JP2009126142A - Tire vulcanizing mold, and pneumatic tire which is manufactured by tire vulcanizing mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively reduce a center slippage in a tire for which excavated grooves are formed before the vulcanization. <P>SOLUTION: At a starting point M, the height J of a frame 41 for a lower lug groove in a lower mold 38 starts becoming larger than the height H on the internal section in the axial direction of the frame 41 for the lower lug groove. The starting point M is made to locate at a position being away to the outside in the axial direction by 0.90 times or more of a distance L from the center C in the axial direction of a cavity, and therefore, the summit section 41a of the frame 41 for the lower lug groove, which is located on the outside in the axial direction more than the summit position B corresponding to the starting point M and greatly tilts to the axial direction, moves downward from the conventional position. Thus, the unvulcanized tire can be more pushed in downward by the distance by which the summit section 41a has moved downward from the conventional position. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

    The present invention relates to a tire vulcanization mold in which a lug groove bone for forming a lug groove in a tread portion of a pneumatic tire is provided on a tread portion molding surface, and a pneumatic tire manufactured by the tire vulcanization mold.

As conventional tire vulcanization molds, for example, those described in Patent Document 1 below are known.
JP 2001-105511 A

  This is provided with lug groove bones extending substantially in the axial direction on the tread portion molding surface, and is composed of a lower mold, and is formed on both sides of the tire equator on the outer surface of the tread portion of the unvulcanized tire. After inserting the lug groove bone into the excavation groove, the lug groove is formed in the tread portion of the pneumatic tire by vulcanization.

  Here, each of the lug grooves described above has an outer end in the axial direction that opens to the outer end in the radial direction on the outer surface of the sidewall portion. At this time, the depth of the lug groove is constant at any position. And the volume of a tread will become large and a tire weight will increase, and the heat dissipation in a shoulder part will deteriorate. In this case, an edge is formed in the opening on the side wall portion side of the lug groove by the groove bottom of the lug groove and the outer surface of the side wall portion. A tread is formed by laminating a plurality of rubber sheets. When this occurs, the extending direction of the rubber sheet changes abruptly at the edge portion, and as a result, the rubber sheet may be peeled off, floated, and may enter air and bear. In order to improve such a situation, conventionally, the depth of the lug groove is gradually increased at the axially outer end, and considering the tire vulcanization mold, the height of the lug groove bone is set to the axially outer end. It gradually increased in the department.

  Here, in the past, tires (tire vulcanization molds) were designed by simply thinking that the groove bottom of the lug groove and the outer surface of the sidewall portion should be connected with a gently changing curved surface. The starting point on the tread part molding surface where the height of the groove bone begins to be larger than the height at the axially inner side of the lug groove bone is the axial direction of the cavity of the tire vulcanization mold when the tire vulcanization mold is closed When the axial direction distance from the center to the axially outer end of the tread portion molding surface of the lower mold is L, a position that is 0.82 to 0.88 times as long as the distance L from the axial center of the cavity. Was located at.

    However, in such a conventional tire vulcanization mold, since the starting point is located at the position as described above, the unvulcanized tire is aligned with the lag groove bone of the lower mold and the excavation groove. However, when it is placed on the lower mold, as shown in FIG. 6, the lug groove bone 11 is located on the outer side in the axial direction from the top position B of the lug groove bone 11 corresponding to the start point M and is greatly inclined with respect to the axial direction. Similarly, the groove bottom 14 which is greatly inclined as the excavation groove 13 comes into contact with the top portion 12 of the excavation groove 13 so that the lug groove bone 11 is not sufficiently inserted into the excavation groove 13. An axial misalignment occurred between the vulcanized tire 16 and the tire equator of the unvulcanized tire 16 slightly lifted upward from the axial center C of the cavity 17 of the tire vulcanized mold 15.

  After that, when the tire vulcanization mold is closed, the unvulcanized tire is slightly pushed downward by the upper mold, but the center deviation exceeding the allowable value may remain in the vulcanized pneumatic tire, and the distribution of the tread gauge There was a problem that a large non-uniformity occurred. Especially when the inclination angle of the non-extensible reinforcement cord embedded in the belt layer with respect to the tire equator is small (less than 8 degrees) and / or when an unvulcanized tire is mounted on the shaping unit Since the expansion rate of the unvulcanized tire in the tire vulcanization mold has to be very small (4% or less), the above-described problem has become more prominent.

