JP2006199085A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire which can reduce a pumping sound which occurs resulting from a bag-like groove being formed on the tread surface. <P>SOLUTION: For this pneumatic tire, a groove section is formed on the tread surface. In the pneumatic tire, the groove section is equipped with the bag-like groove 20 having a sipe head section 17 which has an approximately loop-like internal wall 16 being partially opened, and a sipe neck section 18 which communicates with the opening of the sipe head section 17 with a groove width being smaller than the maximum groove width of the sipe head section 17. Then, a connecting groove 21 which connects the groove or the grounding end being adjacent across a land section with the sipe head section 17 of the bag-like groove 20 is formed on the bag-like groove 20. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire capable of reducing pumping noise generated due to a groove formed on a tread surface.

  Various tread patterns are formed on the tread surface of the pneumatic tire, and various tire performances according to use conditions are imparted. In particular, in a pneumatic tire that emphasizes fashionability, a tread pattern having a shape that not only enhances tire performance but also causes aesthetics through vision is formed. There are various tread patterns that can enhance such fashionability, and grooves and land portions having various shapes are formed on the tread surface.

  FIG. 6 is a perspective view showing an example of a tread surface of a pneumatic tire in which such fashionability is emphasized, and shows an enlarged part of a groove portion. Normally, the groove portion formed on the tread surface is formed with a constant groove width or by gradually decreasing or increasing the groove width, but the groove portion shown in FIG. 6 is a bag in which the groove width is locally expanded at the end portion. It is formed in a shape. The bag-like groove 23 includes a groove head portion 17 having a substantially loop-shaped inner wall 16 partially opened, and a groove neck portion 18 communicating with the opening with a groove width smaller than the maximum groove width of the groove head portion 17. Have.

  When the present inventors researched about the tread surface in which such a bag-like groove | channel was formed, the following matters became clear. That is, on the tread surface in which the bag-like groove as described above is formed, a substantially closed space is formed by the groove head portion 17 and the road surface during traveling, and the compressed air in the substantially closed space has a narrow groove neck 18. It was found that a pumping sound is generated by being suddenly released through the air and the noise performance is lowered. As a measure for reducing such pumping noise, it is conceivable to make air movement smooth by reducing the groove width of the groove head portion 17 or increasing the groove width of the groove neck portion 18. However, in a pneumatic tire that emphasizes fashionability, the range in which the groove width can be taken may be limited due to design reasons, and the above measures cannot always be adopted.

Here, Patent Document 1 below discloses a pneumatic tire in which end portions of lug grooves are connected by narrow grooves. However, such pneumatic tires suppress the shear deformation that occurs in the tread rubber by connecting the ends of the lug grooves that are located across the tire equatorial plane with narrow grooves that are deeper than the lug grooves. This prevents cut separation and does not reduce pumping noise in the bag-like groove as described above.
JP 2004-155335 A

  Accordingly, an object of the present invention is to provide a pneumatic tire that can reduce the pumping sound generated due to the bag-like groove formed on the tread surface.

  The above object can be achieved by the present invention having the following configuration. That is, the present invention relates to a pneumatic tire in which a groove portion is formed on a tread surface, wherein the groove portion has a groove head having a substantially loop-shaped inner wall partially opened, and the groove is formed in the opening of the groove head. A groove neck portion having a groove neck portion communicating with a groove width smaller than the maximum groove width of the head portion, a groove or a grounding end adjacent to the bag-like groove with a land portion interposed therebetween, and a groove of the bag-like groove A connecting groove for connecting the head is formed.

  According to the above configuration, the groove head portion of the bag-like groove is connected to the other groove or grounding end adjacent to the bag-like groove with the land portion interposed therebetween via the connecting groove. The air in the substantially closed space formed by the portion and the road surface is dispersed and discharged from both the groove neck and the connecting groove. As a result, the pressure of the air discharged through the groove neck can be reduced, and the pumping sound can be reduced.

  Here, the “grounding end” is the outermost part in the tire axial direction where the rim is assembled to a regular rim, the tire is placed perpendicular to the plane with the regular internal pressure filled, and the ground is grounded on the flat road surface when a regular load is applied. Refers to the position. The normal load and the normal internal pressure are the maximum load (design normal load in the case of passenger car tires) specified in JIS D4202 (specifications of automobile tires) and the air pressure corresponding to this, and the normal rim is As a rule, the standard rim specified in JIS D4202 etc. shall be used.

