JPH09273688A - Electric fusion coupling - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a defect in which a heating wire is partially bent and short-circuited as it is buckled in an electric fusion coupling. SOLUTION: In an electric fusion coupling in which a heating wire 3 is buried in the inner periphery of a coupling main body 1 made of a thermoplastic resin, the volume resistivity ρ of the heating wire 3 is set in the range of 0.20 to 0.30 (μΩm), and the temperature coefficient of resistance α is set in the range of 40 to 70×10<-5> (/ deg.C). For instance, the heating wire is made of a copper-silicon alloy containing Si in the range of 3.0 to 4.2%, Mn of 0.2% or less, the residual of impurities and Cu in the weight ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric fusion joint (hereinafter sometimes simply referred to as a joint) used for gas or hot water supply hot water supply piping.

[0002]

2. Description of the Related Art Conventionally, a spiral heating wire is wound around the inner peripheral portion of a joint body made of a thermoplastic resin such as polyethylene or polybutene, and a pipe made of the same thermoplastic resin is inserted into the joint portion. A so-called electric fusion joint (electrofusion joint) is well known in which the electric heating wire is energized to heat the electric heating wire to electrically connect the two. In this joint, the input energy (KJ / cm ² ) per unit area required for fusion, so-called fusion energy (En), is individually determined for each type of joint, and adjustment of this is done by the conventional controller. Was the constant voltage control, the resistance value R of the heating wire in En = V ² t / R
Was specifically adjusted by changing the wire diameter. Further, conventionally, a copper nickel (Cu-Ni) alloy standardized in JISC2532 is used for the heating wire, the volume resistivity ρ is 0.10 to 0.49 (μΩm), and the temperature coefficient of resistance α is as shown in the line (b) of FIG. It was in the range of 10 to 70 × 10 ⁻⁵ (/ ° C.).

[0003]

By the way, it is extremely rare to perform welding work in the winter (environment of about 0 ° C. or less) using this joint, but it seems that a part of the heating wire is buckled. There was a problem that the wire was refracted to the side and a short circuit occurred between adjacent lines.

Considering this mechanism, first, when energization is started, the heating wire is heated and tends to expand due to linear expansion. However, the heating rate on the resin side is slow, and the linear expansion of the heating wire is blocked by the resin here. This causes compressive stress in the heating wire. Especially in winter, the initial resin temperature is quite low, while the temperature on the heating wire side rises irrespective of the environmental temperature, so the temperature difference between the resin and the heating wire becomes large, and as a result, the compressive stress also increases. It becomes a form that accumulates a lot. After that, when the resin around the heating wire begins to soften, the heating wire is released and starts linear expansion, but the accumulated compressive stress is also released.

When it is fully released, linear expansion and compressive stress act rapidly on the heating wire, leading to refraction. This is likely to occur because the larger the size of the bore, the larger the heat capacity of the resin and the longer it takes to open the resin. In addition, the temperature difference between the resin and the heating wire is larger on the inlet side and the back side near the cold zones at both ends than at the central part of the wire zone, so the compressive stress accumulated here is large and this part becomes the base point and the refraction part It is thought to have been encouraged.

From the above, as one means for solving the short-circuiting defect of the heating wire due to the refraction, it is conceivable to use a heating wire having a thickness strong enough to withstand compressive stress. However, in the existing electric fusion system,
Since the fusion energy is determined as described above,
It is necessary to increase the wire diameter without changing the resistance value, and for that purpose it is necessary to review the volume resistivity. On the contrary, the resistance temperature coefficient of the heating wire is also set from this value. Here, the fusion energy of the joint is expressed by En = V ² t / R ..., but the resistance value R is R _T = R _t (1+) in relation to the temperature coefficient of resistance α.
Since α (T−t)) ..., α will affect the fusion energy. Therefore, even if the wire diameter is unnecessarily increased to increase the refraction strength, the fusion energy is changed and the fusion performance is deteriorated.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide an electric fusion splicing joint which maintains an appropriate fusion energy and does not cause a short circuit of a heating wire due to refraction. .

