JPH022068B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a refrigeration system, more specifically, a defrost circuit having a hot gas bypass path and a defrost circuit which is disposed downstream of a condenser and which opens and closes upon command to start defrost operation. The present invention relates to a refrigeration system equipped with a valve, which confines refrigerant unnecessary for defrost operation in a liquid reservoir including the condenser during pump-down operation, and performs defrost operation with a certain amount of refrigerant present in the defrost circuit.

(Prior Art) The applicant of this application has developed a refrigeration system that can always perform proper defrost operation without being affected by the operating state immediately before starting defrost operation, and has filed a patent application (Japanese Patent Application No. 58-71770). ), and the device will be explained based on FIG. 5, which schematically shows the outline of the device. In the refrigeration system, a hot gas bypass path F is provided between the condenser B, the liquid receiver D, and the expansion valve E, and the hot gas bypass path F is connected to the high-pressure gas pipe. , a hot gas valve G that controls the amount of hot gas bypassed to the evaporator G and circulates the entire amount of circulating refrigerant to the evaporator C during frosting;
At the same time, an on-off valve H is provided on the downstream side of the condenser B, which closes in response to a defrost operation start command,
A fixed amount outflow mechanism L is provided in the compressor A to flow out a certain amount of refrigerant out of the refrigerant trapped in the liquid reservoir including the condenser B by pump-down operation to a defrost circuit that performs a defrost operation. When the low pressure in the defrost circuit becomes lower than the set value due to the pump down operation, the pump down operation is terminated, and the low pressure in the defrost circuit becomes higher than the set value due to the outflow of the refrigerant from the quantitative outflow mechanism I. A low pressure switch J is provided to start a defrost operation when the refrigerant cools down, and when the defrost operation is performed in conjunction with the operation of the low pressure switch J, a constant amount of refrigerant preset by the quantitative outflow mechanism is circulated through the defrost circuit. The above-mentioned defrost operation is performed.

(Problem to be Solved by the Invention) However, in the above-mentioned refrigeration system, as shown in FIG. 6, for example, the temperature inside the refrigerator reaches a saturation temperature (-22.5°C) corresponding to the set pressure at which the low pressure switch J is turned on.
For example, if the temperature is set to -20℃, there is no problem, but if the temperature inside the refrigerator is the saturation temperature (-
(22.5°C), for example, -25°C, even if the on-off valve H of the low-volume outflow mechanism I opens, the pressure inside the defrost circuit will not reach the set pressure that turns on the low-pressure switch J. Therefore, the defrost operation is not started until the internal temperature naturally rises to -22.5°C or higher, and there is a problem in that it takes a long time from the end of the pump down operation to the start of the defrost operation. .

According to the present invention, the compressor is forcibly driven to start the defrost operation after a predetermined period of time has elapsed after the end of the pump-down operation after the command to start the defrost operation is issued. be.

(Means for solving the problems) The present invention will be explained based on FIGS. 1 and 2.
It is equipped with a defrost circuit having a hot gas bypass path 20 and an on-off valve 30 which is disposed downstream of the condensers 2 and 3 and closes in response to a defrost operation start command. In a refrigeration system that confines refrigerant unnecessary for defrost operation in a reservoir and performs defrost operation with a certain amount of refrigerant present in the defrost circuit, it detects a drop in low pressure due to pump-down operation and turns off the compressor. A low-pressure pressure detector 63L is provided to stop the machine 1 and end the pump-down operation, and a timer 2D3 is provided that starts counting after issuing a defrost operation start command and outputs a defrost operation signal after the end of the pump-down operation. The contact point of the timer 2D3 is connected in parallel with the detector 63L to a series circuit of the compressor motor MC and the low pressure detector 63L.

(Function) As described above, even if the set temperature inside the refrigerator is low and the low-pressure pressure detector 63L does not close after the end of the pump down operation due to the start command of the defrost operation, the timer 2D3 will set the time for the set time. Afterwards, the compressor 1 can be reliably driven and defrost operation can be started.

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

What is shown in FIG. 1 is a container refrigeration system, and in FIG. These devices are each connected by a refrigerant pipe 6, and form a refrigeration cycle in which the evaporator 4 cools the internal chamber.

