Stator of electric motor comprising a system for cooling the teeth

Abstract

The invention relates to a stator of an electric motor comprising teeth (4) and coils mounted on the teeth (4), the stator further comprising a system for cooling the stator with a heat-transfer fluid and at least one opening (5) passing through the tooth (4) so as to allow at least some of the heat-transfer fluid to pass through the tooth (4).

Description

Electric motor stator with tooth cooling system

[0001] The present invention relates to an electric motor stator comprising a tooth cooling system.

[0002] The present invention finds an advantageous but non-limiting application for an electromagnetic motor delivering high power with a high rotor rotation speed. Such a motor or generator can be used, for example, as an electromagnetic motor or generator in a fully electric or hybrid motor vehicle.

[0003] Advantageously but not limited to, the electromagnetic motor or generator may comprise at least one rotor framed by two stators, these elements being able to be superimposed on each other while being separated by at least one air gap on the same shaft.

[0004] In high-speed applications, it is necessary to have not only a compact system made possible by reducing the mass and size of the motor for optimal efficiency, but also very good mechanical strength of the rotating part, i.e. the rotor(s), in order to improve the reliability of the system. It is therefore necessary to reduce losses for optimal efficiency.

[0005] These losses can occur in the rotor(s) of the electric motor or in the stator(s). With respect to rotors, eddy current losses in magnets have been significantly reduced, notably by proposing ironless rotors or by proposing magnet poles consisting of a plurality of small unit magnets.

[0006] The main losses are now the Joule effect losses in the stator coils as well as the magnetic losses in the stator iron.

[0007] Heating therefore occurs mainly in the stators of electric motors and must be reduced as effectively as possible.

[0008] Various solutions exist, for example, circulation of heat transfer fluid in a circuit machined in the electric motor housing or circulation of oil at the level of the coil heads. Thus, a stator is known comprising a system for cooling the coils using oil as heat transfer fluid.

[0009] However, such solutions do not allow cooling the iron of the stators which are not in contact with the fluid.

[0010] The problem underlying the present invention is thus to optimally cool a stator and in particular the irons of said stator.

[0011] To this end, the present invention relates to an electric motor stator comprising teeth and coils mounted on said teeth, the stator further comprising a system for cooling the stator by a heat transfer fluid. Each tooth comprises at least one opening passing through the tooth so as to allow the passage of at least a portion of the heat transfer fluid through the tooth.

[0012] This allows optimal cooling of the stator thanks to the circulation of the heat transfer fluid within the tooth itself.

[0013] Preferably, each tooth extending substantially radially relative to the axis of rotation of the electric motor, the opening passes substantially radially through the tooth. This maximizes heat recovery within the tooth by maximizing the fluid path through the tooth.

[0014] Advantageously, the opening extends substantially parallel to a lateral face of the tooth. This is particularly advantageous when the tooth is obtained by rolling a punched sheet. The lateral face of the tooth and the opening are thus obtained by punching the distance between which remains constant (Iso strike).

[0015] Preferably, the opening has an elongated section extending along the axis of rotation of the motor (corresponding to the winding axis of the coils). This makes it possible to limit magnetic losses due to the section of the opening.

[0016] Advantageously, the tooth having an inner face located on the side of the axis of rotation of the motor and an outer face located radially opposite the tooth relative to the inner face, the fluid circulates through the tooth from the inner face to the outer face so that the fluid entering from the inner side, where the section of the tooth and the coil heads is the smallest and therefore where the most heat is generated, has the lowest temperature to guarantee optimal cooling of the teeth.

[0017] Preferably, the coils being thus arranged next to each other leaving a space between two adjacent coils, the stator cooling system is configured to circulate at least a portion of said fluid in the space between the coils. Thus, the cooling is optimal in cooling both the coils and the teeth.

