WO2007017016A1 - Shaft coupling for torque transmission - Google Patents

Abstract

The invention relates to a shaft coupling (1) for torque transmission, comprising shaft pieces (2, 3) which may be axially inserted into each other and roller bodies (4, 5, 11, 12, 14) arranged between the above for linear support. The inner shaft piece (3) and the outer shaft piece (2) are divided into several circumferential regions (U1, U2, U3) forming the entire circumference, with counter-running freewheel couplings (9, 10) provided in at least one circumferential region (U3) with balls (11, 12) as locking bodies which also serve as the linear support.

Description

 Name of the invention

Shaft coupling for torque transmission

description

Field of the invention

The invention relates to a shaft coupling for torque transmission, which comprises a substantially tubular outer shaft part and an axially displaceable inner shaft part in this.

Background of the invention

A shaft coupling according to the preamble of claim 1 is known for example from DE 31 24 927 A1. This consisting of an inner part and a surrounding outer sleeve shaft coupling has a plurality of axially extending grooves in which balls roll. To eliminate play in the bore of the outer sleeve one of the number of circumferentially distributed rows of balls corresponding number of plates are arranged, each ball is supported on two adjacent, an obtuse angle enclosing plates and the plates are spring-loaded on the inner wall of the outer sleeve. Thus, all plates press with bias against the balls. The plates inevitably take up radial space in the shaft coupling. Object of the invention

The invention has for its object to provide a shaft coupling for torque transmission, which has a particularly compact structure at least almost play-free storage tion of an axially displaceable inner shaft part in an outer shaft part.

Summary of the invention

This object is achieved by a shaft coupling for torque transmission with the features of claim 1. This shaft coupling has between an inner and an outer shaft part of the linear bearing serving rolling elements, so that the shaft parts are axially against each other displaced. By definition, the inner shaft part and the outer shaft part have a plurality of, in particular three, peripheral regions forming the entire circumference, in each of which at least one rolling element is arranged. As explained in more detail below, the individual peripheral regions can be given for example by an approximately triangular cross-sectional shape of the shaft parts; however, a substantially circular formation of the shaft parts is also possible. Typically, each circumferential region extends over 120 ° of the total circumference.

In any case, at least one of the peripheral regions, preferably precisely one circumferential region, has opposite directions, ie one-way clutches acting in opposite directions of rotation. As clamping elements of these freewheel clutches balls are provided, which are at the same time rolling elements of the linear bearing between the shaft parts. The at least one circumferential region of the shaft coupling, in which the one-way clutches are arranged, thus has at least two rolling elements, wherein each of these rolling elements, namely balls, both acts as a clamping element of an overrunning clutch and as a rolling element of a linear bearing. The freewheel clutches lock each other, so that no rotation of the inner shaft part relative to the outer shaft part is possible. Peripheral regions in which no one-way clutches are arranged, preferably two out of three peripheral regions, have exclusively rolling elements serving for the linear bearing. Although these rolling elements may have an anti-rotation function, but have no free-running function. A freewheeling function of a rolling element is only given if it allows a relative rotation of the shaft parts in one direction of rotation and locks in the other direction by clamping.

To keep the balls of the one-way clutches permanently in clamping readiness, for example, a spring between two clamped in opposite directions of rotation balls can be curious. Likewise, however, each ball acting as a clamping element can be spring-loaded separately. Furthermore, it is possible for a ball row extending in the axial direction of the shafts, guided by a cage, to be acted upon in total by the force of a spring. In all cases, the counteracting freewheel device is loaded by spring force such that a radial force component presses the inner shaft part away from the circumferential region in which the freewheel device is arranged, and thus in other peripheral regions, in particular in the remaining two out of three peripheral regions Pressing shaft part. The inner shaft part is thus free of play and at the same time mounted axially displaceable in the outer shaft part. The overrunning clutches preferably have a clamping angle which is close to the self-locking limit in order to prevent sluggishness in the axial adjustment of the shaft coupling, in particular a setting or a jerky tearing of the ball freewheel device.

