US2733901A - sutton - Google Patents

Description

Feb. 7, 1956 R. w. SUTTON 2,733,901

CARBURETOR Filed Sept. 29, 1951 2 Sheets-Sheet 1 INVENTOR.

E0552 W Jurro/v W W. aiw

' ATTORNEY United 3 Claims. c1. 261-41) This invention relates to charge forming devices for internal combustion engines having a variably throttled air supply, and more particularly to idle systems for such engines.

Engine idling. requirements present special problems to be met by an injection carburetor since the air flow to the engine is so low in the idle range that insufiicient air metering forces are set up in the pressure regulator to accurately establish the required fuel to air ratios. Idle valves and various valve adjustments have been used in the past to satisfy the engine requirements in this range. However, the problem of insuring smooth engine running at slow idle remains.

It is therefore a principal object of this invention to insure smooth running of the engine at slow idlecondi tions.

It isa further object of this invention to provide an idle system which will meet wide variations in engine requirements throughout the idle range.

Another object of this invention is to provide an idle systemv which operates independently of manifold suction and. which discharges fuel to the engine throughout the range of operation of the engine.

Other objects and advantages will be readily apparent from. the following detailed description taken in connection with the accompanying drawings in which:

Figure 1: is a schematic sectional view of a carburetor in which one embodiment of my invention is shown;

Figure 2 is a partial section of. the carburetor shown in Figure 1 including another embodiment of my invention;

Figure 3 is a partial section of the carburetor shown in Figure 1 in which a third embodiment of my invention is disclosed;

Figure 4 is a partial section of the carburetor shown in Figure l in which a manual engine priming control is shown in combination with the slow idle system; and

Figure 5 is a plan view of the mechanism shown in Figure 4'.

Referring first to Figure l, a main body or housing is shown at numeral having an air induction passage 12 I therethrough with an air inlet at 14 and an air outlet at 116; Main body 10 is adapted to be connected to an air horn or scoop on theair inlet side and to a supercharger inlet or to the intake manifold of an internal combustion engine on the air outlet side thereof. Housed within said air induction passage is a venturi 18 having an annular passage 20 at the throat thereof subjected to venturi suction. Downstream of venturi 18 in the induction passage tes Patent 0 ice 2- thereto by valve extension 54 and stem 56. When fuel is flowing, a constant rate compression spring 58- abuts diaphragm assembly 30' at 60 and acts to open the regulator valve in opposition to a" small compression spring 62 and the fuel: pressure in chamber 28. Pressurized fuel is supplied to chamber 28 by a pump (not shown) through fuel inlet port 64, conduit 66 and valve controlled port 52.

A main metering jet 68 in series with regulator valve portv 52: connects chamber 28 to main fuel passage 70', which passage is connected to a critical flow nozzle 72 by means of an idle valve port 74, a conduit 76, and a-- main discharge valve port. 78. Air is supplied to the nozzle through conduits 38, 79 and 81 to minimize the effect of engine suction on fuel delivery. The discharge nozzle 72 is described and claimed in Patent No. 2,457,765 to Winkler.

The effective area of idle valve port 74 is controlled by axially movable idle needle valve 80 which is concentric with and: rigidly attached to scaling diaphragm 82. A rightward or closing movement is imparted to valve 80 by manual idle control rod 84 when the throttle lever 86- is moved to an idle position. Chamber 88 to the left of diaphragm 82 is vented to venturi suction through a conduit 90 so that the fuel to air differential pressure across diaphragm 82' will cause valve 80: to follo-wjthe movement of. throttle lever 86 throughout the idle range. v

The basic carburetor shown in Figure 1', including the discharge nozzle valve asembly shown generally at 92-, is described and claimed in Patent No. 2,445,846 to Barfo'd et al.,. said valve assembly being composed of chambers 94 and 96 separated by a diaphragm 98, and said chambers being vented to venturi suction and metered fuel pressure respectively. A compression spring 100, which may be adjusted by an adjustingscrew 101, acts on the venturi side of diaphragm 98 and movements of said diaphragm are imparted to valve 102 which controls the effective area of port 78.

