WO2004059184A1 - Ball-shaped homeocinetic joint - Google Patents

Abstract

The invention relates to a ball-shaped homeocinetic joint for a motor vehicle, comprising an outer part which is provided with bearing surfaces arranged on the inner side thereof, an inner part (3) which is arranged inside the outer part which comprises bearing surfaces (5) on the outer side thereof, which are disposed opposite the bearing surfaces of the outer part. A bearing surface (5) on the outer part and a bearing surface on the inner part (3) respectively form a pair. Said joint also comprises balls which are received in the pairs of the bearing surfaces. One ball (6) is supported at least on one ball bearing surface (4, 5) by means of at least one contact point. The nestling of the ball bearing surface (4, 5) on the contact point(s) becomes narrower or wider along the length of the ball bearing surface (4, 5), i.e. the curvature radius of the profile cross-section of the bearing surface can increase or decrease at both of the contact points. Service life and strength can be increased by the variations of the nestling. Functionality can also be improved for large diffraction angles of said joint. The ball-shaped homeocinetic joint can also be produced in a simple and economical manner.

Description

 CV Joint

The invention relates to a ball constant velocity joint comprising an outer part which has ball raceways on its inside, an inner part which is arranged in the outer part and has ball raceways on its outside which are opposite the ball raceways of the outer part, one in each case Ball-raceway form a pair of raceways on the outer part and on the inner part, and balls which are accommodated in the raceway pairs, wherein a ball is supported on at least one ball-raceway via at least one contact point.

Such constant velocity ball joints are used, for example, in drive shafts of motor vehicles and are generally known from the prior art.

The power transmission between the raceways of the inner part and the raceways of the outer part via the balls is of particular importance for the proper functioning of the joint. In elliptical or Gothic careers, there are two contact points between the track and a ball. Depending on the direction of the torque or direction of rotation, only one of the contact points is loaded during operation, which results in considerable mechanical stress on the raceways.

The position and size of the contact points have a noticeable influence on the breaking strength and service life of the constant velocity joint. It must be taken into account here in particular that in the case of articulation of the joint, the forces arising from the torque are distributed unevenly over the balls. As a result, positions with higher and lower loads result with each rotation under diffraction.

The invention intends to create a constant velocity ball joint of the type mentioned, which is characterized by a long service life and resistance to breakage.

This object is achieved by a constant velocity ball joint with the features of claim 1, which has a variable osculation of the ball raceways on the balls. According to the invention, the osculation of the ball raceway becomes narrower or wider along the course of a ball raceway, ie the radius of curvature of the raceway profile cross section at the two contact points increases or decreases.

The size and position of the contact points can be influenced by a targeted change or variation of the osculation at the more heavily loaded positions, thereby increasing the service life and breaking strength. In this way, the optimal pressure area or surface blackmail in the career can be set over the course of the career. This means a significant improvement compared to today's known raceways with constant cross-sectional contours.

A variable osculation can be provided only on the outer part, only on the inner part or also on the inner part and on the outer part. It is also possible to provide only part of the raceways of the outer part or the inner part with a variable osculation.

According to an advantageous embodiment, the osculation becomes narrower or wider along the course of the ball track. This is advantageous in terms of production technology.

However, in a further advantageous embodiment, a larger radius of curvature can be provided at contact points with greater operating loads than at contact points with lower operating loads, regardless of a continuously narrowing or widening curve.

The radius of curvature of the track profile cross section is preferably a function dependent on the wrap φ of the respective ball through the respective track. By varying the osculation, this enables a reduction in stress in critical areas with little wrap. With a smaller wrap φ, for example, a larger radius of curvature can be selected.

According to a further advantageous embodiment, the radius of curvature of the track profile cross section increases over the course of the ball track on the outer part from the insertion side of the inner part to the opposite side, i. h the osculation decreases or continues. Conventional manufacturing processes can be used to produce the raceways, which can be elliptical or Gothic, for example. For example, it is possible to produce the raceways with variable osculation by machining. Above all, common milling and / or grinding processes come into question. It is also possible to finish forging ball tracks with varying osculation.

Of course, variable osculation can also be provided for circular raceways.

In principle, the contact angle α to the central axis of the track can remain constant over the course of the track for a ball which is supported against a track via two contact points.

However, it is also possible to combine the variable osculation with a variation of the contact angle α for further load and function optimization. For example, the contact angle α of a ball can be varied along the ball track, which is preferably a function dependent on the ball wrap φ.

It has been shown that the contact angle α also has a significant influence on the lifespan and breaking strength of the joint. The design of the contact angle α, which is dependent on the wrap, allows the mechanical load in the respective region of the track to be further optimized, so that the pressure resistance is increased and the service life is extended. In addition, the distribution of forces in the joint is advantageously influenced.

The invention further enables the combination of completely forged and machined raceways or joint components in one joint.

The opposite contact angles α in the ball contact on the inner and outer part are expediently coordinated with one another.

