JP4904049B2 - Pneumatic tire manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing a pneumatic tire including a step of forming a rubber member for a tire by spirally winding an unvulcanized rubber strip in the form of a ribbon around a cylindrical body to be wound, and more particularly, the rubber. The present invention relates to a technique capable of adjusting the thickness of a member.

In recent years, a rubber member for a tire having a desired cross-sectional shape is obtained by winding a ribbon-shaped unvulcanized rubber strip spirally while shifting the position in the axial direction on the outside of a cylindrical body to be wound. Various forming methods have been proposed (see Patent Document 1 below). Such a rubber member manufacturing method is generally called a strip wind method, and it is not necessary to use a large-sized rubber extruder, so that the factory equipment can be simplified, and there is no need for die replacement or adjustment work of the rubber extruder. Therefore, the productivity is improved.
Japanese Patent No. 3566915

  By the way, in the conventional strip winding method, since the rubber strip having a substantially constant thickness is continuously wound, the thickness of the rubber member is formed to be substantially constant in the circumferential direction.

  However, there is a case where it is desired to intentionally change the thickness of the rubber member in the tire circumferential direction. For example, as shown in FIG. 11A, in a ply p of a belt or a carcass, since there is a splice portion f in which both ends in the circumferential direction are overlapped and joined, a step g is generated at that portion. . For the rubber member h stacked on such a step g, it is necessary to provide a portion j having a locally increased thickness and to make the rubber sufficiently filled with the portion j facing the step g. It is preferable to improve the uniformity of the.

  On the other hand, in the splice part f, the weight is locally increased. For this reason, as shown in FIG. 11 (B), the rubber member h that is overlapped facing the splice portion f is provided with a portion k with a locally reduced thickness so that the weight in the tire circumferential direction is increased. It may be preferable to make uniform.

  Therefore, it is effective to provide the rubber member with portions having locally different thicknesses in the tire circumferential direction in order to improve tire uniformity.

  The present invention has been devised in view of the above circumstances, and is based on the fact that a rubber strip having a thickness changing portion whose thickness has locally changed is spirally wound around a wound body, The main object is to provide a method for manufacturing a pneumatic tire that can easily adjust the thickness and / or weight distribution of the rubber member and thereby improve the uniformity.

The invention according to claim 1 of the present invention is characterized in that a rubber strip having a thickness changing portion having a locally changed thickness is spirally wound outside a substantially cylindrical body to be wound and has a predetermined cross section. Forming a rubber member for a tire; and an arranging step of arranging the rubber member outside a ply of a pneumatic tire, wherein the arranging step includes a thickness changing portion of the rubber member, It arrange | positions according to the level | step difference which a splice part forms .

  The invention according to claim 2 is the method for manufacturing a pneumatic tire according to claim 1, wherein the thickness changing portion includes a thickened portion having an increased thickness and / or a reduced thickness portion having a decreased thickness. .

  The invention according to claim 3 is the method for producing a pneumatic tire according to claim 1 or 2, wherein the thickness changing portion has a length less than one circumference of the circumferential length of the rubber member.

According to a fourth aspect of the present invention, in the pneumatic tire according to the first or second aspect, the thickness changing portion has a length that is not less than 0.5 % and less than 10% of the circumferential length of the rubber member. Is the method.

According to a fifth aspect of the present invention, the rubber strip includes the thickness changing portion intermittently, thereby forming a rubber member in which the thickness changing portion is distributed in the circumferential direction and the axial direction. a method of manufacturing a pneumatic tire according to any one of claims 1 to 4. According to a sixth aspect of the present invention, the rubber strip is formed by rolling with a pair of upper and lower calendar rolls, and the rubber strip is adjusted while the rubber strip is continuously formed by the calendar roll. The method of manufacturing a pneumatic tire according to claim 1, wherein the thickness changing portion is formed.

  In the present invention, a rubber member for a tire having a predetermined cross section is formed by spirally winding a rubber strip having a thickness changing portion whose thickness locally changes on the outside of a substantially cylindrical body to be wound. The Therefore, a portion having a large or small thickness can be easily formed at an arbitrary position of the rubber member. And the pneumatic tire excellent in uniformity can be manufactured by arranging this rubber member in association with the position of the splice part of the ply.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows an embodiment of a manufacturing apparatus 1 for carrying out the present invention. The molding apparatus 1 includes a rubber extruder 2, a calender machine 3 that rolls the rubber extruded from the rubber extruder 2, and a rubber strip G2 that is molded into a predetermined shape by the calender machine 3. A molding former 4 that is a wound body and an applicator 5 that is disposed between the molding former 4 and the calendar machine 3 and guides the rubber strip G2 to a predetermined position of the molding former 4 are included.

