WO2012032239A1

WO2012032239A1 - Method and device for the thermal protection of an electric body of a motor vehicle

Info

Publication number: WO2012032239A1
Application number: PCT/FR2011/051854
Authority: WO
Inventors: Marco Marsilia; Samuel Cregut; Yann Chazal
Original assignee: Renault S.A.S.
Priority date: 2010-09-09
Filing date: 2011-08-02
Publication date: 2012-03-15
Also published as: FR2964612B1; FR2964612A1

Abstract

The invention relates to a device for the thermal protection of at least one electric body (2, 3, 4) of a motor vehicle provided with an electric motor (3), said device comprising means (5, 6) for measuring a threshold temperature of said electric body (2) and a rotational speed of the electric motor (3), and a torque limiting means (7) that can produce a torque threshold for the electric motor (3) and comprises a power determining means (9) for determining a maximum mechanical power according to the threshold temperature, said torque threshold being produced according to the rotational speed of the electric motor (3) and the maximum mechanical power determined.

Description

Method and device for thermal protection of an electric organ of a motor vehicle

The invention relates to the thermal protection of electrical components of a motor vehicle with a hybrid or all - electric type of motorization.

In particular, the invention relates to electrical devices dedicated to the propulsion and / or the production of electrical energy of the motor vehicle.

The electrical components of purely electric or hybrid motor vehicles generally comprise a battery for powering an electric motor via an electronic power unit.

In order not to destroy or damage these electrical components, it is necessary to avoid heating them above a limit temperature.

The temperature of these components can be controlled by limiting the current flowing from the battery to the electric motor (in traction mode, when the electric motor is propelling the vehicle) or conversely (in the energy recovery mode, when the electric motor recovers Energy) . But these thermal protection strategies have the disadvantage of generating jolts in the torque delivered or recovered by the electric motor, and are generally poorly felt by the driver of the vehicle.

One can, for example, quote the European patent application EP

1 084 895 which describes a method of controlling the torque of an electric vehicle electric motor from the engine temperature or the battery charge level.

We can also mention the European patent application EP

2 1 10 280 which discloses a control system for an electric vehicle of an electric power unit comprising a battery and an electronic power unit for powering an electric motor. This system limits the torque of the electric motor from a torque setpoint and a low consumption setpoint so as to reduce the losses of the drive unit. In addition, this system uses mappings stored in memory that give the value of power unit losses as a function of torque and rotational speed of the electric motor. But the torque setpoint is in this case limited to the operating points where the losses do not exceed a certain limit value.

One of the aims of the invention is to overcome the drawbacks mentioned above by providing an improved method and an improved device for the thermal protection of the electrical components of a motor vehicle when the temperature of an organ becomes too high.

Another object of the invention is to protect the electrical components while ensuring the safety and drivability of the vehicle.

According to one aspect, there is provided a method of thermal protection of at least one electric member of a motor vehicle equipped with an electric motor, in which a limit temperature of said electric member and a speed of rotation of the electric motor are measured and we limit the torque of the electric motor.

In this method, a maximum mechanical power is determined as a function of the limit temperature and the torque of the electric motor is limited as a function of the rotational speed of the electric motor and of said determined maximum mechanical power.

Thus, limiting the traction torque or energy recovery limit the current consumed or supplied by the electric motor.

There is also an improved strategy for the thermal protection of the organs because the temperature of at least one electric member and the rotational speed of the electric motor are taken into account.

According to one embodiment, a reduction power is developed which is non-zero when the value of the measurement of the limit temperature is greater than a temperature threshold, and otherwise zero, and the maximum mechanical power is determined as a function of a sum between a parameterizable variable representing nominal maximum mechanical power and said elaborated reduction power. Thus, a reduction power is developed as a function of the temperature of an electric member so as to reduce the torque limit of the electric motor when the temperature increases.

Thus effectively protects the electrical member from overheating.

Advantageously, said reduction power is equal to a parameterizable gain that multiplies a difference between said temperature threshold and the value of the measurement of the limit temperature.

With such a parameterizable gain, the torque limit of the electric motor can be modified in order to adapt the speed of the device to limit the torque according to the needs, in traction mode or in energy recovery mode.

According to another mode of implementation, a first maximum torque is calculated as a function of the ratio between the maximum mechanical power and the rotation speed of the electric motor, a second maximum torque is determined from a piecewise affine function of the maximum mechanical power, and limit the torque of the electric motor as a function of the minimum between the first and second maximum torque.

Thus, the torque limit of the motor is further reduced when the rotational speed of the motor is low, which makes it possible to reduce the jolts of the electric motor during transitions between a low rotational speed and a high rotational speed in order to avoid surprising the driver during transitions.

