JP2005193750A - Pneumatic tire for heavy load - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire for a heavy load, which pneumatic tire can suppress the deterioration of the workability of assembling the tire to a rim in the new state and the deterioration of the re-inflating performance in the re-assembling work after running. <P>SOLUTION: In the pneumatic tire for the heavy load, a point Q is an intersection point of an inside periphery (an inside peripheral surface 6 of a tire) in a meridian cross section of the tire with a horizontal line F drawn from the point P nearest to a bead toe 3 among the outside periphery of a bead core 8 so as to be in parallel with the axis of the tire. Recesses 7 are formed circumferentially on the inside peripheral surface 6 of the tire between the bead toe 3 and the intersection point Q in the tire. A flat portion 5c, which is in parallel or nearly in parallel with the horizontal line F, is formed from the bead toe 3 toward a bead heel 4 on a bead base 5 formed between the bead toe 3 and the bead heel 4. The ratio ϕ/D of the inside diameter ϕ of the bead toe 3 to the diameter D of the rim 10, into which the pneumatic tire 1 for the heavy load is assembled, is set to satisfy the following conditions, 0.954≤ϕ/D≤0.960. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a heavy-duty pneumatic tire, and more particularly to a heavy-duty pneumatic tire capable of suppressing a decrease in rim assembling workability in a new article and a reinflation property in re-rim assembling work after traveling. It is.

  In general, a heavy duty pneumatic tire mounted on a vehicle such as a truck or a bus is mounted on a rim having a bead seat taper angle of 15 °. The work of assembling the heavy load pneumatic tire on the rim is first performed by assembling the bead heel of one tire bead portion of the heavy load pneumatic tire so as to be in close contact with one of the rim flanges, and the other tire bead portion of the rim. Assume that it is in the center. Then, air is sent from the air hole of the rim to the space formed by the tire inner peripheral surface of the heavy duty pneumatic tire and the rim, and the heavy duty pneumatic tire is inflated. At this time, the bead base of the other tire bead portion dropped into the center portion of the rim rides on the other bead seat of the rim, and the bead heel comes into close contact with the other rim flange of the rim.

Here, when inflating the heavy-duty pneumatic tire, a frictional force is generated between the tire bead portion and the rim, and a force that rotates the tire bead portion around the bead core acts by this frictional force. This force is a force from the bead heel of the tire bead portion toward the bead toe. Therefore, at the end of the rim assembly work, the bead toe is lifted from the rim. Therefore, in order to prevent this lifting, a technique as shown in Patent Document 1 has been proposed.
JP 2001-239812 A

  The above prior art employs a two-step taper on the bead base of the tire bead portion, and forms a recess along the tire bead portion on the inner surface of the tire to suppress the rise of the bead toe relative to the rim. This prevents rim displacement when overcoming the unevenness of the road surface during traveling or during steering, thereby ensuring good rim assembly workability.

  By the way, when a heavy-duty pneumatic tire assembled with a rim is mounted on a vehicle and traveled, the heavy-duty pneumatic tire becomes a heavy load, a high internal pressure, and a high temperature. Accordingly, when the vehicle travels with the bead toe lifted from the rim, the rubber constituting the heavy duty pneumatic tire is hardened compared to when it is new, and the shape of the tire bead portion is deformed. That is, the inner diameter φ of the bead toe becomes larger after traveling than when it is new. Here, the heavy duty pneumatic tire may be assembled to the rim again. In this case, since the inner diameter φ of the bead toe after traveling is increased, the ratio φ / D between the inner diameter φ of the bead toe and the rim diameter D of the rim is increased. Thereby, in the re-rim assembling work, there is a possibility that the re-inflation property when the heavy-duty pneumatic tire is inflated is deteriorated.

  On the other hand, in order to suppress the deterioration of the reinflation property, the inner diameter φ of the bead toe of the new heavy duty pneumatic tire is reduced, that is, the ratio φ / D between the inner diameter φ of the bead toe and the rim diameter D of the rim is reduced. It is possible to do. However, as described above, when the inner diameter φ of the beat toe when new is reduced, there is a problem that workability of assembling the rim with respect to the rim of the heavy duty pneumatic tire when new is deteriorated.

