JPH05155202A - Precure tread for tire, method for producing the same, and retreaded tire using the same - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a retreaded tire which can secure other performances and at the same time exhibit more excellent wet resistance in the process from the middle stage of wear to the latter stage. [Structure] A front surface groove is provided on the surface of the tire that comes into contact with the ground surface, and a back surface groove that is attached to the base tire is provided with a back surface groove having ventilation holes that communicate with the tire ground surface. A precure tread, which is provided with a sipe that opens into at least the back surface groove of the front surface groove and the back surface groove, a method for manufacturing the precure tread, and a retreaded tire using the same.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a precure tread for a tire, a method for producing the precure tread, and a retreaded tire vulcanized and molded using the precure tread, for example, a truck, Pre-cure tread with excellent performance in slip resistance (hereinafter referred to as wet resistance) on wet road surfaces during the process from the middle to the end of use of retreaded tires for buses, and the production of this pre-cure tread. The present invention further relates to a method and a retreaded tire using the precure tread.

[0002]

2. Description of the Related Art In conventional tires, the groove width along with the groove depth provided in the tread decreases in the process from the middle to the end of wear of the tread. In addition, most of the sipes formed on the tread for slip prevention purposes. Since it disappears, it is customary that the wet resistance is greatly reduced. Furthermore, when the road surface reaches a water depth beyond the water curtain, the cross-sectional area of the groove greatly decreases, and most of the sipes that assist drainage have disappeared, so the drainage efficiency drops significantly and wet resistance Cause a very dangerous situation.

As a proposal for solving the above problem, there is, for example, Japanese Patent Laid-Open No. 1-317807. This proposal is to provide a thin back surface groove on the tire side of the pre-cure tread used for retread tires used for trucks, buses, etc., and the back surface groove appears on the surface of the tread during the period from the middle to the end of wear of the tread, It is intended to ensure wet resistance.
Further, this proposal is to prevent the separation between the pre-cure tread and the base tire, which is likely to occur in a retreaded tire, by providing a ventilation hole that communicates from the rear surface groove to the tread surface.

Further, as another proposal, there is JP-A-3-153406 for the purpose of suppressing the increase in rigidity of the tread rubber due to the progress of wear of the tread and at the same time preventing the skid from decreasing. This proposal is similar to the above-mentioned Japanese Patent Laid-Open No. 1-317807, in which a hidden sipe is provided on the rear surface side on the base tire side so that the sipe is exposed as the tread rubber wears and the slip resistance is not ensured. ..

[0005]

SUMMARY OF THE INVENTION However, among the above proposals, JP-A-1-317807 has a high separation prevention effect and an excellent wet resistance, but the wet resistance depends on the wet road condition. There was a problem that it was not always enough.

If the groove width of the rear surface groove is sufficiently widened to further improve the wet resistance, the tread rigidity of the radially outer portion of the rear surface groove is greatly reduced, and the rigidity of the other tread land portions is reduced. However, there is a problem that the balance is lost and uneven wear occurs. If uneven wear occurs once, it is accelerated, and as a result, the degree of uneven wear becomes severe and the appearance is greatly impaired. In addition, problems such as a marked decrease in wear life and vibration of the vehicle occur. Further, there is a problem that the ground resistance of the tread is deteriorated and the wet resistance is also impaired.

[0007] Therefore, the above-mentioned proposal inevitably limits the widening of the groove width of the rear surface groove because it is necessary to maintain the uneven wear resistance. As a result, depending on the road surface condition and the driving operation. There was a problem that the desired slip resistance could not be obtained. Further, since the rear surface groove is a thin groove, a psychological factor in appearance is added, and there is also a problem that the customer's request cannot be always met in this respect.

Next, according to the proposal in Japanese Patent Laid-Open No. 3-153406, the sipe cannot be communicated with and opened in the surface groove of the tread due to manufacturing restrictions, and the sipe alone must be provided. Therefore, firstly, in the retreaded tire of this proposal, even if sipes appear in the middle to the end of tread wear, the sipes are not closed at both ends, and the original function of the sipes cannot be sufficiently exerted. As a result, effective and efficient removal of the water film on the road surface cannot be expected, and the wet resistance still remains a problem.

Secondly, the above proposal would use a mold in which both ends of the thin blade are not supported in order to manufacture a precure tread with narrow sipes. For this reason, various pressures applied to the blade during vulcanization and molding cause damage to the blade in a short time, and there is a defect in the durability of the mold. As a result, there has been a serious problem in practical use such that the die maintenance cost is extremely high. In the above proposal, the blade width is set to 0.5 mm or more in consideration of this point, and under this constraint, there is a problem that it cannot meet the market demand for various sipe forms.

Thirdly, the above proposal proposes that the unvulcanized cushion rubber, which is indispensable for interposing between the pre-cure tread and the base tire and adhering the two, is a rubber due to a high temperature during vulcanization molding of a retreaded tire. There is a problem that the increase in fluidity and the external pressure of vulcanization work together to flow into and fill the sipe portion, and at least the sipe portion near the back surface part almost disappears.

Fourthly, in the above-mentioned proposal, if the width of the sipe is widened in order to avoid the problem that the cushion rubber is filled in the sipe portion, the internal volume of the sipe portion becomes large, which is described in Japanese Patent Laid-Open No. 1-317807. As described above, this not only reduces the adhesive force between the precure tread and the base tire during vulcanization molding of the retreaded tire, but also causes the gas accumulated in the sipe portion to expand due to high temperature every time it travels. Repeatedly, in combination with the above-mentioned low adhesive strength, there was a problem that eventually resulted in separation.

