JPH04413Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a temperature control circuit for electric heating devices such as electric carpets.

FIG. 1 shows an example of a conventional electric carpet temperature control circuit. This temperature control circuit connects a heater 3 to a power source 2 via relay contacts 1a, 1a to form a heater circuit, while one side of a heat-sensitive resistor 4 made of polyamide resin or the like having negative temperature-impedance characteristics A heat-sensitive electrode 5 made of aluminum foil or the like is stretched on the surface of the heat-sensitive resistor 4, and the heater 3 is stretched on the other side of the heat-sensitive resistor 4, and both surfaces are covered with an insulating film (not shown) to form a heat-sensitive element 6. This heat-sensitive element A partial pressure corresponding to the impedance shown by the heat-sensitive resistor 4 of No. 6 is applied to the heat-sensitive electrode 5, a change in impedance of the heat-sensitive resistor 4 due to temperature change is generated as an output voltage change, and this output voltage is applied to the input/output circuit. The temperature is detected by the temperature detection circuit 9 through the output part of 8, and the detected value is compared with a reference value given corresponding to a predetermined set temperature in the next stage switching circuit 10, and the next step is determined by the comparison judgment output. The transistor 11 in the stage is turned on and off, the relay excitation coil 1 connected in series to this transistor 11 is controlled to be driven, and the power supply path of the heater circuit is connected and disconnected by the on and off operation of the relay contacts 1a and 1a. It is designed to control temperature. In FIG. 1, 12 is a DC power supply circuit for driving the oscillation circuit 7. In FIG.

In this temperature control circuit, the reference value input to the switching circuit 10 is provided by a voltage dividing circuit or the like, and the resistance value of a variable resistor in the voltage dividing circuit is adjusted by operating a temperature setting dial.
The reference value is configured to be set to a value corresponding to a desired temperature.

However, even if a predetermined temperature is set by operating the temperature setting dial, it takes a considerable amount of time to reach the target temperature because the temperature rises slowly in the initial stage of energization. Figure 2 shows the temperature rise characteristics. In order to avoid such a delay in rising and reach the target temperature early, conventionally, the temperature setting dial is set to a temperature scale larger than the target temperature at the initial stage of energization to forcibly accelerate the temperature rise and reach a predetermined temperature. After a certain amount of time has elapsed, the temperature setting dial is readjusted to the target temperature scale, but this method has the drawback of being cumbersome and difficult to use.

In addition, electric heating devices such as electric carpets have a structure in which the heater is covered with a surface material, a back material, nylon, etc., so it is difficult for the heat generation distribution to be uniform due to the heat capacity of these materials, and it is difficult for the heater to reach a predetermined set temperature. In the meantime, the power supply path of the heater circuit will be turned on and off several to several dozen times, and the temperature rise time tends to be further delayed.

Therefore, the purpose of this invention is to provide an easy-to-use product that does not require troublesome operations such as changing the setting of the temperature setting dial midway through, and can significantly shorten the temperature rise time to the desired set temperature. The present invention provides a temperature control circuit for an electric heating device.

An embodiment of this invention is shown in FIGS. 3 and 4. In other words, the temperature control circuit of this electric heating device is
Among the output signals of the switching circuit 10 in the conventional example, it is set in response to the first L output (first heat source drive circuit off control output) that turns off the transistor 11, and is applied to the switching circuit 10 for a predetermined period of time. A timer 13 is provided to correct the input reference value to be lower than the value corresponding to the set temperature by a predetermined value (the detected temperature value input to the switching circuit 10 becomes smaller as the detected temperature increases), and the timer 13 performs a counting operation. Only while
The temperature rise time is accelerated by operating the temperature control circuit with a temperature higher than the desired temperature as the target temperature.

FIG. 4 shows its specific circuit configuration. In the figure, a voltage divider circuit 1 inputs a reference value to a reference value input terminal of a comparator constituting a switching circuit 10.
4 are fixed resistors 15 and 16 connected in series between the DC voltage power supply +V _DD and the ground, and the DC voltage power supply +
It consists of a variable resistor 17 connected between V _DD and ground, and a fixed resistor 18 connected between the sliding tap 17a of this variable resistor 17 and the connection midpoint N of the fixed resistors 15 and 16, and A reference value correction circuit 21 consisting of a series circuit of a transistor 19 and a fixed resistor 20 is connected between point N and the ground, and the timer 13 is
When the transistor 19 is turned on in response to the output, the fixed resistor 20 is connected to the fixed resistor 16 of the voltage divider circuit 14.
are connected in parallel.

