Motor shaft cooling inner structure and manufacturing method thereof

Abstract

The application discloses a motor shaft cooling inner structure and a manufacturing method thereof. The cooling inner structure comprises an inlaid inner flow channel structure inside the motor shaft, the surface of the inlaid inner flow channel structure is provided with a spiral flow channel, the middle part of the spiral tooth shape is designed with a sealing ring, the two end parts of the inlaid inner flow channel structure are designed with connecting threads connected with a cooling liquid inlet / outlet device, and the cooling liquid inlet / outlet device is internally provided with a cooling liquid flow channel. The manufacturing method comprises the following steps: firstly, filling a pressure-resistant deformable core into a pre-processed inner flow channel of a motor shaft blank, and reducing the outer diameter of the motor shaft blank by using a rotary forging technology; and then, embedding the inlaid inner flow channel structure connected with the cooling liquid inlet / outlet device into the inner wall of the motor shaft by uniformly reducing the outer wall of the motor shaft blank through rotary forging, and adopting a small-diameter reduction multi-pass process to form a wall-adhering circulating heat dissipation of the inner wall of the motor shaft. The application can realize near-closed, semi-closed and fully-closed motor shaft cooling inner structure processing, shorten a process flow and improve processing efficiency.

Description

Technical Field

[0001] This invention relates to the field of machining technology, specifically to an internal cooling structure for an electric motor shaft and its manufacturing method. Background Technology

[0002] The motor rotor shaft is a core component of the drive motor in new energy vehicles, bearing and transmitting torsional alternating stress at high speeds. With a maximum torque exceeding 700 N·m, friction and iron losses during high-speed operation increase heat generation. This high heat affects the rotor's magnetic flux and structural safety, and the expansion of components can impact the internal assembly clearances of the highly integrated motor, thus affecting operating efficiency and causing demagnetization of permanent magnets. A lightweight, hollow motor rotor shaft plays a significant role in energy conservation, emission reduction, and improved range in new energy vehicles. Designing a cooling structure within the lightweight hollow motor rotor shaft allows for sufficient coolant flow, significantly improving overall motor heat dissipation and operating efficiency. However, the near-closed, semi-closed, and fully closed internal cavities created by the hollow design also increase the machining difficulty of the motor shaft. Therefore, achieving a lightweight, high-performance hollow motor shaft cooling structure with integrated thermal management and its manufacturing method is particularly important.

[0003] After undergoing a hollow and lightweight design, the blind-hole motor shaft has a closed blind hole on one side and a stepped inner cavity on the other. Current manufacturing processes (Chinese Patent CN202110365221.9, entitled "A Forming and Processing Method for a Blind-Hole Hollow Motor Shaft") divide the shaft into two sections, process the internal structures separately, and then weld them together using techniques such as friction welding. The drawback of this process is that the heat generated during welding can easily deform the shaft, and the resulting weld seam generally has lower strength than the base material, compromising the safety of the motor shaft. Hollow motor shafts with near-closed inner cavities and internal flow channels (Chinese Patent CN202110428694.9, entitled "A Hollow Rotor Shaft"; Chinese Patent CN202110652319.2, entitled "A Rotor Shaft with Oil Pipes and Its Processing Technology") are directly assembled using a segmented structure or achieve internal limiting assembly through external diameter reduction. This process is lengthy, has stringent requirements, and cannot design complex internal flow channels that provide better cooling; cooling is achieved solely through internal oil spray holes. Fully enclosed hollow motor shafts, similar to blind hole motor shafts, can currently be machined using a segmented machining-welding process. However, the internal flow channels of the shaft wall cannot be machined using current techniques.

[0004] Currently, motor rotor shafts with cooling structures are mainly cooled by spraying oil through internal nozzles. This results in high fluid energy consumption, uneven cooling, complex cooling system design, and difficult machining. Furthermore, the cooling fluid can easily affect shaft balance during high-speed rotation. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide an internal cooling structure for motor shaft and its manufacturing method, which can not only realize the processing of near-closed, semi-closed, and fully enclosed internal cooling structures for motor shaft and ensure the forming of the inner hole, but also shorten the process flow and improve the processing efficiency.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] An internal cooling structure for a motor shaft includes an embedded internal flow channel structure 1 inside the motor shaft. The embedded internal flow channel structure 1 is tubular in shape. The surface of the embedded internal flow channel structure 1 is designed with a spiral flow channel 2. A first sealing ring 4 is designed in the middle of the spiral tooth 3 constituting the spiral flow channel 2. The two ends of the embedded internal flow channel structure 1 are designed with connecting threads 5. The connecting threads 5 are used to connect a coolant inlet device 6 and a coolant outlet device 7. Coolant inlet device 6 and coolant outlet device 7 are provided with coolant flow channels 8 inside.

