US2394531A

US2394531A - Engine starter gearing

Info

Publication number: US2394531A
Application number: US559587A
Authority: US
Inventors: James E Buxton
Original assignee: Bendix Aviation Corp
Current assignee: Bendix Aviation Corp
Priority date: 1944-10-20
Filing date: 1944-10-20
Publication date: 1946-02-12
Anticipated expiration: 1963-02-12

Description

Feb. 12, 1946. J. E. BUXTON 7 2,394,531

' ENGINE STARTER GEARING Filed on. 20, 1944 2 Shee ts-Sheet 1 40ml x Q h WITNESS: /ww 36mm.

A TTORN E Y Feb. 12, 1946. J. E. BUXTON ,5

ENGINE STARTER GEARING Filed Oct. 20, 1944 2 Sheets-Sheet 2 A TTORNEY Patented Feb. 12, 1946 ENGINE STARTER GEARIN G flamestE. 'Buxtom Elmira, N. Y.,- assignor to BendixAviation Corporation, South Bend, Ind., a

corporation of Delaware Application October 20, 1944, Serial No.'559,587

11 Claims.

'The present inventionrelates to engine starters and more particularly to a drive of. the automatically engaging and disengaging type which is adapted to maintain its engagement until the engine is reliably self-operative.

It is an object of the'present invention to provide a novel starter drive of the above type which is efiicient and reliable in operation under all conditions of use.

It is another object to provide such a device which is completely under the control of the operator at all times. v

It is another object "to provide such a device in which the armature shaft of the motor/ s shifted longitudinally to maintain engagement of the drive.

It is another object to provide such a device which is so arranged that the longitudinal movement of the armature can be accommodated without elongation or special construction of the commutator and/or brushes of the motor.

'It is a further object to provide such a device in which undesired engagement of the drive is effectively prevented.

It is another objectto provide such a device in which the disengagement of the drive is effected concurrently with the deenergization of "the starting system.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawings in which:

Fig, 1 is a semi-diagrammatic representation of a starting system constituting a preferred embodiment of the invention, the starting motor, starting switch and drive gearing beingshown in side elevation, partly broken away, and or idle position; and

Fig. 2 is a similar view showing the parts in cranking position.

In Fig. 1 of the drawings there is illustrated a starting motor indicated generally by the numeral I comprising a frame or housing 2 in which are mounted the fields 3 in the usual manner, and an armature 4 with a commutator :I' mounted on a shaft '5 which is slidably journalled at its ends in bearings 6 and I formed on the ends of the motor frame 2.

According to the present invention spring means are provided for normally maintaining the armature '4 decentered with respect to the fields 3 of the motor. As here shown this means comprises a thrust member 8 slidablymounte'd in the motor bearing 6 and urged into engagement with the end of the armature shaft 5 by a comin normal pression spring 9 retained in said bearing by suitable means such as'a cap I0 threaded thereon and provided with a vent opening I I to facilitate longitudinal movement of the thrust member in the bearing.

Means for restraining the decenteringmeans is providedin the form of -a latch member I2 mounted for radial sliding movement in the thrust member 8,a compression'spring I3 being provided to urge the latch member I2 in an upward direction as. shown in'Fig. 1. The bearing 6 is preferably provided with a bushing orlining member I4 which bushing is slotted longitudinally as shown at I5 in-order to receive theprojecting end of the latch IZ. Since the bushing I4 is a forced fit in'thebearing 6, theengagement of the latch I2 in the notch I5 preventsrotation of the thrust member 8.

The bearing Sis provided with a'radial opening I6 in communicationwith the slot I5 of the bushing I 4 and adapted to receivetheend of the latch I2 when it is moved'into registry therewith. When the latch so enters the opening Hi, the thrust member 8 is retained against longitudinal movement, the spring 8 being held under compression.

The centered position of the armature 4 is lpreierahly defined by a thrust bearing 5which limits the longitudinal movement of the shaft'to the left in Fig. 2. Brushes 4a are mounted in the motor frame 2 in position to be centered on the commutator 4 when the armature is in its centered position. When the armature is in'its decentered position, the brushes extend slightly beyond the end of the commutator as showninFig. 1,-but since the armature iscentered at all times during the rotation thereof under load, it is unnecessary with this constructionto extend the commutator beyond its normal dimensions.

