JPH05172440A - Refrigerating plant - Google Patents

Abstract

PURPOSE:To assure a liquid injection cooling capability when a defrosting operation in a reverse cycle is started and to prevent an over-heating at a compressor. CONSTITUTION:In a refrigerant plant in which a defrosting operation is carried out under a reverse cycle, a freezing operation is forcedly carried out only for a predetermined short period of time prior to the defrosting operation in the case that the defrosting operation should be carried out as a predetermined specified time elapses during a stopped state of a compressor 1. With such an arrangement, a branch part of a liquid injection pipe 23 in a freezing circuit can be kept at a liquid sealed state under a condition in which a freezing operation is forcedly carried out for a short period of time and it is possible to perform a positive cooling of the compressor 1 under a liquid injection of sufficient amount of liquid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerating apparatus for performing defrosting in a reverse refrigerating cycle, and more specifically, to a stable defrosting operation without overheating of a compressor at a start time of periodically defrosting. Refrigeration equipment.

[0002]

2. Description of the Related Art A liquid injection pipe branched and extended from a liquid pipe in a refrigeration circuit is connected to a suction side of a compressor, and when the temperature of a gas discharged from the compressor rises excessively, an electromagnetic opening / closing provided in the liquid injection pipe A prior art of a refrigerating apparatus in which a compressor is cooled by opening a valve and injecting a liquid refrigerant into a suction side of the compressor is disclosed in, for example, Japanese Patent Application No. 2-113734 by the present applicant. 5 and 6 show the principle of operation of this prior art.

During the freezing (cooling) operation shown in FIG.
Since it is necessary to lower the temperature of the evaporator 6, the freezing expansion mechanism 5
The liquid refrigerant L in the liquid pipe connected to the inlet side of the compressor is guided to the intermediate pressure portion of the compressor 1 via the liquid injection pipe 24, and liquid injection is performed to lower the discharge gas temperature of the compressor 1 to reduce the evaporation temperature. I am trying to lower it.

In this case, the capillary tube 27 has a throttle amount so that the discharge gas temperature can be lowered to an appropriate temperature when the liquid refrigerant flows into the compressor 1.

When the temperature inside the refrigerator is lowered during the freezing operation and the freezing operation is stopped by the stop signal from the temperature detection thermostat,
Due to the pressure difference between the condenser 3 side and the evaporator 6 side, the refrigerant in the refrigeration circuit flows from the high pressure side to the low pressure side evaporator 6 and stays there, and at the branch point of the liquid injection pipe 24, the liquid sealing state. Changes to the liquid gas mixed state.

[0006]

As described above, when the defrost signal is input during the refrigeration operation suspension and the defrost operation of the reverse refrigeration cycle is performed as shown in FIG. 6,
Since the liquid pipe connected to the inlet side of the defrost expansion mechanism 4 is in a liquid / gas mixed state, the branch point of the liquid injection pipe 24 is not liquid-sealed,
A sufficient amount of liquid injection is not ensured, which causes a problem that the compressor 1 is not sufficiently cooled and overheats.

An object of the present invention is to eliminate the deterioration of the liquid injection capacity that occurs at the start of the defrosting operation due to the reverse refrigeration cycle and to prevent the compressor temperature from rising excessively, thereby ensuring a safe and reliable defrosting operation. There is a point to achieve it.

[0008]

According to the present invention, the compressor 1 is suspended due to the internal temperature lowering and reaching the set temperature T1 and the refrigerating operation time becomes a predetermined time W1. In a refrigerating apparatus in which defrosting is performed by a reverse refrigeration cycle, when the compressor 1 is not in operation when the defrosting should be performed for each of the constant times W1, a predetermined short time period before the defrosting operation is performed. The refrigerating apparatus is provided with means for performing a refrigerating operation for a time W2.

