Patent Application
20200164735
The present invention relates to a method of assembling an in-wheel electric motor. Also, the invention relates to an in-wheel electric motor. Furthermore, the invention relates to a drive assembly for a wheel of a vehicle comprising such an electric motor.
Such an in-wheel electric motor is known from WO 2013/025096 that describes an electric vehicle with an in-wheel electric motor in which the rotor is coupled to a rim of the wheel carrying one or more tyres. The stator is mounted on the frame of the vehicle via a wheel suspension system. The known in-wheel motor is part of a direct drive wheel in which the electromagnets of the motor directly drive the rim and the tyre without any intermediate gears. In this manner, weight and space are saved and the number of components in the drive assembly is minimized.
The torque that is generated by the in-wheel motor depends on the flux-carrying surface between the rotor and the stator and is a quadratic function of the rotor radius. The rotor magnets are placed as far outwardly as possible around the stator, to obtain a largest possible rotor radius and the motor design is optimised to minimize the gap between the rotor and the stator for delivering a maximum power and torque to the tyre. The gap width between rotor and stator is on the other hand designed to be large enough to absorb mechanical impacts on the wheel during driving conditions.
The windings of the stator are powered by power electronics that are situated within the stator, which power electronics convert electrical energy from a power supply system of the vehicle, e.g. a battery pack and/or an electric generator, to an AC current that is suitable for use by the electric motor. Such power electronics typically comprise power electronics, e.g. IGBT current modules and a current regulator, such as described in EP 1 252 034. By using the power electronics to control the current and/or voltage supplied to the windings of the stator, the magnetic field vector of the flux generated by the stator is controlled and the electric motor is operated at the desired torque and/or speed of rotation. By integrating the power electronics within the stator, the length of bus bars which run from the power electronics to the electromagnets can remain short, which is highly desirable in view of minimizing losses of the high electrical currents and voltages generally required for operating such an electric motor, which may for instance amount to 300 A at 700V or more.
In order to cool the electrical motor and/or the power electronics, the known drive assembly is provided with a cooling system having one or more cooling channels that are situated close to an outer surface of the stator and/or the power electronics, through which liquid coolant can flow into and out of the drive assembly.
The in-wheel drive assembly can be embodied as a substantially self-contained module, without any moving parts of the vehicle attached to and/or extending into the rotor. The interior space defined by the rotor is preferably substantially closed off to prevent ingress of foreign particles, such as dust and/or wear particles released by a brake system of the vehicle and/or by the road, into said interior.
The in-wheel drive assembly may be mounted on the vehicle in a variety of positions by connecting the vehicle side of the drive assembly to the vehicle frame. A rim for mounting a tire may be attached to the rotor, preferably to a substantially cylindrical outer surface of the rotor.
A disadvantage of the prior art in-wheel electric motor is that repair or replacement of the power electronics requires that the housing is opened and largely removed. Since the electric motor is situated within the wheel, the opening of the housing also requires that the wheel in which the electric motor is accommodated must be removed from the vehicle.
It is an object of the present invention to overcome or mitigate one or more of the disadvantages from the prior art.
The object is achieved by an in-wheel electric motor comprising a stator with at a vehicle side an connector member, a cylindrical hollow stator body connected to the connector member; an outer surface of the stator body being equipped with stator windings, and further comprising a cylindrical rotor body coaxially enclosing the stator; the electric motor further comprising a power electronics device for powering the stator windings, wherein the hollow stator body is provided with a stator body opening at a road side of the electric motor for receiving the power electronics device, and the enclosing rotor body is provided with a removable cover plate covering a rotor body opening of the rotor body at the road side and covering the stator body opening.
By providing a rotor body with a removable cover plate at the road side and a hollow stator body that is open at the road side, the power electronics device can be inserted in or removed from the electric motor in an easily accessible manner without the need for disassembly of the drive wheel from the vehicle. This saves on time for installation and de-installation during maintenance.
According to an embodiment, the in-wheel electric motor is arranged in a manner that the head of the connector member and a casing of the power electronics device are connected by a plugs and sockets arrangement. This arrangement allows that the placement of the power electronics device within the drive wheel assembly is simplified. Preferably, the connector member has an end face facing the road side, wherein the power electronics device is connected to the end face via said plugs and sockets arrangement. According to an embodiment, the connector member is provided with a number of protruding elements or recesses extending from the end face and parallel to an axial direction, and the power electronics device is positioned on the connector member within the hollow stator body with the protruding elements being received in corresponding counter recesses or the recesses on the connector member receiving corresponding protruding elements in a facing surface of the casing of the power electronics device. This significantly facilitates mounting of the power electronics device within the hollow stator body.
