FR2795884A1 - Contactor with variable closing effort, for automobile starter, has maximum effort, applied initially, reduced after plunger movement begins, regulating coil current by PWM technique - Google Patents

Abstract

The present application embodies, with some additional detail, the proposals set out in Application FR2795883 (q.v.). The only significant new matter is a variation of the measurement procedures proposed for the determination by the microcontroller of the intermediate pulse-width ratio (R2). This is presented as an option, not as a substitute. As described in FR2795883, the effective contactor coil current before plunger movementn begins is set at a high value, the microcontroller and associated switching transistor imposing a pulse-width ratio (R1) near to 100%. This is to overcome static friction forces acting onn the plunger. After a brief period (t0-t1) the ratio is reduced because the plunger, when in motion, is subject to kinetic friction forces well below the original static value. As in FR2795883, the new ratio (R2) is obtained by the controller from a memory table using coil resistance and voltage criteria provided by sensors, but the necessary measurements are not made, as therein proposed, before energising the contactor. Instead, the first phase, using the high value (R1) is shortened (t') and a very low, even zero, value imposed till the measurements are complete. The new value (R2) is deduced, as before, from a table, and then applied (t'1). Final stages (t2,t3,t4) follow as before.

Description

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to methods and devices for controlling starters of motor vehicles, and more specifically to methods and devices for driving the contactor core of these starters.

As illustrated in Figure 1, a motor vehicle starter conventionally comprises a contactor 2 and an electric motor M whose output shaft carries a pinion 1. The pinion 1 is intended to cooperate with the gear of the start ring C of the heat engine. It is slidable on the motor shaft M between a position where it is disengaged with respect to said starter ring and a position where it meshes with it.

The contactor 2 extends parallel to the electric motor M above it and comprises a winding 2a and a plunger core 2b.

It controls the supply of the electric motor M by moving a movable contact 3 between an open position and a closed position, said contact 3 being pushed by said plunger core 2b axially movable relative to the electric motor M when the winding 2a is activated.

The contactor 2 also controls the movement of the pinion 1. Its plunger core 2b is for this purpose connected to the pinion 1 by mechanical means referenced by 4 in their entirety.

These mechanical means comprise a fork hitched at its upper end to the plunger core 2b and at its lower end with a launcher to which the pinion 1 belongs.

This launcher comprises a free wheel interposed axially between a hub and the pinion 1. The hub is internally endowed with helical splines in complementary engagement with external helical teeth set locally by the output shaft of the electric motor M. The fork is mounted pivotably between its two ends on a housing internally containing the mechanical means 4 and carrying the motor M and the contactor 2. The launcher with its pinion 1 is driven by a helical movement when it is moved by the fork to come engaged with the starter ring.

This is achieved by feeding the winding 2a following an actuation of the ignition key which allows to move the plunger core 2b then attracted towards a fixed core mounted at the end of a support winding 2a. This support has a U-shaped section for housing the winding 2a and therefore comprises a bottom forming a pad 2C. The core 2b is thus intended to move between a rest position and a contact position in which it bears on the fixed core, this closing position of the magnetic circuit occurring after closure of the movable contact 3 and therefore of the electrical circuit. .

The mechanical means also comprise a return spring mounted around the core 2b to return the latter in the rest position, a breaking spring associated with the movable contact 3 to return the latter in the open position and a spring 5, said spring teeth against teeth, housed inside the core 2b and engaged with a first rod connected by an axis to the upper end of the fork for coupling thereof to the core 2b. This spring 5 has a greater stiffness than the return spring.

The fork is thus interposed at its upper end between the core 2b and the axis. The first rod, mounted inside a blind hole of the core 2b, is intended after a determined race to engage with a second rod secured to the movable contact 3 and slidably mounted within the fixed core. In the closed position the contact 3 cooperates with a fixed contact, in the form of pads respectively connected to the positive terminal of the battery and the electric motor M, thus allowing the power supply of the electric motor.

The studs are integral with the closing cap of the contactor of insulating material.

All these elements are shown in Figure 1 and have not been referenced for simplicity. The pinion 1 can therefore engage with the crown C, that is to say come into meshing position with the crown C, before the movable contact is closed.

Most often the pinion 1 comes axially in abutment contact with the teeth of the crown C before entering it.

Thus, the mechanical means 4 comprise in particular a spring 5 which is mechanically interposed between the plunger core 2b and the pinion 1 and which enables the plunger core 2b to continue its travel in order to ensure, before contact with the fixed core, the positioning of the plunger 2b. closing the movable contact, even if the pinion 1 is blocked in abutment against the teeth of the heat engine crown, in a position where it does not mesh with this ring.

