Axial flux motor and method for limiting shaft voltage and improving electric corrosion of bearing

Abstract

The invention discloses an axial magnetic flux motor and a method for limiting shaft voltage and improving electric corrosion of a bearing, and the axial magnetic flux motor comprises a motor housing which is enclosed by at least one end cover; the stator is arranged in the motor shell; one end of the rotor is rotationally arranged in a bearing chamber through a bearing, and the bearing chamber is arranged in the motor shell; the bearing chamber and the end cover are arranged in a split mode. The bearing chamber and the end cover are connected in a non-conducting mode and are provided with at least one first adjustable capacitor. The stator and the end cover are in non-conducting connection and are provided with at least one second adjustable capacitor; by adjusting the capacitance values of the first adjustable capacitor and the second adjustable capacitor, the specific value of each bridge arm capacitor in the motor shaft voltage equivalent circuit is adjusted. According to the invention, accurate adjustment of the capacitance ratio of each bridge arm in the motor shaft voltage equivalent Wheatstone bridge arm circuit is realized. By adjusting the capacitance value of the capacitor, the bridge arm capacitance meets the balance condition, and electric corrosion of the bearing is avoided from the source.

Description

[0001] This application claims priority to the prior application with the application number: 202510877937.5, the name: motor application system, corrosion protection method and electrical equipment, the priority date: June 26, 2025. TECHNICAL FIELD

[0002] The present application relates to the technical field of electric machines, in particular to an axial flux motor and a method for limiting shaft voltage and improving bearing corrosion. BACKGROUND

[0003] Axial flux motors (disc motors) are increasingly widely used in new energy vehicles, industrial drives and other fields due to their axial magnetic circuits and flat structures. However, high shaft voltage of axial flux motors can easily lead to bearing corrosion, which not only causes bearing noise but also greatly affects the service life of bearings and motors, becoming a key problem restricting their promotion. The prior art pays little attention to the problem of shaft voltage of axial flux motors. The existing axial flux motor scheme has a high risk of bearing corrosion (high shaft voltage) and does not consider many limiting measures. SUMMARY

[0004] Therefore, the present application provides an axial flux motor and a method for limiting shaft voltage and improving bearing corrosion to solve the problem of high shaft voltage of axial flux motors easily leading to bearing corrosion.

[0005] In a first aspect, the present application provides an axial flux motor, comprising:

[0006] A motor housing, the motor housing is surrounded by at least one end cover;

[0007] A stator, the stator is arranged inside the motor housing;

[0008] A rotor, one end of the rotor is rotatably arranged in a bearing chamber through a bearing, and the bearing chamber is arranged inside the motor housing;

[0009] The bearing chamber and the end cover are arranged separately, and the bearing chamber and the end cover are non-conductively connected and provided with at least one first adjustable capacitor; the stator and the end cover are non-conductively connected and provided with at least one second adjustable capacitor;

[0010] The ratio of the capacitances of each bridge arm capacitor in the equivalent circuit of the motor shaft voltage is adjusted by adjusting the capacitances of the first adjustable capacitor and the second adjustable capacitor.

[0011] The axial flux motor has the beneficial effects that: by arranging the first adjustable capacitor between the bearing chamber and the end cover and the second adjustable capacitor between the stator and the end cover, the ratio of the bridge arm capacitors in the equivalent Wheatstone bridge arm circuit of the motor shaft voltage is precisely adjusted. By adjusting the capacitance value to make the bridge arm capacitors meet the balance condition, the shaft voltage peak value can be reduced from 13.3V in the prior art to below 1.4V, thereby avoiding bearing corrosion from the root and solving the problems of bearing abnormal noise and shortened service life of the axial flux motor caused by the excessively high shaft voltage.

[0012] In an optional embodiment, the bearing chamber and the end cover are separated by a first insulating material layer to form a first adjustment capacitor between the bearing chamber and the end cover.

[0013] The technical scheme has the beneficial effects that: the structure design of the bearing chamber-insulating medium-end cover utilizes the conductivity of the metal parts and the dielectric properties of the insulating material to naturally form an adjustable capacitor in the motor without the need of additionally adding independent capacitor elements, thereby simplifying the motor structure.

[0014] In an optional embodiment, the capacitance value of the first adjustment capacitor is adjusted by adjusting the relative area of the bearing chamber and the end cover or the thickness or material of the first insulating material layer.

[0015] In an optional embodiment, the stator and the end cover are separated by a second insulating material layer, the stator and the end cover are connected by a fixing screw, and the contact part of the fixing screw and the end cover is separated by an insulating material to form a second adjustment capacitor.

[0016] In an optional embodiment, the capacitance value of the second adjustment capacitor is adjusted by adjusting the relative area of the stator and the end cover or the thickness or material of the second insulating material layer.

[0017] In an optional embodiment, at least one third adjustment capacitor is arranged between the stator and the end cover, and the ratio of the bridge arm capacitors in the equivalent circuit of the motor shaft voltage is adjusted by adjusting the capacitance values of the first, second and third adjustment capacitors.

