GB2084351A - Carburettor Throttle Control Operating Device - Google Patents

Abstract

A carburettor throttle control device for mounting on or adjacent to a conventional carburettor or its throttle control mechanism the control device acting on the throttle lever of the carburettor to open the throttle to a small extent under particular decelerating conditions and which will allow the throttle to close under engine idle conditions thereby effectively controlling the emission of hydrocarbons and reducing the fuel consumption. Movement of the throttle is controlled by movement of a diaphragm (12) arranged to be exposed to the induction manifold pressure of the engine on which the carburettor is mounted. Normally both sides 19, 22a of the diaphragm are connected to atmosphere through a vent 21 and a bleed aperture 24. Should the manifold pressure fall below a pre-set value, a second diaphragm (30) one side of which is in connection with the manifold, through a pipe 29, opens a valve 25 to connect the diaphragm side 19 to vacuum. <IMAGE>

Description

SPECIFICATION Carburettor Throttle Control Operating Device The invention relates to a carburettor throttle control device for use in conjunction with automotive type carburettors for the purposes set out below.

It is well established that when a motor vehicle is operating under decelerating modes with the throttle of the carburettor closed to a normally preferred low idle speed, considerable unburnt fuel passes through the engine and is emitted to the atmosphere as a hydrocarbon pollutant. It has been recognised that this hydrocarbon pollutant can be substantially reduced by adopting means that admit additional air and fuel to the engine cylinders thus improving combustion efficiency. It has been common practice in emission control strategy simply to set the idle speed of the engine somewhat faster than normal (say 700-950 rpm) so that during decelerating modes the emitting of hydrocarbon is reduced.This, however, has the disadvantage of increasing fuel consumption due to the greater volume of air and fuel thus admitted to the engine whenever the throttle is returned to the set idle position. It has also been proposed to incorporate in a carburettor design an integral device that achieves a similar result to the device described herein.

This, however, requires the carburettor to be of special design. The object of this invention, however, is to provide a completely separate vacuum operated device as an integral unit which can be mounted adjacent to a carburettor or its throttle control mechanism, the device acting to maintain the throttle of the carburettor open slightly under particular decelerating conditions and, in addition, which will also allow the throttle to close to a more normal low engine speed (500-650 rpm) as required for engine idle conditions, thereby effectively controlling the emission of hydrocarbons and reducing fuel consumption which would otherwise be the case.

The invention consists of a carburettor throttle control device adapted to be mounted on or adjacent a conventional carburettor or its throttle control mechanism, the device including a movable throttle operating member having a free end which when installed acts on the throttle lever of the carburettor, a diaphragm chamber, a diaphragm mounted within the chamber and connected to said member, the diaphragm dividing said chamber into a vacuum compartment and a vented compartment, the vented compartment being vented to atmosphere, the vacuum compartment being connected through normally closed valve means to connector means adapted for vacuum connection to the inlet manifold of an engine on which the carburettor throttle control is mounted, second diaphragm operated means arranged to control said valve means whereby, on the increase of the induction maniFold vacuum of the said engine beyond a selected adjustable level, said second diaphragm operated means acts to open said valve means thereby exposing one side of said first mentioned diaphragm to the manifold vacuum and thereby causing the diaphragm to move the throttle operating member to open the throttle of the carburettor to an adjustable predetermined extent, bleed hole or aperture means being provided to admit air to said vacuum compartment.

In order that the invention may be better understood and put into practice a preferred form thereof is hereinafter described by way of example with reference to the accompanying drawings in which: Figure 1 is a sectional view of a carburettor throttle control according to the invention; and Figures 2a and 2b illustrate the manner in which it may be mounted on a conventional carburettor.

In the form of the invention shown in Figure 1 the apparatus consists of a body 10 which may be made, for example, of aluminium, or any suitable material. Affixed to this is a two part housing 11 for the diaphragm 12. The two parts 11 a and 11 b of the housing 11 are adjoined around their circumferences by the crimped joint 13 forming a leak tight seal with the diaphragm 12. Part 11 a of the housing is held in position on the body 10 by a circlip 14 located in a groove of special design which prevents accidental dislodgement. The inner periphery of the part 11 b is secured to the body mounting 15 which is provided with an external thread 1 6.

A throttle operating rod 1 7 passes through the body mounting 1 5 and leakage between the two is prevented by a suitable sealing arrangement typically indicated at 17a. A similar sealina arrangement 1 8 prevents leakage between the rod 17 and the body 10.

The housing 11is divided into two parts by a diaphragm 12 of suitable flexible material supported by a rigid diaphragm plate 20.

Chamber 22a of the housing enclosed by the portion 11 a is vented to the atmosphere through the vent 21. The other chamber 19 is connected via holes 22 to a bore 23 passing through the rod 17 in an axial direction. The chamber 19 is connected to the atmosphere via chamber 22a through the bleed aperture 24, the purpose of which is described below.

