EP0077414A1

EP0077414A1 - Air temperature conditioning system

Info

Publication number: EP0077414A1
Application number: EP81108580A
Authority: EP
Inventors: Fumio C/O Mitsubischi Denki K. K. Matsuoka; Hitoshi C/O Mitsubischi Denki K. K. Iijima
Original assignee: Mitsubishi Electric Corp
Current assignee: OFFERTA DI LICENZA AL PUBBLICO
Priority date: 1981-10-20
Filing date: 1981-10-20
Publication date: 1983-04-27
Also published as: EP0077414B1; DE3175833D1; DE3177054D1

Abstract

A refrigeration cycle apparatus in which the loss of energy encountered during stopping and starting of the compressor is reduced and in which heating can be continuously carried out even when defrosting an outdoor heat exchanger.

A compressor (1), a condenser (4), an expansion device (6) and an evaporator (7) are connected in series with one another with the compressor (1) being coupled to a device such as a thermostat which repeatedly starts and stops the compressor (1) in response to a sensed room temperature. The refrigerant on the high pressure side of the compressor is isolated from the refrigerant on the low pressure side of the compressor when the compressor is stopped by a suitable arrangement (5, 2) so that no high back pressure is imposed upon the compressor when it is started.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a novel refigerant cycle apparatus which reduces the loss of energy produced at the time of starting and stopping the apparatus and which provides a highly efficient operation when operated repeatedly for starting and stopping the operation of an air conditioner or a refrigerator. Specifically, the invention relates to a novel air conditioning system which employs this refrigeration cycle apparatus and in which a continuous heating operation can be continuously carried out while performing defrosting of an outdoor heat exchanger.
A conventional refrigeration cycle apparatus includes a compressor, a condenser, an expansion device such as a capillary tube or an expansion valve, and an evaporator with these components sequentially coupled in series with each other. When the compressor is stopped, the pressure of the refrigerant on a high pressure side is balanced with the pressure of the refrigerant on the low pressure side. As the compressor is started, the difference between the pressures of the high pressure side and the low pressure side is gradually increased until the apparatus is brought to an ordinary operating state. When the compressor is accordingly repeatedly started and stopped, the high pressure side refrigerant is balanced in presence with the low pressure side refrigerant each time the apparatus is stopped. During these times, refrigerant liquid stored on the low-pressure side in an evaporator is drawn into the compressor. The presence of the liquid refrigerant in the condenser increases the load on the compressor at the time of restarting the compressor. This lowers the coefficient of performance (hereinafter abbreviated as "COP") .of the apparatus as compared with that during continuous operation.
When the above-described refrigeraion cycle apparatus is used in an air conditioning system capable of operating in both cooling and heating modes and the air conditioning system is operated in the heating mode, the refrigerant must be made to flow in the reverse direction to perform defrosting. In this case, an outdoor side heat exchanger is used as a condenser and an indoor side heat exchanger is operated as an evaporator. Accordingly, the heating operation of the side heat exchanger must be stopped during defrosting or a heater must be additionally provided.

