JP2002098005A - Carbretor having diaphragm fuel pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce liquid fuel collecting in the pressure pulse chamber of the diaphragm fuel pump of a carburetor. SOLUTION: A fuel pump diaphragm held by the body of the carburetor forms a fuel chamber to receive fuel on its one side, and forms a pressure pulse chamber on the other side. The pressure pulse chamber is in communication with an engine, and receives a pressure pulse to actuate the fuel pump diaphragm. Thereby, the fuel is drawn in the carburetor, and the pressurized fuel is sent to a fuel metering assembly in the downstream. An air passage is provided, its one end is connected to an air source, and the other end is connected to the pressure pulse chamber. Airflow is supplied to the pressure chamber, and liquid fuel in the pressure chamber is scavenged, removed and dissipated, or air is mixed in it, in order to avoid the liquid fuel collecting there.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carburetor, and more particularly to a carburetor having a diaphragm type fuel pump.

[0002]

BACKGROUND OF THE INVENTION Carburettors have recently been used to supply fuel for combustion to a wide range of two- and four-stroke engines, such as hand-held engines such as chain saws and trimmers, and marine engines. Diaphragm carburetors are particularly useful in hand-held engine applications where the engine is operated in almost any posture, including upside down. These carburetors use a fuel metering diaphragm to regulate the delivery of fuel from the carburetor regardless of its position. Some carburetors use a diaphragm fuel pump that responds to engine pressure pulses to draw fuel from a fuel tank and deliver pressurized fuel to a fuel metering assembly.
The diaphragm of the fuel pump forms a fuel chamber for receiving fuel on one side and a pressure pulse chamber on the other side. The pressure pulse chamber receives a pressure pulse that communicates with the engine and activates the fuel pump diaphragm.

[0003] In a two-stroke engine, a pressure pulse chamber, usually leading to a crankcase, receives alternating positive and negative pulses to operate a fuel pump diaphragm.

In a four-stroke engine, a pressure pulse chamber communicates with the engine intake manifold to move the fuel pump diaphragm by its pronounced negative pressure. The pressure waves from the intake manifold include fuel vapor, which may be condensed into liquid fuel and liquid fuel flowing into the pressure pulse chamber. Unfortunately,
This liquid fuel is discharged directly into the engine intake manifold when the direction of the carburetor changes,
When the engine speed rapidly changes from the open throttle state to the idling state, the engine is rapidly pulled.
As a result, the fuel inside the engine becomes excessively rich,
Particularly in an idling state, the stability of the engine is adversely affected, and the engine may stall. In addition, the entry of liquid fuel into the pressure pulse chamber adversely affects the performance of the fuel pump. These problems are particularly pronounced in small four-stroke engines, where the fuel and air mixture delivered to the engine is significantly more sensitive to being richer than predetermined.

[0005]

With respect to the carburetor, at least during idling of the engine, fuel lumps are discharged into the intake manifold by reducing or eliminating the accumulation of liquid fuel in the pressure pulse chamber of the diaphragm fuel pump. Try to avoid
Allow the carburetor to operate in almost any posture.

[0006]

SUMMARY OF THE INVENTION A fuel pump diaphragm is held in the body of a carburetor for a four-stroke engine, the fuel pump diaphragm forming a fuel chamber on one side for receiving fuel and a pressure chamber on the other side. Form a pulse chamber. The pressure pulse chamber receives a pressure pulse that communicates with the engine and activates the fuel pump diaphragm. This draws fuel into the carburetor and delivers pressurized fuel to a downstream fuel metering assembly. An air passage is provided, one end of which communicates with the air source and the other end of which communicates with the pressure pulse chamber to supply an air flow to the pressure pulse chamber and scavenge, remove, dissipate, or remove liquid fuel within the pressure pulse chamber. Entrain air to avoid accumulation of liquid fuel there.

