DE4338637A1 - Control circuit for automobile starter motor protection - Google Patents

Abstract

The control circuit receives an activation signal from a key-operated starter protection device, with a power stage controlling the function of the electric starter motor. The power stage has a MOSFET (T3) inserted between a current source and the coil of an electromechanical protection device, its gate coupled to a voltage lifting circuit for the voltage provided by the current source, provided with an inhibit input coupled to a fault detector.Pref. the voltage lifting circuit uses an oscillator (4) and a voltage multiplier, with the oscillator having an inhibit input.

Description

The present invention relates to a weak current control circuit for a motor vehicle starter. Such a circuit is intended to the in the supply circuit of the electric starter switched on electromechanical contactor Taxes.

A first purpose of the invention is that Wiring costs and the dimensions of the contacts of the key-operated starter contactor to redu adorn.

A second purpose of the invention is that To prevent starter control if the elec motor due to prolonged or repeated Use should be overheated.

A third purpose is the interruption the starter circuit by one of a thief steel security system to enable outgoing signal chen.

For this purpose, the invention relates in particular a circuit that has an input for reception of an activation signal, which of a starter contactor comes, especially one key operated contactor and a power level  to control the functioning of the starter elec tromotors. The power level consists of one Transistor MOSFET that is between the current source and the coil of an electromechanical contactor is building. The grid of the transistor MOSFET is with connected to a voltage increase stage, which is suitable net is a greater tension than that of the To supply current source voltage, where the boost stage is a deactivation has gang, by a low-current signal is controlled.

The step-up voltage preferably includes an oscillator circuit and a voltage multiplier cher, said oscillator circuit one Contains input to prevent vibrations.

The voltage multiplier is advantageously made se from an assembly of diodes and capacitor ren.

According to a preferred embodiment of the The circuit according to the invention contains the invention also a heat protection level that deactivates The voltage signal corresponds to the voltage step chend a signal, which from an am Starter arranged heat transmitter goes out.

The heat protection stage advantageously consists of a transistor, the base of which is connected to the ground via a thermal contact attached to the starter and to the voltage source via a resistor R ₁ , the collector of said transistor being connected to the deactivation input of the voltage boost stage.

According to a variant, the invention contains Circuit a contactor to turn on the span level when the thermal contact is on Deactivation signal delivers.  

Another variant is the deactivation connected to a protection level that a window voltage comparator having a Deactivation signal delivers if that from a Anti-theft circuit outgoing signal not between the terminals of the mentioned voltage fen sters.

The protection level advantageously contains one High voltage comparator and an undervoltage comparator, whose outputs are connected together and provide a deactivation signal if that from Anti-theft circuit outgoing signal except half the range of one of the comparators mentioned lies.

The invention will be better understood in the light of Description of a non-limiting understanding the embodiment, wherein on the attached Drawings are referred to the following represent:

Fig. 1 shows the mimic diagram of the Stromkrei ses.

Fig. 2 shows the basic circuit diagram of the current circuit.

The circuit, an exemplary embodiment of which is shown in FIG. 1, contains:

• - a step ( 1 ) for detecting a warming;
• - a stage ( 2 ) for checking the status of an approval signal AD;
• - A stage ( 3 ) for low-current control.

The stage for detecting a warming ( 1 ) receives an electrical signal from a thermal contact TC, which is arranged on the brush holder disk of the starter. The purpose of this step is to protect the starter against excessive heating that could result from prolonged or repeated use of the starter. If excessive heating is detected, this stage activates a warning signal, for example an optical or acoustic display, and interrupts the control stage ( 3 ) so as to prevent the starter from being supplied with power. In exceptional cases, however, it is possible to neutralize this stage with a forced signal F.

The checking stage ( 2 ) compares the signal AD emanating from the anti-theft system with a fixed value which lies between the voltage of the vehicle battery and ground. This comparison mode allows the security of theft protection to be increased.

In the event of non-confirmation, the output of the checking stage ( 2 ) is activated, which triggers the switching off of the control stage ( 3 ).

The basic circuit diagram of the circuit is shown in Fig. 2.

The circuit has five inputs:

• - an entrance "+ den" which is connected to the key starter contactor is connected;
• - an input "+ Bat" which is connected to the positive terminal of the Battery is connected;
• - an input "- bat" that matches the mass of the Vehicle and therefore with the negative terminal of the battery rie is connected;
• - an input "F", which with a positive contactor of Starter is connected regardless of the detection excessive warming;
• - an input AD connected to the output of an anti-theft system;
  and an output 5 , which is connected to the coil of the electromechanical contactor of the starter.

