Stator for an electric motor and electric motor with this stator

Abstract

A stator for an electric motor that comprises a body (1) of the stator and at least two coils (2) arranged around an axis (3) of the stator. The stator is provided with at least one rib (4) between at least two adjacent coils (2), wherein each rib (4) is attached to the body (1) of the stator. At least one coil (2) is attached to at least one rib (4) for a transfer of loads from the coil (2) to the body (1) of the stator.

Description

[0001] Stator for an Electric Motor and Electric Motor with This Stator

[0002] Technical Field

[0003] The object of the invention is a stator for an electric motor comprising ribs for transferring torque and other loads, as well as heat dissipation, from coils and an electric motor comprising this stator. This solution is mainly suitable for electric motors having a dual rotor.

[0004] Background of the Invention

[0005] Currently there are many types of electric motors. In most electric motors, the cores of stator coils are connected to each other in one piece of stator sheet metal (so-called yoke) and the transfer of the torque to the stator body is transferred through this yoke. Another type is an electric motor having a two-rotor arrangement with the yoke being absent, such as the one disclosed, for example, in the document LIS20130270948 A1.

[0006] Loads are generated in the electric motor during operation. One of the most heavily loaded components is the coils. The loads of the coils are transferred to the stator body and therefore, the connection between the coils and the stator body is highly stressed. In the documents mentioned above and below, the coils are inserted into an opening in the stator body and firmly fastened by fastening elements, e.g. a screw, as disclosed, for example, in the documents EP2066005 B1 and LIS20130270948 A1.

[0007] In the solution of the patent EP2066005 B1 , a large number of screw connections are used to attach the coils and transfer the torque to the stator body, which increase the weight and size of the motor and also introduce manufacturing complications. The connecting screw passing through the core of the coil worsens the magnetic flux in the coil because the screw material does not meet the quality of special materials intended for use in electric motors, thus increasing the overall losses in the motor. In the document LIS20130270948 A1 , the fastening of the front element of the coil (number 2 in the document) is complicated due to the many different small fastening elements, which makes the assembly significantly more complicated and expensive.

[0008] It would be useful to come up with a solution that would improve the transfer of the load of the stator of the electric motor.

[0009] Summary of the Invention

[0010] The above shortcomings are eliminated to a certain extent by a stator for an electric motor that comprises a body of the stator and at least two coils arranged around the axis of the stator. The stator is provided with at least one rib between at least two adjacent coils. Each rib is attached to the body of the stator and at least one coil is attached to at least one rib for transferring the load from the coil to the body of the stator.

[0011] Conventionally, the coil comprises a winding and a core, on which the winding is wound, therefore conventionally, its structure is more complicated than the structure of the rib, and also the way it is fastened to the body of the stator is more complicated than the attachment of the rib to the body of the stator. The rib can be attached to the body of the stator more easily and firmly. Due to the attachment of the coil to the rib, the loads, especially the torque, are transferred from the coil to the rib. This load is then transferred to the body of the stator via the attachment of the rib to the body of the stator. This efficient transfer of the load not only increases the overall stability and strength of the structure but also extends the service life of the stator. Also, the simpler structure of the rib and its attachment may lead to lower manufacturing costs and faster assembly, which is preferable in terms of both manufacture and maintenance.

[0012] Preferably, the axis of the stator is the axis of an opening for the shaft of the electric motor and / or the axis of rotation of the input shaft and / or the axis of rotation of the rotor. The coils on the body of the stator are preferably arranged in a circular shape when viewed in the axis of the stator. The coils are preferably arranged uniformly around the axis of the stator - i.e. there are equal spacings between the adjacent coils, for example when the coils are arranged in a circle there is an equal angle between the adjacent coils from the center of the circle. This ensures a uniform distribution of the magnetic field in the electric motor and therefore a uniform distribution of the load, which contributes to a longer service life and reliability of the stator and the electric motor comprising this stator. The adjacent coils are considered to be the coils around the circumference of the ring, i.e. each coil has two adjacent coils with the same spacings between them. The rib is therefore positioned between two individual coils around the circumference of the ring and can transfer a load mainly from the two nearest coils. Therefore, in this arrangement the transfer of the load may be uniform around the entire circumference.

[0013] The ribs are preferably arranged uniformly around the axis of the stator. Preferably the stator thus comprises a total of at least two ribs arranged uniformly around the axis of the stator such that the transfer of the load is uniform.

[0014] The stator may comprise a smaller number of ribs than the number of coils. A rib can therefore be positioned between any two adjacent coils. This may be at locations experiencing the highest load during the operation of the stator, where a coil is most heavily loaded, etc. Preferably, the stator comprises a total of at least two ribs arranged uniformly around the axis of the stator. Therefore, when viewed in the direction of the axis of the stator and in case the stator comprises exactly two ribs, they are, for example, located opposite each other.

[0015] Preferably, there is at least one rib next to each coil - such that each coil may be connected to at least one rib. Every second gap between the coils can then be provided with at least one rib.

[0016] Between every two adjacent coils, the stator is preferably provided with a total of at least one rib and each coil is attached to at least one rib. Preferably, each coil is connected to at least two ribs - in the above circular arrangement, preferably one rib clockwise and one rib counterclockwise. Therefore, the stator here comprises the same number of ribs as there are coils. This arrangement is suitable for transferring greater loads than with an irregular positioning of ribs (as an example, see the paragraph below). The transfer of the load is thus in this arrangement more uniform along the entire circumference.

