Title: Fuel supply control system for engine
Abstract: A composite control valve is constructed by a valve housing, first and second diaphragms mounted to the valve housing and disposed to be opposed to each other, a negative pressure working chamber defined between the first and second diaphragms to communicate with a negative pressure generating section in an engine, a first control valve adapted to be opened and closed by advancing and returning of the first diaphragm, and a second control valve adapted to be opened and closed by advancing and returning of the second diaphragm. The first control valve is incorporated into an air vent system for a fuel tank, and the second control valve is incorporated into a fuel passage system extending from the fuel tank to a fuel supply section in the engine. Thus, upon stoppage of the operation of the engine, not only the fuel passage system but also the air vent system leading to the upper space in the fuel tank are blocked simultaneously, thereby preventing release of an evaporated fuel generated in the fuel tank to the atmosphere.
Patent Number: 6,973,922 Issued on 12/13/2005 to Yamada, et al.
| Inventors:
|
Yamada; Yoshikazu (Saitama, JP);
Utsugi; Eiichi (Saitama, JP);
Chiba; Shosaku (Saitama, JP);
Sasaki; Tsutomu (Miyagi, JP);
Tsutsui; Katsuhiko (Miyagi, JP)
|
| Assignee:
|
Honda Motor Co., Ltd. (Tokyo, JP);
Keihin Corporation (Tokyo, JP)
|
| Appl. No.:
|
890514 |
| Filed:
|
July 14, 2004 |
Foreign Application Priority Data
| Aug 04, 2003[JP] | 2003-286287 |
| Aug 04, 2003[JP] | 2003-286293 |
| Aug 04, 2003[JP] | 2003-286294 |
| Current U.S. Class: |
123/495; 123/516; 417/395 |
| Intern'l Class: |
F02M 037/00 |
| Field of Search: |
123/495,446,447,516
417/395
|
References Cited [Referenced By]
U.S. Patent Documents
| 2447266 | Aug., 1948 | Beardsley, Jr.
| |
| 3698368 | Oct., 1972 | Yamamoto.
| |
| 3765802 | Oct., 1973 | Leitermann et al.
| |
| 4093403 | Jun., 1978 | Schrimpf et al.
| |
| 4153025 | May., 1979 | Thornburgh.
| |
| 4203401 | May., 1980 | Kingsley et al.
| |
| 4228777 | Oct., 1980 | Haase.
| |
| 5584278 | Dec., 1996 | Satoh et al.
| |
| 6158972 | Dec., 2000 | Ruth.
| |
| 6347614 | Feb., 2002 | Evers et al.
| |
| Foreign Patent Documents |
| 2 264 190 | Oct., 1975 | FR.
| |
| 62-93145 | Jun., 1987 | JP.
| |
Primary Examiner: Moulis; Thomas
Attorney, Agent or Firm: Arent Fox PLLC
Claims
1. A fuel supply control system for an engine, including a composite control
valve which is constructed by a valve housing, first and second diaphragms disposed
to be opposed to each other with their peripheral edges secured to the valve housing,
a negative pressure working chamber defined between the first and second diaphragms
to communicate with a negative pressure generating section in the engine, a first
control valve connected to the first diaphragm and adapted to be opened and closed
by advancing and returning of the first diaphragm due to generation and extinction
of a negative pressure in the negative pressure working chamber, and a second control
valve connected to the second diaphragm and adapted to be opened and closed by
advancing and returning of the second diaphragm due to the generation and extinction
of the negative pressure in the negative pressure working chamber, the first control
valve being incorporated into an air vent system which provides communication between
an upper space in a fuel tank and the atmosphere, the second control valve being
incorporated into a fuel passage system which provides communication between a
portion of the fuel tank below a fuel oil surface and a fuel supply section in
the engine.
2. A fuel supply control system for an engine according to claim 1, wherein the
first control valve is opened prior to opening of the second control valve at an
initial stage of transmission of the negative pressure from the negative pressure
generating section to the negative pressure working chamber.
3. A fuel supply control system for an engine according to claim 1, wherein an
atmospheric air chamber leading to the atmosphere is defined between an inner side
of the valve housing and the first diaphragm; the first control valve is constructed
to open and close an opening of an atmospheric air introducing pipe leading to
the upper space in the fuel tank, the opening opening into the atmospheric air
chamber; and a relief valve is provided between the atmospheric air introducing
pipe and the atmospheric air chamber, and adapted to be opened when the pressure
in the atmospheric air introducing pipe is reduced from a pressure in the atmospheric
pressure chamber by a predetermined value or more.
4. A fuel supply control system for an engine according to claim 1, wherein a
check valve adapted to be opened only upon transmission of a negative pressure
from a crank chamber in the engine, and a constriction bore providing constant
communication between the negative pressure working chamber and the crank chamber
are incorporated in parallel into a flow passage which connects the negative pressure
working chamber to the crank chamber.
5. A fuel supply control system for an engine according to claim 4, wherein the
check valve and the constriction bore are provided at a fitting connection between
the valve housing and a negative pressure introducing pipe leading to the crank chamber.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel supply control system for an engine,
which is adapted to control opening and closing of an air vent system which provides
communication between an upper space in a fuel tank and the atmosphere, and opening
and closing of a fuel passage system which provides communication between a portion
of the fuel tank below a fuel oil surface and a fuel supply section in the engine.
