JPH0440202B2 - - Google Patents

Description

[Detailed description of the invention]

This invention has a structure in which a tread rubber layer is laminated on the upper side of the sidewall rubber layer, the two are joined and integrated, and both ends of the tread rubber layer are located outside the sidewall rubber layer in the tire radial direction and outside in the tire axial direction (hereinafter referred to as This invention relates to a radial tire that easily and reliably suppresses cracks or separations that occur at the annular boundary line where the bonding surface of the sidewall rubber layer and the tread rubber layer intersects with the tire surface in a radial tire with a TOS structure. This type of radial tire with a TOS structure has already been disclosed in Japanese Patent Publication No. 18790/1983. In other words, for a radial tire having a tread rubber layer 4 made of different rubber properties in the crown portion and both side portions as shown in FIG. In order to improve efficiency, the tread rubber layer 4 is formed by integrally molding the side edge rubber 5 made of the same rubber as the sidewall rubber layer 6 on both sides of the crown tread rubber layer 4a. In this case, the sidewall rubber layer 6 and the side edge rubber layer 5 must be firmly bonded and integrated, so it is inevitable that the annular boundary line A formed by the intersection of these bonding surfaces with the outer surface of the tire , cracks or separations often occurred. In order to suppress such cracks or separations occurring at the annular boundary line A in the connection area between the tread rubber layer and the sidewall rubber layer, for example, Japanese Patent Application Laid-Open No. 53-40088 has been proposed. This forms an uneven pattern over the entire circumference of the tire above and below the annular boundary line A between the sidewall rubber layer 6 and the side edge rubber layer 5, and the polymer substance is formed between the sidewall rubber layer 6 and the side edge rubber layer 5. This is an attempt to obtain a strong adhesive force by bonding in a mutually penetrating state. However, although such an uneven pattern improves adhesion, it is still not possible to reduce surface strain in the upper and lower regions of the annular boundary line between the sidewall rubber layer 6 and the side edge rubber layer 5, and the sidewall rubber It is still insufficient as a solution for suppressing cracks or separation at the annular boundary between the layer 6 and the side edge rubber layer 5. On the other hand, Japanese Utility Model Application Publication No. 55-13127 discloses that the bonding surface between the side edge rubber layer 5 and the sidewall rubber layer 6 has a width of at least 5 mm inside and outside of the annular boundary line A that appears to intersect with the outer surface of the radial tire. An annular protrusion with a height equivalent to 0.2 to 1.0 times the thickness of the side rubber layer is formed in an attempt to alleviate the radial surface strain caused by tire rolling. ing. However, the inventor's research has confirmed that even this method is not very effective in alleviating surface strain in the annular boundary region. As mentioned above, the present invention relates to a radial tire having a so-called TOS structure, which is manufactured by laminating and bonding a tread rubber layer onto a sidewall rubber layer.
This was done in order to solve the above problems, and its purpose is to prevent cracks or separation between the sidewall rubber layer and the tread rubber layer, which occur at the annular boundary line A of the radial tire, and particularly to investigate the behavior of surface strain in this area. The object of the present invention is to provide a radial tire that completely prevents this by changing. The present invention provides a radial tire in which both ends of the tread rubber layer are located outside the sidewall rubber layer in the tire radial direction and outside in the tire axial direction, and the joint surface of the sidewall rubber layer and the tread rubber layer appears to intersect with the tire surface. Annular grooves are provided above and below in the radial direction of the tire across the annular boundary line for stress relief, and the ribs between the annular grooves are formed to protrude or enter 1 to 5 mm from the tire surface. It is a radial tire characterized by The TOS structure assumed in the present invention is such that both ends of the tread rubber layer are laminated on top of the sidewall rubber layer so that they overlap, and both are joined and integrated, and the sidewall rubber layer is positioned outward in the tire radial direction and outward in the tire axial direction. It has a structure in which both ends of the tread rubber layer are located at the tread rubber layer, and its manufacturing method is according to the following method as disclosed in Japanese Patent Publication No. 18790/1983. First, a carcass ply layer consisting of cords coated with rubber and arranged in a direction approximately 90 degrees to the circumferential direction of the tire on a cylindrical former is coated with a JIS hardness that has high bending resistance in the vulcanized state. 45
