Motor deterioration determination device and method

Abstract

To properly notify a user of deterioration of a motor by improving determination accuracy of the deterioration of the motor mounted on a vehicle.SOLUTION: A motor deterioration determination device according to the present disclosure includes a first stress acquisition unit that acquires a first cumulative stress that is a time-accumulated value of a thermal stress acting on a predetermined member included in a motor mounted on a vehicle, a second stress acquisition unit that acquires a second cumulative stress that is a time-accumulated value of a mechanical stress applied to the motor according to a rotational motion of the motor based on at least a rotation speed of the motor, and a determination processing unit that compares the first cumulative stress with a first threshold value, compares the second cumulative stress with a second threshold value, and notifies a user of the vehicle of deterioration of the motor when at least one of the first and second cumulative stresses is equal to or greater than the first or second threshold value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a motor deterioration determination device and method for determining deterioration of a motor mounted on a vehicle. [Background technology]

[0002] Conventionally, a controller that determines the deterioration of a motor that includes an annular stator, a rotor, and a coil attached to the core of either the stator or the rotor is known (see, for example, Patent Document 1). This controller includes a first acquisition unit that acquires the impedance between the coil and the core, an estimation unit that estimates the total heat input to the motor based on the magnitude of the impedance between the coil and the core, and a determination unit that determines the remaining life due to thermal deterioration of the motor based on the total heat input estimated by the estimation unit. This makes it possible to determine the remaining life due to thermal deterioration of the motor, including the member that covers the coil and the adhesive interposed between the core and the coil, without destroying the motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2024-20736 Summary of the Invention [Problem to be solved by the invention]

[0004] However, even if only thermal degradation is taken into account when predicting the remaining life of a motor, it is difficult to improve the accuracy of the remaining life prediction, and it becomes impossible to properly notify the vehicle user of motor degradation.

[0005] Therefore, a main object of the present disclosure is to improve the accuracy of determining deterioration of a motor mounted on a vehicle and to make it possible to properly notify a user of the deterioration of the motor. [Means for solving the problem]

[0006] The motor deterioration determination device disclosed herein is a motor deterioration determination device that determines the deterioration of a motor mounted on a vehicle, and includes a first stress acquisition unit that acquires a first cumulative stress, which is a time-accumulated value of thermal stress acting on a specified component included in the motor; a second stress acquisition unit that acquires a second cumulative stress, which is a time-accumulated value of mechanical stress applied to the motor in accordance with the rotational movement of the motor, based at least on the rotation speed of the motor; and a determination processing unit that compares the first cumulative stress with a first threshold value and compares the second cumulative stress with a second threshold value, and notifies the user of the vehicle of deterioration of the motor when at least one of the first and second cumulative stresses becomes equal to or greater than the first or second threshold value.

[0007] The motor deterioration determination device disclosed herein includes a first stress acquisition unit, a second stress acquisition unit, and a determination processing unit. The first stress acquisition unit acquires a first cumulative stress, which is a time-accumulated value of thermal stress acting on a specific component included in the motor. The second stress acquisition unit acquires a second cumulative stress, which is a time-accumulated value of mechanical stress applied to the motor in response to the rotational motion of the motor, based at least on the motor's rotation speed. The determination processing unit then compares the first cumulative stress with a first threshold and the second cumulative stress with a second threshold, and notifies the vehicle user of motor deterioration when at least one of the first and second cumulative stresses exceeds the first or second threshold. In other words, in addition to thermal stress, mechanical stress is applied to the components of the motor in response to the rotational motion of the motor. Therefore, by obtaining the second cumulative stress, which is the time-accumulated value of mechanical stress, in addition to the first cumulative stress, and comparing the first and second cumulative stresses with the first or second threshold value, it becomes possible to improve the accuracy of determining deterioration of the motor installed in a vehicle and properly notify the user of the deterioration of the motor.

[0008] The motor may include a stator, a rotor, and a magnet embedded in the rotor, and the second stress acquisition unit may calculate a centrifugal force acting on the magnet based on the rotation speed of the motor and specifications of the rotor, and acquire a cyclic stress frequency as the second cumulative stress based on the calculated centrifugal force. In other words, in a motor with embedded magnets, centrifugal force acting in response to rotor rotation causes the magnet to move relative to the rotor, which in turn applies mechanical stress to the rotor. Therefore, by acquiring a cyclic stress frequency as the second cumulative stress based on the centrifugal force acting on the magnet, it is possible to accurately determine whether the motor has deteriorated based on the second cumulative stress.

