JPH02282675A - Freezer - Google Patents

Abstract

PURPOSE:To enable a prevention of an opening of an expansion valve during a defrosting operation to be attained by a method wherein a bypassing pipe having a hot gas valve is connected in such a way as it may bypass a condensor and an expansion valve and then a mean pressure pipe is connected in such a way as an outlet port of a hot gas valve is communicated with the expansion valve. CONSTITUTION:A bypassing pipe 20 having a hot gas valve 19 is connected to a freezing circuit 12 in such a way as it may bypass a condensor 14 and an expansion valve 15 and at the same time a mean pressure pipe 22 is connected in such a way as an outlet port of a hot gas valve 19 in the bypassing pipe 20 is communicated with the bypassing pipe 20, resulting in that during a hot gas defrosting operation, a higher pressure than that of the outlet of the expansion valve may act against a diaphragm of the expansion valve 15 and a needle valve of the expansion valve 15 is closed. Only the refrigerant gas of high temperature is flowed stably into an evaporator 2 without being influenced by an external temperature condition and thus an efficient defrosting operation can be carried out. During a freezing operation, the expansion valve 15 may control an evaporating pressure under the same characteristic as that of an inner mean pressure temperature working type expansion valve and then an efficient freezing operation can be carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a refrigeration system including a refrigerant circuit equipped with a bypass pipe having a hot gas valve.

[Prior Art] In addition to the compressor, condenser, and evaporator, the refrigerant circuit of a refrigeration system generally includes an expansion valve to lower the pressure of the refrigerant from the condenser, adjust the flow rate, and send it to the evaporator. A bypass pipe with a hot gas valve is connected to the inlet side of the condenser and the outlet side of the expansion valve so that the refrigerant bypasses the condenser and the expansion valve. By opening the hot gas valve, high-temperature refrigerant gas, ie, hot gas, flows directly into the evaporator, and a defrost operation such as deicing and defrosting using the hot gas is performed.

Various temperature-operated expansion valves are known as m-expansion valves, and generally, a temperature-sensitive cylinder filled with refrigerant detects the pressure corresponding to the temperature of the suction gas of the compressor, and when the temperature drops, the valve expands. The temperature sensing cylinder and the expansion valve are connected so that the valve is closed and the expansion valve is opened when the temperature rises.

Additionally, as the suction pressure to the compressor increases, the motor current also increases, and excessive suction pressure can lead to motor overload and damage. Expansion valves are also known. This pressure limiting function is the maximum operating pressure (MOP).
The thermal expansion valve with MOP performs the same control as the expansion valve described above when the suction pressure is below the maximum operating pressure, and when the maximum operating pressure is reached, the refrigerant is stopped. This prevents pressure from rising excessively by stopping the feed.

[Problems to be Solved by the Invention] As is well known, when the ambient temperature of a refrigeration system decreases, the pressure on the discharge side or high pressure side and the pressure on the suction side or low pressure side of the compressor decrease, and the amount of refrigerant circulation decreases. In addition, in hot gas defrost operation under such low-temperature conditions, the evaporator outlet temperature is affected by the frost and water adhering to it, so the refrigerant temperature at the evaporator outlet is saturated, which corresponds to the low pressure side pressure. The temperature will be higher than the steam temperature. Therefore, the pressure inside the temperature-sensing cylinder of the expansion valve, which is installed at the evaporator outlet and detects almost the same temperature as that temperature, becomes the pressure corresponding to the refrigerant temperature at the evaporator outlet, and even during defrost operation, the expansion valve There is a possibility that the valve may open. When the expansion valve opens, liquid refrigerant flows into the evaporator, reducing the defrosting capacity, making defrosting time abnormally long or even impossible in extreme cases.

Although it is possible to prevent the expansion valve from opening as described above during defrost operation by using a temperature-operated expansion valve with an MOP, it is necessary to set the maximum operating pressure of the expansion valve to a low value. If set, during refrigeration operation,
Since the refrigeration capacity during so-called pull-down, which takes heat until it reaches freezing temperature, is reduced, the refrigeration capacity of the compressor cannot be fully utilized, and the compressor must be made unnecessarily large. This will significantly increase the manufacturing cost of the device.