[0018] The beneficial effects of the above technical solutions are: through the at least two independently adjustable capacitors and the optional third adjustable capacitor, a multi-capacitor combination adjustment mechanism is formed. Each capacitor can be independently or jointly adjusted by changing the relative area, the thickness of the insulating material or the dielectric constant, thereby significantly widening the adjustment interval of the bridge arm capacitance ratio, adapting to the change of the parasitic capacitance of the motor under different rotating speeds and loads, and ensuring that the shaft voltage is stably kept in the safe range for a long time. The embodiment adopts at least three adjustable capacitors, and the combination of multiple capacitors increases flexibility, and through the combination of different ways (different capacitor sizes), the extreme value or the approximate extreme value of the shaft voltage is found, thereby improving the problem of large motor shaft voltage or bearing electric corrosion.

[0019] In an optional embodiment, the third adjustable capacitor comprises a conductive part and a third insulating material layer, one end of the conductive part is connected with the outer side wall of the stator, and the other end of the conductive part is connected with the inner side wall of the end cover through the third insulating material layer.

[0020] In an optional embodiment, the conductive part is a wire or a conductive strip; and / or, the conductive part is attached to the inner side wall of the end cover through the third insulating material layer, and the third insulating material layer is insulating paper or an imine strip.

[0021] In an optional embodiment, the capacitance of the third adjustable capacitor is adjusted by adjusting the relative area of the conductive part and the end cover, or the thickness of the third insulating material layer, or the material of the third insulating material layer.

[0022] In an optional embodiment, the third adjustable capacitor is a replaceable capacitor.

[0023] In an optional embodiment, the first adjustable capacitor, the second adjustable capacitor and the third adjustable capacitor are independently or combined adjusted, so that the bearing voltage is close to zero by changing the capacitance ratio of the shaft voltage equivalent bridge arm.

[0024] In a second aspect, the application further provides a method for limiting shaft voltage and improving bearing electric corrosion, which is applied to an axial flux motor and comprises the following steps:

[0025] At least one first adjustable capacitor is arranged between the bearing chamber and the end cover, so that the bearing chamber and the end cover are formed into a non-conductive connection;

[0026] At least one second adjustable capacitor is arranged between the stator and the end cover, so that the stator and the end cover are formed into a non-conductive connection;

[0027] The capacitances of the first adjustable capacitor and the second adjustable capacitor are adjusted to adjust the ratio of each bridge arm capacitance in the motor shaft voltage equivalent Wheatstone bridge arm circuit, so that the shaft voltage at both ends of the bearing is reduced and the shaft voltage is close to zero, thereby reducing the risk of bearing electric corrosion.

[0028] In an alternative embodiment, further comprising:

[0029] At least one third adjustable capacitor is arranged between the stator and the end cover, one end of the third adjustable capacitor is in conductive connection with the stator, and the other end is opposite to the end cover through a third insulating material layer; by adjusting the capacitance of the third adjustable capacitor, the ratio of the capacitances of the bridge arms in the motor shaft voltage equivalent circuit is further adjusted in cooperation with the first adjustable capacitor and the second adjustable capacitor, so that the ratio of the capacitances of the bridge arms tends to be balanced.

[0030] In an alternative embodiment, the ratio of the capacitances of the bridge arms tends to be balanced, in particular:

[0031] The ratio of the capacitances of the opposite bridge arms of the Wheatstone bridge structure in the motor shaft voltage equivalent circuit satisfies Cfirst bridge arm / Csecond bridge arm=Cthird bridge arm / Cfourth bridge arm, so as to reduce the shaft voltage at both ends of the bearing to below a preset threshold.

[0032] In summary, the technical scheme of the present application has the following advantages:

[0033] The present application forms a multi-capacitor combined adjustment mechanism through at least two independently adjustable capacitors and an optional third adjustable capacitor. Each capacitor can be independently or jointly adjusted by changing the relative area, the thickness of the insulating material or the dielectric constant, significantly widening the adjustment range of the ratio of the capacitances of the bridge arms, adapting to the change of the parasitic capacitance under different speeds and loads of the motor, and ensuring that the shaft voltage is stably kept in a safe range for a long time. The present application uses at least three adjustable capacitors, and the combination of multiple capacitors increases flexibility, and through different combinations, the extreme value or approximate extreme value of the shaft voltage is found, and the problem of large motor shaft voltage or bearing electric corrosion is improved. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical scheme in the specific embodiments or prior art of the present application, the drawings needed in the following specific embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0035] Figure 1 is a cross-sectional view of a current axial flux motor;

[0036] Figure 2 is a cross-sectional view of an axial flux motor provided by the present application;

[0037] Figure 3 is a structural schematic view of a first adjustable capacitor of an axial flux motor provided by the present application;

[0038] Figure 4A structure schematic diagram of a second adjustable capacitor of an axial flux motor provided by the present application;

[0039] Figure 5 A structure schematic diagram of a third adjustable capacitor of an axial flux motor provided by the present application;

[0040] Figure 6 A structure schematic diagram of an axial flux motor provided by the present application by changing the facing area of the conductive part and the inner side wall of the end cover;

