Counter track joint and method for manufacturing the same

Abstract

The present invention relates to a constant velocity joint of counter-track specifications having a dual ball track structure of an outer ring and an inner ring, and a method for manufacturing the same. The present invention optimizes the process by soft milling the entire first and second ball tracks of the outer and inner rings and heat-treating them, and then selectively eliminating the hard milling step for ball tracks of a specific opening angle series.

Description

Technology Field

[0001] The present disclosure relates to a constant velocity joint used in a vehicle power transmission device, and more specifically, to a counter track joint having a structure in which ball tracks axially symmetrically arranged alternately on an outer ring and an inner ring, and a method for manufacturing the same. Background Technology

[0002] Generally, a constant velocity joint used in a vehicle's power transmission system is a component that transmits rotational power output from a transmission or differential to the drive wheels at a constant speed. A constant velocity joint largely comprises an outer race, an inner race, multiple balls that transmit power, and a cage that supports the balls.

[0003] Among these, a Counter Track Joint refers to a configuration consisting of two types of structures in which the ball tracks of the outer and inner rings are mutually symmetrical. Specifically, a first ball track and a second ball track, having shapes inclined in opposite directions or symmetrically along the axial direction, are alternately arranged along the circumference of the outer and inner rings, and the tracks of the outer ring and the inner ring are assembled by matching each other. This dual-track structure has the advantage of maximizing power transmission efficiency by widening the operating angle of the joint and reducing internal play.

[0004] However, the dual track structure of the aforementioned counter-track joint has a problem in that it inevitably requires a complex segmented machining process in terms of the manufacturing process. The conventional manufacturing process for general outer and inner ring ball tracks includes a primary raw machining stage, a heat treatment stage, and a finishing machining stage. First, the first ball track and the second ball track are primarily machined through a raw machining stage (B / G Soft Milling) that performs rough machining before heat treatment. Subsequently, a heat treatment stage is performed to secure the mechanical strength of the machined parts. After the heat treatment is completed, a post-heat treatment finishing machining stage (B / G Hard Milling) is performed to correct thermal deformation and secure final precision. At this time, in the conventional technology, due to the dual track structure unique to the counter-track joint, separate segmented machining had to be performed on the entire area of ​​the first ball track and the second ball track respectively during the post-heat treatment finishing machining stage.

[0005] The method of applying individual hard milling finishing processes to all tracks after heat treatment was a major cause of significant delays in manufacturing cycle times and had process limitations that accelerated the wear of expensive finishing tools and increased the load on equipment, thereby raising overall manufacturing costs.

[0006] 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. The problem to be solved

[0007] The problem that the present invention aims to solve is to provide a counter track joint and a method for manufacturing the same, which can maximize production efficiency by optimizing the manufacturing process of a counter track joint having a dual ball track structure of an outer ring and an inner ring.

[0008] Specifically, the problem that the present invention aims to solve is to provide a method for manufacturing a counter-track joint that can drastically shorten the overall manufacturing cycle time by intentionally omitting the machining process for specific tracks of the outer ring and inner ring during the hard milling step, which involves precisely finishing the metal that has been hardened after heat treatment.

[0009] Another problem that the present invention aims to solve is to provide a manufacturing method that can significantly reduce manufacturing costs and extend the lifespan of machining tools by reducing the number of finishing processes, which require relatively expensive tools and have high operational difficulty, by half.

[0010] Another problem that the present invention aims to solve is to provide a method for manufacturing a counter track joint that can reduce the physical processing load applied to production equipment by shortening the manufacturing process and increase the operational efficiency of limited processing equipment.

[0011] Another problem that the present invention aims to solve is to provide a counter track joint that maintains reliability without degrading final assembly quality and power transmission performance by precisely controlling the offset dimension of the track during the preceding soft milling stage, even if the finishing process of a specific track is omitted.