  In order to solve such a problem, for example, it is conceivable to increase the depth of the excavation groove formed in the unvulcanized tire to avoid the contact between the lug groove bone and the excavation groove. In this way, when the tread has a two-layer structure of the base rubber and the cap rubber, the base rubber is exposed at the groove bottom of the lug groove, and the amount of rubber of the tread that has decreased due to the increase in the amount of excavation is Since it is unavoidable to increase the rubber gauge of the tread in the unvulcanized tire, the outer surface of the tread portion of the unvulcanized tire contacts the tread surface of the vulcanized mold and the tire vulcanized mold and The same amount of misalignment between the tires and the sulfur tires still occurred, which was difficult to say as a practical solution.

  An object of the present invention is to provide a tire vulcanization mold capable of effectively reducing the center shift in a tire in which a digging groove is formed before vulcanization, and a pneumatic tire manufactured by the tire vulcanization mold. To do.

    The purpose of this is to provide lug groove bones extending substantially in the axial direction on the tread portion molding surface, and at least comprise a lower mold, on both sides of the tire equator S on the outer surface of the tread portion of the unvulcanized tire. In the tire vulcanization mold in which the lug groove is formed in the tread portion of the pneumatic tire by vulcanizing after inserting the lug groove bone into each formed excavation groove, When the axial distance from the axial center C of the cavity of the tire vulcanization mold at the time of closing to the axial outer end D of the tread portion molding surface of the lower mold is L, the height of the lug groove bone in the lower mold The starting point M on the tread portion molding surface where J starts to become greater than the height H at the axially inner side of the lug groove bone is set to the distance L from the axial center C of the cavity. The tire vulcanizing mold which is adapted to be positioned in only 0.90 to 1.00 times spaced axially outward position, can be achieved.

  In the present invention, the starting point M on the tread portion molding surface where the height J of the lug groove bone in the lower mold starts to become larger than the height H at the axially inner side portion of the lug groove bone is defined as the axis of the cavity. Since it is located at a position apart from the center C in the axial direction by 0.90 times the distance L or more outside in the axial direction, it is located outside in the axial direction from the apex position B of the lug groove bone corresponding to the starting point M, and The top part of the lug groove bone which is greatly inclined moves downward from the conventional position, and it is possible to push the unvulcanized tire further downward by the distance that the large inclined top part has moved downward. Become.

  As a result, the amount of axial misalignment between the tire vulcanization mold and the unvulcanized tire when the tire vulcanization mold is closed can be easily reduced to an allowable value or less. The distribution of the tread gauge in the pneumatic tire can be effectively made uniform. Moreover, the tire vulcanization mold of the present invention can be obtained simply by partially cutting and grinding the lug groove bone of the existing tire vulcanization mold, and the manufacturing cost can be reduced.

  If the starting point M is positioned at a position exceeding 1.00 times the distance L from the center C in the axial direction, the groove bottom of the lug groove, particularly the groove bottom at the outer end in the axial direction rises and the volume of the tread increases. As the tire weight increases, the heat dissipation at the shoulder portion deteriorates. In addition, when the tread is configured by laminating a plurality of layers of rubber sheets, the extending direction of the rubber sheet changes abruptly at the outer end in the axial direction. , Bear may occur. For this reason, the aforementioned starting point M needs to be located at a position not more than 1.00 times the distance L from the axial center C. For this reason, the starting point M must be located within the range of 0.90 to 1.00 times the distance L from the axial center C.

  Further, if configured as described in claim 2, the radius of curvature at the bottom of the lug groove can be maintained at a relatively large value in any part, and further, configured as described in claim 3. By doing so, the amount of residual center deviation in the pneumatic tire can be kept in a relatively small range, and the quality of the pneumatic tire can be improved. Further, if configured as described in claim 4, a desired narrow groove can be easily formed in the tread portion (land portion) between the lug grooves, and further configured as described in claim 5. Thus, the distribution of the tread gauge in the manufactured pneumatic tire can be effectively uniformed.