  Therefore, the present invention has been made in view of the above, and is a heavy-duty pneumatic that can suppress a decrease in rim assembly workability at the time of a new article and reinflation of re-rim assembly work after traveling. The object is to provide a tire.

  In order to solve the above-described problems and achieve the object, in the present invention, a tire inner circumference in a tire meridian cross section, and a horizontal line drawn parallel to the tire central axis from a point P closest to the bead toe among outer circumferences of the bead core, Is formed on the inner circumferential surface of the tire between the bead toe and the intersection Q in the tire circumferential direction, and the bead base formed between the bead toe and the bead heel is directed from the bead toe toward the bead heel. A flat portion that is parallel or substantially parallel to the tire central axis is formed, and the ratio φ / D between the inner diameter φ of the bead toe and the rim diameter D of the rim for assembling the heavy duty pneumatic tire is 0.954 ≦ φ / D ≦ 0.960. It is in the range of.

  In addition, it is preferable that the whole surface area in the tire inner peripheral surface of a recessed part is 30% or more with respect to the whole area of the tire inner peripheral surface between bead toe and intersection Q.

  According to these inventions, in order to reduce the rigidity in the vicinity of the bead toe of the tire bead portion, the recess is formed in the tire inner circumferential surface between the bead tow and the intersection point Q in the tire circumferential direction, and the inner diameter φ of the bead toe and the tire Rim assembly workability when the ratio of the rim to the rim diameter D of the rim to be assembled is in the range of 0.954 ≦ φ / D ≦ 0.960, that is, a heavy duty pneumatic tire in which this recess is not formed The inner diameter φ of the bead toe may decrease. Therefore, even if the inner diameter φ of the bead toe is smaller than the rim diameter D of the rim to be assembled, the vicinity of the bead toe is easily deformed in the rim assembling work when the heavy duty pneumatic tire is new. Both tire bead portions can be easily inserted into opposite rim flanges of the rim. Thereby, the fall of the rim assembly workability | operativity at the time of a new article can be suppressed.

  Further, when the vehicle travels, the tire bead portion is deformed and the inner diameter φ of the bead toe is larger than the rim diameter D of the rim, that is, no recess is formed even if the inner diameter φ of the new bead toe is larger. The inner diameter φ of the bead toe is previously smaller than the inner diameter φ of the bead toe that can suppress the deterioration of the rim assembly workability when the heavy duty pneumatic tire is new. Therefore, the inner diameter φ of the bead toe after traveling is smaller than the inner diameter φ of the bead toe after traveling of the heavy duty pneumatic tire in which no recess is formed. Thereby, the fall of the reinflation property of the re-rim assembly work after driving | running | working can be suppressed.

  Here, when removing the heavy-duty pneumatic tire after traveling from the rim, the bead toe of the tire bead portion is brought into contact with the beat seat or rim flange of the rim to apply a force in the tire equatorial plane direction. At this time, the rubber constituting the vicinity of the bead toe may be hardened because it is after running, and the force applied in the tire equatorial plane direction may cause cracks and flaking, that is, bead toe chipping. This is more likely to occur as the angle between the tire inner peripheral surface and the bead base becomes sharper. However, according to the above-described invention, a flat portion parallel to or substantially parallel to the tire central axis is formed in the vicinity of the bead toe of the bead base from the bead toe toward the bead heel. Therefore, the occurrence of bead toe chipping can be suppressed by this flat portion.

  According to the present invention, in the heavy duty pneumatic tire, the recess is a groove formed continuously in the tire circumferential direction. According to this invention, since the groove part which is a recessed part is continuously formed in the tire circumferential direction, the rigidity of the tire bead part near the bead toe can be uniformly reduced in the tire circumferential direction. Therefore, even if the inner diameter φ of the bead toe is smaller than the rim diameter D of the rim to be assembled, in the rim assembling work when the heavy duty pneumatic tire is new, the bead toe can be easily located at any position in the tire circumferential direction. Due to the deformation, both tire bead portions of the heavy duty pneumatic tire can be more easily inserted into the rim flanges facing each other of the rim.

