US2278490A - Ignition system - Google Patents

Description

April 7, 1942.

J. J. ROSE 2,278,490

IGNITION SYSTEM Filed May 26, 1938 4 Sheets-Sheet l Array/veg:

April 7, 1942. J. J.- ROSE IGNITION SYSTEM Filed May 26, 1938 4 Sheets-Sheet 2 Avmswrae PO 8 &

April 7, 1942.

J. J. ROSE IGNITION SYSTEM Filed May 26, 1938 27 v Avme/vrae 28 7 g/. Pose;

4 Sheets-Sheet 3 I April 7, 1942.

J. J. ROSE IGNITION SYSTEM 4 Sheets-Sheet 4 Filed May 26, 1938 Patented Apr. 7, 1942 UNITE IGNITION SYSTEM John .7. Rose, Dayton, Ohio P Application May 26, 1938, Serial No. 210,250

(Granted under the act of March 3, 1883, as

amended April so, 1928; 370 o. G. 757) '7 Claims.

me of any royalty thereon.

My invention relates to internal combustion engines of the articulating piston connecting rod type and has for its main object to provide a novel ignition system whereby an ideal relationship is. obtained between the piston positions and the time of firing.

It is well known that, where articulating rods are pivotally connected to an articulating master rod at points remote from the crank-pin, the' pivot points of the articulating rods trace elliptical paths while the crank-pin traces a circle, this difierence resulting in an out of phase syxnmetry relation of the pistons.

Because of this phenomenon, it will be seen that, if articulating rods of equal length, to which the pistons of an engine are connected at one end,

.are virtually connected to a master connecting rod at points equi-distant from and equi'angularly arranged about the engine crank-pin, and if the cylinders of the engine are equiangularly symmetry of the points of connection of the position of the respective pistons, causing either too early or too late firing of the cylinder, with consequent inefliciency and undesirable results.

Attempts have been made to compensate for this variance by varying the angular spacing between the pivotal points of the articulating rods or their radial distances from the crankpin, or both, but because of structural limitations in the engine design, complete compensation for this variance has been a practical impossibility and the maximum extent of these variations has been found to be as high as 9, with the result that overheating takes place in those cylinders having the earliest firing timing, thus limiting the capacity of the engine.

In order to compensate for this error in timing, due to difierences between crank-arm position with reference to top dead center position of the connecting rods with respect to the master rod axis of pivotation.

Heretofore, the firing interval of cylinders has been regulated by a cam and breaker arrange-. ment with the cam having equally spaced lobes and geared to rotate at a speed sufilcient to fire the cylinders in a predetermined firing order.

Since said cam was ultimately geared to the crankshaft, the provision of equally spaced lobes resulted'in the firing of the cylinders at uniformintervals as measured by the revolution of the crankshaft from center line to center line oi the cylinders, or, in other words, the ignition was taking place at regular intervals in relation to inders, provision is made in the ignition system for causing each cylinder to fire in individually predetermined relation with respect to the topdead center position ofthe corresponding piston. For this purpose, I have provided a breaker cam with a plurality of lobes spaced and arranged to correspond with the respective angular relations between the connecting rods of successively firing cylinders and having a speed of rotation such that each lobe is at the make and break position with respect to top dead center.'

Heretofore, breaker cams for regulating the firing intervals have usually been mounted onthe magneto rotor shaft; and therefore made with a number of lobes equal to the number of flux changes .per revolution of the magneto. Consequently. the cam was generally geared to the crankshaft at some uneven ratio which would provide for the revolution of the cam at a rate of speed to provide a make and break of the magneto circuit to correspond to the crankshaft revolution at successively firing cylinders. accordance with my invention, it is required that the camshaft be operated at a. speed whereby eachwill permit, to mount the cam on the distributor shaft. In other designs of magnetos, I have adapted a set of gears to rotate an auxiliary camshaft at the prescribed rate of speed.

By regulating the firing of each cylinder at predetermined intervals with respect to the top dead center position of each piston, more power and economy of operation can be obtained, because the maximum spark advance can be maintained for each cylinder, which was heretofore impossible. This improvement is particularly advantageous in the use of present day high output aviation engines operating with high compression ratios and with the demand for maximum fuel economy.

Although my invention is applicable to radial engines with various numbers of cylinders, I have illustrated the same with a seven-cylinder engine of the four-stroke two-cycle type.

