EP0145676A2

EP0145676A2 - Pneumatic device able to transitorially enrich the mixture delivered by a carburetor for internal combustion engines

Info

Publication number: EP0145676A2
Application number: EP84830301A
Authority: EP
Inventors: Renato Vitto
Original assignee: Weber SRL
Current assignee: Weber SRL
Priority date: 1983-11-08
Filing date: 1984-11-05
Publication date: 1985-06-19
Also published as: IT8303609A0; ES8600656A1; IT1168696B; BR8405772A; SU1400514A3; EP0145676A3; JPS60145450A; ES537431A0

Abstract

A device suitable to transitorially enrich the mixture delivered by a carburetor includes a housing (1), enclosing two chambers (5) and (6), which are separated by a diaphragm (3); chamber (5) communicates with the manifold through a channel (7); chamber (6) communicates with chamber (5) through a metering hole (8), which crosses the plates (4a and 4b); a spring (9) and the forces due to pressures acting on the 2 diaphragm sides (3) act on the diaphragm (3); a chamber (13) separated from the chamber (6) by a diaphragm (11), communicates with the float, chamber (2) through an inlet and with the main circuit (15) through an outlet (16), closed by a valve formed by a spring (18), suitable for pushing a sphere (19) on a seat (17). A bar (20) integral to the diaphragms (3, 11) supports a pushing rod (24), which under the action of pressure forces acting on the diaphragm (3) removes the sphere (19) from the seat (17), opening the outlet passage. The fuel is metered out by a bush (25).

Description

This invention relates to carburetors for internal combustion engines and, in particular, to devices suitable for being assembled on carburetors in order to transitorially enrich the mixture.
Some devices enriching the mixture over certain phases of the engine-stroking are known; some of them, paricularly, have structures suitable for working in reply to a lowering of the vacuum in the intake-manifold, carrying out their function when the load on the engine grows.
The known devices of this kind can be divided up into two types: a first type consisting in enrichment valves, acting as long as the vacuum in the intake manifold keeps lower than a certain value appointed in advance. In this way they supply the traditional carburetor circuits involved (main or minimum) with one more fuel flux, whoose range depends on the intensity of. the suction caused by the speed of air in the carburetor; a second type, consisting in pneumatic control accelerating pumps, which act transitorially, supplying the intake manifold with a certain amount of fuel under pressure.
The above known devices do not solve the problem of enriching the mixture over transitory periods with controlled length, using the metering devices of the tradutional circuits mentioned above, beginning from the very first moment of the transitory period.
The main target of this invention is to work out the said problem with a reliable and cheap device, suitable for bein easily assembled on already exsisting carburetors.
To this aim, this invention consists in a device suitable to transitorially enrich the mixture delivered by a carburetor for motor-veichles engines, characterized by what is explained in the claims; other targets, features and advantages of this invention will be fully understood, once taken into consideration the enclosed pictures, which are a non-restrictive example of this invention.

- Fig. 1 represents a section view of a device, according to the invention, in its first wording condition;
- Fig. 2 represents the same device of Fig.l, but in its second working condition.
- Fig. 3 represents a second constructive version of the invention in a section view.

