CARBURETOR
United States Patent 3841281
In an air valve carburetor, an air bleed passage opens into the region of the mixture conduit intermediate the air valve and the throttle and an air bypass passage extends to the mixture conduit below the throttle from the region of the mixture conduit intermediate the air valve and the throttle. A solenoid energized in accordance with engine operating conditions governs the application of pressure signals to a diaphragm which operates valves in each passage to provide anti-dieseling and deceleration control.
US Patent References:
Carburetor
Carlson - October 1966 - 3278171
Carburetor
Cook et al. - October 1966 - 3278173
Carburetor
Walker - March 1968 - 3374991
INTAKE MANIFOLD VACUUM CONTROL SYSTEM
Nakajima - July 1972 - 3675632
Carburetor
Carlson - October 1966 - 3278171
Carburetor
Cook et al. - October 1966 - 3278173
Carburetor
Walker - March 1968 - 3374991
INTAKE MANIFOLD VACUUM CONTROL SYSTEM
Nakajima - July 1972 - 3675632
Application Number:
05/343563
Publication Date:
10/15/1974
Filing Date:
03/21/1973
View Patent Images:
Export Citation:
Assignee:
General Motors Corporation (Detroit, MI)
Primary Class:
Other Classes:
123/336, 261/50.200, 123/438, 123/325, 261/44.600, 123/DIG.011
International Classes:
F02M7/22; F02M23/08; F02M7/00; F02M23/00; F02M7/12; F02D9/00
Field of Search:
123/97B,DIG.11,124B 261/DIG.19,5A,44R
Primary Examiner:
Antonakas, Manuel A.
Attorney, Agent or Firm:
Veenstra C. K.
Claims:
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows
1. For use with an internal combustion engine, a carburetor comprising a mixture conduit having an air inlet and a mixture outlet, a throttle disposed in said mixture outlet for controlling flow therethrough, an air valve disposed in said air inlet, means controlling said air valve to maintain a substantially constant subatmospheric pressure in said mixture conduit between said air valve and said throttle, a fuel bowl, a fuel passage receiving fuel from said fuel bowl and discharging fuel into said mixture conduit between said air valve and said throttle, an air bleed passage for discharging air at substantially atmospheric pressure into said mixture conduit between said air valve and said throttle, a valve seat formed in said bleed passage, a valve unit engageable with said valve seat to restrict air flow through said bleed pasage, and valve operating means for causing said valve unit to engage said valve seat during open throttle operation and during closed throttle operation at speed below a selected level and for moving said valve unit away from said valve seat during closed throttle operation at speeds above said selected level to thereby permit air to bleed into said mixture conduit between said air valve and said throttle to increase the pressure therein, whereby fuel flow to said mixture conduit is minimized during closed throttle operation at speeds above said selected level.
2. For use with an internal combustion engine having an ignition system energized when engine operation is desired and deenergized when engine operation is not desired, a carburetor comprising a mixture conduit having an air inlet and a mixture outlet, a throttle disposed in said outlet and rotatable betwen open and closed positions for controlling flow therethrough, an air valve disposed in said inlet, means controlling said air valve to maintain substantially constant subatmospheric pressure in the region of said mixture conduit between said air valve and said throttle, a fuel bowl, a fuel passage receiving fuel from said fuel bowl and discharging fuel into said mixture conduit region, an air bleed passage for discharging air at substantially atmospheric pressure into said mixture conduit region, an air bypass passage extending from said region to said mixture conduit downstream of said throttle, valve means for alternatively restricting air flow through said bleed and bypass passages, a diaphragm positioning said valve means, one side of said diaphragm being subjected to the pressure in said bypass passage, the opposite side of said diaphragm being subjected alternatively to the pressure at a first port in said mixture conduit disposed downstream of said throttle and to the pressure at a second port in said mixture conduit disposed adjacent the upstream edge of said throttle when said throttle is in said closed position and traversed by the upstream edge of said throttle as said throttle is rotated from said closed position, and valve means for subjecting said opposite side of said diaphragm to the pressure at said second port when the ignition system is energized and the engine is running at speeds above a selected value and for subjecting said opposite side of said diaphragm to the pressure at said first port at other times, whereby when said ignition system is deenergized and said throttle is rotated to said closed position said diaphragm will position said valve means to restrict air flow through said bypass passage and to permit unrestricted air flow through said bleed passage and thereby reduce air and fuel flow sufficiently to prevent afterrunning of the engine, whereby when the engine is running at speeds above said selected valve and said throttle is rotated to said closed position said diaphragm will position said valve means to restrict air flow through said bypass passage and to permit unrestricted air flow through said bleed passage and thereby reduce air and fuel flow during engine deceleration, and whereby at other times said diaphragm will position said valve means to restrict air flow through said bleed passage and to permit unrestricted flow through said bypass passage.