Referring to the drawings, wherein like reference characters indicate corresponding parts throughout the several views:

Fig. 1 is a fractional side elevation view of a seven-cylinder radial engine showing magneto attached;

Fig. 2 is an enlarged elevational view in fraction of the magneto with the casing partially broken away to show the location of the cam;

Fig. 3 is a detail view showing a breaker unit embodying my invention;

Fig. 4 is an elevational view of a magneto showing parts broken away and in section;

Fig. 5 is a section detail view;

Fig. 6 is a diagrammatic view of my improved cam showing the arrangement of the lobes with relation to the cylinder axes (which are shown in dotted lines) when the cylinder including the master connecting rod constitutes the timing reference;

Fig. 7 is a diagrammatic view similar to Fig. 6 showing the arrangement of the lobes with relation 'to the cylinder axes (which are shown in dotted lines) that obtains when a certain cylinder is used for the timing reference, other than the cylinder including the master rod;

Fig. 8 is an operating diagram of the crankarm and connecting rods showing the same in three difierent positions.

In Fig. 1 the magneto ID of standard design, usually with four poles, is geared to the crankshaft by means of gears II and I2, of such ratio as to rotate the magneto to produce a number of flux changes in two revolutions of the crankshaft, equal to the number of cylinders. .If desired, the number of poles can be made equal to the number of cylinders, whereby the time interval of flux change can be regulated so that the instant of make and break for each cylinder will occur when the voltage is at its maximum value. In Fig. 2 the magneto casing is cut away to show the magneto'rotor I3, which is immediately operated by the gear [2, shown in Fig. 1, and drivingly connected to the distributor shaft I4 by the gears l5 and I6, which are of'such ratio as to rotate the distributor shaft at onehalf engine speed, driving the distributor (not shown). Forward of the gear IS in the housing I1 is the cam l8 drivingly connected to the distributor shaft, and the breaker l9.

Fig. 3 shows my improved cam IS with its seven lobes in the conventional cam arrangement, with breaker is and condenser 20.

The embodiment of my invention in Figs. 4

and 5 is similar to that in Fig. 2, except that the cam is differently constructed and arranged.

In this embodiment the cam 29 is drivingly connected with the rotor shaft 2| instead of with the distributor shaft 22 and rotatably mounted in a housing 23 inclosing the rotor shaft. The housing is illustrated as being made integral with the magneto casing but may be made to be detachable therewith, if desired. As shown, the housing has an upwardly extending supporting arm 24 provided with a journal for rotatably supporting the cam. The stub shaft 25, that is preferably made an integral part with the cam, is supported in the arm 24 of the housing 23 by the bearing 26, and driven by the rotor shaft through a pinion 21 in mesh with an internal gear 28 that is preferably made integral with the cam. The gear ratio between the pinion and internal gear is such as to rotate the cam at onehalf engine speed.

In Fig. 6, my improved cam is diagrammaticaily represented by the solid line construction. The dotted radial lines, numbered in counterclockwise rotation 1--3--5-724--6, represent the axes of those cylinders respectively, in a seven-cylinder engine, in their firing order. Thus, the cam is designed to cause each cylinder to fire once in one revolution, while the engine will have made two revolutions. It is, therefore, seen that the angular distance between the dotted lines. representing the respective cylinder axes on the cam, is one-half of the corresponding angle between the cylinder axes in the engine. Based on the variation in the crank-shaft rotation between the crank-arm position at the top dead center position of the piston and the axes of the corresponding cylinders, I have modified the cam to provide sectors with lobes spaced at angles equal to the angles between the respective crank-arm positions at top dead center positions of the pistons in successively firing cylinders and arranged the lobes in the sequence of the firing order of the corresponding cylinders.

Based on the study of the engine rotation, hereafter made in connection with the description of Fig. 9, these deviations are labeled respectively 11/2, z'/2, :r/2, 10/2, 2/2, and y/2, wherein a: and :r are equal, 1 and y are equal, and z and z are equal.

It will be noted that there are four different sized sectors or chords, (1, b, c and d, and three chords, 'a', b and c, of the same sizes as a, b, and 0 respectively, but, because of the sequence in rotation, all seven lobes are necessary. However. in an engine having two radial rows of cylinders, when the master connecting rods are arranged in the cylinders apart, the sequence of spaced lobes repeats itself, and it is possible to build the cam with but half as many lobes as the number of firing intervals. This is desirable to provide optimum speed ratio relation between the cam and crank-arm to prevent multiplication of errors which might occur in the measurement of the variations.

