JPH0348041B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a tire for snowy roads, and more particularly to a tire for snowy roads that is capable of improving snow performance such as steering stability when driving on icy and snowy roads and general road driving performance without impairing spike retention performance. be. Conventionally, tires suitable for driving on icy and snowy roads, which are generally referred to as tires for snowy roads, take measures such as setting the modulus of the tread portion low in order to improve snow performance such as steering stability and braking performance when driving on icy and snowy roads. If this is done, the holding power of the spike pins planted in the tread will decrease, causing the spike pins to fall off prematurely, while also causing problems such as a decrease in handling stability and durability on general road surfaces. That is the current situation. The present invention was developed as a result of experiments and studies to solve the above-mentioned problems. Therefore, the object of the present invention is to improve the structure of the tread portion and the characteristics of the rubber that constitutes it.
It is an object of the present invention to provide a tire for snowy roads, which can improve snow performance when running on an icy and snowy road and general road running performance without impairing spike retention performance. Here, the term "rubber" refers to a rubber composition (compound) made by mixing rubber such as natural rubber or synthetic rubber with a compounding agent such as carbon black. That is, in the present invention, the tread portion in which the spike pin is implanted is formed of at least two rubber layers, and the tread side rubber layer of these rubber layers is calculated by (loss tangent at -20°C) x (1/(- It is made of rubber having a physical property of 100% modulus at 20℃) x 100) ≧1.80, and the inner side rubber layer in contact with this tread side rubber layer has a physical property of 100% modulus at -20℃ ≧32Kg/ ^cm2 . The gist of the present invention is to provide a tire for snowy roads, characterized in that the large diameter portion of the base of the spike pin is located within the inner rubber layer. Here, −20℃
The reason why we focused on the physical properties is that the tire of the present invention can be used even at a low temperature of -20°C. Hereinafter, the present invention will be specifically described by way of examples with reference to the drawings. 1 and 2 show a tire for snowy roads according to an embodiment of the present invention, FIG. 1 is an explanatory view of a meridional cross section, and FIG. 2 is an enlarged explanatory view of the main part of the same. In the figure, E denotes a snow-covered tire according to an embodiment of the present invention, which includes a pair of left and right bead portions 1, a pair of left and right sidewall portions 2 connected to the bead portions 1, and a space between the sidewall portions 2. This pair of left and right bead portions 1
In between, the cord angle to the tire circumferential direction is 70°~
A carcass layer 4 having an angle of 90° is mounted, and on the carcass layer 4 in the tread portion 3,
Two belt layers 5 are arranged which intersect with each other at cord angles of 10° to 35° with respect to the tire circumferential direction. In the present invention, in particular, the tread portion 3 is formed of at least two rubber layers, and among these rubber layers, the road surface side rubber layer 31 is formed by (loss tangent at -20°C) x (1/(-20°C) The inner side rubber layer 32 is formed of a rubber having physical properties of 100% modulus at -20°C (100% modulus) x 100) ≧ 1.80 and 100% modulus at -20°C < 32 Kg/ ^cm2 , and is in contact with the road side rubber layer 31. is made of rubber having a physical property of 100% modulus ≧32 Kg/cm ² at -20°C. For the tread side rubber layer 31, the reason for using the "loss tangent at -20°C" as a guide is to take into account wet skidding properties, since a water film exists between the tire tread and the ice or snow surface even near this temperature. Is it necessary to do so? Here, the loss tangent refers to the energy loss due to internal heat generation in the rubber, and this loss tangent is a measure of the tire's wet skid performance. Therefore, when the value of the loss tangent is large, the wet skid performance improves, and conversely, when the loss tangent is small, the wet skid performance deteriorates.
In addition, the reason why "100% modulus at -20°C" was used as a guideline was to take into account the ease of movement of blocks on the tire tread at this temperature and the contact area of the tread. The value of (loss tangent at -20°C) x (1/(100% modulus at -20°C) x 100) is a measure of the ice skid performance of the tread side rubber layer 31.
That is, if this value is less than 1.80, the rigidity of the tread-side rubber layer 31 will be too high or the wet skid properties will be poor, resulting in a decrease in ice skid properties and a decrease in snow performance. Further, in the tread side rubber layer 31, the 100% modulus at -20°C is less than 32 kg/cm ² . This is because if the 100% modulus value exceeds 32 Kg/cm ² , the rigidity of the tread-side rubber layer 31 becomes too high and the snow performance deteriorates. In order to prepare a rubber composition having such physical properties, it is sufficient to appropriately select natural rubber or synthetic rubber, select compounding agents, and appropriately consider the proportions of these ingredients. For example, to 100 parts by weight of a rubber mixture consisting of 70 parts by weight of natural rubber and 30 parts by weight of polybutadiene rubber, 75 parts by weight of carbon black, 20 parts by weight of paraffin oil as an extender oil, and 19.25 parts by weight of aromatic oil are blended. good. In the inner side rubber layer 32, at -20°C
100% modulus ≧32Kg/ ^cm2 . 32Kg/
This is because if it is less than cm ² , the rigidity of the inner side rubber layer 32 will be too low and the spike retention performance will be reduced. The rubber composition for the inner side rubber layer 32 may also be prepared by appropriately selecting natural rubber or synthetic rubber, selecting compounding agents, and taking appropriate proportions of these ingredients into account. For example, 70 parts by weight of carbon black and 37.5 parts by weight of aromatic oil may be blended with 100 parts by weight of a rubber mixture consisting of 90 parts by weight of styrene-butadiene copolymer rubber (SBR) and 10 parts by weight of polybutadiene rubber. For reference, the tread part should be at least 2
In conventional tires designed to emphasize handling stability, the rubber layer on the tread side has a ratio of (loss tangent at -20°C) x (1/(-20°C)).
100% modulus) x 100) = about 1.53,
100% modulus at -20°C = approximately 78Kg/cm ² . Further, for the inner side rubber layer, the same rubber as that for the tread side rubber layer is used. In the tread portion 3 in this embodiment, an auxiliary rubber layer 33 is disposed between the inner side rubber layer 32 and the belt layer 5, as shown in the drawing. Therefore, in this embodiment, the tread portion 3 is formed of three rubber layers. This auxiliary rubber layer 33 is arranged to prevent the inner side rubber layer 32 having the above-mentioned physical properties from coming into direct contact with the belt layer 5 and carcass layer 4, and this rubber is similar to that of a normal tire. Any rubber having the same physical properties as the under-red rubber layer may be used. In addition, auxiliary rubber layer 33
It doesn't matter if there is. 7 in the figure is a spike pin implanted in the tread portion 3, and the large diameter portion 7a formed at the base thereof is positioned within the inner rubber layer 32, so that the spike pin 7 is I'm trying not to leave. The effects of the present invention will be explained below using this experimental example. Table 1 (1) and Table 1 (2) are tables showing the compounding contents and physical properties of the compounds used for the tread side rubber layer 31 and the inner side rubber layer 32 of the tire used in this experiment, respectively. .

