Fuel supply system, carburetor for use in the same and method

Abstract

Fuel supply system for an internal combustion engine having at least one cylinder with a moving piston therein to provide a combustion chamber within the cylinder which is adapted to be placed in communication with an intake opening by operation of an intake valve. A carburetor and means for supplying fuel to the carburetor are provided as a part of the system. The carburetor includes means forming a wave tube of substantially constant cross-sectional area with one end open to the atmosphere and with the other end adapted to be placed in communication with the intake opening. Means forming an orifice is disposed in the wave tube for supplying fuel to the interior of the wave tube. Throttle means is disposed in the wave tube between the region in which the fuel is introduced and the intake opening. The means for supplying a liquid fuel to the carburetor includes means for supplying fuel to a level which approximately just covers the orifice.

Parent Case Text

This is a continuation of application Ser. No. 268,736 filed July 3, 1972, now abandoned.

Description

BACKGROUND OF THE INVENTION

This invention relates to fuel supply systems, carburetor for use therein and a method for metering and atomizing liquid fuel for use with internal combustion engines.

Heretofore, many different types of fuel supply systems and carburetors have been provided. However, such systems and carburetors for use therein have suffered from a lack of wide operating ranges. In addition, such systems and carburetors have suffered from inadequate performance often caused gy inefficient atomization of the fuel and with undesirable pressure drops. There is, therefore, need for a new and improved fuel supply system, carburetor for use therein and a method which overcomes these disadvantages.

SUMMARY OF THE INVENTION AND OBJECTS

The fuel supply system is for use with an internal combustion engine having at least one cylinder with a moving piston therein to provide a combustion chamber within the cylinder which is adapted to be placed in communication with an intake opening by operation of an intake valve. Means is provided which forms a wave tube of substantially constant cross-sectional area with one end open to the atmosphere and with the other end adapted to be placed in communication with the intake opening. Means forming an orifice is disposed in the wave tube for supplying fuel to the interior of the wave tube. Fuel supply means supplies fuel at a level which covers the orifice. The cross-sectional area of the wave tube is sufficiently small to permit shock wave metering and atomization of fuel supplied to the wave tube. Throttle means is disposed in the wave tube between the region in which the fuel is introduced and the intake opening. The throttle valve is formed so that when it is in the fully open position, there is substantially no restriction to the airflow through the wave tube.

In general, it is an object of the present invention to provide a fuel supply system, carburetor for use therein and method which makes possible a wide range of operation.

Another object of the invention is to provide a system, carburetor and method of the above character in which marked pressure drops are eliminated.

Another object of the invention is to provide a system, carburetor and method of the above character in which emission of unburned hydrocarbons and carbon monoxide is substantially reduced.

Another object of the invention is to provide a system, carburetor and method of the above character in which the air-to-fuel ratios can be varied through wide ranges if desired.

Another object of the invention is to provide a system, carburetor and method of the above character which are applicable to internal combustion engines whether reciprocating or rotary and whether two-stroke or four-stroke cycle.

Another object of the invention is to provide a system, carburetor and method of the above character in which the correct amount of fuel and the highest possible degree of atomization is provided.

Another object of the invention is to provide a system, carburetor and method of the above character which are applicable to multi-cylinder engines.

Another object of the invention is to provide a system, carburetor and method of the above character which are relatively simple.

Another object of the invention is to provide a system, carburetor and method of the above character which make possible improved throttle response.

Another object of the invention is to provide a system, carburetor and method of the above character which make possible the efficient use of fuel.

Another object of the invention is to provide a system, carburetor and method which can be implemented relatively inexpensively.

Another object of the invention is to provide a system, carburetor and method of the above character in which shock waves are used for causing intake of fuel and atomizing the same.

Additional objects and features of the invention will appear from the following description in which the preferred embodiments are set forth in detail in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of the carburetor utilized in the fuel supply system incorporating the present invention.

FIG. 2 is a top plan view looking along the line 2--2 of FIG. 1.

FIG. 3 is a side elevational view looking along the line 3--3 of FIG. 1.

FIG. 4 is a cross-sectional view taken along the line 4--4 of FIG. 3.

FIG. 5 is a cross-sectional view taken along the line 5--5 of FIG. 1.

FIG. 6 is a cross-sectional view taken along the line 6--6 of FIG. 4.

FIG. 7 is a top plan view of the carburetor similar to FIG. 2 but showing additional details.

FIG. 8 is a crosS-sectional view taken along the line 8--8 of FIG. 7.

FIG. 9 is a schematic illustration of a fuel bowl with which air control is utilized.

FIG. 10 is a schematic illustration showing a fuel supply system incorporating the present invention utilizing air control.

FIG. 11 is a schematic illustration showing a fuel bowl with which pump control is utilized.

FIG. 12 is a schematic illustration of a fuel supply system incorporating the present invention utilizing pump control.

FIG. 13 is a front elevational view partly in cross section of a multi-cylinder internal combustion engine of a four-stroke cycle having a fuel supply system mounted thereon incorporating the present invention.

FIG. 14 is a cross-sectional view taken along the line 14--14 of FIG. 13.