[0009] Furthermore, the motor deterioration determination device may include a status acquisition unit that acquires the stress occurring in the rotor and the strength of the rotor based on the temperature of the motor, and the determination processing unit may correct the first and second thresholds based on the stress and the strength acquired by the status acquisition unit. This makes it possible to use first and second thresholds that take into account the stress occurring in the rotor and the strength of the rotor depending on the motor temperature when determining motor deterioration, thereby further improving the accuracy of determining motor deterioration.

[0010] The state acquisition unit may estimate the temperature of the rotor based on the value of the current flowing through the motor and the temperature of a coolant that cools the motor, and acquire the stress occurring in the rotor and the strength of the electromagnetic steel sheets that form the rotor based on the estimated rotor temperature. This makes it possible to accurately acquire the stress occurring in the rotor and the strength of the electromagnetic steel sheets that correspond to the motor temperature.

[0011] The motor deterioration determination method disclosed herein is a motor deterioration determination method for determining deterioration of a motor mounted on a vehicle, which obtains a first cumulative stress, which is a time-accumulated value of thermal stress acting on a specified component included in the motor, and obtains a second cumulative stress, which is a time-accumulated value of mechanical stress applied to the motor in accordance with the rotational movement of the motor, based at least on the rotation speed of the motor, compares the first cumulative stress with a first threshold value, and compares the second cumulative stress with a second threshold value, and notifies the user of the vehicle of deterioration of the motor when at least one of the first and second cumulative stresses becomes equal to or greater than the first or second threshold value.

[0012] In this method, by obtaining a first cumulative stress, which is the time-accumulated value of thermal stress, as well as a second cumulative stress, which is the time-accumulated value of mechanical stress, and comparing the first and second cumulative stresses with a first or second threshold value, it becomes possible to improve the accuracy of determining deterioration of a motor installed in a vehicle and appropriately notify the user of the deterioration of the motor. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic configuration diagram showing a vehicle including a motor deterioration determination device according to the present disclosure; [Figure 2] 6 is a flowchart illustrating a procedure for acquiring a second cumulative stress in the motor deterioration determination device of the present disclosure. [Figure 3] 10 is a flowchart illustrating a procedure for acquiring stress and strength of a rotor in a motor deterioration determination device according to the present disclosure. [Figure 4] 4 is a flowchart illustrating a procedure for determining motor deterioration in the motor deterioration determination device of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0014] Next, embodiments of the present disclosure will be described with reference to the drawings.

[0015] 1 is a schematic diagram showing a vehicle (electric vehicle) 1 including an electronic control unit (hereinafter referred to as "ECU") 10 that functions as a motor deterioration determination device of the present disclosure. As shown in the figure, the vehicle 1 is a battery electric vehicle (BEV) that includes, in addition to the ECU 10, a motor generator (motor) MG that drives a pair of drive wheels DW, a battery (electric storage device) 2, and an inverter 3.

[0016] The motor generator MG is a synchronous generator motor (three-phase AC motor) with embedded permanent magnets that includes a stator S and a rotor R. The stator S includes a stator core and three stator coils, namely, a U-phase coil, a V-phase coil, and a W-phase coil. The stator core of the stator S is formed, for example, by stacking multiple electromagnetic steel sheets formed into a substantially circular ring shape by press working and connecting them in the stacking direction. However, the stator core may also be formed into a ring shape by, for example, pressure-molding and sintering ferromagnetic powder. Furthermore, each of the three stator coils may be formed by electrically joining multiple segment coils (coil wires) or by electrically joining multiple cassette coils (concentrated winding coils).

[0017] The rotor R includes an annular rotor core RC and multiple permanent magnets RM embedded in the rotor core RC to form multiple magnetic poles. The rotor core RC is formed, for example, by laminating multiple magnetic steel sheets formed into annular shapes by pressing and connecting them in the lamination direction. The rotor core RC also has multiple through holes spaced circumferentially and extending axially. Each permanent magnet RM is positioned in its corresponding through hole, and the gap between each permanent magnet RM and its corresponding through hole is filled with a resin such as varnish. The rotor core RC is then fixed to the cylindrical rotor shaft by an interference fit, such as shrink fitting or press fitting.

