Patent Application
20080302326
This present disclosure generally relates to an induction system for an internal combustion engine, and more particularly relates to an in-line carburetor and manifold for a high-performance internal combustion engine.
An internal combustion engine produces mechanical motion by combusting air and fuel. The engine includes a plurality of cylinders, and each cylinder has one or more intake valves that intermittently open to allow a combustible suspension of air and fuel into the cylinder. One type of internal combustion engine is a V-8 engine that has eight cylinders in two parallel banks of four cylinders arranged in a “V” orientation.
In some cases, the engine employs a carburetor that creates the air and fuel suspension, and an intake manifold that communicates the air and fuel suspension in a stream from the carburetor to the cylinders. More specifically, the carburetor includes one or more open-ended barrels, and air streams drawn by the cylinders of the engine flow through a venturi throat in each open-ended barrel. The air streams are accelerated as they pass the venturi throats and are reduced in pressure. The low pressure air streams at the venturis are used to draw fuel into the air streams and atomize the fuel in the air streams. Runners extending from the carburetor direct the air/fuel streams from the open-ended barrels of the carburetor to a common plenum, or intake area, within the intake manifold, and a plurality of runners extending from the plenum communicate the air/fuel suspension to each of the cylinders of the combustion engine.
One type of carburetor often used with high-performance engines is a four barrel carburetor having four open-ended barrels arranged in a square array. When a four open-ended barrel carburetor is used, the plenum is relatively square in shape and is relatively smaller than the engine, with the runners extending away from the plenum in differing directions to direct the air/fuel mixture to the cylinders of the engine.
The configuration described above enables sequential servicing of a plurality of cylinders with the full output of a single carburetor. However, the configuration may reduce the quality of the air/fuel suspension delivered to some of the cylinders. For example, the intake valves of the engine are located at various positions on the cylinder head and the runners usually have different lengths and shapes to reach from the plenum to the intake valves. Additionally, when the air and fuel suspension enters the intake manifold, the suspension may be relatively farther away from the openings into some runners than into other runners. As a result, the air and fuel suspension may favor entering one runner over another, or may have more difficulty traveling through one runner than another. It is apparent that a need exists for a carburetor and intake manifold that solves these and other problems.
Briefly described, the present invention concerns an induction system for a combustion engine having two banks of parallel cylinders arranged in a V-shape. The induction system includes a four barrel carburetor body that has in sequence first, second, third and fourth barrels, with the barrels arranged in a row that provide air/fuel streams to the cylinders of the engine. Two barrels, such as the first and third barrels comprise primary barrels and the other two barrels, such as the second and fourth barrels comprise secondary barrels. Butterfly valves are positioned in alignment with each of the barrels and control the air/fuel streams passing through the barrels. A valve linkage is connected to the butterfly valves and is configured for opening the butterfly valves of the primary barrels and for opening the butterfly valves of the secondary barrels after the butterfly valves of the primary barrels are opened.
The valve linkage may be configured to rotate the butterfly valves of the primary barrels in opposite directions from the rotation of the butterfly valves of the secondary barrels. The barrels of the carburetor are arranged in a common plane of alignment and the control linkage configured to tilt the butterfly valves about axes normal to the common plane of alignment.
In one embodiment, the carburetor is mounted on a manifold and the manifold is mounted on the engine. The butterfly valves of the adjacent primary and secondary barrels of the carburetor are arranged to tilt when they are being opened so that their top surfaces rotate toward facing relationship. This tends to develop air/fuel streams that move between the butterfly valves to more concentrated locations in the manifold below the adjacent primary and secondary barrels. The concentrated locations in the manifold are close to the cylinders of the engine that they serve. For example, when the induction system is used with a V-8 engine, one of the concentrated positions for the air/fuel streams delivered by the first and second barrels will be adjacent the four cylinders at one end of the engine and the other concentrated position for the air/fuel streams delivered by the third and fourth barrels will be located close to the cylinders at the opposite end of the engine.
Induction runners extend from the concentrated positions in the manifold and deliver air/fuel streams to the nearest cylinders of the engine. This arrangement allows all of the induction runners to be made with substantially equal lengths and therefore with substantially equal resistance applied to their air/fuel streams. This also tends to cause the air/fuel streams to be delivered to the cylinders of the engine in more equal volumes and velocities.
