Method for estimating the cause of abnormal noises

Abstract

This invention provides a method for estimating the cause of abnormal noise, which can distinguish between motor noise and gear noise at an abnormal level. [Solution] In a vehicle 10 equipped with a motor MG which is a power source for driving, and a power transmission device 16 including gears provided between the motor MG and the drive wheels 14, the method for estimating the cause of the abnormal noise is as follows: (a) If it is difficult to distinguish whether the cause of the abnormal noise is motor noise or gear noise using order analysis, then frequency F1, which is the peak frequency of the abnormal noise when the motor temperature THmg is at temperature T1, and frequency F2, which is the peak frequency of the abnormal noise when the motor MG is at temperature T2, are obtained, and (b) if the difference ΔF (=|F1-F2|) from frequency F1 to frequency F2 is greater than or equal to a predetermined judgment value ΔF_jdg determined based on the temperature change from temperature T1 to temperature T2, then it is estimated that the cause of the abnormal noise is motor noise of order p.

Description

Technical Field

[0001] The present invention relates to a vehicle including a motor as a power source for traveling and a power transmission device including a gear provided between the motor and drive wheels, and a method for estimating the cause of abnormal noise generated.

Background Art

[0002] A method for estimating the cause of abnormal noise generated in a vehicle by order analysis is known. For example, the method for estimating the cause of abnormal noise described in Patent Document 1 is such a method. Here, "order analysis" means analyzing the order of noise (= noise, which may include vibration in addition to sound) generated along with rotational motion. "Order" is, for example, a frequency (= vibration number) that is a specific multiple of the rotational speed of a gear. Specifically, "second order" with an order of 2 is a frequency that is twice the vibration number of the rotational speed, and "third order" with an order of 3 is a frequency that is three times the vibration number of the rotational speed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in addition to the case of gears, the cause of abnormal noise may also be the motor. For example, in a vehicle including a motor as a power source for traveling and a power transmission device including a gear provided between the motor and drive wheels, the order of motor noise, which is noise generated by an electrical factor of the motor, and the order of gear noise, which is noise generated by a mechanical factor of the gear, may be the same or very close. In such a case, in the order analysis described in Patent Document 1, it is difficult to distinguish which of the motor noise and the gear noise is the cause of the abnormal noise.

[0005] The present invention was made against the above circumstances, and its objective is to provide a method for estimating the cause of abnormal noise, which can determine whether the abnormal noise is caused by motor noise or gear noise. [Means for solving the problem]

[0006] The gist of the present invention is a method for estimating the cause of an abnormal noise occurring in a vehicle equipped with a motor which is a power source for driving and a power transmission device including gears provided between the motor and the drive wheels, wherein (a) a first peak frequency of the abnormal noise is obtained when the motor temperature is at a first temperature and a second peak frequency of the abnormal noise is obtained when the motor temperature is at a second temperature different from the first temperature, and (b) if the difference between the first peak frequency and the second peak frequency is greater than or equal to a predetermined determination value based on the temperature change from the first temperature to the second temperature, it is estimated that the cause of the abnormal noise is motor noise generated by electrical factors of the motor, and otherwise it is estimated that the cause of the abnormal noise is gear noise generated by mechanical factors of the gears. [Effects of the Invention]

[0007] According to the method for estimating the cause of abnormal noise of the present invention, (a) a first peak frequency of the abnormal noise when the motor temperature is at a first temperature and a second peak frequency of the abnormal noise when the motor temperature is at a second temperature different from the first temperature are obtained, and (b) if the difference between the first peak frequency and the second peak frequency is greater than or equal to a predetermined determination value based on the temperature change from the first temperature to the second temperature, it is estimated that the cause of the abnormal noise is motor noise generated by electrical factors of the motor, and if not, it is estimated that the cause of the abnormal noise is gear noise generated by mechanical factors of the gear. When the cause of the abnormal noise is motor noise, the difference between the first peak frequency and the second peak frequency is larger than when it is gear noise. As a result, if the difference between the first peak frequency and the second peak frequency is greater than or equal to a predetermined determination value, it can be estimated that the cause of the abnormal noise is motor noise, and if it is greater than or equal to a predetermined determination value, it can be estimated that the cause of the abnormal noise is gear noise. In this way, it is possible to estimate whether motor noise or gear noise is causing the abnormal noise. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram of a vehicle to which the present invention is applied. [Figure 2] This diagram illustrates the order analysis and frequency analysis of noise (abnormal sounds) generated in vehicles. [Figure 3] This is an example of a flowchart illustrating the control operation of an electronic control device, and it illustrates the method for estimating the cause of abnormal noise according to the present invention. [Modes for carrying out the invention]

