Internal-combustion engines – Lubricators – Crankcase – pressure control
Reexamination Certificate
2003-05-15
2004-09-07
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Lubricators
Crankcase, pressure control
C123S1960CP
Reexamination Certificate
active
06786188
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a dry-sump lubrication type four-stroke cycle engine suitable for a vehicle, such as a straddle type all-terrain four-wheel vehicle or a motorcycle, and, more specifically to improvements in an oil reserving and circulating system of the engine.
2. Description of the Related Art
A conventional dry-sump lubrication four-stroke cycle engine usually has an oil tank separated from a crank case of the engine, an oil feed pump and an oil return pump, i.e., a scavenging pump. The oil tank holds a predetermined quantity of an engine oil. The oil feed pump pumps up oil from the oil tank and feeds the oil by pressure to parts needing lubrication of the engine, and the scavenging pump pumps up used oil collected in the bottom of the crankcase or an oil pan and returns the used oil into the oil tank. This dry-sump lubrication system increases the weight, component parts and cost of the engine, and needs pipes for connecting the crankcase and the oil tank.
A dry-sump lubrication type four-stroke cycle engine previously proposed by the applicant of the present patent application in JP-A No. 288466/1994 is not provided with any external oil tank and has a transmission chamber having a lower part serving as an oil reservoir chamber.
FIGS. 12 and 13
are side elevations respectively showing the left side surface of a right half-crankcase, and the right side surface of a left half-crankcase of the dry-sump lubrication type four-stroke cycle engine disclosed in JP-A No. 288466/1994.
Referring to
FIG. 12
, a partition wall
123
of a predetermined height is formed between a crankshaft chamber
121
and a transmission chamber
122
in a crankcase
120
to use a lower part of the transmission chamber
122
as an oil reservoir chamber
125
. A triangular oil collecting chamber
126
extending rearward is formed in a lower rear part of the crankshaft chamber
121
, a suction opening
127
is formed in a wall defining an axial end of the oil collecting chamber
126
. A scavenging pump of the engine sucks oil dripped in the crankshaft chamber
121
and collected in the oil collecting chamber
126
through the suction opening
127
and discharges the oil into the transmission chamber
122
to keep the crankshaft chamber
121
in a dry state.
Referring to
FIG. 13
, a connecting hole
131
is formed in a part, in front of the oil collecting chamber
126
, of the left half-crankcase to connect the bottom of the crankshaft chamber
121
and the bottom of a generator chamber (not shown) extending into the paper in
FIG. 13
to let oil dripped into the generator chamber flow through the connecting hole
131
into the crankshaft chamber
121
. Oil flowed into the crankshaft chamber
121
is sucked up together with oil collected in the oil collecting chamber
126
by the scavenging pump through the suction opening
127
.
An engine disclosed in JP-A No. 215411/1986 has a transmission chamber having a lower part serving as an oil reservoir chamber. Although this engine is similar to that disclosed in JP-A No. 288466/1994 in forming a partition wall between a transmission chamber and a crankshaft chamber and using a lower part of the transmission chamber as an oil reservoir chamber, a generator chamber formed on one side of the crankshaft chamber and a clutch chamber formed on the other side of the crankshaft chamber are connected by a connecting passage extending under the crankshaft chamber, and the crankshaft chamber and the generator chamber are connected by a connecting hole. Oil dripped into the crankshaft chamber flows into the generator chamber, oil is contained in both the generator chamber and the clutch chamber at the same oil level, and then a scavenging pump of the engine pumps up the thus collected oil and discharges oil into the oil reservoir chamber.
In the engine disclosed in JP-A No. 288466/1994, which sucks oil from the triangular oil collecting chamber
126
formed in a lower rear part of the crankshaft chamber
121
so as to extend rearward, gases and oil are forced to flow together into the oil collecting chamber
126
by the rotation of crank arms of a crank shaft contained in the crankshaft chamber
121
and therefore, oil is unable to flow smoothly through the suction opening
127
formed in one side of the oil collecting chamber
126
, which affects adversely to the suction efficiency of the scavenging pump.
Since oil dripped into the generator chamber flows into the crankshaft chamber
121
and oil is forced to flow together with oil collected in the crankshaft chamber
121
into the oil collecting chamber
126
, the quantity of oil contained in the crankshaft chamber
121
increases temporarily before oil flows into the oil collecting chamber
126
, which is undesirable in view of keeping the crankshaft chamber
121
of the dry-sump lubrication type engine in a dry state.
In the engine disclosed in UP-A No. 215411/1986, the generator chamber and the clutch chamber formed on the opposite sides of the crankshaft chamber communicate with each other by means of the connecting passage and hence oil remains always in the generator chamber and the clutch chamber. Consequently, a large quantity of oil flows from the generator chamber into the crankshaft chamber when the engine is tilted beyond a certain angle and hence it is possible that the crankshaft chamber cannot be maintained in a dry state.
SUMMARY OF THE INVENTION
The present invention has been made in view of the foregoing problems and it is therefore an object of the present invention to provide a compact dry-sump lubrication type four-stroke cycle engine provided with a lightweight lubricating system comprising a small number of component parts, being capable of efficiently using an oil pump, and having a large oil capacity.
According to one aspect of the present invention, a dry-sump lubrication type four-stroke cycle engine has a crankcase provided with a crankshaft chamber containing a crankshaft in its front part and a transmission chamber in its rear part, a generator chamber on one side of the crankcase in an axial direction of the crankshaft, and a clutch chamber on the other side of the crankcase; wherein the crankshaft chamber and the transmission chamber are separated by a partition wall of a predetermined height to form an oil reservoir chamber in a lower part of the transmission chamber, an auxiliary oil reservoir chamber is formed in a lower part of the clutch chamber so as to communicated with the oil reservoir chamber, a suction chamber is formed integrally with the crankcase under a crankshaft chamber bottom wall defining a bottom of the crankshaft chamber so as to communicate with a suction port of a scavenging pump of the engine, the suction chamber opens into the crankshaft chamber through a first suction hole formed in the crankshaft chamber bottom wall and opens into the generator chamber through a second suction hole formed in a wall defining a bottom of the generator chamber, and the scavenging pump pumps up oil from the suction chamber and discharges oil into the oil reservoir chamber or the auxiliary oil reservoir chamber.
According such a structure, the dry-sump lubrication type four-stroke cycle engine of the present invention is able to save external piping and mounting apace for an external oil tank, and further, is able to increase the quantity of oil that can be reserved in the crankcase without enlarging the crankcase.
Since the dead space under the wall defining the bottom of the crankshaft chamber is used as the suction chamber, the suction passage of the scavenging pump can be formed with a simple structure.
Since oil flowed from the crankshaft chamber into the suction chamber is sucked by the scavenging pump, the flow of oil into the scavenging pump is hardly affected and disturbed directly by the revolution of the crank shaft, oil can be smoothly sucked by the scavenging pump.
Since the generator chamber is connected directly to the suction chamber formed under the wall defining the crankshaft chamber by the
Benton Jason
Kawasaki Jukogyo Kabushiki Kaisha
Yuen Henry C.
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