WO2021123900A1

WO2021123900A1 - Drive assembly with integrated cooling

Info

Publication number: WO2021123900A1
Application number: PCT/IB2019/061233
Authority: WO
Inventors: Sven BJØRKGÅRD; Sindre Abrahamsen
Original assignee: Ka Group Ag
Priority date: 2019-12-20
Filing date: 2019-12-20
Publication date: 2021-06-24
Also published as: SE2250728A1; CN114846730A; DE112019007792T5

Abstract

A drive assembly for an electric vehicle including an electric machine having a stator defining a stator duct. The drive assembly further includes a housing defining a gearing chamber and a thermal chamber fluidly separated from the gearing chamber. The drive assembly further includes a cooling conduit disposed in the thermal chamber. The electric machine is coupled to the housing and disposed in the gearing chamber with the rotor arranged adjacent to the thermal chamber. One of the cooling conduit and the thermal chamber may be fluidly coupled to the stator duct for transferring thermal energy therebetween.

Description

DRIVE ASSEMBLY WITH INTEGRATED COOLING

BACKGROUND

[0001] There is a growing demand to reduce or eliminate vehicle emissions produced during operation. Increasingly, vehicle manufacturers have turned to hybrid and full-electric propulsion systems to reduce vehicle emissions and increase efficiency. Oftentimes, electric machines are integrated into a drive assembly, which is positioned near the vehicle’s drive wheels.

[0002] Accordingly, there is a need to provide a drive assembly that affords increased cooling to an electric machine packaged within a gearbox housing.

SUMMARY

[0003] A drive assembly for an electric vehicle including an electric machine having a motor shaft defining a motor axis and including one or more rotors coupled to the motor shaft. The electric machine may further include a stator arranged about the motor axis defining a stator duct having a duct inlet and a duct outlet. The drive assembly may further include a cooling conduit having a conduit inlet and a conduit outlet fluidly coupled to the duct outlet. The drive assembly may further include a pump fluidly coupled to the conduit outlet and to the duct inlet. The stator duct, the cooling conduit, and the pump cooperate to define a stator cooling circuit. The drive assembly may further include a gearing arrangement operably engaged with the electric machine for transferring rotation of the motor shaft to one or more wheels of the electric vehicle. The drive assembly may further include a housing defining a gearing chamber and a thermal chamber fluidly separated from the gearing chamber. The thermal chamber may contain a second heat transfer fluid. The electric machine may be coupled to the housing such that the rotor is arranged adjacent to the thermal chamber and such that the gearing arrangement is disposed in the gearing chamber. The cooling conduit may be disposed in the thermal chamber for transferring thermal energy between the first heat transfer fluid and the second heat transfer fluid.

BRIEF DESCRIPTION OF THU DRAWINGS

[0004] Advantages of the present disclosure will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings. [0005] Figure 1 is an environmental view of an electric vehicle showing a drive assembly coupled thereto for transferring rotation to one or more wheels of the electric vehicle.

[0006] Figure 2 is a partial perspective view of a chassis for the electric vehicle of Fig. 1 with one of the wheels removed to show a drive shaft and braking assembly and four drive assemblies.

[0007] Figure 3 is a perspective view of one of the drive assemblies of Fig. 2 showing an outboard side of a housing, a thermal chamber defined by the housing and a cooling conduit are shown through a broken line portion of the housing according to a first configuration.

[0008] Figure 4 is a partial section view of one side of the housing showing the thermal chamber and the cooling conduit.

[0009] Figure 5 is an exploded perspective view of the drive assembly showing the thermal chamber, a gearing chamber further defined in the housing, an electric machine, and a gearing arrangement operably engaged with the gearing arrangement.

[0010] Figure 6 is an exploded view of a portion of the housing and the electric machine of Fig. 5 showing the cooling conduit and a pump.

[0011] Figure 7A is a section view of the drive assembly taken along line 7-7 in Fig. 4 showing the thermal chamber, the gearing chamber, and a stator of the electric machine.

[0012] Figure 7B is a close-up detail view of a portion of Fig. 7A.

[0013] Figure 8 is a perspective partial-section view of the cooling conduit and the stator of the electric machine according to the first configuration.

[0014] Figure 9 is a partial section view of one side of the housing showing the thermal chamber and the cooling conduit according to a second configuration of the drive assembly.

[0015] Figure 10 is an exploded view of a portion of the housing and the electric machine of Fig. 9 showing the cooling conduit and a pump.

[0016] Figure 11 is a perspective partial-section view of the cooling conduit and the stator of the electric machine according to the second configuration.

DETAILED DESCRIPTION

[0017] With reference to the Figures, wherein like numerals indicate like parts throughout the several views, the present disclosure includes a vehicle 30 having a chassis 32, which is supported on one or more wheels 34 capable of propelling the vehicle 30. The chassis 32 defines a centerline, or longitudinal axis A3, which is generally parallel to a direction of travel of the vehicle 30. The vehicle 30 shown in Fig. 1 is configured as a vocational truck, which may be utilized for different applications such as, for example, a delivery truck, a passenger bus, an over-the-road tractor for trailer towing, and other upfitting applications. In order for the vehicle 30 to have an increased payload capacity, the chassis 32 may be configured in a tandem configuration with two axles 36 for propelling the vehicle 30. More specifically, the chassis 32 includes two frame rails 38 that each extend parallel to the longitudinal axis A3 between a front and a rear of the vehicle 30. Near the rear of the vehicle 30, the axles 36 may be coupled to the frame rails 38 and spaced longitudinally from each other. The chassis 32 may be configured for “single-wheel” applications (now shown) and “dual-wheel” applications. In “single-wheel” applications a single wheel is coupled to each lateral side of the vehicle 30. Likewise, in “dual-wheel” applications, wheels 34 are arranged in pairs on each lateral side of the vehicle 30. Vehicles requiring increased payload or towing capacity are one example in which a “dual-wheel” configuration may be preferable. Because these vehicles are intended to be adaptable for a variety of uses with specific requirements, the chassis 32 and frame rails 38 are adaptable such that the number of axles 36 and the number of wheels 34 are best suited for a particular use. This may include using tandem axles 36, with one dual- wheel axle and one single wheel axle. Further, one of the axles 36 may selectively movable relative to the chassis 32 into a raised position, wherein the wheels 34 are spaced out of contact with the ground to increase efficiency when operating the vehicle 30 unladen.

