JPH031059A - Refrigerating apparatus - Google Patents

Abstract

PURPOSE:To certainly provide a pressure difference between two outlets of a four-way valve and allow refrigerant flow paths to be changed over by the four-way valve even when a compressor is stopped, by a method wherein one of the inlets of the four-way valve, by which the refrigerant flow paths are changed over corresponding to the pressure difference during cooling and defrosting operation, is connected to the upstream side of a third check valve, i.e., to the outlet side of an evaporator. CONSTITUTION:When the temperature in a space being cooled drops below the specific temperature during cooling operation, a solenoid valve 36 is opened at the same time when a compressor 2 is stopped, and a pressure equalizing circuit is brought in action to gradually equalize the pressures at the suction and delivery sides. As a timer periodically issues change-over instructions to a four-way valve 3 to change the refrigerant flow path from the cooling side to the defrosting side, the flow toward an evaporator 13 side is blocked by a third check valve even if the pressures at the delivery and suction sides of the compressor 2 reaches the equilibrium state and becomes higher than the previous suction side pressure before the compressor is stopped. As a result, a pressure difference can be surely provided between one inlet 31 and the other inlet 34 of the four-way valve 3. Therefore, the four-way valve 3 can bechanged over regardless of operation or stop of the compressor 2 to which a defrosting instruction has been issued, and a controller which halts the change-over action of the four-way valve 3 during stop of the compressor 2 is not necessary to provide.

Description

[Detailed description of the invention] [Purpose of the invention] Industrial applications The present invention relates to improvements in refrigerant circuits in refrigeration equipment.

Conventional technology It is generally known that a refrigerant circuit having a compressor, a condenser, a pressure reducing device, and an evaporator is equipped with a flow path switching valve for switching the refrigerant flow path between cooling operation and defrosting operation. Japanese Patent Publication No. 61-51227 is one example. In this publication, a hot gas bypass pipe (a pipe installed between the flow path switching valve and the refrigerant inlet/side of the evaporator) through which hot gas passes during defrosting is provided with a dew pan directly below the evaporator. A heat exchanger is formed in contact with the refrigerant, and a throttle device is provided on the downstream side of the heat exchanger in the refrigerant flow direction. A four-way valve is used as the flow path switching valve, and check valves are provided between the four-way valve and the condenser and in the bypass pipe.

Problem to be Solved by the Invention In the refrigerant circuit, a connecting pipe having a solenoid valve is provided between the refrigerant discharge side and the refrigerant suction side of the compressor, and the solenoid valve is opened when the compressor is stopped. In order to balance the pressure between the discharge and suction of the compressor and reduce the starting torque when starting the compressor, the low pressure pipe of the four-way valve that switches the flow path using the pressure difference is compressed. Because it is connected to the suction side of the compressor, even if you try to switch the flow path using a four-way valve while the compressor is stopped, the pressure on the discharge side and suction side of the compressor will be balanced by the pressure equalization circuit. As a result, the desired pressure difference cannot be obtained and the four-way valve cannot be moved, resulting in a problem.For this reason, the four-way valve cannot switch the flow path while the compressor is stopped.
A control device that makes the four-way valve switching signal standby when a defrost command is issued by a timer or the like to prevent the flow path from cooling to defrosting from being switched while the compressor is stopped. The refrigerant circuit described above cannot be used alone.

Therefore, the present invention aims to ensure that the four-way valve switching operation can be performed reliably in a pressure balancing circuit that balances the pressure between the discharge and suction sides of the compressor while the compressor is stopped. Take it as a challenge.

[Structure of the invention]

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a refrigerant compressor, a first check valve, a condenser, a second check valve, a pressure reducing device, an evaporator, and a third check valve. This provides a refrigeration system having a pressure equalization pipe with a solenoid valve that opens when the compressor is stopped between the discharge side and the suction side of the compressor, forming a refrigerant circuit at the discharge side of the compressor. A four-way valve is installed to switch the flow path based on the pressure difference, and one inlet of the four-way valve is connected to the discharge side of the compressor, and the other inlet is connected between the outlet of the evaporator and the inlet of the third check valve. One outlet is connected to the first check valve and the other outlet is connected to the bypass pipe, and the other end of the bypass pipe is connected to the inlet side of the evaporator. A heat exchange part and a fourth check valve are provided in the middle, and the four-way valve connects one inlet and one outlet during cooling operation, and connects one inlet and the other outlet during defrosting operation. and one outlet are connected to each other.