Further, in FIG. 1, 7 is a liquid receiver integrated with an accumulator, 7a is a liquid receiving part, 7b is an accumulator part, 8 is a dryer, 9 is a liquid indicator, and 10 is a liquid receiver on the suction side of the evaporator 4. An attached fan 11 is a fan attached to the air-cooled condenser 2.

In the refrigeration cycle configured as described above, the high pressure gas pipe 6a connecting the discharge side of the compressor 1 and the inlet side of the air-cooled condenser 2 is connected to the compressor 1.
The hot gas discharged from each condenser 2,
3. Connect a hot gas bypass path 20 which bypasses the liquid receiving part 7a of the liquid receiver 7 and the temperature-sensitive expansion valve 5 to the evaporator 4, and connects the outlet side thereof to the expansion valve 5 and the evaporator 4. connected to the low pressure liquid pipe 6b between the
A hot gas valve 21 is interposed at the connection portion of the hot gas bypass path 20 to the high pressure gas pipe 6a, and a refrigerating valve is installed downstream of the condenser 3, that is, downstream of the liquid indicator 9 in FIG. An electromagnetic on-off valve 30 that closes upon a command to stop operation or refrigeration operation and a command to start defrost operation is provided to enable pump-down operation. The defrost circuit is configured to confine a certain amount of refrigerant in the liquid reservoir section, and performs a defrost operation on a certain amount of the refrigerant trapped in the liquid reservoir section, namely, the compressor 1, the hot gas valve 21, the hot gas bypass path 20, and the evaporator. 4,
A quantitative outflow mechanism 40 is provided which flows out into a defrost circuit consisting of an accumulator section 7b of the liquid receiver 7.

The hot gas valve 21 is mainly an electric three-way valve that can control the valve opening degree to the hot gas bypass passage 20 from 0% to 100% in proportion to the voltage, and controls the hot gas bypass passage to the evaporator 4. In addition to controlling the amount of refrigerant to adjust the capacity, the entire amount of refrigerant circulating during frosting is transferred to the hot gas bypass path 20.
This is achieved by using a proportional control valve designed to allow the air to flow through the air, and controlled by a controller 22 and an auxiliary relay _2DX2 of the defrost control circuit shown in FIG. 2, which will be described later. Note that the hot gas valve 21 is PID controlled by a controller 22.

This PID control (Proportional−plus−integral
-plus-derivative control) refers to control in which the control signal is proportional to the sum of the deviation signal, its integral, and its function.

Further, the quantitative outflow mechanism 40 is configured to operate the on-off valve 30 in a liquid reservoir section that performs a pump-down operation by closing the on-off valve 30 to confine the refrigerant.
An electromagnetic on-off valve 41 is interposed at a position where a predetermined outflow amount can be obtained with respect to an intervening position where the on-off valve 30 is interposed in the expansion valve 5. The on-off valve 41 is interposed in the high-pressure liquid pipe 6c on the inlet side, and the on-off valve 41 is interposed in the high-pressure liquid pipe 6c on the outlet side of the liquid indicator 9, and is confined in the high-pressure liquid pipe 6c between these intervening positions. This amount of refrigerant can be made to flow out by closing the on-off valve 41 and opening the on-off valve 30.

The amount of refrigerant set by the fixed amount outflow mechanism 40 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. .

Further, the quantitative outflow mechanism 40 uses the on-off valve 41 and the on-off valve 3 by using the high-pressure liquid pipe 6c.
0, but it may be configured on the low-pressure liquid pipe side as long as it is downstream of the condensers 2 and 3, in other words, downstream of the part that becomes the liquid reservoir, or the refrigerant circulation path It may also be formed using special piping or a liquid reservoir instead of using a liquid pipe.

Further, in FIG. 1, reference numeral 23 denotes a energized/closed solenoid valve that is installed in the suction gas pipe 6e, and is connected in parallel with the capillary reach tube 24 and installed in the suction gas pipe 6e.

Further, a low pressure detector 63L consisting of a low pressure switch is provided on the suction side of the compressor 1, and the detector 63L detects a decrease in the low pressure of the defrost circuit due to pump down operation.
It turns off when the predetermined set value is below, and ends the pump-down operation, and detects an increase in the low pressure of the defrost circuit due to the outflow of refrigerant from the quantitative outflow mechanism 40, and turns on when it exceeds the predetermined set value. It works and allows defrost operation to start.

