Abstract:
A decompression braking device in an endothermic engine ( 1 ) is provided of the type comprising a lever axle ( 2 ) on which a plurality of eccentric bushings ( 31 ) of a corresponding plurality of levers ( 3 ) provided with tappets ( 4 ) are rotationally and eccentrically mounted for actuating a plurality of exhaust valves ( 5 ), and a camshaft ( 30 ) for actuating said plurality of levers ( 3 ), the device is characterised in that it comprises an actuating member ( 6, 61 ) mounted externally to said lever axle ( 2 ) and connected to the latter by means of linkages ( 8, 9, 10 ), such that a respective rotation of said bushings ( 31 ) by a predetermined angular value (□), with consequent displacement of the hinging axis of said levers ( 3 ), corresponds to each excursion of said actuating member ( 6, 60 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not Applicable 
       STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT 
       [0002]    Not Applicable 
       BACKGROUND 
       [0003]    The present invention relates to an engine brake actuator device in endothermic engines and, more specifically, to a decompression engine brake actuating device in endothermic engines. 
       BRIEF SUMMARY 
       [0004]    Today, the engine inertia braking principle, by decompression of the combustion chamber during the gas compression stroke, is widely known. Indeed, it is known to exploit the energy accumulated in the form of compressed gas pressure energy during the compression cycle to “brake” the inertia or the mass connected to the crankshaft. 
         [0005]    In lack of adequate systems, following the compression of the gas, the latter would be expanded in the downward piston stroke at the same time as the opening of the exhaust valves. This solution would create an elastic effect which would in part tend to return the piston downwards due to the thrust generated on the latter by the compressed gas, thus disadvantageously decreasing the engine brake efficiency. 
         [0006]    For some types of use where inertia is higher, such as, for example, heavy haulage, a solution contemplating the early opening of the exhaust valve(s) with respect to the piston linkage has been adopted. This is obtained by adding auxiliary exhaust valve openings by means of actuators of various designs. Such solution, despite being more effective than that above, implies the use of sophisticated mechanisms and/or actuators which act on the valve lever shaft or, in some cases, the provision of various cams or levers which are actuated as required. 
         [0007]    EP 0 543 210 requires the rocker arms to be fitted on eccentric bushings, in turn mounted on a rocker arm axle. A hydraulic actuator when required turns the bushing, thus displacing the rotation centre of the rocker arm. 
         [0008]    This solution, however, consequently contemplates the use of devices and/or actuators which increase the complexity of the linkages and therefore displays the disadvantage of being complicated, cumbersome and costly. 
         [0009]    It is therefore the object of the present invention to solve the drawbacks and disadvantages of the state of the art by providing a decompression braking device in endothermic engines which is extremely simple to make and therefore highly reliable. 
         [0010]    A further object of the present invention is to provide a rugged, small-size, low-maintenance and low-cost decompression braking device in endothermic engines. 
         [0011]    Therefore the present invention provides a decompression braking device in endothermic engines according to claim  1 . 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0012]    A detailed description of a preferred embodiment of the decompression braking device in endothermic engines of the present invention will now be provided, by way of non-limitative example, with reference to the accompanying drawings, in which: 
           [0013]      FIG. 1  is a top plan view of a cylinder head partially illustrating the decompression braking device of the present invention; 
           [0014]    Figures from  2 A to  2 C are partial section views partially illustrating the braking device of the present invention; 
           [0015]      FIG. 2D  is a front view of the same cylinder head; 
           [0016]    Figures from  3 A to  3 D show a component of the braking device of the present invention; 
           [0017]      FIG. 4  is a partial section view schematically showing the decompression brake actuation principle by means of eccentric bushings; 
           [0018]      FIGS. 5A and 5B  are perspective view of two parts of a support belonging to the decompression braking device of the present invention; 
           [0019]      FIG. 5C  is a section view of parts of  FIGS. 5A and 5B  reciprocally assembled to constitute the support. 
