JPH0263152B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a refrigeration system, more specifically, a refrigeration system equipped with a capacity control bypass path, which guides hot gas to an evaporator to control the internal temperature of a container or refrigerator, for example - 5℃
The present invention relates to a refrigeration system which controls the temperature to a chilled region higher than ~-6°C, performs defrost operation, and is equipped with a drain pan heater to heat frozen drain in the drain pan to prevent drain clogging.

(Prior art) This type of refrigeration device is configured as follows:
This was first proposed in Japanese Patent Application No. 150750/1983. That is, as shown in FIG. 2, this refrigeration system includes a bypass path H for controlling the ability to supply part or all of the hot gas discharged from the compressor A to the evaporator E without supplying it to the condenser C; By providing a drain pan heater DH that heats the drain in the drain pan, and using a three-way solenoid valve SV and a three-way proportional valve MV that controls the valve opening from 0 to 100% in proportion to the voltage, When controlling the capacity of the evaporator E, the capacity of the evaporator E is controlled by preventing hot gas from flowing through the drain pan heater DH and preventing air cooled by the evaporator E from being heated by the drain pan heater DH; During defrosting, the entire amount of the hot gas is passed through the drain pan heater DH to heat and liquefy the frozen drain that has fallen into the drain pan from the evaporator E.

More specifically, the discharge side of the compressor A and the condenser C
A capacity control bypass path H that bypasses the condenser C and the expansion valve EV is connected in the middle of the discharge path B connecting the inlet side of the evaporator E, and the outlet of this bypass path H is connected to the inlet side of the evaporator E. At the same time, the three-way proportional valve is connected to the junction of the bypass path H with the discharge path B.
A three-way proportional valve MV is installed, and a part of the hot gas flowing in the discharge path B is directly supplied to the evaporator E, so that the temperature of the air blown from the evaporator E and, ultimately, the temperature inside the refrigerator is controlled in the chilled region. control to,
Further, while the entire amount of the hot gas is directly supplied to the evaporator E to perform a defrost operation, a drain pan heater DH for circulating the hot gas is connected in the middle of the bypass path H, and this drain pan heater DH is connected to the evaporator E. A three-way solenoid valve SV is installed at the connection between the inlet of the drain pan heater DH and the bypass path H; During defrost operation, the opening of the three-way solenoid valve SV to the drain pan heater DH is fully opened to supply the entire amount of the hot gas to the drain pan heater DH, and remove the frozen drain that has fallen into the drain pan without being completely liquefied. It is constructed so as to prevent so-called drain clogging, in which ice melts and frozen drain blocks the drain outlet of the drain pan.

(Problem to be solved by the invention) However, among the many types of valves used in refrigeration equipment, this prior invention uses a relatively inexpensive three-way solenoid valve, and also uses a three-way solenoid valve, which is much more expensive than this solenoid valve. Since a proportional valve is used, there is a problem in that the cost of the entire device increases.

An object of the present invention is to solve the problem of the need to use an extremely expensive three-way proportional valve in the refrigeration system of the prior invention, and to solve the problem of the need to use a very expensive three-way proportional valve. , a defrost bypass path is provided adjacent to the discharge path, and the defrost bypass path is provided upstream of the capacity control bypass path;
By using a three-way solenoid valve and a two-way proportional valve, which is much cheaper than the three-way proportional valve described above, it is possible to prevent hot gas from flowing to the drain pan heater when controlling the evaporator capacity, while reducing costs. I made it possible.

(Means for Solving the Problems) Therefore, the present invention bypasses a portion of the hot gas to the hot gas discharge path 9a connected to the compressor 1 through the condenser 2 and bypasses the evaporator 4. A capacity control bypass passage 11 is connected, a two-way proportional valve 12 for adjusting the bypass amount of hot gas is interposed in the capacity control bypass passage 11, and the condenser 2 is bypassed during defrost operation; A defrost bypass passage 15 for bypassing the entire amount of hot gas to the evaporator 4 is formed separately from the capacity control bypass passage 11, and this defrost bypass passage 15 is connected to the capacity control bypass passage 15 in the discharge passage 9a. The defrost bypass passage 15 is connected to the discharge passage 9a via a three-way solenoid valve 13 provided upstream of the connection point of the passage 11.
A drain pan heater 14 disposed in the drain pan 10 of the evaporator 4 is installed so that the entire amount of hot gas is transferred to the drain pan heater 14 during the defrost operation.
The evaporator 4 is bypassed through the evaporator 4.