2. Description of the Related Art
Japanese Utility Model Application Laid-open No. 62-93145 discloses a conventional
fuel supply control system for an engine, wherein a negative-pressure responsive
type automatic fuel cock adapted to be opened by a negative pressure generated
in a negative pressure generating section in the engine is incorporated in a fuel
passage which provides communication between a portion of the fuel tank below a
fuel oil surface and a fuel supply section in the engine, so that upon stoppage
of the operation of the engine, the fuel passage is automatically blocked by the
automatic fuel cock to inhibit flowing-down of a fuel from the fuel tank to the
fuel supply section in the engine.
With such a conventional fuel supply control system for the engine, the flowing-down
of the fuel from the fuel tank to the fuel supply section in the engine can be
inhibited by the automatic fuel cock upon stoppage of the operation of the engine,
but an upper space in the fuel tank is put in a state in which it is opened to
the atmosphere through an air vent, so that if an evaporated fuel is produced in
the fuel tank, the evaporated fuel is released into the atmosphere through the
air vent.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a fuel
supply control system of a simple construction for an engine, wherein upon stoppage
of the operation of the engine, not only the fuel passage system but also the air
vent system leading to the upper space in the fuel tank can be blocked simultaneously,
to thereby prevent release of an evaporated fuel generated in the fuel tank to
the atmosphere.
To achieve the above object, according to a first feature of the present invention,
there is provided a fuel supply control system for an engine, including a composite
control valve which is constructed by a valve housing, first and second diaphragms
disposed to be opposed to each other with their peripheral edges secured to the
valve housing, a negative pressure working chamber defined between the first and
second diaphragms to communicate with a negative pressure generating section in
the engine, a first control valve connected to the first diaphragm and adapted
to be opened and closed by advancing and returning of the first diaphragm due to
generation and extinction of a negative pressure in the negative pressure working
chamber, and a second control valve connected to the second diaphragm and adapted
to be opened and closed by advancing and returning of the second diaphragm due
to the generation and extinction of the negative pressure in the negative pressure
working chamber, the first control valve being incorporated into an air vent system
which provides communication between an upper space in a fuel tank and the atmosphere,
the second control valve being incorporated into a fuel passage system which provides
communication between a portion of the fuel tank below a fuel oil surface and a
fuel supply section in the engine.
With the first feature, during operation of the engine, a negative pressure
generated in a negative pressure generating section of the engine is transmitted
to the negative pressure working chamber in the valve housing, and in response
to this, the first and second diaphragms are advanced to open the first and second
control valves. Therefore, the air vent system and the fuel passage system are
opened, thereby smoothly conducting the supply of the fuel from the fuel tank to
the fuel supply section in the engine.
If the operation of the engine is stopped, not only the negative pressure in
the
negative pressure generating section of the engine but also the negative pressure
in the negative pressure working chamber in the valve housing are lost, and in
response to this, the first and second diaphragms are returned to close the first
and second control valves. Therefore, both the air vent system and the fuel passage
system are closed, and hence, it is possible not only to inhibit the supply of
the fuel from the fuel tank to the fuel supply section in the engine, but also
to prevent the release of the evaporated fuel generated in the fuel tank to the atmosphere.
The above-described effect is achieved by the composite control valve including
the first and second control valves accommodated in the single valve housing and
hence, the construction of the fuel supply control system for the engine can be simplified.
Moreover, the first and second diaphragms for operating the first and second
control valves are disposed to be opposed to each other with the negative pressure
working chamber defined therebetween. This can contribute to the compactness of
the composite control valve.
According to a second feature of the present invention, in addition to
the first feature, the first control valve is opened prior to opening of the second
control valve at an initial stage of transmission of the negative pressure from
the negative pressure generating section to the negative pressure working chamber.
With the second feature, upon starting of the engine, the first control valve
is first opened to open the air vent system, and the second control valve is then
opened to open the fuel passage system. Therefore, it is possible to prevent excessive
supply or insufficient supply of the fuel to the fuel supply section due to the
pressure remaining in the fuel tank, to thereby ensure a good start ability of
the engine.
According to a third feature of the present invention, in addition to the
first or second feature, an atmospheric air chamber leading to the atmosphere is
defined between an inner side of the valve housing and the first diaphragm; the
first control valve is constructed to open and close an opening of an atmospheric
air introducing pipe leading to the upper space in the fuel tank, the opening opening
into the atmospheric air chamber; and a relief valve is provided between the atmospheric
air introducing pipe and the atmospheric air chamber, and adapted to be opened
when the pressure in the atmospheric air introducing pipe is reduced from a pressure
in the atmospheric pressure chamber by a predetermined value or more.
With the third feature, when the fuel tank is cooled by the outside air in an
extremely cold zone, whereby the pressure in the fuel tank is reduced to a level
equal to or lower than a predetermined value, the relief valve mounted between
the atmospheric air introducing pipe and the atmospheric chamber is opened, whereby
the atmospheric air is supplemented from the atmospheric air chamber through the
atmospheric air introducing pipe into the fuel tank. Thus, it is possible to prevent
the constricting deformation of the fuel tank due to an excessive reduction of
the pressure in the fuel tank.
