JPH052905B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a pump-down operation control device for a compressor included in a refrigeration system.

(Prior Art) Conventionally, as a control device for pump-down operation to recover refrigerant in a refrigerant circuit of a refrigeration system, as disclosed in Japanese Utility Model Application Publication No. 57-55454, for example, there is a control device for controlling a thermostat during pump-down operation. By switching, pump-down operation is stopped when the suction pressure drops below a predetermined value or a certain period of time has passed after the start of pump-down operation, thereby preventing the compressor from burning out due to a decrease in refrigerant during pump-down operation. There are known techniques to prevent this.

(Problems to be Solved by the Invention) By the way, when relocating or replacing the indoor unit of a refrigeration system, it is normal to perform a pump-down operation to recover frozen water to the receiver or condenser in the refrigeration system. The procedure is to close the liquid-side manual shut-off valve and operate the compressor, and when it appears that most of the refrigerant has been recovered, the gas-side manual shut-off valve is closed and the compressor is stopped.

However, with this method, the determination of when refrigerant recovery is complete relies only on the skill of the operator, and for this reason, if the gas side closing valve is closed and the compressor is stopped too early, the refrigerant If the recovery of refrigerant is insufficient, or if the pump-down operation time is too long in an attempt to increase the refrigerant recovery rate, the amount of refrigerant sucked into the compressor decreases too much, and the cooling effect of the refrigerant on the compressor decreases. However, since the internal temperature of the compressor rises rapidly, there are problems such as seizure of the compressor.

Therefore, it is conceivable to use the method disclosed in the above publication to reliably recover the refrigerant while preventing the compressor from overheating. However, the above publication does not assume that the closing valve will be operated when installing or relocating the refrigeration system, and in other words, it does not assume that the refrigerant circuit will be opened. I can't get the rate. In other words, even if the pump-down operation is stopped at the same time as the suction pressure decreases, it takes a certain amount of time to close the closing valve, so during that time the refrigerant flows back from the storage side.
A certain amount of unrecovered refrigerant is generated. Note that terminating the pump-down operation after a certain period of time has elapsed after the start of the pump-down operation is simply understood as back-up when the pressure switch is not activated.

The present invention has been made in view of the above, and its purpose is to notify the operator when to open/close the manual shutoff valve on the gas side in response to a drop in suction gas pressure during pump down operation. The objective is to improve the refrigerant recovery rate while preventing accidents such as seizure of the compressor by stopping the compressor after a certain period of time has elapsed.

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention, as shown in FIG. The target is a refrigeration system equipped with a manual shutoff valve 10b.

Then, the manual shutoff valve 1 on the liquid side is installed in the refrigeration equipment.
0a is closed, suction gas pressure detection means LPS detects the pressure of the suction gas refrigerant to the compressor 1;
Alarm output means BZ that receives a signal from the suction gas pressure detection means LPS and outputs a warning to the operator to close the manual shutoff valve 10b on the gas side when the suction gas pressure falls below a predetermined value; and the alarm output means BZ. a time measuring means 13 for measuring a certain period of time corresponding to the overheating period of the compressor 1 from the time when an alarm is output by the time measuring means 1;
The compressor 1 is configured to include an operation control means 12 that stops the operation of the compressor 1 when the compressor 1 receives the output No. 3.

(Function) With the above configuration, in the present invention, when performing pump down operation when relocating a refrigeration system, the compressor 1 is operated with the liquid side closing valve 10a closed, and the refrigerant is stored in the refrigerant storage. It is stored in device 4. When the recovered refrigerant decreases and the suction gas pressure becomes less than a predetermined value, it is detected by the suction gas pressure detection means LPS, and the alarm output means BZ
An alarm is output to warn the operator to close the gas-side manual shutoff valve 10b.

Meanwhile, due to the decrease in refrigerant, the internal temperature of the compressor 1 rises rapidly, and the internal temperature of the compressor 1 is about to reach the overheating danger value. The passage of time is measured, and when this certain period of time has passed, the operation of the compressor 1 is stopped by the operation control means 12.

At that time, it becomes possible to synchronize the timing of the stop of the compressor 1 and the manual closing of the gas side manual shut-off valve 10b, so that after the compressor 1 is stopped, the refrigerant flows backward from the refrigerant storage device 4 through the compressor 1 and becomes unused. Almost no refrigerant will be recovered. Therefore, accidents such as burnout of the compressor 1 are prevented, and the refrigerant recovery rate is improved.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings from FIG. 2 onwards.