The present invention has been made to solve the above problems. That is, it is equipped with various types of sipes that maintain sufficient separation resistance and stop at the backside groove width that does not cause uneven wear on the tread, and yet provide sufficient wet resistance until the final stage of tread wear. And a precure tread for a tire.
Furthermore, the present invention, at a low price, this precure tread,
Moreover, the present invention provides a manufacturing method that can be simply provided, and a retreaded tire having the above-mentioned various performances by applying the precure tread obtained by this manufacturing method.

[0013]

A first aspect of the present invention is to provide a front surface groove on the ground contact surface side of a tire and a back surface groove on the back surface to be attached to a base tire. In a pre-cure tread provided with a ventilation hole communicating with a tire ground contact surface, a pre-cure tread for a tire characterized in that, of the front surface groove and the rear surface groove, a sipe that opens into at least a rear surface groove is provided on the rear surface side. Is.

A second aspect of the present invention is provided inside the mating surface of one of the two upper and lower mold halves which are vertically elongated according to the developed shape of the tire tread. The surface groove on the ground contact surface side of the tire due to the ridge,
In the manufacturing method of vulcanizing and molding the precure tread by forming backside grooves on the side to be attached to the base tire by the ridges provided inside the mating surface of the other mold, the laminated metal forming the backside grooves A sipe that opens into the backside groove is formed by a blade whose one end is embedded in the ridge of the mold, and a plurality of protrusions arranged on this ridge further communicates the backside groove with the surface on the tire grounding side. A method for producing a precure tread for a tire, which comprises:

The third aspect of the present invention is the second aspect of the present invention.
In the manufacturing method for vulcanizing and molding the conventional pre-cure tread described in the invention, a sipe that opens into the back surface groove is formed by a blade whose one end is embedded in the protrusion of the mating die that forms the back surface groove. After demolding the vulcanized precure tread from the mold, a method for producing a precure tread for a tire, characterized by forming a vent hole communicating from the groove on the back surface to the surface which is the ground contact surface side of the tire. Is.

Furthermore, a fourth invention of the present invention is provided in the above-mentioned mating die for forming the above-mentioned back groove in the manufacturing method for vulcanizing the conventional precure tread described in the above-mentioned second invention of the present invention. The vulcanized pre-cure tread is removed from the mold by forming a vent hole that connects the groove on the rear surface to the surface on the ground contact surface side of the tire by means of a plurality of protrusions that are arranged on the ridges and extend toward the tire ground contact surface side. After molding, a sipe that opens into at least the back surface groove of the front surface groove and the back surface groove is processed and formed.

Furthermore, a fifth invention of the present invention is the same as the above-mentioned second invention of the present invention, in the manufacturing method for vulcanizing and molding the precure tread, after the vulcanization and molding is completed, the mold is removed from the mold. Of the demolded pre-cure tread, the sipe that opens to the back surface groove of the above-mentioned front surface groove and the back surface groove is processed and formed, and the ventilation hole that connects the back surface groove to the surface that is the ground contact surface side of the tire is formed. A method for producing a precure tread for a tire, which comprises:

According to a sixth aspect of the present invention, a front surface groove is provided on the surface of the tire which comes into contact with the ground surface, and a back surface groove is provided on the back surface which is the side to which the tire is attached. The back surface groove communicates with the tire ground contact surface. A pre-cure tread provided with a ventilation hole and having a sipe that opens into at least the back surface groove of the front surface groove and the back surface groove is provided on the back surface side, and is attached to the crown portion of a base tire that has been subjected to shaping finish. It is a characteristic retreaded tire.

The first aspect of the present invention will be described more specifically with reference to FIGS. 1 to 6. First, FIG. 1 shows an example of a pattern of a surface of the vulcanization-molded pre-cure tread according to the first aspect of the present invention, which is the tire contact surface side. In the figure, 1 is a central main groove extending in the circumferential direction with a large number of projection groups on the groove bottom,
Reference numerals 2 are outer main grooves that extend in the circumferential direction on both sides of the central main groove. Reference numeral 3 is a shallow branch groove connecting these main grooves. Reference numeral 4 shown by a dotted line is a rear surface groove provided substantially in the middle of the central main groove and the outer main groove, and 5 is a vent hole communicating from the rear surface groove to the tire ground contact surface. Note that P is the pitch length of the main grooves 1 and 2, and in the example of FIG. 1, one back hole is provided with 2 × P ventilation holes.

Next, FIG. 2 illustrates the pattern of the back surface of the precure tread that is to be attached to the base tire.
In this example, two linear rear surface grooves 4 are formed substantially parallel to the central axis line XX in the longitudinal direction of the precure tread, and the ventilation hole 5 is formed from the top of the rear surface grooves to the surface of the tire grounding surface. Is in communication with.

In the example of FIG. 2, the number of the back surface grooves is two, but if necessary, two may be added to the outside of the outer main groove to make four grooves. Further, it is preferable that the number of rear surface grooves be increased or decreased according to the number of main grooves. The total width w of the rear surface grooves is 10% to 40% of the total width of the main grooves, (W ₁ + 2 × W ₂ ) in FIG.
% Is preferable.

Reference numeral 6 in FIG. 2 denotes a sipe, and FIG. 4 shows an enlarged view of a portion of this sipe. As shown in FIG. 4, the sipes are preferably opened to the side wall of the rear surface groove 4 over almost the entire depth thereof. In the arrangement example of the sipes of FIG. 2, one sipes is arranged on each side of one back surface groove per pitch so as to be substantially orthogonal to the back surface groove.

