US2033247A - Charge forming device - Google Patents

Description

March 10, 1936. P. KOEHLY CHARGE FORMING DEVICE 2 sheets-sheet 1 FiledV Nov. 9, 1951 .allA

mi J/ZM 1w /J Ham# dthnmq 2 Sheets-sheet 2 Filed Nov.. 9, 1931 Patented Mar. I10, 1936 CHARGE FO'RMING DEVICE Paul Koehly, Dayton, Ohio, assigner, by mesne assignments, to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application November s, 1931, serial No. 574,016 1 1 claims. (01261-39) l This invention relates to a charge forming device for internal combustion engines, and is disclosed herein as embodied in a charge forming device having a plurality of primary carburetors 5 whichdeliver a'primary mixture of fuel and air to a plurality of secondary carburetors. in which the primary mixture may be mixed withv additional air. However, it will be understood that the present invention is of utility not only in connection with the type of charge forming device in which it is disclosed, but of general application to any form of charge forming device.

It is an object of the present invention to provide means for more accurately proportioning the mixture on changes of temperature more particularly during idling and low speed operation.

It is a. further object of this invention to provide means for facilitatingthe operation of the engine during the Warming-up period of the 20 engine in cold weather.

With these objects in view, the invention consists of the provision of a thermostat operable ln connection with the choke device. for controlling the opening movement of the air valve. The thermostat is so mounted that it controls the pressure of the spring which:` holds the air valve closed and is adapted to increase the pressure of such spring when the atmosphere surrounding the thermostat is relatively cold, so that the air valve will not open to as great a degree when the temperature is low as when the temperature is higher, thus insuring a somewhat richer mixture during operation of the engine in cold weather, or during the Warming-up period under any weather condition.

A charge forming device of the general type disclosed herein is fully illustrated in the patent of Fred E. Aseltine et al., 1,913,741, issued June 13, 1933, and reference is had thereto for a full disclosure of the timer device.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanythe opposite direction to Fig.- 1.

Fig. 5 is a detail.

The manifold which forms a part of a charge forming device of this type`is not disclosed here- 5 in for the sake of simplifying the disclosure, and the general construction of the carburetor is described only sufficiently to give a general idea of the operation of the carburetor, this being all that is deemed necessary to understand the pres 10 ent invention.

The carburetor unit comprises a main lhousing 20, having a ange 22 .by which it may be attached to a corresponding flange on the manifold Fig. 4 is a, fragmentary section 'viewed from in the usual manner. A valve controlled air inlet 15 coupling 24 is secured in position in an opening in the top of the main housing in any desirable way. A casting 26, in which the fuel passages are formed which convey fuel from the fuel reservoir to the nozzles, is secured to the bottom 0f 20 the main housing by screws or in any otherrsuitable manner, and a sheet metal fuel bowl 28 is held tight against an annular shoulder 30, formed on the main housing, by a screw 32, screwed into the casting 26. Fuel is supplied to the fuel bowl 25 from a main source of supply in the conventional manner and a constant level of fuel is maintained in the bowl by a float 33.`

A plurality of primary mixture passages 34 are formed in the bottom wall of the main hous- 30 ing and are adapted to register with corresponding passages in the manifold when the carburetor unit is secured thereto. Communicating with the primary mixture passages through orifices 36, are three chambers 38, which for convenience may 35 be designated fuel supply chambers and fuel is admitteddirectly to these chambers byfuel nozzles 40 and 4I to which fuel is conveyed from the bowl 28 to conduits not shown herein, but fully described in the earlier application above referred 40 to. `A small quantity of air is admitted to these chambers 38 through a slot 42 formed in apartition separating these chambers from a main air chamber 44 to which air is admitted through the coupling 24`and holes 45. `This air mixes with the 45 fuel issuing from the nozzles to form a rich mixture of fuel and air which flows into the primary mixture passages through the orifices 36 to be mixed with additional air therein and conveyed to the secondary mixing chambers, which are formed in the manifold outlet branches, as shown in the earlier application. v

n The flow of mixture through the primary mixture passages 34 is controlled by a. primary throttle valve 46, which extends across all of said passages and is provided with grooves 48, which register with the passages. 'This throttle is adapted to be operated by means o f exactly the same construction as shown in the earlier application, and which need not be described herein.

The air supplied to the carburetor through the coupling 24 is controlled by valve 58, normally held against the seat 52 by a spring 54 received between the valve and a flange 56 projecting from a sleeve 58, slidably mounted on a fixed sleeve 60,

vwhich is held in position in the housing in any suitable manner and guides the stem 62 to which the air valve is'secured. When the engine is not running, the valve is held against the seat in the manner disclosed in Fig. 1 by the spring above referred to. The valve admits air directly to the main air chamber 44 from which the air flows to the fuel supply chambers in a manner previously described, and from which airis also admitted directly to the primary mixture passages 34 through diagonal air passages 63.

