US3741177A - Carburetor throttle valve positioner - Google Patents

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 high idle speed setting for engine starting as well as engine idling; engine deceleration vacuum moves the servo diaphragm to open the throttle valve for better emission control; and, engine shutoff permits vacuum in a reservoir to temporarily move the throttle towards a closed position to prevent dieseling.

Description

1 June 26, 1973 prings initially speed setting for g; engine decelerphragm to open the 3,518,582 11/1971 .Gerlitz.............. TI N R 3,682,148 8/1972 Harrison et al. P08] 0 E 3,327,695 6/1967 Rhodes Thomas C. Schultz, Southfield, Primary Examiner-Al Lawrence Smith [73] Assignee: Ford Motor Company, Dearborn, AS51314"! Emmi'lerDenniS Tom I M Attorney- Keith L. Zerschling and Robert E. Mc- F] d- N 1 1971 comm 57 ABSTRACT [2]] Appl' 194258 The throttle valve of a downdraft type carburetor is controlled in its movement by a servo in turn controlled U.S. CL... 123/97 B, 123/198 DB, l23/DIG. 11 y m nif va um changes; servo s [51] Int. Cl. F02d 11/08, F02d 9/00, F02m 19/12 move the h tl alve to a hlgh Idle Field of Search.................... 123/103 R, 103 A, ng starting as well as engine idlin 123/103 B, 103 C, 103 D, 103 E, 97 B, 198 ation vacuum moves the servo dia DB, DIG, 11 throttle valve for better emission control; and, engine shutoff permits vacuum in a reservoir to temporarily Refe enc Cit d move the throttle towards a closed position to prevent UNITED STATES PATENTS dleselmg- 3,491,737 1/1970 Burnia..................... 123/DIG. 11 6 Claims, 1 Drawing Figure United States Patent 1191 Schultz 1 41 CARBURETOR THROTTLE VALVE [75] Inventor:

'1 CARBURETOR THROTTLE VALVE POSITIONER 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 operating conditions to prevent engine dieseling and minimize the passage of unburned hydrocarbons into the atmosphere, while at the same time position the throttle valve for an engine idling speed and good starting conditions.

The problem of engine dieseling after the engine has been shut off is recognized. The vacuum signal still present in the carburetor throttle bore below the throttle valve 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 interferes with the proper scavenging of the exhaust gases from the combustion chamber. This results in incomplete burning of the idle system fuel pulled into the engine at this time, and, therefore, unburned hydrocarbons may pass out into the atmosphere.

In 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 servo subsequently repositions the throttle valve to the engine start position, which in this case also corresponds to the engine idle speed position.

The prior art devices also generally made no provision for overcoming the induction of a large charge of fuel/air mixture during decelerating operation, when the vacuum signal on the dile system is very high. This often resulted in unburned hydrocarbons in the exhaust system.

The invention again overcomes the above problem by the servo described previously also automatically opening the throttle valve beyond idle speed position, in response to decelerating vacuum, so that the increased flow can better scavenge the combustion chambers of exhaust gases.

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 engine start and idle speed operations; that will prevent engine dieseling upon engine shutdown; and, will minimize the passage of unburned hydrocarbons into th 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 open the throttle valve beyond idle speed position when the manifold vacuum reaches a level indicative of engine decelerating operation; 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 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 air at essentially atmospheric pressure passing 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 rotatably mounted on a shaft 24 fixed 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 beinducted into passage 16 above the throttle valve in a known manner as a function of the rotation of the valve from its fully closed dotted line position 34 to a wide open nearly vertical position, by the change in 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 speed operation. A bypass passage 26 contains the usual transfer port 28 and a discharge port 30 controlled by an adjustable needle valve 32. v

The transfer port 28 is located so that the lower edge is aligned with the edge of the throttle valve plate in its closed dotted line position 34. Alternatively, if desired, the transfer port can be located vertically in other positions relative to the throttle plate edge when in the closed position.