[0018] The motor generator MG exchanges power with the battery 2 via an inverter 3. The battery 2 is, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery having a rated output voltage of about 400 to 800 V. The inverter 3 drives the motor generator MG and includes, for example, six transistors and six diodes connected in parallel to each transistor in the reverse direction. The inverter 3 is connected to the battery 2 via a system main relay SMR.

[0019] As shown in FIG. 1, the rotor R (rotor shaft) of the motor generator MG is connected to a pair of drive wheels DW via a reduction gear 4, a differential gear 5, and a drive shaft 6. The motor generator MG, the reduction gear 4, the differential gear 5, and a portion of each drive shaft 6 are housed in a transaxle case 7, forming a transaxle of the vehicle 1. A hydraulic oil reservoir that stores hydraulic oil (ATF) O as a lubricating / cooling medium is defined below the transaxle case 7, and the hydraulic oil O scooped up by the gears included in the reduction gear 4 and the differential gear 5 is supplied to the gears and bearings within the transaxle case 7 as lubrication / cooling targets via oil passages, guides, etc. (not shown).

[0020] Furthermore, in vehicle 1, a strainer 8 and an electric oil pump 9 are disposed within transaxle case 7. Strainer 8 is fixed within the hydraulic oil reservoir so that an intake port provided at the bottom, for example, opens downward. The intake port of electric oil pump 9 is connected to an oil outlet of strainer 8, and an air-cooled or water-cooled oil cooler (not shown) is connected to the discharge port of electric oil pump 9 via an oil pipe or the like (not shown). Hydraulic oil O that flows out of the oil cooler is supplied to the inside of rotor R of motor generator MG via an oil passage or the like (not shown), and is supplied from the inside of rotor R as a lubricating / cooling medium to stator S, the stator coil wound around stator S, the coil ends of the stator coil, etc.

[0021] In vehicle 1, oil passages are increased around stator S and the like so that a sufficient amount of hydraulic oil O (oil for insulation) can be distributed to parts of motor generator MG that require insulation. This increases the dielectric strength voltage of motor generator MG, enabling a higher voltage for battery 2 and faster switching of inverter 3. In addition, hydraulic oil O from electric oil pump 9 is also supplied to bearings and the like around motor generator MG, and the hydraulic oil O that has passed through objects to be lubricated and cooled, such as motor generator MG, flows down into the hydraulic oil reservoir.

[0022] The ECU 10 includes a computer having a CPU, ROM, RAM, input / output interfaces, etc., various drive circuits, various logic ICs, etc., and controls (switching control) the inverter 3. The ECU 10 also acquires an accelerator opening Acc indicating the depression amount of an accelerator pedal (not shown) detected by an accelerator opening sensor (accelerator pedal position sensor) 11, a vehicle speed V detected by a vehicle speed sensor 12, a wheel speed Vw of each drive wheel DW detected by a wheel speed sensor 13 provided for each drive wheel DW, a rotation speed Nm of the motor generator MG (rotor R) detected by a rotation speed sensor (resolver) 14, an oil temperature To which is the temperature of the hydraulic oil O detected by a temperature sensor 15, and the SOC (state of charge) of the battery 2, a permissible charge power Win (negative value), and a permissible discharge power Wout (positive value) calculated by a battery electronic control unit (hereinafter referred to as the “battery ECU”) 20 that manages the battery 2.

[0023] When vehicle 1 is traveling, ECU 10 sets a required torque required for traveling of vehicle 1 based on accelerator pedal position Acc and vehicle speed V, and sets the required torque as a torque command value Tr* to motor generator MG. Furthermore, ECU 10 sets d-axis and q-axis current command values ​​Id* and Iq* based on the required torque, and controls inverter 3 so that motor generator MG outputs torque corresponding to torque command value (required torque) Tr* to a pair of drive wheels DW within the ranges of allowable charge power Win and allowable discharge power Wout of battery 2. Furthermore, when braking vehicle 1, ECU 10 controls inverter 3 so that motor generator MG outputs a share of regenerative braking torque to a pair of drive wheels DW within the ranges of allowable charge power Win and allowable discharge power Wout of battery 2.

[0024] Furthermore, ECU 10 controls electric oil pump 9 based on the SOC of battery 2, oil temperature to, etc. Furthermore, ECU 10 displays various information to be notified to the driver on a display device 19 installed on an instrument panel (not shown) or the like of vehicle 1 as necessary. In order to determine deterioration of motor generator MG, ECU 10 has a first stress acquisition unit 101, a second stress acquisition unit 102, a state acquisition unit 103, and a determination processing unit 104 configured as functional blocks in cooperation with hardware such as a CPU and a plurality of programs installed in ROM.

[0025] Next, a procedure for determining deterioration of the motor generator MG by the ECU 10 will be described.

[0026] While the vehicle 1 is in system startup, the first stress acquisition unit 101 of the ECU 10 acquires, from a pre-created map (not shown), the time during which the motor-generator MG has been exposed to a high-temperature environment at a predetermined temperature (high-temperature storage time), corresponding to the impedance (capacitance) between the stator core and the stator coil, which is acquired separately, according to a procedure similar to that described in the above-mentioned Patent Document 1, and acquires a first cumulative stress St1 at predetermined time intervals by integrating the acquired time. The first cumulative stress St1 is a time-accumulated value of thermal stress acting on predetermined members (resin members) of the motor-generator MG, i.e., the coating member (enamel coating: predetermined member) of the stator coil (segment coil, etc.), hardened varnish, etc., and indicates the total amount of heat input to the motor-generator MG.

[0027] 2 at predetermined time intervals to acquire a second accumulated stress St2, which is a time-accumulated value of mechanical stress applied to the motor generator MG (rotor R) in response to the rotational motion of the motor generator MG. When the timing for executing the routine of FIG. 2 arrives, the second stress acquisition unit 102 acquires the rotation speed Nm of the motor generator MG (rotor R) detected by the rotation speed sensor 14 (step S100). Next, the second stress acquisition unit 102 determines whether an abnormality has occurred in the rotation speed sensor 14 by referring to the determination result of an abnormality determination routine that is executed separately (step S110).

[0028] If an abnormality has occurred in the rotation speed sensor 14 (step S110: YES), the second stress acquisition unit 102 acquires the wheel speed Vw of each drive wheel DW detected by the wheel speed sensor 13 and the gear ratio Gr of the reduction mechanism 4 (step S120), and calculates the rotation speed Nm of the motor generator MG based on the wheel speed Vw of each drive wheel DW and the gear ratio Gr of the reduction mechanism 4 (step S130).If an abnormality has not occurred in the rotation speed sensor 14 (step S110: NO), the processing of steps S120-S130 is skipped.

[0029] After the process of step S110 or S130, the second stress acquisition unit 102 calculates the centrifugal force fc acting on each permanent magnet Rm as the rotor R rotates based on the rotation speed Nm acquired in step S100 or calculated in step S130, as follows: fc=m×Nm 2 ×r (step S140), where "m" is the mass of the rotor R, and "r" is the distance from the axis of the rotor R to the center of gravity of the permanent magnet Rm. Then, the second stress acquisition unit 102 acquires, using the rainflow method, the repeated stress frequency based on the rotation speed Nm of the motor-generator MG from the time-series data of the centrifugal force fc including the centrifugal force fc calculated in step S140, as a second cumulative stress St2 (step S150), and temporarily ends the routine of FIG. 2.

[0030] Furthermore, while the vehicle 1 is in system startup, the state acquisition unit 103 of the ECU 10 executes the routine illustrated in FIG. 3 at predetermined time intervals to acquire the stress σ generated in the rotor R of the motor-generator MG and the strength Sp of the electromagnetic steel sheet forming the rotor core RC of the rotor R. When the timing for executing the routine of FIG. 3 arrives, the state acquisition unit 103 acquires the oil temperature To of the hydraulic oil O detected by the temperature sensor 15, as well as separately set torque command value Tr* and current command values ​​Id*, Iq* (step S200). After processing step S200, the state acquisition unit 103 derives the d-axis and q-axis actual currents Id, Iq flowing through the motor-generator MG corresponding to the torque command value Tr* and current command values ​​Id*, Iq* acquired in step S200 from a previously created actual current map (not shown) (step S210).

