Internal combustion engine

Details Internal combustion engine Internal combustion engine

2002-02-28

2004-07-20

Argenbright, Tony M. (Department: 3747)

Internal-combustion engines

Frame construction

Horizontal cylinder

Reexamination Certificate

active

06763796

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
This non-provisional application claims priority under 35 U.S.C. § 119(a) on Patent Application Nos. 2001-055135 and 2001-162436 filed in Japan on Feb. 28, 2001 and May 30, 2001, respectively, the entirety of which is herein incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an internal combustion engine in which a piston slidably fitted in a cylinder is connected to a crankshaft via a connecting rod.
2. Description of Background Art
FIGS.
9
(A) to
9
(C) illustrate a background art four-cycle/single-cylinder internal combustion engine.
An internal combustion engine E includes a cylinder
01
, a piston
02
slidably fitted in the cylinder
01
, a cylinder head
03
connected to the cylinder
01
, a combustion chamber
04
formed at a bottom plane of the cylinder head
03
in such a manner as to face to the cylinder
01
, a crankshaft
05
, and a connecting rod
06
for connecting the piston
02
to the crankshaft
05
. The piston
02
is disposed at a position between the cylinder head
03
and the crankshaft
05
.
FIG.
9
(A) illustrates a state where the piston
02
is located at a top dead center position. In this state, a crank angle &thgr; is 0°. FIG.
9
(C) illustrates a state where the piston
02
is located at a bottom dead center position. In this state, the crank angle &thgr; is 180°. FIG.
9
(B) illustrates a state where the piston
02
is located at a mid point between the top dead center and the bottom dead center positions. In this state, the crank angle &thgr; is not 90°, but an angle &thgr;a smaller than 90°. The reason for this the fact that at each of the top dead center and the bottom dead center positions, the connecting rod
06
is located on a cylinder axial line L. However, at the mid point, the connecting rod
06
is inclined by an angle &phgr; from the cylinder axial line L.
Referring to
FIG. 8
, a relationship between the crank angle &thgr; from the top dead center position of the internal combustion engine E and a displacement x of the piston
02
from the top dead center position is shown by a chain line. In the figure, a stroke of the piston
02
between the top dead center and the bottom dead center positions is set to 2R (R: crank radius). As described with reference to FIG.
9
(B), when the piston
02
is located at the mid point between the top dead center and the bottom dead center positions (at which a displacement x of the piston
02
is R), the crank angle &thgr; becomes the angle &thgr;a smaller than 90°. On the other hand, in a solid sine curve (x=R sin (&thgr;−90°)+R), when the piston
02
is located at the mid point between the top dead center and the bottom center, the crank angle &thgr; becomes 90°.
In this way, according to the background art internal combustion engine E, it becomes apparent that the line (shown by the chain line) showing the relationship between the crank angle &thgr; and the displacement x of the piston
02
is positioned over the solid sine curve. This means that when the piston
02
is moved down from the top dead center position at the initial stage of an expansion stroke, a ratio of an increased amount of the displacement x of the piston
02
to an increased amount of the crank angle &thgr; is larger than the characteristic shown by the solid sine curve.
By the way, to increase thermal efficiency of the internal combustion engine E, it may be desirable to increase the degree of constant volume of a fuel-air mixture at the time of combustion. This will be more fully described below. When the piston
02
is located in the vicinity of the top dead center position, combustion of a fuel-air mixture starts, and as the piston
02
is moved down, a volume of the combustion chamber
04
over the piston
02
is increased. At this time, as a ratio of an increased amount of the volume of the combustion chamber
04
to an increased amount of the crank angle &thgr; becomes smaller, the above-described degree of constant volume becomes higher, with a result that the thermal efficiency is improved. From this viewpoint, in the background art internal combustion engine E shown in FIGS.
9
(A) to
9
(C), the ratio of an increased amount of the volume of the combustion chamber
04
to an increased amount of the crank angle &thgr; from the top dead center position becomes larger, so that the degree of constant volume becomes lower. This is inconvenient in terms of increasing the thermal efficiency of the internal combustion engine E.
SUMMARY OF THE INVENTION
In view of the foregoing, the present invention has been made, and an object of the present invention is to increase a thermal efficiency of an internal combustion engine by increasing the degree of constant volume of a fuel-air mixture at the time of combustion in the internal combustion engine.
To solve the above object, according to a first aspect of the present invention, there is provided an internal combustion engine in which a piston slidably fitted in a cylinder is connected to a crankshaft via a connecting rod, wherein a cylinder head in which a combustion chamber is defined is disposed between the piston and the crankshaft.
With this configuration, since a cylinder head in which a combustion chamber is defined is disposed between a piston and a crankshaft in an internal combustion engine, as compared with a background art internal combustion engine in which a combustion chamber is disposed opposite to a crankshaft with a piston located therebetween, a ratio of an increased amount of the volume of the combustion chamber to an increased amount of a crank angle of the piston from the top dead center position can be suppressed at a small value. As a result, it is possible to increase the degree of constant volume of a fuel-air mixture at the time of combustion and hence to increase thermal efficiency of the internal combustion engine. Furthermore, since a tensile load is applied to a connecting rod in an expansion stroke, it is not required to take buckling into account as compared with the background art internal combustion engine in which a compressive load is applied to a connecting rod. As a result, it is possible to lower a strength of the connecting rod and hence to reduce the weight thereof.
According to a second aspect of the present invention, in addition to the configuration of the first aspect of the present invention, an intake valve and an exhaust valve are provided in the cylinder head in such a manner as to be open in a V-shape, and a valve mechanism and the crankshaft are disposed between the intake valve and the exhaust valve.
With this configuration, since a valve mechanism and a crankshaft are disposed between an intake valve and an exhaust valve provided in a cylinder head in such a manner as to be opened in a V-shape, it is possible not only to simplify a power transmission route from the crankshaft to the valve mechanism by making the crankshaft and the valve mechanism closer to each other but also to lower the total height of the internal combustion engine.
According to a third aspect of the present invention, in addition to the configuration of the first aspect of the present invention, a pair of connecting rods are disposed on opposite axial end sides of the crankshaft in such a manner as to locate the piston therebetween.
With this configuration, since a pair of connecting rods are disposed on opposite axial end sides of a crankshaft in such a manner as to locate a piston therebetween, it is possible to prevent an unbalanced load from being applied to the piston while avoiding interference of the connecting rods with the piston.
According to a fourth aspect of the present invention, there is provided a reciprocating internal combustion engine in which a stroke volume is not changed during a cycle, wherein values of x, &thgr;, and R satisfy an equation of x<R sin (&thgr;−90°)+R, where x is a displacement of a piston moved toward a bottom dead center position from a top dead center position taken as a reference p

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