EP1108139B1 - Method for gradually driving a motor vehicle starter switch - Google Patents

Abstract

The invention concerns a method for powering a driving coil of a mobile core of a motor vehicle electrical starter switch, which consists in varying the efficient current in the coil while the core is moving towards its contacting position, and in adopting during said displacement: a first driving phase with sufficiently high efficient current to move the core; then a second driving phase with lower efficient current, whereby after a specific or predetermined time the efficient intensity is continuously increased.

Description

The present invention relates to methods and devices for control of motor vehicle starters, and more specifically to the methods and devices for driving the core of the contactor of these starters.

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

Contactor 2 extends parallel to the electric motor M above of the latter and comprises a coil 2a and a plunger core 2b.

It controls the supply of the electric motor M by displacement of a movable contact 3 between an open position and a closed position, said contact 3 being pushed by said plunger core 2b movable axially 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 therefore connected to the pinion 1 by means mechanical referenced by 4 as a whole.

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

This launcher comprises a freewheel interposed axially between a hub and pinion 1. The hub has internal splines helical in complementary engagement with teeth external helicals carried locally by the motor output shaft electric M.

The fork is pivotally mounted between its two ends on a casing internally containing the mechanical means 4 and carrying the motor M and the contactor 2. The starter with its pinion 1 is animated by a helical movement when it is moved by the fork for engage the starter ring.

This is achieved by supplying the winding 2a following a actuation of the ignition key which allows to set in motion the plunger core 2b then attracted towards a fixed core mounted at the end of a winding support 2a. This support has a shaped section of U to accommodate the winding 2a and therefore has a bottom constituting a 2C bearing. The core 2b is therefore intended to move between a rest position and a contact position in which it is supported on the fixed core, this closed position of the magnetic circuit having place after closing of the moving contact 3 and therefore of the electrical circuit.

The mechanical means also include a return spring mounted around the core 2b to recall the latter in the rest position, a cut-off spring associated with the moving contact 3 to recall the latter in open position and a spring 5, said tooth-to-tooth spring, housed at the interior of the core 2b and engaged with a first rod connected by an axis at the upper end of the fork for coupling it to the core 2b. This spring 5 has a greater stiffness than the return spring.

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

The studs are integral with the closure cover of the contactor insulating material.

All of these are shown in Figure 1 and have not been referenced for simplicity.

The pinion 1 can therefore come into engagement with the crown C, that is to say come into engagement position with crown C, before contact mobile is closed.

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

Thus the mechanical means 4 include in particular a spring 5 which is mechanically interposed between the plunger core 2b and the pinion 1 and which allows the plunger core 2b to continue its course to ensure, before it comes into contact with the fixed core, putting the closed position of the movable contact, even if the pinion 1 is blocked in abutment against the teeth of the crown of the engine, in a position where it does not mesh with this crown.

However, given the speed of movement of the nucleus mobile 2b and the elasticity of the mechanical connecting means 4, due in particular with the presence of the spring 5, there may be phase shifts important between the closing of contact 3 and the translation of pinion 1. Particularly at low temperatures, you can see a rotation of the electric motor M and therefore pinion 1 before the latter had the time to enter the crown. With the electric motor M supplied under full tension, the speed of the pinion 1 increases very quickly, preventing thus the engagement of the pinion in the crown. It follows a rapid destruction of the crown and the 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 pinion not represented. Coil B is supplied via a transistor T in pulse mode, of the pulse width modulation type or "Pulse Width Modulation" (PWM), in French, the transistor being controlled by a microcontroller 10.

We gradually increase a duty cycle of pulsations to obtain an effective current in the coil which increases so progressive. In this way, we want the mobile core to start to move with a minimum of 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 pinion previously described.

This process also aims to reduce the speed of impact of the pinion against the crown to reduce front wear.

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

• une première phase d'entraínement à courant efficace suffisamment élevé pour mettre le noyau en mouvement, puis,
• une seconde phase d'entraínement à courant efficace plus faible.

To further reduce this impact speed, in document US-A-4 418 289, in accordance with the preamble of claim 1, a method has been proposed for supplying a drive coil with a movable contactor core. electric starter of a motor vehicle, in which the effective current in the coil is varied during the displacement of the core towards its contacting position, and in which one adopts during this displacement:

• a first phase of effective current drive high enough to set the nucleus in motion, then,
• a second phase of lower effective current drive.

• une première phase d'entraínement à courant efficace suffisant pour mettre en mouvement le noyau, puis,
• une seconde phase d'entraínement à courant efficace plus faible.

This document also provides a device for controlling the supply of a drive coil to a movable core of a motor vehicle starter switch, provided for varying the effective current in the coil during movement of the core to its contact position, in which it is intended to implement during this movement:

• a first phase of drive with an effective current sufficient to set the nucleus in motion, then,
• a second phase of lower effective current drive.

