FR3067682B1 - METHOD FOR CONTROLLING A POWER UNIT OF A HYBRID VEHICLE TO HEAT THE TRACTION BATTERY - Google Patents

Abstract

The subject of the invention is a method for controlling a power unit of a hybrid motor vehicle comprising a heat engine (2) receiving a torque setpoint coming from a supervisor (16) depending on the driver's request, causing by a clutch (4) a transmission (6), and comprising an electric traction machine (10) delivering a torque of electric machine transmitted to drive wheels (8), powered by a traction battery (12), this method being remarkable in that during a running of the vehicle with the heat engine (2) alone, in case of temperature of the traction battery lower than a temperature threshold, it controls a work of the electric machine (10) to deliver a torque of machine electric, it keeps the torque of the engine constant, and it applies a sliding clutch (4).

Description

The present invention relates to a method for controlling a powertrain of a hybrid motor vehicle, making it possible to increase the temperature. [0001] The present invention relates to a method for controlling a powertrain of a hybrid motor vehicle, making it possible to increase the temperature. a traction battery, and a hybrid vehicle comprising means implementing such a control method.

Hybrid vehicles comprise a first engine equipped with a heat engine, and a second engine comprising an electric machine connected to a power electronics comprising an inverter, receiving the energy of a traction battery.

[0003] Certain types of batteries, in particular batteries comprising lithium-ion cells, must be cooled in order to prevent overheating which may lead to accidents. For this purpose, a heat transfer fluid circuit is generally used, comprising a heat exchanger which dissipates calories.

In addition, these batteries have an optimum working temperature below which the discharge power is reduced, which reduces the performance of the vehicle and its autonomy.

To avoid work with a temperature too low, a type of known temperature control method of the traction battery of a hybrid vehicle, presented in particular by the document EP-B1-985570, performs a temperature measurement. this battery, then for a value less than a predetermined threshold, controls a charge or a discharge of the traction battery by making work an electrical machine connected to this battery, respectively generator or motor.

The current flowing through the traction battery causes the internal resistance of the battery, a joule effect that warms it.

However, in the case of a run using the heat engine alone, and a request for work of the electric machine engine to produce a heating of the traction battery, we obtain an additional torque brought by this electric machine. which poses management problems to deliver to the drive wheels the torque requested by the driver.

The present invention is intended to avoid these disadvantages of the prior art.

It proposes for this purpose a control method of a powertrain of a hybrid motor vehicle comprising a heat engine receiving a torque command from a supervisor dependent on the driver's request, driving a clutch transmission , and comprising an electric traction machine delivering a torque of electric machine transmitted to drive wheels, powered by a traction battery, this process being remarkable in that during a driving of the vehicle with the heat engine alone, in case of temperature of the traction battery lower than a temperature threshold, it controls a work of the electric machine to deliver a torque of electric machine, it maintains the torque of the heat engine constant, and it applies a sliding of the clutch.

An advantage of this control method is that one can add the torque delivered by the electric machine and transmitted to the drive wheels to take a necessary current in the traction battery to warm it by joule effect, while maintaining the torque of the engine without varying it which simplifies the control of this engine, thanks to the dissipation of a portion of this torque in the clutch which is easy to control, to keep on the drive wheels the torque requested by the driver.

Is obtained in a simple and effective way, with limited control to that of the clutch, a rise in temperature of the traction battery depending on the torque delivered by the electric machine.

The control method according to the invention may further comprise one or more of the following characteristics, which may be combined with each other.

Advantageously, the method calculates a torque setpoint delivered by the clutch, corresponding to the torque of the engine to which it subtracts the torque delivered by the electric machine which is reported to the clutch.

Advantageously, the temperature threshold of the traction battery is an adjustable threshold by a calibration.

Advantageously, the temperature threshold of the traction battery comprising lithium-ion cells is less than 25 ° C.

In particular, the method can control a torque delivered by the electric machine, which is less than 30Nm.

The invention also relates to a hybrid vehicle comprising a heat engine driving a transmission by a clutch, and an electric traction machine delivering a pair of electric machine, this vehicle being remarkable in that it comprises means implementing a control method comprising any one of the preceding features.

In particular, the electric machine can be directly connected to an input shaft of the transmission.

In particular, the vehicle may comprise a traction battery supplying the electric traction machine, comprising lithium-ion cells.

Advantageously, the clutch comprises wet discs.

The invention will be better understood, and other objects, features, details and advantages thereof will appear more clearly in the explanatory description which follows, with reference to the accompanying drawings given solely by way of illustrative example. an embodiment of the invention, and in which: - Figure 1 is a diagram of a hybrid vehicle implementing a control method according to the invention; FIG. 2 is a graph showing the power delivered by a lithium-ion traction battery, as a function of its state of charge and its temperature; FIG. 3 is a block diagram showing the operation of this control method; and FIGS. 4 and 5 show, as a function of time, different torques for a control method respectively according to the prior art and according to the invention.

Figure 1 shows a hybrid vehicle having a heat engine 2 driving by a clutch 4 controlled automatically, a transmission 6 having different speed ratios, connected to the front wheels 8 of this vehicle.

An electric traction machine 10 comprising a shaft connected to the input shaft of the transmission 18, disposed downstream of the clutch 4, is powered by a traction battery 12.

A powertrain calculator 14 connected to a vehicle monitoring supervisor 16, controls the operation of the engine 2 and the electric machine 10, to meet the demands of the driver while optimizing energy consumption and emissions of polluting gases, taking into account the level of energy stored in the traction battery 12.

In particular the hybrid vehicle can run only with the engine 2, the clutch 4 being closed to drive the transmission 6. The electric machine 10 does not deliver torque, the traction battery 12 is at rest. a stable temperature.

During driving in electric mode with only the electric machine 10, the clutch 4 is open and the engine 2 is stopped. The electric machine 10 delivers a motor torque to the driving wheels 8 by taking energy from the traction battery 12, or during braking the vehicle works as a generator by producing a charging current of this battery.

In hybrid mode running the heat engine 2 and the electric machine 10 deliver couples that complement each other, to meet the demand of the torque driver on the drive wheels 8. The electric mode and hybrid mode driving a passage of current in the traction battery 12 which can raise its temperature, unlike running with the engine 2 only that has no effect on this temperature.

For a lithium-ion traction battery 12, FIG. 2 shows, according to its charge state SOC expressed as a percentage, the power P that it can deliver, expressed in kilowatts, for different temperatures of this battery.

For a temperature of 40 ° C the power P is substantially constant, between 90 and 100kW for a state of charge less than 20%, and between 100 and 115kW with a constant slope for a state of charge greater than 20 %.

For a temperature of 25 ° C the power P remains very close, with a decrease of about 5kW for a state of charge greater than 20%, and a slightly larger decrease for a lower state of charge, with a minimum value of 65kW.

For a temperature of 0 ° C, the power P drops significantly below a state of charge at 35%, with a minimum value of 20 kW, and above a state of charge at 50%, with a maximum decrease of 20 kW compared to the power at the temperature of 40 ° C.

For a temperature of -10 ° C, the power P is about 10 to 85kW. Above a state of charge at 50% the decrease of the power P is approximately 30 kW compared to the power at the temperature of 40 ° C.

For a temperature of -25 ° C, the power P is about 10 to 55kW. Above a state of charge at 50% the decrease of the power P is about 60kW with respect to the power at the temperature of 40 ° C.

It is found in particular that below 0 ° C, the power P deliverable by the traction battery 12 drops significantly compared to a temperature of 40 ° C. In particular this power P is decreased by more than half for a temperature below -10 ° C. Vehicle performance, including acceleration and range, is greatly reduced.

FIG. 3 shows different operating steps of a control method of the powertrain when driving only with the heat engine 2, comprising the heating of the traction battery 12.

In a first step 20 the supervisor of the vehicle 16 takes into account the request of the driver, for a second step 22 establish a torque demand to the drive wheels.

In a third step 24 the powertrain calculator 14 receives the torque request to the drive wheels, and establishes a rotation speed setpoint and a torque setpoint from the supervisor Ce for the engine 2, to meet this request, which are transmitted to the heat engine 2. In a fourth step 26 the heat engine 2 implements the rotation speed setpoint and the supervisory torque setpoint Ce.

In parallel with these first four steps 20, 22, 24, 26, a fifth step 28 makes measurements of the temperature T ° of the traction battery 12 by sensors, or by an estimate comprising a tracking of the currents through. this battery.

A sixth step 30 makes a comparison of the temperature of the traction battery T ° with a minimum temperature threshold Ts adjustable by a calibration. In particular, it is possible to take a temperature threshold below 25 ° C., in particular a threshold of 20 ° C., giving a decrease in the delivrable power P which becomes substantial.

In the case of a temperature T ° of the traction trove 12 lower than the temperature threshold Ts, a seventh step 32 requires a solicitation of the electrical machine 10 to deliver a pair of electric machine Cmel, which may be in particular less than 30 Nm, for example 20 Nm. These torque values allow in a next step to moderately stress the clutch 4 which heats by sliding.

FIG. 4 shows, as a function of time t, for a control method according to the prior art, in the lower part the temperature of the traction battery T °, and in the upper part, different couples C comprising the supervisory torque set point Ce , the torque delivered by the heat engine Cmth and the torque delivered by the electric machine Cmel. These different torques are applied to the primary shaft 18 of the transmission 6.

FIG. 5 is an alternative for a control method according to the invention, in the upper part the supervisor torque setpoint Ce, the torque of the heat engine Cmth, the torque of the electric machine Cmel and the torque delivered by the clutch. Cemb.

For Figures 4 and 5, the supervisory torque setpoint Ce remains constant. At time t0 the sixth step 30 detects a temperature of the traction battery T ° lower than the minimum temperature threshold Ts, which triggers in the seventh step 32 the operation of the electrical machine 10 delivering a torque Cmel. An increase in the temperature of the traction battery T ° is obtained up to the instant t1 when it reaches a sufficient temperature threshold, which causes the operation of the electric machine 10 to stop, with a pair of electric machine Cmel going back to zero.

For a control method according to the prior art shown in FIG. 4, the torque of the heat engine Cmth is calculated by removing the electric machine torque Cmel from the supervisory torque set point Ce, so as to obtain a torque delivered on the driving wheels 8 which remains constant. It is necessary to apply a reduction in the torque of the heat engine Cmth between times t0 and t1, which can be difficult to manage, in particular to maintain a low pollutant emission level.

For a control method according to the invention shown in FIG. 5, the torque of the heat engine Cmth which remains constant is maintained at time t0. An eighth step 34 finds that the sum of the torque of the heat engine Cmth and the electric machine torque Cmel is greater than the supervisory torque setpoint Ce.

In this case it implements a ninth step 36 which applies to the automated clutch control a clutch torque setpoint Cemb corresponding to the torque of the heat engine Cmth which was subtracted the torque of electric machine Cmel, so as to to obtain a sliding of this clutch dissipating a difference in torque corresponding to this additional torque of electric machine.

Between the instants t0 and t1, a constant total torque delivered to the driving wheels corresponding to the addition of the torque of the electric machine Cmel and the torque delivered by the clutch Cemb, which is equal to the torque set point, is obtained. This. The supervisory torque setpoint Ce delivered to the heat engine 2 does not change, which simplifies the control of this engine.

In particular the clutch 4 may be a clutch comprising wet discs arranged in a cooling fluid, which facilitates the dissipation of thermal energy that it generates during its sliding.

Alternatively the electric machine 10 may apply a torque on a shaft of the transmission 6 rotating at a different speed of the input shaft 18, or at another location of the vehicle, with a speed ratio between them. In this case, the electric machine torque Cmel is understood to be that reported to the input shaft 18 and to the clutch 4 taking into account the gear ratio, in order to obtain a value that is consistent with the torque delivered by the Cemb clutch and the Cmth engine torque.

Claims (9)

1. A method for controlling a power unit of a hybrid motor vehicle comprising a heat engine (2) receiving a torque setpoint (Ce) from a supervisor (16) dependent on the driver's request, driving by a clutch (4) a transmission (6), and comprising an electric traction machine (10) delivering a torque of electric machine (Cmel) transmitted to drive wheels (8), powered by a traction battery (12), characterized in that during driving of the vehicle with the heat engine (2) alone, at a temperature of the traction battery (T °) below a temperature threshold (Ts), it controls a work of the electric machine (10) for delivering a pair of electric machine (Cmel), it maintains the torque of the heat engine (Cmth) constant, and it applies a sliding of the clutch (4). 2. Control method according to claim 1, characterized in that it calculates a torque setpoint delivered by the clutch (Cemb) corresponding to the torque of the heat engine (Cmth), to which it subtracts the torque delivered by the electric machine (Cmel) which is attached to the clutch (4). 3. Control method according to claim 1 or 2, characterized in that the temperature threshold of the traction battery (Ts) is a threshold adjustable by a calibration. 4. Control method according to any one of the preceding claims, characterized in that the temperature threshold of the traction battery (Ts) comprising lithium-ion cells, is less than 25 ° C. 5. Control method according to any one of the preceding claims, characterized in that it controls a torque delivered by the electric machine (Cmel), which is less than 30Nm. Hybrid vehicle comprising a heat engine (2) driving, by a clutch (4), a transmission (6), and an electric traction machine (10) delivering an electric machine torque (Cmel), characterized in that it comprises means implementing a control method according to any one of the preceding claims. Hybrid vehicle according to claim 6, characterized in that the electric machine (10) is directly connected to an input shaft (18) of the transmission (6). 8. Hybrid vehicle according to claim 6 or 7, characterized in that it comprises a traction battery (12) supplying the electric traction machine (10) comprising lithium-ion cells. 9. Hybrid vehicle according to any one of claims 6 to 8, characterized in that the clutch (4) comprises wet discs.