According to an embodiment, the in-wheel electric motor is arranged in a manner that the connector member is provided with a first opening of a feed channel for liquid coolant and a second opening of a return channel opening for liquid coolant, each of the feed and return channels being substantially parallel to the axial direction of the connector member, and the power electronics device is provided with a cooling circuitry, the cooling circuitry comprising a feed connector and a return connector for liquid coolant on the facing surface, with the feed connector arranged for liquid tight coupling to the feed channel and the return connector arranged for liquid tight coupling to the return channel, when positioned on the connector member.
By providing the connector member with internal channels for liquid coolant and by providing corresponding connectors on the casing of the power electronics device, connections and disconnections between the cooling circuitry within the rotating parts and the fixed parts of the vehicle are made during the installation and de-installation respectively without further interactions by maintenance personnel.
According to an embodiment, the connector member is provided with a first opening of a feed channel for liquid coolant and a second opening of a return channel opening for liquid coolant, each of the feed and return channels being substantially parallel to the axial direction of the connector member, wherein the power electronics device is provided with a cooling circuitry, the cooling circuitry comprising a feed connector and a return connector for liquid coolant on the facing surface, with the feed connector arranged for liquid tight coupling to the feed channel and the return connector arranged for liquid tight coupling to the return channel, when positioned on the connector member. Thus, coupling of the feed channel to the facing surface can be achieved by simply sliding the power electronics device towards the facing surface of the flange.
According to an embodiment, the hollow stator body is provided with an inner mounting ridge parallel to the circular opening of the hollow stator body, and the casing of the power electronics device is provided at the road side with a bracket that abuts the inner mounting ridge when the power electronics device is positioned on the connector member.
According to an embodiment, the hollow stator body is provided on its inner circumferential surface with at least two inner mounting ridges which extend parallel to the axis of rotation, and the casing of the power electronics device is provided at the road side with a bracket that abuts the inner mounting ridges when the power electronics device is positioned on the connector member.
According to an embodiment, the rotor cover plate is provided with a circular cover plate opening centred with the electric motor rotation axis, and the power electronics device comprises at the road side a resolver for sensing a relative angular position of the rotor with respect to the stator windings, which resolver has a rotation axis coinciding with the electric motor rotation axis and is arranged within the circular cover plate opening and attached to the cover plate. The resolver can thus easily be reached, even when the in-wheel motor is mounted on a vehicle, from the road side. The relative angular position of the rotor with respect to the stator windings as sensed by the rotor may be used for controlling a current and/or voltage that is to be applied on individual stator windings, as known in the art.
According to an aspect, the invention provides a method for assembling an in-wheel electric motor; the electric motor comprising a stator with at a vehicle side an connector member, a cylindrical hollow stator body with a central axis R, connected to the connector member and on an outer surface of the stator body equipped with stator windings, the electric motor further comprising a power electronics device for powering the stator windings the connector member having a number of protruding or recessed elements parallel to the axial direction and extending towards an opening of the hollow stator body at a road side; a surface of the casing of the power electronics device being provided with complementary protruding or receiving elements for engaging the protruding or recessed elements of the connector member; wherein the casing of the power electronics device is positioned via the road side opening inside the hollow stator body with the surface of the casing facing the connector member, and subsequently moving the power electronics device along the direction of the central axis to the connector member; and engaging the protruding or recessed elements of the connector member each in a corresponding one of the protruding or receiving elements on the surface of the casing of the power electronics device.
Additionally, the invention relates to a drive assembly for a wheel of a vehicle either comprising an in-wheel electric motor as described above, or an in-wheel electric motor manufactured by a method as described above wherein the rotor part and the stator part are both adapted to be arranged at least partially within the wheel.
Advantageous embodiments are further defined by the dependent claims.
The invention will be explained in more detail below with reference to drawings in which illustrative embodiments thereof are shown. The drawings are intended exclusively for illustrative purposes and not as a restriction of the inventive concept.