Embodiment 1 of the present invention will be described below with reference to the drawings.
1 and 2, reference numeral 21 denotes a tire vulcanizing device. The tire vulcanizing device 21 produces a large-sized heavy-duty pneumatic radial tire 22 used for a large construction vehicle or a truck / bus. Here, the pneumatic tire 22 connects a pair of bead portions 23, sidewall portions 24 extending from the bead portions 23 toward the outside in a substantially radial direction, and radially outer ends of the sidewall portions 24. It is composed of a tread portion 25.

  The pneumatic tire 22 has a carcass layer 27 that extends between the bead portions 23 in a toroidal manner and reinforces the sidewall portions 24 and the tread portions 25. The carcass layer 27 has a meridian direction (radial direction). A large number of non-stretchable reinforcing cords 28 extending in the middle) are embedded. In addition, at least two, in this case, two belt plies 29 are disposed outside the carcass layer 27 in the radial direction, and the belt plies 29 are inclined at a predetermined angle with respect to the tire equator S. Many non-stretchable reinforcing cords 31 are embedded. These reinforcing cords 31 are inclined in opposite directions and intersect each other in at least two adjacent belt plies 29.

  33 is a tread arranged radially outside the carcass layer 27 and the belt layer 30. This tread 33 is composed of a base rubber having excellent heat resistance and crack growth resistance, and a radially outer side of the base rubber. The cap rubber has a two-layer structure with excellent wear resistance. Here, the above-described tread 33 is usually configured by laminating a plurality of thin and wide rubber sheets. A plurality of lug grooves, which are wide deep grooves extending substantially in the tire width direction, are provided on both sides of the tire equator S on the outer surface of the tread 33 (tread portion 25), specifically at one end in the width direction and the other end in the width direction. 34a and 34b are respectively formed.

  The lug grooves 34a and 34b open on the outer surface (tread surface) of the tread portion 25 and the outer surface of the radially outer end portion of the sidewall portion 24, and the tire equator S side inner end is the tire equator S. It ends at a position in the middle of a predetermined distance away from the tread end side. The lug grooves 34a and 34b are arranged at an equal distance in the circumferential direction, and the lug groove 34a and the lug groove 34b are shifted by a half pitch in the circumferential direction. In addition, a plurality of narrow grooves inclined with respect to the tire equator S are connected to the land portion located in the center portion in the width direction of the tread portion 25 while connecting the inner ends of the lug grooves 34a and 34b on the tire equator S side. 35 is formed.

  On the other hand, the tire vulcanizing apparatus 21 has a substantially ring-shaped lower mold 38 including a lower platen, and an unvulcanized tire 39 is placed horizontally on the lower mold 38. On the upper surface of the central portion in the radial direction of the lower mold 38, a sidewall portion molding surface 38a for mainly molding one side (lower side) sidewall portion 24 of the unvulcanized tire 39 is formed. Further, the lower mold 38 has a ring portion 40 extending upward at the radially outer end thereof, and the tread portion 25 of the unvulcanized tire 39 is mainly formed on the radially inner side surface of the ring portion 40. A tread part molding surface 40a for molding one end part (lower end part) in the width direction is formed.

  Further, a plurality of lower lug groove bones 41 extending substantially in the axial direction of the lower mold 38 (substantially in the width direction in the horizontal unvulcanized tire 39) on the radially inner side surface (tread portion molding surface 40a) of the ring portion 40. These lower lug groove bones 41 protrude radially inward. Further, these lower lug groove bones 41 are arranged at equal distances in the circumferential direction, and their axial outer ends (lower ends) are continuous with the radial outer end portions of the sidewall portion molding surfaces 38a. These lower lug groove bones 41 are pushed into one end portion in the width direction of the tread 33 of the unvulcanized tire 39 during vulcanization, and the lug groove 34a described above is formed in the tread portion 25 of the pneumatic tire 22.