The chamber 44 also supplies air to the secondary mixing chambers of the manifold by means of the secondary air passage 64, which ls controlled by a manually operable air throttle valve 66, secured to a shaft 68, rotatably mounted in the main housing and by a suction operated valve 10, secured to a shaft 12, which is positioned off center with respect to the passage 64 and is also rotatably mounted in the main housing. The valve 66 is operated by a connection extending from the operating means of the primary throttle and the valve 1D is operated entirely by engine suction in exactly the same manner as in the earlier application. These operating ccnnections of these valves are disclosed herein, in

Fig. 3 but are not described as they have nothing to do with the present invention, and a detailed description would only burden the case. In order that the present invention may be clearly understood, it may be said herein that the operating connections between the throttle valve and the valve 66 are so constructed that the throttle may make a predetermined movement without -any corresponding movement of the valve 66, this movement being such as to permit the vehicle on which the carburetor is used, to operate at a speed of approximately 20 miles per hour on a level before the valve 66 begins to open. Of course, no movement of the valve 10 can take place until the valve 66 makes some opening movement.

The openingmovement of the valve 50 is ret'arded to some extent by a dashpot comprising a cylinder 'I4 formed in the casting 26 and a cooperating piston 16 slidable in the cylinder and secured to the lower end of theA valve stem 62. This dashpot effects some retardation of the opening movement of the air valve following any opening movement of the throttle for the purpose of.

preventing uttering of the valve and to assist in the formation of a mixture of the desired proportions to properly operate the engine during the acceleration period which immediately follows any opening of th throttle.

The devices previously described operate substantially as follows: When the primary throttle is opened to any degree, the suction of the engine is admitted through the air inlet coupling 24 to form what is known as a primary mixture and which is of properly combustible proportions and will operate the engine without admixture of additional air inthe secondary mixing chambers. Up to the speed at which the valve 66 begins to open,'

All of the portions of the device above defl scribed are constructed is substantially the same manner and operated in the same way as fully described in the earlier application and no further description of the device in general is believed necessary.

In order to facilitate starting of the engine, a'y

choke device is providedwhich comprises a lever 80 indicated in its entirety by the reference numeral and pivoted on a pin 82, secured in a boss 83 formed integrally with and on the outer 'surface of the main housing 20. This lever includes an arm 84, which projects through the main housing and extends to a position beneath the flange 56. Lever 88 is also provided with another arm 86 which may be termed the operating arm and extendsupwardly, to the left and toward the carburetor outlet from the pin 82 on the outside of the main housing, as shown in Figs. 2 and 3. This operating arm is provided with a bent-over portion 88, which is adapted to engage an adjustable stop screw 98, screwed into the wall of the main housing to determine the normal position of the choke lever, and held in adjusted position by a detent 9|. 'I'he operating arm is also provided `with a cam 92 pivotally mounted on the arm 86 and having a notch 93 cooperating with a lug 94 projecting from the arm 86,` so that the cam has a limited movement with respect to the arm. A stud 95, having an oriiice 96 controlled by a set screw 91 is pivoted on the cam. Some form of operating connection,'such as a Bowden cable, is adapted to be connected, in the orifice 9 6 and extends to some point convenient to the operator of the vehicle so that the choke lever may be operated manually at any time desired. When the choke lever is operated, it is rst moved very slightly because of engagement of the cam with the stop 98 to secure minute adjustments for idling. The arm'86 is then moved and lifts 'ange 56 and the sleeve 58 to hold the valve 58 closed, thus preventing the admission of but a small quantity of air and enabling the carburetor to supply a very rich mixture in order to facilitate starting of the engine.

It has been found by experience, that when an air valve spring is provided which is stiff enough to hold the air Valve closed with suicient pressure to form a mixture which is rich enough -to operate the engine at idling, or low speed operation under load, satisfactorily, when the engine is cold, that such spring holds the valve closed with suicient pressure to cause too rich a mixture to be formed for proper engine operation at idling and low speeds after the engine has become hot, or for such operation during hot weather. To overcome this difficulty, the present applicant has provided a thermostat in the form of a bimetallic strip,'which is adapted to lift the flange 56 to some extent when the engine is cold, but which is adapted to move downwardly from the ange as the engine becomes hot so as to relieve the pressure on the spring and thus enable the valve 50 to be held closed with a lighter pressure after the engine is hot than in cold weather or during the warming-up period in any Weather.