[0041] Figure 7 A structure schematic diagram of an axial flux motor provided by the present application by changing the thickness of the third insulating material layer;

[0042] Figure 8 A structure schematic diagram of an axial flux motor provided by the present application by changing the material quality of the third insulating material layer;

[0043] Figure 9 A structure schematic diagram of an axial flux motor provided by the present application provided with an external capacitor;

[0044] Figure 10 A structure schematic diagram of an axial flux motor provided by the present application by changing the capacitor area to change the capacitance value of the first adjustable capacitor;

[0045] Figure 11 A structure schematic diagram of an axial flux motor provided by the present application by changing the thickness of the first insulating material layer to change the capacitance value of the first adjustable capacitor;

[0046] Figure 12 A structure schematic diagram of an axial flux motor provided by the present application by changing the thickness of the second insulating material layer to change the capacitance value of the second adjustable capacitor;

[0047] Figure 13 A structure schematic diagram of an axial flux motor provided by the present application in which the first adjustable capacitor and the second adjustable capacitor are formed by an insulating sheath;

[0048] Figure 14 An axial voltage equivalent circuit diagram of a conventional axial flux motor structure;

[0049] Figure 15 An axial voltage equivalent circuit diagram of a conventional axial flux motor structure;

[0050] Figure 16 An axial voltage equivalent circuit diagram of an axial flux motor provided by the present application;

[0051] Figure 17 A simulation waveform diagram of the axial voltage of a conventional axial flux motor for improvement;

[0052] Figure 18 The axial flux motor shaft voltage simulation waveform diagram of the improved new structure of the application.

[0053] Reference signs:

[0054] 1, stator, 11, stator core, 12, stator winding, 2, rotor, 21, rotor disc assembly, 22, shaft, 3, end cover, 31, first end cover, 32, second end cover, 4, bearing, 41, bearing outer ring, 42, bearing inner ring, 43, ball, 5, bearing chamber, 6, first layer of insulating material, 7, second layer of insulating material, 8, third layer of insulating material, 9, fixing screw, 91, insulating sheath, 101, conductive part;

[0055] C1, first adjustable capacitor, C2, second adjustable capacitor, C3, third adjustable capacitor, Cs, parasitic capacitance between winding and stator core, Cn, parasitic capacitance between DC circuit negative pole and end cover, Csn, parasitic capacitance between DC circuit negative pole and shaft, Cm, parasitic capacitance between winding and permanent magnet, Cg, parasitic capacitance between stator core and permanent magnet, Cmg, parasitic capacitance between permanent magnet and shaft, Csb, parasitic capacitance between winding and end cover, Cb1 and Cb2, parasitic capacitance inside bearing. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0057] Axial flux motors (disc motors) are increasingly widely used in new energy vehicles, industrial drives and other fields due to their axial magnetic circuit, flat structure and other characteristics. However, high shaft voltage of axial flux motors is prone to cause bearing electric erosion, which not only causes bearing abnormal noise, but also greatly affects the service life of the bearing and the motor, becoming a key problem restricting its promotion.

[0058] The prior art pays little attention to the problem of shaft voltage of axial flux motors. The existing axial flux motor scheme has a high risk of bearing electric erosion (high shaft voltage) and does not consider many limiting measures. Even for radial flux motors, when optimizing the shaft voltage, most of them only consider one adjusting capacitor, and too few adjusting capacitors mean too few combinations, and the adjustment interval is limited.

[0059] Therefore, there is an urgent need for a shaft voltage limiting scheme for the characteristics of axial flux motors. Based on this, the axial flux motor provided in the present application effectively limits the voltage division of the bearing capacitance in multiple ways to improve the bearing corrosion phenomenon.

[0060] According to an embodiment of the present application, in the first aspect, an axial flux motor is provided, which is combined with Figures 2 to 18 As shown, it comprises a motor housing, a stator 1 and a rotor 2. The motor housing is surrounded by at least one end cover 3, so that Figure 1 and Figure 2 For example, the end cover 3 can be provided in two parts, namely a first end cover 31 and a second end cover 32. The stator 1 is arranged inside the motor housing. One end of the rotor 2 is rotatably arranged in the bearing chamber 5 through the bearing 4, and the bearing chamber 5 is arranged inside the motor housing. The other end of the rotor 2 extends out of the motor housing, and the rotor 2 is coaxially arranged with the stator 1. The bearing 4 comprises a bearing outer ring 41, a bearing inner ring 42 and a ball 43, and the ball 43 is arranged between the bearing outer ring 41 and the bearing inner ring 42. The stator 1 comprises a stator core 11 and a stator winding 12, and the stator winding 12 is arranged on the stator core 11. The rotor 2 comprises a rotor disc assembly 21 and a rotating shaft 22, and the rotating shaft 22 is embedded in the bearing inner ring 42. The bearing outer ring 41 is arranged in the bearing chamber 5, and the rotor disc assembly 21 is arranged opposite to the stator core with an air gap therebetween.

