JP3377262B2 - Pneumatic tires for motorcycles - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire for a motorcycle having improved running performance on ice and snowy roads. 2. Description of the Related Art Conventionally, in motorcycles that run in cold and snowy areas, spike tires have been frequently used to increase the gripping force and braking force against running on icy and snowy roads. . [0003] When traveling on a dry road surface without snow, such a spiked tire reduces the running stability such as rutting due to spikes, and reduces dust by grinding the road surface. It often happens. [0004] In recent years, studless tires using soft rubber on the tread surface have been used instead of spikes.
Rather than the spiked tires described above, demands have been made by consumers for improved spiked tires on icy and snowy roads. As a result of repeated studies in response to the above demand, the inventor (1) increases the radius of curvature of the tread surface. (2) Improve the land ratio of the tread surface. (3) The vertical groove in the shoulder region is made shallow. By taking such measures, it has been found that even with snow tires without spikes, running performance on icy and snowy roads can be enhanced while maintaining running performance on dry road surfaces, and the present invention has been completed. [0006] The present invention provides ice, without spikes,
It is an object of the present invention to provide a pneumatic tire for a motorcycle that can improve running performance on snowy roads and maintain running stability even on a dry road surface. According to the present invention, a tread surface is curved in an arc shape in a meridional section of a tire and a groove is provided, so that a tread surface has a land surface and a sea surface recessed from the land surface. In the formed pneumatic tire for a motorcycle, a radius of curvature of a tread surface in a meridional section in a normal state in which the tire is loaded on a regular rim and filled with a prescribed internal pressure is 0.90 to 1.10 of a sectional width of the tire. In the normal state, the ratio SL / SS between the area SS of the contact surface where the tire contacts the ground when a prescribed maximum load is applied and the area SL of the land surface within the contact surface is 0.55. The inner region and the outer region outside the tire are separated from the equator of the tire by 0.25 times the width of the tread peripheral surface, which is the length between the tread edges along the tread surface. With virtual division Also, on the tread surface, the vertical
A vertical groove comprising a groove and an external vertical groove provided in the outer region; and
Between the inner and outer flutes, between the inner and outer flutes, the outer flutes
With a lateral groove extending between the tread edge
The tread surface is formed in a block pattern, and
Ratio Gh between the groove depth Gh of the vertical groove and the groove depth GH of the internal groove.
/ A GH with a 0.45 to 0.65, said transverse groove
Shallow the groove bottom near the outer longitudinal groove,
It is characterized by being smoothly connected to the groove. [0008] The cross-sectional width is defined as the width obtained by removing the pattern, characters, and the like on the side surface of the tire from the total width of the tire in a normal state without a tread as defined in JIS D4203. The radius of curvature of the tread surface is set to 0.90 of the sectional width.
1.10 times. This value is significantly larger than that of the conventional snow tire which is about 0.75 to 0.85 times. As a result, the area of the ground contact surface becomes larger than that of the conventional tire, so that grip performance and braking performance on ice and snowy roads are improved. If it is less than 0.90, grip performance and braking performance cannot be secured. If it exceeds 1.10 times, the shape of the ground contact surface becomes in the shape of a drum, and the straight running stability decreases when traveling on dry roads. In addition, the running stability when turning with a bank angle is specific to motorcycles. Inferior in sex. Further, the ratio SL / SS of the total area on the ground contact surface to the land area is set to 0.55 to 0.75. In a conventional snow tire, the area ratio SL / SS is set to 0.4
By increasing the land area as compared with the range of 0.5 to 0.5, grip performance and braking performance on ice and snowy roads are improved. If the ratio is less than 0.55, the grip strength is poor, and if it exceeds 0.75, the area of the sea surface is reduced. As a result, drainage during running on rainy weather is poor, and hydroplaning tends to occur. Further, the ratio Gh / GH of the groove depth Gh of the vertical groove in the outer region to the groove depth GH of the vertical groove in the inner region is set to 0.45-0.
