JPH0571863B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a refrigeration system, and more particularly, a refrigeration system comprising a hot gas bypass path and a hot gas valve, and a refrigeration system formed between a compressor and the hot gas bypass path and an evaporator. The present invention relates to a refrigeration system that performs defrost operation by circulating a predetermined amount of refrigerant through a defrost circuit.

(Prior Art) Conventionally, a refrigeration system that uses a hot gas bypass passage and a hot gas valve to enable defrost operation with a predetermined amount of refrigerant has been designed to A device is known in which a certain amount of refrigerant is measured during operation and the measured refrigerant is circulated.

As shown in FIG. 11, this refrigeration system bypasses the hot gas discharged from the compressor CP to the condenser CD and bypasses the evaporator E through the hot gas bypass path H and the evaporator E. It is equipped with a hot gas valve HV that controls the capacity by controlling the amount of hot gas, and a pair of solenoid valves SV ₁ and SV ₂ and these solenoid valves are installed downstream of the condenser CD.
A refrigerant measuring section A consisting of a measuring device T interposed between SV ₁ and SV ₂ is provided, and a certain amount of refrigerant measured by this measuring section A during defrost operation is transferred to the hot gas bypass path H and the evaporator E. The refrigerant is discharged into a defrost circuit formed by the refrigerant and the compressor CP, and defrost is performed with a constant amount of refrigerant.

In FIG. 11, EX is an expansion valve and D is a flow divider.

Therefore, in the refrigeration system configured as described above, the metering section A performs pump-down operation with the downstream solenoid valve SV ₁ closed, and after the pump-down is completed, the metering section A This is done by closing the upstream solenoid valve SV ₂ ,
The refrigerant measured in the metering part A flows out to the defrost circuit for a certain period of time (approximately 20 seconds) after the end of the pump-down operation, using a standby timer.
After that, the upstream solenoid valve SV ₁ is opened to maintain a balance between high and low pressure. In other words, high pressure measuring part A
The refrigerant in the metering section A flows out into the defrost circuit due to the pressure difference between the evaporator E and the defrost circuit on the evaporator E side, which is at a low pressure.

(Problem to be Solved by the Invention) However, when defrosting operation is performed by measuring a certain amount of refrigerant as described above, there is no problem as long as the entire amount of refrigerant measured by the measuring part A circulates through the defrost circuit. However, when the outside temperature is low (e.g. -30℃),
There is a problem that the defrost time is longer than when the outside air temperature is high.

That is, when the outside air temperature is low, there is a large heat loss from the external refrigerant piping system such as the compressor and outdoor piping installed outside the refrigerator.
Since the high pressure is low even if the refrigerant is measured in the measuring part A, the entire amount of refrigerant measured in the measuring part A does not flow out to the defrost circuit. Also, during the defrost operation, the solenoid valve SV ₁ is in the open state, and the expansion Since the valve EX normally uses a temperature-sensitive expansion valve, it is fully open or close to fully open during defrost operation, so the hot gas circulating in the defrost circuit flows back into the metering section A. The amount of refrigerant circulating through the defrost circuit is insufficient, and the defrost time becomes longer due to the aforementioned heat loss and insufficient amount of refrigerant.

Note that the longer the defrost time, the more the compression input will increase, and the temperature inside the refrigerator or room will change.

The purpose of the present invention is to solve the problem of prolonging defrost time due to insufficient amount of refrigerant during defrost operation at low outside air temperatures, and to enable defrost operation to be performed with a predetermined amount of refrigerant even when outside air temperature is low, thereby shortening defrost time. At the point.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides hot gas discharged from the compressor 1 to the condenser 2,
The compressor 1, the hot gas bypass path 20, and the evaporator 4 are provided with a hot gas bypass path 20 that bypasses the hot gas and introduces the hot gas into the evaporator 4, and a hot gas valve 21 that bypasses the hot gas to the bypass path 20. In a refrigeration system in which a defrost circuit is formed between the defrost passage 20 and the evaporator 4 to enable defrost operation, during defrost operation,
It has a refrigerant supply means for supplying refrigerant to the defrost circuit from a liquid reservoir during defrost operation including the condensers 2 and 3, and a high pressure detection sensor PS, which detects the high pressure when a certain period of time has elapsed after the start of defrost operation. a refrigerant amount insufficient detection means for detecting the amount of refrigerant and outputting an insufficient amount of refrigerant in the defrost circuit when the high pressure is below a certain value; and refrigerant replenishment control means for replenishing the insufficient amount of refrigerant.

