Constant velocity joint

Abstract

This constant velocity joint comprises: an outer joint member defining a longitudinal axis and including a first outer ball track and a second outer ball track; an inner joint member including a first inner ball track paired with the first outer ball track, and a second inner ball track paired with the second outer ball track; a plurality of balls; and a ball cage accommodating the plurality of balls. The outer joint member comprises an open side and a coupling side facing each other along the longitudinal axis. The pair of the first outer ball track and the first inner ball track forms a first aperture angle toward the open side in a non-articulated state, and the pair of the second outer ball track and the second inner ball track forms a second aperture angle toward the coupling side in a non-articulated state. The center line of the first outer ball track comprises a first coupling side arc through which a joint center surface passes and a first open side arc connected to the first coupling side arc. The center line of the second outer ball track comprises an intermediate arc through which the joint center surface passes, and a second coupling side arc and a second open side arc respectively connected to both sides of the intermediate arc.

Description

constant velocity joint

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

[0002] A constant velocity joint (CVJ), which functions as a power transmission element, is a component of the drivetrain that transmits the driving force generated by a vehicle's power source, such as an internal combustion engine or electric motor. As is well known, CVJs are designed to transmit rotational driving force while allowing for angular and axial displacements that occur during vehicle operation.

[0003] A so-called fixed constant velocity joint includes an outer joint member, an inner joint member, a plurality of balls arranged in the outer ball track of the outer joint member and the inner ball track of the inner joint member, and a ball cage accommodating the plurality of balls. The balls are rotatably supported on the contact surfaces of the outer ball groove and the inner ball groove, respectively, thereby transmitting torque between the outer joint member and the inner joint member. Among these fixed constant velocity joints, there is a constant velocity joint, the so-called counter track joint, in which some of the pairs of outer ball tracks and inner ball tracks have an aperture angle that faces the open side at the joint center plane, and the rest have an aperture angle that faces the mating side at the joint center plane. Such a counter track joint has advantages in many aspects, but there is room for improvement in terms of maximum cutting angle, efficiency, and durability.

[0004] The matters described in the technical background of this invention are written to enhance understanding of the background of the invention and may include matters that are not already known in the field to which this technology belongs.

[0005] - Prior art document: U.S. Patent Publication No. US7,396,285

[0006] The problem to be solved by the present invention is to provide a counter track type constant velocity joint that not only achieves a large maximum cutting angle but also has improved durability and efficiency.

[0007] The technical problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0008] A constant velocity joint according to an embodiment of the present invention includes an outer joint member defining a longitudinal axis and including a first outer ball track and a second outer ball track; an inner joint member including a first inner ball track paired with the first outer ball track and a second inner ball track paired with the second outer ball track; a plurality of balls respectively arranged in the pairs of the first outer ball track and the first inner ball track and the pairs of the second outer ball track and the second inner ball track; and a ball cage arranged between the outer joint member and the inner joint member and accommodating the plurality of balls. The outer joint member includes an open side and a mating side which are opposite to each other along the longitudinal axis. The pair of the first outer ball track and the first inner ball track forms a first opening angle directed toward the open side in a non-cut state, and the pair of the second outer ball track and the second inner ball track forms a second opening angle directed toward the mating side in a non-cut state. The center line of the first outer ball track includes a first engagement-side arc passing through the joint center plane and a first open-side arc connected to the first engagement-side arc. The center line of the second outer ball track includes a middle arc passing through the joint center plane, and a second engagement-side arc and a second open-side arc connected to each of the two sides of the middle arc.

[0009] The first engagement-side arc may have a curvature that is convex in the radial direction and the first open-side arc may have a curvature that is convex in the radial direction, and the second engagement-side arc and the intermediate arc may each have a curvature that is convex in the radial direction and the second open-side arc may have a curvature that is convex in the radial direction.

[0010] The center of curvature of the first coupling-side arc is spaced apart from the joint center plane to form a first axial offset,

[0011] The center of curvature of the intermediate arc may be spaced apart from the joint center plane to form a second axial offset, and the first axial offset and the second axial offset may be positioned in opposite directions with respect to the joint center plane.

