TORSIONAL VIBRATION DAMPER HAVING A HELICAL SPRING ASSEMBLY

Abstract

Torsional vibration damper for a drivetrain of a motor vehicle, having a primary element rotatable around a rotational axis and a secondary element rotatable relative to the primary element against an energy storage. The energy storage includes a helical compression spring unit. The helical compression spring unit is provided in a spring channel, and the helical compression spring unit includes an outer spring. The outer spring is formed as an arc spring and an inner spring is provided inside of the outer spring and virtually coaxial to the outer spring. The inner spring when disassembled from the helical compression spring unit is formed as a straight helical compression spring. The inner spring has a winding direction that is opposed to a winding direction of the outer spring and the inner spring when installed in the torsional vibration damper, is shorter than the outer spring by a value of x.

Claims

1.-12. (canceled)

13. A torsional vibration damper for a drivetrain of a motor vehicle, comprising: a primary element rotatable around a rotational axis; an energy storage that comprises a helical compression spring unit, wherein the helical compression spring unit comprises: an outer spring formed as an arc spring; and an inner spring is provided inside of the outer spring and virtually coaxial to the outer spring, wherein the inner spring when disassembled from the helical compression spring unit is formed as a straight helical compression spring; a spring channel in which the helical compression spring unit is provided; and a secondary element rotatable relative to the primary element against the energy storage, wherein the inner spring has a winding direction which is opposed to a winding direction of the outer spring, and wherein the inner spring when installed in the torsional vibration damper is shorter than the outer spring by a value of x.

14. The torsional vibration damper according to claim 13, wherein the value x is less than or equal to an outer diameter of the outer spring.

15. The torsional vibration damper according to claim 13, wherein the inner spring in disassembled condition provides at least a first spring region, a second spring region, and a third spring region in axially staggered manner, and wherein the first spring region and the third spring region are at respective ends of the inner spring, and wherein the second spring region is a middle spring region.

16. The torsional vibration damper according to claim 15, wherein the first spring region provides a first winding distance, the second spring region provides a second winding distance, and the third spring region provides a third winding distance, and wherein the first winding distance and the third winding distance are shorter than the second winding distance.

17. The torsional vibration damper according to claim 16, wherein the first winding distance, the second winding distance or the third winding distance extend in one of a constant, progressive, or degressive manner.

18. The torsional vibration damper according to claim 16, wherein an outer diameter of the first spring region and the third spring region of the inner spring decreases toward a respective spring end.

19. The torsional vibration damper according to one of claim 13, wherein each spring end of the inner spring is radially guided by a respective spring plate.

20. The torsional vibration damper according to claim 13, wherein at least one of the outer spring and the inner spring are surface-treated by a hardening process.

21. The torsional vibration damper according to claim 20, wherein the hardening process is a nitriding process.

22. The torsional vibration damper according to claim 13, wherein at least one spring end tip is located radially outward or at least virtually radially outward when installed.

23. The torsional vibration damper according to claim 13, wherein the helical compression spring unit comprising at least the outer spring and the inner spring has in disassembled condition a radius of curvature which is one of virtually identical to or identical to, a radius of curvature of the spring channel.

24. The torsional vibration damper according to claim 13, wherein a distance between an outer diameter of the inner spring and an inner diameter of the outer spring amounts to between 1% and 9% of an outer diameter of the outer spring.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The invention is described by way of example in the following. The drawings show:

[0014] FIG. 1 is a torsional vibration damper according to the invention;

[0015] FIG. 2 is a helical compression spring unit;

[0016] FIG. 3 is a straight inner spring;

[0017] FIG. 4 is a helical compression spring unit with spring plate; and

[0018] FIG. 5 is a helical compression spring unit with spring plate.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