[0012] 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. means of solving the problem

[0013] A constant velocity joint according to an embodiment of the present invention comprises: an outer ring having a coupling side and an opening side facing each other, and having a first outer ball track and a second outer ball track alternately formed along a longitudinal axis on its inner surface along a circumferential direction; an inner ring movably disposed inside the opening side of the outer ring, having a first inner ball track and a second inner ball track formed on its outer surface to face the first and second outer ball tracks; a plurality of balls interposed between the first and second outer ball tracks and the first and second inner ball tracks to transmit rotational torque; and an annular ball cage having a plurality of windows formed to receive and support the plurality of balls. The outer ring and the inner ring implement a counter-track structure by forming a first opening angle in which the first outer ball track and the first inner ball track are mutually matched to spread out toward one side of the outer ring, and forming a second opening angle in which the second outer ball track and the second inner ball track are mutually matched to spread out toward the first opening angle. In either series of the first open-angle series ball track or the second open-angle series ball track, the surface of the ball track of the outer ring is formed as a finished surface after finishing machining following heat treatment, and in the other series, the surface of the ball track of the inner ring is formed as a finished surface after finishing machining following heat treatment. Among the entire ball tracks of the outer ring and the inner ring, a machining removal track is included in which the finishing machining is removed to maintain the raw machining surface state prior to heat treatment.

[0014] The above processing deletion track may be the first outer ball track forming the first opening angle and the second inner ball track forming the second opening angle.

[0015] The above processing deletion track may be the second outer ball track forming the second opening angle and the first inner ball track forming the first opening angle.

[0016] The ratio of the final design reference offset value of the above-mentioned processing deletion track and the raw processing offset value set in the raw processing stage of the above-mentioned processing deletion track can be controlled to a range greater than 1 and less than 1.05.

[0017] The above final design reference offset value and the above raw processing offset value may be axial offset values ​​or radial offset values.

[0018] According to an embodiment of the present invention, a method for manufacturing a constant velocity joint comprising the step of machining ball tracks formed on an outer ring and an inner ring comprises: (a) a step of forming a base track groove by performing raw machining in a state prior to heat treatment on the entirety of first and second outer ball tracks formed on the inner circumference of the outer ring and the entirety of first and second inner ball tracks formed on the outer circumference of the outer ring; (b) a step of performing heat treatment on the outer ring and the inner ring after the raw machining is completed; and (c) a step of performing finish machining on the ball tracks of the outer ring and the inner ring after the heat treatment is completed. The outer ring and the inner ring implement a counter-track structure by forming a first opening angle in which the first outer ball track and the first inner ball track are mutually matched to spread in one direction of the outer ring, and forming a second opening angle in which the second outer ball track and the second inner ball track are mutually matched to spread in the opposite direction to the first opening angle. Step (c) above removes the finishing machining of the outer ring ball track in either the first open angle series ball track or the second open angle series ball track, and removes the finishing machining of the inner ring ball track in the other series.

[0019] In step (c) above, the finishing process of the first outer ball track forming the first opening angle in the outer ring may be omitted and the finishing process performed only on the second outer ball track, and the finishing process of the second inner ball track forming the second opening angle in the inner ring may be omitted and the finishing process performed only on the first inner ball track.

[0020] In step (c) above, in the outer ring, the finishing process of the second outer ball track forming the second opening angle is omitted and the finishing process is performed only on the first outer ball track, and in the inner ring, the finishing process of the first inner ball track forming the first opening angle is omitted and the finishing process is performed only on the second inner ball track.

[0021] The ratio of the final design reference offset value of the above-mentioned processing deletion track and the raw processing offset value set in the raw processing stage of the above-mentioned processing deletion track can be controlled to a range greater than 1 and less than 1.05.

[0022] The above final design reference offset value and the above raw processing offset value may be axial offset values ​​or radial offset values. Effects of the invention

[0023] According to the present invention, by selectively deleting a track process of a specific phase, the number of processing passes per single part is reduced by half, and accordingly, the production cycle time of the entire manufacturing line is drastically shortened, thereby maximizing productivity.

[0024] Furthermore, finishing operations for high-hardness steel require a large number of expensive machining tools (such as CBN bits) and are a process with severe wear. By drastically reducing the total number of finishing operations, friction and wear applied to the machining tools can be suppressed and tool life can be significantly extended, and consequently, the cost of replacing consumable tools can be reduced, thereby greatly lowering the manufacturing cost of the product.

[0025] Furthermore, the mechanical and physical processing load of the processing machine (milling machine or CNC equipment) generated when cutting hardened heat-treated steel can be reduced, which extends the maintenance cycle of the equipment and lowers the rate of sudden failures, and significantly increases the utilization rate of the limited processing equipment line and the operational efficiency of the equipment.

[0026] Furthermore, by pre-controlling the offset margin to within 5% (greater than 1 and less than 1.05) of the final design offset dimension during the preceding raw machining stage, rather than simply omitting the process, it is possible to perfectly absorb minute deformations that occur during heat treatment and, consequently, maintain mechanical reliability without degradation of ball clearance, backlash, and rotational torque transmission performance during final assembly, even if subsequent finishing machining is omitted.

