Radial reducing extrusion cold rolling process for stator production

Abstract

The invention provides a radial diameter-reducing extrusion cold rolling process for stator production, and relates to the technical field of screw drill stator processing, which comprises the following steps: S100, coaxially sleeving an inner core shaft with spiral bulges distributed on the peripheral wall in an inner die cavity of an outer die cylinder, and enabling the outer diameter of the inner core shaft to be smaller than the inner diameter of a stator tube blank; an annular rolling space used for containing and rolling a stator tube blank is formed between the inner mandrel and the side wall of the inner die cavity, the two axial ends of the rolling space are a rolling inlet and a rolling outlet respectively, the outer diameter of the rolling inlet is larger than that of the stator tube blank, and the outer diameter of the rolling outlet is smaller than that of the stator tube blank. The thickness of the radial section of the rolling space is gradually reduced from the rolling inlet to the rolling outlet; s200, performing radial extrusion on the stator tube blank through the outer die cylinder; and S300, the inner core shaft is driven to rotate, the inner wall of the stator pipe blank is spirally machined, metal of the stator pipe blank is guided to plastically flow to achieve shape forming, no redundant metal is ground or removed or corroded, and energy is saved.

Description

Technical Field

[0001] This invention belongs to the field of stator processing technology for screw drills, specifically, it relates to a radial diameter reduction extrusion cold rolling process for stator production. Background Technology

[0002] In the traditional machining process of screw drills, the mainstream methods for forming the internal cavity structure of the stator are machining and electro-erosion machining. Both are material removal processing methods. Although they can meet the basic forming requirements of the stator, they have significant defects in terms of production efficiency, energy consumption control and raw material utilization. Machining is based on grinding, which removes excess material inside the stator blank through the high-speed rotation of the grinding wheel, so that the inner wall of the stator forms a pre-set spiral groove structure. Electro-erosion machining relies on the corrosion effect of electrochemical reaction. Through the contact reaction between the electrolyte and the stator blank, excess material inside the blank is dissolved and removed to complete the forming of the stator cavity.

[0003] Based on these two methods, from the perspective of raw material utilization, both processes inevitably involve material loss. The grinding process in machining generates wear debris, while the corrosion process in electro-optical machining generates material dissolution loss. To ensure the finished stator meets the preset weight and size requirements, a blank heavier than the finished product must be used for processing. For example, if the required weight of the finished stator is 100 kg, in actual production, a blank weighing 120 kg may be needed. The additional 20 kg of material will be lost during processing, reducing raw material utilization and increasing the raw material procurement cost for stator production.

[0004] From the perspective of processing efficiency and energy consumption, the grinding operation in machining requires slow-contact cutting between the grinding wheel and the workpiece to achieve shaping. To ensure the accuracy of the cavity, the grinding speed and feed rate need to be controlled, resulting in a long processing cycle for a single stator. The corrosion reaction in electro-erosion machining is affected by factors such as electrolyte concentration and reaction temperature, resulting in a slower reaction rate. Furthermore, additional processes such as electrolyte cleaning and workpiece drying are required after machining, further extending the processing time. At the same time, both processes consume a large amount of electrical energy. The high-speed rotation of the grinding wheel and the precise positioning of the equipment in machining require a continuous high-power supply, while the electrolyte circulation and electrochemical reaction activation in electro-erosion machining also require a stable high current. Under long-term production, the high power consumption of the equipment significantly increases the energy cost of stator production. Summary of the Invention

[0005] The purpose of this invention is to provide a radial reduction extrusion cold rolling process for stator production, which solves the technical problems of low raw material utilization, high raw material procurement costs, long processing cycles, and high energy consumption in related technologies that use machining and electro-erosion processing.

[0006] At least one embodiment of the present invention provides a radial reduction extrusion cold rolling process for stator production, comprising: S100, coaxially connecting an outer die cylinder and an inner mandrel with spiral protrusions on its peripheral wall, wherein the outer diameter of the inner mandrel is configured to be smaller than the inner diameter of the stator tube blank, and an annular rolling space is formed between the inner mandrel and the outer die cylinder for accommodating and rolling the stator tube blank, wherein the two axial ends of the rolling space are respectively a rolling inlet and a rolling outlet, wherein the outer diameter of the rolling inlet is configured to be larger than the outer diameter of the stator tube blank, and the outer diameter of the rolling outlet is configured to be smaller than the outer diameter of the stator tube blank, wherein the radial cross-sectional thickness of the rolling space gradually decreases from the rolling inlet to the rolling outlet; S200: The stator tube blank is pushed axially into the rolling space and radially extruded through the outer die cylinder; S300 drives the inner mandrel to rotate, performing spiral machining on the inner wall of the stator tube blank.

