Data processing: structural design – modeling – simulation – and em – Structural design
Reexamination Certificate
1998-08-27
2001-05-08
Teska, Kevin J. (Department: 2123)
Data processing: structural design, modeling, simulation, and em
Structural design
C703S006000, C152S450000, C152S454000
Reexamination Certificate
active
06230112
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method for designing a pneumatic tire, and more particularly, to a method for designing a pneumatic tire capable of efficiently and easily designing the development of a design such as the tire structure, shape, and the like which achieve a single object performance, antinomical performances, and the like.
BACKGROUND ART
Conventional methods for designing tires are based on empirical rules achieved by a repetition of numerical experiments using actual experimentation and computers. Therefore, the number of trials and tests required for development is extremely large, which increases development costs, and the development time period cannot be shortened easily.
For example, the shape of the crown portion of a tire is designed on the basis of several arcs in a cross-sectional configuration including a rotational axis of the tire. A value of an arc is determined from data obtained by preparing several molds and testing and evaluating tires prepared from the molds, or is determined by conducting many numerical experiments. Therefore, the development efficiency is not good.
Further, pattern design has many degrees of freedom. Therefore, after grooving a proposed basic pattern in a tire or after actually preparing a mold, a trial tire is made and tested on a vehicle and evaluated. Problems arising at the vehicle are overcome by finely modifying the proposed basic pattern, so as to complete a final pattern. Thus, pattern design is in a field requiring the most processes, as compared with the designing of tire shape and structure.
A pneumatic tire is generally formed with rib grooves in a circumferential direction of the tire and lug grooves in a radial direction of the tire, so as to prevent the hydroplaning phenomenon which occurs during vehicle running in rain, and so as to ensure braking performance and traction performance. A general pattern is a so-called block pattern which includes island shaped land portions surrounded by these rib grooves and lug grooves.
Such a block pattern requires running performances of the tire, in general, both a straight running performance and a cornering performance. The straight running performance requires a grip force in a circumferential direction of the tire, and a relatively hard rubber is suitable. On the other hand, the cornering performance requires a grip force in a widthwise direction of the tire, and a relatively soft rubber is suitable to increase the grip force during cornering. Due to the soft rubber, there is need to increase energy loss, which is antinomical.
For this reason, in order to obtain a plurality of antinomical performances, there has been proposed a so-called widthwisely divided tread in which the tread is divided in a widthwise direction, a soft tread rubber is used in regions in the vicinities of both ends of the tread which contribute greatly to cornering, and a hard tread rubber is used in a center region of the tread which contributes greatly to straight running (Japanese Patent Application Publication Nos. 58-50883 and 63-23925).
However, a tire provided with the widthwisely divided tread as in the conventional art is inferior in productivity, and has a problem that irregular wear or separation occurs at a boundary surface of the division.
Further, in many cases, a block shape of the ground- contacting surface of the tire tread portion is determined so as to prevent the hydroplaning phenomenon, or is determined by requirements in terms of braking performance, traction performance, and design which is fit for aesthetic appearance, and therefore, the degrees of freedom in design are largely limited.
In view of the above circumstances, it is an object of the present invention to provide a method for designing a pneumatic tire, in which when a single performance or a plurality of antinomical performances are to be obtained, the best mode of a tire is designed under a given constraint conditions, and in which the tire can be efficiently designed and developed.
DISCLOSURE OF THE INVENTION
To achieve the above object, according to claim
1
, there is provided a method for designing a pneumatic tire including the steps of: (a) determining: a basic shape model representing one shape selected from a shape of a block including an internal structure, a shape of a pattern of a portion of a tire crown portion including an internal structure, and a shape of a land portion which is continuous in a tire circumferential direction including an internal structure; an object function representing a tire performance evaluation physical characteristic; a design variable for determining the shape of the block, the shape of the pattern or the shape of the land portion; and a constraint condition for constraining at least one of a tire cross-sectional configuration, the tire performance evaluation physical characteristic, and the one shape selected from the shape of the block, the shape of the pattern and the shape of the land portion; (b) determining a value of the design variable by calculating while varying the value of the design variable until the optimal value of the object function is obtained, while taking the constraint condition into account; and (c) designing a tire based on the design variable which provides the optimal value of the object function.
According to claim
2
, there is provided a method for designing a pneumatic tire according to claim
1
, wherein in the step (b), a variation amount of the design variable which provides the optimal value of the object function is estimated while taking the constraint condition into account and on the basis of a sensitivity of the object function, which is a ratio of a unit variation amount of the design variable to a variation amount of the object function, and on the basis of a sensitivity of the constraint condition, which is a ratio of a unit variation amount of the design variable to a variation amount of the constraint condition; a value of the object function when the design variable is varied by an amount corresponding to the estimated amount is calculated and a value of the constraint condition when the design variable is varied by the amount corresponding to the estimated amount is calculated; and a value of the design variable which provides the optimal value of the object function is determined on the basis of the estimated value and the calculated values while taking the constraint condition into account.
According to claim
3
, there is provided a method for designing a pneumatic tire according to claim
1
, wherein in the step (a), a selection group including a plurality of basic shape models representing one shape selected from the shape of the block including the internal structure, the shape of the pattern of a portion of a tire crown portion including the internal structure, and the shape of the land portion which is continuous in a tire circumferential direction including the internal structure is determined; and the object function, the design variable, the constraint condition, and an adaptive function which can be evaluated from the object function and the constraint condition are determined for each basic shape model of the selection group; and in the step (b), two basic shape models are selected from the selection group on the basis of the adaptive function; the design variables of the two basic shape models are crossed at a predetermined probability to create a new basic shape model and/or a portion of the design variable of at least one of the two basic shape models is varied to create a new basic shape model; an object function, a constraint condition and an adaptive function of the basic shape model whose design variable has been varied are determined, the basic shape model whose design variable has been varied and a basic shape model whose design variable has not been varied are stored, the above operations are repeated until the number of stored basic shape models reaches a predetermined number, it is determined whether a new group including the predetermined number of the stored basic shape models sa
Bridgestone Corporation
Sergent Douglas W.
Sughrue Mion Zinn Macpeak & Seas, PLLC
Teska Kevin J.
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