Four cycle engine lubrication structure

Details Four cycle engine lubrication structure Four cycle engine lubrication structure

1999-09-10

2001-07-10

Wolfe, Willis R. (Department: 3747)

Internal-combustion engines

Lubricators

Crankcase, pressure control

Reexamination Certificate

active

06257192

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a four-cycle engine and an improvement to a lubrication structure therefor.
2. Description of Related Art
In, for example, Utility Model Laid-open Publication No. Sho. 63-22356, entitled “Two-cycle Internal Combustion Engine Vibration Control Assembly”, there is disclosed in FIG. 2 a crankcase 3, a crankshaft 7 and a balancing weight 13 housed in a rotatable manner within this crankcase 3, a support shaft 23 extending out of the crankcase 3 from an end of the crankshaft 7, a gear 14 attached to the support shaft 23, a support shaft 24 extending out of the crankcase 3 from an end of the shaft for the balancing weight 13, and a gear 15 attached to the support shaft 24 and meshing with the gear 14 in such a manner as to rotate the balancing weight 13.
In the above technology, it is necessary to lubricate the meshing part of the gear 14 and the gear 15 and special apparatus is therefore necessary to spray oil on the meshing parts and to gather up the remaining oil. Therefore, costs are substantially increased.
The gear 14 and gear 15 have to be sealed from the outside due to this lubrication. Therefore the engine is increased in size, causing many disadvantages.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an engine lubrication structure that does not require a special structure for lubricating a gear set for driving a balancer shaft. This provides the advantage of enabling the engine to be made smaller.
In order to achieve the above object, a first aspect of the present invention includes an inside of a crankcase of a four-cycle engine divided by a bulkhead into a crank chamber and a transmission chamber. A crankshaft and a balancer shaft for suppressing engine vibrations by rotating in accompaniment with rotations of the crankshaft are rotatably attached within the crankshaft. Furthermore, the balancer shaft is driven by the crankshaft via a gear set housed within the crank chamber.
The volume of the crank chamber decreases because the crankcase is divided into a crank chamber and a transmission chamber and a thick oil mist is formed within the crank chamber.
By housing the gear set within the crank chamber the meshing part of the gear set is sufficiently lubricated by the oil mist and special lubricating apparatus is therefore not required.
Furthermore, regarding the related art where the gear set is provided outside of the crankcase, the engine can be made smaller in the present invention without having to form a sealed space for lubricating the gear set.
According to a second aspect of the present invention, an engine accessory driven by the balancer shaft is provided at an end part of the balancer shaft. Furthermore, a supply of oil for a bearing supporting the balancer shaft and a supply of oil for a bearing supporting a rotating axis of the engine accessory attached to the end part of the balancer axis are provided by oil mist filling up the inside of the crank case.
Each bearing can therefore be lubricated uniformly and in a sufficient manner by the oil mist within the crankcase regardless of the arrangement of the bearings, so that freedom of engine design is increased and engine durability is improved.
Furthermore, it is not necessary to separately lubricate the bearing of the engine accessory so that a dedicated structure for lubrication of the engine accessory is no longer necessary.
According to a third aspect of the present invention, a clutch for engaging and disengaging the transmission of force and a water pump constituting the engine accessory driven by the balancer shaft and circulating cooling water within the engine are arranged on the side of the crankcase. The clutch is covered from the outside by a cover. Furthermore, the water pump is completely separate from the cover covering the clutch.
Conventionally, since both the clutch and the water pump are covered by a single cover covering the clutch, the cover is large and a drain hole for the water pump is formed so as to be long enough to reach the cover surface. In the present invention, the water pump is completely separate from the cover covering the clutch and the cover can therefore be made smaller and lighter and can be assembled with greater ease. Furthermore, since the drain hole for the water pump can be made shorter, drainage is improved, since clogging with dirt can be prevented. Furthermore, the process of clearing the hole is made easier.
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: 4793301 (1988-12-01), Ishikawa
patent: 5065841 (1991-11-01), Takagaki
patent: 5960764 (1999-10-01), Araki
patent: 63-22356 (1988-06-01), None
patent: 8-135419 (1996-05-01), None

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