GB2199619A

GB2199619A - A thermostatic device for controlling the choke and throttle valves of a carburettor

Info

Publication number: GB2199619A
Application number: GB08730307A
Authority: GB
Inventors: Osso Carlo Dall; Bruno Cavallari
Original assignee: Weber SRL
Current assignee: Weber SRL
Priority date: 1986-12-30
Filing date: 1987-12-30
Publication date: 1988-07-13
Anticipated expiration: 2007-12-30
Also published as: FR2609110A1; GB8730307D0; IT209006Z2; IT8654267V0; DE3744007A1; GB2199619B

Description

0 0 0 v 1 2199619 A THEMSTATIC DEVICE FOR CONTROLLING THE MAIN AND

AUXILIARY SUPPLY VALVES OF A CARBURET7OR DURING WARM-UP OF THE ENGINE The present invention relates to a device for controlling main and auxiliary supply valves of a carburettor during starting of an internal combustion engine.

As is known, during warm-up, the positions of the main butterfly valve and the auxiliary butterfly valve are progressively regulated so as to close the main supply valve'almost totally to reduce the quantity of fuel inducted, whilst the auxiliary supply valve is opened to a predetermined value to make the mixture progressively leaner. Among the various possible ways of progressively controlling the position of these valves during starting it is known to effect this control through lever mechanisms controlled by an element the angular position of which is controlled by the degree of projection of a rod from a body which contains material the volume of which varies significantly with changes in temperature, and generally constituted by a mixture of waxes, and in which the temperature of the said body is influenced by the temperature of the engine coolant liquid, a temperature which obviously increases as the engine warms up so that there is a progressive increase in the projection of the rod from the body causing a progressive rota - tion of the element which causes closure of the main supply valve and opening of the auxiliary supply valve.

The object of the present invention is that of providing an imptovement to the said control d evice so as to reduce the duration of this initial stage of progressive control of the position of the main and auxiliary supply valve whilst maintaining appropriate - operating conditions for the engine, so as to reduce the time for which the richer mixture is supplied thereby obtaining a lower fuel consumption with a reduction in the initial slow running speed of f the engine and a reduction in the emitted quantity of noxious combustion products caused by a too-rich mixture, according to a characteristic of variability which cannot be obtained by subjecting the body containing the rod only to the influence of the engine coolant liquid.

According to the present invention there is provided a device for controlling the main and auxiliary supply valves of a carburettor during the warm-up stage of an internal combustion engine, and in which the position of the said valve is controlled by at least one element positioned in dependence on the degree of projection of a rod from a body containing material the volume of which varies significantly with temperature, and in which the said body is inserted into a section of a duct traversed by the coolant liquid of the said engine, characterised by the fact that it includes electrical resistor means for providing a supplementary quantity of heat to the said body.

For a better understanding of the present invention a particular embodiment is now described purely by way of non-limitative example, with reference to the.attached drawing, which is a schematic sectional side view of it applied to a carburettor.

Thus, the reference numeral 1 indicates a carburettor of substantially known type for the supply of a fuel mixture to an internal combustion engine, in particular for a motor vehicle. This carburettor 1 has a main butterfly valve 2 and an auxiliary butterfly valve 3. The main valve 2, as well as being controlled, in a known manner, not illustrated, by the vehicle accelerator, is coupled to a lever 5 which at one end 5 has a screw 7 for the slow running adjustment and which abuts against a lever 8 connected to the main valve 2. At a second end 9 this lever 5 carries a roller 10 which, by means of a resilient action exerted in an anti- W l, 1 clockwise sense on the lever 5, is maintained in contact with a cam profile 11 of one end 12 of a double arm lever 13 which is pivoted to a pin 14 on the carburettor 1 and which is thrust by a spring 15 to turn in a clockwise direction. This lever 13 has a second end 16 which has a shaped slot 17 in contact with the internal upper profile of which is maintained a roller 18 carried at one end of a lever 19 which at its other end carries a screw 20 which is also connected, with the possibility of adjustment, within a slot 21 formed at one end of a lever 22 also pivoted on the same pin 23 () which carries the-lever 19 and fixed to the carburettor 1. Between the lever 19 and the lever 13 is connected a tension spring 24 which causes the roller 18 to maintain contact with the inner upper profile of.the shaped slot 17. The other end of the lever 22 opposite that where the screw 20 is located, is connected by means of a pin 25 to one end of a link 26 which at the other end is pivoted to a crank 27 fixed for rotation with the auxiliary butterfly valve 3. The pin 25 is disposed in a slot 28 of a small bar 29 which at its other end is pivoted to the lever 8.

