EP0848160B1 - Enhanced power cut-off control for motor vehicle starter - Google Patents

Description

The present invention relates to a method and a device for the automatic shutdown of a starter of motor vehicle.

Usually cutting off the drive from engine by starter is controlled by the user of the vehicle who releases the ignition key when the engine makes a characteristic noise.

However, the tendency to make engines more and more quiet thermal makes it becomes difficult for the user to detect the end of the start-up. This results in more severe solicitation of the starter.

We already know many devices for cut a motor vehicle starter when the engine has started and is sufficiently autonomous to reach its idle speed by itself.

The most efficient of these devices put generally implemented an analysis of the ripples of the starter supply voltage, ripples which are due to variations in current absorbed by the starter when the engine is compressed before the start of it. Such a device is known from DE-A-19 503 537.

We know that at the end of the training period, when of the first explosions, the engine quickly rises in diet.

To obtain a quick power cut of the starter as soon as the internal combustion engine is sufficiently launched, it has already been proposed in the patent application French filed by the plaintiff under the number 96 11792 (corresponds to EP-A-0 833 051 not pre-published) a cut-off strategy according to which we trigger a polling period for each new ripple and the starter is cut off when no extremum is detected in this scrutiny period. The length of the period for example is proportional to the duration from the previous ripple.

However, this strategy does not resolve cases of acyclisms of the type represented on the Figures 1 and 2.

The acyclism represented in FIG. 1 occurs at the start of the starter operation: the peak C ₁ at the start of compression is embedded in the rising edge of the second peak C ₂ .

In this case, the analysis of the duration T ₁ to reach the peak is distorted and the scanning period D ₁ determined for the next cycle is much longer than necessary.

Therefore, if start-up occurs At that time, the decision to stop taken at the end of the scrutiny is late, which greatly reduces advantages expected by electronic control (reduction wear, reduction of freewheeling noise, ...).

The acyclism shown in Figure 2 occurs during the training phase, in case of difficult start. An explosion not followed by other explosions leads to a punctual bringing together of two successive voltage peaks (peaks C ₃ and C ₄ in Figure 3). As a result, the first of these peaks (peak C ₃ ) may not be detected over the scanning period D ₂ which corresponds to it.

There is therefore a risk that the reconciliation of the two explosions is interpreted as a engine start.

The starter will be prematurely stopped, before engine start, forcing the driver to try to start again.

In addition, the time T ₃ used for determining the next scanning duration is also distorted.

The invention proposes an order for the shutdown of a motor vehicle starter, according to which we detect the ripples of a signal corresponding to the starter voltage or current and we cut the starter when these ripples disappear, which overcomes these drawbacks.

The solution according to the invention consists in that determines on the signal successive durations during which the tension is constantly increasing and we switches off the starter when one of these durations becomes greater than a given threshold and in what we give to this threshold of distinct values on the one hand during a polling period triggered when the starter contactor and on the other hand beyond this polling period, the polling period being of a chosen duration sufficient to encompass cases where the first and second beginning ripples of compression are substantially confused.

The implementation of these two strategies different at the start of starter operation and during the normal training phase eliminates early or too late stops which could otherwise be caused by acyclisms of the voltage signal.

• les valeurs du seuil pendant la période de scrutation et au delà de celle-ci sont fonction de la température ;
• au-delà de la période de scrutation, la valeur seuil est fonction pour chaque nouvelle ondulation d'une (ou de) durée(s) de l'ondulation (ou des ondulations) précédente(s) ;
• pendant la période de scrutation, on ne commence à déterminer les durées successives pendant lesquelles la tension est constamment croissante qu'après un temps d'initialisation donné ;
• pendant la période de scrutation et au-delà, on mémorise les valeurs de signal correspondant à la valeur maximale des tensions crêtes et au delà de la période de scrutation, on ne détermine une durée pendant laquelle la tension est constamment croissante, qu'à partir de l'instant où le signal atteint la valeur précédemment mémorisée correspondant à la valeur de tension crête maximale ;
• le signal sur lequel on détecte les ondulations est la tension d'alimentation du démarreur ;
• pour déterminer les durées pendant lesquelles la tension est constamment croissante, on échantillonne ladite tension et on considère qu'il y a décroissance si la dernière valeur mesurée est inférieure à la valeur précédente diminuée d'une valeur constante dU et qu'il y a croissance sinon ;
• la valeur constante dU est comprise entre 50 et 200 millivolts.