[0012] The first axial offset may be directed toward the open side from the joint center plane, and the second axial offset may be directed toward the engagement side from the joint center plane.

[0013] The center of curvature of the first coupling side arc and the center of curvature of the intermediate arc may be located on the longitudinal axis.

[0014] A turning point connecting the first engagement-side arc and the first open-side arc may be spaced apart from a plane perpendicular to the longitudinal axis toward the open side while passing through the center of curvature of the first engagement-side arc, and a turning point connecting the intermediate arc and the second open-side arc may be spaced apart from the joint center plane toward the open side.

[0015] The center of curvature of the first engagement-side arc may be spaced apart from the joint center plane toward the open side, and the center of curvature of the first open-side arc may be located radially outside the outer joint member. The center of curvature of the intermediate arc may be spaced apart from the joint center plane toward the engagement side. The center of curvature of the second engagement-side arc may be spaced apart from a plane perpendicular to the longitudinal axis while passing through the center of curvature of the intermediate arc, and the center of curvature of the second open-side arc may be located radially outside the outer joint member.

[0016] The radius of curvature of the first joining-side arc may be smaller than the radius of curvature of the first open-side arc, and the radius of curvature of the second joining-side arc may be smaller than the radius of curvature of the intermediate arc and larger than the radius of curvature of the second open-side arc.

[0017] The radius of curvature of the first open-side arc may be greater than the radius of curvature of the second open-side arc.

[0018] According to the present invention, by adjusting the track center lines of a pair of ball tracks having an opening angle facing the open side in a non-cutting state and the track center lines of a pair of ball tracks having an opening angle facing the mating side in a non-cutting state, a constant velocity joint having a large maximum cutting angle and improved durability and efficiency can be implemented.

[0019] In addition, various effects that can be obtained or expected due to embodiments of the present invention are disclosed directly or implicitly in the detailed description of the embodiments of the present invention.

[0020] The accompanying drawings, which are intended to aid in understanding the present invention, provide embodiments of the present invention along with a detailed description. However, the technical features of the present invention are not limited to any specific drawings, and the features disclosed in each drawing may be combined to form new embodiments. The embodiments of the present specification may be better understood by referring to the following description in conjunction with the accompanying drawings, in which similar reference numerals designate identical or functionally similar elements.

[0021] Figure 1 is a front view of a constant velocity joint according to an embodiment of the present invention.

[0022] Figure 2 is an exploded perspective view of a constant velocity joint according to an embodiment of the present invention.

[0023] Figure 3 is a cross-sectional view taken along line AA of Figure 1.

[0024] Figure 4 is a cross-sectional view taken along line BB of Figure 1.

[0025] FIG. 5 is a drawing showing the center line of the outer ball track of the outer joint member illustrated in FIG. 3.

[0026] Fig. 6 is a drawing showing the center line of the inner ball track of the inner joint member illustrated in Fig. 3.

[0027] Fig. 7 is a drawing showing the center line of the outer ball track of the outer joint member illustrated in Fig. 4.

[0028] Fig. 8 is a drawing showing the center line of the inner ball track of the inner joint member illustrated in Fig. 4.

[0029] It should be understood that the drawings referenced above are not necessarily drawn to scale and are intended to provide brief representations of various features that illustrate the fundamental principles of the present invention. For example, specific design features of the present invention, including specific dimensions, orientations, positions, and shapes, will be determined in part by the specific intended application and usage environment.

[0030] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the described embodiments.

[0031] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise. It should also be understood that the terms "comprises" and / or "comprising," as used herein, indicate the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude 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 and all combinations of one or more of the associated listed items. The term "coupled" indicates a physical relationship between two components in which the components are directly connected to one another or are indirectly connected through one or more intervening components.

