JPS62219115A - Temperature control circuit for air conditioner - Google Patents

Abstract

PURPOSE:To execute the indoor temperature control even when a temperature detecting element goes into an abnormal condition by changing over the driving of a compressor from the driving control by means of a comparison output to the driving control by means of the driving signal set beforehand based upon the detecting output from an abnormality detecting part. CONSTITUTION:When a thermister 10 comes to be a disconnecting condition at the time of t1, a detecting value Vf to appear at a connecting point 13 comes to be a zero electric potential, comes to be lower than a lower limit setting value Vrn, and therefore, the output side of the n-th comparator 14n as a disconnection detecting circuit 25 is changed from the L level to the H level. For such a reason, since the output side of an or circuit 23 is changed to the H level, a moving piece 19 of a changing-over switch 17 is changed over from an always closed contact 18 side to an always opened contact 29 side. Thus, a compressor 21 is driven and controlled by the setting driving mode corresponding to the setting driving signal to output from a setting driving signal generating circuit 27 and an indoor temperature control can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a temperature control circuit for an air conditioner.

[Prior Art] Generally, temperature control of an air conditioner uses a thermistor (1) as a temperature detection element and a variable resistor (1) as shown in Fig. 3.
The voltage divided by 2) is set as the detection value Vf, and the fixed resistance (
3) The voltage divided in (4) is set as the set value Vr, this detected value Vf and the set value Vr are compared with the comparator (5), and the comparison output controls the operation of the compressor to control the indoor air. The temperature was controlled to a set temperature.

[Problems to be Solved by the Invention] Therefore, in the conventional air conditioner, when the thermistor (1) becomes short-circuited or disconnected in an abnormal state, indoor temperature control becomes impossible.

For example, if the thermistor (1) is short-circuited, the detected value Vf will always be higher than the set value Vr regardless of the indoor temperature, and the comparator (
In case 5), the indoor temperature is determined to be high, so the compressor does not operate at all during heating operation, making it impossible to control the indoor temperature. In addition, if the thermistor (1) is disconnected, the detected value Vf will always be lower than the set value Vr regardless of the indoor temperature, and the comparator (5) will judge that the indoor temperature is low, so the compressor will not work at all during cooling operation. It won't work, making it impossible to control the temperature inside the room.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to obtain a temperature control circuit for an air conditioner that can control indoor temperature even if the temperature detection element (thermistor) is short-circuited or disconnected. The purpose is to

[Means for Solving the Problems] The temperature control circuit according to the present invention compares a detection value detected using a temperature detection element with a preset setting value, and controls the operation of the compressor using the comparison output. In an air conditioner that performs temperature control by controlling, an abnormality detecting section detects an abnormality of the temperature detecting element, and based on a detection output from the abnormality detecting section, operation of the compressor is controlled by the comparison output. The present invention is characterized by comprising an operation switching unit that switches from the control mode to the operation control based on a preset operation signal.

[Operation] When the temperature detection element is in an abnormal state such as short circuit or disconnection, a detection signal is output from the abnormality detection section. Based on this detection output, the operation switching section switches the operation of the compressor from operation control based on the comparison output to operation control based on a preset operation signal. Therefore, even if the temperature detection element is in an abnormal state, the operation of the compressor is controlled by a preset operation signal, making it possible to control the indoor temperature.

[Embodiment] FIG. 1 shows an embodiment of the present invention, and in this figure, (10) is a thermistor as a temperature detection element. One terminal of the thermistor (10) is connected to the Vcc power supply terminal (11), and the other terminal is connected to the variable resistor (12).
is grounded through. The connection point (13) between the thermistor (10) and the variable resistor (12) is the first, second...nth comparator (14s) (142)-(14n-1)
(14n) and supplies the detected value Vf. The Vcc power supply terminal (11) is connected to the first, second,... nth, and (n+1)th resistors (R1) (R2)... (Rn) (Rn+t) as fixed resistors for setting the reference voltage. Grounded. The connection point between the first resistor (R1) and the second resistor (R2) is connected to the input side of the first comparator (14m), and the second resistor (R2) and the third resistor (R3)
The connection point is connected to the 10 input side of the second comparator (142), and the following connections are made in the same way, so that the first, second,...n-th comparators (141), (142),...(14n-) 1) (14
Set values Vrt, Vr2, .
...Vrn-4, Vrn is supplied. Upper limit setting value V
rl and the lower limit set value Vrn are set so as to satisfy Vrn<Vf<Vrl when the thermistor (10) is normal.

