JP5409181B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire in which a belt layer is interposed between a carcass layer formed in a toroidal shape and a tread rubber.

In this type of pneumatic tire, cushion rubber is disposed on the outer side in the width direction of the belt layer to shape the shape of the tread rubber when the tire is filled with internal pressure.
Patent Document 1 of the prior application related to the same applicant as the present application includes a pneumatic rubber in which a cushion rubber layer is interposed between a widthwise outer end of a belt reinforcing layer provided inside a belt layer and a carcass layer. Tires are described .

JP 2001-121916 A

  The tire supports the load at the tread portion, and the tread is supported by the inner belt reinforcing layer and the side portions continuous to both ends thereof.

Due to the influence of the tension distribution of the belt reinforcing layer, the contact pressure distribution on the road surface becomes non-uniform.
The relationship between the position of the belt reinforcing layer in the tire width direction and the belt tension distribution is shown in the rectangular coordinates of FIG.
In FIG. 4, the horizontal axis indicates the position in the width direction from the center in the tire width direction, the edge position of the maximum ply reinforcement ply of the belt reinforcing layer is 100, the vertical axis indicates belt tension, and the center indicates belt tension 100. It is said.
The belt tension increases as it approaches the center from the edge of the belt reinforcing layer in the tire width direction, and reaches a maximum of 100 at the center.

Under the influence of the tension distribution of the belt reinforcing layer, the contact pressure distribution on the tread rubber tread surface is substantially the same as the tension distribution shown in FIG. 4 in the tire width direction.
That is, the contact pressure on the tread rubber tread increases as the tread shoulder portion approaches the tread center portion, and the tread center portion is maximum.

Therefore, the wear amount of the tread rubber becomes uneven in the tire width direction, and the maximum wear difference, which is the difference in wear amount between the tread center portion with the largest wear amount and the tread shoulder portion with the smallest wear amount, depends on the travel distance. It changed (see the conventional tire in FIG. 3).
Since the cushion rubber layer on the outer side in the width direction of the belt reinforcing layer has a lower hardness than the coating rubber of the belt layer, the cushion rubber layer does not suppress the maximum wear difference.

  The present invention has been made in view of the above points, and the object of the present invention is to make the contact pressure of the tread rubber tread uniform and to reduce the maximum wear difference of the tread rubber even when the travel distance is increased, thereby improving the durability. It is in the point which provides the pneumatic tire which can aim at.

In order to achieve the above object, the invention according to claim 1 is a carcass layer laid in a toroidal shape across a pair of beads, a belt layer circumferentially disposed on a radially outer side of the carcass layer, and the belt layer. A belt reinforcing layer interposed in a circumferential direction between the carcass layer, a tread rubber provided around the outer peripheral surface of the belt layer, and both widthwise sides of the belt layer and the carcass layer. A pneumatic tire provided with cushion rubber provided on both outer sides in the width direction of the belt reinforcing layer , wherein the cushion rubber has a JIS hardness of 80 degrees or more, and the belt layer and 1 times the hardness of the belt coating rubber of the belt reinforcing layer rather smaller than 1.3 times greater than the inner width which defines the existence range of the cushion rubber is 0.8 times the maximum width of the belt reinforcing layer Above, the outer width of pneumatic tire which is characterized in that not more than 1.4 times the maximum width of the belt reinforcing layer.

According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the maximum width of the belt reinforcing layer is 0.6 times or more with respect to the tire width.

  According to the pneumatic tire of the first aspect, the cushion rubber is interposed between the width direction both sides of the belt layer and the carcass layer, and the hardness of the cushion rubber is 1 of the hardness of the belt coating rubber of the belt layer. Therefore, the cushion rubber on both sides supporting the tread shoulder on both sides in the tire width direction is harder than the coating rubber on the belt layer, so that the contact pressure on the tread rubber tread is almost uniform in the tire width direction. Therefore, even if the travel distance is increased, the wear difference (maximum wear difference) between the center portion and the shoulder portion of the tread rubber can be suppressed small, and the durability can be improved.

  In addition, since the hardness of the cushion rubber is less than 1.3 times the hardness of the belt coating rubber of the belt layer, it is possible to suppress an increase in strain applied to the end of the belt layer and to avoid a significant decrease in durability. .