[0007] According to an exemplary embodiment of this disclosure, in S100, the outer mold cylinder has an inner mold cavity, and the angle between the axial section edge of the inner mold cavity and the axis of the outer mold cylinder is α. The inner mandrel includes an inclined shaft section, and the angle between the axial section edge of the inclined shaft section and the axis of the inner mandrel is β, where α > β.

[0008] According to an exemplary embodiment of this disclosure, in S100, the inner mold cavity includes a first mold cavity and a second mold cavity along the axial direction; The diameter of the first die cavity near the rolling inlet is larger than the outer diameter of the stator tube blank; The diameter of the first die cavity near the rolling exit is smaller than the outer diameter of the stator tube blank.

[0009] According to an exemplary embodiment of this disclosure, in S100, the angle between the axial section edge of the first mold cavity and the axis of the outer mold cylinder is α1. The angle between the axial section edge of the second mold cavity and the axis of the outer mold cylinder is α2, where α2 > α1.

[0010] According to an exemplary embodiment of this disclosure, in S100, 0.6°≤α1<0.7°, 0.7°≤α2≤0.8°.

[0011] According to an exemplary embodiment of this disclosure, in S100, the inclined shaft segment includes a first shaft segment and a second shaft segment along the axial direction; The angle between the axial section edge of the first shaft segment and the axis of the inner core shaft is β1; The angle between the axial section edge of the second shaft segment and the axis of the inner core shaft is β2, where β2 < β1.

[0012] According to an exemplary embodiment of this disclosure, 0.2°≤β1<0.3°, 0.02°≤β2≤0.03°.

[0013] According to an exemplary embodiment of this disclosure, in S100, the inner mandrel further includes a constant diameter shaft segment connected to the second shaft segment.

[0014] According to an exemplary embodiment of this disclosure, step S300 further includes the following step: While the inner mandrel rotates, it drives the outer mold cylinder to reciprocate along the axial direction to extrude the outside of the stator tube blank.

[0015] According to an exemplary embodiment of this disclosure, in S300, the reciprocating stroke of the outer mold cylinder along the axial direction is less than the total length of the second shaft segment and the equal-diameter shaft segment.

[0016] The present invention provides a radial reduction extrusion cold rolling process for stator production. Through the radial extrusion of the outer die cylinder and the rotational spiral action of the inner mandrel, the metal of the stator tube blank is guided to undergo plastic flow to achieve shape forming. In the whole process, no excess metal is removed by grinding or corroded and lost. Only the metal morphology is changed by room temperature cold rolling. The entire processing is carried out at room temperature, without the need to heat the tube blank or equipment as in some hot processing processes, thus saving the power consumption required for the heating process. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic cross-sectional view of a radial reduction extrusion cold rolling process for stator production provided in an embodiment of the present invention; Figure 2 This is an embodiment of the present invention. Figure 1 Schematic diagram of the cross-sectional structure of the inner and outer mold cylinders; Figure 3 This is an embodiment of the present invention. Figure 1 Schematic diagram of the inner mandrel; Figure 4 This is an embodiment of the present invention. Figure 3 Schematic diagram of the cross-sectional structure of AA; Figure 5 This is an embodiment of the present invention. Figure 3 Schematic diagram of the cross-sectional structure of BB; Figure 6 This is an embodiment of the present invention. Figure 3 A schematic diagram of the cross-sectional structure of the C-C section; Figure 7 This is an embodiment of the present invention. Figure 2A partially enlarged structural diagram of section III; Figure 8 This is an embodiment of the present invention. Figure 2 A partially enlarged structural diagram of section IV; Figure 9 This is an embodiment of the present invention. Figure 3 A partially enlarged structural diagram of section I; Figure 10 This is an embodiment of the present invention. Figure 3 A partially enlarged structural diagram of section II; Figure 11 This is a flowchart illustrating the steps of a radial reduction extrusion cold rolling process for stator production provided in an embodiment of the present invention.

