Abstract:
Disclosed is a simple, easy-to-produce, and reliable connection between a shaft of a gas exchange valve and an actuator. This connection is detachable and, as a result, can be connected and disconnected multiple times. It is also possible to dispose the coupling piece on the shaft of the gas exchange valve and provide circumferential grooves on the control element of the actuator.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a 35 USC 371 application of PCT/DE 02/02124 filed on Jun. 11, 2002. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to an improved connection for connecting a gas exchange valve of an internal combustion engine to an actuator. 
   2. Description of the Prior Art 
   In internal combustion engines whose gas exchange valves are activated in the conventional manner by way of a camshaft, the activation motion of the camshaft is transmitted to the shaft of the gas exchange valve by way of a bucket tappet, a drag lever, or a rocker, for example, when this gas exchange valve is to be opened. A valve spring clamped between the cylinder head and the gas exchange valve keeps the gas exchange valve in constant contact with the bucket tappet, drag lever, or rocker. In addition, the valve spring serves to close the gas exchange valve. 
   In modern engine designs, gas exchange valves are no longer activated by way of a camshaft, but rather by actuators such as piezoelectric actuators, hydraulic actuators, or pneumatic actuators, for example. In the context of the invention, the term “actuator” is considered to include all regulating elements capable of performing the opening and closing motions of a gas exchange valve, regardless of their physical operating principles. The actuators open and close the gas exchange valves desmodromically, i.e., forcibly. Therefore, it is necessary to produce a connection between the actuator and the gas exchange valve that can reliably transmit the forces necessary for opening and closing the gas exchange valve. 
   The object of the invention is therefore to produce a simple, inexpensive, and reliable connection between the gas exchange valve and the actuator. At the same time, it should be possible for the connection to be disconnected and reconnected multiple times and, at the same time, the connection should require only minor changes to the gas exchange valve and the cylinder head of internal combustion engines that are already in series production. 
   This object is attained according to the invention by a connection of a gas exchange valve of an internal combustion engine to an actuator, having a shaft and a coupling piece in which at least one circumferential groove is provided on the shaft, the coupling piece has a bore whose diameter in the assembled state corresponds to the diameter of the shaft, the bore has at least one circumferential bead that can be connected in a positively engaging fashion to the at least one circumferential groove, and the coupling piece has at least one longitudinal slit in the vicinity of the bead. 
   SUMMARY OF THE INVENTION 
   The connection of the gas exchange valve and actuator according to the invention is based on a positive engagement that has the same loading capacity in both activation directions of the actuator (opening and closing the gas exchange valve). Moreover, with the connection according to the invention, it is possible to use a conventional gas exchange valve because the coupling of the gas exchange valve to the valve spring is also provided with circumferential grooves in the vicinity of the shaft of the gas exchange valve. Another advantage of the connection according to the invention lies in the fact that it has a very small number of components, which simplifies production and assembly as well as repairs. Furthermore, in the connection according to the invention, it is possible to rotate the gas exchange valve in the same manner as in conventional internal combustion engines. 
   In order to increase the forces that can be transmitted between the actuator and the gas exchange valve, the shaft can be provided with a number of circumferential grooves spaced apart from one another in the longitudinal direction. Correspondingly, the bore has a number of beads spaced apart from one another in the longitudinal direction. 
   In one variant of the invention, the shaft is embodied in a cylindrical shape in the vicinity of the at least one circumferential groove and the bore is embodied in a cylindrical shape, so that the object can be attained in a particularly simple manner from a production engineering standpoint. As an alternative, the shaft in the vicinity of the at least one circumferential groove and the bore can be embodied in the shape of a truncated cone. 
   Other enhancements of the invention provide for embodying the at least one circumferential groove with a semicircular, rectangular, or trapezoidal cross-section, thus allowing an optimal variant to be selected depending on the requirements with regard to production, assembly, and the forces to be transmitted. 
   A securing element can be provided in order to prevent the connection according to the invention from becoming detached during operation. 
   In another variant of the invention, the securing element is embodied as an open wire ring and the coupling piece has at least one groove on its outer surface to accommodate the securing ring, so that the connection is secured by sliding the wire ring into the groove. 
