US3789813A

US3789813A - Fuel mixture control

Info

Publication number: US3789813A
Application number: US00255761A
Authority: US
Inventors: D Hunt
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-05-22
Filing date: 1972-05-22
Publication date: 1974-02-05
Anticipated expiration: 1991-02-05

Abstract

Means responsive to the temperature of the engine are employed to adjust the flow of fuel in the carburetor to regulate the mixture during normal operation of the engine. In addition, means are preferably provided which also effect an automatic adjustment of the fuel flow to the engine in accordance with variations in atmospheric pressure such as occurs at different elevations.

Description

Muted States Patent 11 1 1111 3,739,913 Hunt 1 Feb. 5, 1974 1 FUEL MIXTURE CONTROL 1,823,017 9/1931 Wolfard 123/119 1" 1,869,431 3/1932 King et 111.. 123 119 R [75] lnvemor- East Lansmg 2,037,486 4/1936 Rogers 123/119 1' 73 Assignee; Donne" R Matthews, in, East 2,185,578 1/1940 Beardsley, r. e al, 123/119 R Lansing Mich 2,562,656 7 1951 Blakeslee 123 119 R 2,426,741 9 1947 Mock 123 119 R [22] Filed: May 22, 1972 Appl. No.: 255,761

U.S. Cl 123/119 F, 123/179 G, 123/180 T,

[51] Int. Cl [58 Field of S earch..I12/1191i, 1151 179 G,

123/180 R, 180 T; 261/39 A, 39 B, 39 R [56] References Cited UNITED STATES PATENTS 1,392,141 9/1921 Giesler 123/180 T 1,142,824 6/1915 Lund 1,598,677 9/1926 Donning et al. 123/119 F Primary Examiner-Wendell E. Burns Attorney, Agent, or FirmDonald P. Bush 57] ABSTRACT Means responsive to the temperature of the engine are employed to adjust the flow of fuel in the carburetor to regulate the mixture during normal operation of the engine. 111 addition, means are preferably provided which also effect an automatic adjustment of the fuel flow to the engine in accordance with variations in atmospheric pressure such as occurs at different elevations.

2 Drawing Figures FUEL MIXTURE CONTROL BRIEF SUMMARY OF THE INVENTION In conventional internal combustion engines, such as presently employed in automotive vehicles, fuel is mixed with air in the carburetor and is supplied to the cylinders through suitable manifolding. In conventional carburetors flow of air through the carburetor is controlled by a throttle valve and fuel is drawn into the air flowing through the carburetor, usually at a point of low pressure produced by a venturi. The quantity of fuel which is drawn into the air flow is regulated by a needle valve, adjustment of which varies the richness of the fuel mixture.

It is of course recognized that under cold starting conditions a choke is provided which produces a rich fuel-air mixture for starting. The present invention however, is concerned with regulation of flow of fuel into the air stream during normal operation of the engine, and is not concerned with controlling the fuel-air mixture at starting.

At the present time, the adjustment of the so-called needle valve for controlling flow of fuel into the air stream in the carburetor is set at an intermediate position such that the supply of fuel mixture tothe engine is within acceptable limits as to the richness of the fuelair mixture. However, it has been determined that best results, and particularly more complete combustion, occurs when there is a regulation of the supply of fuel in accordance with engine temperature and also in accordance with atmospheric pressure. The result is a cleaner burning of the fuel and less undesirable contaminants in the exhaust.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a more or less diagrammatic view of a fuel supply system constructed in accordance with the present invention, with parts broken away.

FIG. 2 is a sectional view on the line 2-2, FIG. 1.

DETAILED DESCRIPTION Referring now to FIGS. 1 and 2, a carburetor is provided with an air flow passage 12 including a venturi 13 through which air flow is induced by manifold vacuum.

Flow of air through the air passage provides a low pressure zone at the venturi, and fuel is drawn into the flowing air through a

fuel supply passage

18,20. Flow of fuel is regulated by a needle valve 22, movable longitudinally to control 'the fuel-air mixture by a threaded portion 24.

Prior to this invention, needle valve 22 has been adjusted manually to a position in which it'remains during normal engine operation, although conditions may change which for optimum engine performance and complete combustion with minimum harmful products of combustion would require an adjustment of the needle valve.

One condition calling for adjustment of the needle valve to avoid or minimize harmful components in the engine exhaust is engine temperature. In accordance with this invention, means are provided subject to engine temperature for automatically adjusting fuel flow to the carburetor.

For this purpose a thermally responsive element, such as the bi-metal strip 26, is fixedly mounted at one end by a bracket 28 within an air tube 29 connected at one end to the engine block (not shown). The air within the tube is heated by the engine block and attains a temperature which is directly dependent on engine temperature.

