EP1217205A1 - Method and apparatus for controlling the power supply of an electric motor for a vehicle starter motor - Google Patents

Abstract

The method of controlling a motor vehicle starter motor (34) involves having a primary low power operating phase for the motor during displacement of the starter clutch drive pinion (39) from its rest position to its active position. When the pinion is in its active position, a second phase is started with increased power to the motor. The power feed in the first phase can be determined on the rotational speed of the engine.

Description

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

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

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

A contactor 12, which has a coil 12a and a plunger core 12b movable axially relative to the electric motor M when the winding 12a is activated, controls the power supply to the electric motor M by displacement of a movable contact 14 from one position opening to a closed position, being pushed by the plunger 12b.

Contactor 12 also controls movement of the movable pinion 10. Its plunger core 12b is for this connected to the pinion 10 by mechanical means designated by the general reference number 16.

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

This launcher has an interposed freewheel axially between a hub and the pinion 10. The hub is internally fitted with helical grooves with complementary external helical teeth carried locally by the motor output shaft electric M.

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

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

The mechanical means 16 also include a return spring Rr mounted around the core 12b for recall it in the rest position, a spring Rc cut associated with mobile contact 12b to remind this in the open position and a Rd spring says "teeth against teeth" spring, stiffer than that of the Rr Recall spring. This teeth spring against teeth is housed inside the core 12b and is engaged with a first rod 20 connected by an axis at the end upper part of the range for coupling it to 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 secured to the movable contact 14 and sliding mount 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, allowing feeding the latter.

Thus, the contactor 12 first of all causes the displacement of the movable pinion up to the crown of start-up then, at the end of the travel of the mobile core 12b, the power supply of the electric motor M.

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

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

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

However, as soon as the contactor 12 is closed, the electric motor M is powered at full power. The speed of the pinion 10 then increases very quickly, causing relatively shock and stress important, likely to cause wear of the front faces of the teeth of the crown and the pinion which, in time, can prevent correct penetration of the pinion. It follows a rapid destruction of these last.

Furthermore, when the movable contact 12b is located at the end of its travel, the movable pinion 10 is located near an end of travel stop B. The pinion 10, immobilized in rotation by the resistive torque exerted by the crown of drive of the heat engine, is powered by helical grooves connecting the wheel free and the output shaft until it comes to rest 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 speed of rotation while the crown of the engine stay still.

As soon as the pinion comes to rest against the stop, a violent shock occurs following braking of the pinion and the rotation of the heat engine. The level of this shock is a function of the mechanical inertias of the engine and starter motor, the speed of this last at shock, torsional elasticity starter and heat engine. This results in relatively large noises, wear and risks destruction of the crown and pinion.

We tried to overcome these disadvantages by using sufficiently resistant materials and sufficient dimensioning of mechanical parts incriminated. This solution however generates a cost crippling.

Another solution is to limit the starter electric motor supply as long as the pinion is not in the active position and to be put implementing a power supply phase for this motor with a increased power as soon as the pinion is in position active.

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

This is also the case in document FR-A-2 679,717 in which a piloting coil is used actuation of a motor power switch and the advancement of the pinion, the coil being powered by a controlled transistor for example by pulses of the modulation type by pulse width, which increases gradually the duty cycle of the pulses for obtain an effective current in the coil varying from gradually.

However, according to these different techniques, the engine rotation speed 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 supply of an electric starter motor from motor vehicle with a pinion movable between a rest position and an active position in which it cooperates with the gear of a starting crown of the engine of the vehicle, according to which during the displacement of the pinion from its rest position to its active position, a first phase is implemented supply of electric motor with electric energy with reduced power and, when the pinion is located in the active position, a second phase is implemented electric motor supply with power increased, essentially characterized in that at least during the first motor supply phase electric, we control the motor supply electric according to its rotation speed.

Therefore, the engine speed, which remains dependent on a set of parameters that cannot be controlled, such as temperature, wear of parts, viscosity lubricants used, ..., remains under control.

• 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 process can also include one or more of the following characteristics, taken in isolation or in all technically possible combinations:

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

The invention also relates to a device for control of the power supply of an electric motor of a motor vehicle starter, comprising means switch connected to the supply battery of the vehicle, means for detecting the position of a movable pinion for driving a starter ring of the vehicle's engine and a control unit suitable for controlling the supply of the electric motor according to a first phase of power supply to the engine electric with reduced power during which the starter gear is moved rest position to an active position in which it cooperates with the drive crown and a second phase of supplying the electric motor with electrical energy with increased power when the sprocket is in its active position, essentially characterized in that it includes means for measuring the speed of rotation of the starter motor associated with the control unit to control the power supply to the motor electric depending on the rotation speed of this last, at least during the first phase Power.

