JP2009269432A - Tire with lug, and manufacturing method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire for an agricultural machine, enhancing the vibration ride quality performance, in particular, the vibration ride quality performance during the travel on a smooth road without degrading the traction performance. <P>SOLUTION: A first vibration absorbing rubber 32 and a second vibration absorbing rubber 34 having the modulus lower than that of a tread rubber 24 are arranged within a lug 26 corresponding to a center area 40 and within the lug 26 corresponding to a side area 42 of a tire 10 comprising a bead core 20 and a carcass 16, a tread 22 provided on the outer side in the radial direction of the carcass 16 and a plurality of lugs 26 formed in the tread 22. Thus, the vibration ride quality performance is enhanced without degrading the traction performance. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a tire with a lug in which a plurality of lugs are formed on a tread, and more particularly to a tire with a lug suitable for an agricultural vehicle that travels in a farm field such as a wet field, soft land, and muddy land, and a method for manufacturing the tire with lug. .

  2. Description of the Related Art Conventionally, as a tire with a lug in which a plurality of lugs are formed in a square shape with a predetermined interval in a tread, there are agricultural machinery tires and the like. In agricultural machinery tires, in order to ensure traction performance, which is a basic performance, the tread width is set as wide as possible, for example, the tread width is generally set wider than the total width of the tire. However, since tires for agricultural machinery have a trade-off relationship between traction performance and vibration ride comfort performance, there is a problem in that vibration ride comfort performance must be sacrificed in order to ensure a predetermined traction performance.

In order to solve this problem, various methods for improving the vibration ride comfort performance of agricultural machine tires have been proposed and implemented (see, for example, Patent Document 1 and Patent Document 2). Further, as one method for improving the vibration ride comfort performance, a technique is known in which lugs are formed so that the lugs partially overlap each other when viewed from the tire circumferential direction or the tire width direction.
JP 2006-224784 A JP 2004-299459 A

  By the way, in recent years, agricultural vehicles equipped with agricultural machinery tires (for example, agricultural tractors, etc.) have also increased opportunities to travel on good roads such as paved roads. Vibration ride comfort performance is gaining attention. As described above, various methods for improving the vibration riding comfort performance of agricultural machinery tires have been proposed and realized, but with these methods, the user satisfies the vibration riding comfort performance that is in a trade-off relationship with traction performance. It cannot be improved to the level.

  In recent years, agricultural machinery tires have been provided that improve the ride comfort of the vibration without substantially reducing the traction performance by making the total width of the tire and the tread width substantially the same. In the market, it is strongly desired to provide tires for agricultural machinery with further improved vibration ride performance.

  In view of the above, the present invention provides a lug-equipped tire and a lug-equipped tire manufacturing method that improve vibration ride comfort performance, particularly vibration ride comfort performance on a good road, without reducing traction performance. The purpose is to do.

  Considering that the traction performance and the vibration ride performance described above are in a trade-off relationship in a tire with a lug (so-called lug pattern tire), the inventor has determined both the traction performance and the vibration ride performance. The method of maintaining and improving was examined. Generally, a decrease in vibration ride comfort performance of an agricultural vehicle equipped with a lug-equipped tire is mainly caused by a pitch component based on a tread pattern (hereinafter referred to as a pattern pitch component).

  Particularly in the case of tires with lugs, the tread contact pressure distribution is W-shaped and tends to be large. This means that the contact pressure tends to be high at the center of the tread (near the tire equator) and near the end of the tread. That is, the contact pressure of the lug near the tire equatorial plane and the end of the lug on the outer side in the tire width direction are likely to be high. Thus, the inventor has completed the present invention by paying attention to the fact that the pattern pitch component causes vibration due to rolling of the tire with lugs, specifically, radial force variation (hereinafter referred to as RFV).

  Therefore, in the tire with a lug according to claim 1 of the present invention, in the cross section in the tire width direction, the radius of curvature of the tread surface contacting the road surface is smaller in the side area continuous from the central area than in the central area straddling the tire equatorial plane. A tread, a plurality of lugs formed on the tread and extending from a central part in a tire width direction of the tread toward a side part, and the lugs corresponding to the inside and the side part of the lug corresponding to the central area And a vibration-absorbing rubber having a lower modulus than that of the tread rubber forming the tread.

  In the tire with a lug according to claim 1, the inside of the lug corresponding to the central area of the tread (hereinafter referred to as the tread central area) and the inside of the lug corresponding to the side area of the tread (hereinafter referred to as the tread side area). Since a vibration absorbing rubber having a lower modulus than that of the tread rubber is disposed in the tire, displacement of the tread central area and the tread side area in the tire radial direction at the time of load increases, and the contact pressure distribution of the tread becomes uniform. Thereby, the vibration (specifically, RFV) at the time of rolling of the tire with the lug is reduced, and the vibration riding comfort performance is improved. From the above, the lug-equipped tire of the present invention can improve the vibration riding comfort performance, particularly the vibration riding comfort performance when traveling on a good road, without reducing the traction performance. In addition, the tread surface of the lug is included in the tread surface.