[0019] In the figure: 100, outer mold cylinder; 110, inner mold cavity; 111, first mold cavity; 112, second mold cavity; 200, inner mandrel; 210, spiral protrusion; 220, inclined shaft section; 221, first shaft section; 222, second shaft section; 230, equal diameter shaft section; 300, stator tube blank; 400, rolling space; 410, rolling inlet; 420, rolling outlet. Detailed Implementation

[0020] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure. For ease of understanding, the English abbreviations and related technical terms involved in the embodiments of this disclosure will be explained and described below.

[0021] It should be understood that the described embodiments are merely some, not all, of the embodiments disclosed herein. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without inventive effort are within the scope of protection of this disclosure.

[0022] The terminology used in the embodiments of this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure. The singular forms “a,” “the,” and “the” as used in the embodiments of this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0023] It should be understood that the term "and / or" used in this article is merely a way of describing the logical relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0024] Depending on the context, the word "if" as used here can be interpreted as "when" or "when" or "in response to determination" or "in response to detection." Similarly, depending on the context, the phrase "if determination" or "if detection (of the stated condition or event)" can be interpreted as "when determination" or "in response to determination" or "when detection (of the stated condition or event)" or "in response to detection (of the stated condition or event)."

[0025] It should be understood that the terms "first," "second," etc., used in this disclosure are for distinguishing purposes only and should not be construed as indicating or implying relative importance or order.

[0026] In the description of this disclosure, the terms “center,” “upper,” “lower,” “front,” “back,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” and “outer,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this disclosure and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and should not be construed as a limitation of this disclosure.

[0027] In the description of this disclosure, it should be noted that, unless otherwise expressly specified and limited, the terms "installation", "connection" and "joining" should be interpreted broadly, for example, they can be fixed connections, detachable connections, mating connections or integral connections; those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0028] like Figures 1-11 As shown, it illustrates a radial reduction extrusion cold rolling process for all-metal stator production in one embodiment of the present invention. The core of this process is to replace the traditional material removal process with axial gradual rolling at room temperature, thereby solving the problems of low raw material utilization, low processing efficiency, and high energy consumption in the traditional process.

[0029] Specifically, in S100, the outer mold cylinder 100 is coaxially sleeved with the inner mandrel 200, whose peripheral wall is covered with spiral protrusions 210, such as... Figure 1As shown, the outer diameter of the inner mandrel 200 is set to be smaller than the inner diameter of the stator tube blank 300, ensuring that the tube blank can be smoothly fitted onto the outside of the inner mandrel 200. At the same time, an annular rolling space 400 is formed between the outer die cylinder 100 and the inner mandrel 200. This space is used to accommodate and roll the stator tube blank 300. In order to achieve axial gradual diameter reduction and metal flow guidance, the two ends of the rolling space 400 are respectively set as rolling inlet 410 and rolling outlet 420. The outer diameter of the rolling inlet 410 is larger than the outer diameter of the stator tube blank 300, which facilitates the tube blank to enter the rolling space 400 smoothly. The outer diameter of the rolling outlet 420 is smaller than the outer diameter of the stator tube blank 300, realizing the gradual diameter reduction of the tube blank. At the same time, from the rolling inlet 410 to the rolling outlet 420, the radial section thickness of the rolling space 400 gradually decreases, providing a gradual stress environment for the radial extrusion deformation of the tube blank and guiding the metal to flow along the radial inner side.

[0030] After the mold assembly is completed, the rolling process begins. In S200, the stator tube blank 300 is first pushed axially into the annular rolling space 400. At this time, the outer mold cylinder 100 applies radial extrusion force to the stator tube blank 300. Since the radial section thickness of the rolling space 400 gradually decreases from the rolling inlet 410 to the rolling outlet 420, the stator tube blank 300 will be subjected to continuous and gradual radial extrusion by the outer mold cylinder 100 during the axial pushing process. This extrusion force will force the tube blank to undergo radial plastic deformation, gradually reducing the outer diameter of the tube blank. At the same time, the extrusion action will change the inner diameter of the tube blank, pushing the metal on the inner wall of the tube blank to flow inward.