FIG. 15 is a cross-sectional view showing an internal combustion engine of the two-stroke cycle and having a fuel supply system mounted thereon incorporating the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIGS. 1 through 8 there is shown a carburetor 21 for use in a fuel supply system incorporating the present invention. This carburetor 21 has the principal novelty in the system and consists of a body or housing 22 and a base 23 which can be formed of a suitable material such as an aluminum alloy sand casting. If desired, die cast aluminum can be utilized for high volume production. Alignment pins 24 are provided either in the body or the base 23 and are provided for aligning the base 23 on the body 22. The base and the body are fastened together in a suitable manner such as by the use of Allen head screws 26. They extend through the body 22 and are threaded into the base 23 as shown.

The body 22 is provided with a cylindrical bore 28 which is of uniform or constant cross-sectional area. The bore 28 opens into a generally planar oval-shaped recess 29 (see FIG. 5) which receives a throttle plate or a slide valve 31. The slide valve 31 is formed of a suitable material such as a phenolic laminate, Nema grade LE. The slide valve 31 is provided with a bore 32 which has substantially the same diameter as the bore 28 provided in the body or housing 22. The base 23 is also provided with a bore 33 which is in axial alignment with the bore 28 and is of substantially the same size as the bore 23. As can be seen from the drawing, the slide valve 31 is adapted to be moved between a throttle-full open position in which the bore 32 is in axial alignment or registration with the bores 28 and 33 and a throttle-closed position in which the slide valve 31 occludes communication between bores 28 and 33.

Means is provided for retaining the slide valve 31 in the throttle-closed position and consists of a coil spring 36 which has one end seated in a well 37 provided in the slide valve 31 and having the other end engaging the wall forming the recess 29 and encircling a tube 38 mounted in the body (see FIG. 4). Means is provided for causing movement of the slide valve 31 between the throttle-closed position and the throttle-open position and consists of a cable 41 which extends through the sleeve 38, through the coil spring 36 and is fastened into a counterbore 42 in the slide valve 31 by a screw 43.

A tube 45 of a substantially constant or uniform cross section is provided which has an outer flared end portion 46a. As shown in FIG. 4, the tube 46 is secured within a bore 47 provided in the body 22. As shown in the drawings, the tube 46 is cylindrical and has a flow passage 48 extending therethrough which has a diameter which is substantially identical to the diameter of the bore 28 in the body 22 and the bore 33 provide what may be called a "wave tube" of a substantially constant or uniform cross-sectional area extending completely through the carburetor and which is sized as hereinafter described.

Means is provided which forms a fuel supply orifice in the vicinity of the interior of the wave tube between the ends of the wave tube. Thus as shown in FIG. 4, a fitting 51 is threaded into the body 22 and into the tube 46 as shown in FIG. 4. The fitting 51 is provided with a conical inlet recess 52 which opens into a small centrally disposed orifice 53. The orifice 53 opens into a downstream passage or channel 54 in the fitting which opens into and is in communication with the passage 48 in the tube 46. As can be seen from FIG. 4, the exterior end of the fitting 51 and the outer end of the passage or channel 54 are generally flush with the inner cylindrical surface defining the passage 48. The channel 54 extends in a direction at right angles to the axis of the passage 48. Also, the downstream channel 54 is positioned ahead of the slide valve 31 and is spaced from the inlet end of the tube 46.

The inlet recess 52 of the fitting 51 opens into the interior chamber 56 of a fuel bowl 57. The bowl 57 is formed of a suitable material such as an aluminum sand casting. It is provided with a pair of ears 58 (see FIG. 3) which are secured to the main body 22 by Allen head screws 59. A cap 61 closes the open end 62 of the bowl 57. The cap 61 is provided with a small vent hole 63 for venting the interior of the chamber 56 to the atmosphere. Means is provided for introducing a liquid fuel such as gasoline into the chamber 56 of the bowl 57 and includes a fill tube 66 which is mounted in the side wall of the bore 57. The fill tube 66 has an inner conically-shaped end which has a small inlet opening 67 formed therein. A control tube 68 is mounted in the cap 61 and also has an inner tapered conical end which has a small opening 69 formed therein. A drain tube 71 is mounted in the side wall of the bowl and has its inlet end open to the interior of the bowl. The fill tube 66 is normally positioned at a level which would be below the level of the fuel within the chamber 56. The control tube 68 is positioned in such a manner so that the opening 69 is only a slight distance above the axis of the orifice 53 so that the fuel level is just slightly above the orifice. The drain tube 71 is normally positioned in such a manner so that it would be above the normal liquid fuel level within the bowl 57.

The carburetor 21 is adapted to be mounted on an internal combustion engine 76 of a conventional type as shown in FIG. 3. As is well known to those skilled in the art, such internal combustion engine is provided with an engine block 77 having a piston (not shown) which reciprocates or moves therein. The engine block 77 is provided with an inlet passage 78 which is in controlled communication through an inlet valve 79 with the combustion chamber provided above the piston. The carburetor 21 is mounted in a suitable manner such as by a pair of screws 81 which extend through the base 23 and are threaded into the engine block 77. As will be noted from FIG. 8, the passage 78 has substantially the same size as the wave tube for a purpose hereinafter described.

