Fluid transport tube and method for manufacturing the same

Abstract

In a fluid transport tube (1) having a plurality of layers (2, 3) layered therein, an outer layer (3) of the plurality of layers (2, 3) is made of a thermoplastic elastomer foam body. An inner layer (2) of the plurality of layers (2, 3) is made of a thermoplastic elastomer or a thermoplastic resin. The outer layer (3) and the inner layer (2) are tightly attached to each other. The expansion ratio of the thermoplastic elastomer foam body is 2-5.5 fold. This allows an improvement in heat insulation and production stability of the fluid transport tube (1).

Description

Cross-reference to related applications

[0001] This application is based on Japanese Patent Application No. 2022-194106 filed on December 5, 2022, the contents of which are incorporated herein by reference.

Technical Field

[0002] The present disclosure relates to a fluid transport tube for transporting fluids. and the manufacturing method thereof It relates to.

Background Art

[0003] Conventionally, Patent Document 1 describes a heat-insulating hose in which the heat insulation of a fluid transport hose for transporting fluids is improved. The heat-insulating hose of Patent Document 1 includes an outer layer having a foaming material (hereinafter referred to as a foaming layer), a reinforcing layer, and an inner layer. The foaming layer, the reinforcing layer, and the inner layer are vulcanized and integrated.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] The heat-insulating hose of Patent Document 1 described above is formed into a desired shape after covering the inner layer with a reinforcing layer and a foaming layer. Then, by performing vulcanization, the foaming layer, the reinforcing layer, and the inner layer are integrated.

[0006] However, it is difficult to simultaneously satisfy the manufacturing conditions of rubber vulcanization molding and foaming molding. For example, if foaming molding of rubber is prioritized, vulcanization molding becomes insufficient and the strength becomes insufficient. Conversely, if vulcanization molding is prioritized, it is conceivable that the foaming agent does not foam sufficiently, or that as foaming progresses, the foaming gas escapes from the foaming layer and becomes low-foamed. Therefore, it is difficult to stably manufacture the heat-insulating hose.

[0007] In view of the above, this disclosure relates to a fluid transport tube with excellent thermal insulation and manufacturing stability. and the manufacturing method thereof The purpose is to provide.

[0008] To achieve the above objective, a fluid transport tube according to one aspect of this disclosure is mounted on an electric vehicle that obtains all or part of its driving force from an electric motor, and is constructed by laminating multiple layers. Furthermore, the transport of hot water or coolant used as a heat source for heating in the air conditioning system of an electric vehicle, or coolant or hot water for the cooling circuit of at least one of the electric motor and battery of an electric vehicle. In fluid transport tubes, The outer layer of the multi-layered structure is composed of thermoplastic elastomer foam. The inner layer of the multiple layers is composed of a thermoplastic elastomer or thermoplastic resin. The outer and inner layers are tightly bonded around the entire circumference. The foaming ratio of thermoplastic elastomer foam is More than 3 times It is 5.5 times or less.

[0009] This method reduces the thermal conductivity of the outer layer and minimizes variations in thermal conductivity between fluid transport tubes during manufacturing. Therefore, it is possible to improve the thermal insulation and manufacturing stability of fluid transport tubes.

[0010] Furthermore, a fluid transport tube according to one aspect of this disclosure is mounted on an electric vehicle that obtains all or part of its driving force from an electric motor, and is constructed by laminating multiple layers. Furthermore, the transport of hot water or coolant used as a heat source for heating the air conditioning system of the electric vehicle, or coolant or hot water for the cooling circuit of at least one of the electric motor and battery of the electric vehicle. In fluid transport tubes, The outer layer of the multi-layered structure is composed of thermoplastic elastomer foam. The inner layer of the multiple layers is composed of a thermoplastic elastomer or thermoplastic resin. Between the outer layer and the inner layer, a reinforcing layer is provided that adheres tightly to both the outer and inner layers around their entire circumference. The foaming ratio of thermoplastic elastomer foam is More than 3 times It is 5.5 times or less.

[0011] This method reduces the thermal conductivity of the outer layer and minimizes variations in thermal conductivity between fluid transport tubes during manufacturing. Therefore, it is possible to improve the thermal insulation and manufacturing stability of fluid transport tubes. [Brief explanation of the drawing]

[0012] [Figure 1] This is a cross-sectional view of a fluid transport tube according to the first embodiment. [Figure 2] This is an explanatory diagram illustrating a method for manufacturing fluid transport tubes. [Figure 3] This is a characteristic diagram showing the relationship between the foaming ratio and thermal conductivity of olefin-based foamed tubes. [Figure 4] This is a characteristic diagram showing the relationship between the foaming ratio and the variation in thermal conductivity of olefin-based foamed tubes. [Figure 5] This is a characteristic diagram showing the relationship between the foaming ratio and thermal conductivity of styrene foam tubes. [Figure 6] This is a characteristic diagram showing the relationship between the foaming ratio and the variation in thermal conductivity of styrene foam tubes. [Figure 7] This is a micrograph showing a cross-section of the outer layer in the first embodiment. [Figure 8] This is a cross-sectional view of a fluid transport tube according to the second embodiment. [Figure 9] This is a cross-sectional view of a fluid transport tube according to the third embodiment. [Modes for carrying out the invention]

[0013] The following describes multiple embodiments for implementing the present disclosure while referring to the drawings. In each embodiment, the same reference numerals may be assigned to corresponding parts described in the preceding embodiments, and redundant descriptions may be omitted. When only a part of the configuration is described in each embodiment, other embodiments described previously can be applied to other parts of the configuration. Not only combinations of parts that are explicitly stated to be combinable in each embodiment, but also partial combinations of embodiments are possible as long as there is no problem with the combination, even if not explicitly stated.

