JPH03151557A - Method and device for measuring fuel for internal cumbustion engine - Google Patents

Abstract

PURPOSE: To enhance the control stability of the carburetor of a small internal combustion engine suited for a chain saw and the like by sensing the dynamic and static components of engine-tuned pressure waves applied to airflow in a venturi, and applying them to the diaphragm of a fuel metering mechanism. CONSTITUTION: This carburetor 20 has, in a principal main body 22 to which a top cover 24 and a bottom cover assembly 26 are joined, a metering chamber 56 into which fuel discharged from a fuel pump is introduced via a passage 50, a filter 52, and a passage 54. The metering chamber 56 is separated from a vent chamber 62 by a diaphragm 60 and the passage 54 is opened and closed by a valve 58 connected to the diaphragm 60 via a lever 64. A principal fuel nozzle outlet 70 which opens into the venturi 42 of the carburetor is communicated with the metering chamber 56 via a fuel path having a high speed needle valve 36. The diaphragm 60 is driven by venturi negative pressure introduced into the vent chamber 62, the pressure coming from a pitot tube 80 projecting into the venturi 42.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates to fuel metering for engines using carburetors, and in particular for engines such as chainsaws, lawn mowers and other powered lawn or garden portable tools. The present invention relates to a small diaphragm type or float-based carburetor for small internal combustion engines such as those used in equipment and small off-road sports cars.

[Problem to be solved by the invention]

Fuel flow in diaphragm carburetors is dependent on the pressure differential that exists between the venturi of the carburetor and the atmosphere. Venturi pressure depends on engine design features and operating conditions. Diaphragm carburetors generally include a mixture tube that mixes fuel and air for delivery to the engine's intake manifold, and a mixture tube that is closed by a diaphragm and delivers the fuel through a nozzle. A communicating fuel chamber,
and a diaphragm-controlled valve arrangement for controlling the delivery of fuel from the fuel tank to the fuel chamber. An air filter is provided to purify the air entering the mixture tube. A restriction, such as a venturi, is formed in the prototube. When the engine is running, air flows through the mixture tube, creating a pressure drop across the venturi (i.e., creating a vacuum inside the venturi), and the pressure on the outside of the diaphragm causes the diaphragm to deflect inward, creating a maximum pressure drop. Fuel is delivered through a nozzle normally located in the throat of the venturi, and the deflection of the diaphragm causes a valve arrangement to open and deliver fuel to the fuel chamber.

As is well known, the fuel metering characteristics of the carburetor are often adversely affected by engine intake tuning, especially in the case of single cylinder engines with relatively wide speed ranges. Engine intake tuning causes the carburetor to deliver fuel to the airstream at an inaccurate rate, due to the instability of the airflow through the carburetor and due to This is due to the influence of the pressure waveform. Such waveforms are caused by the opening and closing of engine intake valve(s) or port(s) and traveling at the speed of sound, and their behavior will be apparent to those skilled in the art.

The effect of a moving pressure waveform on fuel exiting a carburetor nozzle is a perennial source of problems for carburetor design engineers. The wave effect is superimposed on the normal vacuum created by the engine's intake air flow through the venturi. That is, it is caused by the delivery of fuel from the nozzle without adequately responding to the vacuum created by the air. If the pressure drop P in the main jet (some distance from the nozzle exit in the venturi) is proportional to the square of the airflow density and velocity, i.e. 8P
= ρV”/2, the carburetor functions normally. The harmonic wave overlaps with the pressure drop of the venturi and has an adverse effect on the fuel metering section designed according to the above relationship. In particular, this harmonic wave affects the fuel delivery of the main jet. This adversely affects the desired design value of the pressure drop ΔP in the primary nozzle fuel control restriction.

Such tuned waves, i.e. air pressure waves created in the carburetor mixture line by the sudden opening and closing of the engine intake port, may be caused by certain engine operating conditions and certain abnormal conditions, as well as by changes in the ratio of fuel to air relative to engine speed. Determining the desired engine-carburetor performance curve in such a way that fuel is ``spitted back'' or under conditions that result in an unrecognized deviation from the carburetor performance curve (e.g. undesirable ``over- or under-points'' in the performance curve). It has been found to be the cause of well-known problems such as problems related to parameters such as fuel consumption, engine power, consumables, etc.

Another well-known problem that adversely affects the desired or designed fuel metering characteristics of a carburetor, whether diaphragm or float type, is the intake filter, which is typically located in front of the air inlet to the mixture tube of the carburetor. gradually become clogged with dust, dirt, and/or other airborne solid particles.

It is therefore a principal object of the present invention to improve the air-to-fuel ratio by eliminating or improving the negative effects on the pressure drop in the main jet or other controlling fuel restriction supplying the carburetor venturi. It is an object of the present invention to provide a fuel metering system, apparatus, and method for a carburetor of the type described above that maintains the same.

Another object of the present invention is to act as a venting device for the "dry" side of the diaphragm chamber and to effectively function to prevent or eliminate the negative effects on air filter clogging problems so as to maintain a predetermined air-fuel ratio. An object of the present invention is to provide an improved vaporizer including said device.

A further object of the present invention is to provide a method and apparatus for a fuel metering system having the characteristics described above and which is applicable to float type carburetors as well as diaphragm type carburetors.

Yet another object of the present invention is to utilize the effect of the harmonic wave to effectively adjust a fuel metering device, so that the mixture can be used sparingly in the economic domain and more in the power amplifier domain. It is an object of the present invention to provide a fuel measuring device and method having the above-mentioned characteristics, in which the effect can be adjusted by a method that allows for adjustment of the effect.

