Hydraulic play compensating element

A hydraulic play compensating element (1) for a valve control mechanism in internal combustion engines comprising an outer piston (4) closed on one end and insertable for displacement in the longitudinal direction in a bore (2) of a structural element (3) of the valve drive and which guides an inner piston (5) for longitudinal displacement with slight play in a longitudinal bore wherein both pistons encompass a high pressure chamber (6) therebetween which communicates via a check valve (7) arranged in the inner piston with an oil reservoir (8) provided in the inner piston (5), and wherein the inner piston (5) is supported at its end facing away from the pressure chamber by a disc (9) which is fixed in the bore (2) of the structural element (3) of the valve drive, characterized in that the disc (9) engages the bore (16) of the inner piston (5) with radially resilient clamping projections (15) upon contacting the end of the inner piston (5) facing away from the pressure chamber (16).

STATE OF THE ART 
Hydraulic play compensating elements (1) for a valve control mechanism in 
internal combustion engines comprising an outer piston (4) closed on one 
end and insertable for displacement in the longitudinal direction in a 
bore (2) of a structural element (3) of the valve drive and which guides 
an inner piston (5) for longitudinal displacement with slight play in a 
longitudinal bore wherein both pistons encompass a high pressure chamber 
(6) therebetween which communicates via a check valve (7) arranged in the 
inner piston with an oil reservoir (8) provided in the inner piston (5), 
and wherein the inner piston (5) is supported at its end facing away from 
the pressure chamber by a disc (9) which is fixed in the bore (2) of the 
structural element (3) of the valve drive are known. Such play 
compensating elements are, for example, arranged in bores of rocker arms. 
For manufacturing reasons, the bore in the rocker arms is designed as a 
continuous bore accommodating a disc supported e.g. by a retaining ring 
and itself supports the hydraulic play compensating element. The disc is 
provided on its surface cooperating with the play compensating element 
with indentations which allows transfer of oil from outside into the 
interior of the inner piston. 
These known play compensating elements experienced some problems upon 
installation in a rocker arm because the disc must first be inserted in 
the bore before introducing the hydraulic play compensating element. 
Therefore, it could happen that the disc after being inserted in the bore 
may fall out therefrom again. Furthermore, it could also occur that upon 
insertion of the disc, the latter was turned by 180 degrees so that its 
indentations did not bear against the play compensating element but 
instead by a flat surface which prevents the oil transfer. Finally, it is 
also conceivable that the insertion of the disc in the bore could be 
forgotten altogether. Thus, all these problems could be encountered which 
as experience shows occur during assembly of several separate parts 
wherein those parts in addition have to be assembled in a positional 
dependence. 
OBJECTS OF THE INVENTION 
It is an object of the invention to provide in the simplest technical 
manner an assembly unit which includes the hydraulic compensating element, 
on the one hand, and the disc, on the other hand, to prevent errors during 
assembly. 
This and other objects and advantages of the invention will become obvious 
from the following detailed description. 
THE INVENTION 
The novel hydraulic play compensating element of the invention for a valve 
control mechanism in internal combustion engines comprising an outer 
piston (4) closed on one end and insertable for displacement in the 
longitudinal direction in a bore (2) of a structural element (3) of the 
valve drive and which guides an inner piston (5) for longitudinal 
displacement with slight play in a longitudinal bore wherein both pistons 
encompass a high pressure chamber (6) therebetween which communicates via 
a check valve (7) arranged in the inner piston with an oil reservoir (8) 
provided in the inner piston (5), and wherein the inner piston (5) is 
supported at its end facing away from the pressure chamber by a disc (9) 
which is fixed in the bore (2) of the structural element (3) of the valve 
drive, is characterized in that the disc (9) engages the bore (16) of the 
inner piston (5) with radially resilient clamping projections (15) upon 
contacting the end of the inner piston (5) facing away from the pressure 
chamber (6). 
In this manner, a force-locking connection is attained between the 
hydraulic play compensating element and the disc. If it is desired to 
attain a more improved connection between the play compensating element 
and the disc, the bore of the inner piston may have a circumferential 
groove engaged by the clamping projections to produce a form-fitting 
connection.

FIGS. 1 and 2 illustrate an embodiment in which a hydraulic play 
compensating element 1 is supported in a bore 2 of a rocker arm and the 
hydraulic play compensating element 1 includes an outer piston 4 which is 
closed on its one end and guides in a longitudinal bore the inner piston 
for longitudinal displacement at slight play. Both pistons 4 and 5 
encompass a high pressure chamber 6 therebetween which is connected by a 
check valve 7 arranged in the inner piston 5 with an oil reservoir 8 
provided in the inner piston 5. The hydraulic play compensating element 
bears with its end facing away from the high pressure chamber 6 against a 
disc 9 which is inserted in the bore 2 and is supported therein by a 
retaining ring 10. The disc 9 is provided at its surface facing the 
hydraulic compensating element 1 with molded indentations 11 which allow 
the passage of oil into the oil reservoir 8. The oil supply to the 
hydraulic play compensating element 1 is obtained via the oil bore 12 in 
the rocker arm 3. 
The disc 9 is provided with a central bore 13 in which the central pin 14 
of a plastic element is inserted which element has clamping projections 15 
engaging under radial prestress in the bore 16 of the inner piston and 
thereby fixes the disc 9 to the hydraulic play compensating element 1. The 
connection of the disc 9 may be improved by engaging the clamping 
projections 15 in a circumferential groove 17 of the bore 16. In this 
case, the clamping projections 15 are designed as several 
circumferentially spaced spring tongues curved radially outwardly. 
In the embodiment illustrated in FIGS. 3 and 4, the clamping projection is 
defined by an enlargement 18 which radially exceeds outwardly a 
circumferential ring 19 connected through several spoken 20 with a central 
hub 21 which supports the central pin 14 inserted in the central bore 13 
of the disc 9. The embodiment as illustrated in FIGS. 5 and 6 differs from 
the preceding one essentially in that the enlargement 18 extends only over 
a part of the circumferential areas between two succeeding spokes. 
While the embodiments described so far were designed as plastic elements, 
the following modifications are concerned with metal parts. FIGS. 7 and 8 
show an embodiment in which one clamping projection is defined by a wire 
ring 22 open at one circumferential area and connected at its one open end 
with a radially inwardly directed spoke 23 to which the axially extending 
central pin 24 is connected. 
In the embodiment of FIGS. 9 and 10, the additional structural element is 
designed as a enlement drawn from sheet metal which extends from a central 
plate 25 with a diameter enlarged by two successive steps 26 and 27 and 
ending in a circumferential ring 28 with a projecting collar 29. To allow 
the oil passage and to simulataneously improve the resiliency, the sheet 
metal element is provided with breakthroughs at several circumferential 
areas in the region between the central plate 25 and the circumferential 
ring 28. In this case, the attachment of the sheet metal element to the 
disc 9 is accomplished by an additional rivet 1 inserted in a bore of the 
central plate 25 and pressed in the central bore 13 of the disc 9. The 
embodiment of FIGS. 11 and 12 differs from the preceding one in that the 
breakthroughs 32 also traverse the collar 29. Otherwise, for attachment of 
the sheet metal element 4, a traversing collar 33 is provided which 
extends directly from the central plate 25. 
Various other modifications of the elements of the invention may be made 
without departing from the spirit or scope thereof and it is to be 
understood that the invention is intended to be limited only as defined in 
the appended claims.