Motor

Abstract

The present disclosure provides a motor. The motor comprises: a housing; and a stator accommodated in the housing. The stator comprises: a stator core, the stator core being provided with a plurality of winding slots extending therethrough in an axial direction, each winding slot being circumferentially defined by a pair of sidewalls, and a liquid intake chamber and a liquid collection chamber located on two sides of the stator core in the axial direction being defined within the housing; and a stator winding, the stator winding comprising a plurality of wire groups, each wire group consisting of a plurality of wires inserted in one winding slot in the axial direction and stacked in the radial direction, each wire having a wave shape, so that each wire has a crest close to one sidewall and a trough close to the other sidewall, and the wave shapes of at least two adjacent wires differing from each other in at least one of phase, amplitude, and frequency.

Description

Electric machine TECHNICAL FIELD

[0001] The present disclosure relates to the field of electric machines, and more particularly, to an electric machine with improved liquid cooling design. BACKGROUND

[0002] With the rapid development of electric machines, the power density and lightweight of electric machines are increasingly concerned by people. However, the heat dissipation problem of electric machines has become the main factor restricting the further improvement of the power density of electric machines. Taking the common permanent magnet synchronous type motor as an example, the stator winding generates a rotating magnetic field after passing through an alternating current, and the rotating magnetic field is coupled with the permanent magnet on the rotor, thereby driving the rotor to rotate. However, at the same time, the rotating magnetic field generates eddy currents in the rotor core and the stator core, thereby causing the rotor core and the stator core to heat up, and the alternating current causes the stator winding to heat up, in which the stator winding generates the most heat and is the most difficult to dissipate. In order to improve the power of the motor, a larger alternating current needs to be passed through the stator winding, but the heat generated by the stator core, the stator winding and the rotor core will also increase. If these heat cannot be effectively dissipated, it may cause the service life of the motor to be shortened, and even cause the motor to overheat and burn out. In the prior art, various cooling schemes to help the motor dissipate heat have appeared, including arranging the stator core in a water jacket, machining a cooling liquid channel in the stator core, etc., but these cooling schemes cannot effectively help the stator winding, especially the part of the stator winding in the winding slot, to dissipate heat.

[0003] Therefore, in the field, there is an urgent need for a technical solution that can help the motor to effectively dissipate heat, especially the part of the winding in the winding slot. SUMMARY

[0004] In order to solve the above problems in the prior art, the present disclosure proposes an improved electric machine, which comprises: a housing; and a stator contained in the housing, the stator comprising: a stator core provided with a plurality of winding slots extending through in the axial direction, wherein each winding slot is defined by a pair of side walls in the circumferential direction, and wherein a liquid inlet cavity and a liquid collection cavity are defined in the housing on both sides of the stator core in the axial direction; and a stator winding comprising a plurality of wire groups, wherein each wire group is composed of a plurality of wires inserted into one winding slot in the axial direction and stacked in the radial direction, wherein each wire is in a wave shape, so that each wire has a wave crest close to one side wall and a wave trough close to the other side wall, and wherein the wave shapes of at least two adjacent wires are different from each other in at least one of phase, amplitude and frequency.

[0005] The present disclosure can be embodied as the illustrative embodiments in the accompanying drawings. However, it should be noted that the accompanying drawings are merely illustrative, and any variations envisaged under the teachings of the present disclosure should be considered to be within the scope of the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0006] The accompanying drawings illustrate exemplary embodiments of the present disclosure. These drawings should not necessarily be construed as limiting the scope of the present disclosure, wherein:

[0007] FIG. 1 is a schematic perspective sectional view of an electric machine according to an embodiment of the present disclosure;

[0008] FIG. 2 is a schematic perspective view of a portion of a stator of the electric machine shown in FIG. 1;

[0009] FIG. 3 is a schematic top view of a portion of the stator of the electric machine shown in FIG. 1;

[0010] FIG. 4 is a schematic perspective view of a wire set of a stator winding of the stator of the electric machine shown in FIG. 1;

[0011] FIGS. 5a-5d are schematic sectional views of the stator portion taken along the line A-A in FIG. 3, in which two adjacent wires are configured in four different ways;

[0012] FIG. 6 is a schematic perspective view of an isolation cylinder of the electric machine shown in FIG. 1; and

[0013] FIG. 7 is a schematic perspective view and a partial enlarged view of the isolation cylinder and the stator core of the electric machine shown in FIG. 1. DETAILED DESCRIPTION

[0014] Further features and advantages of the present disclosure will become more apparent from the following description with reference to the accompanying drawings. In the drawings, exemplary embodiments of the present disclosure are illustrated, and each of the drawings is not necessarily drawn to scale. However, the present disclosure can be embodied in many different forms and should not be construed as necessarily being limited to the exemplary embodiments of the disclosure shown herein. Rather, these exemplary embodiments are merely provided for the purpose of illustrating the present disclosure and conveying the spirit and substance of the present disclosure to those skilled in the art.