[0018] More preferably, the stator comprises fluid inlet and outlet manifolds pierced with orifices for sending or recovering fluid to or from the coils, each inlet orifice is associated with a coil and is configured to send a portion of the fluid through the spacings of said tooth with each of the adjacent teeth, and another portion of the fluid through the opening passing through the tooth. Thus, a single circulation system makes it possible to circulate the fluid both at the level of the coils and at the level of the tooth.

[0019] The stator further comprising a coil support, each coil of the stator being configured to be wound around said coil support and said coil support being configured to be mounted on the tooth, said coil support comprising a first groove for fluidically connecting the inlet port, associated with the coil, to the opening passing through the tooth. The coil support thus has a dual function of winding the coils and directing the fluid through the tooth.

[0020] Preferably, the coil holder further comprises a second groove for fluidly connecting the outlet port, associated with the coil, to the opening passing through the tooth.

[0021] More preferably, said groove has an at least partially conical shape so as to guide the fluid towards the through opening.

[0022] The invention also relates to an axial flux electric motor comprising at least one rotor and at least one stator as described above.

[0023] Preferably, the motor defining an axis of rotation, the through opening of each tooth extending substantially radially relative to said axis of rotation.

[0024] The accompanying drawings illustrate the invention:

[0025] represents a front view of a stator according to an embodiment of the present invention after removal of a sealing plate intended to separate the stator from the associated rotor to form an electromagnetic motor or generator.

[0026] represents a view of a part of the stator according to a first embodiment according to the invention.

[0027] represents a front view of a part of the stator according to the first embodiment according to the invention

[0028] represents a front view of a part of the stator according to a second embodiment according to the invention.

[0029] represents a side view of a tooth of the stator according to a third embodiment according to the invention.

[0030] schematically represents the magnetic field at the level of a part of the motor according to the invention.

[0031] The figures are given as examples and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate the understanding of the invention and are not necessarily to the scale of practical applications. In particular, the dimensions of the different parts are not representative of reality.

[0032] In the following, reference is made to all figures taken in combination. When reference is made to one or more specific figures, these figures are to be taken in combination with the other figures for the recognition of the designated reference numerals.

[0033] Referring more particularly to the, this figure shows a stator 1 of an electromagnetic motor or generator which may comprise one or more stators 1 and one or more rotors 10. The represents a motor according to a non-limiting embodiment of the invention comprising a rotor 10 mounted between two stators 1. This figure is an axial sectional view.

[0034] This is a view of the face of the stator 1 facing the rotor 10, thus limiting an air gap between the stator 1 and the rotor 10.

[0035] As can be seen in this figure, the stator 1 of the electric motor, according to a non-limiting embodiment of the present invention, is circular in shape for an axial flux motor, which is not limiting within the scope of the present invention. Reference 2 indicates the center of the stator 1 or of the casing 1a surrounding the stator 1.

[0036] The stator 1 is equipped with coils 3 arranged circumferentially around the center of the stator 1, each advantageously mounted on a tooth 4. Only one coil 3 is referenced in this figure, but what is stated for this coil is applicable to the other coils.

[0037] A coil 3 can be wound around a tooth 4 or the coils 3 can be distributed. In this case, each coil 3 is wound around several teeth 4.

[0038] The coils 3 are arranged next to each other, leaving a gap between two adjacent coils and together delimiting internal and external circumferences in the stator 1.

[0039] With reference to the, a single tooth 4 of the stator 1 will now be described for the sake of clarity. Such a tooth 4 has an elongated shape extending radially relative to the axis of rotation of the motor. In the example illustrated, the tooth is in the form of a prism having two trapezoidal bases. However, it goes without saying that any other shape could be suitable.

[0040] Each base extends in a plane radial to the axis of rotation of the motor. The two bases are offset along the axis of rotation in order to define the height of a tooth 4. Such a tooth 4 thus defines an inner face 4a located near the axis of rotation of the electric motor, and an outer face 4b, located towards the outside of the electric motor. The tooth 4 according to the invention has an opening 5, also called an orifice, passing through the tooth 4 from the inner face 4a to the outer face 4b. In other words, the through opening 5 extends substantially radially relative to the axis of rotation of the motor. This through opening 5 is configured to allow the circulation of a heat transfer fluid inside the tooth 4 in order to allow optimal cooling.