FIG. 2 shows a refrigerant piping system when the present invention is applied to a separate air conditioner, where A is an outdoor unit and B is an indoor unit. a compressor 1 whose capacity is adjusted by a compressor 1, a four-way selector valve 2 which switches as shown by the solid line in FIG. The outdoor heat exchanger 4 serves as an evaporator during operation and serves as a refrigerant storage during pump-down operation, and an electric expansion valve 5 and capillary reach tube 7 that adjust the refrigerant flow rate and throttle the refrigerant are used as main equipment. The indoor unit B is equipped with an indoor heat exchanger 6, which serves as an evaporator during cooling operation and a condenser during heating operation, as main equipment, and each of the above-mentioned main equipment has a liquid side equipped with a service port. They are connected to each other by a refrigerant pipe 8 via the shutoff valve 10a and the gas side shutoff valve 10b so that refrigerant can flow therethrough. In addition, TH1 is a room temperature thermostat that detects the room temperature, TH2 is a temperature sensor placed in the discharge pipe of compressor 1 and detects the temperature T2 of the discharge gas refrigerant (hereinafter referred to as discharge pipe temperature), and LPS is the temperature sensor of the suction gas refrigerant. Detects the pressure LP of LP and reaches the predetermined value Po (0.9
The pressure switch 11 is a control unit which closes when the pressure becomes lower than the pressure (approximately Kg/cm ² G) and is normally in the open state.

FIG. 3 is a schematic wiring diagram showing the connection with the main equipment on the printed circuit board of the control unit 11. The control unit 11 includes a room temperature thermostat TH1, a temperature sensor TH2, a pressure switch LPS, and a An external switch SW1 that issues commands is connected to the input side. A microcomputer 12 as an operation control means is built into the control unit 11, and the memory of the microcomputer 12 stores the discharge pipe temperature when the compressor reaches the dangerous overheating temperature during normal operation. Tc1 (first setting value) (e.g. around 130℃),
The upper limit setting value Tc2 of the appropriate range (for example, about 120℃),
The lower limit set value Tc3 of the appropriate range (for example, about 110°C) and the low pressure overheating limit temperature TL1 (second set value) of the discharge pipe temperature when LP<Po (for example, about 110°C) are stored in advance. In addition, the output side terminal is equipped with a pulse motor EV that adjusts the opening degree of the electric expansion valve 5,
The inverter 9, a buzzer BZ as an alarm output means that continuously emits an alarm sound, and a timer 13 for a set time to (about 30 seconds) are connected. and,
The microcomputer 12 receives the outputs of the sensors and the external switch SW1, and controls the operation of the pulse motor EV of the electric expansion valve 5, the inverter 9, and the pump-down alarm buzzer BZ connected to the output side terminal. ing.

During cooling operation, the flow of refrigerant becomes as shown by the solid arrow in Fig. 2, and the refrigerant discharged from the compressor 1 is condensed and liquefied in the outdoor heat exchanger 4 (condenser), and then electrically expanded. The indoor heat exchanger 6 is subjected to a throttling action by the valve 5 and the capillary reach tube 7.
(evaporator), passes through the accumulator 3, and returns to the compressor 1 again. Further, during heating operation, the flow of refrigerant is as shown by the broken line arrow, and the refrigerant discharged from the compressor 1 is condensed and liquefied in the indoor heat exchanger 6, and then transferred to the electric expansion valve 5 and the capillary reach tube 7.
It is subjected to a throttling action and vaporized in the outdoor heat exchanger 4, and returns to the compressor 1 via the accumulator 3.

During normal cooling/heating operation of the air conditioner, the frequency of the inverter 9 is changed according to the deviation (Ts - Tn) between the set value of the room temperature thermostat TH1 and the intake air temperature, and the capacity of the compressor 1 is controlled. will be held. In addition, the opening degree of the electric expansion valve 5 is set in advance by the microcomputer 1 according to the value of the output frequency.
This is set to the value stored in the storage unit No. 2, so that it does not always enter the wet operation range from the start of operation. At this time, in the above-mentioned normal operation, the degree of superheating of the refrigerant increases and there is a risk that the air conditioning capacity will not be fully utilized or that the compressor 1 will seize, so the control unit 11
According to the signal of the discharge pipe temperature T2, the discharge pipe temperature is compared with the superheating limit temperature Tc1, the upper limit setting value of the appropriate range Tc2, and the lower limit setting value Tc3 of the appropriate range, and if T2>Tc2, the refrigerant is When the temperature reaches the overheating region, the opening degree of the electric expansion valve 5 is controlled by the inverter 9.
By increasing the set value determined by the frequency of , refrigerant overheating operation cancellation control is performed so that the discharge pipe temperature falls within the appropriate range Tc3 to Tc2. Furthermore, when Lp≧Po, in which the suction gas pressure Lp is greater than the set value Po of the pressure switch LPS, when the discharge gas temperature T2 is greater than Tc1, and when Lp<Po, T2≧
At Tc3, the compressor 1 is stopped to prevent seizure or the like due to overheating of the compressor 1.

When it becomes necessary to relocate or replace the indoor unit B of the refrigeration system and it becomes necessary to recover the refrigerant, the pump-down operation is performed in accordance with the procedure shown in the flowchart of FIG.

