GB2197031A

GB2197031A - I.C. engine carburettor

Info

Publication number: GB2197031A
Application number: GB08725153A
Authority: GB
Inventors: Mauro Franchini; Giuseppe Gamberini
Original assignee: Weber SRL
Current assignee: Weber SRL
Priority date: 1986-10-31
Filing date: 1987-10-27
Publication date: 1988-05-11
Also published as: IT208324Z2; FR2606085A1; GB8725153D0; DE3736601A1; IT8654024V0

Abstract

A manifold depression or electrically operated pump 5 is connected through a duct 6 to a fuel nozzle 4. A valve 17 which is closed in response to manifold depression connects the duct 6 to the constant level chamber 15 when the engine is inoperative to prevent fuel flow through the nozzle 4 due to fuel vaporisation. …<IMAGE>…

Description

1 4 GB2197031A 1

SPECIFICATION

A carburettor for an internal combustion engine The present invention relates to a carburettor for an internal combustion engine with which various disadvantages which'are normally en countered upon cold starting when the vehicle is at a very high temperature, because, for 75 example, of operating at high temperature or a prolonged exposure to the sun, are eliminated.

The carburettor comprises, as is known, a choke duct for the air and fuel mixture. along which is disposed a butterfly valve and a fuel 80 supply jet which is arranged to deliver fuel into the choke duct upstream of the butterfly valve. The fuel is supplied to the said jet by the action of an electrically driven pump or by the depression in the induction manifold of the 85 engine. The carburettor further comprises a fuel chamber in which this is maintained at a predetermined level and which can be in corn munication with the first mentioned jet, or with other suitable ducts which open into the mixture choke duct. When the engine must be started with the vehicle at a very high temper ature, a condition which can be encountered easily after a prolonged exposure to the sun, various disadvantages are encountered. First 95 of all, starting can take a particularly long time or give rise to flooding of the engine; more over, there is produced a large quantity of hydrocarbons in the exhaust. These disadvan tages are caused by small quantities of fuel which collect on the walls of the mixture choke duct or the butterfly valve whilst the vehile is stationery and which leave the supply jet in the form of droplets. This phenomenon is caused by fuel vapour which forms in the 105 duct which puts the supply pump into com munication with the jet and which are gener ated following an increase in the temperature of the fuel itself.

The object of the present invention is that of providing a carburettor for an internal com bustion engine of the type first defined, in which the disadvantages which have been de scribed above are eliminated, This object is obtained with a carburettor 115 for an internalcombustion engine comprising a choke duct for the air and fuel mixture, within which is disposed a butterfly valve and a fuel supply jet operable to deliver fuel into the said choke duct upstream of the said butterfly valve, a chamber for the fuel able to contain a predetermined quantity of fuel, and a pump for supplying the fuel to the said jet, charac terised by the fact that it includes a duct which puts a region downstream of the said 125 pump into communication with the said cham ber and an interception valve disposed in the said duct and operable to assume a first, open, position in which the said duct is open and a second, closed, position in which the said duct is closed, and means-for activating the said valve operable to hold the valve in the said first position when the said engine is not running and in the second position when the said engine is running.

For a better understanding of the invention a more detailed description of it will now given by way of example, with reference to the attached drawings, in which:

Figure 1 is a schematic sectional view of a part of a carburettor in which the improvement of the invention is incorporated, in the configuration in which it is found when the engine is switched off; Figure 2 is a section similar to that of the preceding Figure, in which the carburettor is shown in the configuration in which it is found when the engine is running.

The carburettor comprises a body 1 in which is formed a choke duct 2 for the fue]/air mixture, which can be put into communication with the induction manifold of the engine; in this duct there is disposed a butterfly valve 3 and, in a region upstream thereof, there is positioned a supply jet 4 provided to deliver predetermined quantities of fuel for the formation of the mixture.

A pump 5 supplies the fuel to the jet 4 through a duct 6 formed in the body 1 and in this duct, immediately upstream of the jet 4, there is conveniently disposed a non-return valve which acts to prevent the fuel from escaping from the duct itself when the engine is stopped and therefore the pump 5 is not acti- vated. This latter can be of any type, for example, an electric pump; conveniently, as shown in the drawings attached, this pump is of pneumatic type and is actuated by the depression which is created in the induction manifold of the engine; this therefore includes a diaphragm 8, the periperal edge of which is fixed between the body 1 and a cover 10 and the central part of which is fitted between a pair of plates 11. This diaphragm defines a first chamber 13 which can be put in communication with the induction manifold of the engine, and a second chamber 12 in communication with the duct 6; on this diaphragm acts a coil spring 14 disposed in the chamber 13 as is clearly seen in the drawings.

The carburettor includes a chamber 15 which can contain a predetermined quantity of fuel which is maintained in it at a predetermined level by the action of suitable devices not shown; this chamber can be in communication with the jet 4 and with other suitable ducts (not shown) which open into the choke duct 2.

According to the invention, in the body 1 there is formed a duct 16 which puts the chamber 13 of the pump 5 into communication with the chamber 15; this duct can include several sections as has been shown in the drawings.

In the duct 16 there is disposed an inter- 2 GB2197031A 2 ception valve 17 which can assume a first configuration, shown in Figure 1, in which it is open, and in which it therefore allows the chamber 12 to be put into communication with the chamber 15, and a second configuration, shown in Figure 2, in which, on the other hand, the valve is closed and therefore passage along the duct 16 is prevented.

