JPH02169308A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To attempt to reduce the sound pressure level of noise by determining the angle of inclination of each lateral groove against the orthogonal axis according to a specified on a tread consisting of many blocks separately formed by many lateral grooves separated in the circumferential direction having at least one line of block row. CONSTITUTION:Multiple main grooves 2-7 extending in the circumferential direction are formed in the tread part 1, and to a central rib 9 and side ribs 10, 11 separately formed by these main grooves 2-7, and many blocks 15-17 separated in the circumferential direction are separately formed on the central rib 9 and side ribs 10, 11 by many lateral grooves 12-14 respectively provided in the circumferential direction. In the tire like this, the angle of inclination A of each lateral groove against the orthogonal straight line L is set at a value that can be determined by the formula of tan<-1>(sP /W+ or -tanB), provided that: the width of each block in the axial direction is W, the pitch in the circumferential direction is P, the positive integral numbers below 3 is s, and the crossed axes angle between the tangent line 24 against a front edge 21 on the treading side and the orthogonal straight line L against the tire equatorial plane 8 at the crossing point 23 of the front edge on the treading side and a center 22 of each block in the direction of width is B.

Description

DETAILED DESCRIPTION OF THE INVENTION -1 The present invention relates to a pneumatic tire having a large number of plows in the tread portion.

Traditionally, in order to turn the noise of pneumatic tires into white noise and reduce the harshness of the ears, the multiple ribs provided in the tread were each constructed from several types of blocks with different pitches in the circumferential direction. A predetermined number of blocks of type a are sequentially arranged in the circumferential direction. So-called pitch variations are being applied.

However,
When such pitch variation markings are applied to pneumatic tires, the noise becomes white noise and the sensation of harshness is reduced, but the sound pressure level of the noise itself hardly decreases, so it is not an effective noise reduction. There was a problem.

- For this reason, the inventor of the present invention has conducted extensive research in order to reduce the sound pressure level itself. In the course of this research, we discovered that a block 81 was constructed by arranging a large number of blocks 81 in the circumferential direction as shown in Fig. 11.
In the main block row 82, while keeping the radius W and the circumferential pitch P of the blocks 81 constant, the inclination angle A of the lateral groove 83 between the blocks 81 with respect to the tire axial direction is finely changed, and the road surface impact at each inclination angle A is When the sound pressure level of the 12th
As shown in the figure, we found that when the angle of inclination was at a certain value, the sound pressure level suddenly decreased at several locations. The total length of the block row 62 in the simulation, that is, the circumference is 1971 mm, and the block 81 in the block row 82 is
The total number of eom is 6 for each block! The convergence W is 42a+m,
The circumferential pitch P of each block 81 was 32.851 mm, and the running speed was lOO l/h. Here, the circumferential pitch P of each block 81 refers to the circumferential distance from the leading edge on the stepping side of the block 61 to the leading edge on the stepping side of the next block 61 to touch the ground. It has been found that the sound pressure decreases the most when the inclination angle A is the same as the value determined by the formula (%).

This invention has been made based on the above-mentioned knowledge, and has at least one block row consisting of a large number of blocks spaced apart in the circumferential direction in the tread portion, and each block in the block row is arranged in the circumferential direction. In a pneumatic tire defined by a large number of lateral grooves spaced apart, the width of each block is W, the circumferential pitch of each block is P, a positive integer of 3 or less is S, and the contact shape of the When the intersection angle between the tangent to the leading edge on the stepping side and the orthogonal straight line to the tire equatorial plane at the intersection of the side leading edge and the widthwise center of the block is B, the inclination angle A of each lateral groove with respect to the orthogonal straight line is expressed by the formula % This is the value calculated using the formula (%). Here, the reason why the value of S is 3 or less is that if it is 4 or more, the inclination angle A is 8
This is because when the angle approaches 0 degrees, the driving force and braking force during running are significantly reduced, making it impossible to use it practically. Furthermore, the reason why the intersection angle B is included in the above equation is to take into consideration the influence of the curvature of a pneumatic tire, which generally has a curved leading edge on the driving side. This sound pressure level reduction effect is extremely noticeable when the block has a monopitch, that is, when the horizontal grooves are equidistant apart in the circumferential direction, as shown in FIG. 12, but the block has so-called pitch variations. As shown in Figure 13, in the case where the pitch is applied, the pitch is slightly worse than in the case of monopitch, but it is still to a considerable degree.
For example, in this example, the circumferential pitch of 15 blocks out of 80 blocks is set large, and the following
The circumferential pitch of the following blocks is set to medium, and the circumferential pitch of the following <15 blocks is set to small, and the last one is set to medium.
This is a simulation value of the sound pressure level when the circumferential pitch of five blocks is medium. When the pitch is varied in this way, the inclination angle A changes one after another following the change in the circumferential pitch, but there is an effect of reducing the sound pressure level.

