US3678907A

US3678907A - Engine spark timing system

Info

Publication number: US3678907A
Application number: US59500A
Authority: US
Inventors: Richard D Vartanian
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1970-07-30
Filing date: 1970-07-30
Publication date: 1972-07-25
Anticipated expiration: 1989-07-25
Also published as: DE2134901A1; GB1303931A; CA947159A; JPS5037816B1; DE2134901C2

Abstract

A mechanical apparatus between the carburetor spark port and distributor servo includes a main one-way check valve is parallel flow relationship with a vacuum reservoir, the reservoir containing an orifice at the servo end and a one-way orificed check valve at the spark port end, the reservoir providing a quick recovery of the engine spark timing setting after rapid acceleration followed by deceleration and reacceleration conditions of operation, to improve fuel economy, the main check valve quickly lowering the spark advance setting during rapid accelerations, and the orifices providing a delayed spark advance during light accelerations.

Description

United States Patent Vartanian 51 July 25,1972

[72] Inventor:

[52] U.S. Cl. ..l23/l17A, l23/ll7R [51] Int. Cl ..F02p 5/04 [58] FieldofSearch ..l23/ll7.l, H7

[56] References Cited UNITED STATES PATENTS 2,377,566 6/l945 Mallory ..123/l l7.l 2,392,680 1/1946 Mallory .....l23/1l7.1 2,650,581 9/1953 Short ..123/l l7.l 3,l57,l68 ll/l964 Sterner ..l23/ll7.l

3,472,213 10/1969 Walker ..l23/ll7.l

Primary Examiner-Laurence M. Goodridge Assistant Examiner-Ronald B. Cox Attorney-John R. Faulkner and Robert E. McCollum 5 7] ABSTRACT A mechanical apparatus between the carburetor spark portv 8 Claims, 2 Drawing Figures O l J2 O Patented July 25, 1972 M QEQUINW .Wx hk INVENTOR K7/7/V/I4/V Z11 ATTORNEYS ENGINE SPARK TIMING SYSTEM This invention relates, in general, to an engine spark timing control system. More particularly, it relates to an apparatus that provides good operating performance as well as good fuel economy by not only quickly lowering the spark timing advance setting upon rapid vehicle accelerations, but also providing a rapid return to essentially the former setting upon momentary decelerations and return of the engine towards its former condition of operation.

This is an improvement over the spark timing control systems of the type shown in Ser. No. 52,325 and Ser. No. 52,326. The latter shows a mechanical device in the vacuum line between a carburetor spark port and a vacuum servo to control the movement of the distributor breaker plate to advance or retard the engine spark timing setting. The device includes a one-way check valve and an orifice in parallel flow circuits. During rapid vehicle accelerations, the check valve unseats to provide a quick equalization of the pressure at the servo to the spark port vacuum, thereby lowering the spark advance setting to avoid detonation. Upon a momentary deceleration condition of operation, with a subsequent return towards its former operating condition, the orifice provides a slow buildup of the vacuum level at the servo to equal that at the spark port so that the advance setting only slowly returns to normal. This results in lower peak combustion temperatures and pressures and less emission of engine pollutants.

The above reference systems are poor for fuel economy. The slower spark advance buildup due to the orifice bleed of vacuum causes late burning and generally at a point past optimum efficiency, i.e., into the expansion cycle of the engine.

This invention provides all of the advantageous functions described, plus a rapid return of the spark timing advance setting to essentially its former level, after a momentary deceleration, to improve the fuel economy.

More particularly, the invention includes in the vacuum line between the carburetor spark port and distributor servo a first one-way check valve in parallel flow relationship with a vacuum reservoir or accumulator. The reservoir is open at one end to the carburetor spark port and at its opposite end to the distributor servo line, and contains adjacent each end an orifice or flow restricting control. The flow restriction adjacent the spark port end of the reservoir is located in the opening of a second one-way check valve that operates in a direction opposite to that of the first one-way check valve previously described.

