JP4776523B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly to a balance-oriented pneumatic tire that is excellent in drainage performance, steering stability, and uneven wear properties, and also reduces noise.

  In the pneumatic tire, in order to achieve both drainage performance and steering stability, a tread portion is provided with a circumferential groove extending along the tire circumferential direction and an inclined groove extending obliquely with respect to the tire circumferential direction. In this type of tire, drainage in the front-rear direction of the tire can be performed by the circumferential groove, and drainage to the tire side can be performed by the inclined groove.

  However, in general, in such a tire, in order to improve drainage, the inclined groove is opened in the circumferential groove in the tread central region, so that the land portion rigidity of the acute angle portion defined by the inclined groove and the circumferential groove is low. As a result, there are problems that steering stability is deteriorated and uneven wear is likely to occur.

  As a technique for disposing a circumferential groove and an inclined groove in the tread portion and improving both drainage performance and steering stability, for example, in Patent Document 1, a pair of circumferential main grooves is provided in the tread portion in the circumferential direction. In addition to partitioning the ribs, a plurality of inclined main grooves that open to the circumferential main grooves are disposed, and these inclined main grooves have a pattern center side portion as a steeply inclined portion and a tread end side portion as a gently inclined portion. A directional tread pattern having an extended shape and chamfering toward the tip of an acute angle portion defined by a circumferential main groove and an inclined main groove is disclosed. Although the tire described in Patent Document 1 has good drainage and steering stability, the present inventors have further studied, and both sides of the acute angle portion are space main circumferential grooves and inclined main grooves. Due to the division, there is a problem that the land portion rigidity for suppressing the deformation of the block tends to be insufficient particularly when a lateral force is applied.

In Patent Document 2, the central main groove is not disposed in the tread portion, and a large number of inclined grooves are opened in the side main grooves, and the groove depth is decreased toward the pattern center in the inclined grooves. A tire is disclosed in which a groove bottom-up region that terminates in the tread central region is formed. Although the tire described in Patent Document 2 has excellent steering stability, there is no central main groove, and since the central main groove and the inclined groove are not open, sufficient drainage is obtained. There was room for improvement.
JP-A-9-2025 JP 2006-76349 A

  Accordingly, an object of the present invention is to adopt a tread pattern in which a central main groove and a steeply inclined groove opening to the tread portion are arranged in the tread portion, and in the tread pattern, the first main region is defined by the central main groove and the steeply inclined groove. It is an object of the present invention to provide a pneumatic tire that improves noise drainage and steering stability while suppressing noise and uneven wear by optimizing an acute angle portion and a steeply inclined groove.

In order to achieve the above object, the gist of the present invention is as follows.
(1) One central main groove located in the pattern center or in the vicinity thereof and extending along the tire circumferential direction in a half area where the tread portion is divided into two at the pattern center, and the central main groove and the tread end At least one side main groove located between and extending along the tire circumferential direction, and a plurality of steep slopes extending at a relatively small angle with respect to the tire circumferential direction between the central main groove and the side main grooves A central land portion is defined by a central main groove and a first side main groove that is a side main groove adjacent to the central main groove, and the central main groove, the first side main groove, and the tire circumferential direction In a pneumatic tire in which a central land portion is divided into a number of blocks substantially by two steeply inclined grooves adjacent to each other to form a block row, the groove depth of the steeply inclined grooves has a first lateral side. An inclined groove bottom that gradually increases toward the main groove is provided, and is divided into a central main groove and a steeply inclined groove. The first acute angle portion of the lock, a pneumatic tire, characterized in that toward the distal end of the first chamfered portion land portion height decreases gradually provided, and the first chamfered portion and the inclined groove bottom portion is adjacent.
(2) The pneumatic tire according to (1), wherein the chamfered length of the first chamfered portion is shorter than the extended length of the inclined groove bottom.
(3) The pneumatic tire according to (1) or (2), wherein the tip of the first chamfered portion is disposed to face the inclined groove bottom at the same height position.
(4) The pneumatic tire according to any one of (1) to (3), wherein the block is provided with a secondary groove extending in a substantially tire width direction from the first lateral main groove toward the central main groove side.
(5) The above-mentioned (1) to (2), wherein the second chamfered portion in which the land height gradually decreases toward the tip of the second acute angle portion of the block defined by the steeply inclined groove and the first side main groove. The pneumatic tire according to any one of 4).
(6) The pneumatic tire according to any one of (1) to (5), wherein the steeply inclined groove has an angle with respect to the tire circumferential direction of 5 to 50 °.