[0014] (First Embodiment) Hereinafter, the first embodiment will be described with reference to the drawings. In this first embodiment, the fluid transport tube is used as a hot water transport tube for transporting hot water that is used as a heat source for heating in the air conditioning system of an electric vehicle. As the hot water, antifreeze (LLC) or water can be used. As the antifreeze, for example, a glycol-based antifreeze can be used.

[0015] As shown in FIG. 1, the fluid transport tube 1 of this embodiment is composed of multiple layers. The multiple layers are laminated in the order of the inner layer 2 and the outer layer 3 from the inside. An internal space through which hot water flows is formed inside the inner layer 2.

[0016] The inner layer 2 is composed of a thermoplastic elastomer or a thermoplastic resin. As the inner layer 2, for example, an olefin-based thermoplastic elastomer, an olefin-based resin, a polyamide-based resin, a polyphenylene sulfide (PPS) resin, or a mixture thereof can be used.

[0017] The outer layer 3 is composed of a thermoplastic elastomer foam. For example, the outer layer 3 can be an olefin-based thermoplastic elastomer foam, a styrene-based thermoplastic elastomer foam, or a urethane-based thermoplastic elastomer foam. More specifically, the outer layer 3 can be a foam obtained by foaming an olefin-based thermoplastic elastomer, a styrene-based thermoplastic elastomer, or a urethane-based thermoplastic elastomer using thermally expandable microcapsules. A skin layer (not shown) may be provided on the outside of the outer layer 3.

[0018] The inner layer 2 and the outer layer 3 are in close contact. In this specification, "close contact" includes not only the state in which the resin portion or elastomer portion of the outer layer 3 is in contact with the inner layer 2, but also the following state: that is, the state in which air bubbles are uniformly formed in the foam of the outer layer 3, and the air bubbles of the outer layer 3 are in partial contact with the inner layer 2.

[0019] Here, thermoplastic elastomer is a polymer material consisting of a mixture of hard segments, which are resin components, and soft segments, which are made of either resin or rubber components. The hardness of the thermoplastic elastomer can be adjusted by changing the mixing ratio of the hard and soft segments.

[0020] For example, when applying the fluid transport tube 1 to piping in the engine compartment of a vehicle, the mixing ratio of the soft segment of the thermoplastic elastomer is increased. This increases the flexibility of the fluid transport tube 1 and improves its handling.

[0021] Furthermore, when the fluid transport tube 1 is applied to piping located under the vehicle floor, the mixing ratio of hard segments of thermoplastic elastomer is increased. This increases the rigidity of the fluid transport tube 1, thereby reducing the number of fixing points to the vehicle body.

[0022] Olefin-based thermoplastic elastomers are mixtures of hard segments such as PP (polypropylene) and PE (polyethylene), and soft segments such as EPDM (ethylene propylene diene rubber) and EPM (ethylene propylene rubber).

[0023] Styrene-based thermoplastic elastomers use PS (polystyrene) as the hard segment and PE (polyethylene), PB (polybutadiene), or polyethylene-polybutylene as the soft segment. For example, SEBS (styrene-ethylene-butylene-styrene block copolymer) can be used as the styrene-based thermoplastic elastomer.

[0024] The fluid transport tube 1 of this embodiment is formed by co-extrusion molding, in which the material of the inner layer 2 (hereinafter referred to as the inner layer material) and the material of the outer layer 3 (hereinafter referred to as the outer layer material) are simultaneously extruded. Specifically, the fluid transport tube 1, which is a laminate of the inner layer 2 and the outer layer 3, is formed by co-extruding the inner layer material and the outer layer material through a die provided at the tip of a co-extruder.

[0025] This manufacturing method allows for the simultaneous molding of the inner layer 2 and the outer layer 3, thereby improving the adhesive strength between the inner layer 2 and the outer layer 3. Furthermore, it reduces the manufacturing time of the fluid transport tube 1.

[0026] The fluid transport tube 1 of this embodiment may be formed by a method other than co-extrusion. For example, it may be formed by single-layer extrusion molding in a batch process or a continuous process as follows.

[0027] In single-layer extrusion molding in a batch process, first, the inner layer material is fed into the extruder hopper, and the inner layer 2 is extruded individually into a tube shape to form the inner layer tube. Next, the outer layer material is fed into the hopper, and the outer layer 3 is coated onto the inner layer tube while it is being pulled back. This forms a fluid transport tube 1, which is a laminate of the inner layer 2 and the outer layer 3.