[0017] Each coil may be attached to only one rib - in the above circular arrangement, the coil is connected to one rib clockwise and it is not connected to a rib counterclockwise, preferably there is no rib positioned there. In other words, the rib may be positioned uniformly in every second gap between two adjacent coils (alternatively, for example, in every third gap, fourth, etc.).

[0018] Preferably, in total, the stator comprises at least three ribs and three coils arranged on a circle centered in the axis of the stator such that a rib is positioned between all adjacent coils. The cross-section of the ribs, perpendicular to the axis of the stator, is preferably elongated such that in the radial direction relative to the axis, this cross-section is longer than in the direction perpendicular to the radial direction (i.e. , in the tangential direction). Preferably, in the direction indicated, this cross-section is at least 1.5 times, more preferably at least 2 times longer.

[0019] In the direction of the axis of the stator, each rib preferably has a dimension (i.e., length) equal to at least one-third, more preferably one-half, even more preferably two- thirds of the dimension (i.e., length) of the coils (in particular their winding). More preferably, the length of each rib is such that it extends over at least 75% of the length of the space between the coils, still more preferably over at least 90% of the length of that space. The ribs may even extend beyond the coils in this direction. The greater the length of the ribs, the better the load, especially thermal load and load from the torque, is transferred from the coils to the stator.

[0020] Preferably, the radial dimension of each rib in the view in the axis of the stator is at least half of the dimension of the coil (particularly the winding of the coil) in that direction. The space between the coils is then at least half covered by a rib in the direction from each coil to any adjacent coil such that the forces from the coils are better transferred to the stator.

[0021] The stator of the invention may further comprise conventional stator components for electric motors known to persons skilled in the art, such as covers, current supply leads to the coils, insulation, opening(s) for rotor shaft insertion, bearings, etc. Preferably, each rib is attached to the body of the stator by a fixed connection for effective transfer of the load to the body of the stator, e.g., by pressing, welding, bonding, etc. A part of the rib is preferably inserted into the body of the stator for a more fixed attachment of the rib, thus the body of the stator may comprise a non-through opening for the rib. Alternatively, the body of the stator may comprise a through opening for attaching the rib to the body of the stator. Alternatively, each rib may be part of the body of the stator, thus the ribs may be of one material together with the body of the stator for a more efficient transfer of the load. Therefore, the body of the stator together with the ribs may be manufactured, for example, by casting.

[0022] The coil may be bonded to the rib using, for example, an electronics adhesive (e.g., epoxy), potting compound, etc. This improves the strength of attachment of the coils to the stator and to the ribs as well as the entire stator and further increases the heat dissipation from the coils outwards.

[0023] At least one rib, preferably each rib, may comprise a cooling channel for the flow of a cooling liquid, thereby increasing the efficiency of the rib in dissipating the thermal load of the coils. Therefore, the stator preferably comprises a cooling system comprising a cooling liquid and at least one opening in the body of the stator for supplying the cooling liquid to the cooling channel in each rib.

[0024] At least one rib, preferably each rib, may be thermally conductive for dissipating heat from the coil to the body of the stator, e.g., from aluminum, ceramic, composite. The thermal conductivity coefficient may therefore be at least 20 W m"1K"1, preferably at least 40 W m"1K"1.

[0025] Preferably, the rib is a rib of a non-magnetic and electrically non-conductive material to increase the efficiency of the motor, e.g., ceramic, plastic, glass fiber and / or epoxy matrix composite, Kevlar fiber and / or carbon fiber composites, and others. Therefore, the specific electrical resistance is preferably at least 1010O m. The rib is thus preferably simultaneously made of an electrically non-conductive material and a thermally conductive material. Alternatively, if the rib is made of an electrically conductive material, or additionally, if the rib is made of an electrically non-conductive material, the rib may be isolated from the coil, particularly from the winding of the coil, for example by the potting compound, and / or by surface treatment of the rib, whereby a non-conductive layer of material is applied to the surface of the rib (e.g., using a protective spray for insulation), or by other insulating processes and materials. This allows the rib to be of an electrically conductive material, which is preferred for the ribs in terms of other properties, for example, it has high thermal conductivity values (especially metals), or, for example, in cases when the rib is made of a single piece of material together with the stator.

[0026] The rib may preferably have the shape of a cuboid, a thin plate with a rectangular cross-section or a trapezoidal cross-section, or another shape, e.g., oval. These are simple shapes, and therefore, the manufacture of the rib as well as the attachment of the rib to the body of the stator are considerably simpler and faster than when fastening the coil to the body of the stator for the load transfer.

[0027] The coil is preferably attached to the rib by a potting compound for electronics. The potting compound may be a material suitable for interaction with electronics, therefore, it may be a material that is not electrically conductive but is thermally conductive, it can simultaneously have a high heat resistance, and which will not cause degradation of the conductive connections or other components of the stator and electric motor. The potting compound may be, among other things, polyurethane, epoxy resin (preferably epoxy electro-insulating resin MC62-W363), rubber, acrylate, silicone, or silicone-containing material (e.g., silicone resin). Preferably, the coil is also fastened by the potting compound to the body of the stator for a secondary transfer of the thermal load as well as torque directly via the potting compound to the body of the stator.

[0028] Preferably, when the number of the ribs is smaller than the number of the coils on the given stator, the given coils are attached to the rib by means of the potting compound - preferably, all coils are thus potted in the potting compound and are thus indirectly connected. The potting compound improves the transfer of the load from the coils to the body of the stator.