[0032] In describing the components of the present invention, when it is described that a component is “connected,” “coupled,” or “connected” to another component, it should be understood that the component may be directly connected, coupled, or connected to the other component, but another component may also be “connected,” “coupled,” or “connected” between each component.

[0033] FIG. 1 is a front view of a constant velocity joint according to an embodiment of the present invention, and FIG. 2 is an exploded perspective view of a constant velocity joint according to an embodiment of the present invention. FIG. 3 is a cross-sectional view taken along line AA of FIG. 1, and FIG. 4 is a cross-sectional view taken along line BB of FIG. 1. Referring to FIGS. 1 to 4, a constant velocity joint (10) includes an outer joint member (11), an inner joint member (12), a plurality of balls (13), and a ball cage (14). Although not explicitly shown in the drawings, the outer joint member (11) and the inner joint member (12) may be respectively connected to different power transmission elements. The outer joint member (11) and the inner joint member (12) rotate at a constant velocity by the action of the balls (13), and thereby, rotational power, i.e., torque, may be transmitted between the power transmission elements respectively connected to the outer joint member (11) and the inner joint member (12).

[0034] An outer joint member (11) having a roughly U-shape includes a closed-structured coupling side (15), an open side (16), and an inner space (17). The outer joint member (11) forms a longitudinal axis (X), and the coupling side (15) and the open side (16) are positioned opposite to each other along the longitudinal axis (X). An inner joint member (12) is inserted into the inner space (17) of the outer joint (11) through the open side (16). The inner joint member (12) includes a through hole (19) formed along the longitudinal direction, and a power transmission element can be inserted into the through hole (19) and fastened to rotate together with the inner joint member (12), for example, through a spline coupling of a shaft.

[0035] The inner circumferential surface (21) forming the internal space (17) of the outer joint member (11) has an approximately spherical shape, and correspondingly, the outer circumferential surface (22) of the inner joint member (12) may have an approximately spherical shape. In addition, correspondingly, the ball cage (14) may have an approximately spherical outer circumferential surface and an inner circumferential surface. The outer circumferential surface of the ball cage (14) faces the inner circumferential surface (21) of the outer joint member (11), and the inner circumferential surface of the ball cage (14) faces the outer circumferential surface (22) of the inner joint member (12). The ball cage (14) includes a plurality of windows (23) each accommodating a plurality of balls (13). As is known, the inner joint member (12) is configured so that the angle of the outer joint member (11) can be formed. Figures 1, 3 and 4 illustrate a case where the outer joint member (11) and the inner joint member (12) are aligned, i.e., in a non-angled state, and in the angular state, a relative angular displacement occurs between the inner joint member (12) and the outer joint member (11). When an angular displacement occurs between the outer joint member (11) and the inner joint member (12), an angular displacement of the ball cage (14) also occurs, and at this time, a positional displacement of the ball (13) also occurs.

[0036] The outer joint member (11) includes a plurality of first and second outer ball tracks (31, 32) formed on the inner surface (21), and correspondingly, the inner joint member (12) includes a plurality of first and second inner ball tracks (33, 34) formed on the outer surface (22). The first outer ball track (31) and the first inner ball track (33) form a pair, and the second outer ball track (32) and the second inner ball track (34) form a pair. Four first outer ball tracks (31) and four second outer ball tracks (32) may be provided, and the first outer ball tracks (31) and the second outer ball tracks (32) may be arranged alternately at equal intervals along the circumferential direction. The number of balls (13) may be eight, and the balls (13) may be arranged in pairs of outer ball tracks (31, 32) and inner ball tracks (33, 34), respectively. As shown in FIGS. 1, 3, and 4, the pair of first outer and inner ball tracks (31, 33) is arranged to face each other, and the pair of second outer and inner ball tracks (32, 34) is arranged to face each other.