[0031] While the tube blank is radially extruded by the outer mold cylinder 100 and gradually advanced axially, step S300 is also included, driving the inner mandrel 200 to rotate. The spiral protrusions 210 on the peripheral wall of the inner mandrel 200 will simultaneously perform spiral processing on the inner wall of the stator tube blank 300. Since the tube blank metal is in a plastic flow state under the extrusion action, the flowing metal will tightly fill the gap between the spiral protrusions 210 of the inner mandrel 200 and the inner wall of the tube blank, thereby replicating the spiral protrusions 210 structure of the inner mandrel 200 and forming the spiral groove shape required for the stator inner cavity. Finally, through the radial deformation action of the outer mold cylinder 100 and the axial rolling and rotation spiral action of the inner mandrel 200, the stator inner cavity is formed in one step. The entire processing is carried out at room temperature without additional heating. After processing, the surface of the tube blank forms a smooth forming surface with a surface roughness of 1.6, which can be directly used with the rotor without additional grinding, polishing or other subsequent processing steps.

[0032] Based on the above process, traditional machining and electro-erosion machining are both material removal processes. During the process, there will be losses such as grinding debris and material dissolution. It is necessary to select blanks that are much larger than the weight of the finished product, resulting in low raw material utilization and high procurement costs. In this example, the radial extrusion of the outer mold cylinder 100 and the helical rotation of the inner mandrel 200 guide the metal of the stator tube blank 300 to undergo plastic flow and achieve shape forming. In the whole process, there is no excess metal that is removed by grinding or corroded, only a change in the metal morphology.

[0033] Specifically, traditional machining involves slow grinding speeds, and electro-erosion machining has low reaction rates, both requiring additional auxiliary processes, resulting in long processing cycles and low efficiency. In this example, after the billet is pushed axially to the rolling space of 400, the external diameter control, internal diameter adjustment, and inner wall spiral groove formation are completed simultaneously during one axial advance. This eliminates the need for rough grinding followed by fine grinding, as in traditional machining, and for etching, electrolyte cleaning, and drying, as in electro-erosion machining, simplifying the processing steps. Secondly, traditional processes consume significant amounts of electrical energy. The high-speed rotation of the machining die and the electrolyte circulation and electrochemical reaction in electro-erosion machining all require high power and high current, leading to high energy costs. This process uses room-temperature cold rolling, with the entire process carried out at room temperature, eliminating the need to heat the billet or equipment as required by some hot-working processes, thus saving the electrical energy consumed in the heating stage.

[0034] It should be noted that before extrusion and cold rolling, the stator tube blank 300 needs to be heat-treated. The heat treatment includes annealing and full annealing. The example temperature for full annealing is Ac3+ (30-50℃). The purpose is to increase the plastic deformation of the stator tube blank 300, effectively reduce the deformation resistance of the tube blank during cold rolling, and avoid cracking caused by cold working. After heat treatment, the stator tube blank 300 needs to be phosphated and saponified to reduce the frictional resistance between the tube blank and the outer die cylinder 100 and the inner mandrel 200 during subsequent cold rolling. This protects the surface of the tube blank from scratches, reduces die wear, and further ensures forming accuracy. After processing, the stator can be hardened and used as a metal stator to directly cooperate with the rotor to form a high-temperature resistant all-metal motor, which can meet higher working conditions.

[0035] To further clarify, in this example, the outer diameter of the rolling inlet 410 is configured to be larger than the outer diameter of the stator tube blank 300, and the outer diameter of the rolling outlet 420 is configured to be smaller than the outer diameter of the stator tube blank 300. This indicates that the inner cavity 110 of the outer die cylinder 100 is a variable diameter design. During the cold rolling process, when the stator tube blank 300 is pushed axially into the rolling space 400, it will be gradually guided by the gradual structure of the inner cavity 110 of the outer die cylinder 100 to achieve smooth radial diameter reduction deformation. This avoids problems such as cracking and breakage of the tube blank due to sudden excessive force, and at the same time, it can reduce deformation resistance, reduce the force on the die, and extend the service life of the die.

[0036] In one existing example technology, a structure with an inner mold cavity 110 of equal diameter and an outer mold cylinder 100 without a gradual taper is typically used. This leads to a sudden increase in deformation force during the rolling process of the stator tube blank 300, which in turn significantly increases the impact force on the mold. This places high demands on the strength of the mold and requires higher-power equipment to provide sufficient rolling power. Therefore, the tube blank must be heated to reduce deformation resistance and complete the forming process. However, if the stator tube blank 300 is heated immediately before processing using resistance wire, an oxide layer will form on the surface of the heated tube blank, damaging the surface flatness and resulting in low surface roughness. Subsequent processing is required, which will damage the original cross-sectional shape and affect the dimensional stability of the tube blank, leading to uneven heating and deformation deviation, thereby reducing the dimensional accuracy of subsequent processing. At the same time, immediate heating requires continuous power consumption, resulting in energy waste. Furthermore, the processing accuracy of the heated tube blank is difficult to meet the requirements of the precision stator cavity. Therefore, stators processed by this technology usually need to be lined with rubber on the inner surface to be used as stators, and direct mating between the metal stator and the rotor is not possible.

