JPH06180155A - Freezer device - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] Especially during pull-down operation, a predetermined high and low pressure difference can be achieved while continuing the operation of the screw compressor, and the amount of oil supplied to the compressor is secured to prevent seizure. [Structure] The cold water temperature detector 20 of the water evaporator 9 and the cooling water temperature detector 30 of the condensing unit 7 are cooled to a predetermined temperature (20 ° C.) or lower and a cooling water temperature is set to a predetermined temperature (2 ° C.) during pull-down operation.
(0 ° C.) or less, a controller 60 that controls the opening degree of the slide valve 4 that controls the capacity of the screw compressor 1 based on the cold water temperature and the cooling water temperature to a predetermined opening degree (80%) is provided, and pull-down operation is performed. At this time, when the cold water temperature is low and the cooling water temperature is also low, it is predicted that the high / low differential pressure is unlikely to be applied and the amount of oil supply is insufficient, and the opening degree of the slide valve 4 is controlled from low capacity operation to high capacity operation. By this control, the rise of the discharge pressure is promoted, the height difference pressure is maintained at a predetermined pressure difference, the amount of oil supplied to the compressor 1 can be secured, and seizure of the compressor 1 is prevented while continuing the pull-down operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerating apparatus, more specifically, a screw compressor whose capacity can be controlled by adjusting the opening of a slide valve, a water-cooled condenser having a cooling water pipe, an expansion mechanism, and a cold water pipe. With a water vaporizer with
An oil recovery device is provided on the discharge side of the compressor, and an oil supply mechanism is provided for supplying the oil of the oil recovery device to the oil supply location of the compressor by the difference in pressure between the discharge side pressure and the suction side pressure of the compressor. Related to refrigeration equipment.

[0002]

2. Description of the Related Art Conventionally, an oil recovery device is provided on the discharge side of a screw compressor, and the oil of the oil recovery device is supplied to the compressor by the pressure difference between the discharge side pressure and the suction side pressure of the compressor. A device provided with an oil supply mechanism for supplying oil to a location is already known, for example, as disclosed in Japanese Patent Laid-Open No. 3-79959.

In the refrigerating apparatus of this publication, as schematically shown in FIG. 4, the capacity of the screw compressor A whose volume can be controlled by controlling the opening of a slide valve is sequentially changed from a discharge side to a suction side of a condenser B, An expansion mechanism C and an evaporator D are connected via a refrigerant pipe E to form a refrigeration cycle, while an oil recovery unit F, an oil cooler G, and an oil supply pipe H provided on the discharge side of the compressor A are supplied. In the compressor A, the oil, which constitutes a mechanism and is cooled by the oil cooler G through the respective branch pipes of the oil supply pipe H, is generated by the pressure difference between the discharge side pressure and the suction side pressure of the compressor A. It is designed to lubricate multiple lubrication points. In addition, a cooling pipe K having a temperature-sensitive expansion valve J interposed therein is branched from the outlet side of the condenser B, the liquid refrigerant in the branch pipe K is evaporated to cool the oil in the oil cooler G, and further the evaporation is performed. The compressed refrigerant is transferred to the compressor A
It is designed to inject into the compression process part.

[0004]

By the way, in the conventional refrigerating apparatus, generally, the condenser B is a water-cooled condenser having a cooling water pipe, and the evaporator D is a water-evaporating evaporator having a cold water pipe. The slide valve of the compressor A detects the temperature of the chilled water pipe, that is, the cooling load, and controls the opening according to the load.

Therefore, when the cold water temperature of the cold water pipe is low and the refrigerating load is small, the opening degree of the slide valve is reduced to control the low capacity operation. On the other hand, for the oil supply to the oil supply location of the compressor A, generally, the difference in pressure between the discharge side pressure and the suction side pressure of the compressor A is used.

However, in the case of refueling by utilizing the high and low differential pressure as described above, there is no problem if the high and low differential pressure can be sufficiently secured. For example, a refrigerant cylinder is connected to the suction side of the compressor A. When charging the refrigerant while performing the pull-down operation, the pressure of the refrigerant cylinder becomes the suction side pressure and becomes high, so the high and low differential pressure decreases, and during this pull-down operation, the chilled water temperature is low and the control of low-volume operation is possible. When it is performed, the suction side pressure becomes low, but when the cold water temperature is low, generally the cooling water temperature is also low and the discharge side pressure is difficult to rise, so that a high and low differential pressure cannot be sufficiently obtained.