This valve is conveniently of the ball type and can include a bush 18 inserted into a hole 19 of the body 1 and provided with a radial hole 20 and an axial hole 21 which are in communication with the sections of the duct 16 which are found respectively upstream and downstream of the valve itself. The hole 21 is provided with a seat 22 against which can engage a ball 23 thrust by a coil spring 24 housed within the bush 18.

The carburettor further includes means for activation of the valve 17, generally indicated 25, and comprising a rod 26 one end of which can engage on the ball 23 and press on it to separate it from the seat 22, as has been shown in the configuration of Figure 1. These means further comprise a diaphragm 27 the peripheral edge of which is fixed between a cup shaped body 28 and a cover 29 the first of which has a threaded sleeve 30 screwed onto a corresponding threading of the hole 19 of the body 1 and within which the rod 26 is slidable; the second is fixed onto the former in any convenient manner, for example, by upsetting the peripheral edge of the cup shape body 28 over it. The central part of the diaphragm 27 is fixed between a pair of plates 31, and a coil spring 32 interposed between the first and the cover 29 normally holds the rod 26 against the ball 23 as is shown in Figure 2; between the diaphragm and the cover there is defined a chamber 33 which is in communication with the induction manifold of the engine through a hole 34. The carburettor described above operates in the following manner. 45 When the engine is in operation the depression in the induction manifold acts through the hole 34 in the chamber 33 and on the diaphragm 27 of the activation means 25; therefore the reaction exerted by the coil spring 32 is overcome and the central part of the diaphragm itself, and therefore the rod 26, is displaced towards the left of Figure 1: the various members of the activation means assume the configuration shown in Figure 2 and therefore the ball 23, no longer loaded by the rod 26, is thrust by the spring 24 against the seat 22 of the hole 21 to close it. Consequently, the passage of fuel through the duct 16 is prevented and it can only flow through the duct 6 by the action of the pump 5 which is, itself, activated during the operation of the engine.

When the engine is stopped, the depression in the chamber 33 of the activation means 25 is no longer present and the spring 32 130 presses the diaphragm 27 and therefore the rod 26 towards the right in Figure 2 to displace the members of the said means into the configuration of Figure 1, in which the rod 26, acting on the ball 23, separates this from the seat 22 of the hole 21 to open the passage through it.

It is therefore evident that during the period of time in which the engine is stopped, when- ever fuel vapours form in the region downstream of the pump 5 (and in particular, in the chamber 12 and in the duct 16) because of an increase in the temperature thereof, these discharge into the chamber 15 through the duct 16 and do not generate any pressure within the duct 16 which would tend to drive the fuel through the jet 4.

The subsequent starting of the engine therefore takes place in an entirely regular manner since there are no quantities of fuel collected on the surfaces of the choke duct 2 and the butterfly 3.

It is evident that the embodiment of the present invention which has been described and illustrated can have modifications and vari- ations introduced thereto without by this departing from the ambit of the invention itself.

Claims

1. A carburettor for an internal combustion engine comprising a choke duct for the fuel and air mixture, within which is disposed a butter-fly valve and a fuel supply jet operable to delivery fuel into the choke duct upstream of the butterfly valve, a chamber for the fuel for containing a predetermined quantity of fuel, and a pump for supplying the fuel to the said supply jet, characterised by the fact that it includes a duct which puts a region down- stream of the said pump into communication with the said chamber and an interception valve disposed in the said duct and operable to assume a first, open, position in which the said duct is open and a second, closed, posi- tion in which the said duct is closed, and activation means for the said valve operable to hold the said valve in the said first position when the said engine is not running and in the second position when the said engine is running.

2. A carburettor according to Claim 1, characterised by the fact that the said valve activation means are actuated by the depression acting in the induction manifold of the engine. 120

3. A carburettor according to Claim 1 or Claim 2, characterised by the fact that the said valve is a ball valve which comprises a hole for the passage of the said fuel, a ball which can engage on a seat contiguous with the said hole to close it, and a spring for pressing the said ball against the said seat when the valve is located in the said second position, the said activation means comprising a rod which can act on the said ball to separate it from the said seat and open the said 3 GB2197031A 3 hole when the valve is located in the said first position.

4. A carburettor according to any preceding Claim, characterised by the fact that the said valve activation means includes a deformable membrane to which the said rod is connected and which defines one wall of a chamber in communication with the said induction manifold, a second spring acting on the said mem- brane to press the membrane, and therefore the said rod, normally against the said ball of the valve to hold this in the open position in such a manner that when the said depression acts in the said chamber deformation of the said diaphragm is produced overcoming the force exerted by the said second spring and therefore causing displacement of the said rod to separate it from the said ball and displace the valve into the closure position.

5. A carburettor according to any preceding Claim, characterised by the fact that the said pump is a diaphragm pump actuated by the said depression in the induction manifold.

6. A carburettor according to any preceding Claim, characterised by the fact that the said valve further includes a bush in which the said hole is formed and in which the said ball and the said spring are housed, and the said activation means include a cup-shape body in which the said chamber is formed and the said diaphragm is housed, and a sleeve projecting from the said body and in which the said rod is axially movable, the said bush and the said sleeve being housed in the same hole formed in the said carburettor body.

7. A carburettor for an internal combustion engine substantially as described and illustrated in the attached drawings.

Published 1988 at The Patent Office, State House, 66/71 High Holborn, London WC 1 R 4TP. Further copies may be obtained from ThePatentOffice, Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Burgess & Son (Abingdon) Ltd. Con. 1/87.

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