, the arm 8d. When the engine is cold, this thermostatic member occupies the .position shown in Fig. 5, and holds the flange 56 in a position slightly above that which it occupies when the engine is hot, in other words, in the solid line position shown in Fig. of the drawings. As the engine warms, the thermostatic member assumes the position shown in dotted lines in Fig. 5, permitting the flange 5% to drop until it engages the choke lever Scl itself and rests thereon. 'I'husthe warming up of the engine causes a slight expansion of the spring 54 and reduces the pressure with which such spring tends to hold the air valve closed and accomplishes the results above set forth.

While the form of embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

l. A carburetor comprising a mixture passage, air and fuel inlets therefor, aA throttle, an air valve controlling the admission of air to the mixture passage, a spring normally holding the air valve closed, a rigid abutment against which the spring presses to determine the pressure of the spring on the valve when the engine is hot, and thermally responsive means for increasing the pressure of said spring on the valve upon reduction of Iengine temperature.

2. A carburetor comprising a mixture passage,

air and fuel inlets therefor, a throttle, an air valve controlling the admission of air to the mixture passage, a choke device including a member for positively holding the air valve closed and thermally responsive means carried by said member for l yieldingly holding the an" valve closed under certain operating conditions, said choke device being adapted to operate the valve independently of the thermally responsive means.

A carburetor` comprising a mixture passage, air and fuel inlets therefor, a throttle, an air valve controlling the admission of air to the mixture passage, a choke lever adapted to positively close the air valve to facilitate starting and a thermostatic member having one end flxedly g secured to'said4 choke lever and adapted to yielddetermine the closing pressure of the air valve spring under normal operating conditions, and a thermally'responsive member carried by the choke lever and so constructed as to increase the closing pressure of the air valve spring when the engine is cold and the choke lever is in normal position.

5. A charge forming device for internal combustion engines having in combination a primary mixture passage, a fuel inlet therefor, a secondary mixing chamber into which said primary mixture passage is adapted to deliver a primary mixture of fuel and air, a main air valve controlling the admission of air to both the primary mixture passage and-secondary mixing chamber, a choke lever for positively holding the valve closed to facilitate starting when the engine is closed and for controlling the openingA movement of the air valve when the engine is hot, and a thermally responsive element carried by the choke. lever and so constructed as to control the opening movement of the air valve when the engine is cold.

6. A charge forming device for internal combustion engines having in combination a primary a choke lever adapted to be moved to close said air valve to limit the quantity of air admitted whereby starting of the engine is facilitated and a thermally responsive member carried by said choke lever to control the admission of air during operation of the engine when the latter is cold, and the choke lever is in normal position.

7. A carburetor comprising a mixture passage, air and fuel inlets therefor, a throttle, an air Valve controlling the admission of air to the mixture passage, a choke device comprising a manu.- ally operable lever adapted to positively hold the air valve closed to facilitate starting, and a thermally responsive element carried -by the said lever and adapted to yieldingly hold the -air valve closed under other operating conditions, said lever being soconstructed as to be operable to hold the valve positivelyclosed independently of the thermally responsive member.

8. A carburetor comprising a mixture passage, air Aand fuel inlets therefor, a throttle, an air valve controlling the admission of air-to the mixture passage, a choke device comprising a manually operable lever adapted to positively hold the airA valve closed to facilitate starting, and a thermally responsive element having one end xedly secured to the said lever and adapted to yieldingly hold the air valve closed when the engine is cold and the choke lever is in normal position, said thermally responsive element being so constructed that it is inelfective to hold the valve closed when the engine has become hot.

9. A carburetor comprising a mixture passage, air-and fuel inlets therefor, a throttle, an air valve controlling the admission of air to the' mixture passage, a spring adapted to close the air valve, a choke lever adapted to positively hold the air valve closed to facilitate starting and a thermally responsive element carried by said choke lever and adapted to increase the closing pressure on said air valve when the engine is cold i and the choke lever is in normal position, but so constructed that it has no effect on the closing pressure of said spring whren the engine has become hot. A

10. A carburetor comprising a 'mixture passage, air and fuel inlets therefor, a throttle, a

air valve controlling said inlet, a spring normally holding the air valve closed, a rigid abutment 'against' which the spring presses to determine the pressure of the spring on the valve when the engine is hot, and thermally responsive means for increasing the pressure of said spring on the valve upon reduction of engine tempera- 1n ture.

11. A carburetor comprising a mixture `passage, air and fuel inlets therefor, a throttle, a

suction operated airvalve controlling the admission of air to the mixture passage, a spring opposing the opening movement of said valve throughout its movement, a rigid abutment against which the spring presses to determine the pressure of the spring on the valve when the engine is hot, and thermally responsive means for increasing the pressure of said spring on the valve upon reduction of engine temperature.

vPAUL KOEHLY.

Images