[0031] Next, ECU 10 derives the heat generation amount of motor-generator MG corresponding to the actual currents Id and Iq derived in step S210 from a heat generation amount map (not shown) created in advance, and also derives the amount of heat (heat absorption amount) absorbed by the hydraulic oil O from motor-generator MG corresponding to the oil temperature To acquired in step S200 from a heat absorption amount map (not shown) created in advance (step S220). Furthermore, in step S220, ECU 10 estimates the temperature Tm of rotor R (motor-generator MG) based on the difference between the heat generation amount of motor-generator MG and the heat absorption amount of hydraulic oil O. Then, ECU 10 derives the stress σ generated in rotor core RC (rotor R) corresponding to the temperature Tm of rotor R estimated in step S220 from a stress map (not shown) created in advance, and derives the strength Sp of the electromagnetic steel sheets corresponding to the temperature Tm estimated in step S220 from a strength map (not shown) created in advance (step S230), and temporarily ends the routine of FIG. 3.

[0032] After the first and second cumulative stresses St1 and St2, the stress σ, and the intensity Sp are acquired as described above, the determination processing unit 104 of the ECU 10 executes the routine shown in Fig. 4 at predetermined time intervals to determine whether the motor-generator MG has deteriorated. When the timing for executing the routine of Fig. 4 arrives, the determination processing unit 104 acquires the first and second cumulative stresses St1 and St2, the stress σ, and the intensity Sp (step S300). Furthermore, the determination processing unit 104 sets a first threshold value S1 to be compared with the first cumulative stress St1 and a second threshold value S2 to be compared with the second cumulative stress St2, based on the stress σ and the intensity Sp acquired in step S300 (step S310).

[0033] In step S310, the determination processor 104 sets the first threshold S1 to a predetermined base value S1b, corrects the first threshold S1 to be smaller by, for example, a predetermined constant value when the stress σ is equal to or greater than a predetermined value, and corrects the first threshold S1 to be smaller by, for example, a predetermined constant value when the strength Sp is less than a predetermined value. The base value S1b of the first threshold S1 may be determined based on, for example, the relationship between the high-temperature storage time and the tensile strength of the coated member (enamel coating). Also, in step S310, the determination processor 104 sets the second threshold S2 to a predetermined base value S2b, corrects the second threshold S2 to be smaller by, for example, a predetermined constant value when the stress σ is equal to or greater than a predetermined value, and corrects the second threshold S2 to be smaller by, for example, a predetermined constant value when the strength Sp is less than a predetermined value.

[0034] After setting the first and second thresholds S1 and S2, the judgment processing unit 104 determines whether the first cumulative stress St1 acquired in step S300 is less than the first threshold S1 set in step S310 (step S320). If the first cumulative stress St1 is less than the first threshold S1 (step S320: YES), the judgment processing unit 104 determines whether the second cumulative stress St2 acquired in step S300 is equal to or greater than the second threshold S2 set in step S310 (step S330).

[0035] If the first cumulative stress St1 is equal to or greater than the first threshold value S1 (step S320: NO), the determination processing unit 104 determines that the motor-generator MG has deteriorated due to accumulated thermal stress, turns on a predetermined warning light on the display device 19 to notify the user of the vehicle 1 of the deterioration of the motor-generator MG (step S340), and temporarily ends the routine of Fig. 4. Also, even if the first cumulative stress St1 is less than the first threshold value S1 (step S320: YES), if the second cumulative stress St2 is equal to or greater than the second threshold value S2 (step S330: YES), the determination processing unit 104 determines that the motor-generator MG has deteriorated due to accumulated mechanical stress, turns on a predetermined warning light on the display device 19 to notify the user of the vehicle 1 of the deterioration of the motor-generator MG (step S340), and temporarily ends the routine of Fig. 4. In contrast, if the first cumulative stress St1 is less than the first threshold value S1 (step S320: YES) and the second cumulative stress St2 is less than the second threshold value S2 (step S330: NO), the judgment processing unit 104 determines that both thermal stress and mechanical stress have not accumulated to that extent and that the motor generator MG has not deteriorated, and temporarily terminates the routine of Figure 4 without turning on the warning light in step S340.

[0036] As described above, ECU 10 serving as a motor deterioration determination device includes first stress acquisition unit 101, second stress acquisition unit 102, and determination processing unit 104. First stress acquisition unit 101 acquires first accumulated stress St1, which is a time-accumulated value of thermal stress acting on a predetermined member, such as a coated member (e.g., enamel coating) included in motor generator MG. Second stress acquisition unit 102 executes the routine of FIG. 2 to acquire second accumulated stress St2, which is a time-accumulated value of mechanical stress applied to motor generator MG in response to the rotational motion of motor generator MG (rotor R), based on at least the rotation speed Nm of motor generator MG (steps S100-S150 in FIG. 2).

