JPH10122675A - Refrigeration cycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to start a compressor temporarily even when a suction pressure (low pressure side) is low by an open air temperature which is extremely low. SOLUTION: This invention relates to a refrigeration cycle which is provided with a compressor 1, a condenser 4 which condenses the refrigerant discharged from this compressor 1, an expansion means 11 which depressurizes and expands the refrigerant, an evaporator 7 which evaporates the depressurized refrigerant and a low pressure switch 13a which detects the pressure on the suction side of the compressor 1. A bypass valve SV1 is provided so as to communicate the discharge side 2 of the compressor 1 with the suction side 3. The low pressure switch 13a is disabled for a specified time after the starting command of the compressor 1 is given while a control circuit 30 is provided which makes it possible to start the compressor 1 by opening the bypass valve SV1 so as to raise the low pressure where an electric heater H is provided, which is energized when the open air temperature is below 0 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigeration cycle provided with a low pressure switch for stopping the operation of a compressor when a suction side pressure of the compressor is equal to or lower than a predetermined value.
The present invention relates to a refrigeration cycle that can start a compressor in a cold region or the like.

[0002]

2. Description of the Related Art FIG. 3 is an explanatory view for explaining a conventional refrigeration cycle. Reference numeral 1 denotes a compressor, which is driven by being supplied with a three-phase input (not shown).
The refrigerant is supplied to the discharge side 2 of S, and the refrigerant returning to the suction side 3 is compressed and circulated to the discharge side 2 again. 4 is a condenser, which is connected to the compressor 1 via the discharge side 2,
It condenses the refrigerant supplied from the compressor 1,
It is frozen by driving the outdoor fan 17. Reference numeral 7 denotes an evaporator which is connected to a discharge side 8 of the condenser 4 through a dryer 9, a sight glass 10, and an automatic expansion valve 11, and is cooled by evaporating a refrigerant supplied from the automatic expansion valve 11. Reference numeral 12 denotes an indoor fan, which supplies the air frozen by the evaporator 7 to the room. Both the indoor fan 12 and the evaporator 7 are located in a unit (not shown). A low-pressure switch 13a is connected to a low-pressure side (suction side) pipe line 15 branched from the suction side 3 of the refrigeration cycle CS, and detects a pressure difference on the suction side 3 of the refrigeration cycle CS to reduce the low-pressure side pressure. Compressor 1 when below a certain level
To stop driving. That is, for example, when a gas leak occurs or the compressor 1 is driven in a cold region,
Since the pressure on the suction side 3 decreases, the compressor 1 has a function of stopping the compressor 1 to protect the compressor 1 and a function of preventing damage to the compressor 1 due to liquid compression under low-temperature use. In addition, in the refrigeration cycle CS, a high-pressure switch 13b is provided in a pipe 14 branched from the discharge side 2. Reference numeral 16 denotes a condenser pressure switch, which is connected to the pipe 14 and detects the pressure of the refrigerant on the discharge side 2 and drives the outdoor fan 17 when the pressure exceeds a predetermined value, thereby causing the condenser 4 to operate. To stabilize the refrigeration cycle CS.

Next, the operation will be described. Compressor 1
Is driven, the refrigerant from the compressor 1 is sent to the discharge side 2 of the refrigeration cycle CS, from which the condenser 4
Is supplied to the evaporator 7 via the dryer 9, the sight glass 10, and the automatic expansion valve 11. The evaporator 7 is thereby frozen to cool the air, and the air is sent out by the indoor fan 12 into the above-mentioned room to cool the room. Next, the refrigerant is evaporator 7
To the compressor 1 via the suction side 3 of the refrigeration cycle CS
Return to.

Here, the low pressure switch 13a detects the pressure of the refrigerant on the suction side 3 of the refrigeration cycle CS, and stops the compressor 1 when the low pressure side pressure reaches a certain level or less due to refrigerant leakage or the like. Further, the low-pressure switch 13a prevents the compressor 1 from operating in a cold region, thereby preventing liquid compression of the compressor 1. The high pressure switch 13b functions as protection for the refrigeration circuit and the compressor. The pressure switch 16 for the condenser is connected to the discharge side 2.
When the pressure rises excessively, the outdoor fan 17 is rotated to cool the condenser 4, and the pressure of the refrigerant is lowered and stabilized.

[0005]

Conventionally, when an electronic precision device such as a mobile radar device having a large calorific value is operated in a cold region, it is necessary to provide an indoor environment that satisfies the operating temperature conditions of the device. It is necessary to cool the room.

In a cold region where the outside air temperature is as low as -20.degree. C. to -40.degree. C., if the outside air is introduced into the room, the room can be cooled. Therefore, the refrigeration cycle CS including the evaporator 7 is prepared. It is not necessary to cool the room by operating the air conditioner. However, when introducing outside air, if the outside is snowy, snow or moisture may enter the room and deteriorate the characteristics of the electronic precision equipment. Therefore, it is necessary to operate the refrigeration cycle CS even in a cold region where the outside air temperature is low.