[0018] Turning now to Fig. 2, the chassis 32 may further include suspension components such as springs 40 or dampers 42 in order to optimize the performance of the vehicle 30 during operation. The suspension components movably couple the axle 36 to the frame rails 38 to maintain contact between the wheels 34 and the ground. The suspension components allow the axle 36 to move relative to the frame rails 38 and urge the wheels 36 toward the ground when the vehicle 30 encounters imperfections in the ground. More specifically, the springs 40 and dampers 42 absorb movement of the axle 36 and improve ride quality. The vehicle 30 may further include braking components such as air cylinders, brake calipers 44, brake rotors, brake drums, brake hoses, etc. that cooperate to decelerate and/or stop the vehicle 30. The braking components may be coupled to the axle 36 and/or the frame rail 38, as will be discussed in further detail below.

[0019] Generally, the vehicle 30 is propelled by transferring motive power to one or more of the wheels 34 that are in contact with the ground. To that end, a drive assembly 100, which is capable of rotating the wheels 34, may be coupled to the axle 36. In the case of an electric vehicle 30, such as shown in Figs. 1 and 2, the drive assembly 100 transfers rotation of an electric machine to the wheels 34. Here, each axle 36 may include two drive assemblies 100 that are coupled to a bridge 46 and arranged on opposing lateral sides of the vehicle 30, with each drive assembly 100 providing rotation to one pair of wheels 34.

[0020] According to a first configuration, Figs. 3-5 show one of the drive assemblies 100 removed from the axle 36 along with details of a cooling system, as will be discussed in further detail below. The drive assembly 100 generally includes at least one electric machine 106 and a gearing arrangement 108, each of which are disposed in a housing 104. During operation the drive assembly 100 generates heat, primarily through friction in the gearing arrangement 108 and electrical current flowing through the electric machine 106. Performance of the electric machine 106 may be improved by reducing excess heat generated during operation. To this end, the drive assembly 100 further includes a cooling conduit 196 having a conduit inlet 198 and a conduit outlet 200. The cooling conduit 196 is disposed in a thermal chamber 154, which is defined by the housing 104. As will be discussed below, the cooling conduit 196 is configured to transfer thermal energy between two fluids within the drive assembly 100. The thermal chamber 154 is configured to absorb thermal energy from the cooling conduit 196, the gearing chamber 152, the electric machine 104, the lubricant, and the braking components (e.g. brake calipers 44) to be transferred away from the drive assembly 100, thereby reducing the temperature.

[0021] The electric machine 106 is coupled to the housing 104 and operably engaged with the gearing arrangement 108 for transferring power to the wheel 34. The electric machine 106 includes a stator 130, a rotor 132A, 132B, and a motor shaft 134 coupled to the rotor 132A, 132B. The rotor 132A, 132B and the motor shaft 134 are supported for rotation relative to the stator 130 about a motor axis A1 defined by the motor shaft 134. An output pinion 136 is coupled to the motor shaft 134 for engagement with the gearing arrangement 108. The gearing arrangement 108 generally includes a series of gears and shafts supported for rotation within the housing 104.

[0022] The drive assembly 100 may further include a wheel end 105 coupled to the housing 104 and extending toward the wheel 34 to rotatably supporting the wheel 34. The wheel end 105 may include an axle shaft (not shown) that is engaged with the gearing arrangement 108 and rotationally coupled to the wheel 34 for transferring rotation therebetween. The housing 104 and wheel end 105 may be constructed and coupled in a variety of ways, for example using fasteners to couple the wheel end 105 to the housing. In an alternative embodiment the wheel end 105 may be integrally formed with the housing 104. [0023] As mentioned above, the gearing arrangement 108 may include a series of gears and shafts, such as an idle shaft 110, an intermediate shaft 112, and an output shaft 114 that defines a drive axis A2. Each of the shafts are supported for rotation within the housing 104 by bearings; idle bearings 140 support the idle shaft 110, intermediate bearings 142 support the intermediate shaft 112, and output bearings 144 support the output shaft 114. The bearings 140, 142, 144 may be used to reduce friction between rotating components of the gearing arrangement 108. Various bearing types may be used depending on the requirements of the application, for example, journal (plain) bearings, roller bearings, ball bearings, etc. Friction is further reduced through the use of a lubricant, such as gear oil. The lubricant is supplied to contact surfaces between components, such as gear teeth and the bearings 140, 142, 144, to prevent wear and to reduce the amount of heat generated from friction. In addition to reducing the amount of heat generated, the lubricant further cools components of the drive assembly 100 by transferring the thermal energy away from the heat generating source.

[0024] Power is transferred from the electric machine 106 to the wheels 34 via the gearing arrangement 108. In the gearing arrangement 108 shown in Fig. 5, the electric machine 106 may drive the idle shaft 110, which in turn may drive the intermediate shaft 112, which may further drive the output shaft 114. The shafts are driven by rotationally engaged gears of various tooth counts to translate torque at one or more ratios. More specifically, the idle shaft 110 supports an idle gear 116 and an idle pinion 118; the intermediate shaft 112 supports an intermediate gear 120, a first intermediate pinion 122, and a second intermediate pinion 124; and the output shaft 114 supports a first output gear 126 and a second output gear 128.

[0025] With continued reference to Fig. 5, the gearing arrangement 108 is generally configured such that the pinion(s) of one shaft engage the corresponding gear(s) of the adjacent shaft. Specifically, the idle gear 116 is engaged with the output pinion 136 to rotate the idle shaft 110 and the idle pinion 118. The idle pinion 118 is engaged with the intermediate gear 120 to rotate the intermediate shaft 112, the first intermediate pinion 122, and the second intermediate pinion 124. The first intermediate pinion 122 and the second intermediate pinion 124 engage the corresponding first output gear 126 and the second output gear 128 to rotate the output shaft 114. More specifically, the first output gear 126 is engaged with the first intermediate pinion 122 and the second output gear 128 is engaged with the second intermediate pinion 124. [0026] In order to improve launch and velocity performance of the vehicle 30, the gearing arrangement 108 is realized as a two-speed reduction, which is selectively shiftable between a first ratio and a second ratio. The first ratio corresponds to the pairing of the first output gear 126 and the first intermediate pinion 122. Similarly, the second ratio corresponds to the pairing of the second output gear 128 and the second intermediate pinion 124. To this end, the gearing arrangement 108 may include a shift assembly 138 operable to selectively engage the first ratio and the second ratio. Operation of the shift assembly 138 moves a shift fork (not shown) to rotationally couple and/or decouple the first output gear 126 and the second output gear 128 to the output shaft 114. When the first output gear 126 is rotationally coupled to the output shaft 114 torque and rotation can be transferred through the gearing arrangement 108 at the first ratio and when the second output gear 128 is rotationally coupled to the output shaft 114 torque and rotation can be transferred through the gearing arrangement 108 at the second ratio.

