JPS6336963B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a tire for running on soft ground such as fields,
To provide a vehicle for the purpose of running a vehicle smoothly and at high speed with low noise and low vibration both on general roads and in fields such as wet fields.

Conventionally, tires for use on general roads have been formed with a tread pattern to prevent the generation of noise and vibration when the vehicle is running, but when the vehicle is driven into agricultural fields such as wet fields, the tires become damp. In the end, the tire got stuck in the rice field, and mud etc. got stuck in the tread groove, making it impossible for the tire to maintain traction on the wet field surface.
The tires would slip, making it impossible to drive in the wet fields.

On the other hand, tires for soft terrain have a tread pattern with large undulations in order to maintain the rolling resistance of the tire in the field when the vehicle is running in the field. Therefore, when this vehicle is driven on a general road, the noise and vibration of the vehicle are extremely large due to the above-mentioned tread pattern. This was impossible at high speeds.

However, it has been impossible to use tires with conventional tread patterns to drive on both general roads and soft ground such as farm fields. BACKGROUND OF THE INVENTION When moving to another farm, the vehicle is often driven on public roads, and recently there has been a desire to provide a tire that can be used for both general roads and soft soil such as fields.

The present invention was devised in response to such conventional demands, and is capable of running on soft terrain that allows a vehicle to run smoothly and at high speed with low noise and low vibration, whether on a general road or on soft terrain such as sandy soil in a field or snow. The purpose of this tire is to provide a dual-purpose tire, and its characteristics are that the outer surface of the center part of the tread in the meridian section of the tire is crowned with a semi-major radius, and the tread edge from the outer surface edge of the center part to the tread end is The outer surface of the outer surface extends on a tangent to the outer surface end of the central portion to form a crown with a short radius, and a plurality of imaginary lines perpendicular to the tread center line at intervals are set on one half of the tread with respect to the tread center line, The pitch of the above-mentioned imaginary lines adjacent to each other in the circumferential direction of the tread is configured to gradually decrease in one direction in the circumferential direction from the maximum pitch to the minimum pitch, and the tread center line , and adjacent virtual lines are defined as a positive half mode, and virtual lines adjacent in the same circumferential direction from the positive half mode end are arranged at the same pitch opposite to the above. On the other hand, on the other half of the tread, the reverse half mode and the forward half mode are sequentially adjacent to each other in the same circumferential direction. The half modes are integrated into a second mode, and the same number of the first and second modes are arranged as positive integers all around the circumference, and
Both modes are 1 mode circumferential length (1/24 to 5/24)
A phase difference is given in the circumferential direction by a double, and a tread groove is formed in each section that opens from the tread end to the tread side wall and extends from the opening toward the tread center line, and a lug section is formed between the tread grooves. The area ratio of the lug part to the tread groove in each section is approximately the same in each section, and the area ratio of the lug part to the tread groove is (1.2±0.3):1, The tread groove portions of the tread end regions are substantially linear in the longitudinal direction, and the above-mentioned portions of all the tread grooves are formed substantially parallel to each other at an intersecting angle of 0 to 10° with respect to an imaginary line perpendicular to the tread center line. ,
The cross section at each position in the longitudinal direction of each tread groove is configured such that the groove width gradually increases from the bottom of the tread groove toward the opening, and the wall surface of the tread groove near the outer surface of the lug is 20゜～40゜)
On the other hand, in the longitudinal cross section of each tread groove, the groove end on the tread center line side is located in front of the tread center line, the bottom surface of the tread groove on the tread center line side is a concave arc surface, and the tread center line side groove end is located in front of the tread center line. The bottom surface of the intermediate portion extending from the bottom surface of the line side is formed as a convex arc surface, and the bottom surface of the tread end side extending from the bottom surface of the intermediate portion is formed as a second concave arc surface, and these continuous bottom surfaces face toward the tread end. The groove ends on the tread center line side of the tread groove are formed alternately at far and near positions in the tread circumferential direction from the tread center line, and each tread center line at the far position The side groove ends and the adjacent tread centerline side groove ends are located at substantially the same position in the tread width direction.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a meridional cross section of a tire 1 for running on soft terrain. In the meridional cross section of the tire, the central outer surface 3 of the tread 2 is crowned with a semi-major radius _R1 , and the tread end 4 is formed from the central outer surface 3 end. The outer surface 5 of the tread end extends from substantially tangentially to the outer surface 3 of the central portion to form a crown with a short radius _R2 .