By the way, the refrigerant amount shortage detection means may detect the high pressure using the high pressure detection sensor PS, and output the shortage of refrigerant amount in the defrost circuit based on the high pressure when a certain period of time has elapsed after the start of defrosting. However, the rate of change in the high pressure is calculated based on information from the high pressure detection sensor PS during defrost operation, and when this rate of change is less than a certain value, an insufficient amount of refrigerant in the defrost circuit is output. It's okay.

Further, the refrigerant replenishment control means controls the refrigerant supply means by giving an operation command to the refrigerant supply means using the output from the refrigerant amount shortage detection means, and supplies a certain amount of refrigerant through the refrigerant supply means. Although the refrigerant may be replenished to the defrost circuit, it is preferable to replenish a predetermined amount of refrigerant depending on the output value from the refrigerant amount shortage detection means.

The refrigerant supply means mainly includes the injection passage 36 and the injection valve 3.
5, the injection passage 36 is interposed between the liquid reservoir and the defrost circuit, and the injection valve 35 is operated for a certain period of time or a period according to the detected value based on the detection result from the refrigerant amount shortage detection means. By opening the opening, the insufficient amount of refrigerant is supplied through the injection passage 36.

Further, the second opening/closing mechanism 32 of the measuring section 33 using a pair of opening/closing mechanisms 30, 32, that is, the second opening/closing mechanism 32 that is closed during the defrost operation may be used as the refrigerant supply means. In this case, the second
The opening/closing mechanism 32 is opened for a certain period of time or for a period of time according to a detected value based on a command from the refrigerant replenishment control means based on the output from the refrigerant amount shortage detection means to supply the refrigerant to be confined in the liquid reservoir to the defrost circuit. .

(Function) When performing defrost operation when the outside air is low, if the refrigerant supplied to the defrost circuit is insufficient, the high pressure during the defrost operation will be significantly lower than the high pressure when the outside air is high. By detecting high pressure using the detection sensor PS, it is possible to detect a shortage of refrigerant in the defrost circuit more accurately than when detecting the intake gas temperature.

Therefore, the high pressure detection sensor PS detects the high pressure after a certain period of time has passed after the start of defrost operation, and when this high pressure is below a certain value, it outputs an insufficient amount of refrigerant in the defrost circuit and activates the refrigerant supply means. By activating the refrigerant and replenishing the insufficient amount of refrigerant, it is possible to solve the problem of the conventional method in which the defrost time becomes longer by replenishing the insufficient refrigerant amount even if the refrigerant amount is insufficient during defrost operation at low outside air temperature. By using the high-pressure pressure detection sensor PS as the refrigerant amount shortage detection means and detecting the high pressure, the refrigerant amount shortage can be accurately detected.
By replenishing more than necessary, defrost operation can be reliably performed in a protected area where the high voltage switch and compressor overcurrent relay will not be activated.

In addition, the refrigerant replenishment control means replenishes a predetermined amount of refrigerant according to the output of the refrigerant amount shortage detection means, thereby replenishing the refrigerant amount more precisely than when replenishing a fixed amount of refrigerant relative to the output. This makes it possible to satisfy both the requirements of shortening the defrost time and compensating for defrost operation within the protected area.

(Embodiment) The refrigeration system for marine containers shown in FIG. 5
These devices are connected by a refrigerant pipe 6, and the air inside the refrigerator is cooled by the evaporator 4.

In FIG. 1, 7 is a dryer, 8 is a liquid indicator, 8 is an accumulator, 10 is a fan attached to the evaporator 3, and 11 is a fan attached to the air-cooled condenser 2.

