Constant velocity joint

Description

[0001] The invention relates to a constant velocity joint for torque transmission, comprising an outer joint part with outer ball tracks, an inner joint part with inner ball tracks, torque-transmitting balls guided in pairs of outer and inner ball tracks, and a ball cage that accommodates the balls in circumferentially distributed apertures and holds them in a common plane. Constant velocity joints enable torque transmission between the outer and inner joint parts under angular movement.

[0002] Constant velocity joints are generally divided into fixed and plunging constant velocity joints. Fixed constant velocity joints essentially allow only angular movement between the outer and inner joint parts, meaning no axial movement beyond standard tolerances. Constant velocity plunging joints, on the other hand, allow not only angular movement but also axial displacement movement between the outer and inner joint parts.

[0003] A constant velocity joint in the form of a fixed joint is known from DE 10 2012 102 678 A1. In every angular position of the constant velocity joint, a jaw opening angle is enclosed between an outer tangent and an inner tangent to a ball. The track pairs are designed such that, within a small flexion angle range, at least one joint flexion angle has a jaw opening angle of zero. Within a larger flexion angle range, an opening-side jaw opening angle of a ball moving toward the opening side of the outer joint part and a connection-side jaw opening angle of a ball moving toward the connection side of the outer joint part at the same joint flexion angle are not equal to zero and open in the same axial direction.

[0004] WO 2007 / 028436 A1 discloses a counter-track joint with axial play. In the extended state and in a middle position of the relative axial displacement between the outer and inner joint parts, the counter-track joint has opening angles of the first and second track pairs that are less than 8°.

[0005] EP 0 802 341 A1 discloses a constant velocity joint in the form of a fixed joint with eight torque-transmitting balls. The track pairs, each consisting of an outer ball track and an inner ball track, open toward the opening side of the joint. In one embodiment, the ball tracks have a uniform radius along their length. In another embodiment, the ball tracks consist of a radius followed by a straight line; such constant velocity joints are also referred to as undercut-free joints (UF joints).

[0006] A constant velocity universal joint in the form of a fixed joint is known from US 2010 190 558 A1. In one embodiment, the ball tracks of the outer joint part comprise two circular arc sections with different centers and a straight section in between. The straight section connects tangentially to the two circular arc sections. The circular arc sections are designed such that when the joint is bent, one jaw opening angle opens in opposite axial directions for the ball moving toward the opening side and one jaw opening angle opens in opposite axial directions for the ball moving toward the joint base.

[0007] US Pat. No. 8,267,802 B2 discloses a constant velocity joint in which the centers of the outer and inner ball tracks are offset from a sphere center. The ratio of an axial offset (F) relative to the rolling circle radius (PCR) is between 0.045 and 0.065. A constant velocity joint with a curved track section and a straight track section that merge into one another in the joint center plane is also known. A constant velocity joint with a uniformly curved track section over the entire track length is also known.

[0008] When designing constant velocity joints, various, sometimes contradictory, requirements must be met. For example, it is important to keep the reaction forces of the joint components interacting during operation as low as possible in order to minimize power losses and maximize the joint's efficiency. At the same time, the constant velocity joint should operate reliably and with as little wear as possible in all angular positions encountered during operation.

[0009] The present invention is therefore based on the object of proposing a constant velocity joint which enables reliable cage control even at small bending angles and in which only low reaction forces occur between the joint parts in contact, so that friction losses are correspondingly low.

[0010] To solve this problem, a constant velocity joint with the features according to claim 1 is proposed.

[0011] One advantage of this constant velocity joint is that reliable cage control of the ball cage is ensured even at small flexion angles of up to fifteen degrees around the joint centerline. Due to the relatively small jaw opening angle (δ), only minimal reaction forces occur between the contacting joint parts, so friction losses are correspondingly low.

[0012] When the constant velocity joint rotates under unwinding, the torque-transmitting balls move along the ball tracks. Viewed in the joint flexion plane, the ball moving toward the opening side of the outer joint part is guided into a track section on the opening side of the outer joint part and into a track section on the connection side of the inner joint part. Viewed in the joint flexion plane, the ball moving toward the connection side of the outer joint part is guided into a track section on the connection side of the outer joint part and into a track section on the opening side of the inner joint part.

[0013] The jaw opening angles are defined between an outer tangent to the outer ball track and an inner tangent to the inner ball track, each in the contact area with the ball guided in the outer and inner ball tracks. The jaw opening angle refers to the joint flexion plane spanned by the longitudinal axes of the outer and inner joint parts, or to a pair of tracks lying in the joint flexion plane with the ball accommodated in them. The contact area between the ball and ball track can lie directly in the joint flexion plane, for example in the case of a circular track cross-section whose cross-sectional radius corresponds to the radius of the ball, or in planes offset parallel to the joint flexion plane, which are spanned by the ball contact lines between the ball and ball tracks, for example in the case of a ball track cross-section that deviates from the circular shape.In the latter case, the projections of the tangents applied to the respective ball track in the joint flexion plane, which include the jaw opening angle, are considered.