A schematic illustration of the fuel bowl 57 provided in the carburetor 21 utilizing air control is shown in FIG. 9. A schematic illustration of the manner in which fuel is supplied to the bowl 57 is shown in FIG. 10. As shown in FIG. 10, the fuel is carried in a tank 86 formed of a suitable material such as steel or fiberglass. The tank 86 is thermally insulated in a suitable manner such as by a layer 87 of rigid polyurethane foam which may be provided with an epoxy overcoat. The tank 86 is provided with an air tight filler cap 88. Fuel 89 is provided in the tank which flows through an outlet pipe 91 and through a shut-off valve 92 through a pipe 93 to a hose 94 which is connected to the fill tube 66. Fuel 89 flows into the chamber 56 from the fill tube 66 by force of gravity until the opening 69 in the control tube 68 is occluded by the liquid fuel 89. The control tube 68 is connected by a hose 96 which is connected to a tube 97 mounted on the tank 86 and which enters the tank near the fill cap 86 and is in communication with the space 98 in the upper portion of the tank as shown in FIG. 10.

As soon as the opening 69 in the control tube 68 is occluded, air can no longer pass into the space 98 above the liquid fuel 89 so that within a very short time, a partial vacuum or a below atmospheric condition is created in the space 98 which prevents further flow of fuel from the tank 86. In the event there is overfilling of the chamber 56, the excess fuel will pass through the drain tube 71 after which it can be returned to the tank 86 if so desired. Fuel 89 from the chamber 56 is metered through the orifice 53 into the carburetor as hereinafter described.

As pointed out previously, the fuel flows into the bowl until the tip of the control tube is covered and a partial vacuum is generated in the air space 98 above the fuel in the tank. The pressure difference between atmospheric and the air space in the tank is determined by the density of the fuel in the tank times the acceleration of gravity times the difference in height between the fuel level in the tank and the fuel level in the bowl.

In connection with the fuel supply bowl, it is always important that the fuel level be at a level which is just slightly above the orifice 53 so that fuel can be readily drawn into the orifice 53 when the shock wave passes the orifice.

It has been found that the fill and control orifices or openings 67 and 69 should be approximately the same diameter when gasoline is being utilized as a fuel. By establishing a relationship between the orifice sizes and the surface area of fuel in the bowl, overshooting is prevented and maximum accuracy is provided with a predetermined fuel feed rate requirement.

In providing the fitting 51, it has been found that it is desirable to provide a conical entry for the inlet recess 52 and a length-to-diameter ratio of approximately 0.7 for the orifice 53. The downstream channel or bore 54 preferably has an area which is approximately 10 times the cross-sectional area of the orifice 53.

In mounting the careburetor on the engine, it is important that the carburetor 21 be mounted in such a manner that the bowl with its fitting 51 have the inlet orifice 53 of the fitting point in a forward direction or in the direction of movement of the vehicle in which the engine is mounted so that when the vehicle accelerates, a change in fuel level will be in a positive direction so that the orifice 53 will not be starved of fuel.

A phenolic has been chosen for the slide valve because it has a temperature coefficient of expansion which is very similar to that of aluminum alloy castings. In addition, since gasoline is a very poor lubricant, it is desirable to utilize a material for the slide valve which will not bind or stick in its movement in the carburetor. Therefore, preferably, the material should be non-metallic.

Operation and use of the carburetor 21 with a fuel system of the type herein described in conjunction with an internal combustion engine may now be briefly described. Let it be assumed that the slide valve or throttle plate 31 has been moved to a full open position or throttle-open position so that the bore 32 provided therein is in alignment with the bores 33 and 28 whereby there is provided a wave tube of substantially constant cross section extending from the inlet port 78 of the internal combustion engine to which the carburetor is connected to the atmosphere. As is well known to those skilled in the art, a shock wave is created by the combination of piston motion and sudden opening of the inlet valve 79. It has been found that the specific form of the inlet valve or the specific form of the cylinder has relatively little effect on the generation of the shock wave other than to slightly modify the shape of the same. This shock wave is created by these two features of engine operation and is propagated down the intake passage 78 and down the wave tube formed by the bore 33,, the bore 32, the bore 28 and the passage 48 at the velocity of sound in air. The shock wave pressure does not differ markedly in pressure from atmospheric pressure to which the outlet end of the tube 46 is exposed. As hereinafter pointed out, the design parameters for the wave tube are chosen such that the shock wave pressure will not be in excess of 10% from that of atmospheric pressure.