[0027] 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. Brief explanation of the drawing

[0028] 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. FIG. 1 is a front view of a counter track joint according to one embodiment of the present invention. FIG. 2 is an exploded perspective view of a counter track joint according to one embodiment of the present invention. Figure 3 is a cross-sectional view along line AA of Figure 1. Figure 4 is a cross-sectional view along the BB line of Figure 1. FIG. 5 is a perspective view of an outer ring and an inner ring showing a state where hard milling is omitted according to one embodiment of the present invention. FIG. 6 is a perspective view of an outer ring and an inner ring showing a state where finishing machining is omitted according to another embodiment of the present invention. FIG. 7 is a cross-sectional view showing an offset structure applied to the first outer ball track of the outer ring. FIG. 8 is a cross-sectional view showing an offset structure applied to the first inner ball track of the inner ring. FIG. 9 is a cross-sectional view showing an offset structure applied to the second outer ball track of the outer ring. FIG. 10 is a cross-sectional view showing an offset structure applied to the second inner ball track of the inner ring. 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. Specific details for implementing the invention

[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 them. 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. In describing the components of the present invention, where it is stated that one 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 that another component may also be "connected," "coupled," or "connected" between each component.

[0031] Hereinafter, the basic mechanical structure and track arrangement system of a constant velocity joint (10) according to an embodiment of the present invention will be described in detail with reference to the attached FIGS. 1 to 4.

[0032] FIG. 1 illustrates a front view of the assembled state of a constant velocity joint (10) according to one embodiment of the present invention, and FIG. 2 is an exploded perspective view showing the core components constituting the constant velocity joint (10) disassembled and assembled in order. In addition, FIG. 3 shows a vertical cross-section passing through a first pair of ball tracks as a cross-sectional structure along line AA of FIG. 1, and FIG. 4 shows a vertical cross-section passing through a second pair of ball tracks as a cross-sectional structure along line BB of FIG. 1.

[0033] Referring to FIGS. 1 to 4 together, the constant velocity joint (10) according to the present invention is provided as a counter-track joint specification and is composed of an assembly including an outer ring (11), an inner ring (12), a plurality of balls (13), and a ball cage (14), and performs the function of transmitting rotational power generated from a vehicle's transmission or differential gear to the driving wheel side while maintaining constant velocity.

[0034] The outer ring (11) is formed as a hollow body in the shape of an approximate cup with one side open, and includes a coupling side (15) that is coupled to another power transmission element, and an open side (16) that extends integrally from the coupling side (15) and provides a receiving space capable of accommodating an inner ring (12) and a ball cage (14) inside. At this time, on the inner surface of the outer ring (11), a plurality of outer ball tracks (31, 32) extending along the longitudinal axis (X) are formed spaced apart from each other at a constant phase angle along the circumferential direction.

[0035] The inner ring (12) is movably positioned on a receiving space formed inside the open side (16) of the outer ring (11). A through hole (19) is formed in the center of the inner ring (12) and penetrates along the longitudinal axis (X) so that a connecting shaft can be pressed in and spline connected. On the outer surface of the inner ring (12), a plurality of inner ball tracks (33, 34) are formed along the longitudinal axis (X) to face each one-to-one with a plurality of outer ball tracks (31, 32) formed on the inner surface of the outer ring (11).

[0036] A plurality of balls (13) are inserted and interposed between the outer ball tracks (31, 32) of the outer ring (11) and the inner ball tracks (33, 34) of the inner ring (12), and serve as a medium for directly transmitting rotational torque between the outer ring (11) and the inner ring (12).

[0037] The ball cage (14) is provided as an annular ring structure interposed in the gap space between the inner surface of the outer ring (11) and the outer surface of the inner ring (12). The ball cage (14) has a plurality of windows (23) formed through it in a roughly rectangular window shape along the circumferential direction, and each ball (13) is accommodated in one of these windows (23), thereby performing a circumferential guide function that restrains and supports the plurality of balls (13) to maintain a certain phase along the circumferential direction during joint operation.

