Estimator and estimator system

An estimator includes a model unit that calculates a state quantity by using an input signal and a relational expression that expresses a target model, a correction signal measurement sensor that measures a correction signal for correcting the state quantity, a correction unit that outputs a value for correcting the state quantity based on the correction signal to the model unit, and a model changing unit that changes the model unit in accordance with an oil flow related value that relates to a change of flow of cooling oil. The correction signal measurement sensor is arranged to be in contact with a metal member that includes a coil conductive wire that constitutes the stator coil, a terminal connected to the coil conductive wire, and a power line connected between the coil conductive wire and the terminal, at a point on which no cooling oil drops.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2016-125848 filed on Jun. 24, 2016 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an estimator and estimator system that estimate the temperature of a stator coil of an electric rotary machine that is cooled by cooling oil.

2. Description of Related Art

An electric rotary machine that is a motor or a generator includes a stator coil. In such an electric rotary machine, an excessive increase in the coil temperature of the stator coil may lead to a decrease in the performance of the electric rotary machine. Therefore, it is conceivable to cool the stator coil with the use of cooling oil. In addition, the coil temperature is measured by a temperature sensor. For example, in an electric vehicle or hybrid vehicle including a drive motor, a sensor is attached near a stator coil of the motor, and the coil temperature of the stator coil is measured by the sensor.

Japanese Patent Application Publication No. 2010-28887 (JP 2010-28887 A) describes the following configuration. By supplying cooling oil to a stator of an electric rotary machine through a selected one of a plurality of flow passages, the cooling oil is dropped in the central axis direction from substantially just above the electric rotary machine in the vertical direction of the electric rotary machine irrespective of an inclined state of a vehicle body on which the electric rotary machine is mounted.

SUMMARY OF THE INVENTION

With the configuration that the coil temperature is measured by the temperature sensor attached to the stator coil, if oil drops on the temperature sensor, the temperature sensor may measure a temperature close to the oil temperature. Thus, output from the temperature sensor varies depending on whether oil drops on the temperature sensor, so it may not be able to highly accurately estimate the coil temperature. For this reason, when coil current is controlled, it is required to protect the coil at a high factor of safety. Even when the coil temperature has reached a temperature significantly lower than a physically allowable upper limit temperature of the stator coil, motor output is decreased by decreasing the coil current because of the factor of safety. Thus, it may not be able to effectively exercise the output of the electric rotary machine.

On the other hand, in the configuration described in JP 2010-28887 A, it is conceivable to measure the coil temperature of the electric rotary machine with the use of the temperature sensor. In this case, the manner in which cooling oil drops on the temperature sensor may be constant irrespective of an inclination of the vehicle body on which the motor is mounted. However, with this configuration, a flow passage structure becomes considerably complicated.

The invention provides an estimator and estimator system that are able to highly accurately estimate the coil temperature of an electric rotary machine without a complicated flow passage structure of the electric rotary machine that is cooled by cooling oil.

A first aspect of the invention provides an estimator configured to estimate a temperature of a stator coil of an electric rotary machine. The electric rotary machine is cooled by cooling oil. The estimator includes an electronic control unit and a correction signal measurement sensor. The electronic control unit includes a model unit configured to calculate a state quantity by using an input signal and a relational expression that expresses a target model. The correction signal measurement sensor is configured to measure a correction signal for correcting the state quantity. The electronic control unit further includes a correction unit configured to output a value for correcting the state quantity on the basis of the correction signal to the model unit, and a model changing unit configured to change the model unit in accordance with an oil flow related value that relates to a change of flow of the cooling oil. The correction signal measurement sensor is arranged so as to be in contact with a metal member that includes a coil conductive wire that constitutes the stator coil, a terminal connected to the coil conductive wire, and a power line connected between the coil conductive wire and the terminal, at a point on which no cooling oil drops.

