Variable-Stroke Valve Drive With a Double Leg Spring

Abstract

A variable-stroke valve drive includes a double leg spring with a first spring leg and a second spring leg in a cylinder head of an internal combustion engine and a pivot lever. The pivot lever is supported on a guideway track of a guideway by a rolling element having a pivot point and the pivot lever, by way of a control track, is supported so as to be clearance-free on an intermediate element to a charge-cycle valve. The pivot lever is pivotable by a cam of a cam shaft for adjusting a stroke and the pivot point is displaceable parallel to the guideway track by an adjustment installation for adjusting a stroke height. The double leg spring in a central region forms an intermediate leg. A respective end of the first and second spring legs is formed to be largely parallel to a longitudinal axis of the double leg spring.

Claims

1.-4. (canceled)

5. A variable-stroke valve drive, comprising: a double leg spring with a first spring leg and a second spring leg in a cylinder head of an internal combustion engine; and a pivot lever, wherein the pivot lever is supported on a guideway track of a guideway by a rolling element having a pivot point, wherein the pivot lever by way of a control track is supported so as to be clearance-free on an intermediate element to a charge-cycle valve, wherein the pivot lever is pivotable, counter to a force of the double leg spring, in a controlled manner by a cam of a cam shaft for adjusting a stroke, and wherein the pivot point is displaceable in a controlled manner parallel to the guideway track by an adjustment installation for adjusting a stroke height; wherein the double leg spring in a central region of the double leg spring forms an intermediate leg having a reversal of a rotation direction of the first and second spring legs and wherein the double leg spring is able to be assembled in a region of the intermediate leg; wherein a respective end of the first and second spring legs is formed to be largely parallel to a longitudinal axis of the double leg spring.

6. The variable-stroke valve drive according to claim 5, wherein the respective end of the first and second spring legs is formed toward an inside or an outside of the variable-stroke valve drive.

7. The variable-stroke valve drive according to claim 5, wherein the respective end of the first and second spring legs is bent approximately 90° with respect to the respective first and second spring leg.

8. The variable-stroke valve drive according to claim 5, wherein the pivot lever has a respective contact face for the respective end of the first and second spring legs.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1 shows a perspective view of a portion of a generic variable-stroke valve drive according to the prior art;

[0017] FIG. 2 shows a lateral view of a variable-stroke valve drive according to the invention in comparison to the prior art; and

[0018] FIG. 3 shows a perspective view of the variable-stroke valve drive according to the invention in comparison to the prior art.

DETAILED DESCRIPTION OF THE DRAWINGS

[0019] The same reference signs apply hereunder to identical construction elements in FIGS. 1 to 3.

[0020] FIG. 1 shows a perspective view of a portion of a generic variable-stroke valve drive 1 with a double leg spring 2 according to the prior art. The portion is provided for two charge-cycle valves 9, wherein only one charge-cycle valve 9 is provided with a reference sign. This valve drive 1 can be installed in a cylinder head of an internal combustion engine (not illustrated) and is known from the prior art, i.e., DE 10 2006 033 559 A1.

[0021] The valve drive 1 comprises a pivot lever 3 which by way of a rolling element 4 having a pivot point is supported on a guideway track 5 of a guideway 6, on the one hand, and by way of a control track 7 is supported so as to be clearance-free on an intermediate element 8, a roller cam follower, to a charge-cycle valve 9, on the other hand. In order to be supported without any clearance, the intermediate element 8 in relation to the charge-cycle valve 9 is supported on a clearance compensation element 14, preferably a hydraulic clearance compensation element 14. In order for the stroke to be adjusted, the pivot lever 3, counter to a force of the double leg spring 2, is pivotable in a controlled manner between the support points of a cam (not illustrated) of a camshaft, on the one hand, and the pivot point of an adjustment installation 10, an eccentric shaft, for adjusting the stroke height is displaceable in a controlled manner parallel to the guideway track 5, on the other hand. Furthermore, the double leg spring 2 in the central region thereof forms an intermediate leg 11 having a reversal of the rotation direction of the two spring legs 2a, 2b (2b is not provided with the reference sign due to being invisible), wherein the intermediate leg 11 is encased by a sheet-metal assembly plate. Using an assembling means, the double leg spring 2 is able to be fastened either to the cylinder head or to a shaft bearing (not illustrated). In terms of the functional mode of the variable-stroke valve drive 1 reference is also made to international patent application WO 02/092972 A1.

[0022] As has already been illustrated, the known double leg spring embodiment has spring legs 2a, 2b with an S-bend, wherein the spring legs 2a, 2b engage on the contact faces on the pivot lever 3 from “above” and when assembling are introduced into lateral guide tabs (not provided with a reference sign) of the pivot lever 3 from “the rear”.

[0023] FIG. 2 shows a lateral view of a variable-stroke valve drive 1 according to the invention in comparison to the prior art. The same circumstances apply to FIG. 2 as to FIG. 1. The spring leg 2a which is at the bottom in the drawing corresponds to the embodiment according to the prior art; the spring leg 2b which is at the top in the drawing corresponds to the design embodiment according to the invention. According to the invention, the end of the spring leg 2b in this comparison is formed so as to be largely parallel to a longitudinal axis 12 of the double leg spring 2.

[0024] In the present exemplary embodiment, the spring leg 2b is formed toward the inside. In a further exemplary embodiment, the spring leg 2b may also be formed toward the outside.

[0025] Furthermore, the spring leg 2b in the present exemplary embodiment is formed by approx. 90°, larger or smaller forming angles also being possible here.

[0026] In order for the spring leg 2b to bear in the best possible manner, the pivot lever 3 for each end of the spring legs 2a, 2b according to the invention has one corresponding contact face 13.

[0027] FIG. 3 shows a perspective view of the variable-stroke valve drive 1 according to the invention in comparison to the prior art. The same as has been discussed in the context of FIG. 2 applies. Finally, it is to be mentioned that both spring legs 2a, 2b of the double leg spring 2 in reality—and as opposed to FIGS. 2 and 3-have the L-shape, and the pivot lever 3 has one contact face 13 for each spring leg 2a, 2b.

[0028] The following advantages are derived by virtue of the design embodiment according to the invention:

[0029] 1. The spacing of the spring leg 2b in the region of the intermediate lever 3 from the eccentric, the adjustment element 10, is significantly enlarged, thus making possible an enlargement of the rotation angle of the eccentric shaft (up to 300°). As a result, there is a larger adjustment angle available for designing the stroke function of the variable-stroke valve drive 1. A larger eccentric stroke can thus be implemented without enlarging the adjustment torque of the variable-stroke valve drive 1.

[0030] 2. Furthermore, the design embodiment according to the invention leads to improved assembling. The L-shaped spring leg 2b of the double leg spring 2 needs only to be placed on the corresponding contact face 13 of the intermediate lever 3. Advantageously, no additional positioning of the spring leg 2b is required, thus ruling out any assembly error.

LIST OF REFERENCE CHARACTERS

[0031] 1 Valve drive [0032] 2 Double leg spring [0033] 2a Spring leg according to the prior art [0034] 2b Spring leg according to the invention [0035] 3 Pivot lever [0036] 4 Rolling element [0037] 5 Guideway track [0038] 6 Guideway [0039] 7 Control track [0040] 8 Intermediate element [0041] 9 Charge-cycle valve [0042] 10 Adjustment installation [0043] 11 Intermediate leg [0044] 12 Longitudinal axis [0045] 13 Contact face [0046] 14 Clearance compensation element