Method for estimating temperature of rotor magnets of a motor
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- AMPERE SAS
- Filing Date
- 2024-11-15
- Publication Date
- 2026-08-07
Smart Images
Figure CN122536067A_ABST
Abstract
Description
[0001] This invention relates to a method for estimating the temperature of a motor rotor magnet. It also relates to a method for controlling the estimated temperature of a motor rotor magnet. Furthermore, it relates to an apparatus for estimating the temperature of a motor rotor magnet. Further, it relates to a motor vehicle equipped with such an estimation apparatus. It also relates to a method for controlling the powertrain of such a motor vehicle. Finally, it relates to a computer program for implementing the aforementioned estimation or control method. And lastly, it relates to a recording medium on which such a program is recorded.
[0002] This invention relates to the field of rotor magnets for motors, and particularly to the field of permanent magnets for rotors of electric vehicle motors, especially motor vehicles or any other land or air vehicles.
[0003] The temperature of the rotor's permanent magnets must be monitored, as excessive temperature rise can irreversibly reduce the magnets' residual inductance, thereby decreasing the torque generated by the electric motor. To prevent excessive temperature rise in the magnets, heat transfer fluid flow is typically arranged close to the magnets.
[0004] However, a strategy exists to protect the powertrain, particularly in the event of a control failure in a power electronic converter, which involves creating a short circuit between the stator windings. This strategy then generates a high current in the stator windings, producing a large magnetic field directed towards the magnets, thus posing a risk of demagnetizing them. In fact, if the magnets are hot, even a low magnetic field can be sufficient to demagnetize the rotor magnets, ultimately degrading the performance of the electric motor.
[0005] In other words, when the temperature of the rotor magnets is high, a short circuit between the stator windings can cause irreversible damage to the performance of the electric motor.
[0006] Therefore, it is necessary to determine the temperature of the magnet as accurately as possible so that temperature can be taken into account in the powertrain management strategy.
[0007] Solutions exist that allow for the measurement or estimation of the temperature of the rotor magnet. However, these solutions have drawbacks.
[0008] The object of this invention is to provide an apparatus and method for estimating the temperature of a motor rotor magnet, which overcomes the aforementioned drawbacks and improves upon existing methods and apparatuses for estimating the temperature of a motor rotor magnet. In particular, this invention enables the implementation of a simple and reliable apparatus and method.
[0009] Therefore, the present invention relates to a method for estimating the temperature of a magnet in a rotor, the rotor including a channel through which a heat transfer fluid contacts or flows near the magnet, an inlet section of the channel, and an outlet section of the channel, wherein a temperature sensor is arranged in the channel, particularly near the outlet section of the channel, the method comprising:
[0010] • The step of partially or completely reducing the flow rate of the heat transfer fluid flowing in the channel for a given duration.
[0011] • The step of the temperature sensor measuring the temperature of a given heat transfer fluid remaining in the channel throughout the given duration, and
[0012] • The step of determining the estimated temperature of the magnet as the sum of the measured temperature of the given heat transfer fluid and the zero or non-zero constant temperature deviation.
[0013] In one embodiment, the estimation method includes the step of determining the given duration and the constant deviation, which includes implementing a thermal model of the temperature evolution of the heat transfer fluid resulting solely from the transfer of thermal power from the magnet to the heat transfer fluid.
[0014] In one embodiment, the thermal model is:
[0015] - A first model, which is constructed based on the following assumptions: the modeling temperature of the magnet is constant over a given duration and the modeling temperature of the magnet is uniform along the entire length of the magnet, the length of which is measured in the direction of the channel, or
[0016] - The second model is constructed based on the following assumptions: the modeling temperature of the magnet is uniform over its entire length for all times of the given duration, and the modeling temperature of the magnet varies with time.
[0017] Furthermore, the first model and the second model each include a first variant and a second variant, in which the flow rate of the heat transfer fluid is non-zero during the given duration, and in the second variant, the flow rate of the heat transfer fluid is zero during the given duration.
[0018] In one embodiment, the thermal model provides the time evolution of the modeling temperature of the magnet and the time evolution of the modeling temperature of the heat transfer fluid flowing in contact with the magnet.
[0019] Furthermore, the given duration is determined such that:
[0020] - During the given duration, the modeling temperature rise of the magnet is less than a first threshold, which is specifically equal to 6 degrees or even 4 degrees, and
[0021] - During the simulation period starting from that given duration, the difference between the modeling temperature of the magnet and the modeling temperature of the heat transfer fluid is substantially constant and less than a second threshold, for example, less than 3 degrees.
[0022] Furthermore, this constant deviation is equal to the difference between the modeling temperature of the magnet and the modeling temperature of the heat transfer fluid calculated over a simulation period starting from the given duration.
[0023] In one embodiment, the measurement step includes a sub-step of restoring the flow of the heat transfer fluid at an intermediate flow rate, which is less than or equal to the initial flow rate of the heat transfer fluid before the flow rate was reduced.
[0024] The present invention also relates to an apparatus for estimating the temperature of a rotor's magnet, wherein a cooling circuit for cooling the magnet comprises a set of conduits in contact with the magnet to carry out the flow of cooling fluid.
[0025] The device includes means for controlling the flow rate of a solenoid valve on a pipe arranged in the group of pipes, the pipe being located upstream of the magnet relative to the flow direction of the heat transfer fluid approaching or contacting the magnet, and
[0026] The device includes hardware and / or software elements for implementing the method according to the invention, and in particular hardware and / or software elements designed to implement the method according to the invention.
[0027] The present invention also relates to a method for controlling the powertrain of a motor vehicle, the method comprising:
[0028] • The steps of detecting the need to estimate the temperature of the magnet at a given time or at a given frequency based on the operating conditions of the motor vehicle, and then...
[0029] • Perform the steps of the method according to the invention for estimating the current temperature of a magnet at a given time or at a given frequency, and then
[0030] • If the current temperature of the magnet is greater than the temperature threshold, the following steps are taken: reduce the motor torque available from the power transmission system.
[0031] In one embodiment, these usage conditions include motor torque commanded by the driver of the motor vehicle at a given time.
[0032] The present invention also relates to an apparatus for controlling the powertrain of a motor vehicle, the apparatus comprising hardware and / or software elements for implementing the method according to the invention, particularly hardware and / or software elements designed to implement the method according to the invention.
[0033] The present invention relates to a motor vehicle equipped with a control device according to the invention or an estimation device according to the invention.
[0034] The accompanying drawings illustrate, by way of example, an embodiment of a device according to the invention for estimating the temperature of a motor rotor magnet.
[0035] [ Figure 1 [This is a first depiction of a motor vehicle equipped with an embodiment of a device according to the invention for estimating the temperature of the rotor magnet of a motor.]
[0036] [ Figure 2 [This is a first depiction of an embodiment of a device for estimating the temperature of a motor rotor magnet according to the present invention.]
