Double offset constant velocity joint

Abstract

This constant velocity joint comprises: an outer race comprising a plurality of outer ball tracks; an inner race comprising a plurality of inner ball tracks paired with the outer ball tracks; a plurality of balls arranged in respective spaces formed by the outer ball tracks and the inner ball tracks paired with each other; and a ball cage disposed between the outer race and the inner race for accommodating the plurality of balls. In a non-articulated state of the outer race and the inner race, the inner circumferential center line of the ball cage, which is perpendicular to the longitudinal axis of the inner race while passing through the center of curvature of the inner circumference of the ball cage, and the outer circumferential center line of the ball cage, which is perpendicular to the longitudinal axis of the outer race while passing through the center of curvature of the outer circumference of the ball cage, are respectively offset from the ball center line connecting the centers of the plurality of balls. In the inner ball track, at least part of regions other than the ball path of the ball during articulation of the outer race and the inner race is formed by incomplete processing.

Description

Double offset constant velocity joint

[0001] The present disclosure relates to a constant velocity joint used to transmit the driving force of a vehicle.

[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. Typically, the inboard and outboard joints are implemented as constant velocity joints that transmit rotational power at a constant speed.

[0003] An inboard joint is configured to allow for axial strokes based on the displacement angle of the outboard joint and the movement of the vehicle wheels. An example of an inboard joint is a joint configured such that the inner race has an axial offset relative to the ball, while the outer race also has an axial offset relative to the ball (so-called double offset constant velocity joint). In this type of constant velocity joint, the outer ball track provided on the outer race is linear, and axial strokes are realized as the ball and internal components move along the linear outer ball track. Additionally, angular displacement occurs through a connecting shaft splined to the inner race.

[0004] Since the inner race of a constant velocity joint is exposed to heavy loads during operation, various heat treatments and machining processes are required to ensure strength. These heat treatments and machining processes not only complicate the manufacturing process but also contribute to increased manufacturing costs. In this regard, there is a need for a solution that simplifies the manufacturing process and lowers manufacturing costs by eliminating unnecessary steps, taking into account the operation of double offset constant velocity joints.

[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 constant velocity joint that can simplify the manufacturing process and lower manufacturing costs by considering the movement range of the ball.

[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 constant velocity joint according to an embodiment of the present invention comprises: an outer race including a plurality of outer ball tracks; an inner race including a plurality of inner ball tracks paired with the outer ball tracks; a plurality of balls each disposed in the space formed by the paired outer ball tracks and the inner ball tracks; and a ball cage disposed between the outer race and the inner race and accommodating the plurality of balls. In a non-angled state of the outer race and the inner race, the inner circumferential center line of the ball cage, which passes through the center of curvature of the inner circumferential surface of the ball cage and is orthogonal to the longitudinal axis of the inner race, and the outer circumferential center line of the ball cage, which passes through the center of curvature of the outer circumferential surface of the ball cage and is orthogonal to the longitudinal axis of the outer race, are each offset from the ball center line connecting the centers of the plurality of balls. At least a portion of the inner ball track is formed by incomplete machining, excluding the ball movement section when the outer race and the inner race are cut.

[0009] The outer race may include an open side and a joined side, and the section of the inner ball track formed by the incomplete processing may be extended by a predetermined length from the side located on the open side among the two sides of the inner race.

[0010] The section formed by the above incomplete processing may have a length of less than 40% of the total length of the inner ball track.

[0011] Among the entire section of the inner ball track, the section including the ball behavior section at the time of cutting between the outer race and the inner race can be formed by complete machining, and the remaining section excluding the section formed by complete machining can be formed by incomplete machining.

[0012] The above complete processing can form the inner ball track by a forging process, a subsequent forming process, and a heat treatment process, and the above incomplete processing can form the inner ball track by omitting the subsequent forming process and by the forging process and the heat treatment process.

[0013] The above forging process is a cold forging process, the above subsequent forming process is a cold sizing process, and the above heat treatment process may be a carburizing heat treatment process.

[0014] In another embodiment, the forging process may be a hot forging process, the subsequent forming process may be a milling process, and the heat treatment process may be a high-frequency heat treatment process.

