EP0526307B1 - Starter control device for a motor-car type vehicle - Google Patents

Description

The present invention relates to a device for controlling a starter for a motor vehicle.

A starter comprises in particular a contactor whose winding is supplied by the vehicle battery through a start switch and whose role is, on the one hand, to constitute a linear actuator to move a starter pinion along a shaft motor from a rest position to an engagement position with a ring gear located on a flywheel and, on the other hand, to constitute a power relay whose contact allows the supply of the electric motor of the starter, said motor rotating the starter pinion.

A starter for a motor vehicle is called upon to operate in a wide temperature range such as, for example, from -30 ° C to + 120 ° C.

In order for the contactor to trip, in other words to work in all cases, it is necessary to size its winding for the maximum temperature threshold, which corresponds to a maximum value of the ohmic resistance of said winding.

For lower operating temperatures, that is to say in the vast majority of cases, the supply voltage supplied by the battery is very much higher than the voltage necessary for its triggering, triggering voltage commonly known as conjunction hence a very large tripping current which requires a large dimensioning of the start switch and the electrical conductors associated therewith.

Furthermore, this results in numerous drawbacks, such as a violent propulsion of the starter pinion in the crown with the consequence of a rapid deterioration of the front faces of their teeth and a noise of impact of the starter pinion, which can be unpleasant for the driver of the vehicle.

This violent propulsion also causes a phase shift which is difficult to control between the initiation of the translational movement of the starter pinion and the closing of the power contacts causing the power to the electric motor and therefore the rotation of the starter pinion. However, its premature rotation, that is to say before its engagement with the toothed ring, also results in a reduction in the longevity of the starter pinion gear / toothed ring.

These same drawbacks are encountered, whether it is a contactor with one winding or a contactor with two windings, that is to say a contactor comprising a call winding and a holding winding which allows reduce the consumption of the contactor during starter operation.

Although attempts have been made to replace the control systems of such contactors based on electromagnetic relays with static systems using amplifiers whether or not associated with a voltage generator, the problems mentioned above have not been solved.

The document FR-A-2 611 981 shows a starting control device using a voltage ramp generator as described in the document EP-A-0 099 941 allowing the contactor to trip under a reduced voltage, which avoids too violent propulsion of the pinion.

However, since the starter operates over a wide temperature range and the contactor conjunction voltage being proportional to said temperature, it is desirable that this conjunction voltage be reached in as short a time as possible so as to minimize overheating electronic power units.

The present invention solves the problems mentioned above and proposes for this purpose a device for controlling a starter for a motor vehicle comprising a starting switch connected to a battery delivering a battery voltage, a contactor comprising at least one winding and a contact. power whose closing allows the supply of an electric motor, an amplifier intended to deliver a control voltage of the winding, a voltage generator comprising means for varying the control voltage, implemented during the closing the start switch, said variation means being arranged so as to deliver, when the start switch is closed, a voltage lower than the contactor conjunction voltage and to increase the control voltage, so as to control the contactor at a minimum necessary voltage lower than the battery voltage, the generator ension comprising in particular two resistors associated with a capacitor, the junction point of one of the resistors with the capacitor being connected to the input of the amplifier, so as to constitute a voltage ramp generator with positive or negative coefficient characterized in that the voltage generator includes temperature compensation means suitable for delivering, when the switch is closed, a voltage proportional to the operating temperature of the starter.

• la figure 1 est un schéma bloc d'un dispositif de la présente invention,
• la figure 2 est un diagramme temporel de la tension de commande appliquée au contacteur du démarreur,
• la figure 3 est un schéma détaillé d'une première forme de réalisation de l'invention,
• la figure 4 est un schéma détaillé d'une seconde forme de réalisation de l'invention.

The present invention will be better understood on reading the description which follows with reference to the appended drawings in which:

• FIG. 1 is a block diagram of a device of the present invention,
• FIG. 2 is a time diagram of the control voltage applied to the starter contactor,
• FIG. 3 is a detailed diagram of a first embodiment of the invention,
• Figure 4 is a detailed diagram of a second embodiment of the invention.

We first refer to Figure 1 where the device shown comprises a battery B, the negative terminal of which is connected to ground by a conductor 11 and the positive terminal of which is connected to a movable contact of a start switch K.