  In the tire with a lug according to claim 2 of the present invention, the central area of the tread satisfies a range of 40 to 60% of the tread width.

  In the tire with a lug according to claim 2, for example, in the cross section in the tire width direction, when the tread in the tread central area is flat along the tire width direction, the tread central area is less than 40% of the tread width. Since the flat portion is reduced, the projected area of the lag contributing to the traction property is reduced, and the traction property is lowered. In addition, if the range of the tread central area exceeds 60% of the tread width, the flat part increases and the lag projection area increases, improving the traction, but the tread side area from the flat part of the tread central area is improved. Since the falling height to the end portion is reduced, the lateral force variation (LFV) is deteriorated and the vibration riding comfort performance is deteriorated. Therefore, it is preferable that the tread central area satisfies the range of 40 to 60% of the tread width.

  Generally, the displacement of rubber is determined by the modulus physical properties. For this reason, in the tire with lugs according to claim 3 of the present invention, the 100% modulus of the vibration absorbing rubber satisfies the range of 30 to 70% of the 100% modulus of the tread rubber.

  In the tire with a lug according to claim 3, when the 100% modulus of the vibration absorbing rubber exceeds 70% of the 100% modulus of the tread rubber, the displacement in the tire radial direction in the tread central area and the tread side area becomes too small. Thus, the effect of making the ground pressure distribution uniform while reducing the ground pressure of the tread cannot be sufficiently obtained. Also, if the vibration-absorbing rubber 100% modulus is less than 30% of the tread rubber 100% modulus, the tread center area and the tread side area will have excessive displacement in the tire radial direction, and the tread contact pressure will drop too much. The effect of making the ground pressure distribution uniform cannot be obtained. Therefore, the 100% modulus of the vibration absorbing rubber preferably satisfies 30 to 70% of the 100% modulus of the tread rubber.

  In the tire with lugs according to claim 4 of the present invention, the maximum thickness of the vibration absorbing rubber inside the lugs corresponding to the side areas is the lugs between the lugs adjacent in the tire circumferential direction in the tread hump portion. The maximum thickness of the vibration-absorbing rubber inside the lug corresponding to the central zone is 5 to 20% of the groove depth of the groove, and is 10 to 10 of the groove depth on the tire equatorial plane of the lug groove. Fill the range of 40%.

  In the tire with a lug according to claim 4, when the maximum thickness of the vibration absorbing rubber inside the lug corresponding to the tread side area exceeds 20% of the groove depth of the lug groove in the tread hump, the tread side The tire radial displacement of the area becomes too large, and the contact pressure is too low, and the effect of making the contact pressure distribution uniform cannot be obtained sufficiently. As a result, the vibration ride comfort performance cannot be sufficiently improved. Moreover, the influence on uneven wear performance comes out because ground pressure falls too much. On the other hand, if the maximum thickness of the vibration absorbing rubber inside the lug corresponding to the tread side section is less than 5% of the groove depth of the lug groove in the tread hump section, the tire radial displacement in the tread side section becomes small. Thus, the effect of lowering the contact pressure cannot be obtained sufficiently and the contact pressure distribution cannot be made uniform.

  Also, if the maximum thickness of the vibration absorbing rubber inside the lug corresponding to the tread central area exceeds 40% of the groove depth on the tire equator surface of the lug groove, the tire radial displacement in the tread central area becomes too large. As a result, the contact pressure is too low and the effect of making the contact pressure distribution uniform cannot be obtained sufficiently. As a result, the vibration ride comfort performance cannot be sufficiently improved. Moreover, the influence on uneven wear performance comes out because ground pressure falls too much. On the other hand, if the maximum thickness of the vibration absorbing rubber inside the lug corresponding to the tread central area is less than 10% of the groove depth on the tire equator surface of the lug groove, the tire radial displacement in the tread central area becomes too small. Therefore, the effect of lowering the contact pressure cannot be obtained sufficiently, and the contact pressure distribution cannot be made uniform.

  Therefore, the maximum thickness of the vibration-absorbing rubber inside the lug corresponding to the tread side area satisfies 5 to 20% of the groove depth of the lug groove in the tread hump, and the internal thickness of the lug corresponding to the tread central area It is preferable that the maximum thickness of the vibration absorbing rubber satisfy 10 to 40% of the groove depth on the equator plane of the lug groove. In addition, the tread hump part said here has shown the site | part where the thickness of a tread becomes the maximum.

  In the tire with a lug according to claim 5 of the present invention, the vibration absorbing rubber inside the lug corresponding to the central area and the vibration absorbing rubber inside the lug corresponding to the side area are continuous. .

  In the tire with a lug according to claim 5, since the vibration absorbing rubber inside the lug corresponding to the tread central area and the vibration absorbing rubber inside the lug corresponding to the tread side area are continuous, The vibration absorbing effect can be enhanced.