[0015] A constant velocity joint according to another embodiment of the present invention comprises: an outer race including a plurality of outer ball tracks; an inner race including a plurality of inner ball tracks paired with the outer ball tracks; a plurality of balls each disposed in the space formed by the paired outer ball tracks and the inner ball tracks; and a ball cage disposed between the outer race and the inner race and accommodating the plurality of balls. In a non-angled state of the outer race and the inner race, the inner circumferential center line of the ball cage, which passes through the center of curvature of the inner circumferential surface of the ball cage and is orthogonal to the longitudinal axis of the inner race, and the outer circumferential center line of the ball cage, which passes through the center of curvature of the outer circumferential surface of the ball cage and is orthogonal to the longitudinal axis of the outer race, are each offset from the ball center line connecting the centers of the plurality of balls. The inner ball track is configured such that, when the outer race and the inner race are cut, at least a portion of the remaining section excluding the ball's movement section is removed to form a depression.

[0016] The outer race may include an open side and a joined side, and the inner circumferential center line may be offset from the ball center line toward the open side.

[0017] The above outer surface center line can be offset from the ball center line toward the coupling side.

[0018] The inner race may include a spline formed on the inner surface.

[0019] According to the present invention, the manufacturing process can be simplified by forming a section where ball movement does not occur during cutting as an incomplete process or by removing it. This reduces mold wear and improves dimensional accuracy.

[0020] 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.

[0021] 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.

[0022] FIG. 1 is a cross-sectional view of a double offset constant velocity joint according to an embodiment of the present invention.

[0023] FIG. 2 is an exploded perspective view of a double offset constant velocity joint according to an embodiment of the present invention.

[0024] FIG. 3 is a cross-sectional view of a double offset constant velocity joint in the maximum angle of cut according to an embodiment of the present invention.

[0025] FIG. 4 is a drawing showing the maximum range of motion of a ball on the ball track of the inner race of a double offset constant velocity joint according to an embodiment of the present invention.

[0026] FIG. 5 is a cross-sectional view of a double offset constant velocity joint according to another embodiment of the present invention.

[0027] FIG. 6 is a perspective view of the inner race of a double offset constant velocity joint according to another embodiment of the present invention.

[0028] 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.

[0029] Embodiments of the present invention are described below with reference to the attached drawings so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the described embodiments.

[0030] 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.

[0031] 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.

[0032] FIG. 1 is a cross-sectional view of a double offset constant velocity joint according to an embodiment of the present invention, and FIG. 2 is an exploded perspective view of a double offset constant velocity joint according to an embodiment of the present invention. Referring to FIG. 1 and FIG. 2, the constant velocity joint (10) includes an outer race (11), an inner race (12), a plurality of balls (13), and a ball cage (14). The constant velocity joint (10) is configured to allow for angular and axial displacement and can be used as an inboard joint of a drive shaft. Although not shown in the drawings, the outer race (11) is configured to be connected to a transmission or motor of a vehicle to receive rotational power, and the inner race (12) can be connected to a connecting shaft of a drive shaft.

[0033] The outer race (11) has a cup shape with a cross-section that is approximately U-shaped. The outer race (11) has a joining side (15), an opening side (16), and an internal space (17) formed between the joining side (15) and the opening side (16). The outer race (11) has a longitudinal axis (X O It forms a) and the connecting side (15) and the opening side (16) are positioned opposite each other along the longitudinal axis (X). The inner race (12) is inserted into the inner space (17) of the outer race (11) through the opening side (16). The inner race (12) has a through hole (18) into which a connecting shaft can be inserted, and can be fastened to the connecting shaft to rotate together with the connecting shaft through spline coupling by a spline (19) formed on the inner surface forming the through hole (18).