[0037] Furthermore, after the stator tube blank 300 enters the rolling space 400, because the outer diameter of the inner mandrel 200 is smaller than the inner diameter of the stator tube blank 300, a gap is initially left between the inner wall of the stator tube blank 300 and the inner mandrel 200. At this time, the tube blank is first subjected to radial extrusion by the inner mold cavity 110 of the outer mold cylinder 100. During the continuous axial pushing process, the stator tube blank 300 gradually undergoes radial diameter reduction deformation under the gradual constraint of the outer mold cylinder 100, and its own inner diameter continues to shrink. The inner wall of the stator tube blank 300 gradually approaches and fits the inner mandrel 200, and is then supported and formed by the inner mandrel 200.

[0038] Based on this, the axial section edge of the inner cavity 110 of the outer mold cylinder 100 forms an angle α with the axis of the outer mold cylinder 100, and the axial section edge of the inclined shaft segment 220 of the inner mandrel 200 forms an angle β with the axis of the inner mandrel 200. The angle is set to α > β, so that the deformation process of the stator tube blank 300 is more gradual and orderly. The outer mold cylinder 100 achieves the dominant radial diameter reduction with a larger angle gradient, first pushing the outer metal of the stator tube blank 300 to shrink and deform evenly. After the inner diameter of the stator tube blank 300 shrinks to fit the inner mandrel 200, the inner mandrel 200 provides internal support with a smaller angle gradient, guiding the inner metal to flow and fill smoothly. To avoid the billet being subjected to rigid constraints from both inside and outside as soon as it enters the rolling space 400, stress concentration in the early stage of deformation is reduced, and the possibility of billet cracking is lowered. At the same time, the gradual force transmission can further reduce the overall deformation resistance and make the metal flow smoother. This not only helps to improve the filling and forming effect of the spiral structure inside the stator billet 300, but also reduces the load on the mold and equipment.

[0039] Furthermore, the inner mold cavity 110 of the outer mold cylinder 100 is divided into a first mold cavity 111 and a second mold cavity 112 that are interconnected along the axial direction. The angle between the axial section edge of the first mold cavity 111 and the axis of the outer mold cylinder 100 is α1, with a value range of 0.6°≤α1<0.7°. The corresponding angle for the second mold cavity 112 is α2, with a value range of 0.7°≤α2≤0.8°. After the stator tube blank 300 enters the rolling space 400 along the axial direction, it first enters the first mold cavity 111. At this time, because the outer diameter of the inner mandrel 200 is smaller than the inner diameter of the stator tube blank 300, there is a gap between the inner wall of the stator tube blank 300 and the inner mandrel 200. It is only constrained by the outside of the first mold cavity 111. The α1 of the first mold cavity 111 is a small angle that gradually changes. During the advancement process, the stator tube blank 300 undergoes a smooth initial radial reduction in diameter, with a small deformation amplitude and uniform stress. As the stator blank 300 continues to move forward into the second mold cavity 112, the inner wall begins to fit against the inner mandrel 200 and obtain internal support. The second mold cavity 112 α2 is slightly larger than α1, and the mold cavity shrinkage amplitude increases slightly. Under the bidirectional constraints of the inside and outside, the blank completes radial shaping and inner cavity forming.

[0040] Based on the above process, the α1 of the first mold cavity 111 adopts a small angle of 0.6°~0.7° with a gradual change. In the early stage of deformation without the support of the inner mandrel 200, the tube blank only bears a mild radial extrusion force and will not cause stress concentration due to excessive shrinkage of the mold cavity. This can avoid cracking and wrinkling of the tube blank under room temperature cold rolling. As the inner mandrel 200 fully contacts and supports the inner wall of the stator tube blank 300, the α2 of the second mold cavity 112 increases slightly to 0.7°~0.8°, which improves the deformation efficiency while ensuring the stability of the stator tube blank 300 under stress.