  According to a sixth aspect of the present invention, there is provided a method of manufacturing a tire with a lug, the unvulcanized tread rubber and the unvulcanized rubber so that the vibration absorbing rubber is disposed in a central area of the tread and a side area of the tread. A step of forming the first unvulcanized tread member in a band shape by integrally extruding the vibration absorbing rubber, and a second unvulcanized tread member in a band shape by extruding the unvulcanized tread rubber. And the first unvulcanized tread member so that the unvulcanized vibration absorbing rubber is disposed between the first unvulcanized tread member and the second unvulcanized tread member. Laminating the second unvulcanized tread member.

  In the method for manufacturing a tire with lugs according to claim 6, first, the unvulcanized tread rubber and the unvulcanized vibration absorbing rubber are integrally extruded to form the first unvulcanized tread member in a band shape. . Next, an unvulcanized tread rubber is extruded to form a belt-shaped second unvulcanized tread member. Then, the first unvulcanized tread member and the second unvulcanized tread member are arranged such that an unvulcanized vibration absorbing rubber is disposed between the first unvulcanized tread member and the second unvulcanized tread member. A sulfur tread member is laminated. Thereby, the unvulcanized tread (laminated body of the first unvulcanized tread member and the second unvulcanized tread member) in which the unvulcanized vibration absorbing rubber is disposed inside is molded. Here, in order to form the first unvulcanized tread member by integrally extruding the unvulcanized tread rubber and the unvulcanized vibration absorbing rubber, the air enters the first unvulcanized tread member ( Mixing of air) is suppressed. As a result, entry of air into the vulcanized tire is suppressed.

  The lug-equipped tire of the present invention can improve the vibration ride comfort performance, particularly the vibration ride comfort performance when traveling on a good road, without reducing the traction performance. Moreover, the lug-equipped tire produced by the method for producing a lug-equipped tire according to the present invention can improve the vibration ride comfort performance, particularly the vibration ride comfort performance when traveling on a good road, without lowering the traction performance.

[First Embodiment]
(Configuration) Next, a first embodiment of a lug-equipped tire according to the present invention will be described with reference to FIGS. In addition, the tire with a lug of this embodiment is a pneumatic tire 10 for an agricultural machine (hereinafter referred to as a tire 10) for an agricultural vehicle (for example, an agricultural tractor or the like), and its internal structure is a bias structure. FIG. 1 is a plan view showing a tread pattern of the tire 10 of the present embodiment. 2 is a cross-sectional view taken along line 2-2 of FIG.

  As shown in FIG. 2, the tire 10 includes a first carcass ply 12 and a second carcass ply 14 in which a cord extending in a direction intersecting with the tire equatorial plane CL (hereinafter, the equatorial plane CL) is embedded. The carcass 16 is provided. In the present embodiment, the carcass 16 is composed of two carcass plies, but the present invention is not limited to this structure, and the carcass 16 may be composed of one or three or more carcass plies. Good.

(Carcass)
The first carcass ply 12 and the second carcass ply 14 are respectively wound up around the bead core 20 in which both end portions are embedded in the bead portion 18 from the tire inner side to the outer side. The first carcass ply 12 is formed by embedding a plurality of cords (for example, an organic fiber cord such as nylon or a metal fiber cord such as steel) that extend in a direction intersecting the equator plane CL in the coated rubber in parallel. There is also a second carcass ply 14 in which a plurality of cords (for example, an organic fiber cord such as nylon or a metal fiber cord such as steel) extending in a direction intersecting the equator plane CL are embedded in the coated rubber in parallel. It is. Further, the cords of the first carcass ply 12 and the cords of the second carcass ply 14 intersect each other and are inclined in opposite directions with respect to the equator plane CL.

(tread)
A tread 22 is provided outside the carcass 16 in the tire radial direction. The tread 22 is formed by a tread rubber 24. The tread 22 is formed with a plurality of protruding lugs 26 that extend while inclining in the tire circumferential direction from the center in the tire width direction toward the side (see FIG. 1). The lugs 26 are alternately arranged on the left and right sides of the equatorial plane CL at predetermined intervals in the tire circumferential direction. Specifically, the lug 26 is disposed on one side (left side in FIG. 1) with the equator plane CL in between, and on the other side (right side in FIG. 1) with the equator plane CL in between. And the second lug 26B. Note that the concave portion of the tread 22 other than the lug 26 is referred to as a lug groove 28. Further, in the tread 22 of the present embodiment, the tread 22 has a tread 22 with an end portion on the outer side in the tire width direction on the equatorial plane CL in the cross section in the tire width direction and an inner side in the tire radial direction. It is deeper from CL toward the outer end of the tread 22 in the tire width direction.