The tread width W ₁ of the above tread 2 is the tire width W ₂
Approximately 0.9 times the center outer width W ₃ is the tread width
It is assumed to be 0.5±0.2 times W ₁ , and the semi-major axis R ₁ is the tire width W ₂
(1.5±0.3) times the short radius R ₂ of the same tire width W ₂
(0.7±0.2) times the major axis R ₁ is always longer than the minor axis R ₂ . The center point 6 of the semi-major axis R ₁ is
It lies on a tire radial line 8 perpendicular to the tread center point 7.

FIG. 2C shows a part of the tread pattern developed on a plane, and shows one half of the tread 9 with respect to the tread center line 7, that is, the front side of the tread center line 7 shown in FIG. A plurality of virtual lines 10 orthogonal to the line 7 are set at intervals. Then, the virtual lines 1 adjacent to each other in the circumferential direction of the tread
0 pitches l _o , l _o-1 ..., l ₁ , l ₀ are the maximum pitches in one direction in the circumferential direction, that is, in the direction of arrow 11 in Fig. 2C.
The pitch decreases stepwise from l _o to the minimum pitch l ₀ , and from this maximum pitch l _o to the minimum pitch.
A group of sections 12 defined by the tread center line 7 and the adjacent virtual lines 10 up to l ₀ is defined as a positive half mode 13. The relationship between the adjacent pitches above is n = 2 → n (n is a positive integer),
logn/log(n-1)=log(n-1)/log(n-2)
= constant, preferably, and the maximum pitch l _o is the minimum pitch l ₀ (1.4 ~
2.0) times is preferred. In the above case, if the maximum pitch l _o is less than 1.4 times the minimum pitch l ₀ ,
The noise of the tire 1 when running increases, that is, the difference between the noise levels (dB) at each frequency (Hz) increases, which is undesirable, and if the above value becomes more than double, the maximum pitch l _o minimum pitch
The difference between the sections 12 at l ₀ becomes too large, which is undesirable as it causes uneven wear.

Further, the virtual lines 10 adjacent from the end of the forward half mode 13 in the same direction of the arrow 11 as above are arranged at the same pitches l ₀ , l _{1 . .} . , and the above forward/reverse half modes 13, 14
are integrated into the first mode 15, and in the illustrated example, a half mode consists of three pitches, that is, one mode consists of six pitches.

On the other hand, on the other half of the tread 16 relative to the tread centerline 7, the reverse half mode 14 and the forward half mode 13 are successively adjacent to each other in the circumferential direction of the same arrow 11, and these half modes 14 and 13 are integrated into the second half mode. The mode is set to 17. Then, the same number of the first and second modes 15 and 17 are all around the tread,
A positive integer, preferably a large number of pitches in one mode, is arranged as the first mode. Then, both modes 15 and 17 are given a phase difference l in the circumferential direction, which is (1/21 to 5/24) times the _one mode circumferential length L1.

In each of the sections 12, a tread groove 19 is formed which opens into the tread side wall 18 and extends from the opening toward the tread center line 7, and between these tread grooves 19 is a lug section 20.
The area ratio of the lug portion 20 to the tread groove 19 in each section 12 is approximately the same, that is, the area ratio of the lug portion 20 to the tread groove 19 in the unit area of the tread 2 is approximately the same in each portion of the tread 1. Ru. Preferably, the lug portion 20 and the tread groove 1
The area ratio of 9 is (1.2±0.3):1.

The tread groove 19 is formed so that the tread end groove 21 in the tread end 4 region is approximately linear in the longitudinal direction, and the groove center is approximately perpendicular to the tread center line 7. From the side edge of line 7, on one half of the tread 9, arrow 1
A bending groove 22 that curves convexly in plan view extends in the opposite circumferential direction of 1, and on the other half of the tread 16, a bending groove 22 extends in the circumferential direction of arrow 11 in the same manner as above, and each bend The ends of the grooves 22, 22 on the tread center line 7 side are formed into a triangular head shape in which the groove width gradually decreases substantially linearly toward the tread center line 7.

