FIELD OF INVENTION

[001 ] The present disclosure relates generally to a parallel cooling system, and more particularly to a parallel motor cooling system for electric motor that perform optimum cooling of a stator as well as a rotor simultaneously.

BACKGROUND

[002] Achievement of an optimum level of performance and reliability in an electric vehicle demands maintenance of temperature of an electric traction motor within its specified operating range regardless of undesirable ambient conditions or hard driving conditions. The magnetic, resistive, and mechanical losses within the motors during power generation cause a buildup of heat, which must be dissipated to avoid malfunction and/or failure of the vehicular system.

[003] As it is known in the art, the electric motor has two main parts, a stator, and a rotor. Most of the conventional cooling systems are intended to cool any one of the stator or the rotor to cool the electric motor. Few cooling systems have been also developed which intended to cool both the stator and the rotor. As shown in FIG. 1A, conventional cooling systems were using two independent cooling channels for achieving cooling of the stator along with the rotor. This unnecessarily increases the cost, weight, size of the vehicle. Increasing electric motor power output and compactness further exacerbate motor cooling limitations. To use the high-density electric motor for the EV requires an effective cooling system that extracts heat in a greater amount in a short period. Specifically, in the electric motors working with a duty cycle with heavy intermittent loads followed by the halt condition, the halt condition is used by designers for heat withdrawal. Thus, heat withdrawal must be performed at a much higher rate. Conventionally available cooling systems provide limited heat withdrawal capacities that become a major obstacle for the designers to develop high-performance electric vehicles using compact and high power density electric motors.

[004] The disclosed electric machine is directed to overcoming one or more of the problems set forth above. Accordingly, what is needed is an effective cooling system that can be efficiently used with compact and high power density electric motors.

OBJECT OF THE INVENTION

[005] To provide a parallel motor cooling system that extracts heat from both a stator and a rotor of an electric motor simultaneously. [006] To provide a parallel motor cooling system that is capable of being used with high-performance electric vehicles incorporating compact and high power density electric motors.

[007] To provide a parallel motor cooling system that extracts heat from the stator and rotor of the electric motor simultaneously by utilizing a single inlet and single outlet. [008] To provide a parallel motor cooling system that has higher heat withdrawal capacity, that is required to achieve optimum cooling of the electric motor preferably during the halt period of the electric motor.

[009] To provide a parallel motor cooling system that provides optimum cooling of the electric motor by using basic forces of nature, natural convection or gravitational forces only.

[0010] To provide a parallel motor cooling system that extracts heat from the stator, rotor, and bearing of the electric motor at the same time.

[001 1] Other objects and advantages of the system of the present disclosure will be more apparent from the following description when read in conjunction with the accompanying figures, which are not intended to limit the scope of the present disclosure.

SUMMARY

[0012] In one embodiment of the present invention, a parallel cooling system for an electric motor is provided. The parallel cooling system comprises a coolant (C), a coolant supplying means, an inlet, a stator, a cooling jacket, a stator cooling duct, a rotor assembly, an outflow junction, and an outlet. The inlet is configured to receive coolant inflow IC from the coolant supplying means at a first end thereof, and has a coolant inflow IC dividing T-Junction at a second end thereof. The T-Junction is configured to divide the coolant inflow IC into a first coolant inflow IC-1 forming first cooling channel A and a second coolant inflow IC-2 forming a second cooling channel B.

[0013] The stator comprises a stator stack surrounded by a stator housing. The cooling jacket is provided between the stator stack and the stator housing and has at least one groove on its outer surface.

[0014] The stator cooling duct is configured to receive the first coolant inflow IC-1 from the first cooling channel (A), and is extending spirally on the outer surface of the stator stack along the axis of the stator.

[0015] The rotor assembly comprises a rotor stack, a rotor shaft having an inner central hollow region and rotor bearings. The system further comprises a helical rotor cooling pipe which is configured to receive the second coolant inflow IC-2 from the second cooling channel (B). The helical rotor cooling pipe is arranged within the inner central hollow region of the rotor shaft and comprises a cylindrical inner passage and a helical outer edge. [0016] The outflow junction, wherein the outflowing coolant OC-1 from the first cooling channel (A) and outflowing coolant OC-2 from the second cooling channel (B) combine to become a combined coolant outflow OC at the outflow junction, and the outlet configured to discharge the combined coolant outflow OC from the outflow junction.

