Gearbox with internal cooling pins

Abstract

A transmission system includes a housing configured to at least partially contain a liquid lubricant, such as oil, flowing through a gear set. A plurality of bearings are arranged within the housing, the plurality of bearings being configured to constrain respective trajectories of respective shafts. An inner surface of the housing includes a first region surrounding a motor gear bearing that is actively cooled by a coolant. The inner surface also includes a second region that is away from the motor gear bearing and is not actively cooled by the coolant. Cooling pins are arranged in the first region and are configured to provide heat transfer from the liquid lubricant to the coolant. The gear set can include more than one shaft, wherein at least one gear is configured to splash oil onto a cooling pin to transfer heat from the liquid lubricant to the coolant flowing in the motor housing adjacent to the first region.

Description

Technical Field

[0001] The present disclosure relates to gearbox cooling and, more particularly, to a gearbox housing having internal cooling pins. Summary of the invention

[0002] The present disclosure relates to a housing for a transmission system, the housing being configured to at least partially contain a liquid lubricant. The housing includes a plurality of bearings, an inner surface, and a plurality of cooling pins. The plurality of bearings, including a motor gear bearing, are configured to constrain the respective trajectories of the respective shafts. A first region of the inner surface is actively cooled by the coolant. A second region of the inner surface is away from the motor gear bearing and is not actively cooled by the coolant. A plurality of cooling pins are arranged in the first region and are configured to provide heat transfer from the liquid lubricant to the coolant.

[0003] In some embodiments, each of the plurality of cooling pins has a cylindrical shape extending from the first region substantially perpendicular to the inner surface. In some embodiments, each of the plurality of cooling pins includes a cylindrical portion extending from the first region substantially perpendicular to the inner surface and a rounded end portion. In some embodiments, each of the plurality of cooling pins has a corresponding length, and the first cooling pin and the second cooling pin of the plurality of cooling pins have different lengths. In some embodiments, the plurality of cooling pins each include a corresponding shape and a corresponding spacing to increase heat transfer to the coolant at the first region compared to a configuration without the plurality of cooling pins. In some embodiments, the housing includes one or more recesses arranged in the first region to provide increased cooling from the liquid lubricant to the coolant compared to a configuration without the one or more recesses.

[0004] In some embodiments, a plurality of gears are coupled to a plurality of bearings. The plurality of gears are configured to flow a liquid lubricant against at least some of the plurality of cooling pins. In some embodiments, a plurality of gears are fixed to respective shafts and configured to flow a liquid lubricant turbulently around the plurality of cooling pins.

[0005] In some embodiments, the first region is actively cooled by coolant flowing through a motor jacket in a coolant passage passing adjacent an outer surface of the housing corresponding to the first region. In some embodiments, the outer surface of the housing corresponding to the first region forms a portion (e.g., one or more turns) of the coolant passage. In some embodiments, the second region includes a lower region of a retainer configured as a liquid lubricant, and at least one gear coupled to a shaft in the corresponding shaft is configured to rotate through a majority of the liquid lubricant in the retainer.

[0006] In some embodiments, the present disclosure is directed to a transmission system comprising a plurality of bearings, a plurality of gears, and a housing comprising a plurality of cooling pins, the plurality of cooling pins being arranged in a first region of the housing and configured to provide heat transfer from a liquid lubricant to a coolant. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The present disclosure is described in detail according to one or more embodiments with reference to the following drawings. The drawings are provided for illustrative purposes only and depict only typical or exemplary embodiments. These drawings are provided to facilitate understanding of the concepts disclosed herein and should not be considered to limit the breadth, scope or applicability of these concepts. It should be noted that for clarity and ease of illustration, these drawings are not necessarily drawn to scale.