[0038] The constant velocity joint (10) according to the present invention forms a dual ball track system having mutually opposite mechanical directions to increase efficiency during high-angle operation and minimize noise and vibration caused by internal clearance. That is, the constant velocity joint (10) of the present invention has two ball track structures having opposite directions and opening angles. Here, the concept of the opening angle is a matter generally known in the technical field to which the present invention belongs, and may refer to the 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. More specifically, it may be defined as a wedge-shaped angle of inclination formed when the center line of curvature of the outer ring track contact surface and the center line of curvature of the inner ring track contact surface meet on a circumferential cross-section with respect to the joint center plane when the ball (13) is seated within the track. This opening angle determines a mechanical geometric structure that induces the ball (13) to move smoothly while receiving appropriate axial thrust without deviating from the track during joint operation.

[0039] Referring to FIGS. 1, 3 and 4, the track formed on the outer ring (11) is divided into a first outer ball track (31) and a second outer ball track (32), and correspondingly, the track formed on the inner ring (12) is also divided into a first inner ball track (33) and a second inner ball track (34) and arranged alternately.

[0040] As illustrated in FIG. 3, the first ball track pair is formed by mutually matching the first outer ball track (31) of the outer ring (11) and the first inner ball track (33) of the inner ring (12). The first ball track pair forms a first opening angle (α) that spreads outward from the joint side (15) toward the opening side (16). That is, due to the first opening angle (α), the first ball track pair has a wedge-shaped geometric structure that converges toward the joint side (15) and spreads toward the opening side (16).

[0041] On the other hand, as illustrated in FIG. 4, the second ball track pair is formed by mutually matching the second outer ball track (32) of the outer ring (11) and the second inner ball track (34) of the inner ring (12). The second ball track pair is designed to have a directionality opposite to that of the first ball track pair with respect to the longitudinal axis (X). That is, it forms a second opening angle (β) that spreads out from the open side (16) toward the coupling side (15). As a result, due to the second opening angle (β), the second ball track pair has a wedge structure in the opposite direction that converges toward the open side (16) and spreads toward the coupling side (15).

[0042] Thus, the first ball track part having a first opening angle (α) and the second ball track part having a second opening angle (β) in the opposite direction symmetrically formed thereto form a counter track structure that is arranged one by one with a constant phase difference along the circumferential direction of the joint.

[0043] Thanks to this symmetrical open-angle arrangement structure, even if the constant velocity joint (10) is bent at a high angle due to the turning of the vehicle or suspension movement, the internal forces of the balls acting in the opposite direction of the longitudinal axis (X) are mutually canceled out. Therefore, load concentration in a specific direction is prevented, uneven wear of the parts is suppressed, and the durability of the joint, power transmission efficiency, and overall operational reliability can be greatly improved.

[0044] The manufacturing method of a constant velocity joint (10) according to the present invention is characterized by intentionally deleting (omitting) the hard milling step after heat treatment of a ball track having a specific open angle structure among the dual ball tracks of the outer race (11) and inner race (12), thereby optimizing the manufacturing process and drastically shortening the production cycle time.

[0045] In the manufacturing process of conventional counter-track specification joints, soft milling, heat treatment, and finishing machining had to be performed sequentially across the entire areas of the first and second ball tracks of the outer and inner rings. However, the present invention proposes a process sequence that alternately excludes finishing machining—the final finishing process performed after heat treatment—from specific tracks, based on precise offset control during the preceding soft milling stage.

[0046] Hereinafter, a finishing machining removal method according to two different embodiments of the present invention will be described in detail with reference to FIGS. 5 and FIGS. 6.

[0047] FIG. 5 is a perspective view illustrating the state of omission of finishing machining of the outer ring (11) and inner ring (12) according to the first embodiment of the present invention. In FIG. 5, the area shaded by a dark cross-section indicates a machining deletion area where finishing machining is not performed after heat treatment and the raw machining surface state is maintained. The manufacturing process of the ball track of the constant velocity joint (10) according to the first embodiment proceeds specifically in the following steps. First, in the raw machining step, raw machining (ball groove soft milling) in the state before heat treatment is performed on the entire first outer ball track (31) and the second outer ball track (32) formed on the inner circumference of the outer ring (11), and the entire first inner ball track (33) and the second inner ball track (34) formed on the outer circumference of the inner race (12) to form a basic track groove shape. Then, in the heat treatment step, a heat treatment process such as high-frequency heat treatment is performed to secure the surface hardness and mechanical durability of the outer race (11) and inner race (12) that have completed the above raw processing. Then, in the selective finishing step, after the heat treatment process is completed, finishing processing (ball groove hard milling) is performed to precisely correct thermal deformation, but the processing of the alternating symmetrical regions of the outer race (11) and inner race (12) is omitted.

