JPH0334077Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Technical Field of the Invention] The present invention relates to improvements in temperature detection circuits used in electric carpets and the like. [Technical background of the invention] Some electric carpets are used by selectively switching the first and second heaters so that the heat generating area is the left half, the right half, or the entire surface of the carpet body. In such an electric carpet, the temperature of each heater is controlled, and for example, there is a temperature control device disclosed in Japanese Patent Application Laid-Open No. 176680/1983. As shown in FIG. 2, this temperature control device has heaters 3 and 4 connected to an energization control element 2 that receives a control signal from a voltage comparator 1, and switches 5 and 6 connected to each heater 3 and 4. In addition, the primary electrode 8 of the temperature sensor 7 is connected to one input terminal of the voltage comparator 1, the reference voltage source 9 is connected to the other input terminal of the voltage comparator 1, and the primary electrode 8 of the temperature sensor 7 is connected to the other input terminal of the voltage comparator 1.
The configuration is such that a fixed resistor 11 for compensation is connected to the next electrode 10. In this manner, the voltage comparator 1 outputs an energization signal and a power cutoff signal to the energization control element 2 in accordance with each input voltage applied to the voltage comparator 1, thereby performing temperature control. However, in the above device, the temperature impedance characteristics of the temperature sensor 7 are significantly different between the one-side energization mode and the both-side energization mode of the heaters 3 and 4. The temperature sensor 7 will be explained with reference to the temperature impedance characteristic diagram shown in FIG.
shows the characteristics of curve a in single-side energization mode and curve b in both-side energization mode.As a result, at an operating temperature of 25°C, the resistance is 360kΩ in one-side energization mode and 360kΩ in both-side energization mode.
It becomes 330kΩ, and when the operating temperature is 50℃, it becomes 62kΩ in single-side energization mode and 35kΩ in both-side energization mode.
Therefore, by connecting the fixed resistor 11 in series with the temperature sensor 7 with a resistance value of 27 kΩ, the temperature impedance characteristics at each operating temperature (25° C., 50° C.) are compensated. [Problems with Background Art] By the way, it is known that the impedance of the temperature sensor 7 decreases approximately exponentially with temperature. Therefore, if the impedance of the temperature sensor 7 at 25°C is R ₂₅ , the impedance R _T when the temperature sensor 7 is at T°C is R _T = R ₂₅ e-T-25/K (K is the temperature curve The relationship (coefficient of ) almost holds true as an approximate equation. Considering this, the coefficient K of the temperature curve is K=-T-25/n(R _T /R ₂₅ ), so here, at T=50℃, R _T =35KΩ, T=
Substituting R ₂₅ =330KΩ at 25°C, the coefficient K of the temperature curve becomes K=-50-25/n(35KΩ/330KΩ)=11.14. From this, the impedances are R _T and 2R _T when the temperature sensor 7 is in both-side energization mode where the entire surface is heated and in the one-sided energization mode where half the temperature sensor 7 is heated.
2R becomes ₂₀ . (When heating one half, assuming that one half is 2R _T and the other half is at room temperature 20℃, it is 2R ₂₀ , so this parallel impedance is obtained.) Therefore, R _T = 330e−T−25/ 11.14 (KΩ), the sensor temperature is 20, 25, 30, 35, 40, 45,
The table below shows the full surface (both sides energized) impedance and half surface (one side energized) impedance at temperatures of 50 and 60 degrees Celsius. In addition, here 25
℃, the full surface impedance is 330KΩ and the half surface impedance is 403KΩ, and when the temperature is 50℃, the full surface impedance is 35KΩ and the half surface impedance is 66KΩ, which is slightly different from the value of the conventional device shown in the official bulletin, but this can be determined from the above formula. This is because it is the calculated theoretical value.

[Table] Therefore, if the difference in impedance between the full surface and the half surface at 50℃, that is, 66-35 = 31KΩ, is connected in series with the sensor impedance at the full surface, the corrected full surface impedance will be as shown in the table below at each temperature. It comes to show.

[Table] The table below shows how much the corrected full-plane impedance deviates from the half-plane impedance for each temperature as a ratio.

