Tire tube

Abstract: In order to provide a tire tube excellent in sealing performance and durability, in a tire tube in which the inside of a peripheral wall (4) having an approximately circular cross-section is partitioned by a partition wall(5) into an outer peripheral side sealant chamber(7)and an inner peripheral side air chamber(3)and the sealant chamber (7) is filled with a sealant(8), it is proposed that the thickness (t) in the diameter direction of the sealant (8) charged in the sealant chamber (7) is in the range of 0.5 to 1.5 mm.

Description: The present invention relates to a tire tube and particularly to a tire tube including an air chamber filled with air and a sealant chamber filled with a sealant according to the preamble of claim 1. A tire tube according to the preamble of claim 1 is known from EP-A-0 818 302. Fig. 1 is a transverse sectional view of a wheel mounted with a tube containing tire including a sealant chamber; Fig. 5 is a flow chart showing steps of manufacturing a tube; and Fig. 6 is a partial perspective view of an extrusion-molding machine for extrusion-molding a tube material. As shown in Fig. 1, a rim R of a wheel for a motorcycle is connected to a hub (not shown) via wire spokes (not shown). A tube containing tire T having a tire 1 and a tube 2 contained in the tire 1 is mounted on the rim R. The tube 2 includes a peripheral wall 4 and a partition wall 5 for partitioning the inside surrounded by the peripheral wall 4 into two parts. The peripheral wall 4 is composed of an air chamber peripheral wall 41 positioned radially inward of the tube 2, and a sealant chamber peripheral wall 40 positioned radially outward of the tube 2. The partition wall 5 is molded integrally with the peripheral wall 4. An air chamber 3, which is surrounded by the air chamber peripheral wall 41 and the partition wall 5 in an approximately circular shape in cross-section, is filled with air. A sealant chamber 7, which is surrounded by the sealant chamber peripheral wall 40 and the partition wall 5 in an approximately arcuate shape, is filled with a known liquid sealant 8. The air chamber peripheral wall 41 has an air valve 6 for filling the air chamber 3 with air. As shown in Fig. 5, a process of manufacturing the tube 2 includes a material kneading step, a tube material extrusion-molding step, a cutting step, an air valve mounting step, a joining step, and the like. A material composed of a crude rubber kneaded at the material kneading step is extrusion-molded into a tube material 2' by an extrusion-molding machine at the tube material extrusion-molding step. The tube material 2' is cut into a specific length at the cutting step; an air valve 6 is mounted at a suitable position on the air chamber peripheral wall 41 at the air valve mounting step; and both the ends of the tube material 2' are joined to each other at the joining step. After that, the material 2' is subjected to a vulcanizing step and a sealant filling step, to obtain a finished tire tube. As shown in Fig. 6, a nozzle 12 of an extrusion-molding machine 11 has surface lubricant delivery ports 14a and 14b and surface lubricant suction ports 13a and 13b for supplying and discharging a surface lubricant such as talc into the air chamber 3 and the sealant chamber 7, respectively. The general sealing performance of a tire is improved by increasing the charged amount of a sealant 8 into the sealant chamber 7 thereby making large the thickness "t" of the sealant 8; however, when the charged amount of the sealant 8 is increased to make large the thickness of the sealant 8, the weight of a tire tube 2 is increased to thereby degrade the durability of the tire tube 2 at the contact surface with a tire 1. In this way, with the thickness "t" in the diameter direction of the sealant 8 taken as a parameter, since the durability of the tire tube 2 is incompatible with the sealing performance of the tire tube 2, the thickness "t" in the diameter direction of the sealant 8 in the sealant chamber 7 is required to be specified in consideration with both the sealing performance and durability. According to a related art, however, it has failed to examine a relationship between the thickness "t" of the sealant 8 in the sealant chamber 7 and the sealing performance/durability, and therefore, the thickness of the sealant 8 has not been suitably set, thus making it difficult to make compatible the sealing performance with the durability. In the above-described related art extrusion-molding machine 11, while talc is delivered in regions forming the air chamber 3 and the sealant chamber 7 from the different surface lubricant delivery ports 14a and 14b respectively, delivery means such as a pump for imparting a delivery pressure is common to the surface lubricant deliver ports 14a and 14b. Accordingly, if a delivery load at one of the surface lubricant delivery ports becomes larger than that at the other surface lubricant delivery port due to some external cause, the delivery force applied by the pump is concentrated on the other surface lubricant delivery port side. As a result, while the surface lubricant in an excessively larger amount is delivered from the latter surface lubricant delivery port with the small delivery load, the amount of the surface lubricant delivered from the former surface lubricant delivery port with the large delivery load becomes insufficient because