[0014] The at least one ball track is designed such that the jaw opening angle (δ) with the joint extended (β = 0°) is greater than zero degrees (δ > 0°), in particular greater than one degree (δ > 1°). Preferably, the jaw opening angle (δ) with the joint extended (β = 0°) is less than eight degrees (δ < 8°), in particular less than six degrees (δ < 6°). Due to a relatively small jaw opening angle with the joint extended, the axial forces acting between the ball tracks and the balls along the ball tracks are low.

[0015] Starting from the extended position of the joint or the joint center plane, the jaw opening angle essentially increases with increasing angulation of the joint. The at least one track pair is designed such that the jaw opening angle (δ) increases by preferably at least two degrees within the first flexion angle range. The at least one track pair has a second flexion angle range adjoining the central flexion angle range. The second flexion angle range comprises flexion angles (β) that are greater than 15° in magnitude, i.e., that are less than minus 15° or greater than plus 15° (β = 0° ± 15°). In particular, it is provided that at least one jaw opening angle (δ) within the second flexion angle range is greater than a largest jaw opening angle of the central flexion angle range.

[0016] At least one of the track pairs of the constant velocity joint has the shape according to the invention, with a jaw opening angle greater than zero degrees when the joint is extended and a jaw opening angle increasing by at least 2° in the central flexion angle range. This also encompasses the possibility of two or more track pairs having the aforementioned configuration, wherein the number of balls or track pairs is preferably even and two track pairs with the aforementioned configuration are diametrically opposed to one another. It is understood that - insofar as reference is made to at least one, one or the track pair within the scope of the present disclosure - the feature described in each case can also relate to one, several, or all track pairs.

[0017] The at least one ball track is designed, at least in the central bending angle range, such that the jaw opening angles in the opening-side ball track section and in the connection-side ball track section point in the same axial direction. By jaw opening angles pointing in the same axial direction, we mean that the resulting force acting in the joint bending plane on a ball traveling towards the connection side from the outer and inner ball tracks has an axial force component that points in the same axial direction as the resulting axial force component that acts on a ball traveling towards the opening side. This design ensures that the ball cage is steered at least approximately onto the angle-bisecting plane. If present, the other track pairs also have jaw openings that preferably point in the same axial direction as the jaw openings of the track pairs according to the invention.Preferably, all track pairs are designed such that the jaw opening angles δ of all balls open in the same axial direction when the joint is bent, as viewed in the joint flexion plane. This preferably also applies to the second flexion angle region adjacent to the central flexion angle region. Furthermore, for cost-effective production, it is preferably provided that all outer ball tracks are designed identically to one another, and all inner ball tracks are designed identically to one another.

[0018] The number of track pairs or torque-transmitting balls can be chosen arbitrarily, taking into account the specific requirements of the constant velocity joint. In the drive train of a motor vehicle, constant velocity joints with six or eight balls are generally used, although any other numbers, even an odd number, are also conceivable. In an exemplary joint with eight track pairs and eight balls, the jaw opening angle (δ) in the central flexion angle range is preferably less than or equal to six degrees (δ ≤ 6°) and in the second flexion angle range correspondingly greater than six degrees (δ > 6°). In an exemplary joint with six track pairs and six balls, the jaw opening angle (δ) in the central flexion angle range is preferably less than or equal to twelve degrees (δ ≤ 12°) and in the second flexion angle range correspondingly greater than twelve degrees (δ > 12°).The increase in the jaw opening angle (δ) within the central flexion angle range can be at least four degrees for a 6-ball joint (e.g. δ15 - δ0 > 4°).

[0019] According to a preferred embodiment, the ball cage has a spherical outer surface for guiding the ball cage relative to an inner surface of the outer joint part and a spherical inner surface for guiding the ball cage relative to an outer surface of the inner joint part. An axial offset can be provided between a center point of the spherical outer surface and a center point of the spherical inner surface. This measure achieves good cage control when the constant velocity joint is angulated. However, it is also possible for the centers of the spherical inner surface and outer surface to lie in one plane. Radial play is preferably provided between the outer spherical outer surface of the ball cage and the inner spherical surface of the outer joint part and / or between the spherical inner surface of the ball cage and the spherical outer surface of the inner joint part.

