Starter voltage step-up device and combination of starter and of the voltage step-up device

Abstract

A starter battery voltage step-up device (LPF) intended to prevent a drop in the battery voltage (Vbat) produced by a current surge in a power circuit of the starter when the starter is powered on. The device comprises a casing of magnetic material (C, YO, CM, CM), a primary winding circuit (W1) intended to be inserted in series in the power circuit, and a short-circuited secondary winding circuit (W2), in which the primary winding circuit (W1) and/or the secondary winding circuit (W2) comprises a winding formed by at least one flat conductor (3) wound on edge. The invention also relates to the corresponding combination (1) of a starter and a voltage step-up device.

Claims

1. A voltage step-up device (LPF) of a starter for a thermal engine of a motor vehicle, said voltage step-up device (LPF) configured to prevent a drop of a battery voltage (Vbat) produced by a current surge from intervening in a power circuit of said starter when said starter is switched on, said voltage step-up device (LPF) comprising: a casing made of magnetic material (C, YO, CM, CM), said casing comprising a cylindrical head (YO) having a central axis (X), and a primary winding circuit (W1) configured to be inserted in series in said power circuit, and a secondary, short-circuited winding circuit (W2), said primary winding circuit (W1) comprising a winding formed from at least one conductor (3) in the form of a field-wound flattened part, a larger side (L) of said flattened part oriented in a radial direction orthogonal to said central axis (X), and a smaller side (I) oriented in an axial direction parallel to said central axis (X), both said primary winding circuit (W1) and said secondary winding circuit (W2) arranged around said central axis (X) and disposed inside said cylindrical head (YO).

2. The voltage step-up device (LPF) according to claim 1, wherein the winding of said primary winding circuit (W1) comprises a single row of conductors in the radial direction.

3. The voltage step-up device (LPF) according to claim 1, wherein said primary winding circuit (W1) has a direct return (5), such that a current input (E) and output (S) of said primary winding circuit (W1) are positioned on the same side.

4. The voltage step-up device (LPF) according to claim 3, wherein a notch (8) is in an inner face of said cylindrical head ((YO)) of the casing receives said direct return (5) of said primary winding circuit (W1).

5. The voltage step-up device (LPF) according to claim 1, wherein said secondary winding circuit (W2) is juxtaposed axially relative to said primary winding circuit (W1).

6. The voltage step-up device (LPF) according to claim 1, wherein said secondary winding circuit (W2) is arranged around said primary winding circuit (W1).

7. The voltage step-up device (LPF) according to claim 1, wherein said secondary winding circuit (W2) is formed by at least one conductor in the form of a tube.

8. Device according to claim 1, wherein a polarization winding circuit (PW) is configured to be installed in a control circuit of said starter.

9. The voltage step-up device (LPF) according to claim 8, wherein said polarization winding circuit (PW) is wound in a direction which is the inverse of that of said primary winding circuit (W1).

10. The voltage step-up device (LPF) according to claim 8, wherein said polarization winding circuit (PW) is wound around said secondary winding circuit (W2).

11. The voltage step-up device (LPF) according to claim 8, wherein said polarization winding circuit (PW) is arranged at an end of the primary and secondary winding circuits (W1, W2).

12. A combination (1) of a starter for a thermal engine of a motor vehicle, comprising a direct current electric motor (DCM) and an electromagnetic contactor (EC), and a voltage step-up device (LPF), said voltage step-up device (LPF) configured to prevent a drop of a battery voltage (Vbat) produced by a current surge from intervening in a power circuit of said starter when said starter is switched on, said voltage step-up device (LPF) comprising: a casing made of magnetic material (C, YO, CM, CM), said casing comprising a cylindrical head (YO) having a central axis (X), and a primary winding circuit (W1) configured to be inserted in series in said power circuit, and a secondary, short-circuited winding circuit (W2), said primary winding circuit (W1) comprising a winding formed from at least one conductor (3) in the form of a field-wound flattened part, a larger side (L) of said flattened part oriented in a radial direction orthogonal to said central axis (X), and a smaller side (I) oriented in an axial direction parallel to said central axis (X), both said primary winding circuit (W1) and said secondary winding circuit (W2) arranged around said central axis (X) and disposed inside said cylindrical head (YO).

13. The combination according to claim 12, wherein the voltage step-up device (LPF) is fitted in series with said electric motor (DCM) in the power circuit.

14. The combination according to claim 12, wherein the voltage step-up device (LPF) is inserted in the power circuit between a power contact (CP) of the contactor (EC) and the electric motor (DCM).

15. The voltage step-up device (LPF) according to claim 2, wherein said primary winding circuit (W1) has a direct return (5), such that a current input (E) and output (S) of said primary winding circuit (W1) are positioned on the same side.