[Summary of the invention]

In summary, it is an object of the present invention to sense the dynamic and static components of an engine-tuned pressure wave imposed on the airflow within the venturi of a carburetor and to adjust the components so that the pressure waves are better imposed on both sides of the diaphragm. The negative effects of pressure waves are mainly eliminated by directing the pressure to the lower side (the "dry" side) of the diaphragm, leaving only the desired pressure drop ΔP acting between the diaphragm fuel chamber and the main nozzle of the venturi. This is accomplished by providing a diaphragm vaporizer with a vent passageway that further includes: This is accomplished by having one end of the vent passage communicate with the dry side of the diaphragm chamber and the other end of the vent passage communicating with the carburetor venturi via a special air pressure sensing pitot tube, in which case the pitot The tubes are oriented and positionable in a predetermined manner relative to the suction airflow and the main fuel nozzle outlet so that the liquid tubes and fuel nozzles are subjected to the same synchronized pressure waves at the same time.

Alternatively, the pitot tube of the vent passage and the main fuel nozzle opening may be slightly staggered with respect to each other in the venturi passage by a predetermined amount forward or aft in the direction of wave transmission in the carburetor throat bore. It is also possible to establish a leading or trailing wave collision relationship between the two venturi openings. Therefore, based on the predetermined spacing displacement direction and amount between the pitot tube and the main fuel injection nozzle,
In order to improve the efficiency of using relatively small amounts of mixture in the economic zone and relatively large amounts of mixture in the power-up zone, the effect of pressure waves on the measured pressure drop can be A phase shift is formed.

Similarly, in the case of a float-shaped carburetor, the one end of the vent passage is communicated with the fuel reservoir in the float chamber or the head space of the tank, but in this case, the fuel surface and internal float are considered to be equivalent to a diaphragm. , the headspace of the float chamber is treated as a "dry side" chamber.

[Examples and effects]

Other features and advantages of the invention will be described in detail below with reference to the accompanying drawings, which illustrate embodiments of the invention by way of non-limiting example and are drawn to scale unless indicated.

In further detail with reference to the accompanying figures, FIG. 1 shows a diaphragm carburetor designed for use in a chainsaw engine and including a presently known preferred embodiment for implementing the fuel metering device of the present invention. Twenty examples are shown. Except as described below, the vaporizer 20 is of known construction with conventional technical characteristics. The main body 22 of the vaporizer 20 has a top cover or cap plate 24 secured to the top surface thereof;
and a bottom cover assembly 26 secured to the lower surface.

The side view of FIG. 1 shows a choke shaft 28, a throttle shaft 3
0, throttle stop arm 32, throttle stop adjustment screw 34, high speed needle valve 36, and low speed needle valve 38 are shown.

As best seen in FIGS. 2 and 5, it includes a mixture tube or bore 40 and a venturi restriction 42 within the bore. The choke valve 44 is attached to the choke shaft 28 and is located at an inlet (inside the choke bore) leading to the bore 40 upstream of the venturi 42 and located in the bore 40 (throttle bore) downstream of the venturi 42. The throttle shaft 30 is provided with a throttle valve (not shown).

As will be apparent to those skilled in the art, the carburetor is supplied with fuel by a pump (not shown) formed by a component located between the cover 24 and the body 22. The outlet of the fuel pump is connected via a passage 50 and a filter screen 52 to a passage 54 leading to a metering chamber 56 of the carburetor. aisle 5
4 needle valve 58 is controlled by a diaphragm 60 located between the metering or "wet" chamber 56 and the vent or "dry" chamber 62. The diaphragm 60 is spring-loaded in a direction to move the valve 58 to the closed position. A lever 64 energized by 66 connects to valve 58 .

The main fuel nozzle outlet lower 0 opens into the carburetor venturi 42 and, conventionally, its axis is oriented perpendicular to the axis of the venturi 42 and to the direction of the intake air flow in the bore 40. Essentially, therefore, only the static pressure of the airflow is sensed by the nozzle 70.

The nozzle 70 is connected via a main fuel metering device to the metering chamber 56 via a fuel passage network having an adjustable high speed needle valve 36 which supplies the nozzle outlet 70 through a capillary sealing screen 75. fuel tank 7
4 through the network.

Preferably, the high speed needle valve 36 is a temperature compensated needle valve and serves as the primary fuel metering and restriction section, as described by Woody and Sw.
Anson, 1988 July 1988 by the applicant.
Consisting of the specification and claims of U.S. Pat.

According to a main feature of the carburetor according to the invention, the carburetor 20 is provided with improved and/or eliminated effects of the tuned pressure wave transfer venturi 42 that adversely affect the metering function of the needle valve 36 and the cooperating passageway 72. Provide a vent passage device that operates in the same manner.

The vent passage interconnects the specially designed pressure sensing boat within the venturi 42 and the dry side chamber 62.

Next, in FIGS. 5 and 6, a venturi 42 is connected to the air flow drawn through the bore 40 by the intake air of the engine.
The pitot tube protrusion 80 extends through the main body 22.
It is integrally molded with. The protrusion 80 has a flared section 82 defined by an integral hood 84 leading to a short inlet passageway 86.
has. The axis 86 of the passageway 86 is parallel to the axis of the bore 40 so that the mouth 82 faces directly upstream to airflow through the bore 40. Mouth 82 defines the end of the vent passage system that communicates with the throat of the carburetor. Passage 86 defines a blind bore that connects near its blind end with a passage 88 , the axis of which is perpendicular to the axis of blind bore section 86 . The passageway 88 merges with a coaxial bore closed at the outer end by a press-fit ball 91. In the aisle 90,
As best seen in FIG. 7, it is traversed by a rectangular passageway 92 (shown schematically in dotted lines in FIG. 5) that opens into a bottom surface 94 of body 22. The passage 92 is connected to the bottom cover 26 (910th and 1st
The passage 96 communicates with the passage 96 formed in Figure 1).
8 and 100, it is connected to the dry side chamber 62. aisle 10
0 constitutes the opposite end of a vent passage device that communicates with the dry side of the diaphragm metering chamber 62.