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that in the embodiments, the drawings have been simplified or modified as appropriate, and the dimensional ratios and shapes of each part are not necessarily depicted accurately. [Examples]

[0010] Figure 1 is a schematic diagram of a vehicle 10 to which the present invention is applied. The vehicle 10 is an electric vehicle equipped with a motor MG, which is a power source for driving, and a power transmission device 16 including gears provided between the motor MG and the drive wheels 14. The motor MG is a well-known so-called motor generator, for example, a synchronous motor. The power transmission device 16 includes, for example, an automatic transmission 20 and a differential gear 22, which have well-known configurations. The automatic transmission 20 is, for example, a planetary gear type or a normally meshing parallel shaft type.

[0011] The vehicle 10 includes a well-known inverter 50 and battery 52, and an electronic control unit 90. The motor MG is connected to the battery 52 via the inverter 50. The motor torque Tmg [N·m], which is the output torque of the motor MG, is controlled by the inverter 50 controlled by the electronic control unit 90.

[0012] The electronic control unit 90 is composed of, for example, a so-called microcomputer and performs various controls on the vehicle 10 by processing signals according to a pre-stored program. The vehicle 10 is capable of BEV (Battery Electric Vehicle) operation. Various signals (for example, motor rotation speed Nmg [rpm], which is the rotation speed of the motor MG; motor temperature THmg [℃], which is the temperature of the motor MG; vehicle speed V; and interior sound data Ds, which is the interior sound data of the vehicle) are input to the electronic control unit 90 based on detected values ​​from various sensors (for example, rotation speed sensor 80, temperature sensor 82, vehicle speed sensor 84, microphone 86, etc.). For example, the temperature sensor 82 is attached to the stator of the motor MG. Various command signals (for example, motor control signal Smg for controlling the motor MG, shift control signal Sat for executing shift control of the automatic transmission 20, and display control signal Sdis for controlling the display function of the display device 70, etc.) are output from the electronic control unit 90 to each device provided in the vehicle 10 (for example, inverter 50, automatic transmission 20, display device 70, etc.).

[0013] Figure 2 illustrates the order analysis and frequency analysis of noise (abnormal sound) generated in vehicle 10, where (a) is a diagram illustrating the order analysis of noise generated in vehicle 10, and (b) and (c) are diagrams illustrating the frequency analysis of abnormal sound.

[0014] For example, when the motor temperature THmg is at temperature T1, various types of noise are generated in the vehicle 10. The frequency at which the magnitude of each noise peaks (hereinafter referred to as the "peak frequency") increases in proportion to the vehicle speed, i.e., the axle rotation speed, which is the average of the rotational speeds of a pair of axles 24. Note that there is not necessarily only one peak frequency. For example, peak frequencies include motor p-th order (p is a natural number) and counter gear q-th order (q is a natural number). Motor p-th order noise is generated by electrical factors of the motor MG. Counter gear q-th order noise is generated by mechanical factors of the counter gear. p-th order and q-th order are the order of the respective noises. "Order" refers to the frequency, which is a specific multiple of the rotational speed of the rotating member that causes the noise. For example, "order 2" is the frequency, which is twice the frequency of the rotational speed of the rotating member that causes the noise. The order of each noise is predetermined based on structural design factors of the power transmission device 16 (e.g., the number of teeth on the gears, the gear ratio, the number of poles of the motor MG, the harmonic components of the motor MG's drive current, etc.). Specifically, "electrical factors" refer to noise of an order mainly caused by torque ripple of the motor MG. For example, 6th, 12th, 18th, and 24th order electrical noises that easily excite circumferential resonance of the motor MG. "Torque ripple" refers to the pulsation that occurs in the motor torque Tmg when the rotor of the motor MG is rotating, due to the interaction between the magnetic flux of the permanent magnets and the magnetic flux of the stator coils, which causes a variation in magnetic flux density. Specifically, "mechanical factors" refer to noise of an order mainly caused by elastic deformation based on the material and shape of the gears. Noise generated by electrical factors is more susceptible to temperature changes than noise generated by mechanical factors. Note that "motor p-order" corresponds to "motor noise" in this invention. "Counter gear q-order" corresponds to "gear noise" in this invention.

