Noise reduction device for electric fans

Abstract

The present invention provides an electric fan noise reduction device that can reduce noise caused by the operation of the electric fan regardless of the vehicle's driving conditions. [Solution] A speaker 31 that outputs sound in the opposite phase to the noise generated by the electric fan 24 and a control unit 100 capable of controlling the speaker are provided. The frequency of the sound output from the speaker 31 is determined based on the rotational speed of the electric fan 24, and the intensity of the sound output from the speaker 31 is determined based on the vehicle speed such that it is lower when the vehicle speed is a predetermined set vehicle speed V1 (V2) than at other times. The speaker 31 is then output with the determined frequency and intensity, and the set vehicle speed V1 (V2) is set to the vehicle speed at which the direction of the wind passing over the leading edge P1 of the blade 24C of the electric fan 24 is parallel to a virtual line L100 connecting the leading edge P1 and the trailing edge P2 of the blade 24C.

Description

Technical Field

[0001] The present invention relates to a noise reduction device for an electric fan.

Background Art

[0002] Conventionally, in a vehicle, in addition to a heat exchanger through which a refrigerant supplied to a heat-generating component such as a motor flows, an electric fan may be mounted which is disposed opposite to the heat exchanger to cool the refrigerant. Also, in such a vehicle, reducing the noise generated by the electric fan has been studied.

[0003] For example, Patent Document 1 discloses a vehicle configured to store in advance a signal having the same amplitude and opposite phase as the noise generated when an electric fan rotates, and output the above signal as sound from a speaker during operation of the electric fan.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The operating state of the electric fan and the surrounding conditions during vehicle travel are not constant but change. Therefore, by using the configuration of Patent Document 1, if a sound having the same amplitude and opposite phase as the noise of the electric fan when the vehicle is stopped is preset by experiments or the like, and this sound is simply generated from the speaker during vehicle travel and during operation of the electric fan, there is a risk that the noise of the electric fan cannot be sufficiently reduced. Specifically, there is a risk that the sound output from the speaker does not appropriately cancel the noise of the electric fan, or that although the noise of the electric fan is canceled, a part of the sound output from the speaker remains as new noise. That is, the configuration of Patent Document 1 has room for improvement in reducing the noise caused by the operation of the electric fan during vehicle travel.

[0006] This invention has been made in view of the above circumstances, and aims to provide an electric fan noise reduction device that can reduce noise caused by the operation of the electric fan regardless of the vehicle's driving conditions. [Means for solving the problem]

[0007] The inventors of this invention have diligently researched the above-mentioned problem and obtained the following findings: The frequency of the noise generated by the electric fan is highly correlated with the rotational speed of the electric fan, and the intensity of the noise generated by the electric fan is highly correlated with the vehicle speed. Furthermore, they found that the intensity of the noise generated by the electric fan is lowest when the vehicle speed is such that the direction of the wind passing over the leading edge of the electric fan blade is parallel to an imaginary line connecting the leading and trailing edges of the blade.

[0008] The present invention is based on the above findings and provides an electric fan noise reduction device for a vehicle equipped with a component to be cooled, a heat exchanger through which a refrigerant supplied to the component to be cooled flows, and an electric fan positioned opposite the heat exchanger to cool the refrigerant, wherein the device comprises a speaker that outputs sound in opposite phase to the noise generated by the electric fan, and a control unit capable of controlling the speaker, wherein the control unit determines the frequency of the sound output from the speaker based on the rotational speed of the electric fan, determines the intensity of the sound output from the speaker based on the vehicle speed such that it is lower when the vehicle speed is a predetermined set vehicle speed than at other times, and outputs the sound of the determined frequency at the determined intensity from the speaker, the set vehicle speed is set to the vehicle speed at which the direction of the wind passing over the leading edge of the blade of the electric fan is parallel to an imaginary line connecting the leading edge and trailing edge of the blade (Claim 1).

[0009] In this configuration, the frequency of the sound output from the speaker is determined based on the rotational speed of the electric fan, which has a high correlation with the frequency of the noise generated by the electric fan, as described above. Therefore, regardless of the rotational speed of the electric fan, it is possible to output sound with the same frequency as the noise from the electric fan from the speaker, but in the opposite phase to the noise.

[0010] Furthermore, the sound intensity output from the speaker is set based on the vehicle speed, which has a high correlation with the noise intensity generated by the electric fan, as described above. In addition, when the vehicle speed is the set speed at which the direction of the wind passing over the leading edge of the electric fan's blade is parallel to a virtual line connecting the leading and trailing edges of the blade, the sound intensity from the speaker is reduced compared to other speeds. Therefore, regardless of the vehicle speed, the speaker can output sound of an appropriate intensity corresponding to the noise intensity generated by the electric fan.