[0037] [ Figure 3 [This is a second depiction of an embodiment of a device for estimating the temperature of a motor rotor magnet according to the present invention.]
[0038] [ Figure 4 [This is a third depiction of an embodiment of a device for estimating the temperature of a motor rotor magnet according to the present invention.]
[0039] [ Figure 5 [ ] is a flowchart of the estimation method according to the present invention.
[0040] [ Figure 6 [This is a first depiction of a first model of a magnet and a heat transfer fluid flowing near or in contact with the magnet.]
[0041] [ Figure 7 [This is a second depiction of a first model of a magnet and a heat transfer fluid flowing near or in contact with the magnet.]
[0042] [ Figure 8 [This is the third depiction of the first model of a magnet and the heat transfer fluid flowing near or in contact with the magnet.]
[0043] [ Figure 9 [ ] is a graph showing the time evolution of the temperature of the magnet and the heat transfer fluid flowing near or in contact with the magnet, which is modeled according to the first model.
[0044] [ Figure 10 [This is a detailed view of the time evolution of the temperature of the magnet and the heat transfer fluid flowing near or in contact with the magnet, which are modeled according to the first model.]
[0045] [ Figure 11 [This is a graph showing the time evolution of the distance traveled by the heat transfer fluid, modeled according to the first model.]
[0046] [ Figure 12[This is a graph showing the evolution of the temperature of the heat transfer fluid as the distance the fluid travels, modeled according to the first model.]
[0047] [ Figure 13 [ ] is a graph showing the time evolution of the temperature of the magnet and the heat transfer fluid flowing near or in contact with the magnet, which is modeled according to the second model.
[0048] [ Figure 14 [This is a graph showing the evolution of the temperature of the magnet and the heat transfer fluid as a function of the distance the heat transfer fluid travels, modeled according to the second model.]
[0049] [ Figure 15 This is a detailed view of the graph showing the evolution of the temperature of the magnet and the heat transfer fluid as a function of the distance the heat transfer fluid travels, modeled according to the second model.
[0050] [ Figure 16 [This is a graph showing the time evolution of the distance traveled by the heat transfer fluid, modeled according to the second model.]
[0051] [ Figure 17 [This is the first depiction of a second model of a magnet and a heat transfer fluid flowing near or in contact with the heat transfer fluid.]
[0052] [ Figure 18 [This is a second depiction of a second model of a magnet and a heat transfer fluid flowing near or in contact with the heat transfer fluid.]
[0053] [ Figure 19 [ ] is a graph showing the time evolution of the temperature of the magnet and the heat transfer fluid flowing near or in contact with the magnet, which is modeled according to a third model.
[0054] [ Figure 20 This is the first depiction of a third model of a magnet and a heat transfer fluid flowing near or in contact with it.
[0055] [ Figure 21 [This is a second depiction of a third model of a magnet and a heat transfer fluid flowing near or in contact with it.]
[0056] [ Figure 22 [ ] is a graph showing the time evolution of the temperature of each layer of the magnet and the heat transfer fluid flowing near or in contact with the magnet, which is modeled according to the fourth model.
[0057] [ Figure 23 This is the first depiction of a fourth model of a magnet and a heat transfer fluid flowing near or in contact with it.
[0058] [ Figure 24 [This is the second depiction of a fourth model of a magnet and a heat transfer fluid flowing near or in contact with it.]
[0059] [ Figure 25 [ ] is a graph showing the time evolution of the temperature of the magnet and the heat transfer fluid flowing near or in contact with the magnet, which is modeled according to the fourth model.
[0060] [ Figure 26 [ ] is a graph showing the time evolution of the temperature difference between the magnet and the heat transfer fluid flowing near or in contact with the magnet, these temperatures being modeled according to the fourth model.
[0061] [ Figure 27 [ ] is a control timing diagram of a solenoid valve that controls the flow rate of the heat transfer fluid.
[0062] [ Figure 28 [I] is a flowchart of the control method according to the present invention.
[0063] [ Figure 29 [] is a graph used to calculate the Nusselt number in the case of laminar fluid flow.
[0064] The following will refer to Figures 1 to 29 An example of a motor vehicle 100 is described, which is equipped with an embodiment of a device 10 for estimating the temperature of the rotor magnet of a motor.
[0065] Motor vehicle 100 can be any type of vehicle, such as a private passenger vehicle, a multi-purpose vehicle, or a public transport vehicle. Motor vehicle 100 can be an all-electric vehicle or a hybrid vehicle.
[0066] More generally, the devices described in this document can be fitted into any type of electric motor or hybrid motor, such as motors for aircraft, agricultural machinery, ships, etc.
[0067] The motor vehicle 100 includes a powertrain 10, which includes an electric motor 1. The electric motor 1 includes a rotor 11 and a stator 12. A magnet 111 is arranged in the rotor, and the permanent inductance of the magnet 111 is used to generate motor torque for moving the motor vehicle 100.
[0068] The rotor 11 described in this document is a magnet rotor. In an embodiment not described, the rotor may be a torsional magnet rotor, that is, a rotor comprising multiple segments offset at an angle to each other such that the magnets in the respective segments are misaligned. Alternatively, the rotor 11 may be a wound rotor.
[0069] The powertrain also includes a device 2 for controlling the powertrain according to the invention, which includes a device 21 for estimating the temperature of the magnet 111 according to the invention.
[0070] In an advantageous embodiment, the device 2 for controlling the power transmission system also includes its own dynamic model 22 for estimating the temperature of the rotor magnet.
[0071] An embodiment of dynamic model 22 will be briefly described below. The principle of dynamically estimating the temperature of the magnet in a machine, particularly an electric motor, is based on calculating the temperature of the magnet in real time by solving equations related to the heat exchange affecting the magnet.
[0072] Eddy current heat loss occurs in the magnet. These heat losses are evaluated, in particular, by solving Maxwell's electromagnetic equations using the finite element method. Heat loss calculations are performed for all operating points of the machine, each defined by the torque supplied by the machine and the machine's rotational speed. The heat loss values calculated for each operating point of the machine are recorded in memory, for example, in the form of an array, for use by the dynamic model 22. The heat loss values recorded in the array are fixed, that is, they do not change during machine operation.
[0073] In one embodiment, dynamic model 22 is constructed based on the assumption that the thermal power transferred by the magnet to the surrounding iron is negligible (the magnet is inserted into and bonded to a recess created in the iron). The heat loss values, recorded in an array, allow the magnet's temperature to be estimated in real time based on the machine's current operating point. This estimation can be performed at a relatively high frequency, for example, with a period of approximately ten seconds.