  43 is a substantially ring-shaped upper mold that is installed directly above the lower mold 38 and includes an upper platen. The upper mold 43 has a vertical moving force from an elevating means including a connecting rod 42 connected to the upper mold 43. By being applied, it moves up and down, moves away from and approaches the lower mold 38, and rotates around the axis by applying a rotational force. Further, a sidewall portion molding surface 43a for molding the other side (upper side) sidewall portion 24 of the unvulcanized tire 39 is formed on the lower surface of the central portion of the upper mold 43 in the radial direction. Further, the upper mold 43 has a ring portion 44 extending downward at the radially outer end thereof, and the tread portion 25 of the unvulcanized tire 39 is mainly formed on the radially inner side surface of the ring portion 44. A tread portion molding surface 44a for molding the other end portion (upper end portion) in the width direction is formed.

  Further, a plurality of upper lug groove bones 46 extending substantially in the axial direction of the upper mold 43 are formed on the radially inner side surface (tread portion molding surface 44a) of the ring portion 44. The upper lug groove bones 46 are formed in the radial direction. Projects inward. Further, these upper lug groove bones 46 are arranged equidistantly in the circumferential direction, and their axial outer ends (upper ends) are continuous with the radial outer end portions of the sidewall portion molding surfaces 43a. These upper lug groove bones 46 are pushed into the other end in the width direction of the tread 33 of the unvulcanized tire 39 during vulcanization, and the lug groove 34b described above is formed in the tread portion 25 of the pneumatic tire 22.

  Since the lug grooves 34a and 34b are wide deep grooves as described above, when the lower and upper lug groove bones 41 and 46 are pushed into the tread 33 of the unvulcanized tire 39, the carcass layer 27, the belt In order to effectively suppress such a situation, the layer 30 may have a shape approximate to the lug grooves 34a and 34b prior to vulcanization, as shown in FIGS. Excavation grooves 39a and 39b having the same depth as the outer surface of the tread portion 25 of the unvulcanized tire 39 are provided on both sides of the tire equator S, specifically in the width direction and at the other end (here, the lugs). (The same number as the grooves 34a and 34b).

  As a result, these excavation grooves 39a and 39b are also the same as the lug grooves 34a and 34b, the outer surface (tread surface) of the tread portion 25 of the unvulcanized tire 39, and the outer surface in the radial direction outer end portion of the sidewall portion 24. Open in both. Such excavation grooves 39a and 39b are formed by, for example, turning a substantially U-shaped electric heating cutter heated by power feeding around the base end portion and biting into the tread 33, and then Can be formed by moving the rubber in the tire width direction to the tread end and cutting the rubber.

  In FIGS. 1 and 2 again, reference numeral 50 denotes a plurality of arc-shaped sliders placed on the ring portion 40 of the lower mold 38. These sliders 50 are arranged side by side in the circumferential direction, and are attached to each slider 50. A guide groove 51 is formed so as to be inclined outward in the radial direction as it goes downward. On the other hand, an annular guide body 52 is integrally formed on the lower surface of the ring portion 44 of the upper mold 43, and the guide body 52 is inclined so as to go radially outward as it goes downward at the same inclination angle as the guide groove 51. In addition, the thickness of the guide groove 51 is substantially the same as the width of the guide groove 51.

  A sector mold 55 is fixed to the inner surface in the radial direction of each slider 50, and a blade 56 is provided on the tread portion molding surface 55 a located at the inner end in the radial direction of the sector mold 55. As a result, when the upper mold 43 moves up and down with the guide body 52 inserted in the guide groove 51 of each slider 50, the slider 50 and the sector mold 55 can move in the radial direction in synchronization with the lower mold 38. it can. In this way, a plurality of sector molds 55 are arranged in the circumferential direction between the lower and upper molds 38 and 43 and can be moved synchronously in the radial direction.

  When the upper mold 43 moves to the lower limit and the slider 50 and the sector mold 55 move to the radially inner limit, the tire vulcanization mold 57 including the lower, upper molds 38 and 43 and the sector mold 55 is closed. Then, a sealed cavity 58 for accommodating the unvulcanized tire 39 is formed inside, and the blade 56 is pushed into the center portion in the width direction of the tread 33 of the unvulcanized tire 39 to be tread of the pneumatic tire 22 A narrow groove 35 is formed in the portion 25.