[0037] Then, determination processing unit 104 compares first cumulative stress St1 with first threshold value S1 and second cumulative stress St2 with second threshold value S2 (steps S300-S330 in FIG. 4), and when at least one of first and second cumulative stresses St1, St2 becomes equal to or greater than first or second threshold value S1 or S2 (step S320: NO or S330: YES in FIG. 4), it notifies the user of vehicle 1 of deterioration of motor-generator MG via display device 19 (step S340 in FIG. 4). That is, in addition to thermal stress, mechanical stress is applied to the components of motor-generator MG, including rotor R, in accordance with the rotational movement of rotor R. Therefore, by acquiring the first cumulative stress St1, which is the time-accumulated value of thermal stress, and the second cumulative stress St2, which is the time-accumulated value of mechanical stress, and comparing the first and second cumulative stresses St1, St2 with the first or second threshold value S1, S2, it is possible to improve the accuracy of determining the deterioration of the motor-generator MG installed in the vehicle 1 and properly notify the user of the deterioration of the motor-generator MG.

[0038] The motor generator MG also includes a stator S, a rotor R, and a plurality of permanent magnets RM embedded in the rotor R. The second stress acquisition unit 102 calculates the centrifugal force fc acting on each permanent magnet RM based on the rotational speed Nm of the motor generator MG and specifications of the rotor R (step S140 in FIG. 2), and acquires a repetitive stress frequency as a second cumulative stress St2 based on the calculated centrifugal force fc (time-series data) (step S150 in FIG. 2). That is, in an embedded permanent magnet (IPM) motor generator MG, the centrifugal force fc acting in response to the rotation of the rotor R causes each permanent magnet RM to move slightly relative to the rotor core RC, and as a result, each permanent magnet RM applies mechanical stress to the rotor core RC. Therefore, by acquiring the repetitive stress frequency as the second cumulative stress St2 based on the time-series data of the centrifugal force fc acting on each permanent magnet RM, it becomes possible to accurately determine whether the motor generator MG has deteriorated based on the second cumulative stress St2.

[0039] Furthermore, ECU 10 as a motor deterioration determination device includes a status acquisition unit 103 that executes the routine of Fig. 3 to acquire the stress σ generated in rotor R (motor generator MG) and the strength Sp of the electromagnetic steel sheets forming rotor R (rotor core RC) based on the temperature (estimated temperature) Tm of rotor R. Furthermore, determination processing unit 104 corrects first and second threshold values ​​S1, S2 based on the stress σ and the strength Sp acquired by status acquisition unit 103 (step S310 of Fig. 4). As a result, when determining deterioration of motor generator MG, first and second threshold values ​​S1, S2 that take into account the stress σ generated in rotor R and the strength Sp of rotor R corresponding to the temperature Tm of motor generator MG (rotor R) can be used, thereby further improving the accuracy of determining deterioration of motor generator MG.

[0040] Furthermore, the state acquisition unit 103 estimates the temperature Tm of the rotor R based on the actual d-axis and q-axis currents Id, Iq flowing through the motor generator MG and the oil temperature To of the hydraulic oil (refrigerant) O that lubricates and cools the motor generator MG (steps S200-S220 in FIG. 3), and acquires the stress σ generated in the rotor R and the strength Sp of the electromagnetic steel sheets that form the rotor core RC based on the estimated temperature Tm of the rotor R (step S230 in FIG. 3). This makes it possible to accurately acquire the stress σ generated in the rotor R and the strength Sp of the electromagnetic steel sheets that correspond to the temperature Tm of the motor generator MG.

[0041] Note that the vehicle 1 is not limited to a battery electric vehicle, but may also be a hybrid vehicle (HEV or PHEV) that includes an internal combustion engine (engine) in addition to the battery 2 and the motor generator MG. Furthermore, in step S120 of FIG. 2, the vehicle speed V detected by the vehicle speed sensor V may be acquired instead of the wheel speed Vw of each drive wheel DW, and in step S130, the rotation speed Nm of the motor generator MG may be calculated from the vehicle speed V and the gear ratio Gr of the reduction mechanism 4. Furthermore, in step S150 of FIG. 2, the peak method, range method, range-mean method, range pair method, range pair-mean method, or full-wave method may be used instead of the rainflow method. Furthermore, the routine of FIG. 2 may be modified so that the repeated stress frequency is acquired as the second cumulative stress St2 based on the time series data of the rotation speed Nm instead of the time series data of the centrifugal force fc.