  The heavy-duty pneumatic tire according to the present invention has an effect that it is possible to suppress a decrease in rim assembling workability at the time of a new article and a decrease in reinflation of re-rim assembling work after traveling.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same. In addition, since the internal structure of the pneumatic tire in the following embodiments is the same as that of a general radial tire or bias tire, the description thereof is omitted.

  FIG. 1-1 is a diagram illustrating a configuration example of a tire bead portion of a heavy duty pneumatic tire according to the present invention. FIG. 1-2 is a diagram illustrating a recess formed in the tire inner circumferential surface. FIG. 2 is a view showing a rim assembled state of the heavy duty pneumatic tire according to the present invention. In addition, the said FIGS. 1-1 and FIG. 2 are partial sectional drawings of the cross section which cut the pneumatic tire for heavy loads with the meridian surface.

  As shown in FIG. 1-1, in the heavy-duty pneumatic tire 1 according to the present invention, the bead base 5 is disposed between the bead toe 3 and the bead heel 4 of the tire bead portion 2 in the tire circumferential direction (in FIG. (Vertical direction) is formed continuously. A concave portion 7 is formed in the tire inner periphery 6 of the heavy load pneumatic tire 1 over the tire circumferential direction as shown in FIG. Here, 2a is a tire chuck line which is located at the same distance from the tire central axis of the heavy duty pneumatic tire 1 (not shown) and is continuous in the tire circumferential direction. Reference numeral 8 denotes a bead core composed of a plurality of bead wires. Further, 9 is folded back by the bead core 8 and is located on one side of the heavy load pneumatic tire 1 (not shown), the tread, the other side wall, and the opposite side of the center of the heavy load pneumatic tire 1. It is a carcass layer folded by the bead core of the tire bead portion.

  Here, the recesses 7 are formed in two rows in the tire circumferential direction in the vicinity of the bead toe 3 on the tire inner circumferential surface 6. Moreover, the surface shape in the tire internal peripheral surface 6 of this recessed part 7 is circular. The formation position of the recess 7 with respect to the tire inner peripheral surface 6 will be described. First, as shown in the figure, P is the point closest to the bead toe among the outer circumferences of the bead core 8 in the tire meridian direction cross section. In the figure, the bead core 8 has a hexagonal cross section, but the shape of the bead core 8 is not limited to this, and may be a square cross section. Next, a horizontal line F is drawn from this point P in parallel with a tire center axis (not shown). Next, an intersection point between the horizontal line F and the tire inner periphery (tire inner peripheral surface 6) is defined as an intersection point Q. And this recessed part 7 is formed in the tire internal peripheral surface 6 between the bead toe 3 and this intersection Q. Here, the recesses 7 are preferably formed continuously in the tire circumferential direction, but may be formed discretely in the tire circumferential direction.

  Moreover, it is preferable that the depth d of the recessed part 7 is 2 mm or more. This is because if the depth d of the recess 7 is less than 2 mm, the rigidity in the vicinity of the bead toe 3 is not sufficiently lowered, and the rim assembly workability at the time of a new article, which will be described later, may be lowered. The depth d of the recess 7 is more preferably 5 mm or less. This is to suppress a decrease in the fitting force between the heavy-duty pneumatic tire 1 and the rim 10 and the occurrence of cracks at the bottom of the recess 7.

  Moreover, although the recessed part 7 is formed in the tire internal peripheral surface 6 between the bead toe 3 and the intersection Q, More preferably, the distance h from the bead toe 3 to the recessed part 7 closest to this bead toe 3 is 3 mm or more. It is preferable. This is because if the distance h to the concave portion 7 is less than 3 mm, the bead toe 3 is too close, the rigidity in the vicinity of the bead toe 3 is remarkably reduced, and the fitting force between the heavy duty pneumatic tire 1 and the rim 10 may be reduced. Because there is.