Nevertheless, given the rapidity of the movement of the mobile core 2b and the elasticity of the mechanical connection means 4, due in particular to the presence of the spring 5, there may be significant phase shifts between the closure of the contact 3 and the translation of the pinion 1. Particularly at low temperature, it can be seen a rotation of the electric motor M and therefore the pinion 1 before the latter has had time to enter the crown. The electric motor M being powered under full voltage, the speed of the pinion 1 grows very rapidly, thus preventing meshing of the pinion in the ring gear. It follows a rapid destruction of the crown and pinion.

In document FR-A-2 679 717, it has been proposed to overcome this disadvantage of supplying the contactor with a variable pulsed current.

Referring to Figure 2, in this type of arrangement, a coil B controls both a contactor K and the advancement of a not shown pinion. The coil B is fed via a pulse width pulse width T-type transistor or Pulse Width Modulation (PWM), in French, the transistor being controlled by a microcontroller 10.

A cyclic duty cycle is gradually increased to obtain an effective current in the coil which increases progressively. In this way, it is desired that the mobile core begin to move with a minimum magnetic attraction force and therefore a minimum acceleration, so as to avoid a phase shift between the movement of the core and that of the previously described pinion.

This method also aims to reduce the speed of impact of the pinion against the crown to reduce the frontal wear thereof.

Nevertheless, it does not prevent a sudden displacement of the core from its rest position to its activation position.

To further reduce this impact speed, it has been proposed in document US Pat. No. 4,418,289 a method for feeding a driving coil of a mobile motor vehicle starter switch core, in which one the effective current in the coil is varied during the displacement of the core towards its contact position, and in which during this displacement is adopted a first phase of entrainment with an effective current sufficiently high to put the nucleus in motion, then a second lower current driving phase. This document also proposes a device for controlling the supply of a driving coil of a mobile motor vehicle starter switch core, designed to vary the effective current in the coil during the displacement of the core to its contact position, in which it is provided to implement during this displacement - a first phase of driving effective current sufficient to set the core in motion, then, - a second phase of driving more effective current low. In practice it is planned in the second phase to power the electric motor to run it at a reduced speed thanks to an additional disk, additional contacts and additional resistance integrated in the contactor. This second phase ends at the closing of the moving contact, which then cooperates with the fixed contact to power the electric motor at full power.

This solution is not entirely satisfactory because it complicates the realization of the contactor. This solution is not entirely satisfactory because it complicates the realization of the contactor.

In addition it is not entirely reliable because for example the launcher, and thus the pinion can be blocked.

The present invention aims to overcome these disadvantages simply and economically.

According to the invention, a process of the above-mentioned type is characterized in that during the second phase, when the movable core is not in the contacting position, a continuous increase in temperature is carried out after a predetermined or predetermined time. effective intensity.

According to the invention a device of the type indicated above is characterized in that during the second phase, it is planned to implement, after a predetermined or predetermined time, a continuous increase in the effective intensity.

Thanks to the invention the contactor has a simple shape and a sudden displacement of the core, from its rest position to its activation position, is avoided.

In fact, the effective intensity in the first interval of the second phase is less than that starting from the solution of document FR-A-2 679 717 since the core has already taken off. This reduces the noise and the solution is safe.

Indeed, after a predetermined or predetermined time, the progressive increase of the effective intensity makes it possible, on the one hand, to gradually compress the spring, teeth against teeth 5, and, on the other hand, to close the switch to feed the electric motor in the accidental case where the contactor could not have been closed before.

Thus in the accidental case where abnormally high friction forces take place in the contactor, in the mechanical means or at the level of the electric motor shaft is ensured beyond a predetermined time or determined closure of the contactor.

Such cases may occur due to particular weather conditions, seizures, especially when the vehicle has been immobilized for a long time. Dust, dirt may be deposited at the fork and shaft of the electric motor and thus hinder the movement of the pinion.

Thanks to the invention can nevertheless move the launcher and its pinion.

In addition, the sprocket is brought into abutment contact with the starter ring either before the intensity is increased or after increasing the intensity and before closing the moving contact, so that the ignition is switched on. the electric motor from a zero speed in this abutment contact position, which facilitates the penetration of the pinion in the crown while reducing the wear. .

The solution according to the invention is therefore reliable and makes it possible to increase the life of the starter thanks in particular to a reduction in wear. In addition, it reduces energy consumption and noise. The solution is economical because the contactor can have only one winding.