The device represented in Fig.1 and 2 is essentially formed by an housing 1, suitable for being assembled on a carburetor, preferably next to the float chamber at steady level two.
Housing 1 includes a first diaphragm 3, which is made not flexible in the middle by two opposite plates 4a and 4b and which divides up the housing inside 1 into two chambers 5 and 6. The first chamber 5 communicates with the intake manifold through a channal 7 and the second chamber 6 communicates with the first chamber 5 through a metering hole 8, whoose size is not so big and which crosses the two plates 4a and 4b.
Diaphragm 3 shows a first side 3a, facing chamber 5, and a second side 3b facing chamber 6.
Chamber 6 contains a spring 9, whoose left end insists on the plate 4b, and whoose right end is sipported by a wall 10 one the chamber 6 and which acts to shift diaphragm 3 to the left.
Chamber 6 has a relatively big capacity, anyway it is enough to have gradual pressure changements in its inside, even in case of strong pressure differences in the said chambers 5 and 6, as it may occur during the engine stroking. This happens in order to keep the size of hole 8 within technically accomplishable values.
A second diaphragm 11, made rigid in the middle by two opposite plates 12a and 12b, separates the second chamber 6 from a third chamber 13, which communicates with the carburetor float chamber 2 through a relatively big inlet and with channel 15 through an outlet passage; channel 15 schematically represents the main feed circuit of the carburetor, encluding the traditional metering devices of fuel and air, which have not been represented. In outlet 16 there is a metering bush 25, which has to measure the fuel when the above device is at work. Passage 16 is closed by a valve which is formed by a seat 17, a sphere 18 and a spring 19, since the said sphere 18 suitable for closing the seat 17 under the thrust of spring 19.
A bar 20 is integral to plates 4a and 4b of the first diaphragm 3 nad to plates 12a and 12b of the second diaphragm 11; the said bar 20 shows a left end 21 suitable for srtiking a projection 22 without going beyond it, finding itself on a wall 23 of chamber 5, under the action of spring 9; the right end of bar 20 crosses chamber 13 ending with a push rod suitable to cross the outlet 16, in order to remove the sphere 18 from the seat 17 under the action of pressure forces, which stress diaphragm 3 to shift to the right.
In the position of fig.1 the right end of pushing rod 24 is very near to sphere 18, even though they do not touch; this in order to reduce to the minimum the device's operating time.
The elastic diaphragm 11 is the separation surface between the chambers 6 and 13 mentioned above and it has sealig functions for the fuel in chamber 13; the said diaphragm 11 permits axial traverses of bar 20, without any considerable frictional resistance.
The diaphragm surface has to be little enough to check the counter-pressures opposing the traverses to the right of bar 20. The working of the device in Fig.1 and 2 can be explained as follows:

Over a stabilized working-phase at low and minimum engine utilization, the vacuum in the intake manifold is not so high; the same vacuum value acts both within chamber 5 and chamber 6, so the forces brought about by the pressures insisting on the two sides 3a and 3b of diaphragm 3 are balanced; spring 9 is able to keep the said device in the conditions of Fig.1, where chamber 13 does not communicate with channel 15, because sphere 18 closes the seat 17 under the action of spring 19. The strength of the mixture delivered by the carburetor is therefore determined by the traditional metering devices present in the main circuit 15.

When the vacuum in the intake manifold lowers, owing to a sudden opening of the carburetor's throttle valve, or when the load on the engine suddenly grows, the device temporary reaches the position of Fig. 2; in fact the vacuum value in chamber 5 immediately reaches the vacuum value in the intake manifold. It is connected with the latter through a channel 7. Anyway, the vacuum value keeps itself in chamber 6, at least at first, on the value preceding the beginning of the transitory phase. The differences between the pressures applied to the two sides 3a and 3b of diaphragm 3 produce awinning force against the load of spring 9. In this way, the bar 20 moves towards the right, sothat its end 24 removes from the seat 17 the sphere 18, against the action of the spring 19; the outlet 16 can joint chamber 13 with the main circuit 15. This traverse-movement of bar 20 also pushes the diaphragm 11 to the right, lowering the volume of chamber 13 containing the fuel; the consequent not so big pumping effect, which, if you take into consideration the small size of diaphragm 11, becomes fully negligible owing to the relatively big size of inlet 14 in comparison with the bush 25. In such a way, the fuel measured out by bush 25 is not sent under pressure to the main circuit 15. More precisely, it is placed at the latter's disposal and it is added to the fuel measured out by the traditional mesuring devices of the main circuit exactly when the vacuum signal for sucking the fuel is particularly weak; this allows a correct enrichment of the mixture strength, according to the needs coming from the particular working conditions of the engine. In time, the air crossing the hole 8 goes from chamber 5 to chamber 6, persisting in the latter low vacuum conditions, allowing a gradual dicrease in the difference between the pressures insisting on the two sides 3a and 3b of diaphragm 3. Thus the device progressively goes back to the conditions pictured in Fig.2 and Fig.l and consequelntly, at the end of the traverse to the left of bar 20, it interrupts the fuel additive rate towards the circuit 15, as required by the new working conditions of the engine. The period in which the outlet 16 remains open, owing to a certain geometric configuration of the device and to a certain size of the hole 8, depends on the initial difference between the vacuums in the two chambers 5 and 6. The said difference expresses the changement of the load applied to the engine.
.The device in Fig.3 differs from that in the preceding ones only because hole 8 has been replaced with a metering bush 8a. The said bush is located in a channel 7a, branching out from channel 7 in order to connect the manifold with chamber 6 of the device at issue. To an expert it would be clear that the solution suggested by Fig.3 is the same of those suggested py the preseding ones, from a functional point of view; if compared with those, it even shows some constructive advantages and in case of failure or of a clogging of hole 8a it can be repaired more easily.
In a third constructive version, the metering hole (8, 8a) in the devices of the enclosed pictures can be formed by bush of microporous, syntherised stuff.
In a further constructive form, the said metering hole (8a) can be formed by an annular passage resulting from the introduction of a pushing rod into a bush having a diametre something bigger than the rod's one and a suitable length. The pushing rod mentioned above forms the end piece of a screw element, whoose finely thread part has been introduced into a support-hole having the same fine-thread made in a supporting framework suitable to maintain axially the- said rod as to the quoted bush. Other known sealing means, preventing the non-employees from handling the screw element, are present. This solution's. advantage is that the reversal time of the pushing rod 24 from position in Fig.2 to that in Fig.l can be easily imposed. This could occur either during the carburetor's installation or on test bend through a screw-traverse of the rod in the bush, with a load loss proportional to that part of the rod inserted in the bush. Once determined the required value of the traverse time, the sealig means are applied.
These are some of the possible employments of this invention, which can be changed only only if it essentially remains unchanged. Forms, sizes and stuff used do not set limits
to the invention's range, in which each contructive element can be replaced with another, which is technically the same.