[0041] Furthermore, the inclined shaft segment 220 of the inner mandrel 200 is divided into an adjacent first shaft segment 221 and a second shaft segment 222 along the axial direction. The angle between the axial section edge of the first shaft segment 221 and the axis of the inner mandrel 200 is β1, with a value range of 0.2°≤β1<0.3°. The corresponding angle of the second shaft segment 222 is β2, with a value range of 0.02°≤β2≤0.03°. When the stator tube blank 300 is radially compressed by the outer wall in the first mold cavity 111, the inner wall contracts towards the center and fits against the inner mandrel 200. The small inclined angle of 0.2°~0.3° of the first shaft segment 221 can play a smooth guiding role on the inner wall of the tube blank, so that the inner wall fits against the inner mandrel 200 smoothly without impact or hard top, avoiding problems such as wrinkling, bulging, and cracking of the inner wall, and ensuring uniform compression of the tube blank wall thickness. The second shaft section 222β2 has a radius of only 0.02°~0.03° and is almost straight. It focuses on the fine finishing and shaping of the inner cavity, which can effectively reduce the axial taper of the stator inner cavity, improve the straightness of the inner cavity, and make the inner cavity dimensions meet the high-precision matching requirements of the all-metal motor and the rotor.

[0042] Furthermore, the inner mandrel 200 also includes a constant-diameter shaft section 230 connected to the second shaft section 222. After the stator blank 300 is finished by the second shaft section 222, it enters the area of ​​the constant-diameter shaft section 230. The constant-diameter shaft section 230 adopts a fixed diameter design and has no axial taper, which can perform final calibration and shaping of the initially formed stator cavity, ensuring the consistency and stability of the dimensions of the all-metal stator cavity. In addition, the constant-diameter shaft section 230 is a fixed constant-diameter structure. Compared with the inner mandrel 200 with taper throughout, even if normal wear occurs on the surface during long-term cold rolling, it will only be uniform radial wear and will not change the core dimensions of the cavity. However, once the fully taper shaft section wears, it will directly cause the inner cavity taper and inner diameter to shift simultaneously, resulting in product dimensions exceeding tolerance.

[0043] Furthermore, in this example S300, while the inner mandrel 200 rotates, the outer mold cylinder 100 is simultaneously driven to reciprocate axially to extrude the outside of the stator blank 300. The axial reciprocating stroke of the outer mold cylinder 100 is limited to less than the total axial length of the second shaft segment 222 and the equal diameter shaft segment 230. The rotation of the inner mandrel 200 is used to replicate the spiral cavity structure of the stator inner wall. The outer mold cylinder 100 synchronously reciprocates axially to extrude the outside of the blank, and a radial extrusion force can be continuously applied from the outside, forcing the blank metal to flow and fill more fully into the spiral protrusion 210 part of the inner mandrel 200. This effectively avoids defects such as loose forming and blurred contour in the inner cavity, making the spiral cavity forming fuller and the dimensional accuracy higher.

[0044] It should be noted that the reciprocating stroke of the outer mold cylinder 100 is limited to less than the total length of the second shaft section 222 and the equal diameter shaft section 230. The reason is that the first shaft section 221 of the inner mandrel 200 corresponds to the first mold cavity 111 of the outer mold cylinder 100, forming the shaft-guided structure of the stator tube blank 300, completing the initial extrusion of the outer wall of the tube blank and the smooth shaft-guided structure of the inner wall. The second shaft section 222 and the equal diameter shaft section 230 of the inner mandrel 200 correspond to the second mold cavity 112 of the outer mold cylinder 100, forming the finishing and shaping structure of the tube blank, completing the final diameter reduction and size locking of the tube blank. By controlling the reciprocating stroke of the outer mold cylinder 100 within a limited range, the reciprocating extrusion action can be applied only to the finishing and shaping structure area and will not touch the shaft-guided structure area.

[0045] The axial guide structure requires a stable, gradual extrusion environment to achieve orderly initial deformation of the tube blank. Reciprocating extrusion does not enter this region, thus avoiding interference with the axial guide structure and preventing the tube blank from experiencing disordered axial adhesion and uneven wall thickness compression due to repeated stress, thereby ensuring the stability of the initial deformation.

[0046] The annular rolling space 400 formed by the outer mold cylinder 100 and the inner mandrel 200 has a gradual structure in the guide area and a slightly gradual to constant diameter structure in the finishing and shaping area. The stroke limitation can maintain the original structural shape of each area of ​​the rolling space 400, allowing the metal flow to always follow the preset path, first flowing smoothly and centripetally in the guide area, and then densely filling the cavity in the shaping area, avoiding the problem of incomplete cavity filling caused by turbulent metal flow.