Thanks to the invention, measurements can be made during the first phase. This first phase can be broken down into two intervals, namely a first high current interval followed by a second lower current interval than that of the second phase.

Preferably this second gap is made at zero current for better accuracy of the measurement.

Thus one can measure the voltage of the battery during the first phase. During this first phase the core can take off with a smaller stroke, the intensity during the first interval of this first phase being close to the intensity necessary to get the core off and being performed with a shorter time.

If problems arise subsequently, non-detachment of the core, non-closing of the contactor for example, thanks to the continuous increase of the effective intensity according to the invention these problems will be solved.

The core detachment of the core makes it possible to further reduce sudden shocks and reduce energy consumption.

Thanks to the invention, the winding has a dual function because, after a third interval of the second phase, during which the intensity of the rms current is increased, it allows, after rotation of the electric motor, to keep the moving contact closed during a third phase.

It will be appreciated that the electric motor rotates only after abutment of the pinion with the crown, so that the pinion can penetrate more easily into the crown and the wear is reduced.

Thanks to the invention in the first phase, one can be at the limit of the detachment of the core so that the movement thereof is even less brutal.

The time is determined according to abnormal values that occur in case of non-closing of the moving contact.

The time is determined as a function, for example, of the battery voltage or the winding temperature.

The time is easily predetermined so that the continuous increase in intensity occurs only when necessary, that is to say, so that this time is as short as possible and encompasses the majority of the normal cases of operation. .

Other features, objects and advantages of the invention will appear on reading the detailed description which follows, made with reference to the appended figures, in which - Figure 1 shows a motor vehicle starter according to the state of the technical; - Figure 2 shows a power supply of a starter contactor according to the state of the art; - Figure 3 is a plot showing the evolution of a duty cycle of a supply voltage of a contactor coil, according to the invention; - Figure 4 is a partial view similar to Figure 3 for another embodiment.

As illustrated in Figure 1, the plunger core 2b is disposed in the bearing 2C in a sliding relationship which is modulated by the presence of a lubricant providing a role of sealing and braking. The core 2b is a mobile core.

The core has, in its rest position, a force of adhesion to the pad Fa which opposes its setting in motion. When the core is set in motion, this force Fa disappears in favor of a friction force Ff, which is significantly lower than Fa (of the order of 20 to 40% lower).

The presence of the lubricant does not eliminate these forces. On the contrary, by a lubricant scrubbing effect, it further accentuates the fact that the adhesive force Fa exceeds the friction force Ff. The movable core 2b remains at rest as the coil 2a does not exert a driving force of attraction Fm which is greater than Fa.

During the setting in motion of the core 2b, the effective intensity is gradually increased in the coil 2a. The retaining forces of the nucleus decrease abruptly (from F to Ff) to the setting in motion of the nucleus, whereas the force of attraction Fm already reaches a high value starting from the nucleus. This difference between Fm and Ff thus induces at the moment of the unblocking of the nucleus a sharp acceleration of the mobile nucleus so that the progressive supply does not therefore produce the desired effects.

Here is used a feed device of the coil 2a, the mounting of which remains similar to that shown in Figure 1, and in which there is again adopted a supply of the coil 2a according to a PWM pulse voltage.

However, the duty cycle is varied during the displacement of the core according to the evolution shown in FIG. 3 and this after a predetermined or determined time.

On this plot, we have indicated on the abscissa successive instants during the displacement of the nucleus, from its initial rest position (moment To) to a final position (call period of the nucleus) where it is in abutment against the nucleus fixed and where it ensures contact, the movable contact 3 then being closed.

The kernel's calling period is broken down into two main phases, the second of which is broken down into three sub-phases. These two main phases will now be described.

During the first phase ranging from instant to at a time t1, a cyclic ratio R1, which is close to or equal to 100%, is adopted (the duty ratio is the ratio between the conduction duration of transistor T1 and the total duration of a cycle). During this phase, a high effective intensity passes through the coil 2a and the core 2b is subjected to an attractive force Fm sufficient to take it off its rest position and put it in motion. This phase is brief, here of the order of 2 to 10 ms, to produce a high attraction force on the core in order to take off the core.

The second phase takes place between the instant t, and a time t3. In a first interval of this second phase, the transistor T1 controls the contactor in a duty cycle having a value R 2 substantially equal to 50%, so that the effective current in the coil 2a is significantly reduced compared with that obtained during the first phase. phase, just enough to overcome the residual frictional forces Ff after takeoff of core 2b. During this interval which lasts about 30 to 60 ms, the core 2b continues its movement until closing the contactor, without brutality and without excessive speed. During this first interval of the second phase is obtained in the general case axially a stop contact between the pinion 1 and the starter ring between times t1 and t2.