[0048] Specifically, in the above selective finishing step, for the outer ring (11), the finishing process for the first outer ball track (31) forming the first opening angle (α) is omitted, and the finishing process is performed only on the corresponding second outer ball track (32). At the same time, for the inner ring (12) that is assembled and matched with it, the finishing process for the first inner ball track (33) is performed normally, while the finishing process for the second inner ball track (34) forming the second opening angle (β) is omitted. As a result, among the pair of tracks that are assembled to accommodate the same ball (13), the finishing process for only one side of either the outer ring side or the inner ring side is selectively omitted, thereby reducing the number of processing operations by half while maintaining the quality of the assembly.

[0049] FIG. 6 is a perspective view illustrating the state in which finishing machining of the outer ring (11) and inner ring (12) is omitted according to the second embodiment of the present invention. The second embodiment has a symmetric process form in which the phase structure of the ball track in which finishing machining is omitted is designed to be the exact opposite of the first embodiment described above. The manufacturing process of the ball track of the constant velocity joint (10) according to the second embodiment proceeds in the following steps. First, in the raw machining stage, raw machining is performed on the entire first and second outer ball tracks (31, 32) of the outer ring (11) and the first and second inner ball tracks (33, 34) of the inner ring (12) prior to the heat treatment stage. Next, a general heat treatment process is applied to the outer ring (11) and inner ring (12) to ensure mechanical toughness. Next, in the selective finishing machining stage to ensure final dimensional accuracy after the heat treatment is completed, the machining of the track with the opposite phase to that of the first embodiment is omitted. Specifically, in the above selective finishing step, for the outer ring (11), finishing is performed on the first outer ball track (31), while finishing is omitted for the second outer ball track (32) that forms the second opening angle (β). For the inner ring (12) facing it, finishing is omitted for the first inner ball track (33), and finishing is performed normally only on the second inner ball track (34) to form a finished surface.

[0050] Through this alternating finishing machining omission control mechanism, the finishing surface and the raw machining surface are cross-matched in both the first ball track pair area and the second ball track pair area from the perspective of the entire assembly of the constant velocity joint (10). Accordingly, the expensive divided machining cycle time required for machining a single part is drastically reduced, thereby maximizing productivity, and the wear of the machining tool and the load on the equipment that occur when machining hardened heat-treated steel can be minimized.

[0051] Hereinafter, with reference to the attached FIGS. 7 and 8, the offset control structure and center trajectory relationship of the outer ring (11) and inner ring (12) for geometrically realizing the first opening angle (α) in the constant velocity joint (10) according to the first embodiment of the present invention will be described.

[0052] As previously described, in order to maintain the precise assembly quality and power transmission performance of the constant velocity joint while selectively eliminating the finishing step after heat treatment of a specific track, the present invention limits the offset dimension and control ratio of the track to a specific numerical range during the preceding raw machining step.

[0053] FIG. 7 is a detailed cross-sectional view illustrating an offset design structure applied to the first outer ball track (31) of the outer ring (11). Referring to FIG. 7, the first outer ball track (31) of the outer ring (11) has a predetermined eccentric structure with respect to the geometric center of the joint to guide the ball (13) and induce the formation of a first opening angle (α). Specifically, a spherical centerline (CL) which is a straight line passing through the center of the inner circumference of the outer ring (11) and perpendicular to the longitudinal axis (X) SPH.O ) and the track center trajectory (CT) of the first outer ball track (31) O1 A ball track centerline (CL) that is a straight line perpendicular to the longitudinal axis (X) while passing through the center of curvature of the main section of ), for example, a concave arc-shaped section. BT_O1 ) is not located on the same line, and along the longitudinal axis (X) at a certain distance (OS O1 They are spaced apart from each other eccentrically by the amount of ). In this way, the spherical centerline (CL) of the inner circumferential surface of the outer ring (11) SPH.O ) and the ball track centerline (CL BT_O1 The separation distance between ) is the first outer axial offset (OS O1 It is defined as ). Here, the track center trajectory can be understood as the geometric trajectory formed by the center of the ball as it moves along the track.

[0054] This first outer axial offset (OS) O1 As ) is granted, the track center trajectory (CT) of the first outer ball track (31), which is a continuous line of center points along which the ball (13) rolls inside the first outer ball track (31). O1 ) may have a composite profile structure that includes a concave arc-shaped section and a convex reverse arc-shaped section that are not parallel to the longitudinal axis (X) of the joint.