  Furthermore, as shown to FIGS. 1-2, it is that the whole surface area in the tire internal peripheral surface 6 of the recessed part 7 is 30% or more with respect to the total area of the tire internal peripheral surface between the bead toe 3 and the intersection Q. preferable. This is because when the total surface area of the inner peripheral surface 6 of the recess 7 is less than 30% with respect to the entire area of the tire inner peripheral surface between the bead toe 3 and the intersection point Q, the rigidity in the vicinity of the bead toe 3 is reduced. This is not sufficient, and there is a risk that the rim assembly workability at the time of a new article, which will be described later, may deteriorate. The overall surface area of the inner peripheral surface 6 of the recess 7 is more preferably 50% or less with respect to the entire area of the tire inner peripheral surface between the bead toe 3 and the intersection point Q.

  As shown in FIG. 1, the bead base 5 of the tire bead portion 2 includes a first-stage taber 5a, a second-stage taper 5b, and a flat portion 5c from the bead heel 4 to the bead toe 3 in the tire meridian cross section. Has been. That is, the bead base 5 is formed to have a two-step taper. Here, the two-step taper of the bead base 5 is an angle α between the first-step taper 5a and the tire central axis of the heavy-duty pneumatic tire 1, and the second-step taper 5b and the heavy-load pneumatic tire 1 tire. The angle β formed with the central axis is formed such that α <β. The angle α is in the range of 16 ° to 22 °, preferably 17 °, and the angle β is in the range of 25 ° to 50 °, preferably 30 °. In the figure, the bead base 5 has a two-step taper, but the present invention is not limited to this and may be formed by a single-step taper.

  The flat portion 5 c of the bead base 5 is formed between the second-stage taper 5 b and the bead toe 3. In other words, a flat portion 5 c is formed on the bead base 5 formed between the bead toe 3 and the bead heel 4 from the bead toe 3 toward the bead heel 4. Further, the flat portion 5c has an angle γ formed by a horizontal line G drawn in parallel with the tire central axis of the heavy duty pneumatic tire 1 from the bead toe 3 toward the bead heel 4, that is, parallel to or substantially about the tire central axis. It is formed to be parallel. In addition, it is preferable that the width t of this flat part 5c is 3 mm or more and 5 mm or less.

  The inner diameter φ of the bead toe 3 of the tire bead portion 2, that is, the distance between the opposite bead toes 3 passing through the tire central axis of the heavy load pneumatic tire 1 is the rim for assembling the inner diameter φ of the bead tow 3 and the heavy load pneumatic tire 1. The ratio φ / D with respect to the rim diameter D of 10 (two-dot chain line in FIG. 1) is set to be in the range of 0.954 ≦ φ / D ≦ 0.960. Here, when the ratio φ / D is in the range of 0.954 ≦ φ / D ≦ 0.960, the rim assembly workability when a heavy duty pneumatic tire having no concave portion 7 is new is lowered. The inner diameter φ of the bead toe may be set.

  The rim 10 to which the heavy duty pneumatic tire 1 is assembled refers to a standard rim of a standard such as JATMA. The rim 10 includes a bead sheet 11 to which the bead base 5 of the tire bead portion 2 is in close contact and a rim flange 12 to which the bead heel 4 of the tire bead portion 2 is in close contact. The rim 10 is a 15 ° tapered rim in which the bead seat 11 is inclined 15 ° with respect to the rim axis.

  The heavy load pneumatic tire 1 according to the present invention is assembled to the rim 10, that is, a rim assembly operation will be described. Here, a case where the heavy load pneumatic tire 1 is assembled to the rim 10 in a new state will be described. First, a lubricant (not shown) is applied to the tire bead portion 2 of the heavy duty pneumatic tire 1 or at least one of the bead sheet 11 and the rim flange 12 of the rim 10. In this lubricant, when the heavy duty pneumatic tire 1 is assembled to the rim 10, the bead base 5 and the bead heel 4 of the tire bead portion 2 are opposite to the tire equatorial plane direction with respect to the bead seat 11 and the rim flange 12 of the rim 10. It is intended to facilitate movement in the direction.

