DCB stator, stator cooling structure and permanent magnet motor

Abstract

The application discloses a DCB stator, a stator cooling structure and a permanent magnet motor, and belongs to the permanent magnet motor field.The DCB stator comprises a DCB substrate adopting a sandwich eutectic bonding structure of copper-ceramic-copper and a fractional concentrated winding.The fractional concentrated winding is a conductor structure directly formed on the upper and lower surfaces of the DCB substrate through a mask etching process and is used for transferring heat to an outer peripheral heat dissipation area of the DCB stator.The conductor structures on the upper and lower surfaces are electrically connected and fixed through a connecting copper strip distributed through the placement holes in the outer periphery of the DCB substrate.The DCB stator, the stator cooling structure and the permanent magnet motor are used to prepare an integral fractional concentrated winding stator with the DCB substrate adopting the copper-ceramic-copper eutectic bonding as a core, and are matched with a coaxial series type full-peripheral water-cooling structure, so that the power density, the operation efficiency and the structural reliability of the motor are greatly improved, the manufacturing process is simplified, and the mass industrial production is adapted.

Description

Technical Field

[0001] This invention relates to the field of permanent magnet motor technology, and in particular to a DCB stator, a stator cooling structure, and a permanent magnet motor. Background Technology

[0002] Axial magnetic field permanent magnet motors, also known as disc permanent magnet motors, have become the preferred motor type for flat structure applications due to their outstanding advantages such as short axial dimension, high operating efficiency, and high power density. They have broad application prospects in fields such as new energy equipment and industrial servo systems.

[0003] Disc-type permanent magnet motors, constructed with stator windings made of printed circuit boards (PCBs), feature a flattened stator winding structure. This structure is highly compatible with the axial magnetic circuit of the disc motor, significantly compressing the axial space and reducing the overall weight, thus laying the structural foundation for increased power and torque density. Simultaneously, the application of PCB technology simplifies the armature manufacturing process of coreless disc-type permanent magnet motors, eliminating tedious manual or mechanical winding and unwinding processes, effectively improving production efficiency and meeting the demands of mass industrial production.

[0004] However, traditional PCB stator windings commonly use FR4 epoxy resin substrates, which have a thermal conductivity of only about 0.3 W / m·K. This low thermal conductivity leads to a significant accumulation of heat generated by the windings within the substrate, forming a substantial thermal resistance barrier. Even with an efficient external heat dissipation structure, heat cannot quickly penetrate the substrate to be transferred outwards, significantly reducing the effectiveness of the heat dissipation structure. Furthermore, the maximum operating temperature that the FR4 substrate can withstand is approximately 140°C. Once this temperature threshold is exceeded, the substrate is prone to insulation aging, decreased mechanical strength, and even failure and deformation, severely impacting the reliability of motor operation. These inherent defects—low thermal conductivity, low temperature resistance, and low current carrying capacity—result in minimal success in optimizing the motor's heat dissipation structure, becoming a core technological bottleneck restricting further increases in the power density of PCB-type disc permanent magnet motors. Summary of the Invention

[0005] The purpose of this invention is to provide a DCB stator, a stator cooling structure, and a permanent magnet motor to solve the above-mentioned technical problems.

[0006] To achieve the above objectives, the present invention provides a DCB stator, comprising a DCB substrate with a copper-ceramic-copper sandwich eutectic bonding structure and fractional concentrated windings. The fractional concentrated windings are conductor structures directly formed on the upper and lower surfaces of the DCB substrate through masking and etching processes, and are used to transfer heat to the outer peripheral heat dissipation area of ​​the DCB stator. The conductor structures on the top and bottom surfaces are electrically connected and fixed through connecting copper strips that pass through placement holes distributed around the periphery of the DCB substrate.

[0007] Preferably, the fractional concentrated winding is a combined winding, which includes an effective side constituting the main body of electromagnetic energy conversion and an end connecting adjacent effective sides; wherein, the effective side is arranged in the effective magnetic circuit region of the DCB substrate, and its outline is trapezoidal to adapt to the circumferential outline of the effective magnetic circuit region and improve the winding duty cycle; the end is arranged outside the effective magnetic circuit region, and it is arc-shaped to reduce the size of the end winding and optimize the electric field distribution.