3. For use with an internal combustion engine having an ignition system energized when engine operation is desired and deenergized when engine operation is not desired, a carburetor comprising an air induction passage, a throttle disposed in said induction passage for controlling air flow therethrough, an air bypass passage extending from a location in said induction passage upstream of said throttle to a location in said induction passage downstream of said throttle, a valve seat formed in said bypass passage, a diaphragm valve unit engageable with said valve seat to restrict air flow through said bypass passage, said diaphragm valve unit including a diaphragm member having one side subjected to the pressure in said bypass passage and the opposite side alternatively subjected to pressures higher and lower than the pressure in said bypass passage, and means for subjecting said opposite side of said diaphragm to such lower pressure when said ignition system is energized whereby said diaphragm valve member is biased away from said valve seat to permit unrestricted air flow through said bypass passage and for subjecting said opposite side of said diaphragm to such higher pressure when said ignition system is deenergized whereby said diaphragm valve member is biased into engagement with said valve seat to restrict air flow through said bypass passage and thereby reduce the tendency toward afterrunning of the engine.
1. For use with an internal combustion engine, a carburetor comprising a mixture conduit having an air inlet and a mixture outlet, a throttle disposed in said mixture outlet for controlling flow therethrough, an air valve disposed in said air inlet, means controlling said air valve to maintain a substantially constant subatmospheric pressure in said mixture conduit between said air valve and said throttle, a fuel bowl, a fuel passage receiving fuel from said fuel bowl and discharging fuel into said mixture conduit between said air valve and said throttle, an air bleed passage for discharging air at substantially atmospheric pressure into said mixture conduit between said air valve and said throttle, a valve seat formed in said bleed passage, a valve unit engageable with said valve seat to restrict air flow through said bleed pasage, and valve operating means for causing said valve unit to engage said valve seat during open throttle operation and during closed throttle operation at speed below a selected level and for moving said valve unit away from said valve seat during closed throttle operation at speeds above said selected level to thereby permit air to bleed into said mixture conduit between said air valve and said throttle to increase the pressure therein, whereby fuel flow to said mixture conduit is minimized during closed throttle operation at speeds above said selected level.