A second aspect of the invention provides an estimator system. The estimator system includes a plurality of estimators and selection means. The plurality of estimators each are configured to estimate a temperature of a stator coil of an electric rotary machine. The electric rotary machine is cooled by cooling oil. The plurality of estimators each include an electronic control unit and a correction signal measurement sensor. Each electronic control unit includes a model unit configured to calculate a state quantity by using an input signal and a relational expression that expresses a target model. The correction signal measurement sensor is configured to measure a correction signal for correcting the state quantity. Each electronic control unit further includes a correction unit configured to output a value for correcting the state quantity on the basis of the correction signal to the model unit, and a model changing unit configured to change the model unit in accordance with an oil flow related value that relates to a change of flow of the cooling oil. The correction signal measurement sensor is arranged so as to be in contact with a metal member that includes a coil conductive wire that constitutes the stator coil, a terminal connected to the coil conductive wire, and a power line connected between the coil conductive wire and the terminal, at a point on which no cooling oil drops. The selection means is configured to select a maximum temperature of the stator coil from among the temperatures of the stator coil, respectively estimated by the plurality of estimators.

With the estimator and estimator system according to the aspects of the invention, it is possible to highly accurately estimate the coil temperature without a complicated flow passage structure of the electric rotary machine that is cooled by cooling oil. As a result, it is not required to protect the stator coil at a high factor of safety. Therefore, for example, when the electric rotary machine is a motor, it is possible to generate the output of the motor up to a temperature close to an upper limit temperature that is physically allowed by the stator coil.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of the invention will be described with reference to the accompanying drawings. The shape, material and number that will be described below are used for illustrative purposes, and may be modified as needed in accordance with the specifications of an estimator and estimator system. When a plurality of embodiments, alternative embodiments, and the like, are provided in the following description, those may be combined as needed. In the following description, like reference numerals denote equivalent components in all the drawings. In the following description, reference numerals referred to before then are used where necessary. Hereinafter, description will be made on the assumption that an electric rotary machine is a motor; instead, the electric rotary machine may be a generator.

FIG. 1is a view that shows a position at which a correction sensor12is attached in a motor50. The motor50serves as an electric rotary machine to which an estimator10according to the embodiment is applied. The correction sensor12serves as a correction signal measurement sensor that constitutes the estimator10. Initially, the motor50will be described. The motor50includes a stator52and a rotor (not shown). In the stator52, three-phase stator coils54u,54v,54ware wound on an annular stator core53.

Part of each of the three-phase stator coils54u,54v,54wis led to the outside from the stator core53and forms a corresponding one of three power lines56u,56v,56w. Hereinafter, the power lines56u,56v,56ware collectively referred to as power lines56. The stator coils54u,54v,54ware collectively referred to as coils54. A terminal58is fixed to one end of each of the power lines56by crimping part of the terminal58such that the terminal58is in close contact with the corresponding power line56. Thus, the thermal resistance between each power line56and the corresponding terminal58is sufficiently low. Each power line and the corresponding terminal may be fixed to each other by bringing each power line into close contact with the corresponding terminal in a sufficiently low thermal resistance state by means of welding or soldering. Each of the terminals58is fixed to a terminal block (not shown), and is connected to a corresponding one of three-phase electric wires (not shown) connected to a power supply-side inverter via the terminal block.

The rotor is arranged so as to face the radially inner side of the stator52. The rotor is fixed to the radially outer side of a rotary shaft (not shown). The rotor includes magnets arranged at multiple positions in the circumferential direction of a rotor core. When the motor is an induction motor, a rotor coil is arranged on the rotor core. The motor50generates a magnetic field in the stator when the stator coils are energized, and rotates the rotor by magnetic interaction between the stator and the magnets of the rotor.

An annular coil end59is formed at the axial end of the stator. In the motor50, as indicated by the arrow α inFIG. 1, cooling oil is dripped from a dropping portion60. Thus, cooling oil is caused to flow along the surface of the coil end59as indicated by the arrow β inFIG. 1. The dropping portion60is arranged on the upper side of the axial end of the motor50. Thus, the motor50is cooled. Cooling oil that has flowed along the surface of the coil end59is recovered from a lower-side oil reservoir (not shown), flows through an oil passage (not shown), and returns to the dropping portion60.

The thus configured motor50is mounted on a vehicle, such as an electric vehicle and a hybrid vehicle, and is used. The hybrid vehicle includes an engine and a motor as drive sources for wheels. For example, the motor50is a drive motor. The wheels are driven by transmitting power from the drive motor to the wheels.