One working end is connected to the other inlet of the four-way valve, and the other end of the pipe (specifically, the low-pressure pipe for flow path switching) is connected to the evaporator outlet side upstream from the third check valve, so the compression Even if the pressures on the discharge side and suction side of the machine are balanced by the pressure balancing pipe, the third check valve prevents this balanced pressure from being further balanced with the pressure on the evaporator outlet side. Due to the
Even when the compressor is stopped, the third check valve acts to ensure a pressure difference between one inlet of the four-way valve and the other inlet of the four-way valve, so as not to interfere with the switching operation of the four-way valve. There is.

Example Embodiments of the present invention will be described with reference to the drawings.

1 is a refrigerant circuit in a refrigeration system, and a refrigerant compressor 2
, a flow path switching valve 3, a first check valve 4, an air-cooled condenser 6 equipped with a blower 5, a dryer 7, a liquid receiver 8, a second check valve 9,
A supercooling coil 10, a pressure reducing device such as an expansion valve (hereinafter referred to as an expansion valve) 11, an air-cooled evaporator 13 equipped with a blower 12, a third check valve 14, and a gas-liquid separator 15 are connected to the high-pressure gas pipe A1.
The high-pressure liquid pipe B, the low-pressure liquid pipe C, and the low-pressure gas pipe are connected in a ring to form a refrigeration cycle as shown by the solid arrow in Figure 1. By connecting the gas bypass pipe 20, a defrosting cycle as shown by the solid arrow in FIG. 2 is constructed.

The hot gas bypass pipe 20 has a meandering heat exchange section (
21 (hereinafter referred to as a hot gas coil), and a fourth check valve 22 is provided downstream of this hot gas coil 21.
It is equipped with

Reference numeral 25 denotes a low-pressure pipe for flow path switching that connects the flow path switching valve 3 and the refrigerant outlet side of the evaporator 13. As the flow path switching valve 3, a four-way valve called an electromagnetic pilot switching valve is used as a three-way valve, one of which has an inlet 31 in contact with the discharge side of the compressor 2, and an outlet 32. 33 and the other entrance 3
4 has high pressure gas pipe A1 and hot gas bypass pipe 2, respectively.
0, and the wave path switching low pressure pipe 25 are disconnected. The four-way valve 3 performs a switching operation only when there is a certain pressure difference between the pressure at one inlet 31 and the pressure at the other inlet 34.

Moreover, 35 is a pressure balance pipe as a pressure balance circuit connecting the discharge side of the compressor 2 and the inlet side of the gas-liquid separator 15, and is opened when the compressor 2 is stopped and is opened when the compression flA2 is operated. A solenoid valve 36 that closes is connected to the downstream side of the solenoid valve 36 to a capillary tube 37 serving as a pressure reducing device that prevents high-pressure gas refrigerant from being rapidly introduced to the low-pressure side of the compressor 2.

Based on the above configuration, the refrigerant flow path during each operation of cooling operation and defrosting operation will be explained.

First, when performing cooling operation, the compressor 2 is driven by a command from the operation switch (not shown), and the four-way valve 3 is set to the cooling operation side, that is, one inlet 3.
1 and one outlet 32, and the other outlet 33 and the other inlet 34. As a result, the refrigerant gas compressed by the compressor 2 enters the condenser 6 via the four-way valve 3, is cooled and liquefied, is depressurized by the expansion valve 11, enters the evaporator 13, is heated and vaporized, and is sucked into the compressor 2 again. A well-known cooling cycle is used (see Figure 1).

When the refrigerant is heated and vaporized by passing through the evaporator 13,
The surrounding air is cooled to remove heat from the air around the evaporator, and the desired cooling is achieved, but if the cooling operation described above continues, frost builds up on the evaporator 13 and grows. Since it becomes difficult for ambient air to come into contact with the surface of the evaporator and the cooling performance decreases, it becomes necessary to defrost the evaporator 13.

Therefore, the four-way valve 3 switches the flow path to the defrosting operation side, that is, one inlet 31 and the other outlet 33 are made to communicate with each other, and one outlet 32 and the other inlet 34 are made to communicate with each other by a timer device. When a defrosting command is issued periodically to switch the inside of the four-way valve, the high-temperature, high-pressure gas refrigerant compressed by the compressor 2 enters the hot gas bypass pipe 20 via the four-way valve 3, and flows through the hot gas coil 21 and It enters the evaporator 13 through the fourth check valve 22 and is liquefied, and the gas-liquid separator 1
5 and returns to the compressor as gaseous refrigerant. Evaporator 1
The gas refrigerant passing through evaporator 1 is cooled during cooling operation.
Since the pipes and fins in step 3 are heated, the frost adhering to the surfaces of the pipes and fins is rapidly heated to melt and peel off the frost adhering to the surfaces, and the frost deposited on the dew pan is melted and liquefied. . In addition, since the refrigerant guided to the condenser 6 during the cooling operation is at a high pressure during the cooling operation, and is higher than the pressure on the outlet side of the hot gas bypass pipe 20 (especially at the beginning of the defrosting operation), The refrigerant flows from the condenser 6 to the evaporator 13 via the expansion valve 11. However, as the defrosting operation continues, no refrigerant is sent to the condenser 6.
The air around the condenser reduces the pressure to the equilibrium pressure based on the air temperature, and the hot gas bypass pipe 2
Since the O outlet side pressure increases, the refrigerant flows from the condenser side to the evaporator 13 only until the pressure difference disappears.

