Internal-combustion engines – Poppet valve operating mechanism – Lubrication
Reexamination Certificate
1999-10-05
2001-05-08
Lo, Weilun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
Lubrication
C123S1960CP, C184S006500
Reexamination Certificate
active
06227155
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multi-cylinder engine in which a plurality of combustion chambers are formed between a cylinder head fastened to a cylinder block including a plurality of cylinder bores and pistons slidably fitted in the plurality of cylinder bores. A cam shaft linked with a plurality of intake valves and a plurality of exhaust valves for carrying out intake and exhaust operations for the combustion chambers is rotatably supported at a plurality of locations spaced in the axial line direction of said cam shaft by cam bearing portions provided on the cylinder head and a cam holder fastened to the cam bearing portions. Furthermore, an oil passage capable of supplying oil from an oiling passage provided in the cylinder head is formed in the cam shaft. In particular, the present invention relates to a structure for supplying oil from a cylinder head into an oil passage formed in a cam shaft.
2. Description of Related Art
In a conventional multi-cylinder engine, an oil groove for supplying oil into an oil passage in a cam shaft is generally provided in a can bearing portion for supporting one end portion of the cam shaft in the axial direction. The cam bearing portion is disposed outside of the outermost one of a plurality of combustion chambers disposed in the axial line direction of the cam shaft.
A cylinder head is fastened to a cylinder block using fastening bolts disposed at a plurality of locations other than portions corresponding to a plurality of combustion chambers. To shorten the length of the cylinder head in the axial line direction of a cam shaft, it may be desirable to make the fastening bolt disposed outside the outermost combustion chamber as close to the outermost combustion chamber as possible. If the fastening bolt can be disposed in a portion corresponding to a cam bearing portion outside the outermost combustion chamber, the length of the cylinder head can be shortened. However, since an oil groove is generally provided in the above cam bearing portion disposed outside the outermost combustion chamber as described above, it is difficult to dispose the fastening bolt in the portion corresponding to the above cam bearing portion without interference with the oil groove
SUMMARY OF THE INVENTION
In view of the foregoing, the present invention has been made, and a first object of the present invention is to provide a structure for lubricating a cam shaft in a multi-cylinder engine, which is capable of supplying oil in an oil passage formed in the cam shaft while avoiding restriction in location of fastening bolts for fastening the cylinder head to the cylinder block.
On the other hand, in a multi-cylinder engine in which a transmission mechanism is provided between the cam shaft and the crank shaft, if an oil groove is provided in a cam bearing portion between the combustion chamber closest to the transmission mechanism and the transmission mechanism, a fastening bolt is disposed between the cam bearing portion and the transmission mechanism or between the cam bearing portion and the combustion chamber. With this configuration, a gap between the combustion chamber and the transmission mechanism must be made relatively large. This is inconvenient, since the length of the cylinder head becomes longer in the axial line direction of the cam shaft.
Accordingly, a second object of the present invention is to provide a structure for lubricating a cam shaft in a multi-cylinder engine, which is capable of making the length of a cylinder head in the axial direction of the cam shaft as short as possible, and supplying oil in an oil passage formed in the cam shaft.
To achieve the first object, according to a first aspect of the present invention, there is provided a structure for lubricating a cam shaft in a multi-cylinder engine. The multi-cylinder engine is configured such that a plurality of combustion chambers are formed between the cylinder head fastened to the cylinder block including a plurality of cylinder bores and pistons slidably fitted in the plurality of cylinder bores. A cam shaft linked with a plurality of intake valves and a plurality of exhaust valves for carrying out intake and exhaust operations for the combustion chambers is rotatably supported at a plurality of locations spaced in the axial line direction of the cam shaft by cam bearing portions provided on the cylinder head and a cam holder fastened to the cam bearing portions. Furthermore, an oil passage capable of supplying oil from an oiling passage provided in the cylinder head is formed in the cam shaft. The lubricating structure includes an oiling hole provided in the cam shaft in communication with the oil passage, and an oil groove in communication with the outer end of the oiling hole is formed in one of the cam bearing portions provided in the cylinder head at a position corresponding to one of the combustion chambers in such a manner as to face toward the outer surface of the cam shaft. Furthermore, the oiling passage is in communication with the oil groove.
With this configuration, since none of the fastening bolts are disposed at a portion corresponding to the combustion chamber, by forming the oil groove in the cam bearing portion provided on the cylinder head at a position corresponding to one of the plurality of combustion chambers, it is possible to supply oil in the oil passage formed in the cam shaft without restricting the location of the fastening bolts.
To achieve the above second object, according to a second aspect of the present invention, there is provided a structure for lubricating a cam shaft in a multi-cylinder engine. The multi-cylinder engine is configured such that a plurality of combustion chambers are formed between the cylinder head fastened to the cylinder block including a plurality of cylinder bores and pistons slidably fitted in the plurality of cylinder bores. A cam shaft linked with a plurality of intake valves and a plurality of exhaust valves for carrying out intake and exhaust operations for the combustion chambers is rotatably supported at a plurality of locations spaced in the axial line direction of the cam shaft by cam bearing portions provided on the cylinder head and a cam holder fastened to the cam bearing portions. A transmission mechanism for reducing the rotational power of the crank shaft to half and transmitting the reduced rotational power to the cam shaft is provided between the crank shaft and the cam shaft. Furthermore, an oil passage capable of supplying oil from an oiling passage provided in the cylinder head is formed in the cam shaft. The lubricating structure includes a through-hole, into which one of fastening bolts for fastening the cylinder head to the cylinder block is to be inserted, is provided in one of the cam bearing portions. This cam bearing portion is provided in the cylinder head at a position between the transmission mechanism and the combustion chamber closest to the transmission mechanism disposed in the axial direction of the cam shaft. Furthermore, an oiling hole is provided in the cam shaft in communication with the oil passage, and an oil groove in communication with an outer end of the oiling hole is provided in another one of the plurality of the cam bearing portions adjacent to the above cam bearing portion in such a manner as to face toward the outer surface of the cam shaft. The oiling passage is in communication with the oil groove.
With this configuration, the though-hole into which the fastening bolt is to be inserted is provided in one cam bearing portion between the combustion chamber closest to the transmission mechanism and the transmission mechanism, and the oil groove is provided in another cam bearing portion adjacent to the above one cam bearing portion, so that the fastening bolt between the transmission mechanism and the combustion chamber is made as close to the combustion chamber as possible. This makes it possible to shorten the length of the cylinder head in the axial line, direction of the cam shaft.
According to a third aspe
Nakashima Masahiro
Tosaka Tetsuya
Birch & Stewart Kolasch & Birch, LLP
Honda Giken Kogyo Kabushiki Kaisha
Lo Weilun
LandOfFree
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