JPS59124412A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve straight advance stability without reducing drainage performance by arranging the circumferential grooves in sinusoidal form on a tread part and specifying the number of cycles on the outer periphery of a tire which has a tread pattern having circumferential grooves on the tread part. CONSTITUTION:When at least two peripheral grooves 80 are formed on a tread part 40, said groove 80 is arranged in sinusoidal form, and the number of cycles of said sinusoidal wave on the outer periphery of a tire is set to 1-9 cycles. With such constitution, the range (d) where a lane groove edge and a rib edge or a block edge are brought into contact is made very small, in case of straight traveling in the parallel direction to the lane groove 2, and a relative angl is formed between the groove and the lane groove, and the effect for groove wander is improved. Thus, the straight advance stability can be improved, without reducing drainage performance.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pneumatic tire, and more specifically, the present invention relates to a pneumatic tire, and more specifically, to improve straight-line stability when running on a road surface provided with a rain loop.
This invention relates to a pneumatic tire with an improved tread pattern that improves drainage performance without reducing it.

Generally, when driving at high speed on a wet paved road, drainage between the tires and the road surface is important, and if the drainage is poor, the coefficient of friction decreases and accidents are more likely to occur. For this reason, as a measure on the road surface side to ensure drainage, in recent years, a method of arranging a plurality of grooves called rain loops parallel to the traveling direction on the road surface has been proposed and put into practical use.

However, this rain group poses a new problem in that it affects the straight-line stability of the vehicle, causing a phenomenon called ``group wander'' in which the vehicle wanders.

On the other hand, as an example of measures taken on the tire side to ensure drainage performance, there is a pattern in which the grooves arranged in the tire tread are parallel to the direction of rotation of the tire, and in which no part of ribs or blocks protrudes into the grooves. Straight groups are employed.

However, the adoption of the straight group described above has the disadvantage that the above-mentioned group wander becomes even worse when driving on a road surface with rain loops as described above.

The occurrence of this group wander is due to the interaction between the tread pattern 1 and the rain group 2, as shown in Fig. 1. In particular, when the groove edge 3 and the edge 4 of the rain group 2 coincide, the interaction occurs and a certain magnitude occurs. generate vibrations. This phenomenon occurs for the groove edge 3, but especially when the distance t between any groove and another groove (not limited to just one) on the tire tread in the direction perpendicular to the traveling direction is the same as the rain group 2. When the pitch is an integral multiple of P or close to it, group wander becomes noticeable and causes discomfort to the driver.

Furthermore, in the pattern where the groove 5 is straight as shown in FIG. 2, the distance d between the groove end 6 and the end 4 of the rain group 2 is long, so the interaction is strong, and therefore the vibration is also large. .

In other words, group wander will worsen.

Conventionally, as a countermeasure against the above-mentioned group wander, the groove positions of the tire tread portion are set so that two or more grooves do not coincide with rain groups at the same time. However, even if the above-mentioned measures are taken for a single tire, in practice, as shown in Figure 3, it is necessary to consider the groove spacing when the tire is installed on the left and right wheels or the front and rear wheels. In this case, parameters other than the tires, such as the distance between the wheels of the vehicle and the offset amount of the wheels, come into play, so it is not sufficient to take measures based only on the tire groove position.

Furthermore, in the case of straight grooves, the groove shape is changed to a zigzag groove or the rib or block rigidity is reduced in order to reduce the contact area between the groove and the rain group, or to reduce the reaction force that the tread part receives from the rain group. However, the former problem resulted in a decrease in drainage performance, and the latter problem resulted in a decrease in maneuverability and stability.

Therefore, the inventor of the present invention has studied to solve the above-mentioned problems and found that in order to improve the group wander described above, the rib end 6 or the block end 6 as shown in FIG. It is effective to reduce the reaction force received when
narrowing the contact area d between the rain loop end 4 and the rain loop end 4;
Alternatively, as shown in Fig. 4, groove 5 and rain group 2
It has been found that it is effective to have an intersection angle α between the rib ends 6 or the block ends 6 and the rain loop ends 4 to weaken the engagement, thereby improving group wander.