[0029] Alternatively, it is possible to connect the coils to the ribs firmly by welding or screw connections between the core of the coil and the rib. The coils may also be connected to the ribs, for example, by a ring, e.g., of aluminum or copper, which is connected by a screw connection or weld, and / or the coils and the ribs may be slid into precisely manufactured openings in the ring, for example by pressing with each rib and each coil. The ring may be connected to the end of each rib that is opposite the end connected to the body of the stator, and to the other end face of each coil that is not inserted into the body of the stator. Alternatively, the above may be supplemented by complete potting with the potting compound.

[0030] Preferably, each coil comprises a winding and the body of the stator comprises at least one opening for the winding lead. Preferably, at least one opening for the winding lead, more preferably each opening for the winding lead, is positioned closer to the axis of the stator than the given coil from which this winding is routed. Conventionally, the openings for the winding lead are positioned at the location where the coils are fastened to the body of the stator, as known from the prior art. By positioning the openings for the winding lead closer to the axis of the stator, the area for the thermal load transfer at the location at the body of the stator where the ribs (coils in the prior art) are attached can be increased, thus improving the cooling of the electric motor.

[0031] The body of the stator may comprise at least one opening for seating the coil, which is primarily used for locking the coil in place in order to facilitate the manufacture of the stator of the electric motor. Preferably, the opening for seating the coil is a non- through one for better mechanical properties of the body of the stator (bigger area for the transfer of the load, less voltage concentrators, etc.) than in the case of a through opening. Therefore, at least one coil is fastened in the opening for seating the coil. Preferably, the coil may comprise a projection for fastening in the opening for seating the coil. Preferably, the openings for seating the coil are provided on the body of the stator for all the coils.

[0032] Alternatively, the body of the stator may comprise through opening(s) for seating the coil.

[0033] Preferably, all the ribs and all the coils are connected, preferably by the potting compound, to provide greater support to the coils and better transfer of the load. Preferably, each coil is directly connected to two adjacent ribs. When the ribs and the coils are arranged in the shape of a circle, with the coils and the ribs connected by the potting compound, this structure has the shape of a ring.

[0034] Preferably, each coil has a length and width of its own, wherein the length is in the direction of the axis of the stator. Preferably, the width is perpendicular to the length and the radial direction that intersects the center of the given rib or coil. Preferably, the length of the coil is greater than the width of the coil, e.g., at least 1 .5 times. Preferably, each rib has a length and width of its own, wherein the length is in the direction of the axis of the stator. Preferably, the length of the rib is greater than the width of the coil, e.g., at least 2 times.

[0035] Preferably, each coil is segmented or self-supporting. Therefore, the stator comprises at least two, more preferably at least 10 coils representing individual segments with a winding, where each coil has its core and winding. Therefore, if each coil is segmented, it preferably does not have a winding connected in series to the winding of another coil. Each of the coils is connected to the body of the stator for the transfer of the load, especially torque, for example by means of a connection to a rib that is attached to the body of the stator, by means of the potting compound, etc. Therefore, the stator preferably does not comprise a yoke. Alternatively, the coils may be conductively connected by means of a ring for connecting the coils.

[0036] The stator preferably comprises a ring for connecting at least two coils, more preferably each coil of the stator is fastened to the ring. The ring is fastened, preferably removably, to a free end of at least two coils. The free end may preferably be the end opposite to the end of the coil that is positioned at the body of the stator, in the direction of the axis of the stator. Therefore, the ring helps to strengthen the coils, and therefore, the entire stator is more resistant to the negative effects of the load. Also, when assembling the stator, the ring helps with the correct positioning of the coils. Preferably, the ring may comprise at least one opening (through, non-through) or cutout for fastening the coil to the ring. The ring for fastening the coils may be used as an additional support for the coils in the stator, where, for example, the coils are connected together with the ribs by the potting compound. Very preferably, it is used for a stator where the coils are not potted with the ribs with the potting compound but are connected in another way (e.g., screw connection). Preferably, the center of the ring lies on the axis of the stator.

[0037] The ring may comprise at least one cooling rib that assists in the heat dissipation from the coils to other parts of the stator (e.g., ribs, body of the stator), more preferably towards the body of the rotor through an air gap. This arrangement is advantageous especially for an electric motor where the body of the rotor is not fully enclosed but contains openings through which air may flow through the rotor to the stator. The cooling rib may be made of a thermally conductive material and may be attached to the ring in the direction of the axis of the stator similar to the rib. Alternatively, the cooling ribs may be cast together with the entire ring, or they can be formed by bending the ring sheet from the other parts of the ring. The ring may comprise at least one opening of the ring for a rib, more preferably for each rib attached to the body of the stator. The opening of the ring for the rib may be through for the rib to pass through the ring or non-through for the rib to be inserted into the ring. In this opening of the ring for the rib, the rib may be fastened to the ring, or it may just pass through the ring. This allows the ring to be fastened to the free ends of the coils, even if the coils are shorter than the ribs in the direction of the axis of the stator.

[0038] The ring for connecting the coils may be made of an electrically conductive material, e.g., similar to the ribs, the windings of the coils, etc. The electrical conductivity of the ring may preferably be at least 10-106S rrr1, more preferably at least 30 106S nr1. Thus, the ring may conductively connect the individual coils of the stator, which may be advantageous, e.g., when connecting the phases in a star. Preferably, the ring is made of a non-ferromagnetic material, e.g., copper.

[0039] The ring may be of a thermally conductive material, e.g., similar to the ribs, for best heat dissipation from the coils.

[0040] The ring may be made by casting, machining, bending from a blank, punching and pressing etc.

