JPS63222907A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve braking and turning performances by inclining the small grooves of a tire toward the forward side of a rotational direction from the deepest part to the open part thereof, and furthermore inclining the extension direction of the grooves toward an equator surface in a tire having small grooves separated from each other in a peripheral direction on a tread part. CONSTITUTION:A plurality of small grooves 11 are extended approximately in an axial direction at an equal pitch on the periphery of a tread part 3. And the small grooves 11 are so inclined as to be directed toward the forward side of a tire rotational direction 'Q' in the course of extension from the deepest part 10a to the open end 10b thereof. In this case, a crossing angle 'J' is set to about 5 deg.-30 deg. at the intersection of the small grooves 11 with a vertical line 'D' to the surface of the tread part 5 in a cross section in parallel with an equator surface 2. Also, the small grooves 11 are inclined toward the equator surface 2 at an angle 'K' so as to be directed to the rear side of the tire rotational direction 'Q', all the more in the vicinity of said surface 2. The inclination 'K' is set to about 50 deg.-80 deg.. According to the aforesaid constitution, braking and turning performances can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION =--1 The present invention relates to a pneumatic tire having a plurality of thin grooves spaced apart in the circumferential direction on the surface of a tread portion.

Differential speed J and first aid Conventionally, as a pneumatic tire provided with multiple thin grooves (slits), for example, Japanese Patent Application Laid-Open No. 54-12440
The one described in Publication No. 5 is known.

This is a tire in which each slit is inclined at an angle of 45 degrees or less with respect to the perpendicular line of the tread surface, and in a tire that focuses on braking, the slits are inclined in the direction of tire rotation from the deepest part to the open end. In addition, in a tire that focuses on driving, the slit is inclined in the direction of tire rotation, and in a tire that focuses on turning, the slit is inclined in the opposite direction to the direction of action of the axial input. I have to. As a result, when a tangential force is applied to these tires from the ground during braking, driving, or turning, the slits open and the acute edges of the slits catch on the road surface, improving grip.

However, with such tires, the slits open during braking, so they can catch the ground, but they only touch the ground near the acute edges. As a result, the ground contact area is reduced, and as a result, there is a problem in that it is hardly possible to improve the braking performance, etc. Moreover, each tire has the problem that its performance can only be achieved in response to input in one direction among braking, driving, and turning, and it cannot respond to input in multiple directions at all.

2. This problem arises in pneumatic tires that have a plurality of narrow grooves extending substantially axially on the tread surface and spaced apart from each other in the circumferential direction. By making the narrow grooves slope forward in the tire rotational direction as one approaches the open end from the bottom, and by making the extending direction of each narrow groove inclined with respect to the tire equatorial plane, the narrow grooves are extended from the deepest part to the open end. This can be solved by using a pneumatic tire that is tilted toward the direction of action of the axial input as it approaches.

When a braking force is applied to the tire as it moves forward as described above, a frictional braking force is applied to the tire's contact surface from the road surface in the direction of the tire's rotation, and the rubber in the trend area between the narrow grooves is affected by the tire's rotation. It bends and deforms in the direction. Here, in this invention, each of the narrow grooves extends substantially in the axial direction, and is inclined so as to move forward in the tire rotational direction as it approaches the opening end from the deepest part, so that the rotational direction of the narrow groove is The opening edge on the front side is obtuse, and as a result,
Due to the bending deformation of the rubber between the narrow grooves as described above, the front side wall in the tire rotational direction comes into contact with the road surface near the opening end of the narrow groove. This increases the ground contact area and reliably improves braking performance. On the other hand, when turning, the frictional force in the axial direction of the tire acts on the ground contact surface of the tire from the road surface as an axial input, so the rubber in the tread between the narrow grooves bends in the direction in which the frictional force acts, as described above. transform. Here, in this invention, the extending direction of each narrow groove is inclined with respect to the tire equatorial plane, so that the narrow groove is inclined from the deepest part toward the direction of action of the axial input as it approaches the opening end. Therefore, as described above, the front side wall 11 of the thin groove in the action direction comes into contact with the road surface due to the bending deformation caused by the axial input, increasing the ground contact area and reliably improving turning performance.

In the following, a first embodiment of the present invention will be described based on the drawings.

