JP6557064B2 - Heavy duty tire - Google Patents

Description

  The present invention relates to a heavy duty tire, which is a tire used for heavy duty vehicles such as trucks and buses.

  Conventionally, for the purpose of improving the drainage performance of a heavy duty tire, it has been proposed to form a plurality of circumferential narrow grooves extending in the tire circumferential direction on the tread portion tread surface of the heavy duty tire. These circumferential narrow grooves are provided in a central region defined by a pair of circumferential main grooves extending in the tire circumferential direction across the tire equator (see Patent Document 1 described later).

  By the way, the formation of the circumferential narrow groove, on the other hand, brings about a decrease in tire circumferential rigidity and an accompanying increase in rolling resistance. For this reason, the circumferential narrow groove is formed so that two rib-like land portions adjacent to each other with the circumferential narrow groove as a boundary can contact each other and support each other when the tire contacts the ground. Yes. According to this, elastic deformation of the rib-like land portion is suppressed, and a decrease in the circumferential rigidity and an increase in rolling resistance are prevented.

  The contact between the rib-like land portions at the time of tire contact is caused by elastic deformation of the two groove walls of the circumferential narrow groove forming the boundary between the two rib-like land portions toward each other. On the other hand, due to the air filled in the heavy load tire, the circumferential narrow grooves are elastically deformed in a concave shape with respect to the other one of the groove walls, and cracks are formed in the groove bottom. Placed in a pressurized environment. Under such an environment, all or part of the convex elastic deformation of the two groove walls may be offset, and there is a concern that the support between the rib-like land portions may be hindered.

JP 2012-20714 A

  An object of the present invention is a heavy-duty tire, in which two rib-like land portions defined by circumferential narrow grooves provided on the tread surface of the tread are in contact with each other at the time of tire contact, thereby reducing the rolling resistance of the tire. The object is to provide a heavy duty tire that can be lowered.

  The present invention relates to a heavy duty tire, and the heavy duty tire has a circumferential belt layer provided on the heavy duty tire, a tread portion tread, and a tread portion tread that opens to the tire equator and sandwiches the tire circumference. A pair of circumferential main grooves extending in the direction, a central area between the two circumferential main grooves defined on the tread portion tread by the pair of circumferential main grooves, and six circumferences extending the central area in the tire circumferential direction 6 circumferential narrow grooves that define two rib-like land portions that are directional narrow grooves that can contact each other at the time of tire contact, and that are provided at both ends in the tire width direction. An outer ring portion having a center of curvature and curved inward in the tire radial direction, and a tire width direction distance (BW) of the circumferential belt layer is the maximum in the tire width direction across the tire equator. Groove width of two circumferential narrow grooves located outside Tire width direction distance (W) greater than between the two fine grooves comprising.

  According to the present invention, the tire width direction distance (BW) of the circumferential belt layer is a tire width direction distance (W) between two circumferential narrow grooves located on the outermost side in the tire width direction across the tire equator. ) Larger than (BW> W), all of the circumferential narrow grooves are on the outer side in the tire radial direction of the circumferential belt layer, and are within the range between both side ends of the circumferential belt layer in the tire width direction. Exist. For this reason, the pressure of the air in the tire that transmits the tire toward the outer side in the radial direction is absorbed by the circumferential belt layer, and the pressure action of the air does not reach all the circumferential narrow grooves. From this, at the time of tire contact, the convex deformation of the two groove walls of each circumferential narrow groove, the mutual contact between the two rib-shaped land portions defined by these groove walls, and the rib-shaped land portions associated therewith Mutual support will surely occur. As a result, the decrease in the circumferential rigidity of the tire caused by providing the circumferential narrow groove contributing to the improvement of the drainage performance of the heavy duty tire and the accompanying increase in rolling resistance are reliably suppressed. As a result, the rolling resistance is further reduced by increasing the proportion of the primary mode due to the wrinkle effect of the circumferential belt layer and suppressing the deformation of the tread portion by reliably closing the circumferential narrow groove. .

  The tire width direction distance (BW) of the circumferential belt layer is larger than the tire width direction distance (MW) between both circumferential main grooves including the groove width of the pair of circumferential main grooves (BW> MW) When both the circumferential main grooves are present in the range between both ends in the tire width direction of the circumferential belt layer, the circumferential belt layer is formed on the tread part tread surface. It works to compensate for the decrease in rigidity of the tread part due to formation. Further, the circumferential belt layer has a function of making the contact pressure distribution constant with respect to the tread portion, whereby the wear resistance can be improved.

It is a partial expanded view of the tread part of the heavy duty tire. It is sectional drawing obtained along line 2-2 of FIG. However, in order to avoid complication of the drawing, the hatching indicating the cross section is attached only to the circumferential belt layer.

  Referring to FIGS. 1 and 2, a part of a heavy duty tire used for a heavy duty vehicle such as a truck or a bus is indicated by a reference numeral 10 as a whole.

