DEVICE FOR SUPPLYING COOLANT TO A STATOR AND TO A ROTOR OF AN ELECTRIC MOTOR IN A VEHICLE

Abstract

Device (16) for supplying a coolant to a stator (18) and to a rotor (20) of an electric motor (12) in a vehicle having a coolant pump (14), wherein the device (16) comprises: a base (30) defining a plurality of first openings (38), wherein the coolant can flow to the stator (18) through at least one of the first openings (38); and at least one wall (32) extending from the base (30), wherein the base (30) and the at least one wall (32) define a cavity (34) designed to receive the coolant from the coolant pump (14); characterized by: at least one first raised element (40) within the cavity (34), wherein the at least one first raised element (40) extends from the base (30) to a free end and defines at least one second opening (42) at the free end which is aligned with one of the first openings (38), wherein the raised element (40) forms a first passage (43) between the second opening (42) and the first opening (38) aligned therewith, through which the coolant can flow to the rotor (20).

Description

TECHNICAL FIELD

[0001] The present invention relates to a device according to the preamble of claim 1 for supplying a coolant to a stator and to a rotor of an electric motor in a vehicle.

[0002] A generic device is essentially described in DE 11 2010 001 550 T5. BACKGROUND

[0003] Electric vehicles, which include hybrid vehicles, use electric motors, such as induction motors and permanent magnet motors, to propel the vehicles, as well as to generate braking energy when operating like an electric generator. The electric motor generally includes a rotor, which transmits torque through a gear set to the vehicle's drive wheels, and a stator, which contains electrical conductors in the form of motor windings. During operation, the stator and rotor generally require cooling, which is typically achieved by supplying a coolant, such as oil, to the stator (stator flow) and to the rotor (rotor flow). While stator flow is always required when the electric motor is operating, rotor flow is not, and therefore coolant is supplied to the stator and rotor separately. SUMMARY

[0004] According to the invention, a device for providing a coolant to a stator and to a rotor of an electric motor in a vehicle is presented, which is characterized by the features of claim 1.

[0005] A system for supplying coolant to a stator and a rotor of an electric motor in a vehicle is also provided. The system comprises a coolant pump, the device according to claim 1, and a controller. The coolant pump is configured to supply the coolant to the cavity of the device such that the coolant within the cavity is at a coolant level. The coolant pump has an adjustable speed. The controller is configured to adjust the speed of the coolant pump based on at least one parameter such that the coolant level within the cavity is variable.

[0006] Further described is a method for supplying coolant to a stator and a rotor of an electric motor in a vehicle using the system described above. The method includes first determining a temperature of the electric motor. Then, the method includes determining whether the temperature of the electric motor is below or above a threshold temperature.

[0007] If the temperature is below the threshold temperature, the method then includes setting the coolant pump to a low speed setting such that the coolant supplied to the device fills the cavity to a coolant level that does not exceed the at least one first raised element. This allows the coolant to flow only to the stator due to gravity through the plurality of first openings defined by the base of the device.

[0008] If the temperature is above the threshold temperature, the method then includes setting the coolant pump to a high speed setting such that the coolant level within the cavity is above the at least one first raised element. This allows the coolant to flow due to gravity through the plurality of first openings or the at least one first passage to both the stator and the rotor.

[0009] The foregoing features and advantages and other features and advantages of the present invention will be readily apparent from the following detailed description of the best modes for carrying out the invention when read in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic block diagram of a system for cooling an electric motor by means of a device; Fig. 2 is a schematic fragmentary cross-sectional view of the electric motor of Fig. 1; Fig. 3A - 3C are schematic cross-sectional views of the device of Fig. 1; and Fig. 4 is a schematic flow diagram illustrating an exemplary method for cooling the electric motor using the system of Fig. 1 illustrates. DETAILED DESCRIPTION