  Next, the bead heel 4 of one tire bead portion 2 of the heavy-duty pneumatic tire 1 is assembled so as to be in close contact with one rim flange 12 of the rim 10, and the other tire bead portion 2 is attached to the center of the rim 10 (not shown). It is assumed that it has been dropped into the department. At this time, when the opposing tire bead portion 2 is inserted between the opposing rim flanges 12 of the rim 10, the rigidity in the vicinity of the bead toe 3 is lowered due to the deformation of the recess 7. Therefore, the inner diameter φ of the bead toe 3 when this heavy-duty pneumatic tire 1 is new is the inner diameter of the bead toe that may reduce the rim assembly workability when the heavy-duty pneumatic tire is not formed with the recess 7. Even if it is smaller than φ, that is, smaller than the rim diameter D of the rim 10 to which the rim is assembled, the rigidity in the vicinity of the bead toe 3 is reduced. One opposing tire bead portion 2 can be easily inserted into the opposing rim flange of the rim 10. Thereby, the fall of rim assembly workability | operativity at the time of the new article of the heavy duty pneumatic tire 1 can be suppressed.

  Next, the air of normal internal pressure is sent from the air hole of the rim into the space formed by the tire inner peripheral surface 6 of the heavy duty pneumatic tire 1 and the rim 10, that is, inflated. When the inflation starts, the heavy load pneumatic tire 1 starts to expand in the tire width direction, and the bead base 5 of the other tire bead portion 2 dropped into the center portion of the rim 10 is the other bead seat of the rim 10. 11 and the bead base 5 moves on the bead seat 11 in the tire width direction. When air is inflated to some extent, the bead heel 4 of the other tire bead portion 2 comes into close contact with the other rim flange 12 of the rim 10. Furthermore, the rim assembling work of the heavy duty pneumatic tire 1 is completed by inflating the air until the normal internal pressure is reached.

  In the heavy-duty pneumatic tire 1 in which the rim assembling work has been completed, as shown in FIG. 2, the first stage taper 5 a, the second stage taper 5 b, and the flat part 5 c of the bead base 5 are the bead seats 11 of the rim 10. Due to deformation. Here, the bead toe 3 of the tire bead portion 2 does not float with respect to the bead sheet 11. This is because the amount of deformation of the recess 7 deformed in the tire radial direction during the rim assembling work is larger than the amount of lift of the bead toe 3 in the tire radial direction, and the recess 7 returns to its original state, thereby canceling the lift of the bead toe 3. is there.

  As described above, the heavy-duty pneumatic tire 1 assembled with a rim in a new state is mounted on a vehicle such as a truck or a bus for traveling, but the rim 10 may be damaged during traveling. In this case, it is necessary to remove the rim-assembled heavy-duty pneumatic tire 1 from the rim 10 and assemble it to a new rim 10. Further, a tread portion (not shown) of the heavy-duty pneumatic tire 1 may reach the use limit due to traveling, and portions other than the tread portion (for example, the sidewall portion and the tire bead portion 2) may not yet reach the use limit. In this case, in order to perform retreading for regenerating the tread portion, it is necessary to remove the heavy-duty pneumatic tire 1 assembled with the rim from the rim 10 and assemble the rim with the rim 10 again.

  When the rim-assembled heavy duty pneumatic tire 1 after running is removed from the rim, the bead toe 3 of the tire bead portion 2 comes into contact with the bead seat 11 or the rim flange 12 of the rim 10 so that the tire equatorial plane direction is reached. Power is added. Here, in the heavy-duty pneumatic tire 1 after traveling, there is a possibility that rubber constituting the vicinity of the bead toe is cured due to high load, high internal pressure, and high temperature during traveling. However, in this heavy-duty pneumatic tire 1, since the flat portion 5 c is formed in the vicinity of the bead toe 3 of the bead base 5, cracks and flaking, that is, occurrence of bead toe chipping is generated by the force applied in the tire equatorial plane direction. Can be suppressed.