The following statements relate explicitly to embodiments of the shaft coupling with three peripheral regions, of which two have only rolling elements, which serve the linear bearing, wherein in the third peripheral region of the freewheel device is arranged with opposite effective freewheels. In a similar way, however, the statements also apply to Embodiments with a deviating number of peripheral areas, wherein freewheel devices can also be arranged in several peripheral regions.

Both in the first two circumferential regions in which the rolling elements serving the linear bearing are located as well as in the third peripheral region, in which a plurality of balls perform a combined linear bearing and freewheeling function, a plurality of rolling elements are arranged axially one behind the other in a preferred embodiment. In this way, both the transmittable torque between the shaft parts is increased, as well as the inclusion of tilting loads possible. In the third peripheral area, i. In that peripheral region in which the circumferentially effective, self-locking freewheel device is arranged, there is preferably at least one additional rolling element, which, like the rolling elements in the first and second circumferential region, serves for the linear bearing, but without at the same time having a freewheeling function. This at least one additional rolling element in the third circumferential region is preferably located axially between rolling elements, which are parts of freewheel clutches. By thus spread in the axial direction arrangement of several clamping body of the one-way clutch a particularly high tilting safety of the entire shaft coupling is achieved.

If the inner shaft part is designed as a substantially circular shaft, preferably all the rolling elements of the shaft coupling are balls. The balls in the first and second peripheral region are guided in an advantageous embodiment in longitudinal grooves of the inner shaft part and of the tubular outer shaft part, so that they assume an additional anti-rotation function. The same applies if necessary for one or more additional, no free-running function having rolling elements in the third peripheral region. The elastic properties of the freewheel device and the remaining ball bearing are matched to one another such that torsional loads between the shaft parts are distributed in a defined manner to the different rolling elements.

In an embodiment with a substantially triangular cross-section of the inner shaft part, rolling elements in the first and second peripheral regions, i. in those peripheral areas in which there are no one-way clutches, preferably cylindrical rollers or needles provided. These make it possible, on the one hand, to absorb high radial loads and, in conjunction with the spring-biased one-way clutches in the third peripheral region, provide an additional measure against a rotation of the inner shaft part relative to the outer shaft part. The length of a cylindrical roller or needle is preferably at least one half of the minimum radius of the inner shaft part. To guide the cylindrical rollers or needles, a cage arranged between the shaft parts can be provided. Alternatively, it is also possible to guide the cylindrical rollers or needles in axial grooves of the shaft parts.

Hereinafter, three embodiments of the invention will be explained in more detail with reference to a drawing. Herein show:

Short description of the drawing

1 shows in cross section a first embodiment of a shaft coupling for transmitting torque,

Figure 2 shows a second embodiment of a shaft coupling and

Figure 3 shows a third embodiment of a shaft coupling. Detailed description of the drawing

In the figures 1 to 3, an embodiment of a shaft coupling 1 for torque transmission is shown in each case, which can be used for example in a steering column of a motor vehicle. In any case, an inner shaft part 3 is axially displaceably mounted in an outer shaft part 2. While in the exemplary embodiments according to FIGS. 1 and 2 a triangular wave is provided as the inner shaft part 3, in the exemplary embodiment according to FIG. 3 the inner shaft part 3 has a substantially circular cross section. In all exemplary embodiments, three circumferential regions U1, U2, U3, which together form the total circumference of the shaft coupling 1, can be distinguished. Each circumferential region U1, U2, U3 extends over 120 °, wherein in the exemplary embodiments according to FIGS. 1 and 2, a respective triangle side of the inner shaft part 3 lies in a peripheral region U1, U2, U3.

