US3814390A

US3814390A - Carburetor with combined piston motor and diaphragm motor choke valve actuation

Info

Publication number: US3814390A
Application number: US00269124A
Authority: US
Inventors: J Winkley
Original assignee: ACF Industries Inc
Current assignee: Carter Automotive Co Inc
Priority date: 1972-07-05
Filing date: 1972-07-05
Publication date: 1974-06-04
Anticipated expiration: 1991-06-04
Also published as: CA978041A; JPS52156825U; JPS5325053Y2; JPS4951422A

Abstract

Reduction of exhaust emissions is obtained by controlling the carburetor choke valve with greater flexibility. A piston motor responsive to manifold vacuum opens the choke valve partially soon after the engine starts. A diaphragm motor responds to engine vacuum more slowly than the first motor. The diaphragm acts through a modulating spring to open the choke valve, which is connected to a thermostatic coil spring urging the choke valve closed at low ambient temperatures. At high ambient temperatures, actuation of the diaphragm causes wide opening of the choke valve, and at low ambient temperature causes less initial opening, followed by further opening of the choke valve as the engine warms up.

Description

United States Patent 1 1 [11] 3,814,390 Winkley June 4, 1974 CARBURETOR WITH COMBINED PISTON 3,321,194 5/1967 Carlson 261/39 B MOTOR AND DIAPHRAGM MOTOR CHOKE VALVE ACTUATION [75] Inventor: Jerry H. Winkley, St. Louis, Mo.

[73] Assignee: ACF Industries Incorporated, New

York, N.Y.

[22] Filed: July 5, 1972 [2]] Appl. No.: 269,124

[52] US. Cl 261/39 B, 261/39 C [51] Int. Cl. F02m 1/10 [58} Field of Search 261/398, 39 C [56] References Cited UNITED STATES PATENTS 3,159,692 12/1964 Kittler 261/39 B 3,253,781 5/1966 3,262,683 7/1966 Ball et al, 261/39 B 3,272,486 9/1966 Lucas et al 261/39 B 3.321.193 5/1967 Highley 261/39 B Primary Examiner-Tim R. Miles Attorney, Agent, or FirmEdward H. Casey 5 7 ABSTRACT Reduction of exhaust emissions is obtained by controlling the carburetor choke valve with greater flexibility. A piston motor responsive to manifold vacuum opens the choke valve partially soon after the engine starts. A diaphragm motor responds to engine vacuum more slowly than the first motor. The diaphragm acts through a modulating spring to open the choke valve, which is connected to a thermostatic coil spring urging the choke valve closed at low ambient temperatures. At high ambient temperatures, actuation of the diaphragm causes wide opening of the choke valve, and at low ambient temperature causes less initial opening, followed by further opening of the choke valve as the engine warms up.

6 Claims, 4 Drawing Figures PAIENTED B I 3814.390

satin or 2 FIGURE 2.

MTENTEDJUII 4 m4 3814.390 sum 2 or 2 WIVZ/M FIGURE 3.

FIGURE 4.

CARBURETOR WITH COMBINED PISTON MOTOR AND DIAPHRAGM MOTOR CHOKE .VALVE ACTUATION BACKGROUND OF THE INVENTION The automatic choke of a carburetor is required to provide an excess of fuel for the engine during cranking, and a leaner mixture of air and fuel after the engine starts. As the engine heats up, progressive further opening of the choke to provide further leaning of the airfuel mixture is desirable. The choke is usually biased toward its closed position by a thermostatic spring coil, and it has been proposed to connect a vacuum motor acting against the thermostat coil to open the choke to meet the operating requirements. This is disclosed in U.S. Pat. No. 3,321,193, issued to Wenford E. Highley, and U.S. Pat. No. 3,321,194 issued to Harold A. Car]- son, both dated May 23, 1267. Such arrangements, however, are not flexible enough to provide satisfactory adjustments of the choke under the variety of operating conditions normally encountered. It is, therefore, an object of the invention to refine the control of the choke so as to reduce engine exhaust emissions during engine starting and warm up.

