Producing method of resin hose

Abstract

To produce a bent resin hose using a method different from a conventional method.SOLUTION: A producing method of resin hose includes: a mandrel insertion step in which a mandrel covered with a tube containing fluororesin is inserted into a coil spring with a gap of 1 mm or less between adjacent turns of the coil spring while no force is being applied to the resin hose; a pre-heating step in which the resin hose is pre-heated in order to bend it; a bending step in which the resin hose into which the mandrel is inserted is supported from an outside to bend the resin hose into a predetermined shape, after the pre-heating step; a main heating step in which the resin hose is heated while it is bent into a specified shape; a cooling step of cooling the resin hose after the main heating step; and a removing step of removing the mandrel from the resin hose after the cooling step.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a bent resin hose. [Background technology]

[0002] Patent Document 1 describes a method for bending a resin-rubber composite hose in which a resin tube, multiple rubber layers, and a reinforcing layer are laminated in this order from the inside. In this method, a mandrel having a hollow portion is inserted into the resin-rubber composite hose, and then a molding mandrel bent into a predetermined shape is inserted into the hollow portion of the mandrel. The hose is then vulcanized, and the molding mandrel and the mandrel having the hollow portion are then sequentially removed from the hose. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4069140 Summary of the Invention [Problem to be solved by the invention]

[0004] When the molding mandrel bent into a predetermined shape and the mandrel having a hollow portion are successively removed from the resin-rubber composite hose, the hose expands and contracts due to the rubber compounded to the hose. This allows the molding mandrel bent into a predetermined shape and the mandrel having a hollow portion to be removed from the hose. However, when bending a resin hose that is not compounded with rubber, because the resin hose does not have the flexibility, there is a risk that the molding mandrel bent into a predetermined shape or the mandrel having a hollow portion cannot be removed from the hose.

[0005] An object of the present invention is to provide a method for producing a bent resin hose by a method different from the conventional method. [Means for solving the problem]

[0006] The manufacturing method of a plastic hose disclosed in this specification is a method of manufacturing a plastic hose that has been bent into a predetermined shape, and includes the steps of: a mandrel insertion step of inserting a mandrel, which is covered with a tube containing fluororesin, into a coil spring having a gap of 1 mm or less between adjacent windings while no force is applied to the plastic hose; a preheating step of preheating the plastic hose in order to bend the plastic hose; a bending step of supporting the plastic hose with the mandrel inserted therein from the outside after the preheating step, thereby bending the plastic hose into a predetermined shape; a main heating step of heating the plastic hose while the plastic hose is bent into the predetermined shape; a cooling step of cooling the plastic hose after the main heating step; and a removal step of removing the mandrel from the plastic hose after the cooling step. Effect of the Invention

[0007] According to the above method, a bent resin hose can be manufactured by a method different from the conventional method. [Brief description of the drawings]

[0008] [Figure 1] 1A to 1C are schematic diagrams illustrating a method for manufacturing a resin hose before a mandrel is inserted. [Diagram 2] 13(a) and (b) are schematic diagrams showing examples of mandrel springs. [Diagram 3] 1A to 1C are schematic diagrams illustrating the steps of inserting a mandrel, and are used to explain a method for manufacturing a resin hose. [Figure 4] 4 is a flowchart of a method for manufacturing a resin hose. [Diagram 5] FIG. 2 is a plan view of a mold used in a method for manufacturing a resin hose. [Figure 6] 4A to 4C are schematic diagrams illustrating a method for manufacturing a resin hose before removing the mandrel. [Figure 7] 5A to 5C are schematic diagrams illustrating the process for producing a resin hose after the mandrel has been removed. [Figure 8]10(a) and 10(b) are schematic diagrams for explaining how to determine the flattening of a bent portion of a resin hose, and 10(b) is a cross-sectional view taken along line bb in 10(a). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A preferred embodiment will now be described.

[0010] Here, a method for manufacturing a bent resin hose will be described.

