Patent Description:
Conventionally, a pneumatic tire has been known which includes a puncture prevention function whereby a hole in the tire formed during puncture is automatically plugged by a sealant layer provided to the inner surface of the tire. For example, Patent Document <NUM> discloses a pneumatic tire in which a sealant layer is formed by a substantially cord-like sealant material arranged by continuously coating in a spiral shape along the tire inner surface, and a sound absorbing layer is provided to the inner side of the sealant layer. <CIT> describes a method for forming a sealant layer in a tire, which comprise steps of providing a tire and applying a plurality of strip-shaped windings of a sealant material to form a sealant layer to the inside of the tire under the crown of the tire. <CIT> describes a pneumatic tire including a sealant layer located radially inside an inner liner.

When coating the sealant material in a spiral shape, an area in which sealant material overlaps exists long in the circumferential direction, at both ends in the tire-width direction, which is an initial circling portion and a final circling portion. If the overlap area of the sealant material is large, defects will arise such as variation in the thickness of the sealant layer increasing, and leading to a decline in the adhesiveness of the sound absorbing layer to the sealant layer.

The present invention has been made taking account of the above situation, and has an object of providing a pneumatic tire and a method for producing the same whereby an overlap area of a sealant material decreases, variation in thickness of the sealant layer is suppressed, and an improvement in adhesiveness of a sound absorbing layer to the sealant layer is achieved.

According to the present invention, it is possible to provide a pneumatic tire and a method for producing the same whereby an overlap area of a sealant material decreases, variation in thickness of the sealant layer is suppressed, and an improvement in adhesiveness of a sound absorbing layer to the sealant layer is achieved.

Hereinafter, an embodiment will be explained while referencing the drawings. <FIG> is a view showing a tire-width direction cross section of a tire <NUM>, which is a pneumatic tire according to the present embodiment. The tire <NUM> is a tire for a passenger vehicle, for example. The specific structure of the tire <NUM> is left/right symmetrical in a cross section in the tire-width direction. In the drawings, reference symbol S1 is a tire equatorial plane. The tire equatorial plane S1 is a plane intersecting a tire rotational axis (tire meridian axis), and is positioned at the center in the tire-width direction.

It should be noted that the cross-sectional view of <FIG> is a tire-width direction cross-sectional view (tire meridian axis cross-sectional view) of an unloaded state in which the tire <NUM> is mounted to a standard rim and filled with standard internal pressure. It should be noted that standard rim indicates a rim serving as a standard decided by JATMA corresponding to the tire size. In addition, standard internal pressure is <NUM> kPa in the case of the tire being for a passenger vehicle, for example.

Herein, tire-width direction is a direction parallel to the tire rotational axis, and is the left/right direction in the paper plane in the cross-sectional view of <FIG>. In <FIG>, it is illustrated as the tire-width direction X. Then, the tire-width direction inner side is a direction near the tire equatorial plane S1, and is the central side in the paper plane of <FIG>. Tire-width direction outer side is a direction distanced from the tire equatorial plane S1, and is the left side and right side in the paper plane of <FIG>. In addition, tire-radial direction is a direction perpendicular to the tire rotational axis, and is the vertical direction in <FIG>. In <FIG>, it is illustrated as the tire-radial direction Y. Then, a tire-radial direction outer side is a direction distanced from the tire rotational axis, and is a lower side in the paper plane of <FIG>. Tire-radial direction inner side is a direction approaching the tire rotational axis, and is an upper side in the paper plane of <FIG>.

As shown in <FIG>, the tire <NUM> includes: a pair of beads <NUM> provided at both sides in the tire-width direction; a pair of sidewalls <NUM> extending from each of the pair of beads <NUM> to the outer side in the tire-radial direction; tread <NUM> arranged between the pair of sidewalls <NUM>; a carcass ply <NUM> arranged between the pair of beads <NUM>; and an inner liner <NUM> arranged on the tire inner cavity side of the carcass ply <NUM>.

The bead <NUM> includes a bead core <NUM>, bead filler <NUM> extending in the tire-radial direction outer side of the bead core <NUM>, a chafer <NUM>, and rim strip rubber <NUM>.