The tread centerline side groove end 23, which is the groove apex of the tread groove 19, is located at the section 1 of the tread groove 19.
Center line 2 between virtual lines at the center of both virtual lines 10 in 2
4 and in front of the tread groove center line 7. In addition, in the tread one-half surface 9,
a positive direction groove width W ₄ from the center line 24 between the imaginary lines to the edge of the tread end groove 21 at the circumferential position indicated by the arrow 11;
Reverse groove width in the opposite circumferential direction from the center line 24 between virtual lines
The dimensional ratio with W ₅ is approximately 1: (1.15 to 1.35), and the sum of these forward and reverse direction groove widths W ₄ and W ₅ , that is, the groove width of the tread end groove 21, is It is approximately 0.6 times the pitch l of both virtual lines in the forming part 12. On the other hand, on the other half of the tread 16, tread grooves 19 are formed in the opposite circumferential direction of the arrow 11 from the imaginary line center line 24 in the same manner as described above.

The tread center line 7 of each of the tread grooves 21
The side ends are located at approximately the same position in the tread width direction, and approximately 0.36 of the tread width W ₁ from the tread center line 7.
The bending apex 25 of the bending groove 22 is also formed at approximately the same position in the tread width direction,
And the tread width W ₁ from the tread center line 7
Formed at 0.27x position.

The tread centerline side groove ends 23 are formed alternately at far and near positions in the tread circumferential direction with respect to the tread centerline 7, and each tread centerline side groove end 23 at a far position and each tread centerline side groove end at a near position. 23 are located at approximately the same position in the tread width direction, and the tread center line side groove end 23 located near the tread center line is located at a dimension position (0.04 to 0.16) times the tread width W ₁ from the tread center line 7, and the tread center line side groove end 23 located at the far position The center line gutter end 23 is
From tread center line 7 to tread width W ₁ (0.12~
0.25) double dimension position.

The lug portion 20 between the tread grooves 19 facing each other with respect to the tread center line 7 has an annular groove 2 that is continuous along the circumferential direction of the tread and is spaced apart from the tread groove 19.
6 is formed. In the illustrated example, the annular grooves 26 are formed in a zigzag shape so as to bypass the tread centerline side groove ends 23 of the tread grooves 19 that alternately oppose the tread centerline 7 in the tread circumferential direction. W ₆ is an abbreviation of tread width W ₁ , which is 0.1
Preferably, the pitches are twice as long, and the pitches are preferably of substantially equal length, corresponding to the pitches forming the tread pattern. Also, the groove width W ₇ of this annular groove 26 is (0.02 to 0.05) of the tread width W ₁ .
The groove depth _L2 is preferably (0.2 to 0.6) times the depth of the tread groove 19 at the 1/4 point in the width direction of the tread 2.

The annular groove 26 may have a wavy shape in which alternately inverted circular arc shapes are continuously arranged, or may have a linear shape or a plurality of grooves.

FIG. 2a shows a simplified tread pattern in which the tread grooves 19 are inclined with respect to an imaginary line 10 perpendicular to the tread center line 7, and the tread end portions of the tread end regions 4 are approximately linear in the longitudinal direction. Moreover, the above-mentioned portions of all the tread grooves 19, that is, the tread end grooves 21, are formed substantially parallel to each other at a predetermined intersection angle θ ₁ with respect to the above-mentioned imaginary line 10. The crossing angle θ ₁ is preferably 0°, but may be in the range of 0 to 10°.

Each of the figures in FIGS. 3a to 3i shows a cross section at each position in the longitudinal direction of the tread groove 19, and each cross section has a configuration in which the groove width gradually increases from the bottom of the tread groove 19 toward the opening, and the lug portion The wall surface 27 of the tread groove 19 near the outer surface of the lug portion 20 has a groove edge angle θ ₂ (20° to 40°) with respect to the vertical line 28 of the outer surface of the lug portion 20,
The bottom surface of the tread groove 19 has opposing wall surfaces 27,
27 It is formed by a circular arc with the lower end as a tangent. In the above case, the groove edge angles θ ₂ of the opposing wall surfaces 27, 27 do not need to be the same.