[0027] Referring again to the housing 104, the gearing arrangement 108 is disposed in an interior 146 defined in the housing 104. The housing 104 may include a first body 148 and a second body 150 coupled to the first body 148 to define the interior 146. The first body 148 and the second body 150 may be manufactured from a variety of known materials using processes applicable to the selected material. For example, an aluminum alloy that has been formed using a die casting process may be utilized.

[0028] The interior 146 may include a gearing chamber 152 and a thermal chamber 154. Said differently, the housing 104 defines the gearing chamber 152 and the thermal chamber 154, wherein the thermal chamber 154 is fluidly separated from the gearing chamber 152. The gearing chamber 152 and the thermal chamber 154 are each defined by the housing 104 and arranged such that there is no fluid communication therebetween. The first body 148 and the second body 150 cooperate to define the gearing chamber 152. At least a portion of the gearing chamber 152 may be defined by the first body 148 and by the second body 150 such that by coupling the second body 150 to the first body 148 the gearing chamber 152 is substantially enclosed. The second body 150 may at least partially define the gearing chamber 152 so as to allow the gearing arrangement 108 to be disposed within both the first body 148 and the second body 150 when the drive assembly 100 is assembled.

[0029] The electric machine 106 is disposed in the gearing chamber 152 with the motor axis A1 spaced from the drive axis A2. The motor axis A1 and the drive axis A2 are generally oriented perpendicular to the longitudinal axis A3 of the vehicle 30 and, as such, the motor axis A1 is spaced along the longitudinal axis A3 from the drive axis A2. The electric machine 106 and the output shaft 114 are therefore spaced along the longitudinal axis A3 from each other. Spaced arrangement of the electric machine 106 and the output shaft 114 defines two corresponding sides of the housing 104, a motor side 158 and an output side 160. Similarly, the housing 104 defines an outboard side 162 and an inboard side 164 based on relative distance to the longitudinal axis A3, or vehicle centerline. The inboard side 164 generally faces toward and is nearer to the longitudinal axis A3 than the outboard side 162. Conversely, the outboard side 162 generally faces away from and is farther from the longitudinal axis A3 than the inboard side 164.

[0030] As mentioned above, the interior 146 may include the thermal chamber 154, which is fluidly separated from the gearing chamber 152. The thermal chamber 154 is defined in the housing 104 and arranged adjacent to the rotor 132A of the electric machine 106. More specifically, the thermal chamber 154 is defined in the first body 148 and arranged on the outboard side 162 of the outboard rotor 132A. The thermal chamber 154 may have an approximately cylindrical volume that is aligned with the motor axis A1 and may also have a diameter similar to a diameter of the electric machine 106.

[0031] The gearing chamber 152 may further include a sump 156 defined in the housing 104 to store lubricant for the gearing arrangement 108. The sump 156 is positioned at the lowest point of the gearing chamber 152 to collect lubricant that has been dispersed throughout the gearing chamber 152. The dispersed lubricant drains into the sump 156 to cool and deaerate. In the housing 104 illustrated in Fig. 5, the sump 156 is arranged near the motor side 158 of the housing 104 and below the electric machine 106. In order to prevent portions of the gearing arrangement 108 from protruding into the sump 156 and contacting a free surface of lubricant disposed therein, a windage wall 166 is arranged above the sump 156 and coupled to the housing 104. Additionally, slosh baffles 168 may protrude from the windage wall 166 into the sump 156 to reduce the lubricant’s ability to flow in response to the vehicle 30 braking, accelerating, and corning. When the slosh baffles 168 are in contact with the lubricant the slosh baffles act as a heat sink to transfer heat from the lubricant to the housing 104 and the thermal chamber 154.

[0032] Details of the electric machine 106 are further illustrated in Figs. 7A-8. Specifically, Fig. 7A shows the axial arrangement of the electric machine 106 within the gearing chamber 152. The electric machine 106 is axially spaced from the thermal chamber 154 toward the inboard side 164 of the housing 104. The electric machine 106 is axially spaced such that a gap 262 is defined between a first rotor 132A and the thermal chamber 154 permitting access by a lubricant disposed in the gearing chamber 152. The stator 130 is coupled to the housing 104 between the rotors 132A, 132B, which are in turn coupled to the motor shaft 134 for rotation relative to the stator 130. The rotors 132A, 132B are disposed in the gearing chamber 152 and axially spaced from the stator 130 along the motor axis A1.

[0033] Each rotor 132A, 132B has a generally annular shape with the motor shaft 134 extending through each rotor 132A, 132B and coupled with a series of fasteners 184. Further, each rotor 132A, 132B include a series of magnets 186 that are radially arranged about the motor axis A1 with the poles oriented parallel to the motor axis Al.

[0034] The motor shaft 134 extends between the first body 148 and the second body 150 in the motor side 158 of the housing 104. Two motor bearings 218 A, 218B support the motor shaft 134 for rotation about the motor axis Al, the first motor bearing 218A being in the first body 148 and the second motor bearing 218B being in the second body 150. As mentioned above, the output pinion 136 and the rotors 132A, 132B are each coupled to the motor shaft 134. The output pinion 136 may be arranged adjacent to the second bearing 218B and the rotors 132A, 132B may be arranged between the output pinion 136 and the first bearing 218 A. In order to couple the rotors 132A, 132B to the motor shaft 134, the motor shaft 134 may have a shoulder portion 220, which is arranged adjacent to the output pinion 136. The motor shaft 134 may include rotor hub 222, for spacing the rotors 132A, 132B, abutting the shoulder portion 220 and coupled with fasteners 224 extending into the shoulder portion 220. The rotors 132A, 132B may be coupled directly to the rotor hub 222 with the rotor fasteners 184 mentioned above. In addition to the shoulder portion 220, the motor shaft 134 may define a bore 226 extending the length of the motor shaft 134 along the motor axis Al . The rotors 132A, 132B, the rotor hub 222, and the motor shaft 134 are thermally coupled so as to conduct thermal energy therebetween. Specifically, any heat from the rotors 132A, 132B will be transferred into the rotor hub 222 and the motor shaft 134. As will be discussed in further detail below, heat can be transferred out of the motor shaft 134 via the bore 226.

