Cooling system for an electric machine

A vehicle includes an electric machine and a coolant tube. The electric machine is configured to propel the vehicle. The electric machine has a stator that includes an array of windings that are arranged in a radial configuration. The coolant tube forms a loop that is routed along an axial end of the stator and adjacent to the array. The tube defines an inlet orifice configured to receive coolant and a plurality of outlet orifices configured to direct the coolant onto the windings.

TECHNICAL FIELD

The present disclosure relates to hybrid/electric vehicles and electric machines configured to propel hybrid/electric vehicles.

BACKGROUND

Hybrid/electric vehicles may include electric machines that are configured to propel the vehicle.

SUMMARY

A vehicle includes an electric machine and a coolant tube. The electric machine is configured to propel the vehicle. The electric machine has a stator that includes an array of windings that are arranged in a radial configuration. The coolant tube forms a loop that is routed along an axial end of the stator and adjacent to the array. The coolant tube defines an inlet orifice that is configured to receive coolant and a plurality of outlet orifices that are configured to direct the coolant onto the windings.

An electric machine stator includes a core, an array of windings, and a toroidal-shaped coolant tube. The core defines an internal cavity. The array of windings is disposed within the cavity in a radial configuration. The coolant tube is disposed along an axial end of the core and adjacent to the array. The coolant tube defines an inlet orifice that is configured to receive coolant and a plurality of outlet orifices that are configured to direct the coolant onto the windings.

A cooling system for an electric machine includes a coolant tube. The coolant tube is routed along an axial end of an electric machine stator and forms a loop adjacent to an array of radially configured stator windings. The tube defines an inlet orifice that is configured to receive coolant and a plurality of outlet orifices that are configured to direct the coolant onto the windings.

DETAILED DESCRIPTION

Referring toFIG. 1, a schematic diagram of a hybrid electric vehicle (HEV)10is illustrated according to an embodiment of the present disclosure.FIG. 1illustrates representative relationships among the components. Physical placement and orientation of the components within the vehicle may vary. The HEV10includes a powertrain12. The powertrain12includes an engine14that drives a transmission16. As will be described in further detail below, transmission16includes an electric machine such as an electric motor/generator (M/G)18, an associated traction battery20, a torque converter22, and a multiple step-ratio automatic transmission, or gearbox24.

The engine14and the M/G18are both drive sources for the HEV10. The engine14generally represents a power source that may include an internal combustion engine such as a gasoline, diesel, or natural gas powered engine, or a fuel cell. The engine14generates an engine power and corresponding engine torque that is supplied to the M/G18when a disconnect clutch26between the engine14and the M/G18is at least partially engaged. The M/G18may be implemented by any one of a plurality of types of electric machines. For example, M/G18may be a permanent magnet synchronous motor. Power electronics condition direct current (DC) power provided by the battery20to the requirements of the M/G18, as will be described below. For example, power electronics may provide three phase alternating current (AC) to the M/G18.

When the disconnect clutch26is at least partially engaged, power flow from the engine14to the M/G18or from the M/G18to the engine14is possible. For example, the disconnect clutch26may be engaged and M/G18may operate as a generator to convert rotational energy provided by a crankshaft28and M/G shaft30into electrical energy to be stored in the battery20. The disconnect clutch26can also be disengaged to isolate the engine14from the remainder of the powertrain12such that the M/G18can act as the sole drive source for the HEV10. Shaft30extends through the M/G18. The M/G18is continuously drivably connected to the shaft30, whereas the engine14is drivably connected to the shaft30only when the disconnect clutch26is at least partially engaged.

The M/G18is connected to the torque converter22via shaft30. The torque converter22is therefore connected to the engine14when the disconnect clutch26is at least partially engaged. The torque converter22includes an impeller fixed to M/G shaft30and a turbine fixed to a transmission input shaft32. The torque converter22thus provides a hydraulic coupling between shaft30and transmission input shaft32. The torque converter22transmits power from the impeller to the turbine when the impeller rotates faster than the turbine. The magnitude of the turbine torque and impeller torque generally depend upon the relative speeds. When the ratio of impeller speed to turbine speed is sufficiently high, the turbine torque is a multiple of the impeller torque. A torque converter bypass clutch (also known as a torque converter lock-up clutch)34may also be provided that, when engaged, frictionally or mechanically couples the impeller and the turbine of the torque converter22, permitting more efficient power transfer. The torque converter bypass clutch34may be operated as a launch clutch to provide smooth vehicle launch. Alternatively, or in combination, a launch clutch similar to disconnect clutch26may be provided between the M/G18and gearbox24for applications that do not include a torque converter22or a torque converter bypass clutch34. In some applications, disconnect clutch26is generally referred to as an upstream clutch and launch clutch34(which may be a torque converter bypass clutch) is generally referred to as a downstream clutch.