In practice it is planned in the second phase to supply the motor electric to rotate at reduced speed thanks to a disc additional, additional contacts and resistance additional integrated in the contactor. This second phase ends at closing of the movable 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.

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

The object of the present invention is to overcome these drawbacks of simple and economical way.

According to the invention a process of the above-mentioned type is characterized in only during the second phase, when the mobile core is not in contacting position, after a determined time, predetermined, a continuous increase in effective intensity.

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

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

Indeed the effective intensity in the first interval of the second phase is lower than the starting point of the document solution FR-A-2 679 717 since the core has already taken off. So we reduce the noise and the solution is safe.

Indeed, after a determined or predetermined time, the increase progressive effective intensity allows, on the one hand, to compress gradually the spring, teeth against teeth 5, and, on the other hand, the closing of the contactor to supply the electric motor in the case accident where the contactor could not have been closed before.

So in the accidental case where friction forces abnormally high take place in the contactor, in the means mechanical or at the level of the shaft of the electric motor we ensure beyond of a predetermined or determined time the closing of the contactor.

Such cases can occur due to climatic conditions specific, seizures, especially when the vehicle has been immobilized for a long time. Dust, dirt can settle on level of the fork and the shaft of the electric motor and thus hamper the displacement of the pinion.

Thanks to the invention, it is nevertheless possible to move the launcher and its pinion.

Furthermore, the coming into abutment contact of the pinion with the crown of start-up is carried out, either before increasing the intensity, or after increasing the intensity and before closing the moving contact, in so that we start the electric motor from zero speed in this stop contact position, which facilitates the penetration of the pinion in the crown while reducing wear.

The solution according to the invention is therefore reliable and makes it possible to increase the starter life thanks in particular to reduced wear.

In addition, energy consumption and noise are reduced. 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 at know a first high effective current interval followed by a second current interval lower than that of the second phase.

Preferably this second interval is carried out at zero current for better measurement accuracy.

So we can measure the battery voltage during the first phase. During this first phase the nucleus can take off with more weak stroke, the intensity during the first interval of this first phase being close to the intensity necessary to make the core take off and being performed with a shorter time.

If problems arise later, no separation of the nucleus, non-closing of the contactor for example, thanks to the continuous increase effective intensity according to the invention these problems will be solved.

The limited separation of the core makes it possible to further reduce the shocks brutal displacement, and reduce energy consumption.

Thanks to the invention the winding has a double function because, after a third interval of the second phase, during which we increase the intensity of the effective current, it allows after rotation of the motor electric to keep the moving contact closed during a third phase.

It will be appreciated that the electric motor does not turn until after coming in pinion stopper with crown, so the pinion can penetrate more easily in the crown and wear is reduced.

Thanks to the invention in the first phase, we can be at the limit of the separation of the nucleus so that the movement of it is still less brutal.

The time is determined according to abnormal values which are occur in the event of the mobile contact not closing.

The time is determined depending for example on the voltage of the battery or winding temperature.

The time is easily predetermined for the increase continuous intensity only occurs when necessary, i.e. for keep this time as short as possible and cover the majority of cases normal operating conditions.

• la figure 1 représente un démarreur de véhicule automobile conforme à l'état de la technique ;
• la figure 2 représente un montage d'alimentation d'un contacteur de démarreur conforme à l'état de la technique ;
• la figure 3 est un tracé représentant l'évolution d'un rapport cyclique de tension d'alimentation d'une bobine de contacteur, selon l'invention ;
• la figure 4 est une vue partielle analogue à la figure 3 pour un autre exemple de réalisation.

Other characteristics, 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 art;
• FIG. 2 represents a supply arrangement for a starter switch in accordance with the state of the art;
• Figure 3 is a plot showing the evolution of a duty cycle of the 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 FIG. 1, the plunger core 2b is arranged in the bearing 2C according to a sliding relation which is modulated by the presence of a lubricant ensuring a sealing and braking role. The core 2b is therefore a mobile core.

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

The presence of the lubricant does not eliminate these forces. On the contrary, by a lubricant scrub effect, this further accentuates the fact that the adhesion force Fa exceeds the friction force Ff. The mobile core 2b remains at rest as long as the coil 2a does not exert a motive force of attraction Fm which is greater than Fa.

During the setting in motion of the core 2b, one increases gradually the effective intensity in the coil 2a. The forces of core retention abruptly decrease (from F to Ff) when movement of the nucleus, while the force of attraction Fm already reaches a high value from the nucleus. This difference between Fm and Ff induces so when the nucleus is released a sudden acceleration of the movable core so progressive feeding therefore does not produce desired effects.

