JP2010173516A - Road noise reducing system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a road noise reducing system capable of changing the road noise reducing effect taking into consideration the degree of the road noise and the running state. <P>SOLUTION: The road noise reducing system changes the eigenvalue by the resonance vibration of a tire by changing the pneumatic pressure of the tire 12 by an air supply/exhaust device 11, and reduces the road noise at the frequency in a vicinity of the eigenvalue. When the pneumatic pressure of the tire 12 is changed, the same effect as that of changing the rigidity of the tire 12 which is one element for determining the eigenvalue by the resonance vibration of the tire 12 can be obtained, and the road noise can be reduced thereby. Further, the set upper limit level to be used for the determination whether or not the road noise is reduced is changed according to the running condition and the frequency range for reducing the road noise, and the road noise can be reduced more practically. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a road noise reduction system for reducing road noise of a vehicle.

  Conventionally, various techniques have been proposed for reducing road noise during vehicle travel. In the following Patent Document 1, a first tube and a second tube provided in a tire lumen are respectively referred to as a first air chamber and a second air chamber, and further, the first and second tubes and a tire outer surface. The air chamber surrounded by the air chamber is a third air chamber, and the resonance vibration frequency of the air resonance sound generated in each air chamber is configured to be different from each other to reduce road noise. Further, in Patent Document 2 below, road noise is reduced by forming a sub-air chamber that absorbs vibration around 250 Hz corresponding to the air resonance frequency of the tire in the rim of the vehicle wheel in the tire air chamber. Yes. Furthermore, in Patent Document 3 below, a metallic band is wound around the outer periphery of the rim, and by adjusting the tightening force of a fastener that tightens the band, the resonance vibration point of the rim can be adjusted, and road noise can be adjusted. The road noise can be reduced in consideration of the frequency distribution. Furthermore, in Patent Document 4 below, the pneumatic tire is provided with an extension block extending from the shoulder portion to the sidewall portion over the entire circumference of the tire, and the extension block is composed of a plurality of extension blocks having different cross-sectional heights. Thus, vibration in the tire cross-section height direction is suppressed in a relatively wide frequency band, and road noise is reduced.

JP 2006-248327 A JP 2004-291896 A JP-A-2005-145178 JP 2006-199101 A

  The technology for reducing road noise described in the above-mentioned patent document is a static road noise reduction technology in which the reduction effect cannot be changed during traveling, taking into account the degree of road noise and the traveling state. It is not a dynamic road noise reduction technology that can change the road noise reduction effect. This invention is made | formed in view of such a situation, and makes it a subject to provide a dynamic road noise reduction system.

  In order to solve the above-mentioned problems, a road noise reduction system according to the present invention is based on a level of noise detected by a noise detector provided in a passenger compartment of a resonance vibration frequency changing device that changes the frequency of resonance vibration of a tire. And controlling the frequency of the tire resonance vibration so that the noise level decreases when the noise level exceeds a set upper limit level.

  According to the road noise reduction system of the present invention, when the road noise detected in the passenger compartment is large during traveling of the vehicle, the road vibration noise is reduced by changing the resonance vibration frequency of the tire by the resonance vibration frequency changing device. It can be reduced. That is, the system can execute dynamic road noise reduction control based on noise actually heard by the passenger.

Aspects of the Invention

  Hereinafter, embodiments of the present invention will be described. Each of the following items (1) to (4) corresponds to each of claims 1 to 4.

(1) a resonance vibration frequency changing device for changing the frequency of the resonance vibration of the tire;
A noise detector that detects noise in the passenger compartment;
A road noise reduction system comprising a control device for controlling the resonance vibration frequency changing device,
When the noise level detected by the noise detector exceeds a set upper limit level, the control device executes noise reduction control for changing the frequency of the resonance vibration so that the detected noise level is reduced. Road noise reduction system configured to do.

  According to the aspect of this section, it is possible to reduce noise by changing the frequency of the resonance vibration of the tire. The inventor of the present application has obtained knowledge that road noise is reduced in the peripheral frequency region including the resonance vibration frequency when the resonance vibration frequency of the tire is changed, and this section is based on the knowledge. . In other words, if the vibration generated in the tire is close to the resonance vibration frequency, road noise increases due to mutual resonance.By changing the resonance vibration frequency, it is possible to reduce road noise due to resonance. is there.

  The “noise” in the aspect of this section may include not only road noise caused by resonance vibration of the tire but also all sounds generated from the vehicle such as engine sound and wind noise. In addition, the “noise level” in the aspect of this section is an index that represents the magnitude of noise, such as the sound pressure or amplitude of noise. In addition, the noise level is not limited to the noise level in the entire frequency range to be detected, for example, the noise level in the surrounding frequency range including the resonance vibration frequency, or the frequency not including the resonance vibration frequency. It is also possible to set the level based on only the noise in a specific frequency range extracted from the noise in the entire frequency range to be detected.

  The “set upper limit level” in the aspect of this section has a meaning as a threshold value for determining whether or not to perform noise reduction control. The setting upper limit level is not limited to a fixed value, and can be set to change based on some parameter. For example, it can be increased with increasing speed. In this way, the set upper limit level can be changed in accordance with the change in road noise accompanying the change in speed. In addition, when the noise level in a specific frequency range is compared with the noise level in a frequency range other than the specific frequency range extracted from the detected noise, the noise level in the specific frequency range is higher Alternatively, it is possible to adopt a mode in which noise reduction control is executed. In this case, the noise level in a frequency region other than the specific frequency region is the set upper limit level.

(2) The resonance vibration frequency changing device is a pneumatic pressure changing device that changes a tire pressure.
In the road noise reduction system, as the noise reduction control, when the noise level detected by the noise detector exceeds the set upper limit level, the tire pressure is reduced so that the detected noise level is reduced. The road noise reduction system according to item (1), which executes control to change the power.

  In the aspect of this section, the resonance vibration frequency changing device is a device that changes the tire air pressure. In other words, the aspect of this section is configured to change the resonance vibration frequency and reduce the road noise by changing the tire air pressure. As will be described in detail in [Example] described later, by changing the air pressure by the air pressure changing device, it is possible to obtain the same effect as changing the rigidity of the tire, and to change the resonance vibration frequency of the tire. . Therefore, road noise can be easily reduced by changing the resonance vibration frequency by the air pressure changing device.

(3) The resonance vibration frequency changing device is a rim width changing device that changes a rim width of a wheel,
In the road noise reduction system, as the noise reduction control, when the noise level detected by the noise detector exceeds the set upper limit level, the detected noise level is reduced. The road noise reduction system according to item (1), which executes control for changing a rim width.

  In the aspect of this section, the resonance vibration frequency changing device is a device that changes the rim width of the wheel. In other words, the aspect of this section is configured to change the resonance vibration frequency by changing the rim width and reduce the road noise. As will be described in detail later in [Example], by changing the rim width of the wheel, the same effect as changing the rigidity of the tire can be obtained, and the resonant vibration frequency of the tire can be changed. Therefore, road noise can be easily reduced by changing the resonance vibration frequency by the rim width changing device.

(4) The resonance vibration frequency changing device is a tire stiffness changing device that changes the stiffness of at least one of a tread portion and a sidewall portion of a tire,
In the road noise reduction system, as the noise reduction control, when the noise level detected by the noise detector exceeds the set upper limit level, the detected noise level is reduced. The road noise reduction system according to item (1), wherein control for changing the rigidity of at least one of the tread portion and the sidewall portion is executed.

  In the aspect of this section, the resonance vibration frequency changing device is a tire stiffness changing device that changes the stiffness of at least one of the tread portion and the sidewall portion of the tire. In other words, in the aspect of this section, the rigidity of the tire is changed by changing the rigidity of at least one of the tread portion and the sidewall portion of the tire, and thereby the resonance vibration frequency is changed to reduce road noise. It is done like that. The tire stiffness changing device, for example, changes the viscosity of a fluid by applying a magnetic field or an electric field to a magnetic fluid (MR fluid) or an electrorheological fluid (ER fluid) sealed in a tread portion or a sidewall portion of the tire. As a result, it is possible to change the resonance vibration frequency of the tire. It is possible to easily reduce road noise by changing the resonance vibration frequency of the tire by changing the viscosity of the fluid.