The full 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 part of the transfer port 32 above the throttle valve edge subjects passage 26 to an ambient or atmospheric pressure bleed.

' The quantity flowable past the needle valve at this time therefore is 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 full 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 the amount needed to maintain the engine at idling speed.

It will also be clear that when the throttle valve is moved to position 37, increased flow will occur. This 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 and also provides a leaner mixture.

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 48 in a counterclockwise direction at all times to bias the throttle valve towards its closed position 34.

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 includes a shell type housing 44 divided into two vacuum chambers 46 and 48 by an annular flexible diaphragm 50. Vacuum lines 52 and 54 are connected to chambers 46 and 48. A stem type actuator or plunger 56 is secured to one side of diaphragm 50, while a second stem member 58 is fixed to and projects from the diaphragm in the opposite direction. The end of stem 58 is piloted into a recess 60 in housing 44.

' Plunger 56 has an axially adjustably mounted end portion 62 in this instance screwed to a smaller diameter portion 64 of the plunger. Slidably surrounding portion 64 is a sleeve '66 that slidably but sealingly projects through a hole 68 in housing 44. The axial length of sleeve 66 is less than the axial extend of reduced portion 64, to permit relative axial movement between the N10.

A first compression spring 70 is seated between a flange 72 of sleeve 66 and the diaphragm retainer 74. It normally biases sleeve 66 to the right against a pad 76 on housing 44, and the diaphragm 50 to the left until a shoulder on the plunger portion 62 is stopped by abutment against the end of sleeve 66, as shown. A second weaker spring 78 biases the assembly consisting of diaphragm 50, spring 70, and sleeve 66, as a unit to the positions shown. a

The force of spring 78 is chosen to be greater than that of return spring 40 so that in its extended position shown, plunger 56 rotates the throttle valve to the idle speed position 36 as shown. Vacuumapplied to servo chamber 46 on the other hand will retract plunger 56 sufficiently to allow spring 40 to rotate the throttle valve 22 to its dotted line closed position 34.

The vacuum to lines 52 and 54 enamates from an intake manifold vacuum port 80 shown opening into the carburetor body portion 12 belowthe throttle valve. It could equally be tapped directly into the intake manifold below. The intake manifold vacuum is sensed in a line 82 having branches 84 and 86.

The vacuum in line 84 is sensed to line 52 and chamber 46 through a restriction or orifice 88 and a vacuum reservoir or accumulator indicated schematically at 90. The orifice 88 prevents momentary fluctuations in the manifold vacuum from affecting the level of vacuum in the reservoir 90. More importantly, it prevents a sudden decay in the manifold vacuum, such as at engine shutdown, from equally suddenly decaying the vacuum in the reservoir.

Branch 86 connects to line 54 and chamber 48 through a spring vented, electrically connected valve 92 of the on-off type. More specifically, the valve body is illustrated schematically as provided with a straight through passage 94 and a vent or atmospheric passage 96. A solenoid 98 when energized normally positions the valve as shown to connect passage 86 to passage 54 to allow vacuum to be applied to servo chamber 48. A spring 99 moves valve 92 to vent passage 54 when the solenoid is de-energized.

Valve 92 preferably forms part of the conventional engine ignition circuit. Details of the construction and operation of the same are not given since they are known and believed to be unnecessary for an understanding of the invention. Suffice it to say, however, that the latter would include an ignition key operated switch bridging or breaking the circuit from a battery to the coil of solenoid 98. When the coil is energized,

valve 92 will be forced rightwardly against the force of a spring 99 to the position shown.

The operation of the sytem is as follows. Prior to engine start up, servo chambers 46 and 48 are at atmospheric pressure, permitting the stronger spring to locate the plunger end 62 against the end of sleeve 66 and weaker spring 78 to position the secondary spring assembly as a unit to the right as shown with sleeve flange 72 against housing shoulder 76. This positions lever 38 to open the throttle valve to the idle speed or start position 36.