2. For use with an internal combustion engine having an ignition system energized when engine operation is desired and deenergized when engine operation is not desired, a carburetor comprising a mixture conduit having an air inlet and a mixture outlet, a throttle disposed in said outlet and rotatable betwen open and closed positions for controlling flow therethrough, an air valve disposed in said inlet, means controlling said air valve to maintain substantially constant subatmospheric pressure in the region of said mixture conduit between said air valve and said throttle, a fuel bowl, a fuel passage receiving fuel from said fuel bowl and discharging fuel into said mixture conduit region, an air bleed passage for discharging air at substantially atmospheric pressure into said mixture conduit region, an air bypass passage extending from said region to said mixture conduit downstream of said throttle, valve means for alternatively restricting air flow through said bleed and bypass passages, a diaphragm positioning said valve means, one side of said diaphragm being subjected to the pressure in said bypass passage, the opposite side of said diaphragm being subjected alternatively to the pressure at a first port in said mixture conduit disposed downstream of said throttle and to the pressure at a second port in said mixture conduit disposed adjacent the upstream edge of said throttle when said throttle is in said closed position and traversed by the upstream edge of said throttle as said throttle is rotated from said closed position, and valve means for subjecting said opposite side of said diaphragm to the pressure at said second port when the ignition system is energized and the engine is running at speeds above a selected value and for subjecting said opposite side of said diaphragm to the pressure at said first port at other times, whereby when said ignition system is deenergized and said throttle is rotated to said closed position said diaphragm will position said valve means to restrict air flow through said bypass passage and to permit unrestricted air flow through said bleed passage and thereby reduce air and fuel flow sufficiently to prevent afterrunning of the engine, whereby when the engine is running at speeds above said selected valve and said throttle is rotated to said closed position said diaphragm will position said valve means to restrict air flow through said bypass passage and to permit unrestricted air flow through said bleed passage and thereby reduce air and fuel flow during engine deceleration, and whereby at other times said diaphragm will position said valve means to restrict air flow through said bleed passage and to permit unrestricted flow through said bypass passage.
3. For use with an internal combustion engine having an ignition system energized when engine operation is desired and deenergized when engine operation is not desired, a carburetor comprising an air induction passage, a throttle disposed in said induction passage for controlling air flow therethrough, an air bypass passage extending from a location in said induction passage upstream of said throttle to a location in said induction passage downstream of said throttle, a valve seat formed in said bypass passage, a diaphragm valve unit engageable with said valve seat to restrict air flow through said bypass passage, said diaphragm valve unit including a diaphragm member having one side subjected to the pressure in said bypass passage and the opposite side alternatively subjected to pressures higher and lower than the pressure in said bypass passage, and means for subjecting said opposite side of said diaphragm to such lower pressure when said ignition system is energized whereby said diaphragm valve member is biased away from said valve seat to permit unrestricted air flow through said bypass passage and for subjecting said opposite side of said diaphragm to such higher pressure when said ignition system is deenergized whereby said diaphragm valve member is biased into engagement with said valve seat to restrict air flow through said bypass passage and thereby reduce the tendency toward afterrunning of the engine.
Description:
This invention relates to internal combustion engine carburetors.
In recent years, it has become common practice to reduce air flow through the carburetor below idle air flow rates when shutting off the ignition to prevent dieseling or afterrun of the engine. In one well recognized embodiment, an idle air passage bypasses the throttle and a solenoid valve closes the bypass passage when the ignition is shut off.
The carburetor disclosed herein is provided with such an idle air bypass passage, and a novel valve structure closes the bypass passage when the ignition is shut off. The novel valve structure includes a diaphragm valve subjected on one side to the pressure in the bypass passage and on the other side to pressures alternatively higher and lower than the bypass passage pressure. During engine operation, a solenoid is energized to apply the lower pressure to the other side of the diaphragm which results in opening of the valve. When the ignition is shut off, the solenoid is deenergized and the higher pressure is applied to the other side of the diaphragm which results in closing of the valve. Use of the solenoid to control only the pressure signals rather than to directly position the valve in the bypass passage permits use of a much smaller, less expensive, solenoid.
It also has been suggested that, during deceleration or coasting at high speeds, provision should be made to reduce the fuel flow -- and in some instances the air flow -- otherwise provided by the carburetion system.
The carburetor shown herein is of the well-known air valve type which includes an air valve controlled to maintain a substantially constant subatmospheric pressure in a region of the mixture conduit and a metering rod linked to the air valve to control fuel delivery into that region. A novel air bleed passage and valve are controlled to increase the subatmospheric pressure in said region during high speed deceleration and coasting to thereby reduce fuel delivery into the region. Simultaneously, the aforementioned bypass passage is closed to reduce air flow to the engine.