  Here, “in the vicinity of the pattern center” specifically refers to a region in a range of 33% of the tread width TW with the pattern center CL as the center. Further, “one central main groove in a half area” means a rib shape continuously extending in the tire circumferential direction C on the pattern center CL in addition to the case where one central main groove is formed on the pattern center CL. In order to form a land portion, the case where a pair of central main grooves are disposed across the pattern center CL is included. Furthermore, “substantially block” is used in order to include a block even when the opening position of the steeply inclined groove to the central main groove is higher than the groove bottom position of the central main groove.

  According to the present invention, a tread pattern in which a central main groove and a steeply inclined groove opening to the tread portion are provided in the tread portion, and the first tread pattern defined by the central main groove and the steeply inclined groove is provided in the tread pattern. By optimizing the acute angle portion and the steeply inclined groove, it is possible to provide a pneumatic tire that improves both drainage performance and steering stability while suppressing noise and uneven wear.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a tread pattern showing an embodiment of the present invention, FIG. 2 (a) is a cross-sectional view taken along line AA in FIG. 1, FIG. 2 (b) is a cross-sectional view taken along line BB in FIG. (C) is CC sectional drawing of FIG. 1, and FIG.2 (d) is DD sectional drawing of FIG. In the figure, reference numeral 1 denotes a tread portion, 2 denotes a tread end, 3 denotes a central main groove, 4 denotes a rib-like land portion, 5 denotes a first side main groove, 6 denotes a central land portion, 7 denotes a steeply inclined groove, 8 denotes An inclined groove bottom portion 9 is a first chamfered portion.

The tire having the tread pattern shown in FIG. 1 is located in or near the pattern center CL in the half areas S ₁ and S _{2 in} which the tread portion 1 is divided into _two by the pattern center CL, and along the tire circumferential direction C. One central main groove 3 extending, and at least one side main groove located between the central main groove 3 and the tread end 2 and extending along the tire circumferential direction C, one first side in FIG. A steeply inclined groove 7 extending at a relatively small angle with respect to the tire circumferential direction C is disposed between the main main groove 3 and the central main groove 3 and the first lateral main groove 5. The central land portion 6 is partitioned by the one side main groove 5. In FIG. 1, a rib-like land portion 4 that extends continuously in the tire circumferential direction C is formed between the central main groove 3 and the central main groove 3 in the other half section in order to emphasize steering stability. In the present invention, it can be provided as necessary.

  In the tire according to the present invention, the tread portion 1 is provided with a central main groove 3 and a first side main groove 5 extending along the tire circumferential direction C, thereby providing a tread ground plane that is at least necessary as a high-performance tire. A steeply inclined groove 7 extending between the central main groove 3 and the side main grooves at a relatively small angle with respect to the tire circumferential direction C, preferably 5 to 50 °. By providing, it can mainly control the drainage of the water present in the tread ground surface to the side, and the central main groove 3 and the first side main groove 5 which is a side main groove adjacent to the central main groove 3. The central land portion 6 is partitioned by the central main groove 3, the first side main groove 5, and the two steeply inclined grooves 7 adjacent in the tire circumferential direction C. The basic performance of the tire can be ensured by partitioning into 14 and forming the block row 15.

  The main feature of the present invention is that the steeply inclined groove 7 is provided with an inclined groove bottom 8 whose groove depth gradually increases toward the first side main groove 5, and the central main groove 3 and the steeply inclined groove 7 are provided. The first chamfered portion 9 whose land portion height gradually decreases toward the tip thereof is provided at the first acute angle portion of the block 14 that is partitioned by and the inclined groove bottom portion 8 and the first chamfered portion 9 are adjacent to each other. is there.

