Warming temperature control device

Abstract

To provide a warming temperature control device which prevents overheating with high accuracy and stability to ensure safety and is excellent in economy, between both electrodes of a DC stabilization power supply which drives a temperature control section, a fixed resistor with which a capacitor is connected in parallel, a first diode disposed in a forward direction with respect to the power supply, and a temperature detection element wire are connected in series, and an inter-wire short circuit protection circuit is included. A degree of leak of a polymer layer is determined by detecting a difference between a maximum value and a minimum value of an input signal to the temperature control section on a time axis. When the difference increases to reach a predetermined set value, the temperature control section performs control such that a heating signal is not outputted.

Claims

1. A warming temperature control device having a cord-like heating structure comprising: a first wire which is wound spirally on a winding core at a predetermined pitch; a polymer layer which is disposed on the first wire in a close-contact manner and melts at a predetermined temperature; a second wire which is wound spirally on an outer periphery of the polymer layer at a predetermined pitch; and a coating layer which insulates the second wire, wherein one of the first and second wires is composed of a heating element wire, and the other of the first and second wires is composed of a temperature detection element wire; between both electrodes of a DC stabilization power supply which drives a temperature control section, a fixed resistor with which a capacitor is connected in parallel, a first diode disposed in a forward direction relative to the power supply, and the temperature detection element wire are connected in series; anodes of second and third diodes are connected to both ends of the temperature detection element wire, respectively; cathodes of the second and third diodes are connected to one end of a temperature fuse integral type resistor; another end of the temperature fuse integral type resistor is connected to one side of an AC power supply; a voltage of a connection point between a cathode of the first diode and the temperature detection element wire is inputted as an input signal to a voltage comparator; a degree of leak of the polymer layer is determined by detecting a difference between a maximum value and a minimum value of the input signal on a time axis; and when the difference increases to reach a predetermined set value, the temperature control section performs control such that a heating signal is not outputted to prevent overheating to ensure safety.

2. The warming temperature control device according to claim 1, wherein the polymer layer is formed of only a polyamide resin or a mixture of a polyamide resin and polyamide elastomer, and has a melting temperature of not lower than 130 C. and not higher than 190 C.

3. The warming temperature control device according to claim 1, wherein the temperature detection element wire is a metal wire having a positive temperature coefficient.

4. The warming temperature control device according to claim 2, wherein the temperature detection element wire is a metal wire having a positive temperature coefficient.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a circuit diagram showing an embodiment of a temperature control circuit of a warming temperature control device according to the present invention, wherein an AD converter and a processing section of a microcomputer serve as a voltage comparator;

(2) FIG. 2 is a structure diagram showing an embodiment of the warming temperature control device according to the present invention, wherein a part of a cord-like heating wire is omitted;

(3) FIG. 3 is a diagram showing the phase of a load current lh and the phase of a voltage Vi inputted to an AD conversion port AD1 of the microcomputer U1 when a power control switch is ON and a leak position is at S1 and H1 terminals, and a leak resistance is 100 K in the warming temperature control device according to the present invention;

(4) FIG. 4 is a diagram showing the phase of the load current lh and the phase of the input voltage Vi inputted to the AD conversion port AD1 of the microcomputer U1 when the power control switch is ON, a leak position is at a center portion of the cord-like heating wire, and a leak resistance Rx is 100 K in the warming temperature control device according to the present invention;

(5) FIG. 5 is a diagram showing the phase of the load current lh and the phase of the input voltage Vi inputted to the AD conversion port AD1 of the microcomputer U1 when the power control switch is ON, a leak position is at an S2 and H2 terminals, and a leak resistance is 100 K in the warming temperature control device according to the present invention;

(6) FIG. 6 is a circuit diagram showing an example of a temperature control circuit of a warming temperature control device according to a related art; and

(7) FIG. 7 is a diagram showing a relationship between a leak resistance Rx and an input voltage Vi inputted to a minus terminal of a voltage comparator U1 with a leak position as a parameter when a power control switch is ON in the warming temperature control device according to the related art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(8) Embodiments of a warming temperature control device according to the present invention will be described below in more detail with reference to the drawings and the like. The present invention is not limited to the following contents unless departing from the gist of the present invention.

(9) FIG. 2 is a diagram showing one end of a cord-like heating wire 1H according to an embodiment of the present invention, wherein an insulation coating layer, a polymer layer and the like are partially omitted, and the cord-like heating wire 1H has the same configuration as described in the above-described related art.