The above construction permits a quick equalization of the spark port and servo port pressure levels during rapid vehicle accelerations by unseating of the first or main check valve. It also simultaneously seats the reservoir one-way check valve to seal off the bleed of vacuum from the reservoir to the spark port end while allowing only slow leakage of vacuum through the other end and through the open parallel flow check valve. Upon a momentary deceleration and subsequent reacceleration towards its previous condition of operation, the main check valve seats or closes, and the vacuum of the reservoir quickly returns the distributor servo port pressure to the reservoir level. This generally is close to or essentially the level that existed prior to vehicle rapid acceleration depending upon the duration of the deceleration.

Thus, the delay built into the devices of Ser. No. 52,325 and Ser. No. 52,326 is essentially eliminated during an operation of this type, resulting in a higher spark advance timing setting for the same time period, and greater fuel economy by more efficient operation.

It is a primary object of the invention, therefore, to provide an engine spark timing control apparatus that provides correct spark timing setting during rapid vehicle accelerations and a rapid return to the correct setting after a momentary deceleration, for good engine performance and fuel economy purposes, while at the same time providing the other necessary and desirable changes in spark timing to provide efficient engine operation.

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 a preferred embodiment thereof; wherein,

FIG. 1 schematically illustrates a partial cross sectional view of an engine spark timing system embodying the invention; and,

FIG. 2 graphically illustrates different operating conditions of the spark timing system shown in FIG. 1.

FIG. 1 shows, schematically, only those portions of an internal combustion engine that are normally associated with the engine distributor spark timing setting control; such as, for example, a carburetor 10, a distributor breaker plate 12, a vacuum servo 14 to control the movement of breaker plate 12, and a line 16 connected between the carburetor and vacuum servo to automatically change the engine spark timing setting as a function of changes in engine vacuum spark port setting.

More specifically, carburetor 10 is shown as being of the downdraft type having the usual air-fuel induction passage 18 with an atmospheric air inlet 20 at one end and connected to the engine intake manifold 22 at the opposite end. Passage 18 contains the usual fixed area venturi 24 and a throttle valve 26. The latter is rotatably mounted on a part ofthe carburetor body across passage 18 in a manner to control the flow of airfuel mixture into the intake manifold. Fuel would be inducted in the usual manner from a nozzle, not shown, projecting into or adjacent venturi 24, in a known manner.

Throttle valve 26 is shown in its engine idle speed position essentially closing induction passage 18, and is rotatable to a nearly vertical position essentially unblocking passage 18. A spark port 28 is provided at a point just above the idle position of throttle valve 26, to be traversed by the throttle valve during its opening or 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 20 upon closure of the throttle valve. I

As stated previously, the distributor, not shown, includes a breaker plate 12 that is pivotally mounted at 30 on a stationary portion of the distributor, and movable with respect to cam 32. The latter has six peaks 34 corresponding to the number of engine cylinders. Each of the peaks cooperates with the follower 36 of a breaker point set 38 to make and break the spark connection in a known manner for each one-sixth, in this case, rotation of cam 32. Pivotal movement of breaker plate 12 in a counterclockwise spark retard setting direction, or in a clockwise spark advance setting, is provided by an actuator 40 slidably extending from vacuum servo l4.

Servo 14 may be of a conventional construction. It has a hollow housing 42 whose interior is divided into an atmospheric pressure chamber 44 and a vacuum chamber 46 by an annular flexible diaphragm 48. The diaphragm is fixedly secured to actuator 40, and is biased in a rightward retard direction by a compression spring 50. Chamber 44 has an atmospheric or ambient pressure vent, not shown, while the chamber 46 is connected by a bore 52 to line 16.

