JPH0343573Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> This invention relates to a refrigeration device suitable for use in containers, for example.

<Conventional technology> Conventionally, refrigeration equipment that performs defrost operation stores a certain amount of refrigerant liquid in a quantitative outflow device.
There is a system that performs defrost operation by circulating a fixed amount of refrigerant liquid stored in the quantitative outflow device, regardless of the operating state immediately before starting defrost operation (Japanese Patent Application Laid-open No. 197764/1983).

As shown in FIG. 7, this refrigeration system includes a compressor 100, an electromagnetic three-way valve 101, a condenser 102, a fixed amount outflow device 113 consisting of an inlet opening/closing valve 104 and an outlet opening/closing valve 105, an expansion valve 106, and a branching valve. The evaporator 107 and the evaporator 108 are sequentially connected to form a refrigeration circuit in which refrigerant circulates,
and the flow divider 107 are connected by a defrost bypass path 110. And the evaporator 108
When the refrigerant is frosted and a defrost operation is performed, first, a pump-down operation is performed in order to store a certain amount of refrigerant liquid in the quantitative outflow device 113.
That is, the outlet opening/closing valve 105 of the quantitative outflow device 113
is closed, the compressor 100 is driven, and high-temperature, high-pressure refrigerant liquid is stored upstream of the outlet opening/closing valve 105. A predetermined amount of the refrigerant liquid is stored and the pump-down operation ends. Since the pressure inside the pipe on the suction side of the compressor 100 becomes low, the pressure switch 109 is activated and the compressor 100 is stopped. Furthermore, the electromagnetic three-way valve 101 is connected to the condenser 10.
2 side to the bypass path 110 side, the inlet side on-off valve 104 is closed and the outlet side on-off valve 105 is opened. A certain amount of refrigerant liquid between the inlet side on-off valve 104 and the outlet side on-off valve 105 passes through the expansion valve 106 and flows into the evaporator 108, and then the refrigerant gas is sucked into the compressor 100. When the pressure on the suction side becomes equal to or higher than a certain pressure, the pressure switch 109 is reset. The compressor 100 is driven in response to the return signal from the pressure switch 109, and the hot gas is transferred to the condenser 102.
Instead of passing through the air, the air is circulated to a circuit consisting of the compressor 100, the electromagnetic three-way valve 101, the bypass passage 110, and the evaporator 108, where a defrost operation is performed.

<Problem to be solved by the invention> However, in the above-mentioned refrigeration system, when the outside air temperature is extremely low, such as in the Arctic Circle through which containers etc. are transported, the outlet opening/closing valve 105 is opened and the inlet side is closed. A certain amount of refrigerant liquid between the on-off valve 104 and the outlet on-off valve 105 flows into the evaporator 108 and the compressor 100
Even if refrigerant gas is allowed to flow down into the piping on the suction side of the compressor 100, the pressure of the refrigerant gas on the suction side does not increase because the outside air temperature is extremely low, and the pressure switch 109 on the suction side of the compressor 100 does not return to normal. More specifically, the pressure switch 109 is set to -50°C, for example.
Since the pressure switch 109 is set to turn off at a considerable pressure and turn on at a pressure equivalent to -22°C, when the outside temperature falls below -30°C, the pressure switch 109 will not turn on and will not return. Therefore, compressor 10
0 cannot be started and defrost operation cannot be performed. On the other hand, it is also possible to change the set pressure of the pressure switch 109 according to the outside temperature, but since pressure switches generally have on-off set pressures determined at the manufacturing stage, it is not possible to change the set pressure later. is generally difficult. Furthermore, if a pressure switch that can change the set pressure is used, a special pressure switch would be required, which would increase costs.

Therefore, the purpose of this invention is to enable automatic defrost operation to be performed smoothly and quickly by driving the compressor after the end of pump-down operation, even when the outside air temperature is extremely low.

<Means for Solving the Problems> In order to achieve the above object, the refrigeration system of this invention sequentially operates a compressor 1, a condenser 3, an expansion means 6, and an evaporator 8, as illustrated in FIG. The compressor 1 is connected to the refrigeration circuit in which the refrigerant circulates.
a bypass passage 9 connecting the discharge side of the compressor 1 to the upstream side of the evaporator 8, and a valve 2 for causing the entire amount of gas discharged from the compressor 1 to flow to the condenser 3 during pump-down operation and to the bypass passage 9 during defrost operation. , quantitative outflow device 1 for defrosting by pump down operation
In the defrost operation, the refrigerant liquid stored in the expansion means 6 and 70 is circulated through the evaporator 8, the compressor 1, the valve 2, and the bypass passage 9 during the defrost operation. It is provided between the evaporator 8 or downstream of the valve 2 in the bypass path 9, detects a predetermined low pressure, and connects the valve 2 between the discharge side of the compressor 1 and the bypass path 9 side. A control signal is output to the valve 2 to switch the refrigerant liquid in the quantitative outflow devices 13, 70, and a control signal is output to the quantitative outflow devices 13, 70 to switch from pump down operation to defrost operation. It is characterized in that it is equipped with a low pressure switch 10 for switching to.