This process is advantageously supplemented by the following different characteristics, taken alone or in all their technically possible combinations:

• the threshold values during and beyond the scanning period are a function of the temperature;
• beyond the scanning period, the threshold value is a function for each new ripple of one (or more) duration (s) of the previous ripple (s);
• during the scanning period, the successive durations during which the voltage is constantly increasing is not started to determine until after a given initialization time;
• during the scanning period and beyond, the signal values corresponding to the maximum value of the peak voltages are memorized and beyond the scanning period, a duration during which the voltage is constantly increasing is only determined from from the moment when the signal reaches the previously memorized value corresponding to the maximum peak voltage value;
• the signal on which the ripples are detected is the starter supply voltage;
• to determine the durations during which the voltage is constantly increasing, the said voltage is sampled and it is considered that there is a decrease if the last value measured is less than the previous value decreased by a constant value dU and that there is growth if not ;
• the constant value dU is between 50 and 200 millivolts.

The invention also relates to a device for controlling the shutdown of a starter comprising a management unit which includes means for detecting the ripples of a signal corresponding to the voltage or to the intensity of the starter and the means to cut the starter when these ripples disappear, characterized in that this management unit implements the aforementioned treatment.

The invention also relates to a starter for motor vehicle comprising such a device.

• les figures 1 et 2, déjà analysées, sont des graphes sur lesquels on a porté des exemples d'évolution acycliques de la tension du démarreur en fonction du temps lors d'une phase de démarrage ;
• la figure 3 est un schéma d'un dispositif de commande de coupure d'un démarreur conforme à un mode de réalisation possible pour l'invention ;
• la figure 4 est un graphe sur lequel on a porté un exemple d'évolution de la tension du démarreur en fonction du temps, qui illustre une mise en oeuvre conforme à l'invention ;
• la figure 5 est un organigramme d'un traitement permettant une mise en oeuvre de l'invention.

Other characteristics and advantages of the invention will emerge from the description which follows. This description is purely illustrative and not limiting. It must be read in conjunction with the appended drawings in which:

• Figures 1 and 2, already analyzed, are graphs on which we have given examples of acyclic evolution of the starter voltage as a function of time during a starting phase;
• Figure 3 is a diagram of a cut-off control device of a starter according to a possible embodiment for the invention;
• Figure 4 is a graph on which we have shown an example of evolution of the starter voltage as a function of time, which illustrates an implementation according to the invention;
• FIG. 5 is a flow diagram of a processing allowing an implementation of the invention.

FIG. 3 illustrates a device for controlling the supply of a starter DM which comprises an electric motor M mounted between a supply terminal B ⁺ at the voltage of the vehicle battery and ground.

This device comprises a contactor 1 mounted between the terminal B ⁺ of supply to the voltage U of the battery and the starter DM.

This contactor 1 is a relay actuated by a winding 2. One of the ends of this winding 2 is connected to the supply terminal B ⁺ . Its other end is connected on the one hand to the source of a MOSFET transistor 3 and on the other hand to a coil 5 connected to ground.

The drain of transistor 3 is connected to the supply terminal B ⁺ . Its gate is connected to the output of a unit 4, from which it receives a control voltage. The unit 4 is for example a microprocessor.

Of course, transistor 3 could be replaced by any other type of switch.

In the example illustrated in these figures, the unit 4 generates said control voltage as a function on the one hand of the undulations of the voltage of the supply terminal B ⁺ , and on the other hand of the position of the contactor actuated by the ignition key (switch 6).

The processing carried out by the control unit 4 will now be described in detail with reference to Figures 4 and 5.

This treatment implements two strategies different depending on whether you are at the beginning of the starter operation or during phase normal training.

Start of starter operation

A polling window of a predetermined duration D _ini is opened from the activation of the starter (time T ₀ for which the closing of the contactor 1 occurs).

Unit 4 determines the durations dS ₁ , dS ₂ , etc. in this polling window. periods during which the voltage U of the supply terminal B ⁺ is constantly increasing. These periods correspond to the representations in mixed lines on the curve of the undulations.

Preferably, these determinations do not start directly at time T ₀ , but at a time T ₀ + t _ini , where t _ini is chosen so as to eliminate the entire unstable period of the current draw at the time of powering up the starter motor M.

To determine the durations dS ₁ , dS ₂ , etc., the unit 4 implements over the entire scanning window D _ini a sampling of the voltage U and a count which is reset to zero each time a decrease occurs .

She considers that there is a decrease if the last measured value is less than the value minus a constant value dU and that there is growth otherwise.

This constant dU has a value between 50 and 200 millivolts.

The interest of this constant dU is to allow to mask the noise of the signal without distorting the analysis.

As soon as the duration dS of an increasing sequence exceeds a predetermined value TS ₁ , the starter is deactivated.

TS ₁ is of course less than D _ini and is experimentally predetermined as a function of the maximum possible values for T ₁ (FIG. 1).

Thus, if the start takes place during the initial scan window D _ini , the starter is stopped after a fixed time TS ₁ which makes it possible to overcome the irregularities mentioned above and not to have abnormally long cut-off times .

Advantageously, the value of TS ₁ is indexed to the temperature according to a determined law or table of values.