The timer 13 turns off the transistor 11 among the outputs of the switching circuit 10 as described above (therefore, the relay excitation coil 1 connected in series with the transistor 11 stops driving, and the relay contacts 1a, 1a of the power supply path are turned off). It is set upon receiving the first L output (turns off), continues to output an H output that turns on the transistor 19 of the reference value correction circuit 21 by counting a single operation for a predetermined set time, and thereafter maintains the L output state. Configure by behavior type.

The variable resistor 17 forming part of the voltage dividing circuit is
The sliding tap 17a is configured to interlock with a temperature setting dial (not shown).
By changing the position of a, the voltage at the connection midpoint N of the voltage dividing circuit 14, that is, the reference value, is changed.

The operation of the temperature control circuit of this electric heating device is as follows.

When the temperature setting dial is operated to start energizing according to the desired set temperature scale, the switching circuit 10 switches between the reference voltage obtained from the connection midpoint N of the voltage dividing circuit 14 and the temperature detection value obtained from the heat sensitive element 6. is connected, and the transistor 11 is turned on by the H and L comparison outputs of the switching circuit 10.
When the timer 13 receives the first L output from the switching circuit 10, the timer 13 continues to output an H output for a predetermined period of time, and the reference value correction circuit 21 The transistor 19 is turned on, and during this time, the voltage dividing circuit 1
A fixed resistor 20 is connected in parallel to the fixed resistor 16 of the switching circuit 10, and a voltage lower by a predetermined value ΔV than the reference value given by the voltage dividing circuit 14 is input to the reference value input terminal of the switching circuit 10, and the temperature setting is determined by that value. The temperature is automatically corrected to the high temperature side by the correction value ΔV (the relationship between the set temperature and the reference voltage level is shown in FIG. 5 with A before correction and B after correction).

Therefore, compared to the conventional temperature rise characteristic shown by the solid line in Fig. 6, the temperature control circuit has a steep temperature rise operation as shown by the broken line in Fig. 6, and the timer 1
After the set time of 3 has elapsed, the same on/off control as in the conventional case is performed using the original reference voltage generated only by the voltage dividing circuit 14 as a comparison reference value.

Here, the effect of activating the timer 13 using the first heat source drive circuit OFF control output will be explained.

The reason why the timer 13 is provided to correct the reference value to a value corresponding to a temperature higher than the set temperature is to prevent unnecessary on/off of the heat source drive circuit and maintain the on state until the heat source temperature reaches the set temperature. The purpose of this is to make the rise of the heat source temperature steeper.

Suppose that the timer 13 is activated in response to power-on, and the reference value correction circuit 2 is activated for a predetermined period of time after power-on.
In the case of a configuration in which one transistor 19 is turned on, the following problem occurs. In other words, in environments where the temperature of a heat source such as a carpet is difficult to rise, such as when the outside temperature is low or the power supply voltage is low, the temperature of the heat source rises to a certain extent and the heat source drive circuit starts to turn on and off. By then, most of the predetermined time set by timer 13 has been consumed,
The original purpose of preventing unnecessary on/off of the heat source drive circuit and maintaining the on state becomes shorter or disappears altogether. For this reason, the predetermined time by the timer 13 ends before the effect of correcting the reference value to a value corresponding to a temperature higher than the set temperature using the timer 13 is sufficiently obtained, and after that, the reference value is becomes a value corresponding to the set temperature, and the rise of the heat source temperature cannot be sufficiently accelerated, resulting in a problem that it takes time for the temperature of the heat source to reach the set value.

However, as in the embodiment, the transistor 11
A configuration in which the timer 13 is activated by the first L output (first heat source drive circuit OFF control output) that turns off the timer 13, that is, the timer 13 is not activated at first, and the predetermined temperature is maintained at the reference value corresponding to the set temperature. Then, by using the output of the timer 13 to shift the reference value to a higher temperature side by ΔV than the value corresponding to the set temperature for a predetermined period of time, the heat source temperature can be adjusted when the outside temperature is low or the power supply voltage is low. Even in an environment where it is difficult to raise the temperature of the electric carpet, it is possible to prevent the situation where the predetermined time set by the timer 13 has elapsed before the heat source temperature reaches the set temperature and the heat source temperature cannot be raised quickly, and the electric carpet can be quickly turned off. The set temperature can be reached.

