Multi-material gear assembly

Abstract

The present disclosure relates to a multi-material gear assembly including a first gear including a first material, the first gear defining a plurality of first gear teeth, and a gear shaft configured to support the first gear, the gear shaft being formed of a second material that is different from the first material, and the second material has a higher damping coefficient than the first material.

Description

MULTI-MATERIAL GEAR ASSEMBLYCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 634,013, filed on April 15, 2024, the disclosure of which is incorporated herein by reference in its entirety.BACKGROUND

[0002] Gear assemblies are commonly used in a wide range of mechanical systems. These assemblies generally comprise a shaft and one or more gears that transmit torque and rotational motion between components. In traditional designs, the shaft and the gears are typically formed of the same material, such as steel.SUMMARY

[0003] In one aspect of the disclosure, a multi-material gear assembly includes a first gear including a first material, the first gear defining a plurality of first gear teeth, and a gear shaft configured to support the first gear, the gear shaft being formed of a second material that is different from the first material, and the second material has a higher damping coefficient than the first material.

[0004] In one aspect of the disclosure, a gear assembly includes a first gear having a first pitch diameter, a second gear having a second pitch diameter, a shaft configured to support the first gear and the second gear, and a web or core section coupled to the second gear, the web or core section and the shaft are formed of a first material.

[0005] In one aspect of the disclosure, a multi-material gear assembly includes a gear including a first material, the gear defining a plurality of gear teeth, and a gear shaft configured to support the gear, the gear shaft being formed of a second material that is different from the first material, a density of the second material is lower than that of the first material.

[0006] A variety of additional inventive aspects will be set forth in the description that follows. The inventive aspects can relate to individual features and to combinations of features. It is to be understood that both the forgoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the broad inventive concepts upon which the embodiments disclosed herein are based.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The accompanying drawings, which are incorporated in and constitute a part of the description, illustrate several aspects of the present disclosure. A brief description of the drawings is as follows:

[0008] Figure l is a perspective view of a multi-material gear assembly with one gear configured in accordance with the present disclosure.

[0009] Figure 2 is a cross-section of the multi-material gear assembly of Figure 1.

[0010] Figure 3 is a side view of another multi-material gear assembly including two gears configured in accordance with the present disclosure.

[0011] Figure 4 is a cross-section of an embodiment of the multi -material gear assembly of Figure 3.

[0012] Figure 5 is a cross-section of another embodiment of the multi-material gear assembly of Figure 3 where a hub is disposed between the shaft and the web or core.DETAILED DESCRIPTION

[0013] Reference will now be made in detail to exemplary aspects of the present disclosure that are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

[0014] Examples of the disclosure include a gear assembly formed of multiple materials having different physical properties. As such, some components may be formed of materials that are more cost effective or lighter than the materials used to form other components. Other components include materials that provide a higher density and are wear resistant. In other example examples, some gear components can have a higher damping coefficient. In other example examples, some gear components can be selected based on their respective mechanical and thermal properties to optimize the performance of the gear assembly.

[0015] Referring to the figures in general, a gear assembly 20, 120 may have one or more gears 22, 26 formed of a first material mounted to a shaft arrangement 24 that is formed of a second material different from the first material. For example, the first material may have a higher density than the second material to provide strength to the gear 22, 26 while the second material may have a higher damping coefficient than the first material to provide noise attenuation at the shaft arrangement 24.

[0016] In general, the shaft arrangement 24 includes an elongate shaft 25 configured to extend through the gear 22, 26. In some examples, the gear 22, 26 is directly mounted to an outer circumference of the shaft 25 (e.g., see Figures 1-2). In other examples, the shaft arrangement 24 also includes a web or core 246 extending radially outwardly from the shaft 25 to support one or more of the gears 22 as will be discussed in more detail with respect to Figures 3-4. In certain examples, the shaft arrangement 24 may further include a gear hub 248 between the shaft 25 and the web or core 246 as will be discussed in more detail with respect to Figures 5-6.

