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 for accommodating the plurality of balls. The outer joint member includes an open side and a coupling side opposite to each other along the longitudinal axis. A pair of the first outer ball track and the first inner ball track forms a first opening angle toward the opening side in a non-bent state, and a pair of the second outer ball track and the second inner ball track forms a second opening angle toward the coupling side in a non-angled state. The first outer ball track and the first inner ball track include a first outer ball track trajectory and a first inner ball track trajectory, respectively, and the center of curvature of the first outer ball track trajectory and the center of curvature of the first inner ball track trajectory are located beyond the longitudinal axis.

Description

constant velocity joint

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

[0002] A constant velocity joint, used to transmit power in an automobile, is a device that transmits rotational power at a constant velocity. Typically, a constant velocity joint is part of a so-called driveshaft, which transmits power generated by the vehicle's drivetrain, such as the transmission of an internal combustion engine vehicle or the motor of an electric vehicle, to the wheels at a constant velocity. The driveshaft actively responds to the steering of the wheels or vibrations or shocks from the road surface to transmit power while minimizing power loss. A driveshaft typically includes an inboard joint that receives power from the transmission or motor, an outboard joint that transmits rotational power to the wheels, and an intermediate shaft that connects the inboard and outboard joints. Typically, the outboard joint is configured to absorb only the rotational displacement of the wheel side, and the inboard joint is configured to absorb the longitudinal and rotational displacement of the suspension and the wheel side.

[0003] The so-called Rzeppa joint is configured to transmit rotational power by placing balls in the ball grooves of the outer race and the inner race, which are paired. To improve efficiency, a joint in which the ball grooves of the outer and inner joint members intersect has been introduced. While such joints typically use six balls, conventional Rzeppa joints typically use eight balls to reduce the outer diameter package. Applying eight balls to a joint with typical intersecting ball grooves results in a very narrow gap between adjacent ball grooves due to the nature of the intersecting ball grooves, and this reduces the web thickness, which can lead to a reduction in rigidity. For these reasons, applying eight balls to a typical joint with intersecting ball grooves to reduce the outer diameter is difficult.

[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 prior art in the field to which this technology belongs.

[0005] The problem to be solved by the present invention is to provide a constant velocity joint that can reduce the outer diameter while intersecting ball tracks to improve efficiency.

[0006] 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.

[0007] 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 first outer ball track and the first inner ball track each include a first outer ball track trajectory and a first inner ball track trajectory, and the center of curvature of the first outer ball track trajectory and the center of curvature of the first inner ball track trajectory are located beyond the longitudinal axis.

[0008] A line connecting the center of curvature of the first outer ball track trajectory and the center of curvature of the first inner ball track trajectory may be parallel to the longitudinal axis.

[0009] The first outer ball track and the second outer ball track may be arranged alternately along the circumferential direction of the outer joint member.

[0010] The inner surface of the outer joint member may include a cylindrical region to allow movement of the ball cage along the longitudinal axis.

[0011] The above balls can be provided in sets of eight.

[0012] The first inner ball track may further include an additional ball track trajectory for reinforcing rigidity that continues from the first inner ball track trajectory. The additional ball track trajectory may be provided at an end of the inner joint member on either side that has a deeper depth than the first inner ball track.

[0013] The above additional ball track trajectory can be formed as a reverse trajectory having a curvature in the opposite direction to the first inner ball track trajectory.

[0014] The distance (BCD) between the centers of the balls facing each other in a state where the balls aligned on the joint center plane in the non-cutting state move radially inward as much as possible and come into close contact with the first inner ball track I ) and the distance (BCD) between the centers of the balls facing each other in a state where the balls aligned with the joint center plane in the non-cut state move radially outward as much as possible and come into close contact with the first outer ball track O ) of the car (= BCD) I - BCD O ) can range from 0 to 0.050 mm.

[0015] In a non-cut state, when the ball is positioned on the joint center plane, the opening angle formed by the first outer ball track and the first inner ball track, and the opening angle formed by the second outer ball track and the second inner ball track may fall within a range of 4.5 degrees to 25 degrees.

[0016] In a non-cutting state, a ratio between the distance between the centers of the balls arranged facing each other in the pair of the first outer ball track and the first inner ball track and the radius of curvature of the track trajectory of the first outer ball track may fall within a range of 0.45 to 0.55.