In Fig. 7, the cam has simply been rotated on its hub by the y deviation so as to time the #3 cylinder at zero, that is, with the piston in #3 cylinder on top dead center and the modified cam lobe for the #3 cylinder placed in the position on the cam shaft corresponding to the cylinder axis, while the master connecting rod is still located in the #1 cylinder. This illustrates a greater deviation than before, because the y deviation, which was the largest, is now added to all the. other deviations, and the deviations as shown are z/+z'/2. y+-' '/2. y-'v/2, zIz/2, y+y'/2 and 11/2. With my improved cam these deviations are automatically compensated regardless of cam setting, but with a cam ofuniform lobes, such a reference for timing as the above would result in an actual deviation from the correct firing position of the amount indicated.

Fig. 8 represents diagrammatically the paths of the points of connection between the articulating rods and the master connecting rod and the crank-arm in a revolution of a seven-cylinder radial engine. The axes of the cylinders are represented by radiating lines numbered l, 2, 3, i, 5, t, l in counter-clockwise direction. The crankshaft and center of the engine i represented by 30. The master connecting rod 3| is arranged in #1 cylinder and the articulating rods for cylindersv Nos. 2, 3, 4, 5, 6, 7 are repreattached to the master connecting rod by the link pins d2, 43,44, d5, 46 and 41 respectively at the radial distances 52, 53, 54, 55,56, 51 respectively.

The path of the crankspin fil, during a revolution, is the circle Si, and the paths of the link pins 52 to H are the elliptical orbits 62, 68, 6t, 65, 6B, 61 respectively. It will be noted that the orbits 62 and t1, t3 and 55, and M and 65 are symmetrical pairs, which is the natural result of the master rod crankshaft arrangement with respect to the master rod.

As set out in the introductory part or this specification, the articulating rod construction in radial engines causes the pistons to arrive at top dead center position when the crank-arm has revolved a different number of degrees than that number measured from cylinder axis to cylinder axis. Thi is evident from an inspection of the relations of the pistons, connecting rods and crank-arm in three different positions, 1', s and t, of the crank-arm. In the position of the crankarm, as represented by position 1' and shown in solid line, the crank-arm to is shown coinci= dental with the master connecting rod and with the axis of the cylinder, and the piston is at its top dead center position. As the revolution of the crank-arm progresses toward the next firing I cylinder, #3, the crank-pin describes an arc of the circle 6i and the link pins proceed in their respective elliptical paths. In the position 3, which is represented by dot and dash lines, it will be seen that the link pin 93, in traversing its orbit 53, is approaching the aixs of its corresponding cylinder. However, the piston is very near the top dead center position because the orbit $3 is now receding towards the center of firing of the cylinder #3 with reference to top dead center position of the piston is when the crank-arm has revolved two-sevenths of the circle from the position when cylinder #1 was firing,

plus the angle 1;.

By a similar construction, each of the angular 'variations of the crank-arm from the cylinder axes for the top dead center piston positions in the deviations .r', 11' and 2' occur when the crankarm has not yet reached the axes of the cy1in-.

ders, whereasin cylinders 2, 3 and 4 the crank-arm has gone beyond the cylinder axes. It will be seen from the above explanation that the deviations of the crank-arm from the cylinder axes at the 1 top dead center piston positions vary from nothing at zero and 180 degrees of revolution, with respect to the master rod as the timing reference, to maximums at 90 and 270 degrees of revolution. Applying these angular variations to the fir ing intervals of the engine, we find that the first firing interval from cylinder #1 to cylinder #3, labeled a, is measured by the two-sevenths of the circle from cylinder #1 to cylinder #3, plus the angle 1;. The firing interval b between cylinders ured by the two-sevenths of the circle, plus the.

angles 2: and .r. The firing interval 0' from cylinder #2 to cylinder #4, which is of the same size as firing interval 0, is measured by the two sevenths of the circle, plus the angle 2 and minus the angle :0. The firing interval 17' from cylinder #4 to cylinder #6 is equal to the firing interval b and measured by the two-seventhsof the circle, minus the angles a and 11'. The firing interva1 a from cylinder #6 to cylinder #1, thus completing the firing of all the cylinders and two complete revolutions of the crankshaft, is of the same size as the firing interval a and measured by the two-sevenths of the circle, plus the angle My improved cam, as previously described in Fig. 6, is constructed with lobes corresponding to each of the firing intervals as above described. Since the cam makes but one revolution while the crankshaft is making two revolutions, all the angular variations measuring each lobe are cut in the engine. Nevertheless, the piston will travel a still greater distance from the center of the engine and arrive at its top dead cnter position when the link pin 63 has arrived at the position t, shown in dotted line. In thisposition, the crankpin will have travelled in its circular path beyond the axis of the cylinder. The firing interhalf, but as illustrated in Figs. 6 and '7, are enlarged two times for the purpose of illustration.

