KR102040826B1 - Tread of Truck and Bus Radial Tire - Google Patents

Abstract

The present invention relates to a tread of a heavy load tire that reduces cracks in grooves according to the tread shape and physical properties of the heavy load tire.
The present invention consists of a cap tread contacting the ground, and a sub tread formed inside the tread so that heat is not transferred to the inside of the tire, the cap tread and the sub tread are made of a rubber composite material having different physical properties, and grooves are formed on the cap tread. In the formed heavy duty tire, the groove lower layer made of the physical property of a cap tread is formed in the lower side of the groove over the whole depth of a sub tread.
According to the configuration of the present invention, by applying the cap tread properties to the entire groove lower side, while reducing groove cracks caused by ozone, the strain on the lower side of the groove is reduced to effectively reduce the crack of the groove.

Description

Tread of Truck and Bus Radial Tire

The present invention relates to a tread of a heavy duty tire, and more particularly, to a tread of a heavy duty tire that reduces cracks in grooves according to the tread shape and physical properties of the heavy duty tire.

In general, TBR Tire (Truck Truck and Bus Radial Tire) is an inner liner constituting the tire's inner circumference, a tread portion with a belt layer in contact with the road surface, and a tire that supports loads and shocks with a tire inner cord layer. The skeleton of the carcass, the side of the tire protects the carcass, and the side wall for flexion movements, and the end of the cord and wrap the end of the bead (Rim) consists of a bead portion.

Meanwhile, grooves are formed in a tread portion of most vehicle tires to secure various performances such as drainage performance, braking performance, and heat generation. However, depending on the conditions of use of the vehicle and the pavement of the road, quality issues such as groove cracks may occur due to excessive lateral force, road stepping, and biting of stones or other protrusions while the vehicle is running. Done.

In general, in the heavy-loaded tire, the groove is a main groove 2 formed in the middle of the width direction of the tire tread 1 as shown in FIG. 1 and a decoupling groove formed at the outermost side of the tire tread 1 in the width direction. It is divided into (3, decoupling groove). The main groove 2 improves drainage performance for removing water film phenomenon, and the decoupling groove 3 serves to improve durability of the belt 4 by reducing strain on the shoulder side and improving heat generation performance. .

The crack occurring in the main groove 2 among the main groove 2 and the decoupling groove 3 is referred to as a groove crack. Conventionally, the main grooves are all the same depth.

2 (a) and 2 (b) are photographs showing the state and position of groove cracks generated in a conventional heavy-load tire. In order to improve the groove cracks, research on the round value of the groove bottom and groove width has been actively conducted. Conventionally, the main grooves have the same depth, and techniques such as groove side angle adjustment and groove back circle radius adjustment have been applied to prevent groove cracks.

In other words, in order to reduce groove cracks in the related art, a groove depth, a back angle, and a back portion curvature are mainly applied to increase the back curvature. The groove depth is the same depth for the grooves, and the outermost rib width is the fatigue resistance of the belt portion. In order to secure it, it made the direction closer to the shoulder side.

Meanwhile, as shown in FIG. 3, the tread 10 of the tire has a cap tread 11 in contact with the ground and a sub tread 12 formed inside the tread 10 so that heat is not transferred to the inside of the tire. Sub Tread), and the physical properties of the cap tread 11 and the sub tread 12 are different. A groove G1 is formed in the cap tread 11.

Among the tire parts, the cap tread, which uses the most compound in the cap tread, is in contact with the ground and is one of the most important parts of the tire design. Most tire performance felt by the driver is seen on the cap tread. The cap tread should be made of a material that is resistant to impact and abrasion while maintaining optimal performance of each of the performances such as adjustment stability, drainage, braking force and ride comfort.

However, the tire of the prior art does not prevent the phenomenon of stress concentration when excessive strain (Strain) is applied to the rear edge of the groove when the load is applied to proceed to the groove crack, and occurs when the line changes for lane changes during normal driving There is a problem in that the technology to reduce the occurrence of cracks in response to the lateral force to be reduced.

Korean Utility Model Utility Model No. 1999-0014723 (Publication date: May 6, 1999) Korean Laid-Open Patent No. 2014-0076223 (published: 2014.06.20.) Korean Laid-Open Patent No. 2016-0017367 (published: 2016.02.16.) United States Patent Application Publication No. 2008-0142135 (Publish Date: 2008.06.19.)

