US3712279A

US3712279A - Vacuum spark advance cutoff

Info

Publication number: US3712279A
Application number: US00094362A
Authority: US
Inventors: R Vartanian
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1970-12-02
Filing date: 1970-12-02
Publication date: 1973-01-23
Anticipated expiration: 1990-01-23
Also published as: GB1316527A; AU455196B2; CA948056A; AU3360571A; DE2157245A1; JPS5250327B1

Abstract

A mechanical device is inserted between the engine distributor servo actuator and the carburetor spark port comprising an atmospheric air bleed controlled by changes in vacuum level in the spark port during vehicle accelerations from an engine idle speed or any speed without spark port vacuum; the bleed immediately moving the spark timing to a maximum retard position. The device consists of a valve to open and close an air vent in response to a power actuator connected to the spark port and having an orifice interconnecting abutting chambers of the power device.

Description

United States Patent 1 1111 3,712,279 Vartanian 1 1 Jan. 23, 1973 i751 Inventor: inciii'd Divan/1111511, iia'rfidfn.

15 1 VACUUM SPARK ADVANCE CUTOFF 3,476,094 11/1969 Rucins et a1 ..123/117 A Primary Examiner-Laurence M. Goodridge Assistant Examiner-Cort Flint AttrneyJohn R. Faulkner and Robert E. McCollum Mich.

[73] Assignee: Ford Motor Company, Dearborn,

57 ABSTRACT [22] Filed: Dec. 2, 1970 A mechanical device is inserted between the engine distributor servo actuator and the carburetor spark [2H App! 94362 port comprising an atmospheric air bleed controlled by changes in vacuum level in the spark port during [52] US. Cl. ..123/ 117 A vehicle accelerations from an engine idle speed or any [51] Int. Cl ..F02p 5/06 speed i h p r p vacuum; the bleed [58] Field of Search ..123/1l7 mediately moving the spark timing to a maximum retard position. The device consists of a valve to open 5 Ref e Cited and close an air vent in response to a power actuator connected to the spark port and having an orifice in- UNITED STATES PATENTS terconnecting abutting chambers of the power device.

3,606,871 9 1971 Gropp et a1 ....123/117 A 2,361,271 10/1944 Colvin .123/l17 A A a 2,650,581 9/1953 Short ..123/1 17 A 5 Claims, 1 Drawing Figure 3,289,659 12/1966 Koole ..l23/117 A 3,431,897 3/1969 Eltinge ..l23/117 A l J0 Z4- 74- 5a 76 t 42 J4 /2 O 4 JG /6 4 J2/66 O 1 O 636 PATENTEDJANZB 1915 3,712,279

ATTORNEYS VACUUM SPARK ADVANCE CUTOFF This invention relates, in general, to a device that aids in the reduction of exhaust emission pollutants from an internal combustion engine. More specifically, it relates to a mechanical spark timing control device that eliminates carburetor spark port vacuum to the distributor during vehicle accelerations from essentially idle speed conditions to minimize the output of undesirable elements.

Most present day motor vehicles have some sort of a vacuum servo automatically controlling the advance or retard setting of the engine distributor breaker plate as a function of carburetor spark port vacuum to provide good engine performance as well as fuel economy during the different operating conditions of the engine. These vacuum servos, in their simplest forms, generally consists of a housing divided into atmospheric pressure and vacuum chambersby a flexible diaphragm connected to the distributor breaker plate. The diaphragm and breaker plate are normally spring biased to the lowest advance or retard spark timing setting, and carburetor spark port vacuum normally urges the diaphragm in a spark timing advance direction upon opening of the carburetor throttle valve in an engine speed increasing direction.

With the above construction, vehicle accelerations from an idle speed condition cause vacuum at the carburetor spark port to act on the one side of the servo diaphragm to immediately move the distributor breaker plate to an advanced setting. This provides a longer burning time for the fuel mixture before the optimum top or near top dead center position of the piston is attained, generally providing the most desirable operation. However, this longer time permits a build-up to higher combustion temperatures and pressures, which is undesirable insofar as the production of oxides of nitrogen and other undesirable elements are concerned.