In Figure 1, 21 is a pneumatic tire used for trucks, buses, etc., and l is the tire equatorial plane 2.
As a result, it has a tread portion 5 divided into a first tread portion 3 located on one side in the axial direction and a second tread portion 4 located on the other side in the axial direction. On the surfaces of the first and second tread portions 3.4 located on both sides of the tire equatorial plane 2, a plurality of main grooves 6, 7 are formed, respectively, spaced apart from each other by an equal pitch P in the circumferential direction, and these main grooves θ , 7 are circumferentially 17
They are arranged symmetrically with the tire equatorial plane 2 as the axis of symmetry, with a two-pitch shift. These main grooves 8 and 7 extend approximately in the circumferential direction, and as they approach the tire equatorial plane 2, they move toward the front in the rotational direction Q of the tire 1 (the direction in which the tire 1 starts contacting the ground earlier when rotated in the normal direction). It is inclined with respect to the equatorial plane 2. That is, this tire l
The direction of rotation is specified. As a result,
When the tire l rotates in the normal direction, the axially inner ends of the main grooves 6 and 7 that are depressed first become starting ends θδ and 7a, and the axially outer ends that are depressed last become terminal ends 6b and 7b. The intersection angle A between the tangent line and the tire equatorial plane 2 at each point of these main grooves 6.7 is from the starting ends 6a, 7a to the ending end 8b,
Continuously increases gradually towards 7b.

As a result, the main grooves 6, 7 are formed from starting ends 6a, 7a to terminal ends 6b,
7b, it gradually falls down and widens as it moves away from the tire equatorial plane 2, and its terminal end 8b,
? b, that is, it opens at both tread ends 8 and 9 at the outer end in the axial direction.

In FIG. 1.2.3, the first. Second tread part 3
, 4 The surface has multiple thin y111.12 that close when touching the ground.
These narrow grooves 11, 12 extend substantially in the axial direction, and the narrow grooves 111, 111 and 12 are spaced apart from each other by the same distance in the circumferential direction. Each narrow groove 11
,! 2 are both inclined toward the front in the tire rotation direction Q as one approaches the opening end 10b from the deepest part 10a. And the inclination angle J of these narrow grooves 11 and 12,
That is, in the cross section where the narrow grooves 11.12 are cut along a plane parallel to the tire equatorial plane 2, the intersection angle at which the narrow grooves 11.12 intersect with a vertical line perpendicular to the surface of the tread portion 5 is from 5 degrees. The range is preferably up to 30 degrees, because if the inclination fly J is less than 5 degrees or exceeds 30 degrees, the braking performance will hardly improve. An example is shown below. In this test, a tire with no 1m groove formed and the inclination angle J
First, prepare tires with angles of 0 degrees, 10 degrees, 15 degrees, 25 degrees, and 35 degrees. First, apply a sudden brake while driving at 80 degrees per hour, and calculate the distance it takes for each tire to stop. I asked for it. Here, for tires without narrow grooves, it is 38.8
Since the braking was completed at m, the reciprocal of this braking distance of 38.8 m was assumed to be an index of 100, and the braking index of the other tires was determined. As a result, for a tire where the inclination angle J is 0 degrees, 101
．． For a 10 degree tire 105° For a 15 degree tire
It was 10θ for the 10B, 25 degree tire, and 102 for the 35 degree tire. From these results, it can be seen that when the above-mentioned inclination angle J is outside the above-mentioned range, there is almost no difference in braking performance. Further, as the narrow grooves 11, 12 approach the tire equatorial plane 2, they are inclined with respect to the tire equatorial plane 2 so as to move toward the rear in the rotational direction Q of the tire l. As a result, when the tire 1 rotates in the normal direction, the axially outer ends 13 and 14 of these narrow grooves 11 and 12 are depressed first, and the axially inner ends! 5.1G will be the last to be tested.

In this embodiment, the axial inner ends 15.16 of these narrow grooves 11.12 are connected to each other at the tire equatorial plane 2, and as a result, these narrow grooves 11.12 are connected to each other at the tire equatorial plane 2. +2 can be recognized as a chevron-shaped continuous narrow groove that is bent at the center in the longitudinal direction and tapers toward the rear in the rotational direction of the tire l.

