JPS5950037B2 - Defrost control system for refrigeration equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to reducing the starting load after defrosting of a refrigeration system having a heater-type defrost mechanism.

Generally, in refrigerators and the like that employ a heater-type defrost system, the evaporator is heated by a heater, so the pressure on the low-pressure side within the cooling system after defrosting is extremely high.

Moreover, the low pressure side refrigerant gas is in a gas-liquid mixed state,
It is in a dense gas state.

Therefore, if the compressor is started directly from this state, the pressure on the high pressure side will rise very rapidly.
The load placed on the compressor becomes extremely large.

As a result, the compressor becomes nearly locked, an excessive current flows through the compressor motor, the overcurrent prevention device operates, and normal operation cannot continue.

Furthermore, this may cause damage to the contacts of the overcurrent protection device or damage to the compressor motor windings.

An object of the present invention is to forcibly cool the evaporator, which has reached a high temperature after defrosting, to reduce the pressure on the low pressure side, thereby smoothly starting the compressor after defrosting.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

1 is a thermostat for detecting the temperature inside a refrigerator or the like; 2 is a timer having a timer motor 3 and a switching contact piece 4;

A compressor motor 5 is connected at one end to the normally closed contact 8 of the timer 2 and at the other end to the power source 9 via an overload protection device 6 and a starting relay 7.

Reference numeral 10 denotes a fan motor for forcibly circulating cold air produced by an evaporator (not shown) into the refrigerator, and is connected to a power source via a relay contact 12 of a relay 11.

A defrost heater 13 is directly connected to the timer motor 3 and is placed near the evaporator.

14 is a thermostat for detecting the end of defrosting, one end of which is connected to the normally open contact 15 of timer 2, and 16 is the timer motor 3.
This is a relay coil connected in parallel with.

Further, the timer contact piece 4 of the timer 2 is connected to the timer motor 3.
This is generally done by a cam plate (not shown) that rotates at low speed due to the rotation of The normally closed contact 8 has a structure that takes about 2 to 3 minutes.

Next, the operating situation in the above configuration will be explained.

During cooling operation, the switching contact piece 4 of the timer 2 is on the normally closed contact 8 side, and when the thermostat 1 is closed, the compressor 5 is switched on.
is operated, while the timer motor 3 and the blade coil 16
Electricity is supplied through the defrost heater 13, the relay switch 12 is closed, and the fan motor 10 is operated to cool the inside of the refrigerator (section A in FIG. 2).

At this time, the combined resistance of the timer motor 3 and relay coil 16 and the resistance of the Tefloss I/heater 13 are 1000.
The latter is about 40Ω, and most of the voltage is applied to the relay motor 3 and relay coil 16, and the defrost heater 13 generates substantially no heat.

When the predetermined compressor operating time is accumulated and the switching contact piece 4 is switched to the normally open contact 15 side, defrosting is started.

At this time, the defrost completion detection thermostat I.14 is closed and power is applied to the defrost 1 to the heater 13, so power is cut off to the timer motor 3 and relay coil 16, and the operation of the fan motor 10 is stopped. (Figure 2 section B)
.

When the frost is melted by the heat generated by the defrost heater 13 and the temperature of the evaporator reaches a predetermined temperature or higher, the defrost end thermostat 14 is opened, the heat generated by the defrost l-heater 13 is stopped, and the timer motor 3 and fan motor are restarted. Start operation of step 10.

However, as mentioned above, the switching contact piece 4 is still a normally open contact 15.
It takes 2 to 3 minutes of operation of the timer motor 3 for this to switch to the normally closed contact 8 side (section C in Figure 2).
.

The temperature of the evaporator is forcibly lowered by the operation of the fan motor 3, and the pressure on the low pressure side is also lowered at the same time.

This state continues until the switching contact 4 switches to the normally closed contact 8.
Defrosting is performed.

Thereafter, the switching contact piece 4 switches the recompressor 5 to start operation and return to normal cooling operation (second planning section).
.

Therefore, compared to the conventional system in which the compressor and fan motor operate simultaneously after defrosting is completed, residual heat is forcibly removed by the fan motor, and the pressure inside the evaporator can be actively reduced. Since the load when restarting can be reduced, a low-torque compressor can be used.

Further, as an additional effect, water droplets adhering to the evaporator can be drained, so that the amount of frost formed during the next cooling does not increase unnecessarily.

In addition, as for the specific circuit configuration, there is no need for a separate timer or the like to make the fan motor 10 precede the operation of the compressor 5, and the fan motor is operated by independent contacts of a thermostat for inside temperature detection, a timer, and a relay. Since the switching control is controlled, the circuit configuration can be simplified compared to a switch that centrally controls switching using a timer.

As described above, in the present invention, since the timer motor and fan motor are not connected in series, there is no need to set the operating voltage of the timer motor and fan motor by taking into consideration the voltage dividing resistance, and the power supply voltage This will not cause startup problems.

Also, when defrosting, first stop the operation of the compressor and fan motor, start the operation of the defrost heater, then stop the operation of the defrost heater, operate the fan motor, and then operate the compressor. Compared to conventional systems in which the fan motor and compressor operate simultaneously after defrosting, the pressure inside the evaporator is forcibly lowered by operating the fan motor before the compressor operates. Operation after defrosting is easy, and a less expensive low-torque motor can be used.

In addition, since the relay contact that operates when the thermostat for detecting the end of defrosting is opened is connected in series with the fan motor, a separate timer is required to operate the fan motor before the compressor after defrosting is completed. This has the effect of simplifying the circuit configuration without having to do so.

[Brief explanation of the drawing]

FIG. 1 is an electrical wiring diagram showing an embodiment in which the present invention is applied to a refrigerator, and FIG. 2 is a diagram showing its operating state. 2...Timer, 3...Timer motor, 5...Compressor motor, 10...
・Fan motor, 12...Relay contact.

Claims (1)

[Claims] 1 A compressor, a fan motor for forced circulation of cold air, a defrost heater for defrosting, a timer having a switch and a timer motor for stopping the operation of the compressor and energizing the defrost heater, and a timer having a switch to stop the operation of the compressor and energize the defrost heater, and a timer for stopping the operation of the compressor and energizing the defrost heater. A thermostat for detecting the end of defrosting and a relay for controlling the operation of the fan motor, the timer motor and the relay are connected in parallel and connected to a power source via the defrost heater, and the compressor is connected to the timer motor and the relay in parallel. A defrosting control system for a refrigeration apparatus, wherein the timer is connected to a power source via a switch, and the defrosting completion detection thermostat is connected in parallel to the timer motor via a contact on the opposite side of the switch.