Stamping wheel hub for casting plastics

Abstract

A gear includes an inner hub formed of a metallic material, the inner hub having an outer surface defining a plurality of external teeth. The gear further includes an outer ring formed of a non-metallic material, the outer ring having a smooth inner diameter. The outer ring is arranged to be in an interference fit with the external teeth of the inner hub.

Description

[0001] Cross - reference to related applications

[0002] This application claims the benefit of priority of U.S. Provisional Application No. 62 / 988,197, filed on Mar. 11, 2020, the disclosure of which is incorporated herein by reference in its entirety. Technical field

[0003] The present invention relates to gears, and more particularly, to gears including a stamped hub and cast plastic. Background art

[0004] Automobiles are subject to many different types of stresses (e.g., rough driving surfaces, internal vibrations, and exposure to various environments). Various components of an automobile experience these difficulties more than other components, and the failure of one component often leads to the damage of related components and sudden failure of the automobile. Although steel and other metallic materials are strong and durable, they are heavy, which significantly reduces fuel economy. To balance strength and weight, traditional metallic components are being replaced or integrated with components made of non - metallic materials (e.g., polymer or carbon - fiber - based materials).

[0005] One example category of components critical to the operation of an automobile is the numerous gears that transfer motion between components. Some gears include a metallic inner hub having a knurled outer diameter (O.D.) and a non - metallic outer ring that surrounds and is bonded to the knurled outer diameter. Although in certain applications, these gears with an inner hub and an outer ring have certain advantages compared to more traditional gears, problems can still exist during operation. For example, the inner hub is heavy, which has a negative impact on fuel economy, and during operation, the geometry of the knurled outer surface can cause stress fractures and lead to the complete separation or peeling of the outer ring and the hub. One application of these gears with an inner hub and an outer ring is in a power - steering system.

[0006] Accordingly, there is a continuing need to develop gears with an inner hub and an outer ring to minimize weight and reduce the occurrence of sudden separation and inoperability. Summary of the invention

[0007] According to one aspect of the present disclosure, a gear includes an inner hub formed of a metallic material, the inner hub having an outer surface defining a plurality of external teeth. The gear further includes an outer ring formed of a non - metal material (not a metallic material), the outer ring having a smooth inner diameter (the inner diameter is smooth). The outer ring is disposed in an interference fit with the external teeth of the inner hub.

[0008] According to another aspect of the present disclosure, a method of forming a gear is provided. The method includes forming an inner hub formed of a metallic material and defining a plurality of external teeth on an outer diameter of the inner hub. The method further includes forming an outer ring formed of a non-metallic material and defining a smooth inner diameter of the outer ring. The method further includes press-fitting the smooth inner diameter of the outer ring onto the external teeth of the inner hub.

[0009] According to yet another aspect of the present disclosure, a gear includes an inner hub formed of a stamped metallic material, the inner hub having an outer surface defining a plurality of external teeth, wherein at least some of the plurality of external teeth have a pair of external tooth sidewalls and an external tooth top wall, each of the pair of external tooth sidewalls extending perpendicularly from the outer surface of the inner hub, and wherein the external tooth top wall is at a right angle to the pair of external tooth sidewalls and connects the pair of external tooth sidewalls. The gear further includes an outer ring formed of a non-metallic material, the outer ring having a smooth inner diameter. The outer ring is configured to be press-fitted with the internal teeth.

[0010] From the description provided herein, further applicable scopes will become apparent. The description and specific examples in the present invention summary are only for illustrative purposes and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The drawings described herein are only for illustrative purposes of selected embodiments and are not intended to limit the scope of the present disclosure. The inventive concepts related to the present disclosure will be more readily understood by referring to the following description in conjunction with the drawings, wherein:

[0012] Figure 1 is an exploded perspective view of a gear including an inner hub and an outer sleeve;

[0013] Figure 2 is a plan view of the inner hub and the outer ring, showing that the inner hub includes an outer diameter (O.D.) having a series of teeth extending from the outer diameter;

[0014] Figure 3 is a cross-sectional view of the inner hub, showing that the hub includes a front surface and a rear surface;

[0015] Figures 4A to 4E is a series of perspective views showing various types of teeth that can be utilized in accordance with the subject disclosure;

[0016] Figure 5A A perspective view showing the stress distribution on the gear is provided, wherein the inner hub has knurling;

[0017] Figure 5B A perspective view showing the stress distribution on the gear is provided, wherein the inner hub has teeth;

[0018] Figure 6A Shows the tensile test results in a curve, which is a function of displacement and load;

[0019] Figure 6B The peel test results are shown in a curve which is a function of displacement and load; and

[0020] Figure 7 is a flow chart of a method for forming a gear having an inner hub and an outer ring. DETAILED DESCRIPTION

[0021] Example embodiments will now be described more fully with reference to the accompanying drawings. Generally, the subject matter embodiments relate to a gear having an inner hub and an outer ring. However, the example embodiments are provided so that this disclosure will be thorough and will fully convey the scope to those skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that some specific details need not be employed, and the example embodiments may be embodied in many different forms and should not be construed as limiting the scope of the present disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

[0022] Referring to the accompanying drawings, in which like reference numerals indicate corresponding parts in all views, the subject gear is intended to provide an enhanced structure which is made lighter by design and less prone to cracking and delamination that plagued previous versions.

[0023] First referring to Figures 1 to 3 , a gear 10 in an exploded state is depicted. The gear 10 includes an inner hub 12 and an outer ring 14. The inner hub 12 includes a front surface 16 and a rear surface 18 that extend about an axis A to define an outer diameter (O.D.). The outer diameter surface 20 separates the front surface 16 and the rear surface 18. A series of external teeth 22 are circumferentially spaced about the axis A on the outer diameter surface 20 and extend between the front surface 16 and the rear surface 18. The front surface 16 and the rear surface 18 define a tapered portion 24 adjacent to the external teeth 22 and a flat portion 16 that extends radially inward from the tapered portion 24 to the shaft connection hole 26. As Figure 3As best shown, the shaft connection hole 26 includes an axially extending inner sleeve portion 28. The outer teeth 22 are located on an axially extending outer sleeve portion 30. The inner hub 12 is formed of a metallic material. For example, the inner hub 12 can be formed by stamping steel. Alternatively, the inner hub 12 can be formed by other methods, such as casting, forging, machining from solid, etc. The outer ring 14 includes an outer surface 32 that extends radially inwardly to an inner diameter surface 34 that includes an inner diameter (I.D.) sized for an interference fit to engage an outer diameter surface 20 of the inner hub 12. The inner diameter surface 34 is a smooth / flattened surface. The outer ring 14 can be formed of a non-metallic second material. For example, the outer ring 14 can be cast, extruded, or molded from a polymer or more specifically from a nylon material. Each outer tooth 22 includes an outer tooth sidewall 38 that extends radially outwardly to an outer tooth top wall 40.

[0024] Now referring to Figures 4A to 4E , a series of perspective views are provided that illustrate various types of teeth that can be utilized in accordance with the present subject matter disclosure. In Figure 4A , the inner hub 12 is formed of solid steel that has not been stamped. Each outer tooth 22 of the inner hub 12 includes an outer tooth sidewall 38 that tapers toward the outer tooth top wall 40. The taper can extend along all or only a portion of the radially extending outer tooth sidewall 38.

[0025] In Figure 4B , the inner hub 12 is formed of stamped steel. Each outer tooth 22 of the inner hub 12 includes an outer tooth sidewall 38 that tapers toward the outer tooth top wall 40. The taper extends only along a portion of the radially extending outer tooth sidewall 38 such that the outer tooth sidewall is partially tapered. The inner surface 34 of the outer ring 14 is smooth and has an interference fit with the outer diameter of the hub 12.

[0026] In Figure 4C , the inner hub 12 is formed of stamped steel. Each outer tooth 22 of the inner hub 12 includes an outer tooth sidewall 38 that tapers toward the outer tooth top wall 40. The taper extends along the entire radially extending outer tooth sidewall 38 such that the outer tooth sidewall is fully tapered. The inner surface 34 of the outer ring 14 is smooth and has an interference fit with the outer diameter of the hub 12.

[0027] In Figure 4D , the inner hub 12 is formed of stamped steel. Each outer tooth 22 of the inner hub 12 includes an outer tooth sidewall 38 that does not taper toward the outer tooth top wall 40. The outer tooth sidewalls 38 are straight and parallel, and each outer tooth sidewall is at a right angle to the outer tooth top wall 40 such that the teeth are generally straight. The inner surface 34 of the outer ring 14 is smooth and has an interference fit with the outer diameter of the hub 12.

[0028] In Figure 4EIn [the figure], the inner hub 12 is formed of stamped steel. Each outer tooth 22 of the inner hub 12 includes an outer tooth sidewall 38 that tapers away from the outer tooth top wall 40. The taper extends along all or only a portion of the radial extent of the outer tooth sidewall 38 such that each outer tooth 22 forms a dovetail shape. The inner surface 34 of the outer ring 14 is smooth and has an interference fit with the outer diameter of the hub 12.

[0029] Figure 5A A perspective view showing the stress distribution on the gear is provided, wherein the inner hub has knurling. The stress distribution is shown in gray scale, wherein it should be understood that the stress distribution forms relatively straight stress lines (S.L.), indicating that due to stress concentration at the joint surface, the outer ring 14 has a tendency to separate from the inner hub 12.

[0030] Figure 5B A perspective view showing the stress distribution on the gear is provided, wherein the inner hub has teeth. The stress distribution is again shown in gray scale, wherein it should be understood that the stress distribution forms a series of bifurcated stress lines (S.L.), indicating that due to the increased stress distribution at the joint surface, the tendency of the outer ring 14 to separate from the inner hub 12 is reduced. In the case where there are cracks on the surface from the outer ring 14 to the inner hub 12, it may have a certain operating time, wherein the operation is "sticky", and it indicates that replacement is required rather than a complete and sudden separation.

[0031] Figure 6A The tensile test results are shown in gray scale in a curve manner, which is a function of displacement and load. The curve includes the results of tensile tests on Figures 4A to 4E the various types of teeth shown, and also includes the test results with a knurled surface replacing the teeth. It should be understood that a smaller load in the knurled surface results in a larger displacement, while the various teeth still maintain a larger load at a larger displacement.

[0032] Figure 6B The peel test results are shown in gray scale in a curve manner, which is a function of displacement and load. The curve includes the results of peel tests on Figures 4A to 4E the various types of teeth shown, and also includes the test results with a knurled surface replacing the teeth. It should be understood that a larger displacement in the knurled surface results in a smaller load, while the straight teeth and dovetail teeth still maintain a higher load at a larger displacement. It should be understood that the peak load on the surfaces of the straight teeth and dovetail teeth increases.

[0033] Figure 7A flowchart of a method for forming a gear having an inner hub and an outer ring. Method 200 includes forming an inner hub 202 having external teeth. Step 202 may include: forming the inner hub 204 by stamping, forging, casting, machining, etc.; forming partially tapered teeth 206; forming fully tapered teeth 208; forming straight teeth 210; and / or forming dovetail teeth 212. Method 200 continues by forming an outer ring 214 having a smooth inner diameter. Step 214 may include forming the outer ring by casting 216, extrusion 218, or by injection molding 220. Method 200 continues by the following steps: heating the outer ring 14 and pressing it onto the inner hub 12 226; inductively heating the inner hub 12 to melt the plastic inner diameter surface of the outer ring 14 so that it flows into the teeth of the inner hub 12 and bonding the plastic ring to the hub teeth 228 (e.g., via an adhesive or heat application); and assembling the gear into the steering system of an automobile (e.g., an electric power steering system) 230.

[0034] Although the present invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the present invention is not limited to these disclosed embodiments. On the contrary, the present invention can be modified to incorporate any number of variations, alterations, substitutions, or equivalent arrangements not heretofore described but commensurate with the spirit and scope of the present invention. Additionally, although various embodiments of the present invention have been described, it should be understood that aspects of the present invention may only include some of the described embodiments. Therefore, the present invention should not be regarded as being limited by the foregoing description, but only by the scope of the appended claims.

Claims

1. A gear, comprising: an inner hub formed of a metallic material, the inner hub having an outer surface defining a plurality of external teeth; an outer ring formed of a non-metallic material, the outer ring having a smooth inner diameter; and wherein the outer ring is arranged to be in interference fit with the external teeth of the inner hub, wherein a front surface and a rear surface of the inner hub define a tapered portion adjacent to the external teeth and a flat portion extending radially inwards from the tapered portion to a shaft connection hole of the inner hub.

2. The gear according to claim 1, wherein at least some of the plurality of external teeth have a pair of external tooth side walls and an external tooth top wall, each of the pair of external tooth side walls extending perpendicularly from the outer surface of the inner hub, wherein the external tooth top wall is at a right angle to the pair of external tooth side walls and connects the pair of external tooth side walls.

3. The gear according to claim 2, wherein all of the plurality of external teeth have a pair of external tooth side walls and an external tooth top wall, each of the pair of external tooth side walls extending perpendicularly from the outer surface of the inner hub, wherein the external tooth top wall is at a right angle to the pair of external tooth side walls and connects the pair of external tooth side walls.

4. The gear according to claim 1, wherein at least some of the plurality of external teeth have a dovetail geometry, wherein each dovetail geometry tooth has a pair of external tooth side walls and an external tooth top wall, each of the pair of external tooth side walls extending away from each other as each side wall extends away from the outer surface of the inner hub, wherein the external tooth top wall connects the pair of external tooth side walls.

5. The gear according to claim 1, wherein at least some of the plurality of external teeth have a tapered geometry, wherein each tapered geometry tooth has a pair of external tooth side walls and an external tooth top wall, each of the pair of external tooth side walls extending towards each other as each side wall extends away from the outer surface of the inner hub, wherein the external tooth top wall connects the pair of external tooth side walls.

6. The gear according to claim 1, wherein the inner hub is a stamped metal component.

7. The gear according to claim 1, wherein the inner hub is a cast component.

8. The gear according to claim 1, wherein the inner hub is a forged component.

9. The gear according to claim 1, wherein the inner hub is machined from a solid blank.

10. A method of forming a gear, comprising: forming an inner hub formed of a metallic material and defining a plurality of external teeth on an outer diameter of the inner hub; forming an outer ring formed of a non-metallic material and defining a smooth inner diameter of the outer ring; and interference fitting the smooth inner diameter of the outer ring onto the external teeth of the inner hub, wherein a front surface and a rear surface of the inner hub define a tapered portion adjacent to the external teeth and a flat portion extending radially inwards from the tapered portion to a shaft connection hole of the inner hub.

11. The method according to claim 10, wherein forming the inner hub includes stamping a metallic component.

12. The method according to claim 10, wherein forming the inner hub includes casting a metallic component.

13. The method according to claim 10, wherein, forming the inner hub includes forging a metal component.

14. The method according to claim 10, wherein, forming the inner hub includes machining a metal component.

15. A gear, comprising: an inner hub formed of stamped metal material, the inner hub having an outer surface defining a plurality of external teeth, wherein at least some of the plurality of external teeth have a pair of external tooth sidewalls and an external tooth top wall, each of the pair of external tooth sidewalls extending perpendicularly from the outer surface of the inner hub, and wherein the external tooth top wall is at a right angle to the pair of external tooth sidewalls and connects the pair of external tooth sidewalls; an outer ring formed of a non-metallic material, the outer ring having a smooth inner diameter; and wherein, the outer ring is arranged to have an interference fit with the inner hub, wherein, the front surface and the rear surface of the inner hub define a tapered portion adjacent to the external teeth and a flat portion extending radially inward from the tapered portion to a shaft connection hole of the inner hub.

Images