In the thus configured motor50, as a comparative embodiment, it is conceivable that a sensor for estimating a coil temperature, indicated by the alternate long and short dashes line G inFIG. 1, is attached at a position near the coils different from the power lines. In the comparative embodiment, a detected signal of the sensor is transmitted to a controller, and the controller estimates the maximum temperature of the coils. In this comparative embodiment, oil can drop on the sensor, and the manner in which oil drops can vary depending on the inclination of the vehicle, the longitudinal acceleration of the vehicle, or the like. For example, the position at which the coil temperature indicates a maximum temperature in the coils can vary depending on the driving state of the motor50or the moving state of the vehicle. Thus, the accuracy of estimating an estimated temperature of the coils with the use of the sensor can deteriorate. On the other hand, it is conceivable that the sensor is attached at a position significantly remote from the coils around the stator core53such that no oil drops on the coils in order for drops of oil not to influence estimation of the coil temperature. At this time, the temperature is estimated at a position significantly remote from the coils, so the accuracy of estimating the coil temperature can deteriorate.

The estimator10according to the embodiment includes an observer22(FIG. 2,FIG. 3). The observer22has a relational expression that expresses a thermal resistance model of the coils54inside the observer22, and estimates the coil temperature by calculation. At this time, the observer22constantly needs a correction signal for correcting an error, such as a modeling error and a sensor error. The correction signal cannot be utilized in the observer22if the correction signal does not correlate with the coil temperature. In order to obtain a signal having a high correlation, it is conceivable that the temperature of a portion near the coils is used as the correction signal; however, in that case, oil becomes easier to drop on the temperature sensor. The inventor researched the position that correlates with the coil temperature by actual measurement, including a position at which a thermal transmission path is different. As a result, it was found that the terminal and power line remote from the coils also have a high correlation in temperature with respect to the coils. Hereinafter, the case where a correction signal that expresses a temperature measured on a metal material that constitutes one of the terminals is used as the observer22according to the embodiment will be described. A correction signal that expresses the temperature of a position at which no oil drops on the power lines56may be used.

FIG. 2is a block diagram that shows signal processing in the estimator10.FIG. 3is a conceptual view of the observer22that constitutes the estimator10.

The estimator10estimates the coil temperature of the coils54, for example, the maximum temperature of the coils54. The estimator10includes a controller (electronic control unit)20and the correction sensor12(FIG. 1,FIG. 2). The correction sensor12serves as the correction signal measurement sensor. The controller20includes the observer22. The observer22includes a model unit23, a correction unit24and an oil dropping point estimation unit26. The oil dropping point estimation unit26serves as a model changing unit. InFIG. 3, the model changing unit is indicated by the straight-line arrow H.

The model unit23calculates an estimated maximum coil temperature Tm and an estimated terminal temperature Tr as state quantities by using input signals and the relational expression that expresses a target model. The estimated maximum coil temperature Tm is an estimated value of the maximum temperature of the coils54. The estimated terminal temperature Tr is an estimated value of the correction signal.

A specific example of the thermal resistance model that is the target model will be described with reference toFIG. 4.FIG. 4is a view that shows one example of the thermal resistance model of the coils54, which is used in the estimator10. The thermal resistance model includes the coils54and the terminal58that are connected to each other via a thermal resistance Rr. The terminal58is a portion to be detected. The coils54have an estimated maximum coil temperature Tm. The terminal58has an estimated terminal temperature Tr as an estimated correction signal value. A portion that has an atmospheric temperature Ta is connected to the coils54via a thermal resistance Ra, and a portion that has an atmospheric temperature Ta is connected to the terminal58via a thermal resistance Rb. A cooling oil that has a temperature Tois connected to the coils54via a thermal resistance Ro. A copper loss RI2and an iron loss KeI2ω2are input as the rate of heat flowing into the portion that generates the estimated maximum coil temperature Tm. A copper loss RcI2is input as the rate of heat flowing into the terminal58.

The thermal resistance model shown inFIG. 4is expressed by the following relational expressions (1) and (2).

In the mathematical expressions (1) and (2), Ct is the heat capacity of the coils54, R is the electrical resistance of the coils54, I is a motor current that is a current flowing through the coils, Ke is an iron loss coefficient that is an eddy current loss coefficient, and ω is the motor number of revolutions. Cr is the heat capacity of the terminal58, and Rc is the electrical resistance of the terminal58. In the mathematical expression (1), the iron loss may be estimated as KhI2ω on the assumption that a hysteresis loss coefficient is denoted by Kh in the case where the material has a large hysteresis loss.