The body 10 contains a valve member 25 the head of which seats on the seating 26, the valve being held on its seat by means of the spring 27.

The valve member 25 is surrounded by a chamber 28 into which a connecting tube 29 leads. Tube 29 enables the chamber 28 to be connected to the induction manifold of an engine with which the carburettor being controlled is associated. The body 10 also contains a diaphragm and plunger assembly 30 which is spring loaded into the position shown in Figure 1 by the coil spring 31. A threaded adjusting screw 32 is provided in the plunger 33 associated with the diaphragm assembly. 30. The purpose of which is described below.

Figures 2a and 2b show how the carburettor throttle control described above may be mounted on a carburettor indicated generally at 34.

Mounting is effected by means of a bracket 35 secured by screws 36 to the body of the carburettor 34. The body mounting 16 passes through a threaded hole in the bracket 35 and is secured to it by means of a nut 37. The end of the rod 1 7 bears on the throttle lever 38. Movement of the rod 17 out of the body mounting 17 acts to control the throttle of the carburettor. The device may also be mounted remote from the carburettor such that it may act on the throttle mechanism to control the throttle position.

The carburettor throttle control described above operates in the following manner. So long as the vacuum in the inlet manifold, and that in the cavity 28, is below the selected level the spring 31 maintains the plunger 33 in the position shown in Figure 1 and the throttle operating rod 1 7 may rest near the carburettor throttle actuating lever. Once the vacuum has become sufficiently great to overcome the spring 31 the plunger 33 will move to the right as seen in Figure 1 and the end of the adjusting screw 32 will come into contact with the tail of the valve member 25 and move it to the right against the spring 27. The bore 23 and thus the interior of the chamber 19 to the right of the diaphragm 12 will be exposed to the inlet manifold vacuum.This will cause the diaphragm 12 to move to the right and in so moving it will move the rod 17 to the right causing the throttle to open. The purpose of the adjusting screw 32 is to set the required vacuum at which the valve 25 will open. In the event of the inlet manifold vacuum falling below a level in which the spring 31 is overcome, the valve 25 will close on its seat 26 and air will leak through the bleed aperture 24 into the right hand chamber 19 thus ailowing the control rod 17 to be restored to its original rest position near the carburettor throttle actuating lever.

The apparatus is designed and set up so that it comes into operation only during decelerating conditions in which normally the throttle is at or near its idle set position and a high induction manifold vacuum is present. The apparatus acts to hold the throttle slightly open during these conditions and thus reduce the inlet manifold vacuum and thus the emitting of hydrocarbons.

And further, as the initially high inlet manifold vacuum decreases towards the normal vacuum at idle, a normal consequence of speed reduction during deceleration modes, the device will release the throttle at a pre-set vacuum and permit the throttle to return to a low idle set position thus reducing the fuel consumption which would otherwise be the case.

The invention provides a very simple and reliable device which can be used in conjunction with a perfectly standard carburettor. The device may be used with a variety of different carburettors, a suitable mounting bracket such as 35 being provided to suit the construction of the particular carburettor or its associated throttle control mechanism.

The embodiment of the invention described above is given by way of example only as constituting a preferred form of the invention within the broad scope thereof as defined in the succeeding claims.

Claims (3)

Claims

1. A carburettor throttle control device adapted to be mounted on or adjacent a conventional carburettor or its throttle control mechanism, the device including a movable throttle operating member having a free end which when installed acts on the throttle lever of the carburettor, a diaphragm chamber, a diaphragm mounted within the chamber and connected to said member, the diaphragm dividing said chamber into a vacuum compartment and a vented compartment, the vented compartment being vented to atmosphere, the vacuum compartment being connected through normally closed valve means to connector means adapted for vacuum connection to the inlet manifold of an engine on which the carburettor throttle control is mounted, second diaphragm operated means arranged to control said valve means whereby, on the increase of the induction manifold vacuum of the said engine beyond a selected adjustable level, said second diaphragm operated means acts to open said valve means thereby exposing one side of said first mentioned diaphragm to the manifold vacuum and thereby causing the diaphragm to move the throttle operating member to open the throttle of the carburettor to an adjustable predetermined extent, bleed hole or aperture means being provided to admit air to said vacuum compartment.

2. A carburretor throttle control device as claimed in Claim 1 wherein the said selected adjustable level of the induction manifold vacuum is selected by adjustable screw means associated with said second diaphragm operated means, said screw means making contact with said valve means on the said level being exceeded, adjustment of said screw means selecting the level at which contact is made.

3. A carburettor throttle control device substantially as described with reference to and as iliustrated in Figure 1 of the accompanying drawings.