JPS6221889Y2 - - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to an air conditioner.

Generally, when an air conditioner is stopped, liquid refrigerant is stored in the evaporator in a saturated state, so when operation is resumed, the liquid refrigerant returns to the compressor, causing the problem of damage to the compressor due to liquid back-up. .

Therefore, as a means to prevent this liquid back-up at the start of operation, the compressor is operated with the liquid pipes closed, and the liquid refrigerant in the evaporator is gasified, sucked into the compressor, and discharged into the condenser. In addition to performing a so-called pump-down operation in which the liquid refrigerant in the evaporator is removed from the evaporator, a low-pressure switch is installed to automatically perform this pump-down operation to ensure that the liquid refrigerant in the evaporator is sufficiently gasified and the liquid back is removed. It is conceivable that the pump-down operation is terminated and the normal refrigeration operation is started when the low pressure falls below a set value to such an extent that no refrigeration occurs.

However, using only this low pressure switch causes the following problem. In other words, in an air conditioner equipped with a temperature-sensitive expansion valve as an expansion mechanism,
In a transient state for tens of seconds or minutes after the start of operation, a drop in low pressure is instantaneously transmitted to the pressure equalization chamber via the external pressure equalization pipe, whereas the drop in low pressure gas in the low pressure gas pipe due to this drop in low pressure The decrease in refrigerant temperature is transmitted to the refrigerant filled in the temperature sensing cylinder via the low pressure gas pipe and temperature sensing cylinder, so there is a time delay due to the heat capacity of the low pressure gas pipe and temperature sensing cylinder, which corresponds to the refrigerant temperature in the low pressure gas pipe. There is a time delay in the transmission of the low pressure to the pressure equalization chamber. For this reason,
The temperature-sensitive expansion valve opens when it detects that the apparent degree of superheat is greater than the set value. As a result, a larger amount of refrigerant flows through the temperature-sensitive expansion valve than is necessary for the refrigerant at the evaporator outlet to actually reach the set superheat degree, and is sucked into the compressor without evaporating in the evaporator. This causes the liquid to drain and become a liquid bag. Therefore, when the amount of liquid refrigerant stored in the evaporator is low, the low pressure switch is activated and the pump is activated before the temperature drop of the refrigerant in the temperature sensing cylinder of the expansion valve follows the drop in refrigerant temperature in the low pressure gas pipe. There is a problem in terminating the down operation.

Furthermore, if the expansion valve is not able to be completely closed due to dust build-up during pump down operation and a minute area is left open, a minute flow rate of refrigerant flows through the expansion valve (because the flow rate is minute, the liquid back up Therefore, there is a problem that the low pressure does not decrease to the set value and pump-down operation continues, making it impossible to shift to normal refrigeration operation. but,
However, even if the low pressure does not drop to the set value, if pump-down operation continues for a certain period of time, the low pressure will drop to some extent and the temperature of the refrigerant in the temperature sensing cylinder of the expansion valve will follow, resulting in a transition to normal refrigeration operation. It is also known from experience that no liquid back-up occurs even if

Therefore, to solve the problem of not being able to transition to normal refrigeration operation, for example, instead of using a low pressure switch, a timer can be used to control pump down operation for a certain period of time to ensure transition to normal refrigeration operation. It is also possible.

However, the amount of liquid refrigerant that accumulates in the evaporator varies depending on the various operating conditions and is not constant, so if you set it with safety in mind, there may be no problem when the amount of liquid refrigerant is large, but when the amount of liquid refrigerant is small, ,
Pump down operation time is too long,
As a result of excessive pump down operation, there is a problem that the low pressure drops too much, that is, the operation runs out of gas, and lubricating oil does not return to the compressor, causing damage to the compressor due to lack of oil film.

Therefore, the present invention was devised in view of the above problems, and the purpose is to enable the temperature drop of the refrigerant in the temperature sensing cylinder to follow the drop in refrigerant temperature in the low pressure gas pipe during pump down operation. To ensure a reliable transition from pump-down operation to normal refrigeration operation, and to prevent gas-starvation operation due to excessive pump-down operation.

