JP7567313B2 - Tire manufacturing mould - Google Patents

Description

The present invention relates to a mold for tire manufacturing.

A typical tire manufacturing mold has a ring-shaped side plate and multiple arc-shaped segments located radially outward of the side plate. The segments and side plate each have an inner surface (cavity surface) that contacts the row cover.

In tire manufacturing, the raw cover is placed into the mold while it is open (with the segments separated from the side plates). The mold is then closed by bringing the segments into contact with the side plates from the radially outer side while shaping the raw cover. At this time, the raw cover may become trapped where the segments contact the side plates. This can lead to burrs in the tires manufactured with this mold, reducing the appearance quality and increasing the cost of removing the burrs.

A study on a mold that prevents the lower cover from getting caught is reported in JP 2014-113743 A. In this mold, the segments have ridges at the boundaries with the side plates.

JP 2014-113743 A

When a ridge is provided at the boundary between the segment and the side plate, a groove is formed in the corresponding part of the tire manufactured with this mold. Stress is concentrated in this groove, which can cause cracks in the tire. There is a demand for a mold that prevents cracks in the tire while improving the performance of preventing the row cover from getting caught.

The object of the present invention is to provide a mold for tire manufacturing that prevents cracks in tires while also preventing the row cover from getting caught.

The mold for manufacturing tires according to the present invention comprises a ring-shaped side plate and a plurality of arc-shaped segments arranged around the side plate. At least one of the segments comprises a first inner surface that mainly contacts the tread of the low cover and a first contact surface extending from an end of the first inner surface. The side plate comprises a second inner surface that mainly contacts the side portion of the low cover and a second contact surface that extends from an end of the second inner surface and contacts the first contact surface. The first inner surface is provided with a recess that is located at the end on the first contact surface side and extends in the circumferential direction. In a cross section perpendicular to the circumferential direction, the recess has an outwardly convex shape. The width a of the recess at the position of the second contact surface is 2 mm or more.

Preferably, the height of the recess measured along a direction perpendicular to the second contact surface is 2 mm or greater.

Preferably, in a cross section perpendicular to the circumferential direction, the recess has an arc shape, and the radius of curvature R of the recess is 2 mm or more.

Preferably, the recess has a groove extending from the end of the recess on the first contact surface side.

Preferably, the width of the groove is 0.3 mm or more and 1.5 mm or less, and the depth of the groove is 0.2 mm or more and 1.0 mm or less.

Preferably, there are multiple grooves, and the pitch of these grooves is 0.6 mm or more and 3.0 mm or less.

Preferably, the angle θ between the second inner surface and the second contact surface is 90° or less.

The tire manufacturing method according to the present invention includes the steps of setting a raw cover in any of the above molds, and pressurizing and heating the raw cover in the mold.

In this mold, the segment has a first inner surface that contacts the low cover and a first contact surface that contacts the second contact surface of the side plate. The first inner surface has an outwardly protruding recess extending in the circumferential direction at the end on the side of the first contact surface. The width a of the recess at the position of the second contact surface is 2 mm or more. This recess effectively prevents the low cover from being caught between the segment and the side plate. In this mold, no ridge is provided at the boundary between the segment and the side plate. In a tire manufactured with this mold, no groove is formed at a position corresponding to the position of this boundary. In this tire, cracks are prevented.

FIG. 1 is a plan view showing a mold according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a portion of a tire vulcanization apparatus including the mold of FIG. FIG. 3 is an enlarged cross-sectional view of a portion of the apparatus of FIG. FIG. 4 is a perspective view of a portion of a segment of the mold of FIG. FIG. 5 is a cross-sectional view showing the state before the mold is closed in the apparatus of FIG. FIG. 6 is an enlarged cross-sectional view of a portion of the mold of FIG. FIG. 7 is an enlarged view of the segment of FIG. 4 showing the recesses.

The present invention will now be described in detail based on a preferred embodiment, with reference to the drawings as appropriate.

Figure 1 is a plan view showing a mold 2 for manufacturing tires according to the present invention. In Figure 1, the direction indicated by the double-headed arrow A is the circumferential direction of the mold 2, and the direction perpendicular to the paper surface is the axial direction of the mold 2. The mold 2 comprises segments 4, side plates 6, and bead rings 8. In Figure 1, there are segments 4 represented by solid lines and segments 4 represented by two-dot chain lines. The solid lines represent segments 4 when the mold 2 is closed. The two-dot chain lines represent segments 4 before the mold 2 is closed.