As a result, the amount of oil supplied due to the high and low differential pressure becomes insufficient, so that the compressor A is seized, and the compressor A abnormally stops due to the current limitation of the current flowing through the motor. The problem arises that it cannot continue.

Further, in order to solve the above problems, especially the problem of baking, it is also possible to detect the difference in height between the discharge side pressure and the suction side pressure and stop the operation of the compressor A when this difference in height is small. However, in this case, the pressure of the discharge gas does not rise immediately at the time of starting the pull-down operation, and even if it rises, it is not stable.
After 6 minutes have passed, the operation of the compressor A is controlled based on the detection result of the high and low differential pressure. Therefore, if the cooling water temperature at the start of operation is low and the cold water temperature is also low, the operation control of the compressor A is started after the start of operation.
The problem of the compressor A seizing up within ~ 6 minutes still remains.

The present invention relates to a refrigeration system in which a screw compressor whose capacity can be controlled by adjusting the opening of a slide valve is connected to a water-cooled condenser having a cooling water pipe and an anti-water evaporator having a cold water pipe. As described above, it is possible to estimate the high and low differential pressure during operation from the cooling water temperature and the cold water temperature, and the discharge side pressure is higher in the high capacity operation in which the opening of the slide valve is increased compared to the low capacity operation. It was invented paying attention to the fact that it is easy to increase and therefore the high and low differential pressure can be easily made to be a predetermined pressure. Is set to a predetermined pressure difference, the amount of oil supplied to the screw compressor is secured, and seizure of the compressor can be prevented.

[0010]

In order to achieve the above object, according to the present invention, a screw compressor 1 whose capacity can be controlled by adjusting the opening of a slide valve 4 and a water-cooled condenser 7 having a cooling water pipe. And an expansion mechanism 8 and a water evaporator 9 having a cold water pipe, and an oil recovery device 6 on the discharge side of the compressor 1, and a discharge side pressure and a suction side pressure of the compressor 1. In a refrigeration system provided with an oil supply mechanism for supplying the oil of the oil recovery device 6 to the oil supply location of the compressor 1 by the high and low differential pressure, a cold water temperature detector 20 for detecting the cold water temperature of the evaporator 9; A cooling water temperature detector 30 for detecting the cooling water temperature of the condenser 7 and each of the temperature detectors 20, when the cooling water temperature is below a predetermined temperature and the cooling water temperature is below a predetermined temperature during pull-down operation. The slide based on the detection result from 30 4 of the opening is to provided a controller 60 for controlling the predetermined opening.

The predetermined opening of the slide valve 4 controlled by the controller 60 is, for example, a cold water temperature not higher than a predetermined temperature (eg 20 ° C.) and a cooling water temperature not higher than a predetermined temperature (eg 20 ° C.). When the pull-down operation is continued by changing the opening degree of the slide valve 4 under the condition that the high and low differential pressure is hard to be applied, the opening degree that allows the operation without seizure. With the configuration shown in FIG.

[0012]

In the pull-down operation, when the cold water temperature is low and the cooling water temperature is also low, it is predicted that the high / low differential pressure is unlikely to be applied and the oil supply amount is insufficient. By controlling the opening, that is, by controlling from low capacity operation to high capacity operation, it is possible to promote the rise of the discharge side pressure and maintain the high and low differential pressure at a predetermined pressure difference. The amount of oil supplied to the oil supply location of the compressor 1 can be secured.

Therefore, the seizure of the compressor 1 can be prevented while continuing the pull-down operation without stopping.

Moreover, the opening control of the slide valve 4 is
It is possible to detect the cold water temperature and the cooling water temperature and predict that the differential pressure is small at the same time when the pull-down operation is started, that is, the differential pressure is small and the amount of oil supply is insufficient to detect the cause of seizure. Since the control can be performed from the start of the pull-down operation, seizure of the compressor 1 can be effectively prevented while continuing the pull-down operation without stopping.

[0015]

EXAMPLE A screw compressor 1 used in the refrigerating apparatus shown in FIG. 1 includes a screw rotor 3 driven by a motor 2 and a slide valve 4 for capacity control. An oil recovery unit 6, a water-cooled condenser 7, an expansion mechanism 8 and a water evaporator 9 are sequentially connected via a refrigerant pipe 5 to form a refrigeration cycle from the discharge side to the suction side of the compressor 1, and the condensation is performed. A cooling water pipe 71 is connected to the evaporator 7, the discharge gas is condensed by the cooling water flowing through the cooling water pipe 71, and a cold water pipe 91 is connected to the evaporator 9 so that, for example, from the cold water pipe 91. I try to get cold water for cooling.

Further, the oil recovery unit 6 installed in the middle of the refrigerant pipe 5, an oil tank 11 having an oil heater 10, an oil cooler 13 connected to an oil cooling water pipe 12, an oil filter 14, and the compression unit. An oil supply mechanism including an oil supply pipe 15 that connects the machine 1 and the oil tank 11 is configured, and the oil cooled by the oil cooler 13 via each branch pipe of the oil supply pipe 15 is discharged from the compressor 1. The pressure difference between the side pressure and the suction side pressure is used to supply oil to a plurality of lubricating points in the compressor 1 to lubricate, for example, the screw rotor 3 and a gate rotor (not shown) meshing with the screw rotor 3. ing. Incidentally, the motor 2 is stopped by limiting the current so that a current exceeding the rated value does not flow in the motor 2.

Thus, in the refrigerating apparatus configured as described above, as shown in FIG. 1, the cold water temperature detector 20 for detecting the cold water temperature is provided at the inlet side of the evaporator 9 of the cold water pipe 91. , The condenser 7 of the cooling water pipe 71
Cooling water temperature detector 3 for detecting the cooling water temperature on the inlet side of the
0 is provided, while an opening adjustment mechanism 40 including a vane motor for adjusting the opening of the slide valve 4 is provided,
The capacity of the compressor 1 can be continuously controlled by the operation of the opening adjustment mechanism 40, and the opening adjustment mechanism 40 has a potential having a variable resistance for detecting the opening of the slide valve 4. The opening detector 50 consisting of When the slide valve 4 is fully opened, full load operation is performed, and when the slide valve 4 is fully closed, no load operation is performed.

Further, a plurality of tasks such as detecting the temperature and the opening, comparing the detected temperature and the set temperature, and outputting based on the comparison result are performed in parallel. A controller 60 including a microcomputer is provided, and as shown in FIG. 2, the temperature detectors 20 and 30 are provided on the input side of the controller 60.
And the opening degree detector 50, and the opening degree adjusting mechanism 40 is connected to the output side of the controller 60, while the controller 60 is connected to the temperature detectors 20 during pull-down operation, The detection means 61 for detecting the temperature signal output by the unit 30 or the opening signal output by the opening detector 50 is compared with the detection temperature and each predetermined temperature described below, or the detected opening is set to the predetermined opening described below. And an output unit for outputting an opening command, a closing command, an opening holding command, etc. of the slide valve 4 to the opening adjustment mechanism 40 based on the comparison result compared by the comparing unit 62. 6
3 is provided, and the output from the output means 63 controls the cold water temperature at a predetermined temperature (20 ° C.) or less to a low capacity during the pull-down operation, and the cooling water temperature at a predetermined temperature (20 ° C.) or less. Therefore, under the condition that the high and low differential pressure is not easily applied, the opening degree of the slide valve 4 is set to a predetermined opening degree (80%) based on the detection results from the temperature detectors 20 and 30.
Control.

That is, when the temperature of the cold water is 20 ° C. or lower, the cooling load is small, the opening of the slide valve 4 is adjusted to be small, and the low capacity operation is performed. At this time, the temperature of the cooling water is lower than 20 ° C. Therefore, it is predicted that the high and low differential pressure cannot be obtained, and as a result, the high and low differential pressure cannot be obtained. Therefore, under the condition that the cooling water temperature is 20 ° C. or lower and the high and low differential pressure is hard to be applied, The opening is controlled to be larger than the opening corresponding to the load and to a predetermined opening that does not reach the current limit, and the predetermined opening increases the discharge side pressure as described above. The opening is an opening that promotes the high and low differential pressure to be maintained at a predetermined pressure difference to secure the amount of oil to be supplied to the oil supply point of the compressor 1 and is less likely to cause the compressor 1 to abnormally stop due to current limitation.