During engine-off and other operating conditions to be described, atmospheric pressure exists on both sides of the diaphragm 48, permitting spring 50 to force the actuator 40 to the lowest advance or a retard setting position. Application of vacuum to chamber 46 moves diaphragm 48 and actuator 40 toward the left to an engine spark timing advance position, by degree as a function of the change in vacuum level.

Turning now to the invention, the vacuum line 16 consists of two branches 54 and 56 in parallel flow relationship. The branch 54, which may be termed the main branch, contains a conventional one-way check valve 58 having the usual spring pressed ball or other similar device 60 unidirectional in operation. That is, communication between the spark port 28 and servo chamber 46 is usually prevented through line 54 by the seating of ball valve 60 when the pressure level at the spark port is less than that at the servo chamber 46. This, of course, will occur during normal acceleration modes of operation when the intake manifold vacuum is increasing to gradually lower the servo vacuum in chamber 46 and advance the breaker plate 12.

A branch line 56 contains a vacuum reservoir or accumulator 62 consisting of a cylindrical or suitable receptacle having ports 64 and 66 at opposite end connected respectively to the carburetor spark port 28 and distributor servo chamber 46. Adjacent port 66, the reservoir contains an orifice or flow restricting member 68 to provide slow communication of the pressure levels between port 66 and the chamber 70 defined within reservoir 62. The size of the orifice 68, of course, will be chosen to provide the desired delay, in a manner to be described.

Adjacent the opposite end of reservoir 62 is a partition member 72 having a central aperture 74 closed by a unidirectional or one-way check valve 76. The latter consists of a flapper or umbrella type seal having a flexible membrane 78 secured on an axial stem 80. The stem projects through the central bore 74 and is surrounded by a sintered metal type disc or plug orifice 82. The sintered plug 82 consists of randomly oriented and dispersed multitudes of minute metal particles that are bonded together to form labyrinthian type fluid passa'gesconnecting the voids between particles.

Aswill be clear, a pressure level at the carburetor spark port 28, such as during coasting, higher than the level in reservoir 70 will seat check valve 76 and prevent bleed-off of vacuum into the carburetor spark port opening. A lower vacuum in carburetor spark port 28 will unseat check valve 76 and permit only slow equalization of pressure levels between carburetor spark port 28 and reservoir chamber 70, and servo chamber 46 through orifice 68.

In operation, engine-off and engine idle conditions of operation are essentially the same. With a closed throttle valve, carburetor spark port vacuum at port 28 is essentially atmospheric. This unseats main check valve 58 and quickly equalizes the servo chamber 46 pressure level, if not already atmospheric, to that of the spark port, i.e., atmospheric. At starting, the pressure in reservoir 70 generally will also be atmospheric. The atmospheric pressure in servo chamber 46 will be balanced by that on the opposite side in chamber 44, permitting spring 50 to move the breaker plate 12 to its lowest advance or a retard-spark timing setting.

During engine off idle operating conditions, gradual rotation of throttle valve 26 counterclockwise to traverse the carburetor spark port 28 to lightly accelerate the engine increases the vacuum level at the spark port proportionately. Immediately, the lower pressure or vacuum in branch 54a than in 54b ofline 54 maintains the main check valve 58 seated, while the lower vacuum in port 64 than in chamber 70 opens check valve 76. The pressure level in chamber 70, therefore, immediately bleeds slowly through sintered metal orifice 82. This slow bleed is reflected through the second orifice 68 into port 66 so that servo chamber 46 slowly decreases in pressure level below atmospheric. This results in the atmospheric pressure in chamber 44 slowly overcoming the force of spring 50 and moving breaker plate 12 in an advance direction as a function of the changes in vacuum at the carburetor spark port and delay occasioned by the sizes of the sintered metal orifice 82 and the orifice 68. Therefore, it will be seen that under normal light acceleration operating conditions, with a slowly increasing throttle opening increasing the vacuum level, the distributor breaker plate 12 will slowly be moved toward a maximum advance setting position. This is represented by the curve AB in FIG. 2, where spark advance is plotted versus time.