Therefore, an object of the present invention is to provide a refrigeration system that can prevent the expansion valve from opening during defrost operation without impairing the refrigerating ability of the compressor.

[Means for Solving the Problems] The present invention has a refrigeration circuit including a compressor, a condenser, an external pressure equalization type expansion valve, and an evaporator, and the refrigerant temperature at the outlet of the evaporator is controlled by the expansion valve. Detected by the communicating temperature detection unit,
The present invention relates to a refrigeration system in which the expansion valve is controlled to open and close depending on the detected temperature.

According to the invention, to achieve the above objectives.

A bypass pipe having a hot gas valve is connected to the refrigeration circuit so as to bypass the condenser and the expansion valve, and an outlet side of the hot gas valve in the bypass pipe is connected to the expansion valve. A pressure equalizing pipe is connected so that it communicates.

[Function] In the refrigeration circuit (12) in Fig. 1, during refrigeration operation,
The refrigerant gas compressed by the compressor (13) to a high temperature and high pressure is passed through the condenser (14) through the conduit <16) on the discharge side of the compressor.
and is condensed here. This liquid refrigerant is supplied to the expansion valve (1
5), flows into the evaporator (2), removes heat, and evaporates. The evaporated refrigerant returns to the compressor (13) from the pipe (17) on the compressor suction side, is compressed again, and repeats the above operation.During this refrigeration operation, the pot gas valve <19) is engaged. Therefore, the pressure in the pressure equalization pipe (22>) and the pressure at the outlet of the expansion valve are approximately the same, and the expansion valve (15) operates as an internal pressure equalization type temperature-operated expansion valve.

Therefore, the refrigerant pressure on the outlet side of the expansion valve (15) is transferred to the expansion valve (15) via the bypass pipe (20) and the pressure equalization pipe (22).
The opening and closing of the expansion valve (15) is controlled in response to the temperature detected by the temperature sensing tube (15a), which is a temperature detection section.

During hot gas defrost operation, the hot gas valve (19) is open, so the outlet pressure is equal to the pressure equalizing pipe (2).
2), the pressure loss generated in the bypass pipe (20) causes a larger pressure to expand than when the valve operates as an internal pressure-equalizing temperature-operated expansion valve during the above-mentioned refrigeration operation. The expansion valve (15) remains closed. This pressure drop enables hot gas defrost operation without opening the expansion valve (15) even at low temperatures.

[Embodiments] Next, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings, in which the same reference numerals indicate the same or corresponding parts. Further, in the following embodiments, the present invention is implemented in an ice maker as an example, but the present invention can be similarly applied to refrigeration devices such as refrigerators and refrigerated showcases.

Referring to the drawings, and in particular to FIG. 1, the ice making t! 4 (refrigeration system) is schematically shown. In order to facilitate understanding of the present invention, an overview of the ice maker 1 will first be explained. A pair of ice-making plates 3.3 are provided with an evaporator 2 interposed therein to form an ice-making cycle, below which an ice-making water tank 5 is disposed via a guide plate 4, and above which an ice-making cycle ( A water sprinkler 6 is provided to supply ice-making water to the surface of the ice-making plate 3 during the refrigeration cycle (refrigeration cycle) and to the back surface of the ice-making plate 3 during the de-icing cycle (defrost cycle).

During the ice-making cycle operation, ice-making water is sent to the ice-making water supply section 6a of the sprinkler device 6 by the circulation pump 7 provided in the ice-making water tank 5 through the pipe line 8, and from there flows through the evaporator 2. The ice is cooled as it flows down the surface of the ice-making plate 3 cooled by the flowing refrigerant, and returns to the ice-making water tank 5 through a perforation (not shown) in the guide plate 4 . As such circulation is repeated, the temperature of the ice-making water drops to or near zero, and eventually ice forms on the surface of the ice-making plate 3, forming ice particles 9.

As the ice making water level in the ice making water tank 5 decreases as the phase changes from water to ice, and when it drops to a predetermined position, a water level detection device (not shown) detects this and sends an ice making completion signal to the control circuit of the ice making machine 1 ( (not shown).

