NV level determination system and NV level determination method

Abstract

To determine a level of NV (noise vibration) which occurs in a power transmission unit mounted on a vehicle with a simple configuration.SOLUTION: An NV level determination system 1 determines a noise vibration (NV) level which is a level of sound or vibration generated by a power transmission unit 60 of an electric vehicle 100, including: a rotor rotation angle recognition unit 11 for recognizing a rotation angle of a rotor 53 of a drive motor 50; a transmission error recognition unit 12 for, on the basis of a variability rate of a change amount of a rotation angle of the rotor 53 to a change amount of a rotation angle of an axle 71 in a state where an external force for making the axle 71 rotate at a predetermined rotation speed is applied to the axle 71 of the electric vehicle 100, recognizing a transmission error in the power transmission unit 60; and an NV level determination unit 13 for determining an NV level on the basis of the transmission error recognized by the transmission error recognition unit 12.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an NV level determination system and method for determining the level of NV (noise vibration) generated in a power transmission unit mounted on a vehicle. [Background technology]

[0002] Conventionally, a vibration testing device has been proposed that evaluates vibrations occurring in a vehicle reducer by fixing the reducer alone to a support stand of a testing device, attaching a vibration sensor to the reducer, and acquiring a signal from the vibration sensor while applying a rotational force to the reducer (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-132862 Summary of the Invention [Problem to be solved by the invention]

[0004] In the vibration testing device of the above-mentioned background art, in order to evaluate the vibration of a reducer removed from a vehicle, it is necessary to prepare equipment for fixing the reducer and applying a rotational force, and it is also necessary to prepare a measuring device for processing signals from a vibration sensor. The present invention has been made in consideration of the above background, and aims to provide an NV level determination system and an NV level determination method that can determine the level of NV (noise vibration) generated in a power transmission unit installed in a vehicle with a simple configuration. [Means for solving the problem]

[0005] A first aspect for achieving the above object is an NV level determination system for determining the noise vibration (NV) level, which is the level of sound or vibration generated from a power transmission unit, for an electric vehicle having a drive motor and a power transmission unit that transmits the driving force of the drive motor to wheels. The NV level determination system includes: a rotor rotation angle recognition unit that recognizes the rotation angle of the rotor of the drive motor; a transmission error recognition unit that recognizes the transmission error in the power transmission unit based on the degree of fluctuation in the change in rotation angle of the rotor relative to the change in rotation angle of the axle when an external force is applied to the axle of the electric vehicle to rotate the axle at a predetermined rotational speed; and an NV level determination unit that determines the NV level based on the transmission error recognized by the transmission error recognition unit.

[0006] In the above NV level determination system, the predetermined rotational speed may be set within a rotational speed range that includes, within an expected travel speed range of the electric vehicle, a rotational speed that corresponds to a travel speed at which the NV level is expected to be maximum.

[0007] In the above NV level determination system, the predetermined rotation speed may be set for each vehicle type of the electric vehicle.

[0008] As a second aspect for achieving the above object, there is provided an NV level determination method for determining the noise vibration (NV) level, which is the level of sound or vibration generated from a power transmission unit, for an electric vehicle having a drive motor and a power transmission unit that transmits the driving force of the drive motor to wheels, the NV level determination method including: a rotor rotation angle recognition unit that recognizes the rotation angle of the rotor of the drive motor; a transmission error recognition step that recognizes the transmission error in the gears that constitute the power transmission unit based on the degree of fluctuation in the change in rotation angle of the rotor relative to the change in rotation angle of the axle when an external force that rotates the axle at a predetermined rotation speed is applied to the axle of the electric vehicle; and a gear NV level determination step that determines the NV level based on the transmission error recognized in the transmission error recognition step. [Effects of the Invention]

[0009] According to the above NV level determination system and NV level determination method, the level of NV (noise vibration) generated in a power transmission unit mounted on a vehicle can be determined with a simple configuration. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is an explanatory diagram of the configuration of the NV level determination system. [Figure 2] FIG. 2 is an explanatory diagram for determining the NV level of a power transmission unit by the NV level determination system. [Figure 3] FIG. 3 is an explanatory diagram of a transmission system that applies an external force from the tire side of an electric vehicle to rotate a drive motor. [Figure 4] FIG. 4 is an explanatory diagram of the procedure for setting the rotational speed of the axle when determining the NV level. [Figure 5] FIG. 5 is a flowchart of the NV level determination process. DETAILED DESCRIPTION OF THE INVENTION

[0011] [1.Configuration of NV level determination system] The configuration of an NV level determination system 1 of this embodiment will be described with reference to Figures 1 to 4. With reference to Figure 1, the NV level determination system 1 determines an NV (noise vibration) level, which is the level of sound or vibration generated in a power transmission unit 60 mounted on an electric vehicle 100.

