JPH0145723B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a flexible linear temperature sensing wire used in large heating devices such as electric blankets and electric carpets. Conventionally, flexible temperature sensing wires called plastic thermistors have been widely used in planar heating devices such as electric blankets and electric carpets.
By the way, in conventional temperature detection wires, as the size of applied products increases, the temperature detection wires also become longer, so the impedance Z of the temperature detection wires becomes smaller, causing the phenomenon of thermistor breakdown due to self-heating, and thermistor B It was difficult to apply this method to large-sized products while maintaining a high constant. Here, the B constant is B in the relational expression R=R ₀ expB (1/T-1/T ₀ ) for a semiconductor having a large resistance and a negative temperature coefficient. This B is R as can be seen by taking the natural logarithm.
contributes to the slope of Note that this equation expresses the resistance R at the absolute temperature T using the resistance R ₀ at T ₀ . The present invention provides a temperature detection line that can be applied to large-sized heating devices without causing thermistor breakdown. Polymer thermosensors are applied to planar heating devices, and their function is to detect the average temperature as well as detect local overheating temperatures using the large thermistor B constant (meaning that the temperature gradient of resistance R is large). It fulfills the function of keeping it to an extremely small size. For this purpose, it is important that the thermistor B constant is large. The properties of the polymer temperature sensitive body are designed as follows. The temperature detection wire structure is as shown in Figure 1.
and an inner-wound electrode conductor 2 wound around this core yarn 1.
, a polymer temperature sensitive layer 3 attached to the outer periphery, an outer wound electrode conductor 4 wound around the outer periphery of the polymer temperature sensitive layer 3, an outer cover 5 and an adhesive coating 6. configured. And the equivalent circuit is resistance R and capacitance C
It is approximated by a parallel circuit connection of . The values of R and C are the characteristics of the polymer thermosensitive material (ρ: specific resistance, ε: inductivity)
determined by the thickness and electrode structure. This will be explained next using a mathematical formula. The impedance Z [Ω] of a temperature detection line made of a polymer thermosensitive material having a volume-specific impedance Z _sp [Ω·m] is approximately expressed by equation (1). Z=Z _sp・d/S ₀・L ...(1) Here, S ₀ is the area of the electrode (outer-wound electrode conductor 4) in the temperature detection line per unit length [m ² ], and L is the temperature detection line The length [m] and d are the distance [m] between the inner-wound electrode conductor 2 and the outer-wound electrode conductor 4. Incidentally, the equivalent circuit of the temperature detection line is approximated by a parallel circuit of a resistor R and a capacitor C. 1/Z=1/R+ωC (ω: angular frequency)...(2) That is, Z=R/1+RωC...(3) By the way, at low temperatures, the resistance R of the temperature detection line is large, so the impedance Z contributes to C ( 4) It is approximated as shown in Eq. Z=1/ωC (approximation at low temperature)...(4) Also, since C=εS/d=εS ₀ L/d (ε: dielectric constant), equation (4) can be rewritten as follows. Z=ω/1d/εS ₀ L=1/2πfεd/S ₀ L...(
4') = 1/2πfε ₀ ε ₁₀ d/S ₀ L ...(4'') Here, ε ₀ is the permittivity of vacuum, and ε ₁₀ is the relative permittivity at 10℃ (low temperature). In this case, the resistance R for temperature detection becomes small, so the impedance Z contributes to R and is approximated as in equation (5). Z=R (approximation at high temperature) ...(5) Also, R=ρd/S= Since ρd/S ₀ L (ρ: specific resistance [Ω・m]), equation (5) can be rewritten as follows: Z=ρd/S ₀ L ...(5') = ρ ₆₀ d /S ₀ L (5″) Here, ρ ₆₀ is the specific resistance at 60°C (high temperature). From equations (1), (4′), and (5′), it becomes as follows.