Further, a belt reinforcing layer is interposed between the belt layer and the carcass layer in the circumferential direction, and the cushion rubber is provided on both outer sides in the width direction of the belt reinforcing layer. The reinforcement layer and the cushion rubber with higher hardness will be supported, and the contact pressure of the tread rubber tread can be made more uniform in the tire width direction, and the maximum wear difference of the tread rubber can be increased even if the mileage increases. It can be kept small, and durability can be improved.
The cushion rubber exists in the width direction range outside the inner width of 0.8 times the maximum width of the belt reinforcing layer and inside the outer width of 1.4 times the maximum width of the belt reinforcing layer. Can effectively act on the tread rubber to easily equalize the contact pressure on the tread rubber tread. Furthermore, since the cushion rubber has a JIS hardness of 80 degrees or more, the cushion rubber can be reliably applied to the tread rubber, and the contact pressure of the tread rubber tread can be made uniform.

According to the pneumatic tire of claim 2, since the maximum width of the belt reinforcing layer is 0.6 times or more with respect to the tire width, the contact pressure is made uniform over the entire shoulder portion in the width direction of the tread rubber. can do.

1 is a cross-sectional view of a pneumatic tire according to an embodiment of the present invention. It is a table | surface which shows the result of a running test. It is a graph which shows the result of a running test. It is a coordinate which shows the relationship between the tire width direction position of a belt reinforcement layer, and belt tension distribution.

Hereinafter, an embodiment according to the present invention will be described with reference to FIGS.
The pneumatic tire of the present embodiment is a pneumatic radial tire having an aspect ratio of 0,70 or less used for trucks and buses.
The tire size of the pneumatic radial tire T is “435 / 45R22.5”. That is, a radial tire having a tire width of 435 mm, a flatness ratio of 45%, and a rim diameter of 22.5 inches.

In FIG. 1, sectional drawing of this pneumatic radial tire T is shown.
Referring to FIG. 1, a pneumatic radial tire T includes bead portions Tb and Tb in which a pair of left and right ring-shaped beads 2 and 2 are embedded, and sidewall portions extending radially outward from the bead portions Tb and Tb. Ts and Ts and tread part Tt which connects the outer end of sidewall part Ts and Ts.

And the carcass layer 3 is constructed in a toroidal shape between a pair of beads 2 and 2.
The carcass layer 3 is composed of at least one carcass ply 3p, and a large number of non-extensible cords (for example, steel cords) extending in the radial direction are embedded in the circumferential direction.
Both end portions of the carcass layer 3 are wound around the pair of left and right ring-shaped beads 2 and 2 from the inside and folded outward.
A chafer 4 reinforced by, for example, a steel cord is wound around the carcass layer 3 in the bead portion Tb.

A belt layer 5 is provided on the outer side in the radial direction of the carcass layer 3 in the tread portion Tt.
The belt layer 5 is configured by laminating at least two belt plies 5p, and each belt ply 5p has an inextensible reinforcing cord made of steel or aramid fiber in an angle of 40 degrees or more with respect to the circumferential direction. Many of them are buried at an angle.

The inclination directions of the reinforcing cords of the laminated belt plies 5p are opposite to each other.
The belt ply 5p to be laminated is wide and narrow, and the belt layer width Wb which is the width of the belt ply 5p having the maximum width is 360 mm in the case of the present pneumatic radial tire T.

A belt reinforcing layer 6 is interposed between the belt layer 5 and the carcass layer 3 in the circumferential direction.
The belt reinforcing layer 6 includes at least one reinforcing ply 6p, and in the case of the pneumatic radial tire T, two belt reinforcing layers 6 are laminated.
In each reinforcing ply 6p, a large number of non-stretchable reinforcing elements made of steel or aramid fibers are embedded in the circumferential direction.

In the case of the present pneumatic radial tire T, the belt reinforcing layer width Ws that is the width of the reinforcing ply 6p having the maximum width is 300 mm.
Therefore, the belt reinforcing layer 6 provided inside the belt layer 5 is narrower than the belt layer 5.