[0017] The stator cooling duct (105) is defined by the groove of the cooling jacket and the inner surface of the stator housing. In a preferred embodiment of the invention, the stator cooling duct (105) has a shape selected from the group comprising of a rectangle, a trapezoid, or an arc.

[0018] In a still another preferred embodiment of the invention, the coolant is at least one from the group comprising of water, glycol, oil and air.

[0019] In another embodiment of the invention, the first cooling channel (A) is configured to allow the first coolant inflow (IC-1 ) to extract heat from the stator (103), while the second cooling channel (B) is configured to allow the second coolant inflow (IC-2) to extract heat from the rotor assembly (106) at the same time. [0020] The system further comprises a rear end flange (110) configured to direct the second outflowing coolant (OC-2) from the central hollow region (106c) of the rotor shaft (106b) toward the outlet junction (108).

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1 A represents a block-diagram of a conventional cooling system incorporating two independent cooling channels for a stator and a rotor of the electric motor.

[0022] FIG. 1 B represents an exemplary block-diagram of a motor cooling system incorporating parallel cooling channels for a stator and a rotor of the electric motor according to an embodiment of the present invention. [0023] FIG. 2 represents provides a cross-sectional view of a parallel motor cooling system according to an embodiment of the present invention.

[0024] FIG. 3 represents a simplified view of an arrangement for cooling a rotor assembly using a parallel motor cooling system according to an embodiment of the present invention.

[0025] FIG. 4A represents a rear-side view of a parallel motor cooling system according to an embodiment of the present invention. [0026] FIG. 4B represents a simplified rear-view of arrangement for cooling rotor assembly of the parallel motor cooling system according to an embodiment of the present invention.

DESCRIPTION

[0027] Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

[0028] As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises”, “comprising”, “includes”, and/or “including”, as used herein, specify the presence of stated features, elements, and/or components, but do not preclude the presence or addition of one or more other features, elements, components, and/or groups thereof. As used herein, the term “and/or” and the symbol “/” are meant to include any and all combinations of one or more of the associated listed items. Additionally, while the terms first, second, etc. may be used herein to describe various components, these components should not be limited by these terms, rather these terms are only used to distinguish one component from another. For example, a first components could be termed a second components and vice versa without departing from the scope and spirit of this disclosure.

[0029] Spatially relative terms, such as “inner,” “outer,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures.

[0030] In the context of the present invention, the term "parallel" means that a stream is split between two or more channels and a portion of the stream flows through each of the channels at the same time.

[0031] In the context of the present invention, the term "electric vehicle" includes all vehicles equipped with an electric motor as a sole means of propulsion, or vehicles that can use electrical energy to as a means to motivate the vehicle. The electric motor cooling systems described and illustrated herein are generally applicable to any high-performance electric motor, and particularly applicable to vehicles using electric traction motors, e.g., an electric vehicle (EV). In the following text, the terms “electric vehicle” and “EV” may be used interchangeably and may refer to an all-electric vehicle, a plug-in hybrid vehicle, also referred to as a PHEV, or a hybrid vehicle, also referred to as a HEV, where a hybrid vehicle utilizes multiple sources of propulsion including an electric drive system.

[0032] In the context of the present invention, the term "electric motor" includes any kind of electric motor, capable of being implemented in an industrial or automobile application, such as on the work machine or other vehicle. The electric motor can be, but is not limited to, an industrial surface motor or a surface pump motor. [0033] Referring to FIG. 1 B, an exemplary block diagram of a motor cooling system according to an embodiment of the present invention is provided, describing the use of a single volume of coolant for cooling multiple motor components simultaneously. The cooling system according to an embodiment of the present invention incorporates parallel cooling channels for a stator and a rotor of an electric motor using a single inlet and a single outlet. In simpler words, the motor configuration allows both the rotor and the stator to be cooled with the same volume of coolant in parallel.

