Cart tires

Abstract

To provide a cart tire 2 which can achieve acceleration of a turning speed.SOLUTION: A tire 2 comprises: a tread 4 contacting a road surface; a carcass 10 which is positioned inside the tread 4 in a radial direction, and has a bias structure; and a reinforcement layer 18 which is positioned inside the tread 4, and is laminated on an outer side of the carcass 10. An end TE, which is positioned on one side in an axial direction, of both ends TE of the tread 4 is a first end TE1, and an end TE, which is positioned on the other side, is a second end TE2. The reinforcement layer 18 is positioned between an equatorial plane and the first end TE1 of the tread 4. In the axial direction, an inner end 38 of the reinforcement layer 18 is positioned on an inner side with respect to a reference ground contact end PE. The reinforcement layer 18 includes many reinforcement cords 34 juxtaposed in a circumferential direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a tire for a cart. [Background technology]

[0002] In recent years, the performance of racing karts (hereinafter referred to as karts) has improved significantly. Accordingly, further improvements in the performance of the tires mounted on the karts are also required. Various studies have been conducted to meet this demand (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-47810 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to turn karts at higher speeds, tires must have a high level of grip. To improve grip, increasing the contact area is being considered. Widening the contact width is also being considered to prevent skidding during turns.

[0005] In order to increase the contact area while widening the contact width, it is being considered to configure the tread surface with a flatter profile. However, with tires that use a flat profile, the centrifugal force acting on the vehicle when cornering can cause the tread to deform, resulting in a phenomenon known as buckling, in which parts of the tread surface dent inward. In this case, the contact area decreases, and the tire is unable to exert sufficient grip. There is also the risk of uneven wear due to localized areas of high contact pressure on the contact surface.

[0006] Passenger car tires use a radial carcass, while kart tires use a bias carcass. Passenger car tires have a belt between the tread and carcass, while kart tires do not. Furthermore, the internal pressure of kart tires is lower than that of passenger car tires. The rigidity of the tread portion of kart tires is lower than that of passenger car tires. Kart tires are prone to buckling.

[0007] Increasing the rigidity of the carcass increases the rigidity of the tread, which may prevent buckling. However, in this case, the rigidity of the sidewalls also increases, which may reduce steering stability. Increasing the internal pressure of the tire may suppress deformation of the tread, which may prevent buckling. However, in this case, the outer surface of the tread becomes rounded, which may reduce the contact area with the road and reduce grip.

[0008] The present invention has been made in view of the above circumstances, and has as its object to provide a tire for a kart that can achieve a higher cornering speed. [Means for solving the problem]

[0009] A kart tire according to one aspect of the present invention comprises a tread that comes into contact with a road surface, a carcass that is located radially inward of the tread and has a bias structure, and a reinforcing layer that is located radially inward of the tread and laminated on the outside of the carcass. The tire is mounted on a standard rim, the internal pressure of the tire is adjusted to the standard internal pressure, the camber angle is set to 0 degrees, and the maximum load of an actual vehicle is applied to the tire when the tire comes into contact with a flat road surface. The contact surface obtained by this is the reference contact surface, and the position on the outer surface of the tread that corresponds to the axially outer end of the reference contact surface is the reference contact edge. Of the two ends of the tread, the end located on one side in the axial direction is the first end, and the end located on the other side is the second end. The reinforcing layer is located between the equatorial plane and the first end of the tread. In the axial direction, the inner end of the reinforcing layer is located inside the reference contact edge. The reinforcing layer includes a large number of reinforcing cords arranged in parallel in the circumferential direction.

[0010] Preferably, in the cart tire, a ratio of the axial distance from the equatorial plane to an inner end of the reinforcing layer to the axial distance from the equatorial plane to a first end of the tread is equal to or greater than 0.50 and is equal to or less than 0.70.

[0011] Preferably, in the cart tire, a ratio of the axial distance from the equatorial plane to the outer end of the reinforcing layer to the axial distance from the equatorial plane to the first end of the tread is equal to or greater than 0.85.

[0012] Preferably, in this kart tire, the carcass includes at least two carcass plies, each including a number of carcass cords arranged in parallel, and an angle formed between the reinforcing cords and the carcass cords included in the carcass ply on which the reinforcing layer is laminated is 10 degrees or less.

[0013] Preferably, in the cart tire, the angle that the reinforcing cord forms with respect to the equator plane is larger than the angle that the carcass cord forms with respect to the equator plane.

[0014] Preferably, in this cart tire, when mounted on a vehicle, the first end of the tread is positioned on the outer side in the width direction of the vehicle. [Effects of the Invention]

[0015] According to the present invention, a tire for a kart is obtained that can achieve a high cornering speed. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a cross-sectional view showing a part of a cart tire according to one embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged cross-sectional view showing the contour of a shoulder portion of the tire of FIG. [Figure 3] FIG. 3 is an enlarged cross-sectional view showing a portion of the tire of FIG. [Figure 4] FIG. 4 is a schematic diagram illustrating the configuration of the carcass and the reinforcing layer. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, the present invention will be described in detail based on preferred embodiments, with appropriate reference to the drawings.