<Function> Pressure switch 1 between expansion means 6 and evaporator 8
0 is activated to detect a predetermined low pressure and output a control signal, the valve 2 is switched from the condenser 3 side to the bypass path 9 side, and a certain amount of refrigerant liquid in the quantitative outflow device 13 is discharged. It flows into the evaporator 8 side. A defrost operation is performed by circulating a certain amount of the refrigerant liquid through a defrost bypass circuit consisting of an evaporator 8, a compressor 1, a valve 2, and a bypass path 9.

In this way, the low pressure switch 10 is provided between the expansion means 6 and the evaporator 8, that is, on the upstream side of the pressure higher than the suction side of the compressor 1, and the end of the pump down operation is detected by this low pressure switch 10. Therefore, even when the outside air temperature is extremely low, the low pressure switch 10 can detect a predetermined low pressure, and the defrost operation can be performed quickly and reliably.

<Example> This invention will be explained in detail below with reference to the illustrated example.

FIG. 1 is a conceptual diagram showing the refrigerant piping according to the embodiment of this invention, in which 1 is a compressor, 2 is an electric proportional three-way valve as an example of a valve, and 3 is for cooling the refrigerant gas discharged from the compressor 1. 4 is an inlet opening/closing valve, 5 is an outlet opening/closing valve, and 6 is a temperature automatic expansion device that throttles and expands the refrigerant liquid and discharges it in a low-pressure, low-temperature gas-liquid mixed state. valve, 7 is a flow divider,
8 is an evaporator that applies heat to the refrigerant in a gas-liquid mixed state to vaporize it; 9 is a defrost bypass passage that connects the flow divider 7 and the electric proportional three-way valve 2; and 10 is an automatic temperature expansion valve at the end of pump-down operation. 6 and flow divider 7
a low pressure switch for detecting the pressure between 11
13 is a pressure detection part of the low pressure switch 10, and 13 is a fixed quantity pipe 40 between the inlet opening/closing valve 4 and the outlet opening/closing valve 5 provided in the pipeline between the condenser 3 and the thermostatic expansion valve 6. It is an outflow device.

A condenser 3, a thermostatic expansion valve 6, and an evaporator 8 are sequentially connected to the compressor 1 to form a refrigeration circuit. A flow divider 7 is provided at the inlet of the evaporator 8, and a bypass path 9 is provided to connect the flow divider 7 and the discharge gas pipe 14 between the compressor 1 and the condenser 3. At the connection between the discharge gas pipe 14 and the bypass path 9, there is provided an electric proportional three-way valve 2 that selectively connects the discharge side of the compressor 1 to the condenser 3 side or the bypass path 9 side. In addition, the electric proportional three-way valve 2
In addition to the above-mentioned switching function, this also has a function of controlling the flow rate of the discharged gas to the bypass path 9 from 0 to 100% (at this time, from 100% to 0% to the condenser 3) during refrigeration operation. Between the temperature automatic expansion valve 6 and the flow divider 7, a pressure detection section 1 of a low pressure switch 10 is provided.
1 is provided. This low pressure pressure switch 10 is
At the end of the pump down operation, the pressure between the temperature automatic expansion valve 6 and the flow divider 7 is detected and the outlet opening/closing valve 5 is activated.
An opening/closing signal is output to open the outlet opening/closing valve 5, and a control signal is output to the electric proportional three-way valve 2 to fully open the bypass passage 9 side. Further, the low pressure switch 10 outputs an activation signal to the timer 20. This timer 20 is
A drive signal is output to the compressor 1 after a predetermined period of time (for example, 20 seconds) has elapsed since the operation signal was received. The reason why the compressor 1 is stopped for 20 seconds by the timer 20 is to ensure that the refrigerant liquid flows out from the quantitative outflow device 13.

The operation of the refrigeration system having the above configuration will be described below with reference to the flowchart shown in FIG.