[0020] When moving along the outer and inner ball tracks, the centers of the balls define a center line (A, A') as viewed in the joint flexion plane. According to a preferred embodiment, the center line (A, A') has at least two track sections with different curvatures along its length. The at least two track sections with different curvatures can lie within the central section and / or within the opening-side section and / or within the connection-side section of the outer and inner ball tracks. It is also possible for the center line (A, A') to have at least two subsections with different curvatures within at least one of the connection-side track section and the opening-side track section of the outer joint part.

[0021] Preferably, the center line (A, A') has at least one change in curvature within the first bending angle range. In this context, a change in curvature is understood to mean any change in the gradient of the center line in the mathematical sense, such as a change from a circular arc with a larger radius to a circular arc with a smaller radius or to a straight line. It is understood that the center line can also be a higher-order curve, whereby a change in curvature here also means a change in the gradient along the higher-order curve.

[0022] According to one possible embodiment, the outer ball track is designed such that the outer center line (A) in the central bending angle range is formed by an outer circular arc around an outer central section center point (Mz), wherein the outer central section center point (Mz) has an axial distance (offset) in a first axial direction relative to the joint center point (M), and that the inner ball track is designed such that the inner center line (A') in the central bending angle range is formed by an inner circular arc around an inner central section center point (Mz), wherein the inner central section center point (Mz') has an axial distance (offset) in a second axial direction relative to the joint center point (M).

[0023] In the connection-side track section of the outer joint part, the outer ball track can be designed in particular such that the center line (A) runs radially outside a circular arc section (Cr) defined by a reference radius (Rr). The reference radius (Rr) can be defined such that it extends from a reference radius center point (Mr) to the center plane intersection point of the center line (A) with the joint center plane (EM), wherein the reference radius center point (Mr) is offset relative to the joint center plane (EM) toward the opening side of the outer joint part. The reference radius (Rr) is preferably smaller than the curvature of the connection-side track section.

[0024] The track section of the inner joint part adjoining the central section on the opening side is designed to correspond to the connecting-side track section of the outer joint part. This means that the opening-side track section of the inner joint part is designed such that the corresponding center point track of this track section is mirror-symmetrical to the center point track of the connecting-side track section of the outer joint part with respect to a bisecting plane. This applies to each of the track pairs.

[0025] When the constant velocity joint is installed, a bellows may be provided to seal the joint space. The bellows may be preloaded.

[0026] In the context of the present disclosure, the path angle β / 2 is understood to be the angle formed by a radius around the joint center M at the ball center of one of the torque-transmitting balls with the joint center plane EM. In any angular position of the joint, the path angle β / 2 is typically half the joint flexion angle β, i.e., a path angle β / 2 of, for example, up to 15° corresponds to a joint flexion angle of 30°.

[0027] Due to the guidance of the ball cage relative to the spherical inner surface of the outer joint part or the spherical outer surface of the inner joint part, the constant velocity joint is designed in the form of a fixed joint, which only allows displacement movements within the scope of the axial play between the outer and inner joint parts.

[0028] Preferred embodiments are explained below with reference to the drawing figures. Herein: Figure 1A) a constant velocity joint according to the invention in a first embodiment in an extended position in longitudinal section; Figure 1B) the joint from Figure 1A ) when bent at a bending angle of 5°; Figure 1C) the joint from Figure 1A ) when bent at a bending angle of 10°; Figure 1D) the joint from Figure 1A ) when bent at a bending angle of 15°; Figure 1E) the outer joint part of the joint made of Figure 1A ) in longitudinal section; and Figure 2 shows the outer joint part of a constant velocity joint according to the invention in a modified second embodiment in longitudinal section.

[0029] The Figures 1A) to 1E ) as well as Figure 2are initially described together below with regard to their commonalities. A constant velocity joint 11 according to the invention is shown. The constant velocity joint 11 comprises an outer joint part 12, an inner joint part 13, torque-transmitting balls 14, and a ball cage 15. The ball cage 15 has a spherical outer surface 16 guided in the outer joint part 12 and a spherical cage inner surface 17 guided on the inner joint part 13. The balls 14 are held in circumferentially distributed cage windows 18 in the ball cage 15 in the joint center plane EM. A longitudinal axis L12 is designated on the outer joint part 12, and a longitudinal axis L13 on the inner joint part 13. The intersection of the longitudinal axes L12, L13 with the joint center plane EM forms the joint center point M.

[0030] Play is provided between the spherical inner surface 17 of the ball cage 15 and a spherical outer surface of the inner joint part 13 as well as between the spherical outer surface 16 of the ball cage 15 and a spherical inner surface of the outer joint part 12.