[0017] In order to limit the stroke of the inner joint member along the longitudinal axis within the outer joint member, the outer surface of the inner joint member and the inner surface of the ball cage may be configured to interfere with each other at a preset point when the inner joint member is stroked.

[0018] According to another aspect of the present invention, a constant velocity joint 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 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 respectively form opening angles facing opposite directions in a non-cut state. An inner circumferential surface of the outer joint member is configured to allow movement of the ball cage along the longitudinal axis.

[0019] According to another aspect of the present invention, a constant velocity joint 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; eight 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 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 respectively form opening angles facing opposite directions in a non-angled state. The first outer ball track and the first inner ball track each include a first outer ball track trajectory and a first inner ball track trajectory, and the center of curvature of the first outer ball track trajectory and the center of curvature of the first inner ball track trajectory are located beyond the longitudinal axis.

[0020] According to the present invention, by forming ball tracks with different opening angles and intersecting them in the radial direction, efficiency can be improved while reducing the outer diameter.

[0021] 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.

[0022] Figure 1 is a perspective view of a constant velocity joint according to an embodiment of the present invention.

[0023] Figure 2 is a front view of a constant velocity joint according to an embodiment of the present invention.

[0024] Figure 3 is a cross-sectional view taken along line AA of Figure 2.

[0025] Figure 4 is a cross-sectional view taken along line BB of Figure 2.

[0026] Figure 5 is an exploded perspective view of a constant velocity joint according to an embodiment of the present invention.

[0027] Figures 6 and 7 show cross-sectional views of the outer joint member and the inner joint member, respectively, in the ball groove of the outer joint member and the ball groove of the inner joint member, respectively, having an opening angle facing the open side.

[0028] Figures 8 and 9 show cross-sectional views of the outer joint member and the inner joint member, respectively, in the ball groove of the outer joint member and the ball groove of the inner joint member, respectively, having an opening angle toward the joining side.

[0029] Fig. 10 is a drawing for explaining the shape of a ball track of an outer joint member and a ball track of an inner joint member having an opening angle facing the open side.

[0030] FIG. 11 is a drawing for explaining the ball center-to-center distance formed by the outer joint member of the constant velocity joint according to an embodiment of the present invention.

[0031] FIG. 12 is a drawing for explaining the distance between ball centers formed by the inner joint member of a constant velocity joint according to an embodiment of the present invention.

[0032] FIG. 13 is a drawing for explaining an appropriate allowable range of an opening angle toward the open side and an opening angle toward the mating side in a constant velocity joint according to an embodiment of the present invention.

[0033] FIG. 14 is a drawing for explaining the ratio of the radius of curvature of the ball center trajectory and the distance between ball centers in a constant velocity joint according to an embodiment of the present invention.

[0034] FIG. 15 is a drawing for explaining interference between a ball cage and an inner joint member to limit the stroking of the inner joint member in a direction in which the inner joint member is discharged outward from the outer joint member in a constant velocity joint according to an embodiment of the present invention.

[0035] FIG. 16 is a drawing for explaining interference between a ball cage and an inner joint member to limit stroking in the direction in which the inner joint member moves into the outer joint member in a constant velocity joint according to an embodiment of the present invention.

[0036] Figure 17 is a graph comparatively showing the torque loss of a constant velocity joint according to the present invention and a conventional constant velocity joint.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] FIG. 1 is a perspective view of a constant velocity joint according to an embodiment of the present invention, and FIG. 2 is a front 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. 2, and FIG. 4 is a cross-sectional view taken along line BB of FIG. 2. FIG. 5 is an exploded perspective view of a constant velocity joint according to an embodiment of the present invention. Referring to FIGS. 1 to 5, 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 speed by the action of the ball (13), thereby transmitting rotational power, i.e., torque, between the power transmission elements connected to the outer joint member (11) and the inner joint member (12), respectively.

[0042] 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 connected to rotate together with the inner joint member (12), for example, by a spline connection of a shaft.

[0043] The outer surface of the ball cage (14) faces the inner surface (21) of the outer joint member (11), and the inner surface of the ball cage (14) faces the outer 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 to be angled relative to the outer joint member (11). FIGS. 1 and 2 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 angled state, a relative angular displacement occurs between the inner joint member (12) and the outer joint member (11). When an angle 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 balls (13) also occurs.

