JP3495899B2 - Screw refrigerator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw refrigerator in which oil supplied to an oil-cooled screw compressor is cooled by its own refrigerant. 2. Description of the Related Art Conventionally, as shown in FIG.
A screw refrigerating machine that cools the oil supplied to 1 with its own refrigerant is known (JP-A-4-177059). This refrigerator has a closed-stage refrigerant circulation system including a two-stage oil-cooled compressor 21, an oil separation and recovery unit 22, a condenser 23, a liquid receiver 24, a subcooler 25, an expansion valve 26, and an evaporator 27. Channel X
And an oil supply passage Y extending from the oil separation and recovery unit 22 to an oil supply point in the compressor 21 via the oil cooler 28, and a branch from the circulation passage Y in the liquid receiver 24, and open / close valves 29, 30 , Expansion valve 3
The refrigerant branch passage Z passes through the oil cooler 28 through the first and second coolant passages 32 and reaches an intermediate pressure portion in the compressor 21. Then, an oil supply passage Y
Heat is exchanged between the internal oil and the refrigerant in the refrigerant branch channel Z, that is, the own refrigerant is evaporated to cool the oil, and the oil is guided to the oil supply point. . further,
A temperature switch 33 is provided that detects the oil temperature on the secondary side of the oil cooler 28 and opens and closes the on-off valve 30 based on the detected temperature to maintain the oil temperature within a certain range. [0004] The compressor 21 of the conventional screw refrigerator described above is a two-stage compressor having a low-stage compressor main body and a high-stage compressor main body. The refrigerant gas that has cooled the oil in 28 is returned to the intermediate pressure section in the compressor 21. Usually, in the case of a two-stage compressor, the low-stage compressor body has an unload function, and the high-stage compressor body does not have this unload function. The oil cooler 28 is designed on the assumption of a full load in summer when the heat load is maximum. Then, when the load on the evaporator 27 is small, the unload function operates in the low-stage compressor body, and the capacity control is performed. As a result of this capacity control, the pressure in the intermediate pressure section decreases, and if only this point is considered, supercooling of the oil occurs in the oil cooler 28.
In this screw refrigerator, a temperature switch 33 is provided to open and close the on-off valve 30 to increase or decrease the flow rate of the refrigerant, thereby preventing the oil from being supercooled. However, if the oil temperature is adjusted by opening and closing the on-off valve 30 by the temperature switch 33 to increase or decrease the flow rate of the refrigerant, the temperature change on the refrigerant side of the oil cooler 28 is large, and the oil shock is caused by thermal shock. There is a problem that a breakage accident of the cooler 28 may occur. The present invention has been made to eliminate the conventional problems, and has made it possible to prevent an oil cooler supplied to a compressor from being supercooled and to prevent a breakage accident due to a thermal shock of an oil cooler. It is intended to provide a screw refrigerator. [0006] In order to solve the above-mentioned problems, the present invention provides an oil-cooled screw compressor, at least an oil separation and recovery unit, a condenser, a first expansion valve, and an evaporator. A closed circulation flow path of the refrigerant containing the oil, an oil supply flow path from an oil reservoir at the lower part of the oil separation and recovery device to an oil supply point of the compressor through an oil cooler, the condenser and the After branching from the portion of the circulation flow path between the first expansion valve and the second expansion valve, the oil flows through the oil cooler so as to be able to exchange heat with oil in the oil supply flow path. Through the refrigerant branch flow path reaching an intermediate pressure portion from the suction port to the discharge port of the compressor, a secondary portion of the oil cooler of the refrigerant branch flow path, and the pressure control valve Interposed with the valve drive of the
The oil cooler is formed by providing a pressure guiding tube for operating the valve element driving unit so as to keep the pressure of the secondary side part constant. Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a screw refrigerator according to the present invention, in which an oil-cooled screw compressor 1, an oil separation / recovery unit 2, a condenser 3, a first expansion valve 4, and an evaporator 5 are closed circulation passages of refrigerant. I and an oil supply flow path II from an oil reservoir at the lower part of the oil separation and recovery unit 2 to an oil supply point such as a rotor housing space in the compressor 1, a bearing / shaft seal part, etc. via the oil cooler 6.