It will be seen, therefore, that the conventional spark timing control systems may provide goodperformance and fuel economy, but do not necessarily minimize the output of undesirable exhaust gas elements.

Therefore, it is a primary object of the invention to provide an engine spark timing device that has the advantages of the conventional spark timing control system while minimizing the disadvantages; by providing a device that retards the spark timing during vehicle accelerations, to decrease NO X output, while extending burning of the mixture into the exhaust system to reduce the amount of exhaust gas emission of other undesirable elements.

It is another object of the invention to provide an engine spark timing control system including a device that meets the requirements set out immediately above, by including a power operated atmospheric pressure air bleed in the vacuum line to the distributor servo to bleed spark port vacuum during vehicle accelerations.

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 crosssectional view of an engine spark timing control apparatus embodying the invention.

The FIGURE 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 1 8 contains the usual fixed area venturi 24 and a throttle valve 26. The latter is rotatably mounted on a part of the 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.

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 peak 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 sparkretard 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 spring50. Chamber 44 has an atmospheric or ambient pressure vent, not shown, while the chamber 46 is connected 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 av 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, an air bleed device 52 is located in line 16 between servo l4 and spark port 28. The device 52 includes a valve body 54 defining a three passage fluid chamber 56. Passage 58 is a vent and connects to atmospheric pressure. Passage 60 is connected to servo line 16, and passage 62 is connected through an orifice 64 to spark port 28. Orifice 64 does not materially affect flow, but is merely to prevent intermittent momentary pressure fluctuations from influencing upstream pressure levels.

A valve member 66 is sealingly mounted to slide through a wall of valve body 54, as shown. It alternately seats against passage 58 to block it, or is moved to the position shown, to bleed air into line 60. The upper end of valve 66 is fixed to an annular flexible diaphragm 68, which divides a hollow housing 70 into two fluid chambers 72 and 74. Chamber 72 is connected by a passage 75 to spark port 28 on the upstream side of orifice 64. Chamber 74 is closed, and connected to chamber 72 by a metering orifice or flow restricion 76. A spring 78 normally biases diaphragm 68 and valve 66 to close bleed passage 58.

In operation, at engine start up, both chambers 72 and 74 of device 52, and both sides of the servo 14 are at atmospheric pressure. Accordingly, spring 78 biases valve 66 to close bleed 58, and the distributor breaker plate 12 is rotated to its maximum retard spark timing position.

The condition described above also holds for engine idle speed position, in that the pressure in spark port 28 is essentially atmospheric, or that in the air inlet portion 20.

Assume now that the vehicle accelerates, throttle valve 26 rotating counterclockwise. Immediately, spark port 28 is subject to vacuum in the intake manifold 22. Though low, the vacuum acting through chamber 72 permits the atmospheric pressure in chamber 74 to compress spring 78 and move valve 66 to open bleed passage 58. This maintains passage 60 at atmospheric pressure and, therefore, servo chamber 46. Accordingly, the breaker plate 12 is maintained in the maximum engine spark retard position. As the acceleration of the vehicle proceeds, the build-up in vacuum at the spark port 28 will be reflected in chamber 74 by way of the orifice 76. Once the pressure in the two chambers 72 and 74 are balanced, the spring 78 will close the bleed passage 58 and permit vacuum to be applied to the servo chamber 46 via passage 62. As stated previously, the orifice 64 at this time does not interfere with the flow of vacuum to passage 60 in chamber 46. Accordingly, the breaker plate will be rotated slowly in a spark timing advance direction as a function of the degree of throttle rotation.

If the throttle valve is now suddenly moved to a closed position, indicating a decelerating operation, the atmospheric pressure at spark port 28 and chamber 72 will be ineffective to move the bleed valve 66 from the position closing bleed passage '58. Accordingly, the quickly increasing pressure in spark port 28 will be reflected directly through line 62 311C160 to the servo chamber 46 and move the breaker plate towards the maximum spark retard position. It will be understood, of course, that the lowering of the setting will correspond to the degree of closing of the throttle valve; i.e., if the throttle valve is only partially moved to a closed position, the bleed of vacuum at the spark port will slowly lower the spark port setting.