  In this embodiment, the tire vulcanization mold 57 is composed of the lower mold 38, 43 and the sector mold 55. However, in the present invention, the tire vulcanization mold is divided into two parts, the upper mold and the lower mold. It may be configured only from the upper mold and the lower mold. And when it comprises only lower and upper molds, the tread portion on the one side (lower side) in the width direction from the tire equator S is the tread portion on the other side (upper side) in the width direction from the tire equator S. Is molded by the upper mold.

  Reference numeral 60 denotes a shaping unit, and this shaping unit 60 has a one-side support 61 on which a bead portion 23 positioned on one side (lower side) of the unvulcanized tire 39 is seated. 61 can mainly mold the bead portion 23 on one side in the width direction during vulcanization. 62 is an upper support on which a bead portion 23 positioned on the other side (upper side) of the unvulcanized tire 39 is seated, and this other side support 62 is the bead portion on the other side in the width direction during vulcanization. 23 can be mainly typed. And these one side and other side support bodies 61 and 62 are connected so that attachment or detachment is possible by the connection mechanism which is not shown in figure. Reference numeral 63 denotes a bendable bladder in which both ends in the width direction, that is, one end and the other end in the width direction are locked to the one side and the other side supports 61 and 62 in an airtight state.

  Then, after one side of the unvulcanized tire 39 and the other side bead portion 23 are seated on the one side and the other side supports 61 and 62, respectively, the one side and the other side supports 61 and 62 are connected to each other. When the internal pressure is filled in the bladder 63 after being connected by the mechanism, the unvulcanized tire 39 is deformed into a substantially toroidal shape, and the shaping composed of these one side, other side support bodies 61 and 62, and the bladder 63 is formed. Supported by unit 60. Next, the unvulcanized tire 39 attached to the shaping unit 60 in this way is carried into the opened tire vulcanization mold 57 by a conveying means (not shown), and then the lower lug groove bone 41 and lower It is placed on the lower mold 38 while matching with the digging groove 39a for the lug groove.

  At this time, as shown in FIGS. 1, 4, and 5, the height H at the axially inner portions of the lower and upper lug groove bones 41 and 46 is constant, but the height J at the axially outer end portion is the axis. The height is gradually higher than the height H toward the outside in the direction. Here, the height at a certain point F of the lower and upper lug groove bones 41 and 46 means that when the normal to the tread portion molding surfaces 40a and 44a is G, all the lower and upper lug groove bones 41 and 46 are present. Is a linear distance from the intersection of the circle G passing through the point F and the normal G to the intersection K of the tread portion molding surfaces 40a, 44a and the normal G.

  And as mentioned above, since the height J of the lower lug groove bone 41 is gradually increased at the outer end in the axial direction, there is a point where the height J begins to become larger than the height H. Assuming that the intersection point between the normal G passing through the point and the tread part molding surface 40a, that is, the point on the tread part molding surface 40a where the height J starts to be larger than the height H, is the starting point M, the starting point M is In this embodiment, the tire vulcanization mold 57 is positioned at a position apart from the axial center C of the cavity 58 of the tire vulcanization mold 57 to the outside in the axial direction by 0.90 to 1.00 times the distance L when the tire vulcanization mold 57 is closed.

  Here, the distance L refers to the axially outer end D of the tread portion molding surface 40a of the lower mold 38 from the axial center C of the cavity 58, that is, the tread portion molding surface 40a and the sidewall portion molding surface 38a. The axial distance to the boundary. As described above, if the starting point M is positioned at a position that is 0.90 times the distance L or more outward in the axial direction, the axial direction from the apex position B of the lower lug groove bone 41 corresponding to the starting point M. The top 41a of the lower lug groove bone 41 that is located outside and greatly inclined with respect to the axial direction moves downward from the conventional position.

  As a result, when the unvulcanized tire 39 is placed on the lower mold 38 as described above, the lower lug groove bone 41 is inserted into the excavation groove 39a up to the position indicated by the phantom line in FIG. However, at this time, a gap is generated between the top 41a of the lower lug groove bone 41 that is largely inclined and the groove bottom 39c that is greatly inclined with respect to the axial direction of the excavation groove 39a. When the tire vulcanization mold 57 is subsequently closed, if the unvulcanized tire 39 is pushed downward by the upper mold 43, the unvulcanized tire 39 is moved by a distance moved by the top 41a downward, that is, a solid line in FIG. Can be pushed further down to the position indicated by.