[0055] FIG. 8 is a cross-sectional view illustrating an offset design structure applied to the first inner ball track (33) of the inner ring (12). Referring to FIG. 8, the first inner ball track (33) of the inner ring (12) also includes an eccentric control structure for completing the first opening angle (α) by symmetrically matching with the first outer ball track (31). Specifically, a spherical centerline (CL) which is a straight line perpendicular to the longitudinal axis (X) while passing through the spherical center of the outer circumference of the inner ring (12). SPH.I ) and the track center trajectory (CT) of the first inner ball track (33) I1 The ball track centerline (CL) is a straight line perpendicular to the longitudinal axis (X) while passing through the center of curvature of the main section, i.e., the concave arc-shaped section. BT_I1 ) is a predetermined distance (OS) along the longitudinal axis (X). I1 It is formed with an eccentric spacing of ) amount. The spacing distance between these two centerlines is the first inner axial offset (OS I1 Defined as ). The above first inner axial offset (OS) I1 The center trajectory (CT) of the first inner ball track (33) implemented by ) I1 ) includes a convex arc-shaped section and a concave arc-shaped section.

[0056] In the first embodiment of the present invention, the process is optimized by intentionally eliminating the final finishing step for the first outer ball track (31) described above. To this end, the offset value applied in the raw machining step is controlled to a fine range relative to the reference offset dimension so that geometric dimensional accuracy can be maintained even if the finishing step is omitted.

[0057] Here, the outer final offset value (Offset) set in the final processing (design standard) of the first outer ball track (31) α ) and the outer raw machining offset value (Offset) set in the raw machining stage of the first outer ball track (31) where the final finishing machining is omitted α' The ratio of ) (Offset α / Offset α' or Offset α' / Offset α ) is controlled to satisfy greater than 1 and less than 1.05. Likewise, the inner race side offset dimension (specifically the second inner ball track 34 specification to be described later), which is a symmetrical area assembled with the part where finishing machining is omitted in the first embodiment, also satisfies the same range of greater than 1 and less than 1.05 for the ratio relationship between the final offset value and the raw machining offset value. That is, in the counter track specification of the present invention, for a specific track where the finishing machining step is omitted, the offset dimension applied in the raw machining step before heat treatment is precisely managed so that it is formed to be larger or smaller within 5% of the final design standard offset dimension. At this time, the variation and control direction of the offset is designed as a concept that includes not only the axial direction offset form as shown in the drawings, but also the radial direction offset form.

[0058] In this way, by precisely controlling the offset margin to within 5% of the final reference dimension during the raw processing stage, even if fine expansion, contraction, and warping deformation occur during the heat treatment stage, it is possible to secure an appropriate contact trajectory and clearance with the ball (13) without separate subsequent finishing processing, and process optimization can be achieved without deterioration of the bonding quality.

[0059] Hereinafter, with reference to the attached FIGS. 9 and 10, the offset control structure and center trajectory relationship of the outer ring (11) and inner ring (12) for geometrically implementing the second opening angle (β) in the constant velocity joint (10) according to the first embodiment of the present invention will be described.

[0060] The second embodiment of the present invention is a concept symmetric to the first embodiment, characterized by selectively deleting the finishing process of the second outer ball track (32) and the first inner ball track (33), and ensuring assembly reliability by optimizing the offset control ratio of the second open angle series tracks in the preceding raw processing step.

[0061] FIG. 9 is a detailed cross-sectional view illustrating an offset design structure applied to the second outer ball track (32) of the outer ring (11). Referring to FIG. 9, the second outer ball track (32) of the outer ring (11) has a predetermined eccentric structure with respect to the geometric center of the joint to guide the ball (13) and induce the formation of a second opening angle (β). Specifically, a spherical centerline (CL) which is a straight line passing through the center of the inner circumference of the outer ring (11) and perpendicular to the longitudinal axis (X) SPH.O ) and the track center trajectory (CT) of the second outer ball track (32) O2 A ball track centerline (CL) that is a straight line perpendicular to the longitudinal axis (X) while passing through the center of curvature of the main section of ), for example, a concave arc-shaped section. BT_O2 ) is not located on the same line, and along the longitudinal axis (X) at a certain distance (OS O2They are spaced apart from each other eccentrically by the amount of ). In this way, the spherical centerline (CL) of the inner circumferential surface of the outer ring (11) SPH.O ) and the ball track centerline (CL BT_O2 The separation distance between ) is the second outer axial offset (OS O2 Defined as ).