[0008] Preferably, the ceramic material of the DCB substrate is selected from any one of alumina, aluminum nitride, silicon nitride, or silicon carbide.

[0009] Preferably, the connecting copper strip is welded and fixed to the conductor structure on the upper and lower surfaces.

[0010] A stator cooling structure includes an inner stator support and an outer stator support coaxially arranged on both sides of a DCB stator, and a water-cooling pipe wrapped around the outer circumference of the DCB stator. The inner stator support facing the DCB stator and the outer stator support facing the DCB stator are respectively coaxially embedded with an inner water channel and an outer water channel. The inner water channel, the water-cooling pipe and the outer water channel are connected in sequence, and the inner water channel and the outer water channel are aligned with the outer peripheral heat dissipation area of ​​the DCB stator to form a circumferentially fully wrapped cooling water channel. The circumferentially fully wrapped cooling water channel is in contact with the DCB stator.

[0011] Preferably, epoxy resin is filled between the inner water channel and the outer peripheral heat dissipation area of ​​the DCB stator, between the outer water channel and the outer peripheral heat dissipation area of ​​the DCB stator, and between the water cooling pipe and the outer circumferential side of the DCB stator to construct a continuous and gapless heat transfer path.

[0012] Preferably, the top of the outer stator support is provided with a water inlet and a water outlet. The water inlet is connected to the outer water channel embedded in the outer stator support. The outer water channel is threadedly sealed to one end of the water cooling pipe. The other end of the water cooling pipe is threadedly sealed to the inner water channel embedded in the inner stator support. The inner water channel is connected to the water outlet through a guide channel.

[0013] Preferably, both the inner and outer water channels include at least one layer of cooling water channels, and adjacent cooling water channels are connected in parallel or in series.

[0014] Preferably, the outer stator support and the inner stator support are threaded together to form a whole stator support, and the whole stator support is made of aluminum alloy. Water-cooled pipes are rigid metal tubular structures, made of copper, aluminum, or copper-aluminum alloys.

[0015] A permanent magnet motor includes a front cover, an inner bearing, an inner permanent magnet, a stator cooling structure, an outer permanent magnet, an outer bearing, and a rear cover, which are coaxially arranged on a central shaft in sequence. The outer and inner water channels of the stator cooling structure are both circular or arc-shaped water channels coaxial with the central axis of the permanent magnet motor.

[0016] Therefore, the present invention, employing the aforementioned DCB stator, stator cooling structure, and permanent magnet motor, has the following beneficial effects: 1. The DCB (Direct Bonded Copper) substrate, with high thermal conductivity ceramic as its core, has a thermal conductivity far exceeding that of the traditional FR4 epoxy resin substrate, eliminating the internal thermal resistance barrier of the substrate from the root. The copper-ceramic eutectic bonding structure enables seamless heat conduction between the winding and the substrate. Combined with the series-type fully enclosed water-cooling structure surrounding the stator, it uniformly removes the heat accumulated at the edge of the substrate in 360°, completely solving the industry pain points of heat accumulation inside the traditional PCB stator and excessive temperature rise at the edge of the ceramic PCB stator, and significantly increasing the upper limit of the motor's thermal load. 2. A combined fractional concentrated winding that integrates the advantages of circular and trapezoidal windings is adopted. This not only increases the winding linkage flux and improves the no-load back EMF amplitude through the effective trapezoidal sides, but also shortens the length of ineffective windings and reduces end copper losses through the arc ends. Combined with the high temperature resistance and high current carrying capacity of the DCB substrate, the winding current density can be significantly increased. With the support of heat dissipation optimization, the motor power density, torque density and operating efficiency are simultaneously and significantly improved. 3. The stator winding is directly integrally formed on the surface of the DCB substrate through copper foil masking and etching processes, eliminating the cumbersome processes of manual / mechanical winding and unwinding in traditional motors. This results in good process consistency and high production efficiency. The eutectic bonding and etching of the DCB substrate are mature industrial processes, which effectively lowers the mass production threshold of disc-type coreless permanent magnet motors. 4. The ceramic layer of the DCB substrate has high insulation, high mechanical strength and high temperature resistance, avoiding the risks of insulation aging, decreased mechanical strength or even failure and deformation of traditional FR4 substrates at high temperatures; the stator and cooling structure are fixed by thread fastening and epoxy resin potting, which eliminates air gap thermal resistance and improves the structure's vibration resistance and sealing performance. The water-cooled structure has a fully sealed leak-proof design to ensure the long-term stable operation of the motor under harsh conditions. 5. The naturally flat structure of the DCB stator is highly compatible with the axial magnetic circuit of the disc permanent magnet motor, which can significantly reduce the axial dimension of the motor and reduce the overall weight, perfectly meeting the stringent requirements of new energy equipment, industrial servo systems, robots and other application scenarios that have strict requirements for flat, lightweight and high power density motors.

