Manufacturing method of blind cavity type hollow rotating shaft

Abstract

The invention relates to the technical field of rotating shaft machining, in particular to a manufacturing method of a blind cavity type hollow rotating shaft, and mainly solves the technical problem of lack of an effective manufacturing method of the blind cavity type hollow rotating shaft in the prior art. According to the manufacturing method of the blind cavity type hollow rotating shaft, a pipe is adopted as a blank, hole shrinkage of the two ends of the pipe is achieved through rotary forging, and meanwhile a stopper rod is adopted to be matched with rotary forging to achieve plugging of the single end of the pipe. On the first hand, compared with a solid blank, the method has the advantages that the material utilization rate is high, the machining allowance is small, the number of procedures is small, the machining efficiency and cost are excellent, and automatic operation is easy to achieve; and secondly, integral forming of the rotating shaft in the axial direction can be achieved through the method, the structural performance such as torsional fatigue strength is excellent, and the requirements for high rotating speed, heavy loads and long-term vibration loads of scenes such as a motor train unit can be met.

Description

Technical Field

[0001] This invention relates to the field of shaft machining technology, and in particular to a method for manufacturing a blind cavity hollow shaft. Background Technology

[0002] In applications such as high-speed trains and high-end motors, where stringent requirements for speed, energy efficiency, and lightweight design are imposed, the shaft, as a core transmission component, directly impacts the equipment's operational performance and energy utilization. Conventional hollow shafts are mostly through-hole structures, which, while achieving some weight reduction, struggle to meet the demands for higher precision, lightweight design, and functional integration. Therefore, the blind-cavity hollow shaft has emerged. Defined as a hollow shaft with a closed end containing a central cavity, it maximizes weight reduction while maintaining structural rigidity through optimized non-through-cavity design. This, in turn, reduces equipment operating energy consumption and carbon emissions, ultimately adapting to the speed-up and upgrade requirements of scenarios such as high-speed trains.

[0003] To avoid the problem of excessively large outer diameter of the shaft ends leading to higher bearing specifications and significantly increased costs, the structure of a blind cavity hollow shaft is usually designed as follows: the outer diameters at both ends are smaller (to accommodate standard bearing specifications), while the outer diameter in the middle is larger (to ensure transmission rigidity and strength), forming a stepped structure that is "thin at both ends and thick in the middle".

[0004] However, the manufacturing of existing blind cavity hollow shafts faces key technical bottlenecks: On the one hand, the processing of conventional hollow shafts mostly relies on deep hole drilling, but the end inner diameter of the blind cavity hollow shaft is much smaller than the inner diameter of the central cavity. Deep hole drilling is limited by its core working principle of "cannot expand the hole in reverse" (that is, it can only process from the large hole to the small hole diameter in one direction, and cannot process the larger inner diameter central cavity across the small hole diameter area), which makes it impossible to directly apply the deep hole drilling process to the processing of this type of structure; on the other hand, there are existing manufacturing solutions that use split welding (such as the lightweight motor shaft disclosed in the patent with announcement number CN213846440U), which splits the shaft along the axis into a middle section and a reversing section, and then welds them together to form a whole, in order to avoid the problem of deep hole processing. However, this split-welded structure has inherent defects: stress concentration, coarse grains, porosity, and incomplete penetration are prone to occur at the weld seam, which leads to a significant decrease in the overall fatigue resistance of the shaft. It is difficult to withstand the high speed, heavy load and long-term vibration load in scenarios such as EMU trains, which poses a safety hazard and cannot meet the stringent reliability requirements of high-end equipment.

[0005] In summary, existing processing techniques are either limited by the bottleneck of reverse reaming technology in deep hole drilling, making it impossible to achieve one-piece forming of blind cavity hollow shafts; or the use of a split welding solution results in insufficient performance, making it difficult to adapt to high-speed, high-reliability applications. Therefore, there is an urgent need to develop an effective manufacturing method for blind cavity hollow shafts to overcome the shortcomings of existing technologies. Summary of the Invention

[0006] To overcome the technical deficiency of the lack of an effective manufacturing method for blind cavity hollow shafts in the prior art, the present invention provides a manufacturing method for blind cavity hollow shafts.

