertical convex strips 11 on its inner wall;

[0074] The lower end of the anti-rotation lower combination body is connected and fixed to the fixed valve assembly 13 at the lower port of the pump barrel; the anti-rotation lower combination body is of a cylindrical structure with vertical grooves 12 corresponding to the vertical convex strips on its outer wall; the vertical convex strips and the vertical grooves can be inserted into each other.

[0075] Further, the top of the vertical groove of the anti-rotation lower combination is a conical structure, which can introduce the vertical convex strip into the vertical groove.

[0076] Although all of the above embodiments use Figures 1 to 2 , it is clear to those skilled in the art that there is no need to give a separate drawing to show. As long as the missing components or structural features in the embodiment are removed from the drawing. This is clear to those skilled in the art. Of course, the embodiment with more components is just the optimal embodiment, and the embodiment with fewer components is the basic embodiment, but it can also achieve the basic invention purpose. Therefore, all these variant embodiments are within the protection scope of the present invention.

[0077] In this application, the components themselves that are not elaborated and the connection methods of the various components in this application all belong to the well-known technologies in the technical field and will not be elaborated further. Such as welding, screw connection, etc.

[0078] In the present invention, the term "a plurality of" means two or more, unless otherwise clearly defined. Terms such as "installation", "connection", "connection", "fixation" and other terms should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; "connection" can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0079] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "rear", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or unit referred to must have a specific direction, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention.

[0080] In the description of this specification, the description of terms such as "one embodiment", "some embodiments", "specific embodiments", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or instance. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0081] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. Stationary-tubing variable-displacement sucker rod pump, comprising a pump barrel, an outer plunger, and an inner plunger. The outer plunger is disposed within the pump barrel, and the inner plunger is disposed within the outer plunger; It is characterized in that It further includes a plunger locking mechanism, which includes a fixing frame and a plunger anti-rotation mechanism; The outer plunger and the inner plunger are connected and fixed through the fixing frame, and the plunger anti-rotation mechanism is connected to the fixing frame; The fixing frame includes a small fixing frame, a large fixing frame, and a reverse-threaded screw; The small fixing frame is connected and fixed to the inner plunger, the large fixing frame is connected and fixed to the outer plunger. The small fixing frame has a reverse-threaded screw at its center, and the large fixing frame is provided with a threaded hole at its center for fitting the reverse-threaded screw; The plunger anti-rotation mechanism includes an anti-rotation upper combination body and an anti-rotation lower combination body; The upper end of the anti-rotation upper combination body is connected and fixed to the large fixing frame; the anti-rotation upper combination body is of a cylindrical structure with vertical convex strips on its inner wall; The lower end of the anti-rotation lower combination body is connected and fixed to the fixed valve assembly at the lower port of the pump barrel; the anti-rotation lower combination body is of a cylindrical structure with vertical grooves corresponding to the vertical convex strips on its outer wall; the vertical convex strips and the vertical grooves can be inserted into each other.

2. The constant-displacement oil pump with a stationary pipe string according to claim 1, wherein The top end of the vertical groove of the anti-rotation lower combination body is of a conical structure, which can introduce the vertical convex strip into the vertical groove.

3. The fixed string variable displacement oil pump according to claim 2, wherein An upper traveling valve assembly is installed at the upper port of the inner plunger, and a lower traveling valve assembly is installed at the lower port of the inner plunger; a valve cover is installed at the upper end of the upper traveling valve assembly.

4. The non-tubing-displaced variable displacement oil pump according to claim 2, characterized in that, The upper end of the pump barrel is connected to an upper joint, and the lower end of the pump barrel is connected to a lower joint.

5. A method for using the fixed-tubing variable-displacement oil pump as described in claim 1, characterized in that, It includes the following steps: After the stationary-tubing variable-displacement sucker rod pump is lowered into the well, a sucker rod with a disconnecting device is lowered, and the rod string is lifted to determine the lower dead point of the polished rod, and then normal production can be carried out; Since the inner and outer plungers are connected as a whole by a fixing frame with a reverse-threaded screw, during production, liquid enters through the traveling valve assembly of the inner plunger, and liquid is lifted by the up and down movement of the outer plunger; When it is necessary to switch to inner plunger production, lower the rod string to make the vertical convex strip enter the vertical groove and connect into a whole. At this time, rotate the rod string forward, the inner plunger rotates accordingly, the outer plunger does not rotate, and the reverse-threaded screw disengages from the large fixing frame, that is, the inner and outer plungers are disengaged from each other. At this time, the inner and outer plungers are no longer a whole. Lifting the rod string drives the inner plunger, and inner plunger production can be achieved, and finally variable-displacement pumping production is realized.

6. A special plunger locking mechanism for the stationary-tubing variable-displacement sucker rod pump as described in claim 1, comprising a fixing frame and a plunger anti-rotation mechanism; the outer plunger and the inner plunger are connected and fixed through the fixing frame, and the plunger anti-rotation mechanism is connected to the fixing frame; The fixing frame includes a small fixing frame, a large fixing frame, and a reverse-threaded screw; the small fixing frame is connected and fixed to the inner plunger, the large fixing frame is connected and fixed to the outer plunger. The small fixing frame has a reverse-threaded screw at its center, and the large fixing frame is provided with a threaded hole at its center for fitting the reverse-threaded screw; The plunger anti-rotation mechanism includes an upper anti-rotation combination body and a lower anti-rotation combination body; the upper end of the upper anti-rotation combination body is fixedly connected to the large fixed frame; the upper anti-rotation combination body is of a cylindrical structure with vertical convex strips on the inner wall; the lower end of the lower anti-rotation combination body is fixedly connected to the fixed valve assembly at the lower port of the pump barrel; the lower anti-rotation combination body is of a cylindrical structure with vertical grooves corresponding to the vertical convex strips on the outer wall; the vertical convex strips and the vertical grooves can be inserted into each other.

7. The special plunger locking mechanism for the fixed-tubing variable displacement oil pump according to claim 6, characterized in that, The top of the vertical groove of the lower anti-rotation combination body is of a conical structure to introduce the vertical convex strip into the vertical groove.

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