During the time that the shock wave is being propagated, it should be appreciated that there is a relatively steady state airflow entering the wave tube from the inlet end of the wave tube which passes thrugh the wave tube as a moving column of air of generally uniform cross section and then passes into the inlet passage 78 past the inlet valve 79 into the combustion chamber above the piston. During the time this is occurring, the shock wave is being propagated outwardly from the tube through the column of air and as it passes the flow channel 54, it will pump fuel through the orifice 53 and will atomize the same into very fine droplets so that it will be carried by the moving column of air into the combustion chamber above the piston. The amount of fuel which is atomized is dependent upon the time that the shock wave is effective and is directly determined by the length of the wave tube. The outgoing shock wave is of the correct sign of pressure to meter fuel from the orifice 53 and to atomize the same so that it can be carried to the engine by the steady state air stream. The outgoing shock wave propagates outwardly until it reaches the end of the tube at which time a reflected wave is created which is of the opposite sign of pressure which propagates as an ingoing wave. Since this shock wave has a pressure of the incorrect sign, no fuel will be metered from the orifice 53 when this wave passes the orifice 53. This ingoing wave will not have any effect on the fuel which has already been metered out of the orifice 53 by the outgoing wave because the atomized fuel has already been carried inwardly toward the engine combustion chamber. This will always be true because the outgoing and ingoing waves are opposite in sign and will be delayed in time with respect to each other.

The length of time required for the incoming wave to reach the flow channel 54 is determined by the length of the tube and the speed of sound in air. As is hereinafter explained, it has been found desirable to select the length of the wave tube such that the round trip time for sound to travel in the wave tube in air corresponds to approximately 40.degree. of crankshaft travel at the maximum useful engine speed.

In considering the design of the wave tube, it should be considered that the degree of atomization of a liquid fuel in air is dependent upon the relative velocity between the liquid fuel and the air. As this velocity becomes an appreciable fraction of the velocity of sound, both the mean drop size and the variation in drop size decrease to small values, dependent upon the surface tension of the fuel. For this reason, it is desirable to atomize fuel at a sonic velocity if possible to thereby insure the maximum degree of atomization of the liquid fuel.

In considering the wave tube utilized in the present carburetor as one having a constrant or uniform cross-sectional area and having a steady volume air flow rate q, certain determinations can be made. Neglecting friction, the steady-state pressure

p = q.sup.2 d/2A.sup.2

where

d is the density of air in the tube, and

A is the cross-sectional area of the tube.

If it is shown that there is a demand for this volume air flow rate through the tube immediately after the sudden opening of the intake valve, a shock wave will be propagated down the intake tube generating an acoustic pressure

p' = cqd/A

where

c is the velocity of propagation, which for a weak shock wave is equal to the velocity of sound in air.

The ratio of acoustic pressure to steady state pressure is 2cA/q and since q/A = v, where v is the steady state air velocity, then p'/p = 2c/v. Thus, it will be seen at low steady state air velocities, the steady state pressure is negligible compared to the acoustic pressure. This acoustic pressure will persist until the shock wave, traveling at the speed of sound, makes the round trip from the intake valve to the open end of the wave tube and back again.

The length and diameter of the intake wave tube determine the range of engine operation over which sonic atomization, fuel metering linearity and minimum steady state pressure loss may be achieved. For example, if the maximum pressure loss at peak engine speed is chosen not to exceed 5% and the maximum metering non-linearity is chosen not to exceed 5%., the optimum diameter of the intake wave tube is determined by

D = 2.58 .times. 10.sub.-.sup.3 x.sqroot. VNe (cm),

where

V is the displacement volume of the cylinder in cm.sup.3,

N is the maximum engine speed in rpm, and

e is the fractional volumetric efficiency at maximum engine speed.

The length of the intake wave tube is determined by

L = 1.15 .times. 10.sup.5 /N (cm).

Increasing the diameter of the intake wave tube above this value increases the minimum engine speed at which sufficient atomization energy is avaiable, since p' is proportional to the square of the ratio of engine speed to tube area, while decreasing the diameter of the intake tube below this value increases the steady state pressure loss at peak engine speed approximately inversely as the 4th power of the tube diameter. The length of the intake tube is less critical. Decreasing the length of the tube raises the minimum engine speed only inversely as the length, while increasing the length of the wave tube introduces some metering non-linearity and friction loss.

The location of the slide valve or sliding throttle plate 31 relative to its longitudial position with respect to the axis of the wave tube is selected so that at part throttle openings, an increase in air/fuel ratio occurs consistent with the nominal requirements of the engine under part load conditions. This results in better fuel economy and lower carbon monoxide and unburned hydrocarbon emissions. This occurs because the effective length of the intake tube, which directly determines the metering pressure from a given fuel jet size, is reduced. Optimum placement of the slide valve depends on the parameters of the engine on which the carburetor is mounted and the desired operating conditions.

If desired, the physical spacing and the angular orientation of the axis of the fuel jet with respect to the axis of the throttle plate may be varied to tailor the part-throttle air/fuel ratio because the steady state air flow, which carries atomized fuel droplets into the combustion chamber, has a much smaller angle of convergence approaching the throttle plate than the shock wave. Therefore, the air/fuel ratio may be increased at low throttle settings by "hiding" the fuel jet behind the throttle plate by rotation of the jet axis in a plane parallel to the throttle plate and/or increasing the distance between the jet axis and the throttle plate. In this connection, it should be noted that the increase in air/fuel ratio is more strongly controlled by a function of rotation than the distance at very low throttle settings.

