JP2008024270A - Tire for agricultural use - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire for agricultural use capable of reducing vibration during the traveling by uniforming the ground contact pressure of a lug 4. <P>SOLUTION: Each lug 4 comprises a shoulder part 6 formed close to a side wall part 5 of a tire body 2, and a center side ground contact part 7 formed on an equatorial plane EP side from the shoulder part 6 in the width direction X. An edge 16 closer to the equatorial plane of the center side ground contact part 7 is formed in a substantially arc-shaped or substantially straight manner. The length L1 in the circumferential direction Y of the substantially arc-shaped or the substantially straight edge 16 is set to be larger than the length L2 in the circumferential direction Y of the shoulder part 6. The length L1 in the circumferential direction Y of the substantially arc-shaped or substantially straight edge 16 is 35-60% of the pitch P of the center side ground contact part 7 of the first lug 4a and the center side ground contact part 7 of the second lug 4b. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an agricultural tire mounted on an agricultural machine such as a tractor.

Conventionally, as this type of agricultural tire, for example, a lug provided near one sidewall portion of a tire body and a lug provided near the other sidewall portion are alternately formed in the tire circumferential direction. (See, for example, Patent Document 1).
The lug of the agricultural tire is formed in a bent shape in the middle thereof, and each lug is formed so that a part thereof overlaps with each other in the tire circumferential direction.
The lugs of agricultural tires are formed with their tip portions reaching the equator plane, and each lug is formed with its tip portion overlapping in the tire width direction. In addition, each lug is formed with a substantially constant length in the tire circumferential direction (the width of the lug) from the end on the side of the sidewall to the tip in plan view.
Japanese Patent Laid-Open No. 9-109617

In conventional agricultural tires, the width of the lugs is constant, and the tip of each lug is formed to reach the equator, so the tip of the lug is on the other part, especially the shoulder on the side of the sidewall. In comparison, the ground pressure increased, causing vibration during traveling.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an agricultural tire in which the ground contact pressure of a lug is made uniform to reduce vibration during traveling.

In order to solve the above problems, the present invention has taken the following technical means.
That is, the present invention is for agriculture in which the first lug formed on one side in the width direction across the equatorial plane of the tire body and the second lug formed on the other side in the width direction are alternately formed in the circumferential direction. In the tire, each lug includes a shoulder portion formed near the sidewall portion of the tire body, and a center-side grounding portion formed on the equator side from the shoulder portion, and the center-side grounding The edge of the portion near the equator plane is formed in a substantially arc shape or a substantially straight line along the equator plane, and the circumferential length of the substantially arc shape or the substantially straight edge portion is the circumference of the shoulder portion. The circumferential length of the substantially arcuate or substantially straight edge is the pitch dimension of the central grounding portion of the first lug and the central grounding portion of the second lug. It is characterized by being 35% to 60%.

Further, in the present invention, of the first lug and the second lug, a center grounding portion of one lug and a shoulder portion of the other lug are formed so as to overlap in the circumferential direction. A line drawn in the width direction from the widthwise outer end of the shoulder portion at the rear edge portion intersects the substantially arc-shaped or substantially linear edge portion of the center-side grounded portion as a boundary. When the straight edge is divided into a front part and a rear part, the circumferential length of the rear part is longer than the circumferential length of the front part.
Further, according to the present invention, the substantially arcuate or substantially linear edge of the center side grounding portion of each lug is formed substantially coincident with the equator plane of the tire body or formed away from the equator plane in the width direction. It is characterized by being.

Further, according to the present invention, the tread portion between the shoulder portion of the first lug and the shoulder portion of the second lug is formed with a concave portion having an arc shape when viewed from the side. Alternatively, when the lug height of the substantially linear edge is H1, and the lug height at the outer end in the width direction of the shoulder portion of each lug is H2, the ratio of H2 to H1 is 20 to 80%. It is characterized by that.
Further, the present invention is for agriculture in which first lugs formed on one side in the width direction across the equator plane of the tire body and second lugs formed on the other side in the width direction are alternately formed in the circumferential direction. In the tire, each lug is formed in a bent shape in plan view, a shoulder portion formed near the sidewall portion of the tire body, a tip portion formed near the equator plane, a shoulder portion and a tip portion An intermediate portion formed between the front edge portion and the rear edge portion of the intermediate portion. The intermediate edge portion is formed in a substantially arc shape or a substantially straight line shape. And the rear edge is inclined at an angle of 2 ° to 15 ° with respect to the front edge so that the rear edge is divergent from the tip toward the shoulder. It is characterized by being.

