US2793633A

US2793633A - Carburetors

Info

Publication number: US2793633A
Application number: US289755A
Authority: US
Inventors: Heftler Maurice Ben; Heftler Pierre Victor
Original assignee: Individual
Current assignee: Individual
Priority date: 1952-05-24
Filing date: 1952-05-24
Publication date: 1957-05-28
Anticipated expiration: 1974-05-28

Description

i 1: Fri g May 28, 1957 FIG 0 R E i 21--+ 7b ENG/NE J COOL ANT #54 7' Elam/V656 FIGURE 5 M. B. HEFTLER ETAL ENG/NE FIGURE 2 I N VEN TORfS United States Patent Office CARBURETORS Maurice Ben Heftler and Pierre Victor Heftler, Grosse Pointe Park, Mich.

Application May'24, 1952, Serial No. 289,755 6 Claims. (Cl. 1 23-122) This invention provides inexpensive and simple means to feed a relatively rich fuel air mixture to spark ignition gasoline engines during the warming up period and to lean out this rich mixture to the proper running ratio as the engine warms up to normal operating temperature. It is particularly effective at low speeds and light loads, where it is most needed;

This invention solves the problem of supplying a rich mixture to a cold engine in a new way. Instead of restricting the air intake, When the engine is cold, which is the conventional method, this invention operates on theidle fuel channel and restricts the fuel delivered when the engine is warm. It modifies the normal action of the conventional idle by-pass circuit by adding a heat responsive element arranged so that the quantity, or richness, or both, of the mixture'delivered by thefldle bypass is decreased by an increase in temperature. By operating on the fuel instead of the air intake several advantages result. First,-the cost is small. Secondly, there are a variety of methods for easily making the cold engine enrichment automatically responsive to temperature, and some of them require no moving parts. Lastly, by taking advantage of the fact that the idle system, or low speed circuit, of the carburetor, which supplies all of the fuel at idle, becomes of decreasing importance as the throttle is opened, it is possible to provide cold engine enrichment at low speeds where it is most needed, and automatically taper off the enrichmerit as the speed increases.

The drawings schematically show the invention applied to a carburetor, in three different forms, as follows:

In Figure 1 the idle enrichment is reduced by opening an additional air bleed into the idle by-pass circuit in response to increase in temperature. In Figure 2 the idle enrichment is decreased by heating the air-fuel emulsion in the idle by-pass circuit. In Figure 3, an adaptation of Figure 2, the idle by-pass circuit divides into two branches and the fuel emulsion in one branch is heated. For simplicity, the drawings are somewhat schematic and show the invention applied to a conventional, single bore, downdraft carburetor.

Referring to Figure 1, the discharge nozzle 1 draws fuel from below the liquid level LL and discharges it into the throat of the venturi 2. The air flow is controlled by the throttle plate 3, here shown in a low speed position, under which condition fuel is being delivered by the idle by-pass system.

The engine induction vacuum existing in the manifold 4 is applied to the priming holes 5 to draw an emulsion of fuel and air from the idle by'pass circuit. The idle by-pass circuit consists of

idle channels

6, 7, 8 and 9 leading up from the holes 5 and down to the liquid level LL. Associated with these idle channels there is shown, as found in many carburetors, a restriction 10 located at or near the fuel level LL, an air bleed 11, and an adjustable air bleed or an adjustment screw on the lower priming hole. All that has been so far described is conventional, although the particular arrangement of restrictions and of fixed and manually adjusted air-bleeds in the idle by-pass circuit may vary with different makes of carburetors. t

Figure 1 differs from the conventional carburetor in that the idle bypass circuit has an additional specially controlled air-bleed. A restricted air vent 14 admits air.

When the thermostat 16 is cold the valve 15 is closed and,

the mixture delivered by the idle by-pass system out of priming holes 5 is quite rich, as required by a cold engine.

As the engine warms up, thermostat 16 gets Warm and gradually opens valve 15 thus admitting air into channel 7 and leaning out the mixture delivered by priminghole 5. The restricted air vent 14 may be small in relation to the valve 15, so that only the first part of the valve travel is effective in leaning out the mixture, or it may be very large so that equal increments of valve travel are about equally effective in admitting additional air. The choice in design will hinge on the source of heat supplied to the thermostat, and on how rapidly and to what level it getsgwarm compared to the diminishing demand for fuel as the engine warms up. 7

Referring now to Figure 2, we show a second form of the invention. Again there is shown the main jet 1,

ventu ri 2, throttle 3, manifold 4, the priming holes 5 and the idle by-pass circuit leading from the liquid level LL to the holes 5. However, in 7a, the mid-portion of the idle by-pass circuit, there is a heat exchanger 18 through which the fuel-air emulsion of the idle system must flow before it reaches channel 6 and the priming holes 5.

