JP5196109B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire used in, for example, passenger cars, trucks, buses and the like.

Conventionally, as this type of pneumatic tire, one in which both ends of the carcass member in the tire width direction are folded back outward in the tire width direction so as to wind up around the bead portion (see, for example, Patent Document 1). .
JP 2006-199223 A

  However, the conventional pneumatic tire has a problem that a separation failure due to a difference in stress or distortion between members is likely to occur due to a difference in hardness between the folded end portion of the carcass member and the surrounding rubber. Therefore, measures have been taken to arrange the folded end at a position where it is difficult for a difference in stress between the members to occur. However, since the folded end is located on the side part where the elastic deformation is large, adjustment of the position of the folded end is performed. However, the effect of preventing the separation failure is insufficient, and it is extremely difficult particularly when the side portion is narrow like a flat tire.

  The present invention has been made in view of the above problems, and an object of the present invention is to effectively prevent a separation failure due to a difference in hardness between the folded end portion of the carcass member and the surrounding rubber. It is to provide a pneumatic tire.

In order to achieve the above object, the present invention is configured such that both ends of the carcass member in the tire width direction are folded back outward in the tire width direction so as to wind up around the bead portion, and the rubber of the carcass member is disposed on the outer side in the tire width direction of the folded end portion. In a pneumatic tire made of rubber that is harder than the positioned rubber, the hardness of the carcass member is lower than the rubber of the carcass member between the folded end portion of the carcass member and the rubber positioned on the outer side in the tire width direction. A reinforcing rubber made of rubber having a hardness higher than that of the rubber positioned on the outer side in the tire width direction of the folded end portion is provided , and the reinforcing rubber is formed by three or more rubber layers laminated in the tire width direction. Shaped so that the elastic modulus of each rubber layer increases from the rubber located on the outer side in the tire width direction of the folded end to the folded end of the carcass member. And a reinforcing rubber, rubber side rubber layer located on the outer side in the tire width direction of the folded end portion of the carcass member is formed such that the width in the tire radial direction than the folded end side rubber layer of the carcass member is enlarged ing.

Thereby, the reinforcing rubber provided between the folded end portion of the carcass member and the rubber positioned on the outer side in the tire width direction is lower in hardness than the rubber of the carcass member and is positioned on the outer side in the tire width direction. Since it is formed of rubber having a higher hardness, the difference in hardness between the folded end portion of the carcass member and the rubber positioned on the outer side in the tire width direction is alleviated by the reinforcing rubber. In this case, the reinforcing rubber is formed by three or more rubber layers laminated in the tire width direction, and from the rubber located on the outer side in the tire width direction of the folded end portion of the carcass member toward the folded end portion of the carcass member. Since the elastic modulus of each rubber layer is formed to be high, the difference in rubber hardness is gradually reduced. Further, the rubber layer of the rubber-side reinforcing rubber located on the outer side in the tire width direction of the folded end portion of the carcass member is formed so as to be wider in the tire radial direction than the rubber layer on the folded end portion side of the carcass member. As a result, the physical properties of the reinforcing rubber gradually change from the folded end where stress is concentrated, and both ends in the width direction of each rubber layer can be brought into contact with the carcass member.

According to the present invention, since the difference in hardness between the folded end portion of the carcass member and the sidewall member can be reduced, it is possible to effectively prevent the occurrence of a separation failure due to a stress difference or a strain difference between the members. And durability can be improved. In this case, since the difference in the hardness of rubber can be relieved in steps, the difference in stress and strain between members can be further reduced. In addition, since the physical properties of the reinforcing rubber can be gradually changed from the folded end where stress is concentrated, the stress can be more effectively relaxed. Further, since both end sides in the width direction of each rubber layer can be brought into contact with the carcass member, it is effective for preventing the carcass member and the reinforcing rubber from being peeled off.

  1 to 4 show an embodiment of the present invention. FIG. 1 is a partial front sectional view of a pneumatic tire, FIG. 2 is a front sectional view of an essential part thereof, and FIGS. 3 and 4 are diagrams showing test results. It is.

