US2252506A - Ignition system - Google Patents

Description

Aug. l2, 1941. H. L HARTzfELL 2,252,506

IGNITION SYSTEM FLLed May 22, 1939 HHH .HIIIIHI l 2 Liz ArroRNEYA,

Patented Aug. 12, 1941 IGNITION SYSTEM Herman L. llartzell, Anderson, Ind., assignor to General Motors Corporation, Detroit, Mich., a

corporation of Delaware Application May 22, 1939, Serial No. 275,007

(Cl. Zilli-38) Claims.

'I'his -invention relates to ignition systems for automotive internal combustion engines and more particularly to the problem of obtaining flat contact operation in an automotive ignition system. y y

I have discovered that transfer of contact metal to the ignition timer is due to a phenomenon which occurs during each separation of the timer contact.` 'I'his phenomenon is beyond the control of those who design and install the ignition system. I have found that transfer of lcontact metal to the positive timer contact is due to a phenomenon which is within the power of the-designer or installer to control. In my copending application, which has now become Parent No. 2,189,899 of February 13, .1940, I propose to deal with the problem of flat contact operation by balancing negative contact transfer with positive contact transfer which I am able to control to a substantial degree. In lthe case of passenger car service, for example, where the engine operates over a relatively wide range of speeds, I overcompensate for negative transfer during the lower' speeds of driving for example around M; P. H. and under compensate at higher speeds so that, Vtaking a period of automobile operation which represents the average of driving conditions, I am able substantially to balance negative contact transfer by transfer to the positive.

I aim to effect substantially flat contact operation by a different method which I disclose in the present application. Instead of providing positive contact transfer to compensate for negative contact transfer I so construct and arrange the ignition system that only transfer 'to thev negative contact will occur at any speed of the engine. It is my belief that each instance of negative contact transfer is substantially less than each instance of positive contact transfer. Therefore in my new method I propose to deal only with negative contact transfer. In order to compensate for transfer to the negative con- .Y tact, I propose to reverse the polarity of the oontacts by means of a polarity reversing switch which will change the polarity of the contacts each time the ignition is turned on by a. manual switch, or to automatically reverse the polarity,

polarity reversing is employed. So far as I am aware, when `polarity reversing switches have been used in ignition system in the past, no attention whatever was paid to the phenomena which caused contact metal transfer. When the timer contacts were connected for one polarity andthe ignition system was operated, it is my belief that positive contact transfer has occurred as well as negative contact transfer during the time that the' timer contacts were connected up for a certain polarity. Then, 'when the .polarity was reversed, there would have been positive contact transfer as well as negative transfer again under the conditions of reversed polarity. Apparently no one was aware of the fact that both kinds of transfer were taking place while the polarity of fer in one direction and negative transfer in the primary current remained the same. Hitherto, it was supposed .that the direction of contact metal transfer. was always the same until the polarity of the contacts hadbeen reversed.

Since I have discovered that negative contact transfer appears to be less in quantity than positive contact transfer, for each instance of transfer of its kind, I take advantage of the fact that transfer to the negative is the lesser of the two evils and design and arrange the system so that 1 obtain only negative transfer. As stated before, I obtain a balance at least to a practical degree by polarity reversing at intervals suiiiciently frequent to effect -a balance between negative transother direction.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing, wherein a preferred embodiment of one form of the invention is clearly shown. y

In the drawing:

Fig. 1 is a diagram of an electrical system for automotive use embodying the present invention.

Fig. 2 shows the polarity reversing switch of Fig. 1 in a different position.'

In the drawing, 20 designates a storage battery which is grounded at 2i. The battery is charged by the usual automotive generator not shown. Battery supplies current for engine ignition and for engine starting. The main starter circuit is shown in heavy lines and comprisesha wire 22 leading to a starter switch terminal 23. The other starter switch terminal 24 connected by a Wire 25 with a series wound starting motor 26 grounded at 21. The motor operates a shaft 28 along which slides a starter drive 30. having a longitudinal spline connection with the shaft 28 and including a one-way or overrunning clutch 3| for connecting the shaft 28 with a pinion 32 movable into mesh with the iiywheel gear 33 of the engine to be started. The drive 30 is moved along the shaft by a lever 34 pivoted on a stud 35 and urged by a spring 36 normally into the position shown wherein the pinion 32 is out of engagement with the flywheel 33. The apparatus for shifting the lever 34 and for completing the motor circuit is disclosed particularly in John B. Dyer Patent 2,005,723, granted Jan. 18, 1938. This apparatus comprises an electromagnet 40 having a coarse winding 4|, which is the main attracting winding, and a holding winding 42 of iiner wire. One end lead 43 of winding 4| is connected with a relay contact 44, the other end of winding 4| is connected by a wire 45 with motor switch terminal 24. The holding coil 42 is connected at one end with ground at 45 and by wire 4'| with relay contact 44. Relay contact 44 is adapted to be engaged by movable contact 48 carried on the end of an armature 49 spring urged into contact open position and against a vstop 50. Relay armature 49 is magnetizable and is attached to one end of a metal frame supported upon the terminal 23 and providing an electrical connection between the contact 48 and the switch terminal 23. The relay includes a core 52 surrounded by an electric magnet winding 53 grounded at 54.