The present invention has been made to solve the problems as described above, an object of the present invention to provide a tread of a heavy-load tire to reduce the cracks generated in the groove according to the tread shape and physical properties of the heavy-load tire. have.

The tread of the heavy-duty tire according to the present invention for achieving the above object consists of a cap tread in contact with the ground, and a sub tread formed inside the tread so that heat is not transferred into the tire, and the cap tread and the sub tread are different from each other. It is made of a rubber composite material, and is a tread of a heavy-duty tire having grooves formed on the cap tread, and a groove bottom layer made of the physical properties of the cap tread is formed over the entire depth of the sub tread.

The groove is formed deeper than the height of the sub tread, so that the groove bottom layer is formed at a height lower than the sub tread.

The cap tread is a rubber composite material containing NR, BR or SBR as the raw material rubber, and the sub tread is formed of a rubber composite material containing 100% of NR as the raw material rubber. The cap tread contains oil.

The cap tread contains 3 to 5 phr of oil and 2 to 5 phr of anti-oxidant, while the sub-tread combines oil and anti-aging to keep the content below 2 phr.

According to the tread of the heavy-duty tire according to the present invention, by applying the cap tread properties to the entire groove lower side, the groove cracks due to ozone are reduced while the strain under the groove is reduced, thereby effectively reducing the cracks of the grooves.

1 is a configuration diagram showing a main groove and a decoupling groove formed on a tread of a general heavy duty tire.
2 (a) and 2 (b) are photographs showing the state and position of groove cracks generated in a conventional heavy-load tire.
3 is a configuration diagram showing the arrangement of the cap tread and the sub tread in the conventional heavy-load tire.
4 is a configuration diagram showing the arrangement of the cap tread and the sub tread in the tire according to the embodiment of the present invention.
5 is a diagram showing a comparison of the strain test results of the conventional example of Figure 3 and the embodiment of the present invention of FIG.
6 is a photograph showing a comparison of groove crack test results of a conventional example of FIG. 3 and an embodiment of the present invention of FIG. 4.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. At this time, it is noted that the same components in the accompanying drawings are represented by the same reference numerals as possible. In addition, detailed descriptions of well-known functions and configurations that may blur the gist of the present invention will be omitted. For the same reason, in the accompanying drawings, some components are exaggerated, omitted or schematically illustrated.

4 is a configuration diagram showing the arrangement of the cap tread and the sub tread in the tire according to the embodiment of the present invention. As shown in the heavy-loaded tire of the present invention, the tread 100 is composed of a cap tread 110 and a sub tread 120 made of a rubber composite of different properties.

The cap tread 110 is a rubber composite that occupies 80% or more of the tread 100 and specializes mainly in wear resistance, and is a part in contact with the ground. The sub tread 120 is a rubber composite, which occupies 5-20% of the tread 100, and is specialized in durability, and is a portion formed inside the tread 100.

The cap tread 110 is formed with a groove G2 deeper than the height of the sub tread 120. Under the groove G2, the groove lower layer 112, which is made of all the properties of the cap tread, is formed over the entire depth of the sub tread 120. The groove lower layer 112 is formed at a lower height than the sub tread 120. Accordingly, the cap tread 110 is divided into a groove 111 formed between the portion 111 formed above the sub tread 120 and the sub tread 120. As such, the tread under the groove G2 is composed only of the cap tread, and the portion except the groove G2 width is composed of the cap tread and the sub tread. At this time, the lower end of the groove (G2) is dug from the bottom of the cap tread 110 to form a curved bottom surface, the sub tread 120 is the cap tread between the groove (G2) and the adjacent groove (G2) It is formed over the entire width.

The cap tread 110 is a rubber composite material containing NR, BR or SBR as the raw material rubber, and the sub tread 120 is formed of a rubber composite material containing 100% of NR as the raw material rubber. The cap tread 110 necessarily includes oil, and the sub tread 120 may or may not include oil.