  The pneumatic tire shown in the figure includes a tread portion 1 formed on the tire outer peripheral surface side, sidewall portions 2 formed on both sides in the tire width direction, and beads formed on the tire radial direction inner side of the sidewall portions 2. A shoulder portion 4 formed between the portion 3 and the tread portion 1 and the sidewall portion 2 is provided.

  That is, in this pneumatic tire, a sheet-like inner liner 10, a plurality of carcass members 11, and a plurality of belts 12 are formed into a cylindrical shape on a forming drum, and then the carcass member 11 is a pair of left and right bead members. The carcass member 11 is formed in a toroidal shape so as to straddle between the two, and both ends in the tire width direction of the carcass member 11 are wound from the periphery of the bead member 13 to the outer side in the tire width direction and folded back to the side wall portion 2 side. It is formed by sticking the tread member 14 and the side wall member 15 to each other. Further, a reinforcing rubber 16 that covers the folded end portion 11a is provided between the folded end portion 11a of the carcass member 11 and the sidewall member 15 located on the outer side in the tire width direction.

  The inner liner 10 is made of a sheet-like rubber having airtightness, and is disposed on the inner peripheral surface side of the carcass member 11.

  The carcass member 11 is a sheet-like member in which a plurality of carcass cords are covered with rubber, and is formed in a cylindrical shape by splicing one end and the other end in the tire circumferential direction. In this case, the rubber of the carcass member 11 is made of rubber harder than the rubber of the sidewall member 15.

  Each belt 12 is formed by covering a plurality of reinforcing cords made of steel cords, high-strength fibers and the like with sheet-like rubber, and is arranged so as to overlap each other in the tire radial direction.

  The bead member 13 includes a bead core 13a formed by bundling wires such as metal wires, and a bead filler 13b formed of rubber having a substantially triangular cross section. The bead filler 13b is disposed on the outer peripheral side of the bead core 13a.

  The tread member 14 is made of rubber formed by extrusion molding, and is disposed on the outer peripheral surface side of the carcass member 11. A groove 14a having a predetermined pattern is formed on the outer peripheral surface of the tread member 14 during vulcanization molding.

  The sidewall member 15 is made of rubber formed by extrusion molding, and is disposed so as to cover both sides of the carcass member 11 in the tire width direction. The sidewall member 15 is made of rubber having a lower hardness than the rubber of the carcass member 11, and the difference in dynamic elastic modulus at 20 ° C. between the rubber of the carcass member 11 is 0.5 MPa or more.

  The reinforcing rubber 16 is made of rubber having a hardness lower than that of the carcass member 11 and higher than that of the side wall member 15, and is laminated in the tire width direction. 16b and 16c. In this case, each of the rubber layers 16a, 16b, and 16c is made of sheet-like rubber, and the first rubber layer 16a is disposed on the outermost side in the tire width direction, and the second rubber layer 16b and the third rubber layer 16c. It arranges in order in the tire width direction. In this case, the elastic modulus of the rubber of the carcass member 11 is Ec, the elastic modulus of the first rubber layer 16a is E1, the elastic modulus of the second rubber layer 16b is E2, and the elastic modulus of the third rubber layer 16c is E3. When the elastic modulus of the rubber of the sidewall member 15 is Es, the rubber layers 16a, 16b, and 16c are formed to satisfy Es <E1 <E2 <E3 <Ec. The rubber layers 16a, 16b, and 16c are formed so that W3 <W2 <W1 when the widths in the tire radial direction are W1, W2, and W3, respectively, and the thickness t in each tire width direction is one. Is 0.5 mm or more and 2.0 mm or less.

  Here, about the tire for passenger cars, when the durability test of Examples 1-2 of this invention, Comparative Examples 1-2, and a prior art example was done, the result shown in FIG. 3 was obtained. In this test, under the conditions of a tire internal pressure of 290 kPa and a 140% load (regular load 6.04 kN), the test drum was run on a test drum at a speed of 81 km / h, and a running distance in which a side portion separation failure occurred was measured. .