1 is a cross-sectional view showing one wheel of a vehicle in which a road noise reduction system according to a first embodiment of the present invention, that is, a system for reducing road noise by changing tire air pressure is provided. It is a block diagram which shows the structure regarding control of the road noise reduction system of 1st Example. It is a conceptual diagram which shows the resonant vibration of a tire. It is an experimental result which shows the mode of the reduction | decrease of road noise at the time of changing the tire air pressure. It is a graph which shows the relationship between the setting noise level which functions as a threshold value of the noise level for performing control which reduces road noise, and a vehicle speed. It is a flowchart of the road noise reduction program performed in the road noise reduction system of the Example of 1st Example. It is a flowchart of the high frequency side area | region noise reduction control subroutine performed in the road noise reduction control program of FIG. 6 in the case of 1st Example. 7 is a flowchart of a low frequency side region noise reduction control subroutine executed in the road noise reduction control program of FIG. 6 in the case of the first embodiment. FIG. 7 is a flowchart of a standard state realization control subroutine executed in the road noise reduction control program of FIG. 6 in the case of the first embodiment. It is sectional drawing which shows one wheel of the vehicle by which the road noise reduction system as 2nd Example of this invention, ie, the system which reduces a road noise by changing a rim width | variety, was arrange | positioned. It is a block diagram which shows the structure regarding control of the road noise reduction system of 2nd Example. It is a flowchart of the high frequency side area | region noise reduction control subroutine performed in the road noise reduction control program of FIG. 6 in the case of 2nd Example. It is a flowchart of the low frequency side area | region noise reduction control subroutine performed in the road noise reduction control program of FIG. 6 in the case of 2nd Example. 7 is a flowchart of a standard state realization control subroutine executed in the road noise reduction control program of FIG. 6 in the case of the second embodiment. It is sectional drawing which shows one wheel of the vehicle by which the road noise reduction system as 3rd Example of this invention, ie, the system which reduces road noise by the viscosity change of the magnetic fluid with which the inside of a tire was equipped, was arrange | positioned. It is a block diagram which shows the structure regarding control of the road noise reduction system of 3rd Example. It is a flowchart of the high frequency side area | region noise reduction control subroutine performed in the road noise reduction control program of FIG. 6 in the case of 3rd Example. It is a flowchart of the low frequency side area | region noise reduction control subroutine performed in the road noise reduction control program of FIG. 6 in the case of 3rd Example. FIG. 10 is a flowchart of a standard state realization control subroutine executed in the road noise reduction control program of FIG. 6 in the case of the third embodiment.

  Hereinafter, some embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to the following Example, It can implement in the various aspect which gave various change and improvement based on the knowledge of those skilled in the art.

A. Configuration of Road Noise Reduction System FIG. 1 shows one wheel in a vehicle equipped with the road noise reduction system of the first embodiment. The wheel 10 is connected to one air supply / discharge device 11 as described later. The vehicle is equipped with four wheels 10, and the air supply / discharge device 11 is connected to these four wheels. The air supply / discharge device 11 is configured to supply and exhaust air simultaneously to the tires 12 of the four wheels 10. Since the configuration of the four wheels 10 is the same, one wheel 10 that is a non-steered wheel and a non-driven wheel will be described here, and description of the other wheels 10 will be omitted.

  The wheel 10 includes a tire 12 and a wheel main body 14, and the tire 12 is fitted into the wheel main body 14. The wheel main body 14 is fixed to the axle 18 by a plurality of axle bolts 20 with the brake disc 16 sandwiched between the wheel main body 14 and the axle (axle) 18. The axle 18 is rotatably held on the axle carrier 24 via a bearing 22. Incidentally, the bearing 22 is fixed to the axle carrier 24 by a bearing bolt 26 at the outer ring portion thereof.

  The wheel body 14 can be divided into a rim portion 28 that is an outer peripheral portion into which the tire 12 is fitted, a hub portion 30 that is a central portion held by the axle 18, and a plurality of spoke portions 32 that connect them. it can. One of the plurality of spoke portions 32 is formed with an air passage 36 communicating with the inside of the tire 12 through an opening 34 provided in the rim portion 28, and the air passage 36 is formed in the axle 18. It is connected to the air passage 38. The air passage 38 communicates with the air supply / exhaust device 11 described above, and air supply to the tire 12 and exhaust from the tire 12 are performed via the air passages 36 and 40. Although a detailed description is omitted, the air supply / discharge device 11 includes a compressor, a control valve, and the like.

  The control of the air supply / discharge device 11 in the road noise reduction system of the present embodiment is performed by an electronic control unit (ECU) 60 whose control block diagram is shown in FIG. The ECU 60 includes a controller 62 configured mainly by a computer including a CPU, ROM, RAM, and the like, and a driver 64 having a drive circuit that drives the air supply / discharge device 11. The driver 64 is connected to the battery 68 via the converter 66, and the electric power for driving the compressor, control valve and the like of the air supply / discharge device 11 includes the converter 66 and the battery 68. Supplied from the power supply.

  Further, the vehicle includes an ignition switch [I / G] 70, a vehicle speed sensor [v] 72 for detecting the vehicle speed v, an air pressure sensor [P] 74 for detecting the air pressure of the tire 12, and a mode selection switch. [SW] 76, a sound pressure sensor [MC] 78 for detecting the level of noise perceived by the passenger, and the like are provided, and these sensors are connected to the controller 62. Incidentally, the sound pressure sensor 78 is a kind of noise detector mainly composed of a microphone, and is mounted inside the headrest of the driver's seat. In addition, the character in [] is a code | symbol used when the said sensor etc. are represented in drawing.

B. Changes in resonance vibration frequency due to changes in air pressure The tire resonance phenomenon appears as a periodic deformation of the tire. As shown in FIG. 3, there are mainly two vibrations having different frequencies from each other in the resonance vibration of the tire. Each can be called a primary resonance vibration and a secondary resonance vibration, and each becomes a vibration accompanied by deformation as shown in the figure. The thick line in the figure schematically represents the state of deformation of the tire in each resonance vibration. The frequency of these resonance vibrations, that is, the resonance vibration frequency is a specific value depending on the weight of the tire, the weight of the wheel, the rigidity of the tire, and the like. If the frequency of the primary resonance vibration is called a primary eigenvalue and the frequency of the secondary resonance vibration is called a secondary eigenvalue, the primary eigenvalue is generally about 100 Hz, and the secondary eigenvalue is about 300 Hz.

  As described above, the primary eigenvalue and the secondary eigenvalue depend on the tire stiffness, and the eigenvalue changes when the tire stiffness is changed. Generally, if the rigidity of a tire is increased, these eigenvalues become higher values. That is, if the rigidity of the tire is increased, the resonance vibration frequency is increased. The road noise reduction system of the present embodiment is configured to change the tire air pressure in order to change the tire stiffness. More specifically, the rigidity is increased by increasing the tire air pressure, and the rigidity is decreased by decreasing the tire air pressure.

  The graph of FIG. 4 shows the noise measurement result when the tire air pressure is changed, and shows the noise level obtained by the noise detector installed in the vehicle. This measurement result is a measurement result when the vehicle travels on a predetermined rough road. Incidentally, the horizontal axis represents noise frequency and the vertical axis represents sound pressure. In the graph, the change in the sound pressure of noise for each frequency when the tire air pressure is 350 kPa, 230 kPa, and 180 kPa is shown by a broken line, and the primary eigenvalue and the secondary eigenvalue at each air pressure are shown. Yes.

  As can be seen from the graph of FIG. 4, the primary eigenvalue and the secondary eigenvalue change depending on the change in tire air pressure. Specifically, when the air pressure is decreased to 350 kPa, 230 kPa, and 180 kPa, the primary eigenvalue near 100 Hz and the secondary eigenvalue near 300 Hz both become low values. Therefore, if the air pressure of the tire 12 is changed by the air supply / discharge device 11, these eigenvalues can be changed. That is, the resonance vibration frequency of the tire 12 can be changed by changing the air pressure of the tire 12 by the air supply / discharge device 11. Therefore, it can be considered that the road noise reduction system of the present embodiment has a resonance vibration frequency changing device configured to include the air supply / discharge device 11, the air passages 36, 40, and the like.

  More specifically, the change in the frequency of the resonance vibration due to the change in the air pressure will be described. When the air pressure of the tire 12 is increased, the tension in the tread portion and the sidewall portion of the tire 12 increases, so the tire 12 is deformed. It becomes difficult to do. Therefore, by increasing the air pressure, the rigidity of the tire 12 can be increased, and the primary eigenvalue and the secondary eigenvalue can be increased. Conversely, when the air pressure of the tire 12 is reduced, the rigidity of the tire 12 can be reduced, and the primary eigenvalue and the secondary eigenvalue can be reduced.