It is desirable that the number of sipes to be opened in one back groove be two or more per pitch length P determined by the main groove or the branch groove of the tire ground contact surface. Also,
The sipe length L is the number of sipes per pitch P described above.
In this relation, it is desirable that L = 4 × (1 / n) mm or more, and the width of the sipes is preferably 2 mm or less.

Further, FIG. 5 shows a pattern of another example of the back surface of the precure tread which is to be attached to the base tire. As shown in FIG. 5, the sipes are inclined at an inclination angle of α with respect to the central axis X-X, and the value of α is selected within the range of 45 ° to 90 ° according to the required performance of slip resistance. Is preferred. Furthermore, the sipe lengths do not necessarily have to be the same, and the sipe lengths L ₁ and L can be changed according to the required performance.
₂ can be different lengths. In the example of FIG. 5, the central axis X
In this example, the sipe length L ₁ toward −X is longer than the sipe length L ₂ toward the outside.

FIG. 3 is a sectional view taken along the line AA of FIG. Reference numeral 7 is a front surface that is a contact surface side, and 8 is a back surface that is a side to be attached to a base tire. In the example of FIG. 3, the thickness of the precure tread in the width direction is different, but the thickness may be substantially uniform over the entire area. The thickness of the precure tread is appropriately selected according to the required characteristics of the retreaded tire. For example, the thickness T ₁ of the central portion may be thinnest, and the thickness may be increased toward both sides, or vice versa.

In FIG. 3, the depth D ₁ of the central main groove is 55% to 90% of the thickness T ₁ of the precure tread at the center of the central main groove, and D ₂ is the center of the outer main groove. The thickness T ₂ is preferably 55% to 90%.
The rubber thickness at the groove bottom, that is, T ₁ -D ₁ , T _2-
D ₂ is preferably at least 2 mm.

It is preferable to set the height h so that one of the central main groove and the outer main groove has its back surface groove exposed on the ground contact surface side until it disappears due to wear of the tread rubber. Further, any one of the main grooves is 40% to
More preferably, the backside groove is exposed upon 80% wear.

That is, when D ₁ > D ₂ , h> T ₂ −
D ₂ , further, T ₂ −0.4 × D ₂ >h> T ₂ −0.8
× D ₂ is preferred. If D ₂ > D ₁ , h>
T ₁ −D ₁ and further T ₁ −0.4 × D ₁ >h> T ₁ −
0.8 × D ₁ is preferable.

The example of the cross-sectional shape of the sipe shown in FIG. 3 is substantially rectangular. The value of the height H of the sipe 6 is preferably set on the ground contact surface side of the sipe until the main groove of one of the central main groove and the outer main groove disappears due to wear of the tread rubber. Furthermore, it is desirable to separate the surface 7 of the tread by at least 3 mm. Further, it is desirable that H = (0.5 to 1.5) × h.

FIG. 6 shows another example of the cross-sectional shape of the sipe. The cross-sectional shape of the sipe 6a in the longitudinal direction is such that the sipe length Lb on the back surface 8 is the length Lt near the top of the back surface groove.
It is longer and has a trapezoidal shape that widens toward the back surface 8 from the vicinity of the top. A sipe 6a 'shown by a dotted line in FIG. 6 is an example of a sipe having a triangular shape whose bottom side is the back surface side. Although not shown, L
b may be shorter than Lt. Further, if necessary, sipes having the same cross-sectional shape may be provided on both sides of the back surface groove, or sipes having different cross-sectional shapes may be provided as in the above example.

Next, FIG. 7 shows the second invention of the present invention.
Details will be described with reference to FIGS. 8 and 9. FIG. 7 is a perspective explanatory view of a part of an example die 50 related to the manufacturing method of the second invention of the present invention.

In FIG. 7, 50A and 50B are vertically divided two-piece dies corresponding to the developed shape of the tire tread, and in this example, 50A is the lower die.
OB is the upper mold. 50A forms a surface groove on the ground contact side of the precure tread, and 50B forms a back surface and a back surface groove. The alignment die of the example of FIG. 7 is aligned with the knock pin N and the hole Nh fitted therein.

The lower die 50A of the die is provided with ridges 51 and 52, by which the central main groove 1 and the outer main groove 2 are molded on the ground contact surface side of the precure tread. Further, the lower die 50A is provided with the ridge 53, and the shallow groove 3 extending between these main grooves is similarly formed. The surface 7 on the tread contact surface side is formed by the bottom surface 57 of the mold 50A.

In this example, a mold-forming body 50C, which is a metal casting having a relatively low melting point such as an aluminum alloy, is embedded in the upper mold 50B of the mold, and the ridge 5 is formed in the mold-forming body 50C.
4 is provided and the back surface groove 4 is molded and formed, and the ventilation hole 5 is formed by the protrusion 55 extending from the protrusion 54. Further, one end of the blade 56 in the lengthwise direction is almost entirely height H
It is arranged so as to be embedded inside the ridge 54, and when the vulcanization of the precure tread is completed, this blade is
It is configured to form the sipe 6 that opens to the inside. The back surface 8 of the precure tread is a molded body 50C.
The surface 58 is molded.

FIG. 8 is a sectional view taken along the blade 56. As is clear from the figure, when manufacturing the above-mentioned metal casting having a relatively low melting point, one end of the blade 56 is cast into the protrusion 54 that forms the rear surface groove, and a part of the blade 56 is molded. Cast inside the surface 58 of the blade 5
6 is firmly integrated with the molded body 50C. Further, the through hole J is formed in the blade 56 portion cast inside the molded body 50C.
It is desirable to provide a blade to further strengthen the integration of the blade and the molded body and prevent the blade from coming off.
The blade material is preferably stainless steel or the like. Also,
A blade having a relatively long length is preferably provided with a through hole K for smoothing the movement of rubber during vulcanization of the precure tread.