The bead core <NUM> is an annular member formed by winding a bead wire made of metal covered with rubber around several times, and is a member playing the role of fixing the tire <NUM> filled with air to the rim. The bead filler <NUM> is a rubber member which takes on a tapered shape as extending to the outer side in the tire radial direction. The bead filler <NUM> is a member provided to raise the rigidity of a circumferential portion of the bead <NUM>, and ensure high maneuverability and stability. The bead filler <NUM>, for example, is configured from rubber having higher hardness than the surrounding rubber members.

The chafer <NUM> is provided to the inner side in the tire-radial direction of the carcass ply <NUM> provided around the bead core <NUM>. The rim strip rubber <NUM> is arranged on the outer side in the tire-width direction of the chafer <NUM> and carcass ply <NUM>. The rim strip rubber <NUM> is a member which contacts the rim to which the tire <NUM> is mounted.

The sidewall <NUM> includes sidewall rubber <NUM> arranged on the outer side in the tire-width direction of the carcass ply <NUM>. The sidewall rubber <NUM> configures an outer wall surface of the tire <NUM>. The sidewall rubber <NUM> is a portion which bends the most upon the tire <NUM> exhibiting a cushioning action, and usually flexible rubber having fatigue resistance is adopted therein.

The tread <NUM> includes an endless belt <NUM> and cap ply <NUM>, and tread rubber <NUM>.

The belt <NUM> is arranged at an outer side in the tire-radial direction of the carcass ply <NUM>. The cap ply <NUM> is arranged at an outer side in the tire-radial direction of the belt <NUM>. The belt <NUM> is a member reinforcing the tread <NUM>. The belt <NUM> in the present embodiment is a two-layer structure including a belt <NUM> on the inner side and a belt <NUM> on the outer side. The belt <NUM> on the inner side and the belt <NUM> on the outer side both have a structure in which a plurality of cords such as steel cords is covered with rubber. It should be noted that the belt <NUM> is not limited to a two-layer structure, and may have a structure of one layer or three or more layers.

The cap ply <NUM> is a member reinforcing the tread <NUM> together with the belt <NUM>. The cap ply <NUM>, for example, has a structure in which a plurality of organic fiber cords having an insulation property such as polyimide fibers is covered with rubber. By providing the cap ply <NUM>, it is possible to achieve an improvement in durability and a reduction in road noise during travel.

The tread rubber <NUM> is arranged on the outer side in the tire-radial direction of the cap ply <NUM>. The tread rubber <NUM> is a member constituting the tire tread (contact surface with road surface) <NUM> during normal travel. A tread pattern <NUM> configured by a plurality of grooves, for example, is provided in the tire tread <NUM> of the tread rubber <NUM>. The tread pattern <NUM> has a plurality of main grooves <NUM> aligned in the tire-width direction. Each of the plurality of main grooves <NUM> extends along the tire circumferential direction.

The carcass ply <NUM> configures a ply serving as the backbone of the tire <NUM>. The carcass ply <NUM> is embedded within the tire <NUM>, in a form passing through the pair of sidewalls <NUM> and the tread <NUM> between the pair of beads <NUM>. The carcass ply <NUM> includes a plurality of carcass cords serving as the backbone of the tire <NUM>. The plurality of carcass cords extends in the tire-width direction, for example, and are arranged side by side in the tire-circumferential direction. This carcass cord is configured from an insulative organic fiber cord such as polyester or polyamide, or the like. The plurality of carcass cords is coated by rubber, whereby the carcass ply <NUM> is configured.

The carcass ply <NUM> includes a ply main body part <NUM> which extends from one bead core <NUM> to the other bead core <NUM>, and extends between the tread <NUM> and bead <NUM>; a pair of elbow-shaped bends <NUM> which fold back from the ply main body part <NUM> at the bead core <NUM>; and a pair of folding parts <NUM> which extend from each of the elbow-shaped bends <NUM> to an outer side in the tire-radial direction. The ply main body part <NUM>, the elbow-shaped bend <NUM> and folding part <NUM> are continuous.