The endof the armature shaftbwhich projects through the motor bearing I is extended as shown at I'-' and has a drive head and sleeve I8 fixed thereon in any suitable manner as by means of a cross pin I9 retained by a lock ring 20. A screw shaft 2| is slidably journalled on a reduced cylindrical extension 22 of .the drive head I8 and is yieldably connected to rotate with the same by means of a torsion and compression spring 23 which is connected to the drive head I8 by an the pinion from the screw shaft 2i are provided in the form of a nut 28 threaded on the screw shaft, a barrel 29 fixed to the nut, a dental clutch member 30 non-rotatably connected to the barrel as by means of radial lugs 3| projecting into slots 32, and retained therein by means of a thirnble 33 having a flange 34, extending into circumferential groove 35 in the interior of the barrel. The pinion 25 has fixed thereon in any suitable manner a driven dental clutch member 36 adapted to cooperate with the clutch member 30 and held in proximity thereto by an inwardly extending flange 3'! of the thimble 33. A compression spring 38 between the two clutch members 30 and 36 serves to normally maintain their teeth out of engagement as shown in Fig. 1.

The centering effect of the magnetic flux through the field and armature of the starting motor when the motor is energized is utilized to assist in moving the pinion 26 into initial engagement with the engine gear 21 and to maintain the pinion in such engagement. When the motor is first energized, the flux through the field and armature is heavy due to the lack of counter E. M. F. in the armature so that the armature is forcibly centered with respect to the field thus moving the armature shaft into the position illustrated in Fig. 2. At this time, the latch I2 is brought into registry with the opening 56 in the motor bearing 6 whereby the latch holds the thrust member 8 in retracted position and prevents the spring 9 from attempting to decenter the motor armature.

Means under the control of the operator are provided for actuating the latch I2 so as to release the thrust member 8 when it is desired to demesh the drive pinion. As here shown this is accomplished by mounting a magnetic starting switch 39 on the motor bearing 6 and providing the plunger 40 thereof with an extension 4| which traverses the opening I6 and extends to a position where its end enters the slot I5 in the bushing I4 when the switch is in its open position as shown in Fig. 1. When the switch is closed, the extension M of the plunger is retracted as shown in Fig. 2 so as to permit the latch I2 to enter the opening I6.

Means are preferably provided for yieldably holding the armature 4 in its centered position during the starting operation. As here shown this means comprises a spring pressed detent 43 mounted in the bearing 6 in position to enter an annular groove 42 in the end of armature shaft 5 when the armature is centered with respect to the motor fields.

In operation, starting With the parts in the positions illustrated in Fig. l closure of the starting switch by the operator withdraws the plunger extension M and at the same time energizes the starting motor whereby the flux traversing the field and armature thereof causes the armature to be forcibly moved to the left to the position shown in Fig. 2, whereupon the latch I2 enters the opening I6, holding the thrust spring 9 compressed, and the detent 43 enters the groove 42 so as to yieldingly retain the armature in its centered position. The initial rotation of the armature shaft 5 is transmitted through the drive head I8, and spring 23 to the screw shaft 2!, whereby the nut 28 on the screw shaft is traversed to the left, moving the pinion ahead of it by virtue of the spring 38, until the pinion engages the stop collar 44 fixed on the armature shaft. Further movement of the nut 28 forces the clutch member 30 of the barrel into engagement with the driven clutch member 36 of the pinion, after which the pinion is constrained to rotate with the screw shaft to crank the engine.

As long as the operator maintains the starting switch 39 closed, the thrust member 8 is held by the latch I2, and the armature 4 is kept in its centered position both by the flux traversing the armature and field, and by the engagement of the detent 43 in the groove 42 of the armature shaft 5. If the engine should fire during this time, the acceleration of the engine gear 21 will cause the pinion 26 to be accelerated above the speed of the motor, and the initial acceleration will be transmitted back through the clutch members 36, 30 to the nut 28 causing it to move back on the screw shaft 2|. This movement is not suflicient to demesh the pinion from the engine gear however but merely releases the clutch members 36, 30 and permits the pinion to overrun the motor shaft freely while remaining in partial mesh with the engine gear 21.