       
    
    
     DETAILED DESCRIPTION  
       [0020]    Referring now to  FIG. 1 , it is shown a head of an endothermic engine  1  which mounts the decompression braking device of the present invention. According to the invention, a lever axle  2  which rotationally mounts a plurality of levers  3  is provided, each lever  3  displays a tappet  4  which actuates one or more valves, in the case shown a pair of exhaust valves of which spring  5  is visible (actuation which occurs in a manner intrinsically already known and illustrated in better detail below). Each lever  3  is actuated by a corresponding cam integral with a camshaft  30  in the per se known manner. 
         [0021]    A second actuating shaft  6  of the braking device according to the present invention is arranged on the top of lever axle  2 . Shaft  6  is rotationally mounted on a corresponding plurality of supports  7  integrally arranged with the head of engine  1 . 
         [0022]    Furthermore, shaft  6  comprises a plurality of pins  8  integrally mounted on the first and each of which displays a spherically-shaped end  80  adapted to be hingingly connected to a corresponding plurality of arms  9  integrally mounted on a series of eccentric bushings  31  turnably supported by lever axle  2 . Levers  3  are turnably mounted on eccentric bushings  31 . The hinge connection between each pin  8  and arm  9  is obtained by a rigid element  10  (described in better detail below). 
         [0023]    Furthermore, a shaft actuating device  60  (described in better detail below) integrally mounted on an appropriate part of the engine, e.g. on the cylinder head cover, is provided at the end of shaft  6 . 
         [0024]    Figures from  2 A to  2 D partially show some cross section views of the head of  FIG. 1  incorporating the device of the present invention. 
         [0025]    As one may note in the figures, supports  7  provide turnable support to shaft  6  so that each connection element  10  hinged between arm  8  and arm  9  thus forms a four-bar linkage; lever axle  2  is integral with the cylinder head and may, according to a particular embodiment of the invention, be maintained in position either by support  7  itself or in another appropriate manner. 
         [0026]    More precisely and with specific reference to  FIG. 2C , shaft  6  is parallel to lever axle  2 . As apparent in the figure, connection element  10  connects shaft  6  to eccentric bushings  31  supported by axle  2  in virtue of corresponding pins  8  and arms  9  in a linking manner so that a rotation by a predetermined angle of shaft  6  is transformed into a predetermined reciprocal rotation of bushings  31 . 
         [0027]    Furthermore, with particular reference now to  FIG. 2B , the figure shows actuator  60  which may be of the pneumatic type and is connected to shaft  6  by means of a lever  61  integral with the latter. The arrangement in the figure shows that a stroke of actuator  60  induces an angular excursion of shaft  6  and, consequently, due to the linkage illustrated above, also a corresponding angular excursion of bushings  31 . It must be noted at this point that in virtue of the arrangement of actuator  60  connected to an end of shaft  6 , the operation and the maintenance of the decompression braking device of the present invention is eased. 
         [0028]    With particular reference now to  FIG. 2A , the figure shows the linkage between shaft  6  and bushings  31  of levers  3 . Specifically, each lever  3 , corresponding to a pair of exhaust valves  5  of the cylinder head, is mounted on a bushing  31  as mentioned turnably supported by lever axle  2 . Bushing  31 , in turns, displays a predetermined eccentricity with respect to axle  2 . Therefore, a rotation of bushing  31  by a predetermined angular value by means of element  10  on arms  9 , actuated by actuator  60  by means of aforementioned linkage, is it possible to displace the rotation centre of lever  3  supported by bushing  31 . With regard to the displacement of the rotation centre of the lever by means of rotation of the eccentric bushing, the system is similar to that described in EP 0 543 210. The systems differ instead with respect to the whole of the means for causing the rotation of the eccentric bushing, which is the object of the present invention. 
         [0029]    With reference now to  FIGS. 3A to 3D , different views of the conformation of the linkage element  10  are shown, according to a particular embodiment of the invention. As it may be noted in the figures, element  10  displays a first end  11  shaped in complementary manner to spherical end  80  of pin  8  integral with shaft  6 . In this manner, once spherical end  80  is connected to such part  11 , a pivoting connection is obtained between element  10  and pin  8 , also in virtue of grooved region  12  where pin  8  may freely pivot for even greater angular values. The connection between spherical end  80  and part  11  is obtained by elastic insertion by interference and in the per se known manner. 