As soon as the engine is cranked and started, the turning of the ignition key energizes solenoid 98 to move valve 92 to the position shown. Manifold vacuum in chamber 48 may temporarily collapse spring 70 and move plunger 62 to the right, until the vacuum builds up in chamber 46. This would open the throttle valve to the position 37. However, this is momentary, and the throttle valve would quickly return to the idle speed position 36. Accordingly, the throttle valve remains in the position 36 shown, with normal engine idling fuel and air supply being inducted into passage 16 through the orificed discharge 30.

Assume that the engine has been accelerated and the vehicle moved, by the throttle valve being opened wider than the idle position, to accelerate the vehicle.

It will be seen that this is permitted by the clockwise rotation of lever 38 away from engagement with the end 62 of plunger 58. If now the vehicle operator releases his foot from the accelerator pedal, spring 40 will attempt to rotate the throttle valve to its closed position 34. The intake manifold vacuum level will, however, immediately increase to or above say 19 inches Hg, indicative of engine decelerating operating conditions. This will cause an immediate rise in vacuum in chamber 48 in contrast to that in chamber 46. Spring 70 is then collapsed by the higher pressure in chamber 46 plus the force of spring 78, and diaphragm 50 moves plunger 62 rightwardly relative to sleeve 66, which is prevented from rightward movement by abutment of flange 72 against pad 76. The movement continues until the shoulder 100 on the enlarged base of the smaller diameter plunger portion 64 abutts the flange 72 of sleeve 66.

The throttle valve is'now in the position 37, thereby permitting a greater and leaner flow of air and fuel into the combustion chambers sufficient to scavenge the same of exhaust gases. This provides a more complete combustion at this time and minimizes the passage .of unburned hydrocarbons into the atmosphere. It will be noted of course that the vacuum in reservoir will also slowly increase until the vacuum levels in both chambers are equalized. Soon thereafter, the vacuum decrease, and/or the increase in the reservoir vacuum line, will permit the servo springs to reposition the throttle valve to the idle speed position 36 shown.

Assume now that the engine is shut off by turning the ignition key. This opens the ignition switch and deenergizes solenoid 98.'This moves valve 92 to immediately bleed line 54 to atmospheric pressure. As soon as the engine is shut down, the intake manifold vacuum in port 80 decays almost immediately to an atmospheric pressure level. The bleed valve 92 is used merely as a compensator in the event of a delay in the decay of manifold vacuum at engine shutdown, for any reasons. It can be eliminated, if desired. Because of the orifice or flow restrictor 88, the vacuum in reservoir 90, however, is only slowly bled to atmospheric pressure. This delay of several seconds is sufficient to permit the vacuum in servo chamber 48 to be of a level sufficient to retract diaphragm S and plunger end 62 to the left until the latter seats against the housing 44, which positions the throttle valve (by spring 40) to the position 34. This is permitted by the plunger end 62 pushing sleeve 66 against shoulder 100 collapsing spring 70. This reduces the fuel and air flow below the level necessary to sustain running of the engine by dieseling. The time delay of bleeding of the vacuum in reservoir 66 is sufficient, therefore, to' prevent dieseling of the engine upon shutdown.

It will noted, that once the vacuum in reservoir 90 does decay to atmospheric pressure, then servo chamber 46 will be at the same pressure level as chamber 48, and the springs 70 and 78 will return the throttle valve to its engine idle or engine start position36 shown.

Therefore, it will be seen that the invention provides a throttle valve positioner that increases flow of fuel and air to the engine during high engine decelerating operating conditions; prevents engine dieseling after the engine is shut off for a period of time sufficient to permit the engine to come to rest; and repositions the throttle valve to an attitude providing engine starting and idling.