In one embodiment, a throttle valve held on the carburetor body moves between an idle position and a wide open position to control the flow of fluid through its air passage as a function of the throttle valve position. Preferably, the air passage is open when the throttle valve is in the idling position to supply airflow to the pressure pulse chamber to prevent liquid fuel from accumulating in the pressure pulse chamber,
Prevent liquid fuel from discharging from the pressure pulse chamber to the engine intake manifold. During engine idling, the negative pressure transmitted to the pressure pulse chamber is large, so the amount of air flowing from the air passage to the pressure pulse chamber is
It does not significantly affect fuel pump performance. Conversely,
With the throttle wide open, airflow into the pressure pulse chamber adversely affects fuel pump performance. This is because, in the wide open state of the throttle, significantly more fuel is required to satisfy the engine fuel demand than at the time of the eye drink. Therefore, it is desirable, at least in some applications, to close the air passage as the throttle moves to its wide open state to avoid adverse effects on the diaphragm fuel pump. At high engine speeds, the accumulation of liquid fuel in the pressure pulse chamber and discharge from it to the engine does not stall the engine. This is because the engine is more tolerant of a rich fuel mixture when it is operating at high speed with its throttle wide open.

An object, feature, and convenience of the present invention includes providing a carburetor most suitable for a small four-stroke engine, and the carburetor is provided at least during idling operation of the engine in a pressure pulse chamber of a diaphragm type fuel pump. The engine is started and operated by the rich fuel / air mixture necessary for starting and warming up the engine, reducing or eliminating the incorporation of liquid fuel into the air, avoiding fuel lumps to be discharged to the intake manifold. Increases the possibility of driving in almost any posture, does not significantly affect the performance of the fuel pump, stabilizes the fuel pump performance, improves idling operation and engine stability, and switches the engine from idling operation to wide open throttle operation Eliminates engine stall when changing rapidly to
It is applicable to almost any carburetor design, has a relatively simple design, is economical to manufacture and assemble, is robust, reliable and durable, and has a long useful life.

These and other objects, features, and conveniences of the present invention are set forth in the detailed description of the preferred embodiments, the claims,
It becomes clear from the attached drawings.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings in greater detail, FIGS. 1 and 2 illustrate a rotary throttle valve carburetor 10 which includes a fuel pump 12 having a diaphragm 14.
Is provided. The diaphragm 14 partially forms a fuel chamber 16 on one side and the pressure pulse chamber 1 on the other side.
8 is formed. An air passage 20 is provided, one end of which communicates with the supply side of fresh air, and the other end of which communicates with the pressure pulse chamber 18 to direct an air flow to the pressure pulse chamber 18 where liquid fuel accumulates. To reduce or eliminate. Eliminating the accumulation of liquid fuel in the pressure pulse chamber 18 allows the attitude of the carburetor 10 to be changed, allowing the fuel mass that is extremely detrimental to small four stroke engine operation to be expelled from the pressure pulse chamber 18 to the engine intake manifold. Without it, the engine speed can be rapidly reduced from a wide open throttle state to an idling state. Preferably, when the throttle valve 22 moves from the idling position to the wide open position, the air passage 20 is closed to prevent airflow from entering the pressure pulse chamber 18 in the wide open throttle condition. The performance of the fuel pump 12 is not adversely affected.

The carburetor 10 has a main body 24,
A fuel / air mixing passage 26 passing therethrough is formed.
A throttle valve 22 is disposed in the fuel / air mixing passage 26. The throttle valve 22 has a through-bore 28, and when the throttle valve 22 moves between the idling position and the wide open position, the through-bore 28 is selectively aligned with the fuel / air mixing passage 26 so that the carburetor 10 Regulate the flow of air and fuel through. Throttle valve 2
2 is a generally cylindrical shaft 29 rotatably received in a complementary bore 30 in the generally laterally extending main body 24 of the fuel / air mixing passage 26. The throttle valve 22 has a supply plate 32 at one end. The plate 32 extends generally radially outward and engages a cam post or ball 34 held on a throttle valve plate 36 of the main body 24. The plate 32 has a generally inclined cam surface or ramp 37 to move the throttle valve 22 axially as the throttle valve 22 rotates between an idle position and a wide open position. This axial movement of the throttle valve 22 moves the needle 38 held by the throttle valve 22 with respect to the fuel outlet 40 held by the main body 24 to reduce the size of the orifice 42 of the fuel outlet 40. change,
Thereby, the amount of fuel discharged from the orifice 42 is adjusted, at least in part. For calibration, the needle 38 is preferably screwed into a complementary bore 44 in the throttle valve 22 and the needle 3
8 is rotated to change its position with respect to the throttle valve 22. After initial calibration, a spherical ball or plug 46 is press-fit into the complementary bore 44 to prevent entry into the needle 38.