Other systems, devices, methods, features, and advantages of the disclosed induction system will be apparent or will become apparent to one with skill in the art upon examination of the following figures and detailed description. All such additional systems, devices, methods, features, and advantages are intended to be included within the description and are intended to be protected by the accompanying claims.
The present disclosure may be better understood with reference to the following figures. Matching reference numerals designate corresponding parts throughout the figures, and components in the figures are not necessarily to scale.
Described below are embodiments of an in-line induction system 102 for an internal combustion engine. In this embodiment the carburetor is to be mounted on a V-8 combustion engine having four cylinders in a left bank of cylinders and four cylinders in a right bank of cylinders.
The induction system 102 includes an in-line carburetor 104 (
As shown in
As shown in
The power output of the engine is determined by the volume of air and fuel suspension combusted within the cylinders, which in turn is determined by the volume of air flowing through the barrels 106. To control the volume of air flowing through the barrels 106, each barrel has a butterfly valve such as butterfly valves 118A, 118B, 118C and 118D, shown in
Each butterfly valve is mounted on a butterfly valve control shaft 120, and rotation of the valve control shaft 120 pivots the butterfly valve between the opened and closed positions. The valve control shafts 120 project through the carburetor 104 to a side of the carburetor, where the valve control shafts are coupled together by a control linkage 122 (
The butterfly valves are configured to open and close in a progressive, staggered fashion. More particularly, the butterfly valves 118 include primary butterfly valves 118A and 118C and secondary butterfly valves 118B and 118D. The primary butterfly valves 118A, 118C begin opening in advance of the secondary butterfly valves 118B, 118D, such that the primary butterfly valves are at least partially open while the secondary butterfly valves are still in the closed position. For example, in
The secondary butterfly valves 118B, 118D may open at a faster rate than the primary butterfly valves 118A, 118C, the secondary butterfly valves 118B, 118D having a rotational velocity that exceeds a rotational velocity of the primary butterfly valves 118A, 118C. In some cases, the rotational velocity of the secondary butterfly valves 118B, 118D is selected so that all of the butterfly valves achieve the opened position at substantially the same time. For example, the secondary butterfly valves 118B, 118D may begin opening when the primary butterfly valves 118A, 118C are about 40% open, and may open at a rotational velocity that enables all of the butterfly valves to achieve the open position at the same time even though the primary butterfly valves had a head-start in the opening process.
Providing the carburetor 104 with both primary butterfly valves 118A, 118C and secondary butterfly valves 118B, 118D enables slowly increasing the power output of the engine for smooth acceleration. Otherwise, if all of the butterfly valves began opening at the same time and opened at the same rate, the power output of the engine would quickly increase, causing relatively high acceleration that may cause tire slippage against the pavement.
The butterfly valves open in differing directions, which enables balanced distribution of the air and fuel suspension into the intake manifold 140, as described below. More specifically, the butterfly valves are arranged in pairs 127 along the common axis of alignment 114, each pair including one primary butterfly valve 118A, 118C and one secondary butterfly valve 118B, 118D. Two pairs 127A and 127B are shown in
In
As mentioned above, the carburetor includes a control linkage 122 that actuates the butterfly valves. The control linkage 122 is configured to open the primary butterfly valves 118A, 118C in advance of the secondary butterfly valves 118B, 118D to open the secondary butterfly valves at a faster rate than the primary butterfly valves, and to rotate the butterfly valves of a given pair 127 toward each other while opening. The control linkage 122 is coupled to the valve control shafts 120 of the butterfly valves on the side of the carburetor body 107. More specifically, the control linkage 122 includes a primary actuating lever 128 for each primary butterfly valve 118A, 118C a primary transfer linkage 130 that couples the primary actuating levers 128 together, a secondary actuating lever 132 for each secondary butterfly valve 118B, 118D and a secondary transfer linkage 134 that couples together the secondary actuating lever and the primary actuating lever of a given pair 127 of butterfly valves. In
Each primary actuating lever 128 is coupled to the valve control shaft 120 of a primary butterfly valve 118A, 118C such that rotating the primary actuating lever rotates the primary butterfly valve. The primary transfer linkage 130 extends between and transfers movement between the primary actuating levers 128, so that the primary butterfly valves 118A, 118C open substantially in unison.