  As a result, when the tire vulcanization mold 57 is closed, the amount of axial misalignment between the tire vulcanization mold 57 and the unvulcanized tire 39 is easily reduced to an allowable value or less, and a vulcanized pneumatic tire is obtained. The distribution of the tread gauge in 22 can be made uniform effectively. Moreover, the tire vulcanization mold 57 of this embodiment can be obtained simply by partially cutting and grinding the lower lug groove bone 41 of the existing tire vulcanization mold 57, thereby reducing the production cost. Can do.

  When the starting point M of the lower lug groove bone 41 is positioned at a position exceeding 1.00 times the distance L from the axial center C, the groove bottom of the lug groove 34a, particularly the groove bottom at the axially outer end portion. As a result, the volume of the tread 33 increases, the tire weight increases, and the heat dissipation at the shoulder portion deteriorates. Moreover, when the tread 33 is formed by laminating a plurality of layers of rubber sheets, the extending direction of the rubber sheet changes abruptly at the outer end in the axial direction. Enter, bear may occur. For this reason, the aforementioned starting point M needs to be located at a position not more than 1.00 times the distance L from the axial center C. For this reason, the starting point M must be located in a range away from the axial center C by 0.90 to 1.00 times the distance L outward in the axial direction.

  Here, it is preferable that the start point M is positioned at a position apart from the distance L by 0.92 times or more in the axial direction. The reason is that when the starting point M is located at the above-mentioned position, the residual center deviation amount in the pneumatic tire 22 can be kept within a relatively small range, as will be understood from the test results described later. This is because the quality of 22 can be easily improved.

  In addition, the depth gradually changes along the longitudinal direction of the lower lug groove bone 41 at the top of the lower lug groove bone 41 on the axially inner side from the start point M, and the axial outer end is Forming the arcuate recess 65 located on the starting point M is preferable because the radius of curvature at the bottom of the lug groove 34a can be maintained at a relatively large value in any part.

  On the other hand, the upper lug groove bone 46 is preferably the same shape as the lower lug groove bone 41 in order to maintain the symmetry of the tread pattern on both sides of the tire equator S, but the aforementioned symmetry is maintained. If there is no need to do this, for example, the shape may be the same as that of the prior art. Further, if the axial length N of the sector mold 55 is 0.90 times the distance L or less, a desired narrow groove 35 can be easily formed in the tread portion (land portion) 25 between the lug grooves 34a and 34b. Therefore, it is preferable.

Next, the operation of the first embodiment will be described.
When manufacturing the pneumatic tire 22 as described above, first, one side of the unvulcanized tire 39 and the other side bead portion 23 are seated on the one side, other side support members 61, 62, and then one of these side tires is supported. The side and other side supports 61, 62 are connected to each other by a connecting mechanism, and then the bladder 63 is filled with internal pressure. As a result, the unvulcanized tire 39 is attached to the shaping unit 60 while being deformed in a substantially toroidal shape.

  Next, after turning a substantially U-shaped electric heating cutter to bite into the tread 33 of the unvulcanized tire 39, the rubber is cut by moving the cutter in the tire width direction almost beyond the tread end, A plurality of excavation grooves 39a and 39b having shapes similar to the lug grooves 34a and 34b are formed on the outer surface of the tread portion 25 at one end in the width direction and at the other end, respectively. Here, the excavation grooves 39a and 39b may have the same shape as the lug grooves 34a and 34b, but the groove width, the groove depth, the degree of bending, etc. may be slightly different.

  Next, the shaping unit 60 and the unvulcanized tire 39 are carried into the opened tire vulcanization mold 57 by the conveying means, and the lower lug groove bone 41 and the lower lug groove excavation groove 39a are formed. Specifically, the lower lug groove bone 41 is placed on the lower mold 38 while being inserted into the excavation groove 39a. Here, the above-described excavation grooves 39a and 39b may be formed before the unvulcanized tire 39 is mounted on the shaping unit 60, and after the unvulcanized tire 39 is molded, it is placed on the lower mold 38. You can go anytime before.

