JPS5833501Y2 - heat pump - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a defrosting device for a heat pump that defrosts efficiently.

Generally, a heat pump reduces the pressure of refrigerant liquid using an expansion valve and sends it to a low-pressure evaporator, where it absorbs and evaporates ambient heat, and the generated vapor is sucked into a compressor and compressed by the power applied to it. This high-temperature, high-pressure gas is led to a condenser, where it is liquefied by dissipating heat to water, the atmosphere, etc., and is received in a liquid reservoir, from which it is led to an expansion valve to form a heat cycle.

This heat pump can also be used for indoor cooling or heating depending on the installation state of the evaporator and condenser.

In such a heat pump, in order to maintain its cooling and heating effects effectively, it is necessary to periodically remove frost adhering to the evaporator to prevent a decrease in evaporation power.

In addition, as a defrosting means for a heat pump, the heat cycle of the heat exchanger (condenser and evaporator) installed indoors and outdoors is temporarily switched using a four-way valve, and the heat radiation and heat absorption states are reversed. Defrosting is carried out by

Conventionally, defrosting devices for heat pumps constantly monitor the temperature on the inlet side of the evaporator using a defrosting thermostat, etc., and when the temperature falls below a certain value, the four-way valve is switched based on the detected output to defrost. There is something to be done.

However, in a device like this that directly detects the temperature on the inlet side of the evaporator to perform defrosting, especially when the heat pump is used as a heater, the amount of refrigerant circulation is limited when starting the heat pump when the outside temperature is low. Since the refrigerant leaves the expansion valve and heads toward the evaporator, the pressure is reduced and the evaporation temperature becomes lower than normal.

As a result, the defrosting thermostat operates and enters the defrosting state (malfunction) even though no frost has formed yet.

The present invention was devised to eliminate the above-mentioned drawbacks, and provides a defrosting device for a heat pump that can defrost properly according to the amount of frost formation without malfunctioning.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Figure 1 shows the heat cycle of a heat pump.
In the figure, 1 is a compressor, 2 is a four-way valve, 3 is an evaporator, 4 is an expansion valve, and 5 is a condenser.

The defrosting device according to the present invention generally includes a first temperature detector 7 that constantly monitors the temperature on the inlet side of the evaporator 3 of the heat pump to detect the defrosting temperature, and a first temperature detector 7 that constantly monitors the temperature on the outlet side of the evaporator 3. A second temperature detector 9 detects the defrosting temperature.

That is, the first temperature detector 7 detects the temperature on the inlet side of the evaporator 30 using the heat sensitive section 6 provided between the evaporator 3 and the expansion valve 4.

Further, the second temperature detector 9 detects the temperature on the outlet side of the evaporator 3 using a heat sensitive section 8 provided between the evaporator 3 and the compressor 1.

The four-way valve switching circuit (defrosting control circuit) shown in FIG. 2 is configured to be controlled according to the operations of the first and second temperature detectors 7 and 9.

This four-way valve switching circuit includes a contact 7b and a relay coil R of the first temperature detector 7 connected in series between the power supply PN bus, and a second temperature sensor connected in series between the power supply PN bus. The contact 9b of the detector 9, the relay coil R
and a four-way valve coil 2L, between the contact 7b of the first temperature detector 7 and the relay coil R, and between the contact a of the relay coil R and the four-way valve coil 2L. are connected.

The first temperature detector 7 opens its contact 7b when the temperature at the inlet side of the evaporator 30 drops to t1, which requires defrosting, and closes again when the temperature rises to t2, which is sufficient to complete defrosting. The second one is also set to prevent malfunction.
The temperature detector 9 is set to temporarily open its contact 9b when the temperature at the outlet side of the evaporator 3 drops to a temperature t3 (>tl) that requires defrosting.

The operation of the heat pump defrosting device according to the present invention configured as described above will be described below.

1. During normal operation of the heat pump, the evaporator 30
The first and second temperature detectors T are provided on both the inlet side and the outlet side.

9 operating point t1. Since the temperature is higher than t3, the contacts 7b and 9b are closed and the four-way valve coil 2L is in an excited state.

From this operating state, frost gradually builds up on the evaporator 3 from the inlet side to the outlet side of the evaporator 30, and the temperature of the evaporator 3 decreases to a temperature that requires defrosting.

That is, the temperature on the inlet side of the evaporator 3 is t1, and the temperature on the outlet side is t3.
When the temperature drops to 1, the first and second temperature detectors 7 and 9 operate to open their contacts 7bt9b.

As a result, the four-way valve coil 2L is demagnetized, the heat cycle is switched as described above, and defrosting is started using the hot gas.

When defrosting is completed and the temperature on the inlet side of the evaporator 30 rises to t2 by 1, the contact 7b of the first temperature detector 7 closes again and the four-way valve coil 2L is energized, thereby returning the heat pump to normal operation. return to the state.

That is, at the time when the contact 7b is about to be re-closed at the temperature t2, the contact 9 of the second temperature detector 9 for preventing malfunction is generally closed.
b is closed, but since the relay coil R is not energized at that time, the four-way valve coil 2L is not energized.

Furthermore, when the heat pump is started when the outside air is low temperature, the amount of refrigerant circulation is small, so the refrigerant leaving the expansion valve 4 and heading toward the evaporator 3 is under reduced pressure and has a lower evaporation temperature than normal.