Furthermore, in the case of monopitch, since the angle of inclination is constant, the effect of reducing the sound pressure level is significant.

1 In this invention, in a pneumatic tire having a block row in which a large number of blocks are arranged in the circumferential direction and spaced apart by a pitch P, the inclination angle A of the lateral grooves between the blocks with respect to the orthogonal straight line is expressed by the above-mentioned formula. Since the value is determined by , the sound pressure level of the noise decreases. Although such a reduction in the sound pressure level is extremely noticeable in monopitch as described above, it also decreases to a considerable extent even when pitch variation is applied.

1. Hereinafter, a first embodiment of the present invention will be described based on the drawings.

! 1 In the figure, 1 is the tread portion of the pneumatic tire, and this tread portion l has a plurality of continuous main grooves 2, 3, 4, 5, 6, 7 extending in the circumferential direction, and these main grooves The grooves 2.3, 4, 5.8, 7 are spaced apart in the axial direction of the pneumatic tire. A central rib 9 defined by the main grooves 4 and 5 and located on the tire equatorial plane 8, and lateral ribs 10 and main grooves 8.7 defined by the main grooves 2 and 3 on both sides of the central rib 3. A large number of lateral grooves 12, 13, 14 are formed at equal distances apart in the circumferential direction from each other in the side ribs 11 defined by the lateral ribs 11. As a result, the central rib 8, the side rib 10,! 1 has transverse grooves 12 and 13 respectively.
．． A number of blocks 15.1 circumferentially separated by 14
B, 17 is defined. These blocks 15, 16, and 17 have the same shape. A large number of blowholes 15 located on the central rib 9 mentioned above. A large number of blocks 18 located on the side rib 10, a large number of blocks 17 located on the side rib 11
collectively constitute a block sequence 18, 19, 20, respectively. Here, if the inclination angle of the lateral grooves 12, 13, and 14 with respect to the straight line L perpendicular to the tire equatorial plane 8, that is, the tire axial direction, is A, then this inclination angle A is a value determined by the following formula. In this formula, W is the width of each block 15.1B, 17, and P is the width of each block 15.1B, 17.
．． 18.17 circumferential pitch, i.e. the block 15
．． 1B, l? It is the circumferential distance from the stepping edge of the block 15, 18, 17 to the stepping edge of the next block 15, 18, 17, and S is any positive integer of 3 or less. The reason why the value of S is set to be 3 or less is because if it is 4 or more, the inclination angle A will be close to 90 degrees, and the driving force and braking force during running will be significantly reduced, making it unusable for practical use. It is. In addition, in the above formula, B is the front edge 21 of the pneumatic tire's ground contact shape, as shown in FIG.
and the intersection point 23 between the width direction center 22 of any block 15, 18, 17 (here, blow 16 is taken as an example), the tangent 24 to the front edge 21 of the tread, and the orthogonal straight line to the tire equatorial plane 8. is the intersection angle with The above ±tanB was inserted into the above equation in consideration of the influence of the curvature of the leading edge 21 of the pneumatic tire, since the trailing edge 21 of the pneumatic tire is generally curved. , each block 15, by this ± janH! 8.17, the difference in the timing of depression between one end in the width direction and the other end in the width direction is corrected. Here, to show an example of the inclination angle A, the circumferential pitch P is 28.4ts
, width W is 24.0■, s is 1, and block 18.
When B in 17 is 10 degrees, the inclination angle A of the lateral groove 12 is 49.8 degrees because the lateral groove 12 is located on the diamond equatorial plane 8 and no correction is necessary.