  At this time, as described above, the starting point M at which the height J of the lower lug groove bone 41 starts to be larger than the height H is separated from the axial center C of the cavity 58 to the outside in the axial direction by 0.90 times the distance L or more. Therefore, when the tire vulcanization mold 57 is closed, the unvulcanized tire 39 can be pushed further downward from the aforementioned position by the upper mold 43, so that the closed tire vulcanization mold 57 and The amount of axial misalignment with the unvulcanized tire 39 can be easily reduced below the allowable value.

  The axial misalignment described above may occur when the reinforcing cord 31 in the belt layer 30 intersects the tire equator S at 8 degrees or less as described above, and / or when the unvulcanized tire 39 is a shaping unit. It is often large when it is carried into the tire vulcanization mold 57 in a state where it is attached to 60, but it effectively functions even for such a large center deviation and can be effectively reduced. it can. Further, in the pneumatic radial tire for large construction vehicles, since the groove width and groove depth of the lug grooves 34a and 34b are both wide and deep, a large center deviation is likely to occur. Is particularly preferred.

  Next, the upper mold 43 is lowered by the elevating means, and the upper molds 43 and 38 are brought close to each other. At this time, the upper mold 43 is given a rotational force from the elevating means. As a result, the upper lug groove The bone 46 is inserted into the excavation groove 39b while moving in the extending direction of the excavation groove 39b for the upper lug groove by the above-described combination of lowering and rotation. In this way, the lower and upper lug groove bones 41 and 46 are inserted into the excavation grooves 39a and 39b, respectively.

  In addition, the guide body 52 is inserted into the guide groove 51 of the slider 50 in the middle of the above-described lowering. However, since the upper mold 43 continues to descend thereafter, the slider 50 and the sector mold 55 are synchronized on the lower mold 38. And move inward in the radial direction. When the upper mold 43 is moved to the lower limit, and the slider 50 and the sector mold 55 are moved to the inner limit in the radial direction, the tire vulcanization mold 57 is closed and is not added to the cavity 58 in the tire vulcanization mold 57. While storing the sulfur tire 39, the blade 56 is pushed into the center of the tread 33 in the width direction to form the narrow groove 35.

  Next, a high-temperature and high-pressure vulcanizing medium is supplied under the upper and lower molds 38 and 43, into the upper platen and the bladder 63, and the unvulcanized tire 39 stored in the tire vulcanizing mold 57 is vulcanized. Thus, the pneumatic tire 22 in which the lug grooves 34a and 34b are formed in the tread portion 25 is manufactured. In the pneumatic tire 22 manufactured in this way, the distribution of the tread gauge is effectively uniformed for the reasons described above.

  When vulcanization is completed in this manner, the upper mold 43 is raised by the elevating means. At this time, the upper mold 43 is rotated in the reverse direction by the elevating means. The upper lug groove bone 46 is detached from the pneumatic tire 22 while moving in the extending direction of the lug groove 34b by the combination of the rotation and the rise. At this time, the slider 50 and the sector mold 55 are moved by the guide body 52 to the outer limit in the radial direction. When the tire vulcanization mold 57 is thus opened, the vulcanized pneumatic tire 22 and the shaping unit 60 are taken out from the lower mold 38 and carried out to the next process by the conveying means.

    Next, test examples will be described. In this test, the start point M is separated from the axial center C by 0.82 times the distance L, and the conventional mold 1 having the lower lug groove bone and the starting point M is 0.84 times the distance L from the axial center C. A conventional mold 2 having a lower lug groove bone, a comparative mold having a lower lug groove bone, and a starting point M being 0.89 times the distance L from the axial center C, and a starting point M Is separated from the axial center C by 0.90 times the distance L, and the implementation mold 1 has the bone for the lower lug groove, and the starting point M is separated from the axial center C by 0.92 times the distance L, and the lower lug groove An execution mold 2 having a bone for preparation and an execution mold 3 having a starting lug M separated from the center C in the axial direction by 0.97 times the distance L and having a bone for the lower lug groove were prepared.

