EP2737197B1 - Starter circuit of a motor vehicle comprising a device for stepping up the battery voltage, and starter provided therewith - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION

In general, the invention relates to the field of thermal motor starters in motor vehicles. More particularly, the invention relates to the combination of a starter and a device allowing a raising of the voltage across the battery of the vehicle when powering the starter.

BACKGROUND ART OF THE INVENTION.

When a starter is energized to start the vehicle's combustion engine, a large current draw occurs which is close to the short-circuit current level of the starter, ie a current of the starter motor. order of 1000 amperes. This phenomenon is described in the document US2002 / 0023605 A1 . This current draw when the starter is energized then decreases in intensity as the starter armature, corresponding to the rotor of the machine, rises in speed.

At this initial peak of current corresponds a consequent fall of the voltage at the terminals of the battery. Other smaller voltage drops then occur during the start-up phase and correspond to passages through successive high dead points of the engine.

The development of so-called "reinforced" starters adapted for automatic shutdown / restart systems of the combustion engine (so-called "Stop / Start" or "Stop &Go" systems in English terminology) now impose new constraints on automotive equipment manufacturers, relating to the respect of minimum voltage thresholds of the battery when the current is turned on when the starter is energized. Thus, in their specifications, the car manufacturers define a first voltage threshold usually between 7 and 9 Volt below which the battery voltage must not go down. For the following voltage drops, corresponding to the top dead center of the engine, the battery voltage must remain higher than a second voltage threshold usually between 8 and 9 Volt. During the starting of the engine, the voltage of the vehicle electrical system thus remains at a value sufficient to guarantee the expected operation of the equipment of the vehicles.

Reinforced starters generally have higher power than conventional starters to get a quick start for more user comfort. This results in a higher inrush current and therefore a first drop in battery voltage that goes beyond the usual values and that against high requirements. This causes a real difficulty for the designer because it would be necessary to be above battery voltage that the starter has internal voltage drops so high that it would then no longer have the power to drive at sufficient speed the engine thermal at low temperature.

In the prior art, solutions have been proposed to the problem set forth above. A first known solution of the inventive entity is based on the use of electronic voltage-boosting converters in order to avoid a voltage level that is too low on the on-board electrical system. A major disadvantage of these converters lies in the substantial costs they introduce.

Another known solution proposes to control the starter by means of two relays, a delay and a current limiting resistor. In a first phase of operation whose duration is determined by the time delay, an additional resistor is inserted in series in the starting circuit and limits the peak of initial current. In a second phase of operation, the additional resistance is output from the starting circuit in order to allow the passage of a sufficient current in the armature of the starter and allow a rise in speed thereof.

The documents EP2080897A2 and EP2128426A2 describe a starter of the type above. In addition to the additional cost of the additional control relay, the delay and the current limiting resistor, the introduction of this additional relay, which includes moving mechanical parts subjected to wear, has a negative impact on the holding the starter in terms of the number of startup cycles that must be able to support the starter safely. The resistance of the starter in the number of starting cycles is a particularly severe constraint for starters intended for Stop / Start systems. Indeed, such starters are required to hold about 300,000 startup cycles, which is ten times more than the approximately 30,000 cycles required for conventional starters.

In addition to the disadvantages described above, the use of this second solution of the prior art may prove unsuitable when the satisfaction of a binding tension gauge in terms of time is required by the car manufacturer. Such a template generally comprises a low voltage stage corresponding to the first voltage threshold indicated above and a high voltage stage corresponding to the second voltage threshold. A rising voltage ramp is also provided in the template between the low bearing and the high bearing.

The tests carried out by the inventive entity, with the usual values of the builders for the duration of the low step and the slope of the ramp of the template, show the difficulty that there is with this second solution of the prior art to remain in the template. Indeed, it was found a risk of crossing the template at its voltage ramp when the battery voltage, after recovering once the initial peak absorbed current, drops again at the end of the delay, the current flowing through the armature of the starter then increases substantially due to the output of the current limiting resistor of the starter circuit. After this crossing, the battery voltage can remain under the template for a certain period of time and do not return above the template after the end of the ramp up voltage, while the start time of the high voltage stage has already been achieved.

In order to eliminate the disadvantages indicated above, the inventive entity has already proposed improvements to existing starters of the prior art, in particular for applications in motor vehicles of the stop / restart function of the engine.