[0012] The electric vehicle 100 is a battery electric vehicle (BEV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), a fuel cell vehicle (FCV), or the like, which is equipped with a drive motor 50.

[0013] The power transmission unit 60 transmits the driving force of the drive motor 50 to tires 70 connected to an axle (drive shaft) 71. The power transmission unit 60 is composed of a differential 61, multiple gears, etc. A resolver 52 that detects the rotation angle of the rotor of the drive motor 50 is provided on the motor shaft 51 of the drive motor 50.

[0014] The NV level determination system 1 is configured as part of the functions of an ECU (Electronic Control Unit) provided in the electric vehicle 100, and is connected to a resolver 52. When determining the NV level, the NV level determination system 1 is also connected to a measurement device 200 and communicates with the measurement device 200. The NV level determination system 1 includes a processor 10, a memory 20, and a communication unit 30.

[0015] The memory 20 stores a program 21 for controlling the NV level determination system 1 and data of a transmission error / NV level correspondence map 22 that associates the transmission error of the power transmission unit 60 with the NV level during operation of the power transmission unit 60. The transmission error / NV level correspondence map 22 will be described later.

[0016] The processor 10 loads and executes the program 21, thereby functioning as a rotor rotation angle recognition unit 11, a transmission error recognition unit 12, and an NV level determination unit 13. The processing executed by the rotor rotation angle recognition unit 11 corresponds to the rotor rotation angle recognition step in the NV level determination method of the present disclosure, and the processing executed by the transmission error recognition unit 12 corresponds to the transmission error recognition unit 12 in the NV level determination method of the present disclosure. The processing executed by the NV level determination unit 13 corresponds to the NV level determination step in the NV level determination method of the present disclosure.

[0017] The rotor rotation angle recognition unit 11 recognizes the rotation angle of the rotor 53 of the drive motor 50 based on the rotor angle detection signal RSi output from the resolver 52. The transmission error recognition unit 12 recognizes the transmission error of the power transmission unit 60 by placing the electric vehicle 100 on a chassis base 250, bringing the tires 70 of the electric vehicle 100 into contact with rollers 210, and rotating the rollers 210 with roller motors 211 to rotate the tires 70 by an external force, as shown in FIG.

[0018] 3 shows how power is transmitted when the tire 70 is rotated by the roller 210. The driving force imparted to the tire 70 by the roller 210 is transmitted from the axle 71 to the motor shaft 51 of the driven drive motor 50 via the differential and multiple gears of the power transmission unit 60, causing the rotor 53 to rotate, and the rotation angle of the rotor 53 is detected by the resolver 52.

[0019] In an ideal state where there is no transmission error in the power transmission unit 60, the ratio of the amount of change Δθr in the rotational angle of the rotor 53 to the amount of change Δθd in the rotational angle of the axle 71 is a constant value that corresponds to the gear ratio of the power transmission unit 60. However, in reality, a transmission error in the power transmission unit 60 occurs when the rotational angle of the driven gear increases or decreases relative to the rotational angle of the drive gear due to errors in the gear tooth surface shape, etc.

[0020] Therefore, when the tire 70 is rotated at a predetermined rotational speed by the roller 210, the transmission error recognition unit 12 calculates the transmission error (meshing transmission error) of the power transmission unit 60 using the following equation (1) based on the degree of fluctuation in the change in rotational angle Δθr of the rotor 53 recognized by the rotor rotational angle recognition unit 11 relative to the change in rotational angle Δθd of the axle 71 (= tire rotational angle) according to the rotational speed. Transmission error = Δθd - Δθr × Zr / Zd (1) where Δθd is the amount of change in the rotation angle of the axle 71, Δθr is the amount of change in the rotation angle of the rotor 53 recognized by the rotor rotation angle recognition unit 11, Zr is the number of teeth of the driven gear, and Zd is the number of teeth of the drive gear.

[0021] The predetermined rotational speed at which the roller 210 rotates the tire 70 is determined by running a model vehicle of the same model as the electric vehicle 100 over an expected speed range and measuring the NV level at each speed, as shown in Fig. 4. In Fig. 4, the vertical axis represents the measured NV level, and the horizontal axis represents the axle rotational speed corresponding to the model vehicle's running speed, and the measured NV level (amplitude of vibration or sound volume) for each rotational speed is plotted. ΔRvd is the axle rotational speed range corresponding to the expected vehicle speed range.

[0022] In Figure 4, the NV level is at its maximum, Amax, when the rotation speed is Rv3, and it is estimated that a relatively large NV tends to occur at the rotation speed Rv3. Therefore, the predetermined rotation speed of the axle when recognizing the transmission error is set within the rotation speed range ΔRvs that includes Amax.