[Summary of the idea]

The present invention includes a mode changeover switch that switches the first and second heaters to one-side energization mode or both-side energization mode, and a mode switch that detects the heat generation temperature of the first and second heaters and sends an electric signal according to the heat generation temperature. In a temperature detection circuit consisting of a temperature sensor that outputs to a temperature control circuit that controls the power supply to the first and second heaters and a voltage dividing resistor connected in series to this temperature sensor, a mode changeover switch is used to select whether both sides are energized. A compensation switch that is closed is provided, and a first compensation resistor is connected in parallel to the temperature sensor via the compensation switch, and a first compensation resistor is connected in parallel to the voltage dividing resistor via the compensation switch. This is a temperature detection circuit that attempts to solve the above-mentioned problems by including a second compensating resistor. [Embodiment of the invention] An embodiment of the invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a temperature detection circuit according to the present invention. In the figure, H1 and H2 are the first
and a second heater, these heaters H
1.H2 is, for example, the left half of the electric carpet body,
They are each divided into the right half. Mode changeover switches S1 and S2 are connected to one ends of these heaters H1 and H2, respectively, and these mode changeover switches S1 and S2 are opened and closed to selectively heat the left half, right half, or entire surface of the electric carpet body. I'm starting to be able to do it. Further, the other ends of each of the heaters H1 and H2 are commonly connected and connected to a relay contact R _S. This relay contact
R _S is closed by the energization of the relay coil provided in the temperature control circuit 20, and each heater H1,
It is designed to supply power to H2. 21 is a temperature sensor, which is connected to each heater H1, H2.
The first conductor 22 and the second conductor 23 whose one end is connected to the temperature control circuit 20, and the first and second conductor 2
The temperature sensitive layer 24 has an impedance that increases or decreases depending on the temperature change that is present between the temperature sensitive layer 2 and 23. Note that a voltage dividing resistor 2 is connected to the other end of the first conductor 22.
5 is connected, and power is supplied via this voltage dividing resistor 25. Now, SK is each mode selector switch S1, S2
It is a compensating switch that is mechanically interlocked to be closed when both are closed, that is, when the both sides are in energization mode, and one end is connected to the connection point between the first conductor 22 and the voltage dividing resistor 25. is connected. A first compensation resistor R1 is connected to the other end of the compensation switch SK through the compensation switch SK to the temperature sensor 2.
The first compensating resistor R1 is set to have the same resistance value as the impedance of the temperature sensor 21 at room temperature (20° C.). In addition, compensation switch SK
A second compensation resistor R2 having the same resistance value as the voltage dividing resistor 25 is connected between the other end and one end of the voltage dividing resistor 25 via a compensation switch SK.
5 in parallel. Next, the operation of the circuit configured as described above will be explained. In the case of the one-sided energization mode, the mode selector switch S1 or S2 is closed depending on the necessity. In this case, the compensation switch SK is in the open state. Therefore, the first conductor 22 of the temperature sensor 21
A series circuit of the voltage dividing resistor 25 and the voltage dividing resistor 25 is formed. Thus, the detection voltage V _T applied to the temperature control circuit 20 is V _T = R _T /R ₃ + R _T ·V _O (1). Note that R _T is the impedance of the temperature sensor 21, R ₃ is the resistance value of the voltage dividing resistor 25, and V _O is the power supply voltage. Next, when both sides are energized, that is, when mode changeover switches S1 and S2 are both closed, compensation switch SK is closed in conjunction with these mode changeover switches S1 and S2. As a result, the first compensation resistor R1 is connected in parallel to the temperature sensor 21, and the second compensation resistor R2 is connected to the voltage dividing resistor 25.
connected in parallel to Therefore, the resistance value of the parallel circuit of the temperature sensor 21 and the first compensation resistor R1 is half the impedance of the temperature sensor 21 in the one-sided energization mode at room temperature. The combined impedance due to the parallel connection of the resistance values of the first compensation resistor R1 is within a range of 20 to 30°C where the resistance value of the first compensation resistor R1 is close to the impedance of the temperature sensor 21. In this case, the impedance of the temperature sensor 21 when it is alone changes greatly, but as the temperature exceeds 30°C, the degree of change gradually becomes smaller, and as the temperature exceeds 40°C, the resistance value of the temperature sensor 21 changes to the first compensation resistor R.
Since the resistance value is considerably smaller than the resistance value of R1, the influence of the parallel connection of the first compensation resistor R1 is almost eliminated. Therefore, by connecting the first compensation resistor R1 in parallel, the temperature impedance characteristic of the temperature sensor 21 becomes like the curve c shown by the dotted line in FIG. On the other hand, when the compensating switch SK is closed, the voltage dividing resistor 25
Since the second compensating resistor R2 with the same resistance value is connected in parallel, the resistance value of this parallel circuit is equal to the voltage dividing resistor 2.
It is half of the resistance value of 5. This is equivalent to moving curve c in parallel to curve a. That is, the detected voltage V _T is as follows: V _T =R _T/2 /R _3/2 2+R _T/2 V _O (2), which is the same as the detected voltage V _T in the one-sided energization mode. In this way, the detection voltages V _T in the one-sided energization mode and the two-sided energization mode are respectively equal. Then, the temperature control circuit 20 energizes the relay coil by comparing the voltage corresponding to the set temperature and the detected voltage V _T . Then, the relay contact R _S is controlled to open and close, and power is supplied to each of the heaters H1 and H2. In this way, in the above-mentioned embodiment, a compensation switch SK is provided which becomes closed when both the mode changeover switches S1 and S2 are closed, and the closing operation of this compensation switch SK causes the temperature sensor 2 to
A first compensation resistor R1 is connected in parallel to the voltage dividing resistor 25, making the impedance of this parallel circuit half the impedance of the temperature sensor 21 at room temperature. Since this connection makes the impedance of this parallel circuit half that of the voltage dividing resistor 25, the detection voltage V _T becomes equal in both the one-side energization mode and the both-side energization mode. For example, when the power supply voltage V _O is 100V, the resistance values of the second compensation resistor R2 and the voltage dividing resistor 25 are
330KΩ, the resistance value of the first compensation resistor R1 is the impedance of the temperature sensor 21 at 20°C.
Assuming 517KΩ, the detection voltage V _T in both sides (full surface) conduction mode and the detection voltage V _T in one side (half surface) conduction mode are respectively: Full surface V _T =R _T1 R ₁ /R _2/2 +R _T1 R ₁ half surface V _T =R _T2 /R ₃ +R _T2 . Note that R _T1 is the full surface impedance of the temperature sensor 21, and R _T2 is the half surface impedance of the temperature sensor 21. The table below shows the full-plane impedance and the detected voltage at each temperature, and the half-plane impedance and the detected voltage at each temperature.The detected voltage at each temperature is approximate in both double-side conduction mode and single-side conduction mode. temperature detection with high accuracy.