It is possible to limit the traction torque of the electric motor when it is operating in traction mode to propel the motor vehicle.

It is also possible to limit the energy recovery torque of the electric motor when it is operating in an energy recovery mode to supply electric energy to the motor vehicle.

According to another aspect, there is provided a device for thermal protection of at least one electric member of a motor vehicle equipped with an electric motor, comprising means for measuring a limit temperature of said electrical member and a rotational speed of the electric motor and a torque limiting means adapted to develop a torque limit for the electric motor.

The torque limiting means comprises power determining means for determining a maximum mechanical power as a function of the limit temperature, said torque limit being elaborated as a function of the rotational speed of the electric motor and said determined maximum mechanical power.

According to one embodiment, the torque limiting means is configured to calculate a first maximum torque as a function of the ratio between the maximum mechanical power and the rotational speed of the electric motor, to determine a second maximum torque from a function piecewise refining the maximum mechanical power, and to develop the torque limit as a function of the minimum between the first and second maximum torque.

According to another embodiment, the means for measuring the limit temperature comprise temperature sensors for respectively measuring the temperatures of the electrical components of the motor vehicle and a comparison means configured to determine the limit temperature which is equal to the maximum value of the temperatures of the electrical organs measured.

According to yet another embodiment, the torque limiting means comprises a limit temperature control loop which is configured to control the torque value of the electric motor from the torque limit and as a function of a difference between a temperature threshold and said limit temperature.

Thus, from the torque limit, it is possible to regulate the temperature of the organ to be protected around a temperature threshold.

Other objects, features and advantages of the invention will appear on reading the following description, given solely by way of nonlimiting example, and with reference to the appended drawings, in which: Figure 1 schematically illustrates an embodiment of a thermal protection device of a motor vehicle electrical member;

FIG. 2 is a graphical representation of the variations of the maximum mechanical power as a function of the temperature;

FIG. 3 is a graphical representation of the variations in the maximum torque calculated as a function of the speed of rotation of the motor;

Fig. 4 illustrates an exemplary piecewise affine function; and

FIG. 5 is a graphical representation of the variations of the torque limit of the electric motor as a function of the speed of rotation of the electric motor.

FIG. 1 diagrammatically shows a first embodiment of a device for thermal protection 1 of electrical components 2, 3, 4 of a motor vehicle. These electric devices generally comprise a battery 2, an electric motor 3 and a power electronics unit 4. The battery 2 supplies the electric motor 3 via the power electronic unit 4.

The device 1 comprises at least one temperature sensor 5, a speed sensor 6 and a torque limiting means 7.

The sensors 5, 6 make it possible respectively to measure the limit temperature T of an electrical component to be protected among the electric members 2, 3, 4 and the speed of rotation N of the electric motor 3.

By way of nonlimiting example, the limit temperature T of the battery 2 is measured, but it is also possible to measure the temperature of the electronic power unit 4 or the temperature of the electric motor 3 itself.

The torque limiting means 7 produces a Climite torque limit that it transmits, via a connection 8, to the motor 3. This Climite torque limit represents a maximum torque setpoint which limits the torque (traction or recovery) of the electric motor 3 in order to control the limit temperature T of the battery 2. This Climite limit is positive or zero and the principle of its elaboration will be described later.

The limiting means 7 comprises a power determining means 9 for determining a maximum mechanical power Pmax, a calculation means 10 for calculating a first maximum torque Cmax cal, a torque determining module 1 1 for determining a second maximum torque Cmax red and an output module 12 to develop the Climite torque limit, said output module 12 being coupled to the motor 3 by the connection 8.

The power determination means 9 receives the measurement of the limit temperature T of the battery 2 by a connection 13 from the temperature sensor 5. It further comprises an adder 14 which makes the difference ΔΤ between the measured value T of the temperature limit of the battery 2 and a threshold of temperature Tseuil, then transmits this difference ΔΤ by a connection 1 5 to a proportional regulator 16 G variable gain.

The adder 14 calculates the difference ΔΤ according to the following equation (1):

ΔΤ = Tseuil-T (1) with

T: the limit temperature of an electrical component to be protected in ° C, for example the limit temperature of the battery 2;

Tseuil: threshold of temperature beyond which one limits the torque of the electric motor in ° C.

The variable gain proportional controller G generates a reduction power Pred, according to equation (2), which it transmits via a connection 17 to a calculation module 1 8. Pred = Min (0; G-ΔΤ) (2) with

Pred: reduction power in Watt;

Min: function that calculates the minimum value between two variables;

G: Variable gain in W / ° C.

Pred reduction power can be negative or zero. In addition, the temperature threshold Tseuil and the variable gain G are two adjustable parameters.