[0011] Therefore, with this configuration, regardless of the rotation speed of the electric fan or the vehicle speed, that is, regardless of the vehicle's driving conditions, the noise from the electric fan can be canceled out by the sound output from the speaker, and the sound output from the speaker can be prevented from remaining as noise, thereby reducing the noise caused by the operation of the electric fan.

[0012] In the above configuration, preferably, the control unit increases the intensity of the sound output by the speaker as the vehicle speed is less than the set vehicle speed (Claim 2).

[0013] According to the inventors' findings, the lower the vehicle speed is compared to the set vehicle speed, the greater the noise intensity generated by the electric fan. Therefore, with this configuration, regardless of the vehicle speed, the intensity of the sound output from the speaker can be reliably matched to the noise intensity of the electric fan, thereby more reliably reducing the noise caused by the operation of the electric fan.

[0014] In the above configuration, preferably, the control unit increases the intensity of the sound generated by the speaker as the vehicle speed is greater than the set vehicle speed (Claim 3).

[0015] According to the findings of the inventors of the present application, the higher the vehicle speed is than the set vehicle speed, the greater the intensity of the noise generated by the electric fan. From this, according to this configuration, regardless of the vehicle speed, the intensity of the sound output from the speaker can be surely made to correspond to the noise intensity of the electric fan, and the noise caused by the operation of the electric fan can be more surely reduced.

[0016] In the above configuration, preferably, the control unit sets the set vehicle speed to a lower value as the rotational speed of the electric fan is lower (Claim 4).

[0017] According to the findings of the inventors of the present application, the lower the rotational speed of the electric fan is, the lower the vehicle speed at which the direction of the wind passing through the leading edge of the electric fan blade becomes parallel to the virtual line connecting the leading edge and the trailing edge of the blade, that is, the speed at which the intensity of the noise of the electric fan becomes minimum. From this, according to this configuration, the set vehicle speed can be set to an appropriate value.

Effects of the Invention

[0018] As described above, according to the present invention, the noise caused by the operation of the electric fan can be reduced regardless of the running state of the vehicle.

Brief Description of the Drawings

[0019] [Figure 1] It is a schematic configuration diagram showing a part of a vehicle to which a noise reduction device according to an embodiment of the present invention is applied. [Figure 2] It is a front view of the electric fan. [Figure 3] It is a functional block diagram showing a control system of the vehicle. [Figure 4] It is a graph showing the result of frequency analysis of the sound of the electric fan. [Figure 5] It is a graph showing the result of frequency analysis of the sound of the electric fan. [Figure 6] It is a graph showing the relationship between the vehicle speed and the intensity of the fan noise. [Figure 7] It is a graph showing the relationship between the vehicle speed and the intensity of the fan noise. [Figure 8]It is a diagram for explaining the air flow around the wing. [Figure 9] It is a diagram for explaining the air flow around the wing. [Figure 10] It is a diagram for explaining the air flow around the wing. [Figure 11] It is a flowchart showing the content of the control implemented by the sound signal generation unit. [Figure 12] It is a graph showing the relationship between the fan rotation speed and the command frequency. [Figure 13] It is a graph showing the relationship between the shutter opening degree and the correction coefficient.

Mode for Carrying Out the Invention

[0020] FIG. 1 is a schematic configuration diagram showing a part of a vehicle 1 to which a noise reduction device according to an embodiment of the present invention is applied. In this embodiment, the vehicle 1 is an electric vehicle. The vehicle 1 is equipped with a motor 10 used as a driving source and a battery 11 that supplies power to the motor 10. Further, the vehicle 1 is equipped with a DC / DC converter 12, an inverter 13, and an OBC (ON-BOARD CHARGER) 14 for electrical communication between the battery 11, the motor 10, and other electrical devices. Hereinafter, the motor 10, the battery 11, the DC / DC converter 12, the inverter 13, and the OBC 14 are collectively referred to as an electric drive unit 2. Also, the motor 10 used as a driving source is referred to as a driving motor 10.

[0021] Vehicle 1 is equipped with a cooling system 3 for cooling the electric drive unit 2. In this embodiment, the cooling system 3 cools the electric drive unit 2 using water as a coolant. The cooling system 3 includes a cooling water circuit 21 through which cooling water flows (circulates), a grill shutter 22, a radiator 23 provided on the cooling water circuit 21, an electric fan 24, and an electric water pump 25. The electric drive unit 2 is provided on the cooling water circuit 21. The cooling water circulates sequentially through each component of the electric drive unit 2, cooling them by exchanging heat with each component. In this embodiment, the cooling water passes through the DC / DC converter 12, inverter 13, OBC 14, and drive motor 10 in that order. The electric drive unit 2 described above corresponds to the "cooled component" of the present invention.

