US3457905A - Ignition distributors - Google Patents

Description

July 29, 1969 N. A. JUKES 3,457,905

IGNITION DISTRIBUTORS Filed July 27, 1967 x3 4: H 2' \6 E 23m r 04 5a 22 E? a 27 24 :3 t; 3|

:1 a gg L- FIG! 53 II .I v 8 H! II H 5 IO I HII-I United States Patent M 3,457,905 IGNITION DISTRIBUTORS Norman Alfred Jukes, Walsall, England, assignor to Joseph Lucas (Industries) Limited, Birmingham, England Filed July 27, 1967, er. No. 656,585 Claims priority, application Great Britain, Aug. 19, 1966, 37,250/66 Int. Cl. F02p 5/02, 5/10 US. Cl. 123-117 5 Claims ABSTRACT OF THE DISCLOSURE This invention relates to ignition distributors for road vehicles, of the kind comprising a casing, a rotatable shaft extending within the casing and carrying the distributor arm and a contact breaker assembly supported Within the casing for angular movement relative to said shaft, and including a fixed contact and a movable contact, said movable contact being movable into and out of engagement with said fixed contact in response to rotation of said shaft.

According to the invention a distributor of the kind specified includes a first vacuum unit slidably supported on the casing, a second vacuum unit secured to the casing, means interconnecting the first and second vacuum units so that operation of the second vacuum unit causes sliding movement of the first vacuum unit relative to the casing, further means interconnecting the first vacuum unit and the contact breaker assembly so that operation of the first vacuum unit while the second vacuum unit is at rest moves the assembly angularly from a zero position, which it occupies when both the first and the second vacuum units are at rest, in a direction to advance the ignition timing of the distributor and operation of the second vacuum unit while the first vacuum unit is at rest moves the contact breaker assembly, through the first vacuum unit and said further means, angularly from said zero position in a direction to retard the ignition timing of the distributor.

The invention further resides in an ignition timing system utilizing ignition distributor as specfied in the preceding paragraph.

One example of the invention is illustrated in the accompanying drawings wherein:

FIGURE 1 is a partly diagrammatic representation of a distributor and its associated ignition timing system, and

FIGURE 2 is a sectional view of the distributor shown in FIGURE 1.

Referring to the drawings, the distributor includes a casing having rotatable therein an axially extending shaft 11 the periphery of which is shaped to define a cam surface 12. Surrounding the shaft 11 and supported for angular movement relative thereto is an annular plate 13. The plate 13 carries the fixed and movable contacts 14, 15 of the distributor, the movable contact 15 having a cam follower 16 associated therewith. The cam follower 16 engages the cam surface 12, rotation of the shaft 11 serving to open and close the contacts 14, 15 and angular 3,457,905 Patented July 29, 1969 movement of the plate 13 serving to adjust the timing of the distributor in known manner.

A first vacuum unit 17 is mounted on the casing for sliding movement and the diaphragm 18 of unit 17 is connected to the plate 13 by a link 19, conveniently in the form of a tension spring.

A push rod 21 is slidably received in the casing 10 and extends between the body of the unit 17 and the diaphragm 23 of a second vacuum unit 22, the unit 22 being secured to the casing 10 and the arrangement being such that movement of the diaphragm 23 is transmitted to the unit 17 through the rod 21.

The unit 17 is connected by way of a conduit 24 to the air inlet side of a carburetor 25 near to the throttle butterfly valve 26 thereof and by way of a conduit 27 to a two position spool valve 28, the unit 22 being connected by way of a further conduit 29 to the valve 28.

The valve 28 serves in the first position of the spool to close the conduit 27 and to connect the conduit 29 to atmosphere, and in the second position of the spool to connect the conduit 27 to atmosphere and to connect the conduit 29 to the engine manifold side of the carburetor.

During normal running of the engine the throttle butterfly valve 26 is open and the valve 28 is in its first position. Thus the unit 22 is in its rest position, both sides of the diaphragm 23 being subjected to atmospheric pressure and the rod 21 and consequently the unit 17 being in their extreme right hand positions as seen in the drawings. The unit 17, is however, subject to the depression at the air inlet side of the carburetor and changes in this depression serve to move the plate 13, through the intermediary of the diaphragm 18 and the link 19, from the zero position it occupies when both the units 17 and 22 are in their rest position, in a direction to advance the timing of the engine, return movement of the plate 13 towards its zero position being accomplished by a spring 18a acting on the diaphragm 18.