In the embodiment shown in the figure, the low pressure pressure detector 63L
A pressure detection unit is arranged on the suction side of the compressor 1 constituting the defrost circuit, and the setting value for turning off the low pressure pressure detector 63L is set to 0.12Kg/cm ²
(-400mmHg) and the setting value for turning on is 0.36Kg/
It is made up of cm ² .

In the figure, 63H is a high pressure switch, 63CL is a high pressure control switch, 63QL is a hydraulic protection switch,
63W is a water pressure switch.

In the above configuration, the valve opening degree of the hot gas valve 21 is controlled between 0% and 100% by the output signal from the controller 22 during refrigeration operation, while it is always 0% opening degree (bypass amount zero) during refrigeration operation. ).

In addition, the defrost operation start command is mainly sent to the air pressure switch APS and, for example, 12
Defrost timer 2 with time as set time
D ₁ is used. In this case, the air pressure switch APS is given priority over the defrost timer _2D1 , and the defrost timer _2D1 is reset by the operation of the air pressure switch APS.

In addition, due to the defrost operation start command,
The on-off valve 30 is closed to perform pump-down operation, and after the end of the pump-down operation, the defrost operation is started by switching the low pressure switch 6.
It is controlled using 3L.

Furthermore, when the defrost operation is finished, for example, the low pressure gas pipe 6d on the outlet side of the evaporator 4 is
Two thermostats 23D ₁ with different set temperatures,
_23D2 is attached to detect the temperature of the low pressure gas pipe 6d.

In the refrigeration system configured as described above, even if the liquid refrigerant flows out from the quantitative outflow mechanism 40 after the end of the pump down operation in response to the defrost operation start command, the low pressure pressure detector 63L does not turn on. A timer 2 for starting the defrost operation that forcibly drives the compressor 1 when a predetermined time has elapsed after the command to start the defrost operation has elapsed.
D3 is provided, and this point will be described in detail below in the section describing the electric circuit of the present refrigeration system.

Therefore, a controller 22 for adjusting the temperature of the blown air by controlling the hot gas valve 21 is provided.
The electric circuits of the respective control devices for controlling the defrost operation will be explained based on FIG. 2.

What is shown in FIG. 2 is an electric circuit of the refrigeration system shown in FIG. _MF1-1 , MF-1
₂ , _MF1-3 , and three outdoor fan motors _MF2-1 , _MF2-2 , _MF2-3 corresponding to the three fans 11 attached to the air-cooled condenser 2, and a power source for these electrical devices. The circuit is connected to a power source by selecting one of a 200V or 220V constant voltage power supply plug _P1 and a 380 to 415V or 440V high voltage power supply plug _P2 , and is also connected to the power supply circuit via a transformer Tr. The controller 22 and the control circuits of each of the control devices are connected to each other.

In FIG. 2, CB is a circuit breaker, OC is an overcurrent relay, 2X ₁ to 2X ₃ are auxiliary relays and their contacts, and 3-88 is an on/off switch. Further, in the power supply circuit, contacts without symbols are switching contacts that are switched by selecting the plugs P ₁ and P ₂ .

Although not shown, the controller 22 includes an input transformer, a power input device, a sensor input device, an operation input/output device, a central processing unit, and a relay output device. As shown, a return sensor RS is placed on the suction side of the evaporator 4 and detects the temperature of the return air from inside the refrigerator, that is, a suction air, and a supply sensor SS is connected to the outlet side of the evaporator 4 to detect the temperature of the blowing air. In addition, the relay output device includes a relay Y ₂ for controlling the solenoid relay 20LS ₁ of the on-off valve 30, a switching relay U ₁ for switching between freezing operation and refrigeration operation, other relays G ₁ and G ₂ , and a shorting wire Y _1. The electric part 20M of the hot gas valve 21, the solenoid relay 20SL of the electromagnetic valve 23 in the embodiment shown in FIG. 1, the auxiliary relays 2X ₄ and 2X ₅ , and the lamps AL and BL are connected to these.

Additionally, the following relay circuit is configured.

(1) Pump down control circuit 70: Auxiliary relay 2
A parallel circuit of the normally open contacts of X ₄ and 2DX ₂ and a series circuit of the solenoid relay 20LS ₁ of the on-off valve 30 for pump-down operation.