The gearbox24may include gear sets (not shown) that are selectively placed in different gear ratios by selective engagement of friction elements such as clutches and brakes (not shown) to establish the desired multiple discrete or step drive ratios. The friction elements are controllable through a shift schedule that connects and disconnects certain elements of the gear sets to control the ratio between a transmission output shaft36and the transmission input shaft32. The gearbox24is automatically shifted from one ratio to another based on various vehicle and ambient operating conditions by an associated controller, such as a powertrain control unit (PCU). Power and torque from both the engine14and the M/G18may be delivered to and received by gearbox24. The gearbox24then provides powertrain output power and torque to output shaft36.

It should be understood that the hydraulically controlled gearbox24used with a torque converter22is but one example of a gearbox or transmission arrangement; any multiple ratio gearbox that accepts input torque(s) from an engine and/or a motor and then provides torque to an output shaft at the different ratios is acceptable for use with embodiments of the present disclosure. For example, gearbox24may be implemented by an automated mechanical (or manual) transmission (AMT) that includes one or more servo motors to translate/rotate shift forks along a shift rail to select a desired gear ratio. As generally understood by those of ordinary skill in the art, an AMT may be used in applications with higher torque requirements, for example.

As shown in the representative embodiment ofFIG. 1, the output shaft36is connected to a differential40. The differential40drives a pair of wheels42via respective axles44connected to the differential40. The differential transmits approximately equal torque to each wheel42while permitting slight speed differences such as when the vehicle turns a corner. Different types of differentials or similar devices may be used to distribute torque from the powertrain to one or more wheels. In some applications, torque distribution may vary depending on the particular operating mode or condition, for example.

The powertrain12further includes an associated controller50such as a powertrain control unit (PCU). While illustrated as one controller, the controller50may be part of a larger control system and may be controlled by various other controllers throughout the vehicle10, such as a vehicle system controller (VSC). It should therefore be understood that the powertrain control unit50and one or more other controllers can collectively be referred to as a “controller” that controls various actuators in response to signals from various sensors to control functions such as starting/stopping engine14, operating M/G18to provide wheel torque or charge battery20, select or schedule transmission shifts, etc. Controller50may include a microprocessor or central processing unit (CPU) in communication with various types of computer readable storage devices or media. Computer readable storage devices or media may include volatile and nonvolatile storage in read-only memory (ROM), random-access memory (RAM), and keep-alive memory (KAM), for example. KAM is a persistent or non-volatile memory that may be used to store various operating variables while the CPU is powered down. Computer-readable storage devices or media may be implemented using any of a number of known memory devices such as PROMs (programmable read-only memory), EPROMs (electrically PROM), EEPROMs (electrically erasable PROM), flash memory, or any other electric, magnetic, optical, or combination memory devices capable of storing data, some of which represent executable instructions, used by the controller in controlling the engine or vehicle.

The controller communicates with various engine/vehicle sensors and actuators via an input/output (I/O) interface (including input and output channels) that may be implemented as a single integrated interface that provides various raw data or signal conditioning, processing, and/or conversion, short-circuit protection, and the like. Alternatively, one or more dedicated hardware or firmware chips may be used to condition and process particular signals before being supplied to the CPU. As generally illustrated in the representative embodiment ofFIG. 1, controller50may communicate signals to and/or from engine14, disconnect clutch26, M/G18, battery20, launch clutch34, transmission gearbox24, and power electronics56. Although not explicitly illustrated, those of ordinary skill in the art will recognize various functions or components that may be controlled by controller50within each of the subsystems identified above. Representative examples of parameters, systems, and/or components that may be directly or indirectly actuated using control logic and/or algorithms executed by the controller include fuel injection timing, rate, and duration, throttle valve position, spark plug ignition timing (for spark-ignition engines), intake/exhaust valve timing and duration, front-end accessory drive (FEAD) components such as an alternator, air conditioning compressor, battery charging or discharging (including determining the maximum charge and discharge power limits), regenerative braking, M/G operation, clutch pressures for disconnect clutch26, launch clutch34, and transmission gearbox24, and the like. Sensors communicating input through the I/O interface may be used to indicate turbocharger boost pressure, crankshaft position (PIP), engine rotational speed (RPM), wheel speeds (WS1, WS2), vehicle speed (VSS), coolant temperature (ECT), intake manifold pressure (MAP), accelerator pedal position (PPS), ignition switch position (IGN), throttle valve position (TP), air temperature (TMP), exhaust gas oxygen (EGO) or other exhaust gas component concentration or presence, intake air flow (MAF), transmission gear, ratio, or mode, transmission oil temperature (TOT), transmission turbine speed (TS), torque converter bypass clutch34status (TCC), deceleration or shift mode (MDE), battery temperature, voltage, current, or state of charge (SOC) for example.