During normal operation, the thermal contact is closed and the base of the transistor T _{1 is} connected to ground via the thermal contact TC and the collector is at the potential + bat.

The heating of the motor causes the thermal contact TC to open and this leads to the saturation of the transistor T ₁ via the resistor R ₁ . The collector of transistor T ₁ then tilts to the lower level.

The forced switch F nevertheless allows the base of the transistor T ₁ to be grounded regardless of the opening of the thermal contact TC, and thus makes it possible to keep the collector at the upper level even though the starter has been heated.

The checking stage ( 2 ) contains two comparators A ₁ and A ₂ , which define a specific comparator window by the value of the resistors R ₁₃ , R ₁₄ and R ₁₅ .

If the value of the signal AD is in the range of the permitted values, the checking stage ( 2 ) delivers a signal with a high level. If the value of the signal AD is outside this range, the output signal remains at the low level.

The low-current control stage ( 3 ) contains an oscillator ( 4 ) with a blocking input "inhib.", Which is connected to the outputs of the stage for detecting the heating ( 1 ) and the stage for checking the status of a switch-on signal AD ( 2 ), and an activation input "activ." which is connected to the key operated starter contactor. The frequency of the vibrations is determined by the resistors R ₃ , R ₄ and by the capacitor C ₁ . The output of the oscillator is connected to a voltage triplet, which consists of a network of diodes and capacitors.

The voltage supplied by the voltage tripler enables the saturation of a transistor MOSFET (channel N) T ₃ , whose drain connection is at the potential + bat and whose output is connected to the electromagnetic starter contactor.

The present invention has been here in the form of a non-limiting example described.

It goes without saying that the expert in will be able to do numerous variations men by using other types of temperature sensors or other circuits to create a blocking si gnals used for a voltage boost stage.  

Fig. 1

Entr'e de forcage F =
Forced entry F
Protection thermique =
heat protection
Entr´ed ′ authorization de d´marrage AD =
Input for switching on the starter AD
Cl´ d´marrage =
ignition key
Protection anti-vol =
Anti-theft device (steering lock)
Commande faible courrant =
Low power control
Dèmarreur =
Starter

Fig. 2

darreur = starter
Bat = battery
inhib = off
activ = on.

Claims (8)

1. Control circuit for a motor vehicle starter, suitable for receiving an activation signal from a starter contactor, in particular a key operated contactor and a power stage for controlling the functioning of the starter electromotive, characterized in that the power stage consists of a transistor MOSFET T ₃ , which is installed between the current source and the coil of an electromechanical contactor, and that the grid of the transistor MOSFET T _{3 is} connected to a step-up circuit which is suitable for supplying a voltage greater than the voltage supplied by the current source, the step-up circuit having a deactivation tion input "inhib", which is connected to at least one fault detection means. 2. Control circuit for a motor vehicle starter according to claim 1, characterized in that the voltage boost stage has an oscillator circuit ( 4 ) and a voltage multiplier, said oscillator circuit ( 4 ) having an "inhib" input for suppressing vibrations. 3rd control circuit for a motor vehicle starter  from an assembly of diodes and capacitors consists. 4. Control circuit for a motor vehicle starter according to one of the preceding claims, characterized in that it also contains a heat protection stage ( 2 ) which supplies a deactivation signal of the voltage increase stage accordingly a signal which emanates from a TC heat sensor attached to the starter. 5. Control circuit for a motor vehicle starter according to claim 4, characterized in that the heat protection stage consists of a transistor T ₁ , the base of which is connected to the current source via a thermal contact TC arranged on the starter and via a resistor R ₁ , wherein the collector of said transistor T _{1 is} connected to the deactivation input of the boost stage. 6. Control circuit for a motor vehicle starter according to claim 5, characterized records that he has a contactor F to the circuit of the voltage boost stage, if the thermal contact TC has a deactivation signal delivers. 7. Control circuit for a motor vehicle starter according to one of the preceding claims, characterized in that the deactivation input is connected to a comparator stage ( 3 ) which contains a window voltage comparator which provides a deactivation signal if it originates from a theft protection circuit Signal AD is not between the terminals of the voltage window mentioned. 8. Control circuit for a motor vehicle starter according to claim 7, characterized indicates that the protection level has an upper voltage comparator and an undervoltage comparator gate contains whose outputs are switched together and deliver a deactivation signal if that signal AD from the anti-theft system outside the area of one of the named Kompara lies.