JPS6336965B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a tire for running on soft ground such as fields,
This invention relates to the provision of products aimed at allowing vehicles to run 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 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. It was impossible.

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 from one farm to another, 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 created in response to such conventional demands, and it can be used on general roads, in fields, on sandy soil,
The purpose of this tire is to provide a tire that can be used for running on soft terrain, allowing the vehicle to run smoothly and at high speed with low noise and low vibration even on soft terrain such as on snow. A plurality of imaginary lines are set perpendicular to the tread center line at intervals, and the pitch of the imaginary lines adjacent to each other in the tread circumferential direction reaches from the maximum pitch to the minimum pitch in one direction in the circumferential direction. The pitch decreases sequentially, and the group of sections defined by the tread center line and adjacent virtual lines from the maximum pitch to the minimum pitch is defined as a positive half mode. The imaginary lines adjacent from the end in the same circumferential direction are placed at the same pitch opposite to the above, making it a reverse half mode,
These two half modes are integrally defined as a first mode, while the reverse half mode and forward half mode are successively adjacent to each other in the circumferential direction on the other half of the tread, and these two half modes are integrally defined as a second mode. The same number of the first and second modes are arranged as positive integers all around the circumference, and both modes are 1
A phase difference is given in the circumferential direction by (1/24 to 5/24) times the mode circumferential length, and each section has an opening from the tread end to the tread side wall and extends from the opening toward the tread center line. The tread grooves are formed, and the area between these tread grooves is used as a lug portion, and the area ratio of the lug portion to the tread groove in each section is approximately the same, and the area between the lug portion and the tread groove is made to be approximately the same. The area ratio is (1.2±0.3):1, and
The tread groove portions in the tread end regions are substantially straight 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. It is at the point.

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

FIG. 1 shows a meridional cross-sectional shape of a tire 1 for running on soft terrain. In the meridional cross-section of the tire, the outer surface 3 of the center part of the tread 2 is crowned with a major radius R1, and the outer surface ₃ of the center part extends from the outer surface 3 of the tread to the end of the tread. The outer surfaces 5 of the tread ends up to 4 extend substantially tangentially to the ends of the outer surfaces 3 of the central portion and are crowned with a minor radius R ₂ .

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
The major axis R ₁ is (1.5 ± 0.3) times the tire width W _{2, the minor radius R 2 is} (0.7 ± 0.2) times the tire width W 2, and the long axis R ₁ is (0.5 ± 0.2) times the tire width W ₂ . The radius R ₁ is always the longer dimension than the minor radius R ₂ . The center point 6 of the major radius R ₁ is located on a tire radial direction line 8 perpendicular to the tread center line 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. The pitches ln, ln _-1 . . . l ₁ , l ₀ of the virtual lines 10 adjacent to each other in the circumferential direction of the tread are the maximum pitch ln toward one side in the circumferential direction, that is, in the direction of arrow 11 in FIG. 2C. The pitch decreases stepwise from the maximum pitch ln to the minimum pitch _l0 , and the distance from the maximum pitch ln to the minimum pitch _l0 is defined by the tread center line 7 and the adjacent virtual line 10. The sectional part 12 group is set as the positive direction half mode 13. The relationship between the adjacent pitches above is n = 2 → n (n is a positive integer),
log n/log(n _-1 ) = log(n _-1 )/log(n _-2 ) = constant,
is preferable, and the maximum pitch ln is the minimum pitch ln of ₀ (1.4 to 2.0)
Preferably, it is twice as large. In the above case, when the maximum pitch ln becomes less than 1.4 times the minimum pitch _l0 , the noise of the tire 1 during running becomes large, that is, the difference between the noise levels (dB) at each frequency (Hz) becomes large, This is undesirable, and if the above-mentioned value becomes twice or more, the difference between the sections 12 between the maximum pitch ln and the minimum pitch _l0 becomes too large, which causes uneven wear, which is undesirable.

