Electrofusion joints and their power supply devices

Abstract

To provide an electrofusion joint and a power supply device for an electrofusion joint that can be easily used in a wide range of construction environments and have excellent sealing and durability after installation. [Solution] This electrofusion joint consists of a thermoplastic resin pipe joint 2, heating wires 3a, 3b, 3c, 3d, 3e, and a secondary coil 4. Heating wire 3a is embedded on the inner circumferential surface of the socket portion 9a of the pipe joint 2, heating wire 3b is embedded on the inner circumferential surface of the socket portion 9b of the pipe joint 2, and a secondary coil 4 is provided on the outer circumferential surface of the pipe joint 2. The secondary coil 4 has a winding structure of a laminated coil or thin film coil, and the direction of the magnetic field when current flows is approximately perpendicular to the axial direction of the pipe joint 2. Heating wires 3a, 3b, 3c, 3d, and 3e are formed from a part of the secondary coil 4.

Description

[Technical Field]

[0001] The present invention relates to an electrofusion joint used for connecting plastic pipes, and more particularly to an electrofusion joint and power supply device that provides non-contact power to a heating element fitted into a groove in the inner circumference of a thermoplastic resin pipe. [Background technology]

[0002] Electrofusion joints are typically manufactured using injection molding and have a heating element embedded in the inner circumference of the joint body, which is made of thermoplastic resin such as polyethylene or polybutene. They are also called EF (Electro Fusion) joints or EF sockets. Electrofusion joints have a structure in which a spiral groove is provided along the inner surface of the pipe material, and the heating element is fitted into the groove. Electrofusion joints work by inserting a pipe into a joint with embedded heating wires, then applying power from a controller to heat the heating wires, which in turn heats and melts the resin of the joint and pipe to create a bond. This results in a structurally integrated joint between the pipe and the joint, exhibiting joint strength equal to or greater than that of the pipe body itself, thus enabling the construction of highly reliable pipelines.

[0003] However, conventional electrofusion joints have the problem of being time-consuming because the controller connectors must be connected separately to the two terminals. Therefore, an electrofusion joint is known in which the first terminal and the second terminal on the joint side for supplying power to the heating wire are housed together in a single connector mounting section (see Patent Document 1). According to the electrofusion joint of Patent Document 1, the two terminals of the fusion machine that supply power to the heating wire can also be combined into a single connector, so that the two terminals at both ends of the heating wire and the two terminals of the fusion machine can be connected simultaneously, thereby reducing the effort required for connection.

[0004] Conventional electrofusion joints, including the electrofusion joint disclosed in Patent Document 1, use wired connections for power supply. However, these joints require power supply via wires even in harsh environments such as overhead piping, making installation difficult. This necessitates installers bringing wired equipment close to the installation site, increasing the difficulty and danger of the work. Furthermore, wired connections require openings in the joints to install interfaces for connecting electrical wires, and these interfaces can potentially become a source of leaks within the piping system. Furthermore, because thermoplastic resin pipe fittings are often exposed to high temperatures, humidity, and corrosive environments, conventional thermoplastic resin pipe fittings have the problem that the wired connection terminals are susceptible to external environmental influences, leading to deterioration and damage. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-157053 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In view of these circumstances, the present invention aims to provide an electrofusion joint and a power supply device for an electrofusion joint that can be easily used in a wide range of construction environments and have excellent sealing and durability after construction. [Means for solving the problem]

[0007] To solve the above problems, the electrofusion joint of the present invention is a pipe joint in which a heating wire is embedded in the socket portion of a thermoplastic resin pipe joint, and the pipe joint is equipped with a coil connected to the heating wire. An external coil that provides non-contact power to the coil causes current to flow through the heating wire. That is, the external coil, which is separated from the coil, induces a high-frequency electromotive force in the coil by magnetic resonance non-contact power supply, causing current to flow through the heating wire and generating heat.

[0008] In this way, wireless power supply technology, which is contactless power supply, is applied to pipe fittings, and wired pipe fittings are made wireless, resulting in specifications with superior sealing and durability after installation. In particular, wireless power supply technology can greatly improve the ease of installation and safety of pipe fittings installed in ceilings, walls, and confined spaces. It is also suitable when it is necessary to prevent pipe leaks and maintain sealing within the piping system, and can be used in the fields of building equipment and housing equipment. Furthermore, in piping systems used in harsh environments, wireless power supply pipe fittings eliminate the need for contact points via electrical wires, thus reducing the maintenance burden in industrial machinery and factory piping where durability is required. The reduced risk of failure due to corrosion and wear allows for stable use over long periods.

