Electrical machinery

Abstract

The present invention provides an electric machine (100) comprising a stator (111), a rotor (113), a first end cover (114) and a lid (132). The first end cover (114) is thermally connected to said stator (111). The first end cover (114) comprises an outer wall (115) and an end cover annular portion (116). The outer wall (115) is spaced a first distance from the end cover annular portion (116) to form a radially enclosed portion. The outer wall is provided with one or more ports (122, 123) for transferring coolant to the radially enclosed portion. The radially enclosed portion is covered by a base surface (120), which is thermally connected to the stator (111), and which prevents leakage of the coolant into the stator (111).

Description

[Technical field]

[0001] The present invention relates generally to electric machines, and particularly, but not exclusively, to electric machines such as motors. [Background technology]

[0002] Typically, electric machines, such as electric motors and generators, are used for the conversion of electrical energy to mechanical energy and mechanical energy to electrical energy, respectively. An electric motor produces linear or rotational force (torque) from the electrical input it accepts. In general, an electric motor consists of a rotor, a stator, one or more windings, and a commutator. The stator is the stationary part of the motor, usually consisting of a field magnet. In general, the field magnet is an electromagnet or multiple permanent magnets, consisting of wire windings around a ferromagnetic iron core. The magnetic field created passes through the rotor armature. The rotor is the moving part of the electric motor, which turns the shaft to deliver mechanical power. The rotor usually consists of a conductor, which can carry an electric current exerted by the magnetic field of the stator, thereby forcing the shaft to rotate. Alternatively, some motors carry the field magnets, and the stator holds the conductors. Some motors also consist of Hall effect sensors on the stator of the motor. Summary of the Invention [Problem to be solved by the invention]

[0003] Typically, most of the heat is generated by an electric motor or generator during the conversion of electrical energy to mechanical energy or vice versa. Often, one or more windings are used in the stator of the motor to generate a magnetic field. To generate torque, current is forced through the motor windings, which results in an incremental temperature rise in the motor windings. Furthermore, as the temperature rises in the motor windings, the resistance of the windings also increases. Motor winding resistance (Rmt) is one of the major sources of heat generation.

[0004] To check the heat or temperature rise in the motor, various thermal management techniques are used. The two most prominent thermal management techniques are air cooling of electric motors and liquid cooling of electric motors. In air cooling of electric motors, surface fins are provided on the electric motor, which dissipates heat through natural convection or by forced convection, for example, by a fan mounted on the motor shaft. However, forced cooling mechanisms are usually undesirable in vehicles due to layout space constraints. The challenge is greater, especially in compact two-wheeled or three-wheeled vehicles, which may not have the luxury of space as compared to four-wheeled vehicles, and where the addition of a forced cooling system would increase the overall vehicle weight and cost and is undesirable. Such vehicles usually have a compact powertrain, and therefore air cooling of the electric motor is achieved by multiple radial fins around the motor.

[0005] Another means of achieving effective cooling of electric motors is liquid cooling of the electric motor. Liquid cooling systems use features such as pumps, radiators, and hoses to construct a liquid cooling system. Motor heat is removed by flowing coolant and is rejected or dissipated through the radiator.

[0006] In an existing technique, a number of ducts are provided in the stator of the motor through which the coolant passes. The coolant passes through the frame of the stator in an axial partition. In another existing technique, a tangential partition is created on the stator frame through which the coolant is passed.

[0007] In another existing technology, the motor housing has cooling channels connecting an external coolant source. The rotor is provided with injection ports facing the stator, which has a shaft coolant path connected to the cooling channels on the motor housing. The stator core is cooled by a cooling jacket, and direct internal cooling is also applied to the stator windings by fixed point injection of the cooling jacket and by rotating injection of the magnetic separation plates. This results in cooling of the stator windings by forced liquid cooling.

[0008] In another existing technology, the liquid cooling system includes a manifold extending above the stator, the manifold having openings that receive liquid under pressure and direct liquid jets onto the ends of the stator and rotor, and a tray mounted above the stator and rotor that obtains liquid coolant from a manifold injector and distributes the gravity-fed coolant to the other portions. In such a topology, the rotor and stator are directly cooled by the liquid.