[0017] Different materials are utilized to form the first gear 22 and the gear shaft arrangement 24, as each of these components may have varying physical characteristics (e.g., strength, weight, density, damping coefficient, etc.) or provide different affects (e.g., noise attenuation). As such, some components may be formed of materials that are more cost effective or lighter than the materials used to form other components. Other components may be formed of stronger material to withstand wear and tear.

[0018] In certain implementations, the first material is a material (e.g., gear steel, stainless steel, and gear mild steel, e.g., SAE 8620 and DIN 16MnCr5) that provides a higher density and is wear resistant. In certain examples, the second material of the shaft arrangement 24 is lighter in weight and has a higher damping coefficient than the first material of the first gear 22. For example, the damping coefficient of the second material is greater than 2.0%, greater than 2.2%, greater than 2.5%, greater than 1.8%, or greater than 1.5%. For example, the second material can include materials (e.g., iron and / or aluminum alloys or composites, such as aluminum metal matrix composites) that provide weight savings compared to materials such as gear steel. In certain examples, the density of the second material is less than 7.85 g / cm3, less than 7.8 g / cm3, less than 7.5 g / cm3, or less than 7 g / cm3. As a result, the overall cost of the gear assembly 20, 120 may be lowered compared to a gear assembly formed fully of gear steel. In some examples, the second material of the shaft arrangement 24 has a low damping coefficient, but is still higher than that of the first material. For example, the second material can include aluminum.

[0019] Figures 1-2 illustrate a first example of a multi-material gear assembly 20 including an example gear 22 mounted to an example shaft arrangement 24 configured in accordance with the present disclosure. The shaft arrangement 24 of Figures 1-2 includes a shaft 25 without a web or core. Instead, the first gear 22 seats directly on an outer circumference of the shaft 25.

[0020] In various examples, the shaft 25 can have a stepped configuration (e.g., see Figures 1 and 2). The example stepped gear shaft 25 includes at least a higher step 240 and a lower step 242. The lower step 242 has a first diameter DI and the higher step 240 has a second diameter D2. In Figures 1-2, the first gear 22 is coupled to the lower step 242. In certain examples, the higher step 240 can be used to limit the movement of the first gear 22 and the second gear 26, or to mount components, such as another gear. In various examples, ends of the shaft 25 may have different diameters.

[0021] In certain examples, the gear shaft may be configured with multiple longitudinal axes, allowing the gear assembly to support multiple gears that are noncoaxial. For example, a first gear and a second gear may be mounted on separate shaft segments that are angularly offset or laterally displaced relative to one another. This configuration is advantageous in multi-stage transmissions or compact layouts where space constraints prevent gears from being mounted on the same axis.

[0022] In certain examples, the gear teeth 226 of the gear 22 are helical. Other types of gear teeth arrangements are possible. For example, the plurality of gear teeth 226 can be configured to define a spur gear (i.e., straight teeth parallel to an axis of rotation), a bevel gear, a miter gear, and other types of gears. In the depicted example in Figure 2, the first inner surface 222 is smooth. In other examples, the inner surface 222 of the gear 22 can be splined or textured.

[0023] Figures 3-4 illustrate another gear assembly 120 configured in accordance with the present disclosure. In particular, the gear assembly 120 of the present disclosure includes the shaft arrangement 24 of Figure 1 supporting both the first gear 22 and a second gear 26. The second gear 26, which defines a plurality of teeth 266, is disposed at a location axially offset along the shaft 25 from the first gear 22. The second gear 26 is formed of a different material from the shaft arrangement 25. In some examples, the second gear 26 is formed of the same first material as the first gear 22. In other examples, the second gear 26 is formed of a third material that is different from the first and second materials.

[0024] In certain examples, the third material has a higher density and is more wear resistant than the second material. In certain examples, the first and third materials may have similar compositions, but have different properties (e.g., steels having different densities and hardness). In some examples, the first and third materials may include similar elements but have different percentages of elements (e.g., steels having different percentages of carbon, manganese, phosphorus, sulfur, and silicon). In examples, thesecond material of the shaft arrangement 24 is lighter in weight and has a higher damping coefficient than the first material and / or the third material. In examples, a density of the second material is lower than that of the first material and / or the third material. As a result, the overall cost of the gear assembly 20 may be lowered.