These improvements have generally consisted in mounting an inductive type filtering device in series with the electric motor in the starter power circuit, so as to prevent a drop in the battery voltage following a peak current produced. by commissioning the electric motor.

New studies conducted by the inventive entity have made it possible to optimize the embodiments of these improvements.

GENERAL DESCRIPTION OF THE INVENTION

According to a first aspect, the present invention therefore relates to a combination in a starter motor circuit of a motor vehicle of a starter and a battery voltage enhancement device, the starter comprising an electric motor and an electromagnetic contactor, the battery voltage enhancement device being intended to prevent a fall of the battery battery voltage following a current peak produced by the commissioning, in a power circuit, of the starter.

According to the invention, the battery voltage enhancement device consists of an inductive type filtering device which is connected in series with the electric motor in the power circuit, the filtering device comprising a magnetic circuit which consists of a carcass made of magnetic material comprising a cylindrical yoke, two closure pieces and an axial core around which are arranged a primary winding circuit intended to be inserted in series in the power circuit and a secondary winding circuit in short -circuit, and comprising an axial core which has at least one gap.

According to a first particular embodiment, said at least one air gap is a median air gap.

According to a second particular embodiment, said at least one air gap comprises two end air gaps between the closure parts.

According to a third particular embodiment, the closure parts each have an annular air gap. Preferably, the annular gap is axially aligned with the primary winding circuit or with the secondary winding circuit.

According to a particular characteristic, the secondary winding circuit consists of an electrically conductive tube. The tube is made of copper or aluminum and has a predetermined length to radius ratio, as well as a predetermined thickness.

According to another particular embodiment, the filtering device is inserted into the starter power circuit between a positive terminal of a vehicle battery and a power contact of the electromagnetic contactor.

According to yet another particular embodiment, the filtering device is inserted into the starter power circuit between a power contact of the electromagnetic contactor and the electric motor.

In another aspect, the invention also relates to a starter adapted to be integrated in a combination as briefly described above. According to the invention, the filtering device included in the combination is fixed on an outer casing of the starter.

The few specifications above will have made obvious to the skilled person the additional benefits achieved through optimization by the company applicant of its inductive filtering device.

The detailed specifications of the invention are given in the following description in conjunction with the accompanying drawings. It should be noted that these drawings have no other purpose than to illustrate the text of the description and do not constitute in any way a limitation of the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

• The Figure 1 is a perspective view showing a combination of a starter and an inductive type filtering device of the kind previously developed by the applicant company.
• The Figure 2 is a block diagram of a starter electrical circuit comprising a combination as shown in FIG. Figure 1 .
• The Figures 3a, 3b and 3c respectively show the variation of the magnetic flux and the magnetic energy in the filtering device as a function of the current flowing in the power circuit of the starter, as well as the evolution of the current as a function of time, in the case of the filtering device according to the invention (squares) and in the case of prior filtering devices (diamonds).
• The Figure 4 is a sectional view of an inductive type filtering device of the kind previously developed by the applicant company.
• The Figure 5 is an axial sectional view of the filtering device according to the invention in a first preferred embodiment.
• The Figure 6 is an axial sectional view of the filtering device according to the invention in a second preferred embodiment.
• The Figures 7a and 7b are axial sectional views of exemplary filtering device according to the invention in a third preferred embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

The Figure 1 shows a combination 1 of a starter, comprising a DCM DC electric motor and an electromagnetic contactor EC, and an inductive type LPF filtering device to which the optimization efforts of the applicant company have focused.

In this embodiment, the LPF filtering device is mechanically fixed to an outer casing of the starter, close to the contactor EC.

The electrical connections between the LPF filtering device, the EC contactor and the DCM electric motor are shown on the Figure 2 .

The LPF filtering device is electrically connected in series between the power contact CP of the contactor EC and the DCM motor.

In an alternative embodiment (not shown), the LPF filtering device is not integrated in the EC starter, DCM, but is inserted in the power circuit between the positive terminal B + of the battery and the power contact CP .

The EC contactor is here a conventional starter contactor, single power contact CP, and comprises a solenoid formed of a call coil and a holding coil.

Closing a start contact CS of the vehicle controls the excitation of the call and hold coils, and the activation of the starter according to a sequencing well known to those skilled in the art and which will not be detailed here.

The strong initial current peak mentioned above occurs when the power contact CP is closed, when the DCM motor is powered at full power.

Closing the power contact CP also causes the LPF filtering device to flow a power supply to the DCM motor.

