Patent Publication Number: US-7900591-B2

Title: Switchable component for a valve train of an internal combustion engine

Description:
FIELD OF THE INVENTION 
     The invention concerns a switchable component for a valve train of an internal combustion engine, said component comprising a housing in whose bore an axially displaceable inner element comprising coupling elements is received, said coupling elements, for effecting coupling [axially distant relative position of the inner element to the housing], being able to be brought partially into engagement with an entraining surface of the housing, the inner element being biased in outward direction from the housing by a lost motion spring, an axially fully extended position of the inner element being defined by an upper vertical stop means overlapping an annular gap between the inner element and the housing, in which extended position, a coupling position of the coupling elements with coupling lash relative to an entraining surface of the coupling elements is created, and an (outer) anti-rotation device extending from an outer casing of the housing projects beyond a surrounding structure. 
     BACKGROUND OF THE INVENTION 
     A component of the pre-cited type, configured, for instance, as a switchable support element is sufficiently well-known in the technical field. The outer anti-rotation device can be configured, for example, as a pin or the like that is pressed into a reception of an outer casing of the housing and cooperates with a corresponding groove of a surrounding structure (cylinder head). It is clear to a person skilled in the art that this interference fit can get disengaged during operation of the valve train. In addition, this pressing-in is accompanied by an undesired introduction of force into the surrounding material. Furthermore, under certain circumstances, said pin cannot be removed in case of a “faulty pressing”. 
     The aforesaid outer anti-rotation device is required, for example, if it is desired to realize a supply of hydraulic medium, for example, to the at least one coupling element or to a lash adjuster integrated in the component, without having recourse to annular grooves on the outer casing of the housing or in the reception bore of the cylinder head which makes an exact relative positioning of the hydraulic medium channels to each other necessary. 
     OBJECTS OF THE INVENTION 
     It is an object of the invention to provide a component of the pre-cited type in which the aforesaid drawbacks are eliminated with simple measures. 
     SUMMARY OF THE INVENTION 
     The invention achieves the above objects by the fact that the outer anti-rotation device is configured as a C-shaped, thin-walled ring comprising a slit, said ring extends after the manner of a clip in an annular groove in the outer casing of the housing parallel to a transversal plane of the component and, for effecting (outer) anti-rotation, said ring projects with a sickle-like portion of an outer peripheral surface beyond the outer casing of the housing, and a remaining outer peripheral portion of said ring does not protrude beyond the outer casing of the housing. 
     In this way, the aforesaid drawbacks are effectively eliminated. The switchable component is typically a switchable support element or a switchable roller-type or mushroom-type tappet; however, if appropriate, the component can also be a cup tappet or the like. 
     The slit, thin-walled ring (C-shaped or, if required, U-shaped) proposed by the invention can be manufactured extremely economically and, due to its arrangement in an annular groove in the outer casing of the housing, it is assured that the ring does not get disengaged or change its position during operation. 
     Thus, a very easy to mount and an extremely inexpensive outer anti-rotation device (ring) that can serve at the same time as an upper vertical stop means is obtained. Particularly preferably (but not necessarily), this stop means defines at the same time a coupling position of the coupling element with coupling lash relative to its entraining surface. If appropriate, the coupling lash can also be adjusted through other measures, so that only an upper vertical stop means is combined with the outer anti-rotation device in one single component. 
     For installing the component (e.g. support element) in a reception bore of a surrounding structure (cylinder head), it is only necessary to provide the reception bore with a short counterbore offset from the axis and seat the sickle-like portion of the ring in this counterbore for anti-rotation purposes. The additional machining work required is strongly limited also because the machining direction remains the same. A milling tool or the like may also be used in place of a boring tool. 
     Further advantageous features of the invention described below can also contain measures that are patentable on their own. 
     The ring of the invention is thus proposed as a so-called “multi-function” component. If, as proposed above, this ring is to be configured at the same time as an upper vertical stop means, it projects with an appropriate inner peripheral segment through an aperture in the outer casing of the housing, this inner peripheral segment preferably bears against a longitudinal flattened portion on the outer peripheral surface of the inner element, and in the extended position of the inner element, a lower edge of the longitudinal flattened portion cooperates with a lower surface of the inner peripheral segment. 
     In a further development of the invention, it is proposed to use the ring at the same time as an inner anti-rotation device (inner element relative to the housing). For this purpose, an appropriate inner peripheral segment of the ring again projects through an aperture of the housing, a longitudinal flattened portion is likewise arranged in the outer peripheral surface of the inner element, and for achieving anti-rotation, a complementary surface (key surface) of the inner peripheral segment extends directly on this longitudinal flattened portion. Thus, in this embodiment, the ring is used both for realizing an “outer” and an “inner” anti-rotation device. 
     According to a further proposition of the invention, the “outer” and the “inner” anti-rotation device as well as the upper vertical stop for defining the coupling position are embodied in the component “ring”. Thus, as the person skilled in the art will at once understand, separate components for these functions can be dispensed with. 