An accelerator pedal52is used by the driver of the vehicle to provide a demanded torque, power, or drive command to propel the vehicle. In general, depressing and releasing the accelerator pedal52generates an accelerator pedal position signal that may be interpreted by the controller50as a demand for increased power or decreased power, respectively. A brake pedal58is also used by the driver of the vehicle to provide a demanded braking torque to slow the vehicle. In general, depressing and releasing the brake pedal58generates a brake pedal position signal that may be interpreted by the controller50as a demand to decrease the vehicle speed. Based upon inputs from the accelerator pedal52and brake pedal58, the controller50commands the torque to the engine14, M/G18, and friction brakes60. The controller50also controls the timing of gear shifts within the gearbox24, as well as engagement or disengagement of the disconnect clutch26and the torque converter bypass clutch34. Like the disconnect clutch26, the torque converter bypass clutch34can be modulated across a range between the engaged and disengaged positions. This produces a variable slip in the torque converter22in addition to the variable slip produced by the hydrodynamic coupling between the impeller and the turbine. Alternatively, the torque converter bypass clutch34may be operated as locked or open without using a modulated operating mode depending on the particular application.

To drive the vehicle with the engine14, the disconnect clutch26is at least partially engaged to transfer at least a portion of the engine torque through the disconnect clutch26to the M/G18, and then from the M/G18through the torque converter22and gearbox24. The M/G18may assist the engine14by providing additional power to turn the shaft30. This operation mode may be referred to as a “hybrid mode” or an “electric assist mode.”

To drive the vehicle with the M/G18as the sole power source, the power flow remains the same except the disconnect clutch26isolates the engine14from the remainder of the powertrain12. Combustion in the engine14may be disabled or otherwise OFF during this time to conserve fuel. The traction battery20transmits stored electrical energy through wiring54to power electronics56that may include an inverter, for example. The power electronics56convert DC voltage from the battery20into AC voltage to be used by the M/G18. The controller50commands the power electronics56to convert voltage from the battery20to an AC voltage provided to the M/G18to provide positive or negative torque to the shaft30. This operation mode may be referred to as an “electric only” or “EV” operation mode.

In any mode of operation, the M/G18may act as a motor and provide a driving force for the powertrain12. Alternatively, the M/G18may act as a generator and convert kinetic energy from the powertrain12into electric energy to be stored in the battery20. The M/G18may act as a generator while the engine14is providing propulsion power for the vehicle10, for example. The M/G18may additionally act as a generator during times of regenerative braking in which torque and rotational (or motive) energy or power from spinning wheels42is transferred back through the gearbox24, torque converter22, (and/or torque converter bypass clutch34) and is converted into electrical energy for storage in the battery20.

It should be understood that the schematic illustrated inFIG. 1is merely exemplary and is not intended to be limiting. Other configurations are contemplated that utilize selective engagement of both an engine and a motor to transmit through the transmission. For example, the M/G18may be offset from the crankshaft28, an additional motor may be provided to start the engine14, and/or the M/G18may be provided between the torque converter22and the gearbox24. Other configurations are contemplated without deviating from the scope of the present disclosure.

It should be understood that the vehicle configuration described herein is merely exemplary and is not intended to be limited. Other electric or hybrid vehicle configurations should be construed as disclosed herein. Other vehicle configurations may include, but are not limited to, series hybrid vehicles, parallel hybrid vehicles, series-parallel hybrid vehicles, plug-in hybrid electric vehicles (PHEVs), fuel cell hybrid vehicles, battery operated electric vehicles (BEVs), or any other electric or hybrid vehicle configuration known to a person of ordinary skill in the art.

