US3753427A

US3753427A - Engine anti-diesel and deceleration control

Info

Publication number: US3753427A
Application number: US00202913A
Authority: US
Inventors: R Cedar
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1971-11-29
Filing date: 1971-11-29
Publication date: 1973-08-21
Anticipated expiration: 1990-08-21
Also published as: GB1348757A; DE2258077A1; JPS5037330B2; CA965665A; JPS4863121A

Abstract

The throttle valve of a downdraft type carburetor is controlled in its movement by a servo in turn controlled by manifold vacuum changes; servo springs initially move the throttle valve to a closed position for engine anti-dieseling; engine running vacuum moves the servo diaphragm to open the throttle valve to an idle speed position; and, engine decelerations effect a delayed throttle valve closing to reduce emissions.

Description

United States Patent [191 Cedar Aug. 21, 1973 1 ENGINE ANTI-DIESEL AND DECELERATION CONTROL [75] inventor: Raymond J. Cedar, Birmingham,

Mich.

[73] Assignee: Ford Motor Company, Dearbom,

Mich.

[22] Filed: Nov. 29, 1971 [21] Appl. No.: 202,913

[52] US. Cl... 123/198 DB, 123/D1G. 11, 123/97 B, 123/103,123/1l9,123/179 G [51] Int. Cl. F02m 19/12, F02m l/l4, F02d 33/00 [58] Field of Search 123/D1G. ll, 97 B, 123/198 D, 198 DB, 198 DC, 179 86,179 G, 119,180 E, 103

[56] References Cited UNITED STATES PATENTS 3,618,582 11/1971 Gerlitz ..123/198DB 1/1970 Bumia 123/198 DC X 9/1971 Sherwin 123/97 B Primary Examiner-Al Lawrence Smith Attorney-Keith L. Zerschling and Robert E.

McCollum [5 7] ABSTRACT The throttle valve of a downdraft type carburetor is controlled in its movement by a servo in turn controlled by manifold vacuum changes; servo springs initially move the throttle valve to a closed position for engine anti-dieseling; engine running vacuum moves the servo diaphragm to open the throttle valve to an idle speed position; and, engine decelerations effect a delayed throttle valve closing to reduce emissions.

2 Claims, 1 Drawing Figure ENGINE ANTI-DIESEL AND DECELERATION CONTROL This invention relates, in general, to a device for positioning the throttle valve of a carburetor to minimize the emission of undesirable elements into the atmosphere. More particularly, it relates to a vacuum controlled servo to control fuel and air flow through a carburetor after engine shutdown and during engine deceleration to prevent engine dieseling and minimize the passage of unburned hydrocarbons into the atmosphere.

The problem of engine dieseling after the engine has been shut off is recognized. So long as the engine crankshaft continues to rotate, a vacuum signal will be present in the carburetor throttle bore below the throttle valve. This pulls idle system fuel and air into the hot combustion chamber such that combustion is maintained for a few seconds or longer after the engine is shut off. This naturally is undesirable. Also, during engine deceleration, the very high manifold vacuum developed not only draws excessive fuel from the idle system but interferes with the proper scavenging of the exhaust gases from the combustion chamber. This results in incomplete burning at this time, and, therefore, unburned hydrocarbons may pass out into the atmosphere.

ln the prior art devices, the minimum flow and engine idle speed positions of the throttle valve usually are the same. Therefore, when the engine is shut off, the vacuum signal still present for a few seconds draws a sufficient charge of fuel/air mixture into the combustion chamber to maintain the engine running.

The invention eliminates the above problem by providing a servo to essentially close the throttle valve automatically upon engine shutdown; thereby reducing the charge of fuel/air mixture below the level needed to overcome the frictional resistance of the engine to sustain running.

The prior art devices also generally made no provision for overcoming the induction of a rich charge of fuel/air mixture during decelerating operation, when the vacuum signal on the idle system is very high.