The inclination angle A of the lateral groove 13 on the left side of the tire equatorial plane 8 increases due to the influence of the treading front edge 21, and the inclination angle A increases to 53.
7 degrees, and furthermore, the lateral groove 1 on the right side of the tire equatorial plane 8
The inclination angle A of No. 4 is reduced to 45.2 degrees due to the influence of the stepping edge 21. In addition, when the ground contact shape of the pneumatic tire is close to a rectangle as in the second embodiment shown in FIG. 3, it is sufficient to substitute the value O for the intersection angle B. When each transverse groove 12.
The inclination angle A of 13.14 is the same as shown in FIG. 4, and each lateral groove 12, 13.14 has a width of W and a circumferential length of P.
It is located on the diagonal of the rectangle. When S is 2, the lateral groove is located on the diagonal of a rectangle whose width is W1 and circumferential length is 2P, and when S is 3, the width is W, The lateral groove is located on the diagonal of the rectangle whose circumferential length is 3P. Again, in FIG. 1, the tire equatorial plane 8 of the lateral groove 12 in the central rib 9
The direction of inclination with respect to the tire equatorial plane 8 and the direction of inclination of the transverse grooves 13.14 in the lateral ribs 10.11 with respect to the tire equatorial plane 8 are opposite directions. In such a monopitch tire, the lateral grooves 12, 13, 14 between the blocks 15, 18, 17
Since the inclination angle A with respect to the tire equatorial plane 8 was determined by the above-mentioned formula, 5 blocks 15.18
．． The time when one part of the 17 hits the road surface and the time when another part hits the road surface coincide with each other so that the impact sounds of both of them interfere with each other and cancel each other out, and the sound pressure level of the noise decreases. do.

Moreover, at this time, since the inclination angle A of the lateral grooves 12, 13, 14 with respect to the tire equatorial plane 8 is not so large,
The driving force and braking force during running hardly decrease.

In the above-described first embodiment, the inclination angle A of the lateral grooves of all block rows was determined by substituting the same value, that is, 1, for S, but in this invention, the inclination angle A of the lateral grooves of each block row The angle A may be found by substituting different values for S. For example, as in the third embodiment shown in FIG. Find the inclination angle A of 87.1 degrees, and substitute 1 for S to find the inclination angle A of the horizontal grooves 34.35 of the block rows 32.33 on both sides.
You can also find 49.11 degrees. In this case, the other condition is #! It is similar to the one in Figure 4. Also, in this invention.

As in the fourth embodiment shown in FIG.
The blocks 39 of 8 and the blocks 42 and 43 of block rows 40 and 41 on both sides may be shifted in the circumferential direction by 172 of the circumferential pitch P of the blocks. In this way, the generated noise can be reduced. further interfere with each other, further reducing the sound pressure level of the noise. Further, the pitch shift may be such that the center block row 38 and the block rows 40 and 41 on both sides are shifted by 174P, and furthermore, the center block row 3B and the block row 40 on one side may be shifted by 1/ The block row 38 in the center and the block row 41 on the other side may be shifted by 1/4 F by 2F.

FIG. 7 is a diagram showing a fifth embodiment of the present invention. In this embodiment, pitch variations are applied to the blocks 47 of each block row 4B.

That is, the blocks 47 of each block row 4B are divided into three types of blocks 47a and 4? whose circumferential pitches Pi, P2, and P3 are different from each other. b, 4? It consists of c.

Here, the circumferential pitch pt of the block 47a (small block) is 28.05 m5, the circumferential pitch P2 of the block 47b (medium block) is 33 intestinal layers, and the block 47C
(Large block) circumferential pitch P3 is 37.95mm, 10 blocks 47a, 4 blocks 47b,
4 blocks 47c, 5 blocks 47b, 5 blocks 47a, 2 blocks 47b, block 4? cllO pieces.

2 blocks 47b, 4 blocks 47a, 4 blocks 47b, 7 blow 2s 47c, and 3 blocks 47b are arranged in sequence in the circumferential direction to form each block row 4B.
It consists of Therefore, the total number of blocks in each block row 48 is 60, and the tire circumference is 1
It is 989.9mm. Moreover, each block 47 has its circumferential pitch P1. P2. Since P3 is different, the horizontal groove 48a located between each block 47
, 48b, 48c with respect to the orthogonal straight line A
I, A2, and A3 are also different, and in this example, 11
1! Since W is 25a+m, the inclination angle A1 is 48.3
degrees, A2 is 52.9 degrees and A3 is 58.6 degrees. In addition, the said S was set to 1, and B was set to O here.