[0015] The present disclosure aims to provide an electric machine with a novel liquid cooling design that not only enables the cooling liquid to directly contact the stator core of the electric machine, but also enables the cooling liquid to directly contact the stator winding of the electric machine. Therefore, the liquid cooling design according to the present disclosure enables both the stator core and the stator winding to be effectively cooled, thereby enabling the service life of the electric machine to be prolonged and the performance of the electric machine to be improved, especially the performance of the electric machine in terms of acceleration and top speed power. In particular, the liquid cooling design according to the present disclosure also enables the cooling liquid to flow through each winding slot in the stator core, so that the cooling liquid can directly contact the conductors of the stator winding within each winding slot. Therefore, the liquid cooling design according to the present disclosure enables the conductors of the stator winding within each winding slot to be effectively cooled, thereby realizing in-slot direct cooling of the stator winding. More particularly, the liquid cooling design according to the present disclosure also enables the cooling liquid to directly contact each conductor of the stator winding within each winding slot, thereby realizing in-slot direct cooling of each conductor, which form of in-slot direct cooling apparently helps the stator winding to achieve the most effective cooling. In addition, the liquid cooling design according to the present disclosure also enables the stator cavity to be reliably isolated from the rotor cavity, so as to avoid the cooling liquid entering the rotor cavity to increase the rotation resistance of the rotor. Therefore, in addition to various advantages in terms of cooling, the liquid cooling design according to the present disclosure also enables the working efficiency and reliability of the electric machine to be maintained.

[0016] Various alternative but non-limiting embodiments of the electric machine according to the present disclosure are described in detail below with reference to the various drawings. As used herein, the term "axial" refers to a direction parallel to or defined by the rotational axis of the electric machine, "radial" refers to a direction perpendicular to the rotational axis of the electric machine, and "circumferential" refers to a direction encircling the rotational axis of the electric machine, unless explicitly stated otherwise herein, these and other terms indicating orientation have their usual meaning in the art.

[0017] Referring to FIG. 1, a schematic perspective cross-sectional view of an electric machine is shown according to an embodiment of the present disclosure. As shown in FIG. 1, the electric machine 10 generally comprises a housing 100, and a stator 200 and a rotor 300 disposed within the housing 100, wherein the stator 200 can comprise a stator core 210 and stator windings 220 disposed on the stator core 210, and the rotor 300 can comprise a rotor core 310 and a plurality of permanent magnets (not shown) disposed on the rotor core 310. Specifically, the housing 100 defines, internally, a stator cavity 101 and a rotor cavity 102, which are preferably isolated from each other, wherein the stator 200 is fixedly disposed within the stator cavity 101, and the rotor 300 is rotatably disposed within the rotor cavity 102. In particular, in the embodiment shown in FIG. 1, the rotor cavity 102 is a cylindrical chamber, and the stator cavity 101 is an annular chamber that surrounds the rotor cavity 102 radially outwardly of the rotor cavity 102 and is isolated from the rotor cavity 102. In this configuration, the rotor 300 is disposed radially inwardly of the stator 200, such that the electric machine 10 is configured as an inner rotor type electric machine, but this is not necessarily the case, and those skilled in the art will appreciate that the liquid cooling design according to the present disclosure is equally applicable to an outer rotor type electric machine upon understanding the teachings of the present disclosure. In the case where the electric machine 10 is configured as an outer rotor type electric machine, the stator cavity 101 is a cylindrical chamber, and the rotor cavity 102 is an annular chamber that is located radially outwardly of the stator cavity 101 and surrounds the stator cavity 101, and the rotor 300 is arranged to surround the stator 200 radially outwardly of the stator 200. Therefore, the specific type of the electric machine 10 cannot constitute a limitation to the scope of protection of the present disclosure.