(Function) When controlling the capacity of the evaporator 4, the opening degree of the three-way solenoid valve 13 to the defrost bypass passage 15 is fully closed, and the hot gas in the discharge passage 9a is supplied to the evaporator 4 from the capacity control bypass passage 11. , While preventing heating by the drain pan heater 14, during defrost operation, the three-way solenoid valve 13 is fully opened to the defrost bypass passage 15, and the entire amount of hot gas in the discharge passage 9a is allowed to flow into the evaporator 4; The frozen drain in the drain pan 10 is heated to thaw it.

(Example) Next, an example of the present invention will be described based on the drawings.

The refrigeration system shown in FIG. 1 is a container refrigeration system, in which 1 is a compressor, 2 is an air-cooled condenser, 3 is a water-cooled condenser, 4 is an evaporator, and 5 is a temperature sensing section 6 is a liquid receiver in the form of an storage tank, 7 is a dryer, and 8 is a liquid indicator. These devices are connected by refrigerant pipes 9, and are It forms a refrigeration cycle that cools the internal air. Further, on the lower side of the evaporator 4, the evaporator 4
A drain pan 10 is provided to catch drain that has fallen from the drain pan.

Therefore, in the embodiment shown in FIG. Each condenser 2, 3, liquid receiver 6 and temperature-sensitive expansion valve 5 are bypassed and the evaporator 4
A capacity control bypass passage 11 leading to the capacity control bypass passage 11 is connected, and its outlet is connected to the low pressure liquid pipe 9b between the expansion valve 5 and the evaporator 4.
A two-way proportional valve 12 for controlling the bypass amount of hot gas is interposed in the middle of the discharge passage 9a, and a part of the hot gas in the discharge passage 9a is
It is supplied to the evaporator 4 via the capacity control bypass path 11 to control the capacity of the evaporator 4, while the upstream side of the connection point O of the capacity control bypass path 11 in the discharge path 9a is A three-way solenoid valve 13 is interposed on the side (compressor 1 side), and a drain pan heater 14 is provided in the discharge passage 9a via the solenoid valve 13 and disposed below the air blowing side of the evaporator 4, and During defrost operation, a defrost bypass passage 15 that bypasses the entire amount of the hot gas to the evaporator 4 is connected, and its outlet is connected to the exit side of the two-way proportional valve 12 in the capacity control bypass passage 11 (the evaporator 4 side), and the three-way solenoid valve 13 directs the entire amount of hot gas flowing through the discharge path 9a to the defrost bypass path 15.
During this defrosting operation, frozen drain that falls into the drain pan 10 in a frozen state without being completely liquefied is thawed by the drain pan heater 14. .

In the above configuration, the two-way proportional valve 12 is
An electrically operated valve comprising a first and a second port and capable of controlling the valve opening from 0 to 100% in proportion to the voltage,
The controller 120 performs RID control.

This RID control (Rroportional−plus−integr−
(al-derivative control) refers to control in which the control signal is proportional to the deviation signal, its integral, and the sum thereof.

Further, the three-way solenoid valve 13 has first, second, and third solenoid valves.
The discharge passage 9a is connected to the first and second ports 13a and 13b, and the defrost bypass passage 15 is connected to the third port 13c. The second port 13b is closed and the third port 13c is opened.

Therefore, when controlling the capacity of the evaporator 4, the defrost bypass path 1 of the three-way solenoid valve 13 is
The third port 13c communicating with the condenser 5 is closed, the second port 13b communicating with the condenser 2 is opened, and the hot gas in the discharge passage 9a is evaporated from the capacity control bypass passage 11 via the two-way proportional valve 12. The capacity of the evaporator 4 is controlled by supplying it to the evaporator 4. In this case, the hot gas in the discharge passage 9a is not supplied to the defrost bypass passage 15, so that the air leaving the evaporator 4 is transferred to the drain pan heater 14.
Therefore, it is not heated. That is, since there is no need to perform cooling in the evaporator 4 in consideration of reheating by the drain pan heater 14, there is no need to set the cooling temperature by the evaporator 4 lower than the optimum internal temperature for the object to be cooled. As a result, the temperature of the air blown out from the evaporator 4 drops too much as in the conventional case, causing the objects to be cooled such as vegetables stored in the refrigerator to lose weight.
This can prevent quality from deteriorating.

