US 3628516 A
Description (OCR text may contain errors)
nited States Patent Jean-Louis Perrin;
Henri Milliot, both of Billancourt, France 18,043
Mar. 10, 1970 Dec. 21, 1971 v Regie Nationale des Usines Renault Billancourt,
Automobiles Peugeot Paris, France, part interest to each Mar. 10, 1969 France Inventors Appl. No. Filed Patented Assignees Priority INTERNAL COMBUSTION ENGINE CARBURETOR 3 Claims, 1 Drawing Fig.
lU.S.C1 123/136, 261/36A,261/39R,261/72,261/130,261/l51, 123/119R Int. Cl .l F02m 5/10 FieldofSearch 261/3912,
 References Cited UNITED STATES PATENTS 2,963,013 12/1960 Fisher 123/136 3,026,862 3/1962 Fisher... 123/136 3,314,665 4/1967 Tutch 123/136 3,372,912 3/1968 Benmore..... 261/36 A 3,477,238 11/1969 Race 123/136 FOREIGN PATENTS 931,260 2/1948 France 261/36 A Primary Examiner-Tim R. Miles Attorney-Stevens, Davis, Miller & Mosher ABSTRACT: Improvement in internal combustion engine carburetion devices of the type comprising an internal circuit for cooling the fuel, this circuit forming a circulation loop with the fuel tank, characterized in that the cooling circuit comprises a coil tubing mounted within the float chamber and connected in parallel to a fuel-circulation cooling jacket adapted to cool the passages through which fuel is fed to the main jet and idlingjet.
INTERNAL COMBUSTION ENGINE CARBURETOR This invention relates in general to carburetors of internal combustion engines and has specific reference to means adapted to improve the efficiency of carburetors, more particularly the homogeneity of the air-fuel mixture in internal combustion engine carburetors.
It is known that under certain circumstances, due to the heat caused by the surrounding temperature or transmitted by radiation and conduction from the engine after a certain period of continuous operation, the carburetor and fuel feed system reach abnormal temperatures, whereby the gasoline filling the float chamber or the fuel pipelines or passages is vaporized partially or totally, thus causing the so-called percolation effect.
In fact, the fuel vapor develops within closed and limited spaces, thus generating local over pressures due to the considerable volume increment inherent to the vaporization effect.
These fuel vapor locks, under a considerable pressure, prevent the ingress of combustion air into the air-fuel mixture ducts, notably in the case of the idling system through which either only fuel vapor flows and counteracts with its inherent pressure the ingress of combustion air, thus giving an abnormally rich mixture due to the absence of air, which mixture is not sufficient since the gasoline vapor output is limited by the pipeline cross section; or a mixture of air and gasoline vapor in which the insufficient proportion of gasoline is still more pronounced, this mixture remaining relatively heterogeneous, the gaseous nature of both components leading to an instantaneous equilibrium between their relative pressures, without producing an intimate and homogeneous mixture of these two components.
These circumstances are therefore the cause of an irregular engine operation when accelerating under normal driving conditions, and also of bad idling. On the other hand, these engine feed irregularities constitute an important air pollution factor through the exhaust gas, not only under normal driving conditions but also and more particularly when idling, i.e. when the low fuel output facilitates greatly the fuel vaporization.
Conversely, the ideally perfect carburetion produces a mist of minute fuel droplets in the liquid state, in suspension in a stream of combustion air. The reduced volume occupied by the gasoline in liquid phase permits of introducing a greater amount of air into the mixture and this air acting as a vehicle to the fuel droplets forms a homogeneous mixture therewith and is present everywhere for ensuring a combustion. As a result, the engine operation is improved and the pollution is reduced due to the regularity of the mixture combustion.
It has been endeavored to avoid this percolation effect by creating in the fuel feed system temporary or permanent communication with the free atmosphere, to permit the escape of gasoline vapor before the latter creates overpressures capable of interfering with the engine feed. Means for injecting gasoline directly into the induction pipe have also been provided for compensating, notably in the case of hot starting, the insufficiencies of the conventional feed system which are due to said percolation.