[0074] However, the accuracy of dynamic model 22 may be insufficient when applied to machines where performance is critical. In particular, dynamic model 22 cannot accurately determine the temperature of the magnet. In fact, the estimate provided by dynamic model 22 may deviate from the actual temperature of the magnet by a factor of ten or twenty degrees. However, for optimal operation of certain machines, particularly the powertrains of electric vehicles, it is necessary to accurately determine the temperature of the magnet during certain driving phases that cause the magnet temperature to rise. The estimation device 21 according to the invention can then be advantageously used to verify the temperature estimate provided by dynamic model 22. In fact, the accuracy of dynamic model 22 is sufficient as long as the magnet temperature provided by dynamic model 22 remains within a moderate temperature range. When the magnet temperature provided by dynamic model 22 is in a high-temperature range, the data from estimation device 21 advantageously allows for reliable measurement of the magnet temperature to optimize machine performance without the risk of damaging the magnet, and without applying a significant safety margin to the magnet.
[0075] Figures 2 to 4An embodiment of a cooling circuit 3 for cooling the magnets of the rotor is schematically shown. Circuit 3 includes a set of pipes 30 that implement a flow loop for a cooling fluid (e.g., a dielectric fluid) that flows in contact with the magnets 111 of the rotor 11 to cool them. A pump 31 directs the cooling fluid through the set of pipes 30. The fluid passes through an exchanger 32 to cool it. A solenoid valve 33 is integrated into circuit 3, allowing partial or complete reduction of the fluid flow rate in the circuit, particularly in the channels 34 located near or in contact with the magnets 111. The fluid flowing in the set of pipes 30 is distributed into the channels 34 via an input distributor 35 and an output distributor 36. The shape of the channels 34 is advantageously defined such that each magnet is close to or in contact with the heat transfer fluid flowing in the channels.
[0076] In the remainder of this document, the term “complete reduction” in flow rate corresponds to the cessation (i.e., complete cessation) of the flow of the heat transfer fluid.
[0077] The estimation device 21 includes means for controlling the flow rate of fluid flowing near or in contact with the magnet. The means for controlling the flow rate is implemented in the following manner...
[0078] - By directly controlling the flow rate of pump 31 and thus also modifying the flow rate of the fluid used for lubricating and cooling stator 12,
[0079] - Alternatively, by including a solenoid valve 33, which allows for modification of the flow rate of the fluid used to cool the magnets while maintaining the flow rate of the fluid used for other components to cool and / or lubricate the stator 12.
[0080] Solenoid valve 33 is arranged on a pipe in group 30, which is located upstream of magnet 111 relative to the flow direction of the heat transfer fluid near or in contact with the magnet.
[0081] Solenoid valve 33 is controlled by estimation device 21 to implement the method according to the invention for estimating the temperature of the rotor magnet. Solenoid valve 33 allows for a partial or complete reduction in the flow rate of the heat transfer fluid intended to cool the magnet. Advantageously, the solenoid valve allows for a partial or complete reduction in the flow rate of the heat transfer fluid in the rotor without altering the flow rate of the heat transfer fluid in other components of the vehicle. Therefore, solenoid valve 33 allows for frequent measurements of the magnet temperature to be performed without slowing or stopping the flow of heat transfer fluid that may be intended, for example, to lubricate bearings and / or cool the stator.
[0082] For at least one magnet of the rotor, and preferably for each magnet of the rotor, the cooling circuit described above allows heat transfer fluid to flow in contact with or near the magnet 111 between the inlet section 341 and the outlet section 342 of the channel 34 that houses the magnet. A temperature sensor 4 is arranged in the channel, particularly near the outlet section 342 of the channel 34.
[0083] In one embodiment, the temperature sensor 4 may be positioned directly after the junction of at least two channels to contact the heat transfer fluid from at least two channels.
[0084] The estimation device 21 according to the invention includes means for implementing the estimation method according to the invention, particularly a processing unit 210, which includes a microprocessor 211, a memory 212, and a communication interface 213. The microprocessor 211 mainly includes the following modules, which cooperate with each other:
[0085] - Module 2111, which is used to determine the partial or complete reduction of the flow rate of the heat transfer fluid flowing in the channel for a given duration.
[0086] - Module 2112, which is used to partially or completely reduce the flow rate of the heat transfer fluid flowing in the channel for a given duration, and is capable of cooperating with solenoid valve 33.
[0087] - Module 2113, which enables temperature sensor 4 to measure the temperature of the heat transfer fluid, and which can cooperate with temperature sensor 4, and
[0088] - Module 2114, which is used to determine the estimated temperature of the magnet.
[0089] The device 2 for controlling the powertrain advantageously includes means for determining the operating conditions of the motor vehicle 100, which may potentially generate the risk of overheating of the rotor magnets, making them susceptible to damage. These operating conditions particularly include the motor torque commanded by the driver of the motor vehicle.
[0090] For this purpose, control device 2 can use information from the data network onboard the motor vehicle.
[0091] The control device 2 includes means for implementing the control method according to the invention, particularly a processing unit 20, which includes a microprocessor 201, a memory 202, and a communication interface 203. The microprocessor 201 mainly includes the following modules, which cooperate with each other:
[0092] - Module 2011, this module is used to detect the need for estimating the magnet temperature.
[0093] - Module 2012, which is used to implement the estimation method according to the invention.
[0094] - Module 2013, which is used to reduce the motor torque available from the powertrain.
[0095] The motor vehicle 100, particularly the control device 2 and the estimation device 21, preferably includes all hardware and / or software elements configured to implement the methods defined in the subject matter of this invention or the methods described below.
[0096] The following text refers to [ Figure 5 The following describes an execution mode of the estimation method. The estimation method according to the present invention includes steps E1 to E4 executed sequentially.
[0097] The first step E1 includes determining a given duration D_reduc for which the flow rate of the heat transfer fluid flowing in the channel is partially or completely reduced, and a constant deviation EC between the estimated temperature T_estimated of the magnet and the measured temperature T_mes of the heat transfer fluid flowing near the magnet.
[0098] The given duration D_reduc is the duration during which the flow of the heat transfer fluid near the magnet will be completely or partially reduced in the reduction step E2.
[0099] Determining a given duration D_reduc and a constant deviation EC involves implementing thermal models M11, M12, M21, M22, and M23 that represent the temperature evolution of the heat transfer fluid resulting solely from the transfer of heat power from the magnet to the heat transfer fluid.
[0100] In an alternative or additional embodiment, a given duration D_reduc has been determined through a series of experiments before the powertrain control device is implemented, and the duration D_reduc has then been recorded, for example, in the memory of the powertrain control device. Advantageously, these experiments also make it possible to adjust models M11, M12, M21, M22, and M23.
[0101] Figures 6 to 8 The geometry of the magnet and the channels for the heat transfer fluid intended to cool the magnet is shown. The calculations described in the remainder of this document take into account the following dimensions:
[0102] The width of channel 111 is denoted as l_Fluid, and the length of the channel is denoted as L_Channel. In [ Figure 7 In the example shown, the width l_Fluid is 30 mm and the fluid height is 2 mm.