In order to achieve this object, the present invention connects the pressure equalization pipe of a temperature-sensitive expansion valve with an external pressure equalization pipe to a communication pipe that communicates with the high pressure side refrigerant pipe, and connects the pressure equalization pipe and the communication pipe to the pressure equalization pipe. A control valve device is installed in the pressure equalization chamber of the expansion valve to selectively guide the refrigerant pressure on the high pressure side and the refrigerant pressure on the low pressure side. When the refrigerant pressure on the side decreases from the upper limit set value to below the lower limit set value, the first actuation signal is switched and a second actuation signal is issued, and when the refrigerant pressure increases from the lower limit set value to the upper limit set value or more, the second actuation signal is activated. A low pressure switch that issues a first operation signal by switching from a signal, and an automatic reset timer that starts counting from the start of compressor operation and issues a count-up signal when a preset predetermined time within several minutes has elapsed. until the timer issues a count-up signal, the refrigerant pressure on the high pressure side is introduced into the pressure equalization chamber by a first actuation signal of the low pressure switch;
The refrigerant pressure on the low pressure side is guided by a second actuation signal, and when the timer issues a count-up signal, the count-up signal of the timer causes the refrigerant pressure to be set in the pressure equalizing chamber regardless of the first and second actuation signals of the low pressure switch. It is interposed in the control circuit of the control valve device so as to guide the refrigerant pressure on the low pressure side.

As a result, in the air conditioner of the present invention, when the compressor starts operating, the refrigerant pressure on the high pressure side is guided to the pressure equalizing chamber by the first actuation signal of the low pressure switch and the expansion valve is activated until the timer issues a count-up signal. Close and perform pump down operation. When the refrigerant pressure on the low pressure side decreases from the upper limit set value of the low pressure switch to below the lower limit set value, the low pressure side refrigerant pressure is introduced to the pressure equalizing chamber by a second actuation signal. Then, the expansion valve starts superheat degree control and performs normal refrigeration operation. At this time, if the low pressure decreases quickly, the expansion valve opens excessively because the temperature decrease of the refrigerant in the temperature-sensitive cylinder cannot follow the decrease in the temperature of the refrigerant in the low-pressure gas pipe. Because this excessive opening occurs and the upper limit set value is usually set about 1 kg/ ^cm2 higher than the lower limit set value, the refrigerant pressure on the low pressure side increases from the lower limit set value to the upper limit set value or higher. Rise. Therefore, the control valve device is controlled by the first actuation signal so as to introduce the refrigerant pressure on the high pressure side to the pressure equalizing chamber again. Therefore, pump down operation is started again. In this way, until the timer issues a count-up signal, the first
The temperature drop of the refrigerant in the temperature sensing cylinder follows the temperature drop of the refrigerant in the low pressure gas pipe while the pump down operation and the normal refrigeration operation are performed by the actuation signal and the second actuation signal. Incidentally, even if the expansion valve opens excessively, it closes immediately again, so that no liquid back up occurs.
Further, when the low pressure decrease is slow, there is no problem with the following point.

When the timer issues a count-up signal, the control valve device is controlled so as to introduce the low-pressure side refrigerant pressure to the pressure equalization chamber regardless of the first and second actuation signals of the low-pressure switch. Refrigeration operation continues.

Incidentally, if the control valve device is a three-way solenoid valve, 1
Since it can be formed with individual valves, it has the advantage of simple control and structure.

Embodiments of the present invention will be described below with reference to the drawings.

The device shown in FIG. 1 is a heat recovery type hot and cold water machine. In FIG. 1, 1 is a compressor, 2 is a water heating condenser, 3 is a water cooling evaporator, 4 is an air side heat exchanger, 5 is a receiver, and 6 is an accumulator.
These devices are connected to each other by refrigerant piping 7.

The compressor 1 has an unloader mechanism, and has a hot water inlet thermometer that detects the hot water inlet temperature of the condenser 2 and a cold water inlet thermometer that detects the cold water inlet temperature of the evaporator 3.
Its compression capacity can be controlled in three levels: %, 50%, and 25% capacity.

Further, 8 is a four-way switching valve, and 9 is a three-way valve.The four-way switching valve 8 and the three-way valve 9 control the flow of refrigerant discharged from the compressor 1, and the air-side heat exchanger 4 The cooling-only operation, cooling-priority operation, heating-only operation, heating-priority operation, cooling/heating balanced operation, and defrost operation are possible. be.