The details as well as other objects and advantages of this invention are set forth in the remainder of the specification and are shown in the drawings in which:
FIG. 1 is a sectional elevational view of the carburetor showing the basic metering linkage;
FIGS. 2 and 3 are enlarged views of the metering rod showing the configuration of the tapered portion;
FIG. 4 is a view similar to FIG. 1 further showing the anti-dieseling and deceleration controls; and
FIG. 5 is a schematic diagram of a circuit for operating the solenoid shown in FIG. 4.
Referring first to FIG. 1, the carburetor 10 has a mixture conduit 12 including an air inlet 14 and a mixture outlet 16 which discharges to the engine. A throttle 18 is disposed in mixture outlet 16 in the usual manner on a throttle shaft 20.
An air valve 22 is disposed in air inlet 14 on an air valve shaft 24. A spring 26 is hooked over the downstream edge 28 of air valve 22 and extends to a bracket 30 to bias air valve 22 to the position shown.
A tang 32 reaches upwardly from air valve 22 and is connected by a link 34 to a diaphragm 36. A chamber 38, formed between the right side of diaphragm 36 and a cover member 40, is connected by a tube 42 to a region 44 of mixture conduit 12 defined between air valve 22 and throttle 18.
A chamber 46, defined between the left side of diaphragm 36 and a cover member 48, is subjected to substantially atmospheric pressure, present in air inlet 14 and in the air cleaner (not shown), through openings such as 50, 52 and 54. (The air cleaner seats on a rim 56 disposed about the upper portion of carburetor 10.)
In operation, chamber 38 is subjected to the subatmospheric pressure created in region 44 as throttle 18 is opened, and diaphragm 36 acts through link 34 to pull air valve 22 clockwise to an open position. Spring 26 is effective to balance the opening force of diaphragm 36, thereby creating a substantially constant subatmospheric pressure in region 44. By thus establishing a generally constant pressure drop across air valve 22, the area about air valve 22 and thus the rotative position of air valve 22 is determined by and is a measure of the rate of air flow through mixture conduit 12.
A tab 58 extends upwardly from air valve 22 and is connected through a link 60 to one end 62 of a lever 64. The opposite end 66 of lever 64 is pivoted about a pin 68. Intermediate ends 62 and 66, a hanger 70 extends from lever 64 into the carburetor fuel bowl 72. The lower end 74 of hanger 70 has a hook 76 which is received in a recess 78 formed in a metering rod 80.
It may be noted that hanger 70 extends through an opening 82 in the cover 84 for fuel bowl 72. Opening 82 is closed by a slider 86 which shifts horizontally during movement of hanger 70.
Metering rod 80 is disposed in a fuel passage 88 having its lower end 90 disposed to receive fuel from a well 92 formed in the bottom of fuel bowl 72. The upper end 94 of fuel passage 88 has an opening 96 through which fuel is discharged into region 44 of mixture conduit 12. It will be appreciated, therefore, that the fuel in fuel bowl 72 is subjected to a substantially constant metering head -- from the substantially atmospheric pressure in the upper portion of the fuel bowl to the generally constant pressure in region 44.
A metering jet or orifice 98 is disposed in fuel passage 88 around the tip 99 of metering rod 80. As best shown in FIGS. 2 and 3, metering rod 80 has flat tapered surfaces 100 on opposite sides which, upon reciprocation of metering rod 80 in jet 98, varies the area available for fuel flow through jet 98.
In operation, as air valve 22 opens by clockwise rotation, link 60 rotates lever 64 in a clockwise direction. Lever 64 then lifts hanger 70 to move metering rod 80 generally upwardly and rightwardly in fuel passage 88. Thus as air valve 22 is opened to increase the area available for air flow through air inlet 14, metering rod 80 is shifted to increase the area available for fuel flow through metering orifice 98. By this means, a substantially constant air-fuel ratio may be maintained -- the precise proportion being controlled by the geometry of tapered surfaces 100 and of the linkage between air valve 22 and metering rod 80.
A spring 102 extends from an annular ledge 104 formed in fuel passage 88 to the lower end 106 of metering rod 80 to take up any slack in the linkage and to load metering rod 80 against jet 98.