[0018] In this disclosure, a state in which a tire is mounted on a standard rim, the internal pressure of the tire is adjusted to a standard internal pressure, and no load is applied to the tire is referred to as a standard state.

[0019] In this disclosure, unless otherwise specified, the dimensions and angles of each part of a tire are measured in a normal state. The dimensions and angles of each part in a meridian cross section of a tire that cannot be measured when the tire is mounted on a normal rim are measured by cutting the tire along a plane including the rotation axis, and by matching the distance between the left and right beads in the cross section to the distance between the beads in a tire mounted on a normal rim.

[0020] A genuine rim is a rim specified in the standard on which the tire is based. The "standard rim" in the JATMA standard, the "design rim" in the TRA standard, and the "measuring rim" in the ETRTO standard are all genuine rims.

[0021] Normal tire pressure refers to the pressure specified in the standard on which the tire is based. The "maximum tire pressure" in the JATMA standard, the "maximum tire pressure" listed in the TRA standard's "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURE" and the "INFLATION PRESSURE" in the ETRTO standard are normal tire pressures.

[0022] Normal load refers to the load specified in the standard on which the tire is based. The "maximum load capacity" in the JATMA standard, the "maximum value" listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are normal loads.

[0023] In this disclosure, the tread portion of a tire is the portion of the tire that comes into contact with the road surface. The bead portion is the portion of the tire that fits onto the rim. The side portion is the portion of the tire that bridges between the tread portion and the bead portion. A tire has the following portions: a tread portion, a pair of bead portions, and a pair of side portions.

[0024] In this disclosure, the number of cords, including parallel cords, contained in a tire element per 5 cm width is expressed as the cord density (unit: ends / 5 cm) contained in this element. The cord density is obtained in a cross section of the element obtained by cutting the element in a plane perpendicular to the length direction of the cords.

[0025] FIG. 1 shows an example of a cart tire 2 (hereinafter referred to as tire 2) according to one embodiment of the present invention. FIG. 1 shows a portion of a cross section (hereinafter also referred to as a meridian cross section) of the tire 2 taken along a plane including the rotation axis of the tire 2. In FIG. 1, the left-right direction is the axial direction of the tire 2, and the up-down direction is the radial direction of the tire 2. The direction perpendicular to the plane of FIG. 1 is the circumferential direction of the tire 2. In FIG. 1, a dashed dotted line CL represents the equatorial plane of the tire 2.

[0026] In FIG. 1, a tire 2 is mounted on a rim R. The rim R is a regular rim. Air is filled inside the tire 2, and the internal pressure of the tire 2 is adjusted. The tire 2 mounted on the rim R is also called a tire-rim assembly. The tire-rim assembly includes the rim R and the tire 2 mounted on this rim R.

[0027] In FIG. 1, the position indicated by the symbol PW is the axial outer end of the tire 2. If there is a decoration such as a pattern or lettering on the outer surface, the outer end PW is identified based on a virtual outer surface obtained assuming there is no decoration. The axial distance from one outer end PW to the other outer end PW is the maximum width of the tire 2, i.e., the cross-sectional width (see JATMA, etc.). The outer end PW is the position where the tire 2 shows its maximum width (hereinafter referred to as the maximum width position).

[0028] The tire 2 comprises, as elements, a tread 4, a pair of sidewalls 6, a pair of beads 8, a carcass 10, a pair of fillers 12, a pair of chafers 14, an inner liner 16, and a reinforcing layer 18.

[0029] The outer surface of the tread 4 comes into contact with the road surface. The outer surface of the tread 4 has a shape that is convex outward in the radial direction. The tread 4 is made of cross-linked rubber that takes into consideration wear resistance and grip force. In FIG. 1, the position indicated by the symbol PC is the intersection point between the outer surface of the tread 4 and the equatorial plane. This intersection point PC is the equator of the tire 2.

[0030] 1, the position indicated by the symbol PE is a position on the outer surface of the tread 4. This position PE corresponds to the axially outer end of the contact patch (hereinafter also referred to as the contact edge) obtained when the tire 2 comes into contact with the road surface.

[0031] The contact patch for identifying position PE is obtained, for example, using a contact patch shape measuring device (not shown). This contact patch is obtained by applying the maximum load of an actual vehicle to the tire 2 as a vertical load with the camber angle of the tire 2 in a normal state set to 0 degrees, and bringing the tire 2 into contact with a flat road surface. In the present disclosure, the contact patch obtained in this manner is the reference contact patch, and the position on the outer surface of the tread 4 that corresponds to the axially outer end of this reference contact patch is the aforementioned position PE. In the present disclosure, this position PE is the reference contact edge.