In the drawings,
A plurality of permanent magnets 61 is attached on an inner circumferential surface 62 of the rotor 60 and can rotate around electromagnets 41 of the stator 30. The electromagnets 41 are fixed on the stator body 31 and drive rotation of the rotor by interaction between the permanent magnets 61 and the magnetic flux generated by the electromagnets 41. The stator 30 and rotor 60 form an electric motor adapted for directly driving rotation of a wheel around axis of rotation R.
The rotor 60 comprises a substantially cylindrical rotor body 71 which has transverse ends 72,73 respectively at its vehicle side 2 and at its road side 3. Both transverse ends 72,73 are substantially closed off in order to prevent foreign particles, such as dust and wear particles from the road or released by a braking system of the vehicle, from entering the interior of the hollow rotor 60. The vehicle side of the rotor is substantially closed off by a side plate 74 which extends transversely to the axis of rotation R and by a cover plate 75. The side plate 74 and cover plate 75 are each provided with an opening through which the portion 34 of the connector member 33 extends. The side plate 74 supports the vehicle side bearings 52 while the cover plate 75 is attached to the side plate 74 to cover the bearings 51 at their transverse vehicle side 2 and comprises an opening 77 through which portion 34 extends. The cover plate 75, together with a shaft seal 78 which is arranged between the inner circumferential edge 79 of the opening 77 and the outer circumference of the shaft 34, prevents foreign particles from damaging the vehicle side bearings 52. Additionally, the cover plate 75 and shaft seal 78 substantially prevent such particles from entering the interior 5 of the rotor from the vehicle side 2, where the particles could interfere with the electromagnets 41.
The road side bearings 54, which are arranged at an inner side of the stator body 31, are covered on the road side 3 by a detachable second cover plate 80. A resolver 81 rotationally connects the stator 30 to the second side plate 80 and is adapted for detecting an angular position of the rotor 60 relative to the stator 30. A circular opening is provided in the second cover plate 80, in which the resolver 81 is attached to the second cover plate 80 for the rotational connection to the rotor part.
For controlling and powering the electromagnets 41, a casing 100 holding circuitry of power electronics 42 is arranged within the hollow stator body 31. The power electronics 42 comprise components, such as IGBT's, for converting electrical energy from a power supply system of the vehicle, e.g. a battery pack and/or an electric generator, to an AC form suitable for use by the electric motor. A resolver 81 provides an angular position signal indicative of an angular position of the rotor to the power electronics so that the alternating current is supplied in phase with the magnetic field of the rotor.
To prevent overheating of the power electronics when the electric motor is in operation, a cooling circuitry is provided comprising cooling ducts (not shown) close to the power electronics 42 within the interior of the stator body 32 and spaced apart from the stator body 32. Coolant is supplied to the cooling ducts via a coolant supply channel 45 which runs through the connector member 33 from the exterior of the rotor to its interior. After having cooled the power electronics 42, the coolant flows via passage 46 in the connector member 33, to a cooling jacket 37 which is provided on the outer surface 32 of the stator body 30. The cooling jacket 37 is provided with channels 38 which form a circuit that runs along the hollow cylindrical body 31 and provides a passage through which liquid coolant flows to cool the electromagnets 41 which are arranged at an outer side 40 of the cooling jacket 37. Relatively cold coolant can thus be supplied through the coolant supply channel 45 with the coolant warming up during its passage through the cooling ducts and absorbing heat energy from the power electronics 42, and subsequently passing through channels 38 to absorb heat-energy from the electromagnets 41 before being removed from the drive assembly 1 and led back to the vehicle through a coolant discharge channel (not shown) which extends through the connector member 33. The warmed-up coolant is preferably cooled in a heat exchanger on the vehicle, after which it is recirculated through the coolant supply channel 45.
Power supply lines 43a, 43b for supplying power to the power electronics 42 run from the exterior of the rotor 60, through passage 44, comprising a through hole, in the connector member 33, to the power electronics.
According to the invention, the casing of the power electronics 42 is mounted on the head i.e., the flange 35 of the connector member 33. The diameter of the opening 90 in the cylindrical rotor body 71 at the road side is larger than the cross-section of the casing of the power electronics 42. The detachable second cover plate 80 that closes off the opening in the cylindrical rotor body 71 at the road side allows that the power electronics 42 can be mounted by inserting the casing through the opening in the cylindrical rotor body 71 at the road side 3. Also, the detachable second cover plate 80 allows to lock the casing of the power electronics device in place and also to relatively easy access the power electronics 42, when needed.
