JP2007276662A - Pneumatic tire, and pneumatic tire molding die - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of realizing suction and discharge of a water film formed by a sipe (a fine groove) formed in a tread of a studless tire, and, in particular, enhancing the on-ice braking performance, and a pneumatic tire molding die. <P>SOLUTION: A plurality of rows of sipes 2 are formed toward the depth direction Fz from a surface side F of a tread. In the sipes 2, an uneven part 3 with the sipes 2 being not closed during the loading on the tread at the braking in a tire traveling condition is formed at least on one of (or two of) inner wall surfaces of the sipes 2 in the depth direction of the sipes. The uneven part 3 includes various kinds of ones as shown in Fig.2(a), (b) to Fig.9 (not shown). For example, the uneven parts 3 formed on the inner wall surfaces opposite to each other of the sipes 2 are asymmetric, and formed while changing the height, the width, and the wall thickness. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire and a molding die for the pneumatic tire, and more particularly, improves the water film sucking by a sipe (narrow groove) formed on the tread of the tire, and particularly improves the braking performance on ice. The present invention relates to a pneumatic tire and a mold for molding the pneumatic tire.

  In general, a tread of a studless tire is formed with a plurality of blocks in which a plurality of sipes (narrow grooves) are formed on the surface of the ground contact side. It is said that the frictional force is improved by increasing the number of sipe (density) and the edge component is increased to improve the digging effect.

  It is also known that removal of a water film on the contact surface plays an important role in improving the performance on ice, particularly on ice near 0 ° C. For this purpose, it is effective to increase the density of the sipe. However, if the density is increased too much, there is a problem in that the sipe thickness increases the volume of the sipe in the tread and decreases the block rigidity, thereby reducing the contact area. .

  In order to solve this problem, a method of reducing the thickness of the sipe is also conceivable, but the sipe is closed when the tire is loaded, such as during braking of the tire, and the effect of removing the water film in the ground contact surface is reduced. There was a problem to say. That is, as shown in FIGS. 16A and 16B, the conventional sipe has a structure in which the wall surface is smooth and straight, or the amplitude of the irregularities formed on the opposite wall surfaces is synchronized. Therefore, for example, as shown in FIGS. 17A and 17B, the sipe 2 is blocked by the deformation of the block 1 during braking of the tire and during driving, and the water film W on ice particularly in snow performance. There was a problem that the effect of sucking up the water was reduced.

Therefore, a pneumatic tire in which the thickness of the sipe is changed alternately along the longitudinal direction of the sipe, or a pneumatic tire that extends in a straight line or substantially arc shape with the sipe thickness toward the sipe bottom. Tires are known (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 10-86612

  However, the sipe of the pneumatic tire as described above can prevent the sipe from closing when the tire is braked or driven. However, after sucking the water film on the ice, the water is efficiently discharged to the outside. Therefore, there is a problem that it is difficult to improve the braking performance on ice.

  The present invention pays attention to such conventional problems, and a pneumatic tire capable of improving water film suction and drainage by a sipe (narrow groove) formed on a tread in a studless tire, and particularly improving braking performance on ice, and its An object of the present invention is to provide a mold for forming a pneumatic tire.

  In order to achieve the above object, the pneumatic tire according to the present invention has an uneven portion on which at least one of the opposing inner wall surfaces of the sipe does not close when the sipe is loaded when a tread is applied during running or braking of the tire. It is formed in the depth direction of the sipe, and the gist is that the sipe width is formed wider than at least one of the surface side of the tread and the deepest portion than the central portion in the sipe depth direction.

  Here, an uneven portion having an asymmetric shape and at least one of height, width, and thickness is changed on the inner wall surfaces of the opposing sipes, and the amplitude (s) of the uneven portion is set to 0.05. mm to 1 mm, and the pitch (P) of the concave and convex portions is set to 0.05 mm to 5.0 mm.

  Further, in the molding die for a pneumatic tire according to the present invention, the sipe blade has an uneven portion that does not close when the tread is loaded on the longitudinal surface of the sipe blade, and the sipe width is on the surface side of the tread. In addition, at least one of the deepest portions is formed to be wider than the central portion in the sipe depth direction.

  Here, the uneven portion of the siping blade main body changes at least one of height, width, and thickness, and the shape, thickness, and form of the uneven portion of the siping blade main body are pressed and machined. , Machining by at least one machining method of electric discharge machining.

  In this way, by forming an uneven portion in the depth direction of the sipe that does not close when the sipe is loaded during tread loading during tire running and braking, the water film is sucked up and drained by the sipe (thin groove), in particular, The braking performance on ice can be improved.

  Since the present invention is configured as described above, there is an effect that it is possible to improve the water film suction and drainage by sipes (thin grooves) and to improve the braking performance on ice especially when the tire is new or at the end of tire wear. Further, there is an effect that the shape, thickness, and shape of the uneven portion of the siping blade main body can be easily processed by at least one processing method of press processing, machining, and electric discharge processing.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Note that the same components as those in the conventional example are denoted by the same reference numerals and description thereof is omitted.