[0034] In a preferred embodiment of the invention, coolant inflow at the inlet may be divided into two streams, one stream flow outside the stator to cool the stator, and the other is directed to the interior of the rotor to perform cooling of the rotor. The coolant outflow from both streams is combined and drawn out via a single outlet.

[0035] A parallel motor cooling system for an electric motor M according to an embodiment of the present invention, generally indicated by reference numeral 100 will be now described with reference to FIGS. 2 and 3.

[0036] FIG. 2 shows a cross-sectional view of a parallel motor cooling system 100 according to an embodiment of the present invention. The parallel motor cooling system is now referred to as “system 100” from hereinafter for brevity. The electric motor M may include a stator 103, a cooling jacket 104, and a rotor assembly 106 comprising a rotor stack 106a mounted on a rotor shaft 106b, all housed in a stator housing 103b.

[0037] The system 100 comprises a coolant receiving means 101 (not shown) which supplies a coolant (C) for performing the cooling of an electric motor M. The system further comprises an inlet 102 for receiving the coolant inflow (IC) from the coolant receiving means 101 . In a preferred embodiment of the invention, coolant receiving means 101 may include, but may not limited thereto, an electrical pump (not shown). [0038] In a preferred embodiment of the invention, the inlet 102 has a first end 102a and a second end 102b. The inlet 102 is configured to receive the coolant inflow (IC) from the coolant receiving means 101 at its first end 102a, and is adapted to form an inflow dividing T-Junction 102c at its second end 102b. The T-Junction 102c enables the coolant inflow (IC) to be divided into two streams, namely a first coolant inflow (IC-1 ) forming a first cooling channel (A) and a second coolant inflow (IC-2) forming a second cooling channel (B).

[0039] The system 100 comprises an electric motor (M) comprising stator 103 and a rotor assembly 106. The stator 103 comprises a stator stack 103a surrounded by a stator housing 103b. The system further comprises a cooling jacket 104 mounted over the stator stack 103a and is surrounded by the stator housing 103b. The cooling jacket 104 comprises at least one spirally extending groove on its outer surface. In a preferred embodiment of the invention, the groove of the cooling jacket extends axially along the outer surface of the cooling jacket 104. In a still preferred embodiment of the invention, the groove of the cooling jacket comprises a single spiral groove or a plurality of interconnected grooves forming a spirally extending stator cooling duct 105. The grooves of the cooling jacket 104 forms the stator cooling duct 105 in collaboration with the inner surface of the stator housing. The stator cooling duct 105 is extending spirally along the outer surface of the stator stack 103a in an axial direction. The stator cooling duct 105 is in fluid connection with the inlet 102, for receiving the first coolant inflow (IC- 1 ) flowing through the first cooling channel (A). The first cooling channel (A) allows the first coolant inflow (IC-1 ) to extract heat from the stator 103, more preferably, stator stack 103a of the electric motor (M). The first coolant inflow (IC-1 ) enters into a stator cooling duct 105 and is directed to flow spirally along the outer surface of the stator stack in an axial direction such that effective cooling of the stator 103 is achieved. The coolant outflow from the stator cooling duct 105 forms the first coolant outflow (OC-1 ) which is collected in the outflow junction 108, from where it is directed to be drained out via an outlet 109.

[0040] As shown in FIG. 2, the stator cooling duct 105 extends spirally along the outer surface of the stator stack 103a in a manner that the stator cooling duct 105 extends, at least in part, axially along the motor M. In a preferred embodiment of the invention, the stator cooling duct 105 are formed by aligning the grooves of the cooling jacket 104 with the inner surface of the stator housing 103b. In a preferred embodiment, the stator cooling duct 105 has a shape selected from any of rectangular, trapezoidal or arch shape.