[Table] Since 1/2πfε and ρ of Z _sp are constants specific to the polymer temperature sensor, the impedance Z of the temperature detection line contributes to the value of d/S ₀ L, and d/S ₀ L can be changed in the design. By doing so, the impedance Z can be easily changed. According to experiments, in order to protect the temperature detection line from thermistor breakdown due to self-runaway, the value of impedance Z ₉₀ at 60°C per meter must be 5×10 ⁵ Ω or more. In order to detect local heat generation (warm retention) with the temperature detection line, it is necessary to make a large change in impedance Z due to temperature change (for example, from 30℃ (temperature approximately related by equation (4')) to 60℃ ((5' It is necessary that the change in impedance Z at temperature (which is approximately related by the equation ) is one order of magnitude, which is approximately 7500 K when expressed as a B constant. In this way, a large impedance Z is required to maintain large temperature changes in impedance and protect the thermistor from breakdown even on the high temperature side in the temperature range expressed by Z = ρd/S ₀ L. Become.)
To make it possible, make S ₀ small. (d may be made larger). ○Note [If you choose a material for the polymer temperature sensitive body and increase ρ, Z will increase, but in this case (4')
This is not suitable because the impedance Z at low temperatures, which is related by the formula, hardly changes, so the B constant becomes small and the ability of the temperature detection line to detect local heat generation deteriorates. ] The present invention will be described below using specific numerical values and examples. The polymeric thermosensitive material used in the present invention is an ionically conductive polymeric thermosensitive material made by adding an ionic substance to an insulating polymer, and exhibits the characteristics shown in FIG. In other words, in order to take the thermistor B constant to a large value such as _7500〓 or more, the intersection point a of the capacitive reactance It must have a large B constant within the normal operating temperature range. (This is necessary to suppress local overheating.) In other words, in order to set the thermistor B constant to 7500°K or more from 30°C to 60°C, the volume specific impedance (Z _sp ) ₃₀ at 30°C is 1/2πfε=3× 10 ¹⁰ /εΩ・cm [see formula (6)], so assuming ε=8, 3.8×10 ⁹ Ω
cm, but since it actually includes some ρ component, it becomes a slightly smaller value (Z _sp ) ₃₀ ≒ 2×10 ⁹ Ω・cm, and 60
°C volume specific impedance (Z _sp ) ₆₀ ≒2×10 ⁸ Ω・
The value is less than cm. In this case, if the temperature detection line is constructed as shown in FIG. 1, a large difference will occur due to the effects of the present invention, as shown in the conventional example described later. In the present invention, an ion-conducting polymer composition is preferable as the polymer thermosensitive material, and specifically, a polyvinyl chloride composition added with an ionic substance, a polyvinyl chloride-vinyl acetate copolymer, and a polyamide composition. etc. Note that as a polyamide composition, a nylon 12 composition may have low hygroscopicity. Among them, a polymeric temperature sensitive material having a matrix of a polyvinyl chloride composition or a copolymer composition thereof is preferred, and as an ion carrier, a perchlorate has the best heat resistance. Next, details of the conventional example and the present invention will be described. Conventional example, volume specific impedance Z _sp at 30℃ (Z _sp ) ₃₀ = 2×10 ⁹ Ω・cm, at 60℃ (Z _sp ) ₆₀ =
1.38×10 ⁸ Ω・cm perchlorate

A polyvinyl chloride composition containing 6% of [Formula] was used as a polymer temperature sensitive body (thermistor B constant B ₃₀ − ₆₀ = 9000〓),
As shown in Fig. 1, a stainless steel inner-wound electrode conductor 2 (foil width d = 0.32 mm) is wound on the core thread 1 with a pitch P = 0.7 mm, and a polymer temperature sensitive layer 3 is formed using a wire extruder.
After being coated into a 1.3 mmφ tubular shape, a stainless steel outer electrode conductor 4 was wound with a pitch of P=0.75 mm, and a soft polyvinyl chloride outer cover 5 and a polyethylene adhesive coat 6 were sequentially applied to a thickness of 0.5 mm and 0.3 mm. Tubing was used as a temperature detection wire. When the impedance of this temperature detection wire was measured at AC60Hz, it was Z ₃₀ = 4.1 x 10 ⁶ Ω per 1 m.