[0034] The inner surface (21) forming the inner space (17) of the outer race (11) may have a roughly cylindrical shape, and a plurality of outer ball tracks (22) are arranged at equal intervals along the circumferential direction on the inner surface (21). The inner race (12) includes a plurality of inner ball tracks (24) formed on the outer surface (23). The plurality of outer ball tracks (22) and the plurality of inner ball tracks (24) form pairs, and balls (13) are placed in each pair. The ball cage (14) is positioned between the inner surface (21) of the outer race (11) and the outer surface (23) of the inner race (12), and includes a plurality of windows (25) arranged along the circumferential direction. The plurality of balls (13) act as a medium for transmitting rotational power and are placed in the space formed by the pairs of outer ball tracks (22) and inner ball tracks (24) in a state where they are each received in the windows (25) of the ball cage (14). FIG. 2 illustrates an exemplary case in which six balls (13) are provided, but the number of balls (13) is not limited thereto and can be changed. The outer surface of the ball cage (14) may be formed as a curved surface that enables relative angular displacement with respect to the outer race (11), and the inner surface of the ball cage (14) and the outer surface (23) of the inner race (12) may each be formed as curved surfaces that enable relative angular displacement with respect to the ball cage (14).

[0035] The outer ball track (22) may include a straight line parallel to the longitudinal axis (X). Additionally, the inner ball track (24) may include the longitudinal axis (X) of the inner race (12). I It may include a straight line shape parallel to ). Here, the fact that the ball track has a straight line shape can be understood to mean that when the ball moves on the ball track, the trajectory of the center of the ball is a straight line. Referring to FIG. 1, in the alignment state of the constant velocity joint (10), that is, in the non-angle state, the longitudinal axis (X) of the outer race (11) O The longitudinal axis (X) of the inner race (12) and ) I) coincide with each other, and in this non-angled state, the center line (C) of the inner surface (51) of the ball cage (14) I ) and the center line (C) of the outer surface (52) of the ball cage (14). O ) is the ball center line (C B Each is offset with respect to ). Here, the ball center line (C B ) refers to a line connecting the centers of the balls (13) facing each other. Also, the center line (C) of the inner surface (51) of the ball cage (14). I ) passes through the center of curvature of the inner circumference (51) of the ball cage (14) and the longitudinal axis (X) of the inner race (12). I It means a line perpendicular to ), and the center line (C) of the outer surface (52) of the ball cage (14). O ) passes through the center of curvature of the outer surface (52) of the ball cage (14) and the longitudinal axis (X) of the outer race (11). O It means a line orthogonal to ). Here, the inner surface (51) and the outer surface (52) of the ball cage (14) may each be spherical. As shown in FIG. 1, the center line (C) of the inner surface (51) of the ball cage (14) I ) is the ball center line (C B Offset from ) to the open side (16), and the center line (C) of the outer surface (52) of the ball cage (14). O ) is the ball center line (C B It is offset from the coupling side (15). In this aspect, it can be understood that the constant velocity joint (10) according to the embodiment of the present invention has a double offset structure.

[0036] FIG. 3 illustrates a state in which the inner race (12) is maximally cut relative to the outer race (11), and in this state, the angle between the longitudinal axis (XO) of the outer race (11) and the longitudinal axis (XI) of the inner race (12) is the maximum cut angle (A max...becomes ) In this maximum angle of cut state, the center line (C) of the ball located closest to the open side (16) of the outer race (11), that is, the ball (13) located at the top in FIG. 3 B1 The center line (C) of the ball located closest to the joining side (15) of the outer race (11), that is, the ball (13) located at the bottom in FIG. 3. B2 Distance between ) (D max ) corresponds to the maximum displacement of the ball (13) on the inner ball track (24). FIG. 4 shows the maximum movement length (D) of the ball (13) on the inner ball track (24). B ) is indicated, and the maximum movement length (D) of the ball (13) B ) can be understood as the length of the movement range of the ball (13) at the time of cutting. In FIG. 4, the ball (13) on the right corresponds to the position of the ball (13) on the top in FIG. 3, and the ball (14) on the left in FIG. 4 corresponds to the position of the ball (13) on the bottom in FIG. 3. Therefore, the distance between the two balls (13) shown in FIG. 4, i.e., the maximum movement length (D B ) is the two ball center lines (C) shown in FIG. 3. B1 , C B2 Distance between ) (D max It is the same as ).

