Internal-combustion engines – Vibration compensating device – Balancing arrangement
Reexamination Certificate
1999-05-19
2001-02-27
Wolfe, Willis R. (Department: 3747)
Internal-combustion engines
Vibration compensating device
Balancing arrangement
Reexamination Certificate
active
06192851
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to improvements in a vibration reducing system for reducing vibration of an internal combustion engine itself, caused by fluctuation of combustion pressure in the engine, and more particularly to the vibration reducing system for reducing roll vibration of the engine itself by using an inertial mass member which rotates in a right or reverse direction relative to a crankshaft.
Recently, attention has been increasingly paid on improving fuel economy in automotive engines, from the viewpoint of environmental protection, and therefore footlights have been put on direct injection gasoline-fueled engines and direct injection diesel engine in which fuel is directly injected into each engine cylinder, for automotive vehicles. However, such engines are high in combustion exciting force and accordingly large in roll vibration due to torque fluctuation as compared with conventional engines. Thus, such engines will induce booming noise within a passenger compartment, due to the roll vibration of the engine, and increase or degrade floor vibration of a vehicle body.
In view of the above, as a measure for solving the above drawbacks, a vibration reducing system for an internal combustion engine has been proposed in Japanese Patent Provisional Publication No. 6-33990.
BRIEF SUMMARY OF THE INVENTION
In the vibration reducing system proposed in Japanese Patent Provisional Publication No. 6-33990, an auxiliary flywheel is provided in addition to a main flywheel fixedly connected to a rear end section of a crankshaft of the engine. The auxiliary flywheel is driven in an opposite direction to the crankshaft through a belt by a crankshaft pulley which is directly connected to the front end section of the crankshaft. As a result, a moment which is in the opposite direction to a moment to be applied to the engine main body is generated as a reaction of torque generation, thereby canceling roll vibration of the engine main body.
Here, in order to fully remove the roll vibration of the engine with the above conventional vibration reducing system, it is required to theoretically meet a condition of I
1
=&rgr;·I
2
where I
1
is a moment of inertia of a rotational body including the main flywheel and the like in the engine main body; I
2
is a moment of inertia of the auxiliary flywheel; and &rgr; is a speed increasing ratio. Additionally, reduction effect for the roll vibration can be achieved around this condition. To meet the above condition, it is necessary to enlarge the moment of inertia I
2
of the auxiliary flywheel, or the speed increasing ratio &rgr;, since the moment of inertia I
2
of the main flywheel is inherently large.
However, enlarging the moment of inertia I
2
of the auxiliary flywheel causes a weight-increase of the vibration reducing system. Additionally, enlarging the speed increasing ratio &rgr; causes the auxiliary flywheel to rotate at a high speed, thereby contributing to lowering the durability of a bearing section of the auxiliary flywheel. Consequently, it has been actually impossible to fully remove roll vibration of the engine main body, so that the conventional vibration reducing system has been limited in obtaining vibration reduction effect.
In view of the above, an object of the present invention is to provide an improved vibration reducing system for an internal combustion engine, which effectively overcomes drawbacks encountered in conventional vibration reducing systems.
Another object of the present invention is to provide an improved vibration reducing system for an internal combustion engine, which can sharply reduce roll vibration of an engine main body in a certain engine operating range where reduction of the roll vibration is particularly required.
A further object of the present invention is to provide an improved vibration reducing system for an internal combustion engine, which can sharply reduce roll vibration of an engine main body in each of a plurality of engine operating ranges where reduction of the roll vibration is particularly required.
A first aspect of the present invention resides in a vibration reducing system of an internal combustion engine. The vibration reducing system comprises a roll vibration system which generates a roll vibration of an engine main body, the roll vibration having a first vibration mode. Additionally, a rotational vibration system is provided to generate a rotational vibration having a second vibration mode, and includes a crankshaft of the engine, for generating a rotational driving force, a main flywheel fixedly connected to the crankshaft, a driving force transmitting mechanism through which the rotational driving force of the crankshaft is transmitted, the driving force transmitting mechanism being movably secured to the engine main body, and an inertial mass member drivably connected to the driving force transmitting mechanism and rotatable to generate an inertial force upon receiving the rotational driving force transmitted through the driving force transmitting mechanism. In the vibration reducing system, the first and second vibration modes cause antiresonance at an antiresonance frequency. Additionally, the rotational vibration system is adjusted to cause the antiresonance frequency to be generally coincident with one of frequencies which are obtained respectively by multiplying an engine-revolutional frequency at a predetermined engine speed by values each being represented by (a natural number/2).
Another aspect of the present invention resides in a method of reducing vibration in an internal combustion engine including a roll vibration system which generates a roll vibration of an engine main body, the roll vibration having a first vibration mode; and a rotational vibration system which generates a rotational vibration having a second vibration mode, and includes a crankshaft of the engine, for generating a rotational driving force; a main flywheel fixedly connected to the crankshaft; a driving force transmitting mechanism through which the rotational driving force of the crankshaft is transmitted, the driving force transmitting mechanism being movably secured to the engine main body, and an inertial mass member drivably connected to the driving force transmitting mechanism and rotatable to generate an inertial force upon receiving the rotational driving force transmitted through the driving force transmitting mechanism. The method comprises (a) causing the first and second vibration modes to coact so as to make antiresonance at an antiresonance frequency; and (b) adjusting the rotational vibration system so as to cause the antiresonance frequency to be generally coincident with one of frequencies which are obtained respectively by multiplying an engine-revolutional frequency at a predetermined engine speed by values each being represented by (a natural number/2).
REFERENCES:
patent: 3563223 (1971-02-01), Ishida
patent: 4791829 (1988-12-01), Fukushima et al.
patent: 5537967 (1996-07-01), Tashiro et al.
patent: 3230168 (1984-02-01), None
patent: 59-047528 (1984-03-01), None
Asahara Yasuyuki
Hirano Izuho
Foley & Lardner
Harris Katrina B.
Nissan Motor Co,. Ltd.
Wolfe Willis R.
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