In the above description, when the cross section of the groove neck having the smallest groove cross-sectional area is defined as the minimum cross section, the groove cross-sectional area S (mm ² ) in the minimum cross section and the minimum cross section closest to the groove head From the groove head side, the relationship with the groove volume V (mm ³ ) when the connecting groove is not formed is preferably V / S ≧ 25. Here, the cross section of the groove neck means a cross section orthogonal to the direction in which the groove neck extends.

In order to achieve the above-mentioned object more effectively, the present inventors have conducted intensive research on the tread surface on which the bag-like groove is formed, and focused on the relationship between the groove volume of the groove head and the groove cross-sectional area of the groove neck. The results shown in the graph of FIG. 7 were obtained by the method shown in the examples. The horizontal axis of this graph indicates the groove cross-sectional area S (mm ² ) in the minimum cross section and the groove volume V (mm when the connecting groove is not formed on the groove head side from the minimum cross section closest to the groove head. ³ ), and the vertical axis represents the noise level during travel. According to FIG. 7, it was found that the greater the V / S, the greater the volume per groove cross-sectional area of the air passing through the groove neck, and the higher the noise level. In particular, when V / S is 25 or more, it has been found that the noise level becomes a practical problem. That is, the above configuration is such that a connecting groove capable of reducing the pumping noise is formed with respect to the bag-like groove in which the generation of the pumping noise becomes remarkable, and the configuration according to the present invention can be particularly useful. .

  In the above description, when the cross section of the groove neck having the smallest groove cross-sectional area is defined as the minimum cross section, the groove width of the connecting groove is preferably equal to or less than the groove width in the minimum cross section and equal to or greater than 2 mm.

  According to the above configuration, since the groove width of the connecting groove is set to be equal to or smaller than the groove width in the minimum cross section, the connecting groove does not stand out on the tread surface and does not impair the fashionability. It can employ | adopt suitably with respect to a pneumatic tire. Further, since the groove width is set to 2 mm or more, the groove width of the connecting groove can be ensured at the time of grounding, and the effect of reducing the pumping noise is effectively ensured.

  In the above, it is preferable that the groove depth of the connection groove is 20% or more of the groove depth of the groove head.

  According to the above configuration, since the groove depth of the connecting groove is set to 20% or more of the groove depth of the groove head, a volume of air discharged through the connecting groove is ensured above a certain level, The pumping noise reduction effect is effectively ensured.

  Preferred embodiments of the present invention will be described below with reference to the drawings.

  The pneumatic tire of the present invention is the same as a conventionally known tire structure except for the tread surface, and is the same as that shown in FIG.

  The pneumatic tire shown in FIG. 1 has a pair of annular bead portions 2, sidewall portions 5 extending from the bead portions 2 to the tire outer peripheral side, and shoulder portions at the outer peripheral side ends of the sidewall portions 5. And a tread portion 7 connected to each other. Between the bead parts 2, the carcass ply 1 is arranged so as to be bridged, and the end part is wound up so as to sandwich the bead 3 and the bead filler 4. One or more belt layers 8 are disposed outside the carcass ply 1 of the tread portion 7, and a belt reinforcing layer is disposed as necessary. A tread rubber is disposed on the tire outer peripheral side of the belt layer 8, and various tread patterns are formed on the tread surface 6 according to required tire performance and use conditions.

  Examples of the raw rubber for the rubber layer include natural rubber, styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), butyl rubber (IIR), and the like. Used in combination with more than one species. These rubbers are reinforced with fillers such as carbon black and silica, and a vulcanizing agent, a vulcanization accelerator, a plasticizer, an anti-aging agent and the like are appropriately blended.

  Hereinafter, the tread surface of the pneumatic tire according to the present invention will be described. FIG. 2 is a perspective view showing a bag-shaped groove as an example of a tread surface provided in the pneumatic tire of the present invention. FIG. 3 is a plan view of the bag-like groove.

  The tread surface 6 is formed with a groove portion and a plurality of land portions (blocks) divided by the groove portion. The groove portion has a bag-like groove 20 formed by locally expanding the groove width at the end portion. Have. As shown in FIGS. 2 and 3, the bag-like groove 20 includes a groove head 17 having a partially looped inner wall 16 that is partially opened, and a groove head 17 having a maximum at the opening of the groove head 17. And a groove neck portion 18 communicating with a groove width smaller than the groove width W. The groove head portion 17 of the present embodiment is formed in an elliptical shape in plan view, and another bag-like groove 20 is provided in parallel with the land portion 22 interposed therebetween.

  The connecting groove 21 of the present embodiment extends so as to connect the groove head portions 17 of the bag-like groove 20. Thereby, the air in the substantially closed space formed by the groove head portion 17 and the road surface is dispersed and discharged from both the groove neck portion 18 and the connecting groove 21. As a result, the pressure of the air discharged through the groove neck 18 can be reduced, and the pumping sound can be effectively reduced.

  The groove width of the connecting groove 21 is preferably set to be equal to or less than the groove width w in the minimum cross section 19. Here, the minimum cross section 19 is a cross section that minimizes the groove area when crossing the groove neck 18. The groove width w in the minimum cross section 19 is set to be smaller than the maximum groove width W of the groove head portion 17, and the maximum groove width W is set to be at least 1.2 times the groove width w. Moreover, it is preferable that the groove width of the connection groove | channel 21 is set to 2 mm or more. When the groove width of the connecting groove 21 is less than 2 mm, it becomes impossible to secure a groove cross-sectional area necessary for air in and out of the connecting groove 21 at the time of grounding, and the effect of reducing pumping noise tends to be reduced.

  The connecting groove 21 is not limited to a straight line extending and may extend while curving. Moreover, it is not restricted to what has a fixed groove width, You may extend, changing a groove width. In such a case, for the above reason, the maximum groove width of the connecting groove 21 is preferably equal to or less than the groove width w, and the minimum groove width is preferably 2 mm or more.

  The groove depth of the connecting groove 21 is preferably equal to or less than the groove depth of the groove head 17 (the land height of the block), and more preferably 20% or more. If the groove depth of the connecting groove 21 is less than 20% of the groove depth of the groove head portion 17, the volume of air released through the connecting groove 21 decreases, and the pumping noise reduction effect tends to be reduced. is there.

The relationship between the groove cross-sectional area S (mm ² ) in the minimum cross section 19 and the groove volume V (mm ³ ) when the connecting groove 21 on the groove head 17 side is not formed from the minimum cross section 19 is V / S ≧ 25 In this case, since the generation of the pumping sound becomes remarkable as already described, the configuration according to the present invention can be particularly useful. Here, the groove volume when the connecting groove 21 is not formed is a groove volume calculated using the groove head portion 17 when the connecting groove 21 is not formed on the groove head portion 17 as shown in FIG. In addition, when the minimum cross section 19 exists in multiple places, such as when the groove neck part 18 communicates with the groove head 17 with a constant groove width, the groove volume V is the minimum cross section 19 closest to the groove head 17. Is used to calculate.

  FIG. 4 is a plan view showing an example of a tread surface provided in the pneumatic tire of the present invention. The groove portion includes a lateral groove 9 extending while curving from the outer side in the tire width direction toward the center of the tread surface, a narrow groove 10 extending obliquely with respect to the tire circumferential direction so as to connect the lateral grooves 9, and a tread edge E And a lug groove 11 that opens and extends toward the center of the tread surface. Moreover, the tip part 12 of the block which goes to the outer side in the tire width direction has a taper cut part 13 in which the land part height gradually decreases toward the tip side, and extends at a substantially constant land part height from the tip of the taper cut part 13. The bridge portion 14 is formed, and the bridge portion 14 does not have a land portion height that substantially divides the groove portion. Therefore, in FIG. 4, a plurality of lateral grooves 9 that are tapered toward the outer side in the tire width direction are described. However, as shown by oblique lines, the tree branches are substantially directed from the tread edge E toward the center of the tread. A lateral groove 15 extending while branching into a shape is formed.

  On the tread surface shown in FIG. 4, the lug groove 11 corresponds to the bag-shaped groove. Further, when the lateral groove 9 is viewed as a groove head, the lateral groove 15 also corresponds to a bag-shaped groove. Thus, the bag-like groove may be, for example, a lug groove opened at the tread edge, or a lateral groove extending in a direction intersecting the tire circumferential direction and having an end portion disposed near the center of the tread. In such a tread surface, the narrow groove 10 that connects the lateral grooves 9 corresponds to the above-described connecting groove, and the pumping noise can be reduced by the above-described effects.

<Another embodiment>
(1) When a plurality of bag-like grooves are formed adjacent to each other in the tire circumferential direction, the connecting groove preferably connects the groove heads of the bag-like grooves and extends along the tire circumferential direction. Those are preferred. According to such a configuration, the substantially closed space is sequentially formed between the bag-like groove and the road surface as the tire rotates during traveling, and the pumping sound generated due to the substantially closed space is efficiently generated. Can be reduced.

  (2) In the present invention, the pattern pitch of the tread pattern and the shapes of the groove and the land are not particularly limited as long as the bag-shaped groove is formed on the tread surface. Further, the bag-like groove is not limited to the groove head having an elliptical shape in plan view, and may be, for example, circular or rectangular in plan view. The connecting groove is not limited to connecting the groove heads of the bag-shaped groove, but the groove head of the bag-shaped groove and a bag shape such as a circumferential groove or a lateral groove adjacent to the bag-shaped groove with the land portion interposed therebetween. A groove that is not a groove may be connected. Further, the connecting groove may connect the groove head portion of the bag-like groove and the grounding end. The direction in which the connecting groove extends is not particularly limited.

  Next, in order to specifically show the configuration and effects of the present invention, noise performance was evaluated, which will be described below. The evaluation was conducted on a stand-alone bench test (JASO C606-81) using a test tire (tire size LT265 / 75R16 10PR) at an air pressure of 310 kPa, a load of 6700 N, a used rim of 16 × 8.5-JJ, and a speed of 80 km / h. . In this bench evaluation, the noise level was measured using a microphone installed at a height of 0.25 m at a distance of 1 m from the center of the tire. As the test tire, a tire having five bag-shaped grooves shown in Table 1 formed on the tread surface was used.

各袋状溝に連結溝を設けないものを比較例、各袋状溝に連結溝を設けたものを実施例とした。連結溝の溝幅は４ｍｍとし、溝深さはブロックの陸部高さの７割とした。評価結果を図５に示す。

A comparative example was provided with no connecting groove in each bag-like groove, and an example was provided with a connecting groove in each bag-like groove. The groove width of the connecting groove was 4 mm, and the groove depth was 70% of the land height of the block. The evaluation results are shown in FIG.

  From the graph shown in FIG. 5, it can be seen that the noise level of the example is lower than that of the comparative example. This is because the groove head of the bag-shaped groove and the connecting groove that connects the groove adjacent to the bag-shaped groove with the land portion sandwiched between them are formed by the groove head and the road surface. It is thought that this is the effect that the air in the space is dispersed and released.

Tire meridian cross-sectional view showing an example of a pneumatic tire according to the present invention The perspective view which shows an example of the tread surface with which the pneumatic tire of this invention is provided. Plan view of bag-shaped groove The top view which shows an example of the tread surface with which the pneumatic tire which concerns on this invention is equipped Graph showing the evaluation results of noise performance A perspective view showing an example of a bag-like groove Graph showing the relationship between the groove volume at the groove head and the groove cross-sectional area at the groove neck

Explanation of symbols

6 tread surface 9 transverse groove 10 narrow groove 11 lug groove 15 lateral groove 16 inner wall 17 groove head portion 18 groove neck portion 19 minimum cross section 20 bag-like groove 21 connecting groove 22 land portion w groove width W in minimum cross section groove maximum W Groove width

Claims (4)

In pneumatic tires with grooves formed on the tread surface,
A groove head having a substantially loop-shaped inner wall partially opened by the groove, and a groove neck communicating with the opening of the groove head with a groove width smaller than the maximum groove width of the groove head; Having a bag-like groove having
A pneumatic tire characterized in that a connecting groove is formed to connect a groove or a grounding end adjacent to the bag-shaped groove with a land portion interposed therebetween and a groove head portion of the bag-shaped groove. When the cross-section of the groove neck having the smallest groove cross-sectional area is defined as the minimum cross-section, the groove cross-sectional area S (mm ² ) in the minimum cross-section and the groove from the minimum cross-section closest to the groove head 2. The pneumatic tire according to claim 1, wherein a relationship with a groove volume V (mm ³ ) when the connecting groove is not formed on the head side is V / S ≧ 25.   3. The groove width of the connecting groove is equal to or less than the groove width in the minimum cross section and equal to or greater than 2 mm when the cross section of the groove neck portion having the smallest groove cross-sectional area is defined as the minimum cross section. Pneumatic tire. The pneumatic tire according to any one of claims 1 to 3, wherein a groove depth of the connecting groove is 20% or more of a groove depth of the groove head portion.

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