US2437400A - Engine starting mechanism - Google Patents

Description

March 9, 1948. R. M; NARDONEZ ENGINE STARTING MECHANISM Original Filed April 8, 1941 2 Sheets-Sheet 1 q) a INVENTOR 1 1520 1 2120 done ATTORNE March 9, 1948.

R. M. NARDONE 2 431400 ENGINE S TARTI NG MECHANISM Original Filed April 8, 1941 2 Sheets-Sheet 2 fiz van for R0M0 M 11/4900;

flilarney Patented Mar. 9,1948

ENGDIIE STARTING MECHANISM Romeo M. Nardone, Teaneck, N. J., assignor to Bendix Aviation Corporation, Teterboro, N. J., a corporation of Delaware Original application April 8, 1941, Serial No. 387,541, now Patent No. 2,331,077, dated October 5, 1943. Divided and this application September 1, 1943, Serial No. 500,831

4 Claims. (Cl. 171-323) This invention relates to electric starter motors, and particularly to the starting of an internal combustion engine by imparting initial rotary movement to the engine crankshaft, through the agency of a mechanical torque transmitting starter mechanism.

In electric motor-driven inertia starters, the motor is of the high-speed, low-torque type serving the one purpose of accelerating the flywheel to a high speed. In electric direct-cranking starters, the motor again serves only one purpose and it is designed to have low-speed, high-torque characteristics. In a combination inertia directcranking unit, the motor has to serve the dual purpose of first accelerating the flywheel and subsequently cranking the engine; and since this necessitates a compromise in the design of the motor, the efliciency of the unit for either of the two purposes has been comparatively low, and the maximum flywheel speed attainable has been less than is desirable for the starting of the highpowered engines now being used.

An object of the present invention is to provide a novel starter construction combining the advantages of inertia operation with those of direct-cranking, yet without sacrificing motor efliciency or energy storing capacity, but on the contrary effecting an increase therein.

Another object is to provide novel means for journaling a high speed flywheel, so as to render more feasible its rotation at speeds in excess of any heretofore employed in inertia starting mechanism.

Another object is to provide novel means for facilitating acceleration of the flywheel independently of electrical energization of the motor. A feature to this end is the employment of means for releasing, at will, the spring pressure which normally holds the motor brushes in firm engagement with the commutator, and thus facilitating free turning of the motor as the flywheel is being accelerated.

Another object is to provide novel means for controlling the torque transmitting capacity of the starter. A feature to this end is the use of auxiliary screw means to modify the torque-limiting clutch setting in response to motion translation by the conventional screw means constituting a part of the torque-limiting clutch assembly.

These and other objects of the invention will become apparent from inspection of the following specification when read with reference to the accompanying drawings wherein is illustrated one embodiment of the invention.

Figure 1 is a side view, partially in section, of the device, and

Figure 2 is a view of the motor end of the device, with end portions partially broken away.

In the drawings, the inertia element ll (flywheel) is shown as having a hub I2 keyed to a sleeve l3 through which runs a shaft l4 driven from the armature shaft it of an electric motor the field coils ll of which are supported on a frame fastened to section it of the housing. Bolts l9 secure housing section l8 to housing section 2i, and a third housing section 22 supports the sections l8 and 2|, and is in turn supported on a mounting flange 23 of the engine to be started. A rotatable part 21 of the engine has ratchet teeth 28 for engagement by correspondingly shaped teeth on an engine-engaging member 20, and the latter has a cylindrical extension that is mounted for rotation and limited axial movement within the housing section 23.

In order to make it possible for flywheel I! to operate satisfactorily at speeds as high as 30,000 R. P. M., for storage of sufficient energy for starting the heaviest aircraft engines now being produced, yet without radically revising the construction of the electric motor, I interpose a step-up gear train between the armature shaft It and the flywheel hub l2. This gear train will convert a motor speed of 7,500 R. P. M. (which is readily obtainable without changing present motor design) into a flywheel speed of approximately 30,000 R. P. M.; the gears 3|, 32, 33 and 34 providing a step-up ratio of 1 to 4, or thereabouts, in the arrangement shown.

The rotation of flywheel II at a, speed so far in excess of those heretofore employed creates a bearing problem which I have solved by using a two-stage bearing combination comprising bearings 36 on the inner side of armature shaft extension 31, and a bearing assembly 38 on the outer side of said extension 31; the outer races of the bearings 36 being thus urged to rotate at the motor speed, and the ratio of rotation between inner and outer races being correspondingly reduced. The outer race of bearing 30 is, of course, held against rotation, while the inner race rotates with the motor extension 31.