An acceleration pump which is shown generally at 104 consists of chambers 106 and 108 separated by a spring loaded diaphragm 110, chamber 106 being vented to manifold suction through conduit 112 and 'charnber' 108 being vented. to metered fuel pressure in conduit '70 spring loaded diaphragm 122' which controls a valve 124 concentric therewith, so as to vary the effective area of a. port 126 after the differential pressure across said diaphragm reaches a predetermined amount. Chamber 1 18 is vented through conduit 128 to the venturi suction in chamber 26, while chamber is vented to unmetered fuel pressure in chamber 28 through conduit 130. At some predetermined unmetered fuel pressure valve 124 opens allowing the necessary enrichment to occur while the engine is operating in the power range.

A manual mixture control valve 132 controls the effective area of a calibrated passage 134 which connects chamber 24 with chamber 26 through conduits 34, '36 and 40. Valve 132 is remotely controlled by the pilot by means of a linkage (not shown) connected to lever 136. Clockwise rotation of lever 136' moves arm 138 rightwardly to abut cam 140 and move valve 132" varying amounts out of port 134; This provides means for auto rich or auto-lean operationas desired by the pilot. As

valve 132 is moved to open port 134 auto-lean operation 3 is approached since the venturi suction in chamber 26 is progressively bled down, thereby decreasing the unmetered fuel pressure required to balance the air metering force. As valve 132 is moved toward closed position the reverse effect occurs. When the engine is stopped fuel flow thereto is cut off by moving valve 132 to a full rightward position in which position cam 140 depresses lever 142 resulting in an upward movement of idle cutofi plunger 144 against lever 146 to compress spring 58 and allow regulator valve to close.

In parallel with said manual mixture control device is automatic mixture control unit or altitude control 148 covered by Patent No. 2,469,038 to Winkler. Chamber 24 communicates with annulus through conduits 34, 36 and 150, chamber 152, a port 154, conduits 156, 42 and 44, restriction or mixture control bleed 46, and chamber 48, the area of said port 154 varying inversely as a function of altitude density. As entering air density decreases bellows 157 expands moving contoured mixture control valve 157' to further open port 154-.thereby increasing the pressure in chamber 26 as a function of the mass of air flowing to the engine which in turn causes a decrease in unmetered fuel pressure and a decreased fuel flow to maintain a constant fuel air ratio for any given power setting. The reverse operation occurs upon an increase in entering air density.

At slow idle valve 102 is nearly closed, resulting in undue sensitivity of said valve to the fuel flowing through port 78. This sensitivity is due to the velocity of the fuel flowing through said port which tends to draw valve 102 to a fully closed position, resulting in valve vibration and unsatisfactory engine performance at this minimum flow condition. To overcome this ditficulty, a separate system is provided which assures the proper fuel supply during slow idle. This system includes a fuel passageway 158, consisting of a conduit 160, chambers 161 and 162, conduit 163, chamber 164 and port 165, for connecting the unmetered fuel chamber 28 with the induction passage 12 on the engine side of throttle valve 22. A metering jet 166 controlled by a manually adjustable valve 168 is disposed between chambers 161 and 162. Chamber 164 in main body housing 10 communicates with impact air pressure through conduit 38 and passage 79 to minimize the effect of engine suction 'on fuel flow through passageway 158.