  Further, as can be seen from the graph of FIG. 4, when the air pressure of the tire 12 is changed, the sound pressure of noise changes in each frequency region near each eigenvalue. The vicinity of the primary eigenvalue and its high frequency side frequency region (for example, 80 to 130 Hz) are defined as the first high frequency side region, and the vicinity of the secondary eigenvalue and its high frequency side frequency region (for example, 320 to 400 Hz) are In the case of the two high frequency side regions, the sound pressure of noise in each of these frequency regions, that is, the noise level generally decreases as the air pressure of the tire 12 decreases. Further, a frequency region on the low frequency side of the primary eigenvalue (for example, 60 to 80 Hz) is a first low frequency side region, and a frequency region on the low frequency side of the secondary eigenvalue (for example, 250 to 320 Hz) is a second low frequency. In the case of the side region, the noise level in those frequency regions, particularly in the second low frequency side region, conversely decreases as the air pressure of the tire 12 increases. In short, it can be considered that the noise level in each high frequency side region decreases as the stiffness of the tire 12 decreases, and the noise in each low frequency side region decreases as the stiffness of the tire 12 increases. is there. In the road noise reduction system of the present embodiment, in consideration of this, the road noise is reduced by changing the air pressure of the tire 12. Note that the air pressure of the tire 12 has an allowable range from the viewpoint of the running performance of the vehicle. In the road noise reduction system of the present embodiment, within the allowable range (hereinafter sometimes referred to as “allowable air pressure range”). Be changed.

C. Noise reduction control Control for reducing road noise in the road noise reduction system of the present embodiment, that is, noise reduction control, corresponds to two operation modes of the system, noise reduction control in the high frequency side region target mode ( Hereinafter, it may be referred to as “anti-high frequency side region noise reduction control”) and noise reduction control in the low frequency side region target mode (hereinafter also referred to as “low frequency side region noise reduction control”). It is prepared. Below, the noise reduction control in each mode is demonstrated in order. Incidentally, the switching of the operation mode is performed based on the operation of the mode selection switch 76 by the driver. When the vehicle is accelerating, noise based on the engine sound increases and the occupant hears the noise. In that case, in the noise reduction control based on the sound pressure sensor 78, road noise may not be reduced appropriately. Therefore, in a state where it is determined that the vehicle is accelerating due to temporal fluctuations in the vehicle speed v. The noise reduction control in any of the above modes is not executed. Further, when the ignition switch 70 is turned from OFF to ON, standard state realization control is executed. This control is control for setting the tire rigidity to a predetermined standard state, and the standard state realization control will be described below.

i) Anti-high frequency side region noise reduction control Anti-high frequency region noise reduction control is executed when the mode selection switch 76 selects the operation mode as the high frequency side region target mode. As will be described in detail later, in this control, the road noise is reduced in consideration of the fact that the road noise level depends on the vehicle speed. The road noise that is the target of the determination as to whether or not to decrease is one of the two high frequency side regions. Therefore, in the anti-high frequency side region noise reduction control, an operation for reducing the rigidity of the tire 12 (hereinafter sometimes referred to as “tire rigidity reduction operation”) is performed based on the target road noise. It is.

More specifically, first, based on the sound pressure detected by the sound pressure sensor 78, that is, the detection result of the sound pressure sensor 78, the first high frequency side which is the highest level of noise in the first high frequency side region. The noise level L _H1 and the second high frequency side noise level L _H2, which is the highest noise level in the second high frequency region, are extracted. Next, the higher noise among them is set as the target noise, and the level of the target noise is set as the target noise level L _P. When the target noise level L _P exceeds a set upper limit level L _P1 , which is a kind of a set threshold level for determining whether to perform noise reduction control, the controller 62 issues a command to execute a tire stiffness reduction operation. Is announced.

Incidentally, in the road noise reduction system of the present embodiment, the set upper limit level L _P1 is changed according to the vehicle speed v. More specifically, the set upper limit level L _P1 is determined to increase as the vehicle speed v increases. Specifically, map data as shown in the graph of FIG. 5 is stored in the controller 62, and the set upper limit level L _P1 is determined with reference to the map data. When the vehicle speed v is high, road noise generally increases. Therefore, if the same threshold level as that when the vehicle speed v is low is adopted, the tire rigidity reduction operation is facilitated, and from the viewpoint of stabilizing the vehicle running performance. , Will be disadvantaged. In the road noise reduction system of the present embodiment, from that viewpoint, the higher the vehicle speed v, the more the execution of the tire rigidity reduction operation is suppressed.

When the target noise level L _P exceeds the set upper limit level L _P1 , the air supply / discharge device 11 causes the air to be exhausted from the inside of the tire 12 in order to reduce the air pressure of the tire 12 as a tire rigidity reduction operation. The operation (hereinafter sometimes referred to as “air pressure reduction operation”) is performed. The air pressure reduction operation is performed when a command to execute the operation is issued from the controller 62 to the driver 64, and the air supply / discharge device 11 is controlled and driven by the driver 64. Further, in order to prevent the air pressure P from becoming lower than the allowable air pressure range of the tire due to the air pressure reducing operation, when the air pressure P is less than the allowable minimum air pressure P _MIN (P <P _MIN ), the air pressure is reduced. Operation is stopped. Further, in the air pressure reduction operation, the air pressure is reduced to a constant reduction amount at a predetermined time so that noise does not change abruptly.

On the other hand, when the target noise level L _P is lower than the set lower limit level L _P2 set lower than the set upper limit level L _P1, an operation for increasing the rigidity of the tire 12 (hereinafter referred to as “tire stiffness increasing operation”). May be called). That is, in the road noise reduction system of the present embodiment, as the tire rigidity increasing operation, there is a case where the air supply / discharge device 11 supplies air into the tire 12 (hereinafter referred to as “air pressure increasing operation”). )I do. This air pressure increasing operation is performed when a command to execute the operation is issued from the controller 62 to the driver 64, and the air supply / discharge device 11 is controlled and driven by the driver 64. In order to prevent the air pressure P from becoming higher than the allowable air pressure range of the tire due to the air pressure increasing operation, when the air pressure P exceeds the allowable maximum air pressure P _MAX (P> P _MAX ), the air pressure increasing operation is performed. Be stopped. In addition, in the air pressure increasing operation, the air pressure is increased so as to become a constant increase amount at a predetermined time so that noise does not change abruptly.

The set lower limit level L _P2 will be described in detail. The set lower limit level L _P2 is determined so as to increase as the vehicle speed v increases, similarly to the set upper limit level L _P1 . Similarly to the set upper limit level L _P1 , map data as shown in the graph of FIG. 5 is stored in the controller 62, and the set lower limit level L _P2 is determined with reference to the map data. In this map data, between the set upper limit level L _P1 and the set lower limit level L _P2 , so that the phenomenon in which the tire stiffness reducing operation and the tire stiffness increasing operation are frequently performed alternately, so-called control hunting does not occur. A sufficient difference is provided. A region between the set upper limit level L _P1 and the set lower limit level L _P2 functions as a dead zone in the noise reduction control. When the target noise level L _P exists in the dead zone, the tire stiffness reduction operation and the tire stiffness are performed. The increase operation, that is, the air pressure reduction operation and the air pressure increase operation are not started.

ii) Low frequency side region noise reduction control The low frequency side region noise reduction control is executed when the operation mode is selected as the low frequency side region target mode by the mode selection switch 76. The road noise to be reduced is one of the two low frequency side regions. In this anti-low frequency side region noise reduction control, when the target road noise is reduced, the tire rigidity increasing operation is performed unlike the above-described anti-high frequency side region noise reduction control.

More specifically, in the low frequency side region noise reduction control, the first low frequency side noise level L _L1 , which is the noise level of the first low frequency side region, and the second low frequency side region are controlled. second low frequency side noise level L _L2 is the level of noise is extracted. Next, the higher noise among them is set as the target noise, and the level of the target noise is set as the target noise level L _P. As in the case of the high frequency side region noise reduction control, when the target noise level L _P exceeds the set upper limit level L _P1 , the controller 62 issues a command to execute the tire rigidity increasing operation.

When the target noise level L _P exceeds the set upper limit level L _P1 , the air pressure increasing operation is performed as the tire rigidity increasing operation. The air pressure increase operation in the low frequency side region noise reduction control is also performed in the same manner as in the high frequency region noise reduction control in order to prevent the air pressure P from increasing beyond the allowable air pressure range. If the maximum allowable air pressure P _MAX is exceeded (P> P _MAX ), it is stopped.