[0023] The NV level determination unit 13 applies the transmission error of the power transmission unit 60 recognized by the transmission error recognition unit 12 to the transmission error / NV level correspondence map 22 (see FIG. 1) to recognize the NV level of the power transmission unit 60. Here, the relationship between the NV level and the transmission error is expressed by the following equation (1). NV level = transmission error × mesh force × vibration transmission characteristics (1) Mesh force is the dynamic excitation force that strikes the gear tooth surface, and vibration transmission characteristics are the degree of performance of vibration isolation products (such as cases) that determine what type of vibration can be suppressed and to what extent.

[0024] According to the above formula (1), the larger the transmission error of the power transmission unit 60, the larger the NV level, so the NV level can be determined from the recognition results of the transmission error. The transmission error / NV level correspondence map 22 is created based on the results of tests and computer simulations targeting the model or specifications of the electric vehicle 100.

[0025] The NV level determination unit 13 compares the recognized NV level of the power transmission unit 60 with a determination threshold Ath (see FIG. 4) and determines the NV level of the power transmission unit 60 by dividing it into, for example, the following three stages. A judgment: Recognized NV level ≦ judgment threshold. B judgment: Judgment threshold < recognized NV level ≦ upper limit. C rating: Upper limit value < recognized NV level.

[0026] In the case of an A rating, the power transmission unit 60 is reused without taking measures against NV. If the result is B, the power transmission unit 60 is reused after taking measures against NV such as a dynamic damper. If the power transmission unit 60 is rated C, it is discarded and recycled.

[0027] [2. NV level determination process] The procedure for the NV level determination process executed by the NV level determination system 1 will be described with reference to the flowchart shown in Fig. 5. As described above with reference to Fig. 2, the NV level determination system 1 executes the process according to the flowchart shown in Fig. 5 with the electric vehicle 100 placed on the chassis base 250 and the tire 70 rotated at a predetermined rotational speed by the rollers 210.

[0028] 5, the transmission error recognition unit 12 receives and acquires rotational speed information EAi indicating the rotational speed (predetermined rotational speed) of the axle 71 from the measuring device 200. In the following step S2, the rotor rotational angle recognition unit 11 recognizes the rotational angle of the rotor 53 of the drive motor 50 from the rotor angle detection signal RSi of the resolver 52. In the next step S3, the transmission error recognition unit 12 recognizes the amount of change Δθd in the rotational angle of the axle 71 recognized from the predetermined rotational speed, and the amount of change Δθr in the rotational angle of the rotor 53 recognized by the rotor rotational angle recognition unit 11.

[0029] In the next step S4, the transmission error recognition unit 12 recognizes the transmission error of the power transmission unit 60 based on the degree of change in Δθr relative to Δθd using the above equation (1). In the following step S5, the NV level determination unit 13 applies the transmission error recognized by the transmission error recognition unit 12 to the transmission error / NV level correspondence map 22 to recognize the NV level of the power transmission unit 60.

[0030] In the next step S6, the NV level determination unit 13 compares the NV level of the recognized power transmission unit 60 with the determination threshold Ath, and determines the power transmission unit 60 as either an A determination, a B determination, or a C determination, as described above.

[0031] 3. Other Embodiments In the above embodiment, as shown in Figures 1 and 2, the axle 71 is rotated by rotating the tire 70 using the roller 210, but the axle 71 may also be rotated by applying an external force using another method, such as removing the tire 70 and connecting a rotating means to the hub.

[0032] In the above embodiment, the NV level determination system of the present disclosure is configured as part of the functions of an ECU mounted on the electric vehicle 100. However, it may also be configured as a dedicated system mounted on the electric vehicle 100. Alternatively, the NV level determination system of the present disclosure may be configured as a function of a vehicle management system 310 that communicates with the electric vehicle 100, as shown in FIG. 2. In this case, rotational speed information EAi indicating a predetermined rotational speed at which the tire 70 is to rotate is transmitted from the measurement device 200 to the vehicle management system 310, and rotor rotation angle information RAi indicating the rotation angle of the rotor 53 is transmitted from the electric vehicle 100 to the vehicle management system 310. The vehicle management system 310 then executes a process for determining the NV level of the power transmission unit 60, similar to the process according to the flowchart shown in FIG. 5.

[0033] 1 is a schematic diagram showing the configuration of the NV level determination system 1 divided by main processing content to facilitate understanding of the present invention, but the NV level determination system 1 may be divided into other sections. Furthermore, the processing of each component may be executed by a single hardware unit or multiple hardware units. Furthermore, the processing of each component shown in FIG. 5 may be executed by a single program or multiple programs.

[0034] 5. Configurations supported by the above embodiments The above embodiment is a specific example of the following configuration.