[0032] In this disclosure, the maximum load on an actual vehicle means a load twice the maximum load per tire that can be supported by the tires of an actual vehicle (a vehicle such as a racing kart used on an actual circuit) when the vehicle is placed on a level road surface. This maximum load per tire is calculated using the total vehicle mass obtained assuming one driver (mass = 55 kg) is riding in the vehicle, taking into account the center of gravity of the vehicle.

[0033] In the tire 2, the ratio of the axial distance from the equatorial plane to the reference ground contact edge PE to the axial distance L1 from the equatorial plane to the first end TE1 of the tread 4, which will be described later, is equal to or greater than 0.70 and is equal to or less than 0.85.

[0034] Fig. 2 shows a portion of the tire 2 shown in Fig. 1. Fig. 2 shows the outline of the shoulder portion of the tire 2 in a meridian cross section. The outline shown in Fig. 2 is obtained by measuring the outer surface shape of the tire 2 in a normal state with a displacement sensor. Fig. 2 shows the outline of the outer surface of the tire 2 in a meridian cross section of the tire 2 in a normal state.

[0035] In a meridian cross section, the contour of the outer surface of the tire 2 (hereinafter referred to as tire outer surface TS) is formed by connecting multiple contour lines made of straight lines or circular arcs. In this disclosure, a contour line made of straight lines or circular arcs is simply referred to as a contour line. A contour line made of straight lines is referred to as a straight contour line, and a contour line made of circular arcs is referred to as a curved contour line.

[0036] The tire outer surface TS has a tread surface T and a pair of side surfaces S connected to the edges of the tread surface T. In a meridian cross section, the outline of the tread surface T includes a plurality of curved contour lines having different radii. In this tire 2, of the plurality of curved contour lines included in the outline of the tread surface T, the curved contour line having the smallest radius is located at the edge of the tread surface T and connected to the side surfaces S. In a meridian cross section, the outline of the tire outer surface TS includes a curved portion, which is a curved contour line consisting of an arc having the smallest radius among the plurality of curved contour lines included in the outline of the tread surface T and connected to the side surfaces S, at the edge of the tread surface T. In FIG. 2, this curved portion is indicated by the symbol RS.

[0037] In the contour of the tire outer surface TS, the curved portion RS is tangent to a contour line adjacent to the axially inner side (hereinafter referred to as an inner adjacent contour line NT) at a contact point CT. This curved portion RS is tangent to a contour line constituting the contour of the side surface S adjacent to the axially outer side (hereinafter referred to as an outer adjacent contour line NS) at a contact point CS. This contour of the tire outer surface TS includes an inner adjacent contour line NT located axially inner of the curved portion RS and tangent to this curved portion RS, and an outer adjacent contour line NS located axially outer of the curved portion RS and tangent to this curved portion RS.

[0038] In FIG. 2, the solid line LT is a tangent to the curved portion RS at the point of contact CT between the inner adjacent contour line NT and the curved portion RS. The solid line LS is a tangent to the curved portion RS at the point of contact CS between the outer adjacent contour line NS and the curved portion RS. The position indicated by the symbol PV is the intersection of the tangent line LT and the tangent line LS. In FIG. 2, the position indicated by the symbol TE is the intersection of the tread surface T and a straight line that passes through the intersection point PV and extends in the radial direction. This intersection point TE is the end of the tread 4.

[0039] In this tire 2, of both ends TE of the tread 4, one end TE in the axial direction, in other words, the end TE of the tread 4 located on the left side on the paper surface of Fig. 1, is a first end TE1. Of both ends TE of the tread 4, the other end TE in the axial direction, in other words, the end TE of the tread 4 located on the right side on the paper surface of Fig. 1, is a second end TE2. Fig. 3 shows a cross section of the tire 2 shown in Fig. 1, on the side of the first end TE1 of the tread 4.

[0040] Although not described in detail, the tread surface T of this tire 2 is configured with a flat contour in order to increase the contact area while widening the contact width.

[0041] Each sidewall 6 is connected to an edge of the tread 4 and is located radially inward of the tread 4. The sidewalls 6 are located axially outward of the carcass 10. The sidewalls 6 extend radially along the carcass 10. The sidewalls 6 are made of crosslinked rubber that provides cut resistance.

[0042] Each bead 8 is located radially inward of the sidewall 6. The bead 8 includes a core 20 and an apex 22. Although not shown, the core 20 includes a steel wire. The apex 22 is located radially outward of the core 20. The apex 22 tapers radially outward. The apex 22 is made of crosslinked rubber with high rigidity.