In the refrigeration system configured as described above, the hot gas discharged from the compressor 1 is routed through the condensers 2 and 3 and the temperature-sensitive expansion valve 5 to the high-pressure gas pipe 6a, and then passed through the evaporator 4. A hot gas bypass path 20 is connected to the hot gas bypass path 20, the outlet side of which is connected to the flow divider 12 provided on the inlet side of the evaporator 4, and a connection portion of the hot gas bypass path 20 to the high pressure gas pipe 6a is connected. , a hot gas valve 21 consisting of a proportional control valve is installed, and a refrigeration or refrigerating valve is installed downstream of the water-cooled condenser 3, in FIG. 1, downstream of the liquid indicator 8, and upstream of the expansion valve 5. A first opening/closing mechanism (hereinafter simply referred to as a solenoid valve) 30 consisting of a solenoid valve that closes in response to an operation stop command and a defrost operation start command is provided, and a metering tank 3 is provided upstream of the first solenoid valve 30.
1 is provided, the closing operation of the electromagnetic valve 30 enables the pump-down operation, and the metering tank 31
The refrigerant is confined in a liquid reservoir including the condensers 2 and 3, while the liquid indicator 8
A second opening/closing mechanism 4 consisting of a solenoid valve that forms a metering section 33 between the metering tank 31 and the metering tank 31 for metering a certain amount of refrigerant to be used for defrosting out of the refrigerant confined in the liquid reservoir section 4. )3
2, and furthermore, an expansion mechanism 34 such as a capillary reach tube is provided in a liquid reservoir part during defrost operation except for the measuring part 33, that is, in FIG. 1, between the second solenoid valve 32 and the liquid indicator 8. An injection passage 36 equipped with an injection valve 35 mainly composed of a solenoid valve is branched, and this injection passage 36 is connected to a low pressure gas pipe 6d.

Therefore, in the above configuration, the defrost circuit is formed by switching so that the entire amount of hot gas from the compressor 1 flows to the hot gas bypass path 20,
hot gas valve 21, hot gas bypass path 20,
It is formed by an evaporator 4 and an accumulator 9.

Further, in the one shown in FIG. 1, a drain pan heater 37 is connected to the hot gas bypass path 20, and this drain pan heater 37 also forms a part of the defrost circuit.

Further, the hot gas valve 21 changes the valve opening degree to the hot gas bypass path 20 from 0 to 0 in proportion to the voltage.
By controlling the amount of hot gas bypassed to the evaporator 4, the capacity can be adjusted to enable freezing and refrigeration operations, and during defrost operation, the entire amount of hot gas is transferred to the hot gas bypass path 20. A controller 4 with a built-in computer
0 performs PID control.

The injection exit valve 35 and the injection exit passage 36 constitute a refrigerant supply means for supplying insufficient refrigerant from the liquid reservoir to the defrost circuit during defrost operation. 35 is opened based on a command from the refrigerant replenishment control means based on the output of the refrigerant shortage detection means which detects and outputs the shortage of refrigerant in the defrost circuit, and supplies the insufficient amount of refrigerant via the injection exit passage 36. It replenishes.

In the embodiment shown in FIGS. 1 and 2, the refrigerant amount shortage detection means detects the high pressure P after a certain time ( _t1 , for example, 5 minutes) after the start of the defrost operation, and this high pressure P is set to a certain value _P2. A high-pressure pressure detection sensor PS that outputs an output when It is configured by being provided in the defrost circuit. Further, the refrigerant replenishment control means includes:
A quantitative control means is provided for replenishing a certain amount of refrigerant by opening the injection valve 35 for a certain period of time ( _t2, for example, 5 seconds) based on the output from the sensor PS.

That is, when performing defrost operation, the high pressure changes as time passes after the start of defrost operation, but this change varies depending on the outside air temperature, as shown in Figure 3. When the temperature is -30°C, the rate of change is smaller than when the outside air temperature is 50°C. Therefore, the high pressure P when a certain period of time (t ₁ = 5 minutes) has passed after the start of defrosting is less than that of the outside air temperature. A large difference occurs depending on the temperature. In other words, the high pressure P ₁ when the outside air temperature is -30°C does not reach the constant pressure P 2 even after a certain time t ₁ , but the high pressure when the outside air temperature is 50°C does not reach the constant pressure P ₂ after a certain time t _1. Before the elapse of t, the high pressure becomes constant P ₂ immediately after the start of defrost operation, and the high pressure P ₃ after the elapse of a certain time t ₁ greatly exceeds the constant pressure P ₂ , and the change in high pressure due to outside temperature is , which is greater than the change in intake gas temperature. That is, the high pressure P during the defrost operation is the same as that of the measuring section 3 when the outside air is low.
When the amount of refrigerant decreases due to the small amount of outflow from the metering section 3 and the accumulation in the metering section 33 due to backflow to the metering section 33, the amount of refrigerant decreases significantly, and the outside temperature drops to 0°C.
In the following case, it peaks at a certain time before the start of defrost operation and then decreases.