[0031] The outer joint part 12 has a base 19, to which a connection pin 24 is connected, and an opening 20. The inner joint part 13 has an opening into which the pin of a drive shaft 25 is inserted in a rotationally fixed manner to transmit torque. The position of the base 19 hereinafter refers to the axial direction "toward the connection side," while the position of the opening 20 hereinafter refers to the axial direction "toward the opening side." These terms are also used in reference to the inner joint part 13, whereby the actual connection of the shaft 25 to the inner joint part 13 is disregarded. It is understood that the outer joint part can also be designed to be open toward the connection side instead of the base, as is the case, for example, with a disc joint.

[0032] Outer ball tracks 22 are formed in the outer joint part 12, and inner ball tracks 23 are formed in the inner joint part 13 of the constant velocity joint 11. Each outer ball track 22 and inner ball track 23 are located opposite each other and together form a track pair, in each of which a torque-transmitting ball 14 is guided. The opposing outer and inner ball tracks 22, 23 can lie in radial planes around the respective longitudinal axis L12, L13. The radial planes are each equiangularly spaced from each other. However, it is also conceivable for two circumferentially adjacent track pairs to run in mutually parallel planes, which are parallel to the longitudinal axis L12, L13. This design is also referred to as a "twin-ball" joint.When the joint is bent, i.e., when the inner joint part 13 moves at an angle relative to the outer joint part 12, the balls 14 are guided out of the joint center plane EM at least approximately into the angle-bisecting plane between the longitudinal axis L12 of the outer joint part 12 and the longitudinal axis L13 of the inner joint part 13. At least approximately means that the plane spanned by the ball centers of the balls 14 lies within an angular range of ± 10% around the angle-bisecting plane, and in particular can correspond to this.

[0033] The shape of the outer ball tracks 22, which corresponds at least largely to the shape of the inner ball tracks, is particularly in Figure 1Evisible. The balls 14 are in contact with the outer ball tracks 22 in the outer joint part 12 and inner ball tracks 23 in the inner joint part 13. In the longitudinal section, the balls 14 form an outer contact line K in the contact area with the outer ball tracks 22 and an inner contact line K' in the contact area with the inner ball tracks 23. The balls 14 are shown with contact in the track base of the ball tracks 22, 23, which does not necessarily have to be present. Thus, the outer and inner contact lines K, K' can lie in the track base, as shown, i.e. in a radial plane containing the longitudinal axes L12, L13, or in planes parallel to the longitudinal axes. When moving along the outer and inner ball tracks 22, 23, the centers of the balls 14 each define a center line A, A'. The center lines A, A' run parallel to the respective contact line K, K'.To describe the ball tracks 22, 23, reference can be made either to the contact lines K, K' in the track base or to the center lines A, A', which are defined by the sum of the ball centers during angular movements of the joint. The ball center line A denotes the line of the ball centers of the balls 14A along the outer ball tracks 22 in the outer joint part 12, and A' denotes the ball center line of the corresponding inner ball tracks 23 in the inner joint part 13.

[0034] The following describes in more detail the special features of the constant velocity joint according to the invention, in particular the design of the ball tracks 22, 23. In this case, the following definitions apply in connection with the constant velocity joint according to the invention and the design of the ball tracks: The tangent angle α defines the angle enclosed between a tangent T to a center line A, A' or a contact line K, K' of the outer joint part 12 or inner joint part 13 at any point along the path and the longitudinal axis L12, L13 of the outer joint part or inner joint part.

[0035] The joint flexion angle β defines the angle enclosed between the longitudinal axis L12 of the outer joint part 12 and the longitudinal axis L13 of the inner joint part 13. The joint flexion angle β is zero when the joint is extended.

[0036] The path angle β / 2 defines the angle that a radius around the joint center M forms between the center of the sphere and the joint center plane EM. The path angle β / 2 is always half the joint flexion angle β in any angular position of the joint.

[0037] The jaw opening angle δ defines the angle enclosed by tangents T, T' to the balls 14 at the contact points with the first ball tracks 22 and the second ball tracks 23, respectively. The system in the present disclosure is such that the jaw opening angle, which can assume various values ​​across the technically possible range of deflection angles, is generally designated by δ; selected specific deflection angles can be supplemented with the respective deflection angle and an indication of the position of the ball (for example, δ0 for the jaw opening angle at a deflection angle of zero or δ15o for the jaw opening angle on the opening-side ball at a deflection angle of 15°).

[0038] The center plane EM is defined by the ball centers of the torque-transmitting balls 14 when the joint is extended.

[0039] A reference radius Rr for the ball center line A of the outer joint part 12, or for the ball center line A' of the inner joint part 13, is defined around the reference radius center point Mr by a center plane intersection of the respective center line A, A' with the joint center plane EM. The reference radius center point Mr is offset from the joint center plane EM by an axial offset corresponding to the product of the rolling circle radius and the sine of the path angle β / 2.

