JP6970598B2 - Tread pattern generation method, tread pattern generator, and program - Google Patents

Description

The present invention relates to a tread pattern generation method, a tread pattern generation device, and a program for generating a tread pattern of a tire.

When the vehicle is running, so-called pattern noise such as a pattern striking sound and a pumping sound is generated according to the tread pattern of the tire. The pattern striking sound is a sound generated by the tire vibrating due to the impact force when a certain region of the tread comes into contact (collision) with the road surface. The pumping noise is generated by the compression of the air in the space surrounded by the tread groove and the road surface when a region of the tread touches the road surface, and the expansion of the compressed air as this region leaves the road surface. It's a sound.

In order to evaluate the noise generated by the tire, a computer simulation may be performed based on the tread pattern of the tire. For example, by performing image analysis on the tread pattern or by using the finite element method for the three-dimensional model of the tire, the area where the tire contacts the road surface and the area where the tire does not contact can be identified, and the area during one rotation of the tire is identified. Calculate variations in contact area and / or non-contact area. From the fluctuation of the contact area and / or the non-contact area, the magnitude of the noise generated by the tire can be known. This variation in contact area and / or non-contact area is processed in the time domain or frequency domain to evaluate the magnitude of noise. For example, Patent Documents 1 to 4 disclose such a simulation method.

Japanese Patent No. 4049570 Japanese Patent No. 5658249 JP-A-2007-062731 JP-A-2015-091684

The generation of tread patterns is required to meet various requirements.

For example, when a tread pattern is generated so as to reduce the magnitude of noise at one frequency, the tread pattern may increase noise at other frequencies. Therefore, it is required to generate a tread pattern that reduces noise more effectively than in the prior art.

Further, even if the tread pattern is generated so as to reduce the magnitude of noise, performance other than noise such as grip performance may be deteriorated. Such a tread pattern will not be adopted in the end, and as a result, its generation is wasted. Therefore, it is required to prevent unnecessary generation of the tread pattern and efficiently generate the tread pattern.

An object of the present invention is to provide a tread pattern generation method, a tread pattern generation device, and a program capable of generating a tread pattern more effectively and efficiently than in the prior art.

According to the first aspect of the present invention.
It is a tread pattern generation method that generates a tire tread pattern by a computer.
A step of reading out the initial value of the tread pattern and the ground contact area indicating the area where the tire contacts the road surface from the storage device.
A step of scanning the ground contact area in the circumferential direction of the tread pattern and calculating a fluctuation amount of a characteristic value indicating the shape of the tread pattern in a region where the tread pattern and a predetermined portion of the ground contact area overlap.
A step of performing frequency analysis on the fluctuation amount of the characteristic value of the tread pattern to generate a fluctuation level in the frequency domain, and
A step of calculating a predetermined objective function value based on the fluctuation level in at least two frequency bands.
A step of determining a deformation position, a deformation method, and a deformation amount of the tread pattern so that the objective function value satisfies a predetermined criterion in the at least two frequency bands.
Including the step of generating a tread pattern deformed by the determined deformation position, the deformation method, and the amount of deformation.
The tread pattern has a plurality of deformation positions and a plurality of deformation methods.
The step of determining the deformation position, the deformation method, and the deformation amount of the tread pattern restricts the application of at least one of the plurality of deformation methods to at least one of the plurality of deformation positions. receive.

According to the second aspect of the present invention, in the first aspect,
The step of determining the deformation position, the deformation method, and the deformation amount of the tread pattern is a predetermined range for at least one of the plurality of deformation methods in at least one of the plurality of deformation positions. Includes determining the amount of deformation within.

According to the third aspect of the present invention, in the first or second aspect,
The plurality of deformation positions include a plurality of partial patterns of the tread pattern divided by at least one straight line along the circumferential direction of the tread pattern.

According to the fourth aspect of the present invention, in the third aspect,
The plurality of deformation methods are
Changing the ratio of the area of the region where the tire contacts the road surface and the area of the region where the tire does not contact the road surface in the region where the tread pattern and the predetermined portion of the ground contact region overlap. When,
In each of the partial patterns, the length of the region where the tire contacts the road surface and the length of the region where the tire does not contact the road surface are changed with respect to the circumferential direction of the tread pattern.
Distorting the shape of the area where the tire contacts the road surface
It includes at least one of moving the plurality of partial patterns relative to each other along the circumferential direction of the tread pattern.

According to the fifth aspect of the present invention, in one of the first to fourth aspects,
The objective function value is
The first frequency band over the entire frequency range of the fluctuation level and
It is calculated based on the fluctuation level in at least two frequency bands among the plurality of frequency bands including the plurality of second frequency bands that are a part of the first frequency band.

According to the sixth aspect of the present invention, in the fifth aspect,
The plurality of second frequency bands are
A frequency band including a reference frequency corresponding to the period of the tread pattern with respect to the circumferential direction of the tread pattern.
It includes at least one frequency band including a frequency that is an integral fraction of the reference frequency.

According to the seventh aspect of the present invention, in the fifth aspect,
The plurality of second frequency bands are
A frequency band including a reference frequency corresponding to the period of the tread pattern with respect to the circumferential direction of the tread pattern.
It includes at least one frequency band including a frequency that is an integral multiple of the reference frequency.

According to the eighth aspect of the present invention, in one of the first to seventh aspects,
The objective function value is calculated based on the total energy of the fluctuation levels in each of the frequency bands.

According to the ninth aspect of the present invention, in one of the first to seventh aspects,
The objective function value is calculated based on each peak value of the fluctuation level in each frequency band.

According to the tenth aspect of the present invention, in one of the first to seventh aspects,
The characteristic value of the tread pattern is a region in which the tread pattern and a predetermined portion of the ground contact region overlap.
The area of the area where the tire contacts the road surface and
The area of the area where the tire does not contact the road surface and
Includes at least one of the tire grooves and the volume of space surrounded by the road surface.

According to the eleventh aspect of the present invention, in the tenth aspect,
The predetermined portion of the ground contact region is at least a region of the front edge and its vicinity and a region of the rear edge and its vicinity with respect to the traveling direction of the tire in the region where the tire contacts the road surface. Including one.

According to the twelfth aspect of the present invention.
A tread pattern generator that includes a storage device and a processing device and generates a tire tread pattern.
The storage device stores the initial value of the tread pattern and the ground contact area indicating the area where the tire contacts the road surface.
The processing device is
The initial value of the tread pattern and the grounded area are read from the storage device,
The ground contact area is scanned in the circumferential direction of the tread pattern, and the fluctuation amount of the characteristic value indicating the shape of the tread pattern in the region where the tread pattern and the predetermined portion of the ground contact area overlap is calculated.
A frequency analysis is performed on the fluctuation amount of the characteristic value of the tread pattern to generate a fluctuation level in the frequency domain.
A predetermined objective function value is calculated based on the fluctuation level in at least two frequency bands.
The deformation position, deformation method, and deformation amount of the tread pattern are determined so that the objective function value satisfies a predetermined criterion in the at least two frequency bands.
A tread pattern deformed by the determined deformation position, deformation method, and deformation amount is generated.
The tread pattern has a plurality of deformation positions and a plurality of deformation methods.
The step of determining the deformation position, the deformation method, and the deformation amount of the tread pattern restricts the application of at least one of the plurality of deformation methods to at least one of the plurality of deformation positions. receive.

According to the thirteenth aspect of the present invention.
A program that generates a tire tread pattern by being executed by a computer.
A step of reading out the initial value of the tread pattern and the ground contact area indicating the area where the tire contacts the road surface from the storage device.
A step of scanning the ground contact area in the circumferential direction of the tread pattern and calculating a fluctuation amount of a characteristic value indicating the shape of the tread pattern in a region where the tread pattern and a predetermined portion of the ground contact area overlap.
A step of performing frequency analysis on the fluctuation amount of the characteristic value of the tread pattern to generate a fluctuation level in the frequency domain, and
A step of calculating a predetermined objective function value based on the fluctuation level in at least two frequency bands.
A step of determining a deformation position, a deformation method, and a deformation amount of the tread pattern so that the objective function value satisfies a predetermined criterion in the at least two frequency bands.
Including the step of generating a tread pattern deformed by the determined deformation position, the deformation method, and the amount of deformation.
The tread pattern has a plurality of deformation positions and a plurality of deformation methods.
The step of determining the deformation position, the deformation method, and the deformation amount of the tread pattern restricts the application of at least one of the plurality of deformation methods to at least one of the plurality of deformation positions. receive.

