Switchable support element for a valve train of an internal combustion engine

This application is a 371 of PCT/EP2007/063263 filed Dec. 4, 2007.

The invention concerns a switchable support element for a valve train of an internal combustion engine, said support element comprising a housing that can be arranged through an outer peripheral wall in a reception of the internal combustion engine and in whose bore an axially movable inner element extends, a head of the inner element protruding beyond an edge of the housing, coupling elements being associated to the inner element for a selective coupling of the inner element in an axially extended position of the inner element to the housing, and said inner element being biased by at least one lost motion spring in a direction leading out of the housing.

A hydraulically operating support element of the pre-cited type is disclosed in EP 1 411 214 A2 which is considered to be generic. A major drawback of this support element is its relatively large design height due, among other things, to the vertically stacked arrangement of lost motion spring, coupling mechanism and hydraulic unit. It is further noted that in case of a required dismounting (for example for adjusting coupling lash), the pistons arranged as coupling elements in the inner element can only be removed with some difficulty.

In other prior art solutions, a slide forming the coupling element is arranged laterally in the cylinder head and is displaceable for effecting coupling into a corresponding engagement surface of the support element. The person skilled in the art will readily perceive that this requires complex modifications to the design of the cylinder head and that such a device needs an unnecessarily large lateral design space.

The object of the invention is therefore to provide a support element of the pre-cited type in which the aforesaid drawbacks are eliminated.

The invention achieves the above object by the fact that the coupling elements are at least one slide which, in case of uncoupling, is positioned in a guide of the housing extending in radial or secant direction and which comprises a flattened upper side starting from a radially inner front end of the slide, and this flattened upper side can be brought into engagement with a flattened lower side of a recess in the outer peripheral wall of the inner element for effecting coupling.

Through these measures, the aforesaid drawbacks are eliminated. The support element of the present application has a relatively low axial height and requires no extra or only a slightly larger design space even in radial direction, so that no complex modifications are required in the region of the cylinder head as is the case in the initially cited prior art.

It is particularly advantageous if the support element comprises a hydraulic lash adjuster of a type, known per se, but even mechanical lash adjusting means are conceivable and intended within the scope of the invention.

Although the concept of the invention can be implemented even using only one slide as a coupling element, it is particularly advantageous to use two slides as coupling elements situated diametrically opposite each other. The invention preferably uses piston-like elements which, starting from their radially inner front end, are flattened on their upper side and, according to a particularly advantageous further feature of the invention, engage into a recess on the outer peripheral wall of the inner element, said recess being configured as a transverse slit comprising a straight slit base extending in secant direction.

Alternatively, an annular segment or a sickle-shaped configuration may be associated to each slide used as a coupling element, it being, however, also possible to use a circumferential or partially circumferential annular groove on the outer peripheral wall of the inner element for effecting coupling.

It is understood that a person skilled in the art will conceive further configurations for the coupling elements in this context, such as, for instance, flat slides or the like. Where appropriate, it is conceivable and intended to arrange a plurality of circumferentially spaced slides as coupling elements extending in radial direction within the housing.

By reason of the proposed flattened coupling construction, only negligible contact pressures are to be expected in the coupling region.

As a simple and design space-saving displacement means for the slides in coupling direction, the invention proposes to arrange on the outer peripheral wall of the housing at least one clip-like spring whose end pieces act on the outer front ends of the slides constituting the coupling elements. At the same time, this clip-like spring can also embody an anti-rotation feature for the slide or slides forming the coupling elements by providing the end pieces, for example, with a hook-shaped depression, or the like, which is then seated in a corresponding complementary longitudinal slot on the outer front end of the coupling element. Alternatively, it is also possible to let “smooth” end pieces extend in a circumferential slot of each slide.

According to a further advantageous feature of the invention, an anti-rotation device such as a pin or a ball is arranged between the inner element and the housing. Where appropriate, flattened portions can also be used in this region to form an anti-rotation feature of the inner element relative to the housing.

According to a further advantageous proposition of the invention, in case a pin is used, this pin can comprise a flattened lower and upper side so that vertical stops for the inner element relative to the housing are formed on both sides. If desired, it is also possible to create a vertical stop only on one side.

Besides this, it is also imaginable and intended to adjust a coupling lash through the pin as an anti-rotation device, needing no further elucidation at this point. For this purpose, pins grouped according to a height of their lower sides are kept available during the assembly procedure.

