MONITORING THE CORRECT OPERATION OF A HEAT TRANSFER CIRCUIT TEMPERATURE SENSOR OF A TRACTION BATTERY

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The invention relates, in general, to the technical field of diagnosis or monitoring of the proper functioning of thermal sensors installed in heat transfer circuits.

[0002] The invention relates more specifically to a method for monitoring the thermal sensor of the heat transfer circuit of the traction battery of an electric or hybrid vehicle.

[0003] The invention further relates to a monitoring system for a temperature sensor of a heat transfer circuit.

[0004] The invention applies in particular to an electric or hybrid vehicle comprising a powertrain supervisor capable of implementing a method for monitoring the thermal sensor of the traction battery heat transfer circuit. PREVIOUS STATE OF THE ART

[0005] In the following, the description refers to an electric or hybrid vehicle chosen as a non-limiting example of an implementation of the invention. However, the invention can also be applied to any system comprising a heat transfer circuit including at least one thermal sensor, such as internal combustion engine vehicles, boats, or tractors.

[0006] Electric vehicles typically include a thermal management system for an electrical energy storage device, such as a 400V battery, also called a traction battery because the stored electrical energy powers a drivetrain to propel the vehicle. This type of system includes a circulation pump to circulate a heat transfer fluid within the cooling circuit, as well as a device to heat the fluid and a device to cool the fluid circulating within the circuit. The heated or cooled heat transfer fluid is used to regulate the temperature of the 400V battery.

[0007] Electric vehicles also include a thermal management system for a heater core to regulate the passenger compartment temperature. This type of system typically includes a pump to circulate a heat transfer fluid, as well as a device to heat the fluid and a device to cool it. The heated or cooled heat transfer fluid is then used to regulate the temperature of the heater core and, consequently, the passenger compartment temperature.

[0008] Electric vehicles also include a thermal management system for a rotating electrical machine, such as a traction motor. This type of system includes a pump for circulating a heat transfer fluid and a radiator to cool the circulating heat transfer fluid. The cooled heat transfer fluid is then used to regulate the temperature of the rotating electrical machine.

[0009] Currently, each of these heat transfer circuits includes at least one thermal sensor. Specifically, at least one thermal sensor on the heat transfer circuit loop of a traction battery, one thermal sensor on the heat transfer circuit loop of an electric motor, and one thermal sensor on the heat transfer circuit loop of the vehicle's air heater. These thermal sensors are monitored by measuring the deviations in the temperature values ​​measured by these three sensors, using the same principle as in conventional internal combustion engine vehicles.

[0010] With the optimization of the operation of heat transfer circuits in electric vehicles to reduce their energy consumption, the three heat transfer circuits mentioned above have many states where they operate completely independently, and for which the temperatures measured by the three thermal sensors are totally independent and often completely divergent. For example, when the traction battery is being cooled while the vehicle's passenger compartment is being heated.

[0011] To enable the diagnosis of thermal sensor operation despite potential discrepancies between measured temperatures, it is possible to increase the threshold values ​​for temperature differences to avoid false diagnoses of thermal sensor malfunctions. However, increasing these threshold values ​​also increases the likelihood of thermal sensor malfunctions, thus compromising the reliability of the thermal sensor diagnosis.

[0012] In addition, the state of the art is known from documents FR3095004A1 and FR2851299A1.

[0013] Therefore, there is a need for a reliable diagnostic strategy for the operation of the traction battery heat transfer circuit temperature sensor. Indeed, it is imperative to be able to guarantee the proper functioning of the traction battery heat transfer circuit temperature sensor by relying on the accuracy of the temperature readings it provides. The proper functioning of the traction battery heat transfer circuit ensures the protection of users and the integrity of the vehicle against the risk of fire. DESCRIPTION OF THE INVENTION

[0014] The invention aims to overcome all or part of the drawbacks of the prior art by proposing an innovative strategy for diagnosing the relevance of the information sent by the temperature sensor of the vehicle's traction battery heat transfer circuit. This monitoring strategy according to the invention is based on monitoring the temperature gradients returned by the temperature sensor of the traction battery heat transfer circuit over a defined period of time, to verify the plausibility of the temperature values ​​sent by the temperature sensor and ensure its proper functioning.