[0009] Here, the external coil is preferably separated from the coil connected to the heating element by 5 cm or less, and more preferably by 2.5 cm or less. By utilizing electromagnetic resonance, energy transmission can be achieved over long distances of several centimeters.

[0010] In the electrofusion joint of the present invention, it is preferable that the heating element is formed from a part of the coil. Here, "a part of the coil" means that a part of the coil can function as a heating element.

[0011] Furthermore, in the electrofusion joint of the present invention, it is preferable that the coil is provided on the outer circumferential surface of the pipe joint or between the outer circumferential surface and the inner circumferential surface. The outer circumferential surface of the pipe joint includes a portion of the outer circumferential surface, and for example, if the pipe joint is cylindrical, it may be provided in an area of ​​less than half of its circumferential surface. Furthermore, it is preferable that the direction of the magnetic field generated by the coil when current flows is approximately perpendicular to the axial direction of the pipe joint. Alternatively, the coil may have a winding structure of a laminated coil or a thin-film coil.

[0012] In the electrofusion joint of the present invention, a high-frequency current flows through the external coil via an AC-AC converter or a DC-AC converter. A high-frequency current is passed through the external coil, which is several centimeters away from the coil, in order to induce a high-frequency electromotive force in the coil by magnetic resonance non-contact power supply. An AC-AC converter is a circuit that outputs a high-frequency current (AC) from a commercial current (AC) input, and a DC-AC converter is a circuit that outputs a high-frequency current (AC) from a battery (DC) input.

[0013] In an AC-AC converter, it is preferable that the primary coil (external coil) and the first capacitor are connected in parallel, and the secondary coil (coil) and the second capacitor are connected in parallel or in series. There are four possible connection configurations for the primary coil and capacitor, and the secondary coil and capacitor, consisting of LC parallel and LC series configurations (see Figure 13). These combinations allow for the selection of the most appropriate configuration based on output efficiency, stability, and other considerations. However, a direct-type frequency conversion circuit (hereinafter referred to as a direct AC-AC converter) that can directly generate single-phase high-frequency AC from commercial power can be used.

[0014] Here, a direct AC-AC converter is composed of a resonant tank connected to a commercial power supply and a bidirectional switch composed of power devices (see Fig. 14(2)), which can directly generate single-phase high-frequency AC from the commercial power supply, while a conventional IPT (Inductive Power Transfer) system's core element, a high-frequency power conversion inverter, is composed of a rectifier stage, a boost PFC (power factor correction) stage, and a DC / HFAC (DC / high-frequency AC) inverter (see Fig. 14(1)). For example, a direct AC-AC converter of a single-stone type circuit method using one bidirectional switch can be applied (for details, refer to "Tomokazu Mishima et al., 'Demonstration Evaluation of a High-Frequency Induction Heating Applied Three-Phase - Single-Phase Direct AC-AC Converter', The Institute of Electrical Engineers of Japan National Convention, 4-056, 2019"). In the operation of a direct AC-AC converter of a single-stone type circuit method using one bidirectional switch, an LC free oscillation tank is required, so on the primary side, it is necessary to select an LC parallel method in which an external coil and a capacitor are connected in parallel. Note that in other direct AC-AC converters, an LC series method can also be used.

[0015] In the electric fusion joint of the present invention, the second capacitor is preferably disposed between the outer peripheral surface of the pipe joint or between the outer and inner peripheral surfaces. In the electric fusion joint, by connecting the secondary side heating wire in parallel to the coil and further connecting a second capacitor (resonance capacitor) in parallel, the entire electric fusion joint including the secondary side coil can be made to function as the secondary side of a wireless power transfer (WPT) system.

[0016] Next, the power supply device for the electric fusion joint of the present invention will be described. The power supply device for the electric fusion joint of the present invention is a device that performs non-contact power supply to the coil of any of the above electric fusion joints, and includes a power supply unit, an AC-AC converter or a DC-AC converter, a first capacitor, and an external coil. In the power supply device of the electric fusion joint of the present invention, it is preferable that the external coil is provided on a surface covering the outer peripheral surface of the pipe joint. Providing it on a surface covering the outer peripheral surface of the pipe joint means that, for example, when the pipe joint has a cylindrical shape, the external coil also has a curved surface shape. This improves the stability of power supply.