It should be appreciated that full throttle or open throttle is when the passage or bore 32 in the slide valve is in complete registration with the bores or passages 28 and 33 and that this throttle opening can be gradually decreased by releasing the cable 41 and permitting the spring 36 to move the slide valve or throttle plate 31 to the right as viewed in FIG. 4 to progressively close off the wave tube.

The flared outer end of the wave tube minimizes entrance losses.

It should be noted that the fitting 51 is placed in the wall of the wave tube 46 because the axial position of the orifice 53, for the purposes of metering fuel into the wave passages, is relatively immaterial. This is true because the shock wave, after it passes through the slide valve or throttle plate, expands almost immediately so that it will effectively atomize any fuel which it draws into the wave tube.

In connection with the design of the carburetor and the fuel system incorporated in the present invention, it has been found desirable to terminate the returning or incoming shock wave so that no further shock waves are produced. For this purpose a viscous acoustical resistance has been provided in the form of a slot 101 (see FIGS. 2 and 4) formed in the base 23. The slot 101 extends the width of the base 23 and is open to the atmosphere on both sides. The slot has a width which is only slightly greater than the interior diameter of the wave tube. The slot 101 serves as a terminating slot and in effect absorbs the incoming shock wave so that there are no further reflections from the shock tube. Thus, each shock wave can only make one round trip through the wave tube. Further reflections of the shock wave are eliminated to prevent such reflections from causing perturbations in the metering linearity over the operating range of the internal combustion engine on which the carburetor is mounted. As can be seen, the slot 101 is positioned immediately adjacent to and opens into the bore 33.

It is possible under certain conditions of engine operations where a very high air/fuel ratio, that is, a very lean mixture, is desired, as under part throttle conditions, that supplemental means be provided to increase the air/fuel ratio. Because of the form of the throttle plate or slide valve, it is expedient to utilize the movement of this throttle plate to admit supplemental acoustical resistance which is effectively in parallel with the wave tube such that the acoustical impedance looking into the tube becomes much lower. This will lower the shock wave pressure, thus metering less fuel for a given value of steady state airflow thrugh the wave tube and thereby producing the desired increase in air/fuel ratio. For this purpose a thin slot 102 is milled into the body 22 and is open to the recess 29. A hole 103 is formed in the body 22 and is in communication with the slot 102 and is open to the atmosphere. The slot 102 and the hole 103 serve to provide a variable acoustical impedance as the throttle valve is moved. Hole 103 serves merely to expose slot 102 to the atmosphere. By placing this slot 102 close to the longitudinal axis of the slide, a monotonically increasing air/fuel ratio is obtained with a decrease in throttle opening. By proper placement of slot 102, great latitude can be obtained in mixture compensation. It should be appreciated, however, that the depth of slot 102 should be relatively small to maintain the desired ratio of acoustical resistance to inductive reactance of slot 102. The acoustical resistance of the slot 102 varies as the 4th power of the depth of the slot 102 whereas the inductive reactance varies directly as the depth of the slot. It is preferable to maximize the ratio of the acoustical resistance relative to the inductive reactance because it is the acoustical resistance which is most effective in modifying the shock wave pressure.

In operation of the carburetor 21 on an internal combustion engine, the carburetor can be positioned in any desired position. Thus, for example, the wave tube can be positioned so that it is a side draft wave tube or a down draft wave tube. It is only important that the fuel supply bowl and the orifice therein be positioned in such a manner that the level of the fuel in the fuel bowl barely covers the orifice.

Another embodiment of the fuel control system incorporating the present invention is shown in FIGS. 11 and 12, utilizing a pump control. For this purpose, a fuel supply bowl 111 similar to the bowl 57 can be provided. It is provided with an inlet or fill tube 66 as well as a drain tube 71. The control tube 68 is omitted. The fitting 51 and the drain tube 71 are positioned so that the lower-most point of the drain tube is flush with the upper portion of the orifice 53. In such a bowl, fuel is supplied by a pump to the fill tube 66 continuously and the excess fuel which is not utilized drains away through the drain tube 71. At all times the fuel 89 is maintained at a level which just covers the orifice 53.

In FIG. 12, there is shown a fuel supply system utilizing a plurality of fuel supply bowls 111 such as would be used in connection with an eight-cylinder internal combustion engine. The fuel 89 is supplied from the tank 113 through a pipe 114 to an engine-driven pump 116. The pump 116 supplies fuel through a throttle-actuated regulator 117 to a line 118 which is connected to the fill tube 65 of each of the fuel supply bowls 111. A line 119 is connected to the drain tubes 71 and is connected into the space 121 overlying the fuel in the tank 113 so that it can be readily drained into the tank by gravity flow. Thus, fuel will be continuously supplied to each of the fuel supply bowls 111 so that it can be supplied to the wave tube of the carburetor associated therewith.