[0008]

According to the present invention, there is provided an electric fusion joint in which a heating wire is embedded in an inner peripheral portion of a joint body made of a thermoplastic resin, wherein the heating wire has a volume resistivity ρ of 0.20.
~ 0.30 (μΩm) and temperature coefficient of resistance α at this time
Is 40 to 70 × 10 ⁻⁵ (/ ° C.). still,
Here, the volume resistivity ρ may be in the range of 0.23 to 0.25 (μΩm) and the temperature coefficient of resistance α may be in the range of about 43 to 46 × 10 ⁻⁵ (/ ° C.) as shown in FIG. 2C.

Further, according to the present invention, in an electric fusion joint in which a heating wire is embedded in an inner peripheral portion of a joint body made of a thermoplastic resin, the heating wire has a weight ratio of Si: 3.0 to 4.2% and Mn:
0.2% or less, and the balance is an electric fusion-bonded joint made of Cu-silicon (Cu-Si) alloy excluding impurities. still,
If the amount of Si added is 4.2 wt% or more, the workability deteriorates and the winding work becomes difficult.
~ 3.9wt%. Further, if Mn is too much, the temperature coefficient of resistance decreases, so 0.2 wt% or less is desirable.

Generally, in a copper-nickel alloy, the temperature coefficient of resistance α and the volume resistivity ρ are in inverse proportion. That is, in order to increase the wire diameter while maintaining the conductor resistance value, the volume resistivity ρ
Needs to be increased, and then the temperature coefficient of resistance α becomes small. Therefore, from the above formula, the fusion energy tends to be excessive. Therefore, the former of the present invention has a physical characteristic in the range of FIG. 2 (a) that the temperature coefficient of resistance is relatively high, while it is in the range of volume resistivity in which the wire diameter is thick and a certain degree of strength is secured. The above problem is solved by using a heating wire.

The latter is focused on the material of the heating wire. First, when Cu, Ni, Si, Co, Mn, and Zn are added in a total amount of 38.25 wt% or less, the volume resistivity ρ is It was found that the relationship of the temperature coefficient of resistance α deviates from the proportional or inversely proportional relationship, and in particular, the inventors invented the optimum element and addition amount from the above elements.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a half cross-sectional view showing an example of the electric fusion joint of the present invention, and illustrates a socket joint for connecting pipes. This joint is a socket joint in which the electric fusion splicing member A in which the heating wire 3 is embedded in a spiral shape in the inner peripheral portion of the receiving port 5 and the end face 6 of the same splicing member A are butt-joined, that is, butt-fused. It has been completed. However, the present invention is not limited to this, and the joint body may be integrally formed by injection molding, or a multilayer molded body in which three or more resin layers forming this joint are laminated by injection molding. Good. Other joint shapes are T or L
In some cases, a Q-joint or an elbow joint is obtained by butt-fusing an electric fusion-bonding member similar to the one described above with an intermediate member having a shape interposed therebetween. There is also a saddle type joint in which a heating wire is embedded in a spiral shape on the inner peripheral surface, and the present invention can be applied to all of these.

Now, the size of the main part of the joint body 1 in the figure is JI
It is formed according to the basic dimensions of SK 6775, and 3 is a heating wire which is designed to generate heat by passing an electric current through the connector pins 2 and 2 at both ends. This heating wire 3
Is wound along a spiral groove provided on the inner member 1a, is connected to both ends thereof with connector pins 2 and 2 and is embedded in a pedestal or the like. It is buried. The wire zone H around which the heating wire 3 is wound serves as a fusion-bonded portion, and cold zones c are formed at both ends of the fusion zone, particularly on the back side in a considerably thick portion. Reference numeral 4 denotes a recessed hole for inserting a sensor, for example, a temperature sensor such as a thermocouple is inserted and mounted, and the temperature near the fusion interface after energization is continuously measured. When the temperature reaches a preset temperature, energization is performed. I'm trying to stop. The diameter 5 is slightly larger than the outer diameter of the pipe to be connected at the receiving portion. Reference numeral 7 is a flange-shaped thick portion formed over the entire circumference to strengthen the strength.

