DESC:TWO PART REAR END COVER FOR MOTOR OF ELECTRIC VEHICLE

CROSS REFERENCE TO RELATED APPLICTIONS
The present application claims priority from Indian Provisional Patent Application No. 202221040548 filed on 15/07/2022, the entirety of which is incorporated herein by a reference.
TECHNICAL FIELD
The present disclosure relates to a rear end cover for a permanent magnet synchronous reluctance motor (PMSRM) of an electric vehicle. Particularly, the present disclosure relates to a two part rear end cover for the PMSRM of the electric vehicle.
BACKGROUND
Recently, there have been a rapid development in electric vehicles because of their ability to resolve pollution related problems and serve as a clean mode of transportation. Electric vehicles use traction motors which are capable of delivering torque to the wheels. AC motors, such as permanent magnet synchronous reluctance motor are one of the good options to serve as traction motor in electric vehicles due to their high performance and efficiency.
As known in the art, the electric motor has two main parts, a stator, and a rotor, concealed within a motor casing. Further, the motor housing comprises a motor case, a front end cover and a rear end cover. Conventionally available end covers are mono-layer/ single plates and are used for enclosing the stator and the rotor within the motor casing, and for supporting the rotor-shaft from both front and rear ends. One of the challenges in such motor design is to dissipate the heat generated during the operation, to ensure reliability and longevity of the electric motor.
In recent years, to overcome the challenge of heat dissipation, the electric motors are designed with an active cooling system, such as liquid cooling system, to keep the electric motor at optimum temperature during the operation and prevent the electric motor from overheating during extended operation. However, such cooling system can be complex and expensive to implement. In electric motors with such system, hollow rotor shafts are used to facilitate rotor cooling by allowing flow of a coolant through the rotor. The flow of coolant through the hollow rotor shafts ensures the cooling of the rotor. Similarly, liquid cooling channels or cooling jackets are provided on the stator to facilitate the stator cooling. As the liquid coolant flows through the electric motor, coolant flow paths are required to be carefully sealed off to prevent the leakage of coolant into other components of the electric motor. Such cooling system increases the complexity of the electric motor design. Furthermore, the assembling process of the electric motors with such cooling systems is complex due to requirement of fixing multiple sealings during the assembling of the electric motor. There are high chances of dislocations or mis-alignment of coolant seals during the process of assembling the electric motor with conventional mono layer/ single end cover plate due to handling of multiple seals simultaneously. Such dislocations or mis-alignment of the coolant seals may result in the leaking of coolant into the motor casing which may damage the other components of the electric motor resulting into failure of the electric motor. Moreover, the conventional mono layer/ single end cover plate designs are difficult maintain as the removal of the mono layer/ single end cover plate expose all the components of the motor during maintenance of the electrical motor or maintenance of the cooling system. Furthermore, the removal of mono layer/ single end cover plate increases the maintenance complexity by increasing the complexity of reassembly of the electric motor after the maintenance. Moreover, in such design, the whole electric motor is required to be disassembled even if only the cooling system is required to be serviced or maintained. As a result of such complexities in the assembling/disassembling/reassembling and servicing of the hollow shaft liquid cooled electric motors, the cost of maintenance increases significantly.
Therefore, there exists a need for developing a rear end cover for hollow shaft liquid cooled electric motors, that can be assembled with less complexity and easy to disassemble for the purpose of maintenance of the cooling system and overcomes the one or more problems associated with the coolant seals as set forth above.
SUMMARY
An object of the present disclosure is to provide a permanent magnet synchronous reluctance motor PMSRM with a two-part end cover, that can be assembled with ease and ensuring proper fixing of coolant seals.
Another object of the present disclosure is to provide a permanent magnet synchronous reluctance motor PMSRM with a two-part end cover, that is easy to disassemble and reassemble for the purpose of maintenance.
In accordance with an embodiment of the present disclosure, there is provided a permanent magnet synchronous reluctance motor PMSRM for an electric vehicle, the motor comprising:
- a rotor assembly;
- a stator assembly; and
- a motor casing comprising at least one terminal box, a front end cover and a rear end cover,
characterized in that the rear end cover comprises an end cover plate and an end cover cap.