Therefore, by detecting the high pressure P, it is possible to detect a shortage of the refrigerant amount corresponding to the outside air temperature more accurately than when detecting the intake gas temperature.

The high pressure output by the sensor PS is
The high pressure _P2 is set based on, for example, 8 kg when a certain period of time _t1 , for example, 5 minutes has elapsed after the start of the defrost operation at an outside temperature of 0°C, and the time _t2 for opening the injection valve 35 is as follows:
The inner diameter of the capillary reach tube forming the expansion mechanism 34 interposed in the injection passage 36 is insufficient when the high pressure _P2 is not reached after the certain time _t1 , that is, when the outside air temperature is -30°C or less. The setting is based on the amount of refrigerant, and when the valve opening time _t2 is set to 5 seconds, the insufficient amount of refrigerant is replenished in these 5 seconds.

In other words, the amount of refrigerant shortage when the outside air temperature is low can be set in advance based on the cause of the shortage, and
The appropriate amount of refrigerant to be circulated during defrost is set in advance based on the amount of refrigerant required for the optimal defrost time and the amount of refrigerant that allows operation in a protected area where high pressure does not rise during defrost operation and activate the high pressure switch. Since this is possible, the amount of replenishment is determined by taking into consideration this appropriate amount of refrigerant and the amount of shortage. By the way, the replenishment amount set based on the outside temperature of -30℃ is
It is 300c.c.

Further, the command to start the defrost operation is mainly given by the air pressure switch APS and the defrost timer, and the end of the defrost operation is mainly given by the defrost completion thermostat which detects the intake gas temperature at the outlet side of the evaporator 4.
The low pressure switch LPS is used to terminate the pump down operation which is performed by TH and by the command to start defrost operation.

In Figure 1, HPS is a high pressure switch,
HPCS is a high pressure control switch, OPS is a hydraulic protection switch, and WPS is a water pressure switch.

Further, although the measuring section 33 is formed using a measuring tank 31, this measuring tank 31 is not necessarily required, and although it is formed on the high-pressure liquid pipe 6b, it may also be formed on the low-pressure liquid pipe 6c. Because it's good,
If the measuring tank 31 is not used, use a liquid pipe,
What is necessary is to be able to measure a certain amount of refrigerant.

Therefore, when performing freezing or refrigeration operation with the above configuration, the set point temperature is set by the set point selector SPS of the controller 40. The temperature is adjusted to the set temperature by controlling the start and stop of the compressor 1 based on the return sensor RS installed on the suction side of the
Based on SS, adjust the hot gas valve 21 from 0 to 100%.
The temperature is adjusted to the set temperature by controlling the opening to a certain degree and bypassing the hot gas to the evaporator 4 at a flow rate corresponding to this opening.

During freezing or refrigeration operation as described above, if the evaporator 4 is frosted and the air pressure switch APS is activated, or the defrost timer is activated and a defrost command is issued, the following occurs. Defrost operation is performed. First of all,
When a defrost operation start command is issued, the first solenoid valve 30 closes and the hot gas valve 21 closes.
When there is an opening degree to the hot gas bypass 20, the pump down operation is started by controlling to 0%.

In this pump down operation, the liquid refrigerant is transferred to the condensers 2 and 3.
As the confinement of the liquid refrigerant progresses, the low pressure decreases, and this low pressure is applied to the low pressure switch.
When the LPS becomes lower than the set value, the low pressure switch
The LPS turns off and the end of pump down operation is detected.

When the end of the pump down operation by the low pressure switch LPS is detected, the hot gas valve 21 is switched to 100% opening for the hot gas bypass path 20 while the compressor 1 continues to operate. The fan 10 attached to the evaporator 4 is stopped, and simultaneously with these operations, the second solenoid valve 32 is closed and the first solenoid valve 30 is opened.

Accordingly, by the closing operation of the second solenoid valve 32, the amount of refrigerant necessary for the defrost operation is measured in the measuring section 33 out of the refrigerant trapped by the closing operation of the first solenoid valve 30. The measured refrigerant is pushed out to the defrost circuit by the opening operation of the first solenoid valve 30, and defrost operation is started.

