Patent Description:
Conventionally, a pneumatic tire has been known which is equipped with a puncture prevention function whereby a hole in the tire formed during puncture is automatically plugged by a sealant layer provided to the tire inner surface. For example, Patent Document <NUM> discloses a pneumatic tire in which a sealant layer is formed by coating a sealant material of substantially cord-like shape in a spiral shape continuously along the tire inner surface.

Patent Document <NUM>: <CIT>
Document <CIT> describes an inflated tire having a sealed layer which is formed by winding a strip of a sealer in a spiral shape and which is formed on the inner circumference surface of a tread part. A width of the strip at an end of the sealed layer in the tire widthwise direction is smaller than the width of the strip at the center part of the sealed layer in the tire widthwise direction.

In a tire having a sealant layer on the inner surface, there is an issue of the heat dissipation decreasing due to the sealant layer. In particular, when the radiation of heat generated by the portions on both sides in the tire-width direction of the steel belt embedded in the tread deforming is inhibited by the sealant layer, there is concern over leading to damage of the tire caused by physical property variation due to heat. For example, there is a possibility of separation occurring from the decline in adhesion between the steel belts and rubber. This point has not been mentioned in the above-mentioned patent documents, and there is room for improvement.

The present invention has an object of providing the production method of a pneumatic tire which can suppress the occurrence of heat damage, while maintaining the puncture prevention function by the sealant layer.

A production method of a tire according to the present invention is a production method of a tire including tread which includes a belt, in which a sealant layer is provided at least to an inner surface of the tread, the method including: measuring a contact width of the tire; when defining a tire-width direction length from a tire-width direction center until an end of the contact width as CW1, and defining a tire-width direction length from the tire-width direction center until another end of the contact width as CW2, comparing CW1 and CW2 and establishing a larger thereof as CW; establishing a length from the tire-width direction center until an end in the tire-width direction of the belt as BW, and prescribing a tire-width direction length SW of a sealant material coating area on one side in the tire-width direction from the tire-width direction center as CW<SW<BW; and arranging in parallel in the tire-width direction a plurality of annular circling parts of a sealant material extending in the tire-circumferential direction to provide the sealant layer, by establishing a tire-width direction length SW x <NUM> of the sealant material coating area on the inner surface of the tread as a coating area length in the tire-width direction of the sealant material, and coating a belt-like sealant material on the coating area in the tire-width direction of the sealant material, while circling along the tire-circumferential direction, and while transitioning a path of circling thereof to one direction side of the tire-width direction at least once every circling.

According to the present invention, it is possible to provide the production method of a pneumatic tire which can suppress the occurrence of heat damage, while maintaining the puncture prevention function by the sealant layer.

Hereinafter, an embodiment will be explained while referencing the drawings. <FIG> is a side view of a tire <NUM> produced by a production method according to the embodiment. G in <FIG> shows a rotational axis line, which is a center of rotation of the tire <NUM>, extending in a paper plane front/back direction of <FIG> shows a circumferential direction of the tire <NUM> by the arrow R. <FIG> is a view schematically showing a tire-width direction cross-sectional view of the tire <NUM>. The tire <NUM> according to an example is a pneumatic tire mounted to a rim (not shown) in which the internal pressure is filled by air or the like at the inner cavity thereof. The tire <NUM> according to the embodiment is a tire for a passenger vehicle. It should be noted that the production method of the tire according to the embodiment is applicable to a production method of a tire for various vehicles such as light trucks, trucks and buses.

The internal structure of the tire <NUM> will be briefly explained by <FIG> shows a cross section of the tire <NUM> having a left/right symmetrical structure in a direction extending in the rotation axis line G shown in <FIG>. The cross-sectional view of <FIG> shows the state of the tire <NUM> in an unloaded state mounting the tire <NUM> to a standard rim (not shown), and filled with standard internal pressure.

In <FIG>, the symbol S1 is the tire equatorial plane orthogonal to the rotation axis line G. <FIG> shows the tire-width direction and tire-radial direction as referenced in the present disclosure by arrows X and Y, respectively. Tire-width direction (arrow X direction) is a direction parallel to the rotation axis line G, and is the left/right direction in the paper plane of the cross-sectional view of <FIG>. Tire-width direction inner side is a direction approaching the tire equatorial plane S1, and is the paper-plane central side in <FIG>. Tire-width direction outer side is a direction distancing from the tire equatorial plane S1, and is the paper-plane left side and right side in <FIG>. Tire-radial direction (arrow Y direction) is a direction perpendicular to the rotational axis line G, and is the paper-plane up/down direction in <FIG>. <FIG> shows a tire-radial direction Y. Tire-radial direction outer side is a direction distancing from the rotation axis line G, and is the paper-plane upper side in <FIG>. Tire-radial direction inner side is a direction approaching the rotation axis line G, and is the paper-plane lower side in <FIG>.

The tire <NUM> includes a pair of beads <NUM> provided on both sides in the tire-width direction, tread <NUM> forming a contact surface with the road surface, and a pair of sidewalls <NUM> extending between the pair of beads <NUM> and the tread <NUM>.

The pair of beads <NUM> constitute a tire-radial direction inside portion of the tire <NUM>. In order to raise the rigidity of this portion, the bead <NUM> includes high modulus rubber. The bead <NUM> includes an annular bead core <NUM> made by covering a plurality of wound bead wires made of metal with rubber. The bead core <NUM> plays the role of fixing the tire <NUM> to the rim.

The tread <NUM> includes belts <NUM>, and tread rubber <NUM> arranged at the outer side in the tire-radial direction of the belts <NUM>. The tread rubber <NUM> has a contact surface 25a which makes contact with the road surface. A plurality of main grooves <NUM> extending in the circumferential direction are formed in the contact surface 25a. <FIG> shows a contact portion in a state of the contact surface 25a actually contacting the road surface. As shown in <FIG>, the portion in which the contact surface 25a contacts the road surface makes a substantially elliptical shape. As shown in <FIG> and <FIG>, in the tire <NUM>, the tire-width direction length of the contact surface 25a is defined as a contact width TW of the tread <NUM>.

The belt <NUM> is a member reinforcing the tread <NUM>. The belt <NUM> of the embodiment is a two-layer structure including an inside belt <NUM>, and outside belt <NUM> arranged on the outer side in the tire-radial direction of the inside belt <NUM>. The inside belt <NUM> and outside belt <NUM> both have a structure in which belt cords such as a plurality of steel cords are covered with rubber. The inside belt <NUM> is larger in tire-width direction length than the outside belt <NUM>. Therefore, each of the ends 21A on both sides in the tire-width direction of the belt <NUM> is configured by an end in the tire-width direction of the inside belt <NUM>. It should be noted the outside belt <NUM> may be larger in tire-width direction length than the inside belt <NUM>. Furthermore, the belt <NUM> may be a single layer structure, or may be a structure of three or more layers.

The sidewall <NUM> includes sidewall rubber <NUM> which constitutes a side wall surface on the outer side of the tire <NUM>. The sidewall rubber <NUM> bends the most upon the tire <NUM> making a cushion action, and normally is configured by flexible rubber having fatigue resistance.

Although omitted from <FIG>, a carcass ply constituting a ply serving as the backbone of the tire <NUM> is embedded inside of the tire <NUM>. This carcass ply is embedded inside of the tire <NUM>, in a mode passing between the pair of bead cores <NUM>, the pair of sidewalls <NUM> and the tread <NUM>. This carcass ply, for example, has a configuration in which the plurality of ply cords consisting of an insulative organic fiber cord such as polyester or polyamide, or the like are covered by rubber. The above-mentioned belt <NUM> is arranged on the outer side in the tire-radial direction of this carcass ply. In addition, although omitted from <FIG>, the inner liner as the rubber layer constituting the inner wall surface of the tire <NUM> is provided spanning between the pair of beads, at the tire inner cavity side of the carcass ply. This inner liner 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 a sealant layer <NUM>. The sealant layer <NUM> is arranged over the entire circumference in the tire-circumferential direction, in a region of the tire inner cavity surface configured by the inner liner corresponding at least to the tread <NUM>. The sealant layer <NUM> is formed by a belt-like sealant material being wound along the tire-circumferential direction on the tire inner surface. As the sealant material, a material having stickiness is favorably used, and is pasted to the tire inner cavity surface by the stickiness thereof. The thickness of the sealant layer <NUM> of at least <NUM> is said to be favorable.

A production method of a tire according to an embodiment for producing the tire <NUM> equipped with the above configuration will be explained below. The production method of a tire according to the embodiment relates to a method of forming the above-mentioned sealant layer <NUM> on the tire <NUM> obtained by vulcanizing a green tire, which is the source article of the tire <NUM> molded so as to be the above-mentioned configuration.

<FIG> is a flowchart showing a production method according to the embodiment in process order. As shown in <FIG>, as a production method of the tire of the embodiment, first, a contact width of the tire <NUM> is measured (Step S1). The contact width of the tire <NUM> is a contact width TW of the tread <NUM>, as shown in <FIG> and <FIG>. It should be noted that measurement of this contact width TW measures at conditions based on standard internal pressure and maximum load capability of a tire standard such as JATMA, ETRTO and TRA in accordance with the size of the tire <NUM>. By measuring the condition at which the load is the maximum in this way, the contact width TW reaches the maximum contact width of the tire <NUM>.