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a DCB stator according to the present invention; Figure 2 This is a diagram showing the internal water channel arrangement of a stator cooling structure according to the present invention; Figure 3 This is a diagram showing the arrangement of the outer water channels of a stator cooling structure according to the present invention; Figure 4 This is an exploded view of a permanent magnet motor according to the present invention; Figure 5 This is the winding temperature rise curve shown in the test example.

[0019] Figure Labels 1. DCB substrate; 2. Fractional concentrated winding; 21. End; 22. Effective edge; 3. Placement hole; 4. Inner stator support; 41. Inner water channel; 5. Outer stator support; 51. Outer water channel; 6. Water cooling pipe; 7. Central shaft; 8. Front cover; 9. Inner bearing; 10. Inner permanent magnet; 11. Outer permanent magnet; 12. Outer bearing; 13. Rear cover. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the embodiments of the present invention and are not intended to limit the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout.

[0021] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, such as a process, method, system, product, or server that includes a series of steps or units, not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such process, method, product, or device.

[0022] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0023] like Figure 1As shown, a DCB stator includes a DCB substrate 1 with a copper-ceramic-copper sandwich eutectic bonding structure and a fractional concentrated winding 2. The fractional concentrated winding 2 is a conductor structure directly formed on the upper and lower surfaces of the DCB substrate 1 through a masking and etching process, used to transfer heat to the outer peripheral heat dissipation area of ​​the DCB stator. The conductor structures on the upper and lower surfaces are electrically connected and fixed by connecting copper strips that penetrate through placement holes 3 distributed on the outer periphery of the DCB substrate 1. The placement holes 3 are square holes or round holes adapted to the connecting copper strips.

[0024] The fractional concentrated winding 2 is a combined winding, which includes an effective side 22 constituting the main body of electromagnetic energy conversion and an end 21 connecting adjacent effective sides 22; wherein, the effective side 22 is arranged in the effective magnetic circuit region of the DCB substrate 1, and its outline is trapezoidal to adapt to the circumferential outline of the effective magnetic circuit region and improve the winding duty cycle; the end 21 is arranged outside the effective magnetic circuit region, and it is arc-shaped to reduce the size of the end 21 winding and optimize the electric field distribution.

[0025] The ceramic material of the DCB substrate 1 is selected from any one of alumina, aluminum nitride, silicon nitride, or silicon carbide.

[0026] The copper strip is welded and fixed to the conductor structure on the upper and lower sides.

[0027] like Figure 2 and Figure 3 As shown, a stator cooling structure includes an inner stator support 4 and an outer stator support 5 coaxially arranged on both sides of a DCB stator, and a water-cooling pipe 6 wrapped around the outer circumference of the DCB stator. The inner stator support 4 facing the DCB stator and the outer stator support 5 facing the DCB stator are respectively coaxially embedded with an inner water channel 41 and an outer water channel 51. The inner water channel 41, the water-cooling pipe 6 and the outer water channel 51 are connected in sequence, and the inner water channel 41 and the outer water channel 51 are aligned with the outer peripheral heat dissipation area of ​​the DCB stator to form a circumferentially fully wrapped cooling water channel. The circumferentially fully wrapped cooling water channel is in contact with the DCB stator.