In accordance with the present invention, it has been found that the inlet 82 of the vent passage communicating with the bore 40 must be located in the plane of the circle defined by the venturi 42, which also includes the outlet of the nozzle 70. It has also been found desirable to form the inlet to the vent passage as a pitot tube having a flare 82 and a hood 84 as shown in FIG. 5.6. Additionally, the axis of the inlet passageway 86 is aligned with the bore 40.
It should preferably be located in a zone in the face of the venturi where the airflow velocity within and through the venturi 42 is at its maximum under engine operating conditions with the choke valve 44 fully open.

Thus, as can be clearly seen in FIG. 5, when the carburetor 20 is provided with a choke valve plate 44 that cooperates with the choke shaft 28,
Opening 86 is generally centered in a chord tooth segment defined by a portion of venturi 42 between shaft 28 and nozzle 70 and the lower edge of shaft 28 . Similarly, shaft 28
The diametrically opposed chord tooth segments on the plane are selectable for positioning the pitot tube projection 80, while the mounting for the choke plate 44 is such that the head of the stud 102 is aligned with the corresponding part of the choke shaft 28. Said chord tooth zone, which is closer to the nozzle 70 because of its slight lateral protrusion, is selected as a preferred example of the special structure of the invention. If the carburetor 20 is not provided with a choke valve 44 cooperating with the choke shaft 28, the axis of the inlet 86 of the pitot tube 80 will be at the venturi 4 since the air flow velocity is maximum at the center of the unobstructed venturi.
2 (and bore 40). In the operating embodiment shown here, the interconnecting passages 86, 88, 90, 92.96° 98 and 10
The overall axial length of 0 is 0.336 inches (0.85
3 centimeters), and the passageway diameters range from about 0.049 inches (0.124 centimeters) to about 0.062 inches (0.062 centimeters), respectively.
, 157 cm), and the diameter of the venturi 42 is 0.54
6 inches (1,387 cm), diameter of shaft 28 is 0.1
Preferably, the axis of passage 86 is 0.095 inches (0.241 cm) from the nearest point on the surface of venturi 42.

The carburetor 20 is provided with a choke valve 44 and the pitot tube 80 is located immediately downstream of the valve 44 so that, according to another feature of the invention, when starting to close the choke valve, i.e.
After an initial 5° rotation of the choke shaft 28 from the fully open position shown, the "cutoff" of the effect of the vent passages 82-100
A branch passage device will be provided to allow the water to escape. This "close-off" branch passage includes a slot or flat 104 formed in the shaft 28 (FIG. 4), one end of which is connected to the carburetor bore 40.
from the bore 40 into the body 22 a distance sufficient to extend axially of the shaft 28 into selective alignment with a passageway 106 formed in the body 22 in response to rotation of the shaft 28 . Extend. The intersection of the bore 108 receiving the choke shaft 28 and the passage 106 is not aligned with the thrower 104 when the choke valve 44 is in the fully open position and after the first 5° rotation of the shaft 28 from the fully open position to the closed position. Then, it is positioned so that it begins to align with slot 104.

The passage 106 opens at the bottom surface 94 of the main body 22.
and FIGS. 8) and are connected to the passageway 96 by a cross passageway 110 formed in the bottom cover 26 and within the sealed gas ket 112 (FIGS. 4 and 11), which can be integrally molded with the diaphragm 60. The cover 26 is provided with raised ribs 114 (FIG. 10) to attach the gasket 112 to the top surface 11 of the cover assembly 26.
6 to assist in sealing the cross passage 110. Additionally, a recess or recess 118 may be provided within the gasket 112 to cooperate with the rib 114 to sealingly connect the cross passageway 110. Similarly, the slot 104 in the choke shaft 28
Note that 8 faces upstream with respect to the airflow within bore 40 when in the closed state.

The apparatus and method of the invention will become apparent from the operation of the vaporizer 20 as described below. When the choke valve plate 44 is rotated from the fully closed position by the shaft 28 during engine startup, and a high vacuum is created in the bore 40 downstream of the choke plate, resulting in an appropriate startup fuel flow rate through the nozzle 70, the branch passage 104110 is activated. is fully open, so the vent passage 8
2-100 communicates with atmospheric pressure upstream of a closing choke plate (usually just behind the carburetor air filter, not shown). Therefore, the pressure wave transmission capability of the vent passages 82-100 becomes impossible, and the high vacuum immediately behind the choke plate in the vicinity of the pitot tube 80 cannot communicate with the dry side chamber 62 due to the branching effect of the branch passages 104-100. Become.

When the engine begins to run under its own power and the choke 44 rotates toward the open position, the branch passages 104-110 are separated from the slot 104 and passage 106 by the corresponding rotation of the shaft 28 within the bore 108. It is gradually closed by alignment. When the choke 44 is fully open and the engine is running without choke assistance, the branch passage 10
4-110 is completely closed, so the vent passage 82-1
00 is fully activated and transmits the pressure wave effect to the dry side chamber 62.

In a starting engine with the choke 44 open,
The air flow through the carburetor is not stable because a moving pressure wave is created in the manifold that is communicated by the intake air flow in the carburetor bore 40. The waves are formed by the opening and closing of the engine's intake valve(s) or port(s), and their sonic travel and operation are well known. vaporizer nozzle 70
The effect of transfer on fuel from the outlet has been a long-standing issue. The wave effect is superimposed on the normal vacuum created by the velocity of the airflow through the venturi 42, creating an undesirable modulation of pressure changes within the venturi 42. Thus, this conventionally causes the nozzle 70 to deliver fuel differently than in a suitable configuration responsive to the vacuum created by the air flow.