[0061] The bearing chamber 5 and the end cover 3 are provided in two parts, and are non-conductively connected and provided with at least one first adjustable capacitor C1 between the bearing chamber 5 and the end cover 3. The stator 1 and the end cover 3 are non-conductively connected and provided with at least one second adjustable capacitor C2 between the stator 1 and the end cover 3. By adjusting the capacitance values of the first adjustable capacitor C1 and the second adjustable capacitor C2, the ratio of the capacitances of the bridge arms in the equivalent circuit of the motor shaft voltage is adjusted, and then the shaft voltage of the axial flux motor is adjusted.

[0062] The above axial flux motor realizes precise adjustment of the capacitance ratio of each bridge arm in the equivalent H-bridge arm circuit of the motor shaft voltage by arranging the first adjustable capacitor C1 between the bearing chamber 5 and the end cover 3 and the second adjustable capacitor C2 between the stator 1 and the end cover 3. By adjusting the capacitance to make the bridge arm capacitance satisfy the balance condition, the shaft voltage peak value can be reduced from 13.3V (simulation data) in the prior art to below 1.4V, which can avoid bearing corrosion from the root cause and solve the problems of bearing abnormal noise and shortened life caused by excessive shaft voltage of the axial flux motor.

[0063] The adjustment of the adjustable capacitor is realized by mechanical structure parameters (such as area and thickness) or conventional insulating materials, without the need to introduce a complex electronic control system, which is suitable for existing motor production lines and reduces the difficulty of industrialization.

[0064] In some embodiments, the bearing chamber 5 and the end cap 3 are separated by a first insulating material layer 6, thereby forming a first adjustable capacitor C1 between the bearing chamber 5 and the end cap 3. The bearing chamber 5 and the end cap 3 serve as the two electrodes of the capacitor, and the first insulating material layer 6 provides the insulating medium for the capacitor. The bearing chamber-insulating medium-end cap structural design utilizes the conductivity of metal components and the dielectric properties of the insulating material to naturally form an adjustable capacitor within the motor, eliminating the need for additional independent capacitor components and simplifying the motor structure.

[0065] The first insulating material layer 6 can be made of red steel, which has a high dielectric constant and stable physical and chemical properties, ensuring the stability and reliability of the capacitance value. Furthermore, red steel is easy to process, and its area and thickness can be adjusted according to actual needs, thereby conveniently adjusting the capacitance value of the first adjustable capacitor C1.

[0066] The capacitance of the first regulating capacitor C1 can be adjusted independently or in combination by the following parameters to meet the dynamic balance requirements of the shaft voltage equivalent circuit. According to the parallel plate capacitance formula:

[0067]

[0068] Where: ε is the dielectric constant of the capacitor medium, S is the area of ​​the two plates of the capacitor, and d is the distance between the two plates (or the thickness of the medium).

[0069] The first way is to change the effective overlapping area of ​​the capacitor plates by designing the facing contact area between the bearing chamber 5 and the end cover 3. The capacitance is proportional to the area, and the larger the area, the higher the capacitance. The second way is to change the thickness of the first insulating material layer 6. Insulating materials of different thicknesses are selected as the first insulating material layer 6 to adjust the thickness of the dielectric layer. The capacitance is inversely proportional to the thickness, and the smaller the thickness, the higher the capacitance. The third way is to replace the material of the first insulating material layer 6. Replacing insulating materials with different dielectric constants directly changes the energy storage capacity of the medium. The capacitance is proportional to the dielectric constant, and the larger the dielectric constant, the higher the capacitance. In some occasions where it is inconvenient to adjust the thickness, such as strict axial dimension requirements, the size of the first adjustment capacitor C1 can also be effectively changed by adjusting the relative area S between the bearing chamber 5 and the end cover 3.

[0070] In some embodiments, the stator 1 is isolated from the end cover 3 by a second layer of insulating material 7, which is an insulating gasket. The stator 1 is connected to the end cover 3 by a fixing screw 9, and the part of the fixing screw 9 in contact with the end cover 3 is separated by an insulating material, forming a second adjustment capacitor C2. The stator core (metal material) and the end cover (metal shell) serve as the two plates of the capacitor, and the second layer of insulating material 7 serves as the dielectric layer. The insulating treatment of the fixing screw 9 prevents the metal fastener from conducting the stator and the end cover, ensuring that the plates of the second adjustment capacitor C2 form a capacitor only through the insulating dielectric layer, rather than a direct conductive path. This not only preserves the mechanical fixing strength of the stator 1 and the end cover 3, but also achieves stable construction of the capacitor through insulating isolation.

[0071] The bearing chamber 5 and the end cover 3 are separately arranged and connected by an insulating material layer, and the connecting fasteners (such as fixing screws) of the stator 1 and the end cover 3 are also isolated by insulation, avoiding the risk of capacitor short circuit caused by direct conduction of metal components, while not changing the original axial flux path and flat structure characteristics of the motor.