[0044] 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 and 2, the pair of first outer and inner ball tracks (31, 33) are arranged to face each other, and the pair of second outer and inner ball tracks (32, 34) are arranged to face each other. The outer ball tracks (31, 32) are formed in a groove shape that is sunken radially outwardly of the joint on the inner peripheral surface (21) of the outer joint member (11), and the inner ball tracks (33, 34) are formed in a groove shape that is sunken radially inwardly of the joint on the outer peripheral surface (22) of the inner joint member (12). The outer ball tracks (31, 32) and the inner ball tracks (33, 34) extend in a direction approximately parallel to the longitudinal axis (X) of the joint.

[0045] The first outer ball track (31) and the first inner ball track (33) forming a pair form a first aperture angle (or funnel angle) (α) toward the open side (16) in a non-cut state as illustrated in FIG. 3, and the second outer ball track (32) and the second inner ball track (34) forming a pair form a second aperture angle (β) toward the engaging side (15) in a non-cut state as illustrated in FIG. 4. Here, the concept of the opening angle is generally known in the technical field to which the present invention pertains, and may mean an angle formed between the center trajectory of a ball moving on an outer ball track and the center trajectory of a ball moving on an inner ball track. As illustrated in FIGS. 3 and 4, in the non-cut state of the constant velocity joint, i.e., in a state where the joint angle is 0 degrees, a joint center plane (P) is defined by the centers of the plurality of balls (13). When the joint angle is 0 degrees, the centers of the balls (13) are located on the same plane, and the rolling motion of the balls (13) occurs according to the angle of the inner joint member (12) with respect to the outer joint member (11).

[0046] A pair of tracks having opening angles facing opposite directions are arranged alternately along the circumference of the joint, which forms a basic mechanism for implementing a stroke function that allows the inner joint member (12), ball cage (14), and ball (13), which are internal members of the constant velocity joint, to move along the direction of the longitudinal axis (X). In addition, by maintaining the balance of the force induced in the longitudinal axis (X) when torque is applied, the ball cage (14) is prevented from being tilted to one side, thereby minimizing internal friction, which reduces torque loss occurring in the constant velocity joint when the vehicle is driven, thereby improving fuel efficiency or power efficiency of the vehicle.

[0047] Figures 6 and 7 show cross-sectional views of an outer joint member and an inner joint member, respectively, in the ball groove of the outer joint member and the ball groove of the inner joint member, which have an opening angle toward the open side. Figures 8 and 9 show cross-sectional views of an outer joint member and an inner joint member, respectively, in the ball groove of the outer joint member and the ball groove of the inner joint member, which have an opening angle toward the mating side. Referring to Figures 5 and 6, in order to allow axial displacement of the ball cage (14) in the internal space of the outer joint member (11), the inner circumferential surface (21) of the outer joint member (11), which is in contact with the outer circumferential surface of the ball cage (14), includes a cylindrical section (41). As a result, the constant velocity joint (10) according to the embodiment of the present invention is implemented as a so-called plunging type constant velocity joint that allows axial displacement.

[0048] Referring to FIGS. 6 and 7, in the outer ball track (31) and inner ball track (33) having an opening angle toward the open side (16) in a non-cut state, the track tangent line (L) of the outer ball track (31) OUT_1 ) and the angle (α1) between the longitudinal axis (X) of the joint and the track tangent (L) of the inner ball track (33) IN_1 ) and the joint longitudinal axis (X) is the same value as the opening angle (α) mentioned above (α=α1+α2). In addition, referring to FIGS. 8 and 9, in the outer ball track (32) and the inner ball track (34) having an opening angle toward the joint side (15) in the non-cut state, the track tangent (L) of the outer ball track (32) OUT_2 ) and the angle (β1) between the longitudinal axis (X) of the joint and the track tangent (L) of the inner ball track (34) IN_2) and the joint longitudinal axis (X) is the same as the opening angle (β) mentioned above (β = β1 + β2). In this way, in the embodiment of the present invention, since the intersection between the ball tracks has a form that spreads out radially from the longitudinal axis (X) of the joint, the spacing (t1) between the outer ball tracks (31, 32), the spacing (t2) between the inner ball tracks (33, 34), and the thickness (t3) of the web of the ball cage (14) shown in FIG. 5 can be set to a level that can ensure the required rigidity. Here, the track tangent can be defined as a line that is perpendicular to the line connecting the ball (13) and the contact point of each track to the ball center in a non-cut state and passes through the contact point of the ball and the track, and here, the track trajectory corresponds to the trajectory of the line on the floor corresponding to the shape of the track, and can be understood to be parallel to the movement trajectory of the center of the ball moving on the track.

