JPH0476803B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a low-noise tire that can reduce air pumping noise and impacting noise to achieve low noise. [Prior Art] As expressway networks have been developed in recent years, opportunities for vehicles to travel at high speeds have increased, and therefore, there is a desire to reduce tire noise in order to reduce noise during high speed travel. On the other hand, tires with a block pattern are often used to improve grip, but the tire noise of such tires is due to the air generated according to the tread pattern due to the movement of air in and out of the block grooves during rolling. There are pattern noises caused by pumping noises, and impacting noises caused by collisions of blocks with the road surface.When this impacting noise matches the natural frequency of the tire, it resonates and generates resonance noise. Regarding pattern noise, a so-called pitch variation method is known in which the pattern pitch is changed, and although it is effective to some extent, this method makes the tread stiffness non-uniform, and although it disperses the sound frequency, it also reduces the sound itself. It is not possible to reduce energy consumption, and therefore, in order to reduce the noise of block pattern tires, it is desired to reduce air pumping noise and impacting noise. Also, when a tire is installed on a car such as a four-wheeled car, and the tire is divided into left and right at the tire equator, the outer part that is outside the center of the car is smaller than the inner part that is closer to the center of the car.
It is clear that noise is transmitted directly into the open space and has a great impact on passersby, so it is especially desirable to reduce noise in the outside part. The present invention was completed as a result of various experiments conducted on the influence of the inclination of the groove wall surface of the block on block noise in order to reduce noise in block pattern tires. The present invention aims to provide a low-noise tire with a new configuration that can suppress air pumping noise and impacting noise and reduce noise by selecting the inclination of the side and kick-off side. [Means for Solving the Problems] The present invention is a block pattern tire, and the tread portion is located on the outside of the tire equator in the tread portion when facing the direction of travel of the vehicle when the tire is mounted on the vehicle. The inclination angle θ1 that the groove wall on the stepping side of the shoulder lateral groove makes with the tread surface in a plane perpendicular to the tire rotation axis
is smaller than the inclination angle θ2 of the groove wall on the kicking side,
and the inclination angle θ3 of the groove wall on the stepping side of the central lateral groove
is characterized by being formed larger than the inclination angle θ4 on the kicking side. In this way, by setting the inclination angles of the groove walls on the kicking side and the stepping side, the air pumping noise caused by the compression of the air inside the groove and the increase in speed, which tends to occur during the stretching process of the tread rubber on the kicking side, can be suppressed. At the same time, it also reduces the impact noise by alleviating the impact of the blocks when the tires roll. In addition, on the kicking side, the air pumping sound generated during the compression process of the treaded rubber,
It is possible to effectively suppress impacting sound and reduce noise. An embodiment of the present invention will be explained below based on the drawings. Fig. 1 is a partial plan view of a tread pattern, and in the figure, the left side of the tire equatorial CO is oriented outward in the direction of travel when mounted on an automobile. It forms the treaded part where it is located. Further, arrow S indicates the direction of travel. The tread portion T is formed by the longitudinal main grooves 2, 2, which are a pair of straight grooves extending in the circumferential direction of the tire, provided on both sides of the tire equator CO. It is divided symmetrically into a section 3 and left and right shoulder sections 4 and 5 on both sides.In this embodiment, the center section 3 is further provided with a straight groove along the tire equator CO. A groove 7 is provided. Note that the longitudinal main groove is a groove in which a slip sign is usually provided, and has a groove width of about 4 to 8% of the tread width. In addition, the widths W4 and W5 of the shoulder portions 4 and 5, which is the length between the tread edge TE and the outer edge of the longitudinal main groove 2 in the tire axial direction, are 15 of the tread width TW.
~30%. Thereby, the width and length of the central portion 3 and the shoulder portions 4 and 5 are balanced. The center portion 3 is formed by the center groove 7.
The tire is divided into side ribs 10 and 11 on both sides of the equator CO. As shown in FIG. 1, the groove width W7 of the narrow groove 7 is made smaller than the groove width W2 of the longitudinal main grooves 2, 2 to maintain drainage performance and running stability. Note that this narrow groove 7 can also be omitted. Further, shoulder lateral grooves 14..., 15... are formed in the shoulder portions 4, 5 at regular intervals in the tire circumferential direction, one end extending from the tread edge and the other end reaching the vertical main grooves 2, 2. Block 17
. . , 19 . . . are arranged in block rows 20 and 21. Also, in the side ribs 10, 11 of the central portion 3, central lateral grooves 22..., 23... are formed at regular intervals in the circumferential direction, one end extending from the vertical main groove 2 and the other end reaching the narrow grooves 7, 7. By doing so, side rib 1
0 and 11 are formed in block rows 27 and 29 in which blocks 25 . . . , 26 . In this example, the shoulder lateral grooves 14..., 15... and the central lateral grooves 22..., 23... extend in the axial direction of the tire and are shifted in position from each other in the tire circumferential direction to prevent sound synchronization and disperse sound. This is intended to reduce noise. Furthermore, in the block 17 of the shoulder portion 4, which is the outer tread portion, the shoulder lateral groove 14
In the side walls that sandwich the shoulder lateral groove 14, that is, the groove walls, as shown in the cross section in FIG. is smaller than the inclination angle θ2 of the groove wall 14B on the kicking side B. Furthermore, in the central lateral groove 22, as shown in FIG.
Form larger than. Note that the treading side A refers to the side of the groove wall that contacts the ground first when the tire rolls, as shown in Figure 4.
Kicking side B refers to the opposite side of the groove wall. The difference between the inclination angles θ1 and θ2 and the difference between the inclination angles θ3 and θ4 are about 9 to 40 degrees, and the groove walls 14A, 14B,
It is assumed that the inclination angles θ1 to θ4 are constant over the entire length of 22A and 22B. Incidentally, the inclination angles θ1 and θ4 are 85 to 100°,
The inclination angles θ2 and θ3 are approximately 94 to 140°. The reason why the shoulder mechanism 14 and the central lateral groove 22 are made different in terms of inclination angles θ1 to θ4 is as follows.
In the shoulder lateral groove, when the tire is released from contact with the ground during rotation, an air pumping sound or impact sound is generated during the stretching process of the tread rubber on the kicking side, whereas in the center lateral groove, air pumping noise or impact noise is generated when the tire is released from contact with the ground during rotation. At the start, that is, during the compression process of the tread rubber on the stepping side, an air pumping sound or impacting sound is generated. Therefore, by configuring the inclination angles of the side walls of the shoulder lateral groove and the central lateral groove as described above, the deformation of the tread rubber at the time of starting and releasing the ground contact can be minimized, thereby suppressing the air pumping noise or impacting noise. I can do it. In this example, in the right tread portion, the inclination angles of the respective groove walls of the shoulder lateral groove 15 and the central lateral groove 23 are set to be the same as the inclination angles of the respective groove walls of the shoulder lateral groove 14 and the central lateral groove 22, respectively. A radial tire with a tire size of 205/ ^60R15 with the tread pattern shown in Figures 5 and 6, with only shoulder lateral grooves and center lateral grooves (with side wall The inclination angle was the same for both the stepping and kicking sides), and the acoustic energy was measured in an anechoic chamber.
The measurement of acoustic energy is based on the tire noise test method specified by JASOC606, and the sound collecting microphone is placed directly next to the tire, 50 cm from the center of the tire width and 15 cm from the ground contact surface.
I set it up at a height of . FIG. 7 shows the sound pressure waveform of the tread pattern of only the shoulder lateral grooves shown in FIG. 5. The figure shows that the sound pressure increases when the ground is released. On the other hand, in FIG. 8, which shows the sound pressure waveform of the tread pattern of only the central lateral groove shown in FIG. 6, it is recognized that the sound pressure increases at the start of ground contact. As mentioned above, it is clear that the air pumping noise is related to the deformation of the tread rubber on the kicking side in the case of shoulder lateral grooves, and on the stepping side in case of central lateral grooves. The acoustic energy index was calculated for tires with the tread patterns shown in FIGS. 5 and 6 in which the side wall angles of the shoulder lateral groove and the center lateral groove were changed. Here, the acoustic energy E can be calculated from the sound pressure P using the following relational expression. E=1/T∫ ^T _O (P) ² dT When sound intensity I, sound speed c, air density ρ, sound pressure P, and particle density V, I=ρcV ² =P ² /ρc [W/ m ² ], and since the target sound is attenuated sound, the above equation is integrated by time T and divided by time T to obtain the average energy. In addition, relative values are shown for the acoustic energy index, with a pattern in which all groove wall inclination angles are the same as 100. It is clear from the above results obtained by extracting and testing only the characteristics that the acoustic energy index related to air pumping sound and impacting sound can be lowered compared to the case where both groove walls have the same angle.