The four-way switching valve 8 uses an existing four-way switching valve having four ports: a high-pressure side port 81, a low-pressure side port 82, and two first and second switching ports 83 and 84. , and the three-way valve 9
The four-way switching valve 8 has one fixed port 91 and two first and second control ports 92, 93, and is configured to be able to adjust the opening degrees of these control ports 92, 93. The high pressure side port 8 of
1 to the discharge port of the compressor 1, and the low pressure side port 8
2 to the accumulator 6, the first switching port 83 to the fixed port 91 of the three-way valve 9, and the second switching port 84 to either the condenser 2 or the evaporator 3. The first control port 92 of the three-way valve 9 is selectively connected to either the evaporator 3 or the condenser 2, and the second control port 93 is connected to the air side. It is connected to the heat exchanger 4.

The three-way valve 9 controls the opening degrees of the control ports 92 and 93 from 0 to 100% by a control motor, and the high-pressure gas refrigerant is exchanged with the condenser 2 on the air side by switching the four-way switching valve 8. It serves as a high-pressure side control valve that allows the low-pressure gas refrigerant evaporated in the evaporator 3 and air-side heat exchanger 4 to flow at a predetermined ratio. .

Therefore, when working as a high pressure side control valve, when the opening degree to the condenser 2, that is, the opening degree of the first control port 92 is between 100% and 0%, the opening degree to the air side heat exchanger 4, that is, the opening degree of the first control port 92 is between 100% and 0%. The opening degree of 2 control port 93 is 0 to 100%.
Therefore, when the opening degree of the first control port 92 is 100% and the entire amount of high-pressure gas refrigerant flows to the condenser 2, it does not flow to the air side heat exchanger 4. In the opposite case, it does not flow to the condenser 2.

Similarly, when working as a low pressure side control valve, the opening degree of the first control port 92 leading to the evaporator 3 is 100~
When it is 0%, the second
The opening degree of the control port 93 is 0 to 100%, and the first
When the opening degree of the control port 92 is 100% and low-pressure gas refrigerant flows from the full-volume evaporator 3, the second control port 93 is closed and no liquid refrigerant flows into the air-side heat exchanger 4.

Moreover, in the above configuration, the second
The switching port 84 is selectively connected to either the condenser 2 or the evaporator 3, and the three-way valve 9
selectively connects the first control port 92 to either the condenser 2 or the evaporator 3, and the second switching port 84 and the first control port 92,
The condenser 2 and the evaporator 3 are reversibly connected, and this connection method uses four check valves 10a.
A four-port valve 10 such as a four-way check valve or a four-way switching valve is used.

However, in the heat recovery type water chiller/heater constructed as described above, the liquid receiver 5 shown in FIG.
In the middle of the liquid pipe 71 connecting between the evaporator 3 and the evaporator 3,
A temperature-sensitive expansion valve 11 having an external pressure equalizing pipe 13 is interposed, and the heat exchanger 4 is connected to an evaporator in the middle of a liquid pipe 72 connecting the liquid receiver 5 and the air side heat exchanger 4. A temperature-sensitive expansion valve 12 having an external pressure equalizing pipe 14 that operates when the pressure equalizing pipe 13
to the low-pressure gas pipe 73 connecting the evaporator 3 and the four-port valve 10, and the pressure equalization pipe 14,
The three-way valve 9 and the air-side heat exchanger 4 are connected to communication pipes 74, and the pressure-equalizing pipes 13 and 14 are connected to the liquid pipes 71 and 72, which serve as high-pressure refrigerant pipes. The communication pipes 13a, 14a are connected to the pressure equalization pipes 13, 14 and the communication pipes 13a, 14a, and the refrigerant pressure on the high pressure side and the low pressure are connected to the pressure equalization chambers (not shown) of the expansion valves 11, 12. Control valve devices 15 and 16, which are three-way solenoid valves that selectively guide the side refrigerant pressure, are installed.