(2) Defrost control circuit 71: Air pressure switch that issues a command to start defrost operation
A parallel circuit between the APS and the defrost timer 2D ₁ , and an electromagnetic switch 8 for drive control of the compressor 1.
A series circuit with the normally open contact of 8C and a parallel circuit with the manual defrost switch 3D which also issues a command to start defrost operation (defrost command circuit).
Thermostat 23 that detects the end of defrost
A series circuit (defrost end command circuit) of D ₁ and 23D ₂ , a parallel circuit of the defrost start timer 2D3, auxiliary relay 2DX ₂ , and auxiliary relay 2DX ₃ , which are the features of the present invention, and a regular circuit of the electromagnetic on-off valve 88C. Series circuit with closed contact and parallel circuit with defrost relay 2DX ₁ (auxiliary relay circuit)
It consists of a series circuit of these three circuits.

The timer 2D3 counts the normal time required for the liquid refrigerant to flow out from the quantitative outflow mechanism 40 from the end of the pump down operation due to the issuance of the defrost operation start command, and closes the contact. I try to do that.
Further, in this control circuit 71, the normally open contact of the defrost relay 2DX ₁ is a contact that constitutes a self-holding circuit of the circuit 71, and the normally open contact of the defrost relay 2D ₂ is a contact for self-holding of the auxiliary relays 2DX ₂ and ₃ . , 2DX ₂ is a defrost end timer and its contact for forcibly opening the defrost control circuit 71 after a predetermined period of time, for example, 45 minutes, from the defrost operation start command.

Further, the normally open contacts of the switch 88C in the defrost command circuit are connected to the defrost timer 2D ₁ and the air pressure switch APS.
This is to prevent a defrost operation start command from being issued even if the compressor 1 is closed while the compressor 1 is stopped.The purpose of this will be described in detail later, but
The purpose is to ensure that a predetermined amount of refrigerant is always stored in the quantitative outflow mechanism 40 at the start of defrosting operation.

(3) Compressor motor MC start/stop control circuit 72; first
Hydraulic protection switch 63QL ₁ , compressor 1 protection thermostat 49, overcurrent relay OC, high pressure switch HPS for protecting compressor 1, low pressure that detects the suction pressure of compressor 1 and opens when it is below a predetermined set value. It consists of a series circuit of a pressure detector 63L and an electromagnetic switch 88C for controlling the drive of the compressor motor MC, and the defrost operation is carried out in series with the electromagnetic switch 88C and in parallel with the low pressure pressure detector 63L. A contact that closes after the required time of the starting timer 2D3 is connected. In addition, 6
3QL ₂ is the second hydraulic protection switch.

(4) Fixed amount outflow mechanism control and indoor fan motor control circuit; This circuit is connected to the first hydraulic protection switch 6.
3QL ₁ , which is connected in series to the normally closed contact of the auxiliary relay 2DX ₂ , and the solenoid relay 20LS ₂ of one electromagnetic on-off valve 41 of the quantitative outflow mechanism 40 and the indoor fan motor MF.
_1-1 to ₃ This is a circuit in which a parallel circuit with an electromagnetic switch 88F for drive control is connected in series. In this circuit, a series circuit of the normally open contact of the auxiliary relay 2DX ₂ and the normally closed contact of the electromagnetic switch 88C is connected in parallel to the normally closed contact of the auxiliary relay 2DX ₂ and the fan _MF1-1. This circuit is installed in series with the electromagnetic switch 88F for the fan motor _MF1-3 after the end of the pump-down operation after the command to start the defrost operation.
₁ to ₃ temporarily to drive the fan motor MF1.
- The quantitative outflow mechanism 40 utilizes heat generation from ₁ to ₃ .
This is done to promote the evaporation of the liquid refrigerant flowing out. In addition, 2F is the fan motor
MF1- ₁ to ₃ day timer, 2D ₁
is the defrost timer and the fan motor
It is set at the same time as _MF1-1 to ₃ stop.

In Figure 2, CPD is a contact protection diode, GL is a lamp, and 3-
30L is a lamp switch, and the electric part 20M of the hot gas valve 21 is connected to the controller 2.
In addition to the control circuit of 2, the auxiliary relay 2DX ₂
A direct connection circuit is formed in which a normally open contact is inserted, and by closing the normally open contact, the opening degree can be changed to 100%, which bypasses the entire amount of discharged gas.