According to a fourth feature of the present invention, in addition to
the first or second feature, a check valve adapted to be opened only upon transmission
of a negative pressure from a crank chamber in the engine, and a constriction bore
providing constant communication between the negative pressure working chamber
and the crank chamber are incorporated in parallel into a flow passage which connects
the negative pressure working chamber to the crank chamber.
With the fourth feature, during operation of the engine, the check valve is
subjected to the action of the powerful pulsation of pressure generated in the
crank chamber, and opened only upon receipt of a negative pressure. Therefore,
the negative pressure working chamber can be maintained in a constantly stable
high negative pressure state without being influenced by a variation in opening
degree of a throttle valve. When the negative pressure working chamber is brought
into a predetermined negative pressure state, the first and second diaphragms are
advanced to open the first and second control valve and hence, the air vent system
and the fuel passage system are opened. Thus, the supply of the fuel from the fuel
tank to the fuel supply section in the engine can be conducted smoothly. Especially,
because the negative pressure working chamber is maintained in the stable high
negative pressure state, the first and second control valves can be maintained
in good valve-opened states and hence, the supply of the fuel to the fuel supply
section in the engine can be stabilized.
Upon stoppage of the operation of the engine, the negative pressure remaining
in the negative pressure working chamber is returned through the constriction bore
to the crank chamber in response to the returning of the crank chamber to the atmospheric
pressure state, whereby the negative pressure working chamber is also brought into
the atmospheric pressure state, and the first and second diaphragms are returned
to close the first and second control valves. Therefore, both the air vent system
and the fuel passage system are closed and thus, it is possible not only to inhibit
the supply of the fuel from the fuel tank to the fuel supply section in the engine,
but also to prevent the release of the evaporated fuel generated in the fuel tank
to the atmosphere.
According to a fifth feature of the present invention, in addition to the
fourth feature, the check valve and the constriction bore are provided at a fitting
connection between the valve housing and a negative pressure introducing pipe leading
to the crank chamber.
With the fifth feature, also the check valve is incorporated into the composite
control valve, and hence the fuel supply control system for the engine can be further
simplified, and moreover the assemblability of the check valve is improved.
The negative pressure generating section and the fuel supply section correspond
to a crank chamber 1
a and a carburetor C respectively in each of
embodiments of the present invention which will be described hereinafter; the negative
pressure working chamber corresponds to first and second working chambers 44
and 45 communicating with each other; the air vent system corresponds to
an inner air vent pipe 23, an outer air vent pipe 24, an atmospheric
air introducing pipe 49, an atmospheric air chamber 43 and an atmospheric
air inlet pipe 47; and the fuel passage system corresponds to a fuel introducing
pipe 70, a fuel conduit 71, a fuel chamber 46 and a fuel outlet 72.
The above and other objects, features and advantages of the invention will become
apparent from the following description of the preferred embodiments taken in conjunction
with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view of a vertical-type engine provided with a fuel tank according
to a first embodiment of the present invention;
FIG. 2 is a plan view of portions around a carburetor in FIG. 1;
FIG. 3 is a sectional view taken along a line 3—3 in FIG. 2;
FIG. 4 is an enlarged vertical sectional view of essential portions of the fuel tank;
FIG. 5 is an enlarged vertical sectional view of a composite control valve in
FIG. 3 (showing an operation-stopped state of the engine);
FIG. 6 is a view of the composite control valve for explaining the operation
upon increase of a pressure in the fuel tank;
FIG. 7 is a view of the composite control valve for explaining the operation
upon decrease of the pressure in the fuel tank;
FIG. 8 is a view of the composite control valve for explaining the operation
during operation of the engine;
FIG. 9 is a sectional view taken along a line 9—9 in FIG. 5;
FIG. 10 is a sectional view taken along a line 10—10 in
FIG. 2;
FIGS. 11A, 11B and 11C are views for explaining the operation
of an oil flow-out preventing means in FIG. 2;
FIG. 12 is a view similar to FIG. 3, but showing a second embodiment of the
present invention;
FIG. 13 is a view similar to FIG. 3, but showing a third embodiment of the present invention;
FIG. 14 is a side view of a horizontal-type engine provided with a fuel tank
according to a fourth embodiment of the present invention; and
FIG. 15 is an enlarged vertical sectional view of essential portions of FIG. 14.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will now be described by way of preferred embodiments with
reference to the accompanying drawings.
A first embodiment of the present invention shown in FIGS. 1 to 11 will be described
first. In FIGS. 1 and 2, reference character E denotes a general-purpose engine
of a 4-cycle vertical type. A crankshaft
2 supported in a crankcase
1
of the engine E is disposed vertically with its output end protruding downward
below the crankcase
1. A fuel tank T and a recoil starter
4 are mounted
to an upper portion of the crankcase
1.
A cylinder block
5 having a cylinder axis disposed horizontally is connected
to one side of the crankcase
1, and a carburetor C is mounted to one side
of a cylinder head
6 coupled to a tip end of the cylinder block
5.
Referring to FIG. 3, the carburetor C includes a carburetor body
10
having an intake passage
11 leading to an intake port
6a in
the cylinder head
6, a float chamber member
12 coupled to a lower
surface of the carburetor body
10 and having a float chamber
12a,
a fuel nozzle
13 which permits an area below a fuel oil surface in the float
chamber
12a to communicate with a venturi portion of the intake passage
11, a choke valve
14 for opening and closing the intake passage
11
at a location upstream of the intake passage
11, a throttle valve
15
for opening and closing the intake passage
11 at a location downstream of
the intake passage
11, and a float valve
17 for opening and closing
an fuel inlet
16 of the float chamber member
12 to control the oil
surface of a fuel stored in the float chamber
12a to be constant.