As a result of this configuration, for a predetermined period of time set by the timer 13 after the first L output (first heat source drive circuit OFF control output) that turns off the transistor 11 is generated, the reference value is lower than the value for the set temperature. is automatically corrected to a lower value, and temperature control is performed until the target temperature is higher than the set temperature. At this time, the generation of the L output that turns off the transistor 11 is stopped, and the initial output that turns off the transistor 11 is stopped. Even after the L output is generated, power continues to be supplied to the heater 3, making it possible to significantly shorten the temperature rise time, and automatically responding to the original set temperature after the time set in the timer 13 has elapsed. When the temperature returns to the reference value and the user readjusts the temperature setting dial midway through, the temperature rise time can be automatically shortened without requiring any troublesome operations.

As described above, the temperature control device for an electric heating device of this invention includes a heat-sensitive element that detects the heat source temperature and outputs a detected value corresponding to the detected temperature, and a heat-sensitive element that outputs a detected value corresponding to the detected temperature, and a predetermined reference value that corresponds to the set temperature. a switching circuit that performs on/off control of the heat source drive circuit based on the comparison judgment output; a voltage dividing circuit that provides the reference value; a reference value correction circuit that corrects the reference value to a value corresponding to a temperature higher than the set temperature when the switching element enters a predetermined operating state; and an output for controlling the first heat source drive circuit off among the outputs of the switching circuit. and a timer that operates at a specified time and then maintains the switching element of the reference value correction circuit in the predetermined operating state for a predetermined period of time, and after receiving the first heat source drive circuit off control output among the outputs of the switching circuit, The reference value is automatically corrected to a value corresponding to a temperature higher than the set temperature by the reference value correction circuit for a period of time, so that the time for the heat source to reach the set temperature is accelerated, so that the temperature rises earlier and When the user adjusts the temperature setting dial etc. over several degrees, there is no need for troublesome operations, and the device is easy to use.

Further, since the timer is activated by the first heat source drive circuit OFF control output among the outputs of the switching circuit and the switching element of the reference value correction circuit is maintained in the predetermined operating state for a predetermined period of time thereafter, the switching element of the reference value correction circuit is kept in the predetermined operating state. Even in environments where the heat source temperature is difficult to rise, such as when the air temperature is low or the power supply voltage is low, the predetermined time set by the timer may elapse before the heat source temperature reaches the set temperature, causing the heat source temperature to rise almost too quickly. There is no problem, and the heat source can quickly reach the set temperature.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a conventional example, Fig. 2 is a diagram showing its temperature rise characteristics, Fig. 3 is a schematic circuit diagram showing an embodiment of this invention, and Fig. 4 is a main part showing its specific configuration. The circuit diagram, FIG. 5 is an explanatory diagram showing the relationship between the set temperature and the reference value in comparison with the conventional example, and FIG. 6 is an explanatory diagram showing the temperature rise characteristic in comparison with the conventional example. DESCRIPTION OF SYMBOLS 1... Relay excitation coil, 1a... Relay contact, 2... Heat source, 3... Heater, 6... Heat sensitive element, 7... Oscillation circuit, 9... Temperature detection circuit, 10
...Switching circuit, 11...Transistor,
12...DC power supply circuit, 13...Timer, 14...
...Voltage divider circuit, 15, 16, 18...Fixed resistance, 1
7...Variable resistor, 19...Transistor, 20
... Fixed resistance, 21 ... Reference value correction circuit.

Claims (1)

[Claims for Utility Model Registration] A heat-sensitive element that detects a heat source temperature and outputs a detected value corresponding to the detected temperature, and a comparison judgment output that compares the detected value with a predetermined reference value corresponding to a set temperature. A heat source driving circuit, a switching circuit for on/off control, a voltage dividing circuit for providing the reference value, and a switching element, which is connected to a part of the voltage dividing circuit so that the switching element is in a predetermined operating state. a reference value correction circuit that corrects the reference value to a value corresponding to a temperature higher than the set temperature when and a timer for maintaining the switching element of the reference value correction circuit in the predetermined operating state, the reference value correction circuit for a predetermined period of time after receiving the first heat source drive circuit off control output among the outputs of the switching circuit. A temperature control circuit for an electric heating device, wherein the reference value is automatically corrected to a value corresponding to a temperature higher than the set temperature to hasten the time for the heat source to reach the set temperature.