[0041] Advantageously, the tooth 4 has an elongated shape in the direction of the through opening 5. The coils 3 are wound around this elongated shape.

[0042] The through opening 5 has an elongated section extending along the height of the tooth 4. Indeed, the coil 3 which is mounted around the tooth 4 is configured to generate LC field lines extending along the axis of rotation of the motor as illustrated in the. The LC field lines thus generated axially cross the tooth 4 in the height direction then follow radially the yoke 6 to the adjacent tooth 4. The LC field lines axially cross the rotor 10 then the tooth 4 of the second stator 1. The field lines follow a similar path through two adjacent teeth 4 and the yoke 6 of the second stator 1 then cross again the rotor 10 then the tooth 4 of the first stator, thus forming a field loop. Each tooth 4 is thus crossed by two loops of LC field lines, each loop crossing one of the adjacent teeth 4.Thus, the elongated section of the through opening 5 extending parallel to the LC field lines crossing the tooth 4, this makes it possible to limit magnetic losses due to its small thickness depending on the width of the tooth 4. Indeed, the opening 5 extends substantially in the middle of the tooth 4, i.e. between the two loops of LC field lines. Since the tooth 4 has an elongated shape, the LC field lines thus form loops along the length of the tooth 4, in other words along the opening 5. The opening 5 is thus cleverly placed where its impact on the LC field lines is less.

[0043] The through opening 5 has two important dimensions in directions (the height and the length of the tooth 4) having little impact on the magnetic losses and a third dimension (the width of the tooth 4) which is small in a direction which could have an impact on the magnetic losses. Such an opening 5 is thus optimized to allow good circulation of cooling fluid while limiting its impact on the magnetic field.

[0044] The opening 5 has a small width, preferably of the order of 2 mm, more preferably less than 2 mm, in particular of the order of 1 mm, to ensure good circulation of the fluid while limiting the electromagnetic impact. The height and length of the opening 5 depend on the dimensions of the tooth 4.

[0045] A through opening 5 extending in the center of the tooth 4 has been described as illustrated in the. However, the through opening can also extend from the center of the inner face of the tooth 4 and parallel to one of the sides of the tooth 4 as illustrated in the. Such a through opening 5 thus extends substantially radially. However, this advantageously makes it easier to manufacture, in particular in the case where the teeth 4 of the stator 1 are obtained by winding a sheet metal. The contours of the teeth 4 are then obtained by punching the sheet metal at regular intervals. The through opening 5 can thus be manufactured by punching. Such punching having a constant distance with the punching making it possible to obtain one of the sides of the tooth, which makes it possible to obtain a through opening extending parallel to said side of the tooth 4.

[0046] A tooth 4 has been presented comprising a single opening 5, however, the tooth could comprise a different number of openings 5, in particular two openings 5. According to one embodiment, in the case of two openings 5, each could extend parallel to one of the sides of the tooth 4 in order to optimize the cooling at the center of the tooth 4.

[0047] An opening 5 extending to the level of tooth 4 has been shown, but it goes without saying that the opening 5 can also extend to the level of the yoke 6, as illustrated in the. The yoke 6 corresponds to the part of the iron connecting the teeth 4 together.

[0048] The stator 1 further comprises a cooling system (not shown) for the coils 3 using a heat transfer fluid (such as oil).

[0049] The cooling system is configured to circulate the heat transfer fluid through the through opening 5 in order to cool the tooth 4 at its center, in other words where heat is most likely to be generated.

[0050] According to a preferred embodiment of the invention, the heat transfer fluid flows through the through opening 5 from the axis of rotation of the motor to the outside of the motor. In other words, from the inner face 4a of the tooth 4 to the outer face 4b. This allows the heat transfer fluid to enter the through opening 5 on the narrower side of the tooth 4: the head of the coil being shorter, the heat transfer fluid is less heated by said coil head. The heat transfer fluid is thus colder on entering, which optimizes cooling in the narrow area of ​​the tooth 4.

