US2864353A - Spark advance, vacuum-electric control - Google Patents

Description

Dec. 16, 1958 M. MALLORY, JR Y SPARK ADVANCE, VACUUM-ELECTRIC CONTROL 2 Sheets-Sheet 1 Filed April 11, 1957 IN VEN TOR.

MAR/0N MALL 0R Y/R.

BY SM/rwzsmlzwl/mf Dec. 16, 1958 M. MALLORY, JR 6 SPARK ADVANCE, VACUUM-ELECTRIC CONTROL Filed April 11, 1957 2 Sheets-Sheet 2 IE1 Er=E 69 INVENTOR. MAR/0N MALLoRY JR.

SMITH, Ozsmlmfl/M A TTOANEK? SPARK ADVANCE, VACUUM-ELECTRIC CONTROL Marion Mallory, In, Detroit, Mich.

Application April 11, 1957, Serial No. 652,123

2 Claims. (Cl. 123-117) This invention relates to engine ignition systems, and particularly to dual point circuit breaker mechanisms employing two sets of circuit breaker contacts having overlapping closure periods. The invention is an improvement on the system and apparatus disclosed in U. S. Patent No. 1,663,207, issued March 20, 1928.

In the ordinary circuit breaker a single electrical switch both closes and opens the circuit. In the dual point ignition system there are two electrical switches, one closing the circuit and the other opening it. There is never any flashing in the contacts that close the circuit because they never open the circuit. Naturally there is never any corrosion, scale or pitting in the contacts that close the circuit and the current always flows freely through the primary winding of the coil, saturating or magnetizing the coil core to its maximum. During the time both circuit breakers are closed there is bound to be a free flow of primary current through the coil because the surface resistance of two sets of contacts is only one-half the surface resistance of one. Therefore, a good electrical circuit is always established.

With todays high compression eight cylinder engines it is very necessary to have a hot, high voltage spark. To obtain this with a single circuit breaker, the circuit breaker must be gapped closely, and with present day 12- volt electrical systems this causes excessive flashing of the circuit breaker and short life. With dual circuit breakers, a wide spacing can be used, still obtaining a long duration of coil saturation time or dwell with no excessive flashing.

Objects of the present invention are to provide an overlapping dual point ignition system wherein:

(1) Rotary timing vadvance plates and vacuum-piston type advance mechanisms are eliminated while still attaining desired spark advance for better fuel economy at light engine loads.

(2) Spark advance is attained electrically rather than mechanically so as to reduce the time lag between change in engine load and corresponding change in spark advance, the arrangement being such as to obtain increased fuel economy and freedom from advance plate sticking and failure of mechanical vacuum advance structures.

(3) At idle or low manifold vacuum when the engine is under heavy load the overlapping dual point principle is in operation, with the circuit breaker which opens last doing the timing of the engine. When manifold vacuum becomes high and the engine is under light load the circuit breaker which opens last is disconnected through a vacuum-operated electric switch. Thisv automatically causes the breaker which opens first (approximately eight degrees ahead of the breaker which opens last) to control the timing of the engine, therefore automatically advancing the ignition timing for light engine load and decreasing contact dwell or coil saturation time; because only one breaker is in operation at light engine loads the average breaker point temperature is decreased so as to increase contact point life.

(4) The circuit breaker components maybe constructed as relatively low cost items by elimination of the relatively costly movable advance plate and vacuum piston type advance mechanism therefor.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

In the drawings:

Fig. 1 is a plan view of a distributor constructed according to the present invention with its cap removed for illustration purposes, said distributor being shown in position of use relative to the spark coil, condenser, and vacuum-operated switch unit for controlling the distributor action.

Fig. 2 is asectional view on line 2-2 in Fig. 1.

Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

In the drawings there is shown an internal combustion engine ignition system including a line 10 leading from the conventional ignition switch (not shown) to terminal 12 for the primary winding of a single induction spark coil 14. The other primary winding terminal 16 is connected through lines 18 and 19 to condenser 20 and circuit breaker terminal 22.

Terminal 22 is exteriorly insulated and projects through metallic distributor casing 24 into electrical connection with a .line 26. Casing 24 is provided with the conventional Bakelite cap (not shown) and rotor-segment structure for distributing secondary current from coil 14 t0 the engine spark plugs. Secondary current is carried from the coil secondary to the distributor cap via line 25.