[0007] The manufacturing method of the blind cavity hollow rotating shaft provided by the present invention includes:

[0008] S1. Pipes are used as blanks for cutting;

[0009] S2. Induction heating of the first end of the pipe to the austenitizing temperature;

[0010] S3. The first end of the pipe is subjected to rotary forging to reduce its diameter and form a first small-diameter section;

[0011] S4. Prepare a stopper rod, wherein the diameter of the stopper rod is smaller than the inner diameter of the first small diameter segment;

[0012] S5. Insert the stopper rod into the first small diameter section, and make the outer end face of the stopper rod flush with the end face of the first small diameter section;

[0013] S6. Perform rotary forging on the area of ​​the stopper rod corresponding to the first small diameter section to form a metallurgical bond between the first small diameter section and the stopper rod;

[0014] S7. Induction heat the second end of the pipe to the austenitizing temperature;

[0015] S8. The second end of the tube is subjected to rotary forging to reduce its diameter and form a second small diameter section, wherein the inner diameter of the second small diameter section is smaller than the inner diameter of the machining hole;

[0016] S9. Machining the first end and / or the second end of the pipe.

[0017] Furthermore, the pipe is a carbon steel pipe, an alloy steel pipe, or a titanium alloy pipe.

[0018] Furthermore, the outer circular surface of the stopper rod is provided with a plurality of annular bosses, which are distributed at intervals along the axial direction of the stopper rod, and the outer circular surface diameter of the annular bosses is smaller than the inner diameter of the first small diameter segment.

[0019] Furthermore, the axial cross-section of the annular boss of the stopper rod is rectangular or trapezoidal.

[0020] Furthermore, in step S10, the first end and the second end of the pipe are machined to make right-angle transitions between them and the middle section of the pipe.

[0021] Furthermore, a heat treatment step is provided between steps S8 and S9, wherein the heat treatment step is tempering or annealing.

[0022] Furthermore, after step S9, there is an inspection step, which is used to perform non-destructive testing on the machined shaft: if there are no defects, it is finely ground to the finished size; if there are defects, it is repaired or scrapped according to the defects.

[0023] The technical solution provided by this invention has the following advantages compared with the prior art:

[0024] The present invention provides a method for manufacturing a hollow shaft with a blind cavity. A tube is used as the blank, and the diameter at both ends of the tube is reduced through rotary forging. Simultaneously, a stopper rod is used in conjunction with rotary forging to seal one end of the tube. Firstly, compared to using a solid blank, this method has higher material utilization, smaller machining allowance, fewer steps, and better processing efficiency and cost, and is easily automated. Secondly, this method enables the shaft to be integrally formed in the axial direction, resulting in superior structural properties such as torsional fatigue strength, and can meet the high-speed, heavy-load, and long-term vibration load requirements of scenarios such as high-speed trains. Attached Figure Description

[0025] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the structure of the blind cavity hollow rotating shaft in an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of the pipe structure in an embodiment of the present invention;

[0029] Figure 3 This is a schematic diagram of the structure of the first type of stopper rod in an embodiment of the present invention;

[0030] Figure 4 This is a schematic diagram showing the structure of the second type of stopper rod in an embodiment of the present invention;

[0031] Figure 5 This is a schematic diagram showing the structure of the third type of stopper rod in an embodiment of the present invention;

[0032] Figure 6 This is a schematic diagram showing the structure of the fourth type of stopper rod in an embodiment of the present invention;

[0033] Figure 7This is a schematic diagram showing the structure of the fifth type of stopper rod in an embodiment of the present invention.

[0034] In the picture:

[0035] 100, Left section; 200, Middle section; 300, Right section; 400, First process hole; 500, Oil injection hole; 600, Second process hole. Detailed Implementation

[0036] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0037] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0038] Figure 1 The diagram shows a structural schematic of a hollow shaft with a blind cavity manufactured using this method. The shaft is divided into three sections in the axial direction: left, middle, and right. The left section 100 is a solid structure with a smaller diameter, used as the transmission end to ensure the strength and rigidity required to transmit large torque. This section is designed with a first process hole 400 and an oil injection hole 500, etc. The middle section 200 is a hollow structure with a larger diameter, used as the main body to reduce the weight of the shaft. The wall thickness of a certain amount ensures the strength and rigidity to achieve interference fit of the iron core. The right section 300 is a reduced-diameter structure with a smaller diameter, used as the non-transmission end. This section is designed with a second process hole 600.

[0039] The following is combined Figures 1 to 7 Specific embodiments of the present invention will be described in detail below.

[0040] This embodiment provides a method for manufacturing a blind cavity hollow rotating shaft, including steps S1-S9.

[0041] S1. Pipes are used as blanks for cutting.

[0042] It is easy to understand that using pipes as raw materials, compared to solid blanks, results in a higher material utilization rate, smaller machining allowance, and fewer machining steps, which helps to improve processing efficiency and reduce processing costs.