SUMMARY OF THE INVENTION

Accordingly, a primary object of the invention is to provide.a refigeration cycle apparatus which can be repeatedly started and stopped and is of a type including a series connection of a compressor, a condenser, an expansion device and an evaporator. The apparatus should retain refrigerant separately distributed on the high pressure side and low pressure side without mixture thereof when the compressor is stopped thus to eliminate a loss of energy produced at the time of restarting the compressor in the conventional apparatus and to thereby improve the efficiency thereof and to make it possible to attain an ordinary operating state in short time after the compressor is re-started.
A further object of the invention is to provide a novel air conditioning system which incorporates a series connection of a compressor, a condenser, an expansion device and an.evaporator, in which the refrigrant flow is stopped in an indoor side heat exchanger but in which the refrigerant is used in an outdoor heat exchanger while continuing a heating operation.
Another object of the invention is to provide a novel switching element used for the refrigeration cycle apparatus which utilizes a diaphragm opening or closing in accordance with the pressure difference between the two refrigerant pressures in the refrigeration cycle corresponding to the temperature of the refrigerant.
Still another object of this invention is to provide a refrigeration cycle apparatus in which, when it is used as an air conditioning system, evaporation of drain water condensed 6n the evaporator and return thereof into a room to be cooled are substantially eliminated by delaying the starting and stopping operations of the evaporator fan with respect to the starting and stopping operations of the compressor, respectively.
In accordance with these and other objects of the invention, there is provided a refrigeration cycle apparatus including a compressor, a condenser, expansion means and an evaporator connected in series with each other. Means is provided for repeatedly starting and stopping the compressor. Further, means is also included for isolating refrigerant on a high pressure side of the compressor from refrigerant on the low pressure side of the compressor when the compressor is stopped. In one embodiment, the expansion means is an expansion valve and the isolating means is a check valve provided between an outlet of the compressor and an inlet of the condenser with a switching element being coupled between an outlet of the condenser and an inlet of the evaporator which is adaped to close upon stopping of the compressor and to open when the compressor is started. For the switching element, a solenoid valve may be provided. Further, the apparatus means include a thermal-valve heat sensitive tube provided between an outlet of the evaporator and the inlet of the compressor for controlling superheating of outlet refrigerant gas from the evaporator with the expansion valve. Preferably, the expansion valve is of a type having no bleed port..In another embodiment, the expansion means may be implemented with a capillary tube.
The foregoing objects and other objects as well as the characteristic features of the invention will become more apparent and more readily understandable by the following description and the appended claims when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic structural view of a first preferred embodiment of a refrigeration cycle apparatus constructed according to the invention;
Fig. 2 is a view similar to Fig. 1 showing a second preferred embodiment of the apparatus of the invention;
Fig. 3 is a cross-sectional view of an expansion valve used in the embodiment shown in Fig. 1;
Fig. 4 is a cross-sectional view of an expansion valve used in the embodiment shown in Fig. 2;
Fig. 5 is a view similar to Fig. 1 showing a third preferred embodiment of the apparatus of the invention;
Fig. 6 is a view similar to Fig. 1 showing a fourth preferred embodiment of the apparatus of the invention;
Fig. 7 is a cross-sectional view of a switching element used in the embodiment shown in Fig. 6;
Fig. 8 is a view similar to Fig. 1 showing a fifth preferred embodiment of the apparatus of the invention ;
Fig. 9 is a cross-sectional view of an example of a switching element used in the embodiment shown in Fig. 8;
Fig. 10 is a cross-sectional view of an example of a switching element used in the embodiment shown in Fig. 5;
Fig. 11 is a view similar to Fig. 1 showing a sixth preferred embodiment of the apparatus of the invention; and
Fig. 12 is a view similar to Fig. 1 showing a seventh preferred embodiment of the apparatus of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference is now made to the drawings, particularly to Fig. 1 showing a first preferred embodiment of the refrigeration cycle apparatus constructed according to the invention, wherein like reference numerals designate-the same parts in each of the Figures. In Fig. 1, reference numeral 1 designates generally a compressor. A refrigerant gas compressed at high temperature and high pressure by the compressor 1'is fed through a check valve 2 and a four-way valve 3 into a condenser 4. The refrigerant dissipates heat in the condenser 4 and is condensed to a high temperature and high pressure liquid. The refrigerant liquid, increased in temperature and pressure by the condenser 4, is passed through a solenoid valve 5, which acts as a switching valve, and an expansion valve 6 where the refrigerant becomes a low temperature, low pressure liquid and from there is introduced into an evaporator 7. The low temperature. and low pressure refrigerant liquid in the evaporator 7 absorbs heat and thus evaporates to a gas. This refrigerant gas is again fed through the four-way valve 3 into an accumulator 8 which isolates the refrigerant liquid which cannot be evaporated in the evaporator 7 and is retained in the liquid state and which returns only the refrigerant gas again to the compressor 1. While the compressor 1 is operating, the apparatus repeats the refrigeration cycle.
Reference numeral 9 illustrates a fan for the condenser 4 and 10 a fan for the evaporator 7. The four-way valve 3 is a change-over or switching valve which operates so that the condenser 4 can be used as an evaporator and the evaporator 7 used as a condenser.
When this refrigeration cycle apparatus is used in a room air conditioning system, the evaporator 7 is used as an indoor side heat exchanger, and the condenser 4 is used as an outdoor side heat exchanger. In the cooling mode, the apparatus is operated in a refrigeration cycle which in the heating mode the four-way valve 3 is switched so that the indoor side heat exchanger is used as a condenser and the outdoor side heat exchanger is used as an evaporator.