Cushion rubbers 7, 7 are interposed between the width direction side portions protruding from both sides of the belt reinforcing layer width Ws of the belt layer 5 and the carcass layer 3.
Therefore, the cushion rubbers 7 and 7 are generally provided on both outer sides in the width direction of the belt reinforcing layer 6.
The pneumatic radial tire T is symmetrical with respect to the center line CC ′ in the width direction, and includes the carcass layer 3, the belt layer 5, the belt reinforcing layer 6, and the cushion rubbers 7 and 7 of the pneumatic radial tire T. The tire constituent members are also symmetrical with respect to the width direction center line CC ′.

The cushion rubber 7 partially penetrates between the belt reinforcing layer 6 and the carcass layer 3 on the inner side in the width direction (width direction center line CC ′ side), and the outer side in the width direction is somewhat outward from the belt layer 5. It is sticking out.
With reference to FIG. 1, the width direction range in which the cushion rubber 7 exists is a range outside the inner width Wi and inside the outer width Wo.

  In the case of the pneumatic radial tire T, the inner width Wi is about 270 mm and the outer width Wo is about 375 mm, and the cushion rubber 7 exists outside the inner width Wi 270 mm and inside the outer width Wo 375 mm.

A tread rubber 8 is provided around the outer peripheral surface of the belt layer 5.
The tread rubber 8 covers the outer side in the width direction of the belt layer 5 and is continuous with the sidewall portion Ts. The tread rubber 8 has a tread surface (outer peripheral surface) that extends from the tread center portion 8c to the left and right tread shoulder portions 8s, 8s. The width of the tread surface is substantially equal to the belt layer width Wb, and is about 360 mm in the case of the present pneumatic radial tire T.

In the pneumatic radial tire T configured as described above, the JIS hardness of the belt coating rubber for coating the cord of the belt ply 5p in the belt layer 5 is 76 degrees, and the hardness of the tread rubber softer than this coating rubber is 50 degrees (JIS hardness).
The hardness of the cushion rubber 7 used in the pneumatic radial tire T is 88 degrees (JIS hardness), which is harder than the hardness of the belt coating rubber.

The tire specifications of the pneumatic radial tire T are summarized below.
Tire size: 435 / 45R22.5
Tread width (tread rubber tread width): 360mm
Belt layer width Wb: 360mm
Belt reinforcement layer width Ws: 300mm
Cushion rubber width direction position: 270mm ~ 375mm
Tread rubber hardness: 50 degrees (JIS hardness)
Belt coating rubber hardness: 76 degrees (JIS hardness)
Cushion rubber hardness: 88 degrees (JIS hardness)

Results of running test of this pneumatic radial tire T using a rim with a rim width of 14.00 inches and a rim diameter of 22.5 inches, an internal pressure of 900 kPa and a load of 49.03 kN (normal load) (maximum wear difference) ) Is shown in a table in FIG. 2 and graphically in FIG.
For comparison, the tires other than the cushion rubber hardness are the same as above, and the same running is performed for a conventional tire with the cushion rubber hardness of 76 degrees (JIS hardness) the same as the belt coating rubber hardness. The results of the test are also shown in FIGS. 2 and 3.

The measured maximum wear difference is a difference in wear amount between the tread center portion 8c of the tread rubber 8 and the tread shoulder portion 8s.
As shown in Fig. 2 and Fig. 3, in the case of conventional tires, the maximum wear difference gradually increased until the mileage of 22,000 km, where the maximum wear difference was 0.3 mm, but around 22,000 km. The increase rate of the maximum wear difference increases from 38,000 km, and the maximum wear difference becomes 0.8 mm. From this point exceeding 38,000 km, the increase rate of the maximum wear difference changes drastically and increases to 48,000. The maximum wear difference has reached 2.5 mm at km.

On the other hand, in the case of the present pneumatic radial tire T, the mileage is 51,000 km and the maximum wear difference is suppressed to a small value of 0.4 mm, and the maximum wear difference increases very gently during that time.
And even if the travel distance exceeds 51,000 km and reaches 62,000 km, the maximum wear difference remains unchanged at 0.4 mm, and the maximum wear difference is as small as about 0.4 mm when the travel distance exceeds 51,000 km. Is suppressed.