FIG. 9 shows a modification of FIG. This example
Applicable when the blade is long. In this case, for the purpose of preventing the blade from coming off or coming off, a plurality of through holes are formed in the portion of the blade 56a cast inside the surface 58, for example,
It is preferable to provide J ₁ , J ₂ , J _3, etc. Further, a plurality of holes for moving the rubber may be provided, for example, K ₁ and K ₂ .

In the second aspect of the present invention, as described above, by using at least a split mold which can be divided into two, the sipe that opens into the rear surface groove and the rear surface groove communicates with the surface on the tire ground contact surface side. It is a manufacturing method characterized by vulcanizing and molding a pre-cure tread for a tire in which a ventilation hole is formed.

Next, the third invention of the present invention will be explained. A third invention of the present invention is a mold for a precured tread obtained by vulcanization molding without providing projections 55 on the protrusions 54 of the upper mold 50B of the above-mentioned mating mold described in detail in the manufacturing method of the second invention of the present invention. After the mold is removed from the mold, a desired number of vent holes are processed and formed at desired positions so as to communicate with the surface serving as the ground contact surface of the tire from the rear surface groove. For processing the vent holes, for example, a rotating tool blade or a punched tool blade can be used.

Further, FIG. 10 shows the fourth invention of the present invention.
Details will be described with reference to FIGS. 11 and 12. The example shown in FIG.
FIG. 7 is a view of the tire grounding surface side of a vulcanized precure tread according to the manufacturing method of the second invention of the present invention, but having a tread pattern different from that of the second invention of the present invention. The tread pattern is composed of two central main grooves 21 extending in the circumferential direction and one outer main groove 22 extending in the same circumferential direction outside the central main groove. Reference numeral 24 shown by a dotted line is three rear surface grooves, and each rear surface groove is provided with a vent hole 25 communicating with the surface on the tire ground contact surface side at one pitch. In FIG. 10, Y ₁ is the distance between the respective lines of symmetry of the central main groove, and Y ₂ is the distance between the respective lines of symmetry of the central main groove and its outer main grooves.

The example shown in FIG. 11 is the pattern of the back surface of the precure tread described in FIG. 10, and the same as the above, according to the manufacturing method of the second invention of the present invention, but the back surface groove different from the second invention of the present invention. And a pattern in which sipes are arranged.
First, in this example, three rear surface grooves 24 are arranged substantially in the middle of each main groove so as to have a shape similar to the main groove. Also in this example,
The difference from the manufacturing method relating to the sipe formation of the second invention of the present invention is that at least a part of the required sipe is formed by hand processing or machining after the precure tread is combined and released from the mold. ..

In the example shown in FIG. 11, the sipe 26a is processed and formed by a knife-shaped cutter or the like in the back surface of the pre-cure tread removed from the mold, and the sipe 26a is formed in the back surface groove 24. To central main groove 21
Alternatively, the outer main groove 22 is made to communicate with any one of the main grooves and is opened to any of the main grooves.
FIG. 12 is a view showing a state in which this communication is opened.
1 is a cross-sectional view taken along line BB of FIG. 1 (along sipe 26a).

In the example of FIG. 11, the sipe 26a is processed and arranged in all three rear surface grooves, but it is not always necessary, and for example, it may be stopped only in the central rear surface groove having the highest drainage efficiency. Further, the sipe 26b having a shorter length than the sipe 26a may be preformed by a mold according to the second aspect of the present invention, but like the sipe 26a, the sipe 26b may be processed and formed after being released from the mold. Only one edge of the sipe 26b is opened in the rear surface groove 24 and the other edge is closed in rubber.
Although 26a is shown by a thick line in FIG. 11, it is needless to say that it may have a knife cut shape having almost no width.

In the fourth aspect of the present invention, as described above, when a sipe having almost no width like a knife cut to a sipe having a width of about 2 mm is provided on the back surface of the precure tread, the sipe is removed from the mold. On the back surface of the pre-cure tread after molding, a sipe that opens into at least the back surface groove of the front surface groove and the back surface groove is formed by hand or machining. In particular, in the case of providing many types of sipes having different shapes and arrangements, it is preferable to provide the basic sipes in advance and then process and form the desired sipes.

The fifth aspect of the present invention will be described. A fifth invention of the present invention is a manufacturing method using the manufacturing method of the precure tread described in detail in the second invention and the fourth invention of the present invention together. That is, the upper die 50B of the above-mentioned mating die
After releasing the vulcanized precure tread from the mold without providing the projections 55 on the ridges 54, the desired number of passages at desired positions are communicated from the rear surface grooves to the front surface of the tire. By forming pores, and in addition to this, on the back surface of the precure tread after demolding from the mold, a sipe that opens into at least the back surface groove of the front surface groove and the back surface groove is manually or mechanically processed. It is a manufacturing method of forming.

The sixth aspect of the present invention will be described with reference to FIG. FIG. 13 is a cross-sectional view in the width direction of a retreaded tire 150 according to the sixth aspect of the present invention in which a precure tread and a base tire are integrally vulcanized and molded. In the figure, a base tire 100 is composed of a radial carcass 101 straddling a pair of bead cores 102 in a toroidal shape, and three belt layers 103 arranged radially outside the carcass.

The precure tread 10 shown in FIG.
1, 2, 3, and 4 described in the first aspect of the present invention
It is basically the same as the tread of FIG. 3 except that the height of the sipe provided on the rear surface 8 side is substantially the same as the height of the rear surface groove 4. All the symbols are the same as those in the above figures. Retreaded tire 15
No. 0 is obtained by firmly vulcanizing and adhering the precure tread 10 to the base tire 100 through the cushion rubber 9 according to the conventional technique.