[0011] The material of the resin hose is not particularly limited. The material of the resin hose is, for example, a thermoplastic resin. Examples of the thermoplastic resin include polyethylene resin, polypropylene resin, and polyamide resin. Examples of the polyamide resin include PA6, PA66, PA11, PA12, PA612, PA9T, copolymers thereof, modified products thereof, blends thereof, and blends of PA with olefin. Examples of the copolymer include copolymers of PA6 and PA66, copolymers of PA11 and PA12, and the like. The resin hose manufactured by the method according to this embodiment is used, for example, in automobiles.

[0012] The method for manufacturing a resin hose mainly includes a mandrel insertion step, a preheating step, a bending step, a main heating step, a cooling step, and a removal step. The method for manufacturing a resin hose will be described in detail below.

[0013] A mandrel 2 to be inserted inside a hose (resin hose) 1 is prepared (see FIG. 1). The mandrel 2 is used to maintain the hose 1 in a cylindrical shape while the hose 1 is being bent. As shown in FIG. 1, the mandrel 2 has a spring (coil spring) 21 and a hollow cylindrical tube (fluorine tube) 22 that is placed over the spring 21. FIG. 1 shows a cross section of a portion of the mandrel 2.

[0014] The spring 21 is a coil spring in which a wire is wound in a spiral shape. The spring 21 is made of metal. The material of the spring 21 is, for example, SUS. The spring 21 is a spring in which, when no force is applied, the gap between two adjacent windings in the axial direction (winding direction) of the spring 21 is 1 mm or less. The "state in which no force is applied to the spring 21" refers to the state in which the spring 21 is at its natural length. In addition, the "state in which no force is applied to the spring 21" also refers to the state in which no restoring force is applied to the spring 21.

[0015] 2(a) and 2(b) show examples of springs 21. As shown in FIG.

[0016] 2(a) shows a so-called tightly wound coil spring 121. In this embodiment, the "tightly wound coil spring" refers to a spring in which, when no force is applied to the spring 121, the first winding portion 121x and the second winding portion 121y adjacent to each other are in contact with each other at least partially in the axial direction of the spring 121, in other words, a spring in which, when no force is applied to the spring 121, there is a portion where the gap between the first winding portion 121x and the second winding portion 121y adjacent to each other is 0 mm in the axial direction of the spring 121.

[0017] 2(b) shows the spring 221 in which, when no force is acting on the spring 221, a gap exists between the adjacent first winding portion 221x and second winding portion 221y in the axial direction of the spring 221. When a gap exists between the first winding portion 221x and the second winding portion 221y, the gap between the adjacent first winding portion 221x and second winding portion 221y in the axial direction of the spring 221 is greater than 0 mm and equal to or less than 1 mm.

[0018] The spring 21 (121, 221) is covered with a tube 22 (see FIG. 1). The tube 22 is a tube containing a fluororesin. Examples of the fluororesin include at least one selected from the group consisting of polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-ethylene copolymer (EFEP), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), chlorotrifluoroethylene (CTFE)-tetrafluoroethylene (TFE) copolymer, and chlorotrifluoroethylene (CTFE)-tetrafluoroethylene (TFE)-perfluoroalkyl vinyl ether copolymer. One of these groups may be used, or two or more may be blended and used. The tube 22 preferably contains a fluororesin having a melting point higher than that of the hose 1. When the static friction coefficient of the outer surface of the tube 22 is measured by a method conforming to JIS K7125, the static friction coefficient is preferably 0.04 μs or more and 0.09 μs or less. Furthermore, the thickness of the tube 22 is not particularly limited, but may be, for example, 0.5 mm or more and 2.0 mm or less.

[0019] [Mandrel insertion process] The mandrel 2 shown in FIG. 1 is inserted into the inside of the hose 1 (S1 in FIGS. 3 and 4).

[0020] [Preheating process] The hose 1 is heated so that the hose 1 can be easily bent in the "bending step" described below. The heating temperature and heating time of the hose 1 are not particularly limited. The hose 1 should be heated to a degree that allows the hose 1 to bend into a predetermined shape (S2 in FIG. 4). For example, it is preferable to heat the hose 1 at a temperature equal to or higher than the glass transition point of the resin used in the hose 1 and lower than the melting point of the resin used in the hose 1.

[0021] The "mandrel insertion step" and the "preheating step" may be performed in any order.

[0022] [Bending process] After the pre-heating step, the hose 1 with the mandrel 2 inserted therein is supported from the outside, so that the hose 1 is bent into a predetermined shape (S3 in FIG. 4). For example, a mold 3 as shown in FIG. 5 may be used. The mold 3 is formed with a recess 3a into which the hose 1 fits. The recess 3a is bent into the bending shape of the hose 1 to be manufactured. The recess 3a is formed by an inner wall 3A and an outer wall 3B, etc.

[0023] As shown in Fig. 6, the hose 1 is fitted into the recess 3a. The mandrel 2 is inserted into the hose 1. The hose 1 is disposed between the inner wall 3A and the outer wall 3B. The hose 1 is supported from the outside by the inner wall 3A and / or the outer wall 3B, so that the hose 1 is maintained in a bent state in a predetermined shape.

[0024] [Main heating process] As shown in FIG. 6, the hose 1 is heated in a state where it is bent into a predetermined shape. In this way, the hose 1 is bent and shaped into a predetermined shape. The heating temperature and heating time of the hose 1 are not particularly limited. It is preferable to heat the hose 1 at a temperature equal to or higher than the glass transition point of the resin used in the hose 1 and lower than the melting point of the resin used in the hose 1. The heating temperature in the main heating step may be the same as the heating temperature in the preheating step, or may be higher than the heating temperature in the preheating step. The heating time in the main heating step may be the same as the heating time in the preheating step, or may be higher than the heating time in the preheating step.

[0025] [Cooling process] After this heating step, as shown in FIG. 6, the hose 1 is cooled in a state where it is bent into a predetermined shape. This results in a hose 1 bent into a predetermined shape. The cooling temperature and cooling time of the hose 1 are not particularly limited. For example, the hose 1 may be cooled at a temperature lower than the glass transition point of the resin used in the hose 1. For example, the hose 1 may be cooled until the temperature of the hose 1 becomes lower than the glass transition point of the resin used in the hose 1. For example, the hose 1 may be cooled at room temperature until the hose 1 reaches room temperature.

[0026] [Sampling process] After the cooling step, the mandrel 2 is removed from the hose 1. As shown in Fig. 6, the mandrel 2 may be removed while the hose 1 is supported from the outside (Fig. 7). Alternatively, the hose 1 may be removed from the mold 3, and the mandrel 2 may be removed while the hose 1 is not supported from the outside.

[0027] According to the above-mentioned method, it is possible to manufacture the resin hose 1 bent into a predetermined shape by a method different from the conventional method. In addition, the following effects can be obtained.

[0028] Mandrel 2 is inserted inside hose 1. Tube 22 that covers spring 21 of mandrel 2 is a tube containing fluororesin (see FIG. 1). Therefore, even when hose 1, which is made of resin and has little elasticity, is bent into a predetermined shape, mandrel 2 can be removed from hose 1 (see FIGS. 6 and 7). Furthermore, experiments described below have shown that by using tube 22 containing fluororesin, mandrel 2 removed from hose 1 has flexibility and can be repeatedly used to bend other resin hoses.

[0029] As the fluororesin-containing tube 22, for example, a tube containing polytetrafluoroethylene (PTFE) or a tube containing tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA) may be used. The above-mentioned effect can be obtained by using such a tube containing a generally available fluororesin.

[0030] Furthermore, the spring 21 (see FIG. 1) used for the mandrel 2 is a coil spring in which the gap between two adjacent windings is 1 mm or less in the axial direction of the spring 21 when no force is acting on the spring 21. By using such a spring 21 for the mandrel 2, when the resin hose 1 is bent into a predetermined shape, the bent portion of the hose 1 is less likely to flatten and is more likely to maintain a cylindrical shape (see FIG. 6).