A first step of forming a cylindrical green tire by pasting a pair of ~55° sidewall rubber layers;
This first cylindrical green tire is deformed into a toroid shape, and a belt layer consisting of cords coated with rubber in advance arranged in a direction of 10 to 30 degrees with respect to the circumferential direction of the tire is added to the first cylindrical green tire after vulcanization. JIS hardness 55~ with excellent wear resistance and wet grip properties
Composite in which a crown tread rubber layer made of 75° rubber and a side edge rubber layer with a JIS hardness of 45 to 55°, which is highly flex resistant in the same vulcanized state as the sidewall rubber layer, are integrally formed on both sides. The toroidal green tire is manufactured by a second step of pasting the tread rubber layer and joining the side edge rubber layer to the sidewall rubber layer to form a toroidal green tire, and a third step of vulcanizing the toroidal green tire. Therefore, Fig. 2 shows the cross section of the left half of the tire including the equatorial plane obtained in the above process, in which 1 is the carcass ply, 2 is the bead core, 3 is the belt layer, 4 is the crown tread rubber layer, and 5 is on both sides thereof. Both rubber layers 4 and 5 constitute a composite tread rubber layer. 6
is the side wall rubber layer, and the side edge rubber layer 5
The belt layer is made of almost the same rubber material as the sidewall rubber layer 6, and the cylindrical green tire with the sidewall rubber layer 6 bonded onto the carcass ply as described above is deformed into a toroid shape to form the belt layer. After laminating 3, side rubber layer 6
Then, the crown tread rubber layer 4a and the side edge rubber layer 5 are joined. Therefore, the side wall rubber layer 6 and the side edge rubber layer 5
An annular groove 8 for stress relaxation is formed above and below in the tire radial direction across an annular boundary line A defined by the intersection of the joint surface with the outer surface of the radial tire. The interval L of the annular groove 8 along the outer surface of the tire is preferably 5 to 30 mm, and the groove width W is 2 to 10 mm.
Further, the groove depth D is in the range of 20 to 50% of the thickness SW of the sidewall rubber layer at the annular boundary line A. The distance L is important for changing the deformation behavior of the tire shoulder portion, which will be described later, and is not very effective if it is outside the above range. Also, the side edge rubber layer 5
When the crown portion tread rubber layer 4a is formed, when the tread rubber layer is bonded to the sidewall rubber layer, it is normal for the bonding position to vary due to differences in the shape, dimensions, etc. of the side edge rubber layer 5. Preferably, the distance L is at least 5 mm. Furthermore, if the groove width W and the groove depth D are outside the above ranges, the groove becomes a starting point of stress concentration, while it does not contribute much to changing the deformation behavior in the tire shoulder portion. In the present invention, changing the deformation behavior means shifting the regions where compressive, strain, and extensional strains occur in the shoulder section when the tire is loaded, and reducing the absolute value of the surface strain itself of the tire. A tire deforms under a predetermined load, and strain corresponding to the degree of deformation occurs in each part of the tire.
The distribution of strain in the radial direction of the tire is such that compressive strain occurs primarily in the tread portion, tensile strain primarily occurs in the sidewall portion, and compressive strain occurs again in the beat portion.
In the TOS structure described above, the annular boundary line A
From the viewpoint of anti-separation, it is desirable to form in a region where compressive strain occurs. Therefore, the surface distance LE from the annular boundary line A to the tread end TE is
is set in a range of 15 to 30% of the vertical height H of the tire cross section. In conventional structures, this region is a region where extensional strain occurs, and conventional methods have focused efforts solely on how to reduce this extensional strain, but the present invention As a result, the area where the annular boundary line A is located is changed to a compressive strain area, and the absolute value of the strain is also reduced. Experimental Examples Regarding plain radial light track tires with a tire size of 10R15, the conventional tire shown in Fig. 1 (Experimental Example 1), the tire with an annular groove shown in Fig. 2 (Experimental Example 2), and the part shown in Fig. 4 We prototyped a tire (Experimental Example 3) in which protrusions including the annular boundary line shown in the cross-sectional view were formed in the circumferential direction, and
The strain at each part of the tire was measured under a load of 1600 kg. Detailed tire specifications are shown in Table 1, and strain measurement results are shown in Figure 5.