Then, the side vIt11. on the surface of the tread portion 5.
12 and the tire equatorial plane 2 is preferably within the range of 50 degrees to 80 degrees.The reason is that if the intersection angle K is less than 50 degrees, the braking performance will deteriorate. This is because, on the other hand, if the angle exceeds 80 degrees, the turning performance will decrease significantly. Like this 1. intersection angle K
When it comes to turning performance and braking performance, there is a trade-off between them. Further, the axially outer end 13.14 of the narrow groove 11.12 is located at a distance of 40 mm from the tire equatorial plane 2 to the tread width W.
%, that is, the tire equatorial plane 2
The reason for this is that if the axially outer ends 13 and 14 extend beyond the range to the vicinity of the tray ends 8 and 9, the tread This is because heel and toe wear at the ends 8, 8 increases significantly. A test example showing this is shown below.

In this test, the axial outer end 13 of the narrow groove 11.12
, I4 is located at the 100% position of the tread width W (
A tire (extending to the tread edges 8, 9) and a tire similarly located at the 85.75% position were prepared. At this time, the narrow grooves 11 and 12 have an inclination angle J of 15 degrees,
0th order where the crossing angle K was 60 degrees.

After running these tires for 50,000 km, the axial outer end 1
3. The height of the step in 14 was measured. The results are: 1.5 mm at 100% position, 1.2+e+g at 85% position, and 0.3 at 75% position.
It was mm. Therefore, by arranging the axial outer ends 13, 14 within an area of 80% of the tread width W, heel and toe wear can be reliably suppressed.

Furthermore, in this embodiment, the first and second tread portions 3
, 4, these narrow grooves 1 extend in the depth direction of the narrow grooves 11 and 12.
1.12 are provided with circular holes 17.18 connected respectively to their axially outer ends 13.14. Such a circular hole 17, 1
8 is the axially outer end 13.14 of the narrow groove 11.12 when touching the ground, etc.
This prevents cracking from the axially outer ends 13, 14 by dispersing the stress generated in the axially outer ends 13, 14. And the circular hole 17.1
A preferable range of the radius r of B is determined by the following formula.

α=1+2577 Here, α is the stress concentration coefficient, and this stress concentration coefficient α
In the case of rubber, if it is less than 21, cracks will occur.
Note that the circular hole 17.18 does not have to be provided if the axially outer end 13.14 of the narrow groove 11.12 ends in the main groove 6.7.

Next, the operation of the first embodiment of the present invention will be explained.

Suppose now that a truck, bus, etc. equipped with tires 1 as described above is moving forward. Tires in this condition
When a braking force is applied to the tire 1, the contact surface of the tire 1 is moved from the road surface 20 in the tire rotation direction Q, as shown in Fig. 4.5.
A frictional braking force N acts on the rubber of the tread portion 5 between the narrow grooves 11 and 12 to bend and deform it in the tire rotation direction Q. Here, in this embodiment, each of the narrow grooves 11.12 extends approximately in the axial direction, and from the deepest part 10a to the opening end 1.
0b, the opening edge 21 on the forward side in the rotational direction Q of the narrow grooves 11 and 12 is obtuse, as described above. When the rubber between the narrow grooves 11.12 bends and deforms, the front side wall 10c in the tire rotation direction Q comes into contact with the road surface 2o near the open end 10b of the narrow groove 11.12. This increases the ground contact area and reliably improves braking performance. On the other hand, when the vehicle makes a left turn while moving forward, a frictional force in the direction of the arrow from the road surface 20 acts on the contact surface of the tire 1 as an axial input S. Therefore, the rubber of the tread portion 5 between the narrow grooves 11 and 12 bends and deforms in the direction in which the axial human force S acts, as described above. Here, since the narrow groove 11 is inclined toward the rear in the rotational direction Q of the tire l as it approaches the tire equatorial plane 2, the narrow groove 11 increases as it approaches the opening end 10b from the deepest part 10a. It will be tilted toward the direction of action of S. As a result, as described above, due to the bending deformation caused by the axial human force S, the side wall 10c on the front side in the direction of action of the narrow groove 11 is bent to the road surface 2.
0, the ground contact area increases, and turning performance improves reliably.

Moreover, when turning to the left, the footprint changes to a nearly triangular shape with the tread edge 8 as one side due to the lateral deformation of the tire l due to centrifugal force, but as mentioned above, the area where the contact area increases is originally on the outside of the turn, where the contact area is wide. Since it is on the tread end B side, the effect of increasing the ground contact area is large. Conversely, when turning to the right, an axial direction input T in the direction of the arrow acts from the road surface 2o, but the narrow groove 12 is on the tire equatorial plane 2. As you get closer, the rotation direction of the tire l is tilted towards the rear, so
Due to the bending deformation caused by the axial input T, the front side wall 10c of the narrow groove 12 in the action direction comes into contact with the road surface 2o. As a result, the ground contact area can be efficiently increased in the same way as described above. And such axial human force S or T
If you are receiving a
．． The intersection angle U at which the vertical line and the narrow grooves 11 and 12 intersect on a cut surface obtained by cutting the tire 12 along a plane that includes the axis of the tire 1 has a large influence on the increase in the ui ground area.

