Abstract:
An apparatus for adjusting the stroke of a valve that is actuated by a camshaft having at least one cam is provided. A valve lever having an outer lever and an inner lever is provided and has a first end region supported on a fixed component, and a second end region for actuating a valve. The U-shaped outer lever includes two arms and a crosspiece that faces the fixed component. At least one of the arms is provided with an abutment surface for contacting the at least one cam. The inner lever is mounted on a free end of the outer lever between the arms, and has an abutment surface, for contacting cams, that is disposed between the mounting axis of the inner lever on the arms and the support of the first end region of the valve lever on the fixed component. A blocking device is provided for fixing the crosspiece of the outer lever on an end of the inner lever remote from the valve, this end being supported on the fixed component and containing the blocking device.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to an apparatus for the adjustment of the stroke or lift of a valve actuated by a camshaft. 
   Apparatus for the adjustment of the stroke of charge changing valves of internal combustion engines offer great advantages for numerous applications. For example, by reducing the stroke in the partial throttle range the mixture preparation can be improved, thereby reducing consumption and the content of noxious material in the exhaust gas. 
   An apparatus of this type is know from U.S. Pat. No. 4,203,397. With this apparatus, the entire U-shaped outer lever is supported on a hydraulic play-compensating element. The inner lever is mounted at the free end of the arms of the outer lever. A blocking device for blocking the pivotability of the inner lever relative to the outer lever is provided with a pivot element that is mounted on the arms of the outer lever adjacent to the free end region of the inner lever; by means of a stationary electro magnet, the pivot element is pivotable into the path of movement of the inner lever, thereby blocking the pivotability of the inner lever relative to the outer lever. The camshaft has a full stroke cam that cooperates with a contact surface of the inner lever, and partial stroke cams that are disposed on both sides of the full stroke cam and cooperate with contact surfaces of the outer lever. The construction of the blocking mechanism is relatively complicated. Furthermore, the outer lever is a relatively complicated, space-consuming and heavy component due to its support upon the valve play-compensating element and the mounting not only of the inner lever but also of the blocking element on the outer lever. 
   U.S. Pat. No. 5,544,626 discloses a valve disengagement device that has a two-part valve lever, whereby an outer lever has an overall U-shaped configuration and is supported via its crosspiece on a hydraulic valve play-compensating element. Mounted on the ends of the arms of the U is an inner lever that carries a roller for contacting a cam of the camshaft. The free end of the inner lever can be interlocked on the crosspiece of the outer lever in that a pin, which is movably guided in the crosspiece of the outer lever, is moved into a recess formed on the inner lever by means of hydraulic fluid pressure that acts from the hydraulic valve play-compensating element. When the blocking device is arrested, the valve lever acts like a one-part lever that transfers the cam stroke to the valve. When the blocking device is released, the inner lever extends into the outer lever, so that the valve is not actuated. 
   U.S. Pat. No. 5,655,488 describes an apparatus for the adjustment of the stroke of a valve, which is actuated by a camshaft, via an inner lever that is mounted within an outer lever in the region of the support of the outer lever against a component that is secured to the engine. By means of a blocking device, which displaces a blocking component disposed on that end of the outer lever that is on the valve side, the pivotability of the inner lever relative to the outer lever can be blocked. 
   It is an object of the present invention to provide an apparatus for the adjustment of the stroke of a valve that is actuated by a camshaft, wherein the apparatus has a straightforward construction and requires little installation space. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     This object, and other objects and advantages of the present invention, will appear more clearly from the following specification in conjunction with the accompanying schematic drawings, in which: 
       FIG. 1  is a perspective, exploded view of one exemplary embodiment of an inventive apparatus; 
       FIG. 2  is a perspective view of the inventive apparatus; 
       FIG. 3  is an exploded, perspective view of components of the inventive apparatus; 
       FIG. 4  shows valve stroke curves that can be realized with the inventive apparatus; 
       FIG. 5  is a perspective view, similar to that of  FIG. 1 , of a modified embodiment of a an inventive apparatus; 
       FIG. 6  is a partial side view of the apparatus of  FIG. 5 ; 
       FIGS. 7 &amp; 8  are partial side views of the apparatus of  FIG. 5  in different operating positions; and 
       FIG. 9  shows valve stroke curves that can be achieved with the embodiment of  FIG. 5   
     SUMMARY OF THE INVENTION 
     The apparatus of the present invention comprises a valve lever that includes an outer lever and an inner lever and has a first end region that is supported on a fixed component, and a second end region for actuating a valve, wherein the outer lever has an overall U-shaped configuration including two arms and a crosspiece that interconnects the arms and faces the fixed component, wherein at least one of the arms is provided with an abutment surface for contacting the cam or cams of the camshaft, wherein the inner lever is mounted on a free end of the outer lever between the arms thereof, wherein the inner lever has an abutment surface for contacting the cam or cams, and wherein the abutment surface is disposed between the axis of the mounting of the inner lever on the arms of the outer lever and the support of the first end region of the valve lever on the fixed component; and a blocking device for fixing the crosspiece of the lever on an end of the inner lever that is remote from the valve, wherein such end is supported on the fixed component and contains the blocking device. 
