Valve control for a reciprocating piston internal combustion engine

A valve control for a reciprocating piston internal combustion engine in which at least two valves per cylinder are actuated in unison by a traverse moved by a rocker arm; the pivotally constructed traverse adapts itself to different valve stem heights of the valve pair by assuming different inclined positions; a self-adjusting torque support mechanism cooperates with the traverse and limits the inclination of the traverse to the extent resulting from the differences of the valve stem heights; an accurate synchronous operation of the valves actuated in unison is assured thereby.

The present invention relates to a valve control for a reciprocating piston 
internal combustion engine in which at least two valves per cylinder head 
are actuated in unison by a traverse displaced by a rocker arm and in 
which the traverse is constructed so as to be pivotal. The valve control 
is thereby so constructed the the traverse can adapt itself to differences 
in the valve stem heights of the pairwise-actuated valves. 
In a valve control disclosed in the German Gebrauchsmuster No. 1885715, 
valve pair is actuated in unison by means of a traverse. The traverse is 
rotatably supported at the rocker arm on a pin so that it can adapt itself 
to different valve stem heights by assuming different inclined positions. 
The pivot range of the traverse which is dimensioned generous is limited 
by abutments. 
It is disadvantageous in this prior art arrangement that the traverse tilts 
like a scale-beam during the opening phase of the valve pair as soon as 
the opening forces required for the two valves are not in equilibrium. 
Such an imbalance results from different valve spring forces which are 
conditioned on manufacturing tolerances, and by different friction 
conditions at the valve stem guidances of the valve pair. The valve of the 
pair, at which the lower opening forces occur, thereby leads during 
opening with respect to the other valve of the pair. The magnitude of this 
lead depends, at which inclined or tilted position of the traverse the 
opening forces of the two associated valves are in equilibrium. In the 
most unfavorable case, the traverse pivots so far that only the abutments 
prevent the further tilting. In particular for rapidly rotating 
reciprocating piston internal combustion engines, such an imperfect 
equilibrium or deficient synchronous operation of the valves of a commonly 
actuated pair is not permissive. On the one hand, the necessary precision 
of the gas exchange processes is considerably disturbed. On the other 
hand, the trailing valve is torn open with higher velocity than the 
leading valve. Large acceleration forces result therefrom which lead to 
overloads and excessive stresses in the valve control endangering the 
operation. 
It is therefore the task of the present invention to indicate measures 
which automatically limit the tilting of the traverse to the extent which 
results from the differences of the valve stem heights. 
The underlying problems are solved according to the present invention in 
that a bolt rectilinearly guiding the traverse is rotatably arranged at 
the cylinder head transversely to the connecting line of the valves, in 
that the bolt is rotatable by the traverse by way of the rectilinear 
guidances and in that the bolt cooperates with an automatically adjusting 
torque support mechanism. 
The advantages achieved with the present invention consist in particular in 
that the pivot position assumed by the traverse as a result of the 
different valve stem heights remains unchanged during the opening phase of 
the valves, in that the traverse is able to adapt itself to the valve stem 
heights which change slowly during the operation as a result of wear, in 
that in each inclined position of the traverse, an exact synchronous 
operation of a commonly actuated valve pair is assured, in that also the 
inaccuracy in the synchronous operation of the commonly actuated valve 
pair is eliminated which would otherwise result by play in the valve 
control between cam shaft and traverse, and in that the moved masses of 
the valve control are not increased by the proposed arrangement in 
accordance with the present invention.