  As shown in FIG. 2, the tread 22 includes a central area 40 that straddles the equator plane CL, and side areas 42 that are continuous with the central area 40 on both sides in the tire width direction of the central area 40. Further, in the cross section in the tire width direction, the curvature radius (second curvature radius R2) of the tread 22 in the side section 42 is larger than the curvature radius (first curvature radius R1) of the tread 22 in the center section 40. It is getting smaller. That is, in this embodiment, since the tread 22 and the lug 26 have the same tread surface 27, the radius of curvature of the tread surface of the first lug 26A in the central area 40 is the first radius of curvature R1. This means that the radius of curvature of the tread surface of the first lug 26A in the side section 42 is the second radius of curvature R2. Similarly, the curvature radius of the tread surface of the second lug 26B in the central section 40 is the first curvature radius R1, and the curvature radius of the tread surface of the second lug 26B in the side section 42 is the second curvature radius. Means R2.

  The lug 26 has a lug outer wall 46 that extends inward in the tire radial direction from the outermost end surface 44 of the tread surface 27 in the tire width direction. In the present embodiment, since the tread outer end 44 of the lug 26 is angular in the tire width direction cross section, the tread outer end 44A of the first lug 26A and the tread outer end 44B of the second lug 26B The distance along the tire width direction indicates the tread width TW. Further, as shown in FIG. 5, when the tread outer end 44 of the lug 26 is not angular in the tire width direction cross section (for example, in the case of an arc), the tread 27A (curvature radius R2 portion) of the first lug 26A ) And a first intersection of an extension line (two-dot chain line) of the lug outer wall 46A, an extension line of the tread 27B (not shown) of the second lug 26B, and the lug outer wall 46B. The distance along the tire width direction with the second intersection with the extension line (not shown) indicates the tread width TW.

Moreover, it is preferable that the center area 40 of the tread 22 satisfies the range of 40 to 60% of the tread width TW. The range of the central area 40 of the tread 22 is measured along the tire width direction as shown in FIG.
Furthermore, it is preferable that the first radius of curvature R1 is set to be not less than twice the tire radius indicated by the symbol H. In the present embodiment, the first radius of curvature R1 is infinite, that is, a straight line along the tire width direction.
Furthermore, when the distance in the tire radial direction between the tread outer end 44 of the lug 26 and the point on the equatorial plane CL of the tread 22 that is the maximum tire diameter is a drop height H1, the drop height H1 is 6 of the tread width TW. It is preferable to set the second radius of curvature R2 to be -10%.

(Vibration absorbing rubber)
A first vibration absorbing rubber 32 having a modulus lower than that of the tread rubber 24 is disposed inside the lug 26 corresponding to the central area 40. In addition, a second vibration absorbing rubber 34 having a modulus lower than that of the tread rubber 24 is disposed inside the lug 26 corresponding to the side section 42. Specifically, the first vibration absorbing rubber 32 and the second vibration absorbing rubber 34 are disposed in the middle portion of the lug 26 in the thickness direction. Further, the distance between the first vibration absorbing rubber 32 and the carcass 16 is substantially constant, and similarly, the distance between the second vibration absorbing rubber 34 and the carcass is also substantially constant. In other embodiments, the distance between the first vibration absorbing rubber 32 and the carcass 16 may not be substantially constant, and the distance between the second vibration absorbing rubber 34 and the carcass may not be substantially constant. .

  The 100% modulus of the first vibration absorbing rubber 32 preferably satisfies the range of 30 to 70% of the 100% modulus of the tread rubber 24, and the 100% modulus of the second vibration absorbing rubber 32 is the tread rubber. It is preferable to satisfy the range of 30 to 70% of 24 100% modulus.

  The maximum thickness T1 of the first vibration absorbing rubber 32 is preferably 10 to 40% of the groove depth D1 of the lug groove 28 on the equator plane CL. The maximum thickness of the second vibration absorbing rubber 34 is T2 is preferably 5 to 20% of the groove depth D2 at the tread hump portion. Here, the thickness of the vibration absorbing rubber refers to the distance measured in the vertical direction from the surface of the carcass 16, and the groove depth of the lug groove 28 is measured in the vertical direction from the tread surface 27 (tread surface of the tread 22) of the lug 26. Pointing to the distance. In the present embodiment, the tread hump portion is the tread outer end portion 44 of the lug 26.

  The width W1 of the first vibration absorbing rubber 32 preferably satisfies 30 to 100% of the central area 40, and the width W2 of the second vibration absorbing rubber 34 is 30 to 100% of the side area 42. Preferably there is. Here, the width of the vibration-absorbing rubber refers to the distance measured along the tire width direction between one end of the vibration-absorbing rubber in the tire width direction and the other end in the tire width direction.

  As shown in FIG. 2, in the present embodiment, in the tire width direction cross section, the end portions in the tire width direction of the first vibration absorbing rubber 32 and the second vibration absorbing rubber 34 have a trapezoidal shape. The present invention is not necessarily limited to this configuration, and as shown in FIG. 3, the tire width direction end portions of the first vibration absorbing rubber 32 and the second vibration absorbing rubber 34 are substantially in the tire width direction cross section. A substantially rectangular shape that stands vertically (perpendicular to the normal of the carcass 16) may be used.