[0072] The capacitance of the second adjustment capacitor C2 can be flexibly adjusted by the following parameters to adapt to the balance requirements of the shaft voltage equivalent Wheatstone bridge arm circuit. The first way is to adjust the relative area of the stator 1 and the end cover 3. By optimizing the outer diameter size of the stator core or the inner wall profile of the end cover, the facing area of the two is changed. According to the capacitor formula The larger the facing area, the higher the capacitance of the second adjustment capacitor C2. The second way is to change the thickness of the second layer of insulating material 7. Different thicknesses of the second layer of insulating material 7 are selected to adjust the thickness of the dielectric layer. The capacitance is inversely proportional to the thickness. Reducing the thickness can increase the capacitance, and vice versa. The third way is to replace the material of the second layer of insulating material 7. Different insulating materials with different dielectric constants are selected to directly change the energy storage characteristics of the medium. The higher the dielectric constant, the larger the capacitance of the second adjustment capacitor C2, which can be achieved by material selection to adjust the capacitance in steps. Under the stator core, it is costly to place a whole piece of insulating material. An insulating sleeve 91 can be placed on the screw between the stator 1 and the end cover 3. The end cover 3 has a sleeve hole, and the insulating sleeve 91 passes through the sleeve hole and is embedded in the sleeve hole. Then the screw passes through the insulating sleeve, and the stator core is connected to the screw, so that the stator core and the end cover 3 do not form an electrical path, reducing the cost, as shown in Figure 13 Changing the thickness of the screw gasket or the insulating sleeve 91 of the screw can adjust the value of d, changing the size of the second adjustment capacitor C2, as shown in Figure 12 and Figure 13

[0073] ​In some embodiments, at least one third adjusting capacitor C3 is further arranged between the stator 1 and the end cover 3, and the ratio of the capacitances of the bridge arms in the motor shaft voltage equivalent circuit is adjusted by adjusting the capacitances of the first, second and third adjusting capacitors C1, C2 and C3.

[0074] The radial flux motor usually only employs one adjusting capacitor, and the adjustment dimension is single, the combination mode is limited, and it is difficult to cover the shaft voltage optimization requirements under different working conditions; the existing scheme of the axial flux motor lacks targeted shaft voltage limiting measures. The present embodiment forms a multi-capacitor combination adjustment mechanism through at least two independently adjustable capacitors and an optional third adjustable capacitor. Each capacitor can be independently or jointly adjusted by changing the relative area, the thickness or the dielectric constant of the insulating material, thereby significantly widening the adjustment interval of the bridge arm capacitance ratio, adapting to the change of the parasitic capacitance under different motor speeds and loads, and ensuring that the shaft voltage is stably within the safe range for a long time. The present embodiment employs at least three adjustable capacitors, and the combination of multiple capacitors increases flexibility, and through the combination of different modes (different capacitor sizes), the extreme value or the approximate extreme value of the shaft voltage is found, and the motor shaft voltage or bearing electric corrosion problem is improved.

[0075] More specifically, the third adjusting capacitor C3 comprises a conductive part 101 and a third insulating material layer 8, and the conductive part 101 is a wire or a conductive strip. One end of the conductive part 101 is connected to the outer side wall of the stator 1, and the other end of the conductive part 101 is connected to the inner side wall of the end cover 3 through the third insulating material layer 8. The conductive part 101 is attached to the inner side wall of the end cover 3 through the third insulating material layer 8, and the third insulating material layer 8 is insulating paper or an imine strip.

[0076] The conductive part 101 and the end cover 3 serve as the two poles of the capacitor respectively, the third insulating material layer 8 is the dielectric, and the third adjusting capacitor C3 is formed through the conductive part-insulating dielectric-end cover structure. In the present embodiment, an additional capacitor adjustment path is constructed between the stator 1 and the end cover 3 through the independent conductive part, and a multi-dimensional adjustment system is formed in complement with the first and second adjusting capacitors C1 and C2.

[0077] In combination with the adjustment logic of the first and second adjusting capacitors C1 and C2 and the structural features of the third adjusting capacitor C3, the capacitance of the third adjusting capacitor C3 can be regulated in the following ways. The capacitance of C3 can be adjusted more flexibly according to the formula It can be seen that the capacitance can be quickly adjusted by adjusting S and d. In the first way, the relative area of the conductive part 101 and the end cover 3 is adjusted. The extension length or the end area of the conductive part 101 is designed to change the facing area with the inner side wall of the end cover 3, and the capacitance increases with the increase of the area, such as Figure 5 and Figure 6The second way is to change the thickness or material of the third insulating material layer 8. Replace the third insulating material layer 8 with different thickness, the capacitance is inversely proportional to the thickness, and then adjust the size of the third adjusting capacitor C3, such as Figure 7 As shown in the figure; select high dielectric constant material or low dielectric constant material, directly change the medium energy storage capacity, realize the wide range adjustment of capacitance, at this time the dielectric constant ε changes, the capacitance changes, such as Figure 8 As shown in the figure. The third way is to fine-tune the position of the conductive part. Through mechanical structure design, such as the slidable connection of the end of the conductive part, adjust the relative distance or parallelism of the conductive part 101 and the end cover 3, indirectly change the effective plate area or the uniformity of the dielectric layer, and realize the fine-tuning of the capacitance. The above-mentioned ways can quickly and effectively adjust the capacitance of the third adjusting capacitor C3, and do not need too much cost and space.