First, in step S1, it is detected that the evaporator 8 has frosted, an air pressure switch (not shown) is activated, and a command to start the defrost operation is issued. In step S2, the outlet opening/closing valve 5 is closed to perform pump down operation. Then, compressor 1
Refrigerant gas is discharged from the refrigerant gas, this refrigerant gas is liquefied in the condenser 3, and refrigerant liquid is stored upstream of the outlet opening/closing valve 5. At this time, step S3
The low pressure switch 10 confirms whether the pressure in the pressure detection section 11 between the thermostatic expansion valve 6 and the flow divider 7 is below the set value. If the pressure is not below the set value, refrigerant gas is subsequently discharged from the compressor 1 and refrigerant liquid is stored. On the other hand, when the low pressure switch 10 detects that the pressure has become below the set value, the low pressure switch 10 is turned off. That is, the contact 16A of the low pressure switch 10 of the relay circuit 42 shown in FIG. 3 is turned off. In this way, the pump down operation ends. Next, proceeding to step S4, the relay coil _20R2 of the inlet side on-off valve 4 is de-energized by the OFF operation of the contact 16A, and at the same time the inlet side on-off valve 4 is closed, the relay coil 20R2 of the outlet side on-off valve 5 is turned off. _20R1 is excited and the outlet opening/closing valve 5 is opened. As a result, a certain amount of refrigerant liquid between the inlet opening/closing valve 4 and the outlet opening/closing valve 5 flows from the thermostatic expansion valve 6 into the evaporator 8 due to the pressure difference. On the other hand, the low pressure switch 10 outputs a control signal to the electric proportional three-way valve 2, and the electric proportional three-way valve 2 switches the discharge side of the compressor 1 from the condenser 3 side to the bypass path 9 side. It will be done. Then, in step S5, the relay coil 1C of the compressor 1 is de-energized by the OFF operation of the contact 16A, and the compressor 1
stops. In step S6, an activation signal is output from the low pressure switch 10 to the timer 20, and the timer 20 is activated for a predetermined period of time (20 seconds). In step S7, after the timer 20 receives the activation signal,
It is checked whether 20 seconds have elapsed. If 20 seconds have not elapsed, the refrigerant liquid continues to flow into the evaporator 8. On the other hand, after 20 seconds, step S
At step 8, a drive signal is output from the timer 20 to the compressor 1, and the compressor 1 is driven. Then, the refrigerant is circulated through the compressor 1, the electric proportional three-way valve 2, the bypass path 9, and the evaporator 8 to perform a defrost operation. In this way, the compressor 1 is driven by the timer 20 to perform the defrost operation, so the compressor 1 can be driven even when the outside air temperature is extremely low. In step S9, a thermostat (not shown) provided on the discharge side of the evaporator 8 confirms whether the defrost operation has ended. If the thermostat does not operate, the defrost operation continues, but if the thermostat operates, the process advances to step S10 and the inlet opening/closing valve 4 is opened. In step S11, a switching signal is output to the electric proportional three-way valve 2, and the electric proportional three-way valve 2 is switched from the bypass path 9 side to the condenser 3 side. Then, thermo operation, that is, refrigeration operation (electric proportional three-way valve 2
completely closes the bypass path 9) or returns to refrigeration operation (the electric proportional three-way valve 2 has a variable opening degree). This refrigeration operation is performed by controlling the start and stop of the compressor 1 based on the return sensor on the air suction side of the evaporator 8, while the refrigeration operation is performed electrically based on the supply sensor on the air outlet side of the evaporator 8. Proportional three-way valve 2 from 0 to 100
This is done by controlling the opening degree to % and bypassing the hot gas at a flow rate corresponding to this opening degree.
Therefore, the low pressure switch 10 detects the pressure at the pressure detection section 11 at a position higher in pressure than the suction side of the compressor 1, that is, at a position between the thermostatic expansion valve 6 and the flow divider 7. Even when the outside air temperature is extremely low, the pressure switch 10 is turned on, and the defrost operation can be reliably performed when the next defrost operation command is output.

The reason why the pressure switch 10 is turned on in this way is because the discharge gas pressure of the compressor 1 is applied to the pressure detection part 11 during defrost operation. resistance of the device,
This is because the pressure detection unit 11 can detect a pressure that is higher by the resistance of the flow divider.

FIG. 4 shows a different embodiment, and in this embodiment, the metered outflow device 70 includes an inlet opening/closing valve 4, an outlet opening/closing valve 5, a pipe line 40 between them, and a suction pipe 40 and the compressor 1. A point consisting of a bypass path 60 connecting the side pipe 50, an electromagnetic bypass on-off valve 51 provided in this bypass path 60, and a normally open contact CS of the relay circuit 52 shown in FIG. 5 are connected to the low pressure switch 1.
This differs from the embodiment shown in Fig. 1 in that the relay coil IC is turned on and the relay coil IC is energized even after pump-down operation is completed, and the compressor 1 is driven from start to finish to perform defrost operation. It is.

The operation of the above embodiment will be explained below based on the flowchart shown in FIG. Components that are the same as those in the embodiment shown in FIG. 1 are given the same reference numerals and their explanations will be omitted. Here, it is assumed that the compressor 1 is being driven.