   In another embodiment of the invention, the securing element is embodied as a nut and the coupling piece has an external thread on its outer surface, which cooperates with the nut, so that screwing the nut onto the external thread prevents the connection according to the invention from becoming detached. 
   In a further enhancement of the invention, the securing element can be embodied as a sleeve that can be slid over the coupling piece. It is also possible for the sleeve and coupling piece to be pressed against each other in the assembled state and to thus form a force fit. In this embodiment, which is very simple from a production engineering standpoint, the securing element can be effectively prevented from coming off the coupling piece during operation and, moreover, the fact that a specific tool is required to produce a press-fit connection ensures that only authorized garages can perform repairs to the actuator and/or the gas exchange valve. 
   In order to simplify assembly, it is possible for the coupling piece to be spread out in the vicinity of the at least one bead in relation to the mounted state and for the coupling piece to be pressed together by the securing element during assembly. In contrast to the exemplary embodiments described above, the connection between the gas exchange valve and the actuator in this variant is not embodied as a snap connection, but rather the positive engagement is produced only when the coupling piece is pressed together and the securing element is subsequently slid into place. 
   According to the invention, the shaft is part of the gas exchange valve and the coupling piece is part of the actuator. However, it is also possible for the coupling piece to be part of the gas exchange valve and for the shaft to be part of the actuator. Finally, it is also possible to couple a gas exchange valve, which is embodied as a through valve, to the actuator using the connection according to the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other objects and advantages of the invention will become apparent from the description combined herein below, taken in conjunction with the drawings, in which: 
       FIG. 1  shows a full view of a first exemplary embodiment of a connection according to the invention with the short shaft of the gas exchange valve; 
       FIG. 2  shows a full view of a second exemplary embodiment of a connection according to the invention with a through valve; and 
       FIGS. 3 to 6  show detailed views of various exemplary embodiments of the connection according to the invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows a gas exchange valve  1 , which is coupled to an actuator  5  by way of a connection  3 . A control element  7  of the actuator  5  executes the control movements that are to be transmitted to the gas exchange valve  1  by way of the connection  3 . Not shown in  FIG. 1  is a valve seat in a cylinder head of the internal combustion engine, which is also not shown, against which valve seat a valve head  9  of the gas exchange valve  1  rests when it is in the closed state. The connection  3  will be described in greater detail below in conjunction with  FIGS. 3 to 6 . 
     FIG. 2  shows a gas exchange valve  1  that is embodied as a so-called “through valve,” which protrudes through the actuator  5  with its shaft  11  and in which the control element  7  is disposed on the end of the actuator  5  oriented away from the valve head  9 . 
     FIG. 3  shows a first exemplary embodiment of a connection  3  according to the invention in a detailed exploded view. A coupling piece  13 , which is connected to the control element  7  of the actuator  5 , is shown in  FIG. 3  in a partially sectional view. The coupling piece  13  has a cylindrical bore  15 . In the bore  15 , three beads  17  are provided spaced apart from one another in the longitudinal direction of the bore  15 . 
   There is an external thread  19  on the outer diameter of the coupling piece  13 . The coupling piece  13  has multiple slits in the longitudinal direction. Only one slit  21  can be seen in  FIG. 3 . The slits  21  can be clearly seen in  FIGS. 4 and 5 . 
   A shaft  11  of a gas exchange valve  1  is shown below the coupling piece  13 . A number of circumferential grooves  25  are disposed at one end  23  of the shaft  11  oriented away from the valve head (not shown in  FIG. 3 ). The dimensions and spacing of the circumferential grooves  25  apart from one another correspond to the dimensions and spacing of the beads  17  in the bore  15  of the coupling piece  13 . 
