FR3062177B1 - METHOD FOR RESTARTING A THERMAL MOTOR USING AN ALTERNOMETER - Google Patents

Abstract

The invention relates primarily to a method for restarting a motor vehicle engine (11) with an alternator / starter (10) coupled to said engine (11) and comprising a control module (14), characterized in that , in case of failure of the starting of the heat engine (11), said method comprises: - a step of suspension of the torque generated by the alternator-starter (10) for a predetermined duration, and - a second step of activation of the alternator-starter (10) for generating again the starting torque of the heat engine (11) when the rotational speed of the heat engine (11) becomes greater than a predetermined threshold while the heat engine (11) is in a rebound phase.

Description

METHOD FOR RESTARTING A THERMAL ENGINE USING AN ALTERNO-STARTER

The present invention relates to a method of restarting a heat engine by means of an alternator-starter.

Considerations of energy saving and pollution reduction, especially in urban areas, lead motor vehicle manufacturers to equip their models with a system for starting and stopping the engine automatically according to the traffic conditions. , such as the system known as the Anglo-Saxon "Stop and Go".

Such a system is based on the use of a motor calculator able to control an alternator-starter in a start mode. In this mode, the control drives the stator field using power electronics as well as the rotor field of the machine using a chopper to create a starting torque.

Failure to start the engine, however, is likely to occur especially when the alternator-starter is not able to provide the usual starting torque, for example in the case where the vehicle battery is discharged, or when the engine thermal requires a start torque greater than the usual torque for its start, especially when the crankshaft of the engine is in an unfavorable position when the engine is stopped, or when a restart is requested while the engine is still in motion during a stop phase. The invention aims to effectively remedy this drawback by proposing a method of restarting a motor vehicle engine by an alternator-starter coupled to said engine and comprising a control module, said method comprising: a reception step, by the alternator-starter, a request for starting the heat engine, and - a first step of activating the alternator-starter to generate a starting torque of the engine, characterized in that, in case of failure of the starting of the thermal engine, said method comprises: - a step of suspension of the torque generated by the alternator-starter for a predetermined duration, and - a second step of activating the alternator-starter to generate the torque again starting of the heat engine when the rotational speed of the heat engine becomes greater than a predetermined threshold while the heat engine is in a phase of rebound.

By rebound phase is meant a phase in which the speed variation of the engine changes from negative to positive. The invention thus makes it possible, because of the control of the alternator-starter in the rebound phase of the engine, to optimize the chances of success of the second start of the engine using the kinetic energy of the crankshaft.

According to one implementation, the predetermined duration is calculated to allow a cooling of the control module, so that the temperature of the control module of the alternator-starter becomes lower than a maximum threshold of operating temperature.

According to one implementation, the predetermined duration is in particular between 100 ms and 500 ms.

According to one implementation, the predetermined duration may be adjusted according to the temperature of the control module.

According to one implementation, the torque suspension step is implemented following the activation of a thermal protection of the control module.

According to one implementation, the thermal protection is activated when a junction temperature of a switching element of the control module exceeds a threshold.

According to one embodiment, the junction temperature of the switching member is estimated, in particular from a temperature measured at the control module and a rotational speed measurement of the alternator-starter.

According to one embodiment, the junction temperature of the switching member is a measured temperature.

According to one implementation, the thermal protection is activated following the flow of a predetermined operating time of the inverter which depends on a temperature range of the control module.

According to one implementation, in case of failure of the second start of the engine, the method comprises a step of abandoning said method.

According to one implementation, the alternator-starter is able to communicate with an engine ECU according to a communication protocol of LIN or CAN type. The invention also relates to a control module comprising a memory storing software instructions for the implementation of the restart process of the heat engine as defined above. The invention will be better understood on reading the description which follows and on examining the figures which accompany it. These figures are given for illustrative but not limiting of the invention.

FIG. 1 is a functional schematic representation of the alternator-starter implementing the restarting method of the heat engine according to the present invention;

FIG. 2 is a timing diagram illustrating the control according to the invention of the alternator-starter during a failure of the first start followed by the success of the second start of the heat engine;

FIG. 3 is a timing diagram illustrating the control according to the invention of the alternator-starter during a failure of the first and second starts of the heat engine;

FIG. 4 is a graphical representation illustrating the duration of activation of the inverter as a function of the temperature of the control module.

Figure 1 schematically shows an alternator-starter 10 according to the invention. The alternator-starter 10 is intended to be installed in a vehicle having an on-board electrical network connected to a battery 12. The on-board network may be of 12V, 24V, or 48V type. The alternator-starter 10 is coupled to a heat engine 11 in a manner known per se by a belt system 1T or chain implanted accessory facade.

In addition, the alternator-starter 10 is able to communicate with a motor ECU 15 according to a communication protocol of LIN type ("Local Interconnect Network" in English or "Local Internet Network" in French) or CAN ("Control 1st Area" Network "in English which is a serial system bus). The alternator-starter 10 may operate in alternator mode also called generator mode, or in engine mode comprising a starter mode, known to those skilled in the art. The starter-alternator 10 comprises in particular an electrotechnical part 13 and a control module 14.

More precisely, the electrotechnical part 13 comprises an induced element 18 and an inductive element 19. In one example, the armature 18 is the stator, and the inductor 19 is a rotor comprising an excitation coil 20. The stator 18 comprises a number N of phases. In the example considered, the stator 18 comprises three phases U, V and W. As a variant, the number N of phases may be equal to 5 for a pentaphase machine, to 6 for a hexaphase or two-phase type machine or to 7 for a heptaphase machine.

The phases of the stator 18 may be coupled in a triangle or star. A combination of triangle and star coupling is also possible.

The control module 14 comprises an excitation circuit 141 incorporating a chopper for generating an excitation current which is injected into the excitation coil 20. The measurement of the excitation current can be carried out for example by means of FIG. a shunt type resistor.

The measurements of the angular position and the angular velocity of the rotor 19 may be performed by means of analog sensors with hall effect H1, H2, H3 and an associated magnetic target 25 which is integral in rotation with the rotor 19.

The control module 14 further comprises a control circuit 142, comprising for example a microcontroller, which controls an inverter 26 as a function of a control signal from the engine control unit 15 and received via a signal connector 24. The inverter 26 has arms each having two switching elements for selectively connecting a U, V, W corresponding phase of the stator 18 to the ground or to the supply voltage of the battery 12 according to their on state or blocked. The switching elements are preferably MOSFET power transistors.

A module 143 whose operation is detailed in more detail below provides the thermal protection of the alternator-starter 10.

The control module 14 comprises a memory storing software instructions for implementing the control strategies of the inverter 26 described below.

With reference to FIG. 2, the different steps of the starting method of the heat engine 11 by the alternator-starter 10 are described below. At the instant t1, a request for starting the heat engine 11 emitted by the engine control unit 15 is received by the alternator-starter 10. The signal MM_R emitted by the engine computer 15 thus changes from the state corresponding to the neutral state N to the state corresponding to a start mode R.

After a response time, the alternator-starter 10 is activated at time t2 so that an excitation current is injected into the excitation coil 20 in order to flow the rotor over the period T1. The status signal MM_Alt of the alternator-starter thus changes from the state corresponding to the neutral state of the machine to a state corresponding to a starting mode R. Then the alternator-starter 10 is controlled by moment t3 to generate a starting torque of the heat engine 11. At time t4, the thermal protection managed by the module 143 is activated following the exceeding of a threshold by the junction temperature of at least one switching element of the control module 14. The junction temperature of the switching member can be estimated, in particular from a temperature measured at the control module 14 and a rotation speed measurement of the alternator-starter 10 Alternatively, the junction temperature of the switching member may be a measured temperature.

Alternatively, the thermal protection is activated following the flow of a predetermined operating time of the inverter 26 which depends on a temperature range of the control module 14. As illustrated by FIG. define three operating times K1, K2, K3 each respectively corresponding to a temperature range P1, P2, P3 of the control module 14. The higher the temperature range, the longer the operating time K1, K2, K3 of the inverter 26 is short. Of course, the number of temperature ranges and the values of the operating times can be adapted according to the application.

Due to the failure of the start of the engine 11, the speed of the engine 11 (corresponding to the speed of rotation of the machine V_alt in Figure 2) did not exceed its threshold of autonomy at the time of the activation of the thermal protection, the control module 14 controls a suspension of the torque generated by the alternator-starter 10 for a predetermined duration T2. The corresponding signal S_c then goes to state 1 in order to inform the engine computer 15.

The predetermined duration T2 is calculated to allow a cooling of the control module 14, so that the temperature of this module becomes lower than a maximum threshold of operating temperature. This predetermined duration T2 is in particular between 100 ms and 500 ms. The predetermined duration T2 may be adjusted according to the temperature of the control module 14. This duration T2 is the minimum time to respect before resuming the supply of torque when the rebound phase of the engine 11 will be detected. At the end of the duration T2, the alternator-starter 10 is again activated at time t5 to generate the starting torque of the heat engine 11 when the rotation speed of the heat engine 11 (corresponding to V_alt) becomes greater than a predetermined threshold while the heat engine 11 is in a rebound phase, that is to say when the speed variation of the heat engine 11 goes from negative to positive.

At time t6, we then observe the successful start of the engine 11, which has reached its autonomy threshold.

It should be noted that during the torque suspension phase, the rotor 19 preferably remains fluxed to allow a new supply of torque at time t5 as soon as the rebound phase of the heat engine 11 is detected.

As is illustrated in FIG. 3, in the event of failure of the second start of the heat engine 11, that is to say if at time t6, the thermal protection is again activated before the heat engine 11 has reached its autonomy regime, the method comprises a step of abandoning the method.

The control module 14 then sends a signal A_c for abandoning torque for a duration T3 to the engine control unit 15 in order to inform it of the situation and the machine switches to neutral mode (see signals MM_R and MM_Alt).

Of course, the foregoing description has been given by way of example only and does not limit the scope of the invention which would not be overcome by replacing the different elements by any other equivalent.

In addition, the various features, variations, and / or embodiments of the present invention may be associated with each other in various combinations, to the extent that they are not incompatible or exclusive of each other.

Claims (12)

1. A method for restarting a motor vehicle engine (11) with an alternator / starter (10) coupled to said engine (11) and comprising a control module (14), said method comprising: a receiving step by the alternator-starter (10), a starting request of the heat engine (11), and - a first step of activating the alternator-starter (10) to generate a starting torque of the engine (11), characterized in that, in case of failure of the starting of the heat engine (11), said method comprises: - a step of suspension of the torque generated by the alternator-starter (10) for a predetermined duration (T2 ), and a second step of activating the alternator-starter (10) to generate again the starting torque of the heat engine (11) when the rotational speed of the heat engine (11) becomes greater than a predetermined threshold while the heat engine (11) is in a phase of rebound. 2. Method according to claim 1, characterized in that the predetermined duration (T2) is calculated to allow a cooling of the control module (14), so that a temperature of the control module (14) of the alternation starter (10) becomes less than a maximum operating temperature threshold. 3. Method according to claim 2, characterized in that the predetermined duration (T2) is in particular between 100 ms and 500 ms. 4. Method according to any one of claims 1 to 3, characterized in that the predetermined duration (T2) can be adjusted according to a temperature of the control module (14). 5. Method according to any one of claims 1 to 4, characterized in that the torque suspension step is implemented following activation of a thermal protection of the control module (14). 6. Method according to claim 5, characterized in that the thermal protection is activated when a junction temperature of a switching element of the control module (14) exceeds a threshold. 7. Method according to claim 6, characterized in that the junction temperature of the switching member is estimated, in particular from a temperature measured at the control module (14) and a speed measurement of rotation of the alternator-starter (10). 8. Method according to claim 6 or 7, characterized in that the junction temperature of the switching member is a measured temperature. 9. Method according to any one of claims 5 to 8, characterized in that the thermal protection is activated following the flow of a predetermined time (K1-K3) of operation of an inverter (26) which depends on a temperature range (P1-P3) of the control module. 10. Method according to any one of claims 1 to 9, characterized in that in case of failure of the second start of the engine (11), the method comprises a step of abandoning said method. 11. Method according to any one of claims 1 to 10, characterized in that the alternator-starter (10) is adapted to communicate with a motor computer (15) according to a LIN or CAN communication protocol. 12. Control module (14) comprising a memory storing software instructions for implementing the restart method of a heat engine (11) as defined in any one of the preceding claims.