[0043] The carcass 10 is located radially inward of the tread 4. The carcass 10 is located axially inward of the sidewall 6. The carcass 10 bridges between one bead 8 and the other bead 8. The carcass 10 has a bias structure. The carcass 10 includes at least two carcass plies 24.

[0044] The carcass 10 of the tire 2 is made up of two carcass plies 24. Of the two carcass plies 24, the carcass ply 24 located on the inner side is a first ply 26. The carcass ply 24 located on the outer side is a second ply 28.

[0045] The first ply 26 has a first ply body 26a that spans between one core 20 and the other core 20, and a pair of first turned-up portions 26b that are continuous with the first ply body 26a and are turned up from the inside to the outside in the axial direction around each core 20. In the tire 2, ends of the first turned-up portions 26b are located radially outward from the maximum width position PW.

[0046] The second ply 28 has a second ply body 28a that spans between one core 20 and the other core 20, and a pair of second turned-up portions 28b that are continuous with the second ply body 28a and are turned up from the inside to the outside in the axial direction around each core 20. In the tire 2, the end of the second turned-up portion 28b is located radially outward from the end of the apex 22. The end of the second turned-up portion 28b is covered by the first turned-up portion 26b from the outside in the axial direction.

[0047] 4 shows the configuration of the carcass 10 of the tire 2 together with the configuration of the reinforcing layer 18 described below. In this FIG. 4, the left-right direction is the axial direction of the tire 2, and the up-down direction is the circumferential direction of the tire 2.

[0048] In the tire 2, the first ply 26 and the second ply 28 each include a large number of carcass cords 30 arranged in parallel. In Fig. 4, the carcass cords 30 are represented by solid lines for ease of explanation, and the carcass cords 30 are covered with topping rubber 32. The first ply 26 and the second ply 28 each include a large number of carcass cords 30 and the topping rubber 32 that covers the carcass cords 30. In each of the first ply 26 and the second ply 28, the density of the carcass cords 30 is 20 ends / 5 cm or more and 60 ends / 5 cm or less.

[0049] In the tire 2, the carcass cords 30 are inclined with respect to the equatorial plane. As shown in Fig. 4, the direction of inclination of the carcass cords 30 included in the first ply 26 is opposite to the direction of inclination of the carcass cords 30 included in the second ply 28.

[0050] In Fig. 4, the angle indicated by the symbol α1 is the angle that the carcass cord 30 included in the first ply 26 makes with respect to the equatorial plane (hereinafter referred to as the inclination angle). The inclination angle α1 of the carcass cord 30 is equal to or greater than 15° and equal to or less than 45°. The angle indicated by the symbol α2 is the inclination angle of the carcass cord 30 included in the second ply 28. The inclination angle α2 of the carcass cord 30 is equal to or greater than 15° and equal to or less than 45°. In this tire 2, the inclination angle α1 of the carcass cord 30 included in the first ply 26 and the inclination angle α2 of the carcass cord 30 included in the second ply 28 are set to be the same angle.

[0051] In the tire 2, cords made of organic fibers are used as the carcass cords 30. Examples of the organic fibers include nylon fibers, rayon fibers, polyester fibers, and aramid fibers.

[0052] Each filler 12 is located axially inside the bead 8. For example, as shown in FIG. 3, the filler 12 is located between the second ply body 28a and the apex 22. The outer end of the filler 12 is located radially between the end of the first turned-up portion 26b and the end of the second turned-up portion 28b. The inner end of the filler 12 is located radially between the core 20 and the end of the apex 22. In this tire 2, the filler 12 is not an essential element. The filler 12 does not have to be provided.

[0053] Although not shown, the filler 12 is composed of a large number of parallel cords and a topping rubber. Each cord is inclined with respect to the radial direction. The inclination angle is between 30° and 60°. The cords are made of organic fibers. Examples of organic fibers include nylon fibers, rayon fibers, polyester fibers, and aramid fibers.

[0054] Each chafer 14 is located radially inward of the bead 8. The chafers 14 come into contact with the rim (not shown). The chafers 14 of the tire 2 are made of a cloth and rubber impregnated into the cloth.

[0055] The inner liner 16 is positioned inside the carcass 10. The inner liner 16 constitutes the inner surface of the tire 2. The inner liner 16 maintains the internal pressure of the tire 2. The inner liner 16 is made of crosslinked rubber.

[0056] The reinforcing layer 18 is located radially inside the tread 4. The tread 4 covers the reinforcing layer. In this tire 2, no element such as a belt including a belt cord extending at an angle with respect to the equatorial plane or a band including a band cord wound spirally along a substantially circumferential direction is provided between the tread 4 and the reinforcing layer 18. In other words, no other element is provided between the tread 4 and the reinforcing layer 18. The tread 4 is directly laminated on the reinforcing layer 18.