On the other hand, when the target noise level L _P is lower than the set lower limit level L _P2 , unlike the case of the high frequency side region noise reduction control, the tire rigidity reduction operation is performed. Specifically, an air pressure reduction operation is performed. As in the case of the low frequency side area noise reduction control, the air pressure reduction operation is performed when the air pressure P is less than the allowable minimum air pressure P _MIN in order to prevent the air pressure P from becoming lower than the allowable air pressure range. Is stopped (P <P _MIN ).

iii) Standard state realization control When the ignition switch 70 is turned from OFF to ON, it is considered that the state of the vehicle has shifted from a state where the vehicle is not traveling to a state where the vehicle can be driven. Therefore, standard state realization control is executed. The standard state of tire rigidity in the road noise reduction system of the present embodiment is set as a state in which the air pressure P of the tire 12 is a predetermined standard air pressure P _N. Therefore, when the ignition switch 70 is set to the ON, compared with the air pressure P and the standard pressure P _N at that time, if the air pressure P is greater than the standard pressure P _N executes the air pressure reducing operation, the air pressure P If the air pressure is smaller than the standard air pressure P _N , the air pressure increasing operation is executed. If the air pressure P is equal to the standard pressure P _N is pneumatically reducing operation being performed, pneumatically increase operation is stopped.

D. Flow of Control The above-described control performed in the road noise reduction system of the present embodiment is performed by the controller 62 executing a road noise reduction control program whose flowcharts are shown in FIGS. This program is repeatedly executed at short time intervals (for example, several milliseconds to several tens of milliseconds).

In the processing according to the road noise reduction control program, first, in step 1 (hereinafter abbreviated as “S1”, the same applies to other steps), the state of the ignition switch 70 is detected. , Whether the flag F is 1, that is, after the ignition switch is turned on, the standard state realization control is executed to determine whether the standard state has been realized. When the ignition switch 70 is OFF, the flag F is set to 0 in S3. If the flag F is 1 in S2, that is, if the standard state is realized, the vehicle speed v is acquired in S4. Next, in S5, it is determined whether or not the vehicle is in an acceleration state based on the temporal variation of the vehicle speed v. If the vehicle is not in an accelerated state, the set upper limit level L _P1 and the set lower limit level L _P2 are determined in S6 based on the map data shown in FIG. 5 based on the vehicle speed v. When the vehicle is in an acceleration state, one execution of the noise reduction control program is terminated. Next, in S7, the operation mode selected by the mode selection switch 76 is confirmed, and if the operation mode is selected as the high frequency side region target mode, the subroutine for anti-high frequency side region noise reduction control is executed in S8. If the high frequency side region target mode is not selected, that is, if the low frequency side region target mode is selected, a subroutine for low frequency side region noise reduction control is executed in S9. In S2, if the flag F is not 1, that is, 0, the standard state realization control is not executed after the ignition switch is turned on. Therefore, in S10, the standard state realization control subroutine is executed. Is executed.

FIG. 7 shows a flowchart of a subroutine for the high frequency side region noise reduction control, and the high frequency side region noise reduction control is executed according to this flowchart. In S11 of this subroutine, based on the detection result of the sound pressure sensor 78, the first high frequency side noise level L _H1 and the second high frequency side noise level L _H2 are extracted. Next, in S12, it is determined which of the first high frequency side noise level L _H1 and the second high frequency side noise level L _H2 is greater, and the first high frequency side noise level L _H1 is greater than the second high frequency side noise level L _H2. In this case, in S13, if the first high frequency side noise level L _H1 is recognized as the target noise level L _P and the first high frequency side noise level L _H1 is not greater than the second high frequency side noise level L _H2 , S14 2, the second high frequency side noise level L _H2 is recognized as the target noise level L _P.

Next, in S15, it is determined whether the target noise level L _P is greater than the set upper limit level L _P1 . If it is determined that the target noise level L _P is greater than the set upper limit level L _P1, it is determined in S16 whether or not the air pressure P is greater than or equal to the allowable minimum air pressure P _MIN . This determination, if the air pressure P is determined to permit at a minimum pressure P _MIN or more, at S17, pressure reduction operation is performed, if the air pressure P is determined not to be allowable minimum pressure P _MIN above In S18, when the air pressure reduction operation is performed, the operation is stopped, and when the air pressure reduction operation is not performed, the state is maintained.

On the other hand, if it is determined in S15 that the target noise level L _P is not greater than the set upper limit level L _P1 , it is further determined in S19 whether the target noise level L _P is smaller than the set lower limit level L _P2. . If it is determined that the target noise level L _P is lower than the set lower limit level L _P2, it is determined in S20 whether or not the air pressure P is less than or equal to the allowable maximum air pressure P _MAX . If it is determined by this determination that the air pressure P is less than or equal to the allowable maximum air pressure P _MAX , an air pressure increasing operation is performed in S21, and if it is determined that the air pressure P is not less than or equal to the allowable maximum air pressure P _MAX , In S18, when the air pressure increasing operation is performed, the operation is stopped, and when the air pressure increasing operation is not performed, the state is maintained. Even when it is determined in S19 that the target noise level L _P is not smaller than the set lower limit level L _P2 , if the air pressure reduction operation and the air pressure increase operation are performed in S18, those operations are stopped. If these operations are not performed, the state is maintained.

FIG. 8 shows a flowchart of a subroutine for the low frequency side region noise reduction control, and the low frequency side region noise reduction control is executed according to this flowchart. In S31 of this subroutine, based on the detection result of the sound pressure sensor 78, the first low frequency side noise level L _L1 and the second low frequency side noise level L _L2 are extracted. Next, in S32, it is determined which one of the first low frequency side noise level L _L1 and the second low frequency side noise level L _L2 is larger, and the first low frequency side noise level L _L1 is the second low frequency side noise level L. If it is greater than _L2 , in S33, the first low frequency side noise level L _L1 is recognized as the target noise level L _P , and the first low frequency side noise level L _L1 is greater than the second low frequency side noise level L _L2. If not, the second low-frequency noise level L _L2 is recognized as the target noise level L _P in S34.

Then, in S35, the target noise level L _P is determined whether greater than the set upper limit level L _P1, when the target noise level L _P is determined to be greater than the set upper limit level L _P1, in S36, the air pressure P is whether less than the allowable maximum air pressure P _MAX is determined. By this determination, if the air pressure P is determined to permit at maximum air pressure P _MAX less, in S37, the air pressure increase operation is performed, if the air pressure P is determined not less than the allowable maximum air pressure P _MAX, S38 When the air pressure increasing operation is performed, the operation is stopped. When the air pressure increasing operation is not performed, the state is maintained.

On the other hand, if it is determined in S35 that the target noise level L _P is not greater than the set upper limit level L _P1 , it is further determined in S39 whether the target noise level L _P is smaller than the set lower limit level L _P2. . If it is determined that the air pressure P is small, it is determined in S40 whether or not the air pressure P is greater than or equal to the allowable minimum air pressure _PMIN . If it is determined by this determination that the air pressure P is greater than or equal to the allowable minimum air pressure P _MIN , an air pressure reduction operation is performed in S 41, and if it is determined that the air pressure P is not greater than or equal to the allowable minimum air pressure P _MIN , S 38 When the air pressure reduction operation is performed, the operation is stopped, and when the air pressure reduction operation is not performed, the state is maintained. Even when it is determined in S39 that the target noise level L _P is not smaller than the set lower limit level L _P2 , if the air pressure reduction operation and the air pressure increase operation are performed in S38, those operations are stopped. If these operations are not performed, the state is maintained.

FIG. 9 shows a flowchart of a subroutine for the standard state realization control, and the standard state realization control is executed according to this flowchart. First, in S51, the air pressure P is equality in the standard air pressure P _N is determined. If it is determined that the air pressure P is not equal to the standard air pressure P _N , it is determined in S52 whether or not the air pressure P is greater than the standard air pressure P _N. If the air pressure P is determined to be greater than the standard pressure P _N, in S53, the air pressure reducing operation is performed, if it is not greater, in S54, the air pressure increase operation is performed. If it is determined in S51 that the air pressure P is equal to the standard air pressure P _N , the flag F is set to 1 in S55, and if the air pressure reduction operation and the air pressure increase operation are performed in S56, If these operations are stopped and those operations are not performed, the state is maintained.