When the switch K is closed, the voltage Ub delivered by the battery B is applied to the input of a voltage generator 12 whose output is connected to an amplifier 13 delivering a voltage Us for the control of a contactor 14 , more specifically for controlling an exciter winding L, said contactor 14 also comprising a power contact R, one of the terminals of which is connected to the positive pole of the battery B, and the other terminal of which is connected to the electric motor M of the starter, in particular for a motor vehicle.

When the winding L of the contactor 14 is made up of two windings, one called the call and the other called the holding having the role of reducing the consumption of the contactor 14 during the operation of the starter, the device further comprises, as shown in dotted lines in FIG. 1, an economy circuit 15 the commissioning of which is controlled by the contact R and the output of which is connected to the input of the amplifier 13.

The voltage generator 12 includes means for varying the control voltage Us of the contactor 14, means used when the start switch K is closed.

The variation in voltage Us is shown in the diagram in FIG. 2, on which the time t has been plotted on the abscissa and the voltage Us on the ordinate.

When closing K, the voltage generator 12 is arranged so that the voltage Us has a value Uo which is lower than the tripping voltage or conjunction voltage Uc of the contactor and making the voltage Us gradually increase from its initial value Us to the value Uc which, for a given operating temperature, is between Uo and the battery voltage Ub.

Thus, after a time tc, the contactor 14 is closed, at an optimum voltage, lower than the battery voltage Ub which is only reached after a time tb greater than the time tc.

In this way, the drawbacks mentioned above are avoided and in particular too violent propulsion of the starter pinion gear.

To keep the value of the conjunction voltage Uc optimized throughout the operating temperature range of the starter, the voltage generator 12 includes temperature compensation means making it possible to increase the value Uo when the l is closed. start switch K.

Referring now to Figure 3 which illustrates a first embodiment of the device according to the invention, the contactor 14 having a double winding consisting of a call winding La and a holding winding Lm.

The device comprises a battery B, the negative terminal of which is connected to ground by a conductor 11, and the positive terminal of which is connected to a first pad of a movable contact of a starting switch K conventionally controlled by the key contact information.

The other block of the switch K is connected, on the one hand, to a supply terminal of an operational amplifier A, and on the other hand, to resistors R3, R7, the resistor R7 being connected to the conductor mass 11.

A diode D1 is connected in parallel to the resistor R3, the anode of the diode D1 being connected with resistance R3 to a capacitor C1.

The capacitor C1 is also connected, on the one hand, to the non-inverting input of the operational amplifier A, and on the other hand, to ground 11 via a resistor R4 to which a diode D2 is connected in parallel, the anode is at earth 11.

The resistors R3, R4, R7, the capacitor C1 and the diodes D1, D2 constitute the voltage generator 12.

The output of operational amplifier A is connected to its inverting input by a feedback resistor R1 connected to ground 11 via a resistor R2, R1 and R2 determining the gain of operational amplifier A.

The output of the operational amplifier A is also connected to the control gate g of a power transistor T1 produced in P-channel MOS technology.

The gate g is connected to the drain d of the transistor T1 via a resistor R5, said drain d being itself connected to the positive pole of the battery B and to a first pad of the power contact R of the contactor 14.

The source s of the transistor T1 is connected to the junction point of the call windings La and of the holding Lm of the contactor 14.

The other end of the holding winding Lm is connected to earth 11, while the other end of the call winding La is connected to the second contact pad R and to the starter motor M.

Amplifier A, transistor T1, resistors R1, R2, R5 constitute amplifier 13.

In what follows, we will call V1, the voltage existing at the non-inverting input of amplifier A; V2, the voltage applied to the gate g of the transistor T1 and Us the control voltage emitted by the source s of the transistor T1.

The operation of such a device is the next :
When the switch k closes, the amplifier A is supplied by the battery voltage Ub, which is also applied to the variable voltage generator 12 and in particular to the resistors R3, R4 and to the capacitor C.

At time t = 0, the voltage V1 is equal to ub (R4 / R4 + R3).

, Uo étant inférieure à la tension de conjonction du contacteur 14, R3,R4 et C1 constituant un générateur de rampe de tension à coefficient négatif.The gain of amplifier A is chosen so that at a voltage V1, there corresponds a voltage V2 applied to the gate g of transistor T1 so as to have $\text{Us = Uo}$

, Uo being less than the conjunction voltage of the contactor 14, R3, R4 and C1 constituting a voltage ramp generator with negative coefficient.

As time t increases, V1 therefore decreases V2 decreases, which leads to an increasingly negative polarization of the gate g of the transistor T1. Said transistor T1 thus becoming more and more conductive, this results in an increase in the voltage Us on its source s.