[0041] The ring may comprise at least one opening of the ring for the winding lead of the coil, more preferably it comprises at least one opening of the ring for the winding lead of each coil. The opening of the ring for the winding lead may be a through opening, cutout, etc. This opening is used to allow the winding of the coils behind the ring to lead out in a direction away from the body of the stator in the direction of the axis of the stator, i.e., for example, if it is not advantageous to lead the winding at the body of the stator (e.g., when connecting the phases in a star). For example, the ends of the windings of the coils may be fastened to the ring by soldering, resistance welding, ultrasonic welding, screw connection, pressing, etc. Preferably, in a case where the windings of the coils are fastened to the ring, the ring is made of an electrically conductive material. Fastening the windings of the coils to the ring thus creates a conductive connection between the coil and the ring and the ring may thus connect all the connected coils conductively. The ring may comprise a holder for clamping the winding of the coil, which clamps the ends of the winding within itself to advantageously form a conductive connection.

[0042] The ring may electrically conductively connect at least two coils, more preferably, it conductively connects each coil. Preferably, the coils are connected to the ring by connecting the windings of the coils to the ring. This is advantageous especially when connecting the individual phases of the electric motor into a star, as there may not be enough space on the stator end face, there may not be enough room for a technician to connect the winding, etc.

[0043] The ring may comprise a mount for additional devices, e.g., a mount for fastening various sensors, hall probes, etc. The mount may also be the area on which the additional device is fastened, e.g., by bonding.

[0044] Preferably, each rib is offset from each adjacent coil. Therefore, the rib is preferably attached to the coil indirectly - for example by the body of the stator (where both the coil and the rib are inserted into the body of the stator), and / or potting compound, and / or ring, etc. Therefore, the rib preferably does not directly contact the given coil during conventional operation of the stator. Therefore, the load from the coil preferably passes through a certain element before being transferred to the rib. Therefore, the load is transferred from the coil to the rib indirectly - via an additional element. In the case of a thermal load, the body of the stator, the ring, etc., this element may also, for example, be the ambient air. The offset may be at least one tenth, more preferably at least one quarter of the dimension of the coil in the direction perpendicular to the axis of the stator - when viewed in the direction of the axis of the stator. Thus, in the case of a cylindrical coil, it may be the diameter of the coil, etc.

[0045] Preferably, the rib is separated from the coil for most of the length of the rib - therefore, it is not directly connected to the coil (where a part of the rib area would contact a part of the coil area). Therefore, the rib is preferably separated also indirectly along most of its length with the coil - the indirect method is by means of a certain element, for example, by means of the potting compound, the ring, welded-on material (as discussed above).

[0046] Preferably, the body of the stator comprises the stator end face. Preferably, each rib is inserted into the body of the stator in a direction from the stator end face. The coils and ribs are preferably positioned in such a way that their lengths are perpendicular to the stator end face. Therefore, the ribs are attached to the body of the stator from the stator end face with their shorter dimension. Therefore, each coil and each rib preferably project from the stator end face. Preferably, the stator end face has a circular shape. The axis of the stator passes through the center of the stator end face, which is perpendicular to the stator end face. Preferably, the coils and ribs are arranged here in a circular shape, which has a center identical to the center of the stator end face and its radius is smaller than the radius of the stator end face.

[0047] Therefore, the body of the stator preferably comprises a stator end face that has a circular shape. The axis of the stator passes through the center of the stator end face, which is perpendicular to the stator end face. Each rib is preferably inserted into the body of the stator from the stator end face. Preferably, the coils and ribs are arranged here in a circular shape, which has a center identical to the center of the stator end face and its radius is smaller than the radius of the stator end face. The coils and ribs are preferably positioned in such a way that their lengths are perpendicular to the stator end face. Therefore, the ribs are attached to the body of the stator from the stator end face with their shorter dimension.

[0048] The above shortcomings are to a certain extent eliminated by an electric motor, which comprises a rotor and a stator. The stator comprises the stator end face that has a circular shape, wherein the axis of the stator passes through the center of the stator end face, and it is perpendicular to the stator end face as described above. The rotor comprises a rotor end face and a ring of magnets projecting from the rotor end face towards the stator end face. The rotor is rotationally connected to the stator, e.g., by a shaft. The axis of the rotor is preferably identical to the axis of the stator. Each coil is positioned radially from the ring of magnets, in other words, each coil is positioned, in a direction away from the axis of the rotor and the axis of the stator in a radial direction towards the edge of the stator end face and the rotor end face, closer than the given ring of magnets. Thus, the given ring of magnets may have the inner and outer radii larger than the inner and outer radii of the circle of the ring with the coils and ribs. Alternatively, each coil may be positioned further than the given ring of magnets. Thus, the given ring of magnets may have the inner and outer radii smaller than the inner and outer radii of the circle of the ring with the coils and ribs.

[0049] Preferably, the rotor end face has a circular shape.

[0050] The rotor preferably comprises a second ring of magnets, which is offset from the first ring of magnets in the radial direction. The radial direction is the direction from the center of the rotor (i.e. , also the axis of the rotor) to the circular edge of the rotor end face. Each coil of the stator is positioned between the first ring of magnets and the second ring of magnets. Thus, it is an electric motor with a dual rotor, where one ring of magnets rotates around the coils and ribs from the inner side of the ring of the coils and ribs and the second ring of magnets rotates around the coils and ribs from the outer side of the ring of the coils and ribs. Preferably, each coil is positioned between the stator end face and the rotor end face.