The electromagnet 40 includes also a core or Va link 52 having a pin 63 received by a slot 6.4

in the lever 34. When the magnet 40 isenergized, the plunger 6| will move toward the left so as to move the lever 34 counterclockwise in i order to shift the pinion 32 into mesh with the engine gear 33. This movement of the plunger 6| causes the motor switch to be closed so that the motor 26 will operate on current from the battery 20 to eect the cranking of the engine. The motor switch comprises a movable contact 'I0 insulatingly supported by rod 1| which is guided for sliding movement by the core 60. The rod has a shoulder 'l2 which stops movement of the rod 7| Ftoward the right in which direction it is urged by a spring 13 engaging a stationary part I4 and pressing against a shoulder 'i5V provided by the rod 1|. Between the shoulders 12 and 'l5 of the rod 1| the insulation piece 10a which supports the contact 10 is mounted for sliding movement. Normally the insulation piece 'lila is pressed by the spring 16 against the stop shoulder 15. When the magnet is energized, movement of the plunger 6| causes the rod l! to move toward the left to carry the contact 10 into engagement with the switch terminals 23 and 24. The rod 1| is moved a little further than the normal distance between the contact 'I0 and the terminals 23.and 24 so that,

86 of the ignition switch. After the switch 0I is closed, the engine being nonoperative, the car driver then steps on the accelerator pedal whichcauses a lever 88 of the switch 80 to move in such direction as to close the switch 80 whereupon the relay coil 53 will be connected with the battery 20 and the armature 49 will be'moved downwardly rto cause contact 48 to engage contact 44. When this happens both magnet coils 4| and 42 will be connected with the battery and the plunger 6| will be attracted/toward the left to cause fthe motor pinion 32 to engage the engine gear 33 and the motor switch contact 'I0 to engage the terminals 23 and 24 whereupon the motor 26 will be connected with the battery to start the engine. During the cranking o! the engine by the motor 26, the main attracting coil 4| is short circuited but the electromagnet main tains the plunger k6| in the attracted position by the magnetism provided by the holding coil 42. When the engine becomes self operative the suction developed by the engine isv suiilcient to cause the switch 80 to be opened whereupon-the magnet 53 will be disconnected from the battery, the relay contacts 48 and 44 will open, the magnet 40 will be deenergized and the plunger 8| will be returned to its normal position thru the action of the spring 36 which acts directly upon the lever 34. Then the motor will be disconnected from the battery and the pinion 32 will be demeshed from the engine gear 33.

It will be noted that for each engine starting operation' that is -produced by thev operation of the electromagnet 40 there will be a reciprocation of the link 62. I take advantage of this movement of the link B2 to operate a polarity reversing switch in the ignition system which I will now describe. The ignition system comprises an ignition coil having a primary winding |00 connected at one end with ignition switch terminal 85 and yat the other end with terminal |2| of polarity reversing switch |20. The ignition coil has a secondary winding |0| connected at one endwith ground and at the other end with `the center terminal |02 of an ignition distributor '|035 which includes a rotor |04 for distributing sparking impulses to spark plug cable terminals |05 each connected by a cable with a spark plug |06 which is grounded thru the engine as indicated at |01.

TheA ignition timer includes'a cam ||0 driven by the engine thru a shaft which drives also the rotor |02. The cam ||0 is engageable with the rubbing block carried by a lever ||2 which is pivoted at ||3 and which carries a contact |4 engageable with a contact H5.` Lever ||2 is connected electrically with a terminal ||6 by a thru the spring 16 which is additionally compressed. the contact 'l0 will be held in rm engagement with the terminals 23 and 24.

The operation of electromagnet is effected in response to the operation of the automobile accelerator pedal, providing the engine is not self operating. `For this purpose there is provided an accelerator-pedal-closed and engineesuctionopened switch having one terminal 8| connected with the relay coil 53 and the'4 other terminal 82 connected with a switch contact 83 which is one of three equiangularly spaced stationary contacts.83, 84 and 85 adapted to be concurrently connected by the movable contact spring which urges the lever ||2 toward the cam ||0. A condenser ||8 is in parallel with the contacts H4 and ||5. Timer terminal .Hl is connected with reversing switch terminals |22 and |23. Terminal |24 is grounded-and therefore is always of negative polarity. Contact |2| is always of positive polarity. The contact |25 which is connected with timer contact ||5 will be of negative polaritywhen connected with contact |24, as shown in Fig. 1, or oi positive polarity when connected with contact |2|, as shown in Fig. 2. likewise timer terminal ||8 will be of positive polarity when positive contact |2| is connected with contact |22 as shown in Fig. 1; and timer terminal ||6 .will be `of negative polarity when contact |23 connected with terminal ||6 is connected with negative contact |24 `of the polarity reversing switch as shown in Fig. 2.

ments are of suilicient arcuate length to bridge the stationary contacts which are located 60 apart. Hence the mova le contacts are located equiangularly distant 'at 120. fixed to a shaft |35 carrying a ratchet |36 having six equiangulrly spaced teeth |31. The teeth |31 are engageable by pawl |30 pivoted upon a rocking lever |39 loosely journaled on the shaft |35. Lever |39 is provided with a fork end |40 engageable with a pin |4| carried by the link 62 which connects the'plunger 0| with the starter drive shift lever 34. To prevent back- The disc |30 is tion as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scop of the claims which follow.