(10) The cord-like heating wire 1H includes a winding core 1 composed of a fiber bundle of glass fiber, polyester fiber or the like, a heating element wire 2 composed of a rectangular conductor which is made of copper or a copper alloy and twisted on the outer periphery of the winding core 1 in a spiral manner, a polymer layer 3 formed by extruding a polymer resin onto the outer periphery of the heating element wire 2, a temperature detection element wire 4 wound spirally on the outer periphery of the polymer layer 3, and an insulation coating layer 5 formed by extruding a polyvinyl chloride resin or the like onto the outermost periphery.

(11) Here, as the polymer layer 3, nylon 12 which has a low water absorption among polyamide resins, or a mixture of nylon 12 and a polyamide elastomer is preferable. When the molding temperature for the insulation coating layer 5 is low, polyethylene glycol or a polyalkylene oxide such as polyethylene oxide may be added to the mixture to decrease the softening point of the polymer layer 3. These materials are kneaded with a kneader or a multi-screw extruder to obtain the polymer layer 3 as a mixture. These materials may be loaded at one time and kneaded, but may be loaded sequentially and kneaded over a plurality of times.

(12) In order to prevent a plasticizer contained in a polyvinyl chloride resin mixture of the insulation coating layer 5 from shifting to the polymer layer 3, a barrier layer may be formed between the temperature detection element wire 4 and the insulation coating layer 5 by longitudinally lapping a polyester tape.

(13) Various specific data regarding the embodiment shown in FIG. 2 are as follows:

(14) Material of the winding core 1: polyester fiber bundle, 0.44 mm

(15) Material of the heating element wire 2: 0.7% tin-copper alloy

(16) Dimensions of the heating element wire 2: cross section 0.0600.420 mm (rectangular conductor), pitch 0.86 mm

(17) Material of the polymer layer 3: polyamide resin

(18) Dimensions of the polymer layer 3: thickness 0.33 mm

(19) Material of the temperature detection element wire 4: nickel

(20) Dimensions of the temperature detection element wire 4: cross-section diameter 0.080 mm (round conductor), pitch 0.86 mm

(21) Material of the insulation coating layer 5: polyvinyl chloride resin mixture

(22) Dimensions of the insulation coating layer 5: thickness 0.4 mm.

(23) (Commercially-available nylon 12 (3020X15, manufactured by UBE) which does not contain any additive for a thermistor is used as the polyamide resin, and a commercially-available mixture (VM-163, manufactured by APCO) for power supply electric wire, in which a polyvinyl chloride resin with a heat resistance grade is used, is used as the polyvinyl chloride resin mixture.)

(24) The cord-like heating wire 1H having the structure shown in FIG. 2 is made through a spirally winding step and an extrusion step for each layer with the above respective materials, and is cut into a length of 36 m as a sample for measurement. In FIG. 2, the resistance value of the heating element wire 2, which is a component of the cord-like heating wire 1H having a total length of 36 m, is 28.6, and the resistance value of the temperature detection element wire 4 is 1000 at 20 C. (its temperature coefficient is 0.44%/ C.).

(25) The configuration of a temperature control circuit regarding the embodiment of the present invention is shown in FIG. 1, and electric values and operation of each component will be briefly described. R1, R2, R3 and R4 are fixed resistors, R1=1.5 KF, R2=470F, R3=10 K, and R4=5.6 K, 3 W. C1 is a film capacitor, and C1=0.1 F, 50 V. C3 is an electrolytic capacitor, and C3=100 F, 35 V. D1, D2, D3, D4 and D5 are rectifier diodes 1N4004. ZD1 is a Zener diode, and Vz=4.7 V. U1 is a general-purpose one-chip flash type microcomputer equipped with an AD converter. U2 is a three-terminal regulator, and its output voltage is 5 V. GND is a ground for a DC stabilization power supply. SW is a power control switch which controls energization of the heating element wire 2 based on a comparison determination result of the microcomputer U1.

(26) Operation of the circuit in FIG. 1 is as follows. In temperature control operation, a resistance change of the temperature detection element wire 4 is inputted as a temperature signal voltage from a connection point between the diode D1 and the temperature detection element wire 4 via the overvoltage prevention resistor R3 and the Zener diode ZD1 to an AD conversion port AD1 of the microcomputer U1 and stored in a RAM within the microcomputer U1. In the present embodiment, as a frequency of input to the AD converter, a single input per 1 mS is made consecutively 45 times, and the maximum value and the minimum value of 45 pieces of data and the difference therebetween are calculated and stored in the RAM. Here, since the speed of temperature rise or fall of the cord-like heating wire 1H is not so high, it is sufficient if an operation of input to the AD converter which takes 45 mS is performed at one time every about 10 seconds. The input time 45 mS which is one unit is very unlikely to hinder the other processes of the microcomputer U1.