[0025] In certain examples, an inner diameter D3 of the first gear 22 is smaller than an inner diameter D5 of the second gear 26. In certain examples, an outer diameter D4 of the first gear 22 is smaller than the outer diameter D6 of the second gear 26. In certain examples, the outer diameter D4 of the first gear 22 is smaller than the inner diameter D5 of the second gear 26. Thus, the gear assembly 20 can be adapted to different drive requirements including any need to change the gear ratio, e.g., a reduction gear mechanism to slow the high revolutions per minute of the electric motor, or a transmission of an electric vehicle to match the revolutions per minute to the actual wheel rotation.

[0026] In various examples, the gear shaft 25 can be a step shaft, as shown in Figures 3-4. The example stepped gear shaft 25 includes at least a higher step 240 and a lower step 242. In Figures 3-4, the first gear 22 is coupled to the lower step 242 and the second gear 26 is coupled to the higher step 240. In certain examples, the example first gear 22 can abut an edge of the higher step 240 so that the higher step 240 can be used to limit the axial movement of the first gear 22. In certain examples, an axial length of the first gear 22 may be shorter than the axial length of the lower step 242. In certain examples, an axial length of the second gear 26 may be shorter than the axial length of the higher step 240.

[0027] In various examples, the second gear 26 may be radially offset from the shaft 25. For example, a web or core 246 may extend radially outwardly from the shaft 25 to an outer rim 2460 to support the second gear 26. In some examples, the web or core 246 extends radially outwardly from the higher step 240. In other examples, the web or core 246 may extend outwardly from the lower step 242 or from a shaft having a constant diameter. In certain implementations, a material forming the web or core 246 is the same as the second material of the gear shaft 25. In some examples, the web or core 246 can be integral (e.g., monolithically formed) with the shaft 25. In other examples, the web or core 246 can be a separate piece that is welded, molded, or otherwise mounted on the shaft 25.

[0028] In certain implementations, the shaft arrangement 24 includes a hub piece133 configured to mount between the shaft 25 and the web or core 246 (e.g., see FIG.5). In some examples, the web or core 246 is mounted to the hub piece 133, which is subsequently mounted to the shaft 25 to form the shaft arrangement 24. Other arrangements are possible. In some implementations, the hub 248 can be formed of the same material as the shaft 25 (i.e., the second material). In other implementations, the hub 248 can be formed of the same material as the gears 22, 26. In still other implementations, the hub 248 is formed of a fourth material. In examples, the fourth material has a higher strength and density than the material of the web or core 246, e.g., the second material. In certain examples, the fourth material includes steel or cast iron, and the second material includes aluminum. In certain examples, the web or core 246 can be over molded with the hub 268.

[0029] In various examples, the first gear 22 and the gear shaft 24 of the gear assemblies 20, 120, 220 may be manufactured using different manufacturing processes. For example, the first gear 22 utilizes a forging process and the gear shaft 24 utilizes a casting process.

[0030] In various examples, the gear assembly 20, 120, 220 may be formed by various processes and methods to join the first gear 22 and the gear shaft 25 together. In various examples, the first gear 22 may be assembled to the gear shaft 25 using various processes. For example, the gear shaft 25 may be over-molded with the first gear 22. In yet another example, the gear shaft 25 may be splined with the first gear 22.

[0031] In a further example, the first gear 22 may be thermal-fit or shrink-fit to the gear shaft 25. Such examples are the fitting of the first gear 22 around the shaft outer diameter of the gear shaft 25. Then the first gear 22 will be heated and expand its first inner diameter to slightly greater than the shaft outer diameter of the gear shaft 25, and be fitted around it. After cooling, the first gear 22 contracts and binds tightly in place.

[0032] In a further example, the first gear 22 may be pressed-fit, interference-fit, or friction-fit to the gear shaft 25. The press fit between the gear shaft 25 and the first gear 22 can be accomplished by a press that presses the two components together with varying forces depending on the material of the gear shaft 25 and the first gear 22. The edges of the shaft outer diameter of the gear shaft 25 and the first inner diameter of the first gear 22 are chamfered to allow the compression to occur gradually instead of all at once.

[0033] In a further example, the first gear 22 may be welded, brazed, or soldered to the gear shaft 25. Example lower temperature bonding techniques such as brazing and soldering, require flowing a filler metal to solidify their bonds. Examplehigher temperature bonding techniques such as welding melt the first material of the first gear 22 and / or the second material of the gear shaft 25, and may use many different energy sources, including a gas flame, an electric arc , a laser, an electron beam, and ultrasound. In various examples, the web or core 246 and / or the hub 133 may be assembled to the gear shaft 25, e.g., the main portion 244 of the gear shaft 24, using other processes. For example, the gear shaft 25 may be over-molded with the web or core 246 and / or the hub 133. In yet another example, the gear shaft 25 may be splined with the web or core 246 and / or the hub 133. In a further example, the web or core 246 and / or the hub 133 may be thermal-fit or shrink-fit to the gear shaft 25. Such examples are the fitting of the first and / or second gears 22, 26 around the shaft outer diameter of the gear shaft 25. In a further example, the web or core 246 and / or the hub 133 may be pressed-fit, interference-fit, or friction-fit to the gear shaft 25. The press fit between the gear shaft 25 and the web or core 246 and / or the hub 133 can be accomplished by a press that presses the two components together with varying forces depending on the material of the gear shaft 25 and the web or core 246 and / or the hub 133. The edges of the shaft outer diameter of the gear shaft 25 and the inner diameter of the web or core 246 and / or the hub 133 are chamfered to allow the compression to occur gradually instead of all at once. In a further example, the first gear 22 may be welded, brazed, or soldered to the gear shaft 25. Example lower temperature bonding techniques such as brazing and soldering, require flowing a filler metal to solidify their bonds. Example higher temperature bonding techniques such as welding melt the material of the web or core 246, the material of the hub 133, and / or the second material of the gear shaft 25, and may used many different energy sources, including a gas flame, an electric arc, a laser, an electron beam, and ultrasound.

[0034] Referring to the figures in general, a multi-material gear assembly 20, 120 is provided. The gear assembly includes a gear 22, 26 formed from a first material and a gear shaft 24 formed from a second material that differs from the first. The gear 22, 26 defines a plurality of gear teeth for meshing engagement with other gears or components in a transmission system. The gear shaft 24 is configured to support the gear 22, 26 and to transmit torque or rotational motion from the gear 22, 26 to other mechanical components.

[0035] In some examples, the multi-material gear assembly further includes a second gear that defines a second set of gear teeth. The second gear may be coaxially or adjacently mounted relative to the first gear, depending on the transmissionrequirements. In such configurations, the second gear may be formed of the same first material as the first gear, or it may be formed of a third material selected for its performance characteristics.

[0036] In some examples, the gear assembly includes a web or core structure that extends radially outwardly from the gear shaft and is configured to support the second gear. The web or core is also formed of the second material, providing a lightweight and thermally conductive foundation that connects the gear shaft to the second gear. This structure helps distribute mechanical loads evenly across the assembly while reducing rotational inertia.

[0037] In some examples, the gear assembly includes a hub formed of the second material, to which the web or core is mounted. The hub provides a central support structure within the gear assembly, anchoring the web and enabling secure attachment to the shaft. The use of the second material in the hub further contributes to the overall reduction in weight and improved thermal performance of the system.

[0038] The first and second materials of the gear and the gear shaft are selected based on their respective mechanical and thermal properties to optimize the performance of the gear assembly. In one example, the second material has a lower density than the first material, which allows the overall weight of the gear assembly to be reduced while maintaining sufficient strength in the gear teeth. For example, the gear may be made of steel or another high-strength alloy, while the gear shaft may be made of aluminum, cast iron, or a composite material. The use of a lighter shaft material in the gear assembly yields significant advantages in terms of system-wide weight reduction. By selecting a material with a lower density for the shaft, the overall mass of the gear assembly is reduced. This, in turn, contributes to a lighter gearbox structure, which may be designed with less robust housing and support components due to the reduced internal loading. The cumulative effect extends beyond the gearbox, enabling weight savings at the vehicle or mechanical device level, where the gear assembly is integrated. For internal combustion vehicles or electrical vehicles and their engine crankcase or differential, this can result in improved fuel efficiency, enhanced acceleration, and reduced emissions. In industrial machinery or robotics, it can lead to increased speed, reduced energy consumption, and improved dynamic response. Thus, the incorporation of a lightweight shaft supports both performance optimization and system-level efficiency. In certain embodiments, the higher damping coefficient of the shaft may result in better noise attenuation of gear excitation that travels through thegear assemblies and is radiated through the external components, e.g., gear box or housing. In certain embodiments, the second material also has a higher thermal conductivity than the first material. This configuration enhances heat dissipation away from the gear, especially in high-speed or high-torque applications where frictional heating may occur. Improved thermal transfer characteristics in the gear shaft help maintain structural integrity and operational stability of the assembly over time.

[0039] Although various examples and examples are described herein, those of ordinary skill in the art will understand that many modifications may be made thereto within the scope of the present disclosure. Accordingly, it is not intended that the scope of the disclosure in any way be limited by the examples provided.

[0040] Aspect

[0041] Aspect 1. A multi-material gear assembly comprising:

[0042] a first gear formed of a first material, the first gear defining a plurality of first gear teeth; and

[0043] a gear shaft configured to support the first gear, the gear shaft being formed of a second material that is different from the first material,

[0044] wherein the second material has a higher damping coefficient than the first material.

[0045] Aspect 2. The multi-material gear assembly of aspect 1, wherein a density of the second material is lower than that of the first material.

[0046] Aspect 3. The multi-material gear assembly of aspect 1 or 2, further comprising a second gear defining a plurality of second gear teeth.

[0047] Aspect 4. The multi-material gear assembly of aspect 3, further comprising a web or core extending radially outwardly from the gear shaft to support the second gear, the web or core being formed of a different material from the second gear.

[0048] Aspect 5. The multi-material gear assembly of aspect 4, wherein the web or core is formed of the second material.

[0049] Aspect 6. The multi-material gear assembly of aspect 3, wherein the second gear is formed of the first material.

[0050] Aspect 7. The multi-material gear assembly of any of aspects 3-6, further comprising a hub to which the web or core for supporting the second gear is mounted, the hub being configured to mount on the gear shaft.

[0051] Aspect 8. The multi-material gear assembly of aspect 7, wherein a material of the hub has a higher strength and density than the material of the web or core.

[0052] Aspect 9. The multi-material gear assembly of aspect 7 or 8, wherein the web or core is over molded with the hub.

[0053] Aspect 10. A gear assembly comprising:

[0054] a first gear having a first pitch diameter;

[0055] a second gear having a second pitch diameter;

[0056] a shaft configured to support the first gear and the second gear; and

[0057] a web or core section coupled to the second gear,

[0058] wherein the web or core section and the shaft are formed of a first material.

[0059] Aspect 11. The gear assembly of aspect 10, wherein the web or core section is integrated with the shaft.

[0060] Aspect 12. The gear assembly of aspect 10 or 11, wherein the first pitch diameter is different from the second pitch diameter.

[0061] Aspect 13. The gear assembly of aspect 12, wherein the first pitch diameter is smaller than the second pitch diameter.

[0062] Aspect 14. The gear assembly of aspect 10, wherein the first and second gears are formed of the same material.

[0063] Aspect 15. The gear assembly of aspect 10, wherein the first gear is formed of a second material and the second gear is formed of a third material.

[0064] Aspect 16. The gear assembly of aspect 15, wherein the first material has a lower hardness and wear resistance than at least one of the second and third materials.

[0065] Aspect 17. The gear assembly of aspect 15 or 16, wherein the first material has a lower density than at least one of the second and third materials.

[0066] Aspect 18. The gear assembly of any of Aspects 10-17, further comprising a hub portion coupled to the shaft and the web or core section.

[0067] Aspect 19. The gear assembly of aspect 18, wherein the hub portion is formed of the first material.

[0068] Aspect 20. The gear assembly of aspect 10, wherein the first material includes cast iron.

[0069] Aspect 21. A multi-material gear assembly comprising:

[0070] a gear including a first material, the gear defining a plurality of gear teeth; and

[0071] a gear shaft configured to support the gear, the gear shaft being formed of a second material that is different from the first material,

[0072] wherein a density of the second material is lower than that of the first material.

[0073] Aspect 22. The multi -material gear assembly of aspect 21, wherein a thermal conductivity of the second material is higher than that of the first material.

[0074] Aspect 23. The multi -material gear assembly of aspect 21 or 22, further comprising a web or core extending radially outwardly from the gear shaft to support the gear, the web or core being formed of the second material.

[0075] Aspect 24. The multi-material gear assembly of aspect 23, further comprising a hub to which the web or core for supporting the gear is mounted, the hub being formed of the second material.

Claims

CLAIMSWhat is claimed is:

1. A multi-material gear assembly including: a first gear including a first material, the first gear defining a plurality of first gear teeth; and a gear shaft configured to support the first gear, the gear shaft being formed of a second material that is different from the first material; wherein the second material has a higher damping coefficient than the first material.

2. The multi-material gear assembly of claim 1, wherein a density of the second material is lower than that of the first material.

3. The multi-material gear assembly of claim 1, further comprising a second gear defining a plurality of second gear teeth.

4. The multi-material gear assembly of claim 3, further comprising a web or core extending radially outwardly from the gear shaft to support the second gear, the web or core being formed of a different material from the second gear.

5. The multi -material gear assembly of any of claims 1-4, wherein the web or core is formed of the second material.

6. The multi-material gear assembly of claim 5, wherein the second gear is formed of the first material.

7. The multi -material gear assembly of any of claims 1-6, further comprising a hub to which a web or core for supporting a second gear is mounted, the hub being configured to mount on the gear shaft.

8. The multi -material gear assembly of claim 7, wherein a material of the hub has a higher strength and density than the material of the web or core.

9. A gear assembly comprising: a first gear having a first pitch diameter; a second gear having a second pitch diameter; a shaft configured to support the first gear and the second gear; and a web or core section coupled to the second gear, wherein the web or core section and the shaft are formed of a first material.

10. The gear assembly of claim 9, wherein the web or core section is integrated to the shaft.

11. The gear assembly of any of claims 9-10, wherein the first pitch diameter is smaller than the second pitch diameter.

12. The gear assembly of any of claims 9-11, wherein the first gear is formed of a second material, and wherein the second gear is formed of a third material.

13. The gear assembly of any of claims 9-12, wherein the first material has a lower hardness and wear resistance than at least one of the second and third materials.

14. The gear assembly of any of claims 9-13, wherein the first material has a lower density than at least one of the second and third materials.

15. The gear assembly of any of claims 9-14, further comprising a hub portion coupled to the shaft and the web or core section.

16. The gear assembly of any of claims 9-15, wherein the hub portion is formed of the first material.

17. A multi -material gear assembly including: a gear including a first material, the gear defining a plurality of gear teeth; anda gear shaft configured to support the gear, the gear shaft being formed of a second material that is different from the first material; wherein a density of the second material is lower than that of the first material.

18. The multi -material gear assembly of claim 17, wherein a thermal conductivity of the second material is higher than that of the first material.

19. The multi-material gear assembly of any of claims 17-18, further comprising a web or core extending radially outwardly from the gear shaft to support the gear, the web or core being formed of the second material.

20. The multi-material gear assembly of any of claims 17-19, further comprising a hub to which the web or core for supporting the gear is mounted, the hub being formed of the second material.

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