[0051] In conventional electric motors with a dual rotor, such as those of the prior art, the coils are conventionally fastened by the one end thereof in the direction of the length only, which puts considerable stress on the coils, especially their connection to the body of the stator. Thanks to the attachment of the coils to the ribs, and also potting thereof by the potting compound, this electric motor is more efficient, dissipates heat better, and has a longer service life than a conventional electric motor with a dual rotor of the prior art.

[0052] Description of Drawings

[0053] A summary of the invention is further clarified using exemplary embodiments thereof, which are described with reference to the accompanying drawings, in which: fig. 1 is a front view of the stator of the electric motor in the direction of the axis of the stator with the coils and ribs potted with the potting compound, fig. 2 is a cutout A-A of the stator showing a rib inserted into the body of the stator, fig. 3 is a section of an electric motor with a dual rotor showing a rib inserted into the body of the stator and arrangement, fig. 4 is a section B-B through the vertical plane of the electric motor, fig. 5 is a detail of the insertion of the end face of a coil into the body of the stator, fig. 6 is a detail of the arrangement of the coil and rib in the electric motor when viewed in the direction of the axis of the stator, fig. 7 is an isometric view of the stator of the electric motor comprising a ring for connecting the coils, fig. 8 is a section of the stator comprising a ring for connecting the coils, and fig. 9 is a section of the ring for connecting the coils.

[0054] Exemplary Embodiments of the Invention

[0055] The stator of the electric motor will be further clarified using exemplary embodiments with reference to the respective drawings. The first exemplary embodiment of the stator is illustrated in fig. 1 and fig. 2.

[0056] The stator of the electric motor according to the first exemplary embodiment comprises a body 1_ of the stator, a coil 2, and a rib 4. Fig. 2 shows a length direction L and a width direction W of the coil 2 and rib 4. In the first exemplary embodiment, these directions are identical for both the coil 2 and the rib 4. The length direction L of the coil 2 is defined by the direction of the axis 3 of the stator. In the first exemplary embodiment, the dimension of the coil 2 is the longest in this direction. The length direction L of the rib 4 is defined similarly.

[0057] In the first exemplary embodiment, the coil 2 comprises a core 12, a winding 13, and two end faces 14 of the coil 2. It is a conventional coil 2, which serves as an electromagnet in electric motors. The winding 13 of a conductive material is wound on the ferromagnetic core 12. The winding 13 comprises two ends for the winding 13 lead from the stator to the power source of the electric motor. The end faces 14 of the coil 2 are fastened to the core 12 on opposite sides in the length direction L of the coil 2. These end faces 14 of the coil 2 comprise three arms, which are connected in the shape of the letter U. The parallel arms of this shape are offset from each other in the width direction W of the coil 2. The width direction W of the coil 2 is perpendicular to the length direction L, is tangent to the circle passing through the centers of the coils 2 and ribs 4, as can be seen in fig. 6, and is oriented counterclockwise. The winding 13 is wound on the second arm, which connects the two parallel arms, meaning that the winding 13 surrounds the core 12 and the middle arms of both end faces 14 of the coils 2.

[0058] On one end face 14 on each coil 2, there are two parallel arms that comprise protrusions for insertion into the opening 7 for seating the coil 2 in the body 1_ of the stator, as can be seen in fig. 5. These protrusions have small dimensions compared to the dimensions of the end face 14 of the coil 2, as they serve only for the correct positioning of the coil 2 when assembling the stator, not for the attachment of the coil 2 to the stator for load transfer. In the first exemplary embodiment, the ends 14 of each coil 2 are made of an electrically non-conductive material to prevent transfer of electric current to the body 1. of the stator from the coils 2 when the coils 2 are fastened to the body 1_ of the stator. The coil 2 is fastened to the body 1. of the stator in the length direction L only by its one end, the other end of the coil 2 in the length direction L is free.

[0059] In the first exemplary embodiment, the rib 4 is a ceramic plate with a rectangular cross-section, as can be seen in fig. 1 and fig. 2. Thanks to this material, the rib 4 is electrically non-conductive, mechanically very strong and also sufficiently thermally conductive to dissipate the heat from the coils 2 during the electric motor operation.

[0060] The body 1_ of the stator is a plate with a circular shape, as can be seen in fig. 1 , and comprises a stator end face 11 . The stator end face 11 is a circular area that is in contact with the ribs 4. The body 1. of the stator further comprises a center, which is therefore the center of the circular plate, and an axis 3 of the stator, which passes through the center of the body 1_ of the stator and is perpendicular to the stator end face 11 . The body 1. of the stator comprises non-through openings 7 for seating the coil 2, which are primarily used for seating the coil 2 at a desired position on the stator end face 11 during the manufacture of the stator (e.g. prior to potting with the potting compound 5). The openings 7 for seating the coil 2 are complementary to the protrusions on the end face 14 of the coil 2. Due to their small dimensions and the fact that the openings 7 for seating the coil 2 are non-through, the body 1. of the stator is stronger, more resistant to damage around openings 7 for seating the coil 2, and better able to transfer load. The body 1. of the stator comprises an opening for the shaft, the center of which lies on the axis 3 of the stator.