Alternatively, the coupling lash can also be adjusted through off-the-shelf slides grouped according to a height of their flattened upper sides.

A re-displacement of the slides in uncoupling direction completely into the guide of the housing is appropriately effected through a hydraulic medium. This can be routed via an annular groove on the outer peripheral wall of the housing through at least one cross-bore to the inner front end of the corresponding slides.

As lost motion spring, the invention proposes at least one coiled compression spring or the like, that acts at one end against a lower side of the inner element and at another end against a bottom of the housing. For a further reduction of the design height, the base of the inner element can also have a stepped configuration, so that the lost motion spring surrounds, at least partially peripherally, a high pressure chamber arranged in the inner element.

The invention will now be described more closely with reference to the appended drawing.

FIG. 1 shows a longitudinal section through a support element of the invention, taken in a region of slides of the support element,

FIG. 2 shows a longitudinal section corresponding to FIG. 1 but turned through 90° and comprising an anti-rotation device, and

FIG. 3 shows an enlarged representation of a cross-section through the support element of the invention taken in the region of the slides.

The figures show a switchable support element 1 for a valve train of an internal combustion engine. The support element 1 comprises a pot-shaped housing 2 in whose bore 4 an inner element 6 is received for axial displacement, a head 5 of the inner element 1 extending beyond an edge 7 of the housing 2 . The head 5 is a constituent part of a pressure piston 31 of a hydraulic lash adjuster installed in a bore 29 of the inner element 6 .

In its head-distal region, said pressure piston 31 comprises a crossbar 32 comprising a one-way valve 33 which opens in direction of a high pressure chamber 35 which is situated below the one-way valve 33 and defined in head-distal direction by a base 34 of the inner element 6 .

A lost motion spring 9 configured as a stack of springs extends between the base 34 of the inner element 6 and a bottom 37 of the housing 2 .

Two slides as coupling elements 8 are situated diametrically opposite each other in the housing 2 . These slides or coupling elements 8 are seated in respective guides 10 of the housing 2 and comprise, starting from their radially inner front ends 11 , stepped upper sides 12 .

The coupling elements 8 are shown in FIG. 1 in their coupled state in which the flat upper sides 12 cooperate with flat lower sides 13 of corresponding recesses 14 configured in the outer peripheral wall 15 of the inner element 6 . As best seen in FIG. 3 , the recesses 14 are configured as transverse slits comprising a straight slit bottom 16 extending in secant direction.

A radially inward displacement of the slides as coupling elements 8 in their coupling direction is effected through the force of a bow-shaped spring 16 a which is biased in inward direction. This spring 16 a acts through its end pieces 18 on outer front ends 19 of the slides constituting the coupling elements 8 . A guidance and anti-loss feature for the spring 16 a is created through a continuous groove 17 on the outer peripheral wall 3 of the housing 2 , the end pieces 18 of the spring 16 a , which in the present configuration comprise hook-shaped depressions, extend, at the same time, through positive engagement in longitudinal slots 20 of the outer front ends 19 of the slides as coupling elements 8 . In this way, a simple anti-rotation feature for the slides as coupling elements 8 relative to their guides 10 is created.

At the same time, FIGS. 2 , 3 also disclose that the inner element 6 is retained relative to the housing 2 through a pin-like anti-rotation device 21 which is fixed in a recess 22 of the housing 2 . This anti-rotation device 21 comprises, starting from its radially inner front end 24 , a flattened lower side 25 and a flattened upper side 26 which flattened lower and upper sides 25 , 26 limit displacements of the inner element 6 in its two directions of travel and, if desired, enable a coupling lash of the coupling elements 8 in an axially extended condition. By reason of the aforesaid anti-rotation device, a reliable positional association of the slides as coupling elements 8 to their recesses 14 is realized.

A return displacement of the slides as coupling elements 8 in uncoupling direction is effected through hydraulic medium. For this purpose, the outer peripheral wall 3 of the housing 2 comprises an annular groove 38 out of which two opposing cross-bores 39 extend through the housing 2 . Through these cross-bores 39 hydraulic medium can be routed into an annular space in front of radially inner front ends 11 of the slides as coupling elements 8 . As can be clearly seen, the radially inner front ends 11 of the slides as coupling elements 8 have a generally convex shape, so that a “good” delivery of hydraulic medium to these is guaranteed.

The housing 2 represented in the drawings may have a solid configuration but may also be configured as a deep-drawn or extrusion molded light-weight component.