Patent Application
20170009801
This application claims priority to German Patent Application No. 102015009023.2, filed Jul. 11, 2015, which is incorporated herein by reference in its entirety.
The present disclosure pertains to a hollow cast iron crankshaft for an internal combustion engine, particularly suitable for spark-ignition engines or gasoline engines. The hollow casted crankshaft is optimized for oil supply.
As known, the crankshaft, sometimes abbreviated to “crank,” is the part of an internal combustion engine that translates reciprocating linear piston motion into rotation. To convert the reciprocating motion into rotation, the crankshaft has additional bearing surfaces whose axis is offset from a central longitudinal axis of the crank, to which one end of the connecting rods from each cylinder attach. Large engines are usually multi-cylinder to reduce pulsations from individual firing strokes, with more than one piston attached to a complex crankshaft.
The crankshaft rotates about its central longitudinal axis, typically with several bearing journals riding on replaceable bearings (the main bearings) held in the engine block. As the crankshaft undergoes a great deal of sideways load from each cylinder in a multi-cylinder engine, it must be supported by several such hearings, not just one at each end. The crankshaft also includes connecting rod bearing journals for supporting storage of connecting rods.
Crankshafts can be forged from a steel bar usually through roll forging or cast in ductile steel. Today some engines use cast iron crankshafts for low output versions (which are mostly cost driven) while the more expensive high output version use forged steel.
An also known aim of the engine manufacturers is to decrease more and more the global weight of the engine in general and of components in particular, thus getting a reduction of CO2 emissions. In general, ductile cast iron is used for a cast crankshaft. In this case, however, the entire weight of the crankshaft increases because the shaft diameter has to be made larger in order to ensure the mechanical properties. A hollow crankshaft that is formed by enveloped-casting a thin-walled metal pipe to be bonded to the inside of the crankshaft is known as a solution of the above problem. In this crankshaft, reduction in weight is achieved.
Other improvements can be reached working on the oil supply circuit, in order to reduce the oil flow and consequently the oil pump power. Therefore a need exists for a crankshaft, whose design contributes to the above target.
The present disclosure provides a crankshaft for an internal combustion engine, whose design is able to positively impact on engine weight and oil flow amount, obtaining a remarkable reduction of both. In particular, a hollow cast iron crankshaft is provided for an internal combustion engine. An embodiment of the disclosure provides a hollow cast iron crankshaft of an internal combustion engine having at least one main bearing journal, at least two connecting rod bearing journals. The crankshaft has a plurality of internal oil supply bores to lubricate the connecting rod bearing journals. An outer circumference of the main bearing journal is fluid connected with an outer circumference of two connecting rod bearing journals by the supply bores. An advantage of this combination of a hollow cast iron crankshaft with the present oil supply, it is possible to have a weight optimized crankshaft in combination with a reduced oil flow amount. Consequently, these features imply a reduced oil pump power and CO2 reduction.
According to another embodiment, a first oil supply bore is provided to fluid connect the main bearing journal with a first connecting rod bearing journal and a second oil supply bore is provided to fluid connect the same main bearing journal with a second connecting rod bearing journal. As an advantage, it is possible to reduce the oil flow amount, which is needed by the crankshaft bearings.
According to a still further embodiment, each oil supply bore bridges a hollow space of the crankshaft. An advantage of this embodiment is that it combines the hollow crankshaft with an optimized oil circuit, thus keeping both advantages of the two features.
According to another embodiment the oil supply bores are casted. An advantage of this embodiment is that casting would be cheaper and can reduce tool investment.
According to still another embodiment, the oil supply bores are drilled. An advantage of this embodiment is that it simplifies the manufacturing operations.
Another embodiment of the disclosure provides an internal combustion engine provided with a hollow cast iron crankshaft according to any of the previous embodiments.
The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements.
The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description.
Some embodiments may include an internal combustion engine (ICE) 110, as shown in
According to an embodiment of the present invention, a combination of a hollow cast iron crankshaft 145 with an oil supply layout in which one main bearing feeds two rod bearings as hereafter described.
More in detail, among the plurality of oil supply bores, a first oil supply bore 500.1 is provided to connect the main bearing journal 530 with a first connecting rod bearing journal 520.1 bridging a first hollow space 540.1. A second oil supply bore 500.2 is provided to connect the same main bearing journal 530 with a second connecting rod bearing journal 520.2 bridging the second hollow space 540.2. The oil supply bores 500 are preferably casted. As an alternative, the oil supply bores 500 can also be realized by drilling.
As a result of this oil supply layout and the combination of a hollow cast iron crankshaft with the disclosed oil supply, it is possible to have a weight optimized crankshaft in combination with a reduced oil flow. Consequently, these features imply a reduced oil pump power and CO2 reduction.
While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims and their legal equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102015009023.2 | Jul 2015 | DE | national |
