Endless belt power transmission systems or components – Control for variable input to output speed-ratio – Including belt shiftable axially from one to another surface...
Reexamination Certificate
1999-05-05
2001-09-25
Bucci, David A. (Department: 3682)
Endless belt power transmission systems or components
Control for variable input to output speed-ratio
Including belt shiftable axially from one to another surface...
C248S637000, C474S101000
Reexamination Certificate
active
06293880
ABSTRACT:
FIELD OF THE ART
The present invention relates to a structure for vibro-isolating supporting of a vertical crankshaft type internal combustion engine onto a frame such as to be of a vehicle like a lown tractor.
BACKGROUND ART
When a general conventional horizontal crankshaft type (or vertical cylinder type) internal combustion engine (hereinafter, an engine HE) was loaded on a vehicle like a lown tractor as shown in
FIG. 1
, which is provided with a disk mower M under the midsection thereof, a universal joint
4
or a bevel gear unit has been interposed between a horizontal output shaft (a power take-out shaft)
1
of engine HE and a vertical driving shaft
3
of disk mower M.
In the case that engine HE is provided with power transmission endless winding means like a belt or chain wound around the output shaft thereof, or when, as shown in
FIGS. 2
or
3
, a belt (or sprocket)
2
is wound around an output pulley (or sprocket)
1
a
on output shaft
1
of engine HE, output pulley
1
(that shown in
FIG. 3
is apart from a crankshaft CS) is stressed by a tension F
1
of belt (chain)
2
and a rotational torque F
2
of itself (or crankshaft CS).
Tension F
1
is one way directed (in the cases shown in
FIGS. 2 and 3
, it is horizontal) and stresses permanently. Rotational torque F
2
, which is generated during the driving of engine HE (particularly, on starting thereof), mainly causes the vibratory force for engine HE.
The vibratory force mainly caused by rotational torque F
2
is vertically large. Therefore, there has been employed such a vibro-isolating supporting structure for engine HE as shown in
FIG. 2
or
3
, that vibro-isolating members A are interposed between the bottom of engine HE and the upper surface of a frame B serving as a support for engine HE.
In the structure, vibro-isolating member A has vertical and horizontal elasticities, wherein the vertical spring constant thereof is preferably small for absorbing the vertical vibratory force caused by rotational torque F
2
. In this regard, the flexibility of an elastic material like rubber provided in the vibro-isolating member is so enhanced as to absorb the vibration.
Vibro-isolating member A with a horizontally large spring constant, that is, having the elastic member with a small flexibility can resist against horizontal tension F
1
as shown in
FIGS. 2 and 3
, so that the horizontal contortion of output shaft
1
with engine HE pulled by the belt or chain can be reduced, and the belt or chain can be prevented from slipping or waving.
The conventional power transmission system between the horizontal crankshaft type engine and a vertical driving shaft, such as that of the above-mentioned lown tractor, has required a complicated structure comprising such as a universal joint, bevel gears or the like. If the power for the vertical driving shaft is taken out from a vertical output shaft of a vertical crankshaft type internal combustion engine, the power transmission system therefor will be simplified only with power transmission endless winding means like a belt or chain, as shown in
FIG. 4
detailed later, wherein belt
2
is interposed between output pulley
1
a
on output shaft
1
of an engine VE, serving as a vertical crankshaft type internal combustion engine, and a driving pulley
3
a
on driving shaft
3
of disk mower M, thereby being reduced in its cost and easing its maintenance.
Conventionally, vertical crankshaft type engine VE has been directly supported by a support such as a frame B as shown in
FIG. 5
detailed later, so that the problem has arisen that frame B and engine E are vibrated together in a horizontal rotational direction. If frame B was a part of the vehicle body of the lown tractor shown in
FIG. 4
, for example, the vehicle body would be vibrated according to the vibration of frame B. Therefore, it has been thought that the engine was supported onto the frame through vibro-isolating means so as to make the frame vibration-proof. In this case, considered location of the vibro-isolating means can prevent the belt or chain from forcible stress.
However, onto the vertical crankshaft type engine is applied mainly horizontal vibratory force caused by the rotation of its crankshaft, so that the vibro-isolating supporting structures shown in
FIGS. 2 and 3
, which are made resistant against vertical vibration, cannot be used as they are. In this regard, while both forces regarding to the vertical crankshaft type engine comprising the vibratory force caused by the rotary torque and the tension caused by the power transmission endless belt (hereinafter, “belt” may be replaced with “chain”.) are horizontal, each of the vibro-isolating members shown in
FIGS. 2 and 3
, if it was made of elastic material having vertical and horizontal flexibilities, has been located so that a small spring constant direction thereof was set vertical to resist against the vibratory force and a large spring constant direction thereof was set horizontal to resist against the tension, whereby such the large spring constant thereof in the horizontal direction disagrees with that required to make the engine vibro-isolated. Especially, at the position where the directions of the both forces coincide with each other, when the spring constant in thereof parallel to the direction of both forces are set small, or when the flexibility of the elastic material of the vibro-isolating member is set large, the rotational torque is absorbed so as to reduce the vibration, however, the distortion of the engine by the tension of the belt becomes large so as to cause the slipping or waving of the belt, thereby reducing the durability thereof. At the same position, when the spring constant thereof directed in the direction of the both forces is set large, or when the above-mentioned flexibility is set small, the distortion of the engine pulled by the belt is reduced so as to increase the durability of the belt, however, the vibratory force cannot be absorbed, whereby the vibration of the engine becomes large. Thus, the vibro-isolating supporting structure for a vertical crankshaft type engine has included the problems about formation and location of the vibro-isolating member.
Also, while the rotational torque is caused by the rotation of the crankshaft or the output shaft, the fact to be considered for locating the vibro-isolating member is that the rotational vibratory force is generated around the center of gravity of the engine whose weight is entirely unequal.
Furthermore, when the small spring constant direction of the vibro-isolating member coincides with the rotational direction of the vibratory force caused by the rotational torque, the problem has arisen that the deflection of the elastic material, when the engine starts, might exceed the limitation thereof because the rotational torque is considerably large on starting of the engine. To solve the problem, the elastic material of the vibro-isolating member is preferably set to increase its spring constant in the same direction (or to reduce its flexibility) when the deflection thereof exceeds a certain value.
DISCLOSURE OF THE INVENTION
To solve the above-mentioned problems, a vibro-isolating supporting structure for a vertical crankshaft type internal combustion engine according to the present invention is as follows:
For a first structure, a vertical crankshaft type internal combustion engine having an output shaft, around which power transmission endless winding means is wound, is supported onto a support through a plurality of vibro-isolating members.
For a second structure, the support is provided with portions for allowing the vibro-isolating members to pass therethrough, thereby reducing the space for the disposal of the vibro-isolating members between the support member and the engine.
For a third structure according to either the first or second structure, the vibro-isolating members are located at the positions where the torque caused by the rotation of the output shaft is directed in perpendicular to the tension caused by the power transmission endless winding mea
Bucci David A.
Charles Marcus
Sterne Kessler Goldstein & Fox P.L.L.C.
Yanmar Diesel Engine Co. Ltd.
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