[0015] To this end, according to a first aspect of the invention, a method for monitoring a temperature sensor suitable for use in a heat transfer circuit is proposed, in which: A temperature measured by said temperature sensor is recorded at a determined measurement frequency, and temperature gradients obtained from the temperatures measured by the temperature sensor over a defined period of time are monitored by a controller to verify the plausibility of the temperature value measured by the temperature sensor. To obtain the temperature gradients, a stored temperature is obtained by storing one of the temperatures measured by said temperature sensor at a determined storage frequency lower than the measurement frequency. During a storage period, said measured temperature is compared to said stored temperature, and if the temperature difference between the measured temperature and the stored temperature exceeds a predefined temperature threshold, then a counter is incremented, and when the counter reaches a determined threshold value, a reconfiguration mode is activated.This reconfiguration mode includes: storing a fault code specific to the malfunction of said temperature sensor, and / or initiating a cooling strategy via the heat transfer circuit for a predetermined cooling period.

[0016] Thanks to such a combination of features, the monitoring process of a temperature sensor of a heat transfer circuit makes it possible to guarantee, independently of the operation of other temperature sensors, the proper functioning of the temperature sensor of the heat transfer circuit of the traction battery, which ensures the proper functioning of the heat transfer circuit of the traction battery and thus provides more reliable protection for users and for the integrity of the vehicle with regard to the risk of fire.

[0017] Preferably, the measured temperatures are sent to the controller which performs the comparison between the measured temperature and the temperature stored by said controller.

[0018] Advantageously, during the calibration phases of said monitoring process of said temperature sensor in its context of use, the memorization frequency is determined, the temperature threshold is defined for a determined memorization frequency, and the threshold value of the counter is defined.

[0019] Advantageously, during an initialization phase, the counter is at zero, and / or the stored temperature is initialized to a determined initial value until the end of a first storage period where a measured temperature is stored, and / or during an end-of-operation phase, the counter is reset to zero and the last stored temperature is not saved.

[0020] According to a second aspect of the invention, a method is proposed for monitoring a temperature sensor in a heat transfer circuit as described above, in which said heat transfer circuit regulates the temperature of a traction battery powering a powertrain of an electric or hybrid vehicle, and said controller is a powertrain supervisor.

[0021] According to a third aspect of the invention, a monitoring system for a temperature sensor in a heat transfer circuit is proposed, comprising a controller that receives temperature values ​​measured by the thermal sensor at a measurement frequency, wherein the thermal sensor is installed in a heat transfer circuit of a traction battery, said measured temperature values ​​are stored by said controller at a storage frequency, said controller compares the measured temperature to the stored temperature during a storage period, said controller increments a counter if the temperature difference between the measured temperature and the stored temperature is greater than a predefined temperature threshold, and said controller activates a reconfiguration mode if the counter reaches a determined threshold value.This reconfiguration mode includes storing a fault code specific to the malfunction of said temperature sensor and initiating a traction battery cooling strategy via the heat transfer circuit for a predetermined cooling period.

[0022] According to a fourth aspect of the invention, an electric or hybrid vehicle is proposed comprising a powertrain supervisor, a traction battery, and at least one heat transfer circuit capable of regulating the temperature of said traction battery, said at least one heat transfer circuit comprising at least one thermal sensor, in which said powertrain supervisor comprises a monitoring system as described above to implement a method of monitoring a temperature sensor as described above.

[0023] Other features and advantages of the invention are highlighted by the following description of non-limiting examples of implementation of the various aspects of the invention. BRIEF DESCRIPTION OF THE FIGURES

[0024] The description refers to the attached figures, which are also given as non-limiting examples of embodiments of the invention: [ Fig. 1 ] there figure 1 illustrates schematically a thermal management system for different components of a vehicle according to an example of implementation of the invention. DETAILED DESCRIPTION OF A METHOD OF IMPLEMENTATION

[0025] There Figure 1 [Fig 1] illustrates a thermal management system 1 of an electric vehicle comprising three heat transfer circuits: a cabin heat transfer circuit 7 which allows the temperature of the vehicle cabin (not shown) to be regulated by cooling or heating it according to the users' wishes, a powertrain heat transfer circuit 14 which allows an electric machine 17, an inverter 16 and a current converter 15 to be cooled; and a traction battery heat transfer circuit 2 which allows a traction battery 6, for example a 400V battery, to be cooled or heated.

[0026] The traction battery 2 heat transfer circuit includes the following components in series: a first pump 3 for the circulation of the heat transfer fluid in the traction battery heat transfer circuit 2, a first cooling device 4 for the heat transfer fluid circulating in the first circuit 2, this first cooling device 4 being able to be formed by a heat exchanger between the heat transfer fluid and a refrigerant from an air conditioning compressor (not shown) allowing to lower the temperature of the heat transfer fluid (the first cooling device 4 is also known by its English name chiller), a first temperature sensor 5 to measure the temperature of the heat transfer fluid circulating in the traction battery heat transfer circuit 2, and the traction battery 6.