In addition, when performing bypass operation, the second port 13 of the three-way solenoid valve 13 that communicates with the condenser 2
b is closed, the third port 13c communicating with the defrost bypass passage 15 is opened, and the discharge passage 9 is opened.
The entire amount of hot gas in a is flowed from the defrost bypass passage 15 through the drain pan heater 14 to the evaporator 4 to defrost it, and at the same time, the defrost heats the frozen drain that has fallen from the evaporator 4 into the drain pan 10. It melts the ice. In this case, since the entire amount of hot gas is passed through the drain pan heater 14, the time required to thaw the frozen drain in the drain pan 10 can be shortened.

The refrigeration system of the first embodiment shown in FIG. 1 has a command to stop the freezing operation or refrigeration operation and a command to stop the defrost operation on the downstream side of the condenser 3, more specifically on the downstream side of the liquid indicator 8. An electromagnetic on-off valve 21 that closes upon a start command is provided to enable pump-down operation, and to confine the refrigerant in a liquid reservoir including the condensers 2 and 3 and the liquid receiving part of the liquid receiver 6. A defrost circuit that defrosts a certain amount of refrigerant out of the refrigerant confined in the liquid reservoir, that is, a compressor 1 and a three-way solenoid valve 1;
3. A fixed amount outflow mechanism 20 is provided which flows out into the defrost circuit consisting of the defrost bypass path 15, the evaporator 4, and the storage unit of the liquid receiver 6.

This quantitative outflow mechanism 20 includes, for example, the on-off valve 2
1, an electromagnetic on-off valve 22 is installed at a position where a predetermined outflow amount can be obtained, with respect to the interposed position where the on-off valve 21 is installed, of the liquid reservoir part which performs a pump-down operation and confines the refrigerant when the refrigerant is closed. In FIG. 1, the on-off valve 21 is configured as follows.
The on-off valve 22 is installed on the inlet side of the expansion valve 5 in the high pressure liquid pipe 9c connecting the liquid indicator 8 and the expansion valve 5, and the on-off valve 22 is installed on the outlet side of the liquid indicator 8 in the high pressure liquid pipe 9c. A certain amount of refrigerant is interposed between the on-off valves 21 and 22 of the high-pressure liquid pipe 9c and is made to flow out by closing the on-off valve 22 and opening the on-off valve 21. .

The amount of refrigerant set by the fixed amount outflow mechanism 20 is set to an optimum amount so that the steady operation performed after the defrost operation is always kept within the operable range regardless of the operating state, and the defrost time is not prolonged. .

Furthermore, a solenoid valve 26 that is energized and closed and a capillary reach tube 27 are connected in parallel in the middle of the suction gas pipe 9d that connects the inlet side of the compressor 1 and the liquid receiver 6.

The solenoid valve 26 allows the suction gas refrigerant to flow into the capillary reach tube 2 by closing the solenoid valve 26.
The refrigerant is returned to the compressor 1 through the refrigerant 7, and the amount of refrigerant circulated is reduced.The amount of refrigerant is reduced in this way when the outside temperature is high, when steady operation starts after defrosting, or when the pull-down This is to prevent the high and low pressures of the refrigerant from increasing and overloading the refrigerant, and due to the decrease in the amount of circulation, the amount of work of the compressor 1 decreases, and the high pressure and the current value of the compressor motor decrease. This allows the operating range to be expanded.

The solenoid valve 26 detects the suction temperature of the evaporator 4, closes to reduce the circulation amount when the suction temperature exceeds a certain value, and opens when the suction temperature falls below a certain value.

In the above configuration, the two-way proportional valve 12 is controlled by an output signal from the controller 120 and a defrost operation start command, and the opening/closing valve 21 is closed by the defrost operation start command to perform pump down operation. Furthermore, the end of the pump down operation and the start of the defrost operation are mainly controlled using the low pressure switch 63L.

The command to start the defrost operation mainly uses an air pressure switch and a defrost timer whose set time is, for example, 12 hours. In this case, the air pressure switch has priority over the defrost timer, and the operation of the air pressure switch resets the defrost timer.

The defrost operation is terminated by, for example, attaching two thermostats with different set temperatures to the low pressure gas pipe 9e on the outlet side of the evaporator 4 and detecting the temperature of the low pressure gas pipe 9e.