[0103] In the remainder of this document, it is assumed that the flow of the heat transfer fluid in the channel is laminar. Therefore, the Nusselt number is constant. Figure 29 A table is shown for calculating the Nusselt number based on the geometry of the cross-section through which the heat transfer fluid flows.
[0104] The Nusselt number is a dimensionless number used to characterize heat transfer between a fluid and a wall (called convective transfer). It represents the ratio between convective heat transfer and conductive heat transfer across the interface. The Nusselt number is equal to the dimensionless temperature gradient at the surface and provides a measure of the convective transfer of heat occurring at the surface.
[0105] By definition, the Nusselt number is: ,in:
[0106] h is the heat transfer coefficient calculated using the following formula: And expressed in the following units: Wm -2 .K -1 .
[0107] K is the thermal conductivity of the fluid, expressed in W / m. -1 .K -1 express.
[0108] λ is the electrical conductivity of the fluid, expressed in W / m. -1 .K -1 express.
[0109] D is the hydraulic diameter. , expressed in meters.
[0110] By definition, the hydraulic diameter is equal to the quotient of the surface area and the perimeter of the fluid flow section multiplied by 4. That is, for a rectangular section with dimensions a and b, the hydraulic diameter is:
[0111]
[0112] The following symbols will be used in the remainder of this document:
[0113] It is the volume density of the fluid, expressed in kg·m³. -3 express,
[0114] It is the specific heat capacity of the fluid, expressed in J·kg⁻¹. -1 .K -1 express.
[0115] It is the cross-section of the channel, in meters. 2 express.
[0116] Furthermore, the heat transfer coefficient between the magnet and the heat transfer fluid is mentioned in the remainder of this document. .
[0117] A thermal model is a mathematical model used to characterize the time evolution of the temperature of a magnet and the temperature of a heat transfer fluid located near or in contact with the magnet. Various embodiments of the thermal model are proposed based on different modeling assumptions.
[0118] In one embodiment, the thermal model is
[0119] - The first model is constructed based on the following assumptions: the temperature of the magnet is constant during a given duration D_reduc of the decrease in the flow rate of the heat transfer fluid, and the temperature of the magnet is uniform across its entire length, which is measured in the direction of the channel, or
[0120] - The second model is constructed based on the assumption that the temperature of the magnet is uniform along its entire length for all times during a given duration D_reduc of the decreasing flow rate of the heat transfer fluid, and that the temperature of the magnet varies with time.
[0121] The first model and the second model each include a first variant and a second variant, in which the flow rate of the heat transfer fluid is non-zero during a given duration D_reduc, and in the second variant, the flow rate of the heat transfer fluid is zero during a given duration D_reduc.
[0122] In other words,
[0123] The first model is based on the assumption that the magnet is a temperature source, and
[0124] The second model is based on the assumption that the magnet is a component in which heat power is dissipated, generated by eddy currents flowing within the magnet.
[0125] The first assumption concerns the level of reduction in the heat transfer fluid velocity, which can be a complete reduction or a partial reduction. Therefore, two series of models are defined:
[0126] - The first series of models M11 and M12 involve cases where the flow rate of the heat transfer fluid is partially reduced.
[0127] - The second series of M2 models M21, M22, and M23 involve the case where the flow rate of the heat transfer fluid is completely reduced.
[0128] Each of the thermal models M11, M12, M21, M22, and M23 provides
[0129] - The time evolution of the modeling temperature TMA of the magnet, Evol_TMA, and
[0130] - Time evolution of the temperature TMF of the heat transfer fluid flowing in contact with the magnet, Evol_TMF.
[0131] Regarding the first series model M1, two model variants are addressed:
[0132] - First variant M11, which assumes the magnet is isothermal: assuming the magnet's temperature is uniform along its entire length and constant over time.
[0133] - The second variant, M12, assumes that the temperature of the magnet is uniform along its entire length but varies over time.
[0134] In other words, in the first variant M11 and the second variant M12, conductive heat exchange from one region of the magnet to another occurs instantaneously, and the thermal conductivity of the magnet is relatively high to allow for this assumption. Furthermore, in the second variant M12, the temperature of the magnet changes over time. The mass and specific heat capacity of the magnet are taken into account, and therefore the heat capacity of the magnet is also considered.
[0135] refer to Figures 9 to 12 The first thermal model variant M11 is described in the case of a partial reduction in the heat transfer fluid velocity.
[0136] The heat transfer fluid volume element is considered for thickness dx and cross-section Schannel equal to that of the channel.
[0137] The heat power transferred by the magnet through the contact surface with the heat transfer fluid is calculated using the first formula (expressed as...). ):
[0138]
[0139] Furthermore, the heat power transferred by the magnet through the contact surface with the heat transfer fluid is calculated using the second formula:
[0140]
[0141] in, It is the width of the channel.
[0142] Therefore, the following equation is obtained:
[0143]
[0144] The simplified version using dx is given as follows:
[0145]
[0146] Solving this equation using the finite difference method with a time increment Δt yields the following equation:
[0147]
[0148] Therefore, according to mathematical model M11, the temperature evolution of the heat transfer fluid is described by the following curve:
[0149] - First curve graph G111 ([ Figure 9 The diagram illustrates the time evolution of the temperature of the heat transfer fluid between the time T0 when the flow rate begins to decrease and the time Tmax when the flow rate equals 150 seconds.
[0150] - Second curve G112 ([ Figure 10 The paper details the time evolution of the temperature of the heat transfer fluid between the time T0 when the flow rate begins to decrease and the time Tmax when the flow rate equals 100 seconds.
[0151] - Third curve G113 ([ Figure 11 The diagram shows the distance the heat transfer fluid travels in the channel over time.
[0152] - Fourth curve G114 ([ Figure 12 The paper details the evolution of the temperature of the heat transfer fluid as it travels a distance in the channel.
[0153] Graphs G111 and G112 show that the heat transfer fluid essentially reaches the temperature of the magnet after 60 seconds.
[0154] In summary, according to the first thermal model M11, the basic fluid volume of thickness dx heats up as it moves through the channel. Its heating rate is determined by the exchange coefficient, which is constant due to laminar flow, thus producing a constant Nusselt number.
[0155] According to thermal model M11, the flow rate of the heat transfer fluid does not affect its heating rate. Conversely, a high flow rate will cause the fluid element of thickness dx to rapidly exit the channel in contact with the magnet, thus not allowing sufficient time for the fluid element to heat to a point close to the magnet's temperature. Therefore, it is necessary to reduce the flow rate to allow the fluid element the time required to reach the magnet's temperature.
[0156] In the embodiment of the magnet and heat transfer fluid channel under consideration, for a heat transfer fluid flow rate of 0.007 L / min, the time to pass through the channel is 62 seconds, and at the end of this duration, the fluid element reaches a temperature equal to the temperature of the magnet, that is, 150°C.
