JPH0347202B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a solid tire that reduces tire heat generation, improves load-bearing capacity, and reduces material costs. In general, solid tires are required to have excellent performance such as load-bearing capacity, low heat generation, and durability, and low selling prices are also an important factor. If it is a product, it is natural to select an inexpensive product, so there is a need to reduce the cost. On the other hand, as shown in Fig. 1, the pneumatic type solid tire uses hard rubber reinforced with short fibers in the base part a, and a rubber with a JISA hardness of 60 to 70, which is softer than the base part a, in the tread part b. A two-layer structure using . However, in such a tire, energy loss occurs due to repeated bending strain due to tire rotation, and as a result, the tire generates heat. However, because the heat dissipation effect of the short fiber reinforced rubber in the base part a is poor, the temperature rise curve of the tire changes over the running time. It reaches a significantly higher temperature range without becoming saturated over time. Furthermore, if a rubber material with low energy loss is used in order to soften the temperature rise curve of the tire, there is a problem in that the product cost increases. Furthermore, as shown in Figure 2, a relatively hard rubber is used for the base part c and the tread part d, and the middle layer e has a three-layer structure using soft rubber or foam with a JISA hardness of 40 to 58. By doing so,
Tires have been proposed in which the longitudinal spring constant of the tire is reduced to improve the cushioning properties of the tire, but in this case, because the intermediate layer e is made of soft rubber or foam, the load-bearing capacity, handling stability, etc. are inferior. There is a drawback. As a result of various studies on these problems with solid tires, the present invention has developed a base rubber layer using rubber reinforced with short fiber cords,
Between the cap rubber layer and the JISA hardness of 50 to 70 degrees,
Harder than the rubber of the cap rubber layer and JISA
Based on the provision of an intermediate rubber layer made of rubber with a hardness of 65 to 80 degrees, it increases load-bearing capacity, reduces heat generation due to strain and rolling resistance, and simultaneously improves durability and handling stability. This discovery led to the completion of the present invention. Therefore, an object of the present invention is to provide a solid tire that improves low heat generation, load carrying capacity, fuel efficiency, and steering stability, and also enables cost reduction. A base rubber layer located on the inside and made of rubber reinforced with short fiber cords, a cap rubber layer located on the contact surface side and having a JISA hardness in the range of 50 to 70 degrees, and an intermediate layer between the cap rubber layer and the base rubber layer. Located at JISA hardness of 65~
It has a three-layer tread rubber structure with an 80° intermediate rubber layer, and the thickness TB of the base rubber layer is in the range of 20 to 50% of the tire cross-sectional height TH, and the thickness TC of the cap rubber layer is within the range of the tire cross-sectional height TH. It is characterized by a range of 20-30% of TH. An embodiment of the present invention will be described below based on the drawings. In FIG. 3, a solid tire 1 of the present invention is shown.
The base rubber layer 2 is located on the innermost side in the tire radial direction, and the cap rubber layer 3 is located on the contact surface side.
and an intermediate rubber layer 4 located between the cap rubber layer 3 and the base rubber layer 2. The base rubber layer 2 is made of hard rubber reinforced with short fiber cords, and as the short fiber cords, in addition to organic fiber cords such as polyester, nylon, and rayon, inorganic fiber cords such as glass and steel can also be used. Preferably, those cut into lengths of 10 mm or less are used. However, from the viewpoint of reducing product costs, it is preferable to use unvulcanized case material used in pneumatic tires or case material recovered from waste tires cut into a predetermined length using a crusher mill or the like. By using a rubber composition mixed with these short fiber cords for the base rubber layer 2, its rigidity is improved, the fitting pressure between the tire and the rim is increased, and slips between the two can be prevented. However, in rubber compositions containing short fiber cords, when the short fiber cords are mixed into the rubber, air is also taken into the rubber, resulting in a decrease in heat conduction and heat dissipation effects.
The thickness TB is in the range of 20 to 50%, preferably 25 to 35%, of the tire cross-sectional height TH. If the above numerical value is
If it is less than 20%, the fitting pressure with the rim cannot be maintained, and the other