More specifically, the groove edge angle θ ₂ at the tread end groove 21 is preferably approximately 25° (FIGS. 3a and 3b). Furthermore, at the bent groove 22 position, the groove edge angle θ ₂ at the concave arc edge when viewed from the imaginary line center line 24 is approximately 30° on the tread end 4 side (left groove edge in FIG. 3C), and the tread center line 7 It is approximately 35° at the side (Fig. 3 d), and approximately 25° at the convex arc groove edge (Fig. 3 C right groove edge,
Figure 3g). Furthermore, the groove edge angle θ ₂ at the end position on the tread center line 7 side of the bending groove 22 is approximately
35° (Fig. 3e), and approximately 30° on the convex arc groove edge side (Fig. 3f). In this case, as shown in Figure 2c,
In the case of a tread groove 19 having a groove end 23 on the tread center line side located far from the tread center line 7, the groove edge angle θ ₂ at the end position of the bent groove 22 on the tread center line 7 side is The angle is approximately 30° at the edge of the convex arc groove (Fig. 3h), and approximately 25° at the edge of the convex arc groove (Fig. 3i).

In FIG. 1, the tread centerline side groove end 23 in the longitudinal cross section of each tread groove 19 is located in front of the tread centerline 7, and the tread centerline side bottom surface 29 of the tread groove 19 has a concave arc with a first radius _R3 . formed on the surface. The first radius R ₃ is (35±
15) mm, and the concave arc surface passes through the tread centerline side groove end 23 or the vicinity thereof, and is approximately in contact with a circular arc having a second radius R ₄ and having a center on the tire radial direction line 8. The center of the first radius R ₃ is determined as follows. The center of the second radius _R4 is determined as follows. In other words, the S70 value according to JISD4202 (this value indicates the tire width measured when the tire is mounted on a rim that is equivalent to 70% of the tire width in the meridional section of the tire). A circular arc 31 with a second radius R ₄ is drawn so as to pass through an imaginary point 30 at a position perpendicular to the radial direction line 8 and at a predetermined groove depth from the surface of the tread 2. The dimension of radius _R4 is (0.7 to 1.0) times the above S70 value.

The tread end 4 side of the center side bottom surface 29 is formed by a circular arc 31 having the second radius R ₄ , which extends from the center side bottom surface 29 end to the intermediate portion bottom surface 32 as a convex arc surface, and further extends from the center side bottom surface 29 end to the intermediate portion bottom surface 32 . A tread end side bottom surface 33 extends from the tread end 32 as a second concave arc surface, and the tread end side bottom surface 33 opens to the tread end 4 and the tread side wall 18.

The tread end bottom surface 33 is formed by a third radius R ₅ , and the center 34 of the third radius R ₅ is approximately located on a line 35 passing through the tread center line 7 and perpendicular to the tire radial direction line 8 . The dimensions are the second radius R ₄
(0.7 to 1.0) times the tire cross-sectional height L3, and the boundary between the tread end side bottom surface 33 and the tread side wall 18 is spaced from the tread end 4 by (0.2 to 0.35) times the tire cross-sectional height _L3 . be.

The intermediate bottom surface 32 is formed by a fourth radius R ₆ , and both ends of the intermediate bottom surface 32 have a second radius.
Arc 31 due to R ₄ , that is, the center side bottom surface 29 end,
It is in contact with the arc defined by the third radius _R5 , that is, the bottom surface 33 of the tread end, and the dimension of the fourth radius _R6 is:
It is set to be (0.1 to 0.3) times the second radius _R4 .

1 and 4, the cord angle θ ₃ between the carcass 36 and the breaker 37 in the tire 1
has the following structure.

That is, first, the material of the tread rubber has a hardness (JiS-A) of 60° to 65°, a dynamic viscoelastic property of 20°C,
Loss tangent (tanδ) 0.15 or more at 110Hz, dynamic elastic modulus
(E) If the weight is 20 Kg/cm ² or more and the hysteresis loss is relatively large, the cord angle θ ₃ of the carcass 36,
That is, the angle of the cord of the carcass 36 with respect to an imaginary line 38 perpendicular to the tread centerline 7 is from 47° to less than 52°.