  That is, in the case of a conventional tire (for example, Patent Document 2) in which the steeply inclined groove 7 disposed in the tread portion 1 is provided with the inclined groove bottom portion 8 whose groove depth gradually increases toward the first side main groove 5. Since the central main groove 3 and the steeply inclined groove 7 are not open, it cannot be said that sufficient drainage is obtained although the steering stability is excellent, and the central main groove 3 and the steeply inclined groove 7 are not obtained. In the conventional tire (for example, patent document 1) which provided the 1st chamfering part 9 in which the land part height reduces gradually toward the front-end | tip at the 1st acute angle part of the block 14 divided by these, good drainage property Although the steering stability is obtained, the first chamfered portion 9 is partitioned by the central main groove 3 and the steeply inclined groove 7 which are spaces, and in particular for suppressing deformation of the block 14 when a lateral force is applied. Although the land portion rigidity tends to be insufficient, in the present invention, the inclined groove bottom 8 and the first chamfered portion 9 are used. By adjoining, a space (volume) as a groove can be maintained on the tire surface in the vicinity of the central main groove 3, so that drainage can be secured, and the inclined groove bottom portion 8 and the first chamfered portion 9 are adjacent in the groove. Steering stability can be ensured as a result of obtaining high land rigidity by supporting each other.

The details of this configuration will be described below.
In the present invention, by providing the steeply inclined groove 7 with the inclined groove bottom portion 8 whose groove depth gradually increases toward the first side main groove 5, adjacent blocks 14 constituting the central land portion 6 are substantially separated. Are connected to each other, and the rigidity of the land portion of the entire central land portion 6 is increased. As a result, the steering stability is improved. Furthermore, since the inclined groove bottom 8 gradually increases the groove depth toward the first side main groove 5, the groove volume of the steeply inclined groove 7 gradually increases toward the first side main groove 5. There is an effect of accelerating the flow of water taken into the steeply inclined groove 7 in the central region of the tread, and drainage is improved.

  For example, it is preferable that the extending length of the inclined groove bottom 8 is in the range of 10 to 70 mm, that is, in the range shown by hatching in FIG.

  If the extending length of the bottom 8 of the inclined groove is less than 10 mm, the effect of accelerating the flow of water taken into the steeply inclined groove 7 tends to be small, and if it exceeds 70 mm, the groove volume itself of the steeply inclined groove 7 becomes small. This is because drainage tends to be difficult to ensure.

  Further, according to the present invention, the first chamfered portion 9 whose land portion height gradually decreases toward the tip end 9c is provided at the first acute angle portion of the block 14 defined by the central main groove 3 and the steeply inclined groove 7. To increase the rigidity of the tip 9c portion, prevent crushing when the first acute angle portion is grounded, and thus prevent escape deformation into the groove, improve drainage, and ensure smoother grounding. In addition, noise can be reduced. Further, the first chamfered portion 9 has an effect of increasing the tire contact surface pressure at the tip 9c portion, and the steering stability is improved and uneven wear is suppressed.

  For example, the chamfer length of the first chamfered portion 9 is preferably in the range of 2 to 15 mm, and in the range shown by hatching in FIG.

  If the chamfered length of the first chamfered portion 9 is less than 2 mm, the rigidity of the tip 9c portion tends not to be sufficiently obtained. If the chamfered length exceeds 15 mm, the tread surface area decreases and the steering stability tends to deteriorate. It is.

  In the present invention, not only the inclined groove bottom portion 8 and the first chamfered portion 9 are provided, but also the inclined groove bottom portion 8 and the first chamfered portion 9 are adjacent to each other.

  With this configuration, in the present invention, since the inclined groove bottom portion 8 and the first chamfered portion 9 are adjacent to each other in the tread central region, a large volume space as a groove on the tire surface can be formed. improves. Further, the inclined groove bottom portion 8 and the first chamfered portion 9 in the steeply inclined groove 7 are adjacent to and support each other, so that the bending rigidity of the lateral force is particularly improved and the land portion rigidity of the central land portion 6 is further increased. Improves.

  For example, in FIG. 2D, the inclined groove bottom 8 has a start end 8a having a minimum groove depth in the vicinity of the central main groove 3, and an inclined surface 8b in which the groove depth gradually increases linearly from the start end 8a. The end 8c has the maximum groove depth. On the other hand, the first chamfered portion 9 has a starting end 9a in which the land portion height of the block 14 is maximum from the central land portion 6, and a chamfered surface 9b in which the land portion height gradually decreases linearly from the starting end 9a. The tip 9c has a minimum part height.