[0031] 6, the hose 1 is bent into a predetermined shape while being supported from the outside by inner wall 3A and / or outer wall 3B of mold 3. With this method, it is not necessary to insert a molding mandrel bent into a predetermined shape into the inside of resin hose 1.

[0032] It should be noted that the "mandrel insertion step" and the "preheating step" may be performed in any order. For example, by performing the "preheating step" after the "mandrel insertion step", it becomes easier to bend the hose 1 into a predetermined shape in the subsequent "bending step". EXAMPLES

[0033] The present invention will be described in more detail below with reference to examples. However, the following examples do not limit the present invention, and all modifications and variations within the scope of the present invention are included in the technical scope of the present invention.

[0034] [Experiment 1] Using the mandrel shown in Table 1, a resin hose was manufactured by bending into a predetermined shape. No mandrel was used in No.1. A rubber mandrel was used in No.2 and No.3. The mandrels in No.2 and No.3 were made of ethylene propylene diene rubber (EPDM). A release agent was used in No.3. A rod-shaped PTFE mandrel was used in No.4. No.5 used a mandrel with the structure shown in Figure 1. The mandrel in No.5 is a mandrel made of a SUS sealed coil spring (outer diameter 9.5 mm) covered with a PTFE tube (outer diameter 12.0 mm, inner diameter 10.0 mm, thickness 1.0 mm).

[0035] A resin hose was manufactured in the same manner as described in the above embodiment, except for the mandrel. The material of the hose was PA6. In the preliminary heating process, the hose was heated at 180°C or higher for 15 minutes or more. A mold similar to mold 3 shown in FIG. 5 was used for bending. In the main heating process, the hose was heated at 190°C or higher for 15 minutes or more.

[0036] Table 1 shows the ease of bending the hose, the ease of removing the mandrel, the flattening of the bent part of the hose, and whether the mandrel can be reused repeatedly.

[0037] The flattening ratio of the bent portion of the hose was determined by the following method. As shown in Figure 8(a), at the position where the hose bending rate is the highest (part bb), the hose diameter (minor diameter) at the part where the hose diameter (outer diameter) is the shortest and the hose diameter (major diameter) at the part where the hose diameter is the longest were measured (see Figure 8(b)), and (minor diameter / major diameter) x 100[%] was calculated as the "flattening ratio". Figure 8(b) shows a cross-sectional view of the hose at part bb in Figure 8(a) (cross-sectional view along line bb). Note that Figures 8(a) and 8(b) only show the hose, and the mandrel inserted inside the hose is omitted. Taking into consideration the appearance of the hose bend, pressure loss, and stress concentration, it was determined that if the flattening ratio of the hose bend is 80% or more, there is no problem in practical use as a hose product.

[0038] [Table 1]

[0039] From Table 1, the following was found:

[0040] In No. 1, which did not use a mandrel, kinking occurred at the bent part of the hose. Hose No. 1 could not be shipped as a product.

[0041] In No. 2, which used a rubber mandrel, the mandrel could not be removed from the hose. In addition, because the mandrel was deformed during the "main heating process," the mandrel could not be used to bend another hose after use.

[0042] In No.3, the same rubber mandrel as in No.2 was used, and a release agent was applied to the mandrel. In No.3, the mandrel could be removed from the hose. This is believed to be because a release agent was used. However, the flattening ratio of the bent part of the hose was less than 80%, and the amount of flattening was large. In addition, because the mandrel was deformed in the "main heating process", the mandrel after use could not be used to bend another hose.

[0043] In No. 4, which used a PTFE mandrel, it was difficult to bend the hose. This is thought to be due to the rod-shaped PTFE mandrel. However, there were no other problems. Specifically, the mandrel could be removed from the hose. The flattening ratio of the bent part of the hose was over 80%, and the amount of flattening was small. The mandrel was flexible, and the mandrel could be repeatedly used to bend another hose after use.

