JPH04238702A - Spikeless tire - Google Patents

Abstract

PURPOSE:To improve running performance on icy and snowy roads. CONSTITUTION:By using a cellular rubber material 4, binding a grain composed of elastomer of low glass transition point further having a small path-shaped cell, to form a grounded part 3 of a tread part 2, braking performance and slope-ascending power on icy and snowy roads can be improved by holding rubber elasticity further increasing a grip property without worsening wearing resistance even at low temperature.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spikeless tire with excellent performance on ice and snow.

0002

2. Description of the Related Art In order to drive on icy or snowy roads, spiked tires have conventionally been used in which chains are attached to tires or spikes are driven into the tires. However, in recent years, due to the damage caused by spikes to the road surface and the dust raised by the scraping of the road surface, people are refraining from installing spiked tires and chains using hard spikes, and so-called spikeless tires without spikes have become popular. It is being done.

Such spikeless tires are required to have sufficient driving and braking performance on snowy and icy roads, and therefore the tread of the tire has sufficient frictional force ( grip strength). The friction force generation mechanism of conventional spikeless tires has been explained as follows. (1) Frictional force generated when the shearing force of the snow and the pattern grooves engage with each other when the tread pattern grooves compact the snow. (2) Deformation loss friction force generated by deformation of tread rubber. (3) Adhesive friction force that causes the tread rubber surface to adhere to the snow and ice surface. On the other hand, the frictional force generation mechanism of conventional spiked tires is thought to be mainly caused by the frictional force generated when the spikes embedded in the tread rubber scratch the ice surface.

0004

[Problem to be Solved by the Invention] Therefore, in order to improve the driving force and braking force of tires on snowy and icy roads, it is necessary to increase the frictional force mentioned above. However, methods (2) and (3) above to increase the frictional force, or methods (1) in which the tread pattern has a block shape with an acute angle and the area of the grooves is widened so that the tread pattern bites into the snow even further, can be used to increase the frictional force. Methods are being adopted to increase this. However, these tread compositions and tread shapes are not very effective on icy roads or compacted snow roads.For example, the slope climbing performance of this type of tire on smooth compacted snow roads is limited to a slope of 7 to 10 degrees. , which is considerably inferior to the limit gradient of 13° for spiked tires.

[0005] In order to solve part of the above-mentioned problems, it has been proposed in Japanese Patent Publication No. 62-28001 to form a tread using an elastomer material having pores, but it is not possible to sufficiently improve the ice and snow performance. has not yet been reached.

The present invention is based on the use of an elastomer with a low glass transition temperature in the ground-contacting part of the tread, and the use of a rubber material having passage-like bubbles that open on the tread surface, thereby increasing the grip on ice and snow-covered roads. The aim is to provide spikeless tires that can increase braking power and hill-climbing power on icy and snowy roads, and improve performance on ice and snow.

[0007]

[Means for Solving the Problems] The present invention provides a cellular rubber material in which particles made of an elastomer having a glass transition point of -40°C or less are bonded together, and which has passage-like cells that open on the tread surface and communicate with the inside. This is a spikeless tire in which the ground-contacting part of the tread is formed using

[0008] Furthermore, the JISA hardness of the particles at 20°C is preferably 50° or more and 60° or less.

It is further preferred that the particles are made of cured rubber, and that the particles are cured and bonded by one or both of a rubbery adhesive and an isocyanate-functional polyurethane polymer.

0010

[Operation] The glass transition temperature of the tread contact area is -40
By forming using an elastomer below °C,
The contact surface of the tread has elasticity even in a low-temperature atmosphere, so it can increase the frictional force between the contact surface and the contact surface and maintain grip force by having distortion recovery force at low temperatures. Therefore, it is stable without being affected by changes in temperature,
It is possible to increase the braking force on ice and snow, and improve the climbing ability on icy roads.

[0011] Furthermore, since the ground contact portion of the tread portion is formed by bonding particles made of the elastomer having the above structure, and is made of a foam rubber material having passage-like cells that open on the tread surface, the ground contact portion The rubber that forms it retains flexibility and can increase grip strength.

[0012] Furthermore, the particles of the elastomer are
When the A hardness is in the range of 50 to 60 degrees, it becomes possible to improve the flexibility and abrasion resistance of the foamed rubber in a well-balanced manner.

[0013] Furthermore, when the particles are formed of cured rubber and the particles are cured and bonded using a rubber-like adhesive or an isocyanate-functional polyurethane polymer,
Bonds between particles become stronger, making it possible to prevent chipping of the tread surface and improve wear resistance.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In the figure, a spikeless tire 1 has a tread portion 2
The ground contact portion 3 of the tread surface 2 is formed using a foam rubber material 4 having passage-like bubbles, and the passage-shaped bubbles are formed on the tread surface 2.
It opens at a.

The spikeless tire 1 also includes sidewall portions 13, 13 extending inward in the radial direction of the tire from both ends of the tread portion 2, and bead portions 15, 15 located at the inner ends of the sidewall portion 13 in the radial direction. A toroidal carcass 17 passing through the sidewall portions 13, 13 and the tread portion 2 is bridged between the bead cores 16, 16 provided in each bead portion 15, 15. A belt layer 19 is disposed within the portion 2.

The carcass 17 is a so-called radial or semi-radial arrangement in which carcass cords are arranged at an angle of 80° to 90° with respect to the equator C of the tire, and steel cords are used as the carcass cords. Other fiber cords used include nylon, polyester, rayon, and aromatic polyamide. The belt layer 9 is
In this embodiment, three belt plies are arranged from the carcass 17 side toward the outside in the radial direction of the tire. Further, the belt layer 19 includes belt cords arranged at an angle on each belt ply and crossing each other, and the belt cords are made of fibers such as nylon, polyester, rayon, aromatic polyamide, etc. in addition to steel as well as the carcass 17. code is used.