[0043] Specifically, the material of the tubing is not limited, but high-strength materials such as carbon steel, alloy steel, and titanium alloys are preferred to ensure the structural performance of the shaft. These high-strength materials are difficult to machine using conventional methods, but this method significantly reduces the machining difficulty. For example... Figure 2As shown, the pipe used in this embodiment is a 42CrMo alloy steel pipe with an outer diameter of 106mm and a wall thickness of 25mm.

[0044] S2. Induction heat the first end of the pipe to the austenitizing temperature.

[0045] It should be noted that the austenitizing temperature is a range of values, so heating to the austenitizing temperature means heating to a value greater than or equal to the minimum value of that range.

[0046] For the 42CrMo alloy steel pipe in this embodiment, its austenitizing temperature range is 830℃-860℃, so its first end should be heated to a temperature greater than 830℃; in this embodiment, it is specifically designed to be 850℃. Of course, for pipes made of other materials, those skilled in the art can easily determine the appropriate heating temperature based on their austenitizing temperature.

[0047] S3. The first end of the pipe is subjected to rotary forging to reduce its diameter and form the first small diameter section.

[0048] It is easy to understand that rotary forging is a mature operation in this field. The process parameters selected in this embodiment are: radial feed of 7.5 mm and axial deformation of 200 mm.

[0049] S4. Prepare a stopper rod, wherein the diameter of the stopper rod is smaller than the inner diameter of the first minor diameter segment.

[0050] It should be noted that, since the stopper rod needs to form a metallurgical bond with the pipe, the stopper rod must be made of the same material as the pipe.

[0051] It is easy to understand that the diameter of the stopper rod is smaller than the inner diameter of the first minor diameter section, the purpose of which is to facilitate the insertion of the stopper rod. However, the diameter of the stopper rod and the diameter of the first minor diameter section cannot differ too much, with the standard being to maintain the positional stability of the stopper rod within the first minor diameter section. For example, in this embodiment, the diameter of the first minor diameter section is (106-25×2-7.5×2)=41mm, while the diameter of the stopper rod is selected as 40mm.

[0052] To improve the bonding strength between the stopper rod and the pipe, this embodiment also provides multiple annular bosses on the outer circumference of the stopper rod. These annular bosses are spaced apart along the axial direction of the stopper rod, and the outer diameter of the annular bosses is smaller than the inner diameter of the first minor diameter segment. During rotary forging, the inner wall of the pipe deforms along with the annular bosses, ultimately achieving a metallurgical bond between the stopper rod and the pipe.

[0053] Specifically, the axial cross-sectional shape of the annular boss of the stopper rod is not limited. For example, Figure 3 The cross-section of the annular boss shown is rectangular, the width of the rectangle is 10mm, the spacing between the annular bosses is 10mm, the height of the rectangle is 1mm, the total length of the stopper is 130mm, and the outer diameter of the annular boss is 40mm. Figure 4The cross-section of the annular boss shown is rectangular, the width of the rectangle is 10mm, the spacing between the annular bosses is 10mm, the height of the rectangle is 3mm, the total length of the stopper is 130mm, and the outer diameter of the annular boss is 40mm. Figure 5 The cross-section of the annular boss shown is rectangular, the width of the rectangle is 10mm, the spacing between the annular bosses is 10mm, the height of the rectangle is 5mm, the total length of the stopper is 130mm, and the outer diameter of the annular boss is 40mm. Figure 6 The cross-section of the annular boss shown is a right trapezoid. The upper base of the right trapezoid is 7.5 mm long, the spacing between the annular bosses is 7.5 mm, the height of the right trapezoid is 3 mm, the total length of the stopper is 140 mm, and the outer diameter of the annular boss is 40 mm. Figure 7 The cross-section of the annular boss shown is an isosceles trapezoid. The upper base of the isosceles trapezoid is 7.5 mm long, the spacing between the annular bosses is 7.5 mm, the height of the isosceles trapezoid is 3 mm, the total length of the stopper is 140 mm, and the outer diameter of the annular boss is 40 mm.

[0054] S5. Insert the stopper rod into the first small diameter section and make the outer end face of the stopper rod flush with the end face of the first small diameter section.

[0055] S6. Perform rotary forging on the area of ​​the stopper rod corresponding to the first small diameter section to form a metallurgical bond between the first small diameter section and the stopper rod.

[0056] It is important to note that, such as Figure 1 As shown, since the area corresponding to the stopper rod in the first small diameter section was forged twice by rotation, while the other areas of the first small diameter section were forged only once by rotation, the outer diameter of the area corresponding to the stopper rod in the first small diameter section is slightly smaller than that of the other areas.

[0057] S7. Induction heat the second end of the pipe to the austenitizing temperature.

[0058] Specifically, the second end is selected at the same temperature as the first end, namely 850℃.