[0028] Epoxy resin is filled between the inner water channel 41 and the outer peripheral heat dissipation area of ​​the DCB stator, between the outer water channel 51 and the outer peripheral heat dissipation area of ​​the DCB stator, and between the water cooling pipe 6 and the outer circumference of the DCB stator to construct a continuous and gapless heat transfer path.

[0029] The top of the outer stator support 5 is provided with a water inlet and a water outlet. The water inlet is connected to the outer water channel 51 embedded in the outer stator support 5. The outer water channel 51 is threadedly sealed to one end of the water cooling pipe 6. The other end of the water cooling pipe 6 is threadedly sealed to the inner water channel 41 embedded in the inner stator support 4. The inner water channel 41 is connected to the water outlet through a guide channel.

[0030] Both the inner water channel 41 and the outer water channel 51 include at least one layer of cooling water channels, and adjacent cooling water channels are connected in parallel or series. Series arrangement can extend the heat exchange path of the coolant and improve the heat exchange efficiency, while parallel arrangement can increase the coolant flow rate and adapt to high load conditions.

[0031] The outer stator support 5 and the inner stator support 4 are threaded together to form the stator support assembly, which is made of aluminum alloy. The water-cooling pipe 6 is a rigid metal tubular structure made of copper, aluminum, or a copper-aluminum alloy. The aluminum alloy stator support has excellent thermal conductivity, which helps to transfer heat to the water channels. The threaded sealing connection of the rigid water-cooling pipe 6 and the epoxy resin potting seal design ensure that there is no coolant leakage in the cooling circuit. At the same time, a continuous and seamless heat transfer path is constructed, which makes the heat transfer link of winding heat generation → DCB substrate 1 conduction → epoxy resin heat conduction → support / water-cooling pipe 6 heat exchange → coolant discharge efficient and smooth. Ultimately, it achieves uniform and efficient cooling of the DCB stator and permanent magnet motor, ensuring long-term stable operation of the motor under high power density and high load conditions.

[0032] like Figure 4 As shown, a permanent magnet motor includes a front cover 8, an inner bearing 9, an inner permanent magnet 10, a stator cooling structure, an outer permanent magnet 11, an outer bearing 12, and a rear cover 13, which are coaxially arranged on a central shaft 7. The outer water channel 51 and the inner water channel 41 of the stator cooling structure are both circular or arc-shaped water channels coaxial with the central axis of the permanent magnet motor.

[0033] Cooling Principle: During operation of the permanent magnet motor, the fractional concentrated winding 2 on the DCB stator, as the core component for electromagnetic energy conversion, generates electrical energy loss (mainly copper loss) in the process of its effective edge 22 cutting the axial magnetic field formed by the inner permanent magnet 10 and the outer permanent magnet 11. The end conductor 21 also generates additional losses due to current flow. All these losses are released in the form of heat and are concentrated on the winding conductor and the DCB substrate 1, which is directly metallurgically bonded to the conductor. Since the DCB substrate 1 adopts a copper-ceramic-copper sandwich eutectic bonding structure, its ceramic layer (alumina, aluminum nitride, etc.) has extremely high thermal conductivity. The heat generated by the copper foil conductor can be quickly conducted through the eutectic bonding surface to the outer peripheral heat dissipation area of ​​the DCB substrate 1, achieving initial heat dissipation and avoiding insulation aging or decreased conductivity caused by local overheating of the winding.

[0034] To achieve efficient heat dissipation, after the stator cooling structure is activated, the external cooling system injects coolant through the inlet at the top of the outer stator support 5. The coolant flows directly into the outer water channel 51 (circular or arc-shaped) embedded in the outer stator support 5. Since the outer water channel 51 is coaxial with the motor central axis and aligned with the heat dissipation area of ​​the DCB stator, when the coolant flows circumferentially in the outer water channel 51, it achieves close heat exchange through the aluminum alloy support wall, epoxy resin potting layer and the heat dissipation area of ​​the DCB substrate 1, quickly absorbing the heat conducted by the substrate and completing the first heat exchange.