[0009] In existing liquid cooling systems, the coolant actively contacts the stator windings. This interaction limits the operation of the stator windings. The life span of the stator windings is adversely affected by the coolant reaching the stator. Also, when the coolant reaches the stator windings, the user cannot use different types of coolant in the motor. In such cooling systems, only one type of coolant can be used. A change of coolant will cause damage to the stator windings. In such cooling systems, any cleaning of the cooling passages requires a complete motor opening. Moreover, if impurities pass through the coolant, such impurities will reach the stator windings or rotor and cause serious damage to the operation of the motor.

[0010] Also, in other known or existing liquid cooling systems, the coolant passes through either the motor / stator frame. Such cooling systems require modifications in the motor design. Furthermore, modifications in the stator design limit the motor to only liquid cooling mechanisms. Modifications in the motor design on the external frame limit the motor to only cooling by coolant. In such motors, an air cooling system is not possible because the motor's exterior surface cannot accommodate both fins and liquid cooling chambers. Also, if a solution of coolant chambers and fins is provided, the cooling is limited because there are not enough fins for air cooling. Furthermore, with only a liquid cooling system, the motor cooling is limited. The coolant only reaches a limited thermal zone of the motor. Also, motors with manifolds complicate the motor design and limit the motor cooling to liquid cooling. If both air and liquid cooling solutions are provided, the air cooling fins are not utilized to their full potential due to design constraints. The motor frame cannot accommodate fins as well as the coolant chamber or coolant manifold.

[0011] Therefore, there is a need to provide an improved cooling system for a motor that can cool a majority of the thermal zones of the motor while overcoming all of the problems mentioned above and other problems of the known art. More specifically, adequate cooling is provided to the thermal zones that generate the greatest heating. Furthermore, damage to the stator windings by liquid coolants must be prevented. Also, the motor shall be configured to accommodate a variety of coolants. Furthermore, the motor shall be configured to fully optimize the air and liquid cooling systems. [Means for solving the problem]

[0012] In one aspect of the invention, an improved electric machine is disclosed, the electric machine comprising a stator, a rotor, a first end cover, and a lid. The rotor is coupled to the stator. The first end cover is thermally connected to the stator. The lid encloses the first end cover from one side of the electric machine. The first end cover comprises an outer wall and an end cover annular portion. The end cover annular portion is a first distance from the outer wall forming a radially enclosed portion. The radially enclosed portion is covered by a base surface, the base surface being in thermal connection with the stator. The radially enclosed surface receives coolant from the outer wall, the base surface being configured to prevent any leakage of the coolant.

[0013] The summary provided above describes the basic features of the present invention and is not intended to limit the scope of the present invention. The nature and further characteristic features of the present invention will become more apparent from the following description, taken in conjunction with the accompanying drawings. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is an exploded perspective view of an electric machine. [Diagram 2] FIG. 1 is a perspective view of a stator of an electric machine. [Diagram 3] FIG. 2 is a perspective view of a first end cover of the electric machine. [Figure 4] FIG. 2 is a perspective view of the lid of the electric machine. [Diagram 5] FIG. 2 is a perspective view of a second end cover of the electric machine. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The detailed description will now be described with reference to embodiments of a vehicle motor assembly in conjunction with the accompanying drawings, in which like numbers are used to reference like features and components throughout.

[0016] Exemplary embodiments detailing the features of the pedal assembly according to the present invention will be described hereinafter with reference to the accompanying drawings. Various aspects of different embodiments of the present invention will become apparent from the ensuing description set forth hereinafter. Rather, the ensuing description provides a convenient illustration for implementing the exemplary embodiments of the present invention. Furthermore, it should be noted that terms such as "upper", "lower", "right", "left", "front", "forward", "rear", "lower", "upper", "top", "bottom" and the like are used herein based on the illustrated state or in an upright state of the vehicle with the driver seated, unless otherwise detailed. Furthermore, the vertical axis refers to a top-to-bottom axis relative to the vehicle and defines the vertical direction of the vehicle, while the lateral axis refers to a side-to-side or left-to-right axis relative to said vehicle and defines the lateral direction of the vehicle. Furthermore, the longitudinal axis refers to a front-to-rear axis relative to the vehicle and defines the longitudinal direction of the vehicle. It should also be understood that the words and terms used herein are for the purpose of explanation and should not be considered as limiting.