     Due to the fact that the free end of the inner lever is supported on the fixed component, the inner lever can essentially be designed like a conventional valve lever for valves that have no stroke adjustment device. The outer lever can be produced as a simple sheet metal part that spans the inner lever and is mounted on that end of the inner lever that is on the side of the valve. 
     The apparatus of the present invention can be utilized anywhere where it is advantageous to vary the stroke of a valve that is controlled by a camshaft via a valve lever. The present invention is particularly advantageous for use with intake valves of reciprocating piston internal combustion engines. 
     Further specific features of the present invention will be described in detail subsequently. 
   

   DESCRIPTION OF PREFERRED EMBODIMENTS 
   Referring now to the drawings in detail, pursuant to  FIG. 1  an inventive apparatus for the adjustment of the stroke of a valve that is actuated by a camshaft has a valve lever that is composed of an inner lever  4  and an outer lever  6 . 
   The inner lever  4 , when viewed in plan, has an overall U-shaped configuration and contains two curved arms  8  and  10 , which are connected via a crosspiece  12 . The arms  8  and  10  have two pairs of holes  14  and  16  that are disposed across from one another, whereby a pin  18  can be inserted into the pair of holes  14 ; this pin  18  is provided with a flat portion  20  for resting against a valve shaft that is not illustrated in FIG.  1 . In the installed state, the pin  18  projects laterally out of the arms  8  and  10 . 
   A pin  22  can be inserted into the pair of holes  16  for the mounting of a cam roller  24  that can be inserted between the arms  8  and  10 . 
   The crosspiece  12  has a body  26  that contains a blind hole  28  into which can be inserted a piston  32  that has a shaft  30 . A threaded ring  34  can be screwed into the blind hole  28  whereby a spring  36  is provided that surrounds the shaft  30  and is supported between the piston  32  and the threaded ring  34 . 
   The front ends of arms  38  and  40  of the on the whole U-shaped outer lever  6  can, via a pair of holes  42 , be mounted on the ends of the pin  18  that projects laterally out of the arms  8  and  10  of the inner lever  4 . The arms  38  and  40  can be provided with further holes in order to save weight. Provided in the crosspiece  44  of the outer lever  6  is a hole  46  into which the shaft  30  of the piston  32  can be inserted in the assembled state of the inner lever  4  and outer lever  6 . The upper sides of the arms  38  and  40  are formed with abutment surfaces  48  and  50 . The outer lever  6  can be embodied as a simple sheet metal part that has been bent in a U-shaped manner, whereby the upper sides of the arms  38  and  40  are bent away to form the abutment surfaces  48  and  50 . 
   In the assembled state, springs  52 , which are disposed on both sides of the body  26 , are supported between the crosspiece  44  of the outer lever  6  and the crosspiece  12  of the inner lever  4 . The springs  52  have the tendency to cock the outer lever  6  relative to the inner lever  4  in a clockwise direction in FIG.  1 . 
   The camshaft  54 , which is disposed axially parallel to the pin  22 , has a partial stroke cam  56  and full stroke cams  58  that are disposed on both sides of the partial stroke cam  56 . In the installed state, the partial stroke cam  56  is contacted by the cam roller  24 , and the full stroke cams  58  are contacted by the abutment surfaces  48  and  50 . The base circles of the cams can have different diameters. The geometrical coordination is preferably such that the cam roller  24  rests against the pertaining cam base circle when the valve is closed, thereby reducing the friction. 
   The assembly of the inventive apparatus can also be seen with reference to  FIGS. 2 and 3 . The cam roller  24  is disposed in the inner lever  4  and is mounted by means of the pin  22 . The piston  32  is disposed in the blind hole  28 . The spring  36  is placed upon the shaft  30 , and the threaded ring  34  is screwed into the blind hole  28 . The outer lever  6  is shoved over the inner lever  4  and is secured, so that it can tilt or cock, by inserting the pin  18  into the pair of holes  42  and  14  on the outer lever  6  and inner lever  4  respectively. 