  Next, the manufacturing method of the tire 10 of this embodiment is demonstrated. First, an unvulcanized carcass (not shown), an unvulcanized bead core (not shown), and an unvulcanized tire component are manufactured. Next, the unvulcanized tread rubber 24 </ b> A, the first vibration absorbing rubber 32 </ b> A, the first vibration absorbing rubber 32 is disposed in the central area 40 of the tread 22, and the second vibration absorbing rubber 34 is disposed in the side area 42. The unvulcanized vibration absorbing rubber 32A and the second unvulcanized vibration absorbing rubber 34A are integrally extruded to form a first unvulcanized tread member 23A having a trapezoidal cross section. The molded first unvulcanized tread member 23A has a first unvulcanized vibration absorbing rubber 32A and a second unvulcanized vibration on the bottom surface in a cross-sectional view (see a cross section perpendicular to the longitudinal direction). Absorbing rubber 34A is embedded (see FIG. 4A). Next, the unvulcanized tread rubber 24A is extruded to form a second unvulcanized tread member 23B having a trapezoidal cross section and a strip-shaped unvulcanized side tread 25A having a substantially triangular cross section. The unvulcanized side tread 25A becomes the side tread 25 constituting the tire side part shown in FIG. 2 after vulcanization.

  Next, the unvulcanized carcass is made into a cylindrical shape to form an unvulcanized carcass band, unvulcanized bead cores are arranged at both ends of the unvulcanized carcass band, and both end portions are wound inward in the axial direction. An unvulcanized tire constituent member (for example, a bead filler) is disposed in the vicinity. Next, as shown in FIG. 4A, a second unvulcanized tread member 23B is laminated on an unvulcanized carcass band (not shown) so that the bottom surface is in close contact therewith. Next, the first unvulcanized tread member 23A is laminated so that the bottom surface is in close contact with the upper surface of the second unvulcanized tread member 23B. Thus, the first unvulcanized vibration absorbing rubber 32A and the second unvulcanized vibration absorbing rubber 34A are disposed between the first unvulcanized tread member 23A and the second unvulcanized tread member 23B. The unvulcanized tread 22A is formed.

  Next, the unvulcanized side tread 25A is laminated on the unvulcanized carcass band so that one end of the unvulcanized side tread 25A overlaps with both ends of the unvulcanized tread 22A. Thereby, a cylindrical unvulcanized tire case is formed. Then, the central portion is expanded radially outward while bringing both end portions of the unvulcanized tire case closer to each other, thereby making the unvulcanized tire case substantially toroidal. Thereafter, the tire 10 is manufactured by vulcanizing the unvulcanized tire case. When the lug groove 28 is formed by the vulcanization mold at the time of vulcanization molding, the vibration absorbing rubber positioned between the lugs 26 adjacent in the tire circumferential direction is compared with the vibration absorbing rubber disposed inside the lug 26. It becomes a thin and elongated shape.

  Here, the unvulcanized tread rubber 24A, the first unvulcanized vibration absorbing rubber 32A, and the second unvulcanized vibration absorbing rubber 34A are integrally extruded to form the first unvulcanized tread member 23A. Therefore, for example, the unvulcanized tread rubber 24A, the first unvulcanized vibration absorbing rubber 32A, and the second unvulcanized vibration absorbing rubber 34A are formed into separate strips, and then laminated. Rather than forming a member corresponding to the unvulcanized tread member 23A, entry of air into the first unvulcanized tread member 23A is suppressed. As a result, entry of air into the tire 10 after vulcanization is suppressed.

  (Operation) Next, the operation of the tire 10 of this embodiment will be described. According to the tire 10, the first vibration absorbing rubber 32 is arranged inside the lug 26 corresponding to the central area 40, and the second vibration absorbing rubber 34 is arranged inside the lug 26 corresponding to the side area 42. Therefore, the displacement in the tire radial direction of the central area 40 and the side area 42 of the tread 22 during load increases, and the contact pressure distribution in the central area 40 and the side area 42 of the tread 22 becomes uniform. As a result, vibration (specifically, RFV) due to rolling of the tire 10 is reduced, and vibration ride comfort performance is improved. As a result, the tire 10 can improve the vibration ride comfort performance, particularly the vibration ride comfort performance when traveling on a good road, without reducing the traction performance.

  Further, since the first vibration absorbing rubber 32 and the second vibration absorbing rubber 34 are disposed inside the lug 26, the tire 10 has a tread that is more than a tire in which the vibration absorbing rubber is disposed between the tread and the carcass. 22 (lug 26) can be effectively displaced in the tire radial direction. For this reason, the tire 10 has the vibration absorbing rubber (the first vibration absorbing rubber 32 and the second vibration absorbing rubber) in order to obtain vibration riding comfort performance equivalent to that of the tire in which the vibration absorbing rubber is disposed between the tread and the carcass. The thickness of the rubber 34) can be reduced. That is, the tire 10 can reduce the required amount of vibration absorbing rubber compared to a tire in which the vibration absorbing rubber is disposed between the tread and the carcass.

