JPS6336964B2 - - 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 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. An imaginary line adjacent in the same circumferential direction from the mode end is placed at the same pitch opposite to the above, forming a reverse half mode, and these two half modes are collectively called the first mode. The reverse half mode and the forward half mode are sequentially adjacent to each other in the circumferential direction, and these half modes are integrated into a second mode, and the same number of the first and second modes are set as a positive integer of the entire circumference. At the same time, both modes are set to 1.
A phase difference is given in the circumferential direction by (1/24 to 5/24) times the mode circumferential length, and each section is opened from the tread end to the tread side wall and extends from the opening toward the tread center line. 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 made substantially the same in each section.

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 tread 2 is approximately 0.9 times the tire width (W ₂ ), the central outer surface width W ₃ is (0.5±0.2) times the tread width W ₁ , and the major axis R ₁ is the tire width. It is (1.5±0.3) times _W2 , the short radius _R2 is 0.7±0.2 times the tire width _W2 , and the long radius _R1 is always longer than the short radius _R2 . 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, preferably, and the maximum pitch ln is the minimum pitch l ₀ (1.4 ~
2.0) times is preferred. In the above case, if the maximum pitch ln becomes 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. Also, if the above value becomes more than double, the maximum pitch ln and the minimum pitch ln increase. Pituchi
The difference between the sections 12 at l ₀ becomes too large, which is undesirable as it causes uneven wear.

Further, the virtual line 10 adjacent from the end of the forward half mode 13 in the same direction of the arrow ₁₁ as described above is arranged at the same pitches l ₀ , l ₁ . , the above forward/reverse half mode 13,1
4 are integrated into the first mode 15, and in the illustrated example, a half mode consists of 3 pitches, that is, 1 mode consists of 6 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 sequentially 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, which is (1/24 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 the tread 1, and on the other half of the tread 16, a bending groove 22 extends in the circumferential direction of the arrow 11 in the same manner as above, and each bend The ends of the curved 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 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 opposite circumferential direction of 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 26 that is continuous along the circumferential direction of the tread and is spaced apart from the tread groove 1.
is formed. In the illustrated example, tread grooves 1 alternately oppose the tread center line 7 in the tread circumferential direction.
The annular groove 26 is formed in a zigzag shape so as to bypass the tread center line side groove end 23 of No. 9, and the swing width W ₆ of this zigzag shape is approximately 0.1 of the tread width W 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 are connected to the tread center line. They are formed at the same position in the width 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 1 is connected to both opposing wall surfaces 27, 2.
7. 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). In addition, at the bent groove 22 position, the groove edge angle θ ₂ at the concave groove 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), 7 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).

FIG. 3J is a cross-sectional view in the longitudinal direction of the tread groove 19. 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 It is said to be approximately 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 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 is defined by a first radius (R ₃ ). It is formed into a concave arc surface. The first radius R ₃ has a dimension of (35±15 mm), and the concave arc surface passes through the tread center line side groove end 23 or the vicinity thereof, and the first radius R 3 has a radius R 3 having a center on the tire radial direction line 8. 2. The first radius R ₃ is approximately tangent to the arc of radius R ₄ .
The center of is determined. The center of the second radius _R4 is determined as follows. That is, in JISD4202
Approximately 0.1 of the S70 value (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 meridian section).
The second radius is located at a position that is twice the size and is offset in the direction perpendicular to the tire radial direction line 8, and passes through a virtual point 30 that is a predetermined groove depth from the surface of the tread 2.
An arc 31 of R ₄ is drawn, and the dimension of the second radius R ₄ is
It is set to be (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 , and an intermediate bottom surface 32 extends as a convex arc surface from the end of the center side bottom surface 29 . A tread end side bottom surface 33 extends from the end as a second concave arc surface, and the tread end side bottom surface 33 opens into 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 a dimension equal to (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 are each formed by 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, firstly, the material of the tread rubber has a hardness
JIS-A) is 60° to 65°, dynamic viscoelastic properties are 20°C,
When the loss tangent (tan δ) is 0.15 or more at 110 Hz, the dynamic elastic modulus (E) 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, perpendicular to the tread center line 7. virtual line 3
The angle of the cord of the carcass 36 with respect to 8 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°C and 110Hz, loss tangent (tan δ) 0.15 or less, dynamic elastic modulus (E) '15 Kg/cm ² or less, and hysteresis loss relatively small, carcass 36 code. Angle θ ₃ is from 52° or more
It is said to be up 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 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 general roads under the above conditions When I measured the sound inside the car while driving at 80kg/h, 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 was 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 vibration, which is beneficial.

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, respectively from the A-A line arrow view in Figure 2C to -
FIG. 3J is a sectional view showing a modification of the tread groove, and FIG. 4 is an explanatory view showing the cord angle between 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 One half of the tread 9 relative to the tread center line 7
A plurality of imaginary lines 10 are set perpendicular to the tread center line 7 at intervals, and the pitches ln, ln _-1 ...l ₁ , l ₀ of the imaginary lines 10 adjacent to each other in the tread circumferential direction are The pitch gradually decreases in one direction from the maximum pitch ln to the minimum pitch _l0 , and between the maximum pitch ln and the minimum pitch _l0 , the tread center line 7 and the adjacent virtual line 10 A group of 12 divided sections is defined as a positive direction half mode 13, and an imaginary line 1 adjacent in the same circumferential direction from the end of the positive direction half mode 13
0 is arranged at the same pitches l ₀ , _{l 1 .} On the other half of the tread 16, the reverse half mode 14 and the forward half mode 13 are sequentially adjacent to each other in the same circumferential direction. 1, the second modes 15 and 17 are arranged as positive integers all around, and both modes 15 and 17 are arranged as 1.
A phase difference is given in the circumferential direction by (1/24 to 5/24) times the mode circumferential length _L1 . Tread 19 extending towards line 7
is 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 and the tread groove 19 in each section 12 is made to be approximately the same in each section 12. Tire for driving on soft ground.