An air conditioning system operates to detect the temperature in the room by a temperature detector or thermostat (not shown) and to start or stop the compressor 1 so as to maintain the room temperature at a set temperature by operating or stopping the refrigeration cycle apparatus.
The solenoid valve 5, which interlocks the compressor 1, is constructed so as to open when the compressor 1 is started and to close when the compressor 1 is stopped. The solenoid valve 5 and the check valve 2 function to isolate high pressure side refrigerant and low pressure side refrigerant when the compressor 1 is stopped.
In this refrigeration cycle apparatus used in an air conditioning system as descirbed above, when the compressor 1 is repeatedly started and stopped to maintain the room temperature at a set value, the solenoid valve 5 is simultaneously opened and closed. Since the valve 5 is closed when the compressor 1 is stopped, the high temperature and high pressure refrigrant liquid in the condenser 4 does not flow into the expansion valve 6 and accordingly does not flow into the evaporator 7. On the other hand, since the check valve 2 is provided at the exhaust side of the compressor 1, the refrigerant gas in the condenser 4 and the condensed refrigerant liquid cannot return to the compressor 1.
When the compressor 1 is restarted, the high pressure side refrigerant in the refrigeration cycle is isolated from the low pressure side refrigerant. Since the solenoid valve 5 is then opened, a desired pressure difference between the high and low pressure side refrigerant can be attained in short time and the apparatus can reach the ordinary operating state in short time.
The conventional refrigerant cycle incorporating not such an isolating device requires about five minutes to reach the ordinary operation state after restarting. On the other hand, the refrigeration cycle apparatus of the invention :_ requires only about one minute and twenty seconds to make the transition.
It is noted that the aforesaid switching element is not limited to the solenoid valve 5 but may also be another type of switching valve and may be any type which closes when the compressor 1 is stopped and opens when the compressor 1 is started.
Referring now to Fig. 2 which shows a second prefer- ed embodiment of the refrigeration cycle apparatus constructed according to the .invention, there is provided at the outlet side of the evaporator 7 a thermo-valve heat sensitive tube 11, which is filled with a gas whose pressure varies with temperature and detects the refrigerant gas temperature at the outlet of the evaporator 7 for controlling the refrigerant flow rate through the expansion valve 6. Other components of the appa- - ratus are constructed in the same manner as in the first embodiment shown in Fig. 1.
An expansion valve 6 is depicted in Fig. 3 of a type which may be used for the refrigeration cycle apparatus of the invention. When this expansion valve 6 is used as a superheating control device for the refrigerant gas from the evaporator 7, an additional advantageous effect is obtained in addition to those provided by the embodiment of Fig. 1. That is, the refrigerant within the evaporator 7 can be utilized more effectively, particularly, in the coo1ing mode operation of the apparatus.
It is noted that the thermo-valve heat sensitive tube 11 is not limited to the position shown in Fig. 2 but may also be disposed at any position from the output of the evaporator 7 to the inlet of the compressor 1.
It is also noted that thermo-valve heat sensitive tube 11 is not disposed between the evaporator 7 and the compressor 1 but is provided between the condenser 4 and the solenoid valve 5 for controlling the refrigerant flow rate of the expansion valve 6.
With the expansion valve 6 thus constructed used to control the over-cooling of the output refrigerant gas of the condenser 4, the refrigerant in the condenser may be effectively used to improve the efficiency of the apparatus when the condenser 4 is used as the indoor side heat exchanger in the heating mode.
Fig. 4 shows another example of an expansion valve 6 which may be used in the embodiment shown in Fig. 2. This valve 6 has no bleed port 6a, which is different from the valve shown in Fig. 3, but the other components and parts are constructed in the same manner as those of the valve shown in Fig. 3. The thermo-valve heat sensitive tube 11 used for controlling the expansion valve 6 is constructed in the same manner as that shown in Fig. 2 arid is positioned to detect the temperature of the outlet refrigerant gas of the evaporator 7.
When the expansion valve 6 thus constructed is employed, the refrigerant flowing from an inlet 6b upon starting of the compressor 1 urges a diaphragm 6c to thus move a valve 6d, and the passage in the valve is consequently fully opened: When the compressor 1 is, on the other hand, stopped, the refrigerant cannot flow from the inlet 6b and accordingly urges the diaphragm 6c in the opposite direction. Thus, the valve 6d is moved to fully close the passage. Therefore, this expansion valve 6 can also perform the function of the solenoid valve 5 in the embodiment shown in Fig. 2, eliminating the need for a separate solenoid valve.
Since this embodiment employs the expansion valve 6 to control the superheating condition of the output refrigerant gas from the evaporator 7, it similarly effects the efficiency at the time of cooling. Hence, the thermo-valve heat sensitive tube 11 can be disposed at any position between the outlet of the evaporator 7 and the inlet of the compressor 1 in the same manner as in the embodiment shown in Fig. 2.
It is also noted that, when the thermo-valve heat sensitive tube 11 is disposed at the outlet side of the condenser 4 but not between the evaporator 7 and the compressor 1 and the valve 6 is used as a supercooling control device for refrigerant gas of the outlet of the condenser 4, the refrigerant in the condenser 4 is effectively utilized to improve the efficiency of the apparatus when the condenser 4 is used as the indoor side heat exchanger.
Reference is now made to Fig. 5 which shows a further preferred embodiment of the refrigeration cyctem apparatus constructed according to the invention in which capillary tubes 12 and 13 are used instead of the expansion valve 6 of the first embodiment shown in Fig. 1 and a switching element 14 is provided instead of the solenoid valve 5 between the capillary tubes 12 and 13. This switching element 14 is constructed to close when the compressor 1 is stopped and to open when the compressor 1 is started in the same manner as the solenoid valve 5 of the embodiment shown in Fig. 1. There is also provided in parallel with a first capillary tube 13 a check valve 15 which is constructed to pass the refrigerant in the cooling mode and to block the refrigerant in the heating mode. The check valve 15 is provided.to effectively alter the length of the capillary tube since the apparatus will operate more efficiently if the expansion coefficient of the refrigerant is varied between the cooling mode and the heating mode in such a manner that the capillary tube is effectively increased in length in the heating mode.