If no such mobile pressure wave is formed, the venturi 42
If! by the valve 36 (FIG. 5) located a short distance qt from the outlet of the nozzle 70 in the IF! When the static pressure drop ΔP over the main control limit formed at 1172 is proportional to the square of the velocity of the air flow and the concentration, i.e. ΔP=ρV2
It should be understood that the carburetor functions normally when the equation /2 holds true. However, the intake synchronized pressure wave
The same effect on pressure drop ΔP, which exists within 0, adversely affects fuel metering, is eliminated by eliminating the recoil- or modulation effects of the vent passage device 82-100 of the present invention. The vent passages 82-100 are designed to reverse or eliminate the negative effects of pressure waves passing through the nozzle 70 into the wet side chamber 56 of the vaporizer by imposing pressure waves on both sides of the diaphragm 60, thereby allowing the special vaporizer and engine It has been found that it is possible to operate a tuned pressure wave into the dry side chamber 62 of the vaporizer so as to leave only the desired static pressure drop ΔP as a result of predetermined configuration parameters devised to meet the requirements.

As mentioned above, to accomplish this, vent passage 82 is placed in the plane of venturi 42, preferably coplanar with nozzle 70 and located in the zone of maximum air flow velocity when choke valve 44 is open. It has been found that locating the -100 venturi communication opening 82 is important.

Although the theory of operation is not yet fully understood, it is known that the above relationship ensures that the opening 82 and nozzle 70 are subjected to the same pressure wave at the same time. In any event, this orientation and positioning, as well as the pitot tube shape of the protrusion 80, improves or eliminates the harmonic waves, or substantially reduces the negative effects of such harmonic waves on certain fuel metering parameters desired in the carburetor. Vent passage 82-1 for reducing
It is known that there are important things in determining 00's abilities.

Fortunately, it has been found that vent passages 82-100 also serve a second function. That is, it prevents the fuel-air mixture from flooding when the air filter located upstream of the inlet to the carburetor bore becomes clogged with dirt particles. Thus, the vent passageway 82-100 of the present invention also has the advantages of a full inside vent as described in Brown, U.S. Pat. No. 3,174,732, but with further improvements over that patent. It has been found that a predetermined air/fuel ratio can be maintained despite clogging of the air filter.

The apparatus of the present invention has also been found to reduce or eliminate undesirable carburetor performance characteristics resulting from phase shifts between the engine's intake pulse and the tuning panel, which would otherwise The engine speed will change.

It will be appreciated that the principles of the present invention are similarly applicable to float chamber vaporizers. In such a carburetor, the surface of the fuel in the float chamber is treated to correspond to the diaphragm 60, and the vent passage device according to the invention operates in a manner similar to that described with respect to the diaphragm carburetor 20 described above.

A given pressure wave can be applied to the nozzle 70 by slightly changing the positioning of the pitot tube to place the inlet section 82 slightly in front or behind the plane of the venturi 42 (upstream or downstream with respect to the air flow) as desired. impingement and direct or weaken the transfer impingement at the inlet portion 82. Thus, from the foregoing, it will be appreciated by those skilled in the art that the fuel metering effect of the diaphragm 60 is such that in the economic power range, there is less fuel mixture and in the power up power range, there is more mixture. It is possible to create phase shifts according to predetermined dimensional relationships obtained through experience.

Thus, as can be seen from the foregoing, the preferred embodiments of the internal combustion engine fuel metering system, method, and apparatus shown and described herein satisfactorily accomplish the objects of the present invention. However, as will be apparent to those skilled in the art, variations of the invention are possible in view of the foregoing.

For example, the effectiveness of the vent passages 82-100 of the present invention can be modified by venting the dry side chamber 62 to the atmosphere in a controlled manner. As shown in FIGS. 2.3 and 10, the bottom cover assembly 26 includes a vertical hole 1 containing a filter media 132.
30 and an annular array of slots 134 at the bottom of the well 130 to communicate the filter media 132 to the atmosphere. Insert the cover 136 into the vertical hole I3
The cover is provided with spacing ribs 137 to push the filter media 132 down and keep it spaced from the underside of the cover 136. Cover 136 is provided with a restricted orifice 138 that communicates with the headspace above filter media 132. Although orifice 138 is shown enlarged (not to scale), a diameter of 0.025 inches (0.064 centimeters) is desirable in experimentally determined embodiments of vaporizer 20. It is thus possible to use the atmospheric bleed orifice 138 in the "dry" side chamber 62 to eliminate the pressure wave effect provided by the vent passages 82-100, which may be useful when using some types of engines or for a given application. It is desirable to apply it when there are special operating conditions that are considered desirable.

Further, the vent passage system 82-100 of the present invention, due to the pitot tube construction at the venturi end of the vent passage system, allows both dynamic and static pressure conditions within the venturi 42 of the bore 40 to be maintained as described by Brown et al. Patent No. 3.1
No. 74,732 as well as U.S. Pat. No. 3,065,957 to Phlllips, No. 3.1 to Brown et al.
No. 81,843 and No. 4,494 by Yagi et al.
It can be seen that this is superior to the basic static pressure condition as described in No. 504 (Figures 19 and 20).

Although the travel times of pressure waves in the air and liquid differ, within reasonable limits the length of the liquid path from the wet side chamber 56 to the nozzle 70 and from the dry side chamber 62 to the venturi 42 via the vent passages 82-100. It has been found that the ratio of air passage length to air passage length can be varied without significantly affecting the operation of the vent passage in eliminating the adverse effects of suction tuned moving pressure waves in the carburetor bore.

Additionally, the communication of pressure waves through the vent passageway to the dry side chamber 62 adversely affects the diaphragm in performing its primary function of controlling the fuel inlet valve 58 via the cooperating lever linkage 64. It has been found to be effectively transmitted through the diaphragm 60 to the greenhouse 56 without any adverse effects.

As previously mentioned, the main principles of the present invention are also applicable to float type vaporizers, as shown in FIGS. 12-14.

As illustrated by way of non-limiting example, those shown in FIGS. 12-14 include Ohler C,V.