[0035] With continued reference to Figs. 7A-8, the stator 130 has a first side 170 and a second side 172. The stator 130 may be arranged with the first side 170 oriented away from the longitudinal axis A3 of the vehicle 30 and the second side 172 oriented toward the longitudinal axis A3. Here, the first side 170 may be an outboard side and the second side 172 may be an inboard side. The stator 130 includes a stator body 174, which has a generally annular shape having an outer edge 176 and an inner edge 178. The stator body 174 is coupled to the housing 104 via a series of holes 180 defined in the stator body 174 near the outer edge 176. Each of the holes 180 are configured to receive a fastener 182, which may be engageable with the first body 148 and/or the second body 150, to secure the stator body 174 to the housing 104. The stator body 174 may further define a return passage 244 extending through the stator body 174 between the first side 170 and the second side 172, which is discussed in further detail below.

[0036] The stator 130 further includes a plurality of coils 188, each of which are coupled to the stator body 174 and radially arranged about the motor axis Al. Each of the coils 188 may be wound to form a generally trapezoidal-shaped ring defining a flux vector. The coils 188 are coupled to the stator body 174 with the flux vector oriented parallel to the motor axis Al. When electricity is passed through each of the coils 188 a magnetic field is generated, which interacts with the magnets 186 coupled to the rotors 132A, 132B causing the motor shaft 134 to rotate. As current flows through the coils 188, heat is generated, which may affect the performance of the electric machine 106.

[0037] Shown in Figs. 7A-8, the stator 130 defines a stator duct 190 having a duct inlet 192 and a duct outlet 194 according to a first configuration of the drive assembly 100. The stator duct 190 is a cavity within the stator body 174 configured for distributing a first heat transfer fluid throughout the stator body 174 in response to a pressure differential between the duct inlet 192 and the duct outlet 194. Each of the coils 188 is at least partially disposed in the stator duct 190 in contact with the flow of the first heat transfer fluid. The stator duct 190 distributes the flow of the first heat transfer fluid to each of the coils 188 coupled to the stator body 174. Contact between the coils 188 and the first heat transfer fluid allows is the coils 188 to exchange thermal energy therebetween and the flow of the first heat transfer fluid increases the rate the thermal energy can be removed.

[0038] Because the first heat transfer fluid is in contact with the coils 188 of the electric machine 106 electrical conductivity is an important consideration. Due to the relatively large amount of energy that is required to move a fully loaded vehicle 30, and thus operate the drive assembly 100, the voltages and/or current within the coils 188 are also relatively high. Furthermore, efficient operation of a synchronous motor is benefited by precise control of the electrical signals supplied to the coils 188. Electrically insulating the coils 188 reduces the potential of a short circuit and other potentially undesirable effects. In the first configuration, one type of first heat transfer fluid is a dielectric oil, which is non-conductive and therefore prevents electricity from flowing between the coils 188. For example, the first heat transfer fluid could be a mineral oil or a silicone oil. In some implementations (discussed below) the first heat transfer fluid may have lubricating additives for reducing the friction between components of the gearing arrangement 108. Alternatively, in a second configuration to be described, the first heat transfer fluid may be a water/glycol mixture. Alternative fluids are contemplated.

[0039] Turning now to Figs. 5 and 6, the cooling conduit 196 is shown in further detail along with details of a stator cooling circuit 228, according to the first configuration of the drive assembly 100. The stator cooling circuit 228 may be defined by cooperation of the cooling conduit 196, the stator duct 190, and a pump 230 to circulate the first heat transfer fluid. In general, the stator cooling circuit 228 is substantially disposed within the interior 146 of the housing 104. More specifically, the cooling conduit 196, the stator duct 190, and the pump 230 are each arranged in the interior 146 such that the first heat transfer fluid is not circulated outside the housing 104. The drive assembly 100 may be configured such that the stator cooling circuit 228 is fluidly separated from the gearing chamber 152 and from the thermal chamber 154 while portions of the stator cooling circuit 228 are disposed within both the gearing chamber 152 and the thermal chamber 154. The first heat transfer fluid may be sealed within the housing 104 and not combined or contaminated with other fluids that may be used with the drive assembly 100. The drive assembly 100 may also be configured such that the stator cooling circuit 228 is fluidly separated from the thermal chamber 154 but in fluid communication with the gearing chamber 152.

[0040] In Figs. 9-11 a second configuration of the drive assembly 100' is shown. In many respects, the drive assembly 100', may be similar to the first configuration of the drive assembly 100 described herein with like numerals (plus a prime symbol e.g. 100') corresponding to like components. Here, the stator cooling circuit 228' may be defined by cooperation of the thermal chamber 154' and the stator duct 190'. In general, the stator cooling circuit 228' fluidly coupled to a heat exchanger, which may be part of a vehicle cooling system of the electric vehicle 30. More specifically, the thermal chamber 154' is fluidly coupled to the stator duct 190' are fluidly coupled for transferring thermal energy therebetween. The stator cooling circuit 228' is fluidly separated from the gearing chamber 152' such that the first heat transfer fluid, here, a water/glycol mixture, flows between the thermal chamber 154' and the stator duct 190'. In this second configuration, the cooling conduit 196' contains the lubricant, which is circulated via a lubricant pump (described below) between the gearing chamber 152' to cool the lubricant.

[0041] With renewed reference to the first configuration of the drive assembly 100 and the stator cooling circuit 228, further details of the first configuration of the thermal chamber 154 are shown in Fig. 4. As mentioned above, the cooling conduit 196 is disposed in the thermal chamber 154 for exchanging thermal energy therebetween. Thermal energy is exchanged with the cooling conduit 196 by way of a second heat transfer fluid contained in the thermal chamber 154 and in contact with the cooling conduit 196. The thermal chamber 154 includes a thermal chamber inlet 202 and a thermal chamber outlet 204 that cooperate to define a flow path of the second heat transfer fluid. The thermal chamber inlet 202 and the thermal chamber outlet 204 are defined in the housing 106 and configured for fluid communication with a heat exchanger (not shown) of the vehicle 30.