[0040] The reference radius Rr for the center line A, A' defines a reference circular arc Cr.

[0041] The Figures 1A) to 1D ) show the constant velocity joint in different angular positions, Figure 1A) with coaxially aligned outer joint part 12 and inner joint part 13, i.e. bending angle β = 0°, Figure 1B ) at a bending angle of 5°, Figure 1C ) at a bending angle of 10° and Figure 1D ) at a bending angle of 15°. In Figure 1E) the outer joint part 12 is shown with its center line A and contact line K, which run equidistant from one another. The constant velocity joint 11 in the present case comprises a number of six balls 14 or six track pairs 22, 23, although it is understood that a different number is conceivable. The center line A of the outer joint part 12 has, starting from the opening side in the direction of the connection side, in the specified order: an opening-side section Ao, which extends from the opening side of the outer joint part 12 in the direction of the connection side, a central section Az continuously adjoining the opening-side section Ao, and a connection-side section Aa continuously adjoining the central section Az.

[0042] Accordingly, the center line A' of the inner joint part 13, which is not shown separately, has, starting from the opening side in the direction of the connection side, in the specified order, an opening-side section Ao', a continuously adjoining central section Az' and a continuously adjoining connection-side section Aa'.

[0043] The central track section 22z of the outer ball track 22 and the central track section 23z of the inner ball track 23 lie within a joint bending angle range β z of ± 15° around the joint center plane EM and include it. Figure 1A) that an outer central contact line tangent T applied to the outer contact line K at a bending angle β of zero degrees and an inner central contact line tangent T' applied to the inner contact line K' enclose a jaw opening angle δo that is not equal to zero degrees. Preferably, the jaw opening angle δo is at least 1° and / or a maximum of 8° when the joint is extended. In the present case, the ball tracks are designed such that the jaw opening angle δo is approximately 6° when the joint is extended. Due to the comparatively small jaw opening angle δo when the joint is extended, only small axial forces act from the ball tracks 22, 23 on the balls 14, which has a friction-reducing effect on the joint.

[0044] Furthermore, in the Figures 1B) to 1E), which show the constant velocity joint 11 at articulation angles β of 5°, 10°, and 15°, show that the outer and inner ball tracks 22, 23 are designed in such a way that, in the joint articulation plane, jaw opening angles δ are generated both on the ball 14o (upper half of the image), which moves from the joint center plane EM towards the opening side, and on the ball 14a (lower half of the image), which moves from the joint center plane EM towards the connection side, which open in the same axial direction. This means that the resulting axial forces acting on the balls 14 from the ball tracks 22, 23 due to the jaw opening angles δ act in the same axial direction.

[0045] The jaw opening angles δ are each enclosed by an outer contact line tangent T applied to the outer contact line K on the respective ball 14 and an inner contact line tangent T' applied to the inner contact line K' of said ball 14. A central flexion angle range is defined here to encompass flexion angles of up to plus or minus fifteen degrees (β = 0° ± 15°) around the joint center plane EM, i.e., a flexion angle range βz of -15° to +15° (-15° < βz < 15°). A subsequent second flexion angle range encompasses flexion angles β that are greater than fifteen degrees in magnitude, i.e., flexion angles β that are greater than 15° and those that are less than -15° (β < -15° or β > 15°).

[0046] For a bending angle ß of 5° on the ball 14o moving in the joint bending plane in the direction of the opening side between the outer tangent T5o and the inner tangent T5o', a first jaw opening angle δ5o is formed, which in the present embodiment is in particular approximately 2°, while on the ball 14a moving in the joint bending plane in the direction of the connection side between the outer tangent T5a and the inner tangent T5a', a second jaw opening angle δ5a is applied, which is in particular approximately 8°.

[0047] At a larger deflection angle ß of 10°, the jaw opening angles δ10o, δ10a at the opening-side and connection-side balls 14o, 14a are each larger in the present embodiment than at a deflection angle of 5°. The jaw opening angle δ10o at the opening-side ball 14o is in particular approximately 6.5°, while the jaw opening angle δ10a at the connection-side ball 14a is in particular approximately 10°.

[0048] With an even larger deflection angle ß of 15°, the jaw opening angles δ15o, δ15a at the opening-side and connection-side balls 14o, 14a are each larger than with a deflection angle of 10°. The jaw opening angle δ15o at the opening-side ball 14o is approximately 11°, while the jaw opening angle δ15a at the connection-side ball 14a is approximately 10.5°.