[0057] The reinforcing layer 18 is laid on the carcass 10, specifically, on the outer side of the second ply body 28a in the radial direction. In the tire 2, no element such as a belt or band is provided between the carcass 10 and the reinforcing layer 18. In other words, no other element is provided between the carcass 10 and the reinforcing layer 18. The reinforcing layer 18 is laid directly on the second ply body 28a.

[0058] For example, if the reinforcing layer 18 is provided between the first ply 26 and the second ply 28, or between the carcass 10 and the inner liner 16, the reinforcing layer 18 may interfere with the carcass 10 during the manufacture of the tire 2, causing distortion or wrinkling in the carcass 10. In this case, a local increase in ground pressure may occur, and the ground contact shape may become distorted, raising concerns about impaired wear resistance and handling stability. In contrast, in the tire 2, as described above, the reinforcing layer 18 is laminated on the outer side of the carcass 10 in the radial direction. In the tire 2, interference of the reinforcing layer 18 with the carcass 10 is suppressed, preventing distortion or wrinkling in the carcass 10 during the manufacture of the tire 2. In the tire 2, good wear resistance and handling stability are maintained. Moreover, since the reinforcing layer 18 is positioned close to the tread surface T, the reinforcing layer 18 can effectively contribute to controlling the rigidity of the tread surface T.

[0059] As shown in Figure 4, the reinforcing layer 18 includes a large number of reinforcing cords 34 arranged in parallel in the circumferential direction. In Figure 4, the reinforcing cords 34 are represented by solid lines for ease of explanation, and these reinforcing cords 34 are covered with topping rubber 36. The reinforcing layer 18 is made up of a large number of reinforcing cords 34 arranged in parallel in the circumferential direction and the topping rubber 36 that covers these reinforcing cords 34. The density of the reinforcing cords 34 included in this reinforcing layer 18 is set in the range of 30 ends / 5 cm to 70 ends / 5 cm.

[0060] In this tire 2, the density of the reinforcement cords 34 is equal to the density of the carcass cords 30. In this tire 2, the density of the reinforcement cords 34 may be higher than the density of the carcass cords 30, or the density of the reinforcement cords 34 may be lower than the density of the carcass cords 30.

[0061] In the tire 2, there are no particular limitations on the material of the reinforcing cord 34. Cords that are commonly used in the technical field of tires are used as the reinforcing cord 34. The reinforcing cord 34 may be a steel cord. The reinforcing cord 34 may be a cord made of organic fiber. From the viewpoint of ease of manufacturing the tire 2, the reinforcing cord 34 is preferably a cord made of organic fiber. Examples of organic fibers include nylon fiber, rayon fiber, polyester fiber, and aramid fiber. The organic fiber is preferably nylon fiber or polyester fiber.

[0062] In the tire 2, the reinforcement cords 34 are arranged at intervals in the circumferential direction. One end of each reinforcement cord 34 is located at an inner end 38 of the reinforcement layer 18, and the other end of each reinforcement cord 34 is located at an outer end 40 of the reinforcement layer 18. The reinforcement cord 34 spans between the inner end 38 and the outer end 40 of the reinforcement layer 18.

[0063] In this tire 2, the orientation of the tread 4 relative to the cart (hereinafter also referred to as a vehicle) is specified. When this tire 2 is mounted on a vehicle, of both ends TE of the tread 4, a first end TE1 of the tread 4 is disposed on the outer side in the width direction of the vehicle. A second end TE2 of the tread 4 is disposed on the inner side in the width direction of the vehicle.

[0064] Centrifugal force acts on a vehicle when it turns. In the tread of the tire located on the outer wheel side when it turns, strain tends to concentrate near the reference contact edge PE on the first end TE1 side.

[0065] The tread portion of this tire 2 does not include elements such as belts or bands, as in tires for passenger cars. The faster the turning speed, the greater the force acting on the tread 4. As mentioned above, the tread surface T of this tire 2 is configured with a flat contour to increase the contact area while widening the contact width. With this tire 2, there is concern that a phenomenon called buckling may occur, in which part of the tread surface T recesses inward near the aforementioned reference contact edge PE.

[0066] However, in this tire 2, as shown in FIG. 1 or 3, the reinforcing layer 18 is located between the equatorial plane and the first end TE1 of the tread 4. An inner end 38 of the reinforcing layer 18 is located axially inward of the reference ground edge PE. Moreover, the tread 4 is laminated directly onto this reinforcing layer 18. This reinforcing layer 18 includes a large number of reinforcing cords 34 arranged in parallel in the circumferential direction. This reinforcing layer 18 effectively increases the rigidity of the tread surface T, particularly near the reference ground edge PE on the first end TE1 side of the tread 4, where buckling is a concern. In this tire 2, deformation of the tread surface T near the reference ground edge PE is suppressed even when the vehicle turns at high speed. In this tire 2, buckling is prevented even though the tread surface T is configured with a flat contour.