As a result, the inlet side of the evaporator 30 drops to a very low temperature below the operating point t1 of the first temperature detector 7, and the first temperature detector 7 operates to open its contact 7b, but the evaporator 30 On the outlet side of 1, when the refrigerant reaches the outlet side, the temperature of the refrigerant itself rises due to heat absorption from the outside air, so there is a second
Since the operating temperature t3 of the temperature detector 9 does not drop by 1, the contact 9b remains closed, and as a result, the relay coil R is self-held and the four-way valve coil 2L continues to be energized.

Therefore, the heat pump continues to operate normally without malfunctioning.

Since the second temperature detector 9 for preventing malfunctions only needs to detect the temperature of the open contact, the contact mechanism does not require a snap action, and its contact reliability is not particularly required.

Therefore, a simple and inexpensive second temperature sensor 9 is sufficient.

3 shows a second embodiment of the present invention, in which a timer 10 is connected in parallel with the contact 7b of the first temperature detector 7 of the four-way valve switching circuit.

In this case, even if the frost completely melts after the defrosting device according to the embodiment starts defrosting in a cold and windy climate, the low-temperature part of the evaporator 3 remains at the re-closing operating temperature t2t of the first temperature sensor 7. In order to prevent this, the timer 10 will force the defrost operation after a certain period of time (approximately 10 minutes) has passed after the defrost has started. It is configured to remove the frost condition.

That is, after the start of defrosting (the contact 7b is closed to the c2 side and the four-way valve coil 2L is demagnetized), the broken first temperature sensor 7 operates again to close even after the set time of the timer 10 has elapsed (the contact 7b is not closed (closed to the cl side), the timer 10 operates to close its a contact and excite the four-way valve coil, thereby returning the heat cycle to its original normal operating state.

Further, FIG. 4 shows a third embodiment of the present invention, in which a thermostat 11 (its heat sensitive part 12) for detecting the outside air temperature is added as shown by the dotted line in FIG. The contact 11b is connected in series to the contact 9b of the second temperature detector 9 for preventing malfunction in the four-way valve control circuit.

Normally, the amount of frost formed has an almost inverse relationship with the outside temperature, and the higher the outside temperature, the more the amount of frost formed (however, if the outside temperature is high enough, it will not form frost but will form dew, so this case is excluded. ), and when the outside temperature is high, it is desirable to raise the defrosting operating temperature.

In the defrosting device for a heat pump according to this embodiment, defrosting is performed appropriately depending on the state of the outside air temperature while monitoring the temperature on the low temperature side of the evaporator and the outside air temperature.

That is, the operating temperature of the first temperature detector 7 (opening temperature of the contact 7b) is set to a high value, and the operating temperature of the disconnected outside air temperature detection thermostat 11 is set to a low value, and when the outside air temperature is low, the outside air temperature detection thermostat is set to a high value. Defrosting is started from the operating point 11, and when the temperature is high, defrosting is started from the operating point of the first temperature detector 7.

Of course, even in this case, malfunctions are prevented by the second temperature detector 9 for malfunction prevention as described above, and if necessary, the timer 10 (in this embodiment, the b contact of relay R) (which controls this timer circuit) is forced to release the timer circuit.

As described above, the defrosting device for a heat pump according to the present invention constantly monitors the temperature at the inlet side of the evaporator of the heat pump, and has a contact that opens at a temperature t1 that requires defrosting and closes at a temperature t2 that is sufficient to complete defrosting. A first temperature detector having a
a second temperature sensor having a contact that opens at a temperature t3 higher than t2 and lower than t2, and a contact and a relay coil of the first temperature sensor connected in series in sequence between a power supply bus;
A contact point of the second temperature detector, a contact point of the relay coil, and a four-way valve coil are connected in series in series between the power supply bus, and between the contact point of the first temperature detector and the relay coil. Since the contacts of the relay coil and the four-way valve coil are connected, the rain detection signal from the first and second temperature detectors causes the defrosting state to be entered, causing a malfunction when starting the heat pump when the outside temperature is low. It has excellent effects such as being able to prevent.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a heat cycle showing one embodiment of the present invention, Fig. 2 is an electrical connection diagram of a four-way valve control circuit for the same embodiment, and Figs. FIG. 3 is an electrical wiring diagram showing a four-way valve control circuit according to an embodiment of the present invention. 3...Evaporator, 7...First temperature detector, 7b...Contact point of first temperature detector, 9...
...Second temperature sensor, 9b...Contact of second temperature sensor, R...Relay coil, a...
...Relay coil contact, 2L...Four-way valve coil.

Claims (1)

[Scope of utility model registration request] The temperature on the inlet side of the evaporator of the heat pump is constantly monitored, and it is opened at a temperature t1 that requires defrosting, and the temperature t is sufficient to complete defrosting.
A first temperature sensor has a contact that closes when 2 and closes when the temperature at the outlet side of the evaporator is constantly monitored and opens when the temperature at which defrosting is required is higher than tl and lower than t2 at temperature t3. a second temperature sensor having contacts connected in series between the power supply buses; contacts and relay coils of the first temperature detector connected in series between the power supply buses;
a contact point of the first temperature sensor, a contact point of the relay coil, and a four-way valve coil, and a contact point between the first temperature sensor contact point and the relay coil and a contact point of the relay coil and the four-way valve coil. A defrosting device for a heat pump characterized by connecting the