[Effect of idea]

According to the present invention, a compensation switch is provided which is closed when both sides are energized by the mode changeover switch of the first and second heaters, and the closing operation of the compensation switch connects the heaters in parallel to the temperature sensor. Since the first compensating resistor is connected in parallel to the voltage dividing resistor and the second compensating resistor is connected in parallel to the voltage dividing resistor, the difference in temperature impedance characteristics can be extremely minimized in either one-sided or double-sided energization mode. A highly accurate temperature detection circuit can be provided.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a temperature detection circuit according to the present invention, FIG. 2 is a block diagram of a conventional electric carpet temperature control device, and FIG. 3 is a temperature impedance characteristic diagram of a temperature sensor. 20... Temperature control circuit, 21... Temperature sensor,
22...first conductor, 23...second conductor, 24
... Temperature sensitive layer, 25 ... Partial voltage resistance, H1, H2 ...
Heater, S1, S2...Mode change switch,
SK... Compensation switch, R1... First compensation resistor, R2... Second compensation resistor.

Claims (1)

[Scope of utility model registration request] a first and second heater; a mode changeover switch that switches the first and second heaters to a one-sided energization mode or a two-sided energization mode; and a mode changeover switch that detects the heat generation temperature of the first and second heaters; In the temperature detection circuit, the temperature detection circuit includes a temperature sensor that sends an electric signal corresponding to a compensation switch that is closed when the first and second heaters are set to the both-side energization mode by a mode changeover switch; and a first compensation switch that is connected in parallel to the temperature sensor via the compensation switch. and a second compensation resistor connected in parallel to the voltage dividing resistor via the compensation switch, and when the first and second heaters are in a double-sided energization mode, The first compensating resistor and the temperature sensor are connected in parallel to compensate the impedance of the temperature sensor to half of that at room temperature, and the voltage dividing resistor and the second compensating resistor are connected in parallel to output from the temperature sensor. A temperature detection circuit characterized in that the electrical signal generated by the signal is at the same level as in the one-sided energization mode.