In the configuration shown in FIG. 1, the pressure equalizing pipe 1
The connection positions of 3 and 14 are not limited to the low pressure gas pipe 73 and the communication pipe 74, but are connected to the suction pipe 75.
But that's fine. Further, instead of using one three-way solenoid valve as the control valve devices 15 and 16, two two-way solenoid valves may be used. In the case of a three-way solenoid valve, one port of the solenoid valve is
The expansion valves 11 and 12 can be closed more reliably by communicating with the liquid pipes 71 and 72, which serve as the high-pressure side refrigerant pipes, so that when this solenoid valve is switched, the refrigerant pressure on the high-pressure side, that is, the high-pressure liquid refrigerant, can be introduced into the pressure equalization chamber. It is advantageous in that it can be carried out.

Further, the control valve device 15 configured as above,
The opening/closing control of the pressure equalizing pipes 13 and 14 by 16 is performed at startup and when switching from cooling priority operation to heating priority operation, and the air side heat exchanger 4, which was acting as a condenser,
is an evaporator, and the pressure of the refrigerant on the low pressure side is detected as described below. , 12 are closed.

Further details will be given using the electric circuit shown in FIG.

What is shown in FIG. 2 is the control valve device 15,
16 control circuit, a timer T ₁₀ and two control valve devices 1 are connected to the contact 52c that closes when the compressor 1 is driven.
It is formed by connecting three parallel circuits of 5 and 16 in series.

The timer _T10 starts counting from the start of compressor operation, and issues a count-up signal by a contact that closes when a preset period of time within several minutes (for example, 3 minutes) has elapsed, and automatically resets when the power is turned off. It is something to do. It should be noted that the predetermined time may be set in consideration of safety to the extent that the temperature drop of the refrigerant in the temperature sensing cylinder of the expansion valve can follow the temperature drop of the refrigerant in the low pressure gas pipe and that the liquid does not back up.

Further, the two-way parallel circuit of the two control valve devices 15 and 16 has an upper limit setting value and a lower limit setting value lower than this, and the refrigerant pressure on the low pressure side of the refrigeration cycle varies from the upper limit setting value to the lower limit setting value. A low pressure switch that switches from the first actuation signal and issues a second actuation signal when the voltage drops below a set value, and switches from the second actuation signal and issues the first actuation signal when the lower limit setting value increases to or above the upper limit set value. LPS and said timer
A contact point _T10 is provided in parallel.

The control valve devices 15 and 16 operate to guide the refrigerant pressure on the low pressure side to the pressure equalizing chamber when energized, and to guide the refrigerant pressure on the high pressure side to the pressure equalizing chamber when not energized.

In the figure, _R1 is a normally open contact of a relay that switches the four-way switching valve 8 between cooling priority operation and heating priority operation, and when the relay is energized, the four-way switching valve 8
is switched as shown by the dotted line in Figure 1 to set heating priority operation, and the contact _R1 is closed.

In addition, 64 is a contact that opens only during heating-only operation, 6
3 is a contact that opens only when the heating and cooling loads are equal and balanced operation is performed.

Also, _T11 is a timer, which is the normally open contact of the relay.
It is connected in series with R ₁ and has a contact that opens, for example, 5 seconds after energization and closes when no energization occurs.

Further, _R10 is a relay connected in series with the normally open contact _R1 of the relay through the contact of the timer _T11 , and the normally closed contact is connected to the contact 52C and the timer.
It is inserted in a series circuit with _T10 .

Further, 23D is a contact that opens during defrosting and closes when defrosting ends.

In the configuration shown in FIGS. 1 and 2, the four-way switching valve 8 is positioned as shown by the solid line in FIG. 1 when not energized, and is switched as shown by the dotted line in FIG. 1 when energized. At the solid line position in the diagram, high pressure gas refrigerant is introduced from the compressor 1 to the three-way valve 9, and this three-way valve 9 serves as a high-pressure side control valve to direct the high-pressure gas refrigerant to the condenser 2 and the heat exchanger 4. At the dotted line position in Figure 1, the heat exchanger 4 is used as an evaporator, and the three-way valve 9 is a low-pressure side control valve, so that the evaporator 3 and the heat exchanger 4 The evaporated low-pressure gas refrigerant flows at a predetermined ratio.