  In this case, for each tire, the thickness of the sidewall member is 3 mm, the elastic modulus of the rubber of the carcass member is 8.2 MPa, the elastic modulus of the rubber of the sidewall member is 5.0 MPa, and the tire size is 235 / 35R18. Was used. In Example 1, one having a single layer of reinforcing rubber having an elastic modulus of 6.6 MPa and a thickness t of 1.0 mm was used. In Example 2, the elastic modulus of the rubber layer on the carcass member side was 7. A reinforced rubber having a two-layer structure with an elastic modulus of 2 MPa and a rubber layer of the sidewall member of 6.1 MPa was used. Comparative Example 1 uses only one layer of reinforcing rubber having an elastic modulus of 5.0 MPa, which is equal to that of the side wall member, and Comparative Example 2 includes only one layer of reinforcing rubber having an elastic modulus of 8.2 MPa, which is equal to that of the carcass member. Used. In this case, in Examples 1 and 2 and Comparative Examples 1 and 2, four types (0.2 mm to 1.1 mm) of thickness t per rubber layer of the reinforcing rubber were used. In addition, what did not have a reinforcement rubber was used for the prior art example. The elastic modulus is a dynamic elastic modulus measured using a rheograph solid manufactured by Toyo Seiki Seisakusho Co., Ltd. under conditions of static strain 10%, dynamic strain ± 2%, measurement frequency 20 Hz, temperature 20 ° C. Say.

  In this test, the traveling distance in which the separation failure occurred in the side portion in the durability test was indexed, and Examples 1-2 and Comparative Examples 1-2 were evaluated using the conventional example as 100. In this case, it was determined that the greater the index value, the more superior. As a result of the test, Examples 1 and 2 were superior to the conventional examples and Comparative Examples 1 and 2. In this test, the reinforcing rubber having a two-layer structure was shown as Example 2, but better results can be expected if a reinforcing rubber having a three-layer structure or more is used.

  Next, with respect to heavy load tires such as trucks and buses, durability tests of Examples 3 to 4 and the conventional example of the present invention were performed, and the results shown in FIG. 4 were obtained. In this test, under the conditions of a tire internal pressure of 850 kPa and a 140% load (a specified load of 26.73 km), the test drum was run at a speed of 45 km / h, and the running distance at which a side separation failure occurred was measured. .

  In this case, for each tire, the thickness of the sidewall member is 8 mm, the elastic modulus of the rubber of the carcass member is 9.5 MPa, the elastic modulus of the rubber of the sidewall member is 5.0 MPa, and the tire size is 11R22.5 Was used. In Example 3, one having a single layer of reinforcing rubber having an elastic modulus of 7.3 MPa and a thickness t of 1.0 mm was used. In Example 4, the elastic modulus of the rubber layer on the carcass member side was 8. A reinforced rubber having a two-layer structure in which the elastic modulus of the rubber layer of the sidewall member was 0 MPa was used. In this case, in Examples 3 to 4, five types (0.2 mm to 2.5 mm) of thickness t per layer of the rubber layer of the reinforcing rubber were used. In addition, what did not have a reinforcement rubber was used for the prior art example. The elastic modulus is a dynamic elastic modulus measured using a rheograph solid manufactured by Toyo Seiki Seisakusho Co., Ltd. under conditions of static strain 10%, dynamic strain ± 2%, measurement frequency 20 Hz, temperature 20 ° C. Say.

  In this test, the mileage in which the side portion separation failure occurred in the endurance test was indexed, and Examples 3 to 4 were evaluated using the conventional example as 100. In this case, it was determined that the greater the index value, the more superior. As a result of the test, Examples 3 and 4 were superior to the conventional example. In this test, the reinforcing rubber having a two-layer structure was shown as Example 2, but better results can be expected if a reinforcing rubber having a three-layer structure or more is used.

  Thus, according to this embodiment, the hardness is lower than the rubber of the carcass member 11 between the folded end portion 11a of the carcass member 11 and the sidewall member 15 located on the outer side in the tire width direction. Since the reinforcing rubber 16 made of rubber having a higher hardness than the rubber of the wall member 15 is provided, the difference in hardness between the folded end portion 11a of the carcass member 11 and the sidewall member 15 can be reduced by the reinforcing rubber 16. It is possible to effectively prevent the occurrence of a separation failure due to stress difference or strain difference between members.