More specifically, the microcontroller 10 is connected by one of its inputs to a temperature sensor placed inside the contactor 2a in the vicinity of the winding 2b and is also connected by a second input to the power supply terminals of the starter.

The microcontroller 10 draws on these two inputs signals representative of the temperature T of the contactor therefore the coil 2a and the supply voltage U input starter.

The starter's supply voltage is variable depending on the charge status of the vehicle's battery and the temperature. Indeed, the temperature of the coil 2a directly conditions its resistance. However, the average current obtained for a given duty cycle, depends directly on the voltage available across the starter - so across the battery - and the resistance of the coil 2a.

Thus, the microcontroller 10 comprises a memory in which a digital table is recorded which corresponds for a desired effective intensity, the duty ratio R2 to be adopted as a function of the supply voltage of the starter and the temperature of the coil. In practice, R2 is in the range of 0.4 to 0.6 at a temperature of 20.

The effective intensity is substantially constant in this first interval.

Thus, the microcontroller 10 automatically adopts a duty cycle R2 as a function of the supply voltage across the starter and the resistance of the winding (itself dependent on the temperature). The measurements of the voltage U and of the temperature T are advantageously carried out prior to implementation of the first phase described above, at the moment of activation of the starter.

In a second interval of the second phase, which flows between the instant t2 and the instant t3, and according to the invention after a predetermined predetermined time or variant, the microcontroller 10 implements a continuous increase and progressive ratio, from the ratio R2 to find the ratio R1 or alternatively a ratio greater than R1. This interval has a duration of about 20 to 50 ms and ensures, by the progressive increase of the effective intensity, the closing of the contactor, in an accidental case where the contactor could not be closed between t1 and t2. Such an accidental case may occur in particular if abnormally high friction forces take place in the contactor, in the mechanical means 4 and at the level of the motor shaft M. These abnormal forces are due, for example, to climatic phenomena, dilatation, seizing, the presence of impurities of dirt and all other soiling especially at the splines of the electric motor shaft and the joints of the fork.

During this second interval the spring teeth against teeth 5 are compressed to allow the plunger core 2b to actuate the movable contact 3 to power the electric motor and rotate its shaft to ensure penetration of the pinion in the crown and therefore a meshing of the pinion with the crown.

Of course in the case where the movable contact is closed between times t1 and t2, pinion meshing with the ring 3, it is not necessary to achieve the continuous increase in intensity because the meshing is performed before a predetermined time according to the applications. In 90% of cases the mobile contact is closed before this predetermined time as short as possible to encompass the normal operations.

As a variant, this time is determined for example as a function of the battery voltage or the winding temperature 2a, these quantities being influenced by the non-closing of the moving contact generating abnormal values.

In any case, in an additional interval flowing in FIG. 3 between the instant t3 and a time t4, the duty ratio is maintained at R1 or at a value greater than R1 for about 5 to 30 ms. This high duty cycle phase begins with the closing of the movable contact 3 and keeps the core 2b in its contact position (movable contact 3 closed) with a high attraction force which prevents rebounds of the movable core 2b against a stop formed usually by another nucleus, fix that one. This third interval t3, t4 lasts long enough to absorb the current peaks due to the start of the engine by the electric motor M, which according to a feature of the invention is unmanned.

According to a characteristic it is therefore only after abutment of the crown with the pinion is achieved the increase of the duty cycle.

After the third interval, a cyclic ratio R3 is adopted in a third phase across the winding resistance 2a to maintain the moving contact in the closed position.

The effective current is lower in this third phase than in the other two phases.

As will be understood and that it emerges from the description, a single winding 2a is necessary and the microcontroller can be mounted on a support, such as a card, in the starter, more specifically be mounted in the the vicinity of the winding 2a in the space between the movable contact 3 and the cover (not referenced in Figure 1) carrying the fixed contacts. Thanks to the invention and to the modulation of pulse width during the first phase, more precisely at the beginning thereof, it is possible to measure the current and thus the battery voltage, knowing that, as mentioned above, the average current obtained for a given duty cycle depends directly on the voltage available across the battery.

With the help of the digital table recorded in the microcomputer 10, after the start of the first interval of the first phase, the desired duty cycle is adopted.

Thus in Figure 4 the first phase is decomposed into two intervals t0-t 'and t'-t'1.