In the above thermal resistance model, as can be understood from the mathematical expression (1), a conductive wire that constitutes the coils54increases in temperature due to heat that is generated due to the copper loss RI2associated with motor current and the iron loss KeI2ω2of the stator core53due to a variation in magnetic field. On the other hand, as can be understood from the mathematical expression (2), the terminal58increases in temperature almost not under the influence of a variation in magnetic field but under the significant influence of the copper loss RcI2.

As shown inFIG. 4, the temperature of the thermal mass of the coils54and the terminal58as the conductor increases due to heat generated in the conductive wire, and the like. On the other hand, the coils54are cooled by oil, and the heat of the coils54is drawn by oil. At the same time, heat also transfers into an engine room through the stator core53, a motor case (not shown) to which the stator52is fixed, and the like. For this reason, the atmospheric temperature Ta increases. Heat is also exchanged via the conductors, and the like, between the thermal mass of the coils54and the thermal mass of the terminal58. The temperature of each thermal mass is determined as a result of heat generation and heat exchange at this time.

In the mathematical expressions (1) and (2), the motor current I, the motor number of revolutions ω, an oil temperature To and the atmospheric temperature Ta are input as input signals, and the estimated maximum coil temperature Tm and the estimated terminal temperature Tr are calculated.

Referring back toFIG. 2, one or a plurality of signals selected from among the oil temperature To of cooling oil, the motor current I, the motor number of revolutions ω, a carrier frequency fc that is used to control the motor50, and the model atmospheric temperature Ta are input to the model unit23as input signals. For example, in the case of the thermal resistance model shown inFIG. 4, the oil temperature To, the motor current I, the motor number of revolutions ω and the model atmospheric temperature Ta are input to the model unit23as input signals.

Specifically, the estimator10includes an oil temperature sensor30, a motor current sensor31, a motor number-of-revolution sensor32and an atmospheric temperature sensor33. The oil temperature sensor30is cooling oil temperature detecting means. The oil temperature sensor30detects the temperature of cooling oil. The motor current sensor31detects the amount of current that is input to the coils. The motor number-of-revolution sensor32detects the number of revolutions of the rotor per unit time. The atmospheric temperature sensor33detects the model atmospheric temperature Ta that is the atmospheric temperature of the target model. Detected signals of the oil temperature sensor30, motor current sensor31, motor number-of-revolution sensor32and atmospheric temperature sensor33are input to the model unit23. The motor number-of-revolution sensor32may be replaced with a motor rotational speed sensor that detects the rotational speed of the rotor.

The correction sensor12is a temperature sensor that measures a terminal temperature Tra indicated by a correction signal. The correction sensor12is arranged so as to be in contact with a metal member that constitutes the terminals58(FIG. 1) connected to the coil conductive wires that constitute the coils54, at a point on which no cooling oil drops. The correction sensor12outputs a correction signal to the correction unit24.

The correction unit24corrects the state quantities on the basis of the correction signal that indicates the terminal temperature Tra. The state quantities are the estimated maximum coil temperature Tm that is an estimated value of the maximum temperature of the coils54and the estimated terminal temperature Tr that is an estimated value of the correction signal.

The correction sensor12is not limited to the case where the correction sensor12is arranged on the terminals58. For example, the correction sensor12may be arranged so as to be in contact with a metal member that constitutes the coil conductive wires, at a point on which no cooling oil drops. At this time, part of the coil conductive wires may constitute the corresponding power lines.

When power lines are respectively connected as other members between the coil conductive wires and the terminals58, the correction sensor12may be arranged so as to be in contact with a metal member that constitutes the power lines, at a point on which no cooling oil drops.

The model unit23outputs the estimated maximum coil temperature Tm and the estimated terminal temperature Tr. Of these, the estimated terminal temperature Tr is input to the correction unit24. The terminal temperature Tra indicated by the correction signal is also input to the correction unit24, and a coil temperature difference that is calculated in correspondence with a difference between the terminal temperature Tra and the estimated terminal temperature Tr is input to the model unit23. The difference is used to correct the state quantities. The model unit23, as well as the common observer22, corrects the estimated maximum coil temperature Tm and the estimated terminal temperature Tr by using a gain corresponding to the coil temperature difference. Thus, the correction unit24corrects the estimated maximum coil temperature Tm and the estimated terminal temperature Tr as the state quantities by outputting a value corresponding to the difference between the terminal temperature Tra and the estimated terminal temperature Tr to the model unit23through the correction signal.

