Carburetor for Internal Combustion Engines With an Acceleration Pump

The present invention relates to a carburetor for internal combustion engines with an acceleration pump whose pump chamber is connected to the float chamber by a suction duct containing a suction valve, and to the suction line section upstream of the throttle by a delivery duct containing a pressure valve and a calibrated injection opening. The acceleration pump has a displacement member which is actuated depending on the throttle position by means of a lever via a linkage.

Such devices are known, for example, from German Laid-Open Document No. 24 20 171, dated Jan. 2, 1975, where the injection is metered depending on the fuel temperature. However, with the known pumps it is impossible to adapt the acceleration quantity to the requirements of the engine and to the exhaust gas laws. During acceleration in the upper range, that is, with an acceleration based on a specific throttle opening, CO peak values are obtained when measuring the exhaust gases. This is due to the fact that the injected amount is too large. However, if the pump is adjusted so that the injected amount is reduced, it becomes too small for the lower range of throttle opening and the engine runs out of true.

Accordingly, it is an object of the present invention to provide a device which in the lower range of the throttle opening angle injects a larger adjustable volume than in the upper range.

Another object of the present invention is to provide an arrangement of the foregoing character which is substantially simple in construction and may be economically fabricated.

A further object of the present invention is to provide a carburetor, as described, which may be readily maintained in service and which has a substantially long operating life.

The objects of the present invention are achieved by a carburetor in which the pump chamber is provided with a flow duct to the float chamber with a cross section adjustable by a screw. A second adjustable flow duct has an inlet with a valve actuated by the position of the throttle. An advantageous embodiment provides that the valve has a spring which presses a closure member held in a diaphragm, overcoming the force of the fuel pressure, against the inlet, and also presses a plunger against a second arm of the lever actuating the pump.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

FIG. 1 shows a section through the carburetor according to the present invention; and

FIG. 2 shows a pump diagram.

The carburetor 1 is of conventional design and contains all standard systems, even though not shown, since they have no immediate bearing on the present invention. A throttle 4 is located in the intake line 3 downstream of the air funnel 2. The throttle is connected via a linkage 5 in a known manner by means of a lever 6 to the displacement member 7 of an acceleration pump 8. The displacement member 7 is formed by a diaphragm. The pump chamber 9 is filled with fuel during the intake stroke from the float chamber 10 via a suction duct 12 having a suction valve 11.

If the throttle 4 is opened by a specific angle, the diplacement member 7 performs a pressure stroke and the fuel travels via spring-loaded pressure valve 13 and a delivery duct 14 to the intake line 3 portion upstream of the throttle 4 where the fuel is injected via a calibrated opening 15. There is a partial flow of the fuel via a flow duct 17 equipped with a pressure valve 16 preventing return flow due to vacuum pressure influence. This duct 17 is divided into two flow ducts 18, 19 which discharge into the float chamber 10. In case pressure valve 13 is an unloaded valve, ducts 18, 19 may be directly connected to the float chamber. The flow duct 18 has an adjustment screw 20 for adjusting a partial volume. FIG. 2 shows that the injected volume can be adjusted by regulating the return volume for the lower range of the opening angle of the throttle. Since the engine, after its run-up, requires a smaller injection volume than in the mentioned lower range of the opening angle of the throttle, a valve 23 which is actuated by the position of throttle 4 is located on the inlet 21 of flow duct 19 which also has a adjustment screw 22 determining the fuel flow. Valve 23 has a spring 24 which presses a closure member 26 against inlet 21, overcoming the force of the fuel pressure on a portion of diaphragm 7 abutting closure member 26, and on the other end presses a plunger 27 against a second arm 28 of lever 6 actuating the pump 8. If the throttle 4 is opened beyond an angle adjustable on linkage 5 within predetermined limits, arm 28 of lever 6 releases plunger 27 so that additional fuel may flow via duct 19 into float chamber 10 in large amounts. The curve for the injected volume in FIG. 2 clearly shows that the injected volume is greatly reduced after a predetermined opening angle of the throttle. The arrangement of valve 23 has the advantage that the flows through ducts 18, 19 can be adjusted so that the adjusted flow through one duct has no effect on the adjusted flow of the other duct.

It is obvious that the above arrangement may be combined with a known arrangement for further reducing the injected volume depending on the engine operating temperature.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention, and therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.