Starter protection circuit

Details Starter protection circuit Starter protection circuit

1991-12-12

1993-08-31

Dolinar, Andrew M.

Internal-combustion engines

Starting device

Condition responsive control of starting device

290 38R, 318473, 361 25, F02N 1108

Patent

active

052399540

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to a starter protection circuit for the starting device of an internal combustion engine of a vehicle, particularly a motor vehicle.
The internal combustion engines of vehicles, particularly of passenger-carrying motor vehicles and utility vehicles are equipped with an electrically operating starting device. Via a start switch to be operated by means of an ignition key, a starter relay can be operated which connects a starter to a battery of the vehicle and establishes a mechanical coupling between starter and internal combustion engine via a pinion arrangement. As soon as the internal combustion engine has started, the driver of the vehicle opens the start switch by releasing the ignition key as a result of which the starter relay drops out and the starter is taken out of operation. The starter is only suitable for a short-time operation, that is to say it can only withstand a warming caused by the relatively large starter current for the short time of a starting process. Thus, a starter failure (in most cases total loss due to overheating) will occur if, for example, the start switch "hangs up" since this leads to a continuous operation of the starter for which it is not designed.


SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a starter protection circuit which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of the present invention resides, briefly stated, in a starter protection circuit which has a thermoswitch assigned to a starter and when operated, activating a relay interrupting the starter operation and after resumption of the cold switching state of the thermoswitch the starter can be operated again by means of a relay operating key.
When the starter protection circuit is designed in accordance with the present invention it has the advantage that when the start switch hangs up or similar, this will not lead to a destruction of the starting device, particularly its starter. If the starter is operated for an inadmissibly long period, for example due to a fault (particularly the hanging up of the start switch), a thermoswitch assigned to it operates. The operating of the thermoswitch due to a corresponding heating up of the starter has the consequence that a relay is operated which interrupts the starter operation. Thus, the starter is switched off before it destroys itself due to the developing heat. A relay operating key is provided so that the starter can still be operated again after a cooling time in spite of the hung-up start switch. This key can be preferably operated from the drivers seat. The operation causes the relay to switch so that the interruption of the starter operation is eliminated. Thus, the starter protection circuit according to the invention not only offers an overload protection for the starter but also provides the possibility of resuming an initially interrupted starter operation in spite of a fault.
In accordance with a further development of the invention, it is provided that the relay exhibits a self-holding circuit. Thus, the relay position interrupting the starter operation can be maintained by the self-holding circuit.
The relay operating key preferably has a normally-closed contact which is located in the self-holding switching circuit of the self-holding circuit. Operating the relay operating key interrupts the self-holding switching circuit so that the relay previously operated drops out again as a result of which a new starter operation is possible if the thermoswitch has resumed its cold switching state.
According to a preferred further development of the invention, the thermoswitch has a normally-open contact which operates when a limit temperature is exceeded. If the limit temperature is exceeded, this normally-open contact closes as a result of which the winding of the relay is excited and a switching state interrupting the starter operation is assumed. The thermosw

REFERENCES:
patent: 4389692 (1983-06-01), Sander et al.
patent: 4494162 (1985-01-01), Eyler
patent: 4674344 (1987-06-01), Kazino et al.

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