Engine Spark Control And Exhaust Gas Recirculation Vacuum Signal Selector

Abstract

An engine emission control system includes exhaust gas recirculating and engine spark timing devices each normally connected respectively to axially spaced EGR and spark ports in the carburetor induction passage above the closed position of the throttle valve. Valving is provided under the control of temperature changes and changes in the operation of the vehicle transmission to at times switch the connections to the exhaust recirculating device from EGR port to spark port operation and vice versa, to at times improve emissions while maintaining a constant vehicle drive quality, and at other times improve vehicle drive quality while maintaining a constant emission level.

Description

This invention relates in general, to an internal combustion engine in which exhaust gas recirculation and engine spark timing are controlled as functions of ambient temperature changes and other parameters, to at times improve emissions while maintaining a constant drivability level, and at other times to maintain a constant emission level while improving drivability.

The introduction of engine EGR (exhaust gas recirculation) to reduce NO.sub.x levels in most cases also results in a decrease in vehicle drive quality. The greater the proportion of EGR, the greater bleed of the manifold vacuum signal and a lesser induction of fuel/air mixture into the engine. This reduces fuel economy because of the need for more mixture to obtain the same engine power as without EGR. Also, the introduction of EGR into the induction system below the carburetor throttle flange, for example, results in poorer fuel distribution into the manifold runners; i.e., exhaust gases enter into the manifold to one side of the spacer and thus tend to create a difference in flow between the front and rear cylinders. This results in uneven pressure pulsations and overall poorer engine operation.

It is an object of this invention to improve the vehicle drive quality at times while holding a constant emission level; while at other times reducing the emission level while retaining a constant drive quality level.

More specifically, the invention is directed to a mechanism for at times controlling EGR flow as a function of spark port vacuum signal while at other times as a function of EGR port vacuum signal, the two ports being axially spaced along the carburetor induction passage above the closed position of the throttle valve, the switching of signal sources from one port to the other being made as a function of temperature and other operating conditions.

It is a further object of the invention to provide an engine emission control system in which above a predetermined temperature condition EGR flow is scheduled as a function of carburetor spark port level, the attainment of the predetermined temperature switching the vacuum signal from the spark port to an EGR port located above the spark port, to improve vehicle drive quality while maintaining essentially a constant emission level.

It is a still further object of the invention to provide an emission control system of the type described above in which the switching of the EGR signal from the carburetor spark port to the carburetor EGR port is triggered not only in response to predetermined temperature attainment, but also in response to predetermined operation of a transmission associated with the engine; namely, operation of the transmission in low and intermediate gears above the temperature level effecting a connection of spark port vacuum to the EGR valve, while movement of the transmission to a high speed gear ratio switches the EGR valve vacuum signal from the spark port to the EGR port; the change in temperature levels beyond a predetermined point also effecting a switching of the EGR vacuum signal if the transmission control has not already done so.

It is also an object of the invention to provide an engine control device in which a vacuum operated servo controlling the movement of a force movable member is actuated at times by carburetor spark port vacuum so that the force movable member moves as a function of the degree of opening of the carburetor throttle valve, switching of the vacuum source from the carburetor spark port to a port higher in the induction passage effecting a change in the movement of the force movable member for the same degree of throttle valve opening, to thereby vary the movement of the force movable member in a desired manner.

Other objects, features and advantages of the invention will become more apparent upon reference to the succeeding detailed description thereof, and to the drawings illustrating the preferred embodiments thereof; wherein,

FIG. 1 is a schematic illustration of an internal combustion engine emission and spark timing control embodying the invention;

FIG. 2 is a cross-sectional view taken on a plane indicated by and viewed in the direction of the arrows 2--2 of FIG. 1; and,

FIG. 3 is a modification of the FIG. 1 showing.

FIG. 1 illustrates a portion 10 of one-half of a four-barrel carburetor of a known downdraft type. It has an air horn section 12, a main body portion 14, and a throttle body 16, joined by suitable means not shown. The carburetor has the usual air/fuel induction passages 18 open at their upper ends 20 to fresh air from the conventional air cleaner, not shown. The passages 18 have the usual fixed area venturies 22 cooperating with booster venturies 24 through which the main supply of fuel is induced, by means not shown.

Flow of air and fuel through induction passages 18 is controlled by a pair of throttle valve plates 26 each fixed on a shaft 28 rotatably mounted in the side walls of the carburetor body.

The throttle body 16 is flanged as indicated for bolting to the top of the engine intake manifold 30, with a spacer element 32 located between. Manifold 30 has a number of vertical risers or bores 34 that are aligned for cooperation with the discharge end of the carburetor induction passages 18. The risers 34 extend at right angles at their lower ends 36 for passage of the mixture out of the plane of the figure to the intake valves of the engine.