It should be noted that the contact width TW can be determined by a database associating the contact shape and structural information (experimental prediction model), or determined by contact analysis such as FEM, in addition to directly measuring, for example.

Next, as shown in <FIG>, the center 10C between ends on the inner side in the tire-radial direction of the pair of beads <NUM> is set at the tire-width direction center, the tire-width direction length from this tire-width direction center until one end w1 of the contact width TW is defined as CW1, and the tire-width direction length from the tire-width direction center until the other end w2 of the contact width TW is defined as CW2. It should be noted that, in the embodiment, since the structure of the tire <NUM> is left/right symmetrical, the center 10C between the pair of beads <NUM> established as the tire-width direction center matches in the tire equatorial plane S1 in the tire-width direction. Then, the larger by comparing CW1 and CW2, is prescribed as CW (Step S2). In <FIG>, CW1 on the left side is defined as CW. Next, the length from the tire-width direction center to each of the ends 21A in the tire-width direction of the belt <NUM> is defined as BW, and the tire-width direction length SW of the sealant material coating area on one side in the tire-width direction from the tire-width direction center is prescribed as CW<SW<BW (Step S3). Next, a sealant layer <NUM> is formed by the sealant material coating (Step S4).

<FIG> is a view showing an example of a method specifically implementing Step S4, and is an exploded view showing a part in the circumferential direction of a tire inner surface to which the sealant material <NUM> is pasted and the sealant layer <NUM> is formed. <FIG> indicates the tire-circumferential direction by R, and indicates the tire-width direction by X. As shown in <FIG>, the sealant layer <NUM> is formed by one belt-like sealant material <NUM> which is pasted while being wound along the tire-circumferential direction on the tire inner surface. The sealant layer <NUM> has a plurality of annular circling parts <NUM> and plurality of transition parts <NUM> formed by the sealant material <NUM>.

The sealant layer <NUM> is formed by applying the belt-like sealant material <NUM> on the entire circumference of the application region in the tire-width direction of the sealant material <NUM> on the tire inner surface, while being wound around along the tire-circumferential direction, and while transitioning the path of this circling to a side of one direction (right direction in <FIG>) of the tire-width direction every one turn. The annular circling parts <NUM> are arranged in parallel in the tire-width direction by a plurality of sealant material <NUM> extending in the tire-circumferential direction. In the embodiment, as shown in <FIG>, the tire-width direction length SWx2 in the sealant material coating area becomes the coating area length in the tire-width direction of the sealant material <NUM>. It should be noted that the sealant material <NUM> may be pasted to the tire inner surface while transitioning to the tire-width direction every one turn; however, it may be pasted to overlap for two turns or three turns at the same location in the tire-width direction. The coating area length in the tire-width direction of the sealant material <NUM> is an integer multiple of the pitch width, which is the tire-width direction length of the circling part <NUM>.

It should be noted that, in order to set the coating area length of the tire-width direction of the sealant material <NUM> as an integer multiple of the pitch width, which is the tire-width direction length of the circling part <NUM>, and establish so as to satisfy CW<SW<BW, it can be done by adopting the following such calculation step. In other words, the value of the integer satisfying (CWx2)<(pitch width x integer) < (BWx2) is calculated when any pitch number. At this time, in the case of there being no integer value satisfying this equation, the pitch width is varied. For example, in the case of CW being <NUM>, BW being <NUM>, and pitch width being <NUM>, the integer value becomes <NUM>, and the SW satisfying CW<SW<BW is determined as <NUM>, for example.

In <FIG>, the reference symbol 61A indicates the winding start of the sealant material <NUM>, and the reference symbol 61B indicates the winding end of the sealant material <NUM>. The sealant material <NUM> is continuously pasted from one end side to the other end side (left side to right side in <FIG>) in the tire-width direction, while winding around as shown by the arrow F, from the winding start 61A to the winding end 61B.

The circling part <NUM> is formed by the sealant material <NUM> being pasted on the tire inner surface in parallel with the tire-circumferential direction. The plurality of circling parts <NUM> are arranged in parallel so as to be adjacent in a state close to 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 close to each other.

The transition parts <NUM> are provided aligned at predetermined positions in the tire-circumferential direction. 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 for about one turn on the tire inner surface. The next circling part <NUM> is pasted, through the transition part <NUM>, to be adjacent at one side in the tire-width direction of the pasted circling part <NUM>. The next circling part <NUM> adjacent on one side in the tire-width direction is repeatedly formed via the transition part <NUM>, whereby the sealant layer <NUM> is formed. Upon pasting the sealant material <NUM> to the tire inner surface in this way, the pasting method of sequentially arranging and 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. In addition, it is preferable to include a characteristic of the fluidity being low and hardly flowing even during high-speed running.