a specific deliver pressure is not applied to the delivery port. As shown in Fig. 6, for example, when extrusion-molding is performed in a state in which the delivery port 14a is located on the upper side and the delivery port 14b is located on the lower side, a delivery load at the upper delivery port 14a is larger than that at the lower delivery port 14b due to the gravity applied to the tube. As a result, while the surface lubricant in a large amount is delivered from the lower delivery port 14b, the surface lubricant in a sufficient amount is not delivered from the upper delivery port 14a. An object of the invention is to provide a tire tube excellent in sealing performance and durability. To achieve the above object, the present invention provides: a tire tube in which the inside of a peripheral wall having an approximately circular cross-section is partitioned by a partition wall into an outer peripheral side sealant chamber and an inner peripheral side air chamber and said sealant chamber is filled with a sealant, characterized in that the thickness, in the diameter direction, of said sealant charged in said sealant chamber is in a range of 0.5 to 1.5 mm. With the above configuration, the durability and sealing performance of a tube with the thickness "t" in the diameter direction of the sealant taken as a parameter, which are incompatible with each other in terms of physical properties, can be substantially compatible with each other as a matter of practicality. Since the thickness in the diameter direction of the sealant is specified at a value in a range of 0.5 mm to 1.5 mm from the viewpoint of the durability and sealing performance actually required for a tire tube, the durability and sealing performance, which are incompatible with each other in terms of physical properties, can be made substantially compatible with each other as a matter of practicality. Hereinafter, the present invention will be described in detail with reference to the drawings. Fig. 1: A transverse sectional view of a wheel mounted with a tube containing tire including a sealant chamber. Fig. 2: A graph showing a relationship between the durability and the thickness of a sealant. Fig. 3: A graph showing a relationship between the sealing performance and the thickness of the sealant. Figs. 4 (a) and 4(b): A sectional view of an extrusion-molding machine and a front view of a nozzle of the machine. Fig. 5: A flow chart showing steps of manufacturing a tube. Fig. 6: A partial perspective view of an extrusion-molding machine. The present inventor has found such a new technical problem that in a tube including on its peripheral portion a sealant chamber, if the charged amount of a sealant into the sealant chamber is increased to make thick the sealant in the diameter direction, the sealing performance is improved; however, since the weight of the sealant chamber is increased, the durability of the tire tube 2 at the contact surface with the tire 1 is degraded. On the basis of the knowledge, the present inventor has examined a relationship between the thickness of the sealant in the sealant chamber and the sealing performance/durability. Fig. 2 is a graph showing a relationship between the durability (ordinate) of a tube and the thickness (abscissa) of a sealant. Here, a runnable distance was taken as the scale of the durability, and the runnable distance was measured with the thickness of the sealant changed by 0.5 mm for each measurement. The experimental results show that the runnable distance becomes larger as the thickness of the sealant becomes thin. For a motorcycle, the durability of a tire itself is about 10,000 km, and since tube exchange is generally performed simultaneously with tire exchange, the durability of a tube may be set at about 10,000 km as a matter of practicality. Even in consideration of differences between tube products, the durability of a tube may be set at about 15,000 km. From the experimental results shown in Fig. 2, it is revealed that the durability equal to or more than 10,000 km can be ensured by setting the thickness of the sealant at a value equal to or less than about 1.8 mm, and the durability equal to or more than 15,000 km can be ensured by setting the thickness of the sealant at a value equal to or less than 1.5 mm. Fig. 3 is a graph showing a relationship between the sealing performance of a tube (ordinate) and the thickness of a sealant (abscissa). Here, the diameter of a hole allowed to be blocked with the sealant was taken as the scale of the sealing performance, and the diameter of a hole allowed to be blocked with the sealant was measured with the thickness of the sealant changed by 0.5 mm for each measurement. The experimental results show that the sealing performance becomes higher as the thickness of the sealant becomes larger. Incidentally, puncture of a tire may be generally due to the fact that a sharpened body such a nail penetrates the tire to perforate a tube. As a result of examination made by the present inventors, it became apparent that the diameter of a sharpened body causing puncture of a tire is substantially in a range of about 2 to 3 mm, and the diameter of a hole opened in the tube by such a sharpened body is about 6 mm. On the basis of the experimental results shown in Fig. 3, it is revealed that the hole having a diameter of 6 mm can be blocked by setting the thickness of