US3210554A - Electric starter mechanism for internal combustion engines - Google Patents

Description

1965 A. H. SEILLY ETAL 3,210,554

ELECTRIC STARTER MECHANISM FOR INTERNAL COMBUSTION ENGINES Filed April I9, 1963 2 Sheets-Sheet 1 Q Q W MQ -N F "i 5 w i 5 nu 22 s x j S Q R Q j w s w 3\ g m a l 2/ b a N N E N a H N I \m OKYL 5, 1965 A s l ETAL 3,210,554

ELECTRIC STARTER MECHANISM FOR INTERNAL COMBUSTION ENGINES Filed April 19, 1963 2 Sheets-Sheet 2 United States Patent 3,210,554 ELEQTRIC STARTER MECHANISM FOR INTERNAL COMBUSTION ENGINES Alec Harry Seiily, North Wembley, Pierre Henri Peitret, London, and Denis Wheatiey, New Malden, England, assignors to C.A.V. Limited, London, England Filed Apr. 19, 1%3, Ser. No. 274,163 Claims priority, application Great Britain, Apr. 26, 1962, 15,922/62 1 Ciairn. (Cl. 29tl38) This invention relates to electric starter mechanisms for internal combustion engines, and of the kind comprising an electric motor, a shaft extending co-axially from one end of the rotor, a sleeve surrounding said shaft, a quick pitch screw-thread or equivalent connection between the sleeve and shaft, a pinion formed on, or secured to the sleeve, a solenoid including a spring loaded tubular armature surrounding the sleeve, said solenoid when energised being arranged to move the pinion axially on the shaft into engagement with a toothed wheel of the engine, and a motor controlling switch arranged to be closed by the solenoid armature when the latter is moved to its fullest extent under energisation.

The object of the invention is to provide such mechanism in a convenient form.

According to the invention a starter mechanism of the kind specified comprises an abutment on the sleeve, an axially movable part on the solenoid armature disposed to contact the abutment, and resilient means acting on said part in a direction to urge it towards the pinion, the arrangement being such that in the event of a tooth of the pinion engaging a tooth of the engine wheel endto-end, the solenoid armature can be moved against the action of the resilient means into a position to close the switch.

In the accompanying drawings FIGURES l and 2 respectively are sectional side and end views of an example of the invention, FIGURE 1 being a section on the line 11 of FIGURE 2, and FIGURE 2 being a section on the line 22 of FIGURE 1.

Referring to the drawings there is provided a substantially cylindrical casing in which are mounted the stator windings 11 of an electric motor. The rotor 12 of this motor is mounted on a tubular spindle 13 surrounding a central shaft 14. One end of the spindle 13 is co-terminous with the adjacent end of the rotor (hereinafter termed the front end), whilst the rear end of the spindle extends from the rear end of the rotor and has mounted thereon a commutator 15. Also the rear end of the spindle 13 surrounds a bearing bush 16 carried by a central spigot 17 extending forwardly from the interior of a cap 18 forming a rear end closure for the casing 10.

The rear end of the shaft 14 incorporates splines which are formed at a very large helix angle so as to provide an interference engagement with splines in the spindle 13 so as to prevent both relative axial and angular movements. The shaft 14 extends forwardly to a substantial distance beyond the forward end of the rotor 12 to provide an extension 14a which at its forward end is mounted in a bearing 19 in a cover 20 connected to the casing 10. Moreover, within the middle portion of the rotor (considered in an axial direction) the shaft 14 is waisted so as to provide a substantial clearance between the spindle 13 and shaft to render the shaft torsionally resilient to a fairly high degree.

A portion of the extension 14a between the front bearing 19 and the rotor 12 has formed on it a quick pitch screw-thread having a helix angle of approximately 60. With this portion of the shaft is engaged a complementary screw-thread formed on the interior of a sleeve 21 surrounding the extension 14a. On the front end of the sleeve is formed a pinion 22 which is adapted to be moved axially into engagement with a toothed flywheel 23 of the engine with which the starter mechanism is associated.

In the cover 24 is mounted the winding 24 of a solenoid. The armature 25 of the solenoid, which is loaded towards the rotor 12 of the motor by means of a coiled compression spring 26, surrounds the sleeve and is of tubular cylindrical form having a step 25a on its internal periphery. An annular ring 27 is normally held against the step 25a by means of a coiled compression spring 28 reacting at its other end on an abutment mounted at the rear end of the armature. Moreover, the inner edge of the ring 27 is arranged, when the armature is drawn into the winding against the action of the spring 26, to contact an abutment ring 29 located on the sleeve 21.

The cover 26 is provided at its rear end with a flange which is connected by screws to a mounting plate 30, the flange and plate being provided with registering holes for the reception of bolts whereby the mechanism can be mounted on the engine. Since in use, the bolts will serve to clamp the flange and plate together the aforesaid screws may be relatively small. The mounting plate 39 is secured to the casing by means of a pair of relatively long bolts 31 extending through the stator core and rear end cap 18, but between the mounting plate and the casing is interposed a hollow cylindrical part 32 formed from a transparent material such, for example, as a polycarbonate. The ends of the part 32 have integral dowels engaging holes in the casing 10 and plate 30 respectively so that when the long bolts 31 are in position, the part 32 constitutes a rigid forward extension of the casing through which the rear end of the sleeve and other associated parts to be referred to can be viewed.