According to one aspect of the present invention, a tread pattern can be generated more effectively and efficiently than in the prior art.

It is a block diagram which shows the structure of the tread pattern generation system which concerns on 1st Embodiment. It is a figure which shows a part of the exemplary tread pattern 20. It is a figure which shows a part of the tread pattern 20 which concerns on the 1st modification. It is a figure which shows a part of the tread pattern 20 which concerns on the 2nd modification. It is a flowchart which shows the tread pattern generation processing executed by the processing apparatus 1 of FIG. It is a flowchart which shows the subroutine of the tread pattern transformation processing (step S9) of FIG. It is a graph which shows the fluctuation level of the frequency domain of the initial value and the intermediate value of the tread pattern processed in the tread pattern generation process of FIG. It is a figure which shows a part of the tread pattern 20 which concerns on the 3rd modification. It is a figure which shows a part of the tread pattern 20 which concerns on the 4th modification. It is a figure which shows a part of the tread pattern 20 which concerns on 5th modification. It is a figure which shows a part of the tread pattern 20 which concerns on the 6th modification. It is a figure which shows a part of the tread pattern 20 which concerns on 7th modification. It is a figure which shows a part of the tread pattern 20 which concerns on 8th modification. It is a figure which shows a part of the tread pattern 20 which concerns on the 9th modification. It is a figure which shows a part of the tread pattern 20 which concerns on the tenth modification. It is a figure which shows a part of the tread pattern 20 which concerns on 11th modification. It is a figure which shows a part of the tread pattern 20 which concerns on a twelfth modification. It is a figure which shows a part of the tread pattern 20 which concerns on a thirteenth modification. It is a figure which shows a part of the tread pattern 20 which concerns on a 14th modification. It is a figure which shows a part of the tread pattern 20 which concerns on the 15th modification. It is a figure which shows a part of the tread pattern 20 which concerns on the 16th modification. It is a figure which shows a part of the tread pattern 20 which concerns on the 17th modification. It is a flowchart which shows the tread pattern generation process which concerns on 2nd Embodiment. It is a figure which shows the candidate tread pattern table generated by the tread pattern generation process of FIG. It is a flowchart which shows the tread pattern selection process which concerns on 2nd Embodiment.

Hereinafter, the tread pattern generation system according to the embodiment will be described with reference to the drawings.

First embodiment.
FIG. 1 is a block diagram showing a configuration of a tread pattern generation system according to an embodiment. The tread pattern generation system of FIG. 1 includes a processing device 1, an input device 2, a display device 3, and storage devices 4 and 5.

The processing device 1 includes a bus 10, a central processing unit (CPU) 11, a random access memory (RAM) 12, and a hard disk drive (HDD) 13. The processing device 1 may be, for example, a general-purpose computer or any other computing device. The CPU 11, RAM 12, and HDD 13 are connected to each other by a bus 10. The HDD 13 stores a program for tread pattern generation processing, which will be described later with reference to FIGS. 5 and 6. The CPU 11 reads a tread pattern generation processing program from the HDD 13 and executes it on the RAM 12, thereby generating a tread pattern.

The input device 2 includes a keyboard, a mouse, and the like, and receives user input.

The display device 3 displays the contents of the tread pattern generation process (input data, output data, progress, etc.).

The storage device 4 stores input data for the tread pattern generation process, including the initial tread pattern and the grounding area. The initial tread pattern indicates at least one initial value of the pre-given tire tread pattern. The tread pattern is, for example, two-dimensional data (for example, image data) including a region of a structure in contact with the road surface (hereinafter referred to as “block”) and a region of a structure not in contact with the road surface (hereinafter referred to as “groove”). ). The blocks and grooves of the tread pattern are the first direction corresponding to the circumferential direction of the tire (also referred to as the "circumferential direction" of the tread pattern) and the second direction corresponding to the width direction of the tire (the "width direction" of the tread pattern). It is also called). The tread pattern has the length of one lap of the tire in its circumferential direction. The tread pattern may be represented by three-dimensional data instead of two-dimensional data to represent the depth of the groove. Further, the ground contact area indicates a region (footprint) where the tire contacts the road surface.

The storage device 5 stores the output data of the tread pattern generation process, that is, the generated tread pattern. The tread pattern stored in the storage device 5 may be further processed by the processing device 1. Further, the tread pattern stored in the storage device 5 may be sent to another device such as a tire manufacturing device.

Instead of reading the initial tread pattern from the storage device 4, the processing device 1 may internally generate the initial tread pattern, for example, at random.

The storage devices 4 and 5 may be provided as separate devices or may be provided as a single device.

FIG. 2 is a diagram showing a part of an exemplary tread pattern 20. In FIG. 2 and the like, the X direction indicates the width direction of the tread pattern, and the Y direction indicates the circumferential direction of the tread pattern. FIG. 2 and the like show only a part of the tread pattern 20 in the circumferential direction.

The tread pattern 20 of FIG. 2 includes a plurality of blocks 21 having one or a plurality of shapes in a region in contact with a road surface, and a plurality of grooves 22. The tread pattern 20 is divided into a plurality of partial patterns W1 to W5 having a width smaller than the width of the tread pattern 20 and adjacent to each other by a plurality of straight lines along the circumferential direction thereof. In each partial pattern W1, W2, W4, and W5, a plurality of blocks 21 are arranged in a row along the circumferential direction of the tread pattern 20. In the central partial pattern W3, a single block 21 goes around the tread pattern 20 in the circumferential direction. FIG. 2 In another example, the boundary between the partial patterns W1 to W5 is provided on the groove 22 extending in the circumferential direction of the tread pattern 20, but instead, it is provided on the block 21. You may.

The ground contact area 31 in FIG. 2 indicates a region where the tire comes into contact with the road surface as described above, and includes a plurality of blocks 21 and a plurality of grooves 22. The ground contact area 31 has a width equal to or less than the width of the tread pattern 20. The ground contact area 31 moves in the + Y direction on the tread pattern 20 as the tire advances (that is, the rotation of the tire). The ground contact region 31 includes a front edge region 31a including the front edge and its vicinity and a rear edge region 31b including the rear edge and its vicinity in the region where the tire contacts the road surface in the traveling direction of the tire. .. As the tire advances, the tire changes from a state of not contacting the road surface to a state of contacting the road surface in the front edge region 31a, and from a state of contacting the road surface to a state of not contacting the road surface in the rear edge region 31b. Change. Therefore, it is considered that noise is likely to occur especially in the front edge region 31a and the rear edge region 31b when the tire advances. Further, in FIG. 2, regions 31aa and 31ab indicate regions adjacent to the front edge region 31a in the width direction of the tread pattern 20, and regions 31ba and 31bb are adjacent to the rear edge region 31b in the width direction of the tread pattern 20. Areas are shown, and these areas will be described later.

In drawings other than FIG. 2, other reference numerals 21a to 21q may be used to indicate the blocks 21, but these blocks 21a to 21q are also shown together by reference numeral 21. Similarly, in drawings other than FIG. 2, other reference numerals 22a to 22q may be used to indicate the grooves 22, but the reference numerals 22 also collectively indicate these grooves 22a to 22q.

Next, noise reduction by an exemplary tread pattern will be described with reference to FIGS. 3 and 4.

FIG. 3 is a diagram showing a part of the tread pattern 20 according to the first modification. The tread pattern 20 of FIG. 3 includes a plurality of blocks 21a having a rectangular shape and a plurality of grooves 22a.

In order to evaluate the noise generated by the tread pattern 20 of FIG. 3, the tread pattern 20 is scanned in the circumferential direction, and the shape of the tread pattern 20 in the region where the tread pattern 20 and the predetermined portion of the ground contact region 31 overlap. Calculate the amount of fluctuation of the characteristic value indicating. The characteristic value of the tread pattern 20 indicates the area or volume of a predetermined structure in the region where the tread pattern 20 and the predetermined portion of the ground contact region 31 overlap. Here, the predetermined portion of the ground contact area 31 includes at least one of the front edge area 31a and the rear edge area 31b. The characteristic value of the tread pattern 20 includes the area of the front edge region 31a and / or the rear edge region 31b where the tire contacts the road surface (that is, the region of the block 21a). As an addition or alternative, the characteristic value of the tread pattern 20 may include the area of the front edge region 31a and / or the rear edge region 31b where the tire does not contact the road surface (ie, the region of the groove 22a). As an addition or alternative, the characteristic value of the tread pattern 20 may include the volume of the space surrounded by the tire grooves 22a and the road surface in the front edge region 31a and / or the rear edge region 31b. As an addition or alternative, the characteristic value of the tread pattern 20 includes the ratio of the area of the area where the tire contacts the road surface to the area of the area where the tire does not contact the road surface in the front edge region 31a and / or the rear edge region 31b. But it may be. The fluctuation amount of the characteristic value of the tread pattern 20 is shown as the difference or ratio between the characteristic value at a certain position in the circumferential direction of the tread pattern 20 and the average value of the characteristic values when the tread pattern 20 is scanned in the circumferential direction. Will be done.