  The first chamfered portion 9 preferably has a chamfered length 9l of 2 to 15 mm, and its tip 9c contacts the inclined surface 8b of the inclined groove bottom 8.

  This is because when the chamfer length is less than 2 mm, the rigidity of the tip 9c portion tends not to be sufficiently obtained, and when it exceeds 15 mm, the tread surface area decreases and the steering stability tends to deteriorate.

  Since the first chamfered portion 9 is processed in the direction of cutting from the tire surface, if the chamfering length is too long, the tread surface area is reduced, so that the ground contact property of the tire is deteriorated and the steering stability is deteriorated. Further, if the extending length of the inclined groove bottom portion 8 is too short due to the inclination in the steeply inclined groove 7, the effect of supporting the first chamfered portion 9 and the effect of improving the drainage property are deteriorated. As a guide for the length, it is preferable that the chamfer length of the first chamfered portion 9 is shorter than the extended length of the inclined groove bottom portion 8. More preferably, the chamfer length of the first chamfered portion 9 and the extended length of the inclined groove bottom portion 8 are 1: 1.1 to 1:10. This is because if the extending length of the inclined groove bottom portion 8 exceeds 10 times the chamfering length of the first chamfered portion 9, the groove volume tends to be insufficient and sufficient drainage performance may not be ensured.

  The front end 9c of the first chamfered portion 9 is preferably disposed opposite to the inclined groove bottom portion 8 at the same height position. This ensures a good drainage by ensuring the water flow in the groove without being disturbed.

  3 is a tread pattern showing another embodiment of the present invention, FIG. 6A is a cross-sectional view taken along line EE in FIG. 3, and FIG. 6B is a cross-sectional view taken along line FF in FIG. .

  A block 14 defined by the central main groove 3, the two steeply inclined grooves 7, and the first side main groove 5 has a substantially tire width direction from the first side main groove 5 toward the central main groove 3. It is preferable to dispose the extending sub-groove 11, and it is even more preferable that the angle with respect to the tire circumferential direction C is 45 to 135 °. The sub-groove 11 is inclined at a gentler angle than the steeply inclined groove 7, whereby the land portion rigidity can be adjusted. In FIG. 3, the auxiliary groove 11 that terminates in the block 14 is provided. This is because the long block 14 is divided in the tire circumferential direction C to adjust the rigidity of the land portion and ensure the steering stability. And can be provided as necessary.

  It is preferable to provide a second chamfered portion 10 whose land height gradually decreases toward the tip of the second acute angle portion of the block 14 defined by the steeply inclined groove 7 and the first side main groove 5. Having such a second chamfered portion 10 can reinforce the rigidity of the land portion of the central land portion 6 without impairing the drainage of the first side main groove 5 and can further improve the steering stability. .

  The steeply inclined groove 7 preferably has an angle with respect to the tire circumferential direction C of 5 to 50 °. This is because if it is less than 5 °, the rigidity of the tip 9a tends to be insufficient, and if it exceeds 50 °, drainage tends to be insufficient.

  Furthermore, it is preferable that the steeply inclined groove 7 has an extending shape in which an extending angle with respect to the tire circumferential direction C gradually increases from the central main groove 3 side toward the first side main groove 5 side. With this shape, water in the tread contact surface can be efficiently drained to the side of the tire by matching the streamline, and good drainage can be ensured.

  For example, the shape of the steeply inclined groove 7 is in the range of 0 to 30 ° with respect to the tire circumferential direction C in the region of about 5 to 10% of the tread width TW from the pattern center CL in accordance with the flow of water in the tread contact surface. It is preferable to incline and incline at this angle. In FIG. 1 and FIG. 3, the steeply inclined groove 7 has a tread edge at an angle in the range of 70 to 90 ° while being curved with respect to the tire circumferential direction C with the short sipe 16 across the first side main groove 5. Although the part further comprised by the gentle inclination part 17 extended until it opens to 2 is shown, you may make the gentle inclination part 17 open to the 1st side main groove 5 instead of the short sipe 16.

  Further, from the viewpoint of improving ride comfort and wet brake performance, FIG.

