GB2245658A

GB2245658A - I.C. Engine carburettor

Info

Publication number: GB2245658A
Application number: GB9015043A
Authority: GB
Inventors: Henry James Tizzard; Alan James Tizzard
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-07-07
Filing date: 1990-07-07
Publication date: 1992-01-08
Also published as: GB9015043D0

Abstract

The cross-section of the induction passage 3, 19 is controlled by an axially movable throttle body 1 which provides, as it is moved against the bias of a spring 6, an increase in air flow cross-section at an annular fuel outlet 12 and a decrease at an annular fuel outlet 13. The fuel outlets 11, 12, 13 are defined by carburettor body sections 15, 16, 17. A passage 4 in the body 1 transmits the vacuum downstream of the body to the chamber 5 to reduce the force due to the vacuum acting on the body. The vacuum may act on a piston (23, Fig. 3) in the chamber 5. <IMAGE>

Description

CARBURETTOR This invention relates to a carburettor for internal combustion engines.

It is well known that most carburettors have internal projections such as protruding jets, metering needles, throttle slides and butterfly valves causing partial obstruction even at full throttle.

This invention relates to a carburettor with few internal projections, where the throttle slide is co-axial with the gas and air flow combining with a variable venturi.

A specific embodiment will now be described with reference to the accompanying drawings in which: Figure 1: is a longitudinal section showing in particular the streamlined shape of the co-axial throttle slide in both the closed and fully open positions. One of the fuel passages shows the connection from the variable jet screw point to the foremost annulus. Two other fuel passages in part section are shown connecting the centre annulus and rearmost annulus.

Figure 2: shows in part cross-section the three fuel passages in dotted lines terminating at the three annuli.

Figure 3: shows a throttle slide mounted upon a stepped shaft.

Referring to Figure 1, the carburettor comprises a throttle slide 1 sliding on a shaft 2, the shaft being of equal diameter to the inside diameter of the inlet port 3, the hole 4 is a passage connecting the inlet port with a vacuum chamber 5 with the engine suction and maintains equal pressure in the closed throttle position so that the throttle slide is quite free from CARBURETTOR unbalanced forces while closed. The spring 6 is necessary to maintain closure.

Referring to Figure 2, fuel level controlled by the float chamber 7 is distributed by passages 8, 9 and 10 to the annular grooves 11, 12 and 13 the fuel being metered by jets 14. From the annular grooves fuel is drawn by engine suction into the venturi through a circumferencial gap equal to the compressed thickness of the gasket interposed between each of the sections 15, 16 and 17, the main hole in the gasket 18 being larger than the outer diameter of each of the annuli. The co-axially moving throttle slide 1 regulates the airflow and consequently the fuel flow from the circumferential gaps. When the throttle slide is closed or slightly open the cross-sectional area of the venturi towards the air intake 19 has become enlarged thus reducing fuel flow from the annulus 13.As the throttle opens further this area progressively decreases whilst the area towards the inlet port 3 increases, so at full throttle the cross-sectional area of the venturi at any station is in accordance with an ideal venturi maintaining fuel flow from the circumferencial orifaces. The throttle slide is opened by a pull on the eye 20 of the control rod 21 against the spring 6. Sealing ring 22 seals the control rod 21 using the closing spring 6 to assist sealing.

Referring to Figure 3, the vacuum chamber 5 is closed by a piston 23 retained within the throttle slide 2 by a circlip 24 allowing axial clearance. With the throttle slide 2 in the closed position the piston 23 rests against the shaft shoulder 25 thus relieving the throttle slide 2 of unbalanced forces. The initial opening of the throttle slide 2 takes up CARBURETTOR the axial clearance between the piston 23 and the throttle slide 2, thereafter the piston moves with the throttle slide as opening progresses.

Shaft 25 is fixed to bracket 26 with a screw thread and locknut 27, this allows fine adjustment of the position of the shoulder on shaft 25 to obtain the aforementioned axial clearance.

Claims

CARBURETTOR 1. A carburettor for internal combustion engines embodying a housing containing an induction passage and streamlined throttle slide with a vacuum chamber, the throttle slide capable of axial motion and when activated from closed throttle to full throttle produces simultaneously and progressively down stream and upstream of the major diameter of throttle slide an increase and decrease respectively of the annular areas of the induction passage cross section with a complementary reversal when activated from full throttle to closed throttle producing a variable venturi within the induction passage, the passage embodying one or more positions for fuel entry.
2. A carburettor as claimed in Claim 1 embodying an induction passage incorporating one or more circumferential fuel orifaces arranged longitudinally within the said induction passage, the primary oriface being adjacent to the throttle slide closing face, other circumferential orifaces positioned upstream of the closing face within the range traversed by the throttle slide, the orifaces able to distribute fuel by virtue of the pressure differential prevailing under working conditions.
3. A carburettor as claimed in Claims 1 and 2 embodying a housing comprising a sandwich of sections in close contact wherein one or more fuel supply grooves surround an induction passage, each groove connected to a float chamber via separate fuel metering jets.

CLAIMS CARBURETTOR
4. A carburettor as claimed in Claims 1 to 3 embodying an induction channel wherein one or more circumferential gap fuel orifaces arranged longitudinally communicate with adjacent fuel supply grooves,the circumferential gap formed by a lower adjacent surface where normally surfaces would butt together or where interposed gaskets terminate clear of the annular fuel supply grooves.
5. A carburettor as claimed in Claims 1 and 2 embodying a streamlined throttle slide containing a vacuum chamber subject to inlet port depression through a communicating hole, providing a degree of balanced loading assisted by a return spring.
6. A carburettor as claimed in Claim 5 wherein the throttle slide embodies a vacuum chamber closed by piston, the throttle slide and piston mounted upon a fixed stepped shaft, the piston being able to rest against the step when in the closed throttle position, the step being adjustable for longitudinal position, relieves the throttle slide of atmospheric pressure.
7. A carburettor substantially as described herein with reference to Figures 1 to 3 of the accompanying drawings.