Said second, third... n-1th comparators (142) (14
3) The output side of (14n-s) is coupled to a temperature input determination circuit (15), and this temperature input determination circuit (15) outputs indoor temperature data corresponding to the combination of comparison outputs. .

On the output side of the temperature input determination circuit (15), a normally closed contact (18) of a changeover switch (17) inserted into the signal line (Q) and a movable piece (19) are connected to the compressor control circuit (16). and a compressor (21) via a common terminal (20), and this compressor (21) performs a predetermined operation corresponding to an operation control signal from the compressor control circuit (16) based on the indoor temperature data. Controlled by mode.

The output side of the first comparator (14t) is connected to the inverter (2
2), and the output side of the n-th comparator (14n) is coupled to the other input side of the OR circuit (23). The first comparator (141) and the inverter (22) are connected to a short circuit detection circuit (
24), the n-th comparator (14n) forms a disconnection detection circuit (25), and the short circuit detection circuit (24), disconnection detection circuit (25), and OR circuit (23) form an abnormality detection section. (26) is formed. A set operation signal generation circuit (27) and a switch drive circuit (28) are coupled to the output side of the OR circuit (23). The setting operation signal generation circuit (27) is composed of an astable multivibrator formed using a timer IC, for example, and generates an abnormality detection signal (as shown in FIG. 2(a)) from the OR circuit (23).
When an H level signal (H level signal) is input, the H level period is the first set time τ1 (e.g. 8 minutes),
It is configured to output a set operation signal in which the L level period is a second set time of 2 (for example, 12 minutes) and the repetition period is T (=τ1+τ2). The first and second set times τ
1. τ2 assumes the standard usage situation of the air conditioner,
The operating mode is set such that the on time of the compressor (21) is τri and the off time is τ2. The output side of the setting operation signal generation circuit (27) is connected to the changeover switch (17).
is connected to the normally closed contact (29). The switch drive circuit (28) includes voltage dividing resistors (30) and (31);
A switching transistor (32) whose base is connected to the connection point of these resistors (30) and (31), and the collector of this transistor (32) and the Vcc power supply terminal (11)
The movable piece of the changeover switch (17) is inserted between the
19) and a relay coil (33) that drives the relay coil (33).

The changeover switch (17), the setting operation signal generation circuit (2
7) and the switch drive circuit (28) are connected to the operation switching section (3).
4).

Next, the operation of the above embodiment will be explained. First, a case where the thermistor (10) is normal will be described. The detected value Vf appearing at the connection point (13) and the set values Vr2, Vr
3... Vrn-1 is compared with the second, third... n-1 comparators (142) (143)... (14n-s), and the comparison output is sent to the temperature input judgment circuit ( 15) to the compressor control circuit (16) as indoor temperature data. Based on the operation control signal output from the compressor control circuit (16) to the compressor (21) via the normally closed contact (18) of the changeover switch (17), the movable piece (19), and the common terminal (20). The operation of the compressor (21) is controlled in a predetermined operation mode corresponding to the indoor temperature data.

When this thermistor (10) is normal, the upper limit set value Vr1 is higher than the detected value Vf, and the lower limit set value Vr1 is higher than the detected value Vf.
Since n is set lower than the detection value Vf, the output side of the first comparator (14s) is at H level, and the output side of the nth comparator (14s) is set to H level.
The output side of n) is at L level. Therefore, the output side of the OR circuit (23) is at L level and the switch drive circuit (
Since the transistor (32) of the selector switch (17) is off, the movable piece (19) of the changeover switch (17) does not operate and the normally closed contact (1
8) Connected to the side.

Next, a case where the thermistor (10) becomes abnormal will be described.