When a defrost operation start command is issued in step S1, the outlet opening/closing valve 5 is closed in step S2.
Pump down operation begins. In step S3,
When the pressure switch 10 detects the pressure of the pressure detection section 11, the contact 16A of the relay circuit 52 shown in FIG. 5 is turned off. As a result, in step S20, the relay coil _20R2 of the inlet side on-off valve 4 is de-energized, the inlet side on-off valve 4 is closed, and a certain amount of air is generated between the inlet side on-off valve 4 and the outlet side on-off valve 5. While the refrigerant liquid is stored, the relay coil 20 of the electromagnetic bypass on-off valve 51
_R3 is energized, the electromagnetic bypass on-off valve 51 is opened, and a certain amount of refrigerant liquid flows out. Since the compressor 1 is being driven at this time, the refrigerant liquid is reliably sucked into the compressor 1. In step S21, a predetermined amount of refrigerant liquid is forcibly circulated through the bypass path 60, the compressor 1, the electric proportional three-way valve 2, the bypass path 9, and the evaporator 8 by driving the compressor 1, thereby performing a defrost operation. A thermostat provided on the outlet side of the evaporator 8 confirms whether the defrost operation has ended. If the thermostat does not operate, defrost operation continues, but if the thermostat operates, step S is activated.
Proceed to step 22. In step S22, both the inlet side on-off valve 4 and the outlet side on-off valve 5 are opened, while the electromagnetic bypass on-off valve 51 is closed. Next, step S2
Step 3 returns to steady thermo operation.

In this embodiment, since the compressor 1 is constantly driven, there is no possibility that the compressor 1 cannot be driven when the outside air temperature is extremely low as in the conventional example. Therefore, defrost operation can be performed smoothly regardless of the outside temperature. As explained above, the low pressure switch 10 can be reset even in this case.

In the above two embodiments, the drive of the compressor 1 after the end of the pump-down operation is not dependent on the return of the low pressure switch 10 as in the conventional example, but in the present invention, the drive of the compressor 1 after the end of the pump-down operation is not dependent on the return of the low pressure switch 10 as in the conventional example. Needless to say, the drive may be performed in response to a return signal from the low pressure switch 10.

In the above two embodiments, the pressure detection section 11 of the pressure switch 10 is provided between the thermostatic expansion valve 6 and the evaporator 8, but it may also be provided in the defrost bypass path 9. Further, the electric proportional three-way valve 2 may be composed of two two-way valves.

<Effects of the Invention> As is clear from the above explanation, the refrigeration system of this invention is provided with a low pressure switch between the expansion means and the evaporator or in the bypass path. Therefore, according to this invention, even when the outside temperature is extremely low, at the end of pump-down operation, the pump can be installed between the expansion means and the evaporator or in the defrost bypass path, that is, at a position where the pressure is higher than the suction side of the compressor. Since a pressure switch is provided at the bottom, the low pressure switch can be reset even at low temperatures, allowing smooth defrost operation.

[Brief explanation of drawings]

Fig. 1 is a conceptual diagram showing a refrigerant pipe showing one embodiment of this invention, Fig. 2 is a flowchart showing the operation of the above embodiment, Fig. 3 is a schematic diagram showing a relay circuit, and Fig. 4 is a different implementation. A conceptual diagram showing the refrigerant piping of the example, Fig. 5 is a schematic diagram showing the relay circuit of a different embodiment, Fig. 6 is a flowchart showing the operation of the different embodiment, and Fig. 7 is a conceptual diagram showing the refrigerant piping of the conventional example. It is a diagram. 1...Compressor, 2...Valve, 3...Condenser, 6...
…expansion means, 8…evaporator, 9…bypass path,
10...Low pressure switch, 13,70...Quantitative outflow device.

Claims (1)

[Claims for Utility Model Registration] A refrigeration circuit in which a refrigerant circulates, which is formed by sequentially connecting a compressor 1, a condenser 3, an expansion means 6, and an evaporator 8, is connected to the discharge side of the compressor 1 and the evaporator 8. A bypass path 9 connecting the upstream side, a valve 2 that allows the entire amount of gas discharged from the compressor 1 to flow to the condenser 3 during pump-down operation and to the bypass path 9 during defrost operation, In the refrigeration system, the refrigerant liquid stored in the quantitative outflow devices 13 and 70 is circulated through the evaporator 8, the compressor 1, the valve 2, and the bypass path 9 during the defrost operation to perform the defrost operation, It is provided between the expansion means 6 and the evaporator 8 or at a position downstream of the valve 2 in the bypass path 9, and detects a predetermined low pressure and connects the valve 2 to the discharge side of the compressor 1 and the bypass. Outputting a control signal to the valve 2 to switch the valve 2 to communicate with the passage 9 side, and outputting a control signal to the quantitative outflow device 13, 70 to cause the refrigerant liquid in the quantitative outflow device 13, 70 to flow out; A refrigeration system comprising a low pressure switch 10 for switching from pump down operation to defrost operation.