[0157] Furthermore, 37 seconds is sufficient for the heat transfer fluid to reach a temperature within 3 degrees Celsius below the magnet's temperature. The distance traveled is then 7 centimeters, which is significantly less than the length of the magnet. Therefore, the heat transfer fluid velocity can be increased so that the distance traveled in 37 seconds equals the length of the magnet, that is, in the described embodiment of the magnet and heat transfer fluid channel, it equals 12 centimeters.
[0158] In other words, when the flow rate of the heat transfer fluid changes from one time to two times, the recorded temperature change of the heat transfer fluid is limited to only a few degrees. Therefore, it is not necessary to precisely determine the flow rate of the heat transfer fluid, thus making the measurement of the magnet temperature quite robust.
[0159] The following will refer to Figures 5 to 7 and Figures 13 to 16 A description of a second thermal model variant M12 with decreasing flow rate is given, where it is assumed that the temperature of the magnet is uniform along its entire length but varies with time.
[0160] The thermal model used is constructed based on the following assumptions:
[0161] - In model M12, and compared to model M11, the mass and specific heat capacity of the magnet are considered. The temperature of the magnet depends on various heat exchanges with the magnet.
[0162] Therefore, according to this model, the heat power known as "iron loss" (hysteresis and eddy current) is dissipated in the magnet, and the heat power is transferred from the magnet to a heat transfer fluid that is colder than the magnet.
[0163] Analyze the corresponding temperature changes of the magnet and the heat transfer fluid flowing in the channel in order to determine
[0164] - Reduce the fluid velocity to reduce the time required to reach the thermal equilibrium temperature between the magnet and the heat transfer fluid, or
[0165] - If the thermal equilibrium temperature between the magnet and the heat transfer fluid cannot be reached, then the temperature difference DIFF between the magnet and the heat transfer fluid is constant.
[0166] This allows the temperature of the magnet to be derived from the temperature of the heat transfer fluid.
[0167] Compared with the first modeling method M11, the second modeling method M12 advantageously allows for the consideration of more realistic temperature evolution and ongoing physical phenomena, particularly the cooling and heating of magnets.
[0168] The heat transfer fluid volume element is considered for thickness dx and cross-section Schannel equal to that of the channel.
[0169] The heat power transferred by the magnet through the contact surface with the heat transfer fluid is calculated using the first formula (expressed as...). ):
[0170]
[0171] Heat dissipated in the magnet The power is uniformly distributed throughout the volume of the magnet. In the volume of a basic magnet with thickness dx, the power dissipated in the magnet is:
[0172]
[0173] For a magnet, the heat exchange equilibrium is written as:
[0174]
[0175] in, It is the cross-section of the magnet, and It is the volume density of the magnet.
[0176] The following equation is given by dx simplification and formatting:
[0177]
[0178] The following equation is given by applying a solution method known as the finite difference method with a time increment Δt:
[0179]
[0180] For fluids, the heat exchange equilibrium is written as it is in the case of an isothermal magnet. The temperature change of a fluid volume of length dx is determined by the heat power received by that volume. The following equation is given:
[0181]
[0182] This corresponds to the thermal power transferred by the magnet through the contact surface with the fluid. This surface is dx × the width of the channel.
[0183] Heat transfer is determined by the product of the temperature difference between the magnet and the heat transfer fluid and the following exchange coefficient:
[0184]
[0185] Combining the two equations above, we get:
[0186]
[0187] The following equation is obtained by simplifying dx.
[0188]
[0189] Solving this equation using the finite difference method with a time increment Δt yields:
[0190]
[0191] By handling the heat exchange coefficient and its relationship with the Nusselt number using the same method as in model M11, and considering the same embodiment of the magnet, while also taking into account the 20 watts of power dissipated in the magnet, solving the equations above allows us to obtain... Figures 13 to 16 The curve in the graph.
[0192] Therefore, according to mathematical model M12, the temperature evolution of the heat transfer fluid is described by the following curve:
[0193] - First curve graph G121 ([ Figure 13 The diagram illustrates the time evolution of the temperature of the magnet and the heat transfer fluid between the time T0 when the flow rate begins to decrease and the time Tmax when it equals 90 seconds.
[0194] - Second curve G122 ([ Figure 14 The diagram illustrates the time evolution of the temperature of the magnet and the heat transfer fluid as a function of the distance the heat transfer fluid travels.
[0195] - Third curve G123 ([ Figure 15 The paper details the time evolution of the temperature of the magnet and the heat transfer fluid as the heat transfer fluid travels.
[0196] - Fourth curve G124 ([ Figure 16 This describes the distance the heat transfer fluid travels in the channel over time.
[0197] As can be seen in graph G123, the basic fluid volume of thickness dx heats up as it moves through the channel. The heating rate is determined by the exchange coefficient, which is constant due to laminar flow, thus producing a constant Nusselt number.
[0198] Similar to mathematical model M11, in model M12, the flow rate of the heat transfer fluid in the channel does not affect the heating rate of the fluid, but it is necessary to determine a sufficiently low flow rate to allow the fluid element dx to reach the temperature of the magnet.
[0199] In the practical scenario considered here, for a heat transfer fluid flow rate of 0.007 L / min, the time it takes for the fluid to traverse the channel is 62 seconds. In the first half of the simulation, the temperature of the magnet is observed to decrease as heat is transferred from the magnet to the heat transfer fluid. The temperature of the heat transfer fluid gradually increases until it reaches the temperature of the magnet, and both temperatures increase very slightly over time. However, the heat power dissipated in the magnet due to iron losses continues, and thus this balance causes the magnet to heat up.
[0200] It can be seen that at a distance of 10 centimeters, the temperature difference between the magnet and the fluid approaches an asymptote. Furthermore, the magnet's temperature begins to rise, but the temperature difference between the magnet and the fluid is only 2 degrees Celsius. At this point, the magnet's temperature rise does not exceed 2°C.
[0201] A slight increase in flow rate can push the temperature of the heat transfer fluid closest to that of the magnet back by one or two centimeters, without causing the magnet's temperature to begin to rise. Alternatively, one could apply... Figures 13 to 16 As shown in the example, the temperature rise of the magnet is only 2°C.
[0202] Therefore, it can be seen that there are many ways to adjust the flow rate to make it possible to measure the temperature of a magnet.
[0203] Descriptions of models M21, M22, and M23 for the second series of M2 are given, involving the case of completely reducing the flow rate of the heat transfer fluid. In other words, the heat transfer fluid does not flow in the channel during the duration D_reduc.