Figure 6.7.8 shows a second embodiment of the invention. In this embodiment, linear narrow grooves 25 and 26 extending across the tire equatorial plane 2 are respectively formed in the tires 23 and 24, and the narrow grooves 25 of the tire 23 are formed from the tread edge 9 to the tread edge 8. Tire rotation direction Q as it approaches
Tire 24 is tilted forward, while narrow grooves 2 of tire 24 are
6 is inclined toward the front in the tire rotation direction Q as it approaches the tread end 9 from the tread end 8. When the tire 23 described above receives an axial input from the tread end 8 to the tread end 9, the ground contact area increases, so it is attached to the right heavy wheel of the automobile 27 as shown in FIG. The tire 24 is mounted on the left wheel of an automobile 27 because its ground contact area increases when it receives axial human force from the tread end 9 toward the tread end 8. As a result, when the automobile 27 turns left, for example, and a large leftward axial input acts on the tires 23 of the right wheel, the tires 23
On the other hand, when turning right and applying a large rightward axial input to the tire 24 of the left wheel, the narrow groove 26 of the tire 24 deforms and increases the ground contact area. This increases the area and improves turning performance. Incidentally, since the narrow grooves 25 and 26 of these tires 23 and 24 extend substantially in the axial direction, the braking performance is improved in the same manner as described above.

FIG. 9 shows a third embodiment of the present invention. In this embodiment, main grooves 28 and 29 are provided near both sides of the equatorial plane 2, and extend in the circumferential direction without intersecting the main grooves 8 and 7. At the same time, the straight (7) main WIte, 7 is bent on the way to the starting end 8a, 7a and the empty terminal end 8b, 7b, so that the intersection angle A is increased in a stepwise manner.

Moreover, FIG. 10 shows a fourth embodiment of this invention,
In this embodiment, a plurality of main grooves 30 extending in the circumferential direction and intersecting the main grooves 6 and 7 are formed on the surface of the tread portion 5 on both sides of the tire equatorial plane 2, and the crossing angle A is set near the equatorial plane 2. and tread edge 8, small near S;
I'm trying to get bigger between these.

As explained below, according to the present invention, both braking performance and turning performance can be significantly improved.

[Brief explanation of drawings]

FIG. 1 is a plan view of a tread portion showing a first embodiment of the present invention, FIG. 2 is a cross-sectional perspective view of the vicinity of the narrow groove clearly showing one side wall of the narrow groove, and FIG. 4 is a bottom view of the tread portion to explain the external force acting on the narrow grooves;
The figure is a sectional view similar to FIG. 3 to explain the condition of the narrow groove when an external force is applied, FIG. 6 is a perspective view of essential parts of a tire mounted on a right wheel, showing a second embodiment of the present invention, and FIG. 7 is a perspective view of the main parts of a tire mounted on the left wheel similar to that shown in Fig. 6, Fig. 8 is a bottom view of a car equipped with the tire shown in Fig. 6.7, and Fig. 9 is a third embodiment of the present invention. FIG. 10 is a plan view of a tread portion showing a fourth embodiment of the present invention. ■...Pneumatic tire 2...Tire equatorial plane 5...
・Tread part 10a...Deepest part 10b...Opening part 11.12...Narrow groove Q...Tire rotation direction S, T...Axial direction input Patent applicant Brideston Co., Ltd. Agent Patent attorney Tadashi [[1 Toshio Figure 3 Figure 4 S, T... Axial input Figure 5 Figure 6 Figure 7 Figure 8 (-1-, -1) and' Figure 9

Claims (1)

[Claims] A pneumatic tire having a plurality of narrow grooves extending substantially in the axial direction on the surface of the tread portion and spaced apart from each other in the circumferential direction, the narrow grooves extending from the deepest part toward the front in the tire rotational direction as they approach the open end. By inclining the extending direction of each narrow groove with respect to the tire equatorial plane, the narrow groove is inclined toward the direction of action of the axial input as it approaches the opening end from the deepest part of the narrow groove. A pneumatic tire characterized by: