GB2047797A - Fuel injection carburettor - Google Patents

Abstract

An air valve 14 controls the inlet of a tube 16 and fuel under pressure from a duct 13 is directed along the tube axis. The air valve 14 and a fuel metering needle are operated conjointly by a pedal. Tube notches 22 provide an idling air flow. <IMAGE>

Description

SPECIFICATION A carburettor This invention relates to a carburettor for atomizing liquid fuel to produce a fuel/air mixture for feeding to the cylinders of an engine.

According to the invention, there is provided a carburettor having a tubular throat, one end of which is adapted to communicate with the inlet manifold of an engine, and the other end of which is provided with a movable closure member, substantially normal to the axis of the throat, for closing said other end, a fuel inlet duct extending through said closure member and opening into the throat on the axis thereof, air passages for conducting airto an area around the outside of the throat and the closure member, means for metering the fuel supply to the inlet duct, and means adapted to be connected to the engine throttle control for simultaneously moving the movable closure member and altering the setting of the metering means.

In this carburettor, air is drawn into the throat from all around the throat, so that all the air meets in the centre where the fuel enters. Because of the turbulence created by the air, when it impacts against itself, a very efficient atomizing effect is produced.

Movement of the closure member relative to the tubular throat provides a particularly simple and effective way of varying the air gap through which air passes into the atomization zone. Since the closure member can have a single central shaft above the throat by which it is supported, it is easy to move it up and down while maintaining it in the correct orientation relative to the throat so that the air gap is constant all the way round. The control linkage for the closure member is remote from the throat so that there are no obstructions in the throat between the fuel atomization zone and the engine manifold. It is an advantage ofthis invention that the atomized fuel does not come into contact with any components of the carburettor, and thus does not condense out on any such surfaces.

When the feature of claim 2 is incorporated, adjustment ofthe carburettor to vary the fuel/air ratio can be very simply carried out.

The use of the feature of claim 3 ensures that the idling position can easily be set.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a cross-section through a carburettor according to the invention; Figure 2 shows a part ofthe carburettor on a larger scale; and Figure 3 shows the carburettor applied to an engine.

The carburettor 10 is fed with fuel via a fuel line 11 from a metering device, such as a needle valve, which is not shown. Other types of conventional metering device could be used. Air is drawn into the carburettorthrough openings 12, again in a conventional way. The fuel passes along a central duct 13 in a valve member 14. The valve member 14 seats on the top surface 15 of a tubular throat 16. The valve member 14 can be raised and lowered by a rocker arm 17 which is attached to the valve member via a threaded collar 18. The position of the collar 18 on the shaft of the valve member 14 can be adjusted by screwing it along the shaft in either direction. The rocker arm 17 is retained between two flanges 19 on the collar 18.The rocker arm 17 is moved, during operation of the carburettor, buy a cable 20 extending around a pulley 21 and to the throttle control of the engine. If an air filter is employed, the rocker arm 17 would have to operate within the housing shell of the filter.

In operation, air enters the tubularthroat 16 around the whole circumference thereof and is directed in a radial direction towards the centre. The fuel is fed directly into the centre of the tube 16, and the air and fuel thus meet in the middle of the tube, so that the fuel is atomized. The suction from the engine draws the atomized mixture of air and fuel into the individual cylinders.

The air drawn in between the valve member 14 and the top of the throat 16 impacts upon itself in the centre of the tube and also impinges on the fuel which enters at the same point. This design doubles the impact force and produces a turbulence which is greatly superior to that of conventional carburettors.

When the engine is idling, the valve member 14 sits on the top surface 15 ofthe throat 16. At this stage, air is drawn into the centre of the throat 16 via notches 22. These notches allow sufficient air for idling to enter the throat.

Since the operating fuel is fed into the air stream under pressure, the need for an accelerator pump is eliminated. When using a needle valve for metering the fuel, a charge of fuel will be immediately released into the air stream when the needle shaft is withdrawn from the associated port by depression of the throttle pedal. Since the revolutions per minute of the engine have not increased at this point, the charge of fuel causes an enrichment which increases the power.

There will of course be a suitable linkage between the cable 20 controlling the position of the valve member 14 and the operating member of the fuel metering device. Such a linkage is not shown but will present no problems in construction for the skilled man.

The carburettor described can avoid starting problems in cold climates since it provides a fuel that will enable an engine to start in less than 10 revolutions.

It has been found that an air mixture of about 13 to 1 is best for satisfactory starting. This is based upon the fact that conventional carburettor must be set to deliver a 1 to 1 air-fuel mixture under full choke conditions in order to hopefully vapourize 7.7% of the fuel to give the desired 13 to 1 air-fuel ratio.

In a conventional carburettor, if only 7.7% of the fuel vapourizes in a cold engine, the remaining fuel travels through the engine and emerges as both a pollutant and a dilutant in the crank case oil. Due to poor atomization of conventional carburettors, far too much fuel is required to produce sufficient vapour for satisfactory starting.

In the carburettor described, fuel is atomized to a mist without heavy droplets. This creates more surface area to produce the vapor required for cold starts. Less fuel is therefore required to produce the desired 13 to 1 air-fuel ratio, thus saving fuel and cutting down on emissions.

Fuel it not easily vapourized at any intake air temperature. In the carburettor described, fuel is atomized into a fine mist with an increased amount of low temperature vapour. This combination of low temperature mist and vapour is desirable for effi cientoperation as there is then a minimum of droplets in the airstream. Such droplets have a tendancy to enrich only the cylinders at each end of the manifold. In the carburettor described, a more even distribution of fuel for each cylinder is obtained.

In the carburettor described, the intake air is forced to impact against itself in the centre of the tubular throat 16. At this point, the air is forced to change direction through 90 and flow along the throat 16 and enterthe manifold 23 via engine vacuum pressure. The fuel is finely atomized and remains suspended in the throat 16 and enters the manifold without touching the internal surfaces of the carburettor. The fuel will therefore not condense out on the surfaces of the carburettor.

When a needle valve is used for metering the fuel, a fuel pressure regulator may be provided to vary the air-fuel ratio.

Figure 3 shows the general arrangement of a carburettor 10 mounted on an engine 25. An accelerator 26 is indicated behind a fire wall 27 of the engine compartment. An air filter 28 is provided for cleaning the air drawn into the carburettor. The accelerator 26 is connected to the carburettor by cable 20 which is also connected to the fuel metering device (not shown).

The performance of the carburettor can be easily adjusted by rotating the collar 18 on the shaft of the valve member 14. By this means, the amount of opening of the valve for any particular accelerator position can be adjusted.

Claims (4)

1. A carburettor having a tubular throat, one end of which is adapted to communicate with the inlet manifold of an engine, and the other end of which is provided with a movable closure member, substantially normal to the axis of the throat, for closing said other end, a fuel inlet duct extending through said closure member and opening into the throat on the axis thereof, air passages for conducting air to an area around the outside of the throat and the closure member, means for metering the fuel supply to the inlet duct, and means adapted to be connected to the engine throttle control for simultaneously moving the movable closure member and altering the setting of the metering means.

2. A carburettor as claimed in claim 1, wherein said means for moving the closure member includes a pivoted arm which engages with a collar threaded onto a threaded part of the closure member, the collar being rotatable on said part of the closure member so as to adjust its position thereon and to adjust the setting of the closure member.

3. A carburettor as claimed in claim 1 or claim 2, wherein said other end ofthe tubular throat is provided with notches around its periphery so that a limited amount of air can be drawn into the throat even when said other end is closed by the closure member.

4. A carburettor substantially as herein described with reference to the accompanying drawings.