In addition, _F1 in the figure is a fan attached to the evaporator 4,
F ₂ is a fan attached to the air-cooled condenser 2, 63
H is a high pressure switch, 63CL is a high pressure control switch,
63QL is a hydraulic protection switch, and 63W is a water pressure switch.

Next, the effect when the constant flow outflow mechanism 20 is provided will be explained.

First, during freezing or refrigeration operation, when a defrost operation start command is issued, the on-off valve 21 closes and pump-down operation begins.

In this pump-down operation, the liquid refrigerant is transferred to the condensers 2 and 3, the liquid receiving part of the liquid receiver 6, and the on-off valve 21.
The low pressure on the suction side of the compressor 1 decreases, and when the low pressure becomes lower than the set value of the low pressure switch 63L, the low pressure switch 63L is turned off and the low pressure switch 63L is turned off. The compressor 1 stops and the pump-down operation ends.

The three-way solenoid valve 13 has a third port 13.
c is switched so that it is fully open, the indoor fan motor MF ₁ is stopped, and at the same time the on-off valve 2 is switched to be fully open.
2 closes, and the on-off valve 21 opens.

As described above, when the on-off valve 22 is closed and the on-off valve 21 is opened, there is a difference between high and low pressures, so a certain amount of liquid refrigerant trapped in the high-pressure liquid pipe 9c between these on-off valves 21 and 22 is converted into gas. This will lead to the leakage.

The reason why this liquid refrigerant gasifies and flows out to the evaporator 4 side is that the volume of the defrost circuit is considerably larger than the volume of the refrigerant stored in the quantitative outflow mechanism 20, and the pump-down operation causes the evaporator 4 to flow out. Since the refrigerant on the outlet side is in a heated state, the expansion valve 5 must be open. Immediately after the opening/closing valve 21 is opened, the liquid refrigerant boils due to the pressure drop, and therefore flows to the evaporator 4 side in a liquid-gas mixed state. Even if some liquid refrigerant remains, the amount of refrigerant originally stored in the metering mechanism 20 is small;
This is because the above-mentioned part of the liquid refrigerant can be sufficiently evaporated with the amount of heat taken from the liquid capacity held by the high-pressure liquid pipe 9c itself and the outside temperature through the high-pressure liquid pipe 9c.

Due to this outflow, the low pressure increases and becomes higher than the set value of the low pressure switch 63L, so the low pressure switch 63L is turned on, the compressor 1 is started, and a certain amount of refrigerant is circulated through the defrost circuit. Defrosting can be performed by hot gas flowing into the evaporator 4 from the defrosting bypass path 15.

This defrost operation is performed by the quantitative outflow mechanism 20.
Since the defrost is carried out using a fixed amount of refrigerant set by the above, optimal defrosting is always possible regardless of the operating state immediately before the defrosting operation.

Note that during this bypass operation, even if some of the refrigerant is liquefied in the evaporator 4, gas-liquid separation is performed in the storage unit of the receiver 6, so that no liquid backflow to the compressor 1 occurs.

Then, when the defrost is finished as described above,
Of the two thermostats installed on the outlet side of the evaporator 4, the thermostat with the lower set temperature operates, so the defrosting ends, the on-off valves 21 and 22 open, and the refrigeration operation returns or refrigeration begins. During operation, the two-way proportional valve 12 shifts to opening control by the controller 120 and returns to steady operation.

Note that when returning to steady operation after the defrost operation ends, the ambient temperature of the evaporator 4 is more constant than in the steady operation, but since the refrigerant circulation amount during the defrost operation is controlled to a constant amount, Steady operation can always be carried out without the high pressure switch 63h or overcurrent relay being activated due to abnormally high high pressure, but in cases such as when the outside temperature is abnormally high, it is necessary to control the amount of refrigerant to a constant level. The high pressure may become abnormally high even though the

In this case, the setting of the amount of refrigerant may be reduced, but since this is a very rare case, in the embodiment shown in FIG.
A parallel circuit between the electromagnetic valve 26 and the capillary reach tube 27 is inserted, and the electromagnetic valve 26 is closed by detecting the temperature of the blown air, high or low pressure, or outside temperature, and the amount of refrigerant circulated through the capillary reach tube 27 is controlled. Therefore, under operating conditions where the outside temperature is abnormally high and high pressure increases,
The electromagnetic valve 26 is closed to enable operation by reducing the amount of refrigerant circulated, thereby widening the operable range.