Next, this defrost operation will be explained according to the flowchart shown in FIG.

First, simultaneously with the start of the defrost operation, that is, simultaneously with the opening operation of the first solenoid valve 30, a _t1 timer that measures the predetermined time _t1 starts counting (step 101), and the predetermined time ( _t1 =5) starts counting. (step 102), the high pressure P at that time is detected by the sensor PS (step 103), and when the detected high pressure P is less than the preset high pressure _P2 (Step 104),
Open the injection valve 35 (step
105) At the same time, the _t2 timer that measures the predetermined time _t2 starts counting (step 106), and after counting up after the elapse of the predetermined time ( _t2 = 5 seconds) (step 107), the injection valve 35 (step 108).

Further, when the high pressure P after the predetermined time _t1 is higher than the predetermined pressure _P2 , the injection exit valve 35 is not opened and the defrost operation is completed by the operation of the defrost completion thermostat TH (step 109). Step 110).

As described above, in the defrost operation when the outside air is low, a certain amount of refrigerant is supplied to the defrost circuit from the liquid reservoir during the defrost operation via the injection passage 36 by opening the injection extraction valve 35. Therefore, even if the refrigerant metered in the metering section 3 is not completely discharged, or even if hot gas flows backward during defrost operation and accumulates in the metering section 33, the insufficient amount of refrigerant can be replenished. Defrost operation can be performed with an appropriate amount of refrigerant, and defrost time can be shortened.

In the embodiment described above, the injection valve 35 is opened for a certain period of time (t ₂ = 5 seconds); however,
The opening operation time t of the injection valve 35 may be controlled depending on the detected high pressure P.

In this case, the high pressure detection sensor PS for detecting high pressure is configured to output an output value corresponding to the detection values P ₁ to _{P 3 detected by the sensor PS, and the refrigerant replenishment control means is configured to output an output value corresponding to the detection values P 1 to P 3} detected by the sensor PS. Instead of the quantitative control means, the opening operation time t of the injection valve 35 is controlled according to the output value from the sensor PS as shown _{in FIG} . A replenishment amount control means for replenishing refrigerant is provided.

The opening operation time t of the injection valve 35 is set to the opening operation time t ₂ when the outside air temperature is, for example, -30°C, that is, the above-mentioned fixed time (t ₁ =5
The opening operation time t ₂ when the high pressure P after (minutes) becomes a pressure P ₁ lower than the set pressure P ₂ is set as the maximum, and the opening operation time when the high pressure P becomes the above set pressure P ₂ is 0 hours. It is set as .

That is, the opening operation time t is set by a function of the intake gas temperature (T), t=f(T), that is, t=t ₂ /P ₁ -P ₂ ·P+β.

By doing this, the injection valve 35 is kept at the set pressure (P ₂ ) or less for a certain period of time (t ₂ ).
Compared to the case where the opening is open, it becomes possible to replenish the insufficient amount of refrigerant more precisely, and the defrosting time can be shortened while compensating for the defrosting operation within the above-mentioned protected area.

The defrost operation in the case where the opening operation time (t) as described above can be controlled is performed according to the flowchart shown in FIG. 6. _Since this flowchart is the same as the flowchart shown in FIG. 4, its detailed explanation will be omitted and only the differences will be explained. 104), sets the opening operation time (t) of the injection valve 35 (step 105), opens it (step 106), starts the timer (t ₂ ) (step 107), and after that time has elapsed (step 108), The injection valve 3
5 (step 109).

Further, when the high pressure (P) is higher than the set pressure (P ₂ ) (step 104), the opening operation time (t) becomes 0 hours (step 110).

Furthermore, in both the first and second embodiments described above, the injection valve 35 is controlled based on the absolute value of the high pressure (P), but other information from the sensor (PS) is also used to control the injection valve 35. It may also be controlled by the rate of change of high pressure (dP/dt).

In other words, during defrost operation, the high pressure changes over time after the defrost time, but this change changes at different rates of change (dP/dt) depending on the outside temperature, as shown in Figure 3. .

In other words, the lower the outside temperature, the lower the rate of change.
Since the defrost time is longer, the refrigerant shortage can be accurately detected using this rate of change (dP/dt) when the outside air temperature is low.