【table】

【table】

[Table] In Table 1 (2), ()... Value of loss tangent at -20℃ ()... Value of 100% modulus at -20℃ ()... (Loss tangent at -20℃) x ( 1/(-
100% modulus (100% modulus) x 100) at 20℃ The above loss tangent value was calculated using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho, with a width of 5 mm, a thickness of 2 mm, and
Applying an initial strain of 10% to a sample with a length of 20 mm, the frequency
Measured at 20Hz, 2% strain, and -20°C. In addition, the above 100% modulus is based on JISK6301.
100 minutes using JIS No. 3 dumbbells in a -20℃ thermostatic chamber
This is the tensile stress at % elongation. Table 2 below shows how far Compound A and Compound C described in Tables 1 (1) and 1 (2) are placed on the tread side rubber layer 31 and Compound C on the inner side rubber layer 32, respectively, and how far the tread side rubber This is the result of an experiment to determine whether it is preferable for the layer 31 to occupy (the tire used in the experiment was the reference tire No. 12 in Table 3, which will be described later). Second
From the table, regarding the ratio of the tread side rubber layer 31 and the inner side rubber layer 32, up to 50% is the tread side rubber layer 31.
It can be seen that it is preferable that the

[Table] The above total performance is the value obtained by dividing the product of snow performance and spike retention performance by 100. Regarding the above snow performance, tire size
Using 165 SR 13 tires and putting spike pins on them, on a rally specification vehicle (car model TE71),
The climbing tire was measured on a compacted snow road on an uphill slope with a curved road, and No. 12 (tread side rubber layer,
Both the inner rubber layer and the D compound shown in Table 1)
Using the tire time of
It is expressed as an index of 100, and the higher the number, the longer it takes to climb the hill. Furthermore, regarding the above spike retention performance, the Ebisu Circuit was tested for 1 minute 30 to 36 seconds on the same vehicle.
The number of spike pins that have fallen out after driving 20 LAP (total 32.4 km) on LAP is expressed as an index, with the number of pins falling out of the No. 12 tire above as 100. Good performance. Next, Table 3 below shows compounds A, B, C, and D shown in Table 1 (1) and Table 1 (2), respectively, with the ratio of the tread side rubber layer and the inner side rubber layer being 30:70. These are the results of a test similar to that shown in Table 2 above. However, when Compound C shown in Table 1 (1) and Table 1 (2) was applied to the tread side rubber layer, the running performance on snowy roads was significantly inferior, and some of them were not able to climb hills, so they were omitted.