[0041] The system further comprises a rotor assembly 106 may be housed within the stator housing 103b. The rotor assembly 106 may include a rotor stack 106a, which is rigidly mounted on a rotor shaft 106b. The rotor shaft 106b may extend through the center of the rotor stack 106a and may define a motor axis which is an axis for the stator 103, the rotor stack 106a, and the cooling jacket 104. The rotor shaft 106b may be fixed to the rotor stack 106a so that as the rotor stack 106a rotates, it drives the rotor shaft 106b and vice versa. The rotor shaft 106b has an inner central hollow region 106c. The second cooling channel (B) allows the second coolant inflow (IC-2) to extract heat from the rotor assembly (106) to perform the cooling of the same.

[0042] The system comprises a helical rotor cooling pipe 107 (referred to as “pipe 107” for brevity) which is rigidly mounted within the internal central hollow region 106c of the rotor shaft 106b. The pipe 107 comprises a cylindrical inner passage 107a and a helical outer edge 107b. That is, the pipe 107 forms a straight passage for the first coolant inflow (IC-1 ) when flowing inside the pipe 107, while provide helical edges to direct the second coolant inflow (IC-2) to move in a spiral fashion when flowing over the outer edge of the pipe 107. The cylindrical inner passage 107a is in a fluid connection with the inlet 102 for receiving the second coolant inflow (IC-2) flowing through the second cooling channel (B).

[0043] The helical rotor cooling pipe 107 enables faster cooling of the interior of the rotor stack 106a without requiring any additional fluid pressurizing means. As shown in FIG. 2, the cylindrical inner passage 107a directs the first coolant inflow (IC-1 ) received from the inlet 102 to expel outwardly within the central hollow region 106c of the rotor shaft 106b, such that coolant is flown over the outer helical edge 107b of the pipe 107. As the pipe 107 is fixedly mounted within a continuously moving rotor shaft 106b, this creates a positive displacement pump being naturally created as the coolant is continuously moved over the fixedly mounted non-rotating pipe 107 within a continuously rotating rotor shaft 106b. This arrangement is particularly advantageous as it eliminates the need for additional fluid pressurization means for the coolant movement within the system. During vehicle stoppage or halt, this arrangement causes the coolant held in the passage 106c to withdrawn at a higher speed due to the positive displacement pump forces generated within the passage 106c, while a new coolant is filled up in the passage 106c at a same time. This increases the performance and life of the motor. The helical outer edge 107b causes the second coolant inflow (IC-2) to flow spirally along the helical pipe while cooling the interior of the rotor stack 106a and rotor bearing 106d at a higher speed.

[0044] In a preferred embodiment of the invention, the second coolant inflow (IC-2) coming back from the rotor shaft 106b reaches a region where bearings (106d) for rotor stack 106a has been provided and hence cools the same. That is, the second coolant inflow (IC-2) is allowed to cool the rotor stack 106a as well as rotor bearings 106d. Thus, the parallel motor cooling system 100 provides optimum cooling of the electric motor using basic forces of nature, natural convection or gravitational forces only to perform the heat withdrawal from the stator 103, rotor assembly 106, and bearings coolant IC.

[0045] The system 100 further comprises an outlet junction 108. The first coolant outflow (OC-1 ) from the stator cooling duct 105 and the second coolant outflow (OC-2) from the central hollow region 106c of the rotor shaft 106b directed toward an outflow junction 108. Here, both the first coolant outflow (OC-1 ) and the second coolant outflow (OC-2) combine together to form a combined coolant outflow (OC). The combined coolant outflow (OC) is then drained directly from the outlet 109. In this way, the cooling of both the stator and the rotor of the electric motor M has been achieved using two parallel channels using the same inlet and the same outlet. This saves the cost, time and weight of the system 100. As the cooling of the stator 103 and the rotor assembly 106 of the electric motor M have been achieved simultaneously, faster heat withdrawal can be achieved during the halt or stoppage.

[0046] In a preferred embodiment of the present invention, outlet 109 is a simple open pipe enabling the first coolant outflow (OC-1 ) and the second coolant outflow (OC-2) to be directly drained out from outlet 109 simultaneously as soon as it enters within the outlet junction 108.