Subsequent acceleration of the vehicle will again subject spark port 28 to a vacuum and cause an unseating of the bleed valve 66. Therefore, the engine spark timing setting at this time will depend upon whether or not the pressure level at the spark port and chamber 72 is lower than that present in chamber 74. If so, the bleed valve 66 will unseat and immediately condition the breaker plate for a maximum retard setting. If not, the closing of the bleed valve will reflect the spark port vacuum to the servo chamber 46 and position the breaker plate accordingly.

From the above it will be seen that the invention conditions the engine spark timing for a maximum retard setting .at engine idle speed operation and maintains that retard setting during vehicle accelerations from idle speed or from a condition of no spark vacuum at a particular speed. It will also be seen that the device permits normal advance of the spark timing after a predetermined interval of time determined by the orifice between the chambers of the air bleed control device, and that deceleration spark timing is controlled as a function of the movement of the throttle valve to slowly move the breaker plate towards a maximum retard position.

I claim:

1. A spark timing control system comprising, an engine carburetor having an induction passage containing a spark port located just above the idle speed position of a throttle valve controlling flow through the passage and subject to the depression 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 the breaker plate for moving the same, and means for controlling advance and retard of the timing solely as a function of spark port vacuum level changes, the latter means including conduit means connecting the vacuum at the spark port to the servo means, flow rate control means in the conduit means between said spark port and servo means to control the rate of change of application of vacuum from said spark port to said servo means for effecting variable movement of said breaker plate from a maximum retard setting at closed throttle valve idle speed position to a maximum advance setting at high spark port off-idle vacuum levels, and an air bleed means operable in response to a drop in the pressure level at the spark port below its previous level in response to light accelerative movement of the throttle valve to momentarily bleed air to the servo means to move the breaker plate towards a maximum retard setting and subsequently close the bleed to advance the breaker plate setting upon increase in vacuum level at said spark port.

2. A control system as in claim 1, including-second servo means operably connected to said bleed means and to the vacuum at said spark port to be movable thereby.

3. A control system as in claim 1, said bleed means including a valve means operably opened by means movable by vacuum connected thereto from said spark port.

4. A control system as in claim 3, said power means including a vacuum servo having a flexible diaphragm dividing said servo into two pressure chambers connected by an orifice, means connecting said diaphragm to said bleed valve means, spring means biasing said bleed valve means to a closed bleed position, and other conduit means connecting one of said chambers to said spark port.

5. 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 depression 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, and means for controlling advance and retard of the timing solely as a function of spark port vacuum level changes, the latter means including conduit means connecting said spark port and servo means, flow rate control means in the conduit means "said second servo means including a housing containing a movable spring biased diaphragm connected to said valve means and dividing said housing into a pair of chambers with orifice means therebetween, and other conduit means connecting one of said chambers to said spark port, the orifice means providing subsequent equalization of the pressure levels in the chambers after opening of the bleed valve to permit closing of the valve and an advance movement of the breaker plate.

Claims

2. A control system as in claim 1, including second servo means operably connected to said bleed means and to the vacuum at said spark port to be movable thereby.

5. 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 depression 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, and means for controlling advance and retard of the timing solely as a function of spark port vacuum level changes, the latter means including conduit means connecting said spark port and servo means, flow rate control means in the conduit means between said spark port and servo means to control the rate of change of application of vacuum from said spark port to said servo means, an atmospheric pressure air bleed in said conduit means, valve means movable between positions opening and closing said bleed, second servo means connected to said valve means for moving the same and operable at times by and in response to decreases in said spark port pressure level from a previous higher pressure level to open the bleed and thereby momentarily condition the setting of said breaker plate for maximum spark timing retard, said second servo means including a housing containing a movable spring biased diaphragm connected to said valve means and dividing said housing into a pair of chambers with orifice means therebetween, and other conduit means connecting one of said chambers to said spark port, the orifice means providing subsequent equalization of the pressure levels in the chambers after opening of the bleed valve to permit closing of the valve and an advance movement of the breaker plate.