[0042] The flow path of the second heat transfer fluid is influenced by a guide wall 206 disposed in the thermal chamber 154 and protruding from the first body 148. The guide wall 206 has two curved segments that cooperate to define a convoluted path between the thermal chamber inlet 202 and the thermal chamber outlet 204. As the second heat transfer fluid flows from the thermal chamber inlet 202 to the thermal chamber outlet 204 the flow path follows the convoluted path defined by the guide wall 206. The curved segments increase the surface area of the guide wall 206 in contact with the second heat transfer fluid. Additionally, the shape of the convoluted path increases the length of the flow path between the thermal chamber inlet 202 and the thermal chamber outlet 204. By increasing the surface area of the guide wall 206 and length of the flow path conduction between the second heat transfer fluid and the housing 104 is increased.

[0043] Flow of the second heat transfer fluid through the thermal chamber inlet 202 and into the thermal chamber 154 is facilitated via an inlet fitting (not shown), which is coupled to the housing 104 and configured to couple to a cooling system that is circulating in the vehicle 30. Likewise, flow of the second heat transfer fluid through the thermal chamber outlet 204 and out of the thermal chamber 154 is facilitated via an outlet fitting (not shown), which is coupled to the housing 104 and configured to couple to the cooling system. The inlet and outlet fittings may include a threaded portion that sealingly couples the fittings to the housing 104 or may utilize a gasketed flange which is fastened to the housing 104. Similarly, the inlet and outlet fittings may include a hose barb or other fluid coupling to interface with the cooling system in the vehicle. One type of fluid for the second heat transfer fluid is a water-based coolant, which may be treated to inhibit corrosion and lower the freezing point. For example, a glycol type antifreeze/coolant common to automotive applications may be used.

[0044] As shown in Figs. 3 and 4, one exemplary arrangement of the thermal chamber 154 is shown where the thermal chamber inlet 202 may be positioned in the portion of the convoluted path of the thermal chamber 154 that corresponds to the conduit outlet 200. In this exemplary configuration of the thermal chamber 154 the thermal chamber outlet 204 may be positioned in the portion of the convoluted path of the thermal chamber 154 that corresponds to the conduit inlet 198. As such, the flow path of the second heat transfer fluid is arranged in a counter-flow configuration relative to the flow path of the first heat transfer fluid through the cooling conduit 196. In the counter- flow configuration the first heat transfer fluid flows through the cooling conduit 106 in the opposite direction as the second heat transfer fluid flows through the thermal chamber 154. The thermal chamber 154 may also be arranged in a parallel-flow configuration, in which the thermal chamber inlet 202 may be positioned in the portion of the convoluted path of the thermal chamber 154 that corresponds to the conduit inlet 198 and the thermal chamber outlet 204 may be positioned in the portion of the convoluted path of the thermal chamber 154 that corresponds to the conduit outlet 200. In the parallel-flow configuration the first heat transfer fluid flows through the cooling conduit 106 in the same direction that the second heat transfer fluid flows through the thermal chamber 154.

[0045] In order to prevent cross-contamination of the second heat transfer fluid with the lubricant, fluid communication between the thermal chamber 154 and the gearing chamber 152 is prevented. In order to prevent fluid communication, the drive assembly 100 further includes an interface plate 208 coupled to the first body 148 between the gearing chamber 152 and the thermal chamber 154. The interface plate 208 has a generally annular body 210 and a circular outer flange 212 that extends between the annular body 210 and a lip 214. The interface plate 208 may define a hole 216, which allows the cooling conduit 196 to pass into the thermal chamber 154.

[0046] The interface plate 208 is arranged in the interior 146 of the housing 104 with the annular body 210 engaging the guide wall 206. The outer flange 212 engages the first body 148 to enclose the thermal chamber 154. The lip 214 is clamped between the stator 130 and the first body 148 to secure the interface plate 208. The interface plate 208 may be manufactured from a sheet material, which is stamped to form the outer flange 212 and the lip 214. Here, engagement of the outer flange 212 and the first body 148 is sufficient to contain the second heat transfer fluid in the thermal chamber 154, however a gasket and/or a sealant (not shown) may be utilized to further seal the thermal chamber 154.

[0047] As shown in Fig. 7A, one side of the interface plate 208 is in direct contact with the second heat transfer fluid in the thermal chamber 154. The opposite side of the interface plate 208 is in direct contact with the gearing chamber 152. Cooled flow of the second heat transfer fluid into the thermal chamber 154 removes heat from the thermal chamber facing side of the interface plate 208 during operation of the drive assembly 100, which reduces the temperature of the gearing chamber facing side of the interface plate 208 allowing the annular body 210 to function as a cold wall. The annular body 210, which has a similar diameter to both the thermal chamber 154 and the electric machine 106, can advantageously cool the gearing chamber 152 and the electric machine 106 due to the close proximity to the rotor 132A. Removing excess thermal energy from the rotor 132A allows for effective operation of the electric machine 106 and prevents overheating of the magnets 186 coupled to the rotor 132A.

[0048] On the opposite side of the electric machine 106 the drive assembly 100 may further include a rotor shield 270 disposed in the gearing chamber 152. The rotor shield 270 is adjacent to the inboard rotor 132B and axially spaced toward the inboard side 164 of the housing 104. Because the rotors 132A, 132B rotate relatively fast in comparison to the other components of the gearing arrangement 108 drag losses from lubricant are potentially the greatest. The rotor shield 270 prevents excess lubricant that is dispersed within the gearing chamber 152 from collecting on the inboard rotor 132B. Additionally, in order to maximize the efficiency of the electric machine 106, the distance between the rotors 132A, 132B and the stator 130 is relatively small. By preventing dispersed lubricant from getting between the rotors 132A, 132B and the stator 130 losses from viscous effects are greatly reduced.

[0049] In order to effect flow of the first heat transfer fluid the pump 230 is fluidly coupled between the cooling conduit 196 and the stator duct 190. The pump 230 includes a motor and a pumping element (not shown) that may be disposed inside a pump housing 232. The pump 230 further includes a pump inlet 234 and a pump outlet 236 in fluid communication with the pumping element and disposed on the pump housing 232. The pump is operated when electrical power is supplied to the motor to drive the pumping element creating a pressure differential between the pump inlet 234 and the pump outlet 236. The pump 230 may include alternative components in addition, or in alternative, to the motor and or the pumping element operable to effect a pressure differential between the pump inlet 234 and the pump outlet 236. In one exemplary implementation of the pump 230, the pumping element may be a gerotor type positive displacement pump that is operably coupled to the electric machine 106 to rotate the rotors. Alternatively, the pumping element may be implemented as an axial piston pump that is driven by an electric motor within the pump housing 232. Other pumping elements are contemplated.