  According to the present invention, the grounding pressure of the lug can be made uniform to reduce vibration during traveling.

The best mode for carrying out the present invention will be described below with reference to the drawings.
In the first embodiment shown in FIGS. 1 to 3, an agricultural tire 1 according to the present invention is formed by projecting a plurality of lugs 4 on a tread portion 3 of a tire body 2. The agricultural tire 1 moves forward when rotated in the direction of arrow Z in FIG. 1 (hereinafter referred to as “pre-rotation”) in a state where the tire 1 is mounted on a vehicle (agricultural machine) such as a tractor. ing. Hereinafter, the side toward the front rotation direction Z is referred to as “front side”, and the opposite side is referred to as “rear side”.
The lugs 4 are made of rubber and are formed at intervals in the circumferential direction of the tire body 2 (hereinafter simply referred to as “circumferential direction”). Here, the “circumferential direction” refers to the circumferential direction of the tire body 2. Further, this “circumferential direction”, when expressed in a plan view as shown in FIG. 1, is perpendicular to the equator plane EP (the rotation axis of the tire main body 2 passing through the center of the traveling body main body 2 in the width direction) along the paper surface. (Referred to as Y). In this embodiment, the “width direction” refers to a direction parallel to the rotation axis of the tire body 2 (a direction indicated by a symbol X in FIG. 1).

As shown in FIG. 1, the lug 4 includes a first lug 4 a formed on one side in the width direction X across the equator plane EP in the tire body 2 and a first lug formed on the other side in the width direction X. 4b. The first lugs 4 a and the first lugs 4 b are alternately formed in the circumferential direction Y of the tire body 2.
In the first embodiment, the first lug 4a and the first lug 4b are formed by reversing the same shape left and right. The first lug 4a and the first lug 4b are formed on the tire body 2 with a predetermined pitch dimension.
As shown in FIG. 1, each lug 4 (4a, 4b) is formed in the tire body 2 so as to be inclined at a predetermined angle with respect to the equator plane EP in plan view.

Further, sidewall portions 5 are formed on the tire body 2 at both end portions in the width direction X.
The lug 4 includes a shoulder portion 6 formed closer to the sidewall portion 5, and a center side grounding portion 7 provided closer to the center side (equatorial plane EP side) in the width direction X of the tire body 2 than the shoulder portion 6. And have. Of the first lug 4 a and the first lug 4 b, the center side grounding portion 7 of one lug 4 is formed so as to overlap the shoulder portion 6 of the other lug 4 in the circumferential direction Y.

Each lug 4 (4a, 4b) has a front edge 8 and a rear edge 9. A straight leading edge 10 is formed between the front edge 8 and the rear edge 9 at the center grounding portion 7 of the lug 4.
The front edge portion 8 of each lug 4 (4a, 4b) is a portion that exerts traction force by stepping on the ground when the agricultural tire 1 makes a forward rotation and kicking up the ground when leaving the ground. It is.
As shown in FIG. 1, the front edge 8 of the lug 4 is formed in a bent shape at two points A and B. The front edge portion 8 includes a linear first line segment 11 between the sidewall portion 5 of the tire body 2 and the bending point A, and a linear first segment 11 between the bending point A and the bending point B. A straight third line segment 13 is formed between the two line segments 12 and the bending point B to the tip edge 10. The angle formed by the first line segment 11 and the second line segment 12 and the angle formed by the second line segment 12 and the third line segment 13 are obtuse angles.

The rear edge 9 of each lug 4 (4a, 4b) is formed in a bent shape at two points of bending points C and D. The rear edge 9 has a fourth straight line segment 14 between the sidewall 5 and the bending point C, and a curved fifth line between the bending point C and the bending point D. A substantially straight sixth line segment 16 is formed between the segment 15 and the bending point D to the tip edge 10. The sixth line segment 16 may be formed in a substantially arc shape. Here, the “substantially circular arc shape” includes not only one having a constant curvature radius but also a curved shape such as an ellipse or the like whose curvature radius is not constant.
The fourth line segment 14 together with the first line segment 11 of the front edge 8 constitutes the shoulder portion 6 of each lug 4 (4a, 4b). The shoulder portion 6 is a lug portion from the bending point A to the sidewall portion 5 between the first line segment 11 and the fourth line segment 14.