[0009]

According to the present invention, when the defrosting operation should be performed at a constant time W1, for example, a cycle of 3 hours, when the compressor 1 is not operating, the defrosting of the reverse refrigerating cycle is performed. Before starting the operation, the refrigerating operation is forcibly performed for a predetermined short time W2. In this case, the predetermined short time W2 is, for example, the time required for the liquid pipe at the branch connection point of the liquid injection pipe to be sufficiently liquid-sealed, and about 1 minute 30 seconds is an appropriate time.

As described above, the freezing operation is preceded by the short time W2, whereby the liquid sealing is reliably performed at the branch connection point of the liquid injection pipe,
At the start of the subsequent defrost operation, the liquid injection operates properly, so that it is possible to inject the liquid refrigerant that is necessary and sufficient for cooling the compressor 1.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a refrigerant piping system diagram of a refrigerating machine according to an embodiment of the present invention. The illustrated refrigerating apparatus includes a compressor 1 in which a compression element and a motor are axially coupled and housed in a closed casing, a four-way switching valve 2, a condenser 3 provided with an outside fan 17, and a reverse. A defrost expansion mechanism 4 such as a capillary tube, a dryer 13, and a filter 19 in which a stop valve 8, a side conduit having a check valve 11 and a side conduit having an electromagnetic valve 31 for defrost compensation are connected in parallel. A freezing expansion mechanism 5, for example, a temperature-sensitive expansion valve, a check valve 9 connected in parallel to the filter 19 and the temperature-sensitive expansion valve 5, an evaporator 6 provided with an internal fan 18, and a check valve 10. The accumulator 7 is provided, and they are connected by a refrigerant pipe.
It is connected to a reversible circulation circuit through which a refrigerant can flow and is divided into an outdoor unit A and an indoor unit B.

The partial coil 3A on the rear side of the condenser 3 close to the outlet side during the refrigerating operation is drawn out after being introduced into the closed casing of the compressor 1 to exchange heat with the low pressure gas,
The check valve 12 is connected in parallel to the series circuit including the partial coil 3A, the coil 3B on the outlet side of the condenser 3, and the check valve 8. On the other hand, a pipe having a drain pan heater 15 formed of a refrigerant pipe and a check valve 14 in series is a check valve 1.
A fan cover heater 16 which is connected in parallel with 0 and is composed of a refrigerant pipe line is connected in parallel with the drain pan heater 15.

In the refrigerating apparatus having the refrigerant piping system described above, in the case of the refrigerating (cooling) operation, the refrigerant flow indicated by the solid line arrow in FIG. The latent heat is exchanged with the outside air, and in the indoor unit B, the evaporation latent heat is exchanged with the indoor air in the evaporator 6. For example, the outside air temperature is 35 ° C. and the freezing chamber is -30. It is possible to cool to ° C. On the other hand, in the case of the defrosting operation by the reverse refrigeration cycle, the high temperature gas refrigerant is branched to the drain pan heater 15 and the fan cover heater 16 due to the refrigerant flow indicated by the broken arrow, and then flows to the coil of the evaporator 6 to be removed. Frost takes place.

The capillary tube 4 of the outdoor unit A
A branch liquid pipe 22 is branched and connected in the middle of the liquid pipe for connecting between the temperature sensor and the temperature-sensitive expansion valve 5 of the indoor unit B.
A capillary tube 2 for pressure equalization is provided in the branch liquid pipe 22.
5 and the solenoid valve 28 are provided in series relation. Further, the capillary tube 25 and the solenoid valve 28 in the branch liquid pipe 22.
A liquid injection pipe 23 for cooling the compressor and a liquid injection pipe 24 for preventing high-pressure overheating are branched and connected from a pipe line connecting between the solenoid valve 29 and the capillary tube 26. Are connected in series, and the liquid injection pipe 24 has a solenoid valve 3
0 and the capillary tube 27 are provided in series relation.