The throttle valve plate 36 abuts on the throttle valve 22 and encloses the coil spring 48 so that the throttle valve 22 is axially downwardly moved in the inner hole 30 as shown in FIGS. Applying force to move. The annular flexible seal 50 is used for the throttle valve 2
2, which provides a liquid tight seal between the throttle valve 22 and the throttle valve plate 36.
The idling adjustment screw 52 is connected to the throttle valve plate 36.
And abuts a radially outwardly extending flange 54 secured to the throttle valve 22 to ensure that the throttle valve 22 is in the proper idle position. As described above, the throttle valve 22, the throttle valve plate 36, and the fuel injection port 40 may have a conventional structure, and regulate the fuel and air flow passing through the carburetor 10.

The fuel pump 12 includes an end plate 60 and a main body 2.
4 with a diaphragm 14 trapped between them. A gasket 62 is preferably inserted and disposed between the diaphragm 14 and the main body 24. A fuel inlet fitting 64 is press-fit into the end plate 60 and passes the fuel chamber 16 through an internal passage 66 in the main body 24 to a flap-type inlet valve 68 which is preferably integral with the diaphragm 14 to provide fuel. Prevent backflow. Fuel flowing through the flap-type inlet valve 68 enters a fuel chamber 16 formed in part by the diaphragm 14. Fuel from the fuel chamber 16 flows through an outlet valve 70. Outlet valve 70
Is preferably a flap-type valve integral with the diaphragm 14. From there, fuel flows to a conventional fuel metering chamber assembly 72. The fuel metering chamber assembly 72 includes a fuel metering diaphragm 74, a fuel metering chamber 76, and a diaphragm adjusting inlet valve 78. Diaphragm adjustment inlet valve 78 selectively permits flow of fuel into fuel metering chamber 76. From the fuel metering chamber 76, fuel responds to the pressure differential across the fuel outlet 40, as before, to the fuel outlet 40,
Then, it flows to the fuel / air mixing passage 26. Fuel metering chamber assembly 72 is disclosed in U.S. Pat. No. 5,711,901, the entire disclosure of which is incorporated herein by reference.

A pressure pulse chamber 18 is formed on the other side of the diaphragm 14 and communicates with the engine manifold via a pressure pulse passage 80. Thereby, engine pressure pulses from the intake manifold lead to the pressure pulse chamber 18 and change the pressure there. Particularly in a four-stroke engine, the pressure pulse has a significantly greater negative pressure, causing the diaphragm 14 to move in a direction to increase the volume of the fuel chamber 16 and draw fuel therein. A spring 82, preferably a coil spring, exerts a force in the front-rear direction to move the diaphragm 14 in a direction to reduce the volume of the fuel chamber 16 and discharge pressurized fuel from the fuel chamber 16. As described above, the movement of the diaphragm 14 pulls the fuel into the carburetor 10 and moves the pressurized fuel to the fuel metering chamber assembly 7.
2, and can be used by the engine according to the fuel demand of the engine.