It may be noted from FIG. 3 that the thickness of metering rod 80 increases from the end of surfaces 100 most closely adjacent passage inlet 90 to tip 99. Tip 99 is therefore enlarged and assists in discharging fuel from fuel passage 88 as air valve 22 and metering rod 80 are moved to increase air and fuel flow. This offsets the greater inertia of the fuel which otherwise could create a mixture temporarily leaner than desired.
Referring now to FIG. 4, a passage 111 has an inlet 113 opening from region 44 and an outlet 115 opening into mixture outlet 16 downstream of throttle 18. Passage 111 includes a chamber 117 closed by a diaphragm 119. Diaphragm 119 also forms a valve member which cooperates with a valve seat 121 formed in passage 111 adjacent inlet 113.
The opposite side of diaphragm 119 encloses a chamber 123. A valve stem 125 extends through chamber 123 to a valve member 127 disposed in an air bleed passage 129. Bleed passage 129 extends from an inlet 131 exposed to the substantially atmospheric pressure upstream of air valve 22 to an outlet 133 opening into region 44. Bleed passage 129 includes a valve seat 135 receiving valve member 127.
It will be noted that the left side of diaphragm 119 is exposed to an effective pressure intermediate the substantially constant slightly subatmospheric pressure in region 44 and the manifold vacuum in mixture outlet 16 below throttle 18. When the right side of diaphragm 119 is exposed to a higher pressure, diaphragm 119 assumes the position shown -- closing bypass passage 111 and opening bleed passage 129. When the right side of diaphragm 119 is exposed to a lower pressure, diaphragm 119 moves rightwardly -- opening bypass passage 111 and closing bleed passage 129.
A solenoid valve unit 137 alternatively connects chamber 123 to the pressure at a port 139 disposed adjacent and traversed by the upstream edge 140 of throttle 18 and to the manifold vacuum at a port 141 disposed downstream of throttle 18.
The winding 143 of solenoid valve unit 137 is energized through a switch 145 of (FIG. 5) when the ignition is turned on. The solenoid plunger 147 is then pulled rightwardly, unseating the plunger valve tip 149 from a valve seat 151 to apply manifold vacuum from port 141 to chamber 123 and, if desired, seating the right end 153 of plunger 147 against a seat 155 to prevent application of pressure from port 139 to chamber 123. Thus during all low speed operating conditions, the lower pressure of manifold vacuum will cause rightward movement of diaphragm 119 -- moving diaphragm 119 away from seat 121 to open bypass passage 111 and engaging valve member 127 with seat 135 to close bleed passage 129.
When engine or vehicle speed exceeds a certain level, a switch 157 (FIG. 5) opens to deenergize solenoid winding 143. Solenoid plunger 147 then moves leftwardly, under the bias of a spring 159, to engage valve tip 149 with seat 151 and disengage right end 153 from seat 155. Chamber 123 is then subjected to the pressure at port 139.
During open throttle operation, the pressure at port 139 is subjstantially the same as that at port 141. Thus during open throttle operation at either high or low speeds, chamber 123 is subjected to manifold vacuum and, as described above, bypass passage 111 is opened and bleed passage 129 is closed.
When the throttle is closed during high speed operation, as during initial deceleration and during coasting, chamber 123 is subjected to the only slightly subatmospheric pressure in region 44. Since this is higher than the pressure in bypass passage 111, diaphragm 119 moves leftwardly -- engaging valve seat 121 to close bypass passage 111 and disengaging valve member 127 from valve seat 135 to open bleed passage 129.
Two effects occur upon this event: First, air flow through bleed passage 129 into region 44 increases the pressure in region 44, resulting in reduced fuel flow through fuel passage 88 into region 44. Second, air flow through bypass passage 111 is blocked, resulting in reduced air flow to the engine and increased pressure in region 44 which further reduces fuel flow into region 44.