The present disclosure provides a permanent magnet synchronous reluctance motor for an electric vehicle with two part rear end cover. The permanent magnet synchronous reluctance motor for the electric vehicle with two part rear end cover, as disclosed in the present disclosure, is advantageous in terms of ease of assembling and ensuring proper fixing of coolant seals used for sealing coolant flow paths in the electric motor. Furthermore, the PMSRM for the electric vehicle with two part rear end cover is easy to disassemble and reassemble for the purpose of maintenance. Furthermore, the PMSRM with two part rear end cover does not require complete disassembly of the motor assembly for maintenance of cooling system of the electric motor or the coolant flow paths present in the electric motor. Furthermore, the PMSRM with two part rear end cover eliminates the possibilities of coolant seal rupture during operation and servicing of the electric motor as the seals are properly aligned during the process of assembling the electric motor. Such proper alignment of the coolant seals is achieved by simplifying the assembly process. Furthermore, the PMSRM with two part rear end cover reduces the cost of maintenance of the electric motor.
Additional aspects, advantages, features and objects of the present disclosure would be made apparent from the drawings and the detailed description of the illustrative embodiments constructed in conjunction with the appended claims that follow.
It will be appreciated that features of the present disclosure are susceptible to being combined in various combinations without departing from the scope of the present disclosure as defined by the appended claims.
BRIEF DESCRIPTION OF DRAWINGS
The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present disclosure, exemplary constructions of the disclosure are shown in the drawings. However, the present disclosure is not limited to specific methods and instrumentalities disclosed herein. Moreover, those in the art will understand that the drawings are not to scale. Wherever possible, like elements have been indicated by identical numbers.
Embodiments of the present disclosure will now be described, by way of example only, with reference to the following diagrams wherein:
Figure 1 is an exploded view of a permanent magnet synchronous reluctance motor (PMSRM) of an electric vehicle comprising a two-part rear end cover, in accordance with an embodiment of the present disclosure.
Figure 2 is an exploded view of the two-part rear end cover of the PMSRM of the electric vehicle, in accordance with an embodiment of the present disclosure.
In the accompanying drawings, an underlined number is employed to represent an item over which the underlined number is positioned or an item to which the underlined number is adjacent. A non-underlined number relates to an item identified by a line linking the non-underlined number to the item. When a number is non-underlined and accompanied by an associated arrow, the non-underlined number is used to identify a general item at which the arrow is pointing.
DETAILED DESCRIPTION
The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. Although some modes of carrying out the present disclosure have been disclosed, those skilled in the art would recognise that other embodiments for carrying out or practising the present disclosure are also possible.
The description set forth below in connection with the appended drawings is intended as a description of certain embodiments of a motor of an electric vehicle and is not intended to represent the only forms that may be developed or utilised. The description sets forth the various structures and/or functions in connection with the illustrated embodiments; however, it is to be understood that the disclosed embodiments are merely exemplary of the disclosure that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimised to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.
While the disclosure is susceptible to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the drawings and will be described in detail below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure.
The terms “comprise(s)”, “comprising”, “include(s)”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a setup, system that comprises a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or system. In other words, one or more elements in a system or apparatus preceded by “comprises... a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or apparatus.
In the following detailed description of the embodiments of the disclosure, reference is made to the accompanying drawings and which are shown by way of illustration specific embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense.
The present disclosure will be described herein below with reference to the accompanying drawings. In the following description, well known functions or constructions are not described in detail since they would obscure the description with unnecessary detail.
Figure 1 describes an exploded view of a permanent magnet synchronous reluctance motor PMSRM 100 for an electric vehicle. The motor 100 comprises a rotor assembly 102, a stator assembly 104 and a motor casing 106 comprising at least one terminal box 108, a front end cover 110 and a rear end cover 112. The rear end cover 112 comprises an end cover plate 112a and an end cover cap 112b.
The present invention, as defined by the non-limiting embodiments disclosed herein, is an improved PMSRM design with an active cooling system. The PMSRM 100 with two part rear end cover 112, as disclosed herein, is less complex to assemble, disassemble, reassemble and maintain. The present invention is advantageous in terms of providing an electric motor with a less complex assembly procedure as coolant seals used for sealing one or more coolant flow path may now be applied or fixed in a staged manner during the electric motor assembly process. It would be appreciated that the rear end cover plate 112a can be fixed on the motor casing 106 during the assembly process prior to the fixing of the coolant seals at the required places. Once the rear end cover plate 112a is assembled properly, the coolant seals can be fixed at the required places on the coolant flow path. Subsequently, once the coolant seals are fixed at the required places, the end cover cap 112b can be assembled over the rear end cover plate 112a to close the motor casing 106 and complete the electric motor assembly. Such two part end cover 112 design reduces the complexity of the assembling process as it reduces the number of components required to be assembled simultaneously. Furthermore, the present invention is advantageous in terms of preventing dislocations or mis-alignment of the coolant seals during the process of assembling the electric motor. Furthermore, the present invention reduces the chances of failure of the electric motor due to coolant leak. Moreover, the present invention is advantageous in terms of providing ease of maintenance of the electric motor. It would be appreciated that the electric motor 100 of the present invention may not be required to be completely disassembled for the maintenance related to the cooling system comprising the maintenance of the coolant flow paths or the coolant seals. Furthermore, it would be appreciated that the end cover cap 112b may be disassembled to access the components and sealings associated with the cooling system without removing the end cover plate 112a. Such modular disassembly would reduce the effort and time required for the maintenance of the electric motor. Furthermore, it would be appreciated that the present invention would be advantageous in terms of reducing the downtime of the electric motor for maintenance and would reduce the cost of maintenance of the electric motor.