In that case, the refrigerant amount shortage detection means includes a high pressure detection sensor PS that detects high pressure during defrost operation as shown in FIG. dP/dt) and outputs an output when the rate of change (α) becomes negative, that is, when the high pressure (P) decreases, and a refrigerant replenishment control means. Therefore, a quantitative control means is provided which opens the injection valve 35 for a certain period of time ( _t2, for example, 5 seconds) using the output from the output section 70 to replenish a certain amount of refrigerant.

Incidentally, the drop in the high pressure (P) output from the output section 70 occurs when the outside air temperature is 0° C. or lower, and the injection valve 35
The opening operation time (t ₂ ) is set to 5 seconds for the reason explained in the first embodiment.

As described above, when the injection exit valve 35 is controlled based on the rate of change of the high pressure, a shortage of refrigerant can be detected more accurately than when the injection valve 35 is controlled based on the absolute value of the high pressure. .

Further, the defrost operation according to this embodiment is performed according to the flowchart shown in FIG. That is, the rate of change is calculated based on the high pressure detected by the sensor PS at the same time as the start of the defrost operation or after a certain period of time (for example, 5 minutes) (step 201), and when the rate of change becomes negative. , that is, when it is smaller than 0 (step 202), the injection valve 35 is opened (step 203).
At the same time, the _t2 timer that measures the opening operation time ( _t2 ) starts counting (step 204), and after counting up after a certain period of time ( _t2 = 5 seconds) (step 205), the injection valve is closed. 35 (step 206).

If the rate of change is greater than 0, the defrost completion thermostat TH operates without opening the injection valve 35 (step 207).
Then, the defrost operation ends (step 208).

Therefore, even in this embodiment, the injection valve 3 is not suitable for defrost operation when the outside air temperature is low.
5, a certain amount of refrigerant is supplied from the liquid reservoir to the defrost circuit through the injection passage 36, and the defrost time can be shortened.

Further, in the third embodiment, as in the first embodiment, the injection valve 35 is operated for a certain period of time (t ₂ =5 seconds).
Although the injection valve 35 was opened, the opening time (t) of the injection valve 35 may be controlled in accordance with the rate of change (α), as in the second embodiment.

In this case, as shown in FIG. 9, the refrigerant amount shortage detection means detects when the sensor PS and the rate of change calculated based on the information from the sensor PS become negative, that is, when the high pressure (P) Timer (TM) that outputs an output value according to the time (t _o ) when descending
and an output section 80 having a refrigerant replenishment means, and the opening operation time (t) of the injection exit valve 35 is proportional to the time (t _o ) according to the output value from the output section 80 as the refrigerant replenishing means. value (t=
K.tm) (where K is a positive number smaller than 1).

In this case, it is preferable to limit the time (t _o ) for descending at the high pressure (P) to a time shorter (for example, 40 minutes) than the target defrost time (for example, 45 minutes).

Further, the opening operation time (t) of the injection exit valve 35 is set such that the opening operation time (t 2 ) when the outside air temperature is, for example, -30°C is the maximum, and the opening operation time (t ₂ ) when the outside air temperature is 0°C.
The opening operation time at this time is set as 0 hours.

The defrost operation according to this embodiment is performed according to the flowchart shown in FIG. 10, and in this case as well, it is possible to replenish the insufficient amount of refrigerant in a more precise manner than when the valve is opened for a certain period of time.

Since this flowchart is basically the same as the flowchart of the embodiment shown in FIG. 8, the details will be omitted and only the differences will be explained. Step 200), when the rate of change of the high pressure (P) becomes negative (Step 202), the timer (TM)
is counted up to measure the time (t _o ) (step 203), the opening operation time (t) of the injection exit valve 35 is set (step 204), and the injection exit valve 35 is opened (step 205).
A timer (t ₂ ) is started (step 206), and after that time has elapsed (step 207), the injection valve 35 is closed (step 208).

Further, when the rate of change of the high pressure (P) is greater than 0, the opening operation time (t) becomes 0 hours, and the defrost completion thermometer (TH) operates (step 209) without opening the injection exit valve 35. Defrost operation ends (step 210).