When throttle 18 is again opened, or when the speed drops below a selected level and switch 157 again closes to energize solenoid winding 143, chamber 123 is again subjected to manifold vacuum and normal fuel and air flow is restored.
When the engine ignition is turned off, switch 145 is opened to deenergize solenoid winding 143. Spring 159 then biases plunger valve tip 149 into engagement with valve seat 151 and chamber 123 is subjected to the pressure at port 139. Closing of throttle 18, as is customary when shutting off the ignition, applies the only slightly subatmospheric pressure of region 44 to chamber 123, forcing diaphragm 119 leftwardly to the position shown. The engagement of diaphragm 119 with valve seat 121 blocks air flow through bypass passage 111, thus reducing air flow and fuel flow to the engine to prevent dieseling or afterrun.
An additional benefit in preventing dieseling also may be realized by disengagement of valve member 127 from valve seat 135. The resulting air flow through bleed passage 129 increases the pressure in region 44, resulting in reduced fuel flow through fuel passage 88.
It will be appreciated, of course, that the advantages of controlling air flow through bypass passage 111 in the above-described manner and of providing bleed passage 129 and its associated controls may be utilized individually.
In recent years, it has become common practice to reduce air flow through the carburetor below idle air flow rates when shutting off the ignition to prevent dieseling or afterrun of the engine. In one well recognized embodiment, an idle air passage bypasses the throttle and a solenoid valve closes the bypass passage when the ignition is shut off.
The carburetor disclosed herein is provided with such an idle air bypass passage, and a novel valve structure closes the bypass passage when the ignition is shut off. The novel valve structure includes a diaphragm valve subjected on one side to the pressure in the bypass passage and on the other side to pressures alternatively higher and lower than the bypass passage pressure. During engine operation, a solenoid is energized to apply the lower pressure to the other side of the diaphragm which results in opening of the valve. When the ignition is shut off, the solenoid is deenergized and the higher pressure is applied to the other side of the diaphragm which results in closing of the valve. Use of the solenoid to control only the pressure signals rather than to directly position the valve in the bypass passage permits use of a much smaller, less expensive, solenoid.
It also has been suggested that, during deceleration or coasting at high speeds, provision should be made to reduce the fuel flow -- and in some instances the air flow -- otherwise provided by the carburetion system.
The carburetor shown herein is of the well-known air valve type which includes an air valve controlled to maintain a substantially constant subatmospheric pressure in a region of the mixture conduit and a metering rod linked to the air valve to control fuel delivery into that region. A novel air bleed passage and valve are controlled to increase the subatmospheric pressure in said region during high speed deceleration and coasting to thereby reduce fuel delivery into the region. Simultaneously, the aforementioned bypass passage is closed to reduce air flow to the engine.
The details as well as other objects and advantages of this invention are set forth in the remainder of the specification and are shown in the drawings in which:
FIG. 1 is a sectional elevational view of the carburetor showing the basic metering linkage;
FIGS. 2 and 3 are enlarged views of the metering rod showing the configuration of the tapered portion;
FIG. 4 is a view similar to FIG. 1 further showing the anti-dieseling and deceleration controls; and
FIG. 5 is a schematic diagram of a circuit for operating the solenoid shown in FIG. 4.
Referring first to FIG. 1, the carburetor 10 has a mixture conduit 12 including an air inlet 14 and a mixture outlet 16 which discharges to the engine. A throttle 18 is disposed in mixture outlet 16 in the usual manner on a throttle shaft 20.
An air valve 22 is disposed in air inlet 14 on an air valve shaft 24. A spring 26 is hooked over the downstream edge 28 of air valve 22 and extends to a bracket 30 to bias air valve 22 to the position shown.
A tang 32 reaches upwardly from air valve 22 and is connected by a link 34 to a diaphragm 36. A chamber 38, formed between the right side of diaphragm 36 and a cover member 40, is connected by a tube 42 to a region 44 of mixture conduit 12 defined between air valve 22 and throttle 18.