[0018] Taking the electric machine 10 as an example of a permanent magnet synchronous type electric motor, in operation, the stator windings 220 are supplied with an alternating current, thereby generating a rotating magnetic field that rotates around the rotation axis XX’ and is magnetically coupled with the plurality of permanent magnets on the rotor core 310 under the guidance of the stator core 210, thereby driving the rotor core 310 to rotate around the rotation axis XX’, thus achieving the conversion of electric energy to mechanical energy. However, due to the eddy current induced in the stator core 210 and the rotor core 310 by the rotating magnetic field, the alternating current passing through the stator windings 220, and the like, the stator core 210, the stator windings 220, and the rotor core 310 all generate heat during the conversion of electric energy to mechanical energy, among which the stator windings 220 generate the most heat and are the most difficult to dissipate, and whether the stator windings 220 can be effectively cooled or not even directly affects the service life and performance of the electric machine.

[0019] In order to achieve effective heat dissipation of the stator core 210 and the stator winding 220, the motor 10 has an improved liquid cooling design. Specifically, as shown in FIG. 1, the stator core 210 has a front end face 211 and a rear end face 212 opposite to each other along the axial direction, and occupies the middle portion of the stator cavity 101, so that the stator cavity 101 is divided into a liquid inlet cavity 101i and a liquid collection cavity 101c located on both sides of the stator core 210 along the axial direction, that is, the portions of the stator cavity 101 located on both sides of the stator core 210 along the axial direction and not occupied by the stator core 210 form the liquid inlet cavity 101i and the liquid collection cavity 101c, wherein the front end face 211 of the stator core 210 faces the liquid inlet cavity 101i, and the rear end face 212 of the stator core 210 faces the liquid collection cavity 101c. In particular, in the embodiment shown in FIG. 1, the liquid inlet cavity 101i and the liquid collection cavity 101c are both annular chambers located radially outside the rotor cavity 102 and surrounding the rotor cavity 102.

[0020] As shown in FIG. 1, the housing 100 is provided with a liquid inlet pipe 103 and a liquid outlet pipe 104 on its outer surface, wherein the liquid inlet pipe 103 internally defines a pipe cavity leading to the liquid inlet cavity 101i, and the liquid outlet pipe 104 internally defines a pipe cavity leading to the liquid collection cavity 101c. In this configuration, the coolant from outside (e.g., a coolant pump) can be delivered into the liquid inlet cavity 101i through the liquid inlet pipe 103. In addition, as will be described in detail below, both ends of each winding slot of the stator core 210 lead to the liquid inlet cavity 101i and the liquid collection cavity 101c, respectively, and an intra-slot path allowing the coolant to flow through is formed in each winding slot, thereby enabling the coolant in the liquid inlet cavity 101i to flow through the intra-slot path in each winding slot to the liquid collection cavity 101c and be collected in the liquid collection cavity 101c, and the coolant collected in the liquid collection cavity 101c can be discharged to outside (e.g., back to the coolant pump) through the liquid outlet pipe 104. In this configuration, since the stator core 210 separates the liquid inlet cavity 101i and the liquid collection cavity 101c from each other, the liquid inlet cavity 101i and the liquid collection cavity 101c can only be in fluid communication with each other through the intra-slot path in each winding slot of the stator core 210, thereby enabling the flow path of the coolant in the motor 10 to be defined from the liquid inlet cavity 101i to the liquid collection cavity 101c through the intra-slot path in each winding slot, which enables the coolant to facilitate heat dissipation of both the stator core 210 and the stator winding 220, in particular, in each winding slot, thereby achieving effective heat dissipation of the stator core 210 and the stator winding 220. In particular, the positions of the liquid inlet pipe 103 and the liquid outlet pipe 104 are diametrically opposite or opposite to each other when viewed along the axial direction, that is, the position of the liquid inlet pipe 103 and the position of the liquid outlet pipe 104 are offset by an angle of about 180 degrees relative to each other about the rotation axis XX’. In this configuration, the liquid inlet pipe 103 and the liquid outlet pipe 104 are disposed on opposite sides rather than the same side of the rotation axis XX’, which helps to ensure the balance of pressure and flow of the coolant in the liquid inlet cavity 101i and the liquid collection cavity 101c, in particular, in each winding slot, thereby further ensuring effective heat dissipation of both the stator core 210 and the stator winding 220.