Further, although the refrigerant supply means is constructed by the injection passage 36 and the injection exit valve 35, it may be constructed by using the second electromagnetic valve 32 which constitutes the measuring section 33 as shown in FIG.
In this case, during defrost operation, the first solenoid valve 3
0 is open and the second solenoid valve 32 is closed,
By performing an opening operation based on a command from the refrigerant replenishment control means based on the output from the refrigerant amount shortage detection means, the refrigerant trapped in the liquid reservoir on the downstream side of the second electromagnetic valve 32 is removed from the high-pressure liquid pipe. 6b
A portion of the high pressure liquid pipe 6b and the low pressure liquid pipe 6c serve as an injection passage.

Furthermore, although the above embodiments are all so-called metered defrost systems in which a metering section 33 is provided and defrost operation is performed using a metered refrigerant, it is equally applicable to a simple defrost system in which the metering section is not used.

(Effects of the Invention) The present invention provides a refrigerant supply means for supplying refrigerant from a liquid reservoir to a defrost circuit during a defrost operation, and detects an insufficient amount of refrigerant from a detection result from a refrigerant amount shortage detection means during a defrost operation. Since the refrigerant is supplied to the circuit, even when the outside temperature is low, defrost operation can be performed without running out of refrigerant, and therefore the defrost time can be shortened.

Furthermore, by using the high pressure detection sensor PS as the refrigerant amount shortage detection means and detecting the refrigerant amount shortage based on the high pressure after a certain period of time has passed after the start of defrost operation, the internal or indoor temperature conditions are taken into account. Therefore, it is possible to detect a shortage of refrigerant based on the amount of refrigerant, which enables more accurate detection than when detecting the intake gas temperature.

Furthermore, by calculating the rate of change in the high pressure and detecting a refrigerant amount shortage based on this rate of change, more accurate detection is possible than when detecting the absolute value of the high pressure. That is, by using the high pressure detection sensor PS as the refrigerant amount shortage detection means and detecting the refrigerant amount shortage based on the high pressure after a certain period of time has passed after the start of the defrost operation,
Compared to the case of detecting the intake gas temperature, the change in high pressure in response to a change in outside air temperature is large, so more accurate detection is possible, and the high pressure decreases when the outside air is low, that is, below 0°C. Therefore, by detecting this drop, that is, by calculating the rate of change in the high pressure and detecting that the rate of change becomes negative, it is possible to more accurately detect a shortage of refrigerant.

In addition, by detecting the time when the high pressure falls and detecting a refrigerant shortage, it is possible to detect a refrigerant shortage until just before the end of the defrost operation, and the monitoring time can be lengthened accordingly. Furthermore, by providing a replenishment amount control means for replenishing the amount of refrigerant according to the detected value from the refrigerant amount shortage detection means as the refrigerant replenishment control means, it is possible to provide a more detailed replenishment method than when replenishing a fixed amount of refrigerant. Replenishment becomes possible, the defrost time can be shortened, and defrost operation can be performed in a protected area where the high voltage switch and the overcurrent relay of the compressor 1 will not operate.

Furthermore, by using the injection exit valve 35 and the injection exit passage 36 as the refrigerant supply means, it is possible to reliably replenish the insufficient amount of refrigerant at the time of defrosting. By using the second on-off valve 32, it is possible to replenish the insufficient refrigerant without any special additional structure.

[Brief explanation of the drawing]

FIG. 1 is a refrigerant piping system diagram showing a first embodiment of the present invention, FIG. 2 is a control block diagram, and FIG. 3 is a high pressure characteristic diagram showing changes in high pressure corresponding to outside temperature during defrost operation. Fig. 4 is a flowchart during defrost operation in the first embodiment, Fig. 5 is a control diagram showing the relationship between valve opening operation time corresponding to high pressure in the second embodiment, and Fig. 6 is a flowchart in the second embodiment. FIG. 7 is a block diagram of the refrigerant shortage detection means of the third embodiment, FIG. 8 is a flowchart of the defrost operation of the third embodiment, and FIG. 9 is a flowchart of the fourth embodiment. FIG. 10 is a block diagram of the refrigerant amount shortage detection means of the example, FIG. 10 is a flowchart during defrost operation of the fourth embodiment, and FIG. 11 is a refrigerant piping system diagram showing a conventional example. 1... Compressor, 2, 3... Condenser, 4... Evaporator, 2
0...Hot gas bypass path, 21...Hot gas valve, 35...Injection valve, 36...Injection passageway, 70, 80...Output section, PS...High pressure pressure detection sensor.