[0037] Referring to FIGS. 3 and 4, the first outer ball track (31) and the first inner ball track (33) forming a pair form a first aperture angle (α) facing the open side (16) in a non-cut state, and the second outer ball track (32) and the second inner ball track (34) forming a pair form a second aperture angle (β) facing the engagement side (15) in a non-cut state. Here, the concept of the opening angle is generally known in the technical field to which the present invention belongs, and may mean an angle formed between the center trajectory of a ball moving on the outer ball track and the center trajectory of a ball moving on the inner ball track. As illustrated in FIGS. 3 and 4, a joint center plane (P) is defined by the centers of the plurality of balls (13) in the non-cut state of the constant velocity joint.

[0038] Referring to FIGS. 5 to 8, the first and second outer ball tracks (31, 32) each have a center line (35, 36), and the first and second inner ball tracks (33, 34) each have a center line (37, 38). Here, the center line can be understood to mean the center trajectory of a ball moving on the ball track. FIG. 5 illustrates the first outer ball track (31) of the outer joint member (11) and its center line (35), and FIG. 6 illustrates the first inner ball track (33) of the inner joint member (12) and its center line (37). FIG. 7 illustrates the second outer ball track (32) of the outer joint member (11) and its center line (36), and FIG. 8 illustrates the second inner ball track (34) of the inner joint member (12) and its center line (38).

[0039] Referring to Fig. 5, the center line (35) of the first outer ball track (31) includes two arcs (41, 42) connected by a turning point (T1). The joint center plane (P) passes through the engagement-side arc (41). The engagement-side arc (41), which is positioned closer to the engagement side (15), and the open-side arc (42), which is positioned closer to the open side (16), have curvatures in opposite directions with respect to the radial direction. The engagement-side arc (41) has a curvature that is convex radially outward with respect to the longitudinal axis (X), and the open-side arc (42) has a curvature that is convex radially inward. Specifically, the engagement-side arc (41) has a center of curvature (C1) that is positioned on the longitudinal axis (X), and the open-side arc (42) has a center of curvature (C2) that is positioned outside the outer joint member (11). At this time, the radius of curvature (R1) of the joining side arc (41) is formed to be smaller than the radius of curvature (R2) of the opening side arc (42).

[0040] The turning point (T1) is configured to form an inflection point between two arcs (41, 42). Here, as illustrated in FIG. 5, the joining-side arc (41) is located radially inward from the tangent line (L1) at the turning point (T1), and the opening-side arc (42) is located radially outward from the tangent line (L1) at the turning point (T1).

[0041]

[0042] *The center of curvature (C1) of the joint-side arc (41) is formed to have an axial offset (O1) from the joint center plane (P) toward the open side (16). That is, the center of curvature plane (P1) that is perpendicular to the longitudinal axis (X) and includes the center of curvature (C1) is spaced apart from the joint center plane (P) toward the open side (16) in the axial direction by the axial offset (O1). In addition, the turning point (T1) is spaced apart from the center of curvature plane (P1) toward the open side (16). The ratio (= O1 / D1) of the axial offset (O1) of the center of curvature (C1) to the diameter of the circle formed by the centers of the plurality of balls (13) in the non-cut state, the so-called Ball Circle Diameter (BCD) (D1), may be in the range of 0.050 to 0.054.

[0043] The center line (37) of the first inner ball track (33) paired with the first outer ball track (31) is formed to be approximately symmetrical with the center line (35) of the first outer ball track (31) with respect to the joint center plane (P). Referring to Fig. 6, the center line (37) of the first inner ball track (33) includes two arcs (43, 44) connected by a turning point (T2). The open-side arc (43) positioned closer to the open side (16) and the engagement-side arc (44) positioned closer to the engagement side (15) have curvatures that are opposite to each other in the radial direction. The open-side arc (43) has a curvature that is convex radially outward with respect to the longitudinal axis (X), and the engagement-side arc (44) has a curvature that is convex radially inward. Specifically, the open-side arc (43) has a center of curvature (C3) located on the longitudinal axis (X), and the mating-side arc (44) has a center of curvature (C4) located outside the inner joint member (12). At this time, the radius of curvature (R3) of the open-side arc (43) is formed to be smaller than the radius of curvature (R4) of the mating-side arc (44).