If now, the vehicle operator removes his foot from the accelerator pedal, a deceleration condition of operation occurs. Closing of the throttle immediately raises the carburetor spark port 28 pressure level essentially to atmospheric. This is immediately reflected by the closing of the reservoir check valve 76, to prevent bleed of the vacuum in chamber 70 through the spark port, and the opening of main check valve 58 due to the vacuum in branch 54b. This immediately results in a quick equalization of the pressure level in servo chamber 46 to that at the spark port, resulting in spring 50 moving the breaker plate 12 to a lower advance setting or to its maximum retard setting. The setting, of course, will depend upon the position of the throttle valve. If it is returned to its idle speed position shown, then the breaker plate setting will essentially be the maximum retard setting. If, however, the driver only relaxes his foot on the throttle, and it returns only partially to an idle speed setting and, therefore, only partially decays the vacuum at the carburetor spark port, then the total decay in vacuum at the servo chamber 46 will be less than for a closed throttle decel condition, with a resultant less of a reduced setting of the distributor breaker plate. The former condition is represented graphically in FIG. 2 by the line BD showing the decay in spark port vacuum. As soon as the throttle valve is returned to its idle condition, from say a maximum advance setting, the spark port vacuum moves from the maximum advance point B to the maximum retard point D. If the throttle is not returned to a full idle position, the setting will be somewhere along the line BD.

As soon as the pressure levels at the spark port and servo are equalized, main check valve 58 will again close. During this brief interval, the vacuum in reservoir chamber 70 will bleed slowly through orifice 68 into the open line 54b past the open check valve 58. This is represented by the curve BE in FIG. 2, and will move along the curve BC as a function of the length of time of the decel condition, i.e., the length of time that the throttle is maintained in the decel position. As soon as main check valve 58 closes, the continuing bleed of vacuum from chamber 70 through orifice 68 and line 54b will again permit opening of check valve 58 to maintain servo chamber 46 at the pressure level at the spark port. Therefore, the check valve 58 will oscillate or essentially be maintained in an equilibrium position maintaining the servo chamber 46 at the pressure level of the spark port with a continuing slow decay in the vacuum reservoir chamber 70. This slow decay will essentially follow the curve BC in FIG. 2.

Assume now that the vehicle operator wishes to resume the normal cruising or accelerating operation, and, therefore, again depresses the vehicle'accelerator pedal to rotate throttle valve 26 past the carburetor spark port. A gradual depression immediately increases the vacuum in lines 56 and 54, which seats main check valve 58 and opens reservoir check valve 76. Simultaneously, the reservoir vacuum is reflected in servo chamber 46 through bleed orifice 68 so as to quickly pivot the breaker. plate 12 to a more advanced setting that will be close to the previous setting, and determined by the amount of leakage permitted through orifice 68 when the decel condition was in operation. That is, how close to the prior setting the breaker plate will be moved will depend upon how long the vehicle was in the decel condition of operation permitting continued decay of the vacuum in chamber 70, as indicated by, say, the line EF in FIG. 2.

The carburetor spark port vacuum has decayed as indicated by the line BD. However, the reservoir vacuum in chamber 70 has decayed along the line BC to BE, and the rapid recovery of the spark setting is along the E to F. Point E, of course, indicates the point at which the breaker plate setting is located immediately upon shutting of check valve 58 upon reacceleration of the engine. The line EF represents the time interval it takes for the vacuum level in the induction passage to build up to its formal level. If it were not for the reservoir and orifice 68, the normal build up of vacuum would be delayed by orifices 82 and 68 to follow the curve GH.

On the other hand, a heavy depression of the accelerator pedal causes the spark port vacuum to decay essentially to atmospheric pressure and conditions again are similar to a deceleration operation. However,.now the vacuum increases at the spark port, which then will shut check valve 58, open check valve 76, and permits a final slow advance again through orifice 82 after the reservoir vacuum has returned the servo vacuum to its level.