As described above, since the hardness of the cushion rubber is set to be greater than 88 degrees (JIS hardness) and the hardness of the belt coating rubber is 76 degrees (JIS hardness), the pneumatic radial tire T has a travel distance of 40,000 km. Even if the maximum wear difference is exceeded, the maximum wear difference can be suppressed to a small value of about 0.4 mm, and a part of the tread surface of the tread rubber 8, that is, the tread center portion 8c is particularly worn and unevenly worn like a conventional tire. There is nothing, and the entire tread surface of the tread rubber 8 is worn almost uniformly.
Therefore, the durability is greatly improved.

In addition, the hardness of the cushion rubber of this pneumatic radial tire T is 95 degrees (JIS hardness), which is about 1.24 times the hardness of belt coating rubber, 76 degrees, and 100 degrees (JIS, about 1.32 times). Rongrand ram test was performed on the B tire set to (hardness).
This Long Grand ram test was performed using a 14.00 × 22.5 inch rim, an internal pressure of 900 kPa, a load of 53.93 kN (110% of the normal load of 49.03 kN) and a test speed of 65 km / h.

As a result, the A tire was able to complete 100,000 km, while the B tire was 60,000 km, and a failure occurred at the end of the belt layer.
That is, when the hardness of the cushion rubber is set to 1.3 times or more of the hardness of the belt coating rubber, the strain applied to the belt end of the belt ply having the maximum width of the belt layer increases at a traveling distance of about 60,000 km. Failure occurs and durability is greatly reduced.

  Therefore, the hardness of the cushion rubber should be set to be greater than 1 and less than 1.3 times the hardness of the belt coating rubber in order to obtain the effect of improving the durability because the entire tread rubber tread is worn almost uniformly. Is preferred.

The belt reinforcing layer 6 is required to have a width equal to or greater than 0.6 times the tire width as the belt reinforcing layer width Ws that is the width of the maximum width reinforcing ply 6p.
The cushion rubber 7 exists in the range outside the inner width Wi 270 mm and inside the outer width Wo 375 mm. The width direction range where the cushion rubber 7 exists is such that the inner width Wi is 0.8 times or more the belt reinforcing layer width Ws. If the outer width Wo is 1.4 times or less than the belt reinforcing layer width Ws, the cushion rubber 7 is effectively applied to the tread rubber 8 so that the contact pressure on the tread rubber 8 is more easily uniformed and the maximum wear difference is achieved. Can be kept small.

  Further, the hardness of the cushion rubber is at least 80 degrees (JIS hardness) or more in addition to the above range, so that the cushion rubber 7 can surely act on the tread rubber 8 and the tread rubber 8 is grounded on the tread. The pressure can be made uniform evenly.

  The present invention can be applied not only to a pneumatic radial tire but also to a bias tire.

T ... Pneumatic radial tire, Tb ... Bead part, Ts ... Side wall part, Tt ... Tread part,
DESCRIPTION OF SYMBOLS 1 ... 2 ... Bead, 3 ... Carcass layer, 4 ... Chefa, 5 ... Belt layer, 6 ... Belt reinforcement layer, 7 ... Cushion rubber, 8 ... Tread rubber, 8c ... Tread center part, 8s ... Tread shoulder part.

Claims (2)

A carcass layer constructed toroidally across a pair of beads,
A belt layer provided around the radial outside of the carcass layer;
A belt reinforcing layer interposed in a circumferential direction between the belt layer and the carcass layer;
Tread rubber provided around the outer peripheral surface of the belt layer;
In a pneumatic tire comprising a cushion rubber interposed between both side portions in the width direction of the belt layer and the carcass layer, and provided on both outer sides in the width direction of the belt reinforcing layer ,
The hardness of the cushion rubber is not less than 80 degrees in JIS hardness, and rather smaller than 1.3 times greater than 1 times the hardness of the belt coating rubber of the belt layer and the belt reinforcing layer,
A pneumatic tire characterized in that an inner width that defines the existence range of the cushion rubber is not less than 0.8 times the maximum width of the belt reinforcing layer, and an outer width is not more than 1.4 times the maximum width of the belt reinforcing layer. . The maximum width of the belt reinforcing layer, the pneumatic tire according to claim 1, characterized in that there is at least 0.6 times the tire width.

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