As used herein, the terms ‘electric motor’, ‘motor’, ‘permanent magnet synchronous reluctance motor’, ‘PMSR motor’, ‘IPM-SynRM’ and ‘PMSRM’ are used interchangeably and refer to electric motors capable of being implemented in an industrial or automobile application, such as on the work machine or other vehicle. The permanent magnet synchronous reluctance motor is a type of hybrid electric motor that combines the features of Permanent Magnet Synchronous Motor (PMSM) and Reluctance Motor (RM). The PMSRM has permanent magnets in the rotor, which generates a constant magnetic field, and the PMSRM relies on the principle of magnetic reluctance to create a rotating field within the motor. It would be appreciated that combination of technologies allows the PMSRM to achieve higher efficiency and better performance than other types of electric motors. In general, the stator of the PMSRM typically contains three-phase windings, which are used to generate alternating current that powers the electric motor. Typically, the rotor is made of iron or other magnetic materials, contains the permanent magnets that generate the magnetic field. It would be appreciated that the PMSRM can be modified to comprise active cooling system, such as a liquid cooling system. It would be appreciated that such cooling system would employ a coolant liquid circulating through the well-defined coolant flow paths inside the motor to dissipate the heat generated by the electric motor during operation.
As used herein, the terms ‘electric vehicle’, ‘EV’, and ‘EVs’ are used interchangeably and refer to any vehicle having stored electrical energy, including the vehicle capable of being charged from an external electrical power source. This may include vehicles having batteries which are exclusively charged from an external power source, as well as hybrid-vehicles which may include batteries capable of being at least partially recharged via an external power source. Additionally, it is to be understood that the ‘electric vehicle’ as used herein includes electric two-wheeler, electric three-wheeler, electric four-wheeler, electric pickup trucks, electric trucks and so forth.
As used herein, the terms “rubber seals”, “coolant seals” “rubber gaskets”, “rubber O-rings” and “seals” are used interchangeably and refers to mechanical devices made of elastomeric materials designed to create a tight and reliable seal between two surfaces or components. The primary purpose of rubber seals is to prevent the leakage of fluids or gases, provide insulation, and protect against the ingress of contaminants such as dust, dirt, or moisture. They are flexible and deformable, allowing them to conform to irregularities and provide an effective barrier. In the present invention, the rubber seals prevent the leakage of coolant inside the casing of the motor 100.
As used herein, the terms ‘rotor’ and ‘rotor assembly’ are used interchangeably and refer to the rotating part of the motor which is typically made of iron or other magnetic materials. It contains the permanent magnets and the reluctance winding that generate the magnetic field used to drive the rotor. The rotor converts electrical energy supplied to the stator into mechanical energy.
As used herein, the terms ‘stator’ and ‘stator assembly’ are used interchangeably and refer to the stationary part of a motor which provides a magnetic field that drives the rotating armature. The stator may act as a field magnet. In an embodiment, the stator assembly 104 comprises well-defined coolant flow paths for the active cooling of the stator assembly. In an embodiment, the stator assembly 104 comprises a cooling jacket for the cooling of the stator during the operation of the electric motor 100.
As used herein, the term “motor casing” is used to refer to the outer body of a motor enclosure made of up aluminium, which holds the entire motor body. The motor casing 106 comprises a plurality of terminal boxes 108 and end covers 110 & 112.
As used herein, the term “terminal boxes” is used to refer to an opening on the motor casing 106. Wherein one terminal box can be used to establish electrical connection between the motor and a motor controller and the other can be used to place a star-point outside the stator assembly 104.
