Patent Publication Number: US-2023137863-A1

Title: Power inductor with internal cooling passages

Description:
TECHNICAL FIELD 
     This disclosure relates to power inductors and more specifically to power inductors having internal cooling passages. 
     BACKGROUND 
     Electric vehicles may include a voltage converter (e.g., a DC-DC converter) connected between the battery and the electric machine. Electric vehicles that have alternating current (AC) electric machines also include an inverter connected between the DC-DC converter and each electric machine. A voltage converter increases (“boosts”) or decreases (“bucks”) the voltage potential to facilitate torque capability optimization. The DC-DC converter includes an inductor (or reactor), switches and diodes. A typical inductor includes a conductive coil that is wound around a magnetic core. 
     SUMMARY 
     According to one embodiment, a power inductor includes a magnetic core having first and second legs and opposing first and second curved sections, a conductor having a first coil around the first leg and a second coil around the second leg; and a fluid circuit having a first branch disposed between the first leg and the first coil and a second branch disposed between the second leg and the second coil. 
     According to another embodiment, a power inductor includes a magnetic core defining at least one recessed channel and first and second end caps disposed on opposing ends of the core. The first end cap defines an inlet port and the second end cap defines an outlet port. A coil is wrapped around the core and cooperates with the recessed channel to define a cooling passage in fluid communication with the inlet and outlet ports. 
     According to yet another embodiment, a power inductor includes a magnetic core having a first leg having a first side defining a first recessed channel extending along a length of the leg, a second side defining a second recessed channel extending along the length, and a third side defining a third recessed channel along a width of the first leg and interconnecting the first and second channels. The core further has a second leg that is parallel to and spaced apart from the first leg, the second leg having a first side defining a first recessed channel extending along a length of the second leg, a second side defining a second recessed channel extending along the length of the second leg, and a third side defining a third recessed channel along a width of the second leg and interconnecting the first and second channels of the second leg. A conductor has a first coil wrapped around the first leg and cooperating with the channels of the first leg to define cooling passages and has a second coil wrapped around the second leg and cooperating with the channels of the second leg to define additional cooling passages. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a circuit diagram of a variable-voltage converter including a power inductor. 
         FIG.  2    is an exploded perspective view of a subassembly of the power inductor. 
         FIG.  3    is a diagrammatical front view of the power inductor illustrating an internal cooling circuit. 
         FIG.  4    is a diagrammatical side view of the power inductor illustrating the internal cooling circuit. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations. 
     Vehicles may include an electric powertrain that includes at least one traction motor for powering driven wheels. The traction motor may be powered by a traction battery. The battery is a high-voltage battery capable of outputting electrical power to operate the motor. The battery also receives electrical power from the motor when operating as a generator. A high-voltage bus electrically connects the battery to the motor. The vehicle may include one or more controllers for operating various components. The vehicle controllers generally include any number of microprocessors, ASICs, ICs, memory (e.g., FLASH, ROM, RAM, EPROM and/or EEPROM) and software code to co-act with one another to perform a series of operations. The controllers also include predetermined data, or “look-up tables” that are based on calculations and test data and stored within the memory. The controllers communicate with other vehicle systems and each other over one or more wired or wireless vehicle connections using common bus protocols (e.g., CAN and LIN). 
     The vehicle may include a DC-DC converter or variable voltage converter (VVC) and an inverter. The VVC and the inverter are electrically connected between the battery and the motor. The VVC may “boost” or increases the voltage potential of the electrical power provided by the battery and may “buck” or decreases the voltage potential of the electrical power provided to the battery. The inverter inverts the direct current (DC) power supplied by the battery (through the VVC) to AC power for operating the motor. The inverter also rectifies AC to DC. 
     The VVC is an assembly with components that may be mounted both inside and/or outside of a transmission or motor assembly of a vehicle. The VVC includes a power inductor. In one or more embodiments, the inductor is located within the transmission and/or motor housing. By mounting the inductor within a wet housing, e.g., transmission housing, the exposed surface area of the inductor may be directly cooled by transmission fluid which allows for improved thermal performance. The transmission includes additional structure for supporting the inductor while allowing the transmission fluid to flow through the structure to contact the exposed surface area. 
     The transmission may include a fluid, such as oil or automatic transmission fluid (ATF), for lubricating and cooling the gears located within the transmission chamber as well as any electric motors. The transmission housing is sealed to retain the fluid. The transmission may also include valves, pumps and conduits (not shown) for circulating the fluid through the housing. A heat exchanger or ATF cooler may be used to cool the fluid. The fluid may also be used to cool the inductor assembly  14 . The transmission housing may include a sump that collects the fluid in the circulation system that is configured to draw fluid from the sump and redistribute that fluid onto components such as the inductor. As of explain below, the transmission may be configured to directly deliver transmission fluid onto the exposed coils in core of the inductor via one or more conduits. Splash cooling may also occur. Rotating elements (e.g., gears and shafts) may displace or “splash” fluid on other components. 