Figure 2 is a cross-sectional view showing a portion of a tire vulcanizing apparatus 10, including the mold 2 of Figure 1. In addition to the segments 4, side plates 6, and bead rings 8, this vulcanizing apparatus 10 is equipped with an inner sector shoe 12, an outer sector shoe 14, an upper base plate 16, and a lower base plate 18. The figure also shows the row cover R. In Figure 2, the left-right direction is the radial direction, the up-down direction is the axial direction, and the direction perpendicular to the paper surface is the circumferential direction. The mold 2 in Figure 2 is an enlarged cross-sectional view taken along line II-II in Figure 1.

In FIG. 2, the mold 2 is closed. The position of the segment 4 in this figure corresponds to the position of the segment 4 shown in solid lines in FIG. 1. In this state, the segment 4, the side plate 6, and the bead ring 8 are combined to form a cavity that houses the raw cover R.

1, the planar shape of each segment 4 is substantially arc-shaped. A plurality of segments 4 are arranged in a ring shape around the side plate 6. The segments 4 are located radially outward of the side plate 6. As shown in FIG. 2, the segment 4 has a first inner surface 20 and a pair of first contact surfaces 24. The first inner surface 20 mainly contacts the tread of the low cover R. The first inner surface 20 constitutes a part of the cavity surface. Each of the first contact surfaces 24 extends from an end of the first inner surface 20. The first contact surfaces 24 extend axially outward from the corresponding axial end of the first inner surface 20.

As shown in FIG. 1, the side plate 6 is ring-shaped. As shown in FIG. 2, there is a pair of upper and lower side plates 6. Each side plate 6 has a second inner surface 26 and a second contact surface 28. The second inner surface 26 mainly contacts the side portion of the row cover R. The second inner surface 26 constitutes a part of the cavity surface. The second contact surface 28 extends from the end of the second inner surface 26. The second contact surface 28 extends axially outward from the radially outer end of the second inner surface 26. As shown in FIG. 2, when the mold 2 is closed, the second contact surface 28 of the side plate 6 contacts the corresponding first contact surface 24 of the segment 4.

As shown in FIG. 1, the bead ring 8 is ring-shaped. As shown in FIG. 2, there is a pair of upper and lower bead rings 8. Each bead ring 8 has a third inner surface 30 that contacts the corresponding bead portion of the row cover R. The bead ring 8 is fixed to the side plate 6.

As shown in FIG. 2, the inner sector shoe 12 is located radially outside the segment 4. There is one inner sector shoe 12 for one segment 4. Therefore, the number of inner sector shoes 12 is the same as the number of segments 4. Each inner sector shoe 12 is fixed to a corresponding segment 4. As shown in FIG. 2, the radially outer surface of the inner sector shoe 12 is inclined with respect to the axial direction.

As shown in FIG. 2, the outer sector shoe 14 is located radially outward of the inner sector shoe 12. The outer sector shoe 14 abuts against the inner sector shoe 12. This abutment surface is inclined with respect to the axial direction. This inclination angle is the same as the inclination angle of the outer surface of the inner sector shoe 12.

The outer sector shoe 14 can move in the axial direction (Y direction in FIG. 2 and the opposite direction). The inner sector shoe 12 and the segment 4 fixed thereto can move in the radial direction (X direction in FIG. 1 and FIG. 2 and the opposite direction). By moving the outer sector shoe 14 in the Y direction, the inner sector shoe 12 and the segment 4 move in the X direction. By moving the outer sector shoe 14 in the opposite direction to the Y direction, the inner sector shoe 12 and the segment 4 move in the opposite direction to the X direction.

The upper base plate 16 and the lower base plate 18 each fix the corresponding side plate 6. Between the upper base plate 16 and the lower base plate 18, the inner sector shoe 12 and the segment 4 are moved radially.

Figure 3 is an enlarged cross-sectional view of a portion of Figure 2. In this figure, the vicinity of the boundary between the segment 4 and the side plate 6 is shown. Figure 4 is a perspective view showing a portion of the segment 4 of Figure 2. As shown in Figures 3 and 4, the first inner surface 20 of the segment 4 has a recess 32 at the end on the first contact surface 24 side. As shown in Figure 4, the recess 32 extends in the circumferential direction. The recess 32 extends from one end to the other end of the segment 4 in the circumferential direction. In the cross section of Figure 3, the recess 32 has a convex shape toward the outside of the mold 2. In this embodiment, the recess 32 has a circular arc shape. The recess 32 does not have to have a circular arc shape. For example, in the cross section of Figure 3, the recess 32 may be a straight line having a bend in the middle. The recess 32 only needs to have an outwardly convex shape.