As a result, the control circuit stops the operation of the circulation pump 7 and switches the ice maker 1 from ice making cycle operation to deicing cycle operation. In the water removal cycle operation, the solenoid valve 1 of the pipe 10 communicating with the deicing water supply section 6b of the water sprinkler 6
1 is opened, deicing water is supplied to the back side of the ice making plate 3, and the hot gas valve 1, which forms part of the refrigeration circuit described later, is opened.
9 is opened, hot gas is supplied to the evaporator 2, and the ice particles 9 adhering to the surface of the ice making plate 3 are melted by the heat of the deicing water and the heat of the hot gas. , ice making plate 3
It separates from the water tank, slides down on the inclined guide plate 4 as shown, and enters a water storage (not shown). For deicing water, use ice making plate 3.
The ice flows down, passes through the guide plate 4, enters the ice-making water tank 5, and is used as ice-making water during the next ice-making cycle operation.

Excess water is discharged to the outside from the overflow pipe 5a.

The configuration and operation of the ice maker 1 as described above are conventionally well known.

Now, in order to alternately perform ice making and deicing cycle operations of the ice maker 1 as described above, a refrigeration circuit 12 is connected to the evaporator 2. The refrigeration circuit 12 includes pipes 16, 17 and 18 connected to form a closed loop, and in addition to the above-mentioned evaporator 2, the compressor 13,
A condenser 14 and an expansion valve 15 are provided in the order in which the refrigerant flows. The pipe line 1B includes a bypass pipe or a branch pipe 20 having a hot gas valve 19 in parallel with the pipe line 18 provided with the condenser 14 and expansion valve 15 so as to bypass the condenser 14 and the expansion valve 15. The branch pipe 20 is joined to the pipe line 18 on the outlet side of the expansion valve 15.

A conduit extending from the discharge port side of the hot gas valve 19, that is, an external pressure equalizing pipe 22, extends to a predetermined portion of the expansion valve 15, which will be described later, and is connected thereto. The expansion valve 15 has a temperature detection section, and the temperature sensing cylinder 15a is provided on the outer surface of the conduit 17 on the suction side of the compressor 13 near the evaporator 2.

FIG. 3 is a detailed view of the expansion valve 15. The expansion valve 15 includes a housing 15b, and the housing 15b has a temperature sensing tube 15a, a condenser 14, a pressure equalization pipe 22, and each boat communicating with the evaporator 2. It is formed as shown. Also, inside the housing 15b, a needle valve 15c, a spring 15d,
A diaphragm 15e, an actuating rod 15f, etc. are provided, and the diaphragm 15e has a gas pressure P corresponding to the temperature of the temperature sensing cylinder 15a, and a pressure P2 at the connection position of the pressure equalizing pipe 22.
and a pressure P equivalent to the force of the spring 15cl to obtain superheat. Pressure Pl is a force in the direction of opening the needle valve 15c, and pressures P2 and P3 are forces in the direction of closing the needle valve 15c. In a steady state, the three forces are balanced and become P, = P2 + P3. .

In the above-mentioned refrigeration circuit 12, during the ice-making cycle operation of the ice-making machine 1, the refrigerant gas compressed by the compressor 13 to a high temperature and high pressure is sent to the condenser 14 through the pipe line 16 on the discharge side of the compressor.
, where it is condensed by the airflow from the cooling fan 21. This liquid refrigerant enters the expansion valve 15, flows into the evaporator 2, removes heat from the ice-making water, and evaporates. The evaporated refrigerant returns to the compressor 13 from the suction side pipe 17, is compressed again, and repeats the above-mentioned operation.During this ice-making cycle, the hot gas valve 19 is closed, so the pressure equalizing pipe 22
The pressure at the expansion valve 1 and the pressure at the expansion valve outlet are almost the same, and the pressure at the expansion valve 1
5 operates as an internal pressure-equalizing temperature-operated expansion valve.

Therefore, the refrigerant pressure on the outlet side of the expansion valve 15 acts on the inlet side of the expansion valve 15 via the branch pipe 20 and the pressure equalization pipe 22, and 1
The opening and opening of the lij tension valve 15 is controlled in response to the temperature detected by the temperature sensing cylinder 15a. That is, in FIG.
If the temperature of 5 a and the pressure of pressure equalization pipe 22 are in the expansion valve opening region, expansion valve 15 opens and liquid refrigerant flows into evaporator 2 .