As shown by his electrical diagram shown in Figure 2 the LPF filtering device here is an inductive type device which is embodied herein as a battlelike transformer having magnetically coupled windings. It will be noted that, depending on the applications, a simple inductor could have been used to form the low-pass filtering device on which the optimization work was carried out. The embodiment with a transformer, however, provides more parameters to adjust the frequency response of the LPF device depending on the application. Thus, it is possible to optimize this response by adjusting the inductances of the primary and secondary circuits W1, W2 and the mutual inductance introduced by the coupling between these circuits.

The primary winding circuit W1 is the one that is inserted in the power circuit of the starter. The secondary winding circuit W2 is short-circuited.

Typically, the equivalent inductance of the inductive filtering device LPF is between 0.1 and 10 mH approximately for currents having an order of magnitude of 300 to 1000 A.

The effect of raising the battery voltage obtained stems from the fact that When the DCM motor is energized, the initial peak of current is cut off (attenuated by about half) due to the production of strong currents induced in the short circuit W2 short circuit, which oppose the abrupt variation of magnetic flux that generates them.

The Figure 3a shows the variation of the magnetic flux Φ in a magnetic circuit of a non-optimized LPF filtering device (diamond curve 2) and in the magnetic circuit of an optimized LPF filtering device (curve in squares 3) according to the invention.

In the case of the non-optimized LPF filtering device, the magnetic flux Φ increases very rapidly with the intensity to stabilize at a maximum value.

The Figure 3b shows that this saturation value corresponds to the storage of a small amount of magnetic energy Em (diamond curve 4).

It follows that, although the current peak is attenuated, the power current I grows very rapidly as soon as the saturation of the magnetic circuit of the non-optimized LPF filtering device is reached, as is clearly shown in FIG. Figure 3c (diamond curve 5).

In order to delay the appearance of the saturation phenomenon, the LPF filtering device optimized according to the invention comprises a magnetic circuit with at least one gap AG.

The Figure 3a shows that the magnetic flux Φ then increases less strongly according to the power current I (curve in squares 3) than in the case where the magnetic circuit does not have an air gap AG (diamond curve 2). The saturation phenomenon is also less important.

In this case, the stored magnetic energy Em reaches higher values (curve in squares 6 of the Figure 3b ) to the values corresponding to the non-optimized LPF filtering device (diamond curve 4).

The result of the implementation of an airgap AG is a slow evolution (as shown by the curve in squares 7 of the Figure 3c ) of the power current I after saturation, at the time of commissioning of the DCM motor, compared to the non-optimized LPF filtering device.

The Figure 4 shows an inductive type filtering device of the type previously developed by the applicant company, which essentially comprises a carcass C, YO, CM, CM 'of magnetic material such as steel, and primary winding circuits W1 and secondary W2.

The carcass comprises a cylindrical yoke Y0, two closure pieces CM, CM 'and an axial core C around which are arranged the winding circuits W1, W2.

The primary winding circuit W1 is intended to be inserted in series in the power circuit and the secondary winding circuit W2 is short-circuited.

This secondary winding circuit W2 comprises several turns or, alternatively, is in the form of a ring.

In a first preferred embodiment, shown in the Figure 5 , the optimized LPF device comprises the same essential elements as the non-optimized LPF filtering device, that is to say a carcass C, Y0, CM, CM 'of magnetic material and primary winding circuits W1 and secondary W2 . It differs in the presence of a median air gap AG, of the order of 0.5 mm to 5 mm, in an axial direction, located substantially in the middle of the central core C.

In a second preferred embodiment, shown in the Figure 6 , the optimized LPF device comprises an axial core C having two extreme airgaps AG1, AG1 'between the closing parts CM, CM'. These air gaps AG1, AG1 'are preferably of the order of 0.5 mm to 5 mm.

In a third preferred embodiment, shown in the Figure 7a and 7b , the optimized LPF device comprises closure pieces CM, CM 'each having an annular air gap AG2, AG2'; AG3, AG3 '.

These annular air gaps AG2, AG2 '; AG3, AG3 are axially aligned with either the primary winding circuit W1 ( Figure 7a ), or with the secondary winding circuit W2 ( Figure 7b ), that is to say that the generatrices defining them are substantially coincident with those surrounding the primary and secondary winding circuits W1, W2.

An airgap AG in the magnetic circuit C, YO, CM, CM 'makes it possible to reach the saturation of this magnetic circuit C, YO, CM, CM' later, and thus to power the DCM electric motor of the DCM starter longer. , EC by an attenuated current level (by means of the LPF filtering device).