(27) If the difference V between the maximum value and the minimum value of the AD conversion is lower than a set value, it is determined that there is no leak due to overheating, and the maximum value is regarded as a temperature signal and used for temperature control. In temperature control, the maximum value inputted to AD1 and Vref1 which is inputted and stored through an AD0 port as a voltage corresponding to a preset temperature are compared to each other by a processing section of the microcomputer U1, its determination result is outputted from an output port PB1, and the power control switch SW is driven to open or close based on the determination result, whereby energization of the heating element wire 2 is controlled. In overheating protection operation, if the difference V between the maximum value and the minimum value inputted to AD1 is higher than the set value, it is determined that there is leak due to overheating. Its result is outputted from the output port PB1, and the power control switch SW is driven to be OFF based on the result, whereby energization of the heating element wire 2 is stopped.

(28) The inter-wire short circuit protection operation is the same as the contents as described in the BACKGROUND OF THE INVENTION section.

(29) [Leak Test]

(30) The 36 m cord-like heating wire 1H is interposed and fixed between front and back fabrics such as felt by bonding to form an electric carpet heating element, and the ends of the heating element wire 2 are connected to H1 and H2 terminals shown in the temperature control circuit diagram in FIG. 1.

(31) Instead of the temperature detection element wire 4, a 1200 fixed resistor (a resistance value corresponding to 65.5 C.) is connected between S1 and S2 terminals, and the temperature control set voltage Vref1 is set at 5V of Vcc and connected to the AD0 port of the microcomputer U1.

(32) The temperature control circuit was connected to an AC power supply. After an initial stabilization time of 3 minutes elapsed, the input voltage Vi of the AD1 port of the microcomputer U1 was measured to obtain Vi=2.354 V, and this voltage was set as an input voltage Vis in the case of no leak.

(33) Next, the 1200 fixed resistor was removed. Both ends of the temperature detection element wire 4 were connected to the S1 and S2 terminals. The temperature control set voltage Vref1 was set at 2.354 V and inputted to the AD0 port to obtain a state where the electric carpet was operable.

(34) The electric carpet was connected to the AC power supply, and the power control switch SW was operated to be ON/OFF by the temperature control circuit to obtain a stable state.

(35) While the input voltage Vi of the AD1 port of the microcomputer U1 was measured, a leak resistance of 1 K was connected between the S1 and H1 terminals as a leak position at the time when the input voltage Vi of the port AD1 reached 2.354 V during a period when the power control switch SW was ON. After 5 seconds, a waveform of the input voltage Vi was observed with a digital oscilloscope to read the maximum value and the minimum value of the input voltage Vi.

(36) By the same method, for the case with a leak resistance of 10 K, 100 K or 1000 K, the maximum value and the minimum value of Vi were read.

(37) Further, by the same method, for the case where a leak position was at the center portion of the cord-like heating wire 1H and the case where a leak position was between the S2 and H2 terminals, the maximum value and the minimum value of the input voltage Vi were read.

(38) The obtained maximum values and minimum values of Vi and the differences V therebetween are shown in Table 1.

(39) The results of observation of the waveform of the input voltage Vi and a waveform lh of a load current in the case with a leak resistance of 100 K at each leak position described above are shown in FIGS. 3, 4, and 5.

(40) TABLE-US-00001 TABLE 1 Input voltages and differences relative to leak resistance C3 = 0.1 F Power SW = ON Leak Input voltage Difference resistance Vi (V) (V) Average Parameter (K) Max. Min. V Vavg (V) Waveform No leak 2.354 2.346 0.008 2.351 Ripple square wave S1 and H1 1000 2.469 2.347 0.122 2.385 Upward half-wave terminals 100 3.452 2.348 1.104 2.698 Upward half-wave 10 4.721 2.351 2.370 3.418 Upward round half-wave 1 4.871 2.357 2.514 3.556 Upward round half-wave Center 1000 2.391 2.326 0.065 2.355 Distortion sine wave portion 100 2.702 2.146 0.556 2.395 Sine wave 10 4.573 1.127 3.446 2.703 Round trapezoidal wave 1 4.801 1.069 3.732 2.859 Substantially square wave S2 and H2 1000 2.355 2.262 0.093 2.323 Downward half-wave terminals 100 2.349 1.542 0.807 2.091 Downward half-wave 10 2.319 1.004 1.315 1.708 Downward round square wave 1 2.143 0.923 1.220 1.559 Downward round square wave (whiskers at both ends) Criterion >2.465 <2.038 >0.5

(41) Table 1 shows the leak resistance Rx, the maximum value (Max) and the minimum value (Min) of the input voltage Vi inputted to the port AD1 of the microcomputer U1, and the differences (V) therebetween with a leak position as a parameter when the power control switch SW is ON in the warming temperature control device according to the present invention.