[0042] Furthermore, the torque command value (required torque) Tr* acquired in step S200 of FIG. 3 may be set based on the wheel speed Vw of each drive wheel DW and the accelerator pedal position Acc. Furthermore, the actual currents Id and Iq of the d-axis and q-axis may be derived from the current values ​​of each phase detected by a current sensor (not shown). Furthermore, the temperature Tm of the motor-generator MG may be estimated without considering the oil temperature To, i.e., the amount of heat absorbed by the hydraulic oil O. In addition, when estimating the temperature Tm of the motor-generator MG, the longitudinal acceleration and lateral acceleration of the vehicle 1 (the gradient of the oil level of the hydraulic oil O), the SOC of the battery 2, the temperature of the inverter 3, the characteristics of the power cables, the weight of the vehicle 1 (number of occupants, load), etc. may be taken into consideration.

[0043] The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present disclosure. Furthermore, the above-described embodiment is merely a specific form of the invention described in the Summary of the Invention, and does not limit the elements of the invention described in the Summary of the Invention. [Industrial Applicability]

[0044] The invention of the present disclosure can be used in the vehicle manufacturing industry and the like. [Explanation of symbols]

[0045] 1 vehicle, 2 battery, 3 inverter, 4 reduction mechanism, 5 differential gear, 6 drive shaft, 7 transaxle case, 8 strainer, 9 electric oil pump, 10 electronic control unit (ECU), 11 accelerator opening sensor, 12 vehicle speed sensor, 13 wheel speed sensor, 14 rotation speed sensor, 15 temperature sensor, 19 display device, 20 battery electronic control unit (battery ECU), 101 first stress acquisition unit, 102 second stress acquisition unit, 103 status acquisition unit, 104 judgment processing unit, MG motor generator MG, R rotor, RC rotor core, RM permanent magnet, S stator, S1 first threshold, S2 second threshold, St1 first cumulative stress, St2 second cumulative stress.

Claims

1. A motor deterioration determination device for determining deterioration of a motor mounted on a vehicle, comprising: a first stress acquisition unit that acquires a first cumulative stress, which is a time-accumulated value of thermal stress acting on a predetermined member included in the motor; a second stress acquisition unit that acquires, based on at least the rotation speed of the motor, a second cumulative stress that is a time-accumulated value of mechanical stress applied to the motor in response to rotational motion of the motor; a determination processing unit that compares the first cumulative stress with a first threshold value and the second cumulative stress with a second threshold value, and notifies a user of the vehicle of deterioration of the motor when at least one of the first and second cumulative stresses becomes equal to or greater than the first or second threshold value; A motor deterioration determination device comprising:

2. 2. The motor deterioration determination device according to claim 1, The motor includes a stator, a rotor, and a magnet embedded in the rotor; The second stress acquisition unit calculates the centrifugal force acting on the magnet based on the rotation speed of the motor and the specifications of the rotor, and acquires the repeated stress frequency as the second cumulative stress based on the calculated centrifugal force.

3. 3. The motor deterioration determination device according to claim 2, a state acquisition unit that acquires stress generated in the rotor and strength of the rotor based on the temperature of the motor; The motor deterioration determination device, wherein the determination processing unit corrects the first and second threshold values ​​based on the stress and the strength acquired by the state acquisition unit.

4. 4. The motor deterioration determination device according to claim 3, The status acquisition unit estimates the temperature of the rotor based on the value of the current flowing through the motor and the temperature of the refrigerant that cools the motor, and acquires the stress generated in the rotor and the strength of the electromagnetic steel plates that form the rotor based on the estimated rotor temperature.

5. A motor deterioration determination method for determining deterioration of a motor mounted on a vehicle, comprising: a first cumulative stress is acquired, which is a time-accumulated value of thermal stress acting on a predetermined member included in the motor, and a second cumulative stress is acquired, which is a time-accumulated value of mechanical stress applied to the motor in response to rotational motion of the motor, based on at least the rotation speed of the motor; comparing the first cumulative stress with a first threshold value and comparing the second cumulative stress with a second threshold value; notifying a user of the vehicle of deterioration of the motor when at least one of the first and second cumulative stresses becomes equal to or greater than the first or second threshold value; Motor deterioration determination method.

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