JPH0146883B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature control device using a control device such as a microcomputer.

In a temperature control system for a show case that displays and sells products while maintaining them at a desired temperature by cooling or heating the product, after the temperature inside the show case reaches a set value, a microcomputer controls the temperature at a predetermined time interval. or outputs an on/off signal according to the detected temperature of the load,
A control method is known in which each load is controlled to a set temperature by sequentially turning on and off the motor compressor of the cooler of each show case in response to this signal.

Figure 1 shows a control device used in this type of temperature control system, in which on/off signals of a predetermined ratio are sent to a buffer memory 2 at predetermined time intervals from a CPU (central processing unit) 1 using a microcomputer or the like.
is applied via the driver ₃ to drive the relays X1, _X2 , . . .

Relays XL1, XL2,...XLn are connected through the normally open contacts of each relay X1, X2,...Xn, and the motor compressors CM1, CM of each show case are
2,...CMn has the above relays XL1, XL2,...
The normally closed contacts XL1b, XL2b, ..., XLnb of XLn are connected in series, and the motor compressor is activated by turning on and off relays XL1, XL2, ...XLn.
CM1, CM2,...CMn are started or stopped, and the temperature inside each case is controlled to the set value.

In the above circuit, if CPU1 fails, relays X1 to Xn are continuously energized, and relay XL
1, to XLn become excited, motor compressors CM1 to CMn stop, the temperature inside the show case rises, and product loss occurs. In order to prevent this, the output signal of the CPU 1 is applied to the failure detection circuit 4 via the buffer memory 2'.
While a predetermined signal is being generated from the CPU 1, the alarm relay XB is energized via the driver 5 and the buzzer 6 is stopped, while the failure detection circuit 4 The output also disappears, demagnetizing relay XB and making buzzer 6 sound to generate an alarm.

In response to this alarm, the operator switches the changeover switch 7 from the a side contact to the b side contact, and turns on and off the temperature control thermostats 8-1 to 8-n to turn on and off the motor compressors CM1, CM2, . . .
Turn on and off to prevent temperature rise inside the housing.

Note that in FIG. 1, 9 is a suitable power source.

In the conventional control device as described above, if the show case is used in a supermarket or the like, if the above-mentioned CPU 1 malfunctions when the machine is unmanned at night, the changeover switch 7 is switched. Since there is no temperature control, there is a disadvantage that the temperature of the product increases.

This invention was made to eliminate the above-mentioned drawbacks, and eliminates the need for switching operations in the event of a CPU failure.
There is no need to install a separate thermostat, and
The purpose of the present invention is to provide a control device that can reliably control temperature even when a CPU fails. The control device of the present invention connects in series a contact point of the relay that is turned off when the central processing unit is abnormal, to a first relay that is controlled by a heat source on/off signal from the central processing unit, and A thermos that turns on and off depending on whether the temperature of the normally closed contact of the relay or the normally closed contact of the second relay operated by the normally open contact of the first relay and the load is below the set temperature or above the set temperature. A series circuit with a contact point is connected between the heat source and the power source.

According to the above configuration, when the central processing unit is normal, the contact of the relay for abnormality detection is on, and therefore the first relay receives the heat source on or off signal from the central processing unit. It is turned on and off accordingly. The signal from the central processing unit is, for example, a signal that is on at a set first time and off at a set second time.

When the central processing unit malfunctions, the contact of the abnormality detection relay is turned off, and the normally closed contact of the first relay or the normally closed contact of the second relay is turned on.

After the normally closed contact of the first or second relay is turned on, power is supplied to the heat source by the thermostat contact, which turns on or off depending on whether the temperature of the controlled object is below or above the set value. is controlled.

An embodiment of the present invention will be described below with reference to the drawings. Note that parts equivalent to those in the embodiment shown in FIG. 1 are given the same reference numerals, and explanations of those parts will be omitted.

In Fig. 2, the common side terminals of relays X1 to Xn are connected to one terminal of power supply 9 via the normally open contact XB-1a of relay XB, and when relay XB is turned off due to a failure in CPU1, X
1 to Xn are forced to be demagnetized.

