DE2752519C2 - Carburettors for internal combustion engines - Google Patents

Description

25th

The invention relates to the carburetor for internal combustion engines according to the preamble of the claim.

There are known carburettors of this type in which the Auxiliary throttle element is formed by an element which is transverse to the air flow in the inlet line movable 17t. This element is generally formed by a cylindrical plunger, it can but also have the shape of a thin plate, as the FR-PS 21 35 046 shows

This transversely movable element is made possible by a pneumatic device operated, which on one side is below atmospheric pressure and on the other Side is under the pressure, which in the inlet line between the two throttle elements prevails.

In carburetors of the above type this becomes the amount of fuel regulating metering member generally formed by a needle, the cross section of which is along the needle is variable and which more or less enters an opening with a certain cross section, the Fuel can flow through the annular space defined by the needle and the opening.

Such carburettors work as follows:

When the main throttle element is gradually opened, the auxiliary throttle element opens automatically According to the prevailing between the two throttle elements negative pressure, such that the of the Auxiliary throttle element certain passage cross-section for the air and the one determined by the metering member Passage cross-section for the fuel change practically proportionally and that the air and the Fuel, which are formed under the same pressure difference, in normal engine operation Form a mixture with a practically constant mixing ratio.

Such a carburetor has a disadvantage:

When the auxiliary and main throttle are fully open, the Engine at full load and increasing suction pressure continue to suck in air without a corresponding one Increase in the amount of fuel, since the passage cross-section of the fuel metering element is not more changes and you only have a slight increase in the amount of fuel by increasing the amount on the metering device can hope for the negative pressure exerted. As a result, the mixture becomes too poor, reducing the performance, which the engine can reach is limited.

The invention is based on the object of designing a carburetor of the type specified at the outset in such a way that that with a further increase in the air flow under Vo'Jast a corresponding increase in the amount of fuel is possible

This object is achieved by the features in the characterizing part of the claim Auxiliary throttle body connected to a pneumatic control element, which the auxiliary throttle body over the position moves out, so the passage cross-section on the metering device for the fuel further enlarged, so that without increasing the passage cross-section the air flow a correspondingly larger amount of fuel is sucked into the inlet pipe.

The invention is explained below with reference to the drawing

F i g. 1 is a simplified vertical section of a carburetor according to the invention with a plunger piston, wherein the various elements are shown in the idle position.

Fig. 2 shows the same carburetor in full load position, whereby the plunger is in the position, which an "overpowering" of the engine enables

The carburetor is designed as a whole so that it contains an auxiliary throttle element 4 in its inlet line 1 upstream of the main throttle element 2, which opens automatically and steadily according to the increase in the amount of air flowing in the line 1 in the direction of the arrow F.

The auxiliary throttle member 4 is firmly connected to a profiled needle 5, soft in a calibrated opening 6 is displaceable and with this depending on the longitudinal position of the needle 5 a variable Passage cross section 7 delimits. This passage cross-section 7 forms the metering device for the fuel, which in the line 1 via this passage cross section 7 from a with a fuel source connected shaft 8 is sucked. The sucked in fuel emerges at one point in line 1 which practically the same negative pressure as between the throttle elements 2 and 4 prevails.

The illustrated auxiliary throttle element 4 is formed by a cylindrical element or plunger, whose diameter is at least equal to that of the line 1, and which through the wall of this line in a hole 9 occurs. The plunger 4 is connected to the membrane 10 of a pneumatic element 11. This membrane 10 separates two chambers 12 and 13 in the housing of the pneumatic element 11. The chamber 12, or working chamber, stands over a channel 15 provided with a calibrated opening 16 under the negative pressure which prevails between the throttle elements 2 and 4 in the inlet line Chamber 13 is via a channel 18 under the pressure, which is practically the same as that in the air inlet 17 of the Carburetor's prevailing atmospheric pressure. The working chamber 12 contains a spring 19 which the The plunger 4 is in the closed position against the force exerted by the negative pressure prevailing in the chamber 12 seeks to push the inlet line 1 The plunger 4 is not only when it is moved guided by sliding on the wall of the hole 9, but

also by sliding with a slip fit an axial tube 22 carried by the plunger 4 on one firmly to the cover 21 of the pneumatic element 11 connected piston 20, a formed in the piston 20 channel 23 allows the flow of Air between the chamber 12 and the cavity 24 drawn from the piston 20 within the bore 22 is delimited, eliminating any interference with the displacement of the plunger 4 by compression or relaxation of the contained in the cavity 24- ι ο the air is avoided.

In the case of the in FIG. 1 and 2, the pneumatic element 11 is provided in such a way that it drives the plunger 4 in the direction of the opening beyond the position Po (dashed-dotted line in FIG. 2), in which it defines a passage cross-section in the inlet line , which with the cross-section of the. Inlet line near the plunger is equivalent, ie the position for which the pressure drop of the air in the zone of the line 1 in which the plunger 4 operates is the same as if the auxiliary throttle 4 were not present in this zone. In Fig. 2, the plunger 4 can move beyond the position Po by a distance H before the piston 20 strikes. Any other stop means can also be selected which allows the additional displacement to be limited to a certain value

Strictly speaking, the position Po shown in FIG. 2 is not the exact position of the equivalent cross-section defined above, since the bottom of the plunger shown is flat, but since the difference is extremely small, this has practically no meaning. The same applies to that caused by the displacement Over the distance H , the local increase in cross section had no noticeable effect on the pressure drop suffered by the air,

The way it works is as follows;

As long as the amounts of air flowing through the inlet line 1 are of such a size that the Plunger 4 constricts the passage cross-section presented by the inlet line, d. H. when the engine works with part load, the mode of operation of this carburetor, which works with constant negative pressure, is the one usual known.

If, on the other hand, the air flow in the inlet line increases beyond the flow rate corresponding to the position Po of the plunger 4, ie when the engine is working at full load, the negative pressure transmitted through the channel 15 to the chamber 12 increases further, lifting the plunger 4 above the position Po out and also raises the needle 5 for fuel metering. As a result, the passage cross section 7 of the fuel increases. This results in increased fuel flow. The appropriate level is therefore increased which allows greater power to be obtained when the engine is at full load.

The invention can be modified. It is particularly applicable to carburetors with constant negative pressure, where the auxiliary throttle is a flat plate of the type described in FR-PS 21 33 046. The mode of operation is the same as that described above, but with the difference that beyond the position Po there is no local Enlargement of the passage cross-section occurs at the point of the plate forming the auxiliary throttle element

1 sheet of drawings

Claims (1)

Claim: Carburetor for internal combustion engines, in its inlet duct upstream of one operated by the driver Main throttle body contains an auxiliary throttle body, which depends on the increase in the amount of air flowing through the inlet duct opens steadily and controls a metering device which controls the inlet line under the action of the The negative pressure existing between the throttle elements consists of a pressure that is substantially below atmospheric pressure standing fuel source regulates the inflowing amount of fuel so that that of the air from Auxiliary throttle body released passage cross-section of the inlet line to the passage cross-section released for the fuel by the metering element practically proportional and the composition of the supplied to the internal combustion engine Mixture is constant, characterized by that the metering element (5) is displaceable beyond the position which it is at completely opened * auxiliary throttle body (4)