JP6294603B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire having improved performance on snow while maintaining steering stability performance on a dry road surface.

  There has been proposed a pneumatic tire in which a tread portion is provided with main grooves and sipes extending in the tire circumferential direction. Such a pneumatic tire improves the running performance on snow (hereinafter referred to as “snow performance”) by the edge component in the tire circumferential direction, and effectively suppresses the side slip on the snow.

  However, the positions of the main grooves and sipes as described above are particularly important in order to improve the performance on snow. Further, the main grooves and sipes have a problem that the rigidity of the tread portion is lowered and the steering stability performance on the dry road surface is lowered.

  The following Patent Document 1 proposes a pneumatic tire that defines an inclination direction of a belt cord of a belt ply and an inclination direction of a lateral groove of a tread portion. Such a pneumatic tire suppresses a decrease in rigidity of the tread portion.

JP2013-136187A

  However, even the pneumatic tire of the above-mentioned Patent Document 1 is not sufficient in terms of both the steering stability performance on the dry road surface and the performance on snow, and there is room for further improvement.

  The present invention has been devised in view of the above circumstances, and has as its main object to provide a pneumatic tire with improved performance on snow while maintaining steering stability performance on a dry road surface.

  In the tread portion, a pair of shoulder main grooves extending continuously in the tire circumferential direction on the tread ground end side and a center main groove extending continuously on the inner side in the tire axial direction than the shoulder main grooves are provided in the tread portion. A pair of shoulder land portions on the outer side in the tire axial direction than the pair of shoulder main grooves and a pair of middle land portions between the shoulder main grooves and the center main groove. The ratio W1 / W2 between the width W1 of the shoulder land portion in the tire axial direction and the width W2 of the middle land portion in the tire axial direction is 1.6 to 2.0, and the middle land portion Are provided with a plurality of middle lateral grooves extending obliquely with respect to the tire axial direction, and the shoulder land portion has a shoulder width extending continuously in the tire circumferential direction and having a groove width smaller than that of the shoulder main groove. -By providing the sub-groove, the shoulder sub-groove includes a main portion on the outer side in the tire axial direction, and a sub-portion between the shoulder main groove and the shoulder sub-groove, and the sub-portion in the tire axial direction A ratio W3 / W1 between the width W3 and the width W1 of the shoulder land portion in the tire axial direction is 0.15 to 0.30, and the main portion extends inward in the tire axial direction from the tread ground contact end. A plurality of shoulder lug grooves that terminate without communicating with the shoulder sub-grooves are provided.

  In the pneumatic tire according to the present invention, the middle lateral groove includes a first middle lateral groove that communicates with the center main groove and the shoulder main groove, a second middle groove that communicates with the shoulder main groove, and terminates in the middle land portion. Middle lateral grooves are included, and it is desirable that the first middle lateral grooves and the second middle lateral grooves are alternately provided in the tire circumferential direction.

  In the pneumatic tire according to the present invention, the middle lateral groove is preferably inclined at an angle of 40 to 60 ° with respect to the tire axial direction.

  In the pneumatic tire according to the present invention, it is preferable that the main portion is provided with a closed type first shoulder sipe having both ends terminating in the main portion.

  In the pneumatic tire according to the present invention, it is preferable that the shoulder land portion is provided with a second shoulder sipe extending from the inner end of the shoulder lug groove in the tire axial direction to the shoulder main groove.

  In the pneumatic tire according to the present invention, it is preferable that the second shoulder sipe is inclined in the direction opposite to the middle lateral groove with respect to the tire axial direction.

  The pneumatic tire of the present invention has a pair of shoulder main grooves extending continuously in the tire circumferential direction on the tread portion at the most tread ground end side, and a center main extending continuously on the inner side in the tire axial direction from the shoulder main grooves. By providing the groove, a pair of shoulder land portions outside the pair of shoulder main grooves in the tire axial direction and a pair of middle land portions between the shoulder main groove and the center main groove are separated.