A chamber 46, defined between the left side of diaphragm 36 and a cover member 48, is subjected to substantially atmospheric pressure, present in air inlet 14 and in the air cleaner (not shown), through openings such as 50, 52 and 54. (The air cleaner seats on a rim 56 disposed about the upper portion of carburetor 10.)
In operation, chamber 38 is subjected to the subatmospheric pressure created in region 44 as throttle 18 is opened, and diaphragm 36 acts through link 34 to pull air valve 22 clockwise to an open position. Spring 26 is effective to balance the opening force of diaphragm 36, thereby creating a substantially constant subatmospheric pressure in region 44. By thus establishing a generally constant pressure drop across air valve 22, the area about air valve 22 and thus the rotative position of air valve 22 is determined by and is a measure of the rate of air flow through mixture conduit 12.
A tab 58 extends upwardly from air valve 22 and is connected through a link 60 to one end 62 of a lever 64. The opposite end 66 of lever 64 is pivoted about a pin 68. Intermediate ends 62 and 66, a hanger 70 extends from lever 64 into the carburetor fuel bowl 72. The lower end 74 of hanger 70 has a hook 76 which is received in a recess 78 formed in a metering rod 80.
It may be noted that hanger 70 extends through an opening 82 in the cover 84 for fuel bowl 72. Opening 82 is closed by a slider 86 which shifts horizontally during movement of hanger 70.
Metering rod 80 is disposed in a fuel passage 88 having its lower end 90 disposed to receive fuel from a well 92 formed in the bottom of fuel bowl 72. The upper end 94 of fuel passage 88 has an opening 96 through which fuel is discharged into region 44 of mixture conduit 12. It will be appreciated, therefore, that the fuel in fuel bowl 72 is subjected to a substantially constant metering head -- from the substantially atmospheric pressure in the upper portion of the fuel bowl to the generally constant pressure in region 44.
A metering jet or orifice 98 is disposed in fuel passage 88 around the tip 99 of metering rod 80. As best shown in FIGS. 2 and 3, metering rod 80 has flat tapered surfaces 100 on opposite sides which, upon reciprocation of metering rod 80 in jet 98, varies the area available for fuel flow through jet 98.
In operation, as air valve 22 opens by clockwise rotation, link 60 rotates lever 64 in a clockwise direction. Lever 64 then lifts hanger 70 to move metering rod 80 generally upwardly and rightwardly in fuel passage 88. Thus as air valve 22 is opened to increase the area available for air flow through air inlet 14, metering rod 80 is shifted to increase the area available for fuel flow through metering orifice 98. By this means, a substantially constant air-fuel ratio may be maintained -- the precise proportion being controlled by the geometry of tapered surfaces 100 and of the linkage between air valve 22 and metering rod 80.
A spring 102 extends from an annular ledge 104 formed in fuel passage 88 to the lower end 106 of metering rod 80 to take up any slack in the linkage and to load metering rod 80 against jet 98.
It may be noted from FIG. 3 that the thickness of metering rod 80 increases from the end of surfaces 100 most closely adjacent passage inlet 90 to tip 99. Tip 99 is therefore enlarged and assists in discharging fuel from fuel passage 88 as air valve 22 and metering rod 80 are moved to increase air and fuel flow. This offsets the greater inertia of the fuel which otherwise could create a mixture temporarily leaner than desired.
Referring now to FIG. 4, a passage 111 has an inlet 113 opening from region 44 and an outlet 115 opening into mixture outlet 16 downstream of throttle 18. Passage 111 includes a chamber 117 closed by a diaphragm 119. Diaphragm 119 also forms a valve member which cooperates with a valve seat 121 formed in passage 111 adjacent inlet 113.
The opposite side of diaphragm 119 encloses a chamber 123. A valve stem 125 extends through chamber 123 to a valve member 127 disposed in an air bleed passage 129. Bleed passage 129 extends from an inlet 131 exposed to the substantially atmospheric pressure upstream of air valve 22 to an outlet 133 opening into region 44. Bleed passage 129 includes a valve seat 135 receiving valve member 127.