• 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 supplemented by one or more of the following characteristics:

• the switching means consist of an inverter, the switching cells of which are supplied by control signals delivered by the control unit, the frequency of which is modulated as a function of the speed of rotation of the electric motor;
• the switching means are constituted by a switch connected in series between the vehicle supply 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 engine power is cut;
• the means for measuring the speed of rotation of the motor are constituted by a measurement sensor;
• the means for measuring the speed of rotation of the motor are constituted by means for processing the currents induced by the rotor of the electric motor;
• it comprises pinion detection means, capable of detecting the positioning of the latter in the active position, connected to the control unit to cause the implementation of the second supply phase;
• it includes 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 implementation of the second supply phase is authorized .

• 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, characteristics and advantages of the invention will emerge from the following description, given solely by way of example, and made with reference to the appended drawings in which:

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

As illustrated in Figure 2, on which we have represented the electrical diagram of a device supply of an AC motor of a motor vehicle starter, the device comprises essentially an inverter 24 made up of a set of switching cells 26-1, 26-2, ..., 26-n mounted in bridge controlled at 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.

To this end, the control unit 30 is provided with respective outputs connected to the grid of each switching cells of the inverter 24 and provides these a rectangular signal whose frequency is modulated according to the speed of rotation of the electric motor 34.

Furthermore, 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 supply battery. , the source of these switching cells being connected to a respective motor coil.

Regarding switch cells 28-1, 28-2, ..., 28-n of the other branch of the inverter 24, their drain is connected to the power coils, their source being connected to ground.

In addition, the power supply device for the motor 34 is provided with a member 36 for measuring the rotational speed and angular position of the armature of the motor 34, supplying the control unit 30 corresponding measurement signals, as well as a electromagnet 38 controlling the movement of the pinion equipping the motor shaft of the electric motor 34 with a rest position, in which it is disengaged from the vehicle engine crown gear, towards an active position in which it meshes with it to rotate the heat engine.

Furthermore, a control line provided with a switch K controlled by an ignition key is connected to an input e of the control unit 30 on the one hand and to the positive terminal B ⁺ of the supply battery of the vehicle, on the other hand.

It will be noted that the measurement member 36 can be consisting of any type of sensor suitable for supplying to the control unit 30 a signal for measuring the motor speed and a measurement signal the angular position of the armature, for example a sensor inductive, Hall effect, capacitive type, piezoelectric, ...

Regarding the starter, referring to Figure 3 in which there is shown so schematic its main building blocks, this one is provided with the electric motor 34 to which is connected a power electronics module 37 incorporating the components of the circuit shown in Figure 2, at know the inverter circuit and the control unit 30.

The motor shaft of the electric motor is provided with a pinion 39 provided with an axially movable freewheel, as mentioned earlier, between a position of rest, in which the pinion is disengaged from a vehicle engine crown gear, and an active position, in which it meshes with this, under the control of the electromagnet 38, by through mechanical means 40, essentially consisting of a fork mounted so oscillating and cooperating, by one of its ends with a plunger core disposed in the electromagnet 38 and the other end of which ensures the axial displacement of the movable pinion 39.

We also see in this figure 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) placed at the end of pinion stroke 39 and capable of detecting positioning of the latter in active position, this detector being connected to the control unit to control the starter electric motor supply.

We will detail below the operation of the starter and its power supply device which have just been described.

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

So as soon as the user has closed the switch K by actuation of its ignition key, the command 30 causes the electromagnet to be powered 38 so as to cause the pinion 39 to move its rest position towards its active position.

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

Preferably, however, the control unit 30 incorporates means of timing in order to launch this first feeding phase after expiration a predetermined period of time, for example less than or equal to about a second, so that avoid a drop in battery voltage due to the electric motor while the electromagnet 38 is still with a large air gap and that, as a result, the developed attraction forces are likely to be insufficient to overcome the resistant efforts of the nucleus mobile due to friction or the presence of springs reminder. We can then reduce the dimensioning of the electromagnet 38.

Note that, during this first phase, the control unit 30 receives, on one of its inputs, a motor speed measurement signal and modulates the frequency of the applied control signals to the grid of the switching cells so that keep the rotation speed low predetermined.

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

This second phase is implemented as soon as the pinion 38 reaches the limit stop, detected, as previously mentioned by means of a detector appropriate, or when a timeout expires that the pinion has reached this stop, for example understood between 2 and 200 milliseconds, so as to allow meshing of the pinion teeth 39 with those of the motor drive crown. This time delay can however be adjusted according to different operating parameters, such as temperature, electromagnet supply voltage, ...

Note, however, that, as a variant, the means of detection of pinion positioning in active position can be replaced by an appropriate algorithm analysis of 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 couple resistant to the heat engine when the pinion meshes with the drive crown.