  Further, from the viewpoint of improving drainage of the central main groove 3 and promoting drainage to the steeply inclined groove 7, the shape of the groove wall on the central main groove 3 side of the block 14 of the central land portion 6 is seen in a plan view in FIG. In this example, a wavy shape is formed by repeatedly connecting circular arcs having a predetermined curvature radius along the tire circumferential direction C. Also, as shown in FIG. 3, the steep slope 7 and the first lateral main groove 5 are steeply inclined as shown in FIG. The wall surface of the block 14 of the central land portion 6 adjacent to the opening position of the groove 7 and the first side main groove 5 projects into the first side main groove 5, and the land portion height is the groove bottom of the side main groove 5. It is also possible to provide a third chamfered portion 13 that gradually decreases toward.

  Further, the inclined groove bottom 8 can make the inclined surface 8b flat, and, for example, a concave curved surface shown in FIG. 4 (a), a convex curved surface shown in FIG. 4 (b), and an inclination shown in FIG. 4 (c). Various shapes such as a three-dimensional structure in which the groove depth of the surface is different in the width direction can be used. The inclined surface 8b is particularly preferably a flat surface in terms of good drainage and little change in performance after wear.

  Further, the first chamfered portion 9 can make the chamfered surface 9b flat, for example, a concave curved surface shown in FIG. 5 (a), a convex curved surface shown in FIG. 5 (b), and shown in FIG. 5 (c). Various shapes such as a three-dimensional structure in which the land portion height of the chamfered surface is different in the width direction can be used. Furthermore, the 2nd chamfering part 10 and the 3rd chamfering part 13 can also be made into various shapes similarly. About the 1st chamfer part 9 and the 2nd chamfer part 10, the convex curve (FIG.5 (b)) which can be comprised by the contact surface from a tire surface is especially preferable. By making the chamfered portion a convex curved surface, there is an effect of reducing the impact sound when the chamfered portion hits a road surface and an effect of improving drainage. The third chamfered portion 13 is preferably a flat surface or a concave curved surface from the viewpoint that a sufficient groove volume can be secured while increasing the rigidity of the base of the block.

  Further, in FIG. 3, the circumferential narrow groove 18 extending along the tire circumferential direction C toward the pattern center CL side of the rib-like land portion 4 in terms of suppressing the straight traveling performance during traveling and particularly the uneven wear of the tire center portion. The case where is provided is shown.

  The tread pattern configured as described above is a point-symmetric pattern with respect to the pattern center CL in FIGS. 1 and 3, but may be a directional pattern in the present invention.

  In addition, the place mentioned above only showed the example of typical embodiment of this invention, and can change a various change in a claim. For example, FIG. 1 shows the case where only one side main groove (first side main groove 5) is provided as the side main groove, but two or more side main grooves are provided. May be.

  Next, a tire according to the present invention was prototyped and performance evaluation was performed, which will be described below.

The tire of Example 1 has the tread pattern shown in FIG. 3, the flat groove inclined groove bottom portion 8 and the first chamfered portion 9 of FIG. 5B, and the tire size is 195 / 65R15 (tread width TW 150 mm). Yes, specifications such as dimensions of the central main groove 3, the side main groove, the steeply inclined groove 7, the auxiliary groove 11, the rib-like land portion 4, the block 14 and the like are summarized in Tables 1 to 4. In the present invention, since the tire structure other than the tread portion does not require modification, the tire structure is almost the same as that of a conventional pneumatic tire for passenger cars.
Moreover, the curvature radius R of one of the wavy portions constituting the side wall on the central main groove 3 side of the central land portion 6 is 165 mm (average).

  The tire of Comparative Example 1 has the tread pattern shown in FIG. 7 and has the same configuration as the tire of Example 1 except that the inclined groove bottom portion 8 and the first chamfered portion 9 are not provided. The tire of Comparative Example 2 has the same configuration as the tire of Example 1 except that the inclined groove bottom 8 is not provided. The tire of Comparative Example 3 was substantially the same as the tire of Example 1 except that the first chamfered portion 9 was not provided.

(Test method)
Each of the above test tires was mounted on a test vehicle, and the following tests were performed under the conditions of tire pressure: 230 kPa (relative pressure) and tire load load: equivalent to two passengers.

1. Straight running drainage The straight speed traveled on a wet road surface with a water depth of 5 mm, the critical speed at which hydroplaning phenomenon occurred was measured, and this measured value was evaluated.