The fuel nozzle
13 is supported in a nozzle support tube
10a formed
at a lower portion of the carburetor body
10. A composite control valve
V is mounted on one side of the float chamber member
12 for controlling
the opening and closing of an air vent system for the fuel tank T as well as the
opening and closing of a fuel passage system extending from the fuel tank T to
the float chamber
12a depending on the operational state of the engine
E. The composite control valve V will be described later.
Referring to FIG. 4, an oil supply port tube
20 formed on one side
of a ceiling wall of the fuel tank T is tightly closed by a tank cap
21
threadedly engaged with an outer periphery of the oil supply port tube
20.
A ventilation hole
22 opens into an inner surface of the oil supply port
tube
20. The ventilation hole
22 extends vertically within the fuel
tank T and communicates with an inner air vent pipe
23 extending through
a bottom wall of the fuel tank T, and an outer air vent pipe
24 disposed
below the fuel tank T is connected at one end to a lower end of the inner air vent
pipe
23. The inner air vent pipe
23 is formed integrally with the
fuel tank T.
The inner air vent pipe
23 disposed within the fuel tank T is protected
from any contact with other objects. It is unnecessary to extend the air vent pipe
upward above the fuel tank T and hence, the appearance of the fuel tank T can be
maintained to be excellent.
The tank cap
21 is provided with a gas-liquid separating means
25
interposed between an upper space
3 in the fuel tank T and the ventilation
hole
22. The gas-liquid separating means
25 is constructed by a partitioning
member
26 and a porous member
27 made of a urethane foam having open
cells. The partitioning member
26 is made of an elastic material such as
rubber, and includes a cylindrical portion
28 disposed within the oil supply
port tube
20 and having an upper end wall
28a recessed downwards
into a cone-shape, a flange portion
29 which protrudes radially outwards
from an upper end of the cylindrical portion
28 and which is clamped between
an end wall of the tank cap
21 and an end face of the oil supply port tube
20. A seal bead
28b is formed at a lower end of the cylindrical
portion
28 to come into close contact with an inner peripheral surface of
a lower end portion of the oil supply port tube
20. Small bores
30
and
31 are provided in the upper wall
28a and the flange portion
29. The partitioning member
26 divides the inside of the oil supply
port tube
20 into an inner chamber
32 leading to the upper space
3 within the fuel tank T, an outer chamber
33 which surrounds the
inner chamber
32 with the cylinder portion
28 interposed therebetween,
and an upper chamber
35 communicating with the inner and outer chambers
32 and
33 through the small bores
30 and
31, respectively.
The ventilation hole
22 is disposed to open into the outer chamber
33.
The porous member
27 is set in the upper chamber
35 to cover the
small bore
30 in the upper end wall
28a. A cylindrical wave
trap protruding toward the inner chamber
32, i.e., downwards to surround
the small bore
30, is connected to the upper end wall
28a.
Thus, the ventilation hole
22 and the upper space
3 within the
fuel tank T communicate with each other through the outer chamber
33, the
small bore
31, the upper chamber
35, the porous member
27,
the small bore
30 and the inner chamber
32, thereby enabling the
breathing of the inside of the fuel tank T. On the other hand, even if the fuel
in the fuel tank T enters the inner chamber
32 due to waving, the entrance
of the fuel into the small bore
30 can be prevented by the wave trap
34.
However, when the fuel has entered the upper chamber
35 through the small
bore
30, it is absorbed by the porous member
27, and if the fuel
absorbing capability of the porous member
27 reaches a level corresponding
to a saturated state, the fuel flows toward the small bore
30 along the
cone-shaped upper end wall
28a, and is dropped into the fuel tank
T. In this manner, the fuel in the fuel tank T cannot reach the outer chamber
33
through the outer small bore
31 and hence, the entrance of the fuel into
the ventilation hole
22 can be prevented.
The composite control valve V will be described below with reference to FIG. 5.
The composite control valve V has a valve housing
40 which is constructed
by sequentially superposing a first block
40a, a second block
40b
and a third block
40c one on another and coupling them to one
another. In this case, an outer peripheral edge of a first diaphragm
41
is clamped between the first block
40a and the second block
40b,
and an outer peripheral edge of a second diaphragm
42 is clamped between
the second block
40b and the third block
40c. An atmospheric
chamber
43 is defined between the first block
40a and the
first diaphragm
41; a first negative pressure working chamber
44
is defined between the first diaphragm
41 and the second block
40b,
and a second negative pressure working chamber
43 is defined between the
second block
40b and the second diaphragm
42. A fuel chamber
46 is defined between the second diaphragm
42 and the third block
40c.
An atmospheric air inlet pipe
47 is integrally formed on one sidewall
of
the first block
40a so that the atmospheric chamber
43 is
always maintained under an atmospheric pressure. An atmospheric air introducing
pipe
49 is integrally formed on the other sidewall of the first block
40a
to open at its inner end into the atmospheric chamber
43, and the other
end of the outer air vent pipe
24 is connected to an outer end of the atmospheric
air introducing pipe
49.