  Moreover, if the range of the central area 40 of the tread 22 is less than 40% of the tread width TW, the flat portion is reduced, leading to a reduction in the lug projection area contributing to the traction, and the traction is lowered. If the range of the central area 40 of the tread 22 exceeds 60% of the tread width TW, the flat portion increases, the lug projection area increases, and the traction is improved, but the drop height H1 from the road surface in the side area 42 increases. Therefore, the LFV is deteriorated and the vibration ride comfort performance is deteriorated. Therefore, the central area 40 of the tread 22 preferably satisfies a range of 40 to 60% of the tread width TW.

  When the 100% modulus of the first vibration absorbing rubber 32 and the second vibration absorbing rubber 34 exceeds 70% of the 100% modulus of the tread rubber 24, the tire radial direction of the central area 40 and the side area 42 of the tread 22 is increased. Therefore, the effect of making the ground pressure distribution uniform cannot be sufficiently obtained while lowering the ground pressure in the central section 40 and the side section 42. Further, if the 100% modulus of the first vibration absorbing rubber 32 and the second vibration absorbing rubber 34 is less than 30% of the 100% modulus of the tread rubber 24, the tire diameter of the central area 40 and the side area 42 of the tread 22 will be described. Since the displacement in the direction becomes too large, the ground pressure in the central section 40 and the side section 42 falls too much, and the effect of making the ground pressure distribution uniform cannot be obtained. Therefore, the 100% modulus of the first vibration absorbing rubber 32 and the second vibration absorbing rubber 34 preferably satisfies 30 to 70% of the 100% modulus of the tread rubber 24.

  When the maximum thickness T1 of the first vibration absorbing rubber 32 exceeds 40% of the groove depth D1 on the equator plane CL, the tire radial displacement of the first vibration absorbing rubber 32 in the central area 40 increases. Therefore, the contact pressure is too low, and the effect of making the contact pressure distribution uniform cannot be obtained sufficiently. As a result, the vibration ride comfort performance cannot be improved. Moreover, the influence on uneven wear performance comes out because ground pressure falls too much. On the other hand, when the maximum thickness T1 is less than 10% of the groove depth D1, the displacement in the tire radial direction of the first vibration absorbing rubber 32 becomes too small, and the effect of reducing the contact pressure cannot be obtained sufficiently, resulting in a contact pressure distribution. Cannot be uniform.

  If the maximum thickness T2 of the second vibration absorbing rubber 34 exceeds 20% of the groove depth D2 at the tread hump portion, the tire radial displacement of the second vibration absorbing rubber 34 becomes too large, and the ground contact The pressure drops too much and the effect of making the ground pressure distribution uniform cannot be obtained sufficiently. As a result, the vibration ride comfort performance cannot be improved. Moreover, the influence on uneven wear performance comes out because ground pressure falls too much. On the other hand, if the maximum thickness T2 is less than 5% of the groove depth D2, the displacement in the tire radial direction of the second vibration absorbing rubber 34 becomes too small, and the effect of reducing the contact pressure cannot be obtained sufficiently, resulting in a contact pressure distribution. Cannot be uniform.

  Therefore, the maximum thickness T1 of the first vibration absorbing rubber 32 satisfies 10 to 40% of the groove depth D1 on the equator plane CL, and the maximum thickness T2 of the second vibration absorbing rubber 34 is tread hump. It is preferable to satisfy 5 to 20% of the groove depth D2 at the portion.

When the width W1 of the first vibration absorbing rubber 32 is less than 30% of the central area 40, the displacement in the tire radial direction by the first vibration absorbing rubber 32 becomes too small, and the ground pressure in the central area 40 is reduced. If the width W2 of the second vibration absorbing rubber 34 is less than 30% of the side area 42, the displacement in the tire radial direction by the second vibration absorbing rubber 34 becomes too small. The ground pressure in the side section 42 cannot be sufficiently reduced. Therefore, the width W1 of the first vibration absorbing rubber 32 preferably satisfies the range of 30 to 100% of the central area 40, and the width W2 of the second vibration absorbing rubber 34 is 30 to 100% of the side area 42. It is preferable to satisfy the range.
[Other embodiments]

  In the first embodiment, the internal structure of the tire 10 is a bias structure, but the present invention is not limited to this structure, and the internal structure may be a radial structure. In this case, the tire diameter of the carcass 16 One or a plurality of belts or the like that generate an effect for suppressing expansion in the tire radial direction may be disposed on the outer side in the direction.

  In the first embodiment, the first vibration absorbing rubber 32 and the second vibration absorbing rubber 34 are separately provided. However, the present invention is not necessarily limited to this configuration, and the first vibration absorbing rubber. Alternatively, the vibration absorbing rubber layer may be a single (continuous) vibration absorbing rubber layer in which the 32 and the second vibration absorbing rubber 34 are integrally formed. In this case, since the first vibration absorbing rubber 32 and the second vibration absorbing rubber 34 are continuous in the range from the central area 40 to the side area 42 of the tread 22, the vibration absorbing effect is enhanced as a whole. Can do.