Z ₆₀ = 3.0×10 ⁵ Ω and B _30-60 = 8800°K. When this temperature detection wire was made 62 m long to construct an electric carpet for 6 tatami mats, the impedance of the temperature detection wire was Z ₃₀ = 79KΩ and Z ₆₀ = 5.8KΩ. This carpet is connected to R _x = 9KΩ using a detection circuit as shown in Figure 3.
When the temperature was controlled by setting it to , a temperature runaway phenomenon occurred due to self-heating of the thermistor in the local heat insulation state (10 cm square urethane heat insulation), and the temperature detection wire was burnt out. The maximum current at this time was 11 mA. However, the setting of R _x depends on the carpet and heater temperature.
The value was set so that it would turn on and off at 60°C. The detection circuit shown in Fig. 3 is a circuit found in ordinary electric carpets, where R _x is a temperature setting resistor, 7 is a load such as a heating wire, 8 is a temperature control circuit, and 9 is a power control circuit. It is a circuit. Example 1 of the Invention A stainless steel outer-wound electrode-like conductor was wound with a pitch P=1.8 mm in the same manner as in the conventional example, and a temperature detection wire was produced in the same manner. The impedance of this temperature detection line is Z ₃₀ = 8.9 x 10 ⁶ Ω per 1 m at AC60Hz,
Z ₆₀ = 8×10 ⁵ Ω, B _30-60 = 8100K. Similarly, when the temperature detection wire was cut to 62 m to construct an electric carpet for 6 tatami mats, the impedance of the temperature detection wire was Z ₃₀ = 144KΩ and Z ₆₀ = 13KΩ. When the temperature was controlled by setting R _x = 24KΩ using the same detection circuit as in the conventional example, the local temperature was 90°C even in the local heat retention state, and a carpet with excellent local heat retention properties was obtained. This is Z ₆₀ at 62m
This contributes to the fact that the resistance is 13KΩ, which is larger than the conventional example's 5.8KΩ. The relationship between the current in the temperature detection wire and the amount of self-heating during thermistor breakdown is the fourth
It was as shown in the picture. Example 2 of the present invention When a temperature detection wire was constructed by winding the same stainless steel outer-wound electrode conductor with a pitch of P = 1.5 mm using the same method as in Example 1 of the present invention, Z ₃₀ = 5.7 per meter.
×10 ⁶ Ω, Z ₆₀ = 5 × 10 ⁵ Ω, B _30-60 = 8200〓. When this was similarly cut into 62 m lengths and a prototype carpet was made, an excellent carpet with a local heat retention temperature of 86°C was obtained using the same detection circuit with a setting of R _x = 15KΩ. Example 3 of the present invention In the same manner as in Example 1 of the present invention, a temperature detection wire was made by winding the same stainless steel outer electrode conductor with a pitch of 2.6 mm, and its impedance characteristics were measured. Per Z ₃₀ = 1.4×10 ⁷ Ω, Z ₆₀ =
It was 1.5×10 ⁶ Ω, B _30-60 7500〓. When we cut this into 62m lengths and made a prototype carpet, we found that
Using a similar sensing circuit with a setting of R _x 45KΩ, a similar test yielded an excellent electrical carpet with a local insulation temperature of 96°C. Embodiment 4 of the present invention When the temperature detection line of Embodiment 1 of the present invention was constructed using the circuit shown in Fig. 5, an excellent electric carpet with a similar local heat retention temperature of 88°C was obtained at R _s 47KΩ. Obtained. In the circuit shown in FIG. 5, a discharge circuit element 10 is connected to the ends of the inner electrode conductor 2 and the outer electrode conductor 3, and a pulse is generated to operate the temperature control circuit 8 at a set constant pressure. There is. In addition, the outer winding specifications in each of the embodiments of the present invention and the conventional example are as follows: outer winding foil width W/outer winding pitch P (∝area of outer winding electrode conductor 4 per unit length S ₀ ) is 0.21 or less. Conventional example W/P=0.32/0.75 =0.42 Invention example 1 W/P=0.32/1.8 =0.178 Invention example 2 W/P=0.32/1.5 =0.213 Invention example 3 W/P=0.32/ 2.6 = 0.123 Furthermore, in the present invention, in addition to changing the pitch of the electrode conductor of the same foil width as described above, if the foil shape is changed as follows, the impedance can be further changed on the high impedance side. For example, foil width W x foil thickness t is 0.32W x 0.055t → 0.22W (0.15φ) x
By setting it to 0.08t, W/P can be reduced (0.15φ), and in this case, it will be approximately 0.32/0.22≈1.5 times. By narrowing the foil width in this way, high impedance can be achieved without increasing the winding pitch (extending the winding pitch more than necessary has the disadvantage of impairing the reliability of the bending characteristics and characteristics). , the effects of the present invention are exhibited.
