JPH07180917A - Screw tube refrigerator - Google Patents

Abstract

PURPOSE:To provide a screw type refrigerator which cools a motor for driving a compressor with refrigerant and can prevent a decrease of a suction efficiency. CONSTITUTION:A screw type refrigerator comprises, in addition to two stages of screw type compressors 1, 2, a condenser 3, an economizer 4, a first expansion valve 5, a refrigerant circulating closed channel 7 including an evaporator 6, and a cooling channel 10 for cooling a motor 9 for driving the compressors 1, 2 with refrigerant, wherein the channel 10 is branched from the channel 7 at an inlet side of the valve 5, and fed to the motor 9 through a second expansion valve 8. The channel 10 is passed through the motor 9 to communicate with a gas enclosing space without communicating with a suction port and a discharge port of the compressor 2 for feeding the refrigerant to the condenser 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw type refrigerator in which a motor for driving a screw compressor is cooled by a refrigerant.

[0002]

2. Description of the Related Art Conventionally, a screw type refrigerator of a type in which a motor for driving a semi-hermetic screw compressor is cooled by a refrigerant is known, and is disclosed in Japanese Patent Laid-Open Nos. 1-237389 and 1-237.
It is disclosed in Japanese Patent No. 273894. Japanese Patent Laid-Open No. 1-23
In the 7389 publication, a screw compressor driving motor is arranged in a suction portion of a compressor, and a suction refrigerant gas is guided to a stator portion of the motor to be sucked into a rotor chamber to cool the motor. Discloses a screw type refrigerator employing the semi-hermetic screw compressor.

Japanese Unexamined Patent Publication No. 1-273894 discloses a screw type refrigerator using a two-stage semi-hermetic screw compressor, in which the discharge port of the low-pressure stage compressor and the high-pressure stage side are disclosed. A motor for driving the compressor is arranged between the suction port of the compressor and the stator so that the refrigerant gas from the discharge port passes therethrough.

[0004]

Among the conventional screw type refrigerators described in JP-A-1-237389, the refrigerant gasified in the evaporator cools the motor, but the refrigerant gas side. Seen from above, it is overheated. Then, since the refrigerant gas expands and is sucked into the rotor chamber by the amount of overheating, there is a problem that the suction efficiency into the rotor chamber is deteriorated by the expanded amount.

Further, in the one disclosed in Japanese Patent Laid-Open No. 1-237389, the suction efficiency of the compressor is not so bad as that described above, but the suction efficiency to the rotor chamber on the high pressure stage side is lowered, and as a result, The intermediate pressure between the low pressure stage and the high pressure stage becomes high. Therefore, the compression ratio of the low-pressure stage side compressor main body becomes high, which causes a problem that the suction efficiency at the low-pressure stage side becomes low. The present invention has been made to solve the above conventional problems, and cools a compressor driving motor with a refrigerant,
Moreover, it is an object of the present invention to provide a screw type refrigerator capable of preventing a decrease in suction efficiency.

[0006]

In order to solve the above problems, the present invention provides a refrigerant including at least a condenser, a first expansion valve, and an evaporator in addition to a one-stage or multiple-stage screw compressor. In a screw type refrigerator having a circulation closed flow passage and a cooling flow passage for cooling the motor for driving the screw compressor with the refrigerant, the cooling flow passage is provided at the inlet of the first expansion valve. Branch from the circulation closed flow path on the side,
Formed by communicating with a gas confined space that does not communicate with the suction port and the discharge port of a screw compressor that passes through the second expansion valve to the motor, passes through the motor, and sends the refrigerant to the condenser. did.

[0007]

With the configuration as described above, the influence of overheating of the refrigerant gas due to motor cooling does not affect the sucked refrigerant gas.

[0008]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a screw refrigerator according to a first embodiment of the present invention, which includes a low-pressure stage screw compressor 1, a high-pressure stage screw compressor 2, a condenser 3, an economizer 4, and a first expansion valve 5. , And the circulation closed flow path 7 for the refrigerant including the evaporator 6, and the circulation closed flow path 7 on the inlet side of the first expansion valve 5 and branched from the closed flow path 7 through the second expansion valve 8 to the screw compressor 1, A cooling flow path reaching the drive motor 9 and passing through a stator portion in the motor 9 and communicating with a gas confining space that does not communicate with the suction port and the discharge port of the screw compressor 2 on the high pressure stage side. And 10 are provided. In this embodiment, the screw compressors 1 and 2 and the motor 9 are of a semi-hermetic type integrally formed.