[0050] Shown in Fig. 6, the pump inlet 234 and the pump outlet 236 may be defined by the pump housing 232 for receiving a suction line 238 and a pressure line 240, respectively. The suction line 238 is fluidly coupled to the pump inlet 234 to direct the first heat transfer fluid into the pumping element and the pressure line 240 is fluidly coupled to the pump outlet 236 to direct the first heat transfer fluid out of the pumping element. Additionally, the pump housing 232 may include a pump flange 242, which may define hole for receiving fasteners to couple the pump 230 to the housing 104. When coupled to the housing 104, the pump 230 may be partially or fully disposed within the interior 146. In Fig. 7A, the pump 230 is illustrated with the pump housing 232 substantially disposed within the interior 146 having the pump inlet 234 and the pump outlet 236 arranged in the gearing chamber 152 and the pump flange 242 coupled to the housing 104 externally.

[0051] As mentioned above, the cooling conduit 196, the stator duct 190, and the pump 230 cooperate to define the first configuration of the stator cooling circuit 228. To this end, the cooling conduit 196 is in fluid communication with the stator duct 190 and with the pump 230 such that the first heat transfer fluid can flow therebetween. Specifically, as part of the stator cooling circuit 228, the cooling conduit 196 allows thermal energy generated in the stator 130 and transferred to the first heat transfer fluid to be further transferred into the thermal chamber 154 and the second heat transfer fluid. More specifically, the cooling conduit 196 has a conduit inlet 198 and a conduit outlet 200 whereby the conduit inlet 198 is fluidly coupled to the duct outlet 194 of the stator duct 190 and the conduit outlet 200 is fluidly coupled to the pump 230. In some cases, such as here, the cooling conduit 196 may include the suction line 238, which is fluidly coupled to the pump inlet 234.

[0052] The cooling conduit 196 is constructed from a tubular material that has been bent or otherwise formed into the desired shape. One exemplary material that may be used to construct the cooling conduit 196 is aluminum tube, which may be drawn, extruded, welded, or otherwise manufactured using known methods. Other materials, such as copper, are contemplated as well as material enhancing processes such as anodizing and/or alternative coatings. The cooling conduit 196 may be assembled from one or more sections that are joined during manufacturing to form a continuous path between the conduit inlet 198 and the conduit outlet 200. Furthermore, these sections may be joined in series, where the entirety of the first heat transfer fluid flows through each segment in sequence, or in parallel, where flow of the first heat transfer fluid is divided between multiple segments. The cooling conduit 196 may include a plurality of nested segments 246, including an innermost segment 248 and an outermost segment 250, which are coupled in series. The cooling conduit 196 may further include a plurality of axially stacked segments 252 that are coupled in parallel with a manifold 254. The various sections of the cooling conduit 196 may be coupled together via welding, soldering, brazing, swaging, gluing, and other joining processes as appropriate for the particular material of the cooling conduit 196. Alternatively, a coupler or clamp (not shown) may be utilized to couple each of the sections.

[0053] Due to the arrangement of the thermal chamber 154 within the housing 104, the stator cooling circuit 228 is diverted around the outboard rotor 132A and through the hole 216 in the interface plate 208 when routed from the stator duct 190 to the thermal chamber 154. The stator cooling circuit 228 follows the convoluted path defined by the guide wall 206 in the thermal chamber 206. More specifically, the cooling conduit 196 defines an axially centric convoluted shape. The axially centric convoluted shape of the cooling conduit 196 is generally aligned with the motor axis A1. The conduit inlet 198 is radially spaced from the motor axis A1 to receive the flow of the first heat transfer fluid that has been diverted around the outboard rotor 132A and into the thermal chamber 154.

[0054] The aforementioned plurality of nested segments 246 are arranged to form the axially centric convoluted shape of the cooling conduit 196. The plurality of nested segments 246 are further arranged in the thermal chamber 154 to follow the convoluted path defined by the guide wall 206. The innermost segment 248 is positioned nearer to the motor axis A1 and the outermost segment 250 is positioned farther from the motor axis Al. The innermost segment 248 is coupled to the conduit inlet 198 such that as the first heat transfer fluid enters the conduit inlet 248 the flow is directed generally toward the motor axis Al . As the first heat transfer fluid continues to flow through the cooling conduit 196, the flow travels through the nested segments 246 in a semi circular path with alternating radii. The outermost segment 250 is coupled to the conduit outlet 200 such that the first heat transfer fluid exiting the conduit outlet 250 is directed away from the motor axis A1 and out of the thermal chamber 154 around the outboard rotor 132A.

[0055] Referring again to the plurality of axially stacked segments 252 of the cooling conduit 196. In contrast to the nested segments 246, which are arranged forming the axially centric convoluted shape aligned with the motor axis Al, the axially stacked segments 252 are arranged spaced along the motor axis Al. The axially stacked segments 252 are fluidly coupled in parallel via a manifold 254 that divides the flow of the first heat transfer fluid between each of the axially stacked segments 252. As shown in Figs. 7A and 7B, the cooling conduit 196 includes three axial segments 252, each being formed from a plurality of nested segments 246. The nested segments 246 that form each axial segment 252 are coupled in series, and each set of serially coupled nested segments 246 is coupled in parallel. The increased surface area that is provided by the plurality of axially stacked segments 252 affords increased heat transfer between the first heat transfer fluid and the second heat transfer fluid.

[0056] Referring now to Fig. 8 and the routing of the stator cooling circuit 228 between the thermal chamber 154 and the pump 230. As mentioned above, the conduit inlet 198 is fluidly coupled to the duct outlet 194, which is arranged on the first side 170 of the stator 130. In order to route the conduit outlet 200 to the pump inlet 234, the conduit outlet 200 and suction line 238 are disposed in the return passage 244 defined in the stator 130. The return passage 244 reduces the space that would otherwise be required to route the conduit outlet 200 and the suction line 238 around the stator 130 and the inner rotor 132B.