Line 26 engages an insulating washer 27 located one'ar 28 of a metallic mounting bracket 29. Bracket 29 is fixedly secured to a subjacent supporting plate 30 by means of screws 31, said plate 30 being fixedly carried by metallic casing 24.

A second insulating washer 32 is positioned against the other face of ear 28 so as to receive one end of a leaf spring 33, the assembly of elements 33, 32, 27 and 26 being supported on car 28 by means of a bolt 34 and nut 35. The other end of spring 33 is secured to a metallic circuit breaker arm 36, which is mounted for pivotal movement on a pin 37 carried by bracket 30. A fiber bushing 39 insulates arm 36 from pin 37.

Breaker arm 36 includes a plate 38 which carries a contact point 40. Bracket 29 is provided with an upstanding ear 41 which carries a registering point 42.

Opening and closing of points 40 and 42 is accomplished by means of the conventional distributor shaft 43 having a cam surface or lobe for each of the engine cylinders, the illustrated shaft having eight lobes 44 through 51 so as to be used with an eight cylinder engine. It will be appreciated that the number of lobes could be varied in accordance with the number of en gine cylinders since the invention is capable of use with engines having any number of cylinders. During rotation of shaft 43 cam surfaces 44 through 51 ride on extension 52 of arm 36, with spring 33 biasing said arm in the arrow 53 direction so as to maintain extension 52 against the adjacent cam surface, the arrangement being such that points 40 and 42 are opened and closed in accordance with the rotated position of shaft 43.

A second set of contact points 40', 42 receives current from an insulated terminal 54, which is connected with Patented Dec. is, 1958 f terminal 22 by means of conductors 55 and 56, and switch unit 57. The mounting mechanism for points 40, 42' is similar to that employed in conjunction with points 40, 42 and similar reference. numerals are therefore used.

Switch unit 57 is mounted on casing 24 by means of a bracket 58 and screws 59 and 60, with screws 60 extending into a Bakelite housing section 61. Housing section 61 is provided with a terminal which includes a screw 63 retained in section 61 by means of a lock washer 64. Screw 63 serves to mount one end of conductor 56 as well as a leaf spring 65. Spring 65 is stressed to move in the arrow 66 direction. The free end of spring 65 carries a switch contact 67 which registers with a contact 68 carried on the lower face of a screw-type terminal 69. Flat washer 70 cooperates with lock washers 71, 72 and nuts 73, 74 to retain terminal 69 and the adjacent end of conductor 55 in fixed position on housing section 61. When contacts 67 and 68 are engaged with each other (as in Fig. 2) current flow is through conductor 56, flat washer 75, spring 65, contacts 67 and 68, terminal 69, and conductor 55. Movement of spring 65 in the arrow 66 direction separates contact 67 from contact 68 so as to interrupt current flow.

Screws 60 (Fig. 1) not only extend through bracket 58 and Bakelite section 61 but also into a metallic housing 76, the arrangement being such that members 58, 61 and 76 are tied together as a rigid assembly. Housing 76 is provided with a cylindrical bore 77 which forms a cavity 78. A piston 79 is slidably received in bore 77 and carries an insulating washer 80 for preventing short circuit from steel abutment washer 81 through the piston. A com ression spring 82 urges the piston toward the outer end of bore 77.

The bore end wall is provided with an opening which mounts one end of a vacuum line 84, the other end of said line being connected to a fitting 85 screwed into the wall of a carburetor 86. Fitting 85 communicates through opening 87 with the space just upstream from throttle valve 88, the arrangement being such that as the throttle valve is opened line 84 is put in communication with the engine inlet manifold. The vacuum within the manifold is thereby effective through line 84 to move piston 79 downward against the action of spring 82. Spring 65 is a relatively light spring so that its effect on piston 79 is negligible. Spring 82 is so calibrated that nine to eleven inches of mercury manifold vacuum is required to move piston 79 downward so as to allow spring 65 to move contact 67 away from contact 68. Spring 82 may be replaced with a differently calibrated spring to obtain different switch-operating vacuums.

Operation of the Fig. 1 apparatus is such that when the manifold vacuum is low switch contacts 67 and 68 are closed so as to close the circuit through conductors 55 and 56. Some of the spark coil primary current into terminal 22 therefore fiows through members 56, 57 and 55 to terminal 54. The remaining spark coil primary current flows from terminal 22 through line 26, and eventually through points 40, 42 to plate 30 and out to ground. The current at terminal 54 flows through line 26', and eventually through points 40', 42' to plate 30 and out to ground.