Next, the first noise test will be explained. In this test, first, a test tire L with a tread pattern as shown in FIG. Different comparison tires 1, 2.3, and 4 were prepared. Here, the inclination angles of the lateral grooves of Comparative Tires 1, 2, 3, and 4 were determined using the following formula. For Comparative Tire 1, h in the linear formula was set to -6 am, and for Comparative Tire 2, h was set to -31 am. ,
In Comparative Tire 3, h was set to 3 times, and in Comparative Tire No. 4, h was set to 6 times.

tan' (s (P + h) / W± tan
B) Therefore, the inclination angles of the small blocks in comparative tires 1, 2.3.4 are 41.4 degrees, 45.1 degrees, and 45.1 degrees, respectively.
51.2 degrees and 53.7 degrees, and the inclination angles of the medium blocks are 47.2 degrees, 50.2 degrees, 55.2 degrees, and 57.3 degrees, respectively, and roughly speaking, the inclination angles of the large blocks are 52.0 degrees, 54.4 degrees, 58.8 degrees, respectively.
2.3.4 The audible range (10
The noise sound pressure level at a frequency of 0 to 30 OGHz was determined by simulation. The results are shown in Figure 8.
The sound pressure level of the test tire 1 was significantly lower than that of the comparative tires 1, 2, and 3.4, and in particular, the sound pressure level was 17.3 lower than that of the comparative tires 1.
dB is also decreasing.

Next, the second noise test will be explained. In this test, first, a test tire 2 having a tread pattern as shown in FIG. 1 and a comparative tire 5 having a pitch variation as shown in FIG. 9 were prepared. Here, in the test tire 2, the width W of each block was 24.0 mm, the circumferential pitch P was 28.4 mm, S was 1, and the intersection angle B was 10 degrees. As a result, in the test tire 2, the inclination angle A of the lateral groove 12 in one block row
is 49.8 degrees as described above, the inclination angle A of the lateral grooves 13 in the block row 19 is 53.7 degrees, and the inclination angle A of the lateral grooves 14 in the block row 20 is 45.2 degrees, and 1J On the other hand, in Comparative Tire 5, each block row was made up of three types of blocks: a small block with a circumferential pitch P of 28.7 m layers, a medium block with a 33.8 m layer, and a large block with a circumferential pitch P of 38.9 mm. The blocks are arranged in an arrangement as shown in FIG. 1O. Here, @W of each block is a constant 24.0
mm, and the intersection angle B is 10 degrees. In this comparative tire 1, the inclination angle A of each lateral groove was set to a constant 30 degrees, which is different from the value obtained by substituting the above values into the formula (%). In addition, the tire sizes of both tires are
205/80R15. Next, such test tire 2 and comparative tire 5 were placed on a drum at a speed of 1100
The average sound pressure level of the generated noise during loading and decelerating from Km/hr to 40 Km/hr, that is, the total average value on the bench was measured. As a result, the sound pressure level was 72.2 dB for Test Tire 2, but 74.0 dB for Comparative Tire 5, and the sound pressure level of Test Tire 2 was lower than Comparative Tire 5 by 1.8 dB. Further, the test tire 2 and the comparative tire 5 were mounted on a passenger car and driven, and a noise feeling test was conducted by the driver. When the results are expressed as an index, Comparative Tire 2 had an index of 100, while Test Tire 5 had an index of 110, indicating that the tires of the present invention were also good in terms of feeling.