[0061] In the first exemplary embodiment, the body 1. of the stator further comprises through openings for the ribs 4, as can be seen in fig. 2, in which the ribs 4 are inserted and attached. In the first exemplary embodiment, the ribs 4 are attached in the openings for the ribs 4 such that each rib 4 is pressed into a desired opening for the rib 4 to best transfer the load from the rib 4 to the body 1. of the stator. These openings for the ribs 4 are uniformly arranged in a circle centered in the axis 3 of the stator such that the spacing between each opening for the ribs 4 is the same, ensuring uniform loading of the stator. The openings for the ribs 4 have a shape complementary to the rectangular shape of the cross-section of the rib 4. Thus, the ribs 4 are arranged uniformly symmetrically with respect to the axis 3 of the stator, as can be seen in fig. 1 .

[0062] The coils 2 are positioned between the adjacent ribs 4 along the circumference of the circle along which these ribs 4 are arranged and on which the centers of the crosssections of the ribs 4 lie in the plane of the stator end face 11 . These coils 2 are positioned similarly to the ribs 4 - the centers of the cross-sections in the plane of the stator end face 11 lie on the same circle as the ribs 4, the coils 2 have the same spacings between their two adjacent coils 2 along the circumference of the above mentioned circle, etc. At the same time, the coils 2 are positioned between the ribs 4 such that the distance to the two adjacent ribs 4 is the same, as can be seen in fig. 1 , for uniform load transfer.

[0063] In the first exemplary embodiment, all the coils 2 and ribs 4 are potted together with the potting compound 5. In the first exemplary embodiment, the potting compound 5 is a resin. Thus, during the manufacture of the stator according to the first exemplary embodiment, first the ribs 4 are attached to the body 1. of the stator, the coils 2 are fastened to the body 1. of the stator, and then together they are potted with the potting compound 5, which is subsequently cured. Together, the coils 2, the ribs 4, and the potting compound 5 have the shape of a ring. The potting compound 5 allows for transfer of the load, especially torque and thermal, from the coils 2 to the ribs 4 and then to the body 1. of the stator. Thanks to the potting together with the stator end face 11 , part of the heat is transferred directly to the body 1_ of the stator. Further, the potting compound 5 strengthens the coils 2 and the ribs 4, making the stator more resistant to damage, protects against dust and moisture, improves the wiring properties, and increases the overall performance of the electric motor comprising this stator.

[0064] The body 1_ of the stator comprises openings 6 for the winding 13 lead, which in the first exemplary embodiment are positioned closer to the axis 3 of the stator than the coils 2, as can be seen in fig. 1 . The openings 6 for the winding 13 lead are arranged in a circle similar to the coils 2 and ribs 4, which passes through the centers of the openings 6 for the winding 13 lead, with the same center - the center of the stator end face 11 . Therefore, this circle has a smaller radius than the circle that passes through the coils 2 and ribs 4. Due to the fact that these openings 6 for the winding 13 lead are positioned closer to the axis 3 of the stator than usual, i.e. , than at the point where the coils 2 are fastened to the body 1. of the stator, the load, mainly thermal load, is more efficiently removed from the positions with a high load (i.e., at the point where the ribs 4 are fastened). Because there are fewer through openings in these positions with a high load, the stator may have a longer service life. In the first exemplary embodiment, there are two openings 6 for the winding 13 lead for each coil 2, as can be seen in fig. 1 . Therefore, one end of the winding 13 passes through one opening 6 for the winding 13 lead and the other end of the winding 13 of the given coil 2 passes through the other opening 6 for the winding 13 lead (not shown in the drawings).

[0065] The second exemplary embodiment is an electric motor that comprises the stator of the first exemplary embodiment, a rotor, and a shaft. The second exemplary embodiment is shown in fig. 3 to fig. 6. Fig. 4 shows a vertical section through the electric motor, wherein this section is shown in fig. 1 for better clarity, although the rotor is not shown in fig. 1 . The rotor comprises a body of the rotor and a rotor end face 8, which have a similar structure to the stator end face 11 and the body 1. of the stator - the rotor end face 8 has a circular shape, with the axis of the rotor perpendicular to the rotor end face 8 passing through its center, and the body of the rotor has the shape of a plate with a circular cross-section. Here the axis of the rotor (also the axis of rotation of the rotor) and the axis of the shaft are identical to the axis 3 of the stator. The body of the rotor comprises an opening for the shaft and a hub therein, in which the shaft is fastened for the transfer of the rotational motion from the rotor, as can be seen in fig. 4. The center of the opening lies on the axis of the rotor. The rotor is thus connected to the stator by the shaft.

[0066] In the second exemplary embodiment, the rotor comprises a first ring 9 of magnets and a second ring 10 of magnets that project from the rotor end face 8 toward the stator end face 11 , as can be seen in fig. 3. Both rings comprise magnets conventionally used in electric motors and a magnet holder. The magnet holder is a circular plate, in contact with the rotor end face 8 on one its end, and the magnets are fastened to the other end, which is free and positioned closer to the stator end face 1_1_, as can be seen in fig. 3. Further, both circular rings have a common center that lies on the axis of the rotor. The first ring 9 of magnets has a larger radius than the second ring 10 of magnets and also an inner radius (the dimension furthest from the axis of the rotor in the radial direction) larger than the largest radius of the ring of the coils 2 and ribs 4 such that the first ring 9 of magnets can rotate around the ring of the coils 2 and ribs 4. The second ring 10 of magnets has its outer radius (furthest from the axis of the rotor, in the radial direction) smaller than the smallest radius of the ring of the coils 2 and ribs 4 such that the second ring 10 of magnets can rotate around the ring of the coils 2 and ribs 4 on the opposite side from the first ring 9 of magnets. Thus, the first ring 9 of magnets and the second ring 10 of magnets surround the ring of the coils 2 and ribs 4 in the radial direction along most of their length (in the length direction L), as can be seen in fig. 3, fig. 4, and fig. 6.