[0028] According to this manufacturing method, the inner layer 2 and outer layer 3 can be manufactured under arbitrary temperature and flow rate conditions, making it easy to adjust the optimal manufacturing conditions for the dimensions and degree of foaming of the fluid transport tube 1. Furthermore, since the inner layer 2 and outer layer 3 are manufactured sequentially using a single extruder, there is no need to increase the number of extruders, and manufacturing can be carried out on a minimum scale.

[0029] Furthermore, in the continuous single-layer extrusion process, two extruders are prepared, and the fluid transport tube 1 is manufactured in a continuous process. Specifically, as shown in Figure 2, first, the inner layer material is put into the hopper (not shown) of the first extruder 51, extruded by the first cylinder 52 to form the inner layer 2, and then its dimensions are stabilized by passing it through the first water tank. Subsequently, the outer layer material is applied to the inner layer 2 by the second cylinder 55 of the second extruder 54, and then the inner layer 2 and outer layer 3 are cooled again in the second water tank 56. This forms the fluid transport tube 1, which is a laminate of the inner layer 2 and the outer layer 3.

[0030] This manufacturing method uses two extruders, eliminating the need to change the extruded material during production compared to a batch process, thus enabling faster production. Furthermore, compared to co-extrusion molding, where the inner layer 2 is cooled via the outer layer 3, both the inner layer 2 and the outer layer 3 can be cooled in a shorter time.

[0031] Here, the inventors investigated the foaming ratio of the outer layer 3 of the fluid transport tube 1. First, they investigated the foaming ratio of the outer layer 3 when an olefin-based thermoplastic elastomer foam was used as the outer layer 3.

[0032] First, the inventors extruded several types of olefin-based foamed tubes with different foaming ratios and measured the thermal conductivity of each of the resulting olefin-based foamed tubes. Specifically, six types of mixtures were prepared by mixing LE-3170N, manufactured by Riken Technos Co., Ltd., as an olefin-based thermoplastic elastomer, with P501E1, manufactured by Sekisui Chemical Co., Ltd., in amounts of 3, 5, 8, 10, 15, and 25 parts by weight, respectively, as a thermally expandable microcapsule.

[0033] These six types of mixtures were each extruded using a general-purpose resin extruder manufactured by IKG Corporation to produce olefin-based foamed tubes with an inner diameter of φ16 and an outer diameter of φ20. The extrusion molding conditions were: cylinder and die temperature of the general-purpose resin extruder: 170~220°C, extrusion flow rate: 0.01~0.04 kg / s. When the specific gravity of the produced olefin-based foamed tubes was measured, the expansion ratio was found to be 1.4~5.7 times.

[0034] Next, the thermal conductivity of the olefin-based foam tube was measured. First, the olefin-based foam tube was covered with a φ17 aluminum pipe, and a heat flow sensor (model D0001TC) manufactured by Denso Corporation and polyimide tape were attached to it. Then, 80°C hot water was circulated through the aluminum pipe at a flow rate of 5 L / min using a chiller manufactured by Apiste Co., Ltd., and the thermal conductivity was calculated by measuring the heat flow (unit: W) through the olefin-based foam tube. The results are shown in Figure 3.

[0035] The horizontal axis of the graph in Figure 3 shows the foaming ratio of the olefin-based foamed tube. The vertical axis of the graph in Figure 3 shows the thermal conductivity index. The thermal conductivity index is the thermal conductivity expressed as an index, with the value at which the tube does not contain foaming agent, i.e., when the foaming ratio is 1, set to 1.

[0036] Furthermore, when the calculated thermal conductivity values ​​for the olefin-based foamed tubes described above were organized by foaming ratio, multiple data points showing different thermal conductivity values ​​exist for each foaming ratio. In other words, there is variation in thermal conductivity with respect to foaming ratio. The thermal conductivity on the vertical axis of the graph in Figure 3 shows the average value of multiple calculated values.

[0037] As is clear from Figure 3, when the foaming ratio of olefin-based foamed tubes is between 1 and 2 times, the thermal conductivity decreases rapidly as the foaming ratio increases. When the foaming ratio of olefin-based foamed tubes exceeds 2 times, the degree of decrease in thermal conductivity when the foaming ratio is increased becomes smaller. Therefore, by setting the foaming ratio of olefin-based foamed tubes to 2 times or more, low thermal conductivity, i.e., high thermal insulation performance can be ensured.

[0038] Next, the variation in thermal conductivity with respect to the foaming ratio was calculated for the olefin-based foamed tubes described above. The results are shown in Figure 4.

[0039] The horizontal axis of the graph in Figure 4 shows the foaming ratio of the olefin-based foamed tube. The vertical axis of the graph in Figure 4 shows the thermal conductivity variation index. The thermal conductivity variation index is the variation range expressed as an index, with the variation range of thermal conductivity in the state where the tube does not contain a foaming agent, i.e., when the foaming ratio is 1 (hereinafter also referred to as the initial state), set to 1. The variation range of thermal conductivity is the difference between the maximum and minimum values ​​of thermal conductivity. For example, if the variation range of thermal conductivity at a certain foaming ratio is half the variation range of thermal conductivity in the initial state, the thermal conductivity variation index is 0.5.