         [0030]    On the other hand, and again with reference to  FIGS. 3A-3D , the opposite end of element  10  consists of a fork-shaped part  13  adapted to swinging accommodate a corresponding arm  9  of bushing  31 . End  13  displays engagement regions  14  with a corresponding connection pin integrally turnable on arm  9  (shown in better detail in  FIG. 2B ). Also in this case, the conformation of part  13  is such that arm  9  once connected to the latter may pivot within fork  13  (shown in better detail in  FIGS. 1 and 2B ). 
         [0031]    With reference now to  FIG. 4 , this figure shows the decompression braking system already discussed above in better detail to which the device object of the present invention may be advantageously applied. 
         [0032]    There is a cam portion on the opening profile of the camshaft exhaust valve such as to cause a shorter stroke than the clearance value normally existing between tappet and valve. By reducing such clearance by virtue of the eccentric displacement of the fulcrum of lever  3  with respect to axle  2 , as shown in better detail below, such cam portion becomes active and an additional opening of the concerned valve is obtained. 
         [0033]    As shown in the figure, lever  3  is turnably mounted on bushing  31  which in turn is turnably and eccentrically mounted on axle  2 . Bushing  31  is mounted with predetermined eccentricity “e” so that, by its rotation by a value “□”, performed by means of element  10  on arms  9  and corresponding linkage as previously described, it is possible to displace the rotation centre of lever  3 , so as to reduce the clearance by a value “□”. 
         [0034]    Obviously, a rotation in the opposite direction of a value “−□” must be performed to eliminate the decompression braking effect of the gas within the cylinder thus returning the eccentricity “e” to the predetermined value if valve  5  is not actuated by the cam portion corresponding to compression braking. 
         [0035]    Such rotation may be performed also without the need for additional return devices: indeed, lacking the action of the actuator, the force exerted on lever  3  during the actuation of the valve by the main cam portion is sufficient to return the bushing to its original position, a better control of the linkage may be obtained by adopting a possible return spring, not shown in the given example, which facilitates the return of the eccentric bushings to the position they occupied before the actuation of the actuator. 
         [0036]    Lever axle  2  and shaft  6  are secured in any appropriate manner to the cylinder head, shaft  6  being free to rotate as mentioned. 
         [0037]    According to a particular embodiment of the invention, described with the aid of  FIGS. 5A ,  5 B, and  5 C, supports  7  may comprise two parts, which are secured by means of screw to the head. Lower part  90  of figure SA and upper part  91  of  FIG. 5B  are shown reciprocally assembled in  FIG. 5C . The lower part displays a concave seat  92 , adapted to press lever axle  2  against a specific seat on the cylinder head, holding it in position. The upper part displays an eyebolt  93  adapted to turnably accommodate shaft  6 . A through screw in holes  94  and  95 , reciprocally aligned to assembled parts and screwed into a threaded hole obtained on the cylinder head fixes support  7  to it, fastening the lever axle in its position. Cylindrical element  96 , accommodated in specific seats obtained in the aforesaid holes, allows a precise and secure alignment. The conformation of the two parts  90  and  91  is such that eyebolt  93 , on the opposite side with respect to the screw, rests on lower part  90  only by one end  98 . Elements  97  favour centring. The two-part conformation, specifically with the described eyebolt resting system, allows to tighten the screw at a suitable torque, minimising the mechanical tensions on the eyebolt itself. Thus, deformations of the latter which could cause friction on shaft  6  are avoided. According to the invention, the decompression braking device shows a series advantages. 
         [0038]    A first advantage results from the fact that the construction of the braking device thus designed is extremely simple and highly reliable. 
         [0039]    Another advantage of the device is that being actuated from only one end of shaft  6 , i.e. also from the outside of the tappet cover, the device reduces the dimensions within said cover, is rugged, low-maintenance and therefore also low-cost. 
         [0040]    Furthermore, the actuator may be of any suitable type; indeed, an advantage of the present invention is that it is may be located externally to the engine and specifically to the tappet cover. In such a manner, no specific problems of compatibility arise with the environment where the actuator is located due, for example, to temperature, vibrations, presence of oil.