[0059] S8. The second end of the pipe is subjected to rotary forging to reduce its diameter and form a second small diameter section, wherein the inner diameter of the second small diameter section is smaller than the inner diameter of the machined hole.

[0060] like Figure 1 As shown, since the diameter of the right section of the hollow shaft is smaller than that of the left section, this embodiment also divides this step into two rotary forging processes: the first reduction is 15mm, and the outer diameter of the second end is reduced to 91mm; the second reduction is 7mm, and the outer diameter of the second end is reduced to 84mm. Of course, those skilled in the art can determine the number of rotary forging processes and the radial feed amount based on the finished dimensions of the hollow shaft.

[0061] S9. Machining the first and / or second ends of the pipe.

[0062] Specifically, the processing details for this step are determined based on the actual structural requirements of the blind cavity hollow shaft, for example... Figure 1 The left section 100 of the blind cavity hollow shaft shown is provided with a first process hole 400 and an oil injection hole 500, and the right section 300 is provided with a second process hole 600. Therefore, this step requires machining the first process hole 400 and the oil injection hole 500 at the first end and machining the second process hole 600 at the second end.

[0063] To ensure proper positioning of the bearings at both the first and second ends, this embodiment also employs machining to ensure that both the first and second ends of the pipe transition to the middle section of the pipe at right angles.

[0064] In addition, a heat treatment step is provided between steps S8 and S9, which is either quenching and tempering or annealing. For example, for the 42CrMo alloy steel pipe in this embodiment, the heat treatment step involves quenching and tempering, specifically quenching and tempering at 560°C.

[0065] In addition, after step S9, there is an inspection step, which is used to perform non-destructive testing on the machined shaft: if there are no defects, it is finely ground to the finished size; if there are defects, it is repaired or scrapped according to the defects.

[0066] To verify the effectiveness of the method provided in this embodiment, 200MPa hydraulic oil was injected into the cavity in the middle section of the pipe. The experiment showed that there was no leakage when the pressure was held for 30 minutes, proving that the stopper rod and the pipe are tightly connected and can meet the single-end sealing requirements of the blind cavity hollow shaft.

[0067] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the present invention. Although detailed descriptions have been provided with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments, and they should all be covered within the protection scope of the claims.

Claims

1. A method for manufacturing a blind cavity hollow rotating shaft, characterized in that, Includes the following steps: S1. Pipes are used as blanks for cutting; S2. Induction heating of the first end of the pipe to the austenitizing temperature; S3. The first end of the pipe is subjected to rotary forging to reduce its diameter and form a first small-diameter section; S4. Prepare a stopper rod, wherein the diameter of the stopper rod is smaller than the inner diameter of the first small diameter segment; S5. Insert the stopper rod into the first small diameter section, and make the outer end face of the stopper rod flush with the end face of the first small diameter section; S6. Perform rotary forging on the area of ​​the stopper rod corresponding to the first small diameter section to form a metallurgical bond between the first small diameter section and the stopper rod; S7. Induction heat the second end of the pipe to the austenitizing temperature; S8. The second end of the tube is subjected to rotary forging to reduce its diameter and form a second small diameter section, wherein the inner diameter of the second small diameter section is smaller than the inner diameter of the machining hole; S9. Machining the first end and / or the second end of the pipe.

2. The manufacturing method of the blind cavity hollow rotating shaft according to claim 1, characterized in that, The pipe is made of carbon steel, alloy steel, or titanium alloy.

3. The manufacturing method of the blind cavity hollow rotating shaft according to claim 1, characterized in that, The stopper rod has multiple annular protrusions on its outer circular surface. The multiple annular protrusions are distributed at intervals along the axial direction of the stopper rod, and the outer circular diameter of the annular protrusions is smaller than the inner diameter of the first small diameter segment.

4. The manufacturing method of the blind cavity hollow rotating shaft according to claim 3, characterized in that, The axial cross-section of the annular boss of the stopper rod is rectangular or trapezoidal.

5. The manufacturing method of the blind cavity hollow rotating shaft according to claim 1, characterized in that, In step S10, the first and second ends of the pipe are machined to make right-angle transitions between them and the middle section of the pipe.

6. The method for manufacturing a hollow shaft with a blind cavity according to any one of claims 1 to 5, characterized in that, Between steps S8 and S9, there is a heat treatment step, which is a tempering or annealing process.

7. The method for manufacturing a blind cavity hollow rotating shaft according to claim 6, characterized in that, After step S9, there is an inspection step, which is used to perform non-destructive testing on the machined shaft: if there are no defects, it is finely ground to the finished size; if there are defects, it is repaired or scrapped according to the defects.

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