[0078] As an alternative embodiment, the third adjustable capacitor C3 can also be replaced by a real capacitor, such as Figure 9 As shown in the figure, for example, directly purchase a suitable capacitor, one end connected to the stator and the other end connected to the end cover, which is not limited by the size limitation of the capacitance value. The third adjustable capacitor C3 can be replaced directly according to the actual adjustment needs.

[0079] In some embodiments, the first adjustable capacitor C1, the second adjustable capacitor C2, and the third adjustable capacitor C3 are adjusted individually or in combination, so that the bearing voltage equivalent bridge arm capacitance ratio is close to zero by changing the bearing voltage equivalent bridge arm capacitance ratio.

[0080] When a single bridge arm is unbalanced, individual adjustment mode can be used, and the first adjustable capacitor C1, the second adjustable capacitor C2, or the third adjustable capacitor C3 can be adjusted individually. For example, when the bearing side parasitic capacitance fluctuates, the first adjustable capacitor C1 can be adjusted individually; when the stator side parasitic capacitance fluctuates, the second adjustable capacitor C2 can be adjusted individually; and when the end cover inner wall parasitic capacitance fluctuates, the third adjustable capacitor C3 can be adjusted individually.

[0081] When dealing with multi-dimensional collaborative complex working conditions, the first adjustable capacitor C1, the second adjustable capacitor C2, and the third adjustable capacitor C3 can be adjusted in combination, for example, the first adjustable capacitor C1 and the second adjustable capacitor C2 can be adjusted in combination, the first adjustable capacitor C1 and the third adjustable capacitor C3 can be adjusted in combination, the second adjustable capacitor C2 and the third adjustable capacitor C3 can be adjusted in combination, and the first adjustable capacitor C1, the second adjustable capacitor C2, and the third adjustable capacitor C3 can be adjusted in combination. Different combinations of the first adjustable capacitor C1, the second adjustable capacitor C2, and the third adjustable capacitor C3 can flexibly adjust different equivalent capacitances, so as to select the most beneficial combination of shaft voltage (minimum) to improve the shaft magnetic flux motor electric corrosion problem or reduce the shaft magnetic flux motor electric corrosion risk.

[0082] The shaft voltage equivalent circuit diagram of the conventional axial flux motor structure is as follows Figure 14 As shown, the motor shaft voltage equivalent circuit closely resembles a Wheatstone bridge circuit, with the bearing equivalent bridge arm corresponding to the center bridge arm. The magnitude and direction of the shaft voltage (center bridge arm voltage), similar to that of a Wheatstone bridge, are influenced by the magnitude and ratio of the equivalent capacitances in each bridge arm. Conventional parasitic capacitances within the motor (formed by the basic motor dimensions) affect the magnitude and direction of the shaft voltage. However, since the electromagnetic design and structural dimensions of the axial flux motor are fixed, these capacitances are not adjustable. Therefore, when the shaft voltage is excessive, these conventional capacitances cannot or cannot be easily adjusted, making it difficult to reduce the shaft voltage by resizing them.

[0083] Reference Figure 15 As shown, the size and direction of the shaft voltage (center bridge arm voltage) are similar to those of the Wheatstone bridge: affected by the size and ratio of the equivalent capacitance on each bridge arm (the emphasis is on the ratio). That is, the equivalent capacitance in this embodiment is the equivalent capacitance of each bridge arm of the bridge in the equivalent circuit when the motor is working under load. The first bridge arm is the branch where the capacitor Csb is located, the second bridge arm is the branch where the capacitor Cs, capacitor Cg, capacitor Cm and capacitor Cmg are located, the third bridge arm is the branch where the capacitor Cn is located, and the fourth bridge arm is the branch where the capacitor Csn is located. The voltage of the center bridge arm, that is Figure 15 The voltage across capacitor Cb1 is also the voltage across capacitor Cb2. When capacitors Cb1 and Cb2 are connected in parallel, the voltages across them are equal. Normally, the center bridge arm voltage is the voltage of either capacitor Cb1 or capacitor Cb2, and the voltage across capacitors Cb1 and Cb2 is the shaft voltage. Common-mode voltage Vcom refers to the voltage between the motor's neutral point and the reference ground (DC bus midpoint). When the controller's control strategy, hardware, and power supply voltage are fixed, the common-mode voltage is also fixed.

[0084] Where: Cs: parasitic capacitance between the winding and the stator core; Cn: parasitic capacitance between the negative pole of the DC circuit (reference ground) and the end cover; Csn: parasitic capacitance between the negative pole of the DC circuit (reference ground) and the shaft; Cm: parasitic capacitance between the winding and the permanent magnet; Cg: parasitic capacitance between the stator core and the permanent magnet; Cmg: parasitic capacitance between the permanent magnet and the shaft; Csb: parasitic capacitance between the winding and the end cover; Cb1 and Cb2: parasitic capacitance inside the bearing.

[0085] The above axial flux motor has an improved structure and the shaft voltage equivalent circuit diagram is as follows: Figure 16The motor shaft voltage equivalent circuit is shown in Figure 1. This circuit is based on the equivalent circuit of a conventional axial flux motor, but with the addition of the first, second, and third adjustable capacitors C1, C2, and C3. The magnitude and direction of the shaft voltage (center bridge arm voltage) are similar in principle. The presence of parasitic capacitance within the motor affects the magnitude and direction of the shaft voltage.