[0067] 1, in this tire 2, the reinforcing layer 18 is not provided between the equatorial plane and the second end TE2 of the tread 4. Between the inner end 38 of the reinforcing layer 18 and the sidewall 6 on the second end TE2 side of the tread 4, the tread 4 is directly laminated to the carcass 10, specifically, the second ply body 28a.

[0068] In this tire 2, flexibility of the tread surface T is appropriately maintained between the inner end 38 of the reinforcing layer 18 and the second end TE2 of the tread 4. A sufficient contact area is ensured between the inner end 38 of the reinforcing layer 18 and the second end TE2 of the tread 4, as in conventional tires. As described above, the occurrence of buckling is also prevented in this tire 2. In this tire 2, the contact area is increased compared to conventional tires that do not have the reinforcing layer 18. The increased contact area contributes to improved grip.

[0069] In this tire 2, the tread 4 makes sufficient contact with the road surface. This tire 2 is less likely to skid when cornering and can exhibit high grip. This tire 2 can achieve high cornering speeds.

[0070] Furthermore, in this tire 2, the occurrence of uneven wear is suppressed because a local increase in ground contact pressure is prevented. This tire 2 can also achieve improved wear resistance.

[0071] As shown in FIG. 3 , in the tire 2, the outer end 40 of the reinforcing layer 18 is located outward from the reference ground edge PE in the axial direction. The reference ground edge PE is located between the inner end 38 and the outer end 40 of the reinforcing layer 18 in the axial direction. The reinforcing layer 18 more effectively increases the rigidity of the tread surface T in the vicinity of the reference ground edge PE on the first end TE1 side of the tread 4. In the tire 2, the occurrence of buckling is effectively prevented. From this viewpoint, in the tire 2, it is preferable that the outer end 40 of the reinforcing layer 18 is located outward from the reference ground edge PE in the axial direction.

[0072] As shown in Fig. 3, in the tire 2, the outer end 40 of the reinforcing layer 18 is located axially inward of the end 6e of the sidewall 6 on the first end TE1 side of the tread 4. In the tire 2, the outer end 40 of the reinforcing layer 18 may be located axially outward of the end 6e of the sidewall 6 on the first end TE1 side of the tread 4. In other words, the outer end 40 of the reinforcing layer 18 may be sandwiched between the sidewall 6 and the second ply body 28a. In this case, the overlap length between the sidewall 6 and the reinforcing layer 18 is preferably 10 mm or less, and more preferably 5 mm or less.

[0073] 3, the length indicated by the double-headed arrow L1 is the axial distance from the equatorial plane to the first end TE1 of the tread 4. The length indicated by the double-headed arrow L2 is the axial distance from the equatorial plane to the outer end 40 of the reinforcing layer 18. The length indicated by the double-headed arrow L3 is the axial distance from the equatorial plane to the inner end 38 of the reinforcing layer 18.

[0074] In the tire 2, the ratio (L3 / L1) of the axial distance L3 from the equatorial plane to the inner end 38 of the reinforcing layer 18 to the axial distance L1 from the equatorial plane to the first end TE1 of the tread 4 is preferably 0.50 or greater and 0.70 or less.

[0075] By setting the ratio (L3 / L1) to be 0.50 or greater, a necessary contact area is secured in the equatorial plane of the tire 2. The tire 2 can exert high grip. The tire 2 can obtain good steering stability. From this viewpoint, the ratio (L3 / L1) is more preferably 0.55 or greater.

[0076] By setting the ratio (L3 / L1) to 0.70 or less, the reinforcing layer 18 effectively increases the rigidity of the tread surface T in the vicinity of the reference ground contact edge PE. Buckling is prevented from occurring, ensuring a sufficient contact area. The tire 2 can exert high grip, resulting in good steering stability. Local increases in ground contact pressure are also prevented, suppressing the occurrence of uneven wear. The tire 2 achieves good wear resistance. From this perspective, it is more preferable that the ratio (L3 / L1) be 0.65 or less.

[0077] In this tire 2, the ratio (L2 / L1) of the axial distance L2 from the equatorial plane to the outer end 40 of the reinforcing layer 18 to the axial distance L1 from the equatorial plane to the first end TE1 of the tread 4 is preferably 0.85 or greater. This allows the reinforcing layer 18 to effectively increase the rigidity of the tread surface T in the vicinity of the reference contact edge PE. Buckling is prevented from occurring, ensuring a sufficient contact area. This tire 2 can exert high grip, resulting in good steering stability. Local increases in contact pressure are also prevented, suppressing the occurrence of uneven wear. This tire 2 achieves good wear resistance. From this perspective, the ratio (L2 / L1) is more preferably 0.90 or greater. The upper limit of this ratio (L2 / L1) is determined as appropriate, taking into consideration the effect on the mass of the tire 2, etc.