As shown in
Each secondary actuating lever 132 is coupled to the valve control shaft 120 of a secondary butterfly valve 118B, 118D, such that rotating the secondary actuating lever rotates the secondary butterfly valve. The secondary transfer linkage 134 couples the secondary actuating lever 132 of a given pair 127 to the primary actuating lever 128 of the same pair. More specifically, the secondary transfer linkage 134 has a fixed end coupled to the primary actuating lever 128 and a movable end coupled to the secondary actuating lever 132. The fixed end of the secondary transfer linkage 134 is coupled to a point on the primary actuating lever 132 that moves away from the secondary butterfly valve as the primary actuating lever rotates. The movable end is positioned in a slot 136 on the secondary actuating lever 132, shown in
For example, as the primary actuating lever 128 begins rotating in the clockwise direction 124 in
In the illustrated embodiment, the carburetor 104 is configurable. More specifically, the carburetor 104 includes the carburetor body 107 and a base plate 109 that can be detached from and reattached to the body for adjustment purposes. The barrels 106 are formed through both the body 107 and the base plate 109, with the venturi surfaces being positioned within the body 107, and the butterfly valves 118A, 118B, 118C, 118D being positioned within the base plate 109. When assembled, the body 107 and the base plate 109 register with each other. The valve control shafts 120 of the butterfly valves extend through the base plate 109, and the control linkage 122 is coupled to the valve control shafts 120 on the side of the base plate.
As a result of this arrangement, the carburetor 104 is configurable. For example, the venturi surfaces on the interior of the barrels 106 can be formed from interchangeable sleeves that can be inserted into the body 107 by separating the body and the base plate 109, as described in U.S. Pat. No. 5,863,470 entitled “Carburetor with Replaceable Venturi Sleeves”, which issued on Jan. 26, 1999 to the Applicant of the present disclosure and is hereby incorporated herein by reference in its entirety. Additionally, the carburetor 104 may have configurable booster venturi sleeves, as described in U.S. Pat. No. 5,807,512 entitled “Carburetor with Replaceable Booster Venturis”, which issued on Sep. 15, 1998 to the Applicant of the present disclosure and is hereby incorporated herein by reference in its entirety. The carburetor 104 may also include the air entries described in U.S. Pat. No. 6,120,007 entitled “Carburetor with Color-coded Interchangeable Components”, which issued on Sep. 19, 2000 to the Applicant of the present disclosure and is hereby incorporated herein by reference in its entirety. In some embodiments, both the body 107 and the base plate 109 are formed from lightweight cast aluminum, although other configurations are possible. Additionally, the carburetor 104 may include adjustment screws. For example, the carburetor 104 includes three adjustment screws in some embodiments, including two idle-mixture screws and one idle-speed screw.
The carburetor 104 also includes an integral fuel bowl, which may eliminate fuel leaks by eliminating the gaskets that may leak under the float level. When the carburetor is disassembled, the air and fuel metering circuits and float mechanisms are exposed for inspection. All of the tuning components with the exception of the accelerator-pump mechanisms are contained within removable assemblies, which make carburetor maintenance—and tuning—convenient.
As mentioned above, the air and fuel suspension created by the carburetor 104 is delivered to an intake manifold 140, which delivers the air and fuel suspension in separate streams to each cylinder of the engine. The intake manifold 140 is shown in
The plenum 142 is about the same length and width as the carburetor body 107, such that when the intake manifold 140 is coupled to the carburetor 104, the exits 112 of all of the barrels 106 are adjacent the plenum 142. A central axis 146 substantially bisects the plenum, and openings 148 into half of the runners 144 are located on either side of the central axis. For example, in
The runners 144 extend from the openings 148 on one side of the central axis 146 through the intake manifold body and to an exit on the other side of the central axis (not shown). Each of the runners 144 is substantially the same length, between the opening 148 and the exit. The runners 144 are symmetrically disposed about a plane that includes the central axes 146 and substantially bisects the intake manifold 140, which is the common plane of alignment 116 of the carburetor when the two components are coupled together. In the illustrated embodiment, the intake manifold 140 is cast aluminum, although other configurations are possible.
To supply the air and fuel suspension to the cylinders, the induction system 102 is positioned above the engine block. More specifically, the carburetor 104 is mounted on the intake manifold 140, and the intake manifold is mounted on the engine block between the two cylinder banks 804. The common axis of alignment 114 of the carburetor 104 is substantially aligned with the central axis 146 of the intake manifold 140 and the crankvalve control shaft 806 of the engine. In other words, the central axis 146 of the intake manifold 140 and the crankvalve control shaft 806 of the engine 800 then lie in the common plane of alignment 116 that bisects the barrels 106 of the carburetor 104.