The invention again overcomes the above problem by the servo described previously also automatically retarding the closing of the throttle valve in response to deceleration, so that the increased air flow will decrease the idle system fuel signal, will better scavenge the combustion chambers of exhaust gases, and will maintain the air/fuel ratio more in the range of a combustible mixture, all to decrease emissions.

It is one of the objects of the invention, therefore, to provide a carburetor with a throttle valve positioner that will automatically position the throttle valve for idle speed operations; will prevent engine dieseling upon engine shutdown; and, will minimize the passage of unburned hydrocarbons into the exhaust system or atmosphere during engine decelerating operating conditions.

It is also an object of the invention to connect the throttle valve of a carburetor to a servo that is controlled by manifold vacuum that will at times essentially close the throttle valve to reduce the flow of fuel and air to the engine cylinders upon engine shutdown; will only slowly close the throttle valve when the engine is decelerating; or, will normally position the throttle valve for idle speed running.

Other objects, features and advantages of the invention will become more apparent upon reference to the succeeding detailed description thereof, and to the drawing illustrating a preferred embodiment thereof, wherein the figure illustrates schematically a cross sectional view of a portion of a carburetor embodying the invention.

A portion 10 of a downdraft type carburetor is illustrated, although it will be clear as the description proceeds that the invention is equally applicable to other types of carburetors, such as updraft or sidedraft, for example. More particularly, the carburetor is provided with a main body portion 12 having a cylindrical bore 14 providing the conventional air/fuel induction passage 16. The latter is open at its upper end 18 to clean air at near atmospheric pressure that has, for example, passed through the conventional air cleaner, not shown. At its lower end 20, passage 16 is adapted to be connected to a conventional intake manifold from which the air and fuel mixture passes to the engine cylinders, not shown, in a known manner.

The flow of air and fuel through induction passage 16 is controlled in this instance by a conventional throttle valve 22. The latter is fixed on a shaft 24 mounted for rotation in the side walls of body 12, in a known manner. A main fuel system is not shown, since it can be any of many known types. Suffice it to say that the fuel would be inducted into passage 16 from above the throttle valve in a known manner as a function of the rotation of the valve from its fully closed position 34 to a wide open nearly vertical position, by the change in engine manifold vacuum signal.

The carburetor also contains a conventional idle system for supplying the necessary fuel and air to the engine cylinders around the throttle valve during engine idling and off idle speed operation. A bypass passage or channel 26 contains the usual transfer port 28 and a discharge port 30 controlled by an adjustable needle valve 32.

The transfer port 28 is located so that its lower edge is aligned with the edge of the throttle valve plate in its closed full line position 34. Alternatively, if desired, the transfer port can be located vertically in other positions relative to the throttle plate edge when the latter is in the closed position. The dotted line position 36, on the other hand, indicates the idle speed position of the throttle valve, while dotted line position 37 indicates a deceleration position, to be described more fully later.

It will be clear that in the closed position 34, the idle passage area exposed to the vacuum existing below the throttle valve is reduced from that when the throttle valve is in position 36. Therefore, a lower quantity of fuel and air will flow at this time as the area of the transfer port 32 above the throttle valve edges subjects passage 26 to an ambient or atmospheric pressure bleed. The quantity flowable past the needle valve at this time, therefore, is selected to be insufficient to provide the torque necessary to overcome the engine friction.

It will also be seen that when the throttle valve is positioned in its idle speed dotted line position 36, the transfer port area subjected to the vacuum signal below the throttle valve is increased so as to increase the amount of fuel and air to pass through the idle system to an amount needed to maintain the engine at idling speed.

It will also be clear that when the throttle valve is in position 37, increased air flow will occur. This exists during deceleration, as will be described more clearly, later. Portion 37 more efficiently scavenges the combustion chambers of exhaust gases to minimize the passage of any unburned fuel into the exhaust system and atmosphere during engine decelerating operating conditions; it decreases the vacuum signal in idle passage 26; and, provides a more combustible mixture to the engine than when closed.