The invention is explained in more detail below on the basis of an exemplary embodiment shown in the drawing. The drawing shows in: Figure 1 is a spatial representation of an embodiment of a

Ball constant velocity joint with variable osculation according to the invention,

Figure 2 is a spatial representation of the outer part of the ball constant velocity joint

Look at some of the ball raceways,

Figure 3 is a cross-sectional view of the track profile along the line III-III in

Figure 2,

Figure 4 is a cross-sectional view of the track profile along the line IV-IV in

Figure 2,

Figure 5 is a cross-sectional view of the track profile along the line V-V in

Figure 2,

Figure 6 is a diagram illustrating the osculation r _k / r in

Dependence of the wrapping φ of the ball,

Figure 7 is a diagram illustrating a varying

Contact angle course along a track for a modification of the ball constant velocity joint according to Figures 1 to 6, and in

Figure 8 is a diagram illustrating the contact angle α in

Dependency of the wrap φ of the ball for the modification of the ball constant velocity joint with varying contact angle.

The ball constant velocity joint 1 shown by way of example in FIG. 1 comprises an outer part 2 and an inner part 3. Both the outer part 2 and the inner part 3 are provided on their mutually facing radial sides with raceways 4 and 5, which each receive a ball 6 in pairs. The inner part 3, which here has a receptacle 7 for a shaft, can be pivoted relative to the outer part 2. The outer part 2 according to the embodiment has a bell-like shape that surrounds the inner part 3 and has a shaft extension 8. In addition, a cage 9 is provided between the outer part 2 and the inner part 3, which has windows for receiving the balls 6 and possibly also for guiding them.

As FIG. 1 shows, each raceway 4 and 5 form a pair of raceways on the inside of the outer part 2 and on the outside of the inner part 3. The raceways are designed such that the associated balls are supported 6 via two contact points Pi and P ₂ against the respective raceway 4 and 5 respectively. This is particularly the case with elliptical and Gothic careers.

The raceways 4 and 5 are designed with variable osculation. This means that the osculation of the ball raceways 4 and 5 on the respective ball 6 at the two contact points P 1 and P ₂ becomes narrower or wider along the course of the ball raceways. In FIGS. 3 to 5, which show career profile cross sections of a selected career 4 on the outer part 2 at different locations along the career 4, this can be seen from the radii of curvature r _a , r and r _c . A smaller radius of curvature means a closer osculation, a larger radius of curvature, on the other hand, a further osculation at the contact points P ^ and P ₂ . Since the radii of curvature r _a , r _b and r _{c are} larger than the sphere radius r _k , the respective center of curvature M _a , M _b and M _c lies outside the sphere center M _k .

It can be seen from the sequence of FIGS. 3 to 5 that the osculation along the course of the ball raceway 4 is continuously narrowing in one direction. However, this is not mandatory. Rather, the course of the radius of curvature along the ball raceway 4 is selected such that a larger radius of curvature is provided at the contact points with larger operating loads than at contact points with lower operating loads. In most cases, however, the places of greatest stress in the area of large diffraction angles, i. H. are at the end of the career.

In the exemplary embodiment shown here, the smallest radius of curvature r _c for the raceways 4 of the outer part 2 is on the insertion side of the inner part 3. Starting from there, the radius increases continuously to the opposite end of the raceway, so that r _a > r _b > r _c > r _k . On the side of the greatest load, this results in a comparatively wide osculation, as a result of which the contact points that arise in this area with the ones that go beyond the actual contact surface Tension range can still be absorbed by the raceway even with a lower wrap φ there. The edge of the track remains undamaged.

The radius of curvature r _a , r _b , r _c of the cross-sectional profile of the raceway here is a function dependent on the wrap φ of the respective ball 6. FIG. 6 shows, by way of example, the course of the osculation value r / r _k , ie the ratio of raceway radius r to ball radius r _k as a function of the wrap φ. With a smaller wrap φ _{0 there} is a larger raceway radius of curvature r _a , r _b , r _c , with a larger wrap φ _max, on the other hand, a smaller raceway curvature radius r _a , r _b , r _c .

A variable osculation in a corresponding manner is also provided on the raceways 5 of the inner part 3.

However, it is also possible to provide only the raceways 4 of the outer part 2 or the raceways 5 of the inner part 3 with a variable osculation.

In the exemplary embodiment shown here, the contact angle α is constant over the course of the race 4 or 5 for all contact points P 1 or P _{2 of} a race 4 or 5.

The contact angle α is understood here to mean the angle between the central axis A of the track profile cross section to the respective contact point P ₁ or P ₂ .

In a modification of the exemplary embodiment explained above, the contact angle α changes along the raceway 4 or 5. To optimize the mechanical stress on the constant velocity joint 1, the contact angle α is determined as a mathematical function α = f (φ) of the wrap φ of the respective ball 6 the respective track 4 or 5, since the wrap or the wrap angle φ changes along the track 4 or 5. The variation of the contact angle α can also be used to influence the distribution of forces in the joint 1.