[0057] The first heat transfer fluid that has been displaced through the pump 230 exits the pump outlet 236 into the pressure line 240, which is fluidly coupled to both the pump outlet 236 and the duct inlet 192. The pressure line 240 is arranged in the gearing chamber 152 and extends between the pump outlet 236 and the duct inlet 192 to direct the first heat transfer fluid around the inboard rotor 132B. The pressure line 240 may be implemented as a solid tubular material formed in a substantially similar process as the cooling conduit 196 or a flexible hose that promotes increased serviceability of the pump 230 and/or stator cooling circuit 228.

[0058] In addition to the stator cooling circuit 196 discussed herein, the drive assembly 100 may further include a lubrication system for providing a pressurized supply of lubricant to the contact surfaces of the various gears and bearings throughout the gearing arrangement 108. To this end, the lubrication system may include a lubricant pump 256 that may be coupled to the housing 104 having a pickup tube and a lubricant adapter (not shown). The pickup tube is positioned in the sump 156 to collect lubricant that has drained from the gearing chamber 152. The lubricant pump 256 displaces the lubricant out of the sump 156 through the suction tube and to lubricant galleries defined in the housing 104. A first lubricant gallery 258 is shown in Fig. 7A to supply oil to the motor bearings 218A, 218B. Similarly to the pump 230 for the first heat transfer fluid described above, the lubricant pump 256 may include a lubricant pump housing 266, which may have a lubricant pump flange 268 to couple the lubricant pump 256 to the housing 104. When coupled to the housing 104, the lubricant pump 256 may be partially or fully disposed within the interior 146.

[0059] As mentioned above, some configurations of the drive assembly 100 may utilize a stator cooling circuit 228 that is in fluid communication with the gearing chamber 152. To this end, the stator cooling circuit 228 and the lubrication system may be integrated such that the first heat transfer fluid is also used as the lubricant. Here, only one pump would be used to effect flow of a lubricious heat transfer fluid into the stator 130 and the cooling conduit 196 as well as into the lubricant gallery 258.

[0060] The first lubricant gallery 258 is defined in the second body 150 and extends between the lubricant adapter and a gallery tap 260 adjacent to the second motor bearing 218B. Lubricant displaced out of the lubricant pump 256 flows through the lubricant adapter and into the first lubricant gallery 258 to the gallery tap 260. Because the lubricant tap 260 is arranged adjacent to the second motor bearing 218B, a portion of the lubricant flows between inner and outer races of the second motor bearing 218B and a portion of the lubricant flows into the bore 226 of the motor shaft 134. Heat from the rotors 132A, 132B that has transferred into the motor shaft 134 may be absorbed by the lubricant flowing through the bore 226. Lubricant that has been pumped through the second motor bearing 218B and the bore 226 exits through the first motor bearing 218 A, further lubricating and reducing the heat of the contact surfaces. The lubricant flows through the first motor bearing 218 A into the gap 262 between the interface plate 208 and the outboard rotor 132A during operation of the electric machine 106

[0061] With reference to Figs. 7A and 7B, lubricant that enters the gap 262 will make contact with the interface plate 208 and the outboard rotor 132A. During operation of the electric machine 106 the rotors 132A, 132B are rotating about the motor axis A1 relative to the interface plate 208. Lubricant that comes into contact with the rotating outboard rotor 132A is carried around and accelerated away from the motor axis A1 until reaching an edge of the outboard rotor 132A and is dispersed into the gearing chamber 152. Dispersed lubricant settles and collects on the windage wall 166. However, while this lubricant is in contact with the outboard rotor 132A thermal energy generated in the outboard rotor 132A during operation is absorbed. Additionally, the lubricant creates a conductive interface between the outboard rotor 132A and the interface plate 208 for transferring thermal energy into the thermal chamber 154.

[0062] In order to return lubricant that has collected on the windage wall 166 to the sump 156, where it can cool and deaerate, a drain aperture 264 is defined in the windage wall 166. The windage wall 166 is positioned in the gearing chamber 152 below the gap 262 between the outboard rotor 132A and the interface plate 208. Lubricant that drains out of the gap 262 and onto the windage wall 166 is directed toward the drain aperture 264. The flow of the lubricant across the windage wall 166 further transfers heat into the housing 104 and therefore the thermal chamber 154 as well as deaerates the lubricant.

[0063] As mentioned above and shown in Figs. 9-11, in the second configuration of the stator cooling circuit 228' the thermal chamber 154' and the stator duct 190' cooperate to transfer thermal energy therebetween. Specifically, as part of the stator cooling circuit 228', the thermal chamber 154' allows thermal energy generated in the stator 130' and transferred to the first heat transfer fluid to be further transferred out of the drive assembly. More specifically, the first heat transfer fluid from the vehicle cooling system is received in a housing port 274' extending through the housing 104' into the duct inlet 192'. The duct inlet 192' is arranged on the outer edge 176' of the stator body 174' and allows the first heat transfer fluid to flow from the housing port 274' into the stator duct 190'. The first heat transfer fluid in the stator duct 190' absorbs the thermal energy from the coils 188 and subsequently flows out of the duct outlet 194'.

[0064] Here, the thermal chamber inlet 202' is fluidly coupled to the duct outlet 194' to receive the flow of the first heat transfer fluid heated by the coils 188'. In order to route the first heat transfer fluid around the rotor 132A', the duct outlet 194' is defined in the first side 170' of the stator body 174' near the outer edge 176' between the fasteners 182' that secure the stator 130' to the housing 104'. The thermal chamber inlet 202' is defined in the outer flange 212' of the interface plate 208', which seals against the duct outlet 194'. The first heat transfer fluid entering the thermal chamber 154' follows the convoluted path around the motor axis Al, cooling the lubricant contained within the cooling conduit 196', toward the thermal chamber outlet 204'. The first heat transfer fluid in the thermal chamber 154' absorbs the thermal energy from the cooling conduit 196', the housing 104', and the rotor 132A' and subsequently flows out of the thermal chamber outlet 204'. Flow of the first heat transfer fluid out of the thermal chamber 154' may be facilitated via an outlet fitting (not shown), which is coupled to the housing 104' and configured to couple to the cooling system.

