JPH02303907A - Weather-proof pneumatic tire for heavy load - Google Patents

Abstract

PURPOSE:To improve performance on the ice and partial abrasion resistance by providing each side face which inclines at a specified angle in each of plural blocks of a tread, divided by plural grooves, and specifying the depth, angle, and interval of each sipe being formed in each block. CONSTITUTION:Zigzag circumferential main grooves 1A and 1B, linear circumferential sub grooves 2A and 2B, inclined coupling lateral grooves 3, and linear lateral groves 4 are arranged respectively in the treat T of a tire, whereby central blocks 6, shoulder blocks 7, and middle blocks 8 are divided, respectively. A cut (s) is formed individually in each block 6-8. In this case, each side face A-D, which inclines severally at an angle of 45-90 deg. to the tire equator face O-O, is provided in each block 6-8. Each cut (s) is formed in parallel at a depth of 1-7.5mm, at an angle of 35-90 deg. to each side face A-D, and at a mutual interval of 0.5d-1.5d+5/d.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to the improvement of all-weather heavy-duty pneumatic tires, and more specifically, to improving running performance on slippery ice and uneven wear resistance. This invention relates to an improved all-weather heavy-duty pneumatic tire.

(Prior Art) Tires with metal spikes on their treads have been known as winter tires used in the winter because they need to maintain driving force, braking force, and lateral force in order to meet the performance requirements for running on ice. ing.

However, these spiked tires have become a social problem because they damage the road when driving on dry paved roads free of snow or ice and cause problems such as dust pollution.

On the other hand, in recent years, studless tires for driving on snow and ice have been developed as pneumatic winter tires for passenger cars that do not have spikes. The mainstream is those with improved performance.

In other words, the tread of conventional studless tires has
Usually, a plurality of blocks are formed in the circumferential direction of a tire, which are divided by a plurality of circumferential grooves and a plurality of lateral grooves extending from both ends of the tread to intersect with the circumferential grooves. A notch or sipe having a width is appropriately provided.

Therefore, in conventional studless tires, when a driving force or a braking force is applied to the tire, many edges generated by the cuts are caused by the edge effect caused by grasping the hard road surface, and the edges are not easy to move on snow or especially slippery ice. Efforts have been made to improve driving performance, and its effectiveness has been recognized and it is rapidly becoming popular.

(Problem to be Solved by the Invention) However, the notches provided in the blocks of conventional studless tires for passenger cars have a width as described above, albeit slightly, and are also made at a constant angle in the radial direction. Therefore, if this is applied to heavy-duty pneumatic tires that carry heavier loads and have higher ground pressure than pneumatic tires for passenger cars, shearing forces from the road surface will be applied to the blocks during braking, driving, cornering, etc. If this occurs, the block will collapse significantly and its rigidity will decrease, resulting in poor ground contact on dry and icy roads.In addition, uneven wear will impair wear resistance, making it difficult to drive on ice after wear. There was a risk that performance would further deteriorate.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the conventional heavy-duty pneumatic tires.

Therefore, an object of the present invention is to provide an all-weather heavy-duty pneumatic tire that has improved running performance on ice and uneven wear resistance.

[Structure of the Invention] (Means for Solving the Problems) That is, the all-weather heavy-duty pneumatic tire of the present invention has the following features:
The tread includes a pair of annular sidewalls and a tread continuous between the radially outer ends of both sidewalls, a pair of circumferential grooves arranged in the tread at predetermined intervals in the axial direction, and a pair of circumferential grooves arranged at approximately equal intervals in the circumferential direction. In a tire comprising a plurality of lateral grooves and blocks separated by groups of these grooves, and having a plurality of cuts having substantially no width when no external force is applied to the tire on these blocks,
The block has an angle of 45 mm in a direction parallel to the equatorial plane of the tire.
The cuts have a side surface inclined at an angle of ~90 degrees, and the cuts are in the order of 1 to 7.5 in depth, and at an angle of 35 to 90 degrees with respect to the sloped side of the block, and 0.5 d apart from each other.
They are characterized by being formed substantially parallel with an interval of ~1.5d+5/d (d: depth of cut).

(Function) In the tire of the present invention, since the width of the cut is substantially zero when no external force is applied to the tire, the area of each block can be kept large, so that the rigidity of the block is increased. However, the contact between the sub-blocks divided by the notches further increases the rigidity of each block itself.

In addition, the interval between the notches should be adjusted from 0.5d to 1.5d+5/d (
d: Depth of the cut) By making the interval and depth of the cuts almost the same, it is possible to make the cuts densely without reducing the side (edge) rigidity of the sub-block. It can effectively prevent the block from collapsing when shearing force is applied to it.
When driving on dry road surfaces and icy roads, ground contact is improved, uneven wear can be improved, and driving performance on ice is significantly improved.

Furthermore, the sides of the block are inclined at 45 to 95 degrees,
By setting the angle of the cuts formed in these blocks to 35 to 95 degrees with respect to the inclined side surface of the block, the rigidity of the sub-blocks is further increased evenly, and uneven wear at the tip of the block is further reduced. can be effectively improved.

Therefore, the all-weather, heavy-duty pneumatic tire of the present invention has particularly excellent running performance on ice and greatly improved uneven wear resistance, and is particularly suitable for use on small trucks and large vehicles such as trucks and buses. It is useful as a commercial tire.

(Example) Examples of the all-weather heavy-duty pneumatic tire of the present invention will be described in detail below with reference to the drawings.

Although parts other than the tread are not shown in FIGS. 1 to 3, the parts other than the tread, such as the radial carcass, belt layer, and sidewalls, have a well-known structure.

First, the structure of the block pattern of the tread T of the pneumatic winter tire for heavy loads of the present invention will be explained with reference to FIG.

That is, in FIG. 1, the tread T has an equatorial plane O
A pair of zigzag-shaped circumferential main grooves IA and IB are provided approximately at the center of the tread edge. A pair of linear circumferential minor grooves 2A and 2B are provided that extend in the circumferential direction.

The circumferential sub-grooves 2A, 2B are relatively narrow in width, but have a depth equal to or slightly shallower than the circumferential main grooves IA, IB.

Between the circumferential sub-grooves 2A and 2B, an inclined connecting lateral groove 3 is formed in a zigzag shape in the circumferential direction, and this inclined connecting lateral groove 3 has a relatively narrow width and is formed shallowly. There is.

Further, the zigzag apex of the inclined connecting lateral groove 3 and the zigzag apex of the circumferential main grooves IA and IB are the circumferential minor groove 2A,
2B, resulting in a wide empty intersection 5
is formed.

Note that from the other apex of the circumferential main grooves IA and IB to the tread end, linear lateral grooves 4 extend in the axial direction, and these lateral grooves 4 are relatively wide and deep. has been done.

These groove groups define a row of relatively large central blocks 6, a row of shoulder blocks 7, and a row of relatively small intermediate blocks 8.

Each central block 6 has side surfaces A, A that are inclined at a angle a1a'' with respect to the equatorial plane O-O, and a side surface A' that is parallel to the equatorial plane. In contrast, each shoulder block 7 has a side surface CS inclined at C5C- with respect to parallel line q-q with the equatorial plane.
It has a side surface D which is inclined at d, d- with respect to the parallel line "-" with the equatorial plane.

In the present invention, at least the main blocks (the central block 6 and the shoulder blocks 7) have inclined sides AS.
CSD (in the drawing, the intermediate block 8 also includes the inclined side surface B).

And the inclination angle a of these inclined side surfaces A, BSC and D
, a-1c, c- and dSd- are 4 relative to the equatorial plane 0-0.
It is important that the angle is in the range of 5 to 95 degrees.

In this example, a=a--70 degrees, bb-mc
-c---45 degrees, dd---90 degrees.

In addition, the sides A-A, A-A-1 and A of the central block 6
--The intersections of A are chamfered from the outer surface of the block toward the bottom of the groove. This chamfering also applies to the intersection of the side surfaces B--B and B--B of the intermediate block 8.

In the above configuration, the tread T is usually made of relatively hard rubber, but in some cases softer rubber or foamed rubber may be used for at least a portion thereof.

Although the circumferential main grooves IA and IB may be straight lines parallel to the circumferential direction, it is preferable that they have a zigzag shape (deformed flang shape) as shown in the figure, and their width and depth are the largest among the groove groups. Formed widely and deeply.

Next, FIG. 2 shows a state in which cuts S, which are a feature of the present invention, have been formed in each of the blocks 6.7 and 8 of FIG. 1 described above.

That is, in each block 6, 7 and 8, a cut S is formed by, for example, cutting the block with a blade using a machine equipped with a blade such as a knife.

The cuts S are formed to have a depth d with an interval S between them, and when no external force is applied to the tire, that is, when the tire is not filled with internal pressure,
The cut is made in the form of a line with virtually no width.

In the embodiment shown in FIG. 2, the angles formed with the inclined side surfaces of each block are respectively h-40 degrees, 1 to 70 degrees, k-=-90 degrees, js j −-45 degrees, N-1 = -90 degrees, m-m --45 degrees.

An important requirement for the all-weather heavy-duty pneumatic tire of the present invention is that the cut S having the above-mentioned structure has substantially no width when no external force is applied to the tire, and has a depth of 1 to 1.
7.5 order and at an angle of 35 to 90 degrees to the slanted side of said block, 0.5d to 1.56+5 to each other.
/d (d: depth of cut) and are formed almost parallel to each other, and the reason for setting these requirements is based on the rubber sample test results shown in Figures 4 and 5 and Figure 6. This can be explained using the actual vehicle test results shown in the figure.

First, the rubber sample test conditions shown in FIGS. 4 and 5 are as follows.

1. Rubber sample Rubber quality: Same compound size as the rubber used for the tread rubber of winter tires Dimensions: 2 width: 50 mm x length: 36 mm x thickness: 20 m1 Incision: Cut the length of the rubber sample into the surface of the rubber sample with an interval of depth d1. A large number of linear cuts were made in a direction perpendicular to the width direction.

2. Test method Pressure a rubber sample on a smooth water surface (surface pressure near kg/d)
, measured the coefficient of friction when applied at a sliding speed of 5 km/h. The sliding direction (direction of force action) on the ice is perpendicular to the longitudinal direction of the cut, and the temperature of the ice is 13 in Figure 4.
℃, which is -5℃ in Fig. 5.

3. On the vertical axis of the graph, the friction coefficient μ obtained from a rubber sample without notches is 1
Displayed as an index when set to 00.

FIG. 4 is a graph showing the relationship between the width W and depth d of the notches and the coefficient of friction μ when the interval between the notches S is set to 4. From this graph, it is clear that no external force is applied to the tire of the present invention. It is clear that the tire with a notch that has a substantially no width when not added (solid line) has a significantly higher friction coefficient μ compared to the tire with a notch with a conventional notch width of about 0.7 (dotted line). It is.

However, also in the tire of the present invention, the depth d of the cut S
If it exceeds 7.5n+n, the friction coefficient μ decreases significantly, so the depth d of the cut is limited to 1 to 7°5 fins.

In other words, the coefficient of friction μ on the ice surface is closely related to the depth d of the cut, and in the case of the solid line where the width of the cut is practically zero, the coefficient of friction is extremely high at depths of 1 to 7.5 degrees. On the other hand, in the case of the dotted line with a cut width of 0°7 mm, although the coefficient of friction depends on the depth of the cut, the overall level is significantly lower than in the case of the solid line.

Furthermore, from FIG. 5, it is clear that the interval W between the notches S and the depth d have a relationship of 0.5d≦W≦1.5d+5/d, and it is more desirable that d and W be approximately equal. It is.

In other words, in Fig. 5, the notch interval W is 1.5d+5/
It is shown that the friction coefficient μ is high in the range of d or less. Although the level of friction coefficient is high even when the interval W is 0.5d or less, the rigidity near the block surface decreases too much when driving on general roads without ice, causing uneven wear or early wear. This is not desirable because it invites

Furthermore, if the interval W is less than 0.5d, the edge rigidity of the sub-blocks divided by the notches will decrease, so even if a large number of notches are formed, the edge effect will not be fully exerted, and conversely, if the interval W is 1 Above .5d+5/d,
Even if the number of cuts is reduced and water is drained at the edge of one cut during braking, a thin film of water will penetrate by the time the next cut is reached, making it impossible to fully utilize the edge effect.

Furthermore, Fig. 6 shows the results of measuring the level difference between the adjacent block at the point where uneven wear occurred after 5000 cycles in an actual vehicle test, and from the same figure, the angle formed by the notch with the side of the block. It is clear that having the angle of 35 degrees or more brings about a desirable effect on uneven wear resistance.

In other words, the angle between the notch and the side of the block is 35
If the temperature is less than 30 degrees, especially 10 to 30 degrees, the difference in height between the sub-blocks that remain unworn or have a tendency not to wear out and the adjacent sub-blocks becomes large in the tire after running. shows a tendency for uneven wear to occur.
When the angle is 35 degrees or more, the step difference is reduced and uneven wear is eliminated.

Incidentally, here, for the block pattern shown in Fig. 1, we will make a cut that has virtually no width when no external force is applied, so that the depth d and the interval W are 065d≦W≦1.5d+5.
/d, and if each block 6.7 and 8 is formed at an angle of 20 degrees upward to the right, then
At the initial stage of wear after driving 2000 km on a dry asphalt road, as shown in Figure 3, the parts where the angle between the block side surface and the notch is 35 degrees or less remain unworn (black painted parts) and the parts that are worn out. There were areas (hatched areas) where this tendency did not occur, and the level difference between adjacent sub-blocks became large, indicating a tendency for uneven wear to progress.

On the other hand, when the angle between the block side surface and the notch was 35 degrees or more, the step that caused uneven wear was eliminated, and excellent uneven wear resistance could be obtained.

Therefore, the all-weather heavy-duty pneumatic tire of the present invention formed with blocks and cuts as described above can effectively improve running performance and uneven wear resistance, especially on slippery ice. In addition, in the present invention, cuts having substantially no width and cuts having a normal width of about 0.7 mm may coexist.

Further, the depth d of the cuts does not need to be all constant; for example, shallow cuts and deep cuts may exist alternately.

Furthermore, the cut need not necessarily be substantially across the block, but may be interrupted in the middle of the block, or
This also includes a case where no notch is provided at the end of the block.

Furthermore, the cuts can be arranged to be inclined in the depth direction with respect to the tread surface.

Next, the structure and effects of the all-weather heavy-duty pneumatic tire of the present invention will be explained in more detail using test examples.

(Test Example) Tire size: LSR7,50R1614PR1 Rim used: 6.0OGS, Air pressure used: 6°50kg/cd The tread part of an all-weather block pattern radial tire was tested as shown in Figures 1 and 2 above. A block pattern was formed and this tire was evaluated.

Note that other structures such as the radial carcass and belt layer of the tire and manufacturing conditions were similar to those of conventional tires, so details will be omitted.

That is, in FIG. 1, the width of the tread: 1601, the width of the zigzag circumferential main grooves IA and IB: 10, and the depth =
15 order, groove width of circumferential minor grooves 2A and 2B: 5 mm, depth:
10 dragons, inclined connecting lateral groove 3 groove width: 5 mm, depth: 12
When forming a pro-tsuku pattern with ma+, width of horizontal groove 4: 15 mm, depth: 15 m, cut S
The width, depth d1 interval, and angle with the block side were changed as shown in the table below.

The five types of tires obtained were evaluated for running performance on ice and uneven wear resistance by an actual vehicle feeling test under the following conditions, and the results are shown in the following table.

Test vehicle for driving performance on ice: Small truck, 3-ton vehicle Road surface: Frozen road surface in winter in Hokkaido Evaluation method: The braking distance from braking at a speed of 10 kl/h to stopping is expressed as an index using a reciprocal number. [It is shown as an index evaluation when the conventional tire (Comparative Example 1) is set as 100, and the larger the index, the better] Feeling when turning in a circle at a speed of 1'51a++/m ◎ Good O ... Fairly good △ ...Sometimes uneasy × ... Uneasy (No snowfall) Speed: 20-1100k/h (high-speed running) Evaluation method: Appearance comparison of uneven wear after 5000km driving using edge level differences between adjacent sub-blocks. ...Edge step is noticeable O...Edge step is not very noticeable (hereinafter referred to as actual margin) From the above results, the all-weather heavy-duty pneumatic tire of the present invention has excellent ice running performance and resistance to unevenness. It is clear that it has a balanced and high level of abrasion resistance.

[Effects of the Invention] As described above, the all-weather heavy-duty pneumatic tire of the present invention has particularly excellent running performance on ice, has greatly improved uneven wear resistance, and has a good durability life. Because it has excellent performance as a studless tire, it is particularly useful as a tire for small trucks and large vehicles such as trucks and buses.

[Brief explanation of drawings]

Fig. 1 is a developed view of the tread section of the all-weather, heavy-duty pneumatic tire of the present invention before the notches are made, and Fig. 2 is a developed view of the tread section showing the state in which the tread section of Fig. 1 is cut. Developed view, Figure 3 is a developed view of the tread section for comparison showing the state in which cuts are made at the same angle as the conventional one, and Figure 4 shows the relationship between the depth of cuts and the coefficient of friction based on rubber sample tests. Figure 5 is a graph showing the relationship between the spacing corresponding to the depth of the cut and the coefficient of friction, and Figure 6 is the graph showing the relationship between the angle between the sloped side surface of the block and the cut and the edge step between the adjacent sub-block. This is a graph showing. T...Tread IA...Circumferential main groove 1B, 1. 〃 2A... Circumferential minor groove 2B1. ,,,, 〃 3...... Inclined connection lateral groove 4...
...Transverse groove 5...Intersection 6...Central block 7...Shoulder block 8...
・・・・Intermediate block A・・・・・・・Block side B・・・・・・・・・／／ （： 、、、 、、、 、、、 //D ・・・・・・
・・・・・・ 〃 S・・・・・・・・・Cut d・・・・・・・・・ 〃 Depth W・・・・・・・・・ 1/ Spacing Agent Patent Attorney Hide Miyoshi Depth of Japanese cut d (mm) Fig. 4

Claims (1)

[Claims] The tread includes a pair of annular sidewalls and a tread continuous between the radially outer ends of both sidewalls, and a pair of circumferential grooves arranged in the tread at predetermined intervals in the axial direction, and a pair of circumferential grooves arranged at approximately equal intervals in the circumferential direction. In a tire comprising a plurality of lateral grooves and blocks separated by groups of these grooves, and having a plurality of cuts having substantially no width when no external force is applied to the tire on these blocks,
The block has an angle of 45 mm in a direction parallel to the equatorial plane of the tire.
The incisions have sides sloped at an angle of ~90 degrees, and the cuts have a depth of 1 to 7.5 mm and are at an angle of 35 to 90 degrees with respect to the sloped sides of the block and 0.5 to each other.
An all-weather heavy-duty pneumatic tire characterized by being formed substantially parallel to each other with an interval of d to 1.5d+5/d (d: depth of cut).