Resilient tires and wheels – Tires – resilient – Anti-skid devices
Reexamination Certificate
1998-02-26
2001-04-24
Maki, Steven D. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Anti-skid devices
C152S209280
Reexamination Certificate
active
06220320
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pneumatic tire for a two-wheeled vehicle, particularly relates to a pneumatic tire for a two-wheeled vehicle capable of obtaining high lateral stiffness without requiring any tire structural change, material change and the like, and of exhibiting improved steering stability.
2. Description of the Related Art
In a conventional pneumatic tire for a two-wheeled vehicle, it is general to employ a measure for improving steering stability as possible under a specified tire size, and it is also general to improve the lateral stiffness of a tire as an advantageous standard of the measure.
As an effective means for improving the lateral stiffness of a tire, hitherto, it has been mainly conducted for each kind of members for constructing a tire, i. e., carcass ply, cord layers such as belt or breaker, and the like, further bead filler effective for bead portion reinforcement and the like, to improve the material and the structure of these members, and to arrange additional reinforcing members.
The aforesaid means certainly contributes to improvement of the lateral stiffness of a tire, but simultaneously encounters a problem that the lateral stiffness improvement by the change of material and structure increases the vertical spring constant of a tire with the result that the confort against vibration is reversely affected. Moreover, the lateral stiffness improvement contingent to the addition of members is undesirable for not only an increase of the material cost but also an increase of the processing cost.
SUMMARY OF THE INVENTION
Accordingly, an object of the invention is to provide a pneumatic tire for a two-wheeled vehicle capable of obtaining high lateral stiffness without requiring any structural change, material change and the like of a tire, and of exhibiting improved steering stability.
It has been well-known that an increase of the ground-contact area of a load rolling tire at the tread surface as possible is effective for the lateral stiffness improvement of a tire for a two-wheeled vehicle. As one technique for increasing the ground-contact area, it is effective to decrease the flexural stiffness of a tread portion, but this technique tends to deteriorate the shearing stiffness of the tread portion within the ground-contact area, further has a tendency to lower the flexural stiffness at a non-ground-contact area, and both these tendencies are disadvantageous to steering stability. The present inventors have therefore energetically studied by aiming at a tread pattern for increasing the ground-contact area without such disadvantage, and as a result, solved the above problem by forming a predetermined reverse W-shaped pattern in a tread portion, and accomplished the present invention.
According to the invention, there is the provision of a pneumatic tire for a two-wheeled vehicle formed with numerous sets of combination lug groove patterns on the tread surface of a tread portion, wherein one set of the left and right sides of the lug groove patterns is reverse W-shaped as a whole in the tire rolling direction, each of mid bending points P on both sides of the reverse W-shape is arranged at the region of 20-80% of a tire tread half width TW from a tire central circumferential line EC, an angle &agr; of the lug groove component to a tire shoulder portion from the mid bending point P is 20-70° with respect to a tire equatorial plane E, and an angle &bgr; of the lug groove component to the tire central circumferential line EC from the bending point P is 20-70° with respect to the tire equatorial plane E.
The pneumatic tire for a two-wheeled vehicle according to the invention preferably forms at least one circumferential groove in a tread central region and arranges the circumferential groove in the region from the tire central circumferential line EC to 35% of the tire tread half width TW. Moreover, a pitch DP of the lug groove is preferably {fraction (1/100)}-{fraction (1/20)} of the entire circumferential length, and furthermore, an offset amount OF for offsetting left and right patterns by symmetrizing the central circumferential line EC is preferably 0-{fraction (1/20)} of the whole circumferential length. Here, the central circumferential line EC means a crossing line between the tire equatorial plane E and the tread surface.
REFERENCES:
patent: 5358020 (1994-10-01), Haas
patent: 5421389 (1995-06-01), Favre et al.
patent: 368553 (1990-05-01), None
patent: 56-90702 (1981-07-01), None
patent: 63-116907 (1988-05-01), None
patent: 3-135802 (1991-06-01), None
patent: 3-273909 (1991-12-01), None
patent: 8-142609 (1996-06-01), None
patent: 9-48214 (1997-02-01), None
Nakagawa Hidemitsu
Sumida Takashi
Bridgestone Corporation
Maki Steven D.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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