Next, the third noise test will be explained. In this test, a test tire 3 with a tread pattern as shown in FIG. 4, a test tire 4 with a tread pattern as shown in FIG. 5, and the comparative tire 5 with pitch variations were prepared. did. Here, in the test tire 3, the width W of each block is 24.0+am, and the circumferential pitch P is 33.
．． It was 8 mm, and S was 1. Further, since the test tire 3 has a substantially rectangular ground contact shape as shown in FIG. 3, the intersection angle B is 0 degrees. As a result, in the test tire 3, the inclination angles A of the lateral grooves 12, 13, and 14 in the block rows 1B and 19.20 are all equal.54.
It was 8 degrees. On the other hand, in the test tire 4, the width W of each block is 24.0 mm, the circumferential pitch P is 28.4 mm, S is 2 for the block row 30, and S is 1 for the block row 32.33. Met. Further, similarly to the test tire 3, the intersection angle B of this test tire 4 is 0 degrees. As a result, in this test tire 4, the inclination angle A of the lateral grooves 31 in the block row 30 is 67.1 degrees, and the inclination angle A of the lateral grooves 34.35 in the block rows 32.33 is 4 degrees.
It was 9.8 degrees. The tire size of the test tire 3.4 was also 205/80R+5. The above-mentioned total average value was measured. The result was 72.0dB for test tire 3.
and for test tire 4, it was 72.2 dB. Therefore, the sound pressure level of Test Tires 3 and 4 was lower than Comparative Tire 5 by 2.0 dB and 1.8 dB, respectively, and tire noise could be reduced. In addition, a feeling test was also conducted on the sample tire 3.4, and the results showed that the comparison tire 5 was an index of 100.
Assuming this, both test tires 3.4 had an index of 110, and were also good in terms of feeling. in this way,
Even when the intersection angle B is 0 degrees, and even when blocks with different S values are combined, noise can be reliably reduced.

Next, the fourth noise test will be explained. In this test, the test tire 3 and a test tire 5 having a tread pattern as shown in FIG. I prepared it. Here, the test tire 5 is similar to the test tire 3, but the blocks 39 of the block row 38 and the blocks 42, 43 of the block rows 40, 41 are arranged at a circumferential pitch P of the blocks in the circumferential direction. The only difference is that it is shifted by 1/2 of 33.8 mm, that is, 1B, 8 intestines. By performing such a pitch shift, the noise sound pressure level on the drum of test tire 5 could be reduced by 3.9 dB compared to test tire 3.

As explained above, according to the present invention, the noise sound pressure level can be reliably reduced.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a tread portion showing a first embodiment of the present invention, Fig. 2 is an explanatory diagram showing the ground contact shape of the pneumatic tire shown in Fig. 1, and Fig. 3 is a second embodiment of the invention. 4 is a plan view of the tread portion of the pneumatic tire shown in FIG. 3; FIG. 5 is a plan view of the tread portion showing the third embodiment of the present invention; FIG. 6 is a plan view of a tread portion showing a fourth embodiment of the present invention, FIG. 7 is a partial plan view of a tread portion showing a fifth embodiment of the present invention, and FIG. 8 is a tire provided with pitch variation markings. 9 is a plan view of the tread section showing the comparative tire 5 used in the noise test, and FIG. 10 is a graph showing each block row of the comparative tire 5. Fig. 11 is a plan view showing the block row used in simulating the relationship between the inclination angle of the lateral groove and the noise sound pressure level, and Fig. 12 is a plan view showing the
FIG. 13 is a graph showing the results of a simulation performed using the block sequence shown in FIG. 1, and FIG. 13 is a graph showing the same simulation results as FIG. 11 performed using the block sequence subjected to pitch variations. l...Tread portion 8...Tire equatorial plane 12
, 13.14... Horizontal groove 15.16.17... Block 18.19.20... Block row 21... Stepping Bizen edge 22... Width direction center 23
... Intersection point 24 ... Tangent line L ... Orthogonal straight line Patent applicant Brideston Co., Ltd. Agent Patent attorney Ta Tilt angle person ■υ−

Claims (2)

[Claims] (1) A pneumatic tire having at least one block row consisting of a large number of blocks spaced apart in the circumferential direction in the tread portion, each block of the block row being defined by a large number of lateral grooves spaced apart in the circumferential direction. , the axial width of each block is W, the circumferential pitch of each block is P, and 3
When the following positive integer is s, and the intersection angle between the tangent to the leading edge on the stepping side and the straight line perpendicular to the tire equatorial plane at the intersection of the leading edge on the stepping side of the ground contact shape and the widthwise center of the block is denoted as B. , A pneumatic tire characterized in that the inclination angle A of each of the lateral grooves with respect to an orthogonal straight line is determined by the formula tan^-^1 (sP/W±tanB). (2) The pneumatic tire according to claim 1, wherein the lateral grooves are equidistantly spaced apart in the circumferential direction.