[0078] 4, the angle indicated by the symbol β is the angle (hereinafter referred to as the tilt angle) that the reinforcing cord 34 included in the reinforcing layer 18 makes with respect to the equatorial plane. This tilt angle β is represented by the angle that an extension line of the reinforcing cord 34 makes with respect to the equatorial plane.

[0079] In Fig. 4, the angle indicated by the symbol γ is the angle (hereinafter referred to as the crossing angle) formed between the reinforcing cord 34 and the carcass cord 30 included in the carcass ply 24 on which the reinforcing layer 18 is laminated. In the tire 2, the reinforcing layer 18 is laminated on the second ply 28. The crossing angle γ is expressed as the angle formed between the reinforcing cord 34 and the carcass cord 30 included in the second ply 28. The crossing angle γ may be expressed as the absolute value of the difference (β-α2) between the inclination angle β of the reinforcing cord 34 and the inclination angle α2 of the carcass cord 30 included in the second ply 28.

[0080] In this tire 2, the crossing angle γ is preferably 10 degrees or less. This prevents the restraining force of the reinforcing layer 18 from becoming excessively high. In manufacturing this tire 2, deformation of the tire 2 caused by the reinforcing layer 18 restraining other elements is prevented. A tire 2 having an appropriate shape is obtained, allowing the tread 4 to fully perform its functions.

[0081] In this tire 2, the inclination angle β of the reinforcing cord 34 is preferably larger than the inclination angle α2 of the carcass cord 30 included in the second ply 28 as the carcass ply 24 on which this reinforcing layer 18 is laminated. As a result, the reinforcing layer 18 effectively increases the rigidity of the tread surface T in the vicinity of the reference ground edge PE. Buckling is prevented from occurring, thereby ensuring a sufficient contact area. The tire 2 can exert high grip, thereby obtaining good steering stability. Local increases in ground pressure are also prevented, thereby suppressing the occurrence of uneven wear. The tire 2 obtains good wear resistance. From this viewpoint, the difference (β - α2) between the inclination angle β of the reinforcing cord 34 and the inclination angle α2 of the carcass cord 30 included in the second ply 28 is preferably 1 degree or greater, and more preferably 3 degrees or greater. From the viewpoint of obtaining a tire 2 having an appropriate shape and allowing the tread 4 to fully exhibit its functions, this difference (β - α2) is preferably 9 degrees or less, more preferably 7 degrees or less, and even more preferably 5 degrees or less.

[0082] As described above, according to the present invention, a tire for a kart that can achieve a high cornering speed can be obtained. [Example]

[0083] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0084] [Example 1] A kart tire set was obtained, which had the basic configuration shown in Figure 1 and was made up of front and rear tires with the specifications shown in Table 1 below. The tire size of the front tire was "10 x 4.50-5". The tire size of the rear tire was "11 x 7.10-5".

[0085] In Example 1, the inclination angle α1 of the carcass cords included in the first ply was 32 degrees. The inclination angle α2 of the carcass cords included in the second ply was 32 degrees. The inclination direction of the carcass cords included in the first ply was opposite to the inclination direction of the carcass cords included in the second ply. In Example 1, the reinforcing layer was laminated on the outside of the second ply. This is indicated by "outside" in the "Position" column in Table 1 below. The inclination angle β of the reinforcing cord was 35 degrees. The angle formed by the reinforcing cord and the carcass cord included in the second ply, i.e., the crossing angle γ, was 3 degrees. In Example 1, the ratio (L3 / L1) of the axial distance L3 from the equatorial plane to the inner end of the reinforcing layer to the axial distance L1 from the equatorial plane to the first edge TE1 of the tread was 0.60. The ratio (L2 / L1) of the axial distance L2 from the equatorial plane to the outer end of the reinforcing layer to the axial distance L1 was 0.90. The ratio of the axial distance from the equatorial plane to the reference contact edge PE to the axial distance L1 was 0.80.

[0086] [Comparative Example 1] A tire set of Comparative Example 1 was obtained in the same manner as in Example 1, except that no reinforcing layer was provided.

[0087] [Example 2-3] A tire set of Example 2-3 was obtained in the same manner as Example 1, except that the axial distance L3 was changed to set the ratio (L3 / L1) as shown in Table 1 below.

[0088] [Example 4] A tire set of Example 4 was obtained in the same manner as Example 1, except that the axial distance L2 was changed to set the ratio (L2 / L1) as shown in Table 1 below.

[0089] Comparative Example 2 A tire set of Comparative Example 2 was obtained in the same manner as in Example 1, except that a reinforcing layer was provided between the first ply and the second ply.

[0090] [Reference example 1] A tire set identical to the tire set in Example 1 was prepared.