  Next, the heavy duty pneumatic tire 1 after traveling is assembled to the new rim 10 or the existing rim 10 again. The rim assembling work at this time is the same as the rim assembling work at the time of the new article, and the description thereof is omitted. However, in the heavy duty pneumatic tire 1 after traveling, the tire bead portion 2 is deformed and the inner diameter of the bead toe 3 is changed. There exists a possibility that (phi) may become larger than the internal diameter (phi) of the bead toe 3 at the time of a new article. However, the inner diameter φ of the bead toe 3 when the heavy-duty pneumatic tire 1 is new is such that the decrease in workability of the rim assembly work when the heavy-duty pneumatic tire without the recess 7 is new can be suppressed. smaller than φ. In other words, the inner diameter φ of the bead toe after traveling of the heavy duty pneumatic tire 1 is smaller than the inner diameter φ of the bead toe after traveling of the heavy duty pneumatic tire not formed with a recess. Thereby, the fall of the reinflation property of the re-rim assembly work after driving | running | working can be suppressed.

  In addition, as above-mentioned, the arrangement | sequence of the recessed part 7 formed in the tire internal peripheral surface 6 is not limited to 2 rows in a tire peripheral direction, A 1 row or 3 rows may be sufficient. Moreover, although the space | interval of the recessed part 7 adjacent to a tire circumferential direction was made into the equal space | interval, it may be an uneven space | interval. Moreover, although the surface shape of the tire inner peripheral surface 6 of the recess 7 is circular, it may be oval. When the recesses 7 are formed on the tire inner circumferential surface 6 at two equal intervals in the tire circumferential direction, the recesses 7 in the other row are formed between the adjacent recesses 7 in one row. Also good. Further, in addition to the recess 7 formed on the tire inner peripheral surface 6, a recess may be further provided in the beat base 5 in the tire circumferential direction in order to reduce the rigidity in the vicinity of the beat toe 3. For example, a concave portion may be provided in the second stage taper 5b of the bead base 5.

  Moreover, it is good also considering the recessed part 7 as the groove part 13 formed continuously in the tire circumferential direction. FIG. 3 is a view showing a groove formed on the inner circumferential surface of the tire. As shown in the figure, since the groove portion 13 is continuously formed in the tire circumferential direction of the tire inner peripheral surface 6, the rigidity in the vicinity of the bead toe 3 of the tire bead portion 2 is uniformly reduced in the tire circumferential direction. be able to. That is, the vicinity of the bead toe 3 can be uniformly deformed in the tire circumferential direction. Therefore, even if the inner diameter φ of the bead toe 3 is smaller than the inner diameter φ of the bead toe when the rim assembling workability of a heavy duty pneumatic tire in which the groove portion 13 is not formed may be reduced, that is, the rim to be assembled with the rim. Even if it is smaller than the rim diameter D of 10, the vicinity of the bead toe 3 is easily deformed at any position in the tire circumferential direction. Thus, the opposing tire bead portion 2 of the heavy duty pneumatic tire 1 can be more easily inserted into the opposing rim flange 12 of the rim 10, and the rim assembly workability when the heavy duty pneumatic tire 1 is new is improved. Can be further suppressed. Here, the groove portion 13 is continuous, that is, formed in an annular shape on the tire inner peripheral surface 6, but may be formed in an approximately annular shape. For example, you may form the some groove part 13 in which the surface shape in the tire internal peripheral surface 6 becomes a circular arc in cyclic | annular form.

  Below, the implementation result of the running test with the heavy load pneumatic radial tire of a prior art example and a comparative example and the heavy load pneumatic tire 1 concerning this invention is demonstrated. Here, the tire size of each tire used in this running test is common to 11R22.5. In the running test, each of the tires was assembled on a rim having a rim size of 22.5 × 7.50, and the air pressure of each tire was set to 700 kPa. In the heavy-duty pneumatic tires of the present invention 1 and 2 and comparative examples 1 to 4, the bead heel inner diameter S = 0.997D (see FIG. 1), taper angle α = 17 °, β = 30 °, γ = Two rows of recesses 7 were formed in the tire circumferential direction at 0 °, and the width of the recesses 7 was set to 2 mm. The other items are as follows.

