The present invention concerns internal combustion engines - in particular Diesel engines - according to the classifying portion of claim 1.

Internal combustion engines of this sort comprise

a cylinder head comprising at least one intake opening and at least one outlet opening for at least one combustion chamber of the internal combustion engine, at least one intake valve for opening and closing the at least one intake opening, at least one outlet valve for opening and closing the at least one outlet opening, at least one first rocker arm for actuating the at least one intake valve, the at least one first rocker arm being disposed along a first axis, and

at least one second rocker arm for actuating the at least one outlet valve, the at least one second rocker arm being disposed along a second axis.

EP 0 735 244 A1 discloses a Diesel engine with rocker arms for actuating intake and outlet valves. This disclosure teaches certain arrangements of valves, rocker arm bearings and cylinder head bolts in order to reduce the width of the engine. Since the rocker arms are disposed in parallel and perpendicular to the longitudinal axis of the engine, reducing the width of the engine results in shorter rocker arms and therefore more movement during each working stroke and also more rapid movement. Consequently, there is a negative influence on the life time for the bearings of the rocker arms and other valve train bearings.

The object of the invention is therefore to provide an internal combustion engine with a reduced width while at the same time limiting a negative influence on rocker arm bearings.

This object is achieved with the features of claim 1 . This is achieved in that the first axis of the at least one first rocker arm and the second axis of the at least one second rocker arm form a rocker arm angle greater than zero viewed in a top view of the cylinder head. I.e. the at least one first rocker arm and the at least one second rocker arm are not disposed in parallel. By allowing an angle between the first axis of the at least one first rocker arm and the at least one second rocker arm, the width of the engine can be reduced without having to shorten the at least one first rocker arm and the at least one second rocker arm.

Furthermore, the skewed layout proposed by the invention successfully reduces the thrust loads on the valve train bearings and, whilst simultaneously yielding a more homogeneous load distribution during operation, bringing a significant improvement to the system and component life. Thanks to the more homogeneous load distribution, the tipping motion of the assembly is also reduced with respect to a layout for non-overhead camshaft engine configurations according to the prior art.

An additional benefit of this configuration according to the invention is a significant reduction in the overall and effective footprint of the assembly, minimizing the blockage caused by the pushrods in the exhaust port (by bringing them closer together). This yields aerodynamic advantages as well as the possibility for a simplified cylinder head and exhaust manifold design.

The at least one first rocker arm and the at least one second rocker arm are disposed along the first axis and the second axis, respectively. Formulated differently, the at least one first rocker arm and the at least one second rocker arm extend essentially along the first axis and the second axis, respectively. The first axis and the second axis may be perpendicular to rocker shafts supporting the at least one first rocker arm and the at least one second rocker arm, respectively. Flowever, it is in principle possible to design rocker arms that are not perpendicular to rocker shafts supporting the rocker arm.

The at least one first rocker arm and the at least one second rocker arm do not need to be symmetric. The first axis and the second axis are rather determined by the direction in which the at least one first rocker arm and the at least one second rocker arm mainly extend geometrically.

According to the invention the rocker arm angle between the first axis of the at least one first rocker arm and the second axis of the at least one second rocker arm is present in a top view of the cylinder head. This top view can be given by a central axis of a combustion chamber viewed from the direction of the cylinder head. Therefore the top view is not always necessarily a top view with respect to a global horizontal. Rather, if the central axis of the combustion chamber is e.g. slanted, the top view can also be slanted.

Advantageous embodiments of the invention are defined in the dependent claims.

In a preferred embodiment the rocker arm angle viewed in a top view of the cylinder head can lie between 5° and 35°, preferably between 10° and 25° and more preferably between 1 1 ° and 18°.

In a particularly preferred embodiment the at least one first rocker arm and the at least one second rocker arm are arranged at an angle greater than 0° and less than 90° with respect to a longitudinal axis of the internal combustion engine.

The internal combustion engine can comprise a cam shaft for actuating the at least one first rocker arm and/or the at least one second rocker arm via push rods. A cam shaft axis of the cam shaft can be essentially parallel to a longitudinal axis of the internal combustion engine.

It can be provided, that the at least one first rocker arm is mounted on at least one first rocker shaft and/or the at least one second rocker arm is mounted on at least one second rocker shaft, wherein the at least one first rocker shaft and the at least one second rocker shaft are preferably at a rocker shaft angle greater than zero, preferably between 5° and 35°, more preferably between 10° and 25° and even more preferably between 1 1 ° and 18°. This makes it especially easy constructively to realise a non-zero rocker arm angle according to the invention.

Additionally, the at least one first rocker shaft and the at least one second rocker shaft can easily be realised through a common rocker shaft with a bend and/or a kink. Separate first and second rocker shafts are of course also a possibility.

The at least one first rocker shaft and/or the at least one second rocker shaft and/or the common rocker shaft can be mounted on a - preferably asymmetric - pedestal. The asymmetry can be used to easily implement the at least one first rocker shaft and/or the at least one second rocker shaft and/or the common rocker shaft at an angle or with a bend or a kink. This non-conventional layout can be used to bring the pushrods for the at least one intake valve and the at least one outlet valve closer together.

The positioning of the valve train pushrods is a common challenge for the design of non overhead Diesel engines, as they generate a significant flow blockage, commonly in the exhaust port. The proposed layout solves this problem by introducing e.g. a common kinked rocker arm shaft that allows for the at least one first rocker arm and the at least one second rocker arm to be placed at the rocker arm angle relative to each other.

The combination of the rocker arm angle between the at least one first rocker arm and the at least one second rocker arm on the one hand and the asymmetric pedestal on the other hand has the effect that the torsional moment on the assemblies for the at least one intake valve and the at least one outlet valve trains are not aligned, reducing the tipping motion of the entire assembly during operation.