[0047]

First, the precure tread rubber layer according to the first aspect of the present invention will be described. When running on a retreaded tire using this precure tread rubber layer, backside grooves appear as the tread wears, and sipes appear before and after the backside grooves. At this time, in order to secure the wet resistance, it is preferable that the total width or the total cross-sectional area of the back surface groove is commensurate with the decrease in the main groove width or the decrease in the cross-sectional area of the main groove. However, even if the relationship between the groove width and the cross-sectional area is obtained, the tread whose thickness is reduced due to the wear of the tread has a higher rigidity, especially the shear rigidity of the tread surface, which is higher than that when the tread surface is new. It is in a state where slippage is likely to occur due to this increase in rigidity.

The retreaded tire provided with the precure tread according to the first aspect of the present invention makes the tread rubber around the sipe easily move with respect to the road surface by opening the sipe appearing on the tread surface in the groove on the back surface. It is to improve the easiness of slipping due to the increase in the shear rigidity. Further, the ease of movement of the rubber enhances the efficiency of cutting the water film and enables drainage to the back surface groove to further improve the wet resistance.

At this time, in order to remarkably enhance the effect of the wet resistance, the sum of the widths w of the back surface grooves is set to 1 of the sum of the widths of the main grooves.
It is desirable to set it to 0% or more and 40% or less. If the total width of the back surface grooves is less than 10%, the improvement in wet resistance cannot be said to be sufficient, and if it exceeds 40%, the rigidity of the upper part (ground surface side) of the back surface grooves decreases, and the rigidity of the ground surface side This is not preferable because there is a risk that the distribution will be unbalanced and uneven wear will occur from the beginning of running.

Further, the sipe length L is set to the above-mentioned one pitch (P).
In relation to the number n of sipes per hit, L = 4 × (1
/ N) mm or more, because the desired wet resistance cannot be obtained when it is less than 4 × (1 / n).

Further, the reason why the lower limit value is not set with the width of the sipe being 2 mm or less is that even if it is a knife cut whose width is almost impossible to measure, it opens just before the slip starts to cut the water film, This is because the drainage effect to the back surface groove is obtained and the wet resistance is improved. Furthermore, the reason why the thickness is set to 2 mm or less is that if it exceeds 2 mm, the problem of uneven wear occurring due to a decrease in the rigidity of the tread rubber in the peripheral portion of the sipe occurs.

The inclination angle of the sipe is set to 90 ° or less and 45 ° or more with respect to the central axis line XX which coincides with the equatorial plane of the tire, at least when the rear surface groove is relatively close to the center of the tread, at least the rear surface groove. This is because it is preferable from the viewpoint of drainage efficiency to set the inclination angle of the sipe portion near 90 ° to 90 °. Also, if this angle is 45 ° or more, it is preferable in that the edge effect of the sipe is high and the wet resistance is greatly improved when the running state is cornering, and if it is less than 45 °, this preferable performance decreases. ..

The sipe is exposed to the ground contact surface side until the main groove disappears due to wear, thereby contributing to improvement of wet performance. Sipe height H is H = (0.5 to 1.5) x
By setting to h, the rigidity of the sipe forming blade connected to the protrusion forming the rear surface groove can be sufficiently maintained, and the durability of the blade is improved.

Next, the operation of the manufacturing method according to the second aspect of the present invention will be described. First, when manufacturing the precure tread according to the second aspect of the present invention, one end of the blade is embedded in the rear surface groove forming projection 54, and a part of the blade is also embedded in the surface 58 of the molding body. Because
The two end surfaces of the blade will be fixed to the molding body 50C. For this reason, the durability of the thin blade is significantly improved. In addition, since the through hole J of the blade is filled with the metal of the molded body 50C, the blade is more firmly fixed, and the blade is prevented from coming loose even if many temperature history is received. Thus, the durability of the blade is significantly improved.

The above effects allow for an expanded range of blade thickness choices. For example, in the above-mentioned conventional technique, the thinnest blade thickness is limited to 0.5 mm even if durability is sacrificed. According to the second aspect of the present invention, it is possible to reduce the thickness of the blade to about 0.3 mm without sacrificing the durability of the blade. As a result, it is possible to prepare a precure tread having various types of sipes, and it is possible to satisfy a wide range of wet resistance requirements for retreaded tires.

The operation of the manufacturing method of the third invention of the present invention will be described. According to the third aspect of the present invention, the shape, the arrangement, and the number of sipes that open into the rear surface groove are matched, and
It has the flexibility to select the most suitable shape, position and number of ventilation holes according to the material of the unvulcanized cushion rubber and the vulcanization conditions of the retreaded tire. Further, since it is not necessary to provide a comparatively thin protrusion on the protrusion of the mold, there is an advantage that maintenance of the protrusion is not troublesome.

The operation of the manufacturing method according to the fourth aspect of the present invention will be described. First, the problems of the conventional technique will be described more specifically. During vulcanization of the precure tread, multidirectional pressures are applied to the blade as the rubber flows. For example, when a part of a sipe forming blade having a thickness of 0.5 mm or less and a length of 6 mm or more is embedded only inside the mold body on the back surface side, the blade cannot withstand the above pressure and is applied a few times. Sulfur causes great deformation and damage. This durability problem means that the maintenance cost of the mold is extremely high, and it is practically impractical. That is, according to the conventional manufacturing method, there is a problem that it is not possible to meet the market demand for various types of sipe arrangement.

