JP3443443B2 - Screw refrigerator - Google Patents

Description

Description: 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 with a refrigerant. 2. Description of the Related Art Conventionally, screw-type refrigerators of the type in which a motor for driving a semi-hermetic screw compressor is cooled with a refrigerant are known, and are disclosed in Japanese Patent Application Laid-Open Nos. 1-237389 and 1-237.
No. 273894. JP-A-1-23
Japanese Patent No. 7389 discloses a one-stage type in which a screw compressor driving motor is disposed at a suction portion of a compressor, and suction refrigerant gas is guided to a stator portion of the motor and is sucked into a rotor chamber to cool the motor. A screw type refrigerator employing a semi-hermetic screw compressor is disclosed. Japanese Patent Application Laid-Open No. 1-273894 discloses a screw type refrigerator employing a two-stage semi-hermetic screw compressor, in which a discharge port of a low pressure stage side compressor and a high pressure stage side are disclosed. A motor for driving the compressor is arranged between the suction port of the compressor and the refrigerant gas from the discharge port passes through the stator of the motor. [0004] Among the above-mentioned conventional screw type refrigerators, in the case of the one described in Japanese Patent Application Laid-Open No. 1-237389, the refrigerant gasified by the evaporator cools the motor. It is overheated when viewed from the refrigerant gas side. Then, since the refrigerant gas expands and is sucked into the rotor chamber by an amount corresponding to the overheating, there is a problem that the efficiency of suction into the rotor chamber deteriorates by the amount of the expansion. Further, in the apparatus described in Japanese Patent Application Laid-Open No. 1-237389, the suction efficiency of the compressor is not as bad as the above, but the suction efficiency into the rotor chamber on the high pressure stage side is reduced. The intermediate pressure between the low pressure stage and the high pressure stage is higher. For this reason, the compression ratio of the low-pressure-stage-side compressor body becomes high, which causes a problem that the suction efficiency of the low-pressure-stage side becomes low. The present invention has been made in view of such a conventional problem, cooling a compressor drive motor with a refrigerant,
Another object of the present invention is to provide a screw type refrigerator capable of preventing a reduction in suction efficiency. In order to solve the above-mentioned problems, the present invention provides at least a condenser, a first expansion valve, and an evaporator in addition to a one-stage or a plurality of stages of screw compressors. A screw-type refrigerating machine having a closed circulation passage for a refrigerant including: and a cooling passage for cooling a motor for driving the screw compressor with the refrigerant. Branch from the closed circulation channel at the inlet side of the valve,
The second expansion valve leads to the motor, passes through the motor, and communicates with a gas confined space that does not communicate with a suction port and a discharge port of a screw compressor that sends refrigerant to the condenser. At the same time, the temperature and pressure of the refrigerant are detected at the secondary side of the motor in the cooling flow path, and the opening of the second expansion valve is controlled so that the degree of superheat at the detection unit is constant. It was formed by providing a temperature sensing cylinder for adjusting the temperature. According to the above construction, the influence of overheating of the refrigerant gas due to the cooling of the motor does not affect the suction refrigerant gas. Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a screw-type refrigerator according to a first embodiment of the present invention, in which a screw compressor 1, a screw compressor 2, a condenser 3, an economizer 4, and a first expansion valve 5 in a low-pressure stage. , And a circulating closed flow path 7 for the refrigerant including the evaporator 6 and a branch from the circulating closed flow path 7 at the inlet side of the first expansion valve 5, and through the second expansion valve 8, the screw compressors 1, 2. A cooling flow path that leads to the drive motor 9, passes through a stator portion in the motor 9, and communicates with a gas confined space that does not communicate with the suction port and the discharge port of the screw compressor 2 on the high-pressure stage side. 10 are provided. In this embodiment, the screw compressors 1 and 2 and the motor 9 are of a semi-hermetic type integrally formed. At the outlet side of the condenser 3, a closed circulation passage 7 is provided.
From the economizer 4 through the third expansion valve 11.