[0027] The passenger compartment heat transfer circuit 7 allows the passenger compartment temperature to be regulated by means of an air heater 13; it includes the following components in series: a second pump 8 for circulating the heat transfer fluid in the passenger compartment heat transfer circuit 7, a second temperature sensor 9 to measure the temperature of the heat transfer fluid exiting the second pump 8, a second cooling device 10 for the heat transfer fluid circulating in the passenger compartment heat transfer circuit 7, this second cooling device 10 being able to be formed by a heat exchanger between a heat transfer fluid and a refrigerant from an air conditioning compressor (not shown) allowing to lower the temperature of the heat transfer fluid (the second cooling device 10 is also called a condenser), a heating device 11 for the heat transfer fluid, this heating device 11 being formed by a heating element, a third temperature sensor 12 to measure the temperature of the heat transfer fluid exiting the heating device 11,and the air heater 13, formed by a heat exchanger between the heat transfer fluid and the air in the vehicle's passenger compartment, to increase or decrease the passenger compartment temperature.

[0028] The heat transfer circuit of the powertrain unit 14 includes the following components in series: the converter (for example of type OBC DC-DC 15), the inverter 16, the rotating electrical machine 17, a fourth temperature sensor 18 for measuring the temperature of the heat transfer fluid circulating in the heat transfer circuit of the powertrain 14, a third pump 19 for circulating the heat transfer fluid in the heat transfer circuit of the powertrain 14, and a radiator 20 equipped with a motor-fan assembly 21 for cooling the heat transfer fluid circulating in the heat transfer circuit of the powertrain 14.

[0029] System 1 also includes an expansion tank 24 containing the heat transfer fluid and fluid connection means 22a, 22b, 22c arranged to connect the three heat transfer circuits 2, 7 and 14. To this end, the fluid connection means are formed by a first three-way solenoid valve 22a which, depending on whether it is open or closed, allows or prevents the circulation of the heat transfer fluid between the traction battery heat transfer circuit 2 and the powertrain heat transfer circuit 14. The fluid connection means further include a second two-way solenoid valve 22b which allows or prevents, depending on whether it is open or closed, the circulation of the heat transfer fluid between the powertrain heat transfer circuit 14 and the passenger compartment heat transfer circuit 7.The fluidic connection means 22 further include a connection circuit 22c linking a part of the passenger compartment heat transfer circuit 7 located downstream of the air heater 13 with a part of the traction battery heat transfer circuit 2 located upstream of the first pump 3.

[0030] The system 1 further includes a powertrain supervisor (not shown) which controls control means 23 capable of controlling the opening or closing of the first three-way solenoid valve 22a and the second two-way solenoid valve 22b; of activating the first pump 3, the second pump 8 and the third pump 19; of activating the heater 11 to heat the heat transfer fluid circulating in the traction battery and passenger compartment heat transfer circuits 2,7 when connected; and of deactivating the radiator fan assembly 21 20.

[0031] The powertrain supervisor controls one of the operating modes of system 1 engaged by the control means 23. To this end, the powertrain supervisor receives various information, including the temperature values ​​measured by the various temperature sensors mentioned above.

[0032] The heat transfer circuit of the traction battery 2 must allow the temperature of the traction battery 6 to be regulated in order to optimize its operation, avoid the risk of fire in case of overheating of the traction battery 6. Indeed, when the traction battery 6 is too cold, the performance of the traction battery 6 is reduced both during charging (charging times are increased), and during driving phases (the traction battery provides limited energy to the rotating electric machine 17 of the powertrain).

[0033] It is therefore necessary to regulate the temperature of the traction battery 6 by cooling the heat transfer fluid in the traction battery 2 heat transfer circuit with the first cooling device 4, or by heating the heat transfer fluid with a traction battery heating system. In system 1 illustrated by the figure 1 As described above, it is the heating device 11 for the heat transfer fluid in the second heat transfer circuit 7, which is used to heat the passenger compartment, that is also used to heat the traction battery. As indicated above, it is the powertrain supervisor that acts on the control means 23 to regulate the temperature of the heat transfer fluid in the traction battery heat transfer circuit 2.