Assuming the carburetor has not been filled with fuel and the idle cutoff plunger 144 is in the position shown in Figure 1, the spring 58 will urge the diaphragms to the right and open valve 50. Fuel under pressure supplied to conduit 66 enters and fills chamber 28 and flows through metering jet 68 to chamber 96 of the discharge nozzle valve, thence through port 78 and critical flow nozzle 72. As the pressure in chamber 28 increases it acts against the diaphragm 32 and tends to compress spring 58 whereby the valve 50 tends to close. Fuel under pressure supplied to chamber 96 acts on diaphragm 98 and tends to open valve 102., The adjusting screw 101 is normally adjusted to compress spring 100 to such a point that a slightly lower pressure is required in chamber 96 to open the valve 102 than is required in chamber 28 to permit the valve 50 to close. It is apparent that the actual values of the fuel pressures will be determined by the strength of the springs 58 and 100, the pressure required being greater as the strength of the springs is increased.

During operation, assuming the. area ratio of the diaphragms and 32 is two to one, the regulator unit 23 functions to maintain a differential fuel pressure across the metering jet 68 and, if the engine is operating in the high power range, across port 126 which is equal to twice the venturi drop as sensed in chambers 24 and 26. For example, a given decrease in venturi throat pressure as sensed in chambers 26 and 94, i. e. as compensated by automatic mixture control 148 so that said pressure is proportional to the mass of air flowing, results in an A metered fuel pressure.

4: 1 equal increment increase in the unmetered fuel pressure in chamber 28 and in an equal increment decrease in the Consequently the increase in fuel metering differential pressure is equal to twice the increase in air metering differential pressure. Similarly a given increase in air impact pressure is sensed in chamber 24 and since it acts on a diaphragm having twice the area of diaphragm 32, the unmetered fuel pressure in chamber 28 is increased an increment double the increase in impact air pressure.

At slow idle, the required fuel is supplied principally through passageway 15% whereby the required fixed fuel to air ratio is established. Fuel continues to flow through said slow idle system throughout the operating range of the engine. The fuel flows involved are so small however, since the port area 166 is adjusted to meet slow idle requirements, that the slow idle system has very little enrichening effect on the fuel air ratio beyond the idle range. For fuel flows in the idle range but beyond slow idle it is preferable that the adjustment of spring 100 is such that the fuel flow from nozzle 72 plus that from passageway 158 satisfy the-engine requirements in this range. This adjustment is easily made at 101, which functions as a vernier to meet exact flow requirements, the basic idle'flows being established by valve 80.

When throttle valve 22 is substantially closed, as at slow idle, throttle lever 86 holds control rod 84 in its maximum rightward position so that valve establishes a minimum flow area at port 74. The only reason for valve 80 being open at all at slow idle is to prevent an abrupt change in fuel flow when the transition to fast idle occurs. The air metering force acting on diaphragm 30 is insuflicient to open regulator valve 50, but spring 58 opens valve 50 a degree which allows an unmetered fuel pressure buildup in chamber 28 sufficient to balance the spring force. Spring of discharge nozzle valve 92 may be adjusted to establish the desired metered fuel pressure in conduit 76. In this'manner accurate control of the pressure differential across variable metering area 74 is established throughout most of the idle range.

As throttle lever 86 is rotated clockwise, thereby opening throttle valve 22, the pressure differential across diaphragm 82 moves valve 80 out of port 74 allowing the fuel flowto increase at a predetermined rate. When valve 80 no longer acts to restrict port 74 the engine is operating in the cruise range and metering jet 68, being smaller in area than port 74, takes over the metering function.

Figure 2 shows a modification of the slow idle device shown in Figure 1. Similar parts have been similarly numbered. A portion of the air induction passage on the manifold side of the throttle valve is shown at 12. The discharge nozzle is shown generally at 72, impact air being bled thereinto from conduits 38, 79, and 81. The main metering jet is shown at 68. Conduit 70 contains fuel at unmetered pressure when the carburetor is operating in the idle range and at metered pressure beyond the idle range. Chamber 161 f the slow idle system communicates with conduit 79 through conduit 176. The desired slow idlefuel flow isestablished by adjustment of valve 168. At fuel flows beyond the idle range it is apparent that the slow idle system flows a steadily decreasing amount of fuel as the air flow increases since, in this range, the metered fuel pressure is steadily decreasing due to the increasing vacuum in chamber 94 as previously explained. This effect reduces the fuel flow through the slow idle circuit to an absolute minimum at air flows beyond the idle range.

