Patent Publication Number: US-7900592-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 is received, at least one coupling means being arranged in the inner element, said coupling means, 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 at least one lost motion spring, an axially fully extended position of the inner element being defined by a stop means overlapping an annular groove between the inner element and the housing, and an anti-rotation device being arranged between the inner element and the housing. 
     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 anti-rotation device can be configured in the form of crosswise extending pin that is fixed in a reception of one of the components (housing or inner element) and projects into a corresponding groove on the respective other one of the components. This pin is pressed, for instance, into the aforesaid reception. 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, said pin cannot be removed in case dismounting becomes necessary (selective pairing of pins grouped according to thickness for adjusting a coupling lash . . . ). 
     OBJECTS OF THE INVENTION 
     It is an object of the invention to provide a switchable 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 anti-rotation device is a thin-walled ring comprising a slit, a central rectangular extension [situated diametrically opposite the slit] projects inwards from the inner peripheral surface of said ring which extends parallel to a transversal plane of the component on an outer peripheral surface of the housing, the housing comprises an aperture that is complementary in shape to the extension of the ring and said extension extends through said aperture, a counter surface for the extension extends in the form of a longitudinal flattened portion or a longitudinal groove in the outer peripheral surface of the inner element and, for effecting anti-rotation, the extension extends with a complementary inner surface directly on or into said counter surface. 
     Thus a switchable component such as a switchable support element or a switchable roller or mushroom-type tappet that is free of the aforesaid drawbacks is created. The proposed, thin-walled slit ring can be manufactured extremely economically and it is assured in a very simple manner that the ring cannot get disengaged or change its position during operation. In case of a torque being applied by the inner element, during installation of the aforesaid component in a surrounding structure, such as a cylinder head, a support for the ring in radially outward direction is given on the cylinder head, so that the ring cannot be spread further in radially outward direction. 
     The ring according to the invention can be made, for example, of a simple spring steel or the like. However, it is also conceivable to make it out of a plastic material or the like. Additionally, it is both conceivable and intended to use a readily available mass product to make the inventive ring by modifying only the extension. 
     Through the annular groove in the outer peripheral surface of the housing proposed by the invention, the ring is axially fixed in a simple manner and loss of the ring is prevented. If necessary, a plurality of extensions may be provided on the inner peripheral surface of the ring to project radially inwards and cooperates with corresponding apertures in the housing. 
     It is particularly advantageous for the ring to have a C-shaped profile but, if need be, it may also have a U-shaped or similar profile, and it is particularly preferable for the ring to surround more than half of an outer peripheral surface of the housing. 
     Optionally, through an underside of its extension, the ring can at the same time form a stop for an outward movement of the inner element out of the housing. In this way, a maximum extended position of the inner element is defined for transportation but also during operation. However, in this connection, it is particularly preferable for the ring to be used at the same time to adjust a coupling position of the coupling means (for example at least one piston-like slide) with coupling lash. This coupling lash is adjusted by using off-the-shelf rings grouped in thicknesses, but the variation of the coupling lash should be kept as low as possible over a large series of components. By coupling lash is to be understood an idle motion that the inner element, with extended coupling means and in its stop position on the ring, has to execute in direction of the housing till the coupling means comes to abut on the corresponding entraining surface of the housing. 
     The entraining surface of the housing is configured, for instance, as an aperture or lenticular cavity or the like for each coupling means. Also conceivable is an annular groove or the like. 
     Alternatively to the aforesaid, it is also possible to use a circlip or a stack of circlips as a stop means that is seated in an annular groove on the inner peripheral surface of the housing. For effecting stopping, a lower surface of an appropriate diameter reduction of the outer peripheral surface of the inner element comes to abut against a lower edge of the circlip. This circlip or stack of circlips can be used at the same time for adjusting the aforesaid coupling position of the coupling means with coupling lash relative to its entraining surface. It is conceivable and intended in this connection to hold in stock the circlip (or, in the case of a circlip stack, at least one of the circlips) grouped according to thickness. 
     Where appropriate, the switchable component may also be a switchable cup tappet. In this case, too, it is conceivable and intended to arrange the coupling, means in the housing and displace it radially inwards in direction of the inner element for achieving coupling. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The invention will now advantageously be explained more closely with reference to the appended drawing in which 
         FIG. 1  shows a longitudinal section through a switchable component, configured in this example as a switchable support element, and 
         FIG. 2  shows an enlarged cross-section through the component of  FIG. 1  taken in a region of a ring of this component. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWING 
     The figures show a switchable component  1 , configured in the present case as a support element for a valve train of an internal combustion engine. The component  1  has a hollow cylindrical housing  2  comprising a bore  3 . In this bore  3  is seated, for axial displacement relative to an inner peripheral surface  24  of the housing  2 , an inner element  4 . This 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 spring (or a stack of coiled compression springs). 