[0010] With reference to the drawings, in which like reference numerals correspond to like or similar elements wherever possible in the several figures, Fig. 1, a system 10 for cooling an electric motor 12 is shown. The system 10 includes a coolant pump 14 and a device 16. The coolant pump 14 is configured to supply a coolant to the device 16, which in turn supplies the coolant to the electric motor 12, specifically to a stator 18 and a rotor 20 of the electric motor 12, as shown in Fig. 2 and will be described in more detail below. The device 16 is disposed above the electric motor 12 so that the coolant flows from the device 16 to the electric motor 12 due to gravity. The coolant pump 14 may have a variable speed so that it can change the amount of coolant delivered to the device 16 based on certain parameters, such as the temperature of the electric motor 12, as will be described in more detail below. In one embodiment, the coolant may be an oil, and the coolant pump 14 may be an oil pump.

[0011] With reference now to Fig. 2, the electric motor 12 generally includes the stator 18 and the rotor 20 mentioned above. The stator 18 is positioned around the rotor 20, with an air gap 22 between the stator 18 and the rotor 20. In operation, the rotor 20 generally rotates about a drive shaft 21, and the stator 18 remains stationary. The stator 18 includes a plurality of windings 24 separated by gaps. Each winding 24 has a winding tip 26.

[0012] During operation, the electric motor 12 is at a temperature and therefore requires cooling. As explained above, cooling is achieved by supplying coolant to the stator 18, referred to as stator flow 28, and to the rotor 20, referred to as rotor flow 29. The stator flow 28 generally flows toward the winding tips 26. The rotor flow 29 flows through the gaps between the plurality of windings 24 to the rotor 20. When the rotor flow 29 comes into contact with the rotor 20, which is rotating as mentioned above, the coolant is propelled away from the rotor 20 at a high velocity toward the interior of the stator 18, specifically the interior of the windings 24, which is not reached by the stator flow 28. This increases the cooling effectiveness of the coolant.

[0013] However, the rotor flow 29 is only necessary when the temperature of the electric motor 12 is above a threshold temperature. The threshold temperature may depend on factors such as the insulation material of the stator 18. In one embodiment, the threshold temperature may be between 150 degrees Celsius and 180 degrees Celsius. The temperature of the electric motor 12 generally increases when higher torque and power are required from the electric motor 12. The temperature may be calculated by a controller 50, described in more detail below, based on parameters such as the torque and / or power of the electric motor 12. Alternatively, the temperature may be measured by a temperature sensor (not shown) or other measuring device disposed on the electric motor 12.The speed of the coolant pump 14 may be proportional to the temperature of the electric motor 12 so that the rotor flow 29 starts at the appropriate temperature of the electric motor 12, ie, the threshold temperature.

[0014] Now with reference to Fig. 3A-3C, the device 16 generally includes a base 30 and at least one wall 32 defining a cavity 34. The cavity 34 is configured to receive and retain the coolant supplied by the coolant pump 14. The coolant within the cavity 34 is filled to a coolant level 36, which may vary depending on the speed of the coolant pump 14, as mentioned above and described in more detail below.

[0015] The base 30 also defines first openings 38. Although in Fig. 3A-3C, four first openings 38 are shown, it should be appreciated that there may be any number of first openings 38. As explained above, the device 16 is disposed above the electric motor 12. Consequently, the coolant or stator flow 28 may flow due to gravity through some of the first openings 38 to the stator 18, specifically to the winding tips 26, as explained above. The first openings 38 may be disposed in the base 30 such that the coolant can flow directly from the first openings 38 to the winding tips 26. Alternatively, the device 16 may include a conduit (not shown) or other passageway to conduct the coolant from each of the first openings 38 to the winding tips 26.

[0016] The device 16 also includes a first raised element 40 within the cavity 34 that extends from the base 30. Although in Fig. 3A-3C, only a first raised member 40 is shown, it should be appreciated that there may be any number of first raised members 40. The first raised member 40 may be, but is not limited to, a tube, conduit, pedestal, or the like. The first raised member 40 defines at least one second opening 42 substantially aligned with one of the first openings 38 to form a first passageway 43. Analogous to the first openings 38, the coolant or rotor flow 29 may flow through the first passageway 43 to the rotor 20 due to gravity. Additionally, the first raised member 40 and the first passageway 43 may be disposed within the cavity 34 such that the coolant may flow from the first passageway 43 directly to the rotor 20.Alternatively, the device 16 may include a conduit (not shown) or other passageway to convey the coolant from the first passageway 43 to the rotor 20.