[0022] The radiator 23 is a device that cools the coolant circulating in the coolant circuit 21 by heat exchange. The radiator 23 cools the coolant by heat exchange between the coolant and the atmosphere. As shown in Figure 1, the radiator 23 is located at the front of the vehicle 1. When the vehicle is running, the radiator 23 is exposed to the airflow, and the coolant is further cooled by the action of the airflow. The electric water pump 25 is an electrically operated pump for pressurizing and pumping the coolant. In this embodiment, the electric water pump 25 is located in the coolant passage between the OBC 12 and the drive motor 10. The radiator 23 described above corresponds to the "heat exchanger" of the present invention.

[0023] The grill shutter 22 is located between the front grill 4 and the radiator 23, which are located at the front of the vehicle 1. The grill shutter 22 has a plurality of flaps 23A arranged in parallel in the vertical direction, and a motor 23B (hereinafter referred to as GS motor 23B) for rotating the flaps 23A. Each flap 23A is supported so as to be rotatable around an axis extending in the vehicle width direction, and the GS motor 23B rotates each flap 23A around this axis. The GS motor 23B rotates all flaps 23A simultaneously. By rotating the flaps 23A, the grill shutter 22 can be switched between a fully closed state, as shown by the dashed line in Figure 1, that is, a state in which there is almost no gap between the flaps 23A, and an open state, as shown by the solid line in Figure 1, that is, a state in which there is a gap between the flaps 23A. In the following, the opening degree of the grill shutter 22 when it is fully closed is defined as 0 degrees, and the rotation angle of the flap 23A from this fully closed state (α in Figure 1) is referred to as the opening degree of the grill shutter 22.

[0024] When the opening of the grill shutter 22 is less than a predetermined full-open equivalent opening, the larger the opening of the grill shutter 22, the greater the amount of airflow supplied to the radiator 23, and the better the cooling efficiency of the radiator 23. On the other hand, when the opening of the grill shutter 22 is greater than or equal to the full-open equivalent opening, the amount of airflow supplied to the radiator 23, and therefore the cooling efficiency of the radiator 23, remains almost the same regardless of the opening. The full-open equivalent opening is, for example, about 40 degrees.

[0025] The electric fan 24 is an electrically operated fan for cooling the coolant in the radiator 23. Figure 2 is a front view of the electric fan 24. The electric fan 24 has a motor 24A (hereinafter referred to as the fan motor 24A), a hub portion 24B connected to the fan motor 24A, and a plurality of blades 24C extending outward from the outer circumferential surface of the hub portion 24B. In this embodiment, the fan motor 24A is housed inside the hub portion 24B. Also, in this embodiment, the electric fan 24 is a propeller-type fan.

[0026] The electric fan 24 is positioned behind the radiator 23, opposite to it. That is, the electric fan 24 is positioned on the opposite side of the grill shutter 22 from the radiator 23 in the vehicle's longitudinal direction. When the electric fan 24 is driven and the blades 24C rotate, the air in front of the electric fan 24 is drawn in to the rear, increasing the amount of air supplied to the radiator 23. As a result, the coolant in the radiator 23 is cooled, and the cooling efficiency of the radiator 23 is improved.

[0027] Vehicle 1 is equipped with a noise reduction device 5 to reduce the noise generated by the electric fan 24 (hereinafter referred to as "noise from the electric fan 24" as appropriate). The noise reduction device 5 includes a speaker 31 and a microphone 32. The speaker 31 is a device that outputs sound, and as will be described later, the speaker 31 outputs sound that is out of phase with respect to the noise from the electric fan 24. The microphone 32 is a device that collects sound and converts the collected sound into an electrical signal. The electrical signal generated by the microphone 32 is used to detect the phase of the noise from the electric fan 24, and consequently, to output sound that is out of phase with respect to that noise from the speaker 31.

[0028] The speaker 31 and microphone 32 are positioned near the electric fan 24. For example, the speaker 31 and microphone 32 are fixed to the fan shroud 24F that surrounds the electric fan 24.

[0029] (Control system) Figure 3 is a functional block diagram showing the control system of vehicle 1. The PCM100 shown in this figure is a device mounted on the vehicle for comprehensively controlling various parts of vehicle 1. The PCM100 consists of a microcomputer that includes a processor (CPU) for performing various calculations, memory such as ROM and RAM, and various input / output buses. The PCM100 corresponds to the "control unit" in this invention.

[0030] The PCM100 is electrically connected to the vehicle speed sensor SN1, the water temperature sensor SN2, the battery current sensor SN3, the accelerator sensor SN4, and the microphone 32. Signals from these are input to the PCM100 sequentially. The vehicle speed sensor SN1 is a sensor that detects the vehicle speed, i.e., the speed of vehicle 1. The water temperature sensor SN2 is a sensor that detects the coolant temperature, which is the temperature of the coolant flowing through the coolant circuit 21. The battery current sensor SN3 is a sensor that detects the input and output current of the battery 11. The accelerator sensor SN4 is a sensor that detects the opening degree of the accelerator pedal (not shown) that is operated by the driver of the vehicle.