First, in the case of the socket joint having a diameter of 150 mm according to the present embodiment, considering the required strength, the buckling stress σ _k
Is represented by the following equation. σ _k = nπ ² E / (l / k) ² n: Terminal condition coefficient; 4 at both ends fixed. l: length of heating wire for one winding (mm); about 530 mm k: secondary radius of cross section; expressed by 1/4 d (mm). E: Young's modulus of wire; 11000 to 13000 (Kgf / mm ² ) Here, since σ _k needs to be about 0.30 Kgf / mm ² , it is necessary to calculate the wire diameter φd of the heating wire from the above equation: φd = 1.6
It will be ~ 1.7 mm. In fact, φd =
1.3 mm (volume resistivity ρ = 0.15 (μΩm), temperature coefficient of resistance α
= 50 × 10 ⁻⁵ (/ ° C.)) and the strength was insufficient.
From this, if φd is 1.6 mm, the strength is sufficient. However, in the conventional copper-nickel wire, the wire diameter is
In addition to being thickened to 1.6 mm, the volume resistivity ρ is 0.20 to 0.30 (μΩ
m), the temperature coefficient of resistance α is 20 × 10 ^-5 (/ ℃)
And suddenly falls. Therefore, even if the temperature of the heating wire rises with the progress of energization, R _T represented by R _T = R _t (1 + α (T−t)) is smaller than that before increasing the wire diameter. Therefore, the resistance value R of the fusion energy En = V ² t / R also decreases. Therefore, if the energization time t is the same, the fusion energy will naturally be excessive.

However, in the present invention, even if φd = 1.6 mm and the volume resistivity ρ is in the range of 0.20 to 0.30 (μΩm), the temperature coefficient of resistance α is 40 to 70 × 10 ⁻⁵ (/ ° C.), which is a relatively high value. Came to secure. Therefore, even if the temperature of the heating wire rises with the progress of energization, the decrease amount of the resistance value R of the fusion energy En = V ² t / R is kept small, so that the excess fusion energy is suppressed. To be done. The heating wire having the above physical characteristic values is obtained by, for example, a copper silicon alloy described below, but the heating wire material having the above characteristics is not limited to this and may be any heating wire material. Further, in some cases, it may not be linear but may be sheet-like or mesh-like.

Next, an embodiment of the heating wire will be described. First, regarding the Ni-based alloy used for the heating wire,
Total amount of Si, Fe, Al, Co, Mn and Mg added 6.
Volume resistivity ρ and resistance temperature coefficient α when added below 15%
We conducted a characteristic survey. As a result, as shown in FIGS. 3 and 4, the volume resistivity ρ (illustrated by ▪) is proportional to the total addition amount on the horizontal axis, and the temperature coefficient of resistance α (illustrated by ●) is inversely proportional. That is, it was found that the volume resistivity ρ and the temperature coefficient of resistance α can only be in an inversely proportional relationship.

Next, regarding Cu-based alloys, Ni, S
The characteristics of the volume resistivity ρ and the temperature coefficient of resistance α when i, Co, Mn and Sn were added in a total amount of 38.25% or less were similarly investigated. As a result, as shown in FIGS. 5 and 6, it was found that there is no correlation with the volume resistivity ρ (illustrated by ▪) and the temperature coefficient of resistance α (illustrated by ●) with the total addition amount as the horizontal axis. That is, this means that the values of the volume resistivity ρ and the temperature coefficient of resistance α can be adjusted by selecting the additive element and the additive amount. From the above, it was found that it is suitable to use the Cu-based alloy in the present invention.