[0015] Figure 2(b) shows the relationship of noise magnitude at different frequencies when the motor temperature THmg is temperature T1, along the dashed line A shown in Figure 2(a). Here, "abnormal sound peak frequency" refers to the peak frequency of an abnormal sound when the noise magnitude exceeds a predetermined abnormal sound judgment value. "Acceptable sound peak frequency" refers to the peak frequency of an acceptable sound when the noise magnitude does not exceed a predetermined abnormal sound judgment value and is considered an acceptable sound. The abnormal sound judgment value is a predetermined judgment value used to determine whether the driver can tolerate the noise magnitude. The abnormal sound peak frequency when the motor temperature THmg is temperature T1 is denoted as frequency F1 [Hz]. Note that "temperature T1" and "frequency F1" correspond to "first temperature" and "first peak frequency" in this invention, respectively. Frequency F1 is the frequency value fa.

[0016] In Figure 2(a), the frequency value fa on the dashed line A intersects with the characteristics of the motor's p-order and the counter gear's q-order. Therefore, it can be inferred that the cause of the abnormal noise is at least one of the motor's p-order and the counter gear's q-order. However, because the characteristics of the motor's p-order and the counter gear's q-order are very close, it is difficult to determine whether the abnormal noise is caused by the motor's p-order or the counter gear's q-order.

[0017] Figure 2(c) shows the relationship between the magnitude of noise at different frequencies when the motor temperature THmg is at temperature T2 (>T1). The peak frequency of abnormal noise when the motor temperature THmg is at temperature T2 is denoted as frequency F2 [Hz]. Note that the magnitude of the noise at frequency F2 is not necessarily greater than or equal to the abnormal noise detection value. Frequency F2 only needs to correspond to the temperature change of the noise peaking at frequency F1. "Temperature T2" ​​and "frequency F2" correspond to "second temperature" and "second peak frequency" in this invention, respectively. Frequency F2 can be either frequency value fb or frequency value fc. When the motor p-th order is the cause of the abnormal noise, frequency F2 is frequency value fb, and when the counter gear q-th order is the cause of the abnormal noise, frequency F2 is frequency value fc.

[0018] When the motor temperature THmg changes, the amount of change from frequency F1 to frequency F2 differs depending on whether it is motor noise or gear noise. For example, if the motor's p-th order is the cause of the abnormal noise, the difference ΔF (=|F1-F2|) is larger compared to when the counter gear's q-th order is the cause of the abnormal noise. Note that "difference ΔF" corresponds to "the difference between the first peak frequency and the second peak frequency" in this invention.

[0019] Specifically, in the case of a p-order motor, the difference ΔF (=|fa-fb|) is greater than a predetermined judgment value ΔF_jdg[Hz](>0). In the case of a q-order counter gear, the difference ΔF (=|fa-fc|) is less than a predetermined judgment value ΔF_jdg. The predetermined judgment value ΔF_jdg is a value that has been experimentally or design-predetermined to enable differentiation between a p-order motor and a q-order counter gear when it is difficult to differentiate between them using order analysis, at temperatures T1 and T2. The predetermined judgment value ΔF_jdg is stored as a map for each combination of motor noise and gear noise that is the target of differentiation, for example, using temperatures T1 and T2 as parameters.

[0020] FIG. 3 is an example of a flowchart for explaining the control operation of the electronic control device 90, and explains the method for estimating the cause of abnormal noise of the present invention.