[0044] In No. 5, which used the mandrel shown in Figure 1 (a mandrel consisting of a PTFE tube covering a SUS spring), all results were good. Specifically, the hose could be easily bent into the desired shape. The mandrel could be removed from the hose. The flattening ratio of the bent part of the hose was 80% or more, and the amount of flattening was small. The mandrel was flexible, and the mandrel could be repeatedly used to bend other hoses after use.

[0045] From the above, it was found that it was better to use a No. 5 mandrel (a mandrel with a PTFE tube covering a SUS spring).

[0046] Also, from Table 1, it is believed that the material of the mandrel, particularly the material of the outer periphery of the mandrel, affects the ease of removing the mandrel and whether the mandrel can be reused. Furthermore, it is believed that the material and structure of the mandrel's core affect the flattening. Therefore, in the next experiment 2, the material of the tube (outer tube) that covers the spring in mandrel No. 5 was changed to investigate the ease of removing the mandrel and whether the mandrel can be reused. In experiment 3, a coil spring was used in the core of the mandrel, and the flattening was investigated when the gap between the wound parts of the coil spring was different.

[0047] [Experiment 2] Four types of tubes made of different materials were prepared as tubes (outer layer tubes) to be placed over the mandrel spring. Table 2 shows the materials of the mandrel tubes (outer layer tubes). A mandrel was prepared in which a coil spring was placed over the tubes shown in Table 2. The same spring as that used in No. 5 of Experiment 1 was used for the coil spring. A resin hose was manufactured by bending the mandrel into a specified shape. In this experiment, the hose was manufactured under the same conditions as in Experiment 1. The static friction coefficient of the outer surface of the outer layer tube was also measured using a method in accordance with JIS K7125.

[0048] [Table 2]

[0049] From Table 2, the following was found:

[0050] In the case of No. 6 and No. 7, the mandrel could be removed from the hose. In addition, in the case of No. 6 and No. 7, the mandrel could be used to bend hoses 10 times. Even after 10 uses, the mandrel retained flexibility and could be used repeatedly to bend other hoses. The material of the outer layer tube of No. 6 is PTFE, and the material of the outer layer tube of No. 7 is PFA, and both the outer layer tubes of No. 6 and No. 7 contain fluororesin.

[0051] On the other hand, in No. 8 and No. 9, the mandrel could not be removed from the hose. In No. 8, the mandrel (outer tube) was deformed during the first hose bending process, and the mandrel could not be used to bend another hose. In No. 9, the mandrel (outer tube) did not have flexibility during the first hose bending process, and the mandrel could not be used to bend another hose. The material of the outer layer tube of No. 8 is PE, and the material of the outer layer tube of No. 9 is PA6. The outer layer tubes of No. 8 and No. 9 do not contain the fluororesin contained in the outer layer tubes of No. 6 and No. 7.

[0052] From the above, it is believed that by using a tube containing fluororesin as the tube (outer layer tube) that covers the mandrel spring, the mandrel can be easily removed and the mandrel can be reused repeatedly.

[0053] In addition, the static friction coefficient of the outer tube was 0.04 to 0.06 μs in No. 6. The static friction coefficient of the outer tube was 0.07 to 0.09 μs in No. 7. In No. 6 and No. 7, the mandrel could be removed. On the other hand, the static friction coefficient of the outer layer tube was 0.36 to 0.39 μs in No. 8. The static friction coefficient of the outer layer tube was 0.66 to 0.71 μs in No. 9. In No. 8 and No. 9, the mandrel could not be removed. From the above, it can be said that by using an outer layer tube with a static friction coefficient of 0.04 to 0.09 μs for the mandrel, the mandrel can be removed from the resin hose.

[0054] [Experiment 3] Four types of SUS coil springs with different gaps between the windings were prepared as the coil springs to be used with the mandrel. Table 3 shows the gaps between the windings of the four types of coil springs. The "length of the gap between adjacent windings" in Table 3 is the length of the gap between two adjacent windings in the axial direction of the coil spring when no force is acting on the coil spring. The spring used in No. 13 (closely wound coil spring) is a spring in which adjacent windings are in contact with each other at least partially.