  The ratio W1 / W2 between the width W1 of the shoulder land portion in the tire axial direction and the width W2 of the middle land portion in the tire axial direction is 1.6 to 2.0. Thereby, the width | variety of the tire axial direction of a shoulder part is ensured, and the rigidity of a shoulder part improves. For this reason, the steering stability performance on a dry road surface improves. Further, since such a shoulder main groove is provided on the inner side in the tire axial direction than a typical shoulder main groove of a conventional pneumatic tire, a large ground pressure is applied to the shoulder main groove. For this reason, a shoulder main groove exhibits the outstanding edge effect and improves on-snow performance.

  The middle land portion is provided with a plurality of middle lateral grooves that are inclined with respect to the tire axial direction. Such middle lateral grooves exhibit an edge effect in the tire circumferential direction and the tire axial direction, and improve the performance on snow.

  The shoulder land portion is provided with a shoulder sub-groove extending continuously in the tire circumferential direction and having a groove width smaller than that of the shoulder main groove. Thereby, a shoulder land part contains the main part of the tire axial direction outer side of a shoulder subgroove, and the subpart between a shoulder main groove and a shoulder subgroove. Such a shoulder secondary groove further increases the edge component in the tire circumferential direction by the shoulder secondary groove while maintaining the rigidity of the shoulder land portion. Accordingly, the side slip during running on snow is effectively suppressed while maintaining the steering stability performance on the dry road surface.

  A ratio W3 / W1 of the width W3 of the shoulder land portion in the tire axial direction and the width W1 of the shoulder land portion in the tire axial direction is 0.15 to 0.30. Thereby, a shoulder subgroove is also relatively provided in the tire axial direction inside of the shoulder land portion. For this reason, a large ground pressure is applied to the shoulder sub-groove. Therefore, an excellent edge effect is exhibited and the performance on snow is improved.

  The main portion of the shoulder land portion is provided with a plurality of shoulder lug grooves extending inward in the tire axial direction from the tread ground contact end and terminating without communicating with the shoulder sub-groove. Such a shoulder lug groove improves the snow drainage performance when running on a snowy road while maintaining the rigidity of the shoulder land portion on the inner side in the tire axial direction. Therefore, the on-snow performance is improved while maintaining the steering stability performance on the dry road surface.

It is an expanded view of the tread part of the pneumatic tire of this embodiment. It is AA sectional drawing of FIG. It is an enlarged view of the middle land part of FIG. It is BB sectional drawing of FIG. It is an enlarged view of the shoulder land part of FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a development view of a tread portion 2 of a pneumatic tire (hereinafter sometimes simply referred to as “tire”) 1 of the present embodiment. The pneumatic tire 1 of this embodiment is suitably used as a radial tire for passenger cars, for example.

  As shown in FIG. 1, the tread portion 2 of the tire 1 is provided with a pair of shoulder main grooves 3 and 3 and a center main groove 4.

  The shoulder main groove 3 extends continuously in the tire circumferential direction on the tread ground contact end Te side. The shoulder main groove 3 of the present embodiment has a substantially constant groove width and is linear. The shoulder main groove 3 may be wavy or zigzag-shaped.

  The “tread grounding end Te” is a flat surface with a normal load applied to a normal tire 1 which is assembled with a normal rim (not shown) and filled with a normal internal pressure, and which is not loaded, with a camber angle of 0 °. This is the contact position on the outermost side in the tire axial direction when the contact is made on the ground.

  The “regular rim” is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, “Standard Rim” for JATMA, “Design Rim” for TRA, For ETRTO, "Measuring Rim".

  “Regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum value described in “VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO.

  “Regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. “JATMA” is “Maximum load capacity”, TRA is “TIRE LOAD LIMITS” The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”, “LOAD CAPACITY” in the case of ETRTO.

  The center main groove 4 is provided on the inner side in the tire axial direction than the shoulder main groove 3. The center main groove 4 extends continuously in the tire circumferential direction. The center main groove 4 has a substantially constant groove width and is linear. The center main groove 4 of this embodiment consists of one, and is provided on the tire equator C. For example, two center main grooves 4 may be provided on both sides of the tire equator C in the tire axial direction.

  The groove width W4 of the shoulder main groove 3 and the groove width W5 of the center main groove 4 are, for example, 2.5 to 4.5% of the tread ground contact width TW. The shoulder main groove 3 and the center main groove 4 exhibit excellent wet performance while maintaining the rigidity of the tread portion 2. The tread contact width TW is a distance in the tire axial direction between the tread contact ends Te and Te of the tire 1 in the normal state.