The first two peripheral regions U1, U2 arranged in the representations below are arranged symmetrically with respect to a vertical plane V, which centrally intersects the third peripheral region U3. Cylindrical rollers 4 (FIGS. 1, 2) and balls 5 (FIG. 3) are provided as rolling elements serving as the linear bearing of the inner shaft part 3 in the outer shaft part 2. In a manner which is not visible, several, for example four, rolling bodies 4, 5 are arranged one behind the other in the axial direction of the shaft coupling 1. While the cylindrical rollers 4 - usually referred to as needles in the case of diameters of up to 6 mm - roll on smooth circumferential sections of the shaft parts 2, 3, the balls (FIG. 3) used in the case of the round shaft are in longitudinal grooves 6, 7 of the inner shaft part 3 and 3, respectively ., The outer shaft part 2 out. Regardless of the shape of the rolling elements 4, 5, these are in a arranged between the shaft parts 2, 3 cage 8, which may be made of plastic or metal, in particular by chipless deformation, and the rolling elements 4, 5 captive holds. In the third circumferential region U3 3 freewheel clutches 9, 10 are formed between the shaft parts, which are effective in opposite directions of rotation. Each of the one-way clutches 9, 10 has a ball 11, 12, which acts as a clamping body. While in the illustrated arrangements, the ball 11 prevents a rotation of the inner shaft member 3 in a clockwise direction with a fixed outer shaft part 2, the ball 12 blocks the one-way clutch 10 in the opposite direction of rotation. Overall, by means of the counter-rotating one-way clutches 9, 10, the inner shaft part 3 thus held against rotation in the outer shaft part 2. Between the balls 11, 12 designed as a helical spring spring element 13 is tensioned, so that the balls 11, 12 are kept permanently in clamping readiness. The designated α clamping angle is dimensioned such that the one-way clutches 9, 10 are operated approximately at the self-locking limit. It is therefore approximately tan α = μ, ie the clamping angle α is so large that the balls 11, 12 just do not slip (μ = coefficient of friction). The loaded by the spring element 13 balls 11, 12 press the inner shaft part 3 with a significant wedge effect in the direction of the first two peripheral portions U1, U2, in the illustrated arrangements vertically downwards. Thus, not only the freewheel clutches 9, 10, but also the linear bearings in the peripheral areas U1, U2 are permanently biased. Overall, the inner shaft part 3 is thus stored without clearance in the outer shaft part 2.

If the inner shaft part 3 is displaced axially relative to the outer shaft part 2, not only the rolling elements 4, 5 in the peripheral regions U1, U2, but also the balls 11, 12 roll in the third circumferential region U3 between the shaft parts 2, 3. The balls 11, 12 thus have in addition to their freewheeling function and a linear bearing function. In the exemplary embodiments according to FIGS. 2 and 3, in the third peripheral region U3, in addition to the balls 11, 12 realizing the freewheeling function, at least one additional rolling element 14 is axially offset therefrom. In the exemplary embodiments shown, the only one indicated in FIG Rolling element 14 to a ball, but at this point is also a cylindrical roller or Needle usable. Similar to the balls 5 arranged in the first two circumferential regions U1, U2 (FIG. 3), the ball 14 arranged in the third peripheral region U3 is also guided in longitudinal grooves 6, 7 of the inner shaft part 3 and of the outer shaft part 2. Thus, the ball 14 additionally counteracts a rotation of the inner shaft part 3 relative to the outer shaft part 2. At the visible in Figures 2 and 3, pair of oppositely-acting one-way clutches 9, 10 close in the axial direction one behind the other two additional rolling elements 14 at. Following this, there is another pair of one-way clutches 9, 10 between the shaft parts 2, 3, so that the additional rolling elements 14 in the axial direction on both sides of one-way clutches 9, 10 are adjacent.

