Internal-combustion engines – Charge forming device – Having fuel vapor recovery and storage system
Reexamination Certificate
1997-09-12
2001-02-06
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
Having fuel vapor recovery and storage system
C123S357000
Reexamination Certificate
active
06182641
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a fuel vapor control system for an internal-combustion engine and, more particularly, to an improved fuel vapor control system for an internal-combustion engine, capable of reducing the difference in air-fuel ratio between the cylinders of the internal-combustion engine. The present invention also relates to a fuel vapor control system for an internal-combustion engine, capable of being easily manufactured and assembled.
PRIOR ART
A fuel vapor control system for an internal-combustion engine disclosed in Japanese Unexamined Patent Publication (Kokai), i.e., JP-A-No. 6-213084 (U.S. Pat. No. 5,355,862) is a typical conventional fuel vapor control system.
This known fuel vapor control system has a charge passage having one end opening into an upper space in a fuel tank, and the other end connected to a canister connected to a purge (discharging) port. The purge port is connected to an opening formed in a wall defining a throttle bore behind a throttle valve disposed in an intake duct of an engine.
In the conventional fuel vapor control system having the purge port, downstream currents (forward currents) flowing from above toward below a throttle valve
100
and upstream currents (reverse currents) are produced near the inner surface of a wall defining a throttle bore
101
below the throttle valve
100
as shown in
FIG. 19
when the throttle valve
100
is half open. The forward currents flow toward a cylinder #1 and the reverse currents flow toward a cylinder #4 in a surge tank
102
as shown in FIG.
20
. Therefore, a large amount of fuel vapor flows into the cylinder #1 if the purge port opens into a region in which the forward currents prevail, whereas a large amount of fuel vapor (evaporated fuel) flows into the cylinder #4 if the purge port opens into a region in which the reverse currents prevail. Consequently, the resulting difference in air-fuel ratio (A/F ratio) between the cylinder #1 and the cylinder #4 can create problems.
If a large amount of fuel vapor needs to be purged (discharged) to meet a future intensified fuel evaporative emission control regulation, there is the possibility that the difference in A/F ratio between the cylinders of an engine increases, and the deterioration of drivability and the deterioration of exhaust emission attributable to misfiring result. In
FIGS. 19 and 20
, indicated at
103
, is a throttle valve shaft and at
105
is a throttle body.
FIG. 21
illustrates different regions of flows of intake air appearing in a cross section of the throttle body at a position 20 mm behind the throttle valve
100
when the throttle valve
100
is at a predetermined opening, for example, 14°. Indicated at A in
FIG. 21
are boundaries between the forward currents and the reverse currents of intake air. Although the difference in A/F ratio between the cylinders of an internal-combustion engine can be reduced by opening the purge port at a position on the boundary A, the purge port at the position on the boundary A lies inevitably near the shaft
103
of the throttle valve
100
and hence a difficult machining operation is required to form the purge port.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a fuel vapor control system for an internal-combustion engine, capable of solving problems encountered by the prior art.
Another object of the present invention is to provide a fuel vapor control system for an internal-combustion engine, provided with a control system for properly returning fuel vapor to an intake system and capable of suppressing increase in the difference in A/F ratio between the cylinders of an internal-combustion engine.
A further object of the present invention is to provide a fuel vapor control system for an internal-combustion engine, provided with an improved fuel vapor purge port.
A still further object of the present invention is to provide a fuel vapor control system for an internal-combustion engine, capable of being relatively easily manufactured and assembled.
In accordance with one aspect of the present invention, there is provided a fuel vapor control system for an internal-combustion engine which comprises a canister packed with an adsorbent for adsorbing fuel vapor evaporated in a fuel tank, a purge port forming means placed in an intake passage of the internal-combustion engine, a purge passage means fluidly interconnecting the canister and the purge port forming means, a purge rate control means arranged in the purge passage means to control a purge rate at which a fuel vapor is purged, a fuel supply means for supplying fuel to the internal-combustion engine, and a purge correction control means for controlling a fuel supply to the internal-combustion engine depending on the controlled purge rate, the purge port forming means defining a purge port for jetting fuel vapor onto the boundary between forward intake air currents and reverse intake air currents produced in a region below a throttle valve disposed in the intake passage.
Preferably, the purge port is arranged in a throttle body at a position below a throttle valve, and a fuel vapor outlet of the purge port is formed so as to project from the inner surface of a throttle body defining a throttle bore forming a portion of the intake passage into the throttle bore.
The purge port forming means may have a tapered portion tapered toward its extremity and the purge port may be formed at the extremity of the tapered portion.
A purge tube member included in the purge port forming means may be disposed between the shaft of the throttle valve and an end surface of the throttle body connected to a surge tank in the throttle body, and the purge port may be formed in the purge tube member at a position at a distance in the range of 2% to 20% of the diameter of the throttle bore from the surface of the throttle bore.
Preferably, the extremity of the purge tube is formed so as to have a beveled end surface, and an opening formed in the beveled end surface of the purge tube opens toward the surge tank. In this construction, the purge tube member must be held on the throttle body so that the purge tube member is unable to turn relative to the throttle body.
The extremity of the purge tube may be closed and a circumferential slit for adding fuel vapor may be formed in a portion of a side surface facing the surge tank, at a position near the extremity of the purge tube. In this construction, the purge tube member must be held so that the purge tube member is unable to turn relative to the throttle body.
The purge tube may be biased to the right or to the left with respect to the center of a cross section of the throttle bore.
The purge tube may be inclined relative to the throttle body so that the opening formed in its end surface faces the surge tank.
The operation of the present invention will be described.
Suppose that fuel vapor spouts out through the purge port into the throttle bore. Then, the fuel vapor flows into the surge tank, diffusing at the boundary between the forward intake air currents and the reverse intake air current into both the forward intake air currents and the reverse intake air currents produced in the throttle bore, because the purge port is formed at a position on the boundary below the throttle valve. Since the fuel vapor diffuses into the intake air currents, the fuel vapor is distributed evenly to all the cylinders, so that the difference in A/F ratio between the cylinders can be suppressed.
REFERENCES:
patent: 4961412 (1990-10-01), Furuyama
patent: 5216998 (1993-06-01), Hosoda
patent: 5226398 (1993-07-01), Cook
patent: 5445015 (1995-08-01), Namiki
patent: 5559706 (1996-09-01), Fujita
patent: 5592922 (1997-01-01), Denz
patent: 5634451 (1997-06-01), Tomasawa
patent: 5635633 (1997-06-01), Kadota
Kanehara Kenji
Norota Kazuhiko
Okano Hiroshi
Yamada Jun
Miller Carl S.
Nippon Soken Inc.
Pillsbury Madison & Sutro LLP
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