Internal-combustion engines – Poppet valve operating mechanism – Camshaft drive means
Reexamination Certificate
1999-10-05
2001-06-05
Lo, Wellun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
Camshaft drive means
C123S1950HC, C123S055200, C123S055500
Reexamination Certificate
active
06240887
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multi-cylinder engine including a cam shaft linked with intake valves and exhaust valves which are disposed in a cylinder head in such a manner that one of the intake valves and one of the exhaust valves correspond to each of a plurality of combustion chambers. A crank shaft is rotatably supported by a crank case and a plurality of bearing caps are fastened to the crank case; and a transmission mechanism and configured such that an endless chain is wound around a drive sprocket fixed on the crank shaft and a driven sprocket fixed on the cam shaft.
2. Description of Background Art
A chain-type transmission mechanism for reducing a rotational power of a crank shaft to half and transmitting the reduced rotational power to a cam shaft has been known, for example, from Japanese Patent Publication No. Hei 2-60886. For a transmission mechanism using a timing belt, it is required to provide a seal structure on a crank case for preventing leakage of oil onto the transmission mechanism side. However, for the chain-type transmission mechanism, it is possible to eliminate the necessary for the provision of a seal structure on the crank case, and hence it is difficult to make the engine compact.
In the case where the transmission mechanism using an endless chain is provided between a crank shaft and a cam shaft in order to make the engine compact, it is required to turnably support one end of a chain tensioner in the longitudinal direction for the purpose of accurately transmitting power between the crank shaft and the cam shaft by bringing the chain tensioner extending in the running direction of a chain into slide-contact with the chain. However, in a multi-cylinder engine in which the crank shaft is rotatably supported by a crank case and a plurality of bearing caps, if the rotatably supporting-position of the chain tensioner is set on the crank case side, the length of the chain tensioner, that is, the length of the sliding motion of the chain tensioner on the chain is shortened so that the confinement of the action of the chain becomes difficult, and also the above rotatably supporting position is restricted.
SUMMARY AND OBJECTS OF THE INVENTION
In view of the foregoing, the present invention has been made, and an object of the present invention is to provide a multi-cylinder engine adopting a chain-type transmission mechanism in order to make the engine compact, which is capable of moderating the restriction on the rotatably supporting position of the chain tensioner and setting the length of the chain tensioner at a relatively large value.
To achieve the above object, according to the present invention, there is provided a multi-cylinder engine including a cam shaft linked with intake valves and exhaust valves which are disposed in a cylinder head in such a manner that one of the intake valves and one of the exhaust valves correspond to each of a plurality of combustion chambers. A crank shaft is rotatably supported by a crank case and a plurality of bearing caps are fastened to the crank case. A transmission mechanism is configured such that an endless chain is wound around a drive sprocket fixed on the crank shaft and a driven sprocket fixed on the cam shaft. The engine includes one end portion in the longitudinal direction of a chain tensioner extending in the running direction of the chain that is turnably supported by one, closest to the transmission mechanism, of the plurality of bearing caps in such a manner as to be elastically, slidably in contact with the chain.
With this configuration, since the chain-type transmission mechanism is provided between the crank shaft and the cam shaft, it is not required to prevent leakage of oil from the crank case side to the transmission mechanism side. Accordingly, it is possible to eliminate the necessity of the provision of a seal structure on the crank case, and hence to make the engine compact. Further, since the one end portion of the chain tensioner is rotatably supported by one, closest to the transmission mechanism, of the plurality of bearing caps for rotatably supporting the crank shaft in co-operation of the crank case, it is possible to moderate the restriction on the rotatably supporting position of the chain tensioner, and to set the length of the chain tensioner at a relatively large value and hence to certainly confine the action of the chain.
According to the present invention, in addition to the configuration of the invention described above, the transmission mechanism is provided between one end portion of the cam shaft and one end portion of the crank shaft. With this configuration, it is not required to take into account the disposition of the rotatably supporting portion of the chain tensioner at a position where the chain tensioner does not interfere with a crank weight of the crank shaft. This makes it possible to simply set the rotatably supporting position of the chain tensioner.
According to the present invention, in addition to the configuration of the invention described above, a pair of cylinder blocks, each of which includes a plurality of cylinder bores oppositely disposed with the axial lines thereof extending substantially in the horizontal direction on each side of the crank shaft, are connected to a pair of crank cases fastened to each other to form a crank chamber; the plurality of bearing caps are fastened to journal walls integrally formed on a plurality of locations, spaced at intervals in the axial direction of the crank shaft, of one of the crank cases); and one end of the chain tensioner, which is provided for the transmission mechanism on the cylinder block side is integrated with the journal walls, is rotatably supported by one, closest to the transmission mechanism, of the plurality of bearing caps. With this configuration, in the horizontally-opposed type multi-cylinder engine, it is possible to simply set the rotatably supporting position of the chain tensioner by making effective use of one of the bearing caps necessarily provided for the multi-cylinder engine.
As described above, according to the present invention, it is possible to eliminate the necessity of provision of a seal structure on the crank case, and hence to make the engine compact. Further, it is possible to moderate the restriction on the rotatably supporting position of the chain tensioner, and to set the length of the chain tensioner at a relatively large value and hence to certainly confine the action of the chain.
According to the present invention, it is possible to simply set the rotatably supporting position of the chain tensioner.
According to the present invention, it is possible to simply set the rotatably supporting position of the chain tensioner by making effective use of one of the bearing caps necessarily provided for the horizontally-opposed type multi-cylinder engine.
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: 4971000 (1990-11-01), Shimura et al.
patent: 5033421 (1991-07-01), Shimada et al.
patent: 5154144 (1992-10-01), Okui et al.
patent: 5743230 (1998-04-01), Yamazaki et al.
patent: B2 2-60886 (1990-12-01), None
Kanbe Takashi
Nakashima Masahiro
Tosaka Tetsuya
Birch & Stewart Kolasch & Birch, LLP
Honda Giken Kogyo Kabushiki Kaisha
Lo Wellun
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