In addition, the cap tread 110 includes 3 to 5 phr of oil and 2 to 5 phr of an antioxidant, and the content of the sub tread 120 includes an oil and an antioxidant to be 2 phr or less. In this way, the grooves of the cap tread and the sub tread are set to prevent groove cracks. The cap tread suppresses groove cracks caused by ozone depending on the composition of the oil and the anti-aging agent.

Table 1 is a table showing an example of the raw material composition of the cap tread and the sub tread according to the embodiment of the present invention.

division Cap tread Sub tread NR / BR / SBR (phr) 50/30/20 100 /-/- Carbon black / silica (phr) 50 /- 36 (N333) / 10 Oil (phr) 5 - Sulfur / Promoter (phr) 2.5 / 1/0 Antioxidant 6PPD / RD / Wax (phr) 2.0 / 2.0 / 1.0 1.0 / 1.0 /-

Natural Rubbber (NR), Butadiene Rubber (BR) and Styrene Butadiene Rubber (SBR) represent raw rubber. In this example, the cap tread uses a rubber compound of NR 50 phr, BR 30 phr and SBR 20 phr, and the sub tread uses a rubber compound of NR 100 phr. phr represents the weight part with respect to 100 weight part of raw material rubber.

Carbon black and silica are used as reinforcing fillers. In this example, only 50 phr of carbon black is used in the cap tread, and 36 phr of carbon black (N333) is mixed with 10 phr of silica.

Oil is a softening agent added to the rubber composition in order to impart plasticity to the rubber to facilitate processing, or to lower the hardness of the vulcanized rubber. The oil may be any one selected from the group consisting of petroleum oils, vegetable oils, and combinations thereof, and TDAE (Treated distillate aromatic extract) oil is preferable. TDAE oil has excellent low temperature and fuel efficiency performance of tire treads, but also has favorable properties for environmental factors such as the possibility of causing cancer of PAHs (Polycyclic Aromatic Hydrocarbons). In this example, only 5 phr of cap tread oil is used and no oil is used for the sub tread.

Sulfur is a vulcanizing agent and accelerators are vulcanizing accelerators which promote the vulcanization rate or delay the action in the initial vulcanization stage. As vulcanization accelerator, sulfenamide type, thiazole type, thiuram type, thiourea type, guanidine type, dithiocarbamic acid type, aldehyde-amine type, aldehyde-ammonia type, imidazoline type, xanthate type and combinations thereof Any one selected from the group consisting of can be used. In this example, 2.5 phr of sulfur and 1.0 phr of accelerator are used in the sub tread.

Anti-aging agent is an additive used to stop the chain reaction that auto-oxidizes tire by oxygen.In this example, 6PPD 2.0phr and RD 2.0phr and Wax 1.0phr are mixed in cap tread and 6PPD in sub tread. Use a mixture of 1.0phr and RD 1.0phr. Cap tread can be mixed with 6PPD 1 ~ 2phr, RD 1 ~ 2phr and Wax 1.0phr or less. In the sub-tread, the anti-aging agent can be used in a mixture of 6 PPD 1.0phr or less and RD 1.0phr or less. The wax may use waxy hydrocarbon.

Table 2 is a table showing the physical properties of the cap tread and the sub tread according to the composition of Table 1.

division Cap tread Sub tread Hs 62 100M / 300M 34/145 Eb / Tb 455/282 Toughness 592 60 ℃ Tanδ 0.088 0.138 DMTS index 117 115 LAT-100 108 - Actual car wear 108 - Chip & Cut index 100.3 -

In Table 2, Hs represents the sore hardness, 100M represents 100% modulus (kg / cm 2), and 300M represents 300% modulus (kg / cm 2). 100% modulus indicates the stress acting on the specimen when the specimen is stretched 100%, and 300% modulus indicates the stress acting on the specimen when the specimen is stretched 300%. The higher the value, the better the performance. .

Eb represents the breaking strength of the specimen, Eb represents the elongation at break, and Toughness represents the toughness to fracture of the specimen, expressed as the energy per unit volume applied to the failure.

Tanδ of 60 ° C. was measured from −60 ° C. to 80 ° C. under 10 Hz frequency at 0.1% strain using Rheo Dynamic Spectroscopy (RDS). 60 ° C. Tanδ is a measure of rotational resistance at 60 ° C., and the lower the value, the better the low fuel consumption characteristic.