Part No. 12, Michigan, Co., Ltd. under the name LMKI.
A commercially available prior art float vaporizer 20' manufactured and sold by Albro, Inc. of 55 Cities, but with an improved version of the vent passage system according to the present invention, is suitable for use with said diaphragm vaporizer. It operates in the same manner as described for 20. For the sake of brevity and to facilitate understanding of the relative relationships between corresponding structures and functions,
The elements having the structure and function corresponding to the float type vaporizer 20' shown in FIGS. 12 to 14 include the vaporizer 2
I gave it the same number as 0. Further, the same explanation has not been repeated regarding structures that can be understood by those skilled in the art from FIGS. 12 to 14.

As can be clearly seen from Figures 13.15 and 16, the float carburetor 20' has a fixed high speed injection section 36' and a vertical hole section 74.
A vent passage system in accordance with the present invention is provided which operates to modify or eliminate the effectiveness of vent 1742' in passing tuned pressure waves that would adversely affect the metering function of primary nozzle 70'. This vent passage interconnects the pressure sensitive ports configured in the bench 2' and the head space 62' of the float chamber 63. As will be apparent to those skilled in the art, the float chamber 63 contains liquid fuel in a partially submerged fuel reservoir or well with an annular hollow float 60', the float being actuated via a lever 64' to release the fuel. The inlet valve 58'
control.

Thus, similar to the diaphragm carburetor 20, the pitot tube 80' projects from the venturi 42' and is directed into the airflow through the bore 40' by the engine intake air. The pitot tube 80' of the embodiment shown in numbers 12-24 may be integrally formed with the carburetor body as the carburetor 20. However, for the embodiment shown in FIGS. 12-24, a separate brass plug 140 including a cylindrical brass plug 140 having a blind bore 142 drilled therein such that the open end of the bore 142 forms the mouth 82' of the pitot tube 80'. Manufactured in parts. tube 14
One end of the plug 4 is inserted into a side opening drilled in the plug 140 and is press-fitted into a bored passage extending perpendicularly to the axis of the carburetor and whose other end is sealed by a press-fit ball 148. Ru.

Passage 146 intersects a large diameter perforated passage 150 already provided in carburetor 20' and extends downwardly into a larger diameter counterbore 152 (FIG. 13) and, if necessary, at 154 in the conventional manner. The lower end may be closed by a seated Welch plug. When using a Welch plug,
Notch 15 in side wall adapted to receive Welch plug
6 communicates the passage 150 with the hent space 62' of the flow t163. As can be seen in FIG. 16, the large diameter passage 158 extends parallel to the axis of the carburetor and has a
The downstream end of the 9 passage 158 is located adjacent to the choke end of the carburetor just downstream from an air filter (not shown) typically provided upstream of the inlet to the mixing passage 40' of the carburetor. It intersects perpendicularly and therewith provides a main air pressure relief system for the float chamber headspace 62' in a conventional manner.

When using a commercially available float type vaporizer 20' in accordance with the principles of the present invention as illustrated herein, passageway 158 is closed off by plug 162 and is not used. However, in the case of a float type vaporizer uniquely constructed according to the present invention, the previously provided passages 158 and 150 are eliminated and the tube 14 is
4 to the head space 62' can be simplified. Similarly, unless a staggered phase shift relationship is desired as described above, the mouth 82' of the pitot tube 80' is configured to be coplanar with the intermediate plane of the venturi 42' and the centerline of the nozzle 70'. Ru.

As is clear from the foregoing and from FIGS. 13.15 and 16, the pitot tube 80' of the carburetor 20
It is positioned exactly the same as o. The mouth 82' of the inlet bore 142 of the pitot tube 80' is slightly upstream of the plane of the small diameter portion of the venturi 42' and slightly upstream of the same plane as the main nozzle 70'; subject to physical limitations imposed in the case of vaporizer construction. Passage 142, like passage 86, extends parallel to the major axis A of bore 40' and venturi 42'. The carburetor 20' has a choke shaft 28' like the diaphragm type carburetor 2o.
Since the choke plate 44' attached to the pitot tube 8 is provided, the pitot tube 8
0' diverges from axis A towards the side wall of venturi 42' and is approximately midway between axis A and the cooperating side wall of venturi 42'. However, when the carburetor is viewed vertically as shown in FIGS. 13 and 15, the pitot tube 80
' is centered so that it aligns with axis A in the horizontal direction.

In any case, the inlet portion 82' of the pitot tube 80' is in the caliper tooth space just downstream of the choke plate 44', where the choke plate 44' and choke shaft 28' are present and the carburetor bore 40' and Considering their closing effect on the airflow through the venturi 42', the engine induced airflow velocity is maximized at that location.

Similar to the diaphragm type vaporizer 20, the float type vaporizer 2
A choke valve 44' is provided at 0', with a pitot tube 80' located immediately downstream of the choke valve 44' and vent passages 142, 144, 150, 15 when initiating choke valve closure.
Bypassing the effect of 6, a branch passage system is provided such that the 1ffl passage has a perforated passage 170, as is clear from Figures 19-21 and 24. extends parallel to the shaft '41AA from the front of the carburetor 20', and connects to the choke shaft 28 above the choke plate 4'.
' (Fig. 4).

The inner end of the passageway 170 terminates at an intersection with an angled perforated passageway 172 that intersects the upper end of the passageway 150. Passage 17
The outer end of passageway 172 is sealed by a press-fit ball 174, and the outer end of passageway 172 is sealed by a press-fit ball 176.
sealed by.

Another angled perforated passageway 178 opening into carburetor bore 40'
is provided upstream of the choke plate 44' near its upper edge. Passage 178 intersects passage 170 where they meet choke shaft bore 29. The choke shaft 28' is provided with a perforated cross passage i80 extending diametrically opposite the shaft 28' such that its ends rotate in and out of alignment with the passages 170 and 178 as the choke shaft rotates.

