Predictive detection device for electric vehicles

Abstract

To detect sign of deterioration or reduction of endurance of a dynamo-electric motor which has power generation function installed on an electric vehicle accurately.SOLUTION: A sign detection device for an electric vehicle is configured so as to find difference 8a between maximum value and minimum value adjoining each other among temperature variation of a dynamo-electric motor of which maximum value and minimum value appear repeatedly by changing to high and low by driving the dynamo-electric motor and at the same time to section 8b temperature difference into multiple categories according to magnitude and to find cumulative value 8c by accumulating the number of occurrences of the temperature difference for multiple categories and to calculate 8d ratio of the cumulative value to upper limit value, which is preset for the multiple categories, for the multiple categories and to find total value 8e of the ratio for the multiple categories and to output 8g alarm signal when the total value exceeds predefined threshold value 8f whereas the threshold value is predefined value on the basis of divergence amount between indication torque which indicates the output of the dynamo-electric motor and actual torque which is actually generated by the dynamo-electric motor by receiving indication of the indication torque.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a device for detecting signs of some kind of problem, such as abnormality or deterioration, in an electric motor with a power generating function in an electrically powered vehicle such as a battery electric vehicle (BEV) or a hybrid electric vehicle (HEV). [Background technology]

[0002] A device configured to detect or determine the degree of fatigue of the rotor of a rotating electric machine in an electric vehicle and notify the driver is described in Patent Document 1. The device described in Patent Document 1 is configured to detect the rotation speed of the rotor and the temperature of the rotating electric machine, measure the operating time of the rotating electric machine at a predetermined temperature, calculate the degree of fatigue of the rotor or a parameter related thereto based on the operating time, and limit the rotation speed or notify the driver or the like when the degree of fatigue or the parameter exceeds a predetermined threshold value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-158312 Summary of the Invention [Problem to be solved by the invention]

[0004] Fatigue and deterioration of generators, motor-generators (hereinafter collectively referred to as electric motors), or their rotors progress as the motor operates, and the higher the motor's temperature, the greater the degree of fatigue and deterioration. The device described in Patent Document 1 detects or determines the degree of fatigue based on the operating time of the rotating electric motor, enabling detection or determination based on the progression of fatigue and deterioration. Meanwhile, the temperature of an electric motor rises primarily due to heat generation caused by factors such as copper loss and iron loss. Iron loss is affected by the configuration of the core around which the electric wire is wound, and even with the same specifications such as torque, there are individual differences, with some motors being more susceptible to heat generation and others less susceptible to heat generation. Therefore, if electric motors are cooled uniformly or in a uniform manner, the temperature of electric motors that are prone to heat generation will increase over operating time, accelerating their fatigue and deterioration.

[0005] The device described in Patent Document 1 detects or determines the degree of fatigue based on the operating time of the rotating electric machine. However, since the relationship between operating time and the degree of fatigue or deterioration is not constant in electric motors with the above-mentioned individual differences, there is a possibility that an electric motor that is already significantly fatigued or has the potential to become significantly fatigued may be determined to have a low degree of fatigue because of its short operating time. Conversely, an electric motor that does not generate heat easily due to low loss may be determined to have a high degree of fatigue because of its long operating time, even though it has not yet become significantly fatigued or deteriorated. In other words, conventional methods have not taken individual differences into consideration when detecting or determining fatigue or deterioration, and there is still room for improvement in terms of improving the accuracy of determining the degree of fatigue or deterioration or durability of electric motors.

[0006] This invention has been made with an eye on the technical problems mentioned above, and aims to provide a device that can accurately detect signs of deterioration or reduced durability of electric motors such as generators and motor-generators in electric vehicles. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides an indicator detection device for an electric vehicle that detects indicators of deterioration or reduced durability of an electric motor with a power generating function that has a coil in which windings are held around a core made of laminated electromagnetic steel sheets, the indicator detecting device determining the difference between adjacent maximum and minimum values ​​in the temperature change of the electric motor, in which maximum and minimum values ​​repeatedly appear as the temperature change of the electric motor changes from high to low as the electric motor is driven, and dividing the difference into a plurality of groups according to the magnitude of the difference, accumulating the number of times the difference occurs for each of the plurality of groups to determine a cumulative value, calculating the ratio of the cumulative value to a predetermined upper limit value for each of the plurality of groups, determining the sum of the ratios for each of the plurality of groups, and outputting an alarm signal if the sum exceeds a predetermined threshold value, the threshold value being a value that is predetermined based on the amount of deviation between an instruction torque instructed to the electric motor and an actual torque that the electric motor actually generates in response to the instruction torque. [Effects of the Invention]

[0008] When an electric motor is operated, its temperature continuously fluctuates depending on factors such as the current value and the degree of cooling, resulting in alternating maximum and minimum values. The device of the present invention calculates the difference between the maximum and minimum values, divides the temperature into multiple categories, and calculates a cumulative value for each category. That is, the frequency of temperature changes is calculated for each category. The device then calculates the ratio of the cumulative value to a predetermined upper limit for each category. The upper limit can be a predetermined value based on, for example, the strength and durability of an electromagnetic steel sheet or the insulating resin applied to its surface. Therefore, the cumulative value can be the amount or degree of occurrence of factors that cause deterioration or reduced durability. If the cumulative value exceeds a predetermined threshold, a warning signal is output. The warning signal may be a signal to limit operation of the electric motor or a signal to notify the driver or user of the electric vehicle. Furthermore, since the threshold value is determined based on the deviation of the actual torque from the command torque, the threshold value reflects the individual differences expressed as the deviation, thereby eliminating the variation caused by individual differences in the motor and enabling accurate detection of signs of deterioration, etc. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a schematic diagram for explaining a control system of an electric motor and a drive system extending from the electric motor to drive wheels. [Figure 2] 2 is a schematic diagram showing a part of the coil and the laminated state of the electromagnetic steel sheets in the core. FIG. [Figure 3] FIG. 4 is a diagram illustrating the relationship between an instruction torque and an actual torque. [Figure 4] 4 is a diagram conceptually showing an example of a map in which threshold values ​​are determined according to the amount of decrease (deviation) of actual torque from command torque. FIG. [Figure 5] 10 is a diagram illustrating how the maximum and minimum values ​​of the motor temperature appear and the difference between them; FIG. [Figure 6] 10 is a graph illustrating divisions into which temperatures of maximum and minimum values ​​are divided, as well as cumulative values ​​and upper limit values ​​in each division. [Figure 7] FIG. 2 is a block diagram illustrating the functional configuration of a controller. [Figure 8] 3 is a flowchart illustrating an example of control in the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Next, an embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is merely an example of how the present invention can be implemented, and is not intended to limit the present invention.

[0011] The electric vehicle covered by this invention is a vehicle equipped with an electric motor 1, such as an electric vehicle (BEV) using only a motor as a driving force source or a hybrid vehicle (HEV, PHEV) using both an internal combustion engine (engine) and a motor as a driving force source. The electric motor 1 may be a generator that generates electricity when driven by an external force such as an engine, or a motor-generator that functions as both a generator and a motor. FIG. 1 shows a schematic diagram of an example of a vehicle equipped with an electric motor 1 with a power generating function as a driving force source, in which the electric motor 1 is connected to drive wheels 3 via a transmission mechanism (T / M) 2. The electric motor 1 receives electric power to output drive torque and is rotated by an external force transmitted from the drive wheels 3 to generate electricity. A permanent magnet synchronous motor or an induction motor can be used. The electric motor 1 also has a coil 6 formed by winding an electric wire 5 around a core 4. FIG. 2 shows a schematic diagram of a portion of a coil 6 made of distributed windings of rectangular wire. The core 4 is formed into a cylindrical shape by laminating a large number of thin electromagnetic steel sheets 4a, and electric wires (windings) 5 are housed in slots formed on the inner periphery thereof.

[0012] The transmission mechanism 2 includes a gear train, a winding transmission mechanism such as a chain or belt, and a differential mechanism, and is configured to accelerate or decelerate the power output by the electric motor 1 and transmit it to the drive wheels 3. The transmission mechanism 2 may include a transmission that can change the speed ratio, or may be a transmission mechanism with a fixed speed ratio (gear ratio).

[0013] Although not specifically shown, a cooling mechanism is provided to cool the electric motor 1 with fluid (oil) or the like.

[0014] The electric motor 1 is connected to a storage battery (BAT) 8 via an inverter (INV) 7. The inverter 7 is controlled by a controller (CONT) 9 to control the rotation speed, power generation, or torque of the electric motor 1. The controller 9 is mainly composed of a microcomputer, and is configured to use input data and pre-stored data to perform calculations according to pre-stored programs and output control command signals to the inverter 7 and other components. The controller 9 is also configured to detect signs of deterioration or fatigue of the electric motor 1 before it reaches its limit and output a warning signal. To detect such signs, a temperature sensor 10 that detects the temperature of the electric motor 1 inputs a detection signal to the controller 9. If the warning signal is intended to notify the driver, a service engineer, or the like of the signs, an HMI (Human-Machine-Interface) 11, such as an LCD monitor, is connected to the controller 9.

[0015] The following describes the control of the controller 9 for detecting signs of deterioration. Heat generation and the resulting deterioration of the electric motor 1 vary depending on the thickness of the electromagnetic steel sheets 4a that make up the core 4 and the way in which the electromagnetic steel sheets 4a are laminated, even if the diameter and axial length of the windings 5 ​​and core 4 are the same. In other words, since there are individual differences among electric motors 1, the controller 9 is configured to reflect such individual differences and detect signs of deterioration or reduced durability. These individual differences appear, for example, as a discrepancy or difference between the command torque and the actual torque.

[0016] That is, if the electromagnetic steel sheets 4a are thin, eddy current loss can be reduced, but the number of electromagnetic steel sheets 4a increases, which increases the amount of insulating resin covering the surfaces of the electromagnetic steel sheets 4a, and this affects the output torque. Conversely, if the electromagnetic steel sheets 4a are thick, eddy current loss increases, but the fewer electromagnetic steel sheets 4a, the less insulating resin is required, which is advantageous in terms of maintaining torque. In this way, depending on the configuration of the core 4 made up of many electromagnetic steel sheets 4a, the actual torque may differ from the torque assumed in the design (specification torque).

[0017] To explain this graphically, Figure 3 shows the relationship between the command torque and the actual torque. The command torque is the torque that is expected to be output when a certain current is applied according to the design (specifications), and the actual torque is the actual torque of the electric motor 1. When the electric motor 1 is operated so as to achieve a certain command torque, if the actual torque matches or nearly matches the command torque, then the individual (electric motor) is an electric motor as expected in the design (or as expected in the specifications) (let's call it electric motor A), and the relationship between the command torque and the actual torque is as shown by the solid line in Figure 3. On the other hand, in the case of an individual (let's call it electric motor B) where the iron loss in coil 6 is greater than the loss expected in the design, the actual torque will be smaller than the command torque, and the relationship between the actual torque and the command torque will be as shown by the dashed line in Figure 3.

[0018] On the other hand, deterioration or a decrease in the durability of the electric motor 1 progresses as the temperature repeatedly rises due to heat generation. Therefore, the above-mentioned electric motor B is more susceptible to deterioration or has a lower tolerance for commanded torque than electric motor A. Therefore, the threshold value for determining deterioration or signs of deterioration is set smaller the greater the difference (deviation) between the commanded torque and the actual torque, i.e., for an individual (electric motor) that has greater losses and is more likely to generate heat than a specified electric motor. This is schematically shown in Figure 4. For an individual (electric motor) with low iron loss due to thin electromagnetic steel sheets 4a, the thinness of the electromagnetic steel sheets 4a increases the insulating resin layer, which is thought to make the resin more susceptible to sagging. Therefore, the threshold value is set to be more likely to cause a detection of deterioration or signs of deterioration. This threshold value can be determined in advance through experiments, simulations, etc., and stored in controller 9.

[0019] On the other hand, deterioration or reduced durability of the electric motor 1 due to wear of the insulating resin or electromagnetic steel sheet 4a occurs according to the temperature of the electric motor 1 and the amount of change in that temperature. Therefore, the controller 9 detects the temperature and change in the electric motor 1. An example of change in the electric motor temperature is shown schematically in Figure 5, in which the temperature of the electric motor 1 repeatedly rises and falls depending on the required torque, and local maximums and minimums repeatedly appear. Differences between local minimums and maximums that are adjacent in time, such as the difference between the local maximum P1 and the next local minimum p1 of the changing electric motor temperature, the difference between the local minimum p1 and the next local maximum P2, and the difference between that local maximum P2 and the next local minimum, are detected.

[0020] The larger the temperature difference, the greater the impact (i.e., damage) on the electric motor 1. Therefore, the detected temperature difference is divided into appropriately set temperature ranges. FIG. 6 shows these divisions, with temperature differences T1 to T2 (> T1) as division A, T2 to T3 (> T2) as division B, T3 to T4 (> T3) as division C, T4 to T5 (> T4) as division D, and T5 to T6 (> T5) as division E (similarly below). For each division, the temperature differences falling within that temperature range are accumulated to determine the number of occurrences (frequency) H2, H3, H4, H5, H6, etc. Upper limit values ​​G2, G3, G4, G5, G6, etc. are set for each division. These upper limit values ​​are the number of occurrences (frequency) at which the magnetic steel sheet 4a and its insulating resin reach their limit when a temperature change occurs that falls within the respective division. These upper limit values ​​can be determined in advance during design.

[0021] The controller 9 calculates the temperature difference, divides it into each division, calculates the frequency for each division, and then calculates the ratio (Hn / Gn) of the frequency (i.e., cumulative value) in each division to the upper limit value.The controller 9 then calculates the sum of these ratios (=H2 / G2+H3 / G3...+Hn / Gn).

[0022] The threshold value mentioned above is a threshold value for this total value, and when the total value reaches the threshold value, the controller 9 outputs an alarm signal. The alarm signal is a signal that indicates to the outside a sign of deterioration or a decrease in durability, such as the progression of deterioration or a decrease in durability, or the arrival of any of these predetermined states, and is a signal that restricts the operation of the motor 1, a signal that displays an indication of the sign on the HMI 11 shown in Fig. 1, or a signal that sounds an alarm from a speaker (not shown) attached to the HMI 10.

[0023] Therefore, as shown in FIG. 7, the controller 9 according to the embodiment of the present invention has the following functional configuration. It includes a temperature difference detector 9a that detects the temperature difference between the aforementioned maximum (minimum) value of the motor temperature when the motor 1 is operating and the adjacent minimum (maximum) value. This temperature difference can be determined from data obtained by the temperature sensor 10. It includes a division unit 9b that allocates the temperature difference to each of the aforementioned ranges, and an accumulation value calculator 9c that calculates an accumulation value Hn by accumulating the number of occurrences of the temperature differences allocated to each range. Each range is assigned an upper limit value Gn in advance, and it includes a ratio calculator 9d that calculates the ratio Hn / Gn between the ranges. It also includes a sum calculator 9e that calculates a sum by adding up the ratios Hn / Gn thus obtained for each range. Meanwhile, the controller 9 has the aforementioned threshold values ​​for each motor 1 (for each individual motor 1) input in advance. It also includes a comparison unit 9f that compares the aforementioned sum with the previously input threshold values. The comparator 9f also includes an alarm output unit 9g that outputs the above-mentioned alarm signal when the comparison result of the comparator 9f shows that the sum exceeds the threshold value.

[0024] An example of the control by the controller 9 described above will be explained with reference to the flowchart of Fig. 8. The control shown in Fig. 8 is executed each time the electric motor 1 is operated, and first, the temperature difference between the above-mentioned local maximum value (local minimum value) and the local minimum value (local maximum value) of the temperature of the electric motor 1 is detected (step S1). Next, the temperature differences detected successively are sorted into the above-mentioned sections A, B, C, etc. according to their magnitude (step S2), and the cumulative value Hn for each section is calculated (step S3).

[0025] It is determined whether the cumulative value Hn for each section is smaller than the upper limit Gn set for that section (step S4). If the determination in step S4 is affirmative, it means that the electromagnetic steel sheet 4a or the insulating resin on its surface has not been heated to a degree that would cause it to deteriorate. In this case, the aforementioned ratio Hn / Gn is calculated (step S5), and the sum of these ratios Hn / Gn is calculated (step S6). It is then determined whether the sum is equal to or greater than a threshold value (step S7).

[0026] If the determination in step S7 is affirmative, this means that deterioration or a decrease in durability of the electric motor 1 is progressing, and therefore a warning signal is output (step S8). Conversely, if the determination in step S7 is negative, that is, if the above-mentioned sum value has not reached the threshold value, the process returns to continue the above-mentioned control. Note that if the determination in step S4 is negative because the cumulative value Hn in any of the divisions has reached the upper limit value Gn set for that division, the process proceeds to the above-mentioned step S8, and a warning signal is output.

[0027] Therefore, in the above-described control, the threshold value for determining whether to output an alarm signal is a value that corresponds to the deviation between the command torque and the actual torque, and is a value that reflects individual differences, so that signs of deterioration or reduced durability of the electric motor 1 can be detected accurately or precisely, taking into account individual differences. [Explanation of symbols]

[0028] 1 electric motor 2 Transmission mechanism (T / M) 3 drive wheels 4 cores 4a electrical steel sheet 5. Wire (winding wire) 6 coils 7 Inverter (INV) 8 Storage battery (BAT) 9 Controller (CONT) 9a Temperature difference detection section 9b Section 9c Accumulation value calculation section 9d Ratio calculation section 9e Total value calculation section 9f Comparison section 9g alarm output section 10 Temperature Sensor 11 HMI

Claims

1. A symptom detection device for an electric vehicle that detects a symptom of deterioration or a decrease in durability of an electric motor having a power generating function and a coil in which a winding is held on a core made of laminated electromagnetic steel sheets, a temperature change of the electric motor, which changes high and low as the electric motor is driven, and in which maximum and minimum values ​​repeatedly appear, the difference between the maximum and minimum values ​​adjacent to each other is determined, and the difference is divided into a plurality of groups according to the magnitude of the difference; accumulating the number of occurrences of the difference for each of the plurality of sections to obtain a cumulative value; calculating a ratio of the cumulative value to an upper limit value that is preset for each of the plurality of categories, A sum of the ratios for each of the plurality of categories is calculated, When the sum exceeds a predetermined threshold value, an alarm signal is output. The threshold value is a value determined in advance based on the amount of deviation between the command torque commanded to the electric motor and the actual torque actually generated by the electric motor in response to the command of the command torque.

1. A warning sign detection device for an electric vehicle.

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