Internal-combustion engines – Cooling – Internal cooling of moving parts; e.g. – hollow valves,...
Reexamination Certificate
2002-08-23
2004-05-25
Kamen, Noah P. (Department: 3747)
Internal-combustion engines
Cooling
Internal cooling of moving parts; e.g., hollow valves,...
C123S1960CP
Reexamination Certificate
active
06739291
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2001-264491, filed Aug. 31, 2001, the entire contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a piston cooling device for a multicylinder engine, and more particularly to a piston cooling device for a multicylinder engine having a crankshaft rotatably supported by a plurality of journal walls disposed on both sides of a plurality of cylinder bores arrayed in the axial direction of the crankshaft. Oil jets are mounted in each of the plurality of journal walls except one journal wall, and serve the purpose of ejecting oil toward pistons which slide within the cylinder bores.
2. Description of Background Art
Heretofore, a piston cooling device of the type described above has been known, for example, from Japanese Patent Laid-open No. Hei 10-169438.
In the conventional piston cooling device, oil jets are mounted in journal walls between cylinder bores and one of journal walls at opposite ends in the axial direction of a crankshaft.
An oil passage for guiding oil to a cylinder head is defined in one of the journal walls. With the oil jets thus mounted in the journal walls in the conventional piston cooling device, in order to avoid a reduction in the rigidity of a journal wall which would have both the oil passage and the oil jet, the oil passage has to be defined in the other of the journal walls at opposite ends in the axial direction of the crankshaft. The oil passage which extends simply vertically supplies oil to the cylinder head on either side along the axis of the crankshaft. For distributing oil uniformly to the cylinders in the cylinder head, however, it is desirable to supply oil to the cylinder head at a position closer to a central region along the axis of the crankshaft. In the conventional piston cooling device, the oil passage required to adequately supply oil is complex in shape.
The present invention has been made in view of the above problems. It is an object of the present invention to provide a piston cooling device for a multicylinder engine which is capable of supplying oil to a cylinder head at a position closer to a central region along the axis of a crankshaft, while avoiding a complex oil passage shape.
SUMMARY AND OBJECTS OF THE INVENTION
To achieve the above object, according to a first aspect of the present invention, a piston cooling device is provided for a multicylinder engine having a crankshaft rotatably supported by a plurality of journal walls disposed on both sides of a plurality of cylinder bores arrayed in the axial direction of the crankshaft. Oil jets are mounted in each of the journal walls except one journal wall for the purpose of ejecting oil toward pistons which slide within the cylinder bores. An oil passage for guiding oil to a cylinder head is defined in one of the journal walls which are positioned between a pair adjacent cylinder bores, and said oil jets are mounted respectively in each of the other journal walls.
With this arrangement, since the oil passage is defined in one of the journal walls which is positioned at a pair of adjacent cylinder bores, and no oil jet is mounted in that one of the journal wall, oil can be supplied to the cylinder head at a position closer to a central region along the axis of the crankshaft, while maintaining the desired rigidity of the journal wall. The oil passage so disposed has a simple vertically extending shape.
In accordance with a second aspect of the present invention, the journal wall which has said oil passage defined therein is integrally joined to a partition wall disposed between said crankshaft and a transmission shaft which serves as part of a transmission and extends parallel to the crankshaft. Further, the transmission shaft is rotatably supported by a support shaft integrally joined to said partition wall at a position adjacent to the journal wall which has said oil passage defined therein.
With this arrangement, the rigidity of the partition wall and the rigidity of the joint portion of the support wall to the partition wall are kept at a high level. Specifically, since the oil passage is not open at an outer surface of the journal wall, any effect which the oil passage has on the rigidity of the journal wall is small. Also. Since this journal wall does not have oil jet, its rigidity is kept relatively high. Since this journal wall is integrally joined to the partition wall, the rigidity of the partition wall is kept at a high level also. Furthermore, inasmuch as the support wall is integrally joined to the partition wall at a position adjacent to the journal wall whose rigidity is relatively high, the joint portion between the partition wall and the support wall has its rigidity kept at a high level also.
In accordance with a third aspect of the present invention, a clutch is mounted on one end of the transmission shaft which extends through said support wall. Further, a drive gear disposed on said crankshaft is held in mesh with a driven gear relatively rotatably mounted on said transmission shaft for inputting power to the clutch. With this arrangement, regardless of the structure in which the clutch is supported on the support shaft by the transmission shaft, the structure in which a radial load tends to act on the transmission shaft due to the meshing engagement between the drive gears and the driven gears, the support wall, and the partition wall are made lightweight. As such, they can effectively support the transmission shaft without the need for thickening the support wall and the partition wall. This is based on the advantage that the rigidity of the support wall and the rigidity of the joint portion between the support wall and the partition wall are kept at a high level.
In accordance with a fourth aspect of the present invention, the drive gear is disposed on one of a plurality of crank webs of the crankshaft, which is positioned at an axial end of the crankshaft. Further, the oil jet is mounted in the journal wall which is disposed outwardly of said drive gear and has an oil ejection axis (L) displaced from said drive gear. With this arrangement, the drive gear does not obstruct the cooling of the pistons with the ejection of oil from the oil jets, and oil ejected from the oil jets is spread to effectively lubricate the meshing portions of the drive gears and the driven gears.
In accordance with a fifth aspect of the present invention, at least one of a plurality of crank webs of the crankshaft is shaped to traverse an oil ejection axis of the oil jet corresponding to the at least one crank web when the piston corresponding to said at least one crank web is positioned in a predetermined range near the bottom dead center. In this position, the at least one crank web is kept away from the oil ejection axis when the piston corresponding to the at least one crank web is positioned out of the predetermined range. With this arrangement, when at least one piston is positioned in the predetermined range near the bottom dead center, oil ejected from the oil jet does not directly hit the piston from below, preventing the rotational friction of the engine from being increased by the ejection of oil.
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: 4010718 (1977-03-01), Stewart
patent: 5533472 (1996-07-01), Sands et al.
patent: 5896656 (1999-04-01), Laws
patent: 6205971 (2001-03-01), Inumaru et al.
patent: 196 15 234 (1997-07-01), None
patent: 10-169438 (1998-06-01), None
Kawakubo Hiroyuki
Nakayasu Tetsuya
Honda Giken Kogyo Kabushiki Kaisha
Kamen Noah P.
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