Method and device for controlling an alternator-starter of a motor vehicle, and corresponding alternator-starter

Abstract

The method according to the invention is implemented in an alternator-starter (1) comprising phase windings (u,v,w) connected to an inverter (3) linked to an onboard electrical network (2) powered by a battery for operation as a starter. The invention involves controlling the inverter in a chopped full-wave control mode when the rotational speed () of the alternator-starter is lower than at least a threshold speed and in a full-wave control mode when the rotational speed is higher than the threshold speed. According to a specific embodiment, the switching between the chopped full-wave control mode and the full-wave control mode takes place according to a hysteresis cycle using two predefined threshold speeds.

Claims

1. A method for controlling an alternator-starter (1) of a motor vehicle using an electronic control unit, said alternator-starter (1) comprising phase windings (u, v, w) connected to an inverter (3) which is connected to an on-board electrical network (2) supplied by a battery for operation as a starter, said electronic control unit comprising: means for acquisition of a speed of rotation () of said alternator-starter (1); means (13) for storage of at least one predetermined threshold speed (1, 2); means (8, 10) for comparison of a speed of rotation () with said at least one predetermined threshold speed (1, 2); and means for generation of first control signals (S1) which produce first chopped full-wave phase voltages (U1, V1, W1) or second control signals (S2) which produce second full-wave phase voltages (U2, V2, W2), according to states of said means (8, 10) for comparison, said method comprising the steps of: controlling said inverter (3) in a chopped full-wave control mode (9) when the speed of rotation () of said alternator-starter (1) is lower than at least a predetermined threshold speed (1, 2); and switching control of said inverter to a full-wave control mode (11) when the speed of rotation () of said alternator-starter (1) is higher than said at least one predetermined threshold speed (1, ).

2. Method for controlling an alternator-starter (1) of a motor vehicle according to claim 1, wherein the switching between the chopped full-wave control mode (9) and the full-wave control mode (11) takes place according to a hysteresis cycle which uses two predetermined threshold speeds (1, 2).

3. Method for controlling an alternator-starter (1) of a motor vehicle according to claim 2, wherein a duty cycle () of said chopped full-wave control (9) depends on said speed of rotation ().

4. Method for controlling an alternator-starter (1) of a motor vehicle according to claim 2, wherein a duty cycle () of said chopped full-wave control (9) depends on a supply voltage (B+) of said on-board electrical network (2).

5. Method for controlling an alternator-starter (1) of a motor vehicle according to claim 2, wherein a duty cycle () of said chopped full-wave control (9) depends on a temperature (T) of said phase windings (u, v, w).

6. Method for controlling an alternator-starter (1) of a motor vehicle according to claim 1, wherein a duty cycle () of said chopped full-wave control (9) depends on said speed of rotation ().

7. Method for controlling an alternator-starter (1) of a motor vehicle according to claim 1, wherein a duty cycle () of said chopped full-wave control (9) depends on a supply voltage (B+) of said on-board electrical network (2).

8. Method for controlling an alternator-starter (1) of a motor vehicle according to claim 1, wherein a duty cycle () of said chopped full-wave control (9) depends on a temperature (T) of said phase windings (u, v, w).

9. A controller for an alternator-starter (1) of a motor vehicle of the type comprising an electronic control unit (6) which controls an inverter (3) connected to an on-board electrical network (2) which is supplied by a battery, and is designed to be connected to phase windings (u, v, w) of said alternator-starter (1) for operation as a starter, wherein said electronic control unit (6) comprises: means for acquisition of a speed of rotation () of said alternator-starter (1); means (13) for storage of said at least one predetermined threshold speed (1, 2); means (8, 10) for comparison of said speed of rotation () at said at least one predetermined threshold speed (1, 2); means for generation of first control signals (S1) which produce first chopped full-wave phase voltages (U1, V1, W1) or second control signals (S2) which produce second full-wave phase voltages (U2, V2, W2), according to states of said means (8, 10) for comparison; wherein, when said alternator-starter phase windings (u, v, w) are connected to said inverter (3) for operation as a starter, said inverter (3) is controlled in a chopped full-wave control mode (9) when the speed of rotation () of said alternator-starter (1) is lower than at least a predetermined threshold speed (1, 2), and in a full-wave control mode (11) when the speed of rotation () of said alternator-starter (1) is higher than said at least one predetermined threshold speed (1, ).

10. A controller for controlling an alternator-starter (1) of a motor vehicle according to claim 9, wherein said electronic control unit (6) additionally comprises means for controlling duty cycles (, 1-) of said first phase voltages (U1, V1, W1) according to said speed of rotation ().

11. Alternator-starter (1) of a motor vehicle, comprising a controller according to claim 10.

12. A controller for controlling an alternator-starter (1) of a motor vehicle according to claim 9, wherein said electronic control unit (6) additionally comprises: means for measuring a supply voltage (B+) of said on-board electrical network (2); means for controlling duty cycles (, 1-) of said first phase voltages (U1, V1, W1), according to said supply voltage (B+).

13. Alternator-starter (1) of a motor vehicle, comprising a controller according to claim 12.

14. A controller for controlling an alternator-starter (1) of a motor vehicle according to claim 9, wherein said electronic control unit (6) additionally comprises: means for measuring or estimating a temperature (T) of said phase windings (u, v, w); means for controlling duty cycles (, 1-) of said first phase voltages (U1, V1, W1) according to said temperature (T).

15. Alternator-starter (1) of a motor vehicle, comprising a controller according to claim 14.

16. Alternator-starter (1) of a motor vehicle, wherein it comprises a controller according to claim 9.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a simplified wiring diagram of an alternator-starter of a motor vehicle, comprising a control device according to the invention.

(2) FIG. 2 is a diagram of states-transitions of the control method of an alternator-starter of a motor vehicle according to the invention.

(3) FIG. 3 shows an example of phase voltage timing diagrams produced by the control device of an alternator-starter of a motor vehicle according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

(4) An alternator-starter 1 is generally a polyphase rotary electrical machine which is supplied by the on-board electrical network 2 when it is operating as a starter, or which supplies electrical energy to this network 2 when it is operating as an alternator.

(5) A reversible DC/AC converter 3 which is connected to the stator 4 makes it possible to implement these two operating modes.

(6) As represented schematically in FIG. 1 (in the case of a three-phase machine by simplification), the reversible DC/AC converter 3 comprises semiconductor switching elements 5, mostly MOSFET technology power transistors organised in the form of a bridge.

(7) These switching elements 5 are controlled by an electronic control unit 6, such that the converter 3 constitutes a synchronous rectifier for operation as an alternator of the alternator-starter, and constitutes a polyphase generator, or inverter, which creates a rotary field in the stator 4 for operation as a starter.

(8) According to the method of the invention, the inverter 3 is controlled either in chopped full-wave control mode, or in full wave control mode according to the range of the speed of rotation of the alternator-starter 1.

(9) As shown in FIG. 2, in this particular embodiment, the switching between the chopped full-wave control mode and the full-wave control mode is switching with hysteresis carried out by means of two predetermined threshold speeds 1 and 2, where 2 is greater than 1.

(10) Starting from the stoppage 7, where the speed of rotation is equal to zero, for as long as the increasing speed remains lower than the predetermined threshold speed 2, the inverter 3 is controlled in the chopped full-wave control mode 9, i.e., within the context of a three-phase machine, first phase voltages U1, V1, W1 applied to the phase windings u, v, w of the stator 4 are chopped, as shown clearly in FIG. 3.

(11) When the speed of rotation reaches the predetermined threshold speed 2, the inverter 3 control is switched to the full-wave control mode 11, i.e., again within the context of a three-phase machine, second phase voltages U2, V2, W2 applied to the phase windings u, v, w of the stator 4 have rectangular waveforms which are offset by 120, as also shown in FIG. 3.

(12) The switching from the full-wave control mode to the chopped full-wave control mode takes place at a decrease in the speed of rotation , when the latter becomes lower than the predetermined threshold speed 1.

(13) For a three-phase machine, the chopped full-wave control 9 leads to two cases A, B:

(14) Aone phase is commanded to the supply voltage B+ (in this case 12 V), and two phases are earthed: in this case the method according to the invention amounts to chopping the two earthed phases of the full-wave control mode with a duty cycle a, and the supply voltage phase B+ continues to be controlled at the supply voltage B+;

(15) Btwo phases are commanded to the supply voltage B+ (in this case 12 V), and one phase is earthed: in this case the method according to the invention amounts to chopping the two phases at B+ of the full-wave control with a complementary duty cycle 1-, whereas the earthed phase continues to be earthed.

(16) The duty cycle a affects directly the maximum current value reached at starting, and consequently depends on different parameters: supply voltage B+ speed of rotation of the machine 1 temperature T of the stator 4.

(17) For implementation of this method, the electronic control unit 6 of the control device 12 according to the invention thus comprises means for measurement of the supply voltage B+, and means for measurement of the temperature T of the stator 4, as well as means for acquisition of the speed of rotation , means 13 for storage of the first and second predetermined threshold speeds 1, 2, substantially equal to 400 rpm and 500 rpm in this particular embodiment, and means for comparison of this speed of rotation with these first and second predetermined threshold speeds 1, 2.

(18) This electronic control unit 6 comprises means for generation of first and second signals S1, S2 for control of the semiconductor switching elements 5 which produce at the output of the inverter 3 respectively first chopped full-wave phase voltages U1, V1, W1 or second full-wave phase voltages U2, V2, W2 according to output states of comparison of the means for comparison, according to the value of the speed of rotation relative to the predetermined threshold speeds 1, 2.

(19) The first control signals S1 preferably have a frequency of between 1 KHz and 5 KHz.

(20) The electronic control unit 6 also comprises means for controlling the duty cycles of the first phase voltages U1, V1, W1, set, according to the phases, to a common value a which depends on the supply voltage B+, the speed of rotation , and the temperature of the stator 4, or to its complementary value 1- by generating appropriate first control signals S1,

(21) The electronic control unit 6 is preferably produced in the form of a microcontroller, the microprogram of which comprises instructions which are representative of the method according to the invention.

(22) The control device 12 according to the invention, comprising the inverter 3 and an electronic control unit 6, is advantageously integrated on the rear bearing of the alternator-starter 1.

(23) Since the requirement for current at starting is reduced, the semiconductor switching elements 5 do not need to be oversized.

(24) This results in a reduction of the costs, which provides the alternator-starter according to the invention with a certain competitive advantage.

(25) As will be appreciated, the invention is not limited simply to the above-described preferred embodiments.

(26) The timing diagrams of the phase voltages U1, V1, W1; U2, V2, W2 are provided only by way of example for a three-phase machine; similar timing diagrams could illustrate a description relating to a machine with a larger number of phases, and in particular double three-phase.

(27) The numerical values of the first and second predetermined speeds 1, 2 are given for a type of alternator-starter already marketed by the applicant company, which the method and the device according to the invention are intended to improve.

(28) Other numerical values will be predetermined according to the electrical-mechanical characteristics of other types or models.

(29) The invention thus incorporates all the possible variant embodiments which would remain within the context defined by the following claims.