E. Functional Configuration of Control Device In view of the processing executed by executing the load noise reduction control program, the controller 62 is considered to have a noise reduction control unit 80 as one functional unit as shown in FIG. be able to. The noise reduction control unit 80 further performs anti-high frequency side region noise as a part for performing processing according to a high frequency side region noise reduction control subroutine executed when the high frequency side region target mode is selected by the mode selection switch 76. Lowering the low frequency side area noise as a part for performing the process according to the low frequency side area noise lowering control subroutine executed when the low frequency side area target mode is selected by the mode selection switch 76. It can be considered that the control unit 84 has the standard state realization control unit 86 as a part for performing processing according to the standard state realization control subroutine executed when the ignition switch 70 is turned off.

A. Configuration of Road Noise Reduction System FIG. 10 shows one wheel 100 in a vehicle equipped with a road noise reduction system different from the first embodiment. In addition, in the following description, the same code | symbol is used about the component equivalent to the component in the road noise reduction system of 1st Example, The description shall be abbreviate | omitted.

  The wheel 100 includes a tire 12 and a wheel main body 102, and the tire 12 is fitted into the wheel main body 102. The wheel main body 102 can be divided into a rim portion 104 that is an outer peripheral portion into which the tire 12 is fitted, a hub portion 108 that is a central portion held by the axle 106, and a plurality of spoke portions 110 that connect them. it can.

  The rim portion 104 will be described in detail. The rim portion 104 includes an outer rim portion 112 located outside the vehicle and an inner rim portion 114 located inside the vehicle. The outer rim portion 112 is fitted into the inner rim portion 114, and the inner rim portion 114 can move in parallel to the rotation axis of the wheel 10 with respect to the outer rim portion 112. A plurality of recesses 116 are formed on the outer peripheral portion of the outer rim portion 112 so as to extend in the direction of the rotation axis of the wheel 10 and to be arranged at equiangular pitches in the circumferential direction. A plurality of convex portions 118 that engage with the concave portions 116 are formed on the inner peripheral portion of the inner rim portion 114. Therefore, the inner rim portion 114 cannot move in the circumferential direction of the wheel 10 with respect to the outer rim portion 112, and can move in parallel with the rotation axis of the wheel 10.

  On the outer periphery of the rim 104, four actuators 120 (not shown) are installed at an equiangular pitch in the circumferential direction of the rim 104, except for one. The actuator 120 includes an electromagnetic motor 122 (which is a three-phase DC brushless motor, and may be simply referred to as “motor 122” hereinafter), a screw rod 124 in which a thread groove is formed, and a bearing ball. The ball screw mechanism includes a screw rod 124 and a nut 126 to be screwed together. A motor shaft 128 that is a rotation shaft of the motor 122 is integrally connected to an end portion of the screw rod 124. Further, the actuator 120 is arranged such that the rotation axis of the motor shaft 128 and the screw rod 124 is parallel to the rotation axis of the wheel 10. The motor 122 is fixed on the outer rim portion 112, and the nut 126 is fixed on the inner rim portion 114. That is, when the screw rod 124 is rotated by the operation of the motor 122, the nut 126 is moved, and accordingly, the inner rim portion 114 moves in parallel with the rotation axis of the wheel 10 with respect to the outer rim portion 112. It is made possible. Therefore, by operating the actuator 120, it is possible to change the width of the rim portion 104 (hereinafter sometimes simply referred to as “rim width”).

  The power supply line 130 extending from the motor 122 passes through an opening 132 provided in the rim portion 104, a passage 134 formed in the spoke portion 110, and a passage 136 formed in the axle 106 connected to the passage 134. Further, it is led to an inverter 138 through a swivel joint (not shown). That is, the motor 122 is connected to the inverter 138 via the power supply line 130 and is operated by the electric power output from the inverter 138.

  The actuator 120 in the road noise reduction system of this embodiment is controlled by an actuator electronic control unit (actuator ECU) 140 whose control block diagram is shown in FIG. The actuator ECU 140 includes a controller 142 that is configured mainly by a computer including a CPU, ROM, RAM, and the like, and an inverter 138 that drives the motor 122. The inverter 138 is connected to the battery 68 via the converter 144. In the road noise reduction system of this embodiment, a rotation angle sensor 146 [ω] for detecting the rotation angle of the motor 122 is provided.

B. Change in Resonant Vibration Frequency by Changing Rim Width As shown in FIG. 10, it can be said that the rim width is one of the factors that determine the cross-sectional shape of the tire 12. That is, when the rim width is increased, the arc shape of the sidewall portion 150 of the tire 12 is made to be a more linear shape, and the cross-sectional shape of the tire 12 is changed. When the cross-sectional shape of the tire 12 is changed, the rigidity of the tire 12 is also changed. That is, the resonant vibration frequency of the tire 12 can be changed. Therefore, it can be considered that the road noise reduction system of the present embodiment has a resonance vibration frequency changing device configured to include the actuator 120, the power supply line 130, the inverter 138, and the like.

  More specifically, the change in the frequency of the resonance vibration due to the change in the rim width can be described. By increasing the rim width, the rigidity of the tire 12 can be increased, and the primary eigenvalue and the secondary eigenvalue are high values. It can be made. Conversely, when the rim width is reduced, the rigidity of the tire 12 can be reduced, and the primary eigenvalue and the secondary eigenvalue can be reduced.

  In view of the change in the frequency of resonance vibration due to the change in air pressure shown in FIG. 4, when the rigidity of the tire 12 is changed by changing the rim width, the sound pressure of the noise changes in each frequency region near each eigenvalue. Can be made. More specifically, the sound pressure of noise in the first high frequency side region and the second high frequency side region, that is, the noise level generally decreases as the rim width decreases, and conversely, the first low frequency side region. It can be considered that the noise level in the second low frequency side region generally decreases as the rim width increases. In the road noise reduction system according to the present embodiment, in consideration of this, the road noise can be reduced by changing the rim width. The rim width has an allowable range from the viewpoint of the specification of the tire 12 and the running performance of the vehicle. In the road noise reduction system of this embodiment, the allowable range (hereinafter, referred to as “allowable rim width range” may be referred to. It is changed within a certain).

C. Noise reduction control In the road noise reduction system of this embodiment, control for reducing road noise, that is, noise reduction control is performed in the same manner as in the first embodiment. Therefore, two types of operation modes are prepared: anti-high frequency region noise reduction control and anti-low frequency region noise reduction control that are switched based on the operation of the mode selection switch 76. Further, when the ignition switch 70 is turned off, standard state realization control is executed. Hereinafter, the anti-high frequency side region noise reduction control, the low frequency side region noise reduction control, and the standard state realization control will be described. In the following description, description of control equivalent to control in the road noise reduction system of the first embodiment is omitted.

In the noise reduction control of the road noise reduction system of the present embodiment, the motor rotation angle ω of the motor 122 is used as an index representing the rim width. More specifically, since the rim width is changed by the rotation of the motor 122, the ECU 60 can calculate the corresponding rim width by detecting the motor rotation angle ω. Therefore, if an allowable motor rotation angle range corresponding to the allowable rim width range is set, the ECU 60 maintains the rim width within the allowable rim width range from the motor rotation angle ω and the allowable motor rotation angle range. Thus, the motor 122 can be controlled. The allowable motor rotation angle range will be described. For the allowable minimum rim width, which is the minimum value in the allowable rim width range, the corresponding allowable minimum motor rotation angle ω _MIN is set, and the maximum value in the allowable rim width range is set. A corresponding allowable maximum motor rotation angle ω _MAX is set for the allowable maximum rim width. Thereby, the allowable motor rotation angle range corresponding to the allowable rim width range is set. Also, the standard motor rotation angle ω _N corresponding to the rim width in the standard state is set. By using these allowable minimum motor rotation angle ω _MIN , allowable maximum motor rotation angle ω _MAX , and standard motor rotation angle ω _N , noise reduction control is executed.

i) Anti-high frequency side region noise reduction control Anti-high frequency region noise reduction control is executed when the mode selection switch 76 selects the operation mode as the high frequency side region target mode. The first high frequency side noise level L _H1 , the second high frequency side noise level L _H2 , the target noise level L _P , the set upper limit level L _P1 , and the set lower limit level L _P2 are determined in the same manner as in the first embodiment. .