[0040] As is clear from Figure 4, the variation in thermal conductivity decreases as the foaming ratio of the olefin-based foamed tube increases. This is thought to be due to the following reasons.

[0041] In other words, thermoplastic elastomers composed of multiple components with different thermal conductivity exhibit a large variation in thermal conductivity due to the heterogeneity of the materials. As the foaming ratio increases, the components of the thermoplastic elastomer are replaced by hydrocarbon gases encapsulated in thermally expandable microcapsules, hydrocarbon gases released when the thermally expandable microcapsules rupture during manufacturing, air resulting from manufacturing defects, or a mixture of hydrocarbon gases and air. Since hydrocarbon gases and such mixtures have a small variation in thermal conductivity, it is thought that the variation in thermal conductivity of the foamed tube decreases as the foaming ratio increases.

[0042] Furthermore, when the foaming ratio is small, in addition to variations in thermal conductivity due to the heterogeneity of the thermoplastic elastomer material, uneven mixing of thermally expandable microcapsules is likely to occur. When thermally expandable microcapsules are foamed in this state, an uneven distribution of bubbles is likely to occur within the foaming tube, making it difficult to reduce the range of variation in thermal conductivity.

[0043] Furthermore, as is clear from Figure 4, when the foaming ratio of olefin-based foamed tubes is between 1 and 3 times, the variation in thermal conductivity decreases rapidly as the foaming ratio increases. When the foaming ratio of olefin-based foamed tubes exceeds 3 times, the variation in thermal conductivity hardly changes even when the foaming ratio is increased. Therefore, by increasing the foaming ratio of olefin-based foamed tubes to more than 3 times, it is possible to ensure a state where the variation in thermal conductivity is small, thereby ensuring the manufacturing stability of the foamed tubes.

[0044] Next, the crack resistance of the olefin-based foam tubes during bending was evaluated. Specifically, the olefin-based foam tubes were manually guided to a R120 jig at a 90° angle, and the presence or absence of cracks and fissures in the foam tubes was visually checked. As a result, no cracks occurred at foaming ratios of 5.5 times or less, but cracks occurred when the foaming ratio was increased to 5.7 times. Therefore, cracking can be suppressed by keeping the foaming ratio of the olefin-based foam tubes to 5.5 times or less.

[0045] Next, the present inventors investigated the foaming ratio of the outer layer 3 when a styrene-based thermoplastic elastomer foam is used as the outer layer 3.

[0046] First, the inventors extruded several types of styrene-based foamed tubes with different foaming ratios and measured the thermal conductivity of each of the resulting styrene-based foamed tubes. Specifically, styrene-based foamed tubes were manufactured under the same conditions as the above-mentioned olefin-based foamed tubes, except that T-A80NT, manufactured by Aron Kasei Co., Ltd., was used as a styrene-based thermoplastic elastomer instead of LE-3170N. When the manufactured styrene-based foamed tubes were measured with a hydrometer, the foaming ratios ranged from 1.2 to 4.8 times.

[0047] Next, the thermal conductivity of the styrene foam tube was measured. The measurement conditions were the same as those used for measuring the thermal conductivity of the olefin foam tube. The results are shown in Figure 5.

[0048] As is clear from Figure 5, when the foaming ratio of styrene foam tubes is between 1 and 2 times, the thermal conductivity decreases rapidly as the foaming ratio increases. When the foaming ratio of styrene foam tubes exceeds 2 times, the degree of decrease in thermal conductivity when the foaming ratio is increased becomes smaller. Therefore, by setting the foaming ratio of styrene foam tubes to 2 times or more, low thermal conductivity, i.e., high thermal insulation, can be ensured.

[0049] Next, the variation in thermal conductivity with respect to the foaming ratio was calculated for the styrene foam tubes described above. The results are shown in Figure 6.

[0050] As is clear from Figure 6, the variation in thermal conductivity with respect to the foaming ratio showed a similar trend in styrene-based foamed tubes as in olefin-based foamed tubes. Therefore, by increasing the foaming ratio of styrene-based foamed tubes to more than 3 times, it is possible to ensure a state where the variation in thermal conductivity is small, thereby ensuring the manufacturing stability of the foamed tubes.

[0051] Next, the crack resistance of the styrene foam tubes during bending was evaluated. The evaluation conditions were the same as those used for evaluating the crack resistance of the olefin foam tubes during bending. As a result, no cracks occurred at foaming ratios of 4.8 times or less. Therefore, cracking can be suppressed by limiting the foaming ratio of the styrene foam tubes to 4.8 times or less.

[0052] The present disclosure will be described in more detail below with reference to examples. However, the present disclosure is not limited to the following examples.

[0053] (Example 1) As the inner layer material, GA-1190N, an olefin-based thermoplastic elastomer manufactured by Riken Technos Corporation, was prepared. As the outer layer material, a mixture was prepared by mixing LE-3170N, an olefin-based thermoplastic elastomer manufactured by Riken Technos Corporation, with 5 parts by weight of P501E1, a thermally expandable microcapsule manufactured by Sekisui Chemical Co., Ltd.