[0044] The turning point (T2) is configured to form an inflection point between two arcs (43, 44). Here, as illustrated in FIG. 6, the open-side arc (43) is located radially inward from the tangent line (L2) at the turning point (T2), and the joining-side arc (44) is located radially outward from the tangent line (L2) at the turning point (T2).

[0045] The center of curvature (C3) of the open-side arc (43) is formed to have an axial offset (O2) from the joint center plane (P) toward the mating side (15). That is, the center of curvature plane (P2) that is perpendicular to the longitudinal axis (X) and includes the center of curvature (C3) is spaced apart from the joint center plane (P) in the axial direction toward the mating side (15) by the axial offset (O2). In addition, the turning point (T2) is spaced apart from the center of curvature plane (P2) toward the mating side (15). In the non-cut state, the ratio (= O2 / D2) of the axial offset (O2) of the center of curvature (C3) to the BCD (D2) of the plurality of balls (13) may fall within a range of 0.050 to 0.054.

[0046] Referring to Fig. 7, the center line (36) of the second outer ball track (32) includes three arcs (51, 52, 53) that are sequentially connected by turning points (T3, T4). The engagement-side arc (51) and the open-side arc (53) are positioned close to the engagement side (15) and the open side (16), respectively, and the intermediate arc (52) is connected to the engagement-side arc (51) and the open-side arc (53) via the turning points (T3, T4), respectively. At this time, the joint center plane (P) passes through the intermediate arc (52).

[0047] The mating-side arc (51) and the intermediate arc (52) have a curvature that is convex radially outward with respect to the longitudinal axis (X), and the open-side arc (53) has a curvature that is convex radially inward. Specifically, the mating-side arc (51) has a center of curvature (C5) and a radius of curvature (R5) that are spaced radially outwardly closer to the longitudinal axis (X), and the intermediate arc (52) has a center of curvature (C6) and a radius of curvature (R6) that are located on the longitudinal axis (X). Accordingly, the radius of curvature (R5) of the mating-side arc (51) is smaller than the radius of curvature (R6) of the intermediate arc (52). Here, the center of curvature (C6) of the intermediate arc (52) is configured to be spaced from the joint center plane (P) toward the mating side (15) to have an axial offset (O3). In addition, the turning point (T3) connecting the joining side arc (51) and the intermediate arc (52) is spaced from the joining side (15) from the plane perpendicular to the longitudinal axis (X), i.e., the curvature center plane (P3), passing through the center of curvature (C6) of the intermediate arc (52).

[0048] The open-side arc (53) is connected to the intermediate arc (52) by a turning point (T4) spaced from the joint center plane (P) toward the open side (16). The open-side arc (53) has a center of curvature (C7) located on the outside of the outer joint member (11) and a radius of curvature (R7). At this time, the radius of curvature (R7) of the open-side arc (53) is formed to be smaller than the radius of curvature (R5) of the joint-side arc (51), whereby the radius of curvature (R6) of the intermediate arc (52) becomes the largest and the radius of curvature (R7) of the open-side arc (53) becomes the smallest. As a result, in the central portion of the second outer ball track (32), the radial change of the movement trajectory of the ball (13) is relatively gentle, thereby reducing friction and enabling stable operation, and in a portion close to the open side (16), a relatively large change occurs radially outward, enabling implementation of a high cutting angle.

[0049] A turning point (T4) connecting the intermediate arc (52) and the open-side arc (53) is configured to form an inflection point between the intermediate arc (52) and the open-side arc (53). Here, as illustrated in FIG. 7, the intermediate arc (52) is located radially inward from the tangent line (L3) of the center line (36) at the turning point (T4), and the open-side arc (53) is located radially outward from the tangent line (L3).