When Us is equal to Uc corresponding to the optimum conjunction voltage of the contactor 14, the power contact R closes allowing the motor M to be supplied.

The contact R being closed, the two ends of the call winding La being at the same potential, this current is no longer crossed by any current, only the holding winding Lm is supplied.

When the vehicle's engine is running, the ignition key returns from a start position to an on position, which causes the switch K to open.

The amplifier A is no longer supplied becomes inactive and the gate and drain voltages of the transistor T1 are equal, the latter goes into the blocked state, and the contact R opens, the winding Lm is no longer supplied . The capacitor C1 can then discharge rapidly into the resistor R7 thanks to the diodes D1, D2. The entire device is then ready for a new start.

Reference is now made to FIG. 4 which illustrates a second embodiment of the device in the case where the contactor 14 has only one winding L and where it is therefore necessary to incorporate an economy circuit 15.

Elements identical to those of FIG. 3 bear identical references and will therefore not be described in detail.

We find in Figure 4 a battery B; a start switch K; a voltage generator 12 consisting of resistors R3, R4, R7 of capacitor C1 and diodes D1 and D2; an operational amplifier A associated with resistors R1 and R2 which determine the value of its gain.

It should be noted that the non-inverting input of amplifier A is no longer connected to the junction point of resistor R4 and capacitor C1 but to the junction point of resistor R3 and capacitor C1, thus R3, R4 and C1 constitute a positive coefficient voltage ramp generator.

The output of amplifier A is connected to the gate g of a power transistor T1 produced in N-channel MOS technology, the source of which is connected to ground.

The drain d of the transistor T1 is connected to one of the ends of the winding L of the contactor 14, the other end of the winding L being connected to the positive pole of the battery B.

The contactor 14 also includes a power contact R allowing the supply of the motor M.

The junction point of the resistor R5 and the gate g of the transistor T1 is connected to the cathode of a Zener diode DZ whose anode is connected to the collector of a second transistor T2 of the npn type.

The emitter of transistor T2 is connected to ground and its base is connected, via a resistor R6, to the junction point of motor M and power contact R.

The transistor T1, the Zener diode DZ and the resistor R6 constitute, as will be seen below, the economy circuit 15.

In what follows, we will call V1 the voltage existing at the non-inverting input of amplifier A, V2 the voltage applied to the gate g of transistor T1, V3 the voltage present at the output of amplifier A and Us la control voltage emitted by the drain d of the transistor T1.

, Uo étant inférieure à la tension de conjonction du contacteur 14
   A l'instant t = 0, la base du transistor T2 est reliée à la masse 11 via la résistance R6 et la résistance d'induit du moteur. Il en résulte que le deuxième transistor T2 est dans un état bloqué. La tension V2 appliquée à la grille g du transistor T1 est égale à la tension V3 en sortie de l'amplificateur A.The operation of such a device is as follows:
When the switch K closes, the amplifier A is supplied, via its terminal a, by the voltage Ub which is also applied to the variable voltage generator 12 and in particular to the resistors R3 and R4 and to the capacitor C1
At time t = 0, the voltage V1 is equal to Ub (R4 / R4 + R3). The gain of amplifier A is chosen so that a voltage V1 corresponds to a voltage V2 applied to the gate g of transistor T1 so as to have $\text{Us = Uo}$

, Uo being less than the conjunction voltage of the contactor 14
At time t = 0, the base of transistor T2 is connected to ground 11 via resistor R6 and the armature resistance of the motor. As a result, the second transistor T2 is in a blocked state. The voltage V2 applied to the gate g of the transistor T1 is equal to the voltage V3 at the output of the amplifier A.

R3, R4 and C1 constituting a voltage generator with positive coefficient, as time t increases, V1 increases and this results in a proportional increase in voltages V3, V2 and Us.

When Us reaches the value Uc corresponding to the optimum conjunction voltage of the contactor 14, the power contact R closes allowing the motor M to be supplied.

The base of T2 then receives the battery voltage Ub via the resistor R6, T2 goes to the conductive state.

The voltage V2 is then reduced to a value corresponding to the voltage Vz of the Zener diode DZ increased by the saturation voltage of the transistor T1. This results in a reduced voltage Us allowing the state of contactor 14 to be kept in conjunction.

Resistor R5 provides simultaneous protection of the Zener DZ diode and the output of amplifier A.

When the vehicle's engine is running, the ignition key returns from a start position to an on position, which causes the switch K to open.