With two capillary tubes 12 and 13 used instead of the expansion valve 6, the apparatus can be inexpensively constructed, even if the check valve 15 is added and can be operated similarly to the embodiment shown in Fig. 1 with the same advantageous effects.
The switching element 14 is constructed to compare the pressure P₂, determined by the output side refrigerant gas temperature of the evaporator 7 as detected by the heat sensitive tube 11 provided between the outlet of the evaporator 7 and the inlet of the compressor 1, with the pressure P₁ of the refrigerant exhausted from the capillary tube 12, and to open when P₂ > P₁ and to close when P₂< P₁, in the same manner as described above.
Referring to Fig. 6 which shows a yet another embodiment of an apparatus, an on-off element 16 is provided instead of the electromagnetic valve in Fig. 2. The element 16 is on-off controlled by the temperature sensitive tube 11 provided on the output side of the evaporator 7. Fig. 7 shows in cross section the element 16. When the compressor 1 is started, the refrigerant flows from the condenser through an inlet port.l6a of the on-off element 16 and pushes up a diaphragm 16b against a downward pressure corresponding to the temperature detected by the tube 11. Therefore, a valve 16c is allowed to move upwardly with the aid of a spring causing a gas passage from the inlet port 16a to an outlet port 16d to be fully opened.
When the compressor 1 is stopped, the flow of refrigerant toward the inlet. port 16a stops. Therefore, the diaphragm 16b is pushed downwardly with a pressure corresponding to the temperature of the refrigerant detected by the heat sensitive tube 11 at the outlet of the evaporator 7. Therefore, the valve 16c is moved downwardly against the spring force to fully close the gas passage.
Since the on-off element 16 is automatically on-off controlled by the starting and stopping of the operation of the compressor 1 as mentioned above, the necessity of providing of means such as the electromagnetic valve 5 for detecting the starting and stopping of compressor 1 and means for converting this into election signals is eliminated.
The pressure corresponding to the temperature of the refrigerant detected by the heat sensitive tube 11 used to actuate the diaphragm of the on-off element 16 may be derived from the temperature of the refrigerant at the outlet of the condenser 4.
Reference is now made to Fig. 8 which illustrates still another preferred embodiment of an apparatus constructed according to the invention in which there are provided a refrigerant bypass tube 17 which connects the exhaust side of the compressor 1 with the inlet side of the compressor 1 and a switching element 20 disposed in the bypass tube 17 and which opens or close in response to signals from a detector 18 which senses the pressure of high pressure side refrigerant of the condenser 4 and a detector 19 which senses the exhaust pressure before the check valve 2. The switching element 20 is fully closed when the exhaust refigerant pressure of the compressor 1 is higher than the high pressure side refrigerant pressure of the condenser 4 and fully open when the exhaust refrigerant pressure of the compressor 1 is lower than the high pressure side pressure of the condenser 4. The other components and parts in this embodiment shown in Fig. 8 are constructed in the same manner as those of the embodiment shown in 'Fig. 1.
In this embodiment, the solenoid valve 5 is opened when the compressor 1 is operated. The switching element 20 is then closed since the exhaust refrigerant pressure of the compressor 1 is higher than the high pressure side refrigerant pressure of the condenser 4 so that the apparatus operates according to an ordinary refrigeration cycle. Since the solenoid valve is closed when the compressor 1 is stopped, the high pressure side refrigerant is isolated advantageously from the lower pressure side refrigerant during the refrigeration cycle. When the compressor 1 is stopped and the exhaust refrigerant pressure of the compressor 1 becomes lower than the high pressure side refrigerant pressure of the condenser 4, the switching element 20 fully opens to introduce the exhaust side refrigerant of the compressor 1 through the refrigerant bypass tube 17 to the intake side of the compressor 1 so as to thus balance the exhaust side pressure of the compressor 1 with the intake side pressure of the compressor 1. Because the distance between the exhaust side of the compressor 1 and the check valve 2 is short and the gas capacity of the refrigerant therebetween is small, the exhaust side of the compressor ₁ is at a low pressure. Therefore, starting torque of the compressor 1 is low and the electric power consumption of the compressor during starting is correspondingly low.
It is noted that the switching element 20 is not limited to the construction as described heretoforce. It also may be implemented with a solenoid valve or other switching element which can open and close in synchronization with the starting or stopping operation of the compressor 1. This embodiment provides the same advantages as those of the embodiment shown'in Fig. 8.
Referring now to Fig. 9, which shows an example of the switching element 20 used in the embodiment shown in Fig. 8, reference numeral 20a indicates an L-shaped casing, 20b a fluid passage extending longitudinally in the casing 20a, 20c an inlet, 20d an outlet. The passage 20b has a narrow portion extending as a step from the major part of the passage. Reference numeral 20e indicates a valve ball provided at the bent portion of the passage 20b with which the passage 20b'is opened and closed upon movement thereof. Reference numeral 20f depicts a pad making contact with the ball 20e, 20g is a spring making contact at one end with the pad 20f. 20h is a diaphragm housing provided at the top of the casing 20a, and 20i is a segmented diaphragm which divides the housing 20h into two chambers. A pad 20j is in contact with the lower surface of the diaphragm 20i. Reference numeral 20k is a connecting pin which connects the pad 20j with the pad 20f, and 201 is a fluid inlet provided at the top of the housing 20h into which a comparison pressure is introduced.