[0049] It is understood that the stated jaw opening angles δ to the stated bending angles β are exemplary and depend on the selected track shape. Overall, the jaw opening angle δ increases by at least two degrees (δ15 - δ0 > 2°) at least within a sub-range of the central bending angle range βz, and the jaw opening angle δ is less than twelve degrees (δ < 12°) for all bending angles β within the central bending angle range βz.

[0050] The aforementioned jaw opening angles δ are comparatively low compared to known fixed joints, resulting in lower friction losses between the components moving relative to each other. The ball tracks are preferably designed so that the jaw opening angles δ of the balls 14a moving on the opening side and the balls 14a moving on the connection side are at least approximately equal. However, a certain deviation in size between the opening and connection side opening angles is permissible, for example, in the range of up to ± 10%.

[0051] With further angulation outside the central flexion angle range, i.e., flexion angles greater than 15°, the jaw opening angles δ increase further. With a angulation of 30°, the jaw opening angle at the opening-side ball 14o can, for example, be between 30° and 40°, while the jaw opening angle at the connection-side ball 14a can, for example, be between 15° and 30°, without being limited thereto. It is theoretically conceivable that the jaw opening angles δ at the opening-side and connection-side balls 14 could also point in opposite axial directions for larger joint flexion angles β greater than 40°. In any case, the ball tracks are designed in such a way that the jaw opening angles δ on the opening-side and connection-side balls 14 open in the same axial direction at least up to a bending angle β of at least 30° when the joint is bent.This measure ensures good cage control, especially at large bending angles β.

[0052] In Figure 1E ) shows further details of the track shape of the outer ball tracks 22 of the outer joint part 12. The reference radius Rr is shown, the radius center Mr of which is axially and radially offset from the joint center M and the end of which is defined by the intersection of the center line A with the joint center plane EM. The individual track sections 22o, 22z, 22a or the individual center line sections Ao, Az, Aa are characterized by their different curvatures or radii.

[0053] The ball tracks 22 and 23 of this constant velocity joint have a total of two variations in curvature, but are not limited to this. In this context, a variation in curvature refers to any change in the gradient of the center line in the mathematical sense.

[0054] A first curvature change point Pzo is formed between the opening-side track section 22o and the central track section 22z. The curvature change point Pzo is offset from the joint center plane EM toward the opening side. A line passing through the joint center point M and the curvature change point Pzo forms an angle with the joint center plane EM, which may be, for example, less than 5°, in particular less than 4°. The opening-side track section 22o is formed by a straight line in the present case, but is not limited thereto. The straight line runs approximately parallel to the longitudinal axis L12 or forms a small angle with it; a design of the opening-side track section as a circular arc or a higher-order curve would also be conceivable.

[0055] The adjoining central track section 22z is formed by a circular arc with radius Rz around the circle center Mz, without being restricted to this. The circle center Mz is offset axially towards the opening side and radially towards the ball track from the joint center M. The radial offset of the circle center Mz from the center M is greater than the axial offset. The circular arc around the point Mz defines the central center line section Az between the two curvature change points Pzo and Paz. The curvature change point Paz is offset towards the connection side from the joint center plane EM. A line passing through the joint center M and the curvature change point Paz encloses an angle with the joint center plane EM, which angle can be, for example, less than 10°, in particular less than 8°.

[0056] The connection-side track section 22a adjoining the central track section 22z is formed by a circular arc with radius Ra around the circle center Ma. It can be seen that the radius Ra of the connection-side track section 22a is larger than the radius Rz of the central track section 22z. The circle center Ma of the connection-side track section 22a lies on the longitudinal axis L12 in the present case and is offset axially toward the opening side relative to the joint center M, although other configurations with a radial offset of the circle center Ma are also conceivable.

[0057] The central radius Rz defines a reference radius Rr with a reference circular arc around the center point Mz (Mr). In this case, the geometric shape means that the center line A in the opening-side track section Ao lies radially outside the reference circular arc of the reference radius Rr. This is achieved, as described above for the ball track of the present outer joint part 12, by a straight ball track in the direction of the opening side. In the central track section 22z, which extends between the points Pzo and Paz, the center line section Az coincides with the reference radius Rr. The connection-side track section 22a, which extends from the transition point Paz towards the connection side, lies with its corresponding center line section Az radially outside the reference circular arc of the reference radius Rr.However, it is understood that other path shapes are also conceivable here, for example that the center line A runs radially within or on the reference circular arc defined by the reference radius RR in the direction of the connection side.

[0058] The inner joint part 13 (not shown separately) of the constant velocity joint 11 according to the invention has a ball center line A' that is complementary to the ball center line A of the outer joint part 12. This means that the ball center line A' of the inner joint part 13 is mirror-symmetrical to the ball center line A of the outer joint part 12 with respect to the joint center plane EM, or with respect to the angle bisector plane between the longitudinal axis L12 of the outer joint part 12 and the longitudinal axis L13 of the inner joint part 13. To avoid repetition, with regard to the path of the ball center lines A' of the inner joint part 13, reference is made to the explanations made in connection with the description of the ball tracks of the outer joint part 12.