Next, the operation of the refrigerating apparatus configured as described above will be described with reference to the flow chart shown in FIG.

First, after the pull-down operation is started, the cold water inlet temperature (T1) at the inlet of the evaporator 9 and the cooling water inlet temperature (T2) at the inlet of the condenser 7 are read, and first, the cold water inlet temperature (T1). Is the set temperature (20
C.) or lower, and if this cold water inlet temperature (T1) is 20.degree. C. or lower, that is, in the case of YES, the cooling water inlet temperature (T2) is compared with the set temperature (20.degree. C.). If the cold water inlet temperature (T1) is higher than 20 ° C,
That is, in the case of No, it is determined whether the opening degree (S) of the slide valve 4 is equal to or larger than the set opening degree (80%). When the opening (S) at this time is equal to or larger than the set opening (80%), that is, when the answer is YES, the opening of the slide valve 4 is maintained, while the opening (S) at this time is the set opening. When it is smaller than (80%), that is, when it is NO, the cooling water inlet temperature (T2) is compared with the set temperature (20 ° C) as in the case where the cold water inlet temperature (T1) is 20 ° C or lower.

Therefore, by comparing the cooling water inlet temperature (T2) with the set temperature (20 ° C.), it is judged whether the cooling water inlet temperature (T2) is the set temperature (20 ° C.) or less,
When the cooling water inlet temperature (T2) is higher than 20 ° C., that is, when it is NO, the opening of the slide valve 4 is made to correspond to the capacity control corresponding to the cooling load, while the cooling water inlet temperature (T2) is set.
If 2) is 20 ° C. or lower, that is, if yes, it is determined whether the opening degree (S) of the slide valve 4 is larger than the set opening degree (80%).

When the opening (S) of the slide valve 4 is smaller than the set opening (80%), that is, when the slide valve 4 is not open, a slide open command is output to open the slide valve at the set opening (80%) while the slide valve 4 is opened. When the opening degree (S) of No. 4 is larger than the set opening degree (80%), that is, when the answer is YES, the opening degree of the slide valve 4 is maintained.

Therefore, in the embodiment constructed as described above, the cold water temperature is the predetermined temperature (20 ° C.) during the pull-down operation.
When the cooling water temperature is equal to or lower than the predetermined temperature (20 ° C.), it is predicted that the amount of oil supply will be insufficient due to the high and low differential pressure, and the controller 60 controls the opening degree of the slide valve 4 to the cooling load. Regardless of this, the predetermined opening (80%) is forcibly controlled, and by this control, that is, by controlling from low-capacity operation to high-capacity operation, the rise of the discharge side pressure is promoted and the high-low differential pressure is increased. Is maintained at a predetermined pressure difference, and the amount of oil supplied to the oil supply location of the compressor 1 can be secured. Therefore, it is possible to prevent seizure of the screw rotor 3 and the gate rotor of the compressor 1 due to insufficient oil supply, for example, while continuing the pull-down operation without stopping.

The opening control of the slide valve 4 can be performed simultaneously with the start of the pull-down operation by detecting the cold water temperature and the cooling water temperature and predicting that the height difference is small, that is, the height difference. Since the cause of seizure due to low pressure and insufficient oil supply amount can be detected and controlled from the start of the pull-down operation, seizure of the compressor 1 can be effectively prevented while continuing the pull-down operation without stopping. Of.

In the above embodiment, as shown in FIG. 1, the cold water temperature detector 20 is provided on the inlet side of the evaporator 9 of the cold water pipe 91, and the cooling water temperature detector 30 is provided. The cooling water pipe 71 is provided on the inlet side of the condenser 7 to detect the cooling water inlet temperature and the cold water inlet temperature. However, since the heat exchange area in the evaporator 9 and the condenser 7 is constant, The cold water temperature detector 20 is provided at the outlet side of the evaporator 9 of the cold water pipe 91, and the cooling water temperature detector 30 is provided at the outlet side of the condenser 7 of the cooling water pipe 71, and the cooling water outlet temperature and The cold water outlet temperature may be detected. In this case, the cooling water outlet temperature and the preset temperatures to be individually compared with the cold water outlet temperature respectively depend on the heat exchange area in the evaporator 9 and the condenser 7. To change .