  In the above embodiment, the first vibration absorbing rubber 32 and the second vibration absorbing rubber 34 are made of the same rubber material. However, the present invention is not limited to this structure, and the first vibration absorbing rubber. 32 and the second vibration absorbing rubber 34 may be made of different rubber materials. In this case, the rubber material of the first vibration absorbing rubber disposed in the central area 40 or the rubber material of the second vibration absorbing rubber disposed in the side area 42 according to the tire contact pressure distribution and the specifications is used. Riding comfort performance can be improved by making the determination based on 100% modulus. In particular, from the viewpoint of tire contact pressure distribution, the modulus of the second vibration absorbing rubber 34 is preferably smaller than the modulus of the first vibration absorbing rubber 32. By doing in this way, it becomes easy to obtain the effect of making the ground pressure distribution uniform. Further, even if the maximum thickness T2 of the second vibration absorbing rubber 34 is made larger than the maximum thickness T1 of the first vibration absorbing rubber 32, the effect of making the tire contact pressure distribution uniform can be easily obtained. For this reason, it is preferable to make the maximum thickness T2 of the second vibration absorbing rubber 34 thicker than the maximum thickness T1 of the first vibration absorbing rubber 32. Further, the contact pressure distribution of the tire is made uniform by optimizing the relationship between the maximum thickness T2 and modulus of the second vibration absorbing rubber 34 and the maximum thickness T1 and modulus of the first vibration absorbing rubber 32. It becomes easier to obtain the effect.

  In the first embodiment, as shown in FIG. 4A, the first unvulcanized vibration absorbing rubber 32A and the second unvulcanized vibration absorbing rubber 34A are formed on the bottom surface of the first unvulcanized tread member 23A. However, the present invention need not be limited to this configuration. As shown in FIG. 4B, the first unvulcanized vibration absorption is provided on the upper surface of the second unvulcanized tread member 23B. The unvulcanized tread rubber 24A, the first unvulcanized vibration absorbing rubber 32A, and the second unvulcanized vibration absorbing rubber 34A are integrated so that the rubber 32A and the second unvulcanized vibration absorbing rubber 34A are embedded. The second unvulcanized tread member 23B is formed by extrusion, and the bottom surface of the first unvulcanized tread member 23A formed by extruding the unvulcanized tread rubber 24A is laminated on the upper surface of the unvulcanized tread member 23B. The tread 22A may be formed. Further, as shown in FIG. 4 (C), the unvulcanized tread rubber 24A is extruded to form a first unvulcanized tread member 23A having a band shape, and the unvulcanized tread rubber 24A is extruded to form a second band-shaped second rubber. The unvulcanized tread member 23B is molded, the first unvulcanized vibration absorbing rubber 32A is extruded and formed into a band shape, the second unvulcanized vibration absorbing rubber 34A is extruded and formed into a band shape, and these are separated. The unvulcanized tread 22A may be formed by laminating the unvulcanized rubber members. In this case, various unvulcanized rubber members can be molded using existing equipment.

  In the above-described embodiment, the configuration of the tire with a lug of the present invention is applied to a pneumatic tire. However, the configuration is not limited to this configuration, and the configuration of the tire with a lug of the present invention may be applied to a solid tire. . In addition, as a solit tire, the wheel with rubber | gum etc. which arrange | position a tread rubber on the outer periphery of a disk-shaped member (wheel), and form a tread are mentioned, for example. If the structure of the tire with a lug of the present invention is applied to the tread of the rubber wheel, the effects of the present invention can be obtained.

  The embodiments of the present invention have been described above with reference to the embodiments. However, these embodiments are merely examples, and various modifications can be made without departing from the scope of the invention. It goes without saying that the scope of rights of the present invention is not limited to these embodiments.

[Test example]
In order to confirm the performance improvement effect of the present invention, one type of tire of a conventional example, one type of tire of a comparative example, and one type of tire of an example to which the present invention is applied are prepared, vibration measurement by a measuring instrument, And vibration ride performance was evaluated. The purpose of the test is to evaluate whether the vibration ride performance has been improved.

  Next, the test tire will be described. All of the test tire sizes are AGS 13.6-26 4PR T13H tires, and each test tire is assembled on a standard rim specified in JATMA YEAR BOOK (2008 edition, Japan Automobile Tire Association Standard). Used for testing. In addition, an Example is a tire of 1st Embodiment shown by FIG. 2, a conventional example is a tire which does not arrange | position vibration absorption rubber (namely, tire except vibration absorption rubber from an Example), and a comparative example is a tread. And a carcass in which a vibration-absorbing rubber is disposed (that is, a tire in which the vibration-absorbing rubber is disposed differently from the embodiment). Table 1 shows the specifications of each test tire.

