Internal-combustion engines – Two-cycle – Rear compression
Reexamination Certificate
2002-11-06
2004-02-17
Kamen, Noah P. (Department: 3747)
Internal-combustion engines
Two-cycle
Rear compression
Reexamination Certificate
active
06691650
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a piston valve type layered scavenging 2-cycle engine, and particularly to an improved arrangement of cylinder ports, piston shape and scavenging flow passage.
BACKGROUND ART
With respect to an arrangement of an intake port for an air-fuel mixture, a pilot air port and the like in a piston valve type layered scavenging 2-cycle engine (hereinafter, refer to as a layered scavenging 2-cycle engine), there is a structure disclosed in International Laid-Open No. WO98/57053 as one example. In accordance with this publication, a scavenging port
12
, a pilot air port
14
and an exhaust port (not shown) are open to a cylinder chamber
11
(an inner peripheral surface of a cylinder
10
) as shown in FIG.
13
. The cylinder
10
is provided with an intake port
15
, for an air-fuel mixture, which communicates with a crank chamber
3
. A scavenging flow passage
16
connects between the cylinder chamber
11
and the crank chamber
3
. Two pilot air ports
14
are provided in right and left sides with respect to the intake port
15
. The pilot air ports
14
are provided at positions a predetermined distance apart from the scavenging port
12
to a side of the crank chamber
3
in an axial direction of the cylinder
10
. The scavenging port
12
and the pilot air ports
14
are connected via a piston groove
34
a
provided in an outer peripheral portion of a piston
30
a,
whereby an air. Air is sucked into the scavenging flow passage
16
from the pilot air ports
14
via the scavenging port
12
at a time of an intake stroke. In order to prevent the pilot air ports
14
from being directly open to the cylinder chamber
11
during all the strokes of the piston
30
a,
a piston lower edge
31
is positioned below the pilot air ports
14
when at a top dead center of the piston shown by a solid line. A piston upper edge
35
is positioned above the pilot air ports
14
when at a bottom dead center of the piston shown by a narrow two-dot chain line. The piston lower edge
31
is positioned at a closest position to a crank shaft at which the piston lower edge does not interfere with an outer peripheral portion
23
a
of a balance weight
23
provided in the crank shaft, when at the bottom dead center of the piston. Since the intake port
15
is provided in parallel to a lateral direction to the pilot air ports
14
, a vertical groove
40
having a predetermined length F is provided in the piston lower edge
31
portion, in order to communicate the intake port
15
with the crank chamber
3
when at the top dead center of the piston.
In accordance with the structure mentioned above, since an interior portion of the cylinder chamber
11
is at first scavenged by the pilot air at a time of being exhausted, it is possible to prevent an unburned gas from being discharged due to a blow-by of the air-fuel mixture, so that the exhaust gas can be cleaned up.
In the structure of the layered scavenging 2-cycle engine mentioned above, in order to communicate the suction port
15
with the crank chamber
3
at the top dead center of the piston, there is provided the vertical groove
40
having the length F extending from the piston lower edge
31
to the intake port upper edge
15
a.
Accordingly, the piston lower edge
31
is positioned the length F below the intake port upper edge
15
a.
At a time when the piston is at the bottom dead center, the piston upper edge
35
is positioned above the intake port upper edge
15
a,
and the piston lower edge
31
is defined so as to be positioned above the outer peripheral portion
23
a
of the balance weight in the crank shaft
20
. At the top dead center of the piston, when setting a height from the intake port upper edge
15
a
to the piston upper edge
35
to H, it is necessary to set a piston height from the piston lower edge
31
to the piston upper edge
35
to +F.
There has been a requirement of making the height of the engine lower so as to make placing space as small as possible. There has been a strong desire to solve the problems that a length of a connecting rod is increased in correspondence to an increase of the piston height, therefore a height of the engine is increased, the placing space is increased, a weight thereof becomes heavy, and a cost is increased.
The layered scavenging 2-cycle engine has the scavenging flow passage which feeds the pilot air to the interior portion of the cylinder chamber so as to scavenge, in order to exhaust the gas within the cylinder after combustion to the external portion.
FIG. 14
is a front elevational cross sectional view of a layered scavenging 2-cycle engine in accordance with a conventional second example, and
FIG. 15
is a view along a line N—N in
FIG. 14. A
cylinder
82
is mounted to an upper surface of a crank case
81
. A piston
83
is inserted to into a cylinder
82
so as to freely slide in an axial direction of the cylinder
82
. A crank shaft
54
is rotatably mounted to the crank case
81
. The piston
83
and the crank shaft
54
are connected by a connecting rod
55
. An exhaust port
60
is open to a cylinder chamber
56
, a pair of scavenging ports
61
and
61
and a pair of pilot air ports
62
and
62
are provided on a wall surface of the cylinder
82
, and an air-fuel mixture port
63
open to a crank chamber
57
is provided thereon. A pair of scavenging flow passages
90
and
90
which respectively connect a pair of scavenging ports
51
and
51
to the crank chamber
57
are provided within a side wall of the cylinder
82
. Opening portions
91
and
91
are respectively provided in lower end portions of the scavenging flow passages
90
and
90
. A pair of grooves
84
and
84
for respectively connecting a pair of pilot air ports
62
and
62
to a pair of scavenging ports
61
and
61
near a top dead center of the piston are provided on a side surface of the piston
83
. The exhaust port
60
, the scavenging ports
61
and
61
, the pilot air ports
62
and
62
and the air-fuel mixture port
63
are opened and closed on the basis of an upward and downward motion of the piston
83
.
When the piston moves upward, a pressure of the crank chamber
57
is reduced, the pilot air is sucked from the pilot air ports
62
and
62
near the top dead center of the piston and is charged into the scavenging flow passages
90
and
90
from the scavenging ports
61
and
61
through the piston grooves
84
and
84
. At the same time, the air-fuel mixture is sucked within the crank chamber
57
from the air-fuel mixture port
63
. When the air-fuel mixture is ignited and burned in the cylinder chamber
56
, the piston
83
is pressed down, and the pilot air ports
62
and
62
and the air-fuel mixture ports
63
are closed. Thereafter, the exhaust port
60
is at first opened, whereby the exhaust gas is discharged, and next the scavenging ports
61
and
61
are opened. The pressure in the crank chamber
57
is increased, the pilot air within the scavenging flow passages
90
and
90
flows into the cylinder chamber
56
so as to discharge the exhaust gas to an external portion from the exhaust port
60
, and subsequently the air-fuel mixture within the crank chamber
57
flows into the cylinder chamber
56
from the scavenging ports
61
and
61
through the scavenging passages
90
and
90
. An amount of blow-by of the air-fuel mixture from the exhaust port
60
to the external portion is reduced, and the exhaust gas is purified. However, since an amount of the pilot air is equal to a volume of the scavenging flow passage
90
and the amount is insufficient, the blow-by of a part of the air-fuel mixture is generated, so that it is impossible to sufficiently purify the exhaust gas.
In order to solve this, Japanese Unexamined Patent Publication No.
58-5423
is proposed as a conventional third example.
FIG. 16
is a front elevational cross sectional view of a layered scavenging 2-cycle engine described in the publication. A cylinder
82
is mounted to an upper surface of a crank case
85
. A scavenging port
61
communicates with a
Watanabe Takeshi
Zama Ryoji
Armstrong Kratz Quintos Hanson & Brooks, LLP
Kamen Noah P.
Komatsu Zenoah & Co.
LandOfFree
Piston valve type layered scavenging 2-cycle 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 Piston valve type layered scavenging 2-cycle engine, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Piston valve type layered scavenging 2-cycle engine will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3311687