Referring toFIG. 2, a stator62of an electric machine is illustrated. More specifically, the stator62may be the stator of the M/G18described above. A rotor of the electric machine, which is generally disposed within an internal cavity64defined by the stator62and which is configured to rotate within the internal cavity64about a rotational axis66, has been removed for illustrative purposes. The stator62includes a core68and an array of coil windings70that are arranged in a radial configuration relative to the rotational axis66. The core68, more specifically, defines the internal cavity64and the array of coil windings70are disposed within the internal cavity64. The array coil windings70are secured to the core68and protrude inward and into the cavity64from the core68in the radial configuration.

The stator62may include an external peripheral surface72that extends radially about the rotational axis66. The external peripheral surface72may more specifically be an external surface of the core68. The stator62may also include a front axial end74and rear axial end76. The front axial end74and the rear axial end76may more specifically include any surface or feature of the core68and/or the coil windings70that define a front end and a rear end of the stator62, respectively, along the rotational axis66.

A backing plate78may be secured to the either the front axial end74or the rear axial end76of the stator62. In the illustrated embodiment, the backing plate78is secured to the front axial end74of the stator62. Terminal wires80that are configured to electrically connect the coil windings70to a power source (e.g., the battery20via the power electronics56) may be secured to the backing plate78. More specifically, electrical contacts82disposed along ends of the terminal wires80are configured to electrically connect the coil windings70to a power source. The backing plate78may be made front an insulating material, such as plastic, to prevent adjacent terminal wires80from becoming electrically connected to each other and to ensure that each terminal wire80is only connected one phase the coil windings70(i.e., to ensure each terminal wire80is only connected to one of the phases of the coil windings70and is insulated from the other phases of the coil windings70).

A cooling system for the electric machine, or more specifically for the stator62of the electric machine, may include a coolant tube84. The coolant tube84may form a loop that is routed along either the front axial end74or the rear axial end76of the stator62. In the illustrated embodiment, the coolant tube84forms a loop that is routed along the front axial end74of the stator62. More specifically, the loop formed by the coolant tube84may be routed along a flat plane that defines either the front axial end74or the rear axial end76of the stator62. The coolant tube84and the loop formed by the coolant tube84may be adjacent to the to the array of radially configured coil windings70. More specifically, the coolant tube84and the loop formed by the coolant tube84may be ring-shaped or toroidal-shaped such that the coolant tube84mirrors the radial configuration of the coil windings70. The coolant tube84may be secured to a backside of the backing plate78. The coolant tube may be disposed between the backing plate78and the array of coil windings70. Alternatively, the tube84may be integral to the backing plate78adjacent to the array of coil windings70.

Referring toFIG. 3, a partial view of the stator62with the backing plate78removed is illustrated. The backing plate78has been removed inFIG. 3for illustrative purposes. More specifically, the backing plate78has been removed inFIG. 3to further illustrate the details of the coolant tube84. The coolant tube84defines an inlet orifice86that is configured to receive coolant. More specifically, the inlet orifice86may be connected to a pressurized line (not shown) that is configured to deliver transmission fluid (which may act a coolant) from the gear box24to the coolant tube84.

The coolant tube84also defines a plurality of outlet orifices88that are configured to direct the coolant onto the coil windings70. More specifically, the outlet orifices88are configured to direct the coolant onto the coil windings70in a direction that is axial relative to the stator (e.g., in a direction along the rotational axis66which is into the sheet inFIG. 3) and substantially perpendicular relative to the loop (e.g., in a direction that is substantially perpendicular relative to the axial end of the stator62or the flat plane that the loop formed by the coolant tube84is routed along). Substantially perpendicular may refer to any incremental value that is plus or minus 30° from exactly perpendicular. A subset of the plurality of orifices88are configured to direct coolant into the spaces90between adjacent coil windings70. The subset of the plurality of orifices88that are configured to direct coolant into the spaces90between adjacent coil windings70are illustrated inFIG. 3as every other outlet orifice88that overlap one of the spaces90between adjacent coil windings70.

The cross-sectional area of the inlet orifice86may be greater than the total sum of the cross-sectional areas of the plurality of outlet orifices88. When the coolant is introduced into the inlet the orifice86, the difference in cross-sectional areas between the inlet orifice86and the total sum of the cross-sectional areas of the plurality of outlet orifices88allows the pressure to increase within the coolant tube84. The increase in pressure in turn increases the velocity and mass rate at which the coolant flows or “sprays” out of the plurality of outlet orifices88and onto the coil windings70. The increase in the mass rate of coolant that is being directed onto the coil windings results in removing more heat and increased cooling of the coil windings.