In the first interval the duty ratio R'1 is 100%. In the second interval the duty cycle is less than the duty cycle R2. Advantageously in Figure 4 the duty cycle in the second range of the first phase is zero for better accuracy of the measurement. In practice, the effective current during the first interval of the first phase is lower than that of FIG. 3 by being close to it. This effective current is therefore higher than that of the second phase with a duty cycle R2.

The duration t 'of the first interval is less than the duration t1.

The duration t'-t'1 of the second interval is greater than the duration t 'of the first interval. This duration is here more than double that of the first interval and makes it possible to make a good measurement before the beginning of the second phase.

For example, for a time of t1 of 4ms, the time t 'is 3ms and the time of the second interval t'1-t' of 7ms.

The current at the end of phase 1 is approximately 3A less than that of figure 3.

In Figure 4 the displacement of the core in phase 1 is less than half that of Figure 1.

With the ratio R ', we are in the vicinity of the kernel detachment limit. Of course in Figure 4 for simplicity it has not shown the other intervals of the second and third phase. The device and the method proposed here thus make it possible to optimize the progressivity of the movement of the movable core 2b and the pinion 1. An increase in the lifetime of the pinion 1 and the driving ring is thus obtained, as well as a reduction noticeable noise created by the impact of the pinion against the crown.

Even if the core does not take off during the first two phases, we can take off this one. The electric motor is not running.

The solution is simple, reliable and economical.

Of course, in FIG. 3, the intensity of the rms current in the first phase can be decreased. It all depends on the displacement of the plunger which one wishes to have. Compared to the prior art, one can get as close as possible to the kernel detachment limit and better control the movement of the latter by playing in particular on the duration of the first phase. In the prior art it is necessary to provide a greater safety factor to be sure that the core takes off.

Thanks to the invention, the detachment of the core is less abrupt and is better controlled, the first interval of the second phase occurring at substantially constant effective intensity.

As will be understood by placing the microcontroller 10 on a card in the aforementioned manner in the vicinity of the winding 2a, the temperature thereof can be measured by mounting on the card a resistor connected to the microcontroller and variable in size. temperature function, for example with a positive or negative temperature coefficient.

Claims (10)

<B> <U> CLAIMS </ U> </ B> 1. A method for supplying a coil (B) for driving a mobile motor vehicle starter (2) movable core (2b) equipped with an electric motor (M), in which it is varied the effective current in the coil (B) during the displacement of the core (2b) towards its contact position, to close a movable contact (3) and supply the electric motor (M), in which one adopts during this displacement - a first phase (to, t,) driving effective high enough to put the core (2b) in motion, then - a second phase (tl, t2, t3) driving lower effective current, characterized in that during the second phase (t1, t2, t3), after a predetermined or determined time, a continuous increase in the effective intensity is implemented. 2. Method according to claim 1, characterized in that the effective current during the second phase (ti, t2, t3) is of the order of 0.4 to 0.6 times that applied during the first phase (to, t ,). 3. Method according to claim 1 or 2, characterized in that the first phase comprises a first effective current interval sufficiently high to put the core (2b) in motion and a second lower current interval than the second phase see no one. 4. Method according to one of the preceding claims, characterized in that it implements a phase (t3, t4) at high intensity after closure of the movable contact (3). 5. Device for controlling the supply of a motor vehicle starter contactor (2) to a motor vehicle coil (2) for providing a variation of the effective current in the coil (2) B) during the displacement of the core (2b) towards its contact position, to close a movable contact (3) of the contactor (3) and supply the electric motor, in which it is intended to implement during this displacement - a first phase (to, tj) drive effective current sufficient to move the core, then; - a second phase (tl, t2, t3) driving lower effective current, characterized in that it is expected during this second phase to implement after a predetermined time or determined, a continuous increase in intensity effective. 6. Device according to claim 5, characterized in that it comprises means for measuring a supply voltage of the starter and means for adapting as a function of this voltage the level of effective current during the second phase (ti, t2, t3). 7. Device according to claim 5 or claim 6, characterized in that it comprises means for measuring a resistance of the coil (B) and to adapt according to this resistance the effective current during the second phase (ti, t2 , t3). 8. Device according to any one of claims 5 to 7, characterized in that it comprises means for measuring the temperature and means for adapting as a function of this temperature the effective current during the second phase (ti, t2, t3). 9. Device according to one of claims 5 to 8, characterized in that it is provided to provide the coil (B) a crimped voltage whose duty cycle (Rj, R2) is different in the first (ta, ti) and the second phase (ti, t2, t3). 10. Device according to claim 9 in combination with one of claims 6 and 8, characterized in that it comprises means (10) for deriving the duty cycle (R2) of the coil (B) according to the result (s) provided by the means of measurement.