According to the present invention, an air passage 20 is provided, one end of which communicates with the fresh air side, and the other end of which communicates with the pressure pulse chamber 18 to supply air to the pressure pulse chamber 18 so as to supply air to the pressure pulse chamber 18. Dissipates liquid fuel,
Aeration, scavenging, or removal prevents liquid fuel from collecting there. The pressure pulse passage 80 is
, For example via an outer conduit extending directly from the location downstream of the air filter to the pressure pulse chamber 18. The air passage 20 is guided from the downstream point of the air filter to the internal point 84 of the main body 24,
Communicates with the pressure pulse chamber 18 to direct air there. An air passage 20 opens into the pressure pulse passage 80 and communicates with the pressure pulse chamber 18. Preferably, air from the air passage 20 enters the pressure pulse chamber 18 and exits through the pressure pulse passage 80 of the pressure pulse chamber 18 at the same location. Its position is preferably near the lowest point of the pressure pulse chamber 18 with respect to the standard operating position of the carburetor as indicated by the arrow 86 in FIGS. By supplying air to the lowest point of the pressure pulse chamber 18 in the normal operating position of the engine, liquid fuel accumulated at the lowest point of the pressure pulse chamber 18 is dissipated, scavenged, vented, and reduced from the pressure pulse chamber 18. Or be removed.

As seen in FIG. 1, a portion of the air passage 20 preferably extends through a bore 30. When the throttle valve 22 is in the idling position, it is spaced from the air passage 20 and air flows through the air passage 20 to the pressure pulse chamber 18. However, as seen in FIG. 2, when the throttle valve 22 is rotated and moved axially to the wide open position, the cylindrical upper portion 87 of the throttle valve 22 blocks the air passage 20 and at least passes therethrough. Restricts flow significantly. Thus, the throttle valve 22 also functions as a second valve that regulates airflow through the air passage 20 in addition to regulating flow through the fuel / air mixing passage 26. Stopping air from flowing from the air passage 20 to the pressure pulse chamber 18 in the wide open position prevents reducing the pressure pulse driving the diaphragm 14 and, at maximum engine fuel demand, with the throttle wide open, Fuel pump 12
Does not adversely affect the pumping capacity of the pump. In the idling state of the engine, a strong negative pressure wave is supplied to the pressure pulse chamber 18, and the air flow through the air passage 20 does not significantly affect the pumping ability of the fuel pump 12.
The fuel required by the engine during idling is
Much less than required for wide throttle operation.

A second embodiment of the carburetor 100 is shown in FIGS. In the carburetor 100, the air passage 102 has one end thereof and the fuel / air mixing passage 2
6 and to the pressure pulse passage 80 at the other end. The pressure pulse passage 80 is open to the pressure pulse chamber 18 and diverts some of the air flowing through the fuel / air mixing passage 26 to the pressure pulse chamber 18.
When the throttle valve 22 is in the idling position, as seen in FIG. 3, the air passage 102 is open, and as shown in FIG. 4, the throttle valve 22 is rotated to the wide open position. And almost closed as described in the embodiment of FIGS. Compared to the first embodiment of the carburetor 10, the fuel pump 12 is provided in the carburetor 100 at a slightly different position from the carburetor 10, and the fuel metering assembly is provided in the lower part (not shown) of the carburetor 100. . In all other respects, the carburetor 100 shown in FIGS. 3 and 4 is the same as that of FIGS. 1 and 2 and therefore will not be described further.

A carburetor 110 according to a third embodiment of the present invention is shown in FIG. The carburetor 110
3 and 4, except that the air passage 112 is not guided through the inner hole 30. That is, in this embodiment, the air passage 112 opens at one end into the fuel / air mixing passage 26 and opens directly at the other end into the pressure pulse chamber 18. The air passage 112 is open regardless of the position of the throttle valve 22, and always supplies air to the pressure pulse chamber 18 while the engine is running. In all other respects, the carburetor 110 comprises the carburetors 10, 1 of the first and second embodiments.
The configuration is almost the same as 00. Therefore, here
No further explanation is given.

FIG. 6 shows a carburetor 120 according to a fourth embodiment of the present invention. Carburetor 120
Has an air passage 122 configured similarly to that of the carburetor 110 of the third embodiment. The air passage 122 is always open regardless of the state of the throttle valve 22. In the air passage 122 of this embodiment, the pressure pulse passage 124
Has one end open to the fuel / air mixing passage 26 and the other end open to the pressure pulse chamber 18. Therefore, the engine pressure pulse is transmitted to the pressure pulse chamber 18 through the fuel / air mixing passage 26. Preferably, the pressure pulse passage 124 is located in the normal operating position of the carburetor, indicated by arrow 126 in FIG.
At the highest position of the air mixing passage 26, the fuel / air mixing passage 2
Open inside 6. The pressure pulse passage 124 communicates with the highest position of the fuel / air mixing passage 26 so that the liquid fuel
Air and fuel vapor are prevented from flowing from the air mixing passage 26 into the pressure pulse chamber 18, and air and fuel vapor are allowed to flow upward from the highest position in the fuel / air mixing passage 26 into the pressure pulse passage 124 before the pressure pulse chamber 18 To enter. Otherwise, the carburetor 120 of the fourth embodiment comprises:
It is configured similarly to the carburetor 110 of the third embodiment. Therefore, they will not be described further here.

The carburetor 130 of the fifth embodiment shown in FIG. Fuel pump 12
Functions similarly to the fuel pump 12 of the carburetor 10 of the first embodiment, draws fuel into the fuel chamber 16,
It is pressurized and discharged to the fuel metering chamber assembly 72. Fuel is drawn from the fuel metering chamber assembly 72 to the fuel / air mixing passage 26 of the carburetor 130 and sent to the engine. A throttle valve 132 is located in the fuel / air mixing passage 26 to regulate fuel and air flow through the carburetor 130. Throttle valve 13
2 is a shaft 1 rotatably held by the main body 24.
34, and a disk-shaped valve head 136 fixed to the shaft 134 with screws or the like. Throttle valve 132
Rotates between the idling position and the wide open position. In the idle position, the valve head 136 extends generally transverse to the axis of the fuel / air mixing passage 26.
In the wide open position, the valve head 136 is generally parallel to the axis of the fuel / air mixing passage 26.

An air passage 138 (illustrated) opens at one end into the fuel / air mixing passage 26 and at the other end into the pressure pulse chamber 18 of the fuel pump 12,
Air is supplied into the pressure pulse chamber 18 during at least some engine operating conditions to prevent liquid fuel from accumulating in the pressure pulse chamber 18. 7 (B), 7
As clearly shown in (C), a portion of the air passage 138 is formed by a hole 140 extending through the shaft 134. When the throttle valve 132 is at the idling position, as shown in FIG.
4 through holes 140 on both sides of shaft 134
Fluid flows therethrough in alignment with adjacent portions 142, 144 of air passage 138. Conversely,
As shown in FIG. 7C, the throttle valve 132
When fully rotated toward the wide open position, the hole 140 through the shaft 134 rotates to rotate the adjacent portion 14 of the air passage 138.
2, 144, which at least significantly restricts or prevents fluid flow through the air passage 138 to the pressure pulse chamber 18. The air passage 138 is shown in FIG.
Here, it is schematically shown and is shown outside the carburetor 130. But it is preferably the main body 2
4 formed by an internal passage. Anyway, first,
As with the carburetors 10 and 100 of the second embodiment, when the throttle valve 132 moves from its idle position to the wide open position, it closes the air passage 138 and restricts air flow to the pressure pulse chamber 18 at least substantially. I do. Other parts of the carburetor 130 of the fifth embodiment are configured and function substantially the same as the carburetor 10 of the first embodiment. Therefore, its configuration and function will not be further described.

As shown in FIG. 8, the present invention relates to a carburetor 1 having a sliding throttle valve 152.
50 is similarly applicable. The carburetor 150 is a sixth embodiment in which the throttle valve 152 has a generally cylindrical shaft 154. The shaft 154 is received in a complementary bore 156 in the main body 24 and slides axially with a suitable throttle lever to change the position of the throttle valve 152 with respect to the fuel / air mixing passage 26. At the idling position,
The generally frustoconical lower end 158 of the shaft 154
60 is formed to allow proper air flow through the fuel / air mixing passage 26. In the wide open throttle condition, the shaft 154 is pulled outward from the main body 24 and increases the flow cross-sectional area of the gap 160 so that the fuel and air in the fuel / air mixing passage 26 increase in proportion to the fuel demand of the engine. The flow of the water. The axial movement of the throttle valve 152 also affects the movement of the needle 162 held by the shaft 154.
Is moved relative to the valve seat 166 to regulate fuel flow into the fuel / air mixing passage 26 in a conventional manner.

As in the carburetor 10 of the first embodiment,
Air passage 168 leading the air source to pressure pulse chamber 18
Is directed through bore 156. Throttle valve 1
When 52 is in the idling position, as shown in FIG. 8, air passage 168 is opened to allow air to flow to pressure pulse chamber 18 and prevent liquid fuel from accumulating therein. When the throttle valve 152 is moved to the wide open position in the axial direction, the air passage 168 moves to the shaft 154.
This essentially prevents or significantly reduces air flow to the pressure pulse chamber 18 under wide open throttle engine operating conditions, essentially shut off or at least substantially restricted. Otherwise, the carburetor 150 of the sixth embodiment functions substantially the same as the previous embodiment. Therefore, they are not described here.

Therefore, the carburetors 10 and 1 of each embodiment
In 00, 110, 120, 130, 150, the air passages 20, 102, 112, 122, 138, 168
The fuel is removed from the pressure pulse chamber 18 through a pressure pulse chamber 18 of the fuel pump 12 to eliminate or reduce the accumulation of liquid fuel in the pressure pulse chamber 18. In one embodiment of the carburetors 110, 120,
The air passages 112 and 122 are connected to the carburetors 110 and 120.
It remains open regardless of the state of the throttle valve. Carburetor 10, 100, 13 of another embodiment
At 0, 150, the throttle valve or shaft partially configures or functions an airway valve, optionally allowing fluid to pass through the airways 20, 102, 138, 168 and into the pressure pulse chamber 18. Adjust for proper flow. Preferably, the air passages 20, 102, 138,
168 is left open during idling engine operation and the air path is closed by actuation of the throttle valves 22, 132, 152, at least in wide open throttle engine operation, with maximum engine fuel demand and negative pressure pulses generally. Prevents the pressure wave applied to the diaphragm 14 from being adversely affected by the minimum wide open throttle engine operation. The airway valve may, if desired, gradually close the airway when the throttle valve is rotated toward its wide open position, or the airway valve may be closed when the throttle valve is in its fully open position. You may close quickly, long before you reach. In the idling operation of the engine, a large negative pressure is transmitted to the pressure pulse chamber 18 and the fuel pump 12 needs to supply much less fuel than the throttle wide open state. Air supply does not have a significant adverse effect on engine operation.

Air passages 20, 102, 112, 122, 1
Air passages 20, 102, 11 to control the air flowing through the pressure pulse chamber 18 through the pressure pulse chambers 38, 168 in relation to the pressure pulses passing through the pressure pulse chamber 18.
The ratio of the minimum diameter of the pressure pulse passages 80, 124 to the minimum diameter of 2, 122, 138, 168 is 0.05:
1 and 1.5: 1, preferably 0.2
It is between 5: 1 and 1: 1. In a presently preferred form, the pressure pulse passages 80, 124 and the air passages 20,
The minimum diameter of 102, 112, 122, 138, 168 may be from about 0.01 to 0.2, respectively, depending on the application.
Can be changed between inches. Preferably, the air passages 20, 1
02, 112, 122, 138, 168 are smaller than the pressure pulse passages 80, 124 and the pressure pulse chamber 18
Minimize adverse effects such as reducing pressure pulse waves on the diaphragm within. The airways are always open,
Preferably, it may be closed by another valve driven by a throttle valve, or by the throttle valve itself, in which case the throttle valve will move when the throttle valve moves between the idling position and the wide open position. , Also functions as an air passage valve. If necessary,
Other valve types, rotary throttle valves, butterfly valves, or slide valves may be used for similar purposes.