In the top view of the cylinder head the first axis of the at least one first rocker arm and a cam shaft axis of the cam shaft can form a first cam shaft angle greater than zero and less than 90°. The first cam shaft angle can lie between 50° and 85°, preferably between 60° and 80° and more preferably between 65° and 75°.

Similarly, in the top view of the cylinder head the second axis of the at least one second rocker arm and the cam shaft axis of the cam shaft can form a second cam shaft angle greater than zero and less than 90°. The second cam shaft angle can lie between 80° and 89° and preferably between 85° and 88°.

In a particularly space saving embodiment an injector assembly - preferably a Diesel injector assembly - can be disposed between the at least one first rocker arm and the at least one second rocker arm.

It can be provided that on a distal end of the at least one first rocker arm disposed to actuate the at least one intake valve and/or on a distal end of the at least one second rocker arm disposed to actuate the at least one outlet valve there is provided at least one valve bridge for simultaneously actuating at least two intake valves and/or at least two outlet valves. In such an embodiment it can preferably be provided that the at least one valve bridge is at a valve bridge angle greater than zero relative to the first axis of the at least one first rocker arm to which it is attached and/or the second axis of the at least one second rocker arm to which it is attached.

Valve bridges make it especially easy to actuate engines with four valves per combustion chamber, which is a preferred embodiment. I.e. there can be - preferably precisely - two of the following per combustion chamber of the internal combustion engine: intake openings, intake valves and/or outlet openings, outlet valves.

The internal combustion engine according to the invention can be a reciprocating cylinder piston engine with any number of cylinders. The internal combustion engine according to the invention can be a Diesel engine.

For the purposes of the invention angles (viewed in a top view of the engine) of the same absolute value, but measured in different directions, i.e. clock-wise or anti-clock-wise, are to be considered identical.

Further advantages and details of the invention become apparent from the figures and the accompanying description. The figures show:

Fig. 1 a top view of the rocker arm assembly according to the invention for one cylinder,

Fig. 2 a first perspective view of an internal combustion engine according to the invention in the vicinity of the cylinder head,

Fig. 3 a second perspective view of the embodiment of Fig. 2,

Fig. 4a an exploded view of the rocker arm assembly according to the invention,

Fig. 4b a sectional view of the pedestal for a rocker arm assembly according to the invention,

Figs. 5a, 5b perspective views of the rocker arm assembly of Figs. 4a and 4b,

Fig. 6 a further perspective view of the rocker arm assembly of Fig. 2 and

Fig. 7a to 7d different views of a first rocker arm. Fig. 1 depicts a rocker arm assembly according to the invention. It comprises a first rocker arm 4a and a second rocker arm 4b, both swivelable mounted on an asymmetric pedestal 6.

There are provided two valve bridges 9 disposed on distal ends of the first rocker arm 4a and the second rocker arm 4b. These valve bridges are configured to each actuate two valves with one rocking cycle of the first rocker arm 4a and the second rocker arm 4b.

The first rocker arm 4a and the second rocker arm 4b are each actuated through push rods 7. The push rods 7 are set in motion using at least one cam shaft (not depicted).

The first rocker arm 4a is disposed along its first axis Xa and the second rocker arm 4b is disposed along its second axis Xb. In the top view depicted in Fig. 1 the first axis Xa and the second axis Xb intersect and form a rocker arm angle greater than 0°. In this embodiment the rocker arm angle is about 15°.

Fig. 2 shows the rocker arm assembly of Fig. 1 mounted on a cylinder head 2 of an internal combustion engine 1 in a perspective view. The valve bridges 9 actuate two intake valves 3a and two outlet valves 3b, respectively.

In the depiction of Fig. 2 the common rocker shaft 5 can be seen, but regarding the common rocker shaft 5 it is also referred to Fig. 4a.

As is also indicated in Fig. 2 the rocker arm assembly according to Fig. 1 can be used on each of the cylinders of the internal combustion engine 1 as a matter of course.

The injector assembly 8 - in this case a Diesel injector - is disposed between the first rocker arm 4a and the second rocker arm 4b, which makes for a particularly compact embodiment.

This arrangement is also depicted in Fig. 3, which is also otherwise similar to Fig. 2, but differs in the angle of the perspective view. The angle between the direction of the valve bridges 9 and the first and second rocker arms 4a, 4b, respectively is easily visible in Fig. 3. Fig. 4a is an exploded view of the rocker arm assembly of Fig. 1 . Next to the first rocker arm 4a, the second rocker arm 4b, the push rods 7 and the pedestal 6 the common rocker shaft 5 is clearly visible. The common rocker shaft 5 comprises a first rocker shaft 5a and a second rocker shaft 5b which are joined together forming a kink.

Fig. 4b shows a cut through the asymmetric pedestal 6 along the plane marked A-B in Fig. 1 . Also this figure shows the first rocker arm 4a and the second rocker arm 4b being supported on the first rocker shaft 5a and the second rocker shaft 5b, respectively, where the first rocker shaft 5a and the second rocker shaft 5b are joined to form a common rocker shaft 5.

Figures 5a and 5b show further perspective views of the rocker arm assembly of Fig. 1 . Fig. 6 depicts a further perspective view of the internal combustion engine 1 similar to Figs. 2 and 3 albeit from a different angle of view. Fig. 6 shows clearly how the rocker arm angle between the first axis Xa of the first rocker arm 4a and the second axis Xb of the second rocker arm 4b makes it possible to arrange the push rods 7 quite close together while accommodating the injector assembly 8 between the first rocker arm 4a and the second rocker arm 4b.

Figs. 7 a to 7d depict different views of the first rocker arm 4.