[0008] Figure 1 shows an exploded perspective view of an illustrative transmission system according to some embodiments of the present disclosure;

[0009] Figure 2 Some embodiments of the present disclosure are shown Figure 1 A side view of a housing of an illustrative transmission system;

[0010] Figure 3 shows a side perspective view of an illustrative housing for a gearbox having an array of cooling pins according to some embodiments of the present disclosure;

[0011] Figure 4 Some embodiments of the present disclosure are shown Figure 3 an enlarged perspective view of a housing further illustrating an array of cooling pins;

[0012] Figure 5 a system diagram showing an illustrative cooling system for a housing of a transmission system according to some embodiments of the present disclosure; and

[0013] Figure 6 Illustrative cooling pins are shown in accordance with some embodiments of the present disclosure. DETAILED DESCRIPTION

[0014] Heat due to friction and windage in a gearbox (e.g., an electric vehicle drivetrain) can limit the power capacity and ability of the gearbox to deliver continuous output. For example, heat generation can reduce the efficiency of the gearbox and increase component wear over time. In addition, heated components can expand beyond built-in tolerances and cause jamming in the gearbox, thereby preventing or limiting movement (e.g., of gears, bearings, shafts). While one approach is to add a heat exchanger to the system, or otherwise affect coolant flow (e.g., both of which increase cost and complexity), another additional or alternative approach is to design the geometry of the interior of the gearbox housing to account for heat transfer.

[0015] Figure 1 An exploded perspective view of an illustrative transmission system 100 according to some embodiments of the present disclosure is shown. As shown, transmission system 100 includes assembly 110, assembly 120, and intermediate housing 130, which is configured to couple assemblies 110 and 120 together. As shown, assembly 110 includes motor 112, gear set 115, and housing 111. As shown, assembly 120 includes motor 122, gear set 125, and housing 121. As shown, each of gear sets 115 and 125 includes a motor gear, an intermediate gear set (e.g., an intermediate gear and a wheel gear), and a drive gear (e.g., coupled to respective outputs 119 and 129).

[0016] A liquid lubricant (e.g., oil) is used within the transmission system 100 to lubricate the gear sets 115 and 125 (e.g., the gears and their bearings), and is contained by the housing 111, the housing 121, and the intermediate housing 130. For example, the interface between the housings may include a sealant, a gasket, an O-ring, a crush seal, any other suitable seal, or any combination thereof. In some embodiments, the liquid lubricant may be collected or collected near the bottom of the gearbox due to gravity, where an oil scoop (pickup) may be arranged to direct the overall lubricant to a pump. The liquid lubricant is used to reduce friction losses between mating surfaces that undergo motion, such as between meshing gear teeth, within bearings (e.g., roller bearings, tapered roller bearings, ball bearings, or any other suitable bearings), and to provide cooling for components of the transmission system 100. In some embodiments, the liquid lubricant provides convective cooling to the surface. For example, in some embodiments, the liquid lubricant is pumped into a cooling circuit and is thus able to provide external cooling (e.g., a liquid to air heat exchanger). To illustrate, flowing liquid lubricant facilitates heat transfer from components of the transmission system and the environment or other suitable heat sink. In some embodiments, housings 110 and 120, intermediate housing 130, housings of motors 112 and 122, or combinations thereof may include coolant passages for allowing liquid coolant to flow (e.g., separate from the liquid lubricant). The liquid coolant also facilitates the transfer of heat from the transmission system to the environment or heat sink, but does not provide a lubrication function for the moving components of the transmission system.

[0017] In the illustrative example, each of the assemblies 110 and 120 integrates the gearbox cover into the motor A shroud (also referred to as the motor end cap casting, and referred to herein as the housing 111 and 121). On the motor side of the housing (e.g., which may include a casting), coolant flows through to cool the motor. By introducing geometry (e.g., pin fins or similar structures) to increase the surface area on the interior of the gearbox, higher heat rejection can be achieved between the gearbox oil and the motor coolant. For illustration, the cooling effect can be achieved inside the housing without the need for a separate heat exchanger, which may require additional parts, pumps, or cooling channels.

[0018] Figure 2 Some embodiments of the present disclosure are shown Figure 1 1 is a side view of the housing 121 (interior side) of an illustrative transmission system. The housing 121 includes three sections 201, 202, and 203 corresponding to the three gear shafts. For example, each of the sections 201, 202, and 203 is substantially circular and overlaps to form a footprint representing the gear set 125. For illustration, the sections 201, 202, and 203 represent overlapping partial circular sections. Areas 210, 270, and 203 correspond to circular areas on the interior of the housing 121, which generally correspond to the sections 201, 202, and 203, respectively.