The fifth line segment 15 is formed in an arc shape that is recessed toward the second line segment 12 of the front edge 8.
The sixth line segment 16 is formed closest to the equator plane EP in the width direction X in each lug 4 (4a, 4b), and is an edge near the equator plane EP in each lug 4 (4a, 4b), that is, the center. The side grounding portion 7 is an edge near the equator plane EP. As shown in FIG. 1, the sixth line segment 16 is formed along the circumferential direction Y of the tire body 2 (parallel to the circumferential direction Y). Each lug 4 (4a, 4b) is formed such that the sixth line segment 16 substantially coincides with the equator plane EP. Here, “substantially coincide” means that the sixth line segment 16 coincides with the equator plane EP, or that the sixth line segment 16 is slightly separated without reaching the equator plane EP, or On the contrary, the sixth line segment 16 protrudes from the equator plane EP and is slightly separated (see FIG. 1 and the like).

The sixth line segment 16 is “slightly separated” means that the distance in the width direction X between the sixth line segment 16 and the equatorial plane EP is 1% or more of the length T in the width direction X of the tire body 2. It means 15% or less. The separation distance between the sixth line segment 16 and the equator plane EP is more preferably 10% or less of the length T in the width direction X of the tire body 2, and further preferably 5% or less. In this embodiment, this separation distance is 5% or less of the length T in the width direction X of the tire body 2.
The sixth line segment 16, which is an edge portion of the lug 4 near the equator plane EP, is formed such that the length L 1 in the circumferential direction Y is longer than the length L 2 in the circumferential direction Y of the shoulder portion 6.

The length L1 of the sixth line segment 16 in the circumferential direction Y is 35% to 60% of the pitch dimension P of the center side grounding portion 7 of the first lug 4a and the center side grounding portion 7 of the second lug 4b. It is desirable to be within range.
The center side grounding portion 7 of the lug 4 is on the equator plane EP side with respect to the bending point A of the front side edge portion 8, and is the second line segment 12, the third line segment 13, the fifth line segment 15, and the sixth line segment. 16, and a portion surrounded by the tip edge 10.
As shown in FIG. 2, the tread portion 3 of the tire main body 2 has a curved surface such that the surface thereof protrudes outward in the radial direction of the tire main body 2 from the side of the sidewall portion 5 toward the equator plane EP. It has become.

  Therefore, the distance from the tread portion 3 to the top surface of the lug 4 at the position near the sidewall portion 5 (hereinafter referred to as lug height) is the top of the lug 4 from the tread portion 3 at the position near the equatorial plane EP. It is higher than the rug height to the surface. The lug height at the substantially straight edge (sixth line segment 16) of the center side grounding portion 7 of each lug 4 (4a, 4b) is H1, and the shoulder portion 6 of the same lug 4 is outside the width direction X. When the edge lug height is H2, the ratio of H2 to H1 is 20 to 80% as a percentage {(H1 / H2) × 100 = 20 to 80 (%)}.

As shown in FIG. 3, the tread part 3 between the shoulder part 6 of the first lug 4a and the shoulder part 6 of the second lug 4b is formed with a concave part 21 having an arc shape in a side view. The recess 21 is formed continuously from the base of the shoulder 6 of the first lug 4a to the base of the shoulder 6 of the second lug 4b.
According to the above, the 6th line segment 16 along the circumferential direction Y is formed in the edge near the equatorial plane EP of each lug 4 (4a, 4b) of the agricultural tire 1, and the circumference of this 6th line segment 16 is formed. Since the length L1 in the direction Y is longer than the length L2 in the circumferential direction Y of the outer end in the width direction X of the shoulder portion 6 of the lug 4, the grounding of the top surface of the central grounding portion 7 of the lug 4 The area becomes larger than the ground contact area of the top surface of the shoulder portion 6, and thereby the ground pressure of the center side ground contact portion 7 of the lug 4 becomes smaller than when the sixth line segment 16 is not provided.