【table】

[Table] As is clear from the graph in Figure 5, in Experimental Example 3, the position of the annular boundary line A has moved from extensional strain to compressive strain compared to the conventional example, and the absolute value of strain has also decreased. It is clear that this is advantageous in terms of anti-separation. As described above, in Experimental Example 3, the annular grooves were provided across the annular boundary line, so that the stress in the area was relaxed, the deformation behavior under load was changed, and cracking or separation could be effectively achieved. From the above results, the present invention achieves further effects by shifting the surface position of the rib portion formed by the annular groove from the tire surface, in addition to the effect of reducing distortion due to the annular groove. It is something. FIG. 6 is a partially enlarged view showing an example of the present invention. 2
Rib portion 9 formed by being sandwiched between the annular grooves 8 of the book
protrudes from the tire surface and has a step ha between the surface of the rib portion 9 and the tire surface. This step ha is formed in a range of 1 to 5 mm. If it is less than 1 mm, the effect of reducing distortion due to the step difference will be small, and if it exceeds 5 mm, the surface of the rib portion 9 will be easily damaged by curbstones and the like during driving. 7th
The figure is a partially enlarged view showing another example of the present invention. The rib portion 9 formed between two annular grooves 8 is formed by entering from the tire surface, and there is a step ha between the surface of the rib portion 9 and the tire surface.
has. This step ha is formed in a range of 1 to 5 mm. If it is less than 1 mm, the effect of reducing distortion due to the step difference is small, and if it exceeds 5 mm, the required rubber thickness in the rib portion 9 cannot be secured. In the tire of the present invention, in addition to the distortion reduction due to the annular groove, the distortion is further reduced due to the step difference, so that in a radial tire having a TOS structure, the bonding surface of the sidewall rubber layer and the tread rubber layer is on the tire surface. This can effectively prevent cracks and separations that occur at the annular boundary line that intersects with the annular boundary line. Furthermore, the annular groove does not necessarily have to be formed in a straight line in the circumferential direction of the tire, but may be formed in a zigzag shape or a pattern considering the appearance, and it does not necessarily have to be continuous in the circumferential direction. Alternatively, the groove may be partially cut.

[Brief explanation of drawings]

Figure 1 is a partial sectional view of the radial tire of Experimental Example 1, Figure 2 is a partial sectional view of the radial tire of Experimental Example 3, Figure 3 is an enlarged sectional view of the shoulder part of Figure 2, and Figure 4 is the experimental example. FIG. 5 is an enlarged cross-sectional view of the shoulder portion of the radial tire of Example 2, FIG. 5 is a graph showing the strain distribution of the tire, and FIG. 6 and FIG. 7 are enlarged cross-sectional views of the shoulder portion of the embodiment of the present invention. 1...Carcass ply, 2...Bead core, 3
... Belt layer, 4a ... Crown tread rubber layer, 4 ... Tread rubber layer, 5 ... Side edge rubber, 6
... Side wall rubber layer, 7 ... Shoulder part, 8 ... Annular groove, 9 ... Rib part, A ... Annular boundary line, TE ... Tread end.

Claims (1)

[Claims] 1. In a radial tire in which both ends of the tread rubber layer are located outside the sidewall rubber layer in the tire radial direction and axially outside the tire, an annular boundary line that appears where the joint surface of the sidewall rubber layer and the tread rubber layer intersects with the tire surface. Annular grooves for stress relaxation are provided above and below in the radial direction of the tire, with the ribs between the annular grooves protruding or recessing by 1 to 5 mm from the tire surface. Radial tires.