In FIGS. 13 and 14 there is shown how the present carburetor and fuel supply system can be incorporated into an eight-cylinder internal combustion engine having a 4-stroke cycle. Thus, as shown in FIGS. 13 and 14, there has been provided an internal combustion engine 131 of a conventional type. Such an engine includes a block 132 provided with cylinders 133 having reciprocating or moving pistons 134 mounted therein. The combustion chamber 136 is provided above the piston and is adapted to be placed in communication with an intake passage 137 through an intake valve 138 operated by a cam 139. Similarly, the combustion chamber 136 is adapted to be placed in communication with an exhaust passage 141 through an exhaust valve 142 operated by a cam 143.

A carburetor 146 incorporating the present invention is provided for each of the cylinders of the internal combustion engine. As can be seen, the carburetors 146 are mounted upon the engine block. The carburetors 146 are provided with wave tubes 148 of the type hereinbefore described. In addition, the carburetors are also provided with fuel supply bowls 149 similar to those hereinbefore described. As can be seen from FIGS. 13 and 14, the wave tubes of the carburetors are inclined upwardly at a suitable angle such that the wave tubes 148 are coaxial with the intake passages 137. Means is provided on the engine 131 for filtering the air entering the carburetors 146 and consists of a box-like enclosure 151 which is mounted on the engine and which is provided with a removable cover 152 to permit access to the carburetors 146. The housing or casing 151 is provided with louvered openings 153 through which air passes into the housing 151 and thence through filters 154 mounted on the sides of the container as shown in FIG. 13. In this way, all air entering the carburetors 146 will be filtered.

As can be seen from FIG. 14, the four carburetors provided on each side of the enginer are formed from a common body casting 161 which extends substantially the entire length of the engine and a common base casting 162 both of which are fastened together by the screws 147. The base casting is secured to the block 132 by screws 150 (FIG. 13). Similarly, a common throttle plate is therefore provided with four holes or openings 167, one of which is associated with each carburetor.

Means is provided for operating the throttle plate 166 and consists of a linkage mechanism 169. The linkage mechanism consists of a shaft 171 which is rotatively mounted in L-shaped arms 172 and secured to the housing 151. A plate 173 is secured to the shaft 171 and has a linkage 174 connected thereto which extends downwardly through a slot 176 in the housing 151. The linkage 174 is connected to a conventional accelerator mechanism such as that utilized in an automobile so that the shaft 171 can be rotated by operation of the acceleration pedal. Two arms 176 are provided on opposite ends of the shaft 171 and are connected. by ball and pivot assemblies 177 to threaded shafts 178 which are connected to ball and pivot assemblies 179 secured to the throttle plates 166. Thus, it can be seen that as the shaft 171 is rotated, the throttle plates 166 will be moved simultaneously. Means is provided for returning the throttle plates to positions in which the holes 167 are out of registration with the wave tubes of the carburetor and consists of springs 181 secured to posts 182 secured to the body castings 161 and posts 183 secured to the throttle plates 166.

The fuel supply system which is utilized in the embodiment of the invention shown in FIGS. 13 and 14 is of the pump control type and fuel is supplied under pressure from the pump through line 191 to a regulator 192. The regulator 192 supplies its output to a pipe 193 which is connected by lateral extensions 194 through tubes 196 to the filler tubes of the fuel supply bowls 149. The operation of the regulator 192 is controlled through the accelerator linkage as is shown in FIG. 14. The arm 173 is connected by a pivot and ball assembly 201 to a threaded rod 202 which is connected by a pivot and ball assembly 203 to an arm 204 mounted on the regulator.

The drain tubes of the fuel supply bowls 149 are connected to tubes 206 which are connected to two extensions 207 of a drain pipe 208. As can be seen from FIG. 13, the drain pipe 203 is at the level which is substantially below the level of the drain pipes from the carburetors so that in the event the engine is tilted during operation fuel from one carburetor will not flow into the carburetor on the other side.

The operation of this embodiment of the invention is similar to that hereinbefore describedd with the principal difference being that there are a plurality of carburetors and cylinders provided for the internal combustion engine. From the concentration shown it can be seen that all of the carburetors will operate in unison with the cylinders to supply the so-desired fuel/air mixture to the cylinders. All of the advantages described in the preceding embodiments are applicable to the present embodiment. The shock wave is utilized for automization of the fuel. This fuel atomization is accomplished in a very efficient manner without a marked pressure drop which gives increased performance and increased range of operation. The air/fuel ratio is carefully controlled so that there is a reduction of unburned hydrocarbons and carbon monoxide. Since the carburetor utilized is relatively simple, manufacturing and maintenance costs are greatly reduced. While obtaining the maximum degree of atomization and providing for efficient use of fuel, there is excellent throttle response and a 60 : 1 range of efficient airflow rate handling capability.