In this respect reference may be made to the Fr. Pat. No. 1,450,678 and to its Certificate of Addition No. 91,787 of the same applicant, wherein when the vehicle is at rest, means cause a reduction in the fuel level in the carburetor float chamber so as to communicate the fuel feed circuit to the atmosphere and permit the escape of the gasoline vapor. The fuel thus discharged from the float chamber is collected into the auxiliary chamber remote from the hot engine portions, and is returned to the float chamber when it is desired to restart the engine. This arrangement constitutes a satisfactory solution to the percolation problem from the point of view of starting, but the same problem remains unsolved when the engine is running normally or at idling speed, and the abovementioned palliatives as well as the various antipollution systems provide only approximate and/or costly solutions thereto.
It is the essential object of the present invention to avoid the inconveniences resulting from the percolation effect under normal running and idling conditions of an internal combustion engine, so as to complete the efficiently, under starting condition, of the device constituting the subject matter of the aforesaid patent and certificate of addition. This object is obtained, in contrast to hitherto known arrangements, by eliminating the percolation effect itself, due to the regulation, notably under cooling conditions, of "the feed fuel, by maintaining same at the temperature below its vaporization temperature, by using a heat transfer device of the fluid-circulation type.
According to another features characterizing this invention the cooling fluid consists of the fuel itself, which is pumped directly from the fuel tank by the feed pump and forced on the one hand towards the float chamber of the carburetor, and on the other hand towards the circuit for cooling the fuel contained in said float chamber, which includes a coil tubing, and also in the main feed and idling circuits, by using adequate jacket means consistent with the carburetor construction. This cooling circuit is completed by a return line to the fuel tank.
The cooling action produced by the excess fuel delivered by the fuel pump which is not absorbed for engine feed purposes increased as the engine consumption decreases; in other words, during the idling or deceleration periods, that is, when due to the moderate fuel feed output as a whole in an assembly heated by the engine having attained its normal running temperature, the fuel vaporization is most likely to take place. As a result, due to this advantageous disposition, the fuel feed temperature is adjusted automatically irrespective of the fuel output. The capacity of absorbing heat from the ambient heating is compensated by the parallel output of the cooling circuit whereby the sum of the outputs of the cooling and feed circuits by a constant depending on the output characteristics of the feed pump. It is this quantity that determines the heat dissipation capacity of the circuit and therefore the desired temperature of the feed fuel, whatever its output and therefore the engine speed, thus imparting a high degree of homogeneity to the air/fuel mixture while maintaining the fuel at a uniform temperature.
The heat absorbed by the cooling circuit is subsequently dissipated along the return circuit or in the fuel tank proper, the mass of this tank being amply sufficient to absorb the relatively small amount of heat contained in the lower output to the return circuit, without causing any significant increment in the fuel temperature.
This regulation may be completed by a partial or adjustable direct return to the fuel tank whereby the maximum output of the cooling circuit may be adjusted as a function of ambient conditions. 0n the other hand, it would not constitute a departure from the basic principles of this invention to combine this device with carburetor preheating means or system already known per se, such as heating resistance or exhaust gas heating associated with thermostatic regulation means, this arrangement being particularly advantageous in cold countries.
The present invention thus provides a simple yet efficient solution to the problem arising from the detrimental con sequences of the so-called percolation effect by eliminating this effect through maintaining the feed fuel at a temperature below its vaporization value. This ensures a more homogeneous carburation, an improved engine efficiency and performance, and eliminates one of the main causes of irregularity in the exhaust gas composition as a function of engine speed, notably as far as the CO content of said exhaust gas, i.e. the major cause of atmospheric pollution, this content being reduced to and maintained at a reasonable level with the arrangement of this invention.
Another advantageous feature characterizing the arrangement according to this invention is the great facility with which it can be embodied and also its extremely low cost as an extra equipment, since its component elements are somewhat provided gratuitously" by existing installations.
A exemplary but not limiting form of embodiment of the device constituting the practical embodiment of this invention will now be described with reference to the single FIGURE of the attached drawing illustrating a very diagrammatic form and in vertical section a carburetor equipped with fuel feed and cooling circuits according to this invention.
The fuel drawn from the tank 1 by a fuel pump 2 through a suction pipe 3 is forced into a feedline 4 opening above the needle valve 5 carried by the float 6 in the float member 7 of the carburetor.