The predetermined portion of the ground contact area 31 may be the front edge and / or the rear edge of the ground contact area 31 instead of the front edge region 31a and / or the rear edge region 31b. In this case, the characteristic value of the partial pattern W1 indicates the number of pixels of the structure overlapping with these edges.

In the tread pattern 20 of FIG. 3, each block 21a has a front edge and a rear edge substantially parallel to the X direction, and the positions of the front edge and the rear edge of the blocks 21a in each row in the circumferential direction coincide with each other. (Ie, in phase). Therefore, when the tire rotates and the front edge region 31a and the rear edge region 31b intersect the front edge and the rear edge of each block, the characteristic value of the tread pattern 20 fluctuates sharply and significantly. When the characteristic value of the tread pattern 20 fluctuates rapidly and significantly, a large noise is generated from the tire. Therefore, in order to reduce the noise generated by the tire, it is required to gently and reduce the fluctuation of the characteristic value of the tread pattern 20.

FIG. 4 is a diagram showing a part of the tread pattern 20 according to the second modification. The tread pattern 20 of FIG. 4 includes a plurality of blocks 21b having a parallelogram shape and a plurality of grooves 22b. Each block 21b in FIG. 4 is deformed so that two orthogonal sides of each block 21a in FIG. 3 are obliquely crossed by increasing by an angle θ from a right angle. Such deformation is also referred to as strain deformation. In the tread pattern 20 of FIG. 4, each block 21b has a front edge and a rear edge having an angle θ greater than 0 degrees and less than 90 degrees with respect to the X direction, and the front edge and the rear edge of the blocks 21b in each row. The rear edges are arranged so that their circumferential positions are different from each other. Therefore, in the tread pattern 20 of FIG. 4, the fluctuation of the characteristic value can be made more gradual and smaller than in the case of the tread pattern 20 of FIG.

In the generation of a tread pattern according to the prior art, for example, when a tread pattern is generated so as to reduce the magnitude of noise at a certain frequency, the tread pattern may increase noise at other frequencies. Therefore, it is required to generate a tread pattern that reduces noise more effectively than in the prior art.

Further, in the generation of the tread pattern according to the prior art, even if the tread pattern is generated so as to reduce the magnitude of noise, performance other than noise such as grip performance may be deteriorated. Such a tread pattern will not be adopted in the end, and as a result, its generation is wasted. Therefore, it is required to prevent unnecessary generation of the tread pattern and efficiently generate the tread pattern.

Next, with reference to FIGS. 5 and 6, the tread pattern generation system according to the first embodiment generates a tread pattern that reduces noise more effectively than the prior art, more efficiently than the prior art. The method will be described.

FIG. 5 is a flowchart showing a tread pattern generation process executed by the processing device 1 of FIG.

In step S1 of FIG. 5, the processing device 1 reads the initial tread pattern from the storage device 4 as the initial value of the tread pattern 20. In step S2, the processing device 1 reads the grounding area 31 from the storage device 4. In step S3, the processing apparatus 1 scans the tread pattern 20 in the circumferential direction and calculates the amount of fluctuation in the characteristic value of the tread pattern 20. In step S4, the processing apparatus 1 performs frequency analysis on the fluctuation amount of the characteristic value of the tread pattern to generate the fluctuation level in the frequency domain.

FIG. 7 is a graph showing fluctuation levels in the frequency domain of the initial value and the intermediate value of the tread pattern processed in the tread pattern generation process of FIG. In FIG. 7, a frequency band near 300 Hz is shown as a “primary frequency band”, a frequency band near 600 Hz is shown as a “secondary frequency band”, and a frequency band near 1200 Hz is shown as a “fourth frequency band”. show. As described above, since the fluctuation amount of the characteristic value of the tread pattern corresponds to the noise generated by the tire, the graph of FIG. 7 corresponds to the frequency characteristic of the noise generated by the tire. The generated tread pattern is subject to various requirements such as noise reduction in a specific frequency band or noise reduction in all frequency bands. By executing the tread pattern deformation process described later with reference to FIG. 6, a tread pattern deformed to satisfy a predetermined requirement is generated.

In step S5 of FIG. 5, the processing apparatus 1 has at least one frequency band (“1st frequency band” or “all frequency bands”) that is a part of the entire frequency range of the fluctuation level (“first frequency band” or “whole frequency band”). For each "second frequency band" or "specific frequency band"), each fluctuation level of the characteristic value is calculated.

When calculating each fluctuation level of the characteristic value for a plurality of specific frequency bands in step S5, these specific frequency bands include a frequency band including a reference frequency corresponding to the period of the tread pattern 20 with respect to the circumferential direction of the tread pattern 20. It may include at least one frequency band including a frequency that is an integral fraction of the reference frequency. In this case, the reference frequency corresponds to an arbitrary period in which a predetermined number of blocks 21 or grooves 22 are arranged, for example, a minimum period in which the blocks 21 or grooves 22 are arranged, with respect to the circumferential direction of the tread pattern 20. Hereinafter, this cycle is referred to as a "reference cycle". Further, at a frequency that is an integral fraction of the reference frequency, unit structures including blocks 21 or grooves 22 that are multiples of the blocks 21 or grooves 22 related to the reference period are arranged in the circumferential direction of the tread pattern 20. Corresponds to a cycle that is a multiple of the reference cycle. For example, referring to FIG. 7, the fourth frequency band corresponds to the reference cycle in which the block 21 or the groove 22 is arranged, the second frequency band corresponds to a cycle twice the reference cycle, and the primary frequency band corresponds to the reference cycle. Corresponds to a cycle four times that of.

When calculating each fluctuation level of the characteristic value for a plurality of specific frequency bands in step S5, these specific frequency bands include a frequency band including a reference frequency corresponding to the period of the tread pattern 20 with respect to the circumferential direction of the tread pattern 20. It may include at least one frequency band including a frequency that is an integral multiple of the reference frequency. In this case, the reference frequency corresponds to, for example, the frequency of noise generated by the blocks 21 or the grooves 22 arranged in an arbitrary cycle (reference cycle) in the circumferential direction of the tread pattern 20. Further, the frequency that is an integral multiple of the reference frequency corresponds to the frequency of the overtone of the noise generated by the blocks 21 or the grooves 22 arranged in the reference period. For example, referring to FIG. 7, the primary frequency band corresponds to the frequency of noise generated by the blocks 21 or grooves 22 arranged in the reference period, the secondary frequency band corresponds to the frequency of the second harmonic, and the fourth frequency. The band corresponds to the frequency of the 4th overtone.

Although only three frequency bands are shown in FIG. 7, a frequency band including one-third and one-fifth or less of the reference frequency may be included, and a frequency three times or five times or more the reference frequency may be included. It may include a frequency band including.

In step S6, the processing apparatus 1 calculates the fluctuation level of the characteristic value in all frequency bands. The frequency range of the fluctuation level has a finite range because it depends on the shortest and longest periodic structure of the tread pattern 20 and also because it is calculated by frequency analysis.

In step S7 of FIG. 5, the processing apparatus 1 has a predetermined objective function value associated with the shape of the tread pattern based on the fluctuation level in at least two of the plurality of frequency bands calculated in steps S5 to S6. To calculate. The objective function value is calculated based on each total energy or each peak value of the fluctuation level in each frequency band. In the present specification, each total energy of the fluctuation level in each specific frequency band is also referred to as a "POAL (partial overall level) value". Further, the total energy of the fluctuation level in all frequency bands is also referred to as "OAL (overall level) value".

By executing the tread pattern deformation process described later with reference to FIG. 6, the shape of the tread pattern is optimized according to the desired frequency for which noise is to be reduced. In this case, the processing apparatus 1 can use various objective functions under various constraints depending on the content of optimization. For example, the following constraints and objective functions may be used.