At this time, W/t of 2 to 8 can be said to be appropriate. Note that when W/t is large, the electrode foil acts like a knife edge, which also causes difficulty in foil production. Also, W/
When t is less than 2, the contact with the polymer temperature-sensitive layer becomes unstable. In the present invention, the winding pitch of the inner winding is
We investigated the temperature range from 0.4 to 0.8 using 0.32W x 0.055t foil, but it had almost no effect on the temperature-sensitive characteristics. The present invention thus proposes temperature detection line specifications,
The present invention provides a temperature detection line that has a high thermistor B constant and can be easily applied to large heating devices. The effects of the present invention on the temperature detection line can be summarized as follows. (1) Since the outer winding pitch W is coarsely wound and the impedance per meter is high, the voltage drop in the length direction is small and the detection efficiency of whole surface temperature detection is increased. (2) Since the B constant can be maintained high, there is no self-heating and thermistor breakdown is less likely to occur. (3) Easy to apply to large area heating equipment. Furthermore, when the temperature-sensitive material in the present invention is a polyvinyl chloride composition, it is soft and may be deformed during production by hot pressing, such as carpeting. Therefore, this deformation can be prevented by providing a nylon coating on the outside of the outer wrap in a tubular manner, resulting in a high quality sensing wire. This nylon layer also acts as a layer to prevent migration of additives (ionic substances and plasticizers) in the temperature-sensitive material. In addition, the core thread of the temperature detection wire in the present invention can be made of polyester, glass core, aromatic polyamide, nylon thread, etc., and the present invention is particularly effective for temperature detection wires with a core thread diameter of 0.5 mmφ or less. It is. As described above, the present invention provides an excellent temperature detection line and has great industrial value.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a temperature detection line, and FIG. 2 is a diagram showing the temperature characteristics of a polymer thermosensitive body. FIG. 3 is a block diagram of the temperature control circuit, FIG. 4 is a diagram showing the relationship between thermistor current and self-heating amount, and FIG. 5 is a diagram showing the temperature control circuit. DESCRIPTION OF SYMBOLS 1... Core yarn, 2... Conductor for inner wound electrode, 3... Polymer temperature sensitive layer, 4... Conductor for outer wound electrode, 5... Outer cover, 6... Adhesive coating.

Claims (1)

[Scope of Claims] 1. A conductor for an inner-wound electrode, a polymer temperature-sensitive layer, and a conductor for an outer-wound electrode are sequentially provided on the core thread, and the foil width W/outer-wound pitch P of the outer-wound electrode conductor is 0.21 or less. A temperature sensing wire characterized in that the impedance at 60°C is 5×10 ⁵ Ω or more per meter of length. 2 Foil width W/gold foil thickness t of conductor for outer wound electrode is 2 to 8
The temperature detection line according to claim 1, characterized in that: 3. Temperature detection according to claim 1 or 2, wherein the polymer temperature-sensitive layer is made of an ion-conductive polymer composition having a thermistor B constant of 7500 or more at 30 to 60°C. line. 4. The temperature sensing wire according to claim 3, wherein the ion-conductive polymer composition is a perchlorate-containing polyvinyl chloride composition or a copolymer composition thereof.