Therefore, as can be seen by comparing the accompanying FIGS. 19 and 20, when choke valve 44' is in the fully closed position (FIG. 19), the upper end space of passage 150 is It communicates with the upstream bore 40' of the closing choke plate. When choke plate 44' is rotated 15 degrees from the fully closed position by shaft 28', communication through passage 180 is closed. When the choke shaft continues to rotate by more than 15 degrees from the closed position (clockwise as shown in FIGS. 19-21), when the choke plate 44' reaches the fully open position shown in FIG. Since the passages 178 and 150 are not aligned, the passages 178 and 150 are no longer in communication.

Diaphragm carburetor and its choke branch passage 104
- As explained in the preamble regarding 110, pen) passage 1
42, 144, and 146 are disabled when the choke valve closes, as shown in FIG.
The high vacuum immediately behind the choke plate 44' near the pitot tube 80' cannot communicate with the air pressure 62' in the float chamber 63' due to the branching effect of the branch passages 178, 180, and 170. The engine starts under its own power and the choke 44'
is rotated toward the open position, branch passageway 180 is rotated toward shaft 28'.
passages 178 and 170 by corresponding rotation of
becomes misaligned with passage 180 and is gradually closed. When the choke 44' is fully opened and the engine runs without choking, the branch passages 178, 180, and 170 are completely closed, and the vent passages 142, 144, and 146 are fully operable and the float chamber 63 is A pressure wave effect is transmitted to the air chamber 62'.

As in the case of the vaporizer 20, the vent passages 142 and 144
．． 140 can be varied or adjusted within the carburetor 20' by controlling the float chamber headspace 62' in communication with the atmosphere.

To this end, a restrictive orifice 138', such as orifice 138, is provided in the body of the carburetor 20', which communicates the passage 150 with the atmosphere, as described above with respect to the carburetor 20.

It will thus be apparent from the foregoing that the principles of the present invention, as detailed with respect to diaphragm type carburetors, can be applied to float floats by modification in the same manner and with the same purpose as described with respect to diaphragm carburetors 20. It can also be easily implemented in a controlled vaporizer 20'.

It will be appreciated from the foregoing that the present invention is not limited to the preferred embodiments shown and described, but is capable of various modifications without departing from the scope of the appended claims and the applicable prior art.

[Brief explanation of the drawing]

FIG. 1 is a side view of a small, compact diaphragm carburetor designed for use in a chainsaw engine with a modified fuel metering system according to a first embodiment of the present invention; the purpose of the engine intake airflow through the carburetor is The direction is indicated by the arrow A/F. Figure 2 is a cross-sectional view taken along line 2-2 in Figure 1. Figure 3 is the bottom view of the carburetor in Figure 1 rotated 90 degrees from the position in Figure 1. Figure 4 is a cross-sectional view taken along line 4--4 of Figure 3, reversed to Figures 1.2 and 5; Figure 5 is a cross-sectional view of the choke end of the mixing passage, as seen in detail; FIG. 6 is a partial cross-sectional view taken along line 6--6 of FIG. 5; FIG. 7 is FIG. 5 with the bottom plate removed to show the bottom of the carburetor body; Figure 8 is taken along line 7-7 of Figure 7, line 8 of Figure 7.
9 is a partial bottom view of the bottom cover assembly of the carburetor shown as such; FIG. 10 is a partial sectional view at line 10--10 of FIG. 9; FIG. FIG. 12 is a partial top view of a portion of the bottom cover assembly sealing gasket taken along line 11-11 in FIG. 10; FIG. A side view of a small, compact float-type carburetor designed for use in garden mowers, with the intended direction of the engine's intake airflow through the carburetor indicated by arrows A/F. Figure 13 shows line 13 in Figure 12. Figure 14 is a twice-enlarged cross-sectional view at line 14-14 of Figure 12; Figure 15 is a twice-enlarged cross-sectional view at line 14-14 of Figure 12; Figure 15 is a view looking into the choke end of the mixing passage. 12th
16 is a cross-sectional view taken along line 16-16 of FIG. 15, enlarged twice, and FIG. 17 is an end view of the carburetor shown in FIG. 18 is an end view of the carburetor of FIG. 12 looking into the constricted end of the mixing passage; FIGS. 19, 20 and 21 is a partial cross-sectional view taken at line 1919 in Figure 17, enlarged four times, when the choke is in the fully closed position (Figure 19), and when the choke is positioned 15 degrees in front of the fully closed position, respectively. (20th
(Fig. 21), and when the choke is in the fully open position (Fig. 21).
Figure 22 shows the arrangement of the choke plate, choke shaft, and modified branch or bypass passage, respectively.
23 is a cross-sectional view taken at line 23--23 of FIG. 22, enlarged twice, and FIG. -24 is a cross-sectional view doubled. 20... Carburetor, 22... Main body, 28... Choke shaft, 30... Throttle shaft, 36, 38.58...
- Needle valve, 42... Venturi, 44... Chalk plate, 52... Filter screen, 56... Measuring chamber, 6o... Diaphragm, 63... Float chamber, 64... Lever 72 ... Nozzle, 80 ... Pitot tube, 82-100 ... Vent passage, 104-110
... Branch passage, 140... Plug. Fig. 5 Fig. 6 Fig. 7 Fig. 3 Fig. 15 Fig. A7F)'l Fig. 16 Fig. 12 Fig. 13 Fig. 17 Fig. 18 Fig. 19 Fig. 20 Fig. 21 Fig.