In the switching element thus constructed the tension of the spring 20g is suitably determined. The fluid pressure introduced from the inlet 20c acts on the pad 20f which urges up the diaphragm 20i through the connecting pin 20k and the pad 20j. On the other hand, since the comparison fluid pressure introduced from the inlet 20ℓ urges the diaphragm 20i downwardly, the switching element 20 opens when the comparison fluid pressure is higher than the sum of the fluid pressure from the current element inlet 20c and the equivalent pressure provided by the tension of the spring 20g and closes when the comparison.pressure is, on the contrary, lower than that sum. That is, when P₁ > P₂ ⁺ AP, the switching element will open, while when P₁ ≦ P₂ ⁺ ΔP, the switching element will close, where P₁ represents the comparison fluid pressure, P₂ represents the inlet fluid pressure, and AP represents the equivalent pressure provided by the tension of the spring.
With the switching element 20 is provided midway of the tube 17 in the embodiment shown in Fig. 8 and the comparison fluid employed is the high pressure side refrigerant of the condenser 4, that is, when the inlet 20ℓ of the diaphragm housing 20h is connected to the branch tube extending from the high pressure side refrigerant tube of the condenser 4, the apparatus operates in the same manner as the embodiment shown in Fig. 8.
Reference is now made to Fig. 10, which shows an example of the switching element 14 used in the embodiment shown in Fig. 5 in which a thermo-valve heat sensitive tube 11 provided between the outlet of the evaporator 4 and the inlet of the compressor 1 is connected to the inlet 20t for the comparison fluid in the chamber on the top of the diaphragm housing 20h. The thermo-valve heat sensitive tube 11 is filled with a gas the pressure of which varies in response to the sensed temperature thereof. The components and parts of this element are constructed in the same manner as the switching element 20 shown in Fig. 9.
The thermo-valve heat sensitive tube 11 thus constructed varies the internal pressure, that is, the pressure acting on the top of the diaphragm in response to the output side refrigerant gas temperature of.the evaporator. In turn, the switching element 14 controls the flow rate of the refrigerant gas exhausted from the capillary tube 12 into the inlet 20c of the switching element 14. The refrigerant gas pressure is applied to the pad 20f.
While the compressor 1 is operating, the pressure ^p ₁ of the refrigerant gas exhausted from the capillary tube 12 is lower than the pressure P₂ which is determined according to the outlet refrigerant gas temperature of refrigerant from the evaporator 7 and hence the pressure P₂ is higher than the sum of the pressure P₁ and the tension equivalent pressure AP of the spring. That is, P₂ > P_{1 +} ΔP. Accordingly, the valve ball 20e is in its lower position which causes the switching element 14 to be opened. A refrigeration cycle can then be performed. Since the output side refrigerant gas from the capillary tube 12 is, when the compressor 1 is stopped, not absorbed by the compressor 1, the refrigerant pressure P₁ is increased while the pressure P₂ corresponding to the output refrigerant gas temperature of the evaporator 7 is not substantially increased. Consequently, the pressure P₁ ⁺ ΔP becomes higher than P₂₁ i.e., P₂ < P₁ + AP. Therefore, the valve ball 20e is accordingly raised and the switching element 14 is thus closed. Therefore, when the compressor 1 is stopped, the high pressure side refrigerant of the refrigeration cycle is isolated from the low pressure side refrigerant.
Referring now to Fig. 11, which shows still another embodiment of the apparatus constructed according to the invention in which there is provided a controller 23 which starts operation when power to the compressor 1 is cut off. The controller 23 stops the operation of a fan 10 for an evaporator 7 approximately one minute after the controller 23 is activated and operates the fan 10 for the evaporator 7 for several seconds when power to the compressor 1 is turned on. The other components and parts of this apparatus shown in Fig. 11 are constructed in the same manner as those of the embodiment shown in Fig. 1.
The controller 23 is composed of a flip-flop 25 receiving an output signal from a detector 24 for detecting the driving condition of the compressor 1, a At timer 26 adapted to be set in response to an inverted output signal of the flip-flop 25, a At2 timer 27 adapted to be set in response to a non-inverted output signal of the flip-flop 25, and a flip-flop 28 receiving outputs from the timers 26 and 27 to produce an instruction signal for driving or stopping of the fan 10 of the evaporator 7.
The operation of the controller 23 will be described. Upon reception a stop instruction signal of the compressor 1 from the detector 24, the flip-flop 25 operates to produce an inverted output signal to the timer 26 to set the timer 26. Then the timer 26 operates to produce an output signal to the flip-flop circuit 28 after a predetermined time has passed, one minute for instance in this embodiment, so that the flip-flop 28 is reset to produce a driving stop instruction signal. As a result, the fan 10 of the evaporator 7 is stopped. The output signal of the timer 26 is fed back to its reset terminal as a reset signal to the timer 26.
On the other hand, when the flip-flop 25 receives, driving instruction signal for the compressor 1 from the detector 24, the flip-flop 25 produces an output to set the timer 27. After a predetermined period of time, five seconds for instance, the timer 27 operates to produce an output to set the flip-flop 28. The flip-flop 28 produces a driving instruction signal to thereby start driving of the : fan 10. Similar to the above operation, the output signal of the timer 27 is fed back to the reset terminal of the timer 27 to reset the timer 27.
When the apparatus thus constructed is used in an air conditioning system operating in the cooling mode, the following effects other than that of the embodiment of Fig. 1 are obtained. When the compressor 1 is stopped, the temperature of the evaporator 7 gradually increases until the temperature is approximately equal to room temperature. As a result, the saturation humidity becomes higher and therefore drain water condensed on the evaporator 7 is evaporated by the function of the fan 10. This results in increasing the humidity in the room. According to the above described embodiment shown in Fig. 11, however, when the temperature of the evaporator 7 is approximately equal to room temperature, the fan 10 is stopped as a result of which the drain water is not evaporated again. Further, since the fan 10 starts its operation when the temperature of the evaporator 7 is sufficiently low during the operation of the compressor 1, the drain water is not evaporated again. 'Therefore, it is possible to maintain the humidity in the room to be air conditioned at a much lower level than is possible with the conventional apparatus.
