Method and system for managing the flow rate of a motor vehicle electric machine cooling system pump

Abstract

This method for managing the flow rate of a pump (1) intended to circulate a dielectric coolant inside a rotary electric machine (2) of a motor vehicle, comprising a stator and a rotor, comprises steps of: • - determining predefined parameters; • - comparing said predefined parameters against predefined threshold values; • - selecting a necessary flow rate value corresponding to the result of the comparison step; • - comparing with hysteresis; and • - managing flow rate via a flow rate set point (Flow rate D, 4).

Description

Description Title of the invention: Method and system for managing the flow rate of a pump in a cooling system of an electric machine in a motor vehicle technical field

[0001] The present invention relates to the control of a pump in a cooling system of an electrical machine cooled by a dielectric coolant. Previous techniques

[0002] In the cooling systems of electric traction machines by circulating oil on the active parts of these electric machines, in particular their windings, an oil flow sent by a pump makes it possible to remove the thermal losses of the machine so that it does not overheat.

[0003] Generally, the oil flow rate is adjusted based on the measured temperature of the machine being cooled. The flow rate varies linearly between a minimum and a maximum value, corresponding to the minimum and maximum operating temperatures of the machine being cooled, respectively. The minimum oil flow rate also provides lubrication.

[0004] However, for each thermodynamic or electrical system there is an optimal operating point that allows for the best performance.

[0005] For example, in internal combustion engines a thermostat is used to maintain a constant cooling temperature regardless of operating conditions.

[0006] In electrical machines, controlling the temperature of critical machine parts such as the rotor and stator, and controlling the cooling temperature, improves the efficiency of the electrical machine and, consequently, the efficiency of the entire system. These efficiency gains have a positive impact on energy consumption and increased battery life.

[0007] In view of the above, the invention aims to control the cooling temperature to ensure better performance of the electrical machine to be cooled in order to increase the autonomy of the batteries that power it and reduce energy consumption. Description of the invention

[0008] In view of the foregoing, the object of the invention is to propose a method of managing the flow of a pump in a cooling system of an oil-cooled electrical machine, making it possible to improve the efficiency of the electrical machine.

[0009] The invention relates to a method for managing the flow of a pump intended to circulate a dielectric coolant inside a rotating electrical machine of a motor vehicle comprising a stator and a rotor.

[0010] The process includes the following steps:

[0011] - determination of predefined parameters; - comparison of said predefined parameters with predefined threshold values; - selection of a required flow rate value corresponding to the result of the comparison step; - comparison with hysteresis; and - flow management, through a flow setpoint (Flow D).

[0012] For example, dielectric coolant is of the oil type.

[0013] Advantageously, the step of determining the predefined parameters includes a sub-step of measurement and a sub-step of calculation of said predefined parameters.

[0014] According to one characteristic, the predefined parameters include the temperature of the electrical machine through the temperatures of the coolant, stator and rotor.

[0015] According to another feature, the predefined parameters include estimated losses of the electrical machine.

[0016] For example, the predefined threshold values ​​used in the comparison steps include a temperature threshold value.

[0017] Advantageously, the predefined threshold values ​​used in the comparison steps include a loss threshold value and an associated time lag value.

[0018] Taking into account a loss threshold value and an associated time period value makes it possible to anticipate the cooling needs of the electrical machine.

[0019] For example, the required flow rate value selected in the selection step takes one of two possible values, namely a first minimum flow rate value and a second maximum flow rate value.

[0020] Advantageously, the comparison step with hysteresis is performed by imposing a predefined minimum gap between the values ​​compared in the comparison step to allow the change in the setpoint value.

[0021] Using a minimal gap in the comparison step with hysteresis helps to limit the frequency of setpoint changes and improve the durability of the system.

[0022] According to another aspect, the invention relates to a flow management system for a pump intended to circulate a dielectric coolant within a rotating electrical machine of a motor vehicle comprising a stator and a rotor.