According to the fourth aspect of the present invention, since the sipe is formed in the pre-cure tread after manufacturing by hand or machining, the above problems do not occur. That is, it is possible to easily provide a sipe that opens into the rear surface groove without any obstacles, regardless of how narrow and long the sipe is.

Furthermore, it is possible to provide a sipe which imparts preferable wet resistance depending on use conditions, for example, a sipe in which a long sipe and a short sipe are freely combined, while improving the wet resistance on the one hand and the other on the other hand. It is possible to provide a precure tread that maintains uneven wear resistance.

Further, according to the fourth aspect of the present invention, for example, it is possible to provide a precure tread in which laterally asymmetrical sipes and the like are freely formed with the central axis of the tread as a boundary. As a result, if there is a difference in the effect of wet resistance between the inner side and outer side of the tread, or if the wear state such as wear or uneven wear is different, the asymmetric sipe Can be formed.

Further, in the example shown in FIGS. 11 and 12 which is one specific example of the fourth aspect of the present invention, the sipe 26a communicates with the back surface groove 24 and the main groove 21 or the main groove 22, and both sides of the sipe are connected. Since the edges are opened to all the grooves, the sipe 26a appears after the middle stage of wear of the tread where the wet resistance decreases, and the remarkable improvement in wet resistance can be achieved.

The operation of the manufacturing method according to the fifth aspect of the present invention will be described. According to the fifth aspect of the present invention, first, as described in the fourth aspect of the present invention, the sipe that opens into at least the back surface groove of the pre-cured tread after being manufactured is manually processed or machined. It is possible to provide a desired number of sipes in the desired shape at a desired position, and a retreaded tire to which this precure tread is applied can exhibit desired wet resistance after the middle stage of wear.

At the same time, as described in the third aspect of the present invention, the shape, arrangement, and number of sipes opened in the rear surface groove are matched, and the material of the unvulcanized cushion rubber and the vulcanization condition of the retreaded tire are used. It has the freedom to select the most suitable shape, position and number of vent holes according to the above. Further, since it is not necessary to provide a protrusion on the ridge of the mold, there is an advantage that the maintenance and maintenance of the protrusion is not required.

The operation of the retreaded tire according to the sixth aspect of the present invention will be described. Since the retreaded tire of the sixth invention of the present invention is provided with a sipe having a desirable shape that opens at least in the back surface groove extending from the back surface that is the joint surface with the base tire, The residual groove depth is 1.
Sufficient wet resistance is maintained up to 6 mm to 3.2 mm, giving the user a sense of security in appearance.

Further, in the vulcanization process under high temperature and high pressure, even if the unvulcanized cushion rubber increases in fluidity and tries to flow into the sipe, the sipe has a rear surface groove having a vent hole communicating with the tire ground contact surface. The rubber is prevented from flowing into the sipe portion by exerting pressure on the rear surface groove and the sipe from the outside through the ventilation hole. As a result, the retreaded tire of the sixth aspect of the present invention has a sipe having a sufficient depth until the tire is removed, and can maintain wet resistance.

[0066]

【Example】

Example 1 A retreaded tire 1 having a basic configuration of a cross section in the width direction shown in FIG.
50, size is 10.00R for trucks and buses
Twenty. The base tire 100 is formed by straddling a bead core 102 in a toroidal shape, and arranging a carcass 101 made of reinforcing steel cords in a radial arrangement and three belt layers for reinforcing steel cords radially outside the carcass.

The retreaded tire 150 is vulcanized and molded according to the first invention of the present invention described with reference to FIGS. 1, 2, 3 and 4 and according to the manufacturing method of the second invention of the present invention. The tread 10 is applied. The rubber layer has a cross-sectional thickness in the width direction of T ₁ ≈T ₂ and a substantially uniform thickness of 16 mm. The width TW of the tread arc is 188
mm.

The surface 7 of the precure tread 10 on the tire contact surface has three circumferential main grooves and shallow branch grooves. The width W ₁ of the central main groove 1 having the projections on the groove bottom is 11
The width W ₂ of the outer main groove 2 extending in the circumferential direction on both outer sides of the central main groove is 12 mm. The depth D ₁ of the central main groove is 13.6 mm, and the depth D ₂ of the outer main groove is 1
It is 3.6 mm. Further, the depth of the branch groove 3 extending over both main grooves was 3.5 mm. The distance Y between the lines of symmetry of the outer main groove and the central main groove is 49 mm. The average pitch P was 59.5 mm.

Further, on the back surface 8 side, two linear back surface grooves 4 are provided in the circumferential direction between the central main groove and the outer main groove, and the width w is 4 mm on the back surface and 2 at the top thereof. 0.4 mm
And the top portion was formed into a substantially arc shape. Further, the distance Z from the center line XX to the center line of the rear surface groove is 24.1 mm,
The back surface groove is located approximately in the middle of the central main groove and the outer main groove. The height h of the rear surface groove is 7.9 mm. The ventilation holes were formed in a rectangular shape of 4 mm × 10 mm, and one back surface groove was provided at intervals of 2 pitches at approximately equal intervals.

As shown in FIG. 2, two sipes are arranged on each side of one groove per pitch P so as to be substantially perpendicular to the back surface groove, and further shown in FIG. It was opened in the back groove as described above. Sipe width t is 0.7 mm
The length L was 6 mm and the height H was 7.9 mm, which is the same as the back surface groove.

The pre-cure tread 10 constructed as described above is mounted on the base tire 100 through the unvulcanized cushion rubber 9.
Then, the retreaded tire 150 of Example 1 was manufactured by vulcanization molding according to a conventional method.

Example 2 A retreaded tire 1 having a basic configuration of a cross section in the width direction shown in FIG.
60, and the base tire including the cushion rubber 9 was the same as in Example 1.

