Internal-combustion engines – Poppet valve operating mechanism – Plural valve trains – single actuator
Reexamination Certificate
1999-08-10
2001-03-27
Walberg, Teresa (Department: 3742)
Internal-combustion engines
Poppet valve operating mechanism
Plural valve trains, single actuator
C123S090390, C123S090400
Reexamination Certificate
active
06205966
ABSTRACT:
TECHNICAL FIELD
This invention relates to a multiple cylinder internal combustion engine with two inlet or intake valves and two outlet or exhaust valves, the intake valves and the exhaust valves being arranged on opposite longitudinal sides of the engine, and the intake valves and exhaust valves being operated by a camshaft via intake rocker arms and exhaust rocker arms, respectively.
BACKGROUND OF THE INVENTION
The internal combustion engine disclosed in German Patent No. 12 42 045 has intake rocker arms and exhaust rocker arms, which for each cylinder are combined into one forked rocker arm and one bridge rocker arm. The bridge rocker arm, because of the connecting webs, effects a considerable increase in the mass to be moved and a reduction in flexural stiffness.
A similar development is shown in European Patent EP 0 194 922 concerning a spark-ignition internal combustion engine with a central overhead camshaft, in which the valves are operated either by two bridge rocker arms or by one bridge rocker arm and two individual rocker arms.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the invention to avoid the disadvantages of the previously designed engines with a compact size of the cylinder head and of the rocker arm housing.
The objects of this invention are achieved by using an intake rocker arm and an exhaust rocker arm which are made as forked rocker arms, each forked rocker arm operating two like valves per cylinder. The pivot axes of the intake rocker arms and of the exhaust rocker arms, respectively, are offset relative to one another, one above another, the rocker arms being rotatably supported in a rocker arm housing mounted on the cylinder head by individual bearing journals which are removable from the rocker arm housing from the cylinder head side. Less space is required when the axis of the exhaust rocker arm for each cylinder is arranged obliquely above the axis of the intake rocker arm, thus the size of the cylinder head and of the rocker arm housing is very compact. Particularly space-saving is an arrangement in which the axes of the intake rocker arms lie in the parting plane between rocker arm housing and cylinder head. The valve axes may all be parallel to one another or the valve axes may subtend at an acute angle. The exhaust rocker arms of all cylinders of a cylinder bank are supported on a continuous shaft, thus permitting the timing of the exhaust valves to be changed by rotating the shaft or an eccentric sleeve supporting.
This makes it possible to implement an engine brake in a simple fashion. In a preferred embodiment an eccentric sleeve or bearing shell supports the shaft in the region of the support of each exhaust rocker arm and is connected to a rotation mechanism on an end face of the internal combustion engine.
Preferably, the forked rocker arms, viewed in horizontal projection, have an asymmetric shape, so that the push rods for the operation of the rocker arms can be spaced relatively far from one another. The space freed between the push rods can be used for cylinder head bolts and the fuel supply line.
In an especially preferred embodiment of the invention, the axes of the intake rocker arms and exhaust rocker arms are arranged on the intake valve side of the engine longitudinal plane, and the intake ducts as well as the exhaust ducts issue from lateral flange surfaces on the exhaust valve side of the longitudinal plane of the engine. The intake plenum is arranged above the exhaust manifold, so that all breathing ducts can be placed on one engine longitudinal side. The space thereby freed on the opposite engine longitudinal side can be used for the placement of other units, for example the injection pump.
In an embodiment of the invention that is very simple to fabricate and saves space, the bearings for the exhaust rocker shaft are formed by holes in the rocker arm housing.
In further development of the invention, the stems of the intake valves may have a shorter length than the stems of the exhaust valves, the valve springs of the intake valves preferably being shorter than the valve springs of the exhaust valves. It is advantageous to have the stroke of the exhaust valves longer than the stroke of the intake valves. Intake and exhaust rocker arms can be made with unequal mechanical advantages.
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Dahbour Fadi H.
Deutz AG
Hardaway/Mann IP Group
Nexsen Pruet Jacobs & Pollard LLP
Schwab Charles L.
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