65. By making the vertical groove in the outer region shallow, the rigidity of the tread portion is increased, and the running stability on a dry road surface is enhanced. The ratio Gh / GH
Is less than 0.45, when turning on an ice-snow road,
While the grip force is insufficient, if it exceeds 0.65, improvement in running stability on dry road surface cannot be achieved. As described above, according to the present invention, the above-described components are organically combined and integrated, so that even when the motorcycle is in a traveling state peculiar to a motorcycle that turns with a bank angle,
It is possible to increase the grip force when traveling on ice and snow, improve the braking performance, and maintain the stability of traveling on dry road surfaces. An embodiment of the present invention will be described below with reference to the drawings. 1 and 2, a pneumatic tire 1 for a motorcycle
In the tread surface 2, a land surface 4 and a sea surface 5 depressed from the land surface are formed in the tread surface 2 by forming a groove 3 in an arc shape in a tire meridional section. The pneumatic tire 1 for a motorcycle includes a tread portion 12, a sidewall portion 13 extending inward in the tire radial direction from both ends thereof, and a bead located at an inner end of the sidewall portion 13 in the tire radial direction. The motorcycle tire 1 has a body portion extending from the tread portion 12 to the bead core 15 of the bead portion 14 through the sidewall portion 13, and the bead core 15 is provided from the inside in the tire axial direction to the outside. In the present embodiment, the carcass 16 has a carcass 16 having a winding portion extending toward the front and a belt layer 17 disposed inside the tread portion 12 and radially outside the carcass 16. A bead apex 18 having a triangular cross section is set up. The carcass 16 has at least one carcass cord having a radial array inclined at an angle of 70 to 90 degrees with respect to the tire equator C in this embodiment.
The carcass cord is made of one sheet of carcass ply, and the carcass cord is made of organic fibers such as nylon, rayon, polyester, and aromatic polyamide. The belt layer 17 includes at least one belt cord having belt cords arranged in a direction inclined with respect to the tire equator C.
In this embodiment, the belt cords are composed of two belt plies 17A, 17A, and the belt cords of both belt plies 17A, 17A are arranged in a direction crossing each other. As the belt cord, a steel cord is used in addition to organic fibers such as nylon, rayon, polyester, and aromatic polyamide. The belt layer 17 has a belt circumferential width LB which is a width in the tire axial direction along the circumferential surface thereof, and a tread edge E, E along the tread surface.
It is preferable to set the width of the tread circumferential surface L, which is the length between them, to 0.8 to 1.1 times. The tread surface 2 has a curvature radius TR in a meridional cross section of 0.90 to 0.90 of a cross-sectional width WT of the tire in a normal state in which the tire is mounted on a normal rim J and a specified internal pressure is filled. It is formed with a large radius of 1.10 times. Further, the tread surface 2 is moved from the tire equator C to the tread circumferential surface width L of 0.2 in the normal state.
The virtual area is virtually divided into an inner area 6 in a range separated by a distance of 5 times on both sides and a pair of outer areas 7 located outside the inner area 6. On the tread surface 2, outer vertical grooves 9, 9 extending substantially linearly in the circumferential direction are respectively arranged in the outer regions 7, 7, and in the inner region 6, the tire equator is provided. C
A pair of vertical grooves 10, 10 circling around in a zigzag manner is disposed on both sides of the vertical groove 10. Between these inner and outer vertical grooves 9, 10,
The inner horizontal grooves 21 connecting the vertical grooves 10 between the two vertical grooves 10 while being bent in a mountain shape, the intermediate horizontal grooves 22 connecting the inner vertical grooves 10 and the outer vertical grooves 9, and the outer horizontal grooves 22. Outer horizontal grooves 23 extending from the vertical groove 9 to the tread edge E are provided. Therefore, each of these longitudinal grooves 9,
10 and a groove 3 formed by each of the lateral grooves 21, 22, 23 are formed, and a land surface 4 and a sea surface 5 are formed on the tread surface 2 by the groove 3. Further, in this example, a block pattern composed of a large number of blocks separated by the vertical grooves 9 and 10 and the horizontal grooves 21, 22 and 23 is formed on the tread surface 2. In the normal state, the tread surface 2 is naturally provided with a contact surface A on which the tire comes into contact when a maximum load specified for the tire is applied. In this ground plane A, the total area SS of the ground plane
And the ratio SL / S between the land surface 4 and the area SL of the land surface 4 in the ground plane.