The exhaust manifolding part of the engine cylinder head is indicated partially at 38, and includes an exhaust gas crossover passage 40. The gases pass from the exhaust manifold, not shown, on one side of the engine to the opposite side beneath the manifold trunks 36 to provide the usual "hot spot" beneath the carburetor to better vaporize the air/fuel mixture.

As best seen in FIG. 2, the spacer 32 is provided with a worm-like recess 42 that is connected directly to crossover passage 40 in FIG. 1 by a bore 44. Also connected to recess 42 is a passage 46 alternately blocked or connected to a central bore or passage 48 communicating with the risers 34 through a pair of ports 50. Mounted to one side of the spacer is a cup shaped boss 52 forming a chamber 54 through which passages 46 and 48 are interconnected.

As described above, it is necessary and desirable to provide some sort of control to prevent the recirculation of exhaust gases at undesirable times. For this purpose, passage 46 normally is closed by a valve 56 that is moved to an open position by a servo 58. The servo includes a hollow outer shell 64 containing an annular flexible diaphragm 66. The latter divides the interior into an air chamber 68 and a signal vacuum chamber 70. Chamber 68 is connected to atmospheric pressure through a vent 72, while chamber 70 is connected to a vacuum signal force through a line 74. Line 74 is connected to the carburetor induction passage, in a manner to be described later. The stem 75 of valve 56 is fixed to a pair of retainers 76 that are secured to diaphragm 66 and serve as a seat for a compression spring 77 normally biasing the valve to its closed position. The stem slidably and sealingly projects through a plate 78 closing chamber 54.

Returning to FIG. 1, a spark port 80 is tapped into the induction passage at a point just above or aligned with the idle position of throttle valve 26, to be traversed by the edge of the throttle valve during its opening part throttle movements. This will change the vacuum level in spark port 28 as a function of the rotative position of the throttle valve, the spark port reflecting essentially atmospheric pressure in the air inlet upon closure of the throttle valve. A second EGR port 82 is located above the spark port so that the latter port sees vacuum later than the spark port because it is uncovered later, for a purpose that will become clear later.

FIG. 1 also shows schematically an engine distributor 84 that includes a breaker plate 86 pivotably mounted at 88 on a stationary portion of the distributor and movable with respect to a cam 90. The latter has a number of peaks corresponding to the number of engine cylinders. Each peak cooperates with the follower 92 of a breaker point set 94 to make and break the spark connection in a known manner for each one-sixth, in this case, rotation of cam 90. Pivotal movement of breaker plate 86 in a counterclockwise spark retard setting direction, or in a clockwise spark advance setting, is provided by an actuator 96 slidably extending from a vacuum servo 98.

Servo 98 may be of a conventional construction. It has a hollow housing 100 whose interior is divided into an atmospheric pressure chamber 102 and a vacuum chamber 104 by an annular flexible diaphragm 106. The diaphragm is fixedly secured to actuator 96, and is biased in a rightward retard direction by a compression spring 108. Chamber 102 has an atmospheric or ambient pressure vent, not shown, while chamber 104 is connected to a vacuum signal line 110. Line 110, in turn, is also connected to the carburetor induction passage in a manner that will become clear later.

During engine-off and other operating conditions to be described, atmospheric pressure exists on both sides of the diaphragm 106, permitting spring 108 to force the actuator 96 to the lowest spark timing advance or a retard setting position. Application of vacuum to chamber 104 moves diaphragm 106 and actuator 96 toward the left to an engine spark timing advance position, by degree, as a function of a change in vacuum level.

Turning now to the invention, the flow of spark port and EGR port vacuum to the EGR servo 58 and to the spark timing control servo 98 is controlled in FIG. 1 by a conventional one-way check valve 112 and a three port electrically controlled selector valve 114. The check valve 112 is located in a line 116 connecting the EGR port 82 to the EGR servo line 74.

Selector valve 114 includes a valve body having an inlet port 118 and two outlet ports 120 and 122, connected respectively by lines 124, 126 and 128 to spark port 80, EGR line 74, and distributor line 110. Valve 114 includes a two position slide valve 130 biased by a spring 132 to an upper position shown. In this position, it connects spark port vacuum in line 124 through an angled passage 134 to distributor line 110, while blocking outlet 120. A solenoid 136, when energized, pulls the valve 130 downwardly to its second position. In this position, a through passage 138 connects the spark port vacuum line 124 through port 120 and line 126 to EGR line 74, while blocking port 122. The check valve prevents bleed of lower pressures in line 74 back through the EGR port 82.