The switching judgment of the four-way switching valve 8 is based on the capacity of the compressor 1, which controls the capacity based on the cold water inlet or hot water inlet temperature, and the three-way valve that controls the opening degree of the first control port 92 based on the cold water outlet or hot water outlet temperature. This is done in relation to the opening degree of 9. That is, in the cooling priority operation, the capacity of the compressor 1 is controlled by the cold water inlet temperature, and the opening degree of the three-way valve 9 is controlled by the hot water outlet temperature, and in the heating priority operation, the capacity of the compressor 1 is controlled by the hot water inlet temperature. , the opening degree of the three-way valve 9 is controlled by the cold water outlet temperature, and when the capacity of the compressor 1 is controlled with the opening degree of the three-way valve 9 at 100%, that is, in cooling priority operation, the hot water outlet temperature is When the temperature is lower than the set temperature (42°C), the opening degree of the three-way valve 9 is 100%, and the entire amount of high-pressure gas refrigerant is sent to the water heating condenser 2, the cooling load decreases and the cold water inlet temperature reaches the set temperature. (10°C) and the capacity of the compressor 1 is controlled to, for example, 75%, the four-way switching valve 8 is energized to switch over to the heating priority operation, and in the heating priority operation, the cold water outlet temperature is higher than the set temperature (10°C) and the opening degree of the three-way valve 9 is 100% and the entire amount of low-pressure gas refrigerant is flowing from the water cooling evaporator 3, the heating load decreases and the hot water inlet temperature becomes the set temperature. (42°C) and the capacity of the compressor 1 is controlled to, for example, 75%, the four-way selector valve 8 is de-energized and switched to cooling priority operation.

However, at startup, the cold water temperature is the set temperature (10℃)
If the hot water temperature is lower than the set temperature (42° C.), the four-way selector valve 8 is not energized, but is positioned as shown in FIG. 1, and the cooling priority operation is started.

Therefore, when starting up, when the operation switch (not shown) is turned on, the compressor 1 starts to drive and at the same time the contact point 52C closes, so the timer T ₁₀ starts.
starts counting.

At this startup, the contact 63 in FIG.
64 is closed, but contact _R1 is open, so the control valve device 16 is not energized and the pressure equalizing pipe 1
4 is closed, and the communication pipe 14a is open, so that the refrigerant pressure on the high pressure side is introduced into the pressure equalizing chamber, and the expansion valve 12 is closed.

The control valve device 15 is a low pressure switch LPS.
The low pressure switch LPS is controlled by the opening and closing of the low pressure switch LPS.
When 2 is used as a refrigerant, it closes when the lower limit set value is 2 Kg/cm ² or less (the state in which the second operating signal is issued after switching from the first operating signal), and opens when the upper limit set value is 3 Kg/cm ² or higher (the state where the second operating signal is issued after switching from the first operating signal). By setting the difference between the two setting values small, the refrigerant pressure on the low pressure side is reduced to 3 kg/kg.
cm ² or more, the power to the control valve device 15 is cut off, the pressure equalization pipe 13 is closed, and the communication pipe 13a is opened to guide the refrigerant pressure on the high pressure side to the pressure equalization chamber, and the expansion valve 11
, and the liquid pipe 71 is closed. As a result, pump-down operation is performed, and most of the refrigerant remaining in the evaporator is gasified and sucked into the compressor 1, thereby preventing liquid back up. When the refrigerant pressure on the low pressure side drops to 2 kg/cm ² or less, the switch LPS is closed and the control valve device 15 is energized, so that the connecting pipe 1
3a is closed and the pressure equalization pipe 13 is opened, the refrigerant pressure on the low pressure side is guided to the pressure equalization chamber, and the expansion valve 1 is opened.
1 works normally.

Then, while the contact point of the timer _T10 is open, the control valve device 15 is switched to the low pressure switch LPS.
Therefore, when the refrigerant pressure on the low pressure side quickly drops to 2 kg/cm ² or less due to the first pump-down operation and shifts to normal refrigeration operation, that is, cooling priority operation, the expansion valve 11 Even if a large amount of refrigerant begins to flow due to opening excessively, the refrigerant pressure on the low pressure side rises again to the above 3 kg/cm ² or more, so the low pressure switch LPS opens and the expansion valve 11 closes. Therefore, pump down operation will start again, and therefore,
This helps prevent liquid back-up. The reason why the pump-down operation and the normal refrigeration operation can be repeated in this way is to recover from the delay in the temperature drop of the refrigerant in the temperature-sensitive cylinder when the pressure in the evaporator drops quickly. That is, as time passes due to the repetition, the temperature sensing tube and the low pressure gas pipe are cooled by the refrigerant flowing through the low pressure gas pipe,
This is to enable the temperature sensing tube to detect the same temperature as the refrigerant temperature in the low pressure gas pipe.