[0019] As shown, region 210 includes cooling pins 290 and is arranged to overlap segment 201 where housing 121 abuts a corresponding motor (e.g., as shown, Figure 1 122 of the motor). As shown, region 210 may also overlap with sections 202 and 203 to any suitable extent. Region 270 is arranged to overlap with region 210 and includes a portion of the housing 121 surrounding the bearing of the intermediate shaft of the gear set 125, and region 270 may be at least partially cooled by a coolant provided to the motor housing. In some embodiments, the intermediate shaft rotates at a speed less than the speed of the motor gear shaft due to gear reduction. In some such embodiments, a drive shaft (e.g., arranged with an axis in region 280, having a drive gear bearing) may be engaged with the intermediate shaft through meshing gears (e.g., a drive gear and an intermediate gear) and rotate at a speed less than the speed of the intermediate shaft due to gear reduction. To illustrate, since the motor shaft can rotate at a relatively greater speed than the intermediate shaft or the drive shaft, the bearings coupled to the motor shaft may generate more heat. The motor bearings are also more directly cooled by the coolant in the motor housing, and therefore, the motor shaft bearings do not have to achieve the highest temperature (e.g., the intermediate shaft bearings may achieve a higher temperature due to reduced cooling from the coolant in the motor housing).

[0020] In some embodiments, the cooling pins 290 are each shaped as round pins extending from the region 210 into the interior of the housing 121, thereby increasing the internal surface area of ​​the gearbox and increasing conductive heat transfer to the outside of the gearbox. The cooling pins 290 may include any suitable cross-sectional shape according to the present disclosure and may include any suitable length. For example, the cooling pins may have a flat, triangular, rectangular, polygonal, lobate, curved or circular cross-section, any other suitable cross-section or any combination thereof (e.g., a composite cross-section or a cross-section that varies along the length). The cooling pins 290 may have the same length, different lengths, the same cross-sectional shape, or different cross-sectional shapes.

[0021] Cooling pins 290 are distributed over at least some of the regions 210 and some regions outside of the regions 210 (as shown) that are in contact with the motor housing (e.g., section 201 is adjacent to the motor housing). In some embodiments, coolant is provided to the motor housing to cool the motor, and the coolant also receives additional heat transmitted from the attached gearbox (e.g., through the housing 121). The cooling pins 290 allow more conduction through the housing 121 (compared to a housing without cooling pins). In some embodiments, the increased heat transfer provided by the cooling pins 290 allows the cooling of the gearbox to be limited or controlled by the temperature and amount of coolant flowing through the motor cooling loop (e.g., which can be externally controlled). In some embodiments, the cooling pins 290 are arranged so that the gears rotating through the oil tray (e.g., in region 211, as shown) splash oil turbulence onto the cooling pins 290, thereby increasing heat flow (e.g., by convective heat transfer). In some embodiments, due to gravity, the lubricant that transfers heat to the cooling pins drips downward through the collection of cooling pins 290 back to the retaining plate (e.g., region 211). To illustrate, the drive gear can sweep over region 211 and any accumulated lubricant at that location during rotation and cause the lubricant to flow over the cooling pins 290. In some embodiments, the size and arrangement of the plurality of cooling pins is such that the convective boundary layer around each cooling pin is smaller than the spacing between the cooling pins and adjacent cooling pins.

[0022] In an illustrative example, the cooling pin 290 can maximize or otherwise increase conductive heat transfer while minimizing casting challenges such as minimum feature size. In some embodiments, the housing 121 is cast, and the cooling pin 290 is a cast feature of the housing 121. In some embodiments, the cooling pin 290 can be secured to the housing 121 after casting (e.g., brazed, welded, crimped, threaded to the housing 121, or otherwise secured to the housing).

[0023] In another illustrative example, including cooling pins 290 allows the use of an existing coolant system to increase cooling without adding additional coolant lines, pumps, or associated infrastructure. In some embodiments, housing 121 can be included in a gearbox with an existing coolant system to allow the existing coolant system to remove more heat from the gearbox. As shown, region 210 is arranged to provide increased heat transfer to the motor coolant.