16. The voltage step-up device (LPF) according to claim 2, wherein said secondary winding circuit (W2) is juxtaposed axially relative to said primary winding circuit (W1).

17. The voltage step-up device (LPF) according to claim 3, wherein said secondary winding circuit (W2) is juxtaposed axially relative to said primary winding circuit (W1).

18. The voltage step-up device (LPF) according to claim 4, wherein said secondary winding circuit (W2) is juxtaposed axially relative to said primary winding circuit (W1).

19. The voltage step-up device (LPF) according to claim 2, wherein said secondary winding circuit (W2) is arranged around the said primary winding circuit (W1).

20. The voltage step-up device (LPF) according to claim 3, wherein said secondary winding circuit (W2) is arranged around the said primary winding circuit (W1).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be better understood by reading the following description and examining the figures which accompany it. These figures are provided purely by way of non-limiting illustration of the invention.

(2) FIG. 1, already described, is a schematic view in axial cross-section of a primary circuit winding arranged around the core of a filtering device according to the prior art;

(3) FIG. 2, already described, represents a view in perspective of the primary circuit winding in FIG. 1;

(4) FIG. 3 is a view in perspective showing a combination of a starter and a filtering device of an inductive type according to the invention;

(5) FIG. 4 is a schematic diagram of an electric circuit of a starter comprising the combination in FIG. 3;

(6) FIG. 5 is a view in axial cross-section of the filtering device according to the invention in a first embodiment;

(7) FIG. 6 represents a view in perspective of the primary winding circuit of the filtering device in FIGS. 5, 8a and 8b;

(8) FIG. 7 shows a view in transverse cross-section of the head of the filtering device according to the invention;

(9) FIGS. 8a and 8b show respectively a view in perspective and a view in axial cross-section of the filtering device according to the invention, in a second embodiment;

(10) FIG. 9 represents the schematic diagram of the electric circuit of a starter incorporating the filtering device in FIGS. 8a and 8b.

(11) Elements which are identical, similar or analogous retain the same reference from one figure to another.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

(12) FIG. 3 shows a combination 1 of a starter, comprising a direct current electric motor DCM and an electromagnetic contactor EC, and a voltage step-up device consisting of a filtering device LPF of an inductive type. In this embodiment, the filtering device LPF is secured mechanically on an outer housing of the starter, in the vicinity of the contactor EC.

(13) The electrical connections between the filtering device LPF, the contactor EC and the electric motor DCM are shown in FIG. 4. The filtering device LPF is fitted electrically in series between the power contact CP of the contactor EC and the motor DCM.

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

(15) The contactor EC is in this case a conventional starter contactor with a simple power contact CP, and comprises a solenoid formed by a pull-in coil and a hold-in coil. The closure of a starter contact CS of the vehicle controls the excitation of the pull-in and hold-in coils, and the activation of the starter according to sequencing which is well known to persons skilled in the art, and will not be described in detail here.

(16) The strong initial current surge previously referred to intervenes at closure of the power contact CP, when the motor DCM is supplied with full power. Closure of the power contact CP also gives rise to circulation in the filtering device LPF of a power current which supplies the motor DCM.

(17) As is clearly apparent from its wiring diagram, in this case the filtering device LPF is a device of an inductive type which is produced in the form of a transformer of the armoured type with magnetically coupled windings. It will be noted that, depending on the applications, a simple inductive resistor could have been used to form the low-pass filtering device to which the optimisation work relates. However, the embodiment with a transformer makes it possible to have more parameters in order to adjust the frequency response of the device LPF according to the application. Thus, it is possible to optimise this response by regulating the inductive resistors of the primary and secondary circuits W1, W2, and the inductance introduced by the coupling between these circuits.

(18) The primary winding circuit W1 is the one which 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 with an order of magnitude of 300 to 1000 A.

(19) The battery voltage step-up effect obtained is derived from the fact that when the motor DCM is switched on, the initial current surge is cut (attenuated by approximately half) because of the production of strong currents induced in the secondary short-circuited circuit W2, which, by means of their effects, oppose the sudden variation of magnetic flux which has generated them.

(20) As can be seen in FIG. 5, the filtering device LPF of an inductive type substantially comprises a casing C, YO, CM, CM made of magnetic material such as steel, and primary W1 and secondary W2 winding circuits preferably made of copper. The casing comprises a cylindrical head YO having a central axis X, two closure parts CM, CM and an axial core C around which the winding circuits W1, W2 are arranged.

(21) More specifically, as can be seen in FIGS. 5, 6 and 8b, the winding of the primary winding circuit W1 is formed from a rectangular conductor 3 having a larger side L and a smaller side I. The primary winding circuit W1 is formed in the form of a field-wound flattened part, i.e. with the larger side L of the flattened part oriented radially according to the radius of the head YO (i.e., in a radial direction orthogonal to the axial core C), and the smaller side I oriented axially according to the height (i.e., in an axial direction parallel to the axial core C). In this case, the winding of the primary winding circuit arranged around the core C comprises a single row of conductors 3 in the radial direction, which provides the assembly with a compact appearance.