Further, although the predetermined opening degree is set to 80% in the above embodiments, it is not limited to 80% and may be changed according to an individual refrigerating device.

[0028]

As described above, according to the present invention, the screw compressor 1 whose capacity can be controlled by adjusting the opening degree of the slide valve 4, the water cooling condenser 7 having the cooling water pipe, and the expansion mechanism 8 are provided. , A water evaporator 9 having a cold water pipe, and an oil recovery device 6 on the discharge side of the compressor 1, and the pressure difference between the discharge side pressure and the suction side pressure of the compressor 1 In a refrigeration system provided with an oil supply mechanism for supplying the oil of the oil recovery device 6 to the oil supply location of the compressor 1, a cold water temperature detector 20 for detecting the cold water temperature of the evaporator 9 and a cooling water for the condenser 7 A cooling water temperature detector 30 for detecting the temperature, and during the pull-down operation, the cold water temperature is below a predetermined temperature, and
When the cooling water temperature is below a predetermined temperature, each of the temperature detectors 2
A controller 60 for controlling the opening of the slide valve 4 to a predetermined opening based on the detection results from 0 and 30 is provided. Therefore, during pulldown operation, the cold water temperature is low, and the cooling water temperature is also low. Predicting that the differential pressure is unlikely to be applied and the oil supply amount will be insufficient, the opening of the slide valve 4 is set to the predetermined opening by the control of the controller 60, and by this opening control, that is, the low capacity operation is controlled to the high capacity operation. As a result, the rise of the discharge side pressure can be promoted and the high and low differential pressure can be maintained at a predetermined pressure difference, and the amount of oil supplied to the oil supply location of the compressor 1 can be secured. Therefore, the seizure of the compressor 1 can be prevented while continuing the pull-down operation without stopping it.

Moreover, the opening control of the slide valve 4 is
It is possible to detect the cold water temperature and the cooling water temperature and predict that the differential pressure is small at the same time when the pull-down operation is started, that is, the differential pressure is small and the amount of oil supply is insufficient to detect the cause of seizure. Since the control can be performed from the start of the pull-down operation, seizure of the compressor 1 can be effectively prevented while continuing the pull-down operation without stopping.

[Brief description of drawings]

FIG. 1 is a piping system diagram of a refrigeration system of the present invention.

FIG. 2 is a block diagram of a controller.

FIG. 3 is a flowchart showing an example of the operation of the controller.

FIG. 4 is an explanatory diagram showing a conventional example.

[Explanation of symbols]

 1 Screw Compressor 4 Slide Valve 6 Oil Collector 7 Water Cooling Condenser 8 Expansion Mechanism 9 Water Evaporator 20 Cold Water Temperature Detector 30 Cooling Water Temperature Detector 60 Controller

Claims (1)

[Claims] 1. A screw compressor 1 whose capacity is controllable by adjusting the opening of a slide valve 4, a water-cooled condenser 7 having a cooling water pipe, an expansion mechanism 8, and a water evaporator having a cold water pipe. 9 and the oil recovery device 6 is provided on the discharge side of the compressor 1, and the oil of the oil recovery device 6 is transferred to the compressor by the pressure difference between the discharge side pressure and the suction side pressure of the compressor 1. A refrigeration system provided with a refueling mechanism for refueling a refueling point of No. 1, a chilled water temperature detector 20 for detecting a chilled water temperature of the evaporator 9, and a cooling water temperature detection for detecting a chilled water temperature of the condenser 7. When the cold water temperature is lower than or equal to a predetermined temperature and the cooling water temperature is lower than or equal to a predetermined temperature during the pull-down operation with the device 30, the slide valve 4 is opened based on the detection results from the temperature detectors 20 and 30. And a controller 60 that controls the degree of opening to a predetermined opening degree. Refrigerating device characterized in that.