[0059] Figure 2shows an outer joint part 12 of a constant velocity joint according to the invention in a modified second embodiment. This largely corresponds to the embodiment according to Figure 1 , to whose description reference is made. Identical or modified details are provided with the same reference numerals as in Figure 1 .

[0060] One difference from the above embodiment is that the transition point Pzo in this case lies in the joint center plane EM. This results in a path section 22o on the opening side that opens slightly, i.e. the straight center line section Aa forms a small angle with the longitudinal axis L12, for example less than 5°, which opens towards the opening side. The transition point Paz is offset further away from the joint center plane EM than in the above embodiment. In this case, the present embodiment provides that a line running through the joint center point M and the curvature change point Paz forms an angle with the joint center plane EM that is, for example, greater than 10° and less than 15°, without being limited thereto. The inner joint part, which is not shown separately, is designed to be complementary to the outer joint part 12. The remaining details correspond analogously to the above embodiment.

[0061] For both embodiments shown, the jaw opening angle δ is greater than zero degrees (δ > 0°) at a flexion angle β of zero degrees (β = 0°). Furthermore, the jaw opening angle δ increases by at least two degrees (δ15' - δ0 > 2°) at least within the flexion angle range βz of ± 15°, and the jaw opening angle δ is less than twelve degrees for all flexion angles β within the central flexion angle range (δ < 12°). In this way, reliable cage control of the ball cage 15 is ensured even at small flexion angles β of up to fifteen degrees around the joint center plane EM. Due to the relatively small jaw opening angle δ, only small reaction forces occur between the contacting joint parts, so that friction losses are correspondingly low. List of reference symbols

[0062] 11 Constant velocity joint 12 Outer joint part 13 Inner joint part 14 Ball 15 Ball cage 16 Outer spherical surface 17 Inner spherical surface 18 Window 19 Connection side 20 Opening side 22 Outer ball track 22 a, z, o Track sections 23 Inner ball track 24 Pin 25 Drive shaft A, A' Center line Aa, Az, Ao Center lines Cr Reference arc EB Joint flexion plane EM Joint center plane K Contact line LLongitudinal axis Paz Transition point Pzo Curvature change point R, Ra, Rz Radius Rr Reference radius M Joint center Ma, Mz, Mo Center points T, T' Tangent β Joint flexion angle δ Jaw opening angle

Claims

1. Constant velocity joint, comprising: an outer joint part (12) with a longitudinal axis (L12) and outer ball tracks (22), wherein the outer joint part (12) has an attachment side (19) and an opening side (20), an inner joint part (13) with a longitudinal axis (L13) and inner ball tracks (23), wherein an outer ball track (22) and an inner ball track (23) respectively form a pair of tracks (22, 23) with each other, a torque transmitting ball (14) in each pair of tracks (22, 23), a ball cage (15) arranged between the outer joint part (12) and the inner joint part (13) and comprising circumferentially distributed cage windows (18), each of which receiving at least one of the torque-transmitting balls (14), wherein, with coaxially aligned longitudinal axes (L12, L13) of the inner joint part (13) and the outer joint part (12), the balls (14) in the ball cage (15) define a joint center plane (EM), wherein the two longitudinal axes (L12, L13) at articulation angles (β) enclosed between the two longitudinal axes (L12, L13) that deviate from zero degrees (0°) define a joint articulation plane (EB); wherein, viewed in the joint articulation plane (EB), in any angular position of the constant velocity joint (11) an opening angle (δ) is formed between an outer tangent (T) applied to the outer ball track (22) in an outer contact point between the outer ball track (22) and the ball (14) and an inner tangent (T') applied to the inner ball track (23) in an inner contact point between the inner ball track (23) and the ball (14), wherein the centers of the balls (14) each define a center line (A, A') when moving along the outer and inner ball tracks (22, 23), characterised in that it comprises a first articulation angle range including articulation angles (β) that are less than fifteen degrees regarding the absolute value (-15° < β < 15°), and a second articulation angle range including articulation angles (β) that are greater than or equal to 15° regarding the absolute value (β ≤ -15° v β ≥ 15°), wherein at least one opening angle (δ) within the second articulation angle range is greater than a largest opening angle of the first articulation angle range, wherein all ball tracks (22, 23) are configured such that within the second articulation angle range the opening angles (δ) of all balls (14) open in the same axial direction, viewed respectively in the joint articulation plane (EB), wherein at least one of the pairs of tracks (22, 23) for an articulation angle of zero degrees (β = 0°) has an opening angle (δ) greater than zero degrees (δ > 0°), wherein for the at least one of the pairs of tracks (22, 23) the opening angle (δ) is less than twelve degrees (δ < 12°) for all articulation angles (β) within the first articulation angle range, and wherein the opening angle (δ) increases by at least two degrees within at least a portion of the first articulation angle range.