An inner end of the atmospheric air introducing pipe
49 is formed at a
first valve seat
51 protruding toward the atmospheric chamber
43.
A first valve member
52 for opening and closing the atmospheric air introducing
pipe
49 by cooperation with the first valve seat
51 is formed at
a central portion of the first diaphragm
41. A first return spring
53
for biasing the first valve member
52 toward the first valve seat
51
is mounted under compression between the first diaphragm
41 and the second
block
40b. A first control valve
50 for opening and closing
the atmospheric air introducing pipe
49 is constructed by the first valve
member
52 and the first valve seat
51.
A relief valve
54 is mounted on a partition wall between the first block
40a and the atmospheric air introducing pipe
49, and adapted
to be opened to permit the flowing of air from the atmospheric chamber
43
to the atmospheric air introducing pipe
49, only when the pressure in the
fuel tank T is dropped to a level equal to or lower than a predetermined pressure.
A negative pressure introducing pipe
55 communicating with the first negative
pressure working chamber
44 is connected to the second block
40b,
and the negative pressure introducing pipe
55 and a negative pressure pick-up
pipe
56 formed on the crankcase
1 of the engine E to lead to a crank
chamber
1a in the crankcase
1 are connected to each other
by a negative pressure conduit
57.
As shown in FIGS. 5 and 9, a check valve
65 is mounted at a connection
between the second block
40b and the negative pressure introducing
pipe
55. The check valve
65 includes a valve seat plate
66
and a resilient valve plate
67 clamped between the second block
40
band the negative pressure introducing pipe
55. The valve plate
67
is disposed on a side of the valve seat plate
66 closer to the negative
pressure introducing pipe
55, to open and close a valve bore
66a
in the valve seat plate
66 in accordance with a pressure difference
across the valve seat plate
66. Therefore, the check valve
65 permits
only the transmission of a negative pressure from the negative pressure introducing
pipe
55 to the first negative pressure working chamber
44. More specifically,
when the pressure in the negative pressure introducing pipe
55 is lower
than that in the first negative pressure working chamber
44, the check valve
65 is opened, and when the pressure in the negative pressure introducing
pipe
55 is higher that in the first negative pressure working chamber
44,
the check valve
65 is closed. A constriction bore
68 is provided
in the valve seat plate
66 to permit the negative pressure introducing pipe
55 and the first negative pressure working chamber
44 to be always
in communication with each other irrespective of the valve-opening/closing motion
of the valve plate
67. The constriction bore
68 may be provided in
a portion of the valve plate
67 facing the valve bore
66a.
An orifice
58 is provided in the second block
40b to permit
the communication between the first and second negative pressure working chambers
44 and
45.
A fuel introducing pipe
70 is integrally formed on the third block
40c,
and a fuel conduit
71 leading to a bottom portion (see FIG. 4) in the fuel
tank T is connected to the fuel introducing pipe
70. The third block
40c
is provided with a fuel outlet
72 which is connected to the fuel inlet
16 in the float chamber member
12.
An inner end of the fuel introducing pipe
70, which opens into the fuel
chamber
46, is formed at a second valve seat
61 protruding toward
the fuel chamber
46. A second valve member
62 for opening and closing
the fuel introducing pipe
70 by cooperation with the second valve seat
61
is formed at a central portion of the second diaphragm
42, and a second
return spring
63 is mounted under compression for biasing the second valve
member
62 in a direction to seat it on the second valve seat
61.
The second return spring has a preset load larger than that of the first return
spring
53. A second control valve
60 for opening and closing the
fuel introducing pipe
70 is constructed by the second valve member
62
and the second valve seat
61.
The operation of the composite control valve V will be described below.
Upon Stoppage of the Operation of the Engine E (See FIG. 5)
In an operation-stopped state of the engine E, the crank chamber
1a
is in a state under an atmospheric pressure and hence, the first and second
negative pressure chambers
44 and
45 communicating with the crank
chamber
1a through the constriction bore
68 are also under
the atmospheric pressure. As a result, the first and second diaphragms
41
and
42 are biased toward the first and second valve seats
51 and
61 by the preset loads of the first and second return springs
63,
63, respectively, and the first and second valve members
52 and
62
are seated on the first and second valve seats
51 and
61, respectively.
Namely, both the first and second control valves
50 and
60 are concurrently
closed to block the atmospheric air introducing pipe
49 and the fuel introducing
pipe
70, respectively.
On the other hand, if the inside of the fuel tank T is substantially under the
atmospheric pressure, the seating of the first valve member
52 onto the
first valve seat
51 is not obstructed, and the normally-closed type relief
valve
54 is closed to cut off the communication between the atmospheric
air introducing pipe
49 and the atmospheric pressure chamber
43.
When the atmospheric air introducing pipe
49 and the fuel introducing
pipe
70 is disconnected from each other in this manner, the wasteful downward-flowing
of the fuel from the fuel tank T to the carburetor C can be prevented, and the
release of the evaporated fuel generated in the fuel tank T to the atmosphere can
be prevented.