[0021] As shown in FIG. 1, the stator core 210 is provided with a plurality of wire slots 213 uniformly distributed around the rotation axis XX’ (i.e., along the circumferential direction) on the side facing the rotor 300. Each of these wire slots 213 extends along the axial direction between the front end face 211 and the rear end face 212 of the stator core 210 so as to extend through the stator core 210, so that each wire slot 213 has a front end portion and a rear end portion spaced apart along the axial direction, wherein the front end portion of each wire slot 213 opens into the liquid inlet cavity 101i at the front end face 211 of the stator core 210, and the rear end portion of each wire slot 213 opens into the liquid collection cavity 101c at the rear end face 212 of the stator core 210. In this configuration, the cooling liquid in the liquid inlet cavity 101i can flow into each wire slot 213 through the front end portion of each wire slot 213 and be discharged into the liquid collection cavity 101c through the rear end portion of each wire slot 213. In particular, in the embodiment shown in FIGS. 1-3, these wire slots 213 are arranged on the radially inner side of the stator core 210.

[0022] As shown in FIG. 1, the stator winding 220 includes two winding heads (i.e., the front winding head 221 located in the liquid inlet cavity 101i and the rear winding head 222 located in the liquid collection cavity 101c) spaced apart from each other along the axial direction, and a plurality of wire groups 223 connecting these two winding heads, wherein each wire group 223 is inserted into one wire slot 213, in other words, each wire slot 213 is provided with one wire group 223. In this configuration, in addition to facilitating heat dissipation of the stator core 210, the cooling liquid in the liquid inlet cavity 101i can also facilitate heat dissipation of the front winding head 221 of the stator winding 220, the cooling liquid in the liquid collection cavity 101c can also facilitate heat dissipation of the rear winding head 222 of the stator winding 220, and the cooling liquid flowing through each wire slot 213 can also facilitate heat dissipation of each wire group 223, thereby achieving effective heat dissipation of the entire stator winding 220.

[0023] As described previously, in order to allow the coolant to flow through each slot 213, an in-slot path that allows the coolant to flow therethrough is formed within each slot 213. The in-slot path is described below with reference to one slot 213 and one wire set 223 within the slot 213, but it will be understood by those skilled in the art that the descriptions apply to each slot 213 and each wire set 223 therein. Referring to FIGS. 2-4, wherein FIG. 2 shows a schematic perspective view of a portion of the stator of the electric machine shown in FIG. 1, FIG. 3 shows a schematic top view of a portion of the stator of the electric machine shown in FIG. 1, and FIG. 4 shows a schematic perspective view of a wire set of the stator winding of the stator of the electric machine shown in FIG. 1. As shown in FIGS. 2 and 3, the slot 213 includes a pair of side walls 213s opposite each other along a circumferential direction and a bottom wall 213b connecting the pair of side walls 213s, in other words, the slot 213 is defined by the pair of side walls 213s in the circumferential direction and terminates in the radial direction at the bottom wall 213b, wherein the pair of side walls 213s and the bottom wall 213b both extend along the axial direction between the front end face 211 and the rear end face 212 of the stator core 210, such that the slot 213 extends through the stator core 210 along the axial direction. The wire set 223 is composed of a plurality of wires 223w stacked in the slot 213 along the radial direction. In particular, in the embodiment shown in FIGS. 1-4, each wire set 223 is composed of four wires 223w, and each wire 223w is a flat wire, such that the electric machine 10 is configured as a flat wire electric machine.

[0024] As shown in FIGS. 3 and 4, each wire 223w is shaped to have a wave shape (e.g., a sinusoidal shape) extending along the axial direction, and each wire 223w is positioned such that its wave shape has a wave peak (e.g., one or more wave peaks) close to one sidewall 213s of the winding slot 213 and a wave valley (e.g., one or more wave valleys) close to the other sidewall 213s of the winding slot 213. That is, each wire 223w extends in a wave shape between the pair of sidewalls 213s of the winding slot 213 along the axial direction. In this configuration, since each wire 223w extends in a wave shape between the pair of sidewalls 213s of the winding slot 213, a plurality of voids (referred to as first voids for clarity in the following) are defined or left between each wire 223w and any sidewall 213s. Further, as shown in FIGS. 3 and 4, the wave shape of each wire 223w is different from the wave shape of an adjacent wire 223w in at least one of phase, amplitude, and frequency, that is, the wave shape of any two adjacent wires 223w is different from each other in at least one of phase, amplitude, and frequency. In this configuration, since any two adjacent wires 223w are different in phase, amplitude, and / or frequency, any two adjacent wires 223w are staggered with respect to each other, thereby defining or leaving a plurality of voids (referred to as second voids for clarity in the following) between them, which can be in fluid communication with the plurality of first voids between the wires 223w and the sidewalls 213s, thereby combining the plurality of first voids and the plurality of second voids to form an intra-slot path allowing the coolant to flow through the winding slot 213. It is worth mentioning that the intra-slot path formed in the above-described manner is meandering since the first voids and the second voids are arranged alternately, which causes the coolant to flow alternately between the wires 223w and the sidewalls 213s and between the wires 223w and the adjacent wires 223w. In this configuration, the coolant not only facilitates heat dissipation of the stator core 210 within the winding slot 213, but also contacts each wire 223w in the wire set 223 within the winding slot 213, thereby facilitating heat dissipation of each wire 223w within the winding slot 213, which realizes more effective heat dissipation of the stator winding 220. In addition, this configuration also makes it unnecessary to provide a channel dedicated for the coolant to flow within the winding slot 213, thereby helping to maintain the slot fill factor (also referred to as the copper fill factor).