In the center-side grounding portion 7, the ratio of the lug 4 (center-side grounding portion 7) to the tread portion 3 in the vicinity of the equator plane EP increases, and the contact pressure decreases, so that the surface pressure difference near the equator plane EP is reduced. As a result, the agricultural tire 1 can be smoothly rotated.
When viewed from the longitudinal rigidity of the lug 4, the center side grounding portion 7 is formed with the sixth line segment 16 to increase the lug volume (volume) of this portion with respect to the high rigidity of the shoulder portion 6. The rigidity distribution difference in the rotation direction is reduced.
Moreover, if the edge part (6th line segment 16) near the equatorial plane EP of the center side grounding part 7 is a substantially circular arc shape or a substantially straight line shape, it will not affect the soil removal property behind the adjacent lugs 4. .

Moreover, the length L1 of the circumferential direction Y of the edge part (6th line segment 16) near the equatorial plane EP of the center side grounding part 7 of each lug 4 is the center side grounding part 7 and 2nd lug of the 1st lug 4a. By being within the range of 35% to 60% of the pitch dimension P of the center-side grounding portion 7 of 4b, the agricultural tire 1 suppresses vibration during traveling and also exhausts while exhibiting sufficient traction force. It becomes a good soil.
The ratio L1 / P between the length L1 of the sixth line segment 16 in the circumferential direction Y and the pitch dimension P of the central grounding portion 7 of the first lug 4a and the central grounding portion 7 of the second lug 4b is 35%. If it is less, the area of the center grounding portion 7 is small, and the effect of reducing the surface pressure difference is weakened. Moreover, when L1 / P exceeds 60%, cracks between lugs 4 may occur, or the soil removal property may be deteriorated.

Moreover, the recessed part 21 is formed in the tread part 3 between the shoulder part 6 of the 1st lug 4a, and the shoulder part 6 of the 2nd lug 4b, and also the center side grounding part 7 of each lug 4 (4a, 4b) The ratio between the lug height H1 at the substantially straight edge (sixth line segment 16) and the lug height H2 at the outer end in the width direction X of the shoulder portion 6 of the same lug 4 is set to 20 to 80% as a percentage. Accordingly, the agricultural tire 1 has a high traction force of the lug 4 and a good soil removal property. In this case, the agricultural tire 1 is particularly effective when used for wet fields.
Moreover, the agricultural tire 1 according to the present invention can increase the fall angle limit of a traveling vehicle such as a tractor while maintaining the rigidity of the shoulder portion 6.

In the second embodiment of FIG. 4, the shape of the rear edge 9 of the lug 4 is different from that of the first embodiment. In the second embodiment, the rear edge 9 of the lug 4 is formed in a bent shape at one bending point E. The fifth line segment 15 shown in the first embodiment is not formed on the rear edge 9 of the lug 4. A fourth line segment 14 is formed on the rear edge 9 of the lug 4 from the sidewall 5 of the tire body 2 to the equator plane EP. A sixth line segment 16 similar to that of the embodiment is formed along the circumferential direction Y.
Also in the second embodiment, as in the first embodiment, of the first lug 4a and the first lug 4b, one central side grounding portion 7 is in the shoulder portion 6 of the other lug 4 and in the circumferential direction Y. It is formed by overlapping.

The shoulder portion 6 includes a portion where the end portion on the side wall portion 5 side does not contact the ground. Hereinafter, this portion is referred to as a non-grounding portion 6a, and a portion closer to the equator plane EP than the non-grounding portion 6a is referred to as a grounding portion 6b.
The length of the non-grounding portion 6a in the width direction X is about 5 to 6% of the length T of the tire body 2 in the width direction X.
In FIG. 4, a boundary line (two-dot chain line) G between the non-grounding portion 6 a and the grounding portion 6 b is drawn along the circumferential direction Y. Hereinafter, the intersection point between the boundary line G and the rear portion of the shoulder portion 6, that is, the intersection point H between the boundary line and the fourth line segment 14, is referred to as “width direction X of the shoulder portion 6 at the rear edge portion 9 of the lug 4. Is called the outer end H ”.