[0054] Next, the inner and outer layer materials were co-extruded using a co-extruder manufactured by IKG Corporation to produce a fluid transport tube 1 with an inner diameter of φ16 and an outer diameter of φ24. The extrusion molding conditions were set so that the inner layer 2 had an inner diameter of φ16 and an outer diameter of φ20, and the outer layer 3 had an inner diameter of φ20 and an outer diameter of φ24. The cylinder and die temperatures of the co-extruder were set to 170-220°C, and the extrusion flow rate was set to 0.01-0.04 kg / second. When the outer layer 3 of the manufactured fluid transport tube 1 was measured with a hydrometer, the expansion ratio was found to be 2.1 times.

[0055] (Example 2) As the inner layer material, the same material as in Example 1 was prepared. As the outer layer material, a mixture was prepared by mixing LE-3170N, an olefin-based thermoplastic elastomer manufactured by Riken Technos, with 10 parts by weight of P501E1, a thermally expandable microcapsule manufactured by Sekisui Chemical Co., Ltd.

[0056] Next, the inner and outer layer materials were co-extruded under the same conditions as in Example 1 to produce a fluid transport tube 1. When the outer layer 3 of the produced fluid transport tube 1 was measured with a hydrometer, the expansion ratio was found to be 3.2 times.

[0057] (Example 3) As the inner layer material, the same material as in Example 1 was prepared. As the outer layer material, a mixture was prepared by mixing 8 parts by weight of T-A80NT, a styrene-based thermoplastic elastomer manufactured by Aron Kasei Co., Ltd., with P501E1, a thermally expandable microcapsule manufactured by Sekisui Chemical Co., Ltd.

[0058] Next, the inner and outer layer materials were co-extruded under the same conditions as in Example 1 to produce a fluid transport tube 1. When the outer layer 3 of the produced fluid transport tube 1 was measured with a hydrometer, the foaming ratio was found to be 2 times.

[0059] (Example 4) As the inner layer material, the same material as in Example 1 was prepared. As the outer layer material, a mixture was prepared by mixing 15 parts by weight of T-A80NT, a styrene-based thermoplastic elastomer manufactured by Aron Kasei Co., Ltd., with P501E1, a thermally expandable microcapsule manufactured by Sekisui Chemical Co., Ltd.

[0060] Next, the inner and outer layer materials were co-extruded under the same conditions as in Example 1 to produce a fluid transport tube 1. When the outer layer 3 of the produced fluid transport tube 1 was measured with a hydrometer, the foaming ratio was found to be 3 times.

[0061] (Comparative example) As a comparative example, a heater hose was prepared in which both the inner and outer layers were made of ethylene propylene diene (EPDM) rubber. The heater hose had an inner diameter of φ16 and an outer diameter of φ24. In the heater hose, the inner layer had an inner diameter of φ16 and an outer diameter of φ20, and the outer layer had an inner diameter of φ20 and an outer diameter of φ24. A reinforcing layer made of braided polyamide reinforcing yarn was present between the inner and outer layers.

[0062] (Flexibility test) The fluid transport tubes of Examples 1-4 (hereinafter also simply referred to as "Tube 1") and the heater hose of the Comparative Example were each cut to 300 mm. Holding both ends of the cut tube or hose, they were manually guided to a R120 jig at a 90° angle. In this state, they were visually inspected for any abnormalities such as kinks (i.e., bends), cracks, or breaks.

[0063] (Heat dissipation measurement) Tube 1 from Examples 1-4 and the heater hose from the Comparative Example were each covered with aluminum piping with an outer diameter of φ17, and a heat flow sensor (model D0001TC) manufactured by Denso Corporation and polyimide tape were attached on top of them. Then, 80°C hot water was circulated through the aluminum piping at a flow rate of 5 L / min using a chiller manufactured by Apiste Corporation, and the heat flow (unit: W) was measured to calculate the amount of heat dissipation (unit: W / m).

[0064] (Pressure resistance test) Tube 1 from Examples 1-4 and the heater hose from the Comparative Example were each inserted into an aluminum pipe with an outer diameter of φ17 and fastened with a worm drive hose clip (model OX-SS) manufactured by Orbit. Then, a pressure of 108 kPa was applied using a testing machine. Under these conditions, the pipes were visually inspected for any abnormalities such as cracks or breaks.

[0065] (High-temperature storage test) In each of the tubes 1 of Examples 1-4 and the heater hose of the comparative example, aluminum pipes with both ends sealed were inserted and then fastened with Orbit worm drive hose clips (model OX-SS). Next, a mixture of Toyota Motor Corporation's Super Long Life Coolant (model 08889-01005) and purified water diluted in a 1:1 ratio was sealed into tube 1 and the heater hose, and the machine was placed in a 100°C high-temperature test chamber and left for 168 hours. After that, tube 1 and the heater hose were removed and visually inspected for any abnormalities such as cracks or breaks. (evaluation) The results of the above tests and measurements are shown in Table 1.