Advantages of the Invention

[0017] According to the electric fusion joint and the power supply device of the electric fusion joint of the present invention, there are effects that it can be easily used in a wide range of construction environments and has excellent sealing performance and durability after construction.

Brief Description of the Drawings

[0018] [Figure 1] Schematic diagram of the non-contact electric fusion joint of Example 1 [Figure 2] External perspective view of the non-contact electric fusion joint of Example 1 [Figure 3] Explanatory drawing 1 of the non-contact electric fusion joint of Example 1 [Figure 4] Explanatory drawing 2 of the non-contact electric fusion joint of Example 1 [Figure 5] Explanatory drawing 3 of the non-contact electric fusion joint of Example 1 [Figure 6] Usage explanatory drawing 1 of the non-contact electric fusion joint of Example 1 [Figure 7] Usage explanatory drawing 2 of the non-contact electric fusion joint of Example 1 [Figure 8] Usage explanatory drawing 3 of the non-contact electric fusion joint of Example 1 [Figure 9] Circuit diagram of the non-contact electric fusion joint of Example 1 [Figure 10] Schematic diagram of the power supply device of Example 2 [Figure 11] Schematic diagram of the primary coil housing part of Example 3 [Figure 12] Configuration diagram of the main circuit of the direct AC-AC converter [Figure 13] Circuit schematic diagram of the combination of the LC parallel method and the LC series method on the primary side and the secondary side [Figure 14]Schematic diagrams of conventional AC-AC converters and direct AC-AC converters. [Modes for carrying out the invention]

[0019] Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. It should be noted that the scope of the present invention is not limited to the following embodiments or illustrated examples, and numerous modifications and variations are possible. [Examples]

[0020] Figure 1 shows a schematic diagram of one embodiment of the non-contact electrofusion joint of the present invention. As shown in Figure 1, the non-contact electrofusion joint 1 consists of a thermoplastic resin pipe joint 2, heating wires (3a to 3e), and a secondary coil 4. The heating wires (3a, 3b) are embedded on the inner circumferential surface of the socket portion (9a, 9b) of the pipe joint 2. The secondary coil 4 is provided on the outer circumferential surface of the pipe joint 2. The direction of the magnetic field when current flows through the secondary coil 4 is approximately perpendicular to the axial direction of the pipe joint 2. The secondary coil 4 has a winding structure of a laminated coil or a thin film coil. The secondary coil 4 is connected to the heating wires (3a to 3e), and in this embodiment, the heating wires (3a to 3e) are formed from a part of the secondary coil 4.

[0021] Figure 2 shows an external perspective view of a non-contact electrofusion joint. As shown in Figure 2, the non-contact electrofusion joint 1 does not have any openings such as terminals on the outer surface of the joint. Due to this structure, the sealing performance of the joint is ensured, and leakage can be prevented. It is particularly suitable for applications where fluid sealing is required. Furthermore, since wireless power transfer eliminates physical connection points, the risk of failure due to interface aging and corrosion is reduced, and the lifespan of the joint is extended.

[0022] A detailed explanation of the non-contact type electrofusion joint 1 will be given with reference to Figures 3 to 5. As shown in Figures 3 and 5, a heating wire 3a is embedded in the socket portion 9a of the pipe joint 2. Although not shown, a recess is provided in the socket portion 9a of the pipe joint 2, and the heating wire 3a is embedded in this recess. Similarly, as shown in Figures 4 and 5, a heating wire 3b is embedded in the socket portion 9b of the pipe joint 2. A recess (not shown) is also provided in the socket portion 9b of the pipe joint 2, and a heating wire 3b is embedded in this recess.

[0023] Next, the handling of the non-contact type electrofusion joint 1 will be explained with reference to Figures 6 to 8. Here, the example of connecting resin pipes (20a, 20b) using the non-contact type electrofusion joint 1 will be explained. As shown in Figure 6, the second capacitor, capacitor 8, is located on the outer surface of the pipe joint 2. First, as shown in Figure 7, one end of the resin pipe 20a is inserted into the socket 9a of the pipe fitting 2, and similarly, one end of the resin pipe 20b is inserted into the socket 9b of the pipe fitting 2. Here, the resin pipe 20a is inserted into the socket 9a and the resin pipe 20b is inserted into the socket 9b, but it is also possible to insert the resin pipe 20b into the socket 9a and the resin pipe 20a into the socket 9b. In this state, the primary coil 7 is positioned at a distance of 5 cm or less from the secondary coil 4, and magnetic resonance non-contact power supply is performed by the primary coil 7. For the sake of explanation, the detailed power supply equipment is not shown here, and only the primary coil 7 is illustrated. By performing magnetic resonance non-contact power supply by the primary coil 7, a high-frequency electromotive force is induced in the secondary coil 4, and current is passed through the heating wires (3a~3e) to generate heat.