  In the second embodiment, as in the first embodiment, the sixth line segment 16 of each lug 4 (4a, 4b) is formed along the circumferential direction Y at a position corresponding to the equator plane EP. Moreover, the length L1 in the circumferential direction Y of the sixth line segment 16 of each lug 4 (4a, 4b) is longer than the length L2 in the circumferential direction Y of the shoulder portion 6. In addition, when comparing the length L1 in the circumferential direction Y of the sixth line segment 16 and the length L2 in the circumferential direction Y of the shoulder portion 6, for example, the width direction of the shoulder portion 6 in the rear side edge portion 9 is used. The length in the circumferential direction Y at the position of the outer end H of X may be used as a reference.

When the first lug 4a and the first lug 4b are drawn with a line J parallel to the width direction X from the outer end H in the width direction X of the rear edge 9 of the one lug 4, the other lug It overlaps with the circumferential direction Y so that this line J may cross | intersect the 4th 6th line segment 16. FIG. Hereinafter, the intersection of the line J and the sixth line segment 16 is referred to as a bisector K of the sixth line segment 16.
The sixth line segment 16 of each lug 4 (4a, 4b) is divided into a front side portion 16a and a rear side portion 16b with a bisector K as a boundary. The length L3 in the circumferential direction Y of the rear portion 16b is formed longer than the length L4 in the circumferential direction Y of the front portion 16a.

In the second embodiment, as in the first embodiment, the length L1 in the circumferential direction Y of the sixth line segment 16 is in the circumferential direction Y of the shoulder 6 at the position of the outer end H in the width direction X of the shoulder 6. It is made larger than length L2, and the contact pressure of lug 4 is equalized like the case of a 1st embodiment.
In the conventional agricultural tire, when the center side contact portion 7 of the lug 4 overlaps the shoulder portion 6 of the latest lug 4, the contact pressure of the center side contact portion 7 increases. It turns out.

In view of this, in the second embodiment, the length L3 in the circumferential direction Y of the rear portion 16b of the sixth line segment 16 is further made longer than the length L4 in the circumferential direction Y of the front portion 16a. In the center-side grounding portion 7 of each lug 4 (4a, 4b), the grounding area of the non-overlapping portion is made larger than the portion overlapping the shoulder portion 6 of the latest lug 4. Thereby, the ground pressure of the center side grounding part 7 can be made lower than before, and the ground pressure of the lug 4 can be made uniform, and the agricultural tire 1 according to the second embodiment exhibits a higher vibration suppressing effect.
In addition to the above configuration, in the second embodiment, portions common to the first embodiment are denoted by common reference numerals, and the configuration and operation of this portion are the same as those in the first embodiment (hereinafter, referred to as the first embodiment). The same in other embodiments).

In the third embodiment shown in FIG. 5, as in the first embodiment, the first lugs 4a and the first lugs 4b are alternately formed in the circumferential direction Y of the tire body 2, and each lug 4 (4a, 4b) is formed. The front edge 8 and the rear edge 9 are bent at a plurality of locations.
As with the first embodiment, each lug 4 (4a, 4b) has its front edge 8 bent at two bending points A and B, and the front edge 8 has A linear first line segment 11, second line segment 12, and third line segment 13 are formed in this order from the side wall 5 side toward the center-side grounding unit 7. Similarly, the rear edge 9 of each lug 4 (4a, 4b) is formed in a bent shape at two points C and D, and the rear edge 9 is formed on the side wall 5 side. A fourth line segment 14, a fifth line segment 15, and a sixth line segment 16 are formed in this order toward the center-side grounding portion 7.

In the third embodiment, a portion between the first line segment 11 and the fourth line segment 14 is referred to as a shoulder portion 6, and a portion between the second line segment 12 and the fifth line segment 15 is referred to as an intermediate portion 18. A portion between the third line segment 13 and the sixth line segment 16 is referred to as a tip portion 19. The intermediate portion 18 and the tip portion 19 correspond to the center-side grounding portion 7 shown in the first embodiment. The sixth line segment 16 of each lug 4 (4a, 4b) is formed to be inclined at a predetermined angle with respect to the circumferential direction Y.
An intermediate portion 18 between the shoulder portion 6 and the tip end portion 19 of each lug 4 (4a, 4b) has an inclination angle with respect to the equator plane EP of the second line segment 12 which is the front edge thereof, and a fifth line segment. The inclination angles with respect to 15 equatorial planes EP are different.