   Subsequently, the lever assembly is placed via the underside of the crosspiece  12  upon the hydraulic play-compensating element  60  that is secured to the engine housing, and is placed via the flat portion  20  of the pin  18  upon the stem of a valve  62 , and the camshaft  54  is installed. Toward the top, the hydraulic play-compensating element  60  is provided with a non-illustrated opening that is aligned with a non-illustrated opening disposed on the underside of the body  26  and communicating via a duct with that end of the blind hole  28  that is disposed on the valve side, so that a pressure chamber is formed between the piston  32  and the base of the blind hole  28 . This pressure chamber can be supplied with a lot or little pressure by controlling the pressure that is supplied to the hydraulic play-compensating element and that can be varied via a non-illustrated control device that cooperates with hydraulic valves. When a lot of pressure is supplied to the pressure chamber, the piston moves toward the left in  FIG. 1 , so that the shaft  30  moves to the outside accompanied by compression of the springs  36  via the threaded ring  34 , and when aligned with the hole  46  and the crosspiece  44  of the outer lever  6  penetrates into the hole and blocks the ability of the outer lever  6  to cock relative to the inner lever  4 . 
   The inventive apparatus functions as follows. One first assumes that the pressure chamber is supplied with high pressure, thereby blocking the ability of the outer lever to pivot or cock relative to the inner lever. The base circle of the cam  56 , at an appropriate dimensioning of the cam roller  24  and its arrangement relative to the abutment surfaces  48 , then rests against the cam roller  24 , which leads to a low frictional loss. If the camshaft  54  is rotated further, the full stroke cams  58  project beyond the partial stroke cam  56  and come to rest against the abutment surfaces  48  and  50  of the outer lever, which is locked with the inner lever, so that in conformity with the full stroke cams  58  the valve  62  is opened and a movement is carried out in conformity with the curve labeled “large valve stroke” in FIG.  4 . 
   If, in conformity with operating parameters of the internal combustion engine, a switch is to be made from a large valve stroke to a small valve stroke, the pressure in the play-compensating element  60  is reduced, at least while the base circle of the cam passes over the valve lever, so that the shaft  30  is moved out of the hole  46  by the force of the spring  36 , and the outer lever can again pivot relative to the inner layer. If, upon further rotation of the camshaft  54 , the full stroke cams  58  now pass over the abutment surface  48 , the outer lever is pivoted or cocked relative to the inner lever in a counter clockwise direction in  FIG. 1 , so that the cam roller  24  remains in contact against the partial stroke cam  56  and the valve is opened in conformity with such partial stroke cam. The curve indicated by dashed lines in  FIG. 4  indicates the opening of the valve via the partial stroke cam  56 . 
   The inventive apparatus that has been describesd is extraordinarily compact and, as a result of the very space-saving configuration of the outer lever  6 , requires hardly any additional space relative to a conventional cam drive having a one-piece lever. Furthermore, the inventive apparatus is convenient to assemble and is cost efficient. Installation space required for the inner lever  4  corresponds to that of a conventional valve lever. The blocking device integrated into the body  26  requires no additional installation space toward the outside relative to the side facing away from the valve, so that in the direction of the connecting line between valve and mounting of the inner lever, additional space is required only for the thickness of the crosspiece  44 . The lever has a symmetrical configuration, so that the same components can be utilized for all valves, even for multi-valve engines. In addition, the arrangement is not exposed to lateral cocking forces. 
   The inventive apparatus can be modified in a number of ways. For example, the blocking device, which moves only minimally and as a result has little or no disadvantageous effect upon the speed integrity of the valve drive, can be disposed in the inner lever or in a stationary component, and can, for example, be formed by an electromagnet. In the case of the hydraulic actuation of the locking device, a supply of pressure thereto does not necessarily have to be effected by the hydraulic play-compensating element. The cam roller  24  is not mandatory. The inner lever can merely be provided with an abutment surface for the partial stroke cam  56 . The outer lever can also be formed with cam rollers. 
     FIG. 5  shows an embodiment of the inventive apparatus that is modified relative to the embodiment of FIG.  1 . 