[0204] Without an estimation method, the heat transfer fluid flows through the channel at a nominal velocity and traverses the channel within seconds. The temperature change of the fluid between the inlet and outlet of the channel is relatively low. When the fluid suddenly stops flowing, all the fluid present in the channel is at a relatively low, uniform temperature. During the duration D_reduc, heat transfer occurs from the magnet to the heat transfer fluid, causing the fluid temperature to rise until the fluid asymptotically approaches the temperature of the magnet.
[0205] The models in the second series are divided into two subsets.
[0206] - Includes the first subset of the third model M21 and the fourth model M22, where the magnet is considered isothermal, and
[0207] - Includes a second subset of the fifth model M23, in which the magnet is considered to be non-isothermal.
[0208] refer to Figures 17 to 19 The third model, M21, is described. In the third model, M21, it is assumed that the heat transfer fluid is monolithic, that is, the temperature of the fluid is uniform throughout the thickness eF of the channel.
[0209] We are only interested in the temperature change of the heat transfer fluid; the temperature change of the magnet, T_Magnet, is constant. We determine the duration, D_reduc, required to reach thermal equilibrium (i.e., the temperature of the fluid in the channel beneath the magnet stabilizes). Alternatively, we can determine the duration, D_reduc, required for the temperature difference between the magnet and the fluid to remain constant.
[0210] Heat power is transferred from the magnet to the fluid via conduction. The transfer of heat power is determined by the temperature gradient between the magnet and the fluid, as well as the thermal conductivity of the fluid. The transferred heat power is calculated using the following formula:
[0211]
[0212] The equation governing the fluid temperature based on the heat power transfer from the magnet to the fluid is written as follows:
[0213]
[0214] The diffusion rate δ is defined using the following formula.
[0215]
[0216] The following equation is given:
[0217]
[0218] Solve the first-order differential equation literally to obtain the following relationship between the fluid temperature and the magnet temperature:
[0219]
[0220] in, It is constant, and It is the initial temperature of the heat transfer fluid during the time it remains stationary in the channel.
[0221] The equation can also be solved using the finite difference method with time increment Δt, and the following results are given.
[0222]
[0223] [ Figure 19 [Image] is a graph showing the temperature evolution of the heat transfer fluid over time. It demonstrates that the temperature of the heat transfer fluid reaches the temperature of the magnet after approximately 90 to 100 seconds. It should be noted that this duration can be significantly reduced if the heat power transferred from the iron of the rotor to the fluid present in the channels is taken into account.
[0224] refer to Figures 20 to 22 The fourth thermal model, M22, is described. In this model, it is assumed that the heat transfer fluid is a superposition of ten layers of equal thickness, each with a uniform temperature that varies over time. Heat is transferred gradually from the magnet to the fluid via pure thermal conduction, from the hottest region to the coldest.
[0225] This multilayer heat transfer fluid model involves the case where the flow rate of the heat transfer fluid is zero: then the flow of the heat transfer fluid is blocked, and a wait is implemented so that the temperature of the heat transfer fluid becomes substantially equal to the temperature of the magnet over a “reasonable” duration.
[0226] Figure 20 The fluid model is shown in the image. The thickness of a fluid layer is represented as... The thickness of the channel is equal to the thickness of one layer. 10 times.
[0227] As in model M21, it is assumed that in model M22 the heat transfer fluid is heated only by the magnet. In other words, the heat transfer fluid is considered to be isolated from the iron of the rotor in which it flows. The temperature of the fluid is considered to be uniform in each layer and to evolve over time.
[0228] Consider the first fluid layer, that is, the fluid layer closest to the magnet, and express the equations concerning the transfer of heat power through conduction from the magnet to the first fluid layer.
[0229] Therefore, the thermal balance of the first fluid layer is expressed as follows:
[0230]
[0231] The simplified version is as follows:
[0232]
[0233] The diffusion rate δ is defined using the following formula.
[0234] The solution is obtained using the finite difference method with time increment Δt.
[0235]
[0236] The thermal balance of fluid layer i is expressed as follows: layer i receives thermal power from layer i – 1 and transfers thermal power to layer i + 1.
[0237] The heat power received from layer i – 1 is calculated as follows:
[0238] The heat power transferred to layer i+1 is calculated as follows:
[0239]
[0240] Therefore, the total power received by layer i is expressed as follows:
[0241]
[0242] or
[0243]
[0244] The temperature change of layer i is related to the thermal power received by layer i, which leads to the following equation:
[0245]
[0246] The diffusion rate δ is defined using the following formula.
[0247] The following equations are given:
[0248]
[0249] The following is given using the finite difference solution method with time increment Δt:
[0250]
[0251] For the tenth level, we obtain the following formula:
[0252]
[0253] After solving the equations for each layer sequentially using the finite difference method, the time evolution curve of the temperature of the heat transfer fluid flowing in each layer is obtained, as shown in […]. Figure 22 The curve G221 in the figure represents this.
[0254] The duration of fluid flow cessation, D_reduc, is determined by the time it takes for all layers of the fluid to reach the same temperature, corresponding to a duration between 65 and 75 seconds. It should be noted that this duration can be significantly reduced if the heat power transferred from the rotor's iron to the fluid present in the channels is taken into account.
[0255] It can be seen that breaking down the fluid into multiple layers provides a better understanding of the phenomena that are occurring. However, the duration D_reduc required to reach the same limiting temperature in all layers of the heat transfer fluid is essentially the same as the duration obtained using the thermal model M21, that is, essentially the same as the duration obtained using a model that treats the fluid present in the channel as a single block (at least for the reasonable channel thickness considered).
[0256] refer to Figures 23 to 26 The fifth thermal model M23 differs from the other models in that it considers a non-isothermal magnet in the context of a complete reduction in the flow rate of the heat transfer fluid.
[0257] Therefore, the fifth thermal model M23 is defined based on the following assumptions:
[0258] The temperature of the magnet is uniform along its entire length, and because the magnet's thermal conductivity is high enough, conductive heat exchange from one region of the magnet to another occurs instantaneously.
[0259] - The temperature of the magnet changes over time; for this purpose, the mass of the magnet and its specific heat capacity (and therefore its heat capacity) are taken into account.
[0260] - The fluid in the channel is considered as a block of material with a uniform temperature that changes over time.
[0261] The temperature of a magnet depends on the various heat exchanges it undergoes. The first heat power, known as "iron loss," is dissipated within the magnet, while the second heat power is discharged from the magnet to a heat transfer fluid that is cooler than the magnet.
[0262] We are only interested in the temperature changes of the heat transfer fluid and the magnet. We determine the duration, D_reduc, required to reach thermal equilibrium (i.e., when the temperatures of the fluid and magnet stabilize). Alternatively, we can determine the duration, D_reduc, required for the temperature difference EC between the magnet and the fluid to remain constant.
[0263] Therefore, when this temperature is measured, the temperature of the magnet can be derived using basic calculations, which will allow for a precise determination of the magnet's temperature. This method has the advantages of reflecting the reality of temperature evolution and taking into account ongoing physical phenomena, particularly the cooling and heating of the magnet.