The mounting mechanisms for points 40, 42, 40 and 42 are so positioned that points 40 and 42 close before points 40' and 42', as for example by about eight shaft degrees. For approximately the next fifteen degrees both sets of points are closed, for approximately the next eight degrees only points 40', 42' are closed, and for the last fourteen degrees both sets of points are open. This arrangement causes the primary coil circuit to be closed by points 40, 42 and to be opened by points 40', 42' with an overlapping period when both sets of points are closed. The arrangement is advantageous by reason of minimum flashing, minimum corrosion, minimum scale or pitting, and low point surface resistance, while increast 4 ing dwell time or coil saturation time to increase coil efficiency.

At cruising speeds under low load conditions fuel economy is enhanced by advancing the spark from its position at high load conditions. The manifold vacuum is increased at low load conditions so as to act through piston 79 to open the circuit through switch unit 57. As a result all of the current at terminal 22 must flow through points 40, 42. Since these points open approximately eight degrees before points 40', 42 the spark is auto matically advanced by eight distributor shaft degrees or sixteen engine degrees, which is the most favorable advance for enhanced fuel economy.

It will be noted that the change in spark advance is accomplished electrically rather than mechanically, i. e., by switch unit 57 rather than through a linkage system operating between a vacuum unit and rotary advance plate or other mechanical means. At a result the change in spark advance occurs almost instantaneously after change in manifold vacuum with no time lag due to mechanical play of parts. Additionally all rotary support structure for the advance plate is eliminated so as to provide a relatively simple low cost construction. The piston shown in Fig. 2 is fairly light and quickly responsive to vacuum change as compared with the conventional diaphragm structure employed in most previous vacuum units, although other types of pressure responsive movable wall structures can be employed for operation of the switch in accordance with the invention herein disclosed. It will be noted that the control mechanism is located at a point remote from the carburetor 86; consequently when the control mechanism employs a rubber diaphragm-type movable wall gas from the carburetor does not tend to enter into the mechanism housing so as to ruin the diaphragm. The mechanism can be constructed as a relatively low cost structure which gives trouble free performance over a long service life. It can be utilized both with distributors having the conventional centrifugal advance and with distributors not so equipped.

I claim:

1. In an engine ignition system, mechanism for in terrupting spark coil primary current comprising a support structure; first and second contacts fixedly carried by said support structure; first and second breaker arms movably carried on said support structure; third and fourth contacts carried by the breaker arms in registry with respective ones of the first and second contacts; spring means urging the breaker arms to positions wherein the two sets of contacts are closed; a distributor shaft having cam surfaces engaged with the breaker arms for sequentially opening the contacts; a terminal for each set of contacts; a switch housing section of dielectric material; a second housing section secured to said switch section and having a cylindrcial bore therein; a piston within said cylindrical bore; a compression spring between the piston and bore end wall; a vacuum line connected with the space between the piston and bore end wall; third and fourth switch terminals carried on said switch housing section; a first switch contact carried by said third terminal; a light spring arm carried by the fourth terminal and extending between the piston and first switch contact; a second switch contact carried by the spring arm in registry with the first switch contact, said spring arm biasing the second switch contact away from the first switch contact and toward the piston; conductor means connecting the third switch terminal with one of the contact terminals; and conductor means connecting the fourth switch terminal with the other contact terminal.

2. In an engine ignition system, mechanism for interrupting spark coil primary current comprising a fixed support structure; first and second contacts fixedly carried by said support structure; first and second breaker arms movably carried on said support structure; third and fourth contacts carried by the breaker arms in registry sequentially opening the contacts; a terminal for each set of contacts; a switchhousing section of dielectric material; a second housing section secured to said switch housing section and having a cavity therein; a movable wall closing said cavity; a compression spring between the movable wall and cavity end wall; a vacuum line connected with the cavity; third and fourth switch terminals carried on said switch housing section; a first switch contact carried by said third terminal; a light spring arm carried by the fourth terminal and extending between the movable wall and first switch contact; a second switch contact carried by the spring arm in registry with the first switch contact; said spring arm biasing the second switch contact away from the first switch contact toward the movable wall and conductor means connecting the third switch terminal with one of the contact terminals; and conductor means connecting the fourth switch terminal with the other contact terminal.

References tCited in the file of this patent UNITED STATES PATENTS 1,926,781 Mallory Sept. 12, 1933

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