To accomplish the above, a lever or link 38 is fixed on or formed integral with the throttle valve shaft 24 for rotation with it, a tension spring 40 biasing lever 38 in a counterclockwise direction at all times to bias the throttle valve towards its closed position.

The lever 38 is adapted to be moved clockwise to the right, as seen in the Figure, by a servo 42 to rotate throttle valve 22 clockwise to its engine idle speed position 36.

The servo comprises a hollow two-piece shell 44 with an annular flexible diaphragm 46 clamped between. The diaphragm divides the shell into an atmospheric or ambient pressure chamber 48 and a vacuum chamber 50. Apertures 52 connect chamber 48 to the surrounding air. A tube 54 connects chamber 50 to a manifold vacuum sensing port 56 in the carburetor bore.

A sleeve 58 is sealingly clamped at one end to the diaphragm 46 and sealingly projects out through a hole 60 in the wall of shell 44. The outer end of sleeve 58 is crimped inwardly to form an aperture 62 through which a plunger 64 slides with a frictional fit. The plunger forms a part of a dashpot assembly including sleeve 58, and is adapted to abut the throttle valve lever 38 to move, or be moved by the lever, as the case may be.

Plunger 64 is formed integral with a piston 66 that slides within sleeve 58. A light spring 68 normally biases the piston and plunger 64 outwardly against the lever 38. The spring 68, however, is lighter than return spring 40, and cannot push the lever 38 to the right.

Piston 66 contains an air bleed 70 for communicating air only slowly between opposite sides of the piston. The frictional engagement of sleeve 58 with plunger 64 is not so tight as to prevent the flow of air from the outside into the chamber 72 defined between the end of shell 38 and piston 66. As stated previously, sleeve 58 is sealingly secured to the diaphragm. Therefore, a close fit between piston 66 and sleeve 58 provides an air chamber 74 for proper working of the dashpot, in a manner to be described.

Completing the construction, a spring 76 normally biases the diaphragm 46 and sleeve 58 to the position shown, in the absence of vacuum in chamber 50.

In operation, when the engine is shut down, servo chambers 48 and 50 are at atmospheric or ambient pressure, and spring 76 has moved diaphragm 46 to the free position shown. The throttle return spring 40, being stronger than spring 68, has moved the throttle valve 22 to its closed position 34, and moved plunger 64 to the position shown, partially collapsing spring 68.

The engine now would be started by the operator partially depressing the accelerator pedal, in hot weather, or partially depressing and releasing the pedal in cold weather, to open throttle valve 22. In cold weather, the conventional fast idle cam, not shown, would be engaged to maintain the throttle valve open a predetermined angle, not shown. This assures a sufficient air/fuel mixture to the engine upon cranking to overcome the frictional resistance of the engine to start it and maintain it running. As soon as it is running, manifold vacuum acting on port 80 reflected in chamber 50 moves the diaphragm 46 rightwardly until spring 76 essentially bottoms out. Altemately, a stop can be located in chamber 50 projecting from shell 44. The dashpot assembly also moves rightwardly, the spring 68 maintaining piston extended until contact is made with throttle valve lever 38. No further outward movement of piston 66 then will occur at this time.

The position of piston 66 will depend upon the condition of operation of the engine. If the fast idle cam is engaged for a cold weather start, the throttle valve will probably be in a position more like 36, for example. In this case, piston 66 would probably be fully extended. In normal operation, however, when the engine is warm, the spring 68 behind piston 66 will be fully collapsed by the throttle retum spring 40 moving the throttle valve lever 38 towards closed position. The vacuum force acting on the disphragm 46, however, is sufficient to cause rightward movement of the collapsed dashpot assembly as a unit to position lever 38 and throttle valve 22 in the idle speed position 36.