[0035] (Configuration 1) An NV level determination system for determining the noise vibration (NV) level, which is the level of sound or vibration generated from a power transmission unit, for an electric vehicle having a drive motor and a power transmission unit that transmits the driving force of the drive motor to wheels, the NV level determination system comprising: a rotor rotation angle recognition unit that recognizes the rotation angle of the rotor of the drive motor; a transmission error recognition unit that recognizes the transmission error in the power transmission unit based on the degree of fluctuation in the change in rotation angle of the rotor relative to the change in rotation angle of the axle when an external force is applied to the axle of the electric vehicle to rotate the axle at a predetermined rotation speed; and an NV level determination unit that determines the NV level based on the transmission error recognized by the transmission error recognition unit. According to the NV level determination system of configuration 1, the transmission error in the power transmission unit can be recognized and the NV level of the power transmission unit can be determined with a simple configuration in which an external force is applied from the axle side of the electric vehicle to rotate the axle, and the rotation angle of the rotor of the drive motor rotated by the power transmission unit is recognized.

[0036] (Configuration 2) An NV level determination system according to Configuration 1, wherein the predetermined rotational speed is set within a rotational speed range that includes a rotational speed corresponding to a traveling speed at which the NV level is expected to be maximum, among the expected traveling speed range of the electric vehicle. According to the NV level determination system of configuration 2, it is possible to determine the NV level under conditions corresponding to driving situations where there is a high possibility that noise and vibrations that are bothersome to users of electric vehicles will occur.

[0037] (Configuration 3) The NV level determination system according to Configuration 2, wherein the predetermined rotation speed is set for each vehicle type of the electric vehicle. According to the NV level determination system of configuration 3, the predetermined rotation speed for determining the NV level can be appropriately set according to the specifications of the power transmission system, which differ depending on the model of the electric vehicle.

[0038] (Configuration 4) An NV level determination method for determining the noise vibration (NV) level, which is the level of sound or vibration generated from a power transmission unit, for an electric vehicle having a drive motor and a power transmission unit that transmits the driving force of the drive motor to wheels, the NV level determination method including: a rotor rotation angle recognition unit that recognizes the rotation angle of the rotor of the drive motor; a transmission error recognition step that recognizes the transmission error in a gear that constitutes the power transmission unit based on the degree of fluctuation in the change in rotation angle of the rotor relative to the change in rotation angle of the axle when an external force that rotates the axle at a predetermined rotation speed is applied to the axle of the electric vehicle; and a gear NV level determination step that determines the NV level based on the transmission error recognized in the transmission error recognition step. By executing the NV level determination method of the fourth configuration by a computer, the same effects as those of the NV level determination system of the first configuration can be obtained. [Explanation of symbols]

[0039] 1...NV level determination system, 10...processor, 11...rotor rotation angle recognition unit, 12...transmission error recognition unit, 13...NV level determination unit, 20...memory, 21...program, 22...transmission error / NV level correspondence map, 50...drive motor, 52...motor shaft, 52...resolver, 53...rotor, 60...power transmission unit, 62...differential device, 70...tire, 71...axle, 100...electric vehicle, 200...measuring device, 210...roller, 211...roller motor, 300...communication network, 310...vehicle management system.

Claims

1. 1. A noise and vibration (NV) level determination system for an electric vehicle having a drive motor and a power transmission unit that transmits driving force of the drive motor to wheels, the NV level determination system determining a noise and vibration (NV) level, which is the level of sound or vibration generated from the power transmission unit, a rotor rotation angle recognition unit that recognizes a rotation angle of the rotor of the drive motor; a transmission error recognition unit that recognizes a transmission error in the power transmission unit based on a degree of fluctuation in a change in a rotation angle of the rotor relative to a change in a rotation angle of the axle when an external force that rotates the axle at a predetermined rotation speed is applied to the axle of the electric vehicle; an NV level determination unit that determines the NV level based on the transmission error recognized by the transmission error recognition unit; An NV level determination system comprising:

2. The predetermined rotation speed is set within a rotation speed range that includes a rotation speed corresponding to a traveling speed at which the NV level is expected to be maximum, among an expected traveling speed range of the electric vehicle. The NV level determination system according to claim 1 .

3. The predetermined rotation speed is set for each type of electric vehicle. The NV level determination system according to claim 2 .

4. 1. A noise and vibration (NV) level determination method for an electric vehicle having a drive motor and a power transmission unit that transmits a driving force of the drive motor to wheels, the method determining a noise and vibration (NV) level, which is a level of sound or vibration generated from the power transmission unit, comprising: a rotor rotation angle recognition unit that recognizes a rotation angle of the rotor of the drive motor; a transmission error recognition step of recognizing a transmission error in a gear constituting the power transmission unit based on a degree of fluctuation in a change in a rotation angle of the rotor relative to a change in a rotation angle of the axle when an external force that rotates the axle at a predetermined rotation speed is applied to the axle of the electric vehicle; a gear NV level determination step of determining the NV level based on the transmission error recognized in the transmission error recognition step; A method for determining an NV level, comprising:

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