[0035] Subsequently, the coolant flows along the outer water channel 51 to its circumferential connection port, and enters the rigid water-cooling pipe 6 wrapped around the outer circumference of the DCB stator through the threaded sealed interface. The water-cooling pipe 6 is made of copper, aluminum and their alloys, which have high thermal conductivity. Epoxy resin is filled between the water-cooling pipe 6 and the outer circumference of the DCB stator to eliminate air gap thermal resistance. The coolant flows circumferentially within the water-cooling pipe 6, performing 360° full-wrap secondary heat exchange on the outer circumference of the DCB stator, further absorbing the remaining heat conducted to the outer circumference by the DCB substrate 1 and windings, ensuring no heat retention.

[0036] After completing the secondary heat exchange, the coolant flows into the inner water channel 41 embedded in the inner stator support 4 through the threaded sealing interface at the other end of the water-cooling pipe 6. The inner water channel 41 and the outer water channel 51 are symmetrically arranged and coaxially. The coolant continues to flow circumferentially in the outer water channel 51 and completes the third heat exchange through the inner support wall, the epoxy resin potting layer and the heat dissipation area of ​​the outer periphery of the DCB substrate 1, completely removing the residual heat on the substrate.

[0037] Finally, the coolant that has absorbed all the heat flows along the inner water channel 41 to its end, and then flows back to the outlet at the top of the outer stator support 5 through the preset guide channel. It is then discharged to the external cooling system for cooling. The cooled coolant can be injected back into the cooling circuit through the inlet to form a closed loop.

[0038] Test case This experiment is a static test of the motor, which aims to verify the heat dissipation performance, thermal stability and temperature distribution uniformity of the permanent magnet motor described in this invention under high current density conditions. By comparing its performance with that of a traditional FR-4 substrate PCB motor, the superiority of the technical solution of this invention is clarified.

[0039] The experiment adopted a controlled design, selecting two axial flux permanent magnet motors with the same core parameters as test samples: one is a PCB stator axial flux permanent magnet motor with FR-4 epoxy resin substrate (control group), and the other is a DCB stator axial flux permanent magnet motor with silicon nitride ceramic substrate (experimental group); both samples are equipped with an outer circular water-cooling structure, and the stator outer diameter, winding turns and copper foil width are completely identical to ensure that the test variables are unique (only the stator substrate type and matching structure are different).

[0040] During the experiment, a constant DC current was applied to the windings of both samples, with a current density set at 32 A / mm². 2 The test environment temperature was controlled at 25±1℃. Temperature and winding resistance data of the winding measuring points of the two samples were collected in real time and tested continuously until the samples reached a thermally stable state. The key records were the time to reach thermal stability, the winding temperature at thermal stability, the average temperature rise rate and the winding resistance change rate.

[0041] The results are as follows Figure 5 As shown, the diagram clearly illustrates the winding temperature rise under four operating conditions: water-cooled PCB motor, no heat dissipation PCB motor, water-cooled DCB motor, and no heat dissipation DCB motor. It can be seen that when the permanent magnet motor (test group) of this invention reaches thermal stability, the temperature rise of the hottest point of the winding is 70K lower than that of the conventional PCB motor, a reduction of over 65%. In contrast, the water-cooled structure of the conventional PCB motor, compared to the uncooled structure, only reduces the hottest point temperature by about 10K, demonstrating limited heat dissipation efficiency. This fully proves that the motor of this invention has a more efficient heat dissipation capability and can effectively control the winding temperature rise under high current density conditions. Simultaneously, the average temperature rise rate and the maximum temperature difference between winding measurement points of the motor of this invention are significantly lower than those of the conventional PCB motor. This result confirms that the motor of this invention, through the high thermal conductivity of the DCB substrate and the circumferentially enclosed heat exchange layout of the water-cooled structure, can achieve a uniform distribution of winding temperature, effectively avoiding local overheating problems and ensuring winding insulation performance and motor operating stability.