Figure 3 shows another modification of the slow idle system. Similar parts have been numbered as in Figure l. The description of Figure 2 pertains here excepting the venting ofchamber 161. Herein, chamber 161 is vented .to chamber 96 of discharge nozzle valve 92 through. conduit 178. Charnber 96 is at metered fuel pressure throughout the range of operation of the carburetor. Since metered fuel pressure decreases at a rate proportional to the increase in mass air flow as heretofore, explained, the fuel pressure differential across slow idle jet 166 likewise decreases for any given impact air pressure and slow idle fuel flow therefore varies inversely as a function of air flow throughout the range of carburetor operation.

Figures 4 and 5 show the slow idle system of Figures 1, 2 and 3 in combination With an engine primer attachment in which a lever 180 is suitably attached to the slow idle adjustment valve 168, as at 182, at the one end thereof, and is manually controllable by a Bowden wire 184 at the opposite end thereof. Resilient means 186 holds lever 180 against a stop 188 at all times except when manual control 184 is actuated to an operative position. Chamber 161 may be vented to either of chambers 2.8, 70 or 96, as desired, through conduit 190. Arcuate slots 192 and 192' in lever 180 are provided so as to allow adjustment of valve 168.

In operation, actuation of lever 180 turns valve 168 out of jet 166, thereby increasing the flow of fuel through jet 166 and the mixture ratio to the engine. When control 184 is released, resilient means 186 returns lever 180 to the stop abutting position shown in Figure 5, in which position valve 168 is adjusted so that jet 166 flows the desired slow idle fuel. An automatic control means, such as a temperature controlled actuator, may be substituted for the manual control shown at 184.

Although several modifications of the invention have been particularly described, it is understood that many changes might be made inthe form and arrangement of the parts without departing from the scope of the invention.

I claim:

1. In a fuel metering device, an air induction passage, a venturi in said passage, a throttle in said passage downstream of said venturi, a main fuel conduit adapted to supply fuel from a source under super-atmospheric pressure to said passage, a metering jet in said conduit, a valve in said conduit upstream of said jet, a first means responsive to air flow through said passage for controlling said valve, a valve in said conduit downstream of said jet, a second means responsive to air flow through said passage for controlling said second mentioned valve, a passageway connecting said conduit upstream of said jet with said induction passage on the engine side of said throttle, a metering jet in said passageway, a chamber in said passageway adjacent the discharge end thereof, and a conduit connecting said chamber to a source of air at substantially atmospheric pressure.

2. In a fuel metering device, an air induction passage, a venturi in said passage, a throttle in said passage downstream of said venturi, a main fuel conduit adapted to supply fuel from a source under super-atmospheric pressure to said passage, a metering jet in said conduit, a valve in said conduit upstream of said jet, a first means responsive to air flow through said passage for controlling said valve, a valve in said conduit downstream of said jet, a second means responsive to air flow through said passage for controlling said second mentioned valve, and a passageway connecting said conduit upstream of said jet with said induction passage on the engine side of said throttle.

3. In a fuel metering device, an air induction passage, a venturi in said passage, a throttle in said passage downstream of said venturi, a main fuel conduit adapted to supply fuel from a source under super-atmospheric pressure to said passage, a metering jet in said conduit, a valve in said conduit upstream of said jet, a first means responsive to air flow through said passage for controlling'said valve, a valve in said conduit downstream of said jet, a means for controlling said second mentioned valve, a passageway connecting said conduit upstream of said jet with said induction passage on the engine side of said throttle, a metering jet in said passageway, a chamber in said passageway adjacent the discharge end thereof, and

a conduit connecting said chamber to a source of air at substantially atmospheric pressure.

References Cited in the file of this patent UNITED STATES PATENTS

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