The oil cooler 6 branches off from the portion of the circulation flow path I between the condenser 3 and the first expansion valve 4 and passes through the second expansion valve 7 so as to be able to exchange heat with the oil in the oil supply flow path II. After passing through the inside, there is formed a refrigerant branch flow path III that reaches an intermediate pressure portion between the suction port and the discharge port in the compressor 1 via the pressure control valve 8. [0008] Further, the secondary side portion of the oil cooler 6 is interposed between the secondary side portion of the oil cooler 6 in the refrigerant branch flow path III and the valve body driving portion 9 of the pressure control valve 8. A pressure guiding tube 10 for operating the valve body driving unit 9 so as to keep the pressure, that is, the refrigerant gas pressure constant, is provided. In the case of the example shown here, the compressor 1 is not limited, but is of a two-stage type, and has a first compressor body 1A on the lower stage side and a second compressor body 1 on the higher stage side.
B, and the suction port of the first compressor body 1A is the compressor 1
And the discharge port of the second compressor main body 1 </ b> B is the discharge port of the compressor 1. Incidentally, the discharge port of the first compressor main body 1A and the suction port of the second compressor main body 1B communicate with each other via the intermediate flow path 11. On the secondary side of the evaporator 5, the degree of superheat of the refrigerant in this portion is detected, and the opening of the first expansion valve 4 is adjusted so that the degree of superheat falls within a set range. Temperature sensing cylinder 12
Is provided. Further, on the secondary side of the oil cooler 6, the degree of superheat of the refrigerant in this portion is detected, and the opening degree of the second expansion valve 7 is adjusted so that the degree of superheat is within a set range. A warm cylinder 13 is provided. In the screw refrigerating machine having the above-described structure, the pressure of the refrigerant in the oil cooler 6 is kept within a certain range by the pressure regulating valve 8 connected to the pressure guiding tube 10, so that the temperature on the low temperature side, that is, on the low temperature side, The temperature of the refrigerant is kept within a certain range. Therefore, the oil on the high temperature side is not supercooled. Further, since the temperature of the refrigerant on the low temperature side is kept within a certain range, there is no possibility of the oil cooler 6 being damaged by thermal shock. In the above-described embodiment, the condenser 3 is shown as being integral with the receiver, but the present invention does not limit the type of the condenser 3 at all. It may be of a type separated from the above. The compressor 1 is 1
Any of a step shape and a multi-stage shape may be used. As is apparent from the above description, according to the present invention, in addition to the oil-cooled screw compressor, at least the oil separation and recovery unit, the condenser, the first expansion valve and the evaporator are included. A closed circulation path for the refrigerant, an oil supply path from an oil reservoir below the oil separation and recovery unit to an oil supply point of the compressor via an oil cooler, the condenser and the first oil supply path. After branching off from the portion of the circulation flow path between the expansion valve and the second expansion valve and passing through the oil cooler so as to be able to exchange heat with oil in the oil supply flow path, Via, a refrigerant branch flow path reaching an intermediate pressure portion between the suction port and the discharge port of the compressor, a secondary part of the oil cooler of the refrigerant branch flow path, and a pressure control valve. The valve drive is interposed between the valve drive and the valve drive so as to keep the pressure of the secondary part of the oil cooler constant. And a pressure guiding tube for operating the moving part. [0013] Therefore, there is an effect that it is possible to prevent the oil cooler supplied to the compressor from being supercooled and to prevent the oil cooler from being damaged by a thermal shock.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing the overall configuration of a screw refrigerator according to the present invention. FIG. 2 is a diagram showing an entire configuration of a refrigerator using a conventional oil-cooled compressor. [Description of Signs] 1 Oil-cooled screw compressor 2 Oil separation / recovery device 3 Condenser 4 First expansion valve 5 Evaporator 6 Second expansion valve 7 Second expansion valve 8 Pressure control valve 9 Valve drive unit 10 Pressure guiding tube I Circulation channel II Oil supply channel III Refrigerant branch channel

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F04C 29/04

Claims (1)

(57) [Claim 1] In addition to an oil-cooled screw compressor, a closed circulation flow path of a refrigerant including at least an oil separation and recovery unit, a condenser, a first expansion valve, and an evaporator; An oil supply passage extending from an oil reservoir at a lower portion of the oil separation and recovery unit to a lubricating oil supply point of the compressor via an oil cooler, and the circulating flow between the condenser and the first expansion valve. After branching from the path, passing through the oil cooler through the second expansion valve so as to be able to exchange heat with the oil in the oil supply flow path, from the suction port of the compressor through the pressure control valve. A refrigerant branch flow path leading to an intermediate pressure portion up to the discharge port, a secondary part of the oil cooler of the refrigerant branch flow path, and a valve body driving part of the pressure regulating valve interposed therebetween; And
A screw refrigerating machine comprising: a pressure guiding tube for operating the valve body driving unit so as to keep a pressure of a secondary side of the oil cooler constant.