Patent Application
20240316994
This application claims the benefit of foreign priority to Japanese Patent Application No. JP2023-044371, filed Mar. 20, 2023, which is incorporated by reference in their entirety.
The present disclosure relates to a pneumatic tire.
Japanese Unexamined Patent Application Publication No. 2017-074834 describes a pneumatic tire with insulations located between the carcass and inner liner. The insulations each have an insulation bottom portion located radially between a core and a bottom surface of a chafer.
In recent years, there has been a demand for improving cornering performance, which is running stability during cornering. In order to improve the cornering performance, it is important to increase a rim tightening force, which is the fitting pressure between bead portions and a rim, for example. In particular, in motorcycle tires used for motorcycles which are tilted during cornering, it is particularly important to increase the rim tightening force. However, increasing the rim tightening force causes increased vibration and the like when riding over gaps in the road surface.
The present disclosure was made in view of the above, and a primary object thereof is to provide a pneumatic tire capable of improving the cornering performance while maintaining vibration absorbing performance.
The present disclosure is a pneumatic tire including:
By adopting the above configuration, the pneumatic tire of the present disclosure can improve the cornering performance while maintaining the vibration absorbing performance.
An embodiment of the present disclosure will now be described in conjunction with accompanying drawings.
The drawings contain exaggerated representations and representations that differ from the actual dimensional ratios of the structure in order to aid in the understanding of the present disclosure. Further, in cases where there are multiple embodiments, the identical or common elements are denoted by the same reference numerals throughout the specification, and redundant explanations will be omitted.
In the present specification, unless otherwise noted, the dimensions and the like of various parts of the tire 1 are measured under the standard state. The term “standard state” refers to a state in which the tire 1 is assembled on a standard rim (R), inflated to a standard inner pressure, and loaded with no tire load.
The “standard rim (R)” refers to a wheel rim specified for the concerned tire by a standard included in a standardization system on which the tire is based, for example, the “normal wheel rim” in JATMA, “Design Rim” in TRA, and “Measuring Rim” in ETRTO.
The term “standard inner pressure” refers to air pressure specified for the concerned tire by a standard included in a standardization system on which the tire is based, for example, the maximum air pressure in JATMA, maximum value listed in the “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” table in TRA, and “INFLATION PRESSURE” in ETRTO.
The tire 1 in the present embodiment includes a pair of bead portions 4. Each of the bead portions 4 includes a bead bottom surface (4a) and a bead outer side surface (4b). The bead bottom surface (4a) is the outer surface of each of the bead portions 4 facing inward in the tire radial direction, and contacts a rim seat (Rs) of the standard rim (R) (hereinafter, may be simply referred to as “rim (R)”). Generally, the bead bottom surface (4a) has a tapered angle that slopes inward in the tire radial direction toward the inner side in the tire axial direction. The bead outer side surface (4b) is the outer surface of each of the bead portions 4 facing outward in the tire axial direction and contacts a rim flange (Rf) of the rim (R).
Each of the bead portions 4 is provided with a bead core 5. Further, the tire 1 includes a pair of sidewall portions 3 each disposed radially outside a respective one of the bead portions 4, and the tread portion 2 that connects the sidewall portions 3, for example.
At least one of the bead portions 4 is provided with a reinforcing filler 10 made of a rubber composition and arranged along the bead core 5 of the at least one of the bead portions 4. In the present embodiment, the reinforcing filler 10 is disposed in each of the bead portions 4.
The reinforcing filler 10 includes an inner portion 11, an outer portion 12, and a middle portion 13. The inner portion 11 has a part located axially inside the bead core 5 and extends therefrom in the tire radial direction on the axially inner side of the bead core 5. The outer portion 12 extends in the tire radial direction on the axially outer side of the bead core 5. The middle portion 13 extends in the tire axial direction on the radially inner side of the bead core 5 so as to connect the inner portion 11 and the outer portion 12, more specifically, so as to connect the radially inner end of the inner portion 11 and the radially inner end of the outer portion 12. The middle portion 13 configured as such increases the rubber volume on the radially inner side of the bead core 5, therefore, the rim tightening force is increased, thereby, the cornering performance is improved.