Branched off this feedline 4 are in succession a direct return line 9 to the fuel tank 1, in which a valve 9 is inserted for adjusting the return fuel output; a line 11 for feeding fuel to the cooling jacket 10, which has also inserted therein an output adjustment valve 12, and finally a complementary cooling line 13 for supplying fuel to a cooling coil tubing 14 disposed within the float chamber 7. This coil tubing shown in the FIGURE as consisting of a flat or spiral coil may of course have a different configuration and notably accomodate the particular shape of the float chamber without interfering, of course, with the free movement of the float 6.
The cooling circuit comprising the coil tubing 14 is connected via an outlet 15, and the cooling circuit comprising the jacket is connected via another outlet 16, to a common return pipe line 17 leading to the fuel tank 1.
Besides, the carburetor comprises an induction pipe 18 provided with a throttle or butterfly valve 19, a main fuel jet 20 disposed above the venturi, and an idling jet 21 having its orifice located just beneath the throttle valve 19. The main jet 20 is supplied with fuel via a passage 22 and the idling or slowrunning jet 2] is supplied with fuel via another passages 23, these passages 22 and 23 being in maximum mutual surface contact by having common partitions between them and the cooling jacket 10. A screw 24 permits of adjusting the opening of the idlingjet 21.
The direct return circuit 8 is'adjusted beforehand by means of the output adjustment valve 9 as a function of the desired pressure in pipeline 4 and also of the output in cooling circuits 12, ll, l0, l6 and l3, l4, 15, respectively this adjustment being possible from a maximum output to zero output. Thus, the pump 2 will deliver a constant total output to the feed circuit 4 and also to cooling circuits l3, l4, l5 and 12, l1, l0, 16.
Under normal running conditions, with the needle valve 5 open, a larger quantity of unheated fuel is delivered into the float chamber 7, and under these conditions the function devolved to the cooling circuits of which the outputs is reduced in proportion, are less necessary.
On the other hand, when the engine is decelerating or idling, the main jet 20 is inoperative, and fuel is delivered only to the idling jet 21. Thus, the needle valve 5 is practically seated. The gasoline flow is zero in passage 22 and small in passage 23 and float chamber 7. As a compensation, the cooling circuits receive the maximum fuel output and dissipate the same quantity of heat which corresponds to the output of pump 2 in pipeline 4. This quantity of heat, instead of being absorbed by the engine feed as under normal running conditions, is diverted into the return circuit 17 to tank 1. In either case, the temperature of the feed fuel remains practically unchanged, whether this fuel circulates or remains still in the carburetor body, of which the inherent temperature is regulated by a fuel circulation. Under these conditions, the homogeneity of the mixture of gaseous air and liquid gasoline is not more subordinate to atomizing conditions.
According to the variations in the surrounding conditions, this regulation may be adapted to adjust the opening of the output adjustment valve 9 and 12 in order to supply the carburetor circuit a fuel output corresponding to the desired carburetor temperature.
In a practical example of such thermostatic means, the valve 9 and 12 may be controlled through relay means responsive to a thermocouple-type temperature-sensitive device associated with the carburetor.
It would not constitute a departure from the basic principles of this invention to control the fuel output in circuit 4 by thermostatic means known per se, in order to keep the fuel therein at a predetermined temperature consistent with the optimum carburation conditions for the specific engine concerned.
Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can be 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.
What is as new is:
1. Improvement in internal combustion engine carburation devices of the type comprising an internal circuit for cooling the fuel, this circuit forming a circulation loop with the fuel tank, characterized in that the cooling circuit comprises a coil tubing mounted within the float chamber and connected in parallel to a fuel-circulation cooling jacket adapted to cool the passages through which fuel is fed to the main jet and idling jet.
2. Device according to claim 1, of which the circuits for cooling the fuel feed circuit receive in common the fuel pump output, the output fraction fed to the main jet and/or idling jet passages being absorbed by the engine induction pipe and the output fraction fed to the cooling circuits is returned to the fuel tank, the fuel output delivered to the cooling and feed circuits being adjusted by means of an auxiliary circuit constituting a direct return line to the fuel tank.
3. Device according to claim 2, wherein the output adjustment means are responsive to thermostatic regulation means as a function of the desired fuel temperature in the carburetor.