[0065] As used herein spatially relative terms are used for the ease of description to describe an element’s relationship to another element and are not intended to be limiting. Rather, these terms are only used to distinguish one element from another. Certain elements have been described relative to the direction of flow of the fluid contained therein (i.e. entering at an inlet and exiting at an outlet). It should be appreciated that a negative pressure gradient will cause the fluid to flow in the opposite direction (i.e. entering at an outlet and exiting at an inlet) and thus the terms used to describe these elements is for the purpose of explanation only. For example, the terms “inlet” and “outlet” are for the purpose of explaining the interconnection of elements only and not limiting of the direction of fluid flow. More specifically, while the second configuration of the stator cooling circuit 228' has been described such that the first heat transfer fluid is received in the housing port 274 and duct inlet 192' and exits at the thermal chamber outlet 204', the first heat transfer fluid may alternatively be received by the thermal chamber outlet 204' and exit at the duct inlet 192' and housing port 274'.

[0066] Several examples have been discussed in the foregoing description. However, the examples discussed herein are not intended to be exhaustive or limit the invention to any particular form. The terminology that has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations are possible in light of the above teachings and the invention may be practiced otherwise than as specifically described.

Claims

CLAIMS What is claimed is:

1. A drive assembly for an electric vehicle, the drive assembly comprising: an electric machine having a motor shaft defining a motor axis and including a rotor coupled to said motor shaft and further including a stator arranged about said motor axis with said stator defining a stator duct having a duct inlet and a duct outlet; a cooling conduit having a conduit inlet and a conduit outlet with said cooling conduit containing a first heat transfer fluid; a gearing arrangement operably engaged with said electric machine for transferring rotation of said motor shaft to one or more wheels of the electric vehicle; a housing defining a gearing chamber and a thermal chamber fluidly separated from said gearing chamber with said thermal chamber having a thermal chamber inlet and a thermal chamber outlet and containing a second heat transfer fluid; wherein said electric machine is coupled to said housing such that said rotor is arranged adjacent to said thermal chamber and said gearing arrangement is disposed in said gearing chamber; wherein one of said cooling conduit and said thermal chamber is fluidly coupled to said stator duct for transferring thermal energy therebetween; and wherein said cooling conduit is at least partially disposed in said thermal chamber for transferring thermal energy between said first heat transfer fluid and said second heat transfer fluid.

2. The drive assembly of claim 1, wherein said conduit inlet is fluidly coupled to said duct outlet of said stator duct.

3. The drive assembly of claim 2, further comprising a pump fluidly coupled to said conduit outlet and to said duct inlet, wherein said stator duct, said pump, and said cooling conduit cooperate to define a stator cooling circuit.

4. The drive assembly of claim 3, wherein said stator cooling circuit is fluidly separated from said gearing chamber.

5. The drive assembly of claim 1, wherein the other of said cooling conduit and said thermal chamber is configured for fluid coupling to a heat exchanger on the electric vehicle.

6. The drive assembly of claim 1, wherein the other of said cooling conduit and said thermal chamber is in fluid communication with said gearing chamber.

7. The drive assembly of claim 1, further comprising a pump fluidly coupled to said conduit inlet.

8. The drive assembly of claim 7, wherein said duct inlet is fluidly coupled to said thermal chamber outlet.

9. The drive assembly of claim 7, wherein said duct outlet is fluidly coupled to said thermal chamber inlet.

10. The drive assembly of claim 1, wherein said electric machine further includes a plurality of coils coupled to said stator and at least partially disposed in said stator duct for contacting said first heat transfer fluid.

11. The drive assembly of claim 1, further including an interface plate coupled to said housing between said gearing chamber and said thermal chamber, and wherein said interface plate is configured to prevent fluid communication between said gearing chamber and said thermal chamber.

12. The drive assembly of claim 11, wherein a guide wall is disposed in said thermal chamber and extends between said interface plate and said housing to define a convoluted path of said second heat transfer fluid.

13. The drive assembly of claim 1, wherein said housing includes a first body and a second body coupled to said first body and at least partially defining said gearing chamber.

14. The drive assembly of claim 13, further comprising a braking component coupled to said first body for decelerating the electric vehicle, wherein said thermal chamber is arranged in said first body for absorbing heat from said braking component.

15. The drive assembly of claim 1, wherein said cooling conduit defines an axially centric convoluted shape such that said first heat transfer fluid follows said axially centric convoluted shape between said duct outlet and an inlet of said pump.

16. The drive assembly of claim 1, wherein said cooling conduit includes a plurality of nested segments coupled in series, and wherein said conduit inlet is coupled to an innermost segment and said conduit outlet is coupled to an outermost segment.

17. The drive assembly of claim 16, wherein said plurality of nested segments define an axially centric convoluted shape such that said first heat transfer fluid flowing from said conduit inlet to said conduit outlet follows said axially centric convoluted shape.

18. The drive assembly of claim 16, wherein said plurality of nested segments are arranged in said thermal chamber such that said axially centric convoluted shape is aligned with said motor axis.

19. The drive assembly of claim 1 , wherein a gap is defined between said rotor and said thermal chamber, and wherein said gap is open to said gearing chamber permitting access by a lubricant disposed in said gearing chamber.

20. The drive assembly of claim 19, wherein said motor shaft defines a bore in fluid communication with said gap such that a lubricant flowing through said bore is directed into said gap for cooling said lubricant.

21. The drive assembly of claim 1, wherein said cooling conduit includes a plurality of axially stacked segments coupled in parallel and arranged along said motor axis.

22. The drive assembly of claim 1 , wherein said first heat transfer fluid is sealed within said housing.

23. The drive assembly of claim 1, wherein said electric machine further includes an output pinion coupled to said motor shaft and disposed in said gearing chamber connected to said gearing arrangement.

24. The drive assembly of claim 1, wherein said electric machine is configured with said rotor axially spaced from said stator.

25. The drive assembly of claim 24, wherein said stator has a first side and a second side and wherein said rotor is arranged between said first side of said stator and said cooling conduit.

26. The drive assembly of claim 25, wherein said rotor is further defined as an inboard rotor and an outboard rotor, and wherein said outboard rotor is arranged on said first side of said stator and said inboard rotor is arranged said second side of said stator.

27. The drive assembly of claim 25, wherein said stator further defines a return passage extending between said first side and said second side and wherein said conduit outlet is disposed in said return passage.

28. The drive assembly of claim 1, wherein said thermal chamber is arranged in said housing adjacent to said gearing chamber.

29. The drive assembly of claim 1, wherein said first heat transfer fluid is further defined as a dielectric oil.