Internal-combustion engines – Vibration compensating device – Balancing arrangement
Reexamination Certificate
1999-06-24
2001-06-12
Kamen, Noah P. (Department: 3747)
Internal-combustion engines
Vibration compensating device
Balancing arrangement
Reexamination Certificate
active
06244236
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to improvements in a balancer system for a power plant including a reciprocating engine, having a balance shaft for reducing vibration generated under the action of a reciprocating inertia mass.
Hitherto a variety of balancer systems for reciprocating engines have been proposed and put into practical use, in which a balance shaft or balance shafts are rotatably installed to the engine which is combined with a transmission to constitute a power plant. One of them is disclosed in Japanese Patent Provisional Publication No. 5-172187. In this conventional balancer system, a distance (L
F
) between the center of gravity of the power plant and the center of inertia force generated by the engine is smaller than a distance (L
X
) between the center of gravity of the power plant and the center of inertia force generated by the balance shaft, on a plane containing the axis of a crankshaft of the engine. This is intended to balance moments due to the both inertia forces and acting around the center of gravity of the power plant.
BRIEF SUMMARY OF THE INVENTION
In connection with the above conventional balancer system, a pitching moment M
E
around the center of gravity of the power plant under the action of the inertia force F generated by the engine is given by an equation M
E
=FL
F
. A pitching moment M
B
around the center of the gravity of the power plant under the action of the inertia force F
X
generated by the balance shaft is given by an equation M
B
=F
X
L
X
. In order to cancel the pitching moments under the two inertia forces, the relationship FL
F
=F
X
L
X
is to be established.
Here, the relationship F
X
<F can be established by employing the relationship L
X
>L
F
.
Accordingly, the weight of the balance shaft can be reduced from a conventionally required weight corresponding to F to a weight corresponding to Fx smaller than F, without accompanying generation of a pitching moment.
However, with the above conventional balancer system, generation of pitching moment of the power plant may be suppressed; however, vertical rectilinear force (F−F
X
) remains in the power plant and therefore the following problems arise:
This rectilinear force is calculated as follows: Since the relationship FL
F
=F
X
L
X
is established, the relationship F
X
=F(L
F
/L
X
) is made. From this, the relationship F−F
X
=[1−(L
F
/L
X
)] F is established.
Under the action of the remaining rectilinear force, generation of vertical vibration at an engine mount section (through which the engine is installed to a vehicle body) cannot be sufficiently suppressed, for example, in a transversely mounted engine of a front engine front wheel drive type automotive vehicle. The engine mount section is located at one end side of the engine in a direction of axis of a crankshaft. Therefore, it is impossible to reduce booming (reverberation) noise within a passenger compartment of the automotive vehicle.
In connection with booming noise within the passenger compartment, experiments have been conducted to obtain a result represented as a graph shown in
FIG. 4
, using a transversely mounted engine (having a displacement of 2000 cc) of a front engine front wheel drive type automotive vehicle. The graph in
FIG. 4
depicts contribution (rates) to the booming noise within the passenger compartment by a plurality of input sources. The input sources include exhaust noise S
1
, intake noise S
2
, the engine mount section S
3
at the front end section of the engine, and other engine mount sections S
4
. This graph depicts that the engine mount section S
3
at the front end section of the engine has the highest contribution (51%) to the booming noise within the passenger compartment. Accordingly, it is impossible to reduce the booming noise within the passenger compartment if suppression is not made on vertical vibration caused by the rectilinear force at the engine mount section set at the front end section of the engine.
In view of the above, it is an object of the present invention to provide an improved balancer system which can effectively overcome drawbacks encountered in conventional balancer systems for power plants.
Another object of the present invention is to provide an improved balancer system for a power plant, which can effectively reduce booming noise within a passenger compartment in a vehicle, while increasing freedom in layout of the power plant in the vehicle.
A further object of the present invention is to provide an improved balancer system for a power plant, which can effectively suppress vibration of a vehicle caused by inertia force at an engine mount section of an engine which mount section is located at one end section in a direction of axis of the crankshaft, while making it possible to reduce the weight of the balance shaft.
A first aspect of the present invention resides in a balancer system for a power plant including a transversely mounted engine having an engine mount section located at a first side in a direction of an axis of an crankshaft, the engine being supported through the engine mount to a vehicle body on which the power plant is mounted, and a transmission fastened to the engine at a second side opposite to the first side in the direction of the axis of the crankshaft. The balancer system comprises a balance shaft which is rotatably installed to the engine. In the balancer system, a first distance between center of gravity of the power plant and center of inertia force generated by the engine is smaller than a second distance between center of gravity of the power plant and center of inertia force generated by the balance shaft, each of the first and second distances being on a plane containing the axis of the crankshaft. Additionally, an inertia force generated by the balance shaft is determined at a value which reduces vibration to a generally zero level at a support center of the engine mount section, the vibration being caused by the inertia force generated by the engine.
A second aspect of the present invention resides in a balancer system for a power plant including a transversely mounted engine having an engine mount section located at a first side in a direction of an axis of an crankshaft, the engine being supported through the engine mount to a vehicle body on which the power plant is mounted, and a transmission fastened to the engine at a second side opposite to the first side in the direction of the axis of the crankshaft. The balancer system comprises a balance shaft which is rotatably installed to the engine. In the balancer system, a first distance between center of gravity of the power plant and center of inertia force generated by the engine is smaller than a second distance between center of gravity of the power plant and center of inertia force generated by the balance shaft, each of the first and second distances being on a plane containing the axis of the crankshaft. Additionally, an inertia force (F
B
) generated by the balance shaft is given by the following equation:
F
B
=[(I+m·L
1
·L
3
)/(I+m·L
2
·L
3
)]·F
where F is an inertia force generated by the engine; L
1
is the first distance; L
2
is the second distance; L
3
is a third distance (on the plane) between the center of gravity of the power plant and a support center of the engine mount section; I is a moment of inertia of the power plant; and m is a mass of the power plant.
A third aspect of the present invention resides in a power plant for an automotive vehicle. The power plant comprises a transversely mounted engine having an engine mount section located at a first side in a direction of an axis of an crankshaft, the engine being supported through the engine mount to a vehicle body on which the power plant is mounted. A transmission is fastened to the engine at a second side opposite to the first side in the direction of the axis of the crankshaft. Two balance shaft are rotatably installed to the engine, the two balance shafts being located on opposit
Foley & Lardner
Kamen Noah P.
Nissan Motor Co,. Ltd.
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