The ply main body part <NUM> is arranged at the inner side in the tire-width direction of the bead core <NUM> and bead filler <NUM> on the inner side in the tire-radial direction The folding part <NUM> is arranged at the outer side in the tire-width direction of the bead core <NUM> and bead filler <NUM> at the inner side in the tire-radial direction. In a portion other than the bead core <NUM> and bead filler <NUM>, the folding part <NUM> is overlapped with the ply main body part <NUM>. The elbow-shaped bend <NUM> configures a portion most to the inner side in the tire-radial direction of the carcass ply <NUM>.

The carcass ply <NUM> of the present embodiment is a one-layer structure; however, the carcass ply <NUM> is not limited to a one-layer structure, and may have a two-layer or three or more layer-structure.

The aforementioned chafer <NUM> of the bead <NUM> is provided so as to surround the end on the inner side in the tire-radial direction of the carcass ply <NUM> including the elbow-shaped bend <NUM>. In addition, the rim strip rubber <NUM> is arranged at the outer side in the tire-width direction of the chafer <NUM> and the folding part <NUM> of the carcass ply <NUM>. The end on the outer side in the tire-radial direction of the rim strip rubber <NUM> is covered by the aforementioned sidewall rubber <NUM>.

The inner liner <NUM> covers the tire inner surface between the pair of beads. The inner liner <NUM> covers the inner surface of the ply main body part <NUM> of the carcass ply <NUM> and the inner surface of the chafer <NUM> of the pair of beads <NUM>. The inner liner <NUM> is configured by air permeation resistant rubber, whereby the air inside the tire inner cavity is prevented from leaking to outside.

As shown in <FIG>, the tire <NUM> according to the present embodiment further includes the sealant layer <NUM> and sound absorbing layer <NUM>.

The sealant layer <NUM> is arranged at the inner surface <NUM> on the tire inner cavity side corresponding to at least the tread <NUM> of the inner liner <NUM>. The width of the sealant layer <NUM>, i.e. length dimension in the tire-width direction, is set to about <NUM> times the width of the tire tread <NUM> of the tread <NUM> serving as the contact width of the tire <NUM>, for example. The sealant layer <NUM> may be arranged so as to overhang from the tread <NUM> to the outer side in the tire-width direction, and include part on the side of the tread <NUM> of the sidewall <NUM>. The sealant layer <NUM> is pasted to the inner liner <NUM> by the stickiness inherent thereto. The thickness of the sealant layer <NUM> is on the order of <NUM> or greater and <NUM> or less, for example. The sound absorbing layer <NUM> is arranged at the inner surface <NUM> on the tire inner cavity side of the sealant layer <NUM>. The sound absorbing layer <NUM> is pasted to the sealant layer <NUM> by way of the stickiness of the sealant layer <NUM>.

<FIG> is a development view showing the inner surface of the tire <NUM>, and schematically shows the sealant layer <NUM> and sound absorbing layer <NUM> provided to the inner surface of the tire <NUM>. <FIG> shows the tire-width direction by the arrow X, and shows the tire-circumferential direction by the arrow Z.

As shown in <FIG>, the sealant layer <NUM> is formed from one belt-like sealant material <NUM> pasted while circling along the tire-circumferential direction to the inner surface <NUM> of the inner liner <NUM>. The sealant layer <NUM> has a plurality of annular circling parts <NUM> and a plurality of transition parts <NUM> formed by the sealant material <NUM>.

In <FIG>, the reference symbol 61A indicates the pasting starting end of the sealant material <NUM>, and reference symbol 61B indicates the pasting finishing end of the sealant material <NUM>. As shown in <FIG>, the sealant material <NUM> is continuously pasted from one end side in the tire-width direction to the other end side (left side to right side in <FIG>), while circling to configure as shown by the arrow in the middle drawing, from the pasting starting end 61A until the pasting finishing end 61B.