In FIG. 3, the symbol P represents the axially inner end of the first contact surface 24. Due to the presence of the recess 32, the inner end P does not coincide with the axially inner end of the second contact surface 28. The symbol a in FIG. 3 represents the distance between the inner end P and the axially inner end of the second contact surface 28. In other words, the distance a is the width of the recess 32 at the position of the second contact surface 28. In this mold 2, the width a is 2 mm or more.

As shown in FIG. 4, the recess 32 includes a plurality of grooves 34. Each groove 34 extends from an end of the recess 32 on the first contact surface 24 side. The grooves 34 extend to an end of the recess 32 on the opposite side of the first contact surface 24 side. In this embodiment, the grooves 34 extend in a substantially axial direction. The grooves 34 are aligned in the circumferential direction. In this embodiment, the grooves 34 are aligned from one end of the recess 32 to the other end in the circumferential direction.

The following describes a method for manufacturing tires using the above-mentioned device 10.

In this manufacturing method, a raw cover R is formed in a molding process. This raw cover R is placed in the open mold 2 of this device 10. Figure 5 shows the state before the mold 2 in Figure 2 is closed. As mentioned above, the segment 4 in this state is represented by the two-dot chain line in Figure 1. As shown in these figures, in this state, the segment 4 is separated from the side plate 6. The first contact surface 24 of the segment 4 and the second contact surface 28 of the side plate 6 are not in contact.

To close the mold 2, the outer sector shoe 14 moves in the Y direction shown in FIG. 5. Accordingly, the inner sector shoe 12 and the segment 4 move in the X direction shown in FIGS. 1 and 5. In conjunction with this, the raw cover R is shaped. The raw cover R is inflated.

The segment 4 moves further in the X direction. The low cover R is pressed against the segment 4 from the radially inner side toward the radially outer side. The segment 4 moves in the X direction until the first contact surface 24 of the segment 4 and the second contact surface 28 of the side plate 6 come into contact with each other. FIG. 6 shows an enlarged view of the vicinity of the inner end P at this time. Since the recess 32 has an outwardly convex shape, the rubber composition of the low cover R moves in the direction of the arrow B in FIG. 6 relative to the segment 4 at the boundary between the segment 4 and the low cover R. Due to the direction of movement of the rubber composition and the width a of the recess 32 being 2 mm or more, it is difficult for the rubber composition of the low cover R to reach the inner end P of the first contact surface 24. When the first contact surface 24 and the second contact surface 28 come into contact with each other, a gap exists near the inner end P as shown in FIGS. 3 and 6. The mold 2 is closed when the first contact surface 24 and the second contact surface 28 come into contact with each other. The low cover R is set in the mold 2.

The raw cover R is heated while being pressurized in the closed mold 2. The pressure and heat cause the rubber composition of the raw cover R to flow inside the cavity. The rubber composition penetrates near the inner end P, filling any gaps. The heat causes the rubber to undergo a cross-linking reaction. This completes the tire.

The outer sector shoe 14 moves in the opposite direction, the Y direction. Accordingly, the inner sector shoe 12 and the segment 4 move in the opposite direction, the X direction. This opens the mold 2 and removes the tire.

The effects of the present invention are explained below.

In this mold 2, the segment 4 has a first inner surface 20 that contacts the low cover R and a first contact surface 24 that contacts the second contact surface 28 of the side plate 6. The first inner surface 20 has a recess 32 extending in the circumferential direction at the end on the side of the first contact surface 24. The width a of the recess 32 at the position of the second contact surface 28 is 2 mm or more. This recess 32 makes it difficult for the rubber composition of the low cover R to reach the inner end P of the first contact surface 24 when the first contact surface 24 and the second contact surface 28 contact each other. This prevents the rubber of the low cover R from entering between the first contact surface 24 and the second contact surface 28. In this mold 2, the low cover R is effectively prevented from being caught between the segment 4 and the side plate 6.

From the viewpoint of more effectively preventing the lower cover R from getting caught, it is more preferable that the width a of the recess 32 be 3 mm or more.

The width a of the recess 32 is preferably 6 mm or less. By making the width a 6 mm or less, the impact of the protrusion formed in the tire by the recess 32 on the appearance of the tire is suppressed. The tire manufactured with this mold 2 can maintain an excellent appearance. From this viewpoint, the width a is more preferably 5 mm or less.

3, the arrow H indicates the height of the recess 32. The height H of the recess 32 is measured in a direction perpendicular to the second contact surface 28. The height H is preferably 2 mm or more. By making the height H 2 mm or more, the rubber composition of the low cover R can easily move in the direction of B in FIG. 6 along the recess 32. When the mold 2 is closed, the rubber composition of the low cover R is less likely to reach the inner end P of the first contact surface 24. This prevents the rubber composition of the low cover R from entering between the first contact surface 24 and the second contact surface 28. In this mold 2, the low cover R is effectively prevented from being caught between the segment 4 and the side plate 6.