Upon Increase of Pressure in Fuel Tank T (See FIG. 6)
If the fuel tank T is heated by a solar heat or the like when the engine is in
the operation-stopped state, as described above, the internal pressure in the fuel
tank T is raised to a level equal to or higher than the predetermined pressure,
such an internal pressure moves the first valve member
52 away from the
first valve seat
51 against the preset load of the first return spring
52,
i.e., the first control valve
50 is opened to open the atmospheric air introducing
pipe
49 into the atmospheric air chamber
43. Therefore, the excessive
increment in pressure in the fuel tank T is released into the atmosphere, and thus
the expanding deformation of the fuel tank T due to the excessive raising of the
internal pressure can be prevented.
Upon Decrease of Pressure in Fuel Tank T (See FIG. 7)
When the engine E is in the operation-stopped state, for example, in a cold
zone, the fuel tank T is cooled by the outside air, and the pressure in the fuel
tank T is reduced to a level equal to or lower than the predetermined value, the
relief valve
54 is opened due to a pressure difference across the relief
valve
54, to there by permit the flowing of air from the atmospheric pressure
chamber
43 to the atmospheric air introducing pipe
49. Therefore,
the atmospheric air is supplemented into the fuel tank T, whereby the constricting
deformation of the fuel tank T can be prevented.
During Operation of the Engine E (See FIG. 8)
During operation of the engine E, the powerful pressure pulsation, in which
the positive and negative pressures are alternately generated in the crank chamber
1a with the reciprocal movement of a piston, occurs, and is transmitted
through the negative pressure conduit
57 and the negative pressure introducing
pipe
55 to the check valve
65. The check valve
65 is closed
upon the transmission of the positive pressure and opened upon the transmission
of the negative pressure. Therefore, eventually, only the negative pressure is
passed through the check valve
65 and transmitted first to the first negative
pressure working chamber
44 and then through the through-bore
58
to the second negative pressure working chamber
45, whereby the first and
second negative pressure working chambers
44 and
45 can be maintained
in equally stable high negative pressure states without being influenced by a variation
in opening degree of the throttle valve
15 of the carburetor C.
In this case, there is a negative pressure which is leaked from the first and
second negative pressure working chambers
44 and
45 through the constriction
bore
68 into the crank chamber
1a, but the amount of negative
pressure leaked is extremely small, as compared with a negative pressure introduced
from the crank chamber
1a into the first and second negative pressure
working chambers
44 and
45, and hence such a negative pressure can
be disregarded.
When the first negative pressure working chamber
44 has been brought
into a predetermined negative pressure state in this manner, the first diaphragm
41 is pulled toward the first negative pressure working chamber
44
against the preset load of the first return spring
53 to move the first
valve member
52 away from the first valve seat
51, i.e., the first
control valve
50 is opened to open the atmospheric air introducing pipe
49. Therefore, the upper space
3 in the fuel tank T is brought into
a state in which it can freely breathe the external air. When the second negative
pressure working chamber
45 has been brought into a predetermined negative
pressure state, the second diaphragm
42 is pulled toward the second negative
pressure working chamber
45 against the preset load of the second return
spring
63 to move the second valve member
62 away from the second
valve seat
61, i.e., the second control valve
60 is opened to open
the fuel introducing pipe
70. Therefore, the fuel in the fuel tank T is
supplied to the float chamber
12a in the carburetor C through the
fuel conduit
71, the fuel introducing pipe
70 and the fuel chamber
46.
Upon the starting of the engine E, the negative pressure from the crank chamber
1a is transmitted first to the first negative pressure working chamber
44, and then from the first negative pressure working chamber
44
through the orifice
58 to the second negative pressure working chamber
45.
Also, the preset load of the first return spring
53 is set at the value
smaller than that of the second return spring
63. That is, the first diaphragm
41 opens the first control valve
50 to open the atmospheric air introducing
pipe
49, and then the second diaphragm
42 opens the second control
valve
50 to open the fuel introducing pipe
70. Therefore, the positive
or negative pressure remaining in a small amount in the fuel tank T is first released
to the atmosphere by the opening of the first control valve
50, and thereafter
the supply of the fuel to the carburetor C is started, whereby the excessive supply
or insufficient supply of the fuel due to the pressure remaining in the fuel tank
T can be prevented to ensure the good start ability of the engine E.
In order to control the timing for opening the atmospheric air introducing pipe
49 and the fuel introducing pipe
70 in the above-described manner,
the following arrangements are provided in the present embodiment:
(1) The negative pressure introducing pipe 55 is put into communication
with the first negative pressure working chamber 44, and the first and second
negative pressure working chambers 44 and 45 are put into communication
with each other through the orifice 58.
(2) The preset load of the first return spring 53 for biasing the
first valve member 52 in a closing direction is set at a value smaller than
the preset load of the second return spring 63 for biasing the second valve
member 62 in a closing direction.
Both the above arrangements (1) and (2) are employed in the embodiment, but
the control of the timing can be achieved by employing any one of these arrangements.
When only the arrangement (2) is employed, the first and second negative pressure
working chambers
44 and
45 may be formed into a single negative pressure
working chamber without being divided.
The composite control valve V for controlling the opening and closing of the
air vent system for the fuel tank T and the opening and closing of the fuel supply
system extending from the fuel tank T to the carburetor C, as described above,
is constructed by the single valve housing
40, and the first and second
diaphragms
41 and
42 mounted within the valve housing
40,
as well as the first and second control valves
50 and
60. Therefore,
the composite control valve V obtains a simple structure and can be provided at
a relatively low cost. Moreover, the first and second diaphragms
41 and
42 are disposed to be opposed to each other with the first and second negative
pressure working chambers
44 and
45 defined therebetween and hence,
the compactness of the composite control valve V can be achieved.