Although the refrigerating capacity is hardly exhibited during the above-mentioned repeated operation, this operation time is the predetermined time of the timer _T10 and is several minutes, so there is no problem with the refrigerating operation.

The above control by the low pressure switch LPS is performed until the timer _T10 issues a count-up signal.

Then, when the timer T ₁₀ issues a count-up signal, the contact of the timer T ₁₀ is closed, and from then on, regardless of whether the low pressure switch LPS is open or closed (i.e., the state of the first actuation signal or the second actuation signal The control valve device 15 becomes energized, the refrigerant pressure on the low pressure side is introduced to the pressure equalizing chamber, and the temperature sensing tube is activated immediately after the predetermined time of the timer _T10 in the low pressure gas pipe. Since the refrigerant temperature can be detected, the expansion valve 11 operates normally and normal refrigerant operation is performed.

Note that even if the refrigerant pressure on the low-pressure side does not fall below 2 kg/cm ² despite the pump-down operation, the contact closes when the predetermined time of the timer T ₁₀ has elapsed, so the expansion valve 11 operates as described above. It works normally.

Next, when switching from cooling priority operation to heating priority operation after startup, the relay is activated and the four-way selector valve 8 is switched to the dotted line position in Figure 1, and the air side heat exchanger that was acting as a condenser When 4 becomes an evaporator, contact _R1 of the relay closes, so
Timer T ₁₁ is activated, energizing relay R ₁₀ and turning off timer T ₁₀ . Then, for example, after 5 seconds, the contacts of the timer _T11 open and demagnetize the relay _R10 , so that the timer _T10 starts counting.
Since the contacts 63 and 64 are closed at this time, if the refrigerant pressure on the low pressure side is higher than the above-mentioned 3 kg/cm ² , neither of the control valve devices 15 and 16 is energized, and the pressure equalizing pipes 13 and 14 are All closed, connecting pipe 13
a, 14a are both opened, and both expansion valves 11, 12 are closed. Therefore, a large amount of the liquid refrigerant in the air-side heat exchanger 4, which was working as a condenser, is not sucked into the compressor 1, so that so-called liquid backlog does not occur. When the refrigerant pressure on the low pressure side drops below the above 2 kg/cm ² and the timer T ₁₀
When a predetermined period of time has elapsed, the timer contact closes and the control valve devices 15 and 16 are energized, and the communication pipe 13
a, 14a are closed, pressure equalizing pipes 13, 14 are open,
The expansion valves 11 and 12 operate normally.

In the circuit shown in Figure 2, the contacts of the low pressure switch LPS, which closes when the refrigerant pressure on the low pressure side decreases, and the timer _T10 , which closes when a predetermined time elapses, are combined in parallel. Needless to say, in the case of a low pressure switch that opens when the pressure decreases and a timer contact that opens when a predetermined time has elapsed, both may be combined in series. In this case, the control valve devices 15 and 16 need to be operated in such a way that, contrary to the above, when the power supply is cut off, the communication pipes 13a and 14a are closed and the pressure equalization pipes 13 and 14 are opened.

In addition, in FIG. 1, when performing defrost operation, the air side heat exchanger 4 is used as a condenser, and at the same time as the start of this defrost operation, contact 23D
opens, but this contact point 23D closes at the same time as the defrost operation ends, so even when the heating priority operation is performed after the defrost operation ends, the expansion valve 12 can be closed within a predetermined period of time as described above.

In addition, in FIG. 1, 17 is the pressure equalizing pipe 14.
This is a bypass pipe that is interposed between the liquid pipe 72 and the high pressure liquid pipe section when the air side heat exchanger 4 becomes a condenser. When the air-side heat exchanger 4 is operated as a condenser with a check valve 18 that only allows flow and a high-pressure regulating valve 19, the refrigerant pressure on the high-pressure side is
If the value is lower than the set value of the regulating valve 19, the bypass pipe 17 is opened to send the uncondensed gas to the liquid receiver 5, and the condensed liquid is stored in the air side heat exchanger 4 to be condensed in the heat exchanger 4. It increases the pressure.