The amplifier A is no longer supplied becomes inactive, the voltage V1 is zero, and therefore V2 is zero, which causes the transistor T1 to go into the off state. Since winding L is no longer supplied, relay R opens and the starter is stopped.

The capacitor C1 can then discharge rapidly into the resistor R7 thanks to the diodes D1, D2. The entire device is then ready for a new start.

As mentioned above, the starter is called upon to operate in a wide temperature range, where the higher the temperature, the higher the voltage Uc necessary for tripping of the contactor 14. It is moreover desirable that the time tc making it possible to pass from the value Uo to the value Uc is as short as possible so as to minimize the heating which is the object in particular of the transistor T1. It is indeed at high temperature that the dissipable power of such a transistor is the lowest.

It is visible on the diagram of the figure, that to reduce the time tc it is necessary to increase the value of Uo.

To this end, as shown on the left side of FIGS. 3 and 4, the resistor R3 of the voltage generator 12 consists of a fixed resistor Ra in series with a resistor Rb, the value of which varies as a function of the temperature . Preferably, the resistance Rb is a resistance of the CTN type with a negative temperature coefficient.

It will be appreciated that the entire device being mounted inside the starter, the value of the resistance Rb is a function of the actual operating temperature of said starter.

The present invention is not limited to the embodiments described above and shown in the figures, but encompasses any variants or modifications that a person skilled in the art could make to them.

In particular, the amplifier A here of the operational type can be replaced by any amplifier, in the same way the MOS transistor T1 can be replaced by several transistors whether they are of MOS technology with N or P channel or with silicon of the npn type or pnp.

Similarly, the voltage generator 12 described develops a variable DC voltage, but could develop an alternating variable voltage without departing from the scope of the invention.

The same would be true if the voltage generator developed a pulsed voltage with a variable ratio between the duration of full voltage and the duration of zero voltage.

Of course, in these latter two cases, the values of the voltages, in particular of Uo and Ub, to be taken into account would be the effective values of said tensions.

Claims (5)

1. A control device for a motor vehicle starter, comprising a starter circuit breaker (K) connected to a battery (B) which supplies a battery voltage (Ub), a contacter (14) having at least one winding (L) and a power contact (R), closure of which enables an electric motor (M) to be energised, an amplifier (13) adapted to supply a control voltage (Us) to the winding (L), a voltage generator (12) which includes means for varying the control voltage (Us), operative while the starter circuit breaker (K) is being closed, the said means being so arranged as to deliver, during closing of the starter circuit breaker (K), a voltage (Uo) which is lower than the operating voltage (Uc) of the contactor (14), and to cause the control voltage (Us) to increase in such a way as to control the contactor (14) at the minimum necessary voltage (Uc) which is lower than the battery voltage (Ub), the voltage generator comprising, in particular, two resistors (R3, R4) associated with a capacitor (C1), the junction point of one of the resistors (R3, R4) with the capacitor (C1) being connected to the input of the amplifier (13) so as to constitute a ramp voltage generator having a positive or negative coefficient, characterised in that the voltage generator (12) includes temperature compensating means (R3, Ra, Rb) adapted to deliver, during closing of the circuit breaker (K), a voltage (Uo) which is proportional to the operating temperature of the starter.
2. A control device according to Claim 1, characterised in that the temperature compensating means (R3, Ra, Rb) comprise a fixed resistance (Ra) associated with a resistor (Rb) of the CTN type having a negative temperature coefficient.
3. A control device according to one of the preceding Claims, characterised in that the voltage generator (12) includes a circuit (D1, D2, R7) for rapid discharge of the capacitor (C1) after opening of the starter circuit breaker (K).
4. A control device according to one of the preceding Claims, characterised in that it includes an economy circuit (15) which is arranged to deliver to the winding (L) of the contactor (14) a voltage (Us), lower than the operating voltage (Uc), after the power contact (R) has closed.
5. A control device according to Claim 4, characterised in that, the amplifier (13) comprising an operational amplifier (A) associated with a power transistor (T1), the economy circuit (15) comprises a Zener diode (DZ), the cathode of which is connected to the control grid (G) of the transistor (T1), with its anode being connected to the collector of a second transistor (T2), the said second transistor (T2) being in a blocked state after the contact (R) has closed and switching to the conducting state during the closing of the said contact (R), in such a way that the Zener diode (DZ) delivers, via the transistor (T1), a voltage (Us) which is lower than the operating voltage (Uc).

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