1. Sometimes, when the thermistor (10) becomes short-circuited, the detected value Vf appearing at the connection point (13) becomes approximately Vcc, which is higher than the upper limit setting value Vr1, so the short-circuit detection circuit (24
) of the first comparator (14s) changes from H level to L level.
The level changes to the output side of the OR circuit (23) as shown in Figure 2 (
An abnormality detection signal (H level signal) as shown in a) appears, and this signal is input to the setting operation signal generation circuit (27) and the switch drive circuit (28). Therefore, the transistor (32) of the switch drive circuit (28) turns on,
The relay coil (33) is energized and the changeover switch (17) is activated.
The movable piece (19) moves from the normally closed contact (18) side to the normally closed contact (
29) side. -Force setting operation signal generation circuit (2
7), the H level period is τ1 (e.g. 8 minutes) and the L level period is τ2 (8 minutes) as shown in Figure 2(b).
For example, at 12 minutes), a set operation signal with a repetition period of T (= τ1 + τ2) appears, and this operation signal is applied to the changeover switch (
17) through the normally closed contact (29), the movable piece (19), and the common terminal (20) to the compressor (21), so the compressor (21) performs the set operation corresponding to this set operation signal. The operation is controlled by the mode, and the indoor temperature is controlled.

Furthermore, if the thermistor (10) becomes disconnected during L1, the detected value Vf appearing at the connection point (13) becomes zero potential and lower than the lower limit set value Vrn, so the disconnection detection circuit (2
5) The output side of the n-th comparator (14n) changes from L level to H level. Therefore, OR circuit (23)
The output side changes to H level as shown in Fig. 2(a), so the selector switch (1
The movable piece (19) of 7) switches from the normally closed contact (18) side to the normally closed contact (29) side, and the compressor (21) responds to the set operation signal output from the set operation signal generation circuit (27). The operation is controlled in the set operating mode, and the indoor temperature is controlled.

[Effects of the Invention] The temperature control circuit for an air conditioner according to the present invention includes an abnormality detection section that detects abnormalities such as short circuits and disconnections of the temperature detection element, and a detection output from this abnormality detection section as described above. Since it is equipped with an operation switching section that switches the operation of the compressor from operation control based on a comparison output to operation control based on a preset operation signal, even if an abnormal condition such as a short circuit or disconnection of the temperature detection element occurs, , the compressor is controlled by preset operating signals. Therefore, even if the temperature detection element is in an abnormal state, the indoor temperature can be controlled.

[Brief explanation of drawings]

Fig. 1 is an electric circuit diagram showing an embodiment of the temperature control circuit of an air conditioner according to the present invention, Fig. 2 is a waveform diagram showing the operation of the setting operation signal generation circuit, and Fig. 3 is an air conditioner in a conventional example. FIG. 3 is an electrical circuit diagram showing a part of the temperature control circuit of the FIG. (10)...Thermistor (temperature detection element), (14s
) to (14n)... Comparator, (17)... Changeover switch, (21)... Compressor. (24)... Short circuit detection circuit, (25)... Disconnection detection circuit, (26)... Abnormality detection section, (27)... Setting operation signal generation circuit, (28)... Switch drive circuit,
(34)...Operation switching section, Q...signal line, Vf...
・Detected value, Vr□~Vrn...set value.

Claims (3)

[Claims] (1) In an air conditioner that compares a detected value detected using a temperature detection element with a preset set value and controls the operation of a compressor using the comparison output to control the temperature, the temperature detection an abnormality detection section that detects an abnormality in the element; and an operation switching section that switches the operation of the compressor from operation control using the comparison output to operation control using a preset operation signal based on the detection output from the abnormality detection section. A temperature control circuit for an air conditioner, comprising: (2) The abnormality detection section includes a short circuit detection circuit that detects a short circuit in the temperature detection element, a disconnection detection circuit that detects a disconnection in the temperature detection element, and a circuit coupled to the output sides of the short circuit detection circuit and the disconnection detection circuit. A temperature control circuit for an air conditioner according to claim 1, comprising an OR circuit. (3) The operation switching section includes a set operation signal generation circuit that outputs a preset operation signal based on the detection output from the abnormality detection section, and a normally open contact connected to the output side of this set operation signal generation circuit, and a changeover switch in which a normally closed contact and a common terminal on one movable side are inserted into a signal line that sends an operation control signal to the compressor based on a comparison output; 3. A temperature control circuit for an air conditioner according to claim 1 or 2, comprising a switch drive circuit for switching the switch from a normally closed contact side to a normally open contact side.