the sealant at a value equal to or more than 0.5 mm. In this way, according to this embodiment, the optical range of the thickness of the sealant was examined in consideration of both the durability and sealing performance of a tire tube. And, it became apparent that the durability becomes higher as the thickness of the sealant becomes thinner, and that even if the thickness of the sealant is made thick up to 1.5 mm in consideration of the durability of a tire itself as a matter of practicality, a sufficient durability of the tire tube can be substantially ensured. Also, it became apparent that the sealing performance becomes higher as the thickness of the sealant becomes larger, and that even if the thickness of the sealant is made thin to 0.5 mm in consideration of the diameter of a hole actually opened in the tube as a matter of practicality, a sufficient sealing performance can be substantially ensured. From the above experiments and the examined results, in this embodiment, the thickness of the sealant is specified in a value in a range of 0.5 mm to 1.5 mm. As described above, in this embodiment, the thickness in the diameter direction of the sealant is specified at a value in a range of 0.5 mm to 1.5 mm from the viewpoint of the durability and sealing performance actually required for a tire tube, so that the durability and sealing performance, which are incompatible with each other in terms of physical properties, can be made substantially compatible with each other as a matter of practicality. Figs. 4(a) and 4(b) are views showing the configuration of a tube extrusion-molding machine, wherein Fig. 4(a) is a front view of a nozzle plane through which a tube material is extruded, and Fig. 4(b) is a sectional view taken on line A-A of Fig. 4(a). The nozzle plane has a peripheral wall forming gap 31 through which a peripheral wall portion of a tube material is extruded and a partition wall forming gap 32 through which a partition wall portion of the tube material is extruded, and the nozzle plane also has surface lubricant delivery ports 14a and 14b and surface lubricant suction ports 13a and 13b for supplying and discharging a surface lubricant such as talc into an air chamber and a sealant chamber, respectively. The surface lubricant delivery ports 14a and 14b are, as shown in Fig. 4(b), connected to surface lubricant delivery pumps 21 and 22 via pipe lines 23 and 24, respectively. In this way, the surface lubricant delivery pumps 21 and 22 as talc supplying means are connected to the surface lubricant delivery ports 14a and 14b, respectively and accordingly if a delivery load, such as a resistance of the pipe line, at one surface lubricant delivery port is increased, a supply pressure corresponding to the increased delivery load is not escaped from the other surface lubricant delivery port. As a result, a specific supply pressure is always ensured at the one surface lubricant delivery port irrespective of the delivery load, to thereby prevent an extreme reduction in the delivered amount. The supply pressures for supplying the surface lubricant, which are applied by the surface lubricant delivery pumps 21 and 22, are not necessarily made equal to each other. For example, if it is previously estimated that a delivery load on the delivery port 14a side becomes larger than that on the delivery port 14b side, the supply pressure applied by the surface lubricant delivery pump 21 may be set at a value slightly higher than that applied by the surface lubricant delivery pump 22, with a result that the surface lubricant in a specific amount can be stably delivered from each of the delivery ports 14a and 14b. In summary it is an object to provide a tire tube excellent in sealing performance and durability. To achieve this object, in a tire tube in which the inside of a peripheral wall 4 having an approximately circular cross-section is partitioned by a partition wall 5 into an outer peripheral side sealant chamber 7 and an inner peripheral side air chamber 3 and the sealant chamber 7 is filled with a sealant 8, the thickness in the diameter direction of the sealant 8 charged in the sealant chamber 7 is in a range of 0.5 to 1.5 mm. In order to provide a tire tube excellent in sealing performance and durability, in a tire tube in which the inside of a peripheral wall (4) having an approximately circular cross-section is partitioned by a partition wall(5) into an outer peripheral side sealant chamber(7)and an inner peripheral side air chamber(3)and the sealant chamber (7) is filled with a sealant(8), it is proposed that the thickness (t) in the diameter direction of the sealant (8) charged in the sealant chamber (7) is in the range of 0.5 to 1.5 mm.

Claims: A tire tube in which the inside of a peripheral wall (4) having an approximately circular cross-section is partitioned by a partition wall (5) into an outer peripheral side sealant chamber (7) and an inner peripheral side air chamber (3) and said sealant chamber (7) is filled with a sealant (8), characterized in that the thickness (t), in the diameter direction, of said sealant (8) charged in said sealant chamber (7) is in a range of 0.5 to 1.5 mm.

Inventors: YAMAGIWA TOSHIO, YAMAGIWA, TOSHIO
Applicants: HONDA MOTOR CO LTD, HONDA GIKEN KOGYO KABUSHIKI KAISHA
Application year: 1999
Main classification: B60C5
IPC codes: B29D30, B29C47, B29C73, B29C33, B29C37, B60C5, B29D23