[0055] A mandrel was prepared by covering a coil spring shown in Table 3 with a tube. For the mandrel tube (outer tube), a tube containing fluororesin (PTFE tube (outer diameter 12 mm, inner diameter 10 mm, thickness 1 mm)) was used, which was found in Experiment 2 to have good mandrel removal workability and to be capable of repeated use of the mandrel. A resin hose was manufactured by bending the mandrel into a specified shape using the mandrel. In this experiment, the hose was manufactured under the same conditions as in Experiment 1.

[0056] [Table 3]

[0057] From Table 3, the following was found:

[0058] In No. 10, the "length of the gap between adjacent windings" of the coil spring is 5 mm, and the flattening ratio at this time is less than 80%. In No. 11, the "length of the gap between adjacent windings" of the coil spring is 3 mm, and the flattening ratio at this time is less than 80%. In No. 10 and No. 11, the amount of flattening was large.

[0059] In No. 12, the "length of the gap between adjacent windings" of the coil spring is 1 mm, and the flattening ratio at this time is 80% or more. In No. 13, there is no "gap between adjacent windings" of the coil spring, and the flattening ratio at this time is 80% or more. In No. 12 and No. 13, the amount of flattening was small.

[0060] From the above, it is believed that by using a coil spring for the mandrel in which the "length of the gap between adjacent windings" is 1 mm or less, the amount of flattening at the bent part of the hose is reduced.

[0061] From the above experiments 1 to 3, the following was found. When manufacturing a plastic hose that has been bent into a specified shape, a mandrel consisting of a coil spring covered with a cylindrical tube (outer tube) is used as the mandrel to be inserted inside the plastic hose. The coil spring is one in which the gap between adjacent windings is 1 mm or less when no force is applied. The outer tube is a tube containing fluororesin. This allows the hose to be easily bent during the hose bending process. Also, the mandrel can be removed from the hose. Also, the amount of flattening at the bent part of the hose is small. Furthermore, the mandrel used for bending is flexible and can be used repeatedly to bend other hoses.

[0062] Although the embodiments of the present invention have been described above with reference to the drawings, the specific configuration should not be considered to be limited to these embodiments. The scope of the present invention is indicated by the claims, not by the above description, and includes all modifications within the meaning and scope of the claims.

[0063] For example, in the above embodiment, the mold 3 shown in Fig. 3 was used in the bending step. When the mold 3 is used, the hose 1 can be maintained in a bent state while being supported from the outside by the inner wall 3A and / or the outer wall 3B. However, the member supporting the hose 1 from the outside is not limited to the mold 3 shown in Fig. 3, and other members may be used. For example, a jig having a desired bending shape (such as an R-shaped portion) may be used, and the hose 1 may be bent along the jig. [Explanation of symbols]

[0064] 1 Hose (plastic hose) 2 Mandrels Type 3 3a Recess 21, 121, 221 Spring (coil spring) 121x, 221x Volume 1 121y, 221y Volume 2 22 Tube (Outer tube)

Claims

1. A method for manufacturing a resin hose bent into a predetermined shape, comprising the steps of: a mandrel insertion process of inserting a mandrel covered with a tube containing a fluororesin into a coil spring having a gap of 1 mm or less between adjacent windings of the coil spring while no force is being applied to the resin hose; A preheating step of preheating the resin hose in order to bend the resin hose; a bending step of bending the resin hose into a predetermined shape by supporting the resin hose with the mandrel inserted therein from the outside after the preheating step; a main heating step of heating the resin hose in a state in which the resin hose is bent into a predetermined shape; a cooling step of cooling the resin hose after the main heating step; a removing step of removing the mandrel from the resin hose after the cooling step; A method for manufacturing a resin hose comprising:

2. The coil spring is a spring in which adjacent windings are in contact with each other at least partially when no force is applied. The method for producing a resin hose according to claim 1 .

3. The material of the tube is a fluororesin containing PTFE or PFA. The method for producing a resin hose according to claim 1 or 2.

4. The preheating step is performed after the mandrel insertion step. The method for producing a resin hose according to claim 1 .

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