The circling part <NUM> is formed by the sealant material <NUM> being pasted on the inner surface <NUM> of the inner liner <NUM> in parallel to the tire-circumferential direction. A plurality of circling parts <NUM> are arranged in parallel so as to be adjacent in a state in close proximity with each other in the tire-width direction. The plurality of transition parts <NUM> slope with a predetermined angle relative to the tire-circumferential direction, and are arranged in parallel so as to be adjacent in a state in close proximity with each other.

The transition part <NUM> is provided to a part in the tire-circumferential direction of the circling part <NUM>. The transition part <NUM> is a portion at which the sealant material <NUM> transitions to one side in the tire-width direction (right side in <FIG>), after one circling part <NUM> is formed by the sealant material <NUM> being pasted approximately once around the inner surface <NUM> of the inner liner <NUM>. In other words, the transition part <NUM> is a portion provided to part of the circling part <NUM>, and connects adjacent circling parts <NUM> in the tire-width direction to form an angle relative to the tire-circumferential direction. The next circling part <NUM> is pasted adjacent on one side in the tire-width direction of the already pasted circling part <NUM> through the transition part <NUM>. The next circling part <NUM> adjacent on one side in the tire-width direction through the transition part <NUM> is repeatedly formed, whereby the sealant layer <NUM> is provided. In the present embodiment, the plurality of transition parts <NUM> are respectively arranged at approximately the same position in the tire-circumferential direction, and arranged in parallel in the tire-width direction.

In this way, upon pasting the sealant material <NUM> to the tire inner surface, the pasting method of sequentially pasting in the tire-width direction the circling parts <NUM> parallel in the tire-circumferential direction while passing through the transition parts <NUM> may be referred to as step pasting below.

As the sealant material <NUM>, for example, it is possible to use a sealing member having stickiness made by blending a plasticizer such as polyisobutylene and polybutene, a tackifier such as a thermoplastic olefin/diolefin copolymer, and a filler such as carbon black and silica, into unvulcanized or semi-vulcanized butyl rubber, for example. It should be noted that, not limiting thereto, the sealant material <NUM> may be another known sealing member that is being used conventionally.

Next, the method of producing the tire according to the present embodiment including step pasting the sealant material <NUM> will be explained. To step paste the sealant material <NUM>, it is possible to perform by discharging and coating the sealant material <NUM> onto the inner surface <NUM> of the inner liner <NUM>, which is the inner surface of the tire <NUM>, from the nozzle <NUM>, while rotating the tire <NUM> around its axis, and moving the nozzle <NUM> in the tire-width direction, as shown in <FIG>. The nozzle <NUM> is attached to the leading end of an extruder (not shown), and is inserted to the inner side of the tire <NUM>. The sealant material <NUM> extruded from this extruder is discharged and coated on the inner surface of the tire <NUM> from the leading end of the nozzle <NUM>. In <FIG>, the width-direction cross section of the tire <NUM> is shown, and the tire-width direction X, tire-radial direction Y and tire-circumferential direction Z are each shown. In <FIG>, the reference symbol G is the axis of rotation of the tire <NUM>.

One circling part <NUM> is coated by rotating the tire <NUM> approximately one time in a state stopping movement in the tire-width direction, while discharging the sealant material <NUM> continuously from the nozzle <NUM>, and while continuously rotating the tire <NUM> around its axis. Next, when moving the nozzle <NUM> to one side in the tire-width direction by the width of the sealant material <NUM>, the transition part <NUM> is coated meanwhile. Next, the movement in the tire-width direction is stopped, and the circling part <NUM> next to the previously coated circling part <NUM> is coated. By repeating the above operation, it is possible to step paste the sealant material <NUM> onto the formation area of the sealant layer <NUM>. When coating and pasting the sealant material <NUM> to the entirety of the formation area of the sealant layer <NUM>, discharge of sealant material <NUM> from the nozzle <NUM> stops. The sealant layer <NUM> is formed by the sealant material <NUM> in this way, and the sound absorbing layer <NUM> is subsequently arranged on the tire inner cavity side of the sealant layer <NUM>.