     As indicated in  FIG. 1 , at least one coupling means  5  configured as a piston is seated in a radial bore of the inner element  4 . For coupling the inner element  4  to the housing  2 , this coupling means  5  can be displaced into an entraining surface  6  (see indications in  FIG. 2 ) by partially overlapping an annular groove  8  between the housing  2  and the inner element  4 . The entraining surface  6  is configured, for example, as a lenticular cavity or a milled recess or the like. 
       FIG. 1  additionally discloses that an extended position of the inner element  4  out of the housing  2  is defined by a stop means  9  which, in the present case, is configured as a stack of circlips  25  and disposed in an annular groove  23  in the inner peripheral surface  24  of the housing  2 . Advantageously, this stack of circlips  25  at the same time adjusts a coupling position of the coupling means  5  with coupling lash relative to its entraining surface  6 . Appropriately, the uppermost circlip is kept in stock in different thickness groups for assembly. Alternatively, the stack of circlips or the circlip may also be connected to the inner element  4  and cooperate with a corresponding counter surface on the bore  3  of the housing  2  for effecting stopping. 
     As illustrated, an anti-rotation device  10  is arranged between the inner element  4  and the housing  2 . This device comprises a thin-walled ring having a slit  11 . As shown in  FIG. 2 , this slit  11  extends over approximately one quarter of an outer peripheral surface  14  of the housing  2 . 
     As can be seen in  FIG. 2 , a rectangular extension  13  projects inwards from a central position from an inner peripheral surface  12  of the ring  10  and has a flat inner surface  18 . The ring  10  is fixed in an annular groove  19  in the outer peripheral surface  14  of the housing  2 . Advantageously the ring  10  does not project with its outer peripheral surface  20  beyond the outer peripheral surface  14  of the housing  2 . 
     As a person skilled in the art will further understand from the drawing, the aforesaid extension  13  extends in a complementary aperture  15  of the housing  2 . This aperture  15  can be made, for instance, by punching. 
     A longitudinal flattened portion provided on the outer peripheral surface  16  of the inner element  4  constitutes a counter surface  17  for the extension  13 . To prevent rotation, the inner surface  18  of the extension  13  extends directly on this flattened portion. For assembly, the ring  10  is held parallel to a transverse plane of the component  1  and slipped onto the outer peripheral surface  14  of the housing  2 , with the slit foremost or it is pushed axially onto the component  1  from above, with its legs  32  slightly spread out. 
     The aforesaid anti-rotation device  10  formed with the help of the ring is necessary, for instance, for a correct orientation of the piston-type coupling means  5  relative to the segment-shaped cavity that forms the entraining surface  6 . The anti-rotation device can also become necessary if a conveyance of hydraulic medium into the interior of the component  1  (for instance, to a hydraulic lash adjuster or to the coupling means  5  in the inner element  4 ) must be realized without having recourse to annular grooves. 
     If the stack of circlips  25  disclosed in the drawing is omitted, it is also possible to configure the ring  10  at the same time as a stop means  9 . In this case, stopping is achieved by an abutment of a lower edge  21  of the counter surface  17  of the inner element  4  formed by the longitudinal flattened portion against an underside  22  of the extension  13  of the ring  10 . 
     As mentioned above, the component  1  of  FIG. 1  can be designed as a support element. A head  29  (not shown in full) of the inner element  4  protrudes beyond an upper edge  30  of the housing  2  and serves as a support for at least one lever-type cam follower (finger follower). Through an outer peripheral surface  14 , the housing  2  can be fixed in position in a reception of a cylinder head and hydraulic medium can be conveyed to this reception for switching the coupling means  5  and for supply to the hydraulic lash adjuster installed in the inner element  4 . 
     LIST OF REFERENCE NUMERALS 
     
         
           1  Component 
           2  Housing 
           3  Bore 
           4  Inner element 
           5  Coupling means 
           6  Entraining surface 
           7  Lost motion spring 
           8  Annular gap 
           9  Stop means 
           10  Anti-rotation device, ring 
           11  Slit 
           12  Inner peripheral surface 
           13  Extension 
           14  Outer peripheral surface 
           15  Aperture 
           16  Outer peripheral surface of inner element 
           17  Counter surface 
           18  Inner surface 
           19  Annular groove 
           20  Outer peripheral surface of ring 
           21  Lower edge 
           22  Underside of ring 
           23  Annular groove 
           24  Inner peripheral surface of housing 
           25  Circlip, stack of circlips 
           26  Lower edge 
           27  Lower surface 
           28  Diameter reduction 
           29  Head 
           30  Edge 
           31  Underside 
           32  Leg