[0264] refer to Figure 23 and Figure 24 The heat transfer fluid is considered as a whole as a block with thickness eF, width l_Fluid, and length L_Channel. It is assumed that the fluid is heated only through its contact surface with the magnet, and that the fluid portion in contact with the iron is thermally isolated.
[0265] The heat balance of the heat transfer fluid is calculated using the following formula:
[0266]
[0267] The simplified version is as follows:
[0268]
[0269] The diffusion rate δ is defined using the following formula.
[0270]
[0271] Using the finite difference method to solve for the time increment Δt, we can write:
[0272]
[0273] The thermal balance of the magnet is calculated using the following formula:
[0274]
[0275] It is the mass of the magnet, and It is the specific heat capacity of the magnet.
[0276] This then gives
[0277]
[0278] Solving the equation using the finite difference method with a time increment Δt yields the following:
[0279]
[0280] This gives the time evolution curves of the magnet's temperature and the temperature of the heat transfer fluid flowing in the channel, as shown by […]. Figure 25 The curve G231 in the figure is shown.
[0281] Figure 25 and Figure 26 The application of thermal model M23 is demonstrated under the following conditions:
[0282] - The length of the channel and magnet is 12 centimeters, and
[0283] - The power dissipated in the magnet is 20 watts.
[0284] Plot G231 shows the duration, D_reduc, required for the heat transfer fluid velocity to fully decrease for approximately 90 seconds to reach the asymptote between the corresponding temperature curves of the magnet and the fluid. After reaching the asymptote, the temperature difference between the magnet and the fluid is approximately 5 degrees Celsius. During the time it takes for the heat transfer fluid velocity to fully decrease, the magnet temperature increases by 12 degrees Celsius. The full decrease in heat transfer fluid velocity has a non-negligible effect on the cooling of the magnet. However, if the heat power transferred from the iron of the rotor to the fluid present in the channels is considered, this duration can be estimated to be significantly reduced. This reduces the adverse consequences of stopping fluid flow on the magnet temperature. An upper temperature limit can be considered, and this value can constitute a safety margin. When the nominal flow rate is re-established, the magnet will cool down relatively quickly again.
[0285] In summary, the five thermal models M11, M12, M21, M22, and M23 mentioned above are mathematical models that take into account physical quantities, dimensional quantities, and quantities related to the physical properties of materials.
[0286] The model assumes the fluid is reheated solely through heat power transfer from the magnet to the fluid. However, in reality, the fluid is also reheated by other walls of the channels formed by the iron of the rotor. Therefore, in the described model, the fluid temperature rises more rapidly and reaches its maximum temperature earlier than the time D_reduc calculated by the model, allowing the magnet temperature to be obtained more quickly.
[0287] The use of thermal models indicates that reducing the flow rate is preferable to completely interrupting it. The limiting temperature is reached more quickly, and the magnet's temperature rises reasonably. The heat transfer fluid flow rate can be very low, for example, 7 mL / s. The duration of reduction, D_reduc, depends on the characteristics of both the magnet and the heat transfer fluid.
[0288] In one embodiment, a given duration D_reduc is determined based on the following:
[0289] - The corresponding time evolution of the modeling temperature TMA of the magnet, Evol_TMA, and
[0290] - Time evolution of the modeling temperature TMF of the heat transfer fluid, Evol_TMF.
[0291] Specifically, given the duration D_reduc, it is determined such that:
[0292] - During a given duration D_reduc, the modeling temperature TMA of the magnet increases by less than a first threshold S1, which may be equal to 6 degrees or even 4 degrees.
[0293] - During the simulation time starting from a given duration D_reduc, the difference DIFF between the modeling temperature TMA of the magnet and the modeling temperature TMF of the heat transfer fluid is essentially constant and less than the second threshold S2, for example, less than 3 degrees.
[0294] Furthermore, in one embodiment, the constant deviation EC is equal to the difference between the modeling temperature TMA of the magnet and the modeling temperature TMF of the heat transfer fluid calculated over a simulation time starting from a given duration D_reduc.
[0295] Once the duration of the fluid velocity reduction D_reduc, the constant deviation EC, and the applied fluid velocity are determined, the next step is step E2: partially or completely reducing the velocity of the heat transfer fluid flowing in the rotor's channels.
[0296] In step E2, the heat transfer fluid velocity is partially or completely reduced during the duration D_reduc. For this purpose, solenoid valve 33 is controlled to change its state from a first open state to a second closed state for a duration of D_reduc, as shown in […]. Figure 27 As shown in the image.
[0297] The next step is step E3: temperature sensor 4 measures the temperature of the heat transfer fluid.
[0298] Measurement step E3 may include substep E31: restoring the flow of the heat transfer fluid before temperature measurement, in which the heat transfer fluid is set to flow at an intermediate velocity, less than the initial velocity of the heat transfer fluid before the velocity reduction. In other words, the fluid velocity is substantially increased just before measuring the temperature of the fluid at the outlet of the channel, so as to measure the temperature of the heat transfer fluid remaining in the channel during the given velocity reduction duration. More specifically, substep E31 is necessary if the heat transfer fluid flow is completely interrupted during the given duration D_reduc.
[0299] After measuring the temperature T_mes of the heat transfer fluid, in step E4, the estimated temperature T_estimated of the magnet 111 is determined as the sum of the measured temperature T_mes of the heat transfer fluid and the zero or non-zero constant temperature deviation EC calculated in step E1.
[0300] The method for controlling the powertrain of a motor vehicle according to the present invention includes three steps E11, E12, and E13 performed sequentially.
[0301] In the first step E11, the need to estimate the temperature of the magnet 111 of the rotor is detected.
[0302] As described above, the powertrain includes its own dynamic model 22, which allows the temperature of the magnet to be estimated with an accuracy on the order of approximately ten or twenty degrees.
[0303] In step E11, it is determined whether the accuracy of the dynamic model 22 is sufficient to ensure the correct operation of the powertrain or whether it is necessary to use the estimation device 21 according to the invention to more accurately measure the temperature of the magnet in order to verify the temperature estimate provided by the dynamic model 22 and control the powertrain in the best manner.
[0304] In one embodiment, detecting the need to use the estimation device 21 according to the invention includes comparing the temperature of the magnet estimated by the dynamic model 22 with a temperature threshold. Therefore, when the temperature of the magnet estimated by the dynamic model 22 exceeds the temperature threshold, it is determined that the estimation device 21 is needed to measure the temperature of the magnet more accurately.
[0305] Furthermore, the detection requiring the use of the estimation device 21 according to the invention may be related to the operating conditions of the motor vehicle. For example, the detection may involve a large motor torque commanded by the vehicle's driver at a given time. Alternatively, the detection may involve maintaining a high speed of movement for a given duration. Advantageously, the detection involves drive parameters or configurations that readily cause heating of the magnet 111.