Therefore, in experiments conducted by the inventor of the present invention, it was found that a pattern with a straight groove in which the center of the circumferential groove is located at the same location in the tire tread in a direction perpendicular to the tire rotation direction and a pattern with a zigzag groove, Zigzag grooves have better group wander, and even in patterns with straight grooves, when running at even a slight angle to the direction of the rain loop, the occurrence of group wander was significantly reduced.

The present invention has been made based on the above-mentioned knowledge, and provides a pneumatic tire that can improve straight-line stability when running on a road surface provided with rain loops without reducing drainage performance. It is.

That is, the present invention provides a pneumatic tire having a tread pattern consisting of at least two circumferential grooves in the tread portion, in which the circumferential grooves are arranged in a sinusoidal shape, and the period of the sinusoidal wave in the tire outer circumferential number is 1 to 1. The gist is a pneumatic tire characterized by having nine cycles.

Hereinafter, the present invention will be explained in detail by way of examples with reference to the drawings.

FIG. 5 is an explanatory plan view showing a tread pattern of a pneumatic tire according to an embodiment of the present invention, FIG. 6 is an explanatory diagram of a meridional cross section of the same, and FIGS. FIG.

In the figure, reference numeral 10 denotes a pneumatic tire according to an embodiment of the present invention, which includes a pair of left and right bead portions 20, a pair of left and right sidewall portions 60 connected to the bead portions 20, and a position between each of the sidewall portions 60. The cord angle with respect to the tire circumferential direction is substantially 90°.
A single carcass layer 50 is installed between the pair of left and right bead parts 20, and both ends thereof are folded back from the inside to the outside by the pair of left and right bead wires 21 located in the bead parts 20, thereby forming the pair of left and right bead parts 20. folded part 50a of
The folded portions 50a wrap around the pair of left and right bead fillers 60 located on the bead wire 21 and are in close contact with the carcass layer 50 before folding, and furthermore, the tire circumference is formed on the carcass layer 50 in the tread portion 40. Belt layers 70 intersecting each other at cord angles of 15° to 30° with respect to the direction are arranged, and the tread portion 4
0, a tread pattern consisting of at least two circumferential grooves 80 is arranged.

In the present invention, in particular, the circumferential grooves 80 are arranged in a sinusoidal shape, and the period of this sinusoidal wave on the outer circumference of the tire is set to 1 to 9 periods.

When the tire of the present invention runs on a road surface with rain loops in a direction parallel to the rain loops (straight running), as shown in FIG. ) is much smaller than in the case of the straight groove shown in FIG. 2, and since the groove and the rain group have a relative angle, the effect against group wander J is greatly improved.

Further, as mentioned above, the reason why the number of cycles of the circumferential groove 80 on the tire outer circumference is set to 1 to 9 cycles is because the tire tread portion 4
If the groove 80 undulates for more than one cycle in the contact area between the ground and the road surface, the water flow flowing through the groove 80 will change its direction significantly twice at the 174th cycle and the 3/4th cycle, causing drainage. This is because it is preferable that the number of cycles within the contact patch is at most 374 or less, that is, 9 cycles over the entire circumference of the tire. Furthermore, in order to make the change in the direction of the water flow in one direction or to be small within the contact patch, it is preferable to set the cycle to 1/2, that is, 6 cycles or less around the entire circumference of the tire.

On the other hand, for group wander, it is better to have a larger maximum swing width C during the fluctuation of the groove in the direction perpendicular to the tire rotational direction within the contact patch shown in Fig. 11, in the contact patch. In order to make effective use of the undulations, it is preferable to have 1/4 period within the ground contact surface, that is, 3 or more periods around the entire circumference of the tire.

Furthermore, if the cycle on the outer circumference of the tire is less than one cycle, the tread pattern of the tire becomes unbalanced from left to right, which not only deteriorates the rigidity balance of the tire but also significantly reduces the non-aqueous properties, which is not preferable.

On the other hand, regarding the period of the sinusoidal waviness of the circumferential groove 80 and the amplitude a of the sinusoidal waviness as well, as in the case of the above-mentioned waviness period, the larger the amplitude, the greater the relative angle between the groove 80 and the rain group 2. This is advantageous in terms of group wandering as it increases; however, the change in the angle of the groove 80 in the ground contact surface with respect to the tire rotational direction increases, resulting in a decrease in drainage performance.

