Internal-combustion engines – Charge forming device – Crankcase vapor used with combustible mixture
Reexamination Certificate
2000-01-28
2001-08-28
McMahon, Marguerite (Department: 3747)
Internal-combustion engines
Charge forming device
Crankcase vapor used with combustible mixture
Reexamination Certificate
active
06279554
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an engine crankcase ventilation system, and in particular to an engine crankcase ventilation system which allows a relatively large oil separation chamber or passage to be defined without increasing the size of the engine.
BACKGROUND OF THE INVENTION
Typically, a crankcase ventilation passage opens into the crankcase of an engine for recycling the blowby gas, which has passed through the gap between the pistons and cylinders, to the intake system, and to control the pressure pulsation due to the reciprocating motion of the pistons (see Japanese patent laid-open publication No. 61-135914).
The crankcase is filled with lubrication oil mist, and a certain amount of the oil mist inevitably enters the ventilation passage. However, an excessive introduction of oil into the blowby gas is not desirable because it adversely affects the quality of the exhaust gas and contributes to an increase in oil consumption. To avoid such an inconvenience, it has been proposed, for instance, in Japanese patent laid open publication No. 61-135914 to provide an oil separation chamber between the two cylinder banks of a V-engine.
However, to achieve an adequate capability to separate oil, the oil separation chamber is required to have a certain volume, and the provision of such an oil separation chamber in the engine results in an increase in the number of components parts, and the complication and size increase of the overall structure.
The blowby gas removed from the crankcase must be replaced by fresh air from the atmosphere. The pressure pulsation in the crankcase can be transmitted from a fresh air passage for introducing fresh air into the crankcase. Also, it is possible for the blowby gas to flow backward under special circumstances. To address these problems, it is therefore desirable to provide a relatively large passage or chamber for fresh air for both effective noise muffling and oil separation. However, it prevents a compact design of the engine.
The blowby gas is typically passed through a passage which is adapted to remove oil mist therefrom, and is then forwarded to the downstream of a throttle valve so that hydrocarbon that may be contained in the blowby gas may be recycled to the engine intake to improve fuel efficiency and reduce engine emissions. Therefore, a passage must be defined between the crankcase typically provided in a lower part of the engine and the intake system which is typically provided in an upper part of the engine, and the need for such a passage tends to complicate the structure of the engine. Typically, rubber hoses are used for conducting blowby gas from the crankcase to the intake system.
BRIEF SUMMARY OF THE INVENTION
In view of such problems of the prior art, a primary object of the present invention is to provide an engine crankcase ventilation system which allows a relatively large blowby gas passage to be defined without increasing the size of the engine or increasing the number of component parts.
A second object of the present invention is to provide an engine crankcase ventilation system which is provided with a relatively large fresh air passage as well as a relatively large blowby gas passage without increasing the size of the engine.
A third object of the present invention is to provide an engine crankcase ventilation system which is compact in size and effective in removing oil from the blowby gas.
According to the present invention, such objects can be accomplished by providing an engine crankcase ventilation system for an internal combustion engine including a plurality of crankcase members jointly defining a crankcase assembly, comprising: a blowby gas passage and a fresh air passage which are defined between adjoining crankcase members independently from each other. Thus, removal of blowby gas and introduction of fresh air can be accomplished in an efficient manner.
Preferably, the blowby gas passage extends in parallel with a crankshaft axial line along a first side of a lower part of the crankcase assembly; and the fresh air passage extends in parallel with a crankshaft axial line along a second side of a lower part of the crankcase assembly.
Because the crankcase is configured to receive the rotating crankshaft provided with counterweights, it necessarily has a circular cross section. Therefore, by defining the blowby gas passage and the fresh air passage along either side of the lower part of the crankcase assembly, it is possible to effectively utilize the available space. Thus, a cavity of a required volume for effective oil separation and pressure pulsation damping can be formed in the engine main body without increasing the number of components parts, and without complicating or increasing the size of the overall structure.
To effectively remove oil from the blowby gas passage, it is desirable to reduce the flow velocity of the blowby gas. To this end, it is advantageous to ensure a relatively large volume for the blowby gas passage. For the same reason, the blowby gas passage is preferably provided with a middle part which is enlarged as compared with an inlet end thereof so as to define an expansion chamber. Also, providing baffle plates in the blowby gas passage so as to define a tortuous passage contributes to effective removal of oil from the blowby gas.
Similar arrangements for the fresh air passage are advantageous for muffling low frequency engine noise, and effective removal of oil in case of a backflow of blowby gas.
To maximize the effective volume of the blowby gas passage, the blowby gas passage may be defined by a cylinder block lower case and an oil pan upper member, and communicates with a space above oil received in an oil pan via an opening provided in an axial end of the blowby gas passage. According to a particularly preferred embodiment of the present invention, the opening in the axial end of the blowby gas passage is provided in a recess in an axial end of the crankcase assembly, and an opening communicating with the space above the oil is provided also within the recess, a communication passage being defined between these two openings by a cover plate placed over the recess. This arrangement provides an inlet to the blowby gas passage at an axial end thereof without complicating the fabrication process therefor. Similar arrangement may be used for the fresh air passage.
The exit end of the blowby gas passage may be provided at the opposite axial end thereof. In this case, the blowby gas passage communicates with a downstream of a throttle valve via an exit end of the blowby gas passage defined by an opening formed in a recess provided in the opposite axial end of the crankcase assembly, and a communication passage defined between the recess and a cover plate placed over the recess.
When the internal combustion engine consists of a multiple-cylinder V-engine, and an intake system is placed between two cylinder banks of the V-engine, the communication passage may be arranged so as to communicate with the downstream of the throttle body via a first passage defined in an upper middle part of the crankcase assembly in parallel with the crankshaft axial line, and a second passage defined along a side of the cylinder bank and extending perpendicularly from a middle part of the first passage along a cylinder axial line.
To simplify the communication between the blowby gas passage and the intake system, passages may be defined in the cylinder head and the intake system in such a manner that the cylinder head passage and the intake system passage communicate with each other via opposing openings in mating surfaces of the cylinder head and the intake system.
To form the second passage while allowing the intake system to be placed close to a side of a cylinder bank so as make optimum use of the available space, the second passage may defined in a ridge formed in a corresponding part of the cylinder bank while the intake system is provided with a recess for receiving the ridge.
These arrangements for the blowby gas passage are equally applicable to the fresh air passage for si
Akima Kazuhiro
Fujii Noriaki
Sayama Takehiko
Armstrong Westerman Hattori McLeland & Naughton LLP
Honda Giken Kogyo Kabushiki Kaisha
McMahon Marguerite
LandOfFree
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