(1) From the POAL value of any of the frequency bands under the constraint condition that the objective function consisting of the POAL values is set to the threshold value or less in all of the primary frequency band, the secondary frequency band, and the fourth frequency band. Minimize the objective function. In this case, the magnitude of noise can be reduced in the frequency band in which noise is particularly conspicuous among the primary, secondary, and fourth frequency bands.
(2) the objective function consisting POAL value decreased to 80% or less of the POAL value of the initial tread pattern in the secondary frequency band, 110% of the objective function consisting POAL value in fourth order frequency bands POAL value of the initial tread pattern The objective function consisting of POAL values in the secondary frequency band is minimized under the constraints reduced below. In this case, even if the noise in the fourth frequency band increases to some extent, the noise in the second frequency band can be particularly reduced.
(3) The objective function consisting of the POAL value in the secondary frequency band is reduced to 90% or less of the POAL value of the initial tread pattern, and the objective function consisting of the OAL values of all frequency bands is reduced to the OAL value or less of the initial tread pattern. Under constraints, the objective function consisting of POAL values in the secondary frequency band is minimized. In this case, the noise in the secondary frequency band is particularly reduced, but the noise in all frequency bands is not increased more than the noise in the initial tread pattern.
(4) A weighting coefficient of 0.1 is set for the POAL value of the primary frequency band, a weighting coefficient of 0.5 is set for the POAL value of the secondary frequency band, and 0.4 is set for the POAL value of the fourth frequency band. Set the weighting factor of to minimize the summed objective function. In this case, the primary frequency band, the secondary frequency band, and the fourth frequency band are considered, but the secondary frequency band is more important than the fourth frequency band, and the primary frequency band is not so important.
(5) A weighting coefficient of 0.1 is set for the POAL value of the primary frequency band, a weighting coefficient of 0.5 is set for the POAL value of the secondary frequency band, and 0.4 is set for the POAL value of the fourth frequency band. The objective function summed up by setting the weighting coefficients of is repeatedly calculated over a fixed number of times or a fixed time while changing the shape or phase of each partial pattern. In this case, even if the objective function value does not reach some target value (for example, the minimum value), it can be completed in a certain number of times or a certain time, and the optimum one can be selected.
(6) From the peak value of any of the frequency bands under the constraint condition that the objective function consisting of the peak values in all of the primary frequency band, the secondary frequency band, and the fourth frequency band is set to the threshold value or less. Minimize the objective function. In this case, the peak value can be reduced instead of the POAL value of each frequency band.

For example, when generating a tread pattern 20 having a POAL value smaller than the POAL value of the initial tread pattern in the secondary frequency band, the purpose is to be able to achieve other goals while paying attention to the fluctuation level of the secondary frequency band. Functions may be used.

Further, even if the constraint condition or the objective function value does not reach the threshold value, an evaluation value indicating how close to the threshold value may be calculated, and the tread pattern 20 may be generated based on this evaluation value. .. For example, the objective function consisting of the POAL value in the fourth frequency band may be minimized under the constraint condition that the POAL value in the second frequency band is reduced to 80% or less of the POAL value in the initial tread pattern. In this case, if the POAL value in the fourth frequency band is 110% or less of the POAL value of the initial tread pattern, the above-mentioned constraint condition (2) can be satisfied. On the other hand, even if only a solution having a POAL value of 110% or more in the fourth frequency band is found, the objective function value can be minimized under the constraint condition.

The fluctuation level of each frequency band (for example, its POAL value or peak value) is appropriately set for one or both of the constraint condition and the objective function. The fluctuation level of the frequency band, which must be reduced below the threshold, is set as a constraint. On the other hand, the fluctuation level of the frequency band that is desirable to be reduced as much as possible is set as an objective function. Further, the fluctuation level of each frequency band may be set as both a constraint condition and an objective function according to the requirement.

In practice, in relation to performance other than noise performance, for example, a range in which the shape or phase of each partial pattern can be changed is given as a design constraint, and this is a constraint condition (that is, optimization). Prerequisite).

The constraints and objective functions exemplified above may be used in any other combination.

In step S8 of FIG. 5, the processing apparatus 1 determines whether or not the end condition is satisfied, and if YES, the process proceeds to step S10, and if NO, the process proceeds to step S9. The end condition includes whether or not the objective function value has reached the threshold value, or whether or not the tread pattern generation process has been repeated a certain number of times or for a certain period of time.

In step S9, the processing apparatus 1 executes a tread pattern deformation processing in order to optimize the shape of the tread pattern according to a desired frequency for which noise is to be reduced. Here, the processing device 1 determines the deformation position, the deformation method, and the deformation amount of the tread pattern, and generates the tread pattern deformed by the determined deformation position, the deformation method, and the deformation amount.

FIG. 6 is a flowchart showing a subroutine of the tread pattern deformation process (step S9) of FIG. In step S11, the processing device 1 determines the deformation position of the tread pattern 20. In step S12, the processing apparatus 1 determines a method of deforming the tread pattern 20 at the deformation position determined in step S11. In step S13, the processing apparatus 1 determines the amount of deformation of the tread pattern 20 by the deformation method determined in step S12 at the deformation position determined in step S11. In step S14, the processing apparatus 1 deforms the tread pattern 20 according to the determined deformation position, deformation method, and deformation amount.

The tread pattern 20 has a plurality of deformation positions, a plurality of deformation methods, and a plurality of deformation amounts. The plurality of deformation positions include a plurality of partial patterns W1 to W5. The plurality of deformation methods include the area of the region where the tire contacts the road surface in the region where the tread pattern 20 and the front edge region 31a and / or the rear edge region 31b (see FIG. 2) of the ground contact region 31 overlap, and the tire. It may include changing the ratio to the area of the area that does not touch the road surface. The plurality of deformation methods may include changing the length of the region where the tire contacts the road surface and the length of the region where the tire does not contact the road surface in the circumferential direction of the tread pattern 20 in each partial pattern W1 to W5. good. The method of deformation may include distorting the shape of the area where the tire contacts the road surface. The plurality of deformation methods may include relatively moving the plurality of partial patterns W1 to W5 along the circumferential direction of the tread pattern 20.

Next, various deformation methods will be exemplified by reference with reference to the drawings.

As shown in FIG. 4, the tread pattern 20 may be deformed so as to distort the shape of each block 21. In this strain deformation, as in FIG. 4, the orthogonal axis is converted into an oblique axis at an angle θ, and the shapes of the block 21 and the groove 22 are also deformed accordingly. The magnitude of the strain is defined by the angle θ. In the example of FIG. 4, the partial patterns W1, W2, W4, and W5 are deformed by the distortion of the same angle θ, but the partial patterns W1 to W5 may be deformed by the distortion of different angles.

FIG. 8 is a diagram showing a part of the tread pattern 20 according to the third modification. FIG. 9 is a diagram showing a part of the tread pattern 20 according to the fourth modification. In the partial patterns W2 and W4, the tread pattern 20 of FIG. 8 has a plurality of blocks 21c that are smaller than the block 21 of FIG. 2 and a plurality of blocks 21c that are larger than the groove 22 of FIG. 2 in the circumferential direction of the tread pattern 20. The tread 22c and the like are included. Further, the tread pattern 20 of FIG. 9 has a plurality of blocks 21d obtained by dividing the block 21 of FIG. 2 and a plurality of grooves added between the blocks 21d in the partial patterns W2 and W4 in the circumferential direction of the tread pattern 20. Includes 22d. According to the tread pattern 20 of FIGS. 8 and 9, the length of the block 21 and the length of the groove 22 are changed with respect to the circumferential direction of the tread pattern 20. At the same time, the ratio of the area of the block 21 to the area of the groove 22 in the region where the tread pattern 20 and the front edge region 31a and / or the rear edge region 31b overlap is changed.

FIG. 10 is a diagram showing a part of the tread pattern 20 according to the fifth modification. FIG. 11 is a diagram showing a part of the tread pattern 20 according to the sixth modification. The tread pattern 20 of FIG. 10 includes a plurality of blocks 21e and a plurality of grooves 22e formed inward from the circumference of each block 21e in the partial patterns W2 and W4. The tread pattern 20 of FIG. 11 includes a plurality of blocks 21f and a plurality of grooves 22f formed inside each block 21f in the partial patterns W2 and W4. According to the tread pattern 20 of FIGS. 10 and 11, the ratio of the area of the block 21 to the area of the groove 22 in the region where the tread pattern 20 and the front edge region 31a and / or the rear edge region 31b overlap is changed. ..