What is claimed is as follows:

v 1. In an engine starting and ignition system for internal combustion engines, the combination of a current source and electrical ignition apparatus including timer contacts, an enginex starting device including an electricv motor, electromagnetic means for electrically connecting ing up of the pawl |38, there is provided a leaf spring member |42 which is fixed at |43 and is engageable with any of the teethof the ratchet When the star-ting c ircuit is closed by closing the ignition` switch and by closing the accelerator pedal switch 80, the plunger 6| not only moves to effect the starter function, but also to' rotate the shaft |35-a distance of 60 so as to move.

the disc |30 and contacts carried thereby from a position such as shown in Fig. 1 to a difi'erent position such as shown in Fig. 2 thereby causing the polarityof the ignition timer contacts ||4 and ||5 to be reverse/d. Therefore during each function of the starter as effected thru the electromagnet 40 there will be a reversal of polarity of the ignition timer contacts.

I arrange the wiring of the ignition system in such manner and I select a timer vcondenser' ||8 of such capacity that at no time during the operation of the ignition system will there be a positive transfer arc occurring at the ignition contacts at\the time of secondary discharge. I use a fast operating breaker lever so as to make the contact gap as large as possible during the secondary discharge and I use a timer condenser ||8 of such capacity as to retard the rate of secondary build-up to such extent that the primary induced voltage at the time of secondary discharge will be always less than that required to 'start 4ga positive contact transfer arc. Also I separat@ the primary and seconday leads from the ignition coilto @ich extent and may even place them into such close proximity with ground as to prevent any transient voltage derived fromV the high frequency oscillation occurring secondary discharge from reaching such a value that, when added to the primary induced voltage, the resultant voltage would be sufficient to start a positive transfer arc. For example@ disclose in my copending application that about 340 volts at the contacts is necessary to start a positive transfer arc. I so arrange the circuit and so select the condenser |`|8 that the sum of primary the motor with the current source and for mechanically connecting the motor with the, engine, a relay for connecting the electromagnetic means with the source, a switch for reversing the polarity of the current delivered from the current source to the timer contacts, and means for automatically operating the switch in response to the operation of theelectromagnetic means.

2. In an engine starting and ignition system for 'internal combustion engines, the combination of a current source and electrical ignition apparatus including cooperable timer contacts, an engine starting device, a solenoid switch for connecting the starting device with the source, and including a relay, means for energizing the relay only when the timer contacts are conditioned for current conduction, a switch for reversing the polarity of the current traversing the timer contacts, and meansfor operating the reversing switch automatically in response to opinduced voltage and transient voltage at the time of secondary discharge is always substantially below 340 volts. In this way I eliminate the occurrence-of positive transfer arcs and deal only with the :negative transfer problem which is I believe less severe. By reversing polarity at frequent intervals in a system where only negative transfer can occur I am able, at least with eration of the solenoid switch, whereby the polarity of the current traversing thetimer contacts will be reversed each time the solenoid switch is closed.`

3. The combination set forth in claim 2, wherein the solenoid switch and relay are entirely disconnected from the current source when the engine becomes self operative. l

4. In an engine starting' and ignition system for internal combustion engines, the combination of a current source and electrical ignition apparatus including cooperable timer contacts,"an engine starting device, a solenoid switch for connecting the starting device with the source, andv including a relay, means for energizing the relay only when the timer contacts are conditioned for current conduction, a switch for reversing the polarity of the current traversing the timer contacts, and means forroperating the reversing switch automatically in response to operation of the solenoid switch, whereby the polarity of the current traversing the timer contacts will be reversed each time the solenoid switchis closed, and means preventing connection of the solenoid switch with the current source while the enginev is self operative.

5. In an engine starting and ignition system for. internal combustion engines, the combination of a current source and electrical ignition apparatus including timer contacts, an engine starting device including an electric motor, electromagnetic means i'or electrically connecting the motor with the current source and for mechanically connecting the motor with the engine, a relay for connecting the electromagnetic means with the source, a switch for reversing the polarity of the current delivered from the current 'source vto the timer contacts, and means for automatically operating the switch in response to the operation `oi' the electromagnetic means and means for automatically disconnecting the electromagnetic means from the current source directly that the engine becomes self operative.

. L. HARTZEIL.

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