[0031] The PCM100 controls various parts of the vehicle 1 while performing various judgments and calculations based on input information from sensors SN1 to SN4 and the microphone 32. The PCM100 is electrically connected to the drive motor 10, electric water pump 25, fan motor 24A, GS motor 22B, speaker 31, etc., and outputs control signals to these devices based on the results of the above calculations.

[0032] The PCM100 functionally comprises a main control unit 101, a cooling system control unit 102, and an audio signal generation unit 103.

[0033] The main control unit 101 performs determinations and calculations related to the movement of the vehicle 1 and controls the drive motor 10. The main control unit 101 controls the drive motor 10 based on the accelerator opening detected by the accelerator sensor SN4, the State of Charge (SOC) of the battery 11, etc. The SOC of the battery 11 is calculated based on the input and output currents of the battery 11 detected by the battery current sensor SN3.

[0034] The cooling system control unit 102 performs determinations and calculations related to the cooling system 3 and controls the electric water pump 25, fan motor 24A, and GS motor 22B.

[0035] The cooling system control unit 102 controls the electric water pump 25 so that the cooling water temperature detected by the water temperature sensor SN2 falls within a predetermined range.

[0036] The cooling system control unit 102 sets a target value for the opening degree of the grill shutter 22 according to the coolant temperature detected by the water temperature sensor SN2, the vehicle speed, and the operating status of the A / C (air conditioner, not shown) installed in the vehicle 1, and controls the GS motor 22B to achieve this target. For example, when the coolant temperature is above a predetermined temperature, the cooling system control unit 102 controls the GS motor 22B so that the opening degree of the grill shutter 22 increases (towards the open side) as the vehicle speed increases.

[0037] The cooling system control unit 102 drives the fan motor 24A to operate the electric fan 24 when the temperature of the cooling water rises due to a high load on the motor 10, etc. For example, the cooling system control unit 102 operates the electric fan 24 when the load on the motor 10 increases due to the vehicle 1 towing a towed object such as a boat or trailer, or when the battery 11 is being rapidly charged. In addition, the cooling system control unit 102 increases the rotation speed of the electric fan 24 as the load on the motor 10 increases. In this embodiment, the rotation speed of the electric fan 24 can be switched between two rotation speeds (first rotation speed and second rotation speed).

[0038] As described above, driving the electric fan 24 increases the cooling efficiency of the radiator 23 and suppresses the temperature rise of the motor 10. However, the electric fan 24 generates noise when in operation. Therefore, in order to improve the ride comfort of the vehicle 1, it is necessary to reduce this noise, that is, the noise emitted from the electric fan 24. Here, if a sound with the same frequency as the noise emitted from the electric fan 24 is output from the speaker 31 with the same intensity and in opposite phase, the noise emitted from the electric fan 24 can be canceled out by the sound output from the speaker 31.

[0039] The sound signal generation unit 103 is the part that performs the noise reduction control described above. It generates a sound signal that cancels out the noise emitted from the electric fan 24 and controls the speaker 31 so that this sound is output from the speaker 31. Specifically, the sound signal generation unit 103 generates a sound signal with the same frequency and intensity as the noise emitted from the electric fan 24. In addition, based on the sound collected by the microphone 32, the sound signal generation unit 103 outputs a signal to the speaker 31 so that the speaker 31 emits sound in the opposite phase to the noise emitted from the electric fan 24.

[0040] In the following, we will first explain the findings obtained by the inventors of this application as a result of their diligent research regarding the frequency and intensity of noise emitted from the electric fan 24, and then explain the specific control implemented by the sound signal generation unit 103 based on these findings.

[0041] Figures 4 and 5 are graphs showing the frequency analysis results of the sound emitted from the electric fan, with the horizontal axis representing frequency and the vertical axis representing intensity. Figure 4 compares graphs for different fan speeds under the condition that the shutter opening is at or above the fully open position and the wind speed input to the electric fan 24 from the front is the same. Specifically, line L11 in Figure 4 is the graph when the fan speed is the first rotation speed, and line L12 is the graph when the fan speed is the second rotation speed. Figure 5 compares graphs for different wind speeds input to the electric fan 24 under the condition that the shutter opening is at or above the fully open position and the fan speed is the same. Specifically, line L21 in Figure 5 is the graph when the wind speed is greater than that of line L22.

[0042] As shown in Figure 4, the frequencies F11, F12, F13, and F14 at which the intensity is particularly high along line L11 are different from the frequencies F21, F22, and F23 at which the intensity is particularly high along line L12. On the other hand, as shown in Figure 5, the frequencies at which the intensity is particularly high along line L21 and the frequencies at which the intensity is particularly high along line L22 are the same (F11, F12, F13, and F14).