In the case of the sealant material <NUM> being step pasted to the inner surface <NUM> of the inner liner <NUM> in the above way, the initial circling part 62A on one end side in the tire-width direction (left side in <FIG>) formed first among the plurality of circling part <NUM> has a first circling overlap part 62A1 which overlaps in the tire-thickness direction at the transition part <NUM> to the next circling part <NUM> from the initial circling part 62A, as shown in <FIG>. In addition, the finishing circling part 62B on the other end side in the tire-width direction (right side in <FIG>) formed last has a circling overlap part 62B1 which overlaps in the tire-thickness direction with the transition part <NUM> transitioning to the finishing circling part 62B. The first circling overlap part 62A1 is a portion at which the transition part <NUM> overlaps over the pasting start end 61A. The second circling overlap part 62B1 is a portion at which the pasting finish end 61B overlaps over the transition part <NUM>.

The sound absorbing layer <NUM> is formed with a sound absorbing material <NUM> consisting of sponge or the like formed with foaming material. The sound absorbing material <NUM> is an interconnecting foam body including several pores, and having permeability with outside air. As such a material, for example, flexible urethane foam can be exemplified.

The sound absorbing layer <NUM> is pasted by at least one sheet of sound absorbing material <NUM> being wound in a ring shape on the inner surface <NUM> of the sealant layer <NUM>. As shown in <FIG>, the sound absorbing material <NUM> has a joint 71A at which circulation-direction ends opposing each other are joined. It should be noted that the sound absorbing layer <NUM> may be configured by at least two sound absorbing materials <NUM> being arranged in a state linked in a ring shape.

As characteristics of the sound absorbing material <NUM>, from the viewpoint of weight balance of the pneumatic tire, it preferably has density no greater than <NUM>/m<NUM>, and more preferably has density no greater than <NUM>/m<NUM>. In addition, the sound absorbing material <NUM>, from the viewpoint of durability, preferably has a tensile strength of at least <NUM> kPA, and a tear strength of at least <NUM> N/cm (JIS K6400-<NUM>).

The dimension 70W in the tire-width direction of the sound absorbing layer <NUM> is preferably at least <NUM>% to <NUM>% relative to the dimension 60W in the tire-width direction of the sealant layer <NUM>. Then, the sound absorbing layer <NUM> is preferably arranged so as to fit within the tire-width direction of the sealant layer <NUM>. Furthermore, each of both tire-width direction ends <NUM> of the sound absorbing layer <NUM> is preferably located more to the inner side in the tire-radial direction than the first circling overlap part 62A1 and second circling overlap part 62B1 of the sealant layer <NUM>, and not overlapping each other.

In addition, it is preferable for the position of the joint 71A of the sound absorbing layer <NUM> and the position of the first circling overlap part 62A1 and second circling overlap part 62B1 of the sealant layer <NUM> to be shifted in the tire-circumferential direction and not to overlap each other.

According to the tire <NUM> of the aforementioned embodiment, in the case of a nail or the like poking the tread <NUM>, for example, and a hole that reaches the sealant layer <NUM> occurring, this hole is automatically plugged by the sealant layer <NUM>, and the puncture is prevented before it happens. In addition, the road noise during travel is absorbed by the sound absorbing layer <NUM> and decreases.

According to the tire <NUM> of the present embodiment explained above, the following effects are exerted.

Since the overlap area of the sealant material <NUM> drastically decreases compared to a conventional case of winding in a spiral shape, in the sealant layer <NUM>, variation is thickness is suppressed, and unevenness decreases, whereby an improvement in adhesion of the sound absorbing layer <NUM> to the sealant layer <NUM> is achieved.

<FIG> shows an example of coating the sealant material <NUM> in a spiral shape. According to this, the region in which adjacent sealant material <NUM> wound in a spiral shape overlap (shown by the hatched area in the drawing) exist long in the circumferential direction, in the initial circling part 82A along the tire-circumferential direction on the left end in the tire-width direction in the drawing, and the final circling part 82B along the tire-circumferential direction on the right end. If the overlap area of the sealant material <NUM> is large in this way, defects arise such that the variation in thickness of the sealant layer becomes greater, and leads to a decline in adhesiveness of the sound absorbing layer to the sealant layer. In contrast, by performing step pasting which aligns in the tire-width direction the circling parts <NUM> parallel to the tire-circumferential direction, without circling the sealant material <NUM> in a spiral shape in the present embodiment, it is possible to drastically decrease the overlap area of the sealant material <NUM> in the aforementioned way.