[0034] To ensure the proper functioning of the first heat transfer circuit 2 and thus proper temperature regulation of the traction battery 6, the powertrain supervisor monitors the proper operation of the first temperature sensor 5 according to the procedure described below. The monitoring strategy for the first temperature sensor 5 described below will focus on the traction battery heat transfer circuit 2 and the first temperature sensor 5. For convenience, these will be referred to as the heat transfer circuit 2 and the temperature sensor 5, respectively.

[0035] The monitoring strategy for the temperature sensor 5 of the heat transfer circuit 2 according to the invention consists of storing the temperature measured by the temperature sensor 5 at a defined frequency, and then comparing the stored temperature with the temperature measured by the temperature sensor 5 between two storage periods. If the temperature difference between the measured temperature and the stored temperature exceeds a threshold temperature difference, then a counter is incremented. After a certain number of iterations, a reconfiguration strategy is triggered. The monitoring strategy for the temperature sensor 5 of the heat transfer circuit 2 is described in detail below.

[0036] The temperature value transmitted by the temperature sensor 5 of the traction battery 2 heat transfer circuit to the powertrain supervisor is stored at a frequency DT; this stored temperature is named TM. Then, the temperature sensor 5 continues to measure and send the temperature of the heat transfer fluid in the traction battery 2 heat transfer circuit to the powertrain supervisor approximately every 50 milliseconds (i.e., at a measurement frequency of approximately 20 Hz); the measured temperatures are called Tb.

[0037] The powertrain supervisor compares the absolute temperature difference between TM and Tb, which is called ET, with ET = abs TM − Tb .

[0038] Next, the powertrain supervisor compares ET with a temperature threshold called ST. If ET exceeds ST, then the powertrain supervisor increments a counter, called COMP, by one. When the COMP counter reaches a threshold, called SC, the supervisor triggers a reconfiguration mode, which is detailed below.

[0039] The DT frequency can be calibrated during the development phase of this function for monitoring the proper operation of the temperature sensor 5 of the heat transfer circuit 2. For example, the DT frequency can be calibrated to 10 seconds. Thus, every 10 seconds, the powertrain supervisor stores the temperature information received from the temperature sensor 5 of the traction battery 2 heat transfer circuit.

[0040] The temperature threshold ST is calibrable during the development phase of this monitoring function for the proper operation of the temperature sensor 5 of the heat transfer circuit 2. For example, the temperature threshold ST can be calibrated to 16°C. This threshold value is set according to the calibrated frequency DT. These values ​​are determined experimentally for a specific type of heat transfer circuit. Thus, the temperature measured by the temperature sensor 5 cannot change by more than 16°C in less than 10 seconds. Therefore, if the temperature sensor 5 of the heat transfer circuit 2 of the traction battery 6 indicates a temperature change of more than 16°C in less than 10 seconds, then the temperature sensor 5 of the heat transfer circuit 2 of the traction battery 6 is malfunctioning.

[0041] The SC counter threshold can also be calibrated during the development phase of this function for monitoring the proper operation of the temperature sensor 5 in the heat transfer circuit 2. The SC counter threshold value can be set to 3. Thus, if the COMP counter reaches 3, the powertrain supervisor triggers the reconfiguration mode. The reconfiguration mode is described below.

[0042] As described above, when the COMP meter reaches the SC threshold, the powertrain supervisor triggers a reconfiguration mode which proceeds as explained below.

[0043] Initially, the powertrain supervisor stores a fault code so that the after-sales service can be informed of this fault and can, during the overhaul, change the temperature sensor 5 of the heat transfer circuit 2 of the traction battery 5. In parallel, the supervisor triggers a cooling strategy for the traction battery 6 by starting the first water pump 3 to activate the circulation of the heat transfer fluid in the heat transfer circuit 2 of the traction battery 6.

[0044] At the same time, chiller 4 and the air conditioning compressor are activated. Refrigerant is then sent to chiller 4 to cool the heat transfer fluid.

[0045] This reconfiguration mode is launched for a time TR which is also calibrated during the development phase, for example TR can be calibrated to 3 minutes.

[0046] When the reconfiguration is initiated by the powertrain supervisor, the COMP counter resets to zero at the end of the TR time. Thus, after the end of the reconfiguration phase, the COMP counter must return to 3 for the powertrain supervisor to initiate another reconfiguration phase.

[0047] When the driver switches the ignition to ON, an initialization phase is initiated. During this reset phase, the COMP counter is at 0, and the stored temperature TM in the powertrain supervisor's memory is initialized to a value that can be calibrated during the fine-tuning phase; for example, this initial temperature could be 25°C. Only after the first storage period, corresponding to DT, is the actual temperature measured by the temperature sensor 5 of the traction battery's heat transfer circuit 2 stored in the TM variable by the supervisor.