     Referring to  FIG.  1   , a VVC  20  includes a power inductor  22 . The VVC  20  also includes a number of switches and diodes. For example, the VVC  20  includes a first switching unit  24  and a second switching unit  26  for boosting the input voltage (V bat ) to provide output voltage (V dc ). The first switching unit  24  includes a first transistor  28  connected in parallel to a first diode  30 , but with their polarities switched (anti-parallel). The second switching unit  26  includes a second transistor  32  connected anti-parallel to a second diode  34 . Each transistor  28 ,  32  may be any type of controllable switch (e.g., an insulated gate bipolar transistor (IGBT) or field-effect transistor (FET)). Additionally, each transistor  28 ,  32  is individually controlled by a controller. The inductor  22  is depicted as an input inductor connected in series between the battery and the switching units  24 ,  26 . The inductor  22  generates magnetic flux when current is supplied. When the current flowing through the inductor  22  changes, a time-varying magnetic field is created, and voltage is induced. The VVC  20  may also include different circuit configurations (e.g., more than two switches). 
     The following Figures and related text describe example power inductors according to one or more aspects of this disclosure. 
     Referring to  FIGS.  2  and  3   , the power inductor  22  includes a core-and-conductor assembly  111  that may be formed as a dual “C” configuration with two coils. The assembly  111  includes a core  112  having an upper end  116  and a lower end  118  that are each formed in a curved shape. The core  112  also includes a first leg  120  and a second leg  122  for interconnecting the ends  116 ,  118  to collectively form a ring-shaped core  112 . The core  112  may be formed of a magnetic material, such as an iron-silicon alloy powder. 
     Rather than being solid, the core  112  is formed of a plurality of segments that are spaced apart, by spacers, to define a plurality of gaps between adjacent ones of the segments. For example, a C-shaped segment  124  forms the curved end  116  and a C-shaped segment  126  forms the curved end  118 . The first leg  120  includes two segments  128  and  130 , and the second leg  122  includes two segments  132  and  134 . Spacers  136  are provided between the segments. This, of course, is just one example and more or less segments may be used in other embodiments. 
     A conductor  114  is wrapped on the core  112 . For example, the conductor includes two adjacent coils, such as copper or aluminum, that are wound into two adjacent helical coils, a first coil  140  associated with the leg  120  and a second coil  142  associated with the leg  122 . The coils may be formed using a rectangular (or flat) type conductive wire by an edgewise process. Input and output leads extend to connect to other components and a jumper (not shown) is used to connect the two coils  140 ,  142 . 
     A bobbin  144  is provided in some embodiments; in other embodiments, the coils are wound directly onto the core. In the shown embodiment, the bobbin  144  supports the conductor  114 . The bobbin  144  may include a frame that defines openings for receiving the core  112  therein. 
     The power inductor  22  also includes a housing that supports the core  112  and the conductor  114 . The housing may be formed of a pair of molded end caps  150  and  152 . The end caps may be injection molded to the assembly  111 . Portions of the housing (not visible) may interconnect the opposing end caps  150 ,  152  as is known in the art. The end caps  150 ,  152  may include mounts for attaching the power inductor to a structure. For example, the power inductor  22  may be mounted within a transmission housing. 
     The power inductor  22  may be cooled by a fluid. The fluid may be any dielectric fluid. For example, the fluid may be oil such as transmission fluid (ATF). The oil is supplied to the inductor  22  by a circulation system that includes one or more conduit. The circulation system may be plumbed with the valve body of the transmission in one or more embodiments. The circulation system may be open loop in which the oil drains to the sump or closed loop in which the oil exiting the power inductor is piped back to the hydraulic circuit of the transmission. 
     Rather than merely dripping or splashing oil onto the outer surface of the power inductor, the power inductor  22  includes an internal fluid circuit configured to circulate oil to more efficiently cool the power inductor. The internal fluid circuit is in direct contact with the core  112  and coils with portions of the circuit disposed between the core and the coils. 
     Referring to  FIGS.  3  and  4   , the power inductor  22  includes a cooling circuit  160  that is configured to circulate fluid from an inlet  162 , internally through the power inductor  22 , and out an outlet  164 . The upper end cap  150  may define the inlet  162 . An inlet manifold  166  is disposed under the end cap  150  (at least partially). The inlet manifold  166  may be defined mainly by the cooperation of the core  112  and the end cap  150 . The inlet manifold  166  feeds a first branch  168  associated with the first leg  120  and a second branch  170  associated with the second leg  122 . The first branch  168  includes a plurality of interconnected passages defined between the first leg  120  and the coil  140 , and the second branch  170  includes a plurality of interconnected passages defined between the second leg  122  and the coil  142 . The branches  168 ,  170  terminate at the outlet manifold  172  provided under the lower end cap  152 . The outlet manifold  172  may be defined mainly by the cooperation of the core  112  and the end cap  152 . The outlet manifold  172  is in fluid communication with the outlet port  164 . 