In a test related to comparative evaluation, vibration (amplitude level) was measured using a measuring instrument. Furthermore, these test tires were mounted on agricultural vehicles and one person was on board, and the passengers evaluated the feeling. The test conditions for comparative evaluation are as follows.
<Vibration ride performance actual vehicle test>
Traveling road type: Concrete paved road Traveling speed: 16km / h (straight running)
Agricultural vehicle type: agricultural tractor (41 hp)
In addition, the evaluation value of vibration measurement is shown in Table 2 as an index display in which the vibration level (amplitude) of the conventional example is 100. Moreover, it is assumed that the smaller the evaluation value, the better the result.

  As shown in Table 2, in the measurement of the vibration level (amplitude) using the measuring instrument, the vibration levels of the comparative example and the example are significantly lower than those of the conventional example. Further, in the example in which the vibration absorbing rubber is arranged inside the lug, a better result is obtained than in the comparative example in which the vibration absorbing rubber is arranged between the tread and the carcass. Furthermore, it was confirmed that the vibration level (amplitude) of the comparative example and the example was lowered to a level not causing a problem as compared with the conventional example in the feeling evaluation by the occupant. In addition, in the feeling evaluation by the occupant, the result of the example is better than that of the comparative example. From this, it can be seen that better results with respect to vibration riding comfort can be obtained when the vibration absorbing rubber is disposed inside the lug than when the vibration absorbing rubber is disposed between the tread and the carcass.

It is a top view which shows the tread pattern of the tire of 1st Embodiment. FIG. 2 is a sectional view taken along line 2-2 of FIG. It is sectional drawing which shows the modification of the vibration absorption rubber used for the tire of 1st Embodiment. (A) It is explanatory drawing for demonstrating one manufacturing method at the time of manufacturing the tread part of the tire of 1st Embodiment. (B) It is explanatory drawing for demonstrating the two manufacturing methods at the time of manufacturing the tread part of the tire of 1st Embodiment. (C) It is explanatory drawing for demonstrating the other manufacturing method at the time of manufacturing the tread part of the tire of 1st Embodiment. It is sectional drawing which shows the modification of the shape of the edge part of the tread of the tire of 1st Embodiment.

Explanation of symbols

10 tires (tires with lugs)
16 carcass 22 tread 24 tread rubber 24A unvulcanized tread rubber 26 lug 27 tread (tread tread)
28 Lug groove 32 First vibration absorbing rubber (vibration absorbing rubber)
32A First unvulcanized vibration absorbing rubber (unvulcanized vibration absorbing rubber)
34 Second vibration absorbing rubber (vibration absorbing rubber)
34A Second unvulcanized vibration absorbing rubber (unvulcanized vibration absorbing rubber)
40 Central area 42 Side area CL Equatorial plane (tire equatorial plane)
T1 Maximum thickness of the first vibration absorbing rubber T2 Maximum thickness of the second vibration absorbing rubber D1 Groove depth of the lug groove (tread center portion)
D2 Lug groove depth (tread hump)
R1 first radius of curvature (curvature radius)
R2 Second radius of curvature (curvature radius)
TW tread width

Claims (6)

In the cross section in the tire width direction, a tread whose radius of curvature of the tread surface contacting the road surface is smaller in the side area continuous from the central area than the central area straddling the tire equator plane,
A plurality of lugs formed on the tread and extending from a central portion of the tread in a tire width direction toward a side portion;
A vibration absorbing rubber provided in the lug corresponding to the central area and in the lug corresponding to the side area, and having a lower modulus than the tread rubber forming the tread;
A tire with lugs.   The lug-equipped tire according to claim 1, wherein a central area of the tread satisfies a range of 40 to 60% of a tread width.   The tire with a lug according to claim 1 or 2, wherein a 100% modulus of the vibration absorbing rubber satisfies a range of 30 to 70% of a 100% modulus of the tread rubber.   The maximum thickness of the vibration absorbing rubber inside the lug corresponding to the side section satisfies the range of 5 to 20% of the groove depth of the lug groove between the lugs adjacent in the tire circumferential direction in the tread hump portion. The maximum thickness of the vibration-absorbing rubber inside the lug corresponding to the central region satisfies a range of 10 to 40% of the groove depth on the tire equatorial plane of the lug groove. The tire with a lug according to any one of the items.   5. The vibration absorbing rubber inside the lug corresponding to the central area and the vibration absorbing rubber inside the lug corresponding to the side area are continuous. 6. Lug tires. In the manufacturing method of the tire with a lug of any one of Claims 1-5,
The unvulcanized tread rubber and the unvulcanized vibration absorbing rubber are integrally extruded so that the vibration absorbing rubber is disposed in the central area of the tread and the side area of the tread, and the first unshaped rubber band is extruded. Forming a vulcanized tread member;
Extruding the unvulcanized tread rubber to form a strip-shaped second unvulcanized tread member;
The first unvulcanized tread member and the second so that the unvulcanized vibration absorbing rubber is disposed between the first unvulcanized tread member and the second unvulcanized tread member. Laminating an unvulcanized tread member of
The manufacturing method of the tire with a lug provided with.

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