The pair of long bolts 31 are disposed at 180 to one another relative to the axis of the shaft, and pivoted about their rearward end portions within the cap 13 are a pair of brushes 33 co-operating with the commutator 15 and connected to the field windings. Another pair of brushes 33a disposed at to the pair 33 are mounted about pivots 34 extending from an annular carrier 35 through which the bolts 31 extend and clamped in position by the cap 18, the brushes 33a being earthed.

On the mounting plate 30 is the fixed contact 36 of a motor controlling switch, the moving contact 36a of this switch being carried from the rear end of the armature 25 and being arranged to close the switch when the armature has been fully drawn forwardly into the winding 24.

Surrounding the rear portion of the sleeve 21 is a collar 37 which is urged forwardly by a coiled compression spring 38 interposed between it and an abutment ring on the sleeve. The internal periphery of the collar at its front end is of truncated conical cam form, and surrounds a plurality of angularly spaced balls 39 located respectively within holes in the sleeve 21. When the sleeve is at its rearward position the balls 39 are held by the cam form of the collar in engagement with a circumferential groove 40 in the shaft to locate the pinion against inadvertent engagement with the flywheel. However, in the forward position of the sleeve the balls are urged by the collar into a corresponding number of recesses 41 in the shaft and are held positively therein by the rear inner cylindrical surface of the sleeve 37 to locate the pinion against premature disengagement from the flywheel.

When it is required to start the associated engine, a remote switch is closed to cause the energisation of the solenoid winding 24. The armature 25 is acted upon by the magnetic flux created by the current flowing in the winding 24, and is moved against the action of the spring 26 towards the left as seen in FIGURE 1. After a small movement of the armature the ring 27 contacts the abutment 29 and the sleeve 21 is also moved forwardly by an amount sufiicient to engage the teeth of the pinion 22 with the teeth of the flywheel 23. This movement is permitted because the balls 39 are urged outwardly from the groove 40 by the relative movement of the sleeve 21 and shaft 14 and in doing this the collar 37 is moved against the action of its spring. Moreover, during this initial axial movement of the sleeve 21 angular movement is imparted thereto by the screw thread connection between the sleeve and the shaft 14 and this assists smooth engagement of the teeth of the pinion and the teeth of the flywheel. When the armature 25 has moved fully into its winding the switch contacts 36, 36a are closed to start the motor and the axial thrust developed on the sleeve as a result of the transmission of torque through the quick-pitch thread completes the engagement of the teeth of the pinion with the teeth of the flywheel. When the pinion is fully engaged with the flywheel the balls move into the recesses 41 and are positively held therein by the collar 37 which moves forward under the influence of its spring so that its rear inner cylindrical surface contacts the balls.

In the event of a tooth of the pinion 22 engaging a tooth of the flywheel 23 end-to-end and so preventing the engagement as described taking place, the armature 25 can still move fully into its winding due to the permitted relative axial movement of the ring 27 and armature against the action of the spring 28. Thus the motor will be started and will cause the pinion to be rotated until the aforesaid end-to-end engagement is cleared whereupon partial engagement is effected by the spring 28 and full engagement is effected as described by the quick-pitch screw thread.

When the engine is started, and the remotely disposed switch is opened, the armature 25 will return to its original position under the action of the spring 26 and will urge the collar 37 in a direction away from the pinion to allow the balls to be moved out of the recesses 41. At the same time the switch contacts 36, 36a will be opened and the pinion wil be moved out of engagement with the flywheel, partly by the action of the spring 26 acting on the sleeve via the armature 25, the ring 27 and 4 the collar 37, and partly by the action of the quick pitch screw thread. When the sleeve has fully returned to its initial position the balls 39 wil re-engage with the groove 40 in the shaft to prevent inadvertent re-engagement of the pinion with the flywheel. If the remotely disposed switch is not released when the engine is started, an overspeed device such as is described in our co-pending United States patent application Serial No. 258,745, filed February 15, 1963, operates to break the circuit of the solenoid which allows the sequence as described above to take place.

Having thus described our invention what we claim as new and desire to secure by Letters Patent is:

Starting apparatus comprising an electric motor having a rotor, a shaft extending from one end of said rotor, a sleeve surrounding said shaft, a quick pitch thread connection intermediate the sleeve and shaft, a pinion mounted on said sleeve for engagement with a toothed wheel to be driven, an annular solenoid winding surrounding said sleeve in spaced relationship thereto, an axially movable annular solenoid armature surrounding said sleeve, a step defined on the internal periphery of said armature, an annular part situated adjacent said step, a coiled compression spring acting intermediate said part and the sleeve for urging said part into contact with said step, an abutment on the sleeve and positioned to be contacted by said part, when the solenoid armature is moved by the flow of current through the winding, the movement of said armature being imparted to the sleeve so as to cause the pinion to be engaged with the toothed wheel, said spring being arranged to be compressed to allow the solenoid armature to move to its fullest extent when the engagement of the pinion and toothed wheel is hindered, and a motor controlling switch arranged to be closed when the solenoid armature has moved to its fullest extent.

References Cited by the Examiner UNITED STATES PATENTS 1,883,432 10/32 Whitney 123-179 1,905,836 4/33 Fitz Gerald 123179 X 1,970,885 4/34 Chilton 123179 X 3,124,694 3/62 Seilly 123-479 FOREIGN PATENTS 902,996 8/62 Great Britain.

MARK NEWMAN, Primary Examiner.

RICHARD B. WILKINSON, Examiner.

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