Referring now to the drawing wherein like reference numerals are used 
throughout the two views to designate like parts, a rocker arm 13 is 
arranged on a bearing block 12 on a cylinder head 11, indicated only 
schematically, of a reciprocating piston internal combustion engine. 
The rocker arm 13 is operatively connected, on the one hand, by way of a 
push rod 14 with a cam shaft 15 and, on the other, with a traverse 18. The 
traverse 18 rests on the valve stem ends of two adjacent valves 16 and 17 
which are actuated in unison by the traverse 18. 
A mechanism for the elimination of play of any conventional construction is 
arranged in the transmission path for the valve actuation between the cam 
shaft 15 and the traverse 18. In the illustrated embodiment, this 
mechanism consists of a conventional hydraulic adjusting member 32 which 
cooperates in a suitable manner with an eccentric bush of the rocker arm 
bearing support and effects automatically a clearance compensation. 
Transversely to the connecting line of the valve pair, a bolt 19 is 
rotatably supported at the cylinder head 11 in a bearing block 20 
centrally between the valves 16 and 17. The bolt 19 includes at its 
projecting end two mutually parallel surfaces, which cooperate with a 
fork-like slot 21 of the traverse 18 and effect a rectilinear guidance for 
the traverse 18. The bolt 19 is rotatable by the traverse 18 by way of the 
rectilinear guidance if the traverse assumes an inclined position as a 
result of different valve stem heights. A lever 22 is non-rotatably 
connected with the bolt 19 which projects into an opening 23 of the 
bearing block 20. Two pistons 24 and 25 actuated by oil pressure and 
engaging at the lever 22 mutually oppositely are arranged in the bearing 
block 20 at right angle to the lever 22, which together with the lever 22 
form a self-adjusting torque support mechanism for the bolt 19, with 
respect to the traverse 18. 
The cylinder spaces 26 and 27 of the pistons 24 and 25 are communicatingly 
connected with each other by a channel 28. The channel 28 and the cylinder 
spaces 26 and 27 are filled with pressure oil from the lubricating oil 
circulation of the reciprocating piston internal combustion engine by way 
of a line 29. Throttling places 30 and 31 are arranged in the connections 
between the channel 28 and the cylinder spaces 26 and 27 of the pistons 24 
and 25. 
Differing friction conditions at the valve stem guidances and differences 
of the valve spring forces caused by manufacturing tolerances create that 
the forces to be overcome during the opening of the valves which are of 
different magnitudes at the two valves of a commonly actuated pair. The 
force difference resulting therefrom is thereby responsible for the fact 
that the traverse 18, during each valve actuation, seeks to change its 
starting position up to the equalization of the force difference. In the 
interest of an exact synchronous operation of the two valves 16 and 17 of 
a commonly actuated pair, the positional change of the traverse 18 which 
occurs during short periods of time is to be prevented. The torque 
resulting from the force difference defined above and engaging at the 
traverse 18 is transmitted by way of the rectilinear guidance onto the 
bolt 19 and the lever 22 and depending on the direction of rotation of the 
torque is supported at one of the oil pressureactuated pistons 24 and 25. 
Though the piston acted upon by the torque seeks to deflect, the throttle 
places 30 and 31 coordinated to the pistons delay a rapid overflow of 
pressure oil from the one cylinder space by way of the channel 28 into the 
other cylinder space. The openings of the throttle places 30 and 31 are so 
dimensioned that during the opening phase of the valves 16 and 17, 
practically no adjustment of the traverse 18 occurs. 
If during operation a larger valve stem height difference should result due 
to wear at the valve seat of one of the valves 16 and 17 of a commonly 
actuated pair, then the torque resulting therefrom which adjusts the 
traverse 18 is effective only during the closure phase of the valve pair. 
The closure phase of the valves 16 and 17, however, is more than twice as 
long as the opening phase. The piston acted upon by the lever 22 as a 
result of the adjusting force has therefore considerably more time during 
the closing phase to displace pressure oil out of its cylinder space than 
during the opening phase. Additionally the adjusting torque is also larger 
than the torque resulting from the force difference during the opening 
phase because with a larger valve stem height difference, the closure 
force of the respective valve spring becomes effective and not only the 
difference of the valve spring forces since the one valve is already 
closed. The larger torque at the lever 22 effects also a larger pressure 
increase at the supporting piston 24 or 25 in the cylinder space thereof 
so that per time unit more oil volume is displaced out of the cylinder 
space. 
While we have shown and described only one embodiment in accordance with 
the present invention, it is understood that the same is not limited 
thereto but is susceptible of numerous changes and modifications as known 
to those skilled in the art, and we therefore do not wish to be limited to 
the details shown and described herein, but intend to cover all such 
changes and modifications as are encompassed by the scope of the appended 
claims.