Therefore, in the above configuration, the air temperature is adjusted according to the set temperature set by the set point selector CPS of the controller 22, and in the case of refrigeration operation where the set point temperature is lower than, for example, -5°C, the air temperature is adjusted by the return sensor on the suction side. This is done by controlling the compressor 1 to start and stop based on RS. Specifically, when the intake air temperature becomes lower than the set temperature, the conduction of the relay Y2 provided in the controller 22 is cut off and the relay _Y2 is turned off. The auxiliary relay _2X4 connected to the compressor ₂ is opened, and more specifically, the compressor 1 is stopped after the pump down operation is performed as described later.

By the way, relay _Y2 is activated during refrigeration operation.
If the compressor 1 is stopped for a long time after pump-down operation, if the quantitative outflow mechanism 40 is located higher than the liquid receiver 7, the liquid refrigerant stored in the quantitative outflow mechanism 40 will be removed. The refrigerant leaks into the liquid receiver 7, reducing the amount of refrigerant stored, causing the problem that a predetermined amount of refrigerant necessary for defrosting operation cannot be secured. In order to solve this problem, as described above, when the compressor 1 is stopped by the operation of the relay _Y2 , the command to start the defrost operation is not issued.

In addition, in the case of refrigeration operation at 5°C or higher, the hot gas valve 21 is controlled to an opening degree of 0 to 100% based on the supply sensor SS on the blowout side, and the hot gas is bypassed at a flow rate corresponding to this opening degree. This is done by doing this.

Hereinafter, when the refrigeration device is performing refrigeration operation, the air pressure switch APS,
Or, defrost timer 2D ₁ closes,
A case will be explained in which a defrost operation start command is issued.

As described above, when any one of the contacts 2D ₁ and APS for commanding the start of defrost operation is closed, the operation system is divided into two systems depending on whether the relay Y ₂ is conductive or not. Specifically, (a) When the relay _Y2 is conductive and the compressor 1 is driven, in this case, the normally open contact of the electrode switch 88C is closed. For example, by closing the defrost timer 2D ₁ (the same applies to the air pressure switch APS, the explanation will be omitted below for the case of the switch APS), a command to start the defrost operation is output. Then, the defrost relay 2DX ₁ is energized, its normally closed contact is opened, and the auxiliary relay 2X ₄ is demagnetized, and further,
The normally open contact of the relay _2X4 is opened, the solenoid relay _20LS1 of the on-off valve 30 for pump-down operation is deenergized, the valve 30 is closed, and the pump-down operation is started.

Due to this pump down operation, the compressor 1
When the pressure on the suction side of the compressor decreases and the low pressure detector 63L turns off and opens, the electromagnetic switch 88C is demagnetized and the compressor motor MC is stopped.

At the same time, the normally closed contact of the electromagnetic switch 88C is closed, the auxiliary relay 2DX ₂ and the timer 2D3 are energized, and the relay 2
The normally closed contact of DX ₂ is opened and the solenoid relay 20LS ₂ of the on-off valve 41 is demagnetized, and while the on-off valve 41 is closed, the solenoid relay 20LS 2 of the on-off valve 41 is closed.
Relay 2 connected in parallel to the normally open contact of DX ₂
The normally open contact of DX ₂ opens and the fan motor
The electromagnetic switches 88F of _MF1-1 to _MF1-3 continue to be energized to continue operating the motors _MF1-1 to _MF1-3 , and the normally open contact of relay _2DX2 is closed, so that the solenoid relay _20LS1 is excited and the on-off valve 3
0 is opened, and the liquid refrigerant stored in the quantitative outflow mechanism 40 flows out to the evaporator 4 side (defrost circuit).At the same time, the solenoid relay 20M of the hot gas valve 21 is energized. The opening is 100%, and the defrost circuit described above is formed.

●Furthermore, when the timer 2D3 is energized, the timer 2D3 starts counting to close its normally open contact after a predetermined period of time.