Normal training

During the entire period D _ini and beyond it, the unit 4 stores the maximum value UC _max of the voltage U on the different peaks encountered.

If at the end of the polling window D _ini the unit 4 has not commanded the cut-off of the starter, it continues its processing in the following manner.

For each new rising edge, it begins a countdown of the duration of S during which the voltage U of the supply terminal B ⁺ is constantly increasing, from the moment when the voltage U has reached the value UC _max previously memorized.

The starter is deactivated when a duration of S exceeds a predetermined value TS ₂ .

This value TS ₂ can be a fixed value for the entire period after the polling window D _ini .

It can also be a function of the period appearance of the previous undulations, for example being a fraction of the time between the last two peaks, this duration being determined by a counting implemented by unit 4.

Also, the value (s) of TS ₂ may be weighted by a coefficient depending on the ambient temperature of the heat engine. Thus, at low temperature, it will be interesting to increase TS ₂ to ensure a clean and complete start before stopping the starter.

Note that by starting the countdown of a duration d'S that from the moment when the voltage U becomes greater than the previously stored Ucmax value, we eliminates the bottom of the part of the voltage curve whose duration can be variable according to the conditions of startup and therefore we have better precision.

An organization chart allowing the implementation of the treatment is given by way of example in FIG. 5.

In a first step 10, we initialize the microprocessor which constitutes unit 4 and we measure the starter temperature.

In a second step (step 11), the microprocessor 4 determines the durations D _ini , TS ₁ and TS ₂ as a function of the temperature measured in step 10.

Then, unit 4 commands the closing of the contactor 1 (starter activation step 12).

After a time delay up to a time T ₀ + t _ini (step 13), the unit 4 searches for the first series of voltage samples which is increasing for a duration TS ₁ during the polling window up to D _ini and for a time TS ₂ beyond this polling window (step 14).

Simultaneously, it determines and stores, as samples are taken, the value of the maximum peak voltage UC _max .

When unit 4 finds a sequence checking the above conditions, it commands the end of activation of the starter (output 15). She continues her research if not.

Other variants of implementation and realization of the invention are of course possible.

In particular, instead of detecting ripples on the voltage signal we could put implementing the treatment proposed by the invention on a signal corresponding to the intensity absorbed by the starter, since variations of this intensity are inverse to those of voltage.

Of course, the control unit 4 can be integrated into the starter or be constituted by another motor vehicle unit, for example the unit of thermal engine control.

In addition, the starter cut-out command motor vehicle which has just been described present other benefits than those that have been previously exposed: it is independent of the internal combustion engine vehicle, its number of cylinders and its displacement, aging of the battery and wiring, as well as starter technology and power.

Claims (10)

1. Method for controlling the power cutoff for a motor vehicle starter, according to which the ripples of a signal corresponding to the voltage or current of the starter are detected and the starter is cut off when these ripples disappear, characterised in that, on the signal, successive durations are determined during which the voltage is constantly increasing and the starter is cut off when one of these durations becomes greater than a given threshold and in that distinct values are given to this threshold on the one hand during a scrutiny period triggered at the closure of the starter contactor and on the other hand beyond this scrutiny period, the scrutiny period being of a duration chosen so as to be sufficient to encompass the cases where the first and second start-of-compression ripples are substantially merged.
2. Method according to Claim 1, characterised in that the values of the threshold during the scrutiny period and beyond this are a function of the temperature.
3. Method according to one of Claims 1 and 2, characterised in that, beyond the scrutiny period, the threshold value is a function, for each new ripple, of one or more durations of the previous ripple or ripples.
4. Method according to one of Claims 1 or 2, characterised in that, during this scrutiny period, the successive durations during which the voltage is constantly increasing is begun to be determined only after a given initialisation time.
5. Method according to one of the preceding claims, characterised in that, during the scrutiny period and beyond, the signal values corresponding to the maximum value of the peak voltages are stored and in that, beyond the scrutiny period, a duration during which the voltage is constantly increasing is determined only as from the time when the signal attains the previously stored value corresponding to the maximum peak voltage value.
6. Method according to one of the preceding claims, characterised in that the signal on which the ripples is detected is the starter supply voltage.
7. Method according to Claim 6, characterised in that, in order to determine the durations during which the voltage is constantly increasing, the said voltage is sampled and it is considered that there is a decrease if the last value measured is less than the previous value minus a constant value dU and that there is an increase otherwise.
8. Method according to Claim 7, characterised in that the constant value dU is between 50 and 200 millivolts.
9. Device for controlling the power cutoff for a starter having a management unit which includes means for detecting the ripples of a signal corresponding to the voltage or current of the starter and means for cutting off the starter when these ripples disappear, characterised in that this management unit implements the processing according to one of the preceding claims.
10. Motor vehicle starter having a device according to Claim 9.

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