The outer portion 12 has an outer end (12e) in the tire radial direction located radially inside an outer end (11e) in the tire radial direction of the inner portion 11. The outer portion 12 configured as such suppresses an excessive increase in the rigidity of the tire, therefore, the vibration during running is suppressed, thereby, the vibration absorbing performance is maintained high. Further, the region where the inner portion 11 is located is a region where a large amount of deflection occurs during running since the region where the inner portion 11 is located is further away from the rim flange (Rf) than the region where the outer portion 12 is located. Therefore, by arranging the inner portion 11, which has the outer end (11e) located radially outside the outer end (12e) of the outer portion 12, in the area where the inner portion 11 should be arranged, the deflection of the tire during running can be effectively suppressed, thereby, the cornering performance can be further improved.
The reinforcing filler 10 configured as such is formed from the following rubber composition. The rubber composition has a loss tangent tan δ at 70 degrees Celsius of preferably 0.06 or more, more preferably 0.2 or more, and preferably 1.5 or less, more preferably 1.0 or less. Since the loss tangent tan δ is 0.06 or more, a vibration absorbing effect can be maintained high. Since the loss tangent tan δ is 1.5 or less, a decrease in the rigidity due to heat generation can be suppressed, therefore, the cornering performance can be improved. Further, the rubber composition has a rubber hardness at 23 degrees Celsius of preferably 65 degrees or more, more preferably 70 degrees or more, and preferably 85 degrees or less, more preferably 80 degrees or less. Since the rubber hardness is 65 degrees or more, the rigidity of the tire 1 is ensured and the cornering performance can be improved. Since the rubber hardness is 85 degrees or less, the vibration absorbing effect can be maintained high. Furthermore, the rubber composition has an elongation at break at 23 degrees Celsius of preferably 200% or more, and more preferably 350% or more. Since the elongation at break is 200% or more, the deformation of the sidewall portions 3 and the bead portions 4 can be suppressed, thereby, the cornering performance can be improved. If the elongation at break is excessively large, the vibration absorbing performance may be deteriorated. Therefore, it is preferred that the elongation at break is 550% or less and more preferably 500% or less. The reinforcing filler 10 in the present embodiment does not contain any cord.
In the present specification, the “loss tangent tan δ” is measured in accordance with Japanese Industrial Standards JIS-K6394 under the following conditions by using a dynamic viscoelasticity measurement device (EPLEXOR series) manufactured by GABO QUALIMETER Testanlagen GmbH.
Further, in the present specification, the “rubber hardness” refers to hardness measured by using a type-A durometer in accordance with Japanese Industrial Standards JIS-K6253 at a standard temperature of 23 degrees Celsius±2 degrees Celsius.
Furthermore, in the present specification, the “elongation at break” can be measured in accordance with Japanese Industrial Standards JIS K6251 in the section “Rubber, vulcanized or thermoplastic—Determination of tensile stress-strain properties”, for example.
As shown in
Further, the tire 1 includes a belt layer 7 disposed radially outside the carcass 6 and in the tread portion 2. The belt layer 7 includes at least one belt ply, in the present embodiment two belt plies 7A and 7B. The belt ply 7A (radially inner belt ply), which is arranged radially inside the belt ply 7B (radially outer belt ply), is adjacent to (in contact with in the present embodiment) the carcass 6 on the outside in the tire radial direction, for example. The belt ply 7B is adjacent to (in contact with in the present embodiment) the inner belt ply 7A on the outside in the tire radial direction so as to be overlaid with each other in the tire radial direction in the present embodiment, and has a larger width in the tire axial direction than the inner belt ply 7A. The two belt plies 7A and 7B and the carcass ply 6A in the present embodiment are made of well-known constituent materials including cords and topping rubber.