φ / D: a ratio between the inner diameter φ of the bead toe 3 of the tire bead portion 2 and the rim diameter D of the rim to be assembled.
Flat part width t: The width (mm) of the flat part 5c formed in the bead base 5 in the tire width direction is shown.
Depth d of recessed part: Depth d (mm) of the recessed part 7 formed in the tire inner peripheral surface 6 is shown. Here, “-” in Conventional Example 1 indicates a case where the recess 7 is not formed on the tire inner peripheral surface 6. Further, “2.0” in Conventional Example 2 is one concave portion formed in an annular shape in the tire circumferential direction.
Rim assembly workability: This indicates whether or not the rim can be assembled to the rim using only the tire lever. The possible one is “OK” and the impossible one is “NG”.
Re-inflation after running: After running a vehicle equipped with a heavy-duty pneumatic tire assembled with a rim for approximately 100,000 km, it can be removed from the rim and then reassembled again to be inflated in a horizontal position. Whether or not. The possible one is “OK” and the impossible one is “NG”.
Toe chipping after running: Indicates whether or not beat tow chipping occurs when a vehicle equipped with a rim-assembled heavy-duty pneumatic tire is run about 100,000 km and then removed once from the rim. . What has occurred is defined as “Yes”, and what has not occurred is defined as “None”.
Below, the results of the running test are displayed.

  As is apparent from this table, the present inventions 1 and 2, which are heavy-duty pneumatic tires 1 according to the present invention, have reduced rim assembly workability when new, reduced reinflation after traveling, Occurrence of toe chipping can be suppressed. On the other hand, in the conventional example 1 in which the flat portion is not formed on the bead base and the concave portion is not formed on the inner peripheral surface of the tire, the reinflation property after running is deteriorated. Moreover, although the recessed part is formed in the tire internal peripheral surface, the toe chipping after driving | running | working generate | occur | produces in the prior art example 2 in which the flat part is not formed in the bead base.

  Further, when the ratio φ / D is less than 0.954, the occurrence of toe chipping after traveling cannot be suppressed as in Comparative Example 1, and the reinflation property after traveling decreases due to the tow chipping. When the ratio φ / D exceeds 0.960, as in Comparative Example 2, the inner diameter φ of the beat toe 2 of the tire bead portion 2 becomes too large after traveling, and the reinflation property after traveling decreases. When the width t of the flat portion exceeds 5 mm, the rim assembly workability at the time of a new article is deteriorated as in Comparative Example 3. Furthermore, when the width t of the flat portion is less than 3 mm, the occurrence of toe chipping after running cannot be suppressed as in Comparative Example 4.

  As described above, the heavy-duty pneumatic tire according to the present invention is useful for heavy-duty pneumatic tires used for trucks, buses, and the like. It is suitable for suppressing a decrease in work reinflation.

It is a figure which shows the structural example of the tire bead part of the pneumatic tire for heavy loads concerning this invention. It is a figure which shows the recessed part formed in the tire internal peripheral surface. It is a figure which shows the rim assembly state of the heavy duty pneumatic tire concerning this invention. It is a figure which shows the groove part formed in the tire internal peripheral surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heavy load pneumatic tire 2 Tire bead part 2a Tire chuck line 3 Bead toe 4 Bead heel 5 Bead base 6 Tire inner peripheral surface 7 Recess 8 Bead core 9 Carcass layer 10 Rim 11 Bead sheet 12 Rim flange 13 Groove (recess)

Claims (3)

The intersection point between the tire inner circumference in the tire meridian section and the horizontal line drawn in parallel to the tire central axis from the point P closest to the bead toe among the outer circumferences of the bead core is defined as an intersection point Q,
Forming a recess over the tire circumferential direction on the tire inner circumferential surface between the bead toe and the intersection point Q;
A bead base formed between the bead toe and the bead heel is formed with a flat portion parallel to or substantially parallel to the tire central axis from the bead toe toward the bead heel,
The heavy load pneumatic, wherein the ratio φ / D of the inner diameter φ of the bead toe and the rim diameter D of the rim to which the heavy duty pneumatic tire is assembled is in the range of 0.954 ≦ φ / D ≦ 0.960. tire.   The heavy duty pneumatic tire according to claim 1, wherein the recess is a groove formed continuously in the tire circumferential direction.   3. The entire surface area of the concave portion on the tire inner peripheral surface is 30% or more with respect to the entire area of the tire inner peripheral surface between the bead toe and the intersection point Q. 4. Heavy duty pneumatic tire.

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