Still another embodiment of the invention is shown in FIG. 15 which shows the applicability of the invention to two-stroke cycle engines. Thus, as shown in FIG. 15, there is provided a two cycle engine 216 which is provided with a cylinder 217 which has a reciprocating piston 218 therein. The engine block 219 is provided with a transfer passage 221 which is controlled by the piston 218. The block is also provided with an exhaust passage 222 also controlled by the piston. The piston drives the crankshaft 223 which is rotatably mounted on the block. The crankshaft 223 drives a rotary valve 224 which is provided with a bore or passage 226 which is adapted to be moved into registration with an intake port 227 provided in the block. This bore 227 is in registration with the wave tube of a carburetor 231 incorporating the present invention. As shown in FIG. 15, the carburetor 231 is mounted in a side draft fashion and utilizes an air control tube 232 for controlling the flow of fuel into the fuel bowl. The carburetor 231 operates in the manner hereinbefore described as with the other embodiments of the invention. A shock wave is formed within the two cycle engine similar to the four cycle engine and is propagated down the wave tube to atomize the fuel as hereinbefore described. A throttle plate 234 is provided for controlling the fuel supplied to the engine to thereby regulate the speed of operation of the engine.

It is apparent from the foregoing that there has been provided a fuel supply system and carburetor incorporated in the same which utilizes a unique method for atomizing fuel and introducing the same into the combustion chamber of internal combustion engines. An airflow without significant pressure drops is provided for movng the atomized fuel into the combustion chamber. The emission of unburned hydrocarbons and carbon monoxide is substantially reduced. Very accurate control of air/fuel ratio can be obtained.

Claims

I claim:

1. A fuel supply system for an internal combustion engine having at least one combustion chamber which is adapted to be placed in communication with an intake opening during each intake event, comprising wall means forming a wave tube having a substantially unimpeded flow passage with one end open to the atmosphere and with the other end adapted to be placed in communication with the intake opening of the internal combustion engine, means forming an orifice disposed in the wall means forming the wave tube and opening into the flow passage of the wave tube, means for supplying fuel to the orifice so that the fuel has a level which will reach the orifice but will not flow through the orifice solely because of the level of the fuel with respect to the orifice, and throttle valve means disposed in the wave tube between the region in which the fuel is introduced into the wave tube and the intake opening, said throttle valve means being formed so that a shock wave from the engine can be propagated down the wave tube to cause fuel to be drawn into the wave tube through the orifice substantially solely during propagation of the pressure shock wave along the wave tube and to atomize the fuel so that the atomized fuel can be carried into the combustion chamber by the incoming air stream flowing in the wave tube, the pressure effect of said wave serving as substantially the sole means for metering fuel from the orifice, said wall means forming a wave tube including a body, said body being formed with shock wave terminating means for preventing a shock wave from traveling substantially more than one round trip in the flow passage in the wave tube for each intake event.

2. A system as in claim 1 wherein said means for supplying fuel includes a fuel supply bowl, means for supplying liquid fuel to the fuel bowl, control means for preventing liquid fuel from being introduced into the fuel bowl to a level which is significantly above the orifice and a drain tube connected to the fuel bowl for draining off excess liquid fuel from the fuel bowl.

3. A system as in claim 2 wherein said drain tube is connected to the fuel bowl at a position which is above the orifice.

4. A system as in claim 2 wherein said control means for preventing fuel from being introduced into the fuel bowl to a level which is significantly above the orifice includes said drain tube.

5. A system as in claim 1 wherein said body has an elongate recess formed therein with a bore opening into the recess and wherein said throttle valve is in the form of a throttle plate slidably mounted in said recess in said body, for movement between throttle open and throttle closed positions, said throttle plate having an opening therein adapted to be moved into registration with said bore in said body so that it is in alignment with and forms a part of the wave tube when the throttle plate is in the throttle open position and is out of registration with said bore in said body in the throttle closed position.

6. A system as in claim 5 together with yieldable means for urging said throttle plate into a position so that the bore in said body is occluded by said throttle plate.

7. A system as in claim 6 together with means for moving said throttle plate so that the opening in said throttle plate is in registration with said bore in said body against the force of said yieldable means.

8. A system as in claim 1 wherein said terminating means is in the form of at least one opening located in the body and establishes communication between the atmosphere and the flow passage.

9. A system as in claim 5 together with supplemental air bleed means formed in the body in communication with the flow passage under the control of the throttle valve.

10. A system as in claim 9 wherein said supplemental air bleed means is provided by a slot in the body open to the recess in the body and a hole in the body in communication with the slot and being open to the atmosphere.

11. In a carburetor, a body having a bore therein, said body being formed with a recess and a throttle plate slidably mounted in said body, said throttle plate having a hole therein adapted to be moved into and out of registration with said bore in said body by movement of the throttle plate, said bore in said body and said hole in said throttle plate being adapted to form a substantially unimpeded flow passage, said body being formed with terminating means extending substantially transversely to the major axis of the flow passage and establishing communication between the bore in said body and the atmosphere for preventing a shock wave in the flow passage from traveling substantially more than one round trip in the flow passage in the wave tube for each intake event.

12. A carburetor as in claim 11 wherein said terminating means is downstream the throttle plate.

13. A carburetor as in claim 11 together with means for yieldably urging said throttle plate into a position in which said throttle plate occludes said bore in said body.

14. A carburetor as in claim 13 together with means for moving said throttle plate into a position in which said hole is in alignment with said bore against the force of said yieldable means.

15. A carburetor as in claim 11 together with means forming an orifice in the body for admitting liquid fuel into said bore in said body.

16. A carburetor as in claim 15 together with a fuel bowl having a chamber in communication with said means forming the orifice.