In the float chart of Figure 4, the steps
When the switch SW1 is closed in S1 and a pump down command is issued, the shutoff valve 10a on the liquid side is manually operated.
etc. are closed and pump down operation begins. Then, in step S2, the suction gas pressure LP of compressor 1 is
is smaller than a predetermined value Po, and determines whether LP<Po
When the result is YES, the process moves to step S3 and the pressure switch LPS is turned on. At this time, an alarm buzzer sounds at the same time in step S4, so that the operator can complete the refrigerant recovery operation by successively closing the gas side closing valve 10b or the suction side closing valve of the compressor 1, etc. Then, in step S5, it is determined whether or not the set time to (approximately 30 seconds) has elapsed, and the timer 13 is activated and the set time to seconds has elapsed.
If YES, the buzzer BZ stops the alarm sound and outputs a stop signal, and the process proceeds to step S6, where the compressor 1 is stopped and the pump-down operation is completed.

In the above embodiment, the four-way switching valve 2 is switched to the solid line side in the figure, so that the refrigerant is recovered to the outdoor heat exchanger 4. Therefore, although the outdoor heat exchanger 4 functions as a refrigerant storage device,
A receiver may be provided and the refrigerant may be collected in the receiver.

In the embodiment described above, the danger of overheating of the compressor 1 is detected based on when the suction gas pressure reaches a predetermined value Po during pump-down operation and the passage of time from that point on. In other words, the change characteristics of the suction gas pressure, discharge pipe temperature, and discharge port temperature with respect to time changes after the start of pump down have a constant characteristic curve depending on the model and the type of refrigerant, as shown in Figure 5. have. In Fig. 5, TM1 indicates the time when the suction gas pressure becomes lower than Po after closing the liquid side closing valve 10a, and TM2 indicates the time when the suction gas pressure becomes lower than Po.
Each shows the time when to seconds have passed since TM1. In Fig. 5, TM1 is not necessarily constant because it varies depending on conditions such as the amount of refrigerant present in indoor unit B before pump-down operation starts, but the time to from TM1 to TM2 is almost constant. It has been experimentally confirmed that when the suction gas pressure LP reaches Po, the discharge port temperature reaches the dangerous overheating temperature in to seconds. Therefore, LP
By stopping the compressor 1 to seconds after reaching <Po, it is possible to effectively prevent a seizure accident due to an increase in overheating of the compressor 1. Also, to seconds is
TM
By issuing an alarm at 1:00 o'clock, the operator can shut down the gas-side manual shut-off valve 10b when the compressor 1 is stopped.
can be closed.

In other words, if the compressor 1 is stopped at the same time as the alarm is output (that is, at the same time as the suction pressure decreases as in the conventional system), the gas side manual Closing valve 10b
Until the compressor 1 is closed, the refrigerant will flow back from the outdoor heat exchanger 4 side, which is a refrigerant storage device, and the amount of refrigerant recovered will decrease accordingly.
By closing the manual shutoff valve 10b on the gas side when the compressor 1 is stopped, backflow of refrigerant after the compressor 1 is stopped can be almost eliminated. This greatly improves the refrigerant recovery rate.

Note that the warning output means is not limited to the above embodiments, and may be any device that provides any warning to the operator, such as an indicator lamp.

(Effects of the Invention) As explained above, in the present invention, during pump-down operation of a refrigeration system, a decrease in suction gas pressure after the operator closes the liquid side manual shutoff valve is detected, and the suction gas pressure is When the amount of refrigerant falls below a predetermined value, an alarm is issued, and the compressor is stopped when a certain period of time corresponding to the overheating period inside the compressor has elapsed after the alarm is output, so the compressor does not have too much refrigerant. Therefore, it is possible to effectively prevent overheating and seizure accidents while improving the refrigerant recovery rate.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention. Figures 2 to 5 show an embodiment of the present invention, with Figure 2 being a refrigerant system diagram, Figure 3 being a wiring diagram for the control unit's printed circuit board, and Figure 4 being a flowchart showing the pump-down operation procedure. Chart diagram, 5th
The figure is a characteristic diagram showing changes in the state quantity of the refrigerant with respect to time after the start of pump down. 1...Compressor, 4...Outdoor heat exchanger (refrigerant storage), 10a...Liquid side closing valve, 10b...Gas side closing valve, 12...Microcomputer (operation control means), 1
3...Timer (timekeeping means), LPS...pressure switch (suction gas pressure detection means), BZ...buzzer (alarm output means).

Claims (1)

[Claims] 1 In a refrigeration system in which a refrigerant storage device 4, a liquid-side manual shut-off valve 10a, and a gas-side manual shut-off valve 10b are arranged in a refrigerant circuit, the liquid-side manual shut-off valve 1
0a is closed, suction gas pressure detection means LPS detects the pressure of the suction gas refrigerant to the compressor 1;
Alarm output means BZ that receives a signal from the suction gas pressure detection means LPS and outputs a warning to the operator to close the manual shutoff valve 10b on the gas side when the suction gas pressure falls below a predetermined value; and the alarm output means BZ. a time measuring means 13 for measuring a certain period of time corresponding to the overheating period of the compressor 1 from the time when an alarm is output by the time measuring means 1;
3. A pump-down operation control device for a refrigeration system, comprising an operation control means 12 that stops the operation of the compressor 1 when the output of the compressor 1 is received.