Summarizing, in FIG. 2, the line AB illustrates the slow buildup of vacuum at the distributor servo by means of the orifices 82 and 68. The line BD represents the quick decay in spark port vacuum to essential atmospheric pressure upon return of the throttle valve to an idle speed position, the reservoir vacuum at this time decaying slowly through the closed check I valve 76 and the orifice 68 along the line BC. If reacceleration is desired prior to the total decay of the vacuum in the reservoir, such as, for example, at point E, opening of the throttle valve raises the vacuum level at the spark port to a point above the reservoir vacuum so that main check valve 58 seats at point B and the higher vacuum at the spark port is slowly communicated through the open check valve 76 and sintered orifice 82 and orifice 68 into servo chamber 46 to move the breaker plate back to a maximum advance setting. The curve GH in FIG. 2 would represent the condition of recovery of the vacuum at the servo were it not for the reservoir chamber 70, since then there would only be a slow buildup of the vacuum at the spark port through the orifice 82.

HO. 2 also represents the various conditions of operation if only certain portions of the control of FIG. 1 were used. A system with orifice 82 only is represented by curve A to B during acceleration and curve B to C during deceleration. Delay time for acceleration and deceleration are equal. This system would be unsatisfactory during fast acceleration from constant speeds that have full spark advance since the engine requires a lower spark advance at this time. Not capable of achieving this, spark knock would result.

A system with orifice 82 and main check valve 58 corrects spark knock problem described above. The check valve 58 equalizes the vacuum at the distributor vacuum chamber 46 to the spark port vacuum.

Both systems described above, however, are poor for fuel economy since the retarded setting provided requires longer burning into the expansion cycle of the engine when it would not be doing useful but wasteful work. Once the spark advance has dropped to or towards the initial setting, it requires the long delay time through the orifice 82 to reach the cruise speed spark advance. This delay time would be equal to A to B The system of the invention has the advantage of quick spark recovery for fuel economy improvement. As an example, if after accelerating from A to B, the vehicle was decelerated from B to D with a foot-off gas pedal condition, the vacuum advance would drop to its initial setting. If after, say, four seconds, the vehicle was again accelerated to its previous cruise position, the spark advance would quickly recover as shown by curve E to F; whereas a system without the reservoir would be longer, as shown by curve G to H. The fast recovery of the invention, of course, is due to the vacuum reservoir and location and the size of the restriction of both orifices 82 and 68.

From the above, it will be seen that the invention provides for normal spark advance by slow buildup in vacuum in the reservoir chamber 70 through the sintered metal orifice 82 so that lower peak combustion temperatures and pressures are obtained resulting in less exhaust emission of pollutants. It will also be seen that for engine performance, opening of check valve 58 immediately equalizes the servo pressure level to that at the spark port and thereby reduces the advance setting of the distributor to prevent spark detonation. It will also be seen, that upon a temporary deceleration condition of operation, reacceleration to return to or towards the previous setting provides a rapid recovery of the distributor breaker plate to essentially its former setting be seating of the main check valve 58 and equalization of the servo vacuum chamber to that of the reservoir vacuum through the orifice 68, with a subsequent raising of the vacuum level in proportion to the higher vacuum in the induction passage.

I claim:

