Balancer device for a four-cycle V-type eight cylinder engine

Details Balancer device for a four-cycle V-type eight cylinder engine Balancer device for a four-cycle V-type eight cylinder engine

1999-12-02

2001-06-12

Wolfe, Willis R. (Department: 3747)

Internal-combustion engines

Vibration compensating device

Balancing arrangement

Reexamination Certificate

active

06244237

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a balancer device for canceling a vibromotive force of a four-cycle V-type eight cylinder engine, and further relates to an oil return passage for an engine and more particularly to a passage for returning oil from a cylinder head to an oil pan.
2. Description of the Related Art
When a plane crank in which centers of all crank pin shafts are placed on the same plane is adopted in a four-cycle V-type eight cylinder engine having an included bank angle of 90 degrees, both banks operate at a cycle of 180 degrees and intake and exhaust strokes happen in an alternate fashion. According to this construction, intervals between intake and exhaust timings become equal and there is no risk of generation of exhaust interference, this being thereby advantageous in obtaining a high output.
On the contrary, in the case of a V-type eight cylinder engine adopting the plane crank, a secondary imbalance is generated by virtue of the inertia force of a reciprocating mass, and the direction of the inertia force when the engine is viewed as a whole when this happens is similar to a condition in which cylinders of a in-line four cylinder engine are placed horizontally (a horizontal component of the inertia force remains). Therefore, this imbalance can be compensated for by adopting the secondary balancer theory of the conventional in-line four cylinder engine and rotating in opposite directions two balancer shafts disposed on a plane in parallel with a plane bisecting the bank included angle of the engine and passing through a center of a crankshaft thereof (Japanese Unexamined Patent Publication No. HEI 8-193643).
However, in trying to provide balancer shafts on a V-type engine, it is inevitable that the construction of the engine becomes complicated, and since the balancer shaft itself generates an imbalance, a high degree of supporting rigidity is required in order to obtain an expected vibration damping function. Namely, provision of balancer shafts inevitably causes an enlargement of the engine and reduces the productivity thereof.
Further, conventionally, oil returning from a cylinder head is constructed so as to flow into a crank chamber through a passage provided in the cylinder block to be allowed to eventually fall in an oil pan defined below the crank chamber (refer to the Japanese Unexamined Patent Publication No. HEI 2-245413).
On the other hand, the Japanese Unexamined Utility Model Publication No. SHO 64-34449 discloses an engine comprising a cylinder block comprising in turn an upper block, a lower block and an oil pan adapted to be joined to a lower surface of the lower block, the upper and lower blocks being divided from a horizontal plane passing through a center of a crankshaft, wherein a baffle is formed integrally with the lower block for suppressing the generation of a disturbance in the surface of oil in the oil pan by virtue of a wind pressure generated by counterweights provided on the crankshaft or the movement of the oil surface by virtue of a change in the vehicle posture.
According to the aforesaid conventional constructions, since return oil interferes with a balancer shaft or the crank chamber and the oil pan are partitioned by the baffle, oil returning from a cylinder head is prevented from quickly returning into the oil pan, and the atomization of oil is promoted since return oil interferes with the balancer shaft and/or oil in the oil pan is easy to be taken up by the counterweights. This leads to an increase in the volume of oil intruding into a ventilation passage of the crank chamber, and if it gets worse, such atomization of oil may lead to a need to increase the capacity of an oil separator chamber.
SUMMARY OF THE INVENTION
The present invention was made with a view to solving the problem inherent in the related art, and an object thereof is to provide a balancer shaft device for a four-cycle V-type eight cylinder engine for a mass-production vehicle constructed and an oil return passage for the engine such that firstly a reduction in productivity can be restrained as much as possible, that secondarily a high supporting rigidity for balancer shafts can be secured while restraining the enlargement of the engine and that thirdly the return of oil is not deteriorated while restraining the enlargement of the engine.
With a view to attaining the aforesaid objects, there is provided a balancer device for a four-cycle V-type eight cylinder engine having an included bank angle of 90 degrees, wherein a cylinder block comprises an upper block
1
and a lower block
2
divided from a horizontal plane passing through a center of a crankshaft
7
and bearing holes
27
are provided in the upper and lower blocks, respectively, at positions symmetrical with respect to the dividing plane in such a manner that axes of the bearing holes extend in parallel with the crank shaft, and wherein in order to insert a balancer shaft
16
in the bearing holes from one direction for support on the cylinder block, a diameter of a journal portion
28
of the balancer shaft
16
is made equal to or larger than that of a weight portion W of the balancer shaft
16
, the journal portion
28
being located toward a proximal end of the balancer shaft
16
when viewed in a direction in which the balancer shaft
16
is inserted. According to this construction, since the balancer shafts can directly be supported on the bisected cylinder blocks, the enlargement of the engine can be restrained and advantages can be provided in obtaining a high degree of supporting rigidity for the balancer shafts. In addition, since the balancer shafts can easily be assembled to the engine by inserting the balancer shafts thereinto from one of the directions along the crankshaft, whereby the reduction in the productivity of the engine can be restrained.
In addition, bearing holes
27
for balancer shafts
16
may be provided in bearing walls
5
where main bearings
24
are provided on one side of the main bearings so that the balancer shafts
16
are supported in the bearing holes. According to this construction, since the bearing wall where the main bearing is provided is originally highly rigid, the supporting rigidity for the balancer shaft can be largely improved without causing an enlargement of the engine.
Furthermore, the upper and lower blocks may be attached together by tightening bolts B
2
, B
3
provided on both sides of the bearing holes in such a manner as to hold the bearing holes therebetween. According to this construction, since the balancer shafts are clamped together by the bolts at both sides thereof, the supporting rigidity thereof can further be improved.
In addition, with a view to attaining the above object, there is provided an oil return passage for an engine comprising a cylinder block comprising in turn an upper block
1
, a lower block
2
and an oil pan
3
adapted to be joined to a lower surface of the lower block
2
, the upper and lower blocks
1
,
2
being divided from a horizontal plane passing through a center of a crankshaft
7
, the oil return passage being formed so as to extend from a joint surface between the upper block
1
and a cylinder head into the oil pan passing through a portion transversely outwardly of a balancer shaft
16
a
provided in a side wall of the upper block, a joint surface between the upper and lower blocks and a portion transversely inwardly of a balancer shaft provided in a side wall of the lower block. According to this construction, since oil returning from the cylinder head is allowed to directly return to the oil pan through an independent passage which does not pass through the crank chamber and the balancer shaft receiving chambers, the return oil is prevented from interfering with the balancer shaft to thereby constitute a rotational resistance or produce atomized oil, whereby the return oil is allowed to quickly return to the oil pan.
In addition to the above construction, the oil return passage may comprise an inclined passage
43
for establishing a diago

Affiliated with

Also associated with

Rating

Balancer device for a four-cycle V-type eight cylinder engine does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Balancer device for a four-cycle V-type eight cylinder engine, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Balancer device for a four-cycle V-type eight cylinder engine will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2483293