[0024] In another illustrative example, by increasing conductive heat transfer to the outside of the gearbox using cooling pins 290, the gearbox can remain sealed during normal operation without the need for additional coolant lines, thereby reducing the possibility of foreign matter contamination of the gearbox. In some embodiments, a separate oil cooler is not required and the piping associated with a separate oil cooler is avoided.

[0025] In another illustrative example, passively cooling the gearbox using cooling pins 290 increases the useful life of gearbox internal components (e.g., bearings, seals, gears, shafts) and reduces the likelihood of seizing the moving parts of the gearbox. To illustrate, reduced temperatures of gearbox components can improve the durability of the gearbox.

[0026] In another illustrative example, use of cooling pins 290 may enable the gearbox to transmit more power with improved efficiency, thereby expanding the potential uses of the gearbox.

[0027] Figure 3 A side perspective view of an illustrative housing 300 for a gearbox having an array of cooling pins 390 is shown, in accordance with some embodiments of the present disclosure. Figure 4 Some embodiments of the present disclosure are shown Figure 3 An enlarged perspective view of the housing 300 further illustrating an array of cooling pins 390. For example, Figure 4 A magnified view from Figure 3 The direction of axis 399 is shown.

[0028] As shown in the figure, the housing 300 includes a Figure 1-2301, 302 and 303 of the housing 121 of the motor housing. The housing 300 includes an interface 303 for interfacing with the motor housing and accommodating the motor gear, motor gear shaft and motor shaft bearing. Region 310 corresponds to an active cooling region of the housing 300 and includes cooling pins 390 arranged in an array as shown. Region 370 corresponds to an area of ​​the housing 300 adjacent to and partially overlapping the actively cooled portion of the housing 300. Region 380 corresponds to an area of ​​the housing 300 that is not actively cooled and corresponds to a portion of the gearbox surrounding the drive gear, drive shaft and drive bearing. Region 311 corresponds to a retaining plate where lubricant can accumulate due to gravity (e.g., region 311 corresponds to the bottom of the gearbox when oriented for operation). The cooling pins 390 are configured and arranged to provide increased cooling from the lubricant to the housing 300, and thus provide increased cooling to a coolant system (not shown) that cools the motor housing adjacent to the section 301. To illustrate, when the drive gear disposed in region 380 rotates, it causes the liquid lubricant in region 311 to flow into and around cooling pin 390 , thereby causing convective heat transfer to cooling pin 390 .

[0029] Figure 5 A system diagram of an illustrative cooling system 500 for a housing 540 of a transmission system according to some embodiments of the present disclosure is shown. System 500 includes cooling system 530, motor 522, a gear set (e.g., including gears 542, 545, 546, and 550) and bearings (e.g., bearings 541, 543, 544, 547, 548, and 551) arranged in housing 540. Housing 540 includes cooling pins 590 and recesses 591 arranged around motor bearings 541 and near a cooling jacket 523 of motor 522. In some embodiments, the housing includes one or more recesses (e.g., recess 591) to improve heat transfer from cooling pins 590. As shown, cooling jacket 523 extends into housing 540. For example, the housing of motor 522 may include a channel for coolant, and housing 540 may include one or more diverters or plenums to direct coolant back into the motor housing. Additionally, the interface between the housing of motor 522 and housing 540 may include one or more seals, such as, for example, an O-ring, a gasket, or any other suitable seal.

[0030] As shown, the cooling system 530 is coupled to the cooling jacket 523 of the motor 522, and is configured to provide a coolant to remove heat from the motor 522. The heat generated from the gears and bearings in the gearbox can be transferred to the cooling jacket 523 by the flow of lubricants and conduction from the inside of the housing 540 to the cooling pin 590. The cooling system 530 may include a coolant reservoir, a pump, a filter, a pressure regulator, a flow meter, a flow control valve, any other suitable components or any combination thereof. For example, the cooling system 530 may include a pump head fixed to the motor, and may be configured to control based on flow, pressure, temperature or a combination thereof. For illustration, the cooling system 530 may include a centrifugal pump, wherein more coolant may be pumped by increasing the speed of the pump (e.g., by an electric motor). If the main restriction of heat transfer from the lubricant is located inside the housing 540, the heat transfer will not strongly depend on the operating characteristics of the cooling system 530. This weaker dependence may result in the ability to control heat transfer using the cooling system 530 being limited. Including cooling pins 590 relatively improves heat transfer at the interior of housing 540, thereby allowing heat transfer to be more dependent on the operating characteristics of cooling system 530. For example, by including cooling pins 530, changes in operating characteristics of cooling system 530, such as pump speed, pump pressure, or both, can provide a greater effect of heat transfer from housing 540.