[0049] Fig. 10 is a drawing for explaining the shape of the ball track of the outer joint member and the ball track of the inner joint member having an opening angle toward the open side. Referring to Fig. 10, the track trajectory (TR) of the outer ball track (31) forming the opening angle toward the open side (16) O1 ) is the set radius of curvature (R O1 ) and is composed of an arc with a track trajectory (TR O1 ) of the center of curvature (C O1 ) is located beyond the longitudinal axis (X) of the joint. In addition, the track trajectory (TR) of the inner ball track (33) forming an opening angle toward the open side (16) I1 ) is the set radius of curvature (R I1 ) and is composed of an arc with a track trajectory (TR I1 ) of the center of curvature (C I1 ) is located beyond the longitudinal axis (X) of the joint. At this time, the track trajectory (TR) of the outer ball track (31) O1 ) of the center of curvature (C O1 ) and the track trajectory (TR) of the inner ball track (33)I1 ) of the center of curvature (C I1 ) connecting the line (L C1 ) is parallel to the longitudinal axis (X) of the joint. The stroke function and cutting, which are the basic performances of the constant velocity joint, are made possible by this center of curvature. In addition, the track trajectory (TR) of the outer ball track (31) O1 ) of the center of curvature (C O1 ) and the track trajectory (TR) of the inner ball track (33) I1 ) of the center of curvature (C I1 ) is placed beyond the joint longitudinal axis (X) to have a radius of curvature (R O1 , R I1 ) was enlarged to maximize the stroke length for the plunging function. In addition, the track trajectory (TR) of the outer ball track (31) O1 ) by making it curved, the outer diameter of the outer joint member (11) can be kept slim while the thickness of the open side (16) of the joint can be increased to supplement the rigidity. That is, the track trajectory (TR) of the outer ball track (31) O1 ) by forming a curve, the thickness of the flesh at the end of the open side (16) can be increased to increase the rigidity compared to the case of forming a straight trajectory. Referring to Fig. 10, the outer ball track (31) has a curved track trajectory (TR O1 ) the thickness of the opening (16) when the outer ball track has a straight track trajectory (TR S ) than the thickness of the open part when having the value (T) shown in Fig. 10 d ) can be thicker.

[0050] Among the ends of the inner joint member (12), a track trajectory for reinforcing rigidity may be added to the end with a deeper depth of the inner ball track (33, 34). Referring to Fig. 7, the inner ball track (33) forming an open angle toward the open side (16) is the track trajectory (TR) described above. I1 ) in addition to additional track trajectory (TR) for stiffness reinforcement I2) is formed to include the basic track trajectory (TR I1 ) and additional track trajectories (TR I2 ) intersect at the intersection (TP1) and the basic track trajectory (TR I1 ) is located close to the joint side (15) based on the intersection point (TP1), and an additional track trajectory (TR I2 ) is located close to the open side (16) of the joint. At this time, the basic track trajectory (TR I1 ) has a convex shape radially outward, while the additional track trajectory (TR I2 ) is formed in a reverse trajectory and is formed convexly inward in the radial direction. As a result, the thickness between the bottom of the inner ball track (33) and the inner surface of the inner joint member (12) at the end of the inner joint member (12) increases, resulting in increased rigidity of the end of the inner joint member (12), and a shallower ball groove depth, which can further increase the life of the forging die during forging of the ball groove.

[0051] Also, referring to Fig. 9, the inner ball track (34) forming an opening angle toward the joining side (15) is a basic radially outwardly convex track trajectory (TR I3 ) in addition to additional track trajectory (TR) for stiffness reinforcement I4 ) is formed to include the basic track trajectory (TR I3 ) and additional track trajectories (TR I4 ) intersect at the intersection (TP2) and the basic track trajectory (TR I3 ) is located close to the open side (16) of the joint based on the intersection point (TP2), and an additional track trajectory (TR I4 ) is located close to the joint side (15). At this time, the basic track trajectory (TR I3 ) has a convex shape radially outward, while the additional track trajectory (TR I4) is formed in a reverse trajectory and is formed convexly inward in the radial direction. As a result, the thickness between the bottom of the inner ball track (34) and the inner surface of the inner joint member (12) at the end of the inner joint member (12) increases, resulting in increased rigidity of the end of the inner joint member (12), and a shallower depth of the ball groove, which can further increase the life of the forging die during forging of the ball groove.

[0052] Fig. 11 is a drawing for explaining the ball center distance formed by the outer joint member of the constant velocity joint according to an embodiment of the present invention, and Fig. 12 is a drawing for explaining the ball center distance formed by the inner joint member of the constant velocity joint according to an embodiment of the present invention. The ball center distance (BCD) shown in Fig. 11 O ) is the center (BC) of the facing balls (13) aligned to the joint center plane (P) in the non-cutting state, moved radially outward as much as possible and in close contact with the outer ball track (31). O ) is the distance between the ball centers (BCD, Ball Center Dimension). And in Fig. 12, the distance between the ball centers (BCD) I ) is the center of the ball (13) aligned to the joint center plane (P) in the non-cut state, moved radially inward as much as possible and is in close contact with the inner ball track (31) (BC) I ) is the distance between the ball centers (BCD, Ball Center Dimension). In the embodiment of the present invention, when the inner joint member (12), the ball (13) and the ball cage (14) move in the direction of inflow into the inner side of the outer joint member (11) and when they move in the direction of discharge outward from the outer joint member (11), an excessively large stroke load (e.g., a load exceeding 300 N) that makes normal operation difficult is not generated, so that two ball center diameters (BCD) O , BCD I) to ensure proper interference. For smooth stroking operation, the difference in ball center diameter (= BCD) I - BCD O ) should not be less than 0. Considering this, in the embodiment of the present invention, the difference in ball center diameter (= BCD I - BCD O ) is set to fall within the range of 0 to 0.050 mm, thereby ensuring a smooth stroking function without the stroke load becoming too large.

[0053] FIG. 13 is a drawing for explaining the allowable range of the opening angle toward the open side and the opening angle toward the mating side in a constant velocity joint according to an embodiment of the present invention. In FIG. 13, a line including points indicated by triangles shows the change in the opening angle (opening angle 1) according to the stroke of the inner joint in a track pair having an opening angle toward the open side, and a line including points indicated by circles shows the change in the opening angle (opening angle 1) according to the stroke of the inner joint in a track pair having an opening angle toward the engagement side. In an embodiment of the present invention, the range of the opening angle is appropriately limited so that normal stroking is possible. In the graph of FIG. 13, moving to the left from the reference position where the stroke is 0 means a stroke toward the engagement side (15) of the outer joint member (11), and moving to the right means a stroke toward the open side (16) of the outer joint member (11). In FIG. 13, "stroke limit value 1" means a limit value of the stroke toward the engagement side (15) of the outer joint member (11), and "stroke limit value 2" means a limit value of the stroke toward the open side (16) of the outer joint member (11). In an embodiment of the present invention, a stroke allowance range, for example, The opening angle is set to fall within the range of -20 mm to 20 mm and 4 to 25 degrees.

[0054] Fig. 14 is a drawing for explaining the ratio of the radius of curvature of the ball center trajectory and the ball center diameter in a constant velocity joint according to an embodiment of the present invention. Referring to Fig. 14, the center (C) of balls (13) facing each other in a non-cut state B ), i.e. the distance between the ball centers (BCD) and the center of the moving ball (13) (C B ) trajectory, i.e. ball center trajectory (L BC ) radius of curvature (R) BC ) is set to a ratio of 0.45 to 0.55. By this ratio, an appropriate opening angle can be set for each stroke position.

[0055] FIG. 15 is a drawing for explaining interference between a ball cage and an inner joint member for limiting stroking in a direction in which an inner joint member is discharged out of an outer joint member in a constant velocity joint according to an embodiment of the present invention, and FIG. 16 is a drawing for explaining interference between a ball cage and an inner joint member for limiting stroking in a direction in which an inner joint member is introduced into an outer joint member in a constant velocity joint according to an embodiment of the present invention. As illustrated in FIG. 15, when the inner joint member (12) moves in the direction of the arrow and discharges in a direction in which it is discharged out of the outer joint member (11), interference occurs at an appropriate interference point between the outer surface of the inner joint member (12) and the inner surface of the ball cage (14), thereby limiting an appropriate amount of stroking. This can prevent the ball (13) from being detached when stroking in the outward direction. In addition, as illustrated in FIG. 16, when the inner joint member (12) moves in the direction of the arrow and is inserted into the inner joint member (11), interference occurs at an appropriate interference point between the outer surface of the inner joint member (12) and the inner surface of the ball cage (14) during insertion stroking.