The estimator10includes the oil dropping point estimation unit26as the model changing unit. Hereinafter, the oil dropping point estimation unit26is referred to as oil point estimation unit26. The oil point estimation unit26changes the model unit23in accordance with an oil flow related value related to a change of flow of cooling oil. For example, the oil point estimation unit26changes the model unit23in accordance with one or two or more of the inclination of the vehicle with respect to the longitudinal direction of the vehicle, the longitudinal acceleration that is the longitudinal acceleration of the vehicle and the flow rate of cooling oil as the oil flow related values.

InFIG. 2, the estimator10includes an inclination angle sensor35and a longitudinal acceleration sensor36. The inclination angle sensor35detects the inclination angle of the vehicle with respect to the longitudinal direction of the vehicle. The longitudinal acceleration sensor36detects the longitudinal acceleration of the vehicle. Detected signals of the inclination angle sensor35and longitudinal acceleration sensor36are input to the oil point estimation unit26. The oil point estimation unit26changes the model unit23in accordance with a combination of the inclination of the vehicle and the acceleration of the vehicle based on the detected signals of the inclination angle sensor35and longitudinal acceleration sensor36. Specifically, the oil point estimation unit26estimates the oil dropping point on the basis of a combination of the inclination of the vehicle and the acceleration of the vehicle. The oil point estimation unit26changes the coefficient of the relational expression that expresses the model unit23, for example, the thermal resistance Ro, by using a predetermined relationship or map on the basis of the estimated dropping point. Thus, the model unit23is changed.

FIG. 5is a schematic view that shows the influence of the longitudinal acceleration of a vehicle70on flow of oil that cools the motor.FIG. 6is a schematic view that shows the influence of the inclination angle of the vehicle with respect to the longitudinal direction of the vehicle on flow of oil. InFIG. 5, the direction in which oil dropped from the dropping portion60(FIG. 1) flows at the time when the vehicle accelerates in the forward traveling direction (the arrow γ direction inFIG. 5) is schematically indicated by the arrow P1. As is apparent fromFIG. 5, oil flows obliquely rearward at the time of forward acceleration. Thus, the oil dropping point changes. As shown inFIG. 6, when the vehicle70is inclined as in the case where the vehicle70is placed on a hill, oil flows obliquely rearward of the vehicle70(arrow P2direction). Thus, the oil dropping point also changes.

FIG. 7is a graph that shows the results of experiment in which the relationship between the inclination of the vehicle and the maximum temperature of the coils is obtained. InFIG. 7, the motor current, the motor number of revolutions, the oil flow rate and the oil temperature are constant. As shown inFIG. 7, when the vehicle inclines in a state where oil drops from above the motor50, the maximum temperature of the coils varies with a variation in the inclination angle, so it is understood that there is a high correlation between the inclination angle and the maximum temperature.

On the basis of the relationships described with reference toFIG. 5toFIG. 7, the oil point estimation unit26estimates the oil dropping point by using a combination of the inclination of the vehicle and the acceleration of the vehicle, and changes the model unit23in accordance with the estimated point.

InFIG. 2, the oil point estimation unit26is used as the model changing unit; however, another configuration may be employed. For example, the estimator10may include an oil flow rate sensor37(FIG. 2) that detects the oil flow rate, and the model unit23may be changed on the basis of a detected signal of the oil flow rate sensor37. The model changing unit may be configured to change the model unit23on the basis of a combination of the inclination of the vehicle, the acceleration of the vehicle and the oil flow rate of cooling oil.

With the above-described estimator10, it is possible to highly accurately estimate the coil temperature. As a result, it is not required to protect the coils54at a high factor of safety. Therefore, for example, it is possible to generate the output of the motor50up to a temperature close to an upper limit temperature that is physically allowed by the coils54. With the estimator10, different from the configuration described in JP 2010-28887 A, the flow passage structure of the motor50that is cooled by oil is not complicated.