In use, the cylinders of the engine 800 do not fire simultaneously. Instead, the cylinders operate in a staggered fashion with respect to each other. The carburetor 104 continuously feeds the air and fuel suspension into the plenum 142 of the intake manifold 140, where the air and fuel suspension is distributed to the cylinders on an as needed basis. More specifically, when the intake valve 802 of a cylinder opens, the air and fuel suspension is drawn from the plenum 142 through the runner 144. Such an arrangement enables intermittent servicing of a plurality of cylinders with the full-output of a larger carburetor. Because the fuel within the air and fuel suspension has different physical characteristics than the air in which it is suspended, such as inertial differences, the air and fuel suspension may favor entering the opening into one cylinder over another. To mitigate these effects, the carburetor 104 tends to feed the plenum 142 of the intake manifold 140 along the central axis 146 of the intake manifold 140, and the runners are symmetrically disposed with respect to the bisecting plane 116.
More specifically, the barrels 106 are aligned with the central axis 146 of the intake manifold 140 and the butterfly valves open by rotating in the bisecting plane 116, so that the air and fuel suspension flowing through the butterfly valves into the plenum 142 tends to be centered with respect to the central axis of the intake manifold and is not preferentially directed toward runners 144 located on either side of the central axis of the intake manifold. Each half 150 of the plenum is positioned adjacent one primary butterfly valve 118A, 118C and the primary butterfly valves open substantially in unison, so that the air and fuel suspension is equally dispersed between the two halves of the plenum 142 and is not preferentially directed toward runners 144 located in one half of the plenum versus the other half. The primary butterfly valve 118A, 118C opens toward the secondary butterfly valve 118B, 118D with which it is paired, so that the air and fuel suspension flowing through the partially open butterfly valve is directed toward a center 152 of the half 150 of the intake manifold 104 it is servicing. When the primary butterfly valves 118A, 118C have opened to a predetermined degree, the secondary butterfly valves 118B, 118D begin opening substantially in unison toward the primary butterfly valve of its pair 127. Therefore, each half 150 of the intake manifold 140 is serviced with substantially the same volume of air and fuel suspension. The air and fuel suspension tends to be fed along the central axis 146 of the intake manifold 140 and is directed toward the centers 152 of the intake manifold halves without being directed toward particular runners 144 located on one side of the central axis 146 versus the other. This delivers the air/fuel suspensions from the carburetor to the concentrated positions 152 in the halves of the manifold that are substantially equidistant from the entries of the induction runners at each end of the manifold.
The openings 148 into the runners 144 are substantially the same distance from the central axis 146, and are sloped away from the central axis, so that the air and fuel suspension can enter the openings without a significant change in direction. Further, the runners 144 are symmetrically disposed with respect to the bisecting plane 116. Therefore, in embodiments in which the intake manifold 140 is substantially the same length as the engine block, the distance from the central axis 146 of the intake manifold 140 to the intake valve 802 of the cylinder may be substantially the same through each runner 144. In other words, a path that the air and fuel suspension travels from the central axis 146 to the intake valve 802 may be relatively the same in terms of length and angle, despite the fact that different cylinders are located at different positions along the cylinder banks. Equalizing the path traveled by the air and fuel suspension is desirable, because such a configuration enables selecting characteristics of the air and fuel suspension based on the desired performance of the engine, and ensuring the air and fuel suspension entering the intake valves 802 embodies those characteristics regardless of the cylinder to which it is delivered.
Because the fuel is not directed to one central position in the plenum and then distributed out to the cylinders through runners having varied shapes and sizes, the engine 800 is more likely to exhibit lower fuel consumption, improved low-speed idle, improved part-throttle driveability, and improved combustion. The equal length runners 144 allow a larger camvalve control shaft, such as a performance camvalve control shaft, to operate at low engine speeds with low vacuum.
The induction system 102 of the present disclosure can be used with a variety of engine types and sizes including other V-8 engines as well as engines having greater or fewer cylinders and engines having cylinders that are not arranged in a V-orientation. In such embodiments, the carburetor 104 may have greater or fewer barrels 106, and the intake manifold 140 may have greater or fewer runners 144.
While particular embodiments of an induction system have been disclosed in detail in the foregoing description and figures for purposes of example, those skilled in the art will understand that variations and modifications may be made without departing from the scope of the disclosure. All such variations and modifications are intended to be included within the scope of the present disclosure, as protected by the following claims.