  Next, 10 unvulcanized tires were each vulcanized using the tire vulcanization molds described above to produce pneumatic tires. Here, the size of each tire is 46 / 90R57, and its structure is the same as that shown in FIG. Next, after measuring the amount of residual center deviation in the tread portion of the pneumatic tire described above, the deviation was compared with an allowable value (± 13 mm for the tire size described above). In the pneumatic tires vulcanized by the above, four, three, and three pneumatic tires exceeded the allowable values, respectively. On the other hand, in the pneumatic tires vulcanized by the execution molds 1, 2, and 3, there is no pneumatic tire in which the deviation amount exceeds the allowable value, and it has been confirmed that the center deviation is effectively suppressed.

  Moreover, the actual measured values of residual center deviations in the pneumatic tires vulcanized by the conventional molds 1 and 2 and the comparative mold are in the ranges of +6 to +24 mm, +4 to +22 mm, and +1 to +19 mm, respectively. On the other hand, the measured values of the center deviation in the pneumatic tires vulcanized by the working molds 1, 2, and 3 were in the ranges of −4 to +13 mm, −2 to +12 mm, and −5 to 10 mm, respectively. Here, + is a shift to the other side (upward) in the width direction. Thus, if the starting point M is separated from the axial center C by 0.92 times or more of the distance L, the residual center deviation amount can be kept in a relatively small range.

  The present invention can be applied to the industrial field of a tire vulcanization mold provided with bones for forming lug grooves.

It is a partially broken front view which shows Embodiment 1 of this invention. It is a partially broken perspective view of a pneumatic tire. It is explanatory drawing explaining the penetration | invasion state of the bone for lug grooves to a digging groove. It is sectional drawing of the bone vicinity for a lower lug groove. It is sectional drawing of the bone vicinity for a lower lug groove at the time of an unvulcanized tire mounting. It is sectional drawing of the bone | frame for lower lug groove | channels at the time of the conventional unvulcanized tire mounting.

Explanation of symbols

22 ... Pneumatic tire 25 ... Tread
34a, 34b ... lug groove 35 ... narrow groove
38 ... Lower mold 39 ... Unvulcanized tire
39a, 39b ... excavation groove 40a, 44a ... tread part molding surface
41, 46 ... Bone for lug groove 55 ... Sector mold
55a ... Tread part mounting surface 56 ... Blade
57 ... Tire vulcanization mold 58 ... Cavity
65… Arc dent

Claims (5)

    Excavation grooves formed on the outer surface of the tread part of the unvulcanized tire on both sides of the tire equator S, each having a lug groove bone extending substantially in the axial direction on the tread part molding surface In the tire vulcanization mold in which the lug groove is formed in the tread portion of the pneumatic tire by inserting the lug groove bone into the tire and then vulcanizing the tire vulcanization when the tire vulcanization mold is closed When the axial distance from the axial center C of the mold cavity to the axially outer end D of the tread portion molding surface of the lower mold is L, the height J of the lug groove bone in the lower mold is for the lug groove. The starting point M on the tread portion molding surface, which starts to be greater than the height H at the axially inner side of the bone, is axisd by 0.90 to 1.00 times the distance L from the axial center C of the cavity. Tire vulcanizing mold, characterized in that so as to position at a position spaced toward the outside.     At the apex of the lug groove bone on the inner side in the axial direction from the start point M, the depth gradually changes along the longitudinal direction of the lug groove bone, and the axial outer end is positioned on the start point M. The tire vulcanization mold according to claim 1, wherein an arcuate recess is formed.     2. The tire vulcanization mold according to claim 1, wherein the starting point M is located at a position apart from the center C in the axial direction by 0.92 times the distance L to the outside in the axial direction.     Between the upper and lower molds, a plurality of sector molds arranged in the circumferential direction are arranged in the tread part molding surface with blades for forming a narrow groove with respect to the tread part of the unvulcanized tire. The tire vulcanization mold according to any one of claims 1 to 3, wherein an axial length N of the sector mold is 0.90 times or less of the distance L.     A pneumatic tire manufactured by a tire vulcanization mold manufactured by vulcanizing an unvulcanized tire using the tire vulcanization mold according to claim 1.

Images