Internal-combustion engines – Lubricators – Crankcase – pressure control
Reexamination Certificate
1999-10-05
2001-07-03
Kamen, Noah P. (Department: 3747)
Internal-combustion engines
Lubricators
Crankcase, pressure control
C123S1950HC
Reexamination Certificate
active
06253727
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an oil passage structure for returning oil in an engine. A plurality of cylinder bores with substantially horizontal axes are lined up at cylinder blocks. A plurality of combustion chambers individually corresponding to each cylinder bore are formed between pistons fitted in a freely slidable manner into each cylinder bore and cylinder heads. Cam shafts interlocking with and coupled to a plurality of intake valves and a plurality of exhaust valves controlling intake of air to and exhaust emissions from the combustion chambers are positioned within valve chambers formed between the cylinder heads and head covers coupled to the cylinder heads. Furthermore, transmission mechanisms for reducing the rotational force of the crankshaft by half for transmission to the camshafts are provided between the crankshaft to which the pistons are commonly coupled at the crank chamber within the crankcases coupled to the cylinder blocks and the camshafts. More particularly, the present invention relates to an oil passage structure for returning oil from a valve chamber to a crank chamber.
2. Description of Related Art
Conventionally, as disclosed in, for example, Utility Model Laid-open Publication No. Sho. 63-65811, an oil passage for returning oil is typically provided in a cylinder head and cylinder block of an engine.
In the related art, a dedicated oil passage for returning oil is provided in the cylinder block and cylinder head. The cylinder block and cylinder head therefore become larger as a result of space being provided to position this oil passage for returning oil. Furthermore, the weight of the engine is increased.
SUMMARY OF THE INVENTION
In order to resolve the aforementioned situation, it is the object of the present invention to provide an oil passage structure for returning oil in an engine which is both lighter and more compact due to a dedicated oil passage no longer being required. Furthermore, it is an object of the present invention for oil in a valve chamber to be returned to a crank chamber.
In order to achieve the aforementioned object, according to a first aspect of the present invention, an oil passage structure for returning oil in an engine includes a plurality of cylinder bores with substantially horizontal axes lined up at cylinder blocks, a plurality of combustion chambers individually corresponding to each cylinder bore formed between pistons fitted in a freely slidable manner into each cylinder bore and cylinder head, cam shafts interlocking with and coupled to a plurality of intake valves and a plurality of exhaust valves controlling intake of air to and exhaust emissions from the combustion chambers positioned within valve chambers formed between the cylinder heads and head covers coupled to the cylinder heads, and transmission mechanisms for reducing the rotational force of the crankshaft by half for transmission to the camshafts provided between the crankshaft to which the pistons are commonly coupled at the crank chamber within the crankcases coupled to the cylinder blocks and the camshafts. The transmission mechanisms include endless chains wrapped around drive sprockets fixed to one end of the crankshaft and driven sprockets fixed to one end of the camshafts being housed in transmission chambers formed across the head covers, cylinder heads, cylinder blocks and crankcases in such a manner that ends of the transmission mechanisms are made to communicate with the valve chambers and the other ends of the transmission mechanisms are made to face one end in the axial direction of the crankshaft. Furthermore, a return hole causing the lower part of the other end of the transmission chambers to communicate with the crank chamber is provided at the crankcases.
According to this configuration, it is possible to make oil circulate about the transmission chamber housing the transmission mechanism because the transmission mechanism uses a chain to transmit force. Oil can therefore be returned to the crank chamber from the valve chamber via the return hole using the transmission chamber housing the transmission mechanisms provided between the camshaft and the crankshaft. As it is therefore no longer necessary to provide a dedicated oil returning oil passage at the cylinder blocks and the cylinder heads for at least the flow of oil returning to the crank chamber from the transmission chamber, the cylinder blocks and cylinder heads can be made smaller accordingly and can also be made more lightweight.
According to a second aspect of the present invention, in addition to the configuration of the first aspect of the present invention, the crankshaft is supported in a freely rotatable manner by the crankcase and bearing caps fastened to the crankcase at a plurality of places along the axial direction of the crankshaft. The return hole is formed so as to be extended in the direction of fastening the bearing caps to the crankcase. According to this configuration, the surface area of the opening of the return hole can be set to be relatively large without damaging the rigidity with which the crankshaft is supported and the extent to which oil is returned to the crank chamber is improved.
According to a third aspect of the present invention, in addition to the configuration of the second aspect of the present invention, the pair of cylinder blocks equipped with pluralities of cylinder bores positioned opposite each other with substantially horizontal axes on both sides of the crankshaft are established at the pair of mutually fastened crankcases defining the crank chamber. The bearing caps are fastened to a journal wall integrally formed with one of the crankcases. Furthermore, the return hole is provided between the crankcases positioned offset towards the side of one of the crankcases.
According to this configuration, in a horizontally opposed engine where a pair of cylinder bore rows face each other in a substantially horizontal plane, lowering of the rigidity of a crankcase on a side where a journal wall supporting the crankshaft together with bearing caps is not integrally formed is avoided, the surface area of the return hole can be made larger and the extent to which oil is returned to the crank chamber is dramatically improved.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
REFERENCES:
patent: 5755606 (1998-05-01), Takahashi et al.
patent: 6047667 (2000-04-01), Leppanen et al.
patent: 6076495 (2000-06-01), Takahashi et al.
patent: 5-3692 (1993-01-01), None
Nakatsura Masahiko
Tosaka Tetsuya
Birch & Stewart Kolasch & Birch, LLP
Honda Giken Kogyo Kabushiki Kaisha
Huynh Hai
Kamen Noah P.
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