[0048] At the end of the driving period, when the driver turns the vehicle's ignition to OFF, the COMP counter resets to zero and the stored temperature TM is not saved in the powertrain supervisor's read-only memory. Consequently, the last stored temperature for the traction battery's heat transfer circuit 2 is lost. There is no benefit to retaining this temperature, as the initial temperature will be stored in the TM variable the next time the ignition is turned ON.

[0049] Naturally, the invention described above is by way of example. It is understood that a person skilled in the art is able to carry out different embodiments of the invention without departing from the scope of the invention as defined by the claims.

[0050] For example, the temperature sensor monitoring strategy 5 of the heat transfer circuit 2 of the traction battery 2 described above can be implemented in other heat transfer circuits of an electric or hybrid vehicle and also for temperature sensors equipping heat transfer circuits in internal combustion vehicles or other means of transport of passengers or goods, whether land, air, river or sea.

Claims

1. A method for monitoring a temperature sensor (5) suitable for use in a heat transfer circuit (2), <b>characterized in that: - a temperature measured by said temperature sensor (5) is recorded at a determined measurement frequency; and - temperature gradients obtained from the temperatures measured by the temperature sensor (5) over a defined period of time are monitored by a controller to verify the plausibility of the temperature value measured by the temperature sensor (5), - to determine the temperature gradients, a stored temperature is obtained by storing one of the temperatures measured by said temperature sensor (5) at a determined storage frequency lower than the measurement frequency, and during a storage period, said measured temperature is compared with said stored temperature; and if the temperature difference between the measured temperature and the stored temperature exceeds a predefined temperature threshold, then a counter is incremented, and when the counter reaches a determined threshold value, a reconfiguration mode is triggered, this reconfiguration mode comprising: the storage of a fault code specific to the malfunction of said temperature sensor (5); and / or the initiation of a cooling strategy by the heat transfer circuit (2) for a determined cooling duration.

2. A method for monitoring a temperature sensor suitable for use in a heat transfer circuit according to claim 1, characterized in that the measured temperatures are sent to the controller, which compares the measured temperature with the temperature stored by said controller.

3. A method for monitoring a temperature sensor suitable for use in a heat transfer circuit according to one of claims 1 to 2, characterized in that during the calibration phases of said method for monitoring said temperature sensor (5) in its context of use: - the storage frequency is determined; - the temperature threshold is defined for a determined storage frequency; and - the threshold value of the counter is defined.

4. A method for monitoring a temperature sensor suitable for use in a heat transfer circuit according to one of claims 1 to 3, characterized in that: - during an initialization phase, the counter is at zero, and / or the stored temperature is initialized to a determined initialization value until the end of a first storage period in which a measured temperature is stored; and / or - during an end-of-operation phase, the counter is reset to zero and the last stored temperature is not saved.

5. A method for monitoring a temperature sensor in a heat transfer circuit (2) according to the method for monitoring a temperature sensor (5) as defined in one of the preceding claims, characterized in that : - said heat transfer circuit (2) regulates the temperature of a traction battery (6) supplying a powertrain of an electric or hybrid vehicle, and - said controller is a powertrain supervisor.

6. System for monitoring a temperature sensor (5) of a heat transfer circuit (2), comprising a controller receiving, at a measurement frequency, temperature values measured by the thermal sensor (5), characterized in that : - the thermal sensor (5) is installed in a heat transfer circuit (2) of a traction battery (6); - said measured temperature values are stored by said controller at a storage frequency; - said controller compares the measured temperature with the stored temperature during a storage period; - said controller increments a counter if the temperature difference between the measured temperature and the stored temperature is greater than a predefined temperature threshold; and - said controller initiates a reconfiguration mode if the counter reaches a determined threshold value. - the reconfiguration mode includes the storage of a fault code specific to the malfunction of said temperature sensor (5), and the initiation of a strategy for cooling the traction battery (6) by the heat transfer circuit (2) for a determined cooling duration.

7. Electric or hybrid vehicle comprising a powertrain supervisor, a traction battery (6), and at least one heat transfer circuit (2) capable of regulating the temperature of said traction battery (6), said at least one heat transfer circuit (2) comprising at least one thermal sensor (5), characterized in that said powertrain supervisor comprises a monitoring system as defined in claim 6 for implementing a method for monitoring a temperature sensor (5) according to one of claims 1 to 5.