Reference is now made to Fig. 12 which shows a modification of the embodiment shown in Fig. 1, using the latter as an air conditioning system in the cooling mode. In Fig. 12, the four-way valve 3 is . turned to connect the condenser 4 as an outdoor heat exchanger and the evaporator 7 as an indoor heat exchanger. Further, there is provided a refrigerant bypass tube 21 extending between the outlet of the compressor 1 and the inlet of the outdoor side heat exchanger 4. A second solenoid valve 22 is disposed in the bypass tube 21 for opening or closing the bypass tube 21 in addition to the components and parts in the embodiment shown in Fig. 1. The second selonoid valve 22 is operated to be open during the starting of the defrosting operation of the outdoor side heat exchanger and to close at the end of the defrosting operation heat exchanger in the heating mode.
Since in the apparatus thus constructed the second solenoid valve 22 provided in the bypass passage 21 is closed in the heating mode, the high temperature and high pressure refrigerant gas compressed by the compressor 1 passes through the check valve 2 and is introduced from the four-way valve 3 into the indoor side heat exchanger 7 which dissipates heat to the atmosphere to condense the refrigerant gas and to a high pressure and high temperature refrigerant liquid. Thus the refrigerant liquid becomes low pressure and low temperature refrigerand at the expansion valve 6 and is introduced through the solenoid valve 5 into the outdoor side heat exchanger 4 which absorbs heat from the atmosphere to evaporate the refrigerant liquid. The refrigerant gas thus evaporated is again introduced through the four-way valve 3 and the accumulator 8 into the compressor 1 to complete one cycle. The same cycle is continuously repeated.
When the compressor 1 is started and stopped repeatedly to control the temperature in the room the solenoid valve 5 opens when the compressor 1 is started and closes when the compressor 1 is stopped, in the same manner as in the embodiment shown in Fig. 1, to thus isolate the high pressure side refrigerant and the lower pressure side refrigerant. Accodingly, the COP of the compressor 1 is improved.
When frost accumulates on the outdoor side heat exchanger 4 deteriorating the heat exchange rate thereof, the COP of the compressor is lowered and hence a defrosting operation must be carried out to remove the frost.
The solenoid valve 5 is closed by a defrost operation command signal while simultaneously the second solenoid valve 22 in the bypass passage 21 is opened. Accordingly, the high temperature and high pressure refrigerant gas in the indoor side heat exchanger 7 is condensed to become high temperature and high pressure refrigerant liquid while dissipating heat. On the other hand, the high temperature and high pressure refrigerant gas compressed by the compressor 1 is introduced into the outdoor side heat exchanger 4 through the bypass tube 21 to thereby defrost the outdoor side heat exchanger by applying heat thereto to melt the frost. The refrigerant is then introduced through the four-way valve 3 from the accumulator 8 again into the compressor 1 and is again compressed by the compressor 1 to high temperature and high pressure gas which is then introduced through the bypass tube 21 into the outdoor side heat exchanger 4.
Since, in the conventional apparatus, in the defrosting cycle the four-way valve 3 is switched to the state in which the outdoor side heat exchanger 4 is used as a condenser and the indoor side heat exchanger 7 is used as an evaporator, the refrigerant gas exhausted from the outdoor side heat exchanger 4 is introduced through the indoor side heat exchanger 7 into the compressor 1 in one cycle. Accordingly, the heating operation cannot be performed during the defrosting operation. Moreover, with this embodiment of the invention, the two operations can be performed simultaneously by utilizing the high temperature and high pressure refrigerant gas accumulated in the indoor side heat exchanger 7. In ` addition, the refrigerant heat in the indoor side heat exchanger 7 can be utilized. Further, the defrosting operation can be executed without switching the four-way valve 3 in this embodiment.
In the embodiment shown in Fig. 11, the compressor 1 repeats starting and stopping operations in order to control the temperature in the room in heating operation. The opening and closing of the second solenoid valve 22 is synchronized with the starting and stopping operations of the compressor 1. The defrosting operation can also be conducted in the same manner as that executed in the above embodiment.
When the compressor 1 is stopped in the apparatus thus constructed, the second solenoid valve 22 will open, the outlet side refrigerant from the compressor 1 is accordingly introduced through the bypass tube 21 into the outdoor side heat exchanger 4, and the outlet side-pressure of the compressor 1 is thus lowered to balance with the inlet side pressure. Accordingly, since there is no pressure difference between the inlet side and the outlet side of the compressor when the compressor 1 is restarted, the starting torque is low and the_': electric power consumption is thus reduced compared with the prior art apparatus. In addition, since the starting torque of .'the compressor 1 is low, the size and capacity of the compressor may be reduced advantageously.
It is noted that even if the amount of refrigerant between the outlet side and the inlet side of the compressor 1 is small and the solenoid valve 5 is closed, as the check valve 2 is provided, the pressure in the outdoor side heat exchanger 4 will not increase even if the outlet refrigerant from the compressor 1 flows into the outdoor side heat exchanger 4.
The second solenoid valve 22 is operated to open when the compressor 1 is stopped and to close a predetermined time,in the heating mode,after the compressor 1 is started. The second solenoid valve 22 thus operated does not feed the refrigerant compressed through the check valve 2 into the high pressure side but passes it into the lower pressure side, and accordingly decreases the starting torque of the compressor 1.
In the embodiment shown in Fig. 11, the second solenoid valve 21 provided in the bypass passage 21 is opened a short predetermined time before a defrosting operation is started and closed before a predetermined short time after completion of the defrosting operation in a defrosting operation performed in the heating mode. The second solenoid valve 22 receives a control signal from a frost detector (not shown) provided at the outdoor side heat exchanger 4.
Since the second solenoid valve 22 thus constructed introduces rapidly the high temperature and high pressure refrigerant gas into the outdoor side heat exchanger 4 in the defrosting operation, the defrosting time is short. When the second solenoid valve 22 is closed before completion of the defrosting operation, the refrigerant in the outdoor side heat exchanger 4 is used until the defrosting operation is completed. The function of the outdoor heat exchanger 4 as the evaporator is quickly recovered when the operating mode is subsequently switched to the heating mode.