  FIG. 1 shows a perspective view of a sipe 2 (narrow groove) formed in a block 1 of a tread of a tire embodying the present invention, and a plurality of the sipe 2 is formed from the surface side F of the tread toward the depth direction Fz. They are arranged in rows.

  In the sipe 2 according to the embodiment of the present invention, the sipe 2 has at least one of the opposing inner wall surfaces (both surfaces may be both), and the uneven portion 3 where the sipe 2 does not close when the tread is loaded during tire running or braking. Is formed in the depth direction of the sipe 2.

  As shown in FIGS. 7 to 9, the sipe 2 has a sipe width H wider than the central portion in the depth direction of the sipe 2 at least one of the tread surface side and the deepest portion. By widening the width H of the sipe 2 on the tread surface side, drainage performance when the tire is new can be improved without greatly reducing the rigidity of the land portion. Further, by increasing the sipe width H at the deepest portion, drainage at the end of wear of the tire can be improved.

  As the form of the concavo-convex portion 3, various forms are possible as shown in FIGS. 2A and 2B to FIG. 9. For example, the concavo-convex portion 3 formed on the opposing inner wall surfaces of the sipe 2 is asymmetric. It is also possible to form it by changing the shape, height, width and thickness.

  That is, in the form seen from the plane of the tread shown in FIG. 2 (a) and the form seen from the front of the sipe 2 shown in FIG. 2 (b), the corrugated uneven portion 3 is formed on one side of the sipe 2 facing each other. Is formed in parallel to the longitudinal direction of the sipe 2. 3 (a) and 3 (b), the corrugated uneven portion 3 and the smooth surface portion 3a are formed on one of the opposing inner wall surfaces of the sipe 2, and the other of the inner wall surfaces The back surface side of the uneven portion 3 is formed smoothly, and the corrugated uneven portion 3 is formed on the back surface side of the smooth surface portion 3a.

  In the embodiment of FIGS. 4A and 4B, the asymmetric concavo-convex portions 3x and 3y are formed on the opposing inner wall surfaces of the sipe 2, and otherwise, FIG. 5 and FIG. As shown in (e) to (e), a non-continuous (part in the longitudinal direction) concavo-convex portion 3z is formed along one longitudinal side of the sipe 2 along the longitudinal direction of the sipe 2.

  In FIG. 6D, by arranging the concave and convex portions 3z to be inclined, in the case of an open sipe in which the side end portion of the sipe 2 is open, it is possible to drain from the side end portion. ) Is an embodiment in which the concavo-convex portion 3z inclined on the inner wall surface of the sipe 2 and the straight concavo-convex portion 3z are arranged in half along the longitudinal direction of the sipe 2, and has the same effect as described above. It is possible.

  7 to 9, the inner wall surface of the sipe 2 is formed by being curved from the surface side F of the tread toward the depth direction Fz of the sipe 2, and the ridge-shaped uneven portion 4 is formed on the inner wall surface. Further, in the embodiment shown in FIG. 7, the tread sipe width H is formed so that the surface side F of the tread is wide and gradually narrows in the depth direction Fz of the sipe 2, or as shown in FIG. In the embodiment, the sipe width H of the tread is formed so that the surface side F of the tread is narrow and gradually increases toward the depth direction Fz of the sipe 2, and in FIG. 9, the sipe width H of the tread is The surface side F of the tread is wide and can be formed so as to become narrower in the depth direction Fz of the sipe 2. The arrow Q indicates the direction of load acting on the sipe 2.

  10 and 11 show a plan view and a front view of another embodiment in which a corrugated uneven portion 3b is formed on one of opposing inner wall surfaces of the sipe 2, and the sipe 2 of each of the above embodiments. As the form of the uneven portions 3 and 3b formed on the inner wall surface, as shown in FIG. 12, the amplitude (s) of the uneven portions 3 and 3b is set to 0.05 mm to 1 mm, and the pitch (P) of the uneven portion 3 is set. It is preferable to set to 0.05 mm to 5.0 mm.

  In each of the above-described embodiments, drainage can be ensured without deteriorating rigidity even when the tread surface is worn, and braking performance on ice can be improved.

〔Example〕
Tires having each sipe shown in Table 1 below were manufactured and tested on ice.
Here, on-ice performance or on-ice braking performance of a tire means that a test tire is mounted on a passenger car with an air pressure of 200 Kpa and is on ice (on ice at an ice temperature of −7 ° C. to −9 ° C. and an air temperature of −2 ° C. to 0 ° C.). Measure the braking distance when stopping by applying the brake from the state where the test road is traveling at a speed of 30 Km / h to 40 Km / h. The result of the evaluation is shown by an index in which the reciprocal of the braking distance is obtained and the value of the conventional tire is 100. The larger the index value, the better the performance on ice.

 In addition, as for the thickness of this invention, the thickness of the tread surface side is 1.2 mm, the center is 0.6 mm, and the deepest part is 1.2 mm.