Second, the material of the tread rubber has a hardness of 55°~
60゜Dynamic viscoelastic properties at 20℃ and 110Hz, loss tangent (tan δ) 0.15 or less, dynamic elastic modulus (E) ′15Kg/cm ² or less,
In addition, when the hysteresis loss is relatively small, the cord angle θ ₃ of the carcass 36 is set from 52° or more to 57°.

Thirdly, when a breaker 37 is added to the carcass 36 using the second tread rubber material,
The cord angle θ ₃ of the carcass 36 and the breaker 37 is from 47° to less than 52°.

In the above case, the carcass 36 and breaker 37 are made of two strands of 840 denier nylon cord.
Alternatively, it is a 1260 denier two-stranded or polyester cord, the carcass 36 is 2 ply, the playback 37 is 1 or 2 ply,
Adjacent plies are sequentially laminated at a cord angle θ ₃ ' opposite to the virtual line 38.

However, under each of the above conditions, the noise level is small within the range of the code angle θ ₃ , and the noise level is large outside the same range.

Next, experimental results using tires configured as described above will be shown.

<For tires with tire size 5.00-10> Number of modes: 5 Number of pitches in 1 mode: 6 Short radius: 80 mm Long radius: 150 mm Tire internal pressure: 1.8 Kg/cm ² Load: 260 Kg On a general road under the above conditions When driving at 80km/h and measuring the sound inside the car, the noise level was 75.
(dB), which was slightly lower than the noise level measured using snow tires at the same speed, and did not pose any problem for vehicle operation. Moreover, while the noise level (dB) for each frequency (Hz) of the above-mentioned noise has a large difference in snow tires, the tire according to the present invention has a relatively small difference. The tires achieved a perceptible reduction in noise compared to the noise level.

In addition, in a running experiment in a field, when both the front and middle layer hardness (read value) were 25Lbs, the tire according to the present invention was able to run and start, and the snow tire
This would not have been possible with regular ribbed tires.

In addition, in running tests on grass and sand, the tires showed no inferiority in running performance compared to snow tires or regular ribbed tires.

According to the present invention, since the tread 2 is formed with a major radius _R1 and a minor radius _R2 , extreme uneven wear of the four tread end areas (shoulder portions), which has been a problem in the past, can be prevented, and The uniform contact of the tread 2 with the running surface suppresses the generation of noise and vibration, which is advantageous.

In addition, since the pitches of the first and second modes 15 and 17 are varied and both modes 15 and 17 are offset in the circumferential direction, the noise and vibration generated from the tire 1 during driving are dispersed. Beneficially, low noise and vibration are achieved.

Furthermore, since the area ratio between the lug portion 20 and the tread groove 19 is set appropriately, and the tread groove 19 is set at a predetermined intersection angle θ ₁ , the lug portion 20
0 is effectively embedded in the surface on which the vehicle is being driven, making it possible to travel on sandy terrain or in fields, which is beneficial.

In addition, since the tread groove 19 is configured to gradually widen from the bottom toward the opening in its longitudinal cross section, even soil that gets stuck in the tread groove 19 easily separates from the tread groove 19. The breaking performance is improved, which is particularly beneficial when driving in the field. Furthermore, since the bottom surface of the longitudinal cross section of the tread groove 19 is formed to be smooth and gradually deepen toward the tread end 4, the air in the tread groove 19 that is compressed by the running surface is directed outward toward the outside of the tire. Therefore, no abnormal plosive sound is generated during driving, and therefore, noise reduction is achieved, which is beneficial.

In addition, since the tread center line side groove ends 23 are arranged far and near to the tread center line 7, the noise and vibration generated from the tire 1 during driving are dispersed and averaged. Beneficially, low noise and vibration are achieved.

However, in view of the overall structure of the present invention, the tire 1 according to the present invention is advantageous because it can run with low noise and low vibration both on general roads and on soft ground such as fields.