[0086] The equivalent capacitors of conventional axial flux motors are also not adjustable. However, the three newly added equivalent capacitors of the present invention—the first adjustable capacitor C1, the second adjustable capacitor C2, and the third adjustable capacitor C3—can be flexibly adjusted to limit the shaft voltage and thus improve the bearing electrical corrosion problem.

[0087] by Figure 15 Taking the Wheatstone bridge arm as an example, the central bridge arm voltage (that is, the bearing voltage, the shaft voltage) is closely related to the ratio of the first bridge arm, the second bridge arm, the third bridge arm, and the fourth bridge arm.

[0088] Principle of bridge arm capacitance balance: If the equivalent capacitances on the first bridge arm, second bridge arm, third bridge arm, and fourth bridge arm are Cfirst bridge arm, Csecond bridge arm, Cthird bridge arm, and Cfourth bridge arm, respectively, and bridge arm capacitance balance is added (Cfirst bridge arm / Csecond bridge arm=Cthird bridge armCfourth bridge arm), then the center bridge arm voltage is 0, that is, the shaft voltage is 0. However, in actual products, the capacitances of the first bridge arm, second bridge arm, third bridge arm, and fourth bridge arm are difficult to balance. In this case, the first adjustable capacitor C1, the second adjustable capacitor C2, and the third adjustable capacitor C3 are introduced. One end of the second adjustable capacitor C2 and the third adjustable capacitor C3 is connected to the branch where the capacitor Csb and the capacitor Cn are located, and the other end of the second adjustable capacitor C2 and the third adjustable capacitor C3 is connected to the branch where the capacitor Cs and the capacitor Cg are located. The third bridge arm contains the branch where capacitor Cn is located and the branch where the first adjustable capacitor C1 is introduced. The third bridge arm contains the branch where capacitor Csb is located and the branches where the second and third adjustable capacitors C2 and C3 are introduced. The capacitance values ​​of the first, second, and third adjustable capacitors C1, C2, and C3 are adjustable. If the shaft voltage does not meet the requirements during simulation or testing, the values ​​of these capacitors can be adjusted to make the capacitance ratio of the four bridge arms closer to balance after equivalent operation, thereby reducing the shaft voltage.

[0089] by Figure 17 For example, the results shown in the figure are as follows: before improvement, the peak value of the shaft voltage is about 13.3V; Figure 18 As shown in the figure, after the improvement, the peak value of the shaft voltage is about 1.4 V. The effect is very significant, and the improvement method is flexible and simple.

[0090] According to an embodiment of the present invention, in a second aspect, a method for limiting shaft voltage and improving bearing electrical corrosion is provided, comprising the following steps:

[0091] At least one first adjustable capacitor C1 is arranged between the bearing chamber 5 and the end cover 3, so that the bearing chamber 5 and the end cover 3 form a non-conductive connection.

[0092] At least one second adjustable capacitor C2 is arranged between the stator 1 and the end cover 3, so that the stator 1 and the end cover 3 form a non-conductive connection.

[0093] The capacitance of the first adjustable capacitor C1 and the second adjustable capacitor C2 is adjusted to adjust the ratio of the bridge arm capacitors in the motor shaft voltage equivalent Wheatstone bridge arm circuit, reduce the shaft voltage across the bearing 4, and make the shaft voltage close to zero to reduce the risk of bearing 4 electric erosion.

[0094] The above method of limiting shaft voltage and improving bearing electric erosion further comprises: arranging at least one third adjustable capacitor C3 between the stator 1 and the end cover 3, one end of the third adjustable capacitor C3 being in conductive connection with the stator 1 and the other end being opposite to the end cover 3 through a third insulating material layer 8; by adjusting the capacitance of the third adjustable capacitor C3, the first adjustable capacitor C1 and the second adjustable capacitor C2 are coordinated to further adjust the ratio of the bridge arm capacitors in the motor shaft voltage equivalent circuit, so that the ratio of the bridge arm capacitors is close to balance.

[0095] The ratio of the bridge arm capacitors is close to balance, specifically: the ratio of the opposite side bridge arm capacitors in the Wheatstone bridge structure in the motor shaft voltage equivalent circuit satisfies Cfirst bridge arm / Csecond bridge arm=Cthird bridge arm / Cfourth bridge arm, so as to reduce the shaft voltage across the bearing to below a preset threshold.

[0096] Although the embodiments of the present application are described in conjunction with the drawings, various modifications and changes can be made by those skilled in the art without departing from the spirit and scope of the present application, and such modifications and changes fall within the scope defined by the appended claims.