[Table] No.2, No.3, No.4
...Example tire of the present invention.
From Table 2, regarding the ratio of the tread side rubber layer and the inner side rubber layer, it is preferable that the tread side rubber layer accounts for up to 50%, and when the tread side rubber layer reaches 70%, the spike retention performance decreases. It turns out that this is not desirable. Next, from Table 3, No. 1 (comparative example tire) and No. 2
(Tire of this example), the inner rubber layer was -
The 100% modulus at 20℃ must be 32Kg/cm2 or ^more , and No. 2 to No. 4 (tires in this example)
Or, from the test results such as No. 7 and No. 11 (comparative example tires), when considering spike retention performance, No. 3
(Example Tire) If the 100% modulus of the inner rubber layer at -20℃ is 50Kg/cm2 or ^more , as in No. 7 and No. 11 (Comparative Example Tire), the spike retention performance will be improved. It turns out that this is preferable. Next, regarding the tread side rubber layer, in terms of snow performance, No. 1, No. 6, No. 12 (comparative tire) or
Comparing No. 3 (example tire) No. 7 and No. 11 (comparative example tire), (loss tangent at -20°C) x (1/(100% modulus at -20°C) x 100) ≧ 1.80, No. 1, No. 6 (comparative example tire), No. 3 (this example tire), No. 7 (comparative example tire) are better than No. 12, No. 11 (comparative example tire), And No. 1 using compound A of Table 1 (1) and Table 1 (2) for the rubber layer on the tread side.
1 (comparative example tires) No. 2, No. 3, No. 4 (this example tire) and No. 1 using compound B of Table 1 (1) and Table 1 (2) for the tread side rubber layer. 5, No.6, No.7, No.8
(comparative example tire), 100 at -20℃
It can be seen that better test results can be obtained when the %modulus is less than 32Kg/ ^cm2 . In addition, as in No. 7 (comparative example tire), the tread portion was affected by the 100% modulus at -20°C of the compound of the inner side rubber layer (C in Table 1 (1) and Table 1 (2)). No. 6 (comparative example) where both the tread side rubber layer and the inner side rubber layer are formed with compound B of Table 1 (1) and Table 1 (2) No. 7 (comparative tire) has lower snow road driving performance than the tire No. 7 (comparative tire). Therefore, it can be seen that the 100% modulus of the tread side rubber layer at -20°C needs to be less than 32 kg/cm ² . Next, Figure 3 shows No. 3 (example tire), No. 12 (comparative example tire, conventional snow road tire) and No. 1 (comparative example tire, conventional tire) when spike pins are not attached to the tire. These are the results of measuring the cornering force of tires with improved performance on snowy roads. In a conventional tire in which the tread portion is formed of at least two rubber layers, the same rubber is used for the tread side rubber layer and the inner side rubber layer. For this purpose, highly rigid rubber such as Compound D in Table 1 (1) and Table 1 (2) is used for both the tread side rubber layer and the inner side rubber layer (No. 12 tire ), 1st
Rubber with low rigidity, such as Compound A in Tables (1) and (2), is used for both the tread side rubber layer and the inner side rubber layer (No. 1 tire). Therefore, here, for comparison with No. 3 (example tire),
Examples of conventional tires are No. 12 tire and No.
No. 1 tires were used. In FIG. 3, the vertical axis represents the cornering force, and the horizontal axis represents the slip angle. As can be seen from Fig. 3, even when driving on general roads such as all-season radial tires, this example tire (No. 3) has a cornering force similar to that of No. 1 compared to the comparative example (No. 1). There is no extreme decline,
It has performance equal to or better than comparative example (No. 12),
Despite improved driving performance on snowy roads, it can be said that handling stability is excellent. In addition, even when spike pins are not attached, the block rigidity is maintained sufficiently, so it is possible to set the snow performance of the compound used for the tread side rubber layer to be high, so the data measured with spike pins and It also has high snow performance and can be balanced with steering stability at a high level. As described above, the present invention can improve snow performance when driving on icy and snowy roads and general road driving performance without impairing spike retention performance.

[Brief explanation of drawings]

1 and 2 show a tire for snowy roads according to an embodiment of the present invention, and FIG.
The figure is an enlarged explanatory view of the main part of the same as above, and FIG. 3 is a diagram showing the measurement results of the cornering force. 1...Bead part, 2...Side wall part, 3
...Tread portion, 31...Tread side rubber layer, 32...
...Rubber layer on the inner side.

Claims (1)

[Claims] 1. Consists of a pair of left and right bead portions, a pair of left and right sidewall portions connected to the bead portions, and a tread portion in which spike pins are implanted between the sidewall portions. At least 2 treads
The rubber layer is formed of a rubber layer, and the rubber layer on the tread side of the rubber layer is a rubber having the physical properties shown in (a) and (b) below,
In addition, the inner side rubber layer in contact with the tread side rubber layer is shown below.
A tire for snowy roads, characterized in that it is made of rubber having the physical properties of (c), and further has a large diameter portion of the base of the spike pin located within the inner rubber layer. (a) (Loss tangent at -20℃) x (1/(-20℃
(100% modulus at -20°C) x 100) ≧1.80 (b) 100% modulus at -20°C <32Kg/cm ² (c) 100% modulus at -20°C ≧32Kg/cm ²