SUMMARY OF THE INVENTION A carburetor choke is connected to the usual thermostat spring coil which acts to close the choke at low temperatures. A vacuum motor has a movable diaphragm, and a link extending from thediaphragm is urged to a retracted position by a modulator spring. A lever connects the link to the shaft of the choke. One side of the diaphragm is exposed to engine manifold suction through a delay device having a small orifice. The choke shaft also is connected to a piston in a cylinder having a passageway opening into the mixture conduit of the carburetor. When the engine starts, the pressure in the cylinder drops and the piston moves down to open the choke slightly. Thus a relatively rich airfuel mixture is provided for the first few seconds of engine running. The suction applied to the diaphragm builds up slowly over a period possibly as long as 3 to 45 seconds, due to the delay device. When the diaphragm moves. only slightly leaner fuel ratios are provided at cold ambients. since the movement of the diaphragm is partly absorbed by compression of the modulator spring. But considerably leaner ratios are provided at warmer ambient temperatures, because at high temperatures, the spring coil relaxes, and the modulator spring in the suction motor overrides the spring coil to open the choke valve rather widely. The pistonand cylinder motor provides a fail-safe feature, in the event the delay device malfunctions, or becomes blocked, or the diaphragm fails to open the choke sufficiently for the engine to operate. The diaphragm and modulator spring provide an increased lean-out effect after an initial running period at warm ambients, or when the engine warms up, to permit reduced exhaust emissions.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic view, partly in section, showing the choke valve closed.

FIG. 2 is a partial schematic view showing the choke valve operated to an open position by the piston motor.

FIG. 3 is a view similar to that of FIG. 1 with the diaphragm motor actuated.

FIG. 4 is another schematic view showing the position of the choke valve at high ambient temperatures or after the engine has warmed up, with the diaphragm motor actuated.

DESCRIPTION OF THE PREFERRED EMBODIMENT The invention relates to improved apparatus for controlling an automatic choke so as to obtain reliable engine starting with reduced exhaust emissions. To achieve these results, a given program of choke opening is required for low ambient temperatures, and a different program of choke opening is needed at higher ambient temperatures above about F. during engine starting and warm up. The choke valve is opened in stages: first, a minimal opening by a piston motor immediately after engine starting, then delayed further opening of the choke by a spring modulated diaphragm motor, and progressive further opening of the choke valve during engine warm up, if the ambient temperature is low.

Referring to the drawing, carburetor 10 has a body 12 enclosing a mixture chamber 14 provided with a throttle l6 and chokevalve 18. The latter is mounted on shaft 20, which has lever

arms

22 and 24. Thermostatic coil spring 26 has one end 27 fixed and its other end 28 adapted to abut lever arm 24. Choke valve 18 is of the unbalanced type, normally urged open by the air pressure on its top side as well as by gravity. Air motor 30 includes cylinder 31 and piston 32 fixed to link 34, which is looped over the upper edge of lever arm 22. Passage 36 connects the bottom of cylinder 31 to mixture chamber 14 below throttle 16 in order to expose cylinder 31 to engine manifold vacuum.

Vacuum motor 40 mounted on bracket 41 includes a diaphragm 42 urged to the right in FIG. 1 by spring 44. Motor 40 is connected by conduit 46 to engine vacuum through a delayer consisting of a plug 48 having a small orifice 50. Casing 52 has a slidable hub 54 in which link 56 is slidably mounted. The inner end of link 56 has a flange 58 and a modulator spring 60 tends to move link 56 inwardly of hub 54 into engagement with a button 62 at the center of diaphragm 42. Link 56 includes a hollow member 64 in which rod 66 with flanged end 68 has a limited telescoping movement,

and the outer end of rod 66 is connected to lever arm 24 of the choke valve. Link 56 thus provides a lost motion connection between lever arm 24 and motor 40 to permit choke valve 18 to be moved finally to a fully open position by the action of the air stream and gravity on the unbalanced choke valve.