[0066] [Table 1] As shown in Table 1, no abnormalities such as cracks or breaks were observed in the flexibility test, pressure resistance test, or high-temperature storage test for Tube 1 in Examples 1-4 and the heater hose in the comparative example. In the heat dissipation measurement, the heat dissipation of Tube 1 in Examples 1-4 was smaller than that of the heater hose in the comparative example. This clearly shows that the thermal insulation performance of Tube 1 in Examples 1-4 is higher than that of the heater hose in the comparative example.

[0067] (Cross-sectional observation) Next, a cross-sectional observation was performed on the outer layer 3 of the fluid transport tube 1. As with Example 1 above, the outer layer material was prepared by mixing LE-3170N, an olefin-based thermoplastic elastomer manufactured by Riken Technos Co., Ltd., with P501E1, a thermally expandable microcapsule manufactured by Sekisui Chemical Co., Ltd. The foaming ratio of the outer layer 3 when the outer layer material was extruded was 3.8 times. At this time, the particle size of the thermally expandable microcapsules was 22-42 μm (average 28 μm) before foaming and 65-132 μm (average 92 μm) after foaming.

[0068] The created outer layer 3 was cut, and the cut surface was observed under a microscope. The micrograph is shown in Figure 7. As shown in Figure 7, it was confirmed that bubbles 30, caused by thermally expandable microcapsules, were uniformly distributed in the outer layer 3.

[0069] As described above, in the fluid transport tube 1 of this embodiment, the foaming ratio of the thermoplastic elastomer foam of the outer layer 3 is set to 2 times or more and 5.5 times or less. This reduces the thermal conductivity of the outer layer 3 and also reduces variations in the thermal conductivity of each fluid transport tube 1 during manufacturing. Therefore, it is possible to improve the heat insulation and manufacturing stability of the fluid transport tube 1.

[0070] Furthermore, by setting the foaming ratio of the thermoplastic elastomer foam of the outer layer 3 to more than 3 times and 5.5 times or less, the thermal conductivity of the outer layer 3 can be reduced, and variations in the thermal conductivity of each fluid transport tube 1 during manufacturing can be more reliably reduced. Therefore, it becomes possible to more reliably improve the thermal insulation and manufacturing stability of the fluid transport tube 1.

[0071] Furthermore, in this embodiment, an olefin-based thermoplastic elastomer foam or a styrene-based thermoplastic elastomer is used as the outer layer 3. An olefin-based thermoplastic elastomer or an olefin-based thermoplastic resin is used as the inner layer 2.

[0072] Olefin-based thermoplastic elastomers, olefin-based resins, and styrene-based thermoplastic elastomers exhibit excellent heat resistance, low-temperature stability, and weather resistance. Therefore, by using olefin-based thermoplastic elastomers, olefin-based resins, and styrene-based thermoplastic elastomers as the inner layer 2 and outer layer 3, the fluid transport tube 1 can be suitably mounted on a vehicle. Furthermore, because olefin-based thermoplastic elastomers, olefin-based resins, and styrene-based thermoplastic elastomers are inexpensive materials, manufacturing costs can be reduced.

[0073] In this embodiment, the inner layer 2 is made of a different resin from the thermoplastic elastomer contained in the outer layer 3. As a result, since the resin is harder than the thermoplastic elastomer, heat resistance and pressure resistance to the fluid flowing inside can be ensured even when the inner layer 2 is made thinner. Furthermore, by making the inner layer 2 thinner, the outer layer 3 can be made thicker. Therefore, even with a fluid transport tube 1 of the same inner and outer diameter, it is possible to improve the heat insulation performance.

[0074] Furthermore, in the fluid transport tube 1 of this embodiment, the outer layer 3 contains thermally expandable microcapsules. Since the thermally expandable microcapsules have a high expansion ratio and stable expansion properties, the outer layer 3 can be reliably foamed to the desired foaming ratio.

[0075] (Second Embodiment) Next, a second embodiment of this disclosure will be described with reference to the drawings. This embodiment differs from the first embodiment in the configuration between the inner layer 2 and the outer layer 3.

[0076] As shown in Figure 8, the fluid transport tube 1 of this embodiment is made of a rigid resin or elastomer. In the fluid transport tube 1 of this embodiment, a reinforcing layer 4 is provided between the outer layer 3 and the inner layer 2. The reinforcing layer 4 is in close contact with both the outer layer 3 and the inner layer 2.

[0077] The outer layer 3 and inner layer 2 can be made of the same materials as in the first embodiment. For the reinforcing layer 4, for example, a polyamide resin, a polyphenylene sulfide resin or a mixture thereof, or an adhesive such as maleic acid-modified polypropylene can be used.

[0078] An adhesive such as maleic acid-modified polypropylene may be provided between the inner layer 2 and the reinforcing layer 4, and between the outer layer 3 and the reinforcing layer 4 (hereinafter referred to as the interlayer). This improves the adhesive strength between the layers.

[0079] The other components of the fluid transport tube 1 are the same as in the first embodiment. Therefore, the same effects as in the first embodiment can be obtained with the fluid transport tube 1 of this embodiment. In other words, the fluid transport tube 1 of this embodiment makes it possible to improve heat insulation and manufacturing stability.