The reason why the estimator10is able to highly accurately estimate the coil temperature is based on the position of the correction sensor12that is the temperature sensor and a change of the model. First, as for the position of the correction sensor12, when the temperature sensor is arranged near the coils, different from the embodiment, there is a high possibility that oil drops on the temperature sensor. If oil drops on the temperature sensor, a detected temperature of the temperature sensor is a value closer to the temperature of oil than to the coil temperature, so it is difficult to accurately estimate the coil temperature.

On the other hand, when the correction sensor12that is the temperature sensor as described above is arranged so as to be in contact with a metal that constitutes the terminals58arranged at a point on which no oil drops and remote from the coils54, it is understood that the correlation between the temperature of the coils54and the terminal temperature is high. Thus, the observer22is able to highly accurately estimate the coil temperature by using the temperature of the terminals58on which no oil drops.

FIG. 8Ais a graph that shows the relationship between a coherence function and a motor torque. The coherence function expresses the correlation between the temperature of a point at which the temperature is maximum in the coils and the terminal temperature of the terminal block.FIG. 8Bis a graph that shows the relationship between a coherence function and an oil flow rate for the terminal temperature.

The coherence function is obtained by dividing the square of the absolute value of cross-spectrum by the power spectrum of each of measured input and the output of the system. The cross-spectrum is averaged by multiplying predetermined frequency components of spectra of signals of the coil temperature and terminal temperature with each other. A high coherence function indicates that the correlation between the coil temperature and the terminal temperature is high.

From the results shown inFIG. 8AandFIG. 8B, when the motor torque and the oil flow rate are used as parameters as well, the coherence function is high and is substantially higher than or equal to 0.8 irrespective of variations in motor torque and oil flow rate. Thus, it has been verified that the terminal temperature is usable for the observer22.

As for a change of the model, in a cooling manner of dropping oil to the coils, the degree of cooling of the coils significantly depends on the flow state of oil. The biggest factor that dominates the flow state of oil is the inclination of the motor with respect to the longitudinal direction of the motor due to pitch movement of the vehicle. In the embodiment, the model unit is changed by using the inclination of the vehicle as a parameter, so it is possible to improve the accuracy of estimating the coil temperature.

FIG. 9is a view that shows another example of the thermal resistance model of the coils, which is used in the estimator10according to the embodiment. In another example shown inFIG. 9, the heat transfer path from a portion that has the atmospheric temperature to the terminal58is omitted from the model shown inFIG. 4. The model shown inFIG. 9is effectively applicable to the case where transfer of heat into the engine room through the stator core53(FIG. 1), the motor case, and the like, is small. For this reason, the relational expressions that express the model shown inFIG. 9are obtained by omitting the terms including the atmospheric temperature Ta and the thermal resistances Ra, Rb from the mathematical expressions (1) and (2). InFIG. 2, the atmospheric temperature sensor33is omitted. The remaining configuration and operation are similar to the configuration shown inFIG. 1toFIG. 4.

FIG. 10,FIG. 11AandFIG. 11Bshow the results of checking the accuracy of estimating the coil temperature according to the embodiment.FIG. 10is a graph that shows the results of experiment in which the ratio of errors in estimated values of coil temperature in the estimator according to the embodiment to errors in estimated values of coil temperature in a temperature estimator according to a comparative embodiment is obtained where the errors in the estimated values of coil temperature in the temperature estimator according to the comparative embodiment is 1. The abscissa axis ofFIG. 10represents the reference numbers of a plurality of experimental patterns. In the comparative embodiment, the temperature sensor is arranged at a position indicated by the alternate long and two short dashes line G inFIG. 1, and the coil temperature is estimated from the temperature detected by the temperature sensor. In the embodiment, the configuration shown inFIG. 1toFIG. 3is used. InFIG. 10, the wide line C1indicates the comparative embodiment, and the narrow line C2indicates the embodiment. As is apparent from the results shown inFIG. 10, errors in estimating the coil temperature were significantly reduced in the embodiment as compared to the comparative embodiment.

FIG. 11Ais a graph that shows the results of experiment in which the relationship between an error in estimating a coil temperature and a motor torque is obtained in the estimator10according to the embodiment.FIG. 11Bis a graph that shows the results of experiment in which the relationship between an error in estimating a coil temperature and an oil flow rate is obtained. As is apparent from the results shown inFIG. 11AandFIG. 11B, in the embodiment, even when the motor torque or the oil flow rate varies, it is possible to reduce an error in estimating the coil temperature.