2. Steering stability when dry The circuit course in the dry state was driven by sports in various driving modes and evaluated by the feeling of the test driver.

3. Steering stability when wet We drove sports in various driving modes on wet circuit courses and evaluated them based on the feeling of test drivers.

4). Pattern noise The vehicle was run in various driving modes on a smooth road surface in a dry state, and evaluated by feeling by a test driver.

5. Uneven wear resistance A general road in a dry state was traveled in various travel modes, and evaluation was performed based on the amount of step wear between adjacent blocks during travel of 5000 km.

These evaluation results are shown in Table 5.
In addition, all the numerical values of the evaluation results in Table 5 are shown as index ratios when the evaluation result of Comparative Example 1 is 100, and the larger the numerical value, the better.

  According to the present invention, a tread pattern in which a central main groove and a steeply inclined groove opening to the tread portion are provided in the tread portion, and the first acute angle portion defined by the central main groove and the steeply inclined groove in the tread pattern is provided. By optimizing the steeply inclined grooves, it is possible to provide a pneumatic tire that improves both drainage and steering stability, and also suppresses noise and uneven wear.

It is the figure which expanded a part of tread part of the pneumatic tire according to the present invention. (A), (b), (c), (d) is sectional drawing on the AA, BB, CC, and DD line | wire of FIG. 1, respectively. It is the figure which expanded some tread parts of other pneumatic tires according to the present invention. (A), (b), (c) is a perspective view which shows various embodiment of the inclination groove bottom part 8 according to this invention. (A), (b), (c) is a perspective view which shows various embodiment of the 1st chamfering part 9 according to this invention. (A), (b) is sectional drawing on the EE and FF line | wire of FIG. 3, respectively. It is the figure which expanded a part of tread part of a comparison tire (comparative example 1).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Tread end 3 Central main groove 3a, 3b Wall surface 4 Rib-shaped land part 5 1st side main groove 6 Central land part 7 Steeply inclined groove 8 Inclined groove bottom part 9 1st chamfering part 8a, 9a Starting end 8b Inclined surface 9b Chamfered surface 8c End 9c Tip 10 Second chamfered portion 11 Sub-groove 12 Lateral sipe 13 Third chamfered portion 14 Block 15 Block row 16 Short sipe 17 Slightly inclined portion 18 Circumferential narrow groove TW Tread width CL Pattern center C Tire circumferential direction W Tire width direction

Claims (6)

One central main groove located in the pattern center or in the vicinity thereof and extending along the tire circumferential direction, between the central main groove and the tread end, in a half area where the tread portion is divided into two by the pattern center At least one side main groove located and extending along the tire circumferential direction, and a plurality of steeply inclined grooves extending at a relatively small angle with respect to the tire circumferential direction between the central main groove and the side main grooves. A central land portion is defined by the central main groove and the first side main groove which is a side main groove adjacent to the central main groove, and is adjacent to the central main groove, the first side main groove and the tire circumferential direction. In a pneumatic tire formed by dividing a central land portion into a number of blocks substantially by two steeply inclined grooves to form a block row,
The steeply inclined groove is provided with an inclined groove bottom portion where the groove depth gradually increases toward the first side main groove, and the first acute angle portion of the block defined by the central main groove and the steeply inclined groove faces the tip. A pneumatic tire characterized in that a first chamfered portion in which a land portion height gradually decreases and an inclined groove bottom and a first chamfered portion are adjacent to each other.   The pneumatic tire according to claim 1, wherein a chamfer length of the first chamfered portion is shorter than an extended length of the inclined groove bottom portion.   3. The pneumatic tire according to claim 1, wherein a tip of the first chamfered portion is disposed to face the inclined groove bottom at the same height position.   The pneumatic tire according to any one of claims 1 to 3, wherein a secondary groove extending in a substantially tire width direction from the first side main groove toward the central main groove side is disposed in the block.   5. The second chamfered portion in which the land height gradually decreases toward the tip of the second acute angle portion of the block defined by the steeply inclined groove and the first side main groove. The described pneumatic tire.   The pneumatic tire according to any one of claims 1 to 5, wherein the steeply inclined groove has an angle with respect to the tire circumferential direction of 5 to 50 °.

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