●In addition, in this example, as mentioned above,
At this time, the fan motors _MF1-1 to _MF1-3
Since the switch 88F is excited and the motors _MF1-1 to _MF1-3 are driven, the heat generated by the motors _MF1-1 to ₃ heats the refrigerant that is discharged from the quantitative outflow mechanism 40, and the gas is heated. This will promote the development of

Thus, the pressure within the defrost circuit increases due to the evaporation of the refrigerant that has flowed out of the metered flow out mechanism 40. In this case, if the set temperature in the refrigerator is higher than the equivalent saturation temperature of the set pressure for turning on the low pressure pressure detector 63L, the detector 63L quickly detects the
The compressor 1 can be turned on in about seconds and the compressor 1 can be restarted. On the other hand, if the set temperature in the refrigerator is lower than the equivalent saturation temperature of the pressure at which the low pressure detector 63L turns on, the detector 63L does not easily turn on. Even if the low-pressure pressure detector 63L does not turn on, the normally open contact of the timer 2D3 automatically closes after a predetermined period of time after the end of the pump-down operation, and the compressor 1 is forced to start. It will be done. At the same time, the normally closed contact of the switch 88C is opened, the switch 88F is demagnetized, and the fan motors _MF1-1 to _MF1-3 are stopped.

In this way, the defrost operation is reliably started within the predetermined time.

Then, the frost adhering to the evaporator 4 is removed, and the refrigerant temperature on the outlet side of the evaporator 4 rises, causing the thermostats 23D ₁ , 2
_3D2 having a low temperature side set value is opened, the defrost relay _2DX1 is demagnetized, and the defrost control circuit 70 is opened;
The auxiliary relay _2DX2 is demagnetized, the hot gas valve 21 is returned to 0% opening, the opening/closing valve 41 of the quantitative outflow mechanism 40 is opened, and the fan motors _MF1-1 to _MF1-3 are driven to perform defrost operation. As soon as the process is finished, normal operation resumes. Furthermore, the thermostat 23D ₁ ,
Even if _23D2 does not operate, the defrost end timer 2D2 operates and the defrost operation is ended after a predetermined time (45 minutes).

(b) On the other hand, if the relay Y ₂ is in a non-conducting state and the compressor 1 is stopped when the defrost timer 2D ₁ is closed, the defrost operation command is not output, and the defrost timer 2D ₁ simply maintains a closed circuit state.

Then, when the internal temperature rises and the relay Y ₂ is turned on, the auxiliary relay 2X ₄ is energized, the normally open contact of the relay 2X ₄ is closed, and the opening and closing for pump down Valve 3
0 is opened, and in conjunction with this, the pressure in the refrigerant circuit increases, the low pressure pressure detector 63L is closed, the switch 88C is excited, and the compressor 1 is driven.

Furthermore, by energizing the switch 88C, a defrost command is output from the defrost control circuit 70, and a series of steps related to the frosting operation starting from the pump-down operation are performed as in the case (a) above. be. Therefore, a predetermined amount of refrigerant can be reliably stored in the quantitative outflow mechanism 40, and defrosting can be performed quickly with this predetermined amount of refrigerant.

Further, in the above embodiment, since the normally open contact of the switch 88C is not connected in series to the manual defrost switch 3D, when the switch 3D is closed, the compressor 1 starts and stops, that is, the relay Y ₂
The defrosting process described above can be performed regardless of whether the circuit is conductive or not.

Further, in the above embodiment, the timer 2D3 for starting the defrost operation starts counting after the command to start the defrost operation is issued and after the end of the pump down, but as shown in FIG. , the timer 2D3 is connected to the auxiliary relay circuit in the defrost operation control circuit 71 in parallel with the normally closed contact of the switch 88C, so that the timer 2D3 counts a predetermined time immediately after the defrost operation start command is issued. You may also do so.

Further, in the above embodiment, the compressor motor MC
Instead of that, the timer 2D is connected in series to the switch 88C for controlling the drive of the motor MC.
Although the contacts No. 3 are connected, the point is that the compressor motor MC may be started by the operation of the timer 2D3.

In addition to the above-mentioned embodiments, examples of refrigeration equipment that confines refrigerant unnecessary for defrost operation in a liquid reservoir including a condenser 2 and performs defrost operation with a certain amount of refrigerant include those shown in FIGS. 4a to 4d, for example. But that's fine.