Further, the tire 1 in the present embodiment includes an inner liner 9 and a chafer 14. The inner liner 9 constitutes an inner cavity surface (1b) of the tire 1, for example. The inner liner 9 has excellent air shielding properties. The inner liner 9 holds the internal pressure of the tire 1. The chafer 14 in the present embodiment contacts the rim seat (Rs) and the rim flange (Rf) of the rim (R). The chafer 14 is made of a well-known rubber material with excellent wear resistance and is harder than the inner liner 9 and the reinforcing filler 10. The inner liner 9 and the chafer 14 are each formed from well-known rubber materials.
As shown in
Each of the bead portions 4 has a tire thickness (d1) (first tire thickness) between the outer surface (bead outer side surface (4b)) of the bead portion 4 and the turned up portion (6b) in the section height (Ha) (i.e., in the radial range corresponding to the section height (Ha) or in the radial range from the radially innermost end to the radially outermost end of the bead core 5). The tire thickness (d1) is preferably 1.5 mm or more. more preferably 2.0 mm or more, and preferably 4.0 mm or less, and more preferably 3.5 mm or less. Since the tire thickness (d1) is 1.5 mm or more, the bead core 5 can be positioned more toward axially inner side, therefore, the effect of increasing the rubber volume of the radially inner part of the bead core 5 can be exerted. In addition, damage to the bead portions 4 due to contact between the turned up portions (6b) and the rim flange (Rf) can be suppressed, thereby, the cornering performance can be improved. Since the tire thickness (d1) is 4.0 mm or less, the rim tightening force can be maintained high.
Each of the bead portions 4 has a tire thickness (d2) (second tire thickness) between the turned up portion (6b) and the outer surface (bead bottom surface (4a)) of the bead portion 4 in the cross sectional width (Wa) in the tire axial direction (i.e., in the axial range corresponding to the cross sectional width (Wa) or in the axial range from the axially innermost end to the axially outermost end of the bead core 5). The tire thickness (d2) is preferably 2.0 mm or more, more preferably 3.0 mm or more, and preferably 8.0 mm or less, more preferably 7.0 mm or less. Since the tire thickness (d2) is 2.0 mm or more, the rim tightening force can be increased. Since the tire thickness (d2) is 8.0 mm or less, excessive increase in the rim tightening force can be suppressed, therefore, rim assembly performance, which is the ease of mounting the tire on the rim (R), can be maintained.
The outer end (12e) of the outer portion 12 is located radially inside an outer end (Re) in the tire radial direction of the rim flange (Rf). The bead portions 4 which are in contact with the rim flange (Rf) are areas where deformation (including deflection) during running is relatively small. By providing the outer end (12e) radially inside the outer end (Re) of the rim flange (Rf), an excessive increase in the rigidity of the bead portions 4 can be further suppressed, thereby, the vibration absorbing performance can be maintained high. From the point of view of achieving both the vibration absorbing performance and the cornering performance, a separation distance (La) (first separation distance) in the tire radial direction between the outer end (12e) of the outer portion 12 and the outer end (Re) of the rim flange (Rf) is preferably 5 mm or less, and more preferably 3 mm or less, for example. In each of the bead portions 4, the outer end (Re) of the rim flange (Rf) in the present embodiment is located radially inside an outer end (6e) in the tire radial direction of the turned up portion (6b).
In each axial half of the tire 1, the outer end (12e) of the outer portion 12 is located radially inside the outer end (6e) in the tire radial direction of the turned up portion (6b), for example. As a result, the outer end (6e) of the turned up portion (6b) and the outer end (12e) of the outer portion 12 are misaligned in the tire radial direction, therefore, changes in the rigidity of the sidewall portion 3 and the bead portion 4 can be decreased, thereby, the deflection during running can be reduced. In order to achieve both the cornering performance and the vibration absorbing performance, a separation distance (Lb) (second separation distance) in the tire radial direction between the outer end (12e) of the outer portion 12 and the outer end (6e) of the turned up portion (6b) is preferably 2 times or more, more preferably 2.5 times or more the separation distance (La) and preferably 4 times or less, more preferably 3.5 times or less the separation distance (La), for example.