As a result, the amount of refrigerant evaporated in the evaporator 2 increases, the temperature detected by the temperature sensing tube 15a decreases, and the pressure in the pressure equalizing tube 22 increases. Therefore, since the expansion valve enters the closed region, the expansion valve 1
5 is closed. When the expansion valve 15 closes, the amount of refrigerant in the evaporator 2 decreases, so the temperature of the temperature sensing tube 1.5a increases and the pressure of the pressure equalization tube 22 decreases. Since such a state falls within the expansion valve open region, the expansion valve 15 is opened.

In the deicing cycle, the hot gas valve 19 is open, so high-temperature refrigerant gas directly enters the evaporator 2 and warms the ice-making plate 3 from the back side. External tap water (compared to the ice cubes 9 having a relatively high temperature flowing in from the water supply valve 11) is sprayed between the ice making plates 3.3 from the deicing water supply section 6b. Due to the cooperative action of the deicing water and the high-temperature refrigerant gas, the surface of the ice 9 adhering to the ice-making plate 3 melts and falls. When all the ice 9 has fallen, it is detected by a well-known de-icing completion detection device (not shown), and the de-icing completion signal generated as a result allows
The hot gas valve 19 and the water supply valve 11 are closed, and the ice making cycle operation begins. In the deicing cycle, the hot gas valve 19 is opened as described above, and the outlet pressure acts on the expansion valve 15 via the pressure equalization pipe 22, so the branch pipe 2
Due to the pressure drop ΔP that occurs at
), the expansion valve 15 remains closed. This pressure loss AP is
Even if the refrigerant temperature at the evaporator outlet becomes higher than the saturated vapor temperature corresponding to the low pressure side pressure of the compressor 13 under the temperature conditions in the normal region where the refrigeration equipment is installed,
Since the needle valve 15c can be sized to keep it closed, hot gas defrost operation can be performed without the expansion valve 15 opening even at low temperatures.

[Effects of the Invention] As described above, according to the present invention, the bypass pipe 20 having the hot gas valve 19 is connected to the refrigeration circuit 12 so as to bypass the condenser 14 and the expansion valve 15, and Since the pressure equalizing pipe 22 is connected so that the outlet side of the hot gas valve 19 in the bypass pipe 20 is communicated with the expansion valve 15, the diaphragm of the expansion valve 15 is connected to the diaphragm of the expansion valve 15 during the hot gas defrosting operation. Since high pressure acts and closes the needle valve 15c of the expansion valve, only high temperature refrigerant gas stably flows into the evaporator 2 regardless of external temperature conditions, allowing efficient defrosting.

Further, during the refrigeration operation, the expansion valve 15 controls the evaporation pressure with characteristics similar to those of an internal pressure-equalizing temperature-operated expansion valve, so that the refrigeration operation can be performed efficiently.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the overall configuration of a refrigeration system according to the present invention, FIG. 2 is an explanatory diagram of the operation of an embodiment of the present invention, and FIG. FIG. 2 is a schematic diagram of a pressure-equalizing temperature-activated expansion valve. 1... Refrigeration device 2... Evaporator 12... Refrigeration circuit 13... Compressor 14... Condenser
15... Expansion valve 15g... Temperature detection part (temperature sensing cylinder) 19... Hot gas valve 20... Bypass pipe 22.
・・Pressure equalization pipe

Claims (1)

[Claims] It has a refrigeration circuit (12) including a compressor (13), a condenser (14), an external pressure equalization type expansion valve (15), and an evaporator (2), and has a refrigerant temperature at the outlet of the evaporator (2). , in the refrigeration system (1) in which the temperature is detected by a temperature detection unit (15a) communicating with the expansion valve (15) and the expansion valve (15) is controlled to open and close according to the detected temperature, the refrigeration circuit (12)
A bypass pipe (20) having a hot gas valve (19) is connected to the bypass pipe (20) so as to bypass the condenser (14) and the expansion valve (15).
A refrigeration system characterized in that a pressure equalizing pipe (22) is connected so that the outlet side of the hot gas valve (19) located at 0) communicates with the expansion valve (15).