FIG. 12is a view that shows the configuration of an estimator system40according to an embodiment.FIG. 13is a view that shows a plurality of ranges in which a plurality of estimators41,42,43,44that constitute the estimator system40are respectively arranged in the motor50.

The estimator system40includes the four estimators41,42,43,44and selection means45. The configuration of each of the four estimators41,42,43,44is similar to the estimator10shown inFIG. 1toFIG. 3. As shown inFIG. 13, the stator coils of the motor50are allowed to be divided into a plurality of thermal masses by the ranges J1, J2, J3, J4each having the same length in the circumferential direction. The plurality of estimators41,42,43,44respectively estimate maximum temperatures T1, T2, T3, T4of the plurality of thermal masses. Specifically, the four estimators41,42,43,44respectively estimate the maximum temperatures of the four thermal masses J1, J2, J3, J4of the coils. Each of the estimators41,42,43,44may have a different thermal model. The estimated maximum temperatures T1, T2, T3, T4are input to the selection means45.

The selection means45selects the maximum temperature of the coils from among the estimated maximum temperatures T1, T2, T3, T4of the coils, respectively estimated by the four estimators41,42,43,44. Thus, the motor50serves as a model that expresses the distribution of heat, and the distribution of heat in the coils is allowed to be obtained. At this time, in the mathematical expressions (1) and (2), the heat capacity Ct of the coils, the estimated maximum coil temperature Tm, and the thermal resistances Rr, Ra form a matrix.

With the thus configured estimator system40, it is possible to acquire the distribution of the temperature of the coils by increasing the state quantities of the model unit23, so control that takes into consideration a local increase in temperature is possible. Thus, it is possible to reduce the degradation of the motor50due to heat.

In the above-described mathematical expression (1), an iron loss that takes into consideration a carrier frequency fc that is used in control over the motor may be included. The loss in this case is obtained by employing neIc2fc2as an eddy current loss with the use of a current ripple amount Ic due to a carrier, a proportionality constant ne and a carrier frequency fc instead of KeI2ω2in the mathematical expression (1) or by employing nhIc2fc as a hysteresis loss with the use of a proportionality constant nh. At this time, the carrier frequency fc calculated by a carrier frequency calculation unit38(FIG. 2) may be used as an input signal that is used in the observer22. Therefore, an input signal that is used in the estimator10may be a signal that indicates one or a plurality of the oil temperature To, the motor current I, the motor number of revolutions ω, the carrier frequency fc and the atmospheric temperature Ta.

The invention may be defined as follows. An estimator configured to estimate a temperature of a stator coil of an electric rotary machine, the electric rotary machine configured to be cooled by cooling oil, the estimator includes: an electronic control unit configured to calculate a state quantity by using an input signal and a relational expression that expresses a target model; and a correction signal measurement sensor configured to measure a correction signal for correcting the state quantity, the electronic control unit being configured to output a value for correcting the state quantity based on the correction signal, and change the relational expression that expresses the target model in accordance with an oil flow related value that relates to a change of flow of the cooling oil, the correction signal measurement sensor being arranged such that the correction signal measurement sensor is in contact with a metal member that includes a coil conductive wire that constitutes the stator coil, a terminal connected to the coil conductive wire, and a power line connected between the coil conductive wire and the terminal, at a point on which no cooling oil drops. An estimator system comprising: a plurality of estimators each configured to estimate a temperature of a stator coil of an electric rotary machine, the electric rotary machine configured to be cooled by cooling oil, the plurality of estimators each including an electronic control unit configured to calculate a state quantity by using an input signal and a relational expression that expresses a target model, and a correction signal measurement sensor configured to measure a correction signal for correcting the state quantity, each electronic control unit being configured to output a value for correcting the state quantity based on the correction signal, and change the relational expression that expresses the target model in accordance with an oil flow related value that relates to a change of flow of the cooling oil, the correction signal measurement sensor being arranged such that the correction signal measurement sensor is in contact with a metal member that includes a coil conductive wire that constitutes the stator coil, a terminal connected to the coil conductive wire, and a power line connected between the coil conductive wire and the terminal, at a point on which no cooling oil drops; and selection means configured to select a maximum temperature of the stator coil from among the temperatures of the stator coil, respectively estimated by the plurality of estimators.