[0008] The motor shaft includes a motor shaft blank 10, and a pre-machined inner flow channel 9 is provided in the center of the shaft wall of the motor shaft blank 10.

[0009] The aforementioned helical tooth 3 needs to have its hardness adjusted through surface treatment, with an average hardness slightly higher than that of the motor shaft blank 10.

[0010] The pre-processed inner flow channel 9 is machined by deep hole drilling, and the number of channels is no less than 6 and no more than 15, evenly distributed along the circumference, so as not to reduce safety.

[0011] The total length and pitch P0 of the embedded internal flow channel structure 1 are designed based on the length of the inner hole structure of the motor shaft, and the outer diameter D out0 Same as the inner diameter of the motor shaft, wall thickness T0 not exceeding 15mm; spiral flow channel 2 with at least 10 spiral turns; spiral tooth profile 3 with tooth height H0 not exceeding 5mm and tooth width W0 not less than 3mm; pre-machined inner flow channel 9 with diameter D in No more than 1 / 3 of the wall thickness.

[0012] A method for manufacturing an internal cooling structure for a motor shaft includes the following steps:

[0013] 1) Fill the pre-machined inner flow channel 9 of the motor shaft blank 10 with a pressure-resistant deformable core 11, twist the motor shaft blank 10, so that the pre-machined inner flow channel 9 expands with the shaft to increase the heat exchange area, and use rotary forging technology to reduce the outer diameter of the motor shaft blank 10 so that the inner hole reaches the design size, and the pre-machined inner flow channel 9 deforms with the blank wall.

[0014] 2) The coolant inlet device 6 and the coolant outlet device 7 are connected to the embedded inner flow channel structure 1 through the connecting thread 5, and a second sealing ring 13 is provided at the connection gap; the outer wall of the motor shaft blank 10 is uniformly reduced in diameter by rotary forging, and the embedded inner flow channel structure 1, which connects the coolant inlet device 6 and the coolant outlet device 7, is embedded into the inner wall 12 of the motor shaft, so that the embedded inner flow channel structure 1 is tightly connected to the inner wall 12 of the motor shaft. A small diameter reduction multi-pass process is adopted to make the first sealing ring 4 seal the spiral flow channel 2. There is a gap between the spiral flow channel 2 and the inner wall 12 of the motor shaft. When the motor is working, the motor shaft is assembled with the external motor through the assembly connection mechanism 17 at the end of the coolant inlet device 6. The coolant is introduced through the coolant inlet device 6 through the coolant flow channel 8 and flows out through the coolant outlet device 7, forming a wall-mounted circulating heat dissipation of the inner wall of the motor shaft, and at the same time, heat dissipation is provided to the iron core 18 on the motor shaft with interference fit.

[0015] 3) After the internal cooling structure of the motor shaft is formed, it is withdrawn from the machining section of the rotary forging machine along the axial direction.

[0016] After being rotated and forged into an inlay connection, the spiral flow channel 2 forms a flow channel cavity 14 with the inner wall 12 of the motor shaft. The coolant circulates inside the flow channel cavity 14. The cross-sectional area of ​​the flow channel cavity 14 is determined by the wedging depth of the spiral tooth profile 3, satisfying the following formula:

[0017]

[0018] Among them, S 流腔 Δd is the cross-sectional area of ​​the flow channel cavity 12; Δd is the depth of the spiral tooth 3 rotary forging insert wedging; when the coolant is introduced into the flow channel cavity 14, the flow rate is adjusted according to the wedging depth and cross-sectional area parameters.

[0019] The compressive and deformable core 11 is made of alumina ceramic and is extracted from the motor shaft blank 10 by an alkali boiling method.

[0020] Step 1) After the diameter reduction is completed, hydraulic oil is introduced into the pre-processed inner flow channel 9 to pump out the residual compressive deformable core 11.