     The second branch  170  has a plurality of passages including a supply passage  180  that extends axially along the length second leg  122  (vertical in the illustrated orientation). The supply passage  180  extends downwardly from the inlet manifold  166 . The supply passage  180  feeds oil to a plurality of horizontal passages  186  (also referred to as interconnecting passages). The horizontal passages  186  include a set of inner passages  188  located on the inner side of the second leg and a set of outer passages  190  located on the outer side of the second leg  122 . The horizontal passages  186  extend along the width of the second leg  122 . The horizontal passages  186  connect the supply passage  180  in fluid communication with a return passage  192 . The return passage  192  also extends axially along the length of the second leg similar to the supply passage, albeit on an opposite side of the leg  122 . The return passage  192  is in fluid communication with the outlet manifold  172 . The outlet manifold  172  may circulate the oil to the outlet port  164 , which may drain to the sump of the transmission or other housing. 
     The first branch  168  may be the same or similar to the second branch  170  and will not be described in detail for brevity. In short, the first branch  168  includes a vertical supply passage  192 , a plurality of horizontal passages  194 , and a return passage (not visible). The first and second branches  168 ,  170  may connected in parallel between the inlet manifold  166  and the outlet manifold  172 . During operation, fluid circulates through these branches to remove heat from the power inductor. By providing the internal cooling circuit  160 , the cooling oil is in direct contact with both the core  112  and the conductor  114  to provide efficient and effective thermal management of the power inductor  22  even under heavy duty cycles. 
     The inlet port  162  is configured to connect with a tube  198  or other conduit configured to supply fluid to the power inductor  22 . The outlet port  164  may simply be an orifice that drains oil to the sump. Alternatively, the outlet port  164  may connect with a conduit (not shown). 
     The cooling circuit  160  may perform better if back pressure is present within the circuit. As shown in  FIG.  4   , a check valve  200  may be used to maintain a predetermined amount of back pressure. The check valve  200  is biased to the closed position and opens responsive to the pressure within the circuit  160  exceeding a threshold. The check valve  200  may include a ball  202  that is urged against a valve seat by a resilient member such as a spring  204 . The check valve  200  may be a connected to the outlet port  164 . Alternatively, the check valve may be provided internally between the outlet manifold  172  and the outlet port  164 . In a further alternative, the check valve may be provided downstream of the power inductor such as on a tube connecting to the outlet port  164 . A tube may be connected to the outlet of the check valve in some embodiments. 
     Other ways of providing back pressure are also contemplated. For example, the outlet port may be throttled to increase back pressure within the cooling circuit. Alternatively, rather than flowing the fluid from top to bottom, the inlet port may be provided on the bottom of the power inductor and the cooling circuit may circulate from bottom to top. Here, gravity provides sufficient back pressure. In yet another embodiment, the inlet and outlet ports may connect with a closed loop system of a transmission hydraulic circuit. The pressure within the hydraulic circuit may create sufficient back pressure at the outlet port to maintain the desired back pressure within the cooling circuit. 
     Referring back to  FIG.  2   , the cooling network  160  may be generally formed by recessed channels defined in the core  112 . The recessed channels of the core  112  are open channels that become sealed by the coils (or the end caps or bobbins) thus forming closed fluid conduits, i.e., the above-described passages and manifolds of the cooling circuit  160 .  FIG.  2    illustrates a representative set of these channels, but it is to be understood that some of the channels are not visible from the vantage point of this perspective view or are not shown for simplification. 
     In the illustrated embodiment, the segment  124  includes a first side  210  defining a first channel  212  extending in the width direction and second and third channels  214  and  216  extending in the length direction. The first channel  212  is disposed under the end cap  150  and cooperates therewith to define the intake manifold  166 . The second leg  122  includes a first side  220  defining a channel  222  extending along the length of the leg  122 . The channel  222  at least partially defines the supply passage  180 . A second, opposite side  224  of the leg  122  defines a channel  226  that at least partially defines the return passage  192 . An outer side  228  of the leg  122  defines one or more recessed channels  230  that extend between the channel  222  and the channel  226 . The channels  230  form the outer interconnecting passages  190 . An inner side  232  of the leg  122  defines one or more channels  234  that extend between the channel  222  and the channel  226 . The channels  234  form the inner interconnecting passages  188 . The side  240  of the segment  126  includes channels (not visible) similar to the segment  212 . These channels form the outlet manifold  172  and portions of the return passages. The first leg  120  defines channels similar or the same as the channels of the second leg  122  and will not be described for brevity. 
     While the legs are explained as defining channels as a unit, in actuality, each segment has a recessed channel that is aligned with and cooperates with the individual channels of the adjacent segment(s) to form the above-described channel. Similarly, each of the spacers  136  defines one or more notches  242  (two in the illustrated embodiment) that are sized and shaped to match the channels defined in the segments. The notches  242  of the spacers  136  are aligned with and cooperate with the recessed channels of the segments to define continuous open channels. 
     The illustrated embodiment of the cooling circuit is but one example. More or less channeling may be provided in the core depending upon the size of the inductor and the power requirements and heat generation. Therefore, the cooling circuit  160  simply provides a representative basis for forming internal cooling passages within an inductor between the core and the coils. 
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments can be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes can include, but are not limited to, strength, durability, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and can be desirable for particular applications.