[0050] The center of curvature (C6) of the intermediate arc (52) is formed to have an axial offset (O3) from the joint center plane (P) toward the engagement side (15). That is, the center of curvature plane (P3) that is perpendicular to the longitudinal axis (X) and includes the center of curvature (C6) is spaced apart from the joint center plane (P) toward the engagement side (15) in the axial direction by the axial offset (O3). In addition, the turning point (T4) is spaced apart from the joint center plane (P) toward the open side (16). In the non-cut state, the ratio (= O3 / D3) of the axial offset (O3) of the center of curvature (C6) to the BCD (D3) of the plurality of balls (13) may fall within a range of 0.050 to 0.054.

[0051] Referring to FIGS. 5 and 7, the radius of curvature (R2) of the open-side arc (42) of the first outer ball track (31) is larger than the radius of curvature (R7) of the open-side arc (53) of the second outer ball track (32). This means that the open-side end of the second outer ball track (32) having an open angle toward the engagement side (15) has a relatively large radial change, thereby enabling a larger cutting angle to be implemented.

[0052] Referring to FIGS. 5 and 7, the joint-side center line (41) of the first outer ball track (31) and the middle center line (52) of the second outer ball track (32) have offsets (O1, O3) of the same size in opposite directions with respect to the joint center plane (P). As a result, the longitudinal force acting on the ball (13) during operation of the constant velocity joint is offset, thereby reducing friction.

[0053] The center line (38) of the second inner ball track (34) paired with the second outer ball track (32) is formed to be approximately symmetrical with the center line (36) of the second outer ball track (32) with respect to the joint center plane (P). Referring to Fig. 8, the center line (38) of the second inner ball track (34) includes three arcs (55, 56, 57) that are sequentially connected by turning points (T5, T6). The open-side arc (55) and the engaging-side arc (57) are positioned close to the open-side (16) and the engaging-side (15), respectively, and the middle arc (56) is connected to the open-side arc (55) and the engaging-side arc (57), respectively, via the turning points (T5, T6).

[0054] The open-side arc (55) and the intermediate arc (56) have a curvature that is convex radially outward with respect to the longitudinal axis (X), and the joint-side arc (57) has a curvature that is convex radially inward. Specifically, the open-side arc (55) has a center of curvature (C8) and a radius of curvature (R8) that are spaced radially outwardly closer to the longitudinal axis (X), and the intermediate arc (56) has a center of curvature (C9) and a radius of curvature (R9) that are located on the longitudinal axis (X). Accordingly, the radius of curvature (R8) of the open-side arc (55) is smaller than the radius of curvature (R9) of the intermediate arc (56). Here, the center of curvature (C9) of the intermediate arc (56) is configured to be spaced from the joint center plane (P) toward the open side (16) to have an axial offset (O4). In addition, the turning point (T6) connecting the open side arc (55) and the intermediate arc (56) is spaced from the open side (16) from the plane perpendicular to the longitudinal axis (X), i.e., the curvature center plane (P4), passing through the center of curvature (C9) of the intermediate arc (56).

[0055] The joining side arc (57) is connected to the middle arc (56) by a turning point (T6) spaced from the joint center plane (P) to the joining side (15). The joining side arc (57) has a center of curvature (C) located on the outside of the inner joint member (12).10 ) and has a radius of curvature (R 10 ) has. At this time, the radius of curvature (R) of the joining side arc (57) 10 ) is formed to be smaller than the radius of curvature (R8) of the open side arc (55), whereby the radius of curvature (R9) of the middle arc (56) is the largest and the radius of curvature (R) of the joining side arc (57) is the largest. 10 ) becomes the smallest.

[0056] A turning point (T6) connecting the intermediate arc (56) and the joining-side arc (57) is configured to form an inflection point between the intermediate arc (56) and the joining-side arc (57). Here, as illustrated in FIG. 8, the intermediate arc (56) is located radially inward from the tangent line (L4) of the center line (38) at the turning point (T6), and the joining-side arc (57) is located radially outward from the tangent line (L4).

