JPS6222103A - Temperature control circuit for heater - Google Patents

Abstract

PURPOSE:To attain pleasant temperature control by providing a means changing the setting time of a timer in response to the setting temperature so as to keep the on-of control nearly constant independently of the setting temperature thereby decreasing the on-off control temperature width. CONSTITUTION:Resistors R1a, R1b are inserted to a resistance side deciding the charging speed of a capacitor C1 in a timer circuit TIM by using a switch SW whose on/off depends on the vicinity of the midpoint of a variable resistor VR for temperature setting. Further, the setting time of the timer is switched in 2-stage in response to the change in the setting temperature by connecting the switch SW in parallel with the resistor R1a. When the temperature setting is low, the switch SW is turned off, the resistance RA setting the timer time is expressed as RA=R1a+R1b and the time is set by a period decided with time constant C1RA being a product between the resistor RA and the capacitor C1. When the temperature setting is high, the switch SW is closed, the resistance for setting the timer time is expressed as RB=R1b and the time is set by a period comprising a time constant C1RB.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Part W) The present invention relates to a temperature control circuit for a heater used in electric carpets and the like.

(Background technology) There are many methods for on-off control of electric carpets, etc., but in temperature control that uses the current flowing from the commercial power supply applied to the heater to the temperature sensor as a temperature signal, Since the temperature signal disappears when the power supply is stopped, temperature management for off operation (transition from on state to off state) is controlled based on temperature information from the temperature sensor, and temperature control for on operation (transition from off state to on The operation of transitioning to the current state) is generally controlled for a fixed period of time using a timer.

In other words, when the electric carpet reaches the set temperature, a signal is issued to stop energizing the heater, the timer starts counting at the same time as the energization to the heater is stopped, and when the set time has elapsed, a turn-on signal is issued. energization to the heater is started.

FIG. 6 shows the configuration of a conventional temperature control circuit including a timer circuit as described above, and TIM' is the timer circuit. In the figure, the temperature signal is the resistance R,,R,,
After the voltage is divided to a predetermined value by the variable resistor VR, it is compared with a predetermined value by the comparator CP, and the output of the comparator CP1 drives the transistor Tr and excites the relay Ry connected to its collector circuit. , turn on the relay contact S connected between the commercial power supply AC and the heater H.
It's supposed to turn off. Note that the set temperature is changed by adjusting the variable resistor VR.

Further, the timer circuit TIM' is provided between the output terminal of the DC power supply vc0 and the comparator CP, and when the output of the comparator CP becomes low level, that is, when the power supply to the output terminal H is stopped. After a predetermined period of time has elapsed, the programmable unijunction transistor PIJT becomes conductive, inverting the comparator CP1, and energizing the converter H again.

By the way, in the conventional circuit shown in FIG. 6, the set time of the timer circuit TIM' for counting the off time is not constant regardless of the carpet set temperature. As an example, Figure 7 shows the temporal change in temperature during temperature control of an electric carpet when the off time setting is set to 2 minutes.
When the carpet surface temperature is high in the room as in a.
" is the set off time t. The temperature range cooled within □ (difference in carpet surface temperature between when the current is turned on and when it is turned off; on-off width) ΔTl is thick (as shown in b, the carpet surface temperature is When it is low, the set off time t.

The temperature range ΔT2 cooled within the FF becomes smaller. That is, even if the off time is constant, the on-off width varies depending on the temperature setting of the carpet, resulting in a poor heating sensation.

As a means to solve this problem, set an off time t. FF
There is a way to shorten the time, but this increases the frequency of on-off switching, which poses problems with the lifespan of contacts such as relays that control energization to the load (heater), and it has not been possible to shorten it extremely.

(Object of the Invention) The present invention has been proposed in view of the above points, and its purpose is to change the setting of a timer circuit that counts off time according to the set temperature of an electric carpet, etc.
It is an object of the present invention to provide a temperature control circuit for a heater that can perform comfortable temperature control by reducing the on-off control temperature range.

(Disclosure of invention) The present invention will now be described in detail with reference to the drawings showing embodiments.

1 to 3 are circuit configuration diagrams showing first to third embodiments of the present invention, and the circuit configuration is the same as that shown in FIG. 6 except for the timer circuit TIM. The composition of the evening side is omitted.

However, in the first embodiment shown in FIG. 1, the variable resistor VR for temperature setting is used! A switch Sw whose contacts are turned on and off sequentially in conjunction with the timing is provided in the timer circuit TIM, and contacts 31 to S are connected to the resistor side that determines the charging speed of the capacitor C1.
6 are connected to resistors R, . . . -R1, so that the set time of the timer changes in multiple stages in response to changes in the set temperature. Note that the number of contacts of the switch SW is arbitrary.