[0017] The device 16 may further include a second raised member 44 within the cavity 34 extending from the base 30. Although in Fig. 3A-3C, only one second raised member 44 is shown, it should be appreciated that there may be any number of second raised members 44. The second raised member 44 is larger than the first raised member 40, i.e., it extends farther from the base 30 than the first raised member 40. Like the first raised member 40, the second raised member 44 may be, but is not limited to, a conduit, a tube, a pedestal, or the like. The second raised member 44 defines at least a third opening 46 substantially aligned with one of the first openings 38 to form a second passageway 47. Similar to the first passageway 43, the coolant or rotor flow 29 may flow through the second passageway 47 to the rotor 20 due to gravity.The second raised member 44 and the second passage 47 may be disposed within the cavity 34 such that the coolant can flow from the second passage 47 directly to the rotor 20. Alternatively, the device 16 may include a conduit (not shown) or other passage to direct the coolant from the second passage 47 to the rotor 20.

[0018] The second raised member 44 and the second passage 47 allow coolant to be progressively delivered to the rotor 20 as the temperature of the electric motor 12 increases. It should be appreciated that the device 16 may include any number of raised members in addition to the second raised member 44, which increase in height from the first raised member 40 to promote the progressive delivery of coolant to the rotor 20.

[0019] As discussed above, the coolant level 36 may vary depending on the speed of the coolant pump 14, which in turn may depend on parameters such as the temperature of the electric motor 12. Because the first openings 38 are disposed in the base 30, the coolant is always delivered to the stator 18 when the system 10 is operating. However, the varying heights of the first raised member 40 and the second raised member 44 allow the coolant to be selectively delivered to the rotor 20 as the temperature of the electric motor 12, and thus the speed of the coolant pump 14, increases. The heights are determined, along with the speed of the coolant pump 14, based on the threshold temperature at which the rotor flow 29 is required.

[0020] As in Fig. 3A, the coolant level 36 is below the first raised element 40 and the second raised element 44. Consequently, the coolant can only flow through the first openings 38 to the stator 18. As shown in Fig. 3B, the coolant level 36 is located between the first raised member 40 and the second raised member 44. Consequently, the coolant can flow through both the first openings 38 and the first passage 43 to the stator 18 and the rotor 20, respectively. Fig. 3C, the coolant level 36 is above the second raised member 44 and consequently the coolant can flow through the first openings 38 to the stator 18, and through the first passage 43 and the second passage 47 to the rotor 20.

[0021] Again with reference to Fig. 1, the system 10 further includes a controller 50 that may be electrically connected to the coolant pump 14 and / or the electric motor 12. The controller 50 is configured to control the speed of the coolant pump 14 and thus the amount of coolant delivered to the device 16 and the coolant level 36 within the cavity 34 of the device 16. The controller 50 may also be configured to calculate the temperature of the electric motor 12 or to receive the temperature measurement from another device, as explained above.

[0022] With reference now to Fig. 4, a method 100 is shown for supplying coolant to the stator 18 and / or the rotor 20 using the system 10 for cooling the electric motor 12. The method 100 begins at step 102, where the electric motor 12 is operating and therefore at a temperature.

[0023] After step 102, the method 100 proceeds to step 104. At step 104, the temperature of the electric motor 12 is determined. As discussed above, the temperature may be calculated by the controller 50 based on certain parameters, including, but not limited to, the torque and / or power provided by the electric motor 12. Alternatively, the temperature may be measured by a temperature sensor or other device, which may then send the subsequent measurement to the controller 50 for processing.