On the other hand, when the temperature of the cooling space falls below a predetermined temperature during cooling operation, the operation of the compressor 2 is stopped, and when the compressor 2 stops, the solenoid valve 36 is opened and the pressure is balanced. The circuit is activated (see the dotted chain arrow in Figure 1), that is, the high-pressure refrigerant on the discharge side of the compressor 2 is guided to the suction side of the compressor 2 through the pressure equalization pipe 35, and the discharge side and suction side are Gradually equilibrate the pressure.

Since the command to switch the four-way valve 3 from the cooling side to the defrosting side is issued periodically by a timer, the command is issued while the compressor 2 is stopped, and the four-way valve 3 is switched to the defrosting operation side 2. There may be cases where the pressure is switched, but even if the pressure on the discharge side and suction side of the compressor 2 is in equilibrium and the pressure on the suction side is higher than the pressure on the suction side before the compressor is stopped, the third check valve will cause the pressure to be switched to the evaporator side. The flow is blocked, and the pressure on the outlet side of the evaporator 13 can be maintained at the low pressure before the compressor is stopped without being affected by the pressure balance circuit. Therefore, a pressure difference can always be provided between one inlet 31 and the other inlet 34 of the four-way valve 3, and the pressure difference as a condition for switching the four-way valve 3 can be ensured. Valve 3 can be switched. Therefore, when a defrosting command is issued, the four-way valve 3 can be switched regardless of whether the compressor is running or stopped, and there is no need for a control device to wait for switching the four-way valve 3 while the compressor 2 is stopped. Become.

〔Effect of the invention〕

As described in detail above, according to the present invention, in a refrigeration system equipped with a pressure equalization pipe that balances the pressure on the discharge side and the suction side when the compressor is stopped, the refrigerant flow path during the cooling operation and the defrosting operation is Since the other inlet of the four-way valve that switches with a difference is connected to the upstream side of the third check valve, that is, the outlet side of the evaporator, when the pressures on the discharge side and suction side are balanced when the compressor is stopped. Even if the valve is closed, the pressure on the discharge side is definitely higher than the pressure on the suction side just before the valve stops, so it is impossible to ensure a pressure difference between one inlet and the other inlet of the four-way valve. This makes it possible to switch the flow paths using the four-way valve even when the compressor is stopped. Therefore, it is not necessary to provide a mechanism and a control device to prevent the switching operation of the four-way valve from being performed while the compressor is stopped.

[Brief Description of the Drawings] Each figure is a refrigerant circuit diagram showing one embodiment of the present invention, and FIGS. 1 and 2 show the flow of refrigerant during cooling operation and defrosting operation, respectively. . DESCRIPTION OF SYMBOLS 1... Refrigerant circuit, 2... Compressor, 3... Four-way valve (flow path switching valve), 6... Condenser, 11... Pressure reduction device, 13... Evaporator, 14. ...Third check valve, 20...Hot gas bypass pipe, 25...
・Low pressure pipe for flow path switching, 31...one inlet, 3
4...Other inlet, 35...Pressure balance tube, 3
6... Solenoid valve.

Claims (1)

[Claims] 1. A refrigerant circuit is formed by a refrigerant compressor, a first check valve, a condenser, a second check valve, a pressure reducing device, an evaporator, and a third check valve, and the refrigerant circuit is connected to the discharge side of the compressor. In a refrigeration system having a pressure balance pipe having a solenoid valve that is opened when the compressor is stopped between the suction side and the compressor, a four-way valve is disposed on the discharge side of the compressor to switch a flow path based on a pressure difference, and the four-way valve is arranged on the discharge side of the compressor. One inlet of the valve is connected to the discharge side of the compressor, the other inlet is connected to the flow path switching low pressure pipe connected between the outlet of the evaporator and the inlet of the third check valve, and one outlet of the valve is connected to the flow path switching low pressure pipe connected between the outlet of the evaporator and the inlet of the third check valve. is connected to a first check valve, and the other outlet is connected to a bypass pipe, and the bypass pipe has its other end connected to the inlet side of the evaporator, and a heat exchange section and a fourth check valve are connected in the middle thereof. The four-way valve operates to connect one inlet and one outlet during a cooling operation, connect one inlet and another outlet during a defrosting operation, and connect the other outlet and one outlet, respectively. A refrigeration device characterized by: