Face spline structure, and power transmission device having drive shaft and wheel hub assembly coupled to each other through face spline structure

Abstract

The present disclosure relates to a face spline structure, which is used to transmit driving power of a vehicle, and a power transmission device including a drive shaft and a wheel hub assembly coupled to each other by the face spline structure. The face spline structure for transmitting rotational power includes root parts and tip parts that are alternately aligned in the circumferential direction. The root part is formed such that the width thereof has the smallest value at one point between the radially inner end and the radially outer end thereof.

Description

Power transmission device having a face spline structure and a drive shaft and wheel hub assembly joined together through the face spline structure

[0001] The present disclosure relates to a power transmission device comprising a face spline structure used to transmit driving force of a vehicle, and a drive shaft and a wheel hub assembly joined together by the face spline structure.

[0002] A driveshaft, also known as a halfshaft, includes an inboard joint that receives power from a transmission or motor, an outboard joint that transmits power to the wheels, and a connecting shaft that links the inboard and outboard joints. Typically, the outboard joint is configured to compensate for displacement angles resulting from wheel variations, while the inboard joint is configured to compensate for displacement angles and axial lengths resulting from the movement of the outboard joint. Generally, the inboard and outboard joints are implemented as constant velocity joints that transmit rotational power at a constant speed.

[0003] The outboard joint is connected to the wheel hub to enable power transmission, and the outboard joint and wheel hub are typically connected to rotate together through a spline structure. While it is common to connect the outboard joint and wheel hub through splines formed to extend axially on the outboard joint, a method is also used to dynamically connect the joint and wheel hub through splines formed on a surface perpendicular to the joint's axis, known as face splines. In the method using face splines, the outboard joint and wheel hub are assembled to rotate together by interlocking through face splines formed on their respective opposing surfaces.

[0004] With the face splines of the outboard joint and the wheel hub interlocked, the wheel hub and the outboard joint are fixedly fastened together via threaded bolts. In this process, the basic connection conditions between the face splines of the outboard joint and the wheel hub are determined by factors such as the number of teeth, tooth thickness, tooth height, and tooth angle. In the case of straight tooth profiles with a constant tooth width, friction is prone to occur during tooth contact, leading to significant noise and relatively rapid wear. Additionally, as rotational speeds increase, vibration increases, resulting in reduced efficiency. In this regard, there is a demand for improved durability, reduced noise and vibration, and enhanced efficiency through the optimization of tooth profiles in the face spline structure.

[0005] The matters described in the technical background section of this invention are written to enhance understanding of the background of the invention and may include matters that are not prior art already known in the field to which this technology belongs.

[0006] The problem that the present invention aims to solve is to provide a face spline structure that can reduce noise and vibration and improve durability and efficiency through the optimization of the tooth profile.

[0007] The technical problems that the present invention aims to solve are not limited to those mentioned above, and other technical problems not mentioned will be understood by those skilled in the art from the description below.

[0008] A face spline structure for transmitting rotational power according to an embodiment of the present invention includes root portions and tip portions arranged alternately along the circumferential direction. The width of the root portion is formed to have the smallest value at a point between the radially inner end and the radially outer end.

[0009] The root portion may be configured such that its width gradually increases from the radially inner end to the radially outer end and then gradually decreases again. As a result, since the width of the root portion becomes smallest at a point between the radially inner end and the outer end, friction between the tip portions can be reduced, thereby reducing noise and vibration and improving efficiency.

[0010] The width of the above root portion can be formed to have the smallest value at the midpoint between the radial inner end and the radial outer end.

[0011] The above root portion may be configured such that the width at the radially inner end and the width at the radially outer end are equal to each other.

[0012] The above root portion can be formed such that the ratio (=w1 / w3) of the width (w1) at the radial outer end and the smallest width (w3) at one point falls within the range of greater than 1 and less than or equal to 1.25.

[0013] The above root portion can be formed such that the ratio (=w1 / w3) of the width (w1) at the radial outer end and the smallest width (w3) at one point falls between a lower limit value and an upper limit value calculated based on the manufacturing tolerance of the flank connecting the tip portion and the root portion.

[0014] The above root portion may include a curved shape that is sunken in a direction away from the relative spline.

[0015] A power transmission device according to an embodiment of the present invention comprises: a drive shaft including a constant velocity joint having a first face spline; and a wheel hub assembly including a wheel hub having a second face spline engaged with the first face spline to enable the transmission of rotational power. The first face spline includes a root portion and a tip portion arranged alternately along the circumferential direction, and the width of the root portion is formed to have the smallest value at a point between a radially inner end and a radially outer end.

[0016] According to the present invention, by making the width of the root portion have the smallest value at any point between the radial outer end and the radial inner end, the tip portion has a convex shape, and accordingly, the reduction of noise and vibration, and the improvement of durability and efficiency can be achieved.

[0017] In addition to this, various effects that can be obtained or predicted by the embodiments of the present invention are disclosed directly or implicitly in the detailed description of the embodiments of the present invention.

[0018] The drawings attached below are intended to aid in understanding the present invention and provide embodiments of the invention together with the detailed description. However, the technical features of the present invention are not limited to specific drawings, and the features disclosed in each drawing may be combined with one another to form new embodiments. The embodiments of this specification may be better understood by referring to the following description in conjunction with the attached drawings, in which similar reference numerals refer to identical or functionally similar elements.

[0019] FIG. 1 is a perspective view of a drive shaft with a spline structure applied according to an embodiment of the present invention.

[0020] FIG. 2 is a perspective view showing a power transmission device which is a combination of a drive shaft and a wheel hub assembly to which a face spline structure according to an embodiment of the present invention is applied.

[0021] FIG. 3 is an exploded perspective view of a drive shaft and wheel hub assembly in an exploded state with a face spline structure applied according to an embodiment of the present invention.

[0022] FIG. 4 is a drawing showing a face spline structure according to an embodiment of the present invention.

[0023] Figure 5 is a cross-sectional view taken along line AA of Figure 4.

[0024] The drawings referenced above are not necessarily drawn to scale and should be understood as providing a simplified representation of various features illustrating the basic principles of the invention. For example, specific design features of the invention, including specific dimensions, orientations, positions, and shapes, will be partially determined by specific intended applications and usage environments.

[0025] Embodiments of the present invention are described below with reference to the attached drawings so that those skilled in the art can easily implement them. However, the present invention may be embodied in various different forms and is not limited to the described embodiments.

[0026] The terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the invention. As used herein, the singular form is intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising” and / or “comprising” as used herein indicate the presence of the specified features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, components, and / or groups thereof. As used herein, the term “and / or” includes any one or all combinations of one or more items listed in association. The term “combined” indicates a physical relationship between two components where the components are directly connected to each other or indirectly connected through one or more mediating components.

[0027] In describing the components of the present invention, terms such as first, second, A, B, (a), (b), etc., may be used. These terms are intended only to distinguish the components from other components and do not limit the essence, order, or sequence of the components. Where it is stated that a component is "connected," "combined," or "connected" to another component, it should be understood that the component may be directly connected, combined, or connected to the other component, but that another component may also be "connected," "combined," or "connected" between each component.

[0028] FIG. 1 is a perspective view of a drive shaft with a spline structure applied according to an embodiment of the present invention. FIG. 2 is a perspective view showing a combination of a drive shaft with a face spline structure applied according to an embodiment of the present invention and a wheel hub, and FIG. 3 is an exploded perspective view of a drive shaft with a face spline structure applied according to an embodiment of the present invention in an exploded state. FIG. 2 shows the constant velocity joint (10) of the drive shaft and the wheel hub assembly (20) in a partially cut state, and FIG. 3 shows the wheel hub assembly (20) in a partially cut state.

[0029] Referring to FIGS. 1 to 3, a constant velocity joint (10) to which a face spline structure according to an embodiment of the present invention can be applied may be a constant velocity joint of the form called a so-called Rzeppa joint, and includes an outer joint member (12), an inner joint member (13) disposed within the outer joint member (12), a plurality of power transmission balls (14) disposed between the outer joint member (12) and the inner joint member (13), and a ball cage (15) that accommodates the plurality of power transmission balls (14). The power transmission balls (14) may be configured to be disposed in ball grooves provided in the outer joint member (12) and the inner joint member (13), respectively, so as to transmit rotational power of the inner joint member (13) to the outer joint member (12). A connecting shaft (16) is connected to the inner joint member (13) so as to rotate together with the inner joint member (13). A constant velocity joint (10) may be connected to one end of the connecting shaft (16), and another constant velocity joint (not shown) may be connected to the other end of the connecting shaft (16). Typically, a power transmission device comprising a connecting shaft (16) and a pair of constant velocity joints connected to both ends thereof is referred to as a drive shaft.

[0030] The outer joint member (12) may have a cup shape with a U-shaped cross-section that is open on one side, and the inner joint member (13) is disposed in the inner space of the outer joint member (12). A boot (17) for receiving grease may be attached to the open end of the outer joint member (12) and the connecting shaft (16), respectively. Since the components and operating principle of such a constant velocity joint (10) are obvious to a person skilled in the art, a detailed description thereof is omitted.

[0031] For example, a wheel hub assembly (20) includes a wheel hub (21) and a rolling bearing (22). The wheel hub (21) has a roughly cylindrical shape, and the rolling bearing (22) rotatably supports the wheel hub (21). The rolling bearing (22) may include an inner ring (23) that is axially fitted and fastened to the outer surface of the wheel hub (21), an outer ring (24) that is fixedly fastened to a stationary body of the vehicle, such as a car body or knuckle, in a position radially outside the inner ring (23), and a ball-shaped rolling element (25) interposed between the inner ring (23) and the outer ring (24) or between the wheel hub (21) and the outer ring (24). As shown in FIGS. 2 and 3, a plurality of rolling elements (25) may be arranged in two rows.

[0032] A fastening bolt (26) fastens the wheel hub (21) and the outer joint member (12) together so as to fix them in the axial direction. The fastening bolt (26) may be a threaded bolt that passes through the wheel hub (21) and is fastened to the outer joint member (12) to fix the wheel hub (21) and the outer joint member (12). The outer joint member (12) may include a shaft portion (121), a shoulder portion (122), and a mouth portion (123), and the fastening bolt (26) may be fastened to the shaft portion (121). The shaft portion (121) extends along the axial direction of the constant velocity joint (10), and the shoulder portion (122) may be formed by extending radially from the end of the shaft portion (121). The mouth portion (123) may extend from the shoulder portion (122) to form a space into which the inner joint member (13) is inserted. The wheel hub (21) and the outer joint member (12) are each provided with face splines (101, 102) facing each other and are connected to each other so as to rotate together by the meshing of the face splines (101, 102).

[0033] The face spline (101) of the outer joint member (12) may be formed on the outer surface of the shoulder portion (122) so as to face the wheel hub (21). The face spline (102) of the wheel hub (21) is formed on the surface facing the face spline (101) of the outer joint member (12). As the outer joint member (12) and the wheel hub (21) are connected to each other in a state where they are rotationally constrained through the face splines (101, 102), the wheel hub (21) is rotated by the rotation of the outer joint member (12). By doing so, the rotational power of the constant velocity joint (10) can be transmitted to the wheel hub (21).

[0034] FIG. 4 illustrates a face spline structure according to an embodiment of the present invention, namely, a face spline (101) of an outer joint member (12). In FIG. 4, the hatched portion represents the root portion (301) of the face spline (101), and the portion located between them represents the tip portion (302). The root portion (301) and the tip portion (302) are alternately arranged along the circumferential direction to form a tooth profile having a ring shape, and correspondingly, the wheel hub (21) also includes a tip portion and a root portion that are alternately arranged along the circumferential direction. The face spline (102) of the wheel hub (21) may have the same tooth profile as the face spline (101) of the joint member (12).

[0035] In FIG. 4, the root portion (301) and the tip portion (302) are illustrated, and the inclined surface connecting the top of the tip portion (302) and the widthwise boundary of the root portion (301) is omitted. The inclined surface may be a surface formed by a combination of straight lines connecting the widthwise boundary of the root portion (301) and the widthwise boundary of the tip portion (302). Referring to the illustration within the dotted rectangle in FIG. 4, the root portion (301) has a width that varies in size along the radial direction (up and down direction in the dotted rectangle). The root portion (301) has a width that is the distance between the widthwise boundaries (311, 312), and the width of the root portion (301) can be understood as the distance between the widthwise boundaries (311, 312) in a direction perpendicular to the radial direction.

[0036] Referring to FIG. 4, the width of the root portion (301) can be configured to gradually decrease from the radial inner end (313) to the radial outer end (314) and then gradually increase again. At this time, the width-direction boundaries (311, 312) of the root portion (301) may have a curved shape that gets closer to each other and then further apart as they go from the radial inner end (313) to the outer end (314). Accordingly, the width of the root portion (301) reaches a maximum at a point between the radial inner end (313) and the outer end (314). In this embodiment, the width (w3) of the root portion (301) at the midpoint (315) between the radial outer end (314) and the radial inner end (313), i.e., the point where the distance (k1) from the radial outer end (314) and the distance (k2) from the radial inner end (313) are equal (i.e., k1 = k2), is formed to be smaller than the width (w1) at the radial outer end (314) and the width (w2) at the radial inner end (313) (w1, w2 > w3). At this time, the width (w1) at the radial outer end (314) and the width (w2) at the radial inner end (313) may be the same (w1 = w2 > w3).

[0037] The ratio (=w1 / w3) of the width (w1) at the radial outer end (314) of the root portion (301) and the width (w3) at the radial midpoint (314) may be greater than 1 and less than or equal to 1.25 (i.e., 1 < w1 / w3 ≤ 1.25). For example, the upper and lower limits of the width ratio (=w1 / w3) can be determined by considering the manufacturing tolerance of the flank, which is an inclined surface connecting the outer end of the tip portion (302) and the width-direction boundary of the root portion (301). Specifically, the lower limit of the width ratio may be determined as the width ratio in the case of maximum manufacturing tolerance, and the upper limit may be determined as a value 10% greater than the lower limit. Here, the lower limit may be calculated using a geometric method, for example, a trigonometric method, by utilizing the angle of the flank, the height of the tip portion, the tolerance angle, etc.

[0038] Referring to FIG. 5, the root portion (301) may be formed to include a curved surface with a recessed shape. That is, as shown in FIG. 5, the root portion (301) may have a curved surface shape that is recessed in a direction away from the relative spline structure (102). At this time, the entire root portion (301) may be formed as a curved surface with a recessed shape, or a part may be formed as a curved surface with a recessed shape and another part may be formed as a flat surface. By forming the root portion (301) as a curved surface with a recessed shape, a clearance is secured during tooth engagement with the relative spline structure (102) when spline coupling, and the tip portion of the relative spline structure (102) may be prevented from contacting the root portion (301).

[0039] Although embodiments of the present invention have been described above, the scope of the present invention is not limited thereto and includes all changes and modifications within the scope recognized as equivalents that can be easily changed by a person skilled in the art from the embodiments of the present invention.

Claims

1. In a face spline structure for transmitting rotational power, It includes root sections and tip sections arranged alternately along the circumferential direction, A face spline structure in which the width of the above root portion is formed to have the smallest value at a point between the radially inner end and the radially outer end.

2. In Paragraph 1, The above-mentioned root portion is a face spline structure configured such that the width gradually increases from the radially inner end to the radially outer end and then gradually decreases again.

3. In Paragraph 2, A face spline structure in which the width of the above root portion is formed to have the smallest value at the midpoint between the radial inner end and the radial outer end.

4. In Paragraph 3, The above-mentioned root portion is a face spline structure configured such that the width at the radially inner end and the width at the radially outer end are equal to each other.

5. In any one of paragraphs 1 through 4, The above-mentioned root portion is a face spline structure formed such that the ratio (=w1 / w3) of the width (w1) at the radial outer end and the smallest width (w3) at one point falls within the range of greater than 1 and less than or equal to 1.

25.

6. In any one of paragraphs 1 through 4, The above-mentioned root portion is a face spline structure formed such that the ratio (=w1 / w3) of the width (w1) at the radial outer end and the smallest width (w3) at one point falls between a lower limit value and an upper limit value calculated based on the manufacturing tolerance of the flank connecting the tip portion and the root portion.

7. In Paragraph 1, The above-mentioned root portion is a face spline structure including a curved shape that is sunken in a direction away from the relative spline.

8. A drive shaft including a constant velocity joint having a first face spline; and A wheel hub assembly comprising a wheel hub having a second face spline that engages with the first face spline to enable the transmission of rotational power, and The first face spline above includes a root portion and a tip portion that are alternately arranged along the circumferential direction, and A power transmission device in which the width of the above-mentioned root portion is formed to have the smallest value at a point between the radially inner end and the radially outer end.

9. In Paragraph 8, The above root portion is a power transmission device in which the ratio (=w1 / w3) of the width (w1) at the radial outer end and the smallest width (w3) at one point falls within the range of greater than 1 and less than or equal to 1.

25.

10. In Paragraph 8, A power transmission device in which the ratio (=w1 / w3) of the width (w1) at the radial outer end and the smallest width (w3) at one point is formed to fall between a lower limit value and an upper limit value calculated based on the manufacturing tolerance of the flank connecting the tip portion and the root portion.

11. In Paragraph 8, The above-mentioned root portion is a power transmission device comprising a curved shape that is sunken in a direction away from the relative spline.

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