[0021] The present invention has the following advantages:

[0022] 1. Since the present invention adopts internal structure rotation forging and inlay, the inlay structure design has a high degree of freedom and can adapt to the processing of various internal holes and internal structures such as semi-closed, near-closed, and fully closed. Therefore, it has the advantages of simplifying and shortening the process flow and facilitating the development of various internal structures.

[0023] 2. Since the internal structure of the present invention can be designed as a complex embedded flow channel that fits the shape of the inner wall of the motor shaft, or as a pre-machined flow channel inside the shaft wall, the coolant can be cooled against the inner wall or enter the interior of the motor shaft wall for cooling. Therefore, it has the advantages of enhancing heat exchange, improving the cooling efficiency of the motor shaft, achieving uniform cooling, and not affecting the dynamic balance of the motor shaft.

[0024] 3. Since the present invention adopts the rotary forging internal structure inlay method, a firm and permanent connection is achieved through plastic deformation. There is no need to design an additional cooling system support device inside the motor shaft, and the space in the middle cavity of the motor shaft can be reserved to arrange sensors, etc. Therefore, it has the advantages of simplifying the structure and improving the integration level of the motor shaft.

[0025] 4. Since the motor shaft blanks in this invention can all be ordinary tubular blanks, the complexity of blanking can be reduced. There is no need to cut combined blanks such as bar stock and tubular stock, so it has the advantages of simplifying process design and improving the level of lightweighting. Attached Figure Description

[0026] Figure 1 This is an isometric view of the embedded internal flow channel structure of the present invention.

[0027] Figure 2 This is a cross-sectional view of the embedded internal flow channel structure of the present invention.

[0028] Figure 3 This is a cross-sectional view of the embedded internal flow channel structure of the present invention connecting the coolant inlet device and the outlet device.

[0029] Figure 4 This is an isometric view of the motor shaft blank with pre-machined inner flow channels on the shaft wall according to the present invention.

[0030] Figure 5 This is a cross-sectional view of the motor shaft blank with pre-machined inner flow channels on the shaft wall according to the present invention.

[0031] Figure 6 This is an isometric view of the motor shaft blank with pre-machined inner flow channels on the shaft wall after being twisted according to the present invention.

[0032] Figure 7 This is a schematic diagram of the forming of a motor shaft with an embedded internal flow channel structure using rotary forging technology according to the present invention.

[0033] Figure 8 This is a schematic diagram of the motor shaft assembly with an embedded internal flow channel structure after being processed using rotary forging technology according to the present invention.

[0034] Figure 9 This is a schematic diagram illustrating the reduction of the outer diameter of a motor shaft blank with a pre-machined inner flow channel on the shaft wall using rotary forging technology, as per the present invention.

[0035] Figure 10 This is a schematic diagram of the assembly of a motor shaft with a pre-machined inner flow channel on the shaft wall after being processed by rotary forging technology according to the present invention. Detailed Implementation

[0036] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments, but the scope of protection is not limited to the description.

[0037] Reference Figure 1 , Figure 2 , Figure 3 An internal cooling structure for a motor shaft includes an embedded internal flow channel structure 1 inside the motor shaft. The embedded internal flow channel structure 1 is tubular in shape. The surface of the embedded internal flow channel structure 1 is designed with a spiral flow channel 2. A first sealing ring 4 is designed in the middle of the spiral tooth shape 3 constituting the spiral flow channel 2. The two ends of the embedded internal flow channel structure 1 are designed with connecting threads 5. The connecting threads 5 are used to connect a coolant inlet device 6 and a coolant outlet device 7. Coolant inlet device 6 and coolant outlet device 7 are provided with coolant flow channels 8 inside.

[0038] Reference Figure 2 The total length and pitch P0 of the embedded inner flow channel structure 1 are designed based on the length of the inner hole structure of the motor shaft, and the outer diameter D out0 The inner diameter of the motor shaft is the same, and the wall thickness T0 does not exceed 15mm; the spiral flow channel 2 has no less than 10 spirals; the tooth height H0 of the spiral tooth 3 is no higher than 5mm, and the tooth width W0 is no less than 3mm to provide sufficient strength; the size design of the more refined embedded inner flow channel structure 1 needs to be based on the results of finite element simulation and experimental experience.

