This invention relates to a starter motor assembly for an internal combustion engine.

The starter motor is switched ON and OFF by the user by means of a solenoid switch which is usually mounted integrally on the fixing bracket of the starter motor.

When the solenoid is de energized after the motor has cranked and started the engine, the motor armature continues to rotate for some time, on its own, before coming to a complete stop.

An object of this invention is to bring the armature to a complete stop, quickly and easily, by the incorporation of a simple device therein.

Another object of this invention is to avoid any major alteration in the known starter motor assembly while achieving the above mentioned objective.

Accordingly, the proposed starter motor assembly for an internal combustion engine comprises a permanent magnet starter motor and solenoid unit operated by a d.c power source either with grounded negative terminal or insulated version ; means for switching ON and OFF the said power to the starter motor and solenoid unit while starting the engine; and means connecting the positive terminal of the armature to ground whenever the said power is switched OFF.

This invention will now be described with reference to the accompanying drawings which illustrate in Fig. 1, the relevant portion of the known starter motor assembly And in Fig.2, the relevant portion of one of possible embodiments of the starter motor assembly proposed herein, by way of example, and not by way of limitation.

In the known starter motor assembly, once the battery connection to the motor gets interrupted, the armature slows down and comes to a complete stop after some time. This results in mechanical wear of the carbon brushes and bearing bushes. Also, the slowing down movement of the armature creates ar) undesirable noise.

In Fig 1, the starter motor 201 is shown connected to a battery 302, ignition switch 303 (operated by a key by the User) and a magnetic solenoid unit 210.

When the ignition switch 303 is switched ON, the spindle 304 will be pushed forward to cause the moving contact 102 to close the fixed contacts 211 and 212. Consequently, power from the battery is supplied to the motor 202. As a result, cranking of the engine takes place. As soon as the engine fires and the switch 303 is turned OFF, the cranking operation ceases, the spindle 304 along with contact 102 reverts to rest, with the fixed contacts 211 and 212 open, preventing further power supply to the motor 202. However, in this situation, the armature of the motor continues to run freely, coming to rest only after a period of time elapses, giving rise to the drawbacks mentioned earlier.

The relevant portion of the embodiment of the proposed starter motor assembly according to this invention is illustrated in Fig. 2 of the drawings.

In Figs. 1 and 2 like reference letters indicate corresponding parts. The departure which this invention makes from the known starter motor assembly consists in means connecting the positive terminal of armature to ground whenever power to the motor is switched OFF.

One form of such means is the bypass member 100, one end of which is connected to the positive terminal of the armature and the other end 305B of which is grounded when the moving contact 102 connects 305B and 305A which is already grounded. The bypass member 100 has two fixed in-line open contacts 305A and 305B which render the circuit of the said member open when the spindle 304 is thrust forward to cause the moving contact 102 to close the fixed contacts 211 and 212, consequently supplying power from the battery to the starter motor 202 to result in the cranking of the engine taking place. As soon as the engine fires and the switch 303 is turned OFF, the spindle 304 reverts to rest and the fixed contacts 211 and 212 open cutting off power supply to the motor 202. However, what is noteworthy is that when the spindle reverts to rest, moving contact 102 closes the in line contacts 305A and 305B of the by pass member 100, thus connecting the positive terminal of the motor 202 to ground.

It will be observed that it is only when the moving contact 102 comes to rest, that is to say, when the power supply to the armature is cut off, that the grounding of the armature takes place and not otherwise. In other words, power supply to the motor can always be resumed by turning ON the switch 303, to cause the moving contact 102 to close the contacts 211 and 212 and open contacts 305A and 305B of the bypass member 100, to commence the cranking operation.

It will be observed that on cutting off power supply to the motor, after the engine starts up, the armature which is rotating at high speed generates voltage in the presence of a magnetic field and the moving contact 102 along with bypass member 100 and projection on core plate 305 provides a low resistance path for the armature current to ground. Accordingly, a relatively high armature current which is constrained to flow through the low resistance path to ground causes the armature to come to a complete stop in a much shorter period than that of the known starter assembly.

It will be appreciated that various other embodiments of this invention are possible without departing from its scope and ambit.

We Claim:

1. A starter motor assembly for an internal combustion engine comprising a permanent magnet starter motor and solenoid unit operated by a d.c power source with grounded negative terminal; means for switching ON and OFF the power to the starter motor and solenoid unit while starting the engine; and means connecting the positive terminal of the armature of the said motor to ground whenever power to the said motor is switched OFF.

2. A starter motor assembly as claimed in Claim 1 wherein the means connecting the positive terminal of armature to ground consists of a bypass member for conveying armature current to ground whenever power to the said motor is switched OFF and the interaction of the armature current and the magnetic field set UP by the field system creates a torque to bring the armature to stop quickly.

3. A starter motor assembly for an internal combustion engine substantially as herein described with reference to, and as illustrated by, Fig. 2 of the accompanying drawings.