Further, the virtual line 10 adjacent from the end of the forward half mode 13 in the same direction of the arrow 11 as above is arranged at the same pitches l ₀ , l ₁ ......ln _-1 , ln opposite to the above, and the reverse half mode 14 , and the above forward/reverse half mode 1
3 and 14 are integrated into the first mode 15, and in the illustrated example, half mode is 3 pitches, that is, 1 mode is 6 pitches.
It is composed of pituti.

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, are arranged as a single mode. and,
Both modes 15 and 17 are given a phase difference l in the circumferential direction that is (1/24 to 5/24) times the length L ₁ in the circumferential direction of one mode.

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 line 7 side, on the tread plane 9, arrow 11
Bending groove 2 curved convexly in a plan view in the opposite circumferential direction.
2 is extended, and on the other half of the tread 16, arrow 1
A bending groove 22 extends in the circumferential direction of the tread 1 in the same manner as above, and the groove width dimension of each bending groove 22, 22 at the end on the tread center line 7 side gradually becomes substantially linear toward the tread center line 7. It is said to have a triangular head shape that decreases to .

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 the virtual lines at the center of both virtual lines 10 in 2
4 and in front of the tread center line 7. In addition, on one half of the tread 9, the forward 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, and the width W ₄ in the opposite circumferential direction from the center line 24 between the imaginary lines. Reverse groove width
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 the width of the tread groove 19. The pitch is approximately 0.6 times the pitch l of both virtual lines in the section 12. On the other hand, on the other half of the tread 16, tread grooves 19 are formed in the circumferential direction opposite to the arrow 11 from the imaginary line center line 24 in the same manner as described above.

Tread center line 7 of each of the above-mentioned tread end grooves 21
The side ends are located at approximately the same position in the tread width direction, and are located approximately at the tread width W ₁ from the tread center line 7.
The bending apex 25 of the bending groove 22 is also located at approximately the same position in the tread width direction, and is located at a distance W ₁ from the tread center line 7
It is formed at a position approximately 0.27 times that of

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 substantially the same position in the tread width direction, and the tread center line side groove end 23 at the near position 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 at the far position Tread centerline side groove end 23
is a dimensional position from the tread center line 7 to (0.12 to 0.25) times the tread width _W1 .

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, and the runout width of this zigzag shape is 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 groove 19 is inclined with respect to an imaginary line 10 perpendicular to the tread center line 7, and the tread groove portion in the tread end 4 region is 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°.

FIG. 2b is a simplified diagram showing a modified example of the tread groove 19, in which the groove ends 23 on the tread center line side of the tread grooves 19 arranged in the circumferential direction of the tread on each half surface 9, 16 of the tread with respect to the tread center line 7 have a tread width. They are formed at the same position in the direction.

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 bending groove 22 position, the groove edge angle θ ₂ at the concave groove edge when viewed from the imaginary center line 24 is approximately 30° at the tread end 4 (left groove edge in FIG. 3c), and the tread center line 7 It is preferably approximately 35 degrees at the side (Figure 3 d), and approximately 25 degrees at the convex arc groove edge (Figure 3 c, right groove edge, Figure 3 g). In addition, the tread center line 7 of the bending groove 22
The groove edge angle θ ₂ at the side edge position 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).

FIG. 3j is a cross section in the longitudinal direction of the tread groove 19, and the cross section is a U-shaped groove with an upward opening, and the wall surface 27 of the tread groove 19 near the outer surface of the lug portion 20 is approximately parallel to the outer surface of the lug portion 20. considered to be vertical.

In the above case, the bottom surface of the tread groove 19 may be a concave arc surface with the opposing wall surfaces 27, 27 as tangents. Moreover, the cross section of the same as above may also be triangular.