It will be noted that the left side of diaphragm 119 is exposed to an effective pressure intermediate the substantially constant slightly subatmospheric pressure in region 44 and the manifold vacuum in mixture outlet 16 below throttle 18. When the right side of diaphragm 119 is exposed to a higher pressure, diaphragm 119 assumes the position shown -- closing bypass passage 111 and opening bleed passage 129. When the right side of diaphragm 119 is exposed to a lower pressure, diaphragm 119 moves rightwardly -- opening bypass passage 111 and closing bleed passage 129.
A solenoid valve unit 137 alternatively connects chamber 123 to the pressure at a port 139 disposed adjacent and traversed by the upstream edge 140 of throttle 18 and to the manifold vacuum at a port 141 disposed downstream of throttle 18.
The winding 143 of solenoid valve unit 137 is energized through a switch 145 of (FIG. 5) when the ignition is turned on. The solenoid plunger 147 is then pulled rightwardly, unseating the plunger valve tip 149 from a valve seat 151 to apply manifold vacuum from port 141 to chamber 123 and, if desired, seating the right end 153 of plunger 147 against a seat 155 to prevent application of pressure from port 139 to chamber 123. Thus during all low speed operating conditions, the lower pressure of manifold vacuum will cause rightward movement of diaphragm 119 -- moving diaphragm 119 away from seat 121 to open bypass passage 111 and engaging valve member 127 with seat 135 to close bleed passage 129.
When engine or vehicle speed exceeds a certain level, a switch 157 (FIG. 5) opens to deenergize solenoid winding 143. Solenoid plunger 147 then moves leftwardly, under the bias of a spring 159, to engage valve tip 149 with seat 151 and disengage right end 153 from seat 155. Chamber 123 is then subjected to the pressure at port 139.
During open throttle operation, the pressure at port 139 is subjstantially the same as that at port 141. Thus during open throttle operation at either high or low speeds, chamber 123 is subjected to manifold vacuum and, as described above, bypass passage 111 is opened and bleed passage 129 is closed.
When the throttle is closed during high speed operation, as during initial deceleration and during coasting, chamber 123 is subjected to the only slightly subatmospheric pressure in region 44. Since this is higher than the pressure in bypass passage 111, diaphragm 119 moves leftwardly -- engaging valve seat 121 to close bypass passage 111 and disengaging valve member 127 from valve seat 135 to open bleed passage 129.
Two effects occur upon this event: First, air flow through bleed passage 129 into region 44 increases the pressure in region 44, resulting in reduced fuel flow through fuel passage 88 into region 44. Second, air flow through bypass passage 111 is blocked, resulting in reduced air flow to the engine and increased pressure in region 44 which further reduces fuel flow into region 44.
When throttle 18 is again opened, or when the speed drops below a selected level and switch 157 again closes to energize solenoid winding 143, chamber 123 is again subjected to manifold vacuum and normal fuel and air flow is restored.
When the engine ignition is turned off, switch 145 is opened to deenergize solenoid winding 143. Spring 159 then biases plunger valve tip 149 into engagement with valve seat 151 and chamber 123 is subjected to the pressure at port 139. Closing of throttle 18, as is customary when shutting off the ignition, applies the only slightly subatmospheric pressure of region 44 to chamber 123, forcing diaphragm 119 leftwardly to the position shown. The engagement of diaphragm 119 with valve seat 121 blocks air flow through bypass passage 111, thus reducing air flow and fuel flow to the engine to prevent dieseling or afterrun.
An additional benefit in preventing dieseling also may be realized by disengagement of valve member 127 from valve seat 135. The resulting air flow through bleed passage 129 increases the pressure in region 44, resulting in reduced fuel flow through fuel passage 88.
It will be appreciated, of course, that the advantages of controlling air flow through bypass passage 111 in the above-described manner and of providing bleed passage 129 and its associated controls may be utilized individually.