When the target noise level L _P exceeds the set upper limit level L _P1 , as the tire rigidity reduction operation, the actuator 120 reduces the rim width to reduce the rim width of the tire 12 (hereinafter referred to as “rim width”). (Sometimes referred to as “reduction operation”). The rim width reduction operation is performed when a command to execute the operation is issued from the controller 142 to the inverter 138 and the motor 122 is driven by the inverter 138. In order to prevent the motor rotation angle ω from operating beyond the allowable rim width range of the tire due to the rim width reduction operation, when the motor rotation angle ω exceeds the allowable minimum motor rotation angle ω _MIN (ω <Ω _MIN ), rim width reduction operation is stopped. Further, in the rim width reduction operation, the rim width is reduced to a constant reduction amount at a predetermined time so that noise does not change suddenly.

On the other hand, when the target noise level L _P is lower than the set lower limit level L _P2 set lower than the set upper limit level L _P1 , the actuator 120 increases the rim width (hereinafter, “rim (It may be called “width expansion operation”). The rim width expansion operation is performed by issuing a command to execute the operation from the controller 62 to the inverter 138 and driving the motor 122 by the inverter 138. Also, in order to prevent the motor rotation angle ω from operating beyond the allowable rim width range of the tire by the rim width expansion operation, when the motor rotation angle ω exceeds the allowable maximum motor rotation angle ω _MAX (ω > Ω _MAX ), the rim width expansion operation is stopped. Further, in the rim width expansion operation, the rim width is expanded so as to be a constant expansion amount at a predetermined time so that noise does not change suddenly.

ii) Low frequency side region noise reduction control The low frequency side region noise reduction control is executed when the operation mode is selected as the low frequency side region target mode by the mode selection switch 76. The first low frequency side noise level L _L1 and the second low frequency side noise level L _L2 are determined in the same manner as in the first embodiment.

When the target noise level L _P exceeds the set upper limit level L _P1 , the rim width increasing operation is performed as the tire rigidity increasing operation. In the same way as in the case of anti-high frequency region noise reduction control, the rim width expansion operation in the low frequency side region noise reduction control is also performed in order to prevent the motor rotation angle ω from increasing beyond the allowable rim width range. When the rotation angle ω exceeds the allowable maximum motor rotation angle ω _MAX of the tire (ω> ω _MAX ), the rotation is stopped.

On the other hand, when the target noise level L _P is lower than the set lower limit level L _P2 , unlike the case of the high frequency side region noise reduction control, the tire rigidity reduction operation is performed. Specifically, a rim width reduction operation is performed. As in the case of the noise reduction control for the high frequency side region, the rim width reduction operation is performed so that the motor rotation angle ω is the minimum allowable motor rotation in order to prevent the motor rotation angle ω from becoming lower than the allowable rim width range. If the angle is less than ω _MIN (ω <ω _MIN ), it is stopped.

iii) Standard state realization control When the ignition switch 70 is turned from OFF to ON, it is considered that the state of the vehicle has shifted from a state where the vehicle is not traveling to a state where the vehicle can be driven. Therefore, standard state realization control is executed. The standard state of tire rigidity in the road noise reduction system of the present embodiment is set as a state where the motor rotation angle ω of the tire 12 is a predetermined standard motor rotation angle ω _N. Therefore, when the ignition switch 70 is set to the ON, compares the motor rotation angle omega and the standard motor rotation angle omega _N at that time, the motor rotation angle omega is larger than the standard motor rotation angle omega _N is rim width When the reduction operation is performed and the motor rotation angle ω is smaller than the standard motor rotation angle ω _N , the rim width expansion operation is executed. When the motor rotation angle omega is equal to the standard motor rotation angle omega _N is rim width reduction operation being performed, rim width expanding operation is stopped.

D. Flow of Control The above-described control performed in the road noise reduction system of the present embodiment is performed by the controller 62 executing a road noise reduction control program whose flowcharts are shown in FIGS. 6 and 12 to 14. Therefore, since the processing according to the road noise reduction control program is performed according to the flowchart of FIG. 6 as in the first embodiment, the description thereof is omitted. This program is repeatedly executed at short time intervals (for example, several milliseconds to several tens of milliseconds).

FIG. 12 shows a flowchart of a subroutine for the high frequency side region noise reduction control, and the high frequency side region noise reduction control is executed according to this flowchart. The determination of the target noise level L _P in this subroutine is omitted because the same steps as S11 to S14 in the first embodiment are performed in the steps S61 to S64 of this road noise reduction program. To do.

Next, in S65, it is determined whether the target noise level L _P is greater than the set upper limit level L _P1 . If it is determined that the target noise level L _P is greater than the set upper limit level L _P1, it is determined in S66 whether the motor rotation angle ω is equal to or greater than the minimum motor rotation angle ω _MIN . If it is determined by this determination that the motor rotation angle ω is greater than or equal to the minimum motor rotation angle ω _MIN , the rim width reduction operation is performed in S67, and the motor rotation angle ω is greater than or equal to the minimum motor rotation angle ω _MIN. If it is determined that the rim width expansion operation is being performed, the operation is stopped in S68, and if the rim width expansion operation is not being performed, the state is maintained.

On the other hand, if it is determined in S65 that the target noise level L _P is not larger than the set upper limit level L _P1 , it is further determined in S69 whether the target noise level L _P is smaller than the set lower limit level L _P2. . If it is determined that the target noise level L _P is lower than the set lower limit level L _P2, it is determined in S70 whether the motor rotation angle ω is equal to or less than the maximum motor rotation angle ω _MAX . If it is determined by this determination that the motor rotation angle ω is equal to or less than the maximum motor rotation angle ω _MAX , the rim width expansion operation is performed in S71, and if the motor rotation angle ω is equal to or less than the maximum motor rotation angle ω _MAX. If it is determined that the rim width expansion operation is being performed, the rim width expansion operation is stopped in S68, and if the rim width expansion operation is not being performed, the state is maintained. The Even when it is determined in S69 that the target noise level L _P is not smaller than the set lower limit level L _P2 , if the rim width reduction operation and the rim width expansion operation are performed in S68, those operations are performed. Are stopped, and if they are not activated, the state is maintained.

FIG. 13 shows a flowchart of a subroutine for low frequency side area noise reduction control, and low frequency side area noise reduction control is executed according to this flowchart. The determination of the target noise level L _P in this subroutine is omitted because the same steps as S31 to S34 in the first embodiment are performed in the steps S81 to S84 of this road noise reduction program. To do.

Then, in S85, whether the target noise level L _P is larger than the set upper limit level L _P1 is determined, when the target noise level L _P is determined to be greater than the set upper limit level L _P1, in S86, the motor It is determined whether the rotation angle ω is equal to or less than the maximum motor rotation angle ω _MAX . If it is determined by this determination that the motor rotation angle ω is equal to or less than the minimum motor rotation angle ω _MAX , the rim width expansion operation is performed in S87 and the motor rotation angle ω is not equal to or less than the maximum motor rotation angle ω _MAX. If it is determined, in S88, if the rim width expanding operation is performed, the rim width expanding operation is stopped, and if the rim width expanding operation is not performed, the state is maintained.

On the other hand, if it is determined in S85 that the target noise level L _P is not greater than the set upper limit level L _P1 , it is further determined in S89 whether the target noise level L _P is smaller than the set lower limit level L _P2. . If it is determined that the motor rotation angle is small, it is determined in S90 whether or not the motor rotation angle ω is equal to or greater than the minimum motor rotation angle ω _MIN . If it is determined by this determination that the motor rotation angle ω is equal to or greater than the minimum motor rotation angle ω _MIN , the rim width reduction operation is performed in S91, and the motor rotation angle ω is not equal to or greater than the maximum motor rotation angle ω _MIN. If it is determined, in S88, if the rim width reduction operation is being performed, the rim width reduction operation is stopped, and if the rim width reduction operation is not being performed, that state is maintained. Even when it is determined in S89 that the target noise level L _P is not smaller than the set lower limit level L _P2 , if the rim width reduction operation and the rim width expansion operation are performed in S88, those operations are performed. Are stopped, and if they are not activated, the state is maintained.