[0043] Of the sounds emitted from the electric fan 24, those perceived as noise by the driver are primarily those with frequencies that exhibit a particularly high intensity, as described above. Therefore, it can be said that the frequency of the noise emitted from the electric fan 24 does not change depending on the speed of the wind input to the electric fan 24 from the front, but rather changes depending on the fan speed. Here, vehicle speed and shutter opening generally only affect the speed of the wind input to the electric fan 24 from the front. Consequently, the frequency of the noise emitted from the electric fan 24 does not change depending on the vehicle speed or shutter opening, but rather changes depending on the fan speed. Hereafter, the noise emitted from the electric fan 24 will be referred to as fan noise. Also, the wind input to the electric fan 24 from the front will be referred to as input wind.

[0044] Figures 6 and 7 are graphs showing the relationship between vehicle speed and fan noise intensity when the shutter opening is equivalent to or greater than fully open. Figure 6 is the graph when the fan speed is at the first rotation speed, and Figure 7 is the graph when the fan speed is at the second rotation speed. In the graphs of Figures 6 and 7, the horizontal axis is vehicle speed, and the vertical axis is intensity. In Figure 7, the solid line L2 is the graph when the fan speed is at the second rotation speed, and the dashed line L31 is the line L31 shown in Figure 6, that is, the graph when the fan speed is at the first rotation speed.

[0045] As shown by line L31 in Figure 6, when the fan speed is at the first rotational speed, the intensity of the fan noise is lowest when the vehicle speed is a predetermined set vehicle speed V1. Furthermore, the intensity of the fan noise increases as the vehicle speed decreases from the set vehicle speed V1. In other words, when the vehicle speed is less than the set vehicle speed V1, the intensity of the fan noise increases as the vehicle speed decreases. Furthermore, the intensity of the fan noise increases as the vehicle speed increases from the set vehicle speed V1. In other words, when the vehicle speed is equal to or greater than the set vehicle speed V1, the intensity of the fan noise increases as the vehicle speed increases.

[0046] As shown by the solid line L32 in Figure 7, when the fan speed is at the second rotation speed, the intensity of the fan noise is lowest when the vehicle speed is at a predetermined set vehicle speed V2, just as it is when the fan speed is at the first rotation speed. Also, as with the first rotation speed, when the fan speed is at the second rotation speed, the intensity of the fan noise increases as the vehicle speed decreases from the set vehicle speed V2, and increases as the vehicle speed increases from the set vehicle speed V2. Furthermore, as is clear from comparing the solid line L32 and the dashed line L31 in Figure 7, the set vehicle speed V1 when the fan speed is at the first rotation speed is smaller than the set vehicle speed V2 when the fan speed is at the second rotation speed.

[0047] The relationship between vehicle speed and fan noise intensity is as described above and is thought to be due to the following reasons.

[0048] Figures 8 to 10 show parts of the VIII-VIII section of Figure 2, respectively. Figures 8 to 10 schematically show the airflow around the wing 24C, as calculated by the inventors, using dashed lines. Hereinafter, the imaginary line connecting the leading edge (the front edge of the wing 24C in the direction of travel Y1) P1 and the trailing edge (the rear edge of the wing 24C in the direction of travel Y1) P2 of the wing 24C is referred to as the reference line L100. The direction of airflow while driving, i.e., the longitudinal direction of the vehicle, is simply referred to as the longitudinal direction, the upstream side of the airflow direction, i.e., the front side in the longitudinal direction of the vehicle, is simply referred to as the front side, and the opposite side is simply referred to as the rear side.

[0049] In Figure 8, the direction of the wind W11 passing over the leading edge P1 of the wing 24C (hereinafter referred to as the leading edge wind) is from a position ahead of the reference line L100 toward the leading edge P1 of the wing 24C. In Figure 9, the direction of the leading edge wind W12 is from a position behind the reference line L100 toward the leading edge P1 of the wing 24C. In Figure 10, the direction of the leading edge wind W13 is parallel to the reference line L100.

[0050] As shown in Figures 8 and 9, when the direction of the leading edge winds W11 and W12 is not parallel to the reference line L100, vortices Z1 and Z2 are generated around the wing 24C. Specifically, when the direction of the leading edge wind W11 is as shown in Figure 8, vortex Z1 is generated on the rear surface of the wing 24C (the so-called underside of the wing 24C). When the direction of the leading edge wind W12 is as shown in Figure 9, vortex Z2 is generated on the front surface of the wing 24C (the so-called upper surface of the wing 24C). On the other hand, as shown in Figure 10, when the direction of the leading edge wind W13 is parallel to the reference line L100, almost no vortices are generated around the wing 24C.