[0023] The system includes means for determining predefined parameters, means for comparing said predefined parameters with predefined threshold values, means for selecting a necessary flow rate value corresponding to the result of the comparison step, means for comparison with hysteresis, and means for flow rate management, through a flow rate setpoint. Brief description of the drawings

[0024] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example, and made with reference to the accompanying drawings in which:

[0025] [Fig. 1] schematically illustrates a flow control system for a coolant circulation pump; and

[0026] [Fig.2] illustrates a flowchart of a process according to the invention implemented using the system of [Fig.1], Detailed description of at least one embodiment

[0027] Fig. 1 represents the general structure of a flow control system of a pump 1 of a cooling system (not shown) of a rotating electric machine 2 equipping an electric traction motor vehicle.

[0028] This management system is connected on one side between the electric machine 2 and an inverter of the power electronics of the electric machine associated with the traction battery of the vehicle and, on the other side, to the pump 1.

[0029] This system is designed to manage the flow of coolant supplied by the pump to the cooling system.

[0030] It includes a calculator 3 which delivers a control signal to the pump by determining a flow rate setpoint Flow rate D for pump 1.

[0031] Calculator 3 includes a calculation stage 1 for the maximum temperature of the electrical machine 2 and a calculation stage 11b for the losses of the electrical machine 2 which operate in parallel.

[0032] The flow rate setpoint Flow rate D is determined by the calculator 3 by taking into account several temperature parameters such as the temperatures of the oil, the stator and the rotor of the electric machine 2.

[0033] The electric machine 2 is equipped with a sensor 5 capable of measuring the temperature of the oil circulating inside the electric machine 2 and a probe 6 capable of measuring the temperature of the stator of the electric machine 2.

[0034] The software portion of the inverter 7 of the power electronics is equipped with a temperature estimator 8 for the rotor of the electric machine 2. The inverter 7 includes a phase current sensor 9 and a voltage sensor 10 for the voltage supplied by the battery (not shown).

[0035] The calculator 3 includes a first calculation stage l ia capable of determining the maximum temperature Tmax, of the electric machine 1, this maximum temperature value being the maximum of the temperature values ​​of the oil, the stator and the rotor of the electric machine 2.

[0036] The oil temperature is measured by a temperature sensor (not shown) installed in the oil tank, and the stator temperature is measured by a temperature probe (not shown) installed in the stator winding.

[0037] Calculator 3 also includes a comparator 12 capable of comparing the maximum temperature Tmax with a predetermined temperature threshold value Tx.

[0038] When the maximum temperature Tmax is less than the temperature threshold value Tx, calculator 3 estimates that there is no need to increase the flow rate beyond a minimum flow rate Dmin.

[0039] When the maximum temperature Tmax is greater than the temperature threshold value Tx, the calculator 3 considers that a maximum flow rate 13 is necessary to cool the electrical machine 2. The maximum flow rate is noted Dmax.

[0040] In an oil-cooled electric machine, there are three sources of losses: Joule heating losses, mechanical losses, and losses in the ferromagnetic parts of the machine, namely the stator and rotor yokes and, where applicable, the rotor's permanent magnets. Joule heating losses and mechanical losses depend, respectively, on the winding temperature and the oil temperature in the case of oil injection on a rotor. The threshold temperature Tx corresponds to the temperature that minimizes Joule heating losses and mechanical losses.

[0041] Calculator 3 also includes a second stage 11b for calculating the losses of the electrical machine which uses a model for calculating efficiency based on phase current, winding resistance and stator temperature and uses a real-time estimator 13.

[0042] The electrical machine loss estimator 13 is used by the calculator 3 to determine if the load of the electrical machine 2 is very large, with the possibility of anticipating accordingly the cooling of the electrical machine 2, before its maximum temperature Tmax exceeds the temperature threshold value Tx.

[0043] Thus, comparator 12 compares the estimated losses of the machine with a predefined loss threshold value Px and, if the losses of the thermal machine exceed the threshold value Px for a predefined time period t, the computer 3 estimates that a maximum flow rate Dmax is required to cool the electric machine 2. The duration of the predefined time period t varies according to the driving profile of each type of car, and is, for example, shorter for so-called driving profiles "Athletes" who seek to maximize performance in terms of speed or acceleration.

[0044] When the losses of the electrical machine do not exceed the loss threshold value Px during the predefined time period t and the maximum temperature Tmax of the electrical machine 1 is less than the temperature threshold value Tx, the calculator 3 estimates that there is no need to increase the flow rate beyond the minimum flow rate Dmin.