The modification of FIGS. 8 to 11 is not limited to the partial patterns W2 and W4, and may be applied to other partial patterns W1, W3, and W5.

FIG. 12 is a diagram showing a part of the tread pattern 20 according to the seventh modification. FIG. 13 is a diagram showing a part of the tread pattern 20 according to the eighth modification. The tread pattern 20 of FIGS. 12 and 13 includes partial patterns W1 to W5, similarly to the tread pattern 20 of FIG. However, in the tread pattern 20 of FIG. 13, at least one of the partial patterns W1 to W5 of the tread pattern 20 of FIG. 12 is relatively moved along the circumferential direction of the tread pattern 20. In the example of FIG. 13, the partial patterns W4 to W5 are moved relative to the partial patterns W1 to W3 as compared with the state of FIG. In other words, in the tread pattern 20 of FIG. 13, the phases of the partial patterns W1 to W5 (that is, the rotation angle in the circumferential direction of the tire) are changed as compared with the tread pattern 20 of FIG. Reference lines 23g and 23h shown in FIGS. 12 and 13 may be referred to in order to represent the phase of each partial pattern W1 to W5. According to the tread pattern 20 of FIGS. 12 and 13, the ratio of the area of the block 21 to the area of the groove 22 in the region where the tread pattern 20 and the front edge region 31a and / or the rear edge region 31b overlap is changed. ..

When the tread pattern 20 is deformed in the region overlapping the front edge region 31a, the tread pattern 20 is similarly deformed in the region overlapping the regions 31aa and 31ab (see FIG. 2) adjacent to the front edge region 31a. When the tread pattern 20 is deformed in the region overlapping the rear edge region 31b, the tread pattern 20 is similarly deformed in the region overlapping the regions 31ba and 31bb (see FIG. 2) adjacent to the rear edge region 31b. When the width of the ground contact area 31 is smaller than the width of the tread pattern 20, a region where the tread pattern 20 and the front edge region 31a and / or the rear edge region 31b do not overlap is generated at both ends of the tread pattern 20 in the width direction. This non-overlapping region does not affect the fluctuation amount of the characteristic value of the tread pattern 20. However, when the shape of the block 21 is distorted or the partial patterns W1 to W5 are relatively moved along the circumferential direction, the tread pattern 20 must be deformed in the non-overlapping region as well as in the overlapping region. Anomalous tread patterns 20 may be generated, such as those containing significant discontinuities. Therefore, as described above, the tread pattern 20 is also deformed in the region overlapping the regions 31aa, 31ab, 31ba, and 31bb.

FIG. 14 is a diagram showing a part of the tread pattern 20 according to the ninth modification. The tread pattern 20 of FIG. 14 includes a plurality of blocks 21i and a plurality of grooves 22i having a larger distortion than the case of FIG. 2 in the partial patterns W1 and W5.

FIG. 15 is a diagram showing a part of the tread pattern 20 according to the tenth modification. The tread pattern 20 of FIG. 15 includes a plurality of blocks 21j and a plurality of grooves 22j that circulate along the circumferential direction of the tread pattern 20, and includes no or almost no grooves 22 along the directions intersecting the circumferential directions. ..

FIG. 16 is a diagram showing a part of the tread pattern 20 according to the eleventh modification. The tread pattern 20 of FIG. 16 includes a plurality of blocks 21k and a plurality of grooves 22k that are significantly modified from the tread pattern 20 of FIG.

FIG. 17 is a diagram showing a part of the tread pattern 20 according to the twelfth modification. FIG. 18 is a diagram showing a part of the tread pattern 20 according to the thirteenth modification. FIG. 19 is a diagram showing a part of the tread pattern 20 according to the 14th modification. The tread pattern 20 of FIG. 17 includes only the block 21l, that is, the region in contact with the road surface, and does not include the groove. The tread pattern 20 of FIG. 18 includes a block 21m and a plurality of small grooves 22m formed inside the block 21m in a very small number. The tread pattern 20 of FIG. 19 includes two blocks 21n and one groove 22n that go around the tread pattern 20 in the circumferential direction. As described above, the tread pattern 20 of FIGS. 17 to 19 hardly includes a region that does not come into contact with the road surface.

FIG. 20 is a diagram showing a part of the tread pattern 20 according to the fifteenth modification. FIG. 21 is a diagram showing a part of the tread pattern 20 according to the sixteenth modification. FIG. 22 is a diagram showing a part of the tread pattern 20 according to the 17th modification. The tread pattern 20 of FIG. 20 includes only the groove 22o and does not include the block. The tread pattern 20 of FIG. 21 includes a plurality of small blocks 21p formed in a small number and a groove 22p occupying most of the others. The tread pattern 20 of FIG. 22 includes one block 21q that goes around the tread pattern 20 in the circumferential direction, and a groove 22q that occupies most of the other. As described above, the tread pattern 20 of FIGS. 20 to 22 contains almost no region other than the groove.

The step of determining the deformation position, the deformation method, and the deformation amount of the tread pattern 20 is restricted so that at least one of the plurality of deformation methods is not applied at at least one of the plurality of deformation positions. Further, the step of determining the deformation position, the deformation method, and the deformation amount of the tread pattern 20 is a predetermined range for at least one of the plurality of deformation methods in at least one of the plurality of deformation positions. You may be constrained to determine the amount of deformation within.

For example, the following restrictions may be imposed on the deformation position.

(1) No modification is applied to the partial patterns W1 and W5 adjacent to the outer circumference of the tread pattern 20.
(2) In the partial patterns W1 and W5 adjacent to the outer periphery of the tread pattern 20, only the deformation that changes the phase of the partial patterns W1 and W5 with respect to the partial patterns W2 to W4 is applied, and other deformations are not applied.

Applying strain deformation can affect the grip performance of the tire. Therefore, due to these restrictions, it is possible to reduce the influence on the grip performance of the tire in the vicinity of the outer periphery of the tread pattern 20 (that is, in the vicinity of the shoulder portion of the tire).

For example, the following restrictions may be imposed on the transformation method.

(1) Strain deformation is not applied. For example, only the modification that changes the phase of each partial pattern W1 to W5 is applied.
(2) The modification that changes the ratio of the area of the block 21 to the area of the groove 22 in the region where the tread pattern 20 and the front edge region 31a and / or the rear edge region 31b overlap is not applied.
(3) A modification that changes the ratio of the area of the block 21 to the area of the groove 22 in the region where the tread pattern 20 and the front edge region 31a and / or the rear edge region 31b overlap is applied, but a new groove is applied. Increase or decrease the width of the existing groove 22 without adding 22.

When the area of the area where the tire contacts the road surface changes, the performance other than the noise performance also changes significantly. Therefore, by not applying the deformation that changes the ratio between the area of the block 21 and the area of the groove 22, it is possible to reduce such an influence on other performance. Further, by increasing or decreasing the width of the existing groove 22 without adding a new groove 22, it is possible to make it difficult for a large change in the appearance (impression) of the tread pattern 20 to occur.

Further, as shown in FIGS. 12 and 13, when applying a modification for changing the phase of each partial pattern W1 to W5, the user particularly refers to the reference lines 23g and 23h, and the shape thereof is as follows, for example. May be judged. In the case of FIG. 12, the user determines that the shape is smooth. On the other hand, in the case of FIG. 13, the user determines that the shape of the reference line 23h is not smooth because it includes bending at a plurality of large angles. Therefore, when applying the deformation that changes the phase of each partial pattern W1 to W5, a constraint may be imposed so that the shape of the reference line becomes smooth.

For example, the following restrictions may be imposed on the amount of deformation.