The vacuum force acting on the idle air/fuel discharge port 30 and that part of transfer port 28 below the edges of the throttle valve will draw fuel and air sufficient to maintain the desired engine idling speed.

Subsequently, when throttle valve 22 and lever 38 are rotated clockwise towards a wide open position, for engine acceleration, the spring 68 will now fully extend piston 66. Therefore, when the acceleration phase is completed, and the vehicle accelerator pedal released, return spring 40 will attempt to quickly return throttle valve 22 to an idle speed position 36. The following then occurs. First, the lever 38 engages the end of plunger 64 and attempts to move it leftwardly. Since the air behind piston 66 in chamber 74 can only escape through the orifice 70, the piston will collapse the spring 68 only slowly, providing a dashpot action to throttle closing movement of the lever 38.

During engine deceleration, a very high vacuum is developed in the manifold and provides a very high signal in the idle channel 26. However, with the dashpot action, the slowly closing throttle valve maintains increased air flow past the throttle valve, thus decaying the strong idle system signal, and decreasing idle system fuel flow. The air flow helps to dry out the manifold, better scavenge the cylinder of exhaust gases, and tends to maintain a more combustible mixture to the cylinder. Thus, the overall effect is to lessen the emission of unburned hydrocarbons and carbon monoxides and other undesirable elements into the atmosphere during deceleration operations.

Assume now the engine is shut down. Immediately, manifold vacuum in chamber 50 decays, permitting spring 76 to move diaphragm 46 and the dashpot assembly to the left to the positions shown. This permits the throttle return spring 40 to rotate the lever 38 and throttle valve 22 to the closed position 34. This pushes the plunger 64 to the position shown, in which spring 68 is partially collapsed.

The closed position of the throttle valve thus reduces the vacuum signal area on the idle channel to a level insuflicient to pull enough fuel/air mixture into the engine to support combustion. Dieseling thus is prevented.

While the invention has been described and illustrated in its preferred embodiment, it will be clear to those skilled in the arts to which it pertains that many changes and modifications may be made thereto without departing from the scope of the invention.

I claim:

1. A combination anti-dieseling and deceleration carburetor throttle valve position control comprising, in combination, an engine carburetor having an induction passage open to essentially atmospheric pressure at one end and adapted to be connected to an engine intake manifold at the opposite end so as to be subject to engine vacuum varying in level from ambient atmospheric pressure at engine shutdown to a maximum subatmospheric pressure level during engine deceleration operating conditions, a throttle valve rotatably mounted across the passage and movable from an essentially closed position to an engine idle speed position and beyond to a wide open throttle position, and return, for controlling flow through said passage, and control means to move the throttle valve to the various positions, the control means including first means operatively biasing the throttle valve to a closed throttle antidiesel position, engine manifold vacuum sensitive means operable during engine running to move the throttle valve to an open idle speed position, and other means operable in response to deceleration operation slowly returning the throttle valve towards the idle position to delay the return movement, the control means comprising a servo divided into an atmospheric pressure chamber and a vacuum chamber by a flexible diaphragm, and a plunger operably connected to the diaphragm and operably engagable with the throttle valve to move or be moved by the throttle valve, the other means comprising a dashpot including a sleeve sealingly secured to the diaphragm and projecting through the servo housing, a piston slidable within the sleeve and having the plunger secured thereto, the piston havng an air. bleed port therein connecting opposite sides of the piston, and second spring means biasing the piston and plunger towards the throttle valve.