Claims (1)

[Claims] 1) A diaphragm type carburetor comprising a cylinder, a piston and a crankcase that can reciprocate within the cylinder, a main body provided with a venturi, a space within the main body, and a space within the main body. a measuring diaphragm dividing into a measuring chamber and a drying chamber, a device for supplying fuel to the measuring chamber, comprising a measuring valve device operable by the diaphragm, and a main body connected to the measuring chamber via a high-speed needle valve. a two-stroke internal combustion engine assembly including a fuel restriction and a vent passageway connecting the drying chamber with the venturi and having a pitot tube inlet in the venturi, the diaphragm opening and closing of the metering valve arrangement; Design airflow conditions that direct the engine's suction-induced pressure waves into the drying chamber to force them onto the fuel in the metering chamber without adversely affecting normal functioning, and to control the pressure drop in the primary fuel restriction. supplying more or less fuel to the metering chamber and the main fuel restriction during operation of the engine, depending on the engine operation, to eliminate or reduce the adverse effect that such waves have on the pressure drop in the main fuel restriction. The two-stroke internal combustion engine assembly characterized in that the vent passage is configured and arranged in such a manner. 2) A carburetor body to be installed in an engine having a mixing passage comprising a venturi section and a diaphragm chamber having a wet side and a dry side, an inlet control valve, and an inlet control valve in the chamber for controlling the opening and closing of the valve. for transferring liquid fuel from a supply to an engine comprising a diaphragm acting on a valve and a supply passage through the wet side chamber from the fuel supply inlet to a main fuel nozzle opening at a venturi section of the mixing passage; all positions of the carburetor, the assembly with which the carburetor acts as an inlet adapted to couple with the intake airflow induced by the engine to send an intake-entrained pressure wave effect to the dry side chamber; an air passage within the carburetor body having one end of a pitot tube configured and disposed in the venturi portion of the tube; b. a choke valve within the mixing passage movable from an open choke position to a closed choke position; c. activating the air passage to transmit the wave effect to the dry chamber when the choke moves to an open position, and enabling the air passage to transmit the wave effect to the dry chamber when the choke closes; a valve arrangement responsive to movement of the choke valve to disable the flow of the air passageway in the dry side chamber by communicating atmospheric air from a location remote from the venturi section of the mixing passageway with the dry side chamber; An all-position vaporizer device characterized in that it includes an air vent passage for adjusting the operating effect. 3) a body forming a fuel chamber; a tube for a fuel-air mixture passing through the body and having an inlet and an outlet with a venturi restriction intermediate therebetween; a fuel inlet and a venturi restriction intermediate therebetween; a fuel passageway extending to a chamber, an inlet valve in the fuel passageway between the fuel inlet and the fuel chamber, and a main fuel nozzle disposed within the conduit restriction, the body facing upstream; a pitot tube located in the restriction in the zone of maximum air flow, and a fuel connection from the fuel chamber to the main fuel nozzle, with a restriction device therein for controlling the main fuel and the inlet. a diaphragm or float device for actuating the valve; and a device forming a single closed air chamber cooperable with the diaphragm or float device to regulate work on the inlet valve; The body has a first passageway connecting the pitot tube with the air chamber such that the diaphragm or float device connects the pitot tube to the air chamber to vary the constant fuel pressure in the fuel chamber in direct response to changes in air pressure at the nozzle. The pressure drop in the restriction device which is responsive to the air pressure drop in the restriction and which controls the primary fuel is not adversely affected by the presence of an engine intake induced synchronized pressure waveform in the pipe and which controls the operation of the inlet valve. A carburetor assembly characterized in that when controlled, the function of the diaphragm or float device is not adversely affected. 4) The assembly of claim 1, 2, or 3, wherein both the main nozzle opening into the venturi and the pitot tube lie in a common plane substantially perpendicular to the axis of the venturi. . 5) The main nozzle opening into the venturi and the pitot tube are staggered from each other by a predetermined distance with respect to the direction of the engine suction guided air flow through the venturi, so that the spacing portion 3. The assembly of claim 1, 2, or 3, wherein the inlet tuning pressure waveform selectively impinges on the pitot tube and the main nozzle opening to create a predetermined phase shift. 6) A cylinder, a piston and crankcase that can be reciprocally interlocked within the cylinder, a carburetor that includes a main body having a venturi, a space within the main body, and a space that is used as a measurement chamber and a dry room. a dividing metering diaphragm, a device for supplying fuel to the metering chamber having a metering valve device actuated by the diaphragm primary fuel control restriction device, and a primary fuel nozzle connected to the metering chamber via a high speed needle valve. A method for metering fuel to an internal combustion engine comprising: (1) dynamically sensing an engine intake induced pressure wave through the venturi to form a pressure wave signal; (3) transmitting a pressure wave signal to the dry side chamber; (3) passing the engine through the venturi by creating a predetermined phase relationship between the impingement of the wave with the main fuel nozzle and the sensed pressure wave signal; adjusting the wave impingement effect on the static pressure drop across the primary fuel restriction device in response to intake airflow. 7) a carburetor comprising a cylinder, a piston and crankcase reciprocable within the cylinder, a body having a venturi, and a metered inlet valve device operable by a cooperating diaphragm or float device; a single closed air chamber cooperable with the diaphragm or float device to control operation of the inlet valve device; a primary restriction device for controlling fuel;