The retreaded tire 160 of the second embodiment is shown in FIG.
The precure tread 20 manufactured according to the fourth aspect of the present invention described with reference to FIGS. 11 and 12 is applied. The cross-sectional thickness of this precure tread was substantially uniform in the width direction and was set to 16 mm in accordance with Example 1. The width TW of the tread arc was 188 mm.

Four zigzag circumferential main grooves 21 and 22 having an average pitch P of 33.5 mm are provided on the surface 27 on the tire contact surface side, and the main groove depth near the center is 13.6 m.
m, and the depth of the outer main groove was 13.6 mm. The distance Y ₁ between each line of symmetry of the central main groove and the outer main groove is 2
It was 3.6 mm and Y ₂ was 38.9 mm.

On the back surface 28 side, three back surface grooves 24 are provided substantially in the middle of each main groove so that the edge shape thereof is substantially similar to the main groove. The width w in the direction perpendicular to the back groove is 3.6 m
m, and the width at the top thereof was 4 mm. The height of the back surface groove was 8.0 mm. The ventilation holes were formed in a substantially cylindrical shape having a diameter of 2 mm, and one back groove was provided at a substantially equal interval in two pitches.

As shown in FIGS. 11 and 12, the sipe has a long sipe 26a which communicates with the rear surface groove and the main groove and is opened in both grooves. One end of the short sipe 26b is open to the rear surface groove and the other end is closed in rubber. In this embodiment, the short sipes were previously formed in the mold, and the long sipes were processed by knife cutting after demolding. The height H of both sipes is about 8 mm. Short sipes have a length of 4
mm and the width was 0.7 mm. The angle of inclination of these sipes is 90 ° with respect to the central axis X-X.

The pre-cure tread 20 constructed as described above is mounted on the base tire 100 through the unvulcanized cushion rubber 9.
Then, the retreaded tire 160 of Example 2 was manufactured by vulcanization molding according to a conventional method.

In order to demonstrate the effect of the present invention, three kinds of comparative retread tires were prepared. Comparative Example 1 A retreaded tire in which all the sipes were removed from the back surface of the precure tread of Example 1 and all other parts were the same as those of Example 1.

Comparative Example 2 All the sipes were removed from the back surface of the precure tread of Example 1, the width of the back surface side of the back surface groove was 8 mm, and the width of the top thereof was 4.8 mm. It is the same retreaded tire as.

Comparative Example 3 This is a retreaded tire in which all the sipes are removed from the back surface of the precure tread of Example 2 and the other parts are all the same as those of Example 2.

The above five kinds of retreaded tires were used as test tires and tested by the evaluation methods described below. Regarding wear resistance and uneven wear resistance, a total of eight test tires of each of the above-described examples were separately mounted on the rear axles of a 2-D-4 truck, and the tire load was set to 100%, and the tread was set. It was evaluated by running until the wear rate reached about 80%. The road surface was all paved. The uneven wear is evaluated by measuring the step d between the main groove and the ground contact surface of the rear surface groove as shown in FIG.
Compared.

The wet resistance test was carried out using a 2-D track on a substantially horizontal wet road surface having a water depth of about 0.5 mm on the test course. Each of the four test tires, worn by about 70%, was attached to the drive shaft of the rear wheel of the truck, and the tire load was set to 100%. The wet resistance was evaluated by performing a brake test in which the tire was locked at a vehicle speed of 60 Km / H and using the distance until the vehicle stopped.

The results of the above comparison test are shown in Table 1. Table 1 shows the results of comparison between Example 1 and Comparative Examples 1 and 2 as one group, and shows the results of comparison between Example 2 and Comparative Example 3 separately. The wear resistance, the uneven wear resistance, and the wet resistance are 10 in the group of Example 1 and 10 in Comparative Example 1.
With the index being 0, the group of Example 2 was 10 in Comparative Example 3.
It was expressed as an index of 0. All the higher the value, the better. Here, the uneven wear resistance is expressed as an index using the ratio of the reciprocal of the step d shown in FIG.

[0084]

[Table 1]

As is clear from the above test results, the retreaded tire of Example 1 has substantially the same wear resistance and uneven wear resistance as compared with Comparative Example 1, but is extremely excellent in wet resistance. It showed the performance. Further, in comparison with Comparative Example 2 in which the width of the back surface groove was wide, the wet resistance was almost the same, but the wear resistance and the uneven wear resistance were superior. That is,
It can be said that the retreaded tire of Example 1 is an extremely excellent tire having a well-balanced overall performance including wet resistance.

The retreaded tire of Example 2 had almost the same wear resistance and uneven wear resistance as Comparative Example 3, and a particularly remarkable improvement effect was obtained in wet resistance.

[0087]

As described above, when the precure tread according to the present invention is used, the separation resistance is maintained and, at the same time, the excellent uneven wear resistance and the wear resistance are secured, and at the same time, the tread is not worn out in the middle stage. It is possible to provide a retreaded tire exhibiting further improved wet resistance in the process up to the latter stage. Furthermore, by using the manufacturing method according to the present invention,
It is possible to inexpensively manufacture the precure tread which has the above-mentioned performance and can meet various market needs.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a pattern on a ground contact surface side of a tire pre-cure tread of the present invention.

FIG. 2 is a diagram showing an example of a pattern on the back surface side of the tire pre-cure tread of the present invention.

FIG. 3 is a view showing an example of a cross section in the width direction of the tire pre-cure tread of the present invention.

FIG. 4 is an explanatory view showing an example of the sipe arrangement on the back surface of the tire pre-cure tread of the present invention.

FIG. 5 is a diagram showing another example of the pattern on the back surface side of the tire pre-cure tread of the present invention.