Therefore, as an example, the amount of Si added to the Cu metal was changed by about 2.0 to 4.5% by weight, and the characteristics of the volume resistivity ρ and the temperature coefficient of resistance α were investigated. As a result, as shown in FIG. 7, the volume resistivity ρ (illustrated by ▪) is proportional to the horizontal axis of the Si addition amount, and the temperature coefficient of resistance α (illustrated by ●).
Is inversely proportional, but volume resistivity ρ = 0.20 to 0.30 (μ
Ωm) and the temperature coefficient of resistance α = 40 to 70 × 10 ⁻⁵ (/ ° C.) was found to be satisfied in some ranges. That is, Si
Is a copper-silicon alloy of 3.0 to 4.2 wt%. In the subsequent test, Mn is an additive that affects the temperature coefficient of resistance α, but if it is 0.2 wt% or less, the decrease of the temperature coefficient of resistance α can be suppressed. It was also found that if the amount of Si added is 3.0 or less, it has little effect on the characteristics, while if it is 4.2 wt% or more, the workability deteriorates. From the above, S
It is desirable that i is 3.5 to 3.9 wt% and Mn is 0.2 wt% or less. At this time, the volume resistivity ρ is approximately 0.23 to 0.25 (μΩm).
Thus, the temperature coefficient of resistance α was about 43 to 46 × 10 ⁻⁵ (/ ° C.), which was practically applicable. However, the present invention is not limited to this, and it is possible to obtain properties suitable for each within the above-mentioned range of components.

Using this heating wire, a socket joint having the above-mentioned diameter of 150 mm was prototyped, and the electric fusion work was carried out in an environment of -40 ° C. As a result, no abnormalities such as a short circuit defect were found for all (n = 50), and normal fusion was possible.

[0020]

According to the present invention, the short circuit failure of the heating wire caused by the buckling of the heating wire which occurred in winter is eliminated,
It was possible to provide a more reliable electric fusion joint.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of an electric fusion joint showing an embodiment of the present invention.

FIG. 2 shows characteristic value ranges (a) and (C) of the volume resistivity ρ and the resistance temperature coefficient α of the heating wire used for the electric fusion joint of the present invention and the characteristic value (b) of the conventional heating wire. It is a graph.

FIG. 3 is a graph showing the relationship between the additive element amount in Ni and the volume resistivity ρ in the trial experiment.

FIG. 4 is a graph showing the relationship between the amount of an additive element in Ni and the temperature coefficient of resistance α in a trial experiment.

FIG. 5 is a graph showing the relationship between the additive element amount in Cu and the volume resistivity ρ in the trial experiment.

FIG. 6 is a graph showing the relationship between the additive element amount in CuNi and the temperature coefficient of resistance α in the trial experiment.

FIG. 7 is a graph showing the relationship among the amount of Si added, the volume resistivity ρ, and the temperature coefficient of resistance α for the copper-silicon alloy that is the heating wire used in the electric fusion joint of the present invention.

[Explanation of symbols]

1 ... Joint body 1a ... Inner member
1b ... Outer member 2 ... Connector pin 3 ... Heating wire
4 ... Sensor recess 5 ... Receptacle 6 ... Butt fusion end face
7 ... Flange A ... Electrofusion connection member C ... Cold zone
H ... Wire zone

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Ken Kato, 2 Daifuku, Hitachi Metals Co., Ltd., Kuwana City, Mie Prefecture, Kuwana Plant (72) Inventor Nobuhiro Nishikata, 2 Daifuku, Kuwana City, Mie Prefecture, Hitachi Metals, Ltd., Kuwana Plant ( 72) Inventor Takafumi Futami 5-18 Higashi-Hachiman, Hiratsuka City, Kanagawa Prefecture Furukawa Techno Material Co., Ltd. (72) Inventor Takashi Anamizu 21 Itogaya Nado, Shinto-ku, Tokyo 404 (72) Inventor Yoshii Soro 1-10-3 Akabane Minami, Kita-ku, Tokyo Tokyo Gas Akabane Single Dormitory No. 910

Claims (2)

[Claims] 1. An electric fusion joint in which a heating wire is embedded in an inner peripheral portion of a receiving port of a joint body made of a thermoplastic resin, wherein the heating wire has a volume resistivity ρ of 0.20 to 0.30 (μΩm), and The temperature coefficient of resistance α at this time is 40 to 70 × 10 ^-5 (/
(° C) The electric fusion joint. 2. An electric fusion joint in which a heating wire is embedded in an inner peripheral portion of a receiving port of a joint body made of a thermoplastic resin, wherein the heating wire has a weight ratio of Si: 3.0 to 4.2%, Mn: 0.2% or less, The remainder is copper silicon (Cu
-Si) alloy is an electric fusion joint.