[0051] As shown in Figures 8 to 10, the direction of the leading edge wind W11 (W12, W13) is determined by the direction of the input wind W21 (W22, W23) and the direction of the wind W31 (W32, W33) that acts relative to the wing 24C as the wing 24C rotates. Hereafter, the wind that acts relative to the wing 24C as the wing 24C rotates will be referred to as the circumferential wind. Specifically, the vector of the leading edge wind W11 (W12, W13) is the composite vector of the input wind W21 (W22, W23) vector and the circumferential wind W31 (W32, W33) vector.

[0052] The magnitude of the circumferential wind vector W31(W32,W33) is determined by the circumferential speed of the wing 24C, that is, the rotational speed of the electric fan 24. Therefore, when the rotational speed of the electric fan 24 is the same, the leading-edge wind vector W11(W12,W13) changes depending on the magnitude of the input wind vector W21(W22,W23), that is, the wind speed of the input wind W21(W22,W23).

[0053] Specifically, as shown in Figure 10, the reference input wind speed is defined as the wind speed of the input wind W23 when the direction of the leading edge wind W13 is parallel to the reference line L100. If the wind speed of the input wind is higher than this reference input wind speed, as shown in Figure 8, the direction of the leading edge wind W11 will be from a position ahead of the reference line L100 toward the leading edge P1. In this case, the higher the wind speed of the input wind W21, that is, the longer the length of the arrow indicated by W21, the larger the deviation θ between the direction of the leading edge wind W11 and the reference line L100 becomes.

[0054] On the other hand, when the input wind speed is lower than the reference input wind speed, the direction of the leading edge wind W12 is from a position behind the reference line L100 toward the leading edge P1, as shown in Figure 9. In this case, the lower the input wind speed W22, that is, the shorter the length of the arrow indicated by W22, the larger the deviation θ between the direction of the leading edge wind W12 and the reference line L100.

[0055] As described above, when the shutter opening is greater than or equal to the fully open opening, the amount of airflow supplied to the radiator 23 remains constant regardless of the opening. Therefore, when the shutter opening is greater than or equal to the fully open opening, the wind speed of the input air, which is the air input to the electric fan 24 from the front, is approximately proportional to the wind speed of the driving air and, consequently, to the vehicle speed. Furthermore, the larger the vortex, the greater the intensity of the fan noise, and the larger the deviation θ from the reference line L100 of the leading edge air direction, the larger the vortex.

[0056] Therefore, under the conditions that the shutter opening is equivalent to or greater than fully open, and the rotational speed of the electric fan 24 is the same, the intensity of the fan noise is lowest when the vehicle speed is at a predetermined set vehicle speed V1 (V2) and the direction of the leading edge airflow is parallel to the reference line L100, so no vortices are generated, as shown by line L1 in Figure 6 and solid line L2 in Figure 7. In other words, when the vehicle speed is at the set vehicle speed V1 (V2), the direction of the leading edge airflow is parallel to the reference line L100, so no vortices are generated. Furthermore, the intensity of the fan noise increases as the vehicle speed decreases from the set vehicle speed V1 (V2), and also increases as the vehicle speed increases from the set vehicle speed V1 (V2).

[0057] Furthermore, as shown by the dashed line in Figure 10, when the rotational speed of the electric fan 24 is low, the peripheral speed vector W133 becomes small. Therefore, when the rotational speed of the electric fan 24 is low, the input wind speed (reference input wind speed) W123 when the direction of the leading edge wind W113 is parallel to the reference line L100 also becomes small. As a result, as described above, the set vehicle speed V1 when the fan rotational speed is 1st rotational speed is smaller than the set vehicle speed V2 when the fan rotational speed is 2nd rotational speed.

[0058] Next, the control performed by the sound signal generation unit 103 will be explained using the flowchart in Figure 11. The flowchart in Figure 11 starts when the electric fan 24 is driven.

[0059] First, the sound signal generation unit 103 reads the vehicle speed detected by the vehicle speed sensor SN1, the fan speed (rotation speed of the electric fan 24), and the shutter opening (opening degree of the grill shutter 22) (step S1). Specifically, in step S1, the fan speed and shutter opening are read as target values ​​set by the cooling system control unit 102.

[0060] Next, the sound signal generation unit 103 sets a command frequency, which is the frequency of the inverse-phase sound, based on the fan speed read in step S1. There are multiple command frequencies corresponding to a single fan speed, and in step S2, multiple command frequencies corresponding to the fan speed are set. In this embodiment, the command frequencies for each fan speed are pre-set and stored in the PCM 100 as a map. The sound signal generation unit 103 extracts the value corresponding to the fan speed read in step S1 from the stored map and sets it as the command frequency. For example, as shown in Figure 12, four command frequencies F41 to F44 within the audible range are set for the first rotation speed, and three command frequencies F51 to F53 within the audible range are set for the second rotation speed. When the fan speed is the first rotation speed, the four command frequencies F41 to F44 are set as the command frequencies, and when the fan speed is the second rotation speed, the three command frequencies F51 to F54 are set as the command frequencies.