[0047] FIG. 3 represents a simplified view of the second cooling channel (B), an arrangement for cooling the rotor assembly 106 of the system 100 according to a preferred embodiment of the invention. Here, the coolant inflow (IC) entering from the coolant supplying means 101 is divided to form a second coolant inflow (IC-2) at the inflow dividing T-Junction 102c. The coolant is directed to flow therefrom within the inner cylindrical passage 107a of the pipe 107. The pipe 107 has an open end, through which the second coolant inflow (IC-2) is expelled to flow inside the central hollow region 106c of the rotor shaft 106b. The rotation of the rotor shaft 106b causes the coolant flowing along the helical edge of the pipe 107 to flow spirally with high pressure while cooling the rotor stack 106a at the same time. The second coolant outflow (OC-2) is then directed towards outlet junction 108 to be mixed with the first coolant outflow (OC-1 ) from the stator cooling duct 105, and ultimately discharged via outlet 109. In another preferred embodiment of the invention, the coolant outflow (OC-2) while leaving the pipe 107 also comes in contact with the rotor beating 106d and cools the same.

[0048] The system 100 further comprises a plurality of intermediary cooling passages (113, 114, 1 15, 116) to guide the coolant from the inlet (102) toward the outlet 109 via the first cooling channel (A) and the second cooling channel (B).

[0049] The system 100 further comprises a plurality of hollow dowel pin (11 1 , 112) to fluidly connect one or more of the intermediary cooling passages (1 13, 114, 1 15, 1 16), the inlet 102 and the outlet 109 with each other to direct the coolant from inlet 102 to outlet 109 in a predefined manner as explained above. The system 100 further comprises air breathers to balance internal air pressure of motor and allow bidirectional flow of air, especially when rotor stack 106a and bearings 106d operate at high speed. The system 100 further comprises a magnetic stopper to maintain equilibrium temperature inside the stator and around the rotor.

[0050] In still another embodiment of the invention, the system 100 further comprises a plurality of rubber seals to prevent leakage of coolant in the system as known in the art.

[0051] FIG. 4A represents a rear side-view of system 100 according to an embodiment of the present invention showing incorporation of a rear-end flange 1 10 into the second cooling channel (B). The rear end flange 110 directly receives the second coolant outflow (OC-2) from the central hollow region 106c of the rotor shaft 106b. In a preferred embodiment of the invention, the rear end flange 1 10 may comprise a central cavity (1 15) that forms an intermediary passage to achieve pressure drop in the second coolant outflow (OC-2) which has higher pressure due to the action of positive displacement pump created in the rotor shaft 106b while exiting from the passage 106c. The rear end flange 1 10 further comprises an orifice at its rim to direct the second coolant outflow (OC-2) received from the central hollow region 106c of the rotor shaft 106b towards the outlet 109.

[0052] FIG. 4B represents a simplified a rearside-view of an arrangement for cooling rotor stack of the system 100 according to an embodiment of the present invention. FIG. 4B clearly shows the arrangement of the pipe 107 having inner cylindrical passage 107a and outer helical edge 107b within the central hollow region 106c of the rotor shaft 106b.

[0053] The system 100 is especially adapted to be incorporated within the electric vehicles comprising compact and high-density electric motors. The electric vehicle may include, but is not limited to two-wheeler, three-wheeler or four-wheeler vehicles.

[0054] In a preferred embodiment of the invention, the coolant includes, but is not limited thereto, one or more of water, glycol, oil, and air. In a still preferred embodiment of the invention, the coolant includes a mixture of water and glycol.

[0055] Systems and methods have been described in general terms as an aid to understanding details of the invention. In some instances, well-known structures, materials, and/or operations have not been specifically shown or described in detail to avoid obscuring aspects of the invention. In other instances, specific details have been given in order to provide a thorough understanding of the invention. One skilled in the relevant art will recognize that the invention may be embodied in other specific forms, for example to adapt to a particular system or apparatus or component, without departing from the spirit or essential characteristics thereof. Therefore the disclosures and descriptions herein are intended to be illustrative, but not limiting, of the scope of the invention. Any minor modification, equivalent replacement and improvement made to the above embodiments according to the technical essence of the present invention should all be included within the scope of protection of the technical solution of the present invention.