[0025] The four exemplary ways of forming the in-slot path are described in more detail below in connection with Figs. 5a-5d. Referring to Figs. 5a-5d, there are shown schematic cross-sectional views of the stator portion taken along the line A-A in Fig. 3, in which two adjacent conductive wires 223w are configured in four different ways, and for the sake of clarity, one of the conductive wires 223w is shown in dashed line and the other conductive wire 223w is shown in solid line. It is noted, however, that the description below with respect to the two adjacent conductive wires 223w applies equally to all other adjacent conductive wires 223w.

[0026] As shown in Fig. 5a, the wave shapes of the two conductive wires 223w are identical in amplitude and frequency but different in phase, such that the two conductive wires 223w appear to be staggered relative to each other along the axial direction. As a result, a plurality of first gaps Gl is formed between each of the conductive wires 223w and each of the side walls 213s, and a plurality of second gaps G2 is formed between the two conductive wires 223w, both of which are arranged along the axial direction, and adjacent first and second gaps Gl, G2 are in fluid communication, whereby the plurality of first gaps Gl together with the plurality of second gaps G2 make up the in-slot path that allows the coolant to flow through the wire slot 213. In this configuration, since the first and second gaps Gl, G2 are alternately arranged, the in-slot path is configured to have a serpentine shape, and the coolant is able to flow alternately between the conductive wires 223w and the side walls 213s and between the two conductive wires 223w along the in-slot path.

[0027] As shown in Fig. 5b, the wave shapes of the two conductive wires 223w are identical in phase and frequency but different in amplitude, such that the two conductive wires 223w appear to be staggered relative to each other along the circumferential direction. As a result, a plurality of first gaps Gl is formed between each of the conductive wires 223w and each of the side walls 213s, and a plurality of second gaps G2 is formed between the two conductive wires 223w, both of which are arranged along the axial direction, and adjacent first and second gaps Gl, G2 are in fluid communication, whereby the plurality of first gaps Gl together with the plurality of second gaps G2 make up the in-slot path that allows the coolant to flow through the wire slot 213. In this configuration, since the first and second gaps Gl, G2 are also alternately arranged, the coolant is able to flow alternately between the conductive wires 223w and the side walls 213s and between the two conductive wires 223w along the in-slot path.

[0028] As shown in FIG. 5c, the waveforms of the two wires 223w are identical in amplitude but different in frequency (different frequencies result in non-comparable phases, so the phases are no longer compared in this embodiment) so that the two wires 223w appear to be staggered relative to each other along the axial and circumferential directions. Thus, a plurality of first gaps G1 arranged along the axial direction are formed between each wire 223w and each side wall 213s, while a plurality of second gaps G2 also arranged along the axial direction are formed between the two wires 223w, and adjacent first and second gaps G1, G2 are in fluid communication, whereby the plurality of first gaps G1 together with the plurality of second gaps G2 make up a gap-internal passage that allows the coolant to flow through the wire slot 213. In this configuration, since the first and second gaps G1, G2 are also alternately arranged, the coolant is able to flow alternately between the wires 223w and the side walls 213s and between the two wires 223w along the gap-internal passage.