Further, 21 is a check valve installed in a liquid pipe 76 connecting the outlet of the condenser 2 and the liquid receiver 5;
Reference numeral 2 denotes a check valve installed in a liquid pipe 77 connecting the air-side heat exchanger 4 and the liquid receiver 5. The liquid pipe 77 is connected in parallel with the liquid pipe 72 in which the expansion valve 12 is interposed, and the flow direction of the liquid refrigerant flowing through the liquid pipe 72 is from the liquid receiver 5 to the air side heat. The flow direction of the liquid refrigerant flowing through the liquid pipe 77 is the direction from the air side heat exchanger 4 to the liquid receiver 5. That is, in heating-priority operation and heating-only operation in which the air side heat exchanger 4 becomes an evaporator by switching the four-way switching valve 8, liquid refrigerant flows from the liquid receiver 5 through the liquid pipe 72 to the air. In cooling-priority operation and cooling-only operation, the liquid refrigerant flows to the side heat exchanger 4 and serves as an evaporator.The liquid refrigerant flows from the heat exchanger 4 to the liquid receiver 5 via the liquid pipe 77.

Further, 23 is a bypass pipe that bypasses the check valve 21 between the liquid receiver 5 and the outlet of the condenser 2, and a solenoid valve 24 that opens during defrosting and acts as an expansion mechanism is installed in the middle. I am intervening.

Further, 25 is a communication pipe 78 connecting the four-port valve 10 and the second switching port 84 of the four-way switching valve 8;
A bypass pipe is provided between the inlet side of the condenser 2 and a solenoid valve 26 that opens during defrosting is interposed in the middle of the bypass pipe 25.

Further, 27 and 28 have one end communicating with the condenser 2 and the air side heat exchanger 4, and the other end communicating with the evaporator 3.
A bypass pipe for refrigerant recovery that communicates with the low-pressure liquid pipe between the expansion valve 11 and the expansion valve 11. In the case where the condenser 2 is not used, and the air side heat exchanger 4 that functions as a condenser is installed in the middle. Electromagnetic valves 29 and 30 are interposed which open when not in use and act as expansion valves.

Although the embodiment described above is a heat recovery type water chiller/heater, the present invention can be similarly applied to a heat pump type air conditioner/heater as shown in FIG. 3 or a cooling only machine (not shown).

In FIG. 3, 31 is a compressor, 32 is a four-way switching valve, 33 is an indoor coil that serves as an evaporator for cooling and a condenser for heating, 34 is an outdoor coil that serves as a condenser for cooling and an evaporator for heating, and 35 3 is a liquid receiver, 36 is an expansion valve for cooling, and 37 is an expansion valve for heating.
6 and 37 use temperature-sensitive expansion valves with external pressure equalization pipes 38 and 39, and the pressure equalization pipes 38 and 39 are equipped with communication pipes 38a and 39a and control valve devices 40 and 40, respectively, as in the previous example.
There are 41. Further, 42 and 43 are check valves.

The air conditioner/heater shown in Figure 3 is a general type.
Refrigeration cycles are well known. Then, at the time of startup, the start and end of defrost, and the time of switching between air conditioning and heating, the pressure equalizing pipes 38 and 39 are closed, and the connecting pipe 38
a, 39a are opened and the expansion valves 36, 37 are closed, and this operation is the same as in the previous example.

As described above, the present invention provides a temperature-sensitive expansion valve having an external pressure equalizing pipe, in which a communicating pipe that communicates with the high pressure side refrigerant pipe is connected to the pressure equalizing pipe, and the expansion valve is connected to the pressure equalizing pipe and the communicating pipe. A control valve device is installed in the equalizing chamber of the refrigeration cycle to selectively guide the refrigerant pressure on the high pressure side and the refrigerant pressure on the low pressure side. Switching from the first actuation signal to issue a second actuation signal when the refrigerant pressure decreases from the upper limit set value to below the lower limit set value, and from the second actuating signal when the refrigerant pressure increases from the lower limit set value to the upper limit set value or more. The timer includes a low-pressure switch that issues a first operation signal upon switching, and an automatic reset timer that starts counting from the start of compressor operation and issues a count-up signal when a preset time period within several minutes has elapsed. until the timer issues a count-up signal, the high pressure side refrigerant pressure is introduced into the pressure equalizing chamber by the first actuation signal of the low pressure switch, and the low pressure side refrigerant pressure is induced by the second actuation signal, until the timer issues a count-up signal. is interposed in the control circuit of the control valve device so as to guide the refrigerant pressure on the low pressure side to the pressure equalization chamber by the count-up signal of the timer regardless of the first and second actuation signals of the low pressure switch. By doing so, the following effects are achieved.