In all illustrated embodiments, acting as a clamping body balls 11, 12 roll on cylinder jacket-shaped surface portions of the outer shaft part 2, while the inner shaft member 3 is formed in the contacted by the balls 11, 12 areas ramped to produce the desired freewheeling function. Notwithstanding this, it is also possible, in the region of the one-way clutches 9, 10 to make the inner shaft part 3 cylindrical, while the outer shaft part 2 has a ramp contour.

The designated diameter of the additional rolling elements 14 exceeds the diameter Dn of the balls 11, 12 clearly, in the embodiments of Figures 2 and 3 by more than 50%. The length of the cylindrical rollers or needles 4 is denoted by L ₄ , the minimum radius of the inner shaft part 3 by R _m in. The length L ₄ is at least 50%, in the embodiments of Figure 1 and 2 about 80% of the minimum radius R _m j _{n of} the inner shaft part 3. The cylindrical rollers or needles 4 are as well as the balls 5, 11, 12, 14th directly on both shaft parts 2, 3 at. The prestressed mounting of the inner shaft part 3 in the outer shaft part 2 serving spring element 13 does not claim any additional radial space, but uses the existing space between the shaft parts 2, 3 from. This is made possible by the fact that the spring element 13 exerts a force on the balls 11, 12 in the gap space 15 between the shaft parts 2 and 3, mainly in the tangential direction.

LIST OF REFERENCE NUMBERS

1 shaft coupling

2 outer shaft part

3 inner shaft part

4 cylindrical roller

5 ball

6 longitudinal groove

7 longitudinal groove

8 cage

9 overrunning clutch

10 overrunning clutch

11 ball

12 ball

13 spring element

14 rolling elements

15 gap space

α clamping angle μ friction coefficient

Dn diameter

Di ₄ diameter

U length

Rmin minimum radius

U1.U2, U3 circumference area

V vertical plane

Claims

claims 1. shaft coupling (1) for torque transmission, with shaft parts (2, 3) displaceable axially one inside the other, wherein rolling elements (4, 5, 11, 12, 14) are arranged for linear bearing, characterized in that in at least one peripheral region (U3) counteracting one-way clutches (9, 10) are provided, the balls (11, 12) as a clamping body, which also serve the linear bearing. 2. shaft coupling according to claim 1, characterized in that the total circumference of three peripheral regions (U1, U2, U3) is formed, wherein in two peripheral regions (U1, U2) only the linear bearing serving rolling elements (4, 5) are arranged during the third peripheral region (U3) has balls (11, 12) with a Linearlagerungs- and effective in the circumferential direction freewheeling function. 3. Shaft coupling according to claim 1 or 2, characterized in that a peripheral region (U1, U2, U3) has a plurality of axially arranged behind each other rolling elements (4, 5, 11, 12, 14). 4. shaft coupling according to claim 1 or 2, characterized in that in a counter-acting one-way clutches (9, 10) having peripheral portion (U3) at least one additional rolling elements (14) is arranged, which is not part of a one-way clutch (9, 10). 5. shaft coupling according to claim 4, characterized in that the additional rolling elements (14) between the rolling elements (11, 12) is arranged axially, the parts of one-way clutches (9, 10). 6. shaft coupling according to one of claims 1 to 5, characterized in that the inner shaft part (3) is designed as a substantially round shaft. 7. shaft coupling according to claim 6, characterized in that as exclusively the linear bearing serving rolling elements (5) balls are provided. 8. shaft coupling according to claim 7, characterized in that the shaft parts (2, 3) longitudinal grooves (6, 7) for guiding exclusively the Having linear bearing serving balls (5). 9. shaft coupling according to one of claims 1 to 5, characterized in that a triangular wave is provided as the inner shaft part (3). 10. Shaft coupling according to claim 9, characterized in that serving exclusively as the linear bearing rolling elements (4) cylindrical rollers or needles are provided. 11. Shaft coupling according to claim 10, characterized in that the length (L ₄ ) of a cylindrical roller or needle (4) is at least half of the minimum radius (FU _n ) of the inner shaft part (3).