1. A spark timing control system comprising, an engine carburetor having an induction passage containing a spark port located above the idle speed position of a throttle valve controlling flow through the passage and subject to the change in pressure level in the carburetor as a function of the movement of the throttle valve from its idle speed position, an engine distributor having a breaker plate pivotally movable in opposite directions to advance and retard the spark timing, vacuum controlled servo means connected to said breaker plate for moving the same, conduit means connecting said spark port and servo means, and slow-fast flow rate control means in said conduit means to control the rate of change of application of vacuum from said spark port to said servo means, said control means including faster flow rate means operable in response to a change in the vacuum at said spark port to a lesser pressure depression than at said servo means to quickly equalize the pressure level at said servo means to that at the spark port, and slower flow rate means in a fluid flow circuit bypassing said faster flow rate means, said slower flow rate means including a fluid reservoir open at one end to said spark port and open at its opposite end to said distributor servo means and containing a pair of flow restricting means one adjacent each end, the flow restricting means adjacent the spark port end of said reservoir being unidirectional with respect to flow, said flow restricting means being operable in response to a change in the depression at said spark port to a greater pressure depression than at the servo means permitting flow through said unidirectional means to delay the equalization of the pressure level at the servo means to that at the spark port to delay the spark timing change, the pressure level in said reservoir rapidly returning the spark timing setting to a higher setting by a greater depression of the pressure level at said servo means than the change in vacuum level at said spark port upon a momentary deceleration and subsequent reaccelerating condition of operation, said subsequent reacceleration closing said faster flow rate control means.

2. A system as in claim 1, said faster flow rate control means comprising a one-way check valve permitting flow in a direction from the spark port to the servo means only.

3. A system as in claim 1, said slower rate flow restricting means comprising an orifice adjacent one end of said reservoir and a one-way check valve at the opposite end.

4. A system as in claim 3, said one-way check valve having a restricted flow area in its open flow condition of operation.

5. A system as in claim 3, said faster rate flow means comprising a one-way check valve operable in a direction opposite to that of said slower flow rate one-way check valve means.

6. A spark timing control system comprising, an engine carburetor having an induction passage containing a spark port located above the idle speed position of a throttle valve controlling fiow through the passage and subject to the change in vacuum in the induction passage as a function of the movement of the throttle valve from its idle speed position, an engine distributor having a breaker plate pivotally movable in opposite directions to advance and retard the spark timing, vacuum controlled servo means connected to said breaker plate for moving the same, conduit means connecting said spark port and servo means, and slowfast flow rate control means in said conduit means to control the rate of change of application of vacuum from said spark port to said servo means, said control means including slower rate flow restricting means in the conduit means delaying communication of lower pressure levels at the spark port to the servo means, fast rate open-close flow means operably movable to an open position upon the attainment of a higher pressure level at said spark port than at said servo means to immediately equalize the pressure levels and reduce the spark timing setting, and further means operable at times to override the action of the flow restricting means upon the closing of said flow means to immediately return the servo means to near the pressure level thereof attained prior to operation of said flow means to thereby immediately return the spark setting to essentially the

Claims

6. A spark timing control system comprising, an engine carburetor having an induction passage containing a spark port located above the idle speed position of a throttle valve controlling flow through the passage and subject to the change in vacuum in the induction passage as a function of the movement of the throttle valve from its idle speed position, an engine distributor having a breaker plate pivotally movable in opposite directions to advance and retard the spark timing, vacuum controlled servo means connected to said breaker plate for moving the same, conduit means connecting said spark port and servo means, and slow-fast flow rate control means in said conduit means to control the rate of change of application of vacuum from said spark port to said servo means, said control means including slower rate flow restricting means in the conduit means delaying communication of lower pressure levels at the spark port to the servo means, fast rate open-close flow means operably movable to an open position upon the attainment of a higher pressure level at said spark port than at said servo means to immediately equalize the pressure levels and reduce the spark timing setting, and further means operable at times to override the action of the flow restricting means upon the closing of said flow means to immediately return the servo means to near the pressure level thereof attained prior to operation of said flow means to thereby immediately return the spark setting to essentially the prior setting in response to the attainment of a lower pressure level at said spark port than at said servo means.

7. A system as in claim 6, said further means including a vacuum reservoir.

8. A system as in claim 7, said reservoir means including a pair of orifices one at each end connected in flow control relationship respectively to said servo means and spark port, the orifice adjacent said spark port being the flow restricting means and opening through a one-way check valve permitting flow from said servo means to said spark port only.