(42) [Local Overheating Test]

(43) Similarly to the above [Leak Test], the temperature control set voltage Vref1 was set at 2.354 V (corresponding to 65.5 C.) and inputted to the AD0 port to obtain a state where the electric carpet was operating, and the surface temperature of the temperature-controlled cord-like heating wire 1H was measured. The measurement position was a position on the surface of the cord-like heating wire 1H away from the S2 and H2 terminals of the temperature control circuit by 1 m in wire distance, and a temperature sensor for direct measurement was fixed in contact with the position to measure a temperature. In the case of no local overheating, the result was 66 C.2 C. Next, a 30 cm square insulating material having an excellent heat insulating function was put on the electric carpet so as to be centered at the temperature measurement point, and the temperature was measured. The result was 67 C.2 C.

(44) The evaluation of each measured value is as follows. [Evaluation of Leak Test]

(45) In occurrence of leak between the S1 and H1 terminals and at the center portion, when the maximum value of the input voltage Vi is used as a temperature control signal regardless of the value of the leak resistance Rx, it is possible to turn the power switch SW OFF at a low temperature lower than the set temperature, whereby it is recognized that safety is ensured. This matches the results obtained in JP 2015-026458(A) which is an earlier application. In leak between the S2 and H2 terminals, when the leak resistance becomes equal to or less than 100 K, the input voltage Vi does not reach the set voltage Vref1, and the power control switch SW is not turned OFF by the output from the output port PB1 of the microcomputer U1 unless the temperature becomes a high temperature higher than the set temperature. In addition, when the temperature of the cord-like heating wire 1H becomes high, leak also becomes great, so that positive feedback which changes the power control switch SW to a side where the power control switch SW is not turned OFF is provided to the power control switch SW, leading to an increase in risk of overheating.

(46) Here, when the difference V between the maximum value and the minimum value of the input voltage Vi in Table 1 is seen in the cells at the S2 and H2 terminals, it is recognized that it is possible to prevent overheating even when leak increases, if specifications are set in which a region of V>0.8 V is used as a criterion for overheating and the power control switch SW is turned OFF by output from the output port PB1 of the microcomputer U1. Therefore, when allowance is considered from the temperature control circuit diagram in FIG. 1 and all the data in Table 1, and the cord-like heating wire 1H of the present embodiment is controlled under two conditions, temperature control is performed based on the maximum value of the input voltage Vi and the power control switch SW is turned OFF with the difference V>0.5 V as an overheating range, it is recognized that it is possible to provide a highly safe electric carpet which is able to prevent overheating.

(47) According to FIGS. 3, 4 and 5 showing the observed input voltage Vi and load current lh, an AC component which clearly synchronizes with a load current in accordance with the leak position is superimposed on the input voltage Vi in the case with leak. This is an effect by a combination of the capacitor C1, the diode D1, and the inter-wire short circuit protection circuit added in the present invention, which demonstrates that it is possible to accurately and stably separate a temperature signal and an overheating signal by software means after these signals are inputted to the voltage comparator even without separating these signals in a stage previous to the voltage comparator as in the related art.

(48) [Evaluation of Local Overheating Test]

(49) It is demonstrated that, by incorporating the conditions of temperature control and overheating protection described in the above [Leak Test] into a control program, even when a strong local insulation operation is performed near the S2 and H2 terminals which are weak against local overheating, a temperature control result which greatly deviates from the set temperature is not obtained, and highly safe temperature control is enabled.

(50) As described above, according to the present invention, while an existing single-wire type cord-like heating wire is used, between both electrodes of a DC stabilization power supply which drives a temperature control section, a fixed resistor with which a capacitor is connected in parallel, a first diode disposed in a forward direction with respect to the power supply, and a temperature detection element wire are connected in series; an inter-wire short circuit protection circuit is included; a voltage of a connection point between the cathode of the first diode and the temperature detection element wire is inputted as an input signal to a voltage comparator; the degree of leak of the polymer layer is determined by detecting the difference between a maximum value and a minimum value of the input signal on a time axis; and the temperature control section performs control such that a heating signal is not outputted when the difference increases to reach a predetermined set value. Thus, it is possible to provide a warming temperature control device which prevents overheating with high accuracy and stability to ensure safety and is excellent in economy.