FIG. 6 is an explanatory view showing a cross section along a sipe of another example of the tire pre-cure tread of the present invention.

FIG. 7 is a perspective explanatory view showing an example of a mold used in the manufacturing method of the present invention.

FIG. 8 is an explanatory view showing an example of embedding a blade in a mold used in the manufacturing method of the present invention.

FIG. 9 is an explanatory diagram showing another example of embedding a blade in a mold used in the manufacturing method of the present invention.

FIG. 10 is a diagram showing another example of the pattern on the ground contact surface side of the tire pre-cure tread of the present invention.

FIG. 11 is a diagram showing another example of the pattern on the back surface side of the tire pre-cure tread of the present invention.

FIG. 12 is an explanatory view of a cross section along a sipe showing the relationship between the back surface groove, the main groove, and the sipe of the tire pre-cure tread of the present invention.

FIG. 13 is a cross-sectional view in the width direction showing the main configuration of a retreaded tire according to an embodiment of the present invention.

FIG. 14 is a cross-sectional view in the width direction showing the main configuration of a retreaded tire according to another embodiment of the present invention.

FIG. 15 is an explanatory diagram showing a wear step of the tread rubber in a portion where a rear surface groove is provided.

[Explanation of symbols]

1 Central Main Groove 2 Outer Main Groove 3 Branch Groove 4 Back Side Groove 5 Vent Hole 6 Sipe 7 Surface on Ground Side 8 Back Side 9 Cushion Rubber 10 Precure Tread 20 Precure Tread 50 Mold 50A Mold Lower Mold 50B Mold Upper mold 50C Molded body 100 tires 150 Rehabilitated tires 160 Rehabilitated tires TW Width of arc of contact surface of tread w Backside groove width W ₁ center main groove width W ₂ outer main groove width Y center main groove and outer main groove Distance Z Distance between center line and center of backside groove L Sipe length H Sipe height h Backside groove height t Sipe width D ₁ Center main groove depth D ₂ Outer main groove depth T ₁ Precure tread center thickness T ₂ Precure tread thickness in the center of the outer main groove

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Claims (6)

[Claims] 1. A pre-grid having a surface groove on a front surface of a tire which comes into contact with a ground surface and a rear surface groove on a rear surface which is a side to be attached to a base tire, and a vent hole communicating from the rear surface groove to the tire ground surface. In the cure tread, a sipe that opens into at least the back surface groove of the front surface groove and the back surface groove is provided on the back surface side. 2. A tire contact is made by a ridge provided on the inside of a mating surface of either one of an upper mold half and a lower mold half which are vertically long according to the developed shape of the tread of the tire. A surface groove on the ground side, a manufacturing method of vulcanizing and molding a pre-cured tread by forming a back surface groove on the side attached to the base tire by a ridge provided inside the mating surface of the other mold, A sipe that opens into the backside groove is formed by a blade whose one end is embedded in the ridge of the mating die that forms the backside groove, and a plurality of protrusions arranged on this ridge further form the backside groove to the tire ground plane side. A method for producing a precure tread for a tire, which comprises forming a vent hole communicating with a surface of the tire. 3. A tire contact is made by a ridge provided on the inside of the mating surface of one of the two upper and lower mold halves that are vertically elongated according to the developed shape of the tread of the tire. A surface groove on the ground side, a manufacturing method of vulcanizing and molding a pre-cured tread by forming a back surface groove on the side attached to the base tire by a ridge provided inside the mating surface of the other mold, After demolding the vulcanized precured tread formed by forming a sipe that opens into the backside groove by a blade whose one end is embedded in the protrusion of the mating die forming the backside groove, the backside groove A method for producing a pre-cure tread for a tire, characterized by forming a vent hole communicating with the surface of the tire from the ground contact surface side. 4. A tire contact is made by a ridge provided on the inside of a mating surface of either one of an upper mold half and a lower mold half, which are vertically elongated according to the developed shape of the tread of the tire. A surface groove on the ground side, a manufacturing method of vulcanizing and molding a pre-cured tread by forming a back surface groove on the side attached to the base tire by a ridge provided inside the mating surface of the other mold, A plurality of protrusions, which are provided on the ridges provided on the above-mentioned mold for forming the back surface groove, and which face the tire ground contact surface side, form a vent hole communicating from the back surface groove to the ground contact surface side surface of the tire. A method for producing a precure tread for a tire, comprising removing a vulcanized precure tread from a mold, and then forming a sipe that opens into at least a rear surface groove of the front surface groove and the rear surface groove. 5. A tire contact is made with a ridge provided on the inside of the mating surface of one of the two upper and lower mold halves vertically elongated according to the developed shape of the tire tread. Pre-cured tread is vulcanized by forming a surface groove on the surface that is the ground side and forming a back groove on the back surface that is the side to be attached to the base tire with a ridge provided inside the mating surface of the other mold. In the manufacturing method, after vulcanization molding is completed, at least one of the front surface groove and the rear surface groove of the precure tread removed from the mold is processed to form a sipe that opens into the rear surface groove, and A method for producing a precure tread for a tire, characterized by forming a vent hole communicating with a surface of the tire which is a ground contact surface side. 6. A front surface groove is provided on a front surface of the tire, which is a ground contact surface side, and a rear surface groove is provided on a rear surface, which is a side to be attached to the base tire, and a ventilation hole is provided to communicate from the rear surface groove to the tire ground surface. A retreaded tire characterized in that a precure tread having a sipe that opens into at least a back surface groove of the front surface groove and the back surface groove is provided on the back surface side and is attached to a crown portion of a base tire that has been subjected to a shaping finish.