As used herein, the terms “front-end cover”, “rear-end cover” and “end cover” are used to refer to the side structure of the motor casing wherein an end cap is mounted upon the end of the metal motor casing 106. “Front-end cover” and “rear-end cover” refers to the front-end and the rear-end of the metal motor casing structure respectively. It would be appreciated that the person skilled in the art would understand the front end cover as metal motor casing structure fixed at the frontal end or proximal end of the electric motor 100 where a mechanical load is connected to the motor shaft of the electric motor 100. Similarly, the rear end cover should be understood as metal motor casing structure fixed at the rear end or distal end of the electric motor 100 with reference to the connection of the load to the motor shaft of the electric motor 100.
As used herein, the term “motor shaft”, “shaft” and “shaft assembly” are used interchangeably and refer to a cylindrical rotating component for delivering mechanical output. In an embodiment, the motor shaft is hollow and closed from the front end.
In an embodiment, the rotor assembly 102 comprises a motor shaft comprising a front end and a rear end, a rotor stack comprising a front end and a rear end, a plurality of magnets enclosed with in the rotor stack, and a pair of magnet stoppers, a pair of rotor cir-clips, and a pair of bearings. Specifically, in this embodiment, the motor shaft is hollow and closed from the front end. It would be appreciated that the motor shaft is made hollow for the purpose of active cooling of the rotor assembly. The coolant flows through the hollow motor shaft for the active cooling of the rotor assembly. Furthermore, as understood by the person skilled in the art, the pair of rotor cir-clips are used to secure the rotor in place within the motor housing. It would be appreciated that the rotor cir-clips are installed in grooves in the motor shaft, and exert a radial force to hold the rotor in place. Furthermore, as understood by the person skilled in the art, the pair of magnet stoppers are used to secure the magnets that are attached to the rotor. It would be appreciated that the magnets need to be held in place securely to ensure proper alignment with the stator. Furthermore, as understood by the person skilled in the art, the pair of bearings are used to support the rotor and allow it to rotate freely within the stator.
In an embodiment, the at least one of: the end cover plate 112a, the end cover cap 112b, the motor casing 106 and the rotor assembly 102 are concealed together using a plurality of rubber seals. It would be appreciated that the end cover plate 112a, the end cover cap 112b, the motor casing 106 and the rotor assembly 102 are concealed together using the plurality of rubber seals to prevent the entry of coolant into the electrical components of the motor 100. It would be understood that each point of contact between the components housing electronics/electricals of the motor 100 and the one or more coolant flow path is sealed to prevent the leakage of the coolant from the coolant flow path to other components of the motor 100. It would be appreciated that the end cover plate 112a and the end cover cap 112b are removably coupled with each other and concealed together using the plurality of rubber seals. In an embodiment, the end cover plate 112a and the end cover cap 112b are removably coupled via a coupling means. Optionally, the coupling means comprises nut and bolt mechanism or similar mechanisms suitable for the purpose of removably coupling the end cover plate 112a and the end cover cap 112b.
In yet another embodiment, the rear end cover 112 comprises a hollow helical jet pipe 114 to allow flow of a coolant through the motor shaft from a cooling arrangement, wherein the hollow helical jet pipe 114 is coaxial to the motor shaft and removably attached with the end cover cap 112b. The hollow helical jet pipe 114 is rigidly mounted within the internal central hollow region of the motor shaft. It would be appreciated that the helical jet pipe 114 enables faster cooling of the interior of the rotor assembly 102 without requiring any additional fluid pressurizing means.
As used herein, the term “cooling system”, “active cooling system” and “cooling arrangement” are used interchangeably and refer to a system used to remove heat generated by the electric motor 100 during operation. Generally, dissipation of the generated heat is crucial for the efficient functioning and longevity of the electric motor. Optionally, the cooling arrangement supplies a coolant for performing the cooling of the electric motor 100. Optionally, the cooling arrangement may include at least one of: a heat exchanger, a pump, a valve, a thermostat, a temperature sensor and so forth.
In an embodiment, the end cover cap 112b comprises a coolant inlet channel connected to the hollow helical jet pipe 114, to allow flow of the coolant to the motor shaft from the cooling arrangement. It would be appreciated that connection point between the coolant inlet channel and the hollow helical jet pipe 114 is required to be sealed with coolant seals to avoid any leakage of the coolant.
In another embodiment, the end cover cap 112b comprises a coolant gallery to receive the coolant from the motor shaft and a coolant outlet channel connected to the coolant gallery, to allow flow of the coolant to the cooling arrangement. It would be appreciated that connection points between the coolant gallery, coolant outlet channel and the cooling arrangement are required to be sealed with coolant seals to avoid any leakage of the coolant.