  In this case, when the difference in dynamic elastic modulus at 20 ° C. between the rubber of the carcass member 11 and the rubber of the sidewall member 15 is 0.5 MPa or more, the reinforcing rubber 16 is more elastic than the rubber of the carcass member 11. Since the elastic modulus is lower and the elastic modulus of the sidewall member 15 is higher than that of the sidewall member 15, the rubber used for the reinforcing rubber 16 is optimally hardened by defining the hardness of the rubber using the dynamic elastic modulus. Can be.

  Further, the reinforcing rubber 16 is formed by a plurality of rubber layers 16a, 16b, 16c laminated in the tire width direction, and the elastic modulus of each rubber layer 16a, 16b, 16c from the sidewall member 15 toward the carcass member 11 is increased. Since it formed so that it might become high, the difference in the hardness of rubber | gum can be relieve | moderated in steps, and the stress difference and distortion difference between members can be decreased more.

  Further, since the reinforcing rubber 16 is formed so that the thickness t in the tire width direction of each rubber layer 16a, 16b, 16c is 0.5 mm or more and 2.0 mm or less, the thickness t is too small and the effect is ineffective. It will not be enough. Further, the thickness t is not too large and the thickness of other members is not reduced, and the tire weight is not increased more than necessary. Therefore, it is extremely advantageous in preventing the occurrence of a separation failure.

  Further, since the widths W1, W2, and W3 of the rubber layers 16a, 16b, and 16c of the reinforcing rubber 16 are made wider on the side wall member 15 side than the folded end portion 11a side of the carcass member 11, stress is concentrated. The physical properties of the reinforcing rubber 16 can be gradually changed from the folded end portion 11a, and the stress can be relaxed more effectively. Furthermore, since both end sides in the width direction of the rubber layers 16a, 16b, and 16c can be brought into contact with the carcass member 11, it is effective for preventing the carcass member 11 and the reinforcing rubber 16 from being peeled off.

  Further, since the reinforcing rubber 16 is formed of a sheet-like rubber, it can be wound on a molding drum, for example, like other members, which is extremely advantageous in manufacturing.

Partial front sectional view of a pneumatic tire showing an embodiment of the present invention Front sectional view of main parts of pneumatic tire The figure which shows the test result of the tire for passenger cars The figure which shows the test result of the tire for heavy load

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Carcass member, 11a ... Folding edge part, 15 ... Side wall member, 16 ... Reinforcement rubber, 16a ... Rubber layer, 17 ... Reinforcement rubber

Claims (4)

The carcass member is folded back outward in the tire width direction so that both ends in the tire width direction wind up around the bead portion, and the rubber of the carcass member is made of rubber harder than the rubber positioned on the outer side in the tire width direction of the folded end portion. In the tire,
Between the folded end portion of the carcass member and the rubber located on the outer side in the tire width direction, the hardness is lower than the rubber of the carcass member, and than the rubber located on the outer side in the tire width direction of the folded end portion of the carcass member. Reinforcing rubber made of rubber with high hardness is provided ,
The reinforcing rubber is formed by three or more rubber layers laminated in the tire width direction, and each rubber layer is formed from the rubber located on the outer side in the tire width direction of the folded end portion of the carcass member toward the folded end portion of the carcass member. Formed so that the elastic modulus is high,
The reinforcing rubber is formed such that the rubber layer on the rubber side located on the outer side in the tire width direction of the folded end portion of the carcass member is wider in the tire radial direction than the rubber layer on the folded end portion side of the carcass member. Pneumatic tire characterized by. The difference in dynamic elastic modulus at 20 ° C. between the rubber of the carcass member and the rubber around the folded end is 0.5 MPa or more,
The reinforcing rubber is formed of rubber having a lower elastic modulus than that of the carcass member and having a higher elastic modulus than that of the rubber located on the outer side in the tire width direction of the folded end portion of the carcass member. Pneumatic tires. The pneumatic tire according to claim 2, wherein each rubber layer of the reinforcing rubber is formed so that a thickness in a tire width direction is 0.5 mm or more and 2.0 mm or less. The pneumatic tire according to claim 1, 2 or 3, wherein in that the reinforcing rubber is formed by a sheet-shaped rubber.

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