[0017] The present invention will be further described with reference to the accompanying drawings. It should be noted that the description and drawings merely illustrate the principles of the invention. Various arrangements may be devised which, although not explicitly described or shown herein, incorporate the principles of the invention. Moreover, all references herein reciting principles, aspects, and examples of the invention, as well as specific examples thereof, are intended to encompass equivalents thereof.

[0018] FIG. 1 shows an exploded perspective view of an electric machine 100 according to an exemplary embodiment of the present invention. The electric machine 100 comprises a stator 111, a rotor 113, a first end cover 114, a lid 132, and a second end cover 127. The stator 111 is a fixed part and the rotor 113 is a moving part, both of which are electromagnetically coupled to each other. The stator 111 is enclosed in an outer casing 110, and the first end cover 114 covers a first side of the stator 111 and the rotor 113. The first end cover 114 is locked to the outer casing 110 from one side, and the second end cover 127 is locked by the outer casing 110 on the opposite side of the outer casing 110. Additionally, the lid 132 covers the first end cover 114 by being secured to the first end cover 114 and the outer casing 110 through a plurality of mounting holes (130, 131).

[0019] In one embodiment, the outer casing 110 includes one or more fins 128 on an outer surface thereof. The one or more fins 128 are configured to cool the stator 111 via an air cooling mechanism.

[0020] 2 shows a perspective view of the stator 111. The stator 111 comprises a cylindrical surface (111') on the outer part of the stator 111, with lateral end sides (111s) on each side of the cylinder. One or more stator teeth 111A are disposed on the inner cylindrical surface (not shown) of the stator 111. The teeth 111A are covered by one or more field windings 112, and passing a current through the windings turns the stator into a field magnet or electromagnet.

[0021] FIG. 3 shows a perspective view of the first end cover 114. The first end cover 114 comprises a base portion (120), an outer annular wall 115, and an end cover inner annular portion 116 arranged concentrically with the outer wall 115 relative to the rotor axis R-R'. The outer annular wall 115 and the end cover inner annular portion 116 project perpendicularly to the base portion 120, the projection being along the rotor axis R-R'. The outer circumferential annular surface (115') of the outer wall 115 is provided with one or more opening ports 122, 123, which are inlet ports 122 and outlet ports 123 for allowing the flow of a cooling medium. The end cover inner annular portion 116 is spaced apart from the outer wall 115 by a first radial distance "a". Additionally, the outer wall 115 and the end cover inner annular portion 116 and the base portion 120 together form a radially enclosed passage 120' that receives coolant from one or more ports 122, 123. The radially enclosed passage 120' is covered by said base portion 120, one end face of which is configured to be in thermal contact with the coolant and the other end face of which is in thermal contact with the teeth 111A and lateral end faces 111s of the stator 111 for transferring heat from the stator 111 to the base portion 120 by conduction.

[0022] Additionally, in one embodiment, the outer wall 115 includes one or more locking portions 119 having one or more outer wall locking openings 119 ′ for locking the first end cover 114 to the outer casing 110 .

[0023] In one embodiment, the end cover inner annular portion 116 is formed within a central region of the first end cover 114 and has a hollow at the center of the end cover inner annular portion 116. The rotor axis R-R' passes through the hollow at the center of the end cover inner annular portion 116. The end cover inner annular portion 116 also includes a radial surface 118. The radial surface 118 forms an outer boundary of the end cover inner annular portion 116. Additionally, the radial surface 118 and the outer wall 115 form a radially enclosed passage 120' that is configured to receive a cooling fluid from one or more ports 122, 123.

[0024] In another additional embodiment, the base surface 120 includes one or more raised portions 121. The one or more raised portions 121 are uniformly shaped baffles. In another embodiment, the one or more raised portions 121 are non-uniformly shaped baffles, where the baffles can enhance conductive heat transfer to the cooling medium.