In addition to said angular deviations, other considerations such as rate of piston travel as: it approaches top dead center position'may aflect the ignition compensation desired in individual cylinders. It is, therefore, to be understood that proportional to the said angular deviations, but

' may be predetermined for eachindividual cylinder, as based on the various factors to be considered.

Therefore, ,While in describing the construction and operation of this invention, a seven-cylinder radial engine has been used for purposes of illustration, nevertheless, it is to be understood that my invention may be used with engines having any given number of cylinders, and that while I have described the invention in connection with a magneto ignition system in which the lobes of the cam provide an open dwell that is substantially alike for all lobes, it will be understood that the invention contemplates the use of a battery ignitiOn system, and that the dwell, open or closed, for the lobes, may be varied to suit the type and characteristics of the ignition system. employed, and that the invention is not limited to the exact structure which has been described, but various modifications may be employed, as will be clear to those skilled in the art after reading this specification, the scope of the invention being indicated by the accompanying claims.

What I claim is:

1. In combination with an internal combustion engine, having the crank-arm thereof varying alternately between maximums of opposite signs in its angular relations with respect to the axes of the different cylinders for the top dead center piston positions thereof, respectively, an ignition system associated with the crank of said engine, having a cam provided with lobes spaced and arranged to correspond with the angular relations between the crank-arm positions and the axes of successively firing cylinders for the top dead center positions of the different pistons, respectively, the number of lobes and the speed of rotation being such that each cylinder is caused to be fired by only one lobe.

2. In combination with an internal combustion engine of the articulating rod type, having the crank-arm thereof varying in its angular relation with respect to the axis of each cylinder for the top dead center position of the piston, an ignition system associated with the crank of said engine, having a cam provided with lobes spaced at angles proportionate to the angles between the respective crank-arm positions corresponding to the top dead center piston position of each of successively firing cylinders, said lobes being so arranged and said cam being so coupled to the crankshaft that each lobe is at the break position when its corresponding-piston is at an individually predetermined position with respect to the top dead center thereof.

3. In combination with an internal combustion engine of the articulating rod type, having the crank-arm thereof varying in its angular relation with respect to the axis of each cylinder for the Y top dead center position of the piston, an ignition system associated with the crank of said engine, having a. cam provided with a number of lobes equal to the number of cylinders, said lobes being spaced and arranged to correspond with the angular relations between the crank-arm positions and the axes of successively firing cylinders for the top dead center positions of the different pistons.

4. In combination with an internal combustion engine of the articulating rod type, having a crank-arm that varies in its angular relation with respect to the axis of each cylinder for the top dead center position of the piston thereof, through a plurality of like series of variations during each firing cycle of said engine, an ignition system associated with the crank of said engine, having a cam provided with a number of lobes equal to the number of variations in a series of said variations, said lobes being spaced and arranged with respect to the angular relations between the crank-arm positions and axes of successively firing cylinders for the top dead center piston positions, and means for causing said cam to rotate a number of revolutions equal to the number of series of variations during each firing cycle of operation of said engine.

5. An ignition make and break device for use with an internal combustion engine of the articulating rod type having symmetrically arranged cylinders and pistons operating therein in out of phase-symmetry relation, said device comprising cam means having a plurality of lobes arranged in out of phase-symmetry relation corresponding to the out of phase-symmetry relation' of said engine pistons, and breaker means cooperating with said cam means to ignite said cylinders.

6. In a magneto ignition system a make and break device for use with an internal combustion engine of the articulating rod type having symmetrically arranged cylinders and pistons operating therein in out of phase-symmetry relation, said device comprising cam means having a plurality of lobes arranged in out of phase-symmetry relation corresponding to the out of phase-symmetry relation of said engine pistons, and breaker means cooperating with said cam means to ignite said cylinders, said magneto being adapted to operate at a speed to cause a flux change per each cylinder in a complete firing cycle of engine operation, and said cam means being adapted to operate at a speed to make and break said ignition circuit a number of times in a complete firing cycle of engine operation equal to the number of cylinders.

7. An ignition system for internal combustion engines of the radial cylinder type provided with a master connecting rod and secondary connecting rods pivoted thereto, and having non-symmetrical firing intervals due to the irregularities of said connecting rods, including a source of ignition current, means for periodically interrupting the flow of said ignition current and means for distributing said ignition current to the various cylinders in firing sequence, one of said means being adapted to perform its function in said nonsymmetrical firing intervals to thereby initiate combustion at the same period of the cycle in each cylinder.

JOHN J. ROSE.

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