The operation of the choke valve may be summarized as follows. It is assumed that choke valve 18 is closed, as shown in FIG. 1, and the engine is cranked for starting. As soon as the engine starts, a vacuum is created in mixture chamber 14 and communicated through passage 36 to cylinder 31. Piston 32 then moves downward from the position shown in FIG. 1 to the position shown in FIG. 2, and choke valve 18 is pulled open by rod 34, acting against the closing force imposed on lever arm 24 by thermostatic spring coil 26. Thus a slight opening of the choke valve. is obtained promptly to prevent a rich or loading" condition from developing when the engine begins to run. As manifold vacuum is applied to motor 40,

delay device

48, 50 causes diaphragm 42 to move gradually during an interval which may be as long as 30 to 45 seconds. Eventually diaphragm 42 moves from the position shown in FIG. 2 to the position shown in H6. 3, and in so doing compresses spring 44, moves button 62 away from flange 58 of link 56, compresses modulator spring 60, and opens choke valve 18 further. The further opening of choke valve 18 is opposed and limited by thermostatic coil spring 26 in accordance with the temperature thereof. Choke valve may then reach a third position such as shown in FIG. 3, if the ambient temperature is low (appreciably below 70F, say) and the engine has not yet warmed up, because then thermostatic srping 26 is stiff enought to overcome modulator spring 60. As the engine warms up, thermostatic'spring 26 relaxes and is overriden by modulator spring 60, which moves link 56 and opens choke valve 18 further, as indicated in FIG. 4. The lost motion connection between

elements

64 and 66 of link 56 permits choke valve 18 to be moved to the fully open vertical position by the air stream.

The mechanism disclosed herein leans out the airfuel mixture promptly and progressively at low or at high ambient temperatures during engine starting and warm up to permit favorable engine starting conditions and at the same time maintains the air-fuel ratio at values which reduce the generally high emissions during engine starting. Piston motor 30 also may serve as a fail-safe device in the event of failure of diaphragm motor 40, since it independently opens the choke valve sufficiently to allow the engine to run, and the choke valve is then able to open progressively as the engine warms up and causes the thermostatic coil spring to relax and release the choke valve.

Choke lever arm 22 is loose on shaft 21 and is provided with a tab 23. When lever arm 22 moves in clockwise direction, then tab 23 picks up lever arm 24 which is fast on shaft 20. Thus, movement of lever arm 22 by way of tab 23, moves the lever arm 24 causing the partial initial opening of choke 18 as required by the invention. Movement of choke 18 by piston 32 is limited by the fact that the piston can travel downwardly only until it intersects crosspassage 36 which applies vacuum to the piston 32. The length of the piston 32 and the cylinder 31 can be adjusted to give the required amount of movement of piston 32 to satisfy the engine operating conditions. Alternatively, the length of link 34 can be adjusted to achieve the same results.

I claim:

l. A carburetor device for an internal combustion engine having a body, a mixture conduit extending through said body, a movable throttle valve in said mixture conduit, a choke valve in said mixture conduit upstream of said throttle valve and mounted on a shaft for rotation from an open to a closed position, a vacuum motor, means forming a vacuum passage extending from said motor to said mixture conduit at a point below said-throttle valve for providing engine manifold vacuum to said motor, a mechanical connection be tween said vacuum motor and said choke valve to move said choke valve to a partially open position in response to engine vacuum, a temperature responsive spring connected to said choke valve for biasing it closed at temperatures below a predetermined value, said vacuum motor being capable of overriding said temperature responsive spring for partially opening said choke valve when the engine starts, a second vacuum motor having a movable member and being responsive to engine vacuum posterior to said throttle, delay means for retarding the response of said second vacuum motor engine vacuum, a link connected to the shaft of the choke valve, and a resilient connection between said movable member of the second vacuum motor and said link, said resilient connection being capable of overriding said temperature responsive spring when the latter has a temperature above a predetermined value, whereby the choke valve is opened partially by the first vacuum motor when the engine starts running and thereafter is opened further, as the temperature of the temperature responsive spring increases.

2. Apparatus according to claim 1, wherein said movable member of the second vacuum motor includes a diaphragm and a spring urging the diaphragm to its inoperative position.