[0061] Next, the sound signal generation unit 103 identifies an intensity map to be used in step S6, described later, based on the fan speed (step S3). The intensity map is a map that defines the intensity of fan noise in relation to vehicle speed, and corresponds to line L31 in Figure 6 and solid line L32 in Figure 7. In other words, the PCM 100 stores an intensity map corresponding to line L31 in Figure 6 as the intensity map when the fan speed is the first rotation speed, which defines the relationship between vehicle speed and fan noise intensity when the shutter opening is at or above the fully open position. The PCM 100 also stores an intensity map corresponding to solid line L32 in Figure 7 as the intensity map when the fan speed is the second rotation speed, which defines the relationship between vehicle speed and fan noise intensity when the shutter opening is at or above the fully open position. In this embodiment, the intensity map can be switched according to the fan speed only, and the same intensity map is used even if the command frequency is different as long as the fan speed is the same.

[0062] Next, the sound signal generation unit 103 determines whether the shutter opening is greater than or equal to the fully open equivalent opening (step S4). As described above, the fully open equivalent opening is the shutter opening at which, regardless of the shutter opening, the amount of airflow supplied to the radiator 23, i.e., the wind speed, becomes constant, and is preset and stored.

[0063] If the determination in step S4 is YES and the shutter opening is greater than or equal to the fully open opening, the sound signal generation unit 103 extracts the fan noise intensity corresponding to the vehicle speed from the intensity map identified in step S4 and sets it to the command intensity (step S6). After step S6, the process proceeds to step S7.

[0064] As mentioned above, the input wind speed is correlated with the intensity of the fan noise. The intensity map identified in step S4 is a map that defines the relationship between the vehicle speed and the intensity of the fan noise when the shutter opening is equal to or greater than the fully open equivalent opening. When the shutter opening is less than the fully open equivalent opening, the input wind speed decreases as the shutter opening decreases. Therefore, when the shutter opening is less than the fully open equivalent opening, it is necessary to correct the vehicle speed and extract the fan noise intensity from the intensity map based on the corrected value. Specifically, it is necessary to correct the current vehicle speed to the vehicle speed at which the same input wind speed is achieved when the shutter opening is equal to or greater than the fully open equivalent opening, and then extract the fan noise intensity from the intensity map based on the corrected value.

[0065] If the determination in step S4 is NO and the shutter opening is less than the opening equivalent to the fully open position, in step S5, the sound signal generation unit 103 corrects the vehicle speed read in step S1 with the shutter opening to calculate the vehicle speed corresponding to the intensity map (vehicle speed for the map). After that, the sound signal generation unit 103 proceeds to step S6, where it extracts the fan noise intensity corresponding to the corrected vehicle speed (vehicle speed for the map) from the intensity map identified in step S4 and sets this as the command intensity.

[0066] In step S5, the sound signal generation unit 103 sets a correction coefficient K based on the shutter opening and vehicle speed, and calculates the corrected vehicle speed using the formula: corrected vehicle speed = (vehicle speed) × (correction coefficient K). The correction coefficient K is the ratio of the input wind speed to the input wind speed when the shutter opening is equal to or greater than the fully open opening, and is set to a value between 0 and 1.

[0067] Figure 13 is a graph showing the relationship between shutter opening and correction coefficient K in this embodiment. In Figure 13, lines L51, L52, L53, and L54 are lines with different vehicle speeds, with line L51 having the lowest vehicle speed, and lines L51, L52, L53, and L54 in ascending order of vehicle speed. As shown in Figure 13, the correction coefficient K is set to a larger value as the vehicle speed decreases, and also to a larger value as the shutter opening increases. Therefore, the vehicle speed for the map is set to a larger value as the shutter opening increases when the vehicle speed is the same.

[0068] After step S6, the sound signal generation unit 103 outputs a signal to the speaker 31 so that a sound of the command frequency set in step S2 is output from the speaker 31 at the command intensity set in step S6 (step S7). The speaker 31 receives this signal and outputs a sound of the command frequency set in step S2 at the command intensity set in step S6, and also outputs the sound so that its phase is out of phase with the fan noise, as described above.

[0069] (effect, etc.) As explained above, in the above embodiment, based on the knowledge that the frequency of fan noise depends on the rotational speed of the electric fan, the frequency of the sound output from speaker 31 is set based on the rotational speed of the electric fan. Therefore, speaker 31 can output a frequency equivalent to the frequency of fan noise.