FIG. 14 shows a flowchart of a subroutine for the standard state realization control, and the standard state realization control is executed according to this flowchart. First, in S101, it is determined whether or not the motor rotation angle ω is equal to the standard motor rotation angle ω _N. If the motor rotation angle omega is not equal to the standard motor rotation angle omega _N, in S102, the motor rotation angle omega whether greater than the standard motor rotation angle omega _N is determined. If it is determined that the motor rotation angle ω is larger than the standard motor rotation angle ω _N , the rim width reduction operation is performed in S103. If it is determined that the motor rotation angle ω is not large, the rim width expansion operation is performed in S104. Done. If it is determined in S101 that the motor rotation angle ω is equal to the standard motor rotation angle ω _N , the flag F is set to 1 in S105 when the rim width reduction or enlargement operation is being performed. In S106, when the rim width reducing operation and the rim width expanding operation are performed, the operations are stopped, and when the operations are not performed, the state is maintained.

E. Functional Configuration of Control Device In view of the processing executed by executing the load noise reduction control program, the controller 142 is considered to have a noise reduction control unit 160 as one functional unit as shown in FIG. be able to. The noise reduction control unit 160 further performs anti-high frequency side region noise as a part that performs processing according to a high frequency side region noise reduction control subroutine that is executed when the high frequency side region target mode is selected by the mode selection switch 76. The reduction control unit 162 performs a process according to a low-frequency side area noise reduction control subroutine executed when the low-frequency side area target mode is selected by the mode selection switch 76, so that the low-frequency side area noise is reduced. It can be considered that the control unit 164 includes the standard state realization control unit 166 as a part that performs processing according to the standard state realization control subroutine executed when the ignition switch 70 is turned off.

A. Configuration of Road Noise Reduction System FIG. 15 shows one wheel 200 in a vehicle equipped with a road noise reduction system different from the first and second embodiments. In the following description, the same reference numerals are used for the same components as those in the road noise reduction system of the first embodiment, and the description thereof is omitted.

  The wheel 200 includes a tire 202 and a wheel main body 204, and the tire 202 is fitted into the wheel main body 204. The wheel main body 204 can be divided into a rim portion 206 that is an outer peripheral portion into which the tire 12 is fitted, a hub portion 210 that is a central portion held by the axle 208, and a plurality of spoke portions 212 that connect them. it can.

  The tire 202 will be described in detail. The tire 202 includes a plurality of fluid bags 216 in which a magnetic fluid 214 is sealed. These fluid bags 216 are annularly arranged in the circumferential direction of the wheel 200 in the tread portion 218, the sidewall portion 220, and the bead portion 222 of the tire 202. An electric wire 224 connected to the power supply line 130 and guided to the inside of the tire 202 is wound around these fluid bags 216 in a spiral shape. Therefore, when the electric wire 224 is energized to cause electromagnetic induction, the electric wire 224 acts as a winding for the fluid bag 216, and magnetic force acts on the magnetic fluid 214 inside the fluid bag 216. The viscosity of the magnetic fluid 214 is changed by the action of a magnetic force, and the viscosity can be changed by changing the magnetic force according to the magnitude of a current to be supplied. Therefore, the viscosity of the magnetic fluid 214 can be changed by adjusting the current flowing through the electric wire 224.

  The power supply line 130 connected to the electric wire 224 includes a passage 228 formed inside the spoke portion 212 through an opening 226 provided in the rim portion 206, and a passage 230 formed on the axle 208 connected to the passage 228. Then, it is led to a DC / DC converter 232 via a swivel joint (not shown). That is, the electric wire 224 is connected to the DC / DC converter 232 via the feeder line 130, and power is supplied from the DC / DC converter 232.

  Control of the DC / DC converter 232 in the road noise reduction system of the present embodiment is performed by an electronic control unit (ECU) 250 whose control block diagram is shown in FIG. The ECU 250 includes a controller 252 that is configured mainly by a computer including a CPU, a ROM, a RAM, and the like. The controller 252 is connected to the DC / DC converter 232, and the DC / DC converter 232 adjusts the current value I based on a command from the controller 252.

B. Change of Resonant Vibration Frequency Due to Viscosity Change of Magnetic Fluid As shown in FIG. 15, in the magnetic fluid 236 provided in the tire 202, the viscosity changes according to the magnitude of the current flowing through the electric wire 224. The rigidity of the tire 202 can be changed. Therefore, the resonance vibration frequency of the tire 202 can be changed by changing the current. Therefore, it can be considered that the road noise reduction system of the present embodiment has a resonance vibration frequency changing device configured to include the magnetic fluid 214, the DC / DC converter 232, and the like.

  More specifically, the change in the frequency of the resonance vibration caused by the change in the current will be described. When the current is increased, the viscosity of the magnetic fluid 236 increases, so that the tire 202 is hardly deformed. Therefore, by increasing the current, the rigidity of the tire 202 can be increased, and the primary eigenvalue and the secondary eigenvalue can be increased. On the other hand, when the current is decreased, the rigidity of the tire 202 can be lowered, and the primary eigenvalue and the secondary eigenvalue can be lowered.

  In view of the change in the frequency of the resonance vibration due to the change in air pressure shown in FIG. 4, when the stiffness of the tire 12 is changed by changing the current, the sound pressure of the noise is changed in each frequency region near each eigenvalue. be able to. Specifically, the sound pressure of noise in the first high frequency side region and the second high frequency side region, that is, the noise level generally decreases as the current decreases, and conversely, the first low frequency side region and It can be considered that the level of noise in the second low frequency side region generally decreases as the current increases. In the road noise reduction system in the present embodiment, road noise can be reduced by changing the current in consideration of this. The current has an allowable range from the viewpoint of the running performance of the vehicle. In the road noise reduction system of the present embodiment, the current is changed within the allowable range (hereinafter may be referred to as “allowable current range”). .

C. Noise reduction control In the road noise reduction system of this embodiment, control for reducing road noise, that is, noise reduction control is performed in the same manner as in the first embodiment. That is, two types of operation modes are prepared: anti-high frequency side region noise reduction control and low frequency side region noise reduction control that are switched based on the operation of the mode selection switch 76. Further, when the ignition switch 70 is turned off, standard state realization control is executed. Hereinafter, the anti-high frequency side region noise reduction control, the low frequency side region noise reduction control, and the standard state realization control will be described. In the following description, description of control equivalent to control in the road noise reduction system of the first embodiment is omitted.

i) Anti-high frequency side region noise reduction control Anti-high frequency region noise reduction control is executed when the mode selection switch 76 selects the operation mode as the high frequency side region target mode. The first high frequency side noise level L _H1 , the second high frequency side noise level L _H2 , the target noise level L _P , the set upper limit level L _P1 , and the set lower limit level L _P2 are determined in the same manner as in the first embodiment. .

When the target noise level L _P exceeds the set upper limit level L _P1 , adjustment is performed so that the DC / DC converter 232 decreases the current as the tire stiffness reduction operation (hereinafter, referred to as “current reduction adjustment”). ) The current reduction adjustment is performed when the controller 142 issues a command to execute the adjustment to the DC / DC converter 232. Further, in order to prevent the current from being reduced beyond the allowable current range by the current reduction adjustment, when the current value I is less than the allowable minimum current value I _MIN (I <I _MIN ), the current reduction adjustment is performed. Is stopped. Further, in the current reduction adjustment, the current is reduced so as to be a constant reduction amount at a predetermined time so that the noise does not change rapidly.

On the other hand, when the target noise level L _P is lower than the set lower limit level L _P2 set lower than the set upper limit level L _P1 , the DC / DC converter 232 is adjusted so as to increase the current as the tire stiffness increasing operation ( Hereinafter, it may be referred to as “current increase adjustment”. This current increase adjustment is performed when a command to execute the adjustment is issued from the controller 142 to the DC / DC converter 232. Further, in order to prevent the current from increasing beyond the allowable current range of the tire due to the current increase adjustment, when the current value I exceeds the allowable maximum current value I _MAX (I> I _MAX ), the current increase adjustment is performed. Is stopped. Further, in the current increase adjustment, the current is increased so as to be a constant increase amount in a predetermined time so that the noise does not change rapidly.

ii) Low frequency side region noise reduction control The low frequency side region noise reduction control is executed when the operation mode is selected as the low frequency side region target mode by the mode selection switch 76. The first low frequency side noise level L _L1 and the second low frequency side noise level L _L2 are determined in the same manner as in the first embodiment.

When the target noise level L _P exceeds the set upper limit level L _P1 , the current increase adjustment is performed as the tire rigidity increasing operation. In the current increase adjustment in the low frequency side region noise reduction control, as in the case of the high frequency region noise reduction control, in order to prevent the current from exceeding the allowable current range, the current value I is When the allowable maximum current value I _MAX is exceeded (I> I _MAX ), it is stopped.