  The rubber extruder 2 is, for example, a cylinder 2b having a rubber material inlet 2a provided at one end, a screw shaft 2d housed therein and rotated by an electric motor 2c, and extruded by the screw shaft 2d. And an extrusion head 2f having a base 2e for preforming rubber and discharging it to the outside.

  FIG. 2 shows an enlarged cross-sectional view of the tip portion of the rubber extruder 2. A first rubber passage C1 extending in the axial direction is provided inside the cylinder 2b. The extrusion head 2f is, for example, exchangeably fixed to the tip of the cylinder 2b, and thereby has a second rubber channel C2 that communicates with the first rubber channel C1.

  The base 2e is fixed to the extrusion head 2f in a replaceable manner. In this embodiment, as shown in FIG. 3A which is a cross-sectional view taken along the line AA of FIG. 2, a relatively small opening 2g having a horizontally long rectangle is formed. Have Therefore, the rubber G is extruded to the outside as a press trip G1 preliminarily molded in the same cross-sectional shape as the base 2e. Such a rubber extruder 2 only needs to have a relatively small output.

The thickness t1 and the width W1 of the press trip G1 are not particularly limited, but if it is too small, the molding accuracy tends to deteriorate, and if it is too large, it tends to be difficult to give the rubber member a predetermined cross-sectional shape. From this point of view, the thickness t1 of the press trip G1 is preferably 0.4 mm or more, more preferably 0.6 mm or more, and the upper limit is preferably 6 mm or less, more preferably 4 mm or less. Further, the width W1 of the press trip G1 is preferably 4 mm or more, more preferably 6 mm or more, and the upper limit is preferably 40 mm or less, more preferably 30 mm or less. However, the cross-sectional shape of the press trip G1 is not limited to the rectangular shape as described above.

  The calendar machine 3 includes a frame main body 3a and a pair of upper and lower portions for rolling the press trip G1 and forming a rubber strip G2 having a finished cross-sectional shape, which is rotatably supported with respect to the frame main body 3a. Calendar rolls R1 and R2 and gap adjusting means 3d capable of adjusting the gap between the calendar rolls R1 and R2 are included.

  The gap adjusting means 3d includes, for example, a fluid pressure or electric actuator 3d having one end fixed to the frame body 3a and the other end fixed to a bearing 3b that pivotally supports the upper calendar roll R1. The upper calendar roll R1 can be moved up and down by expanding and contracting the actuator 3d. Thereby, the gap between the calendar rolls R1 and R2 can be changed. The actuator 3d can be driven and controlled at a predetermined timing by a controller (not shown).

FIG. 3B is a cross-sectional view taken along the line BB in FIG. In the present embodiment, the calendar rolls R1 and R2 are substantially arranged with their rotation axes in parallel. The gap D, which is the shortest distance between the calendar rolls R1 and R2, is set smaller than the thickness t1 of the press trip G1. Thereby, the press trip G1 is compressed and formed into a flatter rubber strip G2 having a width W2 (> W1 ) and a thickness t2 (<t1).

The thickness t2 and the width W2 of the rubber strip G2 are not particularly limited. However, if the thickness is too small, the strength of the rubber strip G2 may be reduced, and the rubber strip G2 may be broken during winding on the molding former 4, and is too large. And there exists a tendency for a freedom degree to impair the cross-sectional shape of the rubber member 6. FIG. From such a viewpoint, the thickness t2 of the rubber strip G2 is preferably 0.3 mm or more, more preferably 0.4 mm or more, and the upper limit is preferably 5 mm or less, more preferably 4 mm or less. . Further, the width W2 of the rubber strip G2 is preferably 5 mm or more, more preferably 7 mm or more, and the upper limit is preferably 50 mm or less, more preferably 40 mm or less.