Figure 2 describes an exploded view of the two part rear end cover 112, according to an embodiment of the present invention. The two part rear end cover 112 comprises the end cover plate 112a and an end cover cap 112b. In an embodiment, the rear end cover 112 comprises a hollow helical jet pipe 114 to allow flow of a coolant through the motor shaft from a cooling arrangement, wherein the hollow helical jet pipe 114 is coaxial to the motor shaft and removably attached with the end cover cap 112b.
In another embodiment, the motor 100 comprises a plurality of rubber seals (also referred as coolant seals) to prevent leakage of coolant in the motor 100. Advantageously, the coolant seals may be replaced easily without disassembling the end cover plate 112a, thus, without exposing the other components of the electric motor 100. In other words, the coolant seals may be replaced easily by disassembling the end cover cap 112b.
In another embodiment of the invention, the coolant comprises, but is not limited to, one or more of water, glycol, oil, and so forth. In yet another embodiment of the invention, the coolant comprises a mixture of water and glycol in a defined proportion. In yet another embodiment of the invention, the coolant may include a mixture of oil and glycol in a defined proportion. In yet another embodiment, the coolant may include a mixture of fluids suitable for application as coolants.
In another embodiment, there is described a two part end cover 112 for a permanent magnet synchronous reluctance motor 100, characterized in that the two part end cover 112 comprises an end cover plate 112a and an end cover cap 112b concealed together to form the two part end cover 112.
It would be appreciated that all the explanations and embodiments of the motor 100, as described in the previous embodiments, also applies mutatis-mutandis to the two part end cover 112 described in the above embodiment.
In an example, while the motor is being assembled for the first time, the end cover plate 112a is fixed onto the rear end of the motor casing 106 after the assembly of the electronic and electrical components of the motor 100. Thereafter, the components related to the cooling of the motor 100 are assembled into the motor casing 106 through the opening in the end cover plate 112a. Once the components related to the cooling of the motor 100 are assembled, the end cover cap 112b is concealed using a plurality of rubber seals on the end cover plate 112a.
In the description of the present invention, it is also to be noted that, unless otherwise explicitly specified or limited, the terms “disposed,” “mounted,” and “connected” are to be construed broadly, and may for example be fixedly connected, detachably connected, or integrally connected, either mechanically or electrically. They may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Modifications to embodiments of the present disclosure described in the foregoing are possible without departing from the scope of the present disclosure as defined by the accompanying claims. Expressions such as “including”, “comprising”, “incorporating”, “have”, “is” used to describe and claim the present disclosure are intended to be construed in a non- exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural where appropriate.
Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the present disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.

,CLAIMS:WE CLAIM:
1. A permanent magnet synchronous reluctance motor (100) for an electric vehicle, the motor (100) comprising:
- a rotor assembly (102);
- a stator assembly (104); and
- a motor casing (106) comprising at least one terminal box (108), a front end cover (110) and a rear end cover (112),
characterized in that the rear end cover (112) comprises an end cover plate (112a) and an end cover cap (112b).
2. The motor (100) as claimed in claim 1, wherein the rotor assembly (102) comprises a motor shaft comprising a front end and a rear end, a rotor stack comprising a front end and a rear end, a plurality of magnets enclosed with in the rotor stack, and a pair of magnet stoppers, a pair of rotor cir-clips, and a pair of bearings.
3. The motor (100) as claimed in claim 2, wherein the motor shaft is hollow and closed from the front end.
4. The motor (100) as claimed in claim 1, wherein the at least one of: the end cover plate (112a), the end cover cap (112b), the motor casing (106) and the rotor assembly (102) are concealed together using a plurality of rubber seals.
5. The motor (100) as claimed in claim 1, wherein the rear end cover (112) comprises a hollow helical jet pipe (114) to allow flow of a coolant through the motor shaft from a cooling arrangement, wherein the hollow helical jet pipe (114) is coaxial to the motor shaft and removably attached with the end cover cap (112b).
6. The motor (100) as claimed in claim 1, wherein the end cover cap (112b) comprises a coolant inlet channel connected to the hollow helical jet pipe (114), to allow flow of the coolant to the motor shaft from the cooling arrangement.
7. The motor (100) as claimed in claim 1, wherein the end cover cap (112b) comprises a coolant gallery to receive the coolant from the motor shaft and a coolant outlet channel connected to the coolant gallery, to allow flow of the coolant to the cooling arrangement.
8. A two part end cover (112) for a permanent magnet synchronous reluctance motor (100), characterized in that the two part end cover (112) comprises an end cover plate (112a) and an end cover cap (112b) concealed together to form the two part end cover (112).