Claims

1. An axial flux motor, comprising: A motor housing, the motor housing being surrounded by at least one end cover (3); A stator (1), the stator (1) being arranged inside the motor housing; A rotor (2), one end of the rotor (2) being rotatably disposed in a bearing chamber (5) via a bearing (4), the bearing chamber (5) being disposed inside the motor housing, the other end of the rotor (2) extending from the motor housing, and the rotor (2) being coaxially disposed with the stator (1); The invention is characterized in that the bearing chamber (5) and the end cover (3) are separately provided, the bearing chamber (5) and the end cover (3) are non-conductively connected and at least one first adjustable capacitor (C1) is provided; the stator (1) and the end cover (3) are non-conductively connected and at least one second adjustable capacitor (C2) is provided; The capacitance of the first adjustable capacitor (C1) and the second adjustable capacitor (C2) is adjusted to adjust the ratio of the capacitances of the bridge arms in the motor shaft voltage equivalent circuit.

2. The axial flux motor according to claim 1, characterized in that The bearing chamber (5) and the end cover (3) are separated by a first insulating material layer (6), so that a first regulating capacitor (C1) is formed between the bearing chamber (5) and the end cover (3).

3. The axial flux motor according to claim 2, characterized in that The capacitance of the first regulating capacitor (C1) is adjusted by adjusting the relative area between the bearing chamber (5) and the end cover (3) or the thickness of the first insulating material layer (6) or the material of the first insulating material layer (6).

4. The axial flux motor according to claim 1, characterized in that The stator (1) and the end cover (3) are isolated by a second insulating material layer (7), the stator (1) and the end cover (3) are connected by a fixing screw (9), and the contact portion between the fixing screw (9) and the end cover (3) is separated by an insulating material to form a second regulating capacitor (C2).

5. The axial flux motor according to claim 4, characterized in that The capacitance of the second regulating capacitor (C2) is adjusted by adjusting the relative area between the stator (1) and the end cover (3) or the thickness of the second insulating material layer (7) or the material of the second insulating material layer (7).

6. The axial flux motor according to any one of claims 1 to 5, characterized in that: At least one third adjustment capacitor (C3) is also provided between the stator (1) and the end cover (3), and the ratio of the capacitances of each bridge arm in the motor shaft voltage equivalent circuit is adjusted by adjusting the capacitances of the first adjustable capacitor (C1), the second adjustable capacitor (C2), and the third adjustable capacitor (C3).

7. The axial flux motor according to claim 6, characterized in that The third regulating capacitor (C3) comprises a conductive portion (101) and a third insulating material layer (8), one end of the conductive portion (101) is connected to the outer side wall of the stator (1), and the other end of the conductive portion (101) is connected to the inner side wall of the end cover (3) through the third insulating material layer (8).

8. The axial flux motor according to claim 7, characterized in that The capacitance of the third adjustment capacitor (C3) is adjusted by adjusting the relative area between the conductive portion (101) and the end cover (3) or the thickness of the third insulating material layer (8) or the material of the third insulating material layer (8).

9. The axial flux motor according to claim 6, characterized in that The third adjustment capacitor (C3) is a replaceable capacitor.

10. The axial flux motor according to claim 6, characterized in that The first adjustable capacitor (C1), the second adjustable capacitor (C2), and the third adjustable capacitor (C3) are adjusted individually or in combination to change the capacitance ratio of the shaft voltage equivalent bridge arm so that the bearing partial pressure approaches zero.

11. A method for limiting shaft voltage and improving bearing electrocorrosion, characterized in that: The method is applied to the axial flux motor according to any one of claims 1 to 10, comprising the following steps: At least one first adjustable capacitor (C1) is provided between the bearing chamber (5) and the end cover (3), so that the bearing chamber (5) and the end cover (3) form a non-conductive connection; At least one second adjustable capacitor (C2) is provided between the stator (1) and the end cover (3), so that the stator (1) and the end cover (3) form a non-conductive connection; The capacitance values ​​of the first adjustable capacitor (C1) and the second adjustable capacitor (C2) are adjusted to adjust the ratio of the capacitances of each bridge arm in the motor shaft voltage equivalent Wheatstone bridge arm circuit, thereby reducing the shaft voltage at both ends of the bearing (4) and making the shaft voltage approach zero, thereby reducing the risk of electrical corrosion of the bearing (4).

12. The method for limiting shaft voltage and improving bearing electro-corrosion according to claim 11, characterized in that: Also includes: At least one third adjustable capacitor (C3) is provided between the stator (1) and the end cover (3); one end of the third adjustable capacitor (C3) is conductively connected to the stator (1), and the other end is opposite to the end cover (3) via a third insulating material layer (8); by adjusting the capacitance of the third adjustable capacitor (C3), in conjunction with the first adjustable capacitor (C1) and the second adjustable capacitor (C2), the ratio of each bridge arm capacitance in the motor shaft voltage equivalent circuit is further adjusted, so that the ratio of each bridge arm capacitance approaches balance.

13. The method for limiting shaft voltage and improving bearing electro-corrosion according to claim 12, characterized in that: The method of making the ratio of the capacitances of the bridge arms close to balance is specifically as follows: The capacitance ratio of the opposite bridge arms of the Wheatstone bridge structure in the motor shaft voltage equivalent circuit satisfies Cfirst bridge arm / Csecond bridge arm=Cthird bridge arm / Cfourth bridge arm, thereby reducing the shaft voltage at both ends of the bearing to below a preset threshold.

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