[0062] This second outer axial offset (OS) O2 As ) is granted, the track center trajectory (CT) of the second outer ball track (31), which is a continuous line of center points along which the ball (13) rolls inside the second outer ball track (32). O2 ) may have a composite profile structure that includes a concave arc-shaped section and a convex reverse arc-shaped section that are not parallel to the longitudinal axis (X) of the joint.

[0063] FIG. 10 is a cross-sectional view illustrating an offset design structure applied to the second inner ball track (34) of the inner ring (12). Referring to FIG. 10, the second inner ball track (34) of the inner ring (12) also includes an eccentric control structure for completing the second opening angle (β) by symmetrically matching with the second outer ball track (32). Specifically, a spherical centerline (CL) which is a straight line perpendicular to the longitudinal axis (X) while passing through the spherical center of the outer circumference of the inner ring (12). SPH.I ) and the track center trajectory (CT) of the second inner ball track (34) I2 The ball track centerline (CL) is a straight line perpendicular to the longitudinal axis (X) while passing through the center of curvature of the main section, i.e., the concave arc-shaped section. BT_I2 ) is a predetermined distance (OS) along the longitudinal axis (X). I2 It is formed with an eccentric spacing of ) amount. The spacing distance between these two centerlines is the second inner axial offset (OS I2 Defined as ). The above first inner axial offset (OS) I2 The center trajectory (CT) of the second inner ball track (34) implemented by ) I2) includes a convex arc-shaped section and a concave arc-shaped section.

[0064] In the second embodiment of the present invention, the process is optimized by intentionally eliminating the final finishing step for the second outer ball track (32) described above. To this end, the offset value applied in the raw machining step is controlled to a fine range relative to the reference offset dimension so that geometric dimensional accuracy can be maintained even if the finishing step is omitted.

[0065] Here, the outer final offset value (Offset) set in the final processing (design standard) of the second outer ball track (32) λ ) and the outer raw machining offset value (Offset) set in the raw machining stage of the second outer ball track (32) where the final finishing machining is omitted λ' The ratio of ) (Offset λ / Offset λ' or Offset λ' / Offset λ ) is controlled to satisfy greater than 1 and less than 1.05. At the same time, for the specifications of the first inner ball track (33) on the inner race side where finishing machining is omitted in the second embodiment, the ratio relationship between the final offset value and the raw offset value is controlled to satisfy greater than 1 and less than 1.05 (within an error range of 5%). These second open angle series tracks are also designed with the concept that the control and variation direction of the offset includes not only the axial direction offset along the longitudinal axis (X) but also the radial direction offset.

[0066] In this way, by managing the offset margin within 5% of the reference dimension during the raw processing stage, it is possible to achieve manufacturing optimization that completely absorbs micro-deformation occurring during heat treatment and does not reduce the mechanical performance and quality reliability of the constant velocity joint (10) even if the subsequent finishing process is omitted.

[0067] Likewise, in the second embodiment, the inner race side offset dimension (specifically the second inner ball track 34 specification to be described later), which is a symmetrical area assembled with the part where finishing machining is omitted, also equally satisfies the ratio relationship between the final offset value and the raw machining offset value in the range greater than 1 and less than 1.05. That is, in the counter track specification of the present invention, for a specific track where the finishing machining step is omitted, the offset dimension applied in the raw machining step before heat treatment is precisely managed so that it is formed to be larger or smaller within 5% of the final design standard offset dimension. At this time, the variation and control direction of the offset is designed as a concept that includes not only the axial direction offset shape as shown in the drawings, but also the radial direction offset shape.

[0068] In this way, by precisely controlling the offset margin to within 5% of the final reference dimension during the raw processing stage, even if fine expansion, contraction, and warping deformation occur during the heat treatment stage, it is possible to secure an appropriate contact trajectory and clearance with the ball (13) without separate subsequent finishing processing, and process optimization can be achieved without deterioration of the bonding quality.