  FIG. 2 is a cross-sectional view taken along the line AA in FIG. As shown in FIG. 2, the groove depth d1 of the shoulder main groove 3 and the groove depth d2 of the center main groove 4 are preferably 5 to 10 mm, for example.

  As shown in FIG. 1, the tread portion 2 is divided into a pair of shoulder land portions 5, 5 and a pair of middle land portions 6, 6. The shoulder land portion 5 is provided outside the shoulder main groove 3 in the tire axial direction. The middle land portion 6 is provided between the shoulder main groove 3 and the center main groove 4.

  The ratio W1 / W2 between the width W1 of the shoulder land portion 5 in the tire axial direction and the width W2 of the middle land portion 6 in the tire axial direction is 1.6 to 2.0. Thereby, the width in the tire axial direction of the shoulder land portion 5 is sufficiently secured, and the rigidity of the shoulder land portion 5 is improved. For this reason, the steering stability performance on a dry road surface improves. Further, since the shoulder main groove 3 is provided on the inner side in the tire axial direction than the typical shoulder main groove 3 of the conventional pneumatic tire, a large ground pressure is applied to the shoulder main groove 3. For this reason, the shoulder main groove 3 exhibits an excellent edge effect and improves the performance on snow.

  In order to further exhibit the above-described effects, the ratio W1 / W2 is preferably 1.7 or more, and preferably 1.9 or less.

  FIG. 3 shows an enlarged view of the middle land portion 6. As shown in FIG. 3, the middle land portion 6 is provided with a plurality of middle lateral grooves 10. Each middle lateral groove 10 extends in the same direction with respect to the tire axial direction. Such middle lateral groove 10 exhibits an edge effect in the tire circumferential direction and the tire axial direction, and improves performance on snow.

  In order to further exhibit the above-described effects, it is desirable that the middle lateral groove 10 be smoothly curved. The angle θ1 of the middle lateral groove 10 with respect to the tire axial direction gradually increases from the tire axial direction outer side a toward the inner side b. Such middle lateral grooves 10 increase the edge component in the tire circumferential direction on the inner side in the tire axial direction where the contact pressure is higher. For this reason, skidding on the snow is further suppressed.

  In order to further improve the effect of suppressing the side slip on the snow and the improvement of the steering stability performance on the dry road surface, the angle θ1 of the middle lateral groove 10 with respect to the tire axial direction is preferably 40 ° or more, more preferably 45 ° or more. , Preferably 60 ° or less, more preferably 55 ° or less.

  The middle lateral groove 10 extends with a substantially constant groove width W6. The groove width W6 of the middle lateral groove 10 is preferably not less than 0.15 times, more preferably not less than 0.20 times, preferably not more than 0.30 times the groove width W4 of the shoulder main groove 3 (shown in FIG. 1). More preferably, it is 0.25 times or less. Such middle lateral grooves 10 increase the edge component while maintaining the rigidity of the middle land portion 6. For this reason, the on-snow performance is improved while maintaining the stable driving performance on the dry road surface.

  FIG. 4 shows a cross-sectional view of the middle lateral groove 10 in FIG. 3 taken along the line BB. As shown in FIG. 4, the groove depth d3 of the middle lateral groove 10 is preferably 0.08 times or more, more preferably 0.11 times or more of the groove depth d1 of the shoulder main groove 3, preferably Is 0.18 times or less, more preferably 0.15 times or less. Such a middle land portion 6 improves wet performance while maintaining the rigidity of the middle land portion 6.

  It is desirable that a groove bottom sipe 13 is provided on the groove bottom 10 d of the middle lateral groove 10. In this specification, “sipe” means a cut having a width of 0.5 to 1.0 mm, and is distinguished from a drainage groove.

  Such a groove bottom sipe 13 effectively absorbs moisture in the snow compressed in the middle lateral groove 10 when traveling on a snowy road. Therefore, the generation of a water film between the tread surface of the middle land portion 6 and the road surface is suppressed, and the performance on snow is improved. Furthermore, since the groove bottom sipe 13 increases the groove volume by opening the middle lateral groove when running on a snowy road, the performance on snow is improved.

  The depth d6 of the groove bottom sipe 13 is preferably 3.0 times or more, more preferably 3.2 times or more, preferably 3.5 times or less, more preferably 3 times the groove depth d3 of the middle lateral groove 10. Less than 3 times. Such a groove bottom sipe 13 further exhibits the above-described effects while maintaining the rigidity of the middle land portion 6. The depth d6 of the groove bottom sipe is a distance in the tire radial direction from the groove bottom 10d of the middle lateral groove 10 to the groove bottom 13d of the groove bottom sipe 13.

  As shown in FIG. 3, the middle lateral groove 10 includes a first middle lateral groove 11 and a second middle lateral groove 12.

  The first middle lateral groove 11 communicates with the center main groove 4 and the shoulder main groove 3. The second middle lateral groove 12 communicates with the shoulder main groove 3 and terminates in the middle land portion 6. The first middle lateral groove 11 and the second middle lateral groove 12 increase the edge component while maintaining the rigidity on the inner side in the tire axial direction of the middle land portion 6 loaded with a large ground pressure. As a result, the on-snow performance is improved while maintaining the stable driving performance on the dry road surface.

  It is desirable that the first middle lateral grooves 11 and the second middle lateral grooves 12 are provided alternately in the tire circumferential direction. Thereby, the rigidity distribution of the middle land portion 6 becomes smooth, and uneven wear of the middle land portion 6 is suppressed.

  FIG. 5 shows an enlarged view of the shoulder land portion 5. As shown in FIG. 5, a shoulder sub-groove 20 is provided in the shoulder land portion 5.

  The shoulder sub-groove 20 extends continuously in the tire circumferential direction. The shoulder sub-groove 20 of the present embodiment has a substantially constant groove width and is linear. The shoulder minor groove 20 may be wavy or zigzag shaped.

  The shoulder sub-groove 20 has a smaller groove width W7 than the shoulder main groove 3 (shown in FIG. 1). Such a shoulder sub-groove 20 increases the edge component while maintaining the rigidity of the shoulder land portion 5. The groove width W7 of the shoulder sub-groove 20 is preferably 0.35 times or more, more preferably 0.40 times or more, preferably 0.55 times the groove width W4 (shown in FIG. 1) of the shoulder main groove 3. Below, more preferably 0.50 times or less. When the groove width W7 of the shoulder sub-groove 20 is less than 0.35 times the groove width W4 of the shoulder main groove 3, the wet performance may be deteriorated. On the other hand, when the groove width W7 of the shoulder sub-groove 20 is larger than 0.55 times the groove width W3, the rigidity of the shoulder land portion 5 is lowered, and the steering stability performance on the dry road surface may be lowered.

  From the same point of view, as shown in FIG. 2, the groove depth d4 of the shoulder sub-groove 20 is preferably 0.37 times or more, more preferably 0.42 times the groove depth d1 of the shoulder main groove 3. It is more than double, preferably 0.57 times or less, more preferably 0.52 times or less.

  As shown in FIG. 5, the shoulder land portion 5 is divided into a main portion 21 and a sub portion 22 by providing the shoulder sub-groove 20 as described above.

  The sub part 22 is provided between the shoulder main groove 3 and the shoulder sub groove 20. The sub part 22 is a rib not provided with a groove having a groove width larger than that of the sipe. The sub part 22 extends in a straight line with a substantially constant width.

  The ratio W3 / W1 of the width W3 of the auxiliary portion 22 in the tire axial direction and the width W1 of the shoulder land portion 5 in the tire axial direction is 0.15 to 0.30. Thereby, the shoulder sub-groove 20 is also relatively provided on the inner side in the tire axial direction of the shoulder land portion 5. For this reason, a large ground pressure is applied to the shoulder sub-groove 20. Therefore, an excellent edge effect is exhibited and the performance on snow is improved.

  In order to further exert the above-described effects, the ratio W3 / W1 is preferably 0.18 or more, more preferably 0.20 or more, preferably 0.27 or less, more preferably 0.25 or less. .

  The main portion 21 is provided outside the shoulder sub-groove 20 in the tire axial direction. The main portion 21 is provided with a plurality of shoulder lug grooves 30 and shoulder sipes 26.

  The shoulder lug groove 30 extends from the tread ground contact end Te toward the inside in the tire axial direction. The shoulder lug groove 30 terminates without communicating with the shoulder sub-groove 20. Such a shoulder lug groove 30 improves the snow drainage performance when running on a snowy road while maintaining the rigidity of the shoulder land portion 5 on the inner side in the tire axial direction. Therefore, the on-snow performance is improved while maintaining the steering stability performance on the dry road surface.

  The shoulder lug groove 30 includes a first portion 31 and a second portion 32. The first portion 31 of the shoulder lug groove 30 extends parallel to the tire axial direction. The second portion 32 of the shoulder lug groove 30 continues to the inner side in the tire axial direction of the first portion 31 and extends inward in the tire axial direction while gradually increasing the angle θ2 of the shoulder lug groove 30 with respect to the tire axial direction. Such a shoulder lug groove 30 maintains the wandering performance by the first portion 31 and increases the edge component in the tire circumferential direction by the second portion 32, thereby effectively suppressing the skid on the snow.

  The groove width W8 of the shoulder lug groove 30 is preferably 0.45 times or more, more preferably 0.48 times or more, preferably 0.55 times the groove width W4 of the shoulder main groove 3 (shown in FIG. 1). Below, more preferably 0.52 times or less. If the groove width W8 of the shoulder lug groove 30 is smaller than 0.45 times the groove width W4 of the shoulder main groove 3, the wandering performance may be deteriorated. On the other hand, when the groove width W8 of the shoulder lug groove 30 is larger than 0.55 times the groove width W4, the steering stability performance on the dry road surface may be deteriorated.

  From the same viewpoint, the groove depth d5 (shown in FIG. 2) of the shoulder lug groove 30 is preferably 0.80 times or more, more preferably 0.83 times or more than the groove depth d1 of the shoulder main groove 3. , Preferably 0.90 times or less, more preferably 0.87 times or less.

  As shown in FIG. 5, the ratio L1 / W1 between the length L1 of the shoulder lug groove 30 in the tire axial direction and the width W1 of the shoulder land portion 5 in the tire axial direction is preferably 0.40 or more. Preferably it is 0.44 or more, preferably 0.56 or less, more preferably 0.52 or less. When the ratio L1 / W1 is smaller than 0.40, wandering performance may be deteriorated. On the contrary, when the ratio L1 / W1 is larger than 0.56, the rigidity of the shoulder land portion 5 is lowered, and the steering stability performance on the dry road surface may be lowered.

  The shoulder sipe 26 includes a first shoulder sipe 27 and a second shoulder sipe 28.

  The first shoulder sipe 27 is provided between the shoulder lug grooves 30 and 30 adjacent in the tire circumferential direction. The first shoulder sipe 27 extends substantially parallel to the shoulder lug groove 30. The first shoulder sipe 27 is a closed type sipe in which both ends 27 e and 27 e are terminated in the main portion 21. Such a first shoulder sipe 27 increases the edge component while maintaining the rigidity of the shoulder land portion 5. For this reason, the on-snow performance is improved while maintaining the stable driving performance on the dry road surface.

  It is desirable that the first shoulder sipes 27 and the shoulder lug grooves 30 are provided alternately in the tire circumferential direction. Thereby, the rigidity distribution of the shoulder land portion 5 becomes uniform, and uneven wear of the shoulder land portion 5 is suppressed.

  The second shoulder sipe 28 extends from the inner end 30 i of the shoulder lug groove 30 in the tire axial direction to the shoulder main groove 3. The second shoulder sipe 28 is inclined in the same direction as the second portion 32 of the shoulder lug groove 30 with respect to the tire axial direction. The second shoulder sipe 28 is inclined in the direction opposite to the middle lateral groove 10 (shown in FIG. 1) with respect to the tire axial direction. Such a second shoulder sipe 28 exhibits an edge effect in a direction different from the middle lateral groove 10. For this reason, performance on snow improves.

  The second shoulder sipe 28 has a depth larger than that of the shoulder sub-groove 20. Such a second shoulder sipe 28 exhibits the edge effect more effectively and relaxes the rigidity of the shoulder land portion 5 on the inner side in the tire axial direction. For this reason, the rigidity distribution in the tire axial direction of the shoulder land portion 5 becomes smooth. Therefore, on-snow performance is improved and uneven wear of the shoulder land portion 5 is suppressed.

  Although the pneumatic tire of the present invention has been described in detail above, the present invention is not limited to the specific embodiment described above, and can be implemented with various modifications.

A pneumatic tire of size 185 / 60R15 having the basic pattern shown in FIG. 1 was prototyped based on the specifications shown in Table 1 and tested for driving stability and performance on snow on a dry road surface. The common specifications and test methods for each tire are as follows.
Wearing rim: 15 × 6J
Tire internal pressure: 230kPa
Test vehicle: Front-wheel drive vehicle, displacement 1300cc
Tire mounting position: all wheels

<Operation stability on dry road>
Steering stability performance when the test vehicle was run on a test course consisting of a dry asphalt road surface was evaluated by a driver's sensory evaluation. A result is a score which sets the comparative example 1 to 100, and shows that steering stability performance is excellent, so that a numerical value is large.

<Snow performance>
The performance on snow when running on the snow with the test vehicle was evaluated by sensory evaluation of the driver. A result is a score which sets the comparative example 1 to 100, and shows that steering stability performance is excellent, so that a numerical value is large.
The test results are shown in Table 1.

  As a result of the test, it was confirmed that the pneumatic tire of the example improved on-snow performance while maintaining the steering stability performance on the dry road surface.

2 tread portion 3 shoulder main groove 4 center main groove 5 shoulder land portion 6 middle land portion 10 middle lateral groove 20 shoulder sub groove 21 main portion 22 sub portion 30 shoulder lug groove

Claims (6)

A pair of shoulder main grooves extending continuously in the tire circumferential direction on the tread ground end side and one center main groove extending continuously on the inner side in the tire axial direction than the shoulder main grooves are provided in the tread portion. Accordingly, a pair of shoulder land portions between the pair of shoulder main grooves and the tread grounding end, and a pair of middle land portions between the shoulder main grooves and the center main groove are separated into the air. Tire,
The ratio W1 / W2 between the width W1 of the shoulder land portion in the tire axial direction and the width W2 of the middle land portion in the tire axial direction is 1.6 to 2.0,
The middle land portion is provided with a plurality of middle lateral grooves extending obliquely with respect to the tire axial direction,
Wherein the shoulder land portion, by a shoulder sub groove having a smaller groove width than continuously Katsu Nobi the shoulder main grooves in the tire circumferential direction are provided, the main between the tread ground contact edge and the shoulder sub groove and parts, are classified into a secondary portion between the shoulder sub groove and the shoulder main grooves,
The ratio W3 / W1 between the width W3 of the auxiliary portion in the tire axial direction and the width W1 of the shoulder land portion in the tire axial direction is 0.15 to 0.30,
The main portion is provided with a plurality of shoulder lug grooves extending inward in the tire axial direction from the tread grounding end and terminating without communicating with the shoulder sub-groove,
1. A pneumatic tire according to claim 1, wherein the main portion is provided with a closed-type first shoulder sipe having both ends terminating in the main portion. The middle lateral groove includes a first middle lateral groove communicating with the center main groove and the shoulder main groove;
A second middle lateral groove communicating with the shoulder main groove and terminating in the middle land portion;
The pneumatic tire according to claim 1, wherein the first middle lateral groove and the second middle lateral groove are alternately provided in a tire circumferential direction.   The pneumatic tire according to claim 1 or 2, wherein the middle lateral groove is inclined at an angle of 40 to 60 ° with respect to a tire axial direction. The pneumatic tire according to any one of claims 1 to 3, wherein a groove bottom sipe is provided at a groove bottom of the middle lateral groove .
  The pneumatic tire according to any one of claims 1 to 4, wherein the shoulder land portion is provided with a second shoulder sipe extending from an inner end of the shoulder lug groove in the tire axial direction to the shoulder main groove.   The pneumatic tire according to claim 5, wherein the second shoulder sipe is inclined in a direction opposite to the middle lateral groove with respect to a tire axial direction.

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