[0039] The aforementioned helical tooth 3 needs to have its hardness adjusted through surface treatment, with an average hardness slightly higher than that of the motor shaft blank 10, in order to produce the best embedding effect.

[0040] Reference Figure 4 , Figure 5 and Figure 6 The motor shaft includes a motor shaft blank 10, and a pre-machined inner flow channel 9 is provided in the center of the shaft wall of the motor shaft blank 10; the diameter D of the pre-machined inner flow channel 9 is... in The thickness should not exceed 1 / 3 of the wall thickness to ensure sufficient strength; the pre-processed inner flow channel 9 is machined by deep hole drilling, and the number of channels is not less than 6 and not more than 15, evenly distributed along the circumference, so as not to reduce safety.

[0041] Reference Figure 7 , Figure 8 , Figure 9 and Figure 10 A method for manufacturing an internal cooling structure for a motor shaft includes the following steps:

[0042] 1) Fill the pre-machined inner flow channel 9 of the motor shaft blank 10 with a pressure-resistant deformable core 11. Twist the motor shaft blank 10 to make the pre-machined inner flow channel 9 expand with the shaft to increase the heat exchange area. Use rotary forging technology to reduce the outer diameter of the motor shaft blank 10 so that the inner hole reaches the design size. The pre-machined inner flow channel 9 deforms with the blank wall. After the diameter reduction is completed, hydraulic oil is introduced into the pre-machined inner flow channel 9 to pump out the residual pressure-resistant deformable core 11. The pressure-resistant deformable core 11 can be made of alumina ceramic or can be removed from the motor shaft blank 10 by alkaline boiling reaction.

[0043] 2) The coolant inlet device 6 and the coolant outlet device 7 are connected to the embedded inner flow channel structure 1 through the connecting thread 5. A second sealing ring 13 is provided at the connection gap to form a good seal after connection, preventing coolant from entering the internal cavity of the embedded inner flow channel structure 1.

[0044] The outer wall of the motor shaft blank 10 is uniformly reduced in diameter by rotary forging, and the embedded inner flow channel structure 1 is embedded into the inner wall 12 of the motor shaft, so that the embedded inner flow channel structure 1 is tightly connected to the inner wall 12 of the motor shaft. A small diameter reduction multi-pass process is adopted to ensure that the first sealing ring 4 achieves a good seal on the spiral flow channel 2. There is a gap between the spiral flow channel 2 and the inner wall 12 of the motor shaft. When the motor is working, the motor shaft is assembled with the external motor through the assembly connection mechanism 17 at the end of the coolant inlet device 6. The external cooling system inlet 15 and the external cooling system outlet 16 are respectively assembled with the coolant inlet device 6 and the coolant inlet / outlet device 7. The coolant is introduced through the coolant flow channel 8 into the coolant inlet device 6 and flows out through the coolant outlet device 7, forming a wall-mounted circulating heat dissipation of the inner wall of the motor shaft, while simultaneously dissipating heat for the iron core 18 on the motor shaft which is subjected to interference fit.

[0045] 3) After the internal structure of the motor shaft is formed, it is withdrawn from the machining section of the rotary forging machine along the axial direction.

[0046] After being rotated and forged into an inlay connection, the spiral flow channel 2 forms a flow channel cavity 13 with the inner wall 12 of the motor shaft. The coolant circulates inside the flow channel cavity 13. The cross-sectional area of ​​the flow channel cavity 13 is determined by the wedging depth of the spiral tooth 3, satisfying the following formula:

[0047]

[0048] Among them, S 流腔 Δd is the cross-sectional area of ​​the flow channel cavity 13; Δd is the depth of the spiral tooth 3 rotary forging insert wedging; when the coolant is introduced into the flow channel cavity 13, the flow rate is adjusted according to the wedging depth and cross-sectional area parameters.

Claims

1. A method for manufacturing an internal cooling structure for a motor shaft, characterized in that: An internal cooling structure for a motor shaft includes an embedded internal flow channel structure (1) inside the motor shaft. The embedded internal flow channel structure (1) is tubular in shape. The surface of the embedded internal flow channel structure (1) is designed with a spiral flow channel (2). A first sealing ring (4) is designed in the middle of the spiral tooth shape (3) constituting the spiral flow channel (2). The two ends of the embedded internal flow channel structure (1) are designed with connecting threads (5). The connecting threads (5) are used to connect the coolant inlet device (6) and the coolant outlet device (7). The coolant inlet device (6) and the coolant outlet device (7) are provided with coolant flow channels (8) inside. The motor shaft includes a motor shaft blank (10), and a pre-machined inner flow channel (9) is provided in the center of the shaft wall of the motor shaft blank (10); The manufacturing method includes the following steps: 1) Fill the pre-processed inner flow channel (9) of the motor shaft blank (10) with a pressure-resistant deformable core (11), twist the motor shaft blank (10) so that the pre-processed inner flow channel (9) expands with the shaft to increase the heat exchange area, and use rotary forging technology to reduce the outer diameter of the motor shaft blank (10) so that the inner hole reaches the design size. The pre-processed inner flow channel (9) deforms with the blank wall. 2) The coolant inlet device (6) and coolant outlet device (7) are connected to the embedded inner channel structure (1) via connecting threads (5), and a second sealing ring (13) is provided at the connection gap; the outer wall of the motor shaft blank (10) is uniformly reduced in diameter by rotary forging, and the embedded inner channel structure (1) connecting the coolant inlet device (6) and coolant outlet device (7) is embedded into the inner wall (12) of the motor shaft, so that the embedded inner channel structure (1) is tightly connected to the inner wall (12) of the motor shaft, and a small diameter reduction multi-channel is adopted. The next process is to make the first sealing ring (4) seal the spiral flow channel (2). There is a gap between the spiral flow channel (2) and the inner wall (12) of the motor shaft. When the motor is working, the motor shaft is assembled with the external motor through the assembly connection mechanism (17) at the end of the coolant inlet device (6). The coolant is introduced through the coolant flow channel (8) into the coolant inlet device (6) and flows out through the coolant outlet device (7), forming a wall-mounted circulation heat dissipation of the inner wall of the motor shaft. At the same time, the iron core (18) on the motor shaft is heat dissipated by interference fit. 3) After the internal cooling structure of the motor shaft is formed, it is withdrawn from the machining section of the rotary forging machine along the axial direction.

2. The manufacturing method according to claim 1, characterized in that: The aforementioned helical tooth (3) requires surface treatment to adjust its hardness, with an average hardness slightly higher than that of the motor shaft blank (10).

3. The manufacturing method according to claim 1, characterized in that: The pre-processed inner flow channel (9) is machined by deep hole drilling, and the number of channels is not less than 6 and not more than 15, evenly distributed along the circumference, so as not to reduce safety.

4. The manufacturing method according to claim 1, characterized in that: The total length and pitch P0 of the embedded internal flow channel structure (1) are designed based on the length of the inner hole structure of the motor shaft, and the outer diameter D out0 Same as the inner diameter of the motor shaft, wall thickness T0 not exceeding 15mm; spiral flow channel (2) with a spiral line of not less than 10 turns; spiral tooth profile (3) tooth height H0 not higher than 5mm, tooth width W0 not less than 3mm; pre-machined inner flow channel (9) diameter D in No more than 1 / 3 of the wall thickness.

5. The manufacturing method according to claim 1, characterized in that: The spiral flow channel (2) forms a flow channel cavity (14) with the inner wall (12) of the motor shaft after being connected by rotary forging. The coolant circulates inside the flow channel cavity (14). The cross-sectional area of ​​the flow channel cavity (14) is determined by the wedge depth of the spiral tooth profile (3), satisfying the following formula: in, The cross-sectional area of ​​the flow channel cavity (14); The pitch is a helical tooth shape. The tooth width is a helical tooth shape. The depth of the spiral tooth (3) is forged by rotational forging; when the coolant is introduced into the flow channel cavity (14), the flow rate is adjusted according to the wedge depth and cross-sectional area parameters.

6. The manufacturing method according to claim 1, characterized in that: The pressure-resistant deformable core (11) is made of alumina ceramic and is extracted from the motor shaft blank by alkaline boiling.

7. The manufacturing method according to claim 1, characterized in that: Step 1) After the diameter reduction is completed, hydraulic oil is introduced into the pre-processed inner flow channel (9) to pump out the residual compressive deformable core (11).

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