     According to a particularly preferable feature of the invention, the outer peripheral surface of the ring, with the exception of the sickle-shaped portion, should not protrude beyond the outer casing of the housing in the installed state and the ring should possess exactly two inner peripheral segments that are situated opposite each other and enclose the sickle-shaped portion, which sickle-shaped portion should be situated opposite the slit. 
     The invention further proposes to realize the protruding portion of the ring either through an axis-offset annular groove in the housing or through an eccentric portion of the ring, the second measure being particularly economic to implement from a manufacturing point of view. 
     For realizing the ring with the above-discussed “multi-functionality”, it is possible to have recourse to a mass product and modify this slightly. The ring can be made of a spring steel or the like, but a configuration in a plastic material is also possible. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The invention will now advantageously be described more closely with reference to the appended drawing in which 
         FIG. 1  shows a longitudinal section through a switchable component, in the present example, a support element; 
         FIG. 2  shows a component similar to the one of  FIG. 1 , but turned through 90° and not in a sectional view; 
         FIG. 3  is a schematic view of a surrounding structure (cylinder head) for the component, and 
         FIG. 4  shows a transversal section through the component of  FIG. 1  taken in a region of a ring of the component. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWING 
     The figures illustrate a switchable component  1 , in the present case, a support element, for a valve train of an internal combustion engine. The component  1  comprises a hollow cylindrical housing  2  having a bore  3 . An inner element  4  is seated in the bore  3  for axial displacement relative to the housing  2 . The inner element  4  is biased in a direction leading out of the housing  2  by a lost motion spring  7  configured in the present case as a coiled compression spring (or a stack of coiled compression springs). 
     As disclosed in  FIG. 1 , two coupling elements  5  configured in the form of pistons are situated diametrically opposite each other in a radial bore  26  of the inner element  4 . For effecting coupling between the inner element  4  and the housing  2 , these coupling elements  5  are displaced into an entraining surface  6  of the housing  2  and partially overlap an annular gap  8  between the housing  2  and the inner element  4 . The entraining surface  6  can be constituted, for instance, as an aperture, a segment-like cavity or even an annular groove or the like. 
     In an annular groove  14  made in the outer casing  10  of the housing  2  is seated a C-shaped ring  13 . As best seen in  FIG. 2 , this ring  13  projects with a sickle-shaped portion  15  of its outer periphery  16  beyond the outer casing  10  of the housing  2 . The remaining portion of the outer periphery  16  of the ring  13  does not protrude beyond said outer casing  10  of the housing  2 . The projecting portion  15  creates an (outer) anti-rotation device for the entire component  1  relative to the surrounding structure  12   a  (cylinder head  30 ). This ring  13  serves at the same time as an upper vertical stop means  9  and as a means  24  for forming an “inner” anti-rotation device of the inner element  4  relative to the housing  2 . 
     The housing  2  comprises two opposing apertures  18 . Through each aperture  18  projects an appropriately configured inner peripheral segment  19  of the ring  13 . Complementary surfaces  25  of the ring  13  configured as bowstring-like key surfaces are arranged opposite each other on the inner peripheral segments  19 . In the outer peripheral surface  20  of the inner element  4  is arranged facing each of the inner peripheral segments  19 , a longitudinal flattened portion  21 . The complementary surface  25  of each inner peripheral segment  19  cooperates with a respective one of the longitudinal flattened portions  21 . It is thus clear that the aforesaid inner anti-rotation device (means  24 ) is created through the support of the complementary surface  25  on the opposing longitudinal flattened portion  21 . At the same time, when a lower edge  22  of the longitudinal flattened portion  21  comes to abut against a lower surface  23  of the inner peripheral segment  19  in the extended state, the upper vertical stop means  9  becomes operative. This also creates a coupling position of the coupling elements  5  with coupling lash relative to the entraining surface  6  in the housing  2 . This coupling lash is adjusted such that its variation over a large number of like components  1  is extremely small. 
     It is true that the axis of the annular groove  14  for the ring  13  can be configured with an offset, so that the ring  13  projects with its sickle-shaped portion  15  beyond the outer casing  10  of the housing  2 . However, for realizing the outer anti-rotation device  11 , according to a particularly preferred embodiment, the ring  13  in itself is configured with an appropriate eccentric portion. 
     The component  1  disclosed in  FIG. 2  can be inserted, according to  FIG. 3 , into a reception bore  29  of a surrounding structure  12   a  (cylinder head  30 ), the sickle-shaped portion  15  of the ring  13  for realizing anti-rotation then being seated in a counterbore  31 . 
     LIST OF REFERENCE NUMERALS 
     
         
           1  Component 
           2  Housing 
           3  Bore 
           4  Inner element 
           5  Coupling element 
           6  Entraining surface 
           7  Lost motion spring 
           8  Annular gap 
           9  Upper vertical stop means 
           10  Outer casing of housing 
           11  (Outer) anti-rotation device 
           12  Slit 
           12   a ) Surrounding structure 
           13  Ring 
           14  Annular groove 
           15  Sickle-shaped portion 
           16  Outer peripheral surface of ring 
           17  Outer peripheral portion 
           18  Aperture 
           19  Inner peripheral segment 
           20  Outer peripheral surface of inner element 
           21  Longitudinal flattened portion 
           22  Lower edge of longitudinal flattened portion 
           23  Lower surface of inner peripheral segment 
           24  Means (inner anti-rotation device) 
           25  Complementary surface 
           26  Radial bore 
           27  Head 
           28  Edge 
           29  Reception bore 
           30  Cylinder head 
           31  Counterbore