[0051] According to one embodiment of the invention, the cooling system may also include an inlet manifold and a fluid outlet manifold.

[0052] The inlet manifold is drilled with inlet ports to send fluid to the coils 3 and the outlet manifold is drilled with outlet ports to recover the fluid.

[0053] Each coil 3 is associated with at least one input port, that is to say that there can be one input port for a coil 3 but also several input ports for the same coil.

[0054] Each inlet port is placed in the middle part of a coil head 3 which is the widest base of a coil 3 but this is not mandatory.

[0055] In this case, the fluid flow emerging from an inlet orifice circulates mainly in the space between its associated coil and each of the two coils adjacent to the associated coil 3.

[0056] Still in this case, each flow coming from a main flow of an inlet orifice having separated into two, mixes with a flow coming from an adjacent coil also resulting from the separation of a main flow coming from an inlet orifice associated with the adjacent coil.

[0057] It follows that the oil flow from each inlet port splits into two flows with one flow for each gap separating a coil 3 from adjacent coils. Both sides of each coil 3 each bordering a gap with an adjacent coil are thus cooled simultaneously.

[0058] Alternatively, although not shown in the figures, the inlet port may be positioned opposite a gap between its associated coil 3 and one of the two coils adjacent to the associated coil 3.

[0059] In this case, it can be arbitrarily decided that an input port placed after a coil 3 in a clockwise direction is dedicated to it, but the opposite is also possible, the point is that a coil 3, and its adjacent coils all have at least one input port.

[0060] One of the collectors, preferably the outlet collector, goes around the outer circumference while the other collector, preferably the inlet collector, goes around the inner circumference. However, it goes without saying that the direction of circulation could be reversed. In other words, according to an alternative embodiment, the outlet collector goes around the inner circumference while the inlet collector goes around the entire outer circumference.

[0061] An oil flow exits each inlet port and then circulates mainly in the space between its associated coil 3 and at least one of the two coils adjacent to the associated coil 3. Then this oil flow is recovered in the outlet manifold and exits through one of the outlet ports.

[0062] It is however possible that there is only one output port for all coils but this is not preferred.

[0063] There may be a different number of outlet ports and inlet ports. For example, although preferred, it is possible not to associate an outlet port with each coil.

[0064] In the non-limiting case of several inlet ports per coil 3, one of these inlet ports can be closed under certain operating conditions of the stator 1 for which accelerated cooling is not required.

[0065] The opening of such an inlet orifice 10, advantageously provided with a valve, can be done by increasing the oil pressure in the inlet manifold. This makes it possible to regulate the cooling as closely as possible to the actual operating conditions of the stator 1 and the heating of the coils 3.

[0066] When the oil flow from each inlet port splits into two flows with one flow for each spacing, to achieve uniform cooling on both sides of the coil 3, it is advantageous for both sides to have the same flow rate flowing through them.

[0067] As a result, the inlet orifice associated with a coil 3 can be located at an equal distance from the two spacings between the associated coil 3 and each of the two adjacent coils, the two flows having the same flow rate.

[0068] Preferably but not limitingly, at least one output orifice is associated with each coil 3, the input and output orifices being paired by being in equal numbers, in particular in the case where each coil 3 is associated with only one input orifice and one output orifice.

[0069] Thus, the oil arrives directly from the inlet collector on each coil 3 and leaves the magnetic circuit as quickly as possible once its associated coil 3 has cooled to be recovered in the outlet collector.

[0070] According to an embodiment according to the invention, the inlet manifold 8 and the outlet manifold 9 allow the heat transfer fluid to circulate at the level of the coils 3 but also through the through opening. The same circulation system thus allows the stator to be cooled at the level of the coils and at the level of the teeth 4.