The means for facilitating acceleration of the flywheel H independently of electrical energization of the motor windings I! will now be described. A manually operable transversely disposed shaft 41 is journaled in housing section 2! and terminates in a bevel gear 42 meshing with a second bevel gear 43 constituting the low-speed end of the gear train which leads to the flywheel 3 and includes as its higher speed elements the gears 3|, 32, 33 and 34, heretofore referred to; but as the gear 3| is integral with the shaft H! to which is splined the armature shaft, it will be seen that the armature rotates with the gear train during such manual acceleration of thefiywheel N. This creates a problem because of the spring pressure which would cause the commutator brushes to act as a brake upon the gear train, and thus retard accelerationofthe flywheel. This problem is solved .by providing means to relax the tension pfthe brushes, whenever desired, while permitting the brushes themselves to remain in commutating position, rather than attempting to lift them as in certainiprior art patents. Their effect .as aretarding agency is thus eliminated, for in the absence of'spring pressure the brushes have substantially no braking capacity. To provide for relaxingthe spring tension, I use springs of fiat metallic material wound spirally. aboutyshafts 52 which :may be rotated to a limited extent about their;individual axes to either wind or1unwin'dthe-springs 5|, according to the direction of rotation of an annular plate 53 to .whichsaidphafts 152 are linked by suitablecranl; mechanism 5 l-thereibeing a plurality of thesecrank .mechanisms (one for each brush 5%) although the drawing shows only one. To rotate .plate 53 to the limited extent required, I provide :..a pin 58'movable ;in a slot in the end-plate 59 of .;the vmotor housin but normally restrained by the pressure of' spring ti upon the detent cup 52. .This-detentcupGZmust first be pulled outwardly-tofree the in -5B-for movement in its slotin member59. Thepin terminates in a head H toiacilltate manipulation thereof.

The novel means for'controlling theinitialap- 'plication of turning eilortito theenginemember 28, and for absorbing the shock of first engage- 4 or to receive any of th various equivalent prior art structures for controlling movement of the mesh-rod lZl.

The drive from flywheel II to the engine-engaging member 29 includes, in addition to the frictionclutchassembly 86, a planetary reduction set consisting of planet pinions I02 carried on a rotatable cage I63 and meshing with a central driving pinion i23 and also with an outer annular stationaryugear track I06 which, as shown, is integral with housing member 22. The pinioncarryingextensions of rotating cage I03 are se- '1cu1iedt0barre1 Nil by suitable fasteners lill,

wherefore the barrel is constrained to rotate with *inggpinion 18%. "The pinion I84 is in turn driven "frointhe 'fiywheel i l through the reduction gears ment of the members-29 andIZB, will -now be detween. the cooperating threaded elements 2 82 and 83; the element 82.beingrexternallysplinedand hereinafter referred to as the .fshell, and the element .83hereinafter referred to as {the screw-shaft-having tan end portion; externally splined for splines on the .hub .of engines-engaging. member 29. Element St .is lformed with ;a flange til against which bear coiled springs :i=.5,zthe said springs being normally-ethat: is, with the parts in the relationships .zshownpressed lightly against the conventional friotionclutch; assembly 88 by reason of-the reaction :ofithrust-bearing assembly 8? upon .the element ,-B|;and; itsyflange 84; the bearing .81 being :retained "by annular plates 88 andBil, the former being. splineid ;and thelatter threaded to barrel Ill lpwhich enclosesand drives-the friction clutch assembly 36.

Ball-race 96 of thrust-:bearing assembly 87 is in the path of axiaLmovement-of. screweshaft 33; when-shoulder.9|:of said screw-shaft engages stop 9%, such'aXial movement ceases. To bring about such axial i movement thereeistpro vided the usual rod izl with its shoulderl22 to engage and impart axlalthrustrto the screwshaft 33, spring E23, and engine-engaging memshown) corresponding to :actuating yoke .2 38

shown in FigA of Lansing -PatentzNdnfl62,398,

engagement with corresponding r 34,33, 32, 3|, H8, H1, H3 and I09; the lastnained gear being integral with pinion I04, and the gear H3 being integral with a shaft l5 journaled in abearing block|3i constituting an integral part-of housing section 2!. 'Also journaled in bearingmember |3 i is ,a bearing assembly I33 which .coacts with a polled spring |3| to hold the armature-driven shaft i l in its proper axial relationship to the parts associatedtherewith.