[0042] In summary, this static test fully verifies that the permanent magnet motor of the present invention has significantly better heat dissipation performance, thermal stability and operational reliability under high current density conditions than the traditional FR-4 substrate PCB motor solution. It can provide solid test support for the motor to achieve the design goals of high power density and high torque density, and further highlights the innovation and practicality of the technical solution of the present invention.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A DCB stator, characterized in that: It includes a DCB substrate with a copper-ceramic-copper sandwich eutectic bonding structure and fractional concentrated windings. The fractional concentrated windings are conductor structures directly formed on the upper and lower surfaces of the DCB substrate through masking and etching processes, which are used to transfer heat to the outer peripheral heat dissipation area of ​​the DCB stator. The conductor structures on the top and bottom surfaces are electrically connected and fixed through connecting copper strips that pass through placement holes distributed around the periphery of the DCB substrate.

2. A DCB stator according to claim 1, characterized in that: The fractional concentrated winding is a combined winding, which includes an effective side that constitutes the main body of electromagnetic energy conversion and an end that connects adjacent effective sides. The effective side is located in the effective magnetic circuit region of the DCB substrate, and its outline is trapezoidal to adapt to the circumferential outline of the effective magnetic circuit region and improve the winding duty cycle. The end is located outside the effective magnetic circuit region and is arc-shaped to reduce the size of the end winding and optimize the electric field distribution.

3. A DCB stator according to claim 1, characterized in that: The ceramic material of the DCB substrate is selected from any one of alumina, aluminum nitride, silicon nitride, or silicon carbide.

4. A DCB stator according to claim 1, characterized in that: The copper strip is welded and fixed to the conductor structure on the upper and lower sides.

5. A stator cooling structure, characterized in that: The device includes an inner stator support and an outer stator support coaxially arranged on both sides of the DCB stator as described in any one of claims 1-4, and a water-cooling pipe wrapped around the outer circumference of the DCB stator. The inner stator support facing the DCB stator and the outer stator support facing the DCB stator are respectively coaxially embedded with an inner water channel and an outer water channel. The inner water channel, the water-cooling pipe and the outer water channel are connected in sequence, and the inner water channel and the outer water channel are aligned with the outer peripheral heat dissipation area of ​​the DCB stator to form a circumferentially fully wrapped cooling water channel. The circumferentially fully wrapped cooling water channel is in contact with the DCB stator.

6. A stator cooling structure according to claim 5, characterized in that: Epoxy resin is filled between the inner water channel and the outer peripheral heat dissipation area of ​​the DCB stator, between the outer water channel and the outer peripheral heat dissipation area of ​​the DCB stator, and between the water cooling pipe and the outer circumference of the DCB stator to construct a continuous and gapless heat transfer path.

7. A stator cooling structure according to claim 5, characterized in that: The top of the outer stator support has an inlet and an outlet. The inlet is connected to the outer water channel embedded in the outer stator support. The outer water channel is threaded and sealed to one end of the water cooling pipe. The other end of the water cooling pipe is threaded and sealed to the inner water channel embedded in the inner stator support. The inner water channel is connected to the outlet through a guide channel.

8. A stator cooling structure according to claim 5, characterized in that: Both the inner and outer water channels include at least one layer of cooling water channels, and adjacent cooling water channels are connected in parallel or in series.

9. A stator cooling structure according to claim 5, characterized in that: The outer stator support and the inner stator support are threaded together to form the stator support assembly, which is made of aluminum alloy. Water-cooled pipes are rigid metal tubular structures, made of copper, aluminum, or copper-aluminum alloys.

10. A permanent magnet motor, characterized in that: It includes a front cover, an inner bearing, an inner permanent magnet, a stator cooling structure as described in any one of claims 5-9, an outer permanent magnet, an outer bearing, and a rear cover, which are coaxially arranged on a central shaft in sequence. The outer and inner water channels of the stator cooling structure are both circular or arc-shaped water channels coaxial with the central axis of the permanent magnet motor.

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