JPH02141305A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To mainly improve the turning performance of a pneumatic tire by orienting at least one layer of reinforcing element out of strips forming a belt in a wave form, and specifying projected length on a tire equatorial face of the pitch length of the wave form. CONSTITUTION:A pneumatic tire is provided with a toroid-shaped carcass as a body reinforcement. The periphery of a crown of the carcass is provided with a belt formed of strips which use many cords or filaments as a reinforcing element 1 and are coated with high polymer materials having low elastic modulus to reinforce a tread. In this case, at least one layer of the reinforcing element 1 is oriented in a wavelike or a zigzag shape, and a projected length (l) on a tire equatorial face 2 of the pitch length of the wave form is established within a range from 1/6 to 1/2 to a ground length L of a tread center of the tire to which a normal load is applied with normal internal pressure filled in it.

Description

Detailed Description of the Invention (Industrial Application Field) Regarding tread reinforcement for pneumatic tires, the present invention relates to a belt for tread reinforcement placed around the crown of a toroidal carcass that serves to reinforce the body of the tire. In particular, we have improved the tire's turning performance by suppressing buckling (local lifting of the tread from the ground surface) caused by the tread belt that occurs during turning of pneumatic tires. This is an attempt to propose a pneumatic tire.

(Prior Art) In general, in pneumatic tires and radial tires, a belt is placed around the crown of a toroidal carcass to help reinforce the tread, and a large number of cords or filaments are used as reinforcing elements to extend the equator of the tire. It has a plurality of code strips arranged in a diagonal arrangement that intersect with each other, so-called cross belts.

The Conoheld structure can exhibit circumferential rigidity to maintain the troital shape of the carcass and shear resistance to counter the shear force generated when the tire turns. As a result, there is a problem of separation occurring in the tread rubber at the separated end, which poses a serious problem in terms of tire durability.

(Problem to be Solved by the Invention) One means to solve this problem is to use a plurality of cords or filaments that are aligned in a wave or zigzag pattern as a reinforcing element within the layers of the belt. It has been discovered that it is useful to use a tube in a belt with the reinforcing element oriented parallel to the tire's equatorial plane and slightly inclined, and its use is being put into practice.

In the process of conducting a more in-depth analysis of this, the inventors discovered that when using a corrugated or zigzag cord or filament as a reinforcing element, the back that occurs on the tread surface when the tire turns as mentioned above. It has now been discovered that the ring is related to the wavelength of the reinforcing element's corrugation or zigzag shape.

Therefore, as a means for reinforcing the tread of this type of tire, a strip having reinforcing elements consisting of a large number of cords or filaments arranged in a wave or zigzag pattern within the belt layer is used for tread reinforcement. An object of the present invention is to improve the turning performance of the tire by suppressing the buckling phenomenon of the tread that occurs between the tire and the ground contact surface when turning, and by increasing the effective ground contact surface during turning.

(Means for solving problems) The above object can be advantageously achieved by the following configuration.

This invention uses a toroidal carcass as a body reinforcement, and a belt consisting of a strip coated with a polymeric material having a lower elastic modulus than the toroidal carcass, with a large number of cords or filaments around the crown of the carcass as reinforcing elements. The reinforcing elements in at least one layer of the strips constituting the belt are oriented in a wavy or zigzag pattern within the layer, and the tire has a wavy or zigzag pitch length. Projected length on the equatorial plane (I) is within the range of more than 1/6 to 2/3 of the contact length (L) at the tread center when the tire is filled with the regular internal pressure and the regular load is applied. It is a pneumatic tire that is characterized by being a certain thing.

Now, the toroidal carcass is used as a body reinforcement, and around the crown of this carcass a number of cords or filaments are used as reinforcing elements, which consist of at least one layer of a strip coated with a polymeric material having a lower modulus of elasticity, such as rubber. Pneumatic tires each having a belt as tread reinforcement are generally well known and need no particular illustration, so FIG. It was shown in In the figure, for simplicity, several reinforcing elements are shown together with their orientation, but it goes without saying that in an actual tire, a large number of reinforcing elements covering the entire crown of the carcass are used, and as shown in Fig. 3(a). In addition to cases in which the orientation is aligned with the equator 2 of the tire, there are also cases in which the orientation is diagonal with an extremely small inclination θ of up to 5 degrees, as shown in Figure (b), and in either case, the waveform The pitch can be organized by the projection length l onto the tire's equatorial plane.

