JPH0270505A - Pneumatic tire for construction vehicle - Google Patents

Abstract

PURPOSE:To improve traction performance, ride comfortableness at vibration and chain installation performance by setting the lug proportion of the length of a central lug in an axial direction to a tread width and the swing angle to the axial direction of an inclined lug within specified values respectively. CONSTITUTION:An pneumatic tire 21 for construction vehicle has a groove 25 between multiple lugs 23 on the surface of a tread 22 coming in contact with a road surface. Each lug 23 is composed of a central lug 23c axially extending toward a tread center 22a and a inclined lug 23s extending with a particular inclination to the axial direction toward a tread shoulder 22b from the single edge 23a of the central lug 23c and is arranged on the circumferential surface of a tire so that it may have discontinuity and arrow feather-shaped directivity. Moreover, the lug proportion l/L of the length l of the central lug 23c in the axial direction to a tread width L is in the range of 0.07<l/L<0.2 and the swing angle alpha to the axial direction of the inclined lug 23s is 48 - 68 deg.. This not only provides sufficient traction on the relatively soft road while a construction vehicle travels on both the unlevelled ground and levelled road, but also improves ride comfortableness at vibration largely on the relatively hard road, too.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a pneumatic tire for construction vehicles, particularly a pneumatic tire for use in construction vehicles that travel on relatively soft and hard roads, both on uneven ground and on level roads. This invention relates to improving the riding comfort of pneumatic tires for construction vehicles, where traction performance is important, and to improving the performance of attaching chains when driving on snowy or frozen roads in winter.

(Prior Art and Problems to be Solved by the Invention) For example, the tread of a conventional pneumatic tire for construction vehicles (hereinafter simply referred to as a pneumatic tire) seen from the front is as shown in Fig. 9. There is. In Figure 9,
The pneumatic tire 1 is a tire having a so-called traction pattern that emphasizes traction performance, and has a central lug portion 3a extending in the axial direction to the tread center portion 2a, and an I.・
The red shoulder portion 2b has a large number of lugs 3 made up of inclined lug portions 3b extending obliquely with respect to the axial direction. The lugs 3 are arranged discontinuously on the circumference of the tire, usually at approximately equal intervals (so-called monopitch), and with directionality in the shape of arrow feathers. The pneumatic tire 1 has sufficient traction performance, but when driving on a relatively hard road surface, the lugs 3 are arranged discontinuously and contact the road surface discontinuously, causing vibration. However, there is a problem in that it resonates with the vehicle body, resulting in poor ride comfort.

Furthermore, when driving on snowy or frozen roads in winter, pneumatic tires are equipped with tire chains to increase traction. The tire chain 5 is the first
As shown in FIGS. 1(a), (b), and (c), there is a ladder type or a tortoiseshell type, and these horizontal cross pars 5a are provided at approximately equal intervals in the circumferential direction. Therefore, when the tire chain 5 is attached to the pneumatic tire 1, the cross spar 5a is attached to the lug 3 as shown in FIGS. 9(a) and 9(b).
Sometimes most of the tire chain 50, for example, 10 cores to 8 crossers 53, fall into the grooves 4 of the tread center part 2a and shoulder part 2b, and the chain attachment effect is not sufficient. The problem is that it doesn't perform well.

Conventionally, tires with traction patterns that place emphasis on traction performance have been thought to be destined to suffer from poor vibration and riding comfort, and it is also unavoidable that they have insufficient chain mountability. However, no full-scale improvements have been made in either of these areas.

Additionally, in order to improve the vibration riding comfort and chain attachment, there is also a type shown in FIG. 10. A tread 7 of a pneumatic tire 6 shown in FIG. 10 has ribs 8 that are continuous in the circumferential direction on a tread center portion 7a, giving continuity to lugs 9. As a result, although the chain fitability is good, the effect of improving ride comfort performance is very small, but on the other hand, mud removal performance deteriorates, and traction performance, which is the original main performance, decreases. There is.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a pneumatic tire for a construction vehicle that has sufficient traction performance when running on both uneven ground and level road, and has good vibration riding comfort performance and chain attachment performance. .

(Means for Solving the Problem) In order to clarify the vibration state of a vehicle in which body vibration is occurring, the inventors installed an accelerometer on the vehicle, measured the vibration, and conducted frequency analysis. . As a result, it was found that the vibrations generated from the vehicle body vibration and the pitch component of each lug of the tire pattern had completely disappeared, and the tire itself had RFV (Radial Force Variation) caused by the pattern.
tion) It turned out that the level was the problem. Here, the RFV level is the magnitude of the variation in the radial force generated on the axle when the tire is run on an indoor drum testing machine with a normal internal pressure and a normal load.

Therefore, we further conducted various studies regarding the relationship between the RFV level caused by the pattern and the constituent elements of each tire pattern. As a result, we found that vehicle body vibration has a deep relationship with the continuity of the lug contact on the tire's ground contact area during tire rotation, that is, the uniformity of the effective ground contact area within the tire's contact area. In particular, in the pneumatic tire 11 having the tread 12 with the traction pattern shown in FIG. 1, vehicle body vibration can be evaluated at the RFV level. The RFV level is determined by an inclined lug portion 13b extending on the surface of the tread 120 at an angle with respect to the axial direction of the tire.
It has been found that this can be represented by the swing angle α of the center line with respect to the axial direction, and the lug ratio E/L of the length l of the central lug portion 13a in the axial direction of the tread center portion 12a to the tread width.

In addition, regarding the chain attachment performance, the swing angle α
In addition to the lug ratio p/L, it is desirable to optimize the lug groove ratio W/V between the groove width W in the circumferential direction of a part of the tread center and the lug width V, and furthermore, the pitch length of the lug pattern of the tread. We have found that by creating a so-called barrier pull pitch in which multiple types of tires are arranged randomly around the circumference of the tread, both riding comfort and chain attachment performance can be further improved.

This will be explained in more detail below.

Figure 2 shows the RFV level as an index when the negative ratio corresponding to the effective ground contact area of the tread is constant and the lug swing angle α is changed in a pneumatic tire with a traction pattern (the smaller the RFV index, the better) This is shown in . Moreover, FIG. 3 shows the traction performance as an index (the larger the traction index, the better) when the swing angle α of the lug is changed in the above-mentioned pneumatic tire. From these two characteristics, it can be seen that the swing angle α of the lug has a specific range A in which the RFV level can be reduced without significantly reducing the traction performance. Range B shown in Figure 2.3 shows a more preferable range.

In addition, if the swing angle α of the lug is within the above-mentioned specific range A, it has sufficient mud removal performance, but the swing angle of the lug 13 at the tread shoulder portion 12b, which contributes little to the RF V level, is By making β smaller than the swing angle α of the lug in the tread center portion as shown in the following equation β×α, it is possible to minimize the decrease in traction performance without impairing the effect of reducing the RFV level.

Further, FIG. 4 shows the relationship between the lug ratio 1/L of the tread center portion and the RFV index when the swing angle α of the lug is kept constant. In other words, by combining the lug ratio 1/L and the lug swing angle α, the RFV
The level can be significantly reduced.

In addition, regarding the performance of chain installation when driving on snowy or frozen roads in winter, it is important to prevent the chain from falling into the tread grooves. That is, the direction in which the RFV level is greatly reduced is exactly the same as the direction in which the chain is prevented from falling into the groove. Furthermore, by setting the lug groove ratio W/V in the tread center part to a specific range, the traction performance when driving on soft road surfaces is not impaired.
It has been found that the chain attachment performance can be further improved.

In addition, the inventors have made the tread of the lug pattern have a barrier pull pitch, thereby simultaneously improving the vibration riding comfort and the chain attachability. However, with so-called monopitch, where the entire circumference is made up of a single pitch length, the frequency of vibrations generated from the tire pattern becomes monotonous, and the RFV level can be significantly reduced at a certain vehicle speed. At that speed, a resonance phenomenon may occur with a part of the vehicle body, resulting in poor ride comfort at that speed. Therefore, in the present invention, by making the tire pattern a barrier pull pitch, the vibration frequencies generated from the tire pattern are dispersed into multiple frequencies, and the above-mentioned weaknesses of the mono pitch can be practically completely eliminated. This has improved comfort.

Next, we will discuss the chain attachment. Typical examples of commercially available chains are shown in Figure 11 (a) and (b), but there are many types of chain pitches, and if the tire pattern is monopitch, how can the pitch be changed within a practical range? However, it is inevitable that the pitch will match that of some commercially available chain. If they coincide, the chain will tend to fall into the groove, resulting in insufficient traction and braking performance on snowy or icy roads. In the present invention, by using a barrier pull pitch,
The aforementioned pattern pitch and chain pitch no longer match, and the weaknesses of the aforementioned mono pitch can be completely eliminated, and furthermore, the chain mounting performance is improved.

The present inventors continued various studies based on the above-mentioned experimental results and reached the following conclusion.

That is, the pneumatic tire for construction vehicles according to claim 1 of the present application includes a central lug portion extending in the axial direction at the tread center portion and an inclined lug extending from one end of the central lug portion toward the tread shoulder portion at an angle with respect to the axial direction. In a pneumatic tire for construction vehicles having a tread in which a large number of lugs consisting of a central lug are arranged in an irregular manner, the lug ratio 6/L between the length l in the axial direction of the central lug and the width of the heel is given by the following formula: % formula % (in the range of 02, the swing angle α with respect to the axial direction of the inclined lug part
is 48° to 686°.

The pneumatic tire for construction vehicles according to claim 2 further includes a central lug portion extending in the axial direction at a part of the tread center, and an inclined lug portion extending obliquely with respect to the axial direction from one end of the central lug portion to the tread shoulder portion. In a pneumatic tire for construction vehicles having a train l in which a large number of lugs consisting of %, and the inclined lug part extends from the tread center to at least 1/4 of the tread width. If the swing angles of the inner inclined lug portion and the outer inclined lug portion with respect to the axial direction are α and β, respectively, α is in the range of 48° to 68°,
It is characterized by being β and α.

In addition to claim 1 or 2, the pneumatic tire for construction vehicles according to claim 3 further includes, in the tread center portion, a groove width W in the circumferential direction and a lug width V in the circumferential direction of the groove between the center lug portions. It is characterized in that the lug groove ratio W/V is within the range of the following formula %.

Further, in addition to claim 1.2 or 3, the pneumatic night/ear for construction vehicles according to claim 4 is characterized in that the length of the pitch in the circumferential direction of the lug is a ratio of at least three kinds of numerical values, and It is characterized by being randomly arranged in the circumferential direction with a pitch length.

Here, the reason why the lag ratio A/L is less than 0.2 is 0.
This is because if it is 2 or more, the RFV level becomes too high and the effects of the present invention cannot be obtained. Also, the lag ratio l/L is 0
．． The reason why it is set to exceed 0.07 is that if it is 0.07 or less, the lug width becomes too small, resulting in insufficient traction, and the shearing force is too concentrated at the central lug portion, making it easy to cause chipping.

Also, the swing angle α between the inclined lug and the axial direction is 48°.
-68'' is preferred, more preferably 506-63°
It is. Here, the reason why the angle is 48° to 68° is because if it is less than 48°, the RFV level becomes too large and the vibration riding comfort deteriorates. Moreover, if it exceeds 686, traction performance will deteriorate.

Also, the inwardly inclined lug portion of the lug extends at least 1/4 of the tread width.
If it is less than /4, there is a possibility that the outer sloped lug part with a small swing angle β is connected in a range of 1/4 of the tread width from the tread center to the tread width, which contributes to the vibration, and the vibration riding comfort may deteriorate. be.

In addition, the reason why it is preferable that the respective swing angles α and β between the axial direction of the inner inclined lug portion and the outer inclined lug portion are β and α is because the swing angles α and β of the inner inclined lug portion and the outer inclined lug portion are preferably β and α. This is to minimize the decrease in Furthermore, the lug groove ratio W/V of the circumferential groove width W and the groove width ■ in the tread center portion is set to 0.4 to 0.
．． The reason why it is set at 6 is because if it is less than 0.4, the traction performance on soft road surfaces will be insufficient, and if it exceeds 0.6, the chain will fall excessively.

Further, it is preferable that there are at least three types of pitch lengths, and that the numerical ratio of the pitch lengths is approximately 7:9:11. The reason why there are three types of pitch lengths is that two types of pitch lengths would result in an excessive pitch length ratio, which is necessary to effectively improve vibration ride comfort and chain grooving, and would also cause problems such as uneven wear. This is because durability problems arise. Furthermore, the reason why the pitch length ratio is approximately 7:9:11 is that if it is much smaller than this, it will not be possible to effectively improve vibration riding comfort and chain groove drop, and if it is much smaller than this, This is because problems with durability such as uneven wear arise.

In addition, the arrangement of the lugs in the circumferential direction at random with this pitch length means that both the arrangement in the circumferential direction of the tire with a pitch length ratio of 7:9:11 and the number of each pitch length in the tire are random. say something.

(Function) In claim 1 of the present invention, the lug ratio l of the central lug portion
/L is within a specific range, and the lug swing angle α of the inclined lug portion is within a specific range, so it has sufficient traction performance, the RFV level is significantly reduced, and the vibration riding comfort performance is significantly reduced. improves.

In addition, in claim 2 of the present invention, the lug ratio β/L of the central lug portion is within a specific range, and (the inner inclined lug portion of the intermediate lug portion is within a specific range, and the inner inclined lug portion and Since the swing angles α and β of the outer inclined lug portions with respect to the axial direction are within a specific range, in addition to the functions and effects described in claim 1, deterioration in traction performance is further suppressed to a minimum.

In addition to claim 1 or 2, by specifying claim 3, the following effects are added.

In other words, in a part of the tread center, the lug groove ratio W
/V in a certain range, the RFV level is further significantly reduced on soft road surfaces while still having sufficient traction performance. Therefore, the vibration riding comfort performance is significantly improved. Furthermore, the chain attachment performance in winter is improved to a sufficient level.

In addition, in claim 4 of the present invention, since the lug pitch length is composed of three types having ratios within a specific range, in addition to the effects of claim 3, Vibration frequencies are effectively dispersed, resonance with the vehicle body is further suppressed, and vibration ride comfort is greatly improved. Further, the tire chain installed in winter is almost completely prevented from falling into the groove, and the installation performance of the 'F-Ane is improved to a sufficient level.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 5(a) is a front view of a tread of an embodiment of a pneumatic tire for construction vehicles according to claim 1.3.4 of the present application. In FIGS. 5(a) and 5(b), the pneumatic tire 21 for construction vehicles has a tire size of 17.5-
25 is a traction pattern tire. A pneumatic tire 21 for a construction vehicle has a large number of lugs 23 and grooves 25 between the lugs 23 on the surface of a tread 22 that contacts the road surface. The lug 23 includes a center lug portion 23C extending in the axial direction to the tread center portion 22a, and a one end 2 of the center lug portion 23c.
The slanted lug portions 23s extend obliquely from the tread shoulder portion 3a to the tread shoulder portion 22b with respect to the axial direction, and are arranged discontinuously and directionally on the tire circumference.

In addition, the lug 23 has three types of pitch lengths P in the tire circumferential direction.
, Q, and R, and the bi-7chi ratio is approximately 7:9:11. And these three types of rugs 23
are randomly arranged in the circumferential direction of the tire. Hereinafter, the dimensions of each part of the lug will be shown for the intermediate pitch part Q.

The axial length l of the central lug portion 23c is 65 fins, the tread width is 4001i, and the lug ratio N/L, which is the ratio of the axial length l to the tread width, is 0.162.

Further, the acute angle between the center line A of the inclined lug portion 23s and the axial direction G, that is, the swing angle α of the lug 23 is 52°. Further, in the tread center part 22a, the groove 2
5, the circumferential groove width W is 37 stories, and the circumferential lug width V is 14.
mm, and the lug groove ratio W/V is 0.5.

In addition, the pitch length is P 174mm, Q 225mm
, R274m1, and if these three types of pitch length lugs are randomly placed on the evening/ear circumference, for example, if some of them are shown by pitch ratio,...7.11.9.9. 11
．． 9.7.11.9... Arranged as 1
It composes the book's tie A.L.Red. It is preferable that the pitch ratio values are 10% or more apart from each other in order to prevent the chain from falling into the groove. Everything else other than the above is the same as a normal pneumatic tire, so the details will be omitted.

Next, embodiments of claims 2 and 3 of the present application will be described.

FIG. 6 is a diagram showing the middle pitch and seventh pitch portions of the tread 22 in an embodiment of the pneumatic tire for construction vehicles according to claim 2.3.4, and is a diagram showing the intermediate pitch and seventh pitch portions of the tread 22 in an embodiment of the pneumatic tire for construction vehicles according to claim 2.3.4. Identical configurations are given the same reference numerals and explanations will be omitted.

In FIG. 6, the pneumatic tire 31 has a central lug portion 23c of the tread 22 with an axial length β of 70 mm, a tread width of 400 m1, and a lug ratio β/L of 0°17.
It is 5. The inclined lug portion 233 includes an inner inclined lug portion 23s that is connected to one end 23a of the center lug portion 23C and extends from the tread center E- to a position P (distance xIL+) 120 mm in the axial direction, and a tread shoulder portion that is connected to the inner inclined lug portion 23s. an outer sloped lug portion 23s2 extending further to 22b;
It consists of and the inner inclined lug portion 23,
The swing angle α1 (α) of the outer inclined lug portion 23S2 is 61″, and the swing angle α2 (β) of the outer inclined lug portion 23S2 is 40°.Other than the above, the embodiment is the same as the embodiment of claim 1.3.4.

Next, three types of test tires (test tire 1.2 and comparative tire) were tested for RFV index and chain drop rate into grooves, and the effects of the present invention were confirmed and will be explained.

The test tire 1 was tested according to claim 1.3 as shown in FIG.
．． The test tire 2, which is the same as the monopitch tire using only the intermediate pitch portion in Example 4, is shown in FIG.
This is the same as the mono-pitch version using only the middle pitch portion in the embodiment 3.4. The comparative tire is a monopitch tire 41 shown in FIG. 7, in which the axial length l of the central lug portion is 115 mm, and the lug ratio 1/L is 0.
287, the lug swing angle α is 39°. Other than the above, the tire was the same as test tire 1.2.

The RFV level was tested as described above, and the test results are shown in FIG. 8(a). In addition, to test the rate of chain drop into the groove, the above-mentioned ladder-type chain (having 10 crossbars) was attached to the test tire, and the tire was mounted on a front-end loader with four chains and run on snow. chain crossbar
The condition of the drop into the groove and the number thereof were tested and shown in FIG. 8(b). In FIG. 8(b), crossbar 1
The chain drop rate is used to determine how many of the 0 fall into the groove and no longer function as a chain.

The test results are expressed as an index with the RFV index of the tire of the comparative example set as 100. The lower the index, the better. RFV
As shown in Figure 8(a), the index is 1.2 for the test tire.
The RFV indices of both are significantly lower than those of comparison tie-1. As a result, the vibration ride comfort performance has been significantly improved.

Further, as for the rate of chain drop into the groove, as shown in FIG. 8(b), the sample tire 1.2 showed a significantly better result than the comparative tire. As shown in Fig. 7, seven of the ten crossbars of the tire chain of the comparison tire fell into the groove in a part of the center, and further into the groove in a part of the tread shoulder. This is the ratio when the entire crossbar chain is stuck in the groove.

In addition, the reason why the chain drop rate of test tires 1 and 2 is 0 is because most of the IO cores to 8 cores of the crossbar chain are in the grooves in the tread center as shown in Figure 5.6. Even if the chain 5 gets stuck, the groove width is narrow, so the entire chain 5 does not fall down, and there is enough catch to prevent the chain from spinning idle, which is what is called a biting. Furthermore, it did not fall into the grooves on either side of the tread at all, indicating that the chain was doing its job well. It had excellent chain attachment performance and sufficient traction performance.

In addition, as shown in Figure 5.6 above, compared to the test tire 1.2, the Hariable Pisoti had less than half the penetration (not depression) into the center groove, that is, 10 tires. The number decreased to 4 to 4 trees. In addition, L-Red, to which Hariable Bisochi is applied, has the effect of significantly reducing depression into the center groove even when the tire size increases and the groove width W increases. Moreover, the traction performance was also sufficient.

(Effects) As explained above, according to claim 1 of the present application, when driving on both rough and level roads, it has sufficient traction performance especially on relatively soft roads, and also has vibration vibration even on relatively hard roads. Ride comfort performance can be significantly improved. Further, according to the second aspect, in addition to the above, vibration ride comfort performance can be further improved significantly, and deterioration in traction performance can be suppressed to a minimum. Further, by specifying claim 3 in claim 1 or 2, it is possible to sufficiently improve tire chain attachment performance and vibration riding comfort performance when driving on a snowy road or frozen road in winter. Further, by specifying claim 4 in claim 1, 2 or 3, the installation performance of the tire chain in winter can be further improved significantly, and the riding comfort performance can be further improved significantly.

[Brief explanation of the drawing]

Figures 1 to 4 are diagrams for explaining the basic concept of the present application, Figure 1 is a partially schematic front view of the tread of the pneumatic tire for construction vehicles, and Figures 2 to 4 show its characteristics, respectively. It is a graph. FIG. 5(a) and FIG. 6 are a partial front view showing a tread of an embodiment of a pneumatic tire for construction vehicles according to claims 1.3.4 and 2.3.4 of the present application, respectively; FIG. 5(b) is a sectional view of the main part of FIG. 5(a). FIG. 7 is a partial front view of the tread of the comparative tire used in the test, and FIG. 8 (a) < (b) is a graph showing the test results of the test tire. Figures 9 and 10 are partial front views of the tread of conventional tires. Figure 11(a)
, (b) and (C) are diagrams showing a normal tire chain, and FIGS. 11 (a) and (b) are partial schematic diagrams,
Figure (c) is an enlarged front view of the negative part. 11.21.31... Pneumatic tire for construction vehicle, 12.22... Tread, 22a... Tread center portion, 22b...
...Tread shoulder part, 23...Lug, 23c...Central lug part, 23s...Slope lug part, 2381...Inner slope lug part, 23゜・・・・・・
...Outside inclined lug part, 25...Groove, α, α, (α), α2 (β)...Swing angle, P
, Q, R...Pitch length. Figure 1

Claims (1)

[Scope of Claims] (1) A large number of lugs consisting of a central lug portion extending in the axial direction in the tread center portion and an inclined lug portion extending obliquely with respect to the axial direction from one end of the central lug portion to the tread shoulder portion. In a pneumatic tire for construction vehicles having a tread arranged in the form of feathers, the lug ratio l/L between the axial length l of the central lug portion and the tread width L is expressed by the following formula: 0.07<l/L<0 The swing angle α between the inclined lug and the axial direction is within the range of .2.
A pneumatic tire for a construction vehicle, characterized in that the angle is from 48° to 68°. (2) A large number of lugs are arranged in a fletching pattern, consisting of a central lug section extending in the axial direction in the tread center section and an inclined lug section extending obliquely to the axial direction from one end of the central lug section to the tread shoulder section. In a pneumatic tire for construction vehicles having a tread, the lug ratio l/L between the axial length l of the central lug portion and the tread width L is in the range of 0.07 < l/L < 0.2. , the inclined lug portion comprises an inner inclined lug portion extending from the tread center to at least 1/4 of the tread width L and an outer inclined lug portion extending axially outward from the inner inclined lug portion, the inner inclined lug portion and the outer inclined lug. The swing angle with the axial direction of the part is α,
If β is in the range of 48° to 68°, and β
A pneumatic tire for construction vehicles characterized by <α. (3) In the tread center part, the lug groove ratio W between the circumferential groove width W of the groove between the central lug parts and the circumferential lug width V
The pneumatic tire for construction vehicles according to claim 1 or 2, wherein /V is in the range of 0.4 to 0.6. (4) The construction vehicle according to claim 1, 2 or 3, wherein the pitch length of the lugs in the circumferential direction is a ratio of at least three numerical values, and the lugs are randomly arranged in the circumferential direction with this pitch length. pneumatic tires.