(1) The strain deformation may be restricted to the range of, for example, −60 degrees ≦ θ ≦ +60 degrees with respect to the initial tread pattern. The strain deformation may be restricted to a different range between the partial patterns W1 and W5 adjacent to the outer periphery of the tread pattern 20 and the other partial patterns W2 to W4.
(2) In the region where the tread pattern 20 and the front edge region 31a and / or the rear edge region 31b overlap, the range for changing the ratio (area ratio) between the area of the block 21 and the area of the groove 22 is the initial tread pattern. The area ratio may be restricted to, for example, 50% to 200%. Here, 100% indicates that the area ratio after deformation is equal to the area ratio related to the initial tread pattern. 50% indicates that the area ratio after deformation is half of the area ratio related to the initial tread pattern due to the decrease in the area of the block 21. 200% indicates that the area ratio after deformation is twice the area ratio related to the initial tread pattern due to the increase in the area of the block 21. Instead of constraining the range in which the area ratio is changed, the range in which the area of the block 21 or the groove 22 is changed may be constrained equivalently.
(3) The deformation that changes the phase of each partial pattern W1 to W5 is a range of rotation angles corresponding to the minimum period in which the blocks 21 or grooves 22 of each partial pattern W1 to W5 are arranged in the circumferential direction of the tread pattern 20. May be constrained to. When at least one of the partial patterns W1 to W5 has a minimum period different from the minimum period of the other partial patterns, the deformation that changes the phase of each partial pattern W1 to W5 is the maximum value of each minimum period. It may be restricted to the range of the rotation angle corresponding to. Further, since there is no period in the partial pattern having no groove along the direction intersecting the circumferential direction like the partial pattern W3, it is not considered when determining the range for changing the phase.

FIG. 14 shows an example in which no constraint is imposed on the strain deformation. FIG. 15 shows an example in which the area of the groove 22 is not restricted and the area of the groove 22 along the direction intersecting the circumferential direction of the tread pattern 20 becomes zero or almost zero. FIG. 16 also shows an example in which the area of the groove 22 is not restricted and the area of the groove 22 along the circumferential direction of the tread pattern 20 becomes zero. 17 to 19 show an example in which the area of the groove 22 becomes zero or almost zero without limiting the ratio between the area of the block 21 and the area of the groove 22. 20 to 22 also show an example in which the area of the block 21 becomes zero or almost zero without limiting the ratio between the area of the block 21 and the area of the groove 22. By imposing appropriate restrictions on the deformation position, the deformation method, and the amount of deformation, it is possible to make the tread pattern 20 as shown in FIGS. 14 to 22 less likely to occur.

The tread pattern transformation process basically uses an algorithm that further transforms the tread pattern having the best objective function value based on the objective function value calculated in the previous iteration of the tread pattern generation process. Further, in the tread pattern deformation processing, an algorithm that randomly selects and transforms a tread pattern having the best objective function value up to the top 10 may be used. Further, in the tread pattern transformation process, an algorithm that occasionally selects and transforms a tread pattern having a low objective function value may be used in order not to fall into a local solution. These algorithms and other algorithms may be combined. Further, even if the effect is estimated to be high, or even if the tread pattern is randomly selected, the parameters outside the range of the constraint condition are not selected.

The amount of deformation of the tread pattern 20 may be searched using any suitable algorithm such as the steepest gradient method, a genetic algorithm, or an algorithm using a neural network.

After executing the tread pattern deformation process of FIG. 6, the processing apparatus 1 repeats steps S3 to S8 of FIG. When the end condition is satisfied in step S8, the deformation position, the deformation method, and the deformation amount of the tread pattern 20 are determined so that the objective function value satisfies a predetermined criterion in at least two frequency bands, and this determination is made. The tread pattern 20 deformed by the deformation position, the deformation method, and the deformation amount is generated.

FIG. 7 shows the first and second tread patterns as intermediate values of the tread patterns generated by the tread pattern deformation process of FIG. 6 from the initial tread pattern. In the example of FIG. 7, in the primary frequency band, the generated first and second tread patterns have about the same fluctuation level. Further, in the secondary frequency band, the second tread pattern has a smaller fluctuation level than the first tread pattern. Further, in the fourth frequency band, the first tread pattern has a smaller fluctuation level than the second tread pattern. The optimum tread pattern can be determined according to the desired frequency for which noise is being reduced.

When step S8 of FIG. 5 is YES, in step S10, the processing device 1 stores the generated tread pattern in the storage device 5.

As described above, according to the first embodiment, the shape of the tread pattern according to the desired frequency for which noise is to be reduced by calculating the objective function value based on the fluctuation level in a plurality of frequency bands. It is possible to generate a tread pattern that reduces noise more effectively than the conventional technology. Further, by imposing a constraint not to apply at least one of the plurality of deformation methods at at least one of the plurality of deformation positions, unnecessary generation of the tread pattern is less likely to occur, and the tread is efficiently generated. It is required to generate a pattern. This makes it possible to generate a tread pattern more effectively and efficiently than in the prior art.

According to the first embodiment, frequency analysis is performed on the fluctuation amount of the characteristic value of the tread pattern to generate the fluctuation level in the frequency domain, so that the characteristic value is processed in the time domain or the spatial domain as compared with the case where the characteristic value is processed in the time domain or the space domain. , The tread pattern can be examined under conditions close to the noise actually felt by the user.

Second embodiment.
In the generation of tread patterns according to the prior art, in order to generate a tread pattern that meets a desired requirement, a large number of candidate tread patterns are first generated, and a process involving a user's judgment is executed to generate a large number of candidate treads. You may choose one of the patterns.

If the noise performance of one candidate tread pattern is good, but other performance such as grip performance is lower than the initial tread pattern, it is desirable not to use that candidate tread pattern. For example, in the candidate tread pattern having the same shape as that of FIG. 14, since the angle of the groove 22i of the partial patterns W1 and W5 with respect to the circumferential direction is small, for example, with respect to the initial tread pattern having the shape of FIG. Grip performance is reduced. The permissible angle of the groove 22 with respect to the circumferential direction is influenced by the ratio of the groove 22 having a small angle among all the grooves 22, the grip performance at another position in the tread pattern, and the like.

When generating a tread pattern that is somewhat similar to the initial tread pattern, it is desirable not to use a candidate tread pattern that has a significantly different shape from the shape of the initial tread pattern. For example, a candidate tread pattern having the shape shown in FIG. 16 may be generated from the initial tread pattern having the shape shown in FIG. Further, for example, a candidate tread pattern having the shapes of FIGS. 17 to 22 may be generated from the initial tread pattern having the shape of FIG. 2. The smaller the restrictions on the deformation position, the deformation method, and the amount of deformation, the more likely it is that a candidate tread pattern having a shape deviating from the shape of the initial tread pattern will be generated. Normally, when generating a tread pattern similar to the initial tread pattern, restrictions are imposed on the parameters of the deformation position, the deformation method, and the amount of deformation, but the candidate tread pattern having a significantly different shape is not left. May be generated.

In order to exclude candidate tread patterns that should not be used, it may be easier and more reliable for the user to make a visual decision than to let the computer make the decision. However, in the generation of such a tread pattern, the user has to confirm and judge a large number of candidate tread patterns, which takes a lot of time and effort. For example, when the user confirms and determines the candidate tread patterns in the order of having the best objective function value, the larger the number of candidate tread patterns to be examined, the longer it takes. Therefore, in the generation of the tread pattern, it is required to reduce the time and effort of the user while executing the process involving the judgment of the user.

Next, with reference to FIGS. 23 to 25, a method of efficiently generating a tread pattern by the tread pattern generation system according to the second embodiment will be described with less effort for the user than in the prior art.

The tread pattern generation system according to the second embodiment is configured in the same manner as the tread pattern generation system of FIG. The processing device 1 executes the tread pattern generation process described with reference to FIG. 23, generates a candidate tread pattern table shown in FIG. 24, and stores it in the storage device 5. Next, the processing device 1 executes the tread pattern selection process described with reference to FIG. 25, and selects one tread pattern from the candidate tread pattern table shown in FIG. 24.

FIG. 23 is a flowchart showing the tread pattern generation process according to the second embodiment.

Steps S21 to S27 in FIG. 23 are the same as steps S1 to S7 in FIG.

In step S28 of FIG. 23, the processing device 1 uses the tread pattern generated by the tread pattern generation process of FIG. 23 (referred to as “candidate tread pattern” in the second embodiment) as a candidate tread pattern table of the storage device 5. Remember in. When step S28 is executed for the first time, the initial tread pattern read from the storage device 4 is stored as it is in the candidate tread pattern table as a candidate tread pattern.

In step S29, the processing apparatus 1 determines whether or not the end condition is satisfied, and if YES, the process is terminated, and if NO, the process proceeds to step S30. The end condition is specified by the user whether or not the objective function value has reached the threshold value, whether or not the tread pattern generation process is repeated a certain number of times or for a certain period of time, or in the tread pattern deformation process of step S30. Includes whether or not all transformations have been performed, and so on.

In step S30, the processing device 1 executes the tread pattern deformation processing. The tread pattern deformation process in step 30 is the same as the tread pattern deformation process described with reference to FIG. By repeating step S30, the initial tread pattern read out in step S21 is variously deformed by a plurality of deformation positions, a plurality of deformation methods, and a plurality of deformation amounts, and a plurality of candidate tread patterns are generated. These candidate tread patterns are stored in the candidate tread pattern table in step S28.

FIG. 24 is a diagram showing a candidate tread pattern table generated by the tread pattern generation process of FIG. 23.

As shown in FIG. 24, the processing apparatus 1 classifies a plurality of candidate tread patterns P1, P2, P3, ... Remember. In the example of FIG. 24, the candidate tread pattern is the area of the block 21 and the area of the groove 22 in the region where the tread pattern 20 and the front edge region 31a and / or the rear edge region 31b overlap in the partial patterns W1 and W5. The ratio (area ratio) is classified according to whether it is in the first range a1 to a2 or in the second range a3 to a4. Further, the candidate tread patterns are further classified in the partial patterns W1 and W5 according to whether the strain deformation angle θ is in the first range b1 to b2 or in the second range b3 to b4. NS. Further, the candidate tread patterns are classified according to whether the area ratio is in the first range c1 to c2 or in the second range c3 to c4 in the partial patterns W2 to W4. Further, the candidate tread patterns are further classified in the partial patterns W2 to W4 according to whether the strain deformation angle θ is in the first range d1 to d2 or the second range d3 to d4. NS. As a result, the plurality of candidate tread patterns are classified into 16 groups.

The processing device 1 stores a plurality of candidate tread patterns P1, P2, P3, ... In the candidate tread pattern table together with the objective function values e1, e2, e3, .... In the example of FIG. 24, in the candidate tread pattern column of each group, it is assumed that the leftmost candidate tread pattern has the best objective function value, and the objective function value of the candidate tread pattern decreases as it goes to the right.

As will be described later with reference to FIG. 25, the processing device 1 sets an enable flag (also referred to as a “first flag”) indicating “available” or “unusable” of each group according to user input. Set. Here, "usable" of a group means that the candidate tread pattern of the group may be displayed on the display device 3 for consideration by the user. On the other hand, "unusable" of a group means that the candidate tread pattern of the group is not displayed on the display device 3. When the flag for each group is "1", it indicates that the group is "available", and when it is "0", it indicates that the group is "unavailable". The enable flag of each group is "1" in the initial state, and is set to "0" when a user input indicating that it cannot be used is received, as will be described later with reference to FIG. 25.

As will be described later with reference to FIG. 25, the processing device 1 has usable flags f1, f2, f3, ... (Also called the second flag) is set. Here, "usable" of the candidate tread pattern means that the candidate tread pattern may be displayed on the display device 3 for consideration by the user. On the other hand, "unusable" of the group means that the candidate tread pattern is not displayed on the display device 3. The usable flags f1, f2, f3, ... Of each candidate tread pattern indicate that the candidate tread pattern is "usable" when it is "1", and when it is "0", the candidate tread pattern is "usable". Indicates that it is "unusable". The usable flags f1, f2, f3, ... Of each candidate tread pattern are "1" in the initial state, and as will be described later with reference to FIG. 25, when a user input indicating that the tread pattern cannot be used is received. Is set to "0".

In each partial pattern W1 to W5, the candidate tread pattern table has an area ratio of another number range, for example, three ranges (for example, 40% to 80%, 80% to 120%,) instead of the two ranges. And 120% to 160%). In the candidate tread pattern table, in each partial pattern W1 to W5, the distortion is replaced by two ranges and other ranges, for example, three ranges (for example, -60 degrees to -20 degrees and -20 degrees to +20). It may be classified according to which of the degrees and +20 degrees to +60 degrees). The candidate tread pattern table may be additionally or as an alternative classified according to the range in which the phase of each partial pattern W1 to W5 is changed. The candidate tread pattern table may, as an alternative, be classified according to which of the different combinations of partial patterns W1 to W5 the deformation position is, depending on which of the individual partial patterns W1 to W5 the candidate tread pattern table is. It may be classified.

The candidate tread pattern table may be stored in the RAM 12 instead of the storage device 5.

FIG. 25 is a flowchart showing a tread pattern selection process according to the second embodiment.

Similarly, if one candidate tread pattern in a group should not be used for reasons other than noise performance, the other candidate tread patterns in the same group will also have a similar shape. It is considered desirable not to use it. Therefore, when even one group includes a candidate tread pattern of "unusable", it is possible to reduce the time and effort of the user by determining that this group itself is "unusable".

In step S31 of FIG. 25, the processing apparatus 1 sequentially selects from the group including the candidate tread pattern having the best objective function value among all the "available" groups, and the best objective included in the selected group. The candidate tread pattern having the function value is read from the storage device 5 and displayed on the display device 3.

The user determines whether the displayed candidate tread pattern is "usable", "unusable", or "usable with a slight change", and inputs the determination result via the input device 2. Here, "can be used with a slight change" means that a candidate tread pattern in which the displayed candidate tread pattern is slightly changed, that is, another candidate tread pattern included in the same group as the displayed candidate tread pattern is "usable". Indicates that it is presumed to be.

In step S32, the processing device 1 determines which user input is received with respect to the displayed candidate tread pattern among "usable", "unusable", and "usable with a slight change". When "available", the process proceeds to step S38, when "unusable", the process proceeds to step S37, and when "usable with a slight change", the process proceeds to step S33.

In step S33, the processing device 1 sets the "unusable" flag for the displayed candidate tread pattern. In step S34, the processing device 1 displays the candidate tread pattern having the best objective function value among the available candidate tread patterns of the group to which the displayed candidate tread pattern belongs on the display device 3.

The user determines whether the displayed candidate tread pattern is "usable" or "unusable", and inputs the determination result via the input device 2.

In step S35, the processing device 1 determines which user input is received from "usable" and "unusable" with respect to the displayed candidate tread pattern. When it is "available", the process proceeds to step S38, and when it is "unusable", the process proceeds to step S36.

In step S36, the processing apparatus 1 determines whether or not all the candidate tread patterns of the group have been displayed, and if YES, the process proceeds to step S37, and if NO, the process returns to step S33.

In step S37, the processing apparatus 1 sets the "unusable" flag for the group including the displayed candidate tread pattern.

In step S38, the processing device 1 selects a candidate tread pattern displayed on the display device 3 and determined to be "usable" as a tire tread pattern, and stores the selected tread pattern in the storage device 5. do. The processing device 1 may store the selected tread pattern separately from the candidate tread pattern table. Alternatively, the processing apparatus 1 may add a flag to the candidate tread pattern table indicating that a candidate tread pattern has been selected in step S38.

According to the tread pattern selection process of FIG. 25, the processing apparatus 1 sequentially selects from the group including the candidate tread pattern having the best objective function value, and selects a plurality of candidate tread patterns included in the selected group as the best. The candidate tread pattern having the objective function value is read out from the storage device 5 and displayed on the display device 3 in order.

When the processing device 1 receives a user input (also referred to as a "first instruction") indicating selection of a tread pattern in step S32 or S35 for receiving a user's instruction, the processing device 1 displays a candidate tread pattern displayed on the display device 3. Select as the tread pattern for the tire.

The processing device 1 receives a group including the candidate tread pattern displayed on the display device 3 when the user input indicating the change of the group (also referred to as “second instruction”) is received in step S32 for receiving the user's instruction. Set to "Unavailable". The processing device 1 reads one candidate tread pattern included in one group that is not set to "unusable" among the plurality of groups from the storage device 5 and displays it on the display device 3.

The processing device 1 has the same group as the candidate tread pattern displayed on the display device 3 when the user input indicating that the group has not changed (also referred to as a "third instruction") is received in step S32 for receiving the user's instruction. The other candidate tread patterns included in the above are read out from the storage device 5 and displayed on the display device 3.

When the processing device 1 receives a user input (also referred to as a "fourth instruction") indicating a change in the candidate tread pattern in step S35 for receiving the user's instruction, the processing device 1 displays the candidate tread pattern displayed on the display device 3 as "4th instruction". Set to "Unavailable". The processing device 1 stores one candidate tread pattern that is not set as "unusable" among a plurality of candidate tread patterns included in one group that is not set as "unusable". It is read from the device 5 and displayed on the display device 3. When all the candidate tread patterns included in one of the plurality of groups are set to be "unusable", the processing device 1 sets the one group to "unusable".

As described above, according to the second embodiment, the user has trouble by classifying a plurality of candidate tread patterns into groups and displaying the candidate tread patterns having the best objective function values in order. Can be reduced to efficiently generate a tread pattern. According to the second embodiment, it is possible to reduce the time and effort of the user while excluding the candidate tread patterns that should not be used as shown in FIGS. 14 to 22 at the discretion of the user. According to the second embodiment, for example, it takes more time and effort for the user than when the candidate tread patterns are not classified into groups and the user confirms and judges all the candidate tread patterns in the order of having the best objective function value. Can be reduced.

The tread pattern generation method and program described above can be applied to any tire having a tread pattern, for example, a pneumatic tire, a non-pneumatic tire, and a resin tire.

1 ... Processing device,
2 ... Input device,
3 ... Display device,
4, 5 ... Storage device,
10 ... Bus,
11 ... Central processing unit (CPU),
12 ... Random access memory (RAM),
13 ... Hard disk drive (HDD),
20 ... tread pattern,
21,21a-21q ... Block,
22, 22a-22q ... Groove,
23g, 23h ... Reference line,
31 ... Grounding area,
31a ... front edge area,
31b ... Rear edge region,
W1 to W5 ... Partial pattern.

Claims (13)

It is a tread pattern generation method that generates a tire tread pattern by a computer.
A step of reading out the initial value of the tread pattern and the ground contact area indicating the area where the tire contacts the road surface from the storage device.
A step of scanning the ground contact area in the circumferential direction of the tread pattern and calculating a fluctuation amount of a characteristic value indicating the shape of the tread pattern in a region where the tread pattern and a predetermined portion of the ground contact area overlap.
A step of performing frequency analysis on the fluctuation amount of the characteristic value of the tread pattern to generate a fluctuation level in the frequency domain, and
A step of calculating a predetermined objective function value associated with the noise generated by the tread pattern based on the fluctuation level in at least two frequency bands.
Wherein as the objective function value satisfies a predetermined criterion, determining a position of deformation, deformation method, and the amount of deformation of the tread pattern for generating a new tread pattern by deforming the tread pattern,
Including the step of generating the new tread pattern deformed by the determined deformation position, the deformation method, and the amount of deformation.
The tread pattern has a plurality of deformation positions and a plurality of deformation methods.
The step of determining the deformation position, the deformation method, and the deformation amount of the tread pattern restricts the application of at least one of the plurality of deformation methods to at least one of the plurality of deformation positions. receiving,
The fluctuation amount of the characteristic value of the tread pattern represents the difference or ratio between the characteristic value at a certain position in the circumferential direction of the tread pattern and the average value of the characteristic values when the tread pattern is scanned in the circumferential direction.
Tread pattern generation method. The step of determining the deformation position, the deformation method, and the deformation amount of the tread pattern is a predetermined range for at least one of the plurality of deformation methods in at least one of the plurality of deformation positions. Including determining the amount of deformation within
The tread pattern generation method according to claim 1. The plurality of deformation positions include a plurality of partial patterns of the tread pattern divided by at least one straight line along the circumferential direction of the tread pattern.
The tread pattern generation method according to claim 1 or 2. The plurality of deformation methods are
Changing the ratio of the area of the region where the tire contacts the road surface and the area of the region where the tire does not contact the road surface in the region where the tread pattern and the predetermined portion of the ground contact region overlap. When,
In each of the partial patterns, the length of the region where the tire contacts the road surface and the length of the region where the tire does not contact the road surface are changed with respect to the circumferential direction of the tread pattern.
Distorting the shape of the region where the tire contacts the road surface so as to convert the two-dimensional orthogonal axis in the plane of the tread pattern into an oblique axis.
Includes at least one of moving the plurality of partial patterns relative to the circumferential direction of the tread pattern.
The tread pattern generation method according to claim 3. The objective function value is
Said fluctuation level at the first frequency band throughout the frequency range of the fluctuation level, the first based on one or more second of the fluctuation level of definitive frequency band and a part of the frequency band Or,
Calculated based on the fluctuation levels in the plurality of second frequency bands.
The tread pattern generation method according to any one of claims 1 to 4. The plurality of second frequency bands are
A frequency band including a reference frequency corresponding to the period of the tread pattern with respect to the circumferential direction of the tread pattern.
Including at least one frequency band including a frequency that is an integral fraction of the reference frequency.
The tread pattern generation method according to claim 5. The plurality of second frequency bands are
A frequency band including a reference frequency corresponding to the period of the tread pattern with respect to the circumferential direction of the tread pattern.
Including at least one frequency band including a frequency that is an integral multiple of the reference frequency.
The tread pattern generation method according to claim 5. The objective function value is calculated based on the total energy of the fluctuation levels in each of the frequency bands.
The tread pattern generation method according to any one of claims 1 to 7. The objective function value is calculated based on each peak value of the fluctuation level in each frequency band.
The tread pattern generation method according to any one of claims 1 to 7. The characteristic value of the tread pattern is a region in which the tread pattern and a predetermined portion of the ground contact region overlap.
The area of the area where the tire contacts the road surface and
The area of the area where the tire does not contact the road surface and
Includes at least one of the tire grooves and the volume of space surrounded by the road surface.
The tread pattern generation method according to any one of claims 1 to 9. The predetermined portion of the ground contact region is at least a region of the front edge and its vicinity and a region of the rear edge and its vicinity with respect to the traveling direction of the tire in the region where the tire contacts the road surface. Including one,
The tread pattern generation method according to claim 10. A tread pattern generator that includes a storage device and a processing device and generates a tire tread pattern.
The storage device stores the initial value of the tread pattern and the ground contact area indicating the area where the tire contacts the road surface.
The processing device is
The initial value of the tread pattern and the grounded area are read from the storage device,
The ground contact area is scanned in the circumferential direction of the tread pattern, and the fluctuation amount of the characteristic value indicating the shape of the tread pattern in the region where the tread pattern and the predetermined portion of the ground contact area overlap is calculated.
A frequency analysis is performed on the fluctuation amount of the characteristic value of the tread pattern to generate a fluctuation level in the frequency domain.
Based on the fluctuation level in at least two frequency bands, a predetermined objective function value associated with the noise generated by the tread pattern is calculated.
Wherein as the objective function value satisfies a predetermined criterion, determining the deformed position, deformation method, and the amount of deformation of the tread pattern for generating a new tread pattern by deforming the tread pattern,
The new tread pattern deformed by the determined deformation position, deformation method, and deformation amount is generated.
The tread pattern has a plurality of deformation positions and a plurality of deformation methods.
The step of determining the deformation position, the deformation method, and the deformation amount of the tread pattern restricts the application of at least one of the plurality of deformation methods to at least one of the plurality of deformation positions. receiving,
The fluctuation amount of the characteristic value of the tread pattern represents the difference or ratio between the characteristic value at a certain position in the circumferential direction of the tread pattern and the average value of the characteristic values when the tread pattern is scanned in the circumferential direction.
Tread pattern generator. A program that generates a tire tread pattern by being executed by a computer.
A step of reading out the initial value of the tread pattern and the ground contact area indicating the area where the tire contacts the road surface from the storage device.
A step of scanning the ground contact area in the circumferential direction of the tread pattern and calculating a fluctuation amount of a characteristic value indicating the shape of the tread pattern in a region where the tread pattern and a predetermined portion of the ground contact area overlap.
A step of performing frequency analysis on the fluctuation amount of the characteristic value of the tread pattern to generate a fluctuation level in the frequency domain, and
A step of calculating a predetermined objective function value associated with the noise generated by the tread pattern based on the fluctuation level in at least two frequency bands.
Wherein as the objective function value satisfies a predetermined criterion, determining a position of deformation, deformation method, and the amount of deformation of the tread pattern for generating a new tread pattern by deforming the tread pattern,
Including the step of generating the new tread pattern deformed by the determined deformation position, the deformation method, and the amount of deformation.
The tread pattern has a plurality of deformation positions and a plurality of deformation methods.
The step of determining the deformation position, the deformation method, and the deformation amount of the tread pattern restricts the application of at least one of the plurality of deformation methods to at least one of the plurality of deformation positions. receiving,
The fluctuation amount of the characteristic value of the tread pattern represents the difference or ratio between the characteristic value at a certain position in the circumferential direction of the tread pattern and the average value of the characteristic values when the tread pattern is scanned in the circumferential direction.
program.

Images