In the refrigerating apparatus described above, the pressure detecting mechanism is provided with the defrost control pressure switch 20 and the safety pressure switch 21, and the temperature detecting mechanism is the indoor temperature detector 33 and the evaporator cooling temperature detector 34.
Is provided. The pressure switch 20 is provided in association with the gas pipeline through which the low-pressure gas flows during the freezing operation and the high-pressure gas during the defrosting operation, and the pressure switch 21 is provided in the pipeline through which the high-pressure gas flows during both the freezing operation and the defrosting operation. It is provided in association. The pressure switch 20 detects the pressure on the high-pressure side during the defrost operation and detects the set pressure (for example, 23
When the pressure exceeds kg / cm ² · G), it is determined that the defrosting is completed, and a defrosting end (ON) signal is output. On the other hand, the pressure switch 21 detects the pressure on the high-pressure side during the operation of the compressor 1 and determines that the discharge pipe temperature has risen excessively when the pressure exceeds the set pressure, and outputs a discharge pipe high temperature (ON) signal.

On the other hand, the temperature detector 33 is provided to maintain the room temperature at a set temperature T1, for example, -30 ° C., detects the temperature of the suction side air of the evaporator 6, and outputs an OFF signal below the set temperature. Outputs an ON signal when the set temperature is exceeded. Further, the temperature detector 34 detects the temperature of the coil end portion on the inflow side of the evaporator 6 during the refrigerating operation, and judges that it is necessary to continue defrosting at a temperature equal to or lower than the set temperature T2.
The F signal is output, and when the set temperature is exceeded, it is determined that the defrost has ended, and the defrost end (ON) signal is output.

FIG. 2 is a block diagram showing the structure of the control circuit 32 for controlling the operation of the refrigerating apparatus shown in FIG. The control circuit 32 shown in FIG. 2 is a central processing unit (CP).
U) 35, and RAM 37 and RO constituting the storage device
An M38 and a timer circuit 36 are provided. This control circuit 3
2 receives an ON / OFF signal of the defrost control pressure switch 20, the safety pressure switch 21, the indoor temperature detector 33, and the evaporator cooling temperature detector 34 at the input interface, internally processes them, and then through the output interface. To the compressor motor 1M and the fan motors 17M and 18M, and outputs the operation stop to the solenoid 2 of the four-way switching valve 2.
The output of cooling (ON) and defrosting (OFF) with respect to S is supplied to the solenoid 28 of each solenoid valve 28, 29, 30, 31.
Open (ON) and closed (OFF) outputs are given to S, 29S, 30S and 31S.

The operation control mode of the control circuit 32 is shown in FIG.
This will be described below with reference to the flowchart of FIG. After starting the control operation in step A1, the process moves to step A2, and the indoor temperature is detected by the detector 33. When the room temperature is higher than the set temperature T1, the process proceeds to step A3 to start the freezing (cooling) operation. on the other hand,
When the temperature is lower than the set temperature T1, the process goes to step A9 to suspend the refrigeration operation. In this way, the freezing operation is automatically started and stopped.

The refrigerating operation at step A3 is performed by the compressor 1,
The outside fan 17 and the inside fan 18 are operated, the four-way switching valve 2 is turned on to the freezing side, the solenoid valve 29 is opened, and the solenoid valve 2 is opened.
8, 30, and 31 are closed, and the liquid refrigerant is injected into the intermediate pressure portion of the compressor 1 through the branch liquid pipe 22, the capillary tube 25, the solenoid valve 29, and the capillary tube 26 to operate the compressor. The temperature rise of the compressor can be suppressed.

Throughout the operation of the compressor 1, the pressure of the discharge pipe is detected by the pressure switch 21 in step A4, the solenoid valve 30 is opened while the pressure is higher than the set pressure P3, and the liquid is discharged through the capillary tube 27. By increasing the amount of refrigerant to the intermediate pressure portion of the compressor 1 and injecting it, it is possible to suppress an increase in discharge pressure.