According to the main characteristic of the present invention, to the lever 13 is fixed a support element 31 conveniently having a U-shape cross section, which carries, on two arms, two slots 32 in which are housed the ends of a pin 33 which is thus disposed vertically with respect to the plane of the lever 13, and fitted within a prismatic body 34 which is therefore supported. This prismatic body 34 has an axial through hole 35 along the major ength of the body 34, into which is introduced the end section of a rod 36 projecting from a body 37 substantially in the form of a cylinder of known type having-within it a material, conveniently a mixture of waxes, the volume of which varies significantly as a function of temperature. The axial hole 35 at the other end with respect to that into which the rod 36 is inserted, is threaded and carries a screw 38 screwed thereto the depth of penetration o f which is fixed by a nut 39 screwed against the head surface of the prismatic body 34.

The thermosensitive body 37 is housed in a container body 40 conveniently made by casting which forms a first internal chamber 41 in which the main portion of the thermosensitive body 37 ke housed and with which two integral ducts 42 and 43 are in communication for the circulation of engine coolant liquid. Towards the end region of the internal chamber 41 this container body 40 forms two seats for housing two annular seals 44 and 45 which seal against respective cylindrical portions 46 and 47 of the thermosensitive body 37. The container body 40 is then fixed to a support bracket 48 by means of screws 49 which simultaneously fix to the container body 40 a lower plate 50 which retains the thermosensitive body 37 within the container body 40 with convenient squeezing of the annular seal 45. The container body 40 then has, towards the upper end with respect to that closed by the plate 50, a perimetral edge 51 which is closed, conveniently by clenching, onto the perimetral edge of a cover 52 which defines, towards the bottom of the thermosensitive body 37, a closed chamber 53 in which is disposed a resistor element 54 conveniently of the positive temperature coefficient type (PTC) that is to say one provided with a self regulating temperature characteristic. This resistor element 54 is disposed in contact with the bottom of the thermosensitive body 37 and in particular can be secured by adhesive. Positive electrical supply to the resistor element 54 (which is then conveniently connected to earth by means of the bodies 37 and 40) is achieved by means of a terminal blade 55 passing through the cover 52 (conveniently insulating) which is connected at the inner end to this cover 52, and three resilient blade like feet 55 which are pressed into contact with the resistor element 54 by the pressure exerted by the cover 52. The terminal blade 55 is then connected to a supply control block 57 in which a switch element 58 is arranged, which can for example be controlled only by the open or closure condition of the general electrical supply switch for the engine, or can also be controlled by a signal 59 emitted in a predetermined temperature range, for example between 180C and 53C of the engine coolant liquid, detected by a sensor element 60.

The operation of the described control device of the present invention is as follows.