The heat exchanger 18 is heated by the engine or by some part or medium associated with the engine. It can be built into a cylinder head bolt, and on liquid cooled engines its maximum temperature" can be'limited by the coolant thermostat. When the engine is cold the mixture of fuel and air passes through 18 tothe'primin'gwholes 5 substantially unchanged. As the engine warms up, this mixture is expanded in the heat exchanger 18, and when the temperature of the heat exchanger reaches the vaporization temperature of the fuel the expansion becomes very pronounced. When the fuel is alcohol, with a single boiling point, the expansion is very rapid at about F. With gasoline the expansion is spread over a considerable temperature range, because of the boiling characteristics of the fuel.

The amount, by weight, of the fuel-air mixture aspirated into the engine by the suction at priming holes 5 decreases as the mixture is expanded by heat. Thus, when the engine is cold, it is supplied with more fuel than when it is hot.

Referring now to Figure 3, we show a. third form of the invention somewhat similar to Figure 2. Here, the idle by-pass circuit is divided, for part of its length, into two parallel channels 7a and 7b. Channel 7a goes through a heat exchanger 18, as in the case of Figure 2, but channel 7b has no heat exchanger. These two parallel circuits, 7a and 715, may be controlled by

suitable restrictions

19, 20 and 21 so as to divide the fuel-air mixture between them in the best way.

The point of having parallel circuits is this: It may be desirable to heat the heat exchanger 18 by a medium that has a very broad swing in temperature as the engine warms up from a cold start to normal operating temperature, such as the exhaust manifold. In that case Patented May 28, 1957- the expansion-of the fuel due to the heat may be more than is required. The unheated parallel channel 7b provides a means of limiting the effect of this excess expansion, and

restrictions

19, 20, and 21 provide means of-utilizing exactly that amount of the expansion that best meets the needs of the engine. I

We claim:

1. Ina carburetor for an internal combustion engine with a throttle in the mainair stream and a constant level fuel bowl, a low speed throttle by-pass circuit including a fuel restriction to a channel leading to a point above the fuel level in said bowl, an air admission port to said channel, a discharge port from said channel to said main air stream at a point between the throttle and the engine, and means to heat the fuel and air in said channel, said means being heated by the engine coolant, said discharge port and contiguous carburetor parts receiving heat only from the fuel and air in said channel which have been passed by said fuel restriction and said air admission port and mixed before being heated.

2. Means for controlling the ratio of the fuel-air mixture supplied to an internal combustion engine by av carburetor with a throttle by-pass circuit, said by-pass circuit including means for forming a fuel-air emulsion; comprising a heat exchanging element, means for applying heat to said element so that its temperature gradually increases as the engine warms up after starting to a stable maximum value substantially independent of engine speed and load, means for conducting said fuel-air emulsion from said carburetor to said heat exchanging element for the transfer of heat thereto, and means for conducting said fuel-air emulsion so thermally modified back to said throttle by-pass circuit for forming said fuel air mixture whereby the ratio of fuel to air in said mixture is changed by the transfer of heat to said emulsion from a richer value suitable for cold engine idling operation to a leaner value suitable for warm engine idling operation.

3. Fuel-air ratio controlling means according to claim 2, wherein said heat exchanging element is connected to the coolant system of said engine to obtain the heat required for transfer to said fuel-air emulsion.

4. Fuel-air ratio controlling means according to claim 2 further characterized by said throttle by-pass circuit including a conduit by-passing said heat exchanging element, whereby a metered portion of the fuel-air emulsion delivered to the engine intake system is subjected to a change in density by the application of heat thereto.

5. The method of utilizing thermal air expansion and fuel vaporization'to regulate in a gasoline engine'the richness of the charge according to engine temperature where such charge is supplied through a carburetor having an idle by-pass system, comprising the steps of adjusting the jets and air bleeds in said idle by-pass system to deliver a fuel-air mixture sufiiciently rich to operate the engine when cold, conducting said mixture to a heat exchanging device, applying heat to said mixture through said device to partially vaporize the fuel and expand the air therein and thereby reduce the density of said mixture, gradually applying heat to said device so that its temperature increases as the engine warms up afterstarting to a stable maximum value substantially independent of engine speed and load, and conducting said mixture so heated to said engine.

6. The method of utilizing thermal air expansion and fuel vaporization to regulate in a gasoline engine the richness of the charge according to engine temperature, consisting of supplying fuel and air through a carburetor 11mins an idle by'pass System, adjusting the jets and air bleeds in said idle by-pass system to deliver a mixture sufficiently rich to operate the engine when cold, and applying to a fuel conduit in the idle by-pass system regulated engine heat to the end that the temperature of said conduit gradually increases as the engine warms up after starting to a stable maximum value substantially independent of engine speed and load, the heat applied to said fuel conduit expanding the air therein and at least partly vaporizing the fuel therein and thus reducing the fuel delivery of said idle by-pass system to what the engine requires when it is at operating temperature;

References Cited in the file of this'patent