[0021] First, in step S10 (hereinafter, steps are omitted), the order of the noise that is a candidate for the cause of abnormal noise is specified by order analysis. After the execution of S10, in S20, it is determined whether or not there is an order of motor noise and an order of gear noise (hereinafter referred to as "difficult-to-separate order") that are difficult to separate in order analysis in the order of the noise specified in S10. If the determination in S20 is NO, in S30, each order of the noise specified in S10 is estimated to be the cause of abnormal noise. If the determination in S20 is YES, in S40, those other than the difficult-to-separate order among the orders of the noise specified in S10 are each estimated to be the cause of abnormal noise. After the execution of S40, in S50, it is determined whether or not the difficult-to-separate order is an order mainly caused by torque ripple. For example, it is determined that the order of the noise of the circular resonance that is likely to excite the radial resonance of the motor MG such as the second order of electricity is not an order mainly caused by torque ripple. Note that since the resonance frequency of the circular resonance is determined by the elastic deformation of the electromagnetic steel sheet of the motor MG, the influence of temperature change is small. If the determination in S50 is NO, in S60, it is not determined which of the difficult-to-separate orders is the cause of abnormal noise.

[0022] When the determination in S50 is YES, in S70, the motor temperature THmg is acquired as the temperature T1 and the sound data Ds1 of the in-vehicle sound at that time is acquired. After the execution of S70, in S80, the vehicle state is changed so that the motor temperature THmg changes. For example, the vehicle state is controlled so that the motor temperature THmg rises. For example, by increasing the drive current of the motor MG or increasing the rotational speed, the motor temperature THmg can be raised. After the execution of S80, in S90, the motor temperature THmg is acquired as the temperature T2 and the sound data Ds2 of the in-vehicle sound at that time is acquired. After the execution of S90, in S100, it is determined whether or not the difference ΔF from the frequency F1 in the sound data Ds1 to the frequency F2 in the sound data Ds2 is equal to or greater than a predetermined determination value ΔF_jdg. For example, the frequencies F1 and F2 are calculated by performing a fast Fourier transform on the sound data Ds1 and the sound data Ds2, respectively. When the determination in S100 is YES, in S110, regarding the difficulty separation order, it is presumed that the motor noise, that is, the p-th order of the motor is the cause of the abnormal sound. When the determination in S100 is NO, in S120, regarding the difficulty separation order, it is presumed that the gear noise, that is, the q-th order of the counter gear is the cause of the abnormal sound. After the execution of S30, after the execution of S60, after the execution of S110, and after the execution of S120, the flowchart ends in all cases. Incidentally, in S30, S40, S60, S110, and S120, the cause of the abnormal sound presumed in the display device 70 is displayed in all cases.

[0023] According to this embodiment, (a) when it is difficult to distinguish whether the cause of the abnormal noise is motor noise (motor p-order) or gear noise (counter gear q-order) using order analysis, the frequency F1 when the motor temperature THmg is at temperature T1 and the frequency F2 when the motor temperature THmg is at temperature T2 are obtained, and (b) if the difference ΔF (=|F1-F2|) from frequency F1 to frequency F2 is greater than or equal to a predetermined judgment value ΔF_jdg based on the temperature change from temperature T1 to temperature T2, it is estimated that the cause of the abnormal noise is motor noise (motor p-order), and otherwise it is estimated that the cause of the abnormal noise is gear noise (counter gear q-order). When the cause of the abnormal noise is motor noise (motor p-order), the difference ΔF is larger than when the cause is gear noise (counter gear q-order). As a result, if the difference ΔF is greater than or equal to a predetermined judgment value ΔF_jdg, it can be estimated that the cause of the abnormal noise is motor noise (motor p-order), and otherwise it can be estimated that the cause of the abnormal noise is gear noise (counter gear q-order). In this way, it is possible to estimate whether the abnormal noise is caused by motor noise or gear noise.

[0024] The above-described examples are embodiments of the present invention, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art, without departing from its spirit.