A closed circulation channel 7 is provided on the outlet side of the condenser 3.
From the first expansion valve 11 to the economizer 4
There is provided an intermediate cooling flow passage 12 which is passed through the economizer 4 so as to be able to exchange heat with the refrigerant inside and is joined to the intermediate flow passage 7a between the screw compressors 1 and 2 which is a part of the closed circulation flow passage 7. is there. Further, the temperature-sensing cylinder 13 is provided in the closed circulation flow path 7 on the outlet side of the evaporator 6, the flow path 10 between the motor 9 and the screw compressor 2, and the flow path 12 between the economizer 4 and the intermediate flow path 7a. , 14, and 15 are attached. The temperature-sensitive cylinders 13, 14, and 15 detect the temperature and pressure at their respective locations, and the first, second, and third expansion valves 5, 8, so that the degree of superheat in the detection section becomes constant. The opening degree of 11 is adjusted.

With the above configuration, the refrigerant liquid in the flow path 7 cooled in the economizer 4 is
After being vaporized by the second expansion valve 8 to lower the temperature, it is sent into the motor 9 to be cooled.
Further, the refrigerant gas, which has been cooled by heating the motor 9 and has been heated, is introduced into the gas confined space of the screw compressor 2 on the high pressure stage side and merged with the refrigerant gas circulating in the flow path 7. in this way,
Since the motor 9 is cooled and the heated refrigerant gas is sent into the gas confined space of the screw compressor 2 on the high pressure stage side, there is no effect on the suction of both compressors.
It is possible to prevent the suction efficiency of the compressor from being lowered by the refrigerant gas from the motor 9.

FIG. 2 shows a screw refrigerating machine according to a second embodiment of the present invention. The parts common to those of the screw refrigerating machine shown in FIG. In this embodiment, only one stage of the screw compressor 21 is provided, and the economizer 4, the flow path 12, the third expansion valve 11 and the temperature sensing cylinder 15 in the screw refrigerator shown in FIG. 1 are not provided. Further, in this embodiment, the screw compressor 21 and the motor 9 are of a semi-hermetic type integrally formed.

With this structure, the refrigerant liquid discharged from the condenser 3 is vaporized by the second expansion valve 8 to lower the temperature, and then sent to the stator portion in the motor 9 to cool it. I am doing it. Further, the refrigerant gas which has cooled the motor 9 and has been heated is introduced into the gas confined space of the screw compressor 21 and merged with the refrigerant gas circulating in the flow path 7. In this way, similarly to the above, since the motor 9 is cooled and the heated refrigerant gas is sent into the gas confined space of the screw compressor 2, the suction of the compressor is not affected at all, and the motor is not affected. It is possible to prevent the suction efficiency of the compressor from being deteriorated by the refrigerant gas from 9.

The present invention is not limited to the one in which the screw compressors are provided in one stage or two stages, and the screw compressors may be provided in three or more stages. Also,
In the case where screw compressors are provided in multiple stages, the shafts of the screw rotors in each stage are connected via couplings,
You may drive each compressor with one motor,
Alternatively, a gear may be attached to the shaft of the screw rotor, and if necessary, other gears may be interposed to drive each compressor with one motor. Further, the condenser 3 may be either integrated with the liquid receiver or separated.

[0014]

As is apparent from the above description, according to the present invention, in addition to the single-stage or multiple-stage screw type compressor,
At least a condenser, a first expansion valve, a screw-type refrigerator having a circulation closed flow path of a refrigerant including an evaporator, and a cooling flow path for cooling a motor for driving the screw compressor with the refrigerant, The cooling flow path is branched from the closed circulation flow path on the inlet side of the first expansion valve, reaches the motor through the second expansion valve, passes through the motor, and is cooled by the condenser. Is formed so as to communicate with a gas confined space that does not communicate with the suction port and the discharge port of the screw compressor for sending out.

For this reason, the influence of overheating of the refrigerant gas due to the cooling of the compressor driving motor does not affect the suction refrigerant gas, and it is possible to cool the motor by the refrigerant and prevent the suction efficiency of the compressor from decreasing. Play.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of a screw refrigerator according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an overall configuration of a screw refrigerator according to a second embodiment of the present invention.

[Explanation of symbols]

1, 2 screw compressor 3 condenser 5 first expansion valve 7 circulation closed flow path 8 second expansion valve 9 motor 10 flow path 21 screw compressor

Claims (1)

[Claims] 1. In addition to a single-stage or multiple-stage screw compressor, a refrigerant circulation closed flow passage including at least a condenser, a first expansion valve, and an evaporator is provided, and the screw compressor is driven. In a screw type refrigerator having a cooling flow path for cooling a motor with the refrigerant, the cooling flow path is branched from the circulation closed flow path at the inlet side of the first expansion valve,
Formed by communicating with a gas confined space that does not communicate with the suction port and the discharge port of a screw compressor that passes through the second expansion valve to the motor, passes through the motor, and sends the refrigerant to the condenser. A screw type refrigerator characterized in that