Here we use a device for feeding the coil 2a, the mounting remains similar to that shown in Figure 1, and in which here again adopts a supply of the coil 2a according to a voltage in PWM type slot.

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

On this plot, we have indicated on the abscissa successive instants during the displacement of the nucleus, from its initial rest position (instant T ₀ ) to a final position ("nucleus calling period") where it is in abutment against the fixed core and where it provides contact, the movable contact 3 then being closed.

The core call period is broken down into two phases main ones, the second of which is broken down into three sub-phases. We will describe now these two main phases.

During the first phase going from instant t ₀ to instant t ₁ , we adopt a duty cycle R1, close to or equal to 100% (the duty cycle is the ratio between the conduction time of transistor T ₁ and the total time of a cycle). During this phase, a high effective intensity crosses the coil 2a and the core 2b is subjected to an attractive force Fm sufficient to detach it from its rest position and set it in motion. This phase is brief, here of the order of 2 to 10 ms, in order to produce a high attraction force on the nucleus only for the purpose of detaching the latter.

The second phase takes place between time t ₁ and time t ₃ . In a first interval of this second phase, the transistor T ₁ controls the contactor according to a duty cycle having a value R2 substantially equal to 50%, so that the effective current in the coil 2a is significantly reduced compared to that obtained during the first phase, just sufficient to overcome the residual friction forces Ff after takeoff from the core 2b. During this interval which lasts approximately 30 to 60 ms, the core 2b therefore continues its movement until the contactor closes, without brutality and without excessive speed. During this first interval of the second phase, in the general case, an abutment contact is obtained between the pinion 1 and the start-up ring between times t1 and t2.

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

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

The starter supply voltage is variable depending on the state of charge of the vehicle 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, directly depends of the voltage available across the starter - therefore across the battery - and the resistance of the coil 2a.

Thus, the microcontroller 10 has a memory in which is recorded a digital table matching for an intensity desired efficiency, the duty cycle R2 to be adopted according to the starter supply voltage and coil temperature. In practical, R2 is of the order 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 ratio cyclic R2 as a function of the supply voltage across the starter and winding resistance (itself dependent on the temperature). The voltage U and temperature T measurements are advantageously carried out before implementation of the first phase described above, when the starter is activated.

In a second interval of the second phase, which elapses between instant t ₂ and instant t ₃ , and according to the invention after a predetermined time or in a determined variant, the microcontroller 10 implements an increase continuous and progressive of the cyclic ratio, going from the R2 ratio to find the R1 ratio or alternatively a ratio greater than R1. This interval has a duration of approximately 20 to 50 ms and makes it possible to ensure, by the progressive increase in the effective intensity, the closing of the contactor, in an accidental case where the contactor could not have been closed between t1 and t2. Such an accidental case can 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, expansion, seizure, the presence of dirt impurities and all other stains, in particular at the splines of the shaft of the electric motor and the joints of the fork.

During this second interval, the teeth spring is compressed against teeth 5 to allow the plunger core 2b to come into contact mobile 3 to power the electric motor and rotate the sound shaft in order to ensure penetration of the pinion into the crown and therefore a meshing of the pinion with the crown.

Of course in the case where the movable contact is closed between the time t1 and t2, pinion meshing with crown 3, there is no need to carry out the continuous increase in intensity because the meshing is carried out before a predetermined time depending on the applications. In 90% of cases the mobile contact is closed before this shortest possible predetermined time to encompass normal operations.

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

In all cases in an additional interval elapsing at the Figure 3 between time t3 and time t4, the duty cycle is maintained at R1 or at a value greater than R1 for approximately 5 to 30 ms. This phase with high duty cycle starts when the moving contact 3 closes and maintains the core 2b in its contacting position (movable contact 3 closed) with a high attraction force which avoids rebounds of the core movable 2b against a stop usually formed by another core, fixed that one. This third interval t3, t4 lasts long enough to ability to absorb current spikes due to engine starting thermal by the electric motor M, which according to a characteristic of the invention is not piloted.

According to one characteristic, it is therefore only after the abutment of the crown with the pinion that is carried out the increase in the ratio cyclic.

After the third interval we adopt in a third phase a duty cycle R3 across the winding resistance 2a for maintain the movable contact in the closed position.

The rms current is weaker in this third phase than in the other two phases.

As will be understood and it emerges from the description, only one winding 2a is required and the microcontroller can be mounted on a support, such as a card, in the starter, specifically be mounted in the vicinity of the winding 2a in the space between the movable contact 3 and the cover (not referenced in FIG. 1) carrying the fixed contacts.

Thanks to the invention and to the pulse width modulation during the first phase, more precisely at the beginning of it, we can perform a measurement of current and therefore of the battery voltage knowing that, from abovementioned manner, the average current obtained for a given duty cycle depends directly on the voltage available across the battery.