3. Apparatus according to claim 2, wherein said choke valve is an unbalanced valve mounted for free opening by the air stream passing therethrough.

4. Apparatus according to claim 2, wherein said resilient connection is a spring acting between the diaphragm and link to urge the choke valve open.

5. Apparatus according to claim 4, wherein said delay means is a member having a restricted orifice in a conduit connecting the second vacuum 'motor to a source of engine vacuum.

6. A carburetor devicefor an internal combustion engine having a body, a mixture conduit extending through said body,-a movable throttle valve in said mixture conduit, an unbalanced choke valve in said mixture conduit upstream of said throttle valve, a vacuum piston motor, a passage extending from said motor to said mixture conduit for providing a source of engine manifold vacuum to said motor, a mechanical connection between said vacuum motor and said choke valve to move said choke valve to a partially open position in response to engine vacuum, a temperature responsive spring connected to said choke valve for biasing it closed at temperatures below a predetermined value, said vacuum motor being capable of overriding said temperature responsive spring for partially opening said choke valve when the engine starts, a diaphragm vacuum motor responsive to engine vacuum, delay means for retarding the rate at which said diaphragm motor responds to the enginevacuum, a link connecting the diaphragm of the motor to the shaft of the choke valve, and a resilient connection between the diaphragm and said link, said resilient connection being capable of overriding said temperature responsive spring when the latter has a temperature above a predetermined value, whereby the choke valve is opened partially by the first vacuum motor when the engine starts running and thereafter is opened further as the temperature of the temperature responsive spring increases.

Claims

1. A carburetor device for an internal combustion engine having a body, a mixture conduit extending through said body, a movable throttle valve in said mixture conduit, a choke valve in said mixture conduit upstream of said throttle valve and mounted on a shaft for rotation from an open to a closed position, a vacuum motor, means forming a vacuum passage extending from said motor to said mixture conduit at a point below said throttle valve for providing engine manifold vacuum to said motor, a mechanical connection between said vacuum motor and said choke valve to move said choke valve to a partially open position in response to engine vacuum, a temperature responsive spring connected to said choke valve for biasing it closed at temperatures below a predetermined value, said vacuum motor being capable of overriding said temperature responsive spring for partially opening said choke valve when the engine starts, a second vacuum motor having a movable member and being responsive to engine vacuum posterior to said throttle, delay means for retarding the response of said second vacuum motor engine vacuum, a link connected to the shaft of the choke valve, and a resilient connection between said movable member of the second vacuum motor and said link, said resilient connection being capable of overriding said temperature responsive spring when the latter has a temperature above a predetermined value, whereby the choke valve is opened partially by the first vacuum motor when the engine starts running and thereafter is opened further as the temperature of the temperature responsive spring increases.

5. Apparatus according to claim 4, wherein said delay means is a member having a restricted orifice in a conduit connecting the second vacuum motor to a source of engine vacuum.

6. A carburetor device for an internal combustion engine having a body, a mixture conduit extending through said body, a movable throttle valve in said mixture conduit, an unbalanced choke valve in said mixture conduit upstream of said throttle valve, a vacuum piston motor, a passage extending from said motor to said mixture conduit for providing a source of engine manifold vacuum to said motor, a mechanical connection between said vacuum motor and said choke valve to move said choke valve to a partially open position in response to engine vacuum, a temperature responsive spring connected to said choke valve for biasing it closed at temperatures below a predetermined value, said vacuum motor being capable of overriding said temperature responsive spring for partially opening said choke valve when the engine starts, a diaphragm vacuum motor responsive to engine vacuum, delay means for retarding the rate at which said diaphragm motor responds to the engine vacuum, a link connecting the diaphragm of the motor to the shaft of the choke valve, and a resilient connection between the diaphragm and said link, said resilient connection being capable of overriding said temperature responsive spring when the latter has a temperature above a predetermined value, whereby the choke valve is opened partially by the first vacuum motor when the engine starts running and thereafter is opened further as the temperature of the temperature responsive spring increases.