[0029] As shown in FIG. 5d, similar to the embodiment in FIG. 5a, the waveforms of the two wires 223w are identical in amplitude and frequency but different in phase so that the two wires 223w appear to be staggered relative to each other along the axial direction. However, unlike the embodiment in FIG. 5a, in FIG. 5d, the waveforms of the two wires 223w differ in phase by half of their period so that the peaks and troughs of the waveform of one wire 223w are aligned or aligned with the troughs and peaks, respectively, of the waveform of the other wire 223w. Thus, a plurality of first gaps G1 arranged along the axial direction and substantially uniform in size are formed between each wire 223w and each side wall 213s, while a plurality of second gaps G2 also arranged along the axial direction and substantially uniform in size are formed between the two wires 223w, whereby not only do the plurality of first gaps G1 together with the plurality of second gaps G2 make up a gap-internal passage that allows the coolant to flow through the wire slot 213, but also the flow area of the gap-internal passage is substantially uniform everywhere as much as possible. In this configuration, not only is the coolant able to flow alternately between the wires 223w and the side walls 213s and between the two wires 223w along the gap-internal passage, but also the coolant is able to flow stably along the gap-internal passage.

[0030] The above description made with reference to FIGS. 5a-5d can help one skilled in the art to more easily understand that the liquid cooling design according to the present disclosure enables the cooling liquid to both facilitate heat dissipation of the stator core 210 and facilitate heat dissipation of each wire 223w within the slot 213. In particular, through the embodiment shown in FIG. 5d, it is also possible to ensure that the cooling liquid stably flows through the slot 213, thereby further improving heat dissipation of the stator core 210 and each wire 223w. In particular, in addition to the embodiments in FIGS. 5a, 5c and 5d, the amplitude of the wave shape of each wire 223w is configured such that the wave peaks of the wave shape abut against one side wall 213s and the wave troughs of the wave shape abut against the other side wall 213s. In this configuration, each wire 223w is spaced apart from the respective first gaps G1 between the wire 223w and the side wall 213s, resulting in the first gaps G1 having to pass through the respective second gaps G2 to be in fluid communication, thereby enabling the cooling liquid to be forced to flow through the respective second gaps G2 in order to dissipate heat from each wire 223w. Thus, this configuration further ensures effective heat dissipation from each wire 223w. In addition, this configuration also enables each wire 223w to be more reliably positioned within the slot 213 and enables an improved slot fill factor (also referred to as copper fill factor). However, it is noted that the term “abut” used herein does not necessarily equate to “direct contact”, for example, as shown in FIG. 3, the insulation paper 230 can be wrapped around the outside of each wire group 223, which can also be inserted into the slot 213 in order to provide additional insulation between the wire group 223 and the stator core 210 and to protect the wires 223w from damage when inserted into the slot 213. In the embodiment shown in FIG. 3, the wires 223w abut against the side walls 213s of the slot 213 through the insulation paper 230.

[0031] Returning to FIG. 1, the housing 100 includes a substantially cylindrical housing main body 110, and a front end cover 120 and a rear end cover 130 connected to both ends of the housing main body 110 along the axial direction, such that the front end cover 120 and the rear end cover 130 are opposite and spaced apart from each other along the axial direction, and the housing main body 110, together with the front end cover 120 and the rear end cover 130, defines a housing cavity 100c inside the housing 100. In addition, the motor 10 further includes an isolation cylinder 400 located in the housing cavity 100c of the housing 100 and arranged between the stator 200 and the rotor 300, and both ends of the isolation cylinder 400 are connected to the front end cover 120 and the rear end cover 130, respectively (e.g., in a sealed manner), so that the housing cavity 100c is divided by the isolation cylinder 400 into a stator cavity 101 and a rotor cavity 102 located on both sides of the isolation cylinder 400 along the radial direction. In particular, in the embodiment shown in FIG. 1, the stator cavity 101 and the stator 200 are located radially outside the isolation cylinder 400, while the rotor cavity 102 and the rotor 300 are located radially inside the isolation cylinder 400. In this configuration, the isolation cylinder 400 can reliably isolate the stator cavity 101 and the rotor cavity 102 from each other, thereby preventing the cooling liquid in the stator cavity 101 from flowing into the rotor cavity 102 to avoid the cooling liquid increasing the rotational resistance of the rotor 300, thereby improving the operating efficiency of the motor 10. In particular, the isolation cylinder 400 is configured to abut against the stator core 210 and be spaced apart from the rotor 300, thereby eliminating the gap between the isolation cylinder 400 and the stator core 210 and retaining the gap between the isolation cylinder 400 and the rotor 300. In this configuration, the cooling liquid can be prevented from passing through the gap between the isolation cylinder 400 and the stator core 210, thereby maintaining the flow rate of the cooling liquid through each winding slot 213, and the rotor 300 can be prevented from rubbing against the isolation cylinder 400 when rotating.

