JPS595891A - Hydraulic pressure protecting circuit for compressor for refrigeration - Google Patents

Abstract

PURPOSE:To prevent the seizing of a sliding part for the compressor due to the decrease of the hydraulic pressure by a method wherein a delay relay is operated to start or stop the compressor intermittently when the hydraulic pressure is not rising up after a given time is elapsed. CONSTITUTION:When the hydraulic pressure has not risen up after the given time Ta has been elapsed, the delay relay T is operated at a time t1. As a result, a contact T2 is opened and the contacts of a twin timer TT are made active, therefore, a main relay MC is excited intermittently. According to the excitation, the compressor CM repeats starting and stopping intermittently so as to be rotated for 7sec and stopped for 5sec, for example. Thus, the compressor is started and stopped intermittently, therefore, the danger of seizing of the sliding part of the compressor due to the decrease of hydraulic pressure may be reduced compared with the case, in which the compressor is operated continuously.

Description

[Detailed Description of the Invention] Vertical refrigeration compressors are normally structured so that refrigerant (fluorocarbon) scum flows into the crankcase. A large amount of freon gas dissolves in the lubricating oil. This freon gas is
When the compressor starts and lubricating oil is sucked into the lubricating oil pump, it forms bubbles in the oil and separates. If such a forming phenomenon is severe, the operation of the lubricating oil pump 9 will be hindered, so that the oil pressure will not increase, and the oil pressure protection circuit will work to stop the compressor.

In order to eliminate this phenomenon, some conventional compressors are equipped with an electric heater installed in the crankcase, which warms the lubricating oil and prevents the freon gas from melting. However, this type of refrigerator requires a constant supply of power, but it is used for special purposes7@
Freezers do not meet this condition. For example, in the case of a refrigerator built into a refrigerated container for marine transportation, cargo is normally loaded without power being supplied, and when the power is connected for the first time, the heater is not working, so the forming cannot be prevented.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an improved oil pressure protection circuit that can sufficiently protect a compressor from a state of low oil pressure and that also promotes an increase in oil pressure when starting pressure tmt8.

An embodiment of the present invention will be described based on the drawings. In FIG. 1, CM is a hermetic vertical compressor built into a refrigerated container, and the main relay MO controls the starting and stopping of the compressor. A pressure switch PS is connected in series to the coil of this main relay, and this switch controls the suction pressure of the compressor CM (this pressure changes depending on the opening degree of an automatic expansion valve (not shown)).

), if the internal temperature of the container drops too much and the suction pressure drops, it will open; on the other hand, if the internal temperature rises too much and the suction pressure increases, it will close. OPS is a hydraulic protection pressure switch, which consists of a hydraulic switch a, an electric heater b and a bimetal contact C connected in series across this switch, and this contact C is connected in series with the excitation coil of the main relay MO. There is. The oil pressure switch a responds to the pressure of lubricating oil supplied from the bottom of the crankcase to each sliding part by a lubricating oil pump (not shown) that is directly connected to the compressor CM, and opens when this oil pressure is higher than a specified value.

If it is low, it will close. The bimetal contact C has a structure in which when the heater b is energized, the temperature gradually rises and the bimetal contact C opens after approximately a certain period of time, and once the temperature is reached, the bimetal contact C remains open until it is artificially reset. Delay relay T and twin time relay TT are energized through this hydraulic protection pressure switch OPS. Delay relay T.

It has a normally open contact T1 in series with heater b and a normally open contact T2 in series with the coil of main relay MC. The twin time relay TT has a contact that repeatedly opens and closes at set intervals when excited, and this contact is connected in parallel with the contact T2 of the delay relay. In addition, TR is a step-down transformer for obtaining a control voltage, and SW is an on/off switch, which is normally closed.

To explain the function of this hydraulic protection circuit with reference to Fig. 2, the internal temperature of the container has risen and one time tO
Pressure switch PS closes, and main relay MO accordingly closes.
Although the compressor was energized and the compressor started.

Suppose the oil pressure did not rise immediately. In this case, contact T2 of delay relay T does not open immediately, so compressor CM
controls operation even after starting. If the compressor continues to operate in this way, the pressure in the crankcase connected to the suction side of the compressor will decrease, and the temperature of the lubricating oil will increase due to frictional heat, which will eventually cause the Because it is agitated by the shaft, it dissolves and gradually separates from the lubricating oil in the crankcase. When foaming is suppressed in this way and the oil pressure rises above the specified value, the compressor CM enters steady operation. Even after a certain period of time Ta (for example, 2 minutes) has elapsed, the hydraulic pressure 3 upper blade ~
If not, the delay relay T is activated at one time t1. As a result.

Since the contact T2 is opened and the contact force 3 of the twin timer TT is activated, the main relay MO is intermittently energized. Therefore, the compressor CM repeatedly starts and stops intermittently, for example, rotating for 7 seconds and stopping for 5 seconds. in this way,
If the compressor is started and stopped intermittently, there is less risk that the sliding parts of the compressor will burn out due to a drop in oil pressure, compared to when the compressor is in continuous operation. And during this intermittent start and stop.

The melted fron gas continues to separate from the lubricating oil accumulated in the crankcase, and the oil pressure tends to rise. If the oil pressure exceeds the specified value in this way, the compressor CM shifts to steady operation, as shown by the chain line in FIG. On the other hand, the intermittent on-off state remains for a certain period of time Tb.

For example, if the oil pressure still does not increase after 2 minutes.

At time t2, bimetal contact C is opened. This is because contact T1 of delay relay T closes at time t1 before that.

This is because heater b had already started being energized. As a result of the bimetal contact C being opened in this manner, the main relay MO becomes de-energized, the compressor OH is stopped, and damage to the compressor OH is prevented.

As explained above, in the hydraulic protection circuit of the present invention, when trying to stop the compressor due to a drop in hydraulic pressure, there is a first period in which the compressor is continuously operated, and a second period in which the compressor is intermittently started and stopped. The first period can significantly accelerate the rise in oil pressure, and the second period prevents damage to the compressor due to a drop in oil pressure. At the same time, it is possible to wait for the 1T11 pressure to rise by 1 for a long time, and as a result, there is an effect that the refrigeration compressor can be started smoothly.

[Brief explanation of drawings]

FIG. 1 is a hydraulic protection circuit showing an embodiment of the present invention, and FIG. 2 is a time chart showing its operation. CM...Compressor MO...Main relay PS...
・・Pressure switch OPS・・・・Hydraulic protection pressure switch T・・・・Delay relay TT・・Twin time relay Patent attorney Yoshiaki Satake Figure 1

Claims (1)

[Claims] When the oil pressure of the lubricating oil pumped from the bottom of the refrigeration compressor crankcase to each sliding part drops below the specified value,
The operation of the compressor is continued as it is, and if the oil pressure does not rise above the specified value within a certain period of time, the compressor is intermittently started and stopped, and if the oil pressure does not rise above the specified value even after a certain period of time. A hydraulic pressure protection circuit for a refrigeration compressor is configured to stop the compressor and shift the compressor to continuous operation when the hydraulic pressure increases.