According to the inventor's experiments, it is preferable that the maximum swing width C of the groove 80 in the contact patch in the direction perpendicular to the direction of rotation of the tire, that is, in the contact patch, is at least 4 m or more, and if it is less than 4 m1, the tire becomes a group wander. No improvement is seen. Therefore, the ratio of the amplitude a to the period of the sine wave is a/
It is preferable for b to be 0.004 or more for group wander. However, when considering drainage, a/b = 0.
More preferably, the range is from 0.004 to 0.02.

Furthermore, the phase δ with the adjacent sinusoidal grooves 80 is the seventh
As shown in the other embodiments in the figure, it is preferable to offset each other to prevent group wander, and it is more preferable that this phase δ is 1/15 period or more.

Note that even if the circumferential groove 80 has a zigzag shape as shown in FIG. 8 as another embodiment of the present invention, or a chisel shape as shown in FIG. If the center line of the groove 80 is formed in a sinusoidal shape as described above, and if the period of this sinusoidal wave on the outer circumference of the tire is 1 to 9 periods, it is effective against group wander without deteriorating drainage performance. Of course, it is possible to improve straight-line stability when driving on roads with rain loops.

The results of the experiment will be explained below.

Example The specifications of the tires used in this experiment are as shown in Table 1.

(Margins below this page) Comparative Example Tire 1 has four straight grooves in the tread.
All other tires of the present invention have four sinusoidal grooves arranged in the tread portion. Furthermore, each tire has one carcass layer, its reinforcing cord is a polyester cord, and the cord angle to the tire circumferential direction is 90 degrees, and two belt layers are arranged, and the reinforcing cord is a steel cord, and the tire The cords intersect each other at an angle of 17° with respect to the circumferential direction.

The tire size is 185/70 SR, 13, the rim is 5-J x 13, and the air pressure is 1.8 K9/c.
It is nP.

Using the above-mentioned tires, drive at 60-70 km/h on a road surface with a rain loop of 19+++m pitch and 4 widths.
The vehicle ran straight at a speed of /h and evaluated group wander, and the results shown in Table 2 were obtained.

(Margins below this page) Table 2 Examples Examples Each tire used in Experimental Example 1 was used to conduct a water drainage test.

FIG. 12 is a diagram showing the coefficient of friction on a wet road surface averaged at a full speed of 20 to 60 km/h on an asphalt road surface using the above tire and expressed as an index (100 for the comparative tire). Further, FIG. 12 also shows the results of Experimental Example 1. Therefore, the left vertical axis shows the group wander evaluation score, the right vertical axis shows the wet traction, and the horizontal axis shows the a/b value.

From Figure 12, in order to be effective against group wander without reducing drainage performance, a/b should be 0.004 to 0.0.
It can be seen that the range of 2 is preferable, and as is clear from Table 2 and FIG. 12, the tire of the present invention has
It can be seen that compared to the comparative tire, the tire exhibits an effect on group wander without reducing drainage performance, and improves straight-line stability when driving on a road surface with rain loops.

As described above, the present invention is a pneumatic tire having a tread pattern consisting of at least two circumferential grooves in the red portion, which is effective against group wander without reducing the circumferential drainage performance. , it is possible to greatly improve straight-line stability when driving on roads with rain loops.

[Brief explanation of the drawing]

1 to 4 are explanatory diagrams each explaining the relationship between a rain group and a rain wander, FIG. 5 is a plan view explanatory diagram showing a tread pattern of a pneumatic tire according to an embodiment of the present invention, and FIG. 7, 8, and 9 are plan view explanatory views showing other embodiments of the present invention. FIG. 10 is a rain group end and a rib end or block end on the ground plane. FIG. 11 is an explanatory diagram showing the area where the groove contacts the rain group, FIG. 11 is an explanatory diagram showing the maximum swing width of the circumferential groove on the contact surface, and FIG. 80... Circumferential groove. Agent: Patent Attorney Shin Ogawa − Patent Attorney Ken Noguchi Patent Attorney Kazuhiko Saishita Figure 3

Claims (1)

[Claims] In a pneumatic tire having a tread pattern consisting of at least two circumferential grooves in the tread portion, the circumferential grooves are arranged in a sinusoidal shape, and the number of cycles of the sinusoidal wave on the outer circumference of the tire is 1 to 9 cycles. A pneumatic tire featuring