In addition, the check valve
65 is clamped at the fitting connection between
the second block
40b and the negative pressure introducing pipe
55
and hence, the check valve
65 is also incorporated into the composite control
valve V. Thus, it is possible to provide a further simplification with the fuel
supply control system for the engine and moreover, the assemblability of the check
valve
65 is improved.
Referring to FIGS. 2,
10 and
11, a connecting tube
57a
is integrally formed at an upstream end of the negative pressure conduit
57
and fitted to an inner peripheral surface of the negative pressure pick-up pipe
56, and the negative pressure pick-up pipe
56 and the connecting
tube
57a are usually retained at horizontal orientation. The connecting
tube
57a is provided with an oil flow-out preventing means
80
for preventing a lubricating oil from flowing out of the crank chamber
1a
to the negative pressure conduit
57 in any attitude of the engine E
during transportation or storage of the engine E.
The oil flow-out preventing means
80 is fitted and fixed to the inner
peripheral surface of the negative pressure conduit
57 and disposed at a
central portion of the connecting tube
57a, and includes an inner
tube
81 which opens at opposite ends, and an outer tube
82 disposed
concentrically between the inner tube
81 and the connecting tube
57a.
The outer tube
82 has an end wall
82a opposed at a distance
to a tip end of the inner tube
81. A cross-shaped or radial rib
83
is formed to extend from an outer surface of the end wall
82a to
an outer peripheral surface of the outer tube
82. The outer tube
82
is retained at a bottom of the connecting tube
57a by the engagement
of the rib
83 with an inward facing shoulder
87 of an inner periphery
of an open end of the connecting tube
57a. In addition, an outer
ventilation clearance
84 is defined between the connecting tube
57a
and the outer tube
82 by the abutment of the rib
83 against an
inner peripheral surface of the connecting tube
57a. An inner ventilation
clearance
85 is also defined between the outer tube
82 and the inner
tube
81 to communicate with the inner tube
81. Further, a plurality
of notches
86 are provided at a tip end of the outer tube
82 to provide
communication between the ventilation clearances
84 and
85.
During operation of the engine E, as shown in FIG. 11A, the negative pressure
pick-up pipe
56 is normally retained substantially horizontally, and the
crank chamber
1a and the negative pressure conduit
57 are
in communication with each other through the ventilation clearances
84 and
85 between the outer tube
82 and the inner tube
81 and through
the notches
86, thereby enabling the transmission of the pressure pulsation
to the negative pressure conduit
57. In this state, even when a small amount
of the mist of the lubricating oil O in the crank chamber
1a enters
and is accumulated in lower portions of the ventilation clearances
84 and
85, the communication between the crank chamber
1a and the
negative pressure conduit
57 cannot be cut off by the accumulation of the mist.
When the engine E is inclined at a given angle or more during transportation
or storage of the engine E, the negative pressure pick-up pipe
56 is also
inclined or turned upside down, as shown in FIGS. 11B and 11C, whereby the lubricating
oil O in the crank chamber
1a flows into the connecting tube
57a
and fills the outer ventilation clearance
84. When the lubricating oil
O further fills a lower portion of the inner ventilation clearance
85, the
communication between the inner tube
81 and the crank chamber
1a
is cut off by such oil and moreover, the first and second negative pressure
working chambers
44 and
45 with which the inner tube
81 communicates
through the negative pressure conduit
57 are tightly-closed chambers isolated
from the atmosphere, so that the air is not moved within the negative pressure
conduit
57. Therefore, the oil filling the lower portion of the inner ventilation
clearance
85 cannot be raised up to an opening at an upper end of the inner
tube
81, and thus the flowing-out of the oil to the inner tube
81
and the negative pressure conduit
57 can be prevented.
Moreover, the oil flow-out preventing means
80 including the inner
tube
81 and the outer tube
82 has a simple structure, and can be
produced at a low cost.
A second embodiment of the present invention shown in FIG. 12 will now be described.
In a carburetor C, a small fuel chamber
75 is defined in a nozzle-supporting
tube
10a of a carburetor body
10 for supporting a fuel nozzle
13, so that a lower end of the fuel nozzle
13 faces the small fuel
chamber
75, and a valve tube
76 interconnecting a float chamber
12a
and the small fuel chamber
75 is connected to one side of a nozzle support
tube
10a.
On the other hand, in a valve housing of a composite control valve V, a third
block
40 as in the first embodiment is not used, and a second diaphragm
42 is clamped between a second block
40b and an outer side
of a float chamber member
12 to which the second block
40b is
coupled. A piston-shaped second valve member
62 is mounted to the second
diaphragm
42 and slidably fitted in the valve tube
76. The second
valve member
62 has an axial communication groove
77 provided in
an outer peripheral surface of a tip end thereof. A second control valve
60
for opening and closing the communication between the float chamber
12a
and the fuel nozzle
13 is constructed by the second valve member
62
and the valve tube
76.
