EP1217205B1 - Method and apparatus for controlling the power supply of an electric motor for a vehicle starter motor - Google Patents

Description

The present invention relates to methods and devices for controlling the supply of motor vehicle starters.

As illustrated in Figure 1, a motor vehicle starter conventionally comprises an electric motor M whose output shaft carries a movable pinion 10 which is intended to cooperate with the gear of a starting ring of the engine of the engine. vehicle (not shown).

The pinion 10 is slidably mounted on the motor shaft between a rest position in which it is disengaged from the starter ring and an active position in which it meshes with it.

A contactor 12, which comprises a winding 12a and a plunger 12b axially movable relative to the electric motor M when the winding 12a is activated, provides control of the supply of the electric motor M by moving a movable contact 14 of an open position towards a closed position, being pushed by the plunger core 12b.

The contactor 12 also controls the displacement of the movable pinion 10. Its plunger core 12b is for this purpose connected to the pinion 10 by mechanical means designated by the general reference numeral 16.

These mechanical means comprise a fork cooperating, at its upper end, with the plunger core 12b and, at its lower end, with a launcher to which the pinion 10 belongs.

This launcher comprises a freewheel interposed axially between a hub and the pinion 10. The hub is internally provided with helical grooves in engagement with complementary external helical gears borne locally by the output shaft of the electric motor M.

The fork is pivotally mounted between its two ends on a housing internally containing the mechanical means 16 and carrying the motor M and the switch 12. The launcher, with its pinion 10, is driven by a helical movement when it is moved by the fork to engage with the starter ring.

This is achieved by feeding the winding 12a following an actuation of the ignition key of the vehicle, which allows to put in motion the plunger core 12b which is then attracted towards a fixed core 18 mounted at the end of a winding support 12a to a support position on the latter in which the power supply circuit of the electric motor M is closed.

The mechanical means 16 also comprise a return spring Rr mounted around the core 12b to return the latter in the rest position, a cutoff spring Rc associated with the movable contact 12b to return the latter in the open position and a spring Rd said spring "teeth against teeth", of greater stiffness than that of the return spring Rr. This spring teeth against teeth is housed inside the core 12b and is engaged with a first rod 20 connected by an axis to the upper end of the fork for hitching it to the core 12b.

This rod, mounted inside a blind hole of the core 12b is intended, after a determined stroke, to come into engagement with a second rod 22 integral with the movable contact 14 and slidably mounted inside the fixed core 18. In the closed position, the contactor 12 cooperates with a fixed contact made in the form of pads P respectively connected to the positive terminal of the battery and the electric motor M, thus allowing the power supply thereof.

Thus, the contactor 12 firstly causes the moving pinion to move to the start ring and then, at the end of travel of the mobile core 12b, the power supply of the electric motor M.

It often happens that pinion 10 comes axially in abutting contact with the teeth of the crown before entering it.

In this case, the spring called "teeth against teeth" is compressed, which allows the plunger core 12b to continue its race to power the electric motor.

The rotation of the pinion 10 and the thrust of the spring teeth against teeth Rd then jointly allow the penetration of the teeth of the pinion in the ring.

However, as soon as the switch 12 is closed, the electric motor M is powered under full power. The speed of the pinion 10 then grows very rapidly, causing shocks and relatively large stresses, likely to cause wear of the end faces of the teeth of the ring gear and pinion which ultimately can prevent proper penetration of the pinion. It follows a rapid destruction of these.

Furthermore, when the movable contact 12b is at the end of travel, the movable pinion 10 is located near a limit stop B. The pinion 10, immobilized in rotation by the resisting torque exerted by the ring gear. drive of the heat engine, is propelled by the helical grooves connecting the freewheel and the output shaft to abut against a stop B. The pinion is then secured to the shaft and drives the heat engine in rotation.

During this movement, the output shaft of the motor M acquires a high rotational speed while the drive ring of the engine remains stationary.

As soon as the pinion comes to bear against the stop, a violent shock occurs following the braking of the pinion and the rotation of the engine. The level of this shock depends on the mechanical inertia of the engine and the starter, the speed of this last at the moment of the shock, the torsional elasticity of the starter and the engine. This results in relatively significant noise, wear and risk of destruction of the crown and pinion.

It has been attempted to overcome these disadvantages by using sufficiently strong materials and by dimensioning the incriminated mechanical parts sufficiently. This solution, however, generates a prohibitive cost.

Another solution is to limit the power supply of the electric motor of the starter as the pinion is not in the active position and to implement a power supply phase of this engine with increased power as soon as the pinion is in position active.