In the second embodiment shown in FIG. 2, a switch SW is turned on and off near the center of a variable resistor VR that sets the temperature.
using the capacitor C4 in the timer circuit TIM.
By inserting resistors R, , R0 into the resistance side that determines the charging speed of
I'm trying to switch in stages.

In the third embodiment shown in FIG. 3, two sets of variable resistors are used, one of which is used for temperature setting, and the other variable resistor VR2 is used to connect capacitor C1 in timer circuit TIM. It is used as a resistor to determine the charging speed, and the timer setting time is continuously changed in response to changes in the temperature setting.

Therefore, to explain the operation using Fig. 2 as an example, when the temperature setting is low, the switch SW is in the off state, and the resistance value for setting the timer time is R = R + R, and the time constant with the capacitance of the capacitor C1 The time is set according to the cycle determined by CLRA. Also, when the temperature setting is high, the switch SW is closed, the resistance value for setting the timer time is R11 = "lb", and the time is set at the cycle determined by the time constants C, R. In other words, C1RA>C, R, Tona9: When the set temperature is low, the heater energization off time becomes longer, and when the set temperature is high, the off time becomes shorter, which works to cancel out the degree of cooling.Figure 5 shows when the room temperature is constant This shows the temperature change a when the set temperature is high and the temperature change when the set temperature is low, but since the off time changes as 1. and 12 depending on the set temperature, the on-off temperature fluctuation ΔT1.ΔT are approximately equal.

Next, FIG. 4 shows a fourth embodiment, in which a programmable unijunction cyan transistor PUT is used to switch the timer time in the timer circuit TIM.
The resistance value on the gate side is changed.

Programmable unijunction transistor PUT
Since PUT becomes conductive when the anode potential becomes higher than the gate potential by the junction potential, the time it takes for the programmable unijunction transistor PUT to become conductive by changing the gate potential, that is, the timer. You can change the time. In addition, in FIG. 4, resistors R3, R, and b are connected in series, and a switch SW that turns on and off in conjunction with variable resistor VR for temperature setting is connected in parallel with resistor R3. As shown in FIG. 1 or 3, the switching may be performed in multiple stages or continuously.

(Effect of the invention) As shown above, in the present invention, the set time of the timer @ road that sets the off time is changed in conjunction with the variable resistor that sets the control temperature of the heater. Therefore, regardless of the level of the set temperature, the on-off control temperature range of the surface temperature of the electric carpet, etc. can be kept almost constant, and there is an effect that comfortable temperature control can be performed.

[Brief explanation of the drawing]

1 to 4 are circuit configuration diagrams showing the first to fourth embodiments of the present invention, FIG. 5 is an explanatory diagram of its operation, and FIG. 6 is a circuit diagram of a conventional temperature control circuit. FIG. 7 is an explanatory diagram of the operation. TIM・・・・Timer circuit, VR, VRl, V
R,...Variable resistance, S...Switch, S
1 to S6...Contact, PUT...Programmable unijunction transistor, cp,...
... Comparator, Tr, ... Transistor, Ry ... Relay, H ... Heater,
AC...Commercial power supply, R1~R,,R,,~R□
8'RIs' JblR,,,R3b...Resistance, C□......Capacitor Gmonゝ-L鵠[Co., Ltd.] ShikayuzoU) ward ζ Mata

Claims (4)

[Claims] (1) When the controlled temperature becomes higher than the set temperature, the power supply to the heater is stopped, and the power supply to the heater is started after the time set by the timer after the power supply to the heater has stopped. 1. A temperature control circuit for a heater, characterized in that the temperature control circuit is provided with means for changing the set time of the timer in response to a set temperature, so that an on-off control temperature range is kept substantially constant regardless of the set temperature. (2) As a means of changing the set time of the timer, a contact that opens and closes in conjunction with an external controller that sets the temperature is provided in the resistor circuit that sets the oscillation cycle of the timer, and the timer time is switched in two steps. A temperature control circuit for a heater according to claim 1. (3) As a means of changing the set time of the timer, a multi-stage contact that opens and closes in conjunction with an external controller that sets the temperature is provided in the resistor circuit that sets the oscillation cycle of the timer, and the timer time is switched in multiple stages. A temperature control circuit for a heater according to claim 1. (4) As a means for changing the set time of the timer, two variable resistors are used, one for changing the temperature setting and the other for changing the timer time, so that the timer time can be adjusted in conjunction with changing the set temperature. A temperature control circuit for a heater according to claim 1, which is configured by switching.