<FIG> is a view schematically showing an example of a method of applying the sealant material <NUM> to the tire inner surface in the step pasting. In <FIG>, a width-direction cross section of the tire <NUM> is shown, and the tire-width direction X, tire-radial direction Y and tire-circumferential direction R are respectively shown. To step paste the sealant material <NUM>, it is possible to perform by discharging and coating the sealant material <NUM> onto the inner surface of the tire <NUM>, from the nozzle <NUM>, while rotating the tire <NUM> around the axis line G, 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>.

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. Upon step pasting, it is preferable to determine the winding start 61A so that the coating amount does not vary at the left side and right side of the tire-width direction center.

It should be noted that, as shown in <FIG>, the cross-sectional shape of the sealant material <NUM> discharged from the nozzle <NUM> and pasted on the tire inner surface is preferably a substantially rectangular shape. It is thereby possible to equalize the thickness as the sealant layer <NUM>. In addition, the adjacent circling parts <NUM> are in close contact with each other in the tire-width direction, and a gap hardly occurs between the circling parts <NUM>.

In the case of the sealant material <NUM> being step pasted to the tire inner surface 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 parts <NUM> has a first sealant material increasing part 62A1 which overlaps in the tire-thickness direction at the transition part <NUM> from the initial circling part 62A to the next circling part <NUM>, 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 second sealant material increasing part 62B1 which overlaps in the tire-thickness direction with the transition part <NUM> transitioning to the finishing circling part 62B. The first sealant material increasing part 62A1 is a triangular portion at which the transition part <NUM> overlaps over the winding start 61A. The second sealant material increasing part 62B1 is a triangular portion at which the winding end 61B overlaps over the transition part <NUM>.

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 the sealant layer <NUM> formed on the tire inner surface in the above way, the tire-width direction length thereof is larger than the contact width TW, and each of the ends 60A on both sides in the tire-width direction of the sealant layer <NUM> is positioned more to the outer side in the tire-width direction than each of both ends w1, w2 of the contact width TW. Since the contact surface 25a of the tread <NUM> is at the inner side of the tire-width direction area of the sealant layer <NUM>, the puncture prevention function by the sealant layer <NUM> becomes sufficient. On the other hand, the tire-width direction length of the belt <NUM> is larger than the tire-width direction length of the sealant layer <NUM>, and each of the ends 21A on both sides in the tire-width direction of the belt <NUM> is positioned more to the outer side in the tire-width direction than each of the ends 60A on both sides in the tire-width direction of the sealant layer <NUM>. Even if heat is generated by the portion of both ends in the tire-width direction of the belt <NUM> deforming, this heat thereby tends to be radiated without being hindered by the sealant layer <NUM>. Heat damage of the tire <NUM> is thereby suppressed. In other words, according to the production method of the embodiment, it is possible to provide a production method of a pneumatic tire which can suppress the occurrence of heat damage, while maintaining the puncture prevention function by the sealant layer <NUM>.

The following effects are exerted by the above-mentioned embodiment.

Claim 1:
A production method of a tire comprising tread (<NUM>) which includes a belt (<NUM>), wherein a sealant layer (<NUM>) is provided at least to an inner surface of the tread (<NUM>), the method comprising:
measuring a contact width (TW) of the tire (<NUM>);
when defining a tire-width direction length from a tire-width direction center until an end of the contact width (TW) as CW1, and defining a tire-width direction length from the tire-width direction center until another end of the contact width (TW) as CW2, comparing CW1 and CW2 and establishing a larger thereof as CW;
establishing a length from the tire-width direction center until an end in the tire-width direction of the belt (<NUM>) as BW, and prescribing a tire-width direction length SW of a sealant material coating area on one side in the tire-width direction from the tire-width direction center as CW<SW<BW; and
arranging in parallel in the tire-width direction a plurality of annular circling parts (<NUM>) of a sealant material (<NUM>) extending in the tire-circumferential direction to provide the sealant layer (<NUM>), by establishing a tire-width direction length SW x <NUM> of the sealant material coating area on the inner surface of the tread (<NUM>) as a coating area length in the tire-width direction of the sealant material (<NUM>), and coating a belt-like sealant material (<NUM>) on the coating area in the tire-width direction of the sealant material (<NUM>), while circling along the tire-circumferential direction, and while transitioning a path of circling thereof to one direction side of the tire-width direction at least once every circling.