[0071] According to a preferred embodiment of the invention, the stator 1 further comprises coil supports making it easier to mount the coils on the stator 1. Each coil of the stator is configured to be wound around one of said coil supports and said coil support is configured to be mounted on one of said teeth of the stator. This assembly is particularly advantageous in the case of manufacturing the teeth by winding a sheet metal which makes the winding complex around the teeth thus obtained.

[0072] Each coil holder further comprises a first groove for fluidically connecting the inlet port, associated with the coil 3, to the opening passing through the tooth.

[0073] Each coil holder further comprises a second groove for fluidly connecting the outlet port, associated with the coil, to the opening passing through the tooth.

[0074] The inlet and outlet ports described here and connected to the through opening may be the same ports as those described previously to allow cooling of the coils or ports dedicated to cooling the stator tooth. In the latter case, all the cooling ports for the coils and teeth may be connected to the same reservoir in order to minimize the number of elements required.

[0075] The coil support thus fulfills a second function of guiding the fluid towards the through opening, which makes it possible to limit the number of stator parts while optimizing the fluid guidance.

[0076] Preferably, at least one of the first or second grooves has an at least partially conical shape so as to guide the fluid towards the inlet of the through opening.

[0077] A motor comprising two stators 1 and a rotor 10 has been described, in particular on the. However, it goes without saying that the invention is not limited to such a structure but extends to any type of electric motor comprising at least one stator, for example motors with two rotors and one stator.

Claims

Stator (1) of an electric motor comprising teeth (4) and coils (3) mounted on said teeth (4), the stator (1) further comprising a system for cooling the stator (1) by a heat transfer fluid, the stator (1) being characterized in that each tooth (4) comprises at least one opening (5) passing through the tooth (4) so as to allow the passage of at least part of the heat transfer fluid through the tooth (4). Stator (1) according to claim 1, wherein each tooth (4) extending substantially radially relative to the axis of rotation of the electric motor, the opening passes through the tooth (4) substantially radially. Stator (1) according to one of the preceding claims, in which the opening (5) extends substantially parallel to a lateral face of the tooth (4). Stator (1) according to one of the preceding claims, in which the opening (5) has an elongated section extending along the axis of rotation of the motor, corresponding to the winding axis of the coils (3). Stator (1) according to one of the preceding claims, in which, the tooth (3) having an inner face (4a) located on the side of the axis of rotation of the motor and an outer face (4b) located radially opposite the tooth (4) relative to the inner face (4a), the fluid circulates through the tooth (4) from the inner face (4a) to the outer face (4b). Stator (1) according to one of the preceding claims, wherein the coils (3) are thus arranged next to each other leaving a space between two adjacent coils (3), the cooling system of the stator (1) is configured to circulate at least part of said fluid in the space between the coils (3). Stator (1) according to the preceding claim, comprising fluid inlet and outlet manifolds pierced with orifices for sending or recovering fluid to or from the coils (3), each inlet orifice is associated with a coil (3) and is configured to send a portion of the fluid through the spacings of said tooth (4) with each of the adjacent teeth (4), and another portion of the fluid through the opening (5) passing through the tooth (4). Stator (1) according to the preceding claim, further comprising a coil support, each coil (3) of the stator (1) being configured to be wound around said coil support and said coil support being configured to be mounted on the tooth (4), said coil support comprising a first groove for fluidically connecting the inlet port, associated with the coil (3), to the opening (5) passing through the tooth (4). Stator (1) according to the preceding claim, wherein the coil support further comprises a second groove making it possible to fluidically connect the outlet orifice, associated with the coil (3), to the opening (5) passing through the tooth (4). Stator (1) according to one of claims 8 or 9, wherein said groove has an at least partially conical shape so as to guide the fluid towards the through opening (5). Axial flux electric motor comprising at least one rotor (10) and at least one stator (1) according to one of the preceding claims. Motor according to the preceding claim defining an axis of rotation, the through opening (5) of each tooth (4) extending substantially radially relative to said axis of rotation.

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