The molding former 4 includes a former main body 4a having a substantially cylindrical outer peripheral surface, a support base 4b that can support the former main body 4a in a cantilever manner, and an expansion / contraction diameter mechanism 4c that expands / contracts the former main body 4a. including. The former body 4a has a ring shape by arranging the segments 4S in the circumferential direction, for example, and is rotationally driven in a predetermined direction (indicated by an arrow in the present embodiment) by an electric motor (not shown). Thereby, the rubber strip G2 fixed to the former body 4a is wound around itself, and the ring-shaped rubber member 6 is formed. The expansion / contraction diameter mechanism 4c can reduce the outer diameter of the former body 4a from the illustrated state by, for example, alternately retracting the segments 4S in the radial direction. More thereto, the rubber member 4 wound is easily removed from the former body 4a.

  The applicator 5 has, for example, a conveyor shape (details not shown) capable of guiding the rubber strip G2 in the length direction while restraining the rubber strip G2 in the width direction, and is provided so as to be movable at least in the axial direction of the former body 4a. As a result, the applicator 5 can guide the rubber strip G2 to a predetermined axial position of the former body 4a.

  In the present embodiment, the calendar machine 3 drives the actuator 3d and adjusts the gap D during the rolling of the press trip G1 continuously extruded from the rubber extruder 2, so that at least the rubber strip G2 is moved. A step of locally changing the thickness t2 is performed.

  FIG. 4A shows the relationship between the gap D and time T. In this example, while the gap D is set to an arbitrary value “a” and the rubber strip G2 is being continuously formed, the actuator 3d is controlled during the minute time Ts to increase the gap by 1.2 times. Increase processing is performed. The gap D increases substantially linearly during the minute time Ts, then maintains a constant value (1.2a), and returns to the original value a even if it decreases approximately linearly again.

  FIG. 4B shows a cross-sectional view of the rubber strip G2 obtained by such gap control. The rubber strip G2 includes, in the length direction, a base portion 7 having a substantial reference thickness t2a finished with the gap as a and a thickness changing portion 8 whose thickness changes locally. The thickness changing portion 8 includes a thickened portion 8a that increases to the thickness t2b. Both the thicknesses t2a and t2b are preferably within the range of the thickness t2.

  FIG. 5A shows the relationship between the gap D and the time T, while the gap D is set to an arbitrary value “b” and the rubber strip G2 is continuously pushed out. Only during Ts, the actuator 3d is controlled and the gap is reduced by a factor of 0.8. The gap D decreases substantially linearly during the minute time Ts and then maintains a constant value, and returns to the original value b even if it increases almost linearly again.

  FIG. 5B shows a cross-sectional view of the rubber strip G2 obtained by such gap control. The rubber strip G2 includes a base portion 7 having a substantial reference thickness t2a finished with the gap as b, and a thickness changing portion 8 whose thickness changes locally. In this example, the thickness change The portion 8 includes a reduced thickness portion 8b that decreases to a thickness t2c. Both the thicknesses t2a and t2c are preferably within the range of the thickness t2.

  Therefore, in the manufacturing apparatus 1 of this embodiment, the rubber strip G2 having the thickness changing portion 8 whose thickness has locally changed can be supplied to the molding former 4.

  The rubber strip G2 has a substantially flat surface on the inner surface side i wound around the molding former 4, and the thickness changing portion 8 is formed by locally projecting or denting the outer surface o side. The Such a rubber strip G2 is useful for suppressing air confinement during winding.

  FIG. 6 shows a plan view of an embodiment of the rubber member 4 in which the rubber strip G2 is spirally wound around the former body 4a. FIGS. 7A and 7B show an AA sectional view and a BB sectional view of FIG. 6, respectively.

  The rubber member 6 is formed as a tread rubber disposed in a tread portion of a pneumatic tire. Further, in this embodiment, the rubber strip G2 is wound around the regions Y, Y in the tire circumferential direction of the shoulder regions on both sides of the rubber member 4 so that the thickened portion 8a is located. For this reason, in the rubber strip G2, the thickened portion 8a is provided intermittently, specifically, at a constant period substantially equal to the circumferential length of the rubber member 6. Thereby, as shown in FIGS. 7A and 7B, the rubber member 4 is formed with the region Y having a locally increased thickness in the tire circumferential direction.

Such a rubber member is , for example, a pneumatic tire in which a reinforcing ply (for example, an edge band ply) that covers only both shoulder portions of the tread portion is disposed. By using together, it helps to make the thickness of the tread portion of the pneumatic tire uniform in the tire circumferential direction (the mode of FIG. 11A).