S is in the range of 0.55 to 0.75. Moreover, the outer vertical groove 9 located in the outer region 7
The ratio Gh / GH of the groove depth Gh of the inner groove 6 to the groove depth GH of the inner vertical groove 10 located in the inner region 6 is 0.45 to 0.65. The intermediate lateral groove 22 and the outer lateral groove 23 connected to the outer longitudinal groove 9 have a groove depth substantially the same as the inner longitudinal groove 10, and these lateral grooves 22 and 23 are located near the outer longitudinal groove 9. , The groove bottom is made shallow, and the groove is smoothly connected to the outer vertical groove 9. [Specific Examples] Tires (Examples) 1 to 3 having a tire size of 2.75 to 14 and having the structure shown in FIGS. 1 and 2 were prototyped, and their performance was tested.
Note that snow tires having a conventional configuration (Comparative Examples 1 to 3)
A test was also performed on the spiked tire (Comparative Example 4) and the performance was compared. The test conditions are as follows. A) Braking performance on ice A test tire is mounted on a test vehicle, and the vehicle travels on a test road formed by an ice plate at a constant speed of 15 km / H. The braking distance is applied until a sudden brake is applied and the vehicle stops. Was measured and indicated by an index with Comparative Example 2 being 100. The larger the value, the shorter and better the control distance. B) Braking performance on snow The vehicle was driven on a snowy road at a constant speed of 20 km / H, and braking was applied and evaluated in accordance with the above-described braking performance test on ice. C) Driving Stability on Dry Road Surface The test vehicle was run on a general road and judged based on the driver's feeling. The higher the value, the better. D) Braking performance on a wet road surface The test vehicle enters a straight road with a depth of 5 mm at a speed of 50 km / H, and the distance that the vehicle slips when the vehicle is suddenly braked by a four-wheel lock is measured. Then, Comparative Example 2 was changed to 100
It was indicated by an index. The higher the value, the better. Table 1 shows the test results. [Table 1] As a result of the test, the example of the present invention has improved braking performance on icy and snowy roads and steering stability on a dry road surface compared to the conventional snow tires of Conventional Examples 1 and 2, and is a spike tire. It was confirmed that the steering stability on a dry road surface could be significantly improved while maintaining the braking performance on ice, snowy roads and wet road surfaces close to Comparative Example 3. As described above, the pneumatic tire for a motorcycle according to the present invention has the above-described curvature radius ratio, land surface area ratio, and vertical groove depth ratio in the outer region. Grip force at the time of running on ice and snow is increased, braking capability is increased compared to conventional snow tires, and stability of running on dry road surface can be maintained, and it is suitably adopted as a motorcycle tire for running on ice and snow. sell.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing one embodiment of the present invention. FIG. 2 is a developed plan view showing the tread pattern. [Description of Signs] 2 Tread surface 3 Groove portion 4 Land surface 5 Sea surface 6 Inner area 7 Outer area 9 Outer vertical groove 10 Inside vertical groove A Tread surface C Tire equator E Groove depth of vertical groove in tread edge GH Gh Groove depth of the outer vertical groove J Regular rim L Tread peripheral width TR Curvature radius WT Cross-sectional width

Claims (1)

(57) [Claim 1] A tread surface is curved in an arc shape in a meridional section of a tire and a groove is provided to form a land surface on the tread surface and a sea surface recessed from the land surface. A pneumatic tire for a motorcycle, wherein a radius of curvature of a tread surface in a meridional section in a normal state loaded on a regular rim and filled with a prescribed internal pressure is 0.90 to 1.10 times the sectional width of the tire. In the normal state, the ratio SL / SS of the area SS of the contact surface where the tire contacts the ground when a prescribed maximum load is applied and the area SL of the land surface in the contact surface is 0.55 to 0. .75
In addition, from the tire equator, it is virtually divided into an inner area between the two sides at a distance of 0.25 times the tread peripheral width, which is the length between the tread edges along the tread surface, and an outer area outside the inner area. A vertical groove provided in the inner region on the tread surface;
Flutes consisting of outer flutes provided in the area, and inner flutes
Between, between inner flute and outer flute, outer flute and tread edge
The tread surface is provided by providing a transverse groove extending between the tread and the edge.
Are formed in a block pattern, and the groove depth Gh of the outer vertical groove and the groove depth GH of the inner vertical groove are
The ratio Gh / GH is set to 0.45 to 0.65, and the width of the horizontal groove is made shallow near the outer vertical groove.
A motorcycle pneumatic tire characterized by being smoothly connected to the outer vertical groove .