If the engine should not continue to be self operative, the pinion will slow down whereupon the screw shaft 2| will traverse the nut 28 back to cranking position, and rotation of the engine by the starter drive will be resumed. In order to insure such traversal of the nut 28, a spring wire detent 45 is preferably mounted in the pinion clutch member 36 in position to spring outwardly and bear frictionally on the interior of the thimble 33 which is attached to the barrel 29 so that there is always a slight frictional connection between the pinion and the barrel.

When the engine has become reliably self operative, the operator will open the starting switch 39 whereupon the extension II of the switch plunger engages the latch I2 and forces it out of the opening IS in the bearing 5. The spring 9 is thus released so that the energy stored therein is available to move the thrust member 8 to the right and thereby translate the armature 4 to its decentered or idle position thus disengaging the pinion from the engine gear.

In connection with the operation of the spring 9 and thrust member 8 it has been found that the initial centering action of the armature when the starting switch is closed is quite energetic. The spring 9 may therefore be made sufiiciently heavy to insure prompt movement of the armature to its idle position when the starting motor is deenergized and to insure against any undesired shifting of the starting motor toward operative position due to accelerational forces of the vehicle on which the device may be mounted.

Although but one embodiment of the invention has been shown and described in detail, it will be understood that various changes may be made in the design and arrangement of the parts without departing from the spirit of the invention as defined in the claims appended hereto.

What is claimed is:

1. In an engine starter an electric motor comprising a field and an armature having a shaft projecting therefrom, a pinion journalled on the armature shaft having an overrunning connection therewith and movable longitudinally therewith into and out of mesh with a gear of an engine to be started, spring means normally holding the armature decentered with respect to the field to thereby position the pinion out of engagement with the engine gear, and manually controlled means for restraining the decentering means.

2. An engine starter as set forth in claim 1 including further means for controlling the energization of the starting motor and for concurrently controlling said restraining means.

3. An engine starter as set forth in claim 1 including further a switch for controlling the energization of the motor, and means responsive to the closing of said switch for releasing the restraining means.

4. In a starter motor having a longitudinally shiftable armature shaft a pinion journalled thereon having an overrunning connection therewith and shiftable thereby into and out of mesh with a gear of an engine to be started, a spring means biasing the armature shaft in position to demesh the pinion, a latch for restraining the spring means and manually controlled means for releasing the latch.

5. An engine starter as set forth in claim 4 including further a detent for yieldably holding the armature shaft in position to maintain the pinion in mesh with the engine gear.

6. An engine starter as set forth in claim 4 including further a. switch for controlling the starting motor having a movable plunger adapted to engage and release the latch when the switch is open.

7. In a starter for internal combustion engines a motor having a field and an armature with a shaft extending therefrom at both ends, a pinion slidably journalled on one end of the armature shaft, means for actuating the pinion by the shaft including a clutch and a threaded connection, spring means operating on the opposite end of the shaft to move the shaft axially to decenter the armature with respect to the field, a latch for holding said spring means compressed and manually controlled means for releasing the latch.

8. In a starter for internal combustion engines a motor having a field and an armature with a shaft extending therefrom at both ends, a pinion slidably journalled on one end of the armature shaft, means for actuating the pinion by the shaft including an overrunning clutch and a threaded connection, spring means operating on the opposite end of the shaft to move the shaft axially to decenter the armature with respect to the field, a latch for holding said spring means compressed, and means responsive to deenergization of the starting motor for releasing the latch.

9. An engine starter as set forth in claim 8 in which the centering of the armature by magnetic flux when the motor is energized is arranged to move the pinion into partial mesh with a gear of the engine to be started, and said threaded connection is arranged upon rotation of the armature to move the pinion fully into mesh with the engine gear and to close said clutch.

10. In an engine starter a pinion, electromagnetic means for moving the pinion longitudinally into mesh with a gear of an engine to be started and for rotating the pinion to thereby crank the engine, spring means for resisting the magnetic shifting movement of the pinion thereby storing I up energy therein for shifting the pinion out of mesh with the engine gear, and manually controlled means for restraining the spring means.

11. In an engine starter a pinion, electromagnetic means for moving the pinion longitudinally into mesh with a gear of an engine to be started and for rotating the pinion to thereb crank the engine, compression spring means for resisting the magnetic shifting movement of the pinion, thereb storing up energy in the spring for shifting the pinion out of mesh with the engine gear, means for holding the spring compressed, and means responsive to deenergization of the electromagnetic means, for releasing the holding means.

JAMES E. BUXTON.