[0032] Although the embodiment of isolating the stator cavity 101 and the rotor cavity 102 by the isolation cylinder 400 is described above, this is not necessarily the case, and in other embodiments, the stator cavity 101 and the rotor cavity 102 can be isolated from each other in other ways, or need not be isolated from each other. For example, in an embodiment not shown, the stator cavity 101 and the rotor cavity 102 are in fluid communication with each other, such that the liquid inlet cavity 101i and the liquid collection cavity 101c are formed by the portions of the housing cavity 100c located on both sides of the stator 200 and the rotor 300 along the axial direction. In this configuration, the cooling liquid, although it can increase the rotational resistance of the rotor 300, can at the same time promote heat dissipation of the rotor 300, and at the same time, since the cross section of the air gap between the stator 200 and the rotor 300 is small, the cooling liquid still mainly flows from the liquid inlet cavity 101i to the liquid collection cavity 101c through each winding slot 213.

[0033] Referring to FIGS. 6 and 7, wherein FIG. 6 shows a schematic perspective view of the isolation cylinder of the electric machine shown in FIG. 1, and FIG. 7 shows a schematic perspective view and a partial enlarged view of the isolation cylinder and the stator core of the electric machine shown in FIG. 1. As shown in FIGS. 6 and 7, the isolation cylinder 400 includes a cylinder body 410 connected to the front end cover 120 and the rear end cover 130 and substantially in a cylindrical shape, and a plurality of positioning teeth 420 protruding from the cylinder body 410 along a radial direction, each of the positioning teeth 420 extending along an axial direction and arranged along a circumferential direction, and each of the positioning teeth 420 has a wedge-shaped or dovetail-shaped cross section that widens away from the cylinder body 410, as best shown in the partial enlarged view in FIG. 7. As shown in FIG. 7, the stator core 210 is further provided with a plurality of pole shoe gaps 214 on a side facing the rotor 300, each of the pole shoe gaps 214 extending through the stator core 210 along the axial direction, and each of the pole shoe gaps 214 leads to a winding slot 213 along the radial direction, that is, each of the winding slots 213 leads to a radial side surface of the stator core 210 through a pole shoe gap 214, thereby being configured as a half-open slot (also referred to as a half-closed slot). In addition, as shown in the partial enlarged view in FIG. 7, each of the pole shoe gaps 214 has a wedge-shaped or dovetail-shaped cross section that widens close to the winding slot 213, and each of the positioning teeth 420 is inserted into a pole shoe gap 214 along the axial direction. In assembly, the isolation cylinder 400 and the stator core 210 can be assembled together by aligning and inserting each of the positioning teeth 420 into a corresponding pole shoe gap 214 along the axial direction. In this configuration, due to the cooperation of the positioning teeth 420 and the pole shoe gaps 214, the stator core 210 can apply a pulling force along the radial direction to the cylinder body 410 through the plurality of positioning teeth 420, so that the stator core 210 can help maintain the shape of the cylinder body 410, which helps to ensure that the gap between the cylinder body 410 and the stator core 210 is eliminated and the gap between the cylinder body 410 and the rotor 300 is maintained. Of course, the wedge-shaped or dovetail-shaped shape described above is only exemplary, and the positioning teeth 420 and the pole shoe gaps 214 can also be cooperated in other ways (for example, shape cooperation or force cooperation) to prevent the positioning teeth 420 from moving towards the rotor 300, thereby maintaining the gap between the cylinder body 410 and the rotor 300.

[0034] In particular, in the embodiment shown in FIGS. 1-7, the plurality of positioning teeth 420 are disposed radially outward of the cylinder 410, and the plurality of pole shoe gaps 214 are disposed radially inward of the stator core 210 so as to communicate each winding slot 213 with the radially inner side of the stator core 210. In addition, the plurality of positioning teeth 420 can be uniformly distributed along the circumferential direction on the cylinder 410, thereby enabling the stator core 210 to more reliably maintain the shape of the cylinder 410. In addition, the number of positioning teeth 420 can be less than the number of pole shoe gaps 214, thereby enabling the assembly of the spacer cylinder 400 with the stator core 210 to be more easy. In addition, the length of the positioning teeth 420 along the axial direction can be greater than or equal to the length of the stator core 210 along the axial direction, thereby enabling the stator core 210 to maintain the shape of the cylinder 410 over its entire axial length.