2. A combination anti-dieseling and deceleration carburetor throttle valve position control comprising, in combination, an engine carburetor having an induction passage open to atmospheric pressure at one end and adapted to be connected to an engine intake manifold at the opposite end so as to be subject to engine vacuum varying in level from ambient atmospheric pressure at engine shutdown to a maximum subatmospheric pressure level during engine deceleration operating conditions, a throttle valve rotatably mounted across the passage and movable from an essentially closed position to an engine idle speed position and beyond to a wide open throttle position, and return, for controlling flow through said passage, and control means to move the throttle valve to the various positions, the control means including first means operatively biasing the throttle valve to a closed throttle anti-diesel position, the control means comprising a vacuum controlled servo having a shell divided into an atmospheric pressure chamber and a vacuum chamber by a flexible annular diaphragm, a sleeve sealingly secured at one end to the diaphragm in the vacuum chamber and projecting through the shell at the other end, a piston slidably and sealingly movable within the sleeve, a plunger fixed to the piston and projecting through and guided by the end of the sleeve in a frictionally engaging manner permitting communication of air to the one side of the piston, the piston having an orifice therein permitting the slow transfer of air from one side to the other delaying movement thereof during deceleration conditions, and second spring means biasing the piston and plunger outwardly of the shell, the plunger being operably engagable with the throttle valve whereby under no vacuum conditions at engine shutdown the throttle valve is moved to a closed posiion by unitary return movement thereof with the piston and unitary movement of the sleeve and disaphragm and piston by the first spring 1 means.

* l l i

Claims

1. A combination anti-dieseling and deceleration carburetor throttle valve position control comprising, in combination, an engine carburetor having an induction passage open to essentially atmospheric pressure at one end and adapted to be connected to an engine intake manifold at the opposite end so as to be subject to engine vacuum varying in level from ambient atmospheric pressure at engine shutdown to a maximum subatmospheric pressure level during engine deceleration operating conditions, a throttle valve rotatably mounted across the passage and movable from an essentially closed position to an engine idle speed position and beyond to a wide open throttle position, and return, for controlling flow through said passage, and control means to move the throttle valve to the various positions, the control means including first means operatively biasing the throttle valve to a closed throttle anti-diesel position, engine manifold vacuum sensitive means operable during engine running to move the throttle valve to an open idle speed position, and other means operable in response to deceleration operaTion slowly returning the throttle valve towards the idle position to delay the return movement, the control means comprising a servo divided into an atmospheric pressure chamber and a vacuum chamber by a flexible diaphragm, and a plunger operably connected to the diaphragm and operably engagable with the throttle valve to move or be moved by the throttle valve, the other means comprising a dashpot including a sleeve sealingly secured to the diaphragm and projecting through the servo housing, a piston slidable within the sleeve and having the plunger secured thereto, the piston havng an air bleed port therein connecting opposite sides of the piston, and second spring means biasing the piston and plunger towards the throttle valve.

2. A combination anti-dieseling and deceleration carburetor throttle valve position control comprising, in combination, an engine carburetor having an induction passage open to atmospheric pressure at one end and adapted to be connected to an engine intake manifold at the opposite end so as to be subject to engine vacuum varying in level from ambient atmospheric pressure at engine shutdown to a maximum subatmospheric pressure level during engine deceleration operating conditions, a throttle valve rotatably mounted across the passage and movable from an essentially closed position to an engine idle speed position and beyond to a wide open throttle position, and return, for controlling flow through said passage, and control means to move the throttle valve to the various positions, the control means including first means operatively biasing the throttle valve to a closed throttle anti-diesel position, the control means comprising a vacuum controlled servo having a shell divided into an atmospheric pressure chamber and a vacuum chamber by a flexible annular diaphragm, a sleeve sealingly secured at one end to the diaphragm in the vacuum chamber and projecting through the shell at the other end, a piston slidably and sealingly movable within the sleeve, a plunger fixed to the piston and projecting through and guided by the end of the sleeve in a frictionally engaging manner permitting communication of air to the one side of the piston, the piston having an orifice therein permitting the slow transfer of air from one side to the other delaying movement thereof during deceleration conditions, and second spring means biasing the piston and plunger outwardly of the shell, the plunger being operably engagable with the throttle valve whereby under no vacuum conditions at engine shutdown the throttle valve is moved to a closed posiion by unitary return movement thereof with the piston and unitary movement of the sleeve and disaphragm and piston by the first spring means.