(22) As is clearly apparent from FIGS. 6 and 8a, the primary winding circuit W1 has a non-wound direct return 5, such that the current input E and output S of the primary winding circuit W1 are positioned on the same side of the head YO. This return 5 extends substantially axially according to a direction opposite a direction of winding of the layer of the primary winding circuit W1 along the said winding.

(23) In other words, the winding of the primary winding circuit W1 is produced from a handy conductor 3, field-wound only outwardly in order to obtain a winding layer which thus comprises a single row of conductors in the radial direction, then, the conductor 3 is bent according to its larger side in order to provide the return 5, such as to make the current input E and the current output S emerge from the primary winding circuit W1 on the same side.

(24) The return 5 of the winding can be produced on the exterior of the head YO. However, preferably, a notch 8 with axial orientation which can be seen clearly in FIGS. 7 and 8a is provided in an inner face of the head YO in order to receive the return 5 of the conductor inside the casing. The notch 8 has a transverse cross-section with a form substantially complementary to that of the flattened part of the conductor. Thus, as can be seen in FIG. 7, the notch 8 has a substantially tangential dimensional L1 corresponding to the larger side L of the flattened part and a radial dimension L2 corresponding to the smaller side 1 of the flattened part. The axial length of the notch 8 corresponds to the length of the return 5.

(25) In addition, the secondary winding circuit W2 is short-circuited. As shown in FIG. 5, the secondary winding circuit W2 in this case comprises a plurality of turns forming a winding which is positioned around the primary winding circuit W1. As a variant, the secondary winding circuit W2 can be produced in the same manner as the primary winding circuit W1, i.e. from a conductor with a field-wound flattened form.

(26) Alternatively, the secondary winding circuit W2 can advantageously be constituted by a conductive tube (for example made of copper or aluminium) which is concentric to the primary winding circuit W1. This tube can be situated around the primary winding circuit or juxtaposed axially relative to the bottom-mounted primary winding circuit W1, as described in document PCT/FR2011/052638.

(27) A structure of this type can lead to production of a filtering device LPF which is simpler to create than the secondary winding circuit W2 with a plurality of turns. It will be noted that the maintenance of an identical ratio of length to radius, compared with a secondary winding circuit W2 with a plurality of turns, will require correct dimensioning of the thickness of the tube. The electrical functioning of the filtering device LPF will not be modified because of the ratio N2/N1 which characterises the transformer, provided that there is transition from a resistance R for N2 turns, to a resistance R/N2.sup.2 for one turn with the tube, N2 and N1 being respectively the numbers of turns of the winding circuits W2 and W1.

(28) In the embodiment in FIGS. 8a and 8b, the filtering device LPF additionally comprises a polarisation winding circuit PW wound in the direction which is the inverse of that of the primary winding circuit W1. The polarisation winding circuit PW is arranged around the secondary winding circuit W2.

(29) As shown in FIG. 9, the polarisation winding circuit PW is designed to be connected to the control circuit of the starter. More specifically, the polarisation winding circuit PW is connected between the negative terminal B of the battery and the starting contact CS of the vehicle.

(30) Wiring of this type permits establishment of current with a steady state in the polarisation winding circuit PW at the same time as the excitation of the pull-in coils and hold-in coils of the electromagnetic contactor EC, i.e. approximately 25 ms before the closure of the power circuit by the power contact CP.

(31) The pre-polarisation of the magnetic circuit YO, C before the transient establishment of the power circuit 1 makes it possible to benefit from greater variation of induction, which makes it possible to delay the saturation. The electric motor DCM can thus reach a higher speed of rotation, and therefore generates a higher counter-electromotive force at the moment of saturation, which contributes towards limiting the power current 1.

(32) This second embodiment makes it possible to produce a highly efficient optimised filtering device LPF.

(33) Alternatively, the polarisation winding circuit PW can be wound around the axial core C at an end of the primary and secondary windings W1, W2, as described for example in document PCT/FR2012/051610.

(34) It will be appreciated that persons skilled in the art will be able to modify the battery voltage step-up device previously described without departing from the context of the invention. Thus, as a variant, the primary winding circuit W1 and/or the secondary winding circuit W2 will be able to be produced from a plurality of handy conductors, wound on a plurality of layers.

(35) In other variant embodiments, the axial core C can have at least one air gap, as described in document PCT/FR2012/051568. An air gap of this type in the magnetic circuit C, YO, CM, CM makes it possible to obtain the saturation of this magnetic circuit later.