FIG. 8 shows the dependence of the contact angle α on the wrap angle φ as an example as a linearly increasing function α = c ^ φ + c ₂ . However, other functional profiles with increasing characteristics are also conceivable here. On the outer part 2 of the basic shape shown in FIGS. 1 to 5, for example in the direction of the longitudinal extension of the raceway 4 or 5, ie depending on the longitudinal extension parameter x, the course of the contact angle α shown in FIG. 7 with the solid line 11 can be provided if the wrap φ is greatest in the middle of the raceway.

However, it is also possible to match the course of the contact angle to the radius of curvature of the raceway cross section. For example, a smaller contact angle α can be selected for smaller radii r, in order to avoid deformations on the raceway edge in the event of strong joint flexion. Then α = f (φ, r).

The raceways 4 and 5 can be produced by conventional manufacturing processes. Milling and grinding processes are particularly suitable. Furthermore, it is possible to use either forged raceways on the outer part 2 or on the inner part 3 and to combine them with a counterpart whose raceways are machined.

This results in a constant velocity ball joint, which on the one hand has a long service life and high breaking strength, but on the other hand is easy and inexpensive to manufacture.

Due to the variable osculation over the entire course of the ball raceways, the pressure ellipse at the contact points can be optimally adapted to the respective load.

In addition, the shape of the raceways according to the invention improves the function. In particular, at strong flexion angles under high loads, the risk of the joint becoming jammed is reduced.

However, the invention is not limited to the exemplary embodiment explained and the modifications described, but rather encompasses all of the ball constant velocity joints specified in the patent claims. B EZUG SZE ICHEN LIST

1 ball constant velocity joint

2 outer part

3 inner part

4 outer part raceway

5 inner raceway

6 bullet

7 wave recording

8 shaft approach

9 cage

11 Contact angle function depending on the longitudinal extension parameter x

12 Contact angle function depending on the wrap α contact angle φ wrap or wrap angle

A Central axis of the profile section

Wed center

P _T contact point

P ₂ contact point r _a radius of curvature r _b radius of curvature r _c radius of curvature r _k sphere radius

Claims

1. ball constant velocity joint, in particular for installation in a motor vehicle, comprising: - an outer part (2) which has ball raceways (4) on its inside, - An inner part (3), which is arranged in the outer part (2) and has on its outside ball raceways (5), which are opposite the ball raceways (4) of the outer part (2), each with a ball raceway ( 4, 5) form a pair of tracks on the outer part (2) and on the inner part (3), and - Balls (6) which are accommodated in the pairs of tracks, wherein a ball (6) is supported on at least one ball track (4, 5) via at least one contact point (P1, P2), characterized in that along the course of the Ball raceway (4, 5) the osculation of the ball raceway (4, 5) at the contact point (s, P, P ₂ ) becomes narrower or wider, ie the radius of curvature (r _a , r _b , r _c ) of the Career profile cross section at the two contact points (PP ₂ ) increases or decreases. 2. constant velocity ball joint according to claim 1, characterized in that the osculation along the course of the ball raceway (4, 5) is continuously narrower or wider. 3. constant velocity ball joint according to claim 1 or 2, characterized in that a larger radius of curvature (r _a , r _b , r _c ) is provided at contact points (P ^ P ₂ ) with larger operating loads than at contact points (P ^ P ₂ ) with lower operating loads is. 4. Ball constant velocity joint according to one of claims 1 to 3, characterized in that the radius of curvature (r _a , r _b , r _c ) of the track profile cross section is a function of the wrap φ of the respective ball (6) through the respective track (4, 5) dependent function is, in particular such that there is a larger radius of curvature (r _a , r _b , r _c ) with a smaller wrap φ. 5. ball constant velocity joint according to one of claims 1 to 4, characterized in that the radius of curvature (r _a , r, r _c ) of Track profile cross section over the course of the ball track (5) on the outer part (2) from the insertion side of the inner part (3) to the opposite side is larger, that is, the osculation decreases. 6. constant velocity ball joint according to one of claims 1 to 5, characterized in that the ball track (4, 5) is an elliptical or Gothic track. 7. ball constant velocity joint according to one of claims 1 to 5, characterized in that the ball raceway (4, 5) is an arcuate raceway. 8. constant velocity ball joint according to one of claims 1 to 7, characterized in that the ball raceway (4, 5) with variable osculation made by a machining process, in particular milled and / or ground. 9. constant velocity ball joint according to one of claims 1 to 8, characterized in that the ball raceway (4, 5) is forged with variable osculation. 10. constant velocity ball joint according to one of claims 1 to 9, characterized in that for a via two contact points (PP ₂ ) against a ball raceway (4, 5) supported ball (6) the contact angle α to the central axis (A) of the raceway the course of the ball track (4, 5) is constant. 11. Ball constant velocity joint according to one of claims 1 to 9, characterized in that for a ball (6) supported against a ball raceway (4, 5) by means of two contact points (P ^ P ₂ ) the contact angle α along the ball raceway (4, 5) varies and is a function dependent on the wrap φ of the respective ball (6) through the respective raceway (4, 5). 12. Ball constant velocity joint according to claim 11, characterized in that the contact angle α becomes smaller with decreasing wrap φ.