[0031] As shown, the motor gear 542 is engaged with a wheel gear 545 coupled to rotate with an intermediate gear 546. The intermediate gear 546 is engaged with a drive gear 550 fixed to a shaft 549. Bearings 541 and 543 are configured to maintain the alignment of the motor gear 542. Bearings 544 and 547 are configured to maintain the alignment of the wheel gear 545 and the intermediate gear 546 or the intermediate shaft fixed thereto. Bearings 548 and 551 are configured to maintain the alignment of the drive gear shaft 549, and therefore the alignment of the drive gear 550 fixed thereto. As shown, the motor gear 542 rotates faster than the intermediate gear 546, which in turn rotates faster than the drive gear 550.

[0032] Figure 6Illustrative cooling pins according to some embodiments of the present disclosure are shown. Cooling system 600 includes housing 610, pins 611, 612, 613, 614, and 615. Pin 611 may include a circular cross-section, a polygonal cross-section, any other suitable cross-section, or any combination thereof that is constant along the length. Pin 612 has a different length from pin 611 (e.g., pin 612 is shorter than pin 611). In some embodiments, one or more pins may have a different length from other pins. For example, a plurality of cooling pins may include two or more groups of pins, and the length of each group of pins may be different from that of another group of pins. Pin 613 has a different cross-sectional size from pin 611 (e.g., pin 613 has a larger cross-sectional area than pin 611). In some embodiments, one or more pins may have a different cross-sectional area from other pins. For example, a plurality of cooling pins may include two or more groups of pins, and each group of pins has a different cross-sectional area from that of another group of pins. Pin 614 has a tapered profile, which may include a taper of a positive or inclined pyramid or cone. In some embodiments, one or more groups of pins may have a varying cross-sectional area. For example, the plurality of cooling pins may include two or more groups of pins, one or more groups of pins having varying cross-sectional areas. Pin 615 has rounded ends. In some embodiments, one or more pins may have rounded or tapered ends. For example, the plurality of cooling pins may include two or more groups of pins, one or more groups of pins having varying cross-sectional areas. Pin 615 has rounded ends. In some embodiments, one or more pins may have rounded or tapered ends.

[0033] The foregoing is merely an example of the principles of the present disclosure, and various modifications may be made by those skilled in the art without departing from the scope of the present disclosure. The above embodiments are presented for illustrative purposes rather than limiting purposes. The present disclosure may also take many forms other than those explicitly described herein. Therefore, it is emphasized that the present disclosure is not limited to the methods, systems, and devices explicitly disclosed, but is intended to include variations and modifications of the present invention within the spirit of the following claims.

Claims

1. A housing for a transmission system, wherein the housing for the transmission system is configured to at least partially contain a liquid lubricant, the housing for the transmission system comprising: a plurality of bearings configured to constrain respective trajectories of respective shafts, wherein the plurality of bearings includes a motor gear bearing configured to constrain a motor shaft of a motor, wherein the motor includes a motor housing secured to the housing for the transmission system; in: The motor housing defines an outer boundary of a first outer region of the housing for the transmission system, The first inner region of the housing for the transmission system is opposite to the first outer region and surrounds the motor gear bearing, The outer boundary of the first outer region overlaps with the entire first inner region, The first interior region is actively cooled by coolant of the motor housing, and A plurality of cooling pins are disposed in the first interior region and are configured to provide heat transfer from the liquid lubricant to the coolant.

2. A housing for a transmission system according to claim 1, wherein each of the plurality of cooling pins comprises a cylindrical shape extending from the first interior region substantially perpendicular to the inner surface of the first interior region.

3. The housing for a transmission system according to claim 1, wherein each cooling pin of the plurality of cooling pins comprises: a cylindrical portion extending from the first interior region substantially perpendicular to an interior surface of the first interior region; as well as Rounded end sections.