[0037] In the present invention, the forming range of the inner ball track (24) is determined by considering the behavioral region of the ball (13) on the inner ball track (24) during such cutting. Referring to FIG. 4, complete machining is performed on a portion (R1) of the entire longitudinal section of the inner ball track (24), and incomplete machining is performed on the remaining portion (R2). As shown in the drawing, the portion (R2) where incomplete machining is performed may be formed to be recessed lower than the portion (R1) where complete machining is performed. The portion (R1) where complete machining is performed is called the complete machining portion, and the portion (R2) where incomplete machining is performed is called the incomplete machining portion. Here, machining can be understood to include general machining operations performed on the inner race of a constant velocity joint, namely lubrication coating, cold forging, cold sizing, turning, spline broaching, carburizing heat treatment, hard turning, etc. Complete processing refers to processing that includes all generally performed processing steps, while incomplete processing refers to processing in which some of these processes are excluded or replaced with other processes. Therefore, incomplete processing can be understood as processing in which some of the processing steps constituting complete processing are excluded.

[0038] The inner ball track (24) may be formed by a cold forging or hot forging-based processing process. For example, the inner ball track (24) may be formed by a cold forging-based processing process including cold forging, cold sizing, and carburizing heat treatment. As another example, the inner ball track (24) may be formed by a hot forging-based processing process including hot forging, milling, and high-frequency heat treatment. For example, a low-carbon steel material with a relatively low carbon content may be used for cold forging, and a high-carbon steel material with a relatively high carbon content may be used for hot forging. The low-carbon steel used for cold forging may be steel with a carbon content of 0.17 to 0.23 wt%, and the high-carbon steel used for hot forging may be steel with a carbon content of 0.47 to 0.56 wt%.

[0039] For example, complete machining may include lubrication coating treatment on the bar material, cold forging, lubrication coating treatment, cold sizing of the ball track, turning, spline broaching, carburization heat treatment, and hard turning of the outer diameter, and incomplete machining may be a process consisting of lubrication coating treatment on the bar material, cold forging, lubrication coating treatment, and carburization heat treatment among the processes of complete machining. Since applying hot forging allows for the formation of hard materials, the material of the inner race can be changed to a material capable of high-frequency heat treatment. For example, the material of the inner race to which conventional carburization heat treatment is applied may be SCr420H or SAE8620H, and the material of the inner race of the present invention to which high-frequency heat treatment is applied may be SAE1050M. Since the application of high-frequency heat treatment allows for the process to be configured as a process line, unlike carburization heat treatment which is performed in a furnace, production efficiency can also be improved.

[0040] Referring again to FIG. 4, the inner race (12) includes two sides (27, 28). The first side (27) is the side located on the joining side (15) of the outer race (11), and the second side (28) is the side located on the opening side (16) of the outer race (11). As described above, the center line (C) of the inner circumference (51) of the ball cage (14) I ) is the ball center line (C B Because it is offset toward the second side (28) based on ), the ball center line (C) in the non-angled state B ) is positioned towards the first side (27). As a result, the movement area of ​​the ball (13) at the angle is positioned towards the first side (27).

[0041] Considering the movement area of ​​the ball, the section including the movement area of ​​the ball (13) from the first side (27) of the inner race (12) is designated as the fully processed section (R1), and the remaining section is designated as the incompletely processed section (R2). As shown in FIG. 4, the fully processed section (R1) is set to a section slightly exceeding the movement area of ​​the ball (13), and the section from the second side (28) of the inner race (12) to just before reaching the movement area of ​​the ball (13) is set as the incompletely processed section (R2). The length of the movement area of ​​the ball (13), that is, the maximum movement length (D) of the ball (13). B ) is the entire section (R) of the inner ball track (24). T It is set to about 60% of the length of ), and accordingly, the length of the incomplete processing section (R2) is the entire section (R) of the inner ball track (24). TIt can be set to less than 40% of the length of the section. Accordingly, the section where the ball (13) moves during cutting is set as a complete processing section (R1) to ensure complete processing, and all or most of the section where the ball (13) does not move during cutting is set as an incomplete processing section (R2) so that at least some of the processing steps are omitted or replaced with other processes. Accordingly, by omitting some of the processing steps or replacing them with other processes for the incomplete processing section, the lifespan of tools such as molds can be increased and dimensional accuracy can be improved.

[0042] FIG. 5 illustrates a constant velocity joint according to another embodiment of the present invention, and FIG. 6 illustrates the inner race (32) of the constant velocity joint of FIG. 5. The same reference numerals are used for parts identical to those described above, and redundant descriptions are omitted. In this embodiment, a method is applied in which the material itself is removed from the part of the inner ball track corresponding to the incomplete processing section described above.