2. Constant velocity joint of claim 1, characterised in that the opening angle (δ) at the articulation angle of zero degrees (β = 0°) is greater than one degree (δ > 1°) and less than eight degrees (δ < 8°).

3. Constant velocity joint according one of claims 1 or 2, characterised in that the opening angle (δ) increases by at least four degrees within the first articulation angle range.

4. Constant velocity joint according to any one of claims 1 to 3, characterised in that eight pairs of tracks and eight balls are provided, wherein the opening angle (δ) in the first articulation angle range is at most six degrees (δ ≤ 6°), or that six pairs of tracks (22, 23) and six balls (14) are provided, wherein the opening angle (δ) in the first articulation angle range is at most twelve degrees (δ ≤ 12°), and the opening angle (δ) increases by at least four degrees within the first articulation angle range.

5. Constant velocity joint according to any one of claims 1 to 4, characterised in that the at least one pair of tracks (22, 23) is configured such that, at any articulation angle (β) within the first articulation angle range it applies that an opening-sided opening angle (δo) at a ball (14) moving in the joint articulation plane (EB) to the opening side of the outer joint part (12) and a attachment-sidedd opening angle (δa) of a ball (14) moving at the same articulation angle (β) in the joint articulation plane (EB) to the attachment side of the outer joint part (12) open in the same axial direction.

6. Constant velocity joint according to any one of claims 1 to 5, characterised in that the ball cage (15) has a spherical outer face (16) for guiding the ball cage (15) with respect to an inner face of the outer joint part (12) and a spherical inner face (17) for guiding the ball cage (15) with respect to an outer face of the inner joint part (13), wherein an axial offset is provided between a center of the spherical outer face (16) and a center of the spherical inner face (17).

7. Constant velocity joint according to any one of claims 1 to 6, characterised in that the centers of the balls (14) each define a center line (A, A') when moving along the outer and inner ball tracks (22, 23), wherein the center lines (A, A') each having at least two track sections (22a, 22o) with different curvature along their length.

8. A constant velocity joint according to any one of claims 1 to 7, characterised in that the center lines (A, A') respectively have at least one curvature change point (Pzo, Paz) within the first articulation angle range.

9. A constant velocity joint according to any one of claims 1 to 8, characterised in that all ball tracks (22, 23) are configured such that within the second articulation angle range the opening angles (δ) of all balls (14) open in the same axial direction, viewed respectively in the joint articulation plane (EB).

10. Constant velocity joint according to any one of claims 1 to 9, characterised in that the outer ball track (22) is configured such that the outer center line (A) in the central articulation angle range is formed by an outer circular arc about an outer central section center (Mz), the outer central section center (Mz) having an axial offset in a first axial direction relative to the joint center (M), and in that the inner ball track (23) is configured such that the inner center line in the central articulation angle range is formed by an inner circular arc about an inner central section center, the inner central section center having an axial offset in a second axial direction relative to the joint center point (M).

11. Constant velocity joint according to any one of claims 1 to 10, characterised in that the outer ball track (22) is configured such that the center line (A) in the attachment-sided track section (22a) of the outer joint part (12) runs radially outside a circular arc section (Cr) defined by a reference radius (Rr), wherein the reference radius (Rr) extends from a reference radius center (Mr) to the center plane intersection of the center line (A) with the joint center plane (EM), wherein the reference radius center (Mr) is offset with respect to the joint center plane (EM) towards the opening side of the outer joint part (12).

12. Constant velocity joint according to any one of claims 1 to 11, characterised in that the outer ball track (22) is configured such that the center line (A) in the opening-sided track section (22o) of the outer joint part (12) runs radially outside a circular arc section (CR) defined by a reference radius (RR), wherein the reference radius (Rr) extends from a reference radius center (Mr) to the center plane intersection of the center line (A) with the joint center plane (EM), wherein the reference radius center (Mr) is offset with respect to the joint center plane (EM) towards the opening side of the outer joint part (12).

13. Constant velocity joint according to any one of claims 1 to 12, characterised in that the inner ball track (23) is configured mirror symmetrical to the outer ball track (22) with respect to an angle bisecting plane between the longitudinal axis (L12) of the outer joint part (12) and the longitudinal axis (L13) of the inner joint part (13).