[0069] 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. Explanation of the symbols

[0070] 10 constant velocity joints 11 outer ring 12 inner rings 13 balls 14 ball cages 15 connecting side 16 open side 19 through holes 23 Windows 31 1st Outer Ball Track 32 Second Outer Ball Track 33 1st Inner Ball Track 34 Second inner ball track P joint center plane X longitudinal axis α First opening angle β second opening angle

Claims

Claim 1 An outer ring comprising mutually opposing coupling sides and opening sides, wherein a first outer ball track and a second outer ball track are alternately formed along the circumferential direction along the longitudinal axis on the inner surface; an inner ring movably disposed inside the opening side of the outer ring, wherein a first inner ball track and a second inner ball track are formed on the outer surface to face the first and second outer ball tracks; and a plurality of balls interposed between the first and second outer ball tracks and the first and second inner ball tracks to transmit rotational torque. A constant velocity joint comprising an annular ball cage having a plurality of windows formed therein for receiving and supporting the plurality of balls, wherein the outer ring and the inner ring form a first opening angle in which the first outer ball track and the first inner ball track are mutually matched to form a first opening angle that spreads in one direction of the outer ring, and the second outer ball track and the second inner ball track are mutually matched to form a second opening angle that spreads in the opposite direction to the first opening angle, thereby implementing a counter-track structure, wherein in either series of the first opening angle series ball track and the second opening angle series ball track, the surface of the ball track of the outer ring is formed as a finished surface after finishing machining following heat treatment, and in the other series, the surface of the ball track of the inner ring is formed as a finished surface after finishing machining following heat treatment, and a machining removal track among the entire ball tracks of the outer ring and the inner ring, wherein the finishing machining is removed to maintain the raw machining surface state prior to heat treatment. Claim 2 In claim 1, the processing deletion track is a constant velocity joint comprising the first outer ball track forming the first opening angle and the second inner ball track forming the second opening angle. Claim 3 In claim 1, the processing deletion track is a constant velocity joint comprising the second outer ball track forming the second opening angle and the first inner ball track forming the first opening angle. Claim 4 A constant velocity joint according to claim 1, wherein the ratio of the final design reference offset value of the machined deletion track and the raw machining offset value set during the raw machining stage of the machined deletion track is controlled to a range greater than 1 and less than 1.

05. Claim 5 In paragraph 4, the above final design reference offset value and the above raw machining offset value are axial offset values ​​or radial offset values ​​for a constant velocity joint. Claim 6 A method for manufacturing a constant velocity joint comprising the step of machining ball tracks formed on an outer ring and an inner ring, wherein: (a) a step of forming a base track groove by performing raw machining in a state prior to heat treatment on the entirety of first and second outer ball tracks formed on the inner circumference of the outer ring and the entirety of first and second inner ball tracks formed on the outer circumference of the outer ring; (b) a step of performing heat treatment on the outer ring and the inner ring after the raw machining is completed; and (c) a step of performing finishing machining on the ball tracks of the outer ring and the inner ring after the heat treatment is completed, wherein the outer ring and the inner ring form a first opening angle in which the first outer ball track and the first inner ball track are matched to form a first opening angle that spreads in one direction of the outer ring, and the second outer ball track and the second inner ball track are matched to form a second opening angle that spreads in the opposite direction to the first opening angle, thereby implementing a counter-track structure, and the step (c) is a method for manufacturing a constant velocity joint in which finishing machining of the ball track of the outer ring is removed in one series of the first opening angle series ball track and the second opening angle series ball track, and finishing machining of the ball track of the inner ring is removed in the other series. Claim 7 A method for manufacturing a constant velocity joint according to claim 6, wherein in step (c) above, the finishing process of the first outer ball track forming the first opening angle in the outer ring is omitted and the finishing process is performed only on the second outer ball track, and the finishing process of the second inner ball track forming the second opening angle in the inner ring is omitted and the finishing process is performed only on the first inner ball track. Claim 8 A method for manufacturing a constant velocity joint according to claim 6, wherein in step (c) above, the finishing process of the second outer ball track forming the second opening angle is omitted from the outer ring and the finishing process is performed only on the first outer ball track, and the finishing process of the first inner ball track forming the first opening angle is omitted from the inner ring and the finishing process is performed only on the second inner ball track. Claim 9 A method for manufacturing a constant velocity joint according to claim 6, wherein the ratio of the final design reference offset value of the machined deletion track and the raw machining offset value set during the raw machining stage of the machined deletion track is controlled to a range greater than 1 and less than 1.

05. Claim 10 A method for manufacturing a constant velocity joint according to claim 9, wherein the final design reference offset value and the raw processing offset value are axial offset values ​​or radial offset values.

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