As will be described in more detail with reference to
The in-wheel electric motor 4 comprises the stator part 60 and the rotor part 30. The stator part 60 is coupled to the connector member 33 which is part of the chassis of a vehicle.
The rim 82 is arranged at the outer circumference of the rotor part 60. The rim 82 can be attached to the rotor part by a bolted connection as known in the prior art.
On the rim 82, one or more tyres 84 are mounted. The rotor part 60 and the stator part 30 are both arranged at least partially within the wheel.
The connector member 33 comprises a first end 33-1 at the vehicle side 2 that is to be connected to the chassis of the vehicle (not shown). At a second end 33-2 axially opposite the first end 33-1, the connector member 33 comprises the flange 35 that forms the head of the connector member 33 for connecting to the hollow stator body 31. Within the surface of the flange 35 facing towards the road side 3, the connector member 33 is provided with a number of protruding elements 91 extending along the axial direction A.
At predetermined positions, relative to the positions of the protruding elements 91, the surface of the flange 35 is provided with openings for a feed channel 92 for liquid coolant, a return channel 93 for liquid coolant and through holes 94 for electrical conductors, respectively.
Within the body of the connector member 33, through holes are provided along the axial direction A for the feed channel 92, the return channel 93, and the electrical conductors 94.
On the surface of the casing 100 of the power electronics device 42 that faces the flange 35 of the connector member 33 in mounted position, at corresponding positions, counter elements 101 for receiving the protruding elements 91, fluid connectors 102 for liquid tight coupling to the feed and return channels 92, 93, and terminals 103, 104 for the electrical conductors are respectively provided. It will be appreciated that as alternative in the surface of the flange 35 instead of protruding elements 91 recesses are provided and in the surface of the casing that faces the flange 35, protruding counter elements at corresponding positions are provided.
When the casing 100 of the power electronics device 42 is mounted on the flange 35, the protruding elements 91 will be received into the receiving counter elements 101 (or the protruding counter elements will be received in the recesses) and will provide mechanical support for the power electronics device 42 casing 100.
Some play may be allowed between the protruding elements 91 and the counter elements 101 (or the recesses and the protruding counter elements) to provide for some flexibility in the connection when the drive assembly (wheel and in-wheel electric motor) is under dynamic load during operation.
Additionally, the hollow stator body 31 can be provided an inner mounting flange 96 on the inner circumference of the hollow stator body 31 as a secondary support for the power electronics device 42. The inner mounting flange 95 is positioned at a distance from the flange 35 of the connector member 33 that corresponds substantially with a length 106 of the casing from the flange 35. The casing 100 of the power electronics device 42 comprises at the surface facing the road side a bracket 105 which is in connection with the inner mounting flange 95 of the hollow stator body 31. The bracket 105 and inner mounting flange 95 are best seen in
In the mounted position, each of the fluid connectors 102 will couple with one of the respective openings of the feed and return channels 92, 93, and the terminals 103, 104 of the electrical conductors will extend through the connector member's through holes for the electrical conductors to the vehicle side 2.
The electrical conductors are connected to an electrical power source (not shown) inside the vehicle (not shown). The electrical power source is for example a battery or an electrical generator.
In an embodiment, the terminals 103, 104 are elongated strips that are perpendicular to the facing surface of the casing 100 and to the surface of the flange 35. At the side of the power electronics device 42 the terminals are connected to power electronics that feed the stator windings to generate an electromagnetic field for interaction with the magnets 61 arranged in the rotor part 60.
In this cross-section, the respective connections between the feed channel and the feed fluid connector and between the return channel and the return fluid connectors are shown. Also, one of the terminals is shown within the corresponding through hole in the connector member 33.
The connection between the feed channel and the feed fluid connector, and between the return channel and the return fluid connectors are each provided with a seal 107, 108 to be leak-proof.
In an embodiment, the openings of the feed channel 92 and the return channel 93 are provided with seals 107, 108 and check valves (not shown). Advantageously, a check valve will close the coolant circuitry at the vehicle side 2 in case of an open connection at the flange 35 of the connector member 33 when the power electronics device 42 is removed from the flange of the connector member 33.
The invention has been described with reference to the preferred embodiment. Obvious modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019300 | Jul 2017 | NL | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/NL2018/050504 | 7/20/2018 | WO | 00 |