  Next, a molding die provided with a siping blade 5 for forming the sipe 2 of the pneumatic tire as described above will be described.

  When molding the pneumatic tire as described above, a siping blade 5 for forming the sipe 2 in the depth direction Fz from the surface F on the tire tread is formed on the molding surface of the mold body (not shown). is there. As a manufacturing method of the siping blade 5 used in the embodiment of the present invention, as shown in FIGS. 13A to 13E, a flat metal plate K such as stainless steel is used as an upper mold 6a and a lower mold 6b. 14a, 14b, and 14c, after processing the metal plate K with the ball end mill 7 or the overall end mill 8, as shown in FIGS. 14 (a) and 14 (b), wire cutting, laser cutting A machining method for cutting a product into dimensions with a metal plate, etc. Further, as shown in FIGS. 15 (a) and 15 (b), a flat metal plate K is roughened by an electrode 9 formed in advance in a product shape, and wire cut , There are electrical discharge machining methods that cut out products to dimensions by laser cutting.

  Regardless of which of the above processing methods is used, the unevenness of the siping blade 5 can be processed by changing the height, width, and wall thickness. A sipe 2 is formed on a tread portion of a pneumatic tire by being implanted on a molding surface of a mold body (not shown).

It is a perspective view of the sipe (thin groove) formed in the block of the tread of the tire which implemented this invention. 1 shows a first embodiment of the present invention, wherein (a) is a plan view of a sipe viewed from the tread surface side, and (b) is a front view of the sipe. FIG. A 2nd embodiment of this invention is shown, (a) is a top view of a sipe seen from the tread surface side, and (b) is a front view of a sipe. A 3rd embodiment of this invention is shown, (a) is a top view of a sipe seen from the tread surface side, and (b) is a front view of a sipe. It is a top view of the sipe seen from the tread surface side which shows 4th Embodiment of this invention. (A)-(e) has shown 5th Embodiment-9th Embodiment of the sipe, and has shown the front view of the sipe of FIG. It is the perspective view of the sipe seen from the tread surface side which shows 10th Embodiment of this invention. It is a perspective view of the sipe seen from the tread surface side which shows 11th Embodiment of this invention. It is the perspective view of the sipe seen from the tread surface side which shows 12th Embodiment of this invention. It is a top view of the sipe seen from the tread surface side which shows 13th Embodiment of this invention. It is a front view of the sipe of FIG. It is explanatory drawing which prescribes | regulates the dimension of the uneven | corrugated | grooved part of a sipe. (A)-(e) is a process explanatory drawing of the press processing method, showing the processing process of the siping blade of this invention. (A) And (b) shows the machining process of the siping blade of this invention, and is explanatory drawing of the machining method which processes an unevenness | corrugation with a ball end mill or a total form end mill. (A) And (b) is an explanatory view of the electric discharge machining method for showing the machining process of the siping blade of the present invention and for performing uneven processing on a flat metal plate with an electrode formed in a product shape in advance. (A), (b) is the perspective view of the sipe formed in the conventional tread, and the top view at the time of no load of the tread which formed the sipe. (A), (b) is sectional drawing at the time of the load of the sipe formed in the conventional tread, and the top view of the tread at the time of load.

Explanation of symbols

1 block 2 sipes
3 Uneven portion 3a Smooth surface portion 3x, 3y, 3z Uneven portion 4 Uneven portion
5 Siping blade
H Sipe width Q Load direction
F Surface side Fz Depth direction

Claims (6)

In the pneumatic tire formed by forming a sipe in the depth direction from the surface to the tread of the tire,
On at least one of the opposing inner wall surfaces of the sipe, a concavo-convex portion that does not close the sipe when the tread is loaded during tire running or braking is formed in the sipe depth direction, and the sipe width is on the surface side of the tread and A pneumatic tire formed so as to be wider than at least one of the deepest portions in the sipe depth direction central portion. 2. The pneumatic tire according to claim 1, wherein an uneven portion having an asymmetric shape and varying at least one of height, width, and thickness is formed on inner walls of the opposing sipes. The pneumatic tire according to claim 1 or 2, wherein an amplitude (s) of the uneven portion is set to 0.05 mm to 1 mm, and a pitch (P) of the uneven portion is set to 0.05 mm to 5.0 mm. In a mold for forming a pneumatic tire in which a siping blade for forming a sipe in a depth direction from a surface is formed on a tire tread on a surface of a mold body, the siping blade is a siping blade. An uneven portion is formed on the longitudinal surface of the tread so that the sipe does not close when the tread is loaded, and the sipe width is formed wider than at least one of the tread surface side and the deepest portion in the sipe depth direction central portion. Mold for molding pneumatic tires. The mold for molding a pneumatic tire according to claim 4, wherein the uneven portion of the siping blade main body is changed in at least one of height, width, and thickness. The mold for molding a pneumatic tire according to claim 4 or 5, wherein the shape, thickness, and shape of the concavo-convex portion of the siping blade body are processed by at least one of pressing, machining, and electric discharge machining. .

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