This is for example the case of the starter described in document FR-A-2 791 830, in which, as long as the pinion has not reached its active position, a comparison is made of the power supply current of the motor with a threshold value and the power supply of the motor is reduced if this threshold is exceeded.

This is also the case in the document FR-A-2 679 717 in which a coil driving the actuation of a power supply contactor of the electric motor and the advancement of the pinion is used, the coil being fed via the of a transistor controlled for example by pulses of pulse width modulation type, according to which the duty cycle of the pulses is gradually increased to obtain an effective current in the gradually varying coil.

Nevertheless, according to these different techniques, the rotational speed of the engine remains uncontrolled.

The object of the invention is therefore to overcome these disadvantages in a simple and economical way.

It therefore relates to a method for controlling the power supply of an electric starter motor. motor vehicle having a movable pinion between a rest position and an active position in which it cooperates with the gear of a starting ring of the engine of the vehicle, according to which during the movement of the pinion from its rest position up to its active position, a first phase of supplying the electric motor with electrical energy with a reduced power is applied and, when the pinion is in the active position, a second phase is implemented. power supply of the electric motor with increased power, essentially characterized in that at least during the first power supply phase of the electric motor, the power supply of the electric motor is controlled according to its speed of rotation.

Therefore, the speed of the engine, which remains dependent on a set of non-controllable parameters, such as temperature, wear of the parts, the viscosity of the lubricants used, ... remains controlled.

• le pignon mobile étant déplacé de sa position de repos vers sa position active sous l'action d'un électro-aimant, la première phase d'alimentation est mise en oeuvre à l'expiration d'une période de temps prédéterminée après activation de l'électro-aimant ;
• la période de temps est inférieure ou égale à environ une seconde ;
• la deuxième phase d'alimentation du moteur électrique est mise en oeuvre à l'issu d'une temporisation après que le pignon a atteint sa position active ;
• la temporisation est comprise entre environ 2 et 200 millisecondes ;
• la temporisation est déterminée en fonction du déplacement angulaire de l'arbre du moteur électrique.

This method may also include one or more of the following characteristics, taken separately or in any technically possible combination:

• the movable pinion is moved from its rest position to its active position under the action of an electromagnet, the first power phase is implemented at the expiration of a predetermined period of time after activation of the 'electro magnet ;
• the period of time is less than or equal to about one second;
• the second power phase of the electric motor is implemented after a delay after the pinion has reached its active position;
• the time delay is between about 2 and 200 milliseconds;
• the time delay is determined as a function of the angular displacement of the electric motor shaft.

The subject of the invention is also a device for controlling the power supply of an electric motor of a motor vehicle starter, comprising switching means connected to the battery for supplying the vehicle, means for detecting the position a movable pinion for driving a starter ring of the engine of the vehicle and a control unit able to control the power supply of the electric motor in a first phase of supplying the motor with electrical energy with a power reduced to during which the starter gear is moved from a rest position to an active position in which it cooperates with the drive ring and a second phase of supply of the electric motor with electrical energy with increased power when the pinion is located in its active position, essentially characterized in that it comprises means for measuring the speed of rotation of the motor of the demo arreur associated with the control unit for controlling the power supply of the electric motor according to the speed of rotation of the latter, at least during the first power phase.

• les moyens de commutation sont constitués par un onduleur dont les cellules de commutation sont alimentées par des signaux de commande délivrés par l'unité de commande dont la fréquence est modulée en fonction de la vitesse de rotation du moteur électrique ;
• les moyens de commutation sont constitués par un commutateur raccordé en série entre la batterie d'alimentation du véhicule et le moteur électrique, des moyens assurant une comparaison de la vitesse de rotation du moteur avec une valeur minimale de seuil à partir de laquelle le moteur est alimenté et avec une valeur maximale de seuil à partir de laquelle l'alimentation du moteur est coupée ;
• les moyens de mesure de la vitesse de rotation du moteur sont constitués par un capteur de mesure ;
• les moyens de mesure de la vitesse de rotation du moteur sont constitués par des moyens de traitement des courants induits par le rotor du moteur électrique ;
• il comporte des moyens de détection du pignon, aptes à détecter le positionnement de ce dernier en position active, raccordés à l'unité de commande pour provoquer la mise en oeuvre de la deuxième phase d'alimentation ;
• il comporte des moyens de mesure du déplacement angulaire de l'arbre moteur du démarreur et des moyens de comparaison de la valeur mesurée du déplacement angulaire avec une valeur de seuil à partir de laquelle on autorise la mise en oeuvre de la deuxième phase d'alimentation.