【table】

〔Effect of the invention〕

As described above, the present invention provides a tread pattern that includes a shoulder lateral groove communicating with the tread end and a central lateral groove communicating between the central longitudinal groove, in which the inclination angle of the shoulder lateral groove is large on the kicking side, while the central lateral groove is By increasing the inclination angle and the depression side, deformation of the tread rubber at the start of contact and release from the ground is suppressed, and pumping and impacting noises can be effectively suppressed.

[Brief explanation of drawings]

FIG. 1 is a partial front view of the tread portion of the tire of the present invention, FIGS. 2 and 3 are sectional views taken along line AA and BB in FIG. 5 and 6 are schematic diagrams of tread patterns, and FIGS. 7 and 8 are graphs of sound pressure waveforms during tire rotation. 2... Vertical main groove, 7... Center groove, 14... Shoulder lateral groove, 22... Center lateral groove.

Claims (1)

[Scope of Claims] 1. The tread portion is divided into a shoulder portion and a center portion by a pair of left and right vertical main grooves extending in the circumferential direction of the tire, and a shoulder lateral groove is arranged in the shoulder portion and a center lateral groove is arranged in the center portion. By doing so, it is a tire with a block pattern in which blocks are arranged in the tread part and shoulder part in the circumferential direction of the tire, and when the tire is mounted on a car, the tire is centered on the tire equator in the tread part when facing the direction of travel of the car. In the tread portion located on the outside of the shoulder lateral groove, an inclination angle θ1 of the groove wall on the stepping side of the shoulder lateral groove with the tread surface in a plane perpendicular to the tire rotation axis is smaller than an inclination angle θ2 of the groove wall on the kicking side, and A low-noise tire characterized in that the inclination angle θ3 of the groove wall on the stepping side of the central mechanism is larger than the inclination angle θ4 on the kicking side.