17. A carburetor as in claim 16 together with means for controlling the level of the liquid fuel in said chamber so that it is generally at the same level as the orifice.

18. In a fuel supply system for an internal combustion engine of a type having a plurality of combustion chambers and having intake openings adapted to be placed into communication with the combustion chambers during intake events, the system comprising separate carburetor means for each of said intake openings, each of said carburetor means including means forming a wave tube having a flow passage therein with one end open to the atmosphere and the other end in communication with an intake opening, means forming an orifice disposed in the wave tube for supplying fuel to the interior of the wave tube, throttle valve means disposed in the wave tube between the region in which the fuel is introduced and the intake opening, means for supplying liquid fuel to the orifice at a level so that fuel will not flow through the orifice solely under the force of gravity and terminating means in the means forming a wave tube for preventing a shock wave in the flow passage from traveling substantially more than one round trip in the flow passage for each intake event.

19. A system as in claim 18, together with air cleaner means for filtering the air prior to the time it is supplied to the wave tubes.

20. A system as in claim 18 wherein as a part of said throttle valve means certain of said carburetors are provided with a common throttle plate, said throttle plate having an opening therein for each of said certain carburetors.

21. In a method for introducing a fuel and air mixture into the combustion chamber of an internal combustion engine, in which shock waves are formed and in which a column of air flows into the combustion chamber during each intake event, providing a supply of liquid fuel adjacent the column of air propagating a shock wave created in the engine outwardly through the column of air to cause fuel to be drawn into the column of air and to be atomized so that the atomized fuel can travel with the column of air, providing a reflected shock wave which travels inwardly through the column of air, and substantially attentuating the reflected shock wave so that there is substantially only one round trip travel of the shock wave from and back to the engine during each intake event.

22. A method as in claim 21 together with the step of confining the moving column of air in a wave tube having a substantially unimpeded flow passage.

23. A method as in claim 22 together with the step of controlling the time delay between the reflected shock wave and the outgoing propagated shock wave by controlling the length of the wave tube.

24. A method as in claim 22 together with the step of controlling the pressure amplitude of the outgoing and reflected shock waves by controlling the cross-sectional area of the wave tube.

25. A system as in claim 1 wherein said means for maintaining the level of liquid fuel with respect to said orifice comprises a fuel bowl having fuel therein at a predetermined level with an air space above the fuel, a sealed fuel supply vessel located at a level above said fuel bowl, means forming a fuel feed passage connecting said fuel bowl and said fuel supply vessel, means forming a control passage between the air space above the fuel in said fuel supply vessel and down to the predetermined level in the fuel bowl, and means forming a vent passage in the fuel bowl between the air space above the fuel in said fuel bowl and the atmosphere.

26. A system as in claim 1 wherein said means for maintaining the level of liquid fuel with respect to said orifice comprises a fuel bowl having fuel therein at a predetermined level with an air space above the fuel, a fuel supply vessel located at a level below said fuel bowl, means forming a fuel feed passage between said fuel bowl and said fuel supply vessel, fuel pump means connected in said means forming a fuel passage for supplying fuel from said vessel to said bowl, means forming a fuel drain passage connected between said fuel bowl and said fuel supply vessel, said means forming the drain passage being positioned in the bowl so that a predetermined fuel level is maintained in the bowl, and means in the fuel bowl forming a vent passage between the air space above the fuel in said fuel bowl and the atmosphere.

27. A system as in claim 26 together with a fuel flow regulator connected into said means forming said fuel feed passage and which is responsive to engine fuel demand whereby said regulator prevents excess fuel recirculation.

28. A fuel supply system for an internal combustion engine having at least one combustion chamber which is adapted to be placed in communication with an intake opening during each intake event, comprising wall means forming a wave tube having a flow passage for a medium therein with one end open to the atmosphere and with the other end adapted to be placed in communication with the intake opening of the internal combustion engine, means forming an orifice disposed in the wall means forming the wave tube and opening into the flow passage therein, said flow passage being formed so that the maximum pressure effect at the orifice due to a shock wave generated by the engine in said medium in the flow passage is substantially greater than the maximum pressure effect at the orifice due to the velocity of said medium in the flow passage, said wall means forming a wave tube including a body, said body being formed with shock wave terminating means for preventing a shock wave from traveling substantially more than one round trip along the flow passage in the wave tube for each intake event, means for supplying fuel to the orifice so that the fuel will be introduced into the flow passage in the wave tube through the orifice substantially only in response to said pressure effects at the orifice, and throttle valve means disposed in the wave tube between the region in which the fuel is introduced into the flow passage in the wave tube and the intake opening of the internal combustion engine.

29. In a method for introducing a fuel and air mixture into a combustion chamber of an internal combustion engine, in which a shock wave is generated during an intake event in a medium confined by wall means defining an intake passage, the improvement of substantially terminating the progress of the shock wave after one round trip travel from and back to the engine of the shock wave in said medium for each intake event.

30. A method as in claim 29 together with the step of introducing fuel into said medium substantially solely in a region adjacent the wall means defining an intake passage.