While the refrigerating operation is automatically started and stopped, the time W during which the refrigerating operation is continued is measured, and the process proceeds to step A7 or step A10 for a fixed time W1 (for example, 3).
When the refrigerating operation is continued, the process moves to step A8 to switch to the defrost operation, and when the refrigerating operation is stopped, the process moves to step A11 to perform the refrigerating operation. Force. In the defrost operation, the compressor 1 is operated, the external fan 17 and the internal fan 18 are stopped, the four-way switching valve 2 is turned off to the defrost side, the solenoid valve 29 is opened, and the solenoid valves 28 and 31 are closed. It is done by letting. During the defrosting operation, the solenoid valve 30 operates in the same manner as during the refrigerating operation, only while the discharge pipe pressure is higher than the set pressure P3.
Move to A18 and open. After the solenoid valve 30 is closed by moving to step A17 due to the pressure drop in the discharge pipe, the evaporator 6
When the defrosting end signal is output from the pressure switch 20 or the temperature detector 34 after the defrosting is completed in step A20, the defrosting operation ends. After that, the automatic refrigerating operation after step A2 is continued.

On the other hand, when the defrosting operation command is output from the timer after the fixed time W1 has elapsed when the refrigeration operation is stopped in step A9, the operation proceeds to step A11 to force the refrigeration operation. In this case, when the compressor 1 is stopped, the inside of the liquid pipe at the branch point of the branch liquid pipe 22 is not in a liquid-sealed state but in a liquid-gas mixed state, which causes a problem of insufficient liquid injection. By forcing the freezing operation for a short time W2, the liquid sealed state at the branch point is restored.

As described above, when the liquid is completely sealed, the process proceeds to step A13 to perform the defrosting operation, so that the stable liquid defrosting operation can be performed while the liquid injection action is performed as expected. .. In this case, by opening the solenoid valve 31 in steps A13 to A15 for a predetermined short time W3 (for example, about 1.5 minutes), the refrigerant circulation amount in the reverse cycle state in the refrigeration circuit is secured. , The amount of defrost heat can be increased from the start of defrost.

After switching to the defrost operation, the defrost operation after step A16 and the freezing operation after step A2 are performed.

[0025]

As described above, according to the present invention, when it is necessary to perform the defrosting operation by the reverse refrigeration cycle during the refrigerating operation and the compressor 1 is not in operation,
The refrigerating operation is forced prior to the defrosting operation for a predetermined short time W2. As a result, when the compressor 1 is stopped, for example, the liquid-sealed state on the liquid pipe side where the liquid injection pipe is branched can be quickly recovered by the forced refrigeration operation, and the defrost operation can be performed. Immediately after the start of, the compressor 1 is reliably cooled, stable operation is realized, and a sufficient amount of refrigerant circulation can be secured.

[Brief description of drawings]

FIG. 1 is a refrigerant piping system diagram of a refrigeration apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram of a control circuit 32 that controls the operation of the refrigeration system shown in FIG.

3 is a flowchart illustrating an operation control mode of a control circuit 32 shown in FIG.

FIG. 4 is a time chart explaining an operating state of the refrigerating apparatus shown in FIG.

FIG. 5 is a diagram showing a refrigerating operation principle of a refrigerating apparatus which is a prior art.

6 is a defrost operation principle diagram of the refrigerating apparatus shown in FIG.

[Explanation of symbols]

 1 Compressor 2 Four-way switching valve 3 Condenser 4 Expansion mechanism for defrost 5 Expansion mechanism for refrigeration 6 Evaporator 32 Control circuit

Claims (1)

[Claims] 1. The defrosting due to the reverse refrigeration cycle is performed every time the compressor 1 is stopped due to the internal temperature lowering and reaching the set temperature T1 and the refrigerating operation time reaches a predetermined time W1. In the refrigerating apparatus to be performed, when defrosting should be performed for each of the fixed times W1,
A refrigerating apparatus comprising means for performing a refrigerating operation for a predetermined short time W2 prior to the defrosting operation when the compressor 1 is not in operation.