On the other hand, when the target noise level L _P is lower than the set lower limit level L _P2 , current reduction adjustment is performed unlike the case of high frequency side region noise reduction control. As in the case of the noise reduction control for the high frequency side region, the current reduction adjustment is performed when the current value I is less than the allowable minimum current value I _MIN in order to prevent the current from exceeding the allowable current range. Is stopped (I <I _MIN ).

iii) Standard state realization control When the ignition switch 70 is turned from OFF to ON, it is considered that the state of the vehicle has shifted from a state where the vehicle is not traveling to a state where the vehicle can be driven. Therefore, standard state realization control is executed. A standard state of the tire rigidity in the road noise reduction system of the present embodiment, the current value I is set as a state which is a standard current value I _N being predetermined. Therefore, when the ignition switch 70 is set to the ON, compared with the current value I and the standard current value I _N at that time, when the current value I is larger than the standard electric current value I _N performs a current reduction adjustment If the current value I is smaller than the standard current value I _N , the current increase adjustment is executed. When the current value I becomes equal to the standard current value I _N , the current decrease adjustment and current increase adjustment that are being performed are stopped.

D. Control Flow The above-described control performed in the road noise reduction system according to the present embodiment is performed by the controller 62 executing the road noise reduction control program shown in the flowcharts of FIGS. 6 and 17 to 19. Therefore, since the processing according to the road noise reduction control program is performed according to the flowchart of FIG. 6 as in the first embodiment, the description thereof is omitted. This program is repeatedly executed at short time intervals (for example, several milliseconds to several tens of milliseconds).

FIG. 17 shows a flowchart of a subroutine for the high frequency side region noise reduction control, and the high frequency side region noise reduction control is executed according to this flowchart. The determination of the target noise level L _P in this subroutine is omitted because the same steps as S11 to S14 in the first embodiment are performed in the steps S111 to S114 of this road noise reduction program. To do.

Next, in S115, it is determined whether the target noise level L _P is greater than the set upper limit level L _P1 . If it is determined that the target noise level L _P is greater than the set upper limit level L _P1, it is determined in S116 whether the current value I is greater than or equal to the minimum current value I _MIN . If it is determined by this determination that the current value I is equal to or greater than the minimum current value I _MIN , current decrease adjustment is performed in S117, and it is determined that the current value I is not equal to or greater than the minimum current value I _MIN . If the current decrease adjustment is performed in S68, the adjustment is stopped. If the current decrease adjustment is not performed, the state is maintained.

On the other hand, if it is determined in S115 that the target noise level L _P is not greater than the set upper limit level L _P1 , it is further determined in S119 whether the target noise level L _P is smaller than the set lower limit level L _P2. . If it is determined that the target noise level L _P is lower than the set lower limit level L _P2, it is determined in S120 whether or not the current value I is equal to or lower than the maximum current value I _MAX . If it is determined by this determination that the current value I is less than or equal to the maximum current value I _MAX , current increase adjustment is performed in S121, and it is determined that the current value I is not less than or equal to the maximum current value I _MAX . If the current increase adjustment is performed in S118, the adjustment is stopped. If the current increase adjustment is not performed, the state is maintained. Even if it is determined in S119 that the target noise level L _P is not smaller than the set lower limit level L _P2 , if current decrease adjustment and current increase adjustment are performed in S118, those adjustments are stopped. If these adjustments have not been performed, the state is maintained.

FIG. 18 shows a flowchart of a subroutine for the low frequency side region noise reduction control, and the low frequency side region noise reduction control is executed according to this flowchart. The determination of the target noise level L _P in this subroutine is omitted because the same steps as S31 to S34 in the first embodiment are performed in the steps S131 to S134 of this road noise reduction program. To do.

Then, in S135, the target noise level L _P is determined whether greater than the set upper limit level L _P1, when the target noise level L _P is determined to be greater than the set upper limit level L _P1, in S136, the current It is determined whether the value I is less than or equal to the maximum current value _IMAX . If it is determined by this determination that the current value I is less than or equal to the minimum current value I _MAX , current increase adjustment is performed in S137, and if the current value I is determined not to be less than or equal to the maximum current value I _MAX In S138, when the current increase adjustment is performed, the adjustment is stopped, and when the current increase adjustment is not performed, the state is maintained.

On the other hand, if it is determined in S135 that the target noise level L _P is not greater than the set upper limit level L _P1 , it is further determined in S139 whether the target noise level L _P is smaller than the set lower limit level L _P2. . If it is determined that the current value is smaller, it is determined in S90 whether or not the current value I is equal to or greater than the minimum current value _IMIN . If it is determined by this determination that the current value I is greater than or equal to the minimum current value I _MIN , current reduction adjustment is performed in S91, and if it is determined that the current value I is not greater than or equal to the maximum current value I _MIN In S138, if the current reduction adjustment is performed, the adjustment is stopped, and if the current reduction adjustment is not performed, the state is maintained. Even when it is determined in S139 that the target noise level L _P is not smaller than the set lower limit level L _P2 , if current decrease adjustment and current increase adjustment are performed in S138, those adjustments are stopped. If these adjustments are not made, the state is maintained.

FIG. 19 shows a flowchart of a subroutine for the standard state realization control, and the standard state realization control is executed according to this flowchart. First, in S151, it is determined whether or not the current value I is equal to the standard current value I _N. If it is determined that the current value I is not equal to the standard current value I _N , it is determined in S152 whether the current value I is greater than the standard current value I _N. When it is determined that the current value I is greater than the standard current value I _N , current decrease adjustment is performed in S153, and when it is determined that the current value I is not large, current increase adjustment is performed in S154. Further, in S151, when the current value I is determined to be equal to the standard current value I _N, when the current value decreases or increases adjustment is performed, is the flag F is 1 in S155, in S156 When the current decrease adjustment and the current increase adjustment are performed, the adjustments are stopped, and when the adjustments are not performed, the state is maintained.

E. Functional Configuration of Control Device In view of the processing executed by executing the load noise reduction control program, it is considered that the controller 252 has a noise reduction control unit 260 as one functional unit as shown in FIG. be able to. The noise reduction control unit 260 further performs a process according to a high-frequency side region noise reduction control subroutine executed when the high-frequency side region target mode is selected by the mode selection switch 76, as a part for performing a process for the high-frequency side region noise. The reduction control unit 262 performs a process according to a low frequency side area noise reduction control subroutine that is executed when the low frequency side area target mode is selected by the mode selection switch 76, and the low frequency side area noise is reduced. It can be considered that the control unit 264 has the standard state realization control unit 266 as a part for performing processing according to the standard state realization control subroutine executed when the ignition switch 70 is turned off.

  The present invention can be used to reduce road noise of a vehicle having tires.

11: Air supply / discharge device 12: Tire 14: Wheel body 36: Air passage 40: Air passage 60: Electronic control unit (ECU)
62: Controller 74: Air pressure sensor 76: Mode selection switch 78: Sound pressure sensor 80: Noise reduction unit 82: High frequency range noise reduction control unit 84: Low frequency range noise reduction control unit 86: Standard control unit

Claims (4)

A resonance vibration frequency changing device for changing the frequency of resonance vibration of the tire;
A noise detector that detects noise in the passenger compartment;
A road noise reduction system comprising a control device for controlling the resonance vibration frequency changing device,
When the noise level detected by the noise detector exceeds a set upper limit level, the control device executes noise reduction control for changing the frequency of the resonance vibration so that the detected noise level is reduced. Road noise reduction system configured to do. The resonant vibration frequency changing device is an air pressure changing device for changing the tire air pressure,
In the road noise reduction system, as the noise reduction control, when the noise level detected by the noise detector exceeds the set upper limit level, the tire pressure is reduced so that the detected noise level is reduced. The road noise reduction system according to claim 1, wherein control for changing the control is executed.   The resonance vibration frequency changing device is a rim width changing device that changes a rim width of a wheel, and the road noise reduction system sets the level of noise detected by the noise detector as the noise reduction control. 2. The road noise reduction system according to claim 1, wherein when the upper limit level is exceeded, control for changing the rim width of the wheel is executed so that the detected noise level is reduced. The resonant vibration frequency changing device is a tire stiffness changing device that changes the stiffness of at least one of a tire tread portion and a sidewall portion,
In the road noise reduction system, as the noise reduction control, when the noise level detected by the noise detector exceeds the set upper limit level, the detected noise level is reduced. The road noise reduction system according to claim 1, wherein control for changing the rigidity of at least one of the tread portion and the sidewall portion is executed.

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