[0043] Referring to FIGS. 5 and 6, most of the incomplete processing area described above, i.e., the area where the ball does not move during cutting, is removed to form a recess (34). The recess (34) may extend a predetermined length from the second side (26) of the inner race (32). As shown in FIG. 6, the recess (34) may be formed in the part corresponding to the inner ball track (33), and the part between the inner ball tracks (33) is formed normally according to the original length. By applying the recess (34), processing can be simplified and the weight of the product can be reduced.

[0044] Additionally, the inner race (32) includes a spline (35) for spline coupling with the spline (42) of the connecting shaft (41), and at this time, no spline is formed on the inner surface (37) of the normally formed portion between the inner ball tracks (33). By doing so, defects caused by excessive interlocking during assembly with the connecting shaft (41) due to the amount of heat treatment deformation of the spline can be eliminated.

[0045] 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. An outer race including multiple outer ball tracks; An inner race comprising a plurality of inner ball tracks paired with the above outer ball track; A plurality of balls each disposed in the space formed by the paired outer ball track and the inner ball track; and It includes a ball cage disposed between the outer race and the inner race and accommodating the plurality of balls, In the non-angled state of the outer race and the inner race, the inner circumference center line of the ball cage, which passes through the center of curvature of the inner circumference of the ball cage and is orthogonal to the longitudinal axis of the inner race, and the outer circumference center line of the ball cage, which passes through the center of curvature of the outer circumference of the ball cage and is orthogonal to the longitudinal axis of the outer race, are each offset from the ball center line connecting the centers of the plurality of balls. The above inner ball track is a constant velocity joint in which at least some of the remaining sections, excluding the section of the ball's movement when the outer race and the inner race are cut, are formed by incomplete machining.

2. In Paragraph 1, The above outer lace includes an open side and a joined side, and The section formed by the incomplete processing among the sections of the inner ball track is a constant velocity joint extending by a preset length from the side located on the open side among the two sides of the inner race.

3. In Paragraph 2, The section formed by the above incomplete processing is a constant velocity joint having a length of less than 40% of the total length of the inner ball track.

4. In Paragraph 1, A constant velocity joint in which the portion including the ball behavior portion when the outer race and the inner race are cut is formed by complete machining, and the remaining portion excluding the portion formed by complete machining is formed by incomplete machining.

5. In Paragraph 4, The above complete processing forms the inner ball track by a forging process, a subsequent forming process, and a heat treatment process, and The above incomplete processing is a constant velocity joint that forms the inner ball track by omitting the subsequent forming process and by the forging process and the heat treatment process.

6. In Paragraph 5, A constant velocity joint in which the forging process is a cold forging process, the subsequent forming process is a cold sizing process, and the heat treatment process is a carburizing heat treatment process.

7. In Paragraph 5, A constant velocity joint in which the forging process is a hot forging process, the subsequent forming process is a milling process, and the heat treatment process is a high-frequency heat treatment process.

8. An outer race comprising multiple outer ball tracks; An inner race comprising a plurality of inner ball tracks paired with the above outer ball track; A plurality of balls each disposed in the space formed by the paired outer ball track and the inner ball track; and It includes a ball cage disposed between the outer race and the inner race and accommodating the plurality of balls, In the non-angled state of the outer race and the inner race, the inner circumference center line of the ball cage, which passes through the center of curvature of the inner circumference of the ball cage and is orthogonal to the longitudinal axis of the inner race, and the outer circumference center line of the ball cage, which passes through the center of curvature of the outer circumference of the ball cage and is orthogonal to the longitudinal axis of the outer race, are each offset from the ball center line connecting the centers of the plurality of balls. The above inner ball track is a constant velocity joint configured such that at least a portion of the remaining section, excluding the ball movement section when the outer race and the inner race are cut, is removed to form a depression.

9. In Paragraph 1 or Paragraph 8, The above outer lace includes an open side and a joined side, and The above inner surface center line is a constant velocity joint offset from the ball center line toward the open side.

10. In Paragraph 9, The above outer surface center line is a constant velocity joint offset from the ball center line toward the coupling side.

11. In Paragraph 1 or Paragraph 8, The above inner race is a constant velocity joint including a spline formed on the inner surface.

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