In this embodiment, the recess 32 has an arc shape in a cross section perpendicular to the circumferential direction. This makes it easier for the rubber composition of the low cover R to move in the direction of arrow B in FIG. 6. When the mold 2 is closed, the rubber composition of the low cover R is less likely to reach the inner end P of the first contact surface 24. The rubber composition of the low cover R is prevented from entering between the first contact surface 24 and the second contact surface 28. In this mold 2, the low cover R is effectively prevented from being caught between the segment 4 and the side plate 6.

3, the arrow Rd represents the radius of curvature of the recess 32. The radius of curvature Rd is preferably 2 mm or more. By setting the radius of curvature Rd to 2 mm or more, the rubber composition of the low cover R is more likely to move in the direction of the arrow B in FIG. 6. When the mold 2 is closed, the rubber composition of the low cover R is less likely to reach the inner end P of the first contact surface 24. The rubber composition of the low cover R is prevented from entering between the first contact surface 24 and the second contact surface 28. In this mold 2, the low cover R is effectively prevented from being caught between the segment 4 and the side plate 6. From this viewpoint, the radius of curvature Rd is more preferably 3 mm or more. From this viewpoint, the radius of curvature Rd is preferably 100 mm or less, and more preferably 90 mm or less.

In this embodiment, the recess 32 has a number of grooves 34 extending from the end of the recess 32 on the first contact surface 24 side to the opposite end. This reduces the contact area of the first contact surface 24 with the second contact surface 28 at the inner end P. Biting of the rubber composition of the low cover R at this position is suppressed. In this mold 2, biting of the low cover R between the segment 4 and the side plate 6 is effectively prevented. Furthermore, the grooves 34 allow air remaining in the gap near the inner end P to be effectively discharged. In tires manufactured with this mold 2, the occurrence of bare spots due to residual air is suppressed.

Figure 7 is a view of the recess 32 as seen from the inside in the axial direction. In Figure 7, the double-headed arrow GW indicates the width of the groove 34 of the recess 32. The width GW is measured in a direction perpendicular to the direction in which the groove extends. The width GW is preferably 0.3 mm or more. By making the width GW 0.3 mm or more, the rubber composition part of the lower cover R is effectively prevented from being pinched between the segment 4 and the side plate 6. Furthermore, by doing so, air remaining in the gap near the inner end P can be effectively discharged. From these viewpoints, the width GW is more preferably 0.5 mm or more. From the viewpoint of minimizing the impact of this groove 34 on the appearance, the width GW is preferably 1.5 mm or less.

The depth GD of the groove 34 is preferably 0.2 mm or more. By making the depth GD 0.2 mm or more, the rubber composition portion of the lower cover R is effectively prevented from being caught between the segment 4 and the side plate 6. Furthermore, by doing so, air remaining in the gap near the inner end P can be effectively discharged. From these viewpoints, the depth GD is more preferably 0.3 mm or more. From the viewpoint of minimizing the impact of this groove 34 on the appearance, the depth GD is preferably 1.0 mm or less.

In FIG. 7, the double-headed arrow GP indicates the pitch of the groove 34. The pitch GP is preferably 3.0 mm or less. By setting the pitch GP to 3.0 mm or less, the rubber composition of the lower cover R is effectively prevented from being caught between the segment 4 and the side plate 6. Furthermore, by doing so, air remaining in the gap near the inner end P can be effectively discharged. From these viewpoints, the pitch GP is more preferably 2.5 mm or less. From the viewpoint of minimizing the effect of this groove 34 on the appearance, the pitch GP is preferably 0.6 mm or more.

In FIG. 3, the double-headed arrow θ represents the angle between the second inner surface 26 and the second contact surface 28 at the corner between the second inner surface 26 and the second contact surface 28. The angle θ is preferably 90° or less. By setting the angle θ to 90° or less, the rubber composition of the low cover R is prevented from moving toward the inner end P at the boundary between the segment 4 and the bead ring 8 when the mold 2 is closed. When the first contact surface 24 and the second contact surface 28 come into contact with each other, the rubber composition of the low cover R is less likely to reach the inner end P of the first contact surface 24. This prevents the rubber composition of the low cover R from entering between the first contact surface 24 and the second contact surface 28. In this mold 2, the low cover R is effectively prevented from being caught between the segment 4 and the side plate 6.