[0080] Furthermore, in the fluid transport tube 1 of this embodiment, a reinforcing layer 4 is provided between the outer layer 3 and the inner layer 2. By providing the reinforcing layer 4, the heat resistance and pressure resistance of the fluid transport tube 1 can be improved, and thermal deformation can be suppressed.

[0081] (Third embodiment) Next, a third embodiment of this disclosure will be described with reference to the drawings. This embodiment differs from the second embodiment in the configuration of the inner layer 2 and the reinforcing layer 4.

[0082] As shown in Figure 9, the fluid transport tube 1 of this embodiment is made of a highly flexible resin or elastomer. Specifically, the inner layer 2 is made of a highly flexible thermoplastic elastomer. For example, an olefin-based thermoplastic elastomer can be used as the inner layer 2. The same material as in the first embodiment can be used as the outer layer 3.

[0083] As the reinforcing layer 4, known reinforcing layers can be used, which are made by knitting reinforcing threads in a spiral or braided shape. Examples of reinforcing threads that can be used include polyester, polyamide (nylon), polyvinyl alcohol (vinylon), rayon, aramid, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), etc. As reinforcing threads, threads that have been bonded may also be used. Examples of bonded treatments that can be used include resorcinol-formaldehyde-rubber latex (RFL) treatment.

[0084] The other components of the fluid transport tube 1 are the same as in the first embodiment. Therefore, the same effects as in the first embodiment can be obtained with the fluid transport tube 1 of this embodiment. In other words, the fluid transport tube 1 of this embodiment makes it possible to improve heat insulation and manufacturing stability.

[0085] Furthermore, in the fluid transport tube 1 of this embodiment, a highly flexible thermoplastic elastomer is used as the inner layer 2, and a reinforcing layer 4 is provided between the outer layer 3 and the inner layer 2. This allows for improved flexibility through the inner layer 2, while ensuring heat resistance and pressure resistance through the provision of the reinforcing layer 4. Therefore, it is possible to achieve both high flexibility and high heat resistance / high pressure resistance in the fluid transport tube 1.

[0086] This disclosure is not limited to the embodiments described above, and can be modified in various ways without departing from the spirit of this disclosure, as follows.

[0087] (1) In the embodiments described above, examples were given in which the fluid transport tube according to the disclosure is applied to a fluid transport tube 1 having two layers, an inner layer 2 and an outer layer 3, or to a fluid transport tube 1 having three layers, an inner layer 2, an outer layer 3 and a reinforcing layer 4. However, the invention is not limited to these embodiments. The fluid transport tube according to the disclosure may also be applied to a fluid transport tube having four or more layers.

[0088] (2) In the embodiments described above, the fluid transport tube 1 is formed by extrusion molding, but the invention is not limited to this embodiment. For example, the fluid transport tube 1 may be formed by injection molding.

[0089] In this case, first, the inner layer material is filled into the inner layer mold in the injection molding machine, cooled and solidified in the inner layer mold, then the mold is opened and the inner layer 2 is removed. After that, the inner layer 2 is inserted into the core of the outer layer mold. Then, the outer layer material containing a foaming agent (i.e., thermally expandable microcapsules) is put into a hopper and filled into the outer layer mold, covering the inserted inner layer 2 with the outer layer 3. When molding the outer layer 3, a short-shot method may be used in which less outer layer material than the cavity volume of the outer layer mold is filled, and the outer layer material is filled into the entire outer layer mold by the force of foaming (i.e., the force of expanding bubbles).

[0090] (3) In the embodiments described above, an example was given in which the fluid transport tube according to the Disclosure was applied to a hot water transport tube in an electric vehicle, but the application of the fluid transport tube is not limited to this.

[0091] For example, the fluid transport tubes may be applied to the coolant and hot water transport tubes of hybrid vehicles that obtain driving force from an electric motor and an internal combustion engine (i.e., an engine), and also to plug-in hybrid vehicles that can charge their batteries with power supplied from an external power source when the vehicle is stopped. The fluid transport tubes may also be applied to the coolant and hot water transport tubes installed in the cooling circuits of the motors and batteries of electric vehicles.