Solenoid 136 is connected electrically to ground through a connection 140, and through a line 142 to a battery or other suitable power source 144. A pair of switches 146 and 148 located in the line control the energization of solenoid 136.

Switch 146 in this case is an ambient temperature sensitive thermostatic switch that is closed above, say 58.degree.F., to complete the circuit, and opens when the temperature drops below that level. Switch 148 on the other hand, in this case, is a vehicle transmission gear ratio condition responsive switch. That is, when the transmission associated with the engine is conditioned for high gear operation, the switch 148 is open breaking the circuit to the solenoid 136 even though switch 146 may be closed. Moving the transmission gear ratio to low or intermediate gears closes the switch 148 to complete the circuit, energize solenoid 136 (if switch 146 is closed) and move valve 130 downwardly. This will switch spark port vacuum from distributor line 110 to EGR lines 126 and 74, close check valve 112, and cause EGR flow to be scheduled as a function of spark port vacuum changes, with the distributor being conditioned for a maximum retarded setting.

It will be clear of course that other controls can be provided to control the switching function, within the scope of the invention. For example, an engine water temperature sensitive switch could be substituted for the switch 146, while a switch conditioned in response to operation of the vehicle clutch could be used in place of or in addition to switch 148, depending upon the desired operation.

The overall operation is believed to be clear from the above description, and, therefore, will not be given in detail. In brief, below ambient temperatures of 58.degree.F., the circuit to solenoid 136 is broken, and the selector valve 130 is in the position shown. Thus, spark timing advance occurs as a function of throttle valve movement and spark port vacuum level for all gear ratio positions of the vehicle transmission. EGR flow is directly proportional to EGR port vacuum level above the preload of the servo spring 77.

As soon as the temperature rises above 58.degree.F., the switch 146 closes. Then when the transmission is conditioned for low and intermediate gear operations, solenoid 136 will be energized to move valve 130 to connect spark port vacuum to the EGR valve servo, while blocking the EGR line 116 and spark timing advance line 110. Moving the transmission to high gear again breaks the circuit to the solenoid 136, and connects EGR port vacuum to the EGR servo 98 and spark port vacuum to the servo 98.

It will be clear that by using the spark port as a vacuum source for controlling EGR flow in low and intermediate gears, the EGR valve will open sooner and more often than were it connected at all times to the EGR port. Opening the EGR valve in this manner makes it possible to use a smaller EGR orifice (at the opening to the passage 46) or a distributor with more spark advance while maintaining the same emission level. During high gear operation, the EGR valve vacuum source to the EGR port provides, above 58.degree.F., the switching to a less active signal and consequently less EGR flows. Therefore, drive quality is better.

FIG. 3 shows a modified construction in which two single acting valves 150 and 152 are used instead of the three port, two position valve 130 of FIG. 1. In FIG. 3, valve 150 is a normally closed valve opened upon energization of solenoid 154. Valve 152 is a normally open valve closed upon energization of solenoid 156.

Valve 150 controls the connection of spark port vacuum in line 124' to EGR line 126', while valve 152 controls spark port vacuum flow to the distributor servo line 110'. The energizations of the solenoids 154 and 156 are controlled by the same temperature and transmission switches 146 and 148 as in FIG. 1. Thus, in low and intermediate gears, above 58.degree., switch 150 closes and 152 opens, routing spark port vacuum to the EGR valve line 126' while blocking vacuum flow to spark timing servo line 110. Conditioning the transmission for high gear, or the temperature rising above 58.degree.F., opens the circuit to the solenoids and connects the spark and EGR ports as shown.

Claims

I claim:

1. A carburetor controlled servo system comprising in combination, a vacuum servo having a force movable member variably movable by vacuum applied thereto, a carburetor having an induction passage open at one end to ambient air at essentially atmospheric pressure and connected at its opposite end to engine intake manifold vacuum so as to subject the passage to varying engine pressure depressions, a throttle valve rotatably movable across the passage between essentially closed and wide open throttle positions, a number of pressure sensing ports in the induction passage axially spaced from each other along the induction passage and located above the closed position of the throttle valve in a position to be traversed progressively by the edge of the throttle valve as it moves from a closed position towards the wide open throttle position, means connecting the servo to one of the ports for actuating the force transmitting member, and further means for switching the connection of the servo from the one port to another of the remaining number of ports for varying the movement of the force transmitting member for the same movement of the throttle valve.

2. A servo system as in claim 1, the further means including temperature sensitive means responsive to the attainment of a predetermined temperature for switching the connection of the servo from the one port to the another port.

3. A servo system as in claim 1, the force movable member comprising a valve movable to control the recirculation of engine exhaust gases from the exhaust system to the induction system as a function of movement of the servo, the another port constituting a spark port and being located below the one port closer to the closed position of the throttle valve.