An intermediate cooling flow path 12 is provided, which passes through the economizer 4 so as to be able to exchange heat with the refrigerant therein and joins an intermediate flow path 7 a between the screw compressors 1 and 2 which is a part of the closed circulation flow path 7. is there. Further, temperature-sensitive cylinders 13 are provided in the circulation closed 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 the pressure at the respective locations, and adjust the first, second, and third expansion valves 5, 8, and so that the degree of superheat at the detection unit is constant. 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 and lowered in temperature, it is sent into the motor 9 to be cooled.
Further, the refrigerant gas, which has cooled the motor 9 and raised in temperature, is led to the gas confining space of the screw compressor 2 on the high pressure stage side, where it joins 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 to the gas confining space of the screw compressor 2 on the high pressure stage side, it does not affect the suction of both compressors at all.
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-type refrigerator according to a second embodiment of the present invention. Parts common to those of the screw-type refrigerator 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. In this embodiment, the screw compressor 21 and the motor 9 are of a semi-hermetic type integrally formed. Then, the refrigerant liquid having exited from the condenser 3 is vaporized by the second expansion valve 8 to lower the temperature, and then sent to the stator section in the motor 9 to cool it. I have. Further, the refrigerant gas, which has cooled the motor 9 and raised in temperature, is guided to the gas confining space of the screw compressor 21 and is joined with the refrigerant gas circulating in the flow path 7. As described above, since the motor 9 is cooled and the heated refrigerant gas is sent into the gas confining space of the screw compressor 2 in the same manner as described above, there is no influence on the suction of the compressor. 9, it is possible to prevent the suction efficiency of the compressor from being lowered by the refrigerant gas from the compressor 9. Note that the present invention is not limited to the one provided with the screw compressor in one or two stages, but may be provided with the screw compressor in three or more stages. Also,
In the case where screw compressors are provided in multiple stages, the screw rotor shafts of each stage are connected via a coupling,
Each compressor may be driven by one motor,
Alternatively, a gear may be mounted on the shaft of the screw rotor, and if necessary, other gears may be interposed to drive each compressor by one motor. Further, the condenser 3 does not matter whether it is integrated with the liquid receiver or separated. As is apparent from the above description, according to the present invention, in addition to a single-stage or multiple-stage screw compressor,
A screw refrigerator including a refrigerant circulation closed flow path including at least a condenser, a first expansion valve, and an evaporator, and a cooling flow path that cools a motor that drives the screw compressor with the refrigerant. The cooling flow path is branched from the circulation closed flow path at the inlet side of the first expansion valve, reaches the motor via the second expansion valve, passes through the motor, and passes the refrigerant to 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 that sends out the gas. Therefore, the effect of overheating of the refrigerant gas due to cooling of the compressor driving motor does not affect the suctioned refrigerant gas, and the cooling of the motor by the refrigerant and the reduction of the suction efficiency of the compressor can be prevented. Play.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing an entire configuration of a screw refrigerator according to a first embodiment of the present invention. FIG. 2 is a view showing an entire configuration of a screw refrigerator according to a second embodiment of the present invention. [Description of Signs] 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

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F25B 1/047 F25B 1/10 F04C 29/04

Claims (1)

(57) [Claim 1] In addition to a one-stage or a plurality of stages of screw compressors, a refrigerant circulation closed flow path including at least a condenser, a first expansion valve, and an evaporator is provided. In addition, in a screw type refrigerator provided with a cooling passage for cooling a motor for driving the screw compressor with the refrigerant, the cooling passage is provided at the inlet side of the first expansion valve. Branch off the road,
The second expansion valve leads to the motor, passes through the motor, and communicates with a gas confined space that does not communicate with a suction port and a discharge port of a screw compressor that sends refrigerant to the condenser. And the cooling passage
In the secondary part of the motor, the temperature of the refrigerant
Temperature and pressure, and the degree of superheat at this detector becomes constant
In order to adjust the opening of the second expansion valve
A screw type refrigerator characterized by being formed .