The refrigeration system described above is applied to a container refrigeration system in which the drain pan 13 is provided on the air outlet side of the evaporator 4, but it can also be applied to other refrigerators.

Moreover, although the air-cooled condenser 2 and the water-cooled condenser 3 were used together as the condenser, a single condenser 2 or 3 may be used.

(Effects of the Invention) As described above, the present invention provides a capacity control bypass path in which a part of the hot gas bypasses the condenser 2 and bypasses the evaporator 4 in the hot gas discharge path 9a connected to the compressor 1. 11 is connected, and a two-way proportional valve 12 for adjusting the bypass amount of hot gas is interposed in this capacity control bypass path 11. At the same time, during defrost operation, the condenser 2 is bypassed and the entire amount of hot gas is A defrost bypass passage 15 that bypasses the evaporator 4 is formed separately from the capacity control bypass passage 11, and this defrost bypass passage 15 is connected to the connection point of the capacity control bypass passage 11 in the discharge passage 9a. The defrost bypass passage 15 is connected to the discharge passage 9a via a three-way solenoid valve 13 installed on the more upstream side.
A drain pan heater 14 disposed in the drain pan 10 of the evaporator 4 is installed so that the entire amount of hot gas is transferred to the drain pan heater 14 during the defrost operation.
Since the evaporator 4 is bypassed through the evaporator 4, the capacity can be controlled using the two-way proportional valve 12, which is much cheaper than the three-way proportional valve, but when performing this capacity control operation, the drain pan heater 14 is not used. In addition, when performing defrost operation, the drain pan heater 14, which was not in use during capacity control, can be switched to a usable state to allow the entire amount of hot gas to flow through the drain pan heater 14. This is possible.

Therefore, since the expensive three-way proportional valve can be replaced with an inexpensive two-way proportional valve, the cost of the entire device can be reduced.In addition, the capacity control bypass path 11 and the defrost bypass path 15 are provided separately, and this defrost bypass path is provided separately. Since the drain pan heater 14 is installed in the drain pan heater 15, when controlling the capacity of the evaporator 4,
Since the hot gas can be bypassed to the evaporator 4 without flowing to the drain pan heater 14, the air cooled by the evaporator 4 will not be heated by the drain pan heater 14, and as a result, the air cooled by the evaporator 4 will not be heated by the drain pan heater 14. Since there is no need to perform cooling in consideration of reheating by the drain pan heater 14, there is no need to set the cooling temperature by the evaporator 4 lower than the optimal internal temperature for the object to be cooled, and therefore, the air blowing from the evaporator 4 is reduced. It is possible to prevent the temperature of the blown air from becoming too low as in the past, which would cause the objects to be cooled such as vegetables stored in the refrigerator to lose weight or deteriorate in quality. Since the entire amount of water can be flowed to the drain pan heater 14, the time required to thaw the frozen drain in the drain pan 10 can be shortened.

[Brief explanation of the drawing]

FIG. 1 is a refrigerant piping system diagram showing one embodiment of the refrigeration system of the present invention, and FIG. 2 is a refrigerant piping system diagram of a conventional example. 1... Compressor, 2... Condenser, 4... Evaporator,
9a...Discharge path, 11...Capacity control bypass path, 12...Two-way proportional valve, 13...Three-way solenoid valve,
14...Drain pan heater, 15...Defrost bypass path.

Claims (1)

[Claims] 1 Hot gas discharge path 9a connected to compressor 1
A capacity control bypass passage 11 for bypassing a portion of the hot gas through the condenser 2 and bypassing the evaporator 4 is connected to the capacity control bypass passage 11.
A defrost bypass path 1 is provided with a two-way proportional valve 12 for adjusting the bypass amount of hot gas, and bypasses the condenser 2 and bypasses the entire amount of hot gas to the evaporator 4 during defrost operation.
5 is formed separately from the capacity control bypass passage 11, and the defrost bypass passage 15 is interposed in the discharge passage 9a upstream of the connection point of the capacity control bypass passage 11. 1
A drain pan heater 14 is connected to the discharge passage 9a through the drain pan 10 of the evaporator 4, and is connected to the defrost bypass passage 15 through the drain pan 10 of the evaporator 4.
A refrigeration system characterized in that the entire amount of hot gas during defrost operation is bypassed to the evaporator 4 through the drain pan heater 14.