  Further, in this embodiment, when the entire thickened portion 8a is changed to the thinned portion 8b, the region Y is used together with the splice portion of the reinforcing ply as described in FIG. Thus, the weight of the tread portion can be made uniform in the tire circumferential direction (the mode shown in FIG. 11B). In this case, in the rubber strip G2, it is desirable to control the extrusion pressure and the like of the rubber extruder 2 so that the mass per unit volume of the reduced thickness portion 8B is smaller than the mass per unit volume of the base portion 7.

  As described above with reference to FIG. 11, the rubber member 6 as described above is incorporated into the raw cover while taking into account the positional relationship with the splice portion of the ply, and is vulcanized and molded in accordance with a conventional method, thereby achieving uniformity. An excellent pneumatic tire can be manufactured. Here, the length L in the tire circumferential direction of the thickness changing portion 8 is not particularly limited, but the above-described effect tends to be reduced if it is too small or too large. From such a viewpoint, the length L is preferably 0.5% or more of the circumferential length (one circumferential length) of the rubber member 6, more preferably 1% or more, and further preferably 2% or more. The upper limit is preferably less than 10%, more preferably 7% or less, more preferably 6% or less, and still more preferably 5% or less.

  In order to position the thickness changing portion 8 at a predetermined position of the former body 4a, first, from the outer diameter of the molding former 4A, the winding start position of the rubber strip G2 around the molding former 4a, and the helical pitch of the rubber strip G2. The distance from the winding start end of the rubber strip G2 to the thickness changing portion 8 is calculated in advance. Further, since the passing distance between the calender rolls R1 and R2 of the rubber strip G2 can be appropriately measured using a sensor, the expansion and contraction of the actuator 3 is performed based on these parameters, so that the rubber strip G2 A thickness changing portion 8 is formed at a predetermined position, and this is guided by the applicator 5 to an arbitrary position set in advance.

  Further, the difference (t2b-t2a) or (t2a-t2c) between the thickness (t2b or t2c) of the thickness changing portion 8 and the thickness t2a of the base portion 7 is not particularly limited. However, if it is too large, winding becomes difficult and the strength of the rubber strip may be reduced. From such a viewpoint, the difference is preferably 5% or more, more preferably 10% or more of the thickness t2a of the base 7, and the upper limit is preferably 50% or less, more preferably 40% or less. Particularly preferably, 30% or less is desirable.

  8A is a plan view of another embodiment of the rubber member 6 (tread rubber) spirally wound around the former body 4a, and FIG. 8B is a schematic perspective view thereof. In this embodiment, the rubber strip G2 intermittently includes the thickness changing portion 8 (in this embodiment, the thickening portion 8a). The arrangement period of the thickness changing portion 8 is shown to be greater than 100% and less than 200% of the circumferential length of the rubber member 6. Thereby, the thickness change part 8 is disperse | distributed and arrange | positioned in the rubber member 6 both in a tire circumferential direction and a tire axial direction.

  Further, as shown in FIG. 5B, the thickness changing portion 8 is formed on a virtual spiral curve SL1 drawn on the rubber member 6 with the width WR of the rubber member 6 as a substantial lead. It preferably appears intermittently and at approximately the same pitch. In such a rubber member 6, the thickened portions 8 a are intentionally distributed in the tire circumferential direction and the tire axial direction, so that the uneven distribution of the thickness or weight of the rubber member 6 itself is widely dispersed. it can. Therefore, it helps to improve the tire uniformity. Instead of the thickened portion 8a, the thinned portion 8b may be adopted.

FIG. 9A shows a schematic perspective view of another embodiment of the rubber member 6 (tread rubber), and FIG. 9B shows a perspective view of the belt ply p1 disposed inside thereof. Also in this embodiment, the rubber member 6 is provided with the thickness changing portions 8 distributed in the tire circumferential direction and the tire axial direction. Moreover, it is preferable that the thickness change part 8 appears intermittently and on substantially the same pitch on the virtual curve SL2 which crosses the rubber member 6 diagonally. The curve SL2 is substantially the same as the ply edge that appears at the splice portion f of the belt ply p1. Such a rubber member 6 can relieve a uniform thickness of the tread in the tire circumferential direction or an uneven distribution of the weight of the belt ply over a wide range by using the thickness changing portion 8. Therefore, it helps to improve the tire uniformity.