[Brief explanation of drawings]

The figures show embodiments of the present invention, in which Figure 1 is a meridional cross section of the tire, Figure 2C is a partial view of the tread, and Figure 2C is a partial view of the tread.
Figure a is a simplified diagram showing a modified example of the tread, Figure 3 a
Figures i to i are taken from the direction of arrows A-A in Figure 2c to I, respectively.
- FIG. 4 is a partial sectional view corresponding to the direction of the arrow I, and is an explanatory diagram showing the cord angle of the carcass and the breaker. 1...Tire, 2...Tread, 3...Tread center outer surface, 4...Tread end, 5...Tread end outer surface, 7...Tread center line, 9...Tread half surface, 10...Virtual Line, 12...Ku Naribe,
13...Forward half mode, 14...Reverse half mode, 15...First mode, 16...Other half of the tread, 17...Second mode, 18...Tread side wall, 19...Tread groove, 20 ...Lug section, 21
... Tread end groove, 23 ... Tread center line side groove end, 26 ... Annular groove, 27 ... Wall surface, 29 ...
Tread center line side bottom surface, 32...Intermediate portion bottom surface, 3
3...Tread end bottom surface, R ₁ ... Major radius, R ₂ ...
...short radius, W ₁ ... tread width, W ₂ ... tire width, W ₃ ... tread center outer surface width, L ₁ ... 1 mode circumferential length.

Claims (1)

[Claims] 1 The tread center outer surface 3 in the meridian section of the tire is shaped like a crown with a semi-major radius R ₁ , and the tread end outer surface 5 from the center outer surface 3 end to the tread end 4 is on a tangent to the center outer surface 3 end. A plurality of imaginary lines 1 are extended in the form of a crown with a minor radius R ₂ and are perpendicular to the tread center line 7 at intervals on the tread half plane 9 relative to the tread center line 7.
0 is set, and the pitches _lo , _lo-1 ... _l1 , _l0 of the virtual lines 10 adjacent to each other in the circumferential direction of the tread reach the minimum pitch _l0 from the maximum pitch _lo in one direction in the circumferential direction. From the maximum pitch _{l0 to the minimum pitch l0 ,} the tread center line 7 and the adjacent imaginary lines 10 move in the positive direction. half mode 13, and the positive half mode 13
The virtual lines 10 adjacent from the end in the same circumferential direction are arranged at the same pitches l ₀ , _{l 1 . .} .
are integrated into a first mode 15, while the reverse half mode 14 and the forward half mode 13 are successively adjacent to each other in the same circumferential direction on the other half of the tread 16,
These two half modes 14 and 13 are integrated into a second mode 17, and the same number of the first and second modes 15 and 17 are arranged as a positive integer all around the circumference, and both modes 15 and 17 are arranged as a positive integer. A phase difference is given in the circumferential direction by (1/24 to 5/24) times the mode circumferential length _L1 . Tread grooves 19 extending toward the line 7 are formed, and the area between these tread grooves 19 is used as a lug portion 20, and the area ratio of the lug portion 20 to the tread groove 19 in each section 12 is approximately equal to that of each section 12. The area ratio of the lug portion 20 and the tread groove 19 is (1.2±0.3):1, and the tread groove 19 portion in the four tread end areas is substantially straight in the longitudinal direction, and all The above-mentioned portion of the tread groove 19 of
formed approximately parallel to each other with an intersection angle θ ₁ of ~10°,
The cross section at each position in the longitudinal direction of each tread groove 19 is configured such that the groove width gradually increases from the bottom of the tread groove 19 toward the opening. The groove edge angle θ ₂ is (20° to 40°) with respect to the vertical line 28 of , while the longitudinal cross-section of each tread groove 19 is
The tread centerline side groove end 23 is located in front of the tread centerline 7, the tread centerline side bottom surface 29 of the tread groove 19 is a concave arc surface, and the intermediate portion bottom surface 32 extending from the tread centerline side bottom surface 29 is a concave arc surface. convex arc surface,
A tread end side bottom surface 33 extending from the intermediate bottom surface 32 is formed as a second concave arc surface, and these continuous bottom surfaces 29, 32, 33 gradually extend from the outer surface of the lug portion 20 toward the tread end 4. The tread centerline side groove ends 23 of the tread groove 19 are formed at alternately far and near positions in the tread circumferential direction with respect to the tread centerline 7, and the tread centerline side groove ends 23 at the far position and the near side groove ends 23 of the tread centerline A tire for running on soft ground, characterized in that the position is substantially the same as each tread center line side groove end 23 in the tread width direction.