[0024] Figure 8 shows a cross-sectional view (a cross-section along the longitudinal direction of the piping) of a state where one end of the resin pipe (20a, 20b) is inserted into the socket portion (9a, 9b) of the pipe joint 2, and the primary coil 7 is brought close to the secondary coil 4. A high-frequency electromotive force is induced in the secondary coil 4, causing current to flow through the heating wires (3a, 3b), generating heat and fusing the outer surface of the resin pipe (20a, 20b) with the inner surface of the pipe joint 2.

[0025] Figure 9 shows an example of a circuit diagram for a non-contact type electrofusion joint. The circuit shown in Figure 9 is a direct AC-AC converter circuit. As shown in Figure 9, the primary coil 7(L) is the primary coil of the direct AC-AC converter 6a. p ) and the first capacitor (C r) are connected in parallel, and the secondary coil 4 (L s ) and the second capacitor (C s ), which is capacitor 8 (see FIGS. 6 and 7), are connected in parallel. The direct AC-AC converter 6a (see FIG. 12) includes a rectifier circuit (L in ) connected to the commercial power supply (V f , C f ) and is composed of a bidirectional switch and a resonant tank made of a power device (power semiconductor). The resonant tank is shown in a magnetic coupling model, and its primary side is composed of an inductance (coil) L p and a resonant capacitor C r , and the secondary side is composed of an inductance (coil) L s and a capacitor (C s ) and a resistor R о . Also, the bidirectional switch 2 is composed of, for example, power transistors of SiC-MOSFETs connected in series at the drain connection and is driven by a gate. Diodes (D1, D2) are connected in parallel to each switch (S1, S2).

[0026] The characteristics of the circuit shown in FIG. 9 are that it has a simple topology structure, can achieve soft switching in all operations, and the output includes a low-frequency envelope. The fact that the output includes a low-frequency envelope does not affect the application to an electric welding joint. In a direct AC-AC converter, since a rectifier and a low-frequency smoothing filter are not used, the sinusoidal waveform of the input commercial power frequency can be directly converted into a high-frequency output waveform including a low-frequency envelope. Since the oscillation frequency of this envelope waveform is very low compared to the switching frequency, it does not have a negative impact on energy transfer and efficiency. The low-frequency component does not contribute to electric fusion, and mechanical actions such as Lorentz force do not cause mechanical vibrations to the object to be heated. Like the circuit shown in FIG. 9, while there is an advantage of having few components and being component-saving, there is also a demerit that the withstand voltage of the power semiconductor switch needs to be several times the power supply voltage, making it difficult to increase the output power.

[0027] The circuit parameters shown in Figure 9 are, for example, the DC input power supply voltage v in The voltage is 50V, and the operating frequency is f sw This is 112kHz, the first capacitor (C) for primary side resonance. r ) is 0.1μF, second capacitor (C) for secondary resonance s ) is 0.2μF, primary coil 7(L for primary side resonance) p ) is 10μH, secondary coil 4 (L for secondary side resonance) s The inductance (L1·L2) is set to 10 μH, and the coupling coefficient k is set to 0.397. The mutual coupling (M) is M = k√(L1·L2), where L1 and L2 are the self-inductances of the transmitting and receiving coils.

[0028] The heating wires (3a~3e) of the pipe fitting 2 are connected in series with the secondary coil 4, and a resonant capacitor 8 is connected in parallel with the secondary coil 4, thereby making the entire pipe fitting 2 function as the receiving side (secondary side) of the WPT system. A high-frequency alternating current with a frequency matching the Q value of the receiving side is passed through the primary coil 7, which is the transmitting side (primary side) coil, and a high-frequency electromotive force is induced in the secondary coil 4, which is located at a distance of 5 cm or less, by magnetic field resonance. This generates heat by passing current through the heating wires (3a~3e), thereby achieving fusion between the resin pipes (20a, 20b) and the non-contact type electrofusion fitting 1. [Examples]

