FR3062177A1 - 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

Holder (s): VALEO ELECTRIC EQUIPEMENTS MOTOR Simplified joint-stock company.

O Extension request (s):

® Agent (s): VALEO EQUIPEMENTS ELECTRIQUES MOTOR Simplified joint-stock company.

® PROCESS FOR RESTARTING A HEAT ENGINE BY MEANS OF AN ALTERNATOR-STARTER.

FR 3 062 177 - A1 (© The invention relates mainly to a method for restarting a heat engine (11) of a motor vehicle by an alternator-starter (10) coupled to said heat engine (11) and comprising a control module (14), characterized in that, in the event of failure of the engine to start (11), said method comprises:

a step of suspending the torque generated by the alternator-starter (10) for a predetermined duration, and

a second step of activating the alternator-starter (10) to generate again the starting torque of the heat engine (11) when the speed of rotation of the heat engine (11) becomes greater than a predetermined threshold while the heat engine (11) is in a rebound phase.

METHOD FOR RESTARTING A HEAT ENGINE BY MEANS OF AN ALTERNATOR

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

Considerations of energy saving and reduction of pollution, especially in urban areas, lead motor vehicle manufacturers to equip their models with an automatic engine start and stop system according to traffic conditions , such as the system known under the Anglo-Saxon term of Stop and Go.

Such a system is based on the use of an engine computer capable of controlling an alternator-starter in a starting mode. In this mode, the control controls the stator field using power electronics as well as the rotor field of the machine using a chopper to create starting torque.

Failure to start the engine, however, is likely to occur especially when the alternator-starter is not capable of providing the usual starting torque, for example in the case where the vehicle battery is discharged, or when the engine thermal requires a starting torque higher than the usual torque for its starting, in particular when the crankshaft of the thermal engine is in an unfavorable position when the thermal engine is stopped, or when a restart is requested while the thermal engine is still in motion during a stop phase.

The invention aims to effectively remedy this drawback by proposing a method for restarting a heat engine of a motor vehicle by an alternator-starter coupled to said heat engine and comprising a control module, said method comprising:

a step of reception, by the alternator-starter, of a request to start the thermal engine, and

a first step of activating the alternator-starter to generate a starting torque of the thermal engine, characterized in that, in the event of failure of the starting of the thermal engine, said method comprises:

a step of suspending the torque generated by the alternator-starter for a predetermined period, and

- A second step of activating the alternator-starter to generate again the starting torque of the heat engine when the speed of rotation of the heat engine becomes greater than a predetermined threshold while the heat engine is in a rebound phase.

By rebound phase is meant a phase in which the speed variation of the thermal engine goes from negative to positive.

The invention thus makes it possible, due to the control of the alternator-starter in the rebound phase of the heat engine, to optimize the chances of success of the second start of the heat engine by using the kinetic energy of the crankshaft.

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

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

According to an implementation, the predetermined duration may be adjusted as a function of 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 implementation, the junction temperature of the switching member is estimated, in particular from a temperature measured at the level of the control module and a measurement of the speed of rotation of the alternator-starter.

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

According to one implementation, the thermal protection is activated after the expiration of a predetermined inverter operating delay which depends on a temperature range of the control module.

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

According to one implementation, the alternator-starter is able to communicate with an engine computer following a communication protocol of the LIN or CAN type.

The invention also relates to a control module comprising a memory storing software instructions for implementing the method for restarting 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 only by way of illustration but in no way limit the invention.

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

FIG. 2 is a time diagram illustrating the control according to the invention of the alternator-starter when the first start fails, followed by the success of the second start of the heat engine;

FIG. 3 is a time diagram illustrating the control according to the invention of the alternator-starter when the first and second starts of the thermal engine fail;

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 shows schematically an alternator-starter 10 according to the invention. The alternator-starter 10 is intended to be installed in a vehicle comprising an on-board electrical network connected to a battery 12. The on-board network may be of the 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 installed on the accessory front.

In addition, the alternator-starter 10 is able to communicate with an engine computer 15 according to a communication protocol of the LIN type (Local Interconnect Network in English or Local Internet Network in French) or CAN (Control 1er Area Network in English which is a serial system bus).

The alternator-starter 10 can operate in alternator mode also called generator mode, or in engine mode comprising a starter mode, known to those skilled in the art.

The alternator-starter 10 notably comprises an electrotechnical part 13 and a control module 14.

More specifically, the electrotechnical part 13 comprises an armature element 18 and an inductor 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 has three phases U, V and W. As a variant, the number N of phases could be equal to 5 for a five-phase machine, to 6 for a machine of the hexaphased or double three-phase type or to 7 for a heptaphase machine.

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

The control module 14 comprises an excitation circuit 141 integrating a chopper to generate an excitation current which is injected into the excitation coil 20. The measurement of the excitation current can be carried out for example using '' a shunt type resistor.

The angular position and the angular speed of the rotor 19 can be measured by means of analog Hall effect sensors 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 coming from the engine computer 15 and received via a signal connector 24.

The inverter 26 has arms each comprising two switching elements making it possible to selectively connect a corresponding phase U, V, W of the stator 18 to the ground or to the supply voltage of the battery 12 as a function of their on or blocked state. . The switching elements are preferably MOSFET type power transistors.

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

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

A description is given below with reference to FIG. 2, the different stages of the process for starting the heat engine 11 by the alternator-starter 10.

At time t1, a request to start the heat engine 11 sent by the engine computer 15 is received by the alternator-starter 10. The signal MM_R sent by the engine computer 15 thus passes from the state corresponding to the state neutral N in the state corresponding to a starting 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 flux the rotor over the period T1. The state signal MM_Alt of the alternator-starter thus passes 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 at time 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 member switching can be estimated, in particular from a temperature measured at the control module 14 and a measurement of the rotation speed of the alternator-starter 10. As a variant, the junction temperature of the switching could be a measured temperature.

Alternatively, the thermal protection is activated following the expiration of a predetermined operating time delay for the inverter 26 which depends on a temperature range of the control module 14. As illustrated by FIG. 4, it will thus be possible define three operating times K1, K2, K3 each corresponding respectively 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 to start the heat engine 11, the speed of the heat engine 11 (corresponding to the speed of rotation of the machine V_alt in FIG. 2) has not exceeded its autonomy threshold at the time of activation of thermal protection, the control module 14 controls the suspension of the torque generated by the alternator-starter 10 for a predetermined period 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 cooling of the control module 14, so that the temperature of this module becomes below a maximum operating temperature threshold. This predetermined duration T2 is in particular between 100 ms and 500 ms. The predetermined duration T2 can be adjusted as a function of the temperature of the control module 14. This duration T2 is the minimum duration to be observed before resuming the supply of torque when the rebound phase of the heat engine 11 is 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 speed of rotation 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 changes from negative to positive.

We then observe, at time t6, the successful start of the heat engine 11 which has reached its autonomy threshold.

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

As 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 process includes a step of abandoning the process.

The control module 14 then emits a signal A_c of torque abandonment for a duration T3 intended for the engine computer 15 in order to inform it of the situation and the machine goes into neutral mode (cf. 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 from which one would not depart by replacing the various elements with any other equivalent.

Furthermore, the different features, variants, and / or embodiments of the present invention can be combined with one another in various combinations, insofar as they are not incompatible or mutually exclusive of one another.

Claims (12)

1. Method for restarting a heat engine (11) of a motor vehicle by an alternator-starter (10) coupled to said heat engine (11) and comprising a control module (14), said method comprising: a step of reception, by the alternator-starter (10), of a request to start the heat engine (11), and - a first step of activating the alternator-starter (10) to generate a starting torque of the thermal engine (11), characterized in that, in the event of failure of the starting of the thermal engine (11), said method includes: a step of suspending the torque generated by the alternator-starter (10) for a predetermined period (T2), and a second step of activating the alternator-starter (10) to generate again the starting torque of the heat engine (11) when the speed of rotation of the heat engine (11) becomes greater than a predetermined threshold while the heat engine (11) is in a rebound phase. 2. Method according to claim 1, characterized in that the predetermined duration (T2) is calculated to allow cooling of the control module (14), so that a temperature of the control module (14) of the alternator starter (10) becomes below 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 level of 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 expiration of a predetermined time delay (K1-K3) for the 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 the event of failure of the second start of the heat 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 able to communicate with an engine computer (15) according to a communication protocol of the LIN or CAN type. 12. Control module (14) comprising a memory storing software instructions for implementing the method for restarting a heat engine (11) as defined in any one of the preceding claims. 1/2