[0092] (others) The features of the fluid transport tubes disclosed herein are as follows: (Item 1) A fluid transport tube having multiple layers (2, 3) stacked together, Of the aforementioned multiple layers, the outer layer (3) is made of thermoplastic elastomer foam. Of the aforementioned multiple layers, the inner layer (2) is composed of a thermoplastic elastomer or thermoplastic resin. The outer layer and the inner layer are in close contact. A fluid transport tube wherein the foaming ratio of the thermoplastic elastomer foam is 2 times or more and 5.5 times or less. (Item 2) A fluid transport tube having multiple layers (2 to 4) stacked together, Of the aforementioned multiple layers, the outer layer (3) is made of thermoplastic elastomer foam. Of the aforementioned multiple layers, the inner layer (2) is composed of a thermoplastic elastomer or thermoplastic resin. Between the outer layer and the inner layer, a reinforcing layer (4) is provided that is in close contact with the outer layer and the inner layer, respectively. A fluid transport tube wherein the foaming ratio of the thermoplastic elastomer foam is 2 times or more and 5.5 times or less. (Item 3) The fluid transport tube according to item 1 or 2, wherein the foaming ratio of the thermoplastic elastomer foam is greater than 3 times and 5.5 times or less. (Item 4) The outer layer is composed of an olefin-based thermoplastic elastomer foam. The fluid transport tube according to any one of items 1 to 3, wherein the inner layer is composed of an olefin-based thermoplastic elastomer or an olefin-based thermoplastic resin. (Item 5) The outer layer is composed of a styrene-based thermoplastic elastomer foam. The inner layer is composed of an olefin-based thermoplastic elastomer or an olefin-based thermoplastic resin. The fluid transport tube according to item 1 or 2, wherein the foaming ratio of the styrene-based thermoplastic elastomer foam is 2 times or more and 4.8 times or less. (Item 6) The fluid transport tube according to any one of items 1 to 5, wherein the inner layer is composed of a resin different from the thermoplastic elastomer contained in the outer layer. (Item 7) The outer layer is a fluid transport tube according to any one of items 1 to 6, comprising thermally expandable microcapsules.

[0093] This disclosure is described in accordance with the embodiments, but it is understood that this disclosure is not limited to such embodiments or structures. This disclosure also includes various modifications and variations within the equivalence. In addition, various combinations and forms, as well as other combinations and forms that include only one, more, or fewer of those elements, fall within the scope and concept of this disclosure.

Claims

1. A fluid transport tube mounted on an electric vehicle that obtains all or part of its driving force from an electric motor, having multiple layers (2, 3) stacked on top of each other, for transporting hot water or coolant used as a heat source for heating the air conditioning system of the electric vehicle, or for transporting coolant or hot water for the cooling circuit of at least one of the electric motor and battery of the electric vehicle, Of the aforementioned multiple layers, the outer layer (3) is made of thermoplastic elastomer foam. Of the aforementioned multiple layers, the inner layer (2) is composed of a thermoplastic elastomer or thermoplastic resin. The outer layer and the inner layer are in close contact around the entire circumference. A fluid transport tube wherein the foaming ratio of the thermoplastic elastomer foam is greater than 3 and less than or equal to 5.5 times.

2. A fluid transport tube mounted on an electric vehicle that obtains all or part of its driving force from an electric motor, having multiple layers (2 to 4) stacked on top of each other, which transports hot water or coolant used as a heat source for heating the air conditioning system of the electric vehicle, or coolant or hot water for the cooling circuit of at least one of the electric motor and battery of the electric vehicle, Of the aforementioned multiple layers, the outer layer (3) is made of thermoplastic elastomer foam. Of the aforementioned multiple layers, the inner layer (2) is composed of a thermoplastic elastomer or thermoplastic resin. Between the outer layer and the inner layer, a reinforcing layer (4) is provided that adheres tightly to both the outer layer and the inner layer around their entire circumference. A fluid transport tube wherein the foaming ratio of the thermoplastic elastomer foam is greater than 3 and less than or equal to 5.5 times.

3. The fluid transport tube according to claim 2, wherein the reinforcing layer is a polyamide resin, a polyphenylene sulfide resin, a mixture thereof, or an adhesive.

4. The fluid transport tube according to claim 2, wherein the reinforcing layer is formed by braiding together reinforcing threads.

5. The outer layer is composed of an olefin-based thermoplastic elastomer foam. The fluid transport tube according to claim 1 or 2, wherein the inner layer is composed of an olefin-based thermoplastic elastomer or an olefin-based thermoplastic resin.

6. The outer layer is composed of a styrene-based thermoplastic elastomer foam. The inner layer is composed of an olefin-based thermoplastic elastomer or an olefin-based thermoplastic resin. The fluid transport tube according to claim 1 or 2, wherein the foaming ratio of the styrene-based thermoplastic elastomer foam is greater than 3 times and 4.8 times or less.

7. The fluid transport tube according to claim 1 or 2, wherein the inner layer is composed of a resin different from the thermoplastic elastomer contained in the outer layer.

8. The fluid transport tube according to claim 1 or 2, wherein the outer layer contains thermally expandable microcapsules.

9. A method for manufacturing a fluid transport tube according to claim 1 or 2, A method for manufacturing a fluid transport tube, comprising a co-extrusion molding step of simultaneously extruding the inner layer material and the outer layer material.

10. A method for manufacturing a fluid transport tube according to claim 1 or 2, The process involves extruding the inner layer into a tubular shape and forming an inner layer tube. A method for manufacturing a fluid transport tube, comprising the step of covering the outer layer while taking in the inner layer tube.

11. A method for manufacturing a fluid transport tube according to claim 1 or 2, The process involves extruding the inner layer using a first extruder (51) to form it, and then cooling the inner layer in a first water tank. A method for manufacturing a fluid transport tube, comprising the steps of: coating the inner layer with the outer layer material using a second extruder (54); and then cooling the inner layer and the outer layer in a second water tank (56).

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