According to the tire <NUM> explained above, it is possible to reduce the surface area of a portion not covered by the sound absorbing layer <NUM> of the sealant layer <NUM>, and possible to suppress clinging of debris to the sealant layer <NUM> having stickiness. In addition, since the tire-width direction end of the sound absorbing layer <NUM> clings to the sealant layer <NUM>, the sound absorbing layer <NUM> hardly peels from the sealant layer <NUM>, and the sound absorbing performance is maintained.

Since the joint part 71A of the sound absorbing layer <NUM>, and first circling overlap part 62A1 and second circling overlap part 62B1 of the sealant layer <NUM> do not overlap, the joint part 71A of the sound absorbing layer <NUM> will hardly peel from the sealant layer <NUM>, and adhesiveness of the sound absorbing layer <NUM> to the sealant layer <NUM> is maintained.

Since both tire-width direction ends <NUM> of the sound absorbing layer <NUM> do not overlap the first circling overlap part 62A1 and second circling overlap part 62B1 of the sealant layer <NUM>, both tire-width direction ends <NUM> of the sound absorbing layer <NUM> will hardly peel from the sealant layer <NUM>, and adhesiveness of the sound absorbing layer <NUM> to the sealant layer <NUM> is maintained.

Since the overlap area of the sealant material <NUM> in the sealant layer <NUM> drastically decreases compared to the conventional case of winding in a spiral shape, variation in thickness is suppressed, and unevenness decreases, whereby an improvement in adhesion of the sound absorbing layer <NUM> to the sealant layer <NUM> is achieved.

Claim 1:
A pneumatic tire (<NUM>) comprising:
a pair of beads (<NUM>);
a pair of sidewalls (<NUM>) extending from each of the pair of beads (<NUM>) to an outer side in a tire-radial direction;
a tread (<NUM>) disposed between the pair of sidewalls (<NUM>);
a carcass ply (<NUM>) bridged between the pair of beads (<NUM>);
an inner liner (<NUM>) disposed at a tire inner cavity side of the carcass ply (<NUM>); and
a sealant layer (<NUM>) disposed at an inner surface (<NUM>) of the tire inner cavity side corresponding to at least the tread (<NUM>) of the inner liner (<NUM>),
wherein the sealant layer (<NUM>) is formed from a belt-like sealant material (<NUM>) pasted while circling the inner surface (<NUM>) of the inner liner (<NUM>),
wherein the sealant layer (<NUM>) includes: a plurality of annular circling parts (<NUM>) parallel to a tire-circumferential direction in which the sealant material (<NUM>) is disposed in parallel in a state adjacent in the tire-width direction, and
a plurality of transition parts (<NUM>) provided to a part in the tire-circumferential direction of the circling part (<NUM>), and at which the sealant material (<NUM>) transitions to the circling part (<NUM>) adjacent at one side in the tire-width direction, and
wherein an initial circling part (62A) on one end side in the tire-width direction and a final circling part (62B) on another end side in the tire-width direction among the plurality of circling parts (<NUM>) respectively have a circling overlap part (62A1, 62B1) which overlap in the tire-thickness direction at the transition part (<NUM>),
characterized in that
the pneumatic tire (<NUM>) further comprises a sound absorbing layer (<NUM>) disposed at a tire inner cavity side of the sealant layer (<NUM>),
wherein the sound absorbing layer (<NUM>) is formed from a sound absorbing material (<NUM>) wound along the tire-circumferential direction on an inner surface (<NUM>) of the sealant layer (<NUM>) and having a joint part (71A) at which circumferential-direction ends opposing each other join,
wherein positions of the joint part (71A) and the circling overlap part (62A1, 62B1) differ in the tire-circumferential direction, and
wherein both tire-width direction ends of the sound absorbing layer (<NUM>) are located more to an inner side in the tire-width direction than the circling overlap part (62A1, 62B1) .