   If the shaft  11  is now slid into the bore  15  from below, the coupling piece  13  spreads open, which is easily possible because of the slits  21 . As soon as the shaft  11  has reached a position in which the beads  17  engage in detent fashion in the circumferential grooves  25 , the coupling piece  13  returns to its original shape and a positive engagement is produced between the beads  17  of the coupling piece  13  and the circumferential grooves  25  of the shaft  11 . The circumferential grooves  25  can have a semicircular, rectangular, or trapezoidal cross-section. It is also conceivable for the flanks of the circumferential grooves  25  to enclose various angles with the longitudinal axis if, for example, the forces to be transmitted are different for opening and closing the gas exchange valve. It is also possible to provide the coupling piece  13  on the gas exchange valve  1  and the circumferential grooves  25  on the control element  7 . 
   In order to prevent the positively engaging connection between the coupling piece  13  and the shaft  11  from becoming detached during operation, after the shaft  11  is inserted into the bore  15 , a nut  27  is screwed onto the external thread  19  of the coupling piece and tightened. It is recommended that the external thread  19  and the nut  27  be embodied with a fine thread, so as to reliably prevent the nut  27  from coming loose. Naturally, any of the known screw locking devices can also be used to prevent the nut  27  from unintentionally coming loose. 
   Above the external thread  19  on the coupling piece  13 , a recess  29  is provided, which makes it easier for the coupling piece  13  to spread open. 
     FIG. 4  shows a second exemplary embodiment of a connection according to the invention, likewise in an exploded view. The inner contour of the coupling piece  13  corresponds to the inner contour of the coupling piece  13  according to the exemplary embodiment shown in  FIG. 3  and is not visible in  FIG. 4 . The shaft  11  with multiple circumferential grooves  25  spaced apart from one another is embodied exactly the same as explained in the exemplary embodiment shown in  FIG. 3 . 
   The slits  21 , which make it easier for the coupling piece  13  to spread open when the shaft  11  is inserted into the coupling piece  13 , are clearly visible in  FIG. 4 . The number of the slits  21  can be selected as needed. 
   Two grooves  31  are let into the outer circumference of the coupling piece  13  according to the exemplary embodiment shown in  FIG. 4 . When the shaft  11  has been inserted into the coupling piece  13 , two securing rings  33  are placed over the coupling piece  13  and inserted into the grooves  31 . The securing rings  33  can be embodied as open wire rings. The securing rings  33  are dimensioned and produced in such a way that they press the coupling piece together when they are placed in the grooves  31 . This simply and effectively prevents an undesired detachment of the connection between the coupling piece  13  and the shaft  11 . 
     FIG. 5  shows another exemplary embodiment of a connection according to the invention between the coupling piece  13  and the shaft  11 . The contour of the bore in the coupling piece  13 , which is not visible, also corresponds to the contour of the bore  15  according to the exemplary embodiment shown in  FIG. 3  The coupling piece  13  is embodied in the shape of a cylinder in the vicinity of the slits  21 . When the shaft  11  is inserted into the coupling piece  13 , a sleeve  35  is slid over the coupling piece  13  in the vicinity of the slits  21 . The sleeve  35  is shown in  FIG. 5  in a partially sectional view. Once it is slid on, a force fit is formed between the coupling piece  13  and the sleeve  35  such that the sleeve  35  fits snugly and securely on the coupling piece  13 . As an alternative, the sleeve  35  can be compressed onto the coupling piece  13  after being slid into place. 
     FIG. 6  shows another exemplary embodiment of a connection according to the invention. In this exemplary embodiment, the shaft  11  is slid through the control element  7  and the coupling piece  13  from beneath. The coupling piece  13  is shown in a partially sectional view. The coupling piece  13  spreads out in the vicinity of the beads  17  far enough to permit the shaft  11  to freely slide through the bore  15  into its installation position. Then the coupling piece  13  is pressed together so that the beads  17  engage in detent fashion in the circumferential grooves  25 , and a sleeve  35  can be slid onto it from above. A relief groove  37  is provided in the bore  15 , which makes it easier for the coupling piece  13  to spread out and be pressed together. 
   Naturally, all other types of securing elements, such as the securing rings  33  or the nut  27 , for example, can also be used in the embodiments of the coupling piece  13  in which the coupling piece is spread out. Nor is the spreading out of the coupling piece  13  limited to the use of through valves; it can also be used in a configuration according to  FIG. 1 . 
   The foregoing relates to preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.