Usually, when the outside air temperature is extremely low, the air conditioner is started and the refrigeration cycle C is started.
When the compressor 1 constituting the S is started, the compressor 1 is damaged based on the liquid compression. Therefore, the low pressure switch 13a is provided, and the compressor 1 is operated under the low temperature of the outside air.
Cannot be started. Specifically, the low pressure switch 13a operates the suction side (low pressure side) of the compressor 1.
When the outside air temperature is extremely low, the pressure on the low pressure side is low.
The compressor 1 is stopped by operating 3a. The low-pressure switch 13a also has a protection function of detecting gas leakage and stopping the compressor 1. However, under such a system in which the compressor 1 cannot start up when the outside air is at a low temperature, a situation may occur in which the above-mentioned radar operation in a cold region cannot be performed.

Japanese Patent Application Laid-Open No. 4-251163 discloses that
In a refrigeration cycle in which a front evaporator via a first expansion valve and a rear evaporator via a second expansion valve are connected in parallel on the downstream side of the condenser so that the refrigerant of the compressor can be simultaneously supplied thereto. By providing a bypass passage that bypasses the refrigerant inlet of the expansion valve and the refrigerant outlet of the rear evaporator, and when the outside air starts up at a predetermined temperature or lower, the refrigerant is returned to the compressor through the bypass passage, thereby causing a shortage of lubricating oil. A technique for preventing burn-in of a compressor is disclosed.

However, when the above-described low-pressure switch is provided in the above-mentioned refrigeration cycle in consideration of the case where the refrigeration cycle is used in a cold region, the outside air temperature becomes -20 ° C to -40 ° C.
At low temperatures, the compressor cannot be started at all because the operation of the low-pressure switch prohibits the compressor from starting.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has an extremely low outside air temperature in a refrigeration system including a low-pressure switch for stopping a compressor when it detects that the low pressure side of the refrigerant is low. Accordingly, it is an object of the present invention to provide a refrigeration system that can start the compressor temporarily even when the suction side (low pressure side) pressure is low.

[0011]

According to the first aspect of the present invention,
A compressor that compresses and discharges the refrigerant, a condenser that condenses the refrigerant discharged from the compressor, an expansion unit that decompresses and expands the liquefied refrigerant, an evaporator that evaporates the refrigerant depressurized by the expansion unit, and a compressor. In a refrigeration cycle including a low-pressure switch that detects the pressures on the discharge side and the suction side of the compressor and stops the operation of the compressor, a bypass valve communicating the discharge side and the suction side of the compressor is provided. While disabling the low pressure switch for a predetermined time,
By opening the bypass valve, the pressure on the suction side of the compressor is increased so that the compressor can be started. The invention according to claim 2 is a compressor that compresses and discharges the refrigerant, a condenser that condenses the refrigerant discharged from the compressor, expansion means that decompresses and expands the liquefied refrigerant, and refrigerant that is depressurized by the expansion means. In a refrigeration cycle including an evaporator for evaporating the pressure and a low-pressure switch for detecting the pressure on the discharge side and the suction side of the compressor and stopping the operation of the compressor, a bypass valve communicating the discharge side and the suction side of the compressor is provided. The low pressure switch is disabled for a predetermined time after the start command of the compressor, and the compressor is started by starting the compressor by increasing the suction side pressure of the compressor by opening the bypass valve. An electric heater that is energized when the outside air temperature falls below a predetermined temperature Characterized by being adapted to advance warming.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory view for explaining an embodiment of the present invention, and FIG. 2 is an explanatory view of a control circuit 30 of the same. The same reference numerals are given to the same portions as those shown in FIG. In this case, the low-voltage switch 13a is of a low-pressure automatic return type. SV1 is a bypass valve. This bypass valve SV1 is connected to the refrigeration cycle CS1.
The compressor 1 is connected between the discharge side 2 and the suction side 3 of the compressor 1, and when opened, a part of the refrigerant on the discharge side 2 is bypassed to the suction side 3 and returned to the compressor 1. H denotes an electric heater which is installed so as to keep the compressor 1 warm, and is housed in a heater case (not shown). FIG. 3 shows the control circuit. The first thermocouple 37 operates when the outside air reaches −25 ° C. and turns on its contact Ths9.
Reference numeral 8 denotes a second thermo that turns on the contact Ths10 when the outside air reaches 0 ° C., and R8 denotes contacts R8a, R8b, R8c,
A power relay having R8d, T2 is a timer with a timer setting of 2 seconds, and has a contact 2Ta. T6 is timer setting 12
It is a timer of 0 seconds and has contacts T6a and T6b.

Next, the operation will be described. When the outside air is warm rather than extremely cold (for example, when the temperature exceeds 0 ° C.), the voltage is supplied to the timer T2 via an air conditioner switch (not shown), so that the compressor input control contact 1a is turned on and the compressor 1 is driven. Driving is done. When the compressor 1 is started, the refrigerant is circulated in the refrigeration cycle CS1 to cool the evaporator 7, whereby the room is cooled and cooling is performed.