In operation, after the flywheel H has been accelerated by either of the means (4| -or it) heretofore described, the operator moves meshrod EZI to the left, this movement being communicatedto the screw-shaft 83zby reason of shoul-' der 122,.and to the en ine-en a in member 2e by "reason of spring :23. This leftward ,movement 3of-screW-1shait 83 :ceases when shoulder 9| engageslstop 96 (as heretofore noted) but in the meantime the engagement of jaws '29 and 28 causes some .drivingtorque to be transmitted to said members 29 and 2 3 bywaygof the lightly engaged friction plates 85;, the screwsleeve 8i, and: the. screweshaft 83; .but since the latter can move no further to. the left now thatishoulder 9| has reachedstopGil-:screvwsleevafi| iszurged (bythescrew action) to the .right,;to the extent .permittedby the, spacing of shoulders and $2 .on the elements! and .83, respectively. This rightward...movement .of screw sleeve .c8l draws flange I855 =corres ziondingly to the: right, and .increases correspondingly the pressure of springs 35: upon .the :friction clutch assembly 36. The torque transmitting capacity of the friction clutch-is thus raised to its maximum value by a gradual pressure-applying actionthat is synchronized with the initial application of drivinge'ifort to-theengine memberifi. "The result-is-asoftspring-cushioned impact-which reduces-the stress andstrain on the driving and driven parts, and permits use -of-relatively lighter cornponent ele- --ments for anyigiven torque -requirements.

If sleeve 8 I were 'splinedto shell 82, the force necessary to -make it slide through 32 -u-nder torque-would-be considerable-and it would' be necessary to .changethe helix anglebetween filand 513 so as to decrease the" lead to create. the. additional force. "This additional .push, 1 however, would. react on .thrust bearin g' 81. and nut, 89 and load these partsexcessively. It is to preventsuch .a situation thatsleevet I andshell 82 are threadedtogether, the thread angle being made approximately equal to the angle of iriction,- namely, ..between,-10 and 215?. .The hand of thisnthread lSxmadELS'LICh'; that:torquertransmitted:from :82 to :SI tendsi-t i but :doesnot, pull :8 tothe right. Theiangle. is made sma'll enough :so; that'regardless of how much.torque is transmitted from. one

to the other, operating only in themselves, no relative axial movement will result.

When the engine starts, the transmission of torque through the starter mechanism falls to zero and springs 85 then re-expand, carrying sleeve 8| back to its neutral position against thrust-bearing 81. Screw-shaft 83 and jaw 29 are at the same time retracted to their normal positions.

This application is a division of my application No. 387,541, filed April 8, 1941, which matured as U. S. Patent 2,331,077 on October 5, 1948, with claims for the torque-transmitting means including a clutch and for the torque-controlling means therefor.

What is claimed is:

1. In a commutator-type electric starter motor, the combination of a spring for each brush arranged to press its brush toward the commutator, an oscillatable shaft for each spring arranged to vary the stated pressure of its respective brush in accordance with the angular movement of the shaft Without lifting the brushes from the commutator, a manually operable means operatively connected with each shaft to turn them all through substantially the same angle upon a manual operation of said means, and a means for retaining the manually operable means in its last-set position.

2. The combination set forth in claim 1 in which the axes of said shafts are disposed parallel with the motor shaft and at at-least-approximately the same radial distance therefrom, and in which the stated connecting means includes both a crank for each shaft and respectively connected thereto and an annular ring mounted concentrically of the motor shaft to be manually oscillatable and constructed to coact with each of the cranks to move all of them through the same angular distance when the annular ring is moved.

3. In an electric starter motor comprising a commutator and commutator brushes, the combination of spring means each adapted to provide operating pressure for one of the brushes relative to the commutator, regulating means operative to given position to simultaneously nullify the operating pressure and drag of the brushes pressed by the spring means independently of lifting thereof from the commutator, and means adapting said regulating means to be releasably retained in said given position.

4. In an electric starter motor comprising a commutator and commutator brushes, the combination of spring means each adapted to provide pressure for one of the brushes relative to the commutator, and a regulating means operative to reduce the pressure to a predetermined value rendering the brushes pressed by the spring means substantially incapable of drag on the commutator and ineffective as brushes but maintained on, and prevented from lifting from the commutator, said regulating means being adjusted to said value and adapting the latter to be repeatedly reduced and reestablished independently of further adjustment upon successive reverse operations of the regulating means.

ROMEO M. NARDONE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,936,422 Burnham Nov. 21,1933 1,101,917 Flower June 30, 1914 1,287,812 Ahlm et al Dec. 17, 1918 1,855,281 Chilton Apr. 26, 1932 2,128,598 Williamson Aug. 30, 1938 2,301,421 Klingner et al Nov. 10, 1942 2,261,402 Nardone Nov. 4, 1941

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