When the throttle butterfly valve 26 is closed, the spool of the valve 28 is moved to its second position, and owing to the closure of the valve 26 a high depression exists at the engine manifold side of the carburetor. The unit 17 returns to its rest position, since both sides of the diaphragm 18 are now open to atmosphere and the plate 13 is returned to its zero position. However, the unit 22 is subjected to the high depression at the engine manifold side of the carburetor 25 and the unit 17 is moved to the left by movement of the diaphragm 23. This movement serves through the link 19 to move the plate 13 from its zero position in a direction of retard to timing of the engine. Return movement of the plate 13 from its retarded position to its zero position is effected by a spring 23a acting on the diaphragm 23.

The spool of the valve 28 is moved either through a mechanical linkage 31 associated with the accelerator pedal of the vehicle or by a pneumatic linkage 32 (shown in dotted lines in FIGURE 1) responsive to the engine manifold depression.

The ignition system previously described is used in a vehicle having exhaust emission control. It is known that when internal combustion engines are run with their throttle valves closed, for example when idling or during overrun, incomplete combustion of the fuel entering the engine takes place and there is conseqently a high percentage of noxious, unburnt, hydro-carbons in the exhaust products of the engine. In order to minimise the amount of unburnt hydro-carbons in the exhaust products it has been proposed to provide means 33 for allowing extra air to enter the engine 34 during closed throttle conditions to ensure complete combustion of the fuel. However, this more efiicient combustion of the fuel leads to an increase in engine speed which is undesirable both during idling and overrun conditions. The use of the systern described ensures that during closed throttle conditions the increase in engine speed due to the more efiicient combustion is negated by retarding the ignition of the engine.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. An ignition distributor, for a road vehicle, including a casing, a shaft mounted for rotation in the casing, a distributor arm carried by said shaft, a contact breaker assembly operable in response to rotation of said shaft and mounted within the casing for angular movement relative to said shaft, angular movement of the contact breaker assembly relative to said shaft varying the ignition timing of the distributor, a first vacuum unit secured to said casing, a second vacuum unit mounted for sliding movement on the casing, first connecting means operatively connecting said second vacuum unit to said contact breaker assembly, whereby operation of the second vacuum unit, while the second vacuum unit is stationary relative to said casing, moves the contact breaker assembly in a first direction, second connecting means operatively connecting the first vacuum unit to the second vacuum unit whereby operation of the first vacuum unit while the second vacuum unit is inoperative moves the contact breaker assembly, through the second vacuum unit and the first connecting means in a direction opposite to said first direction, said contact breaker assembly having a zero position which it occupies when both the first and th second vacuum units are inoperative, and movement of said contact breaker assembly in said first direction from said zero position serving to advance the ignition timing of the distributor while movement of said contact breaker assembly in said opposite direction from said zero position retards the ignition timing of the distributor.

2. An ignition distributor as claimed in claim 1 in combination with an inlet manifold, an associated throttle valve, and a valve means to form an ignition timing system, the valve means movable from a first position which it occupies during normal running of the engine of the vehicle, and in which it serves to connect the first vacuum unit to the inlet manifold of the engine, and to connect the second vacuum unit to atmosphere so that variations in the manifold depression during normal running serve through the first vacuum unit to advance the ignition timing of the distributor from said zero position, to a second position which it occupies 4 when the engine is running with its throttle valve closed and in which the valve means serves to connect the first vacuum unit to atmosphere and to connect the second vacuum unit to the inlet manifold, so that the high depression which occurs in the manifold when the engine is running with its throttle valve closed is utilized to retard the ignition timing of the distributor from said zero position.

3. A combination as claimed in claim 2 wherein said valve means is operatively connected to the throttle valve of the engine so that as the throttle valve is moved from an open position to a closed position said valve means is moved from its first position to its second position, and as the throttle valve is moved from a closed position to an open position said valve means is moved from its second position to its first position.

4. A combination as claimed in claim 2 wherein said valve means is operatively connected to the inlet mani fold of the engine so that when the depression in the manifold rises above a predetermined value said valve means is moved from its first to its second position and When the depression in the manifold falls below a predetermined value said valve means is moved from its second to its first position.

5. A combination as claimed in claim 2 further in combination with an internal combustion engine having means for allowing extra air to enter the engine during closed throttle conditions, to ensure substantially complete combustion of the fuel entering the engine.

References Cited UNITED STATES PATENTS 2,091,924 8/1937 Harmon 123-117.1 2,557,527 6/1951 Colvin et al. 123-117.1 2,731,523 l/l956 Downing 123-117.1 3,027,884 4/1962 Bale. 3,272,191 9/1966 Walker 123-117.1

FOREIGN PATENTS 616,940 8/1935 Germany.

WENDELL E. BURNS, Primary Examiner US. Cl. X.R. 123-97

Images