In this way, the DCM electric motor has reached a higher rotational speed, and thus generates a higher counter-electromotive force, at the moment of saturation, which contributes to limiting the power current I.

In certain embodiments of the invention, the secondary winding circuit W2 may advantageously consist of a conductive tube (for example example copper or aluminum) concentric with the primary winding circuit W1, and located outside or outside the latter.

Such a structure can lead to an LPF filtering device of simpler embodiment compared to the secondary winding circuit W2 in several turns. It will be noted that the maintenance of an identical length-to-radius ratio, with respect to a secondary winding circuit W2 in several turns, will require a correct dimensioning of the thickness of the tube. The electrical operation of the LPF filtering device will not be modified because of the ratio N2 / N1 which characterizes the transformer, provided to pass from a resistance R for N2 turns to a resistor R / N2 ² for a turn with the tube, N2 and N1 being respectively the numbers of turns of the winding circuits W2 and W1.

It goes without saying that the invention is not limited to the only preferred embodiments described above.

In particular, the various provisions in the magnetic circuit C, Y0, CM, CM 'of the specified gap (s) AG are only exemplary embodiments.

In the description above, the air gaps AG are implicitly free spaces between two parts of the magnetic circuit C, Y0, CM, CM '.

Alternatively, the function of the air gaps AG can be obtained by means of a saturable section in the magnetic circuit C, Y0, CM, CM ', which saturates either abruptly or gradually. For example, a closure piece CM, CM 'of insufficient section to pass the total flow will saturate starting at the center, which is equivalent to a gap that is formed gradually. The saturation can be determined by choosing the thickness of the closing piece CM, CM 'as a function of the radius. Similarly, a throttling in the core C, or in the return of external flux can be used to create by saturation a progressive air gap effect.

The invention therefore embraces all possible variants of embodiment within the scope of the subject of the claims below.

Claims (9)

1. Combination (1) in an electric starter circuit of a motor vehicle of a starter (DCM, EC) and of a battery voltage step-up device (LPF), said starter (DCM, EC) comprising an electric motor (DCM) and an electromagnetic contactor (EC), said battery voltage step-up device (LPF) being intended to prevent a drop in the battery voltage (Vbat) following a current spike produced by the switching on in a power circuit of said starter (DCM, EC), characterized in that said battery voltage step-up device (LPF) consists of a filtering device of inductive type (LPF) which is mounted in series with said electric motor (DCM) in said power circuit, said filtering device comprising a magnetic circuit (YO, C, CM, CM') which is composed of a field frame (YO, C) made of magnetic material comprising a cylindrical yoke (YO), two closure pieces (CM, CM') and an axial core (C) around which are arranged a primary winding circuit (W1) intended to be inserted in series in said power circuit and a secondary winding circuit (W2) intended to be inserted in series in said power circuit and a short-circuited secondary winding circuit (W2), and in that said axial core (C) has at least one air gap (AG; AG1, AG1').
2. Combination according to Claim 1, characterized in that said at least one air gap is a median air gap (AG).
3. Combination according to Claim 1, characterized in that said at least one air gap comprises extremal air gaps (AG1, AG1') between said closure pieces (CM, CM').
4. Combination according to Claim 1, characterized in that said closure pieces (CM, CM') each have an annular air gap (AG2, AG2'; AG3, AG3').
5. Combination according to Claim 4, characterized in that said annular air gap (AG2, AG2'; AG3, AG3') is aligned axially with said primary winding circuit (W1) or with said secondary winding circuit (W2).
6. Combination according to any one of the preceding Claims 1 to 5, characterized in that said secondary winding circuit (W2) is of an electrically conductive tube.
7. Combination according to Claim 6, characterized in that said tube is made of copper or of aluminium and exhibits a predetermined length-to-radius ratio, as well as a predetermined thickness.
8. Combination according to any one of Claims 1 to 7, characterized in that said filtering device (LPF) is inserted in said starter power circuit (DCM, EC) between a positive terminal (B+) of a battery of said vehicle and a power contact (CP) of said electromagnetic contactor (EC).
9. Combination according to any one of Claims 1 to 7, characterized in that said filtering device (LPF) is inserted in said starter power circuit (DCM, EC) between a power contact (CP) of said electromagnetic contactor (EC) and said electric motor (DCM).

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