[0024] After step 104, the method 100 proceeds to step 106. In step 106, the controller 50 determines whether the temperature determined in step 104 is above or below a threshold temperature. As explained above, in one embodiment, the threshold temperature may be between 150 degrees Celsius and 180 degrees Celsius. If the controller 50 determines that the temperature is below the threshold temperature, as in Fig. 4 is indicated by the (-) sign, the method 100 proceeds to step 108. If the controller 50 determines that the temperature is above the threshold temperature, as in Fig. 4 is indicated by the (+) sign, the method 100 proceeds to step 110.

[0025] At step 108, the controller 50 sets the coolant pump 14 to a low speed setting so that the coolant level 36 within the cavity 34 does not exceed the first raised member 40. Consequently, the coolant flows due to gravity only to the stator 18 through the first openings 38, as explained above. After step 108, the method 100 proceeds to step 112, where the method 100 ends.

[0026] At step 110, the controller 50 sets the coolant pump 14 to a high speed setting so that the coolant level 36 within the cavity 34 is above the first raised member 40. Consequently, the coolant flows due to gravity to both the stator 18 and the rotor 20 through the first openings 38 and the first passage 43, respectively, as explained above.

[0027] It should be appreciated that the method 100 may include additional steps of elevating the coolant level via any additional elevated members, such as the second elevated member 44, to achieve progressive delivery of the coolant to the rotor 20 as discussed above.

[0028] After step 110, the method 100 ends at step 112. The method 100 may be consistently repeated while the electric motor 12 is operating and therefore requires cooling to account for changes in the temperature of the electric motor 12, as discussed above.

Claims

[1] A device (16) for supplying a coolant to a stator (18) and to a rotor (20) of an electric motor (12) in a vehicle having a coolant pump (14), the device (16) comprising: a base (30) defining a plurality of first openings (38), wherein the coolant can flow to the stator (18) through at least one of the first openings (38); and at least one wall (32) extending from the base (30), the base (30) and the at least one wall (32) defining a cavity (34) configured to receive the coolant from the coolant pump (14); characterized by : at least one first raised element (40) within the cavity (34), the at least one first raised element (40) extending from the base (30) to a free end and defining at least one second opening (42) at the free end aligned with a single one of the first openings (38), the raised element (40) forming a first passage (43) between the second opening (42) and the aligned first opening (38) through which the coolant can flow to the rotor (20). [2] The device (16) of claim 1, further comprising at least one second raised member (44) within the cavity (34), the at least one second raised member (44) extending from the base (30) further than the at least one first raised member (40), the at least one second raised member (44) defining at least one third opening (46) substantially aligned with one of the first openings (38) to form at least one second passage (47) through which the coolant can flow to the rotor (20). [3] The device (16) of claim 1, wherein the at least one first raised element (40) is a pedestal. [4] The device (16) of claim 1, wherein the at least one first raised element (40) is a conduit. [5] A system for providing a coolant to a stator (18) and to a rotor (20) of an electric motor (12) in a vehicle, the system comprising: a coolant pump (14) configured to supply the coolant, the coolant pump (14) having an adjustable speed; a device (16) according to claim 1; and a controller (50) configured to adjust the speed of the coolant pump (14) based on at least one parameter such that the coolant level within the cavity (34) is variable. [6] The system of claim 5, wherein the coolant is an oil and the coolant pump (14) is an oil pump. [7] The system of claim 5, wherein the at least one parameter is an operating temperature of the electric motor (12). [8] The system of claim 7, wherein the controller is configured to increase the speed of the coolant pump (14) so ​​that the coolant level is above the at least one first elevated element (40) when the operating temperature of the electric motor (12) exceeds a threshold temperature. [9] The system of claim 8, wherein the threshold temperature is between 150 degrees Celsius and 180 degrees Celsius. [10] The system of claim 5, wherein the device (16) further comprises at least one second raised member (44) within the cavity (34), the at least one second raised member (44) extending from the base (30) further than the at least one first raised member (44), the at least one second raised member (44) defining at least one third opening (46) substantially aligned with one of the first openings (38) to form at least one second passage (47) through which the coolant can flow to the rotor (20) when the coolant level is above the at least one second raised member (44).

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