[0091] [Installation of prototype tires] The front tire was mounted on a rim (size = 4.5 x 5.0) and inflated to adjust the internal pressure of the tire to 80 Pa. This front tire was mounted on the front wheel of a test vehicle (a racing kart vehicle with an engine displacement of 125 cc). The rear tire was mounted on a rim (size = 8.0 x 5.0) and inflated to adjust the internal pressure of the tire to 80 Pa. This rear tire was mounted on the rear wheel of the test vehicle. In Examples 1-4 and Comparative Example 2, the tires were mounted on the test vehicle so that the first end TE1 of the tread was located on the outer side in the width direction of the vehicle. This is indicated by "outside" in the "Layout" column of Table 1 below. In Reference Example 1, the tire was mounted on the test vehicle so that the second end TE2 of the tread was located on the outer side in the width direction of the vehicle. This is indicated by "inside" in the "Layout" column of Table 1.

[0092] [lap time] A running test was conducted by having the driver drive the test vehicle for 10 laps on a dedicated racing kart course with a lap length of 1,300 m. In this running test, the lap times were measured to obtain the fastest lap. The difference between the fastest lap of each example and the fastest lap of Comparative Example 1 was calculated. The results are shown in Table 1 below. The smaller the value, the shorter the lap time.

[0093] [Handling stability] In the driving test related to the lap time mentioned above, the drivers were asked to evaluate the driving stability (sensory evaluation). The results are shown as an index in Table 1 below. The higher the value, the better the driving stability.

[0094] [Wear resistance] The driver drove the test vehicle 30 laps on the dedicated course mentioned above. After the run, the amount of wear was measured using the wear indicators attached to the tires. The results are shown as an index in Table 1 below. The higher the number, the better the wear resistance.

[0095] [Table 1]

[0096] As shown in Table 1, in the examples, the handling stability was improved and the lap time was shortened. It is clear that an increase in cornering speed was achieved. Furthermore, in the examples, the wear resistance was also improved. The superiority of the present invention is clear from these evaluation results. [Industrial Applicability]

[0097] The above-described techniques for increasing the turning speed can be applied to various types of tires. [Explanation of symbols]

[0098] 2. Tires 4. Tread 6. Sidewall 10. Carcass 18. Reinforcement layer 24, 26, 28... Carcass ply 30 Carcass Cord 34 Reinforcement cord 38 inner end of reinforcing layer 18 40 outer end of reinforcing layer 18

Claims

1. A tread that comes into contact with the road surface; a carcass located radially inward of the tread and having a bias structure; a reinforcing layer located radially inside the tread and laminated on the outside of the carcass; Equipped with The tire is mounted on a regular rim, the internal pressure is adjusted to the regular internal pressure, the camber angle is set to 0 degrees, and the maximum load is applied to an actual vehicle when the tire comes into contact with a flat road surface. The contact surface thus obtained is the reference contact surface, and the position on the outer surface of the tread that corresponds to the axial outer end of the reference contact surface is the reference contact edge. Of both ends of the tread, an end located on one side in the axial direction is a first end, and an end located on the other side is a second end, the reinforcing layer is located between an equatorial plane and a first end of the tread; an outer end of the reinforcing layer is located inside a first end of the tread and outside a reference ground contact edge in an axial direction; an inner end of the reinforcing layer is located more inward than the reference ground end in the axial direction; the reinforcing layer includes a large number of reinforcing cords arranged in parallel in the circumferential direction, When the tire is mounted on a vehicle, a first end of the tread is located on an outer side in a width direction of the vehicle, the reinforcing layer is provided only between the equatorial plane and the first end of the tread, In the reinforcing layer, each of the multiple reinforcing cords spans between the inner end and the outer end of the reinforcing layer, and the multiple reinforcing cords spanning between the inner end and the outer end of the reinforcing layer are arranged at intervals in the circumferential direction. Kart tires.

2. a ratio of an axial distance from the equatorial plane to an inner end of the reinforcing layer to an axial distance from the equatorial plane to a first end of the tread is 0.50 or more and 0.70 or less; 2. The cart tire according to claim 1.

3. a ratio of an axial distance from the equatorial plane to an outer end of the reinforcing layer to an axial distance from the equatorial plane to a first end of the tread is 0.85 or more; 3. A cart tire according to claim 1 or 2.

4. the carcass includes at least two carcass plies; The carcass ply includes a large number of carcass cords arranged in parallel, an angle formed between the reinforcing cord and a carcass cord included in the carcass ply on which the reinforcing layer is laminated is 10 degrees or less; A cart tire according to any one of claims 1 to 3.

5. an angle formed by the reinforcing cord with respect to the equator plane is larger than an angle formed by the carcass cord with respect to the equator plane; 5. The cart tire according to claim 4.

6. The inclination direction of the reinforcing cord is the same as the inclination direction of the carcass cord included in the carcass ply on which the reinforcing layer is laminated.

6. A cart tire according to claim 4 or 5.

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