In the second embodiment, a negative pressure introducing pipe
49 is adapted
to communicate equally with the first and second negative pressure working chambers
44 and
45. Therefore, in order to open the first control valve
50
prior to the second control valve
60 at the start of the engine E, as described
above, the above-described arrangement (2), i.e., the arrangement in which the
preset load of the first return spring
53 is set at the value smaller than
the preset load of the second return spring
63, may be employed.
A fuel conduit
71 is connected directly to the fuel inlet
16 adapted
to be opened and closed by the float valve
17.
When a negative pressure is introduced into the second negative pressure working
chamber
45, whereby the second diaphragm
42 is advanced toward the
second negative pressure working chamber
45, the second valve member
62
is also advanced to expose a portion of the communication groove
77 to the
float chamber
12a, whereby the float chamber
12a and
the fuel nozzle
13 are brought into communication with each other through
the communication groove
77. Therefore, the flowing of the fuel from the
float chamber
12a into the fuel nozzle
13 is permitted. When
the negative pressure is extinguished from the second negative pressure working
chamber
45, whereby the second diaphragm
42 is returned toward the
float chamber
12a, the communication groove
77 in the second
valve member
62 returning along with the second diaphragm
42 is withdrawn
into the valve tube
76, whereby the communication between the float chamber
12a and the fuel nozzle
13 is cut off.
The arrangement of the other components is basically not different from that
in the first embodiment and hence, portions or components corresponding to those
in the first embodiment are designated by the same reference symbols and numerals
in FIG. 12 and the description of them is omitted.
A third embodiment of the present invention shown in FIG. 13 will now be described.
A composite control valve V is mounted to a bottom surface of a float chamber
member
12 in a carburetor C. A second valve seat
61 is formed on a lower
end face of a nozzle support tube
10a of a carburetor body
10,
and a second valve member
62 cooperating with the second valve seat
61
is connected to a second diaphragm
42 through a collar
78. A second
control valve
60 for opening the closing the communication between a small
fuel chamber
75 in a lower portion of the nozzle support tube
10a
and the float chamber
12a is constructed by the second valve
member
62 and the second valve seat
61.
A diaphragm
74 clamped between the second valve member
62 and the
collar
78 has an outer peripheral portion clamped between the bottom surface
of the float chamber member
12 and a third block
40c of a
valve housing
40, whereby the communication between the float chamber
12a
and the third block
40c is cut off. However, this diaphragm
74
may be disused, whereby the second diaphragm
42 can be exposed to the fuel
in the float chamber
12a.
Also in the third embodiment, a fuel conduit
71 is connected directly
to a fuel inlet
16 adapted to be opened and closed by a float valve
17.
When a negative pressure is introduced into the second negative pressure working
chamber
45, whereby the second diaphragm
42 is advanced toward the
second negative pressure working chamber
45, the second valve member
62
is also advanced away from the second valve seat
61, whereby the float chamber
12a and the fuel nozzle
13 are brought into communication
with each other. Therefore, the flowing of the fuel from the float chamber
12a
into the fuel nozzle
13 is permitted. When the negative pressure from
the second negative pressure working chamber
45 is lost, whereby the second
diaphragm
42 is returned toward the float chamber
12a, the
second valve member
62 returning along with the second diaphragm
42
is seated on the second valve seat
61 and hence, the communication between
the float chamber
12a and the fuel nozzle
13 is cut off.
The arrangement of the other components is basically not different from that
in the first embodiment and hence, portions or components corresponding to those
in the first embodiment are designated by the same reference symbols and numerals
in FIG. 13 and the description of them is omitted.
Finally, a fourth embodiment of the present invention shown in FIG. 14 will
be described below.
An engine E is constructed into a horizontal type with a crankshaft
2
disposed
horizontally. A cylinder block
5 connected to one side of a crankcase
1
supporting the crankshaft
2 is disposed in such a manner that it is inclined
at an angle which is nearly horizontal, and a carburetor C is mounted to one side
of a cylinder head
6 coupled to the cylinder block
5.
A fuel tank T is mounted on an upper portion of the crankcase
1, and a
composite
control valve V is mounted to a bottom surface of the fuel tank T. In this composite
control valve V, a fuel strainer
79 projectingly mounted on an internal
bottom surface of the fuel tank T is connected directly to a fuel introducing pipe
70. An inner air vent pipe
23 extending vertically through the fuel
tank T opens at its lower end directly into an atmospheric air introducing recess
49′ which corresponds to the atmospheric air introducing pipe
49
in the first embodiment and which is formed in a valve housing
40.
The inner air vent pipe
23 also opens at its upper end into a threadedly
engaged portion between a tank cap
21 and an oil supply port tube
20
of the fuel tank T, and the inner air vent pipe
23 communicates with an
upper space
3 in the fuel tank T through a spiral clearance existing at
such a threadedly engaged portion. The spiral clearance functions as a gas-liquid
separating means to inhibit the entrance of a waved fuel in the fuel tank T into
the inner air vent pipe
23.
A fuel conduit
71 leading to a fuel chamber
46 in the composite
control
valve V is connected directly to a fuel inlet in the carburetor C.
The arrangement of the other components is similar to that in the first embodiment
and hence, portions and components corresponding to those in the first embodiment
are designated by the same reference symbols and numerals in FIG. 14 and the description
of them is omitted.
The present invention is not limited to the above-described embodiments, and
various modifications in design maybe made without departing from the subject matter
of the invention.
*