In the case of FIG. 4a, after closing the on-off valve 30 and ending the pump-down operation, the solenoid valve 61 is opened and a certain amount of refrigerant necessary for the defrost operation is supplied to the defrost circuit from the circuit 63 having the capillary 62. After supplying, the solenoid valve 61 is closed.

In FIG. 4b, the on-off valve 30 is closed to leave a certain amount of refrigerant necessary for the defrost operation, thereby ending the pump-down operation.

FIG. 4c shows a refrigerant tank 64 with a certain amount that exchanges heat with the suction pipe of the compressor 1, which is connected to the discharge gas pipe through a connecting pipe 65, so that a certain amount of refrigerant is stored in the refrigerant tank 64 during refrigerant or refrigeration operation. After the pump-down operation is completed, the refrigerant in the refrigerant tank 64 is returned to the defrost circuit through the communication pipe 65. In this circuit, if the refrigerant is difficult to flow out, it is also possible to connect a communication pipe 67 with a solenoid valve 66 shown by a dotted line to the hot gas bypass pipe 20 and open the solenoid valve 66 after the pump-down operation is completed. good.

In FIG. 4d, the inlet of a refrigerant tank 64 provided in the suction pipe is connected to the inlet side of the condenser 2, and the outlet is connected to the suction pipe through a connecting pipe 69 having a solenoid valve 67 and a capillary 68.

Further, in the embodiment described above, the hot gas valve 2
The opening control in step 1 was performed by comparing the temperature with the set temperature using a supply sensor SS that detects the temperature of the blown air. Alternatively, the detection may be performed by detecting the difference between the temperature of the intake air and the temperature of the blown air.

Further, although an electric three-way valve is used as the hot gas valve 21, two two-way valves may be combined.

Further, although the above embodiments are applied to a container refrigeration system, the present invention can also be applied to other refrigerators.

Further, as the condenser, an air-cooled condenser 2 and a water-cooled condenser 3 were used together, but a single condenser 2 or 3 was used.
You can also use only

(Effects of the Invention) As described above, the present invention includes a timer 2D3 that starts counting after a defrost operation start command is issued and outputs a defrost operation signal after the pump-down operation ends, and compresses the contacts of the timer 2D3. Since the detector 63L is connected in parallel to the series circuit of the machine motor MC and the low pressure detector 63L, the predetermined time set by the timer 2D3 is always maintained during defrost operation, regardless of whether the set temperature inside the refrigerator is high or low. As a result, the defrost operation can be reliably prevented from becoming too long.

[Brief explanation of drawings]

Fig. 1 is a refrigerant circuit diagram of an embodiment of the refrigeration system of the present invention, Fig. 2 is an electric circuit diagram of the same embodiment, Fig. 3 is a partial explanatory diagram of an electric circuit diagram of another embodiment, Fig. 4a,
b, c, and d are refrigerant piping system diagrams of other embodiments of the refrigeration system of the present invention, Fig. 5 is an explanatory diagram showing the conventional technology, and Fig. 6 shows the difference in set temperature inside the refrigerator during defrosting with the conventional system. 3 is a graph showing the pressure increase of the refrigerant flowing out from the quantitative outflow mechanism into the defrost circuit. 1...Compressor, 2, 3...Condenser, 20...Hot gas bypass path, 30...Opening/closing valve, 63L...
...Low pressure pressure detector (low pressure switch), 2D3...
Timer, MC...Compressor motor.

Claims (1)

[Claims] 1 A defrost circuit having a hot gas bypass path 20 and an on-off valve 30 that is disposed downstream of the condensers 2 and 3 and closes upon a defrost operation start command, and includes the condensers 2 and 3 in pump-down operation. In a refrigeration system that confines refrigerant unnecessary for defrost operation in a liquid reservoir and performs defrost operation with a certain amount of refrigerant present in the defrost circuit, detects a drop in low pressure due to pump-down operation and performs an off operation, A timer 2D3 is provided with a low-pressure pressure detector 63L that stops the compressor 1 and ends the pump-down operation, and also starts counting after issuing a defrost operation start command and outputs a defrost operation signal after the end time of the pump-down operation.
A refrigeration system characterized in that a contact point of the timer 2D3 is connected in parallel with the detector 63L to a series circuit of the compressor motor MC and the low pressure detector 63L.