  The heavy load tire 10 includes a circumferential belt layer 12 that extends in the tire circumferential direction, a tread portion tread 14 that serves as a contact surface when the heavy load tire 10 travels, and a tread tread 14 that are one of the structural members. A pair of circumferential main grooves 16 that open, and a plurality (six in the illustrated example) of circumferential narrow grooves 18 that similarly open to the tread portion tread surface 14 (more specifically, the center region 20 described later) Is provided. In the figure, TW indicates the tread width of the tire 10.

  The pair of circumferential main grooves 16 extends in the tire circumferential direction with the tire equator (or center line) CL interposed between both ends 14a in the tire width direction. The two circumferential main grooves 16 define a central region 20 between the circumferential main grooves 16 on the tread portion tread surface 14.

  Each circumferential main groove 16 preferably has a groove width of 5 mm or more from the viewpoint of ensuring drainage performance. However, the groove width of the circumferential main grooves 16 should be 30 mm or less in order to avoid a decrease in wear resistance due to a decrease in the area ratio (negative ratio) between the circumferential main grooves 16 and the tread surface 14. Is desirable. The illustrated circumferential main groove 16 extends linearly in the tire circumferential direction. Instead of this example, for example, the circumferential main groove 16 can be extended in a zigzag manner or in a waveform in the tire circumferential direction. According to this, the edge component in the tire width direction is increased, and the driving performance, braking performance, drainage performance, and the like of the heavy load tire 10 are improved.

  The plurality of circumferential narrow grooves 18 contribute to the improvement of drainage performance of the heavy load tire 10. In the illustrated example, a plurality of circumferential narrow grooves 18 are arranged at equal intervals in the tire width direction. The illustrated circumferential narrow groove 18 extends linearly in the tire circumferential direction. Instead, for example, the circumferential narrow groove 18 extends in a zigzag or wave form in the tire circumferential direction as in the circumferential main groove 16. Can do. When the circumferential narrow groove 18 extends zigzag in the tire circumferential direction, the crossing angle between each line segment constituting the zigzag and the circumference extending in the tire circumferential direction on the tread portion tread surface 14 is ± 50 °. It is desirable to be within the range. If the crossing angle exceeds ± 50 °, the corner of the land portion becomes sharp and the rigidity of the corner portion of the land portion becomes small, which may cause problems such as rubber chipping.

  The groove width of the circumferential narrow groove 18 is such that when the tire contacts the ground (when the tire is loaded), the pair of groove walls 18a facing each other in the circumferential narrow groove 18 are elastically deformed in a convex shape toward the other. It is set so that the opening of the circumferential narrow groove 18 can be closed at a place where the circumferential narrow groove 18 is in contact with the road surface. Specifically, it is desirable that the groove width of the circumferential narrow groove 18 be 3 mm or less in consideration of not causing further increase in rolling resistance. However, the groove width of the circumferential narrow groove 18 is preferably set to 0.5 mm or more at which an effect of improving drainage performance is recognized as compared with the land portion. The circumferential narrow groove 18 preferably has substantially the same groove depth as the circumferential main groove 16.

  Further, the number of the circumferential narrow grooves 18 is arbitrarily set to 5 or less, or 7 or more, which is a number other than 6 shown in the drawing, in consideration of the contribution of drainage performance improvement of the heavy load tire 10. Furthermore, it can replace with the example of illustration which makes the mutual space | interval of the circumferential direction fine groove 18 equal, and can make it an unequal space | interval.

  In the present invention, the distance in the tire width direction of the circumferential belt layer 12 (more specifically, the distance or the width dimension between both ends of the circumferential belt layer 12 in the tire width direction) BW is interposed between the tire equator CL and the tire equator CL. It is larger than the distance W in the tire width direction between two circumferential narrow grooves 18A located between the two outer circumferential narrow grooves 18A (for the purpose of distinction from other circumferential narrow grooves). BW> W). Here, the tire width direction distance W of the two circumferential narrow grooves 18A means the distance between the outermost groove walls in the tire width direction of both circumferential direction narrow grooves 18A, and the tire width direction distance W is both The distance includes the groove width of the circumferential narrow groove 18A.

  The pressure of the air filled in the heavy load tire 10 is transmitted toward the outer side in the tire radial direction of the heavy load tire 10 and is absorbed by the circumferential belt layer 12, but is located on the outer side in the tire radial direction of the circumferential belt layer 12. Since all the circumferential narrow grooves 18 are within the width dimension of the circumferential belt layer 12 (BW> W), the action of the air pressure does not reach the groove wall 18 a of any circumferential narrow groove 18. Therefore, the influence of the air pressure on each circumferential narrow groove 18 is blocked by the circumferential belt layer 12, and therefore, a phenomenon that occurs when the air is in a pressurized environment, that is, 2 of the circumferential narrow grooves 18. It is possible to prevent the two groove walls 18a from being elastically deformed in a concave shape toward the other one, and to prevent the groove bottom of each circumferential narrow groove 18 from being cracked.

  As a result, at the time of tire contact, the convex elastic deformation of the two groove walls 18a in each circumferential narrow groove 18 and the mutual contact between the two rib-like land portions 20a adjacent to each other across the grooves 18 and Along with this, the support between the rib-like land portions 20a occurs. As a result, a decrease in the circumferential rigidity of the heavy load tire 10 due to the formation of the circumferential narrow grooves 18 contributing to an improvement in drainage performance of the heavy load tire 10 and an increase in slip resistance associated therewith are suppressed. Further, the eccentric deformation (primary mode) at the time of tire load and the further reduction of the slip resistance associated therewith are realized.

  The tire width direction distance BW of the circumferential belt layer 12 is preferably larger than the tire width direction distance MW between the two circumferential main grooves 16 including the groove width of the pair of circumferential main grooves 16 (BW). > MW). In this example, both circumferential direction main grooves 16 exist within a range between both side ends in the tire width direction of the circumferential belt layer 12. From this, the circumferential belt layer 12 can compensate for the rigidity reduction of the tread portion due to the formation of the circumferential main groove 16 on the tread portion tread surface 14. Further, the circumferential belt layer 12 has a function of making the contact pressure distribution constant with respect to the tread portion, thereby improving the wear resistance performance of the heavy load tire 10.

  Further, preferably, the central region 20 is not provided with grooves and sipes extending in the tire width direction. According to this, compared with the case where the said groove | channel or sipe is provided, the rolling resistance of a tire can be reduced more.

  Below, the result of the rolling resistance measurement test obtained about the some tire for heavy loads (Comparative Examples 1-2 and Examples 1-4) is shown. The rolling resistance was measured by measuring the rolling resistance force of the axle under conditions of a tire internal pressure of 900 kPa and a load load of 3827.6 kgf, using a drum tester (speed 60 km / h) having a steel plate surface with a diameter of 3 m. . This rolling resistance measurement was performed with a smooth drum and a force type in accordance with ISO28580.

  The symbols BW, W, and MW in Table 1 are the above-described “distance in the tire width direction of the circumferential belt layer”, “distance in the tire width direction between the circumferential narrow grooves”, and “tire width between the circumferential main grooves”, respectively. Directional distance ". The values of the symbols BW, W, and MW are each indicated by an index (INDEX) in which the value of BW is 100. Further, the value of the rolling resistance is indicated by an index (INDEX) in which the value in Comparative Example 1 is 100, and the larger this value is, the smaller the rolling resistance is.

  Here, Comparative Example 1 in Table 1 relates to a tire having no circumferential narrow groove and having a thick groove such as a circumferential main groove instead of the circumferential narrow groove, and Comparative Example 2 is Regarding tires having a plurality of circumferential grooves and a relationship of BW (100) <W (101), the rolling resistances were 100 and 92, respectively. In contrast, in the tires of Examples 1 to 4 according to the present invention, BW> W, and the rolling resistances in these Examples were 106, 113, 115, and 120, respectively. From this result, it was shown that the rolling resistance of the tires of Examples 1 to 4 is smaller than the rolling resistance of the tire of Comparative Example 1 and the tire of Comparative Example 2.

  Moreover, in the tire of Example 4 which does not have a sipe, the rolling resistance value (120) is larger than those in the tires of Examples 1 to 3 which have a sipe (106, 113 and 115). From this, it was shown that the rolling resistance of the tire without the sipe is smaller than that of the tire with the sipe.

DESCRIPTION OF SYMBOLS 10 ... Heavy load tire, 12 ... Circumferential belt layer, 14 ... Tread part tread, 16 ... Circumferential main groove, 18 ... Circumferential narrow groove, 18A ... Tire width direction Two outer circumferential narrow grooves, 18a .. groove wall, 20 ... central region, 20a ... rib-like land, CL ... tire equator, W ... circumferential narrow groove Between tire width direction distance, BW ... Tire width direction distance of circumferential belt layer, MW ... Tire width direction distance between circumferential main grooves, TW ... Tread width.

Claims (1)

A heavy duty tire,
A circumferential belt layer provided on the heavy duty tire;
A tread portion tread, a pair of circumferential main grooves that open to the tread portion tread and extend in the tire circumferential direction with the tire equator in between, and a pair of circumferential main grooves defined on the tread portion tread A central area between the circumferential main grooves and six circumferential narrow grooves extending in the circumferential direction of the tire in the circumferential direction, and each circumferential narrow groove is divided into two rib-shaped land portions that can contact each other when the tire contacts the ground And six outer circumferential narrow grooves, and at both ends in the tire width direction, an outer ring portion having a center of curvature outward in the tire radial direction and curved inward in the tire radial direction,
The tire width direction distance (BW) of the circumferential belt layer is the tire width direction between the two narrow grooves including the groove widths of the two circumferential narrow grooves located on the outermost side in the tire width direction with the tire equator in between. Heavy duty tire greater than distance (W).

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