For example, as shown in FIGS.
A check valve 200 is provided in air passage 202 to selectively close air passage 202 during certain engine operating conditions and when the engine is not operating. Preferably,
The check valve 200 is closed when the engine is not running, and the check valve 200 is also closed during the first cranking for starting the engine.
Is closed to stop the air passing through the air passage 202. As a result, since air does not flow through the air passage 202, more air flows through the fuel / air mixing passage 26 to supply a rich air-fuel mixture to the engine, thereby facilitating engine start. During engine idling and other low-speed, low-load operations simultaneously with engine startup, check valves 200 open in their engine operating conditions due to a relatively large pressure drop across check valve 200. As the engine speed increases in the direction of the wide open throttle, the check valve 200 closes due to the decreasing differential pressure across it. Preferably, in high speed, high load operation of the engine, the check valve 200 is closed to shut off the air supply from the fuel / air mixing passage 26 to the pressure pulse chamber 18 so that the fuel pump is Do not affect driving.

The check valve 200 may be another structure, such as a resiliently pressed ball 204 or other valve head seen in FIG. The check valve has a spring 206 trapped between a spring seat 208 and a ball 204 or valve head to provide a ball 20
4 is shifted to the valve seat 210 side. They are all provided in the air passage 202. As can be seen in FIG.
The check valve has a tongue-shaped valve element 212. The valve is calibrated to open at a predetermined differential pressure across the check valve. The check valve may be a flapper type check valve 214 as shown in FIG. 12, or the check valve may be pressed by a spring if necessary. As shown in FIG. 3, the check valve may be a solenoid valve 215. The solenoid valve is a coil 21
6 and a switch that is activated in response to movement of a throttle valve or a plunger 217 in response to a signal supplied from an ignition system. Alternatively, the solenoid valve operates in response to the speed of the engine. Also, as illustrated in FIG. 14, the check valve may have a capillary 218. The thin tube 218 is a heat sensor bulb 2 provided on an engine cylinder or an engine exhaust device such as an engine muffler.
Leads to 20. The thermal sensor bulb 220 can move the valve head 222 relative to the valve seat 224 to control the flow of air through the air passage 202 as described in other embodiments. Of course, additional valves or other fluid control mechanisms may be used to control the flow of fluid through air passage 202 as appropriate.

As a result, each check valve has an air passage that moves between open and closed positions, selectively communicating the air supply side to its pressure pulse chamber. Each valve or other flow control mechanism can close the air passage 202 to facilitate starting the engine. The check valve is preferably open in idling and other low speed, low load engine operating conditions where there is sufficient differential pressure before and after it, while in high engine operating conditions, the differential pressure is small. Is closed.
Preferably, this provides air to the pressure pulse chamber 18 at low engine speeds, while at high engine speeds where the fuel pump requires more fuel and it is not desirable to reduce the pressure wave that operates the fuel pump. Turn off the air flow.

[0029]

The carburetor according to the present invention reduces or eliminates the accumulation of liquid fuel in the pressure pulse chamber of the diaphragm type fuel pump, at least when the engine is idling, and prevents the fuel mass from being discharged to the intake manifold. be able to. Thereby, the idling operation and the stability of the engine are improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a carburetor according to an embodiment of the present invention, in which a rotary throttle valve of the carburetor is in an idling position.

FIG. 2 is a schematic sectional view of the carburetor shown in FIG. 1, in which a rotary throttle valve is in a wide open state.

FIG. 3 is similar to the carburetor shown in FIGS.
FIG. 4 is a cross-sectional view of a slightly modified carburetor, illustrating a second embodiment of the present invention, with the rotary throttle valve in an idle position.

FIG. 4 is a schematic sectional view of the carburetor shown in FIG. 3, in which a rotary throttle valve is in a wide open state.

FIG. 5 is a transverse sectional view of a carburetor according to a third embodiment of the present invention.

FIG. 6 is a sectional view of a carburetor according to a fourth embodiment of the present invention.

FIG. 7A is a schematic sectional view of a carburetor according to a fifth embodiment of the present invention, and the carburetor has a butterfly type throttle valve. FIG. 7 (B)
FIG. 7 is an enlarged cut-away sectional view illustrating a throttle valve shaft of the carburetor of FIG. 7A, and the carburetor is in an idling position. FIG. 7 (C)
FIG. 2A is an enlarged cut-away sectional view illustrating a throttle valve shaft of the carburetor of FIG.