[0019] FIG. 1 is a torsional vibration damper 1 according to the invention with a primary element 5 and a secondary element 8. The primary element 5 and the secondary element 8 are rotatable relative to one another against the force of an energy storage 4, in the present instance a helical compression spring unit 9. The helical compression spring unit comprises at least one outer spring 10 and an inner spring 20 provided coaxial to the outer spring. The outer spring 10 is supported radially outwardly at a spring channel 18. The two springs 10, 20 act in parallel. The outer spring is formed in the present instance as an arc spring 11, and the inner spring is formed as a straight helical compression spring 21. It should be noted for the sake of completeness that the arc spring is a helical compression spring that is also curved, i.e., has a radius of curvature, in a disassembled condition. Conversely, the inner spring 20 is formed as a straight helical compression spring, which is more advantageous than an arc spring in terms of production costs.

[0020] The helical compression spring unit 9 is more readily seen in FIG. 2. In this case, the inner spring 20, which is straight in the uninstalled condition has been inserted into the outer spring 10. It is crucial for reliable functioning that the inner spring 20 is shorter than the outer spring 10. This is because the outer spring 10 can get stuck in the spring channel 18 as a result of the centrifugal force and consequent frictional force, and the inner spring can exit. This can bring about additional bending stresses and can even lead to the two springs 10, 20 getting caught. This exiting or catching effect can be mitigated by an inner spring 20 that is shorter than the outer spring 10, which can also have an advantageous effect on operating reliability and service life. The inner spring is to be formed shorter than the outer spring by a value x. In this regard, it has proven advantageous when the value x is between 1% and 9% of the outer diameter of the outer spring DaA.

[0021] The individual inner spring 20 is shown as straight helical compression spring 21 in FIG. 3. It can be seen clearly that the inner spring is divided into a first spring region 40, a second spring region 42, and a third spring region 44. The first spring region 40 and the third spring region 44 are located at the respective spring ends 46, 47, while the second spring region 42 comprises the middle spring region. FIG. 3 clearly shows that a winding distance WA2 extends in a virtually constant manner in the second spring region 42, while winding distance WA1 becomes smaller toward spring end 46 in the first spring region 40. It is the same case with winding distance WA3 at the third spring region 44, which likewise becomes smaller toward spring end 47. It can also be seen clearly here that the outer diameter of the inner spring DaI measured in the second spring region 42 becomes smaller toward spring ends 46, 47 in the area of the first spring region 40 and third spring region 44.

[0022] A helical compression spring unit 9 is shown in FIG. 4 and FIG. 5, a spring plate 22, 23 being provided at the respective ends of the helical compression spring 9. Spring plates 22, 23 comprise a spring plate pin 24, 25, respectively, and the spring plate pins 24, 25 engage in the inner diameter of the inner spring 20 and guide the inner spring 20 in radially outward direction. It is understood that the spring plates 22, 23 are supported in turn radially outwardly at the spring channel 18 as can be seen particularly clearly in FIG. 5. The contact area K of inner spring 20 with outer spring 10 is shown clearly in FIG. 4. The contact area K is located in the middle region of the helical compression spring unit 9. The outer windings of the inner spring 20 come in contact with the inner windings of the outer spring 10, and the inner spring 20 is supported radially outwardly at the outer spring 10 in this area K. In case no spring plates are used, it should further be noted that the outer spring 10, while certainly formed as an arc spring 11, may be provided in the disassembled condition with a radius of curvature that is smaller than the radius of curvature of the spring channel 18. When the straight inner spring 20 is inserted into the curved outer spring 10, the radius of curvature of the outer spring 10 increases as a result of the inner spring 20. In this regard, it is advantageous when the radius of curvature of the helical spring unit 9 corresponds to the radius of curvature of the spring channel 8 after the inner spring 20 has been inserted into the outer spring 10. This can reduce further stresses on the springs 10, 20.

[0023] It can also be seen clearly in FIG. 4 that the respective spring end tips 31, 32 are directed radially outward. This can reduce further stresses in the inner spring 20 especially during operation.

[0024] Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.