Claims

1. A refrigeration cycle apparatus comprising: a compressor, a condenser, expansion means and an evaporator connected in series with each other; means for repeatedly starting and stopping said compressor; and means for isolating refrigerant on a high pressure of said compressor from side refrigerant on a low pressure side of said compressor when said compressor is stopped.

2. The refrigeration cycle apparatus as claimed in claim 1, wherein said expansion means comprises an expansion valve and wherein said isolating means comprises a check valve provided between an outlet of said compressor and an inlet of said condenser and a switching element provided between an outlet of the condenser and an inlet of said evaporator adapted to close upon stopping of said compressor and to open upon starting of said compressor.

3. The refrigeration cycle apparatus as claimed in claim 1, wherein said expansion means comprises an expansion valve and wherein said isolating means comprises a check valve ,provided between an outlet. of said compressor and an inlet of said condenser, a solenoid valve provided between an outlet of said condenser and an inlet of said evaporator adapted to close when said compressor is stopped and to open when said compressor is started, and further comprising a thermo-valve heat sensitive tube provided between an outlet of said evaporator and an inlet of said compressor for controlling superheating of outlet refrigerant gas from said evaporator with said expansion valve.

4. The refrigeration cycle apparatus as claimed in claim 1, wherein said expansion means comprises an expansion valve having no bleed port, and wherein said isolating means comprises a check valve provided between an outlet of said compressor and an inlet of said condenser, and further comprising a thermo-valve heat sensitive tube provided between an outlet of said evaporator and an inlet of said compressor for controlling superheating of outlet refrigerant gas from said evaporator with said expansion valve.

S. The refrigeration cycle apparatus as claimed in claim 1, wherein said expansion means comprises at least one capillary tube and wherein said isolating means comprises a switching element provided adjacent one said capillary tube adapted to fully close when. said compressor is stopped and to fully open when said compressor is started, and a check-valve provided between an outlet of said compressor and an inlet of said condenser.

6. The refrigeration cycle apparatus as claimed in claim 1, wherein said expansion means comprises an expansion valve and wherein said isolating means comprises a check valve provided between an outlet of said compressor and an inlet of said condenser, a solenoid valve provided between an outlet of said condenser and an inlet of said evaporator adapted to close when said compressor is stopped and to open when said compressor is started, and further comprising a thermo-valve heat sensitive tube provided at an outlet of said condenser for controlling subcooling of outlet refrigerant gas from said condenser with said expansion valve.

7. The refrigeration cycle apparatus as claimed in claim 1, wherein said expansion means comprises an expansion valve having no bleed port, and wherein said isolating means comprises a check valve provided between an outlet of said compressor and an inlet of said condenser, and further comprising a thermo-valve heat sensitive tube provided at an outlet of said condenser for controlling subcoolingof outlet refrigerant gas from said condenser with said expansion valve.

8. The refrigeration cycle apparatus as claimed in claim 1, wherein said expansion means comprises an expansion valve, and wherein said isolating means comprises a check valve provided between an outlet of said compressor and an inlet of said condenser, a switching element controlled by an output of said thermo-valve heat sensitive tuhe provided between an outlet of said condenser and an inlet of said evaporator adapted to close when said compressor is stopped'and to open when said compressor is started, and further comprising a thermo-valve heat sensitive tube provided between an outlet of said evaporator and an inlet of said compressor for controlling superheating of outlet refrigerant gas from said evaporator with said expansion valve.