The opposite end of strip 26 is freely movable and moves in accordance with air temperature within the tube. Strip 26 is connected to the needle valve 11 through a rack 30 and pinion 32, the latter being connected to needle valve 22 by a shaft 32 having one end serrated as seen at 34, and a coupling sleeve 36, the outer end of valve 22 being serrated at 38 to receive the sleeve. Sleeve 36 may conveniently be formed of a plastic.

Means are provided for limiting movement of the free end of the bi-metal strip, and this may take the form of an abutment 40 which is adjustable on a wall of the housing 42 by means of a screw 44 received in a slot formed in arm 46 of the abutment. Movement of the rack 30 in the opposite direction is limited by adjustable abutment screw 48.

With these abutments, the temperature range through which automatic adjustment of the needle valve may be achieved may be as required. For example, engine block temperature range of from -200 F. may be employed. Beyond these temperature limits, the bi-metal strip may bow more or less, but no movement will be imparted to its free end nor to the rack 30.

Another variable condition which required adjustment of the needle valve 22 for most complete combustion is atmospheric pressure. This not only changes due to changes in the so-called barometric pressure, but major changes which make the valve adjusting imperative are altitude changes. In motor vehicles it is not uncommon to have operations in a single day at altitudes which may vary by many thousands of feet.

In order to compensate for changes in barometric pressure, which directly influence the pressure difference inducing fuel flow into the carburetor, a chambered barometric capsule or bellows 50 is provided. This capsule may take different forms but for example may comprise a hollow or chambered disc with a flexible wall. The capsule may contain a charge of gas, or a spring urging the movable wall outwardly against atmospheric pressure, and the movement of the wall provides an effective thickness of the capsule which is a direct function of atmospheric pressure.

As best seen in FIG. 2, capsule 50 is connected directly between bi-metal strip 26 and the end of rack 30, so that the position of the rack at any instant is determined jointly by engine temperature and atmospheric pressure.

In many cases carburetors have two air passages or barrels side by side, and the present control system is operable to adjust two needle valves such as shown at 24 and 24a in FIG. 1, through a second pinion 32a connected to pinion 32 through an idler gear 54.

What I claim as my invention is:

1. In an internal combustion engine comprising an engine block having a combustion chamber therein and having a carburetor provided with an air supply passage through which combustion air flows to said chamber, a fuel supply passage opening into said air supply passage, a valve controlling said fuel supply passage, valve adjusting means responsive to engine temperature throughout its range of temperature variation under normal operating conditions operable to effect a continuous gradual adjustment of said valve to modify the flow of fuel through said fuel supply passage in accordance with changes in engine temperature throughout its temperature range under normal operating conditions, a first means for adjusting the setting of said valve to determine the amount of valve opening for any engine temperature within the range of engine temperatures occurring under normal operating conditions after warm-up, and second means separate from said first means for selecting the minimum engine temperature at which said valve adjusting means initiates its operation.

2. Structure as defined in claim 1 comprising additional means responsive to atmospheric pressure for effecting an additive adjustment of fuel flow through said fuel supply passage.

3. Structure as defined in claim 2 in which the means responsive to engine temperature and the means responsive to atmospheric pressure are connected to produce an adjustment of fuel flow dependent on both engine temperature and atmospheric pressure.

4. Structure as defined in claim 3 in which the means responsive to atmospheric pressure comprises an expansible chambered unit.

5. Structure as defined in claim 2 in which said needle valve is screw threaded for fine adjustment, in which said engine temperature and said atmospheric pressure responsive means are interconnected to a rack to produce longitudinal movement of the rack corresponding to combined variations in engine temperature and atmospheric pressure, and a pinion in mesh with said rack and connected directly to said needle valve.

6. Structure as defined in claim 1 comprising in addition third means separate from said first and second means for selecting the maximum engine temperature to which said valve adjusting means can respond.

7. Structure as defined in claim 6 in which said temperature responsive means comprises a rack movable longitudinally in accordance with changes in engine temperature, a pinion in mesh with said rack, said first means comprising adjustable means operatively connecting said pinion and said threaded needle valve, said second and third means comprising separately adjustable abutment means limiting movement of said rack in both directions.

8. In an internal combustion engine comprising an engine block having a combustion chamber therein and having a carburetor provided with an air supply passage through which combustion air flows to said chamber, a fuel supply passage opening into said air supply passage, a threaded needle valve controlling fuel flow into said air supply passage, a pinion having a shaft connected thereto in alignment with said needle valve, a sleeve adapted to engage adjacent ends of said needle valve and shaft to transmit rotary motion of said shaft to said needle valve and to be shifted axially to disconnect said shaft and valve to provide for adjusting the valve to a selected setting, gear means connected to said pinion to rotate the same, and means responsive to variations in engine temperature connected to said gear means to actuate said gear means to adjust said needle valve throughout the range of engine temperature encountered during normal operating conditions after the engine is warmed up.

9. Structure as defined in claim 8, and separately adjustable stop means for said gear means to limit the range of engine temperature through which said valve is adjusted.