a fuel metering device for an internal combustion engine comprising a main fuel nozzle connected to the fuel supply device via a high speed needle valve, further comprising: (1) dynamically sensing engine intake induced pressure waves passing through the venturi; (2) a device for transmitting the sensed pressure wave signal to the dry side chamber; (3) impingement of the wave with the primary fuel nozzle; and a device for adjusting the wave impingement effect on the static pressure drop created in the primary fuel restriction device in response to engine intake airflow through the venturi by creating a predetermined phase relationship between the venturi and the main fuel restriction device. The fuel measuring device. 8) the primary nozzle opens into the venturi and the sensing device, and the phaser includes a pitot tube located in a common plane with the nozzle, the plane perpendicular to the axis of the venturi and intersecting the primary nozzle; The device according to claim (7). 9) a pitot, the primary nozzle opening into the venturi and the sensing device, the phasing device being staggered from the primary nozzle by a predetermined distance with respect to the direction of engine suction induced air flow through the venturi; 8. The device of claim 7, comprising a tube, the spacing being operable to form a predetermined phase by the shape of a suction tuned pressure wave that alternately impinges on the pitot tube and the main nozzle. 10) A diaphragm type carburetor that includes a cylinder, a piston and a crankcase that can reciprocate within the cylinder, a main body equipped with a venturi, a space within the main body, and a space that is used as a measurement chamber and a dry room. a dividing metering diaphragm, a device for supplying fuel to the metering chamber including a metering valve device actuatable by the diaphragm, an inlet communicating with the metering chamber and having a restriction device therein for controlling the fuel; a fuel outlet positioned within the venturi to provide an outlet opening positioned within the venturi and having an axis generally perpendicular to the direction of engine-induced airflow through the venturi; a main fuel supply passageway having a plane generally parallel to the direction of such air flow; and a vent passageway arrangement connecting the dry chamber with the venturi and having a pitot tube inlet within the venturi; is located such that the inlet opening of the pitot inlet opening faces upstream and the plane of the pitot inlet opening is generally perpendicular to the direction of the airflow, adversely affecting the normal functioning of the diaphragm when opening and closing the metering valve arrangement; the engine's suction induced pressure wave in response to the design airflow conditions to control the pressure drop in the main fuel restriction by sending the engine's suction induced pressure wave into the dry chamber so as to force the wave onto the fuel in the measurement chamber without configuring and arranging the vent passage to supply some fuel to the metering chamber and the primary fuel restriction during travel, and to eliminate or reduce the adverse effect that such waves have on the pressure drop in the primary fuel restriction; An internal combustion engine assembly featuring: 11) a body defining a fuel chamber; a fuel-air mixture tube passing through the body and having an inlet and an outlet with a venturi restriction intermediate therebetween; a fuel inlet and a venturi restriction intermediate therebetween; a fuel passageway extending into the chamber; an inlet valve in the fuel passageway between the fuel inlet and the fuel; and a main fuel nozzle in the mixture tube restriction, the axis of the fuel supply outlet opening being substantially perpendicular to the direction of engine-induced airflow through the venturi restriction such that the plane of the exit opening of the nozzle is generally parallel to such direction of airflow; has a pitot tube facing upstream and located at the restriction in the zone of maximum air flow, the axis of the inlet opening of the pitot tube being substantially parallel to the air flow direction, and the inlet of the pitot tube the plane of the opening is substantially perpendicular to the airflow direction, the body has a fuel connection from the fuel chamber to the primary fuel nozzle and a primary fuel control restriction device disposed therein; further comprising a diaphragm or float device for actuating the valve and a device forming a single closed air chamber cooperable with the diaphragm or float device to regulate work on the inlet valve; The body has a first passageway connecting the pitot tube with the air chamber such that the diaphragm or float device connects the pitot tube with the air chamber to vary constant fuel pressure in the fuel chamber in direct response to changes in air pressure at the nozzle. In response to the air pressure drop in the restriction section,
Moreover, the pressure drop in the restriction device controlling the main fuel is not adversely affected by the existence of various engine intake induced tuning pressure wave shapes in the pipe, and when controlling the operation of the inlet valve, the diaphragm Or a carburetor for an internal combustion engine, characterized in that it does not adversely affect the function of a float device. 12) The assembly of claim 11, wherein both the main nozzle opening into the venturi and the pitot tube lie in a common plane substantially perpendicular to the axis of the venturi. 13) The main nozzles opening into the venturi and the pitot tube inlet openings are staggered from each other by a predetermined distance with respect to the direction of the engine suction induced air flow through the venturi, so that the spacing 13. The assembly of claim 12, wherein the provision is operative to create a predetermined phase shift by the shape of an inlet entrainment pressure wave that selectively impinges on the pitot tube and the main nozzle opening. 14) a choke valve in the mixture pipe movable from an open choke position to a closed choke position, allowing the wave effect to be transmitted to the air chamber by the vent passage when the choke moves to the open position; Claims (11)(12) further comprising a valve arrangement responsive to movement of the choke valve to disable the vent passage to transmit the wave effect to the air side chamber when the choke closes. Or (
13) Assembly. 15) A carburetor including a cylinder, a piston and a crankcase reciprocatable within the cylinder, a body with a venturi, and a metered inlet valve device actuatable by a cooperating diaphragm or float device, the venturi a cavity within the body and a single closed air chamber cooperable with the diaphragm or float device to control operation to the inlet valve system; a primary fuel control restriction device, and a primary fuel nozzle disposed within the venturi, the axis of the outlet opening being substantially perpendicular to the direction of engine intake induced air flow through the venturi, and the nozzle A method for metering fuel into an internal combustion engine coupled to the fuel supply device through a fuel control restriction unit, the method comprising: (1) dynamically sensing an engine intake induced pressure wave passing through the venturi to form a pressure wave signal; (2) sending the sensed pressure wave signal to the dry side chamber; (3) impinging the main fuel nozzle outlet opening with the wave;
adjusting the wave impingement effect on the static pressure drop created in the primary fuel restriction device in response to engine intake airflow through the venturi by creating a predetermined phase relationship between the sensed pressure wave signal and the sensed pressure wave signal. A method for measuring fuel for an internal combustion engine, comprising: 16) the sensing step is carried out in a pitot tube having an inlet opening substantially in a common plane with the nozzle outlet opening, the common plane being perpendicular to the air flow direction and the main nozzle outlet opening; The method of claim (15), which intersects with. 17) the sensing step is carried out in a pitot tube having inlet openings staggered from the main nozzle outlet opening by a predetermined distance with respect to the air flow direction; 16. The method of claim 15, wherein said spacing is provided so as to form a predetermined phase by the shape of the inlet entrainment pressure waves that alternately impinge on the main nozzle outlet opening.