The effects of the present invention will be explained below by way of examples, but the present invention should not be interpreted in a restrictive manner based on the description of these examples.

[Example 1]
The mold shown in Fig. 1-3 was prepared. This mold is for a tire with a size of "195/65 R16". The depression of this mold is arc-shaped in a cross section perpendicular to the circumferential direction. The specifications of this depression are shown in Table 1. This depression does not include a groove. The angle θ between the second contact surface and the second inner side surface was set to 90°.

[Comparative Example 1]
A mold of Comparative Example 1 was produced in the same manner as in Example 1, except that no recess was provided on the first inner side surface of the segment.

[Comparative Example 2]
A mold of Comparative Example 2 was produced in the same manner as in Example 1, except that the width a, height H and radius of curvature Rd of the recess were as shown in Table 1.

[Example 2]
A mold of Example 2 was produced in the same manner as in Example 1, except that the height H and the radius of curvature Rd of the recess were as shown in Table 1.

[Example 3]
The mold of Example 3 was produced in the same manner as Example 2, except that the depression had a plurality of grooves extending in the axial direction. The grooves were provided at equal pitch from one end of the depression to the other end in the circumferential direction. The groove width GW was 1.0 mm, the depth GD was 0.5 mm, and the pitch GP was 2.0 mm.

[Lower cover jammed]
Tires were manufactured using each mold, and the degree of burrs caused by the low cover being pinched was confirmed. The results are shown in Table 1, which is divided into four stages: A, B, C, and D. The order of A is the least amount of burrs, followed by B, C, and D. The order of A is the most preferable.

[Bear]
Tires were manufactured using each mold, and the occurrence of bare spots due to residual air at the boundary between the segment and the side plate was confirmed. The results are shown in Table 1, with three levels, A, B, and C. The occurrence of bare spots is lowest in the order of A, B, and C. The order of A, B, and C is the most preferable.

As shown in Table 1, the mold of the embodiment shows better results than the mold of the comparative example. The superiority of the present invention is clear from these evaluation results.

The mold of the present invention can be used to manufacture a variety of tires.

2: Mold 4: Segment 6: Side plate 8: Bead ring 10: Vulcanizer 12: Inner sector shoe 14: Outer sector shoe 16: Upper base plate 18: Lower base plate 20: First inner surface 24: First contact surface 26: Second inner surface 28: Second contact surface 30: Third inner surface 32: Recess 34: Groove

Claims (8)

The present invention comprises a ring-shaped side plate and a plurality of arc-shaped segments arranged around the side plate,
At least one of the segments has a first inner surface that primarily contacts the tread of the low cover and a first contact surface extending from an end of the first inner surface;
The side plate includes a second inner surface that mainly contacts the side portion of the low cover, and a second contact surface that extends from an end of the second inner surface and contacts the first contact surface,
The first inner surface is provided with a recess located at an end on the first contact surface side and extending in a circumferential direction,
In a cross section perpendicular to the circumferential direction, the recess has an outwardly convex arc shape ,
A mold for manufacturing tires, wherein the width a of the recess at the position of the second contact surface is 2 mm or more. The mold according to claim 1 , wherein the radius of curvature Rd of the recess is 2 mm or more. The present invention comprises a ring-shaped side plate and a plurality of arc-shaped segments arranged around the side plate,
At least one of the segments has a first inner surface that primarily contacts the tread of the low cover and a first contact surface extending from an end of the first inner surface;
The side plate includes a second inner surface that mainly contacts the side portion of the low cover, and a second contact surface that extends from an end of the second inner surface and contacts the first contact surface,
The first inner surface is provided with a recess located at an end on the first contact surface side and extending in a circumferential direction,
In a cross section perpendicular to the circumferential direction, the recess has an outwardly convex shape,
The width a of the recess at the position of the second contact surface is 2 mm or more,
A mold for manufacturing tires , wherein the recess includes a groove extending from an end of the recess on a first contact surface side. 4. The mold of claim 3 , wherein the width of the groove is 0.3 mm or more and 1.5 mm or less, and the depth of the groove is 0.2 mm or more and 1.0 mm or less. 5. The mold according to claim 3 , wherein a plurality of the grooves are present, and the pitch of the grooves is 0.6 mm or more and 3.0 mm or less. 6. The mold of claim 1, wherein the height of the depression, measured along a direction perpendicular to the second contact surface, is 2 mm or greater. The mold according to any one of claims 1 to 6, wherein the angle θ between the second inner surface and the second contact surface is 90° or less. A method for manufacturing a tire, comprising the steps of: setting a raw cover in the mold according to any one of claims 1 to 7; and pressurizing and heating the raw cover in the mold.

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