Claims

1) Device suitable to temporary enrich the mixture delivered by an internal combustion engine carburetor, including at least: a housing enclosing a first and a second chamber divided by an elastic diaphragm, made rigind in the middle by two opposite plates; a channel suitable to connect with the 1st chamber; a space formed by the said channel and/or the above 1st chamber, where the pressure present in the intake manifold acts; a spring suitable for puting the quoted diaphragm in a 1st position defined by the first limit-stop means and for opposing the action of pressure forces acting on the diaphragm in order to put it in a 2nd position determinated by the second limit-stop means; a 3rd chamber divided from the 2nd chamber by a waterproof wall; a first passage suitable to joint the 3rd chamber with the carburetor's floating chamber; a second passage, equipped with fuel metering means, suitable to joint the quoted 3rd chamber with the main and/or minimum circuit of the carburetor, under the control of a valve suitable to close the said 2nd passage; an element jointed to the said plates suitable to act on the above valve in order to open the mentioned 2nd pasage when the diaphragm finds itself in the 2nd position. This passage is characterized by the fact that the 2nd chamber has a volumetric capacity much bigger than that of the first one and by the fact that passage means with metered size are foreseen in order to connect the said space with the 2nd chamber. The second chamber and the said passage means are developed in such a way to work together in order to establish in the above mentioned 2nd chamber the pressure value exsisting in tie said space with a wanted delay.

2) Device, according to claim N^D1, characterized by the fact that the said passage means have an orifice crossing the plates mentioned above.

3) Device, according to claim N°1, characterized by the fact that the said passage means have a metering orifice located in a 2nd channel and directly jointing the said 2nd chamber with the intake manifold.

4) Device, according to at least one of the previous claims, characterized by the fact that said passage means are made up with bushes in sinthered, microporous stuff.

5) Device, according to claim N°1 and N°3, characterized by the fact that the above pasage means have a first bush with suitable diametre and length, a pushing rod suitable to be introduced in the said bush and having a diametre slightly shorter than that ofthe bush;the above mentioned rod forms a part of a screw element, supported by a structure suitable to maintain it axially on the said bush. The above mean and structure are respectively equipped with a screw thread and a screw seat, which is suitable for housing the above pushing rod , in order to axially shift this rod into the bush; known sealing means are present in order to prevent the rod's move.

6) Device, according to claim N°1, characterized by the fact that the sais separation wall between the said 2nd and 3rd chamber consists in an elastic diaphragm.