On the other hand, FIGS. 2(a) and 2(b) show the footprint F of the tread contact area deformed based on the turning movement of the tire, along with its A-A cross section, and the cross-sectional view of FIG. 4 is a tread rubber, and 4 is a belt used for reinforcing the tread. Depending on the form of the reinforcing element of the belt 4, buckling B occurs in the form of local lifting within the footprint F.

As a result of many experiments, it has been found that the interval W of this buckling generally corresponds to approximately 176 points of the tire's tread contact length, and from this, the waveform pitch l of the reinforcing element 1 can be adjusted to the normal internal pressure filling of the tire. Based on the ground contact length at the center of the tread when a regular load is applied to the bottom, it was confirmed that buckling can be prevented by setting the distance between 1/6 and 2/3. be.

(Function) Buckling in a radial tire for a passenger car is determined by the elastic modulus of the tread rubber and the bending rigidity of the belt. A radial tire for a passenger car that is used for boat fishing has a regular internal pressure and a regular load, and the distance W between the bucklings is W in relation to the contact length of the crown center! = iL/6 was discovered through many experiments using a ground pressure color measuring device.

On the other hand, when a belt is constructed with reinforcing elements having a waveform or zigzag shape, variations in the stiffness distribution resulting from the shape of the reinforcing element 1 have an important correlation with buckling, and the pitch length of the waveform or zigzag shape of the reinforcing element 1 Buckling is particularly likely to occur when the projection length l of the tire onto the equatorial plane is less than 76 mm. Because buckling mode L/6
This is because if l is smaller than that, there will be variations in stiffness distribution in the waveform or zigzag reinforcing element 1 in the buckling mode.

Therefore, it was confirmed that as long as β>L/6, buckling is less likely to occur in belt structures using cord strips made of wavy or zigzag cords or filaments.

On the other hand, if A/L is too large than 2/3, the benefits of using a corrugated or zigzag cord or filament as a reinforcing element will be lost, so the ItlL ratio should be in the range of 1/6 to 2/3. is necessary.

Example size of PSR175/70SR13 (regular internal pressure 1.8
kgf/cm2, regular load 390 kg"), the tire is conventional, except that a two-piece belt made of reinforcing elements with various projection lengths l of the pitch length of the waveform on the tire equatorial plane is used for tread reinforcement. The prototype was manufactured according to common practice.

Each prototype tire had a contact length at the tread center of 173 mm, and a contact pressure color measuring device determined the critical slip aggle (SA) at which buckling begins to occur within the tread contact area footprint (F) and cornering. The following table shows a comparison of power CP.

(Effects of the Invention) The pneumatic tire according to the present invention secures an effective ground contact area by effectively suppressing buckling under tread deformation caused by cornering, and improves the tire's cornering performance and enhances belt durability. Realized below.

[Brief explanation of the drawing]

Fig. 1 is an arrangement diagram of reinforcing elements, and Fig. 2 is a schematic diagram of a footprint. ■... Reinforcement element 3... Tread 4...
Belt patent applicant Bridgestone Corporation

Claims (1)

[Claims] 1. A toroid-shaped carcass is used as body reinforcement, and around the crown of this carcass, a coating of a polymeric material with a lower elastic modulus is applied using a large number of cords or filaments as reinforcing elements. The reinforcing elements in at least one layer of the strips constituting the belt are oriented in a wavy or zigzag pattern within the layer, and the reinforcing elements are aligned in a wavy or zigzag pattern within the layer. The projection length (l) of the pitch length onto the tire equatorial plane is the ground contact length (L) at the tread center when the tire is filled with the regular internal pressure and a regular load is applied.
1. A pneumatic tire characterized in that the pneumatic tire is comprised between 1/6 and 2/3 of the above.