[0067] Thus, as can be seen in fig. 4, one end face 14 of the coil 2 is fastened to the stator end face 11 and the other end face 14 of the coil 2 is free in the space between the rotor and the stator. Even though the coils 2 are fastened only by one of their ends and their largest dimension projects from the body 1. of the stator, due to the attachment of the coils 2 to the ribs 4 and potting with the potting compound 5, the electric motor is stronger with a better heat dissipation and has a longer service life than conventional electric motors with a dual rotor of the prior art.

[0068] The third exemplary embodiment is a stator of the electric motor that comprises a ring 15 for connecting the coils 2. The third exemplary embodiment is based on the first exemplary embodiment, however, in the third exemplary embodiment, the body 1_ of the stator does not comprise the openings 6 for the winding 13 lead. The other features of the stator are the same as in the first exemplary embodiment. The third exemplary embodiment is shown in figs. 7 to 9. The ring 15 according to the third exemplary embodiment, which can be seen in fig. 9, comprises openings 17 of the ring 15 for each rib 4, cooling ribs 16, openings 18 of the ring 15 for the winding 13 lead of each coil 2, and openings for the projections of the end faces 14 of the coils 2 for fastening the coils 2 to the ring 15. In the third exemplary embodiment, the ring 15 is a copper sheet that comprises openings, cutouts and bent parts of the sheet, which are the cooling ribs 16 and the projections of the ring 15 for the ends of the windings 13.

[0069] The openings 17 of the ring 15 for the ribs 4, as can be seen in fig. 8 and fig. 9, have larger dimensions in the cross-section in the direction of the axis 3 of the stator than the cross-section of the rib 4, to facilitate mounting of the ring 15 onto the ribs 4 and for potting the ribs 4 and the coils 2 with the potting compound 5.

[0070] In the third exemplary embodiment, the cooling ribs 16 are formed by bending a part of the sheet of the ring 15, and are thus made of the same material as the other parts of the ring 15. These cooling ribs 16 assist in the heat dissipation from the coils 2 through the ribs 4 to the body 1_ of the stator, when using a stator according to the third exemplary embodiment in the electric motor, a major part of the heat is dissipated through an air gap to the body of the rotor. Thus, in the third exemplary embodiment, the potting compound 5 (which is not shown in the drawings of the third exemplary embodiment), the ring 15 (particularly the cooling ribs 16), and the rib 4 contribute to the heat dissipation from the coils 2 the most. Similar to the ribs 4 attached to the body 1. of the stator, the cooling ribs 16 point away from the stator end face 11 to the rotor end face 8.

[0071] In the third exemplary embodiment, the openings of the ring 15 for the projections of the end faces 14 of the coils 2 are cutouts, as can be seen in fig. 8 and fig. 9. For each coil 2, one opening of the ring 15 for the projections of the end faces 14 of the coils 2 is positioned at the outer circumference of the ring 15 and one at the inner circumference of the ring 15 for a more stable fastening of the coil 2. Also, because they are cutouts, the ring 15 can be more easily attached to the coils 2. The ring 15 mounted on the coils 2 and ribs 4 can be seen in fig. 7.

[0072] The ring 15 further comprises projections with an area for fastening the end of the winding 13 of the coil 2 to the ring 15 at the opening 18 of the ring 15 for the winding 13 lead. Thus, the winding 13 of the coil 2 passes through the opening 18 of the ring 15 for the winding 13 lead. The winding 13 is attached by soldering to the area of the projection of the ring 15 for these ends of the winding 13. Therefore, in the third exemplary embodiment, all the coils 2 are electrically conductively connected. In the third exemplary embodiment, the openings 18 of the ring 15 for the winding 13 lead are connected to the cutouts for the projections of the end faces 14 of the coils 2, as can be seen in fig. 8 and fig. 9.

[0073] The fourth exemplary embodiment is a stator of the electric motor that comprises a smaller number of ribs 4 than the number of coils 2 - the ribs 4 are half as many as the coils 2. The fourth exemplary embodiment is based on the first exemplary embodiment, however, each coil 2 is attached to only one rib 4. Looking in the direction of the axis 3 of the stator at the stator end face 1_1_, there is a rib 4 in every second gap clockwise between the coils 2. Similarly to the first exemplary embodiment, the coils 2 with the ribs 4 are potted with the potting compound 5.

[0074] Alternative embodiment:

[0075] The alternatives relating to the individual features or components of the invention, which are briefly set out below, may be used separately or combined at the discretion of one skilled in the art. Unless otherwise indicated for a particular alternative embodiment, the other features of this embodiment are implemented as in any of the embodiments described above and shown in the drawings.

[0076] Each rib 4 alternatively comprises a cooling channel, in which a cooling liquid flows during the operation of the electric motor. The body 1. of the stator thus comprises two openings for the cooling liquid at each rib 4. One opening for the cooling liquid is used for the inflow of the cooling liquid into the rib 4 and the other one for the outflow. The additional heat dissipation by means of the cooling channels and the cooling liquid increases the heat dissipation from the coils 2. Alternatively, the rib 4 contains only one cooling channel, with the liquid not circulating through the rib but the channel being filled with the liquid.

[0077] Alternatively, the stator comprises one opening 6 for the winding 13 lead in the body 1. of the stator, which serves as a control electronics power cable lead. The control electronics are located in the space between the stator and the rotor. The windings 13 of all the coils 2 are connected to the control electronics.