   With this embodiment, the camshaft  54  has only a single cam  64  that passes over the outer lever  6  and the inner lever  4 . Whereas the abutment surfaces  48  and  50  of the outer lever  6  of the embodiment of  FIG. 1  are essentially planar or have a slight crown toward the cam shaft, the abutment surfaces  68  and  70  of the embodiment of  FIG. 5  are provided with concave regions  72  and  74 , the contour of which corresponds approximately to the contour of the base circle of the cam  64 , in other words, has a radius R (see FIG.  6 ). The cam roller  24  that is mounted in the inner lever  4  is, in the interlocked state between the inner lever and the outer lever, positioned in such a way that its outer contour is approximately lined up with the location A ( FIG. 6 ) at which the concave region  72  or  74 , viewed from the mounting location or hole  42  of the outer lever  6 , begins. The outer contour of the cam roller  24  can project slightly beyond the location A, thereby ensuring that the cam roller rests against the base circle of the cam. 
   The embodiment of  FIGS. 5 and 6  functions as follows. One begins on the assumption that the outer lever and the inner lever are blocked relative to one another. The base circle of the camshaft passes over the concave regions  72  and  74 , or rests against the cam roller  24  that minimally extends beyond the introduction into the region (location A). If the cam lobe or elevation now comes into the region of the location A, the cam roller  24  will be pressed away from the axis of the camshaft by the cam lobe, so that the valve is opened somewhat (position shown in FIG.  7 ). Upon further rotation of the camshaft, the cam lobe becomes free of the cam roller  24 , yet remains in contact against the concave regions  72  and  74 , as a result of which the outer lever is increasingly pivoted together with the inner lever until the valve is completely opened when the position shown in  FIG. 8  is reached where the cam  64  passes over the abutment surfaces  68  and  70  behind the end of the concave region  72  or  74 , in other words, the crown of the adjoining convex region. Subsequently, the outer lever and the inner lever are pressed into the closed position by the closure spring of the valve, while maintaining the contact against the cam, until the state shown in  FIG. 6  is again reached. 
   The resulting valve stroke curve corresponds approximately to the curve II in FIG.  9 . 
   If the outer lever  6  is pivotable relative to the inner lever  4 , only the cam roller  24  is pressed away during passing over of the cam, whereby the abutment of the cam against the abutment surfaces  68  or  70  effects no further opening of the valve after becoming free of the cam roller  24 , so that a valve stroke curve II pursuant to  FIG. 9  results that in the starting phase is synchronized with the curve I. 
   If the direction of rotation of the camshaft  54  is opposite to that illustrated, according to which the cam moves from the location A close to the valve over the concave region  74 , there then results, as is readily obligatory, and with the outer lever uncoupled from the inner lever, the valve stroke curve III where the closing side coincides with that of curve I. 
   The embodiment of  FIG. 5 , in particular with regard to the installation space that is required, has the same advantages as does the embodiment of  FIG. 1 , yet requires a simpler camshaft than does the embodiment of FIG.  1 . 
   A further modified embodiment of the inventive apparatus, which is not illustrated in detail, operates with a camshaft having only a single cam similar to the embodiment of  FIG. 5 , and an outer lever similar to that of the embodiment of FIG.  1 . The cam roller  24  of this modified embodiment is, however, formed with a smaller diameter, or due to a different arrangement of the pair of holes  16  in the inner lever  4  is mounted in such a way that its outer surface is recessed relative to the abutment surfaces  68  and  70 . In this way, with the pivotability of the outer lever relative to the inner lever being blocked, the abutment surfaces of the outer lever are effective, so that the full stroke of the cam  64  is effective for actuation of the valve  62 . When the pivotability of the outer lever  6  relative to the inner lever  4  is released, the outer lever  6  is first pivoted by the cam  64  against the force of the springs  52  in a counter clockwise direction. Subsequently, the cam  64  comes to rest against the cam roller  24  and actuates the valve merely with a stroke that corresponds to the cam lobe minus the stroke that is used up until the cam  64  comes into contact against the cam roller  24 . So that the transition of the abutment of the cam  64  from the abutment surfaces of the outer lever to the cam roller is smooth or steady, also with this embodiment the abutment surfaces can have a slightly concave configuration. 
   It is to be understood that in particular the embodiment of  FIG. 5  can also be embodied in such a way that the outer lever  6  is pivotably supported on the hydraulic play-compensating element or some other component, for example the cylinder head, the blocking device is disposed on the crosspiece  44  of the outer lever, and the inner lever is pivotable relative to the outer lever in a counter clockwise direction. The support of the springs  52  is correspondingly different so that the inner lever is pressed upwardly in a clockwise direction. The full stroke transmission is then effected via the inner lever. The partial stroke transmission is effected via the outer lever. 
   The specification incorporates by reference the disclosure of German priority document 102 20 904.9 filed May 10, 2002. 
   The present invention is, of course, in no way restricted to the specific disclosure of the specification and drawings, but also encompasses any modifications within the scope of the appended claims.