[0029] Figure 10 shows a schematic diagram of one embodiment of the power supply device. As shown in Figure 10, the power supply device 5 is a device that provides contactless power to the secondary coil 4 of the electrofusion joint 1, and consists of a primary coil housing section 5a, a circuit board housing section 5b, and a power supply section 5c. The primary coil housing section 5a is provided with an external coil, the primary coil 7. The circuit board housing section 5b is provided with a circuit board 6. Although not shown, the circuit board 6 is provided with a first capacitor and a direct AC-AC converter 6a. According to the power supply device 5, even in harsh environments such as ceiling piping where installation is difficult, the installer can remotely hold a rod-shaped power supply device equipped with a power transmission coil and perform contactless power supply.

[0030] The primary coil accommodating portion 5a of this embodiment has a flat plate shape and does not conform to the outer surface shape of the pipe joint 2. However, since power supply is possible as long as the distance between the primary coil 7 and the secondary coil 4 is 5 cm or less, it has a trouble-free structure. Further, since the primary coil accommodating portion 5a has a flat plate shape, the primary coil accommodating portion 5a can be easily inserted and power supplied even in a narrow space such as a location adjacent to a wall or other piping.

Embodiment

[0031] FIG. 11 shows a schematic diagram of another embodiment of the primary coil accommodating portion of the power supply device. As shown in FIG. 11, unlike the primary coil accommodating portion 5a of the above-described Embodiment 2, the primary coil accommodating portion 50a has a shape curved along the outer surface shape of the pipe joint 2. Along with this, the primary coil 7 also has a shape curved along the outer surface shape of the pipe joint 2. By adopting such a shape, it becomes easy to bring the primary coil 7 and the secondary coil 4 close to each other, and the stability of power supply can be improved. The primary coil 7 may be embedded on a recess (not shown) formed on the surface (outer surface) side of the primary coil accommodating portion 50a shown in FIG. 11, but in order to bring the distance from the secondary coil 4 closer, it may also be embedded on a recess (not shown) formed on the back surface (inner surface) side. <​​​​​​​​​​​​​​​​​​​​​​​​​​​​6 Circuit board 6a Direct AC-AC Converter 7 Primary coil 8 Capacitors 9a,9b Socket part 20a,20b Resin pipe

Claims

1. A pipe fitting having an electric heating wire embedded in the socket portion of a thermoplastic resin pipe fitting, The pipe joint comprises a coil connected to the heating element, An electrofusion joint characterized in that current flows through the heating element via an external coil that provides non-contact power to the aforementioned coil.

2. An external coil separated from the aforementioned coil is powered by magnetic field resonance non-contact power supply. The electrofusion joint according to claim 1, characterized in that a high-frequency electromotive force is induced in the coil and heat is generated by passing an electric current through the heating wire.

3. The electrofusion joint according to claim 2, characterized in that the external coil is spaced 5 cm or less away from the coil.

4. The electric fusion joint according to claim 1, characterized in that the heating element is formed from a part of the coil.

5. The electrofusion joint according to claim 1 or 2, characterized in that the coil is provided on the outer surface of the pipe joint or between the outer surface and the inner surface.

6. The electrofusion joint according to claim 5, characterized in that the direction of the magnetic field when current flows through the coil is substantially perpendicular to the axial direction of the pipe joint.

7. The electrofusion joint according to claim 5, characterized in that the coil has a winding structure of a laminated coil or a thin film coil.

8. The electrofusion joint according to claim 1, characterized in that a high-frequency current flows through the external coil by an AC-AC converter or a DC-AC converter.

9. The electrofusion joint according to claim 5, characterized in that the AC-AC converter has the primary side coil, the external coil, and the first capacitor connected in parallel, and the secondary side coil, the coil, and the second capacitor connected in parallel or in series.

10. The electrofusion joint according to claim 9, characterized in that the second capacitor is disposed on the outer surface of the pipe joint or between the outer surface and the inner surface.

11. A device for non-contact power supply to the coil of an electrofusion joint according to any one of claims 1 to 3, Power supply unit, AC-AC converter, or DC-AC converter, First capacitor and, A power supply device for an electrofusion joint, characterized by comprising the aforementioned external coil.

12. The power supply device for an electrofusion joint according to claim 11, characterized in that the external coil is provided on a surface that covers the outer circumferential surface of the pipe joint.

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