On the other hand, when the outside air is extremely cold at -20.degree. C. to -40.degree. C., the contact PSL1 is conventionally turned off by the low-pressure switch 13a for the purpose of liquid compression of the compressor 1, and the power supply voltage is not input. It has the disadvantage of not being activated. However, according to the present embodiment, the first thermo 37 operates, turns on its contact Ths9, turns on the contact R8a, turns on the timer T2, and turns on the compressor input control contact 1a after 2 seconds. Then, the compressor 1 is driven. On the other hand, at the same time, the contact R
8c is turned on, the bypass valve SV1 is opened,
During this time, the operation of the compressor 1 causes the refrigerant to bypass the bypass valve SV1 that bypasses the discharge side 2 and the suction side 3 of the refrigeration cycle CS1.
Both the temperature and the pressure on the suction side 3 gradually increase.

By the time the timer circuit T6 elapses after 120 seconds, the temperature and pressure of the suction side 3 are both increased by the above operation of the compressor 1. Therefore, the low-pressure alarm setting pressure at which the low-pressure switch 13a automatically returns. Is set to 1 kg / cm ^{2 at} atmospheric pressure, for example, after the compressor 1 runs idle, the low-pressure refrigerant pressure becomes 1 kg / cm ² or more, and the low-pressure switch 13a automatically returns to turn on the contact point PSL1. Keeps driving. When the timer T6 expires, the contact T6a and the contact T
6b is turned off, the bypass valve SV1 is closed, and the normal operation of the refrigeration cycle CS1 is performed.

In this embodiment, when the outside air temperature is 0 ° C. or lower, the second thermo 38 operates and the contact Ths 10 is turned on, so that the electric heater in the heater case provided in the compressor 1 is provided. H is generating heat, the compressor 1 is kept warm and the temperature of the refrigerant therein can be raised, and the compressor 1 can be started more smoothly.

In the present embodiment, a bypass valve SV1 for communicating the discharge side 2 and the suction side 3 of the refrigeration cycle CS1 is provided, and a predetermined time (for example, 1
20 seconds), the low pressure switch 13a of the automatic return type is invalidated, the bypass valve SV1 is opened, the low pressure of the refrigerant is increased, the compressor 1 can be started, and the electric heater H which is energized at an outside air temperature of 0 ° C. or lower is used. Is provided in the compressor 1, the low-pressure switch 13 that stops the compressor 1 when detecting that the low pressure side of the refrigerant is low
In the refrigeration system provided with a, when the compressor 1 is started in a cold region where the outside air temperature is extremely low, the compressor 1 can be started even if the pressure on the low pressure side is low.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating an embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating a configuration of a control circuit 30 used in the embodiment of the present invention.

FIG. 3 is an explanatory diagram illustrating a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compressor 1a Compressor input control contact 2 Discharge side 3 Suction side 4 Condenser 7 Evaporator 8 Discharge side 9 Dryer 10 Sight glass 11 Automatic expansion valve 12 Indoor fan 13a Low pressure switch 13b High pressure switch 14 Pipe 15 Pipe 16 Capacitor pressure switch 17 Outdoor fan 30 Control circuit T2 Timer T2a Contact T6 Timer T6a, T6b Contact SV1 Bypass valve R8 Power relay R8a, R8b, R8c, R8d Contact Ths9, Ths10 Contact H Electric heater 37 First thermo 38 Second thermo CS1 Refrigeration cycle

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Atsushi Terada, Inventor, 5-7-1 Shiba, Minato-ku, Tokyo Within NEC Corporation (72) Inventor Yoshimasa Kawasaki 1114 Yoshibashi, Yachiyo-shi, Chiba Pref.

Claims (2)

[Claims] A compressor for compressing and discharging a refrigerant;
A condenser that condenses the refrigerant discharged from the compressor, an expansion unit that decompresses and expands the liquefied refrigerant,
In a refrigeration cycle including an evaporator that evaporates the refrigerant decompressed by the expansion means and a low-pressure switch that detects the pressure on the suction side of the compressor and stops the operation of the compressor, the discharge side and the suction side of the compressor are A bypass valve for communication is provided, the low-pressure switch is disabled for a predetermined time after a start command of the compressor, and the compressor is started by increasing the suction side pressure of the compressor by opening the bypass valve. A refrigeration cycle characterized by the following. 2. A compressor for compressing and discharging a refrigerant,
A condenser that condenses the refrigerant discharged from the compressor, an expansion unit that decompresses and expands the liquefied refrigerant,
An evaporator for evaporating the refrigerant decompressed by the expansion means, and a refrigeration cycle including a low-pressure switch for detecting the pressure on the discharge side and the suction side of the compressor and stopping the operation of the compressor, By providing a bypass valve communicating with the suction side, disabling the low pressure switch for a predetermined time after the start command of the compressor, and opening the bypass valve to increase the suction side pressure of the compressor to start the compressor. A refrigeration cycle wherein the compressor is preliminarily heated by an electric heater which is energized at an outside air temperature equal to or lower than a predetermined temperature before the start of the compressor.