[0047] In the guide zone, the tube blank is not fully attached to the inner mandrel 200, resulting in poor axial stability and a tendency for shifting or displacement. In the finishing and shaping zone, the tube blank is fully attached to the inner mandrel 200, providing sufficient axial stability. Limiting the reciprocating stroke of the outer mold cylinder 100 concentrates the axial force in a structurally stable area, preventing axial displacement of the tube blank and ensuring the forming accuracy of the stator's axial dimensions and the inner cavity's helical structure.

[0048] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A radial reducing extrusion cold rolling process for stator production, characterized by, include: S100, an inner mandrel (200) with spiral protrusions (210) on its peripheral wall is coaxially inserted into the inner mold cavity (110) of the outer mold cylinder (100). The outer diameter of the inner mandrel (200) is configured to be smaller than the inner diameter of the stator tube blank (300). An annular rolling space (400) for accommodating and rolling the stator tube blank (300) is formed between the outer peripheral wall of the inner mandrel (200) and the peripheral wall of the inner mold cavity (110). The two axial ends of (400) are a rolling inlet (410) and a rolling outlet (420), respectively. The outer diameter of the rolling inlet (410) is configured to be larger than the outer diameter of the stator tube blank (300), and the outer diameter of the rolling outlet (420) is configured to be smaller than the outer diameter of the stator tube blank (300). The radial section thickness of the rolling inlet (410) gradually decreases towards the rolling outlet (420) and the rolling space (400). S200, The stator tube blank (300) is pushed axially from the rolling inlet (410) into the rolling space (400), and the stator tube blank (300) is radially extruded through the outer die cylinder (100); S300: Drive the inner mandrel (200) to rotate and perform spiral processing on the inner wall of the stator tube blank (300).

2. A radial reducing extrusion cold rolling process for stator production according to claim 1, characterized in that, In S100, the angle between the axial section edge of the inner mold cavity (110) and the axis of the outer mold cylinder (100) is α; The angle between the axial section edge of the inner mandrel (200) and the axis of the inner mandrel (200) is β, where α > β.

3. A radial reducing extrusion cold rolling process for stator production according to claim 1, characterized in that, The inner mold cavity (110) includes a first mold cavity (111) and a second mold cavity (112) that are interconnected along the axial direction, and the second mold cavity (112) is located on the outlet side of the first mold cavity (111); The angle between the axial section edge of the first mold cavity (111) and the axis of the outer mold cylinder (100) is α1; The angle between the axial section edge of the second mold cavity (112) and the axis of the outer mold cylinder (100) is α2, where α2 > α1.

4. A radial reducing extrusion cold rolling process for stator production according to claim 3, characterized in that, 0.6°≤α1＜0.7°。 5. A radial reducing extrusion cold rolling process for stator production as claimed in claim 3, wherein, 0.7°≤α2≤0.8°。 6. A radial reducing extrusion cold rolling process for stator production according to claim 3, characterized in that, In S100, the inner mandrel (200) includes an inclined shaft segment (220), and the inclined shaft segment (220) includes an adjacent first shaft segment (221) and a second shaft segment (222) along the axial direction; The angle between the axial section edge of the first shaft segment (221) and the axis of the inner mandrel (200) is β1; The angle between the axial section edge of the second shaft segment (222) and the axis of the inner core shaft (200) is β2, where β2 < β1.

7. The radial reduction extrusion cold rolling process for stator production according to claim 6, characterized in that, 0.2°≤β1＜0.3°，0.02°≤β2≤0.03°。 8. The radial reduction extrusion cold rolling process for stator production according to claim 6, characterized in that, The inner mandrel (200) also includes a constant diameter shaft section (230) connected to the second shaft section (222), the constant diameter shaft section (230) being located at the end of the second shaft section (222) away from the first shaft section (221).

9. A radial reduction extrusion cold rolling process for stator production according to claim 8, characterized in that, The S300 process also includes the following steps: While the inner mandrel (200) rotates, the outer mold cylinder (100) is driven to reciprocate along the axial direction to extrude the outside of the stator tube blank (300).

10. A radial reduction extrusion cold rolling process for stator production according to claim 9, characterized in that, In S300, the reciprocating stroke of the outer mold cylinder (100) along the axial direction is less than the total length of the second shaft segment (222) and the equal diameter shaft segment (230).

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