The intermediate portion 18 is formed such that the length in the circumferential direction Y at the position of the bending point A is longer than the length in the circumferential direction Y at the bending point B. The intermediate portion 18 is formed such that the length in the circumferential direction Y gradually increases from the distal end portion 19 side toward the shoulder portion 6 side.
Further, in the plan view, the intermediate portion 18 has a second line segment 12 which is a front edge portion thereof and a fifth line segment 15 which is a rear edge portion of the intermediate portion 18 from the front end portion 19 side of the lug 4. It is desirable that the fifth line segment 15 is formed so as to be inclined in the range of 2 ° to 15 ° with respect to the second line segment 12 so as to be widened toward the portion 6. The angle formed by the fifth line segment 15 and the second line segment 12 is indicated by θ in the figure.

In the third embodiment, the fifth line segment 15 that is the rear edge of the intermediate portion 18 is at a predetermined angle θ (2 ° to 15 °) with respect to the second line segment 12 that is the front edge. Since it is formed, the ground contact area can be increased as compared with the conventional case where the length of the lug 4 in the circumferential direction Y is constant.
That is, as shown in FIG. 5, when a virtual line segment P parallel to the second line segment 12 is drawn from the bending point C to the bending point D, a predetermined area is grounded behind the virtual line segment P. A portion is formed, and the ground contact area can be increased compared to the case where the second line segment 12 and the fifth line segment 15 of the lug 4 are parallel, and by reducing the ground pressure of this part, By eliminating the difference from the contact pressure of the shoulder 6 and making the contact pressure uniform, the agricultural tire 1 can reduce vibration during traveling.

In the fourth embodiment shown in FIG. 6, the shoulder portion 6, the intermediate portion 18, and the tip portion 19 are formed on the lug 4 as in the third embodiment. As in the third embodiment, the intermediate portion 18 has a fifth line segment 15 that is the rear edge portion in a range of 2 ° to 15 ° with respect to the second line segment 12 that is the front edge portion. It is formed at an inclination angle θ.
In this 4th Embodiment, the shape of the 4th line segment 14 which is the edge part of the rear side of the shoulder part 6 of each lug 4 (4a, 4b) differs from 3rd Embodiment. In the fourth line segment 14, a portion 14a on the side wall portion 5 side is linear, a portion 14b on the intermediate portion 18 side is formed in a curved shape, and the curved portion 14b is formed at a bending point C. It is connected to the fifth line segment 15 which is the rear edge of the intermediate portion 18.

Also in the fourth embodiment, as in the third embodiment, the second line segment 12 and the fifth line segment 15 of the lug 4 are parallel to each other, and the circumferential length (the width of the lug) is constant. Compared to the conventional case, the ground contact area can be increased, the ground pressure of the intermediate portion 18 is reduced, the difference from the ground pressure of the shoulder portion 6 is eliminated, and the ground pressure is made uniform. The tire 1 can reduce vibration during traveling.
In 5th Embodiment shown in FIG. 7, the shape of the front edge part 8 of each lug 4 (4a, 4b) differs from 1st Embodiment. In the first embodiment, the front edge 8 of each lug 4 (4a, 4b) is formed in a bent shape at a plurality of locations in plan view. However, in this fifth embodiment, each lug 4 (4a, 4b) is formed. The front side edge portion 8) is curved in an arc shape in plan view. The other structure of the lug 4 is the same as 1st Embodiment.

In the fifth embodiment, the length of the lug 4 in the width direction X from the end in the width direction X of the lug 4 (refers to the direction from the equatorial plane EP toward the sidewall portion 5 in the width direction X). A portion up to 1/3 is the shoulder portion 6, and the remaining approximately 2/3 portion is the center side grounding portion 7.
Also in the sixth embodiment, the vibration from the center-side grounding portion 7 of the lug 4 is formed by forming a substantially arc-shaped or substantially straight sixth line segment 16 along the circumferential direction Y as in the first embodiment. Can be reduced.