Further, the tread surface 2a has a vertical groove G extending in the circumferential direction of the tire, and a lateral groove G disposed to intersect with the vertical groove G.
By providing these, a tread pattern divided by the longitudinal and lateral grooves G and g is formed.

In this embodiment, the tread portion 2 is composed of an inner layer 9 in which the carcass 17 and the belt layer 19 are embedded, and an outer layer 10 which is outside the inner layer 9 in the tire radial direction and forms the tread surface 2a. , the outer layer 10 is formed of the foam rubber material 4 according to the present invention. In this embodiment, the bottoms of the vertical grooves G and horizontal grooves G are exposed to the inner layer 9.

The cellular rubber material 4 has a glass transition point of -40
°C or lower, such as natural rubber, polyisoprene rubber, polybutadiene rubber, butyl rubber, and low-styrene styrene copolymer rubber, either singly or as a mixture of two or more, and by using these rubbers, even in cold regions. Can maintain rubber elasticity.

The foam rubber material 4 is formed by forming the elastomer having the above structure into particles and bonding the particles.

In this embodiment, the hardness of the elastomer particles is set in the range of 50° or more and 60° or less in terms of JISA hardness at 20°C. If the hardness is less than 50°, the abrasion resistance will be poor, and if it exceeds 60°, the flexibility of the rubber will decrease and the grip strength will decrease.

[0022] Further, the particles of the elastomer are elongated spheres,
The particles have a regular shape such as a prismatic body, and the maximum length in the longitudinal direction of the particles is in the range of 0.4 mm to 24 mm. Moreover, the foam rubber material 4 is not concentrated in specific sizes such as the lower limit, middle limit, upper limit, etc. of the length range, but is dispersed over a wide range.

[0023] The particles are bonded between the particles using an adhesive having a high bonding force, such as a rubber-like adhesive, an isocyanate-functional polyurethane polymer, or a mixture of both. Since the foamed rubber material 4 formed of such particles has a variation in particle size, the particles are entangled with each other in a complicated manner to increase the bonding force and can easily form channel-shaped cells, which improves the flexibility of the foamed rubber 4. Sexuality increases. Moreover, since the particles are firmly bonded using the adhesive described above,
The tread surface is hard and has excellent wear resistance.

The foam rate of the foam rubber 4, that is, the ratio of the total volume of the foam to the apparent volume of the rubber is 20 to 50%.
A range of is appropriate. If the bubble ratio is less than 20%, the elasticity will be poor, and if it is more than 50%, the effective ground contact area of the tread surface 2a will decrease, resulting in excessive ground contact pressure per unit area, resulting in poor wear resistance.

[0025]

[Example] A radial arrangement tire having a tire size of 185/70R 13 and having the configuration shown in Fig. 1 (
Examples 1 to 5) were prototyped and their performance was tested. For comparison, the performance of conventional tires (Comparative Examples 1 and 2) in which the outer layer of the tread portion was made of a solid rubber material instead of a cellular rubber material was also tested.

The test conditions are as follows. Sample tires were attached to the front and rear wheels of the test vehicle, and a braking test and a hill climbing test were conducted. a) Braking test A speedometer and a braking distance measuring device were attached to the test vehicle, and the test vehicle was driven on a flat test road surface, and the test vehicle was stopped at a fixed position by applying sudden braking. The distance from the location was measured. Table 2 shows the measured values as an index with Comparative Example 1 as 100, and the smaller the value, the better. The test road surface was tested under three conditions: normal compacted snow, smooth compacted snow, and ice floes. Here, a) Normally compacted snow is a road surface that has fallen snow compacted by driving a vehicle. b) Smooth compacted snow is a flat, compacted snow surface made by compacting fallen snow with rollers. c) An ice floe refers to a state in which the aforementioned smooth, compacted snow has frozen.

b) Hill-climbing test After stopping the test vehicle once on each slope with a gradient of 13°, 10°, 8°, and 6°, the test vehicle was started and the slope (degree) that could be climbed was measured. show. The test was conducted three times, and the results are shown below if the rider was able to climb the hill at least one time. The slope surface was subjected to two conditions: smooth, compacted snow and ice floes. The test results are in Table 1
Shown below.

[0028]

[Table 1]

As a result of the test, it was found that the example was superior in both braking performance and hill-climbing ability compared to the comparative example.

[0030]

Effects of the Invention As described above, the spikeless tire of the present invention has a ground-contacting portion of the tread portion formed by using a cellular rubber material bonded with particles made of an elastomer having a low glass transition point and having passage-shaped cells. This makes it possible to improve driving performance on icy and snowy roads.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention.

[Explanation of symbols]

2 Tread part 2a Tread surface 3 Grounding part 4 Cellular rubber material

Claims (3)

[Claims] [Claim 1] The ground contact portion of the tread portion is made of a foam rubber material to which particles made of an elastomer having a glass transition point of -40°C or less are bonded, and which has passage-like bubbles that open on the tread surface and communicate with the inside. A spikeless tire formed by forming. 2. The spikeless tire according to claim 1, wherein the JISA hardness at 20° C. of the particles is 50° or more and 60° or less. 3. The spikeless according to claim 1 or 2, wherein the particles are made of cured rubber, and the particles are cured and bonded by one or both of a rubber-like adhesive and an isocyanate-functional polyurethane polymer. tire.