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 dimension is approximately 0.1 times the S70 value in JiS D4202 (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 a virtual point 30 that is at a position perpendicular to the tire radial direction line 8 and is at a predetermined groove depth from the surface of the tread 2. 2 The dimensions of radius R ₄ are as above.
It is assumed to be (0.7 to 1.0) times the 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 , and an intermediate portion bottom surface 32 extends as a convex arc surface from the center side bottom surface 29 end. 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 _R6 , and both ends of the intermediate bottom surface 32 have a second radius.
The arc 31 due to R ₄ , that is, the end of the bottom surface 29 on the center side,
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 as follows:
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 the imaginary line 38 perpendicular to the tread center line 7 is from 47° to
It is considered to be less than 52°.

Second, the material of the tread rubber has a hardness of 55°~
60゜Dynamic viscoelastic properties are loss tangent (tanδ) 0.15 or less, dynamic elastic modulus (E)′15Kg/cm ² or less at 20℃ and 110Hz,
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 material of the carcass 36 and breaker 37 is two-stranded 840 denier nylon cord.
Or it is a 1260 denier two-stranded or polyester cord, the carcass 36 is 2 ply, the breaker 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 difference in the noise level (dB) for each noise frequency (Hz) is large in snow tires, the tire according to the present invention has a relatively small difference. Compared to the noise level, a perceptible reduction in noise was achieved.

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 invention, the first and second modes 15, 17
The pitch of each mode is changed variously, and both modes 1
Since the tires 5 and 17 are offset in the circumferential direction, the noise and vibration generated by the tire 1 during running are dispersed and averaged, thereby achieving low noise and low vibration, which is beneficial.

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 crossing angle θ ₁ , the lug portion 20 is effectively applied to the running surface. It will become embedded,
It is useful because it allows driving on sandy soil or in fields.

However, in view of the overall configuration 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 2 b
Figure 3a is a simplified diagram showing another modification of the tread.
Figures i to i are partial cross-sectional views corresponding to the arrows AA to - in Figure 2C, respectively, Figure 3j is a cross-sectional view showing a modified example of the tread groove, and Figure 4 is a cross-sectional view of the carcass. It is an explanatory view showing the code angle of a 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 One half of the tread 9 relative to the tread center line 7
A plurality of virtual lines 10 are set perpendicularly to the tread center line 7 at intervals, and the pitches of the virtual lines 10 adjacent to each other in the circumferential direction of the tread are ln, ln _-1 . . . l ₁ ,
l ₀ is configured to gradually decrease in one direction in the circumferential direction from the maximum pitch ln to the minimum pitch ln, and between the maximum pitch l ₀ and the minimum pitch l ₀ , the tread center line 7 and The imaginary line 12 adjacent to the adjacent imaginary line 10 is defined as a positive half mode 13, and the imaginary line 10 adjacent in the same circumferential direction from the end of the positive half mode 13 is the same pitch l which is opposite to the above. ₀ ，l ₁ ......ln _-1 ，
ln to form a reverse half mode 14, and these two half modes 13 and 14 together form a first mode 15, while the other half mode 16 of the tread is arranged in the same circumferential direction as the reverse half mode 14. The direction half modes 13 are sequentially adjacent to each other, and both half modes 14,
13 are integrated into a second mode 17, and the same number of the first and second modes 15, 17 are arranged as positive integers all around the circumference, and both modes 15,
17 is 1 mode circumferential length L ₁ (1/24 to 5/24)
A phase difference is given in the circumferential direction by double, and each section 12
A tread groove 19 is formed which opens from the tread end 4 into the tread side wall 18 and extends from the opening toward the tread center line 7, and the space between these tread grooves 19 is a lug portion 20. The area ratio of the lug portion 20 and the tread groove 19 is approximately the same in each section 12, and the lug portion 20
The area ratio between the tread groove 19 and the tread groove 19 is (1.2±0.3):
1, and the tread groove 19 portion in the tread end 4 region is substantially straight in the longitudinal direction, and the above-mentioned portion of all the tread grooves 19 is at an angle of 0 to 10 degrees with respect to the imaginary line 10 perpendicular to the tread center line 7. A tire for running on soft ground, characterized in that the tires are formed substantially parallel to each other at an intersection angle of θ ₁ .