If it exceeds 50%, the heat dissipation effect will be significantly reduced. The short fiber cord is mixed in at most 40 parts by weight, preferably from 5 to 35 parts by weight, per 100 parts by weight of rubber. The cap rubber layer 3 is made of rubber with a JISA hardness of 50 to 70 degrees, and is made of a rubber composition with excellent wear resistance, crack resistance, and grip properties, such as diene rubber such as natural rubber, isoprene rubber, and styrene-butadiene rubber. A so-called treaded rubber compound, in which a predetermined amount of carbon is blended into a base rubber, is used. JISA hardness
If the JISA hardness is smaller than 50°, the wear resistance will be poor, and if the JISA hardness exceeds 70°, the grip performance will deteriorate. The thickness TC of the cap rubber layer 3 is in the range of 20 to 30% of the tire cross-sectional height TH. The thickness TC of the cap rubber layer 3 correlates with the service life due to wear of the solid tire 1, and increasing the thickness can extend the service life, but as the cap rubber layer 3 becomes thicker, the intermediate rubber layer 4 becomes thinner. As described later, low heat generation cannot be achieved. Next, as the intermediate rubber layer 4, a rubber having a JISA hardness of 65 to 80 degrees and harder than the cap rubber 3 is used. As mentioned above, in conventional tires with a three-layer structure, rubber with low energy loss is used for the intermediate rubber layer e, but in the present invention, hard rubber is used to reduce heat generation by suppressing the amount of deformation. It is. Therefore, even if a rubber material with low resilience is used, the amount of deformation is small, so the amount of heat generated is small, the degree of freedom in selecting the rubber material is high, and product costs can be reduced. On the other hand, because the intermediate rubber layer 4 has a high rubber hardness, there is less deformation under high loads, which improves the load-bearing capacity, and also reduces pitching and rolling properties, which greatly improves vehicle handling stability. This increases the safety of forklift operations. Furthermore, since the deformation of the tire is small, the rolling resistance of the tire is reduced, and the fuel efficiency of the vehicle is improved. The thickness TE of the intermediate rubber layer 4 is the thickness of the tread rubber 5.
It is selected in the range of 20 to 60% of TH. In order to prevent cracks from occurring due to sudden changes in rigidity at the interfaces between the base rubber layer 2, cap rubber layer 3, and intermediate rubber layer 4, it is desirable that the difference in JISA hardness between adjacent rubbers be 8° or less. As mentioned above, the solid tire of the present invention has a three-layer structure, and by specifying the hardness and thickness of each layer, it has significantly improved low heat generation, load-bearing capacity, vehicle handling stability, and fuel efficiency. This has made it possible to further reduce product costs. EXAMPLE Solid tires of tire size 6.00-9 were prototyped, one having the conventional structure shown in FIG. 1 and the other shown in FIG. 3. Tread part b of the tire in Figure 1
For the cap rubber layer 3 shown in FIG. 3, the material shown as "cap rubber layer" in Table 1 is used, and for the intermediate rubber layer 4, the material shown as "intermediate rubber layer" in the same table is used. Detailed specifications and performance results are provided in the second section.
Shown in the table. In Table 2, longitudinal strain is the amount of strain expressed in % when a load of 2030 kg is applied to the tire, and the rolling resistance at the above temperature is a load of 1205 kg,
Run on the drum at a speed of 25 km/h and check the value of the comparative example.
Shown as a relative value when set to 100. In all cases, the example products are excellent.

【table】

【table】 [Brief explanation of drawings]

Figures 1 and 2 are cross-sectional views of conventional solid tires.
FIG. 3 is a sectional view of the solid tire of the present invention. 1...Solid tire, 2...Base rubber layer,
3...Cap rubber layer, 4...Intermediate rubber layer, TH
...Tire cross-sectional height, TB...Thickness of the base rubber layer, TC...Thickness of the cap rubber layer, TE...Thickness of the intermediate rubber layer.

Claims (1)

[Claims] 1. A base rubber layer located on the innermost radial side of the tire and made of rubber reinforced with short fiber cords, a cap rubber layer located on the ground contact side and having a JIS hardness in the range of 50 to 70 degrees, and the cap rubber layer and the above-mentioned The tire has a tread rubber having a three-layer structure including an intermediate rubber layer located between the base rubber layer and having a JISA hardness of 65 to 80 degrees and harder than the cap rubber layer, and the thickness TB of the base rubber layer is equal to the cross section of the tire. Height TH 20~
A solid tire characterized in that the thickness TC of the cap rubber layer is in the range of 20 to 30% of the cross-sectional height TH of the tire.