This device can advantageously be completed by one or more of the following characteristics:

• the switching means consist of an inverter whose switching cells are fed by control signals delivered by the control unit whose frequency is modulated according to the speed of rotation of the electric motor;
• the switching means consist of a switch connected in series between the vehicle battery and the electric motor, means ensuring a comparison of the speed of rotation of the motor with a minimum threshold value from which the motor is powered and with a maximum threshold value from which the motor power is cut off;
• the means for measuring the speed of rotation of the motor consist of a measuring sensor;
• the means for measuring the speed of rotation of the motor consist of means for processing the currents induced by the rotor of the electric motor;
• it comprises means for detecting the pinion, able to detect the positioning of the latter in the active position, connected to the control unit to cause the implementation of the second power phase;
• it comprises means for measuring the angular displacement of the starter motor shaft and means for comparing the measured value of the angular displacement with a threshold value from which the second feed phase is authorized to be implemented .

• la figure 1, dont il a déjà fait mention, représente un démarreur de véhicule automobile conforme à l'état de la technique ;
• la figure 2 représente schématiquement un montage d'alimentation d'un démarreur conforme à l'invention ;
• la figure 3 illustre schématiquement la structure d'un démarreur pourvu d'un tel dispositif d'alimentation ;
• la figure 4 illustre un autre mode de réalisation d'un montage d'alimentation d'un démarreur conforme à l'invention ; et
• la figure 5 est une courbe montrant l'évolution de la vitesse de rotation du moteur et du démarreur en fonction du temps, au cours des première et deuxième phases d'alimentation.

Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of example, and with reference to the accompanying drawings in which:

• Figure 1, which has already been mentioned, represents a motor vehicle starter according to the state of the art;
• Figure 2 schematically shows a power supply of a starter according to the invention;
• FIG. 3 schematically illustrates the structure of a starter provided with such a power supply device;
• FIG. 4 illustrates another embodiment of a starter power supply assembly according to the invention; and
• Figure 5 is a graph showing the evolution of the speed of rotation of the motor and the starter as a function of time, during the first and second supply phases.

As illustrated in Figure 2, which shows the circuit diagram of a power supply device of an AC motor of a motor vehicle starter, the device essentially comprises an inverter 24 consisting of a set of switching cells 26-1, 26-2, ..., 26-n mounted in bridge controlled at the opening and closing by a control unit 30 for supplying each of the coils 32-1, 32-2, ..., 32-n of the electric motor 34 of the starter.

For this purpose, the control unit 30 is provided with respective outputs connected to the gate of each of the switching cells of the inverter 24 and supplies the latter with a rectangular-shaped signal whose frequency is modulated according to the speed of rotation of the electric motor 34.

Moreover, the drain of the switching cells 26-1, 26-2 ..., 26-n of one of the branches of the inverter 24 is connected to the positive terminal B ⁺ of the vehicle power supply battery. the source of these switching cells being connected to a respective coil of the motor.

With regard to the switching cells 28-1, 28-2, ..., 28-n of the other branch of the inverter 24, their drain is connected to the supply coils, their source being connected to the mass.

Furthermore, the engine supply device 34 is provided with a device 36 for measuring the speed of rotation and the angular position of the motor armature 34, supplying the control unit 30 with measurement signals. corresponding, and an electromagnet 38 driving the displacement of the pinion equipping the motor shaft of the electric motor 34 of a rest position, in which it is disengaged from the drive ring of the engine of the vehicle, to a active position in which it meshes with it to rotate the engine.

Moreover, a control line provided with a key switch K is connected to an input e of the control unit 30 of a side and to the positive terminal B ⁺ of the vehicle power supply battery, on the other hand.

It will be noted that the measuring member 36 may be constituted by any type of sensor suitable for supplying the control unit 30 with a signal for measuring the rotational speed of the motor and a signal for measuring the angular position of the motor. induced, for example an inductive type sensor, Hall effect, capacitive type, piezoelectric, ...

With regard to the starter, with reference to FIG. 3, in which is schematically represented its main constituent elements, it is provided with the electric motor 34 to which is connected a power electronics module 37 incorporating the components of the circuit shown in FIG. 2, namely the inverter circuit as well as the control unit 30.

The motor shaft of the electric motor is provided with a pinion 39 provided with an axially displaceable freewheel, as mentioned above, between a rest position, in which the pinion is disengaged from a driving ring of the heat engine of the vehicle, and an active position, in which it meshes with it, under the control of the electromagnet 38, by means of mechanical means 40, essentially constituted by a fork mounted oscillatingly and cooperating, by one of its ends with a plunger disposed in the electromagnet 38 and whose other end ensures the axial displacement of the movable pinion 39.

It can be seen in this FIG. 3 that the starter is provided with the measuring member 36.

The starter which has just been described is completed by a detector (not shown) disposed at the end of travel of the pinion 39 and able to detect the positioning of the latter in the active position, this detector being connected to the control unit to control the power supply of the electric motor of the starter.

The operation of the starter and the feed device of the latter just described will be described below.

As previously indicated, the control unit 30 drives the switching cells of the inverter 24 so as to cause the power supply of the electric motor 34 in a first power supply phase at reduced power, implemented when the pinion is moved. from its rest position to its active position, and according to a second power supply phase with increased power, implemented when the pinion is in the active position.

Thus, as soon as the user has closed the switch K by actuation of his ignition key, the control unit 30 causes the electromagnet 38 to be powered so as to cause the pinion 39 to move from its position rest to its active position.

As soon as the switch K is closed, the control unit 30 implements the first supply phase of the low power electric motor 34 by driving the gate of each of the switching cells, in a manner known per se, for example by pulse width modulation, so as to drive the electric motor with a reduced speed, for example between 1 and 500 revolutions per minute.

However, preferably, the control unit 30 incorporates delay means so as to launch this first supply phase after the expiry of a predetermined period of time, for example less than or equal to about one second, so to avoid a voltage drop of the battery due to the start of the electric motor while the electromagnet 38 is still a large air gap and that, therefore, the attraction forces developed may be insufficient to defeat the resistant efforts of the core mobile due to friction or the presence of return springs. We can then reduce the dimensioning of the electromagnet 38.

It will be noted that, during this first phase, the control unit 30 receives, on one of its inputs, a signal for measuring the speed of rotation of the motor and modulates the frequency of the control signals applied to the gate switching cells so as to maintain the rotational speed at the predetermined low value.

As soon as the pinion 39 reaches its active position, the control unit 30 causes the implementation of the second power phase, at increased power, so as to allow the start of the engine of the vehicle.

This second phase is implemented as soon as the pinion 38 reaches the limit stop, detected, as mentioned previously by means of a suitable detector, or at the expiration of a time delay after the pinion has reached this stop. , for example between 2 and 200 milliseconds, so as to allow meshing sprocket teeth 39 with those of the drive ring of the motor. This delay can however be modulated according to different operating parameters, such as the temperature, the supply voltage of the electromagnet, etc.

However, it should be noted that, as a variant, the means for detecting the positioning of the pinion in the active position can be replaced by an appropriate algorithm for analyzing the current absorbed by the electric motor, incorporated in the control unit 30, capable of detecting a abrupt rise of the current generated to overcome the resistive torque of the engine when the pinion meshes with the driving ring.

Moreover, this second power phase at full power can also be implemented after the armature of the electric motor has traveled a distance predetermined angle, which distance corresponds to an angular distance from which, in the worst case, the pinion has reached the stop.

In the embodiment which has just been described, it has been considered that the motor 34 is constituted by an AC motor.

A further embodiment of a feed device according to the invention suitable for feeding a DC motor will now be described with reference to FIGS. 4 and 5.

According to this embodiment, the supply device essentially comprises a control unit 41 receiving, as input, signals e1 and e2 representative of the rotational speed of the electric motor M of the starter, and, on an input e3, an control signal delivered after action on a switch K by means of a ignition key.

The control unit 41 is connected, at the output, to an electromagnet 42 whose function is to control the axial displacement of the starter gear from its rest position to its active position, as well as a transistor 44 operating in switch, placed in series between the motor M, with the interposition of an inductor 46, and the positive terminal B ⁺ supply of the battery of the motor vehicle.

A sensor 48 for measuring the speed of rotation of the motor shaft M and measuring the angular position of the armature thereof, constituted for example by a coded wheel 50 connected to the motor shaft and by a corresponding detector 52, supplied via a shaping circuit 54 and a frequency / voltage converter 56, a voltage Um representative of the speed and the angular position of the motor shaft.

A first comparator 58 makes a comparison between the voltage Um and a first reference voltage Uref1 representative of a minimum value of the speed of rotation of the motor during the first motor supply phase and provides corresponding information on the input e1 of the control unit 41.

Furthermore, a second comparator 60 makes a comparison between this voltage Um and a second reference voltage Uref2 representative of a maximum value of the speed of rotation of the motor M during this first power supply phase.

Thus, during the displacement of the movable pinion from its rest position to its active position, the control unit 41 drives the transistor 44 according to the speed of rotation of the motor M, that is to say that it turns on the transistor 44 when the voltage Um is between e1 and e2, and blocks if the voltage Um is greater than the second threshold value Uref2.

Thus, as can be seen in FIG. 5, the rotation speed N of the engine is perfectly controlled and oscillates, during the first supply phase I, between two extreme values N1 and N2 which each correspond to a threshold value of voltage.

Meanwhile, and as mentioned above, the control unit controls the electromagnet 42 so as to move the starter movable gear.

In particular, it implements the second power supply phase II of the motor M after expiration of a predetermined period of time after positioning the pinion in its active configuration, this positioning being detectable by means of a suitable sensor or deduced from the angular displacement of the motor armature.

Likewise, and as in the embodiment described above, the control unit 41 causes the motor M to be powered during the first supply phase, after the expiry of a time delay, so as to avoid any battery voltage drop due to the start of the motor M while the electromagnet 42 is still large air gap.

Claims (13)

1. Method of controlling the supply to an electric motor (34) for a motor vehicle starter provided with a pinion (39) able to move between an idle position and an active position in which it cooperates with the gearing on the starting ring of the thermal engine of the vehicle, according to which, during the movement of the pinion (39) from its idle position to its active position, a first phase of supplying the electric motor (34) with electrical energy at reduced power is implemented and, when the pinion (39) is situated in the active position, a second phase of supplying the electric motor at increased power is implemented, characterised in that, at least during the first phase of supplying the electric motor, the supply to the electric motor is controlled according to its speed of rotation.
2. Control method according to claim 1, characterised in that, the movable pinion (39) being moved from its idle position to its active position under the action of an electromagnet (38; 42), the first supply phase is implemented at the expiry of a predetermined period of time after activation of the electromagnet.
3. Control method according to claim 2, characterised in that the period of time is less than or equal to approximately one second.
4. Control method according to any one of claims 1 to 3, characterised in that the second supply phase of the electric motor (34) is implemented at the end of a time delay after the pinion has reached its active position.
5. Control method according to claim 4, characterised in that the time delay is between approximately 2 and 200 milliseconds.
6. Control method according to one of claims 4 and 5, characterised in that the time delay is determined according to the angular movement of the shaft of the electric motor.
7. Device for controlling the supply to an electric motor of a motor vehicle starter, comprising switching means (24; 44) connected to the vehicle supply battery, means of detecting the position of a movable pinion (39) driving the starting ring of the thermal engine of the vehicle and a control unit (30; 41) able to control the supply to the electric motor according to a first phase of supplying the motor with electrical energy at reduced power during which the pinion (39) of the starter is moved from an idle position to an active position in which it cooperates with the drive ring and a second phase of supplying the electric motor with electrical energy at increased power when the pinion is situated in the active position, characterised in that it comprises means (36; 48) of measuring the speed of rotation of the starter motor associated with the control unit (30; 41) in order to control the supply to the electric motor according to the speed of rotation of the latter, at least during the first supply phase.
8. Control device according to claim 7, characterised in that the switching means consist of an inverter (24) whose switching cells (26-1, ..., 26-n, 28-1, ..., 28-n) are supplied by control signals delivered by the control unit (30) whose frequency is modulated according to the speed of rotation of the electric motor.
9. Control device according to claim 7, characterised in that the switching means consist of a switch (44) connected in series between the vehicle supply battery and the electric motor, and in that it also comprises means (41) of comparing the speed of rotation of the motor with a minimum threshold value as from which the motor is supplied and with a maximum threshold as from which the supply to the motor is cut off.
10. Control device according to any one of claims 7 to 9, characterised in that the means of measuring the speed of rotation of the motor consist of a measuring sensor (48).
11. Control device according to any one of claims 7 to 9, characterised in that the means of measuring the speed of rotation of the motor consist of means of processing the currents induced by the rotor of the electric motor.
12. Control device according to any one of claims 7 to 11, characterised in that it comprises means of detecting the pinion, able to detect the positioning of the latter in the active position and connected to the control unit in order to cause the implementation of the second supply phase.
13. Control device according to any one of claims 7 to 12, characterised in that it also comprises means (36; 48) of measuring the angular movement of the drive shaft of the starter and means (30; 41) of comparing the measured value of the angular movement with a threshold value as from which the implementation of the second supply phase is enabled.

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