[0025] 4 shows a perspective view of the lid 132. The lid 132 comprises an inner planar base portion 126 and a lid annular wall portion 125 projecting from the base portion 126. The lid annular portion 125 comprises a radial annular surface 125A which fits snugly over the radial surface 118 of the end cover inner portion 116 to act as a guide for positioning the lid 132. The lid 132 is also provided with one or more lid locking portions 124 having one or more lid locking openings 124' which align with one or more locking portions 119 of the end cover 114 and are attached by suitable locking means for sealing the enclosed portion 120' between the outer wall 115 and the inner annular portion 116.

[0026] FIG. 5 shows a second end cover 127, which covers the outer casing 110 and the stator 111 from the opposite side of the first end cover 114 of the stator 111 and the second side of the stator 111. The second end cover 127 includes one or more second locking portions 130 having one or more second end cover locking openings 130', thereby allowing the second end cover 127 to be locked by the outer casing 110. The second end cover 127 is provided with a second circular annular protruding wall portion 131 in a central region of the second end cover 127. The second cover 127 also includes an inner annular planar surface 129 adjacent to the circular annular portion 131. In one embodiment, the second end cover 127 includes one or more Hall sensors for determining the annular position of one or more teeth 111A of the stator 111.

[0027] In one embodiment of the present invention, the stator 111 is a stationary electrical component configured to have one or more teeth 111A on an inner portion of the stator 111. The rotor 113 is concentrically located inside the stator 111 and is attached to the shaft of the electric machine 100 along the rotor axis R-R'. The rotor 113 rotates due to magnetic interaction between the stator 111 and the rotor 113. The rotation of the rotor 113 in turn rotates the shaft of the electric machine 100. In the electric machine 100, all electrical components generate heat. However, the stator 111 and the rotor 113 are the main heat generating elements. To cool the main heating elements, the present invention provides a liquid cooling mechanism that can effectively cool the stator 111 and the rotor 113. According to one embodiment, the air cooling is by fins, while the liquid cooling can be controlled by one or more controllers that can actuate one or more ports (122, 123).

[0028] According to an exemplary embodiment of the present invention, the first end cover 114 receives the coolant from the inlet port 122, which is received by the radially enclosed passages 120' defined by the base surface 120. One end face of the base portion 120 is in thermal contact with the teeth 112 of the stator 111. The base surface 120 is also configured to prevent any leakage of the coolant from the radially enclosed passages 120' to the field magnets 112. In such a configuration, the base portion 120 acts as a partition wall between the radially enclosed portion 120' and the field windings 112. The thermal contact between the base portion 120 and the stator 111 ensures that heat generated from the field windings 112 is effectively conducted to the base portion 120, where such heat is then cooled by the coolant present within the radially enclosed portion 120'. The base portion 120 also ensures that the heat is confined to the stator 111 and is not transferred to the ends of the electric machine 100. Additionally, base portion 120 provides a larger surface area for the coolant to act upon, thereby ensuring that all areas are in thermal contact and effectively cools base surface 120. Coolant is transferred from the radially enclosed portion through exit ports 123.

[0029] In another embodiment, the base surface 120 is provided with one or more protruding portions 121, also referred to as one or more baffles. According to said configuration, the one or more protruding portions 121 collect heat from the stator 111, which is then effectively cooled by the coolant. The coolant acts more effectively within the one or more protruding portions 121, since the heat is confined within a designated surface area, which is an area increased by the baffle. The one or more protruding portions 121 also provide an effective flow to the coolant. The one or more protruding portions 121 ensure a continuous flow of the coolant within the radially enclosed portion, minimizing vortex formation.

[0030] In one embodiment, the one or more protruding portions 121 are uniformly shaped so that no vortex formation occurs during continuous coolant flow and the flow of coolant is uniform.

[0031] In another embodiment, the protruding portion or portions 121 are non-uniformly shaped so that minimal vortex formation occurs. In such a configuration, the coolant flow is often not uniform, but due to the continuous movement of the coolant, cooling efficiency is not compromised.