[0078] Alternatively, the individual wires (windings 13) of the coils 2 are connected inside the stator such that they are connected into individual phases, and only the phase conductors lead from the stator.

[0079] Alternatively, the body 1. of the stator comprises projections for fastening the coils 2, and each coil 2 comprises openings for mounting onto the body 1. of the stator. Alternatively, each rib 4 is bonded to the body 1_ of the stator from the stator end face 11 .

[0080] Alternatively, the winding 13 is fastened by welding to the area of the projection of the ring 15 for these ends of the winding 3. Alternatively, the stator according to the third exemplary embodiment is part of the electric motor, wherein the rotor is based on the second exemplary embodiment. The body of the rotor comprises openings for air flow to the cooling ribs 16 of the ring 1_5, making the heat dissipation from the coils 2 more efficient.

[0081] Industrial Applicability The invention can be used in various electric motors, in particular those with a dual rotor, with a two-phase or multi-phase structure.

[0082] List of Reference Signs

[0083] 1 - Body of the stator

[0084] 2 - Coil

[0085] 3 - Axis of the stator

[0086] 4 - Rib

[0087] 5 - Potting compound

[0088] 6 - Opening for the winding lead

[0089] 7 - Opening for seating the coil

[0090] 8 - Rotor end face

[0091] 9 - First ring of magnets

[0092] 10 - Second ring of magnets

[0093] 11 - Stator end face

[0094] 12 - Core

[0095] 13 - Winding

[0096] 14 - End face of the coil

[0097] 15 - Ring

[0098] 16 - Cooling rib

[0099] 17 - Opening of the ring for the rib

[0100] 18 - Opening of the ring for the winding lead

[0101] L - Length direction

[0102] W - Width direction

Claims

CLAIMS1 . A stator for an electric motor comprising a body (1 ) of the stator and at least two coils (2) arranged around an axis (3) of the stator, characterized in that the stator is provided with at least one rib (4) between at least two adjacent coils (2), wherein each rib (4) is attached to the body (1 ) of the stator, and at least one coil (2) is attached to at least one rib (4) for a transfer of loads from the coil (2) to the body (1 ) of the stator.

2. The stator for an electric motor according to claim 1 , characterized in that at least one rib (4) comprises a cooling channel.

3. The stator for an electric motor according to claim 1 or 2, characterized in that at least one rib (4) is made of a thermally conductive material for heat dissipation from the coil (2) to the body (1 ) of the stator with a thermal conductivity coefficient greater than or equal to 20 W m"1K"1.

4. The stator for an electric motor according to any one of claims 1 to 3, characterized in that each coil (2) is attached to at least one rib (4) with a potting compound (5) for electronics.

5. The stator for an electric motor according to any one of claims 1 to 4, characterized in that each coil (2) comprises a winding, wherein the body (1 ) of the stator comprises at least one opening (6) for a winding lead, wherein the opening (6) for the winding lead is positioned closer to the axis (3) of the stator than the given coil (2).

6. The stator for an electric motor according to any one of claims 1 to 5, characterized in that the body (1 ) of the stator comprises at least one opening (7) for seating the coil (2), wherein the opening (7) for seating the coil (2) is non- through, wherein at least one coil (2) is fastened in the opening (7) for seating the coil.

7. The stator for an electric motor according to any one of claims 1 to 6, characterized in that all ribs (4) and all coils (2) are attached to each other.

8. The stator for an electric motor according to any one of claims 1 to 7, characterized in that each coil (2) is segmented.

9. The stator for an electric motor according to any one of claims 1 to 8, characterized in that the stator comprises a ring (15) for connecting at least two coils (2), wherein the ring (15) is fastened to free ends of at least two coils (2).

10. The stator for an electric motor according to claim 9, characterized in that the ring (15) comprises at least one cooling rib (16) for dissipation of heat from the coils (2).11 . The stator for an electric motor according to claim 9 or 10, characterized in that the ring (15) comprises at least one opening (17) of the ring (15) for a rib (4).

12. The stator for an electric motor according to any one of claims 9 to 11 , characterized in that at least two coils (2) are electrically conductively connected by the ring (15).

13. The stator for an electric motor according to any one of claims 1 to 12, characterized in that the stator is provided with a total of at least one rib (4) between every two adjacent coils (2) and each coil (2) is attached to at least one rib (4).

14. The stator for an electric motor according to any one of claims 1 to 13, characterized in that each rib (4) is offset from each adjacent coil (2).

15. The stator for an electric motor according to any one of claims 1 to 14, characterized in that the body (1 ) of the stator comprises a stator end face (11 ), wherein each coil (2) projects from the stator end face (11 ), wherein each rib (4) is inserted into the body (1 ) of the stator in a direction from the stator end face (11 ) and projects from the stator end face (11 ).

16. The stator for an electric motor according to claim 15, characterized in that the stator end face (11 ) has a circular shape, wherein the axis (3) of the stator, which is perpendicular to the stator end face (11 ), passes through a center of the stator end face (11 ).

17. An electric motor comprising at least one rotor, characterized in that it comprises the stator according to claim 16, wherein the rotor is rotationally connected to the stator, wherein the rotor comprises a rotor end face (8) and a ring of magnets projecting from the rotor end face (8) towards the stator end face (11 ), wherein each coil (2) is positioned radially from the ring of magnets.

18. The electric motor according to claim 17, characterized in that the rotor comprises a second ring (10) of magnets, wherein each coil (2) of the stator is positioned between the first ring (9) of magnets and the second ring (10) of magnets.