On the other hand, relay XL is installed on motor compressor CM1.
The normally closed contact XL1b of No. 1 is connected in series with a temperature sensor 8-1 that turns on and off by detecting the temperature inside the show case. Similarly, for the other motor compressors, a series circuit of the normally closed contact XLnb of the relay XLn and the temperature control thermostat 8-n is connected.

In the above configuration, when the CPU 1 is operating normally, the failure detection circuit 4 outputs a signal that continuously energizes the relay XB, and this output energizes the relay XB, so that the contact XB −
1a is also turned on, and relays X1 to Xn are
It is turned on or off in accordance with a duty cycle operation signal sent from the CPU 1 that is turned on for a predetermined time and off for another predetermined time, and in accordance with this turning on or off, relays XL1 to XLn are also turned off or on, Motor compressor CM1 or
CMn is driven intermittently at predetermined time intervals.

If the CPU 1 fails, the output of the failure detection circuit 4 disappears. When the relay XB is demagnetized, the normally open contact XB-1a of the relay XB is also turned off, and the relays X1 to Xn are demagnetized.

Therefore, relays XL1 to XLn are demagnetized and motor compressor CM1 has contact XL1b.
Power is supplied from the power supply 20 through a series circuit of the thermostat 8-1 and the thermostat 8-1. When the temperature inside the show case falls below the value set in the thermostat 8-1, the temperature regulating thermostat 8-1 is turned off, and the motor compressor CM1 is stopped by turning off the thermostat 8-1. When the temperature inside the show case becomes higher than the value set in the thermostat 8-1, the thermostat 8-1 is turned on and the motor compressor CM1 operates to maintain the temperature inside the show case at the set value. Similar operations are performed for the other motor compressors CM2 to CMn.

In the embodiment shown in FIG.
A series circuit of the normally closed contact X1-1b and the thermostat 8-1 is connected to the motor compressor CM1. For the other motor compressors CM2 to CMn, a series circuit of normally closed contacts X2-1b to Xn-1b of relays X2 to Xn and thermostats 8-2 to 8-n is connected.

In this case, due to the failure of CPU1, the relay
When XB turns off and relays X1 to Xn turn off, motor compressor CM1, for example,
Power is supplied from the power supply 20 via the normally closed contact X1-1b of the relay X1 and the thermostat 8-1, and the motor compressor CM1 is turned on and off by turning on and off the thermostat 8-1, and Temperature control is performed.

As described above, according to the present invention, even if a failure occurs in the CPU, the schedule (duty cycle) operation is automatically switched to the thermostat operation for temperature adjustment, and temperature control is performed. Even if the CPU fails while unattended, the temperature of the thermal load can be controlled reliably.

Furthermore, according to the present invention, there is no need for a changeover switch for troubleshooting as in the past, making the circuit configuration simple, and there is no need to provide a separate thermostat for backup, which also simplifies the configuration. It can contribute to cost reduction.

Note that the load in this invention is not limited to the case.
It can be applied to any thermal load, and can also be applied when the load is heated by a heater.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a conventional circuit of a schedule control device, FIG. 2 is a block diagram showing one embodiment of the present invention, and FIG. 3 is a block diagram showing another embodiment of the present invention. 1...CPU, 2,2'...Batsuhua, 3,5...
...Driver, 4...Failure detection circuit, 8-1 to 8-
n...Temperature control thermostat, X1 to Xn, XL
1~XLn...Relay, XB...Alarm relay,
CM1~CMn...Motor compressor.

Claims (1)

[Claims] 1 A contact point of the relay that turns off when the central processing unit is abnormal is connected in series to a first relay controlled by a heat source on/off signal from the central processing unit, and a normally closed contact of the first relay Alternatively, a normally closed contact of a second relay that operates with a normally open contact of the first relay is connected in series with a thermostat contact that turns on and off depending on whether the temperature of the load is below or above the set temperature. A temperature control device characterized in that a circuit is connected between a heat source and a power source.