In initial starting conditions of the engine, when the thermosensitive body 37 has not yet been provided with an appreciable quantity of heat, the rod 36 is in the most retracted position so that the lever 13, under the action of the spring 15, presses the is prismatic body 34 and therefore the screw 38 against the rod 36 so that this lever 13 is in the configuration illustrated and the lever 5 maintains the main butterfly valve 2 in a predetermined open position, whilst, by-means of the levers 19, 22 and the link 26, the crank 27 maintains the auxiliary butterfly valve 3 in a substantially closed-condition. During warm up of the engine, with the progressive heating of the liquid circulating in the chamber 41 through the ducts 42 and 43, the rod 36 progressively extends, which causes a progressive anti-clockwise rotation of the lever 13 and consequent progressive clockwise.rotation of the lever 5 which controls progressive closure of the main butterfly valve 2 and, on the other hand, progressive anti-clockwise rotation of the levers 19 and 22 which control progressive opening of the auxiliary butterfly valve 3. According to the characteristics of the present invention a supplementary quantity of heat is supplied to the heat sensitive body 37 by the resistor element 54 so that there is a more rapid extension of the rod 36 and a more rapid progressive closing of the main butterfly valve 2 and progressive opening of the auxiliary butterfly valve 3 with respect to conditions - 6 controlled only by the circulation of coolant liquid acting on the thermosensitive body 37. In this way the first mentioned objects are achieved of a lower fuel consumption and less emission of noxious combustion gases in that the supply conditions to the engine are brought more rapidly to those of normal operating conditions. Electrical supply to the resistor element 54 can he maintained continuously and for this may be controlled by the general vehicle switch, and in this case the resistor element 54 is conveniently a PTC, or else this supplementary quantity of heat via 10 the resistor element 54 can be provided to the heat sensitive body 37 only in a predetermined temperature range, for example in an intermediate heating interval of the engine coolant liquid, to accelerate the achievement of the nominal fuel supply conditions. The auxiliary butterfly valve 3 may further have a pneumatic is anti-flooding valve of known type in a conventional manner. The adjustment of the initial position of the lever 13 with respect to initial position of the rod 35 can be effected by means of the screw 38 and the fixing nut 39.

The advantages obtained with the thermostatic control device of the present invention are thus evident from what has been described.

Finally, it is clear that the embodiment of the present invention described and illustrated may have modifications and variations introduced thereto without departing from the ambit of the invention itself.

1 1 1 1 t b

Claims

CLAIKS

1 - A device for controlling the main supply valve and auxiliary supply valve - of a carburettor, during the initial warm up of an internal combustion engine, and in which the position of the said valves is controlled by at least one element positioned as h function of the degree of projection of a rod from a body containing material the volume of which varies significantly as a function of temperature, and in which the said body is positioned in a section of a duct traversed by the engine coolant liquid, characterised by the fact that it includes electrical resistor means for supplying a supple- mentary quantity of heat to the said body

2. A device according to Claim 1, characterised by the fact.that the said electrical resistor means are disposed in direct thermal contact with the said body

3. A device according to Claim 1 or Claim 2, characterised-by the fact that the said electrical resistor means comprise a PTC.

4-. A device according to Claim 3, characterised by the fact that the said electrical resistor means are energised continuously during the operation of the said engine.

5. A device according to any of Claims from 1 to 3, characterised by the fact that the said electrical resistor means are energised over a temperature interval of the said coolant liquid of the said engine.

6. A device according to any preceding Claim, characterised by the fact that it includes means for adjustment of the 1 t;_ X.

- 8 initial position of the maid rod for acting on the &aid element 0

7. A device according to any preceding Claim, characterised by the fact that the said element includes a twin-arm lever to which the said rod is connected by means operable to allow the transformation of rectilinear motion into rotary motion.

8. A device according to Claim 7, characterised by the fact that a first end of the said lever is coupled, by means of a ca.m profile to means operable to control the position of the said main supply valve and in that a second end of the said lever is coupled by a lever- mechanism to is means operable to control the position of the said auxiliary supply valve

9. A device for controlling the main and auxiliary supply valves of a carburettor during the warm-up phase of operation of an internal combustion engine, as described with reference to the attached drawing.

Published 19--te -L The Patent Office. State House, 66'71 High Holborn, London WC1R 4TP. Further copies may be obtained froni The Patent OMce, Sales Branch, St Mary Cray, Orping'Lon, Kent BR5 3FLD Printed by Multiplex tecbxiiques ltd. St Mary Cray, Kent. Con. 1/87.