4. A servo system as in claim 3, the further means including ambient temperature sensitive means responsive to the attainment of a predetermined engine temperature to connect the spark port to the first mentioned servo above the predetermined temperature level to increase exhaust gas recirculation flow for the same throttle valve setting as when the one port is connected to the first mentioned servo.

5. A control system as in claim 4, the further means also including check valve means in the connection between the one port and the first mentioned servo preventing communication of the higher pressure in the one port to the latter servo when the spark port is connected to the latter servo.

6. A control system as in claim 3, the further means including a second valve movable between first and second positions respectively blocking a connection between or connecting the spark port and the servo and a check valve in the connection between the one port and the servo operable to prevent communication of the higher pressure in the one port to the servo when the second valve is in the second position while permitting communication of the higher pressure in the one port to the servo when the second valve is in the first position.

7. A control system as in claim 6, including a second servo connected to an engine distributor spark adjustment means movable in opposite directions to advance and retard respectively the engine spark timing as a function of servo movement, means connecting the second servo to the spark port, the second servo having a second force movable member variably movable by spark port vacuum applied thereto.

8. A control system as in claim 6, the further means including an ambient temperature sensitive means responsive to the attainment of a predetermined ambient temperature level for moving the second valve from its first position to its second position.

9. A control system as in claim 6, the further means including additional means operable in response to the attainment of a predetermined condition of operation of a transmission associated with the engine for moving the second valve from its first position to its second position.

10. A control system as in claim 9, the further means including ambient temperature sensitive means responsive to the attainment of a predetermined engine temperature level for also moving the second valve from its first position to its second position.

11. A control system as in claim 8, the second valve being solenoid controlled and movable to the second position when energized, operation of the ambient temperature sensitive means energizing the second valve.

12. A control system as in claim 7, the second valve having three ports the first of which is connected to the spark port while a second port is connected to the first mentioned servo and the third is connected to the second servo, this first position being an at rest position and interconnecting the first and third ports, the second position interconnecting the first and second ports.

13. A control system as in claim 7, the second valve being solenoid controlled and movable to the second position when energized, operation of the ambient temperature sensitive means energizing the second valve, the second valve comprising first and second solenoid controlled valve means, the first being normally closed and solenoid opened to connect the spark port and first mentioned servo, the second being normally open to connect the spark port to the second servo and being solenoid closed, both valve means being energized in response to operability of the ambient temperature sensitive means.

14. An engine spark timing and exhaust gas recirculation control comprising in combination, a carburetor induction passage having a throttle valve rotatably mounted therein and movable between closed and fully open positions, a spark port in the induction passage located above the closed position of the throttle valve, an exhaust gas recirculation (EGR) port located in the induction passage above and axially spaced from the spark port, an (EGR) servo having an (EGR) valve connected thereto spring biased in a closed direction and movable to an open position by vacuum applied to the servo, the (EGR) valve controlling flow of exhaust gases back into the engine induction system, first conduit means connecting the (EGR) port to the (EGR) servo, a second servo having a force transmitting member connected thereto spring biased in one direction and connected to the movable spark adjusting member of an engine distributor and movable in opposite directions to advance or retard the spark, second conduit means connecting the spark port to the second servo, valve means interconnecting the first and second conduit means movable between a first position connecting the spark port to the second servo while disconnecting the spark port from the (EGR) servo and a second position disconnecting the spark port from the second servo while connecting the spark port to the (EGR) servo, a check valve in the first conduit means between the (EGR) port and the connection to the second conduit means to prevent decay of spark port vacuum acting on the (EGR) servo by the (EGR) port pressure, and further means for moving the valve means between its positions to change the pressure level acting on the (EGR) servo for the same degree of throttle opening and also to control the advance or retard of the engine spark timing.

15. A control as in claim 14, the further means including an ambient temperature responsive means operable above a predetermined temperature level to effect movement of the valve means from its first to its second position to provide more vacuum acting on the (EGR) servo for the same throttle opening.

16. A control as in claim 14, the further means including transmission responsive means sensitive to a predetermined transmission operation for effecting movement of the valve means from the first position to the second position.

17. A control as in claim 16, the valve means being solenoid movable from the first to the second position, conditioning the transmission for low and intermediate gear operations above the predetermined temperature energizing the solenoid to move the valve means to its second position providing (EGR) flow as a function of spark port vacuum level and no spark port flow to the second servo, conditioning the transmission for high speed operation de-energizing the valve means solenoid to move the valve means to its first position providing (EGR) flow as a function of (EGR) port vacuum and spark timing adjustment as a function of spark port vacuum.