Furthermore, this second feeding phase to full power can also be implemented after that 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 cases, the pinion has reached the stop.

In the example of realization which has just been described, it was considered that the motor 34 is constituted by an AC motor.

We will now describe, with reference to the figures 4 and 5, another embodiment of a device supply according to the invention, suitable for the supply of a DC motor.

In accordance with this embodiment, the feed device basically has a control unit 41 receiving, as input, signals e1 and e2 representative of the engine speed electric M of the starter as well as, on an input e3, a control signal delivered after action on a switch K by means of an ignition key.

The control unit 41 is connected, at the output, to an electromagnet 42 having the function of controlling the axial movement of the starter pinion 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 ⁺ for supplying the battery of the motor vehicle.

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

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

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

Thus, when moving the movable pinion from its rest position to its active position, the command 41 drives transistor 44 depending on the motor rotation speed M, i.e. it makes passing transistor 44 when voltage Um is located between e1 and e2, and blocks it if the voltage Um is greater than the second threshold value Uref2.

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

At the same time, and as mentioned earlier, the control unit controls the electromagnet 42 so to move the moving starter pinion.

In particular, it implements the second motor M supply phase II after expiration a predetermined period of time after positioning of the pinion in its active configuration, this positioning can be detected by an appropriate sensor or deduced from the angular displacement of the motor armature.

Similarly, and as in the example of embodiment described above, the control unit 41 causes the supply of the motor M, during the first phase supply, after the expiration of a timer, so as to avoid any drop in battery voltage due to the starting of the motor M while the electromagnet 42 is still with a large air gap.

Claims (13)

Method for controlling the supply of an electric motor (34) of a motor vehicle starter provided with a pinion (39) movable between a rest position and an active position in which it cooperates with the gear of a crown starting the engine of the vehicle, according to which during the movement of the pinion (39) from its rest position to its active position, a first phase of supply of the electric motor (34) is implemented. electrical energy with reduced power and, when the pinion (39) is in the active position, a second power supply phase of the electric motor is implemented with increased power, characterized in that at least during the first supply phase of the electric motor, the supply of the electric motor is controlled as a function of its speed of rotation. Control method according to claim 1, characterized in that the movable pinion (39) being moved from its rest position to its active position under the action of an electromagnet (38; 42), the first supply phase is implemented at the expiration of a predetermined period of time after activation of the electromagnet. Control method according to claim 2, characterized in that the time period is less than or equal to about 1 second. Control method according to any one of Claims 1 to 3, characterized in that the second supply phase of the electric motor (34) is implemented after a time delay after the pinion has reached its position active. Control method according to claim 4, characterized in that the time delay is between approximately 2 and 200 milliseconds. Control method according to one of claims 4 and 5, characterized in that the time delay is determined as a function of the angular displacement of the shaft of the electric motor. Device for controlling the supply of an electric motor to a motor vehicle starter, comprising switching means (24; 44) connected to the vehicle supply battery, means for detecting the position of a movable pinion (39) for driving a starter ring for the vehicle's heat engine and a control unit (30; 41) capable of controlling the supply of the electric motor according to a first phase of supply of the motor with electric energy with a reduced power during which the pinion (39) of the starter is moved from a rest position to an active position in which it cooperates with the drive crown and a second phase of supplying the electric motor with electric energy with increased power when the pinion is in the active position, characterized in that it comprises means (36; 48) for measuring the engine speed of rotation of the associated starter s to the control unit (30; 41) to control the supply of the electric motor as a function of the speed of rotation of the latter, at least during the first supply phase. Control device according to claim 7, characterized in that the switching means consist of an inverter (24), the 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 as a function of the speed of rotation of the electric motor. Control device according to claim 7, characterized in that the switching means consist of a switch (44) connected in series between the vehicle's battery and the electric motor, and in that it further comprises means (41) for comparing the speed of rotation of the motor with a minimum threshold value from which the motor is supplied and with a maximum threshold value from which the motor supply is cut off Control device according to any one of Claims 7 and 9, characterized in that the means for measuring the speed of rotation of the motor are constituted by a measurement sensor (48). Control device according to any one of Claims 7 to 9, characterized in that the means for measuring the speed of rotation of the motor are constituted by means for processing the currents induced by the rotor of the electric motor. Control device according to any one of Claims 7 to 11, characterized in that it comprises pinion detection means, capable of detecting the positioning of the latter in the active position and connected to the control unit to cause the implementation of the second feeding phase. Control device according to any one of Claims 7 to 12, characterized in that it also comprises means for measuring (36; 48) the angular displacement of the starter motor shaft and means (30; 41) for comparing the measured value of the angular displacement with a threshold value from which the implementation of the second supply phase is authorized.

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