The present invention is not limited to the above embodiment, and various modifications and changes can be made.
For example, in the above-described embodiment, the agricultural tire 1 having a shape in which the first lug 4a and the first lug 4b have the same shape and the left and right sides are reversed is illustrated, but the first lug 4a and the first lug 4b have the same shape. Not limited to this, it may be an irregular shape. The fifth line segment 15 of the lug 4 shown in the first embodiment is not limited to a curved shape, and may be formed in a linear shape. Of the first lug 4a and the second lug 4b, the sixth line segment 16 of one lug is made to coincide with the equatorial plane EP, and the sixth line segment 16 of the other lug is formed separated from the equatorial plane EP by a predetermined distance. It may be. In the third and fourth embodiments, the inclination angle (2 ° to 15 °) of the fifth line segment 15 with respect to the second line segment 12 may be different between the first lug 4a and the second lug 4b. The front edge 8 and the rear edge 9 of the lug 4 are bent at one or two places, but may be bent at three or more places.

  The present invention can be used as a wheel of an agricultural machine such as a tractor.

1 is a partial plan view of an agricultural tire according to a first embodiment of the present invention. It is a partial section perspective view of the tire for agriculture similarly. It is a partial side view of an agricultural tire. It is a partial top view of the agricultural tire which concerns on 2nd Embodiment of this invention. It is a fragmentary top view of the agricultural tire which concerns on 3rd Embodiment of this invention. It is a partial top view of the agricultural tire which concerns on 4th Embodiment of this invention. It is a partial top view of the agricultural tire which concerns on 5th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Agricultural tire 2 Tire main body 4 Lug 4a 1st lug 4b 2nd lug 6 Shoulder part 7 Tip part 16 Edge part EP Equatorial plane X Width direction Y Circumferential direction

Claims (5)

In the agricultural tire in which the first lug formed on the one side in the width direction across the equator plane of the tire body and the second lug formed on the other side in the width direction are alternately formed in the circumferential direction,
Each lug has a shoulder portion formed near the sidewall portion of the tire body, and a center-side grounding portion formed on the equator side of the shoulder portion,
The edge near the equator plane of the center side grounding part is formed in a substantially arc shape or a substantially straight line along the equator plane, and the circumferential length of the substantially arcuate or substantially straight edge portion is: It is longer than the circumferential length of the shoulder,
The circumferential length of the substantially arc-shaped or substantially linear edge is 35% to 60% of the pitch dimension of the center-side grounding portion of the first lug and the center-side grounding portion of the second lug. Agricultural tire characterized by. Of the first lug and the second lug, a central grounding portion of one lug and a shoulder portion of the other lug are formed to overlap in the circumferential direction,
The line drawn in the width direction from the widthwise outer end of the shoulder portion at the rear edge of each lug intersects with the substantially arcuate or substantially straight edge of the center side grounding portion. When the arc-shaped or substantially straight edge is divided into the front part and the rear part, the circumferential length of the rear part is longer than the circumferential length of the front part. The agricultural tire according to claim 1.   The substantially arcuate or substantially linear edge of the center side grounding portion of each lug is formed substantially coincident with the equator plane of the tire body, or is formed away from the equator plane in the width direction. The agricultural tire according to claim 1 or 2.   The tread portion between the shoulder portion of the first lug and the shoulder portion of the second lug is formed with a concave portion having an arc shape when viewed from the side, and the substantially arcuate or substantially straight edge of the center side grounding portion of each lug The ratio of H2 to H1 is 20 to 80%, where H1 is the lug height of the portion and H2 is the lug height at the outer end in the width direction of the shoulder portion of each lug. Item 4. The agricultural tire according to any one of Items 1 to 3. In the agricultural tire in which the first lug formed on the one side in the width direction across the equator plane of the tire body and the second lug formed on the other side in the width direction are alternately formed in the circumferential direction,
Each lug is formed in a bent shape in a plan view, a shoulder portion formed near the sidewall portion of the tire body, a tip portion formed near the equator plane, and between the shoulder portion and the tip portion And an intermediate part formed on
The intermediate portion has both a front edge and a rear edge formed in a substantially arc shape or a substantially straight shape, and the front edge and the rear edge are connected to the shoulder portion from the front end portion. The agricultural tire is characterized in that the rear side edge portion is inclined at an angle of 2 ° to 15 ° with respect to the front side edge portion so as to be widened toward the end.

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