[0045] Conversely, if the losses of the electrical machine 2 exceed the loss threshold value Px during the predefined time period t or if the maximum temperature Tmax of the electrical machine 2 is greater than the temperature threshold value Tx, then the calculator 3 considers that a maximum flow rate Dmax is necessary to cool the electrical machine 2.

[0046] Calculator 3 is also equipped with a comparison stage with hysteresis 14 allowing the flow setpoint D of pump 1 to be fixed. The comparison stage with hysteresis 14 allows the speed of change between the minimum flow Dmin and the maximum flow Dmax to be limited, by reducing the frequency of flow changes and thus ensuring better durability of the system.

[0047] We will now describe, with reference to [Fig.2], a method 20 for managing the flow rate of a pump 1 intended to cool an electrical machine as described previously.

[0048] The process 20 includes a preliminary step 21 in which the flow rate value is equal to the minimum flow rate value Dmin. The value Dmin is the minimum oil flow rate value required to ensure the proper operation of the electrical machine 2 by providing lubrication.

[0049] In the following step 22, the calculator 3 determines predefined parameters such as the temperature of the electrical machine 2 through the temperatures of the oil, stator and rotor and / or the estimated losses of the electrical machine 2. The parameter determination step 22 includes a measurement substep 22a and a calculation substep 22b of said predefined parameters.

[0050] The process 20 continues with a step 23 of comparison to predetermined threshold values ​​of the parameters determined in step 22. The predetermined threshold values ​​include a temperature threshold value Tx and / or a loss threshold value Px and an associated time period value t.

[0051] The process 20 continues with a step 24 of selecting a required flow rate value, from two possible values, namely a first minimum flow rate value Dmin and a second maximum flow rate value Dmax.

[0052] The process 20 further includes a comparison step with hysteresis 25. The comparison step with hysteresis 25 consists of decreasing the frequency of Setpoint changes are implemented by imposing a predefined minimum difference between the values ​​compared in step 23, which allows the setpoint change. Generally, the minimum difference used in the comparison step with hysteresis depends on the maximum performance of the electrical machine, namely the maximum torque and maximum power. As a non-limiting example, the minimum difference used in the comparison step with hysteresis is approximately 10°C for temperature and approximately 3 kW for losses.

[0053] The process 20 finally includes a step 26 of pump flow management 1, through a flow setpoint flow D.

Claims

Demands

1. A method for managing the flow rate of a pump (1) for circulating a dielectric coolant within a rotating electrical machine (2) of a motor vehicle comprising a stator and a rotor, characterized in that it comprises the steps of: - determination of predefined parameters; - comparison of said predefined parameters with predefined threshold values; - selection of a required flow rate value corresponding to the result of the comparison step; - comparison with hysteresis; and - flow management, through a flow setpoint (Flow D).

2. A method according to claim 1, wherein the dielectric coolant is of the oil type.

3. A method according to any one of claims 1 or 2, wherein the step of determining the predefined parameters includes a substep of measuring and a substep of calculating said predefined parameters.

4. A method according to any one of claims 1 to 3, wherein the predefined parameters include the temperature of the electric machine (2) through the temperatures of the coolant, stator and rotor.

5. A method according to any one of claims 1 to 4, wherein the predefined parameters include estimated losses of the electrical machine (2).

6. A method according to any one of claims 1 to 4, wherein the predefined threshold values ​​used in the comparison steps include a temperature threshold value (Tx).

7. A method according to claim 5, wherein the predefined threshold values ​​used in the comparison steps include a loss threshold value (Px) and an associated time lag value (t).

8. A method according to any one of claims 1 to 7, wherein the required flow rate value selected at the selection step takes one of two possible values, namely a first minimum flow rate value (Dmin) and a second maximum flow rate value (Dmax).

9. A method according to any one of claims 1 to 8, wherein the comparison step with hysteresis is carried out by imposing a predefined minimum gap between the values ​​compared in the comparison step to allow the change in the setpoint value.

10. Flow control system of a pump (1) intended to circulate a dielectric coolant inside a rotating electrical machine (2) of a motor vehicle comprising a stator and a rotor, characterized in that it comprises: means for determining predefined parameters; means for comparing said predefined parameters with predefined threshold values; means for selecting a necessary flow value corresponding to the result of the comparison step; means for comparison with hysteresis; and means for flow control, through a flow setpoint (Flow D).

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