[0306] The need to measure the temperature of a magnet in a single test, and / or the need to measure the temperature of a magnet periodically.
[0307] This is followed by the steps of implementing the method according to the invention for estimating the current temperature of the magnet at a given time or at a given frequency.
[0308] Once the estimated current temperature exceeds a given temperature threshold, the torque available from the powertrain is reduced. Consequently, the vehicle will temporarily operate with decreased performance, and in the event of a powertrain control failure, the current flowing in the stator windings will be regulated. This will prevent demagnetization of the rotor magnets.
[0309] Ultimately, this invention enables the estimation of the magnet's temperature based on a single temperature measurement of the cooling fluid intended to cool the rotor magnet at the channel's outlet. The estimation method according to the invention does not require determining the temperature of the fluid at the channel inlet or the flow rate of the heat transfer fluid within the channel.
[0310] This invention is based on a very significant, or even complete, reduction in the flow rate of the fluid flowing in a channel beneath the magnet during a given duration. Therefore, the temperature of the heat transfer fluid at the channel outlet reaches the temperature of the magnet. After temperature measurement, the nominal fluid flow rate required to cool the rotor, and particularly the magnet, is returned.
[0311] Using the thermal model implemented in this method, the duration of a partial or complete reduction in the heat transfer fluid velocity is determined such that:
[0312] - At the end of the reduction duration, the fluid temperature at the channel outlet has reached a value very close to the magnet temperature.
[0313] - The temperature of the magnet did not rise unacceptably over the reduced duration.
[0314] The estimation method according to the present invention improves the powertrain control method. The improved accuracy of the rotor magnet temperature estimation makes it easier to reduce the powertrain torque, and thus minimizes the frequency with which the user loses the vehicle's maximum performance. Furthermore, the control method according to the present invention prevents the rotor magnets from undergoing degradation related to short circuits in the stator windings in the event of a powertrain control failure.
Claims
1. A method for estimating the temperature of a magnet (111) of a rotor (11), the rotor (11) comprising a channel (34) through which a heat transfer fluid contacts or approaches the magnet (111), flows between an inlet section (341) and an outlet section (342) of the channel, wherein a temperature sensor (4) is arranged in the channel (34), particularly near the outlet section (342), characterized in that, The method includes: • The step (E2) is to partially or completely reduce the flow rate of the heat transfer fluid flowing in the channel (34) during a given duration (D_reduc). • The temperature sensor (4) measures the temperature (T_mes) of the given heat transfer fluid remaining in the channel (34) throughout the entire given duration (D_reduc), and in step (E3) • The step (E4) to determine the estimated temperature (T_estimated) of the magnet (111) as the sum of the measured temperature (T_mes) of the given heat transfer fluid and the zero or non-zero constant temperature deviation (EC).
2. The estimation method as described in the preceding claim, characterized in that, The method includes the step (E1) of determining the given duration (D_reduc) and the constant deviation (EC), which includes implementing a thermal model (M11, M12, M21, M22, M23) of the temperature evolution of the heat transfer fluid resulting solely from the transfer of thermal power from the magnet to the heat transfer fluid.
3. The estimation method as described in the preceding claim, characterized in that, The thermal model is - A first model is constructed based on the following assumptions: the modeling temperature of the magnet is constant over a given duration and the modeling temperature of the magnet is uniform along the entire length of the magnet, the length of which is measured in the direction of the channel, or - A second model is constructed based on the following assumptions: the modeling temperature of the magnet is uniform across its entire length for all times of the given duration; the modeling temperature of the magnet varies with time. The first model and the second model each include a first variant and a second variant, wherein the flow rate of the heat transfer fluid is non-zero during the given duration (D_reduc), and the flow rate of the heat transfer fluid is zero during the given duration (D_reduc).
4. The estimation method as described in any one of claims 2 and 3, characterized in that, The thermal models (M11, M12, M21, M22, M23) provide the time evolution of the modeling temperature (TMA) of the magnet and the time evolution of the modeling temperature (TMF) of the heat transfer fluid flowing in contact with the magnet. And its characteristic is that the given duration (D_reduc) is determined such that - During the given duration (D_reduc), the rise in the modeling temperature (TMA) of the magnet is less than a first threshold (S1), which is specifically equal to 6 degrees or even 4 degrees, and - During the simulation period starting from this given duration (D_reduc), the difference (DIFF) between the modeling temperature (TMA) of the magnet and the modeling temperature (TMF) of the heat transfer fluid is substantially constant and less than the second threshold (S2), for example, less than 3 degrees. Furthermore, the constant deviation (EC) is characterized by being equal to the difference between the modeling temperature (TMA) of the magnet and the modeling temperature (TMF) of the heat transfer fluid calculated over a simulation period starting from the given duration (D_reduc).
5. The estimation method as described in any one of the preceding claims, characterized in that, The measurement step (E3) includes a sub-step (E31) to restore the flow of the heat transfer fluid at an intermediate flow rate, which is less than or equal to the initial flow rate of the heat transfer fluid before the flow rate was reduced.
6. An apparatus (21) for estimating the temperature of a rotor magnet, wherein a cooling circuit for cooling the magnet comprises a set of pipes (30) in contact with the magnet (111) to carry out the flow of cooling fluid. The device includes means for controlling the flow rate of a solenoid valve (33) arranged on a pipe in the group of pipes (30) located upstream of the magnet relative to the flow direction of the heat transfer fluid approaching or contacting the magnet, and the device includes hardware and / or software elements (210, 211, 212, 213, 2111, 2112, 2113) implementing the method as described in any one of the preceding claims, particularly hardware and / or software elements (210, 211, 212, 213) designed to implement the method as described in any one of the preceding claims.
7. A method for controlling the powertrain of a motor vehicle, characterized in that, The method includes: • The step (E11) of detecting the need to estimate the temperature of the magnet at a given time or at a given frequency based on the operating conditions of the motor vehicle, and then • At that given time or at that given frequency, perform step (E12) of the method for estimating the current temperature of the magnet as described in any one of claims 1 to 5, and then • Step (E13) when the current temperature of the magnet is greater than the temperature threshold: reduce the motor torque that can be obtained from the power transmission system.
8. The control method as described in the preceding claim, characterized in that, These usage conditions include the motor torque commanded by the driver of the motor vehicle at that given time.
9. An apparatus (2) for controlling the powertrain of a motor vehicle (100), the apparatus comprising hardware and / or software elements (20, 21, 22, 201, 202, 203, 2011, 2012, 2013) for implementing the method as described in any one of claims 7 and 8, particularly hardware and / or software elements (20, 21, 22, 201, 202, 203) designed to implement the method as described in any one of claims 7 and 8.
10. A motor vehicle (100) equipped with a control device (2) as described in the preceding claim or an estimation device (21) as described in claim 6.