Claims (1)

[Scope of Claims] 1. A hot gas bypass path 20 that bypasses the condensers 2 and 3 and introduces the hot gas discharged from the compressor 1 into the evaporator 4, and a hot gas bypass path 20 that bypasses the hot gas to the bypass path 20. In the refrigeration system which is equipped with a valve 21, forms a defrost circuit between the compressor 1, the hot gas bypass passage 20, and the evaporator 4, and is capable of defrost operation, the condensers 2 and 3 are closed during the defrost operation. It has a refrigerant supply means that supplies refrigerant to the defrost circuit from a liquid reservoir during defrost operation, and a high pressure detection sensor PS, which detects the high pressure when a certain period of time has passed after the start of the defrost operation, and detects the high pressure a refrigerant shortage detection means for outputting an insufficient amount of refrigerant in the defrost circuit when the amount is below a certain value; and an output from the detection means to give an operation command to the refrigerant supply means to replenish the deficient amount of refrigerant to the defrost circuit. A refrigeration system comprising: a refrigerant replenishment control means. 2. The refrigeration system according to claim 1, wherein the refrigerant replenishment control means includes quantitative control means for instructing the refrigerant supply means to replenish a fixed amount of refrigerant based on the output from the refrigerant amount shortage detection means. 3. The refrigeration system according to claim 1, wherein the refrigerant replenishment control means includes replenishment amount control means for instructing the refrigerant supply means to replenish a predetermined amount of refrigerant in accordance with the output value from the refrigerant amount shortage detection means. 4. Equipped with a hot gas bypass path 20 that bypasses the condensers 2 and 3 and introduces the hot gas discharged from the compressor 1 into the evaporator 4, and a hot gas valve 21 that bypasses the hot gas to the bypass path 20, In a refrigeration system in which a defrost circuit is formed between the compressor 1, the hot gas bypass passage 20, and the evaporator 4, and a defrost operation is possible, during the defrost operation, the liquid including the condensers 2 and 3 during the defrost operation is a refrigerant supply means for supplying refrigerant from the reservoir to the defrost circuit; a high-pressure pressure detection sensor PS; and during defrost operation, calculates a rate of change in the high-pressure pressure based on information from the high-pressure pressure detection sensor PS; a refrigerant amount insufficient detection means having an output section 70 that outputs an insufficient amount of refrigerant in the defrost circuit when the rate of change is below a certain value; A refrigeration system comprising a refrigerant replenishment control means for replenishing a circuit with an insufficient amount of refrigerant. 5. The refrigeration system according to claim 4, wherein the refrigerant replenishment control means includes quantitative control means for instructing the refrigerant supply means to replenish a fixed amount of refrigerant based on the output from the refrigerant amount shortage detection means. 6. The refrigeration system according to claim 4, wherein the refrigerant replenishment control means includes replenishment amount control means for instructing the refrigerant supply means to replenish a predetermined amount of refrigerant in accordance with the output value from the refrigerant amount shortage detection means. 7 On the downstream side of the condensers 2 and 3, the condensers 2 and 3
5. The refrigeration system according to claim 1, further comprising a metering section (33) capable of metering the refrigerant in the liquid reservoir section containing the refrigerant and supplying a certain amount of the refrigerant to the defrost circuit. 8 The metering section 33 is located upstream of the first opening/closing mechanism 30 that closes in response to a defrost operation start command and confines the refrigerant in the liquid reservoir, and is located upstream of the first opening/closing mechanism 30 to close the refrigerant trapped in the liquid reservoir. Of these, it includes a second opening/closing mechanism 32 that measures a certain amount of refrigerant,
The measuring section 33 is opened by the opening operation of the first opening/closing mechanism 30.
8. The refrigeration system according to claim 7, wherein the refrigerant is supplied to the defrost circuit in a measured amount. 9 The second opening/closing mechanism 32 of the metering section 33, which is closed during defrost operation, opens based on a command from the refrigerant replenishment control means based on the output from the refrigerant amount shortage detection means, and transfers the refrigerant confined in the liquid reservoir to the defrost circuit. 9. The refrigeration system according to claim 8, further comprising a refrigerant supply means for supplying the refrigerant to the refrigerant. 10. The refrigeration system according to claim 1, wherein the refrigerant supply means is comprised of an injection passageway 36 connecting the liquid reservoir and the defrost circuit, and an injection valve 35 interposed in the injection passageway 36.