[0056] Fig. 17 is a graph comparatively showing the torque loss of a constant velocity joint according to the present invention and a conventional constant velocity joint. Referring to Fig. 17, the constant velocity joint of the present invention is configured such that the ball tracks intersect in the radial direction, thereby enabling the application of eight balls, which allows for a significant reduction in the outer diameter of the constant velocity joint, thereby significantly reducing torque loss.

[0057] 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 first outer ball track and the first inner ball track each include a first outer ball track trajectory and a first inner ball track trajectory, A constant velocity joint in which the center of curvature of the first outer ball track trajectory and the center of curvature of the first inner ball track trajectory are located beyond the longitudinal axis.

2. In paragraph 1, A constant velocity joint in which a line connecting the center of curvature of the first outer ball track trajectory and the center of curvature of the first inner ball track trajectory is parallel to the longitudinal axis.

3. In paragraph 1, A constant velocity joint in which the first outer ball track and the second outer ball track are alternately arranged along the circumferential direction of the outer joint member.

4. In paragraph 1, A constant velocity joint in which the inner surface of the outer joint member includes a cylindrical region to allow movement of the ball cage along the longitudinal axis.

5. In paragraph 1, The above ball is a constant velocity joint equipped with eight balls.

6. In paragraph 1, The first inner ball track further includes an additional ball track trajectory for reinforcing rigidity that follows the first inner ball track trajectory, A constant velocity joint in which the above additional ball track trajectory is provided at the end of the inner joint member on both sides, at which the depth of the first inner ball track is deeper.

7. In paragraph 6, A constant velocity joint in which the above additional ball track trajectory is formed as a reverse trajectory having a curvature in the opposite direction to the above first inner ball track trajectory.

8. In paragraph 1, The distance (BCD) between the centers of the balls facing each other in a state where the balls aligned on the joint center plane in the non-cutting state move radially inward as much as possible and come into close contact with the first inner ball track I ) and the distance (BCD) between the centers of the balls facing each other in a state where the balls aligned with the joint center plane in the non-cut state move radially outward as much as possible and come into close contact with the first outer ball track O ) of the car (= BCD) I - BCD O ) is a constant velocity joint in the range of 0 to 0.050 mm.

9. In paragraph 1, A constant velocity joint in which, in a non-cut state, the ball is positioned on the joint center plane, an opening angle formed by the first outer ball track and the first inner ball track, and an opening angle formed by the second outer ball track and the second inner ball track are in a range of 4.5 degrees to 25 degrees.

10. In paragraph 1, A constant velocity joint in which the ratio between the distance between the centers of the balls arranged facing each other in the pair of the first outer ball track and the first inner ball track in a non-cutting state and the radius of curvature of the track trajectory of the first outer ball track is in the range of 0.45 to 0.

55.

11. In paragraph 1, A constant velocity joint configured such that the outer surface of the inner joint member and the inner surface of the ball cage interfere with each other at a preset point during the stroking movement of the inner joint member to limit the stroke of the inner joint member along the longitudinal axis within the outer joint member.

12. 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 pair of the first outer ball track and the first inner ball track and the pair of the second outer ball track and the second inner ball track each form an opening angle facing in opposite directions in a non-cut state, A constant velocity joint in which the inner surface of the outer joint member is configured to allow movement of the ball cage along the longitudinal axis.

13. 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; Eight balls each arranged in a pair of the first outer ball track and the first inner ball track, and a pair 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 pair of the first outer ball track and the first inner ball track and the pair of the second outer ball track and the second inner ball track each form an opening angle facing in opposite directions in a non-cut state, The first outer ball track and the first inner ball track each include a first outer ball track trajectory and a first inner ball track trajectory, A constant velocity joint in which the center of curvature of the first outer ball track trajectory and the center of curvature of the first inner ball track trajectory are located beyond the longitudinal axis.

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