DMTS index is a viscoelastic property index tested using a DMTS (Dynamic Material Testing System) tester and is measured by temperature sweep from -60 ℃ to 80 ℃ under 10Hz, static strain 5% and dynamic strain 0.5%. .

LAT100 is a tester that shows the degree of abrasion of rubber, and it can be used for load (N), slip angle, speed and distance (Low Severity and High Severity). After measuring 9 times in consideration of Distance), it is the average value.

Actual vehicle wear indicates an index value, and a higher index value indicates better wear resistance. The Chip & Cut index represents the tear index.

Since the test method for physical properties is based on the general method for testing the properties of tire rubber, detailed description thereof will be omitted.

5 is a diagram showing a strain test results of the conventional example of Figure 3 and the embodiment of the present invention of FIG. The test specimen of the prior art was used tire 385 / 65R22.5 TH22, the specimen of the embodiment of the present invention used the specimen according to the composition of Figure 4 and Table 1. Figure 5 (a) shows the strain measurement results of the product of the conventional example, Figure 5 (b) shows the strain measurement results of the embodiment of the present invention. As shown in the embodiment of the present invention it can be seen that the peripheral portion of the groove is reduced by 26% (Index) compared to the conventional example. Reducing the peripheral strain reduces groove strain and reduces groove cracks.

FIG. 6 is a photograph showing the groove crack test results of the conventional example of FIG. 3 and the embodiment of the present invention of FIG. 4. FIG. 6 illustrates a groove indoor test to quantitatively grasp the effects of the physical properties of the cap tread and the sub tread. . The test specimen of the prior art was used tire 385 / 65R22.5 TH22, the specimen of the embodiment of the present invention used the specimen according to the composition of Figure 4 and [Table 1].

The indoor test conditions were conducted under the condition of 50pphm ozone and 40 ° C temperature in the chamber (Chamber: 1.3m x 1.3m) to maximize the usage conditions on the market. As shown in (a) of FIG. 6, in the conventional example, groove cracks are generated as shown in FIG. 24, and in the embodiment of the present invention, as shown in FIG. 6 (b), no groove cracks are generated in 24 hours. .

Cracks in rubber can be largely classified into cracks and chemical cracks due to mechanical deformation. In the case of chemical cracks, it is caused by breaking double bonds of rubber carbon by ozone. In the case of the product (a) without applying the above technique, a residual crack (ref. A magnification) of 2 to 5 mm occurred on the rear surface of the groove, but as a result of applying the invention technology, no residual crack occurred on the rear surface.

Detailed description of the test method of Figure 5 and Figure 6 is due to the general test method for the tire and will not be described in detail.

On the other hand, the embodiments of the present invention disclosed in the specification and drawings are merely presented specific examples to easily explain the technical contents of the present invention and help the understanding of the present invention, and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention can be carried out in addition to the embodiments disclosed herein.

100: Tread 110: Cap Tread
112 groove lower layer 120 sub tread
G1, G2: Groove

Claims (5)

It consists of a cap tread in contact with the ground, and a sub tread formed on the inside of the tread so that heat is not transferred to the inside of the tire, the cap tread and the sub tread is made of a rubber composite material of different properties, and grooves are formed on the cap tread. As a tread of the heavy duty tire formed,
Under the groove is formed a groove bottom layer made of all the properties of the cap tread over the entire depth of the sub tread,
The groove is formed deeper than the height of the sub tread, the groove lower layer is formed to a height lower than the sub tread,
The lower end of the groove is excavated from the bottom of the cap tread to form a curved bottom surface,
And the sub tread is formed over the entire cap tread width between the groove and the adjacent groove. delete The method according to claim 1,
The cap tread is a rubber composite material containing NR, BR or SBR as the raw material rubber, and the sub tread is formed of a rubber composite material containing 100% of NR as the raw material rubber. The method according to claim 3,
The tread of the heavy-duty tire, characterized in that the cap tread contains oil. The method according to claim 4,
The cap tread includes the oil of 3 to 5 phr and the anti-aging agent 2 to 5 phr, and the sub-tread of the heavy-loaded tire, characterized in that the total content of the oil and the anti-aging agent to 2 phr or less.

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