JP2006193110A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of reducing the pumping sound generated by a bag-shaped groove formed on a tread surface. <P>SOLUTION: The pneumatic tire wherein a groove portion is formed on the tread surface comprises the bag-shaped groove 11 having a groove head portion 17 having an almost loop shaped inside wall 16 partially opening, and a groove neck portion 18 communicating to the opening of the groove head portion 17 with smaller groove width than the maximum groove width of the groove head portion 17. On the groove head portion 17 of the bag-shaped groove 11, a projecting portion 21 protruding from the groove bottom surface 20 is formed. <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 that can improve noise performance by providing a protrusion on the groove bottom. However, such a pneumatic tire is produced by abruptly releasing compressed air through the lateral groove because the protrusion provided in the vicinity of the opening end of the columnar lateral groove serves as a barrier for air passing through the lateral groove. This is to reduce the air column resonance noise and not to reduce the pumping noise in the bag-like groove as described above.
JP-A-6-48119

  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 provides 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 that is partially opened, and the groove is formed in the opening of the groove head. And a groove neck portion communicating with a groove width smaller than the maximum groove width of the head portion, and a protrusion protruding from the groove bottom surface is formed on the groove head portion of the bag-like groove. .

  According to the configuration of the present invention, the protruding portion that protrudes from the groove bottom surface is formed on the groove head portion of the bag-like groove, thereby reducing the substantially closed space formed by the groove head portion and the road surface during traveling. And the volume of air released through the groove neck can be reduced. In addition, there is an effect that vibration of air in the substantially closed space is absorbed by the protrusion. As a result, the pumping sound generated due to the bag-like groove can be effectively reduced, and the noise performance can be enhanced. Moreover, since the pumping sound can be reduced without changing the groove width of the bag-like groove, it can be suitably used for pneumatic tires that emphasize fashion.

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 protrusion is not formed is preferably V / S ≧ 25.

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 protrusion 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 noise level increases as the V / S increases, because the volume per groove cross-sectional area of the air passing through the groove neck increases. 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-described configuration is provided with a protrusion capable of reducing the pumping sound with respect to the bag-like groove where the generation of the pumping sound is significant, and the configuration according to the present invention can be particularly useful. .

  Here, the “transverse section of the groove neck” means a cross section orthogonal to the direction in which the groove neck extends. The “groove volume when no protrusion is formed” means the groove volume calculated using the groove bottom surface when the protrusion is not formed on the groove head.

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 surface area a (mm ² ) of the protrusion and the groove from the minimum cross section closest to the groove head It is preferable that the relationship with the groove surface area A (mm ² ) when the protrusion is not formed on the head side is 0.01 ≦ a / A ≦ 0.5.

  According to the said structure, the magnitude | size of the projection part with respect to a groove head can be made into an appropriate thing in view of noise performance and drainage performance. That is, when the a / A is less than 0.01, the effect of absorbing the vibration of the air in the substantially closed space formed by the groove head and the road surface tends to be reduced. On the other hand, if the a / A exceeds 0.5, the size of the protrusion with respect to the groove head portion increases, and therefore the drainage performance tends to decrease. Therefore, according to the said structure, pumping sound can be reduced effectively, ensuring drainage performance.

  Here, the “groove surface area” is the area of the groove bottom surface and the inner wall surface, and “the groove surface area when the protrusion is not formed on the groove head side from the minimum cross section” means that the protrusion is on the groove head. The area calculated from the groove cross-sectional area of the groove bottom surface, the inner wall surface, and the minimum cross section when not formed.

  In the above, the groove width is equal to or less than the groove width of the portion where the groove cross-sectional area is the smallest when crossing the groove neck of the bag-shaped groove, the groove head of the bag-shaped groove, and the bag-shaped groove It is preferable to include a connecting groove that connects another groove or a grounding end adjacent to each other across the land portion.

  A substantially closed groove formed by the groove head and the road surface is provided with a groove that connects the groove head of the bag-shaped groove and another groove or grounding end adjacent to the bag-shaped groove across the land portion. Air in the space is dispersed and discharged from both the groove neck and the connecting groove. As a result, the pressure of the released air decreases, so that the pumping sound can be reduced more effectively. Moreover, by setting the groove width of the connecting groove to be equal to or less than the groove width of the portion where the groove cross-sectional area becomes the smallest when crossing the groove neck of the bag-like groove, the connecting groove is not noticeable on the tread surface. There is no loss of sex.

  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.

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

[First Embodiment]
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 plan view showing an example of a tread surface provided in the pneumatic tire of the present invention. FIG. 3a is a perspective view of a bag-like groove. FIG. 3b is a plan view of the bag-like groove. 3c is a cross-sectional view taken along the line cc of FIG. 3b.

  The tread pattern formed on the tread surface 6 of the present embodiment is a so-called block type pattern, in which a groove portion and a plurality of land portions (blocks) divided by the groove portion are formed. The groove portion of the present embodiment includes a lateral groove 9 that extends while curving from the outer side in the tire width direction toward the center of the tread surface 6, and a narrow groove 10 that extends obliquely with respect to the tire circumferential direction so as to connect the lateral grooves 9 to each other. , A lug groove 11 (corresponding to the bag-like groove, hereinafter referred to as the bag-like groove 11) formed in a bag shape having an opening at the tread edge E and having a groove width locally expanded at the end. Have

  As shown in FIGS. 3 a and 3 b, the bag-shaped groove 11 includes a groove head 17 having a substantially loop-shaped inner wall 16 that is partially opened, and a maximum of the groove head 17 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 minimum cross section 19 is a cross section that minimizes the groove area when crossing the groove neck 18. Accordingly, 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.

  On the groove head portion 17 of the bag-like groove 11, a protruding portion 21 that protrudes from the groove bottom surface 20 is formed. Thereby, the substantially closed space formed by the groove head portion 17 and the road surface during traveling is reduced, and the volume of air compressed and released in the space can be reduced. As a result, the pumping sound generated due to the bag-like groove 11 can be effectively reduced.

  The relationship between the land height d (mm) of the protrusion 21 and the land height (groove depth of the groove head 17) D (mm) of the block is 0.15 ≦ d / D ≦ 0.75. It is preferable that 0.2 ≦ d / D ≦ 0.6. When d / D is less than 0.15, the effect of reducing the substantially closed space is poor, and the effect of reducing pumping noise tends to be reduced. On the other hand, if d / D exceeds 0.75, the land portion height of the protrusion 21 is too high, and the drainage performance in the bag-like groove 11 tends to decrease.

Further, 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 protrusion 21 is not formed on the groove head 17 side from the minimum cross section 19 is V / When S ≧ 25, since the generation of pumping noise becomes remarkable as already described, the configuration according to the present invention can be particularly useful. The groove volume when the protrusion 21 is not formed is a groove volume calculated using the groove bottom surface 22 when the protrusion 21 is not formed on the groove head 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 with a constant groove width, the groove volume V uses the minimum cross section 19 closest to the groove head 17. Is calculated.

The relationship between the surface area a (mm ² ) of the protrusion 21 and the groove surface area A (mm ² ) when the protrusion 21 is not formed on the groove head 17 side from the minimum cross section 19 is 0.01 ≦ a / A ≦ 0.5 is preferable, and 0.02 ≦ a / A ≦ 0.4 is more preferable. When a / A is less than 0.01, the effect of absorbing the vibration of air in the substantially closed space formed by the groove head portion 17 and the road surface during traveling tends to be reduced. On the other hand, if a / A exceeds 0.5, the size of the protrusion 21 with respect to the groove head portion 17 becomes large, so that the drainage performance tends to decrease. The groove surface area when the protrusion 21 is not formed is calculated using the groove bottom surface 22, the inner wall 16, and the minimum cross section 19 when the protrusion 21 is not formed on the groove head 17 as shown in FIG. 6. It is an area. When the minimum cross section 19 is present at a plurality of locations, the groove surface area A is calculated using the minimum cross section 19 closest to the groove head portion 17.

[Second Embodiment]
Except for the configuration described below for the second embodiment, the configuration and operation are the same as those of the first embodiment, and therefore, common points will be omitted and differences will be mainly described. FIG. 4 a is an example of a tread surface provided in the pneumatic tire of the present invention, and is a perspective view of a bag-like groove. FIG. 4b is a plan view of the bag-like groove.

  The bag-like groove 24 shown in FIGS. 4a and 4b is formed in a bag shape having a groove width locally expanded at the end portion, and has a substantially loop-shaped inner wall 27 partially opened. 25 and a groove neck portion 26 communicating with a groove width smaller than the maximum groove width of the groove head portion 25. The groove head portion 25 is formed in a substantially rectangular shape in plan view, and the groove head portions 25 of other bag-like grooves 24 are juxtaposed with the land portion interposed therebetween.

  The protruding portion 29 that protrudes from the groove bottom surface 28 of the groove head portion 25 is formed in a prismatic shape with a step formed on the side surface. Thus, by forming a step in the protrusion 29, the surface area of the protrusion 29 can be increased, and the vibration of the air in the substantially closed space formed by the groove head 25 and the road surface is absorbed during traveling. The effect to do can be improved.

  The groove head portion 25 is provided with a connecting portion 30 that connects the protruding portion 29 and the inner wall 27. FIG. 4 a shows an example of the connection portion 30 having a land portion height equivalent to that of the lower stage of the protrusion 29, but the land portion height of the connection portion 30 is not limited to this. By providing the connection portion 30, the volume of air in the substantially closed space formed by the groove head 25 and the road surface is reduced, and the rigidity of the protrusion 29 is increased to absorb the vibration of the air in the substantially closed space. Can enhance the effect.

  The connecting groove 31 extends so as to connect the groove heads 25 of the bag-like groove 24. As a result, the air in the substantially closed space formed by the groove head portion 25 and the road surface is dispersed and released from both the groove neck portion 26 and the connecting groove 31, and as a result, the pressure of the released air is reduced. Pumping noise can be reduced more effectively. The groove width of the connecting groove 31 is preferably equal to or less than the groove width in the minimum cross section and 2 mm or more. If the groove width of the connecting groove 31 is less than 2 mm, the groove cross-sectional area required for air in and out cannot be secured at the time of grounding, and the effect of reducing pumping noise tends to be reduced. The groove depth of the connecting groove 31 is preferably equal to or less than the land height of the block (groove depth of the groove head portion 25) and more than 20% thereof. When the groove depth of the connecting groove 31 is less than 20% of the height of the land portion of the block, the volume of air that is dispersed and released is small, and the effect of reducing the pumping noise tends to be small.

[Another embodiment]
(1) The tread pattern formed on the tread surface of the pneumatic tire according to the present invention is not limited to the one shown in the above embodiment as long as the bag-like groove is formed, and the pattern pitch, groove portion, and land The shape of the part is not particularly limited.

  (2) The present invention is not limited to the case where the lug groove has a bag shape as in the first embodiment described above, and can also be applied to the case where the groove formed in the center of the tread has a bag shape, for example. Further, in the above-described embodiment, the example in which the groove head portion and the protruding portion are oval in plan view or substantially rectangular in plan view is not limited thereto, and may be, for example, a gourd shape in plan view. . In addition, a protrusion part is not restricted to what is provided by a single thing, The thing in which several protrusion part is provided in one bag-like groove | channel may be used.

  (3) The connecting groove is not limited to connecting the groove head portions of the bag-like groove as in the second embodiment described above, and the land portion is sandwiched between the groove head portion of the bag-like groove and the bag-like groove. It is also possible to connect other adjacent grooves. 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, and examples include those extending along the tire circumferential direction or inclined.

  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.

各袋状溝に突起部を設けないものを比較例、各袋状溝に突起部を設けたものを実施例１、各袋状溝に突起部および連結溝を設けたものを実施例２とした。各突起部は、それぞれ上記ｄ／Ｄを０．５、上記ａ／Ａを０．２２とした。また、連結溝は、最小横断面における溝幅よりも小さい４ｍｍの溝幅と、ブロックの陸部高さの９割の深さとを有するものとした。評価結果を図５に示す。

A comparative example in which each bag-like groove is not provided with a protrusion, a first example in which each bag-like groove is provided with a protrusion, and a second example in which each bag-like groove is provided with a protrusion and a connecting groove. did. Each projection has a d / D of 0.5 and a / A of 0.22. In addition, the connecting groove has a groove width of 4 mm, which is smaller than the groove width in the minimum cross section, and a depth of 90% of the land portion 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 Example 1 is lower than that of the comparative example. This is because the projection in the groove head of the bag-like groove reduces the volume in the substantially closed space formed by the groove head and the road surface, and the air in the substantially closed space. This is considered to be due to the effect of vibration absorbed by the protrusion. Further, Example 2 is considered to have an effect that the noise level is lower than that of Example 1 and the air in the substantially closed space is dispersed and discharged by forming the connecting groove.

Tire meridian cross-sectional view showing an example of a pneumatic tire according to the present invention The top view which shows an example of the tread surface with which the pneumatic tire of this invention is provided Perspective view of bag-like groove Plan view of bag-shaped groove Cc cross-sectional view in FIG. 3b Perspective view of bag-like groove according to another embodiment Plan view of bag-like groove according to another embodiment 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 Horizontal groove 10 Narrow groove 11 Bag-like groove (lug groove)
16 inner wall 17 groove head 18 groove neck 19 minimum cross section 20 groove bottom surface 21 protrusion 24 bag-like groove 25 groove head 26 groove neck 27 inner wall 28 groove bottom 29 protrusion 30 connecting portion 31 connecting groove d protrusion groove Land height w Groove width D in the minimum cross section Groove depth W of groove head Maximum groove width of groove head

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 protrusion protruding from the groove bottom surface is formed on the groove head 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 projection is not formed on the head side is V / S ≧ 25. When the cross-section of the groove neck having the smallest groove cross-sectional area is the minimum cross-section, the surface area a (mm ² ) of the protrusion and the groove cross-section side from the minimum cross-section closest to the groove head The pneumatic tire according to claim 1, wherein a relationship with the groove surface area A (mm ² ) when the protrusion is not formed is 0.01 ≦ a / A ≦ 0.5. It has a groove width equal to or less than the groove width of the portion where the groove cross-sectional area becomes the smallest when crossing the groove neck of the bag-shaped groove, and the groove head portion of the bag-shaped groove and the land portion in the bag-shaped groove The pneumatic tire according to any one of claims 1 to 3, further comprising a connecting groove that connects another groove or a ground contact end adjacent to each other.

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