The calculation module 1 8 determines the maximum mechanical power Pmax as a function of the reduction power Pred and a parameterizable variable Pmax nom representing a maximum nominal mechanical power.

The calculation module 1 8 calculates the maximum mechanical power Pmax according to the following equation (3):

Pmax = Max (0; Pmax name + Pred) (3) with

Pmax name: nominal maximum mechanical power, parameterizable, in Watt;

Max: function that calculates the maximum value between two variables.

The parameterizable variable Pmax nom represents the maximum mechanical power of the electric motor in traction mode (or in generator mode) and in a nominal situation, that is to say a situation without defects. This variable Pmax name is therefore specific to the type of electric motor used.

The power determining means 9 transmits the maximum mechanical power Pmax via a connection 19 towards the calculation means 10 and towards the torque determining module 11. The calculation means 10 comprises a divider 20 and a control operator 21. The control operator 21 receives the measurement of the rotational speed N of the electric motor 3 by a connection 22 from the speed sensor 6 and supplies a strictly positive value Nabs to the divider 20 via a connection 23 in order to prevent the division by zero. The calculation means 10 transmits, by a connection 24, the result of the calculation of the first maximum torque Cmax cal to the output module 12.

The calculation means 10 calculates the first maximum torque Cmax cal according to the following equations (4 and 5):

, max. _A.

C max cal = (4)

Born

Ne = Max (Nabs; Eps) (5) with

Cmax cal: first maximum torque, also noted maximum calculated torque, in N-m;

Ne: strictly positive parameter in radians ^"1 ;

Nabs: absolute value of the rotation speed N of the electric motor 3 in radians ^"1 ;

Eps: constant equal to 1 in radians ¹ (to avoid division by 0 when the rotation speed N of the electric motor 3 is zero).

The torque determination module 1 1 determines the second maximum torque Cmax red which it transmits, by a connection 25 to the output module 12.

The torque determination module 1 1 determines the second maximum torque Cmax red according to the following equation (6):

Cmax red = f (Pmax) (6) with f: affine function (or right) in pieces;

Cmax red: second maximum torque, also noted maximum torque, in N-m.

This affine function f makes it possible to associate a vector of n values of an input variable with a vector of n values of an output variable. Each element of the input vector corresponds to the element of the same position of the output vector. The intermediate points of the function f are obtained by interpolation.

FIG. 4 shows, by way of example, a curve Fa of a piecewise affine function g.

Let the input vector x1 = (a, b, c, d) with a <b <c <d and the corresponding output vector y1 = (g, h, h, i).

The equation function y = g (x) finite is defined by the vectors xl and yl.

For the affine function f used by the torque determination module 11, the function f may be defined, by way of non-limiting example, by the following vectors:

Pmax = (a1, a2, a3, a4, a5)

Cmax_red = (bl, b2, b2, b3, b3)

Where the values al, a2, a3, a4, a5 of Pmax are such that al <a2 <a3 <a4 <a5 and are expressed in Watt and those of Cmax red are such that bl <b2 <b3 and are expressed in N-m.

The output module 12 generates the Climite torque limit according to the following equation (7):

Climite = Min (Cmax_cal; Cmax_red) (7)

The second maximum torque Cmax Red makes it possible to add a limitation to the engine torque in addition to that established from the first maximum torque Cmax cal. The first maximum torque C max calculated allows to protect the battery 2 from heating due mainly to magnetic losses, also known as hysteresis losses.

The second maximum torque Cmax Red allows, for its part, to protect the battery 2 from heating due mainly to losses by Joule effect.

The use of the first and second maximum couples Cmax cal, Cmax Red effectively protects the electrical component from overheating.

FIG. 2 graphically shows variations of the maximum mechanical power Pmax as a function of the temperature T in the case where Pmax_nom = 45000 Watts and Tseuil = 60 ° C.

FIG. 2 shows two curves representing variations of the maximum mechanical power P max for two respective values G 1, G 2 of the variable gain G.

Curve A represents the variations of the maximum mechanical power Pmax for a first value G l of the variable gain with G l = 5000 W / ° C.

Curve B represents the variations of the maximum mechanical power Pmax for a second value G2 of the variable gain with G2 = 10000 W / ° C.

The variable gain G therefore makes it possible to directly adjust the speed of the limitation of the torque as a function of the heating of the battery 2.

FIG. 3 shows graphically variations of the first maximum torque Cmax cal as a function of the speed of rotation of the motor N.

The three curves C (T 1), D (T2), E (T3) are called iso-power curves because they are established for constant values of the maximum mechanical power Pmax.

Curves C (T 1), D (T2), E (T3) represent the variations of the first maximum torque Cmax cal for three different temperatures of the element to be protected T l, T2, T3, with T l <T2 <T3 . FIG. 5 graphically shows variations in the torque limit of the Climite electric motor as a function of the speed of rotation of the electric motor N.