The inner portion 11 is located axially inside the main body portion (6a). The inner portion 11 configured as such performs a compressive deformation during running and applies a tensile force to the above-mentioned cords in the main body portion (6a), which helps to increase the rigidity of the sidewall portions 3 and improve the cornering performance. In addition, the inner portion 11 configured as such acts like a damper against the load during running, thereby, the vibration absorbing performance is improved. The inner portion 11 in the present embodiment is arranged between the main body portion (6a) and the inner liner 9.
The outer end (11e) of the inner portion 11 is located in the tread portion 2 and axially inside an outer end (7e) in the tire axial direction of the belt layer 7, for example. Therefore, the outer end (11e) is separated from the sidewall portions 3, where the deflection during running is relatively large, thereby, the cornering performance can be further improved. The outer end (11e) of the inner portion 11 in the present embodiment is located in the tread portion 2 and axially inside an outer end (7x) in the tire axial direction of the radially inner belt ply 7A, which has a width smaller than a width of the radially outer belt ply 7B. Although not particularly limited, a separation distance (Lc) (third separation distance) in the tire axial direction between the outer end (11e) of the inner portion 11 and the outer end (7x) of the radially inner belt ply 7A is preferably 1% or more, more preferably 5% or more of the tread width TW, and preferably 20% or less, more preferably 15% or less of the tread width TW.
While detailed description has been made of an especially preferred embodiment of the present disclosure, the present disclosure can be embodied in various forms without being limited to the illustrated embodiment.
Motorcycle tires of size 110/70R17 having the basic structure shown in
The “A” in Table 1 is the configuration shown in
The “B” is the configuration in which the outer end of the outer portion is located radially inside the center position of the section height of the bead core.
The “C” is the configuration shown in
The “D” is the configuration in which the outer end of the inner portion is located in the tread portion and axially outside the outer end of the belt layer.
Each of the test tires was mounted on a front wheel of a motorcycle with a displacement of 250 cc under the following conditions. A test rider drove the above-mentioned vehicle on a test course of a dry asphalt road surface. The test rider sensually evaluated each of the test tires on rigid impression, responsiveness, the cornering performance in terms of steering operability, and the vibration absorbing performance in terms of stability when riding over gaps and the like during the drive. The results are indicated by an evaluation point based on Reference 1 being 100, wherein the larger numerical value is better.
The tire for the rear wheel was common for Examples and Reference 1.
As shown in the table, it is understood that the tires in the Examples achieved both the cornering performance and the vibration absorbing performance compared to the tire in the Reference.
The present disclosure includes the following aspects.
A pneumatic tire including:
The pneumatic tire according to Present Disclosure 1, wherein
The pneumatic tire according to Present Disclosure 2 further including a carcass extending between the bead portions, wherein
The pneumatic tire according to Present Disclosure 3, wherein
The pneumatic tire according to Present Disclosure 3, wherein
The pneumatic tire according to Present Disclosure 3 further including a tread portion, wherein
The pneumatic tire according to any one of Present Disclosures 1 to 6, wherein the reinforcing filler is formed of a rubber composition having a loss tangent tan δ from 0.06 to 1.5 at 70 degrees Celsius, a rubber hardness from 65 to 85 degrees at 23 degrees Celsius, and an elongation at break of 200% or more at 23 degrees Celsius.
The pneumatic tire according to any one of Present Disclosures 1 to 7, wherein the pneumatic tire is a motorcycle tire having a tread width being the maximum width of the pneumatic tire.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-044371 | Mar 2023 | JP | national |