[0035] The above detailed description of the alternative but non-limiting embodiments of the electric machine according to the present disclosure has been made with the aid of the drawings. Modifications and additions to the techniques and structures, as well as re-combinations of features in the various embodiments, will be apparent to those of ordinary skill in the art without departing from the spirit and essence of the present disclosure. Such modifications and additions, as well as re-combinations of features in the various embodiments, are therefore to be construed as falling within the scope of the present disclosure. The scope of the present disclosure includes equivalent technologies known at the time of the filing date of the present disclosure and equivalent technologies not yet foreseen.

Claims

1. An electric machine, the electric machine (10) comprising: a housing (100); and a stator (200) housed within the housing (100), the stator (200) comprising: a stator core (210) provided with a plurality of wire slots (213) extending through in an axial direction, wherein each wire slot (213) is defined in a circumferential direction by a pair of side walls (213s), and wherein a liquid inlet cavity (101i) and a liquid collection cavity (101c) are defined within the housing (100) on both sides of the stator core (210) in the axial direction; and a stator winding (220) comprising a plurality of wire groups (223), wherein each wire group (223) is composed of a plurality of wires (223w) inserted in one wire slot (213) in the axial direction and stacked in a radial direction, wherein each wire (223w) is wavy such that each wire (223w) has a wave crest proximate to one side wall (213s) and a wave trough proximate to the other side wall (213s), and wherein the wave shapes of at least two adjacent wires (223w) differ from each other in at least one of a phase, an amplitude, and a frequency. The wave shapes of the at least two adjacent wires (223w) are the same in the amplitude and the frequency, and different in the phase.

2. The electric machine of claim 1, wherein, The wave shapes of the at least two adjacent wires (223w) are the same in the amplitude and the frequency, and different in the phase by half a period.

3. The electric machine of claim 2, wherein, The wave shapes of the at least two adjacent wires (223w) are the same in the amplitude, and different in the frequency.

4. The electric machine of claim 1, wherein, Each wire (223w) has a wave crest against one side wall (213s) and a wave trough against the other side wall (213s).

5. The electric machine of any of claims 2-4, wherein, The wave shapes of the at least two adjacent wires (223w) are the same in the frequency and the phase, and different in the amplitude.

6. The electric machine of claim 1, wherein, The stator winding (220) further comprises a front winding head (221) housed within the liquid inlet cavity (101i) and a rear winding head (222) housed within the liquid collection cavity (101c), and wherein the front winding head (221) and the rear winding head (222) are connected by the plurality of wire groups (223).

7. The electric machine of any of claims 1-6, wherein, The housing (100) defines a housing cavity (100c) inside, and the electric machine (10) further comprises a rotor (300) and a barrier cylinder (400) housed within the housing cavity (100c) and connected to the housing (100) to separate the housing cavity (100c) into a stator cavity (101) for housing the stator (200) and a rotor cavity (102) for housing the rotor (300).

8. The electric machine of any of claims 1-7, wherein, The stator cavity (101) is separated by the stator core (210) into the liquid inlet cavity (101i) and the liquid collection cavity (101c).

9. The electric machine of claim 8, wherein, The barrier cylinder (400) is configured to abut against the stator core (210) and be spaced apart from the rotor (300).

10. The electric machine of claim 8 or 9, wherein, ​ 11. The electric machine of any of claims 8-10, wherein, The isolation cylinder (400) comprises a cylinder body (410) connected to the shell (100) and a plurality of positioning teeth (420) protruding radially from the cylinder body (410) and extending axially, the stator core (210) is also provided with a plurality of pole shoe gaps (214) extending axially, and wherein each positioning tooth (420) is inserted into and cooperates with one pole shoe gap (214) to prevent the positioning tooth (420) from moving towards the rotor (300).

12. The motor of claim 11, wherein, The plurality of positioning teeth (420) are uniformly distributed circumferentially on the cylinder body (410); and / or The number of positioning teeth (420) of the isolation cylinder (400) is less than the number of pole shoe gaps (214) of the stator core (210); and / or, The axial length of each positioning tooth (420) is greater than or equal to the axial length of the stator core (210).

13. The electric machine of any of claims 1-12, wherein, The shell (100) is provided with a liquid inlet pipe (103) leading to the liquid inlet cavity (101i) and a liquid outlet pipe (104) leading to the liquid collection cavity (101c) on its outer surface.

14. The electric machine of claim 13, wherein, The liquid inlet pipe (103) and the liquid outlet pipe (104) are arranged on opposite sides of the rotation axis (XX') of the motor (10).

15. The electric machine of any of claims 1-14, wherein, The outer periphery of each wire group (223) is wrapped with insulating paper (230).

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