4. A housing for a transmission system according to claim 1, wherein each cooling pin of the plurality of cooling pins comprises a corresponding length, and wherein a first cooling pin and a second cooling pin of the plurality of cooling pins have different lengths.

5. The housing for a transmission system of claim 1, further comprising one or more recesses disposed in the first interior region to provide increased cooling from the liquid lubricant to the coolant compared to a configuration without the one or more recesses.

6. The housing for a transmission system according to claim 1, wherein a plurality of gears are coupled to the plurality of bearings, and wherein, The plurality of gears are configured to flow a liquid lubricant against at least some of the plurality of cooling pins.

7. The housing for a transmission system of claim 6, wherein the plurality of gears are fixed to the respective shafts, and wherein the plurality of gears are configured to cause a turbulent flow of liquid lubricant around the plurality of cooling pins.

8. A housing for a transmission system according to claim 1, wherein each of the plurality of cooling pins includes a corresponding shape and a corresponding spacing to increase heat transfer to the coolant at the first interior region compared to a configuration without the plurality of cooling pins.

9. The housing for a transmission system according to claim 1, wherein the first interior region is actively cooled by coolant of a motor jacket flowing through a coolant channel, and wherein an outer surface of the housing for a transmission system corresponding to the first interior region forms a part of the coolant channel.

10. The housing for a transmission system of claim 1, further comprising a lower region of a retainer configured for liquid lubricant, wherein at least one gear coupled to a shaft of the respective shaft is configured to rotate through a majority of the liquid lubricant in the retainer.

11. A transmission system comprising: a gearbox housing configured to at least partially contain a liquid lubricant; a plurality of bearings configured to constrain respective trajectories of respective shafts, wherein the plurality of bearings includes a motor gear bearing configured to constrain a motor shaft of a motor, wherein the motor includes a motor housing secured to the gearbox housing; a plurality of gears, each of the plurality of gears being secured to one of the respective shafts; in: The motor housing is fixed to the gearbox housing, the motor housing defining an outer boundary of a first outer region of the gearbox housing, The first inner region of the gearbox housing is opposite to the first outer region and surrounds the motor gear bearing, The outer boundary of the first outer region overlaps with the entire first inner region, The first interior region is actively cooled by coolant of the motor housing, and A plurality of cooling pins are disposed in the first interior region and are configured to provide heat transfer from the liquid lubricant to the coolant.

12. The transmission system of claim 11, wherein each of the plurality of cooling pins comprises a cylindrical shape extending from the first interior region substantially perpendicular to an inner surface of the first interior region.

13. The transmission system of claim 11, wherein each cooling pin of the plurality of cooling pins comprises: a cylindrical portion extending from the first interior region substantially perpendicular to an interior surface of the first interior region; as well as Rounded end sections.

14. The transmission system according to claim 11, wherein: Each cooling pin of the plurality of cooling pins comprises a corresponding length, and wherein a first cooling pin and a second cooling pin of the plurality of cooling pins have different lengths.

15. The transmission system of claim 11, wherein the gearbox housing further comprises one or more recesses disposed in the first interior region to provide increased cooling from the liquid lubricant to the coolant compared to a configuration without the one or more recesses.

16. The transmission system of claim 11, wherein the plurality of gears are configured to flow a liquid lubricant against at least some of the plurality of cooling pins.

17. The transmission system of claim 16, wherein the plurality of gears are configured to provide a turbulent flow of the liquid lubricant.

18. The transmission system of claim 11, wherein each of the plurality of cooling pins comprises a corresponding shape and a corresponding spacing to increase heat conduction to the coolant at the first interior region as compared to a configuration without the plurality of cooling pins.

19. The transmission system of claim 11, wherein the first interior region is actively cooled by coolant of a motor jacket flowing through a coolant passage, and wherein an outer surface of the gearbox housing corresponding to the first interior region forms a portion of the coolant passage.

20. The transmission system of claim 11, wherein the gearbox housing includes a lower region configured as a retainer for liquid lubricant, wherein at least one gear coupled to a shaft of the respective shaft is configured to rotate through a majority of the liquid lubricant in the retainer.

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