FIG. 8 is a schematic sectional view of a carburetor according to a sixth embodiment of the present invention, the carburetor having a sliding throttle valve.

FIG. 9 is an illustrative sectional view of a carburetor according to a seventh embodiment of the present invention.

FIG. 10 is an enlarged cut-away sectional view illustrating a check valve that may be used in the carburetor of FIG. 9;

FIG. 11 is an enlarged cut-away sectional view illustrating another check valve that may be used for the carburetor.

FIG. 12 is an enlarged cutaway view illustrating yet another check valve that may be used for the carburetor.

FIG. 13 is an enlarged cut-away sectional view illustrating yet another check valve that may be used for the carburetor.

FIG. 14 is an enlarged cut-away sectional view illustrating yet another check valve that may be used for the carburetor.

[Explanation of symbols]

10, 100, 110, 120, 130, 150 Carburetor 12 Fuel pump 14 Diaphragm 16 Fuel chamber 18 Pressure pulse chamber 20, 102, 112, 122, 138, 168 Air passage 22 Throttle valve 24 Main body 26 Fuel / air mixing passage 38 Needle 40 Fuel injection port 42 Orifice 68 Inlet valve 70 Outlet valve 80 Pressure pulse passage 200 Check valve

Continuing on the front page (72) Inventor Thomas El Schmidt United States Michigan 48726, Kas City, Ekas City Road 3289

Claims (10)

[Claims] 1. A carburetor, comprising: a body; a fuel pump diaphragm held by the body; and a fuel pump diaphragm formed on one side thereof and a pressure pulse chamber formed on the other side thereof. The pressure pulse chamber communicates with a pressure pulse source to transmit a pressure pulse for operating the fuel pump diaphragm to the pressure pulse chamber; and an air passage, one end of which has an air source. And the other end communicates with the pressure pulse chamber to supply air to the pressure pulse chamber and reduce at least the liquid fuel accumulated in the pressure pulse chamber. 2. The carburetor according to claim 1, wherein the other end of the air passage communicates with a lowest position of the pressure pulse chamber in a standard operation posture of the carburetor. 3. An air passage valve held in the body, the air passage valve communicating with the air passage, and allowing a passage of air through the air passage, and the air passage valve. 2. The carburetor of claim 1, wherein the carburetor is movable between at least a second position that restricts air passing therethrough. 4. The carburetor has a throttle valve held on the body, the throttle valve moves between an idling position and a wide open position, and the air passage valve is actuated by the throttle valve. 4. The air passage valve is in the first position when the throttle valve is in the idling position, and the air passage valve is in the second position when the throttle valve is in the wide open position. The carburetor described. 5. A carburetor according to claim 4, wherein said air passage valve is formed in part by said throttle valve. 6. A fuel / air mixing passage formed through the body, the fuel / air mixing passage having one end communicating with the low pressure source and the other end communicating with the air supply side, and a pressure pulse passage. The carburetor according to claim 1, wherein the pressure pulse passage has one end communicating with the pressure pulse chamber and the other end communicating with the pressure pulse source. 7. The carburetor according to claim 5, wherein said pressure pulse passage communicates with said fuel / air mixing passage at the highest point of said fuel / air mixing passage in a standard operating posture of said carburetor. 8. The carburetor according to claim 3, wherein the air passage valve has a check valve for selectively stopping the passage of the pressure pulse chamber to an air supply side communicating with the air passage. 9. The carburetor according to claim 8, wherein the check valve is configured such that the air supply side is not connected to the pressure pulse chamber when the engine is not operating and when the engine is first started. 10. A fuel / air mixing passage formed at least partially within the body, and a throttle valve, wherein the throttle valve moves between an idle position and a wide open position to provide the fuel. The carburetor according to claim 3, wherein the carburetor controls a flow of a fluid through the air mixing passage, wherein the air passage valve is provided separately from the throttle valve and is disposed in the air passage.