While the invention has been showed in its preferred embodiment in the drawing, 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 carburetor throttle valve positioner comprising, in combination, an engine carburetor having an induction passage open to ambient 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 posi tion and beyond to a wide open throttle position, and

return, for controlling flow through the passage, and control means to move the throttle valve to and between its positions,

the control means including a vacuum controlled servo having a hollow shell with a flexible diaphragm dividing the shell into two chambers,

a movable plunger connected to the diaphragm and operatively engaged with the throttle valve,

conduit means connecting each of the chambers to engine intake manifold,

a vacuum reservoir in one of the conduits and a flow restricting means between the reservoir and the manifold vacuum connection for delaying decay of vacuum level in the reservoir upon decay of manifold vacuum,

first spring means biasing the plunger towards an open beyond idle speed throttle valve first position, and second spring means biasing the plunger in the opposite direction to oppose the first spring means and position the throttle valve to an engine idle speed second position below a predetermined intake manifold vacuum level,

an increase in the manifold vacuum level acting on the diaphragm above the predetermined level overcoming the force of the second spring means to move the plunger to the first position, a decay of manifold vacuum level responsive to engine shutdown conditions permitting reservoir vacuum temporarily to move the plunger and throttle valve towards a third throttle valve closed position, subsequent decay in the reservoir vacuum permitting return of the plunger and throttle valve to the second position by the spring means.

2. A positioner as in claim 1, including movable stop means in the path of movement of the plunger in a closing throttle direction positioning the plunger at its second position below the predetermined manifold vacuum level.

3. A positioner as in claim 2, the stop means constituting a sleeve surrounding a portion of the plunger and engagable at times with the plunger and the shell to position the plunger.

4. A positioner as in claim 2, the second spring means biasing the stop means against the shell, and the plunger against the stop means, to position the plunger.

5. A positioner as in claim 2, the second spring means being seated between a first portion of the plunger and the stop means to biasingly separate the two, the stop means engaging a second portion of the plunger at times and the shell to position the plunger.

6. A positioner as in claim 1, the one of the conduits containing an on-off bleed valve in one position permitting passage of manifold vacuum therethrough and in an alternate position venting manifold vacuum therein to the atmosphere.

* t l ll

Claims (6)

1. A carburetor throttle valve positioner comprising, in combination, an engine carburetor having an induction passage open to ambient 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 the passage, and control means to move the throttle valve to and between its positions, the control means including a vacuum controlled servo having a hollow shell with a flexible diaphragm dividing the shell into two chambers, a movable plunger connected to the diaphragm and operatively engaged with the throttle valve, conduit means connecting each of the chambers to engine intake manifold, a vacuum reservoir in one of the conduits and a flow restricting means between the reservoir and the manifold vacuum connection for delaying decay of vacuum level in the reservoir upon decay of manifold vacuum, first spring means biasing the plunger towards an open beyond idle speed throttle valve first position, and second spring means biasing the plunger in the opposite direction to oppose the first spring means and position the throttle valve to an engine idle speed second position below a predetermined intake manifold vacuum level, an increase in the manifold vacuum level acting on the diaphragm above the predetermined level overcoming the force of the second spring means to move the plunger to the first position, a decay of manifold vacuum level responsive to engine shutdown conditions permitting reservoir vacuum temporarily to move the plunger and throttle valve towards a third throttle valve closed position, subsequent decay in the reservoir vacuum permitting return of the plunger and throttle valve to the second position by the spring means.

2. A positioner as in claim 1, including movable stop means in the path of movement of the plunger in a closing throttle direction positioning the plunger at its second position below the predetermined manifold vacuum level.

3. A positioner as in claim 2, the stop means constituting a sleeve surrounding a portion of the plunger and engagable at times with the plunger and the shell to position the plunger.

4. A positioner as in claim 2, the second spring means biasing the stop means against the shell, and the plunger against the stop means, to position the plunger.

5. A positioner as in claim 2, the second spring means being seated between a first portion of the plunger and the stop means tO biasingly separate the two, the stop means engaging a second portion of the plunger at times and the shell to position the plunger.

6. A positioner as in claim 1, the one of the conduits containing an on-off bleed valve in one position permitting passage of manifold vacuum therethrough and in an alternate position venting manifold vacuum therein to the atmosphere.

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