[0057] The center of curvature (C9) of the intermediate arc (56) is formed to have an axial offset (O4) from the joint center plane (P) toward the open side (16). That is, the center of curvature plane (P4) that is perpendicular to the longitudinal axis (X) and includes the center of curvature (C9) is spaced apart from the joint center plane (P) toward the open side (16) in the axial direction by the axial offset (O4). In addition, the turning point (T6) is spaced apart from the joint center plane (P) toward the engaging side (15). In the non-cut state, the ratio (= O4 / D4) of the axial offset (O4) of the center of curvature (C9) to the BCD (D4) of the plurality of balls (13) may fall within a range of 0.050 to 0.054.

[0058] Although the 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 that can be easily modified by a person having ordinary skill in the art to which the present invention pertains and are recognized as equivalent from the embodiments of the present invention.

Claims

1. An outer joint member defining a longitudinal axis and including a first outer ball track and a second outer ball track; An inner joint member including a first inner ball track paired with the first outer ball track, and a second inner ball track paired with the second outer ball track; A plurality of balls arranged in each of the pairs of the first outer ball track and the first inner ball track, and the pairs of the second outer ball track and the second inner ball track; and A ball cage is disposed between the outer joint member and the inner joint member and includes a ball cage that accommodates the plurality of balls. The above outer joint member includes an open side and a joining side which are opposite to each other along the longitudinal axis, The pair of the first outer ball track and the first inner ball track forms a first open angle facing the open side in a non-cut state, The pair of the second outer ball track and the second inner ball track forms a second open angle facing the joining side in a non-cut state, The center line of the first outer ball track includes a first mating-side arc passing through the joint center plane and a first open-side arc connected to the first mating-side arc, A constant velocity joint including a center line of the second outer ball track, a middle arc passing through the joint center plane, and a second engagement-side arc and a second open-side arc extending respectively to both sides of the middle arc.

2. In paragraph 1, The first coupling-side arc has a radially outward convex curvature and the first open-side arc has a radially inward convex curvature, A constant velocity joint in which the second coupling-side arc and the intermediate arc each have a radially outward convex curvature and the second open-side arc has a radially inward convex curvature.

3. In paragraph 2, The center of curvature of the first coupling-side arc is spaced apart from the joint center plane to form a first axial offset, The center of curvature of the above intermediate arc is spaced from the center plane of the above joint to form a second axial offset, A constant velocity joint in which the first axial offset and the second axial offset are located in opposite directions with respect to the joint center plane.

4. In paragraph 3, The first axial offset is directed toward the open side from the joint center plane, The above second axial offset is a constant velocity joint from the joint center plane toward the coupling side.

5. In paragraph 4, A constant velocity joint in which the center of curvature of the first coupling side arc and the center of curvature of the intermediate arc are located on the longitudinal axis.

6. In paragraph 4, The turning point connecting the first coupling-side arc and the first open-side arc is spaced apart from a plane perpendicular to the longitudinal axis toward the open side while passing through the center of curvature of the first coupling-side arc, A constant velocity joint in which the turning point connecting the above-mentioned intermediate arc and the above-mentioned second open-side arc is spaced apart from the joint center plane toward the open side.

7. In paragraph 2, The center of curvature of the first joint-side arc is spaced apart from the joint center plane toward the open side, The center of curvature of the first open-side arc is located radially outside the outer joint member, The center of curvature of the above intermediate arc is spaced from the joint center plane toward the joining side, The center of curvature of the second coupling-side arc is spaced from the plane perpendicular to the longitudinal axis while passing through the center of curvature of the intermediate arc toward the coupling side, A constant velocity joint in which the center of curvature of the second open-side arc is located radially outside the outer joint member.

8. In paragraph 7, The radius of curvature of the first coupling-side arc is smaller than the radius of curvature of the first open-side arc, A constant velocity joint in which the radius of curvature of the second coupling-side arc is smaller than the radius of curvature of the intermediate arc and larger than the radius of curvature of the second open-side arc.

9. In paragraph 7, A constant velocity joint in which the radius of curvature of the first open-side arc is greater than the radius of curvature of the second open-side arc.

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