Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1998-08-27
2003-03-11
Maki, Steven D. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C152S209300, C152S209150, C152S209280, C152S902000, C703S001000, C703S006000, C703S008000
Reexamination Certificate
active
06531012
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 a 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 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 is generated during vehicle running in rain, and so as to ensure the 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 the need to increase energy loss, which is antinomical.
Therefore, a theoretical approach has recently been made to design a tire which is quiet and safe during running at a high speed on a dry, wet or icy road. Grooves and the like forming the tread of the tire are designed by a plurality of variable pitch repetition design cycles in accordance with a standard which is mathematically calculated. Based on the design values, a tread having land portions divided by lateral grooves and circumferential grooves which define pitches and pitch arrays on the circumference of the tire is obtained. Here, the term “pitch” means a relative length of the land portion, and the term “pitch array” means a sequence of pitches used on the circumference of the tire. A ratio of a pitch length (pitch ratio) may be used as the pitch in some cases.
Each of the pitches may have different length, but in terms of practicality, the lengths are limited to about nine kinds. A particular length of a particular pitch in a given pitch array differs depending upon the circumference of the tire (see Japanese Patent Application Laid-Open No. 4-232105).
However, in many cases, the pitch and pitch array are determined for enhancing the sound performance or for preventing the hydroplaning phenomenon, or are determined by design requirements so as to match the aesthetic sense of the consumer. Further, a plurality of pitches are repeatedly used in the pitch array. Therefore, rigidities are not uniform among land portions of different pitches. Thus, there are problems that uneven wear is increased, and roundness during manufacturing deteriorates.
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 plurality of antinomical performances are to be obtained, the best mode of a tire is designed under a given condition, and in which the tire can be efficiently designed and developed.
DISCLOSURE OF THE INVENTION
To achieve the above object, according to an embodiment of the invention, there is provided a method for designing a pneumatic tire including the steps of: (a) determining: a tire basic model including a plurality of different basic shape models representing one shape selected from among a shape of a block alone including an internal structure, a pattern shape 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 objective function representing a tire performance evaluation physical amount; a design variable for determining the shape of the block alone, the pattern shape, or the shape of the land portion; and a constraint condition for restricting at least one of the shape of the block alone, the pattern shape, and the shape of the land portion, and for restricting at least one of a tire cross-sectional shape and the tire performance evaluation physical amount; (b) determining a value of the design variable, until an optimal value of the objective function is obtained, by calculation while varying the value of the design variable and while taking the constraint condition into account; and (c) designing the tire on the basis of the design variable which provides the optimal value of the objective function.
There is also provided in the method for designing a pneumatic tire that the design variable is for determining another shape of the block alone, another pattern shape or another shape of the land portion, by using at least one of the different basic shape models as a reference shape model.
Also provided in the method for designing a pneumatic tire, the shape of the block alone, the pattern shape or the shape of the land portion is determined by using a predetermined basic shape model of the plurality of different basic shape models as a reference model.
There is also provided in the method for designing a pneumatic tire that in the step (b) discussed above, a variation amount of the design variable which provides the optimal value of the objective function while taking the constraint condition into account is estimated based on a sensitivity of the objective function, which is a ratio of a unit variation amount of the design variable to a variation amount of the objective function, and based on 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 objective 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 an amount corresponding to the estimated amount is calculated; and a value of the design variable which provides the optimal value of the objective function while taking the constraint condition into account is determined on the basis of the estimated values and the calculated values.
In the method for designing a pneumatic tire discussed above, a selection group including a plurality of tire basic models including a plurality of different basic shape models representing one shape selected from among a shape of a block alone including an internal structure, a pattern shape 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 is determined; and for each of the tire basic models of the selection grou
Bridgestone Corporation
Maki Steven D.
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