[0025] Unlike the embodiments described above, the present invention may also be applied when it is not difficult to distinguish whether the cause of the abnormal noise is motor noise (motor p-order) or gear noise (counter gear q-order) using order analysis. The "gear noise" in the present invention is not limited to the counter gear q-order exemplified in the embodiments described above, but may also be noise from other gears, such as planetary gear r-order (r is a natural number), which is noise generated by mechanical factors of the planetary gear. Note that r-order is the order of the noise. In the embodiments described above, the motor temperature THmg was the temperature of the motor MG detected by the temperature sensor 82, but it is not limited to this, and for example, the oil temperature detected by the oil temperature sensor of the motor MG's cooling oil may also be used. In short, the motor temperature THmg should be a temperature that changes similarly in response to the temperature rise and fall of the motor MG. For example, the motor temperature THmg learned from the drive current of the motor MG may also be used.

[0026] In the above-described embodiment, at S80 of the flowchart, the motor temperature THmg was raised from temperature T1 to temperature T2. However, the present invention is also applicable to a scenario where, for example, the motor temperature THmg is lowered from temperature T2 to temperature T1. In the above-described embodiment, at S80 of the flowchart, the vehicle state was changed so that the motor temperature THmg changed automatically by the electronic control device 90 without manual operation by the driver. However, the driver may be prompted by the display device 70 to change the motor temperature THmg, and the driver may manually change the vehicle state so that the motor temperature THmg changes. In the above-described embodiment, the judgment at S100 of the flowchart was clearly divided into YES and NO cases, and either S110 or S120 was executed. However, the present invention is not limited to this. For example, if both the motor p-order and the counter gear q-order are the cause of the abnormal noise, that is, the judgment at S90 will be both YES and NO. That is, both S110 and S120 will be executed.

[0027] In the above-described embodiment, frequency F1 was calculated based on sound data Ds1 of the in-vehicle sound, and frequency F2 was calculated based on sound data Ds2. However, frequencies F1 and F2 may also be calculated based on unit radiated sound data emitted from the units constituting the power transmission device 16 and vibration data of the vehicle body.

[0028] In the above-described embodiment, the cause of the abnormal noise was estimated after the abnormal noise occurred. However, it is also possible to acquire indoor sound data Ds in advance at various motor temperatures THmg, and based on that indoor sound data Ds, determine whether or not an abnormal noise occurred when the motor temperature THmg is at any given temperature, and if an abnormal noise occurred, estimate the cause of the abnormal noise.

[0029] The present invention may be implemented during the manufacture of the vehicle 10, or it may be implemented while the vehicle 10 is in operation after its sale. In the above-described embodiment, the vehicle 10 was an electric vehicle equipped with a motor MG but without an engine, but the invention is also applicable to a hybrid vehicle equipped with an engine along with the motor MG and capable of hybrid electric vehicle driving.

[0030] In the above-described embodiment, the estimation of the cause of the abnormal noise was performed in the electronic control unit 90, but the invention is not limited to this, and may be performed, for example, in an inspection device having a similar function to the electronic control unit 90 outside the vehicle 10. [Explanation of Symbols]

[0031] 10: Vehicle, 14: Drive wheels, 16: Power transmission device, F1: Frequency (first peak frequency), F2: Frequency (second peak frequency), MG: Motor, T1: Temperature (first temperature), T2: Temperature (second temperature), THmg: Motor temperature (motor temperature), ΔF: Difference (difference between the first peak frequency and the second peak frequency), ΔF_jdg: Predetermined judgment value

Claims

[Claim 1] A method for estimating the cause of an abnormal noise occurring in a vehicle equipped with a motor, which is a power source for driving, and a power transmission device including gears provided between the motor and the drive wheels, The first peak frequency of the abnormal sound when the motor temperature is a first temperature, and the second peak frequency of the abnormal sound when the motor temperature is a second temperature different from the first temperature are obtained. If the difference between the first peak frequency and the second peak frequency is greater than or equal to a predetermined determination value based on the temperature change from the first temperature to the second temperature, it is estimated that the cause of the abnormal noise is motor noise generated by electrical factors of the motor; otherwise, it is estimated that the cause of the abnormal noise is gear noise generated by mechanical factors of the gear. A method for estimating the cause of an abnormal sound, characterized by the features described above.

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