The three curves C (T 1), D (T2), E (T 3) described in FIG. 3, two values H, I, for the second maximum torque Cmax red and a limiting zone ZC, represented on FIG. Figure 5 by the hatched area.

The values H and I represent the values of the second maximum torque Cmax red, respectively for the temperatures T 1 and T2.

For each iso-power curve C (T1), D (T2), E (T3), a second maximum torque Cmax red is determined. Consequently, for a given temperature T2 greater than the temperature threshold Tseuil, the torque of the electric motor is limited in the limiting zone ZC.

The Climite torque limit can be a simple instruction for the electric motor to prevent the torque of the latter from exceeding the Climite limit.

According to another embodiment, this Climite torque limit can serve as a basis for developing a torque command for controlling the torque value of the electric motor 3. In this variant, the thermal protection device 1 corresponds to a regulator of the limit temperature T of the organ to be protected. Thus, the torque limiting means 7 comprises a regulation loop BR for regulating the limiting temperature T around the temperature threshold Tseuil. This control loop BR is configured to develop the control of the torque of the electric motor 3 from the limit of torque Climite and the difference ΔΤ between the temperature threshold Tseuil and said limit temperature T. The variable gain G of the proportional regulator 16 thus makes it possible to adjust the gain of the thermal protection device 1 and thus to adjust the dynamics of the regulation.

According to yet another embodiment, it is possible to use a temperature sensor for each electrical component to be protected and develop a corresponding temperature limit T, for example the maximum value or the average of the measured temperatures.

Thus, it is possible to effectively protect a particular electrical component, or several electrical components, of a motor vehicle.

Thanks to the present invention, it is possible to control the temperature of at least one electrical element using parameterizable means which offer great freedom of adjustment to adapt the power consumption of the various electrical components according to the needs, and in particular to improve the driving comfort of the driver.

Claims

1. Method for thermal protection of a battery (2) of a motor vehicle equipped with an electric motor (3), in which a limit temperature (T) of said battery and a rotation speed (N) of the electric motor are measured (3) and the torque of the electric motor (3) is limited, characterized in that a maximum mechanical power is determined directly as a function of the limit temperature (T) and the torque of the electric motor (3) is limited as a function of the rotational speed (N) of the electric motor (3) and said determined maximum mechanical power.

2. Method according to claim 1, wherein a reduction power is developed which is non-zero when the value of the measurement of the limit temperature (T) is greater than a temperature threshold (Tseuil), and zero otherwise, and determines the maximum mechanical power as a function of a sum between a parameterizable variable (Pmax nom) representing a maximum nominal mechanical power and said elaborated reduction power.

3. Method according to claim 2, wherein said reduction power is equal to a parameterizable gain (G) multiplied by a difference between said temperature threshold (Tseuil) and the value of the measurement of the limit temperature (T).

4. Method according to any one of claims 1 to 3, wherein a first maximum torque is calculated as a function of the ratio between the maximum mechanical power and the rotational speed (N) of the electric motor (3), a second maximum torque from a piecewise refining function of the maximum mechanical power, and limiting the torque of the electric motor (3) as a function of the minimum between the first and second maximum couples.

5. Method according to any one of claims 1 to 4, wherein limiting the traction torque of the electric motor (3) when it operates in traction mode to propel the motor vehicle.

6. Method according to any one of claims 1 to 4, wherein the energy recovery torque of the electric motor (3) is limited when it operates in energy recovery mode to supply electrical energy. to the motor vehicle.

7. Device for thermal protection of a battery (2) of a motor vehicle equipped with an electric motor (3), comprising means (5, 6) for measuring a limit temperature of said battery (2) and a speed of rotation of the electric motor (3) and a torque limiting means (7) adapted to develop a torque limit for the electric motor (3), characterized in that the torque limiting means (7) comprises a means of power determination (9) for determining a maximum mechanical power directly as a function of the limit temperature, said torque limit being developed as a function of the rotational speed of the electric motor (3) and said determined maximum mechanical power.

8. Device according to claim 7, wherein the torque limiting means (7) is configured to calculate a first maximum torque as a function of the ratio between the maximum mechanical power and the rotational speed of the electric motor (3), to determine a second maximum torque from a piece-wise refinement function of the maximum mechanical power, and to develop the torque limit as a function of the minimum between the first and second maximum couples.

9. Device according to one of claims 7 or 8, wherein the torque limiting means (7) comprises a control loop (BR) of the limit temperature which is configured to control the torque value of the electric motor (3). ) from the torque limit and as a function of a difference between a temperature threshold and said limit temperature.