[0032] The electric machine 100 according to the invention is cooled by a combination of liquid and air cooling mechanisms. In such a configuration, the outer casing 100 is provided with one or more fins 128 that ensure continuous air cooling of the stator 111. Additionally, liquid cooling is provided by the radially enclosed portion 120' and the coolant in the base portion 120, which acts as a partition wall between the field windings 112 of the stator 111 and the coolant. In such a configuration, liquid cooling can be enabled or controlled according to requirements. If the electric machine 100 is only to be air cooled, the inlet port 122 and the outlet port 123 can be plugged or sealed. However, if it is desired that the electric machine 100 is cooled by both air and liquid cooling, the inlet port 122 and the outlet port 123 can be unplugged.

[0033] Although the present invention has been described in some detail with reference to specific embodiments thereof, other embodiments are possible. It is to be understood that the appended claims are not necessarily limited to the features described herein. Rather, the features are disclosed as embodiments of the invention. [Explanation of symbols]

[0034] 100 Electrical Machinery 110 Outer casing 111 Stator 111' Stator cylindrical surface 111A Stator Tooth 111s Stator lateral end face 112 Magnetic Field Winding 113 Rotor 114 First end cover 115 Exterior Wall 115' Circumferential Annular Surface 116 End cover inner annular portion 118 Radial surface 119 Locking part 119' External wall locking opening 120 Base part 120' Enclosed Passage 121 Projection part 122 Inlet Port 123 Exit Port 124 Lid locking part 124' Lid locking opening 125 Lid annular wall part 125A Radial Annular Surface 126 Flat base part 127 Second end cover 128 Finn 129 Inner Annular Planar Surface 130 Second locking portion 130' second end cover locking opening 131 second circular annular wall portion 132 Lid

Claims

1. An electric machine (100), comprising: A stator (111), a rotor (113) electrically coupled to the stator (111); a first end cover (114) in thermally conductive contact with the stator (111) on a first side of the stator (111); a lid (132) attached to the first end cover (114) from one side of the electric machine (100) to enclose a coolant within the first end cover (114); The first end cover (114) comprises: an outer wall (115) having one or more ports (122, 123) for receiving said coolant; an end cover annular portion (116), said end cover annular portion (116) and said outer wall (115) being spaced a first predetermined distance "a" apart; a base portion (120), said outer wall (115) and said end cover annular portion (116) projecting orthogonally to said base portion (120), thereby forming a radially enclosed passageway 120'; the radially enclosed passages (120') are in thermally conductive contact with the stator (111) for transferring heat to the base portion (120); The electric machine (100), wherein the radially enclosed passages (120') are configured to receive the coolant for drawing heat from the base portion (120) and thereby cooling the stator (111).

2. 2. The electric machine of claim 1, wherein the end cover annular portion has a radial surface and the lid includes a lid annular wall portion that fits snugly against the radial surface of the end cover annular portion.

3. The electric machine (100) of claim 1, wherein the base portion (120) includes one or more protruding portions (121).

4. The electric machine (100) of claim 3, wherein the one or more raised portions (121) are uniformly shaped baffles.

5. The electric machine (100) of claim 3, wherein the one or more protruding portions (121) are non-uniformly shaped baffles.

6. The electric machine (100) of claim 1, wherein the outer wall (115) has one or more locking portions (119), the locking portions (119) configured to be attached to an outer casing (110) of the stator (111).

7. The electric machine (100) of claim 1, wherein the one or more ports (122, 123) include an inlet port (122) and an outlet port (123).

8. The electric machine (100) of claim 1, wherein the lid (132) has one or more lid locking portions (124).

9. 2. The electric machine of claim 1, wherein the stator is connected to a second end cover at a second side of the stator, the second end cover covering the stator from an opposite side to the first end cover.

10. The electric machine (100) of claim 1, wherein the stator (111) is configured to be air-cooled by a plurality of fins (128) on an outer casing (110) of the stator (111).

11. 2. The electric machine (100) of claim 1, wherein the stator (111) is configured with one or more teeth (111A) on an inner surface (not shown) of the stator (111), the one or more teeth (111A) being covered by one or more magnetic field windings (112).

12. The electric machine (100) of claim 1, wherein the opening and closing of the one or more ports (122, 123) is electronically controlled by one or more controllers.

Images