[0070] Furthermore, in the above embodiment, based on the knowledge that the intensity of fan noise changes according to the vehicle speed, the command intensity, i.e., the intensity of the sound output from speaker 31, is set based on the vehicle speed. In addition, based on the knowledge that the intensity of fan noise is lowest when the vehicle speed is the set vehicle speed V1 (V2) and the direction of the leading edge airflow is parallel to the reference line L100, the intensity of the sound output from speaker 31 is set to be lowest when the vehicle speed is the set vehicle speed V1 (V2). Therefore, the intensity of the sound output from speaker 31 can be made equivalent to the intensity of fan noise.

[0071] As described above, according to this embodiment, a sound having the same frequency and intensity as the fan noise can be output from the speaker 31 in opposite phase to the fan noise. Therefore, the fan noise itself can be reduced, and the sound from the speaker 31 can be prevented from being transmitted as noise to the driver, etc., thus preventing noise from being generated due to the operation of the electric fan 24.

[0072] In particular, in the above embodiment, based on the finding that the fan noise intensity increases as the vehicle speed decreases when the vehicle speed is below the set vehicle speed, the command intensity is reduced as the vehicle speed decreases when the vehicle speed is below the set vehicle speed. Also, based on the finding that the fan noise intensity increases as the vehicle speed increases when the vehicle speed is above the set vehicle speed, the command intensity is increased as the vehicle speed increases when the vehicle speed is above the set vehicle speed. Therefore, regardless of the vehicle speed, the intensity of the sound output from the speaker 31 can be reliably matched to the intensity of the fan noise, and the noise caused by the operation of the electric fan 24 can be reduced more reliably.

[0073] Furthermore, the lower the rotational speed of the electric fan, the lower the set vehicle speed. Therefore, regardless of the rotational speed of the electric fan, at the vehicle speed where the direction of the leading edge airflow is parallel to the reference line L100 and the fan noise intensity is lowest, the intensity of the sound output from speaker 31 can be made lowest. In other words, the intensity of the sound output from speaker 31 can be appropriately matched to the intensity of the fan noise, and the noise caused by the operation of the electric fan 24 can be reduced more reliably.

[0074] (modified version) In the above embodiment, the intensity map is switched only according to the fan speed, and the same intensity map is used even if the command frequency is different as long as the fan speed is the same. However, the intensity map may also be switched according to the command frequency.

[0075] In the above embodiment, the case in which the rotational speed of the electric fan 24 is switched between two rotational speeds, a first rotational speed and a second rotational speed, was described, but the rotational speed of the electric fan 24 may be fixed to a single value. Also, the rotational speed of the electric fan 24 may be switched between three or more rotational speeds.

[0076] In the above embodiment, the case with a grill shutter 22 was described, but the grill shutter 22 may be omitted. If the grill shutter 22 is omitted, step S6, which corrects the vehicle speed according to the opening degree of the grill shutter 22, is also omitted.

[0077] Furthermore, the specific shape of the electric fan 24 is not limited to the above. Also, the specific conditions under which the electric fan 24 operates are not limited to the above. [Explanation of symbols]

[0078] 2. Electric drive unit (cooled component) 23. Radiator (heat exchanger) 24 Electric Fans 24A fan motor 24C wing 31 speakers 100 PCM (Control Unit) L100 Reference line (virtual line) P1 leading edge P2 trailing edge

Claims

1. A device for reducing noise from an electric fan, provided in a vehicle comprising a component to be cooled, a heat exchanger through which a refrigerant supplied to the component to be cooled flows, and an electric fan positioned opposite the heat exchanger to cool the refrigerant, A speaker that outputs sound in the opposite phase to the noise generated by the aforementioned electric fan, The system includes a control unit capable of controlling the aforementioned speaker, The control unit is The frequency of the sound output from the speaker is determined based on the rotation speed of the electric fan. The intensity of the sound output from the speaker is determined based on the vehicle speed such that it is lower when the vehicle speed is a predetermined set speed than at other times. The speaker outputs a sound of the determined frequency at the determined intensity. The noise reduction device for an electric fan is characterized in that the set vehicle speed is set to the vehicle speed at which the direction of the wind passing over the leading edge of the blade of the electric fan is parallel to a virtual line connecting the leading edge and the trailing edge of the blade.

2. In the noise reduction device for an electric fan according to claim 1, The control unit is a noise reduction device for an electric fan, characterized in that it increases the intensity of the sound output by the speaker as the vehicle speed is less than the set vehicle speed.

3. In the noise reduction device for an electric fan according to claim 1, The control unit is a noise reduction device for an electric fan, characterized in that it increases the intensity of the sound generated by the speaker as the vehicle speed is greater than the set vehicle speed.

4. In the noise reduction device for an electric fan according to claim 1, The control unit is characterized in that it sets the set vehicle speed to a lower value as the rotational speed of the electric fan decreases.

Images