₉. The refrigeration cycle apparatus as claimed in claim 1, wherein said expansion means comprises an expansion valve, and wherein said isolating means comprises a check valve provided between an outlet of said compressor and an inlet of said condenser, a switching element controlled by an output of said thermo-valve heat sensitive tube provided between an outlet of said condenser and an inlet of said evaporator adapted to close when said compressor is stopped and to open when said compressor is started, and further comprising a thermo-valve heat sensitive tube provided between an outlet of said evaporator and an inlet of said compressor for controlling superheating of outlet refrigerant gas from said evaporator with said expansion valve.

10. The refrigeration cycle apparatus is claimed in claim 2 wherein said isolating means further comprises a bypass tube for bypass an inlet of said compressor and an outlet of said evaporator provided between an outlet of said compressor and said check valve, and a switching element provided in said bypass tube adapted to open when said compressor is stopped and to fully close when said compressor is operated.

11. The refrigeration cycle apparatus as claimed in claim 10, wherein said switching element comprises a switching element adapted for opening and closing in response to a high pressure side refrigerant pressure of said condenser and an output refrigerant pressure of said compressor before said check valve.

₁2. The refrigeration cycle apparatus as claimed in claim 11, wherein said isolating means further comprises a switching element provided in a passage for communicating an inlet for inflowing refrigerant exhausted from said compressor ` with an outlet for exhausting said refrigerant, a valve for opening or closing said passage, a pad for operating said valve, and a diaphragm to one side of which an exhaust refrigerant pressure of said compressor is applied through said pad and a high pressure side refrigerant pressure being applied to an opposite side surface of said diaphragm, wherein said passage is opened when said high pressure side refrigerant pressure of said condenser is higher than said exhaust refrigerant pressure of said compressor and is closed when said high pressure side refrigerant pressure of said condenser is lower than said exhaust refrigerant pressure of said compressor:

13. The refrigeration cycle apparatus as claimed in claim 5, wherein said isolating means further comprises a switching element provided in a passage for communication an inlet for inflowing refrigerant exhausted from said at least one capillary tube with an outlet for-exhausting refrigerant, a valve for opening and closing said passage, a pad for operating said valve, and a diaphragm to one side of which an outlet refrigerant pressure of said at least one capillary tube is introduced through said pad and a pressure corresponding to the temperature of said thermo-valve heat sensitive tube being applied to an opposite side surface of said diaphragm, wherein said passage is opened when said refrigerant pressure at said outlet of said at least one capillary tube is lower than said pressure corresponding to said temperature of said thermo-valve heat sensitive tube.

14. The refrigeration cycle apparatus as claimed in claim 3 or 6, further comprising a fan for said evaporator and a controller for driving and stopping said fan for said evaporator with a time delay from starting and stopping of said compressor.

15. An air conditioning system comprising compressor, an indoor side heat exhanger, expansion means, and an outdoor side heat exchanger connected in series with each other;means for repeatedly starting and stopping said compressor in response to room temperature sensing means; means for isolating refrigerant on a high pressure side of said compressor from refrigerant on a lower pressure side of said compressor when said compressor is stopped; and means for defrosting said outdoor side heat exchange while continuing a heating operation with said indoor side heat exchanger.

16. The air conditioning system as claimed-in claim- 2, wherein said isolating means comprises a check valve provided between an outlet of said compressor and an inlet of said indoor side heat exchanger, a first solenoid valve provided between an outlet of said indoor side heat exchanger and an inlet of said outdoor side heat exchanger, a branch tube for refrigerant provided between said outlet of said compressor and said check valve, a second solenoid and a bypass for communicating one end of said branch tube with said refrigerant tube between said first solenoid valve and said outdoor side heat exchanger through said first solenoid valve and said outdoor side heat exchanger through said second solenoid valve, wherein said first solenoid valve is closed when a defrosting operation is performed in a heating mode and said second solenoid valve is open when said defrosting operation is performed in said heating mode.

17. The air conditioning system as claimed in claim 16, wherein in said heating mode said first solenoid valve is closed while said second solenoid valve is opened when said compressor is stopped, and wherein said first solenoid valve is opened while said second solenoid valve is closed when said compressor is started.

18. The air conditioning system as claimed in claim 16, wherein said first solenoid is closed while said second solenoid valve is opened when said compressor is stopped, and said first solenoid valve is opened when said compressor is started, and said second solenoid valve is closed a predetermined time after said compressor is started.

₁9. The air conditioning system as claimed in claim 16, wherein said first and second solenoid valves are closed when said compressor is stopped, and said first solenoid valve is opened and said second solenoid valve is closed when said compressor is started during cooling and heating operations.

20. The air conditioning system as claimed in claim 16, wherein when a defrosting operation is performed in a heating mode, said second solenoid valve is opened a predetermined time before starting said defrosting operation, said first solenoid valve is closed when starting said defrosting operation, said second solenoid valve is closed a predetermined time before said defrosting operation is completed, and said first valve is opened when said defrosting operation is completed.