FIG. 10 shows still another embodiment of the present invention.
In this embodiment, the thickness changing portion 8 includes a start end portion 10 having a predetermined length including the winding start end 10a of the rubber strip G2 and a end portion 11 having a predetermined length including the winding end 11a. (In this embodiment, it is formed by the reduced thickness portion 8b). Since the starting end portion 10 and the terminal end portion 11 of the rubber strip G2 are particularly prone to thickness and weight imbalance, these portions can be improved by locally reducing the thickness of this portion. In this embodiment, it goes without saying that the reduced thickness portion 8b may be changed to the increased thickness portion 8a.

  As mentioned above, although embodiment of this invention was described, this invention can be implemented in a various aspect. For example, the rubber member may be rubber other than tread rubber, for example, side wall rubber, clinch rubber (bead rubber), bead apex rubber, and / or inner liner rubber. Further, the rubber strip G2 forming one rubber member 6 may include both the thickened portion 8a and the thinned portion 8b.

  In order to confirm the effect of the present invention, a pneumatic tire having a tire size of “215 / 60R16 95H” was prototyped based on the specifications in Table 1. In the pneumatic tire of the example, the tread rubber was molded in the manner shown in FIG. In Example 1, the thickness changing part was the thickened part, and in Example 2, the thickness reducing part was arranged along the edge of the belt ply. On the other hand, in the comparative example, the thickness of the rubber strip was constant.

Then, 20 tires were prototyped and their uniformity was tested. For the uniformity, a radial force variation (RFV) was measured using a cornering tester in accordance with the uniformity test conditions of JASO C607: 2000. The evaluation speed was 10 km / h. The results are all expressed as an average value (N) of 20 tires, and the smaller the value, the better.
The test results are shown in Table 1.

  From the test results, it was confirmed that the tires of the examples had small RFV and excellent uniformity compared to the comparative examples.

It is a whole side view showing an example of the manufacture device of the pneumatic tire of the present invention. It is an expanded sectional view of an extrusion head. (A) is an AA enlarged sectional view of Drawing 1, and (B) is a BB sectional view of the same. (A) is a graph which shows the relationship between the gap of a calender roll, and time, (B) shows sectional drawing of the rubber strip obtained by such gap control, respectively. (A) is a graph which shows the relationship between the gap of a calender roll, and time, (B) shows sectional drawing of the rubber strip obtained by such gap control, respectively. It is a top view of the rubber member wound around the forming former. (A) is AA sectional drawing of FIG. 6, (B) is BB sectional drawing of FIG. (A) is a top view of the rubber member which shows other embodiment, (B) is a perspective view which simplifies and shows a rubber member. (A) is the perspective view which simplifies and shows the rubber member which shows other embodiment, (B) is a perspective view of the belt ply distribute | arranged to the inner side. It is a top view of the rubber member which shows other embodiment. (A), (B) is sectional drawing along the circumferential direction which shows the relationship between a ply and a rubber member.

Explanation of symbols

2 Rubber Extruder 3 Calendar Machine 4 Molding Former 4a Former Body 6 Rubber Member 8 Thickness Change Part 8a Thickening Part 8b Thickening Part G2 Rubber Strip D Gap

Claims (6)

A step of forming a rubber member for a tire having a predetermined cross section by spirally winding a rubber strip having a thickness changing portion whose thickness has locally changed on the outside of a substantially cylindrical body to be wound ;
An arrangement step of arranging the rubber member outside the ply of the pneumatic tire,
The method of manufacturing a pneumatic tire characterized in that, in the arranging step, the thickness changing portion of the rubber member is arranged in accordance with a step formed by the splice portion of the ply .   The method of manufacturing a pneumatic tire according to claim 1, wherein the thickness changing portion includes a thickened portion having an increased thickness and / or a reduced thickness portion having a decreased thickness.   The method for manufacturing a pneumatic tire according to claim 1, wherein the thickness changing portion has a length less than one circumference of a circumferential length of the rubber member. The method for manufacturing a pneumatic tire according to claim 1 or 2, wherein the thickness changing portion has a length that is not less than 0.5 % and less than 10% of a circumferential length of the rubber member. The rubber strip includes the thickness changing portion intermittently, thereby forming a rubber member in which the thickness changing portion is distributed in the circumferential direction and the axial direction. the method of manufacturing a pneumatic tire according to item 1. The rubber strip is rolled and formed with a pair of upper and lower calendar rolls, and the thickness change part is adjusted by adjusting a gap of the calendar roll while the rubber strip is continuously formed by the calendar roll. The manufacturing method of the pneumatic tire of Claim 1 formed.

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