Using the digital table stored in the micro-calculator 10 we adopt, after the start of the first interval of the first phase, the desired duty cycle.

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

In the first interval the duty cycle R'1 is 100%. In the second interval the duty cycle is less than the duty cycle R2.

Advantageously in FIG. 4 the duty cycle in the second interval of the first phase is zero for better accuracy of the measured. In practice the effective current during the first interval of the first phase is lower than that of Figure 3 by being close to this one. This effective current is therefore higher than that of the second cyclic ratio phase 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 here is more than double that of the first interval and allows a good measurement before the start of the second phase.

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

The current at the end of phase 1 is approximately 3A lower than that of Figure 3.

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

With the ratio R ', we are in the vicinity of the separation limit of the core. Of course in Figure 4 for simplicity we have not shown the other intervals of the second and third phase.

The device and method proposed here therefore make it possible to optimize the progressive movement of the movable core 2b and the pinion 1. We obtain thus an increase in the life of the pinion 1 and the crown as well as a significant reduction in noise created by the impact of pinion against the crown.

Even if the nucleus does not take off during the first two phases, we can take it off. The electric motor is not piloted in current.

The solution is simple, reliable and economical.

Of course in Figure 3 we can reduce the intensity of the current effective in the first phase. It all depends on the displacement of the nucleus diver you want to have. Compared to the prior art, we can get as close as possible to the separation limit of the core and better control the movement of the latter by playing in particular over the duration of the first phase. In the prior art, it is necessary to provide a coefficient more important to be sure that the nucleus takes off.

Thanks to the invention the separation of the core is less brutal 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 it is possible measure its temperature by mounting a resistor on the card connected to the microcontroller and variable depending on the temperature by example with positive or negative temperature coefficient.

Claims (10)

1. A method of energising a winding (B) for actuating a movable plunger core (2b) of a contactor (2) for an electrical starter, having an electric motor (M), for a motor vehicle, in which the effective current in the winding (B) is caused to vary over the course of displacement of the core (2b) towards its contact position, whereby to close a moving contact (3) and to energise the electric motor (M), wherein, during the said displacement, there are:

   a first phase (t₀, t₁) of actuation with an effective current which is high enough to set the core (2b) in motion, and then

   a second phase (t₁, t₂, t₃) of actuation with a weaker electric current,

   characterised in that, during the second phase (t₁, t₂, t₃), after a predetermined or determined time, a continuous increase is applied to the effective current intensity.
2. A method according to Claim 1, characterised in that the effective current during the second phase (t₁, t₂, t₃) is of the order of 0.4 to 0.6 times that which is applied during the first phase (t₀, t₁).
3. A method according to Claim 1 or Claim 2, characterised in that the first phase includes a first period in which the effective current is high enough to put the core (2b) in motion, and a second period in which the effective current is weaker than that in the second phase, or even nil.
4. A method according to one of the preceding Claims, characterised in that it includes a phase (t3, t4) with an elevated current intensity after the moving contact (3) has been closed.
5. Apparatus for controlling the energisation of a winding (B) for actuating a movable plunger core (2b) for a contactor (2) for a motor vehicle starter, arranged to cause the effective current to vary in the winding (B) in the course of the displacement of the core (2b) towards its contact position, whereby to close a moving contact (3) of the contactor (2) and energise the electric motor, wherein it is so arranged as to perform, in the course of the said displacement:

   a first phase (t₀, t₁) of actuation with an effective current which is high enough to set the core (2b) in motion, and then

   a second phase (t₁, t₂, t₃) of actuation with a weaker electric current,

   characterised in that it is arranged so that during the said second phase, after a predetermined or determined time, there is a continuous increase in the effective current intensity.
6. Apparatus according to Claim 5, characterised in that it includes means for measuring a supply voltage of the starter, and means for adapting, as a function of the said voltage, the effective current level during the second phase (t₁, t₂, t₃).
7. Apparatus according to Claim 5 or Claim 6, characterised in that it includes means for measuring a resistance of the winding (B), and for adapting, as a function of the said resistance, the effective current during the second phase (t₁, t₂, t₃).
8. Apparatus according to any one of Claims 5 to 7, characterised in that it includes means for measuring the temperature and means for adapting, as a function of the said temperature, the effective current during the second phase (t₁, t₂, t₃).
9. Apparatus according to one of Claims 5 to 8, characterised in that it is so arranged as to supply to the winding (B) a pulsed voltage, the cyclic ratio (R₁, R₂) of which is different in the first phase (t₀, t₁) and the second phase (t₁, t₂, t₃).
10. Apparatus according to Claim 9 in combination with one of Claims 6 to 8., characterised in that it includes means (10) for deducing the cyclic ratio (R₂) of the power supply of the winding (B) as a function of the result or results supplied by the said measuring means.

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