In this invention, within a preset time period of several minutes after the start of compressor operation, the low pressure switch activates the pump down operation when the refrigerant pressure on the low pressure side drops from the upper limit setting value to the lower limit setting value. When the lower limit set value rises to or above the upper limit set value, normal refrigeration operation switches to pump-down operation, so even if the low pressure decreases quickly, this pump-down operation and normal refrigeration operation can be repeated. , it is possible to cause the temperature drop of the refrigerant in the temperature-sensitive cylinder to follow the drop in refrigerant temperature in the low-pressure gas pipe. Therefore, even if normal refrigeration operation is initiated by the count-up signal of the timer, the expansion valve will operate upon detecting the actual degree of superheat, and no liquid back up will occur.

In this invention, when the refrigerant pressure on the low pressure side drops from the upper limit set value to the lower limit set value, the pump down operation is changed to normal refrigeration operation, so regardless of the predetermined time of the timer, the pump down operation , the refrigerant pressure on the low pressure side does not drop excessively. Therefore, since the refrigerant pressure on the low pressure side is too low, that is, due to gas starvation operation, lubricating oil does not return to the compressor, and there is no problem of damage to the compressor due to lack of oil film.

The present invention uses the count-up signal of the timer when the predetermined time elapses to ensure a transition to normal refrigeration operation regardless of the first and second activation signals of the low pressure switch. If this is the case, the refrigerant pressure on the low pressure side will not drop to the set value due to dirt in the expansion valve, and normal refrigeration operation will not be possible.

Note that if the control valve device is a three-way solenoid valve, the control and structure will be simplified.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; Fig. 1 is a refrigerant piping system diagram when applied to a heat recovery type water chiller/heater; Fig. 2 is an electric circuit diagram for controlling a control valve device;
FIG. 3 is a refrigerant piping system diagram when applied to a heat pump air conditioner. 11, 12, 36, 37...temperature-sensitive expansion valve, 1
3, 14, 38, 39...External pressure equalization pipe, 13a,
14a, 38a, 39a... connecting pipe, 15, 1
6, 40, 41... Control valve device, T ₁₀ ... Timer, LPS... Low pressure switch.

Claims (1)

[Claims for Utility Model Registration] (1) A connecting pipe that communicates with the high pressure side refrigerant pipe is connected to the pressure equalizing pipe of a temperature-sensitive expansion valve having an external pressure equalizing pipe, and the pressure equalizing pipe and the connecting pipe are connected to the A control valve device is installed in the pressure equalization chamber of the expansion valve to selectively guide the refrigerant pressure on the high pressure side and the refrigerant pressure on the low pressure side. When the refrigerant pressure on the side decreases from the upper limit set value to below the lower limit set value, the first actuation signal is switched and a second actuation signal is issued, and when the refrigerant pressure increases from the lower limit set value to the upper limit set value or more, the second actuation signal is activated. A low pressure switch that issues a first operation signal by switching from a signal, and an automatic reset timer that starts counting from the start of compressor operation and issues a count-up signal when a preset predetermined time within several minutes has elapsed. until the timer issues a count-up signal, the refrigerant pressure on the high pressure side is introduced into the pressure equalization chamber by a first actuation signal of the low pressure switch;
Guide the refrigerant pressure on the low pressure side